[Mesa-dev] [PATCH 0/8] Implement EXT_shader_samples_identical

[Jason Ekstrand]

On Wed, Nov 18, 2015 at 4:23 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On Wednesday, November 18, 2015 03:46:46 PM Ian Romanick wrote:
>> This patch series implements a new GL extension,
>> EXT_shader_samples_identical.  This extension allows shaders to
>> determine when all of the samples in a particular texel are the same.
>> This takes advantage of the way compressed multisample surfaces are
>> stored on modern Intel and AMD hardware.  This enables optimizations in
>> application multisample resolve filters, etc.
>>
>> I really wanted to get this in the next Mesa release.  For some reason,
>> I thought the branch point was after Thanksgiving (which is next
>> Thursday).  Ken reminded me yesterday that the branch point is actually
>> this Friday. :( As a result, I'm sending it out today to get review as
>> soon as possible.
>>
>> I also wanted to get as much time as possible for other drivers to get
>> implementations.  I worked with Graham Sellers on this extension, and he
>> assures me that the implementation on modern Radeons is trivial.  My
>> expectation is that it should be about the same as the Intel
>> implementation.
>>
>> There will be some extra TGSI bits needed, but that should also be
>> trivial.  For the NIR and i965 backend bits, I mostly copied and blended
>> the implementations of txf_ms and query_samples.
>>
>> There are currently only trivial piglit tests, but I am working on more.
>> I basically hacked up tests/spec/arb_texture_multisample/texelfetch.c to
>> use the extension to render different colors based on whether
>> textureSamplesIdenticalEXT returned true or false.  The resulting image
>> and the generated assembly look good.  My plan is to get a set of real
>> tests out by midday tomorrow.
>>
>> As soon as we're confident that the spec is good, I'll submit it to
>> Khronos for publication in the registry.  I'm still waiting on feedback
>> from another closed-source driver writer.
>
> Other than the few comments I had, this looks good to me.
>
> Series is:
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
>
> I look forward to seeing it in action in meta_blit.c.
>
> It sounds like Chris plans to review it as well, which is great.

I made a few comments on the last three patches, only one of which (on
the last patch) is really critical.  The rest we can clean up later if
you don't want to deal with it now.
--Jason