badif.lisp

; Under Lispworks 6.01 32-bit Windows Vista
;
; CL-USER 100 > (test-fun)
; (i & 0x80000000) == 0  time: 0.717
; (i & 0xFFFFFFFF) == 0  time: 0.671
; (i & 0x00000001) == 0  time: 0.718
; (i & 0x00000003) == 0  time: 0.795
; (i & 0x00000002) == 0  time: 0.827
; (i & 0x00000004) == 0  time: 0.78
; (i & 0x00000008) == 0  time: 0.811
; (i & 0x00000010) == 0  time: 0.999
; NIL

(declaim (optimize (speed 3) (compilation-speed 0) (safety 0)
                   (space 0) (debug 0) #+lispworks (hcl:fixnum-safety 0)))

(defparameter *funcs* nil)

(defmacro make-fun (arg)
  (let ((name (intern (format nil "TEST-~A" arg))))
    (pushnew (list arg name) *funcs*)
    `(defun ,name ()
       (let ((s 0))
         (declare (fixnum s))
         (dotimes (n 1073741824)
           (declare (fixnum n))
           (when (= 0 (logand n ,arg))
             (setf s (the fixnum (+ 1 s)))))
         s))))

(make-fun #x80000000)
(make-fun #xFFFFFFFF)
(make-fun #x00000001)
(make-fun #x00000003)
(make-fun #x00000002)
(make-fun #x00000004)
(make-fun #x00000008)
(make-fun #x00000010)

(setf *funcs* (nreverse *funcs*))

(defun time-it (f)
  (let ((time (get-internal-run-time)))
    (funcall f)
    (float (/ (- (get-internal-run-time) time)
              internal-time-units-per-second))))

(defun test-fun ()
  (dolist (l *funcs*)
    (format t "(i & 0x~8,'0X) == 0  time: ~A~&"
            (first l)
            (time-it (second l)))))

#+nil
(test-fun)

Found a bug. I'm over-optimizing, and 1073741824 is bigger than most-positive-fixnum on 32-bit windows which is 536870911