PND_INVALID
if (PERFUSE_NODE_DATA(opc)->pnd_flags & PND_INVALID)
if (PERFUSE_NODE_DATA(pn)->pnd_flags & PND_INVALID)
if (pnd->pnd_flags & PND_INVALID)
if (pnd->pnd_flags & PND_INVALID)
pnd->pnd_flags |= PND_INVALID;