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Re: [PATCH] x86-64: Optimize strcat/strncat, strcpy/strncpy and stpcpy/stpncpy with AVX2

From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
To: libc-alpha at sourceware dot org
Date: Wed, 31 Oct 2018 15:36:10 -0300
Subject: Re: [PATCH] x86-64: Optimize strcat/strncat, strcpy/strncpy and stpcpy/stpncpy with AVX2
References: <20181008135950.9113-1-leonardo.sandoval.gonzalez@linux.intel.com>



> diff --git a/sysdeps/x86_64/multiarch/strcat-avx2.S b/sysdeps/x86_64/multiarch/strcat-avx2.S
> new file mode 100644
> index 00000000000..b0623564276
> --- /dev/null
> +++ b/sysdeps/x86_64/multiarch/strcat-avx2.S
> @@ -0,0 +1,275 @@
> +/* strcat with AVX2

Is this really a gain on real work usage comparing to generic strcat (
(strcpy (dest + strlen (dest), src)) assuming optimized strcpy / strlen?
Wouldn't be simple and more i-cache friendly to use a custom generic 
implementation that calls AVX2 strcpy/strlen (such as powerpc64 does)?

Follow-Ups:
- Re: [PATCH] x86-64: Optimize strcat/strncat, strcpy/strncpy and stpcpy/stpncpy with AVX2
  - From: Rich Felker
- Re: [PATCH] x86-64: Optimize strcat/strncat, strcpy/strncpy and stpcpy/stpncpy with AVX2
  - From: Leonardo Sandoval

References:
- [PATCH] x86-64: Optimize strcat/strncat, strcpy/strncpy and stpcpy/stpncpy with AVX2
  - From: leonardo . sandoval . gonzalez

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