Method findRoot

Find the root of the CONCAT tree of Varnodes marked either isProtoPartial() or isAddrTied(). This will be the maximal Varnode that containing the given Varnode (as storage), with a backward path to it through PIECE operations. All Varnodes along the path, except the root, will be marked as isProtoPartial() or isAddrTied(). \return the root of the CONCAT tree