Refactoring of snapshots. This simplifies and improves

src/serialize.cc

 // Copyright 2012 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 581 matching lines @@
 
 
 bool Serializer::serialization_enabled_ = false;
 bool Serializer::too_late_to_enable_now_ = false;
 
 
 Deserializer::Deserializer(SnapshotByteSource* source)
     : isolate_(NULL),
       source_(source),
       external_reference_decoder_(NULL) {
-}
-
-
-// This routine both allocates a new object, and also keeps
-// track of where objects have been allocated so that we can
-// fix back references when deserializing.
-Address Deserializer::Allocate(int space_index, Space* space, int size) {
-  Address address;
-  if (!SpaceIsLarge(space_index)) {
-    ASSERT(!SpaceIsPaged(space_index) ||
-           size <= Page::kPageSize - Page::kObjectStartOffset);
-    MaybeObject* maybe_new_allocation;
-    if (space_index == NEW_SPACE) {
-      maybe_new_allocation =
-          reinterpret_cast<NewSpace*>(space)->AllocateRaw(size);
-    } else {
-      maybe_new_allocation =
-          reinterpret_cast<PagedSpace*>(space)->AllocateRaw(size);
-    }
-    ASSERT(!maybe_new_allocation->IsFailure());
-    Object* new_allocation = maybe_new_allocation->ToObjectUnchecked();
-    HeapObject* new_object = HeapObject::cast(new_allocation);
-    address = new_object->address();
-    high_water_[space_index] = address + size;
-  } else {
-    ASSERT(SpaceIsLarge(space_index));
-    LargeObjectSpace* lo_space = reinterpret_cast<LargeObjectSpace*>(space);
-    Object* new_allocation;
-    if (space_index == kLargeData || space_index == kLargeFixedArray) {
-      new_allocation =
-          lo_space->AllocateRaw(size, NOT_EXECUTABLE)->ToObjectUnchecked();
-    } else {
-      ASSERT_EQ(kLargeCode, space_index);
-      new_allocation =
-          lo_space->AllocateRaw(size, EXECUTABLE)->ToObjectUnchecked();
-    }
-    HeapObject* new_object = HeapObject::cast(new_allocation);
-    // Record all large objects in the same space.
-    address = new_object->address();
-    pages_[LO_SPACE].Add(address);
+  for (int i = 0; i < LAST_SPACE + 1; i++) {
+    reservations_[i] = kUninitializedReservation;
   }
-  last_object_address_ = address;
-  return address;
-}
-
-
-// This returns the address of an object that has been described in the
-// snapshot as being offset bytes back in a particular space.
-HeapObject* Deserializer::GetAddressFromEnd(int space) {
-  int offset = source_->GetInt();
-  ASSERT(!SpaceIsLarge(space));
-  offset <<= kObjectAlignmentBits;
-  return HeapObject::FromAddress(high_water_[space] - offset);
-}
-
-
-// This returns the address of an object that has been described in the
-// snapshot as being offset bytes into a particular space.
-HeapObject* Deserializer::GetAddressFromStart(int space) {
-  int offset = source_->GetInt();
-  if (SpaceIsLarge(space)) {
-    // Large spaces have one object per 'page'.
-    return HeapObject::FromAddress(pages_[LO_SPACE][offset]);
-  }
-  offset <<= kObjectAlignmentBits;
-  if (space == NEW_SPACE) {
-    // New space has only one space - numbered 0.
-    return HeapObject::FromAddress(pages_[space][0] + offset);
-  }
-  ASSERT(SpaceIsPaged(space));
-  int page_of_pointee = offset >> kPageSizeBits;
-  Address object_address = pages_[space][page_of_pointee] +
-                           (offset & Page::kPageAlignmentMask);
-  return HeapObject::FromAddress(object_address);
 }
 
 
 void Deserializer::Deserialize() {
   isolate_ = Isolate::Current();
   ASSERT(isolate_ != NULL);
-  {
-    // Don't GC while deserializing - just expand the heap.
-    AlwaysAllocateScope always_allocate;
-    // Don't use the free lists while deserializing.
-    LinearAllocationScope allocate_linearly;
-    // No active threads.
-    ASSERT_EQ(NULL, isolate_->thread_manager()->FirstThreadStateInUse());
-    // No active handles.
-    ASSERT(isolate_->handle_scope_implementer()->blocks()->is_empty());
-    ASSERT_EQ(NULL, external_reference_decoder_);
-    external_reference_decoder_ = new ExternalReferenceDecoder();
-    isolate_->heap()->IterateStrongRoots(this, VISIT_ONLY_STRONG);
-    isolate_->heap()->IterateWeakRoots(this, VISIT_ALL);
+  isolate_->heap()->ReserveSpace(&reservations_[0], &high_water_[0]);

[Yang, 2012/09/13 08:47:59]

why dereference and re-reference, and not simply:

ReserveSpace(reservations_, high_water_)

unless you want to make sure it is obvious that we are dealing with arrays?

[Erik Corry, 2012/09/13 12:13:35]

Done.

+  // No active threads.
+  ASSERT_EQ(NULL, isolate_->thread_manager()->FirstThreadStateInUse());
+  // No active handles.
+  ASSERT(isolate_->handle_scope_implementer()->blocks()->is_empty());
+  ASSERT_EQ(NULL, external_reference_decoder_);
+  external_reference_decoder_ = new ExternalReferenceDecoder();
+  isolate_->heap()->IterateStrongRoots(this, VISIT_ONLY_STRONG);
+  isolate_->heap()->RepairFreeListsAfterBoot();
+  isolate_->heap()->IterateWeakRoots(this, VISIT_ALL);
 
-    isolate_->heap()->set_native_contexts_list(
-        isolate_->heap()->undefined_value());
+  isolate_->heap()->set_native_contexts_list(
+      isolate_->heap()->undefined_value());
 
-    // Update data pointers to the external strings containing natives sources.
-    for (int i = 0; i < Natives::GetBuiltinsCount(); i++) {
-      Object* source = isolate_->heap()->natives_source_cache()->get(i);
-      if (!source->IsUndefined()) {
-        ExternalAsciiString::cast(source)->update_data_cache();
-      }
+  // Update data pointers to the external strings containing natives sources.
+  for (int i = 0; i < Natives::GetBuiltinsCount(); i++) {
+    Object* source = isolate_->heap()->natives_source_cache()->get(i);
+    if (!source->IsUndefined()) {
+      ExternalAsciiString::cast(source)->update_data_cache();
     }
   }
 
   // Issue code events for newly deserialized code objects.
   LOG_CODE_EVENT(isolate_, LogCodeObjects());
   LOG_CODE_EVENT(isolate_, LogCompiledFunctions());
 }
 
 
 void Deserializer::DeserializePartial(Object** root) {
   isolate_ = Isolate::Current();
-  // Don't GC while deserializing - just expand the heap.
-  AlwaysAllocateScope always_allocate;
-  // Don't use the free lists while deserializing.
-  LinearAllocationScope allocate_linearly;
+  for (int i = NEW_SPACE; i < kNumberOfSpaces; i++) {
+    ASSERT(reservations_[i] != kUninitializedReservation);
+  }
+  isolate_->heap()->ReserveSpace(&reservations_[0], &high_water_[0]);

[Yang, 2012/09/13 08:47:59]

Ditto.

