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| Previous: <a href="Front-End.html#Front-End" accesskey="p" rel="prev">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> |
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| <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>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> |
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