Improve TBAA for types in anonymous namespaces

[Ian Lance Taylor]

Jan Hubicka <hubicka@ucw.cz> writes:

>> 
>> OK.  I wonder if we can/should carve off some bits to note
>> type_with_linkage_p and type_in_anonymous_namespace_p in the tree
>> itself?  At least in type_common there's plenty of bits left.
>> Not sure how expensive / reliable (non-C++?) those tests otherwise are.
>
> It also makes me wonder if other languages (D, Ada, go, Fortran...) have
> concept of anonymous namespace types - that is types that are never
> interoperable with types from another translation unit.  That would
> justify the extra flag pretty well.
>
> Similarly for types with name mangling defined.  Both these bits can be
> made indpendent of C++.

Go has the concept, but it implements it by mangling the names with the
package-path, which is required to be unique within an application (the
package-path is normally the path used to find an import, so it is
inherently unique within a file system).

Ian