Incorrect value computed in conditional with numeric comparisons

[Paul F. Dietz]

(defun bug2020417a (a b)
  (declare (type real a))
  (if (>= a a)
      (= b a)
      t))

(defun bug2020417b (a b)
  (if (>= a a)
      (= b a)
      t))

(defun doit ()
  (values
   (bug2020417a 0 1)
   (bug2020417b 0 1)))

(doit) ==> T, NIL