Re: [PATCH 15/27] target/s390x: Use tcg_gen_qemu_{ld,st}_i128 for LPQ, STPQ

[David Hildenbrand <david@redhat.com>]

On 20.05.23 18:26, Richard Henderson wrote:
> No need to roll our own, as this is now provided by tcg.
> This was the last use of retxl, so remove that too.

That's nice!

> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> Cc: qemu-s390x@nongnu.org
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Ilya Leoshkevich <iii@linux.ibm.com>
> ---

[...]

>       /* psw.addr */
> @@ -3130,15 +3125,9 @@ static DisasJumpType op_lpd(DisasContext *s, DisasOps *o)
>   
>   static DisasJumpType op_lpq(DisasContext *s, DisasOps *o)
>   {
> -    if (!(tb_cflags(s->base.tb) & CF_PARALLEL)) {
> -        gen_helper_lpq(o->out, cpu_env, o->in2);
> -    } else if (HAVE_ATOMIC128) {
> -        gen_helper_lpq_parallel(o->out, cpu_env, o->in2);
> -    } else {
> -        gen_helper_exit_atomic(cpu_env);
> -        return DISAS_NORETURN;
> -    }
> -    return_low128(o->out2);
> +    o->out_128 = tcg_temp_new_i128();
> +    tcg_gen_qemu_ld_i128(o->out_128, o->in2, get_mem_index(s),
> +                         MO_TE | MO_128 | MO_ALIGN);
>       return DISAS_NEXT;
>   }
>   
> @@ -4533,14 +4522,11 @@ static DisasJumpType op_stmh(DisasContext *s, DisasOps *o)
>   
>   static DisasJumpType op_stpq(DisasContext *s, DisasOps *o)
>   {
> -    if (!(tb_cflags(s->base.tb) & CF_PARALLEL)) {
> -        gen_helper_stpq(cpu_env, o->in2, o->out2, o->out);
> -    } else if (HAVE_ATOMIC128) {
> -        gen_helper_stpq_parallel(cpu_env, o->in2, o->out2, o->out);
> -    } else {
> -        gen_helper_exit_atomic(cpu_env);
> -        return DISAS_NORETURN;
> -    }
> +    TCGv_i128 t16 = tcg_temp_new_i128();
> +
> +    tcg_gen_concat_i64_i128(t16, o->out2, o->out);
> +    tcg_gen_qemu_st_i128(t16, o->in2, get_mem_index(s),
> +                         MO_TE | MO_128 | MO_ALIGN);

I briefly glimpsed at tcg_gen_qemu_ld_i128_int (and 
use_two_i64_for_i128()), does this really provide the atomic guarantees 
we need in all cases?

-- 
Thanks,

David / dhildenb