i965/vec4: Propagate conditional modifiers from compares to adds

i965/vec4: Propagate conditional modifiers from compares to adds

No changes on Broadwell or later as those platforms do not use the vec4
backend.

Ivy Bridge and Haswell had similar results. (Ivy Bridge shown)
total instructions in shared programs: 11682119 -> 11681056 (<.01%)
instructions in affected programs: 150403 -> 149340 (-0.71%)
helped: 950
HURT: 0
helped stats (abs) min: 1 max: 16 x̄: 1.12 x̃: 1
helped stats (rel) min: 0.23% max: 2.78% x̄: 0.82% x̃: 0.71%
95% mean confidence interval for instructions value: -1.19 -1.04
95% mean confidence interval for instructions %-change: -0.84% -0.79%
Instructions are helped.

total cycles in shared programs: 257495842 -> 257495238 (<.01%)
cycles in affected programs: 270302 -> 269698 (-0.22%)
helped: 271
HURT: 13
helped stats (abs) min: 2 max: 14 x̄: 2.42 x̃: 2
helped stats (rel) min: 0.06% max: 1.13% x̄: 0.32% x̃: 0.28%
HURT stats (abs)   min: 2 max: 12 x̄: 4.00 x̃: 4
HURT stats (rel)   min: 0.15% max: 1.18% x̄: 0.30% x̃: 0.26%
95% mean confidence interval for cycles value: -2.41 -1.84
95% mean confidence interval for cycles %-change: -0.31% -0.26%
Cycles are helped.

Sandy Bridge
total instructions in shared programs: 10430493 -> 10429727 (<.01%)
instructions in affected programs: 120860 -> 120094 (-0.63%)
helped: 766
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.30% max: 2.70% x̄: 0.78% x̃: 0.73%
95% mean confidence interval for instructions value: -1.00 -1.00
95% mean confidence interval for instructions %-change: -0.80% -0.75%
Instructions are helped.

total cycles in shared programs: 146138718 -> 146138446 (<.01%)
cycles in affected programs: 244114 -> 243842 (-0.11%)
helped: 132
HURT: 0
helped stats (abs) min: 2 max: 4 x̄: 2.06 x̃: 2
helped stats (rel) min: 0.03% max: 0.43% x̄: 0.16% x̃: 0.19%
95% mean confidence interval for cycles value: -2.12 -2.00
95% mean confidence interval for cycles %-change: -0.18% -0.15%
Cycles are helped.

GM45 and Iron Lake had identical results. (Iron Lake shown)
total instructions in shared programs: 7780251 -> 7780248 (<.01%)
instructions in affected programs: 175 -> 172 (-1.71%)
helped: 3
HURT: 0
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 1.49% max: 2.44% x̄: 1.81% x̃: 1.49%

total cycles in shared programs: 177851584 -> 177851578 (<.01%)
cycles in affected programs: 9796 -> 9790 (-0.06%)
helped: 3
HURT: 0
helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
helped stats (rel) min: 0.05% max: 0.08% x̄: 0.06% x̃: 0.05%

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>