Factor out qualifier checking code for later reuse.

ir.cpp

@@ -338,6 +338,32 @@ ir_function_signature::ir_function_signature(const glsl_type *return_type)
 }
 
 
+const char *
+ir_function_signature::qualifiers_match(exec_list *params)
+{
+   exec_list_iterator iter_a = parameters.iterator();
+   exec_list_iterator iter_b = params->iterator();
+
+   /* check that the qualifiers match. */
+   while (iter_a.has_next()) {
+      ir_variable *a = (ir_variable *)iter_a.get();
+      ir_variable *b = (ir_variable *)iter_b.get();
+
+      if (a->read_only != b->read_only ||
+	  a->interpolation != b->interpolation ||
+	  a->centroid != b->centroid) {
+
+	 /* parameter a's qualifiers don't match */
+	 return a->name;
+      }
+
+      iter_a.next();
+      iter_b.next();
+   }
+   return NULL;
+}
+
+
 ir_function::ir_function(const char *name)
    : name(name)
 {