You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
179 lines
9.0 KiB
HTML
179 lines
9.0 KiB
HTML
4 years ago
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Alignment Output - GNU Compiler Collection (GCC) Internals</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals">
|
||
|
|
<meta name="generator" content="makeinfo 4.13">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="Assembler-Format.html#Assembler-Format" title="Assembler Format">
|
||
|
|
<link rel="prev" href="Exception-Region-Output.html#Exception-Region-Output" title="Exception Region Output">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
Copyright (C) 1988-2015 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with the
|
||
|
|
Invariant Sections being ``Funding Free Software'', the Front-Cover
|
||
|
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
||
|
|
(see below). A copy of the license is included in the section entitled
|
||
|
|
``GNU Free Documentation License''.
|
||
|
|
|
||
|
|
(a) The FSF's Front-Cover Text is:
|
||
|
|
|
||
|
|
A GNU Manual
|
||
|
|
|
||
|
|
(b) The FSF's Back-Cover Text is:
|
||
|
|
|
||
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
||
|
|
software. Copies published by the Free Software Foundation raise
|
||
|
|
funds for GNU development.-->
|
||
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
||
|
|
<style type="text/css"><!--
|
||
|
|
pre.display { font-family:inherit }
|
||
|
|
pre.format { font-family:inherit }
|
||
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallexample { font-size:smaller }
|
||
|
|
pre.smalllisp { font-size:smaller }
|
||
|
|
span.sc { font-variant:small-caps }
|
||
|
|
span.roman { font-family:serif; font-weight:normal; }
|
||
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
||
|
|
--></style>
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<div class="node">
|
||
|
|
<a name="Alignment-Output"></a>
|
||
|
|
<p>
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="Exception-Region-Output.html#Exception-Region-Output">Exception Region Output</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Assembler-Format.html#Assembler-Format">Assembler Format</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h4 class="subsection">17.20.10 Assembler Commands for Alignment</h4>
|
||
|
|
|
||
|
|
<!-- prevent bad page break with this line -->
|
||
|
|
<p>This describes commands for alignment.
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>JUMP_ALIGN</b> (<var>label</var>)<var><a name="index-JUMP_005fALIGN-4737"></a></var><br>
|
||
|
|
<blockquote><p>The alignment (log base 2) to put in front of <var>label</var>, which is
|
||
|
|
a common destination of jumps and has no fallthru incoming edge.
|
||
|
|
|
||
|
|
<p>This macro need not be defined if you don't want any special alignment
|
||
|
|
to be done at such a time. Most machine descriptions do not currently
|
||
|
|
define the macro.
|
||
|
|
|
||
|
|
<p>Unless it's necessary to inspect the <var>label</var> parameter, it is better
|
||
|
|
to set the variable <var>align_jumps</var> in the target's
|
||
|
|
<code>TARGET_OPTION_OVERRIDE</code>. Otherwise, you should try to honor the user's
|
||
|
|
selection in <var>align_jumps</var> in a <code>JUMP_ALIGN</code> implementation.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Target Hook: int <b>TARGET_ASM_JUMP_ALIGN_MAX_SKIP</b> (<var>rtx_insn *label</var>)<var><a name="index-TARGET_005fASM_005fJUMP_005fALIGN_005fMAX_005fSKIP-4738"></a></var><br>
|
||
|
|
<blockquote><p>The maximum number of bytes to skip before <var>label</var> when applying
|
||
|
|
<code>JUMP_ALIGN</code>. This works only if
|
||
|
|
<code>ASM_OUTPUT_MAX_SKIP_ALIGN</code> is defined.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>LABEL_ALIGN_AFTER_BARRIER</b> (<var>label</var>)<var><a name="index-LABEL_005fALIGN_005fAFTER_005fBARRIER-4739"></a></var><br>
|
||
|
|
<blockquote><p>The alignment (log base 2) to put in front of <var>label</var>, which follows
|
||
|
|
a <code>BARRIER</code>.
|
||
|
|
|
||
|
|
<p>This macro need not be defined if you don't want any special alignment
|
||
|
|
to be done at such a time. Most machine descriptions do not currently
|
||
|
|
define the macro.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Target Hook: int <b>TARGET_ASM_LABEL_ALIGN_AFTER_BARRIER_MAX_SKIP</b> (<var>rtx_insn *label</var>)<var><a name="index-TARGET_005fASM_005fLABEL_005fALIGN_005fAFTER_005fBARRIER_005fMAX_005fSKIP-4740"></a></var><br>
|
||
|
|
<blockquote><p>The maximum number of bytes to skip before <var>label</var> when applying
|
||
|
|
<code>LABEL_ALIGN_AFTER_BARRIER</code>. This works only if
|
||
|
|
<code>ASM_OUTPUT_MAX_SKIP_ALIGN</code> is defined.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>LOOP_ALIGN</b> (<var>label</var>)<var><a name="index-LOOP_005fALIGN-4741"></a></var><br>
|
||
|
|
<blockquote><p>The alignment (log base 2) to put in front of <var>label</var> that heads
|
||
|
|
a frequently executed basic block (usually the header of a loop).
