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jeremybenn |
@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
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@c 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
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@c Free Software Foundation, Inc.
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@c This is part of the GCC manual.
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@c For copying conditions, see the file gcc.texi.
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@ignore
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@c man begin INCLUDE
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@include gcc-vers.texi
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@c man end
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@c man begin COPYRIGHT
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Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
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1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
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Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.2 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``GNU General Public License'' and ``Funding
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Free Software'', the Front-Cover texts being (a) (see below), and with
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the Back-Cover Texts being (b) (see below). A copy of the license is
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included in the gfdl(7) man page.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development.
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@c man end
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@c Set file name and title for the man page.
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@setfilename gcc
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@settitle GNU project C and C++ compiler
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@c man begin SYNOPSIS
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gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}]
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[@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
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[@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
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[@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
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[@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
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[@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}]
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[@option{-o} @var{outfile}] [@@@var{file}] @var{infile}@dots{}
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Only the most useful options are listed here; see below for the
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remainder. @samp{g++} accepts mostly the same options as @samp{gcc}.
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@c man end
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@c man begin SEEALSO
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gpl(7), gfdl(7), fsf-funding(7),
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cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
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and the Info entries for @file{gcc}, @file{cpp}, @file{as},
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@file{ld}, @file{binutils} and @file{gdb}.
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@c man end
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@c man begin BUGS
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For instructions on reporting bugs, see
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@w{@value{BUGURL}}.
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@c man end
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@c man begin AUTHOR
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See the Info entry for @command{gcc}, or
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@w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}},
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for contributors to GCC@.
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@c man end
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@end ignore
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@node Invoking GCC
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@chapter GCC Command Options
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@cindex GCC command options
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@cindex command options
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@cindex options, GCC command
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@c man begin DESCRIPTION
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When you invoke GCC, it normally does preprocessing, compilation,
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assembly and linking. The ``overall options'' allow you to stop this
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process at an intermediate stage. For example, the @option{-c} option
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says not to run the linker. Then the output consists of object files
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output by the assembler.
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Other options are passed on to one stage of processing. Some options
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control the preprocessor and others the compiler itself. Yet other
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options control the assembler and linker; most of these are not
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documented here, since you rarely need to use any of them.
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@cindex C compilation options
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Most of the command line options that you can use with GCC are useful
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for C programs; when an option is only useful with another language
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(usually C++), the explanation says so explicitly. If the description
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for a particular option does not mention a source language, you can use
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that option with all supported languages.
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@cindex C++ compilation options
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@xref{Invoking G++,,Compiling C++ Programs}, for a summary of special
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options for compiling C++ programs.
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@cindex grouping options
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@cindex options, grouping
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The @command{gcc} program accepts options and file names as operands. Many
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options have multi-letter names; therefore multiple single-letter options
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may @emph{not} be grouped: @option{-dv} is very different from @w{@samp{-d
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-v}}.
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@cindex order of options
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@cindex options, order
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You can mix options and other arguments. For the most part, the order
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you use doesn't matter. Order does matter when you use several
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options of the same kind; for example, if you specify @option{-L} more
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than once, the directories are searched in the order specified. Also,
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the placement of the @option{-l} option is significant.
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Many options have long names starting with @samp{-f} or with
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@samp{-W}---for example,
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@option{-fmove-loop-invariants}, @option{-Wformat} and so on. Most of
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these have both positive and negative forms; the negative form of
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@option{-ffoo} would be @option{-fno-foo}. This manual documents
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only one of these two forms, whichever one is not the default.
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@c man end
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@xref{Option Index}, for an index to GCC's options.
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@menu
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* Option Summary:: Brief list of all options, without explanations.
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* Overall Options:: Controlling the kind of output:
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an executable, object files, assembler files,
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or preprocessed source.
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* Invoking G++:: Compiling C++ programs.
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* C Dialect Options:: Controlling the variant of C language compiled.
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* C++ Dialect Options:: Variations on C++.
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* Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C
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and Objective-C++.
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* Language Independent Options:: Controlling how diagnostics should be
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formatted.
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* Warning Options:: How picky should the compiler be?
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* Debugging Options:: Symbol tables, measurements, and debugging dumps.
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* Optimize Options:: How much optimization?
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* Preprocessor Options:: Controlling header files and macro definitions.
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Also, getting dependency information for Make.
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* Assembler Options:: Passing options to the assembler.
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* Link Options:: Specifying libraries and so on.
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* Directory Options:: Where to find header files and libraries.
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Where to find the compiler executable files.
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* Spec Files:: How to pass switches to sub-processes.
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* Target Options:: Running a cross-compiler, or an old version of GCC.
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* Submodel Options:: Specifying minor hardware or convention variations,
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such as 68010 vs 68020.
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* Code Gen Options:: Specifying conventions for function calls, data layout
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and register usage.
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* Environment Variables:: Env vars that affect GCC.
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* Precompiled Headers:: Compiling a header once, and using it many times.
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@end menu
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@c man begin OPTIONS
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@node Option Summary
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@section Option Summary
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Here is a summary of all the options, grouped by type. Explanations are
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in the following sections.
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@table @emph
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@item Overall Options
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@xref{Overall Options,,Options Controlling the Kind of Output}.
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@gccoptlist{-c -S -E -o @var{file} -combine -no-canonical-prefixes @gol
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-pipe -pass-exit-codes @gol
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-x @var{language} -v -### --help@r{[}=@var{class}@r{[},@dots{}@r{]]} --target-help @gol
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--version -wrapper@@@var{file} -fplugin=@var{file} -fplugin-arg-@var{name}=@var{arg}}
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@item C Language Options
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@xref{C Dialect Options,,Options Controlling C Dialect}.
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@gccoptlist{-ansi -std=@var{standard} -fgnu89-inline @gol
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-aux-info @var{filename} @gol
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-fno-asm -fno-builtin -fno-builtin-@var{function} @gol
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-fhosted -ffreestanding -fopenmp -fms-extensions @gol
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-trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol
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-fallow-single-precision -fcond-mismatch -flax-vector-conversions @gol
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-fsigned-bitfields -fsigned-char @gol
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-funsigned-bitfields -funsigned-char}
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@item C++ Language Options
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@xref{C++ Dialect Options,,Options Controlling C++ Dialect}.
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@gccoptlist{-fabi-version=@var{n} -fno-access-control -fcheck-new @gol
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-fconserve-space -ffriend-injection @gol
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-fno-elide-constructors @gol
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-fno-enforce-eh-specs @gol
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-ffor-scope -fno-for-scope -fno-gnu-keywords @gol
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-fno-implicit-templates @gol
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-fno-implicit-inline-templates @gol
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-fno-implement-inlines -fms-extensions @gol
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-fno-nonansi-builtins -fno-operator-names @gol
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-fno-optional-diags -fpermissive @gol
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-fno-pretty-templates @gol
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-frepo -fno-rtti -fstats -ftemplate-depth=@var{n} @gol
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-fno-threadsafe-statics -fuse-cxa-atexit -fno-weak -nostdinc++ @gol
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-fno-default-inline -fvisibility-inlines-hidden @gol
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-fvisibility-ms-compat @gol
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-Wabi -Wconversion-null -Wctor-dtor-privacy @gol
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-Wnon-virtual-dtor -Wreorder @gol
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-Weffc++ -Wstrict-null-sentinel @gol
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-Wno-non-template-friend -Wold-style-cast @gol
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-Woverloaded-virtual -Wno-pmf-conversions @gol
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-Wsign-promo}
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@item Objective-C and Objective-C++ Language Options
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@xref{Objective-C and Objective-C++ Dialect Options,,Options Controlling
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Objective-C and Objective-C++ Dialects}.
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@gccoptlist{-fconstant-string-class=@var{class-name} @gol
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-fgnu-runtime -fnext-runtime @gol
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-fno-nil-receivers @gol
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-fobjc-call-cxx-cdtors @gol
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-fobjc-direct-dispatch @gol
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-fobjc-exceptions @gol
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-fobjc-gc @gol
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-freplace-objc-classes @gol
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-fzero-link @gol
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-gen-decls @gol
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-Wassign-intercept @gol
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-Wno-protocol -Wselector @gol
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-Wstrict-selector-match @gol
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-Wundeclared-selector}
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@item Language Independent Options
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@xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}.
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@gccoptlist{-fmessage-length=@var{n} @gol
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-fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]} @gol
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-fdiagnostics-show-option}
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@item Warning Options
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@xref{Warning Options,,Options to Request or Suppress Warnings}.
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@gccoptlist{-fsyntax-only -pedantic -pedantic-errors @gol
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-w -Wextra -Wall -Waddress -Waggregate-return -Warray-bounds @gol
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-Wno-attributes -Wno-builtin-macro-redefined @gol
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-Wc++-compat -Wc++0x-compat -Wcast-align -Wcast-qual @gol
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-Wchar-subscripts -Wclobbered -Wcomment @gol
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-Wconversion -Wcoverage-mismatch -Wno-deprecated @gol
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-Wno-deprecated-declarations -Wdisabled-optimization @gol
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-Wno-div-by-zero -Wempty-body -Wenum-compare -Wno-endif-labels @gol
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-Werror -Werror=* @gol
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-Wfatal-errors -Wfloat-equal -Wformat -Wformat=2 @gol
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-Wno-format-contains-nul -Wno-format-extra-args -Wformat-nonliteral @gol
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-Wformat-security -Wformat-y2k @gol
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-Wframe-larger-than=@var{len} -Wjump-misses-init -Wignored-qualifiers @gol
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-Wimplicit -Wimplicit-function-declaration -Wimplicit-int @gol
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-Winit-self -Winline @gol
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-Wno-int-to-pointer-cast -Wno-invalid-offsetof @gol
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246 |
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-Winvalid-pch -Wlarger-than=@var{len} -Wunsafe-loop-optimizations @gol
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247 |
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-Wlogical-op -Wlong-long @gol
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248 |
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-Wmain -Wmissing-braces -Wmissing-field-initializers @gol
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249 |
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-Wmissing-format-attribute -Wmissing-include-dirs @gol
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250 |
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-Wmissing-noreturn -Wno-mudflap @gol
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251 |
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-Wno-multichar -Wnonnull -Wno-overflow @gol
|
252 |
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-Woverlength-strings -Wpacked -Wpacked-bitfield-compat -Wpadded @gol
|
253 |
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-Wparentheses -Wpedantic-ms-format -Wno-pedantic-ms-format @gol
|
254 |
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-Wpointer-arith -Wno-pointer-to-int-cast @gol
|
255 |
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-Wredundant-decls @gol
|
256 |
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-Wreturn-type -Wsequence-point -Wshadow @gol
|
257 |
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-Wsign-compare -Wsign-conversion -Wstack-protector @gol
|
258 |
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-Wstrict-aliasing -Wstrict-aliasing=n @gol
|
259 |
|
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-Wstrict-overflow -Wstrict-overflow=@var{n} @gol
|
260 |
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-Wswitch -Wswitch-default -Wswitch-enum -Wsync-nand @gol
|
261 |
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|
-Wsystem-headers -Wtrigraphs -Wtype-limits -Wundef -Wuninitialized @gol
|
262 |
|
|
-Wunknown-pragmas -Wno-pragmas @gol
|
263 |
|
|
-Wunsuffixed-float-constants -Wunused -Wunused-function @gol
|
264 |
|
|
-Wunused-label -Wunused-parameter -Wno-unused-result -Wunused-value -Wunused-variable @gol
|
265 |
|
|
-Wvariadic-macros -Wvla @gol
|
266 |
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|
-Wvolatile-register-var -Wwrite-strings}
|
267 |
|
|
|
268 |
|
|
@item C and Objective-C-only Warning Options
|
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|
@gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol
|
270 |
|
|
-Wmissing-parameter-type -Wmissing-prototypes -Wnested-externs @gol
|
271 |
|
|
-Wold-style-declaration -Wold-style-definition @gol
|
272 |
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-Wstrict-prototypes -Wtraditional -Wtraditional-conversion @gol
|
273 |
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-Wdeclaration-after-statement -Wpointer-sign}
|
274 |
|
|
|
275 |
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|
@item Debugging Options
|
276 |
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|
@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
|
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|
@gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol
|
278 |
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-fdbg-cnt-list -fdbg-cnt=@var{counter-value-list} @gol
|
279 |
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-fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links @gol
|
280 |
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-fdump-translation-unit@r{[}-@var{n}@r{]} @gol
|
281 |
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-fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol
|
282 |
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-fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline @gol
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-fdump-statistics @gol
|
284 |
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-fdump-tree-all @gol
|
285 |
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-fdump-tree-original@r{[}-@var{n}@r{]} @gol
|
286 |
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-fdump-tree-optimized@r{[}-@var{n}@r{]} @gol
|
287 |
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-fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias @gol
|
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|
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-fdump-tree-ch @gol
|
289 |
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-fdump-tree-ssa@r{[}-@var{n}@r{]} -fdump-tree-pre@r{[}-@var{n}@r{]} @gol
|
290 |
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-fdump-tree-ccp@r{[}-@var{n}@r{]} -fdump-tree-dce@r{[}-@var{n}@r{]} @gol
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291 |
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-fdump-tree-gimple@r{[}-raw@r{]} -fdump-tree-mudflap@r{[}-@var{n}@r{]} @gol
|
292 |
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-fdump-tree-dom@r{[}-@var{n}@r{]} @gol
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293 |
|
|
-fdump-tree-dse@r{[}-@var{n}@r{]} @gol
|
294 |
|
|
-fdump-tree-phiprop@r{[}-@var{n}@r{]} @gol
|
295 |
|
|
-fdump-tree-phiopt@r{[}-@var{n}@r{]} @gol
|
296 |
|
|
-fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol
|
297 |
|
|
-fdump-tree-copyrename@r{[}-@var{n}@r{]} @gol
|
298 |
|
|
-fdump-tree-nrv -fdump-tree-vect @gol
|
299 |
|
|
-fdump-tree-sink @gol
|
300 |
|
|
-fdump-tree-sra@r{[}-@var{n}@r{]} @gol
|
301 |
|
|
-fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol
|
302 |
|
|
-fdump-tree-fre@r{[}-@var{n}@r{]} @gol
|
303 |
|
|
-fdump-tree-vrp@r{[}-@var{n}@r{]} @gol
|
304 |
|
|
-ftree-vectorizer-verbose=@var{n} @gol
|
305 |
|
|
-fdump-tree-storeccp@r{[}-@var{n}@r{]} @gol
|
306 |
|
|
-fdump-final-insns=@var{file} @gol
|
307 |
|
|
-fcompare-debug@r{[}=@var{opts}@r{]} -fcompare-debug-second @gol
|
308 |
|
|
-feliminate-dwarf2-dups -feliminate-unused-debug-types @gol
|
309 |
|
|
-feliminate-unused-debug-symbols -femit-class-debug-always @gol
|
310 |
|
|
-fenable-icf-debug @gol
|
311 |
|
|
-fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report -fprofile-arcs @gol
|
312 |
|
|
-frandom-seed=@var{string} -fsched-verbose=@var{n} @gol
|
313 |
|
|
-fsel-sched-verbose -fsel-sched-dump-cfg -fsel-sched-pipelining-verbose @gol
|
314 |
|
|
-ftest-coverage -ftime-report -fvar-tracking @gol
|
315 |
|
|
-fvar-tracking-assignments -fvar-tracking-assignments-toggle @gol
|
316 |
|
|
-g -g@var{level} -gtoggle -gcoff -gdwarf-@var{version} @gol
|
317 |
|
|
-ggdb -gstabs -gstabs+ -gstrict-dwarf -gno-strict-dwarf @gol
|
318 |
|
|
-gvms -gxcoff -gxcoff+ @gol
|
319 |
|
|
-fno-merge-debug-strings -fno-dwarf2-cfi-asm @gol
|
320 |
|
|
-fdebug-prefix-map=@var{old}=@var{new} @gol
|
321 |
|
|
-femit-struct-debug-baseonly -femit-struct-debug-reduced @gol
|
322 |
|
|
-femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]} @gol
|
323 |
|
|
-p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol
|
324 |
|
|
-print-multi-directory -print-multi-lib -print-multi-os-directory @gol
|
325 |
|
|
-print-prog-name=@var{program} -print-search-dirs -Q @gol
|
326 |
|
|
-print-sysroot -print-sysroot-headers-suffix @gol
|
327 |
|
|
-save-temps -save-temps=cwd -save-temps=obj -time@r{[}=@var{file}@r{]}}
|
328 |
|
|
|
329 |
|
|
@item Optimization Options
|
330 |
|
|
@xref{Optimize Options,,Options that Control Optimization}.
|
331 |
|
|
@gccoptlist{
|
332 |
|
|
-falign-functions[=@var{n}] -falign-jumps[=@var{n}] @gol
|
333 |
|
|
-falign-labels[=@var{n}] -falign-loops[=@var{n}] -fassociative-math @gol
|
334 |
|
|
-fauto-inc-dec -fbranch-probabilities -fbranch-target-load-optimize @gol
|
335 |
|
|
-fbranch-target-load-optimize2 -fbtr-bb-exclusive -fcaller-saves @gol
|
336 |
|
|
-fcheck-data-deps -fconserve-stack -fcprop-registers -fcrossjumping @gol
|
337 |
|
|
-fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules -fcx-limited-range @gol
|
338 |
|
|
-fdata-sections -fdce -fdce @gol
|
339 |
|
|
-fdelayed-branch -fdelete-null-pointer-checks -fdse -fdse @gol
|
340 |
|
|
-fearly-inlining -fipa-sra -fexpensive-optimizations -ffast-math @gol
|
341 |
|
|
-ffinite-math-only -ffloat-store -fexcess-precision=@var{style} @gol
|
342 |
|
|
-fforward-propagate -ffunction-sections @gol
|
343 |
|
|
-fgcse -fgcse-after-reload -fgcse-las -fgcse-lm @gol
|
344 |
|
|
-fgcse-sm -fif-conversion -fif-conversion2 -findirect-inlining @gol
|
345 |
|
|
-finline-functions -finline-functions-called-once -finline-limit=@var{n} @gol
|
346 |
|
|
-finline-small-functions -fipa-cp -fipa-cp-clone -fipa-matrix-reorg -fipa-pta @gol
|
347 |
|
|
-fipa-pure-const -fipa-reference -fipa-struct-reorg @gol
|
348 |
|
|
-fipa-type-escape -fira-algorithm=@var{algorithm} @gol
|
349 |
|
|
-fira-region=@var{region} -fira-coalesce @gol
|
350 |
|
|
-fira-loop-pressure -fno-ira-share-save-slots @gol
|
351 |
|
|
-fno-ira-share-spill-slots -fira-verbose=@var{n} @gol
|
352 |
|
|
-fivopts -fkeep-inline-functions -fkeep-static-consts @gol
|
353 |
|
|
-floop-block -floop-interchange -floop-strip-mine -fgraphite-identity @gol
|
354 |
|
|
-floop-parallelize-all -flto -flto-compression-level -flto-report -fltrans @gol
|
355 |
|
|
-fltrans-output-list -fmerge-all-constants -fmerge-constants -fmodulo-sched @gol
|
356 |
|
|
-fmodulo-sched-allow-regmoves -fmove-loop-invariants -fmudflap @gol
|
357 |
|
|
-fmudflapir -fmudflapth -fno-branch-count-reg -fno-default-inline @gol
|
358 |
|
|
-fno-defer-pop -fno-function-cse -fno-guess-branch-probability @gol
|
359 |
|
|
-fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol
|
360 |
|
|
-fno-sched-interblock -fno-sched-spec -fno-signed-zeros @gol
|
361 |
|
|
-fno-toplevel-reorder -fno-trapping-math -fno-zero-initialized-in-bss @gol
|
362 |
|
|
-fomit-frame-pointer -foptimize-register-move -foptimize-sibling-calls @gol
|
363 |
|
|
-fpeel-loops -fpredictive-commoning -fprefetch-loop-arrays @gol
|
364 |
|
|
-fprofile-correction -fprofile-dir=@var{path} -fprofile-generate @gol
|
365 |
|
|
-fprofile-generate=@var{path} @gol
|
366 |
|
|
-fprofile-use -fprofile-use=@var{path} -fprofile-values @gol
|
367 |
|
|
-freciprocal-math -fregmove -frename-registers -freorder-blocks @gol
|
368 |
|
|
-freorder-blocks-and-partition -freorder-functions @gol
|
369 |
|
|
-frerun-cse-after-loop -freschedule-modulo-scheduled-loops @gol
|
370 |
|
|
-frounding-math -fsched2-use-superblocks -fsched-pressure @gol
|
371 |
|
|
-fsched-spec-load -fsched-spec-load-dangerous @gol
|
372 |
|
|
-fsched-stalled-insns-dep[=@var{n}] -fsched-stalled-insns[=@var{n}] @gol
|
373 |
|
|
-fsched-group-heuristic -fsched-critical-path-heuristic @gol
|
374 |
|
|
-fsched-spec-insn-heuristic -fsched-rank-heuristic @gol
|
375 |
|
|
-fsched-last-insn-heuristic -fsched-dep-count-heuristic @gol
|
376 |
|
|
-fschedule-insns -fschedule-insns2 -fsection-anchors @gol
|
377 |
|
|
-fselective-scheduling -fselective-scheduling2 @gol
|
378 |
|
|
-fsel-sched-pipelining -fsel-sched-pipelining-outer-loops @gol
|
379 |
|
|
-fsignaling-nans -fsingle-precision-constant -fsplit-ivs-in-unroller @gol
|
380 |
|
|
-fsplit-wide-types -fstack-protector -fstack-protector-all @gol
|
381 |
|
|
-fstrict-aliasing -fstrict-overflow -fthread-jumps -ftracer @gol
|
382 |
|
|
-ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-copy-prop @gol
|
383 |
|
|
-ftree-copyrename -ftree-dce @gol
|
384 |
|
|
-ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre -ftree-loop-im @gol
|
385 |
|
|
-ftree-phiprop -ftree-loop-distribution @gol
|
386 |
|
|
-ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize @gol
|
387 |
|
|
-ftree-parallelize-loops=@var{n} -ftree-pre -ftree-pta -ftree-reassoc @gol
|
388 |
|
|
-ftree-sink -ftree-sra -ftree-switch-conversion @gol
|
389 |
|
|
-ftree-ter -ftree-vect-loop-version -ftree-vectorize -ftree-vrp @gol
|
390 |
|
|
-funit-at-a-time -funroll-all-loops -funroll-loops @gol
|
391 |
|
|
-funsafe-loop-optimizations -funsafe-math-optimizations -funswitch-loops @gol
|
392 |
|
|
-fvariable-expansion-in-unroller -fvect-cost-model -fvpt -fweb @gol
|
393 |
|
|
-fwhole-program -fwhopr -fwpa -fuse-linker-plugin @gol
|
394 |
|
|
--param @var{name}=@var{value}
|
395 |
|
|
-O -O0 -O1 -O2 -O3 -Os}
|
396 |
|
|
|
397 |
|
|
@item Preprocessor Options
|
398 |
|
|
@xref{Preprocessor Options,,Options Controlling the Preprocessor}.
|
399 |
|
|
@gccoptlist{-A@var{question}=@var{answer} @gol
|
400 |
|
|
-A-@var{question}@r{[}=@var{answer}@r{]} @gol
|
401 |
|
|
-C -dD -dI -dM -dN @gol
|
402 |
|
|
-D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol
|
403 |
|
|
-idirafter @var{dir} @gol
|
404 |
|
|
-include @var{file} -imacros @var{file} @gol
|
405 |
|
|
-iprefix @var{file} -iwithprefix @var{dir} @gol
|
406 |
|
|
-iwithprefixbefore @var{dir} -isystem @var{dir} @gol
|
407 |
|
|
-imultilib @var{dir} -isysroot @var{dir} @gol
|
408 |
|
|
-M -MM -MF -MG -MP -MQ -MT -nostdinc @gol
|
409 |
|
|
-P -fworking-directory -remap @gol
|
410 |
|
|
-trigraphs -undef -U@var{macro} -Wp,@var{option} @gol
|
411 |
|
|
-Xpreprocessor @var{option}}
|
412 |
|
|
|
413 |
|
|
@item Assembler Option
|
414 |
|
|
@xref{Assembler Options,,Passing Options to the Assembler}.
|
415 |
|
|
@gccoptlist{-Wa,@var{option} -Xassembler @var{option}}
|
416 |
|
|
|
417 |
|
|
@item Linker Options
|
418 |
|
|
@xref{Link Options,,Options for Linking}.
|
419 |
|
|
@gccoptlist{@var{object-file-name} -l@var{library} @gol
|
420 |
|
|
-nostartfiles -nodefaultlibs -nostdlib -pie -rdynamic @gol
|
421 |
|
|
-s -static -static-libgcc -static-libstdc++ -shared @gol
|
422 |
|
|
-shared-libgcc -symbolic @gol
|
423 |
|
|
-T @var{script} -Wl,@var{option} -Xlinker @var{option} @gol
|
424 |
|
|
-u @var{symbol}}
|
425 |
|
|
|
426 |
|
|
@item Directory Options
|
427 |
|
|
@xref{Directory Options,,Options for Directory Search}.
|
428 |
|
|
@gccoptlist{-B@var{prefix} -I@var{dir} -iquote@var{dir} -L@var{dir}
|
429 |
|
|
-specs=@var{file} -I- --sysroot=@var{dir}}
|
430 |
|
|
|
431 |
|
|
@item Target Options
|
432 |
|
|
@c I wrote this xref this way to avoid overfull hbox. -- rms
|
433 |
|
|
@xref{Target Options}.
|
434 |
|
|
@gccoptlist{-V @var{version} -b @var{machine}}
|
435 |
|
|
|
436 |
|
|
@item Machine Dependent Options
|
437 |
|
|
@xref{Submodel Options,,Hardware Models and Configurations}.
|
438 |
|
|
@c This list is ordered alphanumerically by subsection name.
|
439 |
|
|
@c Try and put the significant identifier (CPU or system) first,
|
440 |
|
|
@c so users have a clue at guessing where the ones they want will be.
|
441 |
|
|
|
442 |
|
|
@emph{ARC Options}
|
443 |
|
|
@gccoptlist{-EB -EL @gol
|
444 |
|
|
-mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text-section} @gol
|
445 |
|
|
-mdata=@var{data-section} -mrodata=@var{readonly-data-section}}
|
446 |
|
|
|
447 |
|
|
@emph{ARM Options}
|
448 |
|
|
@gccoptlist{-mapcs-frame -mno-apcs-frame @gol
|
449 |
|
|
-mabi=@var{name} @gol
|
450 |
|
|
-mapcs-stack-check -mno-apcs-stack-check @gol
|
451 |
|
|
-mapcs-float -mno-apcs-float @gol
|
452 |
|
|
-mapcs-reentrant -mno-apcs-reentrant @gol
|
453 |
|
|
-msched-prolog -mno-sched-prolog @gol
|
454 |
|
|
-mlittle-endian -mbig-endian -mwords-little-endian @gol
|
455 |
|
|
-mfloat-abi=@var{name} -msoft-float -mhard-float -mfpe @gol
|
456 |
|
|
-mfp16-format=@var{name}
|
457 |
|
|
-mthumb-interwork -mno-thumb-interwork @gol
|
458 |
|
|
-mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol
|
459 |
|
|
-mstructure-size-boundary=@var{n} @gol
|
460 |
|
|
-mabort-on-noreturn @gol
|
461 |
|
|
-mlong-calls -mno-long-calls @gol
|
462 |
|
|
-msingle-pic-base -mno-single-pic-base @gol
|
463 |
|
|
-mpic-register=@var{reg} @gol
|
464 |
|
|
-mnop-fun-dllimport @gol
|
465 |
|
|
-mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns @gol
|
466 |
|
|
-mpoke-function-name @gol
|
467 |
|
|
-mthumb -marm @gol
|
468 |
|
|
-mtpcs-frame -mtpcs-leaf-frame @gol
|
469 |
|
|
-mcaller-super-interworking -mcallee-super-interworking @gol
|
470 |
|
|
-mtp=@var{name} @gol
|
471 |
|
|
-mword-relocations @gol
|
472 |
|
|
-mfix-cortex-m3-ldrd}
|
473 |
|
|
|
474 |
|
|
@emph{AVR Options}
|
475 |
|
|
@gccoptlist{-mmcu=@var{mcu} -mno-interrupts @gol
|
476 |
|
|
-mcall-prologues -mtiny-stack -mint8}
|
477 |
|
|
|
478 |
|
|
@emph{Blackfin Options}
|
479 |
|
|
@gccoptlist{-mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]} @gol
|
480 |
|
|
-msim -momit-leaf-frame-pointer -mno-omit-leaf-frame-pointer @gol
|
481 |
|
|
-mspecld-anomaly -mno-specld-anomaly -mcsync-anomaly -mno-csync-anomaly @gol
|
482 |
|
|
-mlow-64k -mno-low64k -mstack-check-l1 -mid-shared-library @gol
|
483 |
|
|
-mno-id-shared-library -mshared-library-id=@var{n} @gol
|
484 |
|
|
-mleaf-id-shared-library -mno-leaf-id-shared-library @gol
|
485 |
|
|
-msep-data -mno-sep-data -mlong-calls -mno-long-calls @gol
|
486 |
|
|
-mfast-fp -minline-plt -mmulticore -mcorea -mcoreb -msdram @gol
|
487 |
|
|
-micplb}
|
488 |
|
|
|
489 |
|
|
@emph{CRIS Options}
|
490 |
|
|
@gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol
|
491 |
|
|
-mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol
|
492 |
|
|
-metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol
|
493 |
|
|
-mstack-align -mdata-align -mconst-align @gol
|
494 |
|
|
-m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol
|
495 |
|
|
-melf -maout -melinux -mlinux -sim -sim2 @gol
|
496 |
|
|
-mmul-bug-workaround -mno-mul-bug-workaround}
|
497 |
|
|
|
498 |
|
|
@emph{CRX Options}
|
499 |
|
|
@gccoptlist{-mmac -mpush-args}
|
500 |
|
|
|
501 |
|
|
@emph{Darwin Options}
|
502 |
|
|
@gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol
|
503 |
|
|
-arch_only -bind_at_load -bundle -bundle_loader @gol
|
504 |
|
|
-client_name -compatibility_version -current_version @gol
|
505 |
|
|
-dead_strip @gol
|
506 |
|
|
-dependency-file -dylib_file -dylinker_install_name @gol
|
507 |
|
|
-dynamic -dynamiclib -exported_symbols_list @gol
|
508 |
|
|
-filelist -flat_namespace -force_cpusubtype_ALL @gol
|
509 |
|
|
-force_flat_namespace -headerpad_max_install_names @gol
|
510 |
|
|
-iframework @gol
|
511 |
|
|
-image_base -init -install_name -keep_private_externs @gol
|
512 |
|
|
-multi_module -multiply_defined -multiply_defined_unused @gol
|
513 |
|
|
-noall_load -no_dead_strip_inits_and_terms @gol
|
514 |
|
|
-nofixprebinding -nomultidefs -noprebind -noseglinkedit @gol
|
515 |
|
|
-pagezero_size -prebind -prebind_all_twolevel_modules @gol
|
516 |
|
|
-private_bundle -read_only_relocs -sectalign @gol
|
517 |
|
|
-sectobjectsymbols -whyload -seg1addr @gol
|
518 |
|
|
-sectcreate -sectobjectsymbols -sectorder @gol
|
519 |
|
|
-segaddr -segs_read_only_addr -segs_read_write_addr @gol
|
520 |
|
|
-seg_addr_table -seg_addr_table_filename -seglinkedit @gol
|
521 |
|
|
-segprot -segs_read_only_addr -segs_read_write_addr @gol
|
522 |
|
|
-single_module -static -sub_library -sub_umbrella @gol
|
523 |
|
|
-twolevel_namespace -umbrella -undefined @gol
|
524 |
|
|
-unexported_symbols_list -weak_reference_mismatches @gol
|
525 |
|
|
-whatsloaded -F -gused -gfull -mmacosx-version-min=@var{version} @gol
|
526 |
|
|
-mkernel -mone-byte-bool}
|
527 |
|
|
|
528 |
|
|
@emph{DEC Alpha Options}
|
529 |
|
|
@gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @gol
|
530 |
|
|
-mieee -mieee-with-inexact -mieee-conformant @gol
|
531 |
|
|
-mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol
|
532 |
|
|
-mtrap-precision=@var{mode} -mbuild-constants @gol
|
533 |
|
|
-mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol
|
534 |
|
|
-mbwx -mmax -mfix -mcix @gol
|
535 |
|
|
-mfloat-vax -mfloat-ieee @gol
|
536 |
|
|
-mexplicit-relocs -msmall-data -mlarge-data @gol
|
537 |
|
|
-msmall-text -mlarge-text @gol
|
538 |
|
|
-mmemory-latency=@var{time}}
|
539 |
|
|
|
540 |
|
|
@emph{DEC Alpha/VMS Options}
|
541 |
|
|
@gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64}
|
542 |
|
|
|
543 |
|
|
@emph{FR30 Options}
|
544 |
|
|
@gccoptlist{-msmall-model -mno-lsim}
|
545 |
|
|
|
546 |
|
|
@emph{FRV Options}
|
547 |
|
|
@gccoptlist{-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 @gol
|
548 |
|
|
-mhard-float -msoft-float @gol
|
549 |
|
|
-malloc-cc -mfixed-cc -mdword -mno-dword @gol
|
550 |
|
|
-mdouble -mno-double @gol
|
551 |
|
|
-mmedia -mno-media -mmuladd -mno-muladd @gol
|
552 |
|
|
-mfdpic -minline-plt -mgprel-ro -multilib-library-pic @gol
|
553 |
|
|
-mlinked-fp -mlong-calls -malign-labels @gol
|
554 |
|
|
-mlibrary-pic -macc-4 -macc-8 @gol
|
555 |
|
|
-mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol
|
556 |
|
|
-moptimize-membar -mno-optimize-membar @gol
|
557 |
|
|
-mscc -mno-scc -mcond-exec -mno-cond-exec @gol
|
558 |
|
|
-mvliw-branch -mno-vliw-branch @gol
|
559 |
|
|
-mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol
|
560 |
|
|
-mno-nested-cond-exec -mtomcat-stats @gol
|
561 |
|
|
-mTLS -mtls @gol
|
562 |
|
|
-mcpu=@var{cpu}}
|
563 |
|
|
|
564 |
|
|
@emph{GNU/Linux Options}
|
565 |
|
|
@gccoptlist{-muclibc}
|
566 |
|
|
|
567 |
|
|
@emph{H8/300 Options}
|
568 |
|
|
@gccoptlist{-mrelax -mh -ms -mn -mint32 -malign-300}
|
569 |
|
|
|
570 |
|
|
@emph{HPPA Options}
|
571 |
|
|
@gccoptlist{-march=@var{architecture-type} @gol
|
572 |
|
|
-mbig-switch -mdisable-fpregs -mdisable-indexing @gol
|
573 |
|
|
-mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol
|
574 |
|
|
-mfixed-range=@var{register-range} @gol
|
575 |
|
|
-mjump-in-delay -mlinker-opt -mlong-calls @gol
|
576 |
|
|
-mlong-load-store -mno-big-switch -mno-disable-fpregs @gol
|
577 |
|
|
-mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol
|
578 |
|
|
-mno-jump-in-delay -mno-long-load-store @gol
|
579 |
|
|
-mno-portable-runtime -mno-soft-float @gol
|
580 |
|
|
-mno-space-regs -msoft-float -mpa-risc-1-0 @gol
|
581 |
|
|
-mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol
|
582 |
|
|
-mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol
|
583 |
|
|
-munix=@var{unix-std} -nolibdld -static -threads}
|
584 |
|
|
|
585 |
|
|
@emph{i386 and x86-64 Options}
|
586 |
|
|
@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
|
587 |
|
|
-mfpmath=@var{unit} @gol
|
588 |
|
|
-masm=@var{dialect} -mno-fancy-math-387 @gol
|
589 |
|
|
-mno-fp-ret-in-387 -msoft-float @gol
|
590 |
|
|
-mno-wide-multiply -mrtd -malign-double @gol
|
591 |
|
|
-mpreferred-stack-boundary=@var{num}
|
592 |
|
|
-mincoming-stack-boundary=@var{num}
|
593 |
|
|
-mcld -mcx16 -msahf -mmovbe -mcrc32 -mrecip @gol
|
594 |
|
|
-mmmx -msse -msse2 -msse3 -mssse3 -msse4.1 -msse4.2 -msse4 -mavx @gol
|
595 |
|
|
-maes -mpclmul -mfused-madd @gol
|
596 |
|
|
-msse4a -m3dnow -mpopcnt -mabm -mfma4 -mxop -mlwp @gol
|
597 |
|
|
-mthreads -mno-align-stringops -minline-all-stringops @gol
|
598 |
|
|
-minline-stringops-dynamically -mstringop-strategy=@var{alg} @gol
|
599 |
|
|
-mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol
|
600 |
|
|
-m96bit-long-double -mregparm=@var{num} -msseregparm @gol
|
601 |
|
|
-mveclibabi=@var{type} -mpc32 -mpc64 -mpc80 -mstackrealign @gol
|
602 |
|
|
-momit-leaf-frame-pointer -mno-red-zone -mno-tls-direct-seg-refs @gol
|
603 |
|
|
-mcmodel=@var{code-model} -mabi=@var{name} @gol
|
604 |
|
|
-m32 -m64 -mlarge-data-threshold=@var{num} @gol
|
605 |
|
|
-msse2avx}
|
606 |
|
|
|
607 |
|
|
@emph{IA-64 Options}
|
608 |
|
|
@gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol
|
609 |
|
|
-mvolatile-asm-stop -mregister-names -msdata -mno-sdata @gol
|
610 |
|
|
-mconstant-gp -mauto-pic -mfused-madd @gol
|
611 |
|
|
-minline-float-divide-min-latency @gol
|
612 |
|
|
-minline-float-divide-max-throughput @gol
|
613 |
|
|
-mno-inline-float-divide @gol
|
614 |
|
|
-minline-int-divide-min-latency @gol
|
615 |
|
|
-minline-int-divide-max-throughput @gol
|
616 |
|
|
-mno-inline-int-divide @gol
|
617 |
|
|
-minline-sqrt-min-latency -minline-sqrt-max-throughput @gol
|
618 |
|
|
-mno-inline-sqrt @gol
|
619 |
|
|
-mdwarf2-asm -mearly-stop-bits @gol
|
620 |
|
|
-mfixed-range=@var{register-range} -mtls-size=@var{tls-size} @gol
|
621 |
|
|
-mtune=@var{cpu-type} -milp32 -mlp64 @gol
|
622 |
|
|
-msched-br-data-spec -msched-ar-data-spec -msched-control-spec @gol
|
623 |
|
|
-msched-br-in-data-spec -msched-ar-in-data-spec -msched-in-control-spec @gol
|
624 |
|
|
-msched-spec-ldc -msched-spec-control-ldc @gol
|
625 |
|
|
-msched-prefer-non-data-spec-insns -msched-prefer-non-control-spec-insns @gol
|
626 |
|
|
-msched-stop-bits-after-every-cycle -msched-count-spec-in-critical-path @gol
|
627 |
|
|
-msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost @gol
|
628 |
|
|
-msched-max-memory-insns-hard-limit -msched-max-memory-insns=@var{max-insns}}
|
629 |
|
|
|
630 |
|
|
@emph{IA-64/VMS Options}
|
631 |
|
|
@gccoptlist{-mvms-return-codes -mdebug-main=@var{prefix} -mmalloc64}
|
632 |
|
|
|
633 |
|
|
@emph{LM32 Options}
|
634 |
|
|
@gccoptlist{-mbarrel-shift-enabled -mdivide-enabled -mmultiply-enabled @gol
|
635 |
|
|
-msign-extend-enabled -muser-enabled}
|
636 |
|
|
|
637 |
|
|
@emph{M32R/D Options}
|
638 |
|
|
@gccoptlist{-m32r2 -m32rx -m32r @gol
|
639 |
|
|
-mdebug @gol
|
640 |
|
|
-malign-loops -mno-align-loops @gol
|
641 |
|
|
-missue-rate=@var{number} @gol
|
642 |
|
|
-mbranch-cost=@var{number} @gol
|
643 |
|
|
-mmodel=@var{code-size-model-type} @gol
|
644 |
|
|
-msdata=@var{sdata-type} @gol
|
645 |
|
|
-mno-flush-func -mflush-func=@var{name} @gol
|
646 |
|
|
-mno-flush-trap -mflush-trap=@var{number} @gol
|
647 |
|
|
-G @var{num}}
|
648 |
|
|
|
649 |
|
|
@emph{M32C Options}
|
650 |
|
|
@gccoptlist{-mcpu=@var{cpu} -msim -memregs=@var{number}}
|
651 |
|
|
|
652 |
|
|
@emph{M680x0 Options}
|
653 |
|
|
@gccoptlist{-march=@var{arch} -mcpu=@var{cpu} -mtune=@var{tune}
|
654 |
|
|
-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol
|
655 |
|
|
-m68060 -mcpu32 -m5200 -m5206e -m528x -m5307 -m5407 @gol
|
656 |
|
|
-mcfv4e -mbitfield -mno-bitfield -mc68000 -mc68020 @gol
|
657 |
|
|
-mnobitfield -mrtd -mno-rtd -mdiv -mno-div -mshort @gol
|
658 |
|
|
-mno-short -mhard-float -m68881 -msoft-float -mpcrel @gol
|
659 |
|
|
-malign-int -mstrict-align -msep-data -mno-sep-data @gol
|
660 |
|
|
-mshared-library-id=n -mid-shared-library -mno-id-shared-library @gol
|
661 |
|
|
-mxgot -mno-xgot}
|
662 |
|
|
|
663 |
|
|
@emph{M68hc1x Options}
|
664 |
|
|
@gccoptlist{-m6811 -m6812 -m68hc11 -m68hc12 -m68hcs12 @gol
|
665 |
|
|
-mauto-incdec -minmax -mlong-calls -mshort @gol
|
666 |
|
|
-msoft-reg-count=@var{count}}
|
667 |
|
|
|
668 |
|
|
@emph{MCore Options}
|
669 |
|
|
@gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol
|
670 |
|
|
-mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol
|
671 |
|
|
-m4byte-functions -mno-4byte-functions -mcallgraph-data @gol
|
672 |
|
|
-mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol
|
673 |
|
|
-mlittle-endian -mbig-endian -m210 -m340 -mstack-increment}
|
674 |
|
|
|
675 |
|
|
@emph{MeP Options}
|
676 |
|
|
@gccoptlist{-mabsdiff -mall-opts -maverage -mbased=@var{n} -mbitops @gol
|
677 |
|
|
-mc=@var{n} -mclip -mconfig=@var{name} -mcop -mcop32 -mcop64 -mivc2 @gol
|
678 |
|
|
-mdc -mdiv -meb -mel -mio-volatile -ml -mleadz -mm -mminmax @gol
|
679 |
|
|
-mmult -mno-opts -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf @gol
|
680 |
|
|
-mtiny=@var{n}}
|
681 |
|
|
|
682 |
|
|
@emph{MIPS Options}
|
683 |
|
|
@gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol
|
684 |
|
|
-mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 @gol
|
685 |
|
|
-mips64 -mips64r2 @gol
|
686 |
|
|
-mips16 -mno-mips16 -mflip-mips16 @gol
|
687 |
|
|
-minterlink-mips16 -mno-interlink-mips16 @gol
|
688 |
|
|
-mabi=@var{abi} -mabicalls -mno-abicalls @gol
|
689 |
|
|
-mshared -mno-shared -mplt -mno-plt -mxgot -mno-xgot @gol
|
690 |
|
|
-mgp32 -mgp64 -mfp32 -mfp64 -mhard-float -msoft-float @gol
|
691 |
|
|
-msingle-float -mdouble-float -mdsp -mno-dsp -mdspr2 -mno-dspr2 @gol
|
692 |
|
|
-mfpu=@var{fpu-type} @gol
|
693 |
|
|
-msmartmips -mno-smartmips @gol
|
694 |
|
|
-mpaired-single -mno-paired-single -mdmx -mno-mdmx @gol
|
695 |
|
|
-mips3d -mno-mips3d -mmt -mno-mt -mllsc -mno-llsc @gol
|
696 |
|
|
-mlong64 -mlong32 -msym32 -mno-sym32 @gol
|
697 |
|
|
-G@var{num} -mlocal-sdata -mno-local-sdata @gol
|
698 |
|
|
-mextern-sdata -mno-extern-sdata -mgpopt -mno-gopt @gol
|
699 |
|
|
-membedded-data -mno-embedded-data @gol
|
700 |
|
|
-muninit-const-in-rodata -mno-uninit-const-in-rodata @gol
|
701 |
|
|
-mcode-readable=@var{setting} @gol
|
702 |
|
|
-msplit-addresses -mno-split-addresses @gol
|
703 |
|
|
-mexplicit-relocs -mno-explicit-relocs @gol
|
704 |
|
|
-mcheck-zero-division -mno-check-zero-division @gol
|
705 |
|
|
-mdivide-traps -mdivide-breaks @gol
|
706 |
|
|
-mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol
|
707 |
|
|
-mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol
|
708 |
|
|
-mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol
|
709 |
|
|
-mfix-r10000 -mno-fix-r10000 -mfix-vr4120 -mno-fix-vr4120 @gol
|
710 |
|
|
-mfix-vr4130 -mno-fix-vr4130 -mfix-sb1 -mno-fix-sb1 @gol
|
711 |
|
|
-mflush-func=@var{func} -mno-flush-func @gol
|
712 |
|
|
-mbranch-cost=@var{num} -mbranch-likely -mno-branch-likely @gol
|
713 |
|
|
-mfp-exceptions -mno-fp-exceptions @gol
|
714 |
|
|
-mvr4130-align -mno-vr4130-align -msynci -mno-synci @gol
|
715 |
|
|
-mrelax-pic-calls -mno-relax-pic-calls -mmcount-ra-address}
|
716 |
|
|
|
717 |
|
|
@emph{MMIX Options}
|
718 |
|
|
@gccoptlist{-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol
|
719 |
|
|
-mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol
|
720 |
|
|
-melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol
|
721 |
|
|
-mno-base-addresses -msingle-exit -mno-single-exit}
|
722 |
|
|
|
723 |
|
|
@emph{MN10300 Options}
|
724 |
|
|
@gccoptlist{-mmult-bug -mno-mult-bug @gol
|
725 |
|
|
-mam33 -mno-am33 @gol
|
726 |
|
|
-mam33-2 -mno-am33-2 @gol
|
727 |
|
|
-mreturn-pointer-on-d0 @gol
|
728 |
|
|
-mno-crt0 -mrelax}
|
729 |
|
|
|
730 |
|
|
@emph{PDP-11 Options}
|
731 |
|
|
@gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol
|
732 |
|
|
-mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol
|
733 |
|
|
-mint16 -mno-int32 -mfloat32 -mno-float64 @gol
|
734 |
|
|
-mfloat64 -mno-float32 -mabshi -mno-abshi @gol
|
735 |
|
|
-mbranch-expensive -mbranch-cheap @gol
|
736 |
|
|
-msplit -mno-split -munix-asm -mdec-asm}
|
737 |
|
|
|
738 |
|
|
@emph{picoChip Options}
|
739 |
|
|
@gccoptlist{-mae=@var{ae_type} -mvliw-lookahead=@var{N}
|
740 |
|
|
-msymbol-as-address -mno-inefficient-warnings}
|
741 |
|
|
|
742 |
|
|
@emph{PowerPC Options}
|
743 |
|
|
See RS/6000 and PowerPC Options.
|
744 |
|
|
|
745 |
|
|
@emph{RS/6000 and PowerPC Options}
|
746 |
|
|
@gccoptlist{-mcpu=@var{cpu-type} @gol
|
747 |
|
|
-mtune=@var{cpu-type} @gol
|
748 |
|
|
-mpower -mno-power -mpower2 -mno-power2 @gol
|
749 |
|
|
-mpowerpc -mpowerpc64 -mno-powerpc @gol
|
750 |
|
|
-maltivec -mno-altivec @gol
|
751 |
|
|
-mpowerpc-gpopt -mno-powerpc-gpopt @gol
|
752 |
|
|
-mpowerpc-gfxopt -mno-powerpc-gfxopt @gol
|
753 |
|
|
-mmfcrf -mno-mfcrf -mpopcntb -mno-popcntb -mpopcntd -mno-popcntd @gol
|
754 |
|
|
-mfprnd -mno-fprnd @gol
|
755 |
|
|
-mcmpb -mno-cmpb -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp @gol
|
756 |
|
|
-mnew-mnemonics -mold-mnemonics @gol
|
757 |
|
|
-mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol
|
758 |
|
|
-m64 -m32 -mxl-compat -mno-xl-compat -mpe @gol
|
759 |
|
|
-malign-power -malign-natural @gol
|
760 |
|
|
-msoft-float -mhard-float -mmultiple -mno-multiple @gol
|
761 |
|
|
-msingle-float -mdouble-float -msimple-fpu @gol
|
762 |
|
|
-mstring -mno-string -mupdate -mno-update @gol
|
763 |
|
|
-mavoid-indexed-addresses -mno-avoid-indexed-addresses @gol
|
764 |
|
|
-mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol
|
765 |
|
|
-mstrict-align -mno-strict-align -mrelocatable @gol
|
766 |
|
|
-mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol
|
767 |
|
|
-mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol
|
768 |
|
|
-mdynamic-no-pic -maltivec -mswdiv @gol
|
769 |
|
|
-mprioritize-restricted-insns=@var{priority} @gol
|
770 |
|
|
-msched-costly-dep=@var{dependence_type} @gol
|
771 |
|
|
-minsert-sched-nops=@var{scheme} @gol
|
772 |
|
|
-mcall-sysv -mcall-netbsd @gol
|
773 |
|
|
-maix-struct-return -msvr4-struct-return @gol
|
774 |
|
|
-mabi=@var{abi-type} -msecure-plt -mbss-plt @gol
|
775 |
|
|
-misel -mno-isel @gol
|
776 |
|
|
-misel=yes -misel=no @gol
|
777 |
|
|
-mspe -mno-spe @gol
|
778 |
|
|
-mspe=yes -mspe=no @gol
|
779 |
|
|
-mpaired @gol
|
780 |
|
|
-mgen-cell-microcode -mwarn-cell-microcode @gol
|
781 |
|
|
-mvrsave -mno-vrsave @gol
|
782 |
|
|
-mmulhw -mno-mulhw @gol
|
783 |
|
|
-mdlmzb -mno-dlmzb @gol
|
784 |
|
|
-mfloat-gprs=yes -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double @gol
|
785 |
|
|
-mprototype -mno-prototype @gol
|
786 |
|
|
-msim -mmvme -mads -myellowknife -memb -msdata @gol
|
787 |
|
|
-msdata=@var{opt} -mvxworks -G @var{num} -pthread}
|
788 |
|
|
|
789 |
|
|
@emph{RX Options}
|
790 |
|
|
@gccoptlist{-m64bit-doubles -m32bit-doubles -fpu -nofpu@gol
|
791 |
|
|
-mcpu= -patch=@gol
|
792 |
|
|
-mbig-endian-data -mlittle-endian-data @gol
|
793 |
|
|
-msmall-data @gol
|
794 |
|
|
-msim -mno-sim@gol
|
795 |
|
|
-mas100-syntax -mno-as100-syntax@gol
|
796 |
|
|
-mrelax@gol
|
797 |
|
|
-mmax-constant-size=@gol
|
798 |
|
|
-mint-register=@gol
|
799 |
|
|
-msave-acc-in-interrupts}
|
800 |
|
|
|
801 |
|
|
@emph{S/390 and zSeries Options}
|
802 |
|
|
@gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol
|
803 |
|
|
-mhard-float -msoft-float -mhard-dfp -mno-hard-dfp @gol
|
804 |
|
|
-mlong-double-64 -mlong-double-128 @gol
|
805 |
|
|
-mbackchain -mno-backchain -mpacked-stack -mno-packed-stack @gol
|
806 |
|
|
-msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol
|
807 |
|
|
-m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol
|
808 |
|
|
-mtpf-trace -mno-tpf-trace -mfused-madd -mno-fused-madd @gol
|
809 |
|
|
-mwarn-framesize -mwarn-dynamicstack -mstack-size -mstack-guard}
|
810 |
|
|
|
811 |
|
|
@emph{Score Options}
|
812 |
|
|
@gccoptlist{-meb -mel @gol
|
813 |
|
|
-mnhwloop @gol
|
814 |
|
|
-muls @gol
|
815 |
|
|
-mmac @gol
|
816 |
|
|
-mscore5 -mscore5u -mscore7 -mscore7d}
|
817 |
|
|
|
818 |
|
|
@emph{SH Options}
|
819 |
|
|
@gccoptlist{-m1 -m2 -m2e @gol
|
820 |
|
|
-m2a-nofpu -m2a-single-only -m2a-single -m2a @gol
|
821 |
|
|
-m3 -m3e @gol
|
822 |
|
|
-m4-nofpu -m4-single-only -m4-single -m4 @gol
|
823 |
|
|
-m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al @gol
|
824 |
|
|
-m5-64media -m5-64media-nofpu @gol
|
825 |
|
|
-m5-32media -m5-32media-nofpu @gol
|
826 |
|
|
-m5-compact -m5-compact-nofpu @gol
|
827 |
|
|
-mb -ml -mdalign -mrelax @gol
|
828 |
|
|
-mbigtable -mfmovd -mhitachi -mrenesas -mno-renesas -mnomacsave @gol
|
829 |
|
|
-mieee -mbitops -misize -minline-ic_invalidate -mpadstruct -mspace @gol
|
830 |
|
|
-mprefergot -musermode -multcost=@var{number} -mdiv=@var{strategy} @gol
|
831 |
|
|
-mdivsi3_libfunc=@var{name} -mfixed-range=@var{register-range} @gol
|
832 |
|
|
-madjust-unroll -mindexed-addressing -mgettrcost=@var{number} -mpt-fixed @gol
|
833 |
|
|
-minvalid-symbols}
|
834 |
|
|
|
835 |
|
|
@emph{SPARC Options}
|
836 |
|
|
@gccoptlist{-mcpu=@var{cpu-type} @gol
|
837 |
|
|
-mtune=@var{cpu-type} @gol
|
838 |
|
|
-mcmodel=@var{code-model} @gol
|
839 |
|
|
-m32 -m64 -mapp-regs -mno-app-regs @gol
|
840 |
|
|
-mfaster-structs -mno-faster-structs @gol
|
841 |
|
|
-mfpu -mno-fpu -mhard-float -msoft-float @gol
|
842 |
|
|
-mhard-quad-float -msoft-quad-float @gol
|
843 |
|
|
-mimpure-text -mno-impure-text -mlittle-endian @gol
|
844 |
|
|
-mstack-bias -mno-stack-bias @gol
|
845 |
|
|
-munaligned-doubles -mno-unaligned-doubles @gol
|
846 |
|
|
-mv8plus -mno-v8plus -mvis -mno-vis
|
847 |
|
|
-threads -pthreads -pthread}
|
848 |
|
|
|
849 |
|
|
@emph{SPU Options}
|
850 |
|
|
@gccoptlist{-mwarn-reloc -merror-reloc @gol
|
851 |
|
|
-msafe-dma -munsafe-dma @gol
|
852 |
|
|
-mbranch-hints @gol
|
853 |
|
|
-msmall-mem -mlarge-mem -mstdmain @gol
|
854 |
|
|
-mfixed-range=@var{register-range} @gol
|
855 |
|
|
-mea32 -mea64 @gol
|
856 |
|
|
-maddress-space-conversion -mno-address-space-conversion @gol
|
857 |
|
|
-mcache-size=@var{cache-size} @gol
|
858 |
|
|
-matomic-updates -mno-atomic-updates}
|
859 |
|
|
|
860 |
|
|
@emph{System V Options}
|
861 |
|
|
@gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}}
|
862 |
|
|
|
863 |
|
|
@emph{V850 Options}
|
864 |
|
|
@gccoptlist{-mlong-calls -mno-long-calls -mep -mno-ep @gol
|
865 |
|
|
-mprolog-function -mno-prolog-function -mspace @gol
|
866 |
|
|
-mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol
|
867 |
|
|
-mapp-regs -mno-app-regs @gol
|
868 |
|
|
-mdisable-callt -mno-disable-callt @gol
|
869 |
|
|
-mv850e1 @gol
|
870 |
|
|
-mv850e @gol
|
871 |
|
|
-mv850 -mbig-switch}
|
872 |
|
|
|
873 |
|
|
@emph{VAX Options}
|
874 |
|
|
@gccoptlist{-mg -mgnu -munix}
|
875 |
|
|
|
876 |
|
|
@emph{VxWorks Options}
|
877 |
|
|
@gccoptlist{-mrtp -non-static -Bstatic -Bdynamic @gol
|
878 |
|
|
-Xbind-lazy -Xbind-now}
|
879 |
|
|
|
880 |
|
|
@emph{x86-64 Options}
|
881 |
|
|
See i386 and x86-64 Options.
|
882 |
|
|
|
883 |
|
|
@emph{i386 and x86-64 Windows Options}
|
884 |
|
|
@gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll
|
885 |
|
|
-mnop-fun-dllimport -mthread -municode -mwin32 -mwindows
|
886 |
|
|
-fno-set-stack-executable}
|
887 |
|
|
|
888 |
|
|
@emph{Xstormy16 Options}
|
889 |
|
|
@gccoptlist{-msim}
|
890 |
|
|
|
891 |
|
|
@emph{Xtensa Options}
|
892 |
|
|
@gccoptlist{-mconst16 -mno-const16 @gol
|
893 |
|
|
-mfused-madd -mno-fused-madd @gol
|
894 |
|
|
-mserialize-volatile -mno-serialize-volatile @gol
|
895 |
|
|
-mtext-section-literals -mno-text-section-literals @gol
|
896 |
|
|
-mtarget-align -mno-target-align @gol
|
897 |
|
|
-mlongcalls -mno-longcalls}
|
898 |
|
|
|
899 |
|
|
@emph{zSeries Options}
|
900 |
|
|
See S/390 and zSeries Options.
|
901 |
|
|
|
902 |
|
|
@item Code Generation Options
|
903 |
|
|
@xref{Code Gen Options,,Options for Code Generation Conventions}.
|
904 |
|
|
@gccoptlist{-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol
|
905 |
|
|
-ffixed-@var{reg} -fexceptions @gol
|
906 |
|
|
-fnon-call-exceptions -funwind-tables @gol
|
907 |
|
|
-fasynchronous-unwind-tables @gol
|
908 |
|
|
-finhibit-size-directive -finstrument-functions @gol
|
909 |
|
|
-finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{} @gol
|
910 |
|
|
-finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{} @gol
|
911 |
|
|
-fno-common -fno-ident @gol
|
912 |
|
|
-fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol
|
913 |
|
|
-fno-jump-tables @gol
|
914 |
|
|
-frecord-gcc-switches @gol
|
915 |
|
|
-freg-struct-return -fshort-enums @gol
|
916 |
|
|
-fshort-double -fshort-wchar @gol
|
917 |
|
|
-fverbose-asm -fpack-struct[=@var{n}] -fstack-check @gol
|
918 |
|
|
-fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol
|
919 |
|
|
-fno-stack-limit -fargument-alias -fargument-noalias @gol
|
920 |
|
|
-fargument-noalias-global -fargument-noalias-anything @gol
|
921 |
|
|
-fleading-underscore -ftls-model=@var{model} @gol
|
922 |
|
|
-ftrapv -fwrapv -fbounds-check @gol
|
923 |
|
|
-fvisibility}
|
924 |
|
|
@end table
|
925 |
|
|
|
926 |
|
|
@menu
|
927 |
|
|
* Overall Options:: Controlling the kind of output:
|
928 |
|
|
an executable, object files, assembler files,
|
929 |
|
|
or preprocessed source.
|
930 |
|
|
* C Dialect Options:: Controlling the variant of C language compiled.
|
931 |
|
|
* C++ Dialect Options:: Variations on C++.
|
932 |
|
|
* Objective-C and Objective-C++ Dialect Options:: Variations on Objective-C
|
933 |
|
|
and Objective-C++.
|
934 |
|
|
* Language Independent Options:: Controlling how diagnostics should be
|
935 |
|
|
formatted.
|
936 |
|
|
* Warning Options:: How picky should the compiler be?
|
937 |
|
|
* Debugging Options:: Symbol tables, measurements, and debugging dumps.
|
938 |
|
|
* Optimize Options:: How much optimization?
|
939 |
|
|
* Preprocessor Options:: Controlling header files and macro definitions.
|
940 |
|
|
Also, getting dependency information for Make.
|
941 |
|
|
* Assembler Options:: Passing options to the assembler.
|
942 |
|
|
* Link Options:: Specifying libraries and so on.
|
943 |
|
|
* Directory Options:: Where to find header files and libraries.
|
944 |
|
|
Where to find the compiler executable files.
|
945 |
|
|
* Spec Files:: How to pass switches to sub-processes.
|
946 |
|
|
* Target Options:: Running a cross-compiler, or an old version of GCC.
|
947 |
|
|
@end menu
|
948 |
|
|
|
949 |
|
|
@node Overall Options
|
950 |
|
|
@section Options Controlling the Kind of Output
|
951 |
|
|
|
952 |
|
|
Compilation can involve up to four stages: preprocessing, compilation
|
953 |
|
|
proper, assembly and linking, always in that order. GCC is capable of
|
954 |
|
|
preprocessing and compiling several files either into several
|
955 |
|
|
assembler input files, or into one assembler input file; then each
|
956 |
|
|
assembler input file produces an object file, and linking combines all
|
957 |
|
|
the object files (those newly compiled, and those specified as input)
|
958 |
|
|
into an executable file.
|
959 |
|
|
|
960 |
|
|
@cindex file name suffix
|
961 |
|
|
For any given input file, the file name suffix determines what kind of
|
962 |
|
|
compilation is done:
|
963 |
|
|
|
964 |
|
|
@table @gcctabopt
|
965 |
|
|
@item @var{file}.c
|
966 |
|
|
C source code which must be preprocessed.
|
967 |
|
|
|
968 |
|
|
@item @var{file}.i
|
969 |
|
|
C source code which should not be preprocessed.
|
970 |
|
|
|
971 |
|
|
@item @var{file}.ii
|
972 |
|
|
C++ source code which should not be preprocessed.
|
973 |
|
|
|
974 |
|
|
@item @var{file}.m
|
975 |
|
|
Objective-C source code. Note that you must link with the @file{libobjc}
|
976 |
|
|
library to make an Objective-C program work.
|
977 |
|
|
|
978 |
|
|
@item @var{file}.mi
|
979 |
|
|
Objective-C source code which should not be preprocessed.
|
980 |
|
|
|
981 |
|
|
@item @var{file}.mm
|
982 |
|
|
@itemx @var{file}.M
|
983 |
|
|
Objective-C++ source code. Note that you must link with the @file{libobjc}
|
984 |
|
|
library to make an Objective-C++ program work. Note that @samp{.M} refers
|
985 |
|
|
to a literal capital M@.
|
986 |
|
|
|
987 |
|
|
@item @var{file}.mii
|
988 |
|
|
Objective-C++ source code which should not be preprocessed.
|
989 |
|
|
|
990 |
|
|
@item @var{file}.h
|
991 |
|
|
C, C++, Objective-C or Objective-C++ header file to be turned into a
|
992 |
|
|
precompiled header.
|
993 |
|
|
|
994 |
|
|
@item @var{file}.cc
|
995 |
|
|
@itemx @var{file}.cp
|
996 |
|
|
@itemx @var{file}.cxx
|
997 |
|
|
@itemx @var{file}.cpp
|
998 |
|
|
@itemx @var{file}.CPP
|
999 |
|
|
@itemx @var{file}.c++
|
1000 |
|
|
@itemx @var{file}.C
|
1001 |
|
|
C++ source code which must be preprocessed. Note that in @samp{.cxx},
|
1002 |
|
|
the last two letters must both be literally @samp{x}. Likewise,
|
1003 |
|
|
@samp{.C} refers to a literal capital C@.
|
1004 |
|
|
|
1005 |
|
|
@item @var{file}.mm
|
1006 |
|
|
@itemx @var{file}.M
|
1007 |
|
|
Objective-C++ source code which must be preprocessed.
|
1008 |
|
|
|
1009 |
|
|
@item @var{file}.mii
|
1010 |
|
|
Objective-C++ source code which should not be preprocessed.
|
1011 |
|
|
|
1012 |
|
|
@item @var{file}.hh
|
1013 |
|
|
@itemx @var{file}.H
|
1014 |
|
|
@itemx @var{file}.hp
|
1015 |
|
|
@itemx @var{file}.hxx
|
1016 |
|
|
@itemx @var{file}.hpp
|
1017 |
|
|
@itemx @var{file}.HPP
|
1018 |
|
|
@itemx @var{file}.h++
|
1019 |
|
|
@itemx @var{file}.tcc
|
1020 |
|
|
C++ header file to be turned into a precompiled header.
|
1021 |
|
|
|
1022 |
|
|
@item @var{file}.f
|
1023 |
|
|
@itemx @var{file}.for
|
1024 |
|
|
@itemx @var{file}.ftn
|
1025 |
|
|
Fixed form Fortran source code which should not be preprocessed.
|
1026 |
|
|
|
1027 |
|
|
@item @var{file}.F
|
1028 |
|
|
@itemx @var{file}.FOR
|
1029 |
|
|
@itemx @var{file}.fpp
|
1030 |
|
|
@itemx @var{file}.FPP
|
1031 |
|
|
@itemx @var{file}.FTN
|
1032 |
|
|
Fixed form Fortran source code which must be preprocessed (with the traditional
|
1033 |
|
|
preprocessor).
|
1034 |
|
|
|
1035 |
|
|
@item @var{file}.f90
|
1036 |
|
|
@itemx @var{file}.f95
|
1037 |
|
|
@itemx @var{file}.f03
|
1038 |
|
|
@itemx @var{file}.f08
|
1039 |
|
|
Free form Fortran source code which should not be preprocessed.
|
1040 |
|
|
|
1041 |
|
|
@item @var{file}.F90
|
1042 |
|
|
@itemx @var{file}.F95
|
1043 |
|
|
@itemx @var{file}.F03
|
1044 |
|
|
@itemx @var{file}.F08
|
1045 |
|
|
Free form Fortran source code which must be preprocessed (with the
|
1046 |
|
|
traditional preprocessor).
|
1047 |
|
|
|
1048 |
|
|
@c FIXME: Descriptions of Java file types.
|
1049 |
|
|
@c @var{file}.java
|
1050 |
|
|
@c @var{file}.class
|
1051 |
|
|
@c @var{file}.zip
|
1052 |
|
|
@c @var{file}.jar
|
1053 |
|
|
|
1054 |
|
|
@item @var{file}.ads
|
1055 |
|
|
Ada source code file which contains a library unit declaration (a
|
1056 |
|
|
declaration of a package, subprogram, or generic, or a generic
|
1057 |
|
|
instantiation), or a library unit renaming declaration (a package,
|
1058 |
|
|
generic, or subprogram renaming declaration). Such files are also
|
1059 |
|
|
called @dfn{specs}.
|
1060 |
|
|
|
1061 |
|
|
@item @var{file}.adb
|
1062 |
|
|
Ada source code file containing a library unit body (a subprogram or
|
1063 |
|
|
package body). Such files are also called @dfn{bodies}.
|
1064 |
|
|
|
1065 |
|
|
@c GCC also knows about some suffixes for languages not yet included:
|
1066 |
|
|
@c Pascal:
|
1067 |
|
|
@c @var{file}.p
|
1068 |
|
|
@c @var{file}.pas
|
1069 |
|
|
@c Ratfor:
|
1070 |
|
|
@c @var{file}.r
|
1071 |
|
|
|
1072 |
|
|
@item @var{file}.s
|
1073 |
|
|
Assembler code.
|
1074 |
|
|
|
1075 |
|
|
@item @var{file}.S
|
1076 |
|
|
@itemx @var{file}.sx
|
1077 |
|
|
Assembler code which must be preprocessed.
|
1078 |
|
|
|
1079 |
|
|
@item @var{other}
|
1080 |
|
|
An object file to be fed straight into linking.
|
1081 |
|
|
Any file name with no recognized suffix is treated this way.
|
1082 |
|
|
@end table
|
1083 |
|
|
|
1084 |
|
|
@opindex x
|
1085 |
|
|
You can specify the input language explicitly with the @option{-x} option:
|
1086 |
|
|
|
1087 |
|
|
@table @gcctabopt
|
1088 |
|
|
@item -x @var{language}
|
1089 |
|
|
Specify explicitly the @var{language} for the following input files
|
1090 |
|
|
(rather than letting the compiler choose a default based on the file
|
1091 |
|
|
name suffix). This option applies to all following input files until
|
1092 |
|
|
the next @option{-x} option. Possible values for @var{language} are:
|
1093 |
|
|
@smallexample
|
1094 |
|
|
c c-header c-cpp-output
|
1095 |
|
|
c++ c++-header c++-cpp-output
|
1096 |
|
|
objective-c objective-c-header objective-c-cpp-output
|
1097 |
|
|
objective-c++ objective-c++-header objective-c++-cpp-output
|
1098 |
|
|
assembler assembler-with-cpp
|
1099 |
|
|
ada
|
1100 |
|
|
f77 f77-cpp-input f95 f95-cpp-input
|
1101 |
|
|
java
|
1102 |
|
|
@end smallexample
|
1103 |
|
|
|
1104 |
|
|
@item -x none
|
1105 |
|
|
Turn off any specification of a language, so that subsequent files are
|
1106 |
|
|
handled according to their file name suffixes (as they are if @option{-x}
|
1107 |
|
|
has not been used at all).
|
1108 |
|
|
|
1109 |
|
|
@item -pass-exit-codes
|
1110 |
|
|
@opindex pass-exit-codes
|
1111 |
|
|
Normally the @command{gcc} program will exit with the code of 1 if any
|
1112 |
|
|
phase of the compiler returns a non-success return code. If you specify
|
1113 |
|
|
@option{-pass-exit-codes}, the @command{gcc} program will instead return with
|
1114 |
|
|
numerically highest error produced by any phase that returned an error
|
1115 |
|
|
indication. The C, C++, and Fortran frontends return 4, if an internal
|
1116 |
|
|
compiler error is encountered.
|
1117 |
|
|
@end table
|
1118 |
|
|
|
1119 |
|
|
If you only want some of the stages of compilation, you can use
|
1120 |
|
|
@option{-x} (or filename suffixes) to tell @command{gcc} where to start, and
|
1121 |
|
|
one of the options @option{-c}, @option{-S}, or @option{-E} to say where
|
1122 |
|
|
@command{gcc} is to stop. Note that some combinations (for example,
|
1123 |
|
|
@samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all.
|
1124 |
|
|
|
1125 |
|
|
@table @gcctabopt
|
1126 |
|
|
@item -c
|
1127 |
|
|
@opindex c
|
1128 |
|
|
Compile or assemble the source files, but do not link. The linking
|
1129 |
|
|
stage simply is not done. The ultimate output is in the form of an
|
1130 |
|
|
object file for each source file.
|
1131 |
|
|
|
1132 |
|
|
By default, the object file name for a source file is made by replacing
|
1133 |
|
|
the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}.
|
1134 |
|
|
|
1135 |
|
|
Unrecognized input files, not requiring compilation or assembly, are
|
1136 |
|
|
ignored.
|
1137 |
|
|
|
1138 |
|
|
@item -S
|
1139 |
|
|
@opindex S
|
1140 |
|
|
Stop after the stage of compilation proper; do not assemble. The output
|
1141 |
|
|
is in the form of an assembler code file for each non-assembler input
|
1142 |
|
|
file specified.
|
1143 |
|
|
|
1144 |
|
|
By default, the assembler file name for a source file is made by
|
1145 |
|
|
replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}.
|
1146 |
|
|
|
1147 |
|
|
Input files that don't require compilation are ignored.
|
1148 |
|
|
|
1149 |
|
|
@item -E
|
1150 |
|
|
@opindex E
|
1151 |
|
|
Stop after the preprocessing stage; do not run the compiler proper. The
|
1152 |
|
|
output is in the form of preprocessed source code, which is sent to the
|
1153 |
|
|
standard output.
|
1154 |
|
|
|
1155 |
|
|
Input files which don't require preprocessing are ignored.
|
1156 |
|
|
|
1157 |
|
|
@cindex output file option
|
1158 |
|
|
@item -o @var{file}
|
1159 |
|
|
@opindex o
|
1160 |
|
|
Place output in file @var{file}. This applies regardless to whatever
|
1161 |
|
|
sort of output is being produced, whether it be an executable file,
|
1162 |
|
|
an object file, an assembler file or preprocessed C code.
|
1163 |
|
|
|
1164 |
|
|
If @option{-o} is not specified, the default is to put an executable
|
1165 |
|
|
file in @file{a.out}, the object file for
|
1166 |
|
|
@file{@var{source}.@var{suffix}} in @file{@var{source}.o}, its
|
1167 |
|
|
assembler file in @file{@var{source}.s}, a precompiled header file in
|
1168 |
|
|
@file{@var{source}.@var{suffix}.gch}, and all preprocessed C source on
|
1169 |
|
|
standard output.
|
1170 |
|
|
|
1171 |
|
|
@item -v
|
1172 |
|
|
@opindex v
|
1173 |
|
|
Print (on standard error output) the commands executed to run the stages
|
1174 |
|
|
of compilation. Also print the version number of the compiler driver
|
1175 |
|
|
program and of the preprocessor and the compiler proper.
|
1176 |
|
|
|
1177 |
|
|
@item -###
|
1178 |
|
|
@opindex ###
|
1179 |
|
|
Like @option{-v} except the commands are not executed and all command
|
1180 |
|
|
arguments are quoted. This is useful for shell scripts to capture the
|
1181 |
|
|
driver-generated command lines.
|
1182 |
|
|
|
1183 |
|
|
@item -pipe
|
1184 |
|
|
@opindex pipe
|
1185 |
|
|
Use pipes rather than temporary files for communication between the
|
1186 |
|
|
various stages of compilation. This fails to work on some systems where
|
1187 |
|
|
the assembler is unable to read from a pipe; but the GNU assembler has
|
1188 |
|
|
no trouble.
|
1189 |
|
|
|
1190 |
|
|
@item -combine
|
1191 |
|
|
@opindex combine
|
1192 |
|
|
If you are compiling multiple source files, this option tells the driver
|
1193 |
|
|
to pass all the source files to the compiler at once (for those
|
1194 |
|
|
languages for which the compiler can handle this). This will allow
|
1195 |
|
|
intermodule analysis (IMA) to be performed by the compiler. Currently the only
|
1196 |
|
|
language for which this is supported is C@. If you pass source files for
|
1197 |
|
|
multiple languages to the driver, using this option, the driver will invoke
|
1198 |
|
|
the compiler(s) that support IMA once each, passing each compiler all the
|
1199 |
|
|
source files appropriate for it. For those languages that do not support
|
1200 |
|
|
IMA this option will be ignored, and the compiler will be invoked once for
|
1201 |
|
|
each source file in that language. If you use this option in conjunction
|
1202 |
|
|
with @option{-save-temps}, the compiler will generate multiple
|
1203 |
|
|
pre-processed files
|
1204 |
|
|
(one for each source file), but only one (combined) @file{.o} or
|
1205 |
|
|
@file{.s} file.
|
1206 |
|
|
|
1207 |
|
|
@item --help
|
1208 |
|
|
@opindex help
|
1209 |
|
|
Print (on the standard output) a description of the command line options
|
1210 |
|
|
understood by @command{gcc}. If the @option{-v} option is also specified
|
1211 |
|
|
then @option{--help} will also be passed on to the various processes
|
1212 |
|
|
invoked by @command{gcc}, so that they can display the command line options
|
1213 |
|
|
they accept. If the @option{-Wextra} option has also been specified
|
1214 |
|
|
(prior to the @option{--help} option), then command line options which
|
1215 |
|
|
have no documentation associated with them will also be displayed.
|
1216 |
|
|
|
1217 |
|
|
@item --target-help
|
1218 |
|
|
@opindex target-help
|
1219 |
|
|
Print (on the standard output) a description of target-specific command
|
1220 |
|
|
line options for each tool. For some targets extra target-specific
|
1221 |
|
|
information may also be printed.
|
1222 |
|
|
|
1223 |
|
|
@item --help=@{@var{class}@r{|[}^@r{]}@var{qualifier}@}@r{[},@dots{}@r{]}
|
1224 |
|
|
Print (on the standard output) a description of the command line
|
1225 |
|
|
options understood by the compiler that fit into all specified classes
|
1226 |
|
|
and qualifiers. These are the supported classes:
|
1227 |
|
|
|
1228 |
|
|
@table @asis
|
1229 |
|
|
@item @samp{optimizers}
|
1230 |
|
|
This will display all of the optimization options supported by the
|
1231 |
|
|
compiler.
|
1232 |
|
|
|
1233 |
|
|
@item @samp{warnings}
|
1234 |
|
|
This will display all of the options controlling warning messages
|
1235 |
|
|
produced by the compiler.
|
1236 |
|
|
|
1237 |
|
|
@item @samp{target}
|
1238 |
|
|
This will display target-specific options. Unlike the
|
1239 |
|
|
@option{--target-help} option however, target-specific options of the
|
1240 |
|
|
linker and assembler will not be displayed. This is because those
|
1241 |
|
|
tools do not currently support the extended @option{--help=} syntax.
|
1242 |
|
|
|
1243 |
|
|
@item @samp{params}
|
1244 |
|
|
This will display the values recognized by the @option{--param}
|
1245 |
|
|
option.
|
1246 |
|
|
|
1247 |
|
|
@item @var{language}
|
1248 |
|
|
This will display the options supported for @var{language}, where
|
1249 |
|
|
@var{language} is the name of one of the languages supported in this
|
1250 |
|
|
version of GCC.
|
1251 |
|
|
|
1252 |
|
|
@item @samp{common}
|
1253 |
|
|
This will display the options that are common to all languages.
|
1254 |
|
|
@end table
|
1255 |
|
|
|
1256 |
|
|
These are the supported qualifiers:
|
1257 |
|
|
|
1258 |
|
|
@table @asis
|
1259 |
|
|
@item @samp{undocumented}
|
1260 |
|
|
Display only those options which are undocumented.
|
1261 |
|
|
|
1262 |
|
|
@item @samp{joined}
|
1263 |
|
|
Display options which take an argument that appears after an equal
|
1264 |
|
|
sign in the same continuous piece of text, such as:
|
1265 |
|
|
@samp{--help=target}.
|
1266 |
|
|
|
1267 |
|
|
@item @samp{separate}
|
1268 |
|
|
Display options which take an argument that appears as a separate word
|
1269 |
|
|
following the original option, such as: @samp{-o output-file}.
|
1270 |
|
|
@end table
|
1271 |
|
|
|
1272 |
|
|
Thus for example to display all the undocumented target-specific
|
1273 |
|
|
switches supported by the compiler the following can be used:
|
1274 |
|
|
|
1275 |
|
|
@smallexample
|
1276 |
|
|
--help=target,undocumented
|
1277 |
|
|
@end smallexample
|
1278 |
|
|
|
1279 |
|
|
The sense of a qualifier can be inverted by prefixing it with the
|
1280 |
|
|
@samp{^} character, so for example to display all binary warning
|
1281 |
|
|
options (i.e., ones that are either on or off and that do not take an
|
1282 |
|
|
argument), which have a description the following can be used:
|
1283 |
|
|
|
1284 |
|
|
@smallexample
|
1285 |
|
|
--help=warnings,^joined,^undocumented
|
1286 |
|
|
@end smallexample
|
1287 |
|
|
|
1288 |
|
|
The argument to @option{--help=} should not consist solely of inverted
|
1289 |
|
|
qualifiers.
|
1290 |
|
|
|
1291 |
|
|
Combining several classes is possible, although this usually
|
1292 |
|
|
restricts the output by so much that there is nothing to display. One
|
1293 |
|
|
case where it does work however is when one of the classes is
|
1294 |
|
|
@var{target}. So for example to display all the target-specific
|
1295 |
|
|
optimization options the following can be used:
|
1296 |
|
|
|
1297 |
|
|
@smallexample
|
1298 |
|
|
--help=target,optimizers
|
1299 |
|
|
@end smallexample
|
1300 |
|
|
|
1301 |
|
|
The @option{--help=} option can be repeated on the command line. Each
|
1302 |
|
|
successive use will display its requested class of options, skipping
|
1303 |
|
|
those that have already been displayed.
|
1304 |
|
|
|
1305 |
|
|
If the @option{-Q} option appears on the command line before the
|
1306 |
|
|
@option{--help=} option, then the descriptive text displayed by
|
1307 |
|
|
@option{--help=} is changed. Instead of describing the displayed
|
1308 |
|
|
options, an indication is given as to whether the option is enabled,
|
1309 |
|
|
disabled or set to a specific value (assuming that the compiler
|
1310 |
|
|
knows this at the point where the @option{--help=} option is used).
|
1311 |
|
|
|
1312 |
|
|
Here is a truncated example from the ARM port of @command{gcc}:
|
1313 |
|
|
|
1314 |
|
|
@smallexample
|
1315 |
|
|
% gcc -Q -mabi=2 --help=target -c
|
1316 |
|
|
The following options are target specific:
|
1317 |
|
|
-mabi= 2
|
1318 |
|
|
-mabort-on-noreturn [disabled]
|
1319 |
|
|
-mapcs [disabled]
|
1320 |
|
|
@end smallexample
|
1321 |
|
|
|
1322 |
|
|
The output is sensitive to the effects of previous command line
|
1323 |
|
|
options, so for example it is possible to find out which optimizations
|
1324 |
|
|
are enabled at @option{-O2} by using:
|
1325 |
|
|
|
1326 |
|
|
@smallexample
|
1327 |
|
|
-Q -O2 --help=optimizers
|
1328 |
|
|
@end smallexample
|
1329 |
|
|
|
1330 |
|
|
Alternatively you can discover which binary optimizations are enabled
|
1331 |
|
|
by @option{-O3} by using:
|
1332 |
|
|
|
1333 |
|
|
@smallexample
|
1334 |
|
|
gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
|
1335 |
|
|
gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
|
1336 |
|
|
diff /tmp/O2-opts /tmp/O3-opts | grep enabled
|
1337 |
|
|
@end smallexample
|
1338 |
|
|
|
1339 |
|
|
@item -no-canonical-prefixes
|
1340 |
|
|
@opindex no-canonical-prefixes
|
1341 |
|
|
Do not expand any symbolic links, resolve references to @samp{/../}
|
1342 |
|
|
or @samp{/./}, or make the path absolute when generating a relative
|
1343 |
|
|
prefix.
|
1344 |
|
|
|
1345 |
|
|
@item --version
|
1346 |
|
|
@opindex version
|
1347 |
|
|
Display the version number and copyrights of the invoked GCC@.
|
1348 |
|
|
|
1349 |
|
|
@item -wrapper
|
1350 |
|
|
@opindex wrapper
|
1351 |
|
|
Invoke all subcommands under a wrapper program. It takes a single
|
1352 |
|
|
comma separated list as an argument, which will be used to invoke
|
1353 |
|
|
the wrapper:
|
1354 |
|
|
|
1355 |
|
|
@smallexample
|
1356 |
|
|
gcc -c t.c -wrapper gdb,--args
|
1357 |
|
|
@end smallexample
|
1358 |
|
|
|
1359 |
|
|
This will invoke all subprograms of gcc under "gdb --args",
|
1360 |
|
|
thus cc1 invocation will be "gdb --args cc1 ...".
|
1361 |
|
|
|
1362 |
|
|
@item -fplugin=@var{name}.so
|
1363 |
|
|
Load the plugin code in file @var{name}.so, assumed to be a
|
1364 |
|
|
shared object to be dlopen'd by the compiler. The base name of
|
1365 |
|
|
the shared object file is used to identify the plugin for the
|
1366 |
|
|
purposes of argument parsing (See
|
1367 |
|
|
@option{-fplugin-arg-@var{name}-@var{key}=@var{value}} below).
|
1368 |
|
|
Each plugin should define the callback functions specified in the
|
1369 |
|
|
Plugins API.
|
1370 |
|
|
|
1371 |
|
|
@item -fplugin-arg-@var{name}-@var{key}=@var{value}
|
1372 |
|
|
Define an argument called @var{key} with a value of @var{value}
|
1373 |
|
|
for the plugin called @var{name}.
|
1374 |
|
|
|
1375 |
|
|
@include @value{srcdir}/../libiberty/at-file.texi
|
1376 |
|
|
@end table
|
1377 |
|
|
|
1378 |
|
|
@node Invoking G++
|
1379 |
|
|
@section Compiling C++ Programs
|
1380 |
|
|
|
1381 |
|
|
@cindex suffixes for C++ source
|
1382 |
|
|
@cindex C++ source file suffixes
|
1383 |
|
|
C++ source files conventionally use one of the suffixes @samp{.C},
|
1384 |
|
|
@samp{.cc}, @samp{.cpp}, @samp{.CPP}, @samp{.c++}, @samp{.cp}, or
|
1385 |
|
|
@samp{.cxx}; C++ header files often use @samp{.hh}, @samp{.hpp},
|
1386 |
|
|
@samp{.H}, or (for shared template code) @samp{.tcc}; and
|
1387 |
|
|
preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes
|
1388 |
|
|
files with these names and compiles them as C++ programs even if you
|
1389 |
|
|
call the compiler the same way as for compiling C programs (usually
|
1390 |
|
|
with the name @command{gcc}).
|
1391 |
|
|
|
1392 |
|
|
@findex g++
|
1393 |
|
|
@findex c++
|
1394 |
|
|
However, the use of @command{gcc} does not add the C++ library.
|
1395 |
|
|
@command{g++} is a program that calls GCC and treats @samp{.c},
|
1396 |
|
|
@samp{.h} and @samp{.i} files as C++ source files instead of C source
|
1397 |
|
|
files unless @option{-x} is used, and automatically specifies linking
|
1398 |
|
|
against the C++ library. This program is also useful when
|
1399 |
|
|
precompiling a C header file with a @samp{.h} extension for use in C++
|
1400 |
|
|
compilations. On many systems, @command{g++} is also installed with
|
1401 |
|
|
the name @command{c++}.
|
1402 |
|
|
|
1403 |
|
|
@cindex invoking @command{g++}
|
1404 |
|
|
When you compile C++ programs, you may specify many of the same
|
1405 |
|
|
command-line options that you use for compiling programs in any
|
1406 |
|
|
language; or command-line options meaningful for C and related
|
1407 |
|
|
languages; or options that are meaningful only for C++ programs.
|
1408 |
|
|
@xref{C Dialect Options,,Options Controlling C Dialect}, for
|
1409 |
|
|
explanations of options for languages related to C@.
|
1410 |
|
|
@xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for
|
1411 |
|
|
explanations of options that are meaningful only for C++ programs.
|
1412 |
|
|
|
1413 |
|
|
@node C Dialect Options
|
1414 |
|
|
@section Options Controlling C Dialect
|
1415 |
|
|
@cindex dialect options
|
1416 |
|
|
@cindex language dialect options
|
1417 |
|
|
@cindex options, dialect
|
1418 |
|
|
|
1419 |
|
|
The following options control the dialect of C (or languages derived
|
1420 |
|
|
from C, such as C++, Objective-C and Objective-C++) that the compiler
|
1421 |
|
|
accepts:
|
1422 |
|
|
|
1423 |
|
|
@table @gcctabopt
|
1424 |
|
|
@cindex ANSI support
|
1425 |
|
|
@cindex ISO support
|
1426 |
|
|
@item -ansi
|
1427 |
|
|
@opindex ansi
|
1428 |
|
|
In C mode, this is equivalent to @samp{-std=c90}. In C++ mode, it is
|
1429 |
|
|
equivalent to @samp{-std=c++98}.
|
1430 |
|
|
|
1431 |
|
|
This turns off certain features of GCC that are incompatible with ISO
|
1432 |
|
|
C90 (when compiling C code), or of standard C++ (when compiling C++ code),
|
1433 |
|
|
such as the @code{asm} and @code{typeof} keywords, and
|
1434 |
|
|
predefined macros such as @code{unix} and @code{vax} that identify the
|
1435 |
|
|
type of system you are using. It also enables the undesirable and
|
1436 |
|
|
rarely used ISO trigraph feature. For the C compiler,
|
1437 |
|
|
it disables recognition of C++ style @samp{//} comments as well as
|
1438 |
|
|
the @code{inline} keyword.
|
1439 |
|
|
|
1440 |
|
|
The alternate keywords @code{__asm__}, @code{__extension__},
|
1441 |
|
|
@code{__inline__} and @code{__typeof__} continue to work despite
|
1442 |
|
|
@option{-ansi}. You would not want to use them in an ISO C program, of
|
1443 |
|
|
course, but it is useful to put them in header files that might be included
|
1444 |
|
|
in compilations done with @option{-ansi}. Alternate predefined macros
|
1445 |
|
|
such as @code{__unix__} and @code{__vax__} are also available, with or
|
1446 |
|
|
without @option{-ansi}.
|
1447 |
|
|
|
1448 |
|
|
The @option{-ansi} option does not cause non-ISO programs to be
|
1449 |
|
|
rejected gratuitously. For that, @option{-pedantic} is required in
|
1450 |
|
|
addition to @option{-ansi}. @xref{Warning Options}.
|
1451 |
|
|
|
1452 |
|
|
The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi}
|
1453 |
|
|
option is used. Some header files may notice this macro and refrain
|
1454 |
|
|
from declaring certain functions or defining certain macros that the
|
1455 |
|
|
ISO standard doesn't call for; this is to avoid interfering with any
|
1456 |
|
|
programs that might use these names for other things.
|
1457 |
|
|
|
1458 |
|
|
Functions that would normally be built in but do not have semantics
|
1459 |
|
|
defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in
|
1460 |
|
|
functions when @option{-ansi} is used. @xref{Other Builtins,,Other
|
1461 |
|
|
built-in functions provided by GCC}, for details of the functions
|
1462 |
|
|
affected.
|
1463 |
|
|
|
1464 |
|
|
@item -std=
|
1465 |
|
|
@opindex std
|
1466 |
|
|
Determine the language standard. @xref{Standards,,Language Standards
|
1467 |
|
|
Supported by GCC}, for details of these standard versions. This option
|
1468 |
|
|
is currently only supported when compiling C or C++.
|
1469 |
|
|
|
1470 |
|
|
The compiler can accept several base standards, such as @samp{c90} or
|
1471 |
|
|
@samp{c++98}, and GNU dialects of those standards, such as
|
1472 |
|
|
@samp{gnu90} or @samp{gnu++98}. By specifying a base standard, the
|
1473 |
|
|
compiler will accept all programs following that standard and those
|
1474 |
|
|
using GNU extensions that do not contradict it. For example,
|
1475 |
|
|
@samp{-std=c90} turns off certain features of GCC that are
|
1476 |
|
|
incompatible with ISO C90, such as the @code{asm} and @code{typeof}
|
1477 |
|
|
keywords, but not other GNU extensions that do not have a meaning in
|
1478 |
|
|
ISO C90, such as omitting the middle term of a @code{?:}
|
1479 |
|
|
expression. On the other hand, by specifying a GNU dialect of a
|
1480 |
|
|
standard, all features the compiler support are enabled, even when
|
1481 |
|
|
those features change the meaning of the base standard and some
|
1482 |
|
|
strict-conforming programs may be rejected. The particular standard
|
1483 |
|
|
is used by @option{-pedantic} to identify which features are GNU
|
1484 |
|
|
extensions given that version of the standard. For example
|
1485 |
|
|
@samp{-std=gnu90 -pedantic} would warn about C++ style @samp{//}
|
1486 |
|
|
comments, while @samp{-std=gnu99 -pedantic} would not.
|
1487 |
|
|
|
1488 |
|
|
A value for this option must be provided; possible values are
|
1489 |
|
|
|
1490 |
|
|
@table @samp
|
1491 |
|
|
@item c90
|
1492 |
|
|
@itemx c89
|
1493 |
|
|
@itemx iso9899:1990
|
1494 |
|
|
Support all ISO C90 programs (certain GNU extensions that conflict
|
1495 |
|
|
with ISO C90 are disabled). Same as @option{-ansi} for C code.
|
1496 |
|
|
|
1497 |
|
|
@item iso9899:199409
|
1498 |
|
|
ISO C90 as modified in amendment 1.
|
1499 |
|
|
|
1500 |
|
|
@item c99
|
1501 |
|
|
@itemx c9x
|
1502 |
|
|
@itemx iso9899:1999
|
1503 |
|
|
@itemx iso9899:199x
|
1504 |
|
|
ISO C99. Note that this standard is not yet fully supported; see
|
1505 |
|
|
@w{@uref{http://gcc.gnu.org/gcc-4.5/c99status.html}} for more information. The
|
1506 |
|
|
names @samp{c9x} and @samp{iso9899:199x} are deprecated.
|
1507 |
|
|
|
1508 |
|
|
@item gnu90
|
1509 |
|
|
@itemx gnu89
|
1510 |
|
|
GNU dialect of ISO C90 (including some C99 features). This
|
1511 |
|
|
is the default for C code.
|
1512 |
|
|
|
1513 |
|
|
@item gnu99
|
1514 |
|
|
@itemx gnu9x
|
1515 |
|
|
GNU dialect of ISO C99. When ISO C99 is fully implemented in GCC,
|
1516 |
|
|
this will become the default. The name @samp{gnu9x} is deprecated.
|
1517 |
|
|
|
1518 |
|
|
@item c++98
|
1519 |
|
|
The 1998 ISO C++ standard plus amendments. Same as @option{-ansi} for
|
1520 |
|
|
C++ code.
|
1521 |
|
|
|
1522 |
|
|
@item gnu++98
|
1523 |
|
|
GNU dialect of @option{-std=c++98}. This is the default for
|
1524 |
|
|
C++ code.
|
1525 |
|
|
|
1526 |
|
|
@item c++0x
|
1527 |
|
|
The working draft of the upcoming ISO C++0x standard. This option
|
1528 |
|
|
enables experimental features that are likely to be included in
|
1529 |
|
|
C++0x. The working draft is constantly changing, and any feature that is
|
1530 |
|
|
enabled by this flag may be removed from future versions of GCC if it is
|
1531 |
|
|
not part of the C++0x standard.
|
1532 |
|
|
|
1533 |
|
|
@item gnu++0x
|
1534 |
|
|
GNU dialect of @option{-std=c++0x}. This option enables
|
1535 |
|
|
experimental features that may be removed in future versions of GCC.
|
1536 |
|
|
@end table
|
1537 |
|
|
|
1538 |
|
|
@item -fgnu89-inline
|
1539 |
|
|
@opindex fgnu89-inline
|
1540 |
|
|
The option @option{-fgnu89-inline} tells GCC to use the traditional
|
1541 |
|
|
GNU semantics for @code{inline} functions when in C99 mode.
|
1542 |
|
|
@xref{Inline,,An Inline Function is As Fast As a Macro}. This option
|
1543 |
|
|
is accepted and ignored by GCC versions 4.1.3 up to but not including
|
1544 |
|
|
4.3. In GCC versions 4.3 and later it changes the behavior of GCC in
|
1545 |
|
|
C99 mode. Using this option is roughly equivalent to adding the
|
1546 |
|
|
@code{gnu_inline} function attribute to all inline functions
|
1547 |
|
|
(@pxref{Function Attributes}).
|
1548 |
|
|
|
1549 |
|
|
The option @option{-fno-gnu89-inline} explicitly tells GCC to use the
|
1550 |
|
|
C99 semantics for @code{inline} when in C99 or gnu99 mode (i.e., it
|
1551 |
|
|
specifies the default behavior). This option was first supported in
|
1552 |
|
|
GCC 4.3. This option is not supported in @option{-std=c90} or
|
1553 |
|
|
@option{-std=gnu90} mode.
|
1554 |
|
|
|
1555 |
|
|
The preprocessor macros @code{__GNUC_GNU_INLINE__} and
|
1556 |
|
|
@code{__GNUC_STDC_INLINE__} may be used to check which semantics are
|
1557 |
|
|
in effect for @code{inline} functions. @xref{Common Predefined
|
1558 |
|
|
Macros,,,cpp,The C Preprocessor}.
|
1559 |
|
|
|
1560 |
|
|
@item -aux-info @var{filename}
|
1561 |
|
|
@opindex aux-info
|
1562 |
|
|
Output to the given filename prototyped declarations for all functions
|
1563 |
|
|
declared and/or defined in a translation unit, including those in header
|
1564 |
|
|
files. This option is silently ignored in any language other than C@.
|
1565 |
|
|
|
1566 |
|
|
Besides declarations, the file indicates, in comments, the origin of
|
1567 |
|
|
each declaration (source file and line), whether the declaration was
|
1568 |
|
|
implicit, prototyped or unprototyped (@samp{I}, @samp{N} for new or
|
1569 |
|
|
@samp{O} for old, respectively, in the first character after the line
|
1570 |
|
|
number and the colon), and whether it came from a declaration or a
|
1571 |
|
|
definition (@samp{C} or @samp{F}, respectively, in the following
|
1572 |
|
|
character). In the case of function definitions, a K&R-style list of
|
1573 |
|
|
arguments followed by their declarations is also provided, inside
|
1574 |
|
|
comments, after the declaration.
|
1575 |
|
|
|
1576 |
|
|
@item -fno-asm
|
1577 |
|
|
@opindex fno-asm
|
1578 |
|
|
Do not recognize @code{asm}, @code{inline} or @code{typeof} as a
|
1579 |
|
|
keyword, so that code can use these words as identifiers. You can use
|
1580 |
|
|
the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__}
|
1581 |
|
|
instead. @option{-ansi} implies @option{-fno-asm}.
|
1582 |
|
|
|
1583 |
|
|
In C++, this switch only affects the @code{typeof} keyword, since
|
1584 |
|
|
@code{asm} and @code{inline} are standard keywords. You may want to
|
1585 |
|
|
use the @option{-fno-gnu-keywords} flag instead, which has the same
|
1586 |
|
|
effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this
|
1587 |
|
|
switch only affects the @code{asm} and @code{typeof} keywords, since
|
1588 |
|
|
@code{inline} is a standard keyword in ISO C99.
|
1589 |
|
|
|
1590 |
|
|
@item -fno-builtin
|
1591 |
|
|
@itemx -fno-builtin-@var{function}
|
1592 |
|
|
@opindex fno-builtin
|
1593 |
|
|
@cindex built-in functions
|
1594 |
|
|
Don't recognize built-in functions that do not begin with
|
1595 |
|
|
@samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in
|
1596 |
|
|
functions provided by GCC}, for details of the functions affected,
|
1597 |
|
|
including those which are not built-in functions when @option{-ansi} or
|
1598 |
|
|
@option{-std} options for strict ISO C conformance are used because they
|
1599 |
|
|
do not have an ISO standard meaning.
|
1600 |
|
|
|
1601 |
|
|
GCC normally generates special code to handle certain built-in functions
|
1602 |
|
|
more efficiently; for instance, calls to @code{alloca} may become single
|
1603 |
|
|
instructions that adjust the stack directly, and calls to @code{memcpy}
|
1604 |
|
|
may become inline copy loops. The resulting code is often both smaller
|
1605 |
|
|
and faster, but since the function calls no longer appear as such, you
|
1606 |
|
|
cannot set a breakpoint on those calls, nor can you change the behavior
|
1607 |
|
|
of the functions by linking with a different library. In addition,
|
1608 |
|
|
when a function is recognized as a built-in function, GCC may use
|
1609 |
|
|
information about that function to warn about problems with calls to
|
1610 |
|
|
that function, or to generate more efficient code, even if the
|
1611 |
|
|
resulting code still contains calls to that function. For example,
|
1612 |
|
|
warnings are given with @option{-Wformat} for bad calls to
|
1613 |
|
|
@code{printf}, when @code{printf} is built in, and @code{strlen} is
|
1614 |
|
|
known not to modify global memory.
|
1615 |
|
|
|
1616 |
|
|
With the @option{-fno-builtin-@var{function}} option
|
1617 |
|
|
only the built-in function @var{function} is
|
1618 |
|
|
disabled. @var{function} must not begin with @samp{__builtin_}. If a
|
1619 |
|
|
function is named that is not built-in in this version of GCC, this
|
1620 |
|
|
option is ignored. There is no corresponding
|
1621 |
|
|
@option{-fbuiltin-@var{function}} option; if you wish to enable
|
1622 |
|
|
built-in functions selectively when using @option{-fno-builtin} or
|
1623 |
|
|
@option{-ffreestanding}, you may define macros such as:
|
1624 |
|
|
|
1625 |
|
|
@smallexample
|
1626 |
|
|
#define abs(n) __builtin_abs ((n))
|
1627 |
|
|
#define strcpy(d, s) __builtin_strcpy ((d), (s))
|
1628 |
|
|
@end smallexample
|
1629 |
|
|
|
1630 |
|
|
@item -fhosted
|
1631 |
|
|
@opindex fhosted
|
1632 |
|
|
@cindex hosted environment
|
1633 |
|
|
|
1634 |
|
|
Assert that compilation takes place in a hosted environment. This implies
|
1635 |
|
|
@option{-fbuiltin}. A hosted environment is one in which the
|
1636 |
|
|
entire standard library is available, and in which @code{main} has a return
|
1637 |
|
|
type of @code{int}. Examples are nearly everything except a kernel.
|
1638 |
|
|
This is equivalent to @option{-fno-freestanding}.
|
1639 |
|
|
|
1640 |
|
|
@item -ffreestanding
|
1641 |
|
|
@opindex ffreestanding
|
1642 |
|
|
@cindex hosted environment
|
1643 |
|
|
|
1644 |
|
|
Assert that compilation takes place in a freestanding environment. This
|
1645 |
|
|
implies @option{-fno-builtin}. A freestanding environment
|
1646 |
|
|
is one in which the standard library may not exist, and program startup may
|
1647 |
|
|
not necessarily be at @code{main}. The most obvious example is an OS kernel.
|
1648 |
|
|
This is equivalent to @option{-fno-hosted}.
|
1649 |
|
|
|
1650 |
|
|
@xref{Standards,,Language Standards Supported by GCC}, for details of
|
1651 |
|
|
freestanding and hosted environments.
|
1652 |
|
|
|
1653 |
|
|
@item -fopenmp
|
1654 |
|
|
@opindex fopenmp
|
1655 |
|
|
@cindex openmp parallel
|
1656 |
|
|
Enable handling of OpenMP directives @code{#pragma omp} in C/C++ and
|
1657 |
|
|
@code{!$omp} in Fortran. When @option{-fopenmp} is specified, the
|
1658 |
|
|
compiler generates parallel code according to the OpenMP Application
|
1659 |
|
|
Program Interface v3.0 @w{@uref{http://www.openmp.org/}}. This option
|
1660 |
|
|
implies @option{-pthread}, and thus is only supported on targets that
|
1661 |
|
|
have support for @option{-pthread}.
|
1662 |
|
|
|
1663 |
|
|
@item -fms-extensions
|
1664 |
|
|
@opindex fms-extensions
|
1665 |
|
|
Accept some non-standard constructs used in Microsoft header files.
|
1666 |
|
|
|
1667 |
|
|
Some cases of unnamed fields in structures and unions are only
|
1668 |
|
|
accepted with this option. @xref{Unnamed Fields,,Unnamed struct/union
|
1669 |
|
|
fields within structs/unions}, for details.
|
1670 |
|
|
|
1671 |
|
|
@item -trigraphs
|
1672 |
|
|
@opindex trigraphs
|
1673 |
|
|
Support ISO C trigraphs. The @option{-ansi} option (and @option{-std}
|
1674 |
|
|
options for strict ISO C conformance) implies @option{-trigraphs}.
|
1675 |
|
|
|
1676 |
|
|
@item -no-integrated-cpp
|
1677 |
|
|
@opindex no-integrated-cpp
|
1678 |
|
|
Performs a compilation in two passes: preprocessing and compiling. This
|
1679 |
|
|
option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the
|
1680 |
|
|
@option{-B} option. The user supplied compilation step can then add in
|
1681 |
|
|
an additional preprocessing step after normal preprocessing but before
|
1682 |
|
|
compiling. The default is to use the integrated cpp (internal cpp)
|
1683 |
|
|
|
1684 |
|
|
The semantics of this option will change if "cc1", "cc1plus", and
|
1685 |
|
|
"cc1obj" are merged.
|
1686 |
|
|
|
1687 |
|
|
@cindex traditional C language
|
1688 |
|
|
@cindex C language, traditional
|
1689 |
|
|
@item -traditional
|
1690 |
|
|
@itemx -traditional-cpp
|
1691 |
|
|
@opindex traditional-cpp
|
1692 |
|
|
@opindex traditional
|
1693 |
|
|
Formerly, these options caused GCC to attempt to emulate a pre-standard
|
1694 |
|
|
C compiler. They are now only supported with the @option{-E} switch.
|
1695 |
|
|
The preprocessor continues to support a pre-standard mode. See the GNU
|
1696 |
|
|
CPP manual for details.
|
1697 |
|
|
|
1698 |
|
|
@item -fcond-mismatch
|
1699 |
|
|
@opindex fcond-mismatch
|
1700 |
|
|
Allow conditional expressions with mismatched types in the second and
|
1701 |
|
|
third arguments. The value of such an expression is void. This option
|
1702 |
|
|
is not supported for C++.
|
1703 |
|
|
|
1704 |
|
|
@item -flax-vector-conversions
|
1705 |
|
|
@opindex flax-vector-conversions
|
1706 |
|
|
Allow implicit conversions between vectors with differing numbers of
|
1707 |
|
|
elements and/or incompatible element types. This option should not be
|
1708 |
|
|
used for new code.
|
1709 |
|
|
|
1710 |
|
|
@item -funsigned-char
|
1711 |
|
|
@opindex funsigned-char
|
1712 |
|
|
Let the type @code{char} be unsigned, like @code{unsigned char}.
|
1713 |
|
|
|
1714 |
|
|
Each kind of machine has a default for what @code{char} should
|
1715 |
|
|
be. It is either like @code{unsigned char} by default or like
|
1716 |
|
|
@code{signed char} by default.
|
1717 |
|
|
|
1718 |
|
|
Ideally, a portable program should always use @code{signed char} or
|
1719 |
|
|
@code{unsigned char} when it depends on the signedness of an object.
|
1720 |
|
|
But many programs have been written to use plain @code{char} and
|
1721 |
|
|
expect it to be signed, or expect it to be unsigned, depending on the
|
1722 |
|
|
machines they were written for. This option, and its inverse, let you
|
1723 |
|
|
make such a program work with the opposite default.
|
1724 |
|
|
|
1725 |
|
|
The type @code{char} is always a distinct type from each of
|
1726 |
|
|
@code{signed char} or @code{unsigned char}, even though its behavior
|
1727 |
|
|
is always just like one of those two.
|
1728 |
|
|
|
1729 |
|
|
@item -fsigned-char
|
1730 |
|
|
@opindex fsigned-char
|
1731 |
|
|
Let the type @code{char} be signed, like @code{signed char}.
|
1732 |
|
|
|
1733 |
|
|
Note that this is equivalent to @option{-fno-unsigned-char}, which is
|
1734 |
|
|
the negative form of @option{-funsigned-char}. Likewise, the option
|
1735 |
|
|
@option{-fno-signed-char} is equivalent to @option{-funsigned-char}.
|
1736 |
|
|
|
1737 |
|
|
@item -fsigned-bitfields
|
1738 |
|
|
@itemx -funsigned-bitfields
|
1739 |
|
|
@itemx -fno-signed-bitfields
|
1740 |
|
|
@itemx -fno-unsigned-bitfields
|
1741 |
|
|
@opindex fsigned-bitfields
|
1742 |
|
|
@opindex funsigned-bitfields
|
1743 |
|
|
@opindex fno-signed-bitfields
|
1744 |
|
|
@opindex fno-unsigned-bitfields
|
1745 |
|
|
These options control whether a bit-field is signed or unsigned, when the
|
1746 |
|
|
declaration does not use either @code{signed} or @code{unsigned}. By
|
1747 |
|
|
default, such a bit-field is signed, because this is consistent: the
|
1748 |
|
|
basic integer types such as @code{int} are signed types.
|
1749 |
|
|
@end table
|
1750 |
|
|
|
1751 |
|
|
@node C++ Dialect Options
|
1752 |
|
|
@section Options Controlling C++ Dialect
|
1753 |
|
|
|
1754 |
|
|
@cindex compiler options, C++
|
1755 |
|
|
@cindex C++ options, command line
|
1756 |
|
|
@cindex options, C++
|
1757 |
|
|
This section describes the command-line options that are only meaningful
|
1758 |
|
|
for C++ programs; but you can also use most of the GNU compiler options
|
1759 |
|
|
regardless of what language your program is in. For example, you
|
1760 |
|
|
might compile a file @code{firstClass.C} like this:
|
1761 |
|
|
|
1762 |
|
|
@smallexample
|
1763 |
|
|
g++ -g -frepo -O -c firstClass.C
|
1764 |
|
|
@end smallexample
|
1765 |
|
|
|
1766 |
|
|
@noindent
|
1767 |
|
|
In this example, only @option{-frepo} is an option meant
|
1768 |
|
|
only for C++ programs; you can use the other options with any
|
1769 |
|
|
language supported by GCC@.
|
1770 |
|
|
|
1771 |
|
|
Here is a list of options that are @emph{only} for compiling C++ programs:
|
1772 |
|
|
|
1773 |
|
|
@table @gcctabopt
|
1774 |
|
|
|
1775 |
|
|
@item -fabi-version=@var{n}
|
1776 |
|
|
@opindex fabi-version
|
1777 |
|
|
Use version @var{n} of the C++ ABI@. Version 2 is the version of the
|
1778 |
|
|
C++ ABI that first appeared in G++ 3.4. Version 1 is the version of
|
1779 |
|
|
the C++ ABI that first appeared in G++ 3.2. Version 0 will always be
|
1780 |
|
|
the version that conforms most closely to the C++ ABI specification.
|
1781 |
|
|
Therefore, the ABI obtained using version 0 will change as ABI bugs
|
1782 |
|
|
are fixed.
|
1783 |
|
|
|
1784 |
|
|
The default is version 2.
|
1785 |
|
|
|
1786 |
|
|
Version 3 corrects an error in mangling a constant address as a
|
1787 |
|
|
template argument.
|
1788 |
|
|
|
1789 |
|
|
Version 4 implements a standard mangling for vector types.
|
1790 |
|
|
|
1791 |
|
|
See also @option{-Wabi}.
|
1792 |
|
|
|
1793 |
|
|
@item -fno-access-control
|
1794 |
|
|
@opindex fno-access-control
|
1795 |
|
|
Turn off all access checking. This switch is mainly useful for working
|
1796 |
|
|
around bugs in the access control code.
|
1797 |
|
|
|
1798 |
|
|
@item -fcheck-new
|
1799 |
|
|
@opindex fcheck-new
|
1800 |
|
|
Check that the pointer returned by @code{operator new} is non-null
|
1801 |
|
|
before attempting to modify the storage allocated. This check is
|
1802 |
|
|
normally unnecessary because the C++ standard specifies that
|
1803 |
|
|
@code{operator new} will only return @code{0} if it is declared
|
1804 |
|
|
@samp{throw()}, in which case the compiler will always check the
|
1805 |
|
|
return value even without this option. In all other cases, when
|
1806 |
|
|
@code{operator new} has a non-empty exception specification, memory
|
1807 |
|
|
exhaustion is signalled by throwing @code{std::bad_alloc}. See also
|
1808 |
|
|
@samp{new (nothrow)}.
|
1809 |
|
|
|
1810 |
|
|
@item -fconserve-space
|
1811 |
|
|
@opindex fconserve-space
|
1812 |
|
|
Put uninitialized or runtime-initialized global variables into the
|
1813 |
|
|
common segment, as C does. This saves space in the executable at the
|
1814 |
|
|
cost of not diagnosing duplicate definitions. If you compile with this
|
1815 |
|
|
flag and your program mysteriously crashes after @code{main()} has
|
1816 |
|
|
completed, you may have an object that is being destroyed twice because
|
1817 |
|
|
two definitions were merged.
|
1818 |
|
|
|
1819 |
|
|
This option is no longer useful on most targets, now that support has
|
1820 |
|
|
been added for putting variables into BSS without making them common.
|
1821 |
|
|
|
1822 |
|
|
@item -fno-deduce-init-list
|
1823 |
|
|
@opindex fno-deduce-init-list
|
1824 |
|
|
Disable deduction of a template type parameter as
|
1825 |
|
|
std::initializer_list from a brace-enclosed initializer list, i.e.
|
1826 |
|
|
|
1827 |
|
|
@smallexample
|
1828 |
|
|
template <class T> auto forward(T t) -> decltype (realfn (t))
|
1829 |
|
|
@{
|
1830 |
|
|
return realfn (t);
|
1831 |
|
|
@}
|
1832 |
|
|
|
1833 |
|
|
void f()
|
1834 |
|
|
@{
|
1835 |
|
|
forward(@{1,2@}); // call forward<std::initializer_list<int>>
|
1836 |
|
|
@}
|
1837 |
|
|
@end smallexample
|
1838 |
|
|
|
1839 |
|
|
This option is present because this deduction is an extension to the
|
1840 |
|
|
current specification in the C++0x working draft, and there was
|
1841 |
|
|
some concern about potential overload resolution problems.
|
1842 |
|
|
|
1843 |
|
|
@item -ffriend-injection
|
1844 |
|
|
@opindex ffriend-injection
|
1845 |
|
|
Inject friend functions into the enclosing namespace, so that they are
|
1846 |
|
|
visible outside the scope of the class in which they are declared.
|
1847 |
|
|
Friend functions were documented to work this way in the old Annotated
|
1848 |
|
|
C++ Reference Manual, and versions of G++ before 4.1 always worked
|
1849 |
|
|
that way. However, in ISO C++ a friend function which is not declared
|
1850 |
|
|
in an enclosing scope can only be found using argument dependent
|
1851 |
|
|
lookup. This option causes friends to be injected as they were in
|
1852 |
|
|
earlier releases.
|
1853 |
|
|
|
1854 |
|
|
This option is for compatibility, and may be removed in a future
|
1855 |
|
|
release of G++.
|
1856 |
|
|
|
1857 |
|
|
@item -fno-elide-constructors
|
1858 |
|
|
@opindex fno-elide-constructors
|
1859 |
|
|
The C++ standard allows an implementation to omit creating a temporary
|
1860 |
|
|
which is only used to initialize another object of the same type.
|
1861 |
|
|
Specifying this option disables that optimization, and forces G++ to
|
1862 |
|
|
call the copy constructor in all cases.
|
1863 |
|
|
|
1864 |
|
|
@item -fno-enforce-eh-specs
|
1865 |
|
|
@opindex fno-enforce-eh-specs
|
1866 |
|
|
Don't generate code to check for violation of exception specifications
|
1867 |
|
|
at runtime. This option violates the C++ standard, but may be useful
|
1868 |
|
|
for reducing code size in production builds, much like defining
|
1869 |
|
|
@samp{NDEBUG}. This does not give user code permission to throw
|
1870 |
|
|
exceptions in violation of the exception specifications; the compiler
|
1871 |
|
|
will still optimize based on the specifications, so throwing an
|
1872 |
|
|
unexpected exception will result in undefined behavior.
|
1873 |
|
|
|
1874 |
|
|
@item -ffor-scope
|
1875 |
|
|
@itemx -fno-for-scope
|
1876 |
|
|
@opindex ffor-scope
|
1877 |
|
|
@opindex fno-for-scope
|
1878 |
|
|
If @option{-ffor-scope} is specified, the scope of variables declared in
|
1879 |
|
|
a @i{for-init-statement} is limited to the @samp{for} loop itself,
|
1880 |
|
|
as specified by the C++ standard.
|
1881 |
|
|
If @option{-fno-for-scope} is specified, the scope of variables declared in
|
1882 |
|
|
a @i{for-init-statement} extends to the end of the enclosing scope,
|
1883 |
|
|
as was the case in old versions of G++, and other (traditional)
|
1884 |
|
|
implementations of C++.
|
1885 |
|
|
|
1886 |
|
|
The default if neither flag is given to follow the standard,
|
1887 |
|
|
but to allow and give a warning for old-style code that would
|
1888 |
|
|
otherwise be invalid, or have different behavior.
|
1889 |
|
|
|
1890 |
|
|
@item -fno-gnu-keywords
|
1891 |
|
|
@opindex fno-gnu-keywords
|
1892 |
|
|
Do not recognize @code{typeof} as a keyword, so that code can use this
|
1893 |
|
|
word as an identifier. You can use the keyword @code{__typeof__} instead.
|
1894 |
|
|
@option{-ansi} implies @option{-fno-gnu-keywords}.
|
1895 |
|
|
|
1896 |
|
|
@item -fno-implicit-templates
|
1897 |
|
|
@opindex fno-implicit-templates
|
1898 |
|
|
Never emit code for non-inline templates which are instantiated
|
1899 |
|
|
implicitly (i.e.@: by use); only emit code for explicit instantiations.
|
1900 |
|
|
@xref{Template Instantiation}, for more information.
|
1901 |
|
|
|
1902 |
|
|
@item -fno-implicit-inline-templates
|
1903 |
|
|
@opindex fno-implicit-inline-templates
|
1904 |
|
|
Don't emit code for implicit instantiations of inline templates, either.
|
1905 |
|
|
The default is to handle inlines differently so that compiles with and
|
1906 |
|
|
without optimization will need the same set of explicit instantiations.
|
1907 |
|
|
|
1908 |
|
|
@item -fno-implement-inlines
|
1909 |
|
|
@opindex fno-implement-inlines
|
1910 |
|
|
To save space, do not emit out-of-line copies of inline functions
|
1911 |
|
|
controlled by @samp{#pragma implementation}. This will cause linker
|
1912 |
|
|
errors if these functions are not inlined everywhere they are called.
|
1913 |
|
|
|
1914 |
|
|
@item -fms-extensions
|
1915 |
|
|
@opindex fms-extensions
|
1916 |
|
|
Disable pedantic warnings about constructs used in MFC, such as implicit
|
1917 |
|
|
int and getting a pointer to member function via non-standard syntax.
|
1918 |
|
|
|
1919 |
|
|
@item -fno-nonansi-builtins
|
1920 |
|
|
@opindex fno-nonansi-builtins
|
1921 |
|
|
Disable built-in declarations of functions that are not mandated by
|
1922 |
|
|
ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit},
|
1923 |
|
|
@code{index}, @code{bzero}, @code{conjf}, and other related functions.
|
1924 |
|
|
|
1925 |
|
|
@item -fno-operator-names
|
1926 |
|
|
@opindex fno-operator-names
|
1927 |
|
|
Do not treat the operator name keywords @code{and}, @code{bitand},
|
1928 |
|
|
@code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as
|
1929 |
|
|
synonyms as keywords.
|
1930 |
|
|
|
1931 |
|
|
@item -fno-optional-diags
|
1932 |
|
|
@opindex fno-optional-diags
|
1933 |
|
|
Disable diagnostics that the standard says a compiler does not need to
|
1934 |
|
|
issue. Currently, the only such diagnostic issued by G++ is the one for
|
1935 |
|
|
a name having multiple meanings within a class.
|
1936 |
|
|
|
1937 |
|
|
@item -fpermissive
|
1938 |
|
|
@opindex fpermissive
|
1939 |
|
|
Downgrade some diagnostics about nonconformant code from errors to
|
1940 |
|
|
warnings. Thus, using @option{-fpermissive} will allow some
|
1941 |
|
|
nonconforming code to compile.
|
1942 |
|
|
|
1943 |
|
|
@item -fno-pretty-templates
|
1944 |
|
|
@opindex fno-pretty-templates
|
1945 |
|
|
When an error message refers to a specialization of a function
|
1946 |
|
|
template, the compiler will normally print the signature of the
|
1947 |
|
|
template followed by the template arguments and any typedefs or
|
1948 |
|
|
typenames in the signature (e.g. @code{void f(T) [with T = int]}
|
1949 |
|
|
rather than @code{void f(int)}) so that it's clear which template is
|
1950 |
|
|
involved. When an error message refers to a specialization of a class
|
1951 |
|
|
template, the compiler will omit any template arguments which match
|
1952 |
|
|
the default template arguments for that template. If either of these
|
1953 |
|
|
behaviors make it harder to understand the error message rather than
|
1954 |
|
|
easier, using @option{-fno-pretty-templates} will disable them.
|
1955 |
|
|
|
1956 |
|
|
@item -frepo
|
1957 |
|
|
@opindex frepo
|
1958 |
|
|
Enable automatic template instantiation at link time. This option also
|
1959 |
|
|
implies @option{-fno-implicit-templates}. @xref{Template
|
1960 |
|
|
Instantiation}, for more information.
|
1961 |
|
|
|
1962 |
|
|
@item -fno-rtti
|
1963 |
|
|
@opindex fno-rtti
|
1964 |
|
|
Disable generation of information about every class with virtual
|
1965 |
|
|
functions for use by the C++ runtime type identification features
|
1966 |
|
|
(@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts
|
1967 |
|
|
of the language, you can save some space by using this flag. Note that
|
1968 |
|
|
exception handling uses the same information, but it will generate it as
|
1969 |
|
|
needed. The @samp{dynamic_cast} operator can still be used for casts that
|
1970 |
|
|
do not require runtime type information, i.e.@: casts to @code{void *} or to
|
1971 |
|
|
unambiguous base classes.
|
1972 |
|
|
|
1973 |
|
|
@item -fstats
|
1974 |
|
|
@opindex fstats
|
1975 |
|
|
Emit statistics about front-end processing at the end of the compilation.
|
1976 |
|
|
This information is generally only useful to the G++ development team.
|
1977 |
|
|
|
1978 |
|
|
@item -ftemplate-depth=@var{n}
|
1979 |
|
|
@opindex ftemplate-depth
|
1980 |
|
|
Set the maximum instantiation depth for template classes to @var{n}.
|
1981 |
|
|
A limit on the template instantiation depth is needed to detect
|
1982 |
|
|
endless recursions during template class instantiation. ANSI/ISO C++
|
1983 |
|
|
conforming programs must not rely on a maximum depth greater than 17
|
1984 |
|
|
(changed to 1024 in C++0x).
|
1985 |
|
|
|
1986 |
|
|
@item -fno-threadsafe-statics
|
1987 |
|
|
@opindex fno-threadsafe-statics
|
1988 |
|
|
Do not emit the extra code to use the routines specified in the C++
|
1989 |
|
|
ABI for thread-safe initialization of local statics. You can use this
|
1990 |
|
|
option to reduce code size slightly in code that doesn't need to be
|
1991 |
|
|
thread-safe.
|
1992 |
|
|
|
1993 |
|
|
@item -fuse-cxa-atexit
|
1994 |
|
|
@opindex fuse-cxa-atexit
|
1995 |
|
|
Register destructors for objects with static storage duration with the
|
1996 |
|
|
@code{__cxa_atexit} function rather than the @code{atexit} function.
|
1997 |
|
|
This option is required for fully standards-compliant handling of static
|
1998 |
|
|
destructors, but will only work if your C library supports
|
1999 |
|
|
@code{__cxa_atexit}.
|
2000 |
|
|
|
2001 |
|
|
@item -fno-use-cxa-get-exception-ptr
|
2002 |
|
|
@opindex fno-use-cxa-get-exception-ptr
|
2003 |
|
|
Don't use the @code{__cxa_get_exception_ptr} runtime routine. This
|
2004 |
|
|
will cause @code{std::uncaught_exception} to be incorrect, but is necessary
|
2005 |
|
|
if the runtime routine is not available.
|
2006 |
|
|
|
2007 |
|
|
@item -fvisibility-inlines-hidden
|
2008 |
|
|
@opindex fvisibility-inlines-hidden
|
2009 |
|
|
This switch declares that the user does not attempt to compare
|
2010 |
|
|
pointers to inline methods where the addresses of the two functions
|
2011 |
|
|
were taken in different shared objects.
|
2012 |
|
|
|
2013 |
|
|
The effect of this is that GCC may, effectively, mark inline methods with
|
2014 |
|
|
@code{__attribute__ ((visibility ("hidden")))} so that they do not
|
2015 |
|
|
appear in the export table of a DSO and do not require a PLT indirection
|
2016 |
|
|
when used within the DSO@. Enabling this option can have a dramatic effect
|
2017 |
|
|
on load and link times of a DSO as it massively reduces the size of the
|
2018 |
|
|
dynamic export table when the library makes heavy use of templates.
|
2019 |
|
|
|
2020 |
|
|
The behavior of this switch is not quite the same as marking the
|
2021 |
|
|
methods as hidden directly, because it does not affect static variables
|
2022 |
|
|
local to the function or cause the compiler to deduce that
|
2023 |
|
|
the function is defined in only one shared object.
|
2024 |
|
|
|
2025 |
|
|
You may mark a method as having a visibility explicitly to negate the
|
2026 |
|
|
effect of the switch for that method. For example, if you do want to
|
2027 |
|
|
compare pointers to a particular inline method, you might mark it as
|
2028 |
|
|
having default visibility. Marking the enclosing class with explicit
|
2029 |
|
|
visibility will have no effect.
|
2030 |
|
|
|
2031 |
|
|
Explicitly instantiated inline methods are unaffected by this option
|
2032 |
|
|
as their linkage might otherwise cross a shared library boundary.
|
2033 |
|
|
@xref{Template Instantiation}.
|
2034 |
|
|
|
2035 |
|
|
@item -fvisibility-ms-compat
|
2036 |
|
|
@opindex fvisibility-ms-compat
|
2037 |
|
|
This flag attempts to use visibility settings to make GCC's C++
|
2038 |
|
|
linkage model compatible with that of Microsoft Visual Studio.
|
2039 |
|
|
|
2040 |
|
|
The flag makes these changes to GCC's linkage model:
|
2041 |
|
|
|
2042 |
|
|
@enumerate
|
2043 |
|
|
@item
|
2044 |
|
|
It sets the default visibility to @code{hidden}, like
|
2045 |
|
|
@option{-fvisibility=hidden}.
|
2046 |
|
|
|
2047 |
|
|
@item
|
2048 |
|
|
Types, but not their members, are not hidden by default.
|
2049 |
|
|
|
2050 |
|
|
@item
|
2051 |
|
|
The One Definition Rule is relaxed for types without explicit
|
2052 |
|
|
visibility specifications which are defined in more than one different
|
2053 |
|
|
shared object: those declarations are permitted if they would have
|
2054 |
|
|
been permitted when this option was not used.
|
2055 |
|
|
@end enumerate
|
2056 |
|
|
|
2057 |
|
|
In new code it is better to use @option{-fvisibility=hidden} and
|
2058 |
|
|
export those classes which are intended to be externally visible.
|
2059 |
|
|
Unfortunately it is possible for code to rely, perhaps accidentally,
|
2060 |
|
|
on the Visual Studio behavior.
|
2061 |
|
|
|
2062 |
|
|
Among the consequences of these changes are that static data members
|
2063 |
|
|
of the same type with the same name but defined in different shared
|
2064 |
|
|
objects will be different, so changing one will not change the other;
|
2065 |
|
|
and that pointers to function members defined in different shared
|
2066 |
|
|
objects may not compare equal. When this flag is given, it is a
|
2067 |
|
|
violation of the ODR to define types with the same name differently.
|
2068 |
|
|
|
2069 |
|
|
@item -fno-weak
|
2070 |
|
|
@opindex fno-weak
|
2071 |
|
|
Do not use weak symbol support, even if it is provided by the linker.
|
2072 |
|
|
By default, G++ will use weak symbols if they are available. This
|
2073 |
|
|
option exists only for testing, and should not be used by end-users;
|
2074 |
|
|
it will result in inferior code and has no benefits. This option may
|
2075 |
|
|
be removed in a future release of G++.
|
2076 |
|
|
|
2077 |
|
|
@item -nostdinc++
|
2078 |
|
|
@opindex nostdinc++
|
2079 |
|
|
Do not search for header files in the standard directories specific to
|
2080 |
|
|
C++, but do still search the other standard directories. (This option
|
2081 |
|
|
is used when building the C++ library.)
|
2082 |
|
|
@end table
|
2083 |
|
|
|
2084 |
|
|
In addition, these optimization, warning, and code generation options
|
2085 |
|
|
have meanings only for C++ programs:
|
2086 |
|
|
|
2087 |
|
|
@table @gcctabopt
|
2088 |
|
|
@item -fno-default-inline
|
2089 |
|
|
@opindex fno-default-inline
|
2090 |
|
|
Do not assume @samp{inline} for functions defined inside a class scope.
|
2091 |
|
|
@xref{Optimize Options,,Options That Control Optimization}. Note that these
|
2092 |
|
|
functions will have linkage like inline functions; they just won't be
|
2093 |
|
|
inlined by default.
|
2094 |
|
|
|
2095 |
|
|
@item -Wabi @r{(C, Objective-C, C++ and Objective-C++ only)}
|
2096 |
|
|
@opindex Wabi
|
2097 |
|
|
@opindex Wno-abi
|
2098 |
|
|
Warn when G++ generates code that is probably not compatible with the
|
2099 |
|
|
vendor-neutral C++ ABI@. Although an effort has been made to warn about
|
2100 |
|
|
all such cases, there are probably some cases that are not warned about,
|
2101 |
|
|
even though G++ is generating incompatible code. There may also be
|
2102 |
|
|
cases where warnings are emitted even though the code that is generated
|
2103 |
|
|
will be compatible.
|
2104 |
|
|
|
2105 |
|
|
You should rewrite your code to avoid these warnings if you are
|
2106 |
|
|
concerned about the fact that code generated by G++ may not be binary
|
2107 |
|
|
compatible with code generated by other compilers.
|
2108 |
|
|
|
2109 |
|
|
The known incompatibilities in @option{-fabi-version=2} (the default) include:
|
2110 |
|
|
|
2111 |
|
|
@itemize @bullet
|
2112 |
|
|
|
2113 |
|
|
@item
|
2114 |
|
|
A template with a non-type template parameter of reference type is
|
2115 |
|
|
mangled incorrectly:
|
2116 |
|
|
@smallexample
|
2117 |
|
|
extern int N;
|
2118 |
|
|
template <int &> struct S @{@};
|
2119 |
|
|
void n (S<N>) @{2@}
|
2120 |
|
|
@end smallexample
|
2121 |
|
|
|
2122 |
|
|
This is fixed in @option{-fabi-version=3}.
|
2123 |
|
|
|
2124 |
|
|
@item
|
2125 |
|
|
SIMD vector types declared using @code{__attribute ((vector_size))} are
|
2126 |
|
|
mangled in a non-standard way that does not allow for overloading of
|
2127 |
|
|
functions taking vectors of different sizes.
|
2128 |
|
|
|
2129 |
|
|
The mangling is changed in @option{-fabi-version=4}.
|
2130 |
|
|
@end itemize
|
2131 |
|
|
|
2132 |
|
|
The known incompatibilities in @option{-fabi-version=1} include:
|
2133 |
|
|
|
2134 |
|
|
@itemize @bullet
|
2135 |
|
|
|
2136 |
|
|
@item
|
2137 |
|
|
Incorrect handling of tail-padding for bit-fields. G++ may attempt to
|
2138 |
|
|
pack data into the same byte as a base class. For example:
|
2139 |
|
|
|
2140 |
|
|
@smallexample
|
2141 |
|
|
struct A @{ virtual void f(); int f1 : 1; @};
|
2142 |
|
|
struct B : public A @{ int f2 : 1; @};
|
2143 |
|
|
@end smallexample
|
2144 |
|
|
|
2145 |
|
|
@noindent
|
2146 |
|
|
In this case, G++ will place @code{B::f2} into the same byte
|
2147 |
|
|
as@code{A::f1}; other compilers will not. You can avoid this problem
|
2148 |
|
|
by explicitly padding @code{A} so that its size is a multiple of the
|
2149 |
|
|
byte size on your platform; that will cause G++ and other compilers to
|
2150 |
|
|
layout @code{B} identically.
|
2151 |
|
|
|
2152 |
|
|
@item
|
2153 |
|
|
Incorrect handling of tail-padding for virtual bases. G++ does not use
|
2154 |
|
|
tail padding when laying out virtual bases. For example:
|
2155 |
|
|
|
2156 |
|
|
@smallexample
|
2157 |
|
|
struct A @{ virtual void f(); char c1; @};
|
2158 |
|
|
struct B @{ B(); char c2; @};
|
2159 |
|
|
struct C : public A, public virtual B @{@};
|
2160 |
|
|
@end smallexample
|
2161 |
|
|
|
2162 |
|
|
@noindent
|
2163 |
|
|
In this case, G++ will not place @code{B} into the tail-padding for
|
2164 |
|
|
@code{A}; other compilers will. You can avoid this problem by
|
2165 |
|
|
explicitly padding @code{A} so that its size is a multiple of its
|
2166 |
|
|
alignment (ignoring virtual base classes); that will cause G++ and other
|
2167 |
|
|
compilers to layout @code{C} identically.
|
2168 |
|
|
|
2169 |
|
|
@item
|
2170 |
|
|
Incorrect handling of bit-fields with declared widths greater than that
|
2171 |
|
|
of their underlying types, when the bit-fields appear in a union. For
|
2172 |
|
|
example:
|
2173 |
|
|
|
2174 |
|
|
@smallexample
|
2175 |
|
|
union U @{ int i : 4096; @};
|
2176 |
|
|
@end smallexample
|
2177 |
|
|
|
2178 |
|
|
@noindent
|
2179 |
|
|
Assuming that an @code{int} does not have 4096 bits, G++ will make the
|
2180 |
|
|
union too small by the number of bits in an @code{int}.
|
2181 |
|
|
|
2182 |
|
|
@item
|
2183 |
|
|
Empty classes can be placed at incorrect offsets. For example:
|
2184 |
|
|
|
2185 |
|
|
@smallexample
|
2186 |
|
|
struct A @{@};
|
2187 |
|
|
|
2188 |
|
|
struct B @{
|
2189 |
|
|
A a;
|
2190 |
|
|
virtual void f ();
|
2191 |
|
|
@};
|
2192 |
|
|
|
2193 |
|
|
struct C : public B, public A @{@};
|
2194 |
|
|
@end smallexample
|
2195 |
|
|
|
2196 |
|
|
@noindent
|
2197 |
|
|
G++ will place the @code{A} base class of @code{C} at a nonzero offset;
|
2198 |
|
|
it should be placed at offset zero. G++ mistakenly believes that the
|
2199 |
|
|
@code{A} data member of @code{B} is already at offset zero.
|
2200 |
|
|
|
2201 |
|
|
@item
|
2202 |
|
|
Names of template functions whose types involve @code{typename} or
|
2203 |
|
|
template template parameters can be mangled incorrectly.
|
2204 |
|
|
|
2205 |
|
|
@smallexample
|
2206 |
|
|
template <typename Q>
|
2207 |
|
|
void f(typename Q::X) @{@}
|
2208 |
|
|
|
2209 |
|
|
template <template <typename> class Q>
|
2210 |
|
|
void f(typename Q<int>::X) @{@}
|
2211 |
|
|
@end smallexample
|
2212 |
|
|
|
2213 |
|
|
@noindent
|
2214 |
|
|
Instantiations of these templates may be mangled incorrectly.
