Subversion Repositories open8_urisc

@c Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,

@c 2006, 2007, 2008, 2009, 2010, 2011  Free Software Foundation, Inc.

@c This is part of the GAS manual.

@c For copying conditions, see the file as.texinfo.

@ifset GENERIC

@page

@node ARM-Dependent

@chapter ARM Dependent Features

@end ifset

@ifclear GENERIC

@node Machine Dependencies

@chapter ARM Dependent Features

@end ifclear

@cindex ARM support

@cindex Thumb support

@menu

* ARM Options::              Options

* ARM Syntax::               Syntax

* ARM Floating Point::       Floating Point

* ARM Directives::           ARM Machine Directives

* ARM Opcodes::              Opcodes

* ARM Mapping Symbols::      Mapping Symbols

* ARM Unwinding Tutorial::   Unwinding

@end menu

@node ARM Options

@section Options

@cindex ARM options (none)

@cindex options for ARM (none)

@table @code

@cindex @code{-mcpu=} command line option, ARM

@item -mcpu=@var{processor}[+@var{extension}@dots{}]

This option specifies the target processor.  The assembler will issue an

error message if an attempt is made to assemble an instruction which

will not execute on the target processor.  The following processor names are

recognized:

@code{arm1},

@code{arm2},

@code{arm250},

@code{arm3},

@code{arm6},

@code{arm60},

@code{arm600},

@code{arm610},

@code{arm620},

@code{arm7},

@code{arm7m},

@code{arm7d},

@code{arm7dm},

@code{arm7di},

@code{arm7dmi},

@code{arm70},

@code{arm700},

@code{arm700i},

@code{arm710},

@code{arm710t},

@code{arm720},

@code{arm720t},

@code{arm740t},

@code{arm710c},

@code{arm7100},

@code{arm7500},

@code{arm7500fe},

@code{arm7t},

@code{arm7tdmi},

@code{arm7tdmi-s},

@code{arm8},

@code{arm810},

@code{strongarm},

@code{strongarm1},

@code{strongarm110},

@code{strongarm1100},

@code{strongarm1110},

@code{arm9},

@code{arm920},

@code{arm920t},

@code{arm922t},

@code{arm940t},

@code{arm9tdmi},

@code{fa526} (Faraday FA526 processor),

@code{fa626} (Faraday FA626 processor),

@code{arm9e},

@code{arm926e},

@code{arm926ej-s},

@code{arm946e-r0},

@code{arm946e},

@code{arm946e-s},

@code{arm966e-r0},

@code{arm966e},

@code{arm966e-s},

@code{arm968e-s},

@code{arm10t},

@code{arm10tdmi},

@code{arm10e},

@code{arm1020},

@code{arm1020t},

@code{arm1020e},

@code{arm1022e},

@code{arm1026ej-s},

@code{fa606te} (Faraday FA606TE processor),

@code{fa616te} (Faraday FA616TE processor),

@code{fa626te} (Faraday FA626TE processor),

@code{fmp626} (Faraday FMP626 processor),

@code{fa726te} (Faraday FA726TE processor),

@code{arm1136j-s},

@code{arm1136jf-s},

@code{arm1156t2-s},

@code{arm1156t2f-s},

@code{arm1176jz-s},

@code{arm1176jzf-s},

@code{mpcore},

@code{mpcorenovfp},

@code{cortex-a5},

@code{cortex-a7},

@code{cortex-a8},

@code{cortex-a9},

@code{cortex-a15},

@code{cortex-r4},

@code{cortex-r4f},

@code{cortex-m4},

@code{cortex-m3},

@code{cortex-m1},

@code{cortex-m0},

@code{ep9312} (ARM920 with Cirrus Maverick coprocessor),

@code{i80200} (Intel XScale processor)

@code{iwmmxt} (Intel(r) XScale processor with Wireless MMX(tm) technology coprocessor)

and

@code{xscale}.

The special name @code{all} may be used to allow the

assembler to accept instructions valid for any ARM processor.

