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

[Tapani Pälli]

On 12/01/2014 05:43 PM, Matteo Bruni wrote:
> 2014-12-01 14:04 GMT+01:00 Eduardo Lima Mitev <elima at igalia.com>:
>> 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
>> ---
>>   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;
>>
>> --
>> 2.1.3
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
>
> AFAICS this restriction is lifted in ES 3.0+ (e.g. see section 3.9.2
> in the OpenGL ES 3.0 spec).

Yep, it seems this check should be against earlier versions and only 
when not having extensions that allow MRT enabled (NV_draw_buffers).

You can still use gl_FragData[] when using OpenGL ES 3 and GLSL ES 1.00, 
however when using GLSL ES 3.00 gl_FragData[] gets deprecated and you 
should use output layout qualifier to bind a output variable and target 
draw buffer together.



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// Tapani