Mesa Developers Eye Removing Clover Once Rusticl OpenCL Code Hits Parity

New to the upcoming Mesa 22.3 release is Rusticl as a Rust-written OpenCL implementation for Mesa drivers. Rusticl supports OpenCL 3.0, handles OpenCL images and other features, works with multiple drivers, and is modern and maintained. Already among Mesa developers is a discussion that has begun around removing the older "Clover" OpenCL Gallium3D implementation once Rusticl has firmly hit parity with that older, unmaintained state tracker.

Rusticl is in better shape than Clover already in many aspects but when it comes to some of the older GPUs/drivers, a few OpenCL extensions not yet implemented, and just needing more real-world testing. Meanwhile the old Clover Gallium3D driver isn't actively maintained by any developers. Clover hasn't been an active developer focus in years while Rusticl is what's seeing the development attention and showing the potential to be a very viable open-source OpenCL GPU implementation.

Last week a merge request discussion started that was entitled "delete clover" while Mike Blumenkrantz who opened the MR summed up Clover as "obviously dead and abandoned."

Among the known blockers prior to deleting Clover are ensuring Rusticl has good support for the R600 and RadeonSI driver, support for function calls, a few CL extensions not yet implemented by Rusticl, support for system shared virtual memory (SVM), and just ensuring that Rusticl is at parity with no possible feature/support found in Clover but not yet in Rusticl.

So once Rusticl has proven to be in good shape and better off than Clover, expect that old OpenCL implementation to be nuked and in turn will lighten the Mesa codebase by around 17k lines of code.