diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 78689933f49..9996ebc2e74 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -727,7 +727,7 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) { if (Instruction::BinaryOps(LHS->getOpcode()) == I.getOpcode()) if (ConstantInt *LHSRHS = dyn_cast<ConstantInt>(LHS->getOperand(1))) { if (MultiplyOverflows(RHS, LHSRHS, - I.getOpcode()==Instruction::SDiv)) + I.getOpcode() == Instruction::SDiv)) return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType())); return BinaryOperator::Create(I.getOpcode(), LHS->getOperand(0), ConstantExpr::getMul(RHS, LHSRHS)); @@ -743,6 +743,25 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) { } } + if (ConstantInt *One = dyn_cast<ConstantInt>(Op0)) { + if (One->isOne() && !I.getType()->isIntegerTy(1)) { + bool isSigned = I.getOpcode() == Instruction::SDiv; + if (isSigned) { + // If Op1 is 0 then it's undefined behaviour, if Op1 is 1 then the + // result is one, if Op1 is -1 then the result is minus one, otherwise + // it's zero. + Value *Inc = Builder->CreateAdd(Op1, One); + Value *Cmp = Builder->CreateICmpULT( + Inc, ConstantInt::get(I.getType(), 3)); + return SelectInst::Create(Cmp, Op1, ConstantInt::get(I.getType(), 0)); + } else { + // If Op1 is 0 then it's undefined behaviour. If Op1 is 1 then the + // result is one, otherwise it's zero. + return new ZExtInst(Builder->CreateICmpEQ(Op1, One), I.getType()); + } + } + } + // See if we can fold away this div instruction. if (SimplifyDemandedInstructionBits(I)) return &I; |
