The trick is to add the following to a game’s launch options in Steam:
RADV_PERFTEST=gpl %command%
This totally and completely eliminated shader cache stutter for me in Resident Evil Revelations, with a cleared shader cache. Prior to doing this the game stuttered every time I fired a gun or entered a new area.
The trick does not work on DX12 games.
My understanding is that this compiles the shaders when games load their D3D shaders, rather than at draw time.
I believe steamOS 3.5 is making this default behavior for games.