diff options
Diffstat (limited to 'llvm/lib/Transforms')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 29 |
1 files changed, 19 insertions, 10 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 4b5891461bc..e8e9e86d08b 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1499,16 +1499,25 @@ Instruction *InstCombiner::foldICmpXorConstant(ICmpInst &Cmp, } } - // (icmp ugt (xor X, C), ~C) -> (icmp ult X, C) - // iff -C is a power of 2 - if (Pred == ICmpInst::ICMP_UGT && *XorC == ~C && (C + 1).isPowerOf2()) - return new ICmpInst(ICmpInst::ICMP_ULT, X, Y); - - // (icmp ult (xor X, C), -C) -> (icmp uge X, C) - // iff -C is a power of 2 - if (Pred == ICmpInst::ICMP_ULT && *XorC == -C && C.isPowerOf2()) - return new ICmpInst(ICmpInst::ICMP_UGE, X, Y); - + // Mask constant magic can eliminate an 'xor' with unsigned compares. + if (Pred == ICmpInst::ICMP_UGT) { + // (xor X, ~C) >u C --> X <u ~C (when C+1 is a power of 2) + if (*XorC == ~C && (C + 1).isPowerOf2()) + return new ICmpInst(ICmpInst::ICMP_ULT, X, Y); + // (xor X, C) >u C --> X >u C (when C+1 is a power of 2) + if (*XorC == C && (C + 1).isPowerOf2()) + return new ICmpInst(ICmpInst::ICMP_UGT, X, Y); + } + if (Pred == ICmpInst::ICMP_ULT) { + // (xor X, -C) <u C --> X >u ~C (when C is a power of 2) + if (*XorC == -C && C.isPowerOf2()) + return new ICmpInst(ICmpInst::ICMP_UGT, X, + ConstantInt::get(X->getType(), ~C)); + // (xor X, C) <u C --> X >u ~C (when -C is a power of 2) + if (*XorC == C && (-C).isPowerOf2()) + return new ICmpInst(ICmpInst::ICMP_UGT, X, + ConstantInt::get(X->getType(), ~C)); + } return nullptr; } |
