[LV] Only skip scalarization overhead for members used as address.
Refine logic to scalarize interleave group member: only skip
scalarization overhead for member being used as addresses. For others,
use the regular scalar memory op cost.
This currently doesn't trigger in practice as far as I could find, but
fixes a potential divergence between VPlan- and legacy cost models.
It fixes a concrete divergence with a follow-up patch,
https://github.com/llvm/llvm-project/pull/161276.
llvm-project
4c46ae39 - [LV] Only skip scalarization overhead for members used as address.
