[PATCH] D42044: X86: Utilize ZeroableElements for canWidenShuffleElements

[Zvi Rackover via Phabricator via llvm-commits]

zvi added inline comments.


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Comment at: lib/Target/X86/X86ISelLowering.cpp:14401
     return DAG.getUNDEF(VT);
+  bool V2IsZero = !V2IsUndef && ISD::isBuildVectorAllZeros(V2.getNode());
 
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RKSimon wrote:
> ISD::isBuildVectorAllZeros allows undef elements (as long as it isn't all undefs) - should we test for a splat build vector of zero and check that we have no undefs at all?
What would be the benefit of that? I mean, undefs can be zeroed if profitable.


Repository:
  rL LLVM

https://reviews.llvm.org/D42044