Reland "[heap] Move initial objects into RO_SPACE"

This is a reland of f8ae62fe

Original change's description:
> [heap] Move initial objects into RO_SPACE
> 
> This moves:
> * the main oddballs (null, undefined, hole, true, false) as well as
> their supporting maps (also adds hole as an internalized string to make
> this work).
> * most of the internalized strings
> * the struct maps
> * empty array
> * empty enum cache
> * the contents of the initial string table
> * the weak_cell_cache for any map in RO_SPACE (and eagerly creates the
> value avoid writing to it during run-time)
> 
> The StartupSerializer stats change as follows:
> 
>      RO_SPACE  NEW_SPACE  OLD_SPACE  CODE_SPACE  MAP_SPACE  LO_SPACE
> old         0          0     270264       32608      12144         0
> new     21776          0     253168       32608       8184         0
> Overall memory usage has increased by 720 bytes due to the eager
> initialization of the Map weak cell caches.
> 
> Also extends --serialization-statistics to print out separate instance
> type stats for objects in RO_SPACE as shown here:
> 
>   Read Only Instance types (count and bytes):
>        404      16736  ONE_BYTE_INTERNALIZED_STRING_TYPE
>          2         32  HEAP_NUMBER_TYPE
>          5        240  ODDBALL_TYPE
>         45       3960  MAP_TYPE
>          1         16  BYTE_ARRAY_TYPE
>          1         24  TUPLE2_TYPE
>          1         16  FIXED_ARRAY_TYPE
>          1         32  DESCRIPTOR_ARRAY_TYPE
>         45        720  WEAK_CELL_TYPE
> 
> Bug: v8:7464
> Change-Id: I12981c39c82a7057f68bbbe03f89fb57b0b4c6a6
> Reviewed-on: https://chromium-review.googlesource.com/973722
> Commit-Queue: Dan Elphick <delphick@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Reviewed-by: Yang Guo <yangguo@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52435}

Bug: v8:7464
Change-Id: I50427edfeb53ca80ec4cf46566368fb2213ccf7b
Reviewed-on: https://chromium-review.googlesource.com/999654
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52638}

src/globals.h

@@ -571,10 +571,10 @@ inline std::ostream& operator<<(std::ostream& os, WriteBarrierKind kind) {
 }
 
 // A flag that indicates whether objects should be pretenured when
-// allocated (allocated directly into the old generation) or not
-// (allocated in the young generation if the object size and type
+// allocated (allocated directly into either the old generation or read-only
+// space), or not (allocated in the young generation if the object size and type
 // allows).
-enum PretenureFlag { NOT_TENURED, TENURED };
+enum PretenureFlag { NOT_TENURED, TENURED, TENURED_READ_ONLY };
 
 inline std::ostream& operator<<(std::ostream& os, const PretenureFlag& flag) {
   switch (flag) {
@@ -582,6 +582,8 @@ inline std::ostream& operator<<(std::ostream& os, const PretenureFlag& flag) {
       return os << "NotTenured";
     case TENURED:
       return os << "Tenured";
+    case TENURED_READ_ONLY:
+      return os << "TenuredReadOnly";
   }
   UNREACHABLE();
 }

src/heap/factory.cc

@@ -663,7 +663,11 @@ Handle<SeqOneByteString> Factory::AllocateRawOneByteInternalizedString(
 
   Map* map = *one_byte_internalized_string_map();
   int size = SeqOneByteString::SizeFor(length);
-  HeapObject* result = AllocateRawWithImmortalMap(size, TENURED, map);
+  HeapObject* result = AllocateRawWithImmortalMap(
+      size,
+      isolate()->heap()->CanAllocateInReadOnlySpace() ? TENURED_READ_ONLY
+                                                      : TENURED,
+      map);
   Handle<SeqOneByteString> answer(SeqOneByteString::cast(result), isolate());
   answer->set_length(length);
   answer->set_hash_field(hash_field);
@@ -707,7 +711,11 @@ Handle<String> Factory::AllocateInternalizedStringImpl(T t, int chars,
     size = SeqTwoByteString::SizeFor(chars);
   }
 
