[parser] Use shared buffer for PreparseDataBuilder children

Get rid of yet another ZoneChunkList.

Change-Id: If63b1b87e007f4d146532b2c66f101280d3fcf2f
Reviewed-on: https://chromium-review.googlesource.com/c/1421319Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59027}

src/parsing/preparse-data.cc

@@ -84,10 +84,11 @@ STATIC_ASSERT(LanguageModeSize <= LanguageField::kNumValues);
  */
 
 PreparseDataBuilder::PreparseDataBuilder(Zone* zone,
-                                         PreparseDataBuilder* parent_builder)
+                                         PreparseDataBuilder* parent_builder,
+                                         std::vector<void*>* children_buffer)
     : parent_(parent_builder),
       byte_data_(),
-      children_(zone),
+      children_buffer_(children_buffer),
       function_scope_(nullptr),
       num_inner_functions_(0),
       num_inner_with_data_(0),
@@ -98,19 +99,22 @@ void PreparseDataBuilder::DataGatheringScope::Start(
     DeclarationScope* function_scope) {
   Zone* main_zone = preparser_->main_zone();
   builder_ = new (main_zone)
-      PreparseDataBuilder(main_zone, preparser_->preparse_data_builder());
+      PreparseDataBuilder(main_zone, preparser_->preparse_data_builder(),
+                          preparser_->preparse_data_builder_buffer());
   preparser_->set_preparse_data_builder(builder_);
   function_scope->set_preparse_data_builder(builder_);
 }
 
 PreparseDataBuilder::DataGatheringScope::~DataGatheringScope() {
   if (builder_ == nullptr) return;
-  // Copy over the data from the buffer into the zone-allocated byte_data_
+
   PreparseDataBuilder* parent = builder_->parent_;
-  if (parent != nullptr && builder_->HasDataForParent()) {
-    parent->children_.push_back(builder_);
-  }
   preparser_->set_preparse_data_builder(parent);
+  builder_->FinalizeChildren(preparser_->main_zone());
+
+  if (parent == nullptr) return;
+  if (!builder_->HasDataForParent()) return;
+  parent->AddChild(builder_);
 }
 
 #ifdef DEBUG
@@ -232,6 +236,21 @@ bool PreparseDataBuilder::HasDataForParent() const {
   return HasData() || function_scope_ != nullptr;
 }
 
+void PreparseDataBuilder::AddChild(PreparseDataBuilder* child) {
+  DCHECK(!finalized_children_);
+  children_buffer_.Add(child);
+}
+
+void PreparseDataBuilder::FinalizeChildren(Zone* zone) {
+  DCHECK(!finalized_children_);
+  Vector<PreparseDataBuilder*> children = children_buffer_.CopyTo(zone);
+  children_buffer_.Rewind();
+  children_ = children;
+#ifdef DEBUG
+  finalized_children_ = true;
+#endif
+}
+
 bool PreparseDataBuilder::ScopeNeedsData(Scope* scope) {
   if (scope->scope_type() == ScopeType::FUNCTION_SCOPE) {
     // Default constructors don't need data (they cannot contain inner functions
@@ -284,7 +303,7 @@ void PreparseDataBuilder::SaveScopeAllocationData(DeclarationScope* scope,
   // Reserve Uint32 for scope_data_start debug info.
   byte_data_.WriteUint32(0);
 #endif
-
+  DCHECK(finalized_children_);
   for (const auto& builder : children_) {
     // Keep track of functions with inner data. {children_} contains also the
     // builders that have no inner functions at all.
@@ -397,6 +416,7 @@ Handle<PreparseData> PreparseDataBuilder::Serialize(Isolate* isolate) {
   Handle<PreparseData> data =
       byte_data_.CopyToHeap(isolate, num_inner_with_data_);
   int i = 0;
+  DCHECK(finalized_children_);
   for (const auto& builder : children_) {
     if (!builder->HasData()) continue;
     Handle<PreparseData> child_data = builder->Serialize(isolate);
@@ -411,6 +431,7 @@ ZonePreparseData* PreparseDataBuilder::Serialize(Zone* zone) {
   DCHECK(!ThisOrParentBailedOut());
   ZonePreparseData* data = byte_data_.CopyToZone(zone, num_inner_with_data_);
   int i = 0;
+  DCHECK(finalized_children_);
   for (const auto& builder : children_) {
     if (!builder->HasData()) continue;
     ZonePreparseData* child = builder->Serialize(zone);

