aco, radv: Navi 1x specific workarounds
This MR deals with two Navi 1x specific HW bug workarounds:
- When GS has zero output, export a triangle with NaN coordinates rather than with zeroes. This is because the all-zeroes triangle would render an unwanted pixel with conservative rasterization. (This done for ACO only - the LLVM side is handled by MR !10813 (merged))
- Emit an
s_barrier
instruction at the beginning of NGG shaders when there isn't one already. This ensures that all waves are launched by the time thegs_alloc_req
is executed.