Subversion Repositories openrisc_2011-10-31

@c Copyright 2002, 2004, 2005 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 MSP430-Dependent

@chapter MSP 430 Dependent Features

@end ifset

@ifclear GENERIC

@node Machine Dependencies

@chapter MSP 430 Dependent Features

@end ifclear

@cindex MSP 430 support

@cindex 430 support

@menu

* MSP430 Options::              Options

* MSP430 Syntax::               Syntax

* MSP430 Floating Point::       Floating Point

* MSP430 Directives::           MSP 430 Machine Directives

* MSP430 Opcodes::              Opcodes

* MSP430 Profiling Capability:: Profiling Capability

@end menu

@node MSP430 Options

@section Options

@cindex MSP 430 options (none)

@cindex options for MSP430 (none)

@table @code

@item -m

select the mpu arch. Currently has no effect.

@item -mP

enables polymorph instructions handler.

@item -mQ

enables relaxation at assembly time. DANGEROUS!

@end table

@node MSP430 Syntax

@section Syntax

@menu

* MSP430-Macros::               Macros

* MSP430-Chars::                Special Characters

* MSP430-Regs::                 Register Names

* MSP430-Ext::                  Assembler Extensions

@end menu

@node MSP430-Macros

@subsection Macros

@cindex Macros, MSP 430

@cindex MSP 430 macros

The macro syntax used on the MSP 430 is like that described in the MSP

430 Family Assembler Specification.  Normal @code{@value{AS}}

macros should still work.

Additional built-in macros are:

@table @code

@item llo(exp)

Extracts least significant word from 32-bit expression 'exp'.

@item lhi(exp)

Extracts most significant word from 32-bit expression 'exp'.

@item hlo(exp)

Extracts 3rd word from 64-bit expression 'exp'.

@item   hhi(exp)

Extracts 4rd word from 64-bit expression 'exp'.

@end table

They normally being used as an immediate source operand.

@smallexample

    mov #llo(1), r10    ;       == mov  #1, r10

    mov #lhi(1), r10    ;       == mov  #0, r10

@end smallexample

@node MSP430-Chars

@subsection Special Characters

@cindex line comment character, MSP 430

@cindex MSP 430 line comment character

@samp{;} is the line comment character.

@cindex identifiers, MSP 430

@cindex MSP 430 identifiers

The character @samp{$} in jump instructions indicates current location and

implemented only for TI syntax compatibility.

@node MSP430-Regs

@subsection Register Names

@cindex MSP 430 register names

@cindex register names, MSP 430

General-purpose registers are represented by predefined symbols of the

form @samp{r@var{N}} (for global registers), where @var{N} represents

a number between @code{0} and @code{15}.  The leading

letters may be in either upper or lower case; for example, @samp{r13}

and @samp{R7} are both valid register names.

@cindex special purpose registers, MSP 430

Register names @samp{PC}, @samp{SP} and @samp{SR} cannot be used as register names

and will be treated as variables. Use @samp{r0}, @samp{r1}, and @samp{r2} instead.

@node MSP430-Ext

@subsection Assembler Extensions

@cindex MSP430 Assembler Extensions

@table @code

@item @@rN

As destination operand being treated as @samp{0(rn)}

@item 0(rN)

As source operand being treated as @samp{@@rn}

@item jCOND +N

Skips next N bytes followed by jump instruction and equivalent to

@samp{jCOND $+N+2}

@end table

Also, there are some instructions, which cannot be found in other assemblers.

These are branch instructions, which has different opcodes upon jump distance.

They all got PC relative addressing mode.

@table @code

@item   beq label

A polymorph instruction which is @samp{jeq label} in case if jump distance

within allowed range for cpu's jump instruction. If not, this unrolls into

a sequence of

@smallexample

  jne $+6

  br  label

@end smallexample

@item bne label

A polymorph instruction which is @samp{jne label} or @samp{jeq +4; br label}

@item blt label

A polymorph instruction which is @samp{jl label} or @samp{jge +4; br label}

@item bltn label

A polymorph instruction which is @samp{jn label} or @samp{jn +2; jmp +4; br label}

@item bltu label

A polymorph instruction which is @samp{jlo label} or @samp{jhs +2; br label}

@item bge label

A polymorph instruction which is @samp{jge label} or @samp{jl +4; br label}

@item bgeu label

A polymorph instruction which is @samp{jhs label} or @samp{jlo +4; br label}

@item bgt label

A polymorph instruction which is @samp{jeq +2; jge label} or @samp{jeq +6; jl  +4; br label}

