llvm dev - Jul 2020 - [RFC] Proposal for CIRCT incubator project

For the past several months, members of the ‘CIRCT’ group have been working
to begin adapting MLIR for hardware design.  We believe that this area
would benefit from good open source infrastructure enabling research and,
eventually, the next generation of commercial tools.  We have collected
several dialects and envision a number of lowering flows using these
dialects.  We have reached the point where we are ready to share our ideas
more widely and would like to be considered as an LLVM incubator project.
Our code exists at https://github.com/circt as an out-of-tree MLIR project
and our group charter can be found at
https://github.com/circt/circt/blob/master/README.md.   We have weekly
discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
contributions.  This project is still early and we see many elements as
highly experimental.  At the same time, we feel that the only way to vet
these ideas is to build larger systems which will likely take some time and
community investment. The LLVM incubator process would be a good way to
help us organize this effort.

Steve Neuendorffer
Xilinx Research Labs
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Hi, Steve,

I think it would be great to have hardware-synthesis capabilities in the 
LLVM project. The incubation process discussion may be ongoing, but as 
that settles, this seems like a good candidate to me.

Out of curiosity, many existing HLS tools use C/C++-derived input 
languages, and as Clang produces LLVM, do you have any plans for a 
converter between LLVM and your MLIR dialects? Or are you just targeting 
other kinds of frontends?

Thanks again,

Hal

On 7/4/20 5:29 PM, Stephen Neuendorffer via llvm-dev
wrote:
>
> For the past several months, members of the ‘CIRCT’ group have been 
> working to begin adapting MLIR for hardware design.  We believe that 
> this area would benefit from good open source infrastructure enabling 
> research and, eventually, the next generation of commercial tools.  We 
> have collected several dialects and envision a number of lowering 
> flows using these dialects.  We have reached the point where we are 
> ready to share our ideas more widely and would like to be considered 
> as an LLVM incubator project.
> Our code exists at https://github.com/circt 
> <https://github.com/circt>as an out-of-tree MLIR project and our
group
> charter can be found at 
> https://github.com/circt/circt/blob/master/README.md 
> <https://github.com/circt/circt/blob/master/README.md>.   We have 
> weekly discussions with a group of about 20 people from Xilinx, 
> SiFive, Microsoft, PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and 
> welcome additional contributions.  This project is still early and we 
> see many elements as highly experimental.  At the same time, we feel 
> that the only way to vet these ideas is to build larger systems which 
> will likely take some time and community investment. The LLVM 
> incubator process would be a good way to help us organize this effort.
>
> Steve Neuendorffer
> Xilinx Research Labs
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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Thanks Hal,

The front-end question is still a tricky one.  Having a low level CDFG in
MLIR doesnt really offer much and I see rebuilding the clang code generator
to emit loops directly in MLIR as a complex piece of work.  I think the
most natural place to interact with Vivado HLS is towards the backend at
the moment where MLIR could give more points of interaction late in the HLS
flow.  Eventually the community will sort out the front-end questions do
tackling that hasn't been high on my list.  Simply rebuilding HLS flows is
also not necessarily the goal here, although it's a natural place to
start.  From a Xilinx perspective we also have heterogeneous devices with
lots of vector VLIW cores.  Integrating them into an HLS-like flow is also
very interesting.

Steve

On Sun, Jul 5, 2020, 8:28 AM Hal Finkel <hfinkel at anl.gov> wrote:
> Hi, Steve,
>
> I think it would be great to have hardware-synthesis capabilities in the
> LLVM project. The incubation process discussion may be ongoing, but as that
> settles, this seems like a good candidate to me.
>
> Out of curiosity, many existing HLS tools use C/C++-derived input
> languages, and as Clang produces LLVM, do you have any plans for a
> converter between LLVM and your MLIR dialects? Or are you just targeting
> other kinds of frontends?
>
> Thanks again,
>
> Hal
> On 7/4/20 5:29 PM, Stephen Neuendorffer via llvm-dev wrote:
>
>
> For the past several months, members of the ‘CIRCT’ group have been
> working to begin adapting MLIR for hardware design.  We believe that this
> area would benefit from good open source infrastructure enabling research
> and, eventually, the next generation of commercial tools.  We have
> collected several dialects and envision a number of lowering flows using
> these dialects.  We have reached the point where we are ready to share our
> ideas more widely and would like to be considered as an LLVM incubator
> project.
> Our code exists at https://github.com/circt as an out-of-tree MLIR
> project and our group charter can be found at
> https://github.com/circt/circt/blob/master/README.md.   We have weekly
> discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
> PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
> contributions.  This project is still early and we see many elements as
> highly experimental.  At the same time, we feel that the only way to vet
> these ideas is to build larger systems which will likely take some time and
> community investment. The LLVM incubator process would be a good way to
> help us organize this effort.
>
> Steve Neuendorffer
> Xilinx Research Labs
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttps://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
> --
> Hal Finkel
> Lead, Compiler Technology and Programming Languages
> Leadership Computing Facility
> Argonne National Laboratory
>
>
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Hi Hal,

