Re: [PATCH v2 2/3] target/arm: Fix SVE2 WHILEWR/WHILERW zero diff boundary case

On Tue, 18 Aug 2026 at 10:29, Peter Maydell <[email protected]> wrote:
>
> On Mon, 17 Aug 2026 at 23:34, Richard Henderson
> <[email protected]> wrote:
> >
> > On 8/17/26 09:37, Peter Maydell wrote:
> > >> +    tcg_gen_addi_i64(diff, diff, -1);
> > >> +    tcg_gen_umin_i64(diff, diff, tcg_constant_i64((vsz >> a->esz) - 1));
> > >> +
> > >> +    /*
> > >> +     * Since we're bounded, pass as a 32-bit type.
> > >> +     * Sink the diff += 1 from above into the 32-bit type.
> > >
> > > Is it worth doing that? Hosts are all 64-bits now, and surely there's
> > > not going to be a perf or codesize difference between "add 1"
> > > on a 32-bit type vs a 64-bit type ?
> > Technically one byte difference on x86_64.
> > But we could drop the whole truncation thing it you like.
>
> I think mostly my feeling was that since the rearrangement of the
> umin() expressions above was already quite complicated, moving
> the last part of that down into the truncate-to-32-bits was
> adding extra complexity on top. Just doing the subtract-one in
> 64 bits and keeping the truncate would be fine, as then the
> two steps aren't interleaved with each other.

...but thinking more about it I don't think it's worth respinning
the series just for this, so I've added it to target-arm.next
(with some cc:stable tags).

-- PMM