Index: gcc/gcc/c-typeck.c
===================================================================
--- gcc.orig/gcc/c-typeck.c	2011-03-24 08:23:42.441173500 +0100
+++ gcc/gcc/c-typeck.c	2011-03-24 09:24:53.445892300 +0100
@@ -1079,7 +1079,7 @@ comptypes_internal (const_tree type1, co
     return 1;
 
   /* 1 if no need for warning yet, 2 if warning cause has been seen.  */
-  if (!(attrval = targetm.comp_type_attributes (t1, t2)))
+  if (!(attrval = comp_type_attributes (t1, t2)))
      return 0;
 
   /* 1 if no need for warning yet, 2 if warning cause has been seen.  */
Index: gcc/gcc/cp/decl.c
===================================================================
--- gcc.orig/gcc/cp/decl.c	2011-03-24 08:23:42.443173500 +0100
+++ gcc/gcc/cp/decl.c	2011-03-24 09:24:53.573408500 +0100
@@ -1012,8 +1012,8 @@ decls_match (tree newdecl, tree olddecl)
 	    types_match =
 	      compparms (p1, p2)
 	      && (TYPE_ATTRIBUTES (TREE_TYPE (newdecl)) == NULL_TREE
-	          || targetm.comp_type_attributes (TREE_TYPE (newdecl),
-						   TREE_TYPE (olddecl)) != 0);
+	          || comp_type_attributes (TREE_TYPE (newdecl),
+					   TREE_TYPE (olddecl)) != 0);
 	}
       else
 	types_match = 0;
Index: gcc/gcc/cp/search.c
===================================================================
--- gcc.orig/gcc/cp/search.c	2011-03-24 08:23:42.444173500 +0100
+++ gcc/gcc/cp/search.c	2011-03-24 09:24:53.645417600 +0100
@@ -1897,7 +1897,7 @@ check_final_overrider (tree overrider, t
     }
 
   /* Check for conflicting type attributes.  */
-  if (!targetm.comp_type_attributes (over_type, base_type))
+  if (!comp_type_attributes (over_type, base_type))
     {
       error ("conflicting type attributes specified for %q+#D", overrider);
       error ("  overriding %q+#D", basefn);
Index: gcc/gcc/cp/typeck.c
===================================================================
--- gcc.orig/gcc/cp/typeck.c	2011-03-24 08:23:42.495173500 +0100
+++ gcc/gcc/cp/typeck.c	2011-03-24 09:24:53.697424200 +0100
@@ -1338,7 +1338,7 @@ structural_comptypes (tree t1, tree t2,
   /* If we get here, we know that from a target independent POV the
      types are the same.  Make sure the target attributes are also
      the same.  */
-  return targetm.comp_type_attributes (t1, t2);
+  return comp_type_attributes (t1, t2);
 }
 
 /* Return true if T1 and T2 are related as allowed by STRICT.  STRICT
Index: gcc/gcc/gimple.c
===================================================================
--- gcc.orig/gcc/gimple.c	2011-03-24 08:23:42.496173500 +0100
+++ gcc/gcc/gimple.c	2011-03-24 09:24:53.793936500 +0100
@@ -3615,7 +3615,7 @@ gimple_types_compatible_p_1 (tree t1, tr
 			 state, sccstack, sccstate, sccstate_obstack))
 	goto different_types;
 
-      if (!targetm.comp_type_attributes (t1, t2))
+      if (!comp_type_attributes (t1, t2))
 	goto different_types;
 
       if (TYPE_ARG_TYPES (t1) == TYPE_ARG_TYPES (t2))
Index: gcc/gcc/tree-ssa.c
===================================================================
--- gcc.orig/gcc/tree-ssa.c	2011-03-24 08:23:42.498173500 +0100
+++ gcc/gcc/tree-ssa.c	2011-03-24 09:24:53.831441200 +0100
@@ -1438,7 +1438,7 @@ useless_type_conversion_p (tree outer_ty
 
