[Mesa-dev] [PATCH v3 06/11] glsl: Add arb_cull_distance support

[Tobias Klausmann]

On 09.05.2016 20:41, Ian Romanick wrote:

> snip
>> +      /* From the ARB_cull_distance spec:
>> +       *
>> +       * It is a compile-time or link-time error for the set of shaders forming
>> +       * a program to have the sum of the sizes of the gl_ClipDistance and
>> +       * gl_CullDistance arrays to be larger than
>> +       * gl_MaxCombinedClipAndCullDistances.
>> +       */
>> +      if ((*clip_distance_array_size + *cull_distance_array_size) >
>> +          ctx->Const.MaxClipPlanes) {
>> +          linker_error(prog, "%s shader: the combined size of "
>> +                       "'gl_ClipDistance' and 'gl_CullDistance' size cannot "
>> +                       "be larger than "
>> +                       "gl_MaxCombinedClipAndCullDistances (%u)",
>> +                       _mesa_shader_stage_to_string(shader->Stage),
>> +                       ctx->Const.MaxClipPlanes);
>> +      }
> I think this is the wrong check for this limitation in the spec.  This
> will only catch cases where the usages within a stage exceed the limit.
>   I *believe* (but it's not 100% clear from the quotation) that a vertex
> shader that writes  MaxClipPlanes elements to gl_ClipDisatnce and a
> geometry shader that also writes MaxClipPlances to gl_CullDistance
> should fail to link.  If that is the case, then we need checks elsewhere
> that use LastClipDistanceArraySize and LastCullDistanceArray size to
> enforce the limits.
>
>

I think you are right, but where would be the best place (stage) to 
check this? (You know the codebase way better)

Thanks,
Tobias