Our cost was 5 which matches the number of instructions we have to
add for a TMU spill (a fill is 4 instructions).
Uniform spills on the other hand add an extra instruction for each
fill and remove one instruction for the spill itself. These have
a cost of 1.
Therefore, if we have a single spill+fill, we end up with +9
instructions if it is a TMU spill and +0 instructions with a uniform
spill, so making the former only 5 times more costly is probably
not a good idea, and this is without even considering the added
latency of the TMU accesses.
Relevant shader-db changes show this causes as a marginal instruction
count increase in a few shaders but better thread counts and lower
TMU spilling overall:
total instructions in shared programs: 13037315 -> 13040711 (0.03%)
instructions in affected programs: 370106 -> 373502 (0.92%)
helped: 187
HURT: 321
total threads in shared programs: 415090 -> 415664 (0.14%)
threads in affected programs: 574 -> 1148 (100.00%)
helped: 287
HURT: 0
total uniforms in shared programs: 3706674 -> 3717266 (0.29%)
uniforms in affected programs: 63075 -> 73667 (16.79%)
helped: 40
HURT: 395
total max-temps in shared programs: 2176080 -> 2174177 (-0.09%)
max-temps in affected programs: 15838 -> 13935 (-12.02%)
helped: 316
HURT: 34
total spills in shared programs: 4247 -> 4010 (-5.58%)
spills in affected programs: 2599 -> 2362 (-9.12%)
helped: 107
HURT: 14
total fills in shared programs: 6121 -> 5820 (-4.92%)
fills in affected programs: 3622 -> 3321 (-8.31%)
helped: 108
HURT: 13
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15168>
Iago Toral Quiroga
cbb4d0dded