[arch-dev-public] ON HOLD - RFC: Use x86_64-v2 architecture

[Allan McRae]

On 13/3/21 6:47 am, Eli Schwartz via arch-dev-public wrote:
> On 3/4/21 6:33 AM, Allan McRae via arch-dev-public wrote:
>> On 3/3/21 10:54 am, Allan McRae via arch-dev-public wrote:
>>> On 2/3/21 9:51 pm, Allan McRae wrote:
>>>> Hi all,
>>>>
>>>> A new RFC has been opened here:
>>>> https://gitlab.archlinux.org/archlinux/rfcs/-/merge_requests/2
>>>>
>>>> Summary:
>>>> Make -march=x86_64-v2 the default for our packages.  This assumes the
>>>> following instruction sets which are essentially available on all but
>>>> the oldest AMD CPUs:
>>>>
>>>> CMPXCHG16B, LAHF-SAHF, POPCNT, SSE3, SSE4.1, SSE4.2, SSSE3
>>>>
>>>> Please visit the above link for discussion.
>>
>> Lets put discussion on this RFC on hold for a while.  Clearly there is a
>> reasonable amount of objection to making x86-64-v2 the default.  While
>> this mostly appears to be objection based on personal circumstances and
>> not on the basis of whether this change is good for the distro, I will
>> work within these limits.
>>
>> A lot of comments have suggested adding x86-64-v2 and -v3 as additional
>> architectures instead.  I will revamp the the proposal to take that
>> approach.  Though, to do this automated would require more work it may
>> be the push we need for a signing enclave to be set up.
> 
> 
> For the record -- the RFC has now been revamped. The new form of the
> proposal is to add a -v3 (skipping right over -v2) additional architecture.
> 
> ```
> Alternatives Considered
> -----------------------
> 
> Moving the baseline to x86-64-v2 was discussed, but the gains were not
> considered enough to justify removal of support for hardware without
> SSE4.2.
> ```

As an FYI - I'm still working on the RFC update.   I forgot that pushing
to my branch updated the merge request...

I'll post a new RFC on the mailing list once it is ready for comment.
People are of course free to comment as I work on it so it is in better
shape once it is submitted.

Allan