[llvm] [llvm][AMDGPU] Add feature for FWD_PROGRESS (PR #181675)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > I'd really prefer we do not expose this, and just unconditionally use it when available and pretend the off option doesn't exist
> 
> That's what we had been doing until now, but it caused significant performance problems in a few cases. The reason for this control is just to make it easier to turn on and off while we investigate those problems.

ok, I think this should be an attribute named amdgpu-no-fwd-progress 

https://github.com/llvm/llvm-project/pull/181675