-  HeapObject* result = AllocateRawWithImmortalMap(size, TENURED, map);
+  HeapObject* result = AllocateRawWithImmortalMap(
+      size,
+      isolate()->heap()->CanAllocateInReadOnlySpace() ? TENURED_READ_ONLY
+                                                      : TENURED,
+      map);
   Handle<String> answer(String::cast(result), isolate());
   answer->set_length(chars);
   answer->set_hash_field(hash_field);
@@ -1607,13 +1615,14 @@ Handle<PropertyCell> Factory::NewPropertyCell(Handle<Name> name) {
   return cell;
 }
 
-Handle<WeakCell> Factory::NewWeakCell(Handle<HeapObject> value) {
+Handle<WeakCell> Factory::NewWeakCell(Handle<HeapObject> value,
+                                      PretenureFlag pretenure) {
   // It is safe to dereference the value because we are embedding it
   // in cell and not inspecting its fields.
   AllowDeferredHandleDereference convert_to_cell;
   STATIC_ASSERT(WeakCell::kSize <= kMaxRegularHeapObjectSize);
   HeapObject* result =
-      AllocateRawWithImmortalMap(WeakCell::kSize, TENURED, *weak_cell_map());
+      AllocateRawWithImmortalMap(WeakCell::kSize, pretenure, *weak_cell_map());
   Handle<WeakCell> cell(WeakCell::cast(result), isolate());
   cell->initialize(*value);
   return cell;

src/heap/factory.h

@@ -435,7 +435,8 @@ class V8_EXPORT_PRIVATE Factory {
 
   Handle<PropertyCell> NewPropertyCell(Handle<Name> name);
 
-  Handle<WeakCell> NewWeakCell(Handle<HeapObject> value);
+  Handle<WeakCell> NewWeakCell(Handle<HeapObject> value,
+                               PretenureFlag pretenure = TENURED);
 
   Handle<FeedbackCell> NewNoClosuresCell(Handle<HeapObject> value);
   Handle<FeedbackCell> NewOneClosureCell(Handle<HeapObject> value);

src/heap/heap-inl.h

@@ -183,6 +183,7 @@ AllocationResult Heap::AllocateRaw(int size_in_bytes, AllocationSpace space,
     DCHECK(isolate_->serializer_enabled());
 #endif
     DCHECK(!large_object);
+    DCHECK(CanAllocateInReadOnlySpace());
     allocation = read_only_space_->AllocateRaw(size_in_bytes, alignment);
   } else {
     // NEW_SPACE is not allowed here.
@@ -261,6 +262,12 @@ void Heap::OnMoveEvent(HeapObject* target, HeapObject* source,
   }
 }
 
+bool Heap::CanAllocateInReadOnlySpace() {
+  return !deserialization_complete_ &&
+         (isolate()->serializer_enabled() ||
+          !isolate()->initialized_from_snapshot());
+}
+
 void Heap::UpdateAllocationsHash(HeapObject* object) {
   Address object_address = object->address();
   MemoryChunk* memory_chunk = MemoryChunk::FromAddress(object_address);

src/heap/heap.h

@@ -943,6 +943,7 @@ class Heap {
   inline void OnMoveEvent(HeapObject* target, HeapObject* source,
                           int size_in_bytes);
 
+  inline bool CanAllocateInReadOnlySpace();
   bool deserialization_complete() const { return deserialization_complete_; }
 
   bool HasLowAllocationRate();
@@ -1807,7 +1808,16 @@ class Heap {
 
   // Selects the proper allocation space based on the pretenuring decision.
   static AllocationSpace SelectSpace(PretenureFlag pretenure) {
-    return (pretenure == TENURED) ? OLD_SPACE : NEW_SPACE;
+    switch (pretenure) {
+      case TENURED_READ_ONLY:
+        return RO_SPACE;
+      case TENURED:
+        return OLD_SPACE;
+      case NOT_TENURED:
+        return NEW_SPACE;
+      default:
+        UNREACHABLE();
+    }
   }
 
   static size_t DefaultGetExternallyAllocatedMemoryInBytesCallback() {
@@ -2132,9 +2142,11 @@ class Heap {
   V8_WARN_UNUSED_RESULT AllocationResult
   AllocatePartialMap(InstanceType instance_type, int instance_size);
 
