diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index f025864ae30..f5f5afb8b83 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2001-09-11  Richard Sandiford  <rsandifo@redhat.com>
+
+	* combine.c (simplify_shift_const): Treat shifts by the mode
+	size as undefined.
+
 2001-09-11  Neil Booth  <neil@daikokuya.demon.co.uk>
 
 	* cpphash.h (struct tokenrun): New.
diff --git a/gcc/combine.c b/gcc/combine.c
index 78bf6ceb91e..1512ef01a12 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -8825,7 +8825,7 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
   /* If we were given an invalid count, don't do anything except exactly
      what was requested.  */
 
-  if (input_count < 0 || input_count > (int) GET_MODE_BITSIZE (mode))
+  if (input_count < 0 || input_count >= (int) GET_MODE_BITSIZE (mode))
     {
       if (x)
 	return x;