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80 lines
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80 lines
3.8 KiB
HTML
4 years ago
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<title>Define Subst Pattern Matching - GNU Compiler Collection (GCC) Internals</title>
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<link rel="up" href="Define-Subst.html#Define-Subst" title="Define Subst">
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<link rel="prev" href="Define-Subst-Example.html#Define-Subst-Example" title="Define Subst Example">
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<link rel="next" href="Define-Subst-Output-Template.html#Define-Subst-Output-Template" title="Define Subst Output Template">
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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="Define-Subst-Pattern-Matching"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Define-Subst-Output-Template.html#Define-Subst-Output-Template">Define Subst Output Template</a>,
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Previous: <a rel="previous" accesskey="p" href="Define-Subst-Example.html#Define-Subst-Example">Define Subst Example</a>,
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Up: <a rel="up" accesskey="u" href="Define-Subst.html#Define-Subst">Define Subst</a>
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<hr>
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</div>
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<h4 class="subsection">16.21.2 Pattern Matching in <code>define_subst</code></h4>
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<p><a name="index-define_005fsubst-3826"></a>
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All expressions, allowed in <code>define_insn</code> or <code>define_expand</code>,
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are allowed in the input-template of <code>define_subst</code>, except
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<code>match_par_dup</code>, <code>match_scratch</code>, <code>match_parallel</code>. The
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meanings of expressions in the input-template were changed:
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<p><code>match_operand</code> matches any expression (possibly, a subtree in
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RTL-template), if modes of the <code>match_operand</code> and this expression
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are the same, or mode of the <code>match_operand</code> is <code>VOIDmode</code>, or
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this expression is <code>match_dup</code>, <code>match_op_dup</code>. If the
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expression is <code>match_operand</code> too, and predicate of
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<code>match_operand</code> from the input pattern is not empty, then the
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predicates are compared. That can be used for more accurate filtering
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of accepted RTL-templates.
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<p><code>match_operator</code> matches common operators (like <code>plus</code>,
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<code>minus</code>), <code>unspec</code>, <code>unspec_volatile</code> operators and
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<code>match_operator</code>s from the original pattern if the modes match and
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<code>match_operator</code> from the input pattern has the same number of
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operands as the operator from the original pattern.
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</body></html>
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