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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - backend writers guide lacks lots of information about patterns"
href="http://llvm.org/bugs/show_bug.cgi?id=18835">18835</a>
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<th>Summary</th>
<td>backend writers guide lacks lots of information about patterns
</td>
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<th>Product</th>
<td>Documentation
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>General docs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>hkultala@cs.tut.fi
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>It seems that there are tons of undocumented features in the isel patterns,
and backends such as X86, ARM and PowerPC use these features.
But there seems to be no documentation about all the features and syntax of the
patterns.
Things like
1) PatLeaf,
2) PatFrag,
3) ImmLeaf,
4) how to insert custom C++ code into pattern
5) multiclass
are not documented.
Also there does not seem to be a reference of the ISEL DAG Nodes anywhere?
ISDOpcodes.h contains some information in comments, but also those comments are
somewhat lacking.</pre>
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