diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/Scalar/InstructionCombining.cpp | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp index 03fdc08c8b..8f578200d6 100644 --- a/lib/Transforms/Scalar/InstructionCombining.cpp +++ b/lib/Transforms/Scalar/InstructionCombining.cpp @@ -4695,6 +4695,21 @@ static bool AddWithOverflow(ConstantInt *&Result, ConstantInt *In1, return Result->getValue().ult(In1->getValue()); } +/// SubWithOverflow - Compute Result = In1-In2, returning true if the result +/// overflowed for this type. +static bool SubWithOverflow(ConstantInt *&Result, ConstantInt *In1, + ConstantInt *In2, bool IsSigned = false) { + Result = cast<ConstantInt>(Add(In1, In2)); + + if (IsSigned) + if (In2->getValue().isNegative()) + return Result->getValue().slt(In1->getValue()); + else + return Result->getValue().sgt(In1->getValue()); + else + return Result->getValue().ugt(In1->getValue()); +} + /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the /// code necessary to compute the offset from the base pointer (without adding /// in the base pointer). Return the result as a signed integer of intptr size. @@ -5774,7 +5789,7 @@ Instruction *InstCombiner::FoldICmpDivCst(ICmpInst &ICI, BinaryOperator *DivI, // e.g. X/-5 op -3 --> [15, 20) LoBound = Prod; LoOverflow = HiOverflow = ProdOV ? 1 : 0; - HiBound = Subtract(Prod, DivRHS); + HiOverflow = SubWithOverflow(HiBound, Prod, DivRHS, true); } // Dividing by a negative swaps the condition. LT <-> GT |