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

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

Thanks for the patch, but this is too early to land. I'm working on non-power-of-2 vectorization (it is WIP and still requires couple more patches to go). Being implemented without some extra patches it leads to perf regression in some cases. Need to handle all this stuff correctly.
Would be good if you could land new tests separately, may help with the perf gains/regressions later.

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