Re: [PATCH v2 4/8] target/sparc: Introduce DYNAMIC_PC_LOOKUP

[Philippe Mathieu-Daudé]

On 21/6/23 20:06, Richard Henderson wrote:
> Create a new artificial "next pc" which also indicates
> that nothing has changed within the cpu state which
> requires returning to the main loop.
>
> Pipe this new value though all pc/npc checks.
> Do not produce this new value yet.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   target/sparc/translate.c | 155 ++++++++++++++++++++++++++++-----------
>   1 file changed, 111 insertions(+), 44 deletions(-)


> @@ -5608,20 +5649,46 @@ static void sparc_tr_translate_insn(DisasContextBase 
> *dcbase, CPUState *cs)
>   static void sparc_tr_tb_stop(DisasContextBase *dcbase, CPUState *cs)
>   {
>       DisasContext *dc = container_of(dcbase, DisasContext, base);
> +    bool may_lookup;
>   
>       switch (dc->base.is_jmp) {
>       case DISAS_NEXT:
>       case DISAS_TOO_MANY:
> -        if (dc->pc != DYNAMIC_PC &&
> -            (dc->npc != DYNAMIC_PC && dc->npc != JUMP_PC)) {
> +        if (((dc->pc | dc->npc) & 3) == 0) {
>               /* static PC and NPC: we can use direct chaining */
>               gen_goto_tb(dc, 0, dc->pc, dc->npc);
> -        } else {
> -            if (dc->pc != DYNAMIC_PC) {
> -                tcg_gen_movi_tl(cpu_pc, dc->pc);
> +            break;
> +        }
> +
> +        if (dc->pc & 3) {
> +            switch (dc->pc) {
> +            case DYNAMIC_PC_LOOKUP:
> +                may_lookup = true;
> +                break;
> +            case DYNAMIC_PC:
> +                may_lookup = false;
> +                break;
> +            default:
> +                g_assert_not_reached();
>               }
> -            save_npc(dc);
> +        } else {
> +            tcg_gen_movi_tl(cpu_pc, dc->pc);
> +            may_lookup = true;
> +        }
> +
> +        save_npc(dc);
> +        switch (dc->npc) {

switch (dc->npc & 3)?

> +        case DYNAMIC_PC_LOOKUP:
> +            if (may_lookup) {
> +                tcg_gen_lookup_and_goto_ptr();
> +                break;
> +            }
> +            /* fall through */
> +        case DYNAMIC_PC:
>               tcg_gen_exit_tb(NULL, 0);
> +            break;
> +        default:
> +            g_assert_not_reached();
>           }
>           break;
>