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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.
*/
//
// Inlining.
//
// For now, this does a conservative inlining of all functions that have
// exactly one use. That should not increase code size, and may have
// speed benefits.
//
#include <wasm.h>
#include <pass.h>
#include <wasm-builder.h>
#include <parsing.h>
namespace wasm {
struct FunctionUseCounter : public WalkerPass<PostWalker<FunctionUseCounter, Visitor<FunctionUseCounter>>> {
bool isFunctionParallel() override { return true; }
FunctionUseCounter(std::map<Name, Index>* output) : output(output) {}
FunctionUseCounter* create() override {
return new FunctionUseCounter(output);
}
void visitCall(Call *curr) {
(*output)[curr->target]++;
}
private:
std::map<Name, Index>* output;
};
struct Action {
Call* call;
Block* block; // the replacement for the call, into which we should inline
Function* contents;
Action(Call* call, Block* block, Function* contents) : call(call), block(block), contents(contents) {}
};
struct InliningState {
std::set<Name> canInline;
std::map<Name, std::vector<Action>> actionsForFunction; // function name => actions that can be performed in it
};
struct Planner : public WalkerPass<PostWalker<Planner, Visitor<Planner>>> {
bool isFunctionParallel() override { return true; }
Planner(InliningState* state) : state(state) {}
Planner* create() override {
return new Planner(state);
}
void visitCall(Call *curr) {
if (state->canInline.count(curr->target)) {
auto* block = Builder(*getModule()).makeBlock();
block->type = curr->type;
replaceCurrent(block);
state->actionsForFunction[getFunction()->name].emplace_back(curr, block, getModule()->getFunction(curr->target));
}
}
void doWalkFunction(Function* func) {
// we shouldn't inline into us if we are to be inlined
// ourselves - that has the risk of cycles
if (state->canInline.count(func->name) == 0) {
walk(func->body);
}
}
private:
InliningState* state;
};
// Core inlining logic. Modifies the outside function (adding locals as
// needed), and returns the inlined code.
// Since we only inline once, and do not need the function afterwards, we
// can just reuse all the nodes and even avoid copying.
static Expression* doInlining(Module* module, Function* into, Action& action) {
Builder builder(*module);
auto* block = action.block;
block->name = Name(std::string("__inlined_func$") + action.contents->name.str);
block->type = action.contents->result;
// set up a locals mapping
struct Updater : public PostWalker<Updater, Visitor<Updater>> {
std::map<Index, Index> localMapping;
Name returnName;
Builder* builder;
void visitReturn(Return* curr) {
replaceCurrent(builder->makeBreak(returnName, curr->value));
}
void visitGetLocal(GetLocal* curr) {
curr->index = localMapping[curr->index];
}
void visitSetLocal(SetLocal* curr) {
curr->index = localMapping[curr->index];
}
} updater;
updater.returnName = block->name;
updater.builder = &builder;
for (Index i = 0; i < action.contents->getNumLocals(); i++) {
updater.localMapping[i] = builder.addVar(into, action.contents->getLocalType(i));
}
// assign the operands into the params
for (Index i = 0; i < action.contents->params.size(); i++) {
block->list.push_back(builder.makeSetLocal(updater.localMapping[i], action.call->operands[i]));
}
// update the inlined contents
updater.walk(action.contents->body);
block->list.push_back(action.contents->body);
action.contents->body = builder.makeUnreachable(); // not strictly needed, since it's going away
return block;
}
struct Inlining : public Pass {
void run(PassRunner* runner, Module* module) override {
// keep going while we inline, to handle nesting. TODO: optimize
while (iteration(runner, module)) {}
}
bool iteration(PassRunner* runner, Module* module) {
// Count uses
std::map<Name, Index> uses;
// fill in uses, as we operate on it in parallel (each function to its own entry)
for (auto& func : module->functions) {
uses[func->name] = 0;
}
{
PassRunner runner(module);
runner.add<FunctionUseCounter>(&uses);
runner.run();
}
for (auto& ex : module->exports) {
if (ex->kind == ExternalKind::Function) {
uses[ex->value] = 2; // too many, so we ignore it
}
}
for (auto& segment : module->table.segments) {
for (auto name : segment.data) {
uses[name]++;
}
}
// decide which to inline
InliningState state;
for (auto iter : uses) {
if (iter.second == 1) {
state.canInline.insert(iter.first);
}
}
// fill in actionsForFunction, as we operate on it in parallel (each function to its own entry)
for (auto& func : module->functions) {
state.actionsForFunction[func->name];
}
// find and plan inlinings
{
PassRunner runner(module);
runner.add<Planner>(&state);
runner.run();
}
// perform inlinings
std::set<Name> inlined;
std::set<Function*> inlinedInto;
for (auto& func : module->functions) {
for (auto& action : state.actionsForFunction[func->name]) {
doInlining(module, func.get(), action);
inlined.insert(action.contents->name);
inlinedInto.insert(func.get());
}
}
// anything we inlined into may now have non-unique label names, fix it up
for (auto func : inlinedInto) {
wasm::UniqueNameMapper::uniquify(func->body);
}
// remove functions that we managed to inline, their one use is gone
auto& funcs = module->functions;
funcs.erase(std::remove_if(funcs.begin(), funcs.end(), [&inlined](const std::unique_ptr<Function>& curr) {
return inlined.count(curr->name) > 0;
}), funcs.end());
// return whether we did any work
return inlined.size() > 0;
}
};
Pass *createInliningPass() {
return new Inlining();
}
} // namespace wasm
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