tree 09a0b12310f6a5c529bc79551bdd45b9043f125a
parent 99afaa1d548ebb18c56ae792efccd9b35f0250ca
author Ian Romanick <ian.d.romanick@intel.com> 1592686099 -0700
committer Ian Romanick <ian.d.romanick@intel.com> 1593723933 -0700

nir/algebraic: Don't distrubte absolute-value into dot-products

Dot product is multiplication followed by addition, and absolute value
does not distribute into addition.

Only vec4 platforms are affected by this change as scalar-only platforms
never have any of the fdot_replicated instructions.  In the shader-db
results, below, shaders in MANY different applications are affected.
Trine, Doom3, Enemy Territory: Quake Wars, Counter Strike: Global
Offensive, Mad Max, Metro Last Light, and on and on...  I'm really
shocked that there were no test regressions!

All Haswell and earlier platforms had similar results. (Haswell shown)
total instructions in shared programs: 16219743 -> 16219820 (<.01%)
instructions in affected programs: 12171 -> 12248 (0.63%)
helped: 1
HURT: 78
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.78% max: 0.78% x̄: 0.78% x̃: 0.78%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 0.35% max: 2.38% x̄: 0.91% x̃: 1.06%
95% mean confidence interval for instructions value: 0.92 1.03
95% mean confidence interval for instructions %-change: 0.78% 1.00%
Instructions are HURT.

total cycles in shared programs: 538481383 -> 538491045 (<.01%)
cycles in affected programs: 470796 -> 480458 (2.05%)
helped: 149
HURT: 142
helped stats (abs) min: 1 max: 1338 x̄: 71.13 x̃: 4
helped stats (rel) min: 0.06% max: 40.99% x̄: 2.76% x̃: 0.67%
HURT stats (abs)   min: 1 max: 2092 x̄: 142.68 x̃: 12
HURT stats (rel)   min: 0.07% max: 55.38% x̄: 5.07% x̃: 1.07%
95% mean confidence interval for cycles value: -5.28 71.69
95% mean confidence interval for cycles %-change: -0.07% 2.19%
Inconclusive result (value mean confidence interval includes 0).

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Fixes: 62795475e8f ("nir/algebraic: Distribute source modifiers into instructions")
Closes: #3129
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5581>