diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 8 | ||||
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 8 |
2 files changed, 10 insertions, 6 deletions
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp index 18bb040008..6b2f54393d 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp @@ -1257,7 +1257,7 @@ void SelectionDAG::ComputeMaskedBits(SDOperand Op, const APInt &Mask, case ISD::UDIV: { // For the purposes of computing leading zeros we can conservatively // treat a udiv as a logical right shift by the power of 2 known to - // be greater than the denominator. + // be less than the denominator. APInt AllOnes = APInt::getAllOnesValue(BitWidth); ComputeMaskedBits(Op.getOperand(0), AllOnes, KnownZero2, KnownOne2, Depth+1); @@ -1267,8 +1267,10 @@ void SelectionDAG::ComputeMaskedBits(SDOperand Op, const APInt &Mask, KnownZero2.clear(); ComputeMaskedBits(Op.getOperand(1), AllOnes, KnownZero2, KnownOne2, Depth+1); - LeadZ = std::min(BitWidth, - LeadZ + BitWidth - KnownOne2.countLeadingZeros()); + unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros(); + if (RHSUnknownLeadingOnes != BitWidth) + LeadZ = std::min(BitWidth, + LeadZ + BitWidth - RHSUnknownLeadingOnes - 1); KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask; return; diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index ce052f724e..d7a5f7be5c 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -780,7 +780,7 @@ void InstCombiner::ComputeMaskedBits(Value *V, const APInt &Mask, case Instruction::UDiv: { // For the purposes of computing leading zeros we can conservatively // treat a udiv as a logical right shift by the power of 2 known to - // be greater than the denominator. + // be less than the denominator. APInt AllOnes = APInt::getAllOnesValue(BitWidth); ComputeMaskedBits(I->getOperand(0), AllOnes, KnownZero2, KnownOne2, Depth+1); @@ -790,8 +790,10 @@ void InstCombiner::ComputeMaskedBits(Value *V, const APInt &Mask, KnownZero2.clear(); ComputeMaskedBits(I->getOperand(1), AllOnes, KnownZero2, KnownOne2, Depth+1); - LeadZ = std::min(BitWidth, - LeadZ + BitWidth - KnownOne2.countLeadingZeros()); + unsigned RHSUnknownLeadingOnes = KnownOne2.countLeadingZeros(); + if (RHSUnknownLeadingOnes != BitWidth) + LeadZ = std::min(BitWidth, + LeadZ + BitWidth - RHSUnknownLeadingOnes - 1); KnownZero = APInt::getHighBitsSet(BitWidth, LeadZ) & Mask; return; |