mirror of https://github.com/pyodide/pyodide.git
f51f4b1603
I figured out a way to remove the super inefficient `calculate_wasm_func_nargs_fallback` and replace it with wasm-gc code. This should perform much better. The cpython patch message says: Part of the ongoing quest to support JSPI. The JSPI spec removed its dependence on JS type reflection, and now the plan is for runtimes to ship JSPI while keeping type reflection in stage 3. So we need an alternative way to count the number of parameters of a function. It is possible to count them by repeatedly trying to instantiate a webassembly module with the function as an import of a different type signature. But this is pretty inefficient. Since WebAssembly gc is now stage 4, there is a new option. WebAssembly gc added the `ref.test` instruction which can ask if a funcref has a given type. It's a bit difficult to apply because even our usual assembler the wasm binary toolkit doesn't support this instruction yet. But all JS engines that support JSPI support it. We just have to do some manual work to produce the binary. This code also has to be written carefully to interact properly with memory snapshots. Importantly, no JS initialization code can be called from the C initialization code. For this reason, we make a C function pointer to fill from JS and fill it in a preRun function. Upstream PR: python/cpython#128628 |
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README.md
Credits
Based on the hard work of @dgym on cpython-emscripten.