[Mesa-dev] [PATCH] mesa: Only update sampler uniforms that are used by the shader stage

[Kenneth Graunke]

On 11/14/2011 11:25 AM, Ian Romanick wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
> 
> Previously a vertex shader that used no samplers would get updated (by
> calling the driver's ProgramStringNotify) when a sampler in the
> fragment shader was updated.  This was discovered while investigating
> some spurious code generation for shaders in Cogs.  The behavior in
> Cogs is especially pessimal because it ping-pongs sampler uniform
> settings:
> 
>     glUniform1i(sampler1, 0);
>     glUniform1i(sampler2, 1);
>     draw();
>     glUniform1i(sampler1, 1);
>     glUniform1i(sampler2, 0);
>     draw();
>     glUniform1i(sampler1, 0);
>     glUniform1i(sampler2, 1);
>     draw();
>     // etc.
> 
> ProgramStringNotify is still too big of a hammer.  Applications like
> Cogs will still defeat the shader cache.  A lighter-weight mechanism
> that can work with the shader cache is needed.  However, this patch at
> least restores the previous behavior.
> 
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>

I could've sworn this was a regression and that I bisected it to your
patch...but apparently Cogs continually recompiles shaders even on 7.11.
 Sorry, Ian.  I honestly don't know how I managed to botch testing that
badly.

Still, this looks like a good patch that will probably help other cases.

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>