[Mesa-dev] SSBO's in UniformBlocks list?

[Ilia Mirkin]

On Tue, Sep 29, 2015 at 4:33 AM, Iago Toral <itoral at igalia.com> wrote:
> Hi ilia,
>
> On Tue, 2015-09-29 at 03:53 -0400, Ilia Mirkin wrote:
>> Hi Samuel, and any other onlookers,
>>
>> I was wondering why the decision was made to stick SSBO's onto the
>> same list as constbufs. Seems like they're entirely separate entities,
>> no? Perhaps I'm missing something?
>
> The reason for this was that there is a lot of code in the compiler to
> handle uniform blocks and all the rules for them and we needed the same
> treatment for SSBOs, so that seemed like a reasonable way forward to
> reuse a lot of the code in the compiler front end. I think the only
> place where we needed to make explicit distinctions is when we check for
> resource limits, since these are different for UBOs and SSBOs of course.
> Although UBOs and SSBOs are separate entities they have a lot of
> similarities too, so that did not look like a terrible idea, considering
> the benefits.

My concern is around indexing... now the per-stage indices are in the
combined UBO/SSBO space -- how do I tease out the individual ones?
Easy enough when you can loop over NumUniformBlocks and just count the
right type, but what about in the shader, where I get the buffer index
in a ir_rvalue?

Thanks,

  -ilia