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diff --git a/share/doc/gccint/Control-Flow.html b/share/doc/gccint/Control-Flow.html new file mode 100644 index 0000000..8995fde --- /dev/null +++ b/share/doc/gccint/Control-Flow.html @@ -0,0 +1,128 @@ +<!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: Control Flow</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Control Flow"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Control Flow"> +<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="index.html#Top" rel="up" title="Top"> +<link href="Basic-Blocks.html#Basic-Blocks" rel="next" title="Basic Blocks"> +<link href="Reading-RTL.html#Reading-RTL" rel="previous" title="Reading RTL"> +<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="Control-Flow"></a> +<div class="header"> +<p> +Next: <a href="Loop-Analysis-and-Representation.html#Loop-Analysis-and-Representation" accesskey="n" rel="next">Loop Analysis and Representation</a>, Previous: <a href="RTL.html#RTL" accesskey="p" rel="previous">RTL</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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="Control-Flow-Graph"></a> +<h2 class="chapter">15 Control Flow Graph</h2> +<a name="index-CFG_002c-Control-Flow-Graph"></a> +<a name="index-basic_002dblock_002eh"></a> + +<p>A control flow graph (CFG) is a data structure built on top of the +intermediate code representation (the RTL or <code>GIMPLE</code> instruction +stream) abstracting the control flow behavior of a function that is +being compiled. The CFG is a directed graph where the vertices +represent basic blocks and edges represent possible transfer of +control flow from one basic block to another. The data structures +used to represent the control flow graph are defined in +<samp>basic-block.h</samp>. +</p> +<p>In GCC, the representation of control flow is maintained throughout +the compilation process, from constructing the CFG early in +<code>pass_build_cfg</code> to <code>pass_free_cfg</code> (see <samp>passes.def</samp>). +The CFG takes various different modes and may undergo extensive +manipulations, but the graph is always valid between its construction +and its release. This way, transfer of information such as data flow, +a measured profile, or the loop tree, can be propagated through the +passes pipeline, and even from <code>GIMPLE</code> to <code>RTL</code>. +</p> +<p>Often the CFG may be better viewed as integral part of instruction +chain, than structure built on the top of it. Updating the compiler’s +intermediate representation for instructions cannot be easily done +without proper maintenance of the CFG simultaneously. +</p> +<table class="menu" border="0" cellspacing="0"> +<tr><td align="left" valign="top">• <a href="Basic-Blocks.html#Basic-Blocks" accesskey="1">Basic Blocks</a>:</td><td> </td><td align="left" valign="top">The definition and representation of basic blocks. +</td></tr> +<tr><td align="left" valign="top">• <a href="Edges.html#Edges" accesskey="2">Edges</a>:</td><td> </td><td align="left" valign="top">Types of edges and their representation. +</td></tr> +<tr><td align="left" valign="top">• <a href="Profile-information.html#Profile-information" accesskey="3">Profile information</a>:</td><td> </td><td align="left" valign="top">Representation of frequencies and probabilities. +</td></tr> +<tr><td align="left" valign="top">• <a href="Maintaining-the-CFG.html#Maintaining-the-CFG" accesskey="4">Maintaining the CFG</a>:</td><td> </td><td align="left" valign="top">Keeping the control flow graph and up to date. +</td></tr> +<tr><td align="left" valign="top">• <a href="Liveness-information.html#Liveness-information" accesskey="5">Liveness information</a>:</td><td> </td><td align="left" valign="top">Using and maintaining liveness information. +</td></tr> +</table> + + +<hr> +<div class="header"> +<p> +Next: <a href="Loop-Analysis-and-Representation.html#Loop-Analysis-and-Representation" accesskey="n" rel="next">Loop Analysis and Representation</a>, Previous: <a href="RTL.html#RTL" accesskey="p" rel="previous">RTL</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</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> |