[Mesa-dev] [Mesa3d-dev] ARB draw buffers + texenv program

[Dave Airlie]

On Tue, Apr 27, 2010 at 7:10 AM, Dave Airlie <airlied at gmail.com> wrote:
>>>> buffers.
>>> But you'll have more shader instructions for writing to all these
>>> outputs right? I think that could still make a difference, though it
>>> might be more theoretical rather than in practice.
>>>
>>
>> Right, I was talking specifically about memory bandwidth. But it would
>> take a few extra instructions as well.  I think the major impact will
>> be the additional memory bandwidth rather than the added instructions.
>>
>
>
> I also thought about this a bit more, and I'm guessing GPUs use this
> to optimise cache usage. If they know they are rendering the same data
> to all 1..n render targets they only need to store one copy in the dst
> cache.

Okay I'm finally getting back to resurrecting this,

http://people.freedesktop.org/~airlied/scratch/0001-gallium-r300g-fix-frag-color-writing-attempt-2.patch

Basically I've added a TGSI property that states whether single writes
are meant to go to single out or all of them.

I've still got to fixup softpipe and there's lots of debugging in
there, but with that r300g passes the fbo-drawbuffers-fragcolor test.

Dave.