Re: [PATCH 1/7] target/nios2: Remove mmu_read_debug

[Peter Maydell]

On Sun, 27 Feb 2022 at 18:23, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> This functionality can be had via plugins, if desired.
> In the meantime, it is unused code.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/nios2/helper.h    |  1 -
>  target/nios2/mmu.h       |  1 -
>  target/nios2/mmu.c       | 20 --------------------
>  target/nios2/op_helper.c |  5 -----
>  target/nios2/translate.c | 17 -----------------
>  5 files changed, 44 deletions(-)

> --- a/target/nios2/translate.c
> +++ b/target/nios2/translate.c
> @@ -448,23 +448,6 @@ static void rdctl(DisasContext *dc, uint32_t code, 
> uint32_t flags)
>      gen_check_supervisor(dc);
>
>      switch (instr.imm5 + CR_BASE) {
> -    case CR_PTEADDR:
> -    case CR_TLBACC:
> -    case CR_TLBMISC:
> -    {
> -#if !defined(CONFIG_USER_ONLY)
> -        if (likely(instr.c != R_ZERO)) {
> -            tcg_gen_mov_tl(cpu_R[instr.c], cpu_R[instr.imm5 + CR_BASE]);
> -#ifdef DEBUG_MMU
> -            TCGv_i32 tmp = tcg_const_i32(instr.imm5 + CR_BASE);
> -            gen_helper_mmu_read_debug(cpu_R[instr.c], cpu_env, tmp);
> -            tcg_temp_free_i32(tmp);
> -#endif
> -        }
> -#endif
> -        break;
> -    }
> -

For a moment I thought this was changing the behaviour of these
registers for linux-user, but gen_check_supervisor() means we
never execute the code generated here. (Side note: it would
be more sensible to stop generating code rather than generating
the "throw an exception" code and then the "write/read reg"
code as known-dead-code after it. But that's a different issue.)

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM