diff options
Diffstat (limited to 'llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index 4a5a6d1ccbc..7c720d80092 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -2363,6 +2363,36 @@ 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(); + ICmpInst::Predicate 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()) && PredL == PredR) { + // (X > -1) ^ (Y > -1) --> (X ^ Y) < 0 + // (X < 0) ^ (Y < 0) --> (X ^ Y) < 0 + if ((match(LHS1, m_AllOnes()) && match(RHS1, m_AllOnes()) && + PredL == CmpInst::ICMP_SGT) || + (match(LHS1, m_Zero()) && match(RHS1, m_Zero()) && + PredL == CmpInst::ICMP_SLT)) { + Value *Zero = ConstantInt::getNullValue(LHS0->getType()); + return Builder.CreateICmpSLT(Builder.CreateXor(LHS0, RHS0), Zero); + } + } + if ((LHS->hasOneUse() || RHS->hasOneUse())) { + // (X > -1) ^ (Y < 0) --> (X ^ Y) > -1 + // (X < 0) ^ (Y > -1) --> (X ^ Y) > -1 + if ((match(LHS1, m_AllOnes()) && match(RHS1, m_Zero()) && + PredL == CmpInst::ICMP_SGT && PredR == CmpInst::ICMP_SLT) || + (match(LHS1, m_Zero()) && match(RHS1, m_AllOnes()) && + PredL == CmpInst::ICMP_SLT && PredR == CmpInst::ICMP_SGT)) { + 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. |