In addition to the basic instruction set, the assembler can be told to

accept various extension mnemonics that extend the processor using the

co-processor instruction space.  For example, @code{-mcpu=arm920+maverick}

is equivalent to specifying @code{-mcpu=ep9312}.

Multiple extensions may be specified, separated by a @code{+}.  The

extensions should be specified in ascending alphabetical order.

Some extensions may be restricted to particular architectures; this is

documented in the list of extensions below.

Extension mnemonics may also be removed from those the assembler accepts.

This is done be prepending @code{no} to the option that adds the extension.

Extensions that are removed should be listed after all extensions which have

been added, again in ascending alphabetical order.  For example,

@code{-mcpu=ep9312+nomaverick} is equivalent to specifying @code{-mcpu=arm920}.

The following extensions are currently supported:

@code{idiv}, (Integer Divide Extensions for v7-A and v7-R architectures),

@code{iwmmxt},

@code{iwmmxt2},

@code{maverick},

@code{mp} (Multiprocessing Extensions for v7-A and v7-R architectures),

@code{os} (Operating System for v6M architecture),

@code{sec} (Security Extensions for v6K and v7-A architectures),

@code{virt} (Virtualization Extensions for v7-A architecture, implies

@code{idiv}),

and

@code{xscale}.

@cindex @code{-march=} command line option, ARM

@item -march=@var{architecture}[+@var{extension}@dots{}]

This option specifies the target architecture.  The assembler will issue

an error message if an attempt is made to assemble an instruction which

will not execute on the target architecture.  The following architecture

names are recognized:

@code{armv1},

@code{armv2},

@code{armv2a},

@code{armv2s},

@code{armv3},

@code{armv3m},

@code{armv4},

@code{armv4xm},

@code{armv4t},

@code{armv4txm},

@code{armv5},

@code{armv5t},

@code{armv5txm},

@code{armv5te},

@code{armv5texp},

@code{armv6},

@code{armv6j},

@code{armv6k},

@code{armv6z},

@code{armv6zk},

@code{armv6-m},

@code{armv6s-m},

@code{armv7},

@code{armv7-a},

@code{armv7-r},

@code{armv7-m},

@code{armv7e-m},

@code{iwmmxt}

and

@code{xscale}.

If both @code{-mcpu} and

@code{-march} are specified, the assembler will use

the setting for @code{-mcpu}.

The architecture option can be extended with the same instruction set

extension options as the @code{-mcpu} option.

@cindex @code{-mfpu=} command line option, ARM

@item -mfpu=@var{floating-point-format}

This option specifies the floating point format to assemble for.  The

assembler will issue an error message if an attempt is made to assemble

an instruction which will not execute on the target floating point unit.

The following format options are recognized:

@code{softfpa},

@code{fpe},

@code{fpe2},

@code{fpe3},

@code{fpa},

@code{fpa10},

@code{fpa11},

@code{arm7500fe},

@code{softvfp},

@code{softvfp+vfp},

@code{vfp},

@code{vfp10},

@code{vfp10-r0},

@code{vfp9},

@code{vfpxd},

@code{vfpv2},

@code{vfpv3},

@code{vfpv3-fp16},

@code{vfpv3-d16},

@code{vfpv3-d16-fp16},

@code{vfpv3xd},

@code{vfpv3xd-d16},

@code{vfpv4},

@code{vfpv4-d16},

@code{fpv4-sp-d16},

@code{arm1020t},

@code{arm1020e},

@code{arm1136jf-s},

@code{maverick},

@code{neon},

and

@code{neon-vfpv4}.

In addition to determining which instructions are assembled, this option

also affects the way in which the @code{.double} assembler directive behaves

when assembling little-endian code.

The default is dependent on the processor selected.  For Architecture 5 or

later, the default is to assembler for VFP instructions; for earlier

architectures the default is to assemble for FPA instructions.

@cindex @code{-mthumb} command line option, ARM

@item -mthumb

This option specifies that the assembler should start assembling Thumb

instructions; that is, it should behave as though the file starts with a

@code{.code 16} directive.

@cindex @code{-mthumb-interwork} command line option, ARM

@item -mthumb-interwork

This option specifies that the output generated by the assembler should

be marked as supporting interworking.

