diff options
| -rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index 75edd8eaf9..7f809e7397 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -673,6 +673,7 @@ namespace { void dump(DenseMap<BasicBlock*, Value*>& d); bool iterateOnFunction(Function &F); Value* CollapsePhi(PHINode* p); + bool isSafeReplacement(PHINode* p, Instruction* inst); }; char GVN::ID = 0; @@ -731,7 +732,8 @@ Value* GVN::CollapsePhi(PHINode* p) { if (constVal) { if (Instruction* inst = dyn_cast<Instruction>(constVal)) { if (DT.dominates(inst, p)) - return inst; + if (isSafeReplacement(p, inst)) + return inst; } else { return constVal; } @@ -740,6 +742,19 @@ Value* GVN::CollapsePhi(PHINode* p) { return 0; } +bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) { + if (!isa<PHINode>(inst)) + return true; + + for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end(); + UI != E; ++UI) + if (PHINode* use_phi = dyn_cast<PHINode>(UI)) + if (use_phi->getParent() == inst->getParent()) + return false; + + return true; +} + /// GetValueForBlock - Get the value to use within the specified basic block. /// available values are in Phis. Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, |