radv: lower ffma in nir.
So it appears the Vulkan SPIR-V fma opcode can be equivalent to a mad operation, and the fma hw opcode on AMD hw is issued like a double opcode so is slower. Also the radeonsi stack does this. This appears to improve performance on a number of games from Feral, and thanks to Feral for noticing the problem. I'm reposting this one as Marek indicated he thinks this is what we should be doing on AMD hw. Reviewed-by: Nicolai Hähnle <email@example.com> Reviewed-by: Marek Olšák <firstname.lastname@example.org> Cc: "17.2" <email@example.com> Signed-off-by: Dave Airlie <firstname.lastname@example.org>