diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 13 | ||||
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 10 |
2 files changed, 13 insertions, 10 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index c608f84bc7b..5f8746e7a15 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1586,6 +1586,19 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) { CI->getValue() == I.getType()->getPrimitiveSizeInBits() - 1) return BinaryOperator::CreateLShr(X, CI); } + + // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known + // zero. + APInt IntVal = C->getValue(); + if ((IntVal + 1).isPowerOf2()) { + unsigned BitWidth = I.getType()->getScalarSizeInBits(); + APInt KnownZero(BitWidth, 0); + APInt KnownOne(BitWidth, 0); + computeKnownBits(&I, KnownZero, KnownOne, 0, &I); + if ((IntVal | KnownZero).isAllOnesValue()) { + return BinaryOperator::CreateXor(Op1, C); + } + } } diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 3dbb1b190be..ac921331a01 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -630,16 +630,6 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, // Otherwise just hand the sub off to computeKnownBits to fill in // the known zeros and ones. computeKnownBits(V, KnownZero, KnownOne, Depth, CxtI); - - // Turn this into a xor if LHS is 2^n-1 and the remaining bits are known - // zero. - if (ConstantInt *C0 = dyn_cast<ConstantInt>(I->getOperand(0))) { - APInt I0 = C0->getValue(); - if ((I0 + 1).isPowerOf2() && (I0 | KnownZero).isAllOnesValue()) { - Instruction *Xor = BinaryOperator::CreateXor(I->getOperand(1), C0); - return InsertNewInstWith(Xor, *I); - } - } break; case Instruction::Shl: if (ConstantInt *SA = dyn_cast<ConstantInt>(I->getOperand(1))) { |
