[PATCH] Do not allow to inline ifunc resolvers (PR ipa/81128).

[Jan Hubicka]

> Hello.
> 
> Currently ifunc is interpreted as normal alias by IPA optimizations. That's problematic
> as should not consider ifunc alias as candidate for inlining, or redirection.
> 
> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
> And survives MVC tests on x86_64-linux-gnu.
> 
> Ready to be installed?

Wasn't this supposed to go with arranging availability to be AVAIL_INTERPOSABLE
(as the target will be interposed by linker to the corect target)

Honza
> Martin
> 
> gcc/ChangeLog:
> 
> 2017-06-22  Martin Liska  <mliska@suse.cz>
> 
> 	* ipa-inline.c (can_inline_edge_p): Return false for ifunc fns.
> 	* ipa-visibility.c (can_replace_by_local_alias): Likewise.
> 
> gcc/c-family/ChangeLog:
> 
> 2017-06-22  Martin Liska  <mliska@suse.cz>
> 
> 	* c-attribs.c (handle_alias_ifunc_attribute): Append ifunc alias
> 	to a function declaration.
> 
> gcc/testsuite/ChangeLog:
> 
> 2017-06-22  Martin Liska  <mliska@suse.cz>
> 
> 	* gcc.target/i386/pr81128.c: New test.
> ---
>  gcc/c-family/c-attribs.c                | 11 ++++--
>  gcc/ipa-inline.c                        |  2 +
>  gcc/ipa-visibility.c                    |  3 +-
>  gcc/testsuite/gcc.target/i386/pr81128.c | 65 +++++++++++++++++++++++++++++++++
>  4 files changed, 77 insertions(+), 4 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/pr81128.c
> 
> 

> diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
> index 2b6845f2cbd..626ffa1cde7 100644
> --- a/gcc/c-family/c-attribs.c
> +++ b/gcc/c-family/c-attribs.c
> @@ -1846,9 +1846,14 @@ handle_alias_ifunc_attribute (bool is_alias, tree *node, tree name, tree args,
>  	TREE_STATIC (decl) = 1;
>  
>        if (!is_alias)
> -	/* ifuncs are also aliases, so set that attribute too.  */
> -	DECL_ATTRIBUTES (decl)
> -	  = tree_cons (get_identifier ("alias"), args, DECL_ATTRIBUTES (decl));
> +	{
> +	  /* ifuncs are also aliases, so set that attribute too.  */
> +	  DECL_ATTRIBUTES (decl)
> +	    = tree_cons (get_identifier ("alias"), args,
> +			 DECL_ATTRIBUTES (decl));
> +	  DECL_ATTRIBUTES (decl) = tree_cons (get_identifier ("ifunc"),
> +					      NULL, DECL_ATTRIBUTES (decl));
> +	}
>      }
>    else
>      {
> diff --git a/gcc/ipa-inline.c b/gcc/ipa-inline.c
> index fb20d3723cc..588fa9c41e4 100644
> --- a/gcc/ipa-inline.c
> +++ b/gcc/ipa-inline.c
> @@ -370,6 +370,8 @@ can_inline_edge_p (struct cgraph_edge *e, bool report,
>        e->inline_failed = CIF_ATTRIBUTE_MISMATCH;
>        inlinable = false;
>      }
> +  else if (lookup_attribute ("ifunc", DECL_ATTRIBUTES (e->callee->decl)))
> +      inlinable = false;
>    /* Check if caller growth allows the inlining.  */
>    else if (!DECL_DISREGARD_INLINE_LIMITS (callee->decl)
>  	   && !disregard_limits
> diff --git a/gcc/ipa-visibility.c b/gcc/ipa-visibility.c
> index d5a3ae56c46..79d05b41085 100644
> --- a/gcc/ipa-visibility.c
> +++ b/gcc/ipa-visibility.c
> @@ -345,7 +345,8 @@ can_replace_by_local_alias (symtab_node *node)
>    
>    return (node->get_availability () > AVAIL_INTERPOSABLE
>  	  && !decl_binds_to_current_def_p (node->decl)
> -	  && !node->can_be_discarded_p ());
> +	  && !node->can_be_discarded_p ()
> +	  && !lookup_attribute ("ifunc", DECL_ATTRIBUTES (node->decl)));
>  }
>  
>  /* Return true if we can replace reference to NODE by local alias
> diff --git a/gcc/testsuite/gcc.target/i386/pr81128.c b/gcc/testsuite/gcc.target/i386/pr81128.c
> new file mode 100644
> index 00000000000..90a567ad690
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr81128.c
> @@ -0,0 +1,65 @@
> +/* PR ipa/81128 */
> +/* { dg-do run } */
> +/* { dg-options "-O3" } */
> +/* { dg-require-ifunc "" } */
> +
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <time.h>
> +
> +int resolver_fn = 0;
> +int resolved_fn = 0;
> +
> +static inline void
> +do_it_right_at_runtime_A ()
> +{
> +  resolved_fn++;
> +}
> +
> +static inline void
> +do_it_right_at_runtime_B ()
> +{
> +  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")));
> +
> +static void (*resolve_do_it_right_at_runtime (void)) (void)
> +{
> +  srand (time (NULL));
> +  int r = rand ();
> +  resolver_fn++;
> +
> +  /* Use intermediate variable to get a warning for non-matching
> +   * prototype. */
> +  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 (void)
> +{
> +  const unsigned int ITERS = 10;
> +
> +  for (int i = ITERS; i > 0; i--)
> +    {
> +      do_it_right_at_runtime ();
> +    }
> +
> +  if (resolver_fn != 1)
> +    __builtin_abort ();
> +
> +  if (resolved_fn != 10)
> +    __builtin_abort ();
> +
> +  return 0;
> +}
>