[Mesa-dev] [PATCH 05/10] glsl: Don't allow gl_FragData[i], with i>0 in GLES shaders

[Ian Romanick]

On 12/01/2014 05:04 AM, Eduardo Lima Mitev wrote:
> The OpenGL ES Shading Language specification describes the
> values that may be output by a fragment shader. These are
> gl_FragColor and gl_FragData[0]. Multiple render targets
> are not supported in GLES.
> 
> Fixes dEQP test:
>   * dEQP-GLES3.functional.shaders.fragdata.invalid_assign_to_1

I think the test needs to be updated for interactions with
GL_NV_draw_buffers.  Right now every Mesa driver enables
GL_NV_draw_buffers by default, so I don't think this check is necessary.

> ---
>  src/glsl/ast_array_index.cpp | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/src/glsl/ast_array_index.cpp b/src/glsl/ast_array_index.cpp
> index ff0c757..b507d34 100644
> --- a/src/glsl/ast_array_index.cpp
> +++ b/src/glsl/ast_array_index.cpp
> @@ -46,7 +46,9 @@ ast_array_specifier::print(void) const
>   *
>   * This function also checks whether the array is a built-in array whose
>   * maximum size is too small to accommodate the given index, and if so uses
> - * loc and state to report the error.
> + * loc and state to report the error. It also checks that the built-in array
> + * gl_FragData is not accessed with indexes greater than zero in OpenGL ES,
> + * where multiple render targets are not allowed.
>   */
>  static void
>  update_max_array_access(ir_rvalue *ir, int idx, YYLTYPE *loc,
> @@ -54,6 +56,23 @@ update_max_array_access(ir_rvalue *ir, int idx, YYLTYPE *loc,
>  {
>     if (ir_dereference_variable *deref_var = ir->as_dereference_variable()) {
>        ir_variable *var = deref_var->var;
> +
> +      /* Page 89 in the section 3.8 (Fragment Shaders) of the the
> +       * OpenGL ES 2.0.25 spec says:
> +       *     "The OpenGL ES Shading Language specification describes the
> +       *     values that may be output by a fragment shader. These are
> +       *     gl_FragColor and gl_FragData[0].
> +       *              ...
> +       *     gl_FragData is supported for compatibility with the desktop
> +       *     OpenGL Shading Language, but only a single fragment color
> +       *     output is allowed in the OpenGL ES Shading Language."
> +       */
> +      if (state->es_shader && idx > 0 &&
> +          strcmp(var->name, "gl_FragData") == 0) {
> +         _mesa_glsl_error(loc, state,
> +                          "multiple render targets are not supported");
> +      }
> +
>        if (idx > (int)var->data.max_array_access) {
>           var->data.max_array_access = idx;
>  
>