Mesa (master): nir/algebraic: Eliminate useless extract before unpack

Mon May 11 19:39:54 UTC 2020

Module: Mesa
Branch: master
Commit: 412e29c277774391c461d0f62c47e54d2f17814a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=412e29c277774391c461d0f62c47e54d2f17814a

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Tue Mar 31 16:57:03 2020 -0700

nir/algebraic: Eliminate useless extract before unpack

The shader helped for spills and fills is the big compute shader in Dirt
Showdown.  One of the shaders hurt for spills and fills on Broadwell is
the big compute shader in Bioshock Infinite, but combined with the
previous commit, it's still an impovement.

Tiger Lake
total instructions in shared programs: 21833218 -> 21832449 (<.01%)
instructions in affected programs: 66104 -> 65335 (-1.16%)
helped: 106
HURT: 14
helped stats (abs) min: 1 max: 67 x̄: 7.87 x̃: 5
helped stats (rel) min: 0.19% max: 5.76% x̄: 1.27% x̃: 0.95%
HURT stats (abs)   min: 1 max: 14 x̄: 4.64 x̃: 1
HURT stats (rel)   min: 0.19% max: 4.12% x̄: 1.41% x̃: 0.19%
95% mean confidence interval for instructions value: -8.51 -4.30
95% mean confidence interval for instructions %-change: -1.23% -0.69%
Instructions are helped.

total cycles in shared programs: 506180109 -> 506196314 (<.01%)
cycles in affected programs: 1671429 -> 1687634 (0.97%)
helped: 37
HURT: 84
helped stats (abs) min: 1 max: 490 x̄: 73.27 x̃: 24
helped stats (rel) min: 0.02% max: 7.98% x̄: 1.25% x̃: 0.41%
HURT stats (abs)   min: 1 max: 5000 x̄: 225.19 x̃: 8
HURT stats (rel)   min: 0.03% max: 10.22% x̄: 1.22% x̃: 0.42%
95% mean confidence interval for cycles value: 2.85 265.00
95% mean confidence interval for cycles %-change: 0.04% 0.88%
Cycles are HURT.

Ice Lake and Skylake had similar results. (Ice Lake shown)
total instructions in shared programs: 19961317 -> 19960543 (<.01%)
instructions in affected programs: 30268 -> 29494 (-2.56%)
helped: 39
HURT: 0
helped stats (abs) min: 1 max: 142 x̄: 19.85 x̃: 7
helped stats (rel) min: 0.19% max: 7.87% x̄: 2.33% x̃: 2.31%
95% mean confidence interval for instructions value: -29.46 -10.23
95% mean confidence interval for instructions %-change: -2.95% -1.71%
Instructions are helped.

total cycles in shared programs: 498863755 -> 498865843 (<.01%)
cycles in affected programs: 1831136 -> 1833224 (0.11%)
helped: 57
HURT: 65
helped stats (abs) min: 1 max: 1400 x̄: 128.93 x̃: 25
helped stats (rel) min: 0.05% max: 3.49% x̄: 0.89% x̃: 0.71%
HURT stats (abs)   min: 1 max: 1887 x̄: 145.18 x̃: 15
HURT stats (rel)   min: 0.02% max: 9.88% x̄: 1.83% x̃: 0.73%
95% mean confidence interval for cycles value: -58.30 92.53
95% mean confidence interval for cycles %-change: 0.16% 0.97%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 8774 -> 8773 (-0.01%)
spills in affected programs: 20 -> 19 (-5.00%)
helped: 1
HURT: 0

total fills in shared programs: 9496 -> 9494 (-0.02%)
fills in affected programs: 40 -> 38 (-5.00%)
helped: 1
HURT: 0

Broadwell
total instructions in shared programs: 17859373 -> 17858548 (<.01%)
instructions in affected programs: 38452 -> 37627 (-2.15%)
helped: 31
HURT: 0
helped stats (abs) min: 1 max: 143 x̄: 26.61 x̃: 10
helped stats (rel) min: 0.19% max: 7.87% x̄: 2.57% x̃: 2.69%
95% mean confidence interval for instructions value: -39.79 -13.44
95% mean confidence interval for instructions %-change: -3.25% -1.89%
Instructions are helped.

total cycles in shared programs: 525858109 -> 525869236 (<.01%)
cycles in affected programs: 2058597 -> 2069724 (0.54%)
helped: 44
HURT: 75
helped stats (abs) min: 2 max: 1330 x̄: 187.84 x̃: 23
helped stats (rel) min: 0.04% max: 31.31% x̄: 2.13% x̃: 0.85%
HURT stats (abs)   min: 1 max: 3915 x̄: 258.56 x̃: 47
HURT stats (rel)   min: 0.02% max: 10.53% x̄: 2.81% x̃: 2.21%
95% mean confidence interval for cycles value: -26.06 213.07
95% mean confidence interval for cycles %-change: 0.19% 1.78%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 25744 -> 25730 (-0.05%)
spills in affected programs: 1578 -> 1564 (-0.89%)
helped: 4
HURT: 2

total fills in shared programs: 31710 -> 31689 (-0.07%)
fills in affected programs: 4346 -> 4325 (-0.48%)
helped: 3
HURT: 3

