On Sun, 9 Sep 2018, Jan Hubicka wrote:
> > On September 8, 2018 10:49:02 AM GMT+01:00, Jan Hubicka <[email protected]>
> > wrote:
> > >Hi
> > >while working on path to replace type variant by first compatible one I
> > >run
> > >into issue that the first vairant was not seen by free_lang_data. I
> > >think this
> > >is a bug becuase nothing prevents middle-end from looking up a variant
> > >there
> > >and using it when it needs to do so.
> > >
> > >I tried to walk the variant lists and free lang data on them but that
> > >crahses
> > >because not all types in variant list passes verify_type (C++ puts
> > >there
> > >incomplete type variants whose canonical type is complete and thus they
> > >are
> > >considered bogus). So pruning those lists seems to be better variant.
> > >
> > >Bootstrapped/regtested x86_64-linux, OK?
> >
> > But if they are still reachable by GC they are now bogously unlinked. We
> > already do not stream unused variants, so what does this achieve? Maybe we
> > should make the variant list GCable somehow?
>
> Main goal is to prevent middle end to walk the TYPE_NEXT_VARIANT list (for
> example by get_qualified_variant)
> and pick up a variant that was not seen by free_lang_data and put it into the
> IL.
> I know that if we end up referring to some type variant in a way not seen
> by free lang data then the type won't be reachable from the list, but why that
> would be a problem?
Duplicate types? Also the type verifier could assert that a type variant
is in the variant list of its main variant - it looks bogus to break that
invariant at least.
Maybe the real fix is to prune the list in lang specific free-lang-data
so free_lang_data _can_ walk the variant list? That is, can we track
down those C++ issues and fix them in some way?
Richard.
> Honza
> >
> > >Honza
> > >
> > > * tree.c (free_lang_data_in_cgraph): Prune TYPE_NEXT_VARIANT lists.
> > >Index: tree.c
> > >===================================================================
> > >--- tree.c (revision 263989)
> > >+++ tree.c (working copy)
> > >@@ -5845,7 +5845,12 @@ free_lang_data_in_cgraph (void)
> > >
> > > /* Traverse every type found freeing its language data. */
> > > FOR_EACH_VEC_ELT (fld.types, i, t)
> > >- free_lang_data_in_type (t);
> > >+ {
> > >+ free_lang_data_in_type (t);
> > >+ while (TYPE_NEXT_VARIANT (t)
> > >+ && !fld.pset.contains (TYPE_NEXT_VARIANT (t)))
> > >+ TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (TYPE_NEXT_VARIANT (t));
> > >+ }
> > > if (flag_checking)
> > > {
> > > FOR_EACH_VEC_ELT (fld.types, i, t)
> >
>
>
--
Richard Biener <[email protected]>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
