[Mesa-dev] [PATCH v3] glsl/linker: dvec3/dvec4 consume twice input vertex attributes

[Michael Schellenberger Costa]

Hi Juan,

Am 18.05.2016 um 13:19 schrieb Juan A. Suarez Romero:
> From the GL 4.5 core spec, section 11.1.1 (Vertex Attributes):
> 
> "A program with more than the value of MAX_VERTEX_ATTRIBS
> active attribute variables may fail to link, unless
> device-dependent optimizations are able to make the program
> fit within available hardware resources. For the purposes
> of this test, attribute variables of the type dvec3, dvec4,
> dmat2x3, dmat2x4, dmat3, dmat3x4, dmat4x3, and dmat4 may
> count as consuming twice as many attributes as equivalent
> single-precision types. While these types use the same number
> of generic attributes as their single-precision equivalents,
> implementations are permitted to consume two single-precision
> vectors of internal storage for each three- or four-component
> double-precision vector."
> 
> This commits makes dvec3, dvec4, dmat2x3, dmat2x4, dmat3, dmat3x4,
> dmat4x3 and dmat4 consume twice as many attributes as equivalent
> single-precision types.
> 
> v3: count doubles as consuming two attributes (Dave Airlie)
> 
> Signed-off-by: Antia Puentes <apuentes at igalia.com>
> Signed-off-by: Juan A. Suarez Romero <jasuarez at igalia.com>
> ---
>  src/compiler/glsl/linker.cpp | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
> index f208d19..ad96a63 100644
> --- a/src/compiler/glsl/linker.cpp
> +++ b/src/compiler/glsl/linker.cpp
> @@ -2873,6 +2873,25 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
>        to_assign[i].var->data.location = generic_base + location;
>        to_assign[i].var->data.is_unmatched_generic_inout = 0;
>        used_locations |= (use_mask << location);
> +
> +      if (to_assign[i].var->type->without_array()->is_dual_slot_double())
> +         double_storage_locations |= (use_mask << location);
> +   }
> +
> +   /* Now that we have all the locations, take in account that dvec3/4 can
> +    * require twice the space of single-precision vectors. Check if we run out
> +    * of attribute slots.
> +    */
Would you mind citing the spec section from the commit message here
(only reference not the text)?
--Michael

> +   if (target_index == MESA_SHADER_VERTEX) {
> +      unsigned total_attribs_size =
> +         _mesa_bitcount(used_locations & ((1 << max_index) - 1)) +
> +         _mesa_bitcount(double_storage_locations);
> +      if (total_attribs_size > max_index) {
> +	 linker_error(prog,
> +		      "attempt to use %d vertex attribute slots only %d available ",
> +		      total_attribs_size, max_index);
> +	 return false;
> +      }
>     }
>  
>     return true;
>