ir3: improve handling of WAR hazards

This series improves the handling of WAR hazards in a few ways:

• Fix bug where WAR hazards were added for const/imm regs;
• Don't add (ss) for WAR hazards already resolved using (sy): although all WAR hazards can be resolved using (ss), if the reader is a (sy)-producer, and it has already been synced using (sy), its sources have definitely been read so an extra (ss) is not necessary.
• Take WAR hazards into account in post-RA scheduling. Note that I have played around with also taking the (sy) syncs for WAR into account but the results were mixed and since it introduced a lot of complexity, I've left this out for now.

This shows some nice shader-db results, especially for (ss) and sstall:

shader-db results

total instructions in shared programs: 4105224 -> 4096025 (-0.22%)
instructions in affected programs: 1677124 -> 1667925 (-0.55%)
helped: 1637
HURT: 1842
helped stats (abs) min: 1 max: 1379 x̄: 11.42 x̃: 2
helped stats (rel) min: 0.02% max: 25.30% x̄: 1.62% x̃: 0.70%
HURT stats (abs)   min: 1 max: 55 x̄: 5.16 x̃: 4
HURT stats (rel)   min: 0.01% max: 11.97% x̄: 1.87% x̃: 1.40%
95% mean confidence interval for instructions value: -4.21 -1.08
95% mean confidence interval for instructions %-change: 0.13% 0.32%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).
total nops in shared programs: 888176 -> 878977 (-1.04%)
nops in affected programs: 436092 -> 426893 (-2.11%)
helped: 1637
HURT: 1842
helped stats (abs) min: 1 max: 1379 x̄: 11.42 x̃: 2
helped stats (rel) min: 0.04% max: 100.00% x̄: 12.91% x̃: 6.06%
HURT stats (abs)   min: 1 max: 55 x̄: 5.16 x̃: 4
HURT stats (rel)   min: 0.00% max: 800.00% x̄: 20.26% x̃: 9.30%
95% mean confidence interval for nops value: -4.21 -1.08
95% mean confidence interval for nops %-change: 3.26% 6.05%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).
total non-nops in shared programs: 3217048 -> 3217048 (0.00%)
non-nops in affected programs: 0 -> 0
helped: 0
HURT: 0
total mov in shared programs: 144229 -> 144229 (0.00%)
mov in affected programs: 0 -> 0
helped: 0
HURT: 0
total cov in shared programs: 88704 -> 88704 (0.00%)
cov in affected programs: 0 -> 0
helped: 0
HURT: 0
total dwords in shared programs: 8778888 -> 8776314 (-0.03%)
dwords in affected programs: 1307308 -> 1304734 (-0.20%)
helped: 437
HURT: 626
helped stats (abs) min: 2 max: 608 x̄: 17.46 x̃: 2
helped stats (rel) min: 0.03% max: 16.25% x̄: 1.28% x̃: 0.73%
HURT stats (abs)   min: 2 max: 32 x̄: 8.08 x̃: 2
HURT stats (rel)   min: 0.04% max: 17.07% x̄: 1.47% x̃: 0.62%
95% mean confidence interval for dwords value: -4.64 -0.20
95% mean confidence interval for dwords %-change: 0.19% 0.49%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).
total last-baryf in shared programs: 130915 -> 131207 (0.22%)
last-baryf in affected programs: 31866 -> 32158 (0.92%)
helped: 65
HURT: 107
helped stats (abs) min: 1 max: 25 x̄: 5.71 x̃: 4
helped stats (rel) min: 0.46% max: 12.73% x̄: 3.45% x̃: 2.19%
HURT stats (abs)   min: 1 max: 26 x̄: 6.20 x̃: 5
HURT stats (rel)   min: 0.39% max: 42.31% x̄: 3.93% x̃: 2.31%
95% mean confidence interval for last-baryf value: 0.47 2.93
95% mean confidence interval for last-baryf %-change: 0.26% 2.02%
Last-baryf are HURT.
total last-helper in shared programs: 1131900 -> 1129140 (-0.24%)
last-helper in affected programs: 622475 -> 619715 (-0.44%)
helped: 735
HURT: 621
helped stats (abs) min: 1 max: 230 x̄: 18.05 x̃: 5
helped stats (rel) min: 0.04% max: 84.36% x̄: 7.24% x̃: 1.82%
HURT stats (abs)   min: 1 max: 307 x̄: 16.92 x̃: 6
HURT stats (rel)   min: 0.03% max: 479.69% x̄: 13.23% x̃: 2.16%
95% mean confidence interval for last-helper value: -4.04 -0.04
95% mean confidence interval for last-helper %-change: 0.47% 3.80%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).
total half in shared programs: 0 -> 0
half in affected programs: 0 -> 0
helped: 0
HURT: 0
total full in shared programs: 254152 -> 254152 (0.00%)
full in affected programs: 0 -> 0
helped: 0
