diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index af116db659f..16e8c4ff92c 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -2363,6 +2363,34 @@ Value *InstCombiner::foldXorOfICmps(ICmpInst *LHS, ICmpInst *RHS) { } } + // TODO: This can be generalized to compares of non-signbits using + // decomposeBitTestICmp(). It could be enhanced more by using (something like) + // foldLogOpOfMaskedICmps(). + ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate(); + Value *LHS0 = LHS->getOperand(0), *LHS1 = LHS->getOperand(1); + Value *RHS0 = RHS->getOperand(0), *RHS1 = RHS->getOperand(1); + if ((LHS->hasOneUse() || RHS->hasOneUse()) && + LHS0->getType() == RHS0->getType()) { + // (X > -1) ^ (Y > -1) --> (X ^ Y) < 0 + // (X < 0) ^ (Y < 0) --> (X ^ Y) < 0 + if ((PredL == CmpInst::ICMP_SGT && match(LHS1, m_AllOnes()) && + PredR == CmpInst::ICMP_SGT && match(RHS1, m_AllOnes())) || + (PredL == CmpInst::ICMP_SLT && match(LHS1, m_Zero()) && + PredR == CmpInst::ICMP_SLT && match(RHS1, m_Zero()))) { + Value *Zero = ConstantInt::getNullValue(LHS0->getType()); + return Builder.CreateICmpSLT(Builder.CreateXor(LHS0, RHS0), Zero); + } + // (X > -1) ^ (Y < 0) --> (X ^ Y) > -1 + // (X < 0) ^ (Y > -1) --> (X ^ Y) > -1 + if ((PredL == CmpInst::ICMP_SGT && match(LHS1, m_AllOnes()) && + PredR == CmpInst::ICMP_SLT && match(RHS1, m_Zero())) || + (PredL == CmpInst::ICMP_SLT && match(LHS1, m_Zero()) && + PredR == CmpInst::ICMP_SGT && match(RHS1, m_AllOnes()))) { + Value *MinusOne = ConstantInt::getAllOnesValue(LHS0->getType()); + return Builder.CreateICmpSGT(Builder.CreateXor(LHS0, RHS0), MinusOne); + } + } + // Instead of trying to imitate the folds for and/or, decompose this 'xor' // into those logic ops. That is, try to turn this into an and-of-icmps // because we have many folds for that pattern. |
