> since getting data then doing something with it is a hidden branch if you already have the data

You mean that the naive, simpler code, despite not having an if, has a "branch" on the microarchitectural state? (which is like.. if we have this already in cache, do something. if not, do something else)

    // Find the optimal encoding for each symbol.
    // Chunk boundaries are located where encodings change.
    uint8_t encoding[n_symbols];
    uint8_t j = 0; // always start with encoding 0 for simplicity
    for (int i = 0; i < n_symbols; i++) {
        j = next_j[i][j];
        encoding[i] = j;
    }