@cindex @code{-mimplicit-it} command line option, ARM

@item -mimplicit-it=never

@itemx -mimplicit-it=always

@itemx -mimplicit-it=arm

@itemx -mimplicit-it=thumb

The @code{-mimplicit-it} option controls the behavior of the assembler when

conditional instructions are not enclosed in IT blocks.

There are four possible behaviors.

If @code{never} is specified, such constructs cause a warning in ARM

code and an error in Thumb-2 code.

If @code{always} is specified, such constructs are accepted in both

ARM and Thumb-2 code, where the IT instruction is added implicitly.

If @code{arm} is specified, such constructs are accepted in ARM code

and cause an error in Thumb-2 code.

If @code{thumb} is specified, such constructs cause a warning in ARM

code and are accepted in Thumb-2 code.  If you omit this option, the

behavior is equivalent to @code{-mimplicit-it=arm}.

@cindex @code{-mapcs-26} command line option, ARM

@cindex @code{-mapcs-32} command line option, ARM

@item -mapcs-26

@itemx -mapcs-32

These options specify that the output generated by the assembler should

be marked as supporting the indicated version of the Arm Procedure.

Calling Standard.

@cindex @code{-matpcs} command line option, ARM

@item -matpcs

This option specifies that the output generated by the assembler should

be marked as supporting the Arm/Thumb Procedure Calling Standard.  If

enabled this option will cause the assembler to create an empty

debugging section in the object file called .arm.atpcs.  Debuggers can

use this to determine the ABI being used by.

@cindex @code{-mapcs-float} command line option, ARM

@item -mapcs-float

This indicates the floating point variant of the APCS should be

used.  In this variant floating point arguments are passed in FP

registers rather than integer registers.

@cindex @code{-mapcs-reentrant} command line option, ARM

@item -mapcs-reentrant

This indicates that the reentrant variant of the APCS should be used.

This variant supports position independent code.

@cindex @code{-mfloat-abi=} command line option, ARM

@item -mfloat-abi=@var{abi}

This option specifies that the output generated by the assembler should be

marked as using specified floating point ABI.

The following values are recognized:

@code{soft},

@code{softfp}

and

@code{hard}.

@cindex @code{-eabi=} command line option, ARM

@item -meabi=@var{ver}

This option specifies which EABI version the produced object files should

conform to.

The following values are recognized:

@code{gnu},

@code{4}

and

@code{5}.

@cindex @code{-EB} command line option, ARM

@item -EB

This option specifies that the output generated by the assembler should

be marked as being encoded for a big-endian processor.

@cindex @code{-EL} command line option, ARM

@item -EL

This option specifies that the output generated by the assembler should

be marked as being encoded for a little-endian processor.

@cindex @code{-k} command line option, ARM

@cindex PIC code generation for ARM

@item -k

This option specifies that the output of the assembler should be marked

as position-independent code (PIC).

@cindex @code{--fix-v4bx} command line option, ARM

@item --fix-v4bx

Allow @code{BX} instructions in ARMv4 code.  This is intended for use with

the linker option of the same name.

@cindex @code{-mwarn-deprecated} command line option, ARM

@item -mwarn-deprecated

@itemx -mno-warn-deprecated

Enable or disable warnings about using deprecated options or

features.  The default is to warn.

@end table

@node ARM Syntax

@section Syntax

@menu

* ARM-Instruction-Set::      Instruction Set

* ARM-Chars::                Special Characters

* ARM-Regs::                 Register Names

* ARM-Relocations::          Relocations

* ARM-Neon-Alignment::       NEON Alignment Specifiers

@end menu

@node ARM-Instruction-Set

@subsection Instruction Set Syntax

Two slightly different syntaxes are support for ARM and THUMB

instructions.  The default, @code{divided}, uses the old style where

ARM and THUMB instructions had their own, separate syntaxes.  The new,

@code{unified} syntax, which can be selected via the @code{.syntax}

directive, and has the following main features:

@table @bullet

@item

Immediate operands do not require a @code{#} prefix.

