src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py

   1 #! /usr/bin/env python
   2 #
   3 # Copyright (C) 2016 Intel Corporation
   4 #
   5 # Permission is hereby granted, free of charge, to any person obtaining a
   6 # copy of this software and associated documentation files (the "Software"),
   7 # to deal in the Software without restriction, including without limitation
   8 # the rights to use, copy, modify, merge, publish, distribute, sublicense,
   9 # and/or sell copies of the Software, and to permit persons to whom the
  10 # Software is furnished to do so, subject to the following conditions:
  11 #
  12 # The above copyright notice and this permission notice (including the next
  13 # paragraph) shall be included in all copies or substantial portions of the
  14 # Software.
  15 #
  16 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  19 # THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  21 # FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  22 # IN THE SOFTWARE.
  23
  24 import nir_algebraic
  25
  26 # Prior to Kaby Lake, The SIN and COS instructions on Intel hardware can
  27 # produce values slightly outside of the [-1.0, 1.0] range for a small set of
  28 # values.  Obviously, this can break everyone's expectations about trig
  29 # functions.  This appears to be fixed in Kaby Lake.
  30 #
  31 # According to an internal presentation, the COS instruction can produce
  32 # a value up to 1.000027 for inputs in the range (0.08296, 0.09888).  One
  33 # suggested workaround is to multiply by 0.99997, scaling down the
  34 # amplitude slightly.  Apparently this also minimizes the error function,
  35 # reducing the maximum error from 0.00006 to about 0.00003.
  36
  37 trig_workarounds = [
  38    (('fsin', 'x'), ('fmul', ('fsin', 'x'), 0.99997)),
  39    (('fcos', 'x'), ('fmul', ('fcos', 'x'), 0.99997)),
  40 ]
  41
  42 print '#include "brw_nir.h"'
  43 print nir_algebraic.AlgebraicPass("brw_nir_apply_trig_workarounds",
  44                                   trig_workarounds).render()