diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 4247d8a..d42e0bb 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -889,15 +889,21 @@ bool InstCombiner::SimplifyDemandedBits(Value *V, uint64_t DemandedMask, KnownZero |= NewBits; } else { // Sign extension. - if (SimplifyDemandedBits(I->getOperand(0), - DemandedMask & SrcTy->getIntegralTypeMask(), + uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1); + int64_t InputDemandedBits = DemandedMask & SrcTy->getIntegralTypeMask(); + + // If any of the sign extended bits are demanded, we know that the sign + // bit is demanded. + if (NewBits & DemandedMask) + InputDemandedBits |= InSignBit; + + if (SimplifyDemandedBits(I->getOperand(0), InputDemandedBits, KnownZero, KnownOne, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); // If the sign bit of the input is known set or clear, then we know the // top bits of the result. - uint64_t InSignBit = 1ULL << (SrcTy->getPrimitiveSizeInBits()-1); // If the input sign bit is known zero, or if the NewBits are not demanded // convert this into a zero extension. |