Revert "[serializer] share class positions tuple across contexts"

This reverts commit a1b431d7.

Reason for revert: https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8%20Linux%20-%20nosnap%20-%20debug/22809

Original change's description:
> [serializer] share class positions tuple across contexts
> 
> Class positions is a struct that stores the start and end positions of a class
> literal. It is stored both on class objects, and the template used to
> instantiate class objects.
> 
> The template is reachable from the bytecode array and therefore serialized by
> the startup serializer. Class objects are context-dependent and therefore
> serialized by the partial serializer. Serializing class positions from both
> serializers violates the assumption that we don't serialize any object twice.
> 
> R=​gsathya@chromium.org
> 
> Bug: v8:8761
> Change-Id: If22c554cc7396d63998a015454ce0c67a7d2e05c
> Reviewed-on: https://chromium-review.googlesource.com/c/1444956
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
> Commit-Queue: Yang Guo <yangguo@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59292}

TBR=yangguo@chromium.org,mstarzinger@chromium.org,gsathya@chromium.org

Change-Id: I9f3fd1b29b5991b450223f8b27dfc7aa7e5a3171
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:8761
Reviewed-on: https://chromium-review.googlesource.com/c/1450116Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59300}

src/compiler/types.cc

@@ -342,7 +342,6 @@ Type::bitset BitsetType::Lub(const MapRefLike& map) {
     case ALIASED_ARGUMENTS_ENTRY_TYPE:
     case PROMISE_CAPABILITY_TYPE:
     case PROMISE_REACTION_TYPE:
-    case CLASS_POSITIONS_TYPE:
     case DEBUG_INFO_TYPE:
     case STACK_FRAME_INFO_TYPE:
     case SMALL_ORDERED_HASH_MAP_TYPE:

src/heap/factory.cc

@@ -3806,14 +3806,6 @@ Handle<String> Factory::NumberToString(Smi number, bool check_cache) {
                                 check_cache);
 }
 
-Handle<ClassPositions> Factory::NewClassPositions(int start, int end) {
-  Handle<ClassPositions> class_positions =
-      Handle<ClassPositions>::cast(NewStruct(CLASS_POSITIONS_TYPE, TENURED));
-  class_positions->set_start(start);
-  class_positions->set_end(end);
-  return class_positions;
-}
-
 Handle<DebugInfo> Factory::NewDebugInfo(Handle<SharedFunctionInfo> shared) {
   DCHECK(!shared->HasDebugInfo());
   Heap* heap = isolate()->heap();

src/heap/factory.h

@@ -892,7 +892,6 @@ class V8_EXPORT_PRIVATE Factory {
       MessageTemplate message, Handle<Object> argument, int start_position,
       int end_position, Handle<Script> script, Handle<Object> stack_frames);
 
-  Handle<ClassPositions> NewClassPositions(int start, int end);
   Handle<DebugInfo> NewDebugInfo(Handle<SharedFunctionInfo> shared);
 
   Handle<CoverageInfo> NewCoverageInfo(const ZoneVector<SourceRange>& slots);

src/objects-debug.cc

@@ -1809,12 +1809,6 @@ void Tuple3::Tuple3Verify(Isolate* isolate) {
   VerifyObjectField(isolate, kValue3Offset);
 }
 
-void ClassPositions::ClassPositionsVerify(Isolate* isolate) {
-  CHECK(IsClassPositions());
-  VerifySmiField(kStartOffset);
-  VerifySmiField(kEndOffset);
-}
-
 void ObjectBoilerplateDescription::ObjectBoilerplateDescriptionVerify(
     Isolate* isolate) {
   CHECK(IsObjectBoilerplateDescription());

