int oldValue = VM_Interface.readAvailableBitsWord(ref); int newValue = (oldValue & ~MARK_BIT_MASK) | value;
VM_Word oldValue = VM_Interface.readAvailableBitsWord(ref); VM_Word newValue = oldValue.and(MARK_BIT_MASK.not()).or(value);
  public static void writeMarkBit(VM_Address ref, int value)    throws VM_PragmaUninterruptible, VM_PragmaInline {    int oldValue = VM_Interface.readAvailableBitsWord(ref);    int newValue = (oldValue & ~MARK_BIT_MASK) | value;    VM_Interface.writeAvailableBitsWord(ref,newValue);  }