|
2215 |
|
|
|
2216 |
|
|
@end itemize
|
2217 |
|
|
|
2218 |
|
|
It also warns psABI related changes. The known psABI changes at this
|
2219 |
|
|
point include:
|
2220 |
|
|
|
2221 |
|
|
@itemize @bullet
|
2222 |
|
|
|
2223 |
|
|
@item
|
2224 |
|
|
For SYSV/x86-64, when passing union with long double, it is changed to
|
2225 |
|
|
pass in memory as specified in psABI. For example:
|
2226 |
|
|
|
2227 |
|
|
@smallexample
|
2228 |
|
|
union U @{
|
2229 |
|
|
long double ld;
|
2230 |
|
|
int i;
|
2231 |
|
|
@};
|
2232 |
|
|
@end smallexample
|
2233 |
|
|
|
2234 |
|
|
@noindent
|
2235 |
|
|
@code{union U} will always be passed in memory.
|
2236 |
|
|
|
2237 |
|
|
@end itemize
|
2238 |
|
|
|
2239 |
|
|
@item -Wctor-dtor-privacy @r{(C++ and Objective-C++ only)}
|
2240 |
|
|
@opindex Wctor-dtor-privacy
|
2241 |
|
|
@opindex Wno-ctor-dtor-privacy
|
2242 |
|
|
Warn when a class seems unusable because all the constructors or
|
2243 |
|
|
destructors in that class are private, and it has neither friends nor
|
2244 |
|
|
public static member functions.
|
2245 |
|
|
|
2246 |
|
|
@item -Wnon-virtual-dtor @r{(C++ and Objective-C++ only)}
|
2247 |
|
|
@opindex Wnon-virtual-dtor
|
2248 |
|
|
@opindex Wno-non-virtual-dtor
|
2249 |
|
|
Warn when a class has virtual functions and accessible non-virtual
|
2250 |
|
|
destructor, in which case it would be possible but unsafe to delete
|
2251 |
|
|
an instance of a derived class through a pointer to the base class.
|
2252 |
|
|
This warning is also enabled if -Weffc++ is specified.
|
2253 |
|
|
|
2254 |
|
|
@item -Wreorder @r{(C++ and Objective-C++ only)}
|
2255 |
|
|
@opindex Wreorder
|
2256 |
|
|
@opindex Wno-reorder
|
2257 |
|
|
@cindex reordering, warning
|
2258 |
|
|
@cindex warning for reordering of member initializers
|
2259 |
|
|
Warn when the order of member initializers given in the code does not
|
2260 |
|
|
match the order in which they must be executed. For instance:
|
2261 |
|
|
|
2262 |
|
|
@smallexample
|
2263 |
|
|
struct A @{
|
2264 |
|
|
int i;
|
2265 |
|
|
int j;
|
2266 |
|
|
A(): j (0), i (1) @{ @}
|
2267 |
|
|
@};
|
2268 |
|
|
@end smallexample
|
2269 |
|
|
|
2270 |
|
|
The compiler will rearrange the member initializers for @samp{i}
|
2271 |
|
|
and @samp{j} to match the declaration order of the members, emitting
|
2272 |
|
|
a warning to that effect. This warning is enabled by @option{-Wall}.
|
2273 |
|
|
@end table
|
2274 |
|
|
|
2275 |
|
|
The following @option{-W@dots{}} options are not affected by @option{-Wall}.
|
2276 |
|
|
|
2277 |
|
|
@table @gcctabopt
|
2278 |
|
|
@item -Weffc++ @r{(C++ and Objective-C++ only)}
|
2279 |
|
|
@opindex Weffc++
|
2280 |
|
|
@opindex Wno-effc++
|
2281 |
|
|
Warn about violations of the following style guidelines from Scott Meyers'
|
2282 |
|
|
@cite{Effective C++} book:
|
2283 |
|
|
|
2284 |
|
|
@itemize @bullet
|
2285 |
|
|
@item
|
2286 |
|
|
Item 11: Define a copy constructor and an assignment operator for classes
|
2287 |
|
|
with dynamically allocated memory.
|
2288 |
|
|
|
2289 |
|
|
@item
|
2290 |
|
|
Item 12: Prefer initialization to assignment in constructors.
|
2291 |
|
|
|
2292 |
|
|
@item
|
2293 |
|
|
Item 14: Make destructors virtual in base classes.
|
2294 |
|
|
|
2295 |
|
|
@item
|
2296 |
|
|
Item 15: Have @code{operator=} return a reference to @code{*this}.
|
2297 |
|
|
|
2298 |
|
|
@item
|
2299 |
|
|
Item 23: Don't try to return a reference when you must return an object.
|
2300 |
|
|
|
2301 |
|
|
@end itemize
|
2302 |
|
|
|
2303 |
|
|
Also warn about violations of the following style guidelines from
|
2304 |
|
|
Scott Meyers' @cite{More Effective C++} book:
|
2305 |
|
|
|
2306 |
|
|
@itemize @bullet
|
2307 |
|
|
@item
|
2308 |
|
|
Item 6: Distinguish between prefix and postfix forms of increment and
|
2309 |
|
|
decrement operators.
|
2310 |
|
|
|
2311 |
|
|
@item
|
2312 |
|
|
Item 7: Never overload @code{&&}, @code{||}, or @code{,}.
|
2313 |
|
|
|
2314 |
|
|
@end itemize
|
2315 |
|
|
|
2316 |
|
|
When selecting this option, be aware that the standard library
|
2317 |
|
|
headers do not obey all of these guidelines; use @samp{grep -v}
|
2318 |
|
|
to filter out those warnings.
|
2319 |
|
|
|
2320 |
|
|
@item -Wstrict-null-sentinel @r{(C++ and Objective-C++ only)}
|
2321 |
|
|
@opindex Wstrict-null-sentinel
|
2322 |
|
|
@opindex Wno-strict-null-sentinel
|
2323 |
|
|
Warn also about the use of an uncasted @code{NULL} as sentinel. When
|
2324 |
|
|
compiling only with GCC this is a valid sentinel, as @code{NULL} is defined
|
2325 |
|
|
to @code{__null}. Although it is a null pointer constant not a null pointer,
|
2326 |
|
|
it is guaranteed to be of the same size as a pointer. But this use is
|
2327 |
|
|
not portable across different compilers.
|
2328 |
|
|
|
2329 |
|
|
@item -Wno-non-template-friend @r{(C++ and Objective-C++ only)}
|
2330 |
|
|
@opindex Wno-non-template-friend
|
2331 |
|
|
@opindex Wnon-template-friend
|
2332 |
|
|
Disable warnings when non-templatized friend functions are declared
|
2333 |
|
|
within a template. Since the advent of explicit template specification
|
2334 |
|
|
support in G++, if the name of the friend is an unqualified-id (i.e.,
|
2335 |
|
|
@samp{friend foo(int)}), the C++ language specification demands that the
|
2336 |
|
|
friend declare or define an ordinary, nontemplate function. (Section
|
2337 |
|
|
14.5.3). Before G++ implemented explicit specification, unqualified-ids
|
2338 |
|
|
could be interpreted as a particular specialization of a templatized
|
2339 |
|
|
function. Because this non-conforming behavior is no longer the default
|
2340 |
|
|
behavior for G++, @option{-Wnon-template-friend} allows the compiler to
|
2341 |
|
|
check existing code for potential trouble spots and is on by default.
|
2342 |
|
|
This new compiler behavior can be turned off with
|
2343 |
|
|
@option{-Wno-non-template-friend} which keeps the conformant compiler code
|
2344 |
|
|
but disables the helpful warning.
|
2345 |
|
|
|
2346 |
|
|
@item -Wold-style-cast @r{(C++ and Objective-C++ only)}
|
2347 |
|
|
@opindex Wold-style-cast
|
2348 |
|
|
@opindex Wno-old-style-cast
|
2349 |
|
|
Warn if an old-style (C-style) cast to a non-void type is used within
|
2350 |
|
|
a C++ program. The new-style casts (@samp{dynamic_cast},
|
2351 |
|
|
@samp{static_cast}, @samp{reinterpret_cast}, and @samp{const_cast}) are
|
2352 |
|
|
less vulnerable to unintended effects and much easier to search for.
|
2353 |
|
|
|
2354 |
|
|
@item -Woverloaded-virtual @r{(C++ and Objective-C++ only)}
|
2355 |
|
|
@opindex Woverloaded-virtual
|
2356 |
|
|
@opindex Wno-overloaded-virtual
|
2357 |
|
|
@cindex overloaded virtual fn, warning
|
2358 |
|
|
@cindex warning for overloaded virtual fn
|
2359 |
|
|
Warn when a function declaration hides virtual functions from a
|
2360 |
|
|
base class. For example, in:
|
2361 |
|
|
|
2362 |
|
|
@smallexample
|
2363 |
|
|
struct A @{
|
2364 |
|
|
virtual void f();
|
2365 |
|
|
@};
|
2366 |
|
|
|
2367 |
|
|
struct B: public A @{
|
2368 |
|
|
void f(int);
|
2369 |
|
|
@};
|
2370 |
|
|
@end smallexample
|
2371 |
|
|
|
2372 |
|
|
the @code{A} class version of @code{f} is hidden in @code{B}, and code
|
2373 |
|
|
like:
|
2374 |
|
|
|
2375 |
|
|
@smallexample
|
2376 |
|
|
B* b;
|
2377 |
|
|
b->f();
|
2378 |
|
|
@end smallexample
|
2379 |
|
|
|
2380 |
|
|
will fail to compile.
|
2381 |
|
|
|
2382 |
|
|
@item -Wno-pmf-conversions @r{(C++ and Objective-C++ only)}
|
2383 |
|
|
@opindex Wno-pmf-conversions
|
2384 |
|
|
@opindex Wpmf-conversions
|
2385 |
|
|
Disable the diagnostic for converting a bound pointer to member function
|
2386 |
|
|
to a plain pointer.
|
2387 |
|
|
|
2388 |
|
|
@item -Wsign-promo @r{(C++ and Objective-C++ only)}
|
2389 |
|
|
@opindex Wsign-promo
|
2390 |
|
|
@opindex Wno-sign-promo
|
2391 |
|
|
Warn when overload resolution chooses a promotion from unsigned or
|
2392 |
|
|
enumerated type to a signed type, over a conversion to an unsigned type of
|
2393 |
|
|
the same size. Previous versions of G++ would try to preserve
|
2394 |
|
|
unsignedness, but the standard mandates the current behavior.
|
2395 |
|
|
|
2396 |
|
|
@smallexample
|
2397 |
|
|
struct A @{
|
2398 |
|
|
operator int ();
|
2399 |
|
|
A& operator = (int);
|
2400 |
|
|
@};
|
2401 |
|
|
|
2402 |
|
|
main ()
|
2403 |
|
|
@{
|
2404 |
|
|
A a,b;
|
2405 |
|
|
a = b;
|
2406 |
|
|
@}
|
2407 |
|
|
@end smallexample
|
2408 |
|
|
|
2409 |
|
|
In this example, G++ will synthesize a default @samp{A& operator =
|
2410 |
|
|
(const A&);}, while cfront will use the user-defined @samp{operator =}.
|
2411 |
|
|
@end table
|
2412 |
|
|
|
2413 |
|
|
@node Objective-C and Objective-C++ Dialect Options
|
2414 |
|
|
@section Options Controlling Objective-C and Objective-C++ Dialects
|
2415 |
|
|
|
2416 |
|
|
@cindex compiler options, Objective-C and Objective-C++
|
2417 |
|
|
@cindex Objective-C and Objective-C++ options, command line
|
2418 |
|
|
@cindex options, Objective-C and Objective-C++
|
2419 |
|
|
(NOTE: This manual does not describe the Objective-C and Objective-C++
|
2420 |
|
|
languages themselves. See @xref{Standards,,Language Standards
|
2421 |
|
|
Supported by GCC}, for references.)
|
2422 |
|
|
|
2423 |
|
|
This section describes the command-line options that are only meaningful
|
2424 |
|
|
for Objective-C and Objective-C++ programs, but you can also use most of
|
2425 |
|
|
the language-independent GNU compiler options.
|
2426 |
|
|
For example, you might compile a file @code{some_class.m} like this:
|
2427 |
|
|
|
2428 |
|
|
@smallexample
|
2429 |
|
|
gcc -g -fgnu-runtime -O -c some_class.m
|
2430 |
|
|
@end smallexample
|
2431 |
|
|
|
2432 |
|
|
@noindent
|
2433 |
|
|
In this example, @option{-fgnu-runtime} is an option meant only for
|
2434 |
|
|
Objective-C and Objective-C++ programs; you can use the other options with
|
2435 |
|
|
any language supported by GCC@.
|
2436 |
|
|
|
2437 |
|
|
Note that since Objective-C is an extension of the C language, Objective-C
|
2438 |
|
|
compilations may also use options specific to the C front-end (e.g.,
|
2439 |
|
|
@option{-Wtraditional}). Similarly, Objective-C++ compilations may use
|
2440 |
|
|
C++-specific options (e.g., @option{-Wabi}).
|
2441 |
|
|
|
2442 |
|
|
Here is a list of options that are @emph{only} for compiling Objective-C
|
2443 |
|
|
and Objective-C++ programs:
|
2444 |
|
|
|
2445 |
|
|
@table @gcctabopt
|
2446 |
|
|
@item -fconstant-string-class=@var{class-name}
|
2447 |
|
|
@opindex fconstant-string-class
|
2448 |
|
|
Use @var{class-name} as the name of the class to instantiate for each
|
2449 |
|
|
literal string specified with the syntax @code{@@"@dots{}"}. The default
|
2450 |
|
|
class name is @code{NXConstantString} if the GNU runtime is being used, and
|
2451 |
|
|
@code{NSConstantString} if the NeXT runtime is being used (see below). The
|
2452 |
|
|
@option{-fconstant-cfstrings} option, if also present, will override the
|
2453 |
|
|
@option{-fconstant-string-class} setting and cause @code{@@"@dots{}"} literals
|
2454 |
|
|
to be laid out as constant CoreFoundation strings.
|
2455 |
|
|
|
2456 |
|
|
@item -fgnu-runtime
|
2457 |
|
|
@opindex fgnu-runtime
|
2458 |
|
|
Generate object code compatible with the standard GNU Objective-C
|
2459 |
|
|
runtime. This is the default for most types of systems.
|
2460 |
|
|
|
2461 |
|
|
@item -fnext-runtime
|
2462 |
|
|
@opindex fnext-runtime
|
2463 |
|
|
Generate output compatible with the NeXT runtime. This is the default
|
2464 |
|
|
for NeXT-based systems, including Darwin and Mac OS X@. The macro
|
2465 |
|
|
@code{__NEXT_RUNTIME__} is predefined if (and only if) this option is
|
2466 |
|
|
used.
|
2467 |
|
|
|
2468 |
|
|
@item -fno-nil-receivers
|
2469 |
|
|
@opindex fno-nil-receivers
|
2470 |
|
|
Assume that all Objective-C message dispatches (e.g.,
|
2471 |
|
|
@code{[receiver message:arg]}) in this translation unit ensure that the receiver
|
2472 |
|
|
is not @code{nil}. This allows for more efficient entry points in the runtime
|
2473 |
|
|
to be used. Currently, this option is only available in conjunction with
|
2474 |
|
|
the NeXT runtime on Mac OS X 10.3 and later.
|
2475 |
|
|
|
2476 |
|
|
@item -fobjc-call-cxx-cdtors
|
2477 |
|
|
@opindex fobjc-call-cxx-cdtors
|
2478 |
|
|
For each Objective-C class, check if any of its instance variables is a
|
2479 |
|
|
C++ object with a non-trivial default constructor. If so, synthesize a
|
2480 |
|
|
special @code{- (id) .cxx_construct} instance method that will run
|
2481 |
|
|
non-trivial default constructors on any such instance variables, in order,
|
2482 |
|
|
and then return @code{self}. Similarly, check if any instance variable
|
2483 |
|
|
is a C++ object with a non-trivial destructor, and if so, synthesize a
|
2484 |
|
|
special @code{- (void) .cxx_destruct} method that will run
|
2485 |
|
|
all such default destructors, in reverse order.
|
2486 |
|
|
|
2487 |
|
|
The @code{- (id) .cxx_construct} and/or @code{- (void) .cxx_destruct} methods
|
2488 |
|
|
thusly generated will only operate on instance variables declared in the
|
2489 |
|
|
current Objective-C class, and not those inherited from superclasses. It
|
2490 |
|
|
is the responsibility of the Objective-C runtime to invoke all such methods
|
2491 |
|
|
in an object's inheritance hierarchy. The @code{- (id) .cxx_construct} methods
|
2492 |
|
|
will be invoked by the runtime immediately after a new object
|
2493 |
|
|
instance is allocated; the @code{- (void) .cxx_destruct} methods will
|
2494 |
|
|
be invoked immediately before the runtime deallocates an object instance.
|
2495 |
|
|
|
2496 |
|
|
As of this writing, only the NeXT runtime on Mac OS X 10.4 and later has
|
2497 |
|
|
support for invoking the @code{- (id) .cxx_construct} and
|
2498 |
|
|
@code{- (void) .cxx_destruct} methods.
|
2499 |
|
|
|
2500 |
|
|
@item -fobjc-direct-dispatch
|
2501 |
|
|
@opindex fobjc-direct-dispatch
|
2502 |
|
|
Allow fast jumps to the message dispatcher. On Darwin this is
|
2503 |
|
|
accomplished via the comm page.
|
2504 |
|
|
|
2505 |
|
|
@item -fobjc-exceptions
|
2506 |
|
|
@opindex fobjc-exceptions
|
2507 |
|
|
Enable syntactic support for structured exception handling in Objective-C,
|
2508 |
|
|
similar to what is offered by C++ and Java. This option is
|
2509 |
|
|
unavailable in conjunction with the NeXT runtime on Mac OS X 10.2 and
|
2510 |
|
|
earlier.
|
2511 |
|
|
|
2512 |
|
|
@smallexample
|
2513 |
|
|
@@try @{
|
2514 |
|
|
@dots{}
|
2515 |
|
|
@@throw expr;
|
2516 |
|
|
@dots{}
|
2517 |
|
|
@}
|
2518 |
|
|
@@catch (AnObjCClass *exc) @{
|
2519 |
|
|
@dots{}
|
2520 |
|
|
@@throw expr;
|
2521 |
|
|
@dots{}
|
2522 |
|
|
@@throw;
|
2523 |
|
|
@dots{}
|
2524 |
|
|
@}
|
2525 |
|
|
@@catch (AnotherClass *exc) @{
|
2526 |
|
|
@dots{}
|
2527 |
|
|
@}
|
2528 |
|
|
@@catch (id allOthers) @{
|
2529 |
|
|
@dots{}
|
2530 |
|
|
@}
|
2531 |
|
|
@@finally @{
|
2532 |
|
|
@dots{}
|
2533 |
|
|
@@throw expr;
|
2534 |
|
|
@dots{}
|
2535 |
|
|
@}
|
2536 |
|
|
@end smallexample
|
2537 |
|
|
|
2538 |
|
|
The @code{@@throw} statement may appear anywhere in an Objective-C or
|
2539 |
|
|
Objective-C++ program; when used inside of a @code{@@catch} block, the
|
2540 |
|
|
@code{@@throw} may appear without an argument (as shown above), in which case
|
2541 |
|
|
the object caught by the @code{@@catch} will be rethrown.
|
2542 |
|
|
|
2543 |
|
|
Note that only (pointers to) Objective-C objects may be thrown and
|
2544 |
|
|
caught using this scheme. When an object is thrown, it will be caught
|
2545 |
|
|
by the nearest @code{@@catch} clause capable of handling objects of that type,
|
2546 |
|
|
analogously to how @code{catch} blocks work in C++ and Java. A
|
2547 |
|
|
@code{@@catch(id @dots{})} clause (as shown above) may also be provided to catch
|
2548 |
|
|
any and all Objective-C exceptions not caught by previous @code{@@catch}
|
2549 |
|
|
clauses (if any).
|
2550 |
|
|
|
2551 |
|
|
The @code{@@finally} clause, if present, will be executed upon exit from the
|
2552 |
|
|
immediately preceding @code{@@try @dots{} @@catch} section. This will happen
|
2553 |
|
|
regardless of whether any exceptions are thrown, caught or rethrown
|
2554 |
|
|
inside the @code{@@try @dots{} @@catch} section, analogously to the behavior
|
2555 |
|
|
of the @code{finally} clause in Java.
|
2556 |
|
|
|
2557 |
|
|
There are several caveats to using the new exception mechanism:
|
2558 |
|
|
|
2559 |
|
|
@itemize @bullet
|
2560 |
|
|
@item
|
2561 |
|
|
Although currently designed to be binary compatible with @code{NS_HANDLER}-style
|
2562 |
|
|
idioms provided by the @code{NSException} class, the new
|
2563 |
|
|
exceptions can only be used on Mac OS X 10.3 (Panther) and later
|
2564 |
|
|
systems, due to additional functionality needed in the (NeXT) Objective-C
|
2565 |
|
|
runtime.
|
2566 |
|
|
|
2567 |
|
|
@item
|
2568 |
|
|
As mentioned above, the new exceptions do not support handling
|
2569 |
|
|
types other than Objective-C objects. Furthermore, when used from
|
2570 |
|
|
Objective-C++, the Objective-C exception model does not interoperate with C++
|
2571 |
|
|
exceptions at this time. This means you cannot @code{@@throw} an exception
|
2572 |
|
|
from Objective-C and @code{catch} it in C++, or vice versa
|
2573 |
|
|
(i.e., @code{throw @dots{} @@catch}).
|
2574 |
|
|
@end itemize
|
2575 |
|
|
|
2576 |
|
|
The @option{-fobjc-exceptions} switch also enables the use of synchronization
|
2577 |
|
|
blocks for thread-safe execution:
|
2578 |
|
|
|
2579 |
|
|
@smallexample
|
2580 |
|
|
@@synchronized (ObjCClass *guard) @{
|
2581 |
|
|
@dots{}
|
2582 |
|
|
@}
|
2583 |
|
|
@end smallexample
|
2584 |
|
|
|
2585 |
|
|
Upon entering the @code{@@synchronized} block, a thread of execution shall
|
2586 |
|
|
first check whether a lock has been placed on the corresponding @code{guard}
|
2587 |
|
|
object by another thread. If it has, the current thread shall wait until
|
2588 |
|
|
the other thread relinquishes its lock. Once @code{guard} becomes available,
|
2589 |
|
|
the current thread will place its own lock on it, execute the code contained in
|
2590 |
|
|
the @code{@@synchronized} block, and finally relinquish the lock (thereby
|
2591 |
|
|
making @code{guard} available to other threads).
|
2592 |
|
|
|
2593 |
|
|
Unlike Java, Objective-C does not allow for entire methods to be marked
|
2594 |
|
|
@code{@@synchronized}. Note that throwing exceptions out of
|
2595 |
|
|
@code{@@synchronized} blocks is allowed, and will cause the guarding object
|
2596 |
|
|
to be unlocked properly.
|
2597 |
|
|
|
2598 |
|
|
@item -fobjc-gc
|
2599 |
|
|
@opindex fobjc-gc
|
2600 |
|
|
Enable garbage collection (GC) in Objective-C and Objective-C++ programs.
|
2601 |
|
|
|
2602 |
|
|
@item -freplace-objc-classes
|
2603 |
|
|
@opindex freplace-objc-classes
|
2604 |
|
|
Emit a special marker instructing @command{ld(1)} not to statically link in
|
2605 |
|
|
the resulting object file, and allow @command{dyld(1)} to load it in at
|
2606 |
|
|
run time instead. This is used in conjunction with the Fix-and-Continue
|
2607 |
|
|
debugging mode, where the object file in question may be recompiled and
|
2608 |
|
|
dynamically reloaded in the course of program execution, without the need
|
2609 |
|
|
to restart the program itself. Currently, Fix-and-Continue functionality
|
2610 |
|
|
is only available in conjunction with the NeXT runtime on Mac OS X 10.3
|
2611 |
|
|
and later.
|
2612 |
|
|
|
2613 |
|
|
@item -fzero-link
|
2614 |
|
|
@opindex fzero-link
|
2615 |
|
|
When compiling for the NeXT runtime, the compiler ordinarily replaces calls
|
2616 |
|
|
to @code{objc_getClass("@dots{}")} (when the name of the class is known at
|
2617 |
|
|
compile time) with static class references that get initialized at load time,
|
2618 |
|
|
which improves run-time performance. Specifying the @option{-fzero-link} flag
|
2619 |
|
|
suppresses this behavior and causes calls to @code{objc_getClass("@dots{}")}
|
2620 |
|
|
to be retained. This is useful in Zero-Link debugging mode, since it allows
|
2621 |
|
|
for individual class implementations to be modified during program execution.
|
2622 |
|
|
|
2623 |
|
|
@item -gen-decls
|
2624 |
|
|
@opindex gen-decls
|
2625 |
|
|
Dump interface declarations for all classes seen in the source file to a
|
2626 |
|
|
file named @file{@var{sourcename}.decl}.
|
2627 |
|
|
|
2628 |
|
|
@item -Wassign-intercept @r{(Objective-C and Objective-C++ only)}
|
2629 |
|
|
@opindex Wassign-intercept
|
2630 |
|
|
@opindex Wno-assign-intercept
|
2631 |
|
|
Warn whenever an Objective-C assignment is being intercepted by the
|
2632 |
|
|
garbage collector.
|
2633 |
|
|
|
2634 |
|
|
@item -Wno-protocol @r{(Objective-C and Objective-C++ only)}
|
2635 |
|
|
@opindex Wno-protocol
|
2636 |
|
|
@opindex Wprotocol
|
2637 |
|
|
If a class is declared to implement a protocol, a warning is issued for
|
2638 |
|
|
every method in the protocol that is not implemented by the class. The
|
2639 |
|
|
default behavior is to issue a warning for every method not explicitly
|
2640 |
|
|
implemented in the class, even if a method implementation is inherited
|
2641 |
|
|
from the superclass. If you use the @option{-Wno-protocol} option, then
|
2642 |
|
|
methods inherited from the superclass are considered to be implemented,
|
2643 |
|
|
and no warning is issued for them.
|
2644 |
|
|
|
2645 |
|
|
@item -Wselector @r{(Objective-C and Objective-C++ only)}
|
2646 |
|
|
@opindex Wselector
|
2647 |
|
|
@opindex Wno-selector
|
2648 |
|
|
Warn if multiple methods of different types for the same selector are
|
2649 |
|
|
found during compilation. The check is performed on the list of methods
|
2650 |
|
|
in the final stage of compilation. Additionally, a check is performed
|
2651 |
|
|
for each selector appearing in a @code{@@selector(@dots{})}
|
2652 |
|
|
expression, and a corresponding method for that selector has been found
|
2653 |
|
|
during compilation. Because these checks scan the method table only at
|
2654 |
|
|
the end of compilation, these warnings are not produced if the final
|
2655 |
|
|
stage of compilation is not reached, for example because an error is
|
2656 |
|
|
found during compilation, or because the @option{-fsyntax-only} option is
|
2657 |
|
|
being used.
|
2658 |
|
|
|
2659 |
|
|
@item -Wstrict-selector-match @r{(Objective-C and Objective-C++ only)}
|
2660 |
|
|
@opindex Wstrict-selector-match
|
2661 |
|
|
@opindex Wno-strict-selector-match
|
2662 |
|
|
Warn if multiple methods with differing argument and/or return types are
|
2663 |
|
|
found for a given selector when attempting to send a message using this
|
2664 |
|
|
selector to a receiver of type @code{id} or @code{Class}. When this flag
|
2665 |
|
|
is off (which is the default behavior), the compiler will omit such warnings
|
2666 |
|
|
if any differences found are confined to types which share the same size
|
2667 |
|
|
and alignment.
|
2668 |
|
|
|
2669 |
|
|
@item -Wundeclared-selector @r{(Objective-C and Objective-C++ only)}
|
2670 |
|
|
@opindex Wundeclared-selector
|
2671 |
|
|
@opindex Wno-undeclared-selector
|
2672 |
|
|
Warn if a @code{@@selector(@dots{})} expression referring to an
|
2673 |
|
|
undeclared selector is found. A selector is considered undeclared if no
|
2674 |
|
|
method with that name has been declared before the
|
2675 |
|
|
@code{@@selector(@dots{})} expression, either explicitly in an
|
2676 |
|
|
@code{@@interface} or @code{@@protocol} declaration, or implicitly in
|
2677 |
|
|
an @code{@@implementation} section. This option always performs its
|
2678 |
|
|
checks as soon as a @code{@@selector(@dots{})} expression is found,
|
2679 |
|
|
while @option{-Wselector} only performs its checks in the final stage of
|
2680 |
|
|
compilation. This also enforces the coding style convention
|
2681 |
|
|
that methods and selectors must be declared before being used.
|
2682 |
|
|
|
2683 |
|
|
@item -print-objc-runtime-info
|
2684 |
|
|
@opindex print-objc-runtime-info
|
2685 |
|
|
Generate C header describing the largest structure that is passed by
|
2686 |
|
|
value, if any.
|
2687 |
|
|
|
2688 |
|
|
@end table
|
2689 |
|
|
|
2690 |
|
|
@node Language Independent Options
|
2691 |
|
|
@section Options to Control Diagnostic Messages Formatting
|
2692 |
|
|
@cindex options to control diagnostics formatting
|
2693 |
|
|
@cindex diagnostic messages
|
2694 |
|
|
@cindex message formatting
|
2695 |
|
|
|
2696 |
|
|
Traditionally, diagnostic messages have been formatted irrespective of
|
2697 |
|
|
the output device's aspect (e.g.@: its width, @dots{}). The options described
|
2698 |
|
|
below can be used to control the diagnostic messages formatting
|
2699 |
|
|
algorithm, e.g.@: how many characters per line, how often source location
|
2700 |
|
|
information should be reported. Right now, only the C++ front end can
|
2701 |
|
|
honor these options. However it is expected, in the near future, that
|
2702 |
|
|
the remaining front ends would be able to digest them correctly.
|
2703 |
|
|
|
2704 |
|
|
@table @gcctabopt
|
2705 |
|
|
@item -fmessage-length=@var{n}
|
2706 |
|
|
@opindex fmessage-length
|
2707 |
|
|
Try to format error messages so that they fit on lines of about @var{n}
|
2708 |
|
|
characters. The default is 72 characters for @command{g++} and 0 for the rest of
|
2709 |
|
|
the front ends supported by GCC@. If @var{n} is zero, then no
|
2710 |
|
|
line-wrapping will be done; each error message will appear on a single
|
2711 |
|
|
line.
|
2712 |
|
|
|
2713 |
|
|
@opindex fdiagnostics-show-location
|
2714 |
|
|
@item -fdiagnostics-show-location=once
|
2715 |
|
|
Only meaningful in line-wrapping mode. Instructs the diagnostic messages
|
2716 |
|
|
reporter to emit @emph{once} source location information; that is, in
|
2717 |
|
|
case the message is too long to fit on a single physical line and has to
|
2718 |
|
|
be wrapped, the source location won't be emitted (as prefix) again,
|
2719 |
|
|
over and over, in subsequent continuation lines. This is the default
|
2720 |
|
|
behavior.
|
2721 |
|
|
|
2722 |
|
|
@item -fdiagnostics-show-location=every-line
|
2723 |
|
|
Only meaningful in line-wrapping mode. Instructs the diagnostic
|
2724 |
|
|
messages reporter to emit the same source location information (as
|
2725 |
|
|
prefix) for physical lines that result from the process of breaking
|
2726 |
|
|
a message which is too long to fit on a single line.
|
2727 |
|
|
|
2728 |
|
|
@item -fdiagnostics-show-option
|
2729 |
|
|
@opindex fdiagnostics-show-option
|
2730 |
|
|
This option instructs the diagnostic machinery to add text to each
|
2731 |
|
|
diagnostic emitted, which indicates which command line option directly
|
2732 |
|
|
controls that diagnostic, when such an option is known to the
|
2733 |
|
|
diagnostic machinery.
|
2734 |
|
|
|
2735 |
|
|
@item -Wcoverage-mismatch
|
2736 |
|
|
@opindex Wcoverage-mismatch
|
2737 |
|
|
Warn if feedback profiles do not match when using the
|
2738 |
|
|
@option{-fprofile-use} option.
|
2739 |
|
|
If a source file was changed between @option{-fprofile-gen} and
|
2740 |
|
|
@option{-fprofile-use}, the files with the profile feedback can fail
|
2741 |
|
|
to match the source file and GCC can not use the profile feedback
|
2742 |
|
|
information. By default, GCC emits an error message in this case.
|
2743 |
|
|
The option @option{-Wcoverage-mismatch} emits a warning instead of an
|
2744 |
|
|
error. GCC does not use appropriate feedback profiles, so using this
|
2745 |
|
|
option can result in poorly optimized code. This option is useful
|
2746 |
|
|
only in the case of very minor changes such as bug fixes to an
|
2747 |
|
|
existing code-base.
|
2748 |
|
|
|
2749 |
|
|
@end table
|
2750 |
|
|
|
2751 |
|
|
@node Warning Options
|
2752 |
|
|
@section Options to Request or Suppress Warnings
|
2753 |
|
|
@cindex options to control warnings
|
2754 |
|
|
@cindex warning messages
|
2755 |
|
|
@cindex messages, warning
|
2756 |
|
|
@cindex suppressing warnings
|
2757 |
|
|
|
2758 |
|
|
Warnings are diagnostic messages that report constructions which
|
2759 |
|
|
are not inherently erroneous but which are risky or suggest there
|
2760 |
|
|
may have been an error.
|
2761 |
|
|
|
2762 |
|
|
The following language-independent options do not enable specific
|
2763 |
|
|
warnings but control the kinds of diagnostics produced by GCC.
|
2764 |
|
|
|
2765 |
|
|
@table @gcctabopt
|
2766 |
|
|
@cindex syntax checking
|
2767 |
|
|
@item -fsyntax-only
|
2768 |
|
|
@opindex fsyntax-only
|
2769 |
|
|
Check the code for syntax errors, but don't do anything beyond that.
|
2770 |
|
|
|
2771 |
|
|
@item -w
|
2772 |
|
|
@opindex w
|
2773 |
|
|
Inhibit all warning messages.
|
2774 |
|
|
|
2775 |
|
|
@item -Werror
|
2776 |
|
|
@opindex Werror
|
2777 |
|
|
@opindex Wno-error
|
2778 |
|
|
Make all warnings into errors.
|
2779 |
|
|
|
2780 |
|
|
@item -Werror=
|
2781 |
|
|
@opindex Werror=
|
2782 |
|
|
@opindex Wno-error=
|
2783 |
|
|
Make the specified warning into an error. The specifier for a warning
|
2784 |
|
|
is appended, for example @option{-Werror=switch} turns the warnings
|
2785 |
|
|
controlled by @option{-Wswitch} into errors. This switch takes a
|
2786 |
|
|
negative form, to be used to negate @option{-Werror} for specific
|
2787 |
|
|
warnings, for example @option{-Wno-error=switch} makes
|
2788 |
|
|
@option{-Wswitch} warnings not be errors, even when @option{-Werror}
|
2789 |
|
|
is in effect. You can use the @option{-fdiagnostics-show-option}
|
2790 |
|
|
option to have each controllable warning amended with the option which
|
2791 |
|
|
controls it, to determine what to use with this option.
|
2792 |
|
|
|
2793 |
|
|
Note that specifying @option{-Werror=}@var{foo} automatically implies
|
2794 |
|
|
@option{-W}@var{foo}. However, @option{-Wno-error=}@var{foo} does not
|
2795 |
|
|
imply anything.
|
2796 |
|
|
|
2797 |
|
|
@item -Wfatal-errors
|
2798 |
|
|
@opindex Wfatal-errors
|
2799 |
|
|
@opindex Wno-fatal-errors
|
2800 |
|
|
This option causes the compiler to abort compilation on the first error
|
2801 |
|
|
occurred rather than trying to keep going and printing further error
|
2802 |
|
|
messages.
|
2803 |
|
|
|
2804 |
|
|
@end table
|
2805 |
|
|
|
2806 |
|
|
You can request many specific warnings with options beginning
|
2807 |
|
|
@samp{-W}, for example @option{-Wimplicit} to request warnings on
|
2808 |
|
|
implicit declarations. Each of these specific warning options also
|
2809 |
|
|
has a negative form beginning @samp{-Wno-} to turn off warnings; for
|
2810 |
|
|
example, @option{-Wno-implicit}. This manual lists only one of the
|
2811 |
|
|
two forms, whichever is not the default. For further,
|
2812 |
|
|
language-specific options also refer to @ref{C++ Dialect Options} and
|
2813 |
|
|
@ref{Objective-C and Objective-C++ Dialect Options}.
|
2814 |
|
|
|
2815 |
|
|
@table @gcctabopt
|
2816 |
|
|
@item -pedantic
|
2817 |
|
|
@opindex pedantic
|
2818 |
|
|
Issue all the warnings demanded by strict ISO C and ISO C++;
|
2819 |
|
|
reject all programs that use forbidden extensions, and some other
|
2820 |
|
|
programs that do not follow ISO C and ISO C++. For ISO C, follows the
|
2821 |
|
|
version of the ISO C standard specified by any @option{-std} option used.
|
2822 |
|
|
|
2823 |
|
|
Valid ISO C and ISO C++ programs should compile properly with or without
|
2824 |
|
|
this option (though a rare few will require @option{-ansi} or a
|
2825 |
|
|
@option{-std} option specifying the required version of ISO C)@. However,
|
2826 |
|
|
without this option, certain GNU extensions and traditional C and C++
|
2827 |
|
|
features are supported as well. With this option, they are rejected.
|
2828 |
|
|
|
2829 |
|
|
@option{-pedantic} does not cause warning messages for use of the
|
2830 |
|
|
alternate keywords whose names begin and end with @samp{__}. Pedantic
|
2831 |
|
|
warnings are also disabled in the expression that follows
|
2832 |
|
|
@code{__extension__}. However, only system header files should use
|
2833 |
|
|
these escape routes; application programs should avoid them.
|
2834 |
|
|
@xref{Alternate Keywords}.
|
2835 |
|
|
|
2836 |
|
|
Some users try to use @option{-pedantic} to check programs for strict ISO
|
2837 |
|
|
C conformance. They soon find that it does not do quite what they want:
|
2838 |
|
|
it finds some non-ISO practices, but not all---only those for which
|
2839 |
|
|
ISO C @emph{requires} a diagnostic, and some others for which
|
2840 |
|
|
diagnostics have been added.
|
2841 |
|
|
|
2842 |
|
|
A feature to report any failure to conform to ISO C might be useful in
|
2843 |
|
|
some instances, but would require considerable additional work and would
|
2844 |
|
|
be quite different from @option{-pedantic}. We don't have plans to
|
2845 |
|
|
support such a feature in the near future.
|
2846 |
|
|
|
2847 |
|
|
Where the standard specified with @option{-std} represents a GNU
|
2848 |
|
|
extended dialect of C, such as @samp{gnu90} or @samp{gnu99}, there is a
|
2849 |
|
|
corresponding @dfn{base standard}, the version of ISO C on which the GNU
|
2850 |
|
|
extended dialect is based. Warnings from @option{-pedantic} are given
|
2851 |
|
|
where they are required by the base standard. (It would not make sense
|
2852 |
|
|
for such warnings to be given only for features not in the specified GNU
|
2853 |
|
|
C dialect, since by definition the GNU dialects of C include all
|
2854 |
|
|
features the compiler supports with the given option, and there would be
|
2855 |
|
|
nothing to warn about.)
|
2856 |
|
|
|
2857 |
|
|
@item -pedantic-errors
|
2858 |
|
|
@opindex pedantic-errors
|
2859 |
|
|
Like @option{-pedantic}, except that errors are produced rather than
|
2860 |
|
|
warnings.
|
2861 |
|
|
|
2862 |
|
|
@item -Wall
|
2863 |
|
|
@opindex Wall
|
2864 |
|
|
@opindex Wno-all
|
2865 |
|
|
This enables all the warnings about constructions that some users
|
2866 |
|
|
consider questionable, and that are easy to avoid (or modify to
|
2867 |
|
|
prevent the warning), even in conjunction with macros. This also
|
2868 |
|
|
enables some language-specific warnings described in @ref{C++ Dialect
|
2869 |
|
|
Options} and @ref{Objective-C and Objective-C++ Dialect Options}.
|
2870 |
|
|
|
2871 |
|
|
@option{-Wall} turns on the following warning flags:
|
2872 |
|
|
|
2873 |
|
|
@gccoptlist{-Waddress @gol
|
2874 |
|
|
-Warray-bounds @r{(only with} @option{-O2}@r{)} @gol
|
2875 |
|
|
-Wc++0x-compat @gol
|
2876 |
|
|
-Wchar-subscripts @gol
|
2877 |
|
|
-Wenum-compare @r{(in C/Objc; this is on by default in C++)} @gol
|
2878 |
|
|
-Wimplicit-int @gol
|
2879 |
|
|
-Wimplicit-function-declaration @gol
|
2880 |
|
|
-Wcomment @gol
|
2881 |
|
|
-Wformat @gol
|
2882 |
|
|
-Wmain @r{(only for C/ObjC and unless} @option{-ffreestanding}@r{)} @gol
|
2883 |
|
|
-Wmissing-braces @gol
|
2884 |
|
|
-Wnonnull @gol
|
2885 |
|
|
-Wparentheses @gol
|
2886 |
|
|
-Wpointer-sign @gol
|
2887 |
|
|
-Wreorder @gol
|
2888 |
|
|
-Wreturn-type @gol
|
2889 |
|
|
-Wsequence-point @gol
|
2890 |
|
|
-Wsign-compare @r{(only in C++)} @gol
|
2891 |
|
|
-Wstrict-aliasing @gol
|
2892 |
|
|
-Wstrict-overflow=1 @gol
|
2893 |
|
|
-Wswitch @gol
|
2894 |
|
|
-Wtrigraphs @gol
|
2895 |
|
|
-Wuninitialized @gol
|
2896 |
|
|
-Wunknown-pragmas @gol
|
2897 |
|
|
-Wunused-function @gol
|
2898 |
|
|
-Wunused-label @gol
|
2899 |
|
|
-Wunused-value @gol
|
2900 |
|
|
-Wunused-variable @gol
|
2901 |
|
|
-Wvolatile-register-var @gol
|
2902 |
|
|
}
|
2903 |
|
|
|
2904 |
|
|
Note that some warning flags are not implied by @option{-Wall}. Some of
|
2905 |
|
|
them warn about constructions that users generally do not consider
|
2906 |
|
|
questionable, but which occasionally you might wish to check for;
|
2907 |
|
|
others warn about constructions that are necessary or hard to avoid in
|
2908 |
|
|
some cases, and there is no simple way to modify the code to suppress
|
2909 |
|
|
the warning. Some of them are enabled by @option{-Wextra} but many of
|
2910 |
|
|
them must be enabled individually.
|
2911 |
|
|
|
2912 |
|
|
@item -Wextra
|
2913 |
|
|
@opindex W
|
2914 |
|
|
@opindex Wextra
|
2915 |
|
|
@opindex Wno-extra
|
2916 |
|
|
This enables some extra warning flags that are not enabled by
|
2917 |
|
|
@option{-Wall}. (This option used to be called @option{-W}. The older
|
2918 |
|
|
name is still supported, but the newer name is more descriptive.)
|
2919 |
|
|
|
2920 |
|
|
@gccoptlist{-Wclobbered @gol
|
2921 |
|
|
-Wempty-body @gol
|
2922 |
|
|
-Wignored-qualifiers @gol
|
2923 |
|
|
-Wmissing-field-initializers @gol
|
2924 |
|
|
-Wmissing-parameter-type @r{(C only)} @gol
|
2925 |
|
|
-Wold-style-declaration @r{(C only)} @gol
|
2926 |
|
|
-Woverride-init @gol
|
2927 |
|
|
-Wsign-compare @gol
|
2928 |
|
|
-Wtype-limits @gol
|
2929 |
|
|
-Wuninitialized @gol
|
2930 |
|
|
-Wunused-parameter @r{(only with} @option{-Wunused} @r{or} @option{-Wall}@r{)} @gol
|
2931 |
|
|
}
|
2932 |
|
|
|
2933 |
|
|
The option @option{-Wextra} also prints warning messages for the
|
2934 |
|
|
following cases:
|
2935 |
|
|
|
2936 |
|
|
@itemize @bullet
|
2937 |
|
|
|
2938 |
|
|
@item
|
2939 |
|
|
A pointer is compared against integer zero with @samp{<}, @samp{<=},
|
2940 |
|
|
@samp{>}, or @samp{>=}.
|
2941 |
|
|
|
2942 |
|
|
@item
|
2943 |
|
|
(C++ only) An enumerator and a non-enumerator both appear in a
|
2944 |
|
|
conditional expression.
|
2945 |
|
|
|
2946 |
|
|
@item
|
2947 |
|
|
(C++ only) Ambiguous virtual bases.
|
2948 |
|
|
|
2949 |
|
|
@item
|
2950 |
|
|
(C++ only) Subscripting an array which has been declared @samp{register}.
|
2951 |
|
|
|
2952 |
|
|
@item
|
2953 |
|
|
(C++ only) Taking the address of a variable which has been declared
|
2954 |
|
|
@samp{register}.
|
2955 |
|
|
|
2956 |
|
|
@item
|
2957 |
|
|
(C++ only) A base class is not initialized in a derived class' copy
|
2958 |
|
|
constructor.
|
2959 |
|
|
|
2960 |
|
|
@end itemize
|
2961 |
|
|
|
2962 |
|
|
@item -Wchar-subscripts
|
2963 |
|
|
@opindex Wchar-subscripts
|
2964 |
|
|
@opindex Wno-char-subscripts
|
2965 |
|
|
Warn if an array subscript has type @code{char}. This is a common cause
|
2966 |
|
|
of error, as programmers often forget that this type is signed on some
|
2967 |
|
|
machines.
|
2968 |
|
|
This warning is enabled by @option{-Wall}.
|
2969 |
|
|
|
2970 |
|
|
@item -Wcomment
|
2971 |
|
|
@opindex Wcomment
|
2972 |
|
|
@opindex Wno-comment
|
2973 |
|
|
Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*}
|
2974 |
|
|
comment, or whenever a Backslash-Newline appears in a @samp{//} comment.
|
2975 |
|
|
This warning is enabled by @option{-Wall}.
|
2976 |
|
|
|
2977 |
|
|
@item -Wformat
|
2978 |
|
|
@opindex Wformat
|
2979 |
|
|
@opindex Wno-format
|
2980 |
|
|
@opindex ffreestanding
|
2981 |
|
|
@opindex fno-builtin
|
2982 |
|
|
Check calls to @code{printf} and @code{scanf}, etc., to make sure that
|
2983 |
|
|
the arguments supplied have types appropriate to the format string
|
2984 |
|
|
specified, and that the conversions specified in the format string make
|
2985 |
|
|
sense. This includes standard functions, and others specified by format
|
2986 |
|
|
attributes (@pxref{Function Attributes}), in the @code{printf},
|
2987 |
|
|
@code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension,
|
2988 |
|
|
not in the C standard) families (or other target-specific families).
|
2989 |
|
|
Which functions are checked without format attributes having been
|
2990 |
|
|
specified depends on the standard version selected, and such checks of
|
2991 |
|
|
functions without the attribute specified are disabled by
|
2992 |
|
|
@option{-ffreestanding} or @option{-fno-builtin}.
|
2993 |
|
|
|
2994 |
|
|
The formats are checked against the format features supported by GNU
|
2995 |
|
|
libc version 2.2. These include all ISO C90 and C99 features, as well
|
2996 |
|
|
as features from the Single Unix Specification and some BSD and GNU
|
2997 |
|
|
extensions. Other library implementations may not support all these
|
2998 |
|
|
features; GCC does not support warning about features that go beyond a
|
2999 |
|
|
particular library's limitations. However, if @option{-pedantic} is used
|
3000 |
|
|
with @option{-Wformat}, warnings will be given about format features not
|
3001 |
|
|
in the selected standard version (but not for @code{strfmon} formats,
|
3002 |
|
|
since those are not in any version of the C standard). @xref{C Dialect
|
3003 |
|
|
Options,,Options Controlling C Dialect}.
|
3004 |
|
|
|
3005 |
|
|
Since @option{-Wformat} also checks for null format arguments for
|
3006 |
|
|
several functions, @option{-Wformat} also implies @option{-Wnonnull}.
|
3007 |
|
|
|
3008 |
|
|
@option{-Wformat} is included in @option{-Wall}. For more control over some
|
3009 |
|
|
aspects of format checking, the options @option{-Wformat-y2k},
|
3010 |
|
|
@option{-Wno-format-extra-args}, @option{-Wno-format-zero-length},
|
3011 |
|
|
@option{-Wformat-nonliteral}, @option{-Wformat-security}, and
|
3012 |
|
|
@option{-Wformat=2} are available, but are not included in @option{-Wall}.
|
3013 |
|
|
|
3014 |
|
|
@item -Wformat-y2k
|
3015 |
|
|
@opindex Wformat-y2k
|
3016 |
|
|
@opindex Wno-format-y2k
|
3017 |
|
|
If @option{-Wformat} is specified, also warn about @code{strftime}
|
3018 |
|
|
formats which may yield only a two-digit year.
|
3019 |
|
|
|
3020 |
|
|
@item -Wno-format-contains-nul
|
3021 |
|
|
@opindex Wno-format-contains-nul
|
3022 |
|
|
@opindex Wformat-contains-nul
|
3023 |
|
|
If @option{-Wformat} is specified, do not warn about format strings that
|
3024 |
|
|
contain NUL bytes.
|
3025 |
|
|
|
3026 |
|
|
@item -Wno-format-extra-args
|
3027 |
|
|
@opindex Wno-format-extra-args
|
3028 |
|
|
@opindex Wformat-extra-args
|
3029 |
|
|
If @option{-Wformat} is specified, do not warn about excess arguments to a
|
3030 |
|
|
@code{printf} or @code{scanf} format function. The C standard specifies
|
3031 |
|
|
that such arguments are ignored.
|
3032 |
|
|
|
3033 |
|
|
Where the unused arguments lie between used arguments that are
|
3034 |
|
|
specified with @samp{$} operand number specifications, normally
|
3035 |
|
|
warnings are still given, since the implementation could not know what
|
3036 |
|
|
type to pass to @code{va_arg} to skip the unused arguments. However,
|
3037 |
|
|
in the case of @code{scanf} formats, this option will suppress the
|
3038 |
|
|
warning if the unused arguments are all pointers, since the Single
|
3039 |
|
|
Unix Specification says that such unused arguments are allowed.
|
3040 |
|
|
|
3041 |
|
|
@item -Wno-format-zero-length @r{(C and Objective-C only)}
|
3042 |
|
|
@opindex Wno-format-zero-length
|
3043 |
|
|
@opindex Wformat-zero-length
|
3044 |
|
|
If @option{-Wformat} is specified, do not warn about zero-length formats.
|
3045 |
|
|
The C standard specifies that zero-length formats are allowed.
|
3046 |
|
|
|
3047 |
|
|
@item -Wformat-nonliteral
|
3048 |
|
|
@opindex Wformat-nonliteral
|
3049 |
|
|
@opindex Wno-format-nonliteral
|
3050 |
|
|
If @option{-Wformat} is specified, also warn if the format string is not a
|
3051 |
|
|
string literal and so cannot be checked, unless the format function
|
3052 |
|
|
takes its format arguments as a @code{va_list}.
|
3053 |
|
|
|
3054 |
|
|
@item -Wformat-security
|
3055 |
|
|
@opindex Wformat-security
|
3056 |
|
|
@opindex Wno-format-security
|
3057 |
|
|
If @option{-Wformat} is specified, also warn about uses of format
|
3058 |
|
|
functions that represent possible security problems. At present, this
|
3059 |
|
|
warns about calls to @code{printf} and @code{scanf} functions where the
|
3060 |
|
|
format string is not a string literal and there are no format arguments,
|
3061 |
|
|
as in @code{printf (foo);}. This may be a security hole if the format
|
3062 |
|
|
string came from untrusted input and contains @samp{%n}. (This is
|
3063 |
|
|
currently a subset of what @option{-Wformat-nonliteral} warns about, but
|
3064 |
|
|
in future warnings may be added to @option{-Wformat-security} that are not
|
3065 |
|
|
included in @option{-Wformat-nonliteral}.)
|
3066 |
|
|
|
3067 |
|
|
@item -Wformat=2
|
3068 |
|
|
@opindex Wformat=2
|
3069 |
|
|
@opindex Wno-format=2
|
3070 |
|
|
Enable @option{-Wformat} plus format checks not included in
|
3071 |
|
|
@option{-Wformat}. Currently equivalent to @samp{-Wformat
|
3072 |
|
|
-Wformat-nonliteral -Wformat-security -Wformat-y2k}.
|
3073 |
|
|
|
3074 |
|
|
@item -Wnonnull @r{(C and Objective-C only)}
|
3075 |
|
|
@opindex Wnonnull
|
3076 |
|
|
@opindex Wno-nonnull
|
3077 |
|
|
Warn about passing a null pointer for arguments marked as
|
3078 |
|
|
requiring a non-null value by the @code{nonnull} function attribute.
|
3079 |
|
|
|
3080 |
|
|
@option{-Wnonnull} is included in @option{-Wall} and @option{-Wformat}. It
|
3081 |
|
|
can be disabled with the @option{-Wno-nonnull} option.
|
3082 |
|
|
|
3083 |
|
|
@item -Winit-self @r{(C, C++, Objective-C and Objective-C++ only)}
|
3084 |
|
|
@opindex Winit-self
|
3085 |
|
|
@opindex Wno-init-self
|
3086 |
|
|
Warn about uninitialized variables which are initialized with themselves.
|
3087 |
|
|
Note this option can only be used with the @option{-Wuninitialized} option.
|
3088 |
|
|
|
3089 |
|
|
For example, GCC will warn about @code{i} being uninitialized in the
|
3090 |
|
|
following snippet only when @option{-Winit-self} has been specified:
|
3091 |
|
|
@smallexample
|
3092 |
|
|
@group
|
3093 |
|
|
int f()
|
3094 |
|
|
@{
|
3095 |
|
|
int i = i;
|
3096 |
|
|
return i;
|
3097 |
|
|
@}
|
3098 |
|
|
@end group
|
3099 |
|
|
@end smallexample
|
3100 |
|
|
|
3101 |
|
|
@item -Wimplicit-int @r{(C and Objective-C only)}
|
3102 |
|
|
@opindex Wimplicit-int
|
3103 |
|
|
@opindex Wno-implicit-int
|
3104 |
|
|
Warn when a declaration does not specify a type.
|
3105 |
|
|
This warning is enabled by @option{-Wall}.
|
3106 |
|
|
|
3107 |
|
|
@item -Wimplicit-function-declaration @r{(C and Objective-C only)}
|
3108 |
|
|
@opindex Wimplicit-function-declaration
|
3109 |
|
|
@opindex Wno-implicit-function-declaration
|
3110 |
|
|
Give a warning whenever a function is used before being declared. In
|
3111 |
|
|
C99 mode (@option{-std=c99} or @option{-std=gnu99}), this warning is
|
3112 |
|
|
enabled by default and it is made into an error by
|
3113 |
|
|
@option{-pedantic-errors}. This warning is also enabled by
|
3114 |
|
|
@option{-Wall}.
|
3115 |
|
|
|
3116 |
|
|
@item -Wimplicit
|
3117 |
|
|
@opindex Wimplicit
|
3118 |
|
|
@opindex Wno-implicit
|
3119 |
|
|
Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}.
|
3120 |
|
|
This warning is enabled by @option{-Wall}.
|
3121 |
|
|
|
3122 |
|
|
@item -Wignored-qualifiers @r{(C and C++ only)}
|
3123 |
|
|
@opindex Wignored-qualifiers
|
3124 |
|
|
@opindex Wno-ignored-qualifiers
|
3125 |
|
|
Warn if the return type of a function has a type qualifier
|
3126 |
|
|
such as @code{const}. For ISO C such a type qualifier has no effect,
|
3127 |
|
|
since the value returned by a function is not an lvalue.
|
3128 |
|
|
For C++, the warning is only emitted for scalar types or @code{void}.
|
3129 |
|
|
ISO C prohibits qualified @code{void} return types on function
|
3130 |
|
|
definitions, so such return types always receive a warning
|
3131 |
|
|
even without this option.
|
3132 |
|
|
|
3133 |
|
|
This warning is also enabled by @option{-Wextra}.
|
3134 |
|
|
|
3135 |
|
|
@item -Wmain
|
3136 |
|
|
@opindex Wmain
|
3137 |
|
|
@opindex Wno-main
|
3138 |
|
|
Warn if the type of @samp{main} is suspicious. @samp{main} should be
|
3139 |
|
|
a function with external linkage, returning int, taking either zero
|
3140 |
|
|
arguments, two, or three arguments of appropriate types. This warning
|
3141 |
|
|
is enabled by default in C++ and is enabled by either @option{-Wall}
|
3142 |
|
|
or @option{-pedantic}.
|
3143 |
|
|
|
3144 |
|
|
@item -Wmissing-braces
|
3145 |
|
|
@opindex Wmissing-braces
|
3146 |
|
|
@opindex Wno-missing-braces
|
3147 |
|
|
Warn if an aggregate or union initializer is not fully bracketed. In
|
3148 |
|
|
the following example, the initializer for @samp{a} is not fully
|
3149 |
|
|
bracketed, but that for @samp{b} is fully bracketed.
|
3150 |
|
|
|
3151 |
|
|
@smallexample
|
3152 |
|
|
int a[2][2] = @{ 0, 1, 2, 3 @};
|
3153 |
|
|
int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @};
|
3154 |
|
|
@end smallexample
|
3155 |
|
|
|
3156 |
|
|
This warning is enabled by @option{-Wall}.
|
3157 |
|
|
|
3158 |
|
|
@item -Wmissing-include-dirs @r{(C, C++, Objective-C and Objective-C++ only)}
|
3159 |
|
|
@opindex Wmissing-include-dirs
|
3160 |
|
|
@opindex Wno-missing-include-dirs
|
3161 |
|
|
Warn if a user-supplied include directory does not exist.
|
3162 |
|
|
|
3163 |
|
|
@item -Wparentheses
|
3164 |
|
|
@opindex Wparentheses
|
3165 |
|
|
@opindex Wno-parentheses
|
3166 |
|
|
Warn if parentheses are omitted in certain contexts, such
|
3167 |
|
|
as when there is an assignment in a context where a truth value
|
3168 |
|
|
is expected, or when operators are nested whose precedence people
|
3169 |
|
|
often get confused about.
|
3170 |
|
|
|
3171 |
|
|
Also warn if a comparison like @samp{x<=y<=z} appears; this is
|
3172 |
|
|
equivalent to @samp{(x<=y ? 1 : 0) <= z}, which is a different
|
3173 |
|
|
interpretation from that of ordinary mathematical notation.
|
3174 |
|
|
|
3175 |
|
|
Also warn about constructions where there may be confusion to which
|
3176 |
|
|
@code{if} statement an @code{else} branch belongs. Here is an example of
|
3177 |
|
|
such a case:
|
3178 |
|
|
|
3179 |
|
|
@smallexample
|
3180 |
|
|
@group
|
3181 |
|
|
@{
|
3182 |
|
|
if (a)
|
3183 |
|
|
if (b)
|
3184 |
|
|
foo ();
|
3185 |
|
|
else
|
3186 |
|
|
bar ();
|
3187 |
|
|
@}
|
3188 |
|
|
@end group
|
3189 |
|
|
@end smallexample
|
3190 |
|
|
|
3191 |
|
|
In C/C++, every @code{else} branch belongs to the innermost possible
|
3192 |
|
|
@code{if} statement, which in this example is @code{if (b)}. This is
|
3193 |
|
|
often not what the programmer expected, as illustrated in the above
|
3194 |
|
|
example by indentation the programmer chose. When there is the
|
3195 |
|
|
potential for this confusion, GCC will issue a warning when this flag
|
3196 |
|
|
is specified. To eliminate the warning, add explicit braces around
|
3197 |
|
|
the innermost @code{if} statement so there is no way the @code{else}
|
3198 |
|
|
could belong to the enclosing @code{if}. The resulting code would
|
3199 |
|
|
look like this:
|
3200 |
|
|
|
3201 |
|
|
@smallexample
|
3202 |
|
|
@group
|
3203 |
|
|
@{
|
3204 |
|
|
if (a)
|
3205 |
|
|
@{
|
3206 |
|
|
if (b)
|
3207 |
|
|
foo ();
|
3208 |
|
|
else
|
3209 |
|
|
bar ();
|
3210 |
|
|
@}
|
3211 |
|
|
@}
|
3212 |
|
|
@end group
|
3213 |
|
|
@end smallexample
|
3214 |
|
|
|
3215 |
|
|
This warning is enabled by @option{-Wall}.
|
3216 |
|
|
|
3217 |
|
|
@item -Wsequence-point
|
3218 |
|
|
@opindex Wsequence-point
|
3219 |
|
|
@opindex Wno-sequence-point
|
3220 |
|
|
Warn about code that may have undefined semantics because of violations
|
3221 |
|
|
of sequence point rules in the C and C++ standards.
|
3222 |
|
|
|
3223 |
|
|
The C and C++ standards defines the order in which expressions in a C/C++
|
3224 |
|
|
program are evaluated in terms of @dfn{sequence points}, which represent
|
3225 |
|
|
a partial ordering between the execution of parts of the program: those
|
3226 |
|
|
executed before the sequence point, and those executed after it. These
|
3227 |
|
|
occur after the evaluation of a full expression (one which is not part
|
3228 |
|
|
of a larger expression), after the evaluation of the first operand of a
|
3229 |
|
|
@code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a
|
3230 |
|
|
function is called (but after the evaluation of its arguments and the
|
3231 |
|
|
expression denoting the called function), and in certain other places.
|
3232 |
|
|
Other than as expressed by the sequence point rules, the order of
|
3233 |
|
|
evaluation of subexpressions of an expression is not specified. All
|
3234 |
|
|
these rules describe only a partial order rather than a total order,
|
3235 |
|
|
since, for example, if two functions are called within one expression
|
3236 |
|
|
with no sequence point between them, the order in which the functions
|
3237 |
|
|
are called is not specified. However, the standards committee have
|
3238 |
|
|
ruled that function calls do not overlap.
|
3239 |
|
|
|
3240 |
|
|
It is not specified when between sequence points modifications to the
|
3241 |
|
|
values of objects take effect. Programs whose behavior depends on this
|
3242 |
|
|
have undefined behavior; the C and C++ standards specify that ``Between
|
3243 |
|
|
the previous and next sequence point an object shall have its stored
|
3244 |
|
|
value modified at most once by the evaluation of an expression.
|
3245 |
|
|
Furthermore, the prior value shall be read only to determine the value
|
3246 |
|
|
to be stored.''. If a program breaks these rules, the results on any
|
3247 |
|
|
particular implementation are entirely unpredictable.
|
3248 |
|
|
|
3249 |
|
|
Examples of code with undefined behavior are @code{a = a++;}, @code{a[n]
|
3250 |
|
|
= b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not
|
3251 |
|
|
diagnosed by this option, and it may give an occasional false positive
|
3252 |
|
|
result, but in general it has been found fairly effective at detecting
|
3253 |
|
|
this sort of problem in programs.
|
3254 |
|
|
|
3255 |
|
|
The standard is worded confusingly, therefore there is some debate
|
3256 |
|
|
over the precise meaning of the sequence point rules in subtle cases.
|
3257 |
|
|
Links to discussions of the problem, including proposed formal
|
3258 |
|
|
definitions, may be found on the GCC readings page, at
|
3259 |
|
|
@w{@uref{http://gcc.gnu.org/readings.html}}.
|
3260 |
|
|
|
3261 |
|
|
This warning is enabled by @option{-Wall} for C and C++.
|
3262 |
|
|
|
3263 |
|
|
@item -Wreturn-type
|
3264 |
|
|
@opindex Wreturn-type
|
3265 |
|
|
@opindex Wno-return-type
|
3266 |
|
|
Warn whenever a function is defined with a return-type that defaults
|
3267 |
|
|
to @code{int}. Also warn about any @code{return} statement with no
|
3268 |
|
|
return-value in a function whose return-type is not @code{void}
|
3269 |
|
|
(falling off the end of the function body is considered returning
|
3270 |
|
|
without a value), and about a @code{return} statement with an
|
3271 |
|
|
expression in a function whose return-type is @code{void}.
|
3272 |
|
|
|
3273 |
|
|
For C++, a function without return type always produces a diagnostic
|
3274 |
|
|
message, even when @option{-Wno-return-type} is specified. The only
|
3275 |
|
|
exceptions are @samp{main} and functions defined in system headers.
|
3276 |
|
|
|
3277 |
|
|
This warning is enabled by @option{-Wall}.
|
3278 |
|
|
|
3279 |
|
|
@item -Wswitch
|
3280 |
|
|
@opindex Wswitch
|
3281 |
|
|
@opindex Wno-switch
|
3282 |
|
|
Warn whenever a @code{switch} statement has an index of enumerated type
|
3283 |
|
|
and lacks a @code{case} for one or more of the named codes of that
|
3284 |
|
|
enumeration. (The presence of a @code{default} label prevents this
|
3285 |
|
|
warning.) @code{case} labels outside the enumeration range also
|
3286 |
|
|
provoke warnings when this option is used (even if there is a
|
3287 |
|
|
@code{default} label).
|
3288 |
|
|
This warning is enabled by @option{-Wall}.
|
3289 |
|
|
|
3290 |
|
|
@item -Wswitch-default
|
3291 |
|
|
@opindex Wswitch-default
|
3292 |
|
|
@opindex Wno-switch-default
|
3293 |
|
|
Warn whenever a @code{switch} statement does not have a @code{default}
|
3294 |
|
|
case.
|
3295 |
|
|
|
3296 |
|
|
@item -Wswitch-enum
|
3297 |
|
|
@opindex Wswitch-enum
|
3298 |
|
|
@opindex Wno-switch-enum
|
3299 |
|
|
Warn whenever a @code{switch} statement has an index of enumerated type
|
3300 |
|
|
and lacks a @code{case} for one or more of the named codes of that
|
3301 |
|
|
enumeration. @code{case} labels outside the enumeration range also
|
3302 |
|
|
provoke warnings when this option is used. The only difference
|
3303 |
|
|
between @option{-Wswitch} and this option is that this option gives a
|
3304 |
|
|
warning about an omitted enumeration code even if there is a
|
3305 |
|
|
@code{default} label.
|
3306 |
|
|
|
3307 |
|
|
@item -Wsync-nand @r{(C and C++ only)}
|
3308 |
|
|
@opindex Wsync-nand
|
3309 |
|
|
@opindex Wno-sync-nand
|
3310 |
|
|
Warn when @code{__sync_fetch_and_nand} and @code{__sync_nand_and_fetch}
|
3311 |
|
|
built-in functions are used. These functions changed semantics in GCC 4.4.
|
3312 |
|
|
|
3313 |
|
|
@item -Wtrigraphs
|
3314 |
|
|
@opindex Wtrigraphs
|
3315 |
|
|
@opindex Wno-trigraphs
|
3316 |
|
|
Warn if any trigraphs are encountered that might change the meaning of
|
3317 |
|
|
the program (trigraphs within comments are not warned about).
|
3318 |
|
|
This warning is enabled by @option{-Wall}.
|
3319 |
|
|
|
3320 |
|
|
@item -Wunused-function
|
3321 |
|
|
@opindex Wunused-function
|
3322 |
|
|
@opindex Wno-unused-function
|
3323 |
|
|
Warn whenever a static function is declared but not defined or a
|
3324 |
|
|
non-inline static function is unused.
|
3325 |
|
|
This warning is enabled by @option{-Wall}.
|
3326 |
|
|
|
3327 |
|
|
@item -Wunused-label
|
3328 |
|
|
@opindex Wunused-label
|
3329 |
|
|
@opindex Wno-unused-label
|
3330 |
|
|
Warn whenever a label is declared but not used.
|
3331 |
|
|
This warning is enabled by @option{-Wall}.
|
3332 |
|
|
|
3333 |
|
|
To suppress this warning use the @samp{unused} attribute
|
3334 |
|
|
(@pxref{Variable Attributes}).
|
3335 |
|
|
|
3336 |
|
|
@item -Wunused-parameter
|
3337 |
|
|
@opindex Wunused-parameter
|
3338 |
|
|
@opindex Wno-unused-parameter
|
3339 |
|
|
Warn whenever a function parameter is unused aside from its declaration.
|
3340 |
|
|
|
3341 |
|
|
To suppress this warning use the @samp{unused} attribute
|
3342 |
|
|
(@pxref{Variable Attributes}).
|
3343 |
|
|
|
3344 |
|
|
@item -Wno-unused-result
|
3345 |
|
|
@opindex Wunused-result
|
3346 |
|
|
@opindex Wno-unused-result
|
3347 |
|
|
Do not warn if a caller of a function marked with attribute
|
3348 |
|
|
@code{warn_unused_result} (@pxref{Variable Attributes}) does not use
|
3349 |
|
|
its return value. The default is @option{-Wunused-result}.
|
3350 |
|
|
|
3351 |
|
|
@item -Wunused-variable
|
3352 |
|
|
@opindex Wunused-variable
|
3353 |
|
|
@opindex Wno-unused-variable
|
3354 |
|
|
Warn whenever a local variable or non-constant static variable is unused
|
3355 |
|
|
aside from its declaration.
|
3356 |
|
|
This warning is enabled by @option{-Wall}.
|
3357 |
|
|
|
3358 |
|
|
To suppress this warning use the @samp{unused} attribute
|
3359 |
|
|
(@pxref{Variable Attributes}).
|
3360 |
|
|
|
3361 |
|
|
@item -Wunused-value
|
3362 |
|
|
@opindex Wunused-value
|
3363 |
|
|
@opindex Wno-unused-value
|
3364 |
|
|
Warn whenever a statement computes a result that is explicitly not
|
3365 |
|
|
used. To suppress this warning cast the unused expression to
|
3366 |
|
|
@samp{void}. This includes an expression-statement or the left-hand
|
3367 |
|
|
side of a comma expression that contains no side effects. For example,
|
3368 |
|
|
an expression such as @samp{x[i,j]} will cause a warning, while
|
3369 |
|
|
@samp{x[(void)i,j]} will not.
|
3370 |
|
|
|
3371 |
|
|
This warning is enabled by @option{-Wall}.
|
3372 |
|
|
|
3373 |
|
|
@item -Wunused
|
3374 |
|
|
@opindex Wunused
|
3375 |
|
|
@opindex Wno-unused
|
3376 |
|
|
All the above @option{-Wunused} options combined.
|
3377 |
|
|
|
3378 |
|
|
In order to get a warning about an unused function parameter, you must
|
3379 |
|
|
either specify @samp{-Wextra -Wunused} (note that @samp{-Wall} implies
|
3380 |
|
|
@samp{-Wunused}), or separately specify @option{-Wunused-parameter}.
|
3381 |
|
|
|
3382 |
|
|
@item -Wuninitialized
|
3383 |
|
|
@opindex Wuninitialized
|
3384 |
|
|
@opindex Wno-uninitialized
|
3385 |
|
|
Warn if an automatic variable is used without first being initialized
|
3386 |
|
|
or if a variable may be clobbered by a @code{setjmp} call. In C++,
|
3387 |
|
|
warn if a non-static reference or non-static @samp{const} member
|
3388 |
|
|
appears in a class without constructors.
|
3389 |
|
|
|
3390 |
|
|
If you want to warn about code which uses the uninitialized value of the
|
3391 |
|
|
variable in its own initializer, use the @option{-Winit-self} option.
|
3392 |
|
|
|
3393 |
|
|
These warnings occur for individual uninitialized or clobbered
|
3394 |
|
|
elements of structure, union or array variables as well as for
|
3395 |
|
|
variables which are uninitialized or clobbered as a whole. They do
|
3396 |
|
|
not occur for variables or elements declared @code{volatile}. Because
|
3397 |
|
|
these warnings depend on optimization, the exact variables or elements
|
3398 |
|
|
for which there are warnings will depend on the precise optimization
|
3399 |
|
|
options and version of GCC used.
|
3400 |
|
|
|
3401 |
|
|
Note that there may be no warning about a variable that is used only
|
3402 |
|
|
to compute a value that itself is never used, because such
|
3403 |
|
|
computations may be deleted by data flow analysis before the warnings
|
3404 |
|
|
are printed.
|
3405 |
|
|
|
3406 |
|
|
These warnings are made optional because GCC is not smart
|
3407 |
|
|
enough to see all the reasons why the code might be correct
|
3408 |
|
|
despite appearing to have an error. Here is one example of how
|
3409 |
|
|
this can happen:
|
3410 |
|
|
|
3411 |
|
|
@smallexample
|
3412 |
|
|
@group
|
3413 |
|
|
@{
|
3414 |
|
|
int x;
|
3415 |
|
|
switch (y)
|
3416 |
|
|
@{
|
3417 |
|
|
case 1: x = 1;
|
3418 |
|
|
break;
|
3419 |
|
|
case 2: x = 4;
|
3420 |
|
|
break;
|
3421 |
|
|
case 3: x = 5;
|
3422 |
|
|
@}
|
3423 |
|
|
foo (x);
|
3424 |
|
|
@}
|
3425 |
|
|
@end group
|
3426 |
|
|
@end smallexample
|
3427 |
|
|
|
3428 |
|
|
@noindent
|
3429 |
|
|
If the value of @code{y} is always 1, 2 or 3, then @code{x} is
|
3430 |
|
|
always initialized, but GCC doesn't know this. Here is
|
3431 |
|
|
another common case:
|
3432 |
|
|
|
3433 |
|
|
@smallexample
|
3434 |
|
|
@{
|
3435 |
|
|
int save_y;
|
3436 |
|
|
if (change_y) save_y = y, y = new_y;
|
3437 |
|
|
@dots{}
|
3438 |
|
|
if (change_y) y = save_y;
|
3439 |
|
|
@}
|
3440 |
|
|
@end smallexample
|
3441 |
|
|
|
3442 |
|
|
@noindent
|
3443 |
|
|
This has no bug because @code{save_y} is used only if it is set.
|
3444 |
|
|
|
3445 |
|
|
@cindex @code{longjmp} warnings
|
3446 |
|
|
This option also warns when a non-volatile automatic variable might be
|
3447 |
|
|
changed by a call to @code{longjmp}. These warnings as well are possible
|
3448 |
|
|
only in optimizing compilation.
|
3449 |
|
|
|
3450 |
|
|
The compiler sees only the calls to @code{setjmp}. It cannot know
|
3451 |
|
|
where @code{longjmp} will be called; in fact, a signal handler could
|
3452 |
|
|
call it at any point in the code. As a result, you may get a warning
|
3453 |
|
|
even when there is in fact no problem because @code{longjmp} cannot
|
3454 |
|
|
in fact be called at the place which would cause a problem.
|
3455 |
|
|
|
3456 |
|
|
Some spurious warnings can be avoided if you declare all the functions
|
3457 |
|
|
you use that never return as @code{noreturn}. @xref{Function
|
3458 |
|
|
Attributes}.
|
3459 |
|
|
|
3460 |
|
|
This warning is enabled by @option{-Wall} or @option{-Wextra}.
|
3461 |
|
|
|
3462 |
|
|
@item -Wunknown-pragmas
|
3463 |
|
|
@opindex Wunknown-pragmas
|
3464 |
|
|
@opindex Wno-unknown-pragmas
|
3465 |
|
|
@cindex warning for unknown pragmas
|
3466 |
|
|
@cindex unknown pragmas, warning
|
3467 |
|
|
@cindex pragmas, warning of unknown
|
3468 |
|
|
Warn when a #pragma directive is encountered which is not understood by
|
3469 |
|
|
GCC@. If this command line option is used, warnings will even be issued
|
3470 |
|
|
for unknown pragmas in system header files. This is not the case if
|
3471 |
|
|
the warnings were only enabled by the @option{-Wall} command line option.
|
3472 |
|
|
|
3473 |
|
|
@item -Wno-pragmas
|
3474 |
|
|
@opindex Wno-pragmas
|
3475 |
|
|
@opindex Wpragmas
|
3476 |
|
|
Do not warn about misuses of pragmas, such as incorrect parameters,
|
3477 |
|
|
invalid syntax, or conflicts between pragmas. See also
|
3478 |
|
|
@samp{-Wunknown-pragmas}.
|
3479 |
|
|
|
3480 |
|
|
@item -Wstrict-aliasing
|
3481 |
|
|
@opindex Wstrict-aliasing
|
3482 |
|
|
@opindex Wno-strict-aliasing
|
3483 |
|
|
This option is only active when @option{-fstrict-aliasing} is active.
|
3484 |
|
|
It warns about code which might break the strict aliasing rules that the
|
3485 |
|
|
compiler is using for optimization. The warning does not catch all
|
3486 |
|
|
cases, but does attempt to catch the more common pitfalls. It is
|
3487 |
|
|
included in @option{-Wall}.
|
3488 |
|
|
It is equivalent to @option{-Wstrict-aliasing=3}
|
3489 |
|
|
|
3490 |
|
|
@item -Wstrict-aliasing=n
|
3491 |
|
|
@opindex Wstrict-aliasing=n
|
3492 |
|
|
@opindex Wno-strict-aliasing=n
|
3493 |
|
|
This option is only active when @option{-fstrict-aliasing} is active.
|
3494 |
|
|
It warns about code which might break the strict aliasing rules that the
|
3495 |
|
|
compiler is using for optimization.
|
3496 |
|
|
Higher levels correspond to higher accuracy (fewer false positives).
|
3497 |
|
|
Higher levels also correspond to more effort, similar to the way -O works.
|
3498 |
|
|
@option{-Wstrict-aliasing} is equivalent to @option{-Wstrict-aliasing=n},
|
3499 |
|
|
with n=3.
|
3500 |
|
|
|
3501 |
|
|
Level 1: Most aggressive, quick, least accurate.
|
3502 |
|
|
Possibly useful when higher levels
|
3503 |
|
|
do not warn but -fstrict-aliasing still breaks the code, as it has very few
|
3504 |
|
|
false negatives. However, it has many false positives.
|
3505 |
|
|
Warns for all pointer conversions between possibly incompatible types,
|
3506 |
|
|
even if never dereferenced. Runs in the frontend only.
|
3507 |
|
|
|
3508 |
|
|
Level 2: Aggressive, quick, not too precise.
|
3509 |
|
|
May still have many false positives (not as many as level 1 though),
|
3510 |
|
|
and few false negatives (but possibly more than level 1).
|
3511 |
|
|
Unlike level 1, it only warns when an address is taken. Warns about
|
3512 |
|
|
incomplete types. Runs in the frontend only.
|
3513 |
|
|
|
3514 |
|
|
Level 3 (default for @option{-Wstrict-aliasing}):
|
3515 |
|
|
Should have very few false positives and few false
|
3516 |
|
|
negatives. Slightly slower than levels 1 or 2 when optimization is enabled.
|
3517 |
|
|
Takes care of the common pun+dereference pattern in the frontend:
|
3518 |
|
|
@code{*(int*)&some_float}.
|
3519 |
|
|
If optimization is enabled, it also runs in the backend, where it deals
|
3520 |
|
|
with multiple statement cases using flow-sensitive points-to information.
|
3521 |
|
|
Only warns when the converted pointer is dereferenced.
|
3522 |
|
|
Does not warn about incomplete types.
|
3523 |
|
|
|
3524 |
|
|
@item -Wstrict-overflow
|
3525 |
|
|
@itemx -Wstrict-overflow=@var{n}
|
3526 |
|
|
@opindex Wstrict-overflow
|
3527 |
|
|
@opindex Wno-strict-overflow
|
3528 |
|
|
This option is only active when @option{-fstrict-overflow} is active.
|
3529 |
|
|
It warns about cases where the compiler optimizes based on the
|
3530 |
|
|
assumption that signed overflow does not occur. Note that it does not
|
3531 |
|
|
warn about all cases where the code might overflow: it only warns
|
3532 |
|
|
about cases where the compiler implements some optimization. Thus
|
3533 |
|
|
this warning depends on the optimization level.
|
3534 |
|
|
|
3535 |
|
|
An optimization which assumes that signed overflow does not occur is
|
3536 |
|
|
perfectly safe if the values of the variables involved are such that
|
3537 |
|
|
overflow never does, in fact, occur. Therefore this warning can
|
3538 |
|
|
easily give a false positive: a warning about code which is not
|
3539 |
|
|
actually a problem. To help focus on important issues, several
|
3540 |
|
|
warning levels are defined. No warnings are issued for the use of
|
3541 |
|
|
undefined signed overflow when estimating how many iterations a loop
|
3542 |
|
|
will require, in particular when determining whether a loop will be
|
3543 |
|
|
executed at all.
|
3544 |
|
|
|
3545 |
|
|
@table @gcctabopt
|
3546 |
|
|
@item -Wstrict-overflow=1
|
3547 |
|
|
Warn about cases which are both questionable and easy to avoid. For
|
3548 |
|
|
example: @code{x + 1 > x}; with @option{-fstrict-overflow}, the
|
3549 |
|
|
compiler will simplify this to @code{1}. This level of
|
3550 |
|
|
@option{-Wstrict-overflow} is enabled by @option{-Wall}; higher levels
|
3551 |
|
|
are not, and must be explicitly requested.
|
3552 |
|
|
|
3553 |
|
|
@item -Wstrict-overflow=2
|
3554 |
|
|
Also warn about other cases where a comparison is simplified to a
|
3555 |
|
|
constant. For example: @code{abs (x) >= 0}. This can only be
|
3556 |
|
|
simplified when @option{-fstrict-overflow} is in effect, because
|
3557 |
|
|
@code{abs (INT_MIN)} overflows to @code{INT_MIN}, which is less than
|
3558 |
|
|
zero. @option{-Wstrict-overflow} (with no level) is the same as
|
3559 |
|
|
@option{-Wstrict-overflow=2}.
|
3560 |
|
|
|
3561 |
|
|
@item -Wstrict-overflow=3
|
3562 |
|
|
Also warn about other cases where a comparison is simplified. For
|
3563 |
|
|
example: @code{x + 1 > 1} will be simplified to @code{x > 0}.
|
3564 |
|
|
|
3565 |
|
|
@item -Wstrict-overflow=4
|
3566 |
|
|
Also warn about other simplifications not covered by the above cases.
|
3567 |
|
|
For example: @code{(x * 10) / 5} will be simplified to @code{x * 2}.
|
3568 |
|
|
|
3569 |
|
|
@item -Wstrict-overflow=5
|
3570 |
|
|
Also warn about cases where the compiler reduces the magnitude of a
|
3571 |
|
|
constant involved in a comparison. For example: @code{x + 2 > y} will
|
3572 |
|
|
be simplified to @code{x + 1 >= y}. This is reported only at the
|
3573 |
|
|
highest warning level because this simplification applies to many
|
3574 |
|
|
comparisons, so this warning level will give a very large number of
|
3575 |
|
|
false positives.
|
3576 |
|
|
@end table
|
3577 |
|
|
|
3578 |
|
|
@item -Warray-bounds
|
3579 |
|
|
@opindex Wno-array-bounds
|
3580 |
|
|
@opindex Warray-bounds
|
3581 |
|
|
This option is only active when @option{-ftree-vrp} is active
|
3582 |
|
|
(default for -O2 and above). It warns about subscripts to arrays
|
3583 |
|
|
that are always out of bounds. This warning is enabled by @option{-Wall}.
|
3584 |
|
|
|
3585 |
|
|
@item -Wno-div-by-zero
|
3586 |
|
|
@opindex Wno-div-by-zero
|
3587 |
|
|
@opindex Wdiv-by-zero
|
3588 |
|
|
Do not warn about compile-time integer division by zero. Floating point
|
3589 |
|
|
division by zero is not warned about, as it can be a legitimate way of
|
3590 |
|
|
obtaining infinities and NaNs.
|
3591 |
|
|
|
3592 |
|
|
@item -Wsystem-headers
|
3593 |
|
|
@opindex Wsystem-headers
|
3594 |
|
|
@opindex Wno-system-headers
|
3595 |
|
|
@cindex warnings from system headers
|
3596 |
|
|
@cindex system headers, warnings from
|
3597 |
|
|
Print warning messages for constructs found in system header files.
|
3598 |
|
|
Warnings from system headers are normally suppressed, on the assumption
|
3599 |
|
|
that they usually do not indicate real problems and would only make the
|
3600 |
|
|
compiler output harder to read. Using this command line option tells
|
3601 |
|
|
GCC to emit warnings from system headers as if they occurred in user
|
3602 |
|
|
code. However, note that using @option{-Wall} in conjunction with this
|
3603 |
|
|
option will @emph{not} warn about unknown pragmas in system
|
3604 |
|
|
headers---for that, @option{-Wunknown-pragmas} must also be used.
|
3605 |
|
|
|
3606 |
|
|
@item -Wfloat-equal
|
3607 |
|
|
@opindex Wfloat-equal
|
3608 |
|
|
@opindex Wno-float-equal
|
3609 |
|
|
Warn if floating point values are used in equality comparisons.
|
3610 |
|
|
|
3611 |
|
|
The idea behind this is that sometimes it is convenient (for the
|
3612 |
|
|
programmer) to consider floating-point values as approximations to
|
3613 |
|
|
infinitely precise real numbers. If you are doing this, then you need
|
3614 |
|
|
to compute (by analyzing the code, or in some other way) the maximum or
|
3615 |
|
|
likely maximum error that the computation introduces, and allow for it
|
3616 |
|
|
when performing comparisons (and when producing output, but that's a
|
3617 |
|
|
different problem). In particular, instead of testing for equality, you
|
3618 |
|
|
would check to see whether the two values have ranges that overlap; and
|
3619 |
|
|
this is done with the relational operators, so equality comparisons are
|
3620 |
|
|
probably mistaken.
|
3621 |
|
|
|
3622 |
|
|
@item -Wtraditional @r{(C and Objective-C only)}
|
3623 |
|
|
@opindex Wtraditional
|
3624 |
|
|
@opindex Wno-traditional
|
3625 |
|
|
Warn about certain constructs that behave differently in traditional and
|
3626 |
|
|
ISO C@. Also warn about ISO C constructs that have no traditional C
|
3627 |
|
|
equivalent, and/or problematic constructs which should be avoided.
|
3628 |
|
|
|
3629 |
|
|
@itemize @bullet
|
3630 |
|
|
@item
|
3631 |
|
|
Macro parameters that appear within string literals in the macro body.
|
3632 |
|
|
In traditional C macro replacement takes place within string literals,
|
3633 |
|
|
but does not in ISO C@.
|
3634 |
|
|
|
3635 |
|
|
@item
|
3636 |
|
|
In traditional C, some preprocessor directives did not exist.
|
3637 |
|
|
Traditional preprocessors would only consider a line to be a directive
|
3638 |
|
|
if the @samp{#} appeared in column 1 on the line. Therefore
|
3639 |
|
|
@option{-Wtraditional} warns about directives that traditional C
|
3640 |
|
|
understands but would ignore because the @samp{#} does not appear as the
|
3641 |
|
|
first character on the line. It also suggests you hide directives like
|
3642 |
|
|
@samp{#pragma} not understood by traditional C by indenting them. Some
|
3643 |
|
|
traditional implementations would not recognize @samp{#elif}, so it
|
3644 |
|
|
suggests avoiding it altogether.
|
3645 |
|
|
|
3646 |
|
|
@item
|
3647 |
|
|
A function-like macro that appears without arguments.
|
3648 |
|
|
|
3649 |
|
|
@item
|
3650 |
|
|
The unary plus operator.
|
3651 |
|
|
|
3652 |
|
|
@item
|
3653 |
|
|
The @samp{U} integer constant suffix, or the @samp{F} or @samp{L} floating point
|
3654 |
|
|
constant suffixes. (Traditional C does support the @samp{L} suffix on integer
|
3655 |
|
|
constants.) Note, these suffixes appear in macros defined in the system
|
3656 |
|
|
headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}.
|
3657 |
|
|
Use of these macros in user code might normally lead to spurious
|
3658 |
|
|
warnings, however GCC's integrated preprocessor has enough context to
|
3659 |
|
|
avoid warning in these cases.
|
3660 |
|
|
|
3661 |
|
|
@item
|
3662 |
|
|
A function declared external in one block and then used after the end of
|
3663 |
|
|
the block.
|
3664 |
|
|
|
3665 |
|
|
@item
|
3666 |
|
|
A @code{switch} statement has an operand of type @code{long}.
|
3667 |
|
|
|
3668 |
|
|
@item
|
3669 |
|
|
A non-@code{static} function declaration follows a @code{static} one.
|
3670 |
|
|
This construct is not accepted by some traditional C compilers.
|
3671 |
|
|
|
3672 |
|
|
@item
|
3673 |
|
|
The ISO type of an integer constant has a different width or
|
3674 |
|
|
signedness from its traditional type. This warning is only issued if
|
3675 |
|
|
the base of the constant is ten. I.e.@: hexadecimal or octal values, which
|
3676 |
|
|
typically represent bit patterns, are not warned about.
|
3677 |
|
|
|
3678 |
|
|
@item
|
3679 |
|
|
Usage of ISO string concatenation is detected.
|
3680 |
|
|
|
3681 |
|
|
@item
|
3682 |
|
|
Initialization of automatic aggregates.
|
3683 |
|
|
|
3684 |
|
|
@item
|
3685 |
|
|
Identifier conflicts with labels. Traditional C lacks a separate
|
3686 |
|
|
namespace for labels.
|
3687 |
|
|
|
3688 |
|
|
@item
|
3689 |
|
|
Initialization of unions. If the initializer is zero, the warning is
|
3690 |
|
|
omitted. This is done under the assumption that the zero initializer in
|
3691 |
|
|
user code appears conditioned on e.g.@: @code{__STDC__} to avoid missing
|
3692 |
|
|
initializer warnings and relies on default initialization to zero in the
|
3693 |
|
|
traditional C case.
|
3694 |
|
|
|
3695 |
|
|
@item
|
3696 |
|
|
Conversions by prototypes between fixed/floating point values and vice
|
3697 |
|
|
versa. The absence of these prototypes when compiling with traditional
|
3698 |
|
|
C would cause serious problems. This is a subset of the possible
|
3699 |
|
|
conversion warnings, for the full set use @option{-Wtraditional-conversion}.
|
3700 |
|
|
|
3701 |
|
|
@item
|
3702 |
|
|
Use of ISO C style function definitions. This warning intentionally is
|
3703 |
|
|
@emph{not} issued for prototype declarations or variadic functions
|
3704 |
|
|
because these ISO C features will appear in your code when using
|
3705 |
|
|
libiberty's traditional C compatibility macros, @code{PARAMS} and
|
3706 |
|
|
@code{VPARAMS}. This warning is also bypassed for nested functions
|
3707 |
|
|
because that feature is already a GCC extension and thus not relevant to
|
3708 |
|
|
traditional C compatibility.
|
3709 |
|
|
@end itemize
|
3710 |
|
|
|
3711 |
|
|
@item -Wtraditional-conversion @r{(C and Objective-C only)}
|
3712 |
|
|
@opindex Wtraditional-conversion
|
3713 |
|
|
@opindex Wno-traditional-conversion
|
3714 |
|
|
Warn if a prototype causes a type conversion that is different from what
|
3715 |
|
|
would happen to the same argument in the absence of a prototype. This
|
3716 |
|
|
includes conversions of fixed point to floating and vice versa, and
|
3717 |
|
|
conversions changing the width or signedness of a fixed point argument
|
3718 |
|
|
except when the same as the default promotion.
|
3719 |
|
|
|
3720 |
|
|
@item -Wdeclaration-after-statement @r{(C and Objective-C only)}
|
3721 |
|
|
@opindex Wdeclaration-after-statement
|
3722 |
|
|
@opindex Wno-declaration-after-statement
|
3723 |
|
|
Warn when a declaration is found after a statement in a block. This
|
3724 |
|
|
construct, known from C++, was introduced with ISO C99 and is by default
|
3725 |
|
|
allowed in GCC@. It is not supported by ISO C90 and was not supported by
|
3726 |
|
|
GCC versions before GCC 3.0. @xref{Mixed Declarations}.
|
3727 |
|
|
|
3728 |
|
|
@item -Wundef
|
3729 |
|
|
@opindex Wundef
|
3730 |
|
|
@opindex Wno-undef
|
3731 |
|
|
Warn if an undefined identifier is evaluated in an @samp{#if} directive.
|
3732 |
|
|
|
3733 |
|
|
@item -Wno-endif-labels
|
3734 |
|
|
@opindex Wno-endif-labels
|
3735 |
|
|
@opindex Wendif-labels
|
3736 |
|
|
Do not warn whenever an @samp{#else} or an @samp{#endif} are followed by text.
|
3737 |
|
|
|
3738 |
|
|
@item -Wshadow
|
3739 |
|
|
@opindex Wshadow
|
3740 |
|
|
@opindex Wno-shadow
|
3741 |
|
|
Warn whenever a local variable shadows another local variable, parameter or
|
3742 |
|
|
global variable or whenever a built-in function is shadowed.
|
3743 |
|
|
|
3744 |
|
|
@item -Wlarger-than=@var{len}
|
3745 |
|
|
@opindex Wlarger-than=@var{len}
|
3746 |
|
|
@opindex Wlarger-than-@var{len}
|
3747 |
|
|
Warn whenever an object of larger than @var{len} bytes is defined.
|
3748 |
|
|
|
3749 |
|
|
@item -Wframe-larger-than=@var{len}
|
3750 |
|
|
@opindex Wframe-larger-than
|
3751 |
|
|
Warn if the size of a function frame is larger than @var{len} bytes.
|
3752 |
|
|
The computation done to determine the stack frame size is approximate
|
3753 |
|
|
and not conservative.
|
3754 |
|
|
The actual requirements may be somewhat greater than @var{len}
|
3755 |
|
|
even if you do not get a warning. In addition, any space allocated
|
3756 |
|
|
via @code{alloca}, variable-length arrays, or related constructs
|
3757 |
|
|
is not included by the compiler when determining
|
3758 |
|
|
whether or not to issue a warning.
|
3759 |
|
|
|
3760 |
|
|
@item -Wunsafe-loop-optimizations
|
3761 |
|
|
@opindex Wunsafe-loop-optimizations
|
3762 |
|
|
@opindex Wno-unsafe-loop-optimizations
|
3763 |
|
|
Warn if the loop cannot be optimized because the compiler could not
|
3764 |
|
|
assume anything on the bounds of the loop indices. With
|
3765 |
|
|
@option{-funsafe-loop-optimizations} warn if the compiler made
|
3766 |
|
|
such assumptions.
|
3767 |
|
|
|
3768 |
|
|
@item -Wno-pedantic-ms-format @r{(MinGW targets only)}
|
3769 |
|
|
@opindex Wno-pedantic-ms-format
|
3770 |
|
|
@opindex Wpedantic-ms-format
|
3771 |
|
|
Disables the warnings about non-ISO @code{printf} / @code{scanf} format
|
3772 |
|
|
width specifiers @code{I32}, @code{I64}, and @code{I} used on Windows targets
|
3773 |
|
|
depending on the MS runtime, when you are using the options @option{-Wformat}
|
3774 |
|
|
and @option{-pedantic} without gnu-extensions.
|
3775 |
|
|
|
3776 |
|
|
@item -Wpointer-arith
|
3777 |
|
|
@opindex Wpointer-arith
|
3778 |
|
|
@opindex Wno-pointer-arith
|
3779 |
|
|
Warn about anything that depends on the ``size of'' a function type or
|
3780 |
|
|
of @code{void}. GNU C assigns these types a size of 1, for
|
3781 |
|
|
convenience in calculations with @code{void *} pointers and pointers
|
3782 |
|
|
to functions. In C++, warn also when an arithmetic operation involves
|
3783 |
|
|
@code{NULL}. This warning is also enabled by @option{-pedantic}.
|
3784 |
|
|
|
3785 |
|
|
@item -Wtype-limits
|
3786 |
|
|
@opindex Wtype-limits
|
3787 |
|
|
@opindex Wno-type-limits
|
3788 |
|
|
Warn if a comparison is always true or always false due to the limited
|
3789 |
|
|
range of the data type, but do not warn for constant expressions. For
|
3790 |
|
|
example, warn if an unsigned variable is compared against zero with
|
3791 |
|
|
@samp{<} or @samp{>=}. This warning is also enabled by
|
3792 |
|
|
@option{-Wextra}.
|
3793 |
|
|
|
3794 |
|
|
@item -Wbad-function-cast @r{(C and Objective-C only)}
|
3795 |
|
|
@opindex Wbad-function-cast
|
3796 |
|
|
@opindex Wno-bad-function-cast
|
3797 |
|
|
Warn whenever a function call is cast to a non-matching type.
|
3798 |
|
|
For example, warn if @code{int malloc()} is cast to @code{anything *}.
|
3799 |
|
|
|
3800 |
|
|
@item -Wc++-compat @r{(C and Objective-C only)}
|
3801 |
|
|
Warn about ISO C constructs that are outside of the common subset of
|
3802 |
|
|
ISO C and ISO C++, e.g.@: request for implicit conversion from
|
3803 |
|
|
@code{void *} to a pointer to non-@code{void} type.
|
3804 |
|
|
|
3805 |
|
|
@item -Wc++0x-compat @r{(C++ and Objective-C++ only)}
|
3806 |
|
|
Warn about C++ constructs whose meaning differs between ISO C++ 1998 and
|
3807 |
|
|
ISO C++ 200x, e.g., identifiers in ISO C++ 1998 that will become keywords
|
3808 |
|
|
in ISO C++ 200x. This warning is enabled by @option{-Wall}.
|
3809 |
|
|
|
3810 |
|
|
@item -Wcast-qual
|
3811 |
|
|
@opindex Wcast-qual
|
3812 |
|
|
@opindex Wno-cast-qual
|
3813 |
|
|
Warn whenever a pointer is cast so as to remove a type qualifier from
|
3814 |
|
|
the target type. For example, warn if a @code{const char *} is cast
|
3815 |
|
|
to an ordinary @code{char *}.
|
3816 |
|
|
|
3817 |
|
|
Also warn when making a cast which introduces a type qualifier in an
|
3818 |
|
|
unsafe way. For example, casting @code{char **} to @code{const char **}
|
3819 |
|
|
is unsafe, as in this example:
|
3820 |
|
|
|
3821 |
|
|
@smallexample
|
3822 |
|
|
/* p is char ** value. */
|
3823 |
|
|
const char **q = (const char **) p;
|
3824 |
|
|
/* Assignment of readonly string to const char * is OK. */
|
3825 |
|
|
*q = "string";
|
3826 |
|
|
/* Now char** pointer points to read-only memory. */
|
3827 |
|
|
**p = 'b';
|
3828 |
|
|
@end smallexample
|
3829 |
|
|
|
3830 |
|
|
@item -Wcast-align
|
3831 |
|
|
@opindex Wcast-align
|
3832 |
|
|
@opindex Wno-cast-align
|
3833 |
|
|
Warn whenever a pointer is cast such that the required alignment of the
|
3834 |
|
|
target is increased. For example, warn if a @code{char *} is cast to
|
3835 |
|
|
an @code{int *} on machines where integers can only be accessed at
|
3836 |
|
|
two- or four-byte boundaries.
|
3837 |
|
|
|
3838 |
|
|
@item -Wwrite-strings
|
3839 |
|
|
@opindex Wwrite-strings
|
3840 |
|
|
@opindex Wno-write-strings
|
3841 |
|
|
When compiling C, give string constants the type @code{const
|
3842 |
|
|
char[@var{length}]} so that copying the address of one into a
|
3843 |
|
|
non-@code{const} @code{char *} pointer will get a warning. These
|
3844 |
|
|
warnings will help you find at compile time code that can try to write
|
3845 |
|
|
into a string constant, but only if you have been very careful about
|
3846 |
|
|
using @code{const} in declarations and prototypes. Otherwise, it will
|
3847 |
|
|
just be a nuisance. This is why we did not make @option{-Wall} request
|
3848 |
|
|
these warnings.
|
3849 |
|
|
|
3850 |
|
|
When compiling C++, warn about the deprecated conversion from string
|
3851 |
|
|
literals to @code{char *}. This warning is enabled by default for C++
|
3852 |
|
|
programs.
|
3853 |
|
|
|
3854 |
|
|
@item -Wclobbered
|
3855 |
|
|
@opindex Wclobbered
|
3856 |
|
|
@opindex Wno-clobbered
|
3857 |
|
|
Warn for variables that might be changed by @samp{longjmp} or
|
3858 |
|
|
@samp{vfork}. This warning is also enabled by @option{-Wextra}.
|
3859 |
|
|
|
3860 |
|
|
@item -Wconversion
|
3861 |
|
|
@opindex Wconversion
|
3862 |
|
|
@opindex Wno-conversion
|
3863 |
|
|
Warn for implicit conversions that may alter a value. This includes
|
3864 |
|
|
conversions between real and integer, like @code{abs (x)} when
|
3865 |
|
|
@code{x} is @code{double}; conversions between signed and unsigned,
|
3866 |
|
|
like @code{unsigned ui = -1}; and conversions to smaller types, like
|
3867 |
|
|
@code{sqrtf (M_PI)}. Do not warn for explicit casts like @code{abs
|
3868 |
|
|
((int) x)} and @code{ui = (unsigned) -1}, or if the value is not
|
3869 |
|
|
changed by the conversion like in @code{abs (2.0)}. Warnings about
|
3870 |
|
|
conversions between signed and unsigned integers can be disabled by
|
3871 |
|
|
using @option{-Wno-sign-conversion}.
|
3872 |
|
|
|
3873 |
|
|
For C++, also warn for confusing overload resolution for user-defined
|
3874 |
|
|
conversions; and conversions that will never use a type conversion
|
3875 |
|
|
operator: conversions to @code{void}, the same type, a base class or a
|
3876 |
|
|
reference to them. Warnings about conversions between signed and
|
3877 |
|
|
unsigned integers are disabled by default in C++ unless
|
3878 |
|
|
@option{-Wsign-conversion} is explicitly enabled.
|
3879 |
|
|
|
3880 |
|
|
@item -Wno-conversion-null @r{(C++ and Objective-C++ only)}
|
3881 |
|
|
@opindex Wconversion-null
|
3882 |
|
|
@opindex Wno-conversion-null
|
3883 |
|
|
Do not warn for conversions between @code{NULL} and non-pointer
|
3884 |
|
|
types. @option{-Wconversion-null} is enabled by default.
|
3885 |
|
|
|
3886 |
|
|
@item -Wempty-body
|
3887 |
|
|
@opindex Wempty-body
|
3888 |
|
|
@opindex Wno-empty-body
|
3889 |
|
|
Warn if an empty body occurs in an @samp{if}, @samp{else} or @samp{do
|
3890 |
|
|
while} statement. This warning is also enabled by @option{-Wextra}.
|
3891 |
|
|
|
3892 |
|
|
@item -Wenum-compare
|
3893 |
|
|
@opindex Wenum-compare
|
3894 |
|
|
@opindex Wno-enum-compare
|
3895 |
|
|
Warn about a comparison between values of different enum types. In C++
|
3896 |
|
|
this warning is enabled by default. In C this warning is enabled by
|
3897 |
|
|
@option{-Wall}.
|
3898 |
|
|
|
3899 |
|
|
@item -Wjump-misses-init @r{(C, Objective-C only)}
|
3900 |
|
|
@opindex Wjump-misses-init
|
3901 |
|
|
@opindex Wno-jump-misses-init
|
3902 |
|
|
Warn if a @code{goto} statement or a @code{switch} statement jumps
|
3903 |
|
|
forward across the initialization of a variable, or jumps backward to a
|
3904 |
|
|
label after the variable has been initialized. This only warns about
|
3905 |
|
|
variables which are initialized when they are declared. This warning is
|
3906 |
|
|
only supported for C and Objective C; in C++ this sort of branch is an
|
3907 |
|
|
error in any case.
|
3908 |
|
|
|
3909 |
|
|
@option{-Wjump-misses-init} is included in @option{-Wc++-compat}. It
|
3910 |
|
|
can be disabled with the @option{-Wno-jump-misses-init} option.
|
3911 |
|
|
|
3912 |
|
|
@item -Wsign-compare
|
3913 |
|
|
@opindex Wsign-compare
|
3914 |
|
|
@opindex Wno-sign-compare
|
3915 |
|
|
@cindex warning for comparison of signed and unsigned values
|
3916 |
|
|
@cindex comparison of signed and unsigned values, warning
|
3917 |
|
|
@cindex signed and unsigned values, comparison warning
|
3918 |
|
|
Warn when a comparison between signed and unsigned values could produce
|
3919 |
|
|
an incorrect result when the signed value is converted to unsigned.
|
3920 |
|
|
This warning is also enabled by @option{-Wextra}; to get the other warnings
|
3921 |
|
|
of @option{-Wextra} without this warning, use @samp{-Wextra -Wno-sign-compare}.
|
3922 |
|
|
|
3923 |
|
|
@item -Wsign-conversion
|
3924 |
|
|
@opindex Wsign-conversion
|
3925 |
|
|
@opindex Wno-sign-conversion
|
3926 |
|
|
Warn for implicit conversions that may change the sign of an integer
|
3927 |
|
|
value, like assigning a signed integer expression to an unsigned
|
3928 |
|
|
integer variable. An explicit cast silences the warning. In C, this
|
3929 |
|
|
option is enabled also by @option{-Wconversion}.
|
3930 |
|
|
|
3931 |
|
|
@item -Waddress
|
3932 |
|
|
@opindex Waddress
|
3933 |
|
|
@opindex Wno-address
|
3934 |
|
|
Warn about suspicious uses of memory addresses. These include using
|
3935 |
|
|
the address of a function in a conditional expression, such as
|
3936 |
|
|
@code{void func(void); if (func)}, and comparisons against the memory
|
3937 |
|
|
address of a string literal, such as @code{if (x == "abc")}. Such
|
3938 |
|
|
uses typically indicate a programmer error: the address of a function
|
3939 |
|
|
always evaluates to true, so their use in a conditional usually
|
3940 |
|
|
indicate that the programmer forgot the parentheses in a function
|
3941 |
|
|
call; and comparisons against string literals result in unspecified
|
3942 |
|
|
behavior and are not portable in C, so they usually indicate that the
|
3943 |
|
|
programmer intended to use @code{strcmp}. This warning is enabled by
|
3944 |
|
|
@option{-Wall}.
|
3945 |
|
|
|
3946 |
|
|
@item -Wlogical-op
|
3947 |
|
|
@opindex Wlogical-op
|
3948 |
|
|
@opindex Wno-logical-op
|
3949 |
|
|
Warn about suspicious uses of logical operators in expressions.
|
3950 |
|
|
This includes using logical operators in contexts where a
|
3951 |
|
|
bit-wise operator is likely to be expected.
|
3952 |
|
|
|
3953 |
|
|
@item -Waggregate-return
|
3954 |
|
|
@opindex Waggregate-return
|
3955 |
|
|
@opindex Wno-aggregate-return
|
3956 |
|
|
Warn if any functions that return structures or unions are defined or
|
3957 |
|
|
called. (In languages where you can return an array, this also elicits
|
3958 |
|
|
a warning.)
|
3959 |
|
|
|
3960 |
|
|
@item -Wno-attributes
|
3961 |
|
|
@opindex Wno-attributes
|
3962 |
|
|
@opindex Wattributes
|
3963 |
|
|
Do not warn if an unexpected @code{__attribute__} is used, such as
|
3964 |
|
|
unrecognized attributes, function attributes applied to variables,
|
3965 |
|
|
etc. This will not stop errors for incorrect use of supported
|
3966 |
|
|
attributes.
|
3967 |
|
|
|
3968 |
|
|
@item -Wno-builtin-macro-redefined
|
3969 |
|
|
@opindex Wno-builtin-macro-redefined
|
3970 |
|
|
@opindex Wbuiltin-macro-redefined
|
3971 |
|
|
Do not warn if certain built-in macros are redefined. This suppresses
|
3972 |
|
|
warnings for redefinition of @code{__TIMESTAMP__}, @code{__TIME__},
|
3973 |
|
|
@code{__DATE__}, @code{__FILE__}, and @code{__BASE_FILE__}.
|
3974 |
|
|
|
3975 |
|
|
@item -Wstrict-prototypes @r{(C and Objective-C only)}
|
3976 |
|
|
@opindex Wstrict-prototypes
|
3977 |
|
|
@opindex Wno-strict-prototypes
|
3978 |
|
|
Warn if a function is declared or defined without specifying the
|
3979 |
|
|
argument types. (An old-style function definition is permitted without
|
3980 |
|
|
a warning if preceded by a declaration which specifies the argument
|
3981 |
|
|
types.)
|
3982 |
|
|
|
3983 |
|
|
@item -Wold-style-declaration @r{(C and Objective-C only)}
|
3984 |
|
|
@opindex Wold-style-declaration
|
3985 |
|
|
@opindex Wno-old-style-declaration
|
3986 |
|
|
Warn for obsolescent usages, according to the C Standard, in a
|
3987 |
|
|
declaration. For example, warn if storage-class specifiers like
|
3988 |
|
|
@code{static} are not the first things in a declaration. This warning
|
3989 |
|
|
is also enabled by @option{-Wextra}.
|
3990 |
|
|
|
3991 |
|
|
@item -Wold-style-definition @r{(C and Objective-C only)}
|
3992 |
|
|
@opindex Wold-style-definition
|
3993 |
|
|
@opindex Wno-old-style-definition
|
3994 |
|
|
Warn if an old-style function definition is used. A warning is given
|
3995 |
|
|
even if there is a previous prototype.
|
3996 |
|
|
|
3997 |
|
|
@item -Wmissing-parameter-type @r{(C and Objective-C only)}
|
3998 |
|
|
@opindex Wmissing-parameter-type
|
3999 |
|
|
@opindex Wno-missing-parameter-type
|
4000 |
|
|
A function parameter is declared without a type specifier in K&R-style
|
4001 |
|
|
functions:
|
4002 |
|
|
|
4003 |
|
|
@smallexample
|
4004 |
|
|
void foo(bar) @{ @}
|
4005 |
|
|
@end smallexample
|
4006 |
|
|
|
4007 |
|
|
This warning is also enabled by @option{-Wextra}.
|
4008 |
|
|
|
4009 |
|
|
@item -Wmissing-prototypes @r{(C and Objective-C only)}
|
4010 |
|
|
@opindex Wmissing-prototypes
|
4011 |
|
|
@opindex Wno-missing-prototypes
|
4012 |
|
|
Warn if a global function is defined without a previous prototype
|
4013 |
|
|
declaration. This warning is issued even if the definition itself
|
4014 |
|
|
provides a prototype. The aim is to detect global functions that fail
|
4015 |
|
|
to be declared in header files.
|
4016 |
|
|
|
4017 |
|
|
@item -Wmissing-declarations
|
4018 |
|
|
@opindex Wmissing-declarations
|
4019 |
|
|
@opindex Wno-missing-declarations
|
4020 |
|
|
Warn if a global function is defined without a previous declaration.
|
4021 |
|
|
Do so even if the definition itself provides a prototype.
|
4022 |
|
|
Use this option to detect global functions that are not declared in
|
4023 |
|
|
header files. In C++, no warnings are issued for function templates,
|
4024 |
|
|
or for inline functions, or for functions in anonymous namespaces.
|
4025 |
|
|
|
4026 |
|
|
@item -Wmissing-field-initializers
|
4027 |
|
|
@opindex Wmissing-field-initializers
|
4028 |
|
|
@opindex Wno-missing-field-initializers
|
4029 |
|
|
@opindex W
|
4030 |
|
|
@opindex Wextra
|
4031 |
|
|
@opindex Wno-extra
|
4032 |
|
|
Warn if a structure's initializer has some fields missing. For
|
4033 |
|
|
example, the following code would cause such a warning, because
|
4034 |
|
|
@code{x.h} is implicitly zero:
|
4035 |
|
|
|
4036 |
|
|
@smallexample
|
4037 |
|
|
struct s @{ int f, g, h; @};
|
4038 |
|
|
struct s x = @{ 3, 4 @};
|
4039 |
|
|
@end smallexample
|
4040 |
|
|
|
4041 |
|
|
This option does not warn about designated initializers, so the following
|
4042 |
|
|
modification would not trigger a warning:
|
4043 |
|
|
|
4044 |
|
|
@smallexample
|
4045 |
|
|
struct s @{ int f, g, h; @};
|
4046 |
|
|
struct s x = @{ .f = 3, .g = 4 @};
|
4047 |
|
|
@end smallexample
|
4048 |
|
|
|
4049 |
|
|
This warning is included in @option{-Wextra}. To get other @option{-Wextra}
|
4050 |
|
|
warnings without this one, use @samp{-Wextra -Wno-missing-field-initializers}.
|
4051 |
|
|
|
4052 |
|
|
@item -Wmissing-noreturn
|
4053 |
|
|
@opindex Wmissing-noreturn
|
4054 |
|
|
@opindex Wno-missing-noreturn
|
4055 |
|
|
Warn about functions which might be candidates for attribute @code{noreturn}.
|
4056 |
|
|
Note these are only possible candidates, not absolute ones. Care should
|
4057 |
|
|
be taken to manually verify functions actually do not ever return before
|
4058 |
|
|
adding the @code{noreturn} attribute, otherwise subtle code generation
|
4059 |
|
|
bugs could be introduced. You will not get a warning for @code{main} in
|
4060 |
|
|
hosted C environments.
|
4061 |
|
|
|
4062 |
|
|
@item -Wmissing-format-attribute
|
4063 |
|
|
@opindex Wmissing-format-attribute
|
4064 |
|
|
@opindex Wno-missing-format-attribute
|
4065 |
|
|
@opindex Wformat
|
4066 |
|
|
@opindex Wno-format
|
4067 |
|
|
Warn about function pointers which might be candidates for @code{format}
|
4068 |
|
|
attributes. Note these are only possible candidates, not absolute ones.
|
4069 |
|
|
GCC will guess that function pointers with @code{format} attributes that
|
4070 |
|
|
are used in assignment, initialization, parameter passing or return
|
4071 |
|
|
statements should have a corresponding @code{format} attribute in the
|
4072 |
|
|
resulting type. I.e.@: the left-hand side of the assignment or
|
4073 |
|
|
initialization, the type of the parameter variable, or the return type
|
4074 |
|
|
of the containing function respectively should also have a @code{format}
|
4075 |
|
|
attribute to avoid the warning.
|
4076 |
|
|
|
4077 |
|
|
GCC will also warn about function definitions which might be
|
4078 |
|
|
candidates for @code{format} attributes. Again, these are only
|
4079 |
|
|
possible candidates. GCC will guess that @code{format} attributes
|
4080 |
|
|
might be appropriate for any function that calls a function like
|
4081 |
|
|
@code{vprintf} or @code{vscanf}, but this might not always be the
|
4082 |
|
|
case, and some functions for which @code{format} attributes are
|
4083 |
|
|
appropriate may not be detected.
|
4084 |
|
|
|
4085 |
|
|
@item -Wno-multichar
|
4086 |
|
|
@opindex Wno-multichar
|
4087 |
|
|
@opindex Wmultichar
|
4088 |
|
|
Do not warn if a multicharacter constant (@samp{'FOOF'}) is used.
|
4089 |
|
|
Usually they indicate a typo in the user's code, as they have
|
4090 |
|
|
implementation-defined values, and should not be used in portable code.
|
4091 |
|
|
|
4092 |
|
|
@item -Wnormalized=<none|id|nfc|nfkc>
|
4093 |
|
|
@opindex Wnormalized=
|
4094 |
|
|
@cindex NFC
|
4095 |
|
|
@cindex NFKC
|
4096 |
|
|
@cindex character set, input normalization
|
4097 |
|
|
In ISO C and ISO C++, two identifiers are different if they are
|
4098 |
|
|
different sequences of characters. However, sometimes when characters
|
4099 |
|
|
outside the basic ASCII character set are used, you can have two
|
4100 |
|
|
different character sequences that look the same. To avoid confusion,
|
4101 |
|
|
the ISO 10646 standard sets out some @dfn{normalization rules} which
|
4102 |
|
|
when applied ensure that two sequences that look the same are turned into
|
4103 |
|
|
the same sequence. GCC can warn you if you are using identifiers which
|
4104 |
|
|
have not been normalized; this option controls that warning.
|
4105 |
|
|
|
4106 |
|
|
There are four levels of warning that GCC supports. The default is
|
4107 |
|
|
@option{-Wnormalized=nfc}, which warns about any identifier which is
|
4108 |
|
|
not in the ISO 10646 ``C'' normalized form, @dfn{NFC}. NFC is the
|
4109 |
|
|
recommended form for most uses.
|
4110 |
|
|
|
4111 |
|
|
Unfortunately, there are some characters which ISO C and ISO C++ allow
|
4112 |
|
|
in identifiers that when turned into NFC aren't allowable as
|
4113 |
|
|
identifiers. That is, there's no way to use these symbols in portable
|
4114 |
|
|
ISO C or C++ and have all your identifiers in NFC@.
|
4115 |
|
|
@option{-Wnormalized=id} suppresses the warning for these characters.
|
4116 |
|
|
It is hoped that future versions of the standards involved will correct
|
4117 |
|
|
this, which is why this option is not the default.
|
4118 |
|
|
|
4119 |
|
|
You can switch the warning off for all characters by writing
|
4120 |
|
|
@option{-Wnormalized=none}. You would only want to do this if you
|
4121 |
|
|
were using some other normalization scheme (like ``D''), because
|
4122 |
|
|
otherwise you can easily create bugs that are literally impossible to see.
|
4123 |
|
|
|
4124 |
|
|
Some characters in ISO 10646 have distinct meanings but look identical
|
4125 |
|
|
in some fonts or display methodologies, especially once formatting has
|
4126 |
|
|
been applied. For instance @code{\u207F}, ``SUPERSCRIPT LATIN SMALL
|
4127 |
|
|
LETTER N'', will display just like a regular @code{n} which has been
|
4128 |
|
|
placed in a superscript. ISO 10646 defines the @dfn{NFKC}
|
4129 |
|
|
normalization scheme to convert all these into a standard form as
|
4130 |
|
|
well, and GCC will warn if your code is not in NFKC if you use
|
4131 |
|
|
@option{-Wnormalized=nfkc}. This warning is comparable to warning
|
4132 |
|
|
about every identifier that contains the letter O because it might be
|
4133 |
|
|
confused with the digit 0, and so is not the default, but may be
|
4134 |
|
|
useful as a local coding convention if the programming environment is
|
4135 |
|
|
unable to be fixed to display these characters distinctly.
|
4136 |
|
|
|
4137 |
|
|
@item -Wno-deprecated
|
4138 |
|
|
@opindex Wno-deprecated
|
4139 |
|
|
@opindex Wdeprecated
|
4140 |
|
|
Do not warn about usage of deprecated features. @xref{Deprecated Features}.
|
4141 |
|
|
|
4142 |
|
|
@item -Wno-deprecated-declarations
|
4143 |
|
|
@opindex Wno-deprecated-declarations
|
4144 |
|
|
@opindex Wdeprecated-declarations
|
4145 |
|
|
Do not warn about uses of functions (@pxref{Function Attributes}),
|
4146 |
|
|
variables (@pxref{Variable Attributes}), and types (@pxref{Type
|
4147 |
|
|
Attributes}) marked as deprecated by using the @code{deprecated}
|
4148 |
|
|
attribute.
|
4149 |
|
|
|
4150 |
|
|
@item -Wno-overflow
|
4151 |
|
|
@opindex Wno-overflow
|
4152 |
|
|
@opindex Woverflow
|
4153 |
|
|
Do not warn about compile-time overflow in constant expressions.
|
4154 |
|
|
|
4155 |
|
|
@item -Woverride-init @r{(C and Objective-C only)}
|
4156 |
|
|
@opindex Woverride-init
|
4157 |
|
|
@opindex Wno-override-init
|
4158 |
|
|
@opindex W
|
4159 |
|
|
@opindex Wextra
|
4160 |
|
|
@opindex Wno-extra
|
4161 |
|
|
Warn if an initialized field without side effects is overridden when
|
4162 |
|
|
using designated initializers (@pxref{Designated Inits, , Designated
|
4163 |
|
|
Initializers}).
|
4164 |
|
|
|
4165 |
|
|
This warning is included in @option{-Wextra}. To get other
|
4166 |
|
|
@option{-Wextra} warnings without this one, use @samp{-Wextra
|
4167 |
|
|
-Wno-override-init}.
|
4168 |
|
|
|
4169 |
|
|
@item -Wpacked
|
4170 |
|
|
@opindex Wpacked
|
4171 |
|
|
@opindex Wno-packed
|
4172 |
|
|
Warn if a structure is given the packed attribute, but the packed
|
4173 |
|
|
attribute has no effect on the layout or size of the structure.
|
4174 |
|
|
Such structures may be mis-aligned for little benefit. For
|
4175 |
|
|
instance, in this code, the variable @code{f.x} in @code{struct bar}
|
4176 |
|
|
will be misaligned even though @code{struct bar} does not itself
|
4177 |
|
|
have the packed attribute:
|
4178 |
|
|
|
4179 |
|
|
@smallexample
|
4180 |
|
|
@group
|
4181 |
|
|
struct foo @{
|
4182 |
|
|
int x;
|
4183 |
|
|
char a, b, c, d;
|
4184 |
|
|
@} __attribute__((packed));
|
4185 |
|
|
struct bar @{
|
4186 |
|
|
char z;
|
4187 |
|
|
struct foo f;
|
4188 |
|
|
@};
|
4189 |
|
|
@end group
|
4190 |
|
|
@end smallexample
|
4191 |
|
|
|
4192 |
|
|
@item -Wpacked-bitfield-compat
|
4193 |
|
|
@opindex Wpacked-bitfield-compat
|
4194 |
|
|
@opindex Wno-packed-bitfield-compat
|
4195 |
|
|
The 4.1, 4.2 and 4.3 series of GCC ignore the @code{packed} attribute
|
4196 |
|
|
on bit-fields of type @code{char}. This has been fixed in GCC 4.4 but
|
4197 |
|
|
the change can lead to differences in the structure layout. GCC
|
4198 |
|
|
informs you when the offset of such a field has changed in GCC 4.4.
|
4199 |
|
|
For example there is no longer a 4-bit padding between field @code{a}
|
4200 |
|
|
and @code{b} in this structure:
|
4201 |
|
|
|
4202 |
|
|
@smallexample
|
4203 |
|
|
struct foo
|
4204 |
|
|
@{
|
4205 |
|
|
char a:4;
|
4206 |
|
|
char b:8;
|
4207 |
|
|
@} __attribute__ ((packed));
|
4208 |
|
|
@end smallexample
|
4209 |
|
|
|
4210 |
|
|
This warning is enabled by default. Use
|
4211 |
|
|
@option{-Wno-packed-bitfield-compat} to disable this warning.
|
4212 |
|
|
|
4213 |
|
|
@item -Wpadded
|
4214 |
|
|
@opindex Wpadded
|
4215 |
|
|
@opindex Wno-padded
|
4216 |
|
|
Warn if padding is included in a structure, either to align an element
|
4217 |
|
|
of the structure or to align the whole structure. Sometimes when this
|
4218 |
|
|
happens it is possible to rearrange the fields of the structure to
|
4219 |
|
|
reduce the padding and so make the structure smaller.
|
4220 |
|
|
|
4221 |
|
|
@item -Wredundant-decls
|
4222 |
|
|
@opindex Wredundant-decls
|
4223 |
|
|
@opindex Wno-redundant-decls
|
4224 |
|
|
Warn if anything is declared more than once in the same scope, even in
|
4225 |
|
|
cases where multiple declaration is valid and changes nothing.
|
4226 |
|
|
|
4227 |
|
|
@item -Wnested-externs @r{(C and Objective-C only)}
|
4228 |
|
|
@opindex Wnested-externs
|
4229 |
|
|
@opindex Wno-nested-externs
|
4230 |
|
|
Warn if an @code{extern} declaration is encountered within a function.
|
4231 |
|
|
|
4232 |
|
|
@item -Winline
|
4233 |
|
|
@opindex Winline
|
4234 |
|
|
@opindex Wno-inline
|
4235 |
|
|
Warn if a function can not be inlined and it was declared as inline.
|
4236 |
|
|
Even with this option, the compiler will not warn about failures to
|
4237 |
|
|
inline functions declared in system headers.
|
4238 |
|
|
|
4239 |
|
|
The compiler uses a variety of heuristics to determine whether or not
|
4240 |
|
|
to inline a function. For example, the compiler takes into account
|
4241 |
|
|
the size of the function being inlined and the amount of inlining
|
4242 |
|
|
that has already been done in the current function. Therefore,
|
4243 |
|
|
seemingly insignificant changes in the source program can cause the
|
4244 |
|
|
warnings produced by @option{-Winline} to appear or disappear.
|
4245 |
|
|
|
4246 |
|
|
@item -Wno-invalid-offsetof @r{(C++ and Objective-C++ only)}
|
4247 |
|
|
@opindex Wno-invalid-offsetof
|
4248 |
|
|
@opindex Winvalid-offsetof
|
4249 |
|
|
Suppress warnings from applying the @samp{offsetof} macro to a non-POD
|
4250 |
|
|
type. According to the 1998 ISO C++ standard, applying @samp{offsetof}
|
4251 |
|
|
to a non-POD type is undefined. In existing C++ implementations,
|
4252 |
|
|
however, @samp{offsetof} typically gives meaningful results even when
|
4253 |
|
|
applied to certain kinds of non-POD types. (Such as a simple
|
4254 |
|
|
@samp{struct} that fails to be a POD type only by virtue of having a
|
4255 |
|
|
constructor.) This flag is for users who are aware that they are
|
4256 |
|
|
writing nonportable code and who have deliberately chosen to ignore the
|
4257 |
|
|
warning about it.
|
4258 |
|
|
|
4259 |
|
|
The restrictions on @samp{offsetof} may be relaxed in a future version
|
4260 |
|
|
of the C++ standard.
|
4261 |
|
|
|
4262 |
|
|
@item -Wno-int-to-pointer-cast @r{(C and Objective-C only)}
|
4263 |
|
|
@opindex Wno-int-to-pointer-cast
|
4264 |
|
|
@opindex Wint-to-pointer-cast
|
4265 |
|
|
Suppress warnings from casts to pointer type of an integer of a
|
4266 |
|
|
different size.
|
4267 |
|
|
|
4268 |
|
|
@item -Wno-pointer-to-int-cast @r{(C and Objective-C only)}
|
4269 |
|
|
@opindex Wno-pointer-to-int-cast
|
4270 |
|
|
@opindex Wpointer-to-int-cast
|
4271 |
|
|
Suppress warnings from casts from a pointer to an integer type of a
|
4272 |
|
|
different size.
|
4273 |
|
|
|
4274 |
|
|
@item -Winvalid-pch
|
4275 |
|
|
@opindex Winvalid-pch
|
4276 |
|
|
@opindex Wno-invalid-pch
|
4277 |
|
|
Warn if a precompiled header (@pxref{Precompiled Headers}) is found in
|
4278 |
|
|
the search path but can't be used.
|
4279 |
|
|
|
4280 |
|
|
@item -Wlong-long
|
4281 |
|
|
@opindex Wlong-long
|
4282 |
|
|
@opindex Wno-long-long
|
4283 |
|
|
Warn if @samp{long long} type is used. This is enabled by either
|
4284 |
|
|
@option{-pedantic} or @option{-Wtraditional} in ISO C90 and C++98
|
4285 |
|
|
modes. To inhibit the warning messages, use @option{-Wno-long-long}.
|
4286 |
|
|
|
4287 |
|
|
@item -Wvariadic-macros
|
4288 |
|
|
@opindex Wvariadic-macros
|
4289 |
|
|
@opindex Wno-variadic-macros
|
4290 |
|
|
Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU
|
4291 |
|
|
alternate syntax when in pedantic ISO C99 mode. This is default.
|
4292 |
|
|
To inhibit the warning messages, use @option{-Wno-variadic-macros}.
|
4293 |
|
|
|
4294 |
|
|
@item -Wvla
|
4295 |
|
|
@opindex Wvla
|
4296 |
|
|
@opindex Wno-vla
|
4297 |
|
|
Warn if variable length array is used in the code.
|
4298 |
|
|
@option{-Wno-vla} will prevent the @option{-pedantic} warning of
|
4299 |
|
|
the variable length array.
|
4300 |
|
|
|
4301 |
|
|
@item -Wvolatile-register-var
|
4302 |
|
|
@opindex Wvolatile-register-var
|
4303 |
|
|
@opindex Wno-volatile-register-var
|
4304 |
|
|
Warn if a register variable is declared volatile. The volatile
|
4305 |
|
|
modifier does not inhibit all optimizations that may eliminate reads
|
4306 |
|
|
and/or writes to register variables. This warning is enabled by
|
4307 |
|
|
@option{-Wall}.
|
4308 |
|
|
|
4309 |
|
|
@item -Wdisabled-optimization
|
4310 |
|
|
@opindex Wdisabled-optimization
|
4311 |
|
|
@opindex Wno-disabled-optimization
|
4312 |
|
|
Warn if a requested optimization pass is disabled. This warning does
|
4313 |
|
|
not generally indicate that there is anything wrong with your code; it
|
4314 |
|
|
merely indicates that GCC's optimizers were unable to handle the code
|
4315 |
|
|
effectively. Often, the problem is that your code is too big or too
|
4316 |
|
|
complex; GCC will refuse to optimize programs when the optimization
|
4317 |
|
|
itself is likely to take inordinate amounts of time.
|
4318 |
|
|
|
4319 |
|
|
@item -Wpointer-sign @r{(C and Objective-C only)}
|
4320 |
|
|
@opindex Wpointer-sign
|
4321 |
|
|
@opindex Wno-pointer-sign
|
4322 |
|
|
Warn for pointer argument passing or assignment with different signedness.
|
4323 |
|
|
This option is only supported for C and Objective-C@. It is implied by
|
4324 |
|
|
@option{-Wall} and by @option{-pedantic}, which can be disabled with
|
4325 |
|
|
@option{-Wno-pointer-sign}.
|
4326 |
|
|
|
4327 |
|
|
@item -Wstack-protector
|
4328 |
|
|
@opindex Wstack-protector
|
4329 |
|
|
@opindex Wno-stack-protector
|
4330 |
|
|
This option is only active when @option{-fstack-protector} is active. It
|
4331 |
|
|
warns about functions that will not be protected against stack smashing.
|
4332 |
|
|
|
4333 |
|
|
@item -Wno-mudflap
|
4334 |
|
|
@opindex Wno-mudflap
|
4335 |
|
|
Suppress warnings about constructs that cannot be instrumented by
|
4336 |
|
|
@option{-fmudflap}.
|
4337 |
|
|
|
4338 |
|
|
@item -Woverlength-strings
|
4339 |
|
|
@opindex Woverlength-strings
|
4340 |
|
|
@opindex Wno-overlength-strings
|
4341 |
|
|
Warn about string constants which are longer than the ``minimum
|
4342 |
|
|
maximum'' length specified in the C standard. Modern compilers
|
4343 |
|
|
generally allow string constants which are much longer than the
|
4344 |
|
|
standard's minimum limit, but very portable programs should avoid
|
4345 |
|
|
using longer strings.
|
4346 |
|
|
|
4347 |
|
|
The limit applies @emph{after} string constant concatenation, and does
|
4348 |
|
|
not count the trailing NUL@. In C90, the limit was 509 characters; in
|
4349 |
|
|
C99, it was raised to 4095. C++98 does not specify a normative
|
4350 |
|
|
minimum maximum, so we do not diagnose overlength strings in C++@.
|
4351 |
|
|
|
4352 |
|
|
This option is implied by @option{-pedantic}, and can be disabled with
|
4353 |
|
|
@option{-Wno-overlength-strings}.
|
4354 |
|
|
|
4355 |
|
|
@item -Wunsuffixed-float-constants @r{(C and Objective-C only)}
|
4356 |
|
|
@opindex Wunsuffixed-float-constants
|
4357 |
|
|
|
4358 |
|
|
GCC will issue a warning for any floating constant that does not have
|
4359 |
|
|
a suffix. When used together with @option{-Wsystem-headers} it will
|
4360 |
|
|
warn about such constants in system header files. This can be useful
|
4361 |
|
|
when preparing code to use with the @code{FLOAT_CONST_DECIMAL64} pragma
|
4362 |
|
|
from the decimal floating-point extension to C99.
|
4363 |
|
|
@end table
|
4364 |
|
|
|
4365 |
|
|
@node Debugging Options
|
4366 |
|
|
@section Options for Debugging Your Program or GCC
|
4367 |
|
|
@cindex options, debugging
|
4368 |
|
|
@cindex debugging information options
|
4369 |
|
|
|
4370 |
|
|
GCC has various special options that are used for debugging
|
4371 |
|
|
either your program or GCC:
|
4372 |
|
|
|
4373 |
|
|
@table @gcctabopt
|
4374 |
|
|
@item -g
|
4375 |
|
|
@opindex g
|
4376 |
|
|
Produce debugging information in the operating system's native format
|
4377 |
|
|
(stabs, COFF, XCOFF, or DWARF 2)@. GDB can work with this debugging
|
4378 |
|
|
information.
|
4379 |
|
|
|
4380 |
|
|
On most systems that use stabs format, @option{-g} enables use of extra
|
4381 |
|
|
debugging information that only GDB can use; this extra information
|
4382 |
|
|
makes debugging work better in GDB but will probably make other debuggers
|
4383 |
|
|
crash or
|
4384 |
|
|
refuse to read the program. If you want to control for certain whether
|
4385 |
|
|
to generate the extra information, use @option{-gstabs+}, @option{-gstabs},
|
4386 |
|
|
@option{-gxcoff+}, @option{-gxcoff}, or @option{-gvms} (see below).
|
4387 |
|
|
|
4388 |
|
|
GCC allows you to use @option{-g} with
|
4389 |
|
|
@option{-O}. The shortcuts taken by optimized code may occasionally
|
4390 |
|
|
produce surprising results: some variables you declared may not exist
|
4391 |
|
|
at all; flow of control may briefly move where you did not expect it;
|
4392 |
|
|
some statements may not be executed because they compute constant
|
4393 |
|
|
results or their values were already at hand; some statements may
|
4394 |
|
|
execute in different places because they were moved out of loops.
|
4395 |
|
|
|
4396 |
|
|
Nevertheless it proves possible to debug optimized output. This makes
|
4397 |
|
|
it reasonable to use the optimizer for programs that might have bugs.
|
4398 |
|
|
|
4399 |
|
|
The following options are useful when GCC is generated with the
|
4400 |
|
|
capability for more than one debugging format.
|
4401 |
|
|
|
4402 |
|
|
@item -ggdb
|
4403 |
|
|
@opindex ggdb
|
4404 |
|
|
Produce debugging information for use by GDB@. This means to use the
|
4405 |
|
|
most expressive format available (DWARF 2, stabs, or the native format
|
4406 |
|
|
if neither of those are supported), including GDB extensions if at all
|
4407 |
|
|
possible.
|
4408 |
|
|
|
4409 |
|
|
@item -gstabs
|
4410 |
|
|
@opindex gstabs
|
4411 |
|
|
Produce debugging information in stabs format (if that is supported),
|
4412 |
|
|
without GDB extensions. This is the format used by DBX on most BSD
|
4413 |
|
|
systems. On MIPS, Alpha and System V Release 4 systems this option
|
4414 |
|
|
produces stabs debugging output which is not understood by DBX or SDB@.
