re PR middle-end/27793 (num_ssa_names inconsistent or immediate use iterator wrong)

	PR middle-end/27793
	* cp-tree.h (cxx_int_tree_map): New struct.
	(struct language_function): Add extern_decl_map field.
	* name-lookup.c (pushdecl_maybe_friend): Add x -> t mapping
	to cp_function_chain->extern_decl_map hash table instead of
	copying over DECL_UID.
	* cp-gimplify.c (cxx_int_tree_map_eq, cxx_int_tree_map_hash): New
	functions.
	(cp_genericize_r): Remap DECL_EXTERN local decls using
	cp_function_chain->extern_decl_map hash table.
	* decl.c (finish_function): Clear extern_decl_map.

	PR c++/26757
	PR c++/27894
	* g++.dg/tree-ssa/pr26757.C: New test.
	* g++.dg/tree-ssa/pr27894.C: New test.

From-SVN: r114607

5 files changed, 82 insertions, 6 deletions

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index f64c233c..129f5df 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,17 @@
+2006-06-13  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/27793
+	* cp-tree.h (cxx_int_tree_map): New struct.
+	(struct language_function): Add extern_decl_map field.
+	* name-lookup.c (pushdecl_maybe_friend): Add x -> t mapping
+	to cp_function_chain->extern_decl_map hash table instead of
+	copying over DECL_UID.
+	* cp-gimplify.c (cxx_int_tree_map_eq, cxx_int_tree_map_hash): New
+	functions.
+	(cp_genericize_r): Remap DECL_EXTERN local decls using
+	cp_function_chain->extern_decl_map hash table.
+	* decl.c (finish_function): Clear extern_decl_map.
+
 2006-06-12  Volker Reichelt  <reichelt@igpm.rwth-aachen.de>
 
 	PR c++/27601
diff --git a/gcc/cp/cp-gimplify.c b/gcc/cp/cp-gimplify.c
index 7ded34f..ca8ff5f 100644
--- a/gcc/cp/cp-gimplify.c
+++ b/gcc/cp/cp-gimplify.c
@@ -601,6 +601,24 @@ is_invisiref_parm (tree t)
 	  && DECL_BY_REFERENCE (t));
 }
 
+/* Return true if the uid in both int tree maps are equal.  */
+
+int
+cxx_int_tree_map_eq (const void *va, const void *vb)
+{
+  const struct cxx_int_tree_map *a = (const struct cxx_int_tree_map *) va;
+  const struct cxx_int_tree_map *b = (const struct cxx_int_tree_map *) vb;
+  return (a->uid == b->uid);
+}
+
+/* Hash a UID in a cxx_int_tree_map.  */
+
+unsigned int
+cxx_int_tree_map_hash (const void *item)
+{
+  return ((const struct cxx_int_tree_map *)item)->uid;
+}
+
 /* Perform any pre-gimplification lowering of C++ front end trees to
    GENERIC.  */
 
@@ -620,6 +638,25 @@ cp_genericize_r (tree *stmt_p, int *walk_subtrees, void *data)
       return NULL;
     }
 
+  /* Map block scope extern declarations to visible declarations with the
+     same name and type in outer scopes if any.  */
+  if (cp_function_chain->extern_decl_map
+      && (TREE_CODE (stmt) == FUNCTION_DECL || TREE_CODE (stmt) == VAR_DECL)
+      && DECL_EXTERNAL (stmt))
+    {
+      struct cxx_int_tree_map *h, in;
+      in.uid = DECL_UID (stmt);
+      h = (struct cxx_int_tree_map *)
+	  htab_find_with_hash (cp_function_chain->extern_decl_map,
+			       &in, in.uid);
+      if (h)
+	{
+	  *stmt_p = h->to;
+	  *walk_subtrees = 0;
+	  return NULL;
+	}
+    }
+
   /* Other than invisiref parms, don't walk the same tree twice.  */
   if (pointer_set_contains (p_set, stmt))
     {
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 77b9067..c0897a0 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -721,6 +721,15 @@ struct saved_scope GTY(())
 
 extern GTY(()) struct saved_scope *scope_chain;
 
+struct cxx_int_tree_map GTY(())
+{
+  unsigned int uid;
+  tree to;
+};
+
+extern unsigned int cxx_int_tree_map_hash (const void *);
+extern int cxx_int_tree_map_eq (const void *, const void *);
+
 /* Global state pertinent to the current function.  */
 
 struct language_function GTY(())
@@ -747,6 +756,7 @@ struct language_function GTY(())
   htab_t GTY((param_is(struct named_label_entry))) x_named_labels;
   struct cp_binding_level *bindings;
   VEC(tree,gc) *x_local_names;
+  htab_t GTY((param_is (struct cxx_int_tree_map))) extern_decl_map;
 };
 
 /* The current C++-specific per-function global variables.  */
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index eb289d6..206fced 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -11102,6 +11102,7 @@ finish_function (int flags)
       f->x_vtt_parm = NULL;
       f->x_return_value = NULL;
       f->bindings = NULL;
+      f->extern_decl_map = NULL;
 
       /* Handle attribute((warn_unused_result)).  Relies on gimple input.  */
       c_warn_unused_result (&DECL_SAVED_TREE (fndecl));
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index 187a41f..3de9999 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -670,14 +670,28 @@ pushdecl_maybe_friend (tree x, bool is_friend)
 	      if (decls_match (x, t))
 		/* The standard only says that the local extern
 		   inherits linkage from the previous decl; in
-		   particular, default args are not shared.  We must
-		   also tell cgraph to treat these decls as the same,
-		   or we may neglect to emit an "unused" static - we
-		   do this by making the DECL_UIDs equal, which should
-		   be viewed as a kludge.  FIXME.  */
+		   particular, default args are not shared.  Add
+		   the decl into a hash table to make sure only
+		   the previous decl in this case is seen by the
+		   middle end.  */
 		{
+		  struct cxx_int_tree_map *h;
+		  void **loc;
+
 		  TREE_PUBLIC (x) = TREE_PUBLIC (t);
-		  DECL_UID (x) = DECL_UID (t);
+
+		  if (cp_function_chain->extern_decl_map == NULL)
+		    cp_function_chain->extern_decl_map
+		      = htab_create_ggc (20, cxx_int_tree_map_hash,
+					 cxx_int_tree_map_eq, NULL);
+
+		  h = GGC_NEW (struct cxx_int_tree_map);
+		  h->uid = DECL_UID (x);
+		  h->to = t;
+		  loc = htab_find_slot_with_hash
+			  (cp_function_chain->extern_decl_map, h,
+			   h->uid, INSERT);
+		  *(struct cxx_int_tree_map **) loc = h;
 		}
 	    }
 	  else if (TREE_CODE (t) == PARM_DECL)