Define-Subst-Pattern-Matching.html 5.0 KB

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  68. <a name="Pattern-Matching-in-define_005fsubst"></a>
  69. <h4 class="subsection">16.21.2 Pattern Matching in <code>define_subst</code></h4>
  70. <a name="index-define_005fsubst-2"></a>
  71. <p>All expressions, allowed in <code>define_insn</code> or <code>define_expand</code>,
  72. are allowed in the input-template of <code>define_subst</code>, except
  73. <code>match_par_dup</code>, <code>match_scratch</code>, <code>match_parallel</code>. The
  74. meanings of expressions in the input-template were changed:
  75. </p>
  76. <p><code>match_operand</code> matches any expression (possibly, a subtree in
  77. RTL-template), if modes of the <code>match_operand</code> and this expression
  78. are the same, or mode of the <code>match_operand</code> is <code>VOIDmode</code>, or
  79. this expression is <code>match_dup</code>, <code>match_op_dup</code>. If the
  80. expression is <code>match_operand</code> too, and predicate of
  81. <code>match_operand</code> from the input pattern is not empty, then the
  82. predicates are compared. That can be used for more accurate filtering
  83. of accepted RTL-templates.
  84. </p>
  85. <p><code>match_operator</code> matches common operators (like <code>plus</code>,
  86. <code>minus</code>), <code>unspec</code>, <code>unspec_volatile</code> operators and
  87. <code>match_operator</code>s from the original pattern if the modes match and
  88. <code>match_operator</code> from the input pattern has the same number of
  89. operands as the operator from the original pattern.
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