anchor.diff:  	      (typep (second x) 'fixnum))
   	 (load-in-r8 y t)
   	 (fixnum-check :r8)
  +         (smash-r8)
   	 ;; Small integers can be encoded directly into the instruction.
   	 (if (typep (second x) '(signed-byte 28))
   	     (emit `(sys.lap-x86:or64 :r8 ,(fixnum-to-raw (second x))))
  
positive.code:     (emit-trailer (type-error-label)
  		  (raise-type-error :r8 '(simple-array * (*))))
      (load-in-r8 array t)
      (emit `(sys.lap-x86:mov8 :al :r8l)
  	  `(sys.lap-x86:and8 :al #b1111)
  	  `(sys.lap-x86:cmp8 :al #b0111)
  
negative.code:   (load-in-reg :r8 divisor t)
    (fixnum-check :r8)
    (load-in-reg :r9 number t)
    (fixnum-check :r9)
    (smash-r8)
    (emit `(sys.lap-x86:mov64 :rax :r9)
          `(sys.lap-x86:cqo)
          `(sys.lap-x86:idiv64 :r8)
  