Fix an icmp+sdiv optimization to check for and handle an overflow
condition. This fixes PR2740.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56076 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 03fdc08..8f57820 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -4695,6 +4695,21 @@
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 @@
// 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