[PATCH] D63138: [Analysis] add isSplatValue() for vectors in IR

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/lib/Analysis/VectorUtils.cpp:333
+    if (isa<UndefValue>(V))
+      return true;
+    // FIXME: Constant splat analysis does not allow undef elements.
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This seems potentially problematic, as there's no guarantee that all (independent) undef values will be chosen to be the same value down the line.

I don't know if this is a problem in the context where this is intended to be used though. Is isSplatValue() going to be used heuristically (for profitability) or is it necessary for transformation correctness?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D63138/new/

https://reviews.llvm.org/D63138