src/passes/Inlining.cpp - external/github.com/WebAssembly/binaryen - Git at Google

 /*
  * 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.
 //
 // By default, this does a conservative inlining of all functions that have
 // exactly one use, and are fairly small. That should not increase code
 // size, and may have speed benefits.
 //
 // When opt level is 3+ (-O3 or above), we more aggressively inline
 // even functions with more than one use, that seem to be "lightweight"
 // (no loops or calls etc.), so inlining them may get rid of call overhead
 // that would be noticeable otherwise
 //

 #include <atomic>

 #include <wasm.h>
 #include <pass.h>
 #include <wasm-builder.h>
 #include <ast_utils.h>
 #include <ast/literal-utils.h>
 #include <parsing.h>

 namespace wasm {

 // A limit on how big a function to inline when being careful about size
 static const int CAREFUL_SIZE_LIMIT = 15;

 // A limit on how big a function to inline when being more flexible. In
 // particular it's nice that with this limit we can inline the clamp
 // functions (i32s-div, f64-to-int, etc.), that can affect perf.
 static const int FLEXIBLE_SIZE_LIMIT = 20;

 // Useful into on a function, helping us decide if we can inline it
 struct FunctionInfo {
   std::atomic<Index> calls;
   Index size;
   bool lightweight = true;
   bool usedGlobally = false; // in a table or export

   bool worthInlining(PassOptions& options, bool allowMultipleInliningsPerFunction) {
     // if it's big, it's just not worth doing (TODO: investigate more)
     if (size > FLEXIBLE_SIZE_LIMIT) return false;
     // if it has one use, then inlining it would likely reduce code size
     // since we are just moving code around, + optimizing, so worth it
     // if small enough that we are pretty sure its ok
     if (calls == 1 && !usedGlobally && size <= CAREFUL_SIZE_LIMIT) return true;
     if (!allowMultipleInliningsPerFunction) return false;
     // more than one use, so we can't eliminate it after inlining,
     // so only worth it if we really care about speed and don't care
     // about size, and if it's lightweight so a good candidate for
     // speeding us up
     return options.optimizeLevel >= 3 && options.shrinkLevel == 0 && lightweight;
   }
 };

 typedef std::unordered_map<Name, FunctionInfo> NameInfoMap;

 struct FunctionInfoScanner : public WalkerPass<PostWalker<FunctionInfoScanner>> {
   bool isFunctionParallel() override { return true; }

   FunctionInfoScanner(NameInfoMap* infos) : infos(infos) {}

   FunctionInfoScanner* create() override {
     return new FunctionInfoScanner(infos);
   }

   void visitLoop(Loop* curr) {
     // having a loop is not lightweight
     (*infos)[getFunction()->name].lightweight = false;
   }

   void visitCall(Call* curr) {
     assert(infos->count(curr->target) > 0); // can't add a new element in parallel
     (*infos)[curr->target].calls++;
     // having a call is not lightweight
     (*infos)[getFunction()->name].lightweight = false;
   }

   void visitFunction(Function* curr) {
     (*infos)[curr->name].size = Measurer::measure(curr->body);
   }

 private:
   NameInfoMap* infos;
 };

 struct InliningAction {
   Expression** callSite;
   Function* contents;

   InliningAction(Expression** callSite, Function* contents) : callSite(callSite), contents(contents) {}
 };

 struct InliningState {
   std::unordered_set<Name> worthInlining;
   std::unordered_map<Name, std::vector<InliningAction>> actionsForFunction; // function name => actions that can be performed in it
 };

 struct Planner : public WalkerPass<PostWalker<Planner>> {
   bool isFunctionParallel() override { return true; }

   Planner(InliningState* state) : state(state) {}

   Planner* create() override {
     return new Planner(state);
   }

   void visitCall(Call* curr) {
     // plan to inline if we know this is valid to inline, and if the call is
     // actually performed - if it is dead code, it's pointless to inline
     if (state->worthInlining.count(curr->target) &&
         curr->type != unreachable) {
       // nest the call in a block. that way the location of the pointer to the call will not
       // change even if we inline multiple times into the same function, otherwise
       // call1(call2()) might be a problem
       auto* block = Builder(*getModule()).makeBlock(curr);
       replaceCurrent(block);
       assert(state->actionsForFunction.count(getFunction()->name) > 0); // can't add a new element in parallel
       state->actionsForFunction[getFunction()->name].emplace_back(&block->list[0], 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->worthInlining.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.
 static Expression* doInlining(Module* module, Function* into, InliningAction& action) {
   Function* from = action.contents;
   auto* call = (*action.callSite)->cast<Call>();
   Builder builder(*module);
   auto* block = Builder(*module).makeBlock();
   block->name = Name(std::string("__inlined_func$") + from->name.str);
   *action.callSite = block;
   // set up a locals mapping
   struct Updater : public PostWalker<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 < from->getNumLocals(); i++) {
     updater.localMapping[i] = builder.addVar(into, from->getLocalType(i));
   }
   // assign the operands into the params
   for (Index i = 0; i < from->params.size(); i++) {
     block->list.push_back(builder.makeSetLocal(updater.localMapping[i], call->operands[i]));
   }
   // zero out the vars (as we may be in a loop, and may depend on their zero-init value
   for (Index i = 0; i < from->vars.size(); i++) {
     block->list.push_back(builder.makeSetLocal(updater.localMapping[from->getVarIndexBase() + i], LiteralUtils::makeZero(from->vars[i], *module)));
   }
   // generate and update the inlined contents
   auto* contents = ExpressionManipulator::copy(from->body, *module);
   updater.walk(contents);
   block->list.push_back(contents);
   block->type = call->type;
   // if the function returned a value, we just set the block containing the
   // inlined code to have that type. or, if the function was void and
   // contained void, that is fine too. a bad case is a void function in which
   // we have unreachable code, so we would be replacing a void call with an
   // unreachable; we need to handle
   if (contents->type == unreachable && block->type == none) {
     // make the block reachable by adding a break to it
     block->list.push_back(builder.makeBreak(block->name));
   }
   return block;
 }

 struct Inlining : public Pass {
   // whether to optimize where we inline
   bool optimize = false;

   NameInfoMap infos;

   bool firstIteration;

   void run(PassRunner* runner, Module* module) override {
     // keep going while we inline, to handle nesting. TODO: optimize
     firstIteration = true;
     while (1) {
       calculateInfos(module);
       if (!iteration(runner, module)) {
         return;
       }
       firstIteration = false;
     }
   }

   void calculateInfos(Module* module) {
     infos.clear();
     // fill in info, as we operate on it in parallel (each function to its own entry)
     for (auto& func : module->functions) {
       infos[func->name];
     }
     PassRunner runner(module);
     runner.setIsNested(true);
     runner.add<FunctionInfoScanner>(&infos);
     runner.run();
     // fill in global uses
     // anything exported or used in a table should not be inlined
     for (auto& ex : module->exports) {
       if (ex->kind == ExternalKind::Function) {
         infos[ex->value].usedGlobally = true;
       }
     }
     for (auto& segment : module->table.segments) {
       for (auto name : segment.data) {
         if (module->getFunctionOrNull(name)) {
           infos[name].usedGlobally = true;
         }
       }
     }
   }

   bool iteration(PassRunner* runner, Module* module) {
     // decide which to inline
     InliningState state;
     for (auto& func : module->functions) {
       // on the first iteration, allow multiple inlinings per function
       if (infos[func->name].worthInlining(runner->options, firstIteration /* allowMultipleInliningsPerFunction */)) {
         state.worthInlining.insert(func->name);
       }
     }
     if (state.worthInlining.size() == 0) return false;
     // 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.setIsNested(true);
       runner.add<Planner>(&state);
       runner.run();
     }
     // perform inlinings TODO: parallelize
     std::unordered_map<Name, Index> inlinedUses; // how many uses we inlined
     std::unordered_set<Function*> inlinedInto; // which functions were inlined into
     for (auto& func : module->functions) {
       for (auto& action : state.actionsForFunction[func->name]) {
         Name inlinedName = action.contents->name;
         doInlining(module, func.get(), action);
         inlinedUses[inlinedName]++;
         inlinedInto.insert(func.get());
         assert(inlinedUses[inlinedName] <= infos[inlinedName].calls);
       }
     }
     // anything we inlined into may now have non-unique label names, fix it up
     for (auto func : inlinedInto) {
       wasm::UniqueNameMapper::uniquify(func->body);
     }
     if (optimize && inlinedInto.size() > 0) {
       doOptimize(inlinedInto, module, runner);
     }
     // remove functions that we no longer need after inlining
     auto& funcs = module->functions;
     funcs.erase(std::remove_if(funcs.begin(), funcs.end(), [&](const std::unique_ptr<Function>& curr) {
       auto name = curr->name;
       auto& info = infos[name];
       return inlinedUses.count(name) && inlinedUses[name] == info.calls && !info.usedGlobally;
     }), funcs.end());
     // return whether we did any work
     return inlinedUses.size() > 0;
   }

