[Mesa-dev] [PATCH 1/2] nir: optimize min(min(a, b), c) to min3(a, b, c) under an option

[Bas Nieuwenhuizen]

On Thu, May 31, 2018 at 11:13 AM, Samuel Pitoiset
<samuel.pitoiset at gmail.com> wrote:
>
>
> On 05/31/2018 01:55 AM, Timothy Arceri wrote:
>>
>> On 31/05/18 03:06, Samuel Pitoiset wrote:
>>>
>>> Similar for max().
>>>
>>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>>> ---
>>>   src/compiler/nir/nir.h                | 3 +++
>>>   src/compiler/nir/nir_opt_algebraic.py | 8 ++++++++
>>>   2 files changed, 11 insertions(+)
>>>
>>> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
>>> index f6086bd6c0..04991b7d04 100644
>>> --- a/src/compiler/nir/nir.h
>>> +++ b/src/compiler/nir/nir.h
>>> @@ -1897,6 +1897,9 @@ typedef struct nir_shader_compiler_options {
>>>      /* lower b2f to iand */
>>>      bool lower_b2f;
>>> +   /* lower min(min(a, b), c) to min3(a, b, c) (same for max()). */
>>> +   bool lower_minmax3;
>>> +
>>>      /* Does the native fdot instruction replicate its result for four
>>>       * components?  If so, then opt_algebraic_late will turn all fdotN
>>>       * instructions into fdot_replicatedN instructions.
>>> diff --git a/src/compiler/nir/nir_opt_algebraic.py
>>> b/src/compiler/nir/nir_opt_algebraic.py
>>> index 909ea3daf4..1d67e2d88c 100644
>>> --- a/src/compiler/nir/nir_opt_algebraic.py
>>> +++ b/src/compiler/nir/nir_opt_algebraic.py
>>> @@ -224,6 +224,14 @@ optimizations = [
>>>      (('imax', a, a), a),
>>>      (('umin', a, a), a),
>>>      (('umax', a, a), a),
>>> +
>>> +   (('fmin', ('fmin', a, b), c), ('fmin3', a, b, c),
>>> 'options->lower_minmax3'),
>>> +   (('imin', ('imin', a, b), c), ('imin3', a, b, c),
>>> 'options->lower_minmax3'),
>>> +   (('umin', ('umin', a, b), c), ('umin3', a, b, c),
>>> 'options->lower_minmax3'),
>>> +   (('fmax', ('fmax', a, b), c), ('fmax3', a, b, c),
>>> 'options->lower_minmax3'),
>>> +   (('imax', ('imax', a, b), c), ('imax3', a, b, c),
>>> 'options->lower_minmax3'),
>>> +   (('umax', ('umax', a, b), c), ('umax3', a, b, c),
>>> 'options->lower_minmax3'),
>>
>>
>> These look like they would be better suited in late_optimizations rather
>> than optimizations?
>
>
> Totals from affected shaders:
> SGPRS: 104 -> 104 (0.00 %)
> VGPRS: 64 -> 64 (0.00 %)
> Spilled SGPRs: 0 -> 0 (0.00 %)
> Spilled VGPRs: 0 -> 0 (0.00 %)
> Private memory VGPRs: 0 -> 0 (0.00 %)
> Scratch size: 0 -> 0 (0.00 %) dwords per thread
> Code Size: 4652 -> 4644 (-0.17 %) bytes
> LDS: 4 -> 4 (0.00 %) blocks
> Max Waves: 24 -> 24 (0.00 %)
> Wait states: 0 -> 0 (0.00 %)
>
> When moved to late_optimizations.

Is that compared to no min3/max3 lowering at all or compared to doing
those non-late?
>
>
>>
>>
>>> +
>>>      (('fmin', a, ('fneg', a)), ('fneg', ('fabs', a))),
>>>      (('imin', a, ('ineg', a)), ('ineg', ('iabs', a))),
>>>      (('fmin', a, ('fneg', ('fabs', a))), ('fneg', ('fabs', a))),
>>>
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