[llvm] [AMDGPU] Schedule independent instructions between s_barrier_signal and s_barrier_wait (PR #172057)

[Dark Steve via llvm-commits]

PrasoonMishra wrote:

> Nice. 16 is a good number, it sounds in the right ballpark for actual barrier latency cycles.
> 
> For future reference, it's welcome practice to add new tests first in a separate commit without code changes, so that the effect of your code change is more obvious in code review.

Thanks for the approval. Going forward, I’ll add lit tests first.

https://github.com/llvm/llvm-project/pull/172057