[PATCH] D92668: [SLP]Merge reorder and reuse shuffles.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


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Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:3510
         }
       }
       int DeadCost = ReuseShuffleCost;
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anton-afanasyev wrote:
> 
I don't get it. What do you want to see here?


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Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:3513
+      if (!NeedToShuffleReuses && !E->ReorderIndices.empty())
         DeadCost += TTI->getShuffleCost(
             TargetTransformInfo::SK_PermuteSingleSrc, VecTy);
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anton-afanasyev wrote:
> Here `+=` looks confusing, we can just set `DeadCost = ...`, since `DeadCost == 0`.
No, `DeadCost` is not `0`, it is `ReuseShuffleCost`


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Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:4634
-      if (NeedToShuffleReuses)
-        V = Builder.CreateShuffleVector(V, E->ReuseShuffleIndices, "shuffle");
 
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anton-afanasyev wrote:
> Why do we ignore `ReuseShuffleIndices` here?
Because stores do not have uses, so this is actually just a dead code.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D92668/new/

https://reviews.llvm.org/D92668