[PATCH] D149742: [SLP]Improve isGatherShuffledEntry by trying per-register shuffle.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:8908
 
-std::optional<TargetTransformInfo::ShuffleKind>
-BoUpSLP::isGatherShuffledEntry(const TreeEntry *TE, ArrayRef<Value *> VL,
-                               SmallVectorImpl<int> &Mask,
-                               SmallVectorImpl<const TreeEntry *> &Entries) {
+SmallVector<std::optional<TargetTransformInfo::ShuffleKind>>
+BoUpSLP::isGatherShuffledEntry(
----------------
reames wrote:
> Stylistic suggestion here.  This function is quite complicated, and following all the changes through are tricky.  I *think* this is just performing the same operation for each sub-range (divided by register).  If so, I'd suggest leaving the function alone, and introducing a wrapper which just calls the old version with a sub-range of the VLs, and builds up the vector results.  
> 
> If this works here, then applying the same basic idea throughout the patch would make it much easier to follow and review.
Yes, it splits the multi-register vector into several one-register vectors and just performs the same analysis, as before, to avoid long multi-vector shuffles. Will try to move the previous logic into a separate function.


Repository:
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  https://reviews.llvm.org/D149742/new/

https://reviews.llvm.org/D149742