The project is still early and we’ve been working on building out some core
infrastructure.  There are lots of things (including existing synthesis
frontends) that could benefit from this work.  I’d love to see folks interested
in clang integration join the group!

-Chris
> On Jul 5, 2020, at 8:28 AM, Hal Finkel via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi, Steve,
> 
> I think it would be great to have hardware-synthesis capabilities in the
LLVM project. The incubation process discussion may be ongoing, but as that
settles, this seems like a good candidate to me.
> 
> Out of curiosity, many existing HLS tools use C/C++-derived input
languages, and as Clang produces LLVM, do you have any plans for a converter
between LLVM and your MLIR dialects? Or are you just targeting other kinds of
frontends?
> 
> Thanks again,
> 
> Hal
> 
> On 7/4/20 5:29 PM, Stephen Neuendorffer via llvm-dev wrote:
>> 
>> For the past several months, members of the ‘CIRCT’ group have been
working to begin adapting MLIR for hardware design.  We believe that this area
would benefit from good open source infrastructure enabling research and,
eventually, the next generation of commercial tools.  We have collected several
dialects and envision a number of lowering flows using these dialects.  We have
reached the point where we are ready to share our ideas more widely and would
like to be considered as an LLVM incubator project.
>> 
>> Our code exists at https://github.com/circt
<https://github.com/circt> as an out-of-tree MLIR project and our group
charter can be found at https://github.com/circt/circt/blob/master/README.md
<https://github.com/circt/circt/blob/master/README.md>.   We have weekly
discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
contributions.  This project is still early and we see many elements as highly
experimental.  At the same time, we feel that the only way to vet these ideas is
to build larger systems which will likely take some time and community
investment.  The LLVM incubator process would be a good way to help us organize
this effort.
>> 
>> Steve Neuendorffer
>> Xilinx Research Labs   
>> 
>> 
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
<https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
> -- 
> Hal Finkel
> Lead, Compiler Technology and Programming Languages
> Leadership Computing Facility
> Argonne National Laboratory
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Thanks Steve!  The incubator process just landed, it would be great to outline
how CIRCT aligns with the new guidelines set out in that document.  As you know,
I’m personally very much in favor of this project landing, but am also have a
conflict of interest, so I’d like to know what other community members think.

-Chris
> On Jul 4, 2020, at 3:29 PM, Stephen Neuendorffer via llvm-dev <llvm-dev
at lists.llvm.org> wrote:
> 
> 
> For the past several months, members of the ‘CIRCT’ group have been working
to begin adapting MLIR for hardware design.  We believe that this area would
benefit from good open source infrastructure enabling research and, eventually,
the next generation of commercial tools.  We have collected several dialects and
envision a number of lowering flows using these dialects.  We have reached the
point where we are ready to share our ideas more widely and would like to be
considered as an LLVM incubator project.
> 
> Our code exists at https://github.com/circt
<https://github.com/circt> as an out-of-tree MLIR project and our group
charter can be found at https://github.com/circt/circt/blob/master/README.md
<https://github.com/circt/circt/blob/master/README.md>.   We have weekly
discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
contributions.  This project is still early and we see many elements as highly
experimental.  At the same time, we feel that the only way to vet these ideas is
to build larger systems which will likely take some time and community
investment.  The LLVM incubator process would be a good way to help us organize
this effort.
> 
> Steve Neuendorffer
> Xilinx Research Labs   
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Hey Stephen,

I'm very positive on this project joining the incubator. I think extending
the LLVM project support for applying compiler infrastructure and
techniques to hardware design is very interesting!
This is also a fantastic application for MLIR, and it will (and already
did) influence the development of the framework.

Looking forward to this!

