[llvm-dev] Scalable Vector Types in IR - Next Steps?

[Finkel, Hal J. via llvm-dev]

On 3/13/19 9:29 AM, Renato Golin wrote:
> On Wed, 13 Mar 2019 at 13:57, Graham Hunter <Graham.Hunter at arm.com> wrote:
>> I did ask them to post their arguments on the list, but I guess they've been busy for the last month (or forgot about it).
> Who is "them" and who will write up a proposal / RFC on the use of
> intrinsics for both lowering and vectorisation?
>
> It goes without saying that those discussions should have been had in
> the mailing list, not behind closed doors.


Renato, I understand your frustration, but I don't want an unproductive
conclusion to be drawn. We should encourage our community members to
talk to each other both on the mailing list and off the mailing list. We
have in-person discussions at the developers' meetings, and my
experience is that sitting in a room with someone, or sometimes talking
with someone over the phone, can really help reach a mutual
understanding more effectively than mailing-list communication. However,
the critical step is that the outcome of that conversation should be
summarized, in a timely manner, for the mailing list (or put in the
relevant code review, bug report, etc.) so that the rest of us can
provide input.

>  Agreeing to implementations
> in private is asking to get bad reviews in public


+1

 -Hal


> , as the SVE process
> has shown *over and over again*.
>
> I don't understand why, after so many problems for so many years, this
> is still the modus operandi...
>
>> The basic argument was that they didn't believe the value gained from enabling VLA autovectorization was worth the added complexity in maintaining the codebase. They were open to changing their minds if we could demonstrate sufficient demand for the feature.
> In that case, the current patches to change the IR should be
> abandoned, as well as reverting the previous change to the types, so
> that we don't carry any unnecessary code forward.
>
> The review you sent seems to be a mechanical change to include the
> intrinsics, but the target lowering change seems to be too small to
> actually be able to lower anything.
>
> Without context, it's hard to know what's going on.
>
> cheers,
> --renato

-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory