On Wed, 2 Sep 2015, Jan Hubicka wrote:
> >
> > I was naiively using ->get_constructor in IPA PTA without proper
> > checking on wheter that succeeds. Now I tried to use ctor_for_folding
> > but that isn't good as we want to analyze non-const globals in IPA
> > PTA and we need to analyze their initialiers as well.
> >
> > Thus I'm trying below with ctor_for_analysis, but I really "just"
> > need the initializer or a "not available" for conservative handling.
> >
> > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> >
> > Honza - I suppose you should doble-check this and suggest sth
> > different (or implement sth more generic in the IPA infrastructure).
>
> Yep, you are correct that we don't currently have way to look into ctor
> without actually loading. But do you need something more than just walking
> references that you already have in ipa-ref lists?
Hmm, no, ipa-ref list should be enough (unless we start field-sensitive
analysis or need NULL inits for correctness). Still have to figure out
how to walk the list and how the reference would look like (what
is ref->use? IPA_REF_ADDR? can those be speculative?)
Richard.
> >
> > Thanks,
> > Richard.
> >
> > 2015-09-02 Richard Biener <rguent...@suse.de>
> >
> > PR ipa/66705
> > * tree-ssa-structalias.c (ctor_for_analysis): New function.
> > (create_variable_info_for_1): Use ctor_for_analysis instead
> > of get_constructor.
> > (create_variable_info_for): Likewise.
>
> Otherwise I would go for making ctor_for_analysis a method of varpool_node
> and...
> >
> > * g++.dg/lto/pr66705_0.C: New testcase.
> >
> > Index: gcc/tree-ssa-structalias.c
> > ===================================================================
> > --- gcc/tree-ssa-structalias.c (revision 227207)
> > +++ gcc/tree-ssa-structalias.c (working copy)
> > @@ -5637,6 +5637,26 @@ check_for_overlaps (vec<fieldoff_s> fiel
> > return false;
> > }
> >
> > +/* We can't use ctor_for_folding as that only returns constant
> > constructors. */
> > +
> > +static tree
> > +ctor_for_analysis (tree decl)
> > +{
> > + varpool_node *node = varpool_node::get (decl);
> > + if (!node)
> > + return error_mark_node;
> > + node = node->ultimate_alias_target ();
> > + if (DECL_INITIAL (node->decl) != error_mark_node
> > + || !in_lto_p)
> > + return (DECL_INITIAL (node->decl)
> > + ? DECL_INITIAL (node->decl) : error_mark_node);
>
> I think returning NULL here is just fine.
> error_mark_node means constructor is not really available. NULL is
> the usual way to say that the variable is not initialized.
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
