Handle weakrefs from callgraph

Index: cgraph.c
===================================================================
--- cgraph.c	(revision 180181)
+++ cgraph.c	(working copy)
@@ -1838,6 +1838,8 @@  dump_cgraph_node (FILE *f, struct cgraph
     fprintf (f, " only_called_at_startup");
   if (node->only_called_at_exit)
     fprintf (f, " only_called_at_exit");
+  else if (node->alias)
+    fprintf (f, " alias");
 
   fprintf (f, "\n");
 
Index: cgraphunit.c
===================================================================
--- cgraphunit.c	(revision 180181)
+++ cgraphunit.c	(working copy)
@@ -1249,6 +1249,18 @@  handle_alias_pairs (void)
 	  varpool_create_variable_alias (p->decl, target_vnode->decl);
 	  VEC_unordered_remove (alias_pair, alias_pairs, i);
 	}
+      /* Weakrefs with target not defined in current unit are easy to handle; they
+	 behave just as external variables except we need to note the alias flag
+	 to later output the weakref pseudo op into asm file.  */
+      else if (lookup_attribute ("weakref", DECL_ATTRIBUTES (p->decl)) != NULL)
+	{
+	  if (TREE_CODE (p->decl) == FUNCTION_DECL)
+	    cgraph_get_create_node (p->decl)->alias = true;
+	  else
+	    varpool_get_node (p->decl)->alias = true;
+	  DECL_EXTERNAL (p->decl) = 1;
+	  VEC_unordered_remove (alias_pair, alias_pairs, i);
+	}
       else
 	{
 	  if (dump_file)
@@ -2064,24 +2078,36 @@  ipa_passes (void)
   bitmap_obstack_release (NULL);
 }
 
+/* Return string alias is alias of.  */
+
+static tree
+get_alias_symbol (tree decl)
+{
+  tree alias = lookup_attribute ("alias", DECL_ATTRIBUTES (decl));
+  return get_identifier (TREE_STRING_POINTER
+			  (TREE_VALUE (TREE_VALUE (alias))));
+}
+
 /* Weakrefs may be associated to external decls and thus not output
    at expansion time.  Emit all neccesary aliases.  */
 
-void
+static void
 output_weakrefs (void)
 {
   struct cgraph_node *node;
   struct varpool_node *vnode;
   for (node = cgraph_nodes; node; node = node->next)
-    if (node->alias && node->thunk.alias && DECL_EXTERNAL (node->decl)
+    if (node->alias && DECL_EXTERNAL (node->decl)
         && !TREE_ASM_WRITTEN (node->decl))
       assemble_alias (node->decl,
-		      DECL_ASSEMBLER_NAME (node->thunk.alias));
+		      node->thunk.alias ? DECL_ASSEMBLER_NAME (node->thunk.alias)
+		      : get_alias_symbol (node->decl));
   for (vnode = varpool_nodes; vnode; vnode = vnode->next)
-    if (vnode->alias && vnode->alias_of && DECL_EXTERNAL (vnode->decl)
+    if (vnode->alias && DECL_EXTERNAL (vnode->decl)
         && !TREE_ASM_WRITTEN (vnode->decl))
       assemble_alias (vnode->decl,
-		      DECL_ASSEMBLER_NAME (vnode->alias_of));
+		      vnode->alias_of ? DECL_ASSEMBLER_NAME (vnode->alias_of)
+		      : get_alias_symbol (vnode->decl));
 }
 
 
Index: lto-cgraph.c
===================================================================
--- lto-cgraph.c	(revision 180181)
+++ lto-cgraph.c	(working copy)
@@ -512,7 +512,13 @@  lto_output_node (struct lto_simple_outpu
 		     || referenced_from_other_partition_p (&node->ref_list, set, vset)), 1);
   bp_pack_value (&bp, node->lowered, 1);
   bp_pack_value (&bp, in_other_partition, 1);
-  bp_pack_value (&bp, node->alias && !boundary_p, 1);
+  /* Real aliases in a boundary become non-aliases. However we still stream
+     alias info on weakrefs. 
+     TODO: We lose a bit of information here - when we know that variable is
+     defined in other unit, we may use the info on aliases to resolve 
+     symbol1 != symbol2 type tests that we can do only for locally defined objects
+     otherwise.  */
+  bp_pack_value (&bp, node->alias && (!boundary_p || DECL_EXTERNAL (node->decl)), 1);
   bp_pack_value (&bp, node->frequency, 2);
   bp_pack_value (&bp, node->only_called_at_startup, 1);
   bp_pack_value (&bp, node->only_called_at_exit, 1);
@@ -530,7 +536,8 @@  lto_output_node (struct lto_simple_outpu
       streamer_write_uhwi_stream (ob->main_stream, node->thunk.fixed_offset);
       streamer_write_uhwi_stream (ob->main_stream, node->thunk.virtual_value);
     }
-  if ((node->alias || node->thunk.thunk_p) && !boundary_p)
+  if ((node->alias || node->thunk.thunk_p)
+      && (!boundary_p || (node->alias && DECL_EXTERNAL (node->decl))))
     {
       streamer_write_hwi_in_range (ob->main_stream, 0, 1,
 					node->thunk.alias != NULL);