GN threading refactor

tools/gn/toolchain_manager.cc

Index: tools/gn/toolchain_manager.cc
diff --git a/tools/gn/toolchain_manager.cc b/tools/gn/toolchain_manager.cc
deleted file mode 100644
index 4edf212218ca747c8b648d9eaf62cae3e6825482..0000000000000000000000000000000000000000
--- a/tools/gn/toolchain_manager.cc
+++ /dev/null
@@ -1,593 +0,0 @@
-// Copyright (c) 2013 The Chromium 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 "tools/gn/toolchain_manager.h"
-
-#include <set>
-
-#include "base/bind.h"
-#include "build/build_config.h"
-#include "tools/gn/err.h"
-#include "tools/gn/item.h"
-#include "tools/gn/item_node.h"
-#include "tools/gn/item_tree.h"
-#include "tools/gn/parse_tree.h"
-#include "tools/gn/scheduler.h"
-#include "tools/gn/scope.h"
-#include "tools/gn/scope_per_file_provider.h"
-#include "tools/gn/trace.h"
-
-// How toolchain loading works
-// ---------------------------
-// When we start loading a build, we'll load the build config file and that
-// will call set_default_toolchain. We'll schedule a load of the file
-// containing the default toolchain definition, and can do this in parallel
-// with all other build files. Targets will have an implicit dependency on the
-// toolchain so we won't write out any files until we've loaded the toolchain
-// definition.
-//
-// When we see a reference to a target using a different toolchain, it gets
-// more complicated. In this case, the toolchain definition contains arguments
-// to pass into the build config file when it is invoked in the context of that
-// toolchain. As a result, we have to actually see the definition of the
-// toolchain before doing anything else.
-//
-// So when we see a reference to a non-default toolchain we do the following:
-//
-//  1. Schedule a load of the file containing the toolchain definition, if it
-//     isn't loaded already.
-//  2. When the toolchain definition is loaded, we schedule a load of the
-//     build config file in the context of that toolchain. We'll use the
-//     arguments from the toolchain definition to execute it.
-//  3. When the build config is set up, then we can load all of the individual
-//     buildfiles in the context of that config that we require.
-
-namespace {
-
-enum ToolchainState {
-  // Toolchain settings have not requested to be loaded. This means we
-  // haven't seen any targets that require this toolchain yet. This means that
-  // we have seen a toolchain definition, but no targets that use it. Not
-  // loading the settings automatically allows you to define a bunch of
-  // toolchains and potentially not use them without much overhead.
-  TOOLCHAIN_NOT_LOADED,
-
-  // The toolchain definition for non-default toolchains has been scheduled
-  // to be loaded but has not completed. When this is done, we can load the
-  // settings file. This is needed to get the arguments out of the toolchain
-  // definition. This is skipped for the default toolchain which has no
-  // arguments (see summary above).
-  TOOLCHAIN_DEFINITION_LOADING,
-
-  // The settings have been scheduled to be loaded but have not completed.
-  TOOLCHAIN_SETTINGS_LOADING,
-
-  // The settings are done being loaded.
-  TOOLCHAIN_SETTINGS_LOADED
-};
-
-SourceFile DirToBuildFile(const SourceDir& dir) {
-  return SourceFile(dir.value() + "BUILD.gn");
-}
-
-}  // namespace
-
-struct ToolchainManager::Info {
-  Info(const BuildSettings* build_settings,
-       const Label& toolchain_name,
-       const std::string& output_subdir_name)
-      : state(TOOLCHAIN_NOT_LOADED),
-        settings(build_settings, output_subdir_name),
-        toolchain(new Toolchain(&settings, toolchain_name)),
-        toolchain_set(false),
-        toolchain_file_loaded(false),
-        item_node(NULL) {
-    settings.set_toolchain_label(toolchain_name);
-  }
-
-  ~Info() {
-    if (!item_node)  // See toolchain definition for more.
