New try: Parser: Delay internalizing strings and values

src/ast-value-factory.h

+// Copyright 2014 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_AST_VALUE_FACTORY_H_
+#define V8_AST_VALUE_FACTORY_H_
+
+#include "src/api.h"
+#include "src/hashmap.h"
+#include "src/utils.h"
+
+// AstString, AstValue and AstValueFactory are for storing strings and values
+// independent of the V8 heap and internalizing them later. During parsing,
+// AstStrings and AstValues are created and stored outside the heap, in
+// AstValueFactory. After parsing, the strings and values are internalized
+// (moved into the V8 heap).
+namespace v8 {
+namespace internal {
+
+class AstString : public ZoneObject {
+ public:
+  AstString(bool is_one_byte, Vector<const byte> literal_bytes, uint32_t hash)
+      : type_(NORMAL),
+        is_one_byte_(is_one_byte),
+        literal_bytes_(literal_bytes),
+        hash_(hash),
+        left_(NULL),
+        right_(NULL) {}
+
+  AstString()
+      : type_(NORMAL),
+        is_one_byte_(true),
+        hash_(0),
+        left_(NULL),
+        right_(NULL) {}
+
+  // Creates a cons string. The only allowed operations for cons strings are

[rossberg, 2014/06/23 09:44:27]

Disallowing a whole set of operations in some cases is kind of nasty, as is
always using space for the cross product of both possible representations.

Do you think it would be possible to have the two different forms of strings as
concrete subclasses of (an abstract) AstString (say AstConsString and
AstRawString?). Then you can get rid of the type thingy and a bunch of
associated asserts, potentially use virtual dispatch for the common functions,
and checked downcasts to get to the representation-specific ones.

[marja, 2014/06/23 11:46:45]

Done.

I named the classes AstStringBase, AstString (the same as AstString used to be
before) and AstConsString.

Most places use AstStrings (like before), only function names are stored as
AstStringBase. We don't need to downcast ever. The only needed operations for
cons strings are string() and length(), and AstStringBase takes care of them.

[rossberg, 2014/06/23 13:30:53]

Hm, from a stylistic point, I don't like naming an abstract interface
something-Base -- that's usually reserved for pure implementation inheritance,
not interface inheritance.

Would renaming AstString->AstRawString, AstStringBase->AstString be particularly
terrible?
Ah, even better then.

