glsl: add support for EXT_blend_func_extended builtins

gl_MaxDualSourceDrawBuffersEXT - Maximum dual-source draw buffers supported

For ESSL 1.0, it provides two builtins since you can't have user-defined
color output variables:
  gl_SecondaryFragColorEXT
  gl_SecondaryFragDataEXT[MaxDSDrawBuffers]

Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/glsl/ast_to_hir.cpp

@@ -7194,6 +7194,8 @@ detect_conflicting_assignments(struct _mesa_glsl_parse_state *state,
 {
    bool gl_FragColor_assigned = false;
    bool gl_FragData_assigned = false;
+   bool gl_FragSecondaryColor_assigned = false;
+   bool gl_FragSecondaryData_assigned = false;
    bool user_defined_fs_output_assigned = false;
    ir_variable *user_defined_fs_output = NULL;
 
@@ -7211,6 +7213,10 @@ detect_conflicting_assignments(struct _mesa_glsl_parse_state *state,
          gl_FragColor_assigned = true;
       else if (strcmp(var->name, "gl_FragData") == 0)
          gl_FragData_assigned = true;
+	else if (strcmp(var->name, "gl_SecondaryFragColorEXT") == 0)
+         gl_FragSecondaryColor_assigned = true;
+	else if (strcmp(var->name, "gl_SecondaryFragDataEXT") == 0)
+         gl_FragSecondaryData_assigned = true;
       else if (!is_gl_identifier(var->name)) {
          if (state->stage == MESA_SHADER_FRAGMENT &&
              var->data.mode == ir_var_shader_out) {
@@ -7242,11 +7248,29 @@ detect_conflicting_assignments(struct _mesa_glsl_parse_state *state,
       _mesa_glsl_error(&loc, state, "fragment shader writes to both "
                        "`gl_FragColor' and `%s'",
                        user_defined_fs_output->name);
+   } else if (gl_FragSecondaryColor_assigned && gl_FragSecondaryData_assigned) {
+      _mesa_glsl_error(&loc, state, "fragment shader writes to both "
+                       "`gl_FragSecondaryColorEXT' and"
+                       " `gl_FragSecondaryDataEXT'");
+   } else if (gl_FragColor_assigned && gl_FragSecondaryData_assigned) {
+      _mesa_glsl_error(&loc, state, "fragment shader writes to both "
+                       "`gl_FragColor' and"
+                       " `gl_FragSecondaryDataEXT'");
+   } else if (gl_FragData_assigned && gl_FragSecondaryColor_assigned) {
+      _mesa_glsl_error(&loc, state, "fragment shader writes to both "
+                       "`gl_FragData' and"
+                       " `gl_FragSecondaryColorEXT'");
    } else if (gl_FragData_assigned && user_defined_fs_output_assigned) {
       _mesa_glsl_error(&loc, state, "fragment shader writes to both "
                        "`gl_FragData' and `%s'",
                        user_defined_fs_output->name);
    }
+
+   if ((gl_FragSecondaryColor_assigned || gl_FragSecondaryData_assigned) &&
+       !state->EXT_blend_func_extended_enable) {
+      _mesa_glsl_error(&loc, state,
+                       "Dual source blending requires EXT_blend_func_extended");
+   }
 }
 
 

src/glsl/builtin_variables.cpp

@@ -377,6 +377,11 @@ private:
       return add_variable(name, type, ir_var_shader_out, slot);
    }
 
+   ir_variable *add_index_output(int slot, int index, const glsl_type *type, const char *name)
+   {
+      return add_index_variable(name, type, ir_var_shader_out, slot, index);
+   }
+
    ir_variable *add_system_value(int slot, const glsl_type *type,
                                  const char *name)
    {
@@ -385,6 +390,8 @@ private:
 
    ir_variable *add_variable(const char *name, const glsl_type *type,
                              enum ir_variable_mode mode, int slot);
+   ir_variable *add_index_variable(const char *name, const glsl_type *type,
+                             enum ir_variable_mode mode, int slot, int index);
    ir_variable *add_uniform(const glsl_type *type, const char *name);
    ir_variable *add_const(const char *name, int value);
    ir_variable *add_const_ivec3(const char *name, int x, int y, int z);
@@ -430,6 +437,46 @@ builtin_variable_generator::builtin_variable_generator(
 {
 }
 
+ir_variable *
+builtin_variable_generator::add_index_variable(const char *name,
+                                         const glsl_type *type,
+                                         enum ir_variable_mode mode, int slot, int index)
+{
+   ir_variable *var = new(symtab) ir_variable(type, name, mode);
+   var->data.how_declared = ir_var_declared_implicitly;
+
+   switch (var->data.mode) {
+   case ir_var_auto:
+   case ir_var_shader_in:
+   case ir_var_uniform:
+   case ir_var_system_value:
+      var->data.read_only = true;
+      break;
+   case ir_var_shader_out:
+   case ir_var_shader_storage:
+      break;
+   default:
+      /* The only variables that are added using this function should be
+       * uniforms, shader storage, shader inputs, and shader outputs, constants
+       * (which use ir_var_auto), and system values.
+       */
+      assert(0);
+      break;
+   }
+
+   var->data.location = slot;
+   var->data.explicit_location = (slot >= 0);
+   var->data.explicit_index = 1;
+   var->data.index = index;
+
+   /* Once the variable is created an initialized, add it to the symbol table
+    * and add the declaration to the IR stream.
+    */
+   instructions->push_tail(var);
+
+   symtab->add_variable(var);
+   return var;
+}
 
 ir_variable *
 builtin_variable_generator::add_variable(const char *name,
@@ -581,6 +628,14 @@ builtin_variable_generator::generate_constants()
          add_const("gl_MaxVaryingVectors",
                    state->ctx->Const.MaxVarying);
       }
+
+      /* EXT_blend_func_extended brings a built in constant
+       * for determining number of dual source draw buffers
+       */
+      if (state->EXT_blend_func_extended_enable) {
+         add_const("gl_MaxDualSourceDrawBuffersEXT",
+                   state->Const.MaxDualSourceDrawBuffers);
+      }
    } else {
       add_const("gl_MaxVertexUniformComponents",
                 state->Const.MaxVertexUniformComponents);
@@ -1017,6 +1072,19 @@ builtin_variable_generator::generate_fs_special_vars()
                  array(vec4_t, state->Const.MaxDrawBuffers), "gl_FragData");
    }
 
+   if (state->es_shader && state->language_version == 100 && state->EXT_blend_func_extended_enable) {
+      /* We make an assumption here that there will only ever be one dual-source draw buffer
+       * In case this assumption is ever proven to be false, make sure to assert here
+       * since we don't handle this case.
+       * In practice, this issue will never arise since no hardware will support it.
+       */
+      assert(state->Const.MaxDualSourceDrawBuffers <= 1);
+      add_index_output(FRAG_RESULT_DATA0, 1, vec4_t, "gl_SecondaryFragColorEXT");
+      add_index_output(FRAG_RESULT_DATA0, 1,
+                       array(vec4_t, state->Const.MaxDualSourceDrawBuffers),
+                       "gl_SecondaryFragDataEXT");
+   }
+
    /* gl_FragDepth has always been in desktop GLSL, but did not appear in GLSL
     * ES 1.00.
     */