Document overflow bug in check_dbra_loop:

	* execute/loop-4b.c: New test.

From-SVN: r21999

gcc/testsuite/gcc.c-torture/ChangeLog

+Wed Aug 26 16:10:00 1997  J"orn Rennecke <amylaar@cygnus.co.uk>
+
+	* execute/loop-4b.c: New test.
+
 Mon Aug 24 14:20:32 1998  Nick Clifton  <nickc@cygnus.com>
 
 	* execute/bcp-1.c (main): Fix optimize test loop to count number

gcc/testsuite/gcc.c-torture/execute/loop-4b.c

+int
+f()
+{
+  int j = 1;
+  long i;
+  i = 0x60000000L;
+  do
+    {
+      j <<= 1;
+      i += 0x10000000L;
+    } while (i < -0x60000000L);
+  return j;
+}
+
+int
+main ()
+{
+  if (f () != 2)
+    abort ();
+  exit (0);
+}