src/objects-definitions.h

@@ -98,7 +98,6 @@ namespace internal {
   V(ALLOCATION_MEMENTO_TYPE)                                       \
   V(ASM_WASM_DATA_TYPE)                                            \
   V(ASYNC_GENERATOR_REQUEST_TYPE)                                  \
-  V(CLASS_POSITIONS_TYPE)                                          \
   V(DEBUG_INFO_TYPE)                                               \
   V(FUNCTION_TEMPLATE_INFO_TYPE)                                   \
   V(FUNCTION_TEMPLATE_RARE_DATA_TYPE)                              \
@@ -322,7 +321,6 @@ namespace internal {
   V(_, ASM_WASM_DATA_TYPE, AsmWasmData, asm_wasm_data)                        \
   V(_, ASYNC_GENERATOR_REQUEST_TYPE, AsyncGeneratorRequest,                   \
     async_generator_request)                                                  \
-  V(_, CLASS_POSITIONS_TYPE, ClassPositions, class_positions)                 \
   V(_, DEBUG_INFO_TYPE, DebugInfo, debug_info)                                \
   V(_, FUNCTION_TEMPLATE_INFO_TYPE, FunctionTemplateInfo,                     \
     function_template_info)                                                   \

src/objects-printer.cc

@@ -1744,13 +1744,6 @@ void Tuple3::Tuple3Print(std::ostream& os) {  // NOLINT
   os << "\n";
 }
 
-void ClassPositions::ClassPositionsPrint(std::ostream& os) {  // NOLINT
-  PrintHeader(os, "ClassPositions");
-  os << "\n - start position: " << start();
-  os << "\n - end position: " << end();
-  os << "\n";
-}
-
 void ArrayBoilerplateDescription::ArrayBoilerplateDescriptionPrint(
     std::ostream& os) {  // NOLINT
   PrintHeader(os, "ArrayBoilerplateDescription");

src/objects.cc

@@ -3146,10 +3146,6 @@ void Tuple3::BriefPrintDetails(std::ostream& os) {
      << Brief(value3());
 }
 
-void ClassPositions::BriefPrintDetails(std::ostream& os) {
-  os << " " << start() << ", " << end();
-}
-
 void ArrayBoilerplateDescription::BriefPrintDetails(std::ostream& os) {
   os << " " << elements_kind() << ", " << Brief(constant_elements());
 }
@@ -9434,11 +9430,10 @@ Handle<String> JSFunction::ToString(Handle<JSFunction> function) {
   // Check if we should print {function} as a class.
   Handle<Object> maybe_class_positions = JSReceiver::GetDataProperty(
       function, isolate->factory()->class_positions_symbol());
-  if (maybe_class_positions->IsClassPositions()) {
-    ClassPositions class_positions =
-        ClassPositions::cast(*maybe_class_positions);
-    int start_position = class_positions->start();
-    int end_position = class_positions->end();
+  if (maybe_class_positions->IsTuple2()) {
+    Tuple2 class_positions = Tuple2::cast(*maybe_class_positions);
+    int start_position = Smi::ToInt(class_positions->value1());
+    int end_position = Smi::ToInt(class_positions->value2());
     Handle<String> script_source(
         String::cast(Script::cast(shared_info->script())->source()), isolate);
     return isolate->factory()->NewSubString(script_source, start_position,

src/objects/instance-type.h

@@ -171,7 +171,6 @@ enum InstanceType : uint16_t {
   ALLOCATION_MEMENTO_TYPE,
   ASM_WASM_DATA_TYPE,
   ASYNC_GENERATOR_REQUEST_TYPE,
-  CLASS_POSITIONS_TYPE,
   DEBUG_INFO_TYPE,
   FUNCTION_TEMPLATE_INFO_TYPE,
   FUNCTION_TEMPLATE_RARE_DATA_TYPE,

src/objects/literal-objects.cc

@@ -493,8 +493,10 @@ Handle<ClassBoilerplate> ClassBoilerplate::BuildClassBoilerplate(
                             attribs);
   }
   {
-    Handle<ClassPositions> class_positions = factory->NewClassPositions(
-        expr->start_position(), expr->end_position());
+    Handle<Smi> start_position(Smi::FromInt(expr->start_position()), isolate);
+    Handle<Smi> end_position(Smi::FromInt(expr->end_position()), isolate);
+    Handle<Tuple2> class_positions =
+        factory->NewTuple2(start_position, end_position, NOT_TENURED);
     static_desc.AddConstant(isolate, factory->class_positions_symbol(),
                             class_positions, DONT_ENUM);
   }

src/objects/struct-inl.h

@@ -24,15 +24,11 @@ Tuple2::Tuple2(Address ptr) : Struct(ptr) {}
 Tuple3::Tuple3(Address ptr) : Tuple2(ptr) {}
 OBJECT_CONSTRUCTORS_IMPL(AccessorPair, Struct)
 
