glsl: add support for shader stencil export

This adds proper support for the GL_ARB_shader_stencil_export extension
to the GLSL compiler. Thanks to Ian for pointing out where I need to add things.

src/glsl/glsl_parser_extras.cpp

@@ -203,6 +203,14 @@ _mesa_glsl_process_extension(const char *name, YYLTYPE *name_locp,
       state->EXT_texture_array_warn = (ext_mode == extension_warn);
 
       unsupported = !state->extensions->EXT_texture_array;
+   } else if (strcmp(name, "GL_ARB_shader_stencil_export") == 0) {
+      if (state->target != fragment_shader) {
+	 unsupported = true;
+      } else {
+	 state->ARB_shader_stencil_export_enable = (ext_mode != extension_disable);
+	 state->ARB_shader_stencil_export_warn = (ext_mode == extension_warn);
+	 unsupported = !state->extensions->ARB_shader_stencil_export;
+      }
    } else {
       unsupported = true;
    }

src/glsl/glsl_parser_extras.h

@@ -133,6 +133,8 @@ struct _mesa_glsl_parse_state {
    unsigned ARB_texture_rectangle_warn:1;
    unsigned EXT_texture_array_enable:1;
    unsigned EXT_texture_array_warn:1;
+   unsigned ARB_shader_stencil_export_enable:1;
+   unsigned ARB_shader_stencil_export_warn:1;
    /*@}*/
 
    /** Extensions supported by the OpenGL implementation. */

src/glsl/ir_variable.cpp

@@ -422,6 +422,20 @@ generate_ARB_draw_buffers_variables(exec_list *instructions,
    }
 }
 
+static void
+generate_ARB_shader_stencil_export_variables(exec_list *instructions,
+					     struct _mesa_glsl_parse_state *state,
+					     bool warn)
+{
+   /* gl_FragStencilRefARB is only available in the fragment shader.
+    */
+   ir_variable *const fd =
+      add_variable("gl_FragStencilRefARB", ir_var_out, FRAG_RESULT_STENCIL,
+		   glsl_type::int_type, instructions, state->symbols);
+
+   if (warn)
+      fd->warn_extension = "GL_ARB_shader_stencil_export";
+}
 
 static void
 generate_120_fs_variables(exec_list *instructions,
@@ -471,6 +485,10 @@ initialize_fs_variables(exec_list *instructions,
       generate_130_fs_variables(instructions, state);
       break;
    }
+
+   if (state->ARB_shader_stencil_export_enable)
+      generate_ARB_shader_stencil_export_variables(instructions, state,
+						   state->ARB_shader_stencil_export_warn);
 }
 
 void

src/mesa/main/extensions.c

@@ -75,6 +75,7 @@ static const struct {
    { OFF, "GL_ARB_sampler_objects",            F(ARB_sampler_objects) },
    { OFF, "GL_ARB_seamless_cube_map",          F(ARB_seamless_cube_map) },
    { OFF, "GL_ARB_shader_objects",             F(ARB_shader_objects) },
+   { OFF, "GL_ARB_shader_stencil_export",      F(ARB_shader_stencil_export) },
    { OFF, "GL_ARB_shading_language_100",       F(ARB_shading_language_100) },
    { OFF, "GL_ARB_shadow",                     F(ARB_shadow) },
    { OFF, "GL_ARB_shadow_ambient",             F(ARB_shadow_ambient) },

src/mesa/main/mtypes.h

@@ -2588,6 +2588,7 @@ struct gl_extensions
    GLboolean ARB_sampler_objects;
    GLboolean ARB_seamless_cube_map;
    GLboolean ARB_shader_objects;
+   GLboolean ARB_shader_stencil_export;
    GLboolean ARB_shading_language_100;
    GLboolean ARB_shadow;
    GLboolean ARB_shadow_ambient;