[PATCH] D157598: [InstCombine] Transform sub(sext(add(X, Y)), sext(add(X, Z))) to sub(Y, Z) given nsw adds

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp:2477
+    Value *S2 = Builder.CreateSExt(Z, Ty);
+    return BinaryOperator::CreateSub(S1, S2);
+  }
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nikic wrote:
> It looks like it's legal to transfer the nsw flag to the sub here (https://alive2.llvm.org/ce/z/cYJh4x). But not in the nuw case (https://alive2.llvm.org/ce/z/jHsEcP).
Okay, I see in the tests that the nsw will get inferred anyway, so I guess there's no need to make it explicit.


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  https://reviews.llvm.org/D157598/new/

https://reviews.llvm.org/D157598