Document WebAssembly target feature expectations #128511

alexcrichton · 2024-08-01T19:01:52Z

This commit is a result of the discussion on #128475 and incorporates parts of #109807 as well. This is all done as a new page of documentation for the wasm32-unknown-unknown target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation.

The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires -Ctarget-cpu=mvp to rustc plus -Zbuild-std to Cargo.

Closes #109807
Closes #119811
Closes #128475

EDIT: for the relnotes label please see this comment for recommended release notes.

This commit is a result of the discussion on rust-lang#128475 and incorporates parts of rust-lang#109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation. The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo. Closes rust-lang#109807 Closes rust-lang#128475

rustbot · 2024-08-01T19:02:00Z

r? @GuillaumeGomez

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rustbot · 2024-08-01T19:02:02Z

Some changes occurred in src/doc/rustc/src/platform-support

cc @Noratrieb

alexcrichton · 2024-08-01T19:05:05Z

If this is accepted then I will additionally comment on #127513 with a recommended rewording of the release notes to indicate that this does affect WebAssembly binaries.

src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md

src/doc/rustc/src/platform-support/wasm32-wasip1.md

src/doc/rustc/src/platform-support/wasm32-unknown-unknown.md

bb010g

A wording nit & spelling nits.

src/doc/rustc/src/platform-support/wasm32-wasip1-threads.md

src/doc/rustc/src/platform-support/wasm32-wasip1.md

src/doc/rustc/src/platform-support/wasm32-wasip2.md

src/doc/rustc/src/platform-support/wasm32-wasip1-threads.md

workingjubilee · 2024-08-06T19:08:58Z

@alexcrichton Is it possible to get an rmake test for the workarounds here, or landing a test in rust-lang/cargo?

alexcrichton · 2024-08-09T06:40:40Z

I was looking into that yeah and was hoping I could combine -Clto somehow to get a test in-tree, but the conclusion ended up being that it didn't have the right behavior of rewriting target features per function that I thought was happening. That means that such a test requires -Zbuild-std which while there is one test in tree that does this that test looks relatively complicated and specialized so I was wary to try to copy it.

I can look into adding a test in Cargo, yeah, but it feels like an odd location for such a test given that the regressions, if any, would likely come from this repo instead of Cargo. One option would be to refactor the existing Zbuild-std test in this repo, but I'm also not sure if folks are keen on expanding that due to the amount of time such a test would take compiling the standard library.

jieyouxu · 2024-08-09T06:45:07Z

I was looking into that yeah and was hoping I could combine -Clto somehow to get a test in-tree, but the conclusion ended up being that it didn't have the right behavior of rewriting target features per function that I thought was happening. That means that such a test requires -Zbuild-std which while there is one test in tree that does this that test looks relatively complicated and specialized so I was wary to try to copy it.

Yeah, unfortunately the compiler-builtins test takes a really long time to build the stdlib again, since it relies on very specific configurations. I don't have a good solution for this either, if it requires building yet another customized version of std.

alexcrichton · 2024-08-19T19:00:34Z

ping @GuillaumeGomez would you be able to review this? Or should I try to get a different sign-off?

GuillaumeGomez · 2024-08-19T19:02:37Z

I'm often assigned for such PRs but I have nothing to do with this part. Please pick someone else. ^^'

jieyouxu

Since we double-checked that this does not need a T-compiler FCP, this LGTM now.

alexcrichton · 2024-08-22T17:49:06Z

@bors: r=jieyouxu

bors · 2024-08-22T17:49:09Z

📌 Commit 7d2595f has been approved by jieyouxu

It is now in the queue for this repository.

