> > This simple (untested) patch doesn't avoid creating the unnecessary
> > as-base types, but it should avoid using them in a way that causes
> > them to be streamed, and should let them be discarded by GC.
> > Thoughts?
>
> Looks better than Honzas patch fixing a single place.
Indeed, I think in this case it is also possible to drop
else if (tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (as_base)))
in call.c since they will now be always different.
>
> I've spent some thoughts on this and I wonder whether we can
> re-implement classtype-as-base with fake inheritance (which would
> also solve the TBAA alias set issue in a natural way). That is,
> we'd lay out structs as-base and make instances of it use a
>
> class as-instance { as-base b; X pad1; Y pad2; };
>
> with either explicit padding fields or with implicit ones
> (I didn't check how we trick stor-layout to not pad the as-base
> type to its natural alignment...).
>
> I realize that this impacts all code building component-refs ontop
> of as-instance typed objects so this might rule out this approach
> completely - but maybe that's reasonably well abstracted into common
> code so only few places need adjustments.
>
> Regular derived classes would simply derive from the as-base type
> (as they do now I guess).
I was trying to construct testcase using this (i.e. have different
access paths one using CLASSTYPE_AS_BASE and other the actual type
and failed to do so. Having one would be nice.
Honza
>
> Richard.