@item

The @code{IT} instruction may appear, and if it does it is validated

against subsequent conditional affixes.  In ARM mode it does not

generate machine code, in THUMB mode it does.

@item

For ARM instructions the conditional affixes always appear at the end

of the instruction.  For THUMB instructions conditional affixes can be

used, but only inside the scope of an @code{IT} instruction.

@item

All of the instructions new to the V6T2 architecture (and later) are

available.  (Only a few such instructions can be written in the

@code{divided} syntax).

@item

The @code{.N} and @code{.W} suffixes are recognized and honored.

@item

All instructions set the flags if and only if they have an @code{s}

affix.

@end table

@node ARM-Chars

@subsection Special Characters

@cindex line comment character, ARM

@cindex ARM line comment character

The presence of a @samp{@@} anywhere on a line indicates the start of

a comment that extends to the end of that line.

If a @samp{#} appears as the first character of a line then the whole

line is treated as a comment, but in this case the line could also be

a logical line number directive (@pxref{Comments}) or a preprocessor

control command (@pxref{Preprocessing}).

@cindex line separator, ARM

@cindex statement separator, ARM

@cindex ARM line separator

The @samp{;} character can be used instead of a newline to separate

statements.

@cindex immediate character, ARM

@cindex ARM immediate character

Either @samp{#} or @samp{$} can be used to indicate immediate operands.

@cindex identifiers, ARM

@cindex ARM identifiers

*TODO* Explain about /data modifier on symbols.

@node ARM-Regs

@subsection Register Names

@cindex ARM register names

@cindex register names, ARM

*TODO* Explain about ARM register naming, and the predefined names.

@node ARM-Neon-Alignment

@subsection NEON Alignment Specifiers

@cindex alignment for NEON instructions

Some NEON load/store instructions allow an optional address

alignment qualifier.

The ARM documentation specifies that this is indicated by

@samp{@@ @var{align}}. However GAS already interprets

the @samp{@@} character as a "line comment" start,

so @samp{: @var{align}} is used instead.  For example:

@smallexample

        vld1.8 @{q0@}, [r0, :128]

@end smallexample

@node ARM Floating Point

@section Floating Point

@cindex floating point, ARM (@sc{ieee})

@cindex ARM floating point (@sc{ieee})

The ARM family uses @sc{ieee} floating-point numbers.

@node ARM-Relocations

@subsection ARM relocation generation

@cindex data relocations, ARM

@cindex ARM data relocations

Specific data relocations can be generated by putting the relocation name

in parentheses after the symbol name.  For example:

@smallexample

        .word foo(TARGET1)

@end smallexample

This will generate an @samp{R_ARM_TARGET1} relocation against the symbol

@var{foo}.

The following relocations are supported:

@code{GOT},

@code{GOTOFF},

@code{TARGET1},

@code{TARGET2},

@code{SBREL},

@code{TLSGD},

@code{TLSLDM},

@code{TLSLDO},

@code{TLSDESC},

@code{TLSCALL},

@code{GOTTPOFF},

@code{GOT_PREL}

and

@code{TPOFF}.

For compatibility with older toolchains the assembler also accepts

@code{(PLT)} after branch targets.  On legacy targets this will

generate the deprecated @samp{R_ARM_PLT32} relocation.  On EABI

targets it will encode either the @samp{R_ARM_CALL} or

@samp{R_ARM_JUMP24} relocation, as appropriate.

@cindex MOVW and MOVT relocations, ARM

Relocations for @samp{MOVW} and @samp{MOVT} instructions can be generated

by prefixing the value with @samp{#:lower16:} and @samp{#:upper16}

respectively.  For example to load the 32-bit address of foo into r0:

@smallexample

        MOVW r0, #:lower16:foo

        MOVT r0, #:upper16:foo

@end smallexample

@node ARM Directives

@section ARM Machine Directives

@cindex machine directives, ARM

@cindex ARM machine directives

@table @code

@c AAAAAAAAAAAAAAAAAAAAAAAAA

@cindex @code{.2byte} directive, ARM

@cindex @code{.4byte} directive, ARM

@cindex @code{.8byte} directive, ARM

@item .2byte @var{expression} [, @var{expression}]*

@itemx .4byte @var{expression} [, @var{expression}]*

@itemx .8byte @var{expression} [, @var{expression}]*

These directives write 2, 4 or 8 byte values to the output section.

