[clang] [llvm] Reapply "[llvm][IR] Extend BranchWeightMetadata to track provenance o… (PR #95281)

[Nikita Popov via cfe-commits]

https://github.com/nikic approved this pull request.

Looks good now, no text size of compile-time changes.

https://github.com/llvm/llvm-project/pull/95281