[Erik Corry, 2012/09/13 12:13:35]

Ditto.

   if (external_reference_decoder_ == NULL) {
     external_reference_decoder_ = new ExternalReferenceDecoder();
   }
 
   // Keep track of the code space start and end pointers in case new
   // code objects were unserialized
   OldSpace* code_space = isolate_->heap()->code_space();
   Address start_address = code_space->top();
   VisitPointer(root);
 
@@ skipping 21 matching lines @@
   ReadChunk(start, end, NEW_SPACE, NULL);
 }
 
 
 // This routine writes the new object into the pointer provided and then
 // returns true if the new object was in young space and false otherwise.
 // The reason for this strange interface is that otherwise the object is
 // written very late, which means the FreeSpace map is not set up by the
 // time we need to use it to mark the space at the end of a page free.
 void Deserializer::ReadObject(int space_number,
-                              Space* space,
                               Object** write_back) {
   int size = source_->GetInt() << kObjectAlignmentBits;
-  Address address = Allocate(space_number, space, size);
+  Address address = Allocate(space_number, size);
   *write_back = HeapObject::FromAddress(address);
   Object** current = reinterpret_cast<Object**>(address);
   Object** limit = current + (size >> kPointerSizeLog2);
   if (FLAG_log_snapshot_positions) {
     LOG(isolate_, SnapshotPositionEvent(address, source_->position()));
   }
   ReadChunk(current, limit, space_number, address);
 #ifdef DEBUG
-  bool is_codespace = (space == HEAP->code_space()) ||
-      ((space == HEAP->lo_space()) && (space_number == kLargeCode));
+  bool is_codespace = (space_number == CODE_SPACE);
   ASSERT(HeapObject::FromAddress(address)->IsCode() == is_codespace);
 #endif
 }
 
-
-// This macro is always used with a constant argument so it should all fold
-// away to almost nothing in the generated code.  It might be nicer to do this
-// with the ternary operator but there are type issues with that.
-#define ASSIGN_DEST_SPACE(space_number)                                        \
-  Space* dest_space;                                                           \
-  if (space_number == NEW_SPACE) {                                             \
-    dest_space = isolate->heap()->new_space();                                \
-  } else if (space_number == OLD_POINTER_SPACE) {                              \
-    dest_space = isolate->heap()->old_pointer_space();                         \
-  } else if (space_number == OLD_DATA_SPACE) {                                 \
-    dest_space = isolate->heap()->old_data_space();                            \
-  } else if (space_number == CODE_SPACE) {                                     \
-    dest_space = isolate->heap()->code_space();                                \
-  } else if (space_number == MAP_SPACE) {                                      \
-    dest_space = isolate->heap()->map_space();                                 \
-  } else if (space_number == CELL_SPACE) {                                     \
-    dest_space = isolate->heap()->cell_space();                                \
-  } else {                                                                     \
-    ASSERT(space_number >= LO_SPACE);                                          \
-    dest_space = isolate->heap()->lo_space();                                  \
-  }
-
-
-static const int kUnknownOffsetFromStart = -1;
-
-
 void Deserializer::ReadChunk(Object** current,
                              Object** limit,
                              int source_space,
                              Address current_object_address) {
   Isolate* const isolate = isolate_;
+  // Write barrier support costs around 1% in startup time.  In fact there
+  // are no new space objects in current boot snapshots, so it's not needed,
+  // but that may change.
   bool write_barrier_needed = (current_object_address != NULL &&
                                source_space != NEW_SPACE &&
                                source_space != CELL_SPACE &&
                                source_space != CODE_SPACE &&
                                source_space != OLD_DATA_SPACE);
   while (current < limit) {
     int data = source_->Get();
     switch (data) {
 #define CASE_STATEMENT(where, how, within, space_number)                       \
       case where + how + within + space_number:                                \
       ASSERT((where & ~kPointedToMask) == 0);                                  \
       ASSERT((how & ~kHowToCodeMask) == 0);                                    \
       ASSERT((within & ~kWhereToPointMask) == 0);                              \
       ASSERT((space_number & ~kSpaceMask) == 0);
 
-#define CASE_BODY(where, how, within, space_number_if_any, offset_from_start)  \
+#define CASE_BODY(where, how, within, space_number_if_any)                     \
       {                                                                        \
         bool emit_write_barrier = false;                                       \
         bool current_was_incremented = false;                                  \
         int space_number =  space_number_if_any == kAnyOldSpace ?              \
                             (data & kSpaceMask) : space_number_if_any;         \
         if (where == kNewObject && how == kPlain && within == kStartOfObject) {\
-          ASSIGN_DEST_SPACE(space_number)                                      \
-          ReadObject(space_number, dest_space, current);                       \
+          ReadObject(space_number, current);                                   \
           emit_write_barrier = (space_number == NEW_SPACE);                    \
         } else {                                                               \
           Object* new_object = NULL;  /* May not be a real Object pointer. */  \
           if (where == kNewObject) {                                           \
-            ASSIGN_DEST_SPACE(space_number)                                    \
-            ReadObject(space_number, dest_space, &new_object);                 \
+            ReadObject(space_number, &new_object);                             \
           } else if (where == kRootArray) {                                    \
             int root_id = source_->GetInt();                                   \
             new_object = isolate->heap()->roots_array_start()[root_id];        \
             emit_write_barrier = isolate->heap()->InNewSpace(new_object);      \
           } else if (where == kPartialSnapshotCache) {                         \
             int cache_index = source_->GetInt();                               \
             new_object = isolate->serialize_partial_snapshot_cache()           \
                 [cache_index];                                                 \
             emit_write_barrier = isolate->heap()->InNewSpace(new_object);      \
           } else if (where == kExternalReference) {                            \
+            int skip = source_->GetInt();                                      \
+            current = reinterpret_cast<Object**>(reinterpret_cast<intptr_t>(   \
+                current) + skip);                                              \

[Yang, 2012/09/13 08:47:59]

It seems easier readable to use Address instead of intptr_t.

