[Mesa-dev] [PATCH 2/2] i965/compiler: Disable trig workarounds on KBL+

[Jason Ekstrand]

The precision of our trig instructions instructions appears to have been
fixed on Kaby Lake.  Neither Ben nor I can find any documentation for this.
However, the dEQP precision tests now pass with INTEL_PRECISE_TRIG=0 where
they fail on Sky Lake.

Signed-off-by: Jason Ekstrand <jason at jlekstrand.net>
---
 src/mesa/drivers/dri/i965/brw_nir.c                   | 5 ++++-
 src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py | 7 ++++---
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_nir.c b/src/mesa/drivers/dri/i965/brw_nir.c
index a93d825..1069438 100644
--- a/src/mesa/drivers/dri/i965/brw_nir.c
+++ b/src/mesa/drivers/dri/i965/brw_nir.c
@@ -449,6 +449,7 @@ nir_optimize(nir_shader *nir, bool is_scalar)
 nir_shader *
 brw_preprocess_nir(const struct brw_compiler *compiler, nir_shader *nir)
 {
+   const struct gen_device_info *devinfo = compiler->devinfo;
    bool progress; /* Written by OPT and OPT_V */
    (void)progress;
 
@@ -457,7 +458,9 @@ brw_preprocess_nir(const struct brw_compiler *compiler, nir_shader *nir)
    if (nir->stage == MESA_SHADER_GEOMETRY)
       OPT(nir_lower_gs_intrinsics);
 
-   if (compiler->precise_trig)
+   /* See also brw_nir_trig_workarounds.py */
+   if (compiler->precise_trig &&
+       !(devinfo->gen >= 10 || devinfo->is_kabylake))
       OPT(brw_nir_apply_trig_workarounds);
 
    static const nir_lower_tex_options tex_options = {
diff --git a/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py b/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py
index 67dab9a..3b8d0ce 100755
--- a/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py
+++ b/src/mesa/drivers/dri/i965/brw_nir_trig_workarounds.py
@@ -23,9 +23,10 @@
 
 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.
+# Prior to Kaby Lake, 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.  This appears to be fixed in Kaby Lake.
 #
 # 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
-- 
2.5.0.400.gff86faf