[PATCH v1 3/3] x86: Add sse42 implementation to strcmp's ifunc

[H.J. Lu]

On Tue, Jun 14, 2022 at 5:25 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> This has been missing since the the ifuncs where added.
>
> The performance of SSE4.2 is preferable to to SSE2.
>
> Measured on Tigerlake with N = 20 runs.
> Geometric Mean of all benchmarks SSE4.2 / SSE2: 0.906
> ---
>  sysdeps/x86_64/multiarch/strcmp.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/sysdeps/x86_64/multiarch/strcmp.c b/sysdeps/x86_64/multiarch/strcmp.c
> index a248c2a6e6..9c1677724c 100644
> --- a/sysdeps/x86_64/multiarch/strcmp.c
> +++ b/sysdeps/x86_64/multiarch/strcmp.c
> @@ -28,6 +28,7 @@
>
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (sse2_unaligned) attribute_hidden;
> +extern __typeof (REDIRECT_NAME) OPTIMIZE (sse42) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (avx2_rtm) attribute_hidden;
>  extern __typeof (REDIRECT_NAME) OPTIMIZE (evex) attribute_hidden;
> @@ -52,6 +53,10 @@ IFUNC_SELECTOR (void)
>         return OPTIMIZE (avx2);
>      }
>
> +  if (CPU_FEATURE_USABLE_P (cpu_features, SSE4_2)
> +      && !CPU_FEATURES_ARCH_P (cpu_features, Slow_SSE4_2))
> +    return OPTIMIZE (sse42);
> +
>    if (CPU_FEATURES_ARCH_P (cpu_features, Fast_Unaligned_Load))
>      return OPTIMIZE (sse2_unaligned);
>
> --
> 2.34.1
>

LGTM.

Thanks.

-- 
H.J.