Revert of [wasm] Implement parallel compilation.

src/wasm/wasm-module.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "src/base/atomic-utils.h"
 #include "src/macro-assembler.h"
 #include "src/objects.h"
 #include "src/property-descriptor.h"
 #include "src/v8.h"
 
 #include "src/simulator.h"
 
 #include "src/wasm/ast-decoder.h"
 #include "src/wasm/module-decoder.h"
 #include "src/wasm/wasm-function-name-table.h"
@@ skipping 107 matching lines @@
       : isolate_(isolate), placeholder_code_(size), function_code_(size) {}
 
   // Get the code object for a function, allocating a placeholder if it has
   // not yet been compiled.
   Handle<Code> GetFunctionCode(uint32_t index) {
     DCHECK(index < function_code_.size());
     if (function_code_[index].is_null()) {
       // Create a placeholder code object and encode the corresponding index in
       // the {constant_pool_offset} field of the code object.
       // TODO(titzer): placeholder code objects are somewhat dangerous.
+      Handle<Code> self(nullptr, isolate_);
       byte buffer[] = {0, 0, 0, 0, 0, 0, 0, 0};  // fake instructions.
       CodeDesc desc = {buffer, 8, 8, 0, 0, nullptr};
       Handle<Code> code = isolate_->factory()->NewCode(
-          desc, Code::KindField::encode(Code::WASM_FUNCTION),
-          Handle<Object>::null());
+          desc, Code::KindField::encode(Code::WASM_FUNCTION), self);
       code->set_constant_pool_offset(index + kPlaceholderMarker);
       placeholder_code_[index] = code;
       function_code_[index] = code;
     }
     return function_code_[index];
   }
 
   void Finish(uint32_t index, Handle<Code> code) {
     DCHECK(index < function_code_.size());
     function_code_[index] = code;
@@ skipping 241 matching lines @@
   }
 
   if (!function->IsJSFunction()) {
     return ReportFFIError(thrower, "not a function", index, module_name,
                           function_name);
   }
 
