Re: [PATCH 5/7] target/hppa: copy new_spc to iasq_f on be,n instruction

[Richard Henderson]

On 3/17/24 12:14, Sven Schnelle wrote:
> Otherwise the first instruction at the new location gets executed from
> the old space.
>
> Signed-off-by: Sven Schnelle <svens@stackframe.org>
> ---
>   target/hppa/translate.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/target/hppa/translate.c b/target/hppa/translate.c
> index 58d7ec1ade..a09112e4ae 100644
> --- a/target/hppa/translate.c
> +++ b/target/hppa/translate.c
> @@ -3777,6 +3777,9 @@ static bool trans_be(DisasContext *ctx, arg_be *a)
>           }
>           copy_iaoq_entry(ctx, cpu_iaoq_b, -1, tmp);
>           tcg_gen_mov_i64(cpu_iasq_b, new_spc);
> +        if (a->n) {
> +            tcg_gen_mov_i64(cpu_iasq_f, new_spc);
> +        }
>           nullify_set(ctx, a->n);
>       }
>       tcg_gen_lookup_and_goto_ptr();


Without use_nullify_skip(), we're going to execute the next instruction even if we know it 
is nullified (a->n).  This is usually because there's a page crossing or breakpoint, and 
we need to take the exception that might be raised there.

So, we advance the queue:

        copy_iaoq_entry(ctx, cpu_iaoq_f, ctx->iaoq_b, cpu_iaoq_b);
        if (ctx->iaoq_b == -1) {
            tcg_gen_mov_i64(cpu_iasq_f, cpu_iasq_b);
        }

then put the branch destination at the back of the queue:

        copy_iaoq_entry(ctx, cpu_iaoq_b, -1, tmp);
        tcg_gen_mov_i64(cpu_iasq_b, new_spc);

Note that iaoq_b is always -1 on a space change.

So your change does not look correct.
What is the issue that you saw?


r~