-- 
Mehdi



On Sat, Jul 4, 2020 at 3:30 PM Stephen Neuendorffer via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
>
> For the past several months, members of the ‘CIRCT’ group have been
> working to begin adapting MLIR for hardware design.  We believe that this
> area would benefit from good open source infrastructure enabling research
> and, eventually, the next generation of commercial tools.  We have
> collected several dialects and envision a number of lowering flows using
> these dialects.  We have reached the point where we are ready to share our
> ideas more widely and would like to be considered as an LLVM incubator
> project.
> Our code exists at https://github.com/circt as an out-of-tree MLIR
> project and our group charter can be found at
> https://github.com/circt/circt/blob/master/README.md.   We have weekly
> discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
> PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
> contributions.  This project is still early and we see many elements as
> highly experimental.  At the same time, we feel that the only way to vet
> these ideas is to build larger systems which will likely take some time and
> community investment. The LLVM incubator process would be a good way to
> help us organize this effort.
>
> Steve Neuendorffer
> Xilinx Research Labs
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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I'm really looking forward to this/supportive.

On Tue, Jul 7, 2020 at 11:05 AM Mehdi AMINI via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hey Stephen,
>
> I'm very positive on this project joining the incubator. I think
extending
> the LLVM project support for applying compiler infrastructure and
> techniques to hardware design is very interesting!
> This is also a fantastic application for MLIR, and it will (and already
> did) influence the development of the framework.
>
> Looking forward to this!
>
> --
> Mehdi
>
>
>
> On Sat, Jul 4, 2020 at 3:30 PM Stephen Neuendorffer via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>>
>> For the past several months, members of the ‘CIRCT’ group have been
>> working to begin adapting MLIR for hardware design.  We believe that
this
>> area would benefit from good open source infrastructure enabling
research
>> and, eventually, the next generation of commercial tools.  We have
>> collected several dialects and envision a number of lowering flows
using
>> these dialects.  We have reached the point where we are ready to share
our
>> ideas more widely and would like to be considered as an LLVM incubator
>> project.
>> Our code exists at https://github.com/circt as an out-of-tree MLIR
>> project and our group charter can be found at
>> https://github.com/circt/circt/blob/master/README.md.   We have weekly
>> discussions with a group of about 20 people from Xilinx, SiFive,
Microsoft,
>> PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
>> contributions.  This project is still early and we see many elements as
>> highly experimental.  At the same time, we feel that the only way to
vet
>> these ideas is to build larger systems which will likely take some time
and
>> community investment. The LLVM incubator process would be a good way to
>> help us organize this effort.
>>
>> Steve Neuendorffer
>> Xilinx Research Labs
>> _______________________________________________
>> 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
>
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Sure, I'll summarize with respect to the criterion in the document:

   - Must be generally aligned with the mission of the LLVM project to
   advance compilers, languages, tools, runtimes, etc.

CIRCT is a compiler which is built around LLVM/MLIR.  We anticipate
building code generation for ASIC and FPGA backends along with specialized
accelerators, while leveraging existing LLVM backends for processor targets.

   - Must conform to the license, patent, and code of conduct policies laid
   out in this developer policy document.

Contributions are currently ApacheV2 licensed and we have adopted the
general structure of the LLVM developer policies already, to the extent
that we can as an external project.

   - Must have a documented charter and development plan, e.g. in the form
   of a README file, mission statement, and/or manifesto.

See  https://github.com/circt/circt and
https://github.com/circt/circt/blob/master/docs/Charter.md

   - Should conform to coding standards, incremental development process,
   and other expectations.

The project mostly consists of MLIR dialects and transformations following
the MLIR standalone dialect example implemented using c++14 and FileCheck
for regressions.  We are currently using Github PRs for code review and a
nifty CI system that caches the most recent LLVM build for good performance
using github hosted builds.  See  https://github.com/circt/circt

   - Should have a sense of the community that it hopes to eventually
   foster, and there should be interest from members with different
   affiliations / organizations.

We have weekly meetings with >20 people from Xilinx, Sifive, Microsoft,
PNNL, ETH, EPFL, Cornell, and Stanford.  Meeting minutes are here:
https://docs.google.com/document/d/1fOSRdyZR2w75D87yU2Ma9h2-_lEPL4NxvhJGJd-s5pk/edit#


   - Should have a feasible path to eventually graduate as a dedicated
   top-level or sub-project within the LLVM monorepo
   <https://github.com/llvm/llvm-project>.

I think this is very feasible from the perspective of code structure, but I
would want to get to the point where we have stable APIs and useful
end-to-end toolflows before advocating for that.

