if (VM.VerifyAssertions) VM.assert(refInHeap(ref));
if (VM.VerifyAssertions) VM._assert(refInHeap(ref));
  boolean isLive (VM_Address ref) throws VM_PragmaUninterruptible {      VM_Address addr = VM_ObjectModel.getPointerInMemoryRegion(ref);      if (VM.VerifyAssertions) VM.assert(refInHeap(ref));      int page_num = addr.diff(start ) >> 12;      return (largeSpaceMark[page_num] != 0);  }