nir/flrp: Lower flrp(a, b, c) differently if another flrp(_, b, c) exists
There is little effect on Intel GPUs now because we almost always take
the "always_precise" path first. It may help on other GPUs, and it does
prevent a bunch of regressions in "intel/compiler: Don't always require
precise lowering of flrp".
No changes on any other Intel platforms.
GM45 and Iron Lake had similar results. (Iron Lake shown)
total cycles in shared programs:
188852500 ->
188852484 (<.01%)
cycles in affected programs: 14612 -> 14596 (-0.11%)
helped: 4
HURT: 0
helped stats (abs) min: 4 max: 4 x̄: 4.00 x̃: 4
helped stats (rel) min: 0.09% max: 0.13% x̄: 0.11% x̃: 0.11%
95% mean confidence interval for cycles value: -4.00 -4.00
95% mean confidence interval for cycles %-change: -0.13% -0.09%
Cycles are helped.
Reviewed-by: Matt Turner <mattst88@gmail.com>