[llvm] [SLP][REVEC] Make ShuffleCostEstimator and ShuffleInstructionBuilder can vectorize vector instructions. (PR #99606)

[Alexey Bataev via llvm-commits]

https://github.com/alexey-bataev commented:

> > Need the tests
> 
> This PR and #99499 are trying to solve the same test (test3 in `llvm/test/Transforms/SLPVectorizer/revec.ll`). Do I need to merge this into #99499?

Probably, the patch is not acceptable without tests

https://github.com/llvm/llvm-project/pull/99606