tree.c (chain_index): New fn.

	* tree.c (chain_index): New fn.
	* tree.h: Declare it.

From-SVN: r151618

gcc/ChangeLog

+2009-09-10  Jason Merrill  <jason@redhat.com>
+
+	* tree.c (chain_index): New fn.
+	* tree.h: Declare it.
+
 2009-09-10  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
 
 	* config/sol2-c.c (cmn_err_length_specs): Initialize

gcc/tree.c

@@ -1905,6 +1905,17 @@ purpose_member (const_tree elem, tree list)
   return NULL_TREE;
 }
 
+/* Returns element number IDX (zero-origin) of chain CHAIN, or
+   NULL_TREE.  */
+
+tree
+chain_index (int idx, tree chain)
+{
+  for (; chain && idx > 0; --idx)
+    chain = TREE_CHAIN (chain);
+  return chain;
+}
+
 /* Return nonzero if ELEM is part of the chain CHAIN.  */
 
 int

gcc/tree.h

@@ -3914,6 +3914,7 @@ extern bool range_in_array_bounds_p (tree);
 
 extern tree value_member (tree, tree);
 extern tree purpose_member (const_tree, tree);
+extern tree chain_index (int, tree);
 
 extern int attribute_list_equal (const_tree, const_tree);
 extern int attribute_list_contained (const_tree, const_tree);