Libatomic 16B

[Florian Weimer]

* Xi Ruoyao via Gcc-help:

> On Fri, 2022-02-25 at 09:35 +0100, Stefan Ring via Gcc-help wrote:
>> On Thu, Feb 24, 2022 at 9:39 PM Satish Vasudeva via Gcc-help
>> <gcc-help@gcc.gnu.org> wrote:
>> > 
>> > Please let into this intel architecture manual , section 8.1.1
>> > 
>> > https://cdrdv2.intel.com/v1/dl/getContent/671190
>> > 
>> > I think Intel claims 16B operations are atomic , unless I am missing
>> > something.
>> 
>> Interesting. This seems to be a somewhat recent addition, and the
>> mailing list discussion linked to above predates it. Coincidentally, I
>> pulled a copy of the Intel manuals at almost exactly the same time as
>> this discussion, and sure enough, it does not yet contain the
>> paragraph about 16 byte operations.
>
> It seems an addition in Dec 2021 revision:
> https://cdrdv2.intel.com/v1/dl/getContent/671294
>
> Create an issue in bugzilla then?

Yes please.  I should have read the whole thread first. 8-)

The AMD manual doesn't say this yet, so any optimization needs to be
restricted to Intel CPUs for now.  I'll reach out to AMD to get
clarification.

Thanks,
Florian