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.
137 lines
6.7 KiB
HTML
137 lines
6.7 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
|
<html>
|
|
<!-- 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".
|
|
-->
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
|
<head>
|
|
<title>Xtensa Directives (Using as)</title>
|
|
|
|
<meta name="description" content="Xtensa Directives (Using as)">
|
|
<meta name="keywords" content="Xtensa Directives (Using as)">
|
|
<meta name="resource-type" content="document">
|
|
<meta name="distribution" content="global">
|
|
<meta name="Generator" content="makeinfo">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
|
<link href="index.html#Top" rel="start" title="Top">
|
|
<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
|
<link href="Xtensa_002dDependent.html#Xtensa_002dDependent" rel="up" title="Xtensa-Dependent">
|
|
<link href="Schedule-Directive.html#Schedule-Directive" rel="next" title="Schedule Directive">
|
|
<link href="Xtensa-Immediate-Relaxation.html#Xtensa-Immediate-Relaxation" rel="prev" title="Xtensa Immediate Relaxation">
|
|
<style type="text/css">
|
|
<!--
|
|
a.summary-letter {text-decoration: none}
|
|
blockquote.indentedblock {margin-right: 0em}
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
|
blockquote.smallquotation {font-size: smaller}
|
|
div.display {margin-left: 3.2em}
|
|
div.example {margin-left: 3.2em}
|
|
div.lisp {margin-left: 3.2em}
|
|
div.smalldisplay {margin-left: 3.2em}
|
|
div.smallexample {margin-left: 3.2em}
|
|
div.smalllisp {margin-left: 3.2em}
|
|
kbd {font-style: oblique}
|
|
pre.display {font-family: inherit}
|
|
pre.format {font-family: inherit}
|
|
pre.menu-comment {font-family: serif}
|
|
pre.menu-preformatted {font-family: serif}
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
|
pre.smallexample {font-size: smaller}
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
|
pre.smalllisp {font-size: smaller}
|
|
span.nolinebreak {white-space: nowrap}
|
|
span.roman {font-family: initial; font-weight: normal}
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
|
ul.no-bullet {list-style: none}
|
|
-->
|
|
</style>
|
|
|
|
|
|
</head>
|
|
|
|
<body lang="en">
|
|
<a name="Xtensa-Directives"></a>
|
|
<div class="header">
|
|
<p>
|
|
Previous: <a href="Xtensa-Relaxation.html#Xtensa-Relaxation" accesskey="p" rel="prev">Xtensa Relaxation</a>, Up: <a href="Xtensa_002dDependent.html#Xtensa_002dDependent" accesskey="u" rel="up">Xtensa-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
<hr>
|
|
<a name="Directives-3"></a>
|
|
<h4 class="subsection">9.54.5 Directives</h4>
|
|
<a name="index-Xtensa-directives"></a>
|
|
<a name="index-directives_002c-Xtensa"></a>
|
|
|
|
<p>The Xtensa assembler supports a region-based directive syntax:
|
|
</p>
|
|
<div class="smallexample">
|
|
<pre class="smallexample"> .begin <var>directive</var> [<var>options</var>]
|
|
…
|
|
.end <var>directive</var>
|
|
</pre></div>
|
|
|
|
<p>All the Xtensa-specific directives that apply to a region of code use
|
|
this syntax.
|
|
</p>
|
|
<p>The directive applies to code between the <code>.begin</code> and the
|
|
<code>.end</code>. The state of the option after the <code>.end</code> reverts to
|
|
what it was before the <code>.begin</code>.
|
|
A nested <code>.begin</code>/<code>.end</code> region can further
|
|
change the state of the directive without having to be aware of its
|
|
outer state. For example, consider:
|
|
</p>
|
|
<div class="smallexample">
|
|
<pre class="smallexample"> .begin no-transform
|
|
L: add a0, a1, a2
|
|
</pre><pre class="smallexample"> .begin transform
|
|
M: add a0, a1, a2
|
|
.end transform
|
|
</pre><pre class="smallexample">N: add a0, a1, a2
|
|
.end no-transform
|
|
</pre></div>
|
|
|
|
<p>The <code>ADD</code> opcodes at <code>L</code> and <code>N</code> in the outer
|
|
<code>no-transform</code> region both result in <code>ADD</code> machine instructions,
|
|
but the assembler selects an <code>ADD.N</code> instruction for the
|
|
<code>ADD</code> at <code>M</code> in the inner <code>transform</code> region.
|
|
</p>
|
|
<p>The advantage of this style is that it works well inside macros which can
|
|
preserve the context of their callers.
|
|
</p>
|
|
<p>The following directives are available:
|
|
</p><table class="menu" border="0" cellspacing="0">
|
|
<tr><td align="left" valign="top">• <a href="Schedule-Directive.html#Schedule-Directive" accesskey="1">Schedule Directive</a>:</td><td> </td><td align="left" valign="top">Enable instruction scheduling.
|
|
</td></tr>
|
|
<tr><td align="left" valign="top">• <a href="Longcalls-Directive.html#Longcalls-Directive" accesskey="2">Longcalls Directive</a>:</td><td> </td><td align="left" valign="top">Use Indirect Calls for Greater Range.
|
|
</td></tr>
|
|
<tr><td align="left" valign="top">• <a href="Transform-Directive.html#Transform-Directive" accesskey="3">Transform Directive</a>:</td><td> </td><td align="left" valign="top">Disable All Assembler Transformations.
|
|
</td></tr>
|
|
<tr><td align="left" valign="top">• <a href="Literal-Directive.html#Literal-Directive" accesskey="4">Literal Directive</a>:</td><td> </td><td align="left" valign="top">Intermix Literals with Instructions.
|
|
</td></tr>
|
|
<tr><td align="left" valign="top">• <a href="Literal-Position-Directive.html#Literal-Position-Directive" accesskey="5">Literal Position Directive</a>:</td><td> </td><td align="left" valign="top">Specify Inline Literal Pool Locations.
|
|
</td></tr>
|
|
<tr><td align="left" valign="top">• <a href="Literal-Prefix-Directive.html#Literal-Prefix-Directive" accesskey="6">Literal Prefix Directive</a>:</td><td> </td><td align="left" valign="top">Specify Literal Section Name Prefix.
|
|
</td></tr>
|
|
<tr><td align="left" valign="top">• <a href="Absolute-Literals-Directive.html#Absolute-Literals-Directive" accesskey="7">Absolute Literals Directive</a>:</td><td> </td><td align="left" valign="top">Control PC-Relative vs. Absolute Literals.
|
|
</td></tr>
|
|
</table>
|
|
|
|
<hr>
|
|
<div class="header">
|
|
<p>
|
|
Previous: <a href="Xtensa-Relaxation.html#Xtensa-Relaxation" accesskey="p" rel="prev">Xtensa Relaxation</a>, Up: <a href="Xtensa_002dDependent.html#Xtensa_002dDependent" accesskey="u" rel="up">Xtensa-Dependent</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
|
|
</div>
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|