nir: Simplify 0 < fabs(a)

Sandy Bridge / Ivy Bridge / Haswell
total instructions in shared programs: 8462180 -> 8462174 (-0.00%)
instructions in affected programs: 564 -> 558 (-1.06%)
helped: 6
HURT: 0

total cycles in shared programs: 117542462 -> 117542276 (-0.00%)
cycles in affected programs: 9768 -> 9582 (-1.90%)
helped: 12
HURT: 0

Broadwell / Skylake
total instructions in shared programs: 8980833 -> 8980826 (-0.00%)
instructions in affected programs: 626 -> 619 (-1.12%)
helped: 7
HURT: 0

total cycles in shared programs: 70077900 -> 70077714 (-0.00%)
cycles in affected programs: 9378 -> 9192 (-1.98%)
helped: 12
HURT: 0

G45 and Ironlake showed no change.

v2: Modify the comments to look more like a proof.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index facc33b4e0ad55c88be974e97fd4b2d413950639..c013fd78d9e88dc13020ba0b4fd0ba6655a6569a 100644 (file)
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -108,6 +108,12 @@ optimizations = [
    # inot(a)
    (('fge', 0.0, ('b2f', a)), ('inot', a)),
 
+   # 0.0 < fabs(a)
+   # fabs(a) > 0.0
+   # fabs(a) != 0.0 because fabs(a) must be >= 0
+   # a != 0.0
+   (('flt', 0.0, ('fabs', a)), ('fne', a, 0.0)),
+
    (('fge', ('fneg', ('fabs', a)), 0.0), ('feq', a, 0.0)),
    (('bcsel', ('flt', a, b), a, b), ('fmin', a, b)),
    (('bcsel', ('flt', a, b), b, a), ('fmax', a, b)),