VM_Interface._assert(bufsenqueued == debugQueueLength());
VM_Interface._assert(checkQueueLength(bufsenqueued));
  public final void enqueue(VM_Address buf, int arity, boolean toTail) {    if (VM_Interface.VerifyAssertions) VM_Interface._assert(arity == this.arity);    lock();    if (toTail) {      // Add to the tail of the queue      setNext(buf, VM_Address.zero());      if (tail.isZero())	head = buf;      else	setNext(tail, buf);      tail = buf;    } else {      // Add to the head of the queue      if (head.isZero())	tail = buf;      setNext(buf, head);      head = buf;    }     if (VM_Interface.VerifyAssertions) {      bufsenqueued++;      VM_Interface._assert(bufsenqueued == debugQueueLength());    }    unlock();  }