|
4415 |
|
|
On System V Release 4 systems this option requires the GNU assembler.
|
4416 |
|
|
|
4417 |
|
|
@item -feliminate-unused-debug-symbols
|
4418 |
|
|
@opindex feliminate-unused-debug-symbols
|
4419 |
|
|
Produce debugging information in stabs format (if that is supported),
|
4420 |
|
|
for only symbols that are actually used.
|
4421 |
|
|
|
4422 |
|
|
@item -femit-class-debug-always
|
4423 |
|
|
Instead of emitting debugging information for a C++ class in only one
|
4424 |
|
|
object file, emit it in all object files using the class. This option
|
4425 |
|
|
should be used only with debuggers that are unable to handle the way GCC
|
4426 |
|
|
normally emits debugging information for classes because using this
|
4427 |
|
|
option will increase the size of debugging information by as much as a
|
4428 |
|
|
factor of two.
|
4429 |
|
|
|
4430 |
|
|
@item -gstabs+
|
4431 |
|
|
@opindex gstabs+
|
4432 |
|
|
Produce debugging information in stabs format (if that is supported),
|
4433 |
|
|
using GNU extensions understood only by the GNU debugger (GDB)@. The
|
4434 |
|
|
use of these extensions is likely to make other debuggers crash or
|
4435 |
|
|
refuse to read the program.
|
4436 |
|
|
|
4437 |
|
|
@item -gcoff
|
4438 |
|
|
@opindex gcoff
|
4439 |
|
|
Produce debugging information in COFF format (if that is supported).
|
4440 |
|
|
This is the format used by SDB on most System V systems prior to
|
4441 |
|
|
System V Release 4.
|
4442 |
|
|
|
4443 |
|
|
@item -gxcoff
|
4444 |
|
|
@opindex gxcoff
|
4445 |
|
|
Produce debugging information in XCOFF format (if that is supported).
|
4446 |
|
|
This is the format used by the DBX debugger on IBM RS/6000 systems.
|
4447 |
|
|
|
4448 |
|
|
@item -gxcoff+
|
4449 |
|
|
@opindex gxcoff+
|
4450 |
|
|
Produce debugging information in XCOFF format (if that is supported),
|
4451 |
|
|
using GNU extensions understood only by the GNU debugger (GDB)@. The
|
4452 |
|
|
use of these extensions is likely to make other debuggers crash or
|
4453 |
|
|
refuse to read the program, and may cause assemblers other than the GNU
|
4454 |
|
|
assembler (GAS) to fail with an error.
|
4455 |
|
|
|
4456 |
|
|
@item -gdwarf-@var{version}
|
4457 |
|
|
@opindex gdwarf-@var{version}
|
4458 |
|
|
Produce debugging information in DWARF format (if that is
|
4459 |
|
|
supported). This is the format used by DBX on IRIX 6. The value
|
4460 |
|
|
of @var{version} may be either 2, 3 or 4; the default version is 2.
|
4461 |
|
|
|
4462 |
|
|
Note that with DWARF version 2 some ports require, and will always
|
4463 |
|
|
use, some non-conflicting DWARF 3 extensions in the unwind tables.
|
4464 |
|
|
|
4465 |
|
|
Version 4 may require GDB 7.0 and @option{-fvar-tracking-assignments}
|
4466 |
|
|
for maximum benefit.
|
4467 |
|
|
|
4468 |
|
|
@item -gstrict-dwarf
|
4469 |
|
|
@opindex gstrict-dwarf
|
4470 |
|
|
Disallow using extensions of later DWARF standard version than selected
|
4471 |
|
|
with @option{-gdwarf-@var{version}}. On most targets using non-conflicting
|
4472 |
|
|
DWARF extensions from later standard versions is allowed.
|
4473 |
|
|
|
4474 |
|
|
@item -gno-strict-dwarf
|
4475 |
|
|
@opindex gno-strict-dwarf
|
4476 |
|
|
Allow using extensions of later DWARF standard version than selected with
|
4477 |
|
|
@option{-gdwarf-@var{version}}.
|
4478 |
|
|
|
4479 |
|
|
@item -gvms
|
4480 |
|
|
@opindex gvms
|
4481 |
|
|
Produce debugging information in VMS debug format (if that is
|
4482 |
|
|
supported). This is the format used by DEBUG on VMS systems.
|
4483 |
|
|
|
4484 |
|
|
@item -g@var{level}
|
4485 |
|
|
@itemx -ggdb@var{level}
|
4486 |
|
|
@itemx -gstabs@var{level}
|
4487 |
|
|
@itemx -gcoff@var{level}
|
4488 |
|
|
@itemx -gxcoff@var{level}
|
4489 |
|
|
@itemx -gvms@var{level}
|
4490 |
|
|
Request debugging information and also use @var{level} to specify how
|
4491 |
|
|
much information. The default level is 2.
|
4492 |
|
|
|
4493 |
|
|
Level 0 produces no debug information at all. Thus, @option{-g0} negates
|
4494 |
|
|
@option{-g}.
|
4495 |
|
|
|
4496 |
|
|
Level 1 produces minimal information, enough for making backtraces in
|
4497 |
|
|
parts of the program that you don't plan to debug. This includes
|
4498 |
|
|
descriptions of functions and external variables, but no information
|
4499 |
|
|
about local variables and no line numbers.
|
4500 |
|
|
|
4501 |
|
|
Level 3 includes extra information, such as all the macro definitions
|
4502 |
|
|
present in the program. Some debuggers support macro expansion when
|
4503 |
|
|
you use @option{-g3}.
|
4504 |
|
|
|
4505 |
|
|
@option{-gdwarf-2} does not accept a concatenated debug level, because
|
4506 |
|
|
GCC used to support an option @option{-gdwarf} that meant to generate
|
4507 |
|
|
debug information in version 1 of the DWARF format (which is very
|
4508 |
|
|
different from version 2), and it would have been too confusing. That
|
4509 |
|
|
debug format is long obsolete, but the option cannot be changed now.
|
4510 |
|
|
Instead use an additional @option{-g@var{level}} option to change the
|
4511 |
|
|
debug level for DWARF.
|
4512 |
|
|
|
4513 |
|
|
@item -gtoggle
|
4514 |
|
|
@opindex gtoggle
|
4515 |
|
|
Turn off generation of debug info, if leaving out this option would have
|
4516 |
|
|
generated it, or turn it on at level 2 otherwise. The position of this
|
4517 |
|
|
argument in the command line does not matter, it takes effect after all
|
4518 |
|
|
other options are processed, and it does so only once, no matter how
|
4519 |
|
|
many times it is given. This is mainly intended to be used with
|
4520 |
|
|
@option{-fcompare-debug}.
|
4521 |
|
|
|
4522 |
|
|
@item -fdump-final-insns@r{[}=@var{file}@r{]}
|
4523 |
|
|
@opindex fdump-final-insns
|
4524 |
|
|
Dump the final internal representation (RTL) to @var{file}. If the
|
4525 |
|
|
optional argument is omitted (or if @var{file} is @code{.}), the name
|
4526 |
|
|
of the dump file will be determined by appending @code{.gkd} to the
|
4527 |
|
|
compilation output file name.
|
4528 |
|
|
|
4529 |
|
|
@item -fcompare-debug@r{[}=@var{opts}@r{]}
|
4530 |
|
|
@opindex fcompare-debug
|
4531 |
|
|
@opindex fno-compare-debug
|
4532 |
|
|
If no error occurs during compilation, run the compiler a second time,
|
4533 |
|
|
adding @var{opts} and @option{-fcompare-debug-second} to the arguments
|
4534 |
|
|
passed to the second compilation. Dump the final internal
|
4535 |
|
|
representation in both compilations, and print an error if they differ.
|
4536 |
|
|
|
4537 |
|
|
If the equal sign is omitted, the default @option{-gtoggle} is used.
|
4538 |
|
|
|
4539 |
|
|
The environment variable @env{GCC_COMPARE_DEBUG}, if defined, non-empty
|
4540 |
|
|
and nonzero, implicitly enables @option{-fcompare-debug}. If
|
4541 |
|
|
@env{GCC_COMPARE_DEBUG} is defined to a string starting with a dash,
|
4542 |
|
|
then it is used for @var{opts}, otherwise the default @option{-gtoggle}
|
4543 |
|
|
is used.
|
4544 |
|
|
|
4545 |
|
|
@option{-fcompare-debug=}, with the equal sign but without @var{opts},
|
4546 |
|
|
is equivalent to @option{-fno-compare-debug}, which disables the dumping
|
4547 |
|
|
of the final representation and the second compilation, preventing even
|
4548 |
|
|
@env{GCC_COMPARE_DEBUG} from taking effect.
|
4549 |
|
|
|
4550 |
|
|
To verify full coverage during @option{-fcompare-debug} testing, set
|
4551 |
|
|
@env{GCC_COMPARE_DEBUG} to say @samp{-fcompare-debug-not-overridden},
|
4552 |
|
|
which GCC will reject as an invalid option in any actual compilation
|
4553 |
|
|
(rather than preprocessing, assembly or linking). To get just a
|
4554 |
|
|
warning, setting @env{GCC_COMPARE_DEBUG} to @samp{-w%n-fcompare-debug
|
4555 |
|
|
not overridden} will do.
|
4556 |
|
|
|
4557 |
|
|
@item -fcompare-debug-second
|
4558 |
|
|
@opindex fcompare-debug-second
|
4559 |
|
|
This option is implicitly passed to the compiler for the second
|
4560 |
|
|
compilation requested by @option{-fcompare-debug}, along with options to
|
4561 |
|
|
silence warnings, and omitting other options that would cause
|
4562 |
|
|
side-effect compiler outputs to files or to the standard output. Dump
|
4563 |
|
|
files and preserved temporary files are renamed so as to contain the
|
4564 |
|
|
@code{.gk} additional extension during the second compilation, to avoid
|
4565 |
|
|
overwriting those generated by the first.
|
4566 |
|
|
|
4567 |
|
|
When this option is passed to the compiler driver, it causes the
|
4568 |
|
|
@emph{first} compilation to be skipped, which makes it useful for little
|
4569 |
|
|
other than debugging the compiler proper.
|
4570 |
|
|
|
4571 |
|
|
@item -feliminate-dwarf2-dups
|
4572 |
|
|
@opindex feliminate-dwarf2-dups
|
4573 |
|
|
Compress DWARF2 debugging information by eliminating duplicated
|
4574 |
|
|
information about each symbol. This option only makes sense when
|
4575 |
|
|
generating DWARF2 debugging information with @option{-gdwarf-2}.
|
4576 |
|
|
|
4577 |
|
|
@item -femit-struct-debug-baseonly
|
4578 |
|
|
Emit debug information for struct-like types
|
4579 |
|
|
only when the base name of the compilation source file
|
4580 |
|
|
matches the base name of file in which the struct was defined.
|
4581 |
|
|
|
4582 |
|
|
This option substantially reduces the size of debugging information,
|
4583 |
|
|
but at significant potential loss in type information to the debugger.
|
4584 |
|
|
See @option{-femit-struct-debug-reduced} for a less aggressive option.
|
4585 |
|
|
See @option{-femit-struct-debug-detailed} for more detailed control.
|
4586 |
|
|
|
4587 |
|
|
This option works only with DWARF 2.
|
4588 |
|
|
|
4589 |
|
|
@item -femit-struct-debug-reduced
|
4590 |
|
|
Emit debug information for struct-like types
|
4591 |
|
|
only when the base name of the compilation source file
|
4592 |
|
|
matches the base name of file in which the type was defined,
|
4593 |
|
|
unless the struct is a template or defined in a system header.
|
4594 |
|
|
|
4595 |
|
|
This option significantly reduces the size of debugging information,
|
4596 |
|
|
with some potential loss in type information to the debugger.
|
4597 |
|
|
See @option{-femit-struct-debug-baseonly} for a more aggressive option.
|
4598 |
|
|
See @option{-femit-struct-debug-detailed} for more detailed control.
|
4599 |
|
|
|
4600 |
|
|
This option works only with DWARF 2.
|
4601 |
|
|
|
4602 |
|
|
@item -femit-struct-debug-detailed@r{[}=@var{spec-list}@r{]}
|
4603 |
|
|
Specify the struct-like types
|
4604 |
|
|
for which the compiler will generate debug information.
|
4605 |
|
|
The intent is to reduce duplicate struct debug information
|
4606 |
|
|
between different object files within the same program.
|
4607 |
|
|
|
4608 |
|
|
This option is a detailed version of
|
4609 |
|
|
@option{-femit-struct-debug-reduced} and @option{-femit-struct-debug-baseonly},
|
4610 |
|
|
which will serve for most needs.
|
4611 |
|
|
|
4612 |
|
|
A specification has the syntax
|
4613 |
|
|
[@samp{dir:}|@samp{ind:}][@samp{ord:}|@samp{gen:}](@samp{any}|@samp{sys}|@samp{base}|@samp{none})
|
4614 |
|
|
|
4615 |
|
|
The optional first word limits the specification to
|
4616 |
|
|
structs that are used directly (@samp{dir:}) or used indirectly (@samp{ind:}).
|
4617 |
|
|
A struct type is used directly when it is the type of a variable, member.
|
4618 |
|
|
Indirect uses arise through pointers to structs.
|
4619 |
|
|
That is, when use of an incomplete struct would be legal, the use is indirect.
|
4620 |
|
|
An example is
|
4621 |
|
|
@samp{struct one direct; struct two * indirect;}.
|
4622 |
|
|
|
4623 |
|
|
The optional second word limits the specification to
|
4624 |
|
|
ordinary structs (@samp{ord:}) or generic structs (@samp{gen:}).
|
4625 |
|
|
Generic structs are a bit complicated to explain.
|
4626 |
|
|
For C++, these are non-explicit specializations of template classes,
|
4627 |
|
|
or non-template classes within the above.
|
4628 |
|
|
Other programming languages have generics,
|
4629 |
|
|
but @samp{-femit-struct-debug-detailed} does not yet implement them.
|
4630 |
|
|
|
4631 |
|
|
The third word specifies the source files for those
|
4632 |
|
|
structs for which the compiler will emit debug information.
|
4633 |
|
|
The values @samp{none} and @samp{any} have the normal meaning.
|
4634 |
|
|
The value @samp{base} means that
|
4635 |
|
|
the base of name of the file in which the type declaration appears
|
4636 |
|
|
must match the base of the name of the main compilation file.
|
4637 |
|
|
In practice, this means that
|
4638 |
|
|
types declared in @file{foo.c} and @file{foo.h} will have debug information,
|
4639 |
|
|
but types declared in other header will not.
|
4640 |
|
|
The value @samp{sys} means those types satisfying @samp{base}
|
4641 |
|
|
or declared in system or compiler headers.
|
4642 |
|
|
|
4643 |
|
|
You may need to experiment to determine the best settings for your application.
|
4644 |
|
|
|
4645 |
|
|
The default is @samp{-femit-struct-debug-detailed=all}.
|
4646 |
|
|
|
4647 |
|
|
This option works only with DWARF 2.
|
4648 |
|
|
|
4649 |
|
|
@item -fenable-icf-debug
|
4650 |
|
|
@opindex fenable-icf-debug
|
4651 |
|
|
Generate additional debug information to support identical code folding (ICF).
|
4652 |
|
|
This option only works with DWARF version 2 or higher.
|
4653 |
|
|
|
4654 |
|
|
@item -fno-merge-debug-strings
|
4655 |
|
|
@opindex fmerge-debug-strings
|
4656 |
|
|
@opindex fno-merge-debug-strings
|
4657 |
|
|
Direct the linker to not merge together strings in the debugging
|
4658 |
|
|
information which are identical in different object files. Merging is
|
4659 |
|
|
not supported by all assemblers or linkers. Merging decreases the size
|
4660 |
|
|
of the debug information in the output file at the cost of increasing
|
4661 |
|
|
link processing time. Merging is enabled by default.
|
4662 |
|
|
|
4663 |
|
|
@item -fdebug-prefix-map=@var{old}=@var{new}
|
4664 |
|
|
@opindex fdebug-prefix-map
|
4665 |
|
|
When compiling files in directory @file{@var{old}}, record debugging
|
4666 |
|
|
information describing them as in @file{@var{new}} instead.
|
4667 |
|
|
|
4668 |
|
|
@item -fno-dwarf2-cfi-asm
|
4669 |
|
|
@opindex fdwarf2-cfi-asm
|
4670 |
|
|
@opindex fno-dwarf2-cfi-asm
|
4671 |
|
|
Emit DWARF 2 unwind info as compiler generated @code{.eh_frame} section
|
4672 |
|
|
instead of using GAS @code{.cfi_*} directives.
|
4673 |
|
|
|
4674 |
|
|
@cindex @command{prof}
|
4675 |
|
|
@item -p
|
4676 |
|
|
@opindex p
|
4677 |
|
|
Generate extra code to write profile information suitable for the
|
4678 |
|
|
analysis program @command{prof}. You must use this option when compiling
|
4679 |
|
|
the source files you want data about, and you must also use it when
|
4680 |
|
|
linking.
|
4681 |
|
|
|
4682 |
|
|
@cindex @command{gprof}
|
4683 |
|
|
@item -pg
|
4684 |
|
|
@opindex pg
|
4685 |
|
|
Generate extra code to write profile information suitable for the
|
4686 |
|
|
analysis program @command{gprof}. You must use this option when compiling
|
4687 |
|
|
the source files you want data about, and you must also use it when
|
4688 |
|
|
linking.
|
4689 |
|
|
|
4690 |
|
|
@item -Q
|
4691 |
|
|
@opindex Q
|
4692 |
|
|
Makes the compiler print out each function name as it is compiled, and
|
4693 |
|
|
print some statistics about each pass when it finishes.
|
4694 |
|
|
|
4695 |
|
|
@item -ftime-report
|
4696 |
|
|
@opindex ftime-report
|
4697 |
|
|
Makes the compiler print some statistics about the time consumed by each
|
4698 |
|
|
pass when it finishes.
|
4699 |
|
|
|
4700 |
|
|
@item -fmem-report
|
4701 |
|
|
@opindex fmem-report
|
4702 |
|
|
Makes the compiler print some statistics about permanent memory
|
4703 |
|
|
allocation when it finishes.
|
4704 |
|
|
|
4705 |
|
|
@item -fpre-ipa-mem-report
|
4706 |
|
|
@opindex fpre-ipa-mem-report
|
4707 |
|
|
@item -fpost-ipa-mem-report
|
4708 |
|
|
@opindex fpost-ipa-mem-report
|
4709 |
|
|
Makes the compiler print some statistics about permanent memory
|
4710 |
|
|
allocation before or after interprocedural optimization.
|
4711 |
|
|
|
4712 |
|
|
@item -fprofile-arcs
|
4713 |
|
|
@opindex fprofile-arcs
|
4714 |
|
|
Add code so that program flow @dfn{arcs} are instrumented. During
|
4715 |
|
|
execution the program records how many times each branch and call is
|
4716 |
|
|
executed and how many times it is taken or returns. When the compiled
|
4717 |
|
|
program exits it saves this data to a file called
|
4718 |
|
|
@file{@var{auxname}.gcda} for each source file. The data may be used for
|
4719 |
|
|
profile-directed optimizations (@option{-fbranch-probabilities}), or for
|
4720 |
|
|
test coverage analysis (@option{-ftest-coverage}). Each object file's
|
4721 |
|
|
@var{auxname} is generated from the name of the output file, if
|
4722 |
|
|
explicitly specified and it is not the final executable, otherwise it is
|
4723 |
|
|
the basename of the source file. In both cases any suffix is removed
|
4724 |
|
|
(e.g.@: @file{foo.gcda} for input file @file{dir/foo.c}, or
|
4725 |
|
|
@file{dir/foo.gcda} for output file specified as @option{-o dir/foo.o}).
|
4726 |
|
|
@xref{Cross-profiling}.
|
4727 |
|
|
|
4728 |
|
|
@cindex @command{gcov}
|
4729 |
|
|
@item --coverage
|
4730 |
|
|
@opindex coverage
|
4731 |
|
|
|
4732 |
|
|
This option is used to compile and link code instrumented for coverage
|
4733 |
|
|
analysis. The option is a synonym for @option{-fprofile-arcs}
|
4734 |
|
|
@option{-ftest-coverage} (when compiling) and @option{-lgcov} (when
|
4735 |
|
|
linking). See the documentation for those options for more details.
|
4736 |
|
|
|
4737 |
|
|
@itemize
|
4738 |
|
|
|
4739 |
|
|
@item
|
4740 |
|
|
Compile the source files with @option{-fprofile-arcs} plus optimization
|
4741 |
|
|
and code generation options. For test coverage analysis, use the
|
4742 |
|
|
additional @option{-ftest-coverage} option. You do not need to profile
|
4743 |
|
|
every source file in a program.
|
4744 |
|
|
|
4745 |
|
|
@item
|
4746 |
|
|
Link your object files with @option{-lgcov} or @option{-fprofile-arcs}
|
4747 |
|
|
(the latter implies the former).
|
4748 |
|
|
|
4749 |
|
|
@item
|
4750 |
|
|
Run the program on a representative workload to generate the arc profile
|
4751 |
|
|
information. This may be repeated any number of times. You can run
|
4752 |
|
|
concurrent instances of your program, and provided that the file system
|
4753 |
|
|
supports locking, the data files will be correctly updated. Also
|
4754 |
|
|
@code{fork} calls are detected and correctly handled (double counting
|
4755 |
|
|
will not happen).
|
4756 |
|
|
|
4757 |
|
|
@item
|
4758 |
|
|
For profile-directed optimizations, compile the source files again with
|
4759 |
|
|
the same optimization and code generation options plus
|
4760 |
|
|
@option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that
|
4761 |
|
|
Control Optimization}).
|
4762 |
|
|
|
4763 |
|
|
@item
|
4764 |
|
|
For test coverage analysis, use @command{gcov} to produce human readable
|
4765 |
|
|
information from the @file{.gcno} and @file{.gcda} files. Refer to the
|
4766 |
|
|
@command{gcov} documentation for further information.
|
4767 |
|
|
|
4768 |
|
|
@end itemize
|
4769 |
|
|
|
4770 |
|
|
With @option{-fprofile-arcs}, for each function of your program GCC
|
4771 |
|
|
creates a program flow graph, then finds a spanning tree for the graph.
|
4772 |
|
|
Only arcs that are not on the spanning tree have to be instrumented: the
|
4773 |
|
|
compiler adds code to count the number of times that these arcs are
|
4774 |
|
|
executed. When an arc is the only exit or only entrance to a block, the
|
4775 |
|
|
instrumentation code can be added to the block; otherwise, a new basic
|
4776 |
|
|
block must be created to hold the instrumentation code.
|
4777 |
|
|
|
4778 |
|
|
@need 2000
|
4779 |
|
|
@item -ftest-coverage
|
4780 |
|
|
@opindex ftest-coverage
|
4781 |
|
|
Produce a notes file that the @command{gcov} code-coverage utility
|
4782 |
|
|
(@pxref{Gcov,, @command{gcov}---a Test Coverage Program}) can use to
|
4783 |
|
|
show program coverage. Each source file's note file is called
|
4784 |
|
|
@file{@var{auxname}.gcno}. Refer to the @option{-fprofile-arcs} option
|
4785 |
|
|
above for a description of @var{auxname} and instructions on how to
|
4786 |
|
|
generate test coverage data. Coverage data will match the source files
|
4787 |
|
|
more closely, if you do not optimize.
|
4788 |
|
|
|
4789 |
|
|
@item -fdbg-cnt-list
|
4790 |
|
|
@opindex fdbg-cnt-list
|
4791 |
|
|
Print the name and the counter upperbound for all debug counters.
|
4792 |
|
|
|
4793 |
|
|
@item -fdbg-cnt=@var{counter-value-list}
|
4794 |
|
|
@opindex fdbg-cnt
|
4795 |
|
|
Set the internal debug counter upperbound. @var{counter-value-list}
|
4796 |
|
|
is a comma-separated list of @var{name}:@var{value} pairs
|
4797 |
|
|
which sets the upperbound of each debug counter @var{name} to @var{value}.
|
4798 |
|
|
All debug counters have the initial upperbound of @var{UINT_MAX},
|
4799 |
|
|
thus dbg_cnt() returns true always unless the upperbound is set by this option.
|
4800 |
|
|
e.g. With -fdbg-cnt=dce:10,tail_call:0
|
4801 |
|
|
dbg_cnt(dce) will return true only for first 10 invocations
|
4802 |
|
|
and dbg_cnt(tail_call) will return false always.
|
4803 |
|
|
|
4804 |
|
|
@item -d@var{letters}
|
4805 |
|
|
@itemx -fdump-rtl-@var{pass}
|
4806 |
|
|
@opindex d
|
4807 |
|
|
Says to make debugging dumps during compilation at times specified by
|
4808 |
|
|
@var{letters}. This is used for debugging the RTL-based passes of the
|
4809 |
|
|
compiler. The file names for most of the dumps are made by appending
|
4810 |
|
|
a pass number and a word to the @var{dumpname}, and the files are
|
4811 |
|
|
created in the directory of the output file. @var{dumpname} is
|
4812 |
|
|
generated from the name of the output file, if explicitly specified
|
4813 |
|
|
and it is not an executable, otherwise it is the basename of the
|
4814 |
|
|
source file. These switches may have different effects when
|
4815 |
|
|
@option{-E} is used for preprocessing.
|
4816 |
|
|
|
4817 |
|
|
Debug dumps can be enabled with a @option{-fdump-rtl} switch or some
|
4818 |
|
|
@option{-d} option @var{letters}. Here are the possible
|
4819 |
|
|
letters for use in @var{pass} and @var{letters}, and their meanings:
|
4820 |
|
|
|
4821 |
|
|
@table @gcctabopt
|
4822 |
|
|
|
4823 |
|
|
@item -fdump-rtl-alignments
|
4824 |
|
|
@opindex fdump-rtl-alignments
|
4825 |
|
|
Dump after branch alignments have been computed.
|
4826 |
|
|
|
4827 |
|
|
@item -fdump-rtl-asmcons
|
4828 |
|
|
@opindex fdump-rtl-asmcons
|
4829 |
|
|
Dump after fixing rtl statements that have unsatisfied in/out constraints.
|
4830 |
|
|
|
4831 |
|
|
@item -fdump-rtl-auto_inc_dec
|
4832 |
|
|
@opindex fdump-rtl-auto_inc_dec
|
4833 |
|
|
Dump after auto-inc-dec discovery. This pass is only run on
|
4834 |
|
|
architectures that have auto inc or auto dec instructions.
|
4835 |
|
|
|
4836 |
|
|
@item -fdump-rtl-barriers
|
4837 |
|
|
@opindex fdump-rtl-barriers
|
4838 |
|
|
Dump after cleaning up the barrier instructions.
|
4839 |
|
|
|
4840 |
|
|
@item -fdump-rtl-bbpart
|
4841 |
|
|
@opindex fdump-rtl-bbpart
|
4842 |
|
|
Dump after partitioning hot and cold basic blocks.
|
4843 |
|
|
|
4844 |
|
|
@item -fdump-rtl-bbro
|
4845 |
|
|
@opindex fdump-rtl-bbro
|
4846 |
|
|
Dump after block reordering.
|
4847 |
|
|
|
4848 |
|
|
@item -fdump-rtl-btl1
|
4849 |
|
|
@itemx -fdump-rtl-btl2
|
4850 |
|
|
@opindex fdump-rtl-btl2
|
4851 |
|
|
@opindex fdump-rtl-btl2
|
4852 |
|
|
@option{-fdump-rtl-btl1} and @option{-fdump-rtl-btl2} enable dumping
|
4853 |
|
|
after the two branch
|
4854 |
|
|
target load optimization passes.
|
4855 |
|
|
|
4856 |
|
|
@item -fdump-rtl-bypass
|
4857 |
|
|
@opindex fdump-rtl-bypass
|
4858 |
|
|
Dump after jump bypassing and control flow optimizations.
|
4859 |
|
|
|
4860 |
|
|
@item -fdump-rtl-combine
|
4861 |
|
|
@opindex fdump-rtl-combine
|
4862 |
|
|
Dump after the RTL instruction combination pass.
|
4863 |
|
|
|
4864 |
|
|
@item -fdump-rtl-compgotos
|
4865 |
|
|
@opindex fdump-rtl-compgotos
|
4866 |
|
|
Dump after duplicating the computed gotos.
|
4867 |
|
|
|
4868 |
|
|
@item -fdump-rtl-ce1
|
4869 |
|
|
@itemx -fdump-rtl-ce2
|
4870 |
|
|
@itemx -fdump-rtl-ce3
|
4871 |
|
|
@opindex fdump-rtl-ce1
|
4872 |
|
|
@opindex fdump-rtl-ce2
|
4873 |
|
|
@opindex fdump-rtl-ce3
|
4874 |
|
|
@option{-fdump-rtl-ce1}, @option{-fdump-rtl-ce2}, and
|
4875 |
|
|
@option{-fdump-rtl-ce3} enable dumping after the three
|
4876 |
|
|
if conversion passes.
|
4877 |
|
|
|
4878 |
|
|
@itemx -fdump-rtl-cprop_hardreg
|
4879 |
|
|
@opindex fdump-rtl-cprop_hardreg
|
4880 |
|
|
Dump after hard register copy propagation.
|
4881 |
|
|
|
4882 |
|
|
@itemx -fdump-rtl-csa
|
4883 |
|
|
@opindex fdump-rtl-csa
|
4884 |
|
|
Dump after combining stack adjustments.
|
4885 |
|
|
|
4886 |
|
|
@item -fdump-rtl-cse1
|
4887 |
|
|
@itemx -fdump-rtl-cse2
|
4888 |
|
|
@opindex fdump-rtl-cse1
|
4889 |
|
|
@opindex fdump-rtl-cse2
|
4890 |
|
|
@option{-fdump-rtl-cse1} and @option{-fdump-rtl-cse2} enable dumping after
|
4891 |
|
|
the two common sub-expression elimination passes.
|
4892 |
|
|
|
4893 |
|
|
@itemx -fdump-rtl-dce
|
4894 |
|
|
@opindex fdump-rtl-dce
|
4895 |
|
|
Dump after the standalone dead code elimination passes.
|
4896 |
|
|
|
4897 |
|
|
@itemx -fdump-rtl-dbr
|
4898 |
|
|
@opindex fdump-rtl-dbr
|
4899 |
|
|
Dump after delayed branch scheduling.
|
4900 |
|
|
|
4901 |
|
|
@item -fdump-rtl-dce1
|
4902 |
|
|
@itemx -fdump-rtl-dce2
|
4903 |
|
|
@opindex fdump-rtl-dce1
|
4904 |
|
|
@opindex fdump-rtl-dce2
|
4905 |
|
|
@option{-fdump-rtl-dce1} and @option{-fdump-rtl-dce2} enable dumping after
|
4906 |
|
|
the two dead store elimination passes.
|
4907 |
|
|
|
4908 |
|
|
@item -fdump-rtl-eh
|
4909 |
|
|
@opindex fdump-rtl-eh
|
4910 |
|
|
Dump after finalization of EH handling code.
|
4911 |
|
|
|
4912 |
|
|
@item -fdump-rtl-eh_ranges
|
4913 |
|
|
@opindex fdump-rtl-eh_ranges
|
4914 |
|
|
Dump after conversion of EH handling range regions.
|
4915 |
|
|
|
4916 |
|
|
@item -fdump-rtl-expand
|
4917 |
|
|
@opindex fdump-rtl-expand
|
4918 |
|
|
Dump after RTL generation.
|
4919 |
|
|
|
4920 |
|
|
@item -fdump-rtl-fwprop1
|
4921 |
|
|
@itemx -fdump-rtl-fwprop2
|
4922 |
|
|
@opindex fdump-rtl-fwprop1
|
4923 |
|
|
@opindex fdump-rtl-fwprop2
|
4924 |
|
|
@option{-fdump-rtl-fwprop1} and @option{-fdump-rtl-fwprop2} enable
|
4925 |
|
|
dumping after the two forward propagation passes.
|
4926 |
|
|
|
4927 |
|
|
@item -fdump-rtl-gcse1
|
4928 |
|
|
@itemx -fdump-rtl-gcse2
|
4929 |
|
|
@opindex fdump-rtl-gcse1
|
4930 |
|
|
@opindex fdump-rtl-gcse2
|
4931 |
|
|
@option{-fdump-rtl-gcse1} and @option{-fdump-rtl-gcse2} enable dumping
|
4932 |
|
|
after global common subexpression elimination.
|
4933 |
|
|
|
4934 |
|
|
@item -fdump-rtl-init-regs
|
4935 |
|
|
@opindex fdump-rtl-init-regs
|
4936 |
|
|
Dump after the initialization of the registers.
|
4937 |
|
|
|
4938 |
|
|
@item -fdump-rtl-initvals
|
4939 |
|
|
@opindex fdump-rtl-initvals
|
4940 |
|
|
Dump after the computation of the initial value sets.
|
4941 |
|
|
|
4942 |
|
|
@itemx -fdump-rtl-into_cfglayout
|
4943 |
|
|
@opindex fdump-rtl-into_cfglayout
|
4944 |
|
|
Dump after converting to cfglayout mode.
|
4945 |
|
|
|
4946 |
|
|
@item -fdump-rtl-ira
|
4947 |
|
|
@opindex fdump-rtl-ira
|
4948 |
|
|
Dump after iterated register allocation.
|
4949 |
|
|
|
4950 |
|
|
@item -fdump-rtl-jump
|
4951 |
|
|
@opindex fdump-rtl-jump
|
4952 |
|
|
Dump after the second jump optimization.
|
4953 |
|
|
|
4954 |
|
|
@item -fdump-rtl-loop2
|
4955 |
|
|
@opindex fdump-rtl-loop2
|
4956 |
|
|
@option{-fdump-rtl-loop2} enables dumping after the rtl
|
4957 |
|
|
loop optimization passes.
|
4958 |
|
|
|
4959 |
|
|
@item -fdump-rtl-mach
|
4960 |
|
|
@opindex fdump-rtl-mach
|
4961 |
|
|
Dump after performing the machine dependent reorganization pass, if that
|
4962 |
|
|
pass exists.
|
4963 |
|
|
|
4964 |
|
|
@item -fdump-rtl-mode_sw
|
4965 |
|
|
@opindex fdump-rtl-mode_sw
|
4966 |
|
|
Dump after removing redundant mode switches.
|
4967 |
|
|
|
4968 |
|
|
@item -fdump-rtl-rnreg
|
4969 |
|
|
@opindex fdump-rtl-rnreg
|
4970 |
|
|
Dump after register renumbering.
|
4971 |
|
|
|
4972 |
|
|
@itemx -fdump-rtl-outof_cfglayout
|
4973 |
|
|
@opindex fdump-rtl-outof_cfglayout
|
4974 |
|
|
Dump after converting from cfglayout mode.
|
4975 |
|
|
|
4976 |
|
|
@item -fdump-rtl-peephole2
|
4977 |
|
|
@opindex fdump-rtl-peephole2
|
4978 |
|
|
Dump after the peephole pass.
|
4979 |
|
|
|
4980 |
|
|
@item -fdump-rtl-postreload
|
4981 |
|
|
@opindex fdump-rtl-postreload
|
4982 |
|
|
Dump after post-reload optimizations.
|
4983 |
|
|
|
4984 |
|
|
@itemx -fdump-rtl-pro_and_epilogue
|
4985 |
|
|
@opindex fdump-rtl-pro_and_epilogue
|
4986 |
|
|
Dump after generating the function pro and epilogues.
|
4987 |
|
|
|
4988 |
|
|
@item -fdump-rtl-regmove
|
4989 |
|
|
@opindex fdump-rtl-regmove
|
4990 |
|
|
Dump after the register move pass.
|
4991 |
|
|
|
4992 |
|
|
@item -fdump-rtl-sched1
|
4993 |
|
|
@itemx -fdump-rtl-sched2
|
4994 |
|
|
@opindex fdump-rtl-sched1
|
4995 |
|
|
@opindex fdump-rtl-sched2
|
4996 |
|
|
@option{-fdump-rtl-sched1} and @option{-fdump-rtl-sched2} enable dumping
|
4997 |
|
|
after the basic block scheduling passes.
|
4998 |
|
|
|
4999 |
|
|
@item -fdump-rtl-see
|
5000 |
|
|
@opindex fdump-rtl-see
|
5001 |
|
|
Dump after sign extension elimination.
|
5002 |
|
|
|
5003 |
|
|
@item -fdump-rtl-seqabstr
|
5004 |
|
|
@opindex fdump-rtl-seqabstr
|
5005 |
|
|
Dump after common sequence discovery.
|
5006 |
|
|
|
5007 |
|
|
@item -fdump-rtl-shorten
|
5008 |
|
|
@opindex fdump-rtl-shorten
|
5009 |
|
|
Dump after shortening branches.
|
5010 |
|
|
|
5011 |
|
|
@item -fdump-rtl-sibling
|
5012 |
|
|
@opindex fdump-rtl-sibling
|
5013 |
|
|
Dump after sibling call optimizations.
|
5014 |
|
|
|
5015 |
|
|
@item -fdump-rtl-split1
|
5016 |
|
|
@itemx -fdump-rtl-split2
|
5017 |
|
|
@itemx -fdump-rtl-split3
|
5018 |
|
|
@itemx -fdump-rtl-split4
|
5019 |
|
|
@itemx -fdump-rtl-split5
|
5020 |
|
|
@opindex fdump-rtl-split1
|
5021 |
|
|
@opindex fdump-rtl-split2
|
5022 |
|
|
@opindex fdump-rtl-split3
|
5023 |
|
|
@opindex fdump-rtl-split4
|
5024 |
|
|
@opindex fdump-rtl-split5
|
5025 |
|
|
@option{-fdump-rtl-split1}, @option{-fdump-rtl-split2},
|
5026 |
|
|
@option{-fdump-rtl-split3}, @option{-fdump-rtl-split4} and
|
5027 |
|
|
@option{-fdump-rtl-split5} enable dumping after five rounds of
|
5028 |
|
|
instruction splitting.
|
5029 |
|
|
|
5030 |
|
|
@item -fdump-rtl-sms
|
5031 |
|
|
@opindex fdump-rtl-sms
|
5032 |
|
|
Dump after modulo scheduling. This pass is only run on some
|
5033 |
|
|
architectures.
|
5034 |
|
|
|
5035 |
|
|
@item -fdump-rtl-stack
|
5036 |
|
|
@opindex fdump-rtl-stack
|
5037 |
|
|
Dump after conversion from GCC's "flat register file" registers to the
|
5038 |
|
|
x87's stack-like registers. This pass is only run on x86 variants.
|
5039 |
|
|
|
5040 |
|
|
@item -fdump-rtl-subreg1
|
5041 |
|
|
@itemx -fdump-rtl-subreg2
|
5042 |
|
|
@opindex fdump-rtl-subreg1
|
5043 |
|
|
@opindex fdump-rtl-subreg2
|
5044 |
|
|
@option{-fdump-rtl-subreg1} and @option{-fdump-rtl-subreg2} enable dumping after
|
5045 |
|
|
the two subreg expansion passes.
|
5046 |
|
|
|
5047 |
|
|
@item -fdump-rtl-unshare
|
5048 |
|
|
@opindex fdump-rtl-unshare
|
5049 |
|
|
Dump after all rtl has been unshared.
|
5050 |
|
|
|
5051 |
|
|
@item -fdump-rtl-vartrack
|
5052 |
|
|
@opindex fdump-rtl-vartrack
|
5053 |
|
|
Dump after variable tracking.
|
5054 |
|
|
|
5055 |
|
|
@item -fdump-rtl-vregs
|
5056 |
|
|
@opindex fdump-rtl-vregs
|
5057 |
|
|
Dump after converting virtual registers to hard registers.
|
5058 |
|
|
|
5059 |
|
|
@item -fdump-rtl-web
|
5060 |
|
|
@opindex fdump-rtl-web
|
5061 |
|
|
Dump after live range splitting.
|
5062 |
|
|
|
5063 |
|
|
@item -fdump-rtl-regclass
|
5064 |
|
|
@itemx -fdump-rtl-subregs_of_mode_init
|
5065 |
|
|
@itemx -fdump-rtl-subregs_of_mode_finish
|
5066 |
|
|
@itemx -fdump-rtl-dfinit
|
5067 |
|
|
@itemx -fdump-rtl-dfinish
|
5068 |
|
|
@opindex fdump-rtl-regclass
|
5069 |
|
|
@opindex fdump-rtl-subregs_of_mode_init
|
5070 |
|
|
@opindex fdump-rtl-subregs_of_mode_finish
|
5071 |
|
|
@opindex fdump-rtl-dfinit
|
5072 |
|
|
@opindex fdump-rtl-dfinish
|
5073 |
|
|
These dumps are defined but always produce empty files.
|
5074 |
|
|
|
5075 |
|
|
@item -fdump-rtl-all
|
5076 |
|
|
@opindex fdump-rtl-all
|
5077 |
|
|
Produce all the dumps listed above.
|
5078 |
|
|
|
5079 |
|
|
@item -dA
|
5080 |
|
|
@opindex dA
|
5081 |
|
|
Annotate the assembler output with miscellaneous debugging information.
|
5082 |
|
|
|
5083 |
|
|
@item -dD
|
5084 |
|
|
@opindex dD
|
5085 |
|
|
Dump all macro definitions, at the end of preprocessing, in addition to
|
5086 |
|
|
normal output.
|
5087 |
|
|
|
5088 |
|
|
@item -dH
|
5089 |
|
|
@opindex dH
|
5090 |
|
|
Produce a core dump whenever an error occurs.
|
5091 |
|
|
|
5092 |
|
|
@item -dm
|
5093 |
|
|
@opindex dm
|
5094 |
|
|
Print statistics on memory usage, at the end of the run, to
|
5095 |
|
|
standard error.
|
5096 |
|
|
|
5097 |
|
|
@item -dp
|
5098 |
|
|
@opindex dp
|
5099 |
|
|
Annotate the assembler output with a comment indicating which
|
5100 |
|
|
pattern and alternative was used. The length of each instruction is
|
5101 |
|
|
also printed.
|
5102 |
|
|
|
5103 |
|
|
@item -dP
|
5104 |
|
|
@opindex dP
|
5105 |
|
|
Dump the RTL in the assembler output as a comment before each instruction.
|
5106 |
|
|
Also turns on @option{-dp} annotation.
|
5107 |
|
|
|
5108 |
|
|
@item -dv
|
5109 |
|
|
@opindex dv
|
5110 |
|
|
For each of the other indicated dump files (@option{-fdump-rtl-@var{pass}}),
|
5111 |
|
|
dump a representation of the control flow graph suitable for viewing with VCG
|
5112 |
|
|
to @file{@var{file}.@var{pass}.vcg}.
|
5113 |
|
|
|
5114 |
|
|
@item -dx
|
5115 |
|
|
@opindex dx
|
5116 |
|
|
Just generate RTL for a function instead of compiling it. Usually used
|
5117 |
|
|
with @option{-fdump-rtl-expand}.
|
5118 |
|
|
|
5119 |
|
|
@item -dy
|
5120 |
|
|
@opindex dy
|
5121 |
|
|
Dump debugging information during parsing, to standard error.
|
5122 |
|
|
@end table
|
5123 |
|
|
|
5124 |
|
|
@item -fdump-noaddr
|
5125 |
|
|
@opindex fdump-noaddr
|
5126 |
|
|
When doing debugging dumps, suppress address output. This makes it more
|
5127 |
|
|
feasible to use diff on debugging dumps for compiler invocations with
|
5128 |
|
|
different compiler binaries and/or different
|
5129 |
|
|
text / bss / data / heap / stack / dso start locations.
|
5130 |
|
|
|
5131 |
|
|
@item -fdump-unnumbered
|
5132 |
|
|
@opindex fdump-unnumbered
|
5133 |
|
|
When doing debugging dumps, suppress instruction numbers and address output.
|
5134 |
|
|
This makes it more feasible to use diff on debugging dumps for compiler
|
5135 |
|
|
invocations with different options, in particular with and without
|
5136 |
|
|
@option{-g}.
|
5137 |
|
|
|
5138 |
|
|
@item -fdump-unnumbered-links
|
5139 |
|
|
@opindex fdump-unnumbered-links
|
5140 |
|
|
When doing debugging dumps (see @option{-d} option above), suppress
|
5141 |
|
|
instruction numbers for the links to the previous and next instructions
|
5142 |
|
|
in a sequence.
|
5143 |
|
|
|
5144 |
|
|
@item -fdump-translation-unit @r{(C++ only)}
|
5145 |
|
|
@itemx -fdump-translation-unit-@var{options} @r{(C++ only)}
|
5146 |
|
|
@opindex fdump-translation-unit
|
5147 |
|
|
Dump a representation of the tree structure for the entire translation
|
5148 |
|
|
unit to a file. The file name is made by appending @file{.tu} to the
|
5149 |
|
|
source file name, and the file is created in the same directory as the
|
5150 |
|
|
output file. If the @samp{-@var{options}} form is used, @var{options}
|
5151 |
|
|
controls the details of the dump as described for the
|
5152 |
|
|
@option{-fdump-tree} options.
|
5153 |
|
|
|
5154 |
|
|
@item -fdump-class-hierarchy @r{(C++ only)}
|
5155 |
|
|
@itemx -fdump-class-hierarchy-@var{options} @r{(C++ only)}
|
5156 |
|
|
@opindex fdump-class-hierarchy
|
5157 |
|
|
Dump a representation of each class's hierarchy and virtual function
|
5158 |
|
|
table layout to a file. The file name is made by appending
|
5159 |
|
|
@file{.class} to the source file name, and the file is created in the
|
5160 |
|
|
same directory as the output file. If the @samp{-@var{options}} form
|
5161 |
|
|
is used, @var{options} controls the details of the dump as described
|
5162 |
|
|
for the @option{-fdump-tree} options.
|
5163 |
|
|
|
5164 |
|
|
@item -fdump-ipa-@var{switch}
|
5165 |
|
|
@opindex fdump-ipa
|
5166 |
|
|
Control the dumping at various stages of inter-procedural analysis
|
5167 |
|
|
language tree to a file. The file name is generated by appending a
|
5168 |
|
|
switch specific suffix to the source file name, and the file is created
|
5169 |
|
|
in the same directory as the output file. The following dumps are
|
5170 |
|
|
possible:
|
5171 |
|
|
|
5172 |
|
|
@table @samp
|
5173 |
|
|
@item all
|
5174 |
|
|
Enables all inter-procedural analysis dumps.
|
5175 |
|
|
|
5176 |
|
|
@item cgraph
|
5177 |
|
|
Dumps information about call-graph optimization, unused function removal,
|
5178 |
|
|
and inlining decisions.
|
5179 |
|
|
|
5180 |
|
|
@item inline
|
5181 |
|
|
Dump after function inlining.
|
5182 |
|
|
|
5183 |
|
|
@end table
|
5184 |
|
|
|
5185 |
|
|
@item -fdump-statistics-@var{option}
|
5186 |
|
|
@opindex fdump-statistics
|
5187 |
|
|
Enable and control dumping of pass statistics in a separate file. The
|
5188 |
|
|
file name is generated by appending a suffix ending in
|
5189 |
|
|
@samp{.statistics} to the source file name, and the file is created in
|
5190 |
|
|
the same directory as the output file. If the @samp{-@var{option}}
|
5191 |
|
|
form is used, @samp{-stats} will cause counters to be summed over the
|
5192 |
|
|
whole compilation unit while @samp{-details} will dump every event as
|
5193 |
|
|
the passes generate them. The default with no option is to sum
|
5194 |
|
|
counters for each function compiled.
|
5195 |
|
|
|
5196 |
|
|
@item -fdump-tree-@var{switch}
|
5197 |
|
|
@itemx -fdump-tree-@var{switch}-@var{options}
|
5198 |
|
|
@opindex fdump-tree
|
5199 |
|
|
Control the dumping at various stages of processing the intermediate
|
5200 |
|
|
language tree to a file. The file name is generated by appending a
|
5201 |
|
|
switch specific suffix to the source file name, and the file is
|
5202 |
|
|
created in the same directory as the output file. If the
|
5203 |
|
|
@samp{-@var{options}} form is used, @var{options} is a list of
|
5204 |
|
|
@samp{-} separated options that control the details of the dump. Not
|
5205 |
|
|
all options are applicable to all dumps, those which are not
|
5206 |
|
|
meaningful will be ignored. The following options are available
|
5207 |
|
|
|
5208 |
|
|
@table @samp
|
5209 |
|
|
@item address
|
5210 |
|
|
Print the address of each node. Usually this is not meaningful as it
|
5211 |
|
|
changes according to the environment and source file. Its primary use
|
5212 |
|
|
is for tying up a dump file with a debug environment.
|
5213 |
|
|
@item asmname
|
5214 |
|
|
If @code{DECL_ASSEMBLER_NAME} has been set for a given decl, use that
|
5215 |
|
|
in the dump instead of @code{DECL_NAME}. Its primary use is ease of
|
5216 |
|
|
use working backward from mangled names in the assembly file.
|
5217 |
|
|
@item slim
|
5218 |
|
|
Inhibit dumping of members of a scope or body of a function merely
|
5219 |
|
|
because that scope has been reached. Only dump such items when they
|
5220 |
|
|
are directly reachable by some other path. When dumping pretty-printed
|
5221 |
|
|
trees, this option inhibits dumping the bodies of control structures.
|
5222 |
|
|
@item raw
|
5223 |
|
|
Print a raw representation of the tree. By default, trees are
|
5224 |
|
|
pretty-printed into a C-like representation.
|
5225 |
|
|
@item details
|
5226 |
|
|
Enable more detailed dumps (not honored by every dump option).
|
5227 |
|
|
@item stats
|
5228 |
|
|
Enable dumping various statistics about the pass (not honored by every dump
|
5229 |
|
|
option).
|
5230 |
|
|
@item blocks
|
5231 |
|
|
Enable showing basic block boundaries (disabled in raw dumps).
|
5232 |
|
|
@item vops
|
5233 |
|
|
Enable showing virtual operands for every statement.
|
5234 |
|
|
@item lineno
|
5235 |
|
|
Enable showing line numbers for statements.
|
5236 |
|
|
@item uid
|
5237 |
|
|
Enable showing the unique ID (@code{DECL_UID}) for each variable.
|
5238 |
|
|
@item verbose
|
5239 |
|
|
Enable showing the tree dump for each statement.
|
5240 |
|
|
@item eh
|
5241 |
|
|
Enable showing the EH region number holding each statement.
|
5242 |
|
|
@item all
|
5243 |
|
|
Turn on all options, except @option{raw}, @option{slim}, @option{verbose}
|
5244 |
|
|
and @option{lineno}.
|
5245 |
|
|
@end table
|
5246 |
|
|
|
5247 |
|
|
The following tree dumps are possible:
|
5248 |
|
|
@table @samp
|
5249 |
|
|
|
5250 |
|
|
@item original
|
5251 |
|
|
@opindex fdump-tree-original
|
5252 |
|
|
Dump before any tree based optimization, to @file{@var{file}.original}.
|
5253 |
|
|
|
5254 |
|
|
@item optimized
|
5255 |
|
|
@opindex fdump-tree-optimized
|
5256 |
|
|
Dump after all tree based optimization, to @file{@var{file}.optimized}.
|
5257 |
|
|
|
5258 |
|
|
@item gimple
|
5259 |
|
|
@opindex fdump-tree-gimple
|
5260 |
|
|
Dump each function before and after the gimplification pass to a file. The
|
5261 |
|
|
file name is made by appending @file{.gimple} to the source file name.
|
5262 |
|
|
|
5263 |
|
|
@item cfg
|
5264 |
|
|
@opindex fdump-tree-cfg
|
5265 |
|
|
Dump the control flow graph of each function to a file. The file name is
|
5266 |
|
|
made by appending @file{.cfg} to the source file name.
|
5267 |
|
|
|
5268 |
|
|
@item vcg
|
5269 |
|
|
@opindex fdump-tree-vcg
|
5270 |
|
|
Dump the control flow graph of each function to a file in VCG format. The
|
5271 |
|
|
file name is made by appending @file{.vcg} to the source file name. Note
|
5272 |
|
|
that if the file contains more than one function, the generated file cannot
|
5273 |
|
|
be used directly by VCG@. You will need to cut and paste each function's
|
5274 |
|
|
graph into its own separate file first.
|
5275 |
|
|
|
5276 |
|
|
@item ch
|
5277 |
|
|
@opindex fdump-tree-ch
|
5278 |
|
|
Dump each function after copying loop headers. The file name is made by
|
5279 |
|
|
appending @file{.ch} to the source file name.
|
5280 |
|
|
|
5281 |
|
|
@item ssa
|
5282 |
|
|
@opindex fdump-tree-ssa
|
5283 |
|
|
Dump SSA related information to a file. The file name is made by appending
|
5284 |
|
|
@file{.ssa} to the source file name.
|
5285 |
|
|
|
5286 |
|
|
@item alias
|
5287 |
|
|
@opindex fdump-tree-alias
|
5288 |
|
|
Dump aliasing information for each function. The file name is made by
|
5289 |
|
|
appending @file{.alias} to the source file name.
|
5290 |
|
|
|
5291 |
|
|
@item ccp
|
5292 |
|
|
@opindex fdump-tree-ccp
|
5293 |
|
|
Dump each function after CCP@. The file name is made by appending
|
5294 |
|
|
@file{.ccp} to the source file name.
|
5295 |
|
|
|
5296 |
|
|
@item storeccp
|
5297 |
|
|
@opindex fdump-tree-storeccp
|
5298 |
|
|
Dump each function after STORE-CCP@. The file name is made by appending
|
5299 |
|
|
@file{.storeccp} to the source file name.
|
5300 |
|
|
|
5301 |
|
|
@item pre
|
5302 |
|
|
@opindex fdump-tree-pre
|
5303 |
|
|
Dump trees after partial redundancy elimination. The file name is made
|
5304 |
|
|
by appending @file{.pre} to the source file name.
|
5305 |
|
|
|
5306 |
|
|
@item fre
|
5307 |
|
|
@opindex fdump-tree-fre
|
5308 |
|
|
Dump trees after full redundancy elimination. The file name is made
|
5309 |
|
|
by appending @file{.fre} to the source file name.
|
5310 |
|
|
|
5311 |
|
|
@item copyprop
|
5312 |
|
|
@opindex fdump-tree-copyprop
|
5313 |
|
|
Dump trees after copy propagation. The file name is made
|
5314 |
|
|
by appending @file{.copyprop} to the source file name.
|
5315 |
|
|
|
5316 |
|
|
@item store_copyprop
|
5317 |
|
|
@opindex fdump-tree-store_copyprop
|
5318 |
|
|
Dump trees after store copy-propagation. The file name is made
|
5319 |
|
|
by appending @file{.store_copyprop} to the source file name.
|
5320 |
|
|
|
5321 |
|
|
@item dce
|
5322 |
|
|
@opindex fdump-tree-dce
|
5323 |
|
|
Dump each function after dead code elimination. The file name is made by
|
5324 |
|
|
appending @file{.dce} to the source file name.
|
5325 |
|
|
|
5326 |
|
|
@item mudflap
|
5327 |
|
|
@opindex fdump-tree-mudflap
|
5328 |
|
|
Dump each function after adding mudflap instrumentation. The file name is
|
5329 |
|
|
made by appending @file{.mudflap} to the source file name.
|
5330 |
|
|
|
5331 |
|
|
@item sra
|
5332 |
|
|
@opindex fdump-tree-sra
|
5333 |
|
|
Dump each function after performing scalar replacement of aggregates. The
|
5334 |
|
|
file name is made by appending @file{.sra} to the source file name.
|
5335 |
|
|
|
5336 |
|
|
@item sink
|
5337 |
|
|
@opindex fdump-tree-sink
|
5338 |
|
|
Dump each function after performing code sinking. The file name is made
|
5339 |
|
|
by appending @file{.sink} to the source file name.
|
5340 |
|
|
|
5341 |
|
|
@item dom
|
5342 |
|
|
@opindex fdump-tree-dom
|
5343 |
|
|
Dump each function after applying dominator tree optimizations. The file
|
5344 |
|
|
name is made by appending @file{.dom} to the source file name.
|
5345 |
|
|
|
5346 |
|
|
@item dse
|
5347 |
|
|
@opindex fdump-tree-dse
|
5348 |
|
|
Dump each function after applying dead store elimination. The file
|
5349 |
|
|
name is made by appending @file{.dse} to the source file name.
|
5350 |
|
|
|
5351 |
|
|
@item phiopt
|
5352 |
|
|
@opindex fdump-tree-phiopt
|
5353 |
|
|
Dump each function after optimizing PHI nodes into straightline code. The file
|
5354 |
|
|
name is made by appending @file{.phiopt} to the source file name.
|
5355 |
|
|
|
5356 |
|
|
@item forwprop
|
5357 |
|
|
@opindex fdump-tree-forwprop
|
5358 |
|
|
Dump each function after forward propagating single use variables. The file
|
5359 |
|
|
name is made by appending @file{.forwprop} to the source file name.
|
5360 |
|
|
|
5361 |
|
|
@item copyrename
|
5362 |
|
|
@opindex fdump-tree-copyrename
|
5363 |
|
|
Dump each function after applying the copy rename optimization. The file
|
5364 |
|
|
name is made by appending @file{.copyrename} to the source file name.
|
5365 |
|
|
|
5366 |
|
|
@item nrv
|
5367 |
|
|
@opindex fdump-tree-nrv
|
5368 |
|
|
Dump each function after applying the named return value optimization on
|
5369 |
|
|
generic trees. The file name is made by appending @file{.nrv} to the source
|
5370 |
|
|
file name.
|
5371 |
|
|
|
5372 |
|
|
@item vect
|
5373 |
|
|
@opindex fdump-tree-vect
|
5374 |
|
|
Dump each function after applying vectorization of loops. The file name is
|
5375 |
|
|
made by appending @file{.vect} to the source file name.
|
5376 |
|
|
|
5377 |
|
|
@item slp
|
5378 |
|
|
@opindex fdump-tree-slp
|
5379 |
|
|
Dump each function after applying vectorization of basic blocks. The file name
|
5380 |
|
|
is made by appending @file{.slp} to the source file name.
|
5381 |
|
|
|
5382 |
|
|
@item vrp
|
5383 |
|
|
@opindex fdump-tree-vrp
|
5384 |
|
|
Dump each function after Value Range Propagation (VRP). The file name
|
5385 |
|
|
is made by appending @file{.vrp} to the source file name.
|
5386 |
|
|
|
5387 |
|
|
@item all
|
5388 |
|
|
@opindex fdump-tree-all
|
5389 |
|
|
Enable all the available tree dumps with the flags provided in this option.
|
5390 |
|
|
@end table
|
5391 |
|
|
|
5392 |
|
|
@item -ftree-vectorizer-verbose=@var{n}
|
5393 |
|
|
@opindex ftree-vectorizer-verbose
|
5394 |
|
|
This option controls the amount of debugging output the vectorizer prints.
|
5395 |
|
|
This information is written to standard error, unless
|
5396 |
|
|
@option{-fdump-tree-all} or @option{-fdump-tree-vect} is specified,
|
5397 |
|
|
in which case it is output to the usual dump listing file, @file{.vect}.
|
5398 |
|
|
For @var{n}=0 no diagnostic information is reported.
|
5399 |
|
|
If @var{n}=1 the vectorizer reports each loop that got vectorized,
|
5400 |
|
|
and the total number of loops that got vectorized.
|
5401 |
|
|
If @var{n}=2 the vectorizer also reports non-vectorized loops that passed
|
5402 |
|
|
the first analysis phase (vect_analyze_loop_form) - i.e.@: countable,
|
5403 |
|
|
inner-most, single-bb, single-entry/exit loops. This is the same verbosity
|
5404 |
|
|
level that @option{-fdump-tree-vect-stats} uses.
|
5405 |
|
|
Higher verbosity levels mean either more information dumped for each
|
5406 |
|
|
reported loop, or same amount of information reported for more loops:
|
5407 |
|
|
if @var{n}=3, vectorizer cost model information is reported.
|
5408 |
|
|
If @var{n}=4, alignment related information is added to the reports.
|
5409 |
|
|
If @var{n}=5, data-references related information (e.g.@: memory dependences,
|
5410 |
|
|
memory access-patterns) is added to the reports.
|
5411 |
|
|
If @var{n}=6, the vectorizer reports also non-vectorized inner-most loops
|
5412 |
|
|
that did not pass the first analysis phase (i.e., may not be countable, or
|
5413 |
|
|
may have complicated control-flow).
|
5414 |
|
|
If @var{n}=7, the vectorizer reports also non-vectorized nested loops.
|
5415 |
|
|
If @var{n}=8, SLP related information is added to the reports.
|
5416 |
|
|
For @var{n}=9, all the information the vectorizer generates during its
|
5417 |
|
|
analysis and transformation is reported. This is the same verbosity level
|
5418 |
|
|
that @option{-fdump-tree-vect-details} uses.
|
5419 |
|
|
|
5420 |
|
|
@item -frandom-seed=@var{string}
|
5421 |
|
|
@opindex frandom-seed
|
5422 |
|
|
This option provides a seed that GCC uses when it would otherwise use
|
5423 |
|
|
random numbers. It is used to generate certain symbol names
|
5424 |
|
|
that have to be different in every compiled file. It is also used to
|
5425 |
|
|
place unique stamps in coverage data files and the object files that
|
5426 |
|
|
produce them. You can use the @option{-frandom-seed} option to produce
|
5427 |
|
|
reproducibly identical object files.
|
5428 |
|
|
|
5429 |
|
|
The @var{string} should be different for every file you compile.
|
5430 |
|
|
|
5431 |
|
|
@item -fsched-verbose=@var{n}
|
5432 |
|
|
@opindex fsched-verbose
|
5433 |
|
|
On targets that use instruction scheduling, this option controls the
|
5434 |
|
|
amount of debugging output the scheduler prints. This information is
|
5435 |
|
|
written to standard error, unless @option{-fdump-rtl-sched1} or
|
5436 |
|
|
@option{-fdump-rtl-sched2} is specified, in which case it is output
|
5437 |
|
|
to the usual dump listing file, @file{.sched1} or @file{.sched2}
|
5438 |
|
|
respectively. However for @var{n} greater than nine, the output is
|
5439 |
|
|
always printed to standard error.
|
5440 |
|
|
|
5441 |
|
|
For @var{n} greater than zero, @option{-fsched-verbose} outputs the
|
5442 |
|
|
same information as @option{-fdump-rtl-sched1} and @option{-fdump-rtl-sched2}.
|
5443 |
|
|
For @var{n} greater than one, it also output basic block probabilities,
|
5444 |
|
|
detailed ready list information and unit/insn info. For @var{n} greater
|
5445 |
|
|
than two, it includes RTL at abort point, control-flow and regions info.
|
5446 |
|
|
And for @var{n} over four, @option{-fsched-verbose} also includes
|
5447 |
|
|
dependence info.
|
5448 |
|
|
|
5449 |
|
|
@item -save-temps
|
5450 |
|
|
@itemx -save-temps=cwd
|
5451 |
|
|
@opindex save-temps
|
5452 |
|
|
Store the usual ``temporary'' intermediate files permanently; place them
|
5453 |
|
|
in the current directory and name them based on the source file. Thus,
|
5454 |
|
|
compiling @file{foo.c} with @samp{-c -save-temps} would produce files
|
5455 |
|
|
@file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a
|
5456 |
|
|
preprocessed @file{foo.i} output file even though the compiler now
|
5457 |
|
|
normally uses an integrated preprocessor.
|
5458 |
|
|
|
5459 |
|
|
When used in combination with the @option{-x} command line option,
|
5460 |
|
|
@option{-save-temps} is sensible enough to avoid over writing an
|
5461 |
|
|
input source file with the same extension as an intermediate file.
|
5462 |
|
|
The corresponding intermediate file may be obtained by renaming the
|
5463 |
|
|
source file before using @option{-save-temps}.
|
5464 |
|
|
|
5465 |
|
|
If you invoke GCC in parallel, compiling several different source
|
5466 |
|
|
files that share a common base name in different subdirectories or the
|
5467 |
|
|
same source file compiled for multiple output destinations, it is
|
5468 |
|
|
likely that the different parallel compilers will interfere with each
|
5469 |
|
|
other, and overwrite the temporary files. For instance:
|
5470 |
|
|
|
5471 |
|
|
@smallexample
|
5472 |
|
|
gcc -save-temps -o outdir1/foo.o indir1/foo.c&
|
5473 |
|
|
gcc -save-temps -o outdir2/foo.o indir2/foo.c&
|
5474 |
|
|
@end smallexample
|
5475 |
|
|
|
5476 |
|
|
may result in @file{foo.i} and @file{foo.o} being written to
|
5477 |
|
|
simultaneously by both compilers.
|
5478 |
|
|
|
5479 |
|
|
@item -save-temps=obj
|
5480 |
|
|
@opindex save-temps=obj
|
5481 |
|
|
Store the usual ``temporary'' intermediate files permanently. If the
|
5482 |
|
|
@option{-o} option is used, the temporary files are based on the
|
5483 |
|
|
object file. If the @option{-o} option is not used, the
|
5484 |
|
|
@option{-save-temps=obj} switch behaves like @option{-save-temps}.
|
5485 |
|
|
|
5486 |
|
|
For example:
|
5487 |
|
|
|
5488 |
|
|
@smallexample
|
5489 |
|
|
gcc -save-temps=obj -c foo.c
|
5490 |
|
|
gcc -save-temps=obj -c bar.c -o dir/xbar.o
|
5491 |
|
|
gcc -save-temps=obj foobar.c -o dir2/yfoobar
|
5492 |
|
|
@end smallexample
|
5493 |
|
|
|
5494 |
|
|
would create @file{foo.i}, @file{foo.s}, @file{dir/xbar.i},
|
5495 |
|
|
@file{dir/xbar.s}, @file{dir2/yfoobar.i}, @file{dir2/yfoobar.s}, and
|
5496 |
|
|
@file{dir2/yfoobar.o}.
|
5497 |
|
|
|
5498 |
|
|
@item -time@r{[}=@var{file}@r{]}
|
5499 |
|
|
@opindex time
|
5500 |
|
|
Report the CPU time taken by each subprocess in the compilation
|
5501 |
|
|
sequence. For C source files, this is the compiler proper and assembler
|
5502 |
|
|
(plus the linker if linking is done).
|
5503 |
|
|
|
5504 |
|
|
Without the specification of an output file, the output looks like this:
|
5505 |
|
|
|
5506 |
|
|
@smallexample
|
5507 |
|
|
# cc1 0.12 0.01
|
5508 |
|
|
# as 0.00 0.01
|
5509 |
|
|
@end smallexample
|
5510 |
|
|
|
5511 |
|
|
The first number on each line is the ``user time'', that is time spent
|
5512 |
|
|
executing the program itself. The second number is ``system time'',
|
5513 |
|
|
time spent executing operating system routines on behalf of the program.
|
5514 |
|
|
Both numbers are in seconds.
|
5515 |
|
|
|
5516 |
|
|
With the specification of an output file, the output is appended to the
|
5517 |
|
|
named file, and it looks like this:
|
5518 |
|
|
|
5519 |
|
|
@smallexample
|
5520 |
|
|
0.12 0.01 cc1 @var{options}
|
5521 |
|
|
0.00 0.01 as @var{options}
|
5522 |
|
|
@end smallexample
|
5523 |
|
|
|
5524 |
|
|
The ``user time'' and the ``system time'' are moved before the program
|
5525 |
|
|
name, and the options passed to the program are displayed, so that one
|
5526 |
|
|
can later tell what file was being compiled, and with which options.
|
5527 |
|
|
|
5528 |
|
|
@item -fvar-tracking
|
5529 |
|
|
@opindex fvar-tracking
|
5530 |
|
|
Run variable tracking pass. It computes where variables are stored at each
|
5531 |
|
|
position in code. Better debugging information is then generated
|
5532 |
|
|
(if the debugging information format supports this information).
|
5533 |
|
|
|
5534 |
|
|
It is enabled by default when compiling with optimization (@option{-Os},
|
5535 |
|
|
@option{-O}, @option{-O2}, @dots{}), debugging information (@option{-g}) and
|
5536 |
|
|
the debug info format supports it.
|
5537 |
|
|
|
5538 |
|
|
@item -fvar-tracking-assignments
|
5539 |
|
|
@opindex fvar-tracking-assignments
|
5540 |
|
|
@opindex fno-var-tracking-assignments
|
5541 |
|
|
Annotate assignments to user variables early in the compilation and
|
5542 |
|
|
attempt to carry the annotations over throughout the compilation all the
|
5543 |
|
|
way to the end, in an attempt to improve debug information while
|
5544 |
|
|
optimizing. Use of @option{-gdwarf-4} is recommended along with it.
|
5545 |
|
|
|
5546 |
|
|
It can be enabled even if var-tracking is disabled, in which case
|
5547 |
|
|
annotations will be created and maintained, but discarded at the end.
|
5548 |
|
|
|
5549 |
|
|
@item -fvar-tracking-assignments-toggle
|
5550 |
|
|
@opindex fvar-tracking-assignments-toggle
|
5551 |
|
|
@opindex fno-var-tracking-assignments-toggle
|
5552 |
|
|
Toggle @option{-fvar-tracking-assignments}, in the same way that
|
5553 |
|
|
@option{-gtoggle} toggles @option{-g}.
|
5554 |
|
|
|
5555 |
|
|
@item -print-file-name=@var{library}
|
5556 |
|
|
@opindex print-file-name
|
5557 |
|
|
Print the full absolute name of the library file @var{library} that
|
5558 |
|
|
would be used when linking---and don't do anything else. With this
|
5559 |
|
|
option, GCC does not compile or link anything; it just prints the
|
5560 |
|
|
file name.
|
5561 |
|
|
|
5562 |
|
|
@item -print-multi-directory
|
5563 |
|
|
@opindex print-multi-directory
|
5564 |
|
|
Print the directory name corresponding to the multilib selected by any
|
5565 |
|
|
other switches present in the command line. This directory is supposed
|
5566 |
|
|
to exist in @env{GCC_EXEC_PREFIX}.
|
5567 |
|
|
|
5568 |
|
|
@item -print-multi-lib
|
5569 |
|
|
@opindex print-multi-lib
|
5570 |
|
|
Print the mapping from multilib directory names to compiler switches
|
5571 |
|
|
that enable them. The directory name is separated from the switches by
|
5572 |
|
|
@samp{;}, and each switch starts with an @samp{@@} instead of the
|
5573 |
|
|
@samp{-}, without spaces between multiple switches. This is supposed to
|
5574 |
|
|
ease shell-processing.
|
5575 |
|
|
|
5576 |
|
|
@item -print-multi-os-directory
|
5577 |
|
|
@opindex print-multi-os-directory
|
5578 |
|
|
Print the path to OS libraries for the selected
|
5579 |
|
|
multilib, relative to some @file{lib} subdirectory. If OS libraries are
|
5580 |
|
|
present in the @file{lib} subdirectory and no multilibs are used, this is
|
5581 |
|
|
usually just @file{.}, if OS libraries are present in @file{lib@var{suffix}}
|
5582 |
|
|
sibling directories this prints e.g.@: @file{../lib64}, @file{../lib} or
|
5583 |
|
|
@file{../lib32}, or if OS libraries are present in @file{lib/@var{subdir}}
|
5584 |
|
|
subdirectories it prints e.g.@: @file{amd64}, @file{sparcv9} or @file{ev6}.
|
5585 |
|
|
|
5586 |
|
|
@item -print-prog-name=@var{program}
|
5587 |
|
|
@opindex print-prog-name
|
5588 |
|
|
Like @option{-print-file-name}, but searches for a program such as @samp{cpp}.
|
5589 |
|
|
|
5590 |
|
|
@item -print-libgcc-file-name
|
5591 |
|
|
@opindex print-libgcc-file-name
|
5592 |
|
|
Same as @option{-print-file-name=libgcc.a}.
|
5593 |
|
|
|
5594 |
|
|
This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs}
|
5595 |
|
|
but you do want to link with @file{libgcc.a}. You can do
|
5596 |
|
|
|
5597 |
|
|
@smallexample
|
5598 |
|
|
gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name`
|
5599 |
|
|
@end smallexample
|
5600 |
|
|
|
5601 |
|
|
@item -print-search-dirs
|
5602 |
|
|
@opindex print-search-dirs
|
5603 |
|
|
Print the name of the configured installation directory and a list of
|
5604 |
|
|
program and library directories @command{gcc} will search---and don't do anything else.
|
5605 |
|
|
|
5606 |
|
|
This is useful when @command{gcc} prints the error message
|
5607 |
|
|
@samp{installation problem, cannot exec cpp0: No such file or directory}.
|
5608 |
|
|
To resolve this you either need to put @file{cpp0} and the other compiler
|
5609 |
|
|
components where @command{gcc} expects to find them, or you can set the environment
|
5610 |
|
|
variable @env{GCC_EXEC_PREFIX} to the directory where you installed them.
|
5611 |
|
|
Don't forget the trailing @samp{/}.
|
5612 |
|
|
@xref{Environment Variables}.
|
5613 |
|
|
|
5614 |
|
|
@item -print-sysroot
|
5615 |
|
|
@opindex print-sysroot
|
5616 |
|
|
Print the target sysroot directory that will be used during
|
5617 |
|
|
compilation. This is the target sysroot specified either at configure
|
5618 |
|
|
time or using the @option{--sysroot} option, possibly with an extra
|
5619 |
|
|
suffix that depends on compilation options. If no target sysroot is
|
5620 |
|
|
specified, the option prints nothing.
|
5621 |
|
|
|
5622 |
|
|
@item -print-sysroot-headers-suffix
|
5623 |
|
|
@opindex print-sysroot-headers-suffix
|
5624 |
|
|
Print the suffix added to the target sysroot when searching for
|
5625 |
|
|
headers, or give an error if the compiler is not configured with such
|
5626 |
|
|
a suffix---and don't do anything else.
|
5627 |
|
|
|
5628 |
|
|
@item -dumpmachine
|
5629 |
|
|
@opindex dumpmachine
|
5630 |
|
|
Print the compiler's target machine (for example,
|
5631 |
|
|
@samp{i686-pc-linux-gnu})---and don't do anything else.
|
5632 |
|
|
|
5633 |
|
|
@item -dumpversion
|
5634 |
|
|
@opindex dumpversion
|
5635 |
|
|
Print the compiler version (for example, @samp{3.0})---and don't do
|
5636 |
|
|
anything else.
|
5637 |
|
|
|
5638 |
|
|
@item -dumpspecs
|
5639 |
|
|
@opindex dumpspecs
|
5640 |
|
|
Print the compiler's built-in specs---and don't do anything else. (This
|
5641 |
|
|
is used when GCC itself is being built.) @xref{Spec Files}.
|
5642 |
|
|
|
5643 |
|
|
@item -feliminate-unused-debug-types
|
5644 |
|
|
@opindex feliminate-unused-debug-types
|
5645 |
|
|
Normally, when producing DWARF2 output, GCC will emit debugging
|
5646 |
|
|
information for all types declared in a compilation
|
5647 |
|
|
unit, regardless of whether or not they are actually used
|
5648 |
|
|
in that compilation unit. Sometimes this is useful, such as
|
5649 |
|
|
if, in the debugger, you want to cast a value to a type that is
|
5650 |
|
|
not actually used in your program (but is declared). More often,
|
5651 |
|
|
however, this results in a significant amount of wasted space.
|
5652 |
|
|
With this option, GCC will avoid producing debug symbol output
|
5653 |
|
|
for types that are nowhere used in the source file being compiled.
|
5654 |
|
|
@end table
|
5655 |
|
|
|
5656 |
|
|
@node Optimize Options
|
5657 |
|
|
@section Options That Control Optimization
|
5658 |
|
|
@cindex optimize options
|
5659 |
|
|
@cindex options, optimization
|
5660 |
|
|
|
5661 |
|
|
These options control various sorts of optimizations.
|
5662 |
|
|
|
5663 |
|
|
Without any optimization option, the compiler's goal is to reduce the
|
5664 |
|
|
cost of compilation and to make debugging produce the expected
|
5665 |
|
|
results. Statements are independent: if you stop the program with a
|
5666 |
|
|
breakpoint between statements, you can then assign a new value to any
|
5667 |
|
|
variable or change the program counter to any other statement in the
|
5668 |
|
|
function and get exactly the results you would expect from the source
|
5669 |
|
|
code.
|
5670 |
|
|
|
5671 |
|
|
Turning on optimization flags makes the compiler attempt to improve
|
5672 |
|
|
the performance and/or code size at the expense of compilation time
|
5673 |
|
|
and possibly the ability to debug the program.
|
5674 |
|
|
|
5675 |
|
|
The compiler performs optimization based on the knowledge it has of the
|
5676 |
|
|
program. Compiling multiple files at once to a single output file mode allows
|
5677 |
|
|
the compiler to use information gained from all of the files when compiling
|
5678 |
|
|
each of them.
|
5679 |
|
|
|
5680 |
|
|
Not all optimizations are controlled directly by a flag. Only
|
5681 |
|
|
optimizations that have a flag are listed in this section.
|
5682 |
|
|
|
5683 |
|
|
Most optimizations are only enabled if an @option{-O} level is set on
|
5684 |
|
|
the command line. Otherwise they are disabled, even if individual
|
5685 |
|
|
optimization flags are specified.
|
5686 |
|
|
|
5687 |
|
|
Depending on the target and how GCC was configured, a slightly different
|
5688 |
|
|
set of optimizations may be enabled at each @option{-O} level than
|
5689 |
|
|
those listed here. You can invoke GCC with @samp{-Q --help=optimizers}
|
5690 |
|
|
to find out the exact set of optimizations that are enabled at each level.
|
5691 |
|
|
@xref{Overall Options}, for examples.
|
5692 |
|
|
|
5693 |
|
|
@table @gcctabopt
|
5694 |
|
|
@item -O
|
5695 |
|
|
@itemx -O1
|
5696 |
|
|
@opindex O
|
5697 |
|
|
@opindex O1
|
5698 |
|
|
Optimize. Optimizing compilation takes somewhat more time, and a lot
|
5699 |
|
|
more memory for a large function.
|
5700 |
|
|
|
5701 |
|
|
With @option{-O}, the compiler tries to reduce code size and execution
|
5702 |
|
|
time, without performing any optimizations that take a great deal of
|
5703 |
|
|
compilation time.
|
5704 |
|
|
|
5705 |
|
|
@option{-O} turns on the following optimization flags:
|
5706 |
|
|
@gccoptlist{
|
5707 |
|
|
-fauto-inc-dec @gol
|
5708 |
|
|
-fcprop-registers @gol
|
5709 |
|
|
-fdce @gol
|
5710 |
|
|
-fdefer-pop @gol
|
5711 |
|
|
-fdelayed-branch @gol
|
5712 |
|
|
-fdse @gol
|
5713 |
|
|
-fguess-branch-probability @gol
|
5714 |
|
|
-fif-conversion2 @gol
|
5715 |
|
|
-fif-conversion @gol
|
5716 |
|
|
-fipa-pure-const @gol
|
5717 |
|
|
-fipa-reference @gol
|
5718 |
|
|
-fmerge-constants
|
5719 |
|
|
-fsplit-wide-types @gol
|
5720 |
|
|
-ftree-builtin-call-dce @gol
|
5721 |
|
|
-ftree-ccp @gol
|
5722 |
|
|
-ftree-ch @gol
|
5723 |
|
|
-ftree-copyrename @gol
|
5724 |
|
|
-ftree-dce @gol
|
5725 |
|
|
-ftree-dominator-opts @gol
|
5726 |
|
|
-ftree-dse @gol
|
5727 |
|
|
-ftree-forwprop @gol
|
5728 |
|
|
-ftree-fre @gol
|
5729 |
|
|
-ftree-phiprop @gol
|
5730 |
|
|
-ftree-sra @gol
|
5731 |
|
|
-ftree-pta @gol
|
5732 |
|
|
-ftree-ter @gol
|
5733 |
|
|
-funit-at-a-time}
|
5734 |
|
|
|
5735 |
|
|
@option{-O} also turns on @option{-fomit-frame-pointer} on machines
|
5736 |
|
|
where doing so does not interfere with debugging.
|
5737 |
|
|
|
5738 |
|
|
@item -O2
|
5739 |
|
|
@opindex O2
|
5740 |
|
|
Optimize even more. GCC performs nearly all supported optimizations
|
5741 |
|
|
that do not involve a space-speed tradeoff.
|
5742 |
|
|
As compared to @option{-O}, this option increases both compilation time
|
5743 |
|
|
and the performance of the generated code.
|
5744 |
|
|
|
5745 |
|
|
@option{-O2} turns on all optimization flags specified by @option{-O}. It
|
5746 |
|
|
also turns on the following optimization flags:
|
5747 |
|
|
@gccoptlist{-fthread-jumps @gol
|
5748 |
|
|
-falign-functions -falign-jumps @gol
|
5749 |
|
|
-falign-loops -falign-labels @gol
|
5750 |
|
|
-fcaller-saves @gol
|
5751 |
|
|
-fcrossjumping @gol
|
5752 |
|
|
-fcse-follow-jumps -fcse-skip-blocks @gol
|
5753 |
|
|
-fdelete-null-pointer-checks @gol
|
5754 |
|
|
-fexpensive-optimizations @gol
|
5755 |
|
|
-fgcse -fgcse-lm @gol
|
5756 |
|
|
-finline-small-functions @gol
|
5757 |
|
|
-findirect-inlining @gol
|
5758 |
|
|
-fipa-sra @gol
|
5759 |
|
|
-foptimize-sibling-calls @gol
|
5760 |
|
|
-fpeephole2 @gol
|
5761 |
|
|
-fregmove @gol
|
5762 |
|
|
-freorder-blocks -freorder-functions @gol
|
5763 |
|
|
-frerun-cse-after-loop @gol
|
5764 |
|
|
-fsched-interblock -fsched-spec @gol
|
5765 |
|
|
-fschedule-insns -fschedule-insns2 @gol
|
5766 |
|
|
-fstrict-aliasing -fstrict-overflow @gol
|
5767 |
|
|
-ftree-switch-conversion @gol
|
5768 |
|
|
-ftree-pre @gol
|
5769 |
|
|
-ftree-vrp}
|
5770 |
|
|
|
5771 |
|
|
Please note the warning under @option{-fgcse} about
|
5772 |
|
|
invoking @option{-O2} on programs that use computed gotos.
|
5773 |
|
|
|
5774 |
|
|
@item -O3
|
5775 |
|
|
@opindex O3
|
5776 |
|
|
Optimize yet more. @option{-O3} turns on all optimizations specified
|
5777 |
|
|
by @option{-O2} and also turns on the @option{-finline-functions},
|
5778 |
|
|
@option{-funswitch-loops}, @option{-fpredictive-commoning},
|
5779 |
|
|
@option{-fgcse-after-reload} and @option{-ftree-vectorize} options.
|
5780 |
|
|
|
5781 |
|
|
@item -O0
|
5782 |
|
|
@opindex O0
|
5783 |
|
|
Reduce compilation time and make debugging produce the expected
|
5784 |
|
|
results. This is the default.
|
5785 |
|
|
|
5786 |
|
|
@item -Os
|
5787 |
|
|
@opindex Os
|
5788 |
|
|
Optimize for size. @option{-Os} enables all @option{-O2} optimizations that
|
5789 |
|
|
do not typically increase code size. It also performs further
|
5790 |
|
|
optimizations designed to reduce code size.
|
5791 |
|
|
|
5792 |
|
|
@option{-Os} disables the following optimization flags:
|
5793 |
|
|
@gccoptlist{-falign-functions -falign-jumps -falign-loops @gol
|
5794 |
|
|
-falign-labels -freorder-blocks -freorder-blocks-and-partition @gol
|
5795 |
|
|
-fprefetch-loop-arrays -ftree-vect-loop-version}
|
5796 |
|
|
|
5797 |
|
|
If you use multiple @option{-O} options, with or without level numbers,
|
5798 |
|
|
the last such option is the one that is effective.
|
5799 |
|
|
@end table
|
5800 |
|
|
|
5801 |
|
|
Options of the form @option{-f@var{flag}} specify machine-independent
|
5802 |
|
|
flags. Most flags have both positive and negative forms; the negative
|
5803 |
|
|
form of @option{-ffoo} would be @option{-fno-foo}. In the table
|
5804 |
|
|
below, only one of the forms is listed---the one you typically will
|
5805 |
|
|
use. You can figure out the other form by either removing @samp{no-}
|
5806 |
|
|
or adding it.
|
5807 |
|
|
|
5808 |
|
|
The following options control specific optimizations. They are either
|
5809 |
|
|
activated by @option{-O} options or are related to ones that are. You
|
5810 |
|
|
can use the following flags in the rare cases when ``fine-tuning'' of
|
5811 |
|
|
optimizations to be performed is desired.
|
5812 |
|
|
|
5813 |
|
|
@table @gcctabopt
|
5814 |
|
|
@item -fno-default-inline
|
5815 |
|
|
@opindex fno-default-inline
|
5816 |
|
|
Do not make member functions inline by default merely because they are
|
5817 |
|
|
defined inside the class scope (C++ only). Otherwise, when you specify
|
5818 |
|
|
@w{@option{-O}}, member functions defined inside class scope are compiled
|
5819 |
|
|
inline by default; i.e., you don't need to add @samp{inline} in front of
|
5820 |
|
|
the member function name.
|
5821 |
|
|
|
5822 |
|
|
@item -fno-defer-pop
|
5823 |
|
|
@opindex fno-defer-pop
|
5824 |
|
|
Always pop the arguments to each function call as soon as that function
|
5825 |
|
|
returns. For machines which must pop arguments after a function call,
|
5826 |
|
|
the compiler normally lets arguments accumulate on the stack for several
|
5827 |
|
|
function calls and pops them all at once.
|
5828 |
|
|
|
5829 |
|
|
Disabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
5830 |
|
|
|
5831 |
|
|
@item -fforward-propagate
|
5832 |
|
|
@opindex fforward-propagate
|
5833 |
|
|
Perform a forward propagation pass on RTL@. The pass tries to combine two
|
5834 |
|
|
instructions and checks if the result can be simplified. If loop unrolling
|
5835 |
|
|
is active, two passes are performed and the second is scheduled after
|
5836 |
|
|
loop unrolling.
|
5837 |
|
|
|
5838 |
|
|
This option is enabled by default at optimization levels @option{-O},
|
5839 |
|
|
@option{-O2}, @option{-O3}, @option{-Os}.
|
5840 |
|
|
|
5841 |
|
|
@item -fomit-frame-pointer
|
5842 |
|
|
@opindex fomit-frame-pointer
|
5843 |
|
|
Don't keep the frame pointer in a register for functions that
|
5844 |
|
|
don't need one. This avoids the instructions to save, set up and
|
5845 |
|
|
restore frame pointers; it also makes an extra register available
|
5846 |
|
|
in many functions. @strong{It also makes debugging impossible on
|
5847 |
|
|
some machines.}
|
5848 |
|
|
|
5849 |
|
|
On some machines, such as the VAX, this flag has no effect, because
|
5850 |
|
|
the standard calling sequence automatically handles the frame pointer
|
5851 |
|
|
and nothing is saved by pretending it doesn't exist. The
|
5852 |
|
|
machine-description macro @code{FRAME_POINTER_REQUIRED} controls
|
5853 |
|
|
whether a target machine supports this flag. @xref{Registers,,Register
|
5854 |
|
|
Usage, gccint, GNU Compiler Collection (GCC) Internals}.
|
5855 |
|
|
|
5856 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
5857 |
|
|
|
5858 |
|
|
@item -foptimize-sibling-calls
|
5859 |
|
|
@opindex foptimize-sibling-calls
|
5860 |
|
|
Optimize sibling and tail recursive calls.
|
5861 |
|
|
|
5862 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
5863 |
|
|
|
5864 |
|
|
@item -fno-inline
|
5865 |
|
|
@opindex fno-inline
|
5866 |
|
|
Don't pay attention to the @code{inline} keyword. Normally this option
|
5867 |
|
|
is used to keep the compiler from expanding any functions inline.
|
5868 |
|
|
Note that if you are not optimizing, no functions can be expanded inline.
|
5869 |
|
|
|
5870 |
|
|
@item -finline-small-functions
|
5871 |
|
|
@opindex finline-small-functions
|
5872 |
|
|
Integrate functions into their callers when their body is smaller than expected
|
5873 |
|
|
function call code (so overall size of program gets smaller). The compiler
|
5874 |
|
|
heuristically decides which functions are simple enough to be worth integrating
|
5875 |
|
|
in this way.
|
5876 |
|
|
|
5877 |
|
|
Enabled at level @option{-O2}.
|
5878 |
|
|
|
5879 |
|
|
@item -findirect-inlining
|
5880 |
|
|
@opindex findirect-inlining
|
5881 |
|
|
Inline also indirect calls that are discovered to be known at compile
|
5882 |
|
|
time thanks to previous inlining. This option has any effect only
|
5883 |
|
|
when inlining itself is turned on by the @option{-finline-functions}
|
5884 |
|
|
or @option{-finline-small-functions} options.
|
5885 |
|
|
|
5886 |
|
|
Enabled at level @option{-O2}.
|
5887 |
|
|
|
5888 |
|
|
@item -finline-functions
|
5889 |
|
|
@opindex finline-functions
|
5890 |
|
|
Integrate all simple functions into their callers. The compiler
|
5891 |
|
|
heuristically decides which functions are simple enough to be worth
|
5892 |
|
|
integrating in this way.
|
5893 |
|
|
|
5894 |
|
|
If all calls to a given function are integrated, and the function is
|
5895 |
|
|
declared @code{static}, then the function is normally not output as
|
5896 |
|
|
assembler code in its own right.
|
5897 |
|
|
|
5898 |
|
|
Enabled at level @option{-O3}.
|
5899 |
|
|
|
5900 |
|
|
@item -finline-functions-called-once
|
5901 |
|
|
@opindex finline-functions-called-once
|
5902 |
|
|
Consider all @code{static} functions called once for inlining into their
|
5903 |
|
|
caller even if they are not marked @code{inline}. If a call to a given
|
5904 |
|
|
function is integrated, then the function is not output as assembler code
|
5905 |
|
|
in its own right.
|
5906 |
|
|
|
5907 |
|
|
Enabled at levels @option{-O1}, @option{-O2}, @option{-O3} and @option{-Os}.
|
5908 |
|
|
|
5909 |
|
|
@item -fearly-inlining
|
5910 |
|
|
@opindex fearly-inlining
|
5911 |
|
|
Inline functions marked by @code{always_inline} and functions whose body seems
|
5912 |
|
|
smaller than the function call overhead early before doing
|
5913 |
|
|
@option{-fprofile-generate} instrumentation and real inlining pass. Doing so
|
5914 |
|
|
makes profiling significantly cheaper and usually inlining faster on programs
|
5915 |
|
|
having large chains of nested wrapper functions.
|
5916 |
|
|
|
5917 |
|
|
Enabled by default.
|
5918 |
|
|
|
5919 |
|
|
@item -fipa-sra
|
5920 |
|
|
@opindex fipa-sra
|
5921 |
|
|
Perform interprocedural scalar replacement of aggregates, removal of
|
5922 |
|
|
unused parameters and replacement of parameters passed by reference
|
5923 |
|
|
by parameters passed by value.
|
5924 |
|
|
|
5925 |
|
|
Enabled at levels @option{-O2}, @option{-O3} and @option{-Os}.
|
5926 |
|
|
|
5927 |
|
|
@item -finline-limit=@var{n}
|
5928 |
|
|
@opindex finline-limit
|
5929 |
|
|
By default, GCC limits the size of functions that can be inlined. This flag
|
5930 |
|
|
allows coarse control of this limit. @var{n} is the size of functions that
|
5931 |
|
|
can be inlined in number of pseudo instructions.
|
5932 |
|
|
|
5933 |
|
|
Inlining is actually controlled by a number of parameters, which may be
|
5934 |
|
|
specified individually by using @option{--param @var{name}=@var{value}}.
|
5935 |
|
|
The @option{-finline-limit=@var{n}} option sets some of these parameters
|
5936 |
|
|
as follows:
|
5937 |
|
|
|
5938 |
|
|
@table @gcctabopt
|
5939 |
|
|
@item max-inline-insns-single
|
5940 |
|
|
is set to @var{n}/2.
|
5941 |
|
|
@item max-inline-insns-auto
|
5942 |
|
|
is set to @var{n}/2.
|
5943 |
|
|
@end table
|
5944 |
|
|
|
5945 |
|
|
See below for a documentation of the individual
|
5946 |
|
|
parameters controlling inlining and for the defaults of these parameters.
|
5947 |
|
|
|
5948 |
|
|
@emph{Note:} there may be no value to @option{-finline-limit} that results
|
5949 |
|
|
in default behavior.
|
5950 |
|
|
|
5951 |
|
|
@emph{Note:} pseudo instruction represents, in this particular context, an
|
5952 |
|
|
abstract measurement of function's size. In no way does it represent a count
|
5953 |
|
|
of assembly instructions and as such its exact meaning might change from one
|
5954 |
|
|
release to an another.
|
5955 |
|
|
|
5956 |
|
|
@item -fkeep-inline-functions
|
5957 |
|
|
@opindex fkeep-inline-functions
|
5958 |
|
|
In C, emit @code{static} functions that are declared @code{inline}
|
5959 |
|
|
into the object file, even if the function has been inlined into all
|
5960 |
|
|
of its callers. This switch does not affect functions using the
|
5961 |
|
|
@code{extern inline} extension in GNU C90@. In C++, emit any and all
|
5962 |
|
|
inline functions into the object file.
|
5963 |
|
|
|
5964 |
|
|
@item -fkeep-static-consts
|
5965 |
|
|
@opindex fkeep-static-consts
|
5966 |
|
|
Emit variables declared @code{static const} when optimization isn't turned
|
5967 |
|
|
on, even if the variables aren't referenced.
|
5968 |
|
|
|
5969 |
|
|
GCC enables this option by default. If you want to force the compiler to
|
5970 |
|
|
check if the variable was referenced, regardless of whether or not
|
5971 |
|
|
optimization is turned on, use the @option{-fno-keep-static-consts} option.
|
5972 |
|
|
|
5973 |
|
|
@item -fmerge-constants
|
5974 |
|
|
@opindex fmerge-constants
|
5975 |
|
|
Attempt to merge identical constants (string constants and floating point
|
5976 |
|
|
constants) across compilation units.
|
5977 |
|
|
|
5978 |
|
|
This option is the default for optimized compilation if the assembler and
|
5979 |
|
|
linker support it. Use @option{-fno-merge-constants} to inhibit this
|
5980 |
|
|
behavior.
|
5981 |
|
|
|
5982 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
5983 |
|
|
|
5984 |
|
|
@item -fmerge-all-constants
|
5985 |
|
|
@opindex fmerge-all-constants
|
5986 |
|
|
Attempt to merge identical constants and identical variables.
|
5987 |
|
|
|
5988 |
|
|
This option implies @option{-fmerge-constants}. In addition to
|
5989 |
|
|
@option{-fmerge-constants} this considers e.g.@: even constant initialized
|
5990 |
|
|
arrays or initialized constant variables with integral or floating point
|
5991 |
|
|
types. Languages like C or C++ require each variable, including multiple
|
5992 |
|
|
instances of the same variable in recursive calls, to have distinct locations,
|
5993 |
|
|
so using this option will result in non-conforming
|
5994 |
|
|
behavior.
|
5995 |
|
|
|
5996 |
|
|
@item -fmodulo-sched
|
5997 |
|
|
@opindex fmodulo-sched
|
5998 |
|
|
Perform swing modulo scheduling immediately before the first scheduling
|
5999 |
|
|
pass. This pass looks at innermost loops and reorders their
|
6000 |
|
|
instructions by overlapping different iterations.
|
6001 |
|
|
|
6002 |
|
|
@item -fmodulo-sched-allow-regmoves
|
6003 |
|
|
@opindex fmodulo-sched-allow-regmoves
|
6004 |
|
|
Perform more aggressive SMS based modulo scheduling with register moves
|
6005 |
|
|
allowed. By setting this flag certain anti-dependences edges will be
|
6006 |
|
|
deleted which will trigger the generation of reg-moves based on the
|
6007 |
|
|
life-range analysis. This option is effective only with
|
6008 |
|
|
@option{-fmodulo-sched} enabled.
|
6009 |
|
|
|
6010 |
|
|
@item -fno-branch-count-reg
|
6011 |
|
|
@opindex fno-branch-count-reg
|
6012 |
|
|
Do not use ``decrement and branch'' instructions on a count register,
|
6013 |
|
|
but instead generate a sequence of instructions that decrement a
|
6014 |
|
|
register, compare it against zero, then branch based upon the result.
|
6015 |
|
|
This option is only meaningful on architectures that support such
|
6016 |
|
|
instructions, which include x86, PowerPC, IA-64 and S/390.
|
6017 |
|
|
|
6018 |
|
|
The default is @option{-fbranch-count-reg}.
|
6019 |
|
|
|
6020 |
|
|
@item -fno-function-cse
|
6021 |
|
|
@opindex fno-function-cse
|
6022 |
|
|
Do not put function addresses in registers; make each instruction that
|
6023 |
|
|
calls a constant function contain the function's address explicitly.
|
6024 |
|
|
|
6025 |
|
|
This option results in less efficient code, but some strange hacks
|
6026 |
|
|
that alter the assembler output may be confused by the optimizations
|
6027 |
|
|
performed when this option is not used.
|
6028 |
|
|
|
6029 |
|
|
The default is @option{-ffunction-cse}
|
6030 |
|
|
|
6031 |
|
|
@item -fno-zero-initialized-in-bss
|
6032 |
|
|
@opindex fno-zero-initialized-in-bss
|
6033 |
|
|
If the target supports a BSS section, GCC by default puts variables that
|
6034 |
|
|
are initialized to zero into BSS@. This can save space in the resulting
|
6035 |
|
|
code.
|
6036 |
|
|
|
6037 |
|
|
This option turns off this behavior because some programs explicitly
|
6038 |
|
|
rely on variables going to the data section. E.g., so that the
|
6039 |
|
|
resulting executable can find the beginning of that section and/or make
|
6040 |
|
|
assumptions based on that.
|
6041 |
|
|
|
6042 |
|
|
The default is @option{-fzero-initialized-in-bss}.
|
6043 |
|
|
|
6044 |
|
|
@item -fmudflap -fmudflapth -fmudflapir
|
6045 |
|
|
@opindex fmudflap
|
6046 |
|
|
@opindex fmudflapth
|
6047 |
|
|
@opindex fmudflapir
|
6048 |
|
|
@cindex bounds checking
|
6049 |
|
|
@cindex mudflap
|
6050 |
|
|
For front-ends that support it (C and C++), instrument all risky
|
6051 |
|
|
pointer/array dereferencing operations, some standard library
|
6052 |
|
|
string/heap functions, and some other associated constructs with
|
6053 |
|
|
range/validity tests. Modules so instrumented should be immune to
|
6054 |
|
|
buffer overflows, invalid heap use, and some other classes of C/C++
|
6055 |
|
|
programming errors. The instrumentation relies on a separate runtime
|
6056 |
|
|
library (@file{libmudflap}), which will be linked into a program if
|
6057 |
|
|
@option{-fmudflap} is given at link time. Run-time behavior of the
|
6058 |
|
|
instrumented program is controlled by the @env{MUDFLAP_OPTIONS}
|
6059 |
|
|
environment variable. See @code{env MUDFLAP_OPTIONS=-help a.out}
|
6060 |
|
|
for its options.
|
6061 |
|
|
|
6062 |
|
|
Use @option{-fmudflapth} instead of @option{-fmudflap} to compile and to
|
6063 |
|
|
link if your program is multi-threaded. Use @option{-fmudflapir}, in
|
6064 |
|
|
addition to @option{-fmudflap} or @option{-fmudflapth}, if
|
6065 |
|
|
instrumentation should ignore pointer reads. This produces less
|
6066 |
|
|
instrumentation (and therefore faster execution) and still provides
|
6067 |
|
|
some protection against outright memory corrupting writes, but allows
|
6068 |
|
|
erroneously read data to propagate within a program.
|
6069 |
|
|
|
6070 |
|
|
@item -fthread-jumps
|
6071 |
|
|
@opindex fthread-jumps
|
6072 |
|
|
Perform optimizations where we check to see if a jump branches to a
|
6073 |
|
|
location where another comparison subsumed by the first is found. If
|
6074 |
|
|
so, the first branch is redirected to either the destination of the
|
6075 |
|
|
second branch or a point immediately following it, depending on whether
|
6076 |
|
|
the condition is known to be true or false.
|
6077 |
|
|
|
6078 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6079 |
|
|
|
6080 |
|
|
@item -fsplit-wide-types
|
6081 |
|
|
@opindex fsplit-wide-types
|
6082 |
|
|
When using a type that occupies multiple registers, such as @code{long
|
6083 |
|
|
long} on a 32-bit system, split the registers apart and allocate them
|
6084 |
|
|
independently. This normally generates better code for those types,
|
6085 |
|
|
but may make debugging more difficult.
|
6086 |
|
|
|
6087 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3},
|
6088 |
|
|
@option{-Os}.
|
6089 |
|
|
|
6090 |
|
|
@item -fcse-follow-jumps
|
6091 |
|
|
@opindex fcse-follow-jumps
|
6092 |
|
|
In common subexpression elimination (CSE), scan through jump instructions
|
6093 |
|
|
when the target of the jump is not reached by any other path. For
|
6094 |
|
|
example, when CSE encounters an @code{if} statement with an
|
6095 |
|
|
@code{else} clause, CSE will follow the jump when the condition
|
6096 |
|
|
tested is false.
|
6097 |
|
|
|
6098 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6099 |
|
|
|
6100 |
|
|
@item -fcse-skip-blocks
|
6101 |
|
|
@opindex fcse-skip-blocks
|
6102 |
|
|
This is similar to @option{-fcse-follow-jumps}, but causes CSE to
|
6103 |
|
|
follow jumps which conditionally skip over blocks. When CSE
|
6104 |
|
|
encounters a simple @code{if} statement with no else clause,
|
6105 |
|
|
@option{-fcse-skip-blocks} causes CSE to follow the jump around the
|
6106 |
|
|
body of the @code{if}.
|
6107 |
|
|
|
6108 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6109 |
|
|
|
6110 |
|
|
@item -frerun-cse-after-loop
|
6111 |
|
|
@opindex frerun-cse-after-loop
|
6112 |
|
|
Re-run common subexpression elimination after loop optimizations has been
|
6113 |
|
|
performed.
|
6114 |
|
|
|
6115 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6116 |
|
|
|
6117 |
|
|
@item -fgcse
|
6118 |
|
|
@opindex fgcse
|
6119 |
|
|
Perform a global common subexpression elimination pass.
|
6120 |
|
|
This pass also performs global constant and copy propagation.
|
6121 |
|
|
|
6122 |
|
|
@emph{Note:} When compiling a program using computed gotos, a GCC
|
6123 |
|
|
extension, you may get better runtime performance if you disable
|
6124 |
|
|
the global common subexpression elimination pass by adding
|
6125 |
|
|
@option{-fno-gcse} to the command line.
|
6126 |
|
|
|
6127 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6128 |
|
|
|
6129 |
|
|
@item -fgcse-lm
|
6130 |
|
|
@opindex fgcse-lm
|
6131 |
|
|
When @option{-fgcse-lm} is enabled, global common subexpression elimination will
|
6132 |
|
|
attempt to move loads which are only killed by stores into themselves. This
|
6133 |
|
|
allows a loop containing a load/store sequence to be changed to a load outside
|
6134 |
|
|
the loop, and a copy/store within the loop.
|
6135 |
|
|
|
6136 |
|
|
Enabled by default when gcse is enabled.
|
6137 |
|
|
|
6138 |
|
|
@item -fgcse-sm
|
6139 |
|
|
@opindex fgcse-sm
|
6140 |
|
|
When @option{-fgcse-sm} is enabled, a store motion pass is run after
|
6141 |
|
|
global common subexpression elimination. This pass will attempt to move
|
6142 |
|
|
stores out of loops. When used in conjunction with @option{-fgcse-lm},
|
6143 |
|
|
loops containing a load/store sequence can be changed to a load before
|
6144 |
|
|
the loop and a store after the loop.
|
6145 |
|
|
|
6146 |
|
|
Not enabled at any optimization level.
|
6147 |
|
|
|
6148 |
|
|
@item -fgcse-las
|
6149 |
|
|
@opindex fgcse-las
|
6150 |
|
|
When @option{-fgcse-las} is enabled, the global common subexpression
|
6151 |
|
|
elimination pass eliminates redundant loads that come after stores to the
|
6152 |
|
|
same memory location (both partial and full redundancies).
|
6153 |
|
|
|
6154 |
|
|
Not enabled at any optimization level.
|
6155 |
|
|
|
6156 |
|
|
@item -fgcse-after-reload
|
6157 |
|
|
@opindex fgcse-after-reload
|
6158 |
|
|
When @option{-fgcse-after-reload} is enabled, a redundant load elimination
|
6159 |
|
|
pass is performed after reload. The purpose of this pass is to cleanup
|
6160 |
|
|
redundant spilling.
|
6161 |
|
|
|
6162 |
|
|
@item -funsafe-loop-optimizations
|
6163 |
|
|
@opindex funsafe-loop-optimizations
|
6164 |
|
|
If given, the loop optimizer will assume that loop indices do not
|
6165 |
|
|
overflow, and that the loops with nontrivial exit condition are not
|
6166 |
|
|
infinite. This enables a wider range of loop optimizations even if
|
6167 |
|
|
the loop optimizer itself cannot prove that these assumptions are valid.
|
6168 |
|
|
Using @option{-Wunsafe-loop-optimizations}, the compiler will warn you
|
6169 |
|
|
if it finds this kind of loop.
|
6170 |
|
|
|
6171 |
|
|
@item -fcrossjumping
|
6172 |
|
|
@opindex fcrossjumping
|
6173 |
|
|
Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The
|
6174 |
|
|
resulting code may or may not perform better than without cross-jumping.
|
6175 |
|
|
|
6176 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6177 |
|
|
|
6178 |
|
|
@item -fauto-inc-dec
|
6179 |
|
|
@opindex fauto-inc-dec
|
6180 |
|
|
Combine increments or decrements of addresses with memory accesses.
|
6181 |
|
|
This pass is always skipped on architectures that do not have
|
6182 |
|
|
instructions to support this. Enabled by default at @option{-O} and
|
6183 |
|
|
higher on architectures that support this.
|
6184 |
|
|
|
6185 |
|
|
@item -fdce
|
6186 |
|
|
@opindex fdce
|
6187 |
|
|
Perform dead code elimination (DCE) on RTL@.
|
6188 |
|
|
Enabled by default at @option{-O} and higher.
|
6189 |
|
|
|
6190 |
|
|
@item -fdse
|
6191 |
|
|
@opindex fdse
|
6192 |
|
|
Perform dead store elimination (DSE) on RTL@.
|
6193 |
|
|
Enabled by default at @option{-O} and higher.
|
6194 |
|
|
|
6195 |
|
|
@item -fif-conversion
|
6196 |
|
|
@opindex fif-conversion
|
6197 |
|
|
Attempt to transform conditional jumps into branch-less equivalents. This
|
6198 |
|
|
include use of conditional moves, min, max, set flags and abs instructions, and
|
6199 |
|
|
some tricks doable by standard arithmetics. The use of conditional execution
|
6200 |
|
|
on chips where it is available is controlled by @code{if-conversion2}.
|
6201 |
|
|
|
6202 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
6203 |
|
|
|
6204 |
|
|
@item -fif-conversion2
|
6205 |
|
|
@opindex fif-conversion2
|
6206 |
|
|
Use conditional execution (where available) to transform conditional jumps into
|
6207 |
|
|
branch-less equivalents.
|
6208 |
|
|
|
6209 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
6210 |
|
|
|
6211 |
|
|
@item -fdelete-null-pointer-checks
|
6212 |
|
|
@opindex fdelete-null-pointer-checks
|
6213 |
|
|
Assume that programs cannot safely dereference null pointers, and that
|
6214 |
|
|
no code or data element resides there. This enables simple constant
|
6215 |
|
|
folding optimizations at all optimization levels. In addition, other
|
6216 |
|
|
optimization passes in GCC use this flag to control global dataflow
|
6217 |
|
|
analyses that eliminate useless checks for null pointers; these assume
|
6218 |
|
|
that if a pointer is checked after it has already been dereferenced,
|
6219 |
|
|
it cannot be null.
|
6220 |
|
|
|
6221 |
|
|
Note however that in some environments this assumption is not true.
|
6222 |
|
|
Use @option{-fno-delete-null-pointer-checks} to disable this optimization
|
6223 |
|
|
for programs which depend on that behavior.
|
6224 |
|
|
|
6225 |
|
|
Some targets, especially embedded ones, disable this option at all levels.
|
6226 |
|
|
Otherwise it is enabled at all levels: @option{-O0}, @option{-O1},
|
6227 |
|
|
@option{-O2}, @option{-O3}, @option{-Os}. Passes that use the information
|
6228 |
|
|
are enabled independently at different optimization levels.
|
6229 |
|
|
|
6230 |
|
|
@item -fexpensive-optimizations
|
6231 |
|
|
@opindex fexpensive-optimizations
|
6232 |
|
|
Perform a number of minor optimizations that are relatively expensive.
|
6233 |
|
|
|
6234 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6235 |
|
|
|
6236 |
|
|
@item -foptimize-register-move
|
6237 |
|
|
@itemx -fregmove
|
6238 |
|
|
@opindex foptimize-register-move
|
6239 |
|
|
@opindex fregmove
|
6240 |
|
|
Attempt to reassign register numbers in move instructions and as
|
6241 |
|
|
operands of other simple instructions in order to maximize the amount of
|
6242 |
|
|
register tying. This is especially helpful on machines with two-operand
|
6243 |
|
|
instructions.
|
6244 |
|
|
|
6245 |
|
|
Note @option{-fregmove} and @option{-foptimize-register-move} are the same
|
6246 |
|
|
optimization.
|
6247 |
|
|
|
6248 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6249 |
|
|
|
6250 |
|
|
@item -fira-algorithm=@var{algorithm}
|
6251 |
|
|
Use specified coloring algorithm for the integrated register
|
6252 |
|
|
allocator. The @var{algorithm} argument should be @code{priority} or
|
6253 |
|
|
@code{CB}. The first algorithm specifies Chow's priority coloring,
|
6254 |
|
|
the second one specifies Chaitin-Briggs coloring. The second
|
6255 |
|
|
algorithm can be unimplemented for some architectures. If it is
|
6256 |
|
|
implemented, it is the default because Chaitin-Briggs coloring as a
|
6257 |
|
|
rule generates a better code.
|
6258 |
|
|
|
6259 |
|
|
@item -fira-region=@var{region}
|
6260 |
|
|
Use specified regions for the integrated register allocator. The
|
6261 |
|
|
@var{region} argument should be one of @code{all}, @code{mixed}, or
|
6262 |
|
|
@code{one}. The first value means using all loops as register
|
6263 |
|
|
allocation regions, the second value which is the default means using
|
6264 |
|
|
all loops except for loops with small register pressure as the
|
6265 |
|
|
regions, and third one means using all function as a single region.
|
6266 |
|
|
The first value can give best result for machines with small size and
|
6267 |
|
|
irregular register set, the third one results in faster and generates
|
6268 |
|
|
decent code and the smallest size code, and the default value usually
|
6269 |
|
|
give the best results in most cases and for most architectures.
|
6270 |
|
|
|
6271 |
|
|
@item -fira-coalesce
|
6272 |
|
|
@opindex fira-coalesce
|
6273 |
|
|
Do optimistic register coalescing. This option might be profitable for
|
6274 |
|
|
architectures with big regular register files.
|
6275 |
|
|
|
6276 |
|
|
@item -fira-loop-pressure
|
6277 |
|
|
@opindex fira-loop-pressure
|
6278 |
|
|
Use IRA to evaluate register pressure in loops for decision to move
|
6279 |
|
|
loop invariants. Usage of this option usually results in generation
|
6280 |
|
|
of faster and smaller code on machines with big register files (>= 32
|
6281 |
|
|
registers) but it can slow compiler down.
|
6282 |
|
|
|
6283 |
|
|
This option is enabled at level @option{-O3} for some targets.
|
6284 |
|
|
|
6285 |
|
|
@item -fno-ira-share-save-slots
|
6286 |
|
|
@opindex fno-ira-share-save-slots
|
6287 |
|
|
Switch off sharing stack slots used for saving call used hard
|
6288 |
|
|
registers living through a call. Each hard register will get a
|
6289 |
|
|
separate stack slot and as a result function stack frame will be
|
6290 |
|
|
bigger.
|
6291 |
|
|
|
6292 |
|
|
@item -fno-ira-share-spill-slots
|
6293 |
|
|
@opindex fno-ira-share-spill-slots
|
6294 |
|
|
Switch off sharing stack slots allocated for pseudo-registers. Each
|
6295 |
|
|
pseudo-register which did not get a hard register will get a separate
|
6296 |
|
|
stack slot and as a result function stack frame will be bigger.
|
6297 |
|
|
|
6298 |
|
|
@item -fira-verbose=@var{n}
|
6299 |
|
|
@opindex fira-verbose
|
6300 |
|
|
Set up how verbose dump file for the integrated register allocator
|
6301 |
|
|
will be. Default value is 5. If the value is greater or equal to 10,
|
6302 |
|
|
the dump file will be stderr as if the value were @var{n} minus 10.
|
6303 |
|
|
|
6304 |
|
|
@item -fdelayed-branch
|
6305 |
|
|
@opindex fdelayed-branch
|
6306 |
|
|
If supported for the target machine, attempt to reorder instructions
|
6307 |
|
|
to exploit instruction slots available after delayed branch
|
6308 |
|
|
instructions.
|
6309 |
|
|
|
6310 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
6311 |
|
|
|
6312 |
|
|
@item -fschedule-insns
|
6313 |
|
|
@opindex fschedule-insns
|
6314 |
|
|
If supported for the target machine, attempt to reorder instructions to
|
6315 |
|
|
eliminate execution stalls due to required data being unavailable. This
|
6316 |
|
|
helps machines that have slow floating point or memory load instructions
|
6317 |
|
|
by allowing other instructions to be issued until the result of the load
|
6318 |
|
|
or floating point instruction is required.
|
6319 |
|
|
|
6320 |
|
|
Enabled at levels @option{-O2}, @option{-O3}.
|
6321 |
|
|
|
6322 |
|
|
@item -fschedule-insns2
|
6323 |
|
|
@opindex fschedule-insns2
|
6324 |
|
|
Similar to @option{-fschedule-insns}, but requests an additional pass of
|
6325 |
|
|
instruction scheduling after register allocation has been done. This is
|
6326 |
|
|
especially useful on machines with a relatively small number of
|
6327 |
|
|
registers and where memory load instructions take more than one cycle.
|
6328 |
|
|
|
6329 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6330 |
|
|
|
6331 |
|
|
@item -fno-sched-interblock
|
6332 |
|
|
@opindex fno-sched-interblock
|
6333 |
|
|
Don't schedule instructions across basic blocks. This is normally
|
6334 |
|
|
enabled by default when scheduling before register allocation, i.e.@:
|
6335 |
|
|
with @option{-fschedule-insns} or at @option{-O2} or higher.
|
6336 |
|
|
|
6337 |
|
|
@item -fno-sched-spec
|
6338 |
|
|
@opindex fno-sched-spec
|
6339 |
|
|
Don't allow speculative motion of non-load instructions. This is normally
|
6340 |
|
|
enabled by default when scheduling before register allocation, i.e.@:
|
6341 |
|
|
with @option{-fschedule-insns} or at @option{-O2} or higher.
|
6342 |
|
|
|
6343 |
|
|
@item -fsched-pressure
|
6344 |
|
|
@opindex fsched-pressure
|
6345 |
|
|
Enable register pressure sensitive insn scheduling before the register
|
6346 |
|
|
allocation. This only makes sense when scheduling before register
|
6347 |
|
|
allocation is enabled, i.e.@: with @option{-fschedule-insns} or at
|
6348 |
|
|
@option{-O2} or higher. Usage of this option can improve the
|
6349 |
|
|
generated code and decrease its size by preventing register pressure
|
6350 |
|
|
increase above the number of available hard registers and as a
|
6351 |
|
|
consequence register spills in the register allocation.
|
6352 |
|
|
|
6353 |
|
|
@item -fsched-spec-load
|
6354 |
|
|
@opindex fsched-spec-load
|
6355 |
|
|
Allow speculative motion of some load instructions. This only makes
|
6356 |
|
|
sense when scheduling before register allocation, i.e.@: with
|
6357 |
|
|
@option{-fschedule-insns} or at @option{-O2} or higher.
|
6358 |
|
|
|
6359 |
|
|
@item -fsched-spec-load-dangerous
|
6360 |
|
|
@opindex fsched-spec-load-dangerous
|
6361 |
|
|
Allow speculative motion of more load instructions. This only makes
|
6362 |
|
|
sense when scheduling before register allocation, i.e.@: with
|
6363 |
|
|
@option{-fschedule-insns} or at @option{-O2} or higher.
|
6364 |
|
|
|
6365 |
|
|
@item -fsched-stalled-insns
|
6366 |
|
|
@itemx -fsched-stalled-insns=@var{n}
|
6367 |
|
|
@opindex fsched-stalled-insns
|
6368 |
|
|
Define how many insns (if any) can be moved prematurely from the queue
|
6369 |
|
|
of stalled insns into the ready list, during the second scheduling pass.
|
6370 |
|
|
@option{-fno-sched-stalled-insns} means that no insns will be moved
|
6371 |
|
|
prematurely, @option{-fsched-stalled-insns=0} means there is no limit
|
6372 |
|
|
on how many queued insns can be moved prematurely.
|
6373 |
|
|
@option{-fsched-stalled-insns} without a value is equivalent to
|
6374 |
|
|
@option{-fsched-stalled-insns=1}.
|
6375 |
|
|
|
6376 |
|
|
@item -fsched-stalled-insns-dep
|
6377 |
|
|
@itemx -fsched-stalled-insns-dep=@var{n}
|
6378 |
|
|
@opindex fsched-stalled-insns-dep
|
6379 |
|
|
Define how many insn groups (cycles) will be examined for a dependency
|
6380 |
|
|
on a stalled insn that is candidate for premature removal from the queue
|
6381 |
|
|
of stalled insns. This has an effect only during the second scheduling pass,
|
6382 |
|
|
and only if @option{-fsched-stalled-insns} is used.
|
6383 |
|
|
@option{-fno-sched-stalled-insns-dep} is equivalent to
|
6384 |
|
|
@option{-fsched-stalled-insns-dep=0}.
|
6385 |
|
|
@option{-fsched-stalled-insns-dep} without a value is equivalent to
|
6386 |
|
|
@option{-fsched-stalled-insns-dep=1}.
|
6387 |
|
|
|
6388 |
|
|
@item -fsched2-use-superblocks
|
6389 |
|
|
@opindex fsched2-use-superblocks
|
6390 |
|
|
When scheduling after register allocation, do use superblock scheduling
|
6391 |
|
|
algorithm. Superblock scheduling allows motion across basic block boundaries
|
6392 |
|
|
resulting on faster schedules. This option is experimental, as not all machine
|
6393 |
|
|
descriptions used by GCC model the CPU closely enough to avoid unreliable
|
6394 |
|
|
results from the algorithm.
|
6395 |
|
|
|
6396 |
|
|
This only makes sense when scheduling after register allocation, i.e.@: with
|
6397 |
|
|
@option{-fschedule-insns2} or at @option{-O2} or higher.
|
6398 |
|
|
|
6399 |
|
|
@item -fsched-group-heuristic
|
6400 |
|
|
@opindex fsched-group-heuristic
|
6401 |
|
|
Enable the group heuristic in the scheduler. This heuristic favors
|
6402 |
|
|
the instruction that belongs to a schedule group. This is enabled
|
6403 |
|
|
by default when scheduling is enabled, i.e.@: with @option{-fschedule-insns}
|
6404 |
|
|
or @option{-fschedule-insns2} or at @option{-O2} or higher.
|
6405 |
|
|
|
6406 |
|
|
@item -fsched-critical-path-heuristic
|
6407 |
|
|
@opindex fsched-critical-path-heuristic
|
6408 |
|
|
Enable the critical-path heuristic in the scheduler. This heuristic favors
|
6409 |
|
|
instructions on the critical path. This is enabled by default when
|
6410 |
|
|
scheduling is enabled, i.e.@: with @option{-fschedule-insns}
|
6411 |
|
|
or @option{-fschedule-insns2} or at @option{-O2} or higher.
|
6412 |
|
|
|
6413 |
|
|
@item -fsched-spec-insn-heuristic
|
6414 |
|
|
@opindex fsched-spec-insn-heuristic
|
6415 |
|
|
Enable the speculative instruction heuristic in the scheduler. This
|
6416 |
|
|
heuristic favors speculative instructions with greater dependency weakness.
|
6417 |
|
|
This is enabled by default when scheduling is enabled, i.e.@:
|
6418 |
|
|
with @option{-fschedule-insns} or @option{-fschedule-insns2}
|
6419 |
|
|
or at @option{-O2} or higher.
|
6420 |
|
|
|
6421 |
|
|
@item -fsched-rank-heuristic
|
6422 |
|
|
@opindex fsched-rank-heuristic
|
6423 |
|
|
Enable the rank heuristic in the scheduler. This heuristic favors
|
6424 |
|
|
the instruction belonging to a basic block with greater size or frequency.
|
6425 |
|
|
This is enabled by default when scheduling is enabled, i.e.@:
|
6426 |
|
|
with @option{-fschedule-insns} or @option{-fschedule-insns2} or
|
6427 |
|
|
at @option{-O2} or higher.
|
6428 |
|
|
|
6429 |
|
|
@item -fsched-last-insn-heuristic
|
6430 |
|
|
@opindex fsched-last-insn-heuristic
|
6431 |
|
|
Enable the last-instruction heuristic in the scheduler. This heuristic
|
6432 |
|
|
favors the instruction that is less dependent on the last instruction
|
6433 |
|
|
scheduled. This is enabled by default when scheduling is enabled,
|
6434 |
|
|
i.e.@: with @option{-fschedule-insns} or @option{-fschedule-insns2} or
|
6435 |
|
|
at @option{-O2} or higher.
|
6436 |
|
|
|
6437 |
|
|
@item -fsched-dep-count-heuristic
|
6438 |
|
|
@opindex fsched-dep-count-heuristic
|
6439 |
|
|
Enable the dependent-count heuristic in the scheduler. This heuristic
|
6440 |
|
|
favors the instruction that has more instructions depending on it.
|
6441 |
|
|
This is enabled by default when scheduling is enabled, i.e.@:
|
6442 |
|
|
with @option{-fschedule-insns} or @option{-fschedule-insns2} or
|
6443 |
|
|
at @option{-O2} or higher.
|
6444 |
|
|
|
6445 |
|
|
@item -freschedule-modulo-scheduled-loops
|
6446 |
|
|
@opindex freschedule-modulo-scheduled-loops
|
6447 |
|
|
The modulo scheduling comes before the traditional scheduling, if a loop
|
6448 |
|
|
was modulo scheduled we may want to prevent the later scheduling passes
|
6449 |
|
|
from changing its schedule, we use this option to control that.
|
6450 |
|
|
|
6451 |
|
|
@item -fselective-scheduling
|
6452 |
|
|
@opindex fselective-scheduling
|
6453 |
|
|
Schedule instructions using selective scheduling algorithm. Selective
|
6454 |
|
|
scheduling runs instead of the first scheduler pass.
|
6455 |
|
|
|
6456 |
|
|
@item -fselective-scheduling2
|
6457 |
|
|
@opindex fselective-scheduling2
|
6458 |
|
|
Schedule instructions using selective scheduling algorithm. Selective
|
6459 |
|
|
scheduling runs instead of the second scheduler pass.
|
6460 |
|
|
|
6461 |
|
|
@item -fsel-sched-pipelining
|
6462 |
|
|
@opindex fsel-sched-pipelining
|
6463 |
|
|
Enable software pipelining of innermost loops during selective scheduling.
|
6464 |
|
|
This option has no effect until one of @option{-fselective-scheduling} or
|
6465 |
|
|
@option{-fselective-scheduling2} is turned on.
|
6466 |
|
|
|
6467 |
|
|
@item -fsel-sched-pipelining-outer-loops
|
6468 |
|
|
@opindex fsel-sched-pipelining-outer-loops
|
6469 |
|
|
When pipelining loops during selective scheduling, also pipeline outer loops.
|
6470 |
|
|
This option has no effect until @option{-fsel-sched-pipelining} is turned on.
|
6471 |
|
|
|
6472 |
|
|
@item -fcaller-saves
|
6473 |
|
|
@opindex fcaller-saves
|
6474 |
|
|
Enable values to be allocated in registers that will be clobbered by
|
6475 |
|
|
function calls, by emitting extra instructions to save and restore the
|
6476 |
|
|
registers around such calls. Such allocation is done only when it
|
6477 |
|
|
seems to result in better code than would otherwise be produced.
|
6478 |
|
|
|
6479 |
|
|
This option is always enabled by default on certain machines, usually
|
6480 |
|
|
those which have no call-preserved registers to use instead.
|
6481 |
|
|
|
6482 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6483 |
|
|
|
6484 |
|
|
@item -fconserve-stack
|
6485 |
|
|
@opindex fconserve-stack
|
6486 |
|
|
Attempt to minimize stack usage. The compiler will attempt to use less
|
6487 |
|
|
stack space, even if that makes the program slower. This option
|
6488 |
|
|
implies setting the @option{large-stack-frame} parameter to 100
|
6489 |
|
|
and the @option{large-stack-frame-growth} parameter to 400.
|
6490 |
|
|
|
6491 |
|
|
@item -ftree-reassoc
|
6492 |
|
|
@opindex ftree-reassoc
|
6493 |
|
|
Perform reassociation on trees. This flag is enabled by default
|
6494 |
|
|
at @option{-O} and higher.
|
6495 |
|
|
|
6496 |
|
|
@item -ftree-pre
|
6497 |
|
|
@opindex ftree-pre
|
6498 |
|
|
Perform partial redundancy elimination (PRE) on trees. This flag is
|
6499 |
|
|
enabled by default at @option{-O2} and @option{-O3}.
|
6500 |
|
|
|
6501 |
|
|
@item -ftree-forwprop
|
6502 |
|
|
@opindex ftree-forwprop
|
6503 |
|
|
Perform forward propagation on trees. This flag is enabled by default
|
6504 |
|
|
at @option{-O} and higher.
|
6505 |
|
|
|
6506 |
|
|
@item -ftree-fre
|
6507 |
|
|
@opindex ftree-fre
|
6508 |
|
|
Perform full redundancy elimination (FRE) on trees. The difference
|
6509 |
|
|
between FRE and PRE is that FRE only considers expressions
|
6510 |
|
|
that are computed on all paths leading to the redundant computation.
|
6511 |
|
|
This analysis is faster than PRE, though it exposes fewer redundancies.
|
6512 |
|
|
This flag is enabled by default at @option{-O} and higher.
|
6513 |
|
|
|
6514 |
|
|
@item -ftree-phiprop
|
6515 |
|
|
@opindex ftree-phiprop
|
6516 |
|
|
Perform hoisting of loads from conditional pointers on trees. This
|
6517 |
|
|
pass is enabled by default at @option{-O} and higher.
|
6518 |
|
|
|
6519 |
|
|
@item -ftree-copy-prop
|
6520 |
|
|
@opindex ftree-copy-prop
|
6521 |
|
|
Perform copy propagation on trees. This pass eliminates unnecessary
|
6522 |
|
|
copy operations. This flag is enabled by default at @option{-O} and
|
6523 |
|
|
higher.
|
6524 |
|
|
|
6525 |
|
|
@item -fipa-pure-const
|
6526 |
|
|
@opindex fipa-pure-const
|
6527 |
|
|
Discover which functions are pure or constant.
|
6528 |
|
|
Enabled by default at @option{-O} and higher.
|
6529 |
|
|
|
6530 |
|
|
@item -fipa-reference
|
6531 |
|
|
@opindex fipa-reference
|
6532 |
|
|
Discover which static variables do not escape cannot escape the
|
6533 |
|
|
compilation unit.
|
6534 |
|
|
Enabled by default at @option{-O} and higher.
|
6535 |
|
|
|
6536 |
|
|
@item -fipa-struct-reorg
|
6537 |
|
|
@opindex fipa-struct-reorg
|
6538 |
|
|
Perform structure reorganization optimization, that change C-like structures
|
6539 |
|
|
layout in order to better utilize spatial locality. This transformation is
|
6540 |
|
|
affective for programs containing arrays of structures. Available in two
|
6541 |
|
|
compilation modes: profile-based (enabled with @option{-fprofile-generate})
|
6542 |
|
|
or static (which uses built-in heuristics). Require @option{-fipa-type-escape}
|
6543 |
|
|
to provide the safety of this transformation. It works only in whole program
|
6544 |
|
|
mode, so it requires @option{-fwhole-program} and @option{-combine} to be
|
6545 |
|
|
enabled. Structures considered @samp{cold} by this transformation are not
|
6546 |
|
|
affected (see @option{--param struct-reorg-cold-struct-ratio=@var{value}}).
|
6547 |
|
|
|
6548 |
|
|
With this flag, the program debug info reflects a new structure layout.
|
6549 |
|
|
|
6550 |
|
|
@item -fipa-pta
|
6551 |
|
|
@opindex fipa-pta
|
6552 |
|
|
Perform interprocedural pointer analysis. This option is experimental
|
6553 |
|
|
and does not affect generated code.
|
6554 |
|
|
|
6555 |
|
|
@item -fipa-cp
|
6556 |
|
|
@opindex fipa-cp
|
6557 |
|
|
Perform interprocedural constant propagation.
|
6558 |
|
|
This optimization analyzes the program to determine when values passed
|
6559 |
|
|
to functions are constants and then optimizes accordingly.
|
6560 |
|
|
This optimization can substantially increase performance
|
6561 |
|
|
if the application has constants passed to functions.
|
6562 |
|
|
This flag is enabled by default at @option{-O2}, @option{-Os} and @option{-O3}.
|
6563 |
|
|
|
6564 |
|
|
@item -fipa-cp-clone
|
6565 |
|
|
@opindex fipa-cp-clone
|
6566 |
|
|
Perform function cloning to make interprocedural constant propagation stronger.
|
6567 |
|
|
When enabled, interprocedural constant propagation will perform function cloning
|
6568 |
|
|
when externally visible function can be called with constant arguments.
|
6569 |
|
|
Because this optimization can create multiple copies of functions,
|
6570 |
|
|
it may significantly increase code size
|
6571 |
|
|
(see @option{--param ipcp-unit-growth=@var{value}}).
|
6572 |
|
|
This flag is enabled by default at @option{-O3}.
|
6573 |
|
|
|
6574 |
|
|
@item -fipa-matrix-reorg
|
6575 |
|
|
@opindex fipa-matrix-reorg
|
6576 |
|
|
Perform matrix flattening and transposing.
|
6577 |
|
|
Matrix flattening tries to replace an @math{m}-dimensional matrix
|
6578 |
|
|
with its equivalent @math{n}-dimensional matrix, where @math{n < m}.
|
6579 |
|
|
This reduces the level of indirection needed for accessing the elements
|
6580 |
|
|
of the matrix. The second optimization is matrix transposing that
|
6581 |
|
|
attempts to change the order of the matrix's dimensions in order to
|
6582 |
|
|
improve cache locality.
|
6583 |
|
|
Both optimizations need the @option{-fwhole-program} flag.
|
6584 |
|
|
Transposing is enabled only if profiling information is available.
|
6585 |
|
|
|
6586 |
|
|
@item -ftree-sink
|
6587 |
|
|
@opindex ftree-sink
|
6588 |
|
|
Perform forward store motion on trees. This flag is
|
6589 |
|
|
enabled by default at @option{-O} and higher.
|
6590 |
|
|
|
6591 |
|
|
@item -ftree-ccp
|
6592 |
|
|
@opindex ftree-ccp
|
6593 |
|
|
Perform sparse conditional constant propagation (CCP) on trees. This
|
6594 |
|
|
pass only operates on local scalar variables and is enabled by default
|
6595 |
|
|
at @option{-O} and higher.
|
6596 |
|
|
|
6597 |
|
|
@item -ftree-switch-conversion
|
6598 |
|
|
Perform conversion of simple initializations in a switch to
|
6599 |
|
|
initializations from a scalar array. This flag is enabled by default
|
6600 |
|
|
at @option{-O2} and higher.
|
6601 |
|
|
|
6602 |
|
|
@item -ftree-dce
|
6603 |
|
|
@opindex ftree-dce
|
6604 |
|
|
Perform dead code elimination (DCE) on trees. This flag is enabled by
|
6605 |
|
|
default at @option{-O} and higher.
|
6606 |
|
|
|
6607 |
|
|
@item -ftree-builtin-call-dce
|
6608 |
|
|
@opindex ftree-builtin-call-dce
|
6609 |
|
|
Perform conditional dead code elimination (DCE) for calls to builtin functions
|
6610 |
|
|
that may set @code{errno} but are otherwise side-effect free. This flag is
|
6611 |
|
|
enabled by default at @option{-O2} and higher if @option{-Os} is not also
|
6612 |
|
|
specified.
|
6613 |
|
|
|
6614 |
|
|
@item -ftree-dominator-opts
|
6615 |
|
|
@opindex ftree-dominator-opts
|
6616 |
|
|
Perform a variety of simple scalar cleanups (constant/copy
|
6617 |
|
|
propagation, redundancy elimination, range propagation and expression
|
6618 |
|
|
simplification) based on a dominator tree traversal. This also
|
6619 |
|
|
performs jump threading (to reduce jumps to jumps). This flag is
|
6620 |
|
|
enabled by default at @option{-O} and higher.
|
6621 |
|
|
|
6622 |
|
|
@item -ftree-dse
|
6623 |
|
|
@opindex ftree-dse
|
6624 |
|
|
Perform dead store elimination (DSE) on trees. A dead store is a store into
|
6625 |
|
|
a memory location which will later be overwritten by another store without
|
6626 |
|
|
any intervening loads. In this case the earlier store can be deleted. This
|
6627 |
|
|
flag is enabled by default at @option{-O} and higher.
|
6628 |
|
|
|
6629 |
|
|
@item -ftree-ch
|
6630 |
|
|
@opindex ftree-ch
|
6631 |
|
|
Perform loop header copying on trees. This is beneficial since it increases
|
6632 |
|
|
effectiveness of code motion optimizations. It also saves one jump. This flag
|
6633 |
|
|
is enabled by default at @option{-O} and higher. It is not enabled
|
6634 |
|
|
for @option{-Os}, since it usually increases code size.
|
6635 |
|
|
|
6636 |
|
|
@item -ftree-loop-optimize
|
6637 |
|
|
@opindex ftree-loop-optimize
|
6638 |
|
|
Perform loop optimizations on trees. This flag is enabled by default
|
6639 |
|
|
at @option{-O} and higher.
|
6640 |
|
|
|
6641 |
|
|
@item -ftree-loop-linear
|
6642 |
|
|
@opindex ftree-loop-linear
|
6643 |
|
|
Perform linear loop transformations on tree. This flag can improve cache
|
6644 |
|
|
performance and allow further loop optimizations to take place.
