macOS Univeral binary for Intel & Apple Silicon

[jelmervdl]

I've been trying to make a universal binary for x86 and M1/2 hardware so we can distribute just one app for all of macOS. This issue is here for tracking findings.

Getting rid of CMAKE_BUILD_ARCH is necessary. Right now I'm stuck on cpuinfo not supporting it, because it does assume it is being built for a single architecture.

Command (and many changes to the CMake files so not entirely useful on its own):

cmake .. \
  -DGIT_SUBMODULE=Off \
  -DCMAKE_SYSTEM_NAME=Darwin \
  -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64" \
  -DSPM_ENABLE_TCMALLOC=Off \
  -DSSPLIT_USE_INTERNAL_PCRE2=On \
  -DBUILD_EXTERNAL_LIBARCHIVE=On \
  -DICU_ROOT_DIR=(brew --prefix icu4c) \
  -DCMAKE_PREFIX_PATH=/Users/jelmer/Qt/6.2.2/macos \
&& ../cmake/fix_ruy_build.sh ../ ./ \
&& make -j8 translateLocally.dmg

Issues:
https://github.com/loongson/cpuinfo/blob/5d5348e000f91baa9849d7b30b22fce8a77ae3da/CMakeLists.txt#L167-L169

https://github.com/loongson/cpuinfo/blob/5d5348e000f91baa9849d7b30b22fce8a77ae3da/CMakeLists.txt#L55-L57

[XapaJIaMnu]

What if we have a separate binary? Would that be too bad? How is usually Apple software distributed?

[jelmervdl]

Usually universal binary. You never really have to choose which chipset you have when downloading stuff. Only open source stuff makes you choose. OBS would be a popular example. So it is not unheard of.

Apple itself is moving towards shipping stripped & pre-optimised binaries through their App Store but that's all automated and not really relevant for us right now.

[XapaJIaMnu]

So, should we open an issue on cpuinfo? What do we use cpuinfo for anyways? Setting the right cmake flags? Our usecase is to compile for generic architecture...

[jelmervdl]

ruy and fbgemm embed cpuinfo. I am able to compile an intel-only or arm-only version now.

My intuition now is that cpuinfo will probably need quite a bit of refactoring to support mutlicpu compilation (because they rely on cmake for defining cpu features…)

[XapaJIaMnu]

We can get rid of fbgemm since their models aren't compatible with multiple architecture... But not ruy... Maybe with onednn later..?

[jelmervdl]

Maybe indeed. My suggestion right now is to just deal with it at a later stage, and distribute an Apple Silicon build separately right now.