Yes, only the 32-bit target, and only the gnu toolchain. Compiling on Windows using the Microsoft toolchain to target 32-bit Windows will still be on the Tier 1 list: https://doc.rust-lang.org/rustc/platform-support.html

Interestingly, Windows on ARM hasn't made it up to Tier 1 yet.

> Windows on ARM hasn't made it up to Tier 1 yet.

Windows on ARM is irelevant. Surface is Microsoft's offering to keep execs away from Apple. And just like Apple, they are toys. All relevant Windows software is x86(-64).

Not true. Key point: "Cloud savings"

To be clear, tier 2 targets are still expected to be well supported. It just doesn't require CI to pass after every PR (meaning PRs aren't blocked on fixing tier 2 specific issues). However, the target is officially distributed and target maintainers are still expected to fix any blocking issues before a release. If they can't then it's likely the target will be demoted to tier 3.

Windows on ARM couldn't be tier 1 until recently as there weren't Windows ARM github runners. Now that there are I think it likely that it'll be promoted to tier 1.

Does that end up meaning, in practice, that stable releases are never broken, but nightly might be, for a tier 2 target?

More or less, yes. It is guaranteed that tier 2 at least builds so they'll be a nightly available every day though it's possible they might have a serious bug. To be honest though that's always a risk for nightlies even with tier 1 targets. Tests don't catch every potential problem (even if they do catch a lot) which is why there is a beta period before a release.

> Interestingly, Windows on ARM hasn't made it up to Tier 1 yet.

An RFC for that has been submitted recently: https://github.com/rust-lang/rfcs/pull/3817

the problem with Windows on Arm is CI. Qualcomm cancelled their dev kit, so you run graviton/Ampere VMs, but it's pretty difficult to do automated tests on the hardware that all 5 users have.

There are Windows ARM GitHub runners now. I'm honestly not sure the dev kit would have helped, the existing Windows ARM hardware could be had for cheaper - just nobody cared to bother with it.

This is looking to go for it though https://github.com/dpaoliello/rfcs/blob/aarch64tier1/text/38... but we'll see if there is enough interest.

Technically there still is, for a few more months. There is a 32-bit version of Windows 10, and that won't end mainline support until October (and then a while of extended support, for those who wish to pay for such).

Windows 10 32 bit Home is supported until October. Some other 32 bit variants will remain in support until ~the end of the decade.

32-bit apps can run natively on 64-bit Windows and are still reasonably common.

Yes, and it's good that it is supported for running old apps. But IMHO there is little reason to build new Windows apps as 32-bit executables.

Though I don't expect Windows targeting tools to leverage it much, using 32 bit pointers can be quite an efficient method to save memory when keeping track of lots of small objects. You're limited by 4GiB of memory per process, of course, but by switching to 32 bit you're practically halving the space spent on pointers.

Using smaller pointers also allows for better data locality and better cache efficiency depending on your data layout. If you're not close to hitting 4GiB of RAM, a few free percentage points in performance aren't a bad deal.

Microsoft isn't going to deprecate 32 bit application support any time soon, so you may as well take advantage. That said, so few people have need for it that the deprecation into tier 2 support is probably the right choice. Whatever the 32 bit ABI can do, a custom allocator can probably do just as well on x64.

Oh, and Office stll comes in 32 bit mode for some reason. If you're building an Office plugin, you may need 32 bit code.

The upside is 32-bit pointers, but the downside is the small register set of x86. Best would be 64-bit ISA with 32-bit pointers, but I don't know if Windows supports such a mode.

That mode is called "x32", and Windows doesn't support it. Linux does, but it's not particularly popular, and I believe many distros that used to support it have dropped such support.

It’s friendly to users running older or LTSC versions (officially supported until 2032) on older hardware and/or in resource-constrained environments (RAM, power efficiency). There’s a large class of programs who are perfectly fine with 2 GB or less.