Radeon: Mesa 10.1 vs. Mesa Git On Ubuntu 14.04
While Xonotic was faster on Mesa Git with the HD 7850 graphics card, with ultra and ultimate image quality settings the game failed due to LLVM register allocation issues with the current stable version of LLVM and its AMD GPU back-end.
Plot3D was slightly faster for the RadeonSI Gallium3D driver on the newer open-source Linux graphics driver code.