[llvm] [SLP] Check for extracts, being replaced by original scalars, for user nodes (PR #149572)

[Gaëtan Bossu via llvm-commits]

https://github.com/gbossu commented:

Drive-by comments. I think I understand what this is attempting to do, but I don't understand how the implementation works. I left a couple of comments, I would be happy to get your thoughts on them. Then I'll probably do another round of review.

https://github.com/llvm/llvm-project/pull/149572