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

["H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>]

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.

> $> 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.