[Erik Corry, 2012/09/13 12:13:35]

Done.

             int reference_id = source_->GetInt();                              \
             Address address = external_reference_decoder_->                    \
                 Decode(reference_id);                                          \
             new_object = reinterpret_cast<Object*>(address);                   \
           } else if (where == kBackref) {                                      \
             emit_write_barrier = (space_number == NEW_SPACE);                  \
             new_object = GetAddressFromEnd(data & kSpaceMask);                 \
           } else {                                                             \
-            ASSERT(where == kFromStart);                                       \
-            if (offset_from_start == kUnknownOffsetFromStart) {                \
-              emit_write_barrier = (space_number == NEW_SPACE);                \
-              new_object = GetAddressFromStart(data & kSpaceMask);             \
-            } else {                                                           \
-              Address object_address = pages_[space_number][0] +               \
-                  (offset_from_start << kObjectAlignmentBits);                 \
-              new_object = HeapObject::FromAddress(object_address);            \
-            }                                                                  \
+            ASSERT(where == kBackrefWithSkip);                                 \
+            int skip = source_->GetInt();                                      \
+            current = reinterpret_cast<Object**>(                              \
+                reinterpret_cast<intptr_t>(current) + skip);                   \

[Yang, 2012/09/13 08:47:59]

Ditto.

[Erik Corry, 2012/09/13 12:13:35]

Ditto

+            emit_write_barrier = (space_number == NEW_SPACE);                  \
+            new_object = GetAddressFromEnd(data & kSpaceMask);                 \
           }                                                                    \
           if (within == kInnerPointer) {                                       \
             if (space_number != CODE_SPACE || new_object->IsCode()) {          \
               Code* new_code_object = reinterpret_cast<Code*>(new_object);     \
               new_object = reinterpret_cast<Object*>(                          \
                   new_code_object->instruction_start());                       \
             } else {                                                           \
-              ASSERT(space_number == CODE_SPACE || space_number == kLargeCode);\
+              ASSERT(space_number == CODE_SPACE);                              \
               JSGlobalPropertyCell* cell =                                     \
                   JSGlobalPropertyCell::cast(new_object);                      \
               new_object = reinterpret_cast<Object*>(                          \
                   cell->ValueAddress());                                       \
             }                                                                  \
           }                                                                    \
           if (how == kFromCode) {                                              \
             Address location_of_branch_data =                                  \
                 reinterpret_cast<Address>(current);                            \
             Assembler::deserialization_set_special_target_at(                  \
@@ skipping 11 matching lines @@
           isolate->heap()->RecordWrite(                                        \
               current_object_address,                                          \
               static_cast<int>(current_address - current_object_address));     \
         }                                                                      \
         if (!current_was_incremented) {                                        \
           current++;                                                           \
         }                                                                      \
         break;                                                                 \
       }                                                                        \
 
-// This generates a case and a body for each space.  The large object spaces are
-// very rare in snapshots so they are grouped in one body.
-#define ONE_PER_SPACE(where, how, within)                                      \
-  CASE_STATEMENT(where, how, within, NEW_SPACE)                                \
-  CASE_BODY(where, how, within, NEW_SPACE, kUnknownOffsetFromStart)            \
-  CASE_STATEMENT(where, how, within, OLD_DATA_SPACE)                           \
-  CASE_BODY(where, how, within, OLD_DATA_SPACE, kUnknownOffsetFromStart)       \
-  CASE_STATEMENT(where, how, within, OLD_POINTER_SPACE)                        \
-  CASE_BODY(where, how, within, OLD_POINTER_SPACE, kUnknownOffsetFromStart)    \
-  CASE_STATEMENT(where, how, within, CODE_SPACE)                               \
-  CASE_BODY(where, how, within, CODE_SPACE, kUnknownOffsetFromStart)           \
-  CASE_STATEMENT(where, how, within, CELL_SPACE)                               \
-  CASE_BODY(where, how, within, CELL_SPACE, kUnknownOffsetFromStart)           \
-  CASE_STATEMENT(where, how, within, MAP_SPACE)                                \
-  CASE_BODY(where, how, within, MAP_SPACE, kUnknownOffsetFromStart)            \
-  CASE_STATEMENT(where, how, within, kLargeData)                               \
-  CASE_STATEMENT(where, how, within, kLargeCode)                               \
-  CASE_STATEMENT(where, how, within, kLargeFixedArray)                         \
-  CASE_BODY(where, how, within, kAnyOldSpace, kUnknownOffsetFromStart)
-
 // This generates a case and a body for the new space (which has to do extra
 // write barrier handling) and handles the other spaces with 8 fall-through
 // cases and one body.
 #define ALL_SPACES(where, how, within)                                         \
   CASE_STATEMENT(where, how, within, NEW_SPACE)                                \
-  CASE_BODY(where, how, within, NEW_SPACE, kUnknownOffsetFromStart)            \
+  CASE_BODY(where, how, within, NEW_SPACE)                                     \
   CASE_STATEMENT(where, how, within, OLD_DATA_SPACE)                           \
   CASE_STATEMENT(where, how, within, OLD_POINTER_SPACE)                        \
   CASE_STATEMENT(where, how, within, CODE_SPACE)                               \
   CASE_STATEMENT(where, how, within, CELL_SPACE)                               \
   CASE_STATEMENT(where, how, within, MAP_SPACE)                                \
-  CASE_STATEMENT(where, how, within, kLargeData)                               \
-  CASE_STATEMENT(where, how, within, kLargeCode)                               \
-  CASE_STATEMENT(where, how, within, kLargeFixedArray)                         \
-  CASE_BODY(where, how, within, kAnyOldSpace, kUnknownOffsetFromStart)
-
-#define ONE_PER_CODE_SPACE(where, how, within)                                 \
-  CASE_STATEMENT(where, how, within, CODE_SPACE)                               \
-  CASE_BODY(where, how, within, CODE_SPACE, kUnknownOffsetFromStart)           \
-  CASE_STATEMENT(where, how, within, kLargeCode)                               \
-  CASE_BODY(where, how, within, kLargeCode, kUnknownOffsetFromStart)
+  CASE_BODY(where, how, within, kAnyOldSpace)
 
 #define FOUR_CASES(byte_code)             \
   case byte_code:                         \
   case byte_code + 1:                     \
   case byte_code + 2:                     \
   case byte_code + 3:
 
 #define SIXTEEN_CASES(byte_code)          \
   FOUR_CASES(byte_code)                   \
   FOUR_CASES(byte_code + 4)               \
@@ skipping 11 matching lines @@
       }
       COMMON_RAW_LENGTHS(RAW_CASE)
 #undef RAW_CASE
 
       // Deserialize a chunk of raw data that doesn't have one of the popular
       // lengths.
       case kRawData: {
         int size = source_->GetInt();
         byte* raw_data_out = reinterpret_cast<byte*>(current);
         source_->CopyRaw(raw_data_out, size);
-        current = reinterpret_cast<Object**>(raw_data_out + size);
         break;
       }
 
