[Mesa-dev] [PATCH 1/3] glsl: Compile error if fs defines conflicting qualifiers for gl_FragCoord

[Ian Romanick]

On 02/10/2014 05:29 PM, Anuj Phogat wrote:
> GLSL 1.50 spec says:
>    "If gl_FragCoord is redeclared in any fragment shader in a program,
>     it must be redeclared in all the fragment shaders in that
>     program that have a static use gl_FragCoord. All redeclarations of
>     gl_FragCoord in all fragment shaders in a single program must
>     have the same set of qualifiers."
> 
> This patch makes the glsl compiler to generate an error if we have a
> fragment shader defined with conflicting layout qualifier declarations
> for gl_FragCoord. For example:
> 
> layout(origin_upper_left, pixel_center_integer) in vec4 gl_FragCoord;
> layout(pixel_center_integer) in vec4 gl_FragCoord;
> void main()
> {
>    gl_FragColor = gl_FragCoord.xyzz;
> }
> 
> Cc: <mesa-stable at lists.freedesktop.org>
> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
> ---
>  src/glsl/ast_to_hir.cpp         | 39 +++++++++++++++++++++++++++++++++++++++
>  src/glsl/glsl_parser_extras.cpp |  3 +++
>  src/glsl/glsl_parser_extras.h   | 10 ++++++++++
>  3 files changed, 52 insertions(+)
> 
> diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
> index c89a26b..7d7d89b 100644
> --- a/src/glsl/ast_to_hir.cpp
> +++ b/src/glsl/ast_to_hir.cpp
> @@ -2374,6 +2374,45 @@ apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
>  		       qual_string);
>     }
>  
> +   /* Make sure all gl_FragCoord redeclarations specify the same layout
> +    * qualifier type.
> +    */
> +   bool conflicting_pixel_center_integer =
> +      state->fs_pixel_center_integer &&
> +      !qual->flags.q.pixel_center_integer;
> +
> +   bool conflicting_origin_upper_left =
> +      state->fs_origin_upper_left &&
> +      !qual->flags.q.origin_upper_left;

I don't think this catches all the cases.  What about

layout(origin_upper_left                      ) in vec4 gl_FragCoord;
layout(origin_upper_left, pixel_center_integer) in vec4 gl_FragCoord;

> +
> +   if (conflicting_pixel_center_integer || conflicting_origin_upper_left) {
> +      const char *const qual_string =
> +         (conflicting_pixel_center_integer && conflicting_origin_upper_left) ?
> +         "pixel_center_integer, origin_upper_left" :
> +         (conflicting_pixel_center_integer ?
> +         "origin_upper_left" : "pixel_center_integer");
> +
> +      const char *const state_string =
> +         (state->fs_pixel_center_integer &&
> +          state->fs_origin_upper_left) ?
> +         "pixel_center_integer, origin_upper_left" :
> +         (state->fs_origin_upper_left ?
> +         "origin_upper_left" : "pixel_center_integer");
> +
> +      _mesa_glsl_error(loc, state,
> +                       "different layout qualifiers were specified with "
> +                       "`gl_FragCoord' (%s) and (%s) "
> +                       "redeclare fragment shader input `gl_FragCoord'",
> +                       state_string,
> +                       qual_string);
> +   }
> +
> +   if (qual->flags.q.pixel_center_integer)
> +      state->fs_pixel_center_integer = true;
> +
> +   if (qual->flags.q.origin_upper_left)
> +      state->fs_origin_upper_left = true;
> +
>     if (qual->flags.q.explicit_location) {
>        validate_explicit_location(qual, var, state, loc);
>     } else if (qual->flags.q.explicit_index) {
> diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
> index b822d22..b06337e 100644
> --- a/src/glsl/glsl_parser_extras.cpp
> +++ b/src/glsl/glsl_parser_extras.cpp
> @@ -193,6 +193,9 @@ _mesa_glsl_parse_state::_mesa_glsl_parse_state(struct gl_context *_ctx,
>     this->default_uniform_qualifier->flags.q.shared = 1;
>     this->default_uniform_qualifier->flags.q.column_major = 1;
>  
> +   this->fs_origin_upper_left = false;
> +   this->fs_pixel_center_integer = false;
> +
>     this->gs_input_prim_type_specified = false;
>     this->gs_input_prim_type = GL_POINTS;
>     this->gs_input_size = 0;
> diff --git a/src/glsl/glsl_parser_extras.h b/src/glsl/glsl_parser_extras.h
> index 7d66147..674dae5 100644
> --- a/src/glsl/glsl_parser_extras.h
> +++ b/src/glsl/glsl_parser_extras.h
> @@ -182,6 +182,16 @@ struct _mesa_glsl_parse_state {
>     struct ast_type_qualifier *default_uniform_qualifier;
>  
>     /**
> +    * True if a fragment shader has an input layout for redeclaring the
> +    * built-in variable gl_FragCoord.
> +    *
> +    * Note: this value is computed at ast_to_hir time rather than at parse
> +    * time.
> +    */
> +   bool fs_origin_upper_left;
> +   bool fs_pixel_center_integer;
> +
> +   /**
>      * True if a geometry shader input primitive type was specified using a
>      * layout directive.
>      *
>