[llvm] [SLP][REVEC] Fix CommonMask is transformed into vector form but used outside finalize. (PR #120952)

[Alexey Bataev via llvm-commits]

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

I don't like this approach. We'd better to operate with actual-sized masks/shuffles, otherwise at least cost is not estimated correctly

https://github.com/llvm/llvm-project/pull/120952