https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92152
--- Comment #10 from Jan Hubicka <hubicka at gcc dot gnu.org> --- Concerning: > Honza, the type_has_components_p check in > > if (compare_type_sizes (TREE_TYPE (ref2), type1) >= 0 > && (!end_struct_ref1 > || compare_type_sizes (TREE_TYPE (ref2), > TREE_TYPE (end_struct_ref1)) >= 0) > && type_has_components_p (TREE_TYPE (ref2)) > && (base1_alias_set == ref2_alias_set > || alias_set_subset_of (base1_alias_set, ref2_alias_set))) > > is a compile-time optimization? Because the alias subset check of course > would trigger here since ref2_alias_set is not the alias-set of > TREE_TYPE (ref2) but of one of its bases. It was not meant as optimization, but to avoid false positives when the base and ref alias sets intersects but the path can not continue this way. I see that here we continue path ending with "long" by path starting by "union". I guess it is only way to continue from "long", so what about simply testing "&& TREE_CODE (TREE_TYPE (base1)) != UNION_TYPE" (or more carefully we can check if first non-union type after base1 is same as TREE_TYPE (ref2) I do not think we need to cut the access path after unions like in your fix. If that union is wrapped inside struct, one can not continue from type with no components. Honza
