target tier policy compliance #116004

davidtwco · 2023-09-20T14:06:20Z

This pull request makes a lot of changes to our targets (nothing that affects their behaviour!) to start making sure that they all comply with our target tier policy.

I've done a quick check to see if each target complies with our policies which don't require documentation (no onerous licensing, etc).
Each target now has a platform support page, most of these are newly added and just have "Missing!" on them a lot. I need your help to populate these!
Each target now has an assembly test in tests/assembly/targets, it's the same simple code in each test, it just confirms that we can in fact produce something resembling assembly given the target triple.
I've moved some things around in compiler/rustc_target/spec. Previously, we had the base targets (e.g. windows_msvc_base, which all the Windows MSVC targets would inherit from) in the same directory as the targets themselves. I've moved these to compiler/rustc_target/spec/base. This change makes the implementation of a new tidy lint easier.
Similarly, in our platform support index, we had pages like windows_msvc.md which would be linked to by all of the Windows MSVC targets. I've changed it so that every target has its own page, and when multiple targets were linking to one page, then only one of those targets has the content of that previous page, and the others symlink to that target. Likewise, this change makes the implementation of a new tidy lint easier.
I've introduced a tidy lint which checks that for every target file in compiler/rustc_target/spec, there exists a test with the same filename in tests/assembly/target and platform support documentation in src/doc/rustc/src/platform-support/. After all of my changes, this tidy lint isn't reporting any errors.

With respect to specific targets:

I've technically added i386-unknown-linux-gnu and i486-unknown-linux-gnu. Originally added in Added support for i386-unknown-linux-gnu and i486-unknown-linux-gnu #80662, these targets never actually got added to the compiler, the target definitions were there but the compiler never knew about them.
NetBSD’s platform support page had some targets listed that no longer existed or had different names (e.g. amd64 to x86_64 and mipsel removed) - I’ve updated it to reflect the targets which exist.
i686-pc-windows-msvc and x86_64-pc-windows-msvc were listed as both tier 1 and tier 3, depending on the version of Windows, which seems like a misuse of the tier system, so I've removed them from tier 3. Support for different versions of the target can be documented in the platform support page.
powerpc-unknown-openbsd wasn't listed in OpenBSD's platform support page like every other OpenBSD target - I've added it but maybe I shouldn't have.

Tier 1 w/ Host Tools

aarch64-unknown-linux-gnu
- Incomplete platform support document
i686-pc-windows-gnu
- Incomplete platform support document
i686-pc-windows-msvc
- Incomplete platform support document
i686-unknown-linux-gnu
- Incomplete platform support document
x86_64-apple-darwin
- Incomplete platform support document
x86_64-pc-windows-gnu
- Incomplete platform support document
x86_64-pc-windows-msvc
- Incomplete platform support document
x86_64-unknown-linux-gnu
- Incomplete platform support document

Tier 2 w/ Host Tools

Tier 2

Tier 3

I intend to go through each of these to try and fix them, but I encourage all contributions helping out!

Please help! If you're interested in being responsible for one of these targets, send me a PR to this PR's branch, adding yourself to the target maintainer list and complete the platform support document.
I'll do plenty of squashing to keep the number of commits managable but I'll preserve any contributions in co-authorship.
Feel free to make multiple targets point to the same platform support document if it makes sense to do. I did this when I could identify that targets were added together, or where they already were.

cc rust-lang/rust-forge#255
r? @wesleywiser

Update target tier policy to require that targets be able to produce object code with a supported backend. Signed-off-by: David Wood <david@davidtw.co>

Signed-off-by: David Wood <david@davidtw.co>

petrochenkov · 2023-09-21T04:21:28Z

@davidtwco
Could you move the infrastructural changes in rustc_target (moving subdirectories, etc) to a separate PR (while also considering #116004 (comment))?
I'll then review and merge it sooner, before info for all the individual targets is populated.

RalfJung · 2023-09-21T10:06:56Z

tests/assembly/targets/aarch64_be_unknown_netbsd.rs

@@ -0,0 +1,17 @@
+// assembly-output: emit-asm
+// compile-flags: --target aarch64_be-unknown-netbsd
+// needs-llvm-components: aarch64


How identical are these tests? Does the assembly test suite support revisions? Would it be worth having a single test with a revision for each target, instead of tons of files?

bors · 2023-09-21T22:10:14Z

☔ The latest upstream changes (presumably #115230) made this pull request unmergeable. Please resolve the merge conflicts.

RalfJung · 2023-09-22T05:26:50Z

tests/assembly/targets/s390x_unknown_linux_gnu.rs

@@ -0,0 +1,17 @@
+// assembly-output: emit-asm
+// compile-flags: --target s390x-unknown-linux-gnu
+// needs-llvm-components: s390x


@cuviper are you saying this should say systemz?

Yep, that's what the component is named in LLVM.

ehuss · 2023-09-22T18:31:57Z

I'm a little concerned about the proliferation of over 200 new chapters in the rustc book. It can overwhelm the navigation, and generally a be a bit too much. Would it be possible to consider the following changes to mitigate that?

