[wasm-reduce] Remove functions with delta debugging#8690
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Also take care not to remove functions that are referenced from module-level code, since in general those references cannot be replaced with anything else. When we remove functions, use ChildLocalizer to keep any children with side effects, since they might be important for reproducing the issue. Also try to replace calls to removed functions with constants if possible to avoid inserting unnecessary traps. Unlike the old implementation, this reduction scheme avoids wasted work by ensuring that the reduced module is still valid.
kripken
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May 12, 2026
| // working set size. We don't want to waste time on very fine-grained | ||
| // partitions when we could switch to a different reduction strategy | ||
| // instead. | ||
| if (size_t sqrtRemaining = std::sqrt(dd.working.size()); |
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The old code uses the factor to guide this work. Should we keep doing that?
In particular, every attempt here calls loadWorking, which is slow on a huge file. Other reduction methods might be faster, and worth doing before we get to a fine grain here.
| module->functions = std::move(newFuncs); | ||
| module->updateFunctionsMap(); | ||
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| std::vector<Name> exportsToRemove; |
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| std::vector<Name> exportsToRemove; | |
| // When we remove a function, we remove its exports. | |
| std::vector<Name> exportsToRemove; |
| return std::make_unique<FunctionReplacer>(); | ||
| }; | ||
| void visitCall(Call* curr) { | ||
| if (getModule()->getFunctionOrNull(curr->target)) { |
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| if (getModule()->getFunctionOrNull(curr->target)) { | |
| // Replace calls to functions we are removing. | |
| if (getModule()->getFunctionOrNull(curr->target)) { |
| auto* block = | ||
| ChildLocalizer(curr, getFunction(), *getModule(), getPassOptions()) | ||
| .getChildrenReplacement(); | ||
| auto* replacement = builder.replaceWithIdenticalType(curr); |
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What happens for uninhabitable types here?
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Also take care not to remove functions that are referenced from module-level code, since in general those references cannot be replaced with anything else. When we remove functions, use ChildLocalizer to keep any children with side effects, since they might be important for reproducing the issue. Also try to replace calls to removed functions with constants if possible to avoid inserting unnecessary traps. Unlike the old implementation, this reduction scheme avoids wasted work by ensuring that the reduced module is still valid.