|
6645 |
|
|
|
6646 |
|
|
@item -floop-interchange
|
6647 |
|
|
Perform loop interchange transformations on loops. Interchanging two
|
6648 |
|
|
nested loops switches the inner and outer loops. For example, given a
|
6649 |
|
|
loop like:
|
6650 |
|
|
@smallexample
|
6651 |
|
|
DO J = 1, M
|
6652 |
|
|
DO I = 1, N
|
6653 |
|
|
A(J, I) = A(J, I) * C
|
6654 |
|
|
ENDDO
|
6655 |
|
|
ENDDO
|
6656 |
|
|
@end smallexample
|
6657 |
|
|
loop interchange will transform the loop as if the user had written:
|
6658 |
|
|
@smallexample
|
6659 |
|
|
DO I = 1, N
|
6660 |
|
|
DO J = 1, M
|
6661 |
|
|
A(J, I) = A(J, I) * C
|
6662 |
|
|
ENDDO
|
6663 |
|
|
ENDDO
|
6664 |
|
|
@end smallexample
|
6665 |
|
|
which can be beneficial when @code{N} is larger than the caches,
|
6666 |
|
|
because in Fortran, the elements of an array are stored in memory
|
6667 |
|
|
contiguously by column, and the original loop iterates over rows,
|
6668 |
|
|
potentially creating at each access a cache miss. This optimization
|
6669 |
|
|
applies to all the languages supported by GCC and is not limited to
|
6670 |
|
|
Fortran. To use this code transformation, GCC has to be configured
|
6671 |
|
|
with @option{--with-ppl} and @option{--with-cloog} to enable the
|
6672 |
|
|
Graphite loop transformation infrastructure.
|
6673 |
|
|
|
6674 |
|
|
@item -floop-strip-mine
|
6675 |
|
|
Perform loop strip mining transformations on loops. Strip mining
|
6676 |
|
|
splits a loop into two nested loops. The outer loop has strides
|
6677 |
|
|
equal to the strip size and the inner loop has strides of the
|
6678 |
|
|
original loop within a strip. The strip length can be changed
|
6679 |
|
|
using the @option{loop-block-tile-size} parameter. For example,
|
6680 |
|
|
given a loop like:
|
6681 |
|
|
@smallexample
|
6682 |
|
|
DO I = 1, N
|
6683 |
|
|
A(I) = A(I) + C
|
6684 |
|
|
ENDDO
|
6685 |
|
|
@end smallexample
|
6686 |
|
|
loop strip mining will transform the loop as if the user had written:
|
6687 |
|
|
@smallexample
|
6688 |
|
|
DO II = 1, N, 51
|
6689 |
|
|
DO I = II, min (II + 50, N)
|
6690 |
|
|
A(I) = A(I) + C
|
6691 |
|
|
ENDDO
|
6692 |
|
|
ENDDO
|
6693 |
|
|
@end smallexample
|
6694 |
|
|
This optimization applies to all the languages supported by GCC and is
|
6695 |
|
|
not limited to Fortran. To use this code transformation, GCC has to
|
6696 |
|
|
be configured with @option{--with-ppl} and @option{--with-cloog} to
|
6697 |
|
|
enable the Graphite loop transformation infrastructure.
|
6698 |
|
|
|
6699 |
|
|
@item -floop-block
|
6700 |
|
|
Perform loop blocking transformations on loops. Blocking strip mines
|
6701 |
|
|
each loop in the loop nest such that the memory accesses of the
|
6702 |
|
|
element loops fit inside caches. The strip length can be changed
|
6703 |
|
|
using the @option{loop-block-tile-size} parameter. For example, given
|
6704 |
|
|
a loop like:
|
6705 |
|
|
@smallexample
|
6706 |
|
|
DO I = 1, N
|
6707 |
|
|
DO J = 1, M
|
6708 |
|
|
A(J, I) = B(I) + C(J)
|
6709 |
|
|
ENDDO
|
6710 |
|
|
ENDDO
|
6711 |
|
|
@end smallexample
|
6712 |
|
|
loop blocking will transform the loop as if the user had written:
|
6713 |
|
|
@smallexample
|
6714 |
|
|
DO II = 1, N, 51
|
6715 |
|
|
DO JJ = 1, M, 51
|
6716 |
|
|
DO I = II, min (II + 50, N)
|
6717 |
|
|
DO J = JJ, min (JJ + 50, M)
|
6718 |
|
|
A(J, I) = B(I) + C(J)
|
6719 |
|
|
ENDDO
|
6720 |
|
|
ENDDO
|
6721 |
|
|
ENDDO
|
6722 |
|
|
ENDDO
|
6723 |
|
|
@end smallexample
|
6724 |
|
|
which can be beneficial when @code{M} is larger than the caches,
|
6725 |
|
|
because the innermost loop will iterate over a smaller amount of data
|
6726 |
|
|
that can be kept in the caches. This optimization applies to all the
|
6727 |
|
|
languages supported by GCC and is not limited to Fortran. To use this
|
6728 |
|
|
code transformation, GCC has to be configured with @option{--with-ppl}
|
6729 |
|
|
and @option{--with-cloog} to enable the Graphite loop transformation
|
6730 |
|
|
infrastructure.
|
6731 |
|
|
|
6732 |
|
|
@item -fgraphite-identity
|
6733 |
|
|
@opindex fgraphite-identity
|
6734 |
|
|
Enable the identity transformation for graphite. For every SCoP we generate
|
6735 |
|
|
the polyhedral representation and transform it back to gimple. Using
|
6736 |
|
|
@option{-fgraphite-identity} we can check the costs or benefits of the
|
6737 |
|
|
GIMPLE -> GRAPHITE -> GIMPLE transformation. Some minimal optimizations
|
6738 |
|
|
are also performed by the code generator CLooG, like index splitting and
|
6739 |
|
|
dead code elimination in loops.
|
6740 |
|
|
|
6741 |
|
|
@item -floop-parallelize-all
|
6742 |
|
|
Use the Graphite data dependence analysis to identify loops that can
|
6743 |
|
|
be parallelized. Parallelize all the loops that can be analyzed to
|
6744 |
|
|
not contain loop carried dependences without checking that it is
|
6745 |
|
|
profitable to parallelize the loops.
|
6746 |
|
|
|
6747 |
|
|
@item -fcheck-data-deps
|
6748 |
|
|
@opindex fcheck-data-deps
|
6749 |
|
|
Compare the results of several data dependence analyzers. This option
|
6750 |
|
|
is used for debugging the data dependence analyzers.
|
6751 |
|
|
|
6752 |
|
|
@item -ftree-loop-distribution
|
6753 |
|
|
Perform loop distribution. This flag can improve cache performance on
|
6754 |
|
|
big loop bodies and allow further loop optimizations, like
|
6755 |
|
|
parallelization or vectorization, to take place. For example, the loop
|
6756 |
|
|
@smallexample
|
6757 |
|
|
DO I = 1, N
|
6758 |
|
|
A(I) = B(I) + C
|
6759 |
|
|
D(I) = E(I) * F
|
6760 |
|
|
ENDDO
|
6761 |
|
|
@end smallexample
|
6762 |
|
|
is transformed to
|
6763 |
|
|
@smallexample
|
6764 |
|
|
DO I = 1, N
|
6765 |
|
|
A(I) = B(I) + C
|
6766 |
|
|
ENDDO
|
6767 |
|
|
DO I = 1, N
|
6768 |
|
|
D(I) = E(I) * F
|
6769 |
|
|
ENDDO
|
6770 |
|
|
@end smallexample
|
6771 |
|
|
|
6772 |
|
|
@item -ftree-loop-im
|
6773 |
|
|
@opindex ftree-loop-im
|
6774 |
|
|
Perform loop invariant motion on trees. This pass moves only invariants that
|
6775 |
|
|
would be hard to handle at RTL level (function calls, operations that expand to
|
6776 |
|
|
nontrivial sequences of insns). With @option{-funswitch-loops} it also moves
|
6777 |
|
|
operands of conditions that are invariant out of the loop, so that we can use
|
6778 |
|
|
just trivial invariantness analysis in loop unswitching. The pass also includes
|
6779 |
|
|
store motion.
|
6780 |
|
|
|
6781 |
|
|
@item -ftree-loop-ivcanon
|
6782 |
|
|
@opindex ftree-loop-ivcanon
|
6783 |
|
|
Create a canonical counter for number of iterations in the loop for that
|
6784 |
|
|
determining number of iterations requires complicated analysis. Later
|
6785 |
|
|
optimizations then may determine the number easily. Useful especially
|
6786 |
|
|
in connection with unrolling.
|
6787 |
|
|
|
6788 |
|
|
@item -fivopts
|
6789 |
|
|
@opindex fivopts
|
6790 |
|
|
Perform induction variable optimizations (strength reduction, induction
|
6791 |
|
|
variable merging and induction variable elimination) on trees.
|
6792 |
|
|
|
6793 |
|
|
@item -ftree-parallelize-loops=n
|
6794 |
|
|
@opindex ftree-parallelize-loops
|
6795 |
|
|
Parallelize loops, i.e., split their iteration space to run in n threads.
|
6796 |
|
|
This is only possible for loops whose iterations are independent
|
6797 |
|
|
and can be arbitrarily reordered. The optimization is only
|
6798 |
|
|
profitable on multiprocessor machines, for loops that are CPU-intensive,
|
6799 |
|
|
rather than constrained e.g.@: by memory bandwidth. This option
|
6800 |
|
|
implies @option{-pthread}, and thus is only supported on targets
|
6801 |
|
|
that have support for @option{-pthread}.
|
6802 |
|
|
|
6803 |
|
|
@item -ftree-pta
|
6804 |
|
|
@opindex ftree-pta
|
6805 |
|
|
Perform function-local points-to analysis on trees. This flag is
|
6806 |
|
|
enabled by default at @option{-O} and higher.
|
6807 |
|
|
|
6808 |
|
|
@item -ftree-sra
|
6809 |
|
|
@opindex ftree-sra
|
6810 |
|
|
Perform scalar replacement of aggregates. This pass replaces structure
|
6811 |
|
|
references with scalars to prevent committing structures to memory too
|
6812 |
|
|
early. This flag is enabled by default at @option{-O} and higher.
|
6813 |
|
|
|
6814 |
|
|
@item -ftree-copyrename
|
6815 |
|
|
@opindex ftree-copyrename
|
6816 |
|
|
Perform copy renaming on trees. This pass attempts to rename compiler
|
6817 |
|
|
temporaries to other variables at copy locations, usually resulting in
|
6818 |
|
|
variable names which more closely resemble the original variables. This flag
|
6819 |
|
|
is enabled by default at @option{-O} and higher.
|
6820 |
|
|
|
6821 |
|
|
@item -ftree-ter
|
6822 |
|
|
@opindex ftree-ter
|
6823 |
|
|
Perform temporary expression replacement during the SSA->normal phase. Single
|
6824 |
|
|
use/single def temporaries are replaced at their use location with their
|
6825 |
|
|
defining expression. This results in non-GIMPLE code, but gives the expanders
|
6826 |
|
|
much more complex trees to work on resulting in better RTL generation. This is
|
6827 |
|
|
enabled by default at @option{-O} and higher.
|
6828 |
|
|
|
6829 |
|
|
@item -ftree-vectorize
|
6830 |
|
|
@opindex ftree-vectorize
|
6831 |
|
|
Perform loop vectorization on trees. This flag is enabled by default at
|
6832 |
|
|
@option{-O3}.
|
6833 |
|
|
|
6834 |
|
|
@item -ftree-slp-vectorize
|
6835 |
|
|
@opindex ftree-slp-vectorize
|
6836 |
|
|
Perform basic block vectorization on trees. This flag is enabled by default at
|
6837 |
|
|
@option{-O3} and when @option{-ftree-vectorize} is enabled.
|
6838 |
|
|
|
6839 |
|
|
@item -ftree-vect-loop-version
|
6840 |
|
|
@opindex ftree-vect-loop-version
|
6841 |
|
|
Perform loop versioning when doing loop vectorization on trees. When a loop
|
6842 |
|
|
appears to be vectorizable except that data alignment or data dependence cannot
|
6843 |
|
|
be determined at compile time then vectorized and non-vectorized versions of
|
6844 |
|
|
the loop are generated along with runtime checks for alignment or dependence
|
6845 |
|
|
to control which version is executed. This option is enabled by default
|
6846 |
|
|
except at level @option{-Os} where it is disabled.
|
6847 |
|
|
|
6848 |
|
|
@item -fvect-cost-model
|
6849 |
|
|
@opindex fvect-cost-model
|
6850 |
|
|
Enable cost model for vectorization.
|
6851 |
|
|
|
6852 |
|
|
@item -ftree-vrp
|
6853 |
|
|
@opindex ftree-vrp
|
6854 |
|
|
Perform Value Range Propagation on trees. This is similar to the
|
6855 |
|
|
constant propagation pass, but instead of values, ranges of values are
|
6856 |
|
|
propagated. This allows the optimizers to remove unnecessary range
|
6857 |
|
|
checks like array bound checks and null pointer checks. This is
|
6858 |
|
|
enabled by default at @option{-O2} and higher. Null pointer check
|
6859 |
|
|
elimination is only done if @option{-fdelete-null-pointer-checks} is
|
6860 |
|
|
enabled.
|
6861 |
|
|
|
6862 |
|
|
@item -ftracer
|
6863 |
|
|
@opindex ftracer
|
6864 |
|
|
Perform tail duplication to enlarge superblock size. This transformation
|
6865 |
|
|
simplifies the control flow of the function allowing other optimizations to do
|
6866 |
|
|
better job.
|
6867 |
|
|
|
6868 |
|
|
@item -funroll-loops
|
6869 |
|
|
@opindex funroll-loops
|
6870 |
|
|
Unroll loops whose number of iterations can be determined at compile
|
6871 |
|
|
time or upon entry to the loop. @option{-funroll-loops} implies
|
6872 |
|
|
@option{-frerun-cse-after-loop}. This option makes code larger,
|
6873 |
|
|
and may or may not make it run faster.
|
6874 |
|
|
|
6875 |
|
|
@item -funroll-all-loops
|
6876 |
|
|
@opindex funroll-all-loops
|
6877 |
|
|
Unroll all loops, even if their number of iterations is uncertain when
|
6878 |
|
|
the loop is entered. This usually makes programs run more slowly.
|
6879 |
|
|
@option{-funroll-all-loops} implies the same options as
|
6880 |
|
|
@option{-funroll-loops},
|
6881 |
|
|
|
6882 |
|
|
@item -fsplit-ivs-in-unroller
|
6883 |
|
|
@opindex fsplit-ivs-in-unroller
|
6884 |
|
|
Enables expressing of values of induction variables in later iterations
|
6885 |
|
|
of the unrolled loop using the value in the first iteration. This breaks
|
6886 |
|
|
long dependency chains, thus improving efficiency of the scheduling passes.
|
6887 |
|
|
|
6888 |
|
|
Combination of @option{-fweb} and CSE is often sufficient to obtain the
|
6889 |
|
|
same effect. However in cases the loop body is more complicated than
|
6890 |
|
|
a single basic block, this is not reliable. It also does not work at all
|
6891 |
|
|
on some of the architectures due to restrictions in the CSE pass.
|
6892 |
|
|
|
6893 |
|
|
This optimization is enabled by default.
|
6894 |
|
|
|
6895 |
|
|
@item -fvariable-expansion-in-unroller
|
6896 |
|
|
@opindex fvariable-expansion-in-unroller
|
6897 |
|
|
With this option, the compiler will create multiple copies of some
|
6898 |
|
|
local variables when unrolling a loop which can result in superior code.
|
6899 |
|
|
|
6900 |
|
|
@item -fpredictive-commoning
|
6901 |
|
|
@opindex fpredictive-commoning
|
6902 |
|
|
Perform predictive commoning optimization, i.e., reusing computations
|
6903 |
|
|
(especially memory loads and stores) performed in previous
|
6904 |
|
|
iterations of loops.
|
6905 |
|
|
|
6906 |
|
|
This option is enabled at level @option{-O3}.
|
6907 |
|
|
|
6908 |
|
|
@item -fprefetch-loop-arrays
|
6909 |
|
|
@opindex fprefetch-loop-arrays
|
6910 |
|
|
If supported by the target machine, generate instructions to prefetch
|
6911 |
|
|
memory to improve the performance of loops that access large arrays.
|
6912 |
|
|
|
6913 |
|
|
This option may generate better or worse code; results are highly
|
6914 |
|
|
dependent on the structure of loops within the source code.
|
6915 |
|
|
|
6916 |
|
|
Disabled at level @option{-Os}.
|
6917 |
|
|
|
6918 |
|
|
@item -fno-peephole
|
6919 |
|
|
@itemx -fno-peephole2
|
6920 |
|
|
@opindex fno-peephole
|
6921 |
|
|
@opindex fno-peephole2
|
6922 |
|
|
Disable any machine-specific peephole optimizations. The difference
|
6923 |
|
|
between @option{-fno-peephole} and @option{-fno-peephole2} is in how they
|
6924 |
|
|
are implemented in the compiler; some targets use one, some use the
|
6925 |
|
|
other, a few use both.
|
6926 |
|
|
|
6927 |
|
|
@option{-fpeephole} is enabled by default.
|
6928 |
|
|
@option{-fpeephole2} enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6929 |
|
|
|
6930 |
|
|
@item -fno-guess-branch-probability
|
6931 |
|
|
@opindex fno-guess-branch-probability
|
6932 |
|
|
Do not guess branch probabilities using heuristics.
|
6933 |
|
|
|
6934 |
|
|
GCC will use heuristics to guess branch probabilities if they are
|
6935 |
|
|
not provided by profiling feedback (@option{-fprofile-arcs}). These
|
6936 |
|
|
heuristics are based on the control flow graph. If some branch probabilities
|
6937 |
|
|
are specified by @samp{__builtin_expect}, then the heuristics will be
|
6938 |
|
|
used to guess branch probabilities for the rest of the control flow graph,
|
6939 |
|
|
taking the @samp{__builtin_expect} info into account. The interactions
|
6940 |
|
|
between the heuristics and @samp{__builtin_expect} can be complex, and in
|
6941 |
|
|
some cases, it may be useful to disable the heuristics so that the effects
|
6942 |
|
|
of @samp{__builtin_expect} are easier to understand.
|
6943 |
|
|
|
6944 |
|
|
The default is @option{-fguess-branch-probability} at levels
|
6945 |
|
|
@option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
6946 |
|
|
|
6947 |
|
|
@item -freorder-blocks
|
6948 |
|
|
@opindex freorder-blocks
|
6949 |
|
|
Reorder basic blocks in the compiled function in order to reduce number of
|
6950 |
|
|
taken branches and improve code locality.
|
6951 |
|
|
|
6952 |
|
|
Enabled at levels @option{-O2}, @option{-O3}.
|
6953 |
|
|
|
6954 |
|
|
@item -freorder-blocks-and-partition
|
6955 |
|
|
@opindex freorder-blocks-and-partition
|
6956 |
|
|
In addition to reordering basic blocks in the compiled function, in order
|
6957 |
|
|
to reduce number of taken branches, partitions hot and cold basic blocks
|
6958 |
|
|
into separate sections of the assembly and .o files, to improve
|
6959 |
|
|
paging and cache locality performance.
|
6960 |
|
|
|
6961 |
|
|
This optimization is automatically turned off in the presence of
|
6962 |
|
|
exception handling, for linkonce sections, for functions with a user-defined
|
6963 |
|
|
section attribute and on any architecture that does not support named
|
6964 |
|
|
sections.
|
6965 |
|
|
|
6966 |
|
|
@item -freorder-functions
|
6967 |
|
|
@opindex freorder-functions
|
6968 |
|
|
Reorder functions in the object file in order to
|
6969 |
|
|
improve code locality. This is implemented by using special
|
6970 |
|
|
subsections @code{.text.hot} for most frequently executed functions and
|
6971 |
|
|
@code{.text.unlikely} for unlikely executed functions. Reordering is done by
|
6972 |
|
|
the linker so object file format must support named sections and linker must
|
6973 |
|
|
place them in a reasonable way.
|
6974 |
|
|
|
6975 |
|
|
Also profile feedback must be available in to make this option effective. See
|
6976 |
|
|
@option{-fprofile-arcs} for details.
|
6977 |
|
|
|
6978 |
|
|
Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
|
6979 |
|
|
|
6980 |
|
|
@item -fstrict-aliasing
|
6981 |
|
|
@opindex fstrict-aliasing
|
6982 |
|
|
Allow the compiler to assume the strictest aliasing rules applicable to
|
6983 |
|
|
the language being compiled. For C (and C++), this activates
|
6984 |
|
|
optimizations based on the type of expressions. In particular, an
|
6985 |
|
|
object of one type is assumed never to reside at the same address as an
|
6986 |
|
|
object of a different type, unless the types are almost the same. For
|
6987 |
|
|
example, an @code{unsigned int} can alias an @code{int}, but not a
|
6988 |
|
|
@code{void*} or a @code{double}. A character type may alias any other
|
6989 |
|
|
type.
|
6990 |
|
|
|
6991 |
|
|
@anchor{Type-punning}Pay special attention to code like this:
|
6992 |
|
|
@smallexample
|
6993 |
|
|
union a_union @{
|
6994 |
|
|
int i;
|
6995 |
|
|
double d;
|
6996 |
|
|
@};
|
6997 |
|
|
|
6998 |
|
|
int f() @{
|
6999 |
|
|
union a_union t;
|
7000 |
|
|
t.d = 3.0;
|
7001 |
|
|
return t.i;
|
7002 |
|
|
@}
|
7003 |
|
|
@end smallexample
|
7004 |
|
|
The practice of reading from a different union member than the one most
|
7005 |
|
|
recently written to (called ``type-punning'') is common. Even with
|
7006 |
|
|
@option{-fstrict-aliasing}, type-punning is allowed, provided the memory
|
7007 |
|
|
is accessed through the union type. So, the code above will work as
|
7008 |
|
|
expected. @xref{Structures unions enumerations and bit-fields
|
7009 |
|
|
implementation}. However, this code might not:
|
7010 |
|
|
@smallexample
|
7011 |
|
|
int f() @{
|
7012 |
|
|
union a_union t;
|
7013 |
|
|
int* ip;
|
7014 |
|
|
t.d = 3.0;
|
7015 |
|
|
ip = &t.i;
|
7016 |
|
|
return *ip;
|
7017 |
|
|
@}
|
7018 |
|
|
@end smallexample
|
7019 |
|
|
|
7020 |
|
|
Similarly, access by taking the address, casting the resulting pointer
|
7021 |
|
|
and dereferencing the result has undefined behavior, even if the cast
|
7022 |
|
|
uses a union type, e.g.:
|
7023 |
|
|
@smallexample
|
7024 |
|
|
int f() @{
|
7025 |
|
|
double d = 3.0;
|
7026 |
|
|
return ((union a_union *) &d)->i;
|
7027 |
|
|
@}
|
7028 |
|
|
@end smallexample
|
7029 |
|
|
|
7030 |
|
|
The @option{-fstrict-aliasing} option is enabled at levels
|
7031 |
|
|
@option{-O2}, @option{-O3}, @option{-Os}.
|
7032 |
|
|
|
7033 |
|
|
@item -fstrict-overflow
|
7034 |
|
|
@opindex fstrict-overflow
|
7035 |
|
|
Allow the compiler to assume strict signed overflow rules, depending
|
7036 |
|
|
on the language being compiled. For C (and C++) this means that
|
7037 |
|
|
overflow when doing arithmetic with signed numbers is undefined, which
|
7038 |
|
|
means that the compiler may assume that it will not happen. This
|
7039 |
|
|
permits various optimizations. For example, the compiler will assume
|
7040 |
|
|
that an expression like @code{i + 10 > i} will always be true for
|
7041 |
|
|
signed @code{i}. This assumption is only valid if signed overflow is
|
7042 |
|
|
undefined, as the expression is false if @code{i + 10} overflows when
|
7043 |
|
|
using twos complement arithmetic. When this option is in effect any
|
7044 |
|
|
attempt to determine whether an operation on signed numbers will
|
7045 |
|
|
overflow must be written carefully to not actually involve overflow.
|
7046 |
|
|
|
7047 |
|
|
This option also allows the compiler to assume strict pointer
|
7048 |
|
|
semantics: given a pointer to an object, if adding an offset to that
|
7049 |
|
|
pointer does not produce a pointer to the same object, the addition is
|
7050 |
|
|
undefined. This permits the compiler to conclude that @code{p + u >
|
7051 |
|
|
p} is always true for a pointer @code{p} and unsigned integer
|
7052 |
|
|
@code{u}. This assumption is only valid because pointer wraparound is
|
7053 |
|
|
undefined, as the expression is false if @code{p + u} overflows using
|
7054 |
|
|
twos complement arithmetic.
|
7055 |
|
|
|
7056 |
|
|
See also the @option{-fwrapv} option. Using @option{-fwrapv} means
|
7057 |
|
|
that integer signed overflow is fully defined: it wraps. When
|
7058 |
|
|
@option{-fwrapv} is used, there is no difference between
|
7059 |
|
|
@option{-fstrict-overflow} and @option{-fno-strict-overflow} for
|
7060 |
|
|
integers. With @option{-fwrapv} certain types of overflow are
|
7061 |
|
|
permitted. For example, if the compiler gets an overflow when doing
|
7062 |
|
|
arithmetic on constants, the overflowed value can still be used with
|
7063 |
|
|
@option{-fwrapv}, but not otherwise.
|
7064 |
|
|
|
7065 |
|
|
The @option{-fstrict-overflow} option is enabled at levels
|
7066 |
|
|
@option{-O2}, @option{-O3}, @option{-Os}.
|
7067 |
|
|
|
7068 |
|
|
@item -falign-functions
|
7069 |
|
|
@itemx -falign-functions=@var{n}
|
7070 |
|
|
@opindex falign-functions
|
7071 |
|
|
Align the start of functions to the next power-of-two greater than
|
7072 |
|
|
@var{n}, skipping up to @var{n} bytes. For instance,
|
7073 |
|
|
@option{-falign-functions=32} aligns functions to the next 32-byte
|
7074 |
|
|
boundary, but @option{-falign-functions=24} would align to the next
|
7075 |
|
|
32-byte boundary only if this can be done by skipping 23 bytes or less.
|
7076 |
|
|
|
7077 |
|
|
@option{-fno-align-functions} and @option{-falign-functions=1} are
|
7078 |
|
|
equivalent and mean that functions will not be aligned.
|
7079 |
|
|
|
7080 |
|
|
Some assemblers only support this flag when @var{n} is a power of two;
|
7081 |
|
|
in that case, it is rounded up.
|
7082 |
|
|
|
7083 |
|
|
If @var{n} is not specified or is zero, use a machine-dependent default.
|
7084 |
|
|
|
7085 |
|
|
Enabled at levels @option{-O2}, @option{-O3}.
|
7086 |
|
|
|
7087 |
|
|
@item -falign-labels
|
7088 |
|
|
@itemx -falign-labels=@var{n}
|
7089 |
|
|
@opindex falign-labels
|
7090 |
|
|
Align all branch targets to a power-of-two boundary, skipping up to
|
7091 |
|
|
@var{n} bytes like @option{-falign-functions}. This option can easily
|
7092 |
|
|
make code slower, because it must insert dummy operations for when the
|
7093 |
|
|
branch target is reached in the usual flow of the code.
|
7094 |
|
|
|
7095 |
|
|
@option{-fno-align-labels} and @option{-falign-labels=1} are
|
7096 |
|
|
equivalent and mean that labels will not be aligned.
|
7097 |
|
|
|
7098 |
|
|
If @option{-falign-loops} or @option{-falign-jumps} are applicable and
|
7099 |
|
|
are greater than this value, then their values are used instead.
|
7100 |
|
|
|
7101 |
|
|
If @var{n} is not specified or is zero, use a machine-dependent default
|
7102 |
|
|
which is very likely to be @samp{1}, meaning no alignment.
|
7103 |
|
|
|
7104 |
|
|
Enabled at levels @option{-O2}, @option{-O3}.
|
7105 |
|
|
|
7106 |
|
|
@item -falign-loops
|
7107 |
|
|
@itemx -falign-loops=@var{n}
|
7108 |
|
|
@opindex falign-loops
|
7109 |
|
|
Align loops to a power-of-two boundary, skipping up to @var{n} bytes
|
7110 |
|
|
like @option{-falign-functions}. The hope is that the loop will be
|
7111 |
|
|
executed many times, which will make up for any execution of the dummy
|
7112 |
|
|
operations.
|
7113 |
|
|
|
7114 |
|
|
@option{-fno-align-loops} and @option{-falign-loops=1} are
|
7115 |
|
|
equivalent and mean that loops will not be aligned.
|
7116 |
|
|
|
7117 |
|
|
If @var{n} is not specified or is zero, use a machine-dependent default.
|
7118 |
|
|
|
7119 |
|
|
Enabled at levels @option{-O2}, @option{-O3}.
|
7120 |
|
|
|
7121 |
|
|
@item -falign-jumps
|
7122 |
|
|
@itemx -falign-jumps=@var{n}
|
7123 |
|
|
@opindex falign-jumps
|
7124 |
|
|
Align branch targets to a power-of-two boundary, for branch targets
|
7125 |
|
|
where the targets can only be reached by jumping, skipping up to @var{n}
|
7126 |
|
|
bytes like @option{-falign-functions}. In this case, no dummy operations
|
7127 |
|
|
need be executed.
|
7128 |
|
|
|
7129 |
|
|
@option{-fno-align-jumps} and @option{-falign-jumps=1} are
|
7130 |
|
|
equivalent and mean that loops will not be aligned.
|
7131 |
|
|
|
7132 |
|
|
If @var{n} is not specified or is zero, use a machine-dependent default.
|
7133 |
|
|
|
7134 |
|
|
Enabled at levels @option{-O2}, @option{-O3}.
|
7135 |
|
|
|
7136 |
|
|
@item -funit-at-a-time
|
7137 |
|
|
@opindex funit-at-a-time
|
7138 |
|
|
This option is left for compatibility reasons. @option{-funit-at-a-time}
|
7139 |
|
|
has no effect, while @option{-fno-unit-at-a-time} implies
|
7140 |
|
|
@option{-fno-toplevel-reorder} and @option{-fno-section-anchors}.
|
7141 |
|
|
|
7142 |
|
|
Enabled by default.
|
7143 |
|
|
|
7144 |
|
|
@item -fno-toplevel-reorder
|
7145 |
|
|
@opindex fno-toplevel-reorder
|
7146 |
|
|
Do not reorder top-level functions, variables, and @code{asm}
|
7147 |
|
|
statements. Output them in the same order that they appear in the
|
7148 |
|
|
input file. When this option is used, unreferenced static variables
|
7149 |
|
|
will not be removed. This option is intended to support existing code
|
7150 |
|
|
which relies on a particular ordering. For new code, it is better to
|
7151 |
|
|
use attributes.
|
7152 |
|
|
|
7153 |
|
|
Enabled at level @option{-O0}. When disabled explicitly, it also imply
|
7154 |
|
|
@option{-fno-section-anchors} that is otherwise enabled at @option{-O0} on some
|
7155 |
|
|
targets.
|
7156 |
|
|
|
7157 |
|
|
@item -fweb
|
7158 |
|
|
@opindex fweb
|
7159 |
|
|
Constructs webs as commonly used for register allocation purposes and assign
|
7160 |
|
|
each web individual pseudo register. This allows the register allocation pass
|
7161 |
|
|
to operate on pseudos directly, but also strengthens several other optimization
|
7162 |
|
|
passes, such as CSE, loop optimizer and trivial dead code remover. It can,
|
7163 |
|
|
however, make debugging impossible, since variables will no longer stay in a
|
7164 |
|
|
``home register''.
|
7165 |
|
|
|
7166 |
|
|
Enabled by default with @option{-funroll-loops}.
|
7167 |
|
|
|
7168 |
|
|
@item -fwhole-program
|
7169 |
|
|
@opindex fwhole-program
|
7170 |
|
|
Assume that the current compilation unit represents the whole program being
|
7171 |
|
|
compiled. All public functions and variables with the exception of @code{main}
|
7172 |
|
|
and those merged by attribute @code{externally_visible} become static functions
|
7173 |
|
|
and in effect are optimized more aggressively by interprocedural optimizers.
|
7174 |
|
|
While this option is equivalent to proper use of the @code{static} keyword for
|
7175 |
|
|
programs consisting of a single file, in combination with option
|
7176 |
|
|
@option{-combine}, @option{-flto} or @option{-fwhopr} this flag can be used to
|
7177 |
|
|
compile many smaller scale programs since the functions and variables become
|
7178 |
|
|
local for the whole combined compilation unit, not for the single source file
|
7179 |
|
|
itself.
|
7180 |
|
|
|
7181 |
|
|
This option implies @option{-fwhole-file} for Fortran programs.
|
7182 |
|
|
|
7183 |
|
|
@item -flto
|
7184 |
|
|
@opindex flto
|
7185 |
|
|
This option runs the standard link-time optimizer. When invoked
|
7186 |
|
|
with source code, it generates GIMPLE (one of GCC's internal
|
7187 |
|
|
representations) and writes it to special ELF sections in the object
|
7188 |
|
|
file. When the object files are linked together, all the function
|
7189 |
|
|
bodies are read from these ELF sections and instantiated as if they
|
7190 |
|
|
had been part of the same translation unit.
|
7191 |
|
|
|
7192 |
|
|
To use the link-timer optimizer, @option{-flto} needs to be specified at
|
7193 |
|
|
compile time and during the final link. For example,
|
7194 |
|
|
|
7195 |
|
|
@smallexample
|
7196 |
|
|
gcc -c -O2 -flto foo.c
|
7197 |
|
|
gcc -c -O2 -flto bar.c
|
7198 |
|
|
gcc -o myprog -flto -O2 foo.o bar.o
|
7199 |
|
|
@end smallexample
|
7200 |
|
|
|
7201 |
|
|
The first two invocations to GCC will save a bytecode representation
|
7202 |
|
|
of GIMPLE into special ELF sections inside @file{foo.o} and
|
7203 |
|
|
@file{bar.o}. The final invocation will read the GIMPLE bytecode from
|
7204 |
|
|
@file{foo.o} and @file{bar.o}, merge the two files into a single
|
7205 |
|
|
internal image, and compile the result as usual. Since both
|
7206 |
|
|
@file{foo.o} and @file{bar.o} are merged into a single image, this
|
7207 |
|
|
causes all the inter-procedural analyses and optimizations in GCC to
|
7208 |
|
|
work across the two files as if they were a single one. This means,
|
7209 |
|
|
for example, that the inliner will be able to inline functions in
|
7210 |
|
|
@file{bar.o} into functions in @file{foo.o} and vice-versa.
|
7211 |
|
|
|
7212 |
|
|
Another (simpler) way to enable link-time optimization is,
|
7213 |
|
|
|
7214 |
|
|
@smallexample
|
7215 |
|
|
gcc -o myprog -flto -O2 foo.c bar.c
|
7216 |
|
|
@end smallexample
|
7217 |
|
|
|
7218 |
|
|
The above will generate bytecode for @file{foo.c} and @file{bar.c},
|
7219 |
|
|
merge them together into a single GIMPLE representation and optimize
|
7220 |
|
|
them as usual to produce @file{myprog}.
|
7221 |
|
|
|
7222 |
|
|
The only important thing to keep in mind is that to enable link-time
|
7223 |
|
|
optimizations the @option{-flto} flag needs to be passed to both the
|
7224 |
|
|
compile and the link commands.
|
7225 |
|
|
|
7226 |
|
|
Note that when a file is compiled with @option{-flto}, the generated
|
7227 |
|
|
object file will be larger than a regular object file because it will
|
7228 |
|
|
contain GIMPLE bytecodes and the usual final code. This means that
|
7229 |
|
|
object files with LTO information can be linked as a normal object
|
7230 |
|
|
file. So, in the previous example, if the final link is done with
|
7231 |
|
|
|
7232 |
|
|
@smallexample
|
7233 |
|
|
gcc -o myprog foo.o bar.o
|
7234 |
|
|
@end smallexample
|
7235 |
|
|
|
7236 |
|
|
The only difference will be that no inter-procedural optimizations
|
7237 |
|
|
will be applied to produce @file{myprog}. The two object files
|
7238 |
|
|
@file{foo.o} and @file{bar.o} will be simply sent to the regular
|
7239 |
|
|
linker.
|
7240 |
|
|
|
7241 |
|
|
Additionally, the optimization flags used to compile individual files
|
7242 |
|
|
are not necessarily related to those used at link-time. For instance,
|
7243 |
|
|
|
7244 |
|
|
@smallexample
|
7245 |
|
|
gcc -c -O0 -flto foo.c
|
7246 |
|
|
gcc -c -O0 -flto bar.c
|
7247 |
|
|
gcc -o myprog -flto -O3 foo.o bar.o
|
7248 |
|
|
@end smallexample
|
7249 |
|
|
|
7250 |
|
|
This will produce individual object files with unoptimized assembler
|
7251 |
|
|
code, but the resulting binary @file{myprog} will be optimized at
|
7252 |
|
|
@option{-O3}. Now, if the final binary is generated without
|
7253 |
|
|
@option{-flto}, then @file{myprog} will not be optimized.
|
7254 |
|
|
|
7255 |
|
|
When producing the final binary with @option{-flto}, GCC will only
|
7256 |
|
|
apply link-time optimizations to those files that contain bytecode.
|
7257 |
|
|
Therefore, you can mix and match object files and libraries with
|
7258 |
|
|
GIMPLE bytecodes and final object code. GCC will automatically select
|
7259 |
|
|
which files to optimize in LTO mode and which files to link without
|
7260 |
|
|
further processing.
|
7261 |
|
|
|
7262 |
|
|
There are some code generation flags that GCC will preserve when
|
7263 |
|
|
generating bytecodes, as they need to be used during the final link
|
7264 |
|
|
stage. Currently, the following options are saved into the GIMPLE
|
7265 |
|
|
bytecode files: @option{-fPIC}, @option{-fcommon} and all the
|
7266 |
|
|
@option{-m} target flags.
|
7267 |
|
|
|
7268 |
|
|
At link time, these options are read-in and reapplied. Note that the
|
7269 |
|
|
current implementation makes no attempt at recognizing conflicting
|
7270 |
|
|
values for these options. If two or more files have a conflicting
|
7271 |
|
|
value (e.g., one file is compiled with @option{-fPIC} and another
|
7272 |
|
|
isn't), the compiler will simply use the last value read from the
|
7273 |
|
|
bytecode files. It is recommended, then, that all the files
|
7274 |
|
|
participating in the same link be compiled with the same options.
|
7275 |
|
|
|
7276 |
|
|
Another feature of LTO is that it is possible to apply interprocedural
|
7277 |
|
|
optimizations on files written in different languages. This requires
|
7278 |
|
|
some support in the language front end. Currently, the C, C++ and
|
7279 |
|
|
Fortran front ends are capable of emitting GIMPLE bytecodes, so
|
7280 |
|
|
something like this should work
|
7281 |
|
|
|
7282 |
|
|
@smallexample
|
7283 |
|
|
gcc -c -flto foo.c
|
7284 |
|
|
g++ -c -flto bar.cc
|
7285 |
|
|
gfortran -c -flto baz.f90
|
7286 |
|
|
g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran
|
7287 |
|
|
@end smallexample
|
7288 |
|
|
|
7289 |
|
|
Notice that the final link is done with @command{g++} to get the C++
|
7290 |
|
|
runtime libraries and @option{-lgfortran} is added to get the Fortran
|
7291 |
|
|
runtime libraries. In general, when mixing languages in LTO mode, you
|
7292 |
|
|
should use the same link command used when mixing languages in a
|
7293 |
|
|
regular (non-LTO) compilation. This means that if your build process
|
7294 |
|
|
was mixing languages before, all you need to add is @option{-flto} to
|
7295 |
|
|
all the compile and link commands.
|
7296 |
|
|
|
7297 |
|
|
If LTO encounters objects with C linkage declared with incompatible
|
7298 |
|
|
types in separate translation units to be linked together (undefined
|
7299 |
|
|
behavior according to ISO C99 6.2.7), a non-fatal diagnostic may be
|
7300 |
|
|
issued. The behavior is still undefined at runtime.
|
7301 |
|
|
|
7302 |
|
|
If object files containing GIMPLE bytecode are stored in a library
|
7303 |
|
|
archive, say @file{libfoo.a}, it is possible to extract and use them
|
7304 |
|
|
in an LTO link if you are using @command{gold} as the linker (which,
|
7305 |
|
|
in turn requires GCC to be configured with @option{--enable-gold}).
|
7306 |
|
|
To enable this feature, use the flag @option{-fuse-linker-plugin} at
|
7307 |
|
|
link-time:
|
7308 |
|
|
|
7309 |
|
|
@smallexample
|
7310 |
|
|
gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo
|
7311 |
|
|
@end smallexample
|
7312 |
|
|
|
7313 |
|
|
With the linker plugin enabled, @command{gold} will extract the needed
|
7314 |
|
|
GIMPLE files from @file{libfoo.a} and pass them on to the running GCC
|
7315 |
|
|
to make them part of the aggregated GIMPLE image to be optimized.
|
7316 |
|
|
|
7317 |
|
|
If you are not using @command{gold} and/or do not specify
|
7318 |
|
|
@option{-fuse-linker-plugin} then the objects inside @file{libfoo.a}
|
7319 |
|
|
will be extracted and linked as usual, but they will not participate
|
7320 |
|
|
in the LTO optimization process.
|
7321 |
|
|
|
7322 |
|
|
Link time optimizations do not require the presence of the whole
|
7323 |
|
|
program to operate. If the program does not require any symbols to
|
7324 |
|
|
be exported, it is possible to combine @option{-flto} and
|
7325 |
|
|
@option{-fwhopr} with @option{-fwhole-program} to allow the
|
7326 |
|
|
interprocedural optimizers to use more aggressive assumptions which
|
7327 |
|
|
may lead to improved optimization opportunities.
|
7328 |
|
|
|
7329 |
|
|
Regarding portability: the current implementation of LTO makes no
|
7330 |
|
|
attempt at generating bytecode that can be ported between different
|
7331 |
|
|
types of hosts. The bytecode files are versioned and there is a
|
7332 |
|
|
strict version check, so bytecode files generated in one version of
|
7333 |
|
|
GCC will not work with an older/newer version of GCC.
|
7334 |
|
|
|
7335 |
|
|
Link time optimization does not play well with generating debugging
|
7336 |
|
|
information. Combining @option{-flto} or @option{-fwhopr} with
|
7337 |
|
|
@option{-g} is experimental.
|
7338 |
|
|
|
7339 |
|
|
This option is disabled by default.
|
7340 |
|
|
|
7341 |
|
|
@item -fwhopr
|
7342 |
|
|
@opindex fwhopr
|
7343 |
|
|
This option is identical in functionality to @option{-flto} but it
|
7344 |
|
|
differs in how the final link stage is executed. Instead of loading
|
7345 |
|
|
all the function bodies in memory, the callgraph is analyzed and
|
7346 |
|
|
optimization decisions are made (whole program analysis or WPA). Once
|
7347 |
|
|
optimization decisions are made, the callgraph is partitioned and the
|
7348 |
|
|
different sections are compiled separately (local transformations or
|
7349 |
|
|
LTRANS)@. This process allows optimizations on very large programs
|
7350 |
|
|
that otherwise would not fit in memory. This option enables
|
7351 |
|
|
@option{-fwpa} and @option{-fltrans} automatically.
|
7352 |
|
|
|
7353 |
|
|
Disabled by default.
|
7354 |
|
|
|
7355 |
|
|
This option is experimental.
|
7356 |
|
|
|
7357 |
|
|
@item -fwpa
|
7358 |
|
|
@opindex fwpa
|
7359 |
|
|
This is an internal option used by GCC when compiling with
|
7360 |
|
|
@option{-fwhopr}. You should never need to use it.
|
7361 |
|
|
|
7362 |
|
|
This option runs the link-time optimizer in the whole-program-analysis
|
7363 |
|
|
(WPA) mode, which reads in summary information from all inputs and
|
7364 |
|
|
performs a whole-program analysis based on summary information only.
|
7365 |
|
|
It generates object files for subsequent runs of the link-time
|
7366 |
|
|
optimizer where individual object files are optimized using both
|
7367 |
|
|
summary information from the WPA mode and the actual function bodies.
|
7368 |
|
|
It then drives the LTRANS phase.
|
7369 |
|
|
|
7370 |
|
|
Disabled by default.
|
7371 |
|
|
|
7372 |
|
|
@item -fltrans
|
7373 |
|
|
@opindex fltrans
|
7374 |
|
|
This is an internal option used by GCC when compiling with
|
7375 |
|
|
@option{-fwhopr}. You should never need to use it.
|
7376 |
|
|
|
7377 |
|
|
This option runs the link-time optimizer in the local-transformation (LTRANS)
|
7378 |
|
|
mode, which reads in output from a previous run of the LTO in WPA mode.
|
7379 |
|
|
In the LTRANS mode, LTO optimizes an object and produces the final assembly.
|
7380 |
|
|
|
7381 |
|
|
Disabled by default.
|
7382 |
|
|
|
7383 |
|
|
@item -fltrans-output-list=@var{file}
|
7384 |
|
|
@opindex fltrans-output-list
|
7385 |
|
|
This is an internal option used by GCC when compiling with
|
7386 |
|
|
@option{-fwhopr}. You should never need to use it.
|
7387 |
|
|
|
7388 |
|
|
This option specifies a file to which the names of LTRANS output files are
|
7389 |
|
|
written. This option is only meaningful in conjunction with @option{-fwpa}.
|
7390 |
|
|
|
7391 |
|
|
Disabled by default.
|
7392 |
|
|
|
7393 |
|
|
@item -flto-compression-level=@var{n}
|
7394 |
|
|
This option specifies the level of compression used for intermediate
|
7395 |
|
|
language written to LTO object files, and is only meaningful in
|
7396 |
|
|
conjunction with LTO mode (@option{-fwhopr}, @option{-flto}). Valid
|
7397 |
|
|
values are 0 (no compression) to 9 (maximum compression). Values
|
7398 |
|
|
outside this range are clamped to either 0 or 9. If the option is not
|
7399 |
|
|
given, a default balanced compression setting is used.
|
7400 |
|
|
|
7401 |
|
|
@item -flto-report
|
7402 |
|
|
Prints a report with internal details on the workings of the link-time
|
7403 |
|
|
optimizer. The contents of this report vary from version to version,
|
7404 |
|
|
it is meant to be useful to GCC developers when processing object
|
7405 |
|
|
files in LTO mode (via @option{-fwhopr} or @option{-flto}).
|
7406 |
|
|
|
7407 |
|
|
Disabled by default.
|
7408 |
|
|
|
7409 |
|
|
@item -fuse-linker-plugin
|
7410 |
|
|
Enables the extraction of objects with GIMPLE bytecode information
|
7411 |
|
|
from library archives. This option relies on features available only
|
7412 |
|
|
in @command{gold}, so to use this you must configure GCC with
|
7413 |
|
|
@option{--enable-gold}. See @option{-flto} for a description on the
|
7414 |
|
|
effect of this flag and how to use it.
|
7415 |
|
|
|
7416 |
|
|
Disabled by default.
|
7417 |
|
|
|
7418 |
|
|
@item -fcprop-registers
|
7419 |
|
|
@opindex fcprop-registers
|
7420 |
|
|
After register allocation and post-register allocation instruction splitting,
|
7421 |
|
|
we perform a copy-propagation pass to try to reduce scheduling dependencies
|
7422 |
|
|
and occasionally eliminate the copy.
|
7423 |
|
|
|
7424 |
|
|
Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}.
|
7425 |
|
|
|
7426 |
|
|
@item -fprofile-correction
|
7427 |
|
|
@opindex fprofile-correction
|
7428 |
|
|
Profiles collected using an instrumented binary for multi-threaded programs may
|
7429 |
|
|
be inconsistent due to missed counter updates. When this option is specified,
|
7430 |
|
|
GCC will use heuristics to correct or smooth out such inconsistencies. By
|
7431 |
|
|
default, GCC will emit an error message when an inconsistent profile is detected.
|
7432 |
|
|
|
7433 |
|
|
@item -fprofile-dir=@var{path}
|
7434 |
|
|
@opindex fprofile-dir
|
7435 |
|
|
|
7436 |
|
|
Set the directory to search the profile data files in to @var{path}.
|
7437 |
|
|
This option affects only the profile data generated by
|
7438 |
|
|
@option{-fprofile-generate}, @option{-ftest-coverage}, @option{-fprofile-arcs}
|
7439 |
|
|
and used by @option{-fprofile-use} and @option{-fbranch-probabilities}
|
7440 |
|
|
and its related options.
|
7441 |
|
|
By default, GCC will use the current directory as @var{path}
|
7442 |
|
|
thus the profile data file will appear in the same directory as the object file.
|
7443 |
|
|
|
7444 |
|
|
@item -fprofile-generate
|
7445 |
|
|
@itemx -fprofile-generate=@var{path}
|
7446 |
|
|
@opindex fprofile-generate
|
7447 |
|
|
|
7448 |
|
|
Enable options usually used for instrumenting application to produce
|
7449 |
|
|
profile useful for later recompilation with profile feedback based
|
7450 |
|
|
optimization. You must use @option{-fprofile-generate} both when
|
7451 |
|
|
compiling and when linking your program.
|
7452 |
|
|
|
7453 |
|
|
The following options are enabled: @code{-fprofile-arcs}, @code{-fprofile-values}, @code{-fvpt}.
|
7454 |
|
|
|
7455 |
|
|
If @var{path} is specified, GCC will look at the @var{path} to find
|
7456 |
|
|
the profile feedback data files. See @option{-fprofile-dir}.
|
7457 |
|
|
|
7458 |
|
|
@item -fprofile-use
|
7459 |
|
|
@itemx -fprofile-use=@var{path}
|
7460 |
|
|
@opindex fprofile-use
|
7461 |
|
|
Enable profile feedback directed optimizations, and optimizations
|
7462 |
|
|
generally profitable only with profile feedback available.
|
7463 |
|
|
|
7464 |
|
|
The following options are enabled: @code{-fbranch-probabilities}, @code{-fvpt},
|
7465 |
|
|
@code{-funroll-loops}, @code{-fpeel-loops}, @code{-ftracer}
|
7466 |
|
|
|
7467 |
|
|
By default, GCC emits an error message if the feedback profiles do not
|
7468 |
|
|
match the source code. This error can be turned into a warning by using
|
7469 |
|
|
@option{-Wcoverage-mismatch}. Note this may result in poorly optimized
|
7470 |
|
|
code.
|
7471 |
|
|
|
7472 |
|
|
If @var{path} is specified, GCC will look at the @var{path} to find
|
7473 |
|
|
the profile feedback data files. See @option{-fprofile-dir}.
|
7474 |
|
|
@end table
|
7475 |
|
|
|
7476 |
|
|
The following options control compiler behavior regarding floating
|
7477 |
|
|
point arithmetic. These options trade off between speed and
|
7478 |
|
|
correctness. All must be specifically enabled.
|
7479 |
|
|
|
7480 |
|
|
@table @gcctabopt
|
7481 |
|
|
@item -ffloat-store
|
7482 |
|
|
@opindex ffloat-store
|
7483 |
|
|
Do not store floating point variables in registers, and inhibit other
|
7484 |
|
|
options that might change whether a floating point value is taken from a
|
7485 |
|
|
register or memory.
|
7486 |
|
|
|
7487 |
|
|
@cindex floating point precision
|
7488 |
|
|
This option prevents undesirable excess precision on machines such as
|
7489 |
|
|
the 68000 where the floating registers (of the 68881) keep more
|
7490 |
|
|
precision than a @code{double} is supposed to have. Similarly for the
|
7491 |
|
|
x86 architecture. For most programs, the excess precision does only
|
7492 |
|
|
good, but a few programs rely on the precise definition of IEEE floating
|
7493 |
|
|
point. Use @option{-ffloat-store} for such programs, after modifying
|
7494 |
|
|
them to store all pertinent intermediate computations into variables.
|
7495 |
|
|
|
7496 |
|
|
@item -fexcess-precision=@var{style}
|
7497 |
|
|
@opindex fexcess-precision
|
7498 |
|
|
This option allows further control over excess precision on machines
|
7499 |
|
|
where floating-point registers have more precision than the IEEE
|
7500 |
|
|
@code{float} and @code{double} types and the processor does not
|
7501 |
|
|
support operations rounding to those types. By default,
|
7502 |
|
|
@option{-fexcess-precision=fast} is in effect; this means that
|
7503 |
|
|
operations are carried out in the precision of the registers and that
|
7504 |
|
|
it is unpredictable when rounding to the types specified in the source
|
7505 |
|
|
code takes place. When compiling C, if
|
7506 |
|
|
@option{-fexcess-precision=standard} is specified then excess
|
7507 |
|
|
precision will follow the rules specified in ISO C99; in particular,
|
7508 |
|
|
both casts and assignments cause values to be rounded to their
|
7509 |
|
|
semantic types (whereas @option{-ffloat-store} only affects
|
7510 |
|
|
assignments). This option is enabled by default for C if a strict
|
7511 |
|
|
conformance option such as @option{-std=c99} is used.
|
7512 |
|
|
|
7513 |
|
|
@opindex mfpmath
|
7514 |
|
|
@option{-fexcess-precision=standard} is not implemented for languages
|
7515 |
|
|
other than C, and has no effect if
|
7516 |
|
|
@option{-funsafe-math-optimizations} or @option{-ffast-math} is
|
7517 |
|
|
specified. On the x86, it also has no effect if @option{-mfpmath=sse}
|
7518 |
|
|
or @option{-mfpmath=sse+387} is specified; in the former case, IEEE
|
7519 |
|
|
semantics apply without excess precision, and in the latter, rounding
|
7520 |
|
|
is unpredictable.
|
7521 |
|
|
|
7522 |
|
|
@item -ffast-math
|
7523 |
|
|
@opindex ffast-math
|
7524 |
|
|
Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations},
|
7525 |
|
|
@option{-ffinite-math-only}, @option{-fno-rounding-math},
|
7526 |
|
|
@option{-fno-signaling-nans} and @option{-fcx-limited-range}.
|
7527 |
|
|
|
7528 |
|
|
This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
|
7529 |
|
|
|
7530 |
|
|
This option is not turned on by any @option{-O} option since
|
7531 |
|
|
it can result in incorrect output for programs which depend on
|
7532 |
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
7533 |
|
|
math functions. It may, however, yield faster code for programs
|
7534 |
|
|
that do not require the guarantees of these specifications.
|
7535 |
|
|
|
7536 |
|
|
@item -fno-math-errno
|
7537 |
|
|
@opindex fno-math-errno
|
7538 |
|
|
Do not set ERRNO after calling math functions that are executed
|
7539 |
|
|
with a single instruction, e.g., sqrt. A program that relies on
|
7540 |
|
|
IEEE exceptions for math error handling may want to use this flag
|
7541 |
|
|
for speed while maintaining IEEE arithmetic compatibility.
|
7542 |
|
|
|
7543 |
|
|
This option is not turned on by any @option{-O} option since
|
7544 |
|
|
it can result in incorrect output for programs which depend on
|
7545 |
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
7546 |
|
|
math functions. It may, however, yield faster code for programs
|
7547 |
|
|
that do not require the guarantees of these specifications.
|
7548 |
|
|
|
7549 |
|
|
The default is @option{-fmath-errno}.
|
7550 |
|
|
|
7551 |
|
|
On Darwin systems, the math library never sets @code{errno}. There is
|
7552 |
|
|
therefore no reason for the compiler to consider the possibility that
|
7553 |
|
|
it might, and @option{-fno-math-errno} is the default.
|
7554 |
|
|
|
7555 |
|
|
@item -funsafe-math-optimizations
|
7556 |
|
|
@opindex funsafe-math-optimizations
|
7557 |
|
|
|
7558 |
|
|
Allow optimizations for floating-point arithmetic that (a) assume
|
7559 |
|
|
that arguments and results are valid and (b) may violate IEEE or
|
7560 |
|
|
ANSI standards. When used at link-time, it may include libraries
|
7561 |
|
|
or startup files that change the default FPU control word or other
|
7562 |
|
|
similar optimizations.
|
7563 |
|
|
|
7564 |
|
|
This option is not turned on by any @option{-O} option since
|
7565 |
|
|
it can result in incorrect output for programs which depend on
|
7566 |
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
7567 |
|
|
math functions. It may, however, yield faster code for programs
|
7568 |
|
|
that do not require the guarantees of these specifications.
|
7569 |
|
|
Enables @option{-fno-signed-zeros}, @option{-fno-trapping-math},
|
7570 |
|
|
@option{-fassociative-math} and @option{-freciprocal-math}.
|
7571 |
|
|
|
7572 |
|
|
The default is @option{-fno-unsafe-math-optimizations}.
|
7573 |
|
|
|
7574 |
|
|
@item -fassociative-math
|
7575 |
|
|
@opindex fassociative-math
|
7576 |
|
|
|
7577 |
|
|
Allow re-association of operands in series of floating-point operations.
|
7578 |
|
|
This violates the ISO C and C++ language standard by possibly changing
|
7579 |
|
|
computation result. NOTE: re-ordering may change the sign of zero as
|
7580 |
|
|
well as ignore NaNs and inhibit or create underflow or overflow (and
|
7581 |
|
|
thus cannot be used on a code which relies on rounding behavior like
|
7582 |
|
|
@code{(x + 2**52) - 2**52)}. May also reorder floating-point comparisons
|
7583 |
|
|
and thus may not be used when ordered comparisons are required.
|
7584 |
|
|
This option requires that both @option{-fno-signed-zeros} and
|
7585 |
|
|
@option{-fno-trapping-math} be in effect. Moreover, it doesn't make
|
7586 |
|
|
much sense with @option{-frounding-math}. For Fortran the option
|
7587 |
|
|
is automatically enabled when both @option{-fno-signed-zeros} and
|
7588 |
|
|
@option{-fno-trapping-math} are in effect.
|
7589 |
|
|
|
7590 |
|
|
The default is @option{-fno-associative-math}.
|
7591 |
|
|
|
7592 |
|
|
@item -freciprocal-math
|
7593 |
|
|
@opindex freciprocal-math
|
7594 |
|
|
|
7595 |
|
|
Allow the reciprocal of a value to be used instead of dividing by
|
7596 |
|
|
the value if this enables optimizations. For example @code{x / y}
|
7597 |
|
|
can be replaced with @code{x * (1/y)} which is useful if @code{(1/y)}
|
7598 |
|
|
is subject to common subexpression elimination. Note that this loses
|
7599 |
|
|
precision and increases the number of flops operating on the value.
|
7600 |
|
|
|
7601 |
|
|
The default is @option{-fno-reciprocal-math}.
|
7602 |
|
|
|
7603 |
|
|
@item -ffinite-math-only
|
7604 |
|
|
@opindex ffinite-math-only
|
7605 |
|
|
Allow optimizations for floating-point arithmetic that assume
|
7606 |
|
|
that arguments and results are not NaNs or +-Infs.
|
7607 |
|
|
|
7608 |
|
|
This option is not turned on by any @option{-O} option since
|
7609 |
|
|
it can result in incorrect output for programs which depend on
|
7610 |
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
7611 |
|
|
math functions. It may, however, yield faster code for programs
|
7612 |
|
|
that do not require the guarantees of these specifications.
|
7613 |
|
|
|
7614 |
|
|
The default is @option{-fno-finite-math-only}.
|
7615 |
|
|
|
7616 |
|
|
@item -fno-signed-zeros
|
7617 |
|
|
@opindex fno-signed-zeros
|
7618 |
|
|
Allow optimizations for floating point arithmetic that ignore the
|
7619 |
|
|
signedness of zero. IEEE arithmetic specifies the behavior of
|
7620 |
|
|
distinct +0.0 and @minus{}0.0 values, which then prohibits simplification
|
7621 |
|
|
of expressions such as x+0.0 or 0.0*x (even with @option{-ffinite-math-only}).
|
7622 |
|
|
This option implies that the sign of a zero result isn't significant.
|
7623 |
|
|
|
7624 |
|
|
The default is @option{-fsigned-zeros}.
|
7625 |
|
|
|
7626 |
|
|
@item -fno-trapping-math
|
7627 |
|
|
@opindex fno-trapping-math
|
7628 |
|
|
Compile code assuming that floating-point operations cannot generate
|
7629 |
|
|
user-visible traps. These traps include division by zero, overflow,
|
7630 |
|
|
underflow, inexact result and invalid operation. This option requires
|
7631 |
|
|
that @option{-fno-signaling-nans} be in effect. Setting this option may
|
7632 |
|
|
allow faster code if one relies on ``non-stop'' IEEE arithmetic, for example.
|
7633 |
|
|
|
7634 |
|
|
This option should never be turned on by any @option{-O} option since
|
7635 |
|
|
it can result in incorrect output for programs which depend on
|
7636 |
|
|
an exact implementation of IEEE or ISO rules/specifications for
|
7637 |
|
|
math functions.
|
7638 |
|
|
|
7639 |
|
|
The default is @option{-ftrapping-math}.
|
7640 |
|
|
|
7641 |
|
|
@item -frounding-math
|
7642 |
|
|
@opindex frounding-math
|
7643 |
|
|
Disable transformations and optimizations that assume default floating
|
7644 |
|
|
point rounding behavior. This is round-to-zero for all floating point
|
7645 |
|
|
to integer conversions, and round-to-nearest for all other arithmetic
|
7646 |
|
|
truncations. This option should be specified for programs that change
|
7647 |
|
|
the FP rounding mode dynamically, or that may be executed with a
|
7648 |
|
|
non-default rounding mode. This option disables constant folding of
|
7649 |
|
|
floating point expressions at compile-time (which may be affected by
|
7650 |
|
|
rounding mode) and arithmetic transformations that are unsafe in the
|
7651 |
|
|
presence of sign-dependent rounding modes.
|
7652 |
|
|
|
7653 |
|
|
The default is @option{-fno-rounding-math}.
|
7654 |
|
|
|
7655 |
|
|
This option is experimental and does not currently guarantee to
|
7656 |
|
|
disable all GCC optimizations that are affected by rounding mode.
|
7657 |
|
|
Future versions of GCC may provide finer control of this setting
|
7658 |
|
|
using C99's @code{FENV_ACCESS} pragma. This command line option
|
7659 |
|
|
will be used to specify the default state for @code{FENV_ACCESS}.
|
7660 |
|
|
|
7661 |
|
|
@item -fsignaling-nans
|
7662 |
|
|
@opindex fsignaling-nans
|
7663 |
|
|
Compile code assuming that IEEE signaling NaNs may generate user-visible
|
7664 |
|
|
traps during floating-point operations. Setting this option disables
|
7665 |
|
|
optimizations that may change the number of exceptions visible with
|
7666 |
|
|
signaling NaNs. This option implies @option{-ftrapping-math}.
|
7667 |
|
|
|
7668 |
|
|
This option causes the preprocessor macro @code{__SUPPORT_SNAN__} to
|
7669 |
|
|
be defined.
|
7670 |
|
|
|
7671 |
|
|
The default is @option{-fno-signaling-nans}.
|
7672 |
|
|
|
7673 |
|
|
This option is experimental and does not currently guarantee to
|
7674 |
|
|
disable all GCC optimizations that affect signaling NaN behavior.
|
7675 |
|
|
|
7676 |
|
|
@item -fsingle-precision-constant
|
7677 |
|
|
@opindex fsingle-precision-constant
|
7678 |
|
|
Treat floating point constant as single precision constant instead of
|
7679 |
|
|
implicitly converting it to double precision constant.
|
7680 |
|
|
|
7681 |
|
|
@item -fcx-limited-range
|
7682 |
|
|
@opindex fcx-limited-range
|
7683 |
|
|
When enabled, this option states that a range reduction step is not
|
7684 |
|
|
needed when performing complex division. Also, there is no checking
|
7685 |
|
|
whether the result of a complex multiplication or division is @code{NaN
|
7686 |
|
|
+ I*NaN}, with an attempt to rescue the situation in that case. The
|
7687 |
|
|
default is @option{-fno-cx-limited-range}, but is enabled by
|
7688 |
|
|
@option{-ffast-math}.
|
7689 |
|
|
|
7690 |
|
|
This option controls the default setting of the ISO C99
|
7691 |
|
|
@code{CX_LIMITED_RANGE} pragma. Nevertheless, the option applies to
|
7692 |
|
|
all languages.
|
7693 |
|
|
|
7694 |
|
|
@item -fcx-fortran-rules
|
7695 |
|
|
@opindex fcx-fortran-rules
|
7696 |
|
|
Complex multiplication and division follow Fortran rules. Range
|
7697 |
|
|
reduction is done as part of complex division, but there is no checking
|
7698 |
|
|
whether the result of a complex multiplication or division is @code{NaN
|
7699 |
|
|
+ I*NaN}, with an attempt to rescue the situation in that case.
|
7700 |
|
|
|
7701 |
|
|
The default is @option{-fno-cx-fortran-rules}.
|
7702 |
|
|
|
7703 |
|
|
@end table
|
7704 |
|
|
|
7705 |
|
|
The following options control optimizations that may improve
|
7706 |
|
|
performance, but are not enabled by any @option{-O} options. This
|
7707 |
|
|
section includes experimental options that may produce broken code.
|
7708 |
|
|
|
7709 |
|
|
@table @gcctabopt
|
7710 |
|
|
@item -fbranch-probabilities
|
7711 |
|
|
@opindex fbranch-probabilities
|
7712 |
|
|
After running a program compiled with @option{-fprofile-arcs}
|
7713 |
|
|
(@pxref{Debugging Options,, Options for Debugging Your Program or
|
7714 |
|
|
@command{gcc}}), you can compile it a second time using
|
7715 |
|
|
@option{-fbranch-probabilities}, to improve optimizations based on
|
7716 |
|
|
the number of times each branch was taken. When the program
|
7717 |
|
|
compiled with @option{-fprofile-arcs} exits it saves arc execution
|
7718 |
|
|
counts to a file called @file{@var{sourcename}.gcda} for each source
|
7719 |
|
|
file. The information in this data file is very dependent on the
|
7720 |
|
|
structure of the generated code, so you must use the same source code
|
7721 |
|
|
and the same optimization options for both compilations.
|
7722 |
|
|
|
7723 |
|
|
With @option{-fbranch-probabilities}, GCC puts a
|
7724 |
|
|
@samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}.
|
7725 |
|
|
These can be used to improve optimization. Currently, they are only
|
7726 |
|
|
used in one place: in @file{reorg.c}, instead of guessing which path a
|
7727 |
|
|
branch is mostly to take, the @samp{REG_BR_PROB} values are used to
|
7728 |
|
|
exactly determine which path is taken more often.
|
7729 |
|
|
|
7730 |
|
|
@item -fprofile-values
|
7731 |
|
|
@opindex fprofile-values
|
7732 |
|
|
If combined with @option{-fprofile-arcs}, it adds code so that some
|
7733 |
|
|
data about values of expressions in the program is gathered.
|
7734 |
|
|
|
7735 |
|
|
With @option{-fbranch-probabilities}, it reads back the data gathered
|
7736 |
|
|
from profiling values of expressions and adds @samp{REG_VALUE_PROFILE}
|
7737 |
|
|
notes to instructions for their later usage in optimizations.
|
7738 |
|
|
|
7739 |
|
|
Enabled with @option{-fprofile-generate} and @option{-fprofile-use}.
|
7740 |
|
|
|
7741 |
|
|
@item -fvpt
|
7742 |
|
|
@opindex fvpt
|
7743 |
|
|
If combined with @option{-fprofile-arcs}, it instructs the compiler to add
|
7744 |
|
|
a code to gather information about values of expressions.
|
7745 |
|
|
|
7746 |
|
|
With @option{-fbranch-probabilities}, it reads back the data gathered
|
7747 |
|
|
and actually performs the optimizations based on them.
|
7748 |
|
|
Currently the optimizations include specialization of division operation
|
7749 |
|
|
using the knowledge about the value of the denominator.
|
7750 |
|
|
|
7751 |
|
|
@item -frename-registers
|
7752 |
|
|
@opindex frename-registers
|
7753 |
|
|
Attempt to avoid false dependencies in scheduled code by making use
|
7754 |
|
|
of registers left over after register allocation. This optimization
|
7755 |
|
|
will most benefit processors with lots of registers. Depending on the
|
7756 |
|
|
debug information format adopted by the target, however, it can
|
7757 |
|
|
make debugging impossible, since variables will no longer stay in
|
7758 |
|
|
a ``home register''.
|
7759 |
|
|
|
7760 |
|
|
Enabled by default with @option{-funroll-loops} and @option{-fpeel-loops}.
|
7761 |
|
|
|
7762 |
|
|
@item -ftracer
|
7763 |
|
|
@opindex ftracer
|
7764 |
|
|
Perform tail duplication to enlarge superblock size. This transformation
|
7765 |
|
|
simplifies the control flow of the function allowing other optimizations to do
|
7766 |
|
|
better job.
|
7767 |
|
|
|
7768 |
|
|
Enabled with @option{-fprofile-use}.
|
7769 |
|
|
|
7770 |
|
|
@item -funroll-loops
|
7771 |
|
|
@opindex funroll-loops
|
7772 |
|
|
Unroll loops whose number of iterations can be determined at compile time or
|
7773 |
|
|
upon entry to the loop. @option{-funroll-loops} implies
|
7774 |
|
|
@option{-frerun-cse-after-loop}, @option{-fweb} and @option{-frename-registers}.
|
7775 |
|
|
It also turns on complete loop peeling (i.e.@: complete removal of loops with
|
7776 |
|
|
small constant number of iterations). This option makes code larger, and may
|
7777 |
|
|
or may not make it run faster.
|
7778 |
|
|
|
7779 |
|
|
Enabled with @option{-fprofile-use}.
|
7780 |
|
|
|
7781 |
|
|
@item -funroll-all-loops
|
7782 |
|
|
@opindex funroll-all-loops
|
7783 |
|
|
Unroll all loops, even if their number of iterations is uncertain when
|
7784 |
|
|
the loop is entered. This usually makes programs run more slowly.
|
7785 |
|
|
@option{-funroll-all-loops} implies the same options as
|
7786 |
|
|
@option{-funroll-loops}.
|
7787 |
|
|
|
7788 |
|
|
@item -fpeel-loops
|
7789 |
|
|
@opindex fpeel-loops
|
7790 |
|
|
Peels the loops for that there is enough information that they do not
|
7791 |
|
|
roll much (from profile feedback). It also turns on complete loop peeling
|
7792 |
|
|
(i.e.@: complete removal of loops with small constant number of iterations).
|
7793 |
|
|
|
7794 |
|
|
Enabled with @option{-fprofile-use}.
|
7795 |
|
|
|
7796 |
|
|
@item -fmove-loop-invariants
|
7797 |
|
|
@opindex fmove-loop-invariants
|
7798 |
|
|
Enables the loop invariant motion pass in the RTL loop optimizer. Enabled
|
7799 |
|
|
at level @option{-O1}
|
7800 |
|
|
|
7801 |
|
|
@item -funswitch-loops
|
7802 |
|
|
@opindex funswitch-loops
|
7803 |
|
|
Move branches with loop invariant conditions out of the loop, with duplicates
|
7804 |
|
|
of the loop on both branches (modified according to result of the condition).
|
7805 |
|
|
|
7806 |
|
|
@item -ffunction-sections
|
7807 |
|
|
@itemx -fdata-sections
|
7808 |
|
|
@opindex ffunction-sections
|
7809 |
|
|
@opindex fdata-sections
|
7810 |
|
|
Place each function or data item into its own section in the output
|
7811 |
|
|
file if the target supports arbitrary sections. The name of the
|
7812 |
|
|
function or the name of the data item determines the section's name
|
7813 |
|
|
in the output file.
|
7814 |
|
|
|
7815 |
|
|
Use these options on systems where the linker can perform optimizations
|
7816 |
|
|
to improve locality of reference in the instruction space. Most systems
|
7817 |
|
|
using the ELF object format and SPARC processors running Solaris 2 have
|
7818 |
|
|
linkers with such optimizations. AIX may have these optimizations in
|
7819 |
|
|
the future.
|
7820 |
|
|
|
7821 |
|
|
Only use these options when there are significant benefits from doing
|
7822 |
|
|
so. When you specify these options, the assembler and linker will
|
7823 |
|
|
create larger object and executable files and will also be slower.
|
7824 |
|
|
You will not be able to use @code{gprof} on all systems if you
|
7825 |
|
|
specify this option and you may have problems with debugging if
|
7826 |
|
|
you specify both this option and @option{-g}.
|
7827 |
|
|
|
7828 |
|
|
@item -fbranch-target-load-optimize
|
7829 |
|
|
@opindex fbranch-target-load-optimize
|
7830 |
|
|
Perform branch target register load optimization before prologue / epilogue
|
7831 |
|
|
threading.
|
7832 |
|
|
The use of target registers can typically be exposed only during reload,
|
7833 |
|
|
thus hoisting loads out of loops and doing inter-block scheduling needs
|
7834 |
|
|
a separate optimization pass.
|
7835 |
|
|
|
7836 |
|
|
@item -fbranch-target-load-optimize2
|
7837 |
|
|
@opindex fbranch-target-load-optimize2
|
7838 |
|
|
Perform branch target register load optimization after prologue / epilogue
|
7839 |
|
|
threading.
|
7840 |
|
|
|
7841 |
|
|
@item -fbtr-bb-exclusive
|
7842 |
|
|
@opindex fbtr-bb-exclusive
|
7843 |
|
|
When performing branch target register load optimization, don't reuse
|
7844 |
|
|
branch target registers in within any basic block.
|
7845 |
|
|
|
7846 |
|
|
@item -fstack-protector
|
7847 |
|
|
@opindex fstack-protector
|
7848 |
|
|
Emit extra code to check for buffer overflows, such as stack smashing
|
7849 |
|
|
attacks. This is done by adding a guard variable to functions with
|
7850 |
|
|
vulnerable objects. This includes functions that call alloca, and
|
7851 |
|
|
functions with buffers larger than 8 bytes. The guards are initialized
|
7852 |
|
|
when a function is entered and then checked when the function exits.
|
7853 |
|
|
If a guard check fails, an error message is printed and the program exits.
|
7854 |
|
|
|
7855 |
|
|
@item -fstack-protector-all
|
7856 |
|
|
@opindex fstack-protector-all
|
7857 |
|
|
Like @option{-fstack-protector} except that all functions are protected.
|
7858 |
|
|
|
7859 |
|
|
@item -fsection-anchors
|
7860 |
|
|
@opindex fsection-anchors
|
7861 |
|
|
Try to reduce the number of symbolic address calculations by using
|
7862 |
|
|
shared ``anchor'' symbols to address nearby objects. This transformation
|
7863 |
|
|
can help to reduce the number of GOT entries and GOT accesses on some
|
7864 |
|
|
targets.
|
7865 |
|
|
|
7866 |
|
|
For example, the implementation of the following function @code{foo}:
|
7867 |
|
|
|
7868 |
|
|
@smallexample
|
7869 |
|
|
static int a, b, c;
|
7870 |
|
|
int foo (void) @{ return a + b + c; @}
|
7871 |
|
|
@end smallexample
|
7872 |
|
|
|
7873 |
|
|
would usually calculate the addresses of all three variables, but if you
|
7874 |
|
|
compile it with @option{-fsection-anchors}, it will access the variables
|
7875 |
|
|
from a common anchor point instead. The effect is similar to the
|
7876 |
|
|
following pseudocode (which isn't valid C):
|
7877 |
|
|
|
7878 |
|
|
@smallexample
|
7879 |
|
|
int foo (void)
|
7880 |
|
|
@{
|
7881 |
|
|
register int *xr = &x;
|
7882 |
|
|
return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
|
7883 |
|
|
@}
|
7884 |
|
|
@end smallexample
|
7885 |
|
|
|
7886 |
|
|
Not all targets support this option.
|
7887 |
|
|
|
7888 |
|
|
@item --param @var{name}=@var{value}
|
7889 |
|
|
@opindex param
|
7890 |
|
|
In some places, GCC uses various constants to control the amount of
|
7891 |
|
|
optimization that is done. For example, GCC will not inline functions
|
7892 |
|
|
that contain more that a certain number of instructions. You can
|
7893 |
|
|
control some of these constants on the command-line using the
|
7894 |
|
|
@option{--param} option.
|
7895 |
|
|
|
7896 |
|
|
The names of specific parameters, and the meaning of the values, are
|
7897 |
|
|
tied to the internals of the compiler, and are subject to change
|
7898 |
|
|
without notice in future releases.
|
7899 |
|
|
|
7900 |
|
|
In each case, the @var{value} is an integer. The allowable choices for
|
7901 |
|
|
@var{name} are given in the following table:
|
7902 |
|
|
|
7903 |
|
|
@table @gcctabopt
|
7904 |
|
|
@item struct-reorg-cold-struct-ratio
|
7905 |
|
|
The threshold ratio (as a percentage) between a structure frequency
|
7906 |
|
|
and the frequency of the hottest structure in the program. This parameter
|
7907 |
|
|
is used by struct-reorg optimization enabled by @option{-fipa-struct-reorg}.
|
7908 |
|
|
We say that if the ratio of a structure frequency, calculated by profiling,
|
7909 |
|
|
to the hottest structure frequency in the program is less than this
|
7910 |
|
|
parameter, then structure reorganization is not applied to this structure.
|
7911 |
|
|
The default is 10.
|
7912 |
|
|
|
7913 |
|
|
@item predictable-branch-outcome
|
7914 |
|
|
When branch is predicted to be taken with probability lower than this threshold
|
7915 |
|
|
(in percent), then it is considered well predictable. The default is 10.
|
7916 |
|
|
|
7917 |
|
|
@item max-crossjump-edges
|
7918 |
|
|
The maximum number of incoming edges to consider for crossjumping.
|
7919 |
|
|
The algorithm used by @option{-fcrossjumping} is @math{O(N^2)} in
|
7920 |
|
|
the number of edges incoming to each block. Increasing values mean
|
7921 |
|
|
more aggressive optimization, making the compile time increase with
|
7922 |
|
|
probably small improvement in executable size.
|
7923 |
|
|
|
7924 |
|
|
@item min-crossjump-insns
|
7925 |
|
|
The minimum number of instructions which must be matched at the end
|
7926 |
|
|
of two blocks before crossjumping will be performed on them. This
|
7927 |
|
|
value is ignored in the case where all instructions in the block being
|
7928 |
|
|
crossjumped from are matched. The default value is 5.
|
7929 |
|
|
|
7930 |
|
|
@item max-grow-copy-bb-insns
|
7931 |
|
|
The maximum code size expansion factor when copying basic blocks
|
7932 |
|
|
instead of jumping. The expansion is relative to a jump instruction.
|
7933 |
|
|
The default value is 8.
|
7934 |
|
|
|
7935 |
|
|
@item max-goto-duplication-insns
|
7936 |
|
|
The maximum number of instructions to duplicate to a block that jumps
|
7937 |
|
|
to a computed goto. To avoid @math{O(N^2)} behavior in a number of
|
7938 |
|
|
passes, GCC factors computed gotos early in the compilation process,
|
7939 |
|
|
and unfactors them as late as possible. Only computed jumps at the
|
7940 |
|
|
end of a basic blocks with no more than max-goto-duplication-insns are
|
7941 |
|
|
unfactored. The default value is 8.
|
7942 |
|
|
|
7943 |
|
|
@item max-delay-slot-insn-search
|
7944 |
|
|
The maximum number of instructions to consider when looking for an
|
7945 |
|
|
instruction to fill a delay slot. If more than this arbitrary number of
|
7946 |
|
|
instructions is searched, the time savings from filling the delay slot
|
7947 |
|
|
will be minimal so stop searching. Increasing values mean more
|
7948 |
|
|
aggressive optimization, making the compile time increase with probably
|
7949 |
|
|
small improvement in executable run time.
|
7950 |
|
|
|
7951 |
|
|
@item max-delay-slot-live-search
|
7952 |
|
|
When trying to fill delay slots, the maximum number of instructions to
|
7953 |
|
|
consider when searching for a block with valid live register
|
7954 |
|
|
information. Increasing this arbitrarily chosen value means more
|
7955 |
|
|
aggressive optimization, increasing the compile time. This parameter
|
7956 |
|
|
should be removed when the delay slot code is rewritten to maintain the
|
7957 |
|
|
control-flow graph.
|
7958 |
|
|
|
7959 |
|
|
@item max-gcse-memory
|
7960 |
|
|
The approximate maximum amount of memory that will be allocated in
|
7961 |
|
|
order to perform the global common subexpression elimination
|
7962 |
|
|
optimization. If more memory than specified is required, the
|
7963 |
|
|
optimization will not be done.
|
7964 |
|
|
|
7965 |
|
|
@item max-pending-list-length
|
7966 |
|
|
The maximum number of pending dependencies scheduling will allow
|
7967 |
|
|
before flushing the current state and starting over. Large functions
|
7968 |
|
|
with few branches or calls can create excessively large lists which
|
7969 |
|
|
needlessly consume memory and resources.
|
7970 |
|
|
|
7971 |
|
|
@item max-inline-insns-single
|
7972 |
|
|
Several parameters control the tree inliner used in gcc.
|
7973 |
|
|
This number sets the maximum number of instructions (counted in GCC's
|
7974 |
|
|
internal representation) in a single function that the tree inliner
|
7975 |
|
|
will consider for inlining. This only affects functions declared
|
7976 |
|
|
inline and methods implemented in a class declaration (C++).
|
7977 |
|
|
The default value is 300.
|
7978 |
|
|
|
7979 |
|
|
@item max-inline-insns-auto
|
7980 |
|
|
When you use @option{-finline-functions} (included in @option{-O3}),
|
7981 |
|
|
a lot of functions that would otherwise not be considered for inlining
|
7982 |
|
|
by the compiler will be investigated. To those functions, a different
|
7983 |
|
|
(more restrictive) limit compared to functions declared inline can
|
7984 |
|
|
be applied.
|
7985 |
|
|
The default value is 50.
|
7986 |
|
|
|
7987 |
|
|
@item large-function-insns
|
7988 |
|
|
The limit specifying really large functions. For functions larger than this
|
7989 |
|
|
limit after inlining, inlining is constrained by
|
7990 |
|
|
@option{--param large-function-growth}. This parameter is useful primarily
|
7991 |
|
|
to avoid extreme compilation time caused by non-linear algorithms used by the
|
7992 |
|
|
backend.
|
7993 |
|
|
The default value is 2700.
|
7994 |
|
|
|
7995 |
|
|
@item large-function-growth
|
7996 |
|
|
Specifies maximal growth of large function caused by inlining in percents.
|
7997 |
|
|
The default value is 100 which limits large function growth to 2.0 times
|
7998 |
|
|
the original size.
|
7999 |
|
|
|
8000 |
|
|
@item large-unit-insns
|
8001 |
|
|
The limit specifying large translation unit. Growth caused by inlining of
|
8002 |
|
|
units larger than this limit is limited by @option{--param inline-unit-growth}.
|
8003 |
|
|
For small units this might be too tight (consider unit consisting of function A
|
8004 |
|
|
that is inline and B that just calls A three time. If B is small relative to
|
8005 |
|
|
A, the growth of unit is 300\% and yet such inlining is very sane. For very
|
8006 |
|
|
large units consisting of small inlineable functions however the overall unit
|
8007 |
|
|
growth limit is needed to avoid exponential explosion of code size. Thus for
|
8008 |
|
|
smaller units, the size is increased to @option{--param large-unit-insns}
|
8009 |
|
|
before applying @option{--param inline-unit-growth}. The default is 10000
|
8010 |
|
|
|
8011 |
|
|
@item inline-unit-growth
|
8012 |
|
|
Specifies maximal overall growth of the compilation unit caused by inlining.
|
8013 |
|
|
The default value is 30 which limits unit growth to 1.3 times the original
|
8014 |
|
|
size.
|
8015 |
|
|
|
8016 |
|
|
@item ipcp-unit-growth
|
8017 |
|
|
Specifies maximal overall growth of the compilation unit caused by
|
8018 |
|
|
interprocedural constant propagation. The default value is 10 which limits
|
8019 |
|
|
unit growth to 1.1 times the original size.
|
8020 |
|
|
|
8021 |
|
|
@item large-stack-frame
|
8022 |
|
|
The limit specifying large stack frames. While inlining the algorithm is trying
|
8023 |
|
|
to not grow past this limit too much. Default value is 256 bytes.
|
8024 |
|
|
|
8025 |
|
|
@item large-stack-frame-growth
|
8026 |
|
|
Specifies maximal growth of large stack frames caused by inlining in percents.
|
8027 |
|
|
The default value is 1000 which limits large stack frame growth to 11 times
|
8028 |
|
|
the original size.
|
8029 |
|
|
|
8030 |
|
|
@item max-inline-insns-recursive
|
8031 |
|
|
@itemx max-inline-insns-recursive-auto
|
8032 |
|
|
Specifies maximum number of instructions out-of-line copy of self recursive inline
|
8033 |
|
|
function can grow into by performing recursive inlining.
|
8034 |
|
|
|
8035 |
|
|
For functions declared inline @option{--param max-inline-insns-recursive} is
|
8036 |
|
|
taken into account. For function not declared inline, recursive inlining
|
8037 |
|
|
happens only when @option{-finline-functions} (included in @option{-O3}) is
|
8038 |
|
|
enabled and @option{--param max-inline-insns-recursive-auto} is used. The
|
8039 |
|
|
default value is 450.
|
8040 |
|
|
|
8041 |
|
|
@item max-inline-recursive-depth
|
8042 |
|
|
@itemx max-inline-recursive-depth-auto
|
8043 |
|
|
Specifies maximum recursion depth used by the recursive inlining.
|
8044 |
|
|
|
8045 |
|
|
For functions declared inline @option{--param max-inline-recursive-depth} is
|
8046 |
|
|
taken into account. For function not declared inline, recursive inlining
|
8047 |
|
|
happens only when @option{-finline-functions} (included in @option{-O3}) is
|
8048 |
|
|
enabled and @option{--param max-inline-recursive-depth-auto} is used. The
|
8049 |
|
|
default value is 8.
|
8050 |
|
|
|
8051 |
|
|
@item min-inline-recursive-probability
|
8052 |
|
|
Recursive inlining is profitable only for function having deep recursion
|
8053 |
|
|
in average and can hurt for function having little recursion depth by
|
8054 |
|
|
increasing the prologue size or complexity of function body to other
|
8055 |
|
|
optimizers.
|
8056 |
|
|
|
8057 |
|
|
When profile feedback is available (see @option{-fprofile-generate}) the actual
|
8058 |
|
|
recursion depth can be guessed from probability that function will recurse via
|
8059 |
|
|
given call expression. This parameter limits inlining only to call expression
|
8060 |
|
|
whose probability exceeds given threshold (in percents). The default value is
|
8061 |
|
|
10.
|
8062 |
|
|
|
8063 |
|
|
@item early-inlining-insns
|
8064 |
|
|
Specify growth that early inliner can make. In effect it increases amount of
|
8065 |
|
|
inlining for code having large abstraction penalty. The default value is 8.
|
8066 |
|
|
|
8067 |
|
|
@item max-early-inliner-iterations
|
8068 |
|
|
@itemx max-early-inliner-iterations
|
8069 |
|
|
Limit of iterations of early inliner. This basically bounds number of nested
|
8070 |
|
|
indirect calls early inliner can resolve. Deeper chains are still handled by
|
8071 |
|
|
late inlining.
|
8072 |
|
|
|
8073 |
|
|
@item min-vect-loop-bound
|
8074 |
|
|
The minimum number of iterations under which a loop will not get vectorized
|
8075 |
|
|
when @option{-ftree-vectorize} is used. The number of iterations after
|
8076 |
|
|
vectorization needs to be greater than the value specified by this option
|
8077 |
|
|
to allow vectorization. The default value is 0.
|
8078 |
|
|
|
8079 |
|
|
@item max-unrolled-insns
|
8080 |
|
|
The maximum number of instructions that a loop should have if that loop
|
8081 |
|
|
is unrolled, and if the loop is unrolled, it determines how many times
|
8082 |
|
|
the loop code is unrolled.
|
8083 |
|
|
|
8084 |
|
|
@item max-average-unrolled-insns
|
8085 |
|
|
The maximum number of instructions biased by probabilities of their execution
|
8086 |
|
|
that a loop should have if that loop is unrolled, and if the loop is unrolled,
|
8087 |
|
|
it determines how many times the loop code is unrolled.
|
8088 |
|
|
|
8089 |
|
|
@item max-unroll-times
|
8090 |
|
|
The maximum number of unrollings of a single loop.
|
8091 |
|
|
|
8092 |
|
|
@item max-peeled-insns
|
8093 |
|
|
The maximum number of instructions that a loop should have if that loop
|
8094 |
|
|
is peeled, and if the loop is peeled, it determines how many times
|
8095 |
|
|
the loop code is peeled.
|
8096 |
|
|
|
8097 |
|
|
@item max-peel-times
|
8098 |
|
|
The maximum number of peelings of a single loop.
|
8099 |
|
|
|
8100 |
|
|
@item max-completely-peeled-insns
|
8101 |
|
|
The maximum number of insns of a completely peeled loop.
|
8102 |
|
|
|
8103 |
|
|
@item max-completely-peel-times
|
8104 |
|
|
The maximum number of iterations of a loop to be suitable for complete peeling.
|
8105 |
|
|
|
8106 |
|
|
@item max-completely-peel-loop-nest-depth
|
8107 |
|
|
The maximum depth of a loop nest suitable for complete peeling.
|
8108 |
|
|
|
8109 |
|
|
@item max-unswitch-insns
|
8110 |
|
|
The maximum number of insns of an unswitched loop.
|
8111 |
|
|
|
8112 |
|
|
@item max-unswitch-level
|
8113 |
|
|
The maximum number of branches unswitched in a single loop.
|
8114 |
|
|
|
8115 |
|
|
@item lim-expensive
|
8116 |
|
|
The minimum cost of an expensive expression in the loop invariant motion.
|
8117 |
|
|
|
8118 |
|
|
@item iv-consider-all-candidates-bound
|
8119 |
|
|
Bound on number of candidates for induction variables below that
|
8120 |
|
|
all candidates are considered for each use in induction variable
|
8121 |
|
|
optimizations. Only the most relevant candidates are considered
|
8122 |
|
|
if there are more candidates, to avoid quadratic time complexity.
|
8123 |
|
|
|
8124 |
|
|
@item iv-max-considered-uses
|
8125 |
|
|
The induction variable optimizations give up on loops that contain more
|
8126 |
|
|
induction variable uses.
|
8127 |
|
|
|
8128 |
|
|
@item iv-always-prune-cand-set-bound
|
8129 |
|
|
If number of candidates in the set is smaller than this value,
|
8130 |
|
|
we always try to remove unnecessary ivs from the set during its
|
8131 |
|
|
optimization when a new iv is added to the set.
|
8132 |
|
|
|
8133 |
|
|
@item scev-max-expr-size
|
8134 |
|
|
Bound on size of expressions used in the scalar evolutions analyzer.
|
8135 |
|
|
Large expressions slow the analyzer.
|
8136 |
|
|
|
8137 |
|
|
@item omega-max-vars
|
8138 |
|
|
The maximum number of variables in an Omega constraint system.
|
8139 |
|
|
The default value is 128.
|
8140 |
|
|
|
8141 |
|
|
@item omega-max-geqs
|
8142 |
|
|
The maximum number of inequalities in an Omega constraint system.
|
8143 |
|
|
The default value is 256.
|
8144 |
|
|
|
8145 |
|
|
@item omega-max-eqs
|
8146 |
|
|
The maximum number of equalities in an Omega constraint system.
|
8147 |
|
|
The default value is 128.
|
8148 |
|
|
|
8149 |
|
|
@item omega-max-wild-cards
|
8150 |
|
|
The maximum number of wildcard variables that the Omega solver will
|
8151 |
|
|
be able to insert. The default value is 18.
|
8152 |
|
|
|
8153 |
|
|
@item omega-hash-table-size
|
8154 |
|
|
The size of the hash table in the Omega solver. The default value is
|
8155 |
|
|
550.
|
8156 |
|
|
|
8157 |
|
|
@item omega-max-keys
|
8158 |
|
|
The maximal number of keys used by the Omega solver. The default
|
8159 |
|
|
value is 500.
|
8160 |
|
|
|
8161 |
|
|
@item omega-eliminate-redundant-constraints
|
8162 |
|
|
When set to 1, use expensive methods to eliminate all redundant
|
8163 |
|
|
constraints. The default value is 0.
|
8164 |
|
|
|
8165 |
|
|
@item vect-max-version-for-alignment-checks
|
8166 |
|
|
The maximum number of runtime checks that can be performed when
|
8167 |
|
|
doing loop versioning for alignment in the vectorizer. See option
|
8168 |
|
|
ftree-vect-loop-version for more information.
|
8169 |
|
|
|
8170 |
|
|
@item vect-max-version-for-alias-checks
|
8171 |
|
|
The maximum number of runtime checks that can be performed when
|
8172 |
|
|
doing loop versioning for alias in the vectorizer. See option
|
8173 |
|
|
ftree-vect-loop-version for more information.
|
8174 |
|
|
|
8175 |
|
|
@item max-iterations-to-track
|
8176 |
|
|
|
8177 |
|
|
The maximum number of iterations of a loop the brute force algorithm
|
8178 |
|
|
for analysis of # of iterations of the loop tries to evaluate.
|
8179 |
|
|
|
8180 |
|
|
@item hot-bb-count-fraction
|
8181 |
|
|
Select fraction of the maximal count of repetitions of basic block in program
|
8182 |
|
|
given basic block needs to have to be considered hot.
|
8183 |
|
|
|
8184 |
|
|
@item hot-bb-frequency-fraction
|
8185 |
|
|
Select fraction of the maximal frequency of executions of basic block in
|
8186 |
|
|
function given basic block needs to have to be considered hot
|
8187 |
|
|
|
8188 |
|
|
@item max-predicted-iterations
|
8189 |
|
|
The maximum number of loop iterations we predict statically. This is useful
|
8190 |
|
|
in cases where function contain single loop with known bound and other loop
|
8191 |
|
|
with unknown. We predict the known number of iterations correctly, while
|
8192 |
|
|
the unknown number of iterations average to roughly 10. This means that the
|
8193 |
|
|
loop without bounds would appear artificially cold relative to the other one.
|
8194 |
|
|
|
8195 |
|
|
@item align-threshold
|
8196 |
|
|
|
8197 |
|
|
Select fraction of the maximal frequency of executions of basic block in
|
8198 |
|
|
function given basic block will get aligned.
|
8199 |
|
|
|
8200 |
|
|
@item align-loop-iterations
|
8201 |
|
|
|
8202 |
|
|
A loop expected to iterate at lest the selected number of iterations will get
|
8203 |
|
|
aligned.
|
8204 |
|
|
|
8205 |
|
|
@item tracer-dynamic-coverage
|
8206 |
|
|
@itemx tracer-dynamic-coverage-feedback
|
8207 |
|
|
|
8208 |
|
|
This value is used to limit superblock formation once the given percentage of
|
8209 |
|
|
executed instructions is covered. This limits unnecessary code size
|
8210 |
|
|
expansion.
|
8211 |
|
|
|
8212 |
|
|
The @option{tracer-dynamic-coverage-feedback} is used only when profile
|
8213 |
|
|
feedback is available. The real profiles (as opposed to statically estimated
|
8214 |
|
|
ones) are much less balanced allowing the threshold to be larger value.
|
8215 |
|
|
|
8216 |
|
|
@item tracer-max-code-growth
|
8217 |
|
|
Stop tail duplication once code growth has reached given percentage. This is
|
8218 |
|
|
rather hokey argument, as most of the duplicates will be eliminated later in
|
8219 |
|
|
cross jumping, so it may be set to much higher values than is the desired code
|
8220 |
|
|
growth.
|
8221 |
|
|
|
8222 |
|
|
@item tracer-min-branch-ratio
|
8223 |
|
|
|
8224 |
|
|
Stop reverse growth when the reverse probability of best edge is less than this
|
8225 |
|
|
threshold (in percent).
|
8226 |
|
|
|
8227 |
|
|
@item tracer-min-branch-ratio
|
8228 |
|
|
@itemx tracer-min-branch-ratio-feedback
|
8229 |
|
|
|
8230 |
|
|
Stop forward growth if the best edge do have probability lower than this
|
8231 |
|
|
threshold.
|
8232 |
|
|
|
8233 |
|
|
Similarly to @option{tracer-dynamic-coverage} two values are present, one for
|
8234 |
|
|
compilation for profile feedback and one for compilation without. The value
|
8235 |
|
|
for compilation with profile feedback needs to be more conservative (higher) in
|
8236 |
|
|
order to make tracer effective.
|
8237 |
|
|
|
8238 |
|
|
@item max-cse-path-length
|
8239 |
|
|
|
8240 |
|
|
Maximum number of basic blocks on path that cse considers. The default is 10.
|
8241 |
|
|
|
8242 |
|
|
@item max-cse-insns
|
8243 |
|
|
The maximum instructions CSE process before flushing. The default is 1000.
|
8244 |
|
|
|
8245 |
|
|
@item ggc-min-expand
|
8246 |
|
|
|
8247 |
|
|
GCC uses a garbage collector to manage its own memory allocation. This
|
8248 |
|
|
parameter specifies the minimum percentage by which the garbage
|
8249 |
|
|
collector's heap should be allowed to expand between collections.
|
8250 |
|
|
Tuning this may improve compilation speed; it has no effect on code
|
8251 |
|
|
generation.
|
8252 |
|
|
|
8253 |
|
|
The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when
|
8254 |
|
|
RAM >= 1GB@. If @code{getrlimit} is available, the notion of "RAM" is
|
8255 |
|
|
the smallest of actual RAM and @code{RLIMIT_DATA} or @code{RLIMIT_AS}. If
|
8256 |
|
|
GCC is not able to calculate RAM on a particular platform, the lower
|
8257 |
|
|
bound of 30% is used. Setting this parameter and
|
8258 |
|
|
@option{ggc-min-heapsize} to zero causes a full collection to occur at
|
8259 |
|
|
every opportunity. This is extremely slow, but can be useful for
|
8260 |
|
|
debugging.
|
8261 |
|
|
|
8262 |
|
|
@item ggc-min-heapsize
|
8263 |
|
|
|
8264 |
|
|
Minimum size of the garbage collector's heap before it begins bothering
|
8265 |
|
|
to collect garbage. The first collection occurs after the heap expands
|
8266 |
|
|
by @option{ggc-min-expand}% beyond @option{ggc-min-heapsize}. Again,
|
8267 |
|
|
tuning this may improve compilation speed, and has no effect on code
|
8268 |
|
|
generation.
|
8269 |
|
|
|
8270 |
|
|
The default is the smaller of RAM/8, RLIMIT_RSS, or a limit which
|
8271 |
|
|
tries to ensure that RLIMIT_DATA or RLIMIT_AS are not exceeded, but
|
8272 |
|
|
with a lower bound of 4096 (four megabytes) and an upper bound of
|
8273 |
|
|
131072 (128 megabytes). If GCC is not able to calculate RAM on a
|
8274 |
|
|
particular platform, the lower bound is used. Setting this parameter
|
8275 |
|
|
very large effectively disables garbage collection. Setting this
|
8276 |
|
|
parameter and @option{ggc-min-expand} to zero causes a full collection
|
8277 |
|
|
to occur at every opportunity.
|
8278 |
|
|
|
8279 |
|
|
@item max-reload-search-insns
|
8280 |
|
|
The maximum number of instruction reload should look backward for equivalent
|
8281 |
|
|
register. Increasing values mean more aggressive optimization, making the
|
8282 |
|
|
compile time increase with probably slightly better performance. The default
|
8283 |
|
|
value is 100.
|
8284 |
|
|
|
8285 |
|
|
@item max-cselib-memory-locations
|
8286 |
|
|
The maximum number of memory locations cselib should take into account.
|
8287 |
|
|
Increasing values mean more aggressive optimization, making the compile time
|
8288 |
|
|
increase with probably slightly better performance. The default value is 500.
|
8289 |
|
|
|
8290 |
|
|
@item reorder-blocks-duplicate
|
8291 |
|
|
@itemx reorder-blocks-duplicate-feedback
|
8292 |
|
|
|
8293 |
|
|
Used by basic block reordering pass to decide whether to use unconditional
|
8294 |
|
|
branch or duplicate the code on its destination. Code is duplicated when its
|
8295 |
|
|
estimated size is smaller than this value multiplied by the estimated size of
|
8296 |
|
|
unconditional jump in the hot spots of the program.
|
8297 |
|
|
|
8298 |
|
|
The @option{reorder-block-duplicate-feedback} is used only when profile
|
8299 |
|
|
feedback is available and may be set to higher values than
|
8300 |
|
|
@option{reorder-block-duplicate} since information about the hot spots is more
|
8301 |
|
|
accurate.
|
8302 |
|
|
|
8303 |
|
|
@item max-sched-ready-insns
|
8304 |
|
|
The maximum number of instructions ready to be issued the scheduler should
|
8305 |
|
|
consider at any given time during the first scheduling pass. Increasing
|
8306 |
|
|
values mean more thorough searches, making the compilation time increase
|
8307 |
|
|
with probably little benefit. The default value is 100.
|
8308 |
|
|
|
8309 |
|
|
@item max-sched-region-blocks
|
8310 |
|
|
The maximum number of blocks in a region to be considered for
|
8311 |
|
|
interblock scheduling. The default value is 10.
|
8312 |
|
|
|
8313 |
|
|
@item max-pipeline-region-blocks
|
8314 |
|
|
The maximum number of blocks in a region to be considered for
|
8315 |
|
|
pipelining in the selective scheduler. The default value is 15.
|
8316 |
|
|
|
8317 |
|
|
@item max-sched-region-insns
|
8318 |
|
|
The maximum number of insns in a region to be considered for
|
8319 |
|
|
interblock scheduling. The default value is 100.
|
8320 |
|
|
|
8321 |
|
|
@item max-pipeline-region-insns
|
8322 |
|
|
The maximum number of insns in a region to be considered for
|
8323 |
|
|
pipelining in the selective scheduler. The default value is 200.
|
8324 |
|
|
|
8325 |
|
|
@item min-spec-prob
|
8326 |
|
|
The minimum probability (in percents) of reaching a source block
|
8327 |
|
|
for interblock speculative scheduling. The default value is 40.
|
8328 |
|
|
|
8329 |
|
|
@item max-sched-extend-regions-iters
|
8330 |
|
|
The maximum number of iterations through CFG to extend regions.
|
8331 |
|
|
|
8332 |
|
|
N - do at most N iterations.
|
8333 |
|
|
The default value is 0.
|
8334 |
|
|
|
8335 |
|
|
@item max-sched-insn-conflict-delay
|
8336 |
|
|
The maximum conflict delay for an insn to be considered for speculative motion.
|
8337 |
|
|
The default value is 3.
|
8338 |
|
|
|
8339 |
|
|
@item sched-spec-prob-cutoff
|
8340 |
|
|
The minimal probability of speculation success (in percents), so that
|
8341 |
|
|
speculative insn will be scheduled.
|
8342 |
|
|
The default value is 40.
|
8343 |
|
|
|
8344 |
|
|
@item sched-mem-true-dep-cost
|
8345 |
|
|
Minimal distance (in CPU cycles) between store and load targeting same
|
8346 |
|
|
memory locations. The default value is 1.
|
8347 |
|
|
|
8348 |
|
|
@item selsched-max-lookahead
|
8349 |
|
|
The maximum size of the lookahead window of selective scheduling. It is a
|
8350 |
|
|
depth of search for available instructions.
|
8351 |
|
|
The default value is 50.
|
8352 |
|
|
|
8353 |
|
|
@item selsched-max-sched-times
|
8354 |
|
|
The maximum number of times that an instruction will be scheduled during
|
8355 |
|
|
selective scheduling. This is the limit on the number of iterations
|
8356 |
|
|
through which the instruction may be pipelined. The default value is 2.
|
8357 |
|
|
|
8358 |
|
|
@item selsched-max-insns-to-rename
|
8359 |
|
|
The maximum number of best instructions in the ready list that are considered
|
8360 |
|
|
for renaming in the selective scheduler. The default value is 2.
|
8361 |
|
|
|
8362 |
|
|
@item max-last-value-rtl
|
8363 |
|
|
The maximum size measured as number of RTLs that can be recorded in an expression
|
8364 |
|
|
in combiner for a pseudo register as last known value of that register. The default
|
8365 |
|
|
is 10000.
|
8366 |
|
|
|
8367 |
|
|
@item integer-share-limit
|
8368 |
|
|
Small integer constants can use a shared data structure, reducing the
|
8369 |
|
|
compiler's memory usage and increasing its speed. This sets the maximum
|
8370 |
|
|
value of a shared integer constant. The default value is 256.
|
8371 |
|
|
|
8372 |
|
|
@item min-virtual-mappings
|
8373 |
|
|
Specifies the minimum number of virtual mappings in the incremental
|
8374 |
|
|
SSA updater that should be registered to trigger the virtual mappings
|
8375 |
|
|
heuristic defined by virtual-mappings-ratio. The default value is
|
8376 |
|
|
100.
|
8377 |
|
|
|
8378 |
|
|
@item virtual-mappings-ratio
|
8379 |
|
|
If the number of virtual mappings is virtual-mappings-ratio bigger
|
8380 |
|
|
than the number of virtual symbols to be updated, then the incremental
|
8381 |
|
|
SSA updater switches to a full update for those symbols. The default
|
8382 |
|
|
ratio is 3.
|
8383 |
|
|
|
8384 |
|
|
@item ssp-buffer-size
|
8385 |
|
|
The minimum size of buffers (i.e.@: arrays) that will receive stack smashing
|
8386 |
|
|
protection when @option{-fstack-protection} is used.
|
8387 |
|
|
|
8388 |
|
|
@item max-jump-thread-duplication-stmts
|
8389 |
|
|
Maximum number of statements allowed in a block that needs to be
|
8390 |
|
|
duplicated when threading jumps.
|
8391 |
|
|
|
8392 |
|
|
@item max-fields-for-field-sensitive
|
8393 |
|
|
Maximum number of fields in a structure we will treat in
|
8394 |
|
|
a field sensitive manner during pointer analysis. The default is zero
|
8395 |
|
|
for -O0, and -O1 and 100 for -Os, -O2, and -O3.
|
8396 |
|
|
|
8397 |
|
|
@item prefetch-latency
|
8398 |
|
|
Estimate on average number of instructions that are executed before
|
8399 |
|
|
prefetch finishes. The distance we prefetch ahead is proportional
|
8400 |
|
|
to this constant. Increasing this number may also lead to less
|
8401 |
|
|
streams being prefetched (see @option{simultaneous-prefetches}).
|
8402 |
|
|
|
8403 |
|
|
@item simultaneous-prefetches
|
8404 |
|
|
Maximum number of prefetches that can run at the same time.
|
8405 |
|
|
|
8406 |
|
|
@item l1-cache-line-size
|
8407 |
|
|
The size of cache line in L1 cache, in bytes.
|
8408 |
|
|
|
8409 |
|
|
@item l1-cache-size
|
8410 |
|
|
The size of L1 cache, in kilobytes.
|
8411 |
|
|
|
8412 |
|
|
@item l2-cache-size
|
8413 |
|
|
The size of L2 cache, in kilobytes.
|
8414 |
|
|
|
8415 |
|
|
@item min-insn-to-prefetch-ratio
|
8416 |
|
|
The minimum ratio between the number of instructions and the
|
8417 |
|
|
number of prefetches to enable prefetching in a loop with an
|
8418 |
|
|
unknown trip count.
|
8419 |
|
|
|
8420 |
|
|
@item prefetch-min-insn-to-mem-ratio
|
8421 |
|
|
The minimum ratio between the number of instructions and the
|
8422 |
|
|
number of memory references to enable prefetching in a loop.
|
8423 |
|
|
|
8424 |
|
|
@item use-canonical-types
|
8425 |
|
|
Whether the compiler should use the ``canonical'' type system. By
|
8426 |
|
|
default, this should always be 1, which uses a more efficient internal
|
8427 |
|
|
mechanism for comparing types in C++ and Objective-C++. However, if
|
8428 |
|
|
bugs in the canonical type system are causing compilation failures,
|
8429 |
|
|
set this value to 0 to disable canonical types.
|
8430 |
|
|
|
8431 |
|
|
@item switch-conversion-max-branch-ratio
|
8432 |
|
|
Switch initialization conversion will refuse to create arrays that are
|
8433 |
|
|
bigger than @option{switch-conversion-max-branch-ratio} times the number of
|
8434 |
|
|
branches in the switch.
|
8435 |
|
|
|
8436 |
|
|
@item max-partial-antic-length
|
8437 |
|
|
Maximum length of the partial antic set computed during the tree
|
8438 |
|
|
partial redundancy elimination optimization (@option{-ftree-pre}) when
|
8439 |
|
|
optimizing at @option{-O3} and above. For some sorts of source code
|
8440 |
|
|
the enhanced partial redundancy elimination optimization can run away,
|
8441 |
|
|
consuming all of the memory available on the host machine. This
|
8442 |
|
|
parameter sets a limit on the length of the sets that are computed,
|
8443 |
|
|
which prevents the runaway behavior. Setting a value of 0 for
|
8444 |
|
|
this parameter will allow an unlimited set length.
|
8445 |
|
|
|
8446 |
|
|
@item sccvn-max-scc-size
|
8447 |
|
|
Maximum size of a strongly connected component (SCC) during SCCVN
|
8448 |
|
|
processing. If this limit is hit, SCCVN processing for the whole
|
8449 |
|
|
function will not be done and optimizations depending on it will
|
8450 |
|
|
be disabled. The default maximum SCC size is 10000.
|
8451 |
|
|
|
8452 |
|
|
@item ira-max-loops-num
|
8453 |
|
|
IRA uses a regional register allocation by default. If a function
|
8454 |
|
|
contains loops more than number given by the parameter, only at most
|
8455 |
|
|
given number of the most frequently executed loops will form regions
|
8456 |
|
|
for the regional register allocation. The default value of the
|
8457 |
|
|
parameter is 100.
|
8458 |
|
|
|
8459 |
|
|
@item ira-max-conflict-table-size
|
8460 |
|
|
Although IRA uses a sophisticated algorithm of compression conflict
|
8461 |
|
|
table, the table can be still big for huge functions. If the conflict
|
8462 |
|
|
table for a function could be more than size in MB given by the
|
8463 |
|
|
parameter, the conflict table is not built and faster, simpler, and
|
8464 |
|
|
lower quality register allocation algorithm will be used. The
|
8465 |
|
|
algorithm do not use pseudo-register conflicts. The default value of
|
8466 |
|
|
the parameter is 2000.
|
8467 |
|
|
|
8468 |
|
|
@item ira-loop-reserved-regs
|
8469 |
|
|
IRA can be used to evaluate more accurate register pressure in loops
|
8470 |
|
|
for decision to move loop invariants (see @option{-O3}). The number
|
8471 |
|
|
of available registers reserved for some other purposes is described
|
8472 |
|
|
by this parameter. The default value of the parameter is 2 which is
|
8473 |
|
|
minimal number of registers needed for execution of typical
|
8474 |
|
|
instruction. This value is the best found from numerous experiments.
|
8475 |
|
|
|
8476 |
|
|
@item loop-invariant-max-bbs-in-loop
|
8477 |
|
|
Loop invariant motion can be very expensive, both in compile time and
|
8478 |
|
|
in amount of needed compile time memory, with very large loops. Loops
|
8479 |
|
|
with more basic blocks than this parameter won't have loop invariant
|
8480 |
|
|
motion optimization performed on them. The default value of the
|
8481 |
|
|
parameter is 1000 for -O1 and 10000 for -O2 and above.
|
8482 |
|
|
|
8483 |
|
|
@item max-vartrack-size
|
8484 |
|
|
Sets a maximum number of hash table slots to use during variable
|
8485 |
|
|
tracking dataflow analysis of any function. If this limit is exceeded
|
8486 |
|
|
with variable tracking at assignments enabled, analysis for that
|
8487 |
|
|
function is retried without it, after removing all debug insns from
|
8488 |
|
|
the function. If the limit is exceeded even without debug insns, var
|
8489 |
|
|
tracking analysis is completely disabled for the function. Setting
|
8490 |
|
|
the parameter to zero makes it unlimited.
|
8491 |
|
|
|
8492 |
|
|
@item min-nondebug-insn-uid
|
8493 |
|
|
Use uids starting at this parameter for nondebug insns. The range below
|
8494 |
|
|
the parameter is reserved exclusively for debug insns created by
|
8495 |
|
|
@option{-fvar-tracking-assignments}, but debug insns may get
|
8496 |
|
|
(non-overlapping) uids above it if the reserved range is exhausted.
|
8497 |
|
|
|
8498 |
|
|
@item ipa-sra-ptr-growth-factor
|
8499 |
|
|
IPA-SRA will replace a pointer to an aggregate with one or more new
|
8500 |
|
|
parameters only when their cumulative size is less or equal to
|
8501 |
|
|
@option{ipa-sra-ptr-growth-factor} times the size of the original
|
8502 |
|
|
pointer parameter.
|
8503 |
|
|
|
8504 |
|
|
@item graphite-max-nb-scop-params
|
8505 |
|
|
To avoid exponential effects in the Graphite loop transforms, the
|
8506 |
|
|
number of parameters in a Static Control Part (SCoP) is bounded. The
|
8507 |
|
|
default value is 10 parameters. A variable whose value is unknown at
|
8508 |
|
|
compile time and defined outside a SCoP is a parameter of the SCoP.
|
8509 |
|
|
|
8510 |
|
|
@item graphite-max-bbs-per-function
|
8511 |
|
|
To avoid exponential effects in the detection of SCoPs, the size of
|
8512 |
|
|
the functions analyzed by Graphite is bounded. The default value is
|
8513 |
|
|
100 basic blocks.
|
8514 |
|
|
|
8515 |
|
|
@item loop-block-tile-size
|
8516 |
|
|
Loop blocking or strip mining transforms, enabled with
|
8517 |
|
|
@option{-floop-block} or @option{-floop-strip-mine}, strip mine each
|
8518 |
|
|
loop in the loop nest by a given number of iterations. The strip
|
8519 |
|
|
length can be changed using the @option{loop-block-tile-size}
|
8520 |
|
|
parameter. The default value is 51 iterations.
|
8521 |
|
|
|
8522 |
|
|
@end table
|
8523 |
|
|
@end table
|
8524 |
|
|
|
8525 |
|
|
@node Preprocessor Options
|
8526 |
|
|
@section Options Controlling the Preprocessor
|
8527 |
|
|
@cindex preprocessor options
|
8528 |
|
|
@cindex options, preprocessor
|
8529 |
|
|
|
8530 |
|
|
These options control the C preprocessor, which is run on each C source
|
8531 |
|
|
file before actual compilation.
|
8532 |
|
|
|
8533 |
|
|
If you use the @option{-E} option, nothing is done except preprocessing.
|
8534 |
|
|
Some of these options make sense only together with @option{-E} because
|
8535 |
|
|
they cause the preprocessor output to be unsuitable for actual
|
8536 |
|
|
compilation.
|
8537 |
|
|
|
8538 |
|
|
@table @gcctabopt
|
8539 |
|
|
@item -Wp,@var{option}
|
8540 |
|
|
@opindex Wp
|
8541 |
|
|
You can use @option{-Wp,@var{option}} to bypass the compiler driver
|
8542 |
|
|
and pass @var{option} directly through to the preprocessor. If
|
8543 |
|
|
@var{option} contains commas, it is split into multiple options at the
|
8544 |
|
|
commas. However, many options are modified, translated or interpreted
|
8545 |
|
|
by the compiler driver before being passed to the preprocessor, and
|
8546 |
|
|
@option{-Wp} forcibly bypasses this phase. The preprocessor's direct
|
8547 |
|
|
interface is undocumented and subject to change, so whenever possible
|
8548 |
|
|
you should avoid using @option{-Wp} and let the driver handle the
|
8549 |
|
|
options instead.
|
8550 |
|
|
|
8551 |
|
|
@item -Xpreprocessor @var{option}
|
8552 |
|
|
@opindex Xpreprocessor
|
8553 |
|
|
Pass @var{option} as an option to the preprocessor. You can use this to
|
8554 |
|
|
supply system-specific preprocessor options which GCC does not know how to
|
8555 |
|
|
recognize.
|
8556 |
|
|
|
8557 |
|
|
If you want to pass an option that takes an argument, you must use
|
8558 |
|
|
@option{-Xpreprocessor} twice, once for the option and once for the argument.
|
8559 |
|
|
@end table
|
8560 |
|
|
|
8561 |
|
|
@include cppopts.texi
|
8562 |
|
|
|
8563 |
|
|
@node Assembler Options
|
8564 |
|
|
@section Passing Options to the Assembler
|
8565 |
|
|
|
8566 |
|
|
@c prevent bad page break with this line
|
8567 |
|
|
You can pass options to the assembler.
|
8568 |
|
|
|
8569 |
|
|
@table @gcctabopt
|
8570 |
|
|
@item -Wa,@var{option}
|
8571 |
|
|
@opindex Wa
|
8572 |
|
|
Pass @var{option} as an option to the assembler. If @var{option}
|
8573 |
|
|
contains commas, it is split into multiple options at the commas.
|
8574 |
|
|
|
8575 |
|
|
@item -Xassembler @var{option}
|
8576 |
|
|
@opindex Xassembler
|
8577 |
|
|
Pass @var{option} as an option to the assembler. You can use this to
|
8578 |
|
|
supply system-specific assembler options which GCC does not know how to
|
8579 |
|
|
recognize.
|
8580 |
|
|
|
8581 |
|
|
If you want to pass an option that takes an argument, you must use
|
8582 |
|
|
@option{-Xassembler} twice, once for the option and once for the argument.
|
8583 |
|
|
|
8584 |
|
|
@end table
|
8585 |
|
|
|
8586 |
|
|
@node Link Options
|
8587 |
|
|
@section Options for Linking
|
8588 |
|
|
@cindex link options
|
8589 |
|
|
@cindex options, linking
|
8590 |
|
|
|
8591 |
|
|
These options come into play when the compiler links object files into
|
8592 |
|
|
an executable output file. They are meaningless if the compiler is
|
8593 |
|
|
not doing a link step.
|
8594 |
|
|
|
8595 |
|
|
@table @gcctabopt
|
8596 |
|
|
@cindex file names
|
8597 |
|
|
@item @var{object-file-name}
|
8598 |
|
|
A file name that does not end in a special recognized suffix is
|
8599 |
|
|
considered to name an object file or library. (Object files are
|
8600 |
|
|
distinguished from libraries by the linker according to the file
|
8601 |
|
|
contents.) If linking is done, these object files are used as input
|
8602 |
|
|
to the linker.
|
8603 |
|
|
|
8604 |
|
|
@item -c
|
8605 |
|
|
@itemx -S
|
8606 |
|
|
@itemx -E
|
8607 |
|
|
@opindex c
|
8608 |
|
|
@opindex S
|
8609 |
|
|
@opindex E
|
8610 |
|
|
If any of these options is used, then the linker is not run, and
|
8611 |
|
|
object file names should not be used as arguments. @xref{Overall
|
8612 |
|
|
Options}.
|
8613 |
|
|
|
8614 |
|
|
@cindex Libraries
|
8615 |
|
|
@item -l@var{library}
|
8616 |
|
|
@itemx -l @var{library}
|
8617 |
|
|
@opindex l
|
8618 |
|
|
Search the library named @var{library} when linking. (The second
|
8619 |
|
|
alternative with the library as a separate argument is only for
|
8620 |
|
|
POSIX compliance and is not recommended.)
|
8621 |
|
|
|
8622 |
|
|
It makes a difference where in the command you write this option; the
|
8623 |
|
|
linker searches and processes libraries and object files in the order they
|
8624 |
|
|
are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z}
|
8625 |
|
|
after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers
|
8626 |
|
|
to functions in @samp{z}, those functions may not be loaded.
|
8627 |
|
|
|
8628 |
|
|
The linker searches a standard list of directories for the library,
|
8629 |
|
|
which is actually a file named @file{lib@var{library}.a}. The linker
|
8630 |
|
|
then uses this file as if it had been specified precisely by name.
|
8631 |
|
|
|
8632 |
|
|
The directories searched include several standard system directories
|
8633 |
|
|
plus any that you specify with @option{-L}.
|
8634 |
|
|
|
8635 |
|
|
Normally the files found this way are library files---archive files
|
8636 |
|
|
whose members are object files. The linker handles an archive file by
|
8637 |
|
|
scanning through it for members which define symbols that have so far
|
8638 |
|
|
been referenced but not defined. But if the file that is found is an
|
8639 |
|
|
ordinary object file, it is linked in the usual fashion. The only
|
8640 |
|
|
difference between using an @option{-l} option and specifying a file name
|
8641 |
|
|
is that @option{-l} surrounds @var{library} with @samp{lib} and @samp{.a}
|
8642 |
|
|
and searches several directories.
|
8643 |
|
|
|
8644 |
|
|
@item -lobjc
|
8645 |
|
|
@opindex lobjc
|
8646 |
|
|
You need this special case of the @option{-l} option in order to
|
8647 |
|
|
link an Objective-C or Objective-C++ program.
|
8648 |
|
|
|
8649 |
|
|
@item -nostartfiles
|
8650 |
|
|
@opindex nostartfiles
|
8651 |
|
|
Do not use the standard system startup files when linking.
|
8652 |
|
|
The standard system libraries are used normally, unless @option{-nostdlib}
|
8653 |
|
|
or @option{-nodefaultlibs} is used.
|
8654 |
|
|
|
8655 |
|
|
@item -nodefaultlibs
|
8656 |
|
|
@opindex nodefaultlibs
|
8657 |
|
|
Do not use the standard system libraries when linking.
|
8658 |
|
|
Only the libraries you specify will be passed to the linker, options
|
8659 |
|
|
specifying linkage of the system libraries, such as @code{-static-libgcc}
|
8660 |
|
|
or @code{-shared-libgcc}, will be ignored.
|
8661 |
|
|
The standard startup files are used normally, unless @option{-nostartfiles}
|
8662 |
|
|
is used. The compiler may generate calls to @code{memcmp},
|
8663 |
|
|
@code{memset}, @code{memcpy} and @code{memmove}.
|
8664 |
|
|
These entries are usually resolved by entries in
|
8665 |
|
|
libc. These entry points should be supplied through some other
|
8666 |
|
|
mechanism when this option is specified.
|
8667 |
|
|
|
8668 |
|
|
@item -nostdlib
|
8669 |
|
|
@opindex nostdlib
|
8670 |
|
|
Do not use the standard system startup files or libraries when linking.
|
8671 |
|
|
No startup files and only the libraries you specify will be passed to
|
8672 |
|
|
the linker, options specifying linkage of the system libraries, such as
|
8673 |
|
|
@code{-static-libgcc} or @code{-shared-libgcc}, will be ignored.
|
8674 |
|
|
The compiler may generate calls to @code{memcmp}, @code{memset},
|
8675 |
|
|
@code{memcpy} and @code{memmove}.
|
8676 |
|
|
These entries are usually resolved by entries in
|
8677 |
|
|
libc. These entry points should be supplied through some other
|
8678 |
|
|
mechanism when this option is specified.
|
8679 |
|
|
|
8680 |
|
|
@cindex @option{-lgcc}, use with @option{-nostdlib}
|
8681 |
|
|
@cindex @option{-nostdlib} and unresolved references
|
8682 |
|
|
@cindex unresolved references and @option{-nostdlib}
|
8683 |
|
|
@cindex @option{-lgcc}, use with @option{-nodefaultlibs}
|
8684 |
|
|
@cindex @option{-nodefaultlibs} and unresolved references
|
8685 |
|
|
@cindex unresolved references and @option{-nodefaultlibs}
|
8686 |
|
|
One of the standard libraries bypassed by @option{-nostdlib} and
|
8687 |
|
|
@option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines
|
8688 |
|
|
that GCC uses to overcome shortcomings of particular machines, or special
|
8689 |
|
|
needs for some languages.
|
8690 |
|
|
(@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler
|
8691 |
|
|
Collection (GCC) Internals},
|
8692 |
|
|
for more discussion of @file{libgcc.a}.)
|
8693 |
|
|
In most cases, you need @file{libgcc.a} even when you want to avoid
|
8694 |
|
|
other standard libraries. In other words, when you specify @option{-nostdlib}
|
8695 |
|
|
or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well.
|
8696 |
|
|
This ensures that you have no unresolved references to internal GCC
|
8697 |
|
|
library subroutines. (For example, @samp{__main}, used to ensure C++
|
8698 |
|
|
constructors will be called; @pxref{Collect2,,@code{collect2}, gccint,
|
8699 |
|
|
GNU Compiler Collection (GCC) Internals}.)
|
8700 |
|
|
|
8701 |
|
|
@item -pie
|
8702 |
|
|
@opindex pie
|
8703 |
|
|
Produce a position independent executable on targets which support it.
|
8704 |
|
|
For predictable results, you must also specify the same set of options
|
8705 |
|
|
that were used to generate code (@option{-fpie}, @option{-fPIE},
|
8706 |
|
|
or model suboptions) when you specify this option.
|
8707 |
|
|
|
8708 |
|
|
@item -rdynamic
|
8709 |
|
|
@opindex rdynamic
|
8710 |
|
|
Pass the flag @option{-export-dynamic} to the ELF linker, on targets
|
8711 |
|
|
that support it. This instructs the linker to add all symbols, not
|
8712 |
|
|
only used ones, to the dynamic symbol table. This option is needed
|
8713 |
|
|
for some uses of @code{dlopen} or to allow obtaining backtraces
|
8714 |
|
|
from within a program.
|
8715 |
|
|
|
8716 |
|
|
@item -s
|
8717 |
|
|
@opindex s
|
8718 |
|
|
Remove all symbol table and relocation information from the executable.
|
8719 |
|
|
|
8720 |
|
|
@item -static
|
8721 |
|
|
@opindex static
|
8722 |
|
|
On systems that support dynamic linking, this prevents linking with the shared
|
8723 |
|
|
libraries. On other systems, this option has no effect.
|
8724 |
|
|
|
8725 |
|
|
@item -shared
|
8726 |
|
|
@opindex shared
|
8727 |
|
|
Produce a shared object which can then be linked with other objects to
|
8728 |
|
|
form an executable. Not all systems support this option. For predictable
|
8729 |
|
|
results, you must also specify the same set of options that were used to
|
8730 |
|
|
generate code (@option{-fpic}, @option{-fPIC}, or model suboptions)
|
8731 |
|
|
when you specify this option.@footnote{On some systems, @samp{gcc -shared}
|
8732 |
|
|
needs to build supplementary stub code for constructors to work. On
|
8733 |
|
|
multi-libbed systems, @samp{gcc -shared} must select the correct support
|
8734 |
|
|
libraries to link against. Failing to supply the correct flags may lead
|
8735 |
|
|
to subtle defects. Supplying them in cases where they are not necessary
|
8736 |
|
|
is innocuous.}
|
8737 |
|
|
|
8738 |
|
|
@item -shared-libgcc
|
8739 |
|
|
@itemx -static-libgcc
|
8740 |
|
|
@opindex shared-libgcc
|
8741 |
|
|
@opindex static-libgcc
|
8742 |
|
|
On systems that provide @file{libgcc} as a shared library, these options
|
8743 |
|
|
force the use of either the shared or static version respectively.
|
8744 |
|
|
If no shared version of @file{libgcc} was built when the compiler was
|
8745 |
|
|
configured, these options have no effect.
|
8746 |
|
|
|
8747 |
|
|
There are several situations in which an application should use the
|
8748 |
|
|
shared @file{libgcc} instead of the static version. The most common
|
8749 |
|
|
of these is when the application wishes to throw and catch exceptions
|
8750 |
|
|
across different shared libraries. In that case, each of the libraries
|
8751 |
|
|
as well as the application itself should use the shared @file{libgcc}.
|
8752 |
|
|
|
8753 |
|
|
Therefore, the G++ and GCJ drivers automatically add
|
8754 |
|
|
@option{-shared-libgcc} whenever you build a shared library or a main
|
8755 |
|
|
executable, because C++ and Java programs typically use exceptions, so
|
8756 |
|
|
this is the right thing to do.
|
8757 |
|
|
|
8758 |
|
|
If, instead, you use the GCC driver to create shared libraries, you may
|
8759 |
|
|
find that they will not always be linked with the shared @file{libgcc}.
|
8760 |
|
|
If GCC finds, at its configuration time, that you have a non-GNU linker
|
8761 |
|
|
or a GNU linker that does not support option @option{--eh-frame-hdr},
|
8762 |
|
|
it will link the shared version of @file{libgcc} into shared libraries
|
8763 |
|
|
by default. Otherwise, it will take advantage of the linker and optimize
|
8764 |
|
|
away the linking with the shared version of @file{libgcc}, linking with
|
8765 |
|
|
the static version of libgcc by default. This allows exceptions to
|
8766 |
|
|
propagate through such shared libraries, without incurring relocation
|
8767 |
|
|
costs at library load time.
|
8768 |
|
|
|
8769 |
|
|
However, if a library or main executable is supposed to throw or catch
|
8770 |
|
|
exceptions, you must link it using the G++ or GCJ driver, as appropriate
|
8771 |
|
|
for the languages used in the program, or using the option
|
8772 |
|
|
@option{-shared-libgcc}, such that it is linked with the shared
|
8773 |
|
|
@file{libgcc}.
|
8774 |
|
|
|
8775 |
|
|
@item -static-libstdc++
|
8776 |
|
|
When the @command{g++} program is used to link a C++ program, it will
|
8777 |
|
|
normally automatically link against @option{libstdc++}. If
|
8778 |
|
|
@file{libstdc++} is available as a shared library, and the
|
8779 |
|
|
@option{-static} option is not used, then this will link against the
|
8780 |
|
|
shared version of @file{libstdc++}. That is normally fine. However, it
|
8781 |
|
|
is sometimes useful to freeze the version of @file{libstdc++} used by
|
8782 |
|
|
the program without going all the way to a fully static link. The
|
8783 |
|
|
@option{-static-libstdc++} option directs the @command{g++} driver to
|
8784 |
|
|
link @file{libstdc++} statically, without necessarily linking other
|
8785 |
|
|
libraries statically.
|
8786 |
|
|
|
8787 |
|
|
@item -symbolic
|
8788 |
|
|
@opindex symbolic
|
8789 |
|
|
Bind references to global symbols when building a shared object. Warn
|
8790 |
|
|
about any unresolved references (unless overridden by the link editor
|
8791 |
|
|
option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support
|
8792 |
|
|
this option.
|
8793 |
|
|
|
8794 |
|
|
@item -T @var{script}
|
8795 |
|
|
@opindex T
|
8796 |
|
|
@cindex linker script
|
8797 |
|
|
Use @var{script} as the linker script. This option is supported by most
|
8798 |
|
|
systems using the GNU linker. On some targets, such as bare-board
|
8799 |
|
|
targets without an operating system, the @option{-T} option may be required
|
8800 |
|
|
when linking to avoid references to undefined symbols.
|
8801 |
|
|
|
8802 |
|
|
@item -Xlinker @var{option}
|
8803 |
|
|
@opindex Xlinker
|
8804 |
|
|
Pass @var{option} as an option to the linker. You can use this to
|
8805 |
|
|
supply system-specific linker options which GCC does not know how to
|
8806 |
|
|
recognize.
|
8807 |
|
|
|
8808 |
|
|
If you want to pass an option that takes a separate argument, you must use
|
8809 |
|
|
@option{-Xlinker} twice, once for the option and once for the argument.
|
8810 |
|
|
For example, to pass @option{-assert definitions}, you must write
|
8811 |
|
|
@samp{-Xlinker -assert -Xlinker definitions}. It does not work to write
|
8812 |
|
|
@option{-Xlinker "-assert definitions"}, because this passes the entire
|
8813 |
|
|
string as a single argument, which is not what the linker expects.
|
8814 |
|
|
|
8815 |
|
|
When using the GNU linker, it is usually more convenient to pass
|
8816 |
|
|
arguments to linker options using the @option{@var{option}=@var{value}}
|
8817 |
|
|
syntax than as separate arguments. For example, you can specify
|
8818 |
|
|
@samp{-Xlinker -Map=output.map} rather than
|
8819 |
|
|
@samp{-Xlinker -Map -Xlinker output.map}. Other linkers may not support
|
8820 |
|
|
this syntax for command-line options.
|
8821 |
|
|
|
8822 |
|
|
@item -Wl,@var{option}
|
8823 |
|
|
@opindex Wl
|
8824 |
|
|
Pass @var{option} as an option to the linker. If @var{option} contains
|
8825 |
|
|
commas, it is split into multiple options at the commas. You can use this
|
8826 |
|
|
syntax to pass an argument to the option.
|
8827 |
|
|
For example, @samp{-Wl,-Map,output.map} passes @samp{-Map output.map} to the
|
8828 |
|
|
linker. When using the GNU linker, you can also get the same effect with
|
8829 |
|
|
@samp{-Wl,-Map=output.map}.
|
8830 |
|
|
|
8831 |
|
|
@item -u @var{symbol}
|
8832 |
|
|
@opindex u
|
8833 |
|
|
Pretend the symbol @var{symbol} is undefined, to force linking of
|
8834 |
|
|
library modules to define it. You can use @option{-u} multiple times with
|
8835 |
|
|
different symbols to force loading of additional library modules.
|
8836 |
|
|
@end table
|
8837 |
|
|
|
8838 |
|
|
@node Directory Options
|
8839 |
|
|
@section Options for Directory Search
|
8840 |
|
|
@cindex directory options
|
8841 |
|
|
@cindex options, directory search
|
8842 |
|
|
@cindex search path
|
8843 |
|
|
|
8844 |
|
|
These options specify directories to search for header files, for
|
8845 |
|
|
libraries and for parts of the compiler:
|
8846 |
|
|
|
8847 |
|
|
@table @gcctabopt
|
8848 |
|
|
@item -I@var{dir}
|
8849 |
|
|
@opindex I
|
8850 |
|
|
Add the directory @var{dir} to the head of the list of directories to be
|
8851 |
|
|
searched for header files. This can be used to override a system header
|
8852 |
|
|
file, substituting your own version, since these directories are
|
8853 |
|
|
searched before the system header file directories. However, you should
|
8854 |
|
|
not use this option to add directories that contain vendor-supplied
|
8855 |
|
|
system header files (use @option{-isystem} for that). If you use more than
|
8856 |
|
|
one @option{-I} option, the directories are scanned in left-to-right
|
8857 |
|
|
order; the standard system directories come after.
|
8858 |
|
|
|
8859 |
|
|
If a standard system include directory, or a directory specified with
|
8860 |
|
|
@option{-isystem}, is also specified with @option{-I}, the @option{-I}
|
8861 |
|
|
option will be ignored. The directory will still be searched but as a
|
8862 |
|
|
system directory at its normal position in the system include chain.
|
8863 |
|
|
This is to ensure that GCC's procedure to fix buggy system headers and
|
8864 |
|
|
the ordering for the include_next directive are not inadvertently changed.
|
8865 |
|
|
If you really need to change the search order for system directories,
|
8866 |
|
|
use the @option{-nostdinc} and/or @option{-isystem} options.
