> On Wed, 20 Apr 2022, Jakub Jelinek wrote:
>
> > Hi!
> >
> > cgraph_node has a semantic_interposition flag which should mirror
> > opt_for_fn (decl, flag_semantic_interposition). But it actually is
> > initialized not from that, but from flag_semantic_interposition in the
> > explicit symtab_node (symtab_type t)
> > : type (t), resolution (LDPR_UNKNOWN), definition (false), alias
> > (false),
> > ...
> > semantic_interposition (flag_semantic_interposition),
> > ...
> > x_comdat_group (NULL_TREE), x_section (NULL)
> > {}
> > ctor. I think that might be fine for varpool nodes, but since
> > flag_semantic_interposition is now implied from -Ofast it isn't correct
> > for cgraph nodes, unless we guarantee that cgraph node for a particular
> > function decl is always created while that function is
> > current_function_decl. That is often the case, but not always as the
> > following function shows.
Normally cgraph_nodes with function bodies are first created, later
finalized and then analyzed. We copy over the semantic_interposition
flag from opt_for_fn to cgraph_node in finalize_function.
The ctor there is indeed only for varpool nodes since these do not have
their opt_for_var.
> > --- gcc/cgraph.cc.jj 2022-02-04 14:36:54.069618372 +0100
> > +++ gcc/cgraph.cc 2022-04-19 13:38:06.223782974 +0200
> > @@ -507,6 +507,7 @@ cgraph_node::create (tree decl)
> > gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);
> >
> > node->decl = decl;
> > + node->semantic_interposition = opt_for_fn (decl,
> > flag_semantic_interposition);
So this change should be unnecessary unless there are nodes that are
missing finalization stage. It also is not good enough since frontends
may change opt_for_fn between node creation and finalization of
compilation unit (so even after cgraph_finalize unforutnately, we had
another bug about that).
The PR was about implicit C++ alias. So the problem is that aliases
bypass finalization becuase they are produced by
cgraph_node::create_alias that sets definition flag to true.
I guess it would be most consistent to give up on having the flag up to
date during cgraph construction (i.e. from finalization time down) and
compute it during the cgraph_finalize_complation_unit. I will look into
that.
> >
> > if ((flag_openacc || flag_openmp)
> > && lookup_attribute ("omp declare target", DECL_ATTRIBUTES (decl)))
> > --- gcc/cgraphclones.cc.jj 2022-01-18 11:58:58.948991114 +0100
> > +++ gcc/cgraphclones.cc 2022-04-19 13:38:43.594262397 +0200
> > @@ -394,6 +394,7 @@ cgraph_node::create_clone (tree new_decl
> > new_node->versionable = versionable;
> > new_node->can_change_signature = can_change_signature;
> > new_node->redefined_extern_inline = redefined_extern_inline;
> > + new_node->semantic_interposition = semantic_interposition;
This indeed makes sense to me.
Honza
> > new_node->tm_may_enter_irr = tm_may_enter_irr;
> > new_node->externally_visible = false;
> > new_node->no_reorder = no_reorder;
> > --- gcc/testsuite/g++.dg/opt/pr105306.C.jj 2022-04-19 13:42:33.908054114
> > +0200
> > +++ gcc/testsuite/g++.dg/opt/pr105306.C 2022-04-19 13:42:08.859403045
> > +0200
> > @@ -0,0 +1,13 @@
> > +// PR ipa/105306
> > +// { dg-do compile }
> > +// { dg-options "-Ofast" }
> > +
> > +#pragma GCC optimize 0
> > +template <typename T> void foo (T);
> > +struct B { ~B () {} };
> > +struct C { B f; };
> > +template <typename> struct E {
> > + void bar () { foo (g); }
> > + C g;
> > +};
> > +template class E<char>;
> >
> > Jakub
> >
> >
>
> --
> Richard Biener <[email protected]>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> Germany; GF: Ivo Totev; HRB 36809 (AG Nuernberg)