   // Run useful optimizations after inlining, things like removing
   // unnecessary new blocks, sharing variables, etc.
   void doOptimize(std::unordered_set<Function*>& funcs, Module* module, PassRunner* parentRunner) {
     // save the full list of functions on the side
     std::vector<std::unique_ptr<Function>> all;
     all.swap(module->functions);
     module->updateMaps();
     for (auto& func : funcs) {
       module->addFunction(func);
     }
     PassRunner runner(module, parentRunner->options);
     runner.setIsNested(true);
     runner.setValidateGlobally(false); // not a full valid module
     runner.add("precompute-propagate");
     runner.add("remove-unused-brs");
     runner.add("remove-unused-names");
     runner.add("coalesce-locals");
     runner.add("simplify-locals");
     runner.add("vacuum");
     runner.add("reorder-locals");
     runner.add("remove-unused-brs");
     runner.add("merge-blocks");
     runner.run();
     // restore all the funcs
     for (auto& func : module->functions) {
       func.release();
     }
     all.swap(module->functions);
     module->updateMaps();
   }
 };

 Pass *createInliningPass() {
   return new Inlining();
 }

 Pass *createInliningOptimizingPass() {
   auto* ret = new Inlining();
   ret->optimize = true;
   return ret;
 }

 } // namespace wasm
	/*
	* 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.
	//
	// By default, this does a conservative inlining of all functions that have
	// exactly one use, and are fairly small. That should not increase code
	// size, and may have speed benefits.
	//
	// When opt level is 3+ (-O3 or above), we more aggressively inline
	// even functions with more than one use, that seem to be "lightweight"
	// (no loops or calls etc.), so inlining them may get rid of call overhead
	// that would be noticeable otherwise
	//

	#include <atomic>

	#include <wasm.h>
	#include <pass.h>
	#include <wasm-builder.h>
	#include <ast_utils.h>
	#include <ast/literal-utils.h>
	#include <parsing.h>

	namespace wasm {

	// A limit on how big a function to inline when being careful about size
	static const int CAREFUL_SIZE_LIMIT = 15;

	// A limit on how big a function to inline when being more flexible. In
	// particular it's nice that with this limit we can inline the clamp
	// functions (i32s-div, f64-to-int, etc.), that can affect perf.
	static const int FLEXIBLE_SIZE_LIMIT = 20;

	// Useful into on a function, helping us decide if we can inline it
	struct FunctionInfo {
	std::atomic<Index> calls;
	Index size;
	bool lightweight = true;
	bool usedGlobally = false; // in a table or export

	bool worthInlining(PassOptions& options, bool allowMultipleInliningsPerFunction) {
	// if it's big, it's just not worth doing (TODO: investigate more)
	if (size > FLEXIBLE_SIZE_LIMIT) return false;
	// if it has one use, then inlining it would likely reduce code size
	// since we are just moving code around, + optimizing, so worth it
	// if small enough that we are pretty sure its ok
	if (calls == 1 && !usedGlobally && size <= CAREFUL_SIZE_LIMIT) return true;
	if (!allowMultipleInliningsPerFunction) return false;
	// more than one use, so we can't eliminate it after inlining,
	// so only worth it if we really care about speed and don't care
	// about size, and if it's lightweight so a good candidate for
	// speeding us up
	return options.optimizeLevel >= 3 && options.shrinkLevel == 0 && lightweight;
	}
	};

	typedef std::unordered_map<Name, FunctionInfo> NameInfoMap;

	struct FunctionInfoScanner : public WalkerPass<PostWalker<FunctionInfoScanner>> {
	bool isFunctionParallel() override { return true; }