Haswell
total instructions in shared programs: 16228399 -> 16227783 (<.01%)
instructions in affected programs: 22201 -> 21585 (-2.77%)
helped: 27
HURT: 0
helped stats (abs) min: 1 max: 68 x̄: 22.81 x̃: 11
helped stats (rel) min: 0.19% max: 7.87% x̄: 2.92% x̃: 2.86%
95% mean confidence interval for instructions value: -31.96 -13.66
95% mean confidence interval for instructions %-change: -3.68% -2.15%
Instructions are helped.

total cycles in shared programs: 538613967 -> 538701354 (0.02%)
cycles in affected programs: 1653044 -> 1740431 (5.29%)
helped: 36
HURT: 81
helped stats (abs) min: 2 max: 708 x̄: 104.50 x̃: 17
helped stats (rel) min: <.01% max: 15.01% x̄: 1.67% x̃: 0.65%
HURT stats (abs)   min: 1 max: 30100 x̄: 1125.30 x̃: 304
HURT stats (rel)   min: 0.02% max: 16.21% x̄: 8.98% x̃: 11.60%
95% mean confidence interval for cycles value: 23.78 1470.01
95% mean confidence interval for cycles %-change: 4.29% 7.12%
Cycles are HURT.

total spills in shared programs: 23418 -> 23409 (-0.04%)
spills in affected programs: 177 -> 168 (-5.08%)
helped: 2
HURT: 0

total fills in shared programs: 25919 -> 25896 (-0.09%)
fills in affected programs: 568 -> 545 (-4.05%)
helped: 3
HURT: 0

Ivy Bridge
total instructions in shared programs: 15265983 -> 15265759 (<.01%)
instructions in affected programs: 8418 -> 8194 (-2.66%)
helped: 5
HURT: 0
helped stats (abs) min: 18 max: 99 x̄: 44.80 x̃: 26
helped stats (rel) min: 1.74% max: 4.26% x̄: 3.12% x̃: 3.00%
95% mean confidence interval for instructions value: -86.29 -3.31
95% mean confidence interval for instructions %-change: -4.43% -1.81%
Instructions are helped.

total cycles in shared programs: 422930336 -> 422929589 (<.01%)
cycles in affected programs: 59347 -> 58600 (-1.26%)
helped: 3
HURT: 2
helped stats (abs) min: 72 max: 1060 x̄: 433.33 x̃: 168
helped stats (rel) min: 1.14% max: 3.48% x̄: 2.23% x̃: 2.06%
HURT stats (abs)   min: 265 max: 288 x̄: 276.50 x̃: 276
HURT stats (rel)   min: 4.79% max: 5.64% x̄: 5.22% x̃: 5.22%
95% mean confidence interval for cycles value: -829.08 530.28
95% mean confidence interval for cycles %-change: -4.43% 5.93%
Inconclusive result (value mean confidence interval includes 0).

total spills in shared programs: 4953 -> 4946 (-0.14%)
spills in affected programs: 344 -> 337 (-2.03%)
helped: 2
HURT: 0

total fills in shared programs: 5548 -> 5521 (-0.49%)
fills in affected programs: 838 -> 811 (-3.22%)
helped: 2
HURT: 0

No shader-db changes on any earlier Intel platform.

Reviewed-by: Rhys Perry <pendingchaos02 at gmail.com>
Reviewed-by: Matt Turner <mattst88 at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4515>

---

 src/compiler/nir/nir_opt_algebraic.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 98ed3299691..b1bc4b46bc7 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -1028,6 +1028,11 @@ optimizations.extend([
    (('unpack_32_2x16_split_y', ('iand', a, 0xffff0000)), ('unpack_32_2x16_split_y', a)),
    (('unpack_64_2x32_split_y', ('iand', a, 0xffffffff00000000)), ('unpack_64_2x32_split_y', a)),
 
+   (('unpack_half_2x16_split_x', ('extract_u16', a, 0)), ('unpack_half_2x16_split_x', a)),
+   (('unpack_half_2x16_split_x', ('extract_u16', a, 1)), ('unpack_half_2x16_split_y', a)),
+   (('unpack_32_2x16_split_x', ('extract_u16', a, 0)), ('unpack_32_2x16_split_x', a)),
+   (('unpack_32_2x16_split_x', ('extract_u16', a, 1)), ('unpack_32_2x16_split_y', a)),
+
    # Optimize half packing
    (('ishl', ('pack_half_2x16', ('vec2', a, 0)), 16), ('pack_half_2x16', ('vec2', 0, a))),
    (('ushr', ('pack_half_2x16', ('vec2', 0, a)), 16), ('pack_half_2x16', ('vec2', a, 0))),

