From dc5d4efbce3e6587b31da8d6d1c502aea80acfcc Mon Sep 17 00:00:00 2001
From: Jeff Law <law@redhat.com>
Date: Mon, 31 Jan 2005 20:48:52 -0700
Subject: fold-const.c (fold, [...]): Do not lose side effects when optimizing
 0 % X.

	* fold-const.c (fold, case CEIL_MOD_EXPR): Do not lose side
	effects when optimizing 0 % X.  Do not try to optimize X % 0.

	* gcc.c-torture/execute/20050131-1.c: New test.
	* gcc.dg/wcaselabel.c: New test.

From-SVN: r94516
---
 gcc/fold-const.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

(limited to 'gcc/fold-const.c')

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 13c57e0..2285742 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -7938,12 +7938,21 @@ fold (tree expr)
     case FLOOR_MOD_EXPR:
     case ROUND_MOD_EXPR:
     case TRUNC_MOD_EXPR:
-      /* 0 % X is always zero as is X % 1.  */
-      if (integer_zerop (arg0) || integer_onep (arg1))
+      /* X % 1 is always zero, but be sure to preserve any side
+	 effects in X.  */
+      if (integer_onep (arg1))
 	return omit_one_operand (type, integer_zero_node, arg0);
+
+      /* X % 0, return X % 0 unchanged so that we can get the
+	 proper warnings and errors.  */
       if (integer_zerop (arg1))
 	return t;
 
+      /* 0 % X is always zero, but be sure to preserve any side
+	 effects in X.  Place this after checking for X == 0.  */
+      if (integer_zerop (arg0))
+	return omit_one_operand (type, integer_zero_node, arg1);
+
       /* X % -1 is zero.  */
       if (!TYPE_UNSIGNED (type)
 	  && TREE_CODE (arg1) == INTEGER_CST
-- 
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