Make heap serialization nondestructive.

src/serialize.cc

 // 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 26 matching lines @@
 #include "runtime.h"
 #include "serialize.h"
 #include "stub-cache.h"
 #include "v8threads.h"
 #include "top.h"
 #include "bootstrapper.h"
 
 namespace v8 {
 namespace internal {
 
+// Mapping objects to their location after deserialization.
+// This is used during building, but not at runtime by V8.
+class SerializationAddressMapper {
+ public:
+  static bool IsMapped(HeapObject* obj) {
+    MapExists();
+    return serialization_map_->Lookup(Key(obj), Hash(obj), false) != NULL;
+  }
+
+  static int MappedTo(HeapObject* obj) {
+    ASSERT(IsMapped(obj));
+    return reinterpret_cast<int>(serialization_map_->Lookup(Key(obj),
+                                 Hash(obj),
+                                 false)->value);
+  }
+
+  static void Map(HeapObject* obj, int to) {
+    MapExists();
+    ASSERT(!IsMapped(obj));
+    HashMap::Entry* entry =
+        serialization_map_->Lookup(Key(obj), Hash(obj), true);
+    entry->value = Value(to);
+  }
+
+  static void Zap() {
+    if (serialization_map_ != NULL) {
+      delete serialization_map_;
+    }
+    serialization_map_ = NULL;
+  }
+
+ private:
+  static bool SerializationMatchFun(void* key1, void* key2) {
+    return key1 == key2;
+  }
+
+  static uint32_t Hash(HeapObject* obj) {
+    return reinterpret_cast<uint32_t>(obj->address());
+  }
+
+  static void* Key(HeapObject* obj) {
+    return reinterpret_cast<void*>(obj->address());
+  }
+
+  static void* Value(int v) {
+    return reinterpret_cast<void*>(v);
+  }
+
+  // Saying it makes it so.
+  static void MapExists() {

[Kasper Lund, 2009/11/25 12:52:03]

EnsureMapExists?

+    if (serialization_map_ == NULL) {
+      serialization_map_ = new HashMap(&SerializationMatchFun);
+    }
+  }
+
+  static HashMap* serialization_map_;
+};
+
+
+HashMap* SerializationAddressMapper::serialization_map_ = NULL;
+
+
+
+
 // -----------------------------------------------------------------------------
 // Coding of external references.
 
 // The encoding of an external reference. The type is in the high word.
 // The id is in the low word.
 static uint32_t EncodeExternal(TypeCode type, uint16_t id) {
   return static_cast<uint32_t>(type) << 16 | id;
 }
 
 
@@ skipping 807 matching lines @@
   // We don't support serializing installed extensions.
   for (RegisteredExtension* ext = RegisteredExtension::first_extension();
        ext != NULL;
        ext = ext->next()) {
     CHECK_NE(v8::INSTALLED, ext->state());
   }
   external_reference_encoder_ = new ExternalReferenceEncoder();
   Heap::IterateRoots(this, VISIT_ONLY_STRONG);
   delete external_reference_encoder_;
   external_reference_encoder_ = NULL;
+  SerializationAddressMapper::Zap();
 }
 
 
 void Serializer::VisitPointers(Object** start, Object** end) {
   for (Object** current = start; current < end; current++) {
     if ((*current)->IsSmi()) {
       sink_->Put(RAW_DATA_SERIALIZATION, "RawData");
       sink_->PutInt(kPointerSize, "length");
       for (int i = 0; i < kPointerSize; i++) {
         sink_->Put(reinterpret_cast<byte*>(current)[i], "Byte");
       }
     } else {
       SerializeObject(*current, TAGGED_REPRESENTATION);
     }
   }
 }
 
