Fixed OptCmp1 with certain code patterns with labels.

test/val/bug1690.c

@@ -0,0 +1,23 @@
+/* OptCmp1 messed up with labels */
+
+#include <stdio.h>
+
+int main(void)
+{
+    register unsigned int x = 0x200;
+    register unsigned int y = 0;
+
+    do
+    {
+        ++y;
+    }
+    while (--x);
+
+    if (y != 0x200)
+	{
+		printf("0x%X\n", y);
+		return 1;
+	}
+
+	return 0;
+}