[PATCH, PR 43812] Dissolve same_comdat_groups when localizing decls in function_and_variable_visibility

[Martin Jambor]

Hi,

the patch below was approved by Honza on IRC and so I committed it as
revision 158777.  I intend to commit it to the 4.5 branch early next
week - should I omit the additions to the verifier?

Thanks,

Martin

On Wed, Apr 21, 2010 at 06:17:56PM +0200, Martin Jambor wrote:
> Hi,
> 
> PR 43812 is caused by the fact that ipa-cp asserts that there is no
> function which has no incoming edges and yet cannot be called
> indirectly or from outside the current compilation unit.  That is
> normally true because we remove all unreachable functions before
> IPA-CP.  However, at -fwhole-program we keep one such function because
> it is in a same_comdat_group list even though
> function_and_variable_visibility has made all of the functions in the
> list local.  The fix is to make the function dissolve the list in the
> process as well.
> 
> This patch also adds stuff to the call graph verifier that checks the
> list is indeed circular, it has more than one member and that all of
> the members have their fndecl in a DECL_COMDAT_GROUP (this last
> property would have caught the problem).
> 
> Bootstrapped and tested on x86-64-linux without any problems.  OK fro
> trunk and the 4.5 branch (without the verifier changes)?
> 
> Thanks,
> 
> Martin
> 
> 2010-04-21  Martin Jambor  <mjambor@suse.cz>
> 
> 	PR middle-end/43812
> 	* ipa.c (dissolve_same_comdat_group_list): New function.
> 	(function_and_variable_visibility): Call
> 	dissolve_same_comdat_group_list when comdat group contains external or
> 	newly local nodes.
> 	* cgraphunit.c (verify_cgraph_node): Verify that same_comdat_group
> 	lists are circular and that they contain only DECL_ONE_ONLY nodes.
> 
> 	* testsuite/g++.dg/ipa/pr43812.C: New test.
> 
> 
> Index: icln/gcc/ipa.c
> ===================================================================
> --- icln.orig/gcc/ipa.c
> +++ icln/gcc/ipa.c
> @@ -353,6 +353,21 @@ cgraph_externally_visible_p (struct cgra
>    return false;
>  }
>  
> +/* Dissolve the same_comdat_group list in which NODE resides.  */
> +
> +static void
> +dissolve_same_comdat_group_list (struct cgraph_node *node)
> +{
> +  struct cgraph_node *n = node, *next;
> +  do
> +    {
> +      next = n->same_comdat_group;
> +      n->same_comdat_group = NULL;
> +      n = next;
> +    }
> +  while (n != node);
> +}
> +
>  /* Mark visibility of all functions.
>  
>     A local function is one whose calls can occur only in the current
> @@ -383,17 +398,17 @@ function_and_variable_visibility (bool w
>  	 and simplifies later passes.  */
>        if (node->same_comdat_group && DECL_EXTERNAL (node->decl))
>  	{
> -	  struct cgraph_node *n = node, *next;
> -	  do
> -	    {
> +#ifdef ENABLE_CHECKING
> +	  struct cgraph_node *n;
> +
> +	  for (n = node->same_comdat_group;
> +	       n != node;
> +	       n = n->same_comdat_group)
>  	      /* If at least one of same comdat group functions is external,
>  		 all of them have to be, otherwise it is a front-end bug.  */
>  	      gcc_assert (DECL_EXTERNAL (n->decl));
> -	      next = n->same_comdat_group;
> -	      n->same_comdat_group = NULL;
> -	      n = next;
> -	    }
> -	  while (n != node);
> +#endif
> +	  dissolve_same_comdat_group_list (node);
>  	}
>        gcc_assert ((!DECL_WEAK (node->decl) && !DECL_COMDAT (node->decl))
>        	          || TREE_PUBLIC (node->decl) || DECL_EXTERNAL (node->decl));
> @@ -409,6 +424,12 @@ function_and_variable_visibility (bool w
>  	{
>  	  gcc_assert (whole_program || !TREE_PUBLIC (node->decl));
>  	  cgraph_make_decl_local (node->decl);
> +	  if (node->same_comdat_group)
> +	    /* cgraph_externally_visible_p has already checked all other nodes
> +	       in the group and they will all be made local.  We need to
> +	       dissolve the group at once so that the predicate does not
> +	       segfault though. */
> +	    dissolve_same_comdat_group_list (node);
>  	}
>        node->local.local = (cgraph_only_called_directly_p (node)
>  			   && node->analyzed
> Index: icln/gcc/testsuite/g++.dg/ipa/pr43812.C
> ===================================================================
> --- /dev/null
> +++ icln/gcc/testsuite/g++.dg/ipa/pr43812.C
> @@ -0,0 +1,38 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fwhole-program -fipa-cp" } */
> +
> +typedef float scoord_t;
> +typedef scoord_t sdist_t;
> +typedef sdist_t dist_t;
> +template<typename T> class TRay { };
> +typedef TRay<dist_t> Ray;
> +class BBox { };
> +class RenderContext { };
> +class RefCounted {
> +public:
> +    void deref () const {
> +        if (--ref_count <= 0) {
> +            delete this;
> +        }
> +    }
> +    mutable int ref_count;
> +};
> +template<class T> class Ref {
> +public:
> +    ~Ref () {
> +        if (obj) obj->deref ();
> +    }
> +    T *obj;
> +};
> +class Material : public RefCounted { };
> +class Surface {
> +public:
> +    virtual ~Surface () { }
> +    class IsecInfo   { };
> +    virtual const IsecInfo *intersect (Ray &ray, RenderContext &context) const;
> +    Ref<const Material> material;
> +};
> +class LocalSurface : public Surface {
> +    virtual BBox bbox () const;
> +};
> +BBox LocalSurface::bbox () const { }
> Index: icln/gcc/cgraphunit.c
> ===================================================================
> --- icln.orig/gcc/cgraphunit.c
> +++ icln/gcc/cgraphunit.c
> @@ -714,6 +714,32 @@ verify_cgraph_node (struct cgraph_node *
>        error ("double linked list of clones corrupted");
>        error_found = true;
>      }
> +  if (node->same_comdat_group)
> +    {
> +      struct cgraph_node *n = node->same_comdat_group;
> +
> +      if (!DECL_ONE_ONLY (node->decl))
> +	{
> +	  error ("non-DECL_ONE_ONLY node in a same_comdat_group list");
> +	  error_found = true;
> +	}
> +      if (n == node)
> +	{
> +	  error ("node is alone in a comdat group");
> +	  error_found = true;
> +	}
> +      do
> +	{
> +	  if (!n->same_comdat_group)
> +	    {
> +	      error ("same_comdat_group is not a circular list");
> +	      error_found = true;
> +	      break;
> +	    }
> +	  n = n->same_comdat_group;
> +	}
> +      while (n != node);
> +    }
>  
>    if (node->analyzed && gimple_has_body_p (node->decl)
>        && !TREE_ASM_WRITTEN (node->decl)