Marek Olšák pushed a number of code commits to Mesa on Sunday that ended with support for binary shaders and shader cache in memory.
The shader cache should cut down on RadeonSI needing to re-compile shaders for the same game. Unlike the proprietary drivers and other shader cache implementations, this RadeonSI shader cache isn't written out to disk but is just stored on a per-screen/process basis. Caching them avoids the process of having to compiler shaders from Gallium3D's IR (TGSI) to the hardware bytecode. Many shader types are cached but not currently compute or geometry shaders.
Those wishing to find out more about the RadeonSI shader cache can find details via the code comments on this Git commit. According to at least one reader, this new shader cache is improving the Linux gaming experience for using this open-source driver on Radeon HD 7000 series and newer GPUs.