TRUNCATE: unable to do inline float coercion (cost 5)

[Michał "phoe" Herda]

SBCL 1.5.0 on Linux.

(defun foo ()
  (declare (optimize speed))
  (let* ((a (make-array 1 :element-type '(unsigned-byte 8)
                          :initial-element 3))
         (b (/ 1.0 (aref a 0))))
    (truncate b 1)))

; in: DEFUN FOO
; (TRUNCATE B 1)
; --> LET
; ==>
; (SB-KERNEL:%UNARY-TRUNCATE/SINGLE-FLOAT SB-C::X)
;
; note: forced to do full call
; unable to do inline float truncate (cost 5) because:
; The result is a (VALUES (INTEGER -1) &OPTIONAL), not a (VALUES
; (SIGNED-BYTE 64)
; &REST T).

; --> LET VALUES - LOCALLY
; ==>
; (SB-KERNEL:%SINGLE-FLOAT SB-C::RES)
;
; note: forced to do full call
; unable to do inline float coercion (cost 5) because:
; The first argument is a (INTEGER -1), not a (SIGNED-BYTE 64).
;
; compilation unit finished
; printed 2 notes

[Stas Boukarev (stassats)]

Because it can be divided by zero producing an infinity.