This really, really helps on platforms where fabs() isn't free. A great
many shaders use a * frsq(fabs(fdot(a, a))) to normalize a vector.
Since the result of the fdot must be non-negative, the fabs can be
eliminated by an existing algebraic rule.
shader-db results:
r300 (run on R420 - X800XL)
total instructions in shared programs: 1369807 -> 1368550 (-0.09%)
instructions in affected programs: 59986 -> 58729 (-2.10%)
helped: 609
HURT: 0
total vinst in shared programs: 512899 -> 512861 (<.01%)
vinst in affected programs: 1522 -> 1484 (-2.50%)
helped: 36
HURT: 0
total sinst in shared programs: 260690 -> 260570 (-0.05%)
sinst in affected programs: 1419 -> 1299 (-8.46%)
helped: 120
HURT: 0
total consts in shared programs: 957295 -> 957230 (<.01%)
consts in affected programs: 849 -> 784 (-7.66%)
helped: 65
HURT: 0
LOST: 0
GAINED: 3
The 3 gained shaders are all vertex shaders from XCom: Enemy Unknown.
I'm guessing that game is never going to run on my X800XL. :)
i915
total instructions in shared programs: 791121 -> 780843 (-1.30%)
instructions in affected programs: 220170 -> 209892 (-4.67%)
helped: 2085
HURT: 0
total temps in shared programs: 47765 -> 47766 (<.01%)
temps in affected programs: 9 -> 10 (11.11%)
helped: 0
HURT: 1
total const in shared programs: 93048 -> 92983 (-0.07%)
const in affected programs: 784 -> 719 (-8.29%)
helped: 65
HURT: 0
LOST: 0
GAINED: 36
Haswell, Ivy Bridge, and Sandy Bridge had similar results. (Haswell shown)
total instructions in shared programs: 16702250 -> 16697908 (-0.03%)
instructions in affected programs: 119277 -> 114935 (-3.64%)
helped: 1065
HURT: 0
helped stats (abs) min: 1 max: 20 x̄: 4.08 x̃: 4
helped stats (rel) min: 0.48% max: 10.17% x̄: 3.66% x̃: 3.94%
95% mean confidence interval for instructions value: -4.26 -3.89
95% mean confidence interval for instructions %-change: -3.76% -3.56%
Instructions are helped.
total cycles in shared programs: 880772068 -> 880734134 (<.01%)
cycles in affected programs: 2134456 -> 2096522 (-1.78%)
helped: 941
HURT: 324
helped stats (abs) min: 2 max: 2180 x̄: 123.06 x̃: 44
helped stats (rel) min: 0.04% max: 49.96% x̄: 7.08% x̃: 3.81%
HURT stats (abs) min: 2 max: 2098 x̄: 240.33 x̃: 35
HURT stats (rel) min: 0.04% max: 77.07% x̄: 12.34% x̃: 3.00%
95% mean confidence interval for cycles value: -47.93 -12.04
95% mean confidence interval for cycles %-change: -2.87% -1.34%
Cycles are helped.
No shader-db changes on any other Intel platform.
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17181>
Ian Romanick
6689fa2ab4