Support for open source DPC++ compiler

[frenchwr]

Hello, I see the following stated from the oneCCL docs:

To enable SYCL devices communication support, specify SYCL compiler (only Intel® oneAPI DPC++/C++ Compiler is supported)

I interpret that to mean oneCCL cannot be built using the open source DPC++ compiler (https://github.com/intel/llvm). Is the correct?

If so, would you mind elaborating on the reason? Are there core features missing, or is a matter of priority?

To provide a bit more context, we have created a Debian package of the open source DPC++ and plan to ship it with Ubuntu 26.04. We also now have a oneDNN-variant debian package (built with DPC++) we plan to land in 26.04. Now we'd like to do the same with oneCCL, if possible.

Thanks!

[sarnex]

While I don't work on or have any ownership for oneCCL, I was able to build oneCCL successfully with the open-source DPC++ compiler with some minor CMake/Header changes. I'll make a PR here and see what the maintainers have to say.

[frenchwr]

Thanks, @sarnex !

[sarnex]

Opened a PR here #194

[blazej-smorawski]

Thanks for you help @sarnex. I'm aware of this problem and I'll help to merge you changes, hopefully this month :)

[sarnex]

Thanks @blazej-smorawski! Feel free to ping me internally as well if needed, internal email is on my GitHub profile page.