	FunctionInfoScanner(NameInfoMap* infos) : infos(infos) {}

	FunctionInfoScanner* create() override {
	return new FunctionInfoScanner(infos);
	}

	void visitLoop(Loop* curr) {
	// having a loop is not lightweight
	(*infos)[getFunction()->name].lightweight = false;
	}

	void visitCall(Call* curr) {
	assert(infos->count(curr->target) > 0); // can't add a new element in parallel
	(*infos)[curr->target].calls++;
	// having a call is not lightweight
	(*infos)[getFunction()->name].lightweight = false;
	}

	void visitFunction(Function* curr) {
	(*infos)[curr->name].size = Measurer::measure(curr->body);
	}

	private:
	NameInfoMap* infos;
	};

	struct InliningAction {
	Expression** callSite;
	Function* contents;

	InliningAction(Expression** callSite, Function* contents) : callSite(callSite), contents(contents) {}
	};

	struct InliningState {
	std::unordered_set<Name> worthInlining;
	std::unordered_map<Name, std::vector<InliningAction>> actionsForFunction; // function name => actions that can be performed in it
	};

	struct Planner : public WalkerPass<PostWalker<Planner>> {
	bool isFunctionParallel() override { return true; }

	Planner(InliningState* state) : state(state) {}

	Planner* create() override {
	return new Planner(state);
	}

	void visitCall(Call* curr) {
	// plan to inline if we know this is valid to inline, and if the call is
	// actually performed - if it is dead code, it's pointless to inline
	if (state->worthInlining.count(curr->target) &&
	curr->type != unreachable) {
	// nest the call in a block. that way the location of the pointer to the call will not
	// change even if we inline multiple times into the same function, otherwise
	// call1(call2()) might be a problem
	auto* block = Builder(*getModule()).makeBlock(curr);
	replaceCurrent(block);
	assert(state->actionsForFunction.count(getFunction()->name) > 0); // can't add a new element in parallel
	state->actionsForFunction[getFunction()->name].emplace_back(&block->list[0], 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->worthInlining.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.
	static Expression* doInlining(Module* module, Function* into, InliningAction& action) {
	Function* from = action.contents;
	auto* call = (*action.callSite)->cast<Call>();
	Builder builder(*module);
	auto* block = Builder(*module).makeBlock();
	block->name = Name(std::string("__inlined_func$") + from->name.str);
	*action.callSite = block;
	// set up a locals mapping
	struct Updater : public PostWalker<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 < from->getNumLocals(); i++) {
	updater.localMapping[i] = builder.addVar(into, from->getLocalType(i));
	}
	// assign the operands into the params
	for (Index i = 0; i < from->params.size(); i++) {
	block->list.push_back(builder.makeSetLocal(updater.localMapping[i], call->operands[i]));
	}
	// zero out the vars (as we may be in a loop, and may depend on their zero-init value
	for (Index i = 0; i < from->vars.size(); i++) {
	block->list.push_back(builder.makeSetLocal(updater.localMapping[from->getVarIndexBase() + i], LiteralUtils::makeZero(from->vars[i], *module)));
	}
	// generate and update the inlined contents
	auto* contents = ExpressionManipulator::copy(from->body, *module);
	updater.walk(contents);
	block->list.push_back(contents);
	block->type = call->type;
	// if the function returned a value, we just set the block containing the
	// inlined code to have that type. or, if the function was void and
	// contained void, that is fine too. a bad case is a void function in which
	// we have unreachable code, so we would be replacing a void call with an
	// unreachable; we need to handle
	if (contents->type == unreachable && block->type == none) {
	// make the block reachable by adding a break to it
	block->list.push_back(builder.makeBreak(block->name));
	}
	return block;
	}

	struct Inlining : public Pass {
	// whether to optimize where we inline
	bool optimize = false;

