151 lines
6.9 KiB
HTML
151 lines
6.9 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2016 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. -->
|
||
|
|
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>GNU Compiler Collection (GCC) Internals: Substitutions</title>
|
||
|
|
|
||
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals: Substitutions">
|
||
|
|
<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Substitutions">
|
||
|
|
<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="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="Mode-Iterators.html#Mode-Iterators" rel="up" title="Mode Iterators">
|
||
|
|
<link href="Examples.html#Examples" rel="next" title="Examples">
|
||
|
|
<link href="Defining-Mode-Iterators.html#Defining-Mode-Iterators" rel="prev" title="Defining Mode Iterators">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.indentedblock {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
|
||
|
|
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.nocodebreak {white-space:nowrap}
|
||
|
|
span.nolinebreak {white-space:nowrap}
|
||
|
|
span.roman {font-family:serif; font-weight:normal}
|
||
|
|
span.sansserif {font-family:sans-serif; font-weight:normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
|
||
|
|
<a name="Substitutions"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Examples.html#Examples" accesskey="n" rel="next">Examples</a>, Previous: <a href="Defining-Mode-Iterators.html#Defining-Mode-Iterators" accesskey="p" rel="prev">Defining Mode Iterators</a>, Up: <a href="Mode-Iterators.html#Mode-Iterators" accesskey="u" rel="up">Mode Iterators</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Substitution-in-Mode-Iterators"></a>
|
||
|
|
<h4 class="subsubsection">16.23.1.2 Substitution in Mode Iterators</h4>
|
||
|
|
<a name="index-define_005fmode_005fattr"></a>
|
||
|
|
|
||
|
|
<p>If an <samp>.md</samp> file construct uses mode iterators, each version of the
|
||
|
|
construct will often need slightly different strings or modes. For
|
||
|
|
example:
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li> When a <code>define_expand</code> defines several <code>add<var>m</var>3</code> patterns
|
||
|
|
(see <a href="Standard-Names.html#Standard-Names">Standard Names</a>), each expander will need to use the
|
||
|
|
appropriate mode name for <var>m</var>.
|
||
|
|
|
||
|
|
</li><li> When a <code>define_insn</code> defines several instruction patterns,
|
||
|
|
each instruction will often use a different assembler mnemonic.
|
||
|
|
|
||
|
|
</li><li> When a <code>define_insn</code> requires operands with different modes,
|
||
|
|
using an iterator for one of the operand modes usually requires a specific
|
||
|
|
mode for the other operand(s).
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>GCC supports such variations through a system of “mode attributes”.
|
||
|
|
There are two standard attributes: <code>mode</code>, which is the name of
|
||
|
|
the mode in lower case, and <code>MODE</code>, which is the same thing in
|
||
|
|
upper case. You can define other attributes using:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define_mode_attr <var>name</var> [(<var>mode1</var> "<var>value1</var>") … (<var>moden</var> "<var>valuen</var>")])
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>where <var>name</var> is the name of the attribute and <var>valuei</var>
|
||
|
|
is the value associated with <var>modei</var>.
|
||
|
|
</p>
|
||
|
|
<p>When GCC replaces some <var>:iterator</var> with <var>:mode</var>, it will scan
|
||
|
|
each string and mode in the pattern for sequences of the form
|
||
|
|
<code><<var>iterator</var>:<var>attr</var>></code>, where <var>attr</var> is the name of a
|
||
|
|
mode attribute. If the attribute is defined for <var>mode</var>, the whole
|
||
|
|
<code><…></code> sequence will be replaced by the appropriate attribute
|
||
|
|
value.
|
||
|
|
</p>
|
||
|
|
<p>For example, suppose an <samp>.md</samp> file has:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define_mode_iterator P [(SI "Pmode == SImode") (DI "Pmode == DImode")])
|
||
|
|
(define_mode_attr load [(SI "lw") (DI "ld")])
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>If one of the patterns that uses <code>:P</code> contains the string
|
||
|
|
<code>"<P:load>\t%0,%1"</code>, the <code>SI</code> version of that pattern
|
||
|
|
will use <code>"lw\t%0,%1"</code> and the <code>DI</code> version will use
|
||
|
|
<code>"ld\t%0,%1"</code>.
|
||
|
|
</p>
|
||
|
|
<p>Here is an example of using an attribute for a mode:
|
||
|
|
</p>
|
||
|
|
<div class="smallexample">
|
||
|
|
<pre class="smallexample">(define_mode_iterator LONG [SI DI])
|
||
|
|
(define_mode_attr SHORT [(SI "HI") (DI "SI")])
|
||
|
|
(define_insn …
|
||
|
|
(sign_extend:LONG (match_operand:<LONG:SHORT> …)) …)
|
||
|
|
</pre></div>
|
||
|
|
|
||
|
|
<p>The <code><var>iterator</var>:</code> prefix may be omitted, in which case the
|
||
|
|
substitution will be attempted for every iterator expansion.
|
||
|
|
</p>
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Next: <a href="Examples.html#Examples" accesskey="n" rel="next">Examples</a>, Previous: <a href="Defining-Mode-Iterators.html#Defining-Mode-Iterators" accesskey="p" rel="prev">Defining Mode Iterators</a>, Up: <a href="Mode-Iterators.html#Mode-Iterators" accesskey="u" rel="up">Mode Iterators</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|