RFC: Rewrite x86-64 IFUNC selector in C

[Erich Elsen]

Here's a patch for memcmp.

I haven't investigated that.  I don't think I understand the implications.

On Wed, Jun 7, 2017 at 3:21 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Jun 7, 2017 at 1:39 PM, Erich Elsen <eriche@google.com> wrote:
>> Here's a patch that also moves memset.S to memset.c.
>
> I integrated your patch into hjl/ifunc/c branch.  Thanks.
>
> BTW, have you investigated using IFUNC internally in libc,so?
>
>> On Tue, May 30, 2017 at 1:32 PM, Adhemerval Zanella
>> <adhemerval.zanella@linaro.org> wrote:
>>>
>>>
>>> On 30/05/2017 17:13, H.J. Lu wrote:
>>>> On Tue, May 30, 2017 at 12:50 PM, Adhemerval Zanella
>>>> <adhemerval.zanella@linaro.org> wrote:
>>>>>
>>>>>
>>>>> On 30/05/2017 13:24, H.J. Lu wrote:
>>>>>> On Mon, May 29, 2017 at 1:34 PM, Adhemerval Zanella
>>>>>> <adhemerval.zanella@linaro.org> wrote:
>>>>>>>
>>>>>>> I think we can simplify it further and use the already existent ifunc macros on
>>>>>>> libc-symbols.h.  Also, for memmove I think we can organize the code better (at
>>>>>>> least for ifunc) and build a extra object with a more meaningful name.  I used
>>>>>>> your logic for the ifunc selection and extended for memmove as well.
>>>>>>>
>>>>>> Here is the combined patch.
>>>>>
>>>>>
>>>>>> diff --git a/sysdeps/x86_64/multiarch/Makefile b/sysdeps/x86_64/multiarch/Makefile
>>>>>> index 3736f54..8a6ff00 100644
>>>>>> --- a/sysdeps/x86_64/multiarch/Makefile
>>>>>> +++ b/sysdeps/x86_64/multiarch/Makefile
>>>>>> @@ -19,6 +19,7 @@ sysdep_routines += strncat-c stpncpy-c strncpy-c strcmp-ssse3 \
>>>>>>                  strchr-sse2-no-bsf memcmp-ssse3 strstr-sse2-unaligned \
>>>>>>                  strcspn-c strpbrk-c strspn-c varshift \
>>>>>>                  memset-avx512-no-vzeroupper \
>>>>>> +                memmove-sse2-unaligned-erms \
>>>>>
>>>>> I still think this is a misleading name file since it build not only memmove but
>>>>> also memcpy and mempcpy implementations.  I would prefer to rename to a more
>>>>> general name as in my suggestion.
>>>>
>>>> I'd like to keep it consistent with memmove-avx-unaligned-erms.S and
>>>> memmove-avx512-unaligned-erms.S.   As for making memcpy an alias
>>>> of memmove, and embedding mempcpy, __memcpy_chk,
>>>> __mempcpy_chk, __memmove_chk is an implementation detail.
>>>>
>>>
>>> Alright, at least I think it should add some comments that the object
>>> is building multiple symbols (it wasn't clear when I started to work
>>> on the patch).
>
>
>
> --
> H.J.
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