       /* Defer to the target if necessary.  */
       if (TYPE_ATTRIBUTES (inner_type) || TYPE_ATTRIBUTES (outer_type))
-	return targetm.comp_type_attributes (outer_type, inner_type) != 0;
+	return comp_type_attributes (outer_type, inner_type) != 0;
 
       return true;
     }
Index: gcc/gcc/tree.c
===================================================================
--- gcc.orig/gcc/tree.c	2011-03-24 08:23:42.499173500 +0100
+++ gcc/gcc/tree.c	2011-03-24 11:54:43.225949400 +0100
@@ -4283,7 +4283,7 @@ build_type_attribute_qual_variant (tree
 	 its canonical type, we will need to use structural equality
 	 checks for this type. */
       if (TYPE_STRUCTURAL_EQUALITY_P (ttype)
-          || !targetm.comp_type_attributes (ntype, ttype))
+          || !comp_type_attributes (ntype, ttype))
 	SET_TYPE_STRUCTURAL_EQUALITY (ntype);
       else if (TYPE_CANONICAL (ntype) == ntype)
 	TYPE_CANONICAL (ntype) = TYPE_CANONICAL (ttype);
@@ -4296,6 +4296,67 @@ build_type_attribute_qual_variant (tree
   return ttype;
 }
 
+/* Return 0 if the attributes for two types are incompatible, 1 if they
+   are compatible, and 2 if they are nearly compatible (which causes a
+   warning to be generated).  */
+int
+comp_type_attributes (const_tree type1, const_tree type2)
+{
+  const_tree a1 = TYPE_ATTRIBUTES (type1);
+  const_tree a2 = TYPE_ATTRIBUTES (type2);
+  const_tree a;
+
+  if (a1 == a2)
+    return 1;
+  for (a = a1; a != NULL_TREE; a = TREE_CHAIN (a))
+    {
+      const struct attribute_spec *as;
+      const_tree attr;
+
+      as = lookup_attribute_spec (TREE_PURPOSE (a));
+      if (!as || as->affects_type_identity == false)
+        continue;
+
+      attr = lookup_attribute (as->name, CONST_CAST_TREE (a2));
+      if (!attr)
+	break;
+
+      if (TREE_VALUE (a) != NULL_TREE
+	  && TREE_CODE (TREE_VALUE (a)) == TREE_LIST
+	  && TREE_VALUE (attr) != NULL
+	  && TREE_CODE (TREE_VALUE (attr)) == TREE_LIST)
+	{
+	  if (simple_cst_list_equal (TREE_VALUE (a),
+				     TREE_VALUE (attr)) == 1)
+	    break;
+	}
+      else if (simple_cst_equal (TREE_VALUE (a), TREE_VALUE (attr)) == 1)
+	break;
+    }
+  if (!a)
+    {
+      for (a = a2; a != NULL_TREE; a = TREE_CHAIN (a))
+	{
+	  const struct attribute_spec *as;
+
+	  as = lookup_attribute_spec (TREE_PURPOSE (a));
+	  if (!as || as->affects_type_identity == false)
+	    continue;
+
+	  if (!lookup_attribute (as->name, CONST_CAST_TREE (a1)))
+	    break;
+	  /* We don't need to compare trees again, as we did this
+	     already in first loop.  */
+	}
+      /* All types - affecting identity - are equal, so
+         there is no need to call target hook for comparison.  */
+      if (!a)
+        return 1;
+    }
+  /* As some type combinations - like default calling-convention - might
+     be compatible, we have to call the target hook to get the final result.  */
+  return targetm.comp_type_attributes (type1, type2);
+}
 
 /* Return a type like TTYPE except that its TYPE_ATTRIBUTE
    is ATTRIBUTE.
Index: gcc/gcc/tree.h
===================================================================
--- gcc.orig/gcc/tree.h	2011-03-24 08:23:42.619173500 +0100
+++ gcc/gcc/tree.h	2011-03-24 09:24:54.041968000 +0100
@@ -4286,6 +4286,11 @@ extern tree build_type_attribute_variant
 extern tree build_decl_attribute_variant (tree, tree);
 extern tree build_type_attribute_qual_variant (tree, tree, int);
 
+/* Return 0 if the attributes for two types are incompatible, 1 if they
+   are compatible, and 2 if they are nearly compatible (which causes a
+   warning to be generated).  */
+extern int comp_type_attributes (const_tree, const_tree);
+
 /* Structure describing an attribute and a function to handle it.  */
 struct attribute_spec
 {
