[llvm] [InstCombine] When -A + B both have nsw flag, set nsw flag. (PR #72127)

[via llvm-commits]

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@@ -1487,7 +1487,11 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
       return BinaryOperator::CreateNeg(Builder.CreateAdd(A, B));
 
     // -A + B --> B - A
-    return BinaryOperator::CreateSub(RHS, A);
+    auto *Sub = BinaryOperator::CreateSub(RHS, A);
+    auto *OB0 = dyn_cast<OverflowingBinaryOperator>(LHS);
+    Sub->setHasNoSignedWrap(I.hasNoSignedWrap() && OB0->hasNoSignedWrap());
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goldsteinn wrote:

yeah, sorry I misread.

https://github.com/llvm/llvm-project/pull/72127