https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110237
--- Comment #21 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
(In reply to rguent...@suse.de from comment #19)
> But the size argument doesn't have anything to do with TBAA (and
> may_alias is about TBAA). I don't think we have any way to circumvent
> C object access rules. That is, for example, with -fno-strict-aliasing
> the following isn't going to work.
>
> int a;
> int b;
>
> int main()
> {
> a = 1;
> b = 2;
> if (&a + 1 == &b) // equality compare of unrelated pointers OK
> {
> long x = *(long *)&a; // access outside of 'a' not OK
> if (x != 0x0000000100000002)
> abort ();
> }
> }
>
> there's no command-line flag or attribute to form a pointer
> to an object composing 'a' and 'b' besides changing how the
> storage is declared.
But store-merging and SLP can introduce a wide long-sized access where on
source level you had two adjacent loads or even memcpy's, so we really seem to
have a problem here and might need to be able to annotate types or individual
accesses as "may-alias-with-oob-ok" in the IR: PR 110431.
