[PATCH] D126939: [SLP] Avoid converting undef to poison when gathering.

[Vasileios Porpodas via Phabricator via llvm-commits]

vporpo added a comment.

Nuno was right, the previous patch was over reduced. The issue happens when the input is reachable and undef. I think in this case SLP is actually changing the program behavior.



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Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:7559
         NumValues = VF;
+      } else if (UniqueValues.size() == 1 && NumValues == 1) {
+        NumValues = VF;
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@ABataev I am not sure this is the right fix for it, please take a look.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D126939/new/

https://reviews.llvm.org/D126939