@cindex @code{.align} directive, ARM

@item .align @var{expression} [, @var{expression}]

This is the generic @var{.align} directive.  For the ARM however if the

first argument is zero (ie no alignment is needed) the assembler will

behave as if the argument had been 2 (ie pad to the next four byte

boundary).  This is for compatibility with ARM's own assembler.

@cindex @code{.arch} directive, ARM

@item .arch @var{name}

Select the target architecture.  Valid values for @var{name} are the same as

for the @option{-march} commandline option.

Specifying @code{.arch} clears any previously selected architecture

extensions.

@cindex @code{.arch_extension} directive, ARM

@item .arch_extension @var{name}

Add or remove an architecture extension to the target architecture.  Valid

values for @var{name} are the same as those accepted as architectural

extensions by the @option{-mcpu} commandline option.

@code{.arch_extension} may be used multiple times to add or remove extensions

incrementally to the architecture being compiled for.

@cindex @code{.arm} directive, ARM

@item .arm

This performs the same action as @var{.code 32}.

@anchor{arm_pad}

@cindex @code{.pad} directive, ARM

@item .pad #@var{count}

Generate unwinder annotations for a stack adjustment of @var{count} bytes.

A positive value indicates the function prologue allocated stack space by

decrementing the stack pointer.

@c BBBBBBBBBBBBBBBBBBBBBBBBBB

@cindex @code{.bss} directive, ARM

@item .bss

This directive switches to the @code{.bss} section.

@c CCCCCCCCCCCCCCCCCCCCCCCCCC

@cindex @code{.cantunwind} directive, ARM

@item .cantunwind

Prevents unwinding through the current function.  No personality routine

or exception table data is required or permitted.

@cindex @code{.code} directive, ARM

@item .code @code{[16|32]}

This directive selects the instruction set being generated. The value 16

selects Thumb, with the value 32 selecting ARM.

@cindex @code{.cpu} directive, ARM

@item .cpu @var{name}

Select the target processor.  Valid values for @var{name} are the same as

for the @option{-mcpu} commandline option.

Specifying @code{.cpu} clears any previously selected architecture

extensions.

@c DDDDDDDDDDDDDDDDDDDDDDDDDD

@cindex @code{.dn} and @code{.qn} directives, ARM

@item @var{name} .dn @var{register name} [@var{.type}] [[@var{index}]]

@itemx @var{name} .qn @var{register name} [@var{.type}] [[@var{index}]]

The @code{dn} and @code{qn} directives are used to create typed

and/or indexed register aliases for use in Advanced SIMD Extension

(Neon) instructions.  The former should be used to create aliases

of double-precision registers, and the latter to create aliases of

quad-precision registers.

If these directives are used to create typed aliases, those aliases can

be used in Neon instructions instead of writing types after the mnemonic

or after each operand.  For example:

@smallexample

        x .dn d2.f32

        y .dn d3.f32

        z .dn d4.f32[1]

        vmul x,y,z

@end smallexample

This is equivalent to writing the following:

@smallexample

        vmul.f32 d2,d3,d4[1]

@end smallexample

Aliases created using @code{dn} or @code{qn} can be destroyed using

@code{unreq}.

@c EEEEEEEEEEEEEEEEEEEEEEEEEE

@cindex @code{.eabi_attribute} directive, ARM

@item .eabi_attribute @var{tag}, @var{value}

Set the EABI object attribute @var{tag} to @var{value}.

