diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index eaadbb4801..50a26c18c9 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -3456,21 +3456,37 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) { PHINode *NewPN = new PHINode(FirstInst->getOperand(0)->getType(), PN.getName()+".in"); NewPN->op_reserve(PN.getNumOperands()); - InsertNewInstBefore(NewPN, PN); + + Value *InVal = FirstInst->getOperand(0); + NewPN->addIncoming(InVal, PN.getIncomingBlock(0)); // Add all operands to the new PHI. - for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) - NewPN->addIncoming(cast<Instruction>(PN.getIncomingValue(i))->getOperand(0), - PN.getIncomingBlock(i)); + for (unsigned i = 1, e = PN.getNumIncomingValues(); i != e; ++i) { + Value *NewInVal = cast<Instruction>(PN.getIncomingValue(i))->getOperand(0); + if (NewInVal != InVal) + InVal = 0; + NewPN->addIncoming(NewInVal, PN.getIncomingBlock(i)); + } + + Value *PhiVal; + if (InVal) { + // The new PHI unions all of the same values together. This is really + // common, so we handle it intelligently here for compile-time speed. + PhiVal = InVal; + delete NewPN; + } else { + InsertNewInstBefore(NewPN, PN); + PhiVal = NewPN; + } // Insert and return the new operation. if (isa<CastInst>(FirstInst)) - return new CastInst(NewPN, PN.getType()); + return new CastInst(PhiVal, PN.getType()); else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst)) - return BinaryOperator::create(BinOp->getOpcode(), NewPN, ConstantOp); + return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp); else return new ShiftInst(cast<ShiftInst>(FirstInst)->getOpcode(), - NewPN, ConstantOp); + PhiVal, ConstantOp); } // PHINode simplification |