[Mesa-dev] [PATCH] i965/fs: Don't try 16-wide if 8-wide uses more than half the registers.

[Eric Anholt]

Kenneth Graunke <kenneth at whitecape.org> writes:

> On 08/21/2012 10:49 PM, Eric Anholt wrote:
>> I don't like the idea of losing 16-wide on apps where it might have
>> succeeded if we just tried.  Note that a chunk of register space gets
>> eaten by things that don't scale with number of pixels, like attribute
>> setup, push constants, and the MRF hack.
>
> Nor do I, which is why I was trying to be conservative.  I figured the
> attribute setup could be accounted for by a large enough fudge factor,
> but I forgot about the MRF hack region.
>
>> I could be convinced otherwise with some shader-db stats, though.
>
> Good call.
>
> total instructions in shared programs: 507477 -> 507477 (0.00%)
> instructions in affected programs:     0 -> 0
>
> However, the margin is more slim than I thought: Unigine Sanctuary
> starts losing out on 16-wide with the cut-off at 70 (my patch was 75).
> Perhaps I should refine the heuristic to account for the non-scaling
> sections.

Sounds good enough for me.
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