[llvm] AMDGPU/GFX12: Do not wait unnecessarily before barriers (PR #154970)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

> Yeah, that was pretty much my thinking. The split barriers in GFX12 eliminate the need to "back off" from the barrier.

Can you elaborate why backoff barrier is not necessary with split barriers ?
We still have a barrier_wait, that needs to be able to "back off" to process signals.

Or are you just talking about the `BackOffBarrier` compiler feature, not the actual HW behavior?

https://github.com/llvm/llvm-project/pull/154970