pan/bi: Schedule for pressure pre-RA
Add a bottom-up pre-RA list scheduler that aims to reduce register pressure, roughly the same as we use on Midgard to great effect. It uses a simple heuristic: greedily select instructions that have reduce liveness. To avoid regressions, the algorithm throws away schedules that increase maximum number of lives (used as an estimate of register pressure -- if we had SSA form, this would be exact).
We'd probably be better off using Sarkar. But for something I could type out in an afternoon, I'll happily accept a >30% reduction in spills.
Results on v7 (similar on other platforms):
total instructions in shared programs: 2438841 -> 2439698 (0.04%)
instructions in affected programs: 1206421 -> 1207278 (0.07%)
helped: 3113
HURT: 4011
helped stats (abs) min: 1.0 max: 50.0 x̄: 3.25 x̃: 2
helped stats (rel) min: 0.13% max: 44.83% x̄: 4.09% x̃: 2.11%
HURT stats (abs) min: 1.0 max: 18.0 x̄: 2.73 x̃: 2
HURT stats (rel) min: 0.11% max: 57.14% x̄: 3.86% x̃: 2.07%
95% mean confidence interval for instructions value: 0.02 0.22
95% mean confidence interval for instructions %-change: 0.23% 0.54%
Instructions are HURT.
total tuples in shared programs: 1927077 -> 1946583 (1.01%)
tuples in affected programs: 1118627 -> 1138133 (1.74%)
helped: 2874
HURT: 6295
helped stats (abs) min: 1.0 max: 82.0 x̄: 3.51 x̃: 2
helped stats (rel) min: 0.17% max: 33.33% x̄: 4.60% x̃: 3.57%
HURT stats (abs) min: 1.0 max: 47.0 x̄: 4.70 x̃: 3
HURT stats (rel) min: 0.20% max: 50.00% x̄: 5.16% x̃: 4.32%
95% mean confidence interval for tuples value: 2.00 2.25
95% mean confidence interval for tuples %-change: 1.97% 2.23%
Tuples are HURT.
total clauses in shared programs: 356053 -> 357793 (0.49%)
clauses in affected programs: 151578 -> 153318 (1.15%)
helped: 2196
HURT: 3813
helped stats (abs) min: 1.0 max: 49.0 x̄: 2.16 x̃: 1
helped stats (rel) min: 0.18% max: 69.01% x̄: 10.26% x̃: 8.33%
HURT stats (abs) min: 1.0 max: 25.0 x̄: 1.70 x̃: 1
HURT stats (rel) min: 0.57% max: 66.67% x̄: 10.64% x̃: 8.33%
95% mean confidence interval for clauses value: 0.22 0.36
95% mean confidence interval for clauses %-change: 2.68% 3.33%
Clauses are HURT.
total cycles in shared programs: 167761.17 -> 167922.04 (0.10%)
cycles in affected programs: 24494.21 -> 24655.08 (0.66%)
helped: 862
HURT: 3054
helped stats (abs) min: 0.041665999999999315 max: 53.0 x̄: 0.69 x̃: 0
helped stats (rel) min: 0.28% max: 76.81% x̄: 5.65% x̃: 3.03%
HURT stats (abs) min: 0.041665999999999315 max: 2.0416659999999993 x̄: 0.25 x̃: 0
HURT stats (rel) min: 0.26% max: 41.18% x̄: 4.91% x̃: 3.92%
95% mean confidence interval for cycles value: -0.04 0.12
95% mean confidence interval for cycles %-change: 2.36% 2.81%
Inconclusive result (value mean confidence interval includes 0).
total arith in shared programs: 73875.37 -> 74393.17 (0.70%)
arith in affected programs: 43142.42 -> 43660.21 (1.20%)
helped: 3632
HURT: 5443
helped stats (abs) min: 0.041665999999999315 max: 1.2083360000000027 x̄: 0.15 x̃: 0
helped stats (rel) min: 0.22% max: 100.00% x̄: 6.70% x̃: 4.76%
HURT stats (abs) min: 0.041665999999999315 max: 2.0416659999999993 x̄: 0.19 x̃: 0
HURT stats (rel) min: 0.00% max: 166.67% x̄: 5.91% x̃: 4.08%
95% mean confidence interval for arith value: 0.05 0.06
95% mean confidence interval for arith %-change: 0.65% 1.07%
Arith are HURT.
total texture in shared programs: 11936 -> 11936 (0.00%)
texture in affected programs: 0 -> 0
helped: 0
HURT: 0
total vary in shared programs: 4180.88 -> 4180.88 (0.00%)
vary in affected programs: 0 -> 0
helped: 0
HURT: 0
total ldst in shared programs: 137551 -> 137028 (-0.38%)
ldst in affected programs: 834 -> 311 (-62.71%)
helped: 13
HURT: 0
helped stats (abs) min: 15.0 max: 53.0 x̄: 40.23 x̃: 53
helped stats (rel) min: 19.15% max: 100.00% x̄: 68.11% x̃: 76.81%
95% mean confidence interval for ldst value: -50.49 -29.98
95% mean confidence interval for ldst %-change: -84.37% -51.84%
Ldst are helped.
total quadwords in shared programs: 1684883 -> 1692021 (0.42%)
quadwords in affected programs: 949463 -> 956601 (0.75%)
helped: 3981
HURT: 5098
helped stats (abs) min: 1.0 max: 86.0 x̄: 3.53 x̃: 3
helped stats (rel) min: 0.18% max: 33.33% x̄: 5.82% x̃: 4.48%
HURT stats (abs) min: 1.0 max: 50.0 x̄: 4.15 x̃: 3
HURT stats (rel) min: 0.17% max: 50.00% x̄: 5.11% x̃: 3.85%
95% mean confidence interval for quadwords value: 0.67 0.90
95% mean confidence interval for quadwords %-change: 0.17% 0.47%
Quadwords are HURT.
total threads in shared programs: 53276 -> 53653 (0.71%)
threads in affected programs: 581 -> 958 (64.89%)
helped: 445
HURT: 68
helped stats (abs) min: 1.0 max: 1.0 x̄: 1.00 x̃: 1
helped stats (rel) min: 100.00% max: 100.00% x̄: 100.00% x̃: 100.00%
HURT stats (abs) min: 1.0 max: 1.0 x̄: 1.00 x̃: 1
HURT stats (rel) min: 50.00% max: 50.00% x̄: 50.00% x̃: 50.00%
95% mean confidence interval for threads value: 0.68 0.79
95% mean confidence interval for threads %-change: 75.70% 84.53%
Threads are helped.
total preloads in shared programs: 116312 -> 116312 (0.00%)
preloads in affected programs: 0 -> 0
helped: 0
HURT: 0
total loops in shared programs: 128 -> 128 (0.00%)
loops in affected programs: 0 -> 0
helped: 0
HURT: 0
total spills in shared programs: 92 -> 37 (-59.78%)
spills in affected programs: 55 -> 0
helped: 13
HURT: 0
total fills in shared programs: 658 -> 190 (-71.12%)
fills in affected programs: 468 -> 0
helped: 13
HURT: 0