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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 duplicate functions. That can happen due to C++ templates,
// and also due to types being different at the source level, but
// identical when finally lowered into concrete wasm code.
//
#include <wasm.h>
#include <pass.h>
#include <ast_utils.h>
namespace wasm {
struct FunctionHasher : public WalkerPass<PostWalker<FunctionHasher, Visitor<FunctionHasher>>> {
bool isFunctionParallel() override { return true; }
FunctionHasher(std::map<Function*, uint32_t>* output) : output(output) {}
FunctionHasher* create() override {
return new FunctionHasher(output);
}
void doWalkFunction(Function* func) {
assert(digest == 0);
hash(func->getNumParams());
for (auto type : func->params) hash(type);
hash(func->getNumVars());
for (auto type : func->vars) hash(type);
hash(func->result);
hash64(func->type.is() ? uint64_t(func->type.str) : uint64_t(0));
hash(ExpressionAnalyzer::hash(func->body));
output->at(func) = digest;
}
private:
std::map<Function*, uint32_t>* output;
uint32_t digest = 0;
void hash(uint32_t hash) {
digest = rehash(digest, hash);
}
void hash64(uint64_t hash) {
digest = rehash(rehash(digest, hash >> 32), uint32_t(hash));
};
};
struct FunctionReplacer : public WalkerPass<PostWalker<FunctionReplacer, Visitor<FunctionReplacer>>> {
bool isFunctionParallel() override { return true; }
FunctionReplacer(std::map<Name, Name>* replacements) : replacements(replacements) {}
FunctionReplacer* create() override {
return new FunctionReplacer(replacements);
}
void visitCall(Call* curr) {
auto iter = replacements->find(curr->target);
if (iter != replacements->end()) {
curr->target = iter->second;
}
}
private:
std::map<Name, Name>* replacements;
};
struct DuplicateFunctionElimination : public Pass {
void run(PassRunner* runner, Module* module) override {
while (1) {
// Hash all the functions
hashes.clear();
for (auto& func : module->functions) {
hashes[func.get()] = 0; // ensure an entry for each function - we must not modify the map shape in parallel, just the values
}
PassRunner hasherRunner(module);
hasherRunner.add<FunctionHasher>(&hashes);
hasherRunner.run();
// Find hash-equal groups
std::map<uint32_t, std::vector<Function*>> hashGroups;
for (auto& func : module->functions) {
hashGroups[hashes[func.get()]].push_back(func.get());
}
// Find actually equal functions and prepare to replace them
std::map<Name, Name> replacements;
std::set<Name> duplicates;
for (auto& pair : hashGroups) {
auto& group = pair.second;
if (group.size() == 1) continue;
// pick a base for each group, and try to replace everyone else to it. TODO: multiple bases per hash group, for collisions
Function* base = group[0];
for (auto* func : group) {
if (func != base && equal(func, base)) {
replacements[func->name] = base->name;
duplicates.insert(func->name);
}
}
}
// perform replacements
if (replacements.size() > 0) {
// remove the duplicates
auto& v = module->functions;
v.erase(std::remove_if(v.begin(), v.end(), [&](const std::unique_ptr<Function>& curr) {
return duplicates.count(curr->name) > 0;
}), v.end());
module->updateFunctionsMap();
// replace direct calls
PassRunner replacerRunner(module);
replacerRunner.add<FunctionReplacer>(&replacements);
replacerRunner.run();
// replace in table
for (auto& segment : module->table.segments) {
for (auto& name : segment.data) {
auto iter = replacements.find(name);
if (iter != replacements.end()) {
name = iter->second;
}
}
}
// replace in start
if (module->start.is()) {
auto iter = replacements.find(module->start);
if (iter != replacements.end()) {
module->start = iter->second;
}
}
// replace in exports
for (auto& exp : module->exports) {
auto iter = replacements.find(exp->value);
if (iter != replacements.end()) {
exp->value = iter->second;
}
}
} else {
break;
}
}
}
private:
std::map<Function*, uint32_t> hashes;
bool equal(Function* left, Function* right) {
if (left->getNumParams() != right->getNumParams()) return false;
if (left->getNumVars() != right->getNumVars()) return false;
for (Index i = 0; i < left->getNumLocals(); i++) {
if (left->getLocalType(i) != right->getLocalType(i)) return false;
}
if (left->result != right->result) return false;
if (left->type != right->type) return false;
return ExpressionAnalyzer::equal(left->body, right->body);
}
};
Pass *createDuplicateFunctionEliminationPass() {
return new DuplicateFunctionElimination();
}
} // namespace wasm
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