Re: [PATCH 01/26] accel/tcg: Introduce translator_use_goto_tb

[Philippe Mathieu-Daudé]

Hi Richard,

On 6/21/21 3:34 AM, Richard Henderson wrote:
> Add a generic version of the common use_goto_tb test.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/exec/translator.h | 10 ++++++++++
>  accel/tcg/translator.c    | 11 +++++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/include/exec/translator.h b/include/exec/translator.h
> index 24232ead41..dd9c06d40d 100644
> --- a/include/exec/translator.h
> +++ b/include/exec/translator.h
> @@ -145,6 +145,16 @@ void translator_loop(const TranslatorOps *ops, 
> DisasContextBase *db,
>  
>  void translator_loop_temp_check(DisasContextBase *db);
>  
> +/**
> + * translator_use_goto_tb
> + * @db: Disassembly context
> + * @dest: target pc of the goto
> + *
> + * Return true if goto_tb is allowed between the current TB
> + * and the destination PC.
> + */
> +bool translator_use_goto_tb(DisasContextBase *db, target_ulong dest);
> +
>  /*
>   * Translator Load Functions
>   *
> diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
> index 1d32732198..59804af37b 100644
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -31,6 +31,17 @@ void translator_loop_temp_check(DisasContextBase *db)
>      }
>  }
>  
> +bool translator_use_goto_tb(DisasContextBase *db, target_ulong dest)
> +{
> +    /* Suppress goto_tb in the case of single-steping.  */
> +    if (db->singlestep_enabled || singlestep) {
> +        return false;
> +    }
> +

I notice various targets do:

#ifdef CONFIG_USER_ONLY
       return true;
#else

> +    /* Check for the dest on the same page as the start of the TB.  */
> +    return ((db->pc_first ^ dest) & TARGET_PAGE_MASK) == 0;

#endif

> +}

Is that OK to remove this case? If so, it might be worth a comment
somewhere.

Regards,

Phil.