diff --git a/src/gn/config_values_extractors.h b/src/gn/config_values_extractors.h
index 6479f21..45b1f25 100644
--- a/src/gn/config_values_extractors.h
+++ b/src/gn/config_values_extractors.h
@@ -30,7 +30,12 @@
 //     DoSomething(iter.cur());
 class ConfigValuesIterator {
  public:
-  explicit ConfigValuesIterator(const Target* target) : target_(target) {}
+  explicit ConfigValuesIterator(const Target* target) : target_(target) {
+    // If the target doesn't have its own config_values()
+    if (!target->has_config_values()) {
+      cur_index_ = 0;
+    }
+  }
 
   bool done() const {
     return cur_index_ >= static_cast<int>(target_->configs().size());
diff --git a/src/gn/rust_values.cc b/src/gn/rust_values.cc
index 6531291..3043458 100644
--- a/src/gn/rust_values.cc
+++ b/src/gn/rust_values.cc
@@ -22,6 +22,8 @@
   if (!target->source_types_used().RustSourceUsed()) {
     return CRATE_AUTO;
   }
+  if (!target->has_rust_values())
+    return CRATE_AUTO;
 
   CrateType crate_type = target->rust_values().crate_type();
   if (crate_type != CRATE_AUTO) {
diff --git a/src/gn/swift_values.cc b/src/gn/swift_values.cc
index a9677a6..a70c72f 100644
--- a/src/gn/swift_values.cc
+++ b/src/gn/swift_values.cc
@@ -14,35 +14,46 @@
 
 SwiftValues::~SwiftValues() = default;
 
-bool SwiftValues::OnTargetResolved(const Target* target, Err* err) {
-  if (!FillModuleOuputFile(target, err))
+// static
+bool SwiftValues::OnTargetResolved(Target* target, Err* err) {
+  if (!FillModuleOutputFile(target, err))
     return false;
 
   FillModuleDependencies(target);
   return true;
 }
 
-void SwiftValues::FillModuleDependencies(const Target* target) {
+// static
+void SwiftValues::FillModuleDependencies(Target* target) {
   for (const auto& pair : target->GetDeps(Target::DEPS_LINKED)) {
+    if (!pair.ptr->has_swift_values())
+      continue;
+
     if (pair.ptr->toolchain() == target->toolchain() ||
         pair.ptr->toolchain()->propagates_configs()) {
-      modules_.Append(pair.ptr->swift_values().public_modules().begin(),
-                      pair.ptr->swift_values().public_modules().end());
+      target->swift_values().modules_.Append(
+          pair.ptr->swift_values().public_modules().begin(),
+          pair.ptr->swift_values().public_modules().end());
     }
   }
 
   for (const auto& pair : target->public_deps()) {
+    if (!pair.ptr->has_swift_values())
+      continue;
+
     if (pair.ptr->toolchain() == target->toolchain() ||
         pair.ptr->toolchain()->propagates_configs())
-      public_modules_.Append(pair.ptr->swift_values().public_modules().begin(),
-                             pair.ptr->swift_values().public_modules().end());
+      target->swift_values().public_modules_.Append(
+          pair.ptr->swift_values().public_modules().begin(),
+          pair.ptr->swift_values().public_modules().end());
   }
 
-  if (builds_module())
-    public_modules_.push_back(target);
+  if (target->swift_values().builds_module())
+    target->swift_values().public_modules_.push_back(target);
 }
 
-bool SwiftValues::FillModuleOuputFile(const Target* target, Err* err) {
+// static
+bool SwiftValues::FillModuleOutputFile(Target* target, Err* err) {
   if (!target->IsBinary() || !target->source_types_used().SwiftSourceUsed())
     return true;
 
@@ -63,8 +74,9 @@
     return false;
   }
 
-  module_output_file_ = std::move(module_output_file);
-  module_output_dir_ = module_output_file_as_source.GetDir();
+  SwiftValues& swift_values = target->swift_values();
+  swift_values.module_output_file_ = std::move(module_output_file);
+  swift_values.module_output_dir_ = module_output_file_as_source.GetDir();
 
   return true;
 }
diff --git a/src/gn/swift_values.h b/src/gn/swift_values.h
index c529738..3852366 100644
--- a/src/gn/swift_values.h
+++ b/src/gn/swift_values.h
@@ -24,8 +24,8 @@
   SwiftValues(const SwiftValues&) = delete;
   SwiftValues& operator=(const SwiftValues&) = delete;
 
