(mod (X)
  (include *standard-cl-23*)

  ;; (+ X 1) should be an eliminated subexpression but it doesn't dominate the
  ;; condition.
  (let ((Z X))
    (if X
      (* (+ Z 1) (+ Z 1) (+ Z 1) (+ X 1) (+ X 1) (+ X 1))
      17
      )
    )
  )