decision here, anything to do with tlbie, or dcbz and cache or mmu in general goes into this Function Unit.

means creating a new FU in the CSV files (adding to power_enums.py)

it will need to be a FSM not a pipeline because it gets too complex otherwise.

changing tlbie etc not expected to be particularly common so this is ok.

 
 -- send MMU-related SPRs to loadstore1
    case sprn is
    when SPR_DAR | SPR_DSISR | SPR_PID | SPR_PRTBL =>
             v.decode.unit := LDST;
                  

in PowerDecoder2 must redirect these SPRs to the MMU FU

        majorop := unsigned(f_in.insn(31 downto 26));
        if f_in.fetch_failed = '1' then
            v.valid := '1';
            -- Only send down a single OP_FETCH_FAILED
            if r.decode.insn_type = OP_FETCH_FAILED then
                v.valid := '0';
            end if;
            v.decode := fetch_fail_inst;


also, like interrupts, if a fetch fails run a new op (microcode style)