The @var{tag} is either an attribute number, or one of the following:

@code{Tag_CPU_raw_name}, @code{Tag_CPU_name}, @code{Tag_CPU_arch},

@code{Tag_CPU_arch_profile}, @code{Tag_ARM_ISA_use},

@code{Tag_THUMB_ISA_use}, @code{Tag_FP_arch}, @code{Tag_WMMX_arch},

@code{Tag_Advanced_SIMD_arch}, @code{Tag_PCS_config},

@code{Tag_ABI_PCS_R9_use}, @code{Tag_ABI_PCS_RW_data},

@code{Tag_ABI_PCS_RO_data}, @code{Tag_ABI_PCS_GOT_use},

@code{Tag_ABI_PCS_wchar_t}, @code{Tag_ABI_FP_rounding},

@code{Tag_ABI_FP_denormal}, @code{Tag_ABI_FP_exceptions},

@code{Tag_ABI_FP_user_exceptions}, @code{Tag_ABI_FP_number_model},

@code{Tag_ABI_align_needed}, @code{Tag_ABI_align_preserved},

@code{Tag_ABI_enum_size}, @code{Tag_ABI_HardFP_use},

@code{Tag_ABI_VFP_args}, @code{Tag_ABI_WMMX_args},

@code{Tag_ABI_optimization_goals}, @code{Tag_ABI_FP_optimization_goals},

@code{Tag_compatibility}, @code{Tag_CPU_unaligned_access},

@code{Tag_FP_HP_extension}, @code{Tag_ABI_FP_16bit_format},

@code{Tag_MPextension_use}, @code{Tag_DIV_use},

@code{Tag_nodefaults}, @code{Tag_also_compatible_with},

@code{Tag_conformance}, @code{Tag_T2EE_use},

@code{Tag_Virtualization_use}

The @var{value} is either a @code{number}, @code{"string"}, or

@code{number, "string"} depending on the tag.

Note - the following legacy values are also accepted by @var{tag}:

@code{Tag_VFP_arch}, @code{Tag_ABI_align8_needed},

@code{Tag_ABI_align8_preserved}, @code{Tag_VFP_HP_extension},

@cindex @code{.even} directive, ARM

@item .even

This directive aligns to an even-numbered address.

@cindex @code{.extend} directive, ARM

@cindex @code{.ldouble} directive, ARM

@item .extend  @var{expression} [, @var{expression}]*

@itemx .ldouble  @var{expression} [, @var{expression}]*

These directives write 12byte long double floating-point values to the

output section.  These are not compatible with current ARM processors

or ABIs.

@c FFFFFFFFFFFFFFFFFFFFFFFFFF

@anchor{arm_fnend}

@cindex @code{.fnend} directive, ARM

@item .fnend

Marks the end of a function with an unwind table entry.  The unwind index

table entry is created when this directive is processed.

If no personality routine has been specified then standard personality

routine 0 or 1 will be used, depending on the number of unwind opcodes

required.

@anchor{arm_fnstart}

@cindex @code{.fnstart} directive, ARM

@item .fnstart

Marks the start of a function with an unwind table entry.

@cindex @code{.force_thumb} directive, ARM

@item .force_thumb

This directive forces the selection of Thumb instructions, even if the

target processor does not support those instructions

@cindex @code{.fpu} directive, ARM

@item .fpu @var{name}

Select the floating-point unit to assemble for.  Valid values for @var{name}

are the same as for the @option{-mfpu} commandline option.

@c GGGGGGGGGGGGGGGGGGGGGGGGGG

@c HHHHHHHHHHHHHHHHHHHHHHHHHH

@cindex @code{.handlerdata} directive, ARM

@item .handlerdata

Marks the end of the current function, and the start of the exception table

entry for that function.  Anything between this directive and the

@code{.fnend} directive will be added to the exception table entry.

Must be preceded by a @code{.personality} or @code{.personalityindex}

directive.

@c IIIIIIIIIIIIIIIIIIIIIIIIII

@cindex @code{.inst} directive, ARM

@item .inst @var{opcode} [ , @dots{} ]

@itemx .inst.n @var{opcode} [ , @dots{} ]

@itemx .inst.w @var{opcode} [ , @dots{} ]

Generates the instruction corresponding to the numerical value @var{opcode}.

@code{.inst.n} and @code{.inst.w} allow the Thumb instruction size to be

specified explicitly, overriding the normal encoding rules.

