[llvm-dev] Should we have a "GPU working group"?

Thu Nov 11 10:53:13 PST 2021

+1

On Thu, Nov 11, 2021 at 10:51 AM Artem Belevich via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> +cc: yaxun.liu at amd.com for HIP.
>
> Also, count me in.
>
> On Thu, Nov 11, 2021 at 10:32 AM Quentin Colombet via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> +1, count me in.
>>
>> Cheers,
>> -Quentin
>>
>> On Nov 11, 2021, at 10:22 AM, Jason Eckhardt via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> +1 here as well, even if in lurk mode initially.
>>
>> Some additional topics of interest:
>>
>>    1. *Occupancy vs resource trade-offs (especially registers)*.
>>    Requires closer coordination of scheduling + register allocation, in
>>    addition to extensions in each.
>>    2. *Divergence analysis/uniformity analysis*. Applications to sync
>>    insertion, scalar vs vector register allocation, instruction selection, etc.
>>    3. *Synchronization insertion*. Some GPUs have instructions to hint
>>    where a good re-convergence point is.
>>    4. *Global instruction scheduling*. Some GPU code is surprisingly
>>    branchy. Numerous out-of-tree/proprietary global schedulers have been
>>    written, we *still* don't have one upstream.
>>    5. I*ncreasing overall back-end speed for JIT compilation*. GPU
>>    back-ends are often situated within graphics drivers where they dynamically
>>    compile shaders with absurdly stringent timing constraints. GlobalISel is a
>>    step in the right direction, but more needs doing (particularly for small
>>    shaders).
>>
>> As an example, #1 is handled (if at all) specially by each target. With
>> the proliferation of GPUs (Teams Red, Green, Blue, and others), it would be
>> useful for "all boats to float higher" with generic code (with
>> target-specific hooks/overrides) supported by the wider community as
>> opposed to redundant re-invention of the wheel (or no wheel at all, as in
>> #4). Then specific targets can expend effort adding value for their
>> particular needs.
>>
>> ------------------------------
>> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Lei
>> Zhang via llvm-dev <llvm-dev at lists.llvm.org>
>> *Sent:* Thursday, November 11, 2021 9:44 AM
>> *To:* Valentin Churavy <v.churavy at gmail.com>
>> *Cc:* Lieberman, Ron <Ron.Lieberman at amd.com>; justin.lebar at gmail.com <
>> justin.lebar at gmail.com>; Chesterfield, Jonathan <
>> Jonathan.Chesterfield at amd.com>; llvm-dev at lists.llvm.org <
>> llvm-dev at lists.llvm.org>; tianshilei1992 at gmail.com <
>> tianshilei1992 at gmail.com>; Rodgers, Gregory <Gregory.Rodgers at amd.com>;
>> Huber, Joseph <huberjn at ornl.gov>; Narayanaswamy, Ravi <
>> ravi.narayanaswamy at intel.com>
>> *Subject:* Re: [llvm-dev] Should we have a "GPU working group"?
>>
>> *External email: Use caution opening links or attachments*
>> +1. There are certainly efforts that need broad collaboration among
>> various interest parties; they would benefit from more interactive
>> discussions to have everybody on the same page. What immediately jumps into
>> my mind include how we can push to have unified/better SPIR-V support in
>> LLVM proper / cross LLVM/MLIR, etc. It's a big one that I'd assume will
>> take a long time to unfold and will have back and forth. Having a place to
>> discuss will actually make sure we put efforts towards it (or at least have
>> plans and revisit periodically). There are certainly many other topics to
>> discuss too, as said by Johannes. I think this is a great idea.
>>
>> Thanks,
>> Lei
>>
>>
>> On Wed, Nov 10, 2021 at 4:03 PM Valentin Churavy via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> I would certainly be interested in joining such an effort.
>>
>> -V
>>
>> On Wed, Nov 10, 2021 at 3:56 PM Johannes Doerfert via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> Hey,
>>
>> We nowadays have various "working groups" that meet regularly to discuss
>> technical topics (incl. RISC-V, MLIR, OpenMP, Alias Analysis, ML, Flang,
>> ...).
>> It's a reasonably nice way for people to connect and present ideas, get
>> feedback, etc. in an interactive environment.
>> While the OpenMP meeting has a strong emphasis on offloading, we do not
>> meet to discuss "generic GPU" topics as a community.
>>
>> This email is to determine if people would be interested in meeting once
>> every N weeks (initially we could say 2) to coordinate efforts in this
>> space, e.g., development of GPU-specific optimizations, organization of
>> driver and backend code, dealing with issues like convergent functions,
>> ...
>>
>> I CC'ed a bunch of people that might want to join such a meeting but
>> certainly this is something everyone would be invited to and I hope
>> people forward this to parties that might not read llvm-dev.
>>
>> Looking forward to hear what people think :)
>>
>> ~ Johannes
>>
>>
>>
>>
>> --
>> ───────────────────
>> ∽ Johannes (he/his)
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.llvm.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fllvm-dev&data=04%7C01%7Cjeckhardt%40nvidia.com%7Cea5003810a644cc981b308d9a52a252b%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637722422720796637%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Wqe0548FXifuicYy39N8YafF3IUqZaATKgAYHctuPv4%3D&reserved=0>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>> <https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.llvm.org%2Fcgi-bin%2Fmailman%2Flistinfo%2Fllvm-dev&data=04%7C01%7Cjeckhardt%40nvidia.com%7Cea5003810a644cc981b308d9a52a252b%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637722422720806639%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=5ygaPNgaF5YXRlFV1wF9VajRsEZsySt7z2OCHokcHBc%3D&reserved=0>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
>
> --
> --Artem Belevich
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20211111/4edb0288/attachment.html>