WebAssembly / WebAssembly/binaryen
Missing 64-bit AtomicCmpxchg causes `__sync_fetch_and_nand` to fail under wasm2js
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Description
Usage of __sync_fetch_and_nand with 64-bit operands in emscripten causes the following error:
wasm2js: /usr/local/google/home/sbc/dev/wasm/binaryen/src/passes/I64ToI32Lowering.cpp:471: void wasm::I64ToI32Lowering::visitAtomicCmpxchg(wasm::AtomicCmpxchg *): Assertion `curr->type != Type::i64 && "64-bit AtomicCmpxchg not implemented"' failed.
I think this is probably super rare and not a huge deal, but creating this issue so I can link to it in the test code.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in I64ToI32Lowering.cpp at visitAtomicCmpxchg and reproduce the __sync_fetch_and_nand case with 64-bit operands under emscripten and wasm2js. The issue is resolved when this usage no longer triggers the reported assertion; no specific test file is named, so inspect the existing test code referenced by the issue.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp, wasm
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100