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<h4 class="subsection">16.23.2 Code Iterators</h4>
<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>
Code iterators operate in a similar way to mode iterators. See <a href="Mode-Iterators.html#Mode-Iterators">Mode Iterators</a>.
<p>The construct:
<pre class="smallexample"> (define_code_iterator <var>name</var> [(<var>code1</var> "<var>cond1</var>") ... (<var>coden</var> "<var>condn</var>")])
</pre>
<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>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>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:
<pre class="smallexample"> (define_code_attr <var>name</var> [(<var>code1</var> "<var>value1</var>") ... (<var>coden</var> "<var>valuen</var>")])
</pre>
<p>Here's an example of code iterators in action, taken from the MIPS port:
<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>
<p>This is equivalent to:
<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;
})
...
</pre>
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