[PATCH v1] x86: Remove wcsnlen-sse4_1 from wcslen ifunc-impl-list [BZ #28064]

[H.J. Lu]

On Thu, Jul 8, 2021 at 5:21 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Thu, Jul 8, 2021 at 1:22 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > The following commit
> >
> > commit 6f573a27b6c8b4236445810a44660612323f5a73
> > Author: Noah Goldstein <goldstein.w.n@gmail.com>
> > Date:   Wed Jun 23 01:19:34 2021 -0400
> >
> >     x86-64: Add wcslen optimize for sse4.1
> >
> > Added wcsnlen-sse4.1 to the wcslen ifunc implementation list and did
> > not add wcslen-sse4.1 to wcslen ifunc implementation list. This commit
> > fixes that by removing wcsnlen-sse4.1 from the wcslen ifunc
> > implementation list and adding wcslen-sse4.1 to the ifunc
> > implementation list.
> >
> > Testing:
> > test-wcslen.c is passing as well as all other tests in wcsmbs and
> > string.
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> > I was unable to actually reproduce the bug on my machine, even after
> > reordering ifunc-wcslen.h to prefer the sse4.1
> > implementation. Although this most definetly is a bug.
> >
> >
> > I ran the following command. Is there an issue with the command? Or
> > does rdx happen to always have a len >= actual length of the string?
>
> That must be the case.   We can do something similar to
>
> sysdeps/x86_64/x32/tst-size_t-strnlen.c
>
> to write a testcase.

Here is the patch with a testcase.   Please include it in your fix and
mention BZ #28064 in your commit log.

> > $> rm -rf build; mkdir -p build/glibc; (cd build/glibc/; unset LD_LIBRARY_PATH; /absolute/path/to/src/glibc/configure --prefix=/usr; make --silent; make xcheck; make -r -C /absolute/path/to/src/glibc/string/ objdir=`pwd` check; make -r -C /absolute/path/to/src/glibc/wcsmbs/ objdir=`pwd` check);
> >
> >
> >
> >  sysdeps/x86_64/multiarch/ifunc-impl-list.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > index dbd1ebf298..39ab10613b 100644
> > --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c
> > @@ -684,9 +684,9 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
> >                                && CPU_FEATURE_USABLE (AVX512BW)
> >                                && CPU_FEATURE_USABLE (BMI2)),
> >                               __wcslen_evex)
> > -             IFUNC_IMPL_ADD (array, i, wcsnlen,
> > +             IFUNC_IMPL_ADD (array, i, wcslen,
> >                               CPU_FEATURE_USABLE (SSE4_1),
> > -                             __wcsnlen_sse4_1)
> > +                             __wcslen_sse4_1)
> >               IFUNC_IMPL_ADD (array, i, wcslen, 1, __wcslen_sse2))
> >
> >    /* Support sysdeps/x86_64/multiarch/wcsnlen.c.  */
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> --
> H.J.



-- 
H.J.
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