On Mon, 8 Jun 2015, Jan Hubicka wrote:
> > On Mon, 8 Jun 2015, Richard Biener wrote:
> >
> > > On Mon, 8 Jun 2015, Joseph Myers wrote:
> > >
> > > > On Mon, 8 Jun 2015, Richard Biener wrote:
> > > >
> > > > > I'm not sure the C standard mandates compatibility between
> > > > >
> > > > > struct { int i; } and struct { unsigned i; } for purposes of TBAA.
> > > > > Joseph?
> > > >
> > > > I don't think they are necessarily compatible for TBAA.
> > >
> > > Ok, but as int and unsigned are reading either structs element
> > > via a pointer to int or a pointer to unsigned must be supported?
> >
> > Yes. The questionable case would be taking an object of one of those
> > structure types, casting a pointer to it to point to the other structure
> > type and then dereferencing.
>
> Are "struct { int i; }" and "struct { unsigned i; }" compatible when one is
> defined
> in one unit and other in another?
> In any cae, I suppose if int and unsigned int pointers can be used
> interchangeably,
> we want to ignore TYPE_UNSGINED for purposes of canonical type calculation
> for LTO.
> So is the second variant of patch OK with a comment update that this is also
> required
> by C?
I think we should instead work towards eliminating the get_alias_set
langhook first. The LTO langhook variant contains the same handling, btw,
so just inline that into get_alias_set and see what remains?
Richard.
> Honza
> >
> > --
> > Joseph S. Myers
> > jos...@codesourcery.com
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham
Norton, HRB 21284 (AG Nuernberg)
