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diff --git a/share/doc/gccint/Back-End.html b/share/doc/gccint/Back-End.html new file mode 100644 index 0000000..281014a --- /dev/null +++ b/share/doc/gccint/Back-End.html @@ -0,0 +1,186 @@ +<!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: Back End</title> + +<meta name="description" content="GNU Compiler Collection (GCC) Internals: Back End"> +<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: Back End"> +<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="gcc-Directory.html#gcc-Directory" rel="up" title="gcc Directory"> +<link href="Testsuites.html#Testsuites" rel="next" title="Testsuites"> +<link href="Front-End-Makefile.html#Front-End-Makefile" rel="previous" title="Front End Makefile"> +<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="Back-End"></a> +<div class="header"> +<p> +Previous: <a href="Front-End.html#Front-End" accesskey="p" rel="previous">Front End</a>, Up: <a href="gcc-Directory.html#gcc-Directory" accesskey="u" rel="up">gcc Directory</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="Anatomy-of-a-Target-Back-End"></a> +<h4 class="subsection">6.3.9 Anatomy of a Target Back End</h4> + +<p>A back end for a target architecture in GCC has the following parts: +</p> +<ul> +<li> A directory <samp><var>machine</var></samp> under <samp>gcc/config</samp>, containing a +machine description <samp><var>machine</var>.md</samp> file (see <a href="Machine-Desc.html#Machine-Desc">Machine Descriptions</a>), header files <samp><var>machine</var>.h</samp> and +<samp><var>machine</var>-protos.h</samp> and a source file <samp><var>machine</var>.c</samp> +(see <a href="Target-Macros.html#Target-Macros">Target Description Macros and Functions</a>), +possibly a target Makefile fragment <samp>t-<var>machine</var></samp> +(see <a href="Target-Fragment.html#Target-Fragment">The Target Makefile Fragment</a>), and maybe +some other files. The names of these files may be changed from the +defaults given by explicit specifications in <samp>config.gcc</samp>. +</li><li> If necessary, a file <samp><var>machine</var>-modes.def</samp> in the +<samp><var>machine</var></samp> directory, containing additional machine modes to +represent condition codes. See <a href="Condition-Code.html#Condition-Code">Condition Code</a>, for further details. +</li><li> An optional <samp><var>machine</var>.opt</samp> file in the <samp><var>machine</var></samp> +directory, containing a list of target-specific options. You can also +add other option files using the <code>extra_options</code> variable in +<samp>config.gcc</samp>. See <a href="Options.html#Options">Options</a>. +</li><li> Entries in <samp>config.gcc</samp> (see <a href="System-Config.html#System-Config">The +<samp>config.gcc</samp> File</a>) for the systems with this target +architecture. +</li><li> Documentation in <samp>gcc/doc/invoke.texi</samp> for any command-line +options supported by this target (see <a href="Run_002dtime-Target.html#Run_002dtime-Target">Run-time +Target Specification</a>). This means both entries in the summary table +of options and details of the individual options. +</li><li> Documentation in <samp>gcc/doc/extend.texi</samp> for any target-specific +attributes supported (see <a href="Target-Attributes.html#Target-Attributes">Defining +target-specific uses of <code>__attribute__</code></a>), including where the +same attribute is already supported on some targets, which are +enumerated in the manual. +</li><li> Documentation in <samp>gcc/doc/extend.texi</samp> for any target-specific +pragmas supported. +</li><li> Documentation in <samp>gcc/doc/extend.texi</samp> of any target-specific +built-in functions supported. +</li><li> Documentation in <samp>gcc/doc/extend.texi</samp> of any target-specific +format checking styles supported. +</li><li> Documentation in <samp>gcc/doc/md.texi</samp> of any target-specific +constraint letters (see <a href="Machine-Constraints.html#Machine-Constraints">Constraints for +Particular Machines</a>). +</li><li> A note in <samp>gcc/doc/contrib.texi</samp> under the person or people who +contributed the target support. +</li><li> Entries in <samp>gcc/doc/install.texi</samp> for all target triplets +supported with this target architecture, giving details of any special +notes about installation for this target, or saying that there are no +special notes if there are none. +</li><li> Possibly other support outside the <samp>gcc</samp> directory for runtime +libraries. FIXME: reference docs for this. The <code>libstdc++</code> porting +manual needs to be installed as info for this to work, or to be a +chapter of this manual. +</li></ul> + +<p>The <samp><var>machine</var>.h</samp> header is included very early in GCC’s +standard sequence of header files, while <samp><var>machine</var>-protos.h</samp> +is included late in the sequence. Thus <samp><var>machine</var>-protos.h</samp> +can include declarations referencing types that are not defined when +<samp><var>machine</var>.h</samp> is included, specifically including those from +<samp>rtl.h</samp> and <samp>tree.h</samp>. Since both RTL and tree types may not +be available in every context where <samp><var>machine</var>-protos.h</samp> is +included, in this file you should guard declarations using these types +inside appropriate <code>#ifdef RTX_CODE</code> or <code>#ifdef TREE_CODE</code> +conditional code segments. +</p> +<p>If the backend uses shared data structures that require <code>GTY</code> markers +for garbage collection (see <a href="Type-Information.html#Type-Information">Type Information</a>), you must declare those +in <samp><var>machine</var>.h</samp> rather than <samp><var>machine</var>-protos.h</samp>. +Any definitions required for building libgcc must also go in +<samp><var>machine</var>.h</samp>. +</p> +<p>GCC uses the macro <code>IN_TARGET_CODE</code> to distinguish between +machine-specific <samp>.c</samp> and <samp>.cc</samp> files and +machine-independent <samp>.c</samp> and <samp>.cc</samp> files. Machine-specific +files should use the directive: +</p> +<div class="example"> +<pre class="example">#define IN_TARGET_CODE 1 +</pre></div> + +<p>before including <code>config.h</code>. +</p> +<p>If the back end is added to the official GCC source repository, the +following are also necessary: +</p> +<ul> +<li> An entry for the target architecture in <samp>readings.html</samp> on the +GCC web site, with any relevant links. +</li><li> Details of the properties of the back end and target architecture in +<samp>backends.html</samp> on the GCC web site. +</li><li> A news item about the contribution of support for that target +architecture, in <samp>index.html</samp> on the GCC web site. +</li><li> Normally, one or more maintainers of that target listed in +<samp>MAINTAINERS</samp>. Some existing architectures may be unmaintained, +but it would be unusual to add support for a target that does not have +a maintainer when support is added. +</li><li> Target triplets covering all <samp>config.gcc</samp> stanzas for the target, +in the list in <samp>contrib/config-list.mk</samp>. +</li></ul> + +<hr> +<div class="header"> +<p> +Previous: <a href="Front-End.html#Front-End" accesskey="p" rel="previous">Front End</a>, Up: <a href="gcc-Directory.html#gcc-Directory" accesskey="u" rel="up">gcc Directory</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> |