Re: [PATCH for-6.2 1/2] target/sparc: Drop use of gen_io_end()

[Mark Cave-Ayland]

On 24/07/2021 14:49, Peter Maydell wrote:

> The gen_io_end() function is obsolete (as documented in
> docs/devel/tcg-icount.rst). Where an instruction is an I/O
> operation, the translator frontend should call gen_io_start()
> before generating the code which does the I/O, and then
> end the TB immediately after this insn.
>
> Remove the calls to gen_io_end() in the SPARC frontend,
> and ensure that the insns which were calling it end the
> TB if they didn't do so already.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/sparc/translate.c | 25 ++++++++++---------------
>   1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/target/sparc/translate.c b/target/sparc/translate.c
> index 11de5a49631..bb70ba17deb 100644
> --- a/target/sparc/translate.c
> +++ b/target/sparc/translate.c
> @@ -3401,7 +3401,8 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                           tcg_temp_free_i32(r_const);
>                           gen_store_gpr(dc, rd, cpu_dst);
>                           if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                            gen_io_end();
> +                            /* I/O operations in icount mode must end the TB */
> +                            dc->base.is_jmp = DISAS_EXIT;
>                           }
>                       }
>                       break;
> @@ -3454,7 +3455,8 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                           tcg_temp_free_i32(r_const);
>                           gen_store_gpr(dc, rd, cpu_dst);
>                           if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                            gen_io_end();
> +                            /* I/O operations in icount mode must end the TB */
> +                            dc->base.is_jmp = DISAS_EXIT;
>                           }
>                       }
>                       break;
> @@ -3588,7 +3590,8 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                           tcg_temp_free_ptr(r_tickptr);
>                           tcg_temp_free_i32(r_const);
>                           if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                            gen_io_end();
> +                            /* I/O operations in icount mode must end the TB */
> +                            dc->base.is_jmp = DISAS_EXIT;
>                           }
>                       }
>                       break;
> @@ -4582,7 +4585,8 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                                   }
>                                   gen_helper_wrpstate(cpu_env, cpu_tmp0);
>                                   if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                                    gen_io_end();
> +                                    /* I/O ops in icount mode must end the TB 
> */
> +                                    dc->base.is_jmp = DISAS_EXIT;
>                                   }
>                                   dc->npc = DYNAMIC_PC;
>                                   break;
> @@ -4598,7 +4602,8 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                                   }
>                                   gen_helper_wrpil(cpu_env, cpu_tmp0);
>                                   if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                                    gen_io_end();
> +                                    /* I/O ops in icount mode must end the TB 
> */
> +                                    dc->base.is_jmp = DISAS_EXIT;
>                                   }
>                                   break;
>                               case 9: // cwp
> @@ -4697,10 +4702,6 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                                       gen_helper_tick_set_limit(r_tickptr,
>                                                                 
> cpu_hstick_cmpr);
>                                       tcg_temp_free_ptr(r_tickptr);
> -                                    if (tb_cflags(dc->base.tb) &
> -                                           CF_USE_ICOUNT) {
> -                                        gen_io_end();
> -                                    }
>                                       /* End TB to handle timer interrupt */
>                                       dc->base.is_jmp = DISAS_EXIT;
>                                   }
> @@ -5327,9 +5328,6 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                                   gen_io_start();
>                               }
>                               gen_helper_done(cpu_env);
> -                            if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                                gen_io_end();
> -                            }
>                               goto jmp_insn;
>                           case 1:
>                               if (!supervisor(dc))
> @@ -5340,9 +5338,6 @@ static void disas_sparc_insn(DisasContext * dc, unsigned 
> int insn)
>                                   gen_io_start();
>                               }
>                               gen_helper_retry(cpu_env);
> -                            if (tb_cflags(dc->base.tb) & CF_USE_ICOUNT) {
> -                                gen_io_end();
> -                            }
>                               goto jmp_insn;
>                           default:
>                               goto illegal_insn;

Thanks Peter, this is something that has been in the back of my mind as a TODO for a 
while but I haven't managed to get around to it. From what I can see the conversion 
looks good so:

Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>


ATB,

Mark.