diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 669ef2d516..b875420e5b 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -3077,6 +3077,14 @@ Instruction *InstCombiner::visitSDiv(BinaryOperator &I) { RHS->getValue().exactLogBase2()); return BinaryOperator::CreateAShr(Op0, ShAmt, I.getName()); } + + // -X/C --> X/-C provided the negation doesn't overflow. + if (SubOperator *Sub = dyn_cast<SubOperator>(Op0)) + if (isa<Constant>(Sub->getOperand(0)) && + cast<Constant>(Sub->getOperand(0))->isNullValue() && + Sub->hasNoSignedOverflow()) + return BinaryOperator::CreateSDiv(Sub->getOperand(1), + ConstantExpr::getNeg(RHS)); } // If the sign bits of both operands are zero (i.e. we can prove they are |