[PATCH] D107597: [DAG] Fold concat_vectors(concat_vectors(x,y),concat_vectors(a,b)) -> concat_vectors(x,y,a,b)

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Thanks. Both Arm parts look OK to me (the MVE code for concating predicate registers just needs to work, it does not need to be very efficient :) )



================
Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:19899
+    for (const SDValue &Sub : Op->ops())
+      ConcatOps.push_back(Sub);
+  }
----------------
Can this use ConcatOps.append?


================
Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:13587
   // canonicalise to that.
   if (N0 == N1 && VT.getVectorNumElements() == 2) {
     assert(VT.getScalarSizeInBits() == 64);
----------------
Can you add a N->getNumOperands() == 2 check here, to be safe.


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