@c JJJJJJJJJJJJJJJJJJJJJJJJJJ

@c KKKKKKKKKKKKKKKKKKKKKKKKKK

@c LLLLLLLLLLLLLLLLLLLLLLLLLL

@item .ldouble  @var{expression} [, @var{expression}]*

See @code{.extend}.

@cindex @code{.ltorg} directive, ARM

@item .ltorg

This directive causes the current contents of the literal pool to be

dumped into the current section (which is assumed to be the .text

section) at the current location (aligned to a word boundary).

@code{GAS} maintains a separate literal pool for each section and each

sub-section.  The @code{.ltorg} directive will only affect the literal

pool of the current section and sub-section.  At the end of assembly

all remaining, un-empty literal pools will automatically be dumped.

Note - older versions of @code{GAS} would dump the current literal

pool any time a section change occurred.  This is no longer done, since

it prevents accurate control of the placement of literal pools.

@c MMMMMMMMMMMMMMMMMMMMMMMMMM

@cindex @code{.movsp} directive, ARM

@item .movsp @var{reg} [, #@var{offset}]

Tell the unwinder that @var{reg} contains an offset from the current

stack pointer.  If @var{offset} is not specified then it is assumed to be

zero.

@c NNNNNNNNNNNNNNNNNNNNNNNNNN

@c OOOOOOOOOOOOOOOOOOOOOOOOOO

@cindex @code{.object_arch} directive, ARM

@item .object_arch @var{name}

Override the architecture recorded in the EABI object attribute section.

Valid values for @var{name} are the same as for the @code{.arch} directive.

Typically this is useful when code uses runtime detection of CPU features.

@c PPPPPPPPPPPPPPPPPPPPPPPPPP

@cindex @code{.packed} directive, ARM

@item .packed  @var{expression} [, @var{expression}]*

This directive writes 12-byte packed floating-point values to the

output section.  These are not compatible with current ARM processors

or ABIs.

@cindex @code{.pad} directive, ARM

@item .pad #@var{count}

Generate unwinder annotations for a stack adjustment of @var{count} bytes.

A positive value indicates the function prologue allocated stack space by

decrementing the stack pointer.

@cindex @code{.personality} directive, ARM

@item .personality @var{name}

Sets the personality routine for the current function to @var{name}.

@cindex @code{.personalityindex} directive, ARM

@item .personalityindex @var{index}

Sets the personality routine for the current function to the EABI standard

routine number @var{index}

@cindex @code{.pool} directive, ARM

@item .pool

This is a synonym for .ltorg.

@c QQQQQQQQQQQQQQQQQQQQQQQQQQ

@c RRRRRRRRRRRRRRRRRRRRRRRRRR

@cindex @code{.req} directive, ARM

@item @var{name} .req @var{register name}

This creates an alias for @var{register name} called @var{name}.  For

example:

@smallexample

        foo .req r0

@end smallexample

@c SSSSSSSSSSSSSSSSSSSSSSSSSS

@anchor{arm_save}

@cindex @code{.save} directive, ARM

@item .save @var{reglist}

Generate unwinder annotations to restore the registers in @var{reglist}.

The format of @var{reglist} is the same as the corresponding store-multiple

instruction.

@smallexample

@exdent @emph{core registers}

  .save @{r4, r5, r6, lr@}

  stmfd sp!, @{r4, r5, r6, lr@}

@exdent @emph{FPA registers}

  .save f4, 2

  sfmfd f4, 2, [sp]!

@exdent @emph{VFP registers}

  .save @{d8, d9, d10@}

  fstmdx sp!, @{d8, d9, d10@}

@exdent @emph{iWMMXt registers}

  .save @{wr10, wr11@}

  wstrd wr11, [sp, #-8]!

  wstrd wr10, [sp, #-8]!

or

  .save wr11

  wstrd wr11, [sp, #-8]!

  .save wr10

  wstrd wr10, [sp, #-8]!

@end smallexample

@anchor{arm_setfp}

@cindex @code{.setfp} directive, ARM

@item .setfp @var{fpreg}, @var{spreg} [, #@var{offset}]

Make all unwinder annotations relative to a frame pointer.  Without this

the unwinder will use offsets from the stack pointer.

