[PATCH] D159205: [SLP]Try to vectorize scalars, being vectorized already, but do not need to be scheduled.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added a comment.

In D159205#4648767 <https://reviews.llvm.org/D159205#4648767>, @bgraur wrote:

> In D159205#4648763 <https://reviews.llvm.org/D159205#4648763>, @ABataev wrote:
>
>> In D159205#4648753 <https://reviews.llvm.org/D159205#4648753>, @bgraur wrote:
>>
>>>> Is there something else above, like assertion message? It would really help more rather than the rest of the stack trace
>>>
>>> No, I've built the code with assertions enabled in the compiler and no assertion was triggered. The stack trace is all I get.
>>
>> Ok, I'll try to prepare a fix, but it would be good to see a reproducer.
>
> Working on the repro. Please CC me to the fix and I can check if it fixes the issue.

I have a patch, could you try it?

  diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
  index 38ef4fa9464f..94abd8ac59da 100644
  --- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
  +++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
  @@ -2916,8 +2916,11 @@ private:
           const TreeEntry *TE = getTreeEntry(V);
           assert((!TE || TE == Last || doesNotNeedToBeScheduled(V)) &&
                  "Scalar already in tree!");
  -        if (TE)
  +        if (TE) {
  +          if (TE != Last)
  +            MultiNodeScalar.insert(V);
             continue;
  +        }
           ScalarToTreeEntry[V] = Last;
         }
         // Update the scheduler bundle to point to this TreeEntry.
  @@ -2976,6 +2979,9 @@ private:
     /// Maps a specific scalar to its tree entry.
     SmallDenseMap<Value *, TreeEntry *> ScalarToTreeEntry;
  
  +  /// List of scalar, used in several vectorize nodes.
  +  SmallDenseSet<Value *> MultiNodeScalar;
  +
     /// Maps a value to the proposed vectorizable size.
     SmallDenseMap<Value *, unsigned> InstrElementSize;
  
  @@ -9843,17 +9849,32 @@ Value *BoUpSLP::vectorizeOperand(TreeEntry *E, unsigned NodeIdx) {
         S = getSameOpcode(*It, *TLI);
     }
     if (S.getOpcode()) {
  -    if (TreeEntry *VE = getTreeEntry(S.OpValue);
  -        VE && VE->isSame(VL) &&
  -        (any_of(VE->UserTreeIndices,
  -                [E, NodeIdx](const EdgeInfo &EI) {
  -                  return EI.UserTE == E && EI.EdgeIdx == NodeIdx;
  -                }) ||
  -         any_of(VectorizableTree,
  -                [E, NodeIdx, VE](const std::unique_ptr<TreeEntry> &TE) {
  -                  return TE->isOperandGatherNode({E, NodeIdx}) &&
  -                         VE->isSame(TE->Scalars);
  -                }))) {
  +    auto CheckSameVE = [&](const TreeEntry *VE) {
  +      return VE->isSame(VL) &&
  +             (any_of(VE->UserTreeIndices,
  +                     [E, NodeIdx](const EdgeInfo &EI) {
  +                       return EI.UserTE == E && EI.EdgeIdx == NodeIdx;
  +                     }) ||
  +              any_of(VectorizableTree,
  +                     [E, NodeIdx, VE](const std::unique_ptr<TreeEntry> &TE) {
  +                       return TE->isOperandGatherNode({E, NodeIdx}) &&
  +                              VE->isSame(TE->Scalars);
  +                     }));
  +    };
  +    TreeEntry *VE = getTreeEntry(S.OpValue);
  +    bool IsSameVE = VE && CheckSameVE(VE);
  +    if (!IsSameVE && MultiNodeScalar.contains(S.OpValue)) {
  +      auto *I =
  +          find_if(VectorizableTree, [&](const std::unique_ptr<TreeEntry> &TE) {
  +            return TE->State != TreeEntry::NeedToGather && TE.get() != VE &&
  +                   CheckSameVE(TE.get());
  +          });
  +      if (I != VectorizableTree.end()) {
  +        VE = I->get();
  +        IsSameVE = true;
  +      }
  +    }
  +    if (IsSameVE) {
         auto FinalShuffle = [&](Value *V, ArrayRef<int> Mask) {
           ShuffleInstructionBuilder ShuffleBuilder(Builder, *this);
           ShuffleBuilder.add(V, Mask);


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