[Mesa-dev] [RFC] [PATCH 0/4] Add frequency declaration for vertex elements

[Alex Deucher]

On Mon, Aug 16, 2010 at 4:53 PM, Luca Barbieri <luca at luca-barbieri.com> wrote:
>> IIRC, the vertex fetch constants for r6xx+ accept 0 stride.
>
> But does the hardware fetch the same value repeatedly, wasting memory
> bandwidth, or is it smart enough to fetch it once and store it?
> (question applies to both r300-r500 and r600-eg)
>
> In other words, is it necessary to rewrite shaders and pass constant
> elements in constant buffers for optimal performance, or are there
> other ways?
>

I'm pretty sure it just fetches it repeatedly.  I don't remember the
fetch details on r300.  I suspect using constants would be better
performance-wise.

Alex