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diff --git a/share/doc/gccint/Overview.html b/share/doc/gccint/Overview.html new file mode 100644 index 0000000..cb99a94 --- /dev/null +++ b/share/doc/gccint/Overview.html @@ -0,0 +1,130 @@ +<!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: Overview</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Overview"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Overview"> +<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="Machine-Desc.html#Machine-Desc" rel="up" title="Machine Desc"> +<link href="Patterns.html#Patterns" rel="next" title="Patterns"> +<link href="Machine-Desc.html#Machine-Desc" rel="previous" title="Machine Desc"> +<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="Overview"></a> +<div class="header"> +<p> +Next: <a href="Patterns.html#Patterns" accesskey="n" rel="next">Patterns</a>, Up: <a href="Machine-Desc.html#Machine-Desc" accesskey="u" rel="up">Machine Desc</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="Overview-of-How-the-Machine-Description-is-Used"></a> +<h3 class="section">17.1 Overview of How the Machine Description is Used</h3> + +<p>There are three main conversions that happen in the compiler: +</p> +<ol> +<li> The front end reads the source code and builds a parse tree. + +</li><li> The parse tree is used to generate an RTL insn list based on named +instruction patterns. + +</li><li> The insn list is matched against the RTL templates to produce assembler +code. + +</li></ol> + +<p>For the generate pass, only the names of the insns matter, from either a +named <code>define_insn</code> or a <code>define_expand</code>. The compiler will +choose the pattern with the right name and apply the operands according +to the documentation later in this chapter, without regard for the RTL +template or operand constraints. Note that the names the compiler looks +for are hard-coded in the compiler—it will ignore unnamed patterns and +patterns with names it doesn’t know about, but if you don’t provide a +named pattern it needs, it will abort. +</p> +<p>If a <code>define_insn</code> is used, the template given is inserted into the +insn list. If a <code>define_expand</code> is used, one of three things +happens, based on the condition logic. The condition logic may manually +create new insns for the insn list, say via <code>emit_insn()</code>, and +invoke <code>DONE</code>. For certain named patterns, it may invoke <code>FAIL</code> to tell the +compiler to use an alternate way of performing that task. If it invokes +neither <code>DONE</code> nor <code>FAIL</code>, the template given in the pattern +is inserted, as if the <code>define_expand</code> were a <code>define_insn</code>. +</p> +<p>Once the insn list is generated, various optimization passes convert, +replace, and rearrange the insns in the insn list. This is where the +<code>define_split</code> and <code>define_peephole</code> patterns get used, for +example. +</p> +<p>Finally, the insn list’s RTL is matched up with the RTL templates in the +<code>define_insn</code> patterns, and those patterns are used to emit the +final assembly code. For this purpose, each named <code>define_insn</code> +acts like it’s unnamed, since the names are ignored. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Patterns.html#Patterns" accesskey="n" rel="next">Patterns</a>, Up: <a href="Machine-Desc.html#Machine-Desc" accesskey="u" rel="up">Machine Desc</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> |