RadeonSI & RADV Now Enabling D16 Support For GFX8 Era GPUs

Thanks to the latest work by Georg Lehmann of Valve's Linux graphics team, the AMD GFX8 generation of GPUs that stretch from GCN Volcanic Islands through Polaris GPUs is still seeing improved Linux support. The latest work to land and benefiting both RadeonSI OpenGL and RADV Vulkan is enabling D16 support. The open-source Radeon 3D graphics driver code had only been enabling D16 support for GFX9 and newer, but with a set of 17 patches hitting Mesa 27.0-devel today, D16 has come to GFX8. D16 is a 16-bit data modifier user on Radeon GPUs with their load and store instructions to help with reducing memory bandwidth pressure and enhancing register efficiency by using packed 16-bit values rather than 32-bit. With AMD GFX8 hardware enabling FP16 support for all Direct3D 12 content running via VKD3D-Proton, D16 has some benefits for these aging GPUs and thus was wired up by Georg. This merge takes care of enabling D16 support on GFX8 hardware by the ACO compiler and making use of it for GFX8 in both the RadeonSI and RADV drivers.