From 73aaeac0a3a46e441953ef6beab665af18180eec Mon Sep 17 00:00:00 2001 From: Ian Romanick Date: Wed, 10 Jul 2019 16:28:38 -0700 Subject: [PATCH] nir/algebraic: Reassociate add-and-shift to be shift-and-add MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit A common thing in many shaders: uniform vs { vec4 bones[...]; }; ... x = some_calculation(bones[i + 0]); y = some_calculation(bones[i + 1]); z = some_calculation(bones[i + 2]); This turns into stuff like vec1 32 ssa_12 = iadd ssa_11, ssa_0 vec1 32 ssa_13 = ishl ssa_12, ssa_3 vec1 32 ssa_14 = intrinsic load_ssbo (ssa_7, ssa_13) (16, 4, 0) vec1 32 ssa_15 = iadd ssa_11, ssa_1 vec1 32 ssa_16 = ishl ssa_15, ssa_3 vec1 32 ssa_17 = intrinsic load_ssbo (ssa_7, ssa_16) (16, 4, 0) vec1 32 ssa_18 = iadd ssa_11, ssa_2 vec1 32 ssa_19 = ishl ssa_18, ssa_3 vec1 32 ssa_20 = intrinsic load_ssbo (ssa_7, ssa_19) (16, 4, 0) By reassociating the shift and the add, we can reduce this to vec1 32 ssa_12 = ishl ssa_11, ssa_3 vec1 32 ssa_13 = iadd ssa_12, ssa_0 vec1 32 ssa_14 = intrinsic load_ssbo (ssa_7, ssa_13) (16, 4, 0) vec1 32 ssa_16 = iadd ssa_12, ssa_1 vec1 32 ssa_17 = intrinsic load_ssbo (ssa_7, ssa_16) (16, 4, 0) vec1 32 ssa_19 = iadd ssa_12, ssa_2 vec1 32 ssa_20 = intrinsic load_ssbo (ssa_7, ssa_19) (16, 4, 0) v2: Add some commentary from Rhys Perry's nearly identical patch. All Intel platforms had similar results. (Ice Lake shown) total instructions in shared programs: 16277758 -> 16250704 (-0.17%) instructions in affected programs: 1440284 -> 1413230 (-1.88%) helped: 4920 HURT: 6 helped stats (abs) min: 1 max: 69 x̄: 5.50 x̃: 4 helped stats (rel) min: 0.10% max: 18.33% x̄: 2.21% x̃: 1.79% HURT stats (abs) min: 1 max: 12 x̄: 4.50 x̃: 3 HURT stats (rel) min: 0.18% max: 3.23% x̄: 1.91% x̃: 2.55% 95% mean confidence interval for instructions value: -5.67 -5.31 95% mean confidence interval for instructions %-change: -2.26% -2.16% Instructions are helped. total cycles in shared programs: 367118526 -> 365895358 (-0.33%) cycles in affected programs: 93504145 -> 92280977 (-1.31%) helped: 2754 HURT: 1269 helped stats (abs) min: 1 max: 47039 x̄: 460.66 x̃: 16 helped stats (rel) min: <.01% max: 34.93% x̄: 3.77% x̃: 1.12% HURT stats (abs) min: 1 max: 1500 x̄: 35.85 x̃: 9 HURT stats (rel) min: 0.01% max: 17.35% x̄: 2.18% x̃: 0.75% 95% mean confidence interval for cycles value: -387.31 -220.78 95% mean confidence interval for cycles %-change: -2.11% -1.68% Cycles are helped. LOST: 1 GAINED: 1 Reviewed-by: Alyssa Rosenzweig Reviewed-by: Jason Ekstrand --- 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 a3a244c..bf5c693 100644 --- a/src/compiler/nir/nir_opt_algebraic.py +++ b/src/compiler/nir/nir_opt_algebraic.py @@ -225,6 +225,11 @@ optimizations = [ # a * (#b << #c) (('ishl', ('imul', a, '#b'), '#c'), ('imul', a, ('ishl', b, c))), + # This is common for address calculations. Reassociating may enable the + # 'a<