From be7d3ba34ab837488f5333edfd06dc08c8b37d3e Mon Sep 17 00:00:00 2001 From: Ian Romanick Date: Thu, 26 Jul 2018 18:26:18 -0700 Subject: [PATCH] nir: Transform -fabs(a) < 0 to a != 0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Unlike the much older -abs(a) >= 0.0 transformation, this is not precise. The behavior changes if a is NaN. All Gen platforms had pretty similar results. (Skylake shown) total instructions in shared programs: 14277216 -> 14277184 (<.01%) instructions in affected programs: 2300 -> 2268 (-1.39%) helped: 8 HURT: 0 helped stats (abs) min: 1 max: 8 x̄: 4.00 x̃: 3 helped stats (rel) min: 0.48% max: 15.15% x̄: 4.41% x̃: 1.01% 95% mean confidence interval for instructions value: -6.45 -1.55 95% mean confidence interval for instructions %-change: -9.96% 1.13% Inconclusive result (%-change mean confidence interval includes 0). total cycles in shared programs: 532577848 -> 532577990 (<.01%) cycles in affected programs: 17486 -> 17628 (0.81%) helped: 2 HURT: 5 helped stats (abs) min: 2 max: 6 x̄: 4.00 x̃: 4 helped stats (rel) min: 0.06% max: 1.81% x̄: 0.93% x̃: 0.93% HURT stats (abs) min: 6 max: 50 x̄: 30.00 x̃: 26 HURT stats (rel) min: 0.55% max: 2.17% x̄: 1.19% x̃: 1.02% 95% mean confidence interval for cycles value: -1.06 41.63 95% mean confidence interval for cycles %-change: -0.58% 1.74% Inconclusive result (value mean confidence interval includes 0). Signed-off-by: Ian Romanick Reviewed-by: Thomas Helland --- src/compiler/nir/nir_opt_algebraic.py | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py index b96a7f93c08..8300d6d01f5 100644 --- a/src/compiler/nir/nir_opt_algebraic.py +++ b/src/compiler/nir/nir_opt_algebraic.py @@ -212,6 +212,10 @@ optimizations = [ # a != 0.0 (('~flt', 0.0, ('fabs', a)), ('fne', a, 0.0)), + # -fabs(a) < 0.0 + # fabs(a) > 0.0 + (('~flt', ('fneg', ('fabs', a)), 0.0), ('fne', a, 0.0)), + (('fmax', ('b2f(is_used_once)', a), ('b2f', b)), ('b2f', ('ior', a, b))), (('fmax', ('fneg(is_used_once)', ('b2f(is_used_once)', a)), ('fneg', ('b2f', b))), ('fneg', ('b2f', ('ior', a, b)))), (('fmin', ('b2f(is_used_once)', a), ('b2f', b)), ('b2f', ('iand', a, b))),