[PATCH] X86-64: Add _dl_runtime_resolve_avx[512]_opt [BZ #20508]

[Adhemerval Zanella]

On 04/10/2016 13:08, H.J. Lu wrote:
> On Tue, Oct 4, 2016 at 8:48 AM, Florian Weimer <fweimer@redhat.com> wrote:
>> On 10/04/2016 05:34 PM, H.J. Lu wrote:
>>>
>>> On Tue, Oct 4, 2016 at 8:24 AM, Florian Weimer <fweimer@redhat.com> wrote:
>>>>
>>>> On 10/04/2016 04:47 PM, H.J. Lu wrote:
>>>>>
>>>>>
>>>>> On Tue, Oct 4, 2016 at 3:52 AM, Florian Weimer <fweimer@redhat.com>
>>>>> wrote:
>>>>>>
>>>>>>
>>>>>> On 09/27/2016 07:35 PM, H.J. Lu wrote:
>>>>>>
>>>>>>>> Any comments? I will check it in next week if there is no objection.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> I'd like to backport it to 2.23 and 2.24 branches.  Any objections?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Just this change, or the requirement for an AVX512F-capable assembler
>>>>>> as
>>>>>> well?
>>>>>>
>>>>>
>>>>> Good question.  This is also needed:
>>>>>
>>>>> commit f43cb35c9b3c35addc6dc0f1427caf51786ca1d2
>>>>> Author: H.J. Lu <hjl.tools@gmail.com>
>>>>> Date:   Fri Jul 1 05:54:43 2016 -0700
>>>>>
>>>>>     Require binutils 2.24 to build x86-64 glibc [BZ #20139]
>>
>>
>>>> That's not really backportable, I'm afraid.  Our users don't expect we
>>>> break
>>>> builds in this way.
>>>>
>>>
>>> Who are those users?
>>
>>
>> We don't know, really.  But moving forward the baseline binutils requirement
>> in a stable release really contradicts what a stable release is about.
>>
>>
> 
> Do our users expect a broken glibc binary of a stable release on AVX512
> machine?
> 

I think 2.24 it is ok since it contains the BZ#20139 fix already.  For 2.23,
although it was not really explicit in NEWS, AVX512 is suppose to be supported
in a set of different implementation (memmove/memcpy/libmvec).  However my
understanding of this issue is limited to be a performance one, so I do not
see a pressing matter to change a release requirements for such change.