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.
163 lines
8.2 KiB
HTML
163 lines
8.2 KiB
HTML
4 years ago
|
<!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>Literal Directive (Using as)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Literal Directive (Using as)">
|
||
|
|
<meta name="keywords" content="Literal Directive (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-Directives.html#Xtensa-Directives" rel="up" title="Xtensa Directives">
|
||
|
|
<link href="Literal-Position-Directive.html#Literal-Position-Directive" rel="next" title="Literal Position Directive">
|
||
|
|
<link href="Transform-Directive.html#Transform-Directive" rel="prev" title="Transform Directive">
|
||
|
|
<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="Literal-Directive"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Literal-Position-Directive.html#Literal-Position-Directive" accesskey="n" rel="next">Literal Position Directive</a>, Previous: <a href="Transform-Directive.html#Transform-Directive" accesskey="p" rel="prev">Transform Directive</a>, Up: <a href="Xtensa-Directives.html#Xtensa-Directives" accesskey="u" rel="up">Xtensa Directives</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="literal"></a>
|
||
|
|
<h4 class="subsubsection">9.54.5.4 literal</h4>
|
||
|
|
<a name="index-literal-directive"></a>
|
||
|
|
|
||
|
|
<p>The <code>.literal</code> directive is used to define literal pool data, i.e.,
|
||
|
|
read-only 32-bit data accessed via <code>L32R</code> instructions.
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample"> .literal <var>label</var>, <var>value</var>[, <var>value</var>…]
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>This directive is similar to the standard <code>.word</code> directive, except
|
||
|
|
that the actual location of the literal data is determined by the
|
||
|
|
assembler and linker, not by the position of the <code>.literal</code>
|
||
|
|
directive. Using this directive gives the assembler freedom to locate
|
||
|
|
the literal data in the most appropriate place and possibly to combine
|
||
|
|
identical literals. For example, the code:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample"> entry sp, 40
|
||
|
|
.literal .L1, sym
|
||
|
|
l32r a4, .L1
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>can be used to load a pointer to the symbol <code>sym</code> into register
|
||
|
|
<code>a4</code>. The value of <code>sym</code> will not be placed between the
|
||
|
|
<code>ENTRY</code> and <code>L32R</code> instructions; instead, the assembler puts
|
||
|
|
the data in a literal pool.
|
||
|
|
</p>
|
||
|
|
<p>Literal pools are placed by default in separate literal sections;
|
||
|
|
however, when using the ‘<samp>--text-section-literals</samp>’
|
||
|
|
option (see <a href="Xtensa-Options.html#Xtensa-Options">Command-line Options</a>), the literal
|
||
|
|
pools for PC-relative mode <code>L32R</code> instructions
|
||
|
|
are placed in the current section.<a name="DOCF3" href="#FOOT3"><sup>3</sup></a>
|
||
|
|
These text section literal
|
||
|
|
pools are created automatically before <code>ENTRY</code> instructions and
|
||
|
|
manually after ‘<samp>.literal_position</samp>’ directives (see <a href="Literal-Position-Directive.html#Literal-Position-Directive">literal_position</a>). If there are no preceding
|
||
|
|
<code>ENTRY</code> instructions, explicit <code>.literal_position</code> directives
|
||
|
|
must be used to place the text section literal pools; otherwise,
|
||
|
|
<code>as</code> will report an error.
|
||
|
|
</p>
|
||
|
|
<p>When literals are placed in separate sections, the literal section names
|
||
|
|
are derived from the names of the sections where the literals are
|
||
|
|
defined. The base literal section names are <code>.literal</code> for
|
||
|
|
PC-relative mode <code>L32R</code> instructions and <code>.lit4</code> for absolute
|
||
|
|
mode <code>L32R</code> instructions (see <a href="Absolute-Literals-Directive.html#Absolute-Literals-Directive">absolute-literals</a>). These base names are used for literals defined in
|
||
|
|
the default <code>.text</code> section. For literals defined in other
|
||
|
|
sections or within the scope of a <code>literal_prefix</code> directive
|
||
|
|
(see <a href="Literal-Prefix-Directive.html#Literal-Prefix-Directive">literal_prefix</a>), the following rules
|
||
|
|
determine the literal section name:
|
||
|
|
</p>
|
||
|
|
<ol>
|
||
|
|
<li> If the current section is a member of a section group, the literal
|
||
|
|
section name includes the group name as a suffix to the base
|
||
|
|
<code>.literal</code> or <code>.lit4</code> name, with a period to separate the base
|
||
|
|
name and group name. The literal section is also made a member of the
|
||
|
|
group.
|
||
|
|
|
||
|
|
</li><li> If the current section name (or <code>literal_prefix</code> value) begins with
|
||
|
|
“<code>.gnu.linkonce.<var>kind</var>.</code>”, the literal section name is formed
|
||
|
|
by replacing “<code>.<var>kind</var></code>” with the base <code>.literal</code> or
|
||
|
|
<code>.lit4</code> name. For example, for literals defined in a section named
|
||
|
|
<code>.gnu.linkonce.t.func</code>, the literal section will be
|
||
|
|
<code>.gnu.linkonce.literal.func</code> or <code>.gnu.linkonce.lit4.func</code>.
|
||
|
|
|
||
|
|
</li><li> If the current section name (or <code>literal_prefix</code> value) ends with
|
||
|
|
<code>.text</code>, the literal section name is formed by replacing that
|
||
|
|
suffix with the base <code>.literal</code> or <code>.lit4</code> name. For example,
|
||
|
|
for literals defined in a section named <code>.iram0.text</code>, the literal
|
||
|
|
section will be <code>.iram0.literal</code> or <code>.iram0.lit4</code>.
|
||
|
|
|
||
|
|
</li><li> If none of the preceding conditions apply, the literal section name is
|
||
|
|
formed by adding the base <code>.literal</code> or <code>.lit4</code> name as a
|
||
|
|
suffix to the current section name (or <code>literal_prefix</code> value).
|
||
|
|
</li></ol>
|
||
|
|
|
||
|
|
<div class="footnote">
|
||
|
|
<hr>
|
||
|
|
<h4 class="footnotes-heading">Footnotes</h4>
|
||
|
|
|
||
|
|
<h3><a name="FOOT3" href="#DOCF3">(3)</a></h3>
|
||
|
|
<p>Literals for the
|
||
|
|
<code>.init</code> and <code>.fini</code> sections are always placed in separate
|
||
|
|
sections, even when ‘<samp>--text-section-literals</samp>’ is enabled.</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Literal-Position-Directive.html#Literal-Position-Directive" accesskey="n" rel="next">Literal Position Directive</a>, Previous: <a href="Transform-Directive.html#Transform-Directive" accesskey="p" rel="prev">Transform Directive</a>, Up: <a href="Xtensa-Directives.html#Xtensa-Directives" accesskey="u" rel="up">Xtensa Directives</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>
|