LLVMpipe is of course, the higher-performance alternative to Mesa's classic software rasterizer (swrast) or the Gallium3D Softpipe implementation. LLVMpipe uses LLVM and does OpenGL on the CPU. Its performance hasn't been the best but is better than the other Mesa software rasterizer options should you not have an actual GPU hardware driver for whatever reason. LLVMpipe really isn't a reliable option for any OpenGL gaming, but can be used for debugging driver issues, etc.
There's been some commits to the LLVMpipe driver during the Mesa 8.1 cycle, but not too many and it's still at OpenGL 2.1 compliance rather than hitting OpenGL 3.0. The Git branches of Mesa master (8.1-devel) and 8.0 (8.0.4+) were compared. The Mesa 8.0 branch doesn't have the fixes to support LLVM 3.1, but at the same time this latest LLVM release wanted to be tested due to more optimizations for the Intel Ivy Bridge Core i7 processor being used in this review. As a result, and to try to make things slightly more interesting, LLVM 3.0 was used with Mesa 8.0 while LLVM 3.1 was paired with Mesa 8.1.
Aside from no major advancements to LLVMpipe in Mesa 8.1, there are also some regressions, as shown earlier on Twitter.