[Mesa-dev] [PATCH V2 1/4] glsl: Compile error if fs defines conflicting qualifiers for gl_FragCoord

[Anuj Phogat]

On Tue, Feb 25, 2014 at 7:43 AM, Ian Romanick <idr at freedesktop.org> wrote:
> On 02/24/2014 05:34 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()
>> {
>> }
>>
>> V2: Some code refactoring for better readability.
>>      Add compiler error conditions for redeclarations like:
>>
>> layout(origin_upper_left) in vec4 gl_FragCoord;
>> layout(origin_upper_left, pixel_center_integer) in vec4 gl_FragCoord;
>>
>> and
>>
>> in vec4 gl_FragCoord;
>> layout(origin_upper_left, pixel_center_integer) in vec4 gl_FragCoord;
>>
>> Signed-off-by: Anuj Phogat <anuj.phogat at gmail.com>
>> Cc: <mesa-stable at lists.freedesktop.org>
>> ---
>> This series is also available at:
>> https://github.com/aphogat/mesa.git, branch='review'
>>
>>   src/glsl/ast_to_hir.cpp         | 60 +++++++++++++++++++++++++++++++++++++++++
>>   src/glsl/glsl_parser_extras.cpp |  5 ++++
>>   src/glsl/glsl_parser_extras.h   | 12 +++++++++
>>   3 files changed, 77 insertions(+)
>>
>> diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
>> index f06baeb..9fe3095 100644
>> --- a/src/glsl/ast_to_hir.cpp
>> +++ b/src/glsl/ast_to_hir.cpp
>> @@ -2295,6 +2295,36 @@ apply_image_qualifier_to_variable(const struct ast_type_qualifier *qual,
>>      }
>>   }
>>
>> +static inline const char*
>> +get_layout_qualifier_string(bool origin_upper_left, bool pixel_center_integer)
>> +{
>> +   if (origin_upper_left && pixel_center_integer)
>> +      return "origin_upper_left, pixel_center_integer";
>> +   else if (origin_upper_left)
>> +      return "origin_upper_left";
>> +   else if (pixel_center_integer)
>> +      return "pixel_center_integer";
>> +   else
>> +      return " ";
>> +}
>> +
>> +static inline bool
>> +is_conflicting_fragcoord_redeclaration(struct _mesa_glsl_parse_state *state,
>> +                                       const struct ast_type_qualifier *qual)
>
> state can also be const.
>
>> +{
>> +   bool conflicting_origin_upper_left =
>> +      (state->fs_origin_upper_left && !qual->flags.q.origin_upper_left) ||
>> +      (!state->fs_origin_upper_left && qual->flags.q.origin_upper_left &&
>> +       state->fs_redeclares_gl_fragcoord);
>> +
>> +   bool conflicting_pixel_center_integer =
>> +      (state->fs_pixel_center_integer && !qual->flags.q.pixel_center_integer) ||
>> +      (!state->fs_pixel_center_integer && qual->flags.q.pixel_center_integer &&
>> +       state->fs_redeclares_gl_fragcoord);
>
> Does this condition also work?  It seems easier to understand.
>
>    /* If gl_FragCoord was previously declared, and the qualifiers were
>     * different in any way, return false.
>     */
>    if (state->fs_redeclares_gl_fragcoord) {
>       return state->fs_pixel_center_integer != qual->flags.q.pixel_center_integer
>          || state->fs_origin_upper_left != qual->flags.q.origin_upper_left;
>    }
>
>    return true;
I think you meant 'return false' here? It works after making this change in last
statement. Using '!=' made the function look simpler. Thanks for suggestion.

>> +
>> +   return (conflicting_origin_upper_left || conflicting_pixel_center_integer);
>> +}
>> +
>>   static void
>>   apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
>>                                ir_variable *var,
>> @@ -2459,6 +2489,36 @@ apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
>>                      qual_string);
>>      }
>>
>> +   if (strcmp(var->name, "gl_FragCoord") == 0) {
>> +
>> +      /* Make sure all gl_FragCoord redeclarations specify the same layout
>> +       * qualifiers.
>> +       */
>> +      if (is_conflicting_fragcoord_redeclaration(state, qual)) {
>> +         const char *const qual_string =
>> +            get_layout_qualifier_string(qual->flags.q.origin_upper_left,
>> +                                        qual->flags.q.pixel_center_integer);
>> +
>> +         const char *const state_string =
>> +            get_layout_qualifier_string(state->fs_origin_upper_left,
>> +                                        state->fs_pixel_center_integer);
>> +
>> +         _mesa_glsl_error(loc, state,
>> +                          "gl_FragCoord redeclared with different layout "
>> +                          "qualifiers (%s) and (%s) ",
>> +                          state_string,
>> +                          qual_string);
>> +      }
>> +      state->fs_origin_upper_left = qual->flags.q.origin_upper_left;
>> +      state->fs_pixel_center_integer = qual->flags.q.pixel_center_integer;
>> +      state->fs_redeclares_gl_fragcoord_with_no_layout_qualifiers =
>> +         !qual->flags.q.origin_upper_left && !qual->flags.q.pixel_center_integer;
>> +      state->fs_redeclares_gl_fragcoord =
>> +         state->fs_origin_upper_left ||
>> +         state->fs_pixel_center_integer ||
>> +         state->fs_redeclares_gl_fragcoord_with_no_layout_qualifiers;
>> +   }
>> +
>>      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 d7f5202..fcbbf44 100644
>> --- a/src/glsl/glsl_parser_extras.cpp
>> +++ b/src/glsl/glsl_parser_extras.cpp
>> @@ -201,6 +201,11 @@ _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_redeclares_gl_fragcoord = false;
>> +   this->fs_origin_upper_left = false;
>> +   this->fs_pixel_center_integer = false;
>> +   this->fs_redeclares_gl_fragcoord_with_no_layout_qualifiers = false;
>> +
>>      this->gs_input_prim_type_specified = false;
>>      this->gs_input_size = 0;
>>      this->in_qualifier = new(this) ast_type_qualifier();
>> diff --git a/src/glsl/glsl_parser_extras.h b/src/glsl/glsl_parser_extras.h
>> index 300d900..2017913 100644
>> --- a/src/glsl/glsl_parser_extras.h
>> +++ b/src/glsl/glsl_parser_extras.h
>> @@ -204,6 +204,18 @@ struct _mesa_glsl_parse_state {
>>      struct ast_type_qualifier *default_uniform_qualifier;
>>
>>      /**
>> +    * Variables to track different cases if a fragment shader redeclares
>> +    * built-in variable gl_FragCoord.
>> +    *
>> +    * Note: These values are computed at ast_to_hir time rather than at parse
>> +    * time.
>> +    */
>> +   bool fs_redeclares_gl_fragcoord;
>> +   bool fs_origin_upper_left;
>> +   bool fs_pixel_center_integer;
>> +   bool fs_redeclares_gl_fragcoord_with_no_layout_qualifiers;
>> +
>> +   /**
>>       * True if a geometry shader input primitive type was specified using a
>>       * layout directive.
>>       *
>>
>