code: public static int getALoadReg(DismantleBytecode dbc, int seen) {
          if (seen == Const.ALOAD) {
              return dbc.getRegisterOperand();
          }
          if (OpcodeUtils.isALoad(seen)) {
              return seen - Const.ALOAD_0;
          }
          return -1;
      }
docs: returns the register used to load a reference
  
  @param dbc
  the dismantle byte code parsing the class
  @param seen
  the opcode of the load
  @return the register loaded from