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/ChangeLog

+2005-01-31  Jeff Law  <law@redhat.com>
+
+        * fold-const.c (fold, case CEIL_MOD_EXPR): Do not lose side
+        effects when optimizing 0 % X.  Do not try to optimize X % 0.
+
 2005-01-31  James E. Wilson  <wilson@specifixinc.com>
 
 	* config/ia64/itanium1.md (1_scall bypass): Change 2_mmalua to

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

gcc/testsuite/ChangeLog

+2005-01-31  Jeff Law  <law@redhat.com>
+
+	* gcc.c-torture/execute/20050131-1.c: New test.
+	* gcc.dg/wcaselabel.c: New test.
+
 2005-01-31  Mark Mitchell  <mark@codesourcery.com>
 
 	* g++.dg/other/warning1.C: Adjust error messags.

gcc/testsuite/gcc.c-torture/execute/20050131-1.c

+/* Verify that we do not lose side effects on a MOD expression.  */
+
+#include <stdlib.h>
+#include <stdio.h>
+
+int
+foo (int a)
+{
+  int x = 0 % a++;
+  return a;
+}
+
+main()
+{
+  if (foo (9) != 10)
+    abort ();
+  exit (0);
+}

gcc/testsuite/gcc.dg/wcaselabel-1.c

+/* { dg-do compile } */
+/* { dg-options "-w" } */
+
+
+int foo(int x)
+{
+  switch(x)
+  {
+
+  case 0 % 0:	 /* { dg-error "case label does not reduce to an integer constant" } */
+    return 1;
+  default:
+    return 2;
+  }
+}