Don't split targets that share a common file, and retain the * groupings that existed before.
Or, use sub-chapters with folding to hide the huge list. For example, it could have separate sub-chapters like "Windows", "Apple", "Wasm", "Linux", "Bare", "Other". Or the sub-chapters could be the tier levels. Or just a single sub-chapter ("Platforms") under the policy chapters. Then use folding (in book.toml) so that they don't all appear at once:

[output.html.fold]
enable = true
level = 1

ehuss · 2023-09-22T18:29:17Z

src/doc/rustc/src/platform-support/arm_unknown_linux_musleabi.md

+**Tier: 2**
+
+| Target                         | Tier                   | Description                                     |
+| ============================== | ====================== | =============================================== |


All of these tables do not render correctly. I believe the header separator must use ----, not ====.

RalfJung · 2023-09-23T06:12:25Z

There will also be a lot of redundancy across these target pages, e.g. once we start documenting things that are wrong with particular targets (such as #113053). However, for those kinds of problems, grouping the pages by OS wouldn't be helpful -- we'd want them grouped by architecture.

ecnelises · 2023-10-09T06:26:23Z

Is it really necessary to list every triple in platform-support document?

Triple consists of arch-variant-vendor-os-abi, variant and abi are optional, single vendor seldom differentiates targets, maintainer or build info of some OS for all architectures do not make sense. So arch-os is usually enough, and details can be explained in full triple docs if necessary.

he32 · 2023-10-21T11:13:25Z

* NetBSD’s platform support page had some targets listed that no longer existed or had different names (e.g. `amd64` to `x86_64` and `mipsel` removed) - I’ve updated it to reflect the targets which exist.

Uh-oh. I care about this. It's evident that I need to get off my butt and upstream the mipsel bits, they currently live as patches in our pkgsrc package.

* [ ]  `x86_64-unknown-netbsd`
  
  * NetBSD's platform support page had some targets listed that no longer existed or had different names (e.g. `amd64` -> `x86_64` and `mipsel` removed) - I've updated it to reflect the targets which exist
  * This target otherwise complies, it's only marked as incomplete so the above gets a look.

Ditto, I'll take a look. "No longer existed" for mipsel is rather "exists elsewhere, not yet upstreamed"; will make a push for having those bits applied "here" instead.

workingjubilee · 2023-10-29T08:01:14Z

tests/assembly/targets/asmjs_unknown_emscripten.rs

+// assembly-output: emit-asm
+// compile-flags: --target asmjs-unknown-emscripten
+// needs-llvm-components: webassembly
+
+#![feature(no_core, lang_items)]
+#![no_std]
+#![no_core]
+#![crate_type = "lib"]
+
+#[lang = "sized"]
+trait Sized {}
+
+pub fn test() -> u8 {
+    42
+}
+
+// CHECK: .section


Being able to write an assembly test here does not mean that this target generates the correct code: the object code this target currently generates is instead wasm, which allows it to pass the "does it generate assembly" question, but will not actually be asm.js (and makes the target redundant with wasm32-unknown-emscripten).

Noratrieb · 2023-10-29T10:36:24Z

In addition to specific targets, it may be useful to have maintainers for specific architectures for issues like #117347. Really, maybe our target maintainership should be a bit more two-dimensional? Maintainers for arches and maintainers for OS/platform. This would significantly reduce the amount of necessary files and would be more useful in practice I think. There are of course exceptions like consoles that are very "single target" focused, but for something like powerpc-unknown-openbsd, it's probably more useful to have "the powerpc people" and "the openbsd people" who will then be consulted depending on the specifics of the kind of problem with the target. The actual "owner" of the target will probably be the OS people, but with this we could reduce the huge list by just listing the target as "openbsd", and having a different table somewhere for the arch specific maintainers for arch questions.

he32 · 2023-10-30T18:18:14Z

I have taken steps to retain the mipsel-unknown-netbsd target, ref. #117356.

RalfJung · 2023-11-02T16:22:16Z

In addition to specific targets, it may be useful to have maintainers for specific architectures for issues like #117347. Really, maybe our target maintainership should be a bit more two-dimensional? Maintainers for arches and maintainers for OS/platform.

It would also be great to have an easier way to ping them. Right now it is quite cumbersome. We could maybe utilize ping groups for that?

davidtwco · 2023-11-08T02:10:12Z

I got busy and let this bitrot a little too much, so I'm going to close this PR and take a different approach taking into account a lot of the feedback here. If you sent me information about your targets then I've kept track of that and will make use of it. If you have more feedback on this then feel free to continue to comment here or message me on Zulip.

