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fix PR5837 by having SSAUpdate reuse phi nodes for the

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'GetValueInMiddleOfBlock' case, instead of inserting 
duplicates.

A similar fix is almost certainly needed by the machine-level
SSAUpdate implementation.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91820 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2009-12-21 07:16:11 +00:00
parent 6a363782fe
commit 4c1e3da0cd
2 changed files with 58 additions and 1 deletions
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24
lib/Transforms/Utils/SSAUpdater.cpp
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@@ -149,7 +149,29 @@ Value *SSAUpdater::GetValueInMiddleOfBlock(BasicBlock *BB) {
if (SingularValue != 0)
return SingularValue;
// Otherwise, we do need a PHI: insert one now.
// Otherwise, we do need a PHI: check to see if we already have one available
// in this block that produces the right value.
if (isa<PHINode>(BB->begin())) {
DenseMap<BasicBlock*, Value*> ValueMapping(PredValues.begin(),
PredValues.end());
PHINode *SomePHI;
for (BasicBlock::iterator It = BB->begin();
(SomePHI = dyn_cast<PHINode>(It)); ++It) {
// Scan this phi to see if it is what we need.
bool Equal = true;
for (unsigned i = 0, e = SomePHI->getNumIncomingValues(); i != e; ++i)
if (ValueMapping[SomePHI->getIncomingBlock(i)] !=
SomePHI->getIncomingValue(i)) {
Equal = false;
break;
}
if (Equal)
return SomePHI;
}
}
// Ok, we have no way out, insert a new one now.
PHINode *InsertedPHI = PHINode::Create(PrototypeValue->getType(),
PrototypeValue->getName(),
&BB->front());