diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 5689c060423..a20f474cbf4 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -417,8 +417,10 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // the highest demanded bit, we just return the other side. if (DemandedFromOps.isSubsetOf(RHSKnown.Zero)) return I->getOperand(0); - // We can't do this with the LHS for subtraction. - if (I->getOpcode() == Instruction::Add && + // We can't do this with the LHS for subtraction, unless we are only + // demanding the LSB. + if ((I->getOpcode() == Instruction::Add || + DemandedFromOps.isOneValue()) && DemandedFromOps.isSubsetOf(LHSKnown.Zero)) return I->getOperand(1); } |
