Valve Has Been Developing A New Mesa Vulkan Shader Compiler For Radeon
ACO is a new Mesa shader compiler designed to deliver "best-possible code generation for game shaders, and fastest-possible compilation speed." They have found very promising results so far for this alternative to AMD's LLVM shader compiler with much faster shader compile times and also helping the in-game FPS for several titles atop the RADV driver. This new compiler doesn't employ the LLVM infrastructure.
This ACO shader compiler is currently living within this Mesa tree. More details at SteamCommunity.com. I'll be firing up some benchmarks shortly.