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

[H.J. Lu]

On Wed, Aug 24, 2016 at 3:55 AM, Florian Weimer <fweimer@redhat.com> wrote:
> On 08/23/2016 11:53 PM, H.J. Lu wrote:
>>
>> Tested on x86-64 with/without AVX/AVX512.  OK for master?
>
>
> Is this supposed to address a performance issue in actually shipping
> silicon?

We only see this performance issue with SSE AES instructions on
AVX512 machines with XGETBV (ECX == 1) and my patch fixes it.
Other AVX machines and other SSE instructions are OK.

> It seems there are implementations out there which support AVX-512F and
> XSAVEOPT, but not the XGETBV functionality required by this patch.

Knights Landing doesn't have this performance issue.

-- 
H.J.