Open-Source AMD Linux Driver Gets Ready For 50% More VGPRs With RDNA3

Ahead of AMD's RDNA3 announcement for tomorrow, 3 November, the Mesa 22.3 open-source Radeon graphics driver code continues seeing more RDNA3/GFX11 enablement work landing.

An important merge that finally landed today is adapting the graphics driver compiler code for RadeonSI and RADV/ACO for GFX11 having 50% more vector general purpose registers (VGPRs) than current RDNA2 hardware.

Back in September it was revealed by an LLVM compiler patch to the AMDGPU shader compiler back-end that there are 50% more VGPRs with RDNA3. Optimizing for optimal VGPR usage / lowering VGPR register pressure is a common shader optimization strategy for performance while having a 50% increase in the number of registers will certainly help in easing the pressure to help with better performance.

The AMDGPU LLVM shader compiler back-end landed its change back in September while finally today this MR made it into Mesa 22.3, notably for the Radeon Vulkan "RADV" use with its alternative ACO compiler back-end developed by Valve. Now the ACO compiler code path can be aware of the number of vector registers at its disposal for GFX11 (RDNA3) rather than incorrectly assuming the same as GFX10.3.

Get ready to learn more about AMD RDNA3 graphics tomorrow ahead of Linux benchmarks in the future. It's looking like Mesa 22.3 will be the good baseline for the next-generation AMD graphics Linux support. On the kernel side it will probably be Linux 6.0 or newer, but I'll know more once delivering a Linux review with hands-on to the new hardware for seeing whether any lingering enablement bits are needed from the in-development Linux 6.1, etc.