anchor.diff:      ((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))
  -    ((in-4-byte-block-p opcode #x80) (parse-group1-opcode opcode))))
  +    ((in-4-byte-block-p opcode #x80) (parse-group1-opcode opcode))
  +    ((in-paired-byte-block-p opcode #xfe) (parse-group4/5-opcode opcode))))
   
   ;;; Main functions
   
  
positive.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")
  
negative.code:        (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)))))
  
  ;; Group 4/5 (inc/dec on EAs)
  
  (defmacro inc-indirect (indirect)
    `(disasm-instr (list "inc" :op1 ,indirect)
       (set-sf-on-op (set-zf-on-op (incf ,indirect)) t)))
  
  (defmacro dec-indirect (indirect)
    `(disasm-instr (list "dec" :op1 ,indirect)
       (set-sf-on-op (set-zf-on-op (decf ,indirect)) t)))
  
  (defmacro parse-group4/5-byte (opcode operation mod-bits r/m-bits)
    `(if (evenp ,opcode)
         (,operation (indirect-address ,mod-bits ,r/m-bits nil))
         (,operation (indirect-address ,mod-bits ,r/m-bits t))))
  
  (defmacro parse-group4/5-opcode (opcode)
    `(with-mod-r/m-byte
       (case reg-bits
         (0 (parse-group4/5-byte ,opcode inc-indirect mod-bits r/m-bits))
         (1 (parse-group4/5-byte ,opcode dec-indirect mod-bits r/m-bits)))))
  
  ;;; Opcode parsing
  
  