Re: [PATCH 09/14] target/s390x: Raise exception from helper_per_branch

[Richard Henderson]

On 5/22/24 15:45, Ilya Leoshkevich wrote:
> On Wed, 2024-05-01 at 22:44 -0700, Richard Henderson wrote:
> > Drop from argument, since gbea has always been updated with
> > this address.  Add ilen argument for setting int_pgm_ilen.
> > Use update_cc_op before calling per_branch.
> >
> > By raising the exception here, we need not call
> > per_check_exception later, which means we can clean up the
> > normal non-exception branch path.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> >   target/s390x/helper.h          |  2 +-
> >   target/s390x/tcg/misc_helper.c | 15 +++++++----
> >   target/s390x/tcg/translate.c   | 48 ++++++++++++--------------------
> > --
> >   3 files changed, 27 insertions(+), 38 deletions(-)
>
> [...]
>
> >   static bool use_goto_tb(DisasContext *s, uint64_t dest)
> >   {
> > -    if (unlikely(s->base.tb->flags & FLAG_MASK_PER_BRANCH)) {
> > -        return false;
> > -    }
>
> Why was this required in the first place and why can we remove it now?

This was required because of the structure of the code: the PER exception was only raised 
from translate_one, and therefore we could not allow the TB to end beforehand with goto_tb.

We can eliminate this now because we're raising the PER branch exception before attempting 
goto_tb.


r~