2008-08-13  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/37103
	* fold-const.c (fold_widened_comparison): Do not allow
	sign changes that change the result even if shorter type
	is wider than arg1_unw's type.

	* gcc.c-torture/execute/20080813-1.c: New test.

--- gcc/fold-const.c.jj	2008-08-13 19:46:11.000000000 +0200
+++ gcc/fold-const.c	2008-08-13 20:18:21.000000000 +0200
@@ -6733,10 +6733,8 @@ fold_widened_comparison (enum tree_code 
   if ((code == EQ_EXPR || code == NE_EXPR
        || TYPE_UNSIGNED (TREE_TYPE (arg0)) == TYPE_UNSIGNED (shorter_type))
       && (TREE_TYPE (arg1_unw) == shorter_type
-	  || (TYPE_PRECISION (shorter_type)
-	      > TYPE_PRECISION (TREE_TYPE (arg1_unw)))
 	  || ((TYPE_PRECISION (shorter_type)
-	       == TYPE_PRECISION (TREE_TYPE (arg1_unw)))
+	       >= TYPE_PRECISION (TREE_TYPE (arg1_unw)))
 	      && (TYPE_UNSIGNED (shorter_type)
 		  == TYPE_UNSIGNED (TREE_TYPE (arg1_unw))))
 	  || (TREE_CODE (arg1_unw) == INTEGER_CST
--- gcc/testsuite/gcc.c-torture/execute/20080813-1.c.jj	2008-08-13 20:22:56.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/execute/20080813-1.c	2008-08-13 20:22:10.000000000 +0200
@@ -0,0 +1,30 @@
+/* PR middle-end/37103 */
+
+extern void abort (void);
+
+void
+foo (unsigned short x)
+{
+  signed char y = -1;
+  if (x == y)
+    abort ();
+}
+
+void
+bar (unsigned short x)
+{
+  unsigned char y = -1;
+  if (x == y)
+    abort ();
+}
+
+int
+main (void)
+{
+  if (sizeof (int) == sizeof (short))
+    return 0;
+  foo (-1);
+  if (sizeof (short) > 1)
+    bar (-1);
+  return 0;
+}