diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8aac434028f..9e806b3f062 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2005-01-28  Jeff Law  <law@redhat.com>
+
+	* fold-const.c (fold, case CEIL_MOD_EXPR): Optimize 0 % X.
+	(case FLOOR_MOD_EXPR, ROUND_MOD_EXPR, TRUNC_MOD_EXPR): Similarly.
+
 2005-01-28  Kazu Hirata  <kazu@cs.umass.edu>
 
 	* cse.c (cse_reg_info_free_list, cse_reg_info_used_list,
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 8e8a821938b..67a0217057a 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -7875,7 +7875,8 @@ fold (tree expr)
     case FLOOR_MOD_EXPR:
     case ROUND_MOD_EXPR:
     case TRUNC_MOD_EXPR:
-      if (integer_onep (arg1))
+      /* 0 % X is always zero as is X % 1.  */
+      if (integer_zerop (arg0) || integer_onep (arg1))
 	return omit_one_operand (type, integer_zero_node, arg0);
       if (integer_zerop (arg1))
 	return t;