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

[Eli Schwartz]

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.
```

-- 
Eli Schwartz
Bug Wrangler and Trusted User

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