[Mesa-dev] [PATCH 4/5] i965: Enable the ARB_transform_feedback3 extension on Gen7+.

[Kenneth Graunke]

On 10/28/2013 10:50 AM, Ian Romanick wrote:
> On 10/26/2013 01:33 PM, Kenneth Graunke wrote:
>> This extension is written a bit strangely.  Although it introduces the
>> concept of multiple transform feedback streams, it doesn't actually
>> provide more than a single stream.
>>
>> The ARB_gpu_shader5 extension is what introduces the ability to write to
>> streams other than stream #0 and increases the required number of streams.
>>
>> Since we don't yet support ARB_gpu_shader5, we can safely enable
>> ARB_transform_feedback3 even though we only support a single stream.
>> This does provide some useful functionality: applications can now use
>> more than one interleaved transform feedback buffer.
>>
>> I believe this extension can be enabled independently from
>> ARB_transform_feedback2, so I've enabled it universally on Gen7+.
> 
> I think that's technically true, but I also think this will make our
> implementation unjustly unique.  That's sure to uncover app bugs that I
> don't think we want to chase.  I think I'd feel more comfortable only
> enabling 3 when 2 is also enabled.

Agreed.  I'll change it to enable all three together or nothing.

Thanks, Ian.

--Ken