+  // is_one_byte(), length(), Internalize() and string().
+  AstString(const AstString* left, const AstString* right)
+      : type_(CONS),
+        is_one_byte_(left->is_one_byte_ && right->is_one_byte_),
+        hash_(0),
+        left_(left),
+        right_(right) {}
+
+  bool AsArrayIndex(uint32_t* index) const;
+
+  // The string is not null-terminated, use length() to find out the length.
+  const unsigned char* raw_data() const {
+    ASSERT(type_ == NORMAL);
+    return literal_bytes_.start();
+  }
+  int length() const {
+    if (type_ == CONS) {
+      return left_->length() + right_->length();
+    }
+    if (is_one_byte_)
+      return literal_bytes_.length();
+    return literal_bytes_.length() / 2;
+  }
+  bool is_one_byte() const { return is_one_byte_; }
+  bool IsEmpty() const { return length() == 0; }
+  bool IsOneByteEqualTo(const char* data) const;
+  uint16_t FirstCharacter() const {
+    ASSERT(type_ == NORMAL);
+    if (is_one_byte_)
+      return literal_bytes_[0];
+    const uint16_t* c =
+        reinterpret_cast<const uint16_t*>(literal_bytes_.start());
+    return *c;
+  }
+
+  // Puts the string into the V8 heap.
+  void Internalize(Isolate* isolate);
+
+  // This function can be called after internalizing.
+  V8_INLINE Handle<String> string() const {
+    ASSERT(!string_.is_null());
+    return string_;
+  }
+
+  // For storing AstStrings in a hash map.
+  uint32_t hash() const {
+    ASSERT(type_ == NORMAL);
+    return hash_;
+  }
+  static bool Compare(void* a, void* b);
+
+ private:
+  friend class AstValueFactory;
+  friend class AstStringInternalizationKey;
+
+  enum Type {
+    NORMAL,
+    CONS
+  };
+
+  Type type_;
+  bool is_one_byte_;
+
+  // For normal strings. Points to memory owned by Zone.
+  Vector<const byte> literal_bytes_;
+  uint32_t hash_;
+
+  // For cons strings.
+  const AstString* left_;
+  const AstString* right_;
+
+  // This is null until the string is internalized.
+  Handle<String> string_;
+};
+
+
+// AstValue is either a string, a number, a string array, a boolean, or a
+// special value (null, undefined, the hole).
+class AstValue : public ZoneObject {
+ public:
+  bool IsString() const {
+    return type_ == STRING;
+  }
+
+  bool IsNumber() const {
+    return type_ == NUMBER || type_ == SMI;
+  }
+
+  const AstString* AsString() const {
+    if (type_ == STRING)
+      return string_;
+    UNREACHABLE();
+    return 0;
+  }
+
+  double AsNumber() const {
+    if (type_ == NUMBER)
+      return number_;
+    if (type_ == SMI)
+      return smi_;
+    UNREACHABLE();
+    return 0;
+  }
+
+  bool EqualsString(const AstString* string) const {
+    return type_ == STRING && string_ == string;
+  }
+
+  bool IsPropertyName() const;
+
+  bool BooleanValue() const;
+
+  void Internalize(Isolate* isolate);
+
+  // Can be called after Internalize has been called.
+  V8_INLINE Handle<Object> value() const {
+    if (type_ == STRING) {
+      return string_->string();
+    }
+    ASSERT(!value_.is_null());
+    return value_;
+  }
+
+ private:
+  friend class AstValueFactory;
+
+  enum Type {
+    STRING,
+    SYMBOL,
+    NUMBER,
+    SMI,
+    BOOLEAN,
+    STRING_ARRAY,
+    NULL_TYPE,
+    UNDEFINED,
+    THE_HOLE
+  };
+
+  explicit AstValue(const AstString* s) : type_(STRING) { string_ = s; }
+
+  explicit AstValue(const char* name) : type_(SYMBOL) { symbol_name_ = name; }
+
+  explicit AstValue(double n) : type_(NUMBER) { number_ = n; }
+
+  AstValue(Type t, int i) : type_(t) {
+    ASSERT(type_ == SMI);
+    smi_ = i;
+  }
+
+  explicit AstValue(bool b) : type_(BOOLEAN) { bool_ = b; }
+
+  explicit AstValue(ZoneList<const AstString*>* s) : type_(STRING_ARRAY) {
+    strings_ = s;
+  }
+
+  explicit AstValue(Type t) : type_(t) {
+    ASSERT(t == NULL_TYPE || t == UNDEFINED || t == THE_HOLE);
+  }
+
+  Type type_;
+
+  // Uninternalized value.
+  union {
+    const AstString* string_;
+    double number_;
+    int smi_;
+    bool bool_;
+    ZoneList<const AstString*>* strings_;
+    const char* symbol_name_;
+  };
+
+  // Internalized value (empty before internalized).
+  Handle<Object> value_;
+};
+
+
+// For generating string constants.
+#define STRING_CONSTANTS(F) \
+  F(anonymous_function, "(anonymous function)") \
+  F(arguments, "arguments") \
+  F(done, "done") \
+  F(dot, ".") \
+  F(dot_for, ".for") \
+  F(dot_generator, ".generator") \
+  F(dot_generator_object, ".generator_object") \
+  F(dot_iterable, ".iterable") \
+  F(dot_iterator, ".iterator") \
+  F(dot_module, ".module") \
+  F(dot_result, ".result") \
+  F(empty, "") \
+  F(eval, "eval") \
+  F(initialize_const_global, "initializeConstGlobal") \
+  F(initialize_var_global, "initializeVarGlobal") \
+  F(make_reference_error, "MakeReferenceError") \
+  F(make_syntax_error, "MakeSyntaxError") \
+  F(make_type_error, "MakeTypeError") \
+  F(module, "module") \
+  F(native, "native") \
+  F(next, "next") \
+  F(proto, "__proto__") \
+  F(prototype, "prototype") \
+  F(this, "this") \
+  F(use_strict, "use strict") \
+  F(value, "value")
+
+class AstValueFactory {
+ public:
+  AstValueFactory(Zone* zone, uint32_t hash_seed)
+      : string_table_(AstString::Compare),
+        zone_(zone),
+        isolate_(NULL),
+        hash_seed_(hash_seed) {
+#define F(name, str) \
+    name##_string_ = NULL;
+    STRING_CONSTANTS(F)
+#undef F
+  }
+
+  const AstString* GetOneByteString(const Vector<const uint8_t>& literal);
+  const AstString* GetTwoByteString(const Vector<const uint16_t>& literal);
+  const AstString* GetString(Handle<String> literal);
+  const AstString* NewConsString(const AstString* left, const AstString* right);
+
+  void Internalize(Isolate* isolate);
+  bool IsInternalized() {
+    return isolate_ != NULL;
+  }
+
+#define F(name, str) \
+  const AstString* name##_string() { \
+    if (name##_string_ == NULL) { \
+      const char* data = str; \
+      name##_string_ = GetOneByteString( \
+          Vector<const uint8_t>(reinterpret_cast<const uint8_t*>(data), \
+                                static_cast<int>(strlen(data)))); \
+    } \
+    return name##_string_; \
+  }
+  STRING_CONSTANTS(F)
+#undef F
+
+  const AstValue* NewString(const AstString* string);
+  // A JavaScript symbol (ECMA-262 edition 6).
+  const AstValue* NewSymbol(const char* name);
+  const AstValue* NewNumber(double number);
+  const AstValue* NewSmi(int number);
+  const AstValue* NewBoolean(bool b);
+  const AstValue* NewStringList(ZoneList<const AstString*>* strings);
+  const AstValue* NewNull();
+  const AstValue* NewUndefined();
+  const AstValue* NewTheHole();
+
+ private:
+  const AstString* GetString(uint32_t hash, bool is_one_byte,
+                             const Vector<const byte>& literal_bytes);
+
+  // All strings are copied here, one after another (no NULLs inbetween).
+  HashMap string_table_;
+  // For keeping track of all AstValues and AstStrings we've created (so that
+  // they can be internalized later).
+  List<AstValue*> values_;
+  List<AstString*> strings_;
+  Zone* zone_;
+  Isolate* isolate_;
+
+  uint32_t hash_seed_;
+
+#define F(name, str) \
+  const AstString* name##_string_;
+  STRING_CONSTANTS(F)
+#undef F
+};
+
+} }  // namespace v8::internal
+
+#undef STRING_CONSTANTS
+
+#endif  // V8_AST_VALUE_FACTORY_H_