-      SIXTEEN_CASES(kRootArrayLowConstants)
-      SIXTEEN_CASES(kRootArrayHighConstants) {
+      SIXTEEN_CASES(kRootArrayConstants + kNoSkipDistance)
+      SIXTEEN_CASES(kRootArrayConstants + kNoSkipDistance + 16) {
         int root_id = RootArrayConstantFromByteCode(data);
         Object* object = isolate->heap()->roots_array_start()[root_id];
         ASSERT(!isolate->heap()->InNewSpace(object));
         *current++ = object;
         break;
       }
 
+      SIXTEEN_CASES(kRootArrayConstants + kHasSkipDistance)
+      SIXTEEN_CASES(kRootArrayConstants + kHasSkipDistance + 16) {
+        int root_id = RootArrayConstantFromByteCode(data);
+        int skip = source_->GetInt();
+        current = reinterpret_cast<Object**>(
+            reinterpret_cast<intptr_t>(current) + skip);
+        Object* object = isolate->heap()->roots_array_start()[root_id];
+        ASSERT(!isolate->heap()->InNewSpace(object));
+        *current++ = object;
+        break;
+      }
+
       case kRepeat: {
         int repeats = source_->GetInt();
         Object* object = current[-1];
         ASSERT(!isolate->heap()->InNewSpace(object));
         for (int i = 0; i < repeats; i++) current[i] = object;
         current += repeats;
         break;
       }
 
       STATIC_ASSERT(kRootArrayNumberOfConstantEncodings ==
                     Heap::kOldSpaceRoots);
-      STATIC_ASSERT(kMaxRepeats == 12);
-      FOUR_CASES(kConstantRepeat)
-      FOUR_CASES(kConstantRepeat + 4)
-      FOUR_CASES(kConstantRepeat + 8) {
+      STATIC_ASSERT(kMaxRepeats == 13);
+      case kConstantRepeat:
+      FOUR_CASES(kConstantRepeat + 1)
+      FOUR_CASES(kConstantRepeat + 5)
+      FOUR_CASES(kConstantRepeat + 9) {
         int repeats = RepeatsForCode(data);
         Object* object = current[-1];
         ASSERT(!isolate->heap()->InNewSpace(object));
         for (int i = 0; i < repeats; i++) current[i] = object;
         current += repeats;
         break;
       }
 
       // Deserialize a new object and write a pointer to it to the current
       // object.
-      ONE_PER_SPACE(kNewObject, kPlain, kStartOfObject)
+      ALL_SPACES(kNewObject, kPlain, kStartOfObject)
       // Support for direct instruction pointers in functions.  It's an inner
       // pointer because it points at the entry point, not at the start of the
       // code object.
-      ONE_PER_CODE_SPACE(kNewObject, kPlain, kInnerPointer)
+      CASE_STATEMENT(kNewObject, kPlain, kInnerPointer, CODE_SPACE)
+      CASE_BODY(kNewObject, kPlain, kInnerPointer, CODE_SPACE)
       // Deserialize a new code object and write a pointer to its first
       // instruction to the current code object.
-      ONE_PER_SPACE(kNewObject, kFromCode, kInnerPointer)
+      ALL_SPACES(kNewObject, kFromCode, kInnerPointer)
       // Find a recently deserialized object using its offset from the current
       // allocation point and write a pointer to it to the current object.
       ALL_SPACES(kBackref, kPlain, kStartOfObject)
+      ALL_SPACES(kBackrefWithSkip, kPlain, kStartOfObject)
 #if V8_TARGET_ARCH_MIPS
       // Deserialize a new object from pointer found in code and write
       // a pointer to it to the current object. Required only for MIPS, and
       // omitted on the other architectures because it is fully unrolled and
       // would cause bloat.
-      ONE_PER_SPACE(kNewObject, kFromCode, kStartOfObject)
+      ALL_SPACES(kNewObject, kFromCode, kStartOfObject)
       // Find a recently deserialized code object using its offset from the
       // current allocation point and write a pointer to it to the current
       // object. Required only for MIPS.
       ALL_SPACES(kBackref, kFromCode, kStartOfObject)
-      // Find an already deserialized code object using its offset from
-      // the start and write a pointer to it to the current object.
-      // Required only for MIPS.
-      ALL_SPACES(kFromStart, kFromCode, kStartOfObject)
+      ALL_SPACES(kBackrefWithSkip, kFromCode, kStartOfObject)
 #endif
       // Find a recently deserialized code object using its offset from the
       // current allocation point and write a pointer to its first instruction
       // to the current code object or the instruction pointer in a function
       // object.
       ALL_SPACES(kBackref, kFromCode, kInnerPointer)
+      ALL_SPACES(kBackrefWithSkip, kFromCode, kInnerPointer)
       ALL_SPACES(kBackref, kPlain, kInnerPointer)
-      // Find an already deserialized object using its offset from the start
-      // and write a pointer to it to the current object.
-      ALL_SPACES(kFromStart, kPlain, kStartOfObject)
-      ALL_SPACES(kFromStart, kPlain, kInnerPointer)
-      // Find an already deserialized code object using its offset from the
-      // start and write a pointer to its first instruction to the current code
-      // object.
-      ALL_SPACES(kFromStart, kFromCode, kInnerPointer)
+      ALL_SPACES(kBackrefWithSkip, kPlain, kInnerPointer)
       // Find an object in the roots array and write a pointer to it to the
       // current object.
       CASE_STATEMENT(kRootArray, kPlain, kStartOfObject, 0)
-      CASE_BODY(kRootArray, kPlain, kStartOfObject, 0, kUnknownOffsetFromStart)
+      CASE_BODY(kRootArray, kPlain, kStartOfObject, 0)
       // Find an object in the partial snapshots cache and write a pointer to it
       // to the current object.
       CASE_STATEMENT(kPartialSnapshotCache, kPlain, kStartOfObject, 0)
       CASE_BODY(kPartialSnapshotCache,
                 kPlain,
                 kStartOfObject,
-                0,
-                kUnknownOffsetFromStart)
+                0)
       // Find an code entry in the partial snapshots cache and
       // write a pointer to it to the current object.
       CASE_STATEMENT(kPartialSnapshotCache, kPlain, kInnerPointer, 0)
       CASE_BODY(kPartialSnapshotCache,
                 kPlain,
                 kInnerPointer,
-                0,
-                kUnknownOffsetFromStart)
+                0)
       // Find an external reference and write a pointer to it to the current
       // object.
       CASE_STATEMENT(kExternalReference, kPlain, kStartOfObject, 0)
       CASE_BODY(kExternalReference,
                 kPlain,
                 kStartOfObject,
-                0,
-                kUnknownOffsetFromStart)
+                0)
       // Find an external reference and write a pointer to it in the current
       // code object.
       CASE_STATEMENT(kExternalReference, kFromCode, kStartOfObject, 0)
       CASE_BODY(kExternalReference,
                 kFromCode,
                 kStartOfObject,
-                0,
-                kUnknownOffsetFromStart)
+                0)
 
