;;; How to make the popcnt instruction available
 (defpackage "POPCNT"
   (:use "CL")
   (:export "POPCNT"))
 
 (in-package "POPCNT")
 
 (sb-c:defknown popcnt ((unsigned-byte 64)) (integer 0 64)
     (sb-c:foldable sb-c:flushable sb-c:movable)
   :overwrite-fndb-silently t)
 
 (in-package "SB-VM")
 
 (define-vop (popcnt:popcnt)
   (:policy :fast-safe)
   (:translate popcnt:popcnt)
   (:args (x :scs (unsigned-reg) :target r))
   (:arg-types unsigned-num)
   (:results (r :scs (unsigned-reg)))
   (:result-types unsigned-num)
   (:generator 3
     (unless (location= r x) ; only break the spurious dep. chain
       (inst xor r r))       ; if r isn't the same register as x.
     (inst popcnt r x)))
 
 (in-package "POPCNT")
 
 (defun popcnt (x)
   (declare (inline))
   (popcnt x))