diff options
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 8461aa75e0..fce23739b6 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -2957,20 +2957,22 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { return BinaryOperator::CreateNeg(Op0); ConstantInt *RHSNeg = cast<ConstantInt>(ConstantExpr::getNeg(RHS)); + APInt RHSNegAPI(RHSNeg->getBitWidth(), RHSNeg->getSExtValue(), true); + + APInt NegOne = -APInt(RHSNeg->getBitWidth(), 1, true); + APInt TwoToExp(RHSNeg->getBitWidth(), 1 << (RHSNeg->getBitWidth() - 1), + true); // -X/C -> X/-C, if and only if negation doesn't overflow. - if ((RHS->getSExtValue() < 0 && - RHS->getSExtValue() < RHSNeg->getSExtValue()) || - (RHS->getSExtValue() > 0 && - RHS->getSExtValue() > RHSNeg->getSExtValue())) { + if ((RHS->getSExtValue() < 0 && RHSNegAPI.slt(TwoToExp - 1)) || + (RHS->getSExtValue() > 0 && RHSNegAPI.sgt(TwoToExp * NegOne))) { if (Value *LHSNeg = dyn_castNegVal(Op0)) { if (ConstantInt *CI = dyn_cast<ConstantInt>(LHSNeg)) { ConstantInt *CINeg = cast<ConstantInt>(ConstantExpr::getNeg(CI)); + APInt CINegAPI(CINeg->getBitWidth(), CINeg->getSExtValue(), true); - if ((CI->getSExtValue() < 0 && - CI->getSExtValue() < CINeg->getSExtValue()) || - (CI->getSExtValue() > 0 && - CI->getSExtValue() > CINeg->getSExtValue())) + if ((CI->getSExtValue() < 0 && CINegAPI.slt(TwoToExp - 1)) || + (CI->getSExtValue() > 0 && CINegAPI.sgt(TwoToExp * NegOne))) return BinaryOperator::CreateSDiv(LHSNeg, ConstantExpr::getNeg(RHS)); } |