cmake: introduce USE_SYSTEM_* flags

[ConnorBaker]

Similar to the work done in pytorch/pytorch#37137, this adds the following CMake options:

• USE_SYSTEM_LIBS
• USE_SYSTEM_ASMJIT
• USE_SYSTEM_CPUINFO
• USE_SYSTEM_GOOGLETEST

This is particularly useful in the context of Nix, where we can build these libraries once and then re-use them elsewhere to avoid rebuilding vendors dependencies.

I'm unsure of how to best enable this for fbgemm_gpu.

What's the relationship between FBGEMM and libtorch? Does libtorch require fbgemm, fbgemm_gpu, or both?

[netlify]

✅ Deploy Preview for pytorch-fbgemm-docs canceled.

Name	Link
🔨 Latest commit	8dc96b9
🔍 Latest deploy log	https://app.netlify.com/sites/pytorch-fbgemm-docs/deploys/64e43cb85fc3e90008b17749

[ConnorBaker]

@q10 I see that you've worked with the CMake in this repo before, would you have the bandwidth to review this?

[q10]

@q10 I see that you've worked with the CMake in this repo before, would you have the bandwidth to review this?

Yes I can. Let me run it through the OSS CI system before reviewing this more thoroughly on Monday.

[ConnorBaker]

Much appreciated! And any insight on changes I'd need to make for the GPU variant would be awesome :)

[facebook-github-bot]

@q10 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@q10 has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[ConnorBaker]

As a followup, any thoughts on offering an fbgemm-config.cmake for users who would like to be able to do find_package(fbgemm)?

I know that fbgemmLibraryConfig.cmake is produced, but that's also located in /share/cmake/fbgemm and so I need to use find_package(fbgemmLibrary) and pass "-DfbgemmLibrary_DIR:PATH=${fbgemm}/share/cmake/fbgemm" to have CMake find it.

Although, I'm not very proficient in writing or interpreting CMake, so that may be working as intended or a best practice.

[q10]

As a followup, any thoughts on offering an fbgemm-config.cmake for users who would like to be able to do find_package(fbgemm)?

I know that fbgemmLibraryConfig.cmake is produced, but that's also located in /share/cmake/fbgemm and so I need to use find_package(fbgemmLibrary) and pass "-DfbgemmLibrary_DIR:PATH=${fbgemm}/share/cmake/fbgemm" to have CMake find it.

Although, I'm not very proficient in writing or interpreting CMake, so that may be working as intended or a best practice.

I think it's a good idea to offer an fbgemm-config.cmake, though we are not experts on CMake either, which is why we have not gotten around to working on this.

I'm looking at the CI builds, and it appears that the CMake changes made in this PR have broken all the CMake-based builds of FBGEMM (see here)...

[ConnorBaker]

@q10 would you mind triggering CI again to see if it's fixed?

[q10]

@q10 would you mind triggering CI again to see if it's fixed?

Looks to be broken still :(

[ConnorBaker]

Alrighty, @q10 would you mind running the CI again?