Normally, we never see NULL in a source. However, starting with
eab1c55590, we can with a SHADER_OPCODE_SEND if it only has the first
payload. We were inserting barriers which adds unnecessary scheduling
dependencies and takes a lot of compile time because inserting a single
barrier is an O(n) operation.
All the extra O(n) can have a surprisingly large effect. This cuts the
runtime of dEQP-VK.binding_model.buffer_device_address.set3.depth3.
basessbo.convertcheckuv2.store.single.std140.frag by a factor of 20x for
a debug build.
Shader-db results on ICL:
total instructions in shared programs: 19918983 -> 19921610 (0.01%)
instructions in affected programs: 884074 -> 886701 (0.30%)
helped: 1688
HURT: 817
helped stats (abs) min: 1 max: 163 x̄: 4.23 x̃: 1
helped stats (rel) min: 0.02% max: 12.50% x̄: 1.08% x̃: 0.61%
HURT stats (abs) min: 1 max: 2674 x̄: 11.95 x̃: 2
HURT stats (rel) min: 0.11% max: 70.22% x̄: 1.71% x̃: 1.03%
95% mean confidence interval for instructions value: -1.97 4.06
95% mean confidence interval for instructions %-change: -0.28% -0.06%
Inconclusive result (value mean confidence interval includes 0).
total cycles in shared programs: 976503324 -> 975884809 (-0.06%)
cycles in affected programs: 82581703 -> 81963188 (-0.75%)
helped: 4144
HURT: 5010
helped stats (abs) min: 1 max: 79294 x̄: 311.31 x̃: 8
helped stats (rel) min: <.01% max: 53.69% x̄: 2.00% x̃: 0.51%
HURT stats (abs) min: 1 max: 92266 x̄: 134.04 x̃: 8
HURT stats (rel) min: <.01% max: 218.09% x̄: 3.25% x̃: 0.53%
95% mean confidence interval for cycles value: -119.85 -15.29
95% mean confidence interval for cycles %-change: 0.68% 1.07%
Inconclusive result (value mean confidence interval and %-change mean confidence interval disagree).
total spills in shared programs: 10659 -> 12014 (12.71%)
spills in affected programs: 441 -> 1796 (307.26%)
helped: 7
HURT: 12
total fills in shared programs: 11551 -> 14429 (24.92%)
fills in affected programs: 993 -> 3871 (289.83%)
helped: 8
HURT: 11
total sends in shared programs: 1025832 -> 1025353 (-0.05%)
sends in affected programs: 2241 -> 1762 (-21.37%)
helped: 105
HURT: 1
helped stats (abs) min: 1 max: 87 x̄: 4.57 x̃: 2
helped stats (rel) min: 5.56% max: 54.72% x̄: 11.37% x̃: 10.00%
HURT stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel) min: 100.00% max: 100.00% x̄: 100.00% x̃: 100.00%
95% mean confidence interval for sends value: -7.39 -1.65
95% mean confidence interval for sends %-change: -12.95% -7.70%
Sends are helped.
LOST: 93
GAINED: 109
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/4648
Fixes: eab1c55590 "intel/fs: Support SENDS in SHADER_OPCODE_SEND"
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10412>
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