private static void atomicWriteMarkBit(VM_Address ref, int value) {
private static void atomicWriteMarkBit(VM_Address ref, VM_Word value) {
  private static void atomicWriteMarkBit(VM_Address ref, int value) {    while (true) {      int oldValue = VM_Interface.prepareAvailableBits(ref);      int newValue = (oldValue & ~GC_MARK_BIT_MASK) | value;      if (VM_Interface.attemptAvailableBits(ref,oldValue,newValue)) break;    }  }