diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 39 |
1 files changed, 21 insertions, 18 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 41ae37ee127..c7092bf3a39 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -2433,29 +2433,32 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) { if (Value *V = SimplifyBSwap(I)) return replaceInstUsesWith(I, V); + // Apply DeMorgan's Law for 'nand' / 'nor' logic with an inverted operand. + Value *X, *Y; + + // We must eliminate the and/or (one-use) for these transforms to not increase + // the instruction count. + // ~(~X & Y) --> (X | ~Y) + // ~(Y & ~X) --> (X | ~Y) + if (match(&I, m_Not(m_OneUse(m_c_And(m_Not(m_Value(X)), m_Value(Y)))))) { + Value *NotY = Builder->CreateNot(Y, Y->getName() + ".not"); + return BinaryOperator::CreateOr(X, NotY); + } + // ~(~X | Y) --> (X & ~Y) + // ~(Y | ~X) --> (X & ~Y) + if (match(&I, m_Not(m_OneUse(m_c_Or(m_Not(m_Value(X)), m_Value(Y)))))) { + Value *NotY = Builder->CreateNot(Y, Y->getName() + ".not"); + return BinaryOperator::CreateAnd(X, NotY); + } + // Is this a 'not' (~) fed by a binary operator? BinaryOperator *NotOp; if (match(&I, m_Not(m_BinOp(NotOp)))) { if (NotOp->getOpcode() == Instruction::And || NotOp->getOpcode() == Instruction::Or) { - // 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 - // ~(X | Y) === (~X & ~Y) - De Morgan's Law + // Apply DeMorgan's Law when inverts are free: + // ~(X & Y) --> (~X | ~Y) + // ~(X | Y) --> (~X & ~Y) if (IsFreeToInvert(NotOp->getOperand(0), NotOp->getOperand(0)->hasOneUse()) && IsFreeToInvert(NotOp->getOperand(1), |
