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- <h2 class="chapter">11 GENERIC</h2>
- <a name="index-GENERIC-1"></a>
-
- <p>The purpose of GENERIC is simply to provide a
- language-independent way of representing an entire function in
- trees. To this end, it was necessary to add a few new tree codes
- to the back end, but almost everything was already there. If you
- can express it with the codes in <code>gcc/tree.def</code>, it’s
- GENERIC.
- </p>
- <p>Early on, there was a great deal of debate about how to think
- about statements in a tree IL. In GENERIC, a statement is
- defined as any expression whose value, if any, is ignored. A
- statement will always have <code>TREE_SIDE_EFFECTS</code> set (or it
- will be discarded), but a non-statement expression may also have
- side effects. A <code>CALL_EXPR</code>, for instance.
- </p>
- <p>It would be possible for some local optimizations to work on the
- GENERIC form of a function; indeed, the adapted tree inliner
- works fine on GENERIC, but the current compiler performs inlining
- after lowering to GIMPLE (a restricted form described in the next
- section). Indeed, currently the frontends perform this lowering
- before handing off to <code>tree_rest_of_compilation</code>, but this
- seems inelegant.
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- <tr><td align="left" valign="top">• <a href="Statements.html#Statements" accesskey="7">Statements</a>:</td><td> </td><td align="left" valign="top">Control flow and related trees.
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- <tr><td align="left" valign="top">• <a href="Functions.html#Functions" accesskey="8">Functions</a>:</td><td> </td><td align="left" valign="top">Function bodies, linkage, and other aspects.
- </td></tr>
- <tr><td align="left" valign="top">• <a href="Language_002ddependent-trees.html#Language_002ddependent-trees" accesskey="9">Language-dependent trees</a>:</td><td> </td><td align="left" valign="top">Topics and trees specific to language front ends.
- </td></tr>
- <tr><td align="left" valign="top">• <a href="C-and-C_002b_002b-Trees.html#C-and-C_002b_002b-Trees">C and C++ Trees</a>:</td><td> </td><td align="left" valign="top">Trees specific to C and C++.
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