…jieyouxu Document WebAssembly target feature expectations This commit is a result of the discussion on rust-lang#128475 and incorporates parts of rust-lang#109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation. The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo. Closes rust-lang#109807 Closes rust-lang#119811 Closes rust-lang#128475

…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#126985 (Implement `-Z embed-source` (DWARFv5 source code embedding extension)) - rust-lang#128511 (Document WebAssembly target feature expectations) - rust-lang#128935 (More work on `zstd` compression) - rust-lang#129263 (Add a missing compatibility note in the 1.80.0 release notes) - rust-lang#129386 (Use a LocalDefId in ResolvedArg.) - rust-lang#129408 (Fix handling of macro arguments within the `dropping_copy_types` lint) - rust-lang#129417 (Don't trigger refinement lint if predicates reference errors) r? `@ghost` `@rustbot` modify labels: rollup

…jieyouxu Document WebAssembly target feature expectations This commit is a result of the discussion on rust-lang#128475 and incorporates parts of rust-lang#109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation. The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo. Closes rust-lang#109807 Closes rust-lang#119811 Closes rust-lang#128475

Rollup of 7 pull requests Successful merges: - rust-lang#126985 (Implement `-Z embed-source` (DWARFv5 source code embedding extension)) - rust-lang#128349 (Enable `f16` tests on x86 and x86-64) - rust-lang#128511 (Document WebAssembly target feature expectations) - rust-lang#129263 (Add a missing compatibility note in the 1.80.0 release notes) - rust-lang#129276 (Stabilize feature `char_indices_offset`) - rust-lang#129350 (adapt integer comparison tests for LLVM 20 IR changes) - rust-lang#129408 (Fix handling of macro arguments within the `dropping_copy_types` lint) r? `@ghost` `@rustbot` modify labels: rollup

…jieyouxu Document WebAssembly target feature expectations This commit is a result of the discussion on rust-lang#128475 and incorporates parts of rust-lang#109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation. The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo. Closes rust-lang#109807 Closes rust-lang#119811 Closes rust-lang#128475

…llaumeGomez Rollup of 9 pull requests Successful merges: - rust-lang#128511 (Document WebAssembly target feature expectations) - rust-lang#129243 (do not build `cargo-miri` by default on stable channel) - rust-lang#129263 (Add a missing compatibility note in the 1.80.0 release notes) - rust-lang#129276 (Stabilize feature `char_indices_offset`) - rust-lang#129350 (adapt integer comparison tests for LLVM 20 IR changes) - rust-lang#129408 (Fix handling of macro arguments within the `dropping_copy_types` lint) - rust-lang#129426 (rustdoc-search: use tighter json for names and parents) - rust-lang#129437 (Fix typo in a help diagnostic) - rust-lang#129457 (kobzol vacation) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#128511 - alexcrichton:doc-wasm-features, r=jieyouxu Document WebAssembly target feature expectations This commit is a result of the discussion on rust-lang#128475 and incorporates parts of rust-lang#109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation. The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo. Closes rust-lang#109807 Closes rust-lang#119811 Closes rust-lang#128475

rustbot assigned GuillaumeGomez Aug 1, 2024

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Can not disable sign-ext feature for wasm32 target #109807

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Generated WebAssembly unexpectedly requires reference types #128475

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WebAssembly platform requirements are not well documented #119811

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alexcrichton added 2 commits August 1, 2024 12:16

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Add a note about libraries and #[target_feature]

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alexcrichton added 2 commits August 1, 2024 14:33

Ignore two new doc blocks in testing

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Document on-by-default features

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bjorn3 reviewed Aug 2, 2024

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jieyouxu added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 22, 2024

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 22, 2024

matthiaskrgr mentioned this pull request Aug 22, 2024

Rollup of 8 pull requests #129427

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Rollup of 7 pull requests #129428

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Rollup of 7 pull requests #129442

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Rollup of 10 pull requests #129463

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Rollup of 9 pull requests #129464

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bors merged commit 440076d into rust-lang:master Aug 23, 2024
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alexcrichton deleted the doc-wasm-features branch August 23, 2024 14:53

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Update to LLVM 19 #127513

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Add a post about changes to WebAssembly targets rust-lang/blog.rust-lang.org#1385

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Mark-Simulacrum added relnotes Marks issues that should be documented in the release notes of the next release. and removed relnotes Marks issues that should be documented in the release notes of the next release. labels Aug 25, 2024

rustbot mentioned this pull request Aug 25, 2024

Tracking issue for release notes of #128511: Document WebAssembly target feature expectations #129565

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Enyium mentioned this pull request Sep 13, 2024

Number types' FromStr impl should recognize Unicode minus #130315

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Can not disable reference-types feature for wasm32 target with -C linker-plugin-lto flag #130604

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Document WebAssembly target feature expectations #128511

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