Working asmjs and wasm targets #36339

brson · 2016-09-08T02:16:44Z

This patch set results in a working standard library for the asmjs-unknown-emscripten and wasm32-unknown-emscripten targets. It is based on the work of @badboy and @rschulman.

It does a few things:

Updates LLVM with the emscripten fastcomp patches, which include the pnacl IR legalizer and the asm.js backend. This patch is thought not to have any significant effect on existing targets.
Teaches rustbuild to correctly link C code with emscripten
Updates gcc-rs to work correctly with emscripten
Teaches rustbuild to run crate tests for emscripten with node
Modifies Thread::new to return an error on emscripten, to facilitate debugging a common failure mode
Modifies libtest to run in single-threaded mode for emscripten
Ignores a host of tests that don't work yet, mostly dealing with threads and I/O
Updates libc with wasm32 definitions (presently the same as asmjs)
Adds a wasm32-unknown-emscripten target that feeds the output of LLVM's asmjs backend through emcc to generate wasm

Notes and caveats:

This is only known to work with --enable-rustbuild.
The wasm32 target can't be tested correctly yet because of issues in compiletest and limitations in node Running wasm output via node does not work when in a different directory emscripten-core/emscripten#4542, but hello.rs does seem to work when run on node via the binaryen interpreter
This requires an up to date installation of the emscripten sdk from its incoming branch
Unwinding is very broken
When enabling the emscripten targets jemalloc is disabled for all targets, which results in test failures for the host

Next steps are to fix the jemalloc issue, start building the two emscripten targets on the auto builders, then start producing nightlies.

#36317 tracks work on this.

Fixes #36515
Fixes #36515
Fixes #36356

rust-highfive · 2016-09-08T02:16:56Z

r? @alexcrichton

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brson · 2016-09-08T04:51:03Z

I have lingering doubts about the modification to Thread::new: why just this function and not others, why an error instead of panic.

brson · 2016-09-08T04:52:38Z

One thing to note about this patch is that debugging crate test failures is quite difficult because many failures result in aborts, not clean test failures. Often this is because of fatal errors in emscripten for various reasons; perhaps some because of the utterly broken unwinding support.

tomaka · 2016-09-08T05:31:44Z

In my opinion we should pass -s ERROR_ON_UNDEFINED_SYMBOLS=1 to emscripten. By default linker error generate an abort at runtime instead of compile-time. See this comment.

Other than that, there's the question of DISABLE_EXCEPTION_CATCHING. See this page.
Since Rust gives the possibility to set panic=abort, I think that this flag should be set to 0 when the panic strategy is unwind and to 1 when it is abort.

alexcrichton · 2016-09-08T22:11:52Z

src/librustc_back/target/wasm32_unknown_emscripten.rs

+        .. Default::default()
+    };
+    Ok(Target {
+        llvm_target: "asmjs-unknown-emscripten".to_string(),


Should this be wasm32-unknown-emscripten?

Oh wait nevermind, this isn't using the wasm backend of LLVM.

alexcrichton · 2016-09-08T22:31:58Z

I've realized one further issue where we may not need to actually include the fastcomp backend, but I would prefer to land this ahead of that and we can decide on it later.

bors · 2016-09-11T22:20:41Z

☔ The latest upstream changes (presumably #36369) made this pull request unmergeable. Please resolve the merge conflicts.

alexcrichton · 2016-09-12T05:03:15Z

This may also want to use the support added in #36256 to figure out which node to run rather than always using "node"

brson · 2016-09-14T17:33:21Z

I've got a patch to make the test changes, remove the Thread::spawn error handling, and fix libtest. Testing it now.

Still have to investigate the jemalloc problems, though this can land without fixes for that. Still have to rebase to incorporate #36256.

tomaka · 2016-09-14T18:34:16Z

Please don't forget my remark. You may have linking errors and not realize it.

brson · 2016-09-15T19:35:38Z

@tomaka Thanks for the reminder. I will definitely add the ERROR_ON_UNDEFINED_SYMBOLS=1 flag. The unwinding stuff for future work.

brson · 2016-09-16T01:07:45Z

@tomaka I looked into adding the flag and it looks impractical to do in this PR because every test case encounters undefined symbols related to the unwinder. I did file a bug #36515

brson · 2016-09-16T02:51:05Z

@alexcrichton I think this is ready to go but still running tests.

… objects

Doing this step for the target results in the build system trying to build rustc for asmjs, which doesn't work.

This is a hack to support building targets that don't support jemalloc alongside hosts that do. The jemalloc build is controlled by a feature of the std crate, and if that feature changes between targets, it invalidates the fingerprint of std's build script (this is a cargo bug); so we must ensure that the feature set used by std is the same across all targets, which means we have to build the alloc_jemalloc crate for targets like emscripten, even if we don't use it.

brson · 2016-09-30T22:33:05Z

I've confirmed this build works with the smaller LLVM patch.

brson · 2016-09-30T22:57:05Z

@bors r=alexcrichton

bors · 2016-09-30T22:57:06Z

📌 Commit afa72b5 has been approved by alexcrichton

bors · 2016-10-01T02:00:36Z

⌛ Testing commit afa72b5 with merge 8b00355...

