[Mesa-dev] [PATCH] glsl: re-enable varying packing in GL4.4+

[Iago Toral]

On Thu, 2016-05-26 at 14:50 +1000, Timothy Arceri wrote:
> The i965 backend currently expects doubles to be packed.

This patch is:
Reviewed-by: Iago Toral Quiroga <itoral at igalia.com>

With that said, I think these two patches from Samuel might have fixed
i965 to handle unpacked doubles, or at least, some cases of that:
https://lists.freedesktop.org/archives/mesa-dev/2016-May/118263.html

Did you have a chance to try them?

Iago

> ---
>  src/compiler/glsl/link_varyings.cpp | 54 +++++++++++++++++--------------------
>  1 file changed, 24 insertions(+), 30 deletions(-)
> 
> diff --git a/src/compiler/glsl/link_varyings.cpp b/src/compiler/glsl/link_varyings.cpp
> index dd5c9cc..a7c859b 100644
> --- a/src/compiler/glsl/link_varyings.cpp
> +++ b/src/compiler/glsl/link_varyings.cpp
> @@ -1372,10 +1372,26 @@ varying_matches::record(ir_variable *producer_var, ir_variable *consumer_var)
>                   sizeof(*this->matches) * this->matches_capacity);
>     }
>  
> -   const ir_variable *const var = (producer_var != NULL)
> -      ? producer_var : consumer_var;
> -   const gl_shader_stage stage = (producer_var != NULL)
> -      ? producer_stage : consumer_stage;
> +   /* We must use the consumer to compute the packing class because in GL4.4+
> +    * there is no guarantee interpolation qualifiers will match across stages.
> +    *
> +    * From Section 4.5 (Interpolation Qualifiers) of the GLSL 4.30 spec:
> +    *
> +    *    "The type and presence of interpolation qualifiers of variables with
> +    *    the same name declared in all linked shaders for the same cross-stage
> +    *    interface must match, otherwise the link command will fail.
> +    *
> +    *    When comparing an output from one stage to an input of a subsequent
> +    *    stage, the input and output don't match if their interpolation
> +    *    qualifiers (or lack thereof) are not the same."
> +    *
> +    * This text was also in at least revison 7 of the 4.40 spec but is no
> +    * longer in revision 9 and not in the 4.50 spec.
> +    */
> +   const ir_variable *const var = (consumer_var != NULL)
> +      ? consumer_var : producer_var;
> +   const gl_shader_stage stage = (consumer_var != NULL)
> +      ? consumer_stage : producer_stage;
>     const glsl_type *type = get_varying_type(var, stage);
>  
>     this->matches[this->num_matches].packing_class
> @@ -1986,40 +2002,18 @@ assign_varying_locations(struct gl_context *ctx,
>     bool xfb_enabled =
>        ctx->Extensions.EXT_transform_feedback && !unpackable_tess;
>  
> -   /* Disable varying packing for GL 4.4+ as there is no guarantee
> -    * that interpolation qualifiers will match between shaders in these
> -    * versions. We also disable packing on outward facing interfaces for
> -    * SSO because in ES we need to retain the unpacked varying information
> -    * for draw time validation. For desktop GL we could allow packing for
> -    * versions < 4.4 but it's just safer not to do packing.
> +   /* Disable packing on outward facing interfaces for SSO because in ES we
> +    * need to retain the unpacked varying information for draw time
> +    * validation.
>      *
>      * Packing is still enabled on individual arrays, structs, and matrices as
>      * these are required by the transform feedback code and it is still safe
>      * to do so. We also enable packing when a varying is only used for
>      * transform feedback and its not a SSO.
> -    *
> -    * Varying packing currently only packs together varyings with matching
> -    * interpolation qualifiers as the backends assume all packed components
> -    * are to be processed in the same way. Therefore we cannot do packing in
> -    * these versions of GL without the risk of mismatching interfaces.
> -    *
> -    * From Section 4.5 (Interpolation Qualifiers) of the GLSL 4.30 spec:
> -    *
> -    *    "The type and presence of interpolation qualifiers of variables with
> -    *    the same name declared in all linked shaders for the same cross-stage
> -    *    interface must match, otherwise the link command will fail.
> -    *
> -    *    When comparing an output from one stage to an input of a subsequent
> -    *    stage, the input and output don't match if their interpolation
> -    *    qualifiers (or lack thereof) are not the same."
> -    *
> -    * This text was also in at least revison 7 of the 4.40 spec but is no
> -    * longer in revision 9 and not in the 4.50 spec.
>      */
>     bool disable_varying_packing =
>        ctx->Const.DisableVaryingPacking || unpackable_tess;
> -   if ((ctx->API == API_OPENGL_CORE && ctx->Version >= 44) ||
> -       (prog->SeparateShader && (producer == NULL || consumer == NULL)))
> +   if (prog->SeparateShader && (producer == NULL || consumer == NULL))
>        disable_varying_packing = true;
>  
>     varying_matches matches(disable_varying_packing, xfb_enabled,