[Mesa-dev] [PATCH 1/5] glsl: Add support for separate reference Z for shadow samplers

[Kenneth Graunke]

On 10/10/2013 12:21 AM, Chris Forbes wrote:
> ARB_gpu_shader5's textureGather*() functions which take shadow samplers
> have a separate `refz` parameter rather than adding it to the
> coordinate.
> 
> Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>
> ---
>  src/glsl/builtin_functions.cpp | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/src/glsl/builtin_functions.cpp b/src/glsl/builtin_functions.cpp
> index db6a0a9..ef8b7bb 100644
> --- a/src/glsl/builtin_functions.cpp
> +++ b/src/glsl/builtin_functions.cpp
> @@ -3383,11 +3383,21 @@ builtin_builder::_texture(ir_texture_opcode opcode,
>     if (flags & TEX_PROJECT)
>        tex->projector = swizzle(P, coord_type->vector_elements - 1, 1);
>  
> -   /* The shadow comparitor is normally in the Z component, but a few types
> -    * have sufficiently large coordinates that it's in W.
> -    */
> -   if (sampler_type->sampler_shadow)
> -      tex->shadow_comparitor = swizzle(P, MAX2(coord_size, SWIZZLE_Z), 1);
> +   if (sampler_type->sampler_shadow) {
> +      if (opcode == ir_tg4) {
> +         /* gather has refz as a separate parameter, immediately after the
> +          * coordinate
> +          */

Interesting.  texture(samplerCubeArrayShadow) is just like this - a vec4
coordinate and an extra float comparitor.  I handled that in a separate
function, since it was a unique case, but that's not true anymore.

It probably makes sense to handle Gather here, since you need all the
offset stuff as well.

As a follow-on, maybe fold _textureCubeArrayShadow() into this function
now that it has support for a separate comparitor parameter?

Patches 1-3 are:
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

> +         ir_variable *refz = in_var(glsl_type::float_type, "refz");
> +         sig->parameters.push_tail(refz);
> +         tex->shadow_comparitor = var_ref(refz);
> +      } else {
> +         /* The shadow comparitor is normally in the Z component, but a few types
> +          * have sufficiently large coordinates that it's in W.
> +          */
> +         tex->shadow_comparitor = swizzle(P, MAX2(coord_size, SWIZZLE_Z), 1);
> +      }
> +   }
>  
>     if (opcode == ir_txl) {
>        ir_variable *lod = in_var(glsl_type::float_type, "lod");
>