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diff --git a/share/doc/gccint/RTL-SSA-Basic-Blocks.html b/share/doc/gccint/RTL-SSA-Basic-Blocks.html new file mode 100644 index 0000000..342f3eb --- /dev/null +++ b/share/doc/gccint/RTL-SSA-Basic-Blocks.html @@ -0,0 +1,159 @@ +<!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: RTL SSA Basic Blocks</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: RTL SSA Basic Blocks"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: RTL SSA Basic Blocks"> +<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="RTL-SSA.html#RTL-SSA" rel="up" title="RTL SSA"> +<link href="RTL-SSA-Resources.html#RTL-SSA-Resources" rel="next" title="RTL SSA Resources"> +<link href="RTL-SSA-Instructions.html#RTL-SSA-Instructions" rel="previous" title="RTL SSA Instructions"> +<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="RTL-SSA-Basic-Blocks"></a> +<div class="header"> +<p> +Next: <a href="RTL-SSA-Resources.html#RTL-SSA-Resources" accesskey="n" rel="next">RTL SSA Resources</a>, Previous: <a href="RTL-SSA-Instructions.html#RTL-SSA-Instructions" accesskey="p" rel="previous">RTL SSA Instructions</a>, Up: <a href="RTL-SSA.html#RTL-SSA" accesskey="u" rel="up">RTL SSA</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="RTL-SSA-Basic-Blocks-1"></a> +<h4 class="subsection">14.21.3 RTL SSA Basic Blocks</h4> + +<a name="index-basic-blocks_002c-RTL-SSA"></a> +<a name="index-basic_005fblock"></a> +<a name="index-rtl_005fssa_003a_003abb_005finfo"></a> +<p>RTL SSA instructions (see <a href="RTL-SSA-Instructions.html#RTL-SSA-Instructions">RTL SSA Instructions</a>) are organized into +basic blocks, with each block being represented by an <code>rtl_ssa:bb_info</code>. +There is a one-to-one mapping between these <code>rtl_ssa:bb_info</code> +structures and the underlying CFG <code>basic_block</code> structures +(see <a href="Basic-Blocks.html#Basic-Blocks">Basic Blocks</a>). +</p> +<a name="index-_0060_0060real_0027_0027-instructions_002c-RTL-SSA"></a> +<a name="real-RTL-SSA-insns"></a><p>If a CFG basic block <var>bb</var> contains an RTL instruction <var>insn</var>, +the RTL SSA represenation of <var>bb</var> also contains an RTL SSA representation +of <var>insn</var><a name="DOCF5" href="#FOOT5"><sup>5</sup></a>. Within RTL SSA, these instructions are referred to as +“real” instructions. These real instructions fall into two groups: +debug instructions and nondebug instructions. Only nondebug instructions +should affect code generation decisions. +</p> +<p>In addition, each RTL SSA basic block has two “artificial” +instructions: a “head” instruction that comes before all the real +instructions and an “end” instruction that comes after all real +instructions. These instructions exist to represent things that +are conceptually defined or used at the start and end of a basic block. +The instructions always exist, even if they do not currently do anything. +</p> +<p>Like instructions, these blocks are chained together in a reverse +postorder. This list includes the entry block (which always comes +first) and the exit block (which always comes last). +</p> +<a name="index-extended-basic-blocks_002c-RTL-SSA"></a> +<a name="index-rtl_005fssa_003a_003aebb_005finfo"></a> +<p>RTL SSA basic blocks are chained together into “extended basic blocks” +(EBBs), represented by an <code>rtl_ssa::ebb_info</code>. Extended basic +blocks contain one or more basic blocks. They have the property +that if a block <var>bby</var> comes immediately after a block <var>bbx</var> +in an EBB, then <var>bby</var> can only be reached by <var>bbx</var>; in other words, +<var>bbx</var> is the sole predecessor of <var>bby</var>. +</p> +<p>Each extended basic block starts with an artificial “phi node” +instruction. This instruction defines all phi nodes for the EBB +(see <a href="RTL-SSA-Phi-Nodes.html#RTL-SSA-Phi-Nodes">RTL SSA Phi Nodes</a>). (Individual blocks in an EBB do not +need phi nodes because their live values can only come from one source.) +</p> +<p>The contents of a function are therefore represented using a +four-level hierarchy: +</p> +<ul> +<li> functions (<code>rtl_ssa::function_info</code>), which contain … + +</li><li> extended basic blocks (<code>rtl_ssa::ebb_info</code>), which contain … + +</li><li> basic blocks (<code>rtl_ssa::bb_info</code>), which contain … + +</li><li> instructions (<code>rtl_ssa::insn_info</code>) +</li></ul> + +<p>In dumps, a basic block is identified as <code>bb<var>n</var></code>, where <var>n</var> +is the index of the associated CFG <code>basic_block</code> structure. +An EBB is in turn identified by the index of its first block. +For example, an EBB that contains ‘<samp>bb10</samp>’, <code>bb5</code>, <code>bb6</code> +and <code>bb9</code> is identified as <var>ebb10</var>. +</p> +<div class="footnote"> +<hr> +<h4 class="footnotes-heading">Footnotes</h4> + +<h3><a name="FOOT5" href="#DOCF5">(5)</a></h3> +<p>Note that this excludes non-instruction things like +<code>note</code>s and <code>barrier</code>s that also appear in the chain of RTL +instructions.</p> +</div> +<hr> +<div class="header"> +<p> +Next: <a href="RTL-SSA-Resources.html#RTL-SSA-Resources" accesskey="n" rel="next">RTL SSA Resources</a>, Previous: <a href="RTL-SSA-Instructions.html#RTL-SSA-Instructions" accesskey="p" rel="previous">RTL SSA Instructions</a>, Up: <a href="RTL-SSA.html#RTL-SSA" accesskey="u" rel="up">RTL SSA</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> |