PowerPC (64) Support

[llebout]

Recent RaptorCS hardware makes PowerPC a modern desktop platform which runs Firefox, currently without a Javascript JIT and without WebAssembly support at all.
I read a plan where Cranelift would be used within Firefox for WebAssembly, it would be nice to have JIT support there.
Free IBM POWER9 hardware available from OSUOSL: https://osuosl.org/services/powerdev/request_hosting/ - for Free/Libre and Open Source Software development only. (This project is eligible)

[sstangl]

PowerPC is a Tier-3 Firefox platform, which means that Mozilla does not commit to maintaining it, and any platform-specific maintenance, development, or testing work must be done by the PowerPC community.

It would likely be the same situation for Cranelift.

[llebout]

@sstangl Mozilla isnt the only entity to provide support for Firefox, for example, RHEL 8 includes Firefox and has first class POWER9+ support.
This issue isnt a request for anyone from Mozilla or else to work or anything, I just wish to submit the idea so that anyone can solve the issue if they wanted. So please keep that open!

[programmerjake]

Libre-SOC is thinking about writing a PowerPC64 backend for Cranelift, since we want to use Cranelift as a backend for our Kazan graphics driver (this is similar to RADV and ACO).

Libre-SOC (formerly Libre-RISCV) is a open-source/libre project that is currently building a completely libre processor that is a hybrid CPU/GPU that implements the Power ISA, as well as custom GPU instructions. We have funding available from NLNet. We plan on selling a 28nm 4-core chip for mobile and embedded applications, and are also potentially building a much higher performance GPU for RaptorCS.

[tschneidereit]

@programmerjake that's great to hear! A few things that might be good to note:

• We recently introduced a new instruction selection framework and register allocator. Both of those are used in the new Aarch64 backend, and we'll eventually move everything over to the new architecture. That means that any work on a new backend should definitely use this new architecture.

Additionally, it'd be good to learn more about what your plans are around this, and what the implications for the cross-isa parts of the code base would be. I.e., do you intend for this work to land in this repository eventually, or do you expect to maintain it in an external downstream repository? If the former, do you plan to introduce robust continuous testing and releases as part of our existing CI pipeline?

We recently had a conversation about similar topics in the context of SPIR-V with @Jasper-Bekkers in our Zulip, which might be interesting to look at. Feel free to drop by the Zulip to chat about this more in general! :)

[bjorn3]

For those who have a hard time finding the powerpc specification like I did: https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0

[programmerjake]

For those who have a hard time finding the powerpc specification like I did: https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0

Version 3.1 has been out for a few months, however the download links appear to have been recently broken. Archive.org does not appear to have a copy.

See replies to: https://twitter.com/carlos_seo/status/1259976682158555139?s=20

[programmerjake]

For those who have a hard time finding the powerpc specification like I did: https://openpowerfoundation.org/?resource_lib=power-isa-version-3-0

Version 3.1 has been out for a few months, however the download links appear to have been recently broken. Archive.org does not appear to have a copy.

Found it: https://wiki.raptorcs.com/w/images/f/f5/PowerISA_public.v3.1.pdf

[programmerjake]

@programmerjake that's great to hear! A few things that might be good to note:

<snip> That means that any work on a new backend should definitely use this new architecture.

Sounds good!

We're currently focusing our efforts on the hardware side, since we have some looming deadlines. We will probably start working on the Cranelift backend in a few months, once we can focus on the software side again.

Additionally, it'd be good to learn more about what your plans are around this, and what the implications for the cross-isa parts of the code base would be. I.e., do you intend for this work to land in this repository eventually, or do you expect to maintain it in an external downstream repository?

We intend to upstream all code, though might have a downstream fork to allow for more rapid development.

If the former, do you plan to introduce robust continuous testing and releases as part of our existing CI pipeline?

We don't have any specific plans yet, though we do have a POWER9 server that RaptorCS has generously lent us. Another option is for Cranelift to apply for their own CI resources, available for free for open-source projects at https://osuosl.org/services/powerdev/

Our processor is not far enough along to run Linux yet.

We recently had a conversation about similar topics in the context of SPIR-V with @Jasper-Bekkers in our Zulip, which might be interesting to look at. Feel free to drop by the Zulip to chat about this more in general! :)

Neat, may do that.

[rjzak]

@programmerjake @Leo-LB is there any progress or updates regarding this? I recently got a Talos II system and would like to help.

[ecnelises]

Hi @programmerjake is there any update on this? If you have some initial work, it would be great to publish it and we can improve by the review.

Otherwise, I'd like to do some work to set up initial support. (to be clear: just personal hobby project, maybe not in very near future)