EXPT with single-float base and integral power can't be optimized

[Michael Fiano]

(declaim (ftype (function (single-float) single-float) quartic-in))
(declaim (inline quartic-in))
(defun quartic-in (x)
  (declare (optimize speed))
  (expt x 4))

; file: /tmp/slimeDWLQ8A
; in: DEFUN QUARTIC-IN
; (EXPT NET.MFIANO.LISP.ORIGIN::X 4)
;
; note: unable to
; optimize
; due to type uncertainty:
; The first argument is a SINGLE-FLOAT, not a (SINGLE-FLOAT 0.0).

In this case, power is of type unsigned-byte, and can't be complex.