|
8867 |
|
|
|
8868 |
|
|
@item -iquote@var{dir}
|
8869 |
|
|
@opindex iquote
|
8870 |
|
|
Add the directory @var{dir} to the head of the list of directories to
|
8871 |
|
|
be searched for header files only for the case of @samp{#include
|
8872 |
|
|
"@var{file}"}; they are not searched for @samp{#include <@var{file}>},
|
8873 |
|
|
otherwise just like @option{-I}.
|
8874 |
|
|
|
8875 |
|
|
@item -L@var{dir}
|
8876 |
|
|
@opindex L
|
8877 |
|
|
Add directory @var{dir} to the list of directories to be searched
|
8878 |
|
|
for @option{-l}.
|
8879 |
|
|
|
8880 |
|
|
@item -B@var{prefix}
|
8881 |
|
|
@opindex B
|
8882 |
|
|
This option specifies where to find the executables, libraries,
|
8883 |
|
|
include files, and data files of the compiler itself.
|
8884 |
|
|
|
8885 |
|
|
The compiler driver program runs one or more of the subprograms
|
8886 |
|
|
@file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries
|
8887 |
|
|
@var{prefix} as a prefix for each program it tries to run, both with and
|
8888 |
|
|
without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}).
|
8889 |
|
|
|
8890 |
|
|
For each subprogram to be run, the compiler driver first tries the
|
8891 |
|
|
@option{-B} prefix, if any. If that name is not found, or if @option{-B}
|
8892 |
|
|
was not specified, the driver tries two standard prefixes, which are
|
8893 |
|
|
@file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc/}. If neither of
|
8894 |
|
|
those results in a file name that is found, the unmodified program
|
8895 |
|
|
name is searched for using the directories specified in your
|
8896 |
|
|
@env{PATH} environment variable.
|
8897 |
|
|
|
8898 |
|
|
The compiler will check to see if the path provided by the @option{-B}
|
8899 |
|
|
refers to a directory, and if necessary it will add a directory
|
8900 |
|
|
separator character at the end of the path.
|
8901 |
|
|
|
8902 |
|
|
@option{-B} prefixes that effectively specify directory names also apply
|
8903 |
|
|
to libraries in the linker, because the compiler translates these
|
8904 |
|
|
options into @option{-L} options for the linker. They also apply to
|
8905 |
|
|
includes files in the preprocessor, because the compiler translates these
|
8906 |
|
|
options into @option{-isystem} options for the preprocessor. In this case,
|
8907 |
|
|
the compiler appends @samp{include} to the prefix.
|
8908 |
|
|
|
8909 |
|
|
The run-time support file @file{libgcc.a} can also be searched for using
|
8910 |
|
|
the @option{-B} prefix, if needed. If it is not found there, the two
|
8911 |
|
|
standard prefixes above are tried, and that is all. The file is left
|
8912 |
|
|
out of the link if it is not found by those means.
|
8913 |
|
|
|
8914 |
|
|
Another way to specify a prefix much like the @option{-B} prefix is to use
|
8915 |
|
|
the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment
|
8916 |
|
|
Variables}.
|
8917 |
|
|
|
8918 |
|
|
As a special kludge, if the path provided by @option{-B} is
|
8919 |
|
|
@file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to
|
8920 |
|
|
9, then it will be replaced by @file{[dir/]include}. This is to help
|
8921 |
|
|
with boot-strapping the compiler.
|
8922 |
|
|
|
8923 |
|
|
@item -specs=@var{file}
|
8924 |
|
|
@opindex specs
|
8925 |
|
|
Process @var{file} after the compiler reads in the standard @file{specs}
|
8926 |
|
|
file, in order to override the defaults that the @file{gcc} driver
|
8927 |
|
|
program uses when determining what switches to pass to @file{cc1},
|
8928 |
|
|
@file{cc1plus}, @file{as}, @file{ld}, etc. More than one
|
8929 |
|
|
@option{-specs=@var{file}} can be specified on the command line, and they
|
8930 |
|
|
are processed in order, from left to right.
|
8931 |
|
|
|
8932 |
|
|
@item --sysroot=@var{dir}
|
8933 |
|
|
@opindex sysroot
|
8934 |
|
|
Use @var{dir} as the logical root directory for headers and libraries.
|
8935 |
|
|
For example, if the compiler would normally search for headers in
|
8936 |
|
|
@file{/usr/include} and libraries in @file{/usr/lib}, it will instead
|
8937 |
|
|
search @file{@var{dir}/usr/include} and @file{@var{dir}/usr/lib}.
|
8938 |
|
|
|
8939 |
|
|
If you use both this option and the @option{-isysroot} option, then
|
8940 |
|
|
the @option{--sysroot} option will apply to libraries, but the
|
8941 |
|
|
@option{-isysroot} option will apply to header files.
|
8942 |
|
|
|
8943 |
|
|
The GNU linker (beginning with version 2.16) has the necessary support
|
8944 |
|
|
for this option. If your linker does not support this option, the
|
8945 |
|
|
header file aspect of @option{--sysroot} will still work, but the
|
8946 |
|
|
library aspect will not.
|
8947 |
|
|
|
8948 |
|
|
@item -I-
|
8949 |
|
|
@opindex I-
|
8950 |
|
|
This option has been deprecated. Please use @option{-iquote} instead for
|
8951 |
|
|
@option{-I} directories before the @option{-I-} and remove the @option{-I-}.
|
8952 |
|
|
Any directories you specify with @option{-I} options before the @option{-I-}
|
8953 |
|
|
option are searched only for the case of @samp{#include "@var{file}"};
|
8954 |
|
|
they are not searched for @samp{#include <@var{file}>}.
|
8955 |
|
|
|
8956 |
|
|
If additional directories are specified with @option{-I} options after
|
8957 |
|
|
the @option{-I-}, these directories are searched for all @samp{#include}
|
8958 |
|
|
directives. (Ordinarily @emph{all} @option{-I} directories are used
|
8959 |
|
|
this way.)
|
8960 |
|
|
|
8961 |
|
|
In addition, the @option{-I-} option inhibits the use of the current
|
8962 |
|
|
directory (where the current input file came from) as the first search
|
8963 |
|
|
directory for @samp{#include "@var{file}"}. There is no way to
|
8964 |
|
|
override this effect of @option{-I-}. With @option{-I.} you can specify
|
8965 |
|
|
searching the directory which was current when the compiler was
|
8966 |
|
|
invoked. That is not exactly the same as what the preprocessor does
|
8967 |
|
|
by default, but it is often satisfactory.
|
8968 |
|
|
|
8969 |
|
|
@option{-I-} does not inhibit the use of the standard system directories
|
8970 |
|
|
for header files. Thus, @option{-I-} and @option{-nostdinc} are
|
8971 |
|
|
independent.
|
8972 |
|
|
@end table
|
8973 |
|
|
|
8974 |
|
|
@c man end
|
8975 |
|
|
|
8976 |
|
|
@node Spec Files
|
8977 |
|
|
@section Specifying subprocesses and the switches to pass to them
|
8978 |
|
|
@cindex Spec Files
|
8979 |
|
|
|
8980 |
|
|
@command{gcc} is a driver program. It performs its job by invoking a
|
8981 |
|
|
sequence of other programs to do the work of compiling, assembling and
|
8982 |
|
|
linking. GCC interprets its command-line parameters and uses these to
|
8983 |
|
|
deduce which programs it should invoke, and which command-line options
|
8984 |
|
|
it ought to place on their command lines. This behavior is controlled
|
8985 |
|
|
by @dfn{spec strings}. In most cases there is one spec string for each
|
8986 |
|
|
program that GCC can invoke, but a few programs have multiple spec
|
8987 |
|
|
strings to control their behavior. The spec strings built into GCC can
|
8988 |
|
|
be overridden by using the @option{-specs=} command-line switch to specify
|
8989 |
|
|
a spec file.
|
8990 |
|
|
|
8991 |
|
|
@dfn{Spec files} are plaintext files that are used to construct spec
|
8992 |
|
|
strings. They consist of a sequence of directives separated by blank
|
8993 |
|
|
lines. The type of directive is determined by the first non-whitespace
|
8994 |
|
|
character on the line and it can be one of the following:
|
8995 |
|
|
|
8996 |
|
|
@table @code
|
8997 |
|
|
@item %@var{command}
|
8998 |
|
|
Issues a @var{command} to the spec file processor. The commands that can
|
8999 |
|
|
appear here are:
|
9000 |
|
|
|
9001 |
|
|
@table @code
|
9002 |
|
|
@item %include <@var{file}>
|
9003 |
|
|
@cindex %include
|
9004 |
|
|
Search for @var{file} and insert its text at the current point in the
|
9005 |
|
|
specs file.
|
9006 |
|
|
|
9007 |
|
|
@item %include_noerr <@var{file}>
|
9008 |
|
|
@cindex %include_noerr
|
9009 |
|
|
Just like @samp{%include}, but do not generate an error message if the include
|
9010 |
|
|
file cannot be found.
|
9011 |
|
|
|
9012 |
|
|
@item %rename @var{old_name} @var{new_name}
|
9013 |
|
|
@cindex %rename
|
9014 |
|
|
Rename the spec string @var{old_name} to @var{new_name}.
|
9015 |
|
|
|
9016 |
|
|
@end table
|
9017 |
|
|
|
9018 |
|
|
@item *[@var{spec_name}]:
|
9019 |
|
|
This tells the compiler to create, override or delete the named spec
|
9020 |
|
|
string. All lines after this directive up to the next directive or
|
9021 |
|
|
blank line are considered to be the text for the spec string. If this
|
9022 |
|
|
results in an empty string then the spec will be deleted. (Or, if the
|
9023 |
|
|
spec did not exist, then nothing will happened.) Otherwise, if the spec
|
9024 |
|
|
does not currently exist a new spec will be created. If the spec does
|
9025 |
|
|
exist then its contents will be overridden by the text of this
|
9026 |
|
|
directive, unless the first character of that text is the @samp{+}
|
9027 |
|
|
character, in which case the text will be appended to the spec.
|
9028 |
|
|
|
9029 |
|
|
@item [@var{suffix}]:
|
9030 |
|
|
Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive
|
9031 |
|
|
and up to the next directive or blank line are considered to make up the
|
9032 |
|
|
spec string for the indicated suffix. When the compiler encounters an
|
9033 |
|
|
input file with the named suffix, it will processes the spec string in
|
9034 |
|
|
order to work out how to compile that file. For example:
|
9035 |
|
|
|
9036 |
|
|
@smallexample
|
9037 |
|
|
.ZZ:
|
9038 |
|
|
z-compile -input %i
|
9039 |
|
|
@end smallexample
|
9040 |
|
|
|
9041 |
|
|
This says that any input file whose name ends in @samp{.ZZ} should be
|
9042 |
|
|
passed to the program @samp{z-compile}, which should be invoked with the
|
9043 |
|
|
command-line switch @option{-input} and with the result of performing the
|
9044 |
|
|
@samp{%i} substitution. (See below.)
|
9045 |
|
|
|
9046 |
|
|
As an alternative to providing a spec string, the text that follows a
|
9047 |
|
|
suffix directive can be one of the following:
|
9048 |
|
|
|
9049 |
|
|
@table @code
|
9050 |
|
|
@item @@@var{language}
|
9051 |
|
|
This says that the suffix is an alias for a known @var{language}. This is
|
9052 |
|
|
similar to using the @option{-x} command-line switch to GCC to specify a
|
9053 |
|
|
language explicitly. For example:
|
9054 |
|
|
|
9055 |
|
|
@smallexample
|
9056 |
|
|
.ZZ:
|
9057 |
|
|
@@c++
|
9058 |
|
|
@end smallexample
|
9059 |
|
|
|
9060 |
|
|
Says that .ZZ files are, in fact, C++ source files.
|
9061 |
|
|
|
9062 |
|
|
@item #@var{name}
|
9063 |
|
|
This causes an error messages saying:
|
9064 |
|
|
|
9065 |
|
|
@smallexample
|
9066 |
|
|
@var{name} compiler not installed on this system.
|
9067 |
|
|
@end smallexample
|
9068 |
|
|
@end table
|
9069 |
|
|
|
9070 |
|
|
GCC already has an extensive list of suffixes built into it.
|
9071 |
|
|
This directive will add an entry to the end of the list of suffixes, but
|
9072 |
|
|
since the list is searched from the end backwards, it is effectively
|
9073 |
|
|
possible to override earlier entries using this technique.
|
9074 |
|
|
|
9075 |
|
|
@end table
|
9076 |
|
|
|
9077 |
|
|
GCC has the following spec strings built into it. Spec files can
|
9078 |
|
|
override these strings or create their own. Note that individual
|
9079 |
|
|
targets can also add their own spec strings to this list.
|
9080 |
|
|
|
9081 |
|
|
@smallexample
|
9082 |
|
|
asm Options to pass to the assembler
|
9083 |
|
|
asm_final Options to pass to the assembler post-processor
|
9084 |
|
|
cpp Options to pass to the C preprocessor
|
9085 |
|
|
cc1 Options to pass to the C compiler
|
9086 |
|
|
cc1plus Options to pass to the C++ compiler
|
9087 |
|
|
endfile Object files to include at the end of the link
|
9088 |
|
|
link Options to pass to the linker
|
9089 |
|
|
lib Libraries to include on the command line to the linker
|
9090 |
|
|
libgcc Decides which GCC support library to pass to the linker
|
9091 |
|
|
linker Sets the name of the linker
|
9092 |
|
|
predefines Defines to be passed to the C preprocessor
|
9093 |
|
|
signed_char Defines to pass to CPP to say whether @code{char} is signed
|
9094 |
|
|
by default
|
9095 |
|
|
startfile Object files to include at the start of the link
|
9096 |
|
|
@end smallexample
|
9097 |
|
|
|
9098 |
|
|
Here is a small example of a spec file:
|
9099 |
|
|
|
9100 |
|
|
@smallexample
|
9101 |
|
|
%rename lib old_lib
|
9102 |
|
|
|
9103 |
|
|
*lib:
|
9104 |
|
|
--start-group -lgcc -lc -leval1 --end-group %(old_lib)
|
9105 |
|
|
@end smallexample
|
9106 |
|
|
|
9107 |
|
|
This example renames the spec called @samp{lib} to @samp{old_lib} and
|
9108 |
|
|
then overrides the previous definition of @samp{lib} with a new one.
|
9109 |
|
|
The new definition adds in some extra command-line options before
|
9110 |
|
|
including the text of the old definition.
|
9111 |
|
|
|
9112 |
|
|
@dfn{Spec strings} are a list of command-line options to be passed to their
|
9113 |
|
|
corresponding program. In addition, the spec strings can contain
|
9114 |
|
|
@samp{%}-prefixed sequences to substitute variable text or to
|
9115 |
|
|
conditionally insert text into the command line. Using these constructs
|
9116 |
|
|
it is possible to generate quite complex command lines.
|
9117 |
|
|
|
9118 |
|
|
Here is a table of all defined @samp{%}-sequences for spec
|
9119 |
|
|
strings. Note that spaces are not generated automatically around the
|
9120 |
|
|
results of expanding these sequences. Therefore you can concatenate them
|
9121 |
|
|
together or combine them with constant text in a single argument.
|
9122 |
|
|
|
9123 |
|
|
@table @code
|
9124 |
|
|
@item %%
|
9125 |
|
|
Substitute one @samp{%} into the program name or argument.
|
9126 |
|
|
|
9127 |
|
|
@item %i
|
9128 |
|
|
Substitute the name of the input file being processed.
|
9129 |
|
|
|
9130 |
|
|
@item %b
|
9131 |
|
|
Substitute the basename of the input file being processed.
|
9132 |
|
|
This is the substring up to (and not including) the last period
|
9133 |
|
|
and not including the directory.
|
9134 |
|
|
|
9135 |
|
|
@item %B
|
9136 |
|
|
This is the same as @samp{%b}, but include the file suffix (text after
|
9137 |
|
|
the last period).
|
9138 |
|
|
|
9139 |
|
|
@item %d
|
9140 |
|
|
Marks the argument containing or following the @samp{%d} as a
|
9141 |
|
|
temporary file name, so that that file will be deleted if GCC exits
|
9142 |
|
|
successfully. Unlike @samp{%g}, this contributes no text to the
|
9143 |
|
|
argument.
|
9144 |
|
|
|
9145 |
|
|
@item %g@var{suffix}
|
9146 |
|
|
Substitute a file name that has suffix @var{suffix} and is chosen
|
9147 |
|
|
once per compilation, and mark the argument in the same way as
|
9148 |
|
|
@samp{%d}. To reduce exposure to denial-of-service attacks, the file
|
9149 |
|
|
name is now chosen in a way that is hard to predict even when previously
|
9150 |
|
|
chosen file names are known. For example, @samp{%g.s @dots{} %g.o @dots{} %g.s}
|
9151 |
|
|
might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches
|
9152 |
|
|
the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is
|
9153 |
|
|
treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g}
|
9154 |
|
|
was simply substituted with a file name chosen once per compilation,
|
9155 |
|
|
without regard to any appended suffix (which was therefore treated
|
9156 |
|
|
just like ordinary text), making such attacks more likely to succeed.
|
9157 |
|
|
|
9158 |
|
|
@item %u@var{suffix}
|
9159 |
|
|
Like @samp{%g}, but generates a new temporary file name even if
|
9160 |
|
|
@samp{%u@var{suffix}} was already seen.
|
9161 |
|
|
|
9162 |
|
|
@item %U@var{suffix}
|
9163 |
|
|
Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a
|
9164 |
|
|
new one if there is no such last file name. In the absence of any
|
9165 |
|
|
@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share
|
9166 |
|
|
the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s}
|
9167 |
|
|
would involve the generation of two distinct file names, one
|
9168 |
|
|
for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was
|
9169 |
|
|
simply substituted with a file name chosen for the previous @samp{%u},
|
9170 |
|
|
without regard to any appended suffix.
|
9171 |
|
|
|
9172 |
|
|
@item %j@var{suffix}
|
9173 |
|
|
Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is
|
9174 |
|
|
writable, and if save-temps is off; otherwise, substitute the name
|
9175 |
|
|
of a temporary file, just like @samp{%u}. This temporary file is not
|
9176 |
|
|
meant for communication between processes, but rather as a junk
|
9177 |
|
|
disposal mechanism.
|
9178 |
|
|
|
9179 |
|
|
@item %|@var{suffix}
|
9180 |
|
|
@itemx %m@var{suffix}
|
9181 |
|
|
Like @samp{%g}, except if @option{-pipe} is in effect. In that case
|
9182 |
|
|
@samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at
|
9183 |
|
|
all. These are the two most common ways to instruct a program that it
|
9184 |
|
|
should read from standard input or write to standard output. If you
|
9185 |
|
|
need something more elaborate you can use an @samp{%@{pipe:@code{X}@}}
|
9186 |
|
|
construct: see for example @file{f/lang-specs.h}.
|
9187 |
|
|
|
9188 |
|
|
@item %.@var{SUFFIX}
|
9189 |
|
|
Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args
|
9190 |
|
|
when it is subsequently output with @samp{%*}. @var{SUFFIX} is
|
9191 |
|
|
terminated by the next space or %.
|
9192 |
|
|
|
9193 |
|
|
@item %w
|
9194 |
|
|
Marks the argument containing or following the @samp{%w} as the
|
9195 |
|
|
designated output file of this compilation. This puts the argument
|
9196 |
|
|
into the sequence of arguments that @samp{%o} will substitute later.
|
9197 |
|
|
|
9198 |
|
|
@item %o
|
9199 |
|
|
Substitutes the names of all the output files, with spaces
|
9200 |
|
|
automatically placed around them. You should write spaces
|
9201 |
|
|
around the @samp{%o} as well or the results are undefined.
|
9202 |
|
|
@samp{%o} is for use in the specs for running the linker.
|
9203 |
|
|
Input files whose names have no recognized suffix are not compiled
|
9204 |
|
|
at all, but they are included among the output files, so they will
|
9205 |
|
|
be linked.
|
9206 |
|
|
|
9207 |
|
|
@item %O
|
9208 |
|
|
Substitutes the suffix for object files. Note that this is
|
9209 |
|
|
handled specially when it immediately follows @samp{%g, %u, or %U},
|
9210 |
|
|
because of the need for those to form complete file names. The
|
9211 |
|
|
handling is such that @samp{%O} is treated exactly as if it had already
|
9212 |
|
|
been substituted, except that @samp{%g, %u, and %U} do not currently
|
9213 |
|
|
support additional @var{suffix} characters following @samp{%O} as they would
|
9214 |
|
|
following, for example, @samp{.o}.
|
9215 |
|
|
|
9216 |
|
|
@item %p
|
9217 |
|
|
Substitutes the standard macro predefinitions for the
|
9218 |
|
|
current target machine. Use this when running @code{cpp}.
|
9219 |
|
|
|
9220 |
|
|
@item %P
|
9221 |
|
|
Like @samp{%p}, but puts @samp{__} before and after the name of each
|
9222 |
|
|
predefined macro, except for macros that start with @samp{__} or with
|
9223 |
|
|
@samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO
|
9224 |
|
|
C@.
|
9225 |
|
|
|
9226 |
|
|
@item %I
|
9227 |
|
|
Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}),
|
9228 |
|
|
@option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}),
|
9229 |
|
|
@option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options)
|
9230 |
|
|
and @option{-imultilib} as necessary.
|
9231 |
|
|
|
9232 |
|
|
@item %s
|
9233 |
|
|
Current argument is the name of a library or startup file of some sort.
|
9234 |
|
|
Search for that file in a standard list of directories and substitute
|
9235 |
|
|
the full name found. The current working directory is included in the
|
9236 |
|
|
list of directories scanned.
|
9237 |
|
|
|
9238 |
|
|
@item %T
|
9239 |
|
|
Current argument is the name of a linker script. Search for that file
|
9240 |
|
|
in the current list of directories to scan for libraries. If the file
|
9241 |
|
|
is located insert a @option{--script} option into the command line
|
9242 |
|
|
followed by the full path name found. If the file is not found then
|
9243 |
|
|
generate an error message. Note: the current working directory is not
|
9244 |
|
|
searched.
|
9245 |
|
|
|
9246 |
|
|
@item %e@var{str}
|
9247 |
|
|
Print @var{str} as an error message. @var{str} is terminated by a newline.
|
9248 |
|
|
Use this when inconsistent options are detected.
|
9249 |
|
|
|
9250 |
|
|
@item %(@var{name})
|
9251 |
|
|
Substitute the contents of spec string @var{name} at this point.
|
9252 |
|
|
|
9253 |
|
|
@item %[@var{name}]
|
9254 |
|
|
Like @samp{%(@dots{})} but put @samp{__} around @option{-D} arguments.
|
9255 |
|
|
|
9256 |
|
|
@item %x@{@var{option}@}
|
9257 |
|
|
Accumulate an option for @samp{%X}.
|
9258 |
|
|
|
9259 |
|
|
@item %X
|
9260 |
|
|
Output the accumulated linker options specified by @option{-Wl} or a @samp{%x}
|
9261 |
|
|
spec string.
|
9262 |
|
|
|
9263 |
|
|
@item %Y
|
9264 |
|
|
Output the accumulated assembler options specified by @option{-Wa}.
|
9265 |
|
|
|
9266 |
|
|
@item %Z
|
9267 |
|
|
Output the accumulated preprocessor options specified by @option{-Wp}.
|
9268 |
|
|
|
9269 |
|
|
@item %a
|
9270 |
|
|
Process the @code{asm} spec. This is used to compute the
|
9271 |
|
|
switches to be passed to the assembler.
|
9272 |
|
|
|
9273 |
|
|
@item %A
|
9274 |
|
|
Process the @code{asm_final} spec. This is a spec string for
|
9275 |
|
|
passing switches to an assembler post-processor, if such a program is
|
9276 |
|
|
needed.
|
9277 |
|
|
|
9278 |
|
|
@item %l
|
9279 |
|
|
Process the @code{link} spec. This is the spec for computing the
|
9280 |
|
|
command line passed to the linker. Typically it will make use of the
|
9281 |
|
|
@samp{%L %G %S %D and %E} sequences.
|
9282 |
|
|
|
9283 |
|
|
@item %D
|
9284 |
|
|
Dump out a @option{-L} option for each directory that GCC believes might
|
9285 |
|
|
contain startup files. If the target supports multilibs then the
|
9286 |
|
|
current multilib directory will be prepended to each of these paths.
|
9287 |
|
|
|
9288 |
|
|
@item %L
|
9289 |
|
|
Process the @code{lib} spec. This is a spec string for deciding which
|
9290 |
|
|
libraries should be included on the command line to the linker.
|
9291 |
|
|
|
9292 |
|
|
@item %G
|
9293 |
|
|
Process the @code{libgcc} spec. This is a spec string for deciding
|
9294 |
|
|
which GCC support library should be included on the command line to the linker.
|
9295 |
|
|
|
9296 |
|
|
@item %S
|
9297 |
|
|
Process the @code{startfile} spec. This is a spec for deciding which
|
9298 |
|
|
object files should be the first ones passed to the linker. Typically
|
9299 |
|
|
this might be a file named @file{crt0.o}.
|
9300 |
|
|
|
9301 |
|
|
@item %E
|
9302 |
|
|
Process the @code{endfile} spec. This is a spec string that specifies
|
9303 |
|
|
the last object files that will be passed to the linker.
|
9304 |
|
|
|
9305 |
|
|
@item %C
|
9306 |
|
|
Process the @code{cpp} spec. This is used to construct the arguments
|
9307 |
|
|
to be passed to the C preprocessor.
|
9308 |
|
|
|
9309 |
|
|
@item %1
|
9310 |
|
|
Process the @code{cc1} spec. This is used to construct the options to be
|
9311 |
|
|
passed to the actual C compiler (@samp{cc1}).
|
9312 |
|
|
|
9313 |
|
|
@item %2
|
9314 |
|
|
Process the @code{cc1plus} spec. This is used to construct the options to be
|
9315 |
|
|
passed to the actual C++ compiler (@samp{cc1plus}).
|
9316 |
|
|
|
9317 |
|
|
@item %*
|
9318 |
|
|
Substitute the variable part of a matched option. See below.
|
9319 |
|
|
Note that each comma in the substituted string is replaced by
|
9320 |
|
|
a single space.
|
9321 |
|
|
|
9322 |
|
|
@item %<@code{S}
|
9323 |
|
|
Remove all occurrences of @code{-S} from the command line. Note---this
|
9324 |
|
|
command is position dependent. @samp{%} commands in the spec string
|
9325 |
|
|
before this one will see @code{-S}, @samp{%} commands in the spec string
|
9326 |
|
|
after this one will not.
|
9327 |
|
|
|
9328 |
|
|
@item %:@var{function}(@var{args})
|
9329 |
|
|
Call the named function @var{function}, passing it @var{args}.
|
9330 |
|
|
@var{args} is first processed as a nested spec string, then split
|
9331 |
|
|
into an argument vector in the usual fashion. The function returns
|
9332 |
|
|
a string which is processed as if it had appeared literally as part
|
9333 |
|
|
of the current spec.
|
9334 |
|
|
|
9335 |
|
|
The following built-in spec functions are provided:
|
9336 |
|
|
|
9337 |
|
|
@table @code
|
9338 |
|
|
@item @code{getenv}
|
9339 |
|
|
The @code{getenv} spec function takes two arguments: an environment
|
9340 |
|
|
variable name and a string. If the environment variable is not
|
9341 |
|
|
defined, a fatal error is issued. Otherwise, the return value is the
|
9342 |
|
|
value of the environment variable concatenated with the string. For
|
9343 |
|
|
example, if @env{TOPDIR} is defined as @file{/path/to/top}, then:
|
9344 |
|
|
|
9345 |
|
|
@smallexample
|
9346 |
|
|
%:getenv(TOPDIR /include)
|
9347 |
|
|
@end smallexample
|
9348 |
|
|
|
9349 |
|
|
expands to @file{/path/to/top/include}.
|
9350 |
|
|
|
9351 |
|
|
@item @code{if-exists}
|
9352 |
|
|
The @code{if-exists} spec function takes one argument, an absolute
|
9353 |
|
|
pathname to a file. If the file exists, @code{if-exists} returns the
|
9354 |
|
|
pathname. Here is a small example of its usage:
|
9355 |
|
|
|
9356 |
|
|
@smallexample
|
9357 |
|
|
*startfile:
|
9358 |
|
|
crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s
|
9359 |
|
|
@end smallexample
|
9360 |
|
|
|
9361 |
|
|
@item @code{if-exists-else}
|
9362 |
|
|
The @code{if-exists-else} spec function is similar to the @code{if-exists}
|
9363 |
|
|
spec function, except that it takes two arguments. The first argument is
|
9364 |
|
|
an absolute pathname to a file. If the file exists, @code{if-exists-else}
|
9365 |
|
|
returns the pathname. If it does not exist, it returns the second argument.
|
9366 |
|
|
This way, @code{if-exists-else} can be used to select one file or another,
|
9367 |
|
|
based on the existence of the first. Here is a small example of its usage:
|
9368 |
|
|
|
9369 |
|
|
@smallexample
|
9370 |
|
|
*startfile:
|
9371 |
|
|
crt0%O%s %:if-exists(crti%O%s) \
|
9372 |
|
|
%:if-exists-else(crtbeginT%O%s crtbegin%O%s)
|
9373 |
|
|
@end smallexample
|
9374 |
|
|
|
9375 |
|
|
@item @code{replace-outfile}
|
9376 |
|
|
The @code{replace-outfile} spec function takes two arguments. It looks for the
|
9377 |
|
|
first argument in the outfiles array and replaces it with the second argument. Here
|
9378 |
|
|
is a small example of its usage:
|
9379 |
|
|
|
9380 |
|
|
@smallexample
|
9381 |
|
|
%@{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)@}
|
9382 |
|
|
@end smallexample
|
9383 |
|
|
|
9384 |
|
|
@item @code{print-asm-header}
|
9385 |
|
|
The @code{print-asm-header} function takes no arguments and simply
|
9386 |
|
|
prints a banner like:
|
9387 |
|
|
|
9388 |
|
|
@smallexample
|
9389 |
|
|
Assembler options
|
9390 |
|
|
=================
|
9391 |
|
|
|
9392 |
|
|
Use "-Wa,OPTION" to pass "OPTION" to the assembler.
|
9393 |
|
|
@end smallexample
|
9394 |
|
|
|
9395 |
|
|
It is used to separate compiler options from assembler options
|
9396 |
|
|
in the @option{--target-help} output.
|
9397 |
|
|
@end table
|
9398 |
|
|
|
9399 |
|
|
@item %@{@code{S}@}
|
9400 |
|
|
Substitutes the @code{-S} switch, if that switch was given to GCC@.
|
9401 |
|
|
If that switch was not specified, this substitutes nothing. Note that
|
9402 |
|
|
the leading dash is omitted when specifying this option, and it is
|
9403 |
|
|
automatically inserted if the substitution is performed. Thus the spec
|
9404 |
|
|
string @samp{%@{foo@}} would match the command-line option @option{-foo}
|
9405 |
|
|
and would output the command line option @option{-foo}.
|
9406 |
|
|
|
9407 |
|
|
@item %W@{@code{S}@}
|
9408 |
|
|
Like %@{@code{S}@} but mark last argument supplied within as a file to be
|
9409 |
|
|
deleted on failure.
|
9410 |
|
|
|
9411 |
|
|
@item %@{@code{S}*@}
|
9412 |
|
|
Substitutes all the switches specified to GCC whose names start
|
9413 |
|
|
with @code{-S}, but which also take an argument. This is used for
|
9414 |
|
|
switches like @option{-o}, @option{-D}, @option{-I}, etc.
|
9415 |
|
|
GCC considers @option{-o foo} as being
|
9416 |
|
|
one switch whose names starts with @samp{o}. %@{o*@} would substitute this
|
9417 |
|
|
text, including the space. Thus two arguments would be generated.
|
9418 |
|
|
|
9419 |
|
|
@item %@{@code{S}*&@code{T}*@}
|
9420 |
|
|
Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options
|
9421 |
|
|
(the order of @code{S} and @code{T} in the spec is not significant).
|
9422 |
|
|
There can be any number of ampersand-separated variables; for each the
|
9423 |
|
|
wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}.
|
9424 |
|
|
|
9425 |
|
|
@item %@{@code{S}:@code{X}@}
|
9426 |
|
|
Substitutes @code{X}, if the @samp{-S} switch was given to GCC@.
|
9427 |
|
|
|
9428 |
|
|
@item %@{!@code{S}:@code{X}@}
|
9429 |
|
|
Substitutes @code{X}, if the @samp{-S} switch was @emph{not} given to GCC@.
|
9430 |
|
|
|
9431 |
|
|
@item %@{@code{S}*:@code{X}@}
|
9432 |
|
|
Substitutes @code{X} if one or more switches whose names start with
|
9433 |
|
|
@code{-S} are specified to GCC@. Normally @code{X} is substituted only
|
9434 |
|
|
once, no matter how many such switches appeared. However, if @code{%*}
|
9435 |
|
|
appears somewhere in @code{X}, then @code{X} will be substituted once
|
9436 |
|
|
for each matching switch, with the @code{%*} replaced by the part of
|
9437 |
|
|
that switch that matched the @code{*}.
|
9438 |
|
|
|
9439 |
|
|
@item %@{.@code{S}:@code{X}@}
|
9440 |
|
|
Substitutes @code{X}, if processing a file with suffix @code{S}.
|
9441 |
|
|
|
9442 |
|
|
@item %@{!.@code{S}:@code{X}@}
|
9443 |
|
|
Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}.
|
9444 |
|
|
|
9445 |
|
|
@item %@{,@code{S}:@code{X}@}
|
9446 |
|
|
Substitutes @code{X}, if processing a file for language @code{S}.
|
9447 |
|
|
|
9448 |
|
|
@item %@{!,@code{S}:@code{X}@}
|
9449 |
|
|
Substitutes @code{X}, if not processing a file for language @code{S}.
|
9450 |
|
|
|
9451 |
|
|
@item %@{@code{S}|@code{P}:@code{X}@}
|
9452 |
|
|
Substitutes @code{X} if either @code{-S} or @code{-P} was given to
|
9453 |
|
|
GCC@. This may be combined with @samp{!}, @samp{.}, @samp{,}, and
|
9454 |
|
|
@code{*} sequences as well, although they have a stronger binding than
|
9455 |
|
|
the @samp{|}. If @code{%*} appears in @code{X}, all of the
|
9456 |
|
|
alternatives must be starred, and only the first matching alternative
|
9457 |
|
|
is substituted.
|
9458 |
|
|
|
9459 |
|
|
For example, a spec string like this:
|
9460 |
|
|
|
9461 |
|
|
@smallexample
|
9462 |
|
|
%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@}
|
9463 |
|
|
@end smallexample
|
9464 |
|
|
|
9465 |
|
|
will output the following command-line options from the following input
|
9466 |
|
|
command-line options:
|
9467 |
|
|
|
9468 |
|
|
@smallexample
|
9469 |
|
|
fred.c -foo -baz
|
9470 |
|
|
jim.d -bar -boggle
|
9471 |
|
|
-d fred.c -foo -baz -boggle
|
9472 |
|
|
-d jim.d -bar -baz -boggle
|
9473 |
|
|
@end smallexample
|
9474 |
|
|
|
9475 |
|
|
@item %@{S:X; T:Y; :D@}
|
9476 |
|
|
|
9477 |
|
|
If @code{S} was given to GCC, substitutes @code{X}; else if @code{T} was
|
9478 |
|
|
given to GCC, substitutes @code{Y}; else substitutes @code{D}. There can
|
9479 |
|
|
be as many clauses as you need. This may be combined with @code{.},
|
9480 |
|
|
@code{,}, @code{!}, @code{|}, and @code{*} as needed.
|
9481 |
|
|
|
9482 |
|
|
|
9483 |
|
|
@end table
|
9484 |
|
|
|
9485 |
|
|
The conditional text @code{X} in a %@{@code{S}:@code{X}@} or similar
|
9486 |
|
|
construct may contain other nested @samp{%} constructs or spaces, or
|
9487 |
|
|
even newlines. They are processed as usual, as described above.
|
9488 |
|
|
Trailing white space in @code{X} is ignored. White space may also
|
9489 |
|
|
appear anywhere on the left side of the colon in these constructs,
|
9490 |
|
|
except between @code{.} or @code{*} and the corresponding word.
|
9491 |
|
|
|
9492 |
|
|
The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are
|
9493 |
|
|
handled specifically in these constructs. If another value of
|
9494 |
|
|
@option{-O} or the negated form of a @option{-f}, @option{-m}, or
|
9495 |
|
|
@option{-W} switch is found later in the command line, the earlier
|
9496 |
|
|
switch value is ignored, except with @{@code{S}*@} where @code{S} is
|
9497 |
|
|
just one letter, which passes all matching options.
|
9498 |
|
|
|
9499 |
|
|
The character @samp{|} at the beginning of the predicate text is used to
|
9500 |
|
|
indicate that a command should be piped to the following command, but
|
9501 |
|
|
only if @option{-pipe} is specified.
|
9502 |
|
|
|
9503 |
|
|
It is built into GCC which switches take arguments and which do not.
|
9504 |
|
|
(You might think it would be useful to generalize this to allow each
|
9505 |
|
|
compiler's spec to say which switches take arguments. But this cannot
|
9506 |
|
|
be done in a consistent fashion. GCC cannot even decide which input
|
9507 |
|
|
files have been specified without knowing which switches take arguments,
|
9508 |
|
|
and it must know which input files to compile in order to tell which
|
9509 |
|
|
compilers to run).
|
9510 |
|
|
|
9511 |
|
|
GCC also knows implicitly that arguments starting in @option{-l} are to be
|
9512 |
|
|
treated as compiler output files, and passed to the linker in their
|
9513 |
|
|
proper position among the other output files.
|
9514 |
|
|
|
9515 |
|
|
@c man begin OPTIONS
|
9516 |
|
|
|
9517 |
|
|
@node Target Options
|
9518 |
|
|
@section Specifying Target Machine and Compiler Version
|
9519 |
|
|
@cindex target options
|
9520 |
|
|
@cindex cross compiling
|
9521 |
|
|
@cindex specifying machine version
|
9522 |
|
|
@cindex specifying compiler version and target machine
|
9523 |
|
|
@cindex compiler version, specifying
|
9524 |
|
|
@cindex target machine, specifying
|
9525 |
|
|
|
9526 |
|
|
The usual way to run GCC is to run the executable called @file{gcc}, or
|
9527 |
|
|
@file{<machine>-gcc} when cross-compiling, or
|
9528 |
|
|
@file{<machine>-gcc-<version>} to run a version other than the one that
|
9529 |
|
|
was installed last. Sometimes this is inconvenient, so GCC provides
|
9530 |
|
|
options that will switch to another cross-compiler or version.
|
9531 |
|
|
|
9532 |
|
|
@table @gcctabopt
|
9533 |
|
|
@item -b @var{machine}
|
9534 |
|
|
@opindex b
|
9535 |
|
|
The argument @var{machine} specifies the target machine for compilation.
|
9536 |
|
|
|
9537 |
|
|
The value to use for @var{machine} is the same as was specified as the
|
9538 |
|
|
machine type when configuring GCC as a cross-compiler. For
|
9539 |
|
|
example, if a cross-compiler was configured with @samp{configure
|
9540 |
|
|
arm-elf}, meaning to compile for an arm processor with elf binaries,
|
9541 |
|
|
then you would specify @option{-b arm-elf} to run that cross compiler.
|
9542 |
|
|
Because there are other options beginning with @option{-b}, the
|
9543 |
|
|
configuration must contain a hyphen, or @option{-b} alone should be one
|
9544 |
|
|
argument followed by the configuration in the next argument.
|
9545 |
|
|
|
9546 |
|
|
@item -V @var{version}
|
9547 |
|
|
@opindex V
|
9548 |
|
|
The argument @var{version} specifies which version of GCC to run.
|
9549 |
|
|
This is useful when multiple versions are installed. For example,
|
9550 |
|
|
@var{version} might be @samp{4.0}, meaning to run GCC version 4.0.
|
9551 |
|
|
@end table
|
9552 |
|
|
|
9553 |
|
|
The @option{-V} and @option{-b} options work by running the
|
9554 |
|
|
@file{<machine>-gcc-<version>} executable, so there's no real reason to
|
9555 |
|
|
use them if you can just run that directly.
|
9556 |
|
|
|
9557 |
|
|
@node Submodel Options
|
9558 |
|
|
@section Hardware Models and Configurations
|
9559 |
|
|
@cindex submodel options
|
9560 |
|
|
@cindex specifying hardware config
|
9561 |
|
|
@cindex hardware models and configurations, specifying
|
9562 |
|
|
@cindex machine dependent options
|
9563 |
|
|
|
9564 |
|
|
Earlier we discussed the standard option @option{-b} which chooses among
|
9565 |
|
|
different installed compilers for completely different target
|
9566 |
|
|
machines, such as VAX vs.@: 68000 vs.@: 80386.
|
9567 |
|
|
|
9568 |
|
|
In addition, each of these target machine types can have its own
|
9569 |
|
|
special options, starting with @samp{-m}, to choose among various
|
9570 |
|
|
hardware models or configurations---for example, 68010 vs 68020,
|
9571 |
|
|
floating coprocessor or none. A single installed version of the
|
9572 |
|
|
compiler can compile for any model or configuration, according to the
|
9573 |
|
|
options specified.
|
9574 |
|
|
|
9575 |
|
|
Some configurations of the compiler also support additional special
|
9576 |
|
|
options, usually for compatibility with other compilers on the same
|
9577 |
|
|
platform.
|
9578 |
|
|
|
9579 |
|
|
@c This list is ordered alphanumerically by subsection name.
|
9580 |
|
|
@c It should be the same order and spelling as these options are listed
|
9581 |
|
|
@c in Machine Dependent Options
|
9582 |
|
|
|
9583 |
|
|
@menu
|
9584 |
|
|
* ARC Options::
|
9585 |
|
|
* ARM Options::
|
9586 |
|
|
* AVR Options::
|
9587 |
|
|
* Blackfin Options::
|
9588 |
|
|
* CRIS Options::
|
9589 |
|
|
* CRX Options::
|
9590 |
|
|
* Darwin Options::
|
9591 |
|
|
* DEC Alpha Options::
|
9592 |
|
|
* DEC Alpha/VMS Options::
|
9593 |
|
|
* FR30 Options::
|
9594 |
|
|
* FRV Options::
|
9595 |
|
|
* GNU/Linux Options::
|
9596 |
|
|
* H8/300 Options::
|
9597 |
|
|
* HPPA Options::
|
9598 |
|
|
* i386 and x86-64 Options::
|
9599 |
|
|
* i386 and x86-64 Windows Options::
|
9600 |
|
|
* IA-64 Options::
|
9601 |
|
|
* IA-64/VMS Options::
|
9602 |
|
|
* LM32 Options::
|
9603 |
|
|
* M32C Options::
|
9604 |
|
|
* M32R/D Options::
|
9605 |
|
|
* M680x0 Options::
|
9606 |
|
|
* M68hc1x Options::
|
9607 |
|
|
* MCore Options::
|
9608 |
|
|
* MeP Options::
|
9609 |
|
|
* MIPS Options::
|
9610 |
|
|
* MMIX Options::
|
9611 |
|
|
* MN10300 Options::
|
9612 |
|
|
* PDP-11 Options::
|
9613 |
|
|
* picoChip Options::
|
9614 |
|
|
* PowerPC Options::
|
9615 |
|
|
* RS/6000 and PowerPC Options::
|
9616 |
|
|
* RX Options::
|
9617 |
|
|
* S/390 and zSeries Options::
|
9618 |
|
|
* Score Options::
|
9619 |
|
|
* SH Options::
|
9620 |
|
|
* SPARC Options::
|
9621 |
|
|
* SPU Options::
|
9622 |
|
|
* System V Options::
|
9623 |
|
|
* V850 Options::
|
9624 |
|
|
* VAX Options::
|
9625 |
|
|
* VxWorks Options::
|
9626 |
|
|
* x86-64 Options::
|
9627 |
|
|
* Xstormy16 Options::
|
9628 |
|
|
* Xtensa Options::
|
9629 |
|
|
* zSeries Options::
|
9630 |
|
|
@end menu
|
9631 |
|
|
|
9632 |
|
|
@node ARC Options
|
9633 |
|
|
@subsection ARC Options
|
9634 |
|
|
@cindex ARC Options
|
9635 |
|
|
|
9636 |
|
|
These options are defined for ARC implementations:
|
9637 |
|
|
|
9638 |
|
|
@table @gcctabopt
|
9639 |
|
|
@item -EL
|
9640 |
|
|
@opindex EL
|
9641 |
|
|
Compile code for little endian mode. This is the default.
|
9642 |
|
|
|
9643 |
|
|
@item -EB
|
9644 |
|
|
@opindex EB
|
9645 |
|
|
Compile code for big endian mode.
|
9646 |
|
|
|
9647 |
|
|
@item -mmangle-cpu
|
9648 |
|
|
@opindex mmangle-cpu
|
9649 |
|
|
Prepend the name of the cpu to all public symbol names.
|
9650 |
|
|
In multiple-processor systems, there are many ARC variants with different
|
9651 |
|
|
instruction and register set characteristics. This flag prevents code
|
9652 |
|
|
compiled for one cpu to be linked with code compiled for another.
|
9653 |
|
|
No facility exists for handling variants that are ``almost identical''.
|
9654 |
|
|
This is an all or nothing option.
|
9655 |
|
|
|
9656 |
|
|
@item -mcpu=@var{cpu}
|
9657 |
|
|
@opindex mcpu
|
9658 |
|
|
Compile code for ARC variant @var{cpu}.
|
9659 |
|
|
Which variants are supported depend on the configuration.
|
9660 |
|
|
All variants support @option{-mcpu=base}, this is the default.
|
9661 |
|
|
|
9662 |
|
|
@item -mtext=@var{text-section}
|
9663 |
|
|
@itemx -mdata=@var{data-section}
|
9664 |
|
|
@itemx -mrodata=@var{readonly-data-section}
|
9665 |
|
|
@opindex mtext
|
9666 |
|
|
@opindex mdata
|
9667 |
|
|
@opindex mrodata
|
9668 |
|
|
Put functions, data, and readonly data in @var{text-section},
|
9669 |
|
|
@var{data-section}, and @var{readonly-data-section} respectively
|
9670 |
|
|
by default. This can be overridden with the @code{section} attribute.
|
9671 |
|
|
@xref{Variable Attributes}.
|
9672 |
|
|
|
9673 |
|
|
@item -mfix-cortex-m3-ldrd
|
9674 |
|
|
@opindex mfix-cortex-m3-ldrd
|
9675 |
|
|
Some Cortex-M3 cores can cause data corruption when @code{ldrd} instructions
|
9676 |
|
|
with overlapping destination and base registers are used. This option avoids
|
9677 |
|
|
generating these instructions. This option is enabled by default when
|
9678 |
|
|
@option{-mcpu=cortex-m3} is specified.
|
9679 |
|
|
|
9680 |
|
|
@end table
|
9681 |
|
|
|
9682 |
|
|
@node ARM Options
|
9683 |
|
|
@subsection ARM Options
|
9684 |
|
|
@cindex ARM options
|
9685 |
|
|
|
9686 |
|
|
These @samp{-m} options are defined for Advanced RISC Machines (ARM)
|
9687 |
|
|
architectures:
|
9688 |
|
|
|
9689 |
|
|
@table @gcctabopt
|
9690 |
|
|
@item -mabi=@var{name}
|
9691 |
|
|
@opindex mabi
|
9692 |
|
|
Generate code for the specified ABI@. Permissible values are: @samp{apcs-gnu},
|
9693 |
|
|
@samp{atpcs}, @samp{aapcs}, @samp{aapcs-linux} and @samp{iwmmxt}.
|
9694 |
|
|
|
9695 |
|
|
@item -mapcs-frame
|
9696 |
|
|
@opindex mapcs-frame
|
9697 |
|
|
Generate a stack frame that is compliant with the ARM Procedure Call
|
9698 |
|
|
Standard for all functions, even if this is not strictly necessary for
|
9699 |
|
|
correct execution of the code. Specifying @option{-fomit-frame-pointer}
|
9700 |
|
|
with this option will cause the stack frames not to be generated for
|
9701 |
|
|
leaf functions. The default is @option{-mno-apcs-frame}.
|
9702 |
|
|
|
9703 |
|
|
@item -mapcs
|
9704 |
|
|
@opindex mapcs
|
9705 |
|
|
This is a synonym for @option{-mapcs-frame}.
|
9706 |
|
|
|
9707 |
|
|
@ignore
|
9708 |
|
|
@c not currently implemented
|
9709 |
|
|
@item -mapcs-stack-check
|
9710 |
|
|
@opindex mapcs-stack-check
|
9711 |
|
|
Generate code to check the amount of stack space available upon entry to
|
9712 |
|
|
every function (that actually uses some stack space). If there is
|
9713 |
|
|
insufficient space available then either the function
|
9714 |
|
|
@samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be
|
9715 |
|
|
called, depending upon the amount of stack space required. The run time
|
9716 |
|
|
system is required to provide these functions. The default is
|
9717 |
|
|
@option{-mno-apcs-stack-check}, since this produces smaller code.
|
9718 |
|
|
|
9719 |
|
|
@c not currently implemented
|
9720 |
|
|
@item -mapcs-float
|
9721 |
|
|
@opindex mapcs-float
|
9722 |
|
|
Pass floating point arguments using the float point registers. This is
|
9723 |
|
|
one of the variants of the APCS@. This option is recommended if the
|
9724 |
|
|
target hardware has a floating point unit or if a lot of floating point
|
9725 |
|
|
arithmetic is going to be performed by the code. The default is
|
9726 |
|
|
@option{-mno-apcs-float}, since integer only code is slightly increased in
|
9727 |
|
|
size if @option{-mapcs-float} is used.
|
9728 |
|
|
|
9729 |
|
|
@c not currently implemented
|
9730 |
|
|
@item -mapcs-reentrant
|
9731 |
|
|
@opindex mapcs-reentrant
|
9732 |
|
|
Generate reentrant, position independent code. The default is
|
9733 |
|
|
@option{-mno-apcs-reentrant}.
|
9734 |
|
|
@end ignore
|
9735 |
|
|
|
9736 |
|
|
@item -mthumb-interwork
|
9737 |
|
|
@opindex mthumb-interwork
|
9738 |
|
|
Generate code which supports calling between the ARM and Thumb
|
9739 |
|
|
instruction sets. Without this option the two instruction sets cannot
|
9740 |
|
|
be reliably used inside one program. The default is
|
9741 |
|
|
@option{-mno-thumb-interwork}, since slightly larger code is generated
|
9742 |
|
|
when @option{-mthumb-interwork} is specified.
|
9743 |
|
|
|
9744 |
|
|
@item -mno-sched-prolog
|
9745 |
|
|
@opindex mno-sched-prolog
|
9746 |
|
|
Prevent the reordering of instructions in the function prolog, or the
|
9747 |
|
|
merging of those instruction with the instructions in the function's
|
9748 |
|
|
body. This means that all functions will start with a recognizable set
|
9749 |
|
|
of instructions (or in fact one of a choice from a small set of
|
9750 |
|
|
different function prologues), and this information can be used to
|
9751 |
|
|
locate the start if functions inside an executable piece of code. The
|
9752 |
|
|
default is @option{-msched-prolog}.
|
9753 |
|
|
|
9754 |
|
|
@item -mfloat-abi=@var{name}
|
9755 |
|
|
@opindex mfloat-abi
|
9756 |
|
|
Specifies which floating-point ABI to use. Permissible values
|
9757 |
|
|
are: @samp{soft}, @samp{softfp} and @samp{hard}.
|
9758 |
|
|
|
9759 |
|
|
Specifying @samp{soft} causes GCC to generate output containing
|
9760 |
|
|
library calls for floating-point operations.
|
9761 |
|
|
@samp{softfp} allows the generation of code using hardware floating-point
|
9762 |
|
|
instructions, but still uses the soft-float calling conventions.
|
9763 |
|
|
@samp{hard} allows generation of floating-point instructions
|
9764 |
|
|
and uses FPU-specific calling conventions.
|
9765 |
|
|
|
9766 |
|
|
The default depends on the specific target configuration. Note that
|
9767 |
|
|
the hard-float and soft-float ABIs are not link-compatible; you must
|
9768 |
|
|
compile your entire program with the same ABI, and link with a
|
9769 |
|
|
compatible set of libraries.
|
9770 |
|
|
|
9771 |
|
|
@item -mhard-float
|
9772 |
|
|
@opindex mhard-float
|
9773 |
|
|
Equivalent to @option{-mfloat-abi=hard}.
|
9774 |
|
|
|
9775 |
|
|
@item -msoft-float
|
9776 |
|
|
@opindex msoft-float
|
9777 |
|
|
Equivalent to @option{-mfloat-abi=soft}.
|
9778 |
|
|
|
9779 |
|
|
@item -mlittle-endian
|
9780 |
|
|
@opindex mlittle-endian
|
9781 |
|
|
Generate code for a processor running in little-endian mode. This is
|
9782 |
|
|
the default for all standard configurations.
|
9783 |
|
|
|
9784 |
|
|
@item -mbig-endian
|
9785 |
|
|
@opindex mbig-endian
|
9786 |
|
|
Generate code for a processor running in big-endian mode; the default is
|
9787 |
|
|
to compile code for a little-endian processor.
|
9788 |
|
|
|
9789 |
|
|
@item -mwords-little-endian
|
9790 |
|
|
@opindex mwords-little-endian
|
9791 |
|
|
This option only applies when generating code for big-endian processors.
|
9792 |
|
|
Generate code for a little-endian word order but a big-endian byte
|
9793 |
|
|
order. That is, a byte order of the form @samp{32107654}. Note: this
|
9794 |
|
|
option should only be used if you require compatibility with code for
|
9795 |
|
|
big-endian ARM processors generated by versions of the compiler prior to
|
9796 |
|
|
2.8.
|
9797 |
|
|
|
9798 |
|
|
@item -mcpu=@var{name}
|
9799 |
|
|
@opindex mcpu
|
9800 |
|
|
This specifies the name of the target ARM processor. GCC uses this name
|
9801 |
|
|
to determine what kind of instructions it can emit when generating
|
9802 |
|
|
assembly code. Permissible names are: @samp{arm2}, @samp{arm250},
|
9803 |
|
|
@samp{arm3}, @samp{arm6}, @samp{arm60}, @samp{arm600}, @samp{arm610},
|
9804 |
|
|
@samp{arm620}, @samp{arm7}, @samp{arm7m}, @samp{arm7d}, @samp{arm7dm},
|
9805 |
|
|
@samp{arm7di}, @samp{arm7dmi}, @samp{arm70}, @samp{arm700},
|
9806 |
|
|
@samp{arm700i}, @samp{arm710}, @samp{arm710c}, @samp{arm7100},
|
9807 |
|
|
@samp{arm720},
|
9808 |
|
|
@samp{arm7500}, @samp{arm7500fe}, @samp{arm7tdmi}, @samp{arm7tdmi-s},
|
9809 |
|
|
@samp{arm710t}, @samp{arm720t}, @samp{arm740t},
|
9810 |
|
|
@samp{strongarm}, @samp{strongarm110}, @samp{strongarm1100},
|
9811 |
|
|
@samp{strongarm1110},
|
9812 |
|
|
@samp{arm8}, @samp{arm810}, @samp{arm9}, @samp{arm9e}, @samp{arm920},
|
9813 |
|
|
@samp{arm920t}, @samp{arm922t}, @samp{arm946e-s}, @samp{arm966e-s},
|
9814 |
|
|
@samp{arm968e-s}, @samp{arm926ej-s}, @samp{arm940t}, @samp{arm9tdmi},
|
9815 |
|
|
@samp{arm10tdmi}, @samp{arm1020t}, @samp{arm1026ej-s},
|
9816 |
|
|
@samp{arm10e}, @samp{arm1020e}, @samp{arm1022e},
|
9817 |
|
|
@samp{arm1136j-s}, @samp{arm1136jf-s}, @samp{mpcore}, @samp{mpcorenovfp},
|
9818 |
|
|
@samp{arm1156t2-s}, @samp{arm1156t2f-s}, @samp{arm1176jz-s}, @samp{arm1176jzf-s},
|
9819 |
|
|
@samp{cortex-a5}, @samp{cortex-a8}, @samp{cortex-a9},
|
9820 |
|
|
@samp{cortex-r4}, @samp{cortex-r4f}, @samp{cortex-m3},
|
9821 |
|
|
@samp{cortex-m1},
|
9822 |
|
|
@samp{cortex-m0},
|
9823 |
|
|
@samp{xscale}, @samp{iwmmxt}, @samp{iwmmxt2}, @samp{ep9312}.
|
9824 |
|
|
|
9825 |
|
|
@item -mtune=@var{name}
|
9826 |
|
|
@opindex mtune
|
9827 |
|
|
This option is very similar to the @option{-mcpu=} option, except that
|
9828 |
|
|
instead of specifying the actual target processor type, and hence
|
9829 |
|
|
restricting which instructions can be used, it specifies that GCC should
|
9830 |
|
|
tune the performance of the code as if the target were of the type
|
9831 |
|
|
specified in this option, but still choosing the instructions that it
|
9832 |
|
|
will generate based on the cpu specified by a @option{-mcpu=} option.
|
9833 |
|
|
For some ARM implementations better performance can be obtained by using
|
9834 |
|
|
this option.
|
9835 |
|
|
|
9836 |
|
|
@item -march=@var{name}
|
9837 |
|
|
@opindex march
|
9838 |
|
|
This specifies the name of the target ARM architecture. GCC uses this
|
9839 |
|
|
name to determine what kind of instructions it can emit when generating
|
9840 |
|
|
assembly code. This option can be used in conjunction with or instead
|
9841 |
|
|
of the @option{-mcpu=} option. Permissible names are: @samp{armv2},
|
9842 |
|
|
@samp{armv2a}, @samp{armv3}, @samp{armv3m}, @samp{armv4}, @samp{armv4t},
|
9843 |
|
|
@samp{armv5}, @samp{armv5t}, @samp{armv5e}, @samp{armv5te},
|
9844 |
|
|
@samp{armv6}, @samp{armv6j},
|
9845 |
|
|
@samp{armv6t2}, @samp{armv6z}, @samp{armv6zk}, @samp{armv6-m},
|
9846 |
|
|
@samp{armv7}, @samp{armv7-a}, @samp{armv7-r}, @samp{armv7-m},
|
9847 |
|
|
@samp{iwmmxt}, @samp{iwmmxt2}, @samp{ep9312}.
|
9848 |
|
|
|
9849 |
|
|
@item -mfpu=@var{name}
|
9850 |
|
|
@itemx -mfpe=@var{number}
|
9851 |
|
|
@itemx -mfp=@var{number}
|
9852 |
|
|
@opindex mfpu
|
9853 |
|
|
@opindex mfpe
|
9854 |
|
|
@opindex mfp
|
9855 |
|
|
This specifies what floating point hardware (or hardware emulation) is
|
9856 |
|
|
available on the target. Permissible names are: @samp{fpa}, @samp{fpe2},
|
9857 |
|
|
@samp{fpe3}, @samp{maverick}, @samp{vfp}, @samp{vfpv3}, @samp{vfpv3-fp16},
|
9858 |
|
|
@samp{vfpv3-d16}, @samp{vfpv3-d16-fp16}, @samp{vfpv3xd}, @samp{vfpv3xd-fp16},
|
9859 |
|
|
@samp{neon}, @samp{neon-fp16}, @samp{vfpv4}, @samp{vfpv4-d16},
|
9860 |
|
|
@samp{fpv4-sp-d16} and @samp{neon-vfpv4}.
|
9861 |
|
|
@option{-mfp} and @option{-mfpe} are synonyms for
|
9862 |
|
|
@option{-mfpu}=@samp{fpe}@var{number}, for compatibility with older versions
|
9863 |
|
|
of GCC@.
|
9864 |
|
|
|
9865 |
|
|
If @option{-msoft-float} is specified this specifies the format of
|
9866 |
|
|
floating point values.
|
9867 |
|
|
|
9868 |
|
|
@item -mfp16-format=@var{name}
|
9869 |
|
|
@opindex mfp16-format
|
9870 |
|
|
Specify the format of the @code{__fp16} half-precision floating-point type.
|
9871 |
|
|
Permissible names are @samp{none}, @samp{ieee}, and @samp{alternative};
|
9872 |
|
|
the default is @samp{none}, in which case the @code{__fp16} type is not
|
9873 |
|
|
defined. @xref{Half-Precision}, for more information.
|
9874 |
|
|
|
9875 |
|
|
@item -mstructure-size-boundary=@var{n}
|
9876 |
|
|
@opindex mstructure-size-boundary
|
9877 |
|
|
The size of all structures and unions will be rounded up to a multiple
|
9878 |
|
|
of the number of bits set by this option. Permissible values are 8, 32
|
9879 |
|
|
and 64. The default value varies for different toolchains. For the COFF
|
9880 |
|
|
targeted toolchain the default value is 8. A value of 64 is only allowed
|
9881 |
|
|
if the underlying ABI supports it.
|
9882 |
|
|
|
9883 |
|
|
Specifying the larger number can produce faster, more efficient code, but
|
9884 |
|
|
can also increase the size of the program. Different values are potentially
|
9885 |
|
|
incompatible. Code compiled with one value cannot necessarily expect to
|
9886 |
|
|
work with code or libraries compiled with another value, if they exchange
|
9887 |
|
|
information using structures or unions.
|
9888 |
|
|
|
9889 |
|
|
@item -mabort-on-noreturn
|
9890 |
|
|
@opindex mabort-on-noreturn
|
9891 |
|
|
Generate a call to the function @code{abort} at the end of a
|
9892 |
|
|
@code{noreturn} function. It will be executed if the function tries to
|
9893 |
|
|
return.
|
9894 |
|
|
|
9895 |
|
|
@item -mlong-calls
|
9896 |
|
|
@itemx -mno-long-calls
|
9897 |
|
|
@opindex mlong-calls
|
9898 |
|
|
@opindex mno-long-calls
|
9899 |
|
|
Tells the compiler to perform function calls by first loading the
|
9900 |
|
|
address of the function into a register and then performing a subroutine
|
9901 |
|
|
call on this register. This switch is needed if the target function
|
9902 |
|
|
will lie outside of the 64 megabyte addressing range of the offset based
|
9903 |
|
|
version of subroutine call instruction.
|
9904 |
|
|
|
9905 |
|
|
Even if this switch is enabled, not all function calls will be turned
|
9906 |
|
|
into long calls. The heuristic is that static functions, functions
|
9907 |
|
|
which have the @samp{short-call} attribute, functions that are inside
|
9908 |
|
|
the scope of a @samp{#pragma no_long_calls} directive and functions whose
|
9909 |
|
|
definitions have already been compiled within the current compilation
|
9910 |
|
|
unit, will not be turned into long calls. The exception to this rule is
|
9911 |
|
|
that weak function definitions, functions with the @samp{long-call}
|
9912 |
|
|
attribute or the @samp{section} attribute, and functions that are within
|
9913 |
|
|
the scope of a @samp{#pragma long_calls} directive, will always be
|
9914 |
|
|
turned into long calls.
|
9915 |
|
|
|
9916 |
|
|
This feature is not enabled by default. Specifying
|
9917 |
|
|
@option{-mno-long-calls} will restore the default behavior, as will
|
9918 |
|
|
placing the function calls within the scope of a @samp{#pragma
|
9919 |
|
|
long_calls_off} directive. Note these switches have no effect on how
|
9920 |
|
|
the compiler generates code to handle function calls via function
|
9921 |
|
|
pointers.
|
9922 |
|
|
|
9923 |
|
|
@item -msingle-pic-base
|
9924 |
|
|
@opindex msingle-pic-base
|
9925 |
|
|
Treat the register used for PIC addressing as read-only, rather than
|
9926 |
|
|
loading it in the prologue for each function. The run-time system is
|
9927 |
|
|
responsible for initializing this register with an appropriate value
|
9928 |
|
|
before execution begins.
|
9929 |
|
|
|
9930 |
|
|
@item -mpic-register=@var{reg}
|
9931 |
|
|
@opindex mpic-register
|
9932 |
|
|
Specify the register to be used for PIC addressing. The default is R10
|
9933 |
|
|
unless stack-checking is enabled, when R9 is used.
|
9934 |
|
|
|
9935 |
|
|
@item -mcirrus-fix-invalid-insns
|
9936 |
|
|
@opindex mcirrus-fix-invalid-insns
|
9937 |
|
|
@opindex mno-cirrus-fix-invalid-insns
|
9938 |
|
|
Insert NOPs into the instruction stream to in order to work around
|
9939 |
|
|
problems with invalid Maverick instruction combinations. This option
|
9940 |
|
|
is only valid if the @option{-mcpu=ep9312} option has been used to
|
9941 |
|
|
enable generation of instructions for the Cirrus Maverick floating
|
9942 |
|
|
point co-processor. This option is not enabled by default, since the
|
9943 |
|
|
problem is only present in older Maverick implementations. The default
|
9944 |
|
|
can be re-enabled by use of the @option{-mno-cirrus-fix-invalid-insns}
|
9945 |
|
|
switch.
|
9946 |
|
|
|
9947 |
|
|
@item -mpoke-function-name
|
9948 |
|
|
@opindex mpoke-function-name
|
9949 |
|
|
Write the name of each function into the text section, directly
|
9950 |
|
|
preceding the function prologue. The generated code is similar to this:
|
9951 |
|
|
|
9952 |
|
|
@smallexample
|
9953 |
|
|
t0
|
9954 |
|
|
.ascii "arm_poke_function_name", 0
|
9955 |
|
|
.align
|
9956 |
|
|
t1
|
9957 |
|
|
.word 0xff000000 + (t1 - t0)
|
9958 |
|
|
arm_poke_function_name
|
9959 |
|
|
mov ip, sp
|
9960 |
|
|
stmfd sp!, @{fp, ip, lr, pc@}
|
9961 |
|
|
sub fp, ip, #4
|
9962 |
|
|
@end smallexample
|
9963 |
|
|
|
9964 |
|
|
When performing a stack backtrace, code can inspect the value of
|
9965 |
|
|
@code{pc} stored at @code{fp + 0}. If the trace function then looks at
|
9966 |
|
|
location @code{pc - 12} and the top 8 bits are set, then we know that
|
9967 |
|
|
there is a function name embedded immediately preceding this location
|
9968 |
|
|
and has length @code{((pc[-3]) & 0xff000000)}.
|
9969 |
|
|
|
9970 |
|
|
@item -mthumb
|
9971 |
|
|
@opindex mthumb
|
9972 |
|
|
Generate code for the Thumb instruction set. The default is to
|
9973 |
|
|
use the 32-bit ARM instruction set.
|
9974 |
|
|
This option automatically enables either 16-bit Thumb-1 or
|
9975 |
|
|
mixed 16/32-bit Thumb-2 instructions based on the @option{-mcpu=@var{name}}
|
9976 |
|
|
and @option{-march=@var{name}} options. This option is not passed to the
|
9977 |
|
|
assembler. If you want to force assembler files to be interpreted as Thumb code,
|
9978 |
|
|
either add a @samp{.thumb} directive to the source or pass the @option{-mthumb}
|
9979 |
|
|
option directly to the assembler by prefixing it with @option{-Wa}.
|
9980 |
|
|
|
9981 |
|
|
@item -mtpcs-frame
|
9982 |
|
|
@opindex mtpcs-frame
|
9983 |
|
|
Generate a stack frame that is compliant with the Thumb Procedure Call
|
9984 |
|
|
Standard for all non-leaf functions. (A leaf function is one that does
|
9985 |
|
|
not call any other functions.) The default is @option{-mno-tpcs-frame}.
|
9986 |
|
|
|
9987 |
|
|
@item -mtpcs-leaf-frame
|
9988 |
|
|
@opindex mtpcs-leaf-frame
|
9989 |
|
|
Generate a stack frame that is compliant with the Thumb Procedure Call
|
9990 |
|
|
Standard for all leaf functions. (A leaf function is one that does
|
9991 |
|
|
not call any other functions.) The default is @option{-mno-apcs-leaf-frame}.
|
9992 |
|
|
|
9993 |
|
|
@item -mcallee-super-interworking
|
9994 |
|
|
@opindex mcallee-super-interworking
|
9995 |
|
|
Gives all externally visible functions in the file being compiled an ARM
|
9996 |
|
|
instruction set header which switches to Thumb mode before executing the
|
9997 |
|
|
rest of the function. This allows these functions to be called from
|
9998 |
|
|
non-interworking code. This option is not valid in AAPCS configurations
|
9999 |
|
|
because interworking is enabled by default.
|
10000 |
|
|
|
10001 |
|
|
@item -mcaller-super-interworking
|
10002 |
|
|
@opindex mcaller-super-interworking
|
10003 |
|
|
Allows calls via function pointers (including virtual functions) to
|
10004 |
|
|
execute correctly regardless of whether the target code has been
|
10005 |
|
|
compiled for interworking or not. There is a small overhead in the cost
|
10006 |
|
|
of executing a function pointer if this option is enabled. This option
|
10007 |
|
|
is not valid in AAPCS configurations because interworking is enabled
|
10008 |
|
|
by default.
|
10009 |
|
|
|
10010 |
|
|
@item -mtp=@var{name}
|
10011 |
|
|
@opindex mtp
|
10012 |
|
|
Specify the access model for the thread local storage pointer. The valid
|
10013 |
|
|
models are @option{soft}, which generates calls to @code{__aeabi_read_tp},
|
10014 |
|
|
@option{cp15}, which fetches the thread pointer from @code{cp15} directly
|
10015 |
|
|
(supported in the arm6k architecture), and @option{auto}, which uses the
|
10016 |
|
|
best available method for the selected processor. The default setting is
|
10017 |
|
|
@option{auto}.
|
10018 |
|
|
|
10019 |
|
|
@item -mword-relocations
|
10020 |
|
|
@opindex mword-relocations
|
10021 |
|
|
Only generate absolute relocations on word sized values (i.e. R_ARM_ABS32).
|
10022 |
|
|
This is enabled by default on targets (uClinux, SymbianOS) where the runtime
|
10023 |
|
|
loader imposes this restriction, and when @option{-fpic} or @option{-fPIC}
|
10024 |
|
|
is specified.
|
10025 |
|
|
|
10026 |
|
|
@end table
|
10027 |
|
|
|
10028 |
|
|
@node AVR Options
|
10029 |
|
|
@subsection AVR Options
|
10030 |
|
|
@cindex AVR Options
|
10031 |
|
|
|
10032 |
|
|
These options are defined for AVR implementations:
|
10033 |
|
|
|
10034 |
|
|
@table @gcctabopt
|
10035 |
|
|
@item -mmcu=@var{mcu}
|
10036 |
|
|
@opindex mmcu
|
10037 |
|
|
Specify ATMEL AVR instruction set or MCU type.
|
10038 |
|
|
|
10039 |
|
|
Instruction set avr1 is for the minimal AVR core, not supported by the C
|
10040 |
|
|
compiler, only for assembler programs (MCU types: at90s1200, attiny10,
|
10041 |
|
|
attiny11, attiny12, attiny15, attiny28).
|
10042 |
|
|
|
10043 |
|
|
Instruction set avr2 (default) is for the classic AVR core with up to
|
10044 |
|
|
8K program memory space (MCU types: at90s2313, at90s2323, attiny22,
|
10045 |
|
|
at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515,
|
10046 |
|
|
at90c8534, at90s8535).
|
10047 |
|
|
|
10048 |
|
|
Instruction set avr3 is for the classic AVR core with up to 128K program
|
10049 |
|
|
memory space (MCU types: atmega103, atmega603, at43usb320, at76c711).
|
10050 |
|
|
|
10051 |
|
|
Instruction set avr4 is for the enhanced AVR core with up to 8K program
|
10052 |
|
|
memory space (MCU types: atmega8, atmega83, atmega85).
|
10053 |
|
|
|
10054 |
|
|
Instruction set avr5 is for the enhanced AVR core with up to 128K program
|
10055 |
|
|
memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323,
|
10056 |
|
|
atmega64, atmega128, at43usb355, at94k).
|
10057 |
|
|
|
10058 |
|
|
@item -mno-interrupts
|
10059 |
|
|
@opindex mno-interrupts
|
10060 |
|
|
Generated code is not compatible with hardware interrupts.
|
10061 |
|
|
Code size will be smaller.
|
10062 |
|
|
|
10063 |
|
|
@item -mcall-prologues
|
10064 |
|
|
@opindex mcall-prologues
|
10065 |
|
|
Functions prologues/epilogues expanded as call to appropriate
|
10066 |
|
|
subroutines. Code size will be smaller.
|
10067 |
|
|
|
10068 |
|
|
@item -mtiny-stack
|
10069 |
|
|
@opindex mtiny-stack
|
10070 |
|
|
Change only the low 8 bits of the stack pointer.
|
10071 |
|
|
|
10072 |
|
|
@item -mint8
|
10073 |
|
|
@opindex mint8
|
10074 |
|
|
Assume int to be 8 bit integer. This affects the sizes of all types: A
|
10075 |
|
|
char will be 1 byte, an int will be 1 byte, a long will be 2 bytes
|
10076 |
|
|
and long long will be 4 bytes. Please note that this option does not
|
10077 |
|
|
comply to the C standards, but it will provide you with smaller code
|
10078 |
|
|
size.
|
10079 |
|
|
@end table
|
10080 |
|
|
|
10081 |
|
|
@node Blackfin Options
|
10082 |
|
|
@subsection Blackfin Options
|
10083 |
|
|
@cindex Blackfin Options
|
10084 |
|
|
|
10085 |
|
|
@table @gcctabopt
|
10086 |
|
|
@item -mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]}
|
10087 |
|
|
@opindex mcpu=
|
10088 |
|
|
Specifies the name of the target Blackfin processor. Currently, @var{cpu}
|
10089 |
|
|
can be one of @samp{bf512}, @samp{bf514}, @samp{bf516}, @samp{bf518},
|
10090 |
|
|
@samp{bf522}, @samp{bf523}, @samp{bf524}, @samp{bf525}, @samp{bf526},
|
10091 |
|
|
@samp{bf527}, @samp{bf531}, @samp{bf532}, @samp{bf533},
|
10092 |
|
|
@samp{bf534}, @samp{bf536}, @samp{bf537}, @samp{bf538}, @samp{bf539},
|
10093 |
|
|
@samp{bf542}, @samp{bf544}, @samp{bf547}, @samp{bf548}, @samp{bf549},
|
10094 |
|
|
@samp{bf542m}, @samp{bf544m}, @samp{bf547m}, @samp{bf548m}, @samp{bf549m},
|
10095 |
|
|
@samp{bf561}.
|
10096 |
|
|
The optional @var{sirevision} specifies the silicon revision of the target
|
10097 |
|
|
Blackfin processor. Any workarounds available for the targeted silicon revision
|
10098 |
|
|
will be enabled. If @var{sirevision} is @samp{none}, no workarounds are enabled.
|
10099 |
|
|
If @var{sirevision} is @samp{any}, all workarounds for the targeted processor
|
10100 |
|
|
will be enabled. The @code{__SILICON_REVISION__} macro is defined to two
|
10101 |
|
|
hexadecimal digits representing the major and minor numbers in the silicon
|
10102 |
|
|
revision. If @var{sirevision} is @samp{none}, the @code{__SILICON_REVISION__}
|
10103 |
|
|
is not defined. If @var{sirevision} is @samp{any}, the
|
10104 |
|
|
@code{__SILICON_REVISION__} is defined to be @code{0xffff}.
|
10105 |
|
|
If this optional @var{sirevision} is not used, GCC assumes the latest known
|
10106 |
|
|
silicon revision of the targeted Blackfin processor.
|
10107 |
|
|
|
10108 |
|
|
Support for @samp{bf561} is incomplete. For @samp{bf561},
|
10109 |
|
|
Only the processor macro is defined.
|
10110 |
|
|
Without this option, @samp{bf532} is used as the processor by default.
|
10111 |
|
|
The corresponding predefined processor macros for @var{cpu} is to
|
10112 |
|
|
be defined. And for @samp{bfin-elf} toolchain, this causes the hardware BSP
|
10113 |
|
|
provided by libgloss to be linked in if @option{-msim} is not given.
|
10114 |
|
|
|
10115 |
|
|
@item -msim
|
10116 |
|
|
@opindex msim
|
10117 |
|
|
Specifies that the program will be run on the simulator. This causes
|
10118 |
|
|
the simulator BSP provided by libgloss to be linked in. This option
|
10119 |
|
|
has effect only for @samp{bfin-elf} toolchain.
|
10120 |
|
|
Certain other options, such as @option{-mid-shared-library} and
|
10121 |
|
|
@option{-mfdpic}, imply @option{-msim}.
|
10122 |
|
|
|
10123 |
|
|
@item -momit-leaf-frame-pointer
|
10124 |
|
|
@opindex momit-leaf-frame-pointer
|
10125 |
|
|
Don't keep the frame pointer in a register for leaf functions. This
|
10126 |
|
|
avoids the instructions to save, set up and restore frame pointers and
|
10127 |
|
|
makes an extra register available in leaf functions. The option
|
10128 |
|
|
@option{-fomit-frame-pointer} removes the frame pointer for all functions
|
10129 |
|
|
which might make debugging harder.
|
10130 |
|
|
|
10131 |
|
|
@item -mspecld-anomaly
|
10132 |
|
|
@opindex mspecld-anomaly
|
10133 |
|
|
When enabled, the compiler will ensure that the generated code does not
|
10134 |
|
|
contain speculative loads after jump instructions. If this option is used,
|
10135 |
|
|
@code{__WORKAROUND_SPECULATIVE_LOADS} is defined.
|
10136 |
|
|
|
10137 |
|
|
@item -mno-specld-anomaly
|
10138 |
|
|
@opindex mno-specld-anomaly
|
10139 |
|
|
Don't generate extra code to prevent speculative loads from occurring.
|
10140 |
|
|
|
10141 |
|
|
@item -mcsync-anomaly
|
10142 |
|
|
@opindex mcsync-anomaly
|
10143 |
|
|
When enabled, the compiler will ensure that the generated code does not
|
10144 |
|
|
contain CSYNC or SSYNC instructions too soon after conditional branches.
|
10145 |
|
|
If this option is used, @code{__WORKAROUND_SPECULATIVE_SYNCS} is defined.
|
10146 |
|
|
|
10147 |
|
|
@item -mno-csync-anomaly
|
10148 |
|
|
@opindex mno-csync-anomaly
|
10149 |
|
|
Don't generate extra code to prevent CSYNC or SSYNC instructions from
|
10150 |
|
|
occurring too soon after a conditional branch.
|
10151 |
|
|
|
10152 |
|
|
@item -mlow-64k
|
10153 |
|
|
@opindex mlow-64k
|
10154 |
|
|
When enabled, the compiler is free to take advantage of the knowledge that
|
10155 |
|
|
the entire program fits into the low 64k of memory.
|
10156 |
|
|
|
10157 |
|
|
@item -mno-low-64k
|
10158 |
|
|
@opindex mno-low-64k
|
10159 |
|
|
Assume that the program is arbitrarily large. This is the default.
|
10160 |
|
|
|
10161 |
|
|
@item -mstack-check-l1
|
10162 |
|
|
@opindex mstack-check-l1
|
10163 |
|
|
Do stack checking using information placed into L1 scratchpad memory by the
|
10164 |
|
|
uClinux kernel.
|
10165 |
|
|
|
10166 |
|
|
@item -mid-shared-library
|
10167 |
|
|
@opindex mid-shared-library
|
10168 |
|
|
Generate code that supports shared libraries via the library ID method.
|
10169 |
|
|
This allows for execute in place and shared libraries in an environment
|
10170 |
|
|
without virtual memory management. This option implies @option{-fPIC}.
|
10171 |
|
|
With a @samp{bfin-elf} target, this option implies @option{-msim}.
|
10172 |
|
|
|
10173 |
|
|
@item -mno-id-shared-library
|
10174 |
|
|
@opindex mno-id-shared-library
|
10175 |
|
|
Generate code that doesn't assume ID based shared libraries are being used.
|
10176 |
|
|
This is the default.
|
10177 |
|
|
|
10178 |
|
|
@item -mleaf-id-shared-library
|
10179 |
|
|
@opindex mleaf-id-shared-library
|
10180 |
|
|
Generate code that supports shared libraries via the library ID method,
|
10181 |
|
|
but assumes that this library or executable won't link against any other
|
10182 |
|
|
ID shared libraries. That allows the compiler to use faster code for jumps
|
10183 |
|
|
and calls.
|
10184 |
|
|
|
10185 |
|
|
@item -mno-leaf-id-shared-library
|
10186 |
|
|
@opindex mno-leaf-id-shared-library
|
10187 |
|
|
Do not assume that the code being compiled won't link against any ID shared
|
10188 |
|
|
libraries. Slower code will be generated for jump and call insns.
|
10189 |
|
|
|
10190 |
|
|
@item -mshared-library-id=n
|
10191 |
|
|
@opindex mshared-library-id
|
10192 |
|
|
Specified the identification number of the ID based shared library being
|
10193 |
|
|
compiled. Specifying a value of 0 will generate more compact code, specifying
|
10194 |
|
|
other values will force the allocation of that number to the current
|
10195 |
|
|
library but is no more space or time efficient than omitting this option.
|
10196 |
|
|
|
10197 |
|
|
@item -msep-data
|
10198 |
|
|
@opindex msep-data
|
10199 |
|
|
Generate code that allows the data segment to be located in a different
|
10200 |
|
|
area of memory from the text segment. This allows for execute in place in
|
10201 |
|
|
an environment without virtual memory management by eliminating relocations
|
10202 |
|
|
against the text section.
|
10203 |
|
|
|
10204 |
|
|
@item -mno-sep-data
|
10205 |
|
|
@opindex mno-sep-data
|
10206 |
|
|
Generate code that assumes that the data segment follows the text segment.
|
10207 |
|
|
This is the default.
|
10208 |
|
|
|
10209 |
|
|
@item -mlong-calls
|
10210 |
|
|
@itemx -mno-long-calls
|
10211 |
|
|
@opindex mlong-calls
|
10212 |
|
|
@opindex mno-long-calls
|
10213 |
|
|
Tells the compiler to perform function calls by first loading the
|
10214 |
|
|
address of the function into a register and then performing a subroutine
|
10215 |
|
|
call on this register. This switch is needed if the target function
|
10216 |
|
|
will lie outside of the 24 bit addressing range of the offset based
|
10217 |
|
|
version of subroutine call instruction.
|
10218 |
|
|
|
10219 |
|
|
This feature is not enabled by default. Specifying
|
10220 |
|
|
@option{-mno-long-calls} will restore the default behavior. Note these
|
10221 |
|
|
switches have no effect on how the compiler generates code to handle
|
10222 |
|
|
function calls via function pointers.
|
10223 |
|
|
|
10224 |
|
|
@item -mfast-fp
|
10225 |
|
|
@opindex mfast-fp
|
10226 |
|
|
Link with the fast floating-point library. This library relaxes some of
|
10227 |
|
|
the IEEE floating-point standard's rules for checking inputs against
|
10228 |
|
|
Not-a-Number (NAN), in the interest of performance.
|
10229 |
|
|
|
10230 |
|
|
@item -minline-plt
|
10231 |
|
|
@opindex minline-plt
|
10232 |
|
|
Enable inlining of PLT entries in function calls to functions that are
|
10233 |
|
|
not known to bind locally. It has no effect without @option{-mfdpic}.
|
10234 |
|
|
|
10235 |
|
|
@item -mmulticore
|
10236 |
|
|
@opindex mmulticore
|
10237 |
|
|
Build standalone application for multicore Blackfin processor. Proper
|
10238 |
|
|
start files and link scripts will be used to support multicore.
|
10239 |
|
|
This option defines @code{__BFIN_MULTICORE}. It can only be used with
|
10240 |
|
|
@option{-mcpu=bf561@r{[}-@var{sirevision}@r{]}}. It can be used with
|
10241 |
|
|
@option{-mcorea} or @option{-mcoreb}. If it's used without
|
10242 |
|
|
@option{-mcorea} or @option{-mcoreb}, single application/dual core
|
10243 |
|
|
programming model is used. In this model, the main function of Core B
|
10244 |
|
|
should be named as coreb_main. If it's used with @option{-mcorea} or
|
10245 |
|
|
@option{-mcoreb}, one application per core programming model is used.
|
10246 |
|
|
If this option is not used, single core application programming
|
10247 |
|
|
model is used.
|
10248 |
|
|
|
10249 |
|
|
@item -mcorea
|
10250 |
|
|
@opindex mcorea
|
10251 |
|
|
Build standalone application for Core A of BF561 when using
|
10252 |
|
|
one application per core programming model. Proper start files
|
10253 |
|
|
and link scripts will be used to support Core A. This option
|
10254 |
|
|
defines @code{__BFIN_COREA}. It must be used with @option{-mmulticore}.
|
10255 |
|
|
|
10256 |
|
|
@item -mcoreb
|
10257 |
|
|
@opindex mcoreb
|
10258 |
|
|
Build standalone application for Core B of BF561 when using
|
10259 |
|
|
one application per core programming model. Proper start files
|
10260 |
|
|
and link scripts will be used to support Core B. This option
|
10261 |
|
|
defines @code{__BFIN_COREB}. When this option is used, coreb_main
|
10262 |
|
|
should be used instead of main. It must be used with
|
10263 |
|
|
@option{-mmulticore}.
|
10264 |
|
|
|
10265 |
|
|
@item -msdram
|
10266 |
|
|
@opindex msdram
|
10267 |
|
|
Build standalone application for SDRAM. Proper start files and
|
10268 |
|
|
link scripts will be used to put the application into SDRAM.
|
10269 |
|
|
Loader should initialize SDRAM before loading the application
|
10270 |
|
|
into SDRAM. This option defines @code{__BFIN_SDRAM}.
|
10271 |
|
|
|
10272 |
|
|
@item -micplb
|
10273 |
|
|
@opindex micplb
|
10274 |
|
|
Assume that ICPLBs are enabled at runtime. This has an effect on certain
|
10275 |
|
|
anomaly workarounds. For Linux targets, the default is to assume ICPLBs
|
10276 |
|
|
are enabled; for standalone applications the default is off.
|
10277 |
|
|
@end table
|
10278 |
|
|
|
10279 |
|
|
@node CRIS Options
|
10280 |
|
|
@subsection CRIS Options
|
10281 |
|
|
@cindex CRIS Options
|
10282 |
|
|
|
10283 |
|
|
These options are defined specifically for the CRIS ports.
|
10284 |
|
|
|
10285 |
|
|
@table @gcctabopt
|
10286 |
|
|
@item -march=@var{architecture-type}
|
10287 |
|
|
@itemx -mcpu=@var{architecture-type}
|
10288 |
|
|
@opindex march
|
10289 |
|
|
@opindex mcpu
|
10290 |
|
|
Generate code for the specified architecture. The choices for
|
10291 |
|
|
@var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for
|
10292 |
|
|
respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX@.
|
10293 |
|
|
Default is @samp{v0} except for cris-axis-linux-gnu, where the default is
|
10294 |
|
|
@samp{v10}.
|
10295 |
|
|
|
10296 |
|
|
@item -mtune=@var{architecture-type}
|
10297 |
|
|
@opindex mtune
|
10298 |
|
|
Tune to @var{architecture-type} everything applicable about the generated
|
10299 |
|
|
code, except for the ABI and the set of available instructions. The
|
10300 |
|
|
choices for @var{architecture-type} are the same as for
|
10301 |
|
|
@option{-march=@var{architecture-type}}.
|
10302 |
|
|
|
10303 |
|
|
@item -mmax-stack-frame=@var{n}
|
10304 |
|
|
@opindex mmax-stack-frame
|
10305 |
|
|
Warn when the stack frame of a function exceeds @var{n} bytes.
|
10306 |
|
|
|
10307 |
|
|
@item -metrax4
|
10308 |
|
|
@itemx -metrax100
|
10309 |
|
|
@opindex metrax4
|
10310 |
|
|
@opindex metrax100
|
10311 |
|
|
The options @option{-metrax4} and @option{-metrax100} are synonyms for
|
10312 |
|
|
@option{-march=v3} and @option{-march=v8} respectively.
|
10313 |
|
|
|
10314 |
|
|
@item -mmul-bug-workaround
|
10315 |
|
|
@itemx -mno-mul-bug-workaround
|
10316 |
|
|
@opindex mmul-bug-workaround
|
10317 |
|
|
@opindex mno-mul-bug-workaround
|
10318 |
|
|
Work around a bug in the @code{muls} and @code{mulu} instructions for CPU
|
10319 |
|
|
models where it applies. This option is active by default.
|
10320 |
|
|
|
10321 |
|
|
@item -mpdebug
|
10322 |
|
|
@opindex mpdebug
|
10323 |
|
|
Enable CRIS-specific verbose debug-related information in the assembly
|
10324 |
|
|
code. This option also has the effect to turn off the @samp{#NO_APP}
|
10325 |
|
|
formatted-code indicator to the assembler at the beginning of the
|
10326 |
|
|
assembly file.
|
10327 |
|
|
|
10328 |
|
|
@item -mcc-init
|
10329 |
|
|
@opindex mcc-init
|
10330 |
|
|
Do not use condition-code results from previous instruction; always emit
|
10331 |
|
|
compare and test instructions before use of condition codes.
|
10332 |
|
|
|
10333 |
|
|
@item -mno-side-effects
|
10334 |
|
|
@opindex mno-side-effects
|
10335 |
|
|
Do not emit instructions with side-effects in addressing modes other than
|
10336 |
|
|
post-increment.
|
10337 |
|
|
|
10338 |
|
|
@item -mstack-align
|
10339 |
|
|
@itemx -mno-stack-align
|
10340 |
|
|
@itemx -mdata-align
|
10341 |
|
|
@itemx -mno-data-align
|
10342 |
|
|
@itemx -mconst-align
|
10343 |
|
|
@itemx -mno-const-align
|
10344 |
|
|
@opindex mstack-align
|
10345 |
|
|
@opindex mno-stack-align
|
10346 |
|
|
@opindex mdata-align
|
10347 |
|
|
@opindex mno-data-align
|
10348 |
|
|
@opindex mconst-align
|
10349 |
|
|
@opindex mno-const-align
|
10350 |
|
|
These options (no-options) arranges (eliminate arrangements) for the
|
10351 |
|
|
stack-frame, individual data and constants to be aligned for the maximum
|
10352 |
|
|
single data access size for the chosen CPU model. The default is to
|
10353 |
|
|
arrange for 32-bit alignment. ABI details such as structure layout are
|
10354 |
|
|
not affected by these options.
|
10355 |
|
|
|
10356 |
|
|
@item -m32-bit
|
10357 |
|
|
@itemx -m16-bit
|
10358 |
|
|
@itemx -m8-bit
|
10359 |
|
|
@opindex m32-bit
|
10360 |
|
|
@opindex m16-bit
|
10361 |
|
|
@opindex m8-bit
|
10362 |
|
|
Similar to the stack- data- and const-align options above, these options
|
10363 |
|
|
arrange for stack-frame, writable data and constants to all be 32-bit,
|
10364 |
|
|
16-bit or 8-bit aligned. The default is 32-bit alignment.
|
10365 |
|
|
|
10366 |
|
|
@item -mno-prologue-epilogue
|
10367 |
|
|
@itemx -mprologue-epilogue
|
10368 |
|
|
@opindex mno-prologue-epilogue
|
10369 |
|
|
@opindex mprologue-epilogue
|
10370 |
|
|
With @option{-mno-prologue-epilogue}, the normal function prologue and
|
10371 |
|
|
epilogue that sets up the stack-frame are omitted and no return
|
10372 |
|
|
instructions or return sequences are generated in the code. Use this
|
10373 |
|
|
option only together with visual inspection of the compiled code: no
|
10374 |
|
|
warnings or errors are generated when call-saved registers must be saved,
|
10375 |
|
|
or storage for local variable needs to be allocated.
|
10376 |
|
|
|
10377 |
|
|
@item -mno-gotplt
|
10378 |
|
|
@itemx -mgotplt
|
10379 |
|
|
@opindex mno-gotplt
|
10380 |
|
|
@opindex mgotplt
|
10381 |
|
|
With @option{-fpic} and @option{-fPIC}, don't generate (do generate)
|
10382 |
|
|
instruction sequences that load addresses for functions from the PLT part
|
10383 |
|
|
of the GOT rather than (traditional on other architectures) calls to the
|
10384 |
|
|
PLT@. The default is @option{-mgotplt}.
|
10385 |
|
|
|
10386 |
|
|
@item -melf
|
10387 |
|
|
@opindex melf
|
10388 |
|
|
Legacy no-op option only recognized with the cris-axis-elf and
|
10389 |
|
|
cris-axis-linux-gnu targets.
|
10390 |
|
|
|
10391 |
|
|
@item -mlinux
|
10392 |
|
|
@opindex mlinux
|
10393 |
|
|
Legacy no-op option only recognized with the cris-axis-linux-gnu target.
|
10394 |
|
|
|
10395 |
|
|
@item -sim
|
10396 |
|
|
@opindex sim
|
10397 |
|
|
This option, recognized for the cris-axis-elf arranges
|
10398 |
|
|
to link with input-output functions from a simulator library. Code,
|
10399 |
|
|
initialized data and zero-initialized data are allocated consecutively.
|
10400 |
|
|
|
10401 |
|
|
@item -sim2
|
10402 |
|
|
@opindex sim2
|
10403 |
|
|
Like @option{-sim}, but pass linker options to locate initialized data at
|
10404 |
|
|
0x40000000 and zero-initialized data at 0x80000000.
|
10405 |
|
|
@end table
|
10406 |
|
|
|
10407 |
|
|
@node CRX Options
|
10408 |
|
|
@subsection CRX Options
|
10409 |
|
|
@cindex CRX Options
|
10410 |
|
|
|
10411 |
|
|
These options are defined specifically for the CRX ports.
|
10412 |
|
|
|
10413 |
|
|
@table @gcctabopt
|
10414 |
|
|
|
10415 |
|
|
@item -mmac
|
10416 |
|
|
@opindex mmac
|
10417 |
|
|
Enable the use of multiply-accumulate instructions. Disabled by default.
|
10418 |
|
|
|
10419 |
|
|
@item -mpush-args
|
10420 |
|
|
@opindex mpush-args
|
10421 |
|
|
Push instructions will be used to pass outgoing arguments when functions
|
10422 |
|
|
are called. Enabled by default.
|
10423 |
|
|
@end table
|
10424 |
|
|
|
10425 |
|
|
@node Darwin Options
|
10426 |
|
|
@subsection Darwin Options
|
10427 |
|
|
@cindex Darwin options
|
10428 |
|
|
|
10429 |
|
|
These options are defined for all architectures running the Darwin operating
|
10430 |
|
|
system.
|
10431 |
|
|
|
10432 |
|
|
FSF GCC on Darwin does not create ``fat'' object files; it will create
|
10433 |
|
|
an object file for the single architecture that it was built to
|
10434 |
|
|
target. Apple's GCC on Darwin does create ``fat'' files if multiple
|
10435 |
|
|
@option{-arch} options are used; it does so by running the compiler or
|
10436 |
|
|
linker multiple times and joining the results together with
|
10437 |
|
|
@file{lipo}.
|
10438 |
|
|
|
10439 |
|
|
The subtype of the file created (like @samp{ppc7400} or @samp{ppc970} or
|
10440 |
|
|
@samp{i686}) is determined by the flags that specify the ISA
|
10441 |
|
|
that GCC is targetting, like @option{-mcpu} or @option{-march}. The
|
10442 |
|
|
@option{-force_cpusubtype_ALL} option can be used to override this.
|
10443 |
|
|
|
10444 |
|
|
The Darwin tools vary in their behavior when presented with an ISA
|
10445 |
|
|
mismatch. The assembler, @file{as}, will only permit instructions to
|
10446 |
|
|
be used that are valid for the subtype of the file it is generating,
|
10447 |
|
|
so you cannot put 64-bit instructions in a @samp{ppc750} object file.
|
10448 |
|
|
The linker for shared libraries, @file{/usr/bin/libtool}, will fail
|
10449 |
|
|
and print an error if asked to create a shared library with a less
|
10450 |
|
|
restrictive subtype than its input files (for instance, trying to put
|
10451 |
|
|
a @samp{ppc970} object file in a @samp{ppc7400} library). The linker
|
10452 |
|
|
for executables, @file{ld}, will quietly give the executable the most
|
10453 |
|
|
restrictive subtype of any of its input files.
|
10454 |
|
|
|
10455 |
|
|
@table @gcctabopt
|
10456 |
|
|
@item -F@var{dir}
|
10457 |
|
|
@opindex F
|
10458 |
|
|
Add the framework directory @var{dir} to the head of the list of
|
10459 |
|
|
directories to be searched for header files. These directories are
|
10460 |
|
|
interleaved with those specified by @option{-I} options and are
|
10461 |
|
|
scanned in a left-to-right order.
|
10462 |
|
|
|
10463 |
|
|
A framework directory is a directory with frameworks in it. A
|
10464 |
|
|
framework is a directory with a @samp{"Headers"} and/or
|
10465 |
|
|
@samp{"PrivateHeaders"} directory contained directly in it that ends
|
10466 |
|
|
in @samp{".framework"}. The name of a framework is the name of this
|
10467 |
|
|
directory excluding the @samp{".framework"}. Headers associated with
|
10468 |
|
|
the framework are found in one of those two directories, with
|
10469 |
|
|
@samp{"Headers"} being searched first. A subframework is a framework
|
10470 |
|
|
directory that is in a framework's @samp{"Frameworks"} directory.
|
10471 |
|
|
Includes of subframework headers can only appear in a header of a
|
10472 |
|
|
framework that contains the subframework, or in a sibling subframework
|
10473 |
|
|
header. Two subframeworks are siblings if they occur in the same
|
10474 |
|
|
framework. A subframework should not have the same name as a
|
10475 |
|
|
framework, a warning will be issued if this is violated. Currently a
|
10476 |
|
|
subframework cannot have subframeworks, in the future, the mechanism
|
10477 |
|
|
may be extended to support this. The standard frameworks can be found
|
10478 |
|
|
in @samp{"/System/Library/Frameworks"} and
|
10479 |
|
|
@samp{"/Library/Frameworks"}. An example include looks like
|
10480 |
|
|
@code{#include <Framework/header.h>}, where @samp{Framework} denotes
|
10481 |
|
|
the name of the framework and header.h is found in the
|
10482 |
|
|
@samp{"PrivateHeaders"} or @samp{"Headers"} directory.
|
10483 |
|
|
|
10484 |
|
|
@item -iframework@var{dir}
|
10485 |
|
|
@opindex iframework
|
10486 |
|
|
Like @option{-F} except the directory is a treated as a system
|
10487 |
|
|
directory. The main difference between this @option{-iframework} and
|
10488 |
|
|
@option{-F} is that with @option{-iframework} the compiler does not
|
10489 |
|
|
warn about constructs contained within header files found via
|
10490 |
|
|
@var{dir}. This option is valid only for the C family of languages.
|
10491 |
|
|
|
10492 |
|
|
@item -gused
|
10493 |
|
|
@opindex gused
|
10494 |
|
|
Emit debugging information for symbols that are used. For STABS
|
10495 |
|
|
debugging format, this enables @option{-feliminate-unused-debug-symbols}.
|
10496 |
|
|
This is by default ON@.
|
10497 |
|
|
|
10498 |
|
|
@item -gfull
|
10499 |
|
|
@opindex gfull
|
10500 |
|
|
Emit debugging information for all symbols and types.
|
10501 |
|
|
|
10502 |
|
|
@item -mmacosx-version-min=@var{version}
|
10503 |
|
|
The earliest version of MacOS X that this executable will run on
|
10504 |
|
|
is @var{version}. Typical values of @var{version} include @code{10.1},
|
10505 |
|
|
@code{10.2}, and @code{10.3.9}.
|
10506 |
|
|
|
10507 |
|
|
If the compiler was built to use the system's headers by default,
|
10508 |
|
|
then the default for this option is the system version on which the
|
10509 |
|
|
compiler is running, otherwise the default is to make choices which
|
10510 |
|
|
are compatible with as many systems and code bases as possible.
|
10511 |
|
|
|
10512 |
|
|
@item -mkernel
|
10513 |
|
|
@opindex mkernel
|
10514 |
|
|
Enable kernel development mode. The @option{-mkernel} option sets
|
10515 |
|
|
@option{-static}, @option{-fno-common}, @option{-fno-cxa-atexit},
|
10516 |
|
|
@option{-fno-exceptions}, @option{-fno-non-call-exceptions},
|
10517 |
|
|
@option{-fapple-kext}, @option{-fno-weak} and @option{-fno-rtti} where
|
10518 |
|
|
applicable. This mode also sets @option{-mno-altivec},
|
10519 |
|
|
@option{-msoft-float}, @option{-fno-builtin} and
|
10520 |
|
|
@option{-mlong-branch} for PowerPC targets.
|
10521 |
|
|
|
10522 |
|
|
@item -mone-byte-bool
|
10523 |
|
|
@opindex mone-byte-bool
|
10524 |
|
|
Override the defaults for @samp{bool} so that @samp{sizeof(bool)==1}.
|
10525 |
|
|
By default @samp{sizeof(bool)} is @samp{4} when compiling for
|
10526 |
|
|
Darwin/PowerPC and @samp{1} when compiling for Darwin/x86, so this
|
10527 |
|
|
option has no effect on x86.
|
10528 |
|
|
|
10529 |
|
|
@strong{Warning:} The @option{-mone-byte-bool} switch causes GCC
|
10530 |
|
|
to generate code that is not binary compatible with code generated
|
10531 |
|
|
without that switch. Using this switch may require recompiling all
|
10532 |
|
|
other modules in a program, including system libraries. Use this
|
10533 |
|
|
switch to conform to a non-default data model.
|
10534 |
|
|
|
10535 |
|
|
@item -mfix-and-continue
|
10536 |
|
|
@itemx -ffix-and-continue
|
10537 |
|
|
@itemx -findirect-data
|
10538 |
|
|
@opindex mfix-and-continue
|
10539 |
|
|
@opindex ffix-and-continue
|
10540 |
|
|
@opindex findirect-data
|
10541 |
|
|
Generate code suitable for fast turn around development. Needed to
|
10542 |
|
|
enable gdb to dynamically load @code{.o} files into already running
|
10543 |
|
|
programs. @option{-findirect-data} and @option{-ffix-and-continue}
|
10544 |
|
|
are provided for backwards compatibility.
|
10545 |
|
|
|
10546 |
|
|
@item -all_load
|
10547 |
|
|
@opindex all_load
|
10548 |
|
|
Loads all members of static archive libraries.
|
10549 |
|
|
See man ld(1) for more information.
|
10550 |
|
|
|
10551 |
|
|
@item -arch_errors_fatal
|
10552 |
|
|
@opindex arch_errors_fatal
|
10553 |
|
|
Cause the errors having to do with files that have the wrong architecture
|
10554 |
|
|
to be fatal.
|
10555 |
|
|
|
10556 |
|
|
@item -bind_at_load
|
10557 |
|
|
@opindex bind_at_load
|
10558 |
|
|
Causes the output file to be marked such that the dynamic linker will
|
10559 |
|
|
bind all undefined references when the file is loaded or launched.
|
10560 |
|
|
|
10561 |
|
|
@item -bundle
|
10562 |
|
|
@opindex bundle
|
10563 |
|
|
Produce a Mach-o bundle format file.
|
10564 |
|
|
See man ld(1) for more information.
|
10565 |
|
|
|
10566 |
|
|
@item -bundle_loader @var{executable}
|
10567 |
|
|
@opindex bundle_loader
|
10568 |
|
|
This option specifies the @var{executable} that will be loading the build
|
10569 |
|
|
output file being linked. See man ld(1) for more information.
|
10570 |
|
|
|
10571 |
|
|
@item -dynamiclib
|
10572 |
|
|
@opindex dynamiclib
|
10573 |
|
|
When passed this option, GCC will produce a dynamic library instead of
|
10574 |
|
|
an executable when linking, using the Darwin @file{libtool} command.
|
10575 |
|
|
|
10576 |
|
|
@item -force_cpusubtype_ALL
|
10577 |
|
|
@opindex force_cpusubtype_ALL
|
10578 |
|
|
This causes GCC's output file to have the @var{ALL} subtype, instead of
|
10579 |
|
|
one controlled by the @option{-mcpu} or @option{-march} option.
|
10580 |
|
|
|
10581 |
|
|
@item -allowable_client @var{client_name}
|
10582 |
|
|
@itemx -client_name
|
10583 |
|
|
@itemx -compatibility_version
|
10584 |
|
|
@itemx -current_version
|
10585 |
|
|
@itemx -dead_strip
|
10586 |
|
|
@itemx -dependency-file
|
10587 |
|
|
@itemx -dylib_file
|
10588 |
|
|
@itemx -dylinker_install_name
|
10589 |
|
|
@itemx -dynamic
|
10590 |
|
|
@itemx -exported_symbols_list
|
10591 |
|
|
@itemx -filelist
|
10592 |
|
|
@itemx -flat_namespace
|
10593 |
|
|
@itemx -force_flat_namespace
|
10594 |
|
|
@itemx -headerpad_max_install_names
|
10595 |
|
|
@itemx -image_base
|
10596 |
|
|
@itemx -init
|
10597 |
|
|
@itemx -install_name
|
10598 |
|
|
@itemx -keep_private_externs
|
10599 |
|
|
@itemx -multi_module
|
10600 |
|
|
@itemx -multiply_defined
|
10601 |
|
|
@itemx -multiply_defined_unused
|
10602 |
|
|
@itemx -noall_load
|
10603 |
|
|
@itemx -no_dead_strip_inits_and_terms
|
10604 |
|
|
@itemx -nofixprebinding
|
10605 |
|
|
@itemx -nomultidefs
|
10606 |
|
|
@itemx -noprebind
|
10607 |
|
|
@itemx -noseglinkedit
|
10608 |
|
|
@itemx -pagezero_size
|
10609 |
|
|
@itemx -prebind
|
10610 |
|
|
@itemx -prebind_all_twolevel_modules
|
10611 |
|
|
@itemx -private_bundle
|
10612 |
|
|
@itemx -read_only_relocs
|
10613 |
|
|
@itemx -sectalign
|
10614 |
|
|
@itemx -sectobjectsymbols
|
10615 |
|
|
@itemx -whyload
|
10616 |
|
|
@itemx -seg1addr
|
10617 |
|
|
@itemx -sectcreate
|
10618 |
|
|
@itemx -sectobjectsymbols
|
10619 |
|
|
@itemx -sectorder
|
10620 |
|
|
@itemx -segaddr
|
10621 |
|
|
@itemx -segs_read_only_addr
|
10622 |
|
|
@itemx -segs_read_write_addr
|
10623 |
|
|
@itemx -seg_addr_table
|
10624 |
|
|
@itemx -seg_addr_table_filename
|
10625 |
|
|
@itemx -seglinkedit
|
10626 |
|
|
@itemx -segprot
|
10627 |
|
|
@itemx -segs_read_only_addr
|
10628 |
|
|
@itemx -segs_read_write_addr
|
10629 |
|
|
@itemx -single_module
|
10630 |
|
|
@itemx -static
|
10631 |
|
|
@itemx -sub_library
|
10632 |
|
|
@itemx -sub_umbrella
|
10633 |
|
|
@itemx -twolevel_namespace
|
10634 |
|
|
@itemx -umbrella
|
10635 |
|
|
@itemx -undefined
|
10636 |
|
|
@itemx -unexported_symbols_list
|
10637 |
|
|
@itemx -weak_reference_mismatches
|
10638 |
|
|
@itemx -whatsloaded
|
10639 |
|
|
@opindex allowable_client
|
10640 |
|
|
@opindex client_name
|
10641 |
|
|
@opindex compatibility_version
|
10642 |
|
|
@opindex current_version
|
10643 |
|
|
@opindex dead_strip
|
10644 |
|
|
@opindex dependency-file
|
10645 |
|
|
@opindex dylib_file
|
10646 |
|
|
@opindex dylinker_install_name
|
10647 |
|
|
@opindex dynamic
|
10648 |
|
|
@opindex exported_symbols_list
|
10649 |
|
|
@opindex filelist
|
10650 |
|
|
@opindex flat_namespace
|
10651 |
|
|
@opindex force_flat_namespace
|
10652 |
|
|
@opindex headerpad_max_install_names
|
10653 |
|
|
@opindex image_base
|
10654 |
|
|
@opindex init
|
10655 |
|
|
@opindex install_name
|
10656 |
|
|
@opindex keep_private_externs
|
10657 |
|
|
@opindex multi_module
|
10658 |
|
|
@opindex multiply_defined
|
10659 |
|
|
@opindex multiply_defined_unused
|
10660 |
|
|
@opindex noall_load
|
10661 |
|
|
@opindex no_dead_strip_inits_and_terms
|
10662 |
|
|
@opindex nofixprebinding
|
10663 |
|
|
@opindex nomultidefs
|
10664 |
|
|
@opindex noprebind
|
10665 |
|
|
@opindex noseglinkedit
|
10666 |
|
|
@opindex pagezero_size
|
10667 |
|
|
@opindex prebind
|
10668 |
|
|
@opindex prebind_all_twolevel_modules
|
10669 |
|
|
@opindex private_bundle
|
10670 |
|
|
@opindex read_only_relocs
|
10671 |
|
|
@opindex sectalign
|
10672 |
|
|
@opindex sectobjectsymbols
|
10673 |
|
|
@opindex whyload
|
10674 |
|
|
@opindex seg1addr
|
10675 |
|
|
@opindex sectcreate
|
10676 |
|
|
@opindex sectobjectsymbols
|
10677 |
|
|
@opindex sectorder
|
10678 |
|
|
@opindex segaddr
|
10679 |
|
|
@opindex segs_read_only_addr
|
10680 |
|
|
@opindex segs_read_write_addr
|
10681 |
|
|
@opindex seg_addr_table
|
10682 |
|
|
@opindex seg_addr_table_filename
|
10683 |
|
|
@opindex seglinkedit
|
10684 |
|
|
@opindex segprot
|
10685 |
|
|
@opindex segs_read_only_addr
|
10686 |
|
|
@opindex segs_read_write_addr
|
10687 |
|
|
@opindex single_module
|
10688 |
|
|
@opindex static
|
10689 |
|
|
@opindex sub_library
|
10690 |
|
|
@opindex sub_umbrella
|
10691 |
|
|
@opindex twolevel_namespace
|
10692 |
|
|
@opindex umbrella
|
10693 |
|
|
@opindex undefined
|
10694 |
|
|
@opindex unexported_symbols_list
|
10695 |
|
|
@opindex weak_reference_mismatches
|
10696 |
|
|
@opindex whatsloaded
|
10697 |
|
|
These options are passed to the Darwin linker. The Darwin linker man page
|
10698 |
|
|
describes them in detail.
|
10699 |
|
|
@end table
|
10700 |
|
|
|
10701 |
|
|
@node DEC Alpha Options
|
10702 |
|
|
@subsection DEC Alpha Options
|
10703 |
|
|
|
10704 |
|
|
These @samp{-m} options are defined for the DEC Alpha implementations:
|
10705 |
|
|
|
10706 |
|
|
@table @gcctabopt
|
10707 |
|
|
@item -mno-soft-float
|
10708 |
|
|
@itemx -msoft-float
|
10709 |
|
|
@opindex mno-soft-float
|
10710 |
|
|
@opindex msoft-float
|
10711 |
|
|
Use (do not use) the hardware floating-point instructions for
|
10712 |
|
|
floating-point operations. When @option{-msoft-float} is specified,
|
10713 |
|
|
functions in @file{libgcc.a} will be used to perform floating-point
|
10714 |
|
|
operations. Unless they are replaced by routines that emulate the
|
10715 |
|
|
floating-point operations, or compiled in such a way as to call such
|
10716 |
|
|
emulations routines, these routines will issue floating-point
|
10717 |
|
|
operations. If you are compiling for an Alpha without floating-point
|
10718 |
|
|
operations, you must ensure that the library is built so as not to call
|
10719 |
|
|
them.
|
10720 |
|
|
|
10721 |
|
|
Note that Alpha implementations without floating-point operations are
|
10722 |
|
|
required to have floating-point registers.
|
10723 |
|
|
|
10724 |
|
|
@item -mfp-reg
|
10725 |
|
|
@itemx -mno-fp-regs
|
10726 |
|
|
@opindex mfp-reg
|
10727 |
|
|
@opindex mno-fp-regs
|
10728 |
|
|
Generate code that uses (does not use) the floating-point register set.
|
10729 |
|
|
@option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point
|
10730 |
|
|
register set is not used, floating point operands are passed in integer
|
10731 |
|
|
registers as if they were integers and floating-point results are passed
|
10732 |
|
|
in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence,
|
10733 |
|
|
so any function with a floating-point argument or return value called by code
|
10734 |
|
|
compiled with @option{-mno-fp-regs} must also be compiled with that
|
10735 |
|
|
option.
|
10736 |
|
|
|
10737 |
|
|
A typical use of this option is building a kernel that does not use,
|
10738 |
|
|
and hence need not save and restore, any floating-point registers.
|
10739 |
|
|
|
10740 |
|
|
@item -mieee
|
10741 |
|
|
@opindex mieee
|
10742 |
|
|
The Alpha architecture implements floating-point hardware optimized for
|
10743 |
|
|
maximum performance. It is mostly compliant with the IEEE floating
|
10744 |
|
|
point standard. However, for full compliance, software assistance is
|
10745 |
|
|
required. This option generates code fully IEEE compliant code
|
10746 |
|
|
@emph{except} that the @var{inexact-flag} is not maintained (see below).
|
10747 |
|
|
If this option is turned on, the preprocessor macro @code{_IEEE_FP} is
|
10748 |
|
|
defined during compilation. The resulting code is less efficient but is
|
10749 |
|
|
able to correctly support denormalized numbers and exceptional IEEE
|
10750 |
|
|
values such as not-a-number and plus/minus infinity. Other Alpha
|
10751 |
|
|
compilers call this option @option{-ieee_with_no_inexact}.
|
10752 |
|
|
|
10753 |
|
|
@item -mieee-with-inexact
|
10754 |
|
|
@opindex mieee-with-inexact
|
10755 |
|
|
This is like @option{-mieee} except the generated code also maintains
|
10756 |
|
|
the IEEE @var{inexact-flag}. Turning on this option causes the
|
10757 |
|
|
generated code to implement fully-compliant IEEE math. In addition to
|
10758 |
|
|
@code{_IEEE_FP}, @code{_IEEE_FP_EXACT} is defined as a preprocessor
|
10759 |
|
|
macro. On some Alpha implementations the resulting code may execute
|
10760 |
|
|
significantly slower than the code generated by default. Since there is
|
10761 |
|
|
very little code that depends on the @var{inexact-flag}, you should
|
10762 |
|
|
normally not specify this option. Other Alpha compilers call this
|
10763 |
|
|
option @option{-ieee_with_inexact}.
|
10764 |
|
|
|
10765 |
|
|
@item -mfp-trap-mode=@var{trap-mode}
|
10766 |
|
|
@opindex mfp-trap-mode
|
10767 |
|
|
This option controls what floating-point related traps are enabled.
|
10768 |
|
|
Other Alpha compilers call this option @option{-fptm @var{trap-mode}}.
|
10769 |
|
|
The trap mode can be set to one of four values:
|
10770 |
|
|
|
10771 |
|
|
@table @samp
|
10772 |
|
|
@item n
|
10773 |
|
|
This is the default (normal) setting. The only traps that are enabled
|
10774 |
|
|
are the ones that cannot be disabled in software (e.g., division by zero
|
10775 |
|
|
trap).
|
10776 |
|
|
|
10777 |
|
|
@item u
|
10778 |
|
|
In addition to the traps enabled by @samp{n}, underflow traps are enabled
|
10779 |
|
|
as well.
|
10780 |
|
|
|
10781 |
|
|
@item su
|
10782 |
|
|
Like @samp{u}, but the instructions are marked to be safe for software
|
10783 |
|
|
completion (see Alpha architecture manual for details).
|
10784 |
|
|
|
10785 |
|
|
@item sui
|
10786 |
|
|
Like @samp{su}, but inexact traps are enabled as well.
|
10787 |
|
|
@end table
|
10788 |
|
|
|
10789 |
|
|
@item -mfp-rounding-mode=@var{rounding-mode}
|
10790 |
|
|
@opindex mfp-rounding-mode
|
10791 |
|
|
Selects the IEEE rounding mode. Other Alpha compilers call this option
|
10792 |
|
|
@option{-fprm @var{rounding-mode}}. The @var{rounding-mode} can be one
|
10793 |
|
|
of:
|
10794 |
|
|
|
10795 |
|
|
@table @samp
|
10796 |
|
|
@item n
|
10797 |
|
|
Normal IEEE rounding mode. Floating point numbers are rounded towards
|
10798 |
|
|
the nearest machine number or towards the even machine number in case
|
10799 |
|
|
of a tie.
|
10800 |
|
|
|
10801 |
|
|
@item m
|
10802 |
|
|
Round towards minus infinity.
|
10803 |
|
|
|
10804 |
|
|
@item c
|
10805 |
|
|
Chopped rounding mode. Floating point numbers are rounded towards zero.
|
10806 |
|
|
|
10807 |
|
|
@item d
|
10808 |
|
|
Dynamic rounding mode. A field in the floating point control register
|
10809 |
|
|
(@var{fpcr}, see Alpha architecture reference manual) controls the
|
10810 |
|
|
rounding mode in effect. The C library initializes this register for
|
10811 |
|
|
rounding towards plus infinity. Thus, unless your program modifies the
|
10812 |
|
|
@var{fpcr}, @samp{d} corresponds to round towards plus infinity.
|
10813 |
|
|
@end table
|
10814 |
|
|
|
10815 |
|
|
@item -mtrap-precision=@var{trap-precision}
|
10816 |
|
|
@opindex mtrap-precision
|
10817 |
|
|
In the Alpha architecture, floating point traps are imprecise. This
|
10818 |
|
|
means without software assistance it is impossible to recover from a
|
10819 |
|
|
floating trap and program execution normally needs to be terminated.
|
10820 |
|
|
GCC can generate code that can assist operating system trap handlers
|
10821 |
|
|
in determining the exact location that caused a floating point trap.
|
10822 |
|
|
Depending on the requirements of an application, different levels of
|
10823 |
|
|
precisions can be selected:
|
10824 |
|
|
|
10825 |
|
|
@table @samp
|
10826 |
|
|
@item p
|
10827 |
|
|
Program precision. This option is the default and means a trap handler
|
10828 |
|
|
can only identify which program caused a floating point exception.
|
10829 |
|
|
|
10830 |
|
|
@item f
|
10831 |
|
|
Function precision. The trap handler can determine the function that
|
10832 |
|
|
caused a floating point exception.
|
10833 |
|
|
|
10834 |
|
|
@item i
|
10835 |
|
|
Instruction precision. The trap handler can determine the exact
|
10836 |
|
|
instruction that caused a floating point exception.
|
10837 |
|
|
@end table
|
10838 |
|
|
|
10839 |
|
|
Other Alpha compilers provide the equivalent options called
|
10840 |
|
|
@option{-scope_safe} and @option{-resumption_safe}.
|
10841 |
|
|
|
10842 |
|
|
@item -mieee-conformant
|
10843 |
|
|
@opindex mieee-conformant
|
10844 |
|
|
This option marks the generated code as IEEE conformant. You must not
|
10845 |
|
|
use this option unless you also specify @option{-mtrap-precision=i} and either
|
10846 |
|
|
@option{-mfp-trap-mode=su} or @option{-mfp-trap-mode=sui}. Its only effect
|
10847 |
|
|
is to emit the line @samp{.eflag 48} in the function prologue of the
|
10848 |
|
|
generated assembly file. Under DEC Unix, this has the effect that
|
10849 |
|
|
IEEE-conformant math library routines will be linked in.
|
10850 |
|
|
|
10851 |
|
|
@item -mbuild-constants
|
10852 |
|
|
@opindex mbuild-constants
|
10853 |
|
|
Normally GCC examines a 32- or 64-bit integer constant to
|
10854 |
|
|
see if it can construct it from smaller constants in two or three
|
10855 |
|
|
instructions. If it cannot, it will output the constant as a literal and
|
10856 |
|
|
generate code to load it from the data segment at runtime.
|
10857 |
|
|
|
10858 |
|
|
Use this option to require GCC to construct @emph{all} integer constants
|
10859 |
|
|
using code, even if it takes more instructions (the maximum is six).
|
10860 |
|
|
|
10861 |
|
|
You would typically use this option to build a shared library dynamic
|
10862 |
|
|
loader. Itself a shared library, it must relocate itself in memory
|
10863 |
|
|
before it can find the variables and constants in its own data segment.
|
10864 |
|
|
|
10865 |
|
|
@item -malpha-as
|
10866 |
|
|
@itemx -mgas
|
10867 |
|
|
@opindex malpha-as
|
10868 |
|
|
@opindex mgas
|
10869 |
|
|
Select whether to generate code to be assembled by the vendor-supplied
|
10870 |
|
|
assembler (@option{-malpha-as}) or by the GNU assembler @option{-mgas}.
|
10871 |
|
|
|
10872 |
|
|
@item -mbwx
|
10873 |
|
|
@itemx -mno-bwx
|
10874 |
|
|
@itemx -mcix
|
10875 |
|
|
@itemx -mno-cix
|
10876 |
|
|
@itemx -mfix
|
10877 |
|
|
@itemx -mno-fix
|
10878 |
|
|
@itemx -mmax
|
10879 |
|
|
@itemx -mno-max
|
10880 |
|
|
@opindex mbwx
|
10881 |
|
|
@opindex mno-bwx
|
10882 |
|
|
@opindex mcix
|
10883 |
|
|
@opindex mno-cix
|
10884 |
|
|
@opindex mfix
|
10885 |
|
|
@opindex mno-fix
|
10886 |
|
|
@opindex mmax
|
10887 |
|
|
@opindex mno-max
|
10888 |
|
|
Indicate whether GCC should generate code to use the optional BWX,
|
10889 |
|
|
CIX, FIX and MAX instruction sets. The default is to use the instruction
|
10890 |
|
|
sets supported by the CPU type specified via @option{-mcpu=} option or that
|
10891 |
|
|
of the CPU on which GCC was built if none was specified.
|
10892 |
|
|
|
10893 |
|
|
@item -mfloat-vax
|
10894 |
|
|
@itemx -mfloat-ieee
|
10895 |
|
|
@opindex mfloat-vax
|
10896 |
|
|
@opindex mfloat-ieee
|
10897 |
|
|
Generate code that uses (does not use) VAX F and G floating point
|
10898 |
|
|
arithmetic instead of IEEE single and double precision.
|
10899 |
|
|
|
10900 |
|
|
@item -mexplicit-relocs
|
10901 |
|
|
@itemx -mno-explicit-relocs
|
10902 |
|
|
@opindex mexplicit-relocs
|
10903 |
|
|
@opindex mno-explicit-relocs
|
10904 |
|
|
Older Alpha assemblers provided no way to generate symbol relocations
|
10905 |
|
|
except via assembler macros. Use of these macros does not allow
|
10906 |
|
|
optimal instruction scheduling. GNU binutils as of version 2.12
|
10907 |
|
|
supports a new syntax that allows the compiler to explicitly mark
|
10908 |
|
|
which relocations should apply to which instructions. This option
|
10909 |
|
|
is mostly useful for debugging, as GCC detects the capabilities of
|
10910 |
|
|
the assembler when it is built and sets the default accordingly.
|
10911 |
|
|
|
10912 |
|
|
@item -msmall-data
|
10913 |
|
|
@itemx -mlarge-data
|
10914 |
|
|
@opindex msmall-data
|
10915 |
|
|
@opindex mlarge-data
|
10916 |
|
|
When @option{-mexplicit-relocs} is in effect, static data is
|
10917 |
|
|
accessed via @dfn{gp-relative} relocations. When @option{-msmall-data}
|
10918 |
|
|
is used, objects 8 bytes long or smaller are placed in a @dfn{small data area}
|
10919 |
|
|
(the @code{.sdata} and @code{.sbss} sections) and are accessed via
|
10920 |
|
|
16-bit relocations off of the @code{$gp} register. This limits the
|
10921 |
|
|
size of the small data area to 64KB, but allows the variables to be
|
10922 |
|
|
directly accessed via a single instruction.
|
10923 |
|
|
|
10924 |
|
|
The default is @option{-mlarge-data}. With this option the data area
|
10925 |
|
|
is limited to just below 2GB@. Programs that require more than 2GB of
|
10926 |
|
|
data must use @code{malloc} or @code{mmap} to allocate the data in the
|
10927 |
|
|
heap instead of in the program's data segment.
|
10928 |
|
|
|
10929 |
|
|
When generating code for shared libraries, @option{-fpic} implies
|
10930 |
|
|
@option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}.
|
10931 |
|
|
|
10932 |
|
|
@item -msmall-text
|
10933 |
|
|
@itemx -mlarge-text
|
10934 |
|
|
@opindex msmall-text
|
10935 |
|
|
@opindex mlarge-text
|
10936 |
|
|
When @option{-msmall-text} is used, the compiler assumes that the
|
10937 |
|
|
code of the entire program (or shared library) fits in 4MB, and is
|
10938 |
|
|
thus reachable with a branch instruction. When @option{-msmall-data}
|
10939 |
|
|
is used, the compiler can assume that all local symbols share the
|
10940 |
|
|
same @code{$gp} value, and thus reduce the number of instructions
|
10941 |
|
|
required for a function call from 4 to 1.
|
10942 |
|
|
|
10943 |
|
|
The default is @option{-mlarge-text}.
|
10944 |
|
|
|
10945 |
|
|
@item -mcpu=@var{cpu_type}
|
10946 |
|
|
@opindex mcpu
|
10947 |
|
|
Set the instruction set and instruction scheduling parameters for
|
10948 |
|
|
machine type @var{cpu_type}. You can specify either the @samp{EV}
|
10949 |
|
|
style name or the corresponding chip number. GCC supports scheduling
|
10950 |
|
|
parameters for the EV4, EV5 and EV6 family of processors and will
|
10951 |
|
|
choose the default values for the instruction set from the processor
|
10952 |
|
|
you specify. If you do not specify a processor type, GCC will default
|
10953 |
|
|
to the processor on which the compiler was built.
|
10954 |
|
|
|
10955 |
|
|
Supported values for @var{cpu_type} are
|
10956 |
|
|
|
10957 |
|
|
@table @samp
|
10958 |
|
|
@item ev4
|
10959 |
|
|
@itemx ev45
|
10960 |
|
|
@itemx 21064
|
10961 |
|
|
Schedules as an EV4 and has no instruction set extensions.
|
10962 |
|
|
|
10963 |
|
|
@item ev5
|
10964 |
|
|
@itemx 21164
|
10965 |
|
|
Schedules as an EV5 and has no instruction set extensions.
|
10966 |
|
|
|
10967 |
|
|
@item ev56
|
10968 |
|
|
@itemx 21164a
|
10969 |
|
|
Schedules as an EV5 and supports the BWX extension.
|
10970 |
|
|
|
10971 |
|
|
@item pca56
|
10972 |
|
|
@itemx 21164pc
|
10973 |
|
|
@itemx 21164PC
|
10974 |
|
|
Schedules as an EV5 and supports the BWX and MAX extensions.
|
10975 |
|
|
|
10976 |
|
|
@item ev6
|
10977 |
|
|
@itemx 21264
|
10978 |
|
|
Schedules as an EV6 and supports the BWX, FIX, and MAX extensions.
|
10979 |
|
|
|
10980 |
|
|
@item ev67
|
10981 |
|
|
@itemx 21264a
|
10982 |
|
|
Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions.
|
10983 |
|
|
@end table
|
10984 |
|
|
|
10985 |
|
|
Native Linux/GNU toolchains also support the value @samp{native},
|
10986 |
|
|
which selects the best architecture option for the host processor.
|
10987 |
|
|
@option{-mcpu=native} has no effect if GCC does not recognize
|
10988 |
|
|
the processor.
|
10989 |
|
|
|
10990 |
|
|
@item -mtune=@var{cpu_type}
|
10991 |
|
|
@opindex mtune
|
10992 |
|
|
Set only the instruction scheduling parameters for machine type
|
10993 |
|
|
@var{cpu_type}. The instruction set is not changed.
|
10994 |
|
|
|
10995 |
|
|
Native Linux/GNU toolchains also support the value @samp{native},
|
10996 |
|
|
which selects the best architecture option for the host processor.
|
10997 |
|
|
@option{-mtune=native} has no effect if GCC does not recognize
|
10998 |
|
|
the processor.
|
10999 |
|
|
|
11000 |
|
|
@item -mmemory-latency=@var{time}
|
11001 |
|
|
@opindex mmemory-latency
|
11002 |
|
|
Sets the latency the scheduler should assume for typical memory
|
11003 |
|
|
references as seen by the application. This number is highly
|
11004 |
|
|
dependent on the memory access patterns used by the application
|
11005 |
|
|
and the size of the external cache on the machine.
|
11006 |
|
|
|
11007 |
|
|
Valid options for @var{time} are
|
11008 |
|
|
|
11009 |
|
|
@table @samp
|
11010 |
|
|
@item @var{number}
|
11011 |
|
|
A decimal number representing clock cycles.
|
11012 |
|
|
|
11013 |
|
|
@item L1
|
11014 |
|
|
@itemx L2
|
11015 |
|
|
@itemx L3
|
11016 |
|
|
@itemx main
|
11017 |
|
|
The compiler contains estimates of the number of clock cycles for
|
11018 |
|
|
``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches
|
11019 |
|
|
(also called Dcache, Scache, and Bcache), as well as to main memory.
|
11020 |
|
|
Note that L3 is only valid for EV5.
|
11021 |
|
|
|
11022 |
|
|
@end table
|
11023 |
|
|
@end table
|
11024 |
|
|
|
11025 |
|
|
@node DEC Alpha/VMS Options
|
11026 |
|
|
@subsection DEC Alpha/VMS Options
|
11027 |
|
|
|
11028 |
|
|
These @samp{-m} options are defined for the DEC Alpha/VMS implementations:
|
11029 |
|
|
|
11030 |
|
|
@table @gcctabopt
|
11031 |
|
|
@item -mvms-return-codes
|
11032 |
|
|
@opindex mvms-return-codes
|
11033 |
|
|
Return VMS condition codes from main. The default is to return POSIX
|
11034 |
|
|
style condition (e.g.@: error) codes.
|
11035 |
|
|
|
11036 |
|
|
@item -mdebug-main=@var{prefix}
|
11037 |
|
|
@opindex mdebug-main=@var{prefix}
|
11038 |
|
|
Flag the first routine whose name starts with @var{prefix} as the main
|
11039 |
|
|
routine for the debugger.
|
11040 |
|
|
|
11041 |
|
|
@item -mmalloc64
|
11042 |
|
|
@opindex mmalloc64
|
11043 |
|
|
Default to 64bit memory allocation routines.
|
11044 |
|
|
@end table
|
11045 |
|
|
|
11046 |
|
|
@node FR30 Options
|
11047 |
|
|
@subsection FR30 Options
|
11048 |
|
|
@cindex FR30 Options
|
11049 |
|
|
|
11050 |
|
|
These options are defined specifically for the FR30 port.
|
11051 |
|
|
|
11052 |
|
|
@table @gcctabopt
|
11053 |
|
|
|
11054 |
|
|
@item -msmall-model
|
11055 |
|
|
@opindex msmall-model
|
11056 |
|
|
Use the small address space model. This can produce smaller code, but
|
11057 |
|
|
it does assume that all symbolic values and addresses will fit into a
|
11058 |
|
|
20-bit range.
|
11059 |
|
|
|
11060 |
|
|
@item -mno-lsim
|
11061 |
|
|
@opindex mno-lsim
|
11062 |
|
|
Assume that run-time support has been provided and so there is no need
|
11063 |
|
|
to include the simulator library (@file{libsim.a}) on the linker
|
11064 |
|
|
command line.
|
11065 |
|
|
|
11066 |
|
|
@end table
|
11067 |
|
|
|
11068 |
|
|
@node FRV Options
|
11069 |
|
|
@subsection FRV Options
|
11070 |
|
|
@cindex FRV Options
|
11071 |
|
|
|
11072 |
|
|
@table @gcctabopt
|
11073 |
|
|
@item -mgpr-32
|
11074 |
|
|
@opindex mgpr-32
|
11075 |
|
|
|
11076 |
|
|
Only use the first 32 general purpose registers.
|
11077 |
|
|
|
11078 |
|
|
@item -mgpr-64
|
11079 |
|
|
@opindex mgpr-64
|
11080 |
|
|
|
11081 |
|
|
Use all 64 general purpose registers.
|
11082 |
|
|
|
11083 |
|
|
@item -mfpr-32
|
11084 |
|
|
@opindex mfpr-32
|
11085 |
|
|
|
11086 |
|
|
Use only the first 32 floating point registers.
|
11087 |
|
|
|
11088 |
|
|
@item -mfpr-64
|
11089 |
|
|
@opindex mfpr-64
|
11090 |
|
|
|
11091 |
|
|
Use all 64 floating point registers
|
11092 |
|
|
|
11093 |
|
|
@item -mhard-float
|
11094 |
|
|
@opindex mhard-float
|
11095 |
|
|
|
11096 |
|
|
Use hardware instructions for floating point operations.
|
11097 |
|
|
|
11098 |
|
|
@item -msoft-float
|
11099 |
|
|
@opindex msoft-float
|
11100 |
|
|
|
11101 |
|
|
Use library routines for floating point operations.
|
11102 |
|
|
|
11103 |
|
|
@item -malloc-cc
|
11104 |
|
|
@opindex malloc-cc
|
11105 |
|
|
|
11106 |
|
|
Dynamically allocate condition code registers.
|
11107 |
|
|
|
11108 |
|
|
@item -mfixed-cc
|
11109 |
|
|
@opindex mfixed-cc
|
11110 |
|
|
|
11111 |
|
|
Do not try to dynamically allocate condition code registers, only
|
11112 |
|
|
use @code{icc0} and @code{fcc0}.
|
11113 |
|
|
|
11114 |
|
|
@item -mdword
|
11115 |
|
|
@opindex mdword
|
11116 |
|
|
|
11117 |
|
|
Change ABI to use double word insns.
|
11118 |
|
|
|
11119 |
|
|
@item -mno-dword
|
11120 |
|
|
@opindex mno-dword
|
11121 |
|
|
|
11122 |
|
|
Do not use double word instructions.
|
11123 |
|
|
|
11124 |
|
|
@item -mdouble
|
11125 |
|
|
@opindex mdouble
|
11126 |
|
|
|
11127 |
|
|
Use floating point double instructions.
|
11128 |
|
|
|
11129 |
|
|
@item -mno-double
|
11130 |
|
|
@opindex mno-double
|
11131 |
|
|
|
11132 |
|
|
Do not use floating point double instructions.
|
11133 |
|
|
|
11134 |
|
|
@item -mmedia
|
11135 |
|
|
@opindex mmedia
|
11136 |
|
|
|
11137 |
|
|
Use media instructions.
|
11138 |
|
|
|
11139 |
|
|
@item -mno-media
|
11140 |
|
|
@opindex mno-media
|
11141 |
|
|
|
11142 |
|
|
Do not use media instructions.
