anchor.diff:          ((equal type '(unsigned-byte 64))
            (incf to-storage (* to-offset 8))
            (dotimes (i nrows)
  -           (dotimes (j ncols)
  -             (setf (memref-unsigned-byte-64 to-storage j) val))
  +           (%fast-set-64 val to-storage ncols)
              (incf to-storage (* to-width 8))))))))
  
positive.code:         (setf from-storage (+ (lisp-object-address from-storage) 1)))
        (incf to-storage (* (+ (* to-row to-width) to-col to-offset) stride))
        (incf from-storage (* (+ (* from-row from-width) from-col from-offset) stride))
        (dotimes (i nrows)
          (%fast-copy to-storage from-storage bytes-per-col)
          (incf to-storage to-stride)
          (incf from-storage from-stride)))))
  
  ;;; (value destination count)
  (define-lap-function %fast-set-8 ()
  
negative.code:   (sys.lap-x86:ret))
  
  (define-lap-function %fast-set-64 ()
    (sys.lap-x86:test64 :r8 7)
    (sys.lap-x86:jnz load-bignum)
    (sys.lap-x86:mov64 :rax :r8)
    (sys.lap-x86:sar64 :rax 3)
    blah
    (sys.lap-x86:mov64 :rdi :r9)
    (sys.lap-x86:mov64 :rcx :r10)
    (sys.lap-x86:sar64 :rdi 3)
    (sys.lap-x86:sar64 :rcx 3)
    (sys.lap-x86:rep)
    (sys.lap-x86:stos64)
    (sys.lap-x86:mov64 :rbx :lsp)
    (sys.lap-x86:ret)
    load-bignum
    (sys.lap-x86:mov64 :rax (:r8 #.(+ (- +tag-array-like+) 8)))
    (sys.lap-x86:jmp blah))
  
  (defun %bitset (nrows ncols val to-array to-row to-col)
    (let ((to-displacement 0))
  