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83 lines
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83 lines
3.4 KiB
HTML
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<title>Reading RTL - GNU Compiler Collection (GCC) Internals</title>
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<link rel="up" href="RTL.html#RTL" title="RTL">
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<link rel="prev" href="Sharing.html#Sharing" title="Sharing">
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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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``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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<a name="Reading-RTL"></a>
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<p>
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Previous: <a rel="previous" accesskey="p" href="Sharing.html#Sharing">Sharing</a>,
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Up: <a rel="up" accesskey="u" href="RTL.html#RTL">RTL</a>
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<h3 class="section">13.22 Reading RTL</h3>
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<p>To read an RTL object from a file, call <code>read_rtx</code>. It takes one
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argument, a stdio stream, and returns a single RTL object. This routine
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is defined in <samp><span class="file">read-rtl.c</span></samp>. It is not available in the compiler
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itself, only the various programs that generate the compiler back end
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from the machine description.
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<p>People frequently have the idea of using RTL stored as text in a file as
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an interface between a language front end and the bulk of GCC. This
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idea is not feasible.
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<p>GCC was designed to use RTL internally only. Correct RTL for a given
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program is very dependent on the particular target machine. And the RTL
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does not contain all the information about the program.
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<p>The proper way to interface GCC to a new language front end is with
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the “tree” data structure, described in the files <samp><span class="file">tree.h</span></samp> and
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<samp><span class="file">tree.def</span></samp>. The documentation for this structure (see <a href="GENERIC.html#GENERIC">GENERIC</a>)
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is incomplete.
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