Emscripten JS trampolines do not interact well with wasm stack switching #106213
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brettcannon
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There is a WIP proposal to enable webassembly stack switching which have been implemented in v8: https://github.com/WebAssembly/js-promise-integration It is not possible to switch stacks that contain JS frames so the Emscripten JS trampolines that allow calling functions with the wrong number of arguments don't work in this case. However, the js-promise-integration proposal requires the [type reflection for Wasm/JS API](https://github.com/WebAssembly/js-types) proposal, which allows us to actually count the number of arguments a function expects. For better compatibility with stack switching, this PR checks if type reflection is available, and if so we use a switch block to decide the appropriate signature. If type reflection is unavailable, we should use the current EMJS trampoline. We cache the function argument counts since when I didn't cache them performance was negatively affected. Co-authored-by: T. Wouters <thomas@python.org> Co-authored-by: Brett Cannon <brett@python.org>
csm10495
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Sep 28, 2023
…-106219) There is a WIP proposal to enable webassembly stack switching which have been implemented in v8: https://github.com/WebAssembly/js-promise-integration It is not possible to switch stacks that contain JS frames so the Emscripten JS trampolines that allow calling functions with the wrong number of arguments don't work in this case. However, the js-promise-integration proposal requires the [type reflection for Wasm/JS API](https://github.com/WebAssembly/js-types) proposal, which allows us to actually count the number of arguments a function expects. For better compatibility with stack switching, this PR checks if type reflection is available, and if so we use a switch block to decide the appropriate signature. If type reflection is unavailable, we should use the current EMJS trampoline. We cache the function argument counts since when I didn't cache them performance was negatively affected. Co-authored-by: T. Wouters <thomas@python.org> Co-authored-by: Brett Cannon <brett@python.org>
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There is a WIP proposal to enable webassembly stack switching which have been implemented in v8.
https://github.com/WebAssembly/js-promise-integration
It is not possible to switch stacks that contain JS frames so the Emscripten JS trampolines that allow calling functions with the wrong number of arguments don't work in this case. However, the js-promise-integration proposal requires the type reflection for Wasm/JS API proposal, which allows us to actually count the number of arguments a function expects. I propose that for better compatibility with stack switching, we check if type reflection is available, and if so we use a switch block to decide the appropriate signature. If type reflection is unavailable, we should use the current EMJS trampoline.
I'm working on a patch for this.
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