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17.22.10 Assembler Commands for Alignment ¶

This describes commands for alignment.

Macro:JUMP_ALIGN(label) ¶

The alignment (log base 2) to put in front oflabel, which isa common destination of jumps and has no fallthru incoming edge.

This macro need not be defined if you don’t want any special alignmentto be done at such a time. Most machine descriptions do not currentlydefine the macro.

Unless it’s necessary to inspect thelabel parameter, it is betterto set the variablealign_jumps in the target’sTARGET_OPTION_OVERRIDE. Otherwise, you should try to honor the user’sselection inalign_jumps in aJUMP_ALIGN implementation.

Macro:LABEL_ALIGN_AFTER_BARRIER(label) ¶

The alignment (log base 2) to put in front oflabel, which followsaBARRIER.

This macro need not be defined if you don’t want any special alignmentto be done at such a time. Most machine descriptions do not currentlydefine the macro.

Macro:LOOP_ALIGN(label) ¶

The alignment (log base 2) to put in front oflabel that headsa frequently executed basic block (usually the header of a loop).

This macro need not be defined if you don’t want any special alignmentto be done at such a time. Most machine descriptions do not currentlydefine the macro.

Unless it’s necessary to inspect thelabel parameter, it is betterto set the variablealign_loops in the target’sTARGET_OPTION_OVERRIDE. Otherwise, you should try to honor the user’sselection inalign_loops in aLOOP_ALIGN implementation.

Macro:LABEL_ALIGN(label) ¶

The alignment (log base 2) to put in front oflabel.IfLABEL_ALIGN_AFTER_BARRIER /LOOP_ALIGN specify a different alignment,the maximum of the specified values is used.

Unless it’s necessary to inspect thelabel parameter, it is betterto set the variablealign_labels in the target’sTARGET_OPTION_OVERRIDE. Otherwise, you should try to honor the user’sselection inalign_labels in aLABEL_ALIGN implementation.

Macro:ASM_OUTPUT_SKIP(stream,nbytes) ¶

A C statement to output to the stdio streamstream an assemblerinstruction to advance the location counter bynbytes bytes.Those bytes should be zero when loaded.nbytes will be a Cexpression of typeunsigned HOST_WIDE_INT.

Macro:ASM_NO_SKIP_IN_TEXT ¶

Define this macro ifASM_OUTPUT_SKIP should not be used in thetext section because it fails to put zeros in the bytes that are skipped.This is true on many Unix systems, where the pseudo–op to skip bytesproduces no-op instructions rather than zeros when used in the textsection.

Macro:ASM_OUTPUT_ALIGN(stream,power) ¶

A C statement to output to the stdio streamstream an assemblercommand to advance the location counter to a multiple of 2 to thepower bytes.power will be a C expression of typeint.

Macro:ASM_OUTPUT_ALIGN_WITH_NOP(stream,power) ¶

LikeASM_OUTPUT_ALIGN, except that the “nop” instruction is usedfor padding, if necessary.

Macro:ASM_OUTPUT_MAX_SKIP_ALIGN(stream,power,max_skip) ¶

A C statement to output to the stdio streamstream an assemblercommand to advance the location counter to a multiple of 2 to thepower bytes, but only ifmax_skip or fewer bytes are needed tosatisfy the alignment request.power andmax_skip will bea C expression of typeint.

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