[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 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.

> 
> 
>> +
>>      (('fmin', a, ('fneg', a)), ('fneg', ('fabs', a))),
>>      (('imin', a, ('ineg', a)), ('ineg', ('iabs', a))),
>>      (('fmin', a, ('fneg', ('fabs', a))), ('fneg', ('fabs', a))),
>>