Re: [PATCH v2] x86-64: AVX2 Optimize strcat/strcpy/stpcpy routines

[Florian Weimer <fweimer at redhat dot com>]

* Leonardo Sandoval:

> On Thu, 2018-12-06 at 10:05 +0100, Florian Weimer wrote:
>> * leonardo sandoval gonzalez:
>> 
>> > Optimize strcat/strcpy/stpcpy routines and its max-offset versions
>> > with
>> > AVX2. It uses vector comparison as much as possible. Observed
>> > speedups
>> > compared to sse2_unaligned:
>> 
>> Shouldn't we keep the stpcpy specialization from the original
>> patch?  Or
>> at least call the new strcpy from a wrapper function?  The generic
>> function uses strlen plus memcpy, which I believe is slower than
>> calling
>> strcpy and recomputing the return value.
>
> benchmarks numbers between old and new are basically the same, so I
> rather stick with this version. The latter applies also so str?cat.
>
>> 
>> How does this new strcpy compare against the old one for short
>> strings?
>
> strcpy did not change between versions, so we have the same numbers.
> strcpy code density was decrease considerably on this version because
> all preprocessor macros for non-strcpy functions were removed but
> strcpy code remains the same.

Okay, the question then is: Why not use strlen + memcpy for strcpy, too?

Thanks,
Florian