   return Handle<JSFunction>::cast(function);
 }
 
-namespace {
-// Fetches the compilation unit of a wasm function and executes its parallel
-// phase.
-bool FetchAndExecuteCompilationUnit(
-    Isolate* isolate,
-    std::vector<compiler::WasmCompilationUnit*>* compilation_units,
-    std::queue<compiler::WasmCompilationUnit*>* executed_units,
-    base::Mutex* result_mutex, base::AtomicNumber<size_t>* next_unit) {
-  DisallowHeapAllocation no_allocation;
-  DisallowHandleAllocation no_handles;
-  DisallowHandleDereference no_deref;
-  DisallowCodeDependencyChange no_dependency_change;
-
-  // - 1 because AtomicIntrement returns the value after the atomic increment.
-  size_t index = next_unit->Increment(1) - 1;
-  if (index >= compilation_units->size()) {
-    return false;
-  }
-
-  compiler::WasmCompilationUnit* unit = compilation_units->at(index);
-  if (unit != nullptr) {
-    compiler::ExecuteCompilation(unit);
-    {
-      base::LockGuard<base::Mutex> guard(result_mutex);
-      executed_units->push(unit);
-    }
-  }
-  return true;
-}
-
-class WasmCompilationTask : public CancelableTask {
- public:
-  WasmCompilationTask(
-      Isolate* isolate,
-      std::vector<compiler::WasmCompilationUnit*>* compilation_units,
-      std::queue<compiler::WasmCompilationUnit*>* executed_units,
-      base::Semaphore* on_finished, base::Mutex* result_mutex,
-      base::AtomicNumber<size_t>* next_unit)
-      : CancelableTask(isolate),
-        isolate_(isolate),
-        compilation_units_(compilation_units),
-        executed_units_(executed_units),
-        on_finished_(on_finished),
-        result_mutex_(result_mutex),
-        next_unit_(next_unit) {}
-
-  void RunInternal() override {
-    while (FetchAndExecuteCompilationUnit(isolate_, compilation_units_,
-                                          executed_units_, result_mutex_,
-                                          next_unit_)) {
-    }
-    on_finished_->Signal();
-  }
-
-  Isolate* isolate_;
-  std::vector<compiler::WasmCompilationUnit*>* compilation_units_;
-  std::queue<compiler::WasmCompilationUnit*>* executed_units_;
-  base::Semaphore* on_finished_;
-  base::Mutex* result_mutex_;
-  base::AtomicNumber<size_t>* next_unit_;
-};
-
-void record_code_size(uint32_t& total_code_size, Code* code) {
-  if (FLAG_print_wasm_code_size) {
-    total_code_size += code->body_size() + code->relocation_info()->length();
-  }
-}
-
-bool CompileWrappersToImportedFunctions(Isolate* isolate, WasmModule* module,
-                                        const Handle<JSReceiver> ffi,
-                                        WasmModuleInstance* instance,
-                                        ErrorThrower* thrower, Factory* factory,
-                                        ModuleEnv* module_env,
-                                        uint32_t& total_code_size) {
-  uint32_t index = 0;
-  if (module->import_table.size() > 0) {
-    instance->import_code.reserve(module->import_table.size());
-    for (const WasmImport& import : module->import_table) {
-      WasmName module_name = module->GetNameOrNull(import.module_name_offset,
-                                                   import.module_name_length);
-      WasmName function_name = module->GetNameOrNull(
-          import.function_name_offset, import.function_name_length);
-      MaybeHandle<JSFunction> function = LookupFunction(
-          *thrower, factory, ffi, index, module_name, function_name);
-      if (function.is_null()) return false;
-
-      Handle<Code> code = compiler::CompileWasmToJSWrapper(
-          isolate, module_env, function.ToHandleChecked(), import.sig,
-          module_name, function_name);
-      instance->import_code.push_back(code);
-      record_code_size(total_code_size, *code);
-      index++;
-    }
-  }
-  return true;
-}
-
-void InitializeParallelCompilation(
-    Isolate* isolate, std::vector<WasmFunction>& functions,
-    std::vector<compiler::WasmCompilationUnit*>& compilation_units,
-    ModuleEnv& module_env, ErrorThrower& thrower) {
-  // Create a placeholder code object for all functions.
-  // TODO(ahaas): Maybe we could skip this for external functions.
-  for (uint32_t i = 0; i < functions.size(); i++) {
-    module_env.linker->GetFunctionCode(i);
-  }
-
-  for (uint32_t i = FLAG_skip_compiling_wasm_funcs; i < functions.size(); i++) {
-    if (!functions[i].external) {
-      compilation_units[i] = compiler::CreateWasmCompilationUnit(
-          &thrower, isolate, &module_env, &functions[i], i);
-    } else {
-      compilation_units[i] = nullptr;
-    }
-  }
-}
-
-uint32_t* StartCompilationTasks(
-    Isolate* isolate,
-    std::vector<compiler::WasmCompilationUnit*>& compilation_units,
-    std::queue<compiler::WasmCompilationUnit*>& executed_units,
-    const base::SmartPointer<base::Semaphore>& pending_tasks,
-    base::Mutex& result_mutex, base::AtomicNumber<size_t>& next_unit) {
-  const size_t num_tasks =
-      Min(static_cast<size_t>(FLAG_wasm_num_compilation_tasks),
-          V8::GetCurrentPlatform()->NumberOfAvailableBackgroundThreads());
-  uint32_t* task_ids = new uint32_t[num_tasks];
-  for (size_t i = 0; i < num_tasks; i++) {