@item bgtu label

A polymorph instruction which is @samp{jeq +2; jhs label} or @samp{jeq +6; jlo +4; br label}

@item bleu label

A polymorph instruction which is @samp{jeq label; jlo label} or @samp{jeq +2; jhs +4; br label}

@item ble label

A polymorph instruction which is @samp{jeq label; jl  label} or @samp{jeq +2; jge +4; br label}

@item jump label

A polymorph instruction which is @samp{jmp label} or @samp{br label}

@end table

@node MSP430 Floating Point

@section Floating Point

@cindex floating point, MSP 430 (@sc{ieee})

@cindex MSP 430 floating point (@sc{ieee})

The MSP 430 family uses @sc{ieee} 32-bit floating-point numbers.

@node MSP430 Directives

@section MSP 430 Machine Directives

@cindex machine directives, MSP 430

@cindex MSP 430 machine directives

@table @code

@cindex @code{file} directive, MSP 430

@item .file

This directive is ignored; it is accepted for compatibility with other

MSP 430 assemblers.

@quotation

@emph{Warning:} in other versions of the @sc{gnu} assembler, @code{.file} is

used for the directive called @code{.app-file} in the MSP 430 support.

@end quotation

@cindex @code{line} directive, MSP 430

@item .line

This directive is ignored; it is accepted for compatibility with other

MSP 430 assemblers.

@cindex @code{sect} directive, MSP 430

@item .arch

Currently this directive is ignored; it is accepted for compatibility with other

MSP 430 assemblers.

@cindex @code{profiler} directive, MSP 430

@item .profiler

This directive instructs assembler to add new profile entry to the object file.

@end table

@node MSP430 Opcodes

@section Opcodes

@cindex MSP 430 opcodes

@cindex opcodes for MSP 430

@code{@value{AS}} implements all the standard MSP 430 opcodes.  No

additional pseudo-instructions are needed on this family.

For information on the 430 machine instruction set, see @cite{MSP430

User's Manual, document slau049d}, Texas Instrument, Inc.

@node MSP430 Profiling Capability

@section Profiling Capability

@cindex MSP 430 profiling capability

@cindex profiling capability for MSP 430

It is a performance hit to use gcc's profiling approach for this tiny target.

Even more -- jtag hardware facility does not perform any profiling functions.

However we've got gdb's built-in simulator where we can do anything.

We define new section @samp{.profiler} which holds all profiling information.

We define new pseudo operation @samp{.profiler} which will instruct assembler to

add new profile entry to the object file. Profile should take place at the

present address.

Pseudo operation format:

@samp{.profiler flags,function_to_profile [, cycle_corrector, extra]}

where:

@table @code

@table @code

@samp{flags} is a combination of the following characters:

@item  s

function entry

@item  x

function exit

@item  i

function is in init section

@item  f

function is in fini section

@item  l

library call

@item  c

libc standard call

@item  d

stack value demand

@item  I

interrupt service routine

@item  P

prologue start

@item  p

prologue end

@item  E

epilogue start

@item  e

epilogue end

@item  j

long jump / sjlj unwind

@item  a

an arbitrary code fragment

@item t

extra parameter saved (a constant value like frame size)

@end table

@item function_to_profile

a function address

@item cycle_corrector

a value which should be added to the cycle counter, zero if omitted.

@item extra

any extra parameter, zero if omitted.

@end table

For example:

@smallexample

.global fxx

.type fxx,@@function

fxx:

.LFrameOffset_fxx=0x08

.profiler "scdP", fxx     ; function entry.

                          ; we also demand stack value to be saved

  push r11

  push r10

  push r9

  push r8

.profiler "cdpt",fxx,0, .LFrameOffset_fxx  ; check stack value at this point

                                          ; (this is a prologue end)

                                          ; note, that spare var filled with

                                          ; the farme size

  mov r15,r8

...

.profiler cdE,fxx         ; check stack

  pop r8

  pop r9

  pop r10

  pop r11

.profiler xcde,fxx,3      ; exit adds 3 to the cycle counter

  ret                     ; cause 'ret' insn takes 3 cycles

@end smallexample