|
||
|
|
|
||
|
|
<p>This macro need not be defined if you don't want any special alignment
|
||
|
|
to be done at such a time. Most machine descriptions do not currently
|
||
|
|
define the macro.
|
||
|
|
|
||
|
|
<p>Unless it's necessary to inspect the <var>label</var> parameter, it is better
|
||
|
|
to set the variable <code>align_loops</code> in the target's
|
||
|
|
<code>TARGET_OPTION_OVERRIDE</code>. Otherwise, you should try to honor the user's
|
||
|
|
selection in <code>align_loops</code> in a <code>LOOP_ALIGN</code> implementation.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Target Hook: int <b>TARGET_ASM_LOOP_ALIGN_MAX_SKIP</b> (<var>rtx_insn *label</var>)<var><a name="index-TARGET_005fASM_005fLOOP_005fALIGN_005fMAX_005fSKIP-4742"></a></var><br>
|
||
|
|
<blockquote><p>The maximum number of bytes to skip when applying <code>LOOP_ALIGN</code> to
|
||
|
|
<var>label</var>. This works only if <code>ASM_OUTPUT_MAX_SKIP_ALIGN</code> is
|
||
|
|
defined.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>LABEL_ALIGN</b> (<var>label</var>)<var><a name="index-LABEL_005fALIGN-4743"></a></var><br>
|
||
|
|
<blockquote><p>The alignment (log base 2) to put in front of <var>label</var>.
|
||
|
|
If <code>LABEL_ALIGN_AFTER_BARRIER</code> / <code>LOOP_ALIGN</code> specify a different alignment,
|
||
|
|
the maximum of the specified values is used.
|
||
|
|
|
||
|
|
<p>Unless it's necessary to inspect the <var>label</var> parameter, it is better
|
||
|
|
to set the variable <code>align_labels</code> in the target's
|
||
|
|
<code>TARGET_OPTION_OVERRIDE</code>. Otherwise, you should try to honor the user's
|
||
|
|
selection in <code>align_labels</code> in a <code>LABEL_ALIGN</code> implementation.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Target Hook: int <b>TARGET_ASM_LABEL_ALIGN_MAX_SKIP</b> (<var>rtx_insn *label</var>)<var><a name="index-TARGET_005fASM_005fLABEL_005fALIGN_005fMAX_005fSKIP-4744"></a></var><br>
|
||
|
|
<blockquote><p>The maximum number of bytes to skip when applying <code>LABEL_ALIGN</code>
|
||
|
|
to <var>label</var>. This works only if <code>ASM_OUTPUT_MAX_SKIP_ALIGN</code>
|
||
|
|
is defined.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_OUTPUT_SKIP</b> (<var>stream, nbytes</var>)<var><a name="index-ASM_005fOUTPUT_005fSKIP-4745"></a></var><br>
|
||
|
|
<blockquote><p>A C statement to output to the stdio stream <var>stream</var> an assembler
|
||
|
|
instruction to advance the location counter by <var>nbytes</var> bytes.
|
||
|
|
Those bytes should be zero when loaded. <var>nbytes</var> will be a C
|
||
|
|
expression of type <code>unsigned HOST_WIDE_INT</code>.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_NO_SKIP_IN_TEXT</b><var><a name="index-ASM_005fNO_005fSKIP_005fIN_005fTEXT-4746"></a></var><br>
|
||
|
|
<blockquote><p>Define this macro if <code>ASM_OUTPUT_SKIP</code> should not be used in the
|
||
|
|
text 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 bytes
|
||
|
|
produces no-op instructions rather than zeros when used in the text
|
||
|
|
section.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_OUTPUT_ALIGN</b> (<var>stream, power</var>)<var><a name="index-ASM_005fOUTPUT_005fALIGN-4747"></a></var><br>
|
||
|
|
<blockquote><p>A C statement to output to the stdio stream <var>stream</var> an assembler
|
||
|
|
command to advance the location counter to a multiple of 2 to the
|
||
|
|
<var>power</var> bytes. <var>power</var> will be a C expression of type <code>int</code>.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_OUTPUT_ALIGN_WITH_NOP</b> (<var>stream, power</var>)<var><a name="index-ASM_005fOUTPUT_005fALIGN_005fWITH_005fNOP-4748"></a></var><br>
|
||
|
|
<blockquote><p>Like <code>ASM_OUTPUT_ALIGN</code>, except that the “nop” instruction is used
|
||
|
|
for padding, if necessary.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Macro: <b>ASM_OUTPUT_MAX_SKIP_ALIGN</b> (<var>stream, power, max_skip</var>)<var><a name="index-ASM_005fOUTPUT_005fMAX_005fSKIP_005fALIGN-4749"></a></var><br>
|
||
|
|
<blockquote><p>A C statement to output to the stdio stream <var>stream</var> an assembler
|
||
|
|
command to advance the location counter to a multiple of 2 to the
|
||
|
|
<var>power</var> bytes, but only if <var>max_skip</var> or fewer bytes are needed to
|
||
|
|
satisfy the alignment request. <var>power</var> and <var>max_skip</var> will be
|
||
|
|
a C expression of type <code>int</code>.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|