static struct cgraph_node *
cgraph_empty_node_for_versioning (struct cgraph_node *old_version,
				 tree new_decl)
 {
   struct cgraph_node *new_version;
   struct cgraph_edge *e, *new_e;
   struct cgraph_edge *next_callee;
   
   gcc_assert (old_version);

   new_version = cgraph_node (new_decl);

   new_version->analyzed = true;
   new_version->local = old_version->local;
   new_version->global = old_version->global;
   new_version->rtl = new_version->rtl;
   new_version->reachable = true;
   new_version->count = old_version->count;

   /* Clone the old node callees.  Recursive calls are
      also cloned.  */
   for (e = old_version->callees;e; e=e->next_callee)
     {
       new_e = cgraph_clone_edge (e, new_version, e->call_stmt, 0, e->frequency,
				  e->loop_nest, true);
       new_e->count = e->count;
     }
   /* Fix recursive calls.
      If OLD_VERSION has a recursive call after the
      previous edge cloning, the new version will have an edge
      pointing to the old version, which is wrong;
      Redirect it to point to the new version. */
   for (e = new_version->callees ; e; e = next_callee)
     {
       next_callee = e->next_callee;
       if (e->callee == old_version)
	 cgraph_redirect_edge_callee (e, new_version);

       if (!next_callee)
	 break;
     }
 
   return new_version;
 }

...
  tree old_decl = old_version_node->decl;
  struct cgraph_node *new_version_node = NULL;
  tree new_decl;

  /* Make a new FUNCTION_DECL tree node for the
     new version. */
  new_decl = copy_node (old_decl);

    new_version_node = 
    cgraph_empty_node_for_versioning (old_version_node, new_decl);
  
  /* Copy the OLD_VERSION_NODE function tree to the new version.  */
  tree_function_versioning (old_decl, new_decl, tree_map, false);
  
...