   - Should include a notice (e.g. in the project README or web page) that
   the project is in ‘incubation status’ and is not included in LLVM releases
   (see suggested wording below).

We can easily add this if accepted by the community.

   - Must be proposed through the LLVM RFC process, and have its addition
   approved by the LLVM community - this ultimately mediates the resolution of
   the “should” concerns above.

'[RFC]' indicated in the subject line.  I assume that this doesn't
yet
qualify as a contentious decision. :)

Steve

On Tue, Jul 7, 2020 at 10:33 AM Chris Lattner <clattner at nondot.org>
wrote:
> Thanks Steve!  The incubator process just landed, it would be great to
> outline how CIRCT aligns with the new guidelines set out in that document.
> As you know, I’m personally very much in favor of this project landing, but
> am also have a conflict of interest, so I’d like to know what other
> community members think.
>
> -Chris
>
> On Jul 4, 2020, at 3:29 PM, Stephen Neuendorffer via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>
> For the past several months, members of the ‘CIRCT’ group have been
> working to begin adapting MLIR for hardware design.  We believe that this
> area would benefit from good open source infrastructure enabling research
> and, eventually, the next generation of commercial tools.  We have
> collected several dialects and envision a number of lowering flows using
> these dialects.  We have reached the point where we are ready to share our
> ideas more widely and would like to be considered as an LLVM incubator
> project.
> Our code exists at https://github.com/circt as an out-of-tree MLIR
> project and our group charter can be found at
> https://github.com/circt/circt/blob/master/README.md.   We have weekly
> discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
> PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
> contributions.  This project is still early and we see many elements as
> highly experimental.  At the same time, we feel that the only way to vet
> these ideas is to build larger systems which will likely take some time and
> community investment. The LLVM incubator process would be a good way to
> help us organize this effort.
>
> Steve Neuendorffer
> Xilinx Research Labs
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
>
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It would be nice to have an external MLIR user in the project, and
this project seems really well organised and relevant. +1 from me,
too.

On Sat, 4 Jul 2020 at 23:30, Stephen Neuendorffer via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
>
> For the past several months, members of the ‘CIRCT’ group have been working
to begin adapting MLIR for hardware design.  We believe that this area would
benefit from good open source infrastructure enabling research and, eventually,
the next generation of commercial tools.  We have collected several dialects and
envision a number of lowering flows using these dialects.  We have reached the
point where we are ready to share our ideas more widely and would like to be
considered as an LLVM incubator project.
> Our code exists at https://github.com/circt as an out-of-tree MLIR project
and our group charter can be found at
https://github.com/circt/circt/blob/master/README.md.   We have weekly
discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
contributions.  This project is still early and we see many elements as highly
experimental.  At the same time, we feel that the only way to vet these ideas is
to build larger systems which will likely take some time and community
investment. The LLVM incubator process would be a good way to help us organize
this effort.
>
> Steve Neuendorffer
> Xilinx Research Labs
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

> On Jul 8, 2020, at 8:52 AM, Renato Golin via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> It would be nice to have an external MLIR user in the project, and
> this project seems really well organised and relevant. +1 from me,
> too.
I think that flang beat us to the punch as the first external MLIR user :-) but
thank you for your support Renato!

-Chris
> 
> On Sat, 4 Jul 2020 at 23:30, Stephen Neuendorffer via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> 
>> 
>> For the past several months, members of the ‘CIRCT’ group have been
working to begin adapting MLIR for hardware design.  We believe that this area
would benefit from good open source infrastructure enabling research and,
eventually, the next generation of commercial tools.  We have collected several
dialects and envision a number of lowering flows using these dialects.  We have
reached the point where we are ready to share our ideas more widely and would
like to be considered as an LLVM incubator project.
>> Our code exists at https://github.com/circt as an out-of-tree MLIR
project and our group charter can be found at
https://github.com/circt/circt/blob/master/README.md.   We have weekly
discussions with a group of about 20 people from Xilinx, SiFive, Microsoft,
PNNL, ETH Zurich, EPFL, Stanford, and Cornell, and welcome additional
contributions.  This project is still early and we see many elements as highly
experimental.  At the same time, we feel that the only way to vet these ideas is
to build larger systems which will likely take some time and community
investment. The LLVM incubator process would be a good way to help us organize
this effort.
>> 
>> Steve Neuendorffer
>> Xilinx Research Labs
>> _______________________________________________
>> 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