setHead(head.sub(WORD_SIZE));
head = head.sub(WORD_SIZE);
  protected final int uncheckedPop() throws VM_PragmaInline {    if (VM.VerifyAssertions) VM._assert(bufferOffset(head) >= WORD_SIZE);    setHead(head.sub(WORD_SIZE));    //    if (VM.VerifyAssertions) enqueued--;    return VM_Magic.getMemoryWord(head);  }