[Mesa-dev] [PATCH 0/5] Emit BRW_AOP_INC or BRW_AOP_DEC

[Ian Romanick]

I don't know why we never did this.  Almost every shader in shader-db
that uses atomicAdd or imageAtomicAdd uses it with a constant of 1 or
-1.

Results on Skylake across the whole series are below.  There is some
discussion in patch 2 about the 189 instructions (!) added.

total instructions in shared programs: 14304116 -> 14304241 (<.01%)
instructions in affected programs: 12811 -> 12936 (0.98%)
helped: 21
HURT: 1
helped stats (abs) min: 1 max: 16 x̄: 3.05 x̃: 1
helped stats (rel) min: 0.05% max: 14.29% x̄: 1.95% x̃: 0.69%
HURT stats (abs)   min: 189 max: 189 x̄: 189.00 x̃: 189
HURT stats (rel)   min: 4.87% max: 4.87% x̄: 4.87% x̃: 4.87%
95% mean confidence interval for instructions value: -12.55 23.91
95% mean confidence interval for instructions %-change: -3.27% -0.01%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 527552861 -> 527531194 (<.01%)
cycles in affected programs: 1459195 -> 1437528 (-1.48%)
helped: 18
HURT: 0
helped stats (abs) min: 2 max: 21328 x̄: 1203.72 x̃: 6
helped stats (rel) min: <.01% max: 5.29% x̄: 0.32% x̃: 0.03%
95% mean confidence interval for cycles value: -3701.36 1293.92
95% mean confidence interval for cycles %-change: -0.94% 0.29%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 8025 -> 8033 (0.10%)
spills in affected programs: 208 -> 216 (3.85%)
helped: 1
HURT: 1

total fills in shared programs: 10989 -> 11040 (0.46%)
fills in affected programs: 444 -> 495 (11.49%)
helped: 1
HURT: 1