Re: [PATCH] Don't mark IFUNC resolver as only called directly

[Jan Hubicka <hubicka at ucw dot cz>]

> On Thu, Apr 12, 2018 at 1:29 PM, H.J. Lu <hongjiu.lu@intel.com> wrote:
> > Since IFUNC resolver is called indirectly, don't mark IFUNC resolver as
> > only called directly.
> >
> > OK for trunk?
> >
> >
> > H.J.
> > ---
> > gcc/
> >
> >         PR target/85345
> >         * cgraph.h: Include stringpool.h" and "attribs.h".
> >         (cgraph_node::only_called_directly_or_aliased_p): Return false
> >         for IFUNC resolver.
> >
> > gcc/testsuite/
> >
> >         PR target/85345
> >         * gcc.target/i386/pr85345.c: New test.
> > ---
> >  gcc/cgraph.h                            |  5 +++-
> >  gcc/testsuite/gcc.target/i386/pr85345.c | 44 +++++++++++++++++++++++++++++++++
> >  2 files changed, 48 insertions(+), 1 deletion(-)
> >  create mode 100644 gcc/testsuite/gcc.target/i386/pr85345.c
> >
> > diff --git a/gcc/cgraph.h b/gcc/cgraph.h
> > index d1ef8408497..9e195824fcc 100644
> > --- a/gcc/cgraph.h
> > +++ b/gcc/cgraph.h
> > @@ -24,6 +24,8 @@ along with GCC; see the file COPYING3.  If not see
> >  #include "profile-count.h"
> >  #include "ipa-ref.h"
> >  #include "plugin-api.h"
> > +#include "stringpool.h"
> > +#include "attribs.h"
> >
> >  class ipa_opt_pass_d;
> >  typedef ipa_opt_pass_d *ipa_opt_pass;
> > @@ -2894,7 +2896,8 @@ cgraph_node::only_called_directly_or_aliased_p (void)
> >           && !DECL_STATIC_CONSTRUCTOR (decl)
> >           && !DECL_STATIC_DESTRUCTOR (decl)
> >           && !used_from_object_file_p ()
> > -         && !externally_visible);
> > +         && !externally_visible
> > +         && !lookup_attribute ("ifunc", DECL_ATTRIBUTES (decl)));
> 
> How's it handled for our own generated resolver functions?  That is,
> isn't there sth cheaper than doing a lookup_attribute here?  I see
> that make_dispatcher_decl nor ix86_get_function_versions_dispatcher
> adds the 'ifunc' attribute (though they are TREE_PUBLIC there).

Is there any drawback of setting force_output flag?
Honza
> 
> Richard.
> 
> >  }
> >
> >  /* Return true when function can be removed from callgraph
> > diff --git a/gcc/testsuite/gcc.target/i386/pr85345.c b/gcc/testsuite/gcc.target/i386/pr85345.c
> > new file mode 100644
> > index 00000000000..63f771294ad
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/i386/pr85345.c
> > @@ -0,0 +1,44 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-O2 -fcf-protection -mcet" } */
> > +/* { dg-final { scan-assembler-times {\mendbr} 4 } } */
> > +
> > +int resolver_fn = 0;
> > +int resolved_fn = 0;
> > +
> > +static inline void
> > +do_it_right_at_runtime_A (void)
> > +{
> > +  resolved_fn++;
> > +}
> > +
> > +static inline void
> > +do_it_right_at_runtime_B (void)
> > +{
> > +  resolved_fn++;
> > +}
> > +
> > +static inline void do_it_right_at_runtime (void);
> > +
> > +void do_it_right_at_runtime (void)
> > +  __attribute__ ((ifunc ("resolve_do_it_right_at_runtime")));
> > +
> > +extern int r;
> > +static void (*resolve_do_it_right_at_runtime (void)) (void)
> > +{
> > +  resolver_fn++;
> > +
> > +  typeof(do_it_right_at_runtime) *func;
> > +  if (r & 1)
> > +    func = do_it_right_at_runtime_A;
> > +  else
> > +    func = do_it_right_at_runtime_B;
> > +
> > +  return (void *) func;
> > +}
> > +
> > +int
> > +main ()
> > +{
> > +  do_it_right_at_runtime ();
> > +  return 0;
> > +}
> > --
> > 2.14.3
> >