diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 24 |
1 files changed, 14 insertions, 10 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index e37ceb58f15..41ae37ee127 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -2438,16 +2438,20 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) { if (match(&I, m_Not(m_BinOp(NotOp)))) { if (NotOp->getOpcode() == Instruction::And || NotOp->getOpcode() == Instruction::Or) { - // ~(~X & Y) --> (X | ~Y) - De Morgan's Law - // ~(~X | Y) === (X & ~Y) - De Morgan's Law - if (dyn_castNotVal(NotOp->getOperand(1))) - NotOp->swapOperands(); - if (Value *Op0NotVal = dyn_castNotVal(NotOp->getOperand(0))) { - Value *NotY = Builder->CreateNot( - NotOp->getOperand(1), NotOp->getOperand(1)->getName() + ".not"); - if (NotOp->getOpcode() == Instruction::And) - return BinaryOperator::CreateOr(Op0NotVal, NotY); - return BinaryOperator::CreateAnd(Op0NotVal, NotY); + // We must eliminate the and/or for this transform to not increase the + // instruction count. + if (NotOp->hasOneUse()) { + // ~(~X & Y) --> (X | ~Y) - De Morgan's Law + // ~(~X | Y) === (X & ~Y) - De Morgan's Law + if (dyn_castNotVal(NotOp->getOperand(1))) + NotOp->swapOperands(); + if (Value *Op0NotVal = dyn_castNotVal(NotOp->getOperand(0))) { + Value *NotY = Builder->CreateNot( + NotOp->getOperand(1), NotOp->getOperand(1)->getName() + ".not"); + if (NotOp->getOpcode() == Instruction::And) + return BinaryOperator::CreateOr(Op0NotVal, NotY); + return BinaryOperator::CreateAnd(Op0NotVal, NotY); + } } // ~(X & Y) --> (~X | ~Y) - De Morgan's Law |