-  // Called when the target is resolved.
-  bool OnTargetResolved(const Target* target, Err* err);
+  // Called when the target is resolved. This may update target->swift_values().
+  static bool OnTargetResolved(Target* target, Err* err);
 
   // Path of the bridging header.
   SourceFile& bridge_header() { return bridge_header_; }
@@ -36,7 +36,7 @@
   const std::string module_name() const { return module_name_; }
 
   // Returns whether the target generates a .swiftmodule.
-  bool builds_module() const { return module_output_file_ != OutputFile(); }
+  bool builds_module() const { return !module_output_file_.value().empty(); }
 
   // Name of the generated .swiftmodule file. Computed when the target
   // is resolved.
@@ -60,10 +60,10 @@
 
  private:
   // Fill informations about .swiftmodule generated by this target.
-  bool FillModuleOuputFile(const Target* target, Err* err);
+  static bool FillModuleOutputFile(Target* target, Err* err);
 
   // Fill dependencies information on other target generating .swiftmodules.
-  void FillModuleDependencies(const Target* target);
+  static void FillModuleDependencies(Target* target);
 
   // Name of the optional bridge header used to import Objective-C classes.
   // Filled from the target, may be empty even if the target include .swift
diff --git a/src/gn/target.cc b/src/gn/target.cc
index d9c02d3..62f17cd 100644
--- a/src/gn/target.cc
+++ b/src/gn/target.cc
@@ -285,6 +285,116 @@
 
 Target::~Target() = default;
 
+// A technical note on accessors defined below: Using a static global
+// constant is much faster at runtime than using a static local one.
+//
+// In other words:
+//
+//   static const Foo kEmptyFoo;
+//
+//   const Foo& Target::foo() const {
+//     return foo_ ? *foo_ : kEmptyFoo;
+//   }
+//
+// Is considerably faster than:
+//
+//   const Foo& Target::foo() const {
+//     if (foo_) {
+//       return *foo_;
+//     } else {
+//       static const Foo kEmptyFoo;
+//       return kEmptyFoo;
+//     }
+//   }
+//
+// Because the latter requires relatively expensive atomic operations
+// in the second branch.
+//
+
+static const BundleData kEmptyBundleData;
+
+const BundleData& Target::bundle_data() const {
+  return bundle_data_ ? *bundle_data_ : kEmptyBundleData;
+}
+
+BundleData& Target::bundle_data() {
+  if (!bundle_data_)
+    bundle_data_ = std::make_unique<BundleData>();
+  return *bundle_data_;
+}
+
+static ConfigValues kEmptyConfigValues;
+
+const ConfigValues& Target::config_values() const {
+  return config_values_ ? *config_values_ : kEmptyConfigValues;
+}
+
+ConfigValues& Target::config_values() {
+  if (!config_values_)
+    config_values_ = std::make_unique<ConfigValues>();
+  return *config_values_;
+}
+
+static const ActionValues kEmptyActionValues;
+
+const ActionValues& Target::action_values() const {
+  return action_values_ ? *action_values_ : kEmptyActionValues;
+}
+
+ActionValues& Target::action_values() {
+  if (!action_values_)
+    action_values_ = std::make_unique<ActionValues>();
+  return *action_values_;
+}
+
+static const RustValues kEmptyRustValues;
+
+const RustValues& Target::rust_values() const {
+  return rust_values_ ? *rust_values_ : kEmptyRustValues;
+}
+
+RustValues& Target::rust_values() {
+  if (!rust_values_)
+    rust_values_ = std::make_unique<RustValues>();
+  return *rust_values_;
+}
+
+static const SwiftValues kEmptySwiftValues;
+
+const SwiftValues& Target::swift_values() const {
+  return swift_values_ ? *swift_values_ : kEmptySwiftValues;
+}
+
+SwiftValues& Target::swift_values() {
+  if (!swift_values_)
+    swift_values_ = std::make_unique<SwiftValues>();
+  return *swift_values_;
+}
+
+static const Metadata kEmptyMetadata;
+
+const Metadata& Target::metadata() const {
+  return metadata_ ? *metadata_ : kEmptyMetadata;
+}
+
+Metadata& Target::metadata() {
+  if (!metadata_)
+    metadata_ = std::make_unique<Metadata>();
+  return *metadata_;
+}
+
+static const Target::GeneratedFile kEmptyGeneratedFile;
+
+const Target::GeneratedFile& Target::generated_file() const {
+  return generated_file_ ? *generated_file_ : kEmptyGeneratedFile;
+}
+
+Target::GeneratedFile& Target::generated_file() {
+  if (!generated_file_)
+    generated_file_ = std::make_unique<Target::GeneratedFile>();
+  return *generated_file_;
+}
+
 // static
 const char* Target::GetStringForOutputType(OutputType type) {
   switch (type) {
@@ -393,7 +503,7 @@
   if (!FillOutputFiles(err))
     return false;
 
