Include binary wheels for ARM Windows

[JukkaL]

Feature

We only ship x64 Windows binary wheels (compiled using mypyc). Maybe we should also ship ARM Windows wheels?

To make this work, we'd probably need help from somebody who has access to an ARM Windows system, at least for testing and perhaps benchmarking.

Pitch

Binary wheels compiled with mypyc could improve performance on ARM Windows systems by 3x to 4x or so. CPython already has an experimental installer for ARM Windows. The latest Microsoft Surface laptops have ARM CPUs, and it would be nice if performance was comparable to x64 on them.

Open questions

• Is Windows ARM popular enough among developers to make this worth it?
• Does GitHub Actions make it easy to build ARM binaries for Windows?
• Are all our dependencies supported on ARM Windows?

[ssbarnea]

Basedo on https://github.blog/news-insights/product-news/arm64-on-github-actions-powering-faster-more-efficient-build-systems/ arm64 windows runners are generally available, so I do not see any reason for not producing them. MacOS users are high likely to use an arm64 Windows installed on their machine instead of x86 one.

[JukkaL]

To move this forward, somebody with access to ARM Windows would have to try compiling mypy and mypyc and ensuring that tests pass and performance is reasonable. We can then look into enabling wheel builds.

[cdce8p]

Is Windows ARM popular enough among developers to make this worth it?

The current PyPI download stats for mypy 1.14.* within the last 28 days.

pypinfo -pc --days 28 --all --limit 100 \
  --where 'details.cpu != "None"' 'mypy==1.14.*' system cpu libc

system_name	cpu	libc_name	percent	download_count	Wheels
Linux	x86_64	glibc	85.90%	8,843,136	x
Windows	AMD64	None	5.13%	528,260	x
Linux	aarch64	glibc	3.26%	335,467	x (added with 1.15)
Darwin	arm64	None	3.04%	312,831	x
Linux	x86_64	None	1.31%	135,131	x
Darwin	x86_64	None	0.84%	86,298	x
Linux	x86_64	musl	0.37%	38,419	x
Linux	aarch64	None	0.06%	6,564
Linux	i686	glibc	0.02%	1,711
Linux	ppc64le	glibc	0.02%	1,571
Linux	aarch64	musl	0.01%	1,070
Linux	armv7l	glibc	0.01%	931
Emscripten	wasm32	glibc	0.01%	778	x (only 3.10)
Linux	s390x	glibc	0.01%	554
Linux	i686	None	0.00%	367
CYGWIN_NT-10.0-20348	x86_64	None	0.00%	305
Linux	armv7l	None	0.00%	276
FreeBSD	amd64	None	0.00%	185
Linux	ppc64le	None	0.00%	172
Windows	ARM64	None	0.00%	165	<--
Windows	x86	None	0.00%	88
NetBSD	amd64	None	0.00%	70
OpenBSD	amd64	None	0.00%	67
Linux	riscv64	glibc	0.00%	66
Linux	armv8l	None	0.00%	37

Does GitHub Actions make it easy to build ARM binaries for Windows?

Windows ARM runners aren't available just yet. Probably soon though github/roadmap#1098
https://docs.github.com/en/actions/using-github-hosted-runners/using-github-hosted-runners/about-github-hosted-runners#standard-github-hosted-runners-for-public-repositories

Are all our dependencies supported on ARM Windows?

So far I haven't seen any ARM Windows wheels on PyPI. That will likely only begin to change after the Github runners are available.

[JukkaL]

Thanks for looking up the stats! Based on them, this doesn't look relevant yet. We can revisit this once Windows ARM accounts for a non-trivial fraction of downloads (say 0.1%).