Avoid (some) symbol lookups at parse time if preparse data is available.

src/parser.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 54 matching lines @@
   void set_end_pos(int value) { backing_[kEndPosOffset] = value; }
 
   int literal_count() { return backing_[kLiteralCountOffset]; }
   void set_literal_count(int value) { backing_[kLiteralCountOffset] = value; }
 
   int property_count() { return backing_[kPropertyCountOffset]; }
   void set_property_count(int value) {
     backing_[kPropertyCountOffset] = value;
   }
 
-  int predata_skip() { return backing_[kPredataSkipOffset]; }
-  void set_predata_skip(int value) {
-    backing_[kPredataSkipOffset] = value;
+  int predata_function_skip() { return backing_[kPredataFunctionSkipOffset]; }
+  void set_predata_function_skip(int value) {
+    backing_[kPredataFunctionSkipOffset] = value;
   }
 
+  int predata_symbol_skip() { return backing_[kPredataSymbolSkipOffset]; }
+  void set_predata_symbol_skip(int value) {
+    backing_[kPredataSymbolSkipOffset] = value;
+  }
+
+  int symbol_id_skip() { return backing_[kSymbolIdSkipOffset]; }
+  void set_symbol_id_skip(int value) {
+    backing_[kSymbolIdSkipOffset] = value;
+  }
+
+
   bool is_valid() { return backing_.length() > 0; }
 
-  static const int kSize = 5;
+  static const int kSize = 7;
 
  private:
   Vector<unsigned> backing_;
   static const int kStartPosOffset = 0;
   static const int kEndPosOffset = 1;
   static const int kLiteralCountOffset = 2;
   static const int kPropertyCountOffset = 3;
-  static const int kPredataSkipOffset = 4;
+  static const int kPredataFunctionSkipOffset = 4;
+  static const int kPredataSymbolSkipOffset = 5;
+  static const int kSymbolIdSkipOffset = 6;
 };
 
 
 class ScriptDataImpl : public ScriptData {
  public:
   explicit ScriptDataImpl(Vector<unsigned> store)
       : store_(store),
-        index_(kHeaderSize) { }
+        function_index_(kHeaderSize),
+        symbol_id_(0),
+        owns_store_(true) {
+    Initialize();
+  }
+
+  void Initialize() {
+    if (store_.length() >= kHeaderSize) {
+      // Otherwise we won't satisfy the SanityCheck.
+      symbol_index_ = kHeaderSize + store_[kFunctionsSizeOffset];
+    }
+  }
+
+  // Create an empty ScriptDataImpl that is guaranteed to not satisfy
+  // a SanityCheck.
+  ScriptDataImpl() : store_(Vector<unsigned>()), owns_store_(false) { }
+
   virtual ~ScriptDataImpl();
   virtual int Length();
   virtual const char* Data();
   virtual bool HasError();
+
   FunctionEntry GetFunctionEntry(int start);
+  int GetSymbolIdentifier(int start);
   void SkipFunctionEntry(int start);
   bool SanityCheck();
 
   Scanner::Location MessageLocation();
   const char* BuildMessage();
   Vector<const char*> BuildArgs();
 
+  int symbol_count() {
+    return (store_.length() > kHeaderSize) ? store_[kSymbolCountOffset] : 0;
+  }
+  // The following functions should only be called if SanityCheck has
+  // returned true.
   bool has_error() { return store_[kHasErrorOffset]; }
   unsigned magic() { return store_[kMagicOffset]; }
   unsigned version() { return store_[kVersionOffset]; }
+
   // Skip forward in the preparser data by the given number
   // of unsigned ints.
-  virtual void Skip(int entries) {
-    ASSERT(entries >= 0);
-    ASSERT(entries <= store_.length() - index_);
-    index_ += entries;
+  virtual void Skip(int function_entries, int symbol_entries, int symbol_ids) {
+    ASSERT(function_entries >= 0);
+    ASSERT(function_entries
+           <= (static_cast<int>(store_[kFunctionsSizeOffset])
+               - (function_index_ - kHeaderSize)));
+    function_index_ += function_entries;
+    symbol_index_ += symbol_entries;
+    symbol_id_ += symbol_ids;
   }
 
   static const unsigned kMagicNumber = 0xBadDead;
-  static const unsigned kCurrentVersion = 1;
+  static const unsigned kCurrentVersion = 2;
 
   static const int kMagicOffset = 0;
   static const int kVersionOffset = 1;
   static const int kHasErrorOffset = 2;
-  static const int kSizeOffset = 3;
-  static const int kHeaderSize = 4;
+  static const int kFunctionsSizeOffset = 3;
+  static const int kSymbolCountOffset = 4;
+  static const int kSizeOffset = 5;
+  static const int kHeaderSize = 6;
+
+  static const int kMessageStartPos = 0;
+  static const int kMessageEndPos = 1;
+  static const int kMessageArgCountPos = 2;
+  static const int kMessageTextPos = 3;
 
  private:
   Vector<unsigned> store_;
-  int index_;
+  int function_index_;
+  int symbol_index_;
+  int symbol_id_;
+  bool owns_store_;
 
   unsigned Read(int position);
   unsigned* ReadAddress(int position);
 
-  void FindStart(int position);
+  ScriptDataImpl(const char* backing_store, int length)
+      : store_(reinterpret_cast<unsigned*>(const_cast<char*>(backing_store)),
+               length / sizeof(unsigned)),
+        function_index_(kHeaderSize),
+        symbol_id_(0),
+        owns_store_(false) {
+    ASSERT_EQ(0, reinterpret_cast<intptr_t>(backing_store) % sizeof(unsigned));
+    Initialize();
+  }
+
   // Read strings written by ParserRecorder::WriteString.
   static const char* ReadString(unsigned* start, int* chars);
+
+  friend class ScriptData;
 };
 
 
 // The parser: Takes a script and and context information, and builds a
 // FunctionLiteral AST node. Returns NULL and deallocates any allocated
 // AST nodes if parsing failed.
 FunctionLiteral* MakeAST(bool compile_in_global_context,
                          Handle<Script> script,
                          v8::Extension* extension,
                          ScriptDataImpl* pre_data,
@@ skipping 53 matching lines @@
   static const int kTypeSlot = 0;
   static const int kElementsSlot = 1;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(CompileTimeValue);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_PARSER_H_