nir: Recognize open-coded fmin/fmax.

And unfortunately other shaders do the same thing but with >=/<= which
we can't apply this optimization to because of NaNs.

instructions in affected programs:     23309 -> 22938 (-1.59%)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

diff --git a/src/glsl/nir/nir_opt_algebraic.py b/src/glsl/nir/nir_opt_algebraic.py
index 2b4259e..83223f7 100644 (file)
--- a/src/glsl/nir/nir_opt_algebraic.py
+++ b/src/glsl/nir/nir_opt_algebraic.py
@@ -82,6 +82,8 @@ optimizations = [
    (('feq', ('fadd', a, b), 0.0), ('feq', a, ('fneg', b))),
    (('fne', ('fadd', a, b), 0.0), ('fne', a, ('fneg', b))),
    (('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)),
    (('fmin', ('fmax', a, 0.0), 1.0), ('fsat', a)),
    # Comparison with the same args.  Note that these are not done for
    # the float versions because NaN always returns false on float