[Mesa-dev] [PATCH 2/3] nir: Simplify feq(fneg(a), a)) -> feq(a, 0.0)

[Thomas Helland]

The positive and negative value of a float can only
be equal to each other if it is -0.0f and 0.0f.
This is safe for Nan and Inf, as -Nan != Nan, and -Inf != Inf
This gives no changes in my shader-db

Signed-off-by: Thomas Helland <thomashelland90 at gmail.com>
---
 src/glsl/nir/nir_opt_algebraic.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/glsl/nir/nir_opt_algebraic.py b/src/glsl/nir/nir_opt_algebraic.py
index 471191b..3e483fb 100644
--- a/src/glsl/nir/nir_opt_algebraic.py
+++ b/src/glsl/nir/nir_opt_algebraic.py
@@ -114,6 +114,7 @@ optimizations = [
    (('seq', a, b), ('b2f', ('feq', a, b)), 'options->lower_scmp'),
    (('sne', a, b), ('b2f', ('fne', a, b)), 'options->lower_scmp'),
    (('fne', ('fneg', a), a), ('fne', a, 0.0)),
+   (('feq', ('fneg', a), a), ('feq', a, 0.0)),
    # Emulating booleans
    (('imul', ('b2i', a), ('b2i', b)), ('b2i', ('iand', a, b))),
    (('fmul', ('b2f', a), ('b2f', b)), ('b2f', ('iand', a, b))),
-- 
2.5.0