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Re: [PATCH] X86-64: Add _dl_runtime_resolve_avx[512]_opt [BZ #20508]
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 4 Oct 2016 18:18:27 -0300
- Subject: Re: [PATCH] X86-64: Add _dl_runtime_resolve_avx[512]_opt [BZ #20508]
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- References: <CAMe9rOojpuFz1jTbMpNcqZK1KVDqaWozNuEuS3E67dvD3Rh=hw@mail.gmail.com> <CAMe9rOo7MmGNPKct=AzzbtR564yH1P96tUcLD7pFv7GtxF3-Ng@mail.gmail.com> <48eeea78-99e8-f255-bd26-b6d28929b4f0@twiddle.net> <CAMe9rOqXhVLVbT90JBfkJnCLzZBrkUHtkO4Ddfk9HPH7jiyEzw@mail.gmail.com> <CAMe9rOoDp7XYwLdDetFNghAdDo_zj-4342LKV4i0zCH36aBWtw@mail.gmail.com> <CAMe9rOo+_TQABBp0eC4nQcJ5ENLrZAOSvtAjo17E6H0ezDpWvg@mail.gmail.com> <CAMe9rOqoATTPzXqjtqenV0h+hMtMYcr+W-ZL3Bi4jFJWYBCUpg@mail.gmail.com> <76f9e5c1-d1de-04d1-49f5-30673bf3060b@redhat.com> <CAMe9rOq8yu+b0-N6UR3vb843NApZ+ZjBwAw5GsERHpvuCrVjrw@mail.gmail.com> <14cc7a47-1a39-6285-d4b5-dab2769c092b@redhat.com> <CAMe9rOrqmLmHLhHL7pDSvR=8=dUUGP07zY5A3DiOubtpvR25WQ@mail.gmail.com> <ea7fe73f-b8cb-6049-d4c4-918d724bd883@redhat.com> <CAMe9rOqxqffhZAb1Sj-qxg_1oU0J=0v7rvhoXVbjbJrrthHucg@mail.gmail.com> <b8e16aaf-146b-7b20-4f35-a9fa0af2e042@linaro.org> <CAMe9rOqbn6UstHwhVwXDapOZvdkEKd7QS5Jjc4pcKb7o3J=4oA@mail.gmail.com>
On 04/10/2016 18:00, H.J. Lu wrote:
> On Tue, Oct 4, 2016 at 11:13 AM, Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>> 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.
>
> It is a regression from glibc 2.22.
Right, but it is functional regression that prevent avx512 binaries to run
correctly on glibc 2.23+ or a performance regression?