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

[H.J. Lu]

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]
>>
>>     If assembler doesn't support AVX512DQ, _dl_runtime_resolve_avx is used
>>     to save the first 8 vector registers, which only saves the lower 256
>>     bits of vector register, for lazy binding.  When it is called on
>> AVX512
>>     platform, the upper 256 bits of ZMM registers are clobbered.
>> Parameters
>>     passed in ZMM registers will be wrong when the function is called the
>>     first time.  This patch requires binutils 2.24, whose assembler can
>> store
>>     and load ZMM registers, to build x86-64 glibc.  Since mathvec library
>>     needs assembler support for AVX512DQ,  we disable mathvec if assembler
>>     doesn't support AVX512DQ.
>
>
> That's not really backportable, I'm afraid.  Our users don't expect we break
> builds in this way.
>

Who are those users?


-- 
H.J.