From the Mesa codebase removed swrast driver for software rendering of OpenGL … The classic swrast driver has been replaced by llvmpipe and softpipe , which are noticeably ahead of swrast in terms of performance and functionality (llvmpipe supports OpenGL 4.5, swrast supports OpenGL 3.3). The swrast driver is based on the classic DRI interface, while llvmpipe and softpipe use the Gallium framework.
The removal of swrast was facilitated by the presence of sets unresolved issues and occurrence regressions , while that this driver is no longer used in distributions. Until this week, swrast continued to be used in Debian with the GNU Hurd kernel and platforms without LLVM support, but has now been replaced by softpipe, which is not LLVM tied.