[Mesa-dev] [PATCH 00/10] glsl: Implement varying packing.

[Paul Berry]

On 12 December 2012 09:09, Marek Olšák <maraeo at gmail.com> wrote:

> R300 and R400 support 4 texture indirections (as defined by
> ARB_fragment_program). Adding ALU instructions before the first TEX
> instruction increases the number of texture indirections by 1, which
> might make some shaders not be executable on the hardware at all.
>
> I think this optimization should be disabled on drivers where the
> texture indirection limit is too low.
>
> Marek
>

Hmm, I see.  Follow up question:

My patches implement varying packing in two ways: (a) within a composite
varying (such as a matrix or array varying) and (b) between varyings.
Disabling (b) on some drivers would be pretty simple.  Disabling (a) would
be more of a pain, because it would require there to be two paths to handle
transform feedback, one that understands how to do feedback for packed
varyings, and one that understands how to do feedback for unpacked
varyings.  I was kind of hoping we could avoid that.  Do you think it would
be adequate to disable just (b) on R300 and R400, or do you think we have
to disable both (a) and (b) on R300 and R400?
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