 
 void Serializer::SerializeObject(
     Object* o,
     ReferenceRepresentation reference_representation) {
   CHECK(o->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(o);
-  MapWord map_word = heap_object->map_word();
-  if (map_word.IsSerializationAddress()) {
+  if (SerializationAddressMapper::IsMapped(heap_object)) {
     int space = SpaceOfAlreadySerializedObject(heap_object);
-    int address = map_word.ToSerializationAddress();
+    int address = SerializationAddressMapper::MappedTo(heap_object);
     int offset = CurrentAllocationAddress(space) - address;
     bool from_start = true;
     if (SpaceIsPaged(space)) {
       if ((CurrentAllocationAddress(space) >> Page::kPageSizeBits) ==
           (address >> Page::kPageSizeBits)) {
         from_start = false;
         address = offset;
       }
     } else if (space == NEW_SPACE) {
       if (offset < address) {
@@ skipping 47 matching lines @@
   int size = object_->Size();
 
   if (reference_representation_ == TAGGED_REPRESENTATION) {
     sink_->Put(OBJECT_SERIALIZATION + space, "ObjectSerialization");
   } else {
     CHECK_EQ(CODE_TARGET_REPRESENTATION, reference_representation_);
     sink_->Put(CODE_OBJECT_SERIALIZATION + space, "ObjectSerialization");
   }
   sink_->PutInt(size >> kObjectAlignmentBits, "Size in words");
 
-  // Get the map before overwriting it.
-  Map* map = object_->map();
   // Mark this object as already serialized.
   bool start_new_page;
-  object_->set_map_word(MapWord::FromSerializationAddress(
-      serializer_->Allocate(space, size, &start_new_page)));
+  SerializationAddressMapper::Map(
+    object_,
+    serializer_->Allocate(space, size, &start_new_page));
   if (start_new_page) {
     sink_->Put(START_NEW_PAGE_SERIALIZATION, "NewPage");
     sink_->PutSection(space, "NewPageSpace");
   }
 
   // Serialize the map (first word of the object).
-  serializer_->SerializeObject(map, TAGGED_REPRESENTATION);
+  serializer_->SerializeObject(object_->map(), TAGGED_REPRESENTATION);
 
   // Serialize the rest of the object.
   CHECK_EQ(0, bytes_processed_so_far_);
   bytes_processed_so_far_ = kPointerSize;
-  object_->IterateBody(map->instance_type(), size, this);
+  object_->IterateBody(object_->map()->instance_type(), size, this);
   OutputRawData(object_->address() + size);
 }
 
 
 void Serializer::ObjectSerializer::VisitPointers(Object** start,
                                                  Object** end) {
   Object** current = start;
   while (current < end) {
     while (current < end && (*current)->IsSmi()) current++;
     if (current < end) OutputRawData(reinterpret_cast<Address>(current));
@@ skipping 41 matching lines @@
   serializer_->SerializeObject(target, CODE_TARGET_REPRESENTATION);
   bytes_processed_so_far_ += Assembler::kCallTargetSize;
 }
 
 
 void Serializer::ObjectSerializer::VisitExternalAsciiString(
     v8::String::ExternalAsciiStringResource** resource_pointer) {
   Address references_start = reinterpret_cast<Address>(resource_pointer);
   OutputRawData(references_start);
   for (int i = 0; i < Natives::GetBuiltinsCount(); i++) {
-    // Use raw_unchecked when maps are munged.
-    Object* source = Heap::raw_unchecked_natives_source_cache()->get(i);
+    Object* source = Heap::natives_source_cache()->get(i);
     if (!source->IsUndefined()) {
-      // Don't use cast when maps are munged.
-      ExternalAsciiString* string =
-          reinterpret_cast<ExternalAsciiString*>(source);
+      ExternalAsciiString* string = ExternalAsciiString::cast(source);
       typedef v8::String::ExternalAsciiStringResource Resource;
       Resource* resource = string->resource();
       if (resource == *resource_pointer) {
         sink_->Put(NATIVES_STRING_RESOURCE, "NativesStringResource");
         sink_->PutSection(i, "NativesStringResourceEnd");
         bytes_processed_so_far_ += sizeof(resource);
         return;
       }
     }
   }
@@ skipping 91 matching lines @@
       fullness_[space] = RoundUp(fullness_[space], Page::kPageSize);
     }
   }
   int allocation_address = fullness_[space];
   fullness_[space] = allocation_address + size;
   return allocation_address;
 }
 
 
 } }  // namespace v8::internal