diff options
Diffstat (limited to 'lib/Transforms/Scalar/InstructionCombining.cpp')
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index c573f7f531..e0e3f49be1 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -3462,16 +3462,21 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) { if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I)) return BinaryOperator::CreateAnd(V, AndRHS); - // (A - N) & AndRHS -> -N & AndRHS where A & AndRHS == 0 - if (Op0I->hasOneUse() && MaskedValueIsZero(Op0LHS, AndRHSMask)) { + // (A - N) & AndRHS -> -N & AndRHS iff A&AndRHS==0 and AndRHS + // has 1's for all bits that the subtraction with A might affect. + if (Op0I->hasOneUse()) { + uint32_t BitWidth = AndRHSMask.getBitWidth(); + uint32_t Zeros = AndRHSMask.countLeadingZeros(); + APInt Mask = APInt::getLowBitsSet(BitWidth, BitWidth - Zeros); + ConstantInt *A = dyn_cast<ConstantInt>(Op0LHS); - if (!A || !A->isZero()) { + if (!(A && A->isZero()) && // avoid infinite recursion. + MaskedValueIsZero(Op0LHS, Mask)) { Instruction *NewNeg = BinaryOperator::CreateNeg(Op0RHS); InsertNewInstBefore(NewNeg, I); return BinaryOperator::CreateAnd(NewNeg, AndRHS); } } - break; case Instruction::Shl: |