int oldValue = VM_Interface.prepareAvailableBits(ref); int newValue = (oldValue & ~GC_MARK_BIT_MASK) | value;
VM_Word oldValue = VM_Interface.prepareAvailableBits(ref); VM_Word newValue = oldValue.and(GC_MARK_BIT_MASK.not()).or(value);
  static void atomicWriteMarkBit(VM_Address ref, int value) throws VM_PragmaUninterruptible {    while (true) {      int oldValue = VM_Interface.prepareAvailableBits(ref);      int newValue = (oldValue & ~GC_MARK_BIT_MASK) | value;      if (VM_Interface.attemptAvailableBits(ref,oldValue,newValue)) break;    }  }