[llvm] AMDGPU: ds.atomic.barrier.arrive.rtn.b64 is a source of divergence (PR #192765)

[Matt Arsenault via llvm-commits]

arsenm wrote:

What is this counter in terms of? I'd assume it would number of waves, which would still be a wave uniform value 

https://github.com/llvm/llvm-project/pull/192765