[PATCH] D33137: [DAGCombiner] use narrow vector ops to eliminate concat/extract (PR32790)

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added a comment.

Couple of minor thoughts but nothing critical.



================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14462
+  if (!ExtractIndex)
+    return SDValue();
+
----------------
visitEXTRACT_SUBVECTOR is doing quite a bit of similar stuff already (constant index, peeling through bitcasts of the source vector, etc.) is it worth reusing some of that?


================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:14516
+  if (!ConcatL && !ConcatR)
+    return SDValue();
+
----------------
x86 has a tendency to convert to concat_vector to chains of insert_subvectors quite early - have you noticed if we're missing anything because of this?


https://reviews.llvm.org/D33137