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diff --git a/share/doc/gccint/C-Constraint-Interface.html b/share/doc/gccint/C-Constraint-Interface.html new file mode 100644 index 0000000..aec653a --- /dev/null +++ b/share/doc/gccint/C-Constraint-Interface.html @@ -0,0 +1,174 @@ +<!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: C Constraint Interface</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: C Constraint Interface"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: C Constraint Interface"> +<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="Constraints.html#Constraints" rel="up" title="Constraints"> +<link href="Standard-Names.html#Standard-Names" rel="next" title="Standard Names"> +<link href="Define-Constraints.html#Define-Constraints" rel="previous" title="Define Constraints"> +<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="C-Constraint-Interface"></a> +<div class="header"> +<p> +Previous: <a href="Define-Constraints.html#Define-Constraints" accesskey="p" rel="previous">Define Constraints</a>, Up: <a href="Constraints.html#Constraints" accesskey="u" rel="up">Constraints</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="Testing-constraints-from-C"></a> +<h4 class="subsection">17.8.8 Testing constraints from C</h4> +<a name="index-testing-constraints"></a> +<a name="index-constraints_002c-testing"></a> + +<p>It is occasionally useful to test a constraint from C code rather than +implicitly via the constraint string in a <code>match_operand</code>. The +generated file <samp>tm_p.h</samp> declares a few interfaces for working +with constraints. At present these are defined for all constraints +except <code>g</code> (which is equivalent to <code>general_operand</code>). +</p> +<p>Some valid constraint names are not valid C identifiers, so there is a +mangling scheme for referring to them from C. Constraint names that +do not contain angle brackets or underscores are left unchanged. +Underscores are doubled, each ‘<samp><</samp>’ is replaced with ‘<samp>_l</samp>’, and +each ‘<samp>></samp>’ with ‘<samp>_g</samp>’. Here are some examples: +</p> +<div class="example"> +<table> +<tr><td><pre class="example"><strong>Original</strong></pre></td><td><pre class="example"><strong>Mangled</strong></pre></td></tr> +<tr><td><pre class="example"><code>x</code></pre></td><td><pre class="example"><code>x</code></pre></td></tr> +<tr><td><pre class="example"><code>P42x</code></pre></td><td><pre class="example"><code>P42x</code></pre></td></tr> +<tr><td><pre class="example"><code>P4_x</code></pre></td><td><pre class="example"><code>P4__x</code></pre></td></tr> +<tr><td><pre class="example"><code>P4>x</code></pre></td><td><pre class="example"><code>P4_gx</code></pre></td></tr> +<tr><td><pre class="example"><code>P4>></code></pre></td><td><pre class="example"><code>P4_g_g</code></pre></td></tr> +<tr><td><pre class="example"><code>P4_g></code></pre></td><td><pre class="example"><code>P4__g_g</code></pre></td></tr> +</table> +</div> + +<p>Throughout this section, the variable <var>c</var> is either a constraint +in the abstract sense, or a constant from <code>enum constraint_num</code>; +the variable <var>m</var> is a mangled constraint name (usually as part of +a larger identifier). +</p> +<dl> +<dt><a name="index-constraint_005fnum"></a>Enum: <strong>constraint_num</strong></dt> +<dd><p>For each constraint except <code>g</code>, there is a corresponding +enumeration constant: ‘<samp>CONSTRAINT_</samp>’ plus the mangled name of the +constraint. Functions that take an <code>enum constraint_num</code> as an +argument expect one of these constants. +</p></dd></dl> + +<dl> +<dt><a name="index-satisfies_005fconstraint_005f"></a>Function: <em>inline bool</em> <strong>satisfies_constraint_</strong> <em><var>m</var> (rtx <var>exp</var>)</em></dt> +<dd><p>For each non-register constraint <var>m</var> except <code>g</code>, there is +one of these functions; it returns <code>true</code> if <var>exp</var> satisfies the +constraint. These functions are only visible if <samp>rtl.h</samp> was included +before <samp>tm_p.h</samp>. +</p></dd></dl> + +<dl> +<dt><a name="index-constraint_005fsatisfied_005fp"></a>Function: <em>bool</em> <strong>constraint_satisfied_p</strong> <em>(rtx <var>exp</var>, enum constraint_num <var>c</var>)</em></dt> +<dd><p>Like the <code>satisfies_constraint_<var>m</var></code> functions, but the +constraint to test is given as an argument, <var>c</var>. If <var>c</var> +specifies a register constraint, this function will always return +<code>false</code>. +</p></dd></dl> + +<dl> +<dt><a name="index-reg_005fclass_005ffor_005fconstraint"></a>Function: <em>enum reg_class</em> <strong>reg_class_for_constraint</strong> <em>(enum constraint_num <var>c</var>)</em></dt> +<dd><p>Returns the register class associated with <var>c</var>. If <var>c</var> is not +a register constraint, or those registers are not available for the +currently selected subtarget, returns <code>NO_REGS</code>. +</p></dd></dl> + +<p>Here is an example use of <code>satisfies_constraint_<var>m</var></code>. In +peephole optimizations (see <a href="Peephole-Definitions.html#Peephole-Definitions">Peephole Definitions</a>), operand +constraint strings are ignored, so if there are relevant constraints, +they must be tested in the C condition. In the example, the +optimization is applied if operand 2 does <em>not</em> satisfy the +‘<samp>K</samp>’ constraint. (This is a simplified version of a peephole +definition from the i386 machine description.) +</p> +<div class="smallexample"> +<pre class="smallexample">(define_peephole2 + [(match_scratch:SI 3 "r") + (set (match_operand:SI 0 "register_operand" "") + (mult:SI (match_operand:SI 1 "memory_operand" "") + (match_operand:SI 2 "immediate_operand" "")))] + + "!satisfies_constraint_K (operands[2])" + + [(set (match_dup 3) (match_dup 1)) + (set (match_dup 0) (mult:SI (match_dup 3) (match_dup 2)))] + + "") +</pre></div> + +<hr> +<div class="header"> +<p> +Previous: <a href="Define-Constraints.html#Define-Constraints" accesskey="p" rel="previous">Define Constraints</a>, Up: <a href="Constraints.html#Constraints" accesskey="u" rel="up">Constraints</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> |