[Mesa-dev] [PATCH 11/22 v2] nir: Recognize some more open-coded fmin / fmax

[Ian Romanick]

On 02/28/2018 12:48 PM, Jason Ekstrand wrote:
> Rb

For both or just this one?

> On Wed, Feb 28, 2018 at 12:18 PM, Ian Romanick <idr at freedesktop.org
> <mailto:idr at freedesktop.org>> wrote:
> 
>     From: Ian Romanick <ian.d.romanick at intel.com
>     <mailto:ian.d.romanick at intel.com>>
> 
>     This transformation is inexact because section 4.7.1 (Range and
>     Precision) says:
> 
>         Operations and built-in functions that operate on a NaN are not
>         required to return a NaN as the result.
> 
>     The fmin or fmax might not return NaN in cases where the original
>     expression would be required to return NaN.
> 
>     v2: Reorder operands and mark as inexact.  The latter suggested by
>     Jason.
> 
>     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
>     <mailto: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..17f4d9c 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', a, b), b, a), ('fmin', a, b)),
>     +   (('~bcsel', ('fge', b, a), b, a), ('fmax', a, b)),
>         (('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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>