Support polyfilling multi-memory #125
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guybedford merged 4 commits intobytecodealliance:mainfrom Aug 8, 2023
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This commit updates the Wasmtime dependency to the, currently unreleased, Wasmtime 12.0.0 branch. A number of changes happened to component translation in Wasmtime 12 to account for resources which required changes here as well. Additionally Wasmtime 12 disallows empty types in components which WASI was previously using, so this additionally updates the preview1 shims and test components.
Currently JS does not generally support the WebAssembly multi-memory proposal. Wasmtime will, however, generate adapter modules which use multi-memory to communicate between components. This means that composed components are typically not compatible with the transpile process as they produce a core module that doesn't actually run in any JS runtime. This commit fixes this issue by adding polyfill support for multi-memory. Whenever an adapter is produced that uses multi-memory jco will now rewrite the module such that any references to memory that isn't at index 0 to be indirected through functions. These imported functions then operate on the specified memory on behalf of the wasm itself. This is a horribly slow process because all memory reads/writes become function calls, but given that the baseline is otherwise "does not work" it's hopefully a bit better than before. The end goal here is to work up towards strings between components, but for now this just gets everything else working with multi-memory such as transferring lists.
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Fantastic, I've been worried about this. Will try it out first thing tomorrow.
guybedford
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| //! support for more instructions but such support isn't required at this time. | ||
| //! Examples of unsupported instructions are `i64.load8_u` and `memory.copy`. | ||
| //! Additionally core wasm sections such as data sections and tables are not | ||
| //! supported because, again, Wasmtime doesn't use it at this time. |
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I was wondering if it might make sense to use a full wasm2js solution here (eg something like https://github.com/evanw/polywasm), but this certainly seems adequate as well.
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I think any of those would work myself, this was just the first thing I thought of so I figured I'd take a stab implementing it while stuck delayed in an airport :)
If you'd prefer to go with those though I think it's ok to hold this open or close it, either way's fine by me
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Currently JS does not generally support the WebAssembly multi-memory
proposal. Wasmtime will, however, generate adapter modules which use
multi-memory to communicate between components. This means that composed
components are typically not compatible with the transpile process as
they produce a core module that doesn't actually run in any JS runtime.
This commit fixes this issue by adding polyfill support for
multi-memory. Whenever an adapter is produced that uses multi-memory jco
will now rewrite the module such that any references to memory that
isn't at index 0 to be indirected through functions. These imported
functions then operate on the specified memory on behalf of the wasm
itself. This is a horribly slow process because all memory reads/writes
become function calls, but given that the baseline is otherwise "does
not work" it's hopefully a bit better than before.
The end goal here is to work up towards strings between components, but
for now this just gets everything else working with multi-memory such as
transferring lists.