Re: [PATCH v3] wcrtomb: Make behavior POSIX compliant

[Siddhesh Poyarekar <siddhesh@sourceware.org>]

On 13/05/2022 17:08, Florian Weimer via Libc-alpha wrote:
> * Siddhesh Poyarekar:
> 
>> On 13/05/2022 10:58, Paul Eggert wrote:
>>> On 5/12/22 21:56, Paul Eggert wrote:
>>>> Hope you don't mind my bikeshedding.
>>> Better yet, this:
>>>     s[0] = buf[0];
>>>     if (2 <= result && result <= 4)
>>>       {
>>>         s[1] = buf[1];
>>>         memcpy (&s[result - 2], &buf[result - 2], 2);
>>>       }
>>>     else
>>>       memcpy (s, buf, result);
>>> On x86-64 with GCC 12.1 -O2 and a glibc-supplied charmap, this is
>>> only 9 straight-line instructions, counting the compare insn and the
>>> conditional-branch insn that is never taken.
>>>
>>
>> Sorry I missed this one.  I tried it and with gcc 11 it seems to
>> produce worse code, merging the two memcpys instead of inlining the
>> first one.
> 
> Can we please use the simplified code?

So just a memcpy call?  I could push that and attempt to micro-optimize 
if there are reports of slowdown due to this.

Siddhesh