[PATCH] D79003: [DAG] Add SimplifyDemandedVectorElts binop SimplifyMultipleUseDemandedBits handling

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Seems reasonable to me in general.



================
Comment at: llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp:2646-2649
     KnownUndef = getKnownUndefForVectorBinop(Op, TLO.DAG, UndefLHS, UndefRHS);
+
+    // Attempt to avoid multi-use ops if we don't need anything from them.
+    if (!DemandedElts.isAllOnesValue()) {
----------------
Just wondering, should we not demand elts that are `KnownUndef`?


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  https://reviews.llvm.org/D79003/new/

https://reviews.llvm.org/D79003