Re: [PATCH 0/4] target/s390x: CC fixes

[David Hildenbrand]

On 03.11.23 17:44, Ilya Leoshkevich wrote:
> On Tue, 2023-10-31 at 09:38 +0100, David Hildenbrand wrote:
> > On 31.10.23 06:32, Ilya Leoshkevich wrote:
> > > Hi,
> > >
> > > This series fixes two issues with updating CC. David was suggesting
> > > a
> > > bigger rewrite [1], but I did not dare do this (yet). Instead,
> > > these
> >
> > I started coding that up but was distracted by other things; last
> > time I
> > looked at that, I concluded that the way we are calculating the carry
> > in
> > not suitable when we're doing two additions (like ADD LOGICAL WITH
> > CARRY).
>
> Do you per chance remember any details? IIUC the code in question is:

Unfortunately, I don't. I thought there would be a case where we could 
overflow twice, and result in a carry value of 2. Or some other weird 
corner case where the result would not be expressive.

Maybe I was daydreaming, let me see if I can re-discover what I found 
(should have taken notes but was just briefly looking at this).

If not, your fixes might be just good enough.

--
Cheers,

David / dhildenb