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<title>GNU Compiler Collection (GCC) Internals: Reading RTL</title>

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Previous: <a href="Sharing.html#Sharing" accesskey="p" rel="prev">Sharing</a>, Up: <a href="RTL.html#RTL" accesskey="u" rel="up">RTL</a> &nbsp; [<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="Reading-RTL-1"></a>
<h3 class="section">13.22 Reading RTL</h3>

<p>To read an RTL object from a file, call <code>read_rtx</code>.  It takes one
argument, a stdio stream, and returns a single RTL object.  This routine
is defined in <samp>read-rtl.c</samp>.  It is not available in the compiler
itself, only the various programs that generate the compiler back end
from the machine description.
</p>
<p>People frequently have the idea of using RTL stored as text in a file as
an interface between a language front end and the bulk of GCC.  This
idea is not feasible.
</p>
<p>GCC was designed to use RTL internally only.  Correct RTL for a given
program is very dependent on the particular target machine.  And the RTL
does not contain all the information about the program.
</p>
<p>The proper way to interface GCC to a new language front end is with
the &ldquo;tree&rdquo; data structure, described in the files <samp>tree.h</samp> and
<samp>tree.def</samp>.  The documentation for this structure (see <a href="GENERIC.html#GENERIC">GENERIC</a>)
is incomplete.
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