1 files changed, 66 insertions, 0 deletions

diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 80ea8bc4af6..e24914b832a 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -57,6 +57,10 @@
 #include "program/hash_table.h"
 #include "ir.h"
 
+static void
+detect_conflicting_assignments(struct _mesa_glsl_parse_state *state,
+			       exec_list *instructions);
+
 void
 _mesa_ast_to_hir(exec_list *instructions, struct _mesa_glsl_parse_state *state)
 {
@@ -87,6 +91,7 @@ _mesa_ast_to_hir(exec_list *instructions, struct _mesa_glsl_parse_state *state)
       ast->hir(instructions, state);
 
    detect_recursion_unlinked(state, instructions);
+   detect_conflicting_assignments(state, instructions);
 
    state->toplevel_ir = NULL;
 }
@@ -4017,3 +4022,64 @@ ast_struct_specifier::hir(exec_list *instructions,
     */
    return NULL;
 }
+
+static void
+detect_conflicting_assignments(struct _mesa_glsl_parse_state *state,
+			       exec_list *instructions)
+{
+   bool gl_FragColor_assigned = false;
+   bool gl_FragData_assigned = false;
+   bool user_defined_fs_output_assigned = false;
+   ir_variable *user_defined_fs_output = NULL;
+
+   /* It would be nice to have proper location information. */
+   YYLTYPE loc;
+   memset(&loc, 0, sizeof(loc));
+
+   foreach_list(node, instructions) {
+      ir_variable *var = ((ir_instruction *)node)->as_variable();
+
+      if (!var)
+	 continue;
+
+      if (strcmp(var->name, "gl_FragColor") == 0)
+	 gl_FragColor_assigned = var->assigned;
+      else if (strcmp(var->name, "gl_FragData") == 0)
+	 gl_FragData_assigned = var->assigned;
+      else if (strncmp(var->name, "gl_", 3) != 0) {
+	 if (state->target == fragment_shader &&
+	     (var->mode == ir_var_out || var->mode == ir_var_inout)) {
+	    user_defined_fs_output_assigned = true;
+	    user_defined_fs_output = var;
+	 }
+      }
+   }
+
+   /* From the GLSL 1.30 spec:
+    *
+    *     "If a shader statically assigns a value to gl_FragColor, it
+    *      may not assign a value to any element of gl_FragData. If a
+    *      shader statically writes a value to any element of
+    *      gl_FragData, it may not assign a value to
+    *      gl_FragColor. That is, a shader may assign values to either
+    *      gl_FragColor or gl_FragData, but not both. Multiple shaders
+    *      linked together must also consistently write just one of
+    *      these variables.  Similarly, if user declared output
+    *      variables are in use (statically assigned to), then the
+    *      built-in variables gl_FragColor and gl_FragData may not be
+    *      assigned to. These incorrect usages all generate compile
+    *      time errors."
+    */
+   if (gl_FragColor_assigned && gl_FragData_assigned) {
+      _mesa_glsl_error(&loc, state, "fragment shader writes to both "
+		       "`gl_FragColor' and `gl_FragData'\n");
+   } else if (gl_FragColor_assigned && user_defined_fs_output_assigned) {
+      _mesa_glsl_error(&loc, state, "fragment shader writes to both "
+		       "`gl_FragColor' and `%s'\n",
+		       user_defined_fs_output->name);
+   } else if (gl_FragData_assigned && user_defined_fs_output_assigned) {
+      _mesa_glsl_error(&loc, state, "fragment shader writes to both "
+		       "`gl_FragData' and `%s'\n",
+		       user_defined_fs_output->name);
+   }
+}