[clang] [llvm] [profcheck][coro] Adding Branch weights PGO in Coroutines Passes (PR #184466)

[Mircea Trofin via cfe-commits]

mtrofin wrote:

I'd put the explanation from [here](https://github.com/llvm/llvm-project/issues/185949#issuecomment-4703198841) in the commit message. IMHO the way `resume` is handled is the important thing (for performance), and how that's handled deserves focus, rather than a side-note.

Can you also add an explanation as to why the 3 places (Coro{Split|Frame|Cleanup}) cover profile propagation for coroutines - or is there anything major left after this? I.e. it's less interesting that 3 files got patched (since one can just read the diff), and more interesting as to how the overall change addresses the overall problem (==profile propagation for coroutines) - since that's design information not immediately apparent from the change itself, and, thus, worth communicating.

https://github.com/llvm/llvm-project/pull/184466