102 lines
5.5 KiB
HTML
102 lines
5.5 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Bundle directives - Using as</title>
|
|
<meta http-equiv="Content-Type" content="text/html">
|
|
<meta name="description" content="Using as">
|
|
<meta name="generator" content="makeinfo 4.13">
|
|
<link title="Top" rel="start" href="index.html#Top">
|
|
<link rel="up" href="Pseudo-Ops.html#Pseudo-Ops" title="Pseudo Ops">
|
|
<link rel="prev" href="Balign.html#Balign" title="Balign">
|
|
<link rel="next" href="Byte.html#Byte" title="Byte">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
This file documents the GNU Assembler "as".
|
|
|
|
Copyright (C) 1991-2019 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 no Invariant Sections, with no Front-Cover Texts, and with no
|
|
Back-Cover Texts. A copy of the license is included in the
|
|
section entitled ``GNU Free Documentation License''.
|
|
|
|
-->
|
|
<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="Bundle-directives"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Byte.html#Byte">Byte</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="Balign.html#Balign">Balign</a>,
|
|
Up: <a rel="up" accesskey="u" href="Pseudo-Ops.html#Pseudo-Ops">Pseudo Ops</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h3 class="section">7.8 Bundle directives</h3>
|
|
|
|
<h4 class="subsection">7.8.1 <code>.bundle_align_mode </code><var>abs-expr</var></h4>
|
|
|
|
<p><a name="index-g_t_0040code_007bbundle_005falign_005fmode_007d-directive-292"></a><a name="index-bundle-293"></a><a name="index-instruction-bundle-294"></a><a name="index-aligned-instruction-bundle-295"></a><code>.bundle_align_mode</code> enables or disables <dfn>aligned instruction
|
|
bundle</dfn> mode. In this mode, sequences of adjacent instructions are grouped
|
|
into fixed-sized <dfn>bundles</dfn>. If the argument is zero, this mode is
|
|
disabled (which is the default state). If the argument it not zero, it
|
|
gives the size of an instruction bundle as a power of two (as for the
|
|
<code>.p2align</code> directive, see <a href="P2align.html#P2align">P2align</a>).
|
|
|
|
<p>For some targets, it's an ABI requirement that no instruction may span a
|
|
certain aligned boundary. A <dfn>bundle</dfn> is simply a sequence of
|
|
instructions that starts on an aligned boundary. For example, if
|
|
<var>abs-expr</var> is <code>5</code> then the bundle size is 32, so each aligned
|
|
chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
|
|
effect, no single instruction may span a boundary between bundles. If an
|
|
instruction would start too close to the end of a bundle for the length of
|
|
that particular instruction to fit within the bundle, then the space at the
|
|
end of that bundle is filled with no-op instructions so the instruction
|
|
starts in the next bundle. As a corollary, it's an error if any single
|
|
instruction's encoding is longer than the bundle size.
|
|
|
|
<h4 class="subsection">7.8.2 <code>.bundle_lock</code> and <code>.bundle_unlock</code></h4>
|
|
|
|
<p><a name="index-g_t_0040code_007bbundle_005flock_007d-directive-296"></a><a name="index-g_t_0040code_007bbundle_005funlock_007d-directive-297"></a>The <code>.bundle_lock</code> and directive <code>.bundle_unlock</code> directives
|
|
allow explicit control over instruction bundle padding. These directives
|
|
are only valid when <code>.bundle_align_mode</code> has been used to enable
|
|
aligned instruction bundle mode. It's an error if they appear when
|
|
<code>.bundle_align_mode</code> has not been used at all, or when the last
|
|
directive was <code>.bundle_align_mode 0</code><!-- /@w -->.
|
|
|
|
<p><a name="index-bundle_002dlocked-298"></a>For some targets, it's an ABI requirement that certain instructions may
|
|
appear only as part of specified permissible sequences of multiple
|
|
instructions, all within the same bundle. A pair of <code>.bundle_lock</code>
|
|
and <code>.bundle_unlock</code> directives define a <dfn>bundle-locked</dfn>
|
|
instruction sequence. For purposes of aligned instruction bundle mode, a
|
|
sequence starting with <code>.bundle_lock</code> and ending with
|
|
<code>.bundle_unlock</code> is treated as a single instruction. That is, the
|
|
entire sequence must fit into a single bundle and may not span a bundle
|
|
boundary. If necessary, no-op instructions will be inserted before the
|
|
first instruction of the sequence so that the whole sequence starts on an
|
|
aligned bundle boundary. It's an error if the sequence is longer than the
|
|
bundle size.
|
|
|
|
<p>For convenience when using <code>.bundle_lock</code> and <code>.bundle_unlock</code>
|
|
inside assembler macros (see <a href="Macro.html#Macro">Macro</a>), bundle-locked sequences may be
|
|
nested. That is, a second <code>.bundle_lock</code> directive before the next
|
|
<code>.bundle_unlock</code> directive has no effect except that it must be
|
|
matched by another closing <code>.bundle_unlock</code> so that there is the
|
|
same number of <code>.bundle_lock</code> and <code>.bundle_unlock</code> directives.
|
|
|
|
</body></html>
|
|
|