|
11143 |
|
|
|
11144 |
|
|
@item -mmuladd
|
11145 |
|
|
@opindex mmuladd
|
11146 |
|
|
|
11147 |
|
|
Use multiply and add/subtract instructions.
|
11148 |
|
|
|
11149 |
|
|
@item -mno-muladd
|
11150 |
|
|
@opindex mno-muladd
|
11151 |
|
|
|
11152 |
|
|
Do not use multiply and add/subtract instructions.
|
11153 |
|
|
|
11154 |
|
|
@item -mfdpic
|
11155 |
|
|
@opindex mfdpic
|
11156 |
|
|
|
11157 |
|
|
Select the FDPIC ABI, that uses function descriptors to represent
|
11158 |
|
|
pointers to functions. Without any PIC/PIE-related options, it
|
11159 |
|
|
implies @option{-fPIE}. With @option{-fpic} or @option{-fpie}, it
|
11160 |
|
|
assumes GOT entries and small data are within a 12-bit range from the
|
11161 |
|
|
GOT base address; with @option{-fPIC} or @option{-fPIE}, GOT offsets
|
11162 |
|
|
are computed with 32 bits.
|
11163 |
|
|
With a @samp{bfin-elf} target, this option implies @option{-msim}.
|
11164 |
|
|
|
11165 |
|
|
@item -minline-plt
|
11166 |
|
|
@opindex minline-plt
|
11167 |
|
|
|
11168 |
|
|
Enable inlining of PLT entries in function calls to functions that are
|
11169 |
|
|
not known to bind locally. It has no effect without @option{-mfdpic}.
|
11170 |
|
|
It's enabled by default if optimizing for speed and compiling for
|
11171 |
|
|
shared libraries (i.e., @option{-fPIC} or @option{-fpic}), or when an
|
11172 |
|
|
optimization option such as @option{-O3} or above is present in the
|
11173 |
|
|
command line.
|
11174 |
|
|
|
11175 |
|
|
@item -mTLS
|
11176 |
|
|
@opindex mTLS
|
11177 |
|
|
|
11178 |
|
|
Assume a large TLS segment when generating thread-local code.
|
11179 |
|
|
|
11180 |
|
|
@item -mtls
|
11181 |
|
|
@opindex mtls
|
11182 |
|
|
|
11183 |
|
|
Do not assume a large TLS segment when generating thread-local code.
|
11184 |
|
|
|
11185 |
|
|
@item -mgprel-ro
|
11186 |
|
|
@opindex mgprel-ro
|
11187 |
|
|
|
11188 |
|
|
Enable the use of @code{GPREL} relocations in the FDPIC ABI for data
|
11189 |
|
|
that is known to be in read-only sections. It's enabled by default,
|
11190 |
|
|
except for @option{-fpic} or @option{-fpie}: even though it may help
|
11191 |
|
|
make the global offset table smaller, it trades 1 instruction for 4.
|
11192 |
|
|
With @option{-fPIC} or @option{-fPIE}, it trades 3 instructions for 4,
|
11193 |
|
|
one of which may be shared by multiple symbols, and it avoids the need
|
11194 |
|
|
for a GOT entry for the referenced symbol, so it's more likely to be a
|
11195 |
|
|
win. If it is not, @option{-mno-gprel-ro} can be used to disable it.
|
11196 |
|
|
|
11197 |
|
|
@item -multilib-library-pic
|
11198 |
|
|
@opindex multilib-library-pic
|
11199 |
|
|
|
11200 |
|
|
Link with the (library, not FD) pic libraries. It's implied by
|
11201 |
|
|
@option{-mlibrary-pic}, as well as by @option{-fPIC} and
|
11202 |
|
|
@option{-fpic} without @option{-mfdpic}. You should never have to use
|
11203 |
|
|
it explicitly.
|
11204 |
|
|
|
11205 |
|
|
@item -mlinked-fp
|
11206 |
|
|
@opindex mlinked-fp
|
11207 |
|
|
|
11208 |
|
|
Follow the EABI requirement of always creating a frame pointer whenever
|
11209 |
|
|
a stack frame is allocated. This option is enabled by default and can
|
11210 |
|
|
be disabled with @option{-mno-linked-fp}.
|
11211 |
|
|
|
11212 |
|
|
@item -mlong-calls
|
11213 |
|
|
@opindex mlong-calls
|
11214 |
|
|
|
11215 |
|
|
Use indirect addressing to call functions outside the current
|
11216 |
|
|
compilation unit. This allows the functions to be placed anywhere
|
11217 |
|
|
within the 32-bit address space.
|
11218 |
|
|
|
11219 |
|
|
@item -malign-labels
|
11220 |
|
|
@opindex malign-labels
|
11221 |
|
|
|
11222 |
|
|
Try to align labels to an 8-byte boundary by inserting nops into the
|
11223 |
|
|
previous packet. This option only has an effect when VLIW packing
|
11224 |
|
|
is enabled. It doesn't create new packets; it merely adds nops to
|
11225 |
|
|
existing ones.
|
11226 |
|
|
|
11227 |
|
|
@item -mlibrary-pic
|
11228 |
|
|
@opindex mlibrary-pic
|
11229 |
|
|
|
11230 |
|
|
Generate position-independent EABI code.
|
11231 |
|
|
|
11232 |
|
|
@item -macc-4
|
11233 |
|
|
@opindex macc-4
|
11234 |
|
|
|
11235 |
|
|
Use only the first four media accumulator registers.
|
11236 |
|
|
|
11237 |
|
|
@item -macc-8
|
11238 |
|
|
@opindex macc-8
|
11239 |
|
|
|
11240 |
|
|
Use all eight media accumulator registers.
|
11241 |
|
|
|
11242 |
|
|
@item -mpack
|
11243 |
|
|
@opindex mpack
|
11244 |
|
|
|
11245 |
|
|
Pack VLIW instructions.
|
11246 |
|
|
|
11247 |
|
|
@item -mno-pack
|
11248 |
|
|
@opindex mno-pack
|
11249 |
|
|
|
11250 |
|
|
Do not pack VLIW instructions.
|
11251 |
|
|
|
11252 |
|
|
@item -mno-eflags
|
11253 |
|
|
@opindex mno-eflags
|
11254 |
|
|
|
11255 |
|
|
Do not mark ABI switches in e_flags.
|
11256 |
|
|
|
11257 |
|
|
@item -mcond-move
|
11258 |
|
|
@opindex mcond-move
|
11259 |
|
|
|
11260 |
|
|
Enable the use of conditional-move instructions (default).
|
11261 |
|
|
|
11262 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11263 |
|
|
in a future version.
|
11264 |
|
|
|
11265 |
|
|
@item -mno-cond-move
|
11266 |
|
|
@opindex mno-cond-move
|
11267 |
|
|
|
11268 |
|
|
Disable the use of conditional-move instructions.
|
11269 |
|
|
|
11270 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11271 |
|
|
in a future version.
|
11272 |
|
|
|
11273 |
|
|
@item -mscc
|
11274 |
|
|
@opindex mscc
|
11275 |
|
|
|
11276 |
|
|
Enable the use of conditional set instructions (default).
|
11277 |
|
|
|
11278 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11279 |
|
|
in a future version.
|
11280 |
|
|
|
11281 |
|
|
@item -mno-scc
|
11282 |
|
|
@opindex mno-scc
|
11283 |
|
|
|
11284 |
|
|
Disable the use of conditional set instructions.
|
11285 |
|
|
|
11286 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11287 |
|
|
in a future version.
|
11288 |
|
|
|
11289 |
|
|
@item -mcond-exec
|
11290 |
|
|
@opindex mcond-exec
|
11291 |
|
|
|
11292 |
|
|
Enable the use of conditional execution (default).
|
11293 |
|
|
|
11294 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11295 |
|
|
in a future version.
|
11296 |
|
|
|
11297 |
|
|
@item -mno-cond-exec
|
11298 |
|
|
@opindex mno-cond-exec
|
11299 |
|
|
|
11300 |
|
|
Disable the use of conditional execution.
|
11301 |
|
|
|
11302 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11303 |
|
|
in a future version.
|
11304 |
|
|
|
11305 |
|
|
@item -mvliw-branch
|
11306 |
|
|
@opindex mvliw-branch
|
11307 |
|
|
|
11308 |
|
|
Run a pass to pack branches into VLIW instructions (default).
|
11309 |
|
|
|
11310 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11311 |
|
|
in a future version.
|
11312 |
|
|
|
11313 |
|
|
@item -mno-vliw-branch
|
11314 |
|
|
@opindex mno-vliw-branch
|
11315 |
|
|
|
11316 |
|
|
Do not run a pass to pack branches into VLIW instructions.
|
11317 |
|
|
|
11318 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11319 |
|
|
in a future version.
|
11320 |
|
|
|
11321 |
|
|
@item -mmulti-cond-exec
|
11322 |
|
|
@opindex mmulti-cond-exec
|
11323 |
|
|
|
11324 |
|
|
Enable optimization of @code{&&} and @code{||} in conditional execution
|
11325 |
|
|
(default).
|
11326 |
|
|
|
11327 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11328 |
|
|
in a future version.
|
11329 |
|
|
|
11330 |
|
|
@item -mno-multi-cond-exec
|
11331 |
|
|
@opindex mno-multi-cond-exec
|
11332 |
|
|
|
11333 |
|
|
Disable optimization of @code{&&} and @code{||} in conditional execution.
|
11334 |
|
|
|
11335 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11336 |
|
|
in a future version.
|
11337 |
|
|
|
11338 |
|
|
@item -mnested-cond-exec
|
11339 |
|
|
@opindex mnested-cond-exec
|
11340 |
|
|
|
11341 |
|
|
Enable nested conditional execution optimizations (default).
|
11342 |
|
|
|
11343 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11344 |
|
|
in a future version.
|
11345 |
|
|
|
11346 |
|
|
@item -mno-nested-cond-exec
|
11347 |
|
|
@opindex mno-nested-cond-exec
|
11348 |
|
|
|
11349 |
|
|
Disable nested conditional execution optimizations.
|
11350 |
|
|
|
11351 |
|
|
This switch is mainly for debugging the compiler and will likely be removed
|
11352 |
|
|
in a future version.
|
11353 |
|
|
|
11354 |
|
|
@item -moptimize-membar
|
11355 |
|
|
@opindex moptimize-membar
|
11356 |
|
|
|
11357 |
|
|
This switch removes redundant @code{membar} instructions from the
|
11358 |
|
|
compiler generated code. It is enabled by default.
|
11359 |
|
|
|
11360 |
|
|
@item -mno-optimize-membar
|
11361 |
|
|
@opindex mno-optimize-membar
|
11362 |
|
|
|
11363 |
|
|
This switch disables the automatic removal of redundant @code{membar}
|
11364 |
|
|
instructions from the generated code.
|
11365 |
|
|
|
11366 |
|
|
@item -mtomcat-stats
|
11367 |
|
|
@opindex mtomcat-stats
|
11368 |
|
|
|
11369 |
|
|
Cause gas to print out tomcat statistics.
|
11370 |
|
|
|
11371 |
|
|
@item -mcpu=@var{cpu}
|
11372 |
|
|
@opindex mcpu
|
11373 |
|
|
|
11374 |
|
|
Select the processor type for which to generate code. Possible values are
|
11375 |
|
|
@samp{frv}, @samp{fr550}, @samp{tomcat}, @samp{fr500}, @samp{fr450},
|
11376 |
|
|
@samp{fr405}, @samp{fr400}, @samp{fr300} and @samp{simple}.
|
11377 |
|
|
|
11378 |
|
|
@end table
|
11379 |
|
|
|
11380 |
|
|
@node GNU/Linux Options
|
11381 |
|
|
@subsection GNU/Linux Options
|
11382 |
|
|
|
11383 |
|
|
These @samp{-m} options are defined for GNU/Linux targets:
|
11384 |
|
|
|
11385 |
|
|
@table @gcctabopt
|
11386 |
|
|
@item -mglibc
|
11387 |
|
|
@opindex mglibc
|
11388 |
|
|
Use the GNU C library instead of uClibc. This is the default except
|
11389 |
|
|
on @samp{*-*-linux-*uclibc*} targets.
|
11390 |
|
|
|
11391 |
|
|
@item -muclibc
|
11392 |
|
|
@opindex muclibc
|
11393 |
|
|
Use uClibc instead of the GNU C library. This is the default on
|
11394 |
|
|
@samp{*-*-linux-*uclibc*} targets.
|
11395 |
|
|
@end table
|
11396 |
|
|
|
11397 |
|
|
@node H8/300 Options
|
11398 |
|
|
@subsection H8/300 Options
|
11399 |
|
|
|
11400 |
|
|
These @samp{-m} options are defined for the H8/300 implementations:
|
11401 |
|
|
|
11402 |
|
|
@table @gcctabopt
|
11403 |
|
|
@item -mrelax
|
11404 |
|
|
@opindex mrelax
|
11405 |
|
|
Shorten some address references at link time, when possible; uses the
|
11406 |
|
|
linker option @option{-relax}. @xref{H8/300,, @code{ld} and the H8/300,
|
11407 |
|
|
ld, Using ld}, for a fuller description.
|
11408 |
|
|
|
11409 |
|
|
@item -mh
|
11410 |
|
|
@opindex mh
|
11411 |
|
|
Generate code for the H8/300H@.
|
11412 |
|
|
|
11413 |
|
|
@item -ms
|
11414 |
|
|
@opindex ms
|
11415 |
|
|
Generate code for the H8S@.
|
11416 |
|
|
|
11417 |
|
|
@item -mn
|
11418 |
|
|
@opindex mn
|
11419 |
|
|
Generate code for the H8S and H8/300H in the normal mode. This switch
|
11420 |
|
|
must be used either with @option{-mh} or @option{-ms}.
|
11421 |
|
|
|
11422 |
|
|
@item -ms2600
|
11423 |
|
|
@opindex ms2600
|
11424 |
|
|
Generate code for the H8S/2600. This switch must be used with @option{-ms}.
|
11425 |
|
|
|
11426 |
|
|
@item -mint32
|
11427 |
|
|
@opindex mint32
|
11428 |
|
|
Make @code{int} data 32 bits by default.
|
11429 |
|
|
|
11430 |
|
|
@item -malign-300
|
11431 |
|
|
@opindex malign-300
|
11432 |
|
|
On the H8/300H and H8S, use the same alignment rules as for the H8/300.
|
11433 |
|
|
The default for the H8/300H and H8S is to align longs and floats on 4
|
11434 |
|
|
byte boundaries.
|
11435 |
|
|
@option{-malign-300} causes them to be aligned on 2 byte boundaries.
|
11436 |
|
|
This option has no effect on the H8/300.
|
11437 |
|
|
@end table
|
11438 |
|
|
|
11439 |
|
|
@node HPPA Options
|
11440 |
|
|
@subsection HPPA Options
|
11441 |
|
|
@cindex HPPA Options
|
11442 |
|
|
|
11443 |
|
|
These @samp{-m} options are defined for the HPPA family of computers:
|
11444 |
|
|
|
11445 |
|
|
@table @gcctabopt
|
11446 |
|
|
@item -march=@var{architecture-type}
|
11447 |
|
|
@opindex march
|
11448 |
|
|
Generate code for the specified architecture. The choices for
|
11449 |
|
|
@var{architecture-type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA
|
11450 |
|
|
1.1, and @samp{2.0} for PA 2.0 processors. Refer to
|
11451 |
|
|
@file{/usr/lib/sched.models} on an HP-UX system to determine the proper
|
11452 |
|
|
architecture option for your machine. Code compiled for lower numbered
|
11453 |
|
|
architectures will run on higher numbered architectures, but not the
|
11454 |
|
|
other way around.
|
11455 |
|
|
|
11456 |
|
|
@item -mpa-risc-1-0
|
11457 |
|
|
@itemx -mpa-risc-1-1
|
11458 |
|
|
@itemx -mpa-risc-2-0
|
11459 |
|
|
@opindex mpa-risc-1-0
|
11460 |
|
|
@opindex mpa-risc-1-1
|
11461 |
|
|
@opindex mpa-risc-2-0
|
11462 |
|
|
Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively.
|
11463 |
|
|
|
11464 |
|
|
@item -mbig-switch
|
11465 |
|
|
@opindex mbig-switch
|
11466 |
|
|
Generate code suitable for big switch tables. Use this option only if
|
11467 |
|
|
the assembler/linker complain about out of range branches within a switch
|
11468 |
|
|
table.
|
11469 |
|
|
|
11470 |
|
|
@item -mjump-in-delay
|
11471 |
|
|
@opindex mjump-in-delay
|
11472 |
|
|
Fill delay slots of function calls with unconditional jump instructions
|
11473 |
|
|
by modifying the return pointer for the function call to be the target
|
11474 |
|
|
of the conditional jump.
|
11475 |
|
|
|
11476 |
|
|
@item -mdisable-fpregs
|
11477 |
|
|
@opindex mdisable-fpregs
|
11478 |
|
|
Prevent floating point registers from being used in any manner. This is
|
11479 |
|
|
necessary for compiling kernels which perform lazy context switching of
|
11480 |
|
|
floating point registers. If you use this option and attempt to perform
|
11481 |
|
|
floating point operations, the compiler will abort.
|
11482 |
|
|
|
11483 |
|
|
@item -mdisable-indexing
|
11484 |
|
|
@opindex mdisable-indexing
|
11485 |
|
|
Prevent the compiler from using indexing address modes. This avoids some
|
11486 |
|
|
rather obscure problems when compiling MIG generated code under MACH@.
|
11487 |
|
|
|
11488 |
|
|
@item -mno-space-regs
|
11489 |
|
|
@opindex mno-space-regs
|
11490 |
|
|
Generate code that assumes the target has no space registers. This allows
|
11491 |
|
|
GCC to generate faster indirect calls and use unscaled index address modes.
|
11492 |
|
|
|
11493 |
|
|
Such code is suitable for level 0 PA systems and kernels.
|
11494 |
|
|
|
11495 |
|
|
@item -mfast-indirect-calls
|
11496 |
|
|
@opindex mfast-indirect-calls
|
11497 |
|
|
Generate code that assumes calls never cross space boundaries. This
|
11498 |
|
|
allows GCC to emit code which performs faster indirect calls.
|
11499 |
|
|
|
11500 |
|
|
This option will not work in the presence of shared libraries or nested
|
11501 |
|
|
functions.
|
11502 |
|
|
|
11503 |
|
|
@item -mfixed-range=@var{register-range}
|
11504 |
|
|
@opindex mfixed-range
|
11505 |
|
|
Generate code treating the given register range as fixed registers.
|
11506 |
|
|
A fixed register is one that the register allocator can not use. This is
|
11507 |
|
|
useful when compiling kernel code. A register range is specified as
|
11508 |
|
|
two registers separated by a dash. Multiple register ranges can be
|
11509 |
|
|
specified separated by a comma.
|
11510 |
|
|
|
11511 |
|
|
@item -mlong-load-store
|
11512 |
|
|
@opindex mlong-load-store
|
11513 |
|
|
Generate 3-instruction load and store sequences as sometimes required by
|
11514 |
|
|
the HP-UX 10 linker. This is equivalent to the @samp{+k} option to
|
11515 |
|
|
the HP compilers.
|
11516 |
|
|
|
11517 |
|
|
@item -mportable-runtime
|
11518 |
|
|
@opindex mportable-runtime
|
11519 |
|
|
Use the portable calling conventions proposed by HP for ELF systems.
|
11520 |
|
|
|
11521 |
|
|
@item -mgas
|
11522 |
|
|
@opindex mgas
|
11523 |
|
|
Enable the use of assembler directives only GAS understands.
|
11524 |
|
|
|
11525 |
|
|
@item -mschedule=@var{cpu-type}
|
11526 |
|
|
@opindex mschedule
|
11527 |
|
|
Schedule code according to the constraints for the machine type
|
11528 |
|
|
@var{cpu-type}. The choices for @var{cpu-type} are @samp{700}
|
11529 |
|
|
@samp{7100}, @samp{7100LC}, @samp{7200}, @samp{7300} and @samp{8000}. Refer
|
11530 |
|
|
to @file{/usr/lib/sched.models} on an HP-UX system to determine the
|
11531 |
|
|
proper scheduling option for your machine. The default scheduling is
|
11532 |
|
|
@samp{8000}.
|
11533 |
|
|
|
11534 |
|
|
@item -mlinker-opt
|
11535 |
|
|
@opindex mlinker-opt
|
11536 |
|
|
Enable the optimization pass in the HP-UX linker. Note this makes symbolic
|
11537 |
|
|
debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9
|
11538 |
|
|
linkers in which they give bogus error messages when linking some programs.
|
11539 |
|
|
|
11540 |
|
|
@item -msoft-float
|
11541 |
|
|
@opindex msoft-float
|
11542 |
|
|
Generate output containing library calls for floating point.
|
11543 |
|
|
@strong{Warning:} the requisite libraries are not available for all HPPA
|
11544 |
|
|
targets. Normally the facilities of the machine's usual C compiler are
|
11545 |
|
|
used, but this cannot be done directly in cross-compilation. You must make
|
11546 |
|
|
your own arrangements to provide suitable library functions for
|
11547 |
|
|
cross-compilation.
|
11548 |
|
|
|
11549 |
|
|
@option{-msoft-float} changes the calling convention in the output file;
|
11550 |
|
|
therefore, it is only useful if you compile @emph{all} of a program with
|
11551 |
|
|
this option. In particular, you need to compile @file{libgcc.a}, the
|
11552 |
|
|
library that comes with GCC, with @option{-msoft-float} in order for
|
11553 |
|
|
this to work.
|
11554 |
|
|
|
11555 |
|
|
@item -msio
|
11556 |
|
|
@opindex msio
|
11557 |
|
|
Generate the predefine, @code{_SIO}, for server IO@. The default is
|
11558 |
|
|
@option{-mwsio}. This generates the predefines, @code{__hp9000s700},
|
11559 |
|
|
@code{__hp9000s700__} and @code{_WSIO}, for workstation IO@. These
|
11560 |
|
|
options are available under HP-UX and HI-UX@.
|
11561 |
|
|
|
11562 |
|
|
@item -mgnu-ld
|
11563 |
|
|
@opindex mgnu-ld
|
11564 |
|
|
Use GNU ld specific options. This passes @option{-shared} to ld when
|
11565 |
|
|
building a shared library. It is the default when GCC is configured,
|
11566 |
|
|
explicitly or implicitly, with the GNU linker. This option does not
|
11567 |
|
|
have any affect on which ld is called, it only changes what parameters
|
11568 |
|
|
are passed to that ld. The ld that is called is determined by the
|
11569 |
|
|
@option{--with-ld} configure option, GCC's program search path, and
|
11570 |
|
|
finally by the user's @env{PATH}. The linker used by GCC can be printed
|
11571 |
|
|
using @samp{which `gcc -print-prog-name=ld`}. This option is only available
|
11572 |
|
|
on the 64 bit HP-UX GCC, i.e.@: configured with @samp{hppa*64*-*-hpux*}.
|
11573 |
|
|
|
11574 |
|
|
@item -mhp-ld
|
11575 |
|
|
@opindex mhp-ld
|
11576 |
|
|
Use HP ld specific options. This passes @option{-b} to ld when building
|
11577 |
|
|
a shared library and passes @option{+Accept TypeMismatch} to ld on all
|
11578 |
|
|
links. It is the default when GCC is configured, explicitly or
|
11579 |
|
|
implicitly, with the HP linker. This option does not have any affect on
|
11580 |
|
|
which ld is called, it only changes what parameters are passed to that
|
11581 |
|
|
ld. The ld that is called is determined by the @option{--with-ld}
|
11582 |
|
|
configure option, GCC's program search path, and finally by the user's
|
11583 |
|
|
@env{PATH}. The linker used by GCC can be printed using @samp{which
|
11584 |
|
|
`gcc -print-prog-name=ld`}. This option is only available on the 64 bit
|
11585 |
|
|
HP-UX GCC, i.e.@: configured with @samp{hppa*64*-*-hpux*}.
|
11586 |
|
|
|
11587 |
|
|
@item -mlong-calls
|
11588 |
|
|
@opindex mno-long-calls
|
11589 |
|
|
Generate code that uses long call sequences. This ensures that a call
|
11590 |
|
|
is always able to reach linker generated stubs. The default is to generate
|
11591 |
|
|
long calls only when the distance from the call site to the beginning
|
11592 |
|
|
of the function or translation unit, as the case may be, exceeds a
|
11593 |
|
|
predefined limit set by the branch type being used. The limits for
|
11594 |
|
|
normal calls are 7,600,000 and 240,000 bytes, respectively for the
|
11595 |
|
|
PA 2.0 and PA 1.X architectures. Sibcalls are always limited at
|
11596 |
|
|
240,000 bytes.
|
11597 |
|
|
|
11598 |
|
|
Distances are measured from the beginning of functions when using the
|
11599 |
|
|
@option{-ffunction-sections} option, or when using the @option{-mgas}
|
11600 |
|
|
and @option{-mno-portable-runtime} options together under HP-UX with
|
11601 |
|
|
the SOM linker.
|
11602 |
|
|
|
11603 |
|
|
It is normally not desirable to use this option as it will degrade
|
11604 |
|
|
performance. However, it may be useful in large applications,
|
11605 |
|
|
particularly when partial linking is used to build the application.
|
11606 |
|
|
|
11607 |
|
|
The types of long calls used depends on the capabilities of the
|
11608 |
|
|
assembler and linker, and the type of code being generated. The
|
11609 |
|
|
impact on systems that support long absolute calls, and long pic
|
11610 |
|
|
symbol-difference or pc-relative calls should be relatively small.
|
11611 |
|
|
However, an indirect call is used on 32-bit ELF systems in pic code
|
11612 |
|
|
and it is quite long.
|
11613 |
|
|
|
11614 |
|
|
@item -munix=@var{unix-std}
|
11615 |
|
|
@opindex march
|
11616 |
|
|
Generate compiler predefines and select a startfile for the specified
|
11617 |
|
|
UNIX standard. The choices for @var{unix-std} are @samp{93}, @samp{95}
|
11618 |
|
|
and @samp{98}. @samp{93} is supported on all HP-UX versions. @samp{95}
|
11619 |
|
|
is available on HP-UX 10.10 and later. @samp{98} is available on HP-UX
|
11620 |
|
|
11.11 and later. The default values are @samp{93} for HP-UX 10.00,
|
11621 |
|
|
@samp{95} for HP-UX 10.10 though to 11.00, and @samp{98} for HP-UX 11.11
|
11622 |
|
|
and later.
|
11623 |
|
|
|
11624 |
|
|
@option{-munix=93} provides the same predefines as GCC 3.3 and 3.4.
|
11625 |
|
|
@option{-munix=95} provides additional predefines for @code{XOPEN_UNIX}
|
11626 |
|
|
and @code{_XOPEN_SOURCE_EXTENDED}, and the startfile @file{unix95.o}.
|
11627 |
|
|
@option{-munix=98} provides additional predefines for @code{_XOPEN_UNIX},
|
11628 |
|
|
@code{_XOPEN_SOURCE_EXTENDED}, @code{_INCLUDE__STDC_A1_SOURCE} and
|
11629 |
|
|
@code{_INCLUDE_XOPEN_SOURCE_500}, and the startfile @file{unix98.o}.
|
11630 |
|
|
|
11631 |
|
|
It is @emph{important} to note that this option changes the interfaces
|
11632 |
|
|
for various library routines. It also affects the operational behavior
|
11633 |
|
|
of the C library. Thus, @emph{extreme} care is needed in using this
|
11634 |
|
|
option.
|
11635 |
|
|
|
11636 |
|
|
Library code that is intended to operate with more than one UNIX
|
11637 |
|
|
standard must test, set and restore the variable @var{__xpg4_extended_mask}
|
11638 |
|
|
as appropriate. Most GNU software doesn't provide this capability.
|
11639 |
|
|
|
11640 |
|
|
@item -nolibdld
|
11641 |
|
|
@opindex nolibdld
|
11642 |
|
|
Suppress the generation of link options to search libdld.sl when the
|
11643 |
|
|
@option{-static} option is specified on HP-UX 10 and later.
|
11644 |
|
|
|
11645 |
|
|
@item -static
|
11646 |
|
|
@opindex static
|
11647 |
|
|
The HP-UX implementation of setlocale in libc has a dependency on
|
11648 |
|
|
libdld.sl. There isn't an archive version of libdld.sl. Thus,
|
11649 |
|
|
when the @option{-static} option is specified, special link options
|
11650 |
|
|
are needed to resolve this dependency.
|
11651 |
|
|
|
11652 |
|
|
On HP-UX 10 and later, the GCC driver adds the necessary options to
|
11653 |
|
|
link with libdld.sl when the @option{-static} option is specified.
|
11654 |
|
|
This causes the resulting binary to be dynamic. On the 64-bit port,
|
11655 |
|
|
the linkers generate dynamic binaries by default in any case. The
|
11656 |
|
|
@option{-nolibdld} option can be used to prevent the GCC driver from
|
11657 |
|
|
adding these link options.
|
11658 |
|
|
|
11659 |
|
|
@item -threads
|
11660 |
|
|
@opindex threads
|
11661 |
|
|
Add support for multithreading with the @dfn{dce thread} library
|
11662 |
|
|
under HP-UX@. This option sets flags for both the preprocessor and
|
11663 |
|
|
linker.
|
11664 |
|
|
@end table
|
11665 |
|
|
|
11666 |
|
|
@node i386 and x86-64 Options
|
11667 |
|
|
@subsection Intel 386 and AMD x86-64 Options
|
11668 |
|
|
@cindex i386 Options
|
11669 |
|
|
@cindex x86-64 Options
|
11670 |
|
|
@cindex Intel 386 Options
|
11671 |
|
|
@cindex AMD x86-64 Options
|
11672 |
|
|
|
11673 |
|
|
These @samp{-m} options are defined for the i386 and x86-64 family of
|
11674 |
|
|
computers:
|
11675 |
|
|
|
11676 |
|
|
@table @gcctabopt
|
11677 |
|
|
@item -mtune=@var{cpu-type}
|
11678 |
|
|
@opindex mtune
|
11679 |
|
|
Tune to @var{cpu-type} everything applicable about the generated code, except
|
11680 |
|
|
for the ABI and the set of available instructions. The choices for
|
11681 |
|
|
@var{cpu-type} are:
|
11682 |
|
|
@table @emph
|
11683 |
|
|
@item generic
|
11684 |
|
|
Produce code optimized for the most common IA32/AMD64/EM64T processors.
|
11685 |
|
|
If you know the CPU on which your code will run, then you should use
|
11686 |
|
|
the corresponding @option{-mtune} option instead of
|
11687 |
|
|
@option{-mtune=generic}. But, if you do not know exactly what CPU users
|
11688 |
|
|
of your application will have, then you should use this option.
|
11689 |
|
|
|
11690 |
|
|
As new processors are deployed in the marketplace, the behavior of this
|
11691 |
|
|
option will change. Therefore, if you upgrade to a newer version of
|
11692 |
|
|
GCC, the code generated option will change to reflect the processors
|
11693 |
|
|
that were most common when that version of GCC was released.
|
11694 |
|
|
|
11695 |
|
|
There is no @option{-march=generic} option because @option{-march}
|
11696 |
|
|
indicates the instruction set the compiler can use, and there is no
|
11697 |
|
|
generic instruction set applicable to all processors. In contrast,
|
11698 |
|
|
@option{-mtune} indicates the processor (or, in this case, collection of
|
11699 |
|
|
processors) for which the code is optimized.
|
11700 |
|
|
@item native
|
11701 |
|
|
This selects the CPU to tune for at compilation time by determining
|
11702 |
|
|
the processor type of the compiling machine. Using @option{-mtune=native}
|
11703 |
|
|
will produce code optimized for the local machine under the constraints
|
11704 |
|
|
of the selected instruction set. Using @option{-march=native} will
|
11705 |
|
|
enable all instruction subsets supported by the local machine (hence
|
11706 |
|
|
the result might not run on different machines).
|
11707 |
|
|
@item i386
|
11708 |
|
|
Original Intel's i386 CPU@.
|
11709 |
|
|
@item i486
|
11710 |
|
|
Intel's i486 CPU@. (No scheduling is implemented for this chip.)
|
11711 |
|
|
@item i586, pentium
|
11712 |
|
|
Intel Pentium CPU with no MMX support.
|
11713 |
|
|
@item pentium-mmx
|
11714 |
|
|
Intel PentiumMMX CPU based on Pentium core with MMX instruction set support.
|
11715 |
|
|
@item pentiumpro
|
11716 |
|
|
Intel PentiumPro CPU@.
|
11717 |
|
|
@item i686
|
11718 |
|
|
Same as @code{generic}, but when used as @code{march} option, PentiumPro
|
11719 |
|
|
instruction set will be used, so the code will run on all i686 family chips.
|
11720 |
|
|
@item pentium2
|
11721 |
|
|
Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support.
|
11722 |
|
|
@item pentium3, pentium3m
|
11723 |
|
|
Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set
|
11724 |
|
|
support.
|
11725 |
|
|
@item pentium-m
|
11726 |
|
|
Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set
|
11727 |
|
|
support. Used by Centrino notebooks.
|
11728 |
|
|
@item pentium4, pentium4m
|
11729 |
|
|
Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support.
|
11730 |
|
|
@item prescott
|
11731 |
|
|
Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction
|
11732 |
|
|
set support.
|
11733 |
|
|
@item nocona
|
11734 |
|
|
Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE,
|
11735 |
|
|
SSE2 and SSE3 instruction set support.
|
11736 |
|
|
@item core2
|
11737 |
|
|
Intel Core2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3
|
11738 |
|
|
instruction set support.
|
11739 |
|
|
@item atom
|
11740 |
|
|
Intel Atom CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3
|
11741 |
|
|
instruction set support.
|
11742 |
|
|
@item k6
|
11743 |
|
|
AMD K6 CPU with MMX instruction set support.
|
11744 |
|
|
@item k6-2, k6-3
|
11745 |
|
|
Improved versions of AMD K6 CPU with MMX and 3DNow!@: instruction set support.
|
11746 |
|
|
@item athlon, athlon-tbird
|
11747 |
|
|
AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow!@: and SSE prefetch instructions
|
11748 |
|
|
support.
|
11749 |
|
|
@item athlon-4, athlon-xp, athlon-mp
|
11750 |
|
|
Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow!@: and full SSE
|
11751 |
|
|
instruction set support.
|
11752 |
|
|
@item k8, opteron, athlon64, athlon-fx
|
11753 |
|
|
AMD K8 core based CPUs with x86-64 instruction set support. (This supersets
|
11754 |
|
|
MMX, SSE, SSE2, 3DNow!, enhanced 3DNow!@: and 64-bit instruction set extensions.)
|
11755 |
|
|
@item k8-sse3, opteron-sse3, athlon64-sse3
|
11756 |
|
|
Improved versions of k8, opteron and athlon64 with SSE3 instruction set support.
|
11757 |
|
|
@item amdfam10, barcelona
|
11758 |
|
|
AMD Family 10h core based CPUs with x86-64 instruction set support. (This
|
11759 |
|
|
supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!, enhanced 3DNow!, ABM and 64-bit
|
11760 |
|
|
instruction set extensions.)
|
11761 |
|
|
@item winchip-c6
|
11762 |
|
|
IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction
|
11763 |
|
|
set support.
|
11764 |
|
|
@item winchip2
|
11765 |
|
|
IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3DNow!@:
|
11766 |
|
|
instruction set support.
|
11767 |
|
|
@item c3
|
11768 |
|
|
Via C3 CPU with MMX and 3DNow!@: instruction set support. (No scheduling is
|
11769 |
|
|
implemented for this chip.)
|
11770 |
|
|
@item c3-2
|
11771 |
|
|
Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is
|
11772 |
|
|
implemented for this chip.)
|
11773 |
|
|
@item geode
|
11774 |
|
|
Embedded AMD CPU with MMX and 3DNow!@: instruction set support.
|
11775 |
|
|
@end table
|
11776 |
|
|
|
11777 |
|
|
While picking a specific @var{cpu-type} will schedule things appropriately
|
11778 |
|
|
for that particular chip, the compiler will not generate any code that
|
11779 |
|
|
does not run on the i386 without the @option{-march=@var{cpu-type}} option
|
11780 |
|
|
being used.
|
11781 |
|
|
|
11782 |
|
|
@item -march=@var{cpu-type}
|
11783 |
|
|
@opindex march
|
11784 |
|
|
Generate instructions for the machine type @var{cpu-type}. The choices
|
11785 |
|
|
for @var{cpu-type} are the same as for @option{-mtune}. Moreover,
|
11786 |
|
|
specifying @option{-march=@var{cpu-type}} implies @option{-mtune=@var{cpu-type}}.
|
11787 |
|
|
|
11788 |
|
|
@item -mcpu=@var{cpu-type}
|
11789 |
|
|
@opindex mcpu
|
11790 |
|
|
A deprecated synonym for @option{-mtune}.
|
11791 |
|
|
|
11792 |
|
|
@item -mfpmath=@var{unit}
|
11793 |
|
|
@opindex mfpmath
|
11794 |
|
|
Generate floating point arithmetics for selected unit @var{unit}. The choices
|
11795 |
|
|
for @var{unit} are:
|
11796 |
|
|
|
11797 |
|
|
@table @samp
|
11798 |
|
|
@item 387
|
11799 |
|
|
Use the standard 387 floating point coprocessor present majority of chips and
|
11800 |
|
|
emulated otherwise. Code compiled with this option will run almost everywhere.
|
11801 |
|
|
The temporary results are computed in 80bit precision instead of precision
|
11802 |
|
|
specified by the type resulting in slightly different results compared to most
|
11803 |
|
|
of other chips. See @option{-ffloat-store} for more detailed description.
|
11804 |
|
|
|
11805 |
|
|
This is the default choice for i386 compiler.
|
11806 |
|
|
|
11807 |
|
|
@item sse
|
11808 |
|
|
Use scalar floating point instructions present in the SSE instruction set.
|
11809 |
|
|
This instruction set is supported by Pentium3 and newer chips, in the AMD line
|
11810 |
|
|
by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE
|
11811 |
|
|
instruction set supports only single precision arithmetics, thus the double and
|
11812 |
|
|
extended precision arithmetics is still done using 387. Later version, present
|
11813 |
|
|
only in Pentium4 and the future AMD x86-64 chips supports double precision
|
11814 |
|
|
arithmetics too.
|
11815 |
|
|
|
11816 |
|
|
For the i386 compiler, you need to use @option{-march=@var{cpu-type}}, @option{-msse}
|
11817 |
|
|
or @option{-msse2} switches to enable SSE extensions and make this option
|
11818 |
|
|
effective. For the x86-64 compiler, these extensions are enabled by default.
|
11819 |
|
|
|
11820 |
|
|
The resulting code should be considerably faster in the majority of cases and avoid
|
11821 |
|
|
the numerical instability problems of 387 code, but may break some existing
|
11822 |
|
|
code that expects temporaries to be 80bit.
|
11823 |
|
|
|
11824 |
|
|
This is the default choice for the x86-64 compiler.
|
11825 |
|
|
|
11826 |
|
|
@item sse,387
|
11827 |
|
|
@itemx sse+387
|
11828 |
|
|
@itemx both
|
11829 |
|
|
Attempt to utilize both instruction sets at once. This effectively double the
|
11830 |
|
|
amount of available registers and on chips with separate execution units for
|
11831 |
|
|
387 and SSE the execution resources too. Use this option with care, as it is
|
11832 |
|
|
still experimental, because the GCC register allocator does not model separate
|
11833 |
|
|
functional units well resulting in instable performance.
|
11834 |
|
|
@end table
|
11835 |
|
|
|
11836 |
|
|
@item -masm=@var{dialect}
|
11837 |
|
|
@opindex masm=@var{dialect}
|
11838 |
|
|
Output asm instructions using selected @var{dialect}. Supported
|
11839 |
|
|
choices are @samp{intel} or @samp{att} (the default one). Darwin does
|
11840 |
|
|
not support @samp{intel}.
|
11841 |
|
|
|
11842 |
|
|
@item -mieee-fp
|
11843 |
|
|
@itemx -mno-ieee-fp
|
11844 |
|
|
@opindex mieee-fp
|
11845 |
|
|
@opindex mno-ieee-fp
|
11846 |
|
|
Control whether or not the compiler uses IEEE floating point
|
11847 |
|
|
comparisons. These handle correctly the case where the result of a
|
11848 |
|
|
comparison is unordered.
|
11849 |
|
|
|
11850 |
|
|
@item -msoft-float
|
11851 |
|
|
@opindex msoft-float
|
11852 |
|
|
Generate output containing library calls for floating point.
|
11853 |
|
|
@strong{Warning:} the requisite libraries are not part of GCC@.
|
11854 |
|
|
Normally the facilities of the machine's usual C compiler are used, but
|
11855 |
|
|
this can't be done directly in cross-compilation. You must make your
|
11856 |
|
|
own arrangements to provide suitable library functions for
|
11857 |
|
|
cross-compilation.
|
11858 |
|
|
|
11859 |
|
|
On machines where a function returns floating point results in the 80387
|
11860 |
|
|
register stack, some floating point opcodes may be emitted even if
|
11861 |
|
|
@option{-msoft-float} is used.
|
11862 |
|
|
|
11863 |
|
|
@item -mno-fp-ret-in-387
|
11864 |
|
|
@opindex mno-fp-ret-in-387
|
11865 |
|
|
Do not use the FPU registers for return values of functions.
|
11866 |
|
|
|
11867 |
|
|
The usual calling convention has functions return values of types
|
11868 |
|
|
@code{float} and @code{double} in an FPU register, even if there
|
11869 |
|
|
is no FPU@. The idea is that the operating system should emulate
|
11870 |
|
|
an FPU@.
|
11871 |
|
|
|
11872 |
|
|
The option @option{-mno-fp-ret-in-387} causes such values to be returned
|
11873 |
|
|
in ordinary CPU registers instead.
|
11874 |
|
|
|
11875 |
|
|
@item -mno-fancy-math-387
|
11876 |
|
|
@opindex mno-fancy-math-387
|
11877 |
|
|
Some 387 emulators do not support the @code{sin}, @code{cos} and
|
11878 |
|
|
@code{sqrt} instructions for the 387. Specify this option to avoid
|
11879 |
|
|
generating those instructions. This option is the default on FreeBSD,
|
11880 |
|
|
OpenBSD and NetBSD@. This option is overridden when @option{-march}
|
11881 |
|
|
indicates that the target cpu will always have an FPU and so the
|
11882 |
|
|
instruction will not need emulation. As of revision 2.6.1, these
|
11883 |
|
|
instructions are not generated unless you also use the
|
11884 |
|
|
@option{-funsafe-math-optimizations} switch.
|
11885 |
|
|
|
11886 |
|
|
@item -malign-double
|
11887 |
|
|
@itemx -mno-align-double
|
11888 |
|
|
@opindex malign-double
|
11889 |
|
|
@opindex mno-align-double
|
11890 |
|
|
Control whether GCC aligns @code{double}, @code{long double}, and
|
11891 |
|
|
@code{long long} variables on a two word boundary or a one word
|
11892 |
|
|
boundary. Aligning @code{double} variables on a two word boundary will
|
11893 |
|
|
produce code that runs somewhat faster on a @samp{Pentium} at the
|
11894 |
|
|
expense of more memory.
|
11895 |
|
|
|
11896 |
|
|
On x86-64, @option{-malign-double} is enabled by default.
|
11897 |
|
|
|
11898 |
|
|
@strong{Warning:} if you use the @option{-malign-double} switch,
|
11899 |
|
|
structures containing the above types will be aligned differently than
|
11900 |
|
|
the published application binary interface specifications for the 386
|
11901 |
|
|
and will not be binary compatible with structures in code compiled
|
11902 |
|
|
without that switch.
|
11903 |
|
|
|
11904 |
|
|
@item -m96bit-long-double
|
11905 |
|
|
@itemx -m128bit-long-double
|
11906 |
|
|
@opindex m96bit-long-double
|
11907 |
|
|
@opindex m128bit-long-double
|
11908 |
|
|
These switches control the size of @code{long double} type. The i386
|
11909 |
|
|
application binary interface specifies the size to be 96 bits,
|
11910 |
|
|
so @option{-m96bit-long-double} is the default in 32 bit mode.
|
11911 |
|
|
|
11912 |
|
|
Modern architectures (Pentium and newer) would prefer @code{long double}
|
11913 |
|
|
to be aligned to an 8 or 16 byte boundary. In arrays or structures
|
11914 |
|
|
conforming to the ABI, this would not be possible. So specifying a
|
11915 |
|
|
@option{-m128bit-long-double} will align @code{long double}
|
11916 |
|
|
to a 16 byte boundary by padding the @code{long double} with an additional
|
11917 |
|
|
32 bit zero.
|
11918 |
|
|
|
11919 |
|
|
In the x86-64 compiler, @option{-m128bit-long-double} is the default choice as
|
11920 |
|
|
its ABI specifies that @code{long double} is to be aligned on 16 byte boundary.
|
11921 |
|
|
|
11922 |
|
|
Notice that neither of these options enable any extra precision over the x87
|
11923 |
|
|
standard of 80 bits for a @code{long double}.
|
11924 |
|
|
|
11925 |
|
|
@strong{Warning:} if you override the default value for your target ABI, the
|
11926 |
|
|
structures and arrays containing @code{long double} variables will change
|
11927 |
|
|
their size as well as function calling convention for function taking
|
11928 |
|
|
@code{long double} will be modified. Hence they will not be binary
|
11929 |
|
|
compatible with arrays or structures in code compiled without that switch.
|
11930 |
|
|
|
11931 |
|
|
@item -mlarge-data-threshold=@var{number}
|
11932 |
|
|
@opindex mlarge-data-threshold=@var{number}
|
11933 |
|
|
When @option{-mcmodel=medium} is specified, the data greater than
|
11934 |
|
|
@var{threshold} are placed in large data section. This value must be the
|
11935 |
|
|
same across all object linked into the binary and defaults to 65535.
|
11936 |
|
|
|
11937 |
|
|
@item -mrtd
|
11938 |
|
|
@opindex mrtd
|
11939 |
|
|
Use a different function-calling convention, in which functions that
|
11940 |
|
|
take a fixed number of arguments return with the @code{ret} @var{num}
|
11941 |
|
|
instruction, which pops their arguments while returning. This saves one
|
11942 |
|
|
instruction in the caller since there is no need to pop the arguments
|
11943 |
|
|
there.
|
11944 |
|
|
|
11945 |
|
|
You can specify that an individual function is called with this calling
|
11946 |
|
|
sequence with the function attribute @samp{stdcall}. You can also
|
11947 |
|
|
override the @option{-mrtd} option by using the function attribute
|
11948 |
|
|
@samp{cdecl}. @xref{Function Attributes}.
|
11949 |
|
|
|
11950 |
|
|
@strong{Warning:} this calling convention is incompatible with the one
|
11951 |
|
|
normally used on Unix, so you cannot use it if you need to call
|
11952 |
|
|
libraries compiled with the Unix compiler.
|
11953 |
|
|
|
11954 |
|
|
Also, you must provide function prototypes for all functions that
|
11955 |
|
|
take variable numbers of arguments (including @code{printf});
|
11956 |
|
|
otherwise incorrect code will be generated for calls to those
|
11957 |
|
|
functions.
|
11958 |
|
|
|
11959 |
|
|
In addition, seriously incorrect code will result if you call a
|
11960 |
|
|
function with too many arguments. (Normally, extra arguments are
|
11961 |
|
|
harmlessly ignored.)
|
11962 |
|
|
|
11963 |
|
|
@item -mregparm=@var{num}
|
11964 |
|
|
@opindex mregparm
|
11965 |
|
|
Control how many registers are used to pass integer arguments. By
|
11966 |
|
|
default, no registers are used to pass arguments, and at most 3
|
11967 |
|
|
registers can be used. You can control this behavior for a specific
|
11968 |
|
|
function by using the function attribute @samp{regparm}.
|
11969 |
|
|
@xref{Function Attributes}.
|
11970 |
|
|
|
11971 |
|
|
@strong{Warning:} if you use this switch, and
|
11972 |
|
|
@var{num} is nonzero, then you must build all modules with the same
|
11973 |
|
|
value, including any libraries. This includes the system libraries and
|
11974 |
|
|
startup modules.
|
11975 |
|
|
|
11976 |
|
|
@item -msseregparm
|
11977 |
|
|
@opindex msseregparm
|
11978 |
|
|
Use SSE register passing conventions for float and double arguments
|
11979 |
|
|
and return values. You can control this behavior for a specific
|
11980 |
|
|
function by using the function attribute @samp{sseregparm}.
|
11981 |
|
|
@xref{Function Attributes}.
|
11982 |
|
|
|
11983 |
|
|
@strong{Warning:} if you use this switch then you must build all
|
11984 |
|
|
modules with the same value, including any libraries. This includes
|
11985 |
|
|
the system libraries and startup modules.
|
11986 |
|
|
|
11987 |
|
|
@item -mpc32
|
11988 |
|
|
@itemx -mpc64
|
11989 |
|
|
@itemx -mpc80
|
11990 |
|
|
@opindex mpc32
|
11991 |
|
|
@opindex mpc64
|
11992 |
|
|
@opindex mpc80
|
11993 |
|
|
|
11994 |
|
|
Set 80387 floating-point precision to 32, 64 or 80 bits. When @option{-mpc32}
|
11995 |
|
|
is specified, the significands of results of floating-point operations are
|
11996 |
|
|
rounded to 24 bits (single precision); @option{-mpc64} rounds the
|
11997 |
|
|
significands of results of floating-point operations to 53 bits (double
|
11998 |
|
|
precision) and @option{-mpc80} rounds the significands of results of
|
11999 |
|
|
floating-point operations to 64 bits (extended double precision), which is
|
12000 |
|
|
the default. When this option is used, floating-point operations in higher
|
12001 |
|
|
precisions are not available to the programmer without setting the FPU
|
12002 |
|
|
control word explicitly.
|
12003 |
|
|
|
12004 |
|
|
Setting the rounding of floating-point operations to less than the default
|
12005 |
|
|
80 bits can speed some programs by 2% or more. Note that some mathematical
|
12006 |
|
|
libraries assume that extended precision (80 bit) floating-point operations
|
12007 |
|
|
are enabled by default; routines in such libraries could suffer significant
|
12008 |
|
|
loss of accuracy, typically through so-called "catastrophic cancellation",
|
12009 |
|
|
when this option is used to set the precision to less than extended precision.
|
12010 |
|
|
|
12011 |
|
|
@item -mstackrealign
|
12012 |
|
|
@opindex mstackrealign
|
12013 |
|
|
Realign the stack at entry. On the Intel x86, the @option{-mstackrealign}
|
12014 |
|
|
option will generate an alternate prologue and epilogue that realigns the
|
12015 |
|
|
runtime stack if necessary. This supports mixing legacy codes that keep
|
12016 |
|
|
a 4-byte aligned stack with modern codes that keep a 16-byte stack for
|
12017 |
|
|
SSE compatibility. See also the attribute @code{force_align_arg_pointer},
|
12018 |
|
|
applicable to individual functions.
|
12019 |
|
|
|
12020 |
|
|
@item -mpreferred-stack-boundary=@var{num}
|
12021 |
|
|
@opindex mpreferred-stack-boundary
|
12022 |
|
|
Attempt to keep the stack boundary aligned to a 2 raised to @var{num}
|
12023 |
|
|
byte boundary. If @option{-mpreferred-stack-boundary} is not specified,
|
12024 |
|
|
the default is 4 (16 bytes or 128 bits).
|
12025 |
|
|
|
12026 |
|
|
@item -mincoming-stack-boundary=@var{num}
|
12027 |
|
|
@opindex mincoming-stack-boundary
|
12028 |
|
|
Assume the incoming stack is aligned to a 2 raised to @var{num} byte
|
12029 |
|
|
boundary. If @option{-mincoming-stack-boundary} is not specified,
|
12030 |
|
|
the one specified by @option{-mpreferred-stack-boundary} will be used.
|
12031 |
|
|
|
12032 |
|
|
On Pentium and PentiumPro, @code{double} and @code{long double} values
|
12033 |
|
|
should be aligned to an 8 byte boundary (see @option{-malign-double}) or
|
12034 |
|
|
suffer significant run time performance penalties. On Pentium III, the
|
12035 |
|
|
Streaming SIMD Extension (SSE) data type @code{__m128} may not work
|
12036 |
|
|
properly if it is not 16 byte aligned.
|
12037 |
|
|
|
12038 |
|
|
To ensure proper alignment of this values on the stack, the stack boundary
|
12039 |
|
|
must be as aligned as that required by any value stored on the stack.
|
12040 |
|
|
Further, every function must be generated such that it keeps the stack
|
12041 |
|
|
aligned. Thus calling a function compiled with a higher preferred
|
12042 |
|
|
stack boundary from a function compiled with a lower preferred stack
|
12043 |
|
|
boundary will most likely misalign the stack. It is recommended that
|
12044 |
|
|
libraries that use callbacks always use the default setting.
|
12045 |
|
|
|
12046 |
|
|
This extra alignment does consume extra stack space, and generally
|
12047 |
|
|
increases code size. Code that is sensitive to stack space usage, such
|
12048 |
|
|
as embedded systems and operating system kernels, may want to reduce the
|
12049 |
|
|
preferred alignment to @option{-mpreferred-stack-boundary=2}.
|
12050 |
|
|
|
12051 |
|
|
@item -mmmx
|
12052 |
|
|
@itemx -mno-mmx
|
12053 |
|
|
@itemx -msse
|
12054 |
|
|
@itemx -mno-sse
|
12055 |
|
|
@itemx -msse2
|
12056 |
|
|
@itemx -mno-sse2
|
12057 |
|
|
@itemx -msse3
|
12058 |
|
|
@itemx -mno-sse3
|
12059 |
|
|
@itemx -mssse3
|
12060 |
|
|
@itemx -mno-ssse3
|
12061 |
|
|
@itemx -msse4.1
|
12062 |
|
|
@itemx -mno-sse4.1
|
12063 |
|
|
@itemx -msse4.2
|
12064 |
|
|
@itemx -mno-sse4.2
|
12065 |
|
|
@itemx -msse4
|
12066 |
|
|
@itemx -mno-sse4
|
12067 |
|
|
@itemx -mavx
|
12068 |
|
|
@itemx -mno-avx
|
12069 |
|
|
@itemx -maes
|
12070 |
|
|
@itemx -mno-aes
|
12071 |
|
|
@itemx -mpclmul
|
12072 |
|
|
@itemx -mno-pclmul
|
12073 |
|
|
@itemx -msse4a
|
12074 |
|
|
@itemx -mno-sse4a
|
12075 |
|
|
@itemx -mfma4
|
12076 |
|
|
@itemx -mno-fma4
|
12077 |
|
|
@itemx -mxop
|
12078 |
|
|
@itemx -mno-xop
|
12079 |
|
|
@itemx -mlwp
|
12080 |
|
|
@itemx -mno-lwp
|
12081 |
|
|
@itemx -m3dnow
|
12082 |
|
|
@itemx -mno-3dnow
|
12083 |
|
|
@itemx -mpopcnt
|
12084 |
|
|
@itemx -mno-popcnt
|
12085 |
|
|
@itemx -mabm
|
12086 |
|
|
@itemx -mno-abm
|
12087 |
|
|
@opindex mmmx
|
12088 |
|
|
@opindex mno-mmx
|
12089 |
|
|
@opindex msse
|
12090 |
|
|
@opindex mno-sse
|
12091 |
|
|
@opindex m3dnow
|
12092 |
|
|
@opindex mno-3dnow
|
12093 |
|
|
These switches enable or disable the use of instructions in the MMX,
|
12094 |
|
|
SSE, SSE2, SSE3, SSSE3, SSE4.1, AVX, AES, PCLMUL, SSE4A, FMA4, XOP,
|
12095 |
|
|
LWP, ABM or 3DNow!@: extended instruction sets.
|
12096 |
|
|
These extensions are also available as built-in functions: see
|
12097 |
|
|
@ref{X86 Built-in Functions}, for details of the functions enabled and
|
12098 |
|
|
disabled by these switches.
|
12099 |
|
|
|
12100 |
|
|
To have SSE/SSE2 instructions generated automatically from floating-point
|
12101 |
|
|
code (as opposed to 387 instructions), see @option{-mfpmath=sse}.
|
12102 |
|
|
|
12103 |
|
|
GCC depresses SSEx instructions when @option{-mavx} is used. Instead, it
|
12104 |
|
|
generates new AVX instructions or AVX equivalence for all SSEx instructions
|
12105 |
|
|
when needed.
|
12106 |
|
|
|
12107 |
|
|
These options will enable GCC to use these extended instructions in
|
12108 |
|
|
generated code, even without @option{-mfpmath=sse}. Applications which
|
12109 |
|
|
perform runtime CPU detection must compile separate files for each
|
12110 |
|
|
supported architecture, using the appropriate flags. In particular,
|
12111 |
|
|
the file containing the CPU detection code should be compiled without
|
12112 |
|
|
these options.
|
12113 |
|
|
|
12114 |
|
|
@item -mfused-madd
|
12115 |
|
|
@itemx -mno-fused-madd
|
12116 |
|
|
@opindex mfused-madd
|
12117 |
|
|
@opindex mno-fused-madd
|
12118 |
|
|
Do (don't) generate code that uses the fused multiply/add or multiply/subtract
|
12119 |
|
|
instructions. The default is to use these instructions.
|
12120 |
|
|
|
12121 |
|
|
@item -mcld
|
12122 |
|
|
@opindex mcld
|
12123 |
|
|
This option instructs GCC to emit a @code{cld} instruction in the prologue
|
12124 |
|
|
of functions that use string instructions. String instructions depend on
|
12125 |
|
|
the DF flag to select between autoincrement or autodecrement mode. While the
|
12126 |
|
|
ABI specifies the DF flag to be cleared on function entry, some operating
|
12127 |
|
|
systems violate this specification by not clearing the DF flag in their
|
12128 |
|
|
exception dispatchers. The exception handler can be invoked with the DF flag
|
12129 |
|
|
set which leads to wrong direction mode, when string instructions are used.
|
12130 |
|
|
This option can be enabled by default on 32-bit x86 targets by configuring
|
12131 |
|
|
GCC with the @option{--enable-cld} configure option. Generation of @code{cld}
|
12132 |
|
|
instructions can be suppressed with the @option{-mno-cld} compiler option
|
12133 |
|
|
in this case.
|
12134 |
|
|
|
12135 |
|
|
@item -mcx16
|
12136 |
|
|
@opindex mcx16
|
12137 |
|
|
This option will enable GCC to use CMPXCHG16B instruction in generated code.
|
12138 |
|
|
CMPXCHG16B allows for atomic operations on 128-bit double quadword (or oword)
|
12139 |
|
|
data types. This is useful for high resolution counters that could be updated
|
12140 |
|
|
by multiple processors (or cores). This instruction is generated as part of
|
12141 |
|
|
atomic built-in functions: see @ref{Atomic Builtins} for details.
|
12142 |
|
|
|
12143 |
|
|
@item -msahf
|
12144 |
|
|
@opindex msahf
|
12145 |
|
|
This option will enable GCC to use SAHF instruction in generated 64-bit code.
|
12146 |
|
|
Early Intel CPUs with Intel 64 lacked LAHF and SAHF instructions supported
|
12147 |
|
|
by AMD64 until introduction of Pentium 4 G1 step in December 2005. LAHF and
|
12148 |
|
|
SAHF are load and store instructions, respectively, for certain status flags.
|
12149 |
|
|
In 64-bit mode, SAHF instruction is used to optimize @code{fmod}, @code{drem}
|
12150 |
|
|
or @code{remainder} built-in functions: see @ref{Other Builtins} for details.
|
12151 |
|
|
|
12152 |
|
|
@item -mmovbe
|
12153 |
|
|
@opindex mmovbe
|
12154 |
|
|
This option will enable GCC to use movbe instruction to implement
|
12155 |
|
|
@code{__builtin_bswap32} and @code{__builtin_bswap64}.
|
12156 |
|
|
|
12157 |
|
|
@item -mcrc32
|
12158 |
|
|
@opindex mcrc32
|
12159 |
|
|
This option will enable built-in functions, @code{__builtin_ia32_crc32qi},
|
12160 |
|
|
@code{__builtin_ia32_crc32hi}. @code{__builtin_ia32_crc32si} and
|
12161 |
|
|
@code{__builtin_ia32_crc32di} to generate the crc32 machine instruction.
|
12162 |
|
|
|
12163 |
|
|
@item -mrecip
|
12164 |
|
|
@opindex mrecip
|
12165 |
|
|
This option will enable GCC to use RCPSS and RSQRTSS instructions (and their
|
12166 |
|
|
vectorized variants RCPPS and RSQRTPS) with an additional Newton-Raphson step
|
12167 |
|
|
to increase precision instead of DIVSS and SQRTSS (and their vectorized
|
12168 |
|
|
variants) for single precision floating point arguments. These instructions
|
12169 |
|
|
are generated only when @option{-funsafe-math-optimizations} is enabled
|
12170 |
|
|
together with @option{-finite-math-only} and @option{-fno-trapping-math}.
|
12171 |
|
|
Note that while the throughput of the sequence is higher than the throughput
|
12172 |
|
|
of the non-reciprocal instruction, the precision of the sequence can be
|
12173 |
|
|
decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994).
|
12174 |
|
|
|
12175 |
|
|
Note that GCC implements 1.0f/sqrtf(x) in terms of RSQRTSS (or RSQRTPS)
|
12176 |
|
|
already with @option{-ffast-math} (or the above option combination), and
|
12177 |
|
|
doesn't need @option{-mrecip}.
|
12178 |
|
|
|
12179 |
|
|
@item -mveclibabi=@var{type}
|
12180 |
|
|
@opindex mveclibabi
|
12181 |
|
|
Specifies the ABI type to use for vectorizing intrinsics using an
|
12182 |
|
|
external library. Supported types are @code{svml} for the Intel short
|
12183 |
|
|
vector math library and @code{acml} for the AMD math core library style
|
12184 |
|
|
of interfacing. GCC will currently emit calls to @code{vmldExp2},
|
12185 |
|
|
@code{vmldLn2}, @code{vmldLog102}, @code{vmldLog102}, @code{vmldPow2},
|
12186 |
|
|
@code{vmldTanh2}, @code{vmldTan2}, @code{vmldAtan2}, @code{vmldAtanh2},
|
12187 |
|
|
@code{vmldCbrt2}, @code{vmldSinh2}, @code{vmldSin2}, @code{vmldAsinh2},
|
12188 |
|
|
@code{vmldAsin2}, @code{vmldCosh2}, @code{vmldCos2}, @code{vmldAcosh2},
|
12189 |
|
|
@code{vmldAcos2}, @code{vmlsExp4}, @code{vmlsLn4}, @code{vmlsLog104},
|
12190 |
|
|
@code{vmlsLog104}, @code{vmlsPow4}, @code{vmlsTanh4}, @code{vmlsTan4},
|
12191 |
|
|
@code{vmlsAtan4}, @code{vmlsAtanh4}, @code{vmlsCbrt4}, @code{vmlsSinh4},
|
12192 |
|
|
@code{vmlsSin4}, @code{vmlsAsinh4}, @code{vmlsAsin4}, @code{vmlsCosh4},
|
12193 |
|
|
@code{vmlsCos4}, @code{vmlsAcosh4} and @code{vmlsAcos4} for corresponding
|
12194 |
|
|
function type when @option{-mveclibabi=svml} is used and @code{__vrd2_sin},
|
12195 |
|
|
@code{__vrd2_cos}, @code{__vrd2_exp}, @code{__vrd2_log}, @code{__vrd2_log2},
|
12196 |
|
|
@code{__vrd2_log10}, @code{__vrs4_sinf}, @code{__vrs4_cosf},
|
12197 |
|
|
@code{__vrs4_expf}, @code{__vrs4_logf}, @code{__vrs4_log2f},
|
12198 |
|
|
@code{__vrs4_log10f} and @code{__vrs4_powf} for corresponding function type
|
12199 |
|
|
when @option{-mveclibabi=acml} is used. Both @option{-ftree-vectorize} and
|
12200 |
|
|
@option{-funsafe-math-optimizations} have to be enabled. A SVML or ACML ABI
|
12201 |
|
|
compatible library will have to be specified at link time.
|
12202 |
|
|
|
12203 |
|
|
@item -mabi=@var{name}
|
12204 |
|
|
@opindex mabi
|
12205 |
|
|
Generate code for the specified calling convention. Permissible values
|
12206 |
|
|
are: @samp{sysv} for the ABI used on GNU/Linux and other systems and
|
12207 |
|
|
@samp{ms} for the Microsoft ABI. The default is to use the Microsoft
|
12208 |
|
|
ABI when targeting Windows. On all other systems, the default is the
|
12209 |
|
|
SYSV ABI. You can control this behavior for a specific function by
|
12210 |
|
|
using the function attribute @samp{ms_abi}/@samp{sysv_abi}.
|
12211 |
|
|
@xref{Function Attributes}.
|
12212 |
|
|
|
12213 |
|
|
@item -mpush-args
|
12214 |
|
|
@itemx -mno-push-args
|
12215 |
|
|
@opindex mpush-args
|
12216 |
|
|
@opindex mno-push-args
|
12217 |
|
|
Use PUSH operations to store outgoing parameters. This method is shorter
|
12218 |
|
|
and usually equally fast as method using SUB/MOV operations and is enabled
|
12219 |
|
|
by default. In some cases disabling it may improve performance because of
|
12220 |
|
|
improved scheduling and reduced dependencies.
|
12221 |
|
|
|
12222 |
|
|
@item -maccumulate-outgoing-args
|
12223 |
|
|
@opindex maccumulate-outgoing-args
|
12224 |
|
|
If enabled, the maximum amount of space required for outgoing arguments will be
|
12225 |
|
|
computed in the function prologue. This is faster on most modern CPUs
|
12226 |
|
|
because of reduced dependencies, improved scheduling and reduced stack usage
|
12227 |
|
|
when preferred stack boundary is not equal to 2. The drawback is a notable
|
12228 |
|
|
increase in code size. This switch implies @option{-mno-push-args}.
|
12229 |
|
|
|
12230 |
|
|
@item -mthreads
|
12231 |
|
|
@opindex mthreads
|
12232 |
|
|
Support thread-safe exception handling on @samp{Mingw32}. Code that relies
|
12233 |
|
|
on thread-safe exception handling must compile and link all code with the
|
12234 |
|
|
@option{-mthreads} option. When compiling, @option{-mthreads} defines
|
12235 |
|
|
@option{-D_MT}; when linking, it links in a special thread helper library
|
12236 |
|
|
@option{-lmingwthrd} which cleans up per thread exception handling data.
|
12237 |
|
|
|
12238 |
|
|
@item -mno-align-stringops
|
12239 |
|
|
@opindex mno-align-stringops
|
12240 |
|
|
Do not align destination of inlined string operations. This switch reduces
|
12241 |
|
|
code size and improves performance in case the destination is already aligned,
|
12242 |
|
|
but GCC doesn't know about it.
|
12243 |
|
|
|
12244 |
|
|
@item -minline-all-stringops
|
12245 |
|
|
@opindex minline-all-stringops
|
12246 |
|
|
By default GCC inlines string operations only when destination is known to be
|
12247 |
|
|
aligned at least to 4 byte boundary. This enables more inlining, increase code
|
12248 |
|
|
size, but may improve performance of code that depends on fast memcpy, strlen
|
12249 |
|
|
and memset for short lengths.
|
12250 |
|
|
|
12251 |
|
|
@item -minline-stringops-dynamically
|
12252 |
|
|
@opindex minline-stringops-dynamically
|
12253 |
|
|
For string operation of unknown size, inline runtime checks so for small
|
12254 |
|
|
blocks inline code is used, while for large blocks library call is used.
|
12255 |
|
|
|
12256 |
|
|
@item -mstringop-strategy=@var{alg}
|
12257 |
|
|
@opindex mstringop-strategy=@var{alg}
|
12258 |
|
|
Overwrite internal decision heuristic about particular algorithm to inline
|
12259 |
|
|
string operation with. The allowed values are @code{rep_byte},
|
12260 |
|
|
@code{rep_4byte}, @code{rep_8byte} for expanding using i386 @code{rep} prefix
|
12261 |
|
|
of specified size, @code{byte_loop}, @code{loop}, @code{unrolled_loop} for
|
12262 |
|
|
expanding inline loop, @code{libcall} for always expanding library call.
|
12263 |
|
|
|
12264 |
|
|
@item -momit-leaf-frame-pointer
|
12265 |
|
|
@opindex momit-leaf-frame-pointer
|
12266 |
|
|
Don't keep the frame pointer in a register for leaf functions. This
|
12267 |
|
|
avoids the instructions to save, set up and restore frame pointers and
|
12268 |
|
|
makes an extra register available in leaf functions. The option
|
12269 |
|
|
@option{-fomit-frame-pointer} removes the frame pointer for all functions
|
12270 |
|
|
which might make debugging harder.
|
12271 |
|
|
|
12272 |
|
|
@item -mtls-direct-seg-refs
|
12273 |
|
|
@itemx -mno-tls-direct-seg-refs
|
12274 |
|
|
@opindex mtls-direct-seg-refs
|
12275 |
|
|
Controls whether TLS variables may be accessed with offsets from the
|
12276 |
|
|
TLS segment register (@code{%gs} for 32-bit, @code{%fs} for 64-bit),
|
12277 |
|
|
or whether the thread base pointer must be added. Whether or not this
|
12278 |
|
|
is legal depends on the operating system, and whether it maps the
|
12279 |
|
|
segment to cover the entire TLS area.
|
12280 |
|
|
|
12281 |
|
|
For systems that use GNU libc, the default is on.
|
12282 |
|
|
|
12283 |
|
|
@item -msse2avx
|
12284 |
|
|
@itemx -mno-sse2avx
|
12285 |
|
|
@opindex msse2avx
|
12286 |
|
|
Specify that the assembler should encode SSE instructions with VEX
|
12287 |
|
|
prefix. The option @option{-mavx} turns this on by default.
|
12288 |
|
|
@end table
|
12289 |
|
|
|
12290 |
|
|
These @samp{-m} switches are supported in addition to the above
|
12291 |
|
|
on AMD x86-64 processors in 64-bit environments.
|
12292 |
|
|
|
12293 |
|
|
@table @gcctabopt
|
12294 |
|
|
@item -m32
|
12295 |
|
|
@itemx -m64
|
12296 |
|
|
@opindex m32
|
12297 |
|
|
@opindex m64
|
12298 |
|
|
Generate code for a 32-bit or 64-bit environment.
|
12299 |
|
|
The 32-bit environment sets int, long and pointer to 32 bits and
|
12300 |
|
|
generates code that runs on any i386 system.
|
12301 |
|
|
The 64-bit environment sets int to 32 bits and long and pointer
|
12302 |
|
|
to 64 bits and generates code for AMD's x86-64 architecture. For
|
12303 |
|
|
darwin only the -m64 option turns off the @option{-fno-pic} and
|
12304 |
|
|
@option{-mdynamic-no-pic} options.
|
12305 |
|
|
|
12306 |
|
|
@item -mno-red-zone
|
12307 |
|
|
@opindex mno-red-zone
|
12308 |
|
|
Do not use a so called red zone for x86-64 code. The red zone is mandated
|
12309 |
|
|
by the x86-64 ABI, it is a 128-byte area beyond the location of the
|
12310 |
|
|
stack pointer that will not be modified by signal or interrupt handlers
|
12311 |
|
|
and therefore can be used for temporary data without adjusting the stack
|
12312 |
|
|
pointer. The flag @option{-mno-red-zone} disables this red zone.
|
12313 |
|
|
|
12314 |
|
|
@item -mcmodel=small
|
12315 |
|
|
@opindex mcmodel=small
|
12316 |
|
|
Generate code for the small code model: the program and its symbols must
|
12317 |
|
|
be linked in the lower 2 GB of the address space. Pointers are 64 bits.
|
12318 |
|
|
Programs can be statically or dynamically linked. This is the default
|
12319 |
|
|
code model.
|
12320 |
|
|
|
12321 |
|
|
@item -mcmodel=kernel
|
12322 |
|
|
@opindex mcmodel=kernel
|
12323 |
|
|
Generate code for the kernel code model. The kernel runs in the
|
12324 |
|
|
negative 2 GB of the address space.
|
12325 |
|
|
This model has to be used for Linux kernel code.
|
12326 |
|
|
|
12327 |
|
|
@item -mcmodel=medium
|
12328 |
|
|
@opindex mcmodel=medium
|
12329 |
|
|
Generate code for the medium model: The program is linked in the lower 2
|
12330 |
|
|
GB of the address space. Small symbols are also placed there. Symbols
|
12331 |
|
|
with sizes larger than @option{-mlarge-data-threshold} are put into
|
12332 |
|
|
large data or bss sections and can be located above 2GB. Programs can
|
12333 |
|
|
be statically or dynamically linked.
|
12334 |
|
|
|
12335 |
|
|
@item -mcmodel=large
|
12336 |
|
|
@opindex mcmodel=large
|
12337 |
|
|
Generate code for the large model: This model makes no assumptions
|
12338 |
|
|
about addresses and sizes of sections.
|
12339 |
|
|
@end table
|
12340 |
|
|
|
12341 |
|
|
@node IA-64 Options
|
12342 |
|
|
@subsection IA-64 Options
|
12343 |
|
|
@cindex IA-64 Options
|
12344 |
|
|
|
12345 |
|
|
These are the @samp{-m} options defined for the Intel IA-64 architecture.
|
12346 |
|
|
|
12347 |
|
|
@table @gcctabopt
|
12348 |
|
|
@item -mbig-endian
|
12349 |
|
|
@opindex mbig-endian
|
12350 |
|
|
Generate code for a big endian target. This is the default for HP-UX@.
|
12351 |
|
|
|
12352 |
|
|
@item -mlittle-endian
|
12353 |
|
|
@opindex mlittle-endian
|
12354 |
|
|
Generate code for a little endian target. This is the default for AIX5
|
12355 |
|
|
and GNU/Linux.
|
12356 |
|
|
|
12357 |
|
|
@item -mgnu-as
|
12358 |
|
|
@itemx -mno-gnu-as
|
12359 |
|
|
@opindex mgnu-as
|
12360 |
|
|
@opindex mno-gnu-as
|
12361 |
|
|
Generate (or don't) code for the GNU assembler. This is the default.
|
12362 |
|
|
@c Also, this is the default if the configure option @option{--with-gnu-as}
|
12363 |
|
|
@c is used.
|
12364 |
|
|
|
12365 |
|
|
@item -mgnu-ld
|
12366 |
|
|
@itemx -mno-gnu-ld
|
12367 |
|
|
@opindex mgnu-ld
|
12368 |
|
|
@opindex mno-gnu-ld
|
12369 |
|
|
Generate (or don't) code for the GNU linker. This is the default.
|
12370 |
|
|
@c Also, this is the default if the configure option @option{--with-gnu-ld}
|
12371 |
|
|
@c is used.
|
12372 |
|
|
|
12373 |
|
|
@item -mno-pic
|
12374 |
|
|
@opindex mno-pic
|
12375 |
|
|
Generate code that does not use a global pointer register. The result
|
12376 |
|
|
is not position independent code, and violates the IA-64 ABI@.
|
12377 |
|
|
|
12378 |
|
|
@item -mvolatile-asm-stop
|
12379 |
|
|
@itemx -mno-volatile-asm-stop
|
12380 |
|
|
@opindex mvolatile-asm-stop
|
12381 |
|
|
@opindex mno-volatile-asm-stop
|
12382 |
|
|
Generate (or don't) a stop bit immediately before and after volatile asm
|
12383 |
|
|
statements.
|
12384 |
|
|
|
12385 |
|
|
@item -mregister-names
|
12386 |
|
|
@itemx -mno-register-names
|
12387 |
|
|
@opindex mregister-names
|
12388 |
|
|
@opindex mno-register-names
|
12389 |
|
|
Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for
|
12390 |
|
|
the stacked registers. This may make assembler output more readable.
|
12391 |
|
|
|
12392 |
|
|
@item -mno-sdata
|
12393 |
|
|
@itemx -msdata
|
12394 |
|
|
@opindex mno-sdata
|
12395 |
|
|
@opindex msdata
|
12396 |
|
|
Disable (or enable) optimizations that use the small data section. This may
|
12397 |
|
|
be useful for working around optimizer bugs.
|
12398 |
|
|
|
12399 |
|
|
@item -mconstant-gp
|
12400 |
|
|
@opindex mconstant-gp
|
12401 |
|
|
Generate code that uses a single constant global pointer value. This is
|
12402 |
|
|
useful when compiling kernel code.
|
12403 |
|
|
|
12404 |
|
|
@item -mauto-pic
|
12405 |
|
|
@opindex mauto-pic
|
12406 |
|
|
Generate code that is self-relocatable. This implies @option{-mconstant-gp}.
|
12407 |
|
|
This is useful when compiling firmware code.
|
12408 |
|
|
|
12409 |
|
|
@item -minline-float-divide-min-latency
|
12410 |
|
|
@opindex minline-float-divide-min-latency
|
12411 |
|
|
Generate code for inline divides of floating point values
|
12412 |
|
|
using the minimum latency algorithm.
|
12413 |
|
|
|
12414 |
|
|
@item -minline-float-divide-max-throughput
|
12415 |
|
|
@opindex minline-float-divide-max-throughput
|
12416 |
|
|
Generate code for inline divides of floating point values
|
12417 |
|
|
using the maximum throughput algorithm.
|
12418 |
|
|
|
12419 |
|
|
@item -mno-inline-float-divide
|
12420 |
|
|
@opindex mno-inline-float-divide
|
12421 |
|
|
Do not generate inline code for divides of floating point values.
|
12422 |
|
|
|
12423 |
|
|
@item -minline-int-divide-min-latency
|
12424 |
|
|
@opindex minline-int-divide-min-latency
|
12425 |
|
|
Generate code for inline divides of integer values
|
12426 |
|
|
using the minimum latency algorithm.
|
12427 |
|
|
|
12428 |
|
|
@item -minline-int-divide-max-throughput
|
12429 |
|
|
@opindex minline-int-divide-max-throughput
|
12430 |
|
|
Generate code for inline divides of integer values
|
12431 |
|
|
using the maximum throughput algorithm.
|
12432 |
|
|
|
12433 |
|
|
@item -mno-inline-int-divide
|
12434 |
|
|
@opindex mno-inline-int-divide
|
12435 |
|
|
Do not generate inline code for divides of integer values.
|
12436 |
|
|
|
12437 |
|
|
@item -minline-sqrt-min-latency
|
12438 |
|
|
@opindex minline-sqrt-min-latency
|
12439 |
|
|
Generate code for inline square roots
|
12440 |
|
|
using the minimum latency algorithm.
|
12441 |
|
|
|
12442 |
|
|
@item -minline-sqrt-max-throughput
|
12443 |
|
|
@opindex minline-sqrt-max-throughput
|
12444 |
|
|
Generate code for inline square roots
|
12445 |
|
|
using the maximum throughput algorithm.
|
12446 |
|
|
|
12447 |
|
|
@item -mno-inline-sqrt
|
12448 |
|
|
@opindex mno-inline-sqrt
|
12449 |
|
|
Do not generate inline code for sqrt.
|
12450 |
|
|
|
12451 |
|
|
@item -mfused-madd
|
12452 |
|
|
@itemx -mno-fused-madd
|
12453 |
|
|
@opindex mfused-madd
|
12454 |
|
|
@opindex mno-fused-madd
|
12455 |
|
|
Do (don't) generate code that uses the fused multiply/add or multiply/subtract
|
12456 |
|
|
instructions. The default is to use these instructions.
|
12457 |
|
|
|
12458 |
|
|
@item -mno-dwarf2-asm
|
12459 |
|
|
@itemx -mdwarf2-asm
|
12460 |
|
|
@opindex mno-dwarf2-asm
|
12461 |
|
|
@opindex mdwarf2-asm
|
12462 |
|
|
Don't (or do) generate assembler code for the DWARF2 line number debugging
|
12463 |
|
|
info. This may be useful when not using the GNU assembler.
|
12464 |
|
|
|
12465 |
|
|
@item -mearly-stop-bits
|
12466 |
|
|
@itemx -mno-early-stop-bits
|
12467 |
|
|
@opindex mearly-stop-bits
|
12468 |
|
|
@opindex mno-early-stop-bits
|
12469 |
|
|
Allow stop bits to be placed earlier than immediately preceding the
|
12470 |
|
|
instruction that triggered the stop bit. This can improve instruction
|
12471 |
|
|
scheduling, but does not always do so.
|
12472 |
|
|
|
12473 |
|
|
@item -mfixed-range=@var{register-range}
|
12474 |
|
|
@opindex mfixed-range
|
12475 |
|
|
Generate code treating the given register range as fixed registers.
|
12476 |
|
|
A fixed register is one that the register allocator can not use. This is
|
12477 |
|
|
useful when compiling kernel code. A register range is specified as
|
12478 |
|
|
two registers separated by a dash. Multiple register ranges can be
|
12479 |
|
|
specified separated by a comma.
|
12480 |
|
|
|
12481 |
|
|
@item -mtls-size=@var{tls-size}
|
12482 |
|
|
@opindex mtls-size
|
12483 |
|
|
Specify bit size of immediate TLS offsets. Valid values are 14, 22, and
|
12484 |
|
|
64.
|
12485 |
|
|
|
12486 |
|
|
@item -mtune=@var{cpu-type}
|
12487 |
|
|
@opindex mtune
|
12488 |
|
|
Tune the instruction scheduling for a particular CPU, Valid values are
|
12489 |
|
|
itanium, itanium1, merced, itanium2, and mckinley.
|
12490 |
|
|
|
12491 |
|
|
@item -milp32
|
12492 |
|
|
@itemx -mlp64
|
12493 |
|
|
@opindex milp32
|
12494 |
|
|
@opindex mlp64
|
12495 |
|
|
Generate code for a 32-bit or 64-bit environment.
|
12496 |
|
|
The 32-bit environment sets int, long and pointer to 32 bits.
|
12497 |
|
|
The 64-bit environment sets int to 32 bits and long and pointer
|
12498 |
|
|
to 64 bits. These are HP-UX specific flags.
|
12499 |
|
|
|
12500 |
|
|
@item -mno-sched-br-data-spec
|
12501 |
|
|
@itemx -msched-br-data-spec
|
12502 |
|
|
@opindex mno-sched-br-data-spec
|
12503 |
|
|
@opindex msched-br-data-spec
|
12504 |
|
|
(Dis/En)able data speculative scheduling before reload.
|
12505 |
|
|
This will result in generation of the ld.a instructions and
|
12506 |
|
|
the corresponding check instructions (ld.c / chk.a).
|
12507 |
|
|
The default is 'disable'.
|
12508 |
|
|
|
12509 |
|
|
@item -msched-ar-data-spec
|
12510 |
|
|
@itemx -mno-sched-ar-data-spec
|
12511 |
|
|
@opindex msched-ar-data-spec
|
12512 |
|
|
@opindex mno-sched-ar-data-spec
|
12513 |
|
|
(En/Dis)able data speculative scheduling after reload.
|
12514 |
|
|
This will result in generation of the ld.a instructions and
|
12515 |
|
|
the corresponding check instructions (ld.c / chk.a).
|
12516 |
|
|
The default is 'enable'.
|
12517 |
|
|
|
12518 |
|
|
@item -mno-sched-control-spec
|
12519 |
|
|
@itemx -msched-control-spec
|
12520 |
|
|
@opindex mno-sched-control-spec
|
12521 |
|
|
@opindex msched-control-spec
|
12522 |
|
|
(Dis/En)able control speculative scheduling. This feature is
|
12523 |
|
|
available only during region scheduling (i.e.@: before reload).
|
12524 |
|
|
This will result in generation of the ld.s instructions and
|
12525 |
|
|
the corresponding check instructions chk.s .
|
12526 |
|
|
The default is 'disable'.
|
12527 |
|
|
|
12528 |
|
|
@item -msched-br-in-data-spec
|
12529 |
|
|
@itemx -mno-sched-br-in-data-spec
|
12530 |
|
|
@opindex msched-br-in-data-spec
|
12531 |
|
|
@opindex mno-sched-br-in-data-spec
|
12532 |
|
|
(En/Dis)able speculative scheduling of the instructions that
|
12533 |
|
|
are dependent on the data speculative loads before reload.
|
12534 |
|
|
This is effective only with @option{-msched-br-data-spec} enabled.
|
12535 |
|
|
The default is 'enable'.
|
12536 |
|
|
|
12537 |
|
|
@item -msched-ar-in-data-spec
|
12538 |
|
|
@itemx -mno-sched-ar-in-data-spec
|
12539 |
|
|
@opindex msched-ar-in-data-spec
|
12540 |
|
|
@opindex mno-sched-ar-in-data-spec
|
12541 |
|
|
(En/Dis)able speculative scheduling of the instructions that
|
12542 |
|
|
are dependent on the data speculative loads after reload.
|
12543 |
|
|
This is effective only with @option{-msched-ar-data-spec} enabled.
|
12544 |
|
|
The default is 'enable'.
|
12545 |
|
|
|
12546 |
|
|
@item -msched-in-control-spec
|
12547 |
|
|
@itemx -mno-sched-in-control-spec
|
12548 |
|
|
@opindex msched-in-control-spec
|
12549 |
|
|
@opindex mno-sched-in-control-spec
|
12550 |
|
|
(En/Dis)able speculative scheduling of the instructions that
|
12551 |
|
|
are dependent on the control speculative loads.
|
12552 |
|
|
This is effective only with @option{-msched-control-spec} enabled.
|
12553 |
|
|
The default is 'enable'.
|
12554 |
|
|
|
12555 |
|
|
@item -mno-sched-prefer-non-data-spec-insns
|
12556 |
|
|
@itemx -msched-prefer-non-data-spec-insns
|
12557 |
|
|
@opindex mno-sched-prefer-non-data-spec-insns
|
12558 |
|
|
@opindex msched-prefer-non-data-spec-insns
|
12559 |
|
|
If enabled, data speculative instructions will be chosen for schedule
|
12560 |
|
|
only if there are no other choices at the moment. This will make
|
12561 |
|
|
the use of the data speculation much more conservative.
|
12562 |
|
|
The default is 'disable'.
|
12563 |
|
|
|
12564 |
|
|
@item -mno-sched-prefer-non-control-spec-insns
|
12565 |
|
|
@itemx -msched-prefer-non-control-spec-insns
|
12566 |
|
|
@opindex mno-sched-prefer-non-control-spec-insns
|
12567 |
|
|
@opindex msched-prefer-non-control-spec-insns
|
12568 |
|
|
If enabled, control speculative instructions will be chosen for schedule
|
12569 |
|
|
only if there are no other choices at the moment. This will make
|
12570 |
|
|
the use of the control speculation much more conservative.
|
12571 |
|
|
The default is 'disable'.
|
12572 |
|
|
|
12573 |
|
|
@item -mno-sched-count-spec-in-critical-path
|
12574 |
|
|
@itemx -msched-count-spec-in-critical-path
|
12575 |
|
|
@opindex mno-sched-count-spec-in-critical-path
|
12576 |
|
|
@opindex msched-count-spec-in-critical-path
|
12577 |
|
|
If enabled, speculative dependencies will be considered during
|
12578 |
|
|
computation of the instructions priorities. This will make the use of the
|
12579 |
|
|
speculation a bit more conservative.
|
12580 |
|
|
The default is 'disable'.
|
12581 |
|
|
|
12582 |
|
|
@item -msched-spec-ldc
|
12583 |
|
|
@opindex msched-spec-ldc
|
12584 |
|
|
Use a simple data speculation check. This option is on by default.
|
12585 |
|
|
|
12586 |
|
|
@item -msched-control-spec-ldc
|
12587 |
|
|
@opindex msched-spec-ldc
|
12588 |
|
|
Use a simple check for control speculation. This option is on by default.
|
12589 |
|
|
|
12590 |
|
|
@item -msched-stop-bits-after-every-cycle
|
12591 |
|
|
@opindex msched-stop-bits-after-every-cycle
|
12592 |
|
|
Place a stop bit after every cycle when scheduling. This option is on
|
12593 |
|
|
by default.
|
12594 |
|
|
|
12595 |
|
|
@item -msched-fp-mem-deps-zero-cost
|
12596 |
|
|
@opindex msched-fp-mem-deps-zero-cost
|
12597 |
|
|
Assume that floating-point stores and loads are not likely to cause a conflict
|
12598 |
|
|
when placed into the same instruction group. This option is disabled by
|
12599 |
|
|
default.
|
12600 |
|
|
|
12601 |
|
|
@item -msel-sched-dont-check-control-spec
|
12602 |
|
|
@opindex msel-sched-dont-check-control-spec
|
12603 |
|
|
Generate checks for control speculation in selective scheduling.
|
12604 |
|
|
This flag is disabled by default.
|
12605 |
|
|
|
12606 |
|
|
@item -msched-max-memory-insns=@var{max-insns}
|
12607 |
|
|
@opindex msched-max-memory-insns
|
12608 |
|
|
Limit on the number of memory insns per instruction group, giving lower
|
12609 |
|
|
priority to subsequent memory insns attempting to schedule in the same
|
12610 |
|
|
instruction group. Frequently useful to prevent cache bank conflicts.
|
12611 |
|
|
The default value is 1.
|
12612 |
|
|
|
12613 |
|
|
@item -msched-max-memory-insns-hard-limit
|
12614 |
|
|
@opindex msched-max-memory-insns-hard-limit
|
12615 |
|
|
Disallow more than `msched-max-memory-insns' in instruction group.
|
12616 |
|
|
Otherwise, limit is `soft' meaning that we would prefer non-memory operations
|
12617 |
|
|
when limit is reached but may still schedule memory operations.
|
12618 |
|
|
|
12619 |
|
|
@end table
|
12620 |
|
|
|
12621 |
|
|
@node IA-64/VMS Options
|
12622 |
|
|
@subsection IA-64/VMS Options
|
12623 |
|
|
|
12624 |
|
|
These @samp{-m} options are defined for the IA-64/VMS implementations:
|
12625 |
|
|
|
12626 |
|
|
@table @gcctabopt
|
12627 |
|
|
@item -mvms-return-codes
|
12628 |
|
|
@opindex mvms-return-codes
|
12629 |
|
|
Return VMS condition codes from main. The default is to return POSIX
|
12630 |
|
|
style condition (e.g.@ error) codes.
|
12631 |
|
|
|
12632 |
|
|
@item -mdebug-main=@var{prefix}
|
12633 |
|
|
@opindex mdebug-main=@var{prefix}
|
12634 |
|
|
Flag the first routine whose name starts with @var{prefix} as the main
|
12635 |
|
|
routine for the debugger.
|
12636 |
|
|
|
12637 |
|
|
@item -mmalloc64
|
12638 |
|
|
@opindex mmalloc64
|
12639 |
|
|
Default to 64bit memory allocation routines.
|
12640 |
|
|
@end table
|
12641 |
|
|
|
12642 |
|
|
@node LM32 Options
|
12643 |
|
|
@subsection LM32 Options
|
12644 |
|
|
@cindex LM32 options
|
12645 |
|
|
|
12646 |
|
|
These @option{-m} options are defined for the Lattice Mico32 architecture:
|
12647 |
|
|
|
12648 |
|
|
@table @gcctabopt
|
12649 |
|
|
@item -mbarrel-shift-enabled
|
12650 |
|
|
@opindex mbarrel-shift-enabled
|
12651 |
|
|
Enable barrel-shift instructions.
|
12652 |
|
|
|
12653 |
|
|
@item -mdivide-enabled
|
12654 |
|
|
@opindex mdivide-enabled
|
12655 |
|
|
Enable divide and modulus instructions.
|
12656 |
|
|
|
12657 |
|
|
@item -mmultiply-enabled
|
12658 |
|
|
@opindex multiply-enabled
|
12659 |
|
|
Enable multiply instructions.
|
12660 |
|
|
|
12661 |
|
|
@item -msign-extend-enabled
|
12662 |
|
|
@opindex msign-extend-enabled
|
12663 |
|
|
Enable sign extend instructions.
|
12664 |
|
|
|
12665 |
|
|
@item -muser-enabled
|
12666 |
|
|
@opindex muser-enabled
|
12667 |
|
|
Enable user-defined instructions.
|
12668 |
|
|
|
12669 |
|
|
@end table
|
12670 |
|
|
|
12671 |
|
|
@node M32C Options
|
12672 |
|
|
@subsection M32C Options
|
12673 |
|
|
@cindex M32C options
|
12674 |
|
|
|
12675 |
|
|
@table @gcctabopt
|
12676 |
|
|
@item -mcpu=@var{name}
|
12677 |
|
|
@opindex mcpu=
|
12678 |
|
|
Select the CPU for which code is generated. @var{name} may be one of
|
12679 |
|
|
@samp{r8c} for the R8C/Tiny series, @samp{m16c} for the M16C (up to
|
12680 |
|
|
/60) series, @samp{m32cm} for the M16C/80 series, or @samp{m32c} for
|
12681 |
|
|
the M32C/80 series.
|
12682 |
|
|
|
12683 |
|
|
@item -msim
|
12684 |
|
|
@opindex msim
|
12685 |
|
|
Specifies that the program will be run on the simulator. This causes
|
12686 |
|
|
an alternate runtime library to be linked in which supports, for
|
12687 |
|
|
example, file I/O@. You must not use this option when generating
|
12688 |
|
|
programs that will run on real hardware; you must provide your own
|
12689 |
|
|
runtime library for whatever I/O functions are needed.
|
12690 |
|
|
|
12691 |
|
|
@item -memregs=@var{number}
|
12692 |
|
|
@opindex memregs=
|
12693 |
|
|
Specifies the number of memory-based pseudo-registers GCC will use
|
12694 |
|
|
during code generation. These pseudo-registers will be used like real
|
12695 |
|
|
registers, so there is a tradeoff between GCC's ability to fit the
|
12696 |
|
|
code into available registers, and the performance penalty of using
|
12697 |
|
|
memory instead of registers. Note that all modules in a program must
|
12698 |
|
|
be compiled with the same value for this option. Because of that, you
|
12699 |
|
|
must not use this option with the default runtime libraries gcc
|
12700 |
|
|
builds.
|
12701 |
|
|
|
12702 |
|
|
@end table
|
12703 |
|
|
|
12704 |
|
|
@node M32R/D Options
|
12705 |
|
|
@subsection M32R/D Options
|
12706 |
|
|
@cindex M32R/D options
|
12707 |
|
|
|
12708 |
|
|
These @option{-m} options are defined for Renesas M32R/D architectures:
|
12709 |
|
|
|
12710 |
|
|
@table @gcctabopt
|
12711 |
|
|
@item -m32r2
|
12712 |
|
|
@opindex m32r2
|
12713 |
|
|
Generate code for the M32R/2@.
|
12714 |
|
|
|
12715 |
|
|
@item -m32rx
|
12716 |
|
|
@opindex m32rx
|
12717 |
|
|
Generate code for the M32R/X@.
|
12718 |
|
|
|
12719 |
|
|
@item -m32r
|
12720 |
|
|
@opindex m32r
|
12721 |
|
|
Generate code for the M32R@. This is the default.
|
12722 |
|
|
|
12723 |
|
|
@item -mmodel=small
|
12724 |
|
|
@opindex mmodel=small
|
12725 |
|
|
Assume all objects live in the lower 16MB of memory (so that their addresses
|
12726 |
|
|
can be loaded with the @code{ld24} instruction), and assume all subroutines
|
12727 |
|
|
are reachable with the @code{bl} instruction.
|
12728 |
|
|
This is the default.
|
12729 |
|
|
|
12730 |
|
|
The addressability of a particular object can be set with the
|
12731 |
|
|
@code{model} attribute.
|
12732 |
|
|
|
12733 |
|
|
@item -mmodel=medium
|
12734 |
|
|
@opindex mmodel=medium
|
12735 |
|
|
Assume objects may be anywhere in the 32-bit address space (the compiler
|
12736 |
|
|
will generate @code{seth/add3} instructions to load their addresses), and
|
12737 |
|
|
assume all subroutines are reachable with the @code{bl} instruction.
|
12738 |
|
|
|
12739 |
|
|
@item -mmodel=large
|
12740 |
|
|
@opindex mmodel=large
|
12741 |
|
|
Assume objects may be anywhere in the 32-bit address space (the compiler
|
12742 |
|
|
will generate @code{seth/add3} instructions to load their addresses), and
|
12743 |
|
|
assume subroutines may not be reachable with the @code{bl} instruction
|
12744 |
|
|
(the compiler will generate the much slower @code{seth/add3/jl}
|
12745 |
|
|
instruction sequence).
|
12746 |
|
|
|
12747 |
|
|
@item -msdata=none
|
12748 |
|
|
@opindex msdata=none
|
12749 |
|
|
Disable use of the small data area. Variables will be put into
|
12750 |
|
|
one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the
|
12751 |
|
|
@code{section} attribute has been specified).
|
12752 |
|
|
This is the default.
|
12753 |
|
|
|
12754 |
|
|
The small data area consists of sections @samp{.sdata} and @samp{.sbss}.
|
12755 |
|
|
Objects may be explicitly put in the small data area with the
|
12756 |
|
|
@code{section} attribute using one of these sections.
|
12757 |
|
|
|
12758 |
|
|
@item -msdata=sdata
|
12759 |
|
|
@opindex msdata=sdata
|
12760 |
|
|
Put small global and static data in the small data area, but do not
|
12761 |
|
|
generate special code to reference them.
|
12762 |
|
|
|
12763 |
|
|
@item -msdata=use
|
12764 |
|
|
@opindex msdata=use
|
12765 |
|
|
Put small global and static data in the small data area, and generate
|
12766 |
|
|
special instructions to reference them.
|
12767 |
|
|
|
12768 |
|
|
@item -G @var{num}
|
12769 |
|
|
@opindex G
|
12770 |
|
|
@cindex smaller data references
|
12771 |
|
|
Put global and static objects less than or equal to @var{num} bytes
|
12772 |
|
|
into the small data or bss sections instead of the normal data or bss
|
12773 |
|
|
sections. The default value of @var{num} is 8.
|
12774 |
|
|
The @option{-msdata} option must be set to one of @samp{sdata} or @samp{use}
|
12775 |
|
|
for this option to have any effect.
|
12776 |
|
|
|
12777 |
|
|
All modules should be compiled with the same @option{-G @var{num}} value.
|
12778 |
|
|
Compiling with different values of @var{num} may or may not work; if it
|
12779 |
|
|
doesn't the linker will give an error message---incorrect code will not be
|
12780 |
|
|
generated.
|
12781 |
|
|
|
12782 |
|
|
@item -mdebug
|
12783 |
|
|
@opindex mdebug
|
12784 |
|
|
Makes the M32R specific code in the compiler display some statistics
|
12785 |
|
|
that might help in debugging programs.
|
12786 |
|
|
|
12787 |
|
|
@item -malign-loops
|
12788 |
|
|
@opindex malign-loops
|
12789 |
|
|
Align all loops to a 32-byte boundary.
|
12790 |
|
|
|
12791 |
|
|
@item -mno-align-loops
|
12792 |
|
|
@opindex mno-align-loops
|
12793 |
|
|
Do not enforce a 32-byte alignment for loops. This is the default.
|
12794 |
|
|
|
12795 |
|
|
@item -missue-rate=@var{number}
|
12796 |
|
|
@opindex missue-rate=@var{number}
|
12797 |
|
|
Issue @var{number} instructions per cycle. @var{number} can only be 1
|
12798 |
|
|
or 2.
|
12799 |
|
|
|
12800 |
|
|
@item -mbranch-cost=@var{number}
|
12801 |
|
|
@opindex mbranch-cost=@var{number}
|
12802 |
|
|
@var{number} can only be 1 or 2. If it is 1 then branches will be
|
12803 |
|
|
preferred over conditional code, if it is 2, then the opposite will
|
12804 |
|
|
apply.
|
12805 |
|
|
|
12806 |
|
|
@item -mflush-trap=@var{number}
|
12807 |
|
|
@opindex mflush-trap=@var{number}
|
12808 |
|
|
Specifies the trap number to use to flush the cache. The default is
|
12809 |
|
|
12. Valid numbers are between 0 and 15 inclusive.
|
12810 |
|
|
|
12811 |
|
|
@item -mno-flush-trap
|
12812 |
|
|
@opindex mno-flush-trap
|
12813 |
|
|
Specifies that the cache cannot be flushed by using a trap.
|
12814 |
|
|
|
12815 |
|
|
@item -mflush-func=@var{name}
|
12816 |
|
|
@opindex mflush-func=@var{name}
|
12817 |
|
|
Specifies the name of the operating system function to call to flush
|
12818 |
|
|
the cache. The default is @emph{_flush_cache}, but a function call
|
12819 |
|
|
will only be used if a trap is not available.
|
12820 |
|
|
|
12821 |
|
|
@item -mno-flush-func
|
12822 |
|
|
@opindex mno-flush-func
|
12823 |
|
|
Indicates that there is no OS function for flushing the cache.
|
12824 |
|
|
|
12825 |
|
|
@end table
|
12826 |
|
|
|
12827 |
|
|
@node M680x0 Options
|
12828 |
|
|
@subsection M680x0 Options
|
12829 |
|
|
@cindex M680x0 options
|
12830 |
|
|
|
12831 |
|
|
These are the @samp{-m} options defined for M680x0 and ColdFire processors.
|
12832 |
|
|
The default settings depend on which architecture was selected when
|
12833 |
|
|
the compiler was configured; the defaults for the most common choices
|
12834 |
|
|
are given below.
|
12835 |
|
|
|
12836 |
|
|
@table @gcctabopt
|
12837 |
|
|
@item -march=@var{arch}
|
12838 |
|
|
@opindex march
|
12839 |
|
|
Generate code for a specific M680x0 or ColdFire instruction set
|
12840 |
|
|
architecture. Permissible values of @var{arch} for M680x0
|
12841 |
|
|
architectures are: @samp{68000}, @samp{68010}, @samp{68020},
|
12842 |
|
|
@samp{68030}, @samp{68040}, @samp{68060} and @samp{cpu32}. ColdFire
|
12843 |
|
|
architectures are selected according to Freescale's ISA classification
|
12844 |
|
|
and the permissible values are: @samp{isaa}, @samp{isaaplus},
|
12845 |
|
|
@samp{isab} and @samp{isac}.
|
12846 |
|
|
|
12847 |
|
|
gcc defines a macro @samp{__mcf@var{arch}__} whenever it is generating
|
12848 |
|
|
code for a ColdFire target. The @var{arch} in this macro is one of the
|
12849 |
|
|
@option{-march} arguments given above.
|
12850 |
|
|
|
12851 |
|
|
When used together, @option{-march} and @option{-mtune} select code
|
12852 |
|
|
that runs on a family of similar processors but that is optimized
|
12853 |
|
|
for a particular microarchitecture.
|
12854 |
|
|
|
12855 |
|
|
@item -mcpu=@var{cpu}
|
12856 |
|
|
@opindex mcpu
|
12857 |
|
|
Generate code for a specific M680x0 or ColdFire processor.
|
12858 |
|
|
The M680x0 @var{cpu}s are: @samp{68000}, @samp{68010}, @samp{68020},
|
12859 |
|
|
@samp{68030}, @samp{68040}, @samp{68060}, @samp{68302}, @samp{68332}
|
12860 |
|
|
and @samp{cpu32}. The ColdFire @var{cpu}s are given by the table
|
12861 |
|
|
below, which also classifies the CPUs into families:
|
12862 |
|
|
|
12863 |
|
|
@multitable @columnfractions 0.20 0.80
|
12864 |
|
|
@item @strong{Family} @tab @strong{@samp{-mcpu} arguments}
|
12865 |
|
|
@item @samp{51} @tab @samp{51} @samp{51ac} @samp{51cn} @samp{51em} @samp{51qe}
|
12866 |
|
|
@item @samp{5206} @tab @samp{5202} @samp{5204} @samp{5206}
|
12867 |
|
|
@item @samp{5206e} @tab @samp{5206e}
|
12868 |
|
|
@item @samp{5208} @tab @samp{5207} @samp{5208}
|
12869 |
|
|
@item @samp{5211a} @tab @samp{5210a} @samp{5211a}
|
12870 |
|
|
@item @samp{5213} @tab @samp{5211} @samp{5212} @samp{5213}
|
12871 |
|
|
@item @samp{5216} @tab @samp{5214} @samp{5216}
|
12872 |
|
|
@item @samp{52235} @tab @samp{52230} @samp{52231} @samp{52232} @samp{52233} @samp{52234} @samp{52235}
|
12873 |
|
|
@item @samp{5225} @tab @samp{5224} @samp{5225}
|
12874 |
|
|
@item @samp{52259} @tab @samp{52252} @samp{52254} @samp{52255} @samp{52256} @samp{52258} @samp{52259}
|
12875 |
|
|
@item @samp{5235} @tab @samp{5232} @samp{5233} @samp{5234} @samp{5235} @samp{523x}
|
12876 |
|
|
@item @samp{5249} @tab @samp{5249}
|
12877 |
|
|
@item @samp{5250} @tab @samp{5250}
|
12878 |
|
|
@item @samp{5271} @tab @samp{5270} @samp{5271}
|
12879 |
|
|
@item @samp{5272} @tab @samp{5272}
|
12880 |
|
|
@item @samp{5275} @tab @samp{5274} @samp{5275}
|
12881 |
|
|
@item @samp{5282} @tab @samp{5280} @samp{5281} @samp{5282} @samp{528x}
|
12882 |
|
|
@item @samp{53017} @tab @samp{53011} @samp{53012} @samp{53013} @samp{53014} @samp{53015} @samp{53016} @samp{53017}
|
12883 |
|
|
@item @samp{5307} @tab @samp{5307}
|
12884 |
|
|
@item @samp{5329} @tab @samp{5327} @samp{5328} @samp{5329} @samp{532x}
|
12885 |
|
|
@item @samp{5373} @tab @samp{5372} @samp{5373} @samp{537x}
|
12886 |
|
|
@item @samp{5407} @tab @samp{5407}
|
12887 |
|
|
@item @samp{5475} @tab @samp{5470} @samp{5471} @samp{5472} @samp{5473} @samp{5474} @samp{5475} @samp{547x} @samp{5480} @samp{5481} @samp{5482} @samp{5483} @samp{5484} @samp{5485}
|
12888 |
|
|
@end multitable
|
12889 |
|
|
|
12890 |
|
|
@option{-mcpu=@var{cpu}} overrides @option{-march=@var{arch}} if
|
12891 |
|
|
@var{arch} is compatible with @var{cpu}. Other combinations of
|
12892 |
|
|
@option{-mcpu} and @option{-march} are rejected.
|
12893 |
|
|
|
12894 |
|
|
gcc defines the macro @samp{__mcf_cpu_@var{cpu}} when ColdFire target
|
12895 |
|
|
@var{cpu} is selected. It also defines @samp{__mcf_family_@var{family}},
|
12896 |
|
|
where the value of @var{family} is given by the table above.
|
12897 |
|
|
|
12898 |
|
|
@item -mtune=@var{tune}
|
12899 |
|
|
@opindex mtune
|
12900 |
|
|
Tune the code for a particular microarchitecture, within the
|
12901 |
|
|
constraints set by @option{-march} and @option{-mcpu}.
|
12902 |
|
|
The M680x0 microarchitectures are: @samp{68000}, @samp{68010},
|
12903 |
|
|
@samp{68020}, @samp{68030}, @samp{68040}, @samp{68060}
|
12904 |
|
|
and @samp{cpu32}. The ColdFire microarchitectures
|
12905 |
|
|
are: @samp{cfv1}, @samp{cfv2}, @samp{cfv3}, @samp{cfv4} and @samp{cfv4e}.
|
12906 |
|
|
|
12907 |
|
|
You can also use @option{-mtune=68020-40} for code that needs
|
12908 |
|
|
to run relatively well on 68020, 68030 and 68040 targets.
|
12909 |
|
|
@option{-mtune=68020-60} is similar but includes 68060 targets
|
12910 |
|
|
as well. These two options select the same tuning decisions as
|
12911 |
|
|
@option{-m68020-40} and @option{-m68020-60} respectively.
|
12912 |
|
|
|
12913 |
|
|
gcc defines the macros @samp{__mc@var{arch}} and @samp{__mc@var{arch}__}
|
12914 |
|
|
when tuning for 680x0 architecture @var{arch}. It also defines
|
12915 |
|
|
@samp{mc@var{arch}} unless either @option{-ansi} or a non-GNU @option{-std}
|
12916 |
|
|
option is used. If gcc is tuning for a range of architectures,
|
12917 |
|
|
as selected by @option{-mtune=68020-40} or @option{-mtune=68020-60},
|
12918 |
|
|
it defines the macros for every architecture in the range.
|
12919 |
|
|
|
12920 |
|
|
gcc also defines the macro @samp{__m@var{uarch}__} when tuning for
|
12921 |
|
|
ColdFire microarchitecture @var{uarch}, where @var{uarch} is one
|
12922 |
|
|
of the arguments given above.
|
12923 |
|
|
|
12924 |
|
|
@item -m68000
|
12925 |
|
|
@itemx -mc68000
|
12926 |
|
|
@opindex m68000
|
12927 |
|
|
@opindex mc68000
|
12928 |
|
|
Generate output for a 68000. This is the default
|
12929 |
|
|
when the compiler is configured for 68000-based systems.
|
12930 |
|
|
It is equivalent to @option{-march=68000}.
|
12931 |
|
|
|
12932 |
|
|
Use this option for microcontrollers with a 68000 or EC000 core,
|
12933 |
|
|
including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
|
12934 |
|
|
|
12935 |
|
|
@item -m68010
|
12936 |
|
|
@opindex m68010
|
12937 |
|
|
Generate output for a 68010. This is the default
|
12938 |
|
|
when the compiler is configured for 68010-based systems.
|
12939 |
|
|
It is equivalent to @option{-march=68010}.
|
12940 |
|
|
|
12941 |
|
|
@item -m68020
|
12942 |
|
|
@itemx -mc68020
|
12943 |
|
|
@opindex m68020
|
12944 |
|
|
@opindex mc68020
|
12945 |
|
|
Generate output for a 68020. This is the default
|
12946 |
|
|
when the compiler is configured for 68020-based systems.
|
12947 |
|
|
It is equivalent to @option{-march=68020}.
|
12948 |
|
|
|
12949 |
|
|
@item -m68030
|
12950 |
|
|
@opindex m68030
|
12951 |
|
|
Generate output for a 68030. This is the default when the compiler is
|
12952 |
|
|
configured for 68030-based systems. It is equivalent to
|
12953 |
|
|
@option{-march=68030}.
|
12954 |
|
|
|
12955 |
|
|
@item -m68040
|
12956 |
|
|
@opindex m68040
|
12957 |
|
|
Generate output for a 68040. This is the default when the compiler is
|
12958 |
|
|
configured for 68040-based systems. It is equivalent to
|
12959 |
|
|
@option{-march=68040}.
|
12960 |
|
|
|
12961 |
|
|
This option inhibits the use of 68881/68882 instructions that have to be
|
12962 |
|
|
emulated by software on the 68040. Use this option if your 68040 does not
|
12963 |
|
|
have code to emulate those instructions.
|
12964 |
|
|
|
12965 |
|
|
@item -m68060
|
12966 |
|
|
@opindex m68060
|
12967 |
|
|
Generate output for a 68060. This is the default when the compiler is
|
12968 |
|
|
configured for 68060-based systems. It is equivalent to
|
12969 |
|
|
@option{-march=68060}.
|
12970 |
|
|
|
12971 |
|
|
This option inhibits the use of 68020 and 68881/68882 instructions that
|
12972 |
|
|
have to be emulated by software on the 68060. Use this option if your 68060
|
12973 |
|
|
does not have code to emulate those instructions.
|
12974 |
|
|
|
12975 |
|
|
@item -mcpu32
|
12976 |
|
|
@opindex mcpu32
|
12977 |
|
|
Generate output for a CPU32. This is the default
|
12978 |
|
|
when the compiler is configured for CPU32-based systems.
|
12979 |
|
|
It is equivalent to @option{-march=cpu32}.
|
12980 |
|
|
|
12981 |
|
|
Use this option for microcontrollers with a
|
12982 |
|
|
CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,
|
12983 |
|
|
68336, 68340, 68341, 68349 and 68360.
|
12984 |
|
|
|
12985 |
|
|
@item -m5200
|
12986 |
|
|
@opindex m5200
|
12987 |
|
|
Generate output for a 520X ColdFire CPU@. This is the default
|
12988 |
|
|
when the compiler is configured for 520X-based systems.
|
12989 |
|
|
It is equivalent to @option{-mcpu=5206}, and is now deprecated
|
12990 |
|
|
in favor of that option.
|
12991 |
|
|
|
12992 |
|
|
Use this option for microcontroller with a 5200 core, including
|
12993 |
|
|
the MCF5202, MCF5203, MCF5204 and MCF5206.
|
12994 |
|
|
|
12995 |
|
|
@item -m5206e
|
12996 |
|
|
@opindex m5206e
|
12997 |
|
|
Generate output for a 5206e ColdFire CPU@. The option is now
|
12998 |
|
|
deprecated in favor of the equivalent @option{-mcpu=5206e}.
|
12999 |
|
|
|
13000 |
|
|
@item -m528x
|
13001 |
|
|
@opindex m528x
|
13002 |
|
|
Generate output for a member of the ColdFire 528X family.
|
13003 |
|
|
The option is now deprecated in favor of the equivalent
|
13004 |
|
|
@option{-mcpu=528x}.
|
13005 |
|
|
|
13006 |
|
|
@item -m5307
|
13007 |
|
|
@opindex m5307
|
13008 |
|
|
Generate output for a ColdFire 5307 CPU@. The option is now deprecated
|
13009 |
|
|
in favor of the equivalent @option{-mcpu=5307}.
|
13010 |
|
|
|
13011 |
|
|
@item -m5407
|
13012 |
|
|
@opindex m5407
|
13013 |
|
|
Generate output for a ColdFire 5407 CPU@. The option is now deprecated
|
13014 |
|
|
in favor of the equivalent @option{-mcpu=5407}.
|
13015 |
|
|
|
13016 |
|
|
@item -mcfv4e
|
13017 |
|
|
@opindex mcfv4e
|
13018 |
|
|
Generate output for a ColdFire V4e family CPU (e.g.@: 547x/548x).
|
13019 |
|
|
This includes use of hardware floating point instructions.
|
13020 |
|
|
The option is equivalent to @option{-mcpu=547x}, and is now
|
13021 |
|
|
deprecated in favor of that option.
|
13022 |
|
|
|
13023 |
|
|
@item -m68020-40
|
13024 |
|
|
@opindex m68020-40
|
13025 |
|
|
Generate output for a 68040, without using any of the new instructions.
|
13026 |
|
|
This results in code which can run relatively efficiently on either a
|
13027 |
|
|
68020/68881 or a 68030 or a 68040. The generated code does use the
|
13028 |
|
|
68881 instructions that are emulated on the 68040.
|
13029 |
|
|
|
13030 |
|
|
The option is equivalent to @option{-march=68020} @option{-mtune=68020-40}.
|
13031 |
|
|
|
13032 |
|
|
@item -m68020-60
|
13033 |
|
|
@opindex m68020-60
|
13034 |
|
|
Generate output for a 68060, without using any of the new instructions.
|
13035 |
|
|
This results in code which can run relatively efficiently on either a
|
13036 |
|
|
68020/68881 or a 68030 or a 68040. The generated code does use the
|
13037 |
|
|
68881 instructions that are emulated on the 68060.
|
13038 |
|
|
|
13039 |
|
|
The option is equivalent to @option{-march=68020} @option{-mtune=68020-60}.
|
13040 |
|
|
|
13041 |
|
|
@item -mhard-float
|
13042 |
|
|
@itemx -m68881
|
13043 |
|
|
@opindex mhard-float
|
13044 |
|
|
@opindex m68881
|
13045 |
|
|
Generate floating-point instructions. This is the default for 68020
|
13046 |
|
|
and above, and for ColdFire devices that have an FPU@. It defines the
|
13047 |
|
|
macro @samp{__HAVE_68881__} on M680x0 targets and @samp{__mcffpu__}
|
13048 |
|
|
on ColdFire targets.
|
13049 |
|
|
|
13050 |
|
|
@item -msoft-float
|
13051 |
|
|
@opindex msoft-float
|
13052 |
|
|
Do not generate floating-point instructions; use library calls instead.
|
13053 |
|
|
This is the default for 68000, 68010, and 68832 targets. It is also
|
13054 |
|
|
the default for ColdFire devices that have no FPU.
|
13055 |
|
|
|
13056 |
|
|
@item -mdiv
|
13057 |
|
|
@itemx -mno-div
|
13058 |
|
|
@opindex mdiv
|
13059 |
|
|
@opindex mno-div
|
13060 |
|
|
Generate (do not generate) ColdFire hardware divide and remainder
|
13061 |
|
|
instructions. If @option{-march} is used without @option{-mcpu},
|
13062 |
|
|
the default is ``on'' for ColdFire architectures and ``off'' for M680x0
|
13063 |
|
|
architectures. Otherwise, the default is taken from the target CPU
|
13064 |
|
|
(either the default CPU, or the one specified by @option{-mcpu}). For
|
13065 |
|
|
example, the default is ``off'' for @option{-mcpu=5206} and ``on'' for
|
13066 |
|
|
@option{-mcpu=5206e}.
|
13067 |
|
|
|
13068 |
|
|
gcc defines the macro @samp{__mcfhwdiv__} when this option is enabled.
|
13069 |
|
|
|
13070 |
|
|
@item -mshort
|
13071 |
|
|
@opindex mshort
|
13072 |
|
|
Consider type @code{int} to be 16 bits wide, like @code{short int}.
|
13073 |
|
|
Additionally, parameters passed on the stack are also aligned to a
|
13074 |
|
|
16-bit boundary even on targets whose API mandates promotion to 32-bit.
|
13075 |
|
|
|
13076 |
|
|
@item -mno-short
|
13077 |
|
|
@opindex mno-short
|
13078 |
|
|
Do not consider type @code{int} to be 16 bits wide. This is the default.
|
13079 |
|
|
|
13080 |
|
|
@item -mnobitfield
|
13081 |
|
|
@itemx -mno-bitfield
|
13082 |
|
|
@opindex mnobitfield
|
13083 |
|
|
@opindex mno-bitfield
|
13084 |
|
|
Do not use the bit-field instructions. The @option{-m68000}, @option{-mcpu32}
|
13085 |
|
|
and @option{-m5200} options imply @w{@option{-mnobitfield}}.
|
13086 |
|
|
|
13087 |
|
|
@item -mbitfield
|
13088 |
|
|
@opindex mbitfield
|
13089 |
|
|
Do use the bit-field instructions. The @option{-m68020} option implies
|
13090 |
|
|
@option{-mbitfield}. This is the default if you use a configuration
|
13091 |
|
|
designed for a 68020.
|
13092 |
|
|
|
13093 |
|
|
@item -mrtd
|
13094 |
|
|
@opindex mrtd
|
13095 |
|
|
Use a different function-calling convention, in which functions
|
13096 |
|
|
that take a fixed number of arguments return with the @code{rtd}
|
13097 |
|
|
instruction, which pops their arguments while returning. This
|
13098 |
|
|
saves one instruction in the caller since there is no need to pop
|
13099 |
|
|
the arguments there.
|
13100 |
|
|
|
13101 |
|
|
This calling convention is incompatible with the one normally
|
13102 |
|
|
used on Unix, so you cannot use it if you need to call libraries
|
13103 |
|
|
compiled with the Unix compiler.
|
13104 |
|
|
|
13105 |
|
|
Also, you must provide function prototypes for all functions that
|
13106 |
|
|
take variable numbers of arguments (including @code{printf});
|
13107 |
|
|
otherwise incorrect code will be generated for calls to those
|
13108 |
|
|
functions.
|
13109 |
|
|
|
13110 |
|
|
In addition, seriously incorrect code will result if you call a
|
13111 |
|
|
function with too many arguments. (Normally, extra arguments are
|
13112 |
|
|
harmlessly ignored.)
|
13113 |
|
|
|
13114 |
|
|
The @code{rtd} instruction is supported by the 68010, 68020, 68030,
|
13115 |
|
|
68040, 68060 and CPU32 processors, but not by the 68000 or 5200.
|
13116 |
|
|
|
13117 |
|
|
@item -mno-rtd
|
13118 |
|
|
@opindex mno-rtd
|
13119 |
|
|
Do not use the calling conventions selected by @option{-mrtd}.
|
13120 |
|
|
This is the default.
|
13121 |
|
|
|
13122 |
|
|
@item -malign-int
|
13123 |
|
|
@itemx -mno-align-int
|
13124 |
|
|
@opindex malign-int
|
13125 |
|
|
@opindex mno-align-int
|
13126 |
|
|
Control whether GCC aligns @code{int}, @code{long}, @code{long long},
|
13127 |
|
|
@code{float}, @code{double}, and @code{long double} variables on a 32-bit
|
13128 |
|
|
boundary (@option{-malign-int}) or a 16-bit boundary (@option{-mno-align-int}).
|
13129 |
|
|
Aligning variables on 32-bit boundaries produces code that runs somewhat
|
13130 |
|
|
faster on processors with 32-bit busses at the expense of more memory.
|
13131 |
|
|
|
13132 |
|
|
@strong{Warning:} if you use the @option{-malign-int} switch, GCC will
|
13133 |
|
|
align structures containing the above types differently than
|
13134 |
|
|
most published application binary interface specifications for the m68k.
|
13135 |
|
|
|
13136 |
|
|
@item -mpcrel
|
13137 |
|
|
@opindex mpcrel
|
13138 |
|
|
Use the pc-relative addressing mode of the 68000 directly, instead of
|
13139 |
|
|
using a global offset table. At present, this option implies @option{-fpic},
|
13140 |
|
|
allowing at most a 16-bit offset for pc-relative addressing. @option{-fPIC} is
|
13141 |
|
|
not presently supported with @option{-mpcrel}, though this could be supported for
|
13142 |
|
|
68020 and higher processors.
|
13143 |
|
|
|
13144 |
|
|
@item -mno-strict-align
|
13145 |
|
|
@itemx -mstrict-align
|
13146 |
|
|
@opindex mno-strict-align
|
13147 |
|
|
@opindex mstrict-align
|
13148 |
|
|
Do not (do) assume that unaligned memory references will be handled by
|
13149 |
|
|
the system.
|
13150 |
|
|
|
13151 |
|
|
@item -msep-data
|
13152 |
|
|
Generate code that allows the data segment to be located in a different
|
13153 |
|
|
area of memory from the text segment. This allows for execute in place in
|
13154 |
|
|
an environment without virtual memory management. This option implies
|
13155 |
|
|
@option{-fPIC}.
|
13156 |
|
|
|
13157 |
|
|
@item -mno-sep-data
|
13158 |
|
|
Generate code that assumes that the data segment follows the text segment.
|
13159 |
|
|
This is the default.
|
13160 |
|
|
|
13161 |
|
|
@item -mid-shared-library
|
13162 |
|
|
Generate code that supports shared libraries via the library ID method.
|
13163 |
|
|
This allows for execute in place and shared libraries in an environment
|
13164 |
|
|
without virtual memory management. This option implies @option{-fPIC}.
|
13165 |
|
|
|
13166 |
|
|
@item -mno-id-shared-library
|
13167 |
|
|
Generate code that doesn't assume ID based shared libraries are being used.
|
13168 |
|
|
This is the default.
|
13169 |
|
|
|
13170 |
|
|
@item -mshared-library-id=n
|
13171 |
|
|
Specified the identification number of the ID based shared library being
|
13172 |
|
|
compiled. Specifying a value of 0 will generate more compact code, specifying
|
13173 |
|
|
other values will force the allocation of that number to the current
|
13174 |
|
|
library but is no more space or time efficient than omitting this option.
|
13175 |
|
|
|
13176 |
|
|
@item -mxgot
|
13177 |
|
|
@itemx -mno-xgot
|
13178 |
|
|
@opindex mxgot
|
13179 |
|
|
@opindex mno-xgot
|
13180 |
|
|
When generating position-independent code for ColdFire, generate code
|
13181 |
|
|
that works if the GOT has more than 8192 entries. This code is
|
13182 |
|
|
larger and slower than code generated without this option. On M680x0
|
13183 |
|
|
processors, this option is not needed; @option{-fPIC} suffices.
|
13184 |
|
|
|
13185 |
|
|
GCC normally uses a single instruction to load values from the GOT@.
|
13186 |
|
|
While this is relatively efficient, it only works if the GOT
|
13187 |
|
|
is smaller than about 64k. Anything larger causes the linker
|
13188 |
|
|
to report an error such as:
|
13189 |
|
|
|
13190 |
|
|
@cindex relocation truncated to fit (ColdFire)
|
13191 |
|
|
@smallexample
|
13192 |
|
|
relocation truncated to fit: R_68K_GOT16O foobar
|
13193 |
|
|
@end smallexample
|
13194 |
|
|
|
13195 |
|
|
If this happens, you should recompile your code with @option{-mxgot}.
|
13196 |
|
|
It should then work with very large GOTs. However, code generated with
|
13197 |
|
|
@option{-mxgot} is less efficient, since it takes 4 instructions to fetch
|
13198 |
|
|
the value of a global symbol.
|
13199 |
|
|
|
13200 |
|
|
Note that some linkers, including newer versions of the GNU linker,
|
13201 |
|
|
can create multiple GOTs and sort GOT entries. If you have such a linker,
|
13202 |
|
|
you should only need to use @option{-mxgot} when compiling a single
|
13203 |
|
|
object file that accesses more than 8192 GOT entries. Very few do.
|
13204 |
|
|
|
13205 |
|
|
These options have no effect unless GCC is generating
|
13206 |
|
|
position-independent code.
|
13207 |
|
|
|
13208 |
|
|
@end table
|
13209 |
|
|
|
13210 |
|
|
@node M68hc1x Options
|
13211 |
|
|
@subsection M68hc1x Options
|
13212 |
|
|
@cindex M68hc1x options
|
13213 |
|
|
|
13214 |
|
|
These are the @samp{-m} options defined for the 68hc11 and 68hc12
|
13215 |
|
|
microcontrollers. The default values for these options depends on
|
13216 |
|
|
which style of microcontroller was selected when the compiler was configured;
|
13217 |
|
|
the defaults for the most common choices are given below.
|
13218 |
|
|
|
13219 |
|
|
@table @gcctabopt
|
13220 |
|
|
@item -m6811
|
13221 |
|
|
@itemx -m68hc11
|
13222 |
|
|
@opindex m6811
|
13223 |
|
|
@opindex m68hc11
|
13224 |
|
|
Generate output for a 68HC11. This is the default
|
13225 |
|
|
when the compiler is configured for 68HC11-based systems.
|
13226 |
|
|
|
13227 |
|
|
@item -m6812
|
13228 |
|
|
@itemx -m68hc12
|
13229 |
|
|
@opindex m6812
|
13230 |
|
|
@opindex m68hc12
|
13231 |
|
|
Generate output for a 68HC12. This is the default
|
13232 |
|
|
when the compiler is configured for 68HC12-based systems.
|
13233 |
|
|
|
13234 |
|
|
@item -m68S12
|
13235 |
|
|
@itemx -m68hcs12
|
13236 |
|
|
@opindex m68S12
|
13237 |
|
|
@opindex m68hcs12
|
13238 |
|
|
Generate output for a 68HCS12.
|
13239 |
|
|
|
13240 |
|
|
@item -mauto-incdec
|
13241 |
|
|
@opindex mauto-incdec
|
13242 |
|
|
Enable the use of 68HC12 pre and post auto-increment and auto-decrement
|
13243 |
|
|
addressing modes.
|
13244 |
|
|
|
13245 |
|
|
@item -minmax
|
13246 |
|
|
@itemx -mnominmax
|
13247 |
|
|
@opindex minmax
|
13248 |
|
|
@opindex mnominmax
|
13249 |
|
|
Enable the use of 68HC12 min and max instructions.
|
13250 |
|
|
|
13251 |
|
|
@item -mlong-calls
|
13252 |
|
|
@itemx -mno-long-calls
|
13253 |
|
|
@opindex mlong-calls
|
13254 |
|
|
@opindex mno-long-calls
|
13255 |
|
|
Treat all calls as being far away (near). If calls are assumed to be
|
13256 |
|
|
far away, the compiler will use the @code{call} instruction to
|
13257 |
|
|
call a function and the @code{rtc} instruction for returning.
|
13258 |
|
|
|
13259 |
|
|
@item -mshort
|
13260 |
|
|
@opindex mshort
|
13261 |
|
|
Consider type @code{int} to be 16 bits wide, like @code{short int}.
|
13262 |
|
|
|
13263 |
|
|
@item -msoft-reg-count=@var{count}
|
13264 |
|
|
@opindex msoft-reg-count
|
13265 |
|
|
Specify the number of pseudo-soft registers which are used for the
|
13266 |
|
|
code generation. The maximum number is 32. Using more pseudo-soft
|
13267 |
|
|
register may or may not result in better code depending on the program.
|
13268 |
|
|
The default is 4 for 68HC11 and 2 for 68HC12.
|
13269 |
|
|
|
13270 |
|
|
@end table
|
13271 |
|
|
|
13272 |
|
|
@node MCore Options
|
13273 |
|
|
@subsection MCore Options
|
13274 |
|
|
@cindex MCore options
|
13275 |
|
|
|
13276 |
|
|
These are the @samp{-m} options defined for the Motorola M*Core
|
13277 |
|
|
processors.
|
13278 |
|
|
|
13279 |
|
|
@table @gcctabopt
|
13280 |
|
|
|
13281 |
|
|
@item -mhardlit
|
13282 |
|
|
@itemx -mno-hardlit
|
13283 |
|
|
@opindex mhardlit
|
13284 |
|
|
@opindex mno-hardlit
|
13285 |
|
|
Inline constants into the code stream if it can be done in two
|
13286 |
|
|
instructions or less.
|
13287 |
|
|
|
13288 |
|
|
@item -mdiv
|
13289 |
|
|
@itemx -mno-div
|
13290 |
|
|
@opindex mdiv
|
13291 |
|
|
@opindex mno-div
|
13292 |
|
|
Use the divide instruction. (Enabled by default).
|
13293 |
|
|
|
13294 |
|
|
@item -mrelax-immediate
|
13295 |
|
|
@itemx -mno-relax-immediate
|
13296 |
|
|
@opindex mrelax-immediate
|
13297 |
|
|
@opindex mno-relax-immediate
|
13298 |
|
|
Allow arbitrary sized immediates in bit operations.
|
13299 |
|
|
|
13300 |
|
|
@item -mwide-bitfields
|
13301 |
|
|
@itemx -mno-wide-bitfields
|
13302 |
|
|
@opindex mwide-bitfields
|
13303 |
|
|
@opindex mno-wide-bitfields
|
13304 |
|
|
Always treat bit-fields as int-sized.
|
13305 |
|
|
|
13306 |
|
|
@item -m4byte-functions
|
13307 |
|
|
@itemx -mno-4byte-functions
|
13308 |
|
|
@opindex m4byte-functions
|
13309 |
|
|
@opindex mno-4byte-functions
|
13310 |
|
|
Force all functions to be aligned to a four byte boundary.
|
13311 |
|
|
|
13312 |
|
|
@item -mcallgraph-data
|
13313 |
|
|
@itemx -mno-callgraph-data
|
13314 |
|
|
@opindex mcallgraph-data
|
13315 |
|
|
@opindex mno-callgraph-data
|
13316 |
|
|
Emit callgraph information.
|
13317 |
|
|
|
13318 |
|
|
@item -mslow-bytes
|
13319 |
|
|
@itemx -mno-slow-bytes
|
13320 |
|
|
@opindex mslow-bytes
|
13321 |
|
|
@opindex mno-slow-bytes
|
13322 |
|
|
Prefer word access when reading byte quantities.
|
13323 |
|
|
|
13324 |
|
|
@item -mlittle-endian
|
13325 |
|
|
@itemx -mbig-endian
|
13326 |
|
|
@opindex mlittle-endian
|
13327 |
|
|
@opindex mbig-endian
|
13328 |
|
|
Generate code for a little endian target.
|
13329 |
|
|
|
13330 |
|
|
@item -m210
|
13331 |
|
|
@itemx -m340
|
13332 |
|
|
@opindex m210
|
13333 |
|
|
@opindex m340
|
13334 |
|
|
Generate code for the 210 processor.
|
13335 |
|
|
|
13336 |
|
|
@item -mno-lsim
|
13337 |
|
|
@opindex mno-lsim
|
13338 |
|
|
Assume that run-time support has been provided and so omit the
|
13339 |
|
|
simulator library (@file{libsim.a)} from the linker command line.
|
13340 |
|
|
|
13341 |
|
|
@item -mstack-increment=@var{size}
|
13342 |
|
|
@opindex mstack-increment
|
13343 |
|
|
Set the maximum amount for a single stack increment operation. Large
|
13344 |
|
|
values can increase the speed of programs which contain functions
|
13345 |
|
|
that need a large amount of stack space, but they can also trigger a
|
13346 |
|
|
segmentation fault if the stack is extended too much. The default
|
13347 |
|
|
value is 0x1000.
|
13348 |
|
|
|
13349 |
|
|
@end table
|
13350 |
|
|
|
13351 |
|
|
@node MeP Options
|
13352 |
|
|
@subsection MeP Options
|
13353 |
|
|
@cindex MeP options
|
13354 |
|
|
|
13355 |
|
|
@table @gcctabopt
|
13356 |
|
|
|
13357 |
|
|
@item -mabsdiff
|
13358 |
|
|
@opindex mabsdiff
|
13359 |
|
|
Enables the @code{abs} instruction, which is the absolute difference
|
13360 |
|
|
between two registers.
|
13361 |
|
|
|
13362 |
|
|
@item -mall-opts
|
13363 |
|
|
@opindex mall-opts
|
13364 |
|
|
Enables all the optional instructions - average, multiply, divide, bit
|
13365 |
|
|
operations, leading zero, absolute difference, min/max, clip, and
|
13366 |
|
|
saturation.
|
13367 |
|
|
|
13368 |
|
|
|
13369 |
|
|
@item -maverage
|
13370 |
|
|
@opindex maverage
|
13371 |
|
|
Enables the @code{ave} instruction, which computes the average of two
|
13372 |
|
|
registers.
|
13373 |
|
|
|
13374 |
|
|
@item -mbased=@var{n}
|
13375 |
|
|
@opindex mbased=
|
13376 |
|
|
Variables of size @var{n} bytes or smaller will be placed in the
|
13377 |
|
|
@code{.based} section by default. Based variables use the @code{$tp}
|
13378 |
|
|
register as a base register, and there is a 128 byte limit to the
|
13379 |
|
|
@code{.based} section.
|
13380 |
|
|
|
13381 |
|
|
@item -mbitops
|
13382 |
|
|
@opindex mbitops
|
13383 |
|
|
Enables the bit operation instructions - bit test (@code{btstm}), set
|
13384 |
|
|
(@code{bsetm}), clear (@code{bclrm}), invert (@code{bnotm}), and
|
13385 |
|
|
test-and-set (@code{tas}).
|
13386 |
|
|
|
13387 |
|
|
@item -mc=@var{name}
|
13388 |
|
|
@opindex mc=
|
13389 |
|
|
Selects which section constant data will be placed in. @var{name} may
|
13390 |
|
|
be @code{tiny}, @code{near}, or @code{far}.
