[PATCH] D121187: [DAGCombiner][VP] Add DAGCombine for VP_MUL.

[Jianjian Guan via Phabricator via llvm-commits]

jacquesguan added inline comments.


================
Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:22807
+
+  // fold vp_mul X, (splat 0), Mask, EVL -> vp_select Mask, undef, (splat 0),
+  // EVL
----------------
simoll wrote:
> craig.topper wrote:
> > If one of the true/false values of the VP_SELECT is undef can we ignore the mask and EVL and return the other operand? @simoll @frasercrmck
> I believe so. Also for vp ops other than select or merge, if the mask is undef, we can scratch the operation entirely. If evl is undef, we can cut short to `unreachable`.
Done, thanks.


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https://reviews.llvm.org/D121187