 #undef CASE_STATEMENT
 #undef CASE_BODY
-#undef ONE_PER_SPACE
 #undef ALL_SPACES
-#undef ASSIGN_DEST_SPACE
 
-      case kNewPage: {
-        int space = source_->Get();
-        pages_[space].Add(last_object_address_);
-        if (space == CODE_SPACE) {
-          CPU::FlushICache(last_object_address_, Page::kPageSize);
-        }
+      case kSkip: {
+        int size = source_->GetInt();
+        current = reinterpret_cast<Object**>(
+            reinterpret_cast<intptr_t>(current) + size);
         break;
       }
 
-      case kSkip: {
-        current++;
-        break;
-      }
-
       case kNativesStringResource: {
         int index = source_->Get();
         Vector<const char> source_vector = Natives::GetRawScriptSource(index);
         NativesExternalStringResource* resource =
             new NativesExternalStringResource(isolate->bootstrapper(),
                                               source_vector.start(),
                                               source_vector.length());
         *current++ = reinterpret_cast<Object*>(resource);
         break;
       }
 
       case kSynchronize: {
         // If we get here then that indicates that you have a mismatch between
         // the number of GC roots when serializing and deserializing.
         UNREACHABLE();
       }
 
       default:
         UNREACHABLE();
     }
   }
-  ASSERT_EQ(current, limit);
+  ASSERT_EQ(limit, current);
 }
 
 
 void SnapshotByteSink::PutInt(uintptr_t integer, const char* description) {
-  const int max_shift = ((kPointerSize * kBitsPerByte) / 7) * 7;
-  for (int shift = max_shift; shift > 0; shift -= 7) {
-    if (integer >= static_cast<uintptr_t>(1u) << shift) {
-      Put((static_cast<int>((integer >> shift)) & 0x7f) | 0x80, "IntPart");
-    }
-  }
-  PutSection(static_cast<int>(integer & 0x7f), "IntLastPart");
+  ASSERT(integer <= 0x3fffff);

[Yang, 2012/09/13 08:47:59]

I'd prefer integer < (1 << 22)

[Erik Corry, 2012/09/13 12:13:35]

Done.

+  integer <<= 2;
+  int bytes = 1;
+  if (integer > 0xff) bytes = 2;
+  if (integer > 0xffff) bytes = 3;
+  integer |= bytes;
+  Put(static_cast<int>(integer & 0xff), "IntPart1");
+  if (bytes > 1) Put(static_cast<int>((integer >> 8) & 0xff), "IntPart2");
+  if (bytes > 2) Put(static_cast<int>((integer >> 16) & 0xff), "IntPart3");
 }
 
 
 Serializer::Serializer(SnapshotByteSink* sink)
     : sink_(sink),
       current_root_index_(0),
       external_reference_encoder_(new ExternalReferenceEncoder),
-      large_object_total_(0),
       root_index_wave_front_(0) {
   isolate_ = Isolate::Current();
   // The serializer is meant to be used only to generate initial heap images
   // from a context in which there is only one isolate.
   ASSERT(isolate_->IsDefaultIsolate());
   for (int i = 0; i <= LAST_SPACE; i++) {
     fullness_[i] = 0;
   }
 }
 
@@ skipping 12 matching lines @@
   CHECK_EQ(0, isolate->global_handles()->NumberOfWeakHandles());
   // We don't support serializing installed extensions.
   CHECK(!isolate->has_installed_extensions());
 
   HEAP->IterateStrongRoots(this, VISIT_ONLY_STRONG);
 }
 
 
 void PartialSerializer::Serialize(Object** object) {
   this->VisitPointer(object);
+  Pad();
 }
 
 
 void Serializer::VisitPointers(Object** start, Object** end) {
   Isolate* isolate = Isolate::Current();
 
   for (Object** current = start; current < end; current++) {
     if (start == isolate->heap()->roots_array_start()) {
       root_index_wave_front_ =
           Max(root_index_wave_front_, static_cast<intptr_t>(current - start));
     }
     if (reinterpret_cast<Address>(current) ==
         isolate->heap()->store_buffer()->TopAddress()) {
       sink_->Put(kSkip, "Skip");
+      sink_->PutInt(kPointerSize, "SkipOneWord");
     } else if ((*current)->IsSmi()) {
-      sink_->Put(kRawData, "RawData");
-      sink_->PutInt(kPointerSize, "length");
+      sink_->Put(kRawData + kPointerSize / 4, "Smi");

[Yang, 2012/09/13 08:47:59]

The 4 in here obviously refers to the factor 4 in COMMON_RAW_LENGTH. Can we
somehow make a constant out of this?

[Erik Corry, 2012/09/13 12:13:35]

Now the 4 is gone.

       for (int i = 0; i < kPointerSize; i++) {
         sink_->Put(reinterpret_cast<byte*>(current)[i], "Byte");
       }
     } else {
-      SerializeObject(*current, kPlain, kStartOfObject);
+      SerializeObject(*current, kPlain, kStartOfObject, 0);
     }
   }
 }
 
 
 // This ensures that the partial snapshot cache keeps things alive during GC and
 // tracks their movement.  When it is called during serialization of the startup
 // snapshot nothing happens.  When the partial (context) snapshot is created,
 // this array is populated with the pointers that the partial snapshot will
 // need. As that happens we emit serialized objects to the startup snapshot
@@ skipping 66 matching lines @@
 
 
 // Encode the location of an already deserialized object in order to write its
 // location into a later object.  We can encode the location as an offset from
 // the start of the deserialized objects or as an offset backwards from the
 // current allocation pointer.
 void Serializer::SerializeReferenceToPreviousObject(
     int space,
     int address,
     HowToCode how_to_code,
-    WhereToPoint where_to_point) {
+    WhereToPoint where_to_point,
+    int skip) {
   int offset = CurrentAllocationAddress(space) - address;
-  bool from_start = true;
-  if (SpaceIsPaged(space)) {
-    // For paged space it is simple to encode back from current allocation if
-    // the object is on the same page as the current allocation pointer.
-    if ((CurrentAllocationAddress(space) >> kPageSizeBits) ==
-        (address >> kPageSizeBits)) {
-      from_start = false;
-      address = offset;
-    }
-  } else if (space == NEW_SPACE) {
-    // For new space it is always simple to encode back from current allocation.
-    if (offset < address) {
-      from_start = false;
-      address = offset;
-    }
+  // Shift out the bits that are always 0.
+  offset >>= kObjectAlignmentBits;
+  if (skip == 0) {
+    sink_->Put(kBackref + how_to_code + where_to_point + space, "BackRefSer");
+  } else {
+    sink_->Put(kBackrefWithSkip + how_to_code + where_to_point + space,
+               "BackRefSerWithSkip");
+    sink_->PutInt(skip, "BackRefSkipDistance");
   }
-  // If we are actually dealing with real offsets (and not a numbering of
-  // all objects) then we should shift out the bits that are always 0.
-  if (!SpaceIsLarge(space)) address >>= kObjectAlignmentBits;
-  if (from_start) {
-    sink_->Put(kFromStart + how_to_code + where_to_point + space, "RefSer");
-    sink_->PutInt(address, "address");
-  } else {
-    sink_->Put(kBackref + how_to_code + where_to_point + space, "BackRefSer");
-    sink_->PutInt(address, "address");
-  }
+  sink_->PutInt(offset, "offset");
 }
 
