Re: [Qemu-devel] [PATCH 2/2][SPARC] Fix TA0_Shutdown feature

[Blue Swirl <blauwirbel@gmail.com>]

On Tue, May 17, 2011 at 6:32 PM, Julien Grall <julien.grall@gmail.com> wrote:
> Fix TA0_SHUTDOWN feature

But what would be the bug?

> Signed-off-by: Julien Grall <julien.grall@gmail.com>
> ---
>  target-sparc/op_helper.c |   13 +++++++++++--
>  target-sparc/translate.c |    9 +--------
>  2 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/target-sparc/op_helper.c b/target-sparc/op_helper.c
> index a6fabad..cb775f5 100644
> --- a/target-sparc/op_helper.c
> +++ b/target-sparc/op_helper.c
> @@ -326,8 +326,17 @@ void HELPER(raise_exception)(int tt)
>
>  void HELPER(trap_always)(int tt)
>  {
> -    env->exception_index = tt;
> -    do_interrupt(env);
> +    if (tt == TT_TRAP
> +        && env->def->features & CPU_FEATURE_TA0_SHUTDOWN
> +#ifndef TARGET_SPARC64
> +        && env->psret == 0
> +#endif
> +        ) {
> +        helper_shutdown();
> +    } else {
> +        env->exception_index = tt;
> +        do_interrupt(env);
> +    }
>  }
>
>  void helper_shutdown(void)
> diff --git a/target-sparc/translate.c b/target-sparc/translate.c
> index b30003b..a47a2de 100644
> --- a/target-sparc/translate.c
> +++ b/target-sparc/translate.c
> @@ -2009,14 +2009,7 @@ static void disas_sparc_insn(DisasContext * dc)
>                     tcg_gen_addi_tl(cpu_dst, cpu_dst, TT_TRAP);
>                     tcg_gen_trunc_tl_i32(cpu_tmp32, cpu_dst);
>
> -                    if (rs2 == 0 &&
> -                        dc->def->features & CPU_FEATURE_TA0_SHUTDOWN) {
> -
> -                        gen_helper_shutdown();
> -
> -                    } else {
> -                        gen_helper_trap_always(cpu_tmp32);
> -                    }
> +                    gen_helper_trap_always(cpu_tmp32);

No, this would actually be just opposite to how QEMU works.
Performance comes from doing more work at translation time in order to
save time during executing the generated code.