[PATCH v1 12/23] x86: Fix fallback for wcsncmp_avx2 in strcmp-avx2.S [BZ #28896]

[Noah Goldstein]

On Thu, Mar 24, 2022 at 2:34 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Mar 24, 2022 at 12:18 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > On Thu, Mar 24, 2022 at 2:00 PM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >
> > > On Wed, Mar 23, 2022 at 3:01 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > > >
> > > > Overflow case for __wcsncmp_avx2_rtm should be __wcscmp_avx2_rtm not
> > > > __wcscmp_avx2.
> > > >
> > > > All string/memory tests pass.
> > > > ---
> > > >  sysdeps/x86_64/multiarch/strcmp-avx2.S | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > > index 52ff5ad724..86a86b68e3 100644
> > > > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > > @@ -122,7 +122,7 @@ ENTRY(STRCMP)
> > > >            are cases where length is large enough that it can never be a
> > > >            bound on valid memory so just use wcscmp.  */
> > > >         shrq    $56, %rcx
> > > > -       jnz     __wcscmp_avx2
> > > > +       jnz     OVERFLOW_STRCMP
> > > >
> > > >         leaq    (, %rdx, 4), %rdx
> > > >  #  endif
> > > > --
> > > > 2.25.1
> > > >
> > >
> > > Isn't it a bug?  Is there a glibc bug? Should this also be fixed on release
> > > branches?
> >
> > It is bug but no need for backport.
>
> Why no need for backport? Is there a testcase?

Oh no, you're right. It needs to be backported. Had thought it was a different
commit that introduced.

Sorry, I'll update the commit message with more info, ping on the bugzilla,
and add a test case.

Going to push the rest of the patchset, will add v2 for this shortly.
>
> --
> H.J.