[Mesa-dev] [PATCH] mesa/st: glsl_to_tgsi: Dissolve arrays who's elements are only accessed directly

[Timothy Arceri]

On 29/11/17 00:54, Gert Wollny wrote:
> Am Dienstag, den 28.11.2017, 08:45 +1100 schrieb Timothy Arceri:
>>
>>
>>>
>>> If I understand the comments in opt_array_splitting, arrays of
>>> arrays are not properly handled there. Curretly, I don't see how I
>>> can fix this, because I simply didn't look at any code there
>>> before.
>>
>> There is more to it than that. We don't even split varyings at all
>> currently.
>>
>> "This skips uniform/varying arrays, which would need careful
>> handling  due to their ir->location fields tying them to the GL API
>> and other
>> shader stages."
>>
>> This is enforced in get_variable_entry() via:
>>
>>      if (var->data.mode != ir_var_auto &&
>>          var->data.mode != ir_var_temporary)
>>         return NULL;
>>
>> As per my previous email I don't think there is much value in putting
>> a bunch of work into this pass.
> 
> For me this raises the question whether it would make sense to push the
> patch that I sent (probably changing the name of the method to
> "split_arrays") and that addresses the problem in the glsl->tgsi stage
> (I can't push it anyway) and is currently useful at least for r600?
> 
> Since I think about another improvement in this stage(*) that would
> further reduce the register pression, I wonder whether it is worth to
> put effort in this or whether this change you talked about switch to
> nir->tgsi can be expected to replace glsl->tgsi anytime soon?
> 

Seems not, I was sure a nir->tgsi pass with limited support already 
existed but seems I was dreaming.

> 
> (*) The idea is to also implement array merging and interleaving,
> because with r600 the number of registers is quite limited, and arrays
> really cut into that, especially if the arrays use only one component.

Yes I have NIR patches to do the same thing, they also do some cross 
linking so that undefined or unused components are remove across stages.

> 
> many thanks,
> Gert
> 
> 
> 
>   
> 
>>
>>>
>>> Best,
>>> Gert
>>>