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167 lines
6.7 KiB
HTML
167 lines
6.7 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- Copyright (C) 1988-2018 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being "Funding Free Software", the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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"GNU Free Documentation License".
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Code Iterators (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="Code Iterators (GNU Compiler Collection (GCC) Internals)">
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<meta name="keywords" content="Code Iterators (GNU Compiler Collection (GCC) Internals)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Iterators.html#Iterators" rel="up" title="Iterators">
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<link href="Int-Iterators.html#Int-Iterators" rel="next" title="Int Iterators">
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<link href="Examples.html#Examples" rel="prev" title="Examples">
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<style type="text/css">
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a.summary-letter {text-decoration: none}
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Code-Iterators"></a>
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<div class="header">
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<p>
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Next: <a href="Int-Iterators.html#Int-Iterators" accesskey="n" rel="next">Int Iterators</a>, Previous: <a href="Mode-Iterators.html#Mode-Iterators" accesskey="p" rel="prev">Mode Iterators</a>, Up: <a href="Iterators.html#Iterators" accesskey="u" rel="up">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>
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</div>
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<hr>
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<a name="Code-Iterators-1"></a>
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<h4 class="subsection">17.23.2 Code Iterators</h4>
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<a name="index-code-iterators-in-_002emd-files"></a>
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<a name="index-define_005fcode_005fiterator"></a>
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<a name="index-define_005fcode_005fattr"></a>
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<p>Code iterators operate in a similar way to mode iterators. See <a href="Mode-Iterators.html#Mode-Iterators">Mode Iterators</a>.
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</p>
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<p>The construct:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(define_code_iterator <var>name</var> [(<var>code1</var> "<var>cond1</var>") … (<var>coden</var> "<var>condn</var>")])
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</pre></div>
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<p>defines a pseudo rtx code <var>name</var> that can be instantiated as
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<var>codei</var> if condition <var>condi</var> is true. Each <var>codei</var>
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must have the same rtx format. See <a href="RTL-Classes.html#RTL-Classes">RTL Classes</a>.
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</p>
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<p>As with mode iterators, each pattern that uses <var>name</var> will be
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expanded <var>n</var> times, once with all uses of <var>name</var> replaced by
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<var>code1</var>, once with all uses replaced by <var>code2</var>, and so on.
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See <a href="Defining-Mode-Iterators.html#Defining-Mode-Iterators">Defining Mode Iterators</a>.
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</p>
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<p>It is possible to define attributes for codes as well as for modes.
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There are two standard code attributes: <code>code</code>, the name of the
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code in lower case, and <code>CODE</code>, the name of the code in upper case.
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Other attributes are defined using:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(define_code_attr <var>name</var> [(<var>code1</var> "<var>value1</var>") … (<var>coden</var> "<var>valuen</var>")])
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</pre></div>
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<p>Here’s an example of code iterators in action, taken from the MIPS port:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(define_code_iterator any_cond [unordered ordered unlt unge uneq ltgt unle ungt
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eq ne gt ge lt le gtu geu ltu leu])
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(define_expand "b<code>"
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[(set (pc)
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(if_then_else (any_cond:CC (cc0)
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(const_int 0))
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(label_ref (match_operand 0 ""))
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(pc)))]
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""
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{
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gen_conditional_branch (operands, <CODE>);
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DONE;
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})
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</pre></div>
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<p>This is equivalent to:
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</p>
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<div class="smallexample">
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<pre class="smallexample">(define_expand "bunordered"
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[(set (pc)
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(if_then_else (unordered:CC (cc0)
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(const_int 0))
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(label_ref (match_operand 0 ""))
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(pc)))]
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""
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{
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gen_conditional_branch (operands, UNORDERED);
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DONE;
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})
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(define_expand "bordered"
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[(set (pc)
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(if_then_else (ordered:CC (cc0)
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(const_int 0))
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(label_ref (match_operand 0 ""))
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(pc)))]
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""
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{
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gen_conditional_branch (operands, ORDERED);
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DONE;
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})
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…
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</pre></div>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Int-Iterators.html#Int-Iterators" accesskey="n" rel="next">Int Iterators</a>, Previous: <a href="Mode-Iterators.html#Mode-Iterators" accesskey="p" rel="prev">Mode Iterators</a>, Up: <a href="Iterators.html#Iterators" accesskey="u" rel="up">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>
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</div>
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</body>
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</html>
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