nir/algebraic: Pull common addition out of flrp arguments

nir/algebraic: Pull common addition out of flrp arguments

v2: Augment the late optimization patterns with a couple pre-ffma pass
patterns.

All Gen7+ platforms had similar results. (Skylake shown)
total instructions in shared programs: 15342982 -> 15342485 (<.01%)
instructions in affected programs: 56304 -> 55807 (-0.88%)
helped: 235
HURT: 0
helped stats (abs) min: 1 max: 8 x̄: 2.11 x̃: 1
helped stats (rel) min: 0.11% max: 8.82% x̄: 1.27% x̃: 0.74%
95% mean confidence interval for instructions value: -2.31 -1.92
95% mean confidence interval for instructions %-change: -1.46% -1.09%
Instructions are helped.

total cycles in shared programs: 355734740 -> 355734320 (<.01%)
cycles in affected programs: 1028807 -> 1028387 (-0.04%)
helped: 134
HURT: 104
helped stats (abs) min: 1 max: 212 x̄: 25.69 x̃: 8
helped stats (rel) min: <.01% max: 9.36% x̄: 1.33% x̃: 0.61%
HURT stats (abs)   min: 1 max: 203 x̄: 29.06 x̃: 8
HURT stats (rel)   min: 0.02% max: 15.76% x̄: 1.76% x̃: 0.46%
95% mean confidence interval for cycles value: -8.51 4.98
95% mean confidence interval for cycles %-change: -0.35% 0.39%
Inconclusive result (value mean confidence interval includes 0).

Sandy Bridge
total instructions in shared programs: 10886815 -> 10886390 (<.01%)
instructions in affected programs: 36883 -> 36458 (-1.15%)
helped: 147
HURT: 0
helped stats (abs) min: 1 max: 7 x̄: 2.89 x̃: 3
helped stats (rel) min: 0.35% max: 8.00% x̄: 1.60% x̃: 1.23%
95% mean confidence interval for instructions value: -3.12 -2.67
95% mean confidence interval for instructions %-change: -1.83% -1.38%
Instructions are helped.

total cycles in shared programs: 154188360 -> 154186902 (<.01%)
cycles in affected programs: 388094 -> 386636 (-0.38%)
helped: 90
HURT: 58
helped stats (abs) min: 1 max: 243 x̄: 36.80 x̃: 15
helped stats (rel) min: 0.04% max: 9.23% x̄: 1.26% x̃: 0.83%
HURT stats (abs)   min: 1 max: 684 x̄: 31.97 x̃: 10
HURT stats (rel)   min: 0.03% max: 13.50% x̄: 1.15% x̃: 0.51%
95% mean confidence interval for cycles value: -22.62 2.92
95% mean confidence interval for cycles %-change: -0.68% 0.05%
Inconclusive result (value mean confidence interval includes 0).

Iron Lake and GM45 had similar results. (Iron Lake shown)
total instructions in shared programs: 8221239 -> 8220357 (-0.01%)
instructions in affected programs: 54560 -> 53678 (-1.62%)
helped: 186
HURT: 0
helped stats (abs) min: 1 max: 14 x̄: 4.74 x̃: 3
helped stats (rel) min: 0.34% max: 10.77% x̄: 1.97% x̃: 1.17%
95% mean confidence interval for instructions value: -5.21 -4.28
95% mean confidence interval for instructions %-change: -2.23% -1.72%
Instructions are helped.

total cycles in shared programs: 188654442 -> 188650364 (<.01%)
cycles in affected programs: 1454384 -> 1450306 (-0.28%)
helped: 204
HURT: 0
helped stats (abs) min: 2 max: 84 x̄: 19.99 x̃: 18
helped stats (rel) min: 0.02% max: 4.69% x̄: 0.56% x̃: 0.22%
95% mean confidence interval for cycles value: -22.38 -17.60
95% mean confidence interval for cycles %-change: -0.67% -0.46%
Cycles are helped.

Reviewed-by: Matt Turner <mattst88@gmail.com>