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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [InstCombine] unary operations are assigned the wrong complexity"
href="https://llvm.org/bugs/show_bug.cgi?id=28296">28296</a>
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<th>Summary</th>
<td>[InstCombine] unary operations are assigned the wrong complexity
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
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</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>I noticed this while figuring out how InstCombine's commutation transforms work
for <a href="http://reviews.llvm.org/rL273702">http://reviews.llvm.org/rL273702</a>:
/// \brief Assign a complexity or rank value to LLVM Values.
///
/// This routine maps IR values to various complexity ranks:
/// 0 -> undef
/// 1 -> Constants
/// 2 -> Other non-instructions
/// 3 -> Arguments
/// 3 -> Unary operations
/// 4 -> Other instructions
static inline unsigned getComplexity(Value *V) {
if (isa<Instruction>(V)) {
if (BinaryOperator::isNeg(V) || BinaryOperator::isFNeg(V) ||
BinaryOperator::isNot(V))
return 3;
return 4;
}
if (isa<Argument>(V))
return 3;
return isa<Constant>(V) ? (isa<UndefValue>(V) ? 0 : 1) : 2;
}
--------------------------------------------------------------------------
The logic doesn't match the comments: only fake binary operators (neg/not/fneg)
are assigned complexity of 3. Actual unary operators like cast instructions get
complexity 4.</pre>
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