-      delete toolchain;
-  }
-
-  // Makes sure that an ItemNode is created for the toolchain, which lets
-  // targets depend on the (potentially future) loading of the toolchain.
-  //
-  // We can't always do this at the beginning since when doing the default
-  // build config, we don't know the toolchain name yet. We also need to go
-  // through some effort to avoid doing this inside the toolchain manager's
-  // lock (to avoid holding two locks at once).
-  void EnsureItemNode() {
-    if (!item_node) {
-      ItemTree& tree = settings.build_settings()->item_tree();
-      item_node = new ItemNode(toolchain);
-      tree.AddNodeLocked(item_node);
-    }
-  }
-
-  ToolchainState state;
-
-  // The first place in the build that we saw a reference for this toolchain.
-  // This allows us to report errors if it can't be loaded and blame some
-  // reasonable place of the code. This will be empty for the default toolchain.
-  LocationRange specified_from;
-
-  // When the state is TOOLCHAIN_SETTINGS_LOADED, the settings should be
-  // considered read-only and can be read without locking. Otherwise, they
-  // should not be accessed at all except to load them (which can therefore
-  // also be done outside of the lock). This works as long as the state flag
-  // is only ever read or written inside the lock.
-  Settings settings;
-
-  // When we create an item node, this pointer will be owned by that node
-  // so it's lifetime is managed by the dependency graph. Before we've created
-  // the ItemNode, this class has to takre responsibility for this pointer.
-  Toolchain* toolchain;
-  bool toolchain_set;
-  LocationRange toolchain_definition_location;
-
-  // Set when the file corresponding to the toolchain definition is loaded.
-  // This will normally be set right after "toolchain_set". However, if the
-  // toolchain definition is missing, the file might be marked loaded but the
-  // toolchain definition could still be unset.
-  bool toolchain_file_loaded;
-
-  // While state == TOOLCHAIN_SETTINGS_LOADING || TOOLCHAIN_DEFINITION_LOADING,
-  // this will collect all scheduled invocations using this toolchain. They'll
-  // be issued once the settings file has been interpreted.
-  //
-  // The map maps the source file to "some" location it was invoked from (so
-  // we can give good error messages). It does NOT map to the root of the
-  // file to be invoked (the file still needs loading). This will be NULL
-  // for internally invoked files.
-  typedef std::map<SourceFile, LocationRange> ScheduledInvocationMap;
-  ScheduledInvocationMap scheduled_invocations;
-
-  // Tracks all scheduled and executed invocations for this toolchain. This
-  // is used to avoid invoking a file more than once for a toolchain.
-  std::set<SourceFile> all_invocations;
-
-  // Filled in by EnsureItemNode, see that for more.
-  ItemNode* item_node;
-};
-
-ToolchainManager::ToolchainManager(const BuildSettings* build_settings)
-    : build_settings_(build_settings) {
-}
-
-ToolchainManager::~ToolchainManager() {
-  for (ToolchainMap::iterator i = toolchains_.begin();
-       i != toolchains_.end(); ++i)
-    delete i->second;
-  toolchains_.clear();
-}
-
-void ToolchainManager::StartLoadingUnlocked(const SourceFile& build_file_name) {
-  // How the default build config works: Initially we don't have a toolchain
-  // name to call the settings for the default build config. So we create one
-  // with an empty toolchain name and execute the default build config file.
-  // When that's done, we'll go and fix up the name to the default build config
-  // that the script set.
-  base::AutoLock lock(GetLock());
-  Err err;
-  Info* info = LoadNewToolchainLocked(LocationRange(), Label(), &err);
-  if (err.has_error())
-    g_scheduler->FailWithError(err);
-  CHECK(info);
-  info->scheduled_invocations[build_file_name] = LocationRange();
-  info->all_invocations.insert(build_file_name);
-
-  if (!ScheduleBuildConfigLoadLocked(info, true, &err))
-    g_scheduler->FailWithError(err);
-}
-
-const Settings* ToolchainManager::GetSettingsForToolchainLocked(
-    const LocationRange& from_here,
-    const Label& toolchain_name,
-    Err* err) {
-  GetLock().AssertAcquired();
-  ToolchainMap::iterator found = toolchains_.find(toolchain_name);
-  Info* info = NULL;
-  if (found == toolchains_.end()) {
-    info = LoadNewToolchainLocked(from_here, toolchain_name, err);
-    if (!info)
-      return NULL;
-  } else {
-    info = found->second;
-  }
-  info->EnsureItemNode();
-
-  return &info->settings;
-}
-
-const Toolchain* ToolchainManager::GetToolchainDefinitionUnlocked(
-    const Label& toolchain_name) {
-  base::AutoLock lock(GetLock());
-  ToolchainMap::iterator found = toolchains_.find(toolchain_name);
-  if (found == toolchains_.end() || !found->second->toolchain_set)
-    return NULL;
-
-  // Since we don't allow defining a toolchain more than once, we know that
-  // once it's set it won't be mutated, so we can safely return this pointer
-  // for reading outside the lock.
-  return found->second->toolchain;
-}
-
-bool ToolchainManager::SetDefaultToolchainUnlocked(
-    const Label& default_toolchain,
-    const LocationRange& defined_here,
-    Err* err) {
-  base::AutoLock lock(GetLock());
-  if (!default_toolchain_.is_null()) {
-    *err = Err(defined_here, "Default toolchain already set.");
-    err->AppendSubErr(Err(default_toolchain_defined_here_,
-                          "Previously defined here.",
-                          "You can only set this once."));
-    return false;
-  }
-
-  if (default_toolchain.is_null()) {
-    *err = Err(defined_here, "Bad default toolchain name.",
-        "You can't set the default toolchain name to nothing.");
-    return false;
-  }
-  if (!default_toolchain.toolchain_dir().is_null() ||
-      !default_toolchain.toolchain_name().empty()) {
-    *err = Err(defined_here, "Toolchain name has toolchain.",
-        "You can't specify a toolchain (inside the parens) for a toolchain "
-        "name. I got:\n" + default_toolchain.GetUserVisibleName(true));
-    return false;
-  }
-
-  default_toolchain_ = default_toolchain;
-  default_toolchain_defined_here_ = defined_here;
-  return true;
-}
-
-Label ToolchainManager::GetDefaultToolchainUnlocked() const {
-  base::AutoLock lock(GetLock());
-  return default_toolchain_;
-}
-
-bool ToolchainManager::SetToolchainDefinitionLocked(
-    const Toolchain& tc,
-    const LocationRange& defined_from,
-    Err* err) {
-  GetLock().AssertAcquired();
-
-  ToolchainMap::iterator found = toolchains_.find(tc.label());
-  Info* info = NULL;
-  if (found == toolchains_.end()) {
-    // New toolchain.
-    info = LoadNewToolchainLocked(defined_from, tc.label(), err);
-    if (!info)
-      return false;
-  } else {
-    // It's important to preserve the exact Toolchain object in our tree since
-    // it will be in the ItemTree and targets may have dependencies on it.
-    info = found->second;
-  }
-
-  // The labels should match or else we're setting the wrong one!
-  CHECK(info->toolchain->label() == tc.label());
-
-  // Save the toolchain. We can just overwrite our definition.
-  *info->toolchain = tc;
-
-  if (info->toolchain_set) {
-    *err = Err(defined_from, "Duplicate toolchain definition.");
-    err->AppendSubErr(Err(
-        info->toolchain_definition_location,
-        "Previously defined here.",
-        "A toolchain can only be defined once. One tricky way that this could\n"
-        "happen is if your definition is itself in a file that's interpreted\n"
-        "under different toolchains, which would result in multiple\n"
-        "definitions as the file is loaded multiple times. So be sure your\n"
-        "toolchain definitions are in files that either don't define any\n"
-        "targets (probably best) or at least don't contain targets executed\n"
-        "with more than one toolchain."));
-    return false;
-  }
-
-  info->EnsureItemNode();
-
-  info->toolchain_set = true;
-  info->toolchain_definition_location = defined_from;
-  return true;
-}
-
-bool ToolchainManager::ScheduleInvocationLocked(
-    const LocationRange& specified_from,
-    const Label& toolchain_name,
-    const SourceDir& dir,
-    Err* err) {
-  GetLock().AssertAcquired();
-  SourceFile build_file(DirToBuildFile(dir));
-
-  // If there's no specified toolchain name, use the default.
-  ToolchainMap::iterator found;
-  if (toolchain_name.is_null())
-    found = toolchains_.find(default_toolchain_);
-  else
-    found = toolchains_.find(toolchain_name);
-
-  Info* info = NULL;
-  if (found == toolchains_.end()) {
-    // New toolchain.
-    info = LoadNewToolchainLocked(specified_from, toolchain_name, err);
-    if (!info)
-      return false;
-  } else {
-    // Use existing one.
-    info = found->second;
-    if (info->all_invocations.find(build_file) !=
-        info->all_invocations.end()) {
-      // We've already seen this source file for this toolchain, don't need
-      // to do anything.
-      return true;
-    }
-  }
-
-  info->all_invocations.insert(build_file);
-
-  switch (info->state) {
-    case TOOLCHAIN_NOT_LOADED:
-      // Toolchain needs to be loaded. Start loading it and push this buildfile
-      // on the wait queue. The actual toolchain build file will have been
-      // scheduled to be loaded by LoadNewToolchainLocked() above, so we just
-      // need to request that the build settings be loaded when that toolchain
-      // file is done executing (recall toolchain files are executed in the
-      // context of the default toolchain, which is why we need to do the extra
-      // Info lookup in the make_pair).
-      DCHECK(!default_toolchain_.is_null());
-      pending_build_config_map_[
-              std::make_pair(DirToBuildFile(toolchain_name.dir()),
-                             toolchains_[default_toolchain_])] =
-          info;
-      info->scheduled_invocations[build_file] = specified_from;
-
-      // Transition to the loading state.
-      info->specified_from = specified_from;
-      info->state = TOOLCHAIN_DEFINITION_LOADING;
-      return true;
-
-    case TOOLCHAIN_DEFINITION_LOADING:
-    case TOOLCHAIN_SETTINGS_LOADING:
-      // Toolchain is in the process of loading, push this buildfile on the
-      // wait queue to run when the config is ready.
-      info->scheduled_invocations[build_file] = specified_from;
-      return true;
-
-    case TOOLCHAIN_SETTINGS_LOADED:
-      // Everything is ready, just schedule the build file to load.
-      return ScheduleBackgroundInvoke(info, specified_from, build_file, err);
-
-    default:
-      NOTREACHED();
-      return false;
-  }
-}
-
-// static
-std::string ToolchainManager::ToolchainToOutputSubdir(
-    const Label& toolchain_name) {
-  // For now just assume the toolchain name is always a valid dir name. We may
-  // want to clean up the in the future.
-  return toolchain_name.name();
-}
-
-ToolchainManager::Info* ToolchainManager::LoadNewToolchainLocked(
-    const LocationRange& specified_from,
-    const Label& toolchain_name,
-    Err* err) {
-  GetLock().AssertAcquired();
-  Info* info = new Info(build_settings_,
-                        toolchain_name,
-                        ToolchainToOutputSubdir(toolchain_name));
-
-  toolchains_[toolchain_name] = info;
-
-  // Invoke the file containing the toolchain definition so that it gets
-  // defined. The default one (label is empty) will be done spearately.
-  if (!toolchain_name.is_null()) {
-    // The default toolchain should be specified whenever we're requesting
-    // another one. This is how we know under what context we should execute
-    // the invoke for the toolchain file.
-    CHECK(!default_toolchain_.is_null());
-    ScheduleInvocationLocked(specified_from, default_toolchain_,
-                             toolchain_name.dir(), err);
-  }
-  return info;
-}
-
-void ToolchainManager::FixupDefaultToolchainLocked() {
-  // Now that we've run the default build config, we should know the
-  // default toolchain name. Fix up our reference.
-  // See Start() for more.
-  GetLock().AssertAcquired();
-  if (default_toolchain_.is_null()) {
-    g_scheduler->FailWithError(Err(Location(),
-        "Default toolchain not set.",
-        "Your build config file \"" +
-        build_settings_->build_config_file().value() +
-        "\"\ndid not call set_default_toolchain(). This is needed so "
-        "I know how to actually\ncompile your code."));
-    return;
-  }
-
-  ToolchainMap::iterator old_default = toolchains_.find(Label());
-  CHECK(old_default != toolchains_.end());
-  Info* info = old_default->second;
-  toolchains_[default_toolchain_] = info;
-  toolchains_.erase(old_default);
-
-  // Toolchain should not have been loaded in the build config file.
-  CHECK(!info->toolchain_set);
-
-  // We need to set the toolchain label now that we know it. There's no way
-  // to set the label, but we can assign the toolchain to a new one. Loading
-  // the build config can not change the toolchain, so we won't be overwriting
-  // anything useful.
-  *info->toolchain = Toolchain(&info->settings, default_toolchain_);
-  info->settings.set_is_default(true);
-  info->settings.set_toolchain_label(default_toolchain_);
-  info->EnsureItemNode();
-
-  // The default toolchain is loaded in greedy mode so all targets we
-  // encounter are generated. Non-default toolchain settings stay in non-greedy
-  // so we only generate the minimally required set.
-  info->settings.set_greedy_target_generation(true);
-
-  // Schedule a load of the toolchain build file.
-  Err err;
-  ScheduleInvocationLocked(LocationRange(), default_toolchain_,
-                           default_toolchain_.dir(), &err);
-  if (err.has_error())
-    g_scheduler->FailWithError(err);
-}
-
-bool ToolchainManager::ScheduleBackgroundInvoke(
-    Info* info,
-    const LocationRange& specified_from,
-    const SourceFile& build_file,
-    Err* err) {
-  g_scheduler->IncrementWorkCount();
-  if (!g_scheduler->input_file_manager()->AsyncLoadFile(
-           specified_from, build_settings_, build_file,
-           base::Bind(&ToolchainManager::BackgroundInvoke,
-                      base::Unretained(this), info, build_file),
-           err)) {
-    g_scheduler->DecrementWorkCount();
-    return false;
-  }
-  return true;
-}
-
-bool ToolchainManager::ScheduleBuildConfigLoadLocked(Info* info,
-                                                     bool is_default,
-                                                     Err* err) {
-  GetLock().AssertAcquired();
-
-  g_scheduler->IncrementWorkCount();
-  if (!g_scheduler->input_file_manager()->AsyncLoadFile(
-           info->specified_from, build_settings_,
-           build_settings_->build_config_file(),
-           base::Bind(&ToolchainManager::BackgroundLoadBuildConfig,
-                      base::Unretained(this), info, is_default),
-           err)) {
-    g_scheduler->DecrementWorkCount();
-    return false;
-  }
-  info->state = TOOLCHAIN_SETTINGS_LOADING;
-  return true;
-}
-
-void ToolchainManager::BackgroundLoadBuildConfig(Info* info,
-                                                 bool is_default,
-                                                 const ParseNode* root) {
-  // Danger: No early returns without decrementing the work count.
-  if (root && !g_scheduler->is_failed()) {
-    // Nobody should be accessing settings at this point other than us since we
-    // haven't marked it loaded, so we can do it outside the lock.
-    Scope* base_config = info->settings.base_config();
-    base_config->set_source_dir(SourceDir("//"));
-
-    info->settings.build_settings()->build_args().SetupRootScope(
-        base_config, info->toolchain->args());
-
-    base_config->SetProcessingBuildConfig();
-    if (is_default)
-      base_config->SetProcessingDefaultBuildConfig();
-
-    ScopedTrace trace(TraceItem::TRACE_FILE_EXECUTE,
-        info->settings.build_settings()->build_config_file().value());
-    trace.SetToolchain(info->settings.toolchain_label());
-
-    const BlockNode* root_block = root->AsBlock();
-    Err err;
-    root_block->ExecuteBlockInScope(base_config, &err);
-
-    trace.Done();
-
-    base_config->ClearProcessingBuildConfig();
-    if (is_default)
-      base_config->ClearProcessingDefaultBuildConfig();
-
-    if (err.has_error()) {
-      g_scheduler->FailWithError(err);
-    } else {
-      // Base config processing succeeded.
-      Info::ScheduledInvocationMap schedule_these;
-      {
-        base::AutoLock lock(GetLock());
-        schedule_these.swap(info->scheduled_invocations);
-        info->state = TOOLCHAIN_SETTINGS_LOADED;
-        if (is_default)
-          FixupDefaultToolchainLocked();
-      }
-
-      // Schedule build files waiting on this settings. There can be many so we
-      // want to load them in parallel on the pool.
-      for (Info::ScheduledInvocationMap::iterator i = schedule_these.begin();
-           i != schedule_these.end() && !g_scheduler->is_failed(); ++i) {
-        if (!ScheduleBackgroundInvoke(info, i->second, i->first, &err)) {
-          g_scheduler->FailWithError(err);
-          break;
-        }
-      }
-    }
-  }
-  g_scheduler->DecrementWorkCount();
-}
-
-void ToolchainManager::BackgroundInvoke(const Info* info,
-                                        const SourceFile& file_name,
-                                        const ParseNode* root) {
-  if (root && !g_scheduler->is_failed()) {
-    if (g_scheduler->verbose_logging()) {
-      g_scheduler->Log("Running", file_name.value() + " with toolchain " +
-                       info->toolchain->label().GetUserVisibleName(false));
-    }
-
-    Scope our_scope(info->settings.base_config());
-    ScopePerFileProvider per_file_provider(&our_scope);
-    our_scope.set_source_dir(file_name.GetDir());
-
-    ScopedTrace trace(TraceItem::TRACE_FILE_EXECUTE, file_name.value());
-    trace.SetToolchain(info->settings.toolchain_label());
-
-    Err err;
-    root->Execute(&our_scope, &err);
-    if (err.has_error())
-      g_scheduler->FailWithError(err);
-
-    trace.Done();
-
-    {
-      // Check to see if any build config invocations depend on this file and
-      // invoke them.
-      base::AutoLock lock(GetLock());
-      BuildConfigInvokeMap::iterator found_file =
-          pending_build_config_map_.find(std::make_pair(file_name, info));
-      if (found_file != pending_build_config_map_.end()) {
-        // The toolchain state should be waiting on the definition, which
-        // should be the thing we just loaded.
-        Info* info_to_load = found_file->second;
-        DCHECK(info_to_load->state == TOOLCHAIN_DEFINITION_LOADING);
-        DCHECK(!info_to_load->toolchain_file_loaded);
-        info_to_load->toolchain_file_loaded = true;
-
-        if (!ScheduleBuildConfigLoadLocked(info_to_load, false, &err))
-          g_scheduler->FailWithError(err);
-        pending_build_config_map_.erase(found_file);
-      }
-    }
-  }
-
-  g_scheduler->DecrementWorkCount();
-}
-
-base::Lock& ToolchainManager::GetLock() const {
-  return build_settings_->item_tree().lock();
-}