[PATCH] D56875: [DAGCombiner] narrow vector binop with 2 insert subvector operands

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon accepted this revision.
RKSimon added a comment.
This revision is now accepted and ready to land.

LGTM with one minor



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Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:18209
+        TLI.isOperationLegalOrCustomOrPromote(N->getOpcode(), NarrowVT)) {
+      // bo (ins undef, X, Z), (ins undef, Y, Z) --> ins undef, (bo X, Y), Z
+      SDValue NarrowBO = DAG.getNode(N->getOpcode(), SDLoc(N), NarrowVT, X, Y);
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(very minor) Move this comment to the outer if() and use the same terms as we used in the shuffle fold above. 

Also, explain that this is likely to occur in reduction patterns.


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https://reviews.llvm.org/D56875