fix PR5837 by having SSAUpdate reuse phi nodes for the
'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
diff --git a/lib/Transforms/Utils/SSAUpdater.cpp b/lib/Transforms/Utils/SSAUpdater.cpp
index ba41bf9..729fb09 100644
--- a/lib/Transforms/Utils/SSAUpdater.cpp
+++ b/lib/Transforms/Utils/SSAUpdater.cpp
@@ -149,7 +149,29 @@
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());