HURT: 0
total constlen in shared programs: 628940 -> 628940 (0.00%)
constlen in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat0 in shared programs: 986933 -> 977734 (-0.93%)
cat0 in affected programs: 473889 -> 464690 (-1.94%)
helped: 1637
HURT: 1842
helped stats (abs) min: 1 max: 1379 x̄: 11.42 x̃: 2
helped stats (rel) min: 0.04% max: 66.67% x̄: 10.76% x̃: 5.66%
HURT stats (abs)   min: 1 max: 55 x̄: 5.16 x̃: 4
HURT stats (rel)   min: 0.03% max: 600.00% x̄: 21.57% x̃: 9.57%
95% mean confidence interval for cat0 value: -4.21 -1.08
95% mean confidence interval for cat0 %-change: 5.00% 7.72%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).
total cat1 in shared programs: 234377 -> 234377 (0.00%)
cat1 in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat2 in shared programs: 1501600 -> 1501600 (0.00%)
cat2 in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat3 in shared programs: 1196828 -> 1196828 (0.00%)
cat3 in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat4 in shared programs: 84089 -> 84089 (0.00%)
cat4 in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat5 in shared programs: 48109 -> 48109 (0.00%)
cat5 in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat6 in shared programs: 50156 -> 50156 (0.00%)
cat6 in affected programs: 0 -> 0
helped: 0
HURT: 0
total cat7 in shared programs: 3132 -> 3132 (0.00%)
cat7 in affected programs: 0 -> 0
helped: 0
HURT: 0
total stp in shared programs: 2448 -> 2448 (0.00%)
stp in affected programs: 0 -> 0
helped: 0
HURT: 0
total ldp in shared programs: 568 -> 568 (0.00%)
ldp in affected programs: 0 -> 0
helped: 0
HURT: 0
total sstall in shared programs: 335784 -> 315300 (-6.10%)
sstall in affected programs: 149340 -> 128856 (-13.72%)
helped: 2261
HURT: 685
helped stats (abs) min: 1 max: 270 x̄: 10.36 x̃: 7
helped stats (rel) min: 0.75% max: 100.00% x̄: 29.64% x̃: 22.22%
HURT stats (abs)   min: 1 max: 23 x̄: 4.28 x̃: 3
HURT stats (rel)   min: 0.00% max: 450.00% x̄: 34.25% x̃: 14.29%
95% mean confidence interval for sstall value: -7.47 -6.44
95% mean confidence interval for sstall %-change: -16.37% -13.20%
Sstall are helped.
total (ss) in shared programs: 85394 -> 76205 (-10.76%)
(ss) in affected programs: 45455 -> 36266 (-20.22%)
helped: 4688
HURT: 225
helped stats (abs) min: 1 max: 90 x̄: 2.01 x̃: 1
helped stats (rel) min: 0.92% max: 100.00% x̄: 43.31% x̃: 28.57%
HURT stats (abs)   min: 1 max: 4 x̄: 1.13 x̃: 1
HURT stats (rel)   min: 1.85% max: 50.00% x̄: 19.26% x̃: 16.67%
95% mean confidence interval for (ss) value: -1.99 -1.75
95% mean confidence interval for (ss) %-change: -41.46% -39.43%
(ss) are helped.
total systall in shared programs: 650040 -> 652696 (0.41%)
systall in affected programs: 111692 -> 114348 (2.38%)
helped: 289
HURT: 668
helped stats (abs) min: 1 max: 39 x̄: 5.36 x̃: 3
helped stats (rel) min: 0.10% max: 100.00% x̄: 17.05% x̃: 8.15%
HURT stats (abs)   min: 1 max: 98 x̄: 6.29 x̃: 5
HURT stats (rel)   min: 0.00% max: 2100.00% x̄: 25.98% x̃: 7.89%
95% mean confidence interval for systall value: 2.17 3.38
95% mean confidence interval for systall %-change: 7.52% 18.45%
Systall are HURT.
total (sy) in shared programs: 35562 -> 35586 (0.07%)
(sy) in affected programs: 500 -> 524 (4.80%)
helped: 27
HURT: 51
helped stats (abs) min: 1 max: 2 x̄: 1.07 x̃: 1
helped stats (rel) min: 4.26% max: 50.00% x̄: 21.94% x̃: 20.00%
HURT stats (abs)   min: 1 max: 2 x̄: 1.04 x̃: 1
HURT stats (rel)   min: 3.70% max: 50.00% x̄: 28.69% x̃: 25.00%
95% mean confidence interval for (sy) value: 0.07 0.54
95% mean confidence interval for (sy) %-change: 5.10% 17.23%
(sy) are HURT.
total waves in shared programs: 630114 -> 630114 (0.00%)
waves in affected programs: 0 -> 0
helped: 0
HURT: 0
total loops in shared programs: 1085 -> 1085 (0.00%)
loops in affected programs: 0 -> 0
helped: 0
HURT: 0
LOST:   0
GAINED: 0
Total CPU time (seconds): 1194.68 -> 1181.02 (-1.14%)

I've also measure a modest 0.3% improvement in render pass time in some d3d11 traces on a750.