-    WasmCompilationTask* task =
-        new WasmCompilationTask(isolate, &compilation_units, &executed_units,
-                                pending_tasks.get(), &result_mutex, &next_unit);
-    task_ids[i] = task->id();
-    V8::GetCurrentPlatform()->CallOnBackgroundThread(
-        task, v8::Platform::kShortRunningTask);
-  }
-  return task_ids;
-}
-
-void WaitForCompilationTasks(
-    Isolate* isolate, uint32_t* task_ids,
-    const base::SmartPointer<base::Semaphore>& pending_tasks) {
-  const size_t num_tasks =
-      Min(static_cast<size_t>(FLAG_wasm_num_compilation_tasks),
-          V8::GetCurrentPlatform()->NumberOfAvailableBackgroundThreads());
-  for (size_t i = 0; i < num_tasks; i++) {
-    // If the task has not started yet, then we abort it. Otherwise we wait for
-    // it to finish.
-    if (!isolate->cancelable_task_manager()->TryAbort(task_ids[i])) {
-      pending_tasks->Wait();
-    }
-  }
-}
-
-void FinishCompilationUnits(
-    WasmModule* module,
-    std::queue<compiler::WasmCompilationUnit*>& executed_units,
-    std::vector<Handle<Code>>& results, base::Mutex& result_mutex) {
-  while (!executed_units.empty()) {
-    compiler::WasmCompilationUnit* unit = nullptr;
-    {
-      base::LockGuard<base::Mutex> guard(&result_mutex);
-      unit = executed_units.front();
-      executed_units.pop();
-    }
-    int j = compiler::GetIndexOfWasmCompilationUnit(unit);
-    if (!module->functions[j].external) {
-      results[j] = compiler::FinishCompilation(unit);
-    }
-  }
-}
-
-bool FinishCompilation(Isolate* isolate, WasmModule* module,
-                       const Handle<JSReceiver> ffi,
-                       const std::vector<Handle<Code>>& results,
-                       const WasmModuleInstance& instance,
-                       const Handle<FixedArray>& code_table,
-                       ErrorThrower& thrower, Factory* factory,
-                       ModuleEnv& module_env, uint32_t& total_code_size,
-                       PropertyDescriptor& desc) {
-  for (uint32_t i = FLAG_skip_compiling_wasm_funcs;
-       i < module->functions.size(); i++) {
-    const WasmFunction& func = module->functions[i];
-    if (thrower.error()) break;
-
-    DCHECK_EQ(i, func.func_index);
-    WasmName str = module->GetName(func.name_offset, func.name_length);
-    WasmName str_null = {nullptr, 0};
-    Handle<String> name = factory->InternalizeUtf8String(str);
-    Handle<Code> code = Handle<Code>::null();
-    Handle<JSFunction> function = Handle<JSFunction>::null();
-    if (func.external) {
-      // Lookup external function in FFI object.
-      MaybeHandle<JSFunction> function =
-          LookupFunction(thrower, factory, ffi, i, str, str_null);
-      if (function.is_null()) {
-        return false;
-      }
-      code = compiler::CompileWasmToJSWrapper(isolate, &module_env,
-                                              function.ToHandleChecked(),
-                                              func.sig, str, str_null);
-    } else {
-      if (FLAG_wasm_num_compilation_tasks != 0) {
-        code = results[i];
-      } else {
-        // Compile the function.
-        code = compiler::CompileWasmFunction(&thrower, isolate, &module_env,
-                                             &func);
-      }
-      if (code.is_null()) {
-        thrower.Error("Compilation of #%d:%.*s failed.", i, str.length(),
-                      str.start());
-        return false;
-      }
-      if (func.exported) {
-        function = compiler::CompileJSToWasmWrapper(
-            isolate, &module_env, name, code, instance.js_object, i);
-        record_code_size(total_code_size, function->code());
-      }
-    }
-    if (!code.is_null()) {
-      // Install the code into the linker table.
-      module_env.linker->Finish(i, code);
-      code_table->set(i, *code);
-      record_code_size(total_code_size, *code);
-    }
-    if (func.exported) {
-      // Exported functions are installed as read-only properties on the
-      // module.
-      desc.set_value(function);
-      Maybe<bool> status = JSReceiver::DefineOwnProperty(
-          isolate, instance.js_object, name, &desc, Object::THROW_ON_ERROR);
-      if (!status.IsJust())
-        thrower.Error("export of %.*s failed.", str.length(), str.start());
-    }
-  }
-  return true;
-}
-}  // namespace
-
 // Instantiates a wasm module as a JSObject.
 //  * allocates a backing store of {mem_size} bytes.
 //  * installs a named property "memory" for that buffer if exported
 //  * installs named properties on the object for exported functions
 //  * compiles wasm code to machine code
 MaybeHandle<JSObject> WasmModule::Instantiate(Isolate* isolate,
                                               Handle<JSReceiver> ffi,
                                               Handle<JSArrayBuffer> memory) {
   HistogramTimerScope wasm_instantiate_module_time_scope(
       isolate->counters()->wasm_instantiate_module_time());
   this->shared_isolate = isolate;  // TODO(titzer): have a real shared isolate.
   ErrorThrower thrower(isolate, "WasmModule::Instantiate()");
   Factory* factory = isolate->factory();
 