The syntax of this directive is the same as the @code{add} or @code{mov}

instruction used to set the frame pointer.  @var{spreg} must be either

@code{sp} or mentioned in a previous @code{.movsp} directive.

@smallexample

.movsp ip

mov ip, sp

@dots{}

.setfp fp, ip, #4

add fp, ip, #4

@end smallexample

@cindex @code{.secrel32} directive, ARM

@item .secrel32 @var{expression} [, @var{expression}]*

This directive emits relocations that evaluate to the section-relative

offset of each expression's symbol.  This directive is only supported

for PE targets.

@cindex @code{.syntax} directive, ARM

@item .syntax [@code{unified} | @code{divided}]

This directive sets the Instruction Set Syntax as described in the

@ref{ARM-Instruction-Set} section.

@c TTTTTTTTTTTTTTTTTTTTTTTTTT

@cindex @code{.thumb} directive, ARM

@item .thumb

This performs the same action as @var{.code 16}.

@cindex @code{.thumb_func} directive, ARM

@item .thumb_func

This directive specifies that the following symbol is the name of a

Thumb encoded function.  This information is necessary in order to allow

the assembler and linker to generate correct code for interworking

between Arm and Thumb instructions and should be used even if

interworking is not going to be performed.  The presence of this

directive also implies @code{.thumb}

This directive is not neccessary when generating EABI objects.  On these

targets the encoding is implicit when generating Thumb code.

@cindex @code{.thumb_set} directive, ARM

@item .thumb_set

This performs the equivalent of a @code{.set} directive in that it

creates a symbol which is an alias for another symbol (possibly not yet

defined).  This directive also has the added property in that it marks

the aliased symbol as being a thumb function entry point, in the same

way that the @code{.thumb_func} directive does.

@cindex @code{.tlsdescseq} directive, ARM

@item .tlsdescseq @var{tls-variable}

This directive is used to annotate parts of an inlined TLS descriptor

trampoline.  Normally the trampoline is provided by the linker, and

this directive is not needed.

@c UUUUUUUUUUUUUUUUUUUUUUUUUU

@cindex @code{.unreq} directive, ARM

@item .unreq @var{alias-name}

This undefines a register alias which was previously defined using the

@code{req}, @code{dn} or @code{qn} directives.  For example:

@smallexample

        foo .req r0

        .unreq foo

@end smallexample

An error occurs if the name is undefined.  Note - this pseudo op can

be used to delete builtin in register name aliases (eg 'r0').  This

should only be done if it is really necessary.

@cindex @code{.unwind_raw} directive, ARM

@item .unwind_raw @var{offset}, @var{byte1}, @dots{}

Insert one of more arbitary unwind opcode bytes, which are known to adjust

the stack pointer by @var{offset} bytes.

For example @code{.unwind_raw 4, 0xb1, 0x01} is equivalent to

@code{.save @{r0@}}

@c VVVVVVVVVVVVVVVVVVVVVVVVVV

@cindex @code{.vsave} directive, ARM

@item .vsave @var{vfp-reglist}

Generate unwinder annotations to restore the VFP registers in @var{vfp-reglist}

using FLDMD.  Also works for VFPv3 registers

that are to be restored using VLDM.

The format of @var{vfp-reglist} is the same as the corresponding store-multiple

instruction.

@smallexample

@exdent @emph{VFP registers}

  .vsave @{d8, d9, d10@}

  fstmdd sp!, @{d8, d9, d10@}

@exdent @emph{VFPv3 registers}

  .vsave @{d15, d16, d17@}

  vstm sp!, @{d15, d16, d17@}

@end smallexample

Since FLDMX and FSTMX are now deprecated, this directive should be

used in favour of @code{.save} for saving VFP registers for ARMv6 and above.

@c WWWWWWWWWWWWWWWWWWWWWWWWWW

@c XXXXXXXXXXXXXXXXXXXXXXXXXX

@c YYYYYYYYYYYYYYYYYYYYYYYYYY

@c ZZZZZZZZZZZZZZZZZZZZZZZZZZ

@end table

@node ARM Opcodes

@section Opcodes