RadeonSI Enables NGG Shader Culling For Navi 1x Consumer GPUs

As another possible performance win for RadeonSI Gallium3D as AMD's open-source Radeon OpenGL driver on Linux systems is enabling of NGG culling for Navi 1x consumer graphics processors rather than limiting it only to newer Navi 2x (RDNA2) GPUs.

Merged on Monday was a patch to enable shader culling for Navi 1x consumer SKUs with no longer limiting it to Navi 2x / GFX10.3 or when using various debug options. This culling was also enabled for Navi 1x GPUs but only for the "Pro" graphics SKUs.

The change was made by AMD's Marek Olšák so apparently they feel comfortable enough flipping on that culling optimization for Navi 1x hardware and is a worthwhile change.

Meanwhile on the Vulkan driver side, Mesa 21.3's RADV enables NGG culling but only for the latest Navi 2x GPUs. At least with that driver, Navi 1x didn't benefit much at all from this next-gen geometry culling feature.

This shader culling change is in place for Mesa 22.0 which will debut as stable in mid-Q1'2022. Current Mesa code can also force-enable its usage via the "shader_culling" RadeonSI debug option.