   PropertyDescriptor desc;
   desc.set_writable(false);
 
   // If FLAG_print_wasm_code_size is set, this aggregates the sum of all code
   // objects created for this module.
   // TODO(titzer): switch this to TRACE_EVENT
   uint32_t total_code_size = 0;
+  auto record_code_size = [&total_code_size](Code* code) {
+    if (FLAG_print_wasm_code_size)
+      total_code_size += code->body_size() + code->relocation_info()->length();
+  };
 
   //-------------------------------------------------------------------------
   // Allocate the instance and its JS counterpart.
   //-------------------------------------------------------------------------
   Handle<Map> map = factory->NewMap(
       JS_OBJECT_TYPE,
       JSObject::kHeaderSize + kWasmModuleInternalFieldCount * kPointerSize);
   WasmModuleInstance instance(this);
   instance.context = isolate->native_context();
   instance.js_object = factory->NewJSObjectFromMap(map, TENURED);
@@ skipping 26 matching lines @@
     return MaybeHandle<JSObject>();
   }
   if (!instance.globals_buffer.is_null()) {
     instance.js_object->SetInternalField(kWasmGlobalsArrayBuffer,
                                          *instance.globals_buffer);
   }
 
   HistogramTimerScope wasm_compile_module_time_scope(
       isolate->counters()->wasm_compile_module_time());
 
+  //-------------------------------------------------------------------------
+  // Compile wrappers to imported functions.
+  //-------------------------------------------------------------------------
+  uint32_t index = 0;
   instance.function_table = BuildFunctionTable(isolate, this);
   WasmLinker linker(isolate, functions.size());
   ModuleEnv module_env;
   module_env.module = this;
   module_env.instance = &instance;
   module_env.linker = &linker;
   module_env.origin = origin;
 
-  //-------------------------------------------------------------------------
-  // Compile wrappers to imported functions.
-  //-------------------------------------------------------------------------
-  if (!CompileWrappersToImportedFunctions(isolate, this, ffi, &instance,
-                                          &thrower, factory, &module_env,
-                                          total_code_size)) {
-    return MaybeHandle<JSObject>();
+  if (import_table.size() > 0) {
+    instance.import_code.reserve(import_table.size());
+    for (const WasmImport& import : import_table) {
+      WasmName module_name =
+          GetNameOrNull(import.module_name_offset, import.module_name_length);
+      WasmName function_name = GetNameOrNull(import.function_name_offset,
+                                             import.function_name_length);
+      MaybeHandle<JSFunction> function = LookupFunction(
+          thrower, factory, ffi, index, module_name, function_name);
+      if (function.is_null()) return MaybeHandle<JSObject>();
+      Handle<Code> code = compiler::CompileWasmToJSWrapper(
+          isolate, &module_env, function.ToHandleChecked(), import.sig,
+          module_name, function_name);
+      instance.import_code.push_back(code);
+      record_code_size(*code);
+      index++;
+    }
   }
+
   //-------------------------------------------------------------------------
   // Compile all functions in the module.
   //-------------------------------------------------------------------------
   {
     isolate->counters()->wasm_functions_per_module()->AddSample(
         static_cast<int>(functions.size()));
 
-    // Data structures for the parallel compilation.
     std::vector<compiler::WasmCompilationUnit*> compilation_units(
         functions.size());
     std::queue<compiler::WasmCompilationUnit*> executed_units;
     std::vector<Handle<Code>> results(functions.size());
 
