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From: Florian Weimer <fw@deneb.enyo.de>
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: "H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>,  Noah Goldstein
 <goldstein.w.n@gmail.com>,  GCC Development <gcc@gcc.gnu.org>,  Arjan van
 de Ven <arjan@linux.intel.com>
Subject: Re: [PATCH] x86-64: Optimize memset for zeroing
References: <20211231182010.107040-1-hjl.tools@gmail.com>
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Date: Fri, 31 Dec 2021 22:02:45 +0100
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 (H. J. Lu's message of "Fri, 31 Dec 2021 12:52:52 -0800")
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* H. J. Lu:

> On Fri, Dec 31, 2021 at 12:43 PM Florian Weimer <fw@deneb.enyo.de> wrote:
>>
>> * H. J. Lu via Libc-alpha:
>>
>> > bzero is an alias of SSE2 memset in glibc.   Should we add __memsetzero
>> > like __memcmpeq?  It should be almost free in glibc.  GCC can use
>> > __memsetzero if it is available.
>>
>> bzero does not have the interface ambiguity that bcmp has.  So the
>> only reason for not using it would be namespace cleanliness.
>
> bzero isn't a standard C function and it isn't optimized like memset
> in glibc.

GCC already uses non-standard functions whose names are not
implementation-defined for optimization purposes if a suitable
prototype is available.  stpcpy is an example, for:

  strcpy (a, b);
  return a + strlen (a);