tibOffset = ObjectLayout.TIB_SLOT * refSize;
    public HeapHelperImpl(VmArchitecture arch) {        if (Vm.getVm() != null) { throw new SecurityException(                "Cannot instantiate HeapHelpImpl at runtime"); }        final int refSize = arch.getReferenceSize();        flagsOffset = ObjectLayout.FLAGS_SLOT * refSize;        tibOffset = ObjectLayout.TIB_SLOT * refSize;    }