[PATCH] D59777: [x86] improve AVX lowering of vector zext

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:9899
+  return true;
+}
+
----------------
This might fail if one half has an undef mask value and the other doesn't and we then use the mask half with the undef (there's probably a better way to phrase that....) - we need to return a merged mask with the mask value set to the non-undef case. IIRC we used to have a helper to do this but it evolved into isRepeatedShuffleMask which assumes sublane offsets.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D59777/new/

https://reviews.llvm.org/D59777