[llvm] [VPlan] Only apply forced cost to recipes with underlying values. (PR #168372)

[Florian Hahn via llvm-commits]

fhahn wrote:

> LGTM, although I still think there isn't much value in trying to maintain the legacy/vplan cost model assert when the user is explicitly trying to assign arbitrary costs to things.

Thanks, it should help to keep the cases where we apply the forced costs consistent with where we apply VPlan-based costs without forced costs.

https://github.com/llvm/llvm-project/pull/168372