newValue = (oldValue & ~MARK_BIT_MASK) | value;
newValue = oldValue.and(MARK_BIT_MASK.not()).or(value);
  public static void atomicWriteMarkBit(VM_Address ref, int value)    throws VM_PragmaUninterruptible, VM_PragmaInline {    int oldValue, newValue;    do {      oldValue = VM_Interface.prepareAvailableBits(ref);      newValue = (oldValue & ~MARK_BIT_MASK) | value;    } while (!VM_Interface.attemptAvailableBits(ref,oldValue,newValue));  }