The R600g Driver May Soon Be Working, But Lacks A Compiler
For those not monitoring the Mesa Git log, today the R600g driver had its compiler "stuff" dropped, RSQ token support was added, and other tokens were fixed. More interestingly, however, is Jerome's message regarding this work. Jerome dropped the Gallium3D R600g compiler as "it was getting messy and kind of stopped anyone else from working on other part of r600g." Rather than having a full-fledged compiler for now, Jerome just wrote a very simple TGSI (Tungsten Graphics Shader Infrastructure) to R600 assembler to serve as an interim solution. With this very basic assembler, the R600/700 Gallium3D driver can even run glxgears and other non-textured OpenGL demos.
Jerome plans to add texture support to the R600g driver in "the next few days" to the point that the Quake engine should now run on this Gallium3D driver that supports newer ATI graphics processors. Jerome also shared his R600g TODO list, which roughly comes down to:
- Texture support
- Using the constant buffer rather than cfile
- Avoid recompiling the shader with each draw command (this will bring up the performance significantly)
- Stencil support
- Support for more states such as blending, alpha, and rasterization
- Geometry support
- Tiling support
- Color-mask support
- Hyper-Z support
- A proper shader compiler
A proper R600g driver is quite far down on Jerome's work list so it may be sometime until the performance and capabilities of this driver are proper or even comparable to that of the R600 classic driver and older R300g driver. Alex Deucher though has already replied to Jerome asking about using the R600 classic Mesa compiler at least as an interim solution and Corbin Simpson (the main author of the R300 Gallium3D driver) about utilizing more code sharing between these two drivers with their compiler.
Jerome's mailing list message can be found on mesa-dev. We'll continue to be monitoring the progress of this open-source ATI graphics driver, but for the time being the "classic" Mesa R600/700 driver will be the best option for end-users. For those with R300-R500 GPUs (up through the ATI Radeon X1000 series), there is the R300g Gallium3D driver, which is running great and quickly evolving with it already being in a better state than its respective classic Mesa driver.