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diff --git a/share/doc/gccint/Define-Subst-Example.html b/share/doc/gccint/Define-Subst-Example.html new file mode 100644 index 0000000..c668f79 --- /dev/null +++ b/share/doc/gccint/Define-Subst-Example.html @@ -0,0 +1,177 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). 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The instructions of the second type could be +generated with the following <code>define_subst</code>: +</p> +<div class="smallexample"> +<pre class="smallexample">(define_subst "add_clobber_subst" + [(set (match_operand:SI 0 "" "") + (match_operand:SI 1 "" ""))] + "" + [(set (match_dup 0) + (match_dup 1)) + (clobber (reg:CC FLAGS_REG))]) +</pre></div> + +<p>This <code>define_subst</code> can be applied to any RTL pattern containing +<code>set</code> of mode SI and generates a copy with clobber when it is +applied. +</p> +<p>Assume there is an RTL template for a <code>max</code> instruction to be used +in <code>define_subst</code> mentioned above: +</p> +<div class="smallexample"> +<pre class="smallexample">(define_insn "maxsi" + [(set (match_operand:SI 0 "register_operand" "=r") + (max:SI + (match_operand:SI 1 "register_operand" "r") + (match_operand:SI 2 "register_operand" "r")))] + "" + "max\t{%2, %1, %0|%0, %1, %2}" + […]) +</pre></div> + +<p>To mark the RTL template for <code>define_subst</code> application, +subst-attributes are used. They should be declared in advance: +</p> +<div class="smallexample"> +<pre class="smallexample">(define_subst_attr "add_clobber_name" "add_clobber_subst" "_noclobber" "_clobber") +</pre></div> + +<p>Here ‘<samp>add_clobber_name</samp>’ is the attribute name, +‘<samp>add_clobber_subst</samp>’ is the name of the corresponding +<code>define_subst</code>, the third argument (‘<samp>_noclobber</samp>’) is the +attribute value that would be substituted into the unchanged version of +the source RTL template, and the last argument (‘<samp>_clobber</samp>’) is the +value that would be substituted into the second, transformed, +version of the RTL template. +</p> +<p>Once the subst-attribute has been defined, it should be used in RTL +templates which need to be processed by the <code>define_subst</code>. So, +the original RTL template should be changed: +</p> +<div class="smallexample"> +<pre class="smallexample">(define_insn "maxsi<add_clobber_name>" + [(set (match_operand:SI 0 "register_operand" "=r") + (max:SI + (match_operand:SI 1 "register_operand" "r") + (match_operand:SI 2 "register_operand" "r")))] + "" + "max\t{%2, %1, %0|%0, %1, %2}" + […]) +</pre></div> + +<p>The result of the <code>define_subst</code> usage would look like the following: +</p> +<div class="smallexample"> +<pre class="smallexample">(define_insn "maxsi_noclobber" + [(set (match_operand:SI 0 "register_operand" "=r") + (max:SI + (match_operand:SI 1 "register_operand" "r") + (match_operand:SI 2 "register_operand" "r")))] + "" + "max\t{%2, %1, %0|%0, %1, %2}" + […]) +(define_insn "maxsi_clobber" + [(set (match_operand:SI 0 "register_operand" "=r") + (max:SI + (match_operand:SI 1 "register_operand" "r") + (match_operand:SI 2 "register_operand" "r"))) + (clobber (reg:CC FLAGS_REG))] + "" + "max\t{%2, %1, %0|%0, %1, %2}" + […]) +</pre></div> + +<hr> +<div class="header"> +<p> +Next: <a href="Define-Subst-Pattern-Matching.html#Define-Subst-Pattern-Matching" accesskey="n" rel="next">Define Subst Pattern Matching</a>, Up: <a href="Define-Subst.html#Define-Subst" accesskey="u" rel="up">Define Subst</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> +</div> + + + +</body> +</html> |