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

[Ian Romanick]

On 03/05/2018 02:07 PM, Jason Ekstrand wrote:
> On Mon, Mar 5, 2018 at 11:11 AM, Ian Romanick <idr at freedesktop.org
> <mailto:idr at freedesktop.org>> wrote:
> 
>     On 02/28/2018 12:48 PM, Jason Ekstrand wrote:
>     > Rb
> 
>     For both or just this one?
> 
> 
> If you put the ~ on there, both.

I'm not sure what you mean.  That's all the other patch ([PATCH 11.1/22]
nir: Mark bcsel-to-fmin (or fmax) transformations as inexact) does.

>     > On Wed, Feb 28, 2018 at 12:18 PM, Ian Romanick <idr at freedesktop.org <mailto:idr at freedesktop.org>
>     > <mailto: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>
>     >     <mailto: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>
>     >     <mailto: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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