[wasm-split] Add a multi-split mode #6943
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Wasm-split generally assumes that calls to secondary functions made before the secondary module has been loaded and instantiated should go to imported placeholder functions that can be responsible for loading the secondary module and forwarding the call to the loaded function. That scheme makes the loading entirely transparent from the application's point of view, which is not always a good thing. Other schemes would make it impossible for a secondary function to be called before the secondary module has been explicitly loaded, in which case the placeholder functions would never be called. To improve code size and simplify instantiation under these schemes, add a new `--no-placeholders` option that skips adding imported placeholder functions.
Add a mode that splits a module into arbitrarily many parts based on a simple manifest file. This is currently implemented by splitting out one module at a time in a loop, but this could change in the future if splitting out all the modules at once would improve the quality of the output.
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cc @dschuff FYI |
| Module wasm; | ||
| parseInput(wasm, options); | ||
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| std::map<std::string, std::unordered_set<std::string>> moduleFuncs; |
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Not hard to figure these out, but some comments would be nice I think.
| } | ||
| auto splitResults = ModuleSplitting::splitFunctions(wasm, config); | ||
| // TODO: symbolMap, placeholderMap, emitModuleNames | ||
| // TODO: Support --emit-text and use .wast in that case. |
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Our special option validation that checks that each flag is allowed in the selected mode already takes care of that.
| // TODO: Support --emit-text and use .wast in that case. | ||
| auto moduleName = options.outPrefix + mod + ".wasm"; | ||
| PassRunner runner(&*splitResults.secondary); | ||
| runner.add("remove-unused-module-elements"); |
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Why is this needed here but not in single-split?
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We should probably add it to the normal split mode as well. In experiments with hundreds of relatively small modules, this was obviously very necessary. I guess it's harder to tell by visual inspection that it is necessary for larger secondary modules.
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Makes sense. Maybe add a TODO for the normal mode?
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Just uploaded #6945 to do this for all secondary modules.
Add a mode that splits a module into arbitrarily many parts based on a
simple manifest file. This is currently implemented by splitting out one
module at a time in a loop, but this could change in the future if
splitting out all the modules at once would improve the quality of the
output.