168 lines
6.8 KiB
HTML
168 lines
6.8 KiB
HTML
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<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GNU Compiler Collection (GCC) Internals: Code Iterators</title>
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<meta name="description" content="GNU Compiler Collection (GCC) Internals: Code Iterators">
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<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Code Iterators">
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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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<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">16.23.2 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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