nir: Transform expressions of b2f(a) and b2f(b) to !(a || b)

nir: Transform expressions of b2f(a) and b2f(b) to !(a || b)

All Gen6+ platforms had similar results. (Skylake shown)
total instructions in shared programs: 14276961 -> 14276892 (<.01%)
instructions in affected programs: 3215 -> 3146 (-2.15%)
helped: 28
HURT: 0
helped stats (abs) min: 1 max: 6 x̄: 2.46 x̃: 2
helped stats (rel) min: 0.47% max: 9.52% x̄: 4.34% x̃: 1.92%
95% mean confidence interval for instructions value: -2.87 -2.06
95% mean confidence interval for instructions %-change: -5.73% -2.95%
Instructions are helped.

total cycles in shared programs: 532577068 -> 532578400 (<.01%)
cycles in affected programs: 121864 -> 123196 (1.09%)
helped: 35
HURT: 30
helped stats (abs) min: 2 max: 268 x̄: 42.34 x̃: 22
helped stats (rel) min: 0.12% max: 12.14% x̄: 3.22% x̃: 1.86%
HURT stats (abs)   min: 2 max: 246 x̄: 93.80 x̃: 36
HURT stats (rel)   min: 0.09% max: 13.63% x̄: 4.47% x̃: 2.58%
95% mean confidence interval for cycles value: -5.02 46.01
95% mean confidence interval for cycles %-change: -0.99% 1.65%
Inconclusive result (value mean confidence interval includes 0).

Iron Lake and GM45 had similar results. (Iron Lake shown)
total instructions in shared programs: 7781299 -> 7781342 (<.01%)
instructions in affected programs: 22300 -> 22343 (0.19%)
helped: 13
HURT: 40
helped stats (abs) min: 2 max: 3 x̄: 2.85 x̃: 3
helped stats (rel) min: 1.15% max: 7.69% x̄: 3.72% x̃: 3.33%
HURT stats (abs)   min: 2 max: 2 x̄: 2.00 x̃: 2
HURT stats (rel)   min: 0.26% max: 1.30% x̄: 0.47% x̃: 0.43%
95% mean confidence interval for instructions value: 0.23 1.39
95% mean confidence interval for instructions %-change: -1.18% 0.07%
Inconclusive result (%-change mean confidence interval includes 0).

total cycles in shared programs: 177878928 -> 177879332 (<.01%)
cycles in affected programs: 383298 -> 383702 (0.11%)
helped: 7
HURT: 43
helped stats (abs) min: 2 max: 18 x̄: 10.00 x̃: 10
helped stats (rel) min: 0.17% max: 4.81% x̄: 2.62% x̃: 3.40%
HURT stats (abs)   min: 2 max: 38 x̄: 11.02 x̃: 12
HURT stats (rel)   min: 0.08% max: 1.54% x̄: 0.25% x̃: 0.09%
95% mean confidence interval for cycles value: 5.21 10.95
95% mean confidence interval for cycles %-change: -0.51% 0.21%
Inconclusive result (%-change mean confidence interval includes 0).

v2: s/fmin/fmax/.  Noticed by Thomas Helland.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Thomas Helland <thomashelland90@gmail.com>