pan/bi: Support message preloading

pan/bi: Support message preloading

Preload LD_VAR_IMM or VAR_TEX instructions in the first block of fragment
shaders on v7. Preloaded messages write to fixed registers; when replacing
instructions we insert moves from the registers at the start of the program and
hope coalescing goes to town. (Admittedly we don't do any coalescing yet...)
The extra moves hurts instruction count in some cases; the win for cycle count
should cancel this out. When we get smarter copy prop or RA, those moves should
go away anyway.

This optimization may hurt register pressure by extending the lifetime of up to
eight registers written in the first block. This is expected to be acceptable:
on a large shader-db, there are no additional spills/fills, and only two shaders
are hurt on thread count.

This optimization only applies to v7, as the hardware was not introduced on v6
and was removed for Valhall.

total instructions in shared programs: 2451624 -> 2454286 (0.11%)
instructions in affected programs: 909046 -> 911708 (0.29%)
helped: 4719
HURT: 3341
helped stats (abs) min: 1.0 max: 10.0 x̄: 1.49 x̃: 1
helped stats (rel) min: 0.08% max: 33.33% x̄: 6.79% x̃: 3.92%
HURT stats (abs)   min: 1.0 max: 50.0 x̄: 2.90 x̃: 2
HURT stats (rel)   min: 0.12% max: 66.67% x̄: 6.39% x̃: 3.45%
95% mean confidence interval for instructions value: 0.27 0.39
95% mean confidence interval for instructions %-change: -1.55% -1.11%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).

total tuples in shared programs: 1969529 -> 1963429 (-0.31%)
tuples in affected programs: 601327 -> 595227 (-1.01%)
helped: 5907
HURT: 1297
helped stats (abs) min: 1.0 max: 8.0 x̄: 1.41 x̃: 1
helped stats (rel) min: 0.07% max: 33.33% x̄: 7.25% x̃: 5.26%
HURT stats (abs)   min: 1.0 max: 40.0 x̄: 1.73 x̃: 1
HURT stats (rel)   min: 0.16% max: 31.75% x̄: 3.38% x̃: 2.02%
95% mean confidence interval for tuples value: -0.88 -0.81
95% mean confidence interval for tuples %-change: -5.52% -5.15%
Tuples are helped.

total clauses in shared programs: 401689 -> 387830 (-3.45%)
clauses in affected programs: 136944 -> 123085 (-10.12%)
helped: 8427
HURT: 4
helped stats (abs) min: 1.0 max: 4.0 x̄: 1.65 x̃: 2
helped stats (rel) min: 0.49% max: 50.00% x̄: 19.88% x̃: 18.18%
HURT stats (abs)   min: 1.0 max: 4.0 x̄: 2.50 x̃: 2
HURT stats (rel)   min: 1.96% max: 19.05% x̄: 14.18% x̃: 17.86%
95% mean confidence interval for clauses value: -1.66 -1.63
95% mean confidence interval for clauses %-change: -20.15% -19.58%
Clauses are helped.

total cycles in shared programs: 202735.83 -> 201862.21 (-0.43%)
cycles in affected programs: 16295.46 -> 15421.83 (-5.36%)
helped: 3349
HURT: 1962
helped stats (abs) min: 0.041665999999999315 max: 1.0 x̄: 0.32 x̃: 0
helped stats (rel) min: 0.24% max: 100.00% x̄: 40.77% x̃: 33.33%
HURT stats (abs)   min: 0.041665999999999315 max: 1.5833329999999997 x̄: 0.10 x̃: 0
HURT stats (rel)   min: 0.09% max: 31.40% x̄: 2.95% x̃: 1.94%
95% mean confidence interval for cycles value: -0.17 -0.16
95% mean confidence interval for cycles %-change: -25.48% -23.76%
Cycles are helped.

total arith in shared programs: 74665.50 -> 74920.00 (0.34%)
arith in affected programs: 16059.92 -> 16314.42 (1.58%)
helped: 860
HURT: 3409
helped stats (abs) min: 0.041665999999999315 max: 0.25 x̄: 0.06 x̃: 0
helped stats (rel) min: 0.24% max: 37.50% x̄: 4.73% x̃: 2.56%
HURT stats (abs)   min: 0.041665999999999315 max: 1.5833329999999997 x̄: 0.09 x̃: 0
HURT stats (rel)   min: 0.09% max: 100.00% x̄: 8.99% x̃: 4.21%
95% mean confidence interval for arith value: 0.06 0.06
95% mean confidence interval for arith %-change: 5.83% 6.62%
Arith are HURT.

total texture in shared programs: 13083.50 -> 11877 (-9.22%)
texture in affected programs: 1663 -> 456.50 (-72.55%)
helped: 2377
HURT: 3
helped stats (abs) min: 0.5 max: 1.0 x̄: 0.51 x̃: 0
helped stats (rel) min: 6.25% max: 100.00% x̄: 87.12% x̃: 100.00%
HURT stats (abs)   min: 0.5 max: 0.5 x̄: 0.50 x̃: 0
HURT stats (rel)   min: 0.00% max: 25.00% x̄: 16.67% x̃: 25.00%
95% mean confidence interval for texture value: -0.51 -0.50
95% mean confidence interval for texture %-change: -87.98% -86.00%
Texture are helped.

total vary in shared programs: 10220.62 -> 4183.88 (-59.06%)
vary in affected programs: 10126.50 -> 4089.75 (-59.61%)
helped: 8538
HURT: 0
helped stats (abs) min: 0.125 max: 1.0 x̄: 0.71 x̃: 0
helped stats (rel) min: 7.14% max: 100.00% x̄: 74.74% x̃: 87.50%
95% mean confidence interval for vary value: -0.71 -0.70
95% mean confidence interval for vary %-change: -75.32% -74.16%
Vary are helped.

total quadwords in shared programs: 1766717 -> 1757161 (-0.54%)
quadwords in affected programs: 553801 -> 544245 (-1.73%)
helped: 6760
HURT: 711
helped stats (abs) min: 1.0 max: 11.0 x̄: 1.58 x̃: 1
helped stats (rel) min: 0.09% max: 29.41% x̄: 5.31% x̃: 4.84%
HURT stats (abs)   min: 1.0 max: 33.0 x̄: 1.54 x̃: 1
HURT stats (rel)   min: 0.10% max: 31.13% x̄: 2.53% x̃: 1.61%
95% mean confidence interval for quadwords value: -1.31 -1.25
95% mean confidence interval for quadwords %-change: -4.67% -4.46%
Quadwords are helped.

total threads in shared programs: 52899 -> 52897 (<.01%)
threads in affected programs: 4 -> 2 (-50.00%)
helped: 0
HURT: 2

total preloads in shared programs: 0 -> 116492
preloads in affected programs: 0 -> 116492
helped: 0
HURT: 8604
HURT stats (abs)   min: 2.0 max: 24.0 x̄: 13.54 x̃: 14
HURT stats (rel)   min: 0.00% max: 0.00% x̄: 0.00% x̃: 0.00%
95% mean confidence interval for preloads value: 13.45 13.63
95% mean confidence interval for preloads %-change: 0.00% 0.00%
Preloads are HURT.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9438>