Re: check_qualified_type

[Martin Uecker <uecker@tugraz.at>]

Am Montag, dem 17.06.2024 um 15:40 +0200 schrieb Jakub Jelinek:
> On Mon, Jun 17, 2024 at 03:33:05PM +0200, Martin Uecker wrote:
> > > I've done that and that was because build_qualified_type uses that
> > > predicate, where qualified types created by build_qualified_type have
> > > as TYPE_CANONICAL the qualified type of the main variant of the canonical
> > > type, while in all other cases TYPE_CANONICAL is just the main variant of
> > > the type.
> > > Guess we could also just do
> > >           if (TYPE_QUALS (x) == TYPE_QUALS (t))
> > >             TYPE_CANONICAL (x) = TYPE_CANONICAL (t);
> > >           else if (TYPE_CANONICAL (t) != t
> > > 		   || TYPE_QUALS (x) != TYPE_QUALS (TYPE_CANONICAL (t)))
> > >             TYPE_CANONICAL (x)
> > >               = build_qualified_type (TYPE_CANONICAL (t), TYPE_QUALS (x));
> > >           else
> > >             TYPE_CANONICAL (x) = x;
> > > 
> > 
> > Ok, that works. I think the final "else" is then then impossible to reach
> > and can be eliminated as well, because if TYPE_CANONICAL (t) == t then 
> > TYPE_QUALS (x) == TYPE_QUALS (TYPE_CANONICAL (t)) is identical to
> > TYPE_QUALS (x) == TYPE_QUALS (t) which is the first case.
> 
> If c_update_type_canonical is only ever called for the main variants of the
> type and they always have !TYPE_QUALS (t), then yes.
> But if we rely on that, perhaps we should gcc_checking_assert that.
> So
>   gcc_checking_assert (t == TYPE_MAIN_VARIANT (t) && !TYPE_QUALS (t));
> or something similar at the start of the function.

It calls itself recursively on pointers to the type.  But to
me the third branch looks dead in any case, because the first
two cover all possibilities.

Martin

> Then we could also change the
>   for (tree x = TYPE_MAIN_VARIANT (t); x; x = TYPE_NEXT_VARIANT (x))
> to
>   for (tree x = t; x; x = TYPE_NEXT_VARIANT (x))
> and
> 	  if (TYPE_QUALS (x) == TYPE_QUALS (t))
> ...
> to
> 	  if (!TYPE_QUALS (x))
> 	    TYPE_CANONICAL (x) = TYPE_CANONICAL (t);
> 	  else
> 	    build_qualified_type (TYPE_CANONICAL (t), TYPE_QUALS (x));
> 





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