|
13391 |
|
|
|
13392 |
|
|
@item -mclip
|
13393 |
|
|
@opindex mclip
|
13394 |
|
|
Enables the @code{clip} instruction. Note that @code{-mclip} is not
|
13395 |
|
|
useful unless you also provide @code{-mminmax}.
|
13396 |
|
|
|
13397 |
|
|
@item -mconfig=@var{name}
|
13398 |
|
|
@opindex mconfig=
|
13399 |
|
|
Selects one of the build-in core configurations. Each MeP chip has
|
13400 |
|
|
one or more modules in it; each module has a core CPU and a variety of
|
13401 |
|
|
coprocessors, optional instructions, and peripherals. The
|
13402 |
|
|
@code{MeP-Integrator} tool, not part of GCC, provides these
|
13403 |
|
|
configurations through this option; using this option is the same as
|
13404 |
|
|
using all the corresponding command line options. The default
|
13405 |
|
|
configuration is @code{default}.
|
13406 |
|
|
|
13407 |
|
|
@item -mcop
|
13408 |
|
|
@opindex mcop
|
13409 |
|
|
Enables the coprocessor instructions. By default, this is a 32-bit
|
13410 |
|
|
coprocessor. Note that the coprocessor is normally enabled via the
|
13411 |
|
|
@code{-mconfig=} option.
|
13412 |
|
|
|
13413 |
|
|
@item -mcop32
|
13414 |
|
|
@opindex mcop32
|
13415 |
|
|
Enables the 32-bit coprocessor's instructions.
|
13416 |
|
|
|
13417 |
|
|
@item -mcop64
|
13418 |
|
|
@opindex mcop64
|
13419 |
|
|
Enables the 64-bit coprocessor's instructions.
|
13420 |
|
|
|
13421 |
|
|
@item -mivc2
|
13422 |
|
|
@opindex mivc2
|
13423 |
|
|
Enables IVC2 scheduling. IVC2 is a 64-bit VLIW coprocessor.
|
13424 |
|
|
|
13425 |
|
|
@item -mdc
|
13426 |
|
|
@opindex mdc
|
13427 |
|
|
Causes constant variables to be placed in the @code{.near} section.
|
13428 |
|
|
|
13429 |
|
|
@item -mdiv
|
13430 |
|
|
@opindex mdiv
|
13431 |
|
|
Enables the @code{div} and @code{divu} instructions.
|
13432 |
|
|
|
13433 |
|
|
@item -meb
|
13434 |
|
|
@opindex meb
|
13435 |
|
|
Generate big-endian code.
|
13436 |
|
|
|
13437 |
|
|
@item -mel
|
13438 |
|
|
@opindex mel
|
13439 |
|
|
Generate little-endian code.
|
13440 |
|
|
|
13441 |
|
|
@item -mio-volatile
|
13442 |
|
|
@opindex mio-volatile
|
13443 |
|
|
Tells the compiler that any variable marked with the @code{io}
|
13444 |
|
|
attribute is to be considered volatile.
|
13445 |
|
|
|
13446 |
|
|
@item -ml
|
13447 |
|
|
@opindex ml
|
13448 |
|
|
Causes variables to be assigned to the @code{.far} section by default.
|
13449 |
|
|
|
13450 |
|
|
@item -mleadz
|
13451 |
|
|
@opindex mleadz
|
13452 |
|
|
Enables the @code{leadz} (leading zero) instruction.
|
13453 |
|
|
|
13454 |
|
|
@item -mm
|
13455 |
|
|
@opindex mm
|
13456 |
|
|
Causes variables to be assigned to the @code{.near} section by default.
|
13457 |
|
|
|
13458 |
|
|
@item -mminmax
|
13459 |
|
|
@opindex mminmax
|
13460 |
|
|
Enables the @code{min} and @code{max} instructions.
|
13461 |
|
|
|
13462 |
|
|
@item -mmult
|
13463 |
|
|
@opindex mmult
|
13464 |
|
|
Enables the multiplication and multiply-accumulate instructions.
|
13465 |
|
|
|
13466 |
|
|
@item -mno-opts
|
13467 |
|
|
@opindex mno-opts
|
13468 |
|
|
Disables all the optional instructions enabled by @code{-mall-opts}.
|
13469 |
|
|
|
13470 |
|
|
@item -mrepeat
|
13471 |
|
|
@opindex mrepeat
|
13472 |
|
|
Enables the @code{repeat} and @code{erepeat} instructions, used for
|
13473 |
|
|
low-overhead looping.
|
13474 |
|
|
|
13475 |
|
|
@item -ms
|
13476 |
|
|
@opindex ms
|
13477 |
|
|
Causes all variables to default to the @code{.tiny} section. Note
|
13478 |
|
|
that there is a 65536 byte limit to this section. Accesses to these
|
13479 |
|
|
variables use the @code{%gp} base register.
|
13480 |
|
|
|
13481 |
|
|
@item -msatur
|
13482 |
|
|
@opindex msatur
|
13483 |
|
|
Enables the saturation instructions. Note that the compiler does not
|
13484 |
|
|
currently generate these itself, but this option is included for
|
13485 |
|
|
compatibility with other tools, like @code{as}.
|
13486 |
|
|
|
13487 |
|
|
@item -msdram
|
13488 |
|
|
@opindex msdram
|
13489 |
|
|
Link the SDRAM-based runtime instead of the default ROM-based runtime.
|
13490 |
|
|
|
13491 |
|
|
@item -msim
|
13492 |
|
|
@opindex msim
|
13493 |
|
|
Link the simulator runtime libraries.
|
13494 |
|
|
|
13495 |
|
|
@item -msimnovec
|
13496 |
|
|
@opindex msimnovec
|
13497 |
|
|
Link the simulator runtime libraries, excluding built-in support
|
13498 |
|
|
for reset and exception vectors and tables.
|
13499 |
|
|
|
13500 |
|
|
@item -mtf
|
13501 |
|
|
@opindex mtf
|
13502 |
|
|
Causes all functions to default to the @code{.far} section. Without
|
13503 |
|
|
this option, functions default to the @code{.near} section.
|
13504 |
|
|
|
13505 |
|
|
@item -mtiny=@var{n}
|
13506 |
|
|
@opindex mtiny=
|
13507 |
|
|
Variables that are @var{n} bytes or smaller will be allocated to the
|
13508 |
|
|
@code{.tiny} section. These variables use the @code{$gp} base
|
13509 |
|
|
register. The default for this option is 4, but note that there's a
|
13510 |
|
|
65536 byte limit to the @code{.tiny} section.
|
13511 |
|
|
|
13512 |
|
|
@end table
|
13513 |
|
|
|
13514 |
|
|
@node MIPS Options
|
13515 |
|
|
@subsection MIPS Options
|
13516 |
|
|
@cindex MIPS options
|
13517 |
|
|
|
13518 |
|
|
@table @gcctabopt
|
13519 |
|
|
|
13520 |
|
|
@item -EB
|
13521 |
|
|
@opindex EB
|
13522 |
|
|
Generate big-endian code.
|
13523 |
|
|
|
13524 |
|
|
@item -EL
|
13525 |
|
|
@opindex EL
|
13526 |
|
|
Generate little-endian code. This is the default for @samp{mips*el-*-*}
|
13527 |
|
|
configurations.
|
13528 |
|
|
|
13529 |
|
|
@item -march=@var{arch}
|
13530 |
|
|
@opindex march
|
13531 |
|
|
Generate code that will run on @var{arch}, which can be the name of a
|
13532 |
|
|
generic MIPS ISA, or the name of a particular processor.
|
13533 |
|
|
The ISA names are:
|
13534 |
|
|
@samp{mips1}, @samp{mips2}, @samp{mips3}, @samp{mips4},
|
13535 |
|
|
@samp{mips32}, @samp{mips32r2}, @samp{mips64} and @samp{mips64r2}.
|
13536 |
|
|
The processor names are:
|
13537 |
|
|
@samp{4kc}, @samp{4km}, @samp{4kp}, @samp{4ksc},
|
13538 |
|
|
@samp{4kec}, @samp{4kem}, @samp{4kep}, @samp{4ksd},
|
13539 |
|
|
@samp{5kc}, @samp{5kf},
|
13540 |
|
|
@samp{20kc},
|
13541 |
|
|
@samp{24kc}, @samp{24kf2_1}, @samp{24kf1_1},
|
13542 |
|
|
@samp{24kec}, @samp{24kef2_1}, @samp{24kef1_1},
|
13543 |
|
|
@samp{34kc}, @samp{34kf2_1}, @samp{34kf1_1},
|
13544 |
|
|
@samp{74kc}, @samp{74kf2_1}, @samp{74kf1_1}, @samp{74kf3_2},
|
13545 |
|
|
@samp{1004kc}, @samp{1004kf2_1}, @samp{1004kf1_1},
|
13546 |
|
|
@samp{loongson2e}, @samp{loongson2f},
|
13547 |
|
|
@samp{m4k},
|
13548 |
|
|
@samp{octeon},
|
13549 |
|
|
@samp{orion},
|
13550 |
|
|
@samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400},
|
13551 |
|
|
@samp{r4600}, @samp{r4650}, @samp{r6000}, @samp{r8000},
|
13552 |
|
|
@samp{rm7000}, @samp{rm9000},
|
13553 |
|
|
@samp{r10000}, @samp{r12000}, @samp{r14000}, @samp{r16000},
|
13554 |
|
|
@samp{sb1},
|
13555 |
|
|
@samp{sr71000},
|
13556 |
|
|
@samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300},
|
13557 |
|
|
@samp{vr5000}, @samp{vr5400}, @samp{vr5500}
|
13558 |
|
|
and @samp{xlr}.
|
13559 |
|
|
The special value @samp{from-abi} selects the
|
13560 |
|
|
most compatible architecture for the selected ABI (that is,
|
13561 |
|
|
@samp{mips1} for 32-bit ABIs and @samp{mips3} for 64-bit ABIs)@.
|
13562 |
|
|
|
13563 |
|
|
Native Linux/GNU toolchains also support the value @samp{native},
|
13564 |
|
|
which selects the best architecture option for the host processor.
|
13565 |
|
|
@option{-march=native} has no effect if GCC does not recognize
|
13566 |
|
|
the processor.
|
13567 |
|
|
|
13568 |
|
|
In processor names, a final @samp{000} can be abbreviated as @samp{k}
|
13569 |
|
|
(for example, @samp{-march=r2k}). Prefixes are optional, and
|
13570 |
|
|
@samp{vr} may be written @samp{r}.
|
13571 |
|
|
|
13572 |
|
|
Names of the form @samp{@var{n}f2_1} refer to processors with
|
13573 |
|
|
FPUs clocked at half the rate of the core, names of the form
|
13574 |
|
|
@samp{@var{n}f1_1} refer to processors with FPUs clocked at the same
|
13575 |
|
|
rate as the core, and names of the form @samp{@var{n}f3_2} refer to
|
13576 |
|
|
processors with FPUs clocked a ratio of 3:2 with respect to the core.
|
13577 |
|
|
For compatibility reasons, @samp{@var{n}f} is accepted as a synonym
|
13578 |
|
|
for @samp{@var{n}f2_1} while @samp{@var{n}x} and @samp{@var{b}fx} are
|
13579 |
|
|
accepted as synonyms for @samp{@var{n}f1_1}.
|
13580 |
|
|
|
13581 |
|
|
GCC defines two macros based on the value of this option. The first
|
13582 |
|
|
is @samp{_MIPS_ARCH}, which gives the name of target architecture, as
|
13583 |
|
|
a string. The second has the form @samp{_MIPS_ARCH_@var{foo}},
|
13584 |
|
|
where @var{foo} is the capitalized value of @samp{_MIPS_ARCH}@.
|
13585 |
|
|
For example, @samp{-march=r2000} will set @samp{_MIPS_ARCH}
|
13586 |
|
|
to @samp{"r2000"} and define the macro @samp{_MIPS_ARCH_R2000}.
|
13587 |
|
|
|
13588 |
|
|
Note that the @samp{_MIPS_ARCH} macro uses the processor names given
|
13589 |
|
|
above. In other words, it will have the full prefix and will not
|
13590 |
|
|
abbreviate @samp{000} as @samp{k}. In the case of @samp{from-abi},
|
13591 |
|
|
the macro names the resolved architecture (either @samp{"mips1"} or
|
13592 |
|
|
@samp{"mips3"}). It names the default architecture when no
|
13593 |
|
|
@option{-march} option is given.
|
13594 |
|
|
|
13595 |
|
|
@item -mtune=@var{arch}
|
13596 |
|
|
@opindex mtune
|
13597 |
|
|
Optimize for @var{arch}. Among other things, this option controls
|
13598 |
|
|
the way instructions are scheduled, and the perceived cost of arithmetic
|
13599 |
|
|
operations. The list of @var{arch} values is the same as for
|
13600 |
|
|
@option{-march}.
|
13601 |
|
|
|
13602 |
|
|
When this option is not used, GCC will optimize for the processor
|
13603 |
|
|
specified by @option{-march}. By using @option{-march} and
|
13604 |
|
|
@option{-mtune} together, it is possible to generate code that will
|
13605 |
|
|
run on a family of processors, but optimize the code for one
|
13606 |
|
|
particular member of that family.
|
13607 |
|
|
|
13608 |
|
|
@samp{-mtune} defines the macros @samp{_MIPS_TUNE} and
|
13609 |
|
|
@samp{_MIPS_TUNE_@var{foo}}, which work in the same way as the
|
13610 |
|
|
@samp{-march} ones described above.
|
13611 |
|
|
|
13612 |
|
|
@item -mips1
|
13613 |
|
|
@opindex mips1
|
13614 |
|
|
Equivalent to @samp{-march=mips1}.
|
13615 |
|
|
|
13616 |
|
|
@item -mips2
|
13617 |
|
|
@opindex mips2
|
13618 |
|
|
Equivalent to @samp{-march=mips2}.
|
13619 |
|
|
|
13620 |
|
|
@item -mips3
|
13621 |
|
|
@opindex mips3
|
13622 |
|
|
Equivalent to @samp{-march=mips3}.
|
13623 |
|
|
|
13624 |
|
|
@item -mips4
|
13625 |
|
|
@opindex mips4
|
13626 |
|
|
Equivalent to @samp{-march=mips4}.
|
13627 |
|
|
|
13628 |
|
|
@item -mips32
|
13629 |
|
|
@opindex mips32
|
13630 |
|
|
Equivalent to @samp{-march=mips32}.
|
13631 |
|
|
|
13632 |
|
|
@item -mips32r2
|
13633 |
|
|
@opindex mips32r2
|
13634 |
|
|
Equivalent to @samp{-march=mips32r2}.
|
13635 |
|
|
|
13636 |
|
|
@item -mips64
|
13637 |
|
|
@opindex mips64
|
13638 |
|
|
Equivalent to @samp{-march=mips64}.
|
13639 |
|
|
|
13640 |
|
|
@item -mips64r2
|
13641 |
|
|
@opindex mips64r2
|
13642 |
|
|
Equivalent to @samp{-march=mips64r2}.
|
13643 |
|
|
|
13644 |
|
|
@item -mips16
|
13645 |
|
|
@itemx -mno-mips16
|
13646 |
|
|
@opindex mips16
|
13647 |
|
|
@opindex mno-mips16
|
13648 |
|
|
Generate (do not generate) MIPS16 code. If GCC is targetting a
|
13649 |
|
|
MIPS32 or MIPS64 architecture, it will make use of the MIPS16e ASE@.
|
13650 |
|
|
|
13651 |
|
|
MIPS16 code generation can also be controlled on a per-function basis
|
13652 |
|
|
by means of @code{mips16} and @code{nomips16} attributes.
|
13653 |
|
|
@xref{Function Attributes}, for more information.
|
13654 |
|
|
|
13655 |
|
|
@item -mflip-mips16
|
13656 |
|
|
@opindex mflip-mips16
|
13657 |
|
|
Generate MIPS16 code on alternating functions. This option is provided
|
13658 |
|
|
for regression testing of mixed MIPS16/non-MIPS16 code generation, and is
|
13659 |
|
|
not intended for ordinary use in compiling user code.
|
13660 |
|
|
|
13661 |
|
|
@item -minterlink-mips16
|
13662 |
|
|
@itemx -mno-interlink-mips16
|
13663 |
|
|
@opindex minterlink-mips16
|
13664 |
|
|
@opindex mno-interlink-mips16
|
13665 |
|
|
Require (do not require) that non-MIPS16 code be link-compatible with
|
13666 |
|
|
MIPS16 code.
|
13667 |
|
|
|
13668 |
|
|
For example, non-MIPS16 code cannot jump directly to MIPS16 code;
|
13669 |
|
|
it must either use a call or an indirect jump. @option{-minterlink-mips16}
|
13670 |
|
|
therefore disables direct jumps unless GCC knows that the target of the
|
13671 |
|
|
jump is not MIPS16.
|
13672 |
|
|
|
13673 |
|
|
@item -mabi=32
|
13674 |
|
|
@itemx -mabi=o64
|
13675 |
|
|
@itemx -mabi=n32
|
13676 |
|
|
@itemx -mabi=64
|
13677 |
|
|
@itemx -mabi=eabi
|
13678 |
|
|
@opindex mabi=32
|
13679 |
|
|
@opindex mabi=o64
|
13680 |
|
|
@opindex mabi=n32
|
13681 |
|
|
@opindex mabi=64
|
13682 |
|
|
@opindex mabi=eabi
|
13683 |
|
|
Generate code for the given ABI@.
|
13684 |
|
|
|
13685 |
|
|
Note that the EABI has a 32-bit and a 64-bit variant. GCC normally
|
13686 |
|
|
generates 64-bit code when you select a 64-bit architecture, but you
|
13687 |
|
|
can use @option{-mgp32} to get 32-bit code instead.
|
13688 |
|
|
|
13689 |
|
|
For information about the O64 ABI, see
|
13690 |
|
|
@w{@uref{http://gcc.gnu.org/projects/mipso64-abi.html}}.
|
13691 |
|
|
|
13692 |
|
|
GCC supports a variant of the o32 ABI in which floating-point registers
|
13693 |
|
|
are 64 rather than 32 bits wide. You can select this combination with
|
13694 |
|
|
@option{-mabi=32} @option{-mfp64}. This ABI relies on the @samp{mthc1}
|
13695 |
|
|
and @samp{mfhc1} instructions and is therefore only supported for
|
13696 |
|
|
MIPS32R2 processors.
|
13697 |
|
|
|
13698 |
|
|
The register assignments for arguments and return values remain the
|
13699 |
|
|
same, but each scalar value is passed in a single 64-bit register
|
13700 |
|
|
rather than a pair of 32-bit registers. For example, scalar
|
13701 |
|
|
floating-point values are returned in @samp{$f0} only, not a
|
13702 |
|
|
@samp{$f0}/@samp{$f1} pair. The set of call-saved registers also
|
13703 |
|
|
remains the same, but all 64 bits are saved.
|
13704 |
|
|
|
13705 |
|
|
@item -mabicalls
|
13706 |
|
|
@itemx -mno-abicalls
|
13707 |
|
|
@opindex mabicalls
|
13708 |
|
|
@opindex mno-abicalls
|
13709 |
|
|
Generate (do not generate) code that is suitable for SVR4-style
|
13710 |
|
|
dynamic objects. @option{-mabicalls} is the default for SVR4-based
|
13711 |
|
|
systems.
|
13712 |
|
|
|
13713 |
|
|
@item -mshared
|
13714 |
|
|
@itemx -mno-shared
|
13715 |
|
|
Generate (do not generate) code that is fully position-independent,
|
13716 |
|
|
and that can therefore be linked into shared libraries. This option
|
13717 |
|
|
only affects @option{-mabicalls}.
|
13718 |
|
|
|
13719 |
|
|
All @option{-mabicalls} code has traditionally been position-independent,
|
13720 |
|
|
regardless of options like @option{-fPIC} and @option{-fpic}. However,
|
13721 |
|
|
as an extension, the GNU toolchain allows executables to use absolute
|
13722 |
|
|
accesses for locally-binding symbols. It can also use shorter GP
|
13723 |
|
|
initialization sequences and generate direct calls to locally-defined
|
13724 |
|
|
functions. This mode is selected by @option{-mno-shared}.
|
13725 |
|
|
|
13726 |
|
|
@option{-mno-shared} depends on binutils 2.16 or higher and generates
|
13727 |
|
|
objects that can only be linked by the GNU linker. However, the option
|
13728 |
|
|
does not affect the ABI of the final executable; it only affects the ABI
|
13729 |
|
|
of relocatable objects. Using @option{-mno-shared} will generally make
|
13730 |
|
|
executables both smaller and quicker.
|
13731 |
|
|
|
13732 |
|
|
@option{-mshared} is the default.
|
13733 |
|
|
|
13734 |
|
|
@item -mplt
|
13735 |
|
|
@itemx -mno-plt
|
13736 |
|
|
@opindex mplt
|
13737 |
|
|
@opindex mno-plt
|
13738 |
|
|
Assume (do not assume) that the static and dynamic linkers
|
13739 |
|
|
support PLTs and copy relocations. This option only affects
|
13740 |
|
|
@samp{-mno-shared -mabicalls}. For the n64 ABI, this option
|
13741 |
|
|
has no effect without @samp{-msym32}.
|
13742 |
|
|
|
13743 |
|
|
You can make @option{-mplt} the default by configuring
|
13744 |
|
|
GCC with @option{--with-mips-plt}. The default is
|
13745 |
|
|
@option{-mno-plt} otherwise.
|
13746 |
|
|
|
13747 |
|
|
@item -mxgot
|
13748 |
|
|
@itemx -mno-xgot
|
13749 |
|
|
@opindex mxgot
|
13750 |
|
|
@opindex mno-xgot
|
13751 |
|
|
Lift (do not lift) the usual restrictions on the size of the global
|
13752 |
|
|
offset table.
|
13753 |
|
|
|
13754 |
|
|
GCC normally uses a single instruction to load values from the GOT@.
|
13755 |
|
|
While this is relatively efficient, it will only work if the GOT
|
13756 |
|
|
is smaller than about 64k. Anything larger will cause the linker
|
13757 |
|
|
to report an error such as:
|
13758 |
|
|
|
13759 |
|
|
@cindex relocation truncated to fit (MIPS)
|
13760 |
|
|
@smallexample
|
13761 |
|
|
relocation truncated to fit: R_MIPS_GOT16 foobar
|
13762 |
|
|
@end smallexample
|
13763 |
|
|
|
13764 |
|
|
If this happens, you should recompile your code with @option{-mxgot}.
|
13765 |
|
|
It should then work with very large GOTs, although it will also be
|
13766 |
|
|
less efficient, since it will take three instructions to fetch the
|
13767 |
|
|
value of a global symbol.
|
13768 |
|
|
|
13769 |
|
|
Note that some linkers can create multiple GOTs. If you have such a
|
13770 |
|
|
linker, you should only need to use @option{-mxgot} when a single object
|
13771 |
|
|
file accesses more than 64k's worth of GOT entries. Very few do.
|
13772 |
|
|
|
13773 |
|
|
These options have no effect unless GCC is generating position
|
13774 |
|
|
independent code.
|
13775 |
|
|
|
13776 |
|
|
@item -mgp32
|
13777 |
|
|
@opindex mgp32
|
13778 |
|
|
Assume that general-purpose registers are 32 bits wide.
|
13779 |
|
|
|
13780 |
|
|
@item -mgp64
|
13781 |
|
|
@opindex mgp64
|
13782 |
|
|
Assume that general-purpose registers are 64 bits wide.
|
13783 |
|
|
|
13784 |
|
|
@item -mfp32
|
13785 |
|
|
@opindex mfp32
|
13786 |
|
|
Assume that floating-point registers are 32 bits wide.
|
13787 |
|
|
|
13788 |
|
|
@item -mfp64
|
13789 |
|
|
@opindex mfp64
|
13790 |
|
|
Assume that floating-point registers are 64 bits wide.
|
13791 |
|
|
|
13792 |
|
|
@item -mhard-float
|
13793 |
|
|
@opindex mhard-float
|
13794 |
|
|
Use floating-point coprocessor instructions.
|
13795 |
|
|
|
13796 |
|
|
@item -msoft-float
|
13797 |
|
|
@opindex msoft-float
|
13798 |
|
|
Do not use floating-point coprocessor instructions. Implement
|
13799 |
|
|
floating-point calculations using library calls instead.
|
13800 |
|
|
|
13801 |
|
|
@item -msingle-float
|
13802 |
|
|
@opindex msingle-float
|
13803 |
|
|
Assume that the floating-point coprocessor only supports single-precision
|
13804 |
|
|
operations.
|
13805 |
|
|
|
13806 |
|
|
@item -mdouble-float
|
13807 |
|
|
@opindex mdouble-float
|
13808 |
|
|
Assume that the floating-point coprocessor supports double-precision
|
13809 |
|
|
operations. This is the default.
|
13810 |
|
|
|
13811 |
|
|
@item -mllsc
|
13812 |
|
|
@itemx -mno-llsc
|
13813 |
|
|
@opindex mllsc
|
13814 |
|
|
@opindex mno-llsc
|
13815 |
|
|
Use (do not use) @samp{ll}, @samp{sc}, and @samp{sync} instructions to
|
13816 |
|
|
implement atomic memory built-in functions. When neither option is
|
13817 |
|
|
specified, GCC will use the instructions if the target architecture
|
13818 |
|
|
supports them.
|
13819 |
|
|
|
13820 |
|
|
@option{-mllsc} is useful if the runtime environment can emulate the
|
13821 |
|
|
instructions and @option{-mno-llsc} can be useful when compiling for
|
13822 |
|
|
nonstandard ISAs. You can make either option the default by
|
13823 |
|
|
configuring GCC with @option{--with-llsc} and @option{--without-llsc}
|
13824 |
|
|
respectively. @option{--with-llsc} is the default for some
|
13825 |
|
|
configurations; see the installation documentation for details.
|
13826 |
|
|
|
13827 |
|
|
@item -mdsp
|
13828 |
|
|
@itemx -mno-dsp
|
13829 |
|
|
@opindex mdsp
|
13830 |
|
|
@opindex mno-dsp
|
13831 |
|
|
Use (do not use) revision 1 of the MIPS DSP ASE@.
|
13832 |
|
|
@xref{MIPS DSP Built-in Functions}. This option defines the
|
13833 |
|
|
preprocessor macro @samp{__mips_dsp}. It also defines
|
13834 |
|
|
@samp{__mips_dsp_rev} to 1.
|
13835 |
|
|
|
13836 |
|
|
@item -mdspr2
|
13837 |
|
|
@itemx -mno-dspr2
|
13838 |
|
|
@opindex mdspr2
|
13839 |
|
|
@opindex mno-dspr2
|
13840 |
|
|
Use (do not use) revision 2 of the MIPS DSP ASE@.
|
13841 |
|
|
@xref{MIPS DSP Built-in Functions}. This option defines the
|
13842 |
|
|
preprocessor macros @samp{__mips_dsp} and @samp{__mips_dspr2}.
|
13843 |
|
|
It also defines @samp{__mips_dsp_rev} to 2.
|
13844 |
|
|
|
13845 |
|
|
@item -msmartmips
|
13846 |
|
|
@itemx -mno-smartmips
|
13847 |
|
|
@opindex msmartmips
|
13848 |
|
|
@opindex mno-smartmips
|
13849 |
|
|
Use (do not use) the MIPS SmartMIPS ASE.
|
13850 |
|
|
|
13851 |
|
|
@item -mpaired-single
|
13852 |
|
|
@itemx -mno-paired-single
|
13853 |
|
|
@opindex mpaired-single
|
13854 |
|
|
@opindex mno-paired-single
|
13855 |
|
|
Use (do not use) paired-single floating-point instructions.
|
13856 |
|
|
@xref{MIPS Paired-Single Support}. This option requires
|
13857 |
|
|
hardware floating-point support to be enabled.
|
13858 |
|
|
|
13859 |
|
|
@item -mdmx
|
13860 |
|
|
@itemx -mno-mdmx
|
13861 |
|
|
@opindex mdmx
|
13862 |
|
|
@opindex mno-mdmx
|
13863 |
|
|
Use (do not use) MIPS Digital Media Extension instructions.
|
13864 |
|
|
This option can only be used when generating 64-bit code and requires
|
13865 |
|
|
hardware floating-point support to be enabled.
|
13866 |
|
|
|
13867 |
|
|
@item -mips3d
|
13868 |
|
|
@itemx -mno-mips3d
|
13869 |
|
|
@opindex mips3d
|
13870 |
|
|
@opindex mno-mips3d
|
13871 |
|
|
Use (do not use) the MIPS-3D ASE@. @xref{MIPS-3D Built-in Functions}.
|
13872 |
|
|
The option @option{-mips3d} implies @option{-mpaired-single}.
|
13873 |
|
|
|
13874 |
|
|
@item -mmt
|
13875 |
|
|
@itemx -mno-mt
|
13876 |
|
|
@opindex mmt
|
13877 |
|
|
@opindex mno-mt
|
13878 |
|
|
Use (do not use) MT Multithreading instructions.
|
13879 |
|
|
|
13880 |
|
|
@item -mlong64
|
13881 |
|
|
@opindex mlong64
|
13882 |
|
|
Force @code{long} types to be 64 bits wide. See @option{-mlong32} for
|
13883 |
|
|
an explanation of the default and the way that the pointer size is
|
13884 |
|
|
determined.
|
13885 |
|
|
|
13886 |
|
|
@item -mlong32
|
13887 |
|
|
@opindex mlong32
|
13888 |
|
|
Force @code{long}, @code{int}, and pointer types to be 32 bits wide.
|
13889 |
|
|
|
13890 |
|
|
The default size of @code{int}s, @code{long}s and pointers depends on
|
13891 |
|
|
the ABI@. All the supported ABIs use 32-bit @code{int}s. The n64 ABI
|
13892 |
|
|
uses 64-bit @code{long}s, as does the 64-bit EABI; the others use
|
13893 |
|
|
32-bit @code{long}s. Pointers are the same size as @code{long}s,
|
13894 |
|
|
or the same size as integer registers, whichever is smaller.
|
13895 |
|
|
|
13896 |
|
|
@item -msym32
|
13897 |
|
|
@itemx -mno-sym32
|
13898 |
|
|
@opindex msym32
|
13899 |
|
|
@opindex mno-sym32
|
13900 |
|
|
Assume (do not assume) that all symbols have 32-bit values, regardless
|
13901 |
|
|
of the selected ABI@. This option is useful in combination with
|
13902 |
|
|
@option{-mabi=64} and @option{-mno-abicalls} because it allows GCC
|
13903 |
|
|
to generate shorter and faster references to symbolic addresses.
|
13904 |
|
|
|
13905 |
|
|
@item -G @var{num}
|
13906 |
|
|
@opindex G
|
13907 |
|
|
Put definitions of externally-visible data in a small data section
|
13908 |
|
|
if that data is no bigger than @var{num} bytes. GCC can then access
|
13909 |
|
|
the data more efficiently; see @option{-mgpopt} for details.
|
13910 |
|
|
|
13911 |
|
|
The default @option{-G} option depends on the configuration.
|
13912 |
|
|
|
13913 |
|
|
@item -mlocal-sdata
|
13914 |
|
|
@itemx -mno-local-sdata
|
13915 |
|
|
@opindex mlocal-sdata
|
13916 |
|
|
@opindex mno-local-sdata
|
13917 |
|
|
Extend (do not extend) the @option{-G} behavior to local data too,
|
13918 |
|
|
such as to static variables in C@. @option{-mlocal-sdata} is the
|
13919 |
|
|
default for all configurations.
|
13920 |
|
|
|
13921 |
|
|
If the linker complains that an application is using too much small data,
|
13922 |
|
|
you might want to try rebuilding the less performance-critical parts with
|
13923 |
|
|
@option{-mno-local-sdata}. You might also want to build large
|
13924 |
|
|
libraries with @option{-mno-local-sdata}, so that the libraries leave
|
13925 |
|
|
more room for the main program.
|
13926 |
|
|
|
13927 |
|
|
@item -mextern-sdata
|
13928 |
|
|
@itemx -mno-extern-sdata
|
13929 |
|
|
@opindex mextern-sdata
|
13930 |
|
|
@opindex mno-extern-sdata
|
13931 |
|
|
Assume (do not assume) that externally-defined data will be in
|
13932 |
|
|
a small data section if that data is within the @option{-G} limit.
|
13933 |
|
|
@option{-mextern-sdata} is the default for all configurations.
|
13934 |
|
|
|
13935 |
|
|
If you compile a module @var{Mod} with @option{-mextern-sdata} @option{-G
|
13936 |
|
|
@var{num}} @option{-mgpopt}, and @var{Mod} references a variable @var{Var}
|
13937 |
|
|
that is no bigger than @var{num} bytes, you must make sure that @var{Var}
|
13938 |
|
|
is placed in a small data section. If @var{Var} is defined by another
|
13939 |
|
|
module, you must either compile that module with a high-enough
|
13940 |
|
|
@option{-G} setting or attach a @code{section} attribute to @var{Var}'s
|
13941 |
|
|
definition. If @var{Var} is common, you must link the application
|
13942 |
|
|
with a high-enough @option{-G} setting.
|
13943 |
|
|
|
13944 |
|
|
The easiest way of satisfying these restrictions is to compile
|
13945 |
|
|
and link every module with the same @option{-G} option. However,
|
13946 |
|
|
you may wish to build a library that supports several different
|
13947 |
|
|
small data limits. You can do this by compiling the library with
|
13948 |
|
|
the highest supported @option{-G} setting and additionally using
|
13949 |
|
|
@option{-mno-extern-sdata} to stop the library from making assumptions
|
13950 |
|
|
about externally-defined data.
|
13951 |
|
|
|
13952 |
|
|
@item -mgpopt
|
13953 |
|
|
@itemx -mno-gpopt
|
13954 |
|
|
@opindex mgpopt
|
13955 |
|
|
@opindex mno-gpopt
|
13956 |
|
|
Use (do not use) GP-relative accesses for symbols that are known to be
|
13957 |
|
|
in a small data section; see @option{-G}, @option{-mlocal-sdata} and
|
13958 |
|
|
@option{-mextern-sdata}. @option{-mgpopt} is the default for all
|
13959 |
|
|
configurations.
|
13960 |
|
|
|
13961 |
|
|
@option{-mno-gpopt} is useful for cases where the @code{$gp} register
|
13962 |
|
|
might not hold the value of @code{_gp}. For example, if the code is
|
13963 |
|
|
part of a library that might be used in a boot monitor, programs that
|
13964 |
|
|
call boot monitor routines will pass an unknown value in @code{$gp}.
|
13965 |
|
|
(In such situations, the boot monitor itself would usually be compiled
|
13966 |
|
|
with @option{-G0}.)
|
13967 |
|
|
|
13968 |
|
|
@option{-mno-gpopt} implies @option{-mno-local-sdata} and
|
13969 |
|
|
@option{-mno-extern-sdata}.
|
13970 |
|
|
|
13971 |
|
|
@item -membedded-data
|
13972 |
|
|
@itemx -mno-embedded-data
|
13973 |
|
|
@opindex membedded-data
|
13974 |
|
|
@opindex mno-embedded-data
|
13975 |
|
|
Allocate variables to the read-only data section first if possible, then
|
13976 |
|
|
next in the small data section if possible, otherwise in data. This gives
|
13977 |
|
|
slightly slower code than the default, but reduces the amount of RAM required
|
13978 |
|
|
when executing, and thus may be preferred for some embedded systems.
|
13979 |
|
|
|
13980 |
|
|
@item -muninit-const-in-rodata
|
13981 |
|
|
@itemx -mno-uninit-const-in-rodata
|
13982 |
|
|
@opindex muninit-const-in-rodata
|
13983 |
|
|
@opindex mno-uninit-const-in-rodata
|
13984 |
|
|
Put uninitialized @code{const} variables in the read-only data section.
|
13985 |
|
|
This option is only meaningful in conjunction with @option{-membedded-data}.
|
13986 |
|
|
|
13987 |
|
|
@item -mcode-readable=@var{setting}
|
13988 |
|
|
@opindex mcode-readable
|
13989 |
|
|
Specify whether GCC may generate code that reads from executable sections.
|
13990 |
|
|
There are three possible settings:
|
13991 |
|
|
|
13992 |
|
|
@table @gcctabopt
|
13993 |
|
|
@item -mcode-readable=yes
|
13994 |
|
|
Instructions may freely access executable sections. This is the
|
13995 |
|
|
default setting.
|
13996 |
|
|
|
13997 |
|
|
@item -mcode-readable=pcrel
|
13998 |
|
|
MIPS16 PC-relative load instructions can access executable sections,
|
13999 |
|
|
but other instructions must not do so. This option is useful on 4KSc
|
14000 |
|
|
and 4KSd processors when the code TLBs have the Read Inhibit bit set.
|
14001 |
|
|
It is also useful on processors that can be configured to have a dual
|
14002 |
|
|
instruction/data SRAM interface and that, like the M4K, automatically
|
14003 |
|
|
redirect PC-relative loads to the instruction RAM.
|
14004 |
|
|
|
14005 |
|
|
@item -mcode-readable=no
|
14006 |
|
|
Instructions must not access executable sections. This option can be
|
14007 |
|
|
useful on targets that are configured to have a dual instruction/data
|
14008 |
|
|
SRAM interface but that (unlike the M4K) do not automatically redirect
|
14009 |
|
|
PC-relative loads to the instruction RAM.
|
14010 |
|
|
@end table
|
14011 |
|
|
|
14012 |
|
|
@item -msplit-addresses
|
14013 |
|
|
@itemx -mno-split-addresses
|
14014 |
|
|
@opindex msplit-addresses
|
14015 |
|
|
@opindex mno-split-addresses
|
14016 |
|
|
Enable (disable) use of the @code{%hi()} and @code{%lo()} assembler
|
14017 |
|
|
relocation operators. This option has been superseded by
|
14018 |
|
|
@option{-mexplicit-relocs} but is retained for backwards compatibility.
|
14019 |
|
|
|
14020 |
|
|
@item -mexplicit-relocs
|
14021 |
|
|
@itemx -mno-explicit-relocs
|
14022 |
|
|
@opindex mexplicit-relocs
|
14023 |
|
|
@opindex mno-explicit-relocs
|
14024 |
|
|
Use (do not use) assembler relocation operators when dealing with symbolic
|
14025 |
|
|
addresses. The alternative, selected by @option{-mno-explicit-relocs},
|
14026 |
|
|
is to use assembler macros instead.
|
14027 |
|
|
|
14028 |
|
|
@option{-mexplicit-relocs} is the default if GCC was configured
|
14029 |
|
|
to use an assembler that supports relocation operators.
|
14030 |
|
|
|
14031 |
|
|
@item -mcheck-zero-division
|
14032 |
|
|
@itemx -mno-check-zero-division
|
14033 |
|
|
@opindex mcheck-zero-division
|
14034 |
|
|
@opindex mno-check-zero-division
|
14035 |
|
|
Trap (do not trap) on integer division by zero.
|
14036 |
|
|
|
14037 |
|
|
The default is @option{-mcheck-zero-division}.
|
14038 |
|
|
|
14039 |
|
|
@item -mdivide-traps
|
14040 |
|
|
@itemx -mdivide-breaks
|
14041 |
|
|
@opindex mdivide-traps
|
14042 |
|
|
@opindex mdivide-breaks
|
14043 |
|
|
MIPS systems check for division by zero by generating either a
|
14044 |
|
|
conditional trap or a break instruction. Using traps results in
|
14045 |
|
|
smaller code, but is only supported on MIPS II and later. Also, some
|
14046 |
|
|
versions of the Linux kernel have a bug that prevents trap from
|
14047 |
|
|
generating the proper signal (@code{SIGFPE}). Use @option{-mdivide-traps} to
|
14048 |
|
|
allow conditional traps on architectures that support them and
|
14049 |
|
|
@option{-mdivide-breaks} to force the use of breaks.
|
14050 |
|
|
|
14051 |
|
|
The default is usually @option{-mdivide-traps}, but this can be
|
14052 |
|
|
overridden at configure time using @option{--with-divide=breaks}.
|
14053 |
|
|
Divide-by-zero checks can be completely disabled using
|
14054 |
|
|
@option{-mno-check-zero-division}.
|
14055 |
|
|
|
14056 |
|
|
@item -mmemcpy
|
14057 |
|
|
@itemx -mno-memcpy
|
14058 |
|
|
@opindex mmemcpy
|
14059 |
|
|
@opindex mno-memcpy
|
14060 |
|
|
Force (do not force) the use of @code{memcpy()} for non-trivial block
|
14061 |
|
|
moves. The default is @option{-mno-memcpy}, which allows GCC to inline
|
14062 |
|
|
most constant-sized copies.
|
14063 |
|
|
|
14064 |
|
|
@item -mlong-calls
|
14065 |
|
|
@itemx -mno-long-calls
|
14066 |
|
|
@opindex mlong-calls
|
14067 |
|
|
@opindex mno-long-calls
|
14068 |
|
|
Disable (do not disable) use of the @code{jal} instruction. Calling
|
14069 |
|
|
functions using @code{jal} is more efficient but requires the caller
|
14070 |
|
|
and callee to be in the same 256 megabyte segment.
|
14071 |
|
|
|
14072 |
|
|
This option has no effect on abicalls code. The default is
|
14073 |
|
|
@option{-mno-long-calls}.
|
14074 |
|
|
|
14075 |
|
|
@item -mmad
|
14076 |
|
|
@itemx -mno-mad
|
14077 |
|
|
@opindex mmad
|
14078 |
|
|
@opindex mno-mad
|
14079 |
|
|
Enable (disable) use of the @code{mad}, @code{madu} and @code{mul}
|
14080 |
|
|
instructions, as provided by the R4650 ISA@.
|
14081 |
|
|
|
14082 |
|
|
@item -mfused-madd
|
14083 |
|
|
@itemx -mno-fused-madd
|
14084 |
|
|
@opindex mfused-madd
|
14085 |
|
|
@opindex mno-fused-madd
|
14086 |
|
|
Enable (disable) use of the floating point multiply-accumulate
|
14087 |
|
|
instructions, when they are available. The default is
|
14088 |
|
|
@option{-mfused-madd}.
|
14089 |
|
|
|
14090 |
|
|
When multiply-accumulate instructions are used, the intermediate
|
14091 |
|
|
product is calculated to infinite precision and is not subject to
|
14092 |
|
|
the FCSR Flush to Zero bit. This may be undesirable in some
|
14093 |
|
|
circumstances.
|
14094 |
|
|
|
14095 |
|
|
@item -nocpp
|
14096 |
|
|
@opindex nocpp
|
14097 |
|
|
Tell the MIPS assembler to not run its preprocessor over user
|
14098 |
|
|
assembler files (with a @samp{.s} suffix) when assembling them.
|
14099 |
|
|
|
14100 |
|
|
@item -mfix-r4000
|
14101 |
|
|
@itemx -mno-fix-r4000
|
14102 |
|
|
@opindex mfix-r4000
|
14103 |
|
|
@opindex mno-fix-r4000
|
14104 |
|
|
Work around certain R4000 CPU errata:
|
14105 |
|
|
@itemize @minus
|
14106 |
|
|
@item
|
14107 |
|
|
A double-word or a variable shift may give an incorrect result if executed
|
14108 |
|
|
immediately after starting an integer division.
|
14109 |
|
|
@item
|
14110 |
|
|
A double-word or a variable shift may give an incorrect result if executed
|
14111 |
|
|
while an integer multiplication is in progress.
|
14112 |
|
|
@item
|
14113 |
|
|
An integer division may give an incorrect result if started in a delay slot
|
14114 |
|
|
of a taken branch or a jump.
|
14115 |
|
|
@end itemize
|
14116 |
|
|
|
14117 |
|
|
@item -mfix-r4400
|
14118 |
|
|
@itemx -mno-fix-r4400
|
14119 |
|
|
@opindex mfix-r4400
|
14120 |
|
|
@opindex mno-fix-r4400
|
14121 |
|
|
Work around certain R4400 CPU errata:
|
14122 |
|
|
@itemize @minus
|
14123 |
|
|
@item
|
14124 |
|
|
A double-word or a variable shift may give an incorrect result if executed
|
14125 |
|
|
immediately after starting an integer division.
|
14126 |
|
|
@end itemize
|
14127 |
|
|
|
14128 |
|
|
@item -mfix-r10000
|
14129 |
|
|
@itemx -mno-fix-r10000
|
14130 |
|
|
@opindex mfix-r10000
|
14131 |
|
|
@opindex mno-fix-r10000
|
14132 |
|
|
Work around certain R10000 errata:
|
14133 |
|
|
@itemize @minus
|
14134 |
|
|
@item
|
14135 |
|
|
@code{ll}/@code{sc} sequences may not behave atomically on revisions
|
14136 |
|
|
prior to 3.0. They may deadlock on revisions 2.6 and earlier.
|
14137 |
|
|
@end itemize
|
14138 |
|
|
|
14139 |
|
|
This option can only be used if the target architecture supports
|
14140 |
|
|
branch-likely instructions. @option{-mfix-r10000} is the default when
|
14141 |
|
|
@option{-march=r10000} is used; @option{-mno-fix-r10000} is the default
|
14142 |
|
|
otherwise.
|
14143 |
|
|
|
14144 |
|
|
@item -mfix-vr4120
|
14145 |
|
|
@itemx -mno-fix-vr4120
|
14146 |
|
|
@opindex mfix-vr4120
|
14147 |
|
|
Work around certain VR4120 errata:
|
14148 |
|
|
@itemize @minus
|
14149 |
|
|
@item
|
14150 |
|
|
@code{dmultu} does not always produce the correct result.
|
14151 |
|
|
@item
|
14152 |
|
|
@code{div} and @code{ddiv} do not always produce the correct result if one
|
14153 |
|
|
of the operands is negative.
|
14154 |
|
|
@end itemize
|
14155 |
|
|
The workarounds for the division errata rely on special functions in
|
14156 |
|
|
@file{libgcc.a}. At present, these functions are only provided by
|
14157 |
|
|
the @code{mips64vr*-elf} configurations.
|
14158 |
|
|
|
14159 |
|
|
Other VR4120 errata require a nop to be inserted between certain pairs of
|
14160 |
|
|
instructions. These errata are handled by the assembler, not by GCC itself.
|
14161 |
|
|
|
14162 |
|
|
@item -mfix-vr4130
|
14163 |
|
|
@opindex mfix-vr4130
|
14164 |
|
|
Work around the VR4130 @code{mflo}/@code{mfhi} errata. The
|
14165 |
|
|
workarounds are implemented by the assembler rather than by GCC,
|
14166 |
|
|
although GCC will avoid using @code{mflo} and @code{mfhi} if the
|
14167 |
|
|
VR4130 @code{macc}, @code{macchi}, @code{dmacc} and @code{dmacchi}
|
14168 |
|
|
instructions are available instead.
|
14169 |
|
|
|
14170 |
|
|
@item -mfix-sb1
|
14171 |
|
|
@itemx -mno-fix-sb1
|
14172 |
|
|
@opindex mfix-sb1
|
14173 |
|
|
Work around certain SB-1 CPU core errata.
|
14174 |
|
|
(This flag currently works around the SB-1 revision 2
|
14175 |
|
|
``F1'' and ``F2'' floating point errata.)
|
14176 |
|
|
|
14177 |
|
|
@item -mr10k-cache-barrier=@var{setting}
|
14178 |
|
|
@opindex mr10k-cache-barrier
|
14179 |
|
|
Specify whether GCC should insert cache barriers to avoid the
|
14180 |
|
|
side-effects of speculation on R10K processors.
|
14181 |
|
|
|
14182 |
|
|
In common with many processors, the R10K tries to predict the outcome
|
14183 |
|
|
of a conditional branch and speculatively executes instructions from
|
14184 |
|
|
the ``taken'' branch. It later aborts these instructions if the
|
14185 |
|
|
predicted outcome was wrong. However, on the R10K, even aborted
|
14186 |
|
|
instructions can have side effects.
|
14187 |
|
|
|
14188 |
|
|
This problem only affects kernel stores and, depending on the system,
|
14189 |
|
|
kernel loads. As an example, a speculatively-executed store may load
|
14190 |
|
|
the target memory into cache and mark the cache line as dirty, even if
|
14191 |
|
|
the store itself is later aborted. If a DMA operation writes to the
|
14192 |
|
|
same area of memory before the ``dirty'' line is flushed, the cached
|
14193 |
|
|
data will overwrite the DMA-ed data. See the R10K processor manual
|
14194 |
|
|
for a full description, including other potential problems.
|
14195 |
|
|
|
14196 |
|
|
One workaround is to insert cache barrier instructions before every memory
|
14197 |
|
|
access that might be speculatively executed and that might have side
|
14198 |
|
|
effects even if aborted. @option{-mr10k-cache-barrier=@var{setting}}
|
14199 |
|
|
controls GCC's implementation of this workaround. It assumes that
|
14200 |
|
|
aborted accesses to any byte in the following regions will not have
|
14201 |
|
|
side effects:
|
14202 |
|
|
|
14203 |
|
|
@enumerate
|
14204 |
|
|
@item
|
14205 |
|
|
the memory occupied by the current function's stack frame;
|
14206 |
|
|
|
14207 |
|
|
@item
|
14208 |
|
|
the memory occupied by an incoming stack argument;
|
14209 |
|
|
|
14210 |
|
|
@item
|
14211 |
|
|
the memory occupied by an object with a link-time-constant address.
|
14212 |
|
|
@end enumerate
|
14213 |
|
|
|
14214 |
|
|
It is the kernel's responsibility to ensure that speculative
|
14215 |
|
|
accesses to these regions are indeed safe.
|
14216 |
|
|
|
14217 |
|
|
If the input program contains a function declaration such as:
|
14218 |
|
|
|
14219 |
|
|
@smallexample
|
14220 |
|
|
void foo (void);
|
14221 |
|
|
@end smallexample
|
14222 |
|
|
|
14223 |
|
|
then the implementation of @code{foo} must allow @code{j foo} and
|
14224 |
|
|
@code{jal foo} to be executed speculatively. GCC honors this
|
14225 |
|
|
restriction for functions it compiles itself. It expects non-GCC
|
14226 |
|
|
functions (such as hand-written assembly code) to do the same.
|
14227 |
|
|
|
14228 |
|
|
The option has three forms:
|
14229 |
|
|
|
14230 |
|
|
@table @gcctabopt
|
14231 |
|
|
@item -mr10k-cache-barrier=load-store
|
14232 |
|
|
Insert a cache barrier before a load or store that might be
|
14233 |
|
|
speculatively executed and that might have side effects even
|
14234 |
|
|
if aborted.
|
14235 |
|
|
|
14236 |
|
|
@item -mr10k-cache-barrier=store
|
14237 |
|
|
Insert a cache barrier before a store that might be speculatively
|
14238 |
|
|
executed and that might have side effects even if aborted.
|
14239 |
|
|
|
14240 |
|
|
@item -mr10k-cache-barrier=none
|
14241 |
|
|
Disable the insertion of cache barriers. This is the default setting.
|
14242 |
|
|
@end table
|
14243 |
|
|
|
14244 |
|
|
@item -mflush-func=@var{func}
|
14245 |
|
|
@itemx -mno-flush-func
|
14246 |
|
|
@opindex mflush-func
|
14247 |
|
|
Specifies the function to call to flush the I and D caches, or to not
|
14248 |
|
|
call any such function. If called, the function must take the same
|
14249 |
|
|
arguments as the common @code{_flush_func()}, that is, the address of the
|
14250 |
|
|
memory range for which the cache is being flushed, the size of the
|
14251 |
|
|
memory range, and the number 3 (to flush both caches). The default
|
14252 |
|
|
depends on the target GCC was configured for, but commonly is either
|
14253 |
|
|
@samp{_flush_func} or @samp{__cpu_flush}.
|
14254 |
|
|
|
14255 |
|
|
@item mbranch-cost=@var{num}
|
14256 |
|
|
@opindex mbranch-cost
|
14257 |
|
|
Set the cost of branches to roughly @var{num} ``simple'' instructions.
|
14258 |
|
|
This cost is only a heuristic and is not guaranteed to produce
|
14259 |
|
|
consistent results across releases. A zero cost redundantly selects
|
14260 |
|
|
the default, which is based on the @option{-mtune} setting.
|
14261 |
|
|
|
14262 |
|
|
@item -mbranch-likely
|
14263 |
|
|
@itemx -mno-branch-likely
|
14264 |
|
|
@opindex mbranch-likely
|
14265 |
|
|
@opindex mno-branch-likely
|
14266 |
|
|
Enable or disable use of Branch Likely instructions, regardless of the
|
14267 |
|
|
default for the selected architecture. By default, Branch Likely
|
14268 |
|
|
instructions may be generated if they are supported by the selected
|
14269 |
|
|
architecture. An exception is for the MIPS32 and MIPS64 architectures
|
14270 |
|
|
and processors which implement those architectures; for those, Branch
|
14271 |
|
|
Likely instructions will not be generated by default because the MIPS32
|
14272 |
|
|
and MIPS64 architectures specifically deprecate their use.
|
14273 |
|
|
|
14274 |
|
|
@item -mfp-exceptions
|
14275 |
|
|
@itemx -mno-fp-exceptions
|
14276 |
|
|
@opindex mfp-exceptions
|
14277 |
|
|
Specifies whether FP exceptions are enabled. This affects how we schedule
|
14278 |
|
|
FP instructions for some processors. The default is that FP exceptions are
|
14279 |
|
|
enabled.
|
14280 |
|
|
|
14281 |
|
|
For instance, on the SB-1, if FP exceptions are disabled, and we are emitting
|
14282 |
|
|
64-bit code, then we can use both FP pipes. Otherwise, we can only use one
|
14283 |
|
|
FP pipe.
|
14284 |
|
|
|
14285 |
|
|
@item -mvr4130-align
|
14286 |
|
|
@itemx -mno-vr4130-align
|
14287 |
|
|
@opindex mvr4130-align
|
14288 |
|
|
The VR4130 pipeline is two-way superscalar, but can only issue two
|
14289 |
|
|
instructions together if the first one is 8-byte aligned. When this
|
14290 |
|
|
option is enabled, GCC will align pairs of instructions that it
|
14291 |
|
|
thinks should execute in parallel.
|
14292 |
|
|
|
14293 |
|
|
This option only has an effect when optimizing for the VR4130.
|
14294 |
|
|
It normally makes code faster, but at the expense of making it bigger.
|
14295 |
|
|
It is enabled by default at optimization level @option{-O3}.
|
14296 |
|
|
|
14297 |
|
|
@item -msynci
|
14298 |
|
|
@itemx -mno-synci
|
14299 |
|
|
@opindex msynci
|
14300 |
|
|
Enable (disable) generation of @code{synci} instructions on
|
14301 |
|
|
architectures that support it. The @code{synci} instructions (if
|
14302 |
|
|
enabled) will be generated when @code{__builtin___clear_cache()} is
|
14303 |
|
|
compiled.
|
14304 |
|
|
|
14305 |
|
|
This option defaults to @code{-mno-synci}, but the default can be
|
14306 |
|
|
overridden by configuring with @code{--with-synci}.
|
14307 |
|
|
|
14308 |
|
|
When compiling code for single processor systems, it is generally safe
|
14309 |
|
|
to use @code{synci}. However, on many multi-core (SMP) systems, it
|
14310 |
|
|
will not invalidate the instruction caches on all cores and may lead
|
14311 |
|
|
to undefined behavior.
|
14312 |
|
|
|
14313 |
|
|
@item -mrelax-pic-calls
|
14314 |
|
|
@itemx -mno-relax-pic-calls
|
14315 |
|
|
@opindex mrelax-pic-calls
|
14316 |
|
|
Try to turn PIC calls that are normally dispatched via register
|
14317 |
|
|
@code{$25} into direct calls. This is only possible if the linker can
|
14318 |
|
|
resolve the destination at link-time and if the destination is within
|
14319 |
|
|
range for a direct call.
|
14320 |
|
|
|
14321 |
|
|
@option{-mrelax-pic-calls} is the default if GCC was configured to use
|
14322 |
|
|
an assembler and a linker that supports the @code{.reloc} assembly
|
14323 |
|
|
directive and @code{-mexplicit-relocs} is in effect. With
|
14324 |
|
|
@code{-mno-explicit-relocs}, this optimization can be performed by the
|
14325 |
|
|
assembler and the linker alone without help from the compiler.
|
14326 |
|
|
|
14327 |
|
|
@item -mmcount-ra-address
|
14328 |
|
|
@itemx -mno-mcount-ra-address
|
14329 |
|
|
@opindex mmcount-ra-address
|
14330 |
|
|
@opindex mno-mcount-ra-address
|
14331 |
|
|
Emit (do not emit) code that allows @code{_mcount} to modify the
|
14332 |
|
|
calling function's return address. When enabled, this option extends
|
14333 |
|
|
the usual @code{_mcount} interface with a new @var{ra-address}
|
14334 |
|
|
parameter, which has type @code{intptr_t *} and is passed in register
|
14335 |
|
|
@code{$12}. @code{_mcount} can then modify the return address by
|
14336 |
|
|
doing both of the following:
|
14337 |
|
|
@itemize
|
14338 |
|
|
@item
|
14339 |
|
|
Returning the new address in register @code{$31}.
|
14340 |
|
|
@item
|
14341 |
|
|
Storing the new address in @code{*@var{ra-address}},
|
14342 |
|
|
if @var{ra-address} is nonnull.
|
14343 |
|
|
@end itemize
|
14344 |
|
|
|
14345 |
|
|
The default is @option{-mno-mcount-ra-address}.
|
14346 |
|
|
|
14347 |
|
|
@end table
|
14348 |
|
|
|
14349 |
|
|
@node MMIX Options
|
14350 |
|
|
@subsection MMIX Options
|
14351 |
|
|
@cindex MMIX Options
|
14352 |
|
|
|
14353 |
|
|
These options are defined for the MMIX:
|
14354 |
|
|
|
14355 |
|
|
@table @gcctabopt
|
14356 |
|
|
@item -mlibfuncs
|
14357 |
|
|
@itemx -mno-libfuncs
|
14358 |
|
|
@opindex mlibfuncs
|
14359 |
|
|
@opindex mno-libfuncs
|
14360 |
|
|
Specify that intrinsic library functions are being compiled, passing all
|
14361 |
|
|
values in registers, no matter the size.
|
14362 |
|
|
|
14363 |
|
|
@item -mepsilon
|
14364 |
|
|
@itemx -mno-epsilon
|
14365 |
|
|
@opindex mepsilon
|
14366 |
|
|
@opindex mno-epsilon
|
14367 |
|
|
Generate floating-point comparison instructions that compare with respect
|
14368 |
|
|
to the @code{rE} epsilon register.
|
14369 |
|
|
|
14370 |
|
|
@item -mabi=mmixware
|
14371 |
|
|
@itemx -mabi=gnu
|
14372 |
|
|
@opindex mabi=mmixware
|
14373 |
|
|
@opindex mabi=gnu
|
14374 |
|
|
Generate code that passes function parameters and return values that (in
|
14375 |
|
|
the called function) are seen as registers @code{$0} and up, as opposed to
|
14376 |
|
|
the GNU ABI which uses global registers @code{$231} and up.
|
14377 |
|
|
|
14378 |
|
|
@item -mzero-extend
|
14379 |
|
|
@itemx -mno-zero-extend
|
14380 |
|
|
@opindex mzero-extend
|
14381 |
|
|
@opindex mno-zero-extend
|
14382 |
|
|
When reading data from memory in sizes shorter than 64 bits, use (do not
|
14383 |
|
|
use) zero-extending load instructions by default, rather than
|
14384 |
|
|
sign-extending ones.
|
14385 |
|
|
|
14386 |
|
|
@item -mknuthdiv
|
14387 |
|
|
@itemx -mno-knuthdiv
|
14388 |
|
|
@opindex mknuthdiv
|
14389 |
|
|
@opindex mno-knuthdiv
|
14390 |
|
|
Make the result of a division yielding a remainder have the same sign as
|
14391 |
|
|
the divisor. With the default, @option{-mno-knuthdiv}, the sign of the
|
14392 |
|
|
remainder follows the sign of the dividend. Both methods are
|
14393 |
|
|
arithmetically valid, the latter being almost exclusively used.
|
14394 |
|
|
|
14395 |
|
|
@item -mtoplevel-symbols
|
14396 |
|
|
@itemx -mno-toplevel-symbols
|
14397 |
|
|
@opindex mtoplevel-symbols
|
14398 |
|
|
@opindex mno-toplevel-symbols
|
14399 |
|
|
Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly
|
14400 |
|
|
code can be used with the @code{PREFIX} assembly directive.
|
14401 |
|
|
|
14402 |
|
|
@item -melf
|
14403 |
|
|
@opindex melf
|
14404 |
|
|
Generate an executable in the ELF format, rather than the default
|
14405 |
|
|
@samp{mmo} format used by the @command{mmix} simulator.
|
14406 |
|
|
|
14407 |
|
|
@item -mbranch-predict
|
14408 |
|
|
@itemx -mno-branch-predict
|
14409 |
|
|
@opindex mbranch-predict
|
14410 |
|
|
@opindex mno-branch-predict
|
14411 |
|
|
Use (do not use) the probable-branch instructions, when static branch
|
14412 |
|
|
prediction indicates a probable branch.
|
14413 |
|
|
|
14414 |
|
|
@item -mbase-addresses
|
14415 |
|
|
@itemx -mno-base-addresses
|
14416 |
|
|
@opindex mbase-addresses
|
14417 |
|
|
@opindex mno-base-addresses
|
14418 |
|
|
Generate (do not generate) code that uses @emph{base addresses}. Using a
|
14419 |
|
|
base address automatically generates a request (handled by the assembler
|
14420 |
|
|
and the linker) for a constant to be set up in a global register. The
|
14421 |
|
|
register is used for one or more base address requests within the range 0
|
14422 |
|
|
to 255 from the value held in the register. The generally leads to short
|
14423 |
|
|
and fast code, but the number of different data items that can be
|
14424 |
|
|
addressed is limited. This means that a program that uses lots of static
|
14425 |
|
|
data may require @option{-mno-base-addresses}.
|
14426 |
|
|
|
14427 |
|
|
@item -msingle-exit
|
14428 |
|
|
@itemx -mno-single-exit
|
14429 |
|
|
@opindex msingle-exit
|
14430 |
|
|
@opindex mno-single-exit
|
14431 |
|
|
Force (do not force) generated code to have a single exit point in each
|
14432 |
|
|
function.
|
14433 |
|
|
@end table
|
14434 |
|
|
|
14435 |
|
|
@node MN10300 Options
|
14436 |
|
|
@subsection MN10300 Options
|
14437 |
|
|
@cindex MN10300 options
|
14438 |
|
|
|
14439 |
|
|
These @option{-m} options are defined for Matsushita MN10300 architectures:
|
14440 |
|
|
|
14441 |
|
|
@table @gcctabopt
|
14442 |
|
|
@item -mmult-bug
|
14443 |
|
|
@opindex mmult-bug
|
14444 |
|
|
Generate code to avoid bugs in the multiply instructions for the MN10300
|
14445 |
|
|
processors. This is the default.
|
14446 |
|
|
|
14447 |
|
|
@item -mno-mult-bug
|
14448 |
|
|
@opindex mno-mult-bug
|
14449 |
|
|
Do not generate code to avoid bugs in the multiply instructions for the
|
14450 |
|
|
MN10300 processors.
|
14451 |
|
|
|
14452 |
|
|
@item -mam33
|
14453 |
|
|
@opindex mam33
|
14454 |
|
|
Generate code which uses features specific to the AM33 processor.
|
14455 |
|
|
|
14456 |
|
|
@item -mno-am33
|
14457 |
|
|
@opindex mno-am33
|
14458 |
|
|
Do not generate code which uses features specific to the AM33 processor. This
|
14459 |
|
|
is the default.
|
14460 |
|
|
|
14461 |
|
|
@item -mreturn-pointer-on-d0
|
14462 |
|
|
@opindex mreturn-pointer-on-d0
|
14463 |
|
|
When generating a function which returns a pointer, return the pointer
|
14464 |
|
|
in both @code{a0} and @code{d0}. Otherwise, the pointer is returned
|
14465 |
|
|
only in a0, and attempts to call such functions without a prototype
|
14466 |
|
|
would result in errors. Note that this option is on by default; use
|
14467 |
|
|
@option{-mno-return-pointer-on-d0} to disable it.
|
14468 |
|
|
|
14469 |
|
|
@item -mno-crt0
|
14470 |
|
|
@opindex mno-crt0
|
14471 |
|
|
Do not link in the C run-time initialization object file.
|
14472 |
|
|
|
14473 |
|
|
@item -mrelax
|
14474 |
|
|
@opindex mrelax
|
14475 |
|
|
Indicate to the linker that it should perform a relaxation optimization pass
|
14476 |
|
|
to shorten branches, calls and absolute memory addresses. This option only
|
14477 |
|
|
has an effect when used on the command line for the final link step.
|
14478 |
|
|
|
14479 |
|
|
This option makes symbolic debugging impossible.
|
14480 |
|
|
@end table
|
14481 |
|
|
|
14482 |
|
|
@node PDP-11 Options
|
14483 |
|
|
@subsection PDP-11 Options
|
14484 |
|
|
@cindex PDP-11 Options
|
14485 |
|
|
|
14486 |
|
|
These options are defined for the PDP-11:
|
14487 |
|
|
|
14488 |
|
|
@table @gcctabopt
|
14489 |
|
|
@item -mfpu
|
14490 |
|
|
@opindex mfpu
|
14491 |
|
|
Use hardware FPP floating point. This is the default. (FIS floating
|
14492 |
|
|
point on the PDP-11/40 is not supported.)
|
14493 |
|
|
|
14494 |
|
|
@item -msoft-float
|
14495 |
|
|
@opindex msoft-float
|
14496 |
|
|
Do not use hardware floating point.
|
14497 |
|
|
|
14498 |
|
|
@item -mac0
|
14499 |
|
|
@opindex mac0
|
14500 |
|
|
Return floating-point results in ac0 (fr0 in Unix assembler syntax).
|
14501 |
|
|
|
14502 |
|
|
@item -mno-ac0
|
14503 |
|
|
@opindex mno-ac0
|
14504 |
|
|
Return floating-point results in memory. This is the default.
|
14505 |
|
|
|
14506 |
|
|
@item -m40
|
14507 |
|
|
@opindex m40
|
14508 |
|
|
Generate code for a PDP-11/40.
|
14509 |
|
|
|
14510 |
|
|
@item -m45
|
14511 |
|
|
@opindex m45
|
14512 |
|
|
Generate code for a PDP-11/45. This is the default.
|
14513 |
|
|
|
14514 |
|
|
@item -m10
|
14515 |
|
|
@opindex m10
|
14516 |
|
|
Generate code for a PDP-11/10.
|
14517 |
|
|
|
14518 |
|
|
@item -mbcopy-builtin
|
14519 |
|
|
@opindex mbcopy-builtin
|
14520 |
|
|
Use inline @code{movmemhi} patterns for copying memory. This is the
|
14521 |
|
|
default.
|
14522 |
|
|
|
14523 |
|
|
@item -mbcopy
|
14524 |
|
|
@opindex mbcopy
|
14525 |
|
|
Do not use inline @code{movmemhi} patterns for copying memory.
|
14526 |
|
|
|
14527 |
|
|
@item -mint16
|
14528 |
|
|
@itemx -mno-int32
|
14529 |
|
|
@opindex mint16
|
14530 |
|
|
@opindex mno-int32
|
14531 |
|
|
Use 16-bit @code{int}. This is the default.
|
14532 |
|
|
|
14533 |
|
|
@item -mint32
|
14534 |
|
|
@itemx -mno-int16
|
14535 |
|
|
@opindex mint32
|
14536 |
|
|
@opindex mno-int16
|
14537 |
|
|
Use 32-bit @code{int}.
|
14538 |
|
|
|
14539 |
|
|
@item -mfloat64
|
14540 |
|
|
@itemx -mno-float32
|
14541 |
|
|
@opindex mfloat64
|
14542 |
|
|
@opindex mno-float32
|
14543 |
|
|
Use 64-bit @code{float}. This is the default.
|
14544 |
|
|
|
14545 |
|
|
@item -mfloat32
|
14546 |
|
|
@itemx -mno-float64
|
14547 |
|
|
@opindex mfloat32
|
14548 |
|
|
@opindex mno-float64
|
14549 |
|
|
Use 32-bit @code{float}.
|
14550 |
|
|
|
14551 |
|
|
@item -mabshi
|
14552 |
|
|
@opindex mabshi
|
14553 |
|
|
Use @code{abshi2} pattern. This is the default.
|
14554 |
|
|
|
14555 |
|
|
@item -mno-abshi
|
14556 |
|
|
@opindex mno-abshi
|
14557 |
|
|
Do not use @code{abshi2} pattern.
|
14558 |
|
|
|
14559 |
|
|
@item -mbranch-expensive
|
14560 |
|
|
@opindex mbranch-expensive
|
14561 |
|
|
Pretend that branches are expensive. This is for experimenting with
|
14562 |
|
|
code generation only.
|
14563 |
|
|
|
14564 |
|
|
@item -mbranch-cheap
|
14565 |
|
|
@opindex mbranch-cheap
|
14566 |
|
|
Do not pretend that branches are expensive. This is the default.
|
14567 |
|
|
|
14568 |
|
|
@item -msplit
|
14569 |
|
|
@opindex msplit
|
14570 |
|
|
Generate code for a system with split I&D@.
|
14571 |
|
|
|
14572 |
|
|
@item -mno-split
|
14573 |
|
|
@opindex mno-split
|
14574 |
|
|
Generate code for a system without split I&D@. This is the default.
|
14575 |
|
|
|
14576 |
|
|
@item -munix-asm
|
14577 |
|
|
@opindex munix-asm
|
14578 |
|
|
Use Unix assembler syntax. This is the default when configured for
|
14579 |
|
|
@samp{pdp11-*-bsd}.
|
14580 |
|
|
|
14581 |
|
|
@item -mdec-asm
|
14582 |
|
|
@opindex mdec-asm
|
14583 |
|
|
Use DEC assembler syntax. This is the default when configured for any
|
14584 |
|
|
PDP-11 target other than @samp{pdp11-*-bsd}.
|
14585 |
|
|
@end table
|
14586 |
|
|
|
14587 |
|
|
@node picoChip Options
|
14588 |
|
|
@subsection picoChip Options
|
14589 |
|
|
@cindex picoChip options
|
14590 |
|
|
|
14591 |
|
|
These @samp{-m} options are defined for picoChip implementations:
|
14592 |
|
|
|
14593 |
|
|
@table @gcctabopt
|
14594 |
|
|
|
14595 |
|
|
@item -mae=@var{ae_type}
|
14596 |
|
|
@opindex mcpu
|
14597 |
|
|
Set the instruction set, register set, and instruction scheduling
|
14598 |
|
|
parameters for array element type @var{ae_type}. Supported values
|
14599 |
|
|
for @var{ae_type} are @samp{ANY}, @samp{MUL}, and @samp{MAC}.
|
14600 |
|
|
|
14601 |
|
|
@option{-mae=ANY} selects a completely generic AE type. Code
|
14602 |
|
|
generated with this option will run on any of the other AE types. The
|
14603 |
|
|
code will not be as efficient as it would be if compiled for a specific
|
14604 |
|
|
AE type, and some types of operation (e.g., multiplication) will not
|
14605 |
|
|
work properly on all types of AE.
|
14606 |
|
|
|
14607 |
|
|
@option{-mae=MUL} selects a MUL AE type. This is the most useful AE type
|
14608 |
|
|
for compiled code, and is the default.
|
14609 |
|
|
|
14610 |
|
|
@option{-mae=MAC} selects a DSP-style MAC AE. Code compiled with this
|
14611 |
|
|
option may suffer from poor performance of byte (char) manipulation,
|
14612 |
|
|
since the DSP AE does not provide hardware support for byte load/stores.
|
14613 |
|
|
|
14614 |
|
|
@item -msymbol-as-address
|
14615 |
|
|
Enable the compiler to directly use a symbol name as an address in a
|
14616 |
|
|
load/store instruction, without first loading it into a
|
14617 |
|
|
register. Typically, the use of this option will generate larger
|
14618 |
|
|
programs, which run faster than when the option isn't used. However, the
|
14619 |
|
|
results vary from program to program, so it is left as a user option,
|
14620 |
|
|
rather than being permanently enabled.
|
14621 |
|
|
|
14622 |
|
|
@item -mno-inefficient-warnings
|
14623 |
|
|
Disables warnings about the generation of inefficient code. These
|
14624 |
|
|
warnings can be generated, for example, when compiling code which
|
14625 |
|
|
performs byte-level memory operations on the MAC AE type. The MAC AE has
|
14626 |
|
|
no hardware support for byte-level memory operations, so all byte
|
14627 |
|
|
load/stores must be synthesized from word load/store operations. This is
|
14628 |
|
|
inefficient and a warning will be generated indicating to the programmer
|
14629 |
|
|
that they should rewrite the code to avoid byte operations, or to target
|
14630 |
|
|
an AE type which has the necessary hardware support. This option enables
|
14631 |
|
|
the warning to be turned off.
|
14632 |
|
|
|
14633 |
|
|
@end table
|
14634 |
|
|
|
14635 |
|
|
@node PowerPC Options
|
14636 |
|
|
@subsection PowerPC Options
|
14637 |
|
|
@cindex PowerPC options
|
14638 |
|
|
|
14639 |
|
|
These are listed under @xref{RS/6000 and PowerPC Options}.
|
14640 |
|
|
|
14641 |
|
|
@node RS/6000 and PowerPC Options
|
14642 |
|
|
@subsection IBM RS/6000 and PowerPC Options
|
14643 |
|
|
@cindex RS/6000 and PowerPC Options
|
14644 |
|
|
@cindex IBM RS/6000 and PowerPC Options
|
14645 |
|
|
|
14646 |
|
|
These @samp{-m} options are defined for the IBM RS/6000 and PowerPC:
|
14647 |
|
|
@table @gcctabopt
|
14648 |
|
|
@item -mpower
|
14649 |
|
|
@itemx -mno-power
|
14650 |
|
|
@itemx -mpower2
|
14651 |
|
|
@itemx -mno-power2
|
14652 |
|
|
@itemx -mpowerpc
|
14653 |
|
|
@itemx -mno-powerpc
|
14654 |
|
|
@itemx -mpowerpc-gpopt
|
14655 |
|
|
@itemx -mno-powerpc-gpopt
|
14656 |
|
|
@itemx -mpowerpc-gfxopt
|
14657 |
|
|
@itemx -mno-powerpc-gfxopt
|
14658 |
|
|
@itemx -mpowerpc64
|
14659 |
|
|
@itemx -mno-powerpc64
|
14660 |
|
|
@itemx -mmfcrf
|
14661 |
|
|
@itemx -mno-mfcrf
|
14662 |
|
|
@itemx -mpopcntb
|
14663 |
|
|
@itemx -mno-popcntb
|
14664 |
|
|
@itemx -mpopcntd
|
14665 |
|
|
@itemx -mno-popcntd
|
14666 |
|
|
@itemx -mfprnd
|
14667 |
|
|
@itemx -mno-fprnd
|
14668 |
|
|
@itemx -mcmpb
|
14669 |
|
|
@itemx -mno-cmpb
|
14670 |
|
|
@itemx -mmfpgpr
|
14671 |
|
|
@itemx -mno-mfpgpr
|
14672 |
|
|
@itemx -mhard-dfp
|
14673 |
|
|
@itemx -mno-hard-dfp
|
14674 |
|
|
@opindex mpower
|
14675 |
|
|
@opindex mno-power
|
14676 |
|
|
@opindex mpower2
|
14677 |
|
|
@opindex mno-power2
|
14678 |
|
|
@opindex mpowerpc
|
14679 |
|
|
@opindex mno-powerpc
|
14680 |
|
|
@opindex mpowerpc-gpopt
|
14681 |
|
|
@opindex mno-powerpc-gpopt
|
14682 |
|
|
@opindex mpowerpc-gfxopt
|
14683 |
|
|
@opindex mno-powerpc-gfxopt
|
14684 |
|
|
@opindex mpowerpc64
|
14685 |
|
|
@opindex mno-powerpc64
|
14686 |
|
|
@opindex mmfcrf
|
14687 |
|
|
@opindex mno-mfcrf
|
14688 |
|
|
@opindex mpopcntb
|
14689 |
|
|
@opindex mno-popcntb
|
14690 |
|
|
@opindex mpopcntd
|
14691 |
|
|
@opindex mno-popcntd
|
14692 |
|
|
@opindex mfprnd
|
14693 |
|
|
@opindex mno-fprnd
|
14694 |
|
|
@opindex mcmpb
|
14695 |
|
|
@opindex mno-cmpb
|
14696 |
|
|
@opindex mmfpgpr
|
14697 |
|
|
@opindex mno-mfpgpr
|
14698 |
|
|
@opindex mhard-dfp
|
14699 |
|
|
@opindex mno-hard-dfp
|
14700 |
|
|
GCC supports two related instruction set architectures for the
|
14701 |
|
|
RS/6000 and PowerPC@. The @dfn{POWER} instruction set are those
|
14702 |
|
|
instructions supported by the @samp{rios} chip set used in the original
|
14703 |
|
|
RS/6000 systems and the @dfn{PowerPC} instruction set is the
|
14704 |
|
|
architecture of the Freescale MPC5xx, MPC6xx, MPC8xx microprocessors, and
|
14705 |
|
|
the IBM 4xx, 6xx, and follow-on microprocessors.
|
14706 |
|
|
|
14707 |
|
|
Neither architecture is a subset of the other. However there is a
|
14708 |
|
|
large common subset of instructions supported by both. An MQ
|
14709 |
|
|
register is included in processors supporting the POWER architecture.
|
14710 |
|
|
|
14711 |
|
|
You use these options to specify which instructions are available on the
|
14712 |
|
|
processor you are using. The default value of these options is
|
14713 |
|
|
determined when configuring GCC@. Specifying the
|
14714 |
|
|
@option{-mcpu=@var{cpu_type}} overrides the specification of these
|
14715 |
|
|
options. We recommend you use the @option{-mcpu=@var{cpu_type}} option
|
14716 |
|
|
rather than the options listed above.
|
14717 |
|
|
|
14718 |
|
|
The @option{-mpower} option allows GCC to generate instructions that
|
14719 |
|
|
are found only in the POWER architecture and to use the MQ register.
|
14720 |
|
|
Specifying @option{-mpower2} implies @option{-power} and also allows GCC
|
14721 |
|
|
to generate instructions that are present in the POWER2 architecture but
|
14722 |
|
|
not the original POWER architecture.
|
14723 |
|
|
|
14724 |
|
|
The @option{-mpowerpc} option allows GCC to generate instructions that
|
14725 |
|
|
are found only in the 32-bit subset of the PowerPC architecture.
|
14726 |
|
|
Specifying @option{-mpowerpc-gpopt} implies @option{-mpowerpc} and also allows
|
14727 |
|
|
GCC to use the optional PowerPC architecture instructions in the
|
14728 |
|
|
General Purpose group, including floating-point square root. Specifying
|
14729 |
|
|
@option{-mpowerpc-gfxopt} implies @option{-mpowerpc} and also allows GCC to
|
14730 |
|
|
use the optional PowerPC architecture instructions in the Graphics
|
14731 |
|
|
group, including floating-point select.
|
14732 |
|
|
|
14733 |
|
|
The @option{-mmfcrf} option allows GCC to generate the move from
|
14734 |
|
|
condition register field instruction implemented on the POWER4
|
14735 |
|
|
processor and other processors that support the PowerPC V2.01
|
14736 |
|
|
architecture.
|
14737 |
|
|
The @option{-mpopcntb} option allows GCC to generate the popcount and
|
14738 |
|
|
double precision FP reciprocal estimate instruction implemented on the
|
14739 |
|
|
POWER5 processor and other processors that support the PowerPC V2.02
|
14740 |
|
|
architecture.
|
14741 |
|
|
The @option{-mpopcntd} option allows GCC to generate the popcount
|
14742 |
|
|
instruction implemented on the POWER7 processor and other processors
|
14743 |
|
|
that support the PowerPC V2.06 architecture.
|
14744 |
|
|
The @option{-mfprnd} option allows GCC to generate the FP round to
|
14745 |
|
|
integer instructions implemented on the POWER5+ processor and other
|
14746 |
|
|
processors that support the PowerPC V2.03 architecture.
|
14747 |
|
|
The @option{-mcmpb} option allows GCC to generate the compare bytes
|
14748 |
|
|
instruction implemented on the POWER6 processor and other processors
|
14749 |
|
|
that support the PowerPC V2.05 architecture.
|
14750 |
|
|
The @option{-mmfpgpr} option allows GCC to generate the FP move to/from
|
14751 |
|
|
general purpose register instructions implemented on the POWER6X
|
14752 |
|
|
processor and other processors that support the extended PowerPC V2.05
|
14753 |
|
|
architecture.
|
14754 |
|
|
The @option{-mhard-dfp} option allows GCC to generate the decimal floating
|
14755 |
|
|
point instructions implemented on some POWER processors.
|
14756 |
|
|
|
14757 |
|
|
The @option{-mpowerpc64} option allows GCC to generate the additional
|
14758 |
|
|
64-bit instructions that are found in the full PowerPC64 architecture
|
14759 |
|
|
and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to
|
14760 |
|
|
@option{-mno-powerpc64}.
|
14761 |
|
|
|
14762 |
|
|
If you specify both @option{-mno-power} and @option{-mno-powerpc}, GCC
|
14763 |
|
|
will use only the instructions in the common subset of both
|
14764 |
|
|
architectures plus some special AIX common-mode calls, and will not use
|
14765 |
|
|
the MQ register. Specifying both @option{-mpower} and @option{-mpowerpc}
|
14766 |
|
|
permits GCC to use any instruction from either architecture and to
|
14767 |
|
|
allow use of the MQ register; specify this for the Motorola MPC601.
|
14768 |
|
|
|
14769 |
|
|
@item -mnew-mnemonics
|
14770 |
|
|
@itemx -mold-mnemonics
|
14771 |
|
|
@opindex mnew-mnemonics
|
14772 |
|
|
@opindex mold-mnemonics
|
14773 |
|
|
Select which mnemonics to use in the generated assembler code. With
|
14774 |
|
|
@option{-mnew-mnemonics}, GCC uses the assembler mnemonics defined for
|
14775 |
|
|
the PowerPC architecture. With @option{-mold-mnemonics} it uses the
|
14776 |
|
|
assembler mnemonics defined for the POWER architecture. Instructions
|
14777 |
|
|
defined in only one architecture have only one mnemonic; GCC uses that
|
14778 |
|
|
mnemonic irrespective of which of these options is specified.
|
14779 |
|
|
|
14780 |
|
|
GCC defaults to the mnemonics appropriate for the architecture in
|
14781 |
|
|
use. Specifying @option{-mcpu=@var{cpu_type}} sometimes overrides the
|
14782 |
|
|
value of these option. Unless you are building a cross-compiler, you
|
14783 |
|
|
should normally not specify either @option{-mnew-mnemonics} or
|
14784 |
|
|
@option{-mold-mnemonics}, but should instead accept the default.
|
14785 |
|
|
|
14786 |
|
|
@item -mcpu=@var{cpu_type}
|
14787 |
|
|
@opindex mcpu
|
14788 |
|
|
Set architecture type, register usage, choice of mnemonics, and
|
14789 |
|
|
instruction scheduling parameters for machine type @var{cpu_type}.
|
14790 |
|
|
Supported values for @var{cpu_type} are @samp{401}, @samp{403},
|
14791 |
|
|
@samp{405}, @samp{405fp}, @samp{440}, @samp{440fp}, @samp{464}, @samp{464fp},
|
14792 |
|
|
@samp{476}, @samp{476fp}, @samp{505}, @samp{601}, @samp{602}, @samp{603},
|
14793 |
|
|
@samp{603e}, @samp{604}, @samp{604e}, @samp{620}, @samp{630}, @samp{740},
|
14794 |
|
|
@samp{7400}, @samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823},
|
14795 |
|
|
@samp{860}, @samp{970}, @samp{8540}, @samp{a2}, @samp{e300c2},
|
14796 |
|
|
@samp{e300c3}, @samp{e500mc}, @samp{e500mc64}, @samp{ec603e}, @samp{G3},
|
14797 |
|
|
@samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3},
|
14798 |
|
|
@samp{power4}, @samp{power5}, @samp{power5+}, @samp{power6}, @samp{power6x},
|
14799 |
|
|
@samp{power7}, @samp{common}, @samp{powerpc}, @samp{powerpc64}, @samp{rios},
|
14800 |
|
|
@samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64}.
|
14801 |
|
|
|
14802 |
|
|
@option{-mcpu=common} selects a completely generic processor. Code
|
14803 |
|
|
generated under this option will run on any POWER or PowerPC processor.
|
14804 |
|
|
GCC will use only the instructions in the common subset of both
|
14805 |
|
|
architectures, and will not use the MQ register. GCC assumes a generic
|
14806 |
|
|
processor model for scheduling purposes.
|
14807 |
|
|
|
14808 |
|
|
@option{-mcpu=power}, @option{-mcpu=power2}, @option{-mcpu=powerpc}, and
|
14809 |
|
|
@option{-mcpu=powerpc64} specify generic POWER, POWER2, pure 32-bit
|
14810 |
|
|
PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine
|
14811 |
|
|
types, with an appropriate, generic processor model assumed for
|
14812 |
|
|
scheduling purposes.
|
14813 |
|
|
|
14814 |
|
|
The other options specify a specific processor. Code generated under
|
14815 |
|
|
those options will run best on that processor, and may not run at all on
|
14816 |
|
|
others.
|
14817 |
|
|
|
14818 |
|
|
The @option{-mcpu} options automatically enable or disable the
|
14819 |
|
|
following options:
|
14820 |
|
|
|
14821 |
|
|
@gccoptlist{-maltivec -mfprnd -mhard-float -mmfcrf -mmultiple @gol
|
14822 |
|
|
-mnew-mnemonics -mpopcntb -mpopcntd -mpower -mpower2 -mpowerpc64 @gol
|
14823 |
|
|
-mpowerpc-gpopt -mpowerpc-gfxopt -msingle-float -mdouble-float @gol
|
14824 |
|
|
-msimple-fpu -mstring -mmulhw -mdlmzb -mmfpgpr -mvsx}
|
14825 |
|
|
|
14826 |
|
|
The particular options set for any particular CPU will vary between
|
14827 |
|
|
compiler versions, depending on what setting seems to produce optimal
|
14828 |
|
|
code for that CPU; it doesn't necessarily reflect the actual hardware's
|
14829 |
|
|
capabilities. If you wish to set an individual option to a particular
|
14830 |
|
|
value, you may specify it after the @option{-mcpu} option, like
|
14831 |
|
|
@samp{-mcpu=970 -mno-altivec}.
|
14832 |
|
|
|
14833 |
|
|
On AIX, the @option{-maltivec} and @option{-mpowerpc64} options are
|
14834 |
|
|
not enabled or disabled by the @option{-mcpu} option at present because
|
14835 |
|
|
AIX does not have full support for these options. You may still
|
14836 |
|
|
enable or disable them individually if you're sure it'll work in your
|
14837 |
|
|
environment.
|
14838 |
|
|
|
14839 |
|
|
@item -mtune=@var{cpu_type}
|
14840 |
|
|
@opindex mtune
|
14841 |
|
|
Set the instruction scheduling parameters for machine type
|
14842 |
|
|
@var{cpu_type}, but do not set the architecture type, register usage, or
|
14843 |
|
|
choice of mnemonics, as @option{-mcpu=@var{cpu_type}} would. The same
|
14844 |
|
|
values for @var{cpu_type} are used for @option{-mtune} as for
|
14845 |
|
|
@option{-mcpu}. If both are specified, the code generated will use the
|
14846 |
|
|
architecture, registers, and mnemonics set by @option{-mcpu}, but the
|
14847 |
|
|
scheduling parameters set by @option{-mtune}.
|
14848 |
|
|
|
14849 |
|
|
@item -mswdiv
|
14850 |
|
|
@itemx -mno-swdiv
|
14851 |
|
|
@opindex mswdiv
|
14852 |
|
|
@opindex mno-swdiv
|
14853 |
|
|
Generate code to compute division as reciprocal estimate and iterative
|
14854 |
|
|
refinement, creating opportunities for increased throughput. This
|
14855 |
|
|
feature requires: optional PowerPC Graphics instruction set for single
|
14856 |
|
|
precision and FRE instruction for double precision, assuming divides
|
14857 |
|
|
cannot generate user-visible traps, and the domain values not include
|
14858 |
|
|
Infinities, denormals or zero denominator.
|
14859 |
|
|
|
14860 |
|
|
@item -maltivec
|
14861 |
|
|
@itemx -mno-altivec
|
14862 |
|
|
@opindex maltivec
|
14863 |
|
|
@opindex mno-altivec
|
14864 |
|
|
Generate code that uses (does not use) AltiVec instructions, and also
|
14865 |
|
|
enable the use of built-in functions that allow more direct access to
|
14866 |
|
|
the AltiVec instruction set. You may also need to set
|
14867 |
|
|
@option{-mabi=altivec} to adjust the current ABI with AltiVec ABI
|
14868 |
|
|
enhancements.
|
14869 |
|
|
|
14870 |
|
|
@item -mvrsave
|
14871 |
|
|
@itemx -mno-vrsave
|
14872 |
|
|
@opindex mvrsave
|
14873 |
|
|
@opindex mno-vrsave
|
14874 |
|
|
Generate VRSAVE instructions when generating AltiVec code.
|
14875 |
|
|
|
14876 |
|
|
@item -mgen-cell-microcode
|
14877 |
|
|
@opindex mgen-cell-microcode
|
14878 |
|
|
Generate Cell microcode instructions
|
14879 |
|
|
|
14880 |
|
|
@item -mwarn-cell-microcode
|
14881 |
|
|
@opindex mwarn-cell-microcode
|
14882 |
|
|
Warning when a Cell microcode instruction is going to emitted. An example
|
14883 |
|
|
of a Cell microcode instruction is a variable shift.
|
14884 |
|
|
|
14885 |
|
|
@item -msecure-plt
|
14886 |
|
|
@opindex msecure-plt
|
14887 |
|
|
Generate code that allows ld and ld.so to build executables and shared
|
14888 |
|
|
libraries with non-exec .plt and .got sections. This is a PowerPC
|
14889 |
|
|
32-bit SYSV ABI option.
|
14890 |
|
|
|
14891 |
|
|
@item -mbss-plt
|
14892 |
|
|
@opindex mbss-plt
|
14893 |
|
|
Generate code that uses a BSS .plt section that ld.so fills in, and
|
14894 |
|
|
requires .plt and .got sections that are both writable and executable.
|
14895 |
|
|
This is a PowerPC 32-bit SYSV ABI option.
|
14896 |
|
|
|
14897 |
|
|
@item -misel
|
14898 |
|
|
@itemx -mno-isel
|
14899 |
|
|
@opindex misel
|
14900 |
|
|
@opindex mno-isel
|
14901 |
|
|
This switch enables or disables the generation of ISEL instructions.
|
14902 |
|
|
|
14903 |
|
|
@item -misel=@var{yes/no}
|
14904 |
|
|
This switch has been deprecated. Use @option{-misel} and
|
14905 |
|
|
@option{-mno-isel} instead.
|
14906 |
|
|
|
14907 |
|
|
@item -mspe
|
14908 |
|
|
@itemx -mno-spe
|
14909 |
|
|
@opindex mspe
|
14910 |
|
|
@opindex mno-spe
|
14911 |
|
|
This switch enables or disables the generation of SPE simd
|
14912 |
|
|
instructions.
|
14913 |
|
|
|
14914 |
|
|
@item -mpaired
|
14915 |
|
|
@itemx -mno-paired
|
14916 |
|
|
@opindex mpaired
|
14917 |
|
|
@opindex mno-paired
|
14918 |
|
|
This switch enables or disables the generation of PAIRED simd
|
14919 |
|
|
instructions.
|
14920 |
|
|
|
14921 |
|
|
@item -mspe=@var{yes/no}
|
14922 |
|
|
This option has been deprecated. Use @option{-mspe} and
|
14923 |
|
|
@option{-mno-spe} instead.
|
14924 |
|
|
|
14925 |
|
|
@item -mvsx
|
14926 |
|
|
@itemx -mno-vsx
|
14927 |
|
|
@opindex mvsx
|
14928 |
|
|
@opindex mno-vsx
|
14929 |
|
|
Generate code that uses (does not use) vector/scalar (VSX)
|
14930 |
|
|
instructions, and also enable the use of built-in functions that allow
|
14931 |
|
|
more direct access to the VSX instruction set.
|
14932 |
|
|
|
14933 |
|
|
@item -mfloat-gprs=@var{yes/single/double/no}
|
14934 |
|
|
@itemx -mfloat-gprs
|
14935 |
|
|
@opindex mfloat-gprs
|
14936 |
|
|
This switch enables or disables the generation of floating point
|
14937 |
|
|
operations on the general purpose registers for architectures that
|
14938 |
|
|
support it.
|
14939 |
|
|
|
14940 |
|
|
The argument @var{yes} or @var{single} enables the use of
|
14941 |
|
|
single-precision floating point operations.
|
14942 |
|
|
|
14943 |
|
|
The argument @var{double} enables the use of single and
|
14944 |
|
|
double-precision floating point operations.
|
14945 |
|
|
|
14946 |
|
|
The argument @var{no} disables floating point operations on the
|
14947 |
|
|
general purpose registers.
|
14948 |
|
|
|
14949 |
|
|
This option is currently only available on the MPC854x.
|
14950 |
|
|
|
14951 |
|
|
@item -m32
|
14952 |
|
|
@itemx -m64
|
14953 |
|
|
@opindex m32
|
14954 |
|
|
@opindex m64
|
14955 |
|
|
Generate code for 32-bit or 64-bit environments of Darwin and SVR4
|
14956 |
|
|
targets (including GNU/Linux). The 32-bit environment sets int, long
|
14957 |
|
|
and pointer to 32 bits and generates code that runs on any PowerPC
|
14958 |
|
|
variant. The 64-bit environment sets int to 32 bits and long and
|
14959 |
|
|
pointer to 64 bits, and generates code for PowerPC64, as for
|
14960 |
|
|
@option{-mpowerpc64}.
|
14961 |
|
|
|
14962 |
|
|
@item -mfull-toc
|
14963 |
|
|
@itemx -mno-fp-in-toc
|
14964 |
|
|
@itemx -mno-sum-in-toc
|
14965 |
|
|
@itemx -mminimal-toc
|
14966 |
|
|
@opindex mfull-toc
|
14967 |
|
|
@opindex mno-fp-in-toc
|
14968 |
|
|
@opindex mno-sum-in-toc
|
14969 |
|
|
@opindex mminimal-toc
|
14970 |
|
|
Modify generation of the TOC (Table Of Contents), which is created for
|
14971 |
|
|
every executable file. The @option{-mfull-toc} option is selected by
|
14972 |
|
|
default. In that case, GCC will allocate at least one TOC entry for
|
14973 |
|
|
each unique non-automatic variable reference in your program. GCC
|
14974 |
|
|
will also place floating-point constants in the TOC@. However, only
|
14975 |
|
|
16,384 entries are available in the TOC@.
|
14976 |
|
|
|
14977 |
|
|
If you receive a linker error message that saying you have overflowed
|
14978 |
|
|
the available TOC space, you can reduce the amount of TOC space used
|
14979 |
|
|
with the @option{-mno-fp-in-toc} and @option{-mno-sum-in-toc} options.
|
14980 |
|
|
@option{-mno-fp-in-toc} prevents GCC from putting floating-point
|
14981 |
|
|
constants in the TOC and @option{-mno-sum-in-toc} forces GCC to
|
14982 |
|
|
generate code to calculate the sum of an address and a constant at
|
14983 |
|
|
run-time instead of putting that sum into the TOC@. You may specify one
|
14984 |
|
|
or both of these options. Each causes GCC to produce very slightly
|
14985 |
|
|
slower and larger code at the expense of conserving TOC space.
|
14986 |
|
|
|
14987 |
|
|
If you still run out of space in the TOC even when you specify both of
|
14988 |
|
|
these options, specify @option{-mminimal-toc} instead. This option causes
|
14989 |
|
|
GCC to make only one TOC entry for every file. When you specify this
|
14990 |
|
|
option, GCC will produce code that is slower and larger but which
|
14991 |
|
|
uses extremely little TOC space. You may wish to use this option
|
14992 |
|
|
only on files that contain less frequently executed code.
|
14993 |
|
|
|
14994 |
|
|
@item -maix64
|
14995 |
|
|
@itemx -maix32
|
14996 |
|
|
@opindex maix64
|
14997 |
|
|
@opindex maix32
|
14998 |
|
|
Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit
|
14999 |
|
|
@code{long} type, and the infrastructure needed to support them.
|
15000 |
|
|
Specifying @option{-maix64} implies @option{-mpowerpc64} and
|
15001 |
|
|
@option{-mpowerpc}, while @option{-maix32} disables the 64-bit ABI and
|
15002 |
|
|
implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}.
|
15003 |
|
|
|
15004 |
|
|
@item -mxl-compat
|
15005 |
|
|
@itemx -mno-xl-compat
|
15006 |
|
|
@opindex mxl-compat
|
15007 |
|
|
@opindex mno-xl-compat
|
15008 |
|
|
Produce code that conforms more closely to IBM XL compiler semantics
|
15009 |
|
|
when using AIX-compatible ABI@. Pass floating-point arguments to
|
15010 |
|
|
prototyped functions beyond the register save area (RSA) on the stack
|
15011 |
|
|
in addition to argument FPRs. Do not assume that most significant
|
15012 |
|
|
double in 128-bit long double value is properly rounded when comparing
|
15013 |
|
|
values and converting to double. Use XL symbol names for long double
|
15014 |
|
|
support routines.
|
15015 |
|
|
|
15016 |
|
|
The AIX calling convention was extended but not initially documented to
|
15017 |
|
|
handle an obscure K&R C case of calling a function that takes the
|
15018 |
|
|
address of its arguments with fewer arguments than declared. IBM XL
|
15019 |
|
|
compilers access floating point arguments which do not fit in the
|
15020 |
|
|
RSA from the stack when a subroutine is compiled without
|
15021 |
|
|
optimization. Because always storing floating-point arguments on the
|
15022 |
|
|
stack is inefficient and rarely needed, this option is not enabled by
|
15023 |
|
|
default and only is necessary when calling subroutines compiled by IBM
|
15024 |
|
|
XL compilers without optimization.
|
15025 |
|
|
|
15026 |
|
|
@item -mpe
|
15027 |
|
|
@opindex mpe
|
15028 |
|
|
Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an
|
15029 |
|
|
application written to use message passing with special startup code to
|
15030 |
|
|
enable the application to run. The system must have PE installed in the
|
15031 |
|
|
standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file
|
15032 |
|
|
must be overridden with the @option{-specs=} option to specify the
|
15033 |
|
|
appropriate directory location. The Parallel Environment does not
|
15034 |
|
|
support threads, so the @option{-mpe} option and the @option{-pthread}
|
15035 |
|
|
option are incompatible.
|
15036 |
|
|
|
15037 |
|
|
@item -malign-natural
|
15038 |
|
|
@itemx -malign-power
|
15039 |
|
|
@opindex malign-natural
|
15040 |
|
|
@opindex malign-power
|
15041 |
|
|
On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
|
15042 |
|
|
@option{-malign-natural} overrides the ABI-defined alignment of larger
|
15043 |
|
|
types, such as floating-point doubles, on their natural size-based boundary.
|
15044 |
|
|
The option @option{-malign-power} instructs GCC to follow the ABI-specified
|
15045 |
|
|
alignment rules. GCC defaults to the standard alignment defined in the ABI@.
|
15046 |
|
|
|
15047 |
|
|
On 64-bit Darwin, natural alignment is the default, and @option{-malign-power}
|
15048 |
|
|
is not supported.
|
15049 |
|
|
|
15050 |
|
|
@item -msoft-float
|
15051 |
|
|
@itemx -mhard-float
|
15052 |
|
|
@opindex msoft-float
|
15053 |
|
|
@opindex mhard-float
|
15054 |
|
|
Generate code that does not use (uses) the floating-point register set.
|
15055 |
|
|
Software floating point emulation is provided if you use the
|
15056 |
|
|
@option{-msoft-float} option, and pass the option to GCC when linking.
|
15057 |
|
|
|
15058 |
|
|
@item -msingle-float
|
15059 |
|
|
@itemx -mdouble-float
|
15060 |
|
|
@opindex msingle-float
|
15061 |
|
|
@opindex mdouble-float
|
15062 |
|
|
Generate code for single or double-precision floating point operations.
|
15063 |
|
|
@option{-mdouble-float} implies @option{-msingle-float}.
|
15064 |
|
|
|
15065 |
|
|
@item -msimple-fpu
|
15066 |
|
|
@opindex msimple-fpu
|
15067 |
|
|
Do not generate sqrt and div instructions for hardware floating point unit.
|
15068 |
|
|
|
15069 |
|
|
@item -mfpu
|
15070 |
|
|
@opindex mfpu
|
15071 |
|
|
Specify type of floating point unit. Valid values are @var{sp_lite}
|
15072 |
|
|
(equivalent to -msingle-float -msimple-fpu), @var{dp_lite} (equivalent
|
15073 |
|
|
to -mdouble-float -msimple-fpu), @var{sp_full} (equivalent to -msingle-float),
|
15074 |
|
|
and @var{dp_full} (equivalent to -mdouble-float).
|
15075 |
|
|
|
15076 |
|
|
@item -mxilinx-fpu
|
15077 |
|
|
@opindex mxilinx-fpu
|
15078 |
|
|
Perform optimizations for floating point unit on Xilinx PPC 405/440.
|
15079 |
|
|
|
15080 |
|
|
@item -mmultiple
|
15081 |
|
|
@itemx -mno-multiple
|
15082 |
|
|
@opindex mmultiple
|
15083 |
|
|
@opindex mno-multiple
|
15084 |
|
|
Generate code that uses (does not use) the load multiple word
|
15085 |
|
|
instructions and the store multiple word instructions. These
|
15086 |
|
|
instructions are generated by default on POWER systems, and not
|
15087 |
|
|
generated on PowerPC systems. Do not use @option{-mmultiple} on little
|
15088 |
|
|
endian PowerPC systems, since those instructions do not work when the
|
15089 |
|
|
processor is in little endian mode. The exceptions are PPC740 and
|
15090 |
|
|
PPC750 which permit the instructions usage in little endian mode.
|
15091 |
|
|
|
15092 |
|
|
@item -mstring
|
15093 |
|
|
@itemx -mno-string
|
15094 |
|
|
@opindex mstring
|
15095 |
|
|
@opindex mno-string
|
15096 |
|
|
Generate code that uses (does not use) the load string instructions
|
15097 |
|
|
and the store string word instructions to save multiple registers and
|
15098 |
|
|
do small block moves. These instructions are generated by default on
|
15099 |
|
|
POWER systems, and not generated on PowerPC systems. Do not use
|
15100 |
|
|
@option{-mstring} on little endian PowerPC systems, since those
|
15101 |
|
|
instructions do not work when the processor is in little endian mode.
|
15102 |
|
|
The exceptions are PPC740 and PPC750 which permit the instructions
|
15103 |
|
|
usage in little endian mode.
|
15104 |
|
|
|
15105 |
|
|
@item -mupdate
|
15106 |
|
|
@itemx -mno-update
|
15107 |
|
|
@opindex mupdate
|
15108 |
|
|
@opindex mno-update
|
15109 |
|
|
Generate code that uses (does not use) the load or store instructions
|
15110 |
|
|
that update the base register to the address of the calculated memory
|
15111 |
|
|
location. These instructions are generated by default. If you use
|
15112 |
|
|
@option{-mno-update}, there is a small window between the time that the
|
15113 |
|
|
stack pointer is updated and the address of the previous frame is
|
15114 |
|
|
stored, which means code that walks the stack frame across interrupts or
|
15115 |
|
|
signals may get corrupted data.
|
15116 |
|
|
|
15117 |
|
|
@item -mavoid-indexed-addresses
|
15118 |
|
|
@itemx -mno-avoid-indexed-addresses
|
15119 |
|
|
@opindex mavoid-indexed-addresses
|
15120 |
|
|
@opindex mno-avoid-indexed-addresses
|
15121 |
|
|
Generate code that tries to avoid (not avoid) the use of indexed load
|
15122 |
|
|
or store instructions. These instructions can incur a performance
|
15123 |
|
|
penalty on Power6 processors in certain situations, such as when
|
15124 |
|
|
stepping through large arrays that cross a 16M boundary. This option
|
15125 |
|
|
is enabled by default when targetting Power6 and disabled otherwise.
|
15126 |
|
|
|
15127 |
|
|
@item -mfused-madd
|
15128 |
|
|
@itemx -mno-fused-madd
|
15129 |
|
|
@opindex mfused-madd
|
15130 |
|
|
@opindex mno-fused-madd
|
15131 |
|
|
Generate code that uses (does not use) the floating point multiply and
|
15132 |
|
|
accumulate instructions. These instructions are generated by default if
|
15133 |
|
|
hardware floating is used.
|
15134 |
|
|
|
15135 |
|
|
@item -mmulhw
|
15136 |
|
|
@itemx -mno-mulhw
|
15137 |
|
|
@opindex mmulhw
|
15138 |
|
|
@opindex mno-mulhw
|
15139 |
|
|
Generate code that uses (does not use) the half-word multiply and
|
15140 |
|
|
multiply-accumulate instructions on the IBM 405, 440, 464 and 476 processors.
|
15141 |
|
|
These instructions are generated by default when targetting those
|
15142 |
|
|
processors.
|
15143 |
|
|
|
15144 |
|
|
@item -mdlmzb
|
15145 |
|
|
@itemx -mno-dlmzb
|
15146 |
|
|
@opindex mdlmzb
|
15147 |
|
|
@opindex mno-dlmzb
|
15148 |
|
|
Generate code that uses (does not use) the string-search @samp{dlmzb}
|
15149 |
|
|
instruction on the IBM 405, 440, 464 and 476 processors. This instruction is
|
15150 |
|
|
generated by default when targetting those processors.
|
15151 |
|
|
|
15152 |
|
|
@item -mno-bit-align
|
15153 |
|
|
@itemx -mbit-align
|
15154 |
|
|
@opindex mno-bit-align
|
15155 |
|
|
@opindex mbit-align
|
15156 |
|
|
On System V.4 and embedded PowerPC systems do not (do) force structures
|
15157 |
|
|
and unions that contain bit-fields to be aligned to the base type of the
|
15158 |
|
|
bit-field.
|
15159 |
|
|
|
15160 |
|
|
For example, by default a structure containing nothing but 8
|
15161 |
|
|
@code{unsigned} bit-fields of length 1 would be aligned to a 4 byte
|
15162 |
|
|
boundary and have a size of 4 bytes. By using @option{-mno-bit-align},
|
15163 |
|
|
the structure would be aligned to a 1 byte boundary and be one byte in
|
15164 |
|
|
size.
|
15165 |
|
|
|
15166 |
|
|
@item -mno-strict-align
|
15167 |
|
|
@itemx -mstrict-align
|
15168 |
|
|
@opindex mno-strict-align
|
15169 |
|
|
@opindex mstrict-align
|
15170 |
|
|
On System V.4 and embedded PowerPC systems do not (do) assume that
|
15171 |
|
|
unaligned memory references will be handled by the system.
|
15172 |
|
|
|
15173 |
|
|
@item -mrelocatable
|
15174 |
|
|
@itemx -mno-relocatable
|
15175 |
|
|
@opindex mrelocatable
|
15176 |
|
|
@opindex mno-relocatable
|
15177 |
|
|
On embedded PowerPC systems generate code that allows (does not allow)
|
15178 |
|
|
the program to be relocated to a different address at runtime. If you
|
15179 |
|
|
use @option{-mrelocatable} on any module, all objects linked together must
|
15180 |
|
|
be compiled with @option{-mrelocatable} or @option{-mrelocatable-lib}.
|
15181 |
|
|
|
15182 |
|
|
@item -mrelocatable-lib
|
15183 |
|
|
@itemx -mno-relocatable-lib
|
15184 |
|
|
@opindex mrelocatable-lib
|
15185 |
|
|
@opindex mno-relocatable-lib
|
15186 |
|
|
On embedded PowerPC systems generate code that allows (does not allow)
|
15187 |
|
|
the program to be relocated to a different address at runtime. Modules
|
15188 |
|
|
compiled with @option{-mrelocatable-lib} can be linked with either modules
|
15189 |
|
|
compiled without @option{-mrelocatable} and @option{-mrelocatable-lib} or
|
15190 |
|
|
with modules compiled with the @option{-mrelocatable} options.
|
15191 |
|
|
|
15192 |
|
|
@item -mno-toc
|
15193 |
|
|
@itemx -mtoc
|
15194 |
|
|
@opindex mno-toc
|
15195 |
|
|
@opindex mtoc
|
15196 |
|
|
On System V.4 and embedded PowerPC systems do not (do) assume that
|
15197 |
|
|
register 2 contains a pointer to a global area pointing to the addresses
|
15198 |
|
|
used in the program.
|
15199 |
|
|
|
15200 |
|
|
@item -mlittle
|
15201 |
|
|
@itemx -mlittle-endian
|
15202 |
|
|
@opindex mlittle
|
15203 |
|
|
@opindex mlittle-endian
|
15204 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15205 |
|
|
processor in little endian mode. The @option{-mlittle-endian} option is
|
15206 |
|
|
the same as @option{-mlittle}.
|
15207 |
|
|
|
15208 |
|
|
@item -mbig
|
15209 |
|
|
@itemx -mbig-endian
|
15210 |
|
|
@opindex mbig
|
15211 |
|
|
@opindex mbig-endian
|
15212 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15213 |
|
|
processor in big endian mode. The @option{-mbig-endian} option is
|
15214 |
|
|
the same as @option{-mbig}.
|
15215 |
|
|
|
15216 |
|
|
@item -mdynamic-no-pic
|
15217 |
|
|
@opindex mdynamic-no-pic
|
15218 |
|
|
On Darwin and Mac OS X systems, compile code so that it is not
|
15219 |
|
|
relocatable, but that its external references are relocatable. The
|
15220 |
|
|
resulting code is suitable for applications, but not shared
|
15221 |
|
|
libraries.
|
15222 |
|
|
|
15223 |
|
|
@item -mprioritize-restricted-insns=@var{priority}
|
15224 |
|
|
@opindex mprioritize-restricted-insns
|
15225 |
|
|
This option controls the priority that is assigned to
|
15226 |
|
|
dispatch-slot restricted instructions during the second scheduling
|
15227 |
|
|
pass. The argument @var{priority} takes the value @var{0/1/2} to assign
|
15228 |
|
|
@var{no/highest/second-highest} priority to dispatch slot restricted
|
15229 |
|
|
instructions.
|
15230 |
|
|
|
15231 |
|
|
@item -msched-costly-dep=@var{dependence_type}
|
15232 |
|
|
@opindex msched-costly-dep
|
15233 |
|
|
This option controls which dependences are considered costly
|
15234 |
|
|
by the target during instruction scheduling. The argument
|
15235 |
|
|
@var{dependence_type} takes one of the following values:
|
15236 |
|
|
@var{no}: no dependence is costly,
|
15237 |
|
|
@var{all}: all dependences are costly,
|
15238 |
|
|
@var{true_store_to_load}: a true dependence from store to load is costly,
|
15239 |
|
|
@var{store_to_load}: any dependence from store to load is costly,
|
15240 |
|
|
@var{number}: any dependence which latency >= @var{number} is costly.
|
15241 |
|
|
|
15242 |
|
|
@item -minsert-sched-nops=@var{scheme}
|
15243 |
|
|
@opindex minsert-sched-nops
|
15244 |
|
|
This option controls which nop insertion scheme will be used during
|
15245 |
|
|
the second scheduling pass. The argument @var{scheme} takes one of the
|
15246 |
|
|
following values:
|
15247 |
|
|
@var{no}: Don't insert nops.
|
15248 |
|
|
@var{pad}: Pad with nops any dispatch group which has vacant issue slots,
|
15249 |
|
|
according to the scheduler's grouping.
|
15250 |
|
|
@var{regroup_exact}: Insert nops to force costly dependent insns into
|
15251 |
|
|
separate groups. Insert exactly as many nops as needed to force an insn
|
15252 |
|
|
to a new group, according to the estimated processor grouping.
|
15253 |
|
|
@var{number}: Insert nops to force costly dependent insns into
|
15254 |
|
|
separate groups. Insert @var{number} nops to force an insn to a new group.
|
15255 |
|
|
|
15256 |
|
|
@item -mcall-sysv
|
15257 |
|
|
@opindex mcall-sysv
|
15258 |
|
|
On System V.4 and embedded PowerPC systems compile code using calling
|
15259 |
|
|
conventions that adheres to the March 1995 draft of the System V
|
15260 |
|
|
Application Binary Interface, PowerPC processor supplement. This is the
|
15261 |
|
|
default unless you configured GCC using @samp{powerpc-*-eabiaix}.
|
15262 |
|
|
|
15263 |
|
|
@item -mcall-sysv-eabi
|
15264 |
|
|
@itemx -mcall-eabi
|
15265 |
|
|
@opindex mcall-sysv-eabi
|
15266 |
|
|
@opindex mcall-eabi
|
15267 |
|
|
Specify both @option{-mcall-sysv} and @option{-meabi} options.
|
15268 |
|
|
|
15269 |
|
|
@item -mcall-sysv-noeabi
|
15270 |
|
|
@opindex mcall-sysv-noeabi
|
15271 |
|
|
Specify both @option{-mcall-sysv} and @option{-mno-eabi} options.
|
15272 |
|
|
|
15273 |
|
|
@item -mcall-aixdesc
|
15274 |
|
|
@opindex m
|
15275 |
|
|
On System V.4 and embedded PowerPC systems compile code for the AIX
|
15276 |
|
|
operating system.
|
15277 |
|
|
|
15278 |
|
|
@item -mcall-linux
|
15279 |
|
|
@opindex mcall-linux
|
15280 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15281 |
|
|
Linux-based GNU system.
|
15282 |
|
|
|
15283 |
|
|
@item -mcall-gnu
|
15284 |
|
|
@opindex mcall-gnu
|
15285 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15286 |
|
|
Hurd-based GNU system.
|
15287 |
|
|
|
15288 |
|
|
@item -mcall-freebsd
|
15289 |
|
|
@opindex mcall-freebsd
|
15290 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15291 |
|
|
FreeBSD operating system.
|
15292 |
|
|
|
15293 |
|
|
@item -mcall-netbsd
|
15294 |
|
|
@opindex mcall-netbsd
|
15295 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15296 |
|
|
NetBSD operating system.
|
15297 |
|
|
|
15298 |
|
|
@item -mcall-openbsd
|
15299 |
|
|
@opindex mcall-netbsd
|
15300 |
|
|
On System V.4 and embedded PowerPC systems compile code for the
|
15301 |
|
|
OpenBSD operating system.
|
15302 |
|
|
|
15303 |
|
|
@item -maix-struct-return
|
15304 |
|
|
@opindex maix-struct-return
|
15305 |
|
|
Return all structures in memory (as specified by the AIX ABI)@.
|
15306 |
|
|
|
15307 |
|
|
@item -msvr4-struct-return
|
15308 |
|
|
@opindex msvr4-struct-return
|
15309 |
|
|
Return structures smaller than 8 bytes in registers (as specified by the
|
15310 |
|
|
SVR4 ABI)@.
|
15311 |
|
|
|
15312 |
|
|
@item -mabi=@var{abi-type}
|
15313 |
|
|
@opindex mabi
|
15314 |
|
|
Extend the current ABI with a particular extension, or remove such extension.
|
15315 |
|
|
Valid values are @var{altivec}, @var{no-altivec}, @var{spe},
|
15316 |
|
|
@var{no-spe}, @var{ibmlongdouble}, @var{ieeelongdouble}@.
|
15317 |
|
|
|
15318 |
|
|
@item -mabi=spe
|
15319 |
|
|
@opindex mabi=spe
|
15320 |
|
|
Extend the current ABI with SPE ABI extensions. This does not change
|
15321 |
|
|
the default ABI, instead it adds the SPE ABI extensions to the current
|
15322 |
|
|
ABI@.
|
15323 |
|
|
|
15324 |
|
|
@item -mabi=no-spe
|
15325 |
|
|
@opindex mabi=no-spe
|
15326 |
|
|
Disable Booke SPE ABI extensions for the current ABI@.
|
15327 |
|
|
|
15328 |
|
|
@item -mabi=ibmlongdouble
|
15329 |
|
|
@opindex mabi=ibmlongdouble
|
15330 |
|
|
Change the current ABI to use IBM extended precision long double.
|
15331 |
|
|
This is a PowerPC 32-bit SYSV ABI option.
|
15332 |
|
|
|
15333 |
|
|
@item -mabi=ieeelongdouble
|
15334 |
|
|
@opindex mabi=ieeelongdouble
|
15335 |
|
|
Change the current ABI to use IEEE extended precision long double.
|
15336 |
|
|
This is a PowerPC 32-bit Linux ABI option.
|
15337 |
|
|
|
15338 |
|
|
@item -mprototype
|
15339 |
|
|
@itemx -mno-prototype
|
15340 |
|
|
@opindex mprototype
|
15341 |
|
|
@opindex mno-prototype
|
15342 |
|
|
On System V.4 and embedded PowerPC systems assume that all calls to
|
15343 |
|
|
variable argument functions are properly prototyped. Otherwise, the
|
15344 |
|
|
compiler must insert an instruction before every non prototyped call to
|
15345 |
|
|
set or clear bit 6 of the condition code register (@var{CR}) to
|
15346 |
|
|
indicate whether floating point values were passed in the floating point
|
15347 |
|
|
registers in case the function takes a variable arguments. With
|
15348 |
|
|
@option{-mprototype}, only calls to prototyped variable argument functions
|
15349 |
|
|
will set or clear the bit.
|
15350 |
|
|
|
15351 |
|
|
@item -msim
|
15352 |
|
|
@opindex msim
|
15353 |
|
|
On embedded PowerPC systems, assume that the startup module is called
|
15354 |
|
|
@file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and
|
15355 |
|
|
@file{libc.a}. This is the default for @samp{powerpc-*-eabisim}
|
15356 |
|
|
configurations.
|
15357 |
|
|
|
15358 |
|
|
@item -mmvme
|
15359 |
|
|
@opindex mmvme
|
15360 |
|
|
On embedded PowerPC systems, assume that the startup module is called
|
15361 |
|
|
@file{crt0.o} and the standard C libraries are @file{libmvme.a} and
|
15362 |
|
|
@file{libc.a}.
|
15363 |
|
|
|
15364 |
|
|
@item -mads
|
15365 |
|
|
@opindex mads
|
15366 |
|
|
On embedded PowerPC systems, assume that the startup module is called
|
15367 |
|
|
@file{crt0.o} and the standard C libraries are @file{libads.a} and
|
15368 |
|
|
@file{libc.a}.
|
15369 |
|
|
|
15370 |
|
|
@item -myellowknife
|
15371 |
|
|
@opindex myellowknife
|
15372 |
|
|
On embedded PowerPC systems, assume that the startup module is called
|
15373 |
|
|
@file{crt0.o} and the standard C libraries are @file{libyk.a} and
|
15374 |
|
|
@file{libc.a}.
|
15375 |
|
|
|
15376 |
|
|
@item -mvxworks
|
15377 |
|
|
@opindex mvxworks
|
15378 |
|
|
On System V.4 and embedded PowerPC systems, specify that you are
|
15379 |
|
|
compiling for a VxWorks system.
|
15380 |
|
|
|
15381 |
|
|
@item -memb
|
15382 |
|
|
@opindex memb
|
15383 |
|
|
On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags
|
15384 |
|
|
header to indicate that @samp{eabi} extended relocations are used.
|
15385 |
|
|
|
15386 |
|
|
@item -meabi
|
15387 |
|
|
@itemx -mno-eabi
|
15388 |
|
|
@opindex meabi
|
15389 |
|
|
@opindex mno-eabi
|
15390 |
|
|
On System V.4 and embedded PowerPC systems do (do not) adhere to the
|
15391 |
|
|
Embedded Applications Binary Interface (eabi) which is a set of
|
15392 |
|
|
modifications to the System V.4 specifications. Selecting @option{-meabi}
|
15393 |
|
|
means that the stack is aligned to an 8 byte boundary, a function
|
15394 |
|
|
@code{__eabi} is called to from @code{main} to set up the eabi
|
15395 |
|
|
environment, and the @option{-msdata} option can use both @code{r2} and
|
15396 |
|
|
@code{r13} to point to two separate small data areas. Selecting
|
15397 |
|
|
@option{-mno-eabi} means that the stack is aligned to a 16 byte boundary,
|
15398 |
|
|
do not call an initialization function from @code{main}, and the
|
15399 |
|
|
@option{-msdata} option will only use @code{r13} to point to a single
|
15400 |
|
|
small data area. The @option{-meabi} option is on by default if you
|
15401 |
|
|
configured GCC using one of the @samp{powerpc*-*-eabi*} options.
|
15402 |
|
|
|
15403 |
|
|
@item -msdata=eabi
|
15404 |
|
|
@opindex msdata=eabi
|
15405 |
|
|
On System V.4 and embedded PowerPC systems, put small initialized
|
15406 |
|
|
@code{const} global and static data in the @samp{.sdata2} section, which
|
15407 |
|
|
is pointed to by register @code{r2}. Put small initialized
|
15408 |
|
|
non-@code{const} global and static data in the @samp{.sdata} section,
|
15409 |
|
|
which is pointed to by register @code{r13}. Put small uninitialized
|
15410 |
|
|
global and static data in the @samp{.sbss} section, which is adjacent to
|
15411 |
|
|
the @samp{.sdata} section. The @option{-msdata=eabi} option is
|
15412 |
|
|
incompatible with the @option{-mrelocatable} option. The
|
15413 |
|
|
@option{-msdata=eabi} option also sets the @option{-memb} option.
|
15414 |
|
|
|
15415 |
|
|
@item -msdata=sysv
|
15416 |
|
|
@opindex msdata=sysv
|
15417 |
|
|
On System V.4 and embedded PowerPC systems, put small global and static
|
15418 |
|
|
data in the @samp{.sdata} section, which is pointed to by register
|
15419 |
|
|
@code{r13}. Put small uninitialized global and static data in the
|
15420 |
|
|
@samp{.sbss} section, which is adjacent to the @samp{.sdata} section.
|
15421 |
|
|
The @option{-msdata=sysv} option is incompatible with the
|
15422 |
|
|
@option{-mrelocatable} option.
|
15423 |
|
|
|
15424 |
|
|
@item -msdata=default
|
15425 |
|
|
@itemx -msdata
|
15426 |
|
|
@opindex msdata=default
|
15427 |
|
|
@opindex msdata
|
15428 |
|
|
On System V.4 and embedded PowerPC systems, if @option{-meabi} is used,
|
15429 |
|
|
compile code the same as @option{-msdata=eabi}, otherwise compile code the
|
15430 |
|
|
same as @option{-msdata=sysv}.
|
15431 |
|
|
|
15432 |
|
|
@item -msdata=data
|
15433 |
|
|
@opindex msdata=data
|
15434 |
|
|
On System V.4 and embedded PowerPC systems, put small global
|
15435 |
|
|
data in the @samp{.sdata} section. Put small uninitialized global
|
15436 |
|
|
data in the @samp{.sbss} section. Do not use register @code{r13}
|
15437 |
|
|
to address small data however. This is the default behavior unless
|
15438 |
|
|
other @option{-msdata} options are used.
|
15439 |
|
|
|
15440 |
|
|
@item -msdata=none
|
15441 |
|
|
@itemx -mno-sdata
|
15442 |
|
|
@opindex msdata=none
|
15443 |
|
|
@opindex mno-sdata
|
15444 |
|
|
On embedded PowerPC systems, put all initialized global and static data
|
15445 |
|
|
in the @samp{.data} section, and all uninitialized data in the
|
15446 |
|
|
@samp{.bss} section.
|
15447 |
|
|
|
15448 |
|
|
@item -G @var{num}
|
15449 |
|
|
@opindex G
|
15450 |
|
|
@cindex smaller data references (PowerPC)
|
15451 |
|
|
@cindex .sdata/.sdata2 references (PowerPC)
|
15452 |
|
|
On embedded PowerPC systems, put global and static items less than or
|
15453 |
|
|
equal to @var{num} bytes into the small data or bss sections instead of
|
15454 |
|
|
the normal data or bss section. By default, @var{num} is 8. The
|
15455 |
|
|
@option{-G @var{num}} switch is also passed to the linker.
|
15456 |
|
|
All modules should be compiled with the same @option{-G @var{num}} value.
|
15457 |
|
|
|
15458 |
|
|
@item -mregnames
|
15459 |
|
|
@itemx -mno-regnames
|
15460 |
|
|
@opindex mregnames
|
15461 |
|
|
@opindex mno-regnames
|
15462 |
|
|
On System V.4 and embedded PowerPC systems do (do not) emit register
|
15463 |
|
|
names in the assembly language output using symbolic forms.
|
15464 |
|
|
|
15465 |
|
|
@item -mlongcall
|
15466 |
|
|
@itemx -mno-longcall
|
15467 |
|
|
@opindex mlongcall
|
15468 |
|
|
@opindex mno-longcall
|
15469 |
|
|
By default assume that all calls are far away so that a longer more
|
15470 |
|
|
expensive calling sequence is required. This is required for calls
|
15471 |
|
|
further than 32 megabytes (33,554,432 bytes) from the current location.
|
15472 |
|
|
A short call will be generated if the compiler knows
|
15473 |
|
|
the call cannot be that far away. This setting can be overridden by
|
15474 |
|
|
the @code{shortcall} function attribute, or by @code{#pragma
|
15475 |
|
|
longcall(0)}.
|
15476 |
|
|
|
15477 |
|
|
Some linkers are capable of detecting out-of-range calls and generating
|
15478 |
|
|
glue code on the fly. On these systems, long calls are unnecessary and
|
15479 |
|
|
generate slower code. As of this writing, the AIX linker can do this,
|
15480 |
|
|
as can the GNU linker for PowerPC/64. It is planned to add this feature
|
15481 |
|
|
to the GNU linker for 32-bit PowerPC systems as well.
|
15482 |
|
|
|
15483 |
|
|
On Darwin/PPC systems, @code{#pragma longcall} will generate ``jbsr
|
15484 |
|
|
callee, L42'', plus a ``branch island'' (glue code). The two target
|
15485 |
|
|
addresses represent the callee and the ``branch island''. The
|
15486 |
|
|
Darwin/PPC linker will prefer the first address and generate a ``bl
|
15487 |
|
|
callee'' if the PPC ``bl'' instruction will reach the callee directly;
|
15488 |
|
|
otherwise, the linker will generate ``bl L42'' to call the ``branch
|
15489 |
|
|
island''. The ``branch island'' is appended to the body of the
|
15490 |
|
|
calling function; it computes the full 32-bit address of the callee
|
15491 |
|
|
and jumps to it.
|
15492 |
|
|
|
15493 |
|
|
On Mach-O (Darwin) systems, this option directs the compiler emit to
|
15494 |
|
|
the glue for every direct call, and the Darwin linker decides whether
|
15495 |
|
|
to use or discard it.
|
15496 |
|
|
|
15497 |
|
|
In the future, we may cause GCC to ignore all longcall specifications
|
15498 |
|
|
when the linker is known to generate glue.
|
15499 |
|
|
|
15500 |
|
|
@item -mtls-markers
|
15501 |
|
|
@itemx -mno-tls-markers
|
15502 |
|
|
@opindex mtls-markers
|
15503 |
|
|
@opindex mno-tls-markers
|
15504 |
|
|
Mark (do not mark) calls to @code{__tls_get_addr} with a relocation
|
15505 |
|
|
specifying the function argument. The relocation allows ld to
|
15506 |
|
|
reliably associate function call with argument setup instructions for
|
15507 |
|
|
TLS optimization, which in turn allows gcc to better schedule the
|
15508 |
|
|
sequence.
|
15509 |
|
|
|
15510 |
|
|
@item -pthread
|
15511 |
|
|
@opindex pthread
|
15512 |
|
|
Adds support for multithreading with the @dfn{pthreads} library.
|
15513 |
|
|
This option sets flags for both the preprocessor and linker.
|
15514 |
|
|
|
15515 |
|
|
@end table
|
15516 |
|
|
|
15517 |
|
|
@node RX Options
|
15518 |
|
|
@subsection RX Options
|
15519 |
|
|
@cindex RX Options
|
15520 |
|
|
|
15521 |
|
|
These command line options are defined for RX targets:
|
15522 |
|
|
|
15523 |
|
|
@table @gcctabopt
|
15524 |
|
|
@item -m64bit-doubles
|
15525 |
|
|
@itemx -m32bit-doubles
|
15526 |
|
|
@opindex m64bit-doubles
|
15527 |
|
|
@opindex m32bit-doubles
|
15528 |
|
|
Make the @code{double} data type be 64-bits (@option{-m64bit-doubles})
|
15529 |
|
|
or 32-bits (@option{-m32bit-doubles}) in size. The default is
|
15530 |
|
|
@option{-m32bit-doubles}. @emph{Note} RX floating point hardware only
|
15531 |
|
|
works on 32-bit values, which is why the default is
|
15532 |
|
|
@option{-m32bit-doubles}.
|
15533 |
|
|
|
15534 |
|
|
@item -fpu
|
15535 |
|
|
@itemx -nofpu
|
15536 |
|
|
@opindex fpu
|
15537 |
|
|
@opindex nofpu
|
15538 |
|
|
Enables (@option{-fpu}) or disables (@option{-nofpu}) the use of RX
|
15539 |
|
|
floating point hardware. The default is enabled for the @var{RX600}
|
15540 |
|
|
series and disabled for the @var{RX200} series.
|
15541 |
|
|
|
15542 |
|
|
Floating point instructions will only be generated for 32-bit floating
|
15543 |
|
|
point values however, so if the @option{-m64bit-doubles} option is in
|
15544 |
|
|
use then the FPU hardware will not be used for doubles.
|
15545 |
|
|
|
15546 |
|
|
@emph{Note} If the @option{-fpu} option is enabled then
|
15547 |
|
|
@option{-funsafe-math-optimizations} is also enabled automatically.
|
15548 |
|
|
This is because the RX FPU instructions are themselves unsafe.
|
15549 |
|
|
|
15550 |
|
|
@item -mcpu=@var{name}
|
15551 |
|
|
@itemx -patch=@var{name}
|
15552 |
|
|
@opindex -mcpu
|
15553 |
|
|
@opindex -patch
|
15554 |
|
|
Selects the type of RX CPU to be targeted. Currently three types are
|
15555 |
|
|
supported, the generic @var{RX600} and @var{RX200} series hardware and
|
15556 |
|
|
the specific @var{RX610} cpu. The default is @var{RX600}.
|
15557 |
|
|
|
15558 |
|
|
The only difference between @var{RX600} and @var{RX610} is that the
|
15559 |
|
|
@var{RX610} does not support the @code{MVTIPL} instruction.
|
15560 |
|
|
|
15561 |
|
|
The @var{RX200} series does not have a hardware floating point unit
|
15562 |
|
|
and so @option{-nofpu} is enabled by default when this type is
|
15563 |
|
|
selected.
|
15564 |
|
|
|
15565 |
|
|
@item -mbig-endian-data
|
15566 |
|
|
@itemx -mlittle-endian-data
|
15567 |
|
|
@opindex mbig-endian-data
|
15568 |
|
|
@opindex mlittle-endian-data
|
15569 |
|
|
Store data (but not code) in the big-endian format. The default is
|
15570 |
|
|
@option{-mlittle-endian-data}, ie to store data in the little endian
|
15571 |
|
|
format.
|
15572 |
|
|
|
15573 |
|
|
@item -msmall-data-limit=@var{N}
|
15574 |
|
|
@opindex msmall-data-limit
|
15575 |
|
|
Specifies the maximum size in bytes of global and static variables
|
15576 |
|
|
which can be placed into the small data area. Using the small data
|
15577 |
|
|
area can lead to smaller and faster code, but the size of area is
|
15578 |
|
|
limited and it is up to the programmer to ensure that the area does
|
15579 |
|
|
not overflow. Also when the small data area is used one of the RX's
|
15580 |
|
|
registers (@code{r13}) is reserved for use pointing to this area, so
|
15581 |
|
|
it is no longer available for use by the compiler. This could result
|
15582 |
|
|
in slower and/or larger code if variables which once could have been
|
15583 |
|
|
held in @code{r13} are now pushed onto the stack.
|
15584 |
|
|
|
15585 |
|
|
Note, common variables (variables which have not been initialised) and
|
15586 |
|
|
constants are not placed into the small data area as they are assigned
|
15587 |
|
|
to other sections in the output executable.
|
15588 |
|
|
|
15589 |
|
|
The default value is zero, which disables this feature. Note, this
|
15590 |
|
|
feature is not enabled by default with higher optimization levels
|
15591 |
|
|
(@option{-O2} etc) because of the potentially detrimental effects of
|
15592 |
|
|
reserving register @code{r13}. It is up to the programmer to
|
15593 |
|
|
experiment and discover whether this feature is of benefit to their
|
15594 |
|
|
program.
|
15595 |
|
|
|
15596 |
|
|
@item -msim
|
15597 |
|
|
@itemx -mno-sim
|
15598 |
|
|
@opindex msim
|
15599 |
|
|
@opindex mno-sim
|
15600 |
|
|
Use the simulator runtime. The default is to use the libgloss board
|
15601 |
|
|
specific runtime.
|
15602 |
|
|
|
15603 |
|
|
@item -mas100-syntax
|
15604 |
|
|
@itemx -mno-as100-syntax
|
15605 |
|
|
@opindex mas100-syntax
|
15606 |
|
|
@opindex mno-as100-syntax
|
15607 |
|
|
When generating assembler output use a syntax that is compatible with
|
15608 |
|
|
Renesas's AS100 assembler. This syntax can also be handled by the GAS
|
15609 |
|
|
assembler but it has some restrictions so generating it is not the
|
15610 |
|
|
default option.
|
15611 |
|
|
|
15612 |
|
|
@item -mmax-constant-size=@var{N}
|
15613 |
|
|
@opindex mmax-constant-size
|
15614 |
|
|
Specifies the maximum size, in bytes, of a constant that can be used as
|
15615 |
|
|
an operand in a RX instruction. Although the RX instruction set does
|
15616 |
|
|
allow constants of up to 4 bytes in length to be used in instructions,
|
15617 |
|
|
a longer value equates to a longer instruction. Thus in some
|
15618 |
|
|
circumstances it can be beneficial to restrict the size of constants
|
15619 |
|
|
that are used in instructions. Constants that are too big are instead
|
15620 |
|
|
placed into a constant pool and referenced via register indirection.
|
15621 |
|
|
|
15622 |
|
|
The value @var{N} can be between 0 and 4. A value of 0 (the default)
|
15623 |
|
|
or 4 means that constants of any size are allowed.
|
15624 |
|
|
|
15625 |
|
|
@item -mrelax
|
15626 |
|
|
@opindex mrelax
|
15627 |
|
|
Enable linker relaxation. Linker relaxation is a process whereby the
|
15628 |
|
|
linker will attempt to reduce the size of a program by finding shorter
|
15629 |
|
|
versions of various instructions. Disabled by default.
