Contributing Intel Tofino compiler backend to p4c

[hanw]

This pull request introduces the compiler backend for Intel Tofino 1 and Tofino 2 programmable switch ASICs, licensed under the Apache License 2.0. Due to the large number of files, this PR has been divided into a series of commits, organized primarily by directory structure.

To build the backend, use the -DENABLE_TOFINO=ON flag during bootstrapping. This flag is enabled by default.

Please note that this PR contains only the source code for the Tofino backend and does not include additional regression tests. A separate PR will be submitted to provide a set of PTF and STF tests for this backend.

A big thank you to all the team members who contributed to this compiler -- you know who you are!

-- Glen, Prathima, Han

[fruffy]

Exciting!

I would consider using something like https://github.com/p4lang/p4c/blob/main/backends/p4tools/cmake/common.cmake#L16 to fix the Z3 issues. At least it has worked well in the tools back end. We can put that script into top-level cmake folder as Z3.cmake.

[fruffy]

I would disable this by default and only build Tofino on the Ubuntu 22.04 Github actions.

[asl]

Another thing is that this backend is really... large :) So not all breaking changes might be quite non-trivial :)

[fruffy]

Another thing is that this backend is really... large :) So not all breaking changes might be quite non-trivial :)

This might actually be a good thing. bf-p4c pushes the limits of what you can do as a back end. So if we introduce breaking changes it can act as a canary.

[asl]

Yes, it has both pros and cons. I am talking mostly about the amount of possible changes required if we'd introduce, say, some IR change or something like this :)