-    if (FLAG_wasm_num_compilation_tasks != 0) {
-      //-----------------------------------------------------------------------
-      // For parallel compilation:
-      // 1) The main thread allocates a compilation unit for each wasm function
-      //    and stores them in the vector {compilation_units}.
-      // 2) The main thread spawns {WasmCompilationTask} instances which run on
-      //    the background threads.
-      // 3.a) The background threads and the main thread pick one compilation
-      //      unit at a time and execute the parallel phase of the compilation
-      //      unit. After finishing the execution of the parallel phase, the
-      //      result is enqueued in {executed_units}.
-      // 3.b) If {executed_units} contains a compilation unit, the main thread
-      //      dequeues it and finishes the compilation.
-      // 4) After the parallel phase of all compilation units has started, the
-      //    main thread waits for all {WasmCompilationTask} instances to finish.
-      // 5) The main thread finishes the compilation.
+    if (FLAG_wasm_parallel_compilation) {
+      // Create a placeholder code object for all functions.
+      // TODO(ahaas): Maybe we could skip this for external functions.
+      for (uint32_t i = 0; i < functions.size(); i++) {
+        linker.GetFunctionCode(i);
+      }
 
-      // Turn on the {CanonicalHandleScope} so that the background threads can
-      // use the node cache.
-      CanonicalHandleScope canonical(isolate);
+      for (uint32_t i = FLAG_skip_compiling_wasm_funcs; i < functions.size();
+           i++) {
+        if (!functions[i].external) {
+          compilation_units[i] = compiler::CreateWasmCompilationUnit(
+              &thrower, isolate, &module_env, &functions[i], i);
+        }
+      }
 
-      // 1) The main thread allocates a compilation unit for each wasm function
-      //    and stores them in the vector {compilation_units}.
-      InitializeParallelCompilation(isolate, functions, compilation_units,
-                                    module_env, thrower);
-
-      // Objects for the synchronization with the background threads.
-      base::SmartPointer<base::Semaphore> pending_tasks(new base::Semaphore(0));
-      base::Mutex result_mutex;
-      base::AtomicNumber<size_t> next_unit(
-          static_cast<size_t>(FLAG_skip_compiling_wasm_funcs));
-
-      // 2) The main thread spawns {WasmCompilationTask} instances which run on
-      //    the background threads.
-      base::SmartArrayPointer<uint32_t> task_ids(
-          StartCompilationTasks(isolate, compilation_units, executed_units,
-                                pending_tasks, result_mutex, next_unit));
-
-      // 3.a) The background threads and the main thread pick one compilation
-      //      unit at a time and execute the parallel phase of the compilation
-      //      unit. After finishing the execution of the parallel phase, the
-      //      result is enqueued in {executed_units}.
-      while (FetchAndExecuteCompilationUnit(isolate, &compilation_units,
-                                            &executed_units, &result_mutex,
-                                            &next_unit)) {
-        // 3.b) If {executed_units} contains a compilation unit, the main thread
-        //      dequeues it and finishes the compilation unit. Compilation units
-        //      are finished concurrently to the background threads to save
-        //      memory.
-        FinishCompilationUnits(this, executed_units, results, result_mutex);
+      index = FLAG_skip_compiling_wasm_funcs;
+      while (true) {
+        while (!executed_units.empty()) {
+          compiler::WasmCompilationUnit* unit = executed_units.front();
+          executed_units.pop();
+          int i = compiler::GetIndexOfWasmCompilationUnit(unit);
+          results[i] = compiler::FinishCompilation(unit);
+        }
+        if (index < functions.size()) {
+          if (!functions[index].external) {
+            compiler::ExecuteCompilation(compilation_units[index]);
+            executed_units.push(compilation_units[index]);
+            index++;
+          }
+        } else {
+          break;
+        }
       }
-      // 4) After the parallel phase of all compilation units has started, the
-      //    main thread waits for all {WasmCompilationTask} instances to finish.
-      WaitForCompilationTasks(isolate, task_ids.get(), pending_tasks);
-      // Finish the compilation of the remaining compilation units.
-      FinishCompilationUnits(this, executed_units, results, result_mutex);
-    }
-    // 5) The main thread finishes the compilation.
-    if (!FinishCompilation(isolate, this, ffi, results, instance, code_table,
-                           thrower, factory, module_env, total_code_size,
-                           desc)) {
-      return MaybeHandle<JSObject>();
     }
 
