diff options
| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
|---|---|---|
| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
| commit | abdaadbcae30fe0c9a66c7516798279fdfd97750 (patch) | |
| tree | 00a54a6e25601e43876d03c1a4a12a749d4a914c /share/doc/gccint/Define-Subst-Example.html | |
https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
Change-Id: I7303388733328cd98ab9aa3c30236db67f2e9e9c
Diffstat (limited to 'share/doc/gccint/Define-Subst-Example.html')
| -rw-r--r-- | share/doc/gccint/Define-Subst-Example.html | 177 |
1 files changed, 177 insertions, 0 deletions
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). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>GNU Compiler Collection (GCC) Internals: Define Subst Example</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Define Subst Example"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Define Subst Example"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Define-Subst.html#Define-Subst" rel="up" title="Define Subst"> +<link href="Define-Subst-Pattern-Matching.html#Define-Subst-Pattern-Matching" rel="next" title="Define Subst Pattern Matching"> +<link href="Define-Subst.html#Define-Subst" rel="previous" title="Define Subst"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Define-Subst-Example"></a> +<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> +<hr> +<a name="define_005fsubst-Example"></a> +<h4 class="subsection">17.21.1 <code>define_subst</code> Example</h4> +<a name="index-define_005fsubst-1"></a> + +<p>To illustrate how <code>define_subst</code> works, let us examine a simple +template transformation. +</p> +<p>Suppose there are two kinds of instructions: one that touches flags and +the other that does not. 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> |