[PATCH] D62613: [DAGCombiner] Replace gathers with a zero mask with the passthru value

[Benjamin Kramer via Phabricator via llvm-commits]

bkramer marked 4 inline comments as done.
bkramer added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:8092
+  // Zap gathers with a zero mask.
+  if (isNullOrNullSplat(Mask))
+    return CombineTo(N, MGT->getPassThru(), MGT->getChain());
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craig.topper wrote:
> I wonder if we should just use ISD::isBuildVectorAllZeros here.
That's indeed simpler. Why do we have so many of these things? :(


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Comment at: llvm/test/CodeGen/AArch64/vecreduce-bool.ll:100
 ; CHECK-NEXT:    and v0.16b, v0.16b, v1.16b
+; CHECK-NEXT:    cmlt v0.16b, v0.16b, #0
 ; CHECK-NEXT:    uminv b0, v0.16b
----------------
craig.topper wrote:
> I assume this was caused by the isNullOrNullSplat change?
Yeah. It's a minor improvement. But I dropped this for now.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62613/new/

https://reviews.llvm.org/D62613