[Mesa-dev] [PATCH v2] glsl/linker: Check the invariance of built-in special variables

[Tapani Pälli]

r-b (as already did with previous) and if no objections, will push

On 09/07/2018 03:14 PM, Vadym Shovkoplias wrote:
>  From Section 4.6.4 (Invariance and Linkage) of the GLSL ES 1.0 specification
> 
>      "The invariance of varyings that are declared in both the vertex and
>       fragment shaders must match. For the built-in special variables,
>       gl_FragCoord can only be declared invariant if and only if
>       gl_Position is declared invariant. Similarly gl_PointCoord can only
>       be declared invariant if and only if gl_PointSize is declared
>       invariant. It is an error to declare gl_FrontFacing as invariant.
>       The invariance of gl_FrontFacing is the same as the invariance of
>       gl_Position."
> 
> Fixes:
>      * glsl-pcoord-invariant.shader_test
>      * glsl-fcoord-invariant.shader_test
>      * glsl-fface-invariant.shader_test
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107734
> Signed-off-by: Vadym Shovkoplias <vadym.shovkoplias at globallogic.com>
> ---
>   src/compiler/glsl/linker.cpp | 66 ++++++++++++++++++++++++++++++++++++
>   1 file changed, 66 insertions(+)
> 
> diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
> index dbd76b7fcc..e502149932 100644
> --- a/src/compiler/glsl/linker.cpp
> +++ b/src/compiler/glsl/linker.cpp
> @@ -1286,6 +1286,66 @@ interstage_cross_validate_uniform_blocks(struct gl_shader_program *prog,
>      return true;
>   }
>   
> +/**
> + * Verifies the invariance of built-in special variables.
> + */
> +static bool
> +validate_invariant_builtins(struct gl_shader_program *prog,
> +                            const gl_linked_shader *vert,
> +                            const gl_linked_shader *frag)
> +{
> +   const ir_variable *var_vert;
> +   const ir_variable *var_frag;
> +
> +   if (!vert || !frag)
> +      return true;
> +
> +   /*
> +    * From OpenGL ES Shading Language 1.0 specification
> +    * (4.6.4 Invariance and Linkage):
> +    *     "The invariance of varyings that are declared in both the vertex and
> +    *     fragment shaders must match. For the built-in special variables,
> +    *     gl_FragCoord can only be declared invariant if and only if
> +    *     gl_Position is declared invariant. Similarly gl_PointCoord can only
> +    *     be declared invariant if and only if gl_PointSize is declared
> +    *     invariant. It is an error to declare gl_FrontFacing as invariant.
> +    *     The invariance of gl_FrontFacing is the same as the invariance of
> +    *     gl_Position."
> +    */
> +   var_frag = frag->symbols->get_variable("gl_FragCoord");
> +   if (var_frag && var_frag->data.invariant) {
> +      var_vert = vert->symbols->get_variable("gl_Position");
> +      if (var_vert && !var_vert->data.invariant) {
> +         linker_error(prog,
> +               "fragment shader built-in `%s' has invariant qualifier, "
> +               "but vertex shader built-in `%s' lacks invariant qualifier\n",
> +               var_frag->name, var_vert->name);
> +         return false;
> +      }
> +   }
> +
> +   var_frag = frag->symbols->get_variable("gl_PointCoord");
> +   if (var_frag && var_frag->data.invariant) {
> +      var_vert = vert->symbols->get_variable("gl_PointSize");
> +      if (var_vert && !var_vert->data.invariant) {
> +         linker_error(prog,
> +               "fragment shader built-in `%s' has invariant qualifier, "
> +               "but vertex shader built-in `%s' lacks invariant qualifier\n",
> +               var_frag->name, var_vert->name);
> +         return false;
> +      }
> +   }
> +
> +   var_frag = frag->symbols->get_variable("gl_FrontFacing");
> +   if (var_frag && var_frag->data.invariant) {
> +      linker_error(prog,
> +            "fragment shader built-in `%s' can not be declared as invariant\n",
> +            var_frag->name);
> +      return false;
> +   }
> +
> +   return true;
> +}
>   
>   /**
>    * Populates a shaders symbol table with all global declarations
> @@ -5011,6 +5071,12 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog)
>            lower_named_interface_blocks(mem_ctx, prog->_LinkedShaders[i]);
>      }
>   
> +   if (prog->IsES && prog->data->Version == 100)
> +      if (!validate_invariant_builtins(prog,
> +            prog->_LinkedShaders[MESA_SHADER_VERTEX],
> +            prog->_LinkedShaders[MESA_SHADER_FRAGMENT]))
> +         goto done;
> +
>      /* Implement the GLSL 1.30+ rule for discard vs infinite loops Do
>       * it before optimization because we want most of the checks to get
>       * dropped thanks to constant propagation.
>