[PATCH] D31961: DAGCombine: Combine shuffles of splat-shuffles

[Sanjay Patel via Phabricator via llvm-commits]

spatel added inline comments.


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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14622-14624
+// If splat-mask contains undef elements, we need to be careful about
+// introducing undef's in the folded mask which are not the result of composing
+// the masks of the shuffles.
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Do you think we'll need to distinguish between the "strict" splat and splat-with-undef cases anywhere else? I'm wondering if it would be better to add a bool "HasAnyUndefs" param to ShuffleVectorSDNode::isSplat(). Even if we don't have another use case at the moment, that would at least make the API more like BuildVectorSDNode::isConstantSplat().


Repository:
  rL LLVM

https://reviews.llvm.org/D31961