nir: Remove f2i(i2f(x)) conversions

nir: Remove f2i(i2f(x)) conversions

Broadwell and Skylake had similar results. (Skylake shown)
total instructions in shared programs: 14277978 -> 14277620 (<.01%)
instructions in affected programs: 36957 -> 36599 (-0.97%)
helped: 76
HURT: 1
helped stats (abs) min: 2 max: 90 x̄: 4.89 x̃: 4
helped stats (rel) min: 0.44% max: 5.88% x̄: 1.04% x̃: 0.87%
HURT stats (abs)   min: 14 max: 14 x̄: 14.00 x̃: 14
HURT stats (rel)   min: 0.36% max: 0.36% x̄: 0.36% x̃: 0.36%
95% mean confidence interval for instructions value: -7.06 -2.24
95% mean confidence interval for instructions %-change: -1.28% -0.77%
Instructions are helped.

total cycles in shared programs: 532584581 -> 532580716 (<.01%)
cycles in affected programs: 973591 -> 969726 (-0.40%)
helped: 76
HURT: 1
helped stats (abs) min: 2 max: 9940 x̄: 159.80 x̃: 32
helped stats (rel) min: <.01% max: 8.70% x̄: 1.15% x̃: 1.19%
HURT stats (abs)   min: 8280 max: 8280 x̄: 8280.00 x̃: 8280
HURT stats (rel)   min: 2.10% max: 2.10% x̄: 2.10% x̃: 2.10%
95% mean confidence interval for cycles value: -386.98 286.59
95% mean confidence interval for cycles %-change: -1.41% -0.81%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 8127 -> 8116 (-0.14%)
spills in affected programs: 108 -> 97 (-10.19%)
helped: 1
HURT: 0

total fills in shared programs: 11090 -> 11086 (-0.04%)
fills in affected programs: 440 -> 436 (-0.91%)
helped: 1
HURT: 1

Haswell
total instructions in shared programs: 12979174 -> 12979054 (<.01%)
instructions in affected programs: 9040 -> 8920 (-1.33%)
helped: 14
HURT: 1
helped stats (abs) min: 2 max: 34 x̄: 8.79 x̃: 6
helped stats (rel) min: 0.41% max: 7.04% x̄: 2.66% x̃: 1.14%
HURT stats (abs)   min: 3 max: 3 x̄: 3.00 x̃: 3
HURT stats (rel)   min: 0.19% max: 0.19% x̄: 0.19% x̃: 0.19%
95% mean confidence interval for instructions value: -13.58 -2.42
95% mean confidence interval for instructions %-change: -3.94% -1.01%
Instructions are helped.

total cycles in shared programs: 411227148 -> 411212880 (<.01%)
cycles in affected programs: 630506 -> 616238 (-2.26%)
helped: 15
HURT: 0
helped stats (abs) min: 2 max: 11192 x̄: 951.20 x̃: 38
helped stats (rel) min: <.01% max: 16.01% x̄: 3.92% x̃: 0.17%
95% mean confidence interval for cycles value: -2544.28 641.88
95% mean confidence interval for cycles %-change: -6.89% -0.94%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 78626 -> 78623 (<.01%)
spills in affected programs: 42 -> 39 (-7.14%)
helped: 1
HURT: 0

total fills in shared programs: 80111 -> 80104 (<.01%)
fills in affected programs: 140 -> 133 (-5.00%)
helped: 1
HURT: 1

Ivy Bridge
total instructions in shared programs: 11684101 -> 11684030 (<.01%)
instructions in affected programs: 3080 -> 3009 (-2.31%)
helped: 4
HURT: 1
helped stats (abs) min: 5 max: 59 x̄: 18.50 x̃: 5
helped stats (rel) min: 6.47% max: 7.04% x̄: 6.87% x̃: 6.99%
HURT stats (abs)   min: 3 max: 3 x̄: 3.00 x̃: 3
HURT stats (rel)   min: 0.15% max: 0.15% x̄: 0.15% x̃: 0.15%
95% mean confidence interval for instructions value: -45.59 17.19
95% mean confidence interval for instructions %-change: -9.38% -1.56%
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 258407697 -> 258389653 (<.01%)
cycles in affected programs: 328323 -> 310279 (-5.50%)
helped: 5
HURT: 0
helped stats (abs) min: 32 max: 14908 x̄: 3608.80 x̃: 32
helped stats (rel) min: 1.26% max: 17.22% x̄: 9.30% x̃: 10.60%
95% mean confidence interval for cycles value: -11616.71 4399.11
95% mean confidence interval for cycles %-change: -16.56% -2.03%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 4537 -> 4528 (-0.20%)
spills in affected programs: 64 -> 55 (-14.06%)
helped: 1
HURT: 0

total fills in shared programs: 4823 -> 4815 (-0.17%)
fills in affected programs: 189 -> 181 (-4.23%)
helped: 1
HURT: 1

Sandy Bridge
total instructions in shared programs: 10488464 -> 10488449 (<.01%)
instructions in affected programs: 272 -> 257 (-5.51%)
helped: 3
HURT: 0
helped stats (abs) min: 5 max: 5 x̄: 5.00 x̃: 5
helped stats (rel) min: 5.49% max: 5.56% x̄: 5.51% x̃: 5.49%

total cycles in shared programs: 150263359 -> 150263263 (<.01%)
cycles in affected programs: 7978 -> 7882 (-1.20%)
helped: 3
HURT: 0
helped stats (abs) min: 32 max: 32 x̄: 32.00 x̃: 32
helped stats (rel) min: 1.15% max: 1.23% x̄: 1.20% x̃: 1.23%

No changes on Iron Lake or GM45.

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