Sorry, but I found some commenting issues and reworked them a bit. Attached is the updated patch.
Kai
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 {