support wasm inline assembly in `naked_asm!` #135648

folkertdev · 2025-01-17T19:26:13Z

Webassembly was overlooked previously, but now naked_asm! and #[naked] functions work on the webassembly targets.

Or, they almost do right now. I guess this is no surprise, but the wasm32-unknown-unknown target causes me some trouble. I'll add some inline comments with more details.

r? @bjorn3

cc @daxpedda, @tgross35

compiler/rustc_codegen_ssa/src/mir/naked_asm.rs

tgross35 · 2025-01-17T21:11:20Z

@rustbot ping wasm

rustbot · 2025-01-17T21:11:39Z

Hey WASM notification group! This issue or PR could use some WebAssembly-specific
guidance. Could one of you weigh in? Thanks <3

(In case it's useful, here are some instructions for tackling these sorts of
issues).

cc @alexcrichton @burakemir @hoodmane @juntyr

bjorn3 · 2025-01-17T21:16:36Z

To clarify how the wasm32-unknown-unknown ABI is broken: For each ABI we implement there is supposed to be some code adjusting the PassMode from something guessed based on the BackendRepr to the actual ABI for the target. When wasm32-unknown-unknown we unfortunately forgot to implement this code causing us to pass everything as PassMode::Direct or PassMode::Pair. In doing so the internal representation of rust types at the LLVM IR level leaked out as well as causing LLVM to make up some random ABI for struct types. While we discovered this years ago, unfortunately by that point wasm-bindgen depended on the broken ABI. As such newer wasm targets like wasm32-unknown-emscripten and wasm32-wasip1 did get the correct ABI implemented, but wasm32-unknown-unknown was forced to keep the broken ABI. Only somewhat recently did wasm-bindgen add support for the correct ABI allowing us to move to the correct ABI on wasm32-unknown-unknown too in the hopefully near future. #133951 will make using an old wasm-bindgen from before the fix a hard error, while #133952 will move wasm32-unknown-unknown to the correct ABI.

alexcrichton · 2025-01-17T22:04:04Z

compiler/rustc_codegen_ssa/src/mir/naked_asm.rs

+                    // FIXME: remove this branch once the wasm32-unknown-unknown ABI is fixed
+                    bug!(
+                        "cannot use memory args (the wasm32-unknown-unknown ABI is broken, see https://github.com/rust-lang/rust/issues/115666"
+                    );


Would it be possible to refer to WasmCAbi::Legacy whenever these bug! statements are emitted? That should help ensure that when #133952 lands this'll all get naturally updated.

Additionally, would it be possible to attach a span of some kind to this bug! or the unreachable! statements (or asserts)? In case this triggers and ICE that might make it much easier to track down what the cause is

sure, I added some let _ = WasmCAbi::Legacy; statements that will make noise when the WasmCAbi enum gets removed, and the bug!s are now tied to the span of the surrounding naked function.

alexcrichton

Looks great to me! (although someone else should probably also sign off on this how knows more about naked functions and naked_asm than I)

compiler/rustc_codegen_ssa/src/mir/naked_asm.rs

bjorn3 · 2025-01-20T14:28:09Z

r=me with the above changes

tgross35 · 2025-01-20T19:50:17Z

@bors r=bjorn3

bors · 2025-01-20T19:50:20Z

📌 Commit bcf478b has been approved by bjorn3

It is now in the queue for this repository.

support wasm inline assembly in `naked_asm!` fixes rust-lang#135518 Webassembly was overlooked previously, but now `naked_asm!` and `#[naked]` functions work on the webassembly targets. Or, they almost do right now. I guess this is no surprise, but the `wasm32-unknown-unknown` target causes me some trouble. I'll add some inline comments with more details. r? `@bjorn3` cc `@daxpedda,` `@tgross35`

support wasm inline assembly in `naked_asm!` fixes rust-lang#135518 Webassembly was overlooked previously, but now `naked_asm!` and `#[naked]` functions work on the webassembly targets. Or, they almost do right now. I guess this is no surprise, but the `wasm32-unknown-unknown` target causes me some trouble. I'll add some inline comments with more details. r? ``@bjorn3`` cc ``@daxpedda,`` ``@tgross35``

support wasm inline assembly in `naked_asm!` fixes rust-lang#135518 Webassembly was overlooked previously, but now `naked_asm!` and `#[naked]` functions work on the webassembly targets. Or, they almost do right now. I guess this is no surprise, but the `wasm32-unknown-unknown` target causes me some trouble. I'll add some inline comments with more details. r? ```@bjorn3``` cc ```@daxpedda,``` ```@tgross35```

Rollup of 10 pull requests Successful merges: - rust-lang#132232 (CI: build FreeBSD artifacts on FreeBSD 13.4) - rust-lang#135625 ([cfg_match] Document the use of expressions.) - rust-lang#135638 (Make it possible to build GCC on CI) - rust-lang#135648 (support wasm inline assembly in `naked_asm!`) - rust-lang#135707 (Shorten linker output even more when `--verbose` is not present) - rust-lang#135750 (Add an example of using `carrying_mul_add` to write wider multiplication) - rust-lang#135779 (CI: free disk on linux arm runner) - rust-lang#135793 (Ignore `mermaid.min.js`) - rust-lang#135810 (Add Kobzol on vacation) - rust-lang#135814 (ci: use ghcr buildkit image) r? `@ghost` `@rustbot` modify labels: rollup

support wasm inline assembly in `naked_asm!` fixes rust-lang#135518 Webassembly was overlooked previously, but now `naked_asm!` and `#[naked]` functions work on the webassembly targets. Or, they almost do right now. I guess this is no surprise, but the `wasm32-unknown-unknown` target causes me some trouble. I'll add some inline comments with more details. r? ````@bjorn3```` cc ````@daxpedda,```` ````@tgross35````

Rollup of 8 pull requests Successful merges: - rust-lang#135557 (Point at invalid utf-8 span on user's source code) - rust-lang#135596 (Properly note when query stack is being cut off) - rust-lang#135638 (Make it possible to build GCC on CI) - rust-lang#135648 (support wasm inline assembly in `naked_asm!`) - rust-lang#135826 (Misc. `rustc_resolve` cleanups) - rust-lang#135827 (CI: free disk with in-tree script instead of GitHub Action) - rust-lang#135850 (Update the `wasm-component-ld` tool) - rust-lang#135855 (Only assert the `Parser` size on specific arches) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned bjorn3 Jan 17, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jan 17, 2025

folkertdev commented Jan 17, 2025

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rustbot added the O-wasm Target: WASM (WebAssembly), http://webassembly.org/ label Jan 17, 2025

alexcrichton reviewed Jan 17, 2025

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folkertdev force-pushed the naked-asm-wasm branch from 1cb81d2 to 7cf6260 Compare January 17, 2025 22:50

alexcrichton approved these changes Jan 17, 2025

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bjorn3 reviewed Jan 20, 2025

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folkertdev added 2 commits January 20, 2025 16:57

support wasm inline assembly in naked functions

8dec09f

work around the wasm32-unknown-unknown ABI being broken

bcf478b

folkertdev force-pushed the naked-asm-wasm branch from e894314 to bcf478b Compare January 20, 2025 15:57

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 Jan 20, 2025

jhpratt mentioned this pull request Jan 21, 2025

Rollup of 5 pull requests #135803

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Rollup of 10 pull requests #135820

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support wasm inline assembly in `naked_asm!` #135648

support wasm inline assembly in `naked_asm!` #135648

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support wasm inline assembly in naked_asm! #135648

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support wasm inline assembly in `naked_asm!` #135648

support wasm inline assembly in `naked_asm!` #135648

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