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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: libc-alpha at sourceware dot org
- Date: Tue, 4 Oct 2016 12:18:10 -0300
- Subject: Re: [PATCH] X86-64: Add _dl_runtime_resolve_avx[512]_opt [BZ #20508]
- Authentication-results: sourceware.org; auth=none
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On 04/10/2016 11:47, 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.
This is ok for 2.23 and 2.24.