+  void FinalizePartialMap(Map* map);
+
   // Allocate empty fixed typed array of given type.
-  V8_WARN_UNUSED_RESULT AllocationResult
-  AllocateEmptyFixedTypedArray(ExternalArrayType array_type);
+  V8_WARN_UNUSED_RESULT AllocationResult AllocateEmptyFixedTypedArray(
+      ExternalArrayType array_type, AllocationSpace space = OLD_SPACE);
 
   void set_force_oom(bool value) { force_oom_ = value; }
 

src/heap/spaces-inl.h

@@ -315,6 +315,7 @@ HeapObject* PagedSpace::TryAllocateLinearlyAligned(
 
 AllocationResult PagedSpace::AllocateRawUnaligned(
     int size_in_bytes, UpdateSkipList update_skip_list) {
+  DCHECK_IMPLIES(identity() == RO_SPACE, heap()->CanAllocateInReadOnlySpace());
   if (!EnsureLinearAllocationArea(size_in_bytes)) {
     return AllocationResult::Retry(identity());
   }
@@ -330,7 +331,8 @@ AllocationResult PagedSpace::AllocateRawUnaligned(
 
 AllocationResult PagedSpace::AllocateRawAligned(int size_in_bytes,
                                                 AllocationAlignment alignment) {
-  DCHECK(identity() == OLD_SPACE);
+  DCHECK(identity() == OLD_SPACE || identity() == RO_SPACE);
+  DCHECK_IMPLIES(identity() == RO_SPACE, heap()->CanAllocateInReadOnlySpace());
   int allocation_size = size_in_bytes;
   HeapObject* object = TryAllocateLinearlyAligned(&allocation_size, alignment);
   if (object == nullptr) {

src/heap/spaces.cc

@@ -1923,7 +1923,8 @@ void PagedSpace::Verify(ObjectVisitor* visitor) {
       // be in map space.
       Map* map = object->map();
       CHECK(map->IsMap());
-      CHECK(heap()->map_space()->Contains(map));
+      CHECK(heap()->map_space()->Contains(map) ||
+            heap()->read_only_space()->Contains(map));
 
       // Perform space-specific object verification.
       VerifyObject(object);
@@ -2374,10 +2375,11 @@ void NewSpace::Verify() {
       HeapObject* object = HeapObject::FromAddress(current);
 
       // The first word should be a map, and we expect all map pointers to
-      // be in map space.
+      // be in map space or read-only space.
       Map* map = object->map();
       CHECK(map->IsMap());
-      CHECK(heap()->map_space()->Contains(map));
+      CHECK(heap()->map_space()->Contains(map) ||
+            heap()->read_only_space()->Contains(map));
 
       // The object should not be code or a map.
       CHECK(!object->IsMap());
@@ -3452,10 +3454,11 @@ void LargeObjectSpace::Verify() {
     CHECK(object->address() == page->area_start());
 
     // The first word should be a map, and we expect all map pointers to be
-    // in map space.
+    // in map space or read-only space.
     Map* map = object->map();
     CHECK(map->IsMap());
-    CHECK(heap()->map_space()->Contains(map));
+    CHECK(heap()->map_space()->Contains(map) ||
+          heap()->read_only_space()->Contains(map));
 
