anchor.diff:       (set-zf-on-op (set-sf-on-op (setf ,dest (logxor ,src ,dest)) ,is-word))
        (setf (flag-p :cf) nil)))
   
  +(defmacro parse-group1-byte (opcode operation mod-bits r/m-bits)
  +  `(case (mod ,opcode 4)
  +    (0 (,operation (next-instruction) (indirect-address ,mod-bits ,r/m-bits nil) nil))
  +    (1 (,operation (next-word) (indirect-address ,mod-bits ,r/m-bits t) t))
  +    (3 (,operation (sign-extend (next-instruction)) (indirect-address ,mod-bits ,r/m-bits t) t))))
  +
  +(defmacro parse-group1-opcode (opcode)
  +  `(with-mod-r/m-byte
  +     (case reg-bits
  +       (0 (parse-group1-byte ,opcode add-without-carry mod-bits r/m-bits))
  +       (1 (parse-group1-byte ,opcode or-operation mod-bits r/m-bits))
  +       (2 (parse-group1-byte ,opcode add-with-carry mod-bits r/m-bits))
  +       (3 (parse-group1-byte ,opcode sub-with-borrow mod-bits r/m-bits))
  +       (4 (parse-group1-byte ,opcode and-operation mod-bits r/m-bits))
  +       (5 (parse-group1-byte ,opcode sub-without-borrow mod-bits r/m-bits))
  +       (6 (parse-group1-byte ,opcode xor-operation mod-bits r/m-bits))
  +       (7 (parse-group1-byte ,opcode cmp-operation mod-bits r/m-bits)))))
  +
   ;;; Opcode parsing
   
   (defun in-paired-byte-block-p (opcode block)
     (= (truncate (/ opcode 2)) (/ block 2)))
  +
  +(defun in-4-byte-block-p (opcode block)
  +  (= (truncate (/ opcode 4)) (/ block 4)))
   
   (defun in-8-byte-block-p (opcode block)
     (= (truncate (/ opcode 8)) (/ block 8)))
  
positive.code:     ((in-6-byte-block-p opcode #x20) (parse-alu-opcode opcode and-operation))
      ((in-6-byte-block-p opcode #x28) (parse-alu-opcode opcode sub-without-borrow))
      ((in-6-byte-block-p opcode #x30) (parse-alu-opcode opcode xor-operation))
      ((in-6-byte-block-p opcode #x38) (parse-alu-opcode opcode cmp-operation))))
  
  ;;; Main functions
  
  
negative.code: 
  ;;; Test instructions
  
  (defparameter *test-instructions* #(#x40 #x40 #x05 #x03 #x00 #x91 #xb0 #xff #x04 #x01 #x72 #x04 #x50 #x5a #x51 #x52 #x48 #x4b #x43 #x74 #x03 #xbe #x02 #x03 #x01 #b11001111 #x47 #x83 #b11000111 #xfe #xf4) "Test instructions")
  