[llvm] [SLP] Vectorize non-power-of-2 ops. (PR #77790)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

Updated the PR with the version without padding, including addressing @alexey-bataev 's comments at 0ddbdd3052e694eedef6bccce3b17f92dff7add7

https://github.com/llvm/llvm-project/pull/77790