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122 lines
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HTML
122 lines
7.0 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>Back End - GNU Compiler Collection (GCC) Internals</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="GNU Compiler Collection (GCC) Internals">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="gcc-Directory.html#gcc-Directory" title="gcc Directory">
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<link rel="prev" href="Front-End.html#Front-End" title="Front End">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Funding Free Software'', the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development.-->
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<style type="text/css"><!--
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span.sansserif { font-family:sans-serif; font-weight:normal; }
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="Back-End"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Front-End.html#Front-End">Front End</a>,
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Up: <a rel="up" accesskey="u" href="gcc-Directory.html#gcc-Directory">gcc Directory</a>
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<hr>
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</div>
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<h4 class="subsection">6.3.9 Anatomy of a Target Back End</h4>
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<p>A back end for a target architecture in GCC has the following parts:
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<ul>
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<li>A directory <samp><var>machine</var></samp> under <samp><span class="file">gcc/config</span></samp>, containing a
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machine description <samp><var>machine</var><span class="file">.md</span></samp> file (see <a href="Machine-Desc.html#Machine-Desc">Machine Descriptions</a>), header files <samp><var>machine</var><span class="file">.h</span></samp> and
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<samp><var>machine</var><span class="file">-protos.h</span></samp> and a source file <samp><var>machine</var><span class="file">.c</span></samp>
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(see <a href="Target-Macros.html#Target-Macros">Target Description Macros and Functions</a>),
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possibly a target Makefile fragment <samp><span class="file">t-</span><var>machine</var></samp>
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(see <a href="Target-Fragment.html#Target-Fragment">The Target Makefile Fragment</a>), and maybe
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some other files. The names of these files may be changed from the
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defaults given by explicit specifications in <samp><span class="file">config.gcc</span></samp>.
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<li>If necessary, a file <samp><var>machine</var><span class="file">-modes.def</span></samp> in the
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<samp><var>machine</var></samp> directory, containing additional machine modes to
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represent condition codes. See <a href="Condition-Code.html#Condition-Code">Condition Code</a>, for further details.
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<li>An optional <samp><var>machine</var><span class="file">.opt</span></samp> file in the <samp><var>machine</var></samp>
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directory, containing a list of target-specific options. You can also
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add other option files using the <code>extra_options</code> variable in
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<samp><span class="file">config.gcc</span></samp>. See <a href="Options.html#Options">Options</a>.
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<li>Entries in <samp><span class="file">config.gcc</span></samp> (see <a href="System-Config.html#System-Config">The <samp><span class="file">config.gcc</span></samp> File</a>) for the systems with this target
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architecture.
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<li>Documentation in <samp><span class="file">gcc/doc/invoke.texi</span></samp> for any command-line
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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
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of options and details of the individual options.
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<li>Documentation in <samp><span class="file">gcc/doc/extend.texi</span></samp> for any target-specific
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attributes supported (see <a href="Target-Attributes.html#Target-Attributes">Defining target-specific uses of <code>__attribute__</code></a>), including where the
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same attribute is already supported on some targets, which are
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enumerated in the manual.
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<li>Documentation in <samp><span class="file">gcc/doc/extend.texi</span></samp> for any target-specific
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pragmas supported.
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<li>Documentation in <samp><span class="file">gcc/doc/extend.texi</span></samp> of any target-specific
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built-in functions supported.
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<li>Documentation in <samp><span class="file">gcc/doc/extend.texi</span></samp> of any target-specific
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format checking styles supported.
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<li>Documentation in <samp><span class="file">gcc/doc/md.texi</span></samp> of any target-specific
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constraint letters (see <a href="Machine-Constraints.html#Machine-Constraints">Constraints for Particular Machines</a>).
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<li>A note in <samp><span class="file">gcc/doc/contrib.texi</span></samp> under the person or people who
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contributed the target support.
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<li>Entries in <samp><span class="file">gcc/doc/install.texi</span></samp> for all target triplets
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supported with this target architecture, giving details of any special
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notes about installation for this target, or saying that there are no
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special notes if there are none.
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<li>Possibly other support outside the <samp><span class="file">gcc</span></samp> directory for runtime
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libraries. FIXME: reference docs for this. The <code>libstdc++</code> porting
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manual needs to be installed as info for this to work, or to be a
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chapter of this manual.
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</ul>
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<p>If the back end is added to the official GCC source repository, the
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following are also necessary:
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<ul>
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<li>An entry for the target architecture in <samp><span class="file">readings.html</span></samp> on the
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GCC web site, with any relevant links.
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<li>Details of the properties of the back end and target architecture in
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<samp><span class="file">backends.html</span></samp> on the GCC web site.
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<li>A news item about the contribution of support for that target
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architecture, in <samp><span class="file">index.html</span></samp> on the GCC web site.
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<li>Normally, one or more maintainers of that target listed in
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<samp><span class="file">MAINTAINERS</span></samp>. Some existing architectures may be unmaintained,
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but it would be unusual to add support for a target that does not have
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a maintainer when support is added.
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<li>Target triplets covering all <samp><span class="file">config.gcc</span></samp> stanzas for the target,
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in the list in <samp><span class="file">contrib/config-list.mk</span></samp>.
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</ul>
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</body></html>
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