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/*
* Copyright 2019 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.
*/
//
// Turn indirect calls into direct calls. This is possible if we know
// the table cannot change, and if we see a constant argument for the
// indirect call's index.
//
#include <unordered_map>
#include "ir/table-utils.h"
#include "ir/utils.h"
#include "pass.h"
#include "wasm-builder.h"
#include "wasm-traversal.h"
#include "wasm.h"
namespace wasm {
namespace {
struct FunctionDirectizer : public WalkerPass<PostWalker<FunctionDirectizer>> {
bool isFunctionParallel() override { return true; }
Pass* create() override { return new FunctionDirectizer(tables); }
FunctionDirectizer(
const std::unordered_map<Name, TableUtils::FlatTable>& tables)
: tables(tables) {}
void visitCallIndirect(CallIndirect* curr) {
auto it = tables.find(curr->table);
if (it == tables.end()) {
return;
}
auto& flatTable = it->second;
if (auto* c = curr->target->dynCast<Const>()) {
Index index = c->value.geti32();
// If the index is invalid, or the type is wrong, we can
// emit an unreachable here, since in Binaryen it is ok to
// reorder/replace traps when optimizing (but never to
// remove them, at least not by default).
if (index >= flatTable.names.size()) {
replaceWithUnreachable(curr);
return;
}
auto name = flatTable.names[index];
if (!name.is()) {
replaceWithUnreachable(curr);
return;
}
auto* func = getModule()->getFunction(name);
if (curr->sig != func->sig) {
replaceWithUnreachable(curr);
return;
}
// Everything looks good!
replaceCurrent(
Builder(*getModule())
.makeCall(name, curr->operands, curr->type, curr->isReturn));
}
}
void visitCallRef(CallRef* curr) {
if (auto* ref = curr->target->dynCast<RefFunc>()) {
// We know the target!
replaceCurrent(
Builder(*getModule())
.makeCall(ref->func, curr->operands, curr->type, curr->isReturn));
}
}
void doWalkFunction(Function* func) {
WalkerPass<PostWalker<FunctionDirectizer>>::doWalkFunction(func);
if (changedTypes) {
ReFinalize().walkFunctionInModule(func, getModule());
}
}
private:
const std::unordered_map<Name, TableUtils::FlatTable> tables;
bool changedTypes = false;
void replaceWithUnreachable(CallIndirect* call) {
Builder builder(*getModule());
for (auto*& operand : call->operands) {
operand = builder.makeDrop(operand);
}
replaceCurrent(builder.makeSequence(builder.makeBlock(call->operands),
builder.makeUnreachable()));
changedTypes = true;
}
};
struct Directize : public Pass {
void run(PassRunner* runner, Module* module) override {
std::unordered_map<Name, TableUtils::FlatTable> validTables;
for (auto& table : module->tables) {
if (!table->imported()) {
bool canOptimizeCallIndirect = true;
for (auto& ex : module->exports) {
if (ex->kind == ExternalKind::Table && ex->value == table->name) {
canOptimizeCallIndirect = false;
}
}
if (canOptimizeCallIndirect) {
TableUtils::FlatTable flatTable(*module, *table);
if (flatTable.valid) {
validTables.emplace(table->name, flatTable);
}
}
}
}
// Without typed function references, all we can do is optimize table
// accesses, so if we can't do that, stop.
if (validTables.empty() && !module->features.hasTypedFunctionReferences()) {
return;
}
// The table exists and is constant, so this is possible.
FunctionDirectizer(validTables).run(runner, module);
}
};
} // anonymous namespace
Pass* createDirectizePass() { return new Directize(); }
} // namespace wasm
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