-  if (!swift_values_.OnTargetResolved(this, err))
+  if (!SwiftValues::OnTargetResolved(this, err))
     return false;
 
   if (!CheckSourceSetLanguages(err))
@@ -785,15 +895,19 @@
       continue;
 
     // Direct dependency on a bundle_data target.
-    if (pair.ptr->output_type() == BUNDLE_DATA)
-      bundle_data_.AddBundleData(pair.ptr);
+    if (pair.ptr->output_type() == BUNDLE_DATA) {
+      bundle_data().AddBundleData(pair.ptr);
+    }
 
     // Recursive bundle_data informations from all dependencies.
-    for (auto* target : pair.ptr->bundle_data().bundle_deps())
-      bundle_data_.AddBundleData(target);
+    if (pair.ptr->has_bundle_data()) {
+      for (auto* target : pair.ptr->bundle_data().bundle_deps())
+        bundle_data().AddBundleData(target);
+    }
   }
 
-  bundle_data_.OnTargetResolved(this);
+  if (has_bundle_data())
+    bundle_data().OnTargetResolved(this);
 }
 
 bool Target::FillOutputFiles(Err* err) {
@@ -891,7 +1005,8 @@
 
   // Count anything generated from bundle_data dependencies.
   if (output_type_ == CREATE_BUNDLE) {
-    if (!bundle_data_.GetOutputFiles(settings(), this, &computed_outputs_, err))
+    if (!bundle_data().GetOutputFiles(settings(), this, &computed_outputs_,
+                                      err))
       return false;
   }
 
@@ -910,10 +1025,13 @@
   }
 
   // Also count anything the target has declared to be an output.
-  std::vector<SourceFile> outputs_as_sources;
-  action_values_.GetOutputsAsSourceFiles(this, &outputs_as_sources);
-  for (const SourceFile& out : outputs_as_sources)
-    computed_outputs_.push_back(OutputFile(settings()->build_settings(), out));
+  if (action_values_.get()) {
+    std::vector<SourceFile> outputs_as_sources;
+    action_values_->GetOutputsAsSourceFiles(this, &outputs_as_sources);
+    for (const SourceFile& out : outputs_as_sources)
+      computed_outputs_.push_back(
+          OutputFile(settings()->build_settings(), out));
+  }
 
   return true;
 }
@@ -930,8 +1048,10 @@
   // places must match.
 
   // Track where the current settings came from for issuing errors.
+  bool has_precompiled_headers =
+      config_values_.get() && config_values_->has_precompiled_headers();
   const Label* pch_header_settings_from = NULL;
-  if (config_values_.has_precompiled_headers())
+  if (has_precompiled_headers)
     pch_header_settings_from = &label();
 
   for (ConfigValuesIterator iter(this); !iter.done(); iter.Next()) {
@@ -943,10 +1063,10 @@
     if (!cur.has_precompiled_headers())
       continue;  // This one has no precompiled header info, skip.
 