 
 void StartupSerializer::SerializeObject(
     Object* o,
     HowToCode how_to_code,
-    WhereToPoint where_to_point) {
+    WhereToPoint where_to_point,
+    int skip) {
   CHECK(o->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(o);
 
   int root_index;
   if ((root_index = RootIndex(heap_object, how_to_code)) != kInvalidRootIndex) {
-    PutRoot(root_index, heap_object, how_to_code, where_to_point);
+    PutRoot(root_index, heap_object, how_to_code, where_to_point, skip);
     return;
   }
 
   if (address_mapper_.IsMapped(heap_object)) {
-    int space = SpaceOfAlreadySerializedObject(heap_object);
+    int space = SpaceOfObject(heap_object);
     int address = address_mapper_.MappedTo(heap_object);
     SerializeReferenceToPreviousObject(space,
                                        address,
                                        how_to_code,
-                                       where_to_point);
+                                       where_to_point,
+                                       skip);
   } else {
+    if (skip != 0) {
+      sink_->Put(kSkip, "FlushPendingSkip");
+      sink_->PutInt(skip, "SkipDistance");
+    }
+
     // Object has not yet been serialized.  Serialize it here.
     ObjectSerializer object_serializer(this,
                                        heap_object,
                                        sink_,
                                        how_to_code,
                                        where_to_point);
     object_serializer.Serialize();
   }
 }
 
 
 void StartupSerializer::SerializeWeakReferences() {
   // This phase comes right after the partial serialization (of the snapshot).
   // After we have done the partial serialization the partial snapshot cache
   // will contain some references needed to decode the partial snapshot.  We
   // add one entry with 'undefined' which is the sentinel that the deserializer
   // uses to know it is done deserializing the array.
   Isolate* isolate = Isolate::Current();
   Object* undefined = isolate->heap()->undefined_value();
   VisitPointer(&undefined);
   HEAP->IterateWeakRoots(this, VISIT_ALL);
 }
 
 
 void Serializer::PutRoot(int root_index,
                          HeapObject* object,
                          SerializerDeserializer::HowToCode how_to_code,
-                         SerializerDeserializer::WhereToPoint where_to_point) {
+                         SerializerDeserializer::WhereToPoint where_to_point,
+                         int skip) {
   if (how_to_code == kPlain &&
       where_to_point == kStartOfObject &&
       root_index < kRootArrayNumberOfConstantEncodings &&
       !HEAP->InNewSpace(object)) {
-    if (root_index < kRootArrayNumberOfLowConstantEncodings) {
-      sink_->Put(kRootArrayLowConstants + root_index, "RootLoConstant");
+    if (skip == 0) {
+      sink_->Put(kRootArrayConstants + kNoSkipDistance + root_index,
+                 "RootConstant");
     } else {
-      sink_->Put(kRootArrayHighConstants + root_index -
-                     kRootArrayNumberOfLowConstantEncodings,
-                 "RootHiConstant");
+      sink_->Put(kRootArrayConstants + kHasSkipDistance + root_index,
+                 "RootConstant");
+      sink_->PutInt(skip, "SkipInPutRoot");
     }
   } else {
+    if (skip != 0) {
+      sink_->Put(kSkip, "SkipFromPutRoot");
+      sink_->PutInt(skip, "SkipFromPutRootDistance");
+    }
     sink_->Put(kRootArray + how_to_code + where_to_point, "RootSerialization");
     sink_->PutInt(root_index, "root_index");
   }
 }
 
 
 void PartialSerializer::SerializeObject(
     Object* o,
     HowToCode how_to_code,
-    WhereToPoint where_to_point) {
+    WhereToPoint where_to_point,
+    int skip) {
   CHECK(o->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(o);
 
   if (heap_object->IsMap()) {
     // The code-caches link to context-specific code objects, which
     // the startup and context serializes cannot currently handle.
     ASSERT(Map::cast(heap_object)->code_cache() ==
            heap_object->GetHeap()->raw_unchecked_empty_fixed_array());
   }
 
   int root_index;
   if ((root_index = RootIndex(heap_object, how_to_code)) != kInvalidRootIndex) {
-    PutRoot(root_index, heap_object, how_to_code, where_to_point);
+    PutRoot(root_index, heap_object, how_to_code, where_to_point, skip);
     return;
   }
 
   if (ShouldBeInThePartialSnapshotCache(heap_object)) {
+    if (skip != 0) {
+      sink_->Put(kSkip, "SkipFromSerializeObject");
+      sink_->PutInt(skip, "SkipDistanceFromSerializeObject");
+    }
+
     int cache_index = PartialSnapshotCacheIndex(heap_object);
     sink_->Put(kPartialSnapshotCache + how_to_code + where_to_point,
                "PartialSnapshotCache");
     sink_->PutInt(cache_index, "partial_snapshot_cache_index");
     return;
   }
 
   // Pointers from the partial snapshot to the objects in the startup snapshot
   // should go through the root array or through the partial snapshot cache.
   // If this is not the case you may have to add something to the root array.
   ASSERT(!startup_serializer_->address_mapper()->IsMapped(heap_object));
   // All the symbols that the partial snapshot needs should be either in the
   // root table or in the partial snapshot cache.
   ASSERT(!heap_object->IsSymbol());
 
   if (address_mapper_.IsMapped(heap_object)) {
-    int space = SpaceOfAlreadySerializedObject(heap_object);
+    int space = SpaceOfObject(heap_object);
     int address = address_mapper_.MappedTo(heap_object);
     SerializeReferenceToPreviousObject(space,
                                        address,
                                        how_to_code,
-                                       where_to_point);
+                                       where_to_point,
+                                       skip);
   } else {
+    if (skip != 0) {
+      sink_->Put(kSkip, "SkipFromSerializeObject");
+      sink_->PutInt(skip, "SkipDistanceFromSerializeObject");
+    }
     // Object has not yet been serialized.  Serialize it here.
     ObjectSerializer serializer(this,
                                 heap_object,
                                 sink_,
                                 how_to_code,
                                 where_to_point);
     serializer.Serialize();
   }
 }
 
 
 void Serializer::ObjectSerializer::Serialize() {
   int space = Serializer::SpaceOfObject(object_);
   int size = object_->Size();
 
   sink_->Put(kNewObject + reference_representation_ + space,
              "ObjectSerialization");
   sink_->PutInt(size >> kObjectAlignmentBits, "Size in words");
 
