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/*
* Copyright 2016 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//
// Removes functions that are never used.
//
#include <memory>
#include "wasm.h"
#include "pass.h"
#include "ast_utils.h"
namespace wasm {
struct RemoveUnusedFunctions : public Pass {
void run(PassRunner* runner, Module* module) override {
std::vector<Function*> root;
// Module start is a root.
if (module->start.is()) {
root.push_back(module->getFunction(module->start));
}
// Exports are roots.
for (auto& curr : module->exports) {
if (curr->kind == ExternalKind::Function) {
root.push_back(module->getFunction(curr->value));
}
}
// For now, all functions that can be called indirectly are marked as roots.
for (auto& segment : module->table.segments) {
for (auto& curr : segment.data) {
root.push_back(module->getFunction(curr));
}
}
// Compute function reachability starting from the root set.
DirectCallGraphAnalyzer analyzer(module, root);
// Remove unreachable functions.
auto& v = module->functions;
v.erase(std::remove_if(v.begin(), v.end(), [&](const std::unique_ptr<Function>& curr) {
return analyzer.reachable.count(curr.get()) == 0;
}), v.end());
assert(module->functions.size() == analyzer.reachable.size());
module->updateFunctionsMap();
}
};
Pass *createRemoveUnusedFunctionsPass() {
return new RemoveUnusedFunctions();
}
} // namespace wasm
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