-    // Patch all direct call sites.
+    // First pass: compile each function and initialize the code table.
+    for (uint32_t i = FLAG_skip_compiling_wasm_funcs; i < functions.size();
+         i++) {
+      const WasmFunction& func = functions[i];
+      if (thrower.error()) break;
+      DCHECK_EQ(i, func.func_index);
+
+      WasmName str = GetName(func.name_offset, func.name_length);
+      WasmName str_null = {nullptr, 0};
+      Handle<String> name = factory->InternalizeUtf8String(str);
+      Handle<Code> code = Handle<Code>::null();
+      Handle<JSFunction> function = Handle<JSFunction>::null();
+      if (func.external) {
+        // Lookup external function in FFI object.
+        MaybeHandle<JSFunction> function =
+            LookupFunction(thrower, factory, ffi, i, str, str_null);
+        if (function.is_null()) return MaybeHandle<JSObject>();
+        code = compiler::CompileWasmToJSWrapper(isolate, &module_env,
+                                                function.ToHandleChecked(),
+                                                func.sig, str, str_null);
+      } else {
+        if (FLAG_wasm_parallel_compilation) {
+          code = results[i];
+        } else {
+          // Compile the function.
+          code = compiler::CompileWasmFunction(&thrower, isolate, &module_env,
+                                               &func);
+        }
+        if (code.is_null()) {
+          thrower.Error("Compilation of #%d:%.*s failed.", i, str.length(),
+                        str.start());
+          return MaybeHandle<JSObject>();
+        }
+        if (func.exported) {
+          function = compiler::CompileJSToWasmWrapper(
+              isolate, &module_env, name, code, instance.js_object, i);
+          record_code_size(function->code());
+        }
+      }
+      if (!code.is_null()) {
+        // Install the code into the linker table.
+        linker.Finish(i, code);
+        code_table->set(i, *code);
+        record_code_size(*code);
+      }
+      if (func.exported) {
+        // Exported functions are installed as read-only properties on the
+        // module.
+        desc.set_value(function);
+        Maybe<bool> status = JSReceiver::DefineOwnProperty(
+            isolate, instance.js_object, name, &desc, Object::THROW_ON_ERROR);
+        if (!status.IsJust())
+          thrower.Error("export of %.*s failed.", str.length(), str.start());
+      }
+    }
+
+    // Second pass: patch all direct call sites.
     linker.Link(instance.function_table, this->function_table);
     instance.js_object->SetInternalField(kWasmModuleFunctionTable,
                                          Smi::FromInt(0));
 
     //-------------------------------------------------------------------------
     // Create and populate the exports object.
     //-------------------------------------------------------------------------
     if (export_table.size() > 0 || mem_export) {
       // Create the "exports" object.
       Handle<JSFunction> object_function = Handle<JSFunction>(
           isolate->native_context()->object_function(), isolate);
       Handle<JSObject> exports_object =
           factory->NewJSObject(object_function, TENURED);
       Handle<String> exports_name = factory->InternalizeUtf8String("exports");
       JSObject::AddProperty(instance.js_object, exports_name, exports_object,
                             READ_ONLY);
 
       // Compile wrappers and add them to the exports object.
       for (const WasmExport& exp : export_table) {
         if (thrower.error()) break;
         WasmName str = GetName(exp.name_offset, exp.name_length);
         Handle<String> name = factory->InternalizeUtf8String(str);
         Handle<Code> code = linker.GetFunctionCode(exp.func_index);
         Handle<JSFunction> function = compiler::CompileJSToWasmWrapper(
             isolate, &module_env, name, code, instance.js_object,
             exp.func_index);
-        record_code_size(total_code_size, function->code());
+        record_code_size(function->code());
         desc.set_value(function);
         Maybe<bool> status = JSReceiver::DefineOwnProperty(
             isolate, exports_object, name, &desc, Object::THROW_ON_ERROR);
         if (!status.IsJust())
           thrower.Error("export of %.*s failed.", str.length(), str.start());
       }
 
       if (mem_export) {
         // Export the memory as a named property.
         Handle<String> name = factory->InternalizeUtf8String("memory");
@@ skipping 168 matching lines @@
       wasm->GetInternalField(kWasmFunctionNamesArray), wasm->GetIsolate());
   if (func_names_arr_obj->IsUndefined())
     return func_names_arr_obj;  // Return undefined.
   return GetWasmFunctionNameFromTable(
       Handle<ByteArray>::cast(func_names_arr_obj), func_index);
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8