   LOG(i::Isolate::Current(),
       SnapshotPositionEvent(object_->address(), sink_->Position()));
 
   // Mark this object as already serialized.
-  bool start_new_page;
-  int offset = serializer_->Allocate(space, size, &start_new_page);
+  int offset = serializer_->Allocate(space, size);
   serializer_->address_mapper()->AddMapping(object_, offset);
-  if (start_new_page) {
-    sink_->Put(kNewPage, "NewPage");
-    sink_->PutSection(space, "NewPageSpace");
-  }
 
   // Serialize the map (first word of the object).
-  serializer_->SerializeObject(object_->map(), kPlain, kStartOfObject);
+  serializer_->SerializeObject(object_->map(), kPlain, kStartOfObject, 0);
 
   // Serialize the rest of the object.
   CHECK_EQ(0, bytes_processed_so_far_);
   bytes_processed_so_far_ = kPointerSize;
   object_->IterateBody(object_->map()->instance_type(), size, this);
   OutputRawData(object_->address() + size);
 }
 
 
 void Serializer::ObjectSerializer::VisitPointers(Object** start,
@@ skipping 20 matching lines @@
         }
         current += repeat_count;
         bytes_processed_so_far_ += repeat_count * kPointerSize;
         if (repeat_count > kMaxRepeats) {
           sink_->Put(kRepeat, "SerializeRepeats");
           sink_->PutInt(repeat_count, "SerializeRepeats");
         } else {
           sink_->Put(CodeForRepeats(repeat_count), "SerializeRepeats");
         }
       } else {
-        serializer_->SerializeObject(current_contents, kPlain, kStartOfObject);
+        serializer_->SerializeObject(
+                current_contents, kPlain, kStartOfObject, 0);
         bytes_processed_so_far_ += kPointerSize;
         current++;
       }
     }
   }
 }
 
 
 void Serializer::ObjectSerializer::VisitEmbeddedPointer(RelocInfo* rinfo) {
   Object** current = rinfo->target_object_address();
 
-  OutputRawData(rinfo->target_address_address());
+  int skip = OutputRawData(rinfo->target_address_address(),
+                           kCanReturnSkipInsteadOfSkipping);
   HowToCode representation = rinfo->IsCodedSpecially() ? kFromCode : kPlain;
-  serializer_->SerializeObject(*current, representation, kStartOfObject);
+  serializer_->SerializeObject(*current, representation, kStartOfObject, skip);
   bytes_processed_so_far_ += rinfo->target_address_size();
 }
 
 
 void Serializer::ObjectSerializer::VisitExternalReferences(Address* start,
                                                            Address* end) {
   Address references_start = reinterpret_cast<Address>(start);
-  OutputRawData(references_start);
+  int skip = OutputRawData(references_start, kCanReturnSkipInsteadOfSkipping);
 
   for (Address* current = start; current < end; current++) {
     sink_->Put(kExternalReference + kPlain + kStartOfObject, "ExternalRef");
+    sink_->PutInt(skip, "SkipB4ExternalRef");
+    skip = 0;
     int reference_id = serializer_->EncodeExternalReference(*current);
     sink_->PutInt(reference_id, "reference id");
   }
   bytes_processed_so_far_ += static_cast<int>((end - start) * kPointerSize);
 }
 
 
 void Serializer::ObjectSerializer::VisitExternalReference(RelocInfo* rinfo) {
   Address references_start = rinfo->target_address_address();
-  OutputRawData(references_start);
+  int skip = OutputRawData(references_start, kCanReturnSkipInsteadOfSkipping);
 
   Address* current = rinfo->target_reference_address();
   int representation = rinfo->IsCodedSpecially() ?
                        kFromCode + kStartOfObject : kPlain + kStartOfObject;
   sink_->Put(kExternalReference + representation, "ExternalRef");
+  sink_->PutInt(skip, "SkipB4ExternalRef");
   int reference_id = serializer_->EncodeExternalReference(*current);
   sink_->PutInt(reference_id, "reference id");
   bytes_processed_so_far_ += rinfo->target_address_size();
 }
 
 
 void Serializer::ObjectSerializer::VisitRuntimeEntry(RelocInfo* rinfo) {
   Address target_start = rinfo->target_address_address();
-  OutputRawData(target_start);
+  int skip = OutputRawData(target_start, kCanReturnSkipInsteadOfSkipping);
   Address target = rinfo->target_address();
   uint32_t encoding = serializer_->EncodeExternalReference(target);
   CHECK(target == NULL ? encoding == 0 : encoding != 0);
   int representation;
   // Can't use a ternary operator because of gcc.
   if (rinfo->IsCodedSpecially()) {
     representation = kStartOfObject + kFromCode;
   } else {
     representation = kStartOfObject + kPlain;
   }
   sink_->Put(kExternalReference + representation, "ExternalReference");
+  sink_->PutInt(skip, "SkipB4ExternalRef");
   sink_->PutInt(encoding, "reference id");
   bytes_processed_so_far_ += rinfo->target_address_size();
 }
 
 
 void Serializer::ObjectSerializer::VisitCodeTarget(RelocInfo* rinfo) {
   CHECK(RelocInfo::IsCodeTarget(rinfo->rmode()));
   Address target_start = rinfo->target_address_address();
-  OutputRawData(target_start);
+  int skip = OutputRawData(target_start, kCanReturnSkipInsteadOfSkipping);
   Code* target = Code::GetCodeFromTargetAddress(rinfo->target_address());
-  serializer_->SerializeObject(target, kFromCode, kInnerPointer);
+  serializer_->SerializeObject(target, kFromCode, kInnerPointer, skip);
   bytes_processed_so_far_ += rinfo->target_address_size();
 }
 
 
 void Serializer::ObjectSerializer::VisitCodeEntry(Address entry_address) {
   Code* target = Code::cast(Code::GetObjectFromEntryAddress(entry_address));
-  OutputRawData(entry_address);
-  serializer_->SerializeObject(target, kPlain, kInnerPointer);
+  int skip = OutputRawData(entry_address, kCanReturnSkipInsteadOfSkipping);
+  serializer_->SerializeObject(target, kPlain, kInnerPointer, skip);
   bytes_processed_so_far_ += kPointerSize;
 }
 
 
 void Serializer::ObjectSerializer::VisitGlobalPropertyCell(RelocInfo* rinfo) {
   ASSERT(rinfo->rmode() == RelocInfo::GLOBAL_PROPERTY_CELL);
   JSGlobalPropertyCell* cell =
       JSGlobalPropertyCell::cast(rinfo->target_cell());
-  OutputRawData(rinfo->pc());
-  serializer_->SerializeObject(cell, kPlain, kInnerPointer);
+  int skip = OutputRawData(rinfo->pc(), kCanReturnSkipInsteadOfSkipping);
+  serializer_->SerializeObject(cell, kPlain, kInnerPointer, skip);
 }
 
