[llvm] [InlineCost] Consider the default branch when calculating cost (PR #77856)

[Nikita Popov via llvm-commits]

nikic wrote:

We need to understand what is no longer getting inlined and see whether there is either some optimization of cost modelling improvement we can make to compensate. (E.g. I think doing switch-to-arithmetic conversion pre-inline would be worthwhile.)

https://github.com/llvm/llvm-project/pull/77856