[PATCH] D90338: [SCEV] Infer addrec nowrap flags while calculating ranges (WIP)

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev added inline comments.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:5701
+                                MaxBECountValue, BitWidth, /* Signed = */ true);
+  RangeAndFlags SignedRes(SignedRes1.first.unionWith(SignedRes2.first),
+                          maskFlags(SignedRes1.second, SignedRes2.second));
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I understand why the union will retain `nsw` in this case, but what about `nuw`? See example in my comment below.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:5893
+  return {TrueRes.first.unionWith(FalseRes.first),
+          maskFlags(TrueRes.second, FalseRes.second)};
 }
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If first range is `[-5; -1]<nuw><nsw>` and second range is `[1; 5]<nuw><nsw>`, we'll end up with smth like `[-5; 5]<nuw><nsw>`. This doesn't feel right.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D90338/new/

https://reviews.llvm.org/D90338