int oldValue = VM_Interface.readAvailableBitsWord(ref); int newValue = (oldValue & ~GC_BITS_MASK) | Plan.getInitialHeaderValue(size);
VM_Word oldValue = VM_Interface.readAvailableBitsWord(ref); VM_Word newValue = oldValue.and(GC_BITS_MASK.not()).or(Plan.getInitialHeaderValue(size));
  public static void initializeLOSHeader(VM_Address ref, Object[] tib,                                         int size, boolean isScalar)    throws VM_PragmaUninterruptible, VM_PragmaInline {    if (VM_Interface.VerifyAssertions && MM_Interface.gcInProgress())      VM_Interface._assert(false);    int oldValue = VM_Interface.readAvailableBitsWord(ref);    int newValue = (oldValue & ~GC_BITS_MASK) | Plan.getInitialHeaderValue(size);    VM_Interface.writeAvailableBitsWord(ref, newValue);  }