--- a/src/cmp/cmpvar.lsp
+++ b/src/cmp/cmpvar.lsp
@@ -255,6 +255,10 @@
   (let ((kind (var-kind var)))
     (or (eq kind 'global)
         (eq kind 'special))))
+
+(defun useful-var-p (var)
+  (or (plusp (var-ref var))
+      (global-var-p var)))
 
 (defun c2var/location (c1form loc)
   #+(or)