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.
129 lines
6.7 KiB
HTML
129 lines
6.7 KiB
HTML
<html lang="en">
|
|
<head>
|
|
<title>Literal Directive - 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="Xtensa-Directives.html#Xtensa-Directives" title="Xtensa Directives">
|
|
<link rel="prev" href="Transform-Directive.html#Transform-Directive" title="Transform Directive">
|
|
<link rel="next" href="Literal-Position-Directive.html#Literal-Position-Directive" title="Literal Position Directive">
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
|
<!--
|
|
This file documents the GNU Assembler "as".
|
|
|
|
Copyright (C) 1991-2015 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 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="Literal-Directive"></a>
|
|
<p>
|
|
Next: <a rel="next" accesskey="n" href="Literal-Position-Directive.html#Literal-Position-Directive">Literal Position Directive</a>,
|
|
Previous: <a rel="previous" accesskey="p" href="Transform-Directive.html#Transform-Directive">Transform Directive</a>,
|
|
Up: <a rel="up" accesskey="u" href="Xtensa-Directives.html#Xtensa-Directives">Xtensa Directives</a>
|
|
<hr>
|
|
</div>
|
|
|
|
<h5 class="subsubsection">9.52.5.4 literal</h5>
|
|
|
|
<p><a name="index-g_t_0040code_007bliteral_007d-directive-2494"></a>
|
|
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.
|
|
|
|
<pre class="smallexample"> .literal <var>label</var>, <var>value</var>[, <var>value</var>...]
|
|
</pre>
|
|
<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:
|
|
|
|
<pre class="smallexample"> entry sp, 40
|
|
.literal .L1, sym
|
|
l32r a4, .L1
|
|
</pre>
|
|
<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>Literal pools are placed by default in separate literal sections;
|
|
however, when using the ‘<samp><span class="samp">--text-section-literals</span></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 rel="footnote" href="#fn-1" name="fnd-1"><sup>1</sup></a>
|
|
These text section literal
|
|
pools are created automatically before <code>ENTRY</code> instructions and
|
|
manually after ‘<samp><span class="samp">.literal_position</span></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,
|
|
<samp><span class="command">as</span></samp> will report an error.
|
|
|
|
<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:
|
|
|
|
<ol type=1 start=1>
|
|
<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>If the current section name (or <code>literal_prefix</code> value) begins with
|
|
“<code>.gnu.linkonce.</code><var>kind</var><code>.</code>”, the literal section name is formed
|
|
by replacing “<code>.</code><var>kind</var>” 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>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>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).
|
|
</ol>
|
|
|
|
<div class="footnote">
|
|
<hr>
|
|
<h4>Footnotes</h4><p class="footnote"><small>[<a name="fn-1" href="#fnd-1">1</a>]</small> Literals for the
|
|
<code>.init</code> and <code>.fini</code> sections are always placed in separate
|
|
sections, even when ‘<samp><span class="samp">--text-section-literals</span></samp>’ is enabled.</p>
|
|
|
|
<hr></div>
|
|
|
|
</body></html>
|
|
|