@badboy

Working asmjs and wasm targets This patch set results in a working standard library for the asmjs-unknown-emscripten and wasm32-unknown-emscripten targets. It is based on the work of @badboy and @rschulman. It does a few things: - Updates LLVM with the emscripten [fastcomp](rust-lang/llvm#50) patches, which include the pnacl IR legalizer and the asm.js backend. This patch is thought not to have any significant effect on existing targets. - Teaches rustbuild to correctly link C code with emscripten - Updates gcc-rs to work correctly with emscripten - Teaches rustbuild to run crate tests for emscripten with node - Modifies Thread::new to return an error on emscripten, to facilitate debugging a common failure mode - Modifies libtest to run in single-threaded mode for emscripten - Ignores a host of tests that don't work yet, mostly dealing with threads and I/O - Updates libc with wasm32 definitions (presently the same as asmjs) - Adds a wasm32-unknown-emscripten target that feeds the output of LLVM's asmjs backend through emcc to generate wasm Notes and caveats: - This is only known to work with `--enable-rustbuild`. - The wasm32 target can't be tested correctly yet because of issues in compiletest and limitations in node emscripten-core/emscripten#4542, but hello.rs does seem to work when run on node via the binaryen interpreter - This requires an up to date installation of the emscripten sdk from its incoming branch - Unwinding is very broken - When enabling the emscripten targets jemalloc is disabled for all targets, which results in test failures for the host Next steps are to fix the jemalloc issue, start building the two emscripten targets on the auto builders, then start producing nightlies. #36317 tracks work on this. Fixes #36515 Fixes #36515 Fixes #36356

bors · 2016-10-01T06:48:58Z

rust-lang/rust#36339

rust-highfive assigned alexcrichton Sep 8, 2016

brson mentioned this pull request Sep 8, 2016

design a deployment workflow neon-bindings/neon#117

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alexcrichton reviewed Sep 8, 2016
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alexcrichton mentioned this pull request Sep 8, 2016

Does our LLVM need the fastcomp backend for emscripten? #36356

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alexcrichton mentioned this pull request Sep 12, 2016

WebAssembly backend for rustc #33205

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joshuawarner32 mentioned this pull request Sep 13, 2016

Upgrade to nightly brson/miri#39

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japaric mentioned this pull request Sep 15, 2016

Issues found so far japaric-archived/smoke#12

Open

brson force-pushed the emscripten-new branch 2 times, most recently from 2ea0371 to 80a1288 Compare September 16, 2016 01:01

brson force-pushed the emscripten-new branch from 80a1288 to 3a4ac8a Compare September 16, 2016 02:50

brson added 17 commits September 30, 2016 14:02

Ignore lots and lots of std tests on emscripten

9c4a01e

Ignore all debuginfo tests on emscripten

00e377c

Update LLVM with fastcomp patches

10a52d5

Tidy

37abec0

Ignore entire test modules on emscripten instead of individual tests

183b2dd

Change the sigs of set_print/set_panic to allow restoring the default…

a4c3288

… objects

Update bootstrap and compiletest to use the detected nodejs

8401e37

Ignore another emscripten test because missing intrinsics

7c0bf41

Rewrite emscripten unwinding to use libcxx

525a798

Ignore various entire test modules on emscripten

096670c

rustbuild: Only build 'dist' when building the host

834bbab

Doing this step for the target results in the build system trying to build rustc for asmjs, which doesn't work.

Call emcc with ERROR_ON_UNDEFINED_SYMBOLS

d997a62

Unignore some working emscripten tests

21b987e

Cleanup bootstrap

badfd62

Document emscripten's unwind impl and remove unused function

3c038c0

Don't build any native compiler-builtin components for emscripten

afa72b5

brson force-pushed the emscripten-new branch from a5f5f9d to afa72b5 Compare September 30, 2016 22:31

bors merged commit afa72b5 into rust-lang:master Oct 1, 2016

This was referenced Oct 1, 2016

add Thumbs to the compiler #36874

Merged

Restrict where in the tree platform-specific cfgs may be mentioned #36807

Merged

maleadt mentioned this pull request Oct 2, 2016

META: CUDA external language implementation JuliaLang/julia#18338

Closed

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japaric pushed a commit to rust-lang/compiler-builtins that referenced this pull request Feb 6, 2017

Don't build any native compiler-builtin components for emscripten

c30dcb0

rust-lang/rust#36339

davidtwco mentioned this pull request Sep 20, 2023

target tier policy compliance #116004

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Working asmjs and wasm targets #36339

Working asmjs and wasm targets #36339

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Working asmjs and wasm targets #36339

Working asmjs and wasm targets #36339

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