diff --git a/include/ChangeLog b/include/ChangeLog
index 95a00be6eef..30f281e11a7 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,7 @@
+2000-09-10  Mark Mitchell  <mark@codesourcery.com>
+
+	* splay-tree.h (splay_tree_predecessor): Declare.
+
 2000-09-05  John David Anglin <dave@hiauly1.hia.nrc.ca>
 
 	* md5.h (md5_uint32): Choose via INT_MAX instead of UINT_MAX.
diff --git a/include/splay-tree.h b/include/splay-tree.h
index 39882a4beac..f53f855767b 100644
--- a/include/splay-tree.h
+++ b/include/splay-tree.h
@@ -1,5 +1,5 @@
 /* A splay-tree datatype.  
-   Copyright (C) 1998 Free Software Foundation, Inc.
+   Copyright (C) 1998, 2000 Free Software Foundation, Inc.
    Contributed by Mark Mitchell (mark@markmitchell.com).
 
 This file is part of GNU CC.
@@ -104,6 +104,12 @@ extern void splay_tree_remove		PARAMS((splay_tree,
 extern splay_tree_node splay_tree_lookup   
                                         PARAMS((splay_tree,
 					        splay_tree_key));
+extern splay_tree_node splay_tree_predecessor
+                                        PARAMS((splay_tree,
+						splay_tree_key));
+extern splay_tree_node splay_tree_successor
+                                        PARAMS((splay_tree,
+						splay_tree_key));
 extern int splay_tree_foreach           PARAMS((splay_tree,
 					        splay_tree_foreach_fn,
 					        void*));
diff --git a/libiberty/ChangeLog b/libiberty/ChangeLog
index 4b5923e284b..ee879c4ca8b 100644
--- a/libiberty/ChangeLog
+++ b/libiberty/ChangeLog
@@ -1,3 +1,8 @@
+2000-09-10  Mark Mitchell  <mark@codesourcery.com>
+
+	* splay-tree.c (splay_tree_predecessor): New function.
+	(splay_tree_successor): Likewise.
+
 2000-09-10  Hans-Peter Nilsson  <hp@axis.com>
 
 	* testsuite/demangle-expected: Add four tests for type_info
diff --git a/libiberty/splay-tree.c b/libiberty/splay-tree.c
index de66d11bf56..9a684899d4a 100644
--- a/libiberty/splay-tree.c
+++ b/libiberty/splay-tree.c
@@ -1,5 +1,5 @@
 /* A splay-tree datatype.  
-   Copyright (C) 1998, 1999 Free Software Foundation, Inc.
+   Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
    Contributed by Mark Mitchell (mark@markmitchell.com).
 
 This file is part of GNU CC.
@@ -366,6 +366,72 @@ splay_tree_lookup (sp, key)
     return 0;
 }
 
+/* Return the immediate predecessor KEY, or NULL if there is no
+   predecessor.  KEY need not be present in the tree.  */
+
+splay_tree_node
+splay_tree_predecessor (sp, key)
+     splay_tree sp;
+     splay_tree_key key;
+{
+  int comparison;
+  splay_tree_node node;
+
+  /* If the tree is empty, there is certainly no predecessor.  */
+  if (!sp->root)
+    return NULL;
+
+  /* Splay the tree around KEY.  That will leave either the KEY
+     itself, its predecessor, or its successor at the root.  */
+  splay_tree_splay (sp, key);
+  comparison = (*sp->comp)(sp->root->key, key);
+
+  /* If the predecessor is at the root, just return it.  */
+  if (comparison < 0)
+    return sp->root;
+
+  /* Otherwise, find the rightmost element of the left subtree.  */
+  node = sp->root->left;
+  if (node)
+    while (node->right)
+      node = node->right;
+
+  return node;
+}
+
+/* Return the immediate successor KEY, or NULL if there is no
+   predecessor.  KEY need not be present in the tree.  */
+
+splay_tree_node
+splay_tree_successor (sp, key)
+     splay_tree sp;
+     splay_tree_key key;
+{
+  int comparison;
+  splay_tree_node node;
+
+  /* If the tree is empty, there is certainly no predecessor.  */
+  if (!sp->root)
+    return NULL;
+
+  /* Splay the tree around KEY.  That will leave either the KEY
+     itself, its predecessor, or its successor at the root.  */
+  splay_tree_splay (sp, key);
+  comparison = (*sp->comp)(sp->root->key, key);
+
+  /* If the successor is at the root, just return it.  */
+  if (comparison > 0)
+    return sp->root;
+
+  /* Otherwise, find the rightmost element of the left subtree.  */
+  node = sp->root->right;
+  if (node)
+    while (node->left)
+      node = node->left;
+
+  return node;
+}
+
 /* Call FN, passing it the DATA, for every node in SP, following an
    in-order traversal.  If FN every returns a non-zero value, the
    iteration ceases immediately, and the value is returned.