[llvm] [KeyInstr] Hide new MDNodeKeyImpl<DILocation> fields (PR #138296)

[Nikita Popov via llvm-commits]

nikic wrote:

> Are you expecting the perf drop to go away once KI is finished?

It's expected to go away / be greatly mitigated once https://discourse.llvm.org/t/rfc-refactoring-dilocation-to-use-compact-function-local-storage/85618 is implemented.

https://github.com/llvm/llvm-project/pull/138296