Handle data dependence relations with different bases

[Bernhard Reutner-Fischer]

On 4 May 2017 14:12:04 CEST, Richard Biener <richard.guenther@gmail.com> wrote:

>nonoverlapping_component_refs_of_decl_p
>should simply skip ARRAY_REFs - but I also see there:
>
>    /* ??? We cannot simply use the type of operand #0 of the refs here
>      as the Fortran compiler smuggles type punning into COMPONENT_REFs
>      for common blocks instead of using unions like everyone else.  */
>      tree type1 = DECL_CONTEXT (field1);
>      tree type2 = DECL_CONTEXT (field2);
>
>so you probably can't simply use TREE_TYPE (outer_ref) for type
>compatibility.
>You also may not use types_compatible_p here as for LTO that is _way_
>too
>lax for aggregates.  The above uses
>
>    /* We cannot disambiguate fields in a union or qualified union.  */
>      if (type1 != type2 || TREE_CODE (type1) != RECORD_TYPE)
>         return false;
>
>so you should also bail out on unions here, rather than the check you
>do later.
>
>You seem to rely on getting an access_fn entry for each
>handled_component_p.
>It looks like this is the case -- we even seem to stop at unions (with
>the same
>fortran "issue").  I'm not sure that's the best thing to do but you
>rely on that.

Is there a PR for the (IIUC) common as union?
Maybe around
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41227
COMMON block, BIND(C) and LTO interoperability issues

Thanks