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127 lines
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127 lines
5.2 KiB
HTML
4 years ago
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<html lang="en">
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<title>Code Iterators - GNU Compiler Collection (GCC) Internals</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Iterators.html#Iterators" title="Iterators">
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<link rel="prev" href="Mode-Iterators.html#Mode-Iterators" title="Mode Iterators">
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<link rel="next" href="Int-Iterators.html#Int-Iterators" title="Int Iterators">
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Copyright (C) 1988-2015 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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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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<body>
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<div class="node">
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<a name="Code-Iterators"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Int-Iterators.html#Int-Iterators">Int Iterators</a>,
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Previous: <a rel="previous" accesskey="p" href="Mode-Iterators.html#Mode-Iterators">Mode Iterators</a>,
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Up: <a rel="up" accesskey="u" href="Iterators.html#Iterators">Iterators</a>
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<hr>
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</div>
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<h4 class="subsection">16.23.2 Code Iterators</h4>
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<p><a name="index-code-iterators-in-_0040file_007b_002emd_007d-files-3840"></a><a name="index-define_005fcode_005fiterator-3841"></a><a name="index-define_005fcode_005fattr-3842"></a>
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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>The construct:
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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>
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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>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>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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<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>
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<p>Here's an example of code iterators in action, taken from the MIPS port:
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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>
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<p>This is equivalent to:
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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>
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</body></html>
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