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improve PHINode::hasConstantValue() to detect recursive cases like %phi = phi(%phi,42) as constant

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159666 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nuno Lopes 2012-07-03 17:10:28 +00:00
parent 9ccc83e7f7
commit 44d5c06488
1 changed files with 6 additions and 2 deletions
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8
lib/VMCore/Instructions.cpp
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@ -161,8 +161,12 @@ Value *PHINode::hasConstantValue() const {
// Exploit the fact that phi nodes always have at least one entry.
Value *ConstantValue = getIncomingValue(0);
for (unsigned i = 1, e = getNumIncomingValues(); i != e; ++i)
if (getIncomingValue(i) != ConstantValue)
return 0; // Incoming values not all the same.
if (getIncomingValue(i) != ConstantValue && getIncomingValue(i) != this) {
if (ConstantValue != this)
return 0; // Incoming values not all the same.
// The case where the first value is this PHI.
ConstantValue = getIncomingValue(i);
}
return ConstantValue;
}