[clang] [llvm] [PGO] Implement PGO counter promotion for atomic updates (PR #202487)

[Wael Yehia via cfe-commits]

w2yehia wrote:

@david-xl thanks for the review. I'm addressed your comments in a separate commit that I just merged: https://github.com/llvm/llvm-project/commit/19f6c18e389bfea2885179fb4f50e019ef7ea002

https://github.com/llvm/llvm-project/pull/202487