[clang] [Profile] Add binary profile correlation to offload profile metadata at runtime. (PR #69493)

[Reid Kleckner via cfe-commits]

rnk wrote:

> I think there should be a proper Clang flag to control this, instead of requiring users to pass internal `-mllvm` flags. (Also the flag should be well documented.)

I believe Zequan did that at one point, but he ran into the problem that Rust and Clang need to agree on the coverage metadata section flags. Using an mllvm flag means we can opt into the new mode for both clang and rust simultaneously, hopefully without waiting for rustc changes.

It's interesting that historically we have discouraged mllvm flags, but in a new world of multiple frontends outside the llvm-project monorepo, having a direct command line interface to the middle-end becomes more valuable.

https://github.com/llvm/llvm-project/pull/69493