src/parsing/preparse-data.h

@@ -89,7 +89,9 @@ class PreparseDataBuilder : public ZoneObject,
  public:
   // Create a PreparseDataBuilder object which will collect data as we
   // parse.
-  explicit PreparseDataBuilder(Zone* zone, PreparseDataBuilder* parent_builder);
+  explicit PreparseDataBuilder(Zone* zone, PreparseDataBuilder* parent_builder,
+                               std::vector<void*>* children_buffer);
+  ~PreparseDataBuilder() {}
 
   PreparseDataBuilder* parent() const { return parent_; }
 
@@ -191,6 +193,9 @@ class PreparseDataBuilder : public ZoneObject,
   Handle<PreparseData> Serialize(Isolate* isolate);
   ZonePreparseData* Serialize(Zone* zone);
 
+  void FinalizeChildren(Zone* zone);
+  void AddChild(PreparseDataBuilder* child);
+
   void SaveDataForScope(Scope* scope);
   void SaveDataForVariable(Variable* var);
   void SaveDataForInnerScopes(Scope* scope);
@@ -200,7 +205,10 @@ class PreparseDataBuilder : public ZoneObject,
 
   PreparseDataBuilder* parent_;
   ByteData byte_data_;
-  ZoneChunkList<PreparseDataBuilder*> children_;
+  union {
+    ScopedPtrList<PreparseDataBuilder> children_buffer_;
+    Vector<PreparseDataBuilder*> children_;
+  };
 
   DeclarationScope* function_scope_;
   int num_inner_functions_;
@@ -210,6 +218,10 @@ class PreparseDataBuilder : public ZoneObject,
   bool bailed_out_ : 1;
   bool has_data_ : 1;
 
+#ifdef DEBUG
+  bool finalized_children_ = false;
+#endif
+
   DISALLOW_COPY_AND_ASSIGN(PreparseDataBuilder);
 };
 

src/parsing/preparser.h

@@ -943,7 +943,10 @@ class PreParser : public ParserBase<PreParser> {
                               runtime_call_stats, logger, script_id,
                               parsing_module, parsing_on_main_thread),
         use_counts_(nullptr),
-        preparse_data_builder_(nullptr) {}
+        preparse_data_builder_(nullptr),
+        preparse_data_builder_buffer_() {
+    preparse_data_builder_buffer_.reserve(16);
+  }
 
   static bool IsPreParser() { return true; }
 
@@ -977,6 +980,10 @@ class PreParser : public ParserBase<PreParser> {
     preparse_data_builder_ = preparse_data_builder;
   }
 
+  std::vector<void*>* preparse_data_builder_buffer() {
+    return &preparse_data_builder_buffer_;
+  }
+
  private:
   friend class i::ExpressionScope<ParserTypes<PreParser>>;
   friend class i::VariableDeclarationParsingScope<ParserTypes<PreParser>>;
@@ -1640,6 +1647,7 @@ class PreParser : public ParserBase<PreParser> {
   PreParserLogger log_;
 
   PreparseDataBuilder* preparse_data_builder_;
+  std::vector<void*> preparse_data_builder_buffer_;
 };
 
 PreParserExpression PreParser::SpreadCall(const PreParserExpression& function,

src/zone/zone.h

@@ -364,6 +364,13 @@ class ScopedPtrList final {
     target->AddAll(Vector<T*>(data, length()), zone);
   }
 
+  Vector<T*> CopyTo(Zone* zone) {
+    DCHECK_LE(end_, buffer_.size());
+    T** data = zone->NewArray<T*>(length());
+    MemCopy(data, &buffer_[start_], length() * sizeof(T*));
+    return Vector<T*>(data, length());
+  }
+
   void Add(T* value) {
     DCHECK_EQ(buffer_.size(), end_);
     buffer_.push_back(value);