[PATCH] D134477: [isel] Lower vector interleave into unpck and perm

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon added inline comments.


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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:17802
+  bool IsFirstHalf = IsInterleavingPattern(Mask, 0, 32);
+  bool IsSecondHalf = IsInterleavingPattern(Mask, 16, 48);
+  if (!IsFirstHalf && !IsSecondHalf)
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I'd probably replace these hard coded numbers with more general NumElts / NumEltsPerLane variables.


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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:17841
+    DAG.ReplaceAllUsesWith(SecondHalf, &Perm2);
+    return Perm1;
+  }
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Why are the ReplaceAllUsesWith calls necessary? We usually just rely on combines / demandedelts to replace these.


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Comment at: llvm/lib/Target/X86/X86ISelLowering.cpp:18513
+          lowerShufflePairAsUNPCKAndPermute(DL, MVT::v32i8, V1, V2, Mask, DAG))
+    return V;
+
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I'm still not certain if we're better off trying to perform this in lowering or via shuffle combining or maybe combineConcatVectorOps?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134477/new/

https://reviews.llvm.org/D134477