-    if (config_values_.has_precompiled_headers()) {
+    if (has_precompiled_headers) {
       // Already have a precompiled header values, the settings must match.
-      if (config_values_.precompiled_header() != cur.precompiled_header() ||
-          config_values_.precompiled_source() != cur.precompiled_source()) {
+      if (config_values_->precompiled_header() != cur.precompiled_header() ||
+          config_values_->precompiled_source() != cur.precompiled_source()) {
         *err = Err(
             defined_from(), "Precompiled header setting conflict.",
             "The target " + label().GetUserVisibleName(false) +
@@ -955,8 +1075,8 @@
                 "\n"
                 "From " +
                 pch_header_settings_from->GetUserVisibleName(false) +
-                "\n  header: " + config_values_.precompiled_header() +
-                "\n  source: " + config_values_.precompiled_source().value() +
+                "\n  header: " + config_values_->precompiled_header() +
+                "\n  source: " + config_values_->precompiled_source().value() +
                 "\n\n"
                 "From " +
                 config->label().GetUserVisibleName(false) +
@@ -967,8 +1087,8 @@
     } else {
       // Have settings from a config, apply them to ourselves.
       pch_header_settings_from = &config->label();
-      config_values_.set_precompiled_header(cur.precompiled_header());
-      config_values_.set_precompiled_source(cur.precompiled_source());
+      config_values().set_precompiled_header(cur.precompiled_header());
+      config_values().set_precompiled_source(cur.precompiled_source());
     }
   }
 
@@ -1103,11 +1223,11 @@
     // Origin is null because this isn't declared anywhere, and should never
     // trigger any errors.
     next_walk_keys.push_back(Value(nullptr, ""));
-  } else {
+  } else if (has_metadata()) {
     // Otherwise, we walk this target and collect the appropriate data.
-    if (!metadata_.WalkStep(settings()->build_settings(), keys_to_extract,
-                            keys_to_walk, rebase_dir, &next_walk_keys,
-                            &current_result, err))
+    if (!metadata().WalkStep(settings()->build_settings(), keys_to_extract,
+                             keys_to_walk, rebase_dir, &next_walk_keys,
+                             &current_result, err))
       return false;
   }
 
diff --git a/src/gn/target.h b/src/gn/target.h
index fec9731..ee5061b 100644
--- a/src/gn/target.h
+++ b/src/gn/target.h
@@ -161,8 +161,9 @@
   }
 
   // Metadata. Target takes ownership of the resulting scope.
-  const Metadata& metadata() const { return metadata_; }
-  Metadata& metadata() { return metadata_; }
+  const Metadata& metadata() const;
+  Metadata& metadata();
+  bool has_metadata() const { return metadata_.get(); }
 
   // Get metadata from this target and its dependencies. This is intended to
   // be called after the target is resolved.
@@ -177,18 +178,37 @@
   // GeneratedFile-related methods.
   bool GenerateFile(Err* err) const;
 
-  const Value& contents() const { return contents_; }
-  void set_contents(const Value& value) { contents_ = value; }
-  const Value& output_conversion() const { return output_conversion_; }
-  void set_output_conversion(const Value& value) { output_conversion_ = value; }
-
   // Metadata collection methods for GeneratedFile targets.
-  const SourceDir& rebase() const { return rebase_; }
-  void set_rebase(const SourceDir& value) { rebase_ = value; }
-  const std::vector<std::string>& data_keys() const { return data_keys_; }
-  std::vector<std::string>& data_keys() { return data_keys_; }
-  const std::vector<std::string>& walk_keys() const { return walk_keys_; }
-  std::vector<std::string>& walk_keys() { return walk_keys_; }
+  struct GeneratedFile {
+    Value output_conversion_;
+    Value contents_;  // Value::NONE if metadata collection should occur.
+    SourceDir rebase_;
+    std::vector<std::string> data_keys_;
+    std::vector<std::string> walk_keys_;
+  };
+  const GeneratedFile& generated_file() const;
+  GeneratedFile& generated_file();
+  bool has_generated_file() const { return generated_file_.get(); }
+
+  const Value& contents() const { return generated_file().contents_; }
+  void set_contents(const Value& value) { generated_file().contents_ = value; }
+  const Value& output_conversion() const {
+    return generated_file().output_conversion_;
+  }
+  void set_output_conversion(const Value& value) {
+    generated_file().output_conversion_ = value;
+  }
+
+  const SourceDir& rebase() const { return generated_file().rebase_; }
+  void set_rebase(const SourceDir& value) { generated_file().rebase_ = value; }
+  const std::vector<std::string>& data_keys() const {
+    return generated_file().data_keys_;
+  }
+  std::vector<std::string>& data_keys() { return generated_file().data_keys_; }
+  const std::vector<std::string>& walk_keys() const {
+    return generated_file().walk_keys_;
+  }
+  std::vector<std::string>& walk_keys() { return generated_file().walk_keys_; }
 
   bool testonly() const { return testonly_; }
   void set_testonly(bool value) { testonly_ = value; }
@@ -208,8 +228,9 @@
 
   // Information about the bundle. Only valid for CREATE_BUNDLE target after
   // they have been resolved.
-  const BundleData& bundle_data() const { return bundle_data_; }
-  BundleData& bundle_data() { return bundle_data_; }
+  const BundleData& bundle_data() const;
+  BundleData& bundle_data();
+  bool has_bundle_data() const { return bundle_data_.get(); }
 
   // Returns true if targets depending on this one should have an order
   // dependency.
@@ -217,7 +238,7 @@
     return output_type_ == ACTION || output_type_ == ACTION_FOREACH ||
            output_type_ == COPY_FILES || output_type_ == CREATE_BUNDLE ||
            output_type_ == BUNDLE_DATA || output_type_ == GENERATED_FILE ||
-           (IsBinary() && swift_values().builds_module());
+           (IsBinary() && has_swift_values() && swift_values().builds_module());
   }
 
   // Returns the iterator range which can be used in range-based for loops
@@ -272,17 +293,21 @@
   }
 
   // This config represents the configuration set directly on this target.
-  ConfigValues& config_values() { return config_values_; }
-  const ConfigValues& config_values() const { return config_values_; }
+  ConfigValues& config_values();
+  const ConfigValues& config_values() const;
+  bool has_config_values() const { return config_values_.get(); }
 
-  ActionValues& action_values() { return action_values_; }
-  const ActionValues& action_values() const { return action_values_; }
+  ActionValues& action_values();
+  const ActionValues& action_values() const;
+  bool has_action_values() const { return action_values_.get(); }
 
-  SwiftValues& swift_values() { return swift_values_; }
-  const SwiftValues& swift_values() const { return swift_values_; }
+  SwiftValues& swift_values();
+  const SwiftValues& swift_values() const;
+  bool has_swift_values() const { return swift_values_.get(); }
 
-  RustValues& rust_values() { return rust_values_; }
-  const RustValues& rust_values() const { return rust_values_; }
+  RustValues& rust_values();
+  const RustValues& rust_values() const;
+  bool has_rust_values() const { return rust_values_.get(); }
 
   // Transitive closure of libraries that are depended on by this target
   InheritedLibraries& rust_transitive_libs() { return rust_transitive_libs_; }
@@ -444,7 +469,7 @@
   bool complete_static_lib_ = false;
   bool testonly_ = false;
   std::vector<std::string> data_;
-  BundleData bundle_data_;
+  std::unique_ptr<BundleData> bundle_data_;
   OutputFile write_runtime_deps_output_;
 
   LabelTargetVector private_deps_;
@@ -483,19 +508,19 @@
   // Used for all binary targets, and for inputs in regular targets. The
   // precompiled header values in this struct will be resolved to the ones to
   // use for this target, if precompiled headers are used.
-  ConfigValues config_values_;
+  std::unique_ptr<ConfigValues> config_values_;
 
   // Used for action[_foreach] targets.
-  ActionValues action_values_;
+  std::unique_ptr<ActionValues> action_values_;
 
   // Used for Rust targets.
-  RustValues rust_values_;
+  std::unique_ptr<RustValues> rust_values_;
 
   // Used by all targets, only useful to generate Rust targets though.
   InheritedLibraries rust_transitive_libs_;
 
   // User for Swift targets.
-  SwiftValues swift_values_;
+  std::unique_ptr<SwiftValues> swift_values_;
 
   // Toolchain used by this target. Null until target is resolved.
   const Toolchain* toolchain_ = nullptr;
@@ -506,16 +531,10 @@
   OutputFile dependency_output_file_;
   std::vector<OutputFile> runtime_outputs_;
 
-  Metadata metadata_;
-
-  // GeneratedFile values.
-  Value output_conversion_;
-  Value contents_;  // Value::NONE if metadata collection should occur.
+  std::unique_ptr<Metadata> metadata_;
 
   // GeneratedFile as metadata collection values.
-  SourceDir rebase_;
-  std::vector<std::string> data_keys_;
-  std::vector<std::string> walk_keys_;
+  std::unique_ptr<GeneratedFile> generated_file_;
 
   Target(const Target&) = delete;
   Target& operator=(const Target&) = delete;