     // We have only code, sequential strings, external strings (sequential
     // strings that have been morphed into external strings), thin strings

src/snapshot/serializer.cc

@@ -25,13 +25,19 @@ Serializer<AllocatorT>::Serializer(Isolate* isolate)
   if (FLAG_serialization_statistics) {
     instance_type_count_ = NewArray<int>(kInstanceTypes);
     instance_type_size_ = NewArray<size_t>(kInstanceTypes);
+    read_only_instance_type_count_ = NewArray<int>(kInstanceTypes);
+    read_only_instance_type_size_ = NewArray<size_t>(kInstanceTypes);
     for (int i = 0; i < kInstanceTypes; i++) {
       instance_type_count_[i] = 0;
       instance_type_size_[i] = 0;
+      read_only_instance_type_count_[i] = 0;
+      read_only_instance_type_size_[i] = 0;
     }
   } else {
     instance_type_count_ = nullptr;
     instance_type_size_ = nullptr;
+    read_only_instance_type_count_ = nullptr;
+    read_only_instance_type_size_ = nullptr;
   }
 #endif  // OBJECT_PRINT
 }
@@ -43,16 +49,24 @@ Serializer<AllocatorT>::~Serializer() {
   if (instance_type_count_ != nullptr) {
     DeleteArray(instance_type_count_);
     DeleteArray(instance_type_size_);
+    DeleteArray(read_only_instance_type_count_);
+    DeleteArray(read_only_instance_type_size_);
   }
 #endif  // OBJECT_PRINT
 }
 
 #ifdef OBJECT_PRINT
 template <class AllocatorT>
-void Serializer<AllocatorT>::CountInstanceType(Map* map, int size) {
+void Serializer<AllocatorT>::CountInstanceType(Map* map, int size,
+                                               AllocationSpace space) {
   int instance_type = map->instance_type();
-  instance_type_count_[instance_type]++;
-  instance_type_size_[instance_type] += size;
+  if (space != RO_SPACE) {
+    instance_type_count_[instance_type]++;
+    instance_type_size_[instance_type] += size;
+  } else {
+    read_only_instance_type_count_[instance_type]++;
+    read_only_instance_type_size_[instance_type] += size;
+  }
 }
 #endif  // OBJECT_PRINT
 
@@ -72,6 +86,21 @@ void Serializer<AllocatorT>::OutputStatistics(const char* name) {
   }
   INSTANCE_TYPE_LIST(PRINT_INSTANCE_TYPE)
 #undef PRINT_INSTANCE_TYPE
+  size_t read_only_total = 0;
+#define UPDATE_TOTAL(Name) \
+  read_only_total += read_only_instance_type_size_[Name];
+  INSTANCE_TYPE_LIST(UPDATE_TOTAL)
+#undef UPDATE_TOTAL
+  if (read_only_total > 0) {
+    PrintF("\n  Read Only Instance types (count and bytes):\n");
+#define PRINT_INSTANCE_TYPE(Name)                                           \
+  if (read_only_instance_type_count_[Name]) {                               \
+    PrintF("%10d %10" PRIuS "  %s\n", read_only_instance_type_count_[Name], \
+           read_only_instance_type_size_[Name], #Name);                     \
+  }
+    INSTANCE_TYPE_LIST(PRINT_INSTANCE_TYPE)
+#undef PRINT_INSTANCE_TYPE
+  }
   PrintF("\n");
 #endif  // OBJECT_PRINT
 }
@@ -362,7 +391,7 @@ void Serializer<AllocatorT>::ObjectSerializer::SerializePrologue(
 
 #ifdef OBJECT_PRINT
   if (FLAG_serialization_statistics) {
-    serializer_->CountInstanceType(map, size);
+    serializer_->CountInstanceType(map, size, space);
   }
 #endif  // OBJECT_PRINT
 

src/snapshot/serializer.h

@@ -226,7 +226,7 @@ class Serializer : public SerializerDeserializer {
   void OutputStatistics(const char* name);
 
 #ifdef OBJECT_PRINT
-  void CountInstanceType(Map* map, int size);
+  void CountInstanceType(Map* map, int size, AllocationSpace space);
 #endif  // OBJECT_PRINT
 
 #ifdef DEBUG
@@ -256,6 +256,8 @@ class Serializer : public SerializerDeserializer {
   static const int kInstanceTypes = LAST_TYPE + 1;
   int* instance_type_count_;
   size_t* instance_type_size_;
+  int* read_only_instance_type_count_;
+  size_t* read_only_instance_type_size_;
 #endif  // OBJECT_PRINT
 
 #ifdef DEBUG