this is more explicit than vec2's and hence has fewer footguns. in particular
it's easier to handle with preambles in a sane way.
modelled on what ir3 does.
there's probably room for more clean up but for now this unblocks what I want to
do.
stats don't seem concerning.
Totals from 692 (1.29% of 53701) affected shaders:
MaxWaves: 441920 -> 442112 (+0.04%)
Instrs: 1588748 -> 1589304 (+0.03%); split: -0.05%, +0.08%
CodeSize: 11487976 -> 11491620 (+0.03%); split: -0.04%, +0.07%
ALU: 1234867 -> 1235407 (+0.04%); split: -0.06%, +0.10%
FSCIB: 1234707 -> 1235249 (+0.04%); split: -0.06%, +0.10%
IC: 380514 -> 380518 (+0.00%)
GPRs: 117292 -> 117332 (+0.03%); split: -0.08%, +0.11%
Preamble instrs: 314064 -> 313948 (-0.04%); split: -0.05%, +0.01%
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35949>
Alyssa Rosenzweig
ee26938faf