[llvm] [SLP][TTI]Add support for strided loads. (PR #80310)

[Philip Reames via llvm-commits]

https://github.com/preames commented:

Can I ask you to separate the TTI pieces to a separate review?  I'd be comfortable LGTMing that with some pretty minimal changes, but can't reasonable review the SLP changes in any depth.

https://github.com/llvm/llvm-project/pull/80310