move a transformation to a more logical place, simplifying it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122183 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index b215ee8..5fa930e 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1147,6 +1147,13 @@
EraseInstFromFunction(*II);
return BinaryOperator::CreateAdd(LHS, RHS);
}
+
+ // If the normal result of the add is dead, and the RHS is a constant,
+ // we can transform this into a range comparison.
+ // overflow = uadd a, -4 --> overflow = icmp ugt a, 3
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1)))
+ return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0),
+ ConstantExpr::getNot(CI));
break;
case Intrinsic::usub_with_overflow:
case Intrinsic::ssub_with_overflow: