[PATCH] D116276: [IndVarS] Keep the nsw/nuw flags after simplifyAndExtend

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

@guopeilin This doesn't really answer my question. You say that the SCEV for the wide IV at this point is `{((sext i32 %arg1 to i64) + (sext i32 %arg2 to i64)),+,(sext i32 %arg2 to i64)}<nsw><%body>`, which has the `<nsw>` flag. My baseline expectation would be that SCEVExpander will also add the nsw flag to the expanded IR (see the code around https://github.com/llvm/llvm-project/blob/015ff729cb90317e4e75cf48b1e5dd7850f0cbd0/llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp#L1300-L1304). My question is why that doesn't happen, because making sure SCEVExpander propagates the flag from SCEV to IR seems like the more principled way to address this problem.


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  https://reviews.llvm.org/D116276/new/

https://reviews.llvm.org/D116276