[wasm-split] Precompute ownership info (NFC) - #8986
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Given a module element name, many parts of the code queries for its owning modules (where the module element has to be placed) or secondary modules using that module element. This adds `OwnershipTracker`, which precomputes and manages that information. All calls to `getOwner` or `getUsingSecondaries` that required computations iterating on all secondary modules which can be as many as thousands, has been replaced with a call that simply returns prcomputed information. For the Jul 2026 version of the applications received from the Dart team, this reduces the running time of wasm-split by 17% for acx_gallery (30s -> 25s) and by 33% for essentials (230s -> 153s). Suggested in #8832 (comment).
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Previously we removed module elements one by one within a loop. But because `Module` stores a module element in both a map and a vector, removing a single module element using `removeModuleElement` is O(N), because it needs to shift all vector elements after it: https://github.com/WebAssembly/binaryen/blob/302396a676433152a32375a81d71e74687c97a1b/src/wasm/wasm.cpp#L1970-L1979 This removes module elements in bulk using `removeModuleElements`, which does the shifting only once. https://github.com/WebAssembly/binaryen/blob/302396a676433152a32375a81d71e74687c97a1b/src/wasm/wasm.cpp#L2004-L2018 Combining with #8986, acx_gallery's running time improved by 50.3% (30s -> 15s), and essentials by 60.8% (230s -> 90s). (for Jul 2026 version) I guess the main reason for the running time increase in #8441 was this O(N) `removeModuleElement` called within a loop after all.
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Given a module element name, many parts of the code queries for its owning modules (where the module element has to be placed) or secondary modules using that module element. This adds
OwnershipTracker, which precomputes and manages that information. All calls togetOwnerorgetUsingSecondariesthat required computations iterating on all secondary modules which can be as many as thousands, has been replaced with a call that simply returns prcomputed information.For the Jul 2026 version of the applications received from the Dart team, this reduces the running time of wasm-split by 17% for acx_gallery (30s -> 25s) and by 33% for essentials (230s -> 153s).
Suggested in #8832 (comment).