	NameInfoMap infos;

	bool firstIteration;

	void run(PassRunner* runner, Module* module) override {
	// keep going while we inline, to handle nesting. TODO: optimize
	firstIteration = true;
	while (1) {
	calculateInfos(module);
	if (!iteration(runner, module)) {
	return;
	}
	firstIteration = false;
	}
	}

	void calculateInfos(Module* module) {
	infos.clear();
	// fill in info, as we operate on it in parallel (each function to its own entry)
	for (auto& func : module->functions) {
	infos[func->name];
	}
	PassRunner runner(module);
	runner.setIsNested(true);
	runner.add<FunctionInfoScanner>(&infos);
	runner.run();
	// fill in global uses
	// anything exported or used in a table should not be inlined
	for (auto& ex : module->exports) {
	if (ex->kind == ExternalKind::Function) {
	infos[ex->value].usedGlobally = true;
	}
	}
	for (auto& segment : module->table.segments) {
	for (auto name : segment.data) {
	if (module->getFunctionOrNull(name)) {
	infos[name].usedGlobally = true;
	}
	}
	}
	}

	bool iteration(PassRunner* runner, Module* module) {
	// decide which to inline
	InliningState state;
	for (auto& func : module->functions) {
	// on the first iteration, allow multiple inlinings per function
	if (infos[func->name].worthInlining(runner->options, firstIteration /* allowMultipleInliningsPerFunction */)) {
	state.worthInlining.insert(func->name);
	}
	}
	if (state.worthInlining.size() == 0) return false;
	// 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.setIsNested(true);
	runner.add<Planner>(&state);
	runner.run();
	}
	// perform inlinings TODO: parallelize
	std::unordered_map<Name, Index> inlinedUses; // how many uses we inlined
	std::unordered_set<Function*> inlinedInto; // which functions were inlined into
	for (auto& func : module->functions) {
	for (auto& action : state.actionsForFunction[func->name]) {
	Name inlinedName = action.contents->name;
	doInlining(module, func.get(), action);
	inlinedUses[inlinedName]++;
	inlinedInto.insert(func.get());
	assert(inlinedUses[inlinedName] <= infos[inlinedName].calls);
	}
	}
	// anything we inlined into may now have non-unique label names, fix it up
	for (auto func : inlinedInto) {
	wasm::UniqueNameMapper::uniquify(func->body);
	}
	if (optimize && inlinedInto.size() > 0) {
	doOptimize(inlinedInto, module, runner);
	}
	// remove functions that we no longer need after inlining
	auto& funcs = module->functions;
	funcs.erase(std::remove_if(funcs.begin(), funcs.end(), [&](const std::unique_ptr<Function>& curr) {
	auto name = curr->name;
	auto& info = infos[name];
	return inlinedUses.count(name) && inlinedUses[name] == info.calls && !info.usedGlobally;
	}), funcs.end());
	// return whether we did any work
	return inlinedUses.size() > 0;
	}

	// Run useful optimizations after inlining, things like removing
	// unnecessary new blocks, sharing variables, etc.
	void doOptimize(std::unordered_set<Function>& funcs, Module module, PassRunner* parentRunner) {
	// save the full list of functions on the side
	std::vector<std::unique_ptr<Function>> all;
	all.swap(module->functions);
	module->updateMaps();
	for (auto& func : funcs) {
	module->addFunction(func);
	}
	PassRunner runner(module, parentRunner->options);
	runner.setIsNested(true);
	runner.setValidateGlobally(false); // not a full valid module
	runner.add("precompute-propagate");
	runner.add("remove-unused-brs");
	runner.add("remove-unused-names");
	runner.add("coalesce-locals");
	runner.add("simplify-locals");
	runner.add("vacuum");
	runner.add("reorder-locals");
	runner.add("remove-unused-brs");
	runner.add("merge-blocks");
	runner.run();
	// restore all the funcs
	for (auto& func : module->functions) {
	func.release();
	}
	all.swap(module->functions);
	module->updateMaps();
	}
	};

	Pass *createInliningPass() {
	return new Inlining();
	}

	Pass *createInliningOptimizingPass() {
	auto* ret = new Inlining();
	ret->optimize = true;
	return ret;
	}

	} // namespace wasm