On Saturday published to the mailing list was the "r600g: cache shader variants instead of rebuilding" patch. This modestly-sized patch was authored by Vadim Girlin.
This patch is said to improve performance for some applications like FlightGear. From a bug report, with FlightGear on R600g the frame-rate went from around 20 FPS with the normal rendering back-end to now around 40 FPS with the patched copy. With the R600g LLVM back-end, originally it was around three FPS but is now also up around 40 FPS.