…=petrochenkov target: move base and target specifications Follow-up to rust-lang#116004. In anticipation of later PRs where we'll want to add tidy checks to ensure that, for each target, we have a test or a platform support document or something like that, this PR moves target specifications into a directory on their own so that we can just list the files in this directory to get a list of all targets. - Base specifications are moved to `rustc_target::spec::base`. - Target specifications are moved to `rustc_target::spec::targets`. - All the other source files containing types used in the target specs remain in `rustc_target::spec`. - `rustc_target/src/spec/abi.rs` is moved to `rustc_target/src/spec/abi/mod.rs` (where there was already a `tests.rs`) for uniformity. r? `@petrochenkov`

…=petrochenkov target: move base and target specifications Follow-up to rust-lang#116004. In anticipation of later PRs where we'll want to add tidy checks to ensure that, for each target, we have a test or a platform support document or something like that, this PR moves target specifications into a directory on their own so that we can just list the files in this directory to get a list of all targets. - Base specifications are moved to `rustc_target::spec::base`. - Target specifications are moved to `rustc_target::spec::targets`. - All the other source files containing types used in the target specs remain in `rustc_target::spec`. - `rustc_target/src/spec/abi.rs` is moved to `rustc_target/src/spec/abi/mod.rs` (where there was already a `tests.rs`) for uniformity. r? ``@petrochenkov``

Rollup merge of rust-lang#117702 - davidtwco:target-tier-refactors, r=petrochenkov target: move base and target specifications Follow-up to rust-lang#116004. In anticipation of later PRs where we'll want to add tidy checks to ensure that, for each target, we have a test or a platform support document or something like that, this PR moves target specifications into a directory on their own so that we can just list the files in this directory to get a list of all targets. - Base specifications are moved to `rustc_target::spec::base`. - Target specifications are moved to `rustc_target::spec::targets`. - All the other source files containing types used in the target specs remain in `rustc_target::spec`. - `rustc_target/src/spec/abi.rs` is moved to `rustc_target/src/spec/abi/mod.rs` (where there was already a `tests.rs`) for uniformity. r? ``@petrochenkov``

davidtwco added 30 commits September 20, 2023 14:28

doc: target tier policy with compiler-team#655

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Update target tier policy to require that targets be able to produce object code with a supported backend. Signed-off-by: David Wood <david@davidtw.co>

target compliance: x86_64h-apple-darwin

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target compliance: *-wrs-vxworks

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target compliance: *-unknown-openbsd

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target compliance: *-unknown-linux-ohos

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target compliance: x86_64-unknown-l4re-uclibc

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target compliance: *-unknown-hermit

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target compliance: *-unknown-haiku

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target compliance: x86_64-unknown-dragonfly

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target compliance: x86_64-unikraft-linux-musl

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target compliance: *-uwp-windows-{msvc,gnu}

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target compliance: x86_64-sun-solaris

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target compliance: drop windows xp in tier 3

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target compliance: x86_64-pc-windows-gnullvm

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target compliance: x86_64-pc-nto-qnx710

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target compliance: *-apple-watchos{,-*}

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target compliance: *-apple-tvos

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target compliance: *-apple-ios-macabi

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target compliance: wasm64-unknown-unknown

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target compliance: wasm32-wasi-preview1-threads

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target compliance: thumbv7neon-unknown-linux-musleabihf

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target compliance: thumbv7a-pc-windows-msvc

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target compliance: {arm,thumb}v5te-none-eabi

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target compliance: {arm,thumb}v4t-none-eabi

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target compliance: sparc-unknown-none-elf

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target compliance: sparc-unknown-linux-gnu

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target compliance: s390x-unknown-linux-musl

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target compliance: riscv64-linux-android

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target compliance: netbsd

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target compliance: fuchsia

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petrochenkov added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Sep 21, 2023

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riscv64gc-unknown-linux-gnu extern "C" ABI violates repr(transparent) on unions #115481

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RalfJung mentioned this pull request Sep 22, 2023

run abi/compatibility test against a whole bunch of targets #116030

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RalfJung mentioned this pull request Sep 23, 2023

What guarantees are provided about whether the reference/stdlib docs are valid on target architectures? rust-lang/unsafe-code-guidelines#461

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jackh726 mentioned this pull request Oct 4, 2023

Add arm64e-apple-ios & arm64e-apple-darwin targets #115526

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adamgreig mentioned this pull request Oct 8, 2023

Maintainers for embedded targets rust-embedded/wg#704

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ecnelises mentioned this pull request Oct 9, 2023

Add AIX platform support document #114316

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jacobbramley mentioned this pull request Oct 13, 2023

Update and split "arm" team. rust-lang/team#1094

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Document tier 3 platform support rust-lang/rust-forge#255

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workingjubilee reviewed Oct 29, 2023

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target: move base and target specifications #117702

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doc/rustc: fill out target platform-support docs davidtwco/rust#1

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davidtwco deleted the target-tier-policy-compliance branch August 7, 2025 13:38

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target tier policy compliance #116004

target tier policy compliance #116004

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Tier 1 w/ Host Tools

Tier 2 w/ Host Tools

Tier 2

Tier 3

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