i965: Port INTEL_PRECISE_TRIG=1 to NIR.

[mesa.git] / src / mesa / drivers / dri / i965 / brw_nir_trig_workarounds.py

diff --git a/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py b/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py
new file mode 100755 (executable)
index 0000000..67dab9a
--- /dev/null
+++ b/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py
@@ -0,0 +1,43 @@
+#! /usr/bin/env python
+#
+# Copyright (C) 2016 Intel Corporation
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice (including the next
+# paragraph) shall be included in all copies or substantial portions of the
+# Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+# IN THE SOFTWARE.
+
+import nir_algebraic
+
+# The SIN and COS instructions on Intel hardware can produce values
+# slightly outside of the [-1.0, 1.0] range for a small set of values.
+# Obviously, this can break everyone's expectations about trig functions.
+#
+# According to an internal presentation, the COS instruction can produce
+# a value up to 1.000027 for inputs in the range (0.08296, 0.09888).  One
+# suggested workaround is to multiply by 0.99997, scaling down the
+# amplitude slightly.  Apparently this also minimizes the error function,
+# reducing the maximum error from 0.00006 to about 0.00003.
+
+trig_workarounds = [
+   (('fsin', 'x'), ('fmul', ('fsin', 'x'), 0.99997)),
+   (('fcos', 'x'), ('fmul', ('fcos', 'x'), 0.99997)),
+]
+
+print '#include "brw_nir.h"'
+print nir_algebraic.AlgebraicPass("brw_nir_apply_trig_workarounds",
+                                  trig_workarounds).render()