[CVP] Set NSW/NUW flags when simplifying with.overflow

When CVP determines that a with.overflow intrinsic cannot overflow,
it currently inserts a simple add/sub. As we already determined that
there can be no overflow, we should add the appropriate NUW/NSW flag.

Differential Revision: https://reviews.llvm.org/D60585

llvm-svn: 358298

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
index e6dd42d893f..e9af934fbb6 100644
--- a/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
+++ b/llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
@@ -435,12 +435,16 @@ static void processOverflowIntrinsic(IntrinsicInst *II) {
   default:
     llvm_unreachable("Unexpected instruction.");
   case Intrinsic::uadd_with_overflow:
+    NewOp = B.CreateNUWAdd(II->getOperand(0), II->getOperand(1), II->getName());
+    break;
   case Intrinsic::sadd_with_overflow:
-    NewOp = B.CreateAdd(II->getOperand(0), II->getOperand(1), II->getName());
+    NewOp = B.CreateNSWAdd(II->getOperand(0), II->getOperand(1), II->getName());
     break;
   case Intrinsic::usub_with_overflow:
+    NewOp = B.CreateNUWSub(II->getOperand(0), II->getOperand(1), II->getName());
+    break;
   case Intrinsic::ssub_with_overflow:
-    NewOp = B.CreateSub(II->getOperand(0), II->getOperand(1), II->getName());
+    NewOp = B.CreateNSWSub(II->getOperand(0), II->getOperand(1), II->getName());
     break;
   }
   ++NumOverflows;