[llvm] [SLP]Do not account external uses in EH block and in non-returning blocks (PR #112045)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> By bailing on unreachable are we affecting existing reduced regression tests that insert them?

Yes. I will update such tests and remove unreachable terminator. Actually, SLP vectorizer should ignore such blocks, no need to vectorize anything there to save compile time. And in EH blocks too.

https://github.com/llvm/llvm-project/pull/112045