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

[Samuel Pitoiset]

On 05/31/2018 11:25 AM, Bas Nieuwenhuizen wrote:
> 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?

Compared to "default" for both.

>>
>>
>>>
>>>
>>>> +
>>>>       (('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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