[PATCH] x86-64: Optimize memset for zeroing

[Florian Weimer]

* 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);