Add the nsw flag when we detect that an add will not signed overflow.

We already had a function for checking this, we were just using it only in
specialized cases.

llvm-svn: 210029

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index c37a9cf2..4d8a1ef 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1191,6 +1191,11 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
       return BinaryOperator::CreateOr(A, B);
   }
 
+  if (!I.hasNoSignedWrap() && WillNotOverflowSignedAdd(LHS, RHS)) {
+    Changed = true;
+    I.setHasNoSignedWrap(true);
+  }
+
   return Changed ? &I : nullptr;
 }