|
15630 |
|
|
|
15631 |
|
|
@item -mint-register=@var{N}
|
15632 |
|
|
@opindex mint-register
|
15633 |
|
|
Specify the number of registers to reserve for fast interrupt handler
|
15634 |
|
|
functions. The value @var{N} can be between 0 and 4. A value of 1
|
15635 |
|
|
means that register @code{r13} will be reserved for the exclusive use
|
15636 |
|
|
of fast interrupt handlers. A value of 2 reserves @code{r13} and
|
15637 |
|
|
@code{r12}. A value of 3 reserves @code{r13}, @code{r12} and
|
15638 |
|
|
@code{r11}, and a value of 4 reserves @code{r13} through @code{r10}.
|
15639 |
|
|
A value of 0, the default, does not reserve any registers.
|
15640 |
|
|
|
15641 |
|
|
@item -msave-acc-in-interrupts
|
15642 |
|
|
@opindex msave-acc-in-interrupts
|
15643 |
|
|
Specifies that interrupt handler functions should preserve the
|
15644 |
|
|
accumulator register. This is only necessary if normal code might use
|
15645 |
|
|
the accumulator register, for example because it performs 64-bit
|
15646 |
|
|
multiplications. The default is to ignore the accumulator as this
|
15647 |
|
|
makes the interrupt handlers faster.
|
15648 |
|
|
|
15649 |
|
|
@end table
|
15650 |
|
|
|
15651 |
|
|
@emph{Note:} The generic GCC command line @option{-ffixed-@var{reg}}
|
15652 |
|
|
has special significance to the RX port when used with the
|
15653 |
|
|
@code{interrupt} function attribute. This attribute indicates a
|
15654 |
|
|
function intended to process fast interrupts. GCC will will ensure
|
15655 |
|
|
that it only uses the registers @code{r10}, @code{r11}, @code{r12}
|
15656 |
|
|
and/or @code{r13} and only provided that the normal use of the
|
15657 |
|
|
corresponding registers have been restricted via the
|
15658 |
|
|
@option{-ffixed-@var{reg}} or @option{-mint-register} command line
|
15659 |
|
|
options.
|
15660 |
|
|
|
15661 |
|
|
@node S/390 and zSeries Options
|
15662 |
|
|
@subsection S/390 and zSeries Options
|
15663 |
|
|
@cindex S/390 and zSeries Options
|
15664 |
|
|
|
15665 |
|
|
These are the @samp{-m} options defined for the S/390 and zSeries architecture.
|
15666 |
|
|
|
15667 |
|
|
@table @gcctabopt
|
15668 |
|
|
@item -mhard-float
|
15669 |
|
|
@itemx -msoft-float
|
15670 |
|
|
@opindex mhard-float
|
15671 |
|
|
@opindex msoft-float
|
15672 |
|
|
Use (do not use) the hardware floating-point instructions and registers
|
15673 |
|
|
for floating-point operations. When @option{-msoft-float} is specified,
|
15674 |
|
|
functions in @file{libgcc.a} will be used to perform floating-point
|
15675 |
|
|
operations. When @option{-mhard-float} is specified, the compiler
|
15676 |
|
|
generates IEEE floating-point instructions. This is the default.
|
15677 |
|
|
|
15678 |
|
|
@item -mhard-dfp
|
15679 |
|
|
@itemx -mno-hard-dfp
|
15680 |
|
|
@opindex mhard-dfp
|
15681 |
|
|
@opindex mno-hard-dfp
|
15682 |
|
|
Use (do not use) the hardware decimal-floating-point instructions for
|
15683 |
|
|
decimal-floating-point operations. When @option{-mno-hard-dfp} is
|
15684 |
|
|
specified, functions in @file{libgcc.a} will be used to perform
|
15685 |
|
|
decimal-floating-point operations. When @option{-mhard-dfp} is
|
15686 |
|
|
specified, the compiler generates decimal-floating-point hardware
|
15687 |
|
|
instructions. This is the default for @option{-march=z9-ec} or higher.
|
15688 |
|
|
|
15689 |
|
|
@item -mlong-double-64
|
15690 |
|
|
@itemx -mlong-double-128
|
15691 |
|
|
@opindex mlong-double-64
|
15692 |
|
|
@opindex mlong-double-128
|
15693 |
|
|
These switches control the size of @code{long double} type. A size
|
15694 |
|
|
of 64bit makes the @code{long double} type equivalent to the @code{double}
|
15695 |
|
|
type. This is the default.
|
15696 |
|
|
|
15697 |
|
|
@item -mbackchain
|
15698 |
|
|
@itemx -mno-backchain
|
15699 |
|
|
@opindex mbackchain
|
15700 |
|
|
@opindex mno-backchain
|
15701 |
|
|
Store (do not store) the address of the caller's frame as backchain pointer
|
15702 |
|
|
into the callee's stack frame.
|
15703 |
|
|
A backchain may be needed to allow debugging using tools that do not understand
|
15704 |
|
|
DWARF-2 call frame information.
|
15705 |
|
|
When @option{-mno-packed-stack} is in effect, the backchain pointer is stored
|
15706 |
|
|
at the bottom of the stack frame; when @option{-mpacked-stack} is in effect,
|
15707 |
|
|
the backchain is placed into the topmost word of the 96/160 byte register
|
15708 |
|
|
save area.
|
15709 |
|
|
|
15710 |
|
|
In general, code compiled with @option{-mbackchain} is call-compatible with
|
15711 |
|
|
code compiled with @option{-mmo-backchain}; however, use of the backchain
|
15712 |
|
|
for debugging purposes usually requires that the whole binary is built with
|
15713 |
|
|
@option{-mbackchain}. Note that the combination of @option{-mbackchain},
|
15714 |
|
|
@option{-mpacked-stack} and @option{-mhard-float} is not supported. In order
|
15715 |
|
|
to build a linux kernel use @option{-msoft-float}.
|
15716 |
|
|
|
15717 |
|
|
The default is to not maintain the backchain.
|
15718 |
|
|
|
15719 |
|
|
@item -mpacked-stack
|
15720 |
|
|
@itemx -mno-packed-stack
|
15721 |
|
|
@opindex mpacked-stack
|
15722 |
|
|
@opindex mno-packed-stack
|
15723 |
|
|
Use (do not use) the packed stack layout. When @option{-mno-packed-stack} is
|
15724 |
|
|
specified, the compiler uses the all fields of the 96/160 byte register save
|
15725 |
|
|
area only for their default purpose; unused fields still take up stack space.
|
15726 |
|
|
When @option{-mpacked-stack} is specified, register save slots are densely
|
15727 |
|
|
packed at the top of the register save area; unused space is reused for other
|
15728 |
|
|
purposes, allowing for more efficient use of the available stack space.
|
15729 |
|
|
However, when @option{-mbackchain} is also in effect, the topmost word of
|
15730 |
|
|
the save area is always used to store the backchain, and the return address
|
15731 |
|
|
register is always saved two words below the backchain.
|
15732 |
|
|
|
15733 |
|
|
As long as the stack frame backchain is not used, code generated with
|
15734 |
|
|
@option{-mpacked-stack} is call-compatible with code generated with
|
15735 |
|
|
@option{-mno-packed-stack}. Note that some non-FSF releases of GCC 2.95 for
|
15736 |
|
|
S/390 or zSeries generated code that uses the stack frame backchain at run
|
15737 |
|
|
time, not just for debugging purposes. Such code is not call-compatible
|
15738 |
|
|
with code compiled with @option{-mpacked-stack}. Also, note that the
|
15739 |
|
|
combination of @option{-mbackchain},
|
15740 |
|
|
@option{-mpacked-stack} and @option{-mhard-float} is not supported. In order
|
15741 |
|
|
to build a linux kernel use @option{-msoft-float}.
|
15742 |
|
|
|
15743 |
|
|
The default is to not use the packed stack layout.
|
15744 |
|
|
|
15745 |
|
|
@item -msmall-exec
|
15746 |
|
|
@itemx -mno-small-exec
|
15747 |
|
|
@opindex msmall-exec
|
15748 |
|
|
@opindex mno-small-exec
|
15749 |
|
|
Generate (or do not generate) code using the @code{bras} instruction
|
15750 |
|
|
to do subroutine calls.
|
15751 |
|
|
This only works reliably if the total executable size does not
|
15752 |
|
|
exceed 64k. The default is to use the @code{basr} instruction instead,
|
15753 |
|
|
which does not have this limitation.
|
15754 |
|
|
|
15755 |
|
|
@item -m64
|
15756 |
|
|
@itemx -m31
|
15757 |
|
|
@opindex m64
|
15758 |
|
|
@opindex m31
|
15759 |
|
|
When @option{-m31} is specified, generate code compliant to the
|
15760 |
|
|
GNU/Linux for S/390 ABI@. When @option{-m64} is specified, generate
|
15761 |
|
|
code compliant to the GNU/Linux for zSeries ABI@. This allows GCC in
|
15762 |
|
|
particular to generate 64-bit instructions. For the @samp{s390}
|
15763 |
|
|
targets, the default is @option{-m31}, while the @samp{s390x}
|
15764 |
|
|
targets default to @option{-m64}.
|
15765 |
|
|
|
15766 |
|
|
@item -mzarch
|
15767 |
|
|
@itemx -mesa
|
15768 |
|
|
@opindex mzarch
|
15769 |
|
|
@opindex mesa
|
15770 |
|
|
When @option{-mzarch} is specified, generate code using the
|
15771 |
|
|
instructions available on z/Architecture.
|
15772 |
|
|
When @option{-mesa} is specified, generate code using the
|
15773 |
|
|
instructions available on ESA/390. Note that @option{-mesa} is
|
15774 |
|
|
not possible with @option{-m64}.
|
15775 |
|
|
When generating code compliant to the GNU/Linux for S/390 ABI,
|
15776 |
|
|
the default is @option{-mesa}. When generating code compliant
|
15777 |
|
|
to the GNU/Linux for zSeries ABI, the default is @option{-mzarch}.
|
15778 |
|
|
|
15779 |
|
|
@item -mmvcle
|
15780 |
|
|
@itemx -mno-mvcle
|
15781 |
|
|
@opindex mmvcle
|
15782 |
|
|
@opindex mno-mvcle
|
15783 |
|
|
Generate (or do not generate) code using the @code{mvcle} instruction
|
15784 |
|
|
to perform block moves. When @option{-mno-mvcle} is specified,
|
15785 |
|
|
use a @code{mvc} loop instead. This is the default unless optimizing for
|
15786 |
|
|
size.
|
15787 |
|
|
|
15788 |
|
|
@item -mdebug
|
15789 |
|
|
@itemx -mno-debug
|
15790 |
|
|
@opindex mdebug
|
15791 |
|
|
@opindex mno-debug
|
15792 |
|
|
Print (or do not print) additional debug information when compiling.
|
15793 |
|
|
The default is to not print debug information.
|
15794 |
|
|
|
15795 |
|
|
@item -march=@var{cpu-type}
|
15796 |
|
|
@opindex march
|
15797 |
|
|
Generate code that will run on @var{cpu-type}, which is the name of a system
|
15798 |
|
|
representing a certain processor type. Possible values for
|
15799 |
|
|
@var{cpu-type} are @samp{g5}, @samp{g6}, @samp{z900}, @samp{z990},
|
15800 |
|
|
@samp{z9-109}, @samp{z9-ec} and @samp{z10}.
|
15801 |
|
|
When generating code using the instructions available on z/Architecture,
|
15802 |
|
|
the default is @option{-march=z900}. Otherwise, the default is
|
15803 |
|
|
@option{-march=g5}.
|
15804 |
|
|
|
15805 |
|
|
@item -mtune=@var{cpu-type}
|
15806 |
|
|
@opindex mtune
|
15807 |
|
|
Tune to @var{cpu-type} everything applicable about the generated code,
|
15808 |
|
|
except for the ABI and the set of available instructions.
|
15809 |
|
|
The list of @var{cpu-type} values is the same as for @option{-march}.
|
15810 |
|
|
The default is the value used for @option{-march}.
|
15811 |
|
|
|
15812 |
|
|
@item -mtpf-trace
|
15813 |
|
|
@itemx -mno-tpf-trace
|
15814 |
|
|
@opindex mtpf-trace
|
15815 |
|
|
@opindex mno-tpf-trace
|
15816 |
|
|
Generate code that adds (does not add) in TPF OS specific branches to trace
|
15817 |
|
|
routines in the operating system. This option is off by default, even
|
15818 |
|
|
when compiling for the TPF OS@.
|
15819 |
|
|
|
15820 |
|
|
@item -mfused-madd
|
15821 |
|
|
@itemx -mno-fused-madd
|
15822 |
|
|
@opindex mfused-madd
|
15823 |
|
|
@opindex mno-fused-madd
|
15824 |
|
|
Generate code that uses (does not use) the floating point multiply and
|
15825 |
|
|
accumulate instructions. These instructions are generated by default if
|
15826 |
|
|
hardware floating point is used.
|
15827 |
|
|
|
15828 |
|
|
@item -mwarn-framesize=@var{framesize}
|
15829 |
|
|
@opindex mwarn-framesize
|
15830 |
|
|
Emit a warning if the current function exceeds the given frame size. Because
|
15831 |
|
|
this is a compile time check it doesn't need to be a real problem when the program
|
15832 |
|
|
runs. It is intended to identify functions which most probably cause
|
15833 |
|
|
a stack overflow. It is useful to be used in an environment with limited stack
|
15834 |
|
|
size e.g.@: the linux kernel.
|
15835 |
|
|
|
15836 |
|
|
@item -mwarn-dynamicstack
|
15837 |
|
|
@opindex mwarn-dynamicstack
|
15838 |
|
|
Emit a warning if the function calls alloca or uses dynamically
|
15839 |
|
|
sized arrays. This is generally a bad idea with a limited stack size.
|
15840 |
|
|
|
15841 |
|
|
@item -mstack-guard=@var{stack-guard}
|
15842 |
|
|
@itemx -mstack-size=@var{stack-size}
|
15843 |
|
|
@opindex mstack-guard
|
15844 |
|
|
@opindex mstack-size
|
15845 |
|
|
If these options are provided the s390 back end emits additional instructions in
|
15846 |
|
|
the function prologue which trigger a trap if the stack size is @var{stack-guard}
|
15847 |
|
|
bytes above the @var{stack-size} (remember that the stack on s390 grows downward).
|
15848 |
|
|
If the @var{stack-guard} option is omitted the smallest power of 2 larger than
|
15849 |
|
|
the frame size of the compiled function is chosen.
|
15850 |
|
|
These options are intended to be used to help debugging stack overflow problems.
|
15851 |
|
|
The additionally emitted code causes only little overhead and hence can also be
|
15852 |
|
|
used in production like systems without greater performance degradation. The given
|
15853 |
|
|
values have to be exact powers of 2 and @var{stack-size} has to be greater than
|
15854 |
|
|
@var{stack-guard} without exceeding 64k.
|
15855 |
|
|
In order to be efficient the extra code makes the assumption that the stack starts
|
15856 |
|
|
at an address aligned to the value given by @var{stack-size}.
|
15857 |
|
|
The @var{stack-guard} option can only be used in conjunction with @var{stack-size}.
|
15858 |
|
|
@end table
|
15859 |
|
|
|
15860 |
|
|
@node Score Options
|
15861 |
|
|
@subsection Score Options
|
15862 |
|
|
@cindex Score Options
|
15863 |
|
|
|
15864 |
|
|
These options are defined for Score implementations:
|
15865 |
|
|
|
15866 |
|
|
@table @gcctabopt
|
15867 |
|
|
@item -meb
|
15868 |
|
|
@opindex meb
|
15869 |
|
|
Compile code for big endian mode. This is the default.
|
15870 |
|
|
|
15871 |
|
|
@item -mel
|
15872 |
|
|
@opindex mel
|
15873 |
|
|
Compile code for little endian mode.
|
15874 |
|
|
|
15875 |
|
|
@item -mnhwloop
|
15876 |
|
|
@opindex mnhwloop
|
15877 |
|
|
Disable generate bcnz instruction.
|
15878 |
|
|
|
15879 |
|
|
@item -muls
|
15880 |
|
|
@opindex muls
|
15881 |
|
|
Enable generate unaligned load and store instruction.
|
15882 |
|
|
|
15883 |
|
|
@item -mmac
|
15884 |
|
|
@opindex mmac
|
15885 |
|
|
Enable the use of multiply-accumulate instructions. Disabled by default.
|
15886 |
|
|
|
15887 |
|
|
@item -mscore5
|
15888 |
|
|
@opindex mscore5
|
15889 |
|
|
Specify the SCORE5 as the target architecture.
|
15890 |
|
|
|
15891 |
|
|
@item -mscore5u
|
15892 |
|
|
@opindex mscore5u
|
15893 |
|
|
Specify the SCORE5U of the target architecture.
|
15894 |
|
|
|
15895 |
|
|
@item -mscore7
|
15896 |
|
|
@opindex mscore7
|
15897 |
|
|
Specify the SCORE7 as the target architecture. This is the default.
|
15898 |
|
|
|
15899 |
|
|
@item -mscore7d
|
15900 |
|
|
@opindex mscore7d
|
15901 |
|
|
Specify the SCORE7D as the target architecture.
|
15902 |
|
|
@end table
|
15903 |
|
|
|
15904 |
|
|
@node SH Options
|
15905 |
|
|
@subsection SH Options
|
15906 |
|
|
|
15907 |
|
|
These @samp{-m} options are defined for the SH implementations:
|
15908 |
|
|
|
15909 |
|
|
@table @gcctabopt
|
15910 |
|
|
@item -m1
|
15911 |
|
|
@opindex m1
|
15912 |
|
|
Generate code for the SH1.
|
15913 |
|
|
|
15914 |
|
|
@item -m2
|
15915 |
|
|
@opindex m2
|
15916 |
|
|
Generate code for the SH2.
|
15917 |
|
|
|
15918 |
|
|
@item -m2e
|
15919 |
|
|
Generate code for the SH2e.
|
15920 |
|
|
|
15921 |
|
|
@item -m2a-nofpu
|
15922 |
|
|
@opindex m2a-nofpu
|
15923 |
|
|
Generate code for the SH2a without FPU, or for a SH2a-FPU in such a way
|
15924 |
|
|
that the floating-point unit is not used.
|
15925 |
|
|
|
15926 |
|
|
@item -m2a-single-only
|
15927 |
|
|
@opindex m2a-single-only
|
15928 |
|
|
Generate code for the SH2a-FPU, in such a way that no double-precision
|
15929 |
|
|
floating point operations are used.
|
15930 |
|
|
|
15931 |
|
|
@item -m2a-single
|
15932 |
|
|
@opindex m2a-single
|
15933 |
|
|
Generate code for the SH2a-FPU assuming the floating-point unit is in
|
15934 |
|
|
single-precision mode by default.
|
15935 |
|
|
|
15936 |
|
|
@item -m2a
|
15937 |
|
|
@opindex m2a
|
15938 |
|
|
Generate code for the SH2a-FPU assuming the floating-point unit is in
|
15939 |
|
|
double-precision mode by default.
|
15940 |
|
|
|
15941 |
|
|
@item -m3
|
15942 |
|
|
@opindex m3
|
15943 |
|
|
Generate code for the SH3.
|
15944 |
|
|
|
15945 |
|
|
@item -m3e
|
15946 |
|
|
@opindex m3e
|
15947 |
|
|
Generate code for the SH3e.
|
15948 |
|
|
|
15949 |
|
|
@item -m4-nofpu
|
15950 |
|
|
@opindex m4-nofpu
|
15951 |
|
|
Generate code for the SH4 without a floating-point unit.
|
15952 |
|
|
|
15953 |
|
|
@item -m4-single-only
|
15954 |
|
|
@opindex m4-single-only
|
15955 |
|
|
Generate code for the SH4 with a floating-point unit that only
|
15956 |
|
|
supports single-precision arithmetic.
|
15957 |
|
|
|
15958 |
|
|
@item -m4-single
|
15959 |
|
|
@opindex m4-single
|
15960 |
|
|
Generate code for the SH4 assuming the floating-point unit is in
|
15961 |
|
|
single-precision mode by default.
|
15962 |
|
|
|
15963 |
|
|
@item -m4
|
15964 |
|
|
@opindex m4
|
15965 |
|
|
Generate code for the SH4.
|
15966 |
|
|
|
15967 |
|
|
@item -m4a-nofpu
|
15968 |
|
|
@opindex m4a-nofpu
|
15969 |
|
|
Generate code for the SH4al-dsp, or for a SH4a in such a way that the
|
15970 |
|
|
floating-point unit is not used.
|
15971 |
|
|
|
15972 |
|
|
@item -m4a-single-only
|
15973 |
|
|
@opindex m4a-single-only
|
15974 |
|
|
Generate code for the SH4a, in such a way that no double-precision
|
15975 |
|
|
floating point operations are used.
|
15976 |
|
|
|
15977 |
|
|
@item -m4a-single
|
15978 |
|
|
@opindex m4a-single
|
15979 |
|
|
Generate code for the SH4a assuming the floating-point unit is in
|
15980 |
|
|
single-precision mode by default.
|
15981 |
|
|
|
15982 |
|
|
@item -m4a
|
15983 |
|
|
@opindex m4a
|
15984 |
|
|
Generate code for the SH4a.
|
15985 |
|
|
|
15986 |
|
|
@item -m4al
|
15987 |
|
|
@opindex m4al
|
15988 |
|
|
Same as @option{-m4a-nofpu}, except that it implicitly passes
|
15989 |
|
|
@option{-dsp} to the assembler. GCC doesn't generate any DSP
|
15990 |
|
|
instructions at the moment.
|
15991 |
|
|
|
15992 |
|
|
@item -mb
|
15993 |
|
|
@opindex mb
|
15994 |
|
|
Compile code for the processor in big endian mode.
|
15995 |
|
|
|
15996 |
|
|
@item -ml
|
15997 |
|
|
@opindex ml
|
15998 |
|
|
Compile code for the processor in little endian mode.
|
15999 |
|
|
|
16000 |
|
|
@item -mdalign
|
16001 |
|
|
@opindex mdalign
|
16002 |
|
|
Align doubles at 64-bit boundaries. Note that this changes the calling
|
16003 |
|
|
conventions, and thus some functions from the standard C library will
|
16004 |
|
|
not work unless you recompile it first with @option{-mdalign}.
|
16005 |
|
|
|
16006 |
|
|
@item -mrelax
|
16007 |
|
|
@opindex mrelax
|
16008 |
|
|
Shorten some address references at link time, when possible; uses the
|
16009 |
|
|
linker option @option{-relax}.
|
16010 |
|
|
|
16011 |
|
|
@item -mbigtable
|
16012 |
|
|
@opindex mbigtable
|
16013 |
|
|
Use 32-bit offsets in @code{switch} tables. The default is to use
|
16014 |
|
|
16-bit offsets.
|
16015 |
|
|
|
16016 |
|
|
@item -mbitops
|
16017 |
|
|
@opindex mbitops
|
16018 |
|
|
Enable the use of bit manipulation instructions on SH2A.
|
16019 |
|
|
|
16020 |
|
|
@item -mfmovd
|
16021 |
|
|
@opindex mfmovd
|
16022 |
|
|
Enable the use of the instruction @code{fmovd}. Check @option{-mdalign} for
|
16023 |
|
|
alignment constraints.
|
16024 |
|
|
|
16025 |
|
|
@item -mhitachi
|
16026 |
|
|
@opindex mhitachi
|
16027 |
|
|
Comply with the calling conventions defined by Renesas.
|
16028 |
|
|
|
16029 |
|
|
@item -mrenesas
|
16030 |
|
|
@opindex mhitachi
|
16031 |
|
|
Comply with the calling conventions defined by Renesas.
|
16032 |
|
|
|
16033 |
|
|
@item -mno-renesas
|
16034 |
|
|
@opindex mhitachi
|
16035 |
|
|
Comply with the calling conventions defined for GCC before the Renesas
|
16036 |
|
|
conventions were available. This option is the default for all
|
16037 |
|
|
targets of the SH toolchain except for @samp{sh-symbianelf}.
|
16038 |
|
|
|
16039 |
|
|
@item -mnomacsave
|
16040 |
|
|
@opindex mnomacsave
|
16041 |
|
|
Mark the @code{MAC} register as call-clobbered, even if
|
16042 |
|
|
@option{-mhitachi} is given.
|
16043 |
|
|
|
16044 |
|
|
@item -mieee
|
16045 |
|
|
@opindex mieee
|
16046 |
|
|
Increase IEEE-compliance of floating-point code.
|
16047 |
|
|
At the moment, this is equivalent to @option{-fno-finite-math-only}.
|
16048 |
|
|
When generating 16 bit SH opcodes, getting IEEE-conforming results for
|
16049 |
|
|
comparisons of NANs / infinities incurs extra overhead in every
|
16050 |
|
|
floating point comparison, therefore the default is set to
|
16051 |
|
|
@option{-ffinite-math-only}.
|
16052 |
|
|
|
16053 |
|
|
@item -minline-ic_invalidate
|
16054 |
|
|
@opindex minline-ic_invalidate
|
16055 |
|
|
Inline code to invalidate instruction cache entries after setting up
|
16056 |
|
|
nested function trampolines.
|
16057 |
|
|
This option has no effect if -musermode is in effect and the selected
|
16058 |
|
|
code generation option (e.g. -m4) does not allow the use of the icbi
|
16059 |
|
|
instruction.
|
16060 |
|
|
If the selected code generation option does not allow the use of the icbi
|
16061 |
|
|
instruction, and -musermode is not in effect, the inlined code will
|
16062 |
|
|
manipulate the instruction cache address array directly with an associative
|
16063 |
|
|
write. This not only requires privileged mode, but it will also
|
16064 |
|
|
fail if the cache line had been mapped via the TLB and has become unmapped.
|
16065 |
|
|
|
16066 |
|
|
@item -misize
|
16067 |
|
|
@opindex misize
|
16068 |
|
|
Dump instruction size and location in the assembly code.
|
16069 |
|
|
|
16070 |
|
|
@item -mpadstruct
|
16071 |
|
|
@opindex mpadstruct
|
16072 |
|
|
This option is deprecated. It pads structures to multiple of 4 bytes,
|
16073 |
|
|
which is incompatible with the SH ABI@.
|
16074 |
|
|
|
16075 |
|
|
@item -mspace
|
16076 |
|
|
@opindex mspace
|
16077 |
|
|
Optimize for space instead of speed. Implied by @option{-Os}.
|
16078 |
|
|
|
16079 |
|
|
@item -mprefergot
|
16080 |
|
|
@opindex mprefergot
|
16081 |
|
|
When generating position-independent code, emit function calls using
|
16082 |
|
|
the Global Offset Table instead of the Procedure Linkage Table.
|
16083 |
|
|
|
16084 |
|
|
@item -musermode
|
16085 |
|
|
@opindex musermode
|
16086 |
|
|
Don't generate privileged mode only code; implies -mno-inline-ic_invalidate
|
16087 |
|
|
if the inlined code would not work in user mode.
|
16088 |
|
|
This is the default when the target is @code{sh-*-linux*}.
|
16089 |
|
|
|
16090 |
|
|
@item -multcost=@var{number}
|
16091 |
|
|
@opindex multcost=@var{number}
|
16092 |
|
|
Set the cost to assume for a multiply insn.
|
16093 |
|
|
|
16094 |
|
|
@item -mdiv=@var{strategy}
|
16095 |
|
|
@opindex mdiv=@var{strategy}
|
16096 |
|
|
Set the division strategy to use for SHmedia code. @var{strategy} must be
|
16097 |
|
|
one of: call, call2, fp, inv, inv:minlat, inv20u, inv20l, inv:call,
|
16098 |
|
|
inv:call2, inv:fp .
|
16099 |
|
|
"fp" performs the operation in floating point. This has a very high latency,
|
16100 |
|
|
but needs only a few instructions, so it might be a good choice if
|
16101 |
|
|
your code has enough easily exploitable ILP to allow the compiler to
|
16102 |
|
|
schedule the floating point instructions together with other instructions.
|
16103 |
|
|
Division by zero causes a floating point exception.
|
16104 |
|
|
"inv" uses integer operations to calculate the inverse of the divisor,
|
16105 |
|
|
and then multiplies the dividend with the inverse. This strategy allows
|
16106 |
|
|
cse and hoisting of the inverse calculation. Division by zero calculates
|
16107 |
|
|
an unspecified result, but does not trap.
|
16108 |
|
|
"inv:minlat" is a variant of "inv" where if no cse / hoisting opportunities
|
16109 |
|
|
have been found, or if the entire operation has been hoisted to the same
|
16110 |
|
|
place, the last stages of the inverse calculation are intertwined with the
|
16111 |
|
|
final multiply to reduce the overall latency, at the expense of using a few
|
16112 |
|
|
more instructions, and thus offering fewer scheduling opportunities with
|
16113 |
|
|
other code.
|
16114 |
|
|
"call" calls a library function that usually implements the inv:minlat
|
16115 |
|
|
strategy.
|
16116 |
|
|
This gives high code density for m5-*media-nofpu compilations.
|
16117 |
|
|
"call2" uses a different entry point of the same library function, where it
|
16118 |
|
|
assumes that a pointer to a lookup table has already been set up, which
|
16119 |
|
|
exposes the pointer load to cse / code hoisting optimizations.
|
16120 |
|
|
"inv:call", "inv:call2" and "inv:fp" all use the "inv" algorithm for initial
|
16121 |
|
|
code generation, but if the code stays unoptimized, revert to the "call",
|
16122 |
|
|
"call2", or "fp" strategies, respectively. Note that the
|
16123 |
|
|
potentially-trapping side effect of division by zero is carried by a
|
16124 |
|
|
separate instruction, so it is possible that all the integer instructions
|
16125 |
|
|
are hoisted out, but the marker for the side effect stays where it is.
|
16126 |
|
|
A recombination to fp operations or a call is not possible in that case.
|
16127 |
|
|
"inv20u" and "inv20l" are variants of the "inv:minlat" strategy. In the case
|
16128 |
|
|
that the inverse calculation was nor separated from the multiply, they speed
|
16129 |
|
|
up division where the dividend fits into 20 bits (plus sign where applicable),
|
16130 |
|
|
by inserting a test to skip a number of operations in this case; this test
|
16131 |
|
|
slows down the case of larger dividends. inv20u assumes the case of a such
|
16132 |
|
|
a small dividend to be unlikely, and inv20l assumes it to be likely.
|
16133 |
|
|
|
16134 |
|
|
@item -mdivsi3_libfunc=@var{name}
|
16135 |
|
|
@opindex mdivsi3_libfunc=@var{name}
|
16136 |
|
|
Set the name of the library function used for 32 bit signed division to
|
16137 |
|
|
@var{name}. This only affect the name used in the call and inv:call
|
16138 |
|
|
division strategies, and the compiler will still expect the same
|
16139 |
|
|
sets of input/output/clobbered registers as if this option was not present.
|
16140 |
|
|
|
16141 |
|
|
@item -mfixed-range=@var{register-range}
|
16142 |
|
|
@opindex mfixed-range
|
16143 |
|
|
Generate code treating the given register range as fixed registers.
|
16144 |
|
|
A fixed register is one that the register allocator can not use. This is
|
16145 |
|
|
useful when compiling kernel code. A register range is specified as
|
16146 |
|
|
two registers separated by a dash. Multiple register ranges can be
|
16147 |
|
|
specified separated by a comma.
|
16148 |
|
|
|
16149 |
|
|
@item -madjust-unroll
|
16150 |
|
|
@opindex madjust-unroll
|
16151 |
|
|
Throttle unrolling to avoid thrashing target registers.
|
16152 |
|
|
This option only has an effect if the gcc code base supports the
|
16153 |
|
|
TARGET_ADJUST_UNROLL_MAX target hook.
|
16154 |
|
|
|
16155 |
|
|
@item -mindexed-addressing
|
16156 |
|
|
@opindex mindexed-addressing
|
16157 |
|
|
Enable the use of the indexed addressing mode for SHmedia32/SHcompact.
|
16158 |
|
|
This is only safe if the hardware and/or OS implement 32 bit wrap-around
|
16159 |
|
|
semantics for the indexed addressing mode. The architecture allows the
|
16160 |
|
|
implementation of processors with 64 bit MMU, which the OS could use to
|
16161 |
|
|
get 32 bit addressing, but since no current hardware implementation supports
|
16162 |
|
|
this or any other way to make the indexed addressing mode safe to use in
|
16163 |
|
|
the 32 bit ABI, the default is -mno-indexed-addressing.
|
16164 |
|
|
|
16165 |
|
|
@item -mgettrcost=@var{number}
|
16166 |
|
|
@opindex mgettrcost=@var{number}
|
16167 |
|
|
Set the cost assumed for the gettr instruction to @var{number}.
|
16168 |
|
|
The default is 2 if @option{-mpt-fixed} is in effect, 100 otherwise.
|
16169 |
|
|
|
16170 |
|
|
@item -mpt-fixed
|
16171 |
|
|
@opindex mpt-fixed
|
16172 |
|
|
Assume pt* instructions won't trap. This will generally generate better
|
16173 |
|
|
scheduled code, but is unsafe on current hardware. The current architecture
|
16174 |
|
|
definition says that ptabs and ptrel trap when the target anded with 3 is 3.
|
16175 |
|
|
This has the unintentional effect of making it unsafe to schedule ptabs /
|
16176 |
|
|
ptrel before a branch, or hoist it out of a loop. For example,
|
16177 |
|
|
__do_global_ctors, a part of libgcc that runs constructors at program
|
16178 |
|
|
startup, calls functions in a list which is delimited by @minus{}1. With the
|
16179 |
|
|
-mpt-fixed option, the ptabs will be done before testing against @minus{}1.
|
16180 |
|
|
That means that all the constructors will be run a bit quicker, but when
|
16181 |
|
|
the loop comes to the end of the list, the program crashes because ptabs
|
16182 |
|
|
loads @minus{}1 into a target register. Since this option is unsafe for any
|
16183 |
|
|
hardware implementing the current architecture specification, the default
|
16184 |
|
|
is -mno-pt-fixed. Unless the user specifies a specific cost with
|
16185 |
|
|
@option{-mgettrcost}, -mno-pt-fixed also implies @option{-mgettrcost=100};
|
16186 |
|
|
this deters register allocation using target registers for storing
|
16187 |
|
|
ordinary integers.
|
16188 |
|
|
|
16189 |
|
|
@item -minvalid-symbols
|
16190 |
|
|
@opindex minvalid-symbols
|
16191 |
|
|
Assume symbols might be invalid. Ordinary function symbols generated by
|
16192 |
|
|
the compiler will always be valid to load with movi/shori/ptabs or
|
16193 |
|
|
movi/shori/ptrel, but with assembler and/or linker tricks it is possible
|
16194 |
|
|
to generate symbols that will cause ptabs / ptrel to trap.
|
16195 |
|
|
This option is only meaningful when @option{-mno-pt-fixed} is in effect.
|
16196 |
|
|
It will then prevent cross-basic-block cse, hoisting and most scheduling
|
16197 |
|
|
of symbol loads. The default is @option{-mno-invalid-symbols}.
|
16198 |
|
|
@end table
|
16199 |
|
|
|
16200 |
|
|
@node SPARC Options
|
16201 |
|
|
@subsection SPARC Options
|
16202 |
|
|
@cindex SPARC options
|
16203 |
|
|
|
16204 |
|
|
These @samp{-m} options are supported on the SPARC:
|
16205 |
|
|
|
16206 |
|
|
@table @gcctabopt
|
16207 |
|
|
@item -mno-app-regs
|
16208 |
|
|
@itemx -mapp-regs
|
16209 |
|
|
@opindex mno-app-regs
|
16210 |
|
|
@opindex mapp-regs
|
16211 |
|
|
Specify @option{-mapp-regs} to generate output using the global registers
|
16212 |
|
|
2 through 4, which the SPARC SVR4 ABI reserves for applications. This
|
16213 |
|
|
is the default.
|
16214 |
|
|
|
16215 |
|
|
To be fully SVR4 ABI compliant at the cost of some performance loss,
|
16216 |
|
|
specify @option{-mno-app-regs}. You should compile libraries and system
|
16217 |
|
|
software with this option.
|
16218 |
|
|
|
16219 |
|
|
@item -mfpu
|
16220 |
|
|
@itemx -mhard-float
|
16221 |
|
|
@opindex mfpu
|
16222 |
|
|
@opindex mhard-float
|
16223 |
|
|
Generate output containing floating point instructions. This is the
|
16224 |
|
|
default.
|
16225 |
|
|
|
16226 |
|
|
@item -mno-fpu
|
16227 |
|
|
@itemx -msoft-float
|
16228 |
|
|
@opindex mno-fpu
|
16229 |
|
|
@opindex msoft-float
|
16230 |
|
|
Generate output containing library calls for floating point.
|
16231 |
|
|
@strong{Warning:} the requisite libraries are not available for all SPARC
|
16232 |
|
|
targets. Normally the facilities of the machine's usual C compiler are
|
16233 |
|
|
used, but this cannot be done directly in cross-compilation. You must make
|
16234 |
|
|
your own arrangements to provide suitable library functions for
|
16235 |
|
|
cross-compilation. The embedded targets @samp{sparc-*-aout} and
|
16236 |
|
|
@samp{sparclite-*-*} do provide software floating point support.
|
16237 |
|
|
|
16238 |
|
|
@option{-msoft-float} changes the calling convention in the output file;
|
16239 |
|
|
therefore, it is only useful if you compile @emph{all} of a program with
|
16240 |
|
|
this option. In particular, you need to compile @file{libgcc.a}, the
|
16241 |
|
|
library that comes with GCC, with @option{-msoft-float} in order for
|
16242 |
|
|
this to work.
|
16243 |
|
|
|
16244 |
|
|
@item -mhard-quad-float
|
16245 |
|
|
@opindex mhard-quad-float
|
16246 |
|
|
Generate output containing quad-word (long double) floating point
|
16247 |
|
|
instructions.
|
16248 |
|
|
|
16249 |
|
|
@item -msoft-quad-float
|
16250 |
|
|
@opindex msoft-quad-float
|
16251 |
|
|
Generate output containing library calls for quad-word (long double)
|
16252 |
|
|
floating point instructions. The functions called are those specified
|
16253 |
|
|
in the SPARC ABI@. This is the default.
|
16254 |
|
|
|
16255 |
|
|
As of this writing, there are no SPARC implementations that have hardware
|
16256 |
|
|
support for the quad-word floating point instructions. They all invoke
|
16257 |
|
|
a trap handler for one of these instructions, and then the trap handler
|
16258 |
|
|
emulates the effect of the instruction. Because of the trap handler overhead,
|
16259 |
|
|
this is much slower than calling the ABI library routines. Thus the
|
16260 |
|
|
@option{-msoft-quad-float} option is the default.
|
16261 |
|
|
|
16262 |
|
|
@item -mno-unaligned-doubles
|
16263 |
|
|
@itemx -munaligned-doubles
|
16264 |
|
|
@opindex mno-unaligned-doubles
|
16265 |
|
|
@opindex munaligned-doubles
|
16266 |
|
|
Assume that doubles have 8 byte alignment. This is the default.
|
16267 |
|
|
|
16268 |
|
|
With @option{-munaligned-doubles}, GCC assumes that doubles have 8 byte
|
16269 |
|
|
alignment only if they are contained in another type, or if they have an
|
16270 |
|
|
absolute address. Otherwise, it assumes they have 4 byte alignment.
|
16271 |
|
|
Specifying this option avoids some rare compatibility problems with code
|
16272 |
|
|
generated by other compilers. It is not the default because it results
|
16273 |
|
|
in a performance loss, especially for floating point code.
|
16274 |
|
|
|
16275 |
|
|
@item -mno-faster-structs
|
16276 |
|
|
@itemx -mfaster-structs
|
16277 |
|
|
@opindex mno-faster-structs
|
16278 |
|
|
@opindex mfaster-structs
|
16279 |
|
|
With @option{-mfaster-structs}, the compiler assumes that structures
|
16280 |
|
|
should have 8 byte alignment. This enables the use of pairs of
|
16281 |
|
|
@code{ldd} and @code{std} instructions for copies in structure
|
16282 |
|
|
assignment, in place of twice as many @code{ld} and @code{st} pairs.
|
16283 |
|
|
However, the use of this changed alignment directly violates the SPARC
|
16284 |
|
|
ABI@. Thus, it's intended only for use on targets where the developer
|
16285 |
|
|
acknowledges that their resulting code will not be directly in line with
|
16286 |
|
|
the rules of the ABI@.
|
16287 |
|
|
|
16288 |
|
|
@item -mimpure-text
|
16289 |
|
|
@opindex mimpure-text
|
16290 |
|
|
@option{-mimpure-text}, used in addition to @option{-shared}, tells
|
16291 |
|
|
the compiler to not pass @option{-z text} to the linker when linking a
|
16292 |
|
|
shared object. Using this option, you can link position-dependent
|
16293 |
|
|
code into a shared object.
|
16294 |
|
|
|
16295 |
|
|
@option{-mimpure-text} suppresses the ``relocations remain against
|
16296 |
|
|
allocatable but non-writable sections'' linker error message.
|
16297 |
|
|
However, the necessary relocations will trigger copy-on-write, and the
|
16298 |
|
|
shared object is not actually shared across processes. Instead of
|
16299 |
|
|
using @option{-mimpure-text}, you should compile all source code with
|
16300 |
|
|
@option{-fpic} or @option{-fPIC}.
|
16301 |
|
|
|
16302 |
|
|
This option is only available on SunOS and Solaris.
|
16303 |
|
|
|
16304 |
|
|
@item -mcpu=@var{cpu_type}
|
16305 |
|
|
@opindex mcpu
|
16306 |
|
|
Set the instruction set, register set, and instruction scheduling parameters
|
16307 |
|
|
for machine type @var{cpu_type}. Supported values for @var{cpu_type} are
|
16308 |
|
|
@samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite},
|
16309 |
|
|
@samp{f930}, @samp{f934}, @samp{hypersparc}, @samp{sparclite86x},
|
16310 |
|
|
@samp{sparclet}, @samp{tsc701}, @samp{v9}, @samp{ultrasparc},
|
16311 |
|
|
@samp{ultrasparc3}, @samp{niagara} and @samp{niagara2}.
|
16312 |
|
|
|
16313 |
|
|
Default instruction scheduling parameters are used for values that select
|
16314 |
|
|
an architecture and not an implementation. These are @samp{v7}, @samp{v8},
|
16315 |
|
|
@samp{sparclite}, @samp{sparclet}, @samp{v9}.
|
16316 |
|
|
|
16317 |
|
|
Here is a list of each supported architecture and their supported
|
16318 |
|
|
implementations.
|
16319 |
|
|
|
16320 |
|
|
@smallexample
|
16321 |
|
|
v7: cypress
|
16322 |
|
|
v8: supersparc, hypersparc
|
16323 |
|
|
sparclite: f930, f934, sparclite86x
|
16324 |
|
|
sparclet: tsc701
|
16325 |
|
|
v9: ultrasparc, ultrasparc3, niagara, niagara2
|
16326 |
|
|
@end smallexample
|
16327 |
|
|
|
16328 |
|
|
By default (unless configured otherwise), GCC generates code for the V7
|
16329 |
|
|
variant of the SPARC architecture. With @option{-mcpu=cypress}, the compiler
|
16330 |
|
|
additionally optimizes it for the Cypress CY7C602 chip, as used in the
|
16331 |
|
|
SPARCStation/SPARCServer 3xx series. This is also appropriate for the older
|
16332 |
|
|
SPARCStation 1, 2, IPX etc.
|
16333 |
|
|
|
16334 |
|
|
With @option{-mcpu=v8}, GCC generates code for the V8 variant of the SPARC
|
16335 |
|
|
architecture. The only difference from V7 code is that the compiler emits
|
16336 |
|
|
the integer multiply and integer divide instructions which exist in SPARC-V8
|
16337 |
|
|
but not in SPARC-V7. With @option{-mcpu=supersparc}, the compiler additionally
|
16338 |
|
|
optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and
|
16339 |
|
|
2000 series.
|
16340 |
|
|
|
16341 |
|
|
With @option{-mcpu=sparclite}, GCC generates code for the SPARClite variant of
|
16342 |
|
|
the SPARC architecture. This adds the integer multiply, integer divide step
|
16343 |
|
|
and scan (@code{ffs}) instructions which exist in SPARClite but not in SPARC-V7.
|
16344 |
|
|
With @option{-mcpu=f930}, the compiler additionally optimizes it for the
|
16345 |
|
|
Fujitsu MB86930 chip, which is the original SPARClite, with no FPU@. With
|
16346 |
|
|
@option{-mcpu=f934}, the compiler additionally optimizes it for the Fujitsu
|
16347 |
|
|
MB86934 chip, which is the more recent SPARClite with FPU@.
|
16348 |
|
|
|
16349 |
|
|
With @option{-mcpu=sparclet}, GCC generates code for the SPARClet variant of
|
16350 |
|
|
the SPARC architecture. This adds the integer multiply, multiply/accumulate,
|
16351 |
|
|
integer divide step and scan (@code{ffs}) instructions which exist in SPARClet
|
16352 |
|
|
but not in SPARC-V7. With @option{-mcpu=tsc701}, the compiler additionally
|
16353 |
|
|
optimizes it for the TEMIC SPARClet chip.
|
16354 |
|
|
|
16355 |
|
|
With @option{-mcpu=v9}, GCC generates code for the V9 variant of the SPARC
|
16356 |
|
|
architecture. This adds 64-bit integer and floating-point move instructions,
|
16357 |
|
|
3 additional floating-point condition code registers and conditional move
|
16358 |
|
|
instructions. With @option{-mcpu=ultrasparc}, the compiler additionally
|
16359 |
|
|
optimizes it for the Sun UltraSPARC I/II/IIi chips. With
|
16360 |
|
|
@option{-mcpu=ultrasparc3}, the compiler additionally optimizes it for the
|
16361 |
|
|
Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips. With
|
16362 |
|
|
@option{-mcpu=niagara}, the compiler additionally optimizes it for
|
16363 |
|
|
Sun UltraSPARC T1 chips. With @option{-mcpu=niagara2}, the compiler
|
16364 |
|
|
additionally optimizes it for Sun UltraSPARC T2 chips.
|
16365 |
|
|
|
16366 |
|
|
@item -mtune=@var{cpu_type}
|
16367 |
|
|
@opindex mtune
|
16368 |
|
|
Set the instruction scheduling parameters for machine type
|
16369 |
|
|
@var{cpu_type}, but do not set the instruction set or register set that the
|
16370 |
|
|
option @option{-mcpu=@var{cpu_type}} would.
|
16371 |
|
|
|
16372 |
|
|
The same values for @option{-mcpu=@var{cpu_type}} can be used for
|
16373 |
|
|
@option{-mtune=@var{cpu_type}}, but the only useful values are those
|
16374 |
|
|
that select a particular cpu implementation. Those are @samp{cypress},
|
16375 |
|
|
@samp{supersparc}, @samp{hypersparc}, @samp{f930}, @samp{f934},
|
16376 |
|
|
@samp{sparclite86x}, @samp{tsc701}, @samp{ultrasparc},
|
16377 |
|
|
@samp{ultrasparc3}, @samp{niagara}, and @samp{niagara2}.
|
16378 |
|
|
|
16379 |
|
|
@item -mv8plus
|
16380 |
|
|
@itemx -mno-v8plus
|
16381 |
|
|
@opindex mv8plus
|
16382 |
|
|
@opindex mno-v8plus
|
16383 |
|
|
With @option{-mv8plus}, GCC generates code for the SPARC-V8+ ABI@. The
|
16384 |
|
|
difference from the V8 ABI is that the global and out registers are
|
16385 |
|
|
considered 64-bit wide. This is enabled by default on Solaris in 32-bit
|
16386 |
|
|
mode for all SPARC-V9 processors.
|
16387 |
|
|
|
16388 |
|
|
@item -mvis
|
16389 |
|
|
@itemx -mno-vis
|
16390 |
|
|
@opindex mvis
|
16391 |
|
|
@opindex mno-vis
|
16392 |
|
|
With @option{-mvis}, GCC generates code that takes advantage of the UltraSPARC
|
16393 |
|
|
Visual Instruction Set extensions. The default is @option{-mno-vis}.
|
16394 |
|
|
@end table
|
16395 |
|
|
|
16396 |
|
|
These @samp{-m} options are supported in addition to the above
|
16397 |
|
|
on SPARC-V9 processors in 64-bit environments:
|
16398 |
|
|
|
16399 |
|
|
@table @gcctabopt
|
16400 |
|
|
@item -mlittle-endian
|
16401 |
|
|
@opindex mlittle-endian
|
16402 |
|
|
Generate code for a processor running in little-endian mode. It is only
|
16403 |
|
|
available for a few configurations and most notably not on Solaris and Linux.
|
16404 |
|
|
|
16405 |
|
|
@item -m32
|
16406 |
|
|
@itemx -m64
|
16407 |
|
|
@opindex m32
|
16408 |
|
|
@opindex m64
|
16409 |
|
|
Generate code for a 32-bit or 64-bit environment.
|
16410 |
|
|
The 32-bit environment sets int, long and pointer to 32 bits.
|
16411 |
|
|
The 64-bit environment sets int to 32 bits and long and pointer
|
16412 |
|
|
to 64 bits.
|
16413 |
|
|
|
16414 |
|
|
@item -mcmodel=medlow
|
16415 |
|
|
@opindex mcmodel=medlow
|
16416 |
|
|
Generate code for the Medium/Low code model: 64-bit addresses, programs
|
16417 |
|
|
must be linked in the low 32 bits of memory. Programs can be statically
|
16418 |
|
|
or dynamically linked.
|
16419 |
|
|
|
16420 |
|
|
@item -mcmodel=medmid
|
16421 |
|
|
@opindex mcmodel=medmid
|
16422 |
|
|
Generate code for the Medium/Middle code model: 64-bit addresses, programs
|
16423 |
|
|
must be linked in the low 44 bits of memory, the text and data segments must
|
16424 |
|
|
be less than 2GB in size and the data segment must be located within 2GB of
|
16425 |
|
|
the text segment.
|
16426 |
|
|
|
16427 |
|
|
@item -mcmodel=medany
|
16428 |
|
|
@opindex mcmodel=medany
|
16429 |
|
|
Generate code for the Medium/Anywhere code model: 64-bit addresses, programs
|
16430 |
|
|
may be linked anywhere in memory, the text and data segments must be less
|
16431 |
|
|
than 2GB in size and the data segment must be located within 2GB of the
|
16432 |
|
|
text segment.
|
16433 |
|
|
|
16434 |
|
|
@item -mcmodel=embmedany
|
16435 |
|
|
@opindex mcmodel=embmedany
|
16436 |
|
|
Generate code for the Medium/Anywhere code model for embedded systems:
|
16437 |
|
|
64-bit addresses, the text and data segments must be less than 2GB in
|
16438 |
|
|
size, both starting anywhere in memory (determined at link time). The
|
16439 |
|
|
global register %g4 points to the base of the data segment. Programs
|
16440 |
|
|
are statically linked and PIC is not supported.
|
16441 |
|
|
|
16442 |
|
|
@item -mstack-bias
|
16443 |
|
|
@itemx -mno-stack-bias
|
16444 |
|
|
@opindex mstack-bias
|
16445 |
|
|
@opindex mno-stack-bias
|
16446 |
|
|
With @option{-mstack-bias}, GCC assumes that the stack pointer, and
|
16447 |
|
|
frame pointer if present, are offset by @minus{}2047 which must be added back
|
16448 |
|
|
when making stack frame references. This is the default in 64-bit mode.
|
16449 |
|
|
Otherwise, assume no such offset is present.
|
16450 |
|
|
@end table
|
16451 |
|
|
|
16452 |
|
|
These switches are supported in addition to the above on Solaris:
|
16453 |
|
|
|
16454 |
|
|
@table @gcctabopt
|
16455 |
|
|
@item -threads
|
16456 |
|
|
@opindex threads
|
16457 |
|
|
Add support for multithreading using the Solaris threads library. This
|
16458 |
|
|
option sets flags for both the preprocessor and linker. This option does
|
16459 |
|
|
not affect the thread safety of object code produced by the compiler or
|
16460 |
|
|
that of libraries supplied with it.
|
16461 |
|
|
|
16462 |
|
|
@item -pthreads
|
16463 |
|
|
@opindex pthreads
|
16464 |
|
|
Add support for multithreading using the POSIX threads library. This
|
16465 |
|
|
option sets flags for both the preprocessor and linker. This option does
|
16466 |
|
|
not affect the thread safety of object code produced by the compiler or
|
16467 |
|
|
that of libraries supplied with it.
|
16468 |
|
|
|
16469 |
|
|
@item -pthread
|
16470 |
|
|
@opindex pthread
|
16471 |
|
|
This is a synonym for @option{-pthreads}.
|
16472 |
|
|
@end table
|
16473 |
|
|
|
16474 |
|
|
@node SPU Options
|
16475 |
|
|
@subsection SPU Options
|
16476 |
|
|
@cindex SPU options
|
16477 |
|
|
|
16478 |
|
|
These @samp{-m} options are supported on the SPU:
|
16479 |
|
|
|
16480 |
|
|
@table @gcctabopt
|
16481 |
|
|
@item -mwarn-reloc
|
16482 |
|
|
@itemx -merror-reloc
|
16483 |
|
|
@opindex mwarn-reloc
|
16484 |
|
|
@opindex merror-reloc
|
16485 |
|
|
|
16486 |
|
|
The loader for SPU does not handle dynamic relocations. By default, GCC
|
16487 |
|
|
will give an error when it generates code that requires a dynamic
|
16488 |
|
|
relocation. @option{-mno-error-reloc} disables the error,
|
16489 |
|
|
@option{-mwarn-reloc} will generate a warning instead.
|
16490 |
|
|
|
16491 |
|
|
@item -msafe-dma
|
16492 |
|
|
@itemx -munsafe-dma
|
16493 |
|
|
@opindex msafe-dma
|
16494 |
|
|
@opindex munsafe-dma
|
16495 |
|
|
|
16496 |
|
|
Instructions which initiate or test completion of DMA must not be
|
16497 |
|
|
reordered with respect to loads and stores of the memory which is being
|
16498 |
|
|
accessed. Users typically address this problem using the volatile
|
16499 |
|
|
keyword, but that can lead to inefficient code in places where the
|
16500 |
|
|
memory is known to not change. Rather than mark the memory as volatile
|
16501 |
|
|
we treat the DMA instructions as potentially effecting all memory. With
|
16502 |
|
|
@option{-munsafe-dma} users must use the volatile keyword to protect
|
16503 |
|
|
memory accesses.
|
16504 |
|
|
|
16505 |
|
|
@item -mbranch-hints
|
16506 |
|
|
@opindex mbranch-hints
|
16507 |
|
|
|
16508 |
|
|
By default, GCC will generate a branch hint instruction to avoid
|
16509 |
|
|
pipeline stalls for always taken or probably taken branches. A hint
|
16510 |
|
|
will not be generated closer than 8 instructions away from its branch.
|
16511 |
|
|
There is little reason to disable them, except for debugging purposes,
|
16512 |
|
|
or to make an object a little bit smaller.
|
16513 |
|
|
|
16514 |
|
|
@item -msmall-mem
|
16515 |
|
|
@itemx -mlarge-mem
|
16516 |
|
|
@opindex msmall-mem
|
16517 |
|
|
@opindex mlarge-mem
|
16518 |
|
|
|
16519 |
|
|
By default, GCC generates code assuming that addresses are never larger
|
16520 |
|
|
than 18 bits. With @option{-mlarge-mem} code is generated that assumes
|
16521 |
|
|
a full 32 bit address.
|
16522 |
|
|
|
16523 |
|
|
@item -mstdmain
|
16524 |
|
|
@opindex mstdmain
|
16525 |
|
|
|
16526 |
|
|
By default, GCC links against startup code that assumes the SPU-style
|
16527 |
|
|
main function interface (which has an unconventional parameter list).
|
16528 |
|
|
With @option{-mstdmain}, GCC will link your program against startup
|
16529 |
|
|
code that assumes a C99-style interface to @code{main}, including a
|
16530 |
|
|
local copy of @code{argv} strings.
|
16531 |
|
|
|
16532 |
|
|
@item -mfixed-range=@var{register-range}
|
16533 |
|
|
@opindex mfixed-range
|
16534 |
|
|
Generate code treating the given register range as fixed registers.
|
16535 |
|
|
A fixed register is one that the register allocator can not use. This is
|
16536 |
|
|
useful when compiling kernel code. A register range is specified as
|
16537 |
|
|
two registers separated by a dash. Multiple register ranges can be
|
16538 |
|
|
specified separated by a comma.
|
16539 |
|
|
|
16540 |
|
|
@item -mea32
|
16541 |
|
|
@itemx -mea64
|
16542 |
|
|
@opindex mea32
|
16543 |
|
|
@opindex mea64
|
16544 |
|
|
Compile code assuming that pointers to the PPU address space accessed
|
16545 |
|
|
via the @code{__ea} named address space qualifier are either 32 or 64
|
16546 |
|
|
bits wide. The default is 32 bits. As this is an ABI changing option,
|
16547 |
|
|
all object code in an executable must be compiled with the same setting.
|
16548 |
|
|
|
16549 |
|
|
@item -maddress-space-conversion
|
16550 |
|
|
@itemx -mno-address-space-conversion
|
16551 |
|
|
@opindex maddress-space-conversion
|
16552 |
|
|
@opindex mno-address-space-conversion
|
16553 |
|
|
Allow/disallow treating the @code{__ea} address space as superset
|
16554 |
|
|
of the generic address space. This enables explicit type casts
|
16555 |
|
|
between @code{__ea} and generic pointer as well as implicit
|
16556 |
|
|
conversions of generic pointers to @code{__ea} pointers. The
|
16557 |
|
|
default is to allow address space pointer conversions.
|
16558 |
|
|
|
16559 |
|
|
@item -mcache-size=@var{cache-size}
|
16560 |
|
|
@opindex mcache-size
|
16561 |
|
|
This option controls the version of libgcc that the compiler links to an
|
16562 |
|
|
executable and selects a software-managed cache for accessing variables
|
16563 |
|
|
in the @code{__ea} address space with a particular cache size. Possible
|
16564 |
|
|
options for @var{cache-size} are @samp{8}, @samp{16}, @samp{32}, @samp{64}
|
16565 |
|
|
and @samp{128}. The default cache size is 64KB.
|
16566 |
|
|
|
16567 |
|
|
@item -matomic-updates
|
16568 |
|
|
@itemx -mno-atomic-updates
|
16569 |
|
|
@opindex matomic-updates
|
16570 |
|
|
@opindex mno-atomic-updates
|
16571 |
|
|
This option controls the version of libgcc that the compiler links to an
|
16572 |
|
|
executable and selects whether atomic updates to the software-managed
|
16573 |
|
|
cache of PPU-side variables are used. If you use atomic updates, changes
|
16574 |
|
|
to a PPU variable from SPU code using the @code{__ea} named address space
|
16575 |
|
|
qualifier will not interfere with changes to other PPU variables residing
|
16576 |
|
|
in the same cache line from PPU code. If you do not use atomic updates,
|
16577 |
|
|
such interference may occur; however, writing back cache lines will be
|
16578 |
|
|
more efficient. The default behavior is to use atomic updates.
|
16579 |
|
|
|
16580 |
|
|
@item -mdual-nops
|
16581 |
|
|
@itemx -mdual-nops=@var{n}
|
16582 |
|
|
@opindex mdual-nops
|
16583 |
|
|
By default, GCC will insert nops to increase dual issue when it expects
|
16584 |
|
|
it to increase performance. @var{n} can be a value from 0 to 10. A
|
16585 |
|
|
smaller @var{n} will insert fewer nops. 10 is the default, 0 is the
|
16586 |
|
|
same as @option{-mno-dual-nops}. Disabled with @option{-Os}.
|
16587 |
|
|
|
16588 |
|
|
@item -mhint-max-nops=@var{n}
|
16589 |
|
|
@opindex mhint-max-nops
|
16590 |
|
|
Maximum number of nops to insert for a branch hint. A branch hint must
|
16591 |
|
|
be at least 8 instructions away from the branch it is effecting. GCC
|
16592 |
|
|
will insert up to @var{n} nops to enforce this, otherwise it will not
|
16593 |
|
|
generate the branch hint.
|
16594 |
|
|
|
16595 |
|
|
@item -mhint-max-distance=@var{n}
|
16596 |
|
|
@opindex mhint-max-distance
|
16597 |
|
|
The encoding of the branch hint instruction limits the hint to be within
|
16598 |
|
|
256 instructions of the branch it is effecting. By default, GCC makes
|
16599 |
|
|
sure it is within 125.
|
16600 |
|
|
|
16601 |
|
|
@item -msafe-hints
|
16602 |
|
|
@opindex msafe-hints
|
16603 |
|
|
Work around a hardware bug which causes the SPU to stall indefinitely.
|
16604 |
|
|
By default, GCC will insert the @code{hbrp} instruction to make sure
|
16605 |
|
|
this stall won't happen.
|
16606 |
|
|
|
16607 |
|
|
@end table
|
16608 |
|
|
|
16609 |
|
|
@node System V Options
|
16610 |
|
|
@subsection Options for System V
|
16611 |
|
|
|
16612 |
|
|
These additional options are available on System V Release 4 for
|
16613 |
|
|
compatibility with other compilers on those systems:
|
16614 |
|
|
|
16615 |
|
|
@table @gcctabopt
|
16616 |
|
|
@item -G
|
16617 |
|
|
@opindex G
|
16618 |
|
|
Create a shared object.
|
16619 |
|
|
It is recommended that @option{-symbolic} or @option{-shared} be used instead.
|
16620 |
|
|
|
16621 |
|
|
@item -Qy
|
16622 |
|
|
@opindex Qy
|
16623 |
|
|
Identify the versions of each tool used by the compiler, in a
|
16624 |
|
|
@code{.ident} assembler directive in the output.
|
16625 |
|
|
|
16626 |
|
|
@item -Qn
|
16627 |
|
|
@opindex Qn
|
16628 |
|
|
Refrain from adding @code{.ident} directives to the output file (this is
|
16629 |
|
|
the default).
|
16630 |
|
|
|
16631 |
|
|
@item -YP,@var{dirs}
|
16632 |
|
|
@opindex YP
|
16633 |
|
|
Search the directories @var{dirs}, and no others, for libraries
|
16634 |
|
|
specified with @option{-l}.
|
16635 |
|
|
|
16636 |
|
|
@item -Ym,@var{dir}
|
16637 |
|
|
@opindex Ym
|
16638 |
|
|
Look in the directory @var{dir} to find the M4 preprocessor.
|
16639 |
|
|
The assembler uses this option.
|
16640 |
|
|
@c This is supposed to go with a -Yd for predefined M4 macro files, but
|
16641 |
|
|
@c the generic assembler that comes with Solaris takes just -Ym.
|
16642 |
|
|
@end table
|
16643 |
|
|
|
16644 |
|
|
@node V850 Options
|
16645 |
|
|
@subsection V850 Options
|
16646 |
|
|
@cindex V850 Options
|
16647 |
|
|
|
16648 |
|
|
These @samp{-m} options are defined for V850 implementations:
|
16649 |
|
|
|
16650 |
|
|
@table @gcctabopt
|
16651 |
|
|
@item -mlong-calls
|
16652 |
|
|
@itemx -mno-long-calls
|
16653 |
|
|
@opindex mlong-calls
|
16654 |
|
|
@opindex mno-long-calls
|
16655 |
|
|
Treat all calls as being far away (near). If calls are assumed to be
|
16656 |
|
|
far away, the compiler will always load the functions address up into a
|
16657 |
|
|
register, and call indirect through the pointer.
|
16658 |
|
|
|
16659 |
|
|
@item -mno-ep
|
16660 |
|
|
@itemx -mep
|
16661 |
|
|
@opindex mno-ep
|
16662 |
|
|
@opindex mep
|
16663 |
|
|
Do not optimize (do optimize) basic blocks that use the same index
|
16664 |
|
|
pointer 4 or more times to copy pointer into the @code{ep} register, and
|
16665 |
|
|
use the shorter @code{sld} and @code{sst} instructions. The @option{-mep}
|
16666 |
|
|
option is on by default if you optimize.
|
16667 |
|
|
|
16668 |
|
|
@item -mno-prolog-function
|
16669 |
|
|
@itemx -mprolog-function
|
16670 |
|
|
@opindex mno-prolog-function
|
16671 |
|
|
@opindex mprolog-function
|
16672 |
|
|
Do not use (do use) external functions to save and restore registers
|
16673 |
|
|
at the prologue and epilogue of a function. The external functions
|
16674 |
|
|
are slower, but use less code space if more than one function saves
|
16675 |
|
|
the same number of registers. The @option{-mprolog-function} option
|
16676 |
|
|
is on by default if you optimize.
|
16677 |
|
|
|
16678 |
|
|
@item -mspace
|
16679 |
|
|
@opindex mspace
|
16680 |
|
|
Try to make the code as small as possible. At present, this just turns
|
16681 |
|
|
on the @option{-mep} and @option{-mprolog-function} options.
|
16682 |
|
|
|
16683 |
|
|
@item -mtda=@var{n}
|
16684 |
|
|
@opindex mtda
|
16685 |
|
|
Put static or global variables whose size is @var{n} bytes or less into
|
16686 |
|
|
the tiny data area that register @code{ep} points to. The tiny data
|
16687 |
|
|
area can hold up to 256 bytes in total (128 bytes for byte references).
|
16688 |
|
|
|
16689 |
|
|
@item -msda=@var{n}
|
16690 |
|
|
@opindex msda
|
16691 |
|
|
Put static or global variables whose size is @var{n} bytes or less into
|
16692 |
|
|
the small data area that register @code{gp} points to. The small data
|
16693 |
|
|
area can hold up to 64 kilobytes.
|
16694 |
|
|
|
16695 |
|
|
@item -mzda=@var{n}
|
16696 |
|
|
@opindex mzda
|
16697 |
|
|
Put static or global variables whose size is @var{n} bytes or less into
|
16698 |
|
|
the first 32 kilobytes of memory.
|
16699 |
|
|
|
16700 |
|
|
@item -mv850
|
16701 |
|
|
@opindex mv850
|
16702 |
|
|
Specify that the target processor is the V850.
|
16703 |
|
|
|
16704 |
|
|
@item -mbig-switch
|
16705 |
|
|
@opindex mbig-switch
|
16706 |
|
|
Generate code suitable for big switch tables. Use this option only if
|
16707 |
|
|
the assembler/linker complain about out of range branches within a switch
|
16708 |
|
|
table.
|
16709 |
|
|
|
16710 |
|
|
@item -mapp-regs
|
16711 |
|
|
@opindex mapp-regs
|
16712 |
|
|
This option will cause r2 and r5 to be used in the code generated by
|
16713 |
|
|
the compiler. This setting is the default.
|
16714 |
|
|
|
16715 |
|
|
@item -mno-app-regs
|
16716 |
|
|
@opindex mno-app-regs
|
16717 |
|
|
This option will cause r2 and r5 to be treated as fixed registers.
|
16718 |
|
|
|
16719 |
|
|
@item -mv850e1
|
16720 |
|
|
@opindex mv850e1
|
16721 |
|
|
Specify that the target processor is the V850E1. The preprocessor
|
16722 |
|
|
constants @samp{__v850e1__} and @samp{__v850e__} will be defined if
|
16723 |
|
|
this option is used.
|
16724 |
|
|
|
16725 |
|
|
@item -mv850e
|
16726 |
|
|
@opindex mv850e
|
16727 |
|
|
Specify that the target processor is the V850E@. The preprocessor
|
16728 |
|
|
constant @samp{__v850e__} will be defined if this option is used.
|
16729 |
|
|
|
16730 |
|
|
If neither @option{-mv850} nor @option{-mv850e} nor @option{-mv850e1}
|
16731 |
|
|
are defined then a default target processor will be chosen and the
|
16732 |
|
|
relevant @samp{__v850*__} preprocessor constant will be defined.
|
16733 |
|
|
|
16734 |
|
|
The preprocessor constants @samp{__v850} and @samp{__v851__} are always
|
16735 |
|
|
defined, regardless of which processor variant is the target.
|
16736 |
|
|
|
16737 |
|
|
@item -mdisable-callt
|
16738 |
|
|
@opindex mdisable-callt
|
16739 |
|
|
This option will suppress generation of the CALLT instruction for the
|
16740 |
|
|
v850e and v850e1 flavors of the v850 architecture. The default is
|
16741 |
|
|
@option{-mno-disable-callt} which allows the CALLT instruction to be used.
|
16742 |
|
|
|
16743 |
|
|
@end table
|
16744 |
|
|
|
16745 |
|
|
@node VAX Options
|
16746 |
|
|
@subsection VAX Options
|
16747 |
|
|
@cindex VAX options
|
16748 |
|
|
|
16749 |
|
|
These @samp{-m} options are defined for the VAX:
|
16750 |
|
|
|
16751 |
|
|
@table @gcctabopt
|
16752 |
|
|
@item -munix
|
16753 |
|
|
@opindex munix
|
16754 |
|
|
Do not output certain jump instructions (@code{aobleq} and so on)
|
16755 |
|
|
that the Unix assembler for the VAX cannot handle across long
|
16756 |
|
|
ranges.
|
16757 |
|
|
|
16758 |
|
|
@item -mgnu
|
16759 |
|
|
@opindex mgnu
|
16760 |
|
|
Do output those jump instructions, on the assumption that you
|
16761 |
|
|
will assemble with the GNU assembler.
|
16762 |
|
|
|
16763 |
|
|
@item -mg
|
16764 |
|
|
@opindex mg
|
16765 |
|
|
Output code for g-format floating point numbers instead of d-format.
|
16766 |
|
|
@end table
|
16767 |
|
|
|
16768 |
|
|
@node VxWorks Options
|
16769 |
|
|
@subsection VxWorks Options
|
16770 |
|
|
@cindex VxWorks Options
|
16771 |
|
|
|
16772 |
|
|
The options in this section are defined for all VxWorks targets.
|
16773 |
|
|
Options specific to the target hardware are listed with the other
|
16774 |
|
|
options for that target.
|
16775 |
|
|
|
16776 |
|
|
@table @gcctabopt
|
16777 |
|
|
@item -mrtp
|
16778 |
|
|
@opindex mrtp
|
16779 |
|
|
GCC can generate code for both VxWorks kernels and real time processes
|
16780 |
|
|
(RTPs). This option switches from the former to the latter. It also
|
16781 |
|
|
defines the preprocessor macro @code{__RTP__}.
|
16782 |
|
|
|
16783 |
|
|
@item -non-static
|
16784 |
|
|
@opindex non-static
|
16785 |
|
|
Link an RTP executable against shared libraries rather than static
|
16786 |
|
|
libraries. The options @option{-static} and @option{-shared} can
|
16787 |
|
|
also be used for RTPs (@pxref{Link Options}); @option{-static}
|
16788 |
|
|
is the default.
|
16789 |
|
|
|
16790 |
|
|
@item -Bstatic
|
16791 |
|
|
@itemx -Bdynamic
|
16792 |
|
|
@opindex Bstatic
|
16793 |
|
|
@opindex Bdynamic
|
16794 |
|
|
These options are passed down to the linker. They are defined for
|
16795 |
|
|
compatibility with Diab.
|
16796 |
|
|
|
16797 |
|
|
@item -Xbind-lazy
|
16798 |
|
|
@opindex Xbind-lazy
|
16799 |
|
|
Enable lazy binding of function calls. This option is equivalent to
|
16800 |
|
|
@option{-Wl,-z,now} and is defined for compatibility with Diab.
|
16801 |
|
|
|
16802 |
|
|
@item -Xbind-now
|
16803 |
|
|
@opindex Xbind-now
|
16804 |
|
|
Disable lazy binding of function calls. This option is the default and
|
16805 |
|
|
is defined for compatibility with Diab.
|
16806 |
|
|
@end table
|
16807 |
|
|
|
16808 |
|
|
@node x86-64 Options
|
16809 |
|
|
@subsection x86-64 Options
|
16810 |
|
|
@cindex x86-64 options
|
16811 |
|
|
|
16812 |
|
|
These are listed under @xref{i386 and x86-64 Options}.
|
16813 |
|
|
|
16814 |
|
|
@node i386 and x86-64 Windows Options
|
16815 |
|
|
@subsection i386 and x86-64 Windows Options
|
16816 |
|
|
@cindex i386 and x86-64 Windows Options
|
16817 |
|
|
|
16818 |
|
|
These additional options are available for Windows targets:
|
16819 |
|
|
|
16820 |
|
|
@table @gcctabopt
|
16821 |
|
|
@item -mconsole
|
16822 |
|
|
@opindex mconsole
|
16823 |
|
|
This option is available for Cygwin and MinGW targets. It
|
16824 |
|
|
specifies that a console application is to be generated, by
|
16825 |
|
|
instructing the linker to set the PE header subsystem type
|
16826 |
|
|
required for console applications.
|
16827 |
|
|
This is the default behavior for Cygwin and MinGW targets.
|
16828 |
|
|
|
16829 |
|
|
@item -mcygwin
|
16830 |
|
|
@opindex mcygwin
|
16831 |
|
|
This option is available for Cygwin targets. It specifies that
|
16832 |
|
|
the Cygwin internal interface is to be used for predefined
|
16833 |
|
|
preprocessor macros, C runtime libraries and related linker
|
16834 |
|
|
paths and options. For Cygwin targets this is the default behavior.
|
16835 |
|
|
This option is deprecated and will be removed in a future release.
|
16836 |
|
|
|
16837 |
|
|
@item -mno-cygwin
|
16838 |
|
|
@opindex mno-cygwin
|
16839 |
|
|
This option is available for Cygwin targets. It specifies that
|
16840 |
|
|
the MinGW internal interface is to be used instead of Cygwin's, by
|
16841 |
|
|
setting MinGW-related predefined macros and linker paths and default
|
16842 |
|
|
library options.
|
16843 |
|
|
This option is deprecated and will be removed in a future release.
|
16844 |
|
|
|
16845 |
|
|
@item -mdll
|
16846 |
|
|
@opindex mdll
|
16847 |
|
|
This option is available for Cygwin and MinGW targets. It
|
16848 |
|
|
specifies that a DLL - a dynamic link library - is to be
|
16849 |
|
|
generated, enabling the selection of the required runtime
|
16850 |
|
|
startup object and entry point.
|
16851 |
|
|
|
16852 |
|
|
@item -mnop-fun-dllimport
|
16853 |
|
|
@opindex mnop-fun-dllimport
|
16854 |
|
|
This option is available for Cygwin and MinGW targets. It
|
16855 |
|
|
specifies that the dllimport attribute should be ignored.
|
16856 |
|
|
|
16857 |
|
|
@item -mthread
|
16858 |
|
|
@opindex mthread
|
16859 |
|
|
This option is available for MinGW targets. It specifies
|
16860 |
|
|
that MinGW-specific thread support is to be used.
|
16861 |
|
|
|
16862 |
|
|
@item -municode
|
16863 |
|
|
@opindex municode
|
16864 |
|
|
This option is available for mingw-w64 targets. It specifies
|
16865 |
|
|
that the UNICODE macro is getting pre-defined and that the
|
16866 |
|
|
unicode capable runtime startup code is chosen.
|
16867 |
|
|
|
16868 |
|
|
@item -mwin32
|
16869 |
|
|
@opindex mwin32
|
16870 |
|
|
This option is available for Cygwin and MinGW targets. It
|
16871 |
|
|
specifies that the typical Windows pre-defined macros are to
|
16872 |
|
|
be set in the pre-processor, but does not influence the choice
|
16873 |
|
|
of runtime library/startup code.
|
16874 |
|
|
|
16875 |
|
|
@item -mwindows
|
16876 |
|
|
@opindex mwindows
|
16877 |
|
|
This option is available for Cygwin and MinGW targets. It
|
16878 |
|
|
specifies that a GUI application is to be generated by
|
16879 |
|
|
instructing the linker to set the PE header subsystem type
|
16880 |
|
|
appropriately.
|
16881 |
|
|
|
16882 |
|
|
@item -fno-set-stack-executable
|
16883 |
|
|
@opindex fno-set-stack-executable
|
16884 |
|
|
This option is available for MinGW targets. It specifies that
|
16885 |
|
|
the executable flag for stack used by nested functions isn't
|
16886 |
|
|
set. This is necessary for binaries running in kernel mode of
|
16887 |
|
|
Windows, as there the user32 API, which is used to set executable
|
16888 |
|
|
privileges, isn't available.
|
16889 |
|
|
|
16890 |
|
|
@item -mpe-aligned-commons
|
16891 |
|
|
@opindex mpe-aligned-commons
|
16892 |
|
|
This option is available for Cygwin and MinGW targets. It
|
16893 |
|
|
specifies that the GNU extension to the PE file format that
|
16894 |
|
|
permits the correct alignment of COMMON variables should be
|
16895 |
|
|
used when generating code. It will be enabled by default if
|
16896 |
|
|
GCC detects that the target assembler found during configuration
|
16897 |
|
|
supports the feature.
|
16898 |
|
|
@end table
|
16899 |
|
|
|
16900 |
|
|
See also under @ref{i386 and x86-64 Options} for standard options.
|
16901 |
|
|
|
16902 |
|
|
@node Xstormy16 Options
|
16903 |
|
|
@subsection Xstormy16 Options
|
16904 |
|
|
@cindex Xstormy16 Options
|
16905 |
|
|
|
16906 |
|
|
These options are defined for Xstormy16:
|
16907 |
|
|
|
16908 |
|
|
@table @gcctabopt
|
16909 |
|
|
@item -msim
|
16910 |
|
|
@opindex msim
|
16911 |
|
|
Choose startup files and linker script suitable for the simulator.
|
16912 |
|
|
@end table
|
16913 |
|
|
|
16914 |
|
|
@node Xtensa Options
|
16915 |
|
|
@subsection Xtensa Options
|
16916 |
|
|
@cindex Xtensa Options
|
16917 |
|
|
|
16918 |
|
|
These options are supported for Xtensa targets:
|
16919 |
|
|
|
16920 |
|
|
@table @gcctabopt
|
16921 |
|
|
@item -mconst16
|
16922 |
|
|
@itemx -mno-const16
|
16923 |
|
|
@opindex mconst16
|
16924 |
|
|
@opindex mno-const16
|
16925 |
|
|
Enable or disable use of @code{CONST16} instructions for loading
|
16926 |
|
|
constant values. The @code{CONST16} instruction is currently not a
|
16927 |
|
|
standard option from Tensilica. When enabled, @code{CONST16}
|
16928 |
|
|
instructions are always used in place of the standard @code{L32R}
|
16929 |
|
|
instructions. The use of @code{CONST16} is enabled by default only if
|
16930 |
|
|
the @code{L32R} instruction is not available.
|
16931 |
|
|
|
16932 |
|
|
@item -mfused-madd
|
16933 |
|
|
@itemx -mno-fused-madd
|
16934 |
|
|
@opindex mfused-madd
|
16935 |
|
|
@opindex mno-fused-madd
|
16936 |
|
|
Enable or disable use of fused multiply/add and multiply/subtract
|
16937 |
|
|
instructions in the floating-point option. This has no effect if the
|
16938 |
|
|
floating-point option is not also enabled. Disabling fused multiply/add
|
16939 |
|
|
and multiply/subtract instructions forces the compiler to use separate
|
16940 |
|
|
instructions for the multiply and add/subtract operations. This may be
|
16941 |
|
|
desirable in some cases where strict IEEE 754-compliant results are
|
16942 |
|
|
required: the fused multiply add/subtract instructions do not round the
|
16943 |
|
|
intermediate result, thereby producing results with @emph{more} bits of
|
16944 |
|
|
precision than specified by the IEEE standard. Disabling fused multiply
|
16945 |
|
|
add/subtract instructions also ensures that the program output is not
|
16946 |
|
|
sensitive to the compiler's ability to combine multiply and add/subtract
|
16947 |
|
|
operations.
|
16948 |
|
|
|
16949 |
|
|
@item -mserialize-volatile
|
16950 |
|
|
@itemx -mno-serialize-volatile
|
16951 |
|
|
@opindex mserialize-volatile
|
16952 |
|
|
@opindex mno-serialize-volatile
|
16953 |
|
|
When this option is enabled, GCC inserts @code{MEMW} instructions before
|
16954 |
|
|
@code{volatile} memory references to guarantee sequential consistency.
|
16955 |
|
|
The default is @option{-mserialize-volatile}. Use
|
16956 |
|
|
@option{-mno-serialize-volatile} to omit the @code{MEMW} instructions.
|
16957 |
|
|
|
16958 |
|
|
@item -mtext-section-literals
|
16959 |
|
|
@itemx -mno-text-section-literals
|
16960 |
|
|
@opindex mtext-section-literals
|
16961 |
|
|
@opindex mno-text-section-literals
|
16962 |
|
|
Control the treatment of literal pools. The default is
|
16963 |
|
|
@option{-mno-text-section-literals}, which places literals in a separate
|
16964 |
|
|
section in the output file. This allows the literal pool to be placed
|
16965 |
|
|
in a data RAM/ROM, and it also allows the linker to combine literal
|
16966 |
|
|
pools from separate object files to remove redundant literals and
|
16967 |
|
|
improve code size. With @option{-mtext-section-literals}, the literals
|
16968 |
|
|
are interspersed in the text section in order to keep them as close as
|
16969 |
|
|
possible to their references. This may be necessary for large assembly
|
16970 |
|
|
files.
|
16971 |
|
|
|
16972 |
|
|
@item -mtarget-align
|
16973 |
|
|
@itemx -mno-target-align
|
16974 |
|
|
@opindex mtarget-align
|
16975 |
|
|
@opindex mno-target-align
|
16976 |
|
|
When this option is enabled, GCC instructs the assembler to
|
16977 |
|
|
automatically align instructions to reduce branch penalties at the
|
16978 |
|
|
expense of some code density. The assembler attempts to widen density
|
16979 |
|
|
instructions to align branch targets and the instructions following call
|
16980 |
|
|
instructions. If there are not enough preceding safe density
|
16981 |
|
|
instructions to align a target, no widening will be performed. The
|
16982 |
|
|
default is @option{-mtarget-align}. These options do not affect the
|
16983 |
|
|
treatment of auto-aligned instructions like @code{LOOP}, which the
|
16984 |
|
|
assembler will always align, either by widening density instructions or
|
16985 |
|
|
by inserting no-op instructions.
|
16986 |
|
|
|
16987 |
|
|
@item -mlongcalls
|
16988 |
|
|
@itemx -mno-longcalls
|
16989 |
|
|
@opindex mlongcalls
|
16990 |
|
|
@opindex mno-longcalls
|
16991 |
|
|
When this option is enabled, GCC instructs the assembler to translate
|
16992 |
|
|
direct calls to indirect calls unless it can determine that the target
|
16993 |
|
|
of a direct call is in the range allowed by the call instruction. This
|
16994 |
|
|
translation typically occurs for calls to functions in other source
|
16995 |
|
|
files. Specifically, the assembler translates a direct @code{CALL}
|
16996 |
|
|
instruction into an @code{L32R} followed by a @code{CALLX} instruction.
|
16997 |
|
|
The default is @option{-mno-longcalls}. This option should be used in
|
16998 |
|
|
programs where the call target can potentially be out of range. This
|
16999 |
|
|
option is implemented in the assembler, not the compiler, so the
|
17000 |
|
|
assembly code generated by GCC will still show direct call
|
17001 |
|
|
instructions---look at the disassembled object code to see the actual
|
17002 |
|
|
instructions. Note that the assembler will use an indirect call for
|
17003 |
|
|
every cross-file call, not just those that really will be out of range.
|
17004 |
|
|
@end table
|
17005 |
|
|
|
17006 |
|
|
@node zSeries Options
|
17007 |
|
|
@subsection zSeries Options
|
17008 |
|
|
@cindex zSeries options
|
17009 |
|
|
|
17010 |
|
|
These are listed under @xref{S/390 and zSeries Options}.
|
17011 |
|
|
|
17012 |
|
|
@node Code Gen Options
|
17013 |
|
|
@section Options for Code Generation Conventions
|
17014 |
|
|
@cindex code generation conventions
|
17015 |
|
|
@cindex options, code generation
|
17016 |
|
|
@cindex run-time options
|
17017 |
|
|
|
17018 |
|
|
These machine-independent options control the interface conventions
|
17019 |
|
|
used in code generation.
|
17020 |
|
|
|
17021 |
|
|
Most of them have both positive and negative forms; the negative form
|
17022 |
|
|
of @option{-ffoo} would be @option{-fno-foo}. In the table below, only
|
17023 |
|
|
one of the forms is listed---the one which is not the default. You
|
17024 |
|
|
can figure out the other form by either removing @samp{no-} or adding
|
17025 |
|
|
it.
|
17026 |
|
|
|
17027 |
|
|
@table @gcctabopt
|
17028 |
|
|
@item -fbounds-check
|
17029 |
|
|
@opindex fbounds-check
|
17030 |
|
|
For front-ends that support it, generate additional code to check that
|
17031 |
|
|
indices used to access arrays are within the declared range. This is
|
17032 |
|
|
currently only supported by the Java and Fortran front-ends, where
|
17033 |
|
|
this option defaults to true and false respectively.
|
17034 |
|
|
|
17035 |
|
|
@item -ftrapv
|
17036 |
|
|
@opindex ftrapv
|
17037 |
|
|
This option generates traps for signed overflow on addition, subtraction,
|
17038 |
|
|
multiplication operations.
|
17039 |
|
|
|
17040 |
|
|
@item -fwrapv
|
17041 |
|
|
@opindex fwrapv
|
17042 |
|
|
This option instructs the compiler to assume that signed arithmetic
|
17043 |
|
|
overflow of addition, subtraction and multiplication wraps around
|
17044 |
|
|
using twos-complement representation. This flag enables some optimizations
|
17045 |
|
|
and disables others. This option is enabled by default for the Java
|
17046 |
|
|
front-end, as required by the Java language specification.
|
17047 |
|
|
|
17048 |
|
|
@item -fexceptions
|
17049 |
|
|
@opindex fexceptions
|
17050 |
|
|
Enable exception handling. Generates extra code needed to propagate
|
17051 |
|
|
exceptions. For some targets, this implies GCC will generate frame
|
17052 |
|
|
unwind information for all functions, which can produce significant data
|
17053 |
|
|
size overhead, although it does not affect execution. If you do not
|
17054 |
|
|
specify this option, GCC will enable it by default for languages like
|
17055 |
|
|
C++ which normally require exception handling, and disable it for
|
17056 |
|
|
languages like C that do not normally require it. However, you may need
|
17057 |
|
|
to enable this option when compiling C code that needs to interoperate
|
17058 |
|
|
properly with exception handlers written in C++. You may also wish to
|
17059 |
|
|
disable this option if you are compiling older C++ programs that don't
|
17060 |
|
|
use exception handling.
|
17061 |
|
|
|
17062 |
|
|
@item -fnon-call-exceptions
|
17063 |
|
|
@opindex fnon-call-exceptions
|
17064 |
|
|
Generate code that allows trapping instructions to throw exceptions.
|
17065 |
|
|
Note that this requires platform-specific runtime support that does
|
17066 |
|
|
not exist everywhere. Moreover, it only allows @emph{trapping}
|
17067 |
|
|
instructions to throw exceptions, i.e.@: memory references or floating
|
17068 |
|
|
point instructions. It does not allow exceptions to be thrown from
|
17069 |
|
|
arbitrary signal handlers such as @code{SIGALRM}.
|
17070 |
|
|
|
17071 |
|
|
@item -funwind-tables
|
17072 |
|
|
@opindex funwind-tables
|
17073 |
|
|
Similar to @option{-fexceptions}, except that it will just generate any needed
|
17074 |
|
|
static data, but will not affect the generated code in any other way.
|
17075 |
|
|
You will normally not enable this option; instead, a language processor
|
17076 |
|
|
that needs this handling would enable it on your behalf.
|
17077 |
|
|
|
17078 |
|
|
@item -fasynchronous-unwind-tables
|
17079 |
|
|
@opindex fasynchronous-unwind-tables
|
17080 |
|
|
Generate unwind table in dwarf2 format, if supported by target machine. The
|
17081 |
|
|
table is exact at each instruction boundary, so it can be used for stack
|
17082 |
|
|
unwinding from asynchronous events (such as debugger or garbage collector).
|
17083 |
|
|
|
17084 |
|
|
@item -fpcc-struct-return
|
17085 |
|
|
@opindex fpcc-struct-return
|
17086 |
|
|
Return ``short'' @code{struct} and @code{union} values in memory like
|
17087 |
|
|
longer ones, rather than in registers. This convention is less
|
17088 |
|
|
efficient, but it has the advantage of allowing intercallability between
|
17089 |
|
|
GCC-compiled files and files compiled with other compilers, particularly
|
17090 |
|
|
the Portable C Compiler (pcc).
|
17091 |
|
|
|
17092 |
|
|
The precise convention for returning structures in memory depends
|
17093 |
|
|
on the target configuration macros.
|
17094 |
|
|
|
17095 |
|
|
Short structures and unions are those whose size and alignment match
|
17096 |
|
|
that of some integer type.
|
17097 |
|
|
|
17098 |
|
|
@strong{Warning:} code compiled with the @option{-fpcc-struct-return}
|
17099 |
|
|
switch is not binary compatible with code compiled with the
|
17100 |
|
|
@option{-freg-struct-return} switch.
|
17101 |
|
|
Use it to conform to a non-default application binary interface.
|
17102 |
|
|
|
17103 |
|
|
@item -freg-struct-return
|
17104 |
|
|
@opindex freg-struct-return
|
17105 |
|
|
Return @code{struct} and @code{union} values in registers when possible.
|
17106 |
|
|
This is more efficient for small structures than
|
17107 |
|
|
@option{-fpcc-struct-return}.
|
17108 |
|
|
|
17109 |
|
|
If you specify neither @option{-fpcc-struct-return} nor
|
17110 |
|
|
@option{-freg-struct-return}, GCC defaults to whichever convention is
|
17111 |
|
|
standard for the target. If there is no standard convention, GCC
|
17112 |
|
|
defaults to @option{-fpcc-struct-return}, except on targets where GCC is
|
17113 |
|
|
the principal compiler. In those cases, we can choose the standard, and
|
17114 |
|
|
we chose the more efficient register return alternative.
|
17115 |
|
|
|
17116 |
|
|
@strong{Warning:} code compiled with the @option{-freg-struct-return}
|
17117 |
|
|
switch is not binary compatible with code compiled with the
|
17118 |
|
|
@option{-fpcc-struct-return} switch.
|
17119 |
|
|
Use it to conform to a non-default application binary interface.
|
17120 |
|
|
|
17121 |
|
|
@item -fshort-enums
|
17122 |
|
|
@opindex fshort-enums
|
17123 |
|
|
Allocate to an @code{enum} type only as many bytes as it needs for the
|
17124 |
|
|
declared range of possible values. Specifically, the @code{enum} type
|
17125 |
|
|
will be equivalent to the smallest integer type which has enough room.
|
17126 |
|
|
|
17127 |
|
|
@strong{Warning:} the @option{-fshort-enums} switch causes GCC to generate
|
17128 |
|
|
code that is not binary compatible with code generated without that switch.
|
17129 |
|
|
Use it to conform to a non-default application binary interface.
|
17130 |
|
|
|
17131 |
|
|
@item -fshort-double
|
17132 |
|
|
@opindex fshort-double
|
17133 |
|
|
Use the same size for @code{double} as for @code{float}.
|
17134 |
|
|
|
17135 |
|
|
@strong{Warning:} the @option{-fshort-double} switch causes GCC to generate
|
17136 |
|
|
code that is not binary compatible with code generated without that switch.
|
17137 |
|
|
Use it to conform to a non-default application binary interface.
|
17138 |
|
|
|
17139 |
|
|
@item -fshort-wchar
|
17140 |
|
|
@opindex fshort-wchar
|
17141 |
|
|
Override the underlying type for @samp{wchar_t} to be @samp{short
|
17142 |
|
|
unsigned int} instead of the default for the target. This option is
|
17143 |
|
|
useful for building programs to run under WINE@.
|
17144 |
|
|
|
17145 |
|
|
@strong{Warning:} the @option{-fshort-wchar} switch causes GCC to generate
|
17146 |
|
|
code that is not binary compatible with code generated without that switch.
|
17147 |
|
|
Use it to conform to a non-default application binary interface.
|
17148 |
|
|
|
17149 |
|
|
@item -fno-common
|
17150 |
|
|
@opindex fno-common
|
17151 |
|
|
In C code, controls the placement of uninitialized global variables.
|
17152 |
|
|
Unix C compilers have traditionally permitted multiple definitions of
|
17153 |
|
|
such variables in different compilation units by placing the variables
|
17154 |
|
|
in a common block.
|
17155 |
|
|
This is the behavior specified by @option{-fcommon}, and is the default
|
17156 |
|
|
for GCC on most targets.
|
17157 |
|
|
On the other hand, this behavior is not required by ISO C, and on some
|
17158 |
|
|
targets may carry a speed or code size penalty on variable references.
|
17159 |
|
|
The @option{-fno-common} option specifies that the compiler should place
|
17160 |
|
|
uninitialized global variables in the data section of the object file,
|
17161 |
|
|
rather than generating them as common blocks.
|
17162 |
|
|
This has the effect that if the same variable is declared
|
17163 |
|
|
(without @code{extern}) in two different compilations,
|
17164 |
|
|
you will get a multiple-definition error when you link them.
|
17165 |
|
|
In this case, you must compile with @option{-fcommon} instead.
|
17166 |
|
|
Compiling with @option{-fno-common} is useful on targets for which
|
17167 |
|
|
it provides better performance, or if you wish to verify that the
|
17168 |
|
|
program will work on other systems which always treat uninitialized
|
17169 |
|
|
variable declarations this way.
|
17170 |
|
|
|
17171 |
|
|
@item -fno-ident
|
17172 |
|
|
@opindex fno-ident
|
17173 |
|
|
Ignore the @samp{#ident} directive.
|
17174 |
|
|
|
17175 |
|
|
@item -finhibit-size-directive
|
17176 |
|
|
@opindex finhibit-size-directive
|
17177 |
|
|
Don't output a @code{.size} assembler directive, or anything else that
|
17178 |
|
|
would cause trouble if the function is split in the middle, and the
|
17179 |
|
|
two halves are placed at locations far apart in memory. This option is
|
17180 |
|
|
used when compiling @file{crtstuff.c}; you should not need to use it
|
17181 |
|
|
for anything else.
|
17182 |
|
|
|
17183 |
|
|
@item -fverbose-asm
|
17184 |
|
|
@opindex fverbose-asm
|
17185 |
|
|
Put extra commentary information in the generated assembly code to
|
17186 |
|
|
make it more readable. This option is generally only of use to those
|
17187 |
|
|
who actually need to read the generated assembly code (perhaps while
|
17188 |
|
|
debugging the compiler itself).
|
17189 |
|
|
|
17190 |
|
|
@option{-fno-verbose-asm}, the default, causes the
|
17191 |
|
|
extra information to be omitted and is useful when comparing two assembler
|
17192 |
|
|
files.
|
17193 |
|
|
|
17194 |
|
|
@item -frecord-gcc-switches
|
17195 |
|
|
@opindex frecord-gcc-switches
|
17196 |
|
|
This switch causes the command line that was used to invoke the
|
17197 |
|
|
compiler to be recorded into the object file that is being created.
|
17198 |
|
|
This switch is only implemented on some targets and the exact format
|
17199 |
|
|
of the recording is target and binary file format dependent, but it
|
17200 |
|
|
usually takes the form of a section containing ASCII text. This
|
17201 |
|
|
switch is related to the @option{-fverbose-asm} switch, but that
|
17202 |
|
|
switch only records information in the assembler output file as
|
17203 |
|
|
comments, so it never reaches the object file.
|
17204 |
|
|
|
17205 |
|
|
@item -fpic
|
17206 |
|
|
@opindex fpic
|
17207 |
|
|
@cindex global offset table
|
17208 |
|
|
@cindex PIC
|
17209 |
|
|
Generate position-independent code (PIC) suitable for use in a shared
|
17210 |
|
|
library, if supported for the target machine. Such code accesses all
|
17211 |
|
|
constant addresses through a global offset table (GOT)@. The dynamic
|
17212 |
|
|
loader resolves the GOT entries when the program starts (the dynamic
|
17213 |
|
|
loader is not part of GCC; it is part of the operating system). If
|
17214 |
|
|
the GOT size for the linked executable exceeds a machine-specific
|
17215 |
|
|
maximum size, you get an error message from the linker indicating that
|
17216 |
|
|
@option{-fpic} does not work; in that case, recompile with @option{-fPIC}
|
17217 |
|
|
instead. (These maximums are 8k on the SPARC and 32k
|
17218 |
|
|
on the m68k and RS/6000. The 386 has no such limit.)
|
17219 |
|
|
|
17220 |
|
|
Position-independent code requires special support, and therefore works
|
17221 |
|
|
only on certain machines. For the 386, GCC supports PIC for System V
|
17222 |
|
|
but not for the Sun 386i. Code generated for the IBM RS/6000 is always
|
17223 |
|
|
position-independent.
|
17224 |
|
|
|
17225 |
|
|
When this flag is set, the macros @code{__pic__} and @code{__PIC__}
|
17226 |
|
|
are defined to 1.
|
17227 |
|
|
|
17228 |
|
|
@item -fPIC
|
17229 |
|
|
@opindex fPIC
|
17230 |
|
|
If supported for the target machine, emit position-independent code,
|
17231 |
|
|
suitable for dynamic linking and avoiding any limit on the size of the
|
17232 |
|
|
global offset table. This option makes a difference on the m68k,
|
17233 |
|
|
PowerPC and SPARC@.
|
17234 |
|
|
|
17235 |
|
|
Position-independent code requires special support, and therefore works
|
17236 |
|
|
only on certain machines.
|
17237 |
|
|
|
17238 |
|
|
When this flag is set, the macros @code{__pic__} and @code{__PIC__}
|
17239 |
|
|
are defined to 2.
|
17240 |
|
|
|
17241 |
|
|
@item -fpie
|
17242 |
|
|
@itemx -fPIE
|
17243 |
|
|
@opindex fpie
|
17244 |
|
|
@opindex fPIE
|
17245 |
|
|
These options are similar to @option{-fpic} and @option{-fPIC}, but
|
17246 |
|
|
generated position independent code can be only linked into executables.
|
17247 |
|
|
Usually these options are used when @option{-pie} GCC option will be
|
17248 |
|
|
used during linking.
|
17249 |
|
|
|
17250 |
|
|
@option{-fpie} and @option{-fPIE} both define the macros
|
17251 |
|
|
@code{__pie__} and @code{__PIE__}. The macros have the value 1
|
17252 |
|
|
for @option{-fpie} and 2 for @option{-fPIE}.
|
17253 |
|
|
|
17254 |
|
|
@item -fno-jump-tables
|
17255 |
|
|
@opindex fno-jump-tables
|
17256 |
|
|
Do not use jump tables for switch statements even where it would be
|
17257 |
|
|
more efficient than other code generation strategies. This option is
|
17258 |
|
|
of use in conjunction with @option{-fpic} or @option{-fPIC} for
|
17259 |
|
|
building code which forms part of a dynamic linker and cannot
|
17260 |
|
|
reference the address of a jump table. On some targets, jump tables
|
17261 |
|
|
do not require a GOT and this option is not needed.
|
17262 |
|
|
|
17263 |
|
|
@item -ffixed-@var{reg}
|
17264 |
|
|
@opindex ffixed
|
17265 |
|
|
Treat the register named @var{reg} as a fixed register; generated code
|
17266 |
|
|
should never refer to it (except perhaps as a stack pointer, frame
|
17267 |
|
|
pointer or in some other fixed role).
|
17268 |
|
|
|
17269 |
|
|
@var{reg} must be the name of a register. The register names accepted
|
17270 |
|
|
are machine-specific and are defined in the @code{REGISTER_NAMES}
|
17271 |
|
|
macro in the machine description macro file.
|
17272 |
|
|
|
17273 |
|
|
This flag does not have a negative form, because it specifies a
|
17274 |
|
|
three-way choice.
|
17275 |
|
|
|
17276 |
|
|
@item -fcall-used-@var{reg}
|
17277 |
|
|
@opindex fcall-used
|
17278 |
|
|
Treat the register named @var{reg} as an allocable register that is
|
17279 |
|
|
clobbered by function calls. It may be allocated for temporaries or
|
17280 |
|
|
variables that do not live across a call. Functions compiled this way
|
17281 |
|
|
will not save and restore the register @var{reg}.
|
17282 |
|
|
|
17283 |
|
|
It is an error to used this flag with the frame pointer or stack pointer.
|
17284 |
|
|
Use of this flag for other registers that have fixed pervasive roles in
|
17285 |
|
|
the machine's execution model will produce disastrous results.
|
17286 |
|
|
|
17287 |
|
|
This flag does not have a negative form, because it specifies a
|
17288 |
|
|
three-way choice.
|
17289 |
|
|
|
17290 |
|
|
@item -fcall-saved-@var{reg}
|
17291 |
|
|
@opindex fcall-saved
|
17292 |
|
|
Treat the register named @var{reg} as an allocable register saved by
|
17293 |
|
|
functions. It may be allocated even for temporaries or variables that
|
17294 |
|
|
live across a call. Functions compiled this way will save and restore
|
17295 |
|
|
the register @var{reg} if they use it.
|
17296 |
|
|
|
17297 |
|
|
It is an error to used this flag with the frame pointer or stack pointer.
|
17298 |
|
|
Use of this flag for other registers that have fixed pervasive roles in
|
17299 |
|
|
the machine's execution model will produce disastrous results.
|
17300 |
|
|
|
17301 |
|
|
A different sort of disaster will result from the use of this flag for
|
17302 |
|
|
a register in which function values may be returned.
|
17303 |
|
|
|
17304 |
|
|
This flag does not have a negative form, because it specifies a
|
17305 |
|
|
three-way choice.
|
17306 |
|
|
|
17307 |
|
|
@item -fpack-struct[=@var{n}]
|
17308 |
|
|
@opindex fpack-struct
|
17309 |
|
|
Without a value specified, pack all structure members together without
|
17310 |
|
|
holes. When a value is specified (which must be a small power of two), pack
|
17311 |
|
|
structure members according to this value, representing the maximum
|
17312 |
|
|
alignment (that is, objects with default alignment requirements larger than
|
17313 |
|
|
this will be output potentially unaligned at the next fitting location.
|
17314 |
|
|
|
17315 |
|
|
@strong{Warning:} the @option{-fpack-struct} switch causes GCC to generate
|
17316 |
|
|
code that is not binary compatible with code generated without that switch.
|
17317 |
|
|
Additionally, it makes the code suboptimal.
|
17318 |
|
|
Use it to conform to a non-default application binary interface.
|
17319 |
|
|
|
17320 |
|
|
@item -finstrument-functions
|
17321 |
|
|
@opindex finstrument-functions
|
17322 |
|
|
Generate instrumentation calls for entry and exit to functions. Just
|
17323 |
|
|
after function entry and just before function exit, the following
|
17324 |
|
|
profiling functions will be called with the address of the current
|
17325 |
|
|
function and its call site. (On some platforms,
|
17326 |
|
|
@code{__builtin_return_address} does not work beyond the current
|
17327 |
|
|
function, so the call site information may not be available to the
|
17328 |
|
|
profiling functions otherwise.)
|
17329 |
|
|
|
17330 |
|
|
@smallexample
|
17331 |
|
|
void __cyg_profile_func_enter (void *this_fn,
|
17332 |
|
|
void *call_site);
|
17333 |
|
|
void __cyg_profile_func_exit (void *this_fn,
|
17334 |
|
|
void *call_site);
|
17335 |
|
|
@end smallexample
|
17336 |
|
|
|
17337 |
|
|
The first argument is the address of the start of the current function,
|
17338 |
|
|
which may be looked up exactly in the symbol table.
|
17339 |
|
|
|
17340 |
|
|
This instrumentation is also done for functions expanded inline in other
|
17341 |
|
|
functions. The profiling calls will indicate where, conceptually, the
|
17342 |
|
|
inline function is entered and exited. This means that addressable
|
17343 |
|
|
versions of such functions must be available. If all your uses of a
|
17344 |
|
|
function are expanded inline, this may mean an additional expansion of
|
17345 |
|
|
code size. If you use @samp{extern inline} in your C code, an
|
17346 |
|
|
addressable version of such functions must be provided. (This is
|
17347 |
|
|
normally the case anyways, but if you get lucky and the optimizer always
|
17348 |
|
|
expands the functions inline, you might have gotten away without
|
17349 |
|
|
providing static copies.)
|
17350 |
|
|
|
17351 |
|
|
A function may be given the attribute @code{no_instrument_function}, in
|
17352 |
|
|
which case this instrumentation will not be done. This can be used, for
|
17353 |
|
|
example, for the profiling functions listed above, high-priority
|
17354 |
|
|
interrupt routines, and any functions from which the profiling functions
|
17355 |
|
|
cannot safely be called (perhaps signal handlers, if the profiling
|
17356 |
|
|
routines generate output or allocate memory).
|
17357 |
|
|
|
17358 |
|
|
@item -finstrument-functions-exclude-file-list=@var{file},@var{file},@dots{}
|
17359 |
|
|
@opindex finstrument-functions-exclude-file-list
|
17360 |
|
|
|
17361 |
|
|
Set the list of functions that are excluded from instrumentation (see
|
17362 |
|
|
the description of @code{-finstrument-functions}). If the file that
|
17363 |
|
|
contains a function definition matches with one of @var{file}, then
|
17364 |
|
|
that function is not instrumented. The match is done on substrings:
|
17365 |
|
|
if the @var{file} parameter is a substring of the file name, it is
|
17366 |
|
|
considered to be a match.
|
17367 |
|
|
|
17368 |
|
|
For example,
|
17369 |
|
|
@code{-finstrument-functions-exclude-file-list=/bits/stl,include/sys}
|
17370 |
|
|
will exclude any inline function defined in files whose pathnames
|
17371 |
|
|
contain @code{/bits/stl} or @code{include/sys}.
|
17372 |
|
|
|
17373 |
|
|
If, for some reason, you want to include letter @code{','} in one of
|
17374 |
|
|
@var{sym}, write @code{'\,'}. For example,
|
17375 |
|
|
@code{-finstrument-functions-exclude-file-list='\,\,tmp'}
|
17376 |
|
|
(note the single quote surrounding the option).
|
17377 |
|
|
|
17378 |
|
|
@item -finstrument-functions-exclude-function-list=@var{sym},@var{sym},@dots{}
|
17379 |
|
|
@opindex finstrument-functions-exclude-function-list
|
17380 |
|
|
|
17381 |
|
|
This is similar to @code{-finstrument-functions-exclude-file-list},
|
17382 |
|
|
but this option sets the list of function names to be excluded from
|
17383 |
|
|
instrumentation. The function name to be matched is its user-visible
|
17384 |
|
|
name, such as @code{vector<int> blah(const vector<int> &)}, not the
|
17385 |
|
|
internal mangled name (e.g., @code{_Z4blahRSt6vectorIiSaIiEE}). The
|
17386 |
|
|
match is done on substrings: if the @var{sym} parameter is a substring
|
17387 |
|
|
of the function name, it is considered to be a match. For C99 and C++
|
17388 |
|
|
extended identifiers, the function name must be given in UTF-8, not
|
17389 |
|
|
using universal character names.
|
17390 |
|
|
|
17391 |
|
|
@item -fstack-check
|
17392 |
|
|
@opindex fstack-check
|
17393 |
|
|
Generate code to verify that you do not go beyond the boundary of the
|
17394 |
|
|
stack. You should specify this flag if you are running in an
|
17395 |
|
|
environment with multiple threads, but only rarely need to specify it in
|
17396 |
|
|
a single-threaded environment since stack overflow is automatically
|
17397 |
|
|
detected on nearly all systems if there is only one stack.
|
17398 |
|
|
|
17399 |
|
|
Note that this switch does not actually cause checking to be done; the
|
17400 |
|
|
operating system or the language runtime must do that. The switch causes
|
17401 |
|
|
generation of code to ensure that they see the stack being extended.
|
17402 |
|
|
|
17403 |
|
|
You can additionally specify a string parameter: @code{no} means no
|
17404 |
|
|
checking, @code{generic} means force the use of old-style checking,
|
17405 |
|
|
@code{specific} means use the best checking method and is equivalent
|
17406 |
|
|
to bare @option{-fstack-check}.
|
17407 |
|
|
|
17408 |
|
|
Old-style checking is a generic mechanism that requires no specific
|
17409 |
|
|
target support in the compiler but comes with the following drawbacks:
|
17410 |
|
|
|
17411 |
|
|
@enumerate
|
17412 |
|
|
@item
|
17413 |
|
|
Modified allocation strategy for large objects: they will always be
|
17414 |
|
|
allocated dynamically if their size exceeds a fixed threshold.
|
17415 |
|
|
|
17416 |
|
|
@item
|
17417 |
|
|
Fixed limit on the size of the static frame of functions: when it is
|
17418 |
|
|
topped by a particular function, stack checking is not reliable and
|
17419 |
|
|
a warning is issued by the compiler.
|
17420 |
|
|
|
17421 |
|
|
@item
|
17422 |
|
|
Inefficiency: because of both the modified allocation strategy and the
|
17423 |
|
|
generic implementation, the performances of the code are hampered.
|
17424 |
|
|
@end enumerate
|
17425 |
|
|
|
17426 |
|
|
Note that old-style stack checking is also the fallback method for
|
17427 |
|
|
@code{specific} if no target support has been added in the compiler.
|
17428 |
|
|
|
17429 |
|
|
@item -fstack-limit-register=@var{reg}
|
17430 |
|
|
@itemx -fstack-limit-symbol=@var{sym}
|
17431 |
|
|
@itemx -fno-stack-limit
|
17432 |
|
|
@opindex fstack-limit-register
|
17433 |
|
|
@opindex fstack-limit-symbol
|
17434 |
|
|
@opindex fno-stack-limit
|
17435 |
|
|
Generate code to ensure that the stack does not grow beyond a certain value,
|
17436 |
|
|
either the value of a register or the address of a symbol. If the stack
|
17437 |
|
|
would grow beyond the value, a signal is raised. For most targets,
|
17438 |
|
|
the signal is raised before the stack overruns the boundary, so
|
17439 |
|
|
it is possible to catch the signal without taking special precautions.
|
17440 |
|
|
|
17441 |
|
|
For instance, if the stack starts at absolute address @samp{0x80000000}
|
17442 |
|
|
and grows downwards, you can use the flags
|
17443 |
|
|
@option{-fstack-limit-symbol=__stack_limit} and
|
17444 |
|
|
@option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit
|
17445 |
|
|
of 128KB@. Note that this may only work with the GNU linker.
|
17446 |
|
|
|
17447 |
|
|
@cindex aliasing of parameters
|
17448 |
|
|
@cindex parameters, aliased
|
17449 |
|
|
@item -fargument-alias
|
17450 |
|
|
@itemx -fargument-noalias
|
17451 |
|
|
@itemx -fargument-noalias-global
|
17452 |
|
|
@itemx -fargument-noalias-anything
|
17453 |
|
|
@opindex fargument-alias
|
17454 |
|
|
@opindex fargument-noalias
|
17455 |
|
|
@opindex fargument-noalias-global
|
17456 |
|
|
@opindex fargument-noalias-anything
|
17457 |
|
|
Specify the possible relationships among parameters and between
|
17458 |
|
|
parameters and global data.
|
17459 |
|
|
|
17460 |
|
|
@option{-fargument-alias} specifies that arguments (parameters) may
|
17461 |
|
|
alias each other and may alias global storage.@*
|
17462 |
|
|
@option{-fargument-noalias} specifies that arguments do not alias
|
17463 |
|
|
each other, but may alias global storage.@*
|
17464 |
|
|
@option{-fargument-noalias-global} specifies that arguments do not
|
17465 |
|
|
alias each other and do not alias global storage.
|
17466 |
|
|
@option{-fargument-noalias-anything} specifies that arguments do not
|
17467 |
|
|
alias any other storage.
|
17468 |
|
|
|
17469 |
|
|
Each language will automatically use whatever option is required by
|
17470 |
|
|
the language standard. You should not need to use these options yourself.
|
17471 |
|
|
|
17472 |
|
|
@item -fleading-underscore
|
17473 |
|
|
@opindex fleading-underscore
|
17474 |
|
|
This option and its counterpart, @option{-fno-leading-underscore}, forcibly
|
17475 |
|
|
change the way C symbols are represented in the object file. One use
|
17476 |
|
|
is to help link with legacy assembly code.
|
17477 |
|
|
|
17478 |
|
|
@strong{Warning:} the @option{-fleading-underscore} switch causes GCC to
|
17479 |
|
|
generate code that is not binary compatible with code generated without that
|
17480 |
|
|
switch. Use it to conform to a non-default application binary interface.
|
17481 |
|
|
Not all targets provide complete support for this switch.
|
17482 |
|
|
|
17483 |
|
|
@item -ftls-model=@var{model}
|
17484 |
|
|
@opindex ftls-model
|
17485 |
|
|
Alter the thread-local storage model to be used (@pxref{Thread-Local}).
|
17486 |
|
|
The @var{model} argument should be one of @code{global-dynamic},
|
17487 |
|
|
@code{local-dynamic}, @code{initial-exec} or @code{local-exec}.
|
17488 |
|
|
|
17489 |
|
|
The default without @option{-fpic} is @code{initial-exec}; with
|
17490 |
|
|
@option{-fpic} the default is @code{global-dynamic}.
|
17491 |
|
|
|
17492 |
|
|
@item -fvisibility=@var{default|internal|hidden|protected}
|
17493 |
|
|
@opindex fvisibility
|
17494 |
|
|
Set the default ELF image symbol visibility to the specified option---all
|
17495 |
|
|
symbols will be marked with this unless overridden within the code.
|
17496 |
|
|
Using this feature can very substantially improve linking and
|
17497 |
|
|
load times of shared object libraries, produce more optimized
|
17498 |
|
|
code, provide near-perfect API export and prevent symbol clashes.
|
17499 |
|
|
It is @strong{strongly} recommended that you use this in any shared objects
|
17500 |
|
|
you distribute.
|
17501 |
|
|
|
17502 |
|
|
Despite the nomenclature, @code{default} always means public ie;
|
17503 |
|
|
available to be linked against from outside the shared object.
|
17504 |
|
|
@code{protected} and @code{internal} are pretty useless in real-world
|
17505 |
|
|
usage so the only other commonly used option will be @code{hidden}.
|
17506 |
|
|
The default if @option{-fvisibility} isn't specified is
|
17507 |
|
|
@code{default}, i.e., make every
|
17508 |
|
|
symbol public---this causes the same behavior as previous versions of
|
17509 |
|
|
GCC@.
|
17510 |
|
|
|
17511 |
|
|
A good explanation of the benefits offered by ensuring ELF
|
17512 |
|
|
symbols have the correct visibility is given by ``How To Write
|
17513 |
|
|
Shared Libraries'' by Ulrich Drepper (which can be found at
|
17514 |
|
|
@w{@uref{http://people.redhat.com/~drepper/}})---however a superior
|
17515 |
|
|
solution made possible by this option to marking things hidden when
|
17516 |
|
|
the default is public is to make the default hidden and mark things
|
17517 |
|
|
public. This is the norm with DLL's on Windows and with @option{-fvisibility=hidden}
|
17518 |
|
|
and @code{__attribute__ ((visibility("default")))} instead of
|
17519 |
|
|
@code{__declspec(dllexport)} you get almost identical semantics with
|
17520 |
|
|
identical syntax. This is a great boon to those working with
|
17521 |
|
|
cross-platform projects.
|
17522 |
|
|
|
17523 |
|
|
For those adding visibility support to existing code, you may find
|
17524 |
|
|
@samp{#pragma GCC visibility} of use. This works by you enclosing
|
17525 |
|
|
the declarations you wish to set visibility for with (for example)
|
17526 |
|
|
@samp{#pragma GCC visibility push(hidden)} and
|
17527 |
|
|
@samp{#pragma GCC visibility pop}.
|
17528 |
|
|
Bear in mind that symbol visibility should be viewed @strong{as
|
17529 |
|
|
part of the API interface contract} and thus all new code should
|
17530 |
|
|
always specify visibility when it is not the default ie; declarations
|
17531 |
|
|
only for use within the local DSO should @strong{always} be marked explicitly
|
17532 |
|
|
as hidden as so to avoid PLT indirection overheads---making this
|
17533 |
|
|
abundantly clear also aids readability and self-documentation of the code.
|
17534 |
|
|
Note that due to ISO C++ specification requirements, operator new and
|
17535 |
|
|
operator delete must always be of default visibility.
|
17536 |
|
|
|
17537 |
|
|
Be aware that headers from outside your project, in particular system
|
17538 |
|
|
headers and headers from any other library you use, may not be
|
17539 |
|
|
expecting to be compiled with visibility other than the default. You
|
17540 |
|
|
may need to explicitly say @samp{#pragma GCC visibility push(default)}
|
17541 |
|
|
before including any such headers.
|
17542 |
|
|
|
17543 |
|
|
@samp{extern} declarations are not affected by @samp{-fvisibility}, so
|
17544 |
|
|
a lot of code can be recompiled with @samp{-fvisibility=hidden} with
|
17545 |
|
|
no modifications. However, this means that calls to @samp{extern}
|
17546 |
|
|
functions with no explicit visibility will use the PLT, so it is more
|
17547 |
|
|
effective to use @samp{__attribute ((visibility))} and/or
|
17548 |
|
|
@samp{#pragma GCC visibility} to tell the compiler which @samp{extern}
|
17549 |
|
|
declarations should be treated as hidden.
|
17550 |
|
|
|
17551 |
|
|
Note that @samp{-fvisibility} does affect C++ vague linkage
|
17552 |
|
|
entities. This means that, for instance, an exception class that will
|
17553 |
|
|
be thrown between DSOs must be explicitly marked with default
|
17554 |
|
|
visibility so that the @samp{type_info} nodes will be unified between
|
17555 |
|
|
the DSOs.
|
17556 |
|
|
|
17557 |
|
|
An overview of these techniques, their benefits and how to use them
|
17558 |
|
|
is at @w{@uref{http://gcc.gnu.org/wiki/Visibility}}.
|
17559 |
|
|
|
17560 |
|
|
@end table
|
17561 |
|
|
|
17562 |
|
|
@c man end
|
17563 |
|
|
|
17564 |
|
|
@node Environment Variables
|
17565 |
|
|
@section Environment Variables Affecting GCC
|
17566 |
|
|
@cindex environment variables
|
17567 |
|
|
|
17568 |
|
|
@c man begin ENVIRONMENT
|
17569 |
|
|
This section describes several environment variables that affect how GCC
|
17570 |
|
|
operates. Some of them work by specifying directories or prefixes to use
|
17571 |
|
|
when searching for various kinds of files. Some are used to specify other
|
17572 |
|
|
aspects of the compilation environment.
|
17573 |
|
|
|
17574 |
|
|
Note that you can also specify places to search using options such as
|
17575 |
|
|
@option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These
|
17576 |
|
|
take precedence over places specified using environment variables, which
|
17577 |
|
|
in turn take precedence over those specified by the configuration of GCC@.
|
17578 |
|
|
@xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint,
|
17579 |
|
|
GNU Compiler Collection (GCC) Internals}.
|
17580 |
|
|
|
17581 |
|
|
@table @env
|
17582 |
|
|
@item LANG
|
17583 |
|
|
@itemx LC_CTYPE
|
17584 |
|
|
@c @itemx LC_COLLATE
|
17585 |
|
|
@itemx LC_MESSAGES
|
17586 |
|
|
@c @itemx LC_MONETARY
|
17587 |
|
|
@c @itemx LC_NUMERIC
|
17588 |
|
|
@c @itemx LC_TIME
|
17589 |
|
|
@itemx LC_ALL
|
17590 |
|
|
@findex LANG
|
17591 |
|
|
@findex LC_CTYPE
|
17592 |
|
|
@c @findex LC_COLLATE
|
17593 |
|
|
@findex LC_MESSAGES
|
17594 |
|
|
@c @findex LC_MONETARY
|
17595 |
|
|
@c @findex LC_NUMERIC
|
17596 |
|
|
@c @findex LC_TIME
|
17597 |
|
|
@findex LC_ALL
|
17598 |
|
|
@cindex locale
|
17599 |
|
|
These environment variables control the way that GCC uses
|
17600 |
|
|
localization information that allow GCC to work with different
|
17601 |
|
|
national conventions. GCC inspects the locale categories
|
17602 |
|
|
@env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do
|
17603 |
|
|
so. These locale categories can be set to any value supported by your
|
17604 |
|
|
installation. A typical value is @samp{en_GB.UTF-8} for English in the United
|
17605 |
|
|
Kingdom encoded in UTF-8.
|
17606 |
|
|
|
17607 |
|
|
The @env{LC_CTYPE} environment variable specifies character
|
17608 |
|
|
classification. GCC uses it to determine the character boundaries in
|
17609 |
|
|
a string; this is needed for some multibyte encodings that contain quote
|
17610 |
|
|
and escape characters that would otherwise be interpreted as a string
|
17611 |
|
|
end or escape.
|
17612 |
|
|
|
17613 |
|
|
The @env{LC_MESSAGES} environment variable specifies the language to
|
17614 |
|
|
use in diagnostic messages.
|
17615 |
|
|
|
17616 |
|
|
If the @env{LC_ALL} environment variable is set, it overrides the value
|
17617 |
|
|
of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE}
|
17618 |
|
|
and @env{LC_MESSAGES} default to the value of the @env{LANG}
|
17619 |
|
|
environment variable. If none of these variables are set, GCC
|
17620 |
|
|
defaults to traditional C English behavior.
|
17621 |
|
|
|
17622 |
|
|
@item TMPDIR
|
17623 |
|
|
@findex TMPDIR
|
17624 |
|
|
If @env{TMPDIR} is set, it specifies the directory to use for temporary
|
17625 |
|
|
files. GCC uses temporary files to hold the output of one stage of
|
17626 |
|
|
compilation which is to be used as input to the next stage: for example,
|
17627 |
|
|
the output of the preprocessor, which is the input to the compiler
|
17628 |
|
|
proper.
|
17629 |
|
|
|
17630 |
|
|
@item GCC_EXEC_PREFIX
|
17631 |
|
|
@findex GCC_EXEC_PREFIX
|
17632 |
|
|
If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the
|
17633 |
|
|
names of the subprograms executed by the compiler. No slash is added
|
17634 |
|
|
when this prefix is combined with the name of a subprogram, but you can
|
17635 |
|
|
specify a prefix that ends with a slash if you wish.
|
17636 |
|
|
|
17637 |
|
|
If @env{GCC_EXEC_PREFIX} is not set, GCC will attempt to figure out
|
17638 |
|
|
an appropriate prefix to use based on the pathname it was invoked with.
|
17639 |
|
|
|
17640 |
|
|
If GCC cannot find the subprogram using the specified prefix, it
|
17641 |
|
|
tries looking in the usual places for the subprogram.
|
17642 |
|
|
|
17643 |
|
|
The default value of @env{GCC_EXEC_PREFIX} is
|
17644 |
|
|
@file{@var{prefix}/lib/gcc/} where @var{prefix} is the prefix to
|
17645 |
|
|
the installed compiler. In many cases @var{prefix} is the value
|
17646 |
|
|
of @code{prefix} when you ran the @file{configure} script.
|
17647 |
|
|
|
17648 |
|
|
Other prefixes specified with @option{-B} take precedence over this prefix.
|
17649 |
|
|
|
17650 |
|
|
This prefix is also used for finding files such as @file{crt0.o} that are
|
17651 |
|
|
used for linking.
|
17652 |
|
|
|
17653 |
|
|
In addition, the prefix is used in an unusual way in finding the
|
17654 |
|
|
directories to search for header files. For each of the standard
|
17655 |
|
|
directories whose name normally begins with @samp{/usr/local/lib/gcc}
|
17656 |
|
|
(more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries
|
17657 |
|
|
replacing that beginning with the specified prefix to produce an
|
17658 |
|
|
alternate directory name. Thus, with @option{-Bfoo/}, GCC will search
|
17659 |
|
|
@file{foo/bar} where it would normally search @file{/usr/local/lib/bar}.
|
17660 |
|
|
These alternate directories are searched first; the standard directories
|
17661 |
|
|
come next. If a standard directory begins with the configured
|
17662 |
|
|
@var{prefix} then the value of @var{prefix} is replaced by
|
17663 |
|
|
@env{GCC_EXEC_PREFIX} when looking for header files.
|
17664 |
|
|
|
17665 |
|
|
@item COMPILER_PATH
|
17666 |
|
|
@findex COMPILER_PATH
|
17667 |
|
|
The value of @env{COMPILER_PATH} is a colon-separated list of
|
17668 |
|
|
directories, much like @env{PATH}. GCC tries the directories thus
|
17669 |
|
|
specified when searching for subprograms, if it can't find the
|
17670 |
|
|
subprograms using @env{GCC_EXEC_PREFIX}.
|
17671 |
|
|
|
17672 |
|
|
@item LIBRARY_PATH
|
17673 |
|
|
@findex LIBRARY_PATH
|
17674 |
|
|
The value of @env{LIBRARY_PATH} is a colon-separated list of
|
17675 |
|
|
directories, much like @env{PATH}. When configured as a native compiler,
|
17676 |
|
|
GCC tries the directories thus specified when searching for special
|
17677 |
|
|
linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking
|
17678 |
|
|
using GCC also uses these directories when searching for ordinary
|
17679 |
|
|
libraries for the @option{-l} option (but directories specified with
|
17680 |
|
|
@option{-L} come first).
|
17681 |
|
|
|
17682 |
|
|
@item LANG
|
17683 |
|
|
@findex LANG
|
17684 |
|
|
@cindex locale definition
|
17685 |
|
|
This variable is used to pass locale information to the compiler. One way in
|
17686 |
|
|
which this information is used is to determine the character set to be used
|
17687 |
|
|
when character literals, string literals and comments are parsed in C and C++.
|
17688 |
|
|
When the compiler is configured to allow multibyte characters,
|
17689 |
|
|
the following values for @env{LANG} are recognized:
|
17690 |
|
|
|
17691 |
|
|
@table @samp
|
17692 |
|
|
@item C-JIS
|
17693 |
|
|
Recognize JIS characters.
|
17694 |
|
|
@item C-SJIS
|
17695 |
|
|
Recognize SJIS characters.
|
17696 |
|
|
@item C-EUCJP
|
17697 |
|
|
Recognize EUCJP characters.
|
17698 |
|
|
@end table
|
17699 |
|
|
|
17700 |
|
|
If @env{LANG} is not defined, or if it has some other value, then the
|
17701 |
|
|
compiler will use mblen and mbtowc as defined by the default locale to
|
17702 |
|
|
recognize and translate multibyte characters.
|
17703 |
|
|
@end table
|
17704 |
|
|
|
17705 |
|
|
@noindent
|
17706 |
|
|
Some additional environments variables affect the behavior of the
|
17707 |
|
|
preprocessor.
|
17708 |
|
|
|
17709 |
|
|
@include cppenv.texi
|
17710 |
|
|
|
17711 |
|
|
@c man end
|
17712 |
|
|
|
17713 |
|
|
@node Precompiled Headers
|
17714 |
|
|
@section Using Precompiled Headers
|
17715 |
|
|
@cindex precompiled headers
|
17716 |
|
|
@cindex speed of compilation
|
17717 |
|
|
|
17718 |
|
|
Often large projects have many header files that are included in every
|
17719 |
|
|
source file. The time the compiler takes to process these header files
|
17720 |
|
|
over and over again can account for nearly all of the time required to
|
17721 |
|
|
build the project. To make builds faster, GCC allows users to
|
17722 |
|
|
`precompile' a header file; then, if builds can use the precompiled
|
17723 |
|
|
header file they will be much faster.
|
17724 |
|
|
|
17725 |
|
|
To create a precompiled header file, simply compile it as you would any
|
17726 |
|
|
other file, if necessary using the @option{-x} option to make the driver
|
17727 |
|
|
treat it as a C or C++ header file. You will probably want to use a
|
17728 |
|
|
tool like @command{make} to keep the precompiled header up-to-date when
|
17729 |
|
|
the headers it contains change.
|
17730 |
|
|
|
17731 |
|
|
A precompiled header file will be searched for when @code{#include} is
|
17732 |
|
|
seen in the compilation. As it searches for the included file
|
17733 |
|
|
(@pxref{Search Path,,Search Path,cpp,The C Preprocessor}) the
|
17734 |
|
|
compiler looks for a precompiled header in each directory just before it
|
17735 |
|
|
looks for the include file in that directory. The name searched for is
|
17736 |
|
|
the name specified in the @code{#include} with @samp{.gch} appended. If
|
17737 |
|
|
the precompiled header file can't be used, it is ignored.
|
17738 |
|
|
|
17739 |
|
|
For instance, if you have @code{#include "all.h"}, and you have
|
17740 |
|
|
@file{all.h.gch} in the same directory as @file{all.h}, then the
|
17741 |
|
|
precompiled header file will be used if possible, and the original
|
17742 |
|
|
header will be used otherwise.
|
17743 |
|
|
|
17744 |
|
|
Alternatively, you might decide to put the precompiled header file in a
|
17745 |
|
|
directory and use @option{-I} to ensure that directory is searched
|
17746 |
|
|
before (or instead of) the directory containing the original header.
|
17747 |
|
|
Then, if you want to check that the precompiled header file is always
|
17748 |
|
|
used, you can put a file of the same name as the original header in this
|
17749 |
|
|
directory containing an @code{#error} command.
|
17750 |
|
|
|
17751 |
|
|
This also works with @option{-include}. So yet another way to use
|
17752 |
|
|
precompiled headers, good for projects not designed with precompiled
|
17753 |
|
|
header files in mind, is to simply take most of the header files used by
|
17754 |
|
|
a project, include them from another header file, precompile that header
|
17755 |
|
|
file, and @option{-include} the precompiled header. If the header files
|
17756 |
|
|
have guards against multiple inclusion, they will be skipped because
|
17757 |
|
|
they've already been included (in the precompiled header).
|
17758 |
|
|
|
17759 |
|
|
If you need to precompile the same header file for different
|
17760 |
|
|
languages, targets, or compiler options, you can instead make a
|
17761 |
|
|
@emph{directory} named like @file{all.h.gch}, and put each precompiled
|
17762 |
|
|
header in the directory, perhaps using @option{-o}. It doesn't matter
|
17763 |
|
|
what you call the files in the directory, every precompiled header in
|
17764 |
|
|
the directory will be considered. The first precompiled header
|
17765 |
|
|
encountered in the directory that is valid for this compilation will
|
17766 |
|
|
be used; they're searched in no particular order.
|
17767 |
|
|
|
17768 |
|
|
There are many other possibilities, limited only by your imagination,
|
17769 |
|
|
good sense, and the constraints of your build system.
|
17770 |
|
|
|
17771 |
|
|
A precompiled header file can be used only when these conditions apply:
|
17772 |
|
|
|
17773 |
|
|
@itemize
|
17774 |
|
|
@item
|
17775 |
|
|
Only one precompiled header can be used in a particular compilation.
|
17776 |
|
|
|
17777 |
|
|
@item
|
17778 |
|
|
A precompiled header can't be used once the first C token is seen. You
|
17779 |
|
|
can have preprocessor directives before a precompiled header; you can
|
17780 |
|
|
even include a precompiled header from inside another header, so long as
|
17781 |
|
|
there are no C tokens before the @code{#include}.
|
17782 |
|
|
|
17783 |
|
|
@item
|
17784 |
|
|
The precompiled header file must be produced for the same language as
|
17785 |
|
|
the current compilation. You can't use a C precompiled header for a C++
|
17786 |
|
|
compilation.
|
17787 |
|
|
|
17788 |
|
|
@item
|
17789 |
|
|
The precompiled header file must have been produced by the same compiler
|
17790 |
|
|
binary as the current compilation is using.
|
17791 |
|
|
|
17792 |
|
|
@item
|
17793 |
|
|
Any macros defined before the precompiled header is included must
|
17794 |
|
|
either be defined in the same way as when the precompiled header was
|
17795 |
|
|
generated, or must not affect the precompiled header, which usually
|
17796 |
|
|
means that they don't appear in the precompiled header at all.
|
17797 |
|
|
|
17798 |
|
|
The @option{-D} option is one way to define a macro before a
|
17799 |
|
|
precompiled header is included; using a @code{#define} can also do it.
|
17800 |
|
|
There are also some options that define macros implicitly, like
|
17801 |
|
|
@option{-O} and @option{-Wdeprecated}; the same rule applies to macros
|
17802 |
|
|
defined this way.
|
17803 |
|
|
|
17804 |
|
|
@item If debugging information is output when using the precompiled
|
17805 |
|
|
header, using @option{-g} or similar, the same kind of debugging information
|
17806 |
|
|
must have been output when building the precompiled header. However,
|
17807 |
|
|
a precompiled header built using @option{-g} can be used in a compilation
|
17808 |
|
|
when no debugging information is being output.
|
17809 |
|
|
|
17810 |
|
|
@item The same @option{-m} options must generally be used when building
|
17811 |
|
|
and using the precompiled header. @xref{Submodel Options},
|
17812 |
|
|
for any cases where this rule is relaxed.
|
17813 |
|
|
|
17814 |
|
|
@item Each of the following options must be the same when building and using
|
17815 |
|
|
the precompiled header:
|
17816 |
|
|
|
17817 |
|
|
@gccoptlist{-fexceptions}
|
17818 |
|
|
|
17819 |
|
|
@item
|
17820 |
|
|
Some other command-line options starting with @option{-f},
|
17821 |
|
|
@option{-p}, or @option{-O} must be defined in the same way as when
|
17822 |
|
|
the precompiled header was generated. At present, it's not clear
|
17823 |
|
|
which options are safe to change and which are not; the safest choice
|
17824 |
|
|
is to use exactly the same options when generating and using the
|
17825 |
|
|
precompiled header. The following are known to be safe:
|
17826 |
|
|
|
17827 |
|
|
@gccoptlist{-fmessage-length= -fpreprocessed -fsched-interblock @gol
|
17828 |
|
|
-fsched-spec -fsched-spec-load -fsched-spec-load-dangerous @gol
|
17829 |
|
|
-fsched-verbose=<number> -fschedule-insns -fvisibility= @gol
|
17830 |
|
|
-pedantic-errors}
|
17831 |
|
|
|
17832 |
|
|
@end itemize
|
17833 |
|
|
|
17834 |
|
|
For all of these except the last, the compiler will automatically
|
17835 |
|
|
ignore the precompiled header if the conditions aren't met. If you
|
17836 |
|
|
find an option combination that doesn't work and doesn't cause the
|
17837 |
|
|
precompiled header to be ignored, please consider filing a bug report,
|
17838 |
|
|
see @ref{Bugs}.
|
17839 |
|
|
|
17840 |
|
|
If you do use differing options when generating and using the
|
17841 |
|
|
precompiled header, the actual behavior will be a mixture of the
|
17842 |
|
|
behavior for the options. For instance, if you use @option{-g} to
|
17843 |
|
|
generate the precompiled header but not when using it, you may or may
|
17844 |
|
|
not get debugging information for routines in the precompiled header.
|