Fix a copy+paste bug that Duncan spotted. For several
cases it was still getting lucky and detecting overflow
but it was clearly incorrect.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56113 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 46ac762..5a9d1de 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -4699,7 +4699,7 @@
 /// overflowed for this type.
 static bool SubWithOverflow(ConstantInt *&Result, ConstantInt *In1,
                             ConstantInt *In2, bool IsSigned = false) {
-  Result = cast<ConstantInt>(Add(In1, In2));
+  Result = cast<ConstantInt>(Subtract(In1, In2));
 
   if (IsSigned)
     if (In2->getValue().isNegative())