[PATCH] D124769: [SLP] AdjustExtractsCost - remove redundant subvector extraction code

[Alexey Bataev via Phabricator via llvm-commits]

ABataev added a comment.

I rather doubt that it is redundant. This code is for the case, where the buildvector of extractelements results in the different vector size rather than the original size of vector(say, we extract elements from <4x i32> but the the resulting vector is <8xi32> or <2 x i32>). In this case we need to take the inser/extract subvector cost, especially if the we insert somewhere in the middle of the vector register. Instead, we need to adjust/fix the idx for TargetTransformInfo::SK_InsertSubvector shuffle kind, currently it is too optimistic. I used 0 here because TTI cost model was not optimal and in many cases we ended up with scalarization overhead rather than actual shuffles.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D124769/new/

https://reviews.llvm.org/D124769