riscv: Implement skinning in vertexjit

[unknownbrackets]

At this point, the vertexjit basically has everything implemented for RISC-V.

-[Unknown]

[hrydgard]

How's performance?

[unknownbrackets]

All the vertex decoding variants perform at least 3x the speed of non-jit, and some higher (like 6-7x), but overall it hasn't moved FPS all that much. Crisis Core doesn't use morph/skin, for example, so it's still at 77% in game. Some areas are faster, of course.

I think jitting the CPU will move the needle more, but I wanted to complete this and use it to get a better sense of some tradeoffs (like SD vs SW speed, unrolling vs small loops, whether B instructions are worthwhile, etc.)

-[Unknown]

[hrydgard]

Ah, right, yeah morph+skin is pretty rare. Nice for the morphskin.elf demo hough :)

Yeah, makes sense. Great progress so far, it'll be good to be ready when more popular RISC-V devices appear.