[Mesa-dev] [PATCH 3/7] i965/fs: Use the sampler for FS pull constant loading on Ivybridge.

[Eric Anholt]

Kenneth Graunke <kenneth at whitecape.org> writes:

> Data port reads are absurdly slow on Ivybridge due to cache issues.
>
> The LD message ignores the sampler unit index and SAMPLER_STATE pointer,
> instead relying on hard-wired default state.  Thus, there's no need to
> worry about running out of sampler units or providing SAMPLER_STATE;
> this small patch should be all that's required.
>
> NOTE: This is a candidate for all release branches.
>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/brw_fs.h        |  3 +++
>  src/mesa/drivers/dri/i965/brw_fs_emit.cpp | 36 ++++++++++++++++++++++++++++++-
>  2 files changed, 38 insertions(+), 1 deletion(-)
>
> I did this a long time ago for VS pull constant loading, which resulted in
> a 2-5x speedup for certain benchmarks.  Apparently at the time I never got
> FS pull constant loading working, and didn't have a benchmark that needed
> it, so I never finished and pushed it.
>
> Now I have a game that needs it.  No concrete data as I haven't figured out
> how to get consistent FPS numbers out of it.

I'd rather hold off for some numbers, and I object to cherry-picking
performance patches to release branches.
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