[Mesa-dev] [PATCH 11/22] nir: Recognize some more open-coded fmin / fmax

[Jason Ekstrand]

On Fri, Feb 23, 2018 at 3:55 PM, Ian Romanick <idr at freedesktop.org> wrote:

> From: Ian Romanick <ian.d.romanick at intel.com>
>
> shader-db results:
>
> Haswell, Broadwell, and Skylake had similar results. (Skylake shown)
> total instructions in shared programs: 14514817 -> 14514808 (<.01%)
> instructions in affected programs: 229 -> 220 (-3.93%)
> helped: 3
> HURT: 0
> helped stats (abs) min: 1 max: 4 x̄: 3.00 x̃: 4
> helped stats (rel) min: 2.86% max: 4.12% x̄: 3.70% x̃: 4.12%
>
> total cycles in shared programs: 533145211 -> 533144939 (<.01%)
> cycles in affected programs: 37268 -> 36996 (-0.73%)
> helped: 8
> HURT: 0
> helped stats (abs) min: 2 max: 134 x̄: 34.00 x̃: 2
> helped stats (rel) min: 0.02% max: 14.22% x̄: 3.53% x̃: 0.05%
>
> Sandy Bridge and Ivy Bridge had similar results. (Ivy Bridge shown)
> total cycles in shared programs: 257618409 -> 257618403 (<.01%)
> cycles in affected programs: 12582 -> 12576 (-0.05%)
> helped: 3
> HURT: 0
> helped stats (abs) min: 2 max: 2 x̄: 2.00 x̃: 2
> helped stats (rel) min: 0.05% max: 0.05% x̄: 0.05% x̃: 0.05%
>
> No changes on Iron Lake or GM45.
>
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>  src/compiler/nir/nir_opt_algebraic.py | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/src/compiler/nir/nir_opt_algebraic.py
> b/src/compiler/nir/nir_opt_algebraic.py
> index d40d59b..f5f9e94 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -170,6 +170,8 @@ optimizations = [
>     (('fge', ('fneg', ('fabs', a)), 0.0), ('feq', a, 0.0)),
>     (('bcsel', ('flt', b, a), b, a), ('fmin', a, b)),
>     (('bcsel', ('flt', a, b), b, a), ('fmax', a, b)),
> +   (('bcsel', ('fge', b, a), a, b), ('fmin', a, b)),
> +   (('bcsel', ('fge', a, b), a, b), ('fmax', a, b)),
>

Please flag as inexact.  As per the stupid GLSL definition, these are not
the same as fmin/fmax when you throw in a NaN.


>     (('bcsel', ('inot', a), 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)),
> --
> 2.9.5
>
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