[llvm] [SLP] Loop aware cost model/tree building (PR #150450)

[Nikita Popov via llvm-commits]

nikic wrote:

This also causes a compile-time regression: https://llvm-compile-time-tracker.com/compare.php?from=9d8810cbd39f0d0cf9eddea81bf149ce034df6c0&to=8963edb534e28d548d8381675bb18af1770c3041&stat=instructions:u

https://github.com/llvm/llvm-project/pull/150450