[Mesa-dev] [PATCH 3/3] nir: Simplify a bcsel to logical-or

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Oddly, this did not affect the shader where I first noticed the pattern.
That particular shader doesn't get its if-statement converted to a bcsel
because there are two assignments in the else-statement.  This led to me
submitting https://bugs.freedesktop.org/show_bug.cgi?id=94747.

shader-db results:

Sandy Bridge
total instructions in shared programs: 8467384 -> 8467069 (-0.00%)
instructions in affected programs: 36594 -> 36279 (-0.86%)
helped: 46
HURT: 0

total cycles in shared programs: 117573448 -> 117568518 (-0.00%)
cycles in affected programs: 339114 -> 334184 (-1.45%)
helped: 46
HURT: 0

Ivy Bridge / Haswell / Broadwell / Skylake:
total instructions in shared programs: 7774258 -> 7773999 (-0.00%)
instructions in affected programs: 30874 -> 30615 (-0.84%)
helped: 46
HURT: 0

total cycles in shared programs: 65739190 -> 65734530 (-0.01%)
cycles in affected programs: 180380 -> 175720 (-2.58%)
helped: 45
HURT: 1

No change on G45 or Ironlake.

I also tried these expressions, but none of them affected any shaders in
shader-db:

   (('bcsel', a, 'a at bool', 'b at bool'), ('ior', a, b)),
   (('bcsel', a, 'b at bool', False),    ('iand', a, b)),
   (('bcsel', a, 'b at bool', 'a at bool'), ('iand', a, b)),

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/compiler/nir/nir_opt_algebraic.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 5363323..59c3c36 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -126,6 +126,7 @@ optimizations = [
    (('bcsel', ('flt', a, b), b, a), ('fmax', a, b)),
    (('bcsel', ('inot', 'a at bool'), b, c), ('bcsel', a, c, b)),
    (('bcsel', a, ('bcsel', a, b, c), d), ('bcsel', a, b, d)),
+   (('bcsel', a, True, 'b at bool'), ('ior', a, b)),
    (('fmin', a, a), a),
    (('fmax', a, a), a),
    (('imin', a, a), a),
-- 
2.5.5