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| <a name="Code-Iterators-1"></a> |
| <h4 class="subsection">16.23.2 Code Iterators</h4> |
| <a name="index-code-iterators-in-_002emd-files"></a> |
| <a name="index-define_005fcode_005fiterator"></a> |
| <a name="index-define_005fcode_005fattr"></a> |
| |
| <p>Code iterators operate in a similar way to mode iterators. See <a href="Mode-Iterators.html#Mode-Iterators">Mode Iterators</a>. |
| </p> |
| <p>The construct: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_code_iterator <var>name</var> [(<var>code1</var> "<var>cond1</var>") … (<var>coden</var> "<var>condn</var>")]) |
| </pre></div> |
| |
| <p>defines a pseudo rtx code <var>name</var> that can be instantiated as |
| <var>codei</var> if condition <var>condi</var> is true. Each <var>codei</var> |
| must have the same rtx format. See <a href="RTL-Classes.html#RTL-Classes">RTL Classes</a>. |
| </p> |
| <p>As with mode iterators, each pattern that uses <var>name</var> will be |
| expanded <var>n</var> times, once with all uses of <var>name</var> replaced by |
| <var>code1</var>, once with all uses replaced by <var>code2</var>, and so on. |
| See <a href="Defining-Mode-Iterators.html#Defining-Mode-Iterators">Defining Mode Iterators</a>. |
| </p> |
| <p>It is possible to define attributes for codes as well as for modes. |
| There are two standard code attributes: <code>code</code>, the name of the |
| code in lower case, and <code>CODE</code>, the name of the code in upper case. |
| Other attributes are defined using: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_code_attr <var>name</var> [(<var>code1</var> "<var>value1</var>") … (<var>coden</var> "<var>valuen</var>")]) |
| </pre></div> |
| |
| <p>Here’s an example of code iterators in action, taken from the MIPS port: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_code_iterator any_cond [unordered ordered unlt unge uneq ltgt unle ungt |
| eq ne gt ge lt le gtu geu ltu leu]) |
| |
| (define_expand "b<code>" |
| [(set (pc) |
| (if_then_else (any_cond:CC (cc0) |
| (const_int 0)) |
| (label_ref (match_operand 0 "")) |
| (pc)))] |
| "" |
| { |
| gen_conditional_branch (operands, <CODE>); |
| DONE; |
| }) |
| </pre></div> |
| |
| <p>This is equivalent to: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">(define_expand "bunordered" |
| [(set (pc) |
| (if_then_else (unordered:CC (cc0) |
| (const_int 0)) |
| (label_ref (match_operand 0 "")) |
| (pc)))] |
| "" |
| { |
| gen_conditional_branch (operands, UNORDERED); |
| DONE; |
| }) |
| |
| (define_expand "bordered" |
| [(set (pc) |
| (if_then_else (ordered:CC (cc0) |
| (const_int 0)) |
| (label_ref (match_operand 0 "")) |
| (pc)))] |
| "" |
| { |
| gen_conditional_branch (operands, ORDERED); |
| DONE; |
| }) |
| |
| … |
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