Index: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp =================================================================== --- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1714,22 +1714,6 @@ } } - // (X & C2) > C1 --> (X & C2) != 0, if any bit set in (X & C2) will produce a - // result greater than C1. Also handle (X & C2) < C1 --> (X & C2) == 0. - if (!C2->isNullValue()) { - unsigned NumTZ = C2->countTrailingZeros(); - if (Cmp.getPredicate() == ICmpInst::ICMP_UGT && - NumTZ >= C1->getActiveBits()) { - Constant *Zero = Constant::getNullValue(And->getType()); - return new ICmpInst(ICmpInst::ICMP_NE, And, Zero); - } - if (Cmp.getPredicate() == ICmpInst::ICMP_ULT && - NumTZ >= C1->ceilLogBase2()) { - Constant *Zero = Constant::getNullValue(And->getType()); - return new ICmpInst(ICmpInst::ICMP_EQ, And, Zero); - } - } - return nullptr; } @@ -4221,6 +4205,11 @@ if (Op1Min == Op0Min + 1) return new ICmpInst(ICmpInst::ICMP_EQ, Op0, ConstantInt::get(Op0->getType(), Op1Min - 1)); + // X X == 0, if the number of zero bits in the bottom of X + // exceeds the log2 of C. + if (Op0Known.countMinTrailingZeros() >= Op1Min.ceilLogBase2()) + return new ICmpInst(ICmpInst::ICMP_EQ, Op0, + Constant::getNullValue(Op1->getType())); } break; } @@ -4237,6 +4226,11 @@ if (Op1Min == Op0Max - 1) return new ICmpInst(ICmpInst::ICMP_EQ, Op0, ConstantInt::get(Op1->getType(), Op1Min + 1)); + // X >u C --> X != 0, if the number of zero bits in the bottom of X + // exceeds the log2 of C. + if (Op0Known.countMinTrailingZeros() >= Op1Min.getActiveBits()) + return new ICmpInst(ICmpInst::ICMP_NE, Op0, + Constant::getNullValue(Op1->getType())); } break; }