 
 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++) {
     Object* source = HEAP->natives_source_cache()->get(i);
     if (!source->IsUndefined()) {
       ExternalAsciiString* string = ExternalAsciiString::cast(source);
       typedef v8::String::ExternalAsciiStringResource Resource;
       const Resource* resource = string->resource();
       if (resource == *resource_pointer) {
         sink_->Put(kNativesStringResource, "NativesStringResource");
         sink_->PutSection(i, "NativesStringResourceEnd");
         bytes_processed_so_far_ += sizeof(resource);
         return;
       }
     }
   }
   // One of the strings in the natives cache should match the resource.  We
   // can't serialize any other kinds of external strings.
   UNREACHABLE();
 }
 
 
-void Serializer::ObjectSerializer::OutputRawData(Address up_to) {
+int Serializer::ObjectSerializer::OutputRawData(
+    Address up_to, Serializer::ObjectSerializer::ReturnSkip return_skip) {
   Address object_start = object_->address();
+  Address base = object_start + bytes_processed_so_far_;
   int up_to_offset = static_cast<int>(up_to - object_start);
-  int skipped = up_to_offset - bytes_processed_so_far_;
+  int to_skip = up_to_offset - bytes_processed_so_far_;
+  int bytes_to_output = to_skip;
+  bytes_processed_so_far_ +=  to_skip;
   // This assert will fail if the reloc info gives us the target_address_address
   // locations in a non-ascending order.  Luckily that doesn't happen.
-  ASSERT(skipped >= 0);
-  if (skipped != 0) {
-    Address base = object_start + bytes_processed_so_far_;
+  ASSERT(to_skip >= 0);
+  bool outputting_code = false;
+  if (to_skip != 0 && code_object_ && !code_has_been_output_) {
+    // Output the code all at once and fix later.
+    bytes_to_output = object_->Size() + to_skip - bytes_processed_so_far_;
+    outputting_code = true;
+    code_has_been_output_ = true;
+  }
+  if (bytes_to_output != 0 &&
+      (!code_object_ || outputting_code)) {
 #define RAW_CASE(index, length)                                                \
-    if (skipped == length) {                                                   \
+    if (!outputting_code && bytes_to_output == length && length == to_skip) {  \
       sink_->PutSection(kRawData + index, "RawDataFixed");                     \
+      to_skip = 0;  /* This insn already skips. */                             \
     } else  /* NOLINT */
     COMMON_RAW_LENGTHS(RAW_CASE)
 #undef RAW_CASE
     {  /* NOLINT */
+      // We always end up here if we are outputting the code of a code object.
       sink_->Put(kRawData, "RawData");
-      sink_->PutInt(skipped, "length");
+      sink_->PutInt(bytes_to_output, "length");
     }
-    for (int i = 0; i < skipped; i++) {
+    for (int i = 0; i < bytes_to_output; i++) {
       unsigned int data = base[i];
       sink_->PutSection(data, "Byte");
     }
-    bytes_processed_so_far_ += skipped;
   }
+  if (to_skip != 0 && return_skip == kIgnoringReturn) {
+    sink_->Put(kSkip, "Skip");
+    sink_->PutInt(to_skip, "SkipDistance");
+    to_skip = 0;
+  }
+  return to_skip;
 }
 
 
 int Serializer::SpaceOfObject(HeapObject* object) {
   for (int i = FIRST_SPACE; i <= LAST_SPACE; i++) {
     AllocationSpace s = static_cast<AllocationSpace>(i);
     if (HEAP->InSpace(object, s)) {
-      if (i == LO_SPACE) {
-        if (object->IsCode()) {
-          return kLargeCode;
-        } else if (object->IsFixedArray()) {
-          return kLargeFixedArray;
-        } else {
-          return kLargeData;
-        }
-      }
+      ASSERT(i < kNumberOfSpaces);
       return i;
     }
   }
   UNREACHABLE();
   return 0;
 }
 
 
-int Serializer::SpaceOfAlreadySerializedObject(HeapObject* object) {
-  for (int i = FIRST_SPACE; i <= LAST_SPACE; i++) {
-    AllocationSpace s = static_cast<AllocationSpace>(i);
-    if (HEAP->InSpace(object, s)) {
-      return i;
-    }
-  }
-  UNREACHABLE();
-  return 0;
-}
-
-
-int Serializer::Allocate(int space, int size, bool* new_page) {
+int Serializer::Allocate(int space, int size) {
   CHECK(space >= 0 && space < kNumberOfSpaces);
-  if (SpaceIsLarge(space)) {
-    // In large object space we merely number the objects instead of trying to
-    // determine some sort of address.
-    *new_page = true;
-    large_object_total_ += size;
-    return fullness_[LO_SPACE]++;
-  }
-  *new_page = false;
-  if (fullness_[space] == 0) {
-    *new_page = true;
-  }
-  if (SpaceIsPaged(space)) {
-    // Paged spaces are a little special.  We encode their addresses as if the
-    // pages were all contiguous and each page were filled up in the range
-    // 0 - Page::kObjectAreaSize.  In practice the pages may not be contiguous
-    // and allocation does not start at offset 0 in the page, but this scheme
-    // means the deserializer can get the page number quickly by shifting the
-    // serialized address.
-    CHECK(IsPowerOf2(Page::kPageSize));
-    int used_in_this_page = (fullness_[space] & (Page::kPageSize - 1));
-    CHECK(size <= SpaceAreaSize(space));
-    if (used_in_this_page + size > SpaceAreaSize(space)) {
-      *new_page = true;
-      fullness_[space] = RoundUp(fullness_[space], Page::kPageSize);
-    }
-  }
   int allocation_address = fullness_[space];
   fullness_[space] = allocation_address + size;
   return allocation_address;
 }
 
 
 int Serializer::SpaceAreaSize(int space) {
   if (space == CODE_SPACE) {
     return isolate_->memory_allocator()->CodePageAreaSize();
   } else {
     return Page::kPageSize - Page::kObjectStartOffset;
   }
 }
 
 
+void Serializer::Pad() {
+  // The non-branching GetInt will read up to 3 bytes too far, so we need
+  // to pad the snapshot to make sure we don't read over the end.
+  for (unsigned i = 0; i < sizeof(int32_t) - 1; i++) {
+    sink_->Put(kNop, "Padding");
+  }
+}
+
+
+bool SnapshotByteSource::AtEOF() {
+  if (0u + length_ - position_ > sizeof(uint32_t)) return false;
+  for (int x = position_; x < length_; x++) {
+    if (data_[x] != SerializerDeserializer::nop()) return false;
+  }
+  return true;
+}
+
 } }  // namespace v8::internal