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

[Richard Biener]

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).

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
>