diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6d93bab5cc04..e2fff6c77bd7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2013-09-20  Jeff Law  <law@redhat.com>
+
+	* tree-ssa-dom.c (record_temporary_equivalences): Add comment.
+
 2013-09-20  Yufeng Zhang  <yufeng.zhang@arm.com>
 
 	* config/aarch64/aarch64-builtins.c (aarch64_simd_expand_args):
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index f5613862dcfe..f0cc0ee728bd 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -1070,6 +1070,10 @@ simplify_stmt_for_jump_threading (gimple stmt,
   return lookup_avail_expr (stmt, false);
 }
 
+/* Record into the equivalence tables any equivalences implied by
+   traversing edge E (which are cached in E->aux).
+
+   Callers are responsible for managing the unwinding markers.  */
 static void
 record_temporary_equivalences (edge e)
 {