But the user-space portions are probably more significant for performance than the kernel drivers. Here we have:

- r300 and r600 (open source OpenGL backend for older hardware, sits on top of the radeon kernel driver, not much development happening)

- radeonsi (open source OpenGL backend for newer hardware, sits on top of either the radeon or amdgpu kernel drivers depending on hardware version and kernel configuration)

- fglrx (closed source OpenGL driver on top of the fglrx kernel driver, both obsolete now)

- radv (open source Vulkan driver on top of amdgpu)

- amgpu-pro (closed source Vulkan driver on top of amdgpu) - not sure if there is also still a proprietary OpenGL driver but if there is no one should care since radeonsi works well enough

- amdvlk (open source dumps of amdgpu-pro without proprietary shader compiler on top of amdgpu)

Then you have different shader compilers which also significantly affect both shader compile time and runtime performance:

- internal compiler used by r600

- LLVM (used by radeonsi and amdvlk)

- ACO (used by radv and possibly radeonsi these days)

- AMD's proprietary compiler (used by fglrx and amdgpu-pro)

And for X.org you also have different display drivers (fglrx, radeon, modesetting).