-OBJECT_CONSTRUCTORS_IMPL(ClassPositions, Struct)
-
 CAST_ACCESSOR(AccessorPair)
 CAST_ACCESSOR(Struct)
 CAST_ACCESSOR(Tuple2)
 CAST_ACCESSOR(Tuple3)
 
-CAST_ACCESSOR(ClassPositions)
-
 void Struct::InitializeBody(int object_size) {
   Object value = GetReadOnlyRoots().undefined_value();
   for (int offset = kHeaderSize; offset < object_size; offset += kPointerSize) {
@@ -47,9 +43,6 @@ ACCESSORS(Tuple3, value3, Object, kValue3Offset)
 ACCESSORS(AccessorPair, getter, Object, kGetterOffset)
 ACCESSORS(AccessorPair, setter, Object, kSetterOffset)
 
-SMI_ACCESSORS(ClassPositions, start, kStartOffset)
-SMI_ACCESSORS(ClassPositions, end, kEndOffset)
-
 Object AccessorPair::get(AccessorComponent component) {
   return component == ACCESSOR_GETTER ? getter() : setter();
 }

src/objects/struct.h

@@ -119,31 +119,6 @@ class AccessorPair : public Struct {
   OBJECT_CONSTRUCTORS(AccessorPair, Struct);
 };
 
-class ClassPositions : public Struct {
- public:
-  DECL_INT_ACCESSORS(start)
-  DECL_INT_ACCESSORS(end)
-
-  DECL_CAST(ClassPositions)
-
-  // Dispatched behavior.
-  DECL_PRINTER(ClassPositions)
-  DECL_VERIFIER(ClassPositions)
-  void BriefPrintDetails(std::ostream& os);
-
-// Layout description.
-#define CLASS_POSITIONS_FIELDS(V) \
-  V(kStartOffset, kTaggedSize)    \
-  V(kEndOffset, kTaggedSize)      \
-  /* Total size. */               \
-  V(kSize, 0)
-
-  DEFINE_FIELD_OFFSET_CONSTANTS(HeapObject::kHeaderSize, CLASS_POSITIONS_FIELDS)
-#undef CLASS_POSITIONS_FIELDS
-
-  OBJECT_CONSTRUCTORS(ClassPositions, Struct);
-};
-
 }  // namespace internal
 }  // namespace v8
 

src/snapshot/partial-serializer.cc

@@ -133,7 +133,7 @@ bool PartialSerializer::ShouldBeInThePartialSnapshotCache(HeapObject o) {
   DCHECK(!o->IsScript());
   return o->IsName() || o->IsSharedFunctionInfo() || o->IsHeapNumber() ||
          o->IsCode() || o->IsScopeInfo() || o->IsAccessorInfo() ||
-         o->IsTemplateInfo() || o->IsClassPositions() ||
+         o->IsTemplateInfo() ||
          o->map() == ReadOnlyRoots(startup_serializer_->isolate())
                          .fixed_cow_array_map();
 }

test/cctest/test-serialize.cc

@@ -3923,27 +3923,5 @@ TEST(CachedCompileFunctionInContext) {
   }
 }
 
-TEST(SnapshotCreatorAnonClassWithKeep) {
-  DisableAlwaysOpt();
-  v8::SnapshotCreator creator;
-  v8::Isolate* isolate = creator.GetIsolate();
-  {
-    v8::HandleScope handle_scope(isolate);
-    {
-      v8::Local<v8::Context> context = v8::Context::New(isolate);
-      v8::Context::Scope context_scope(context);
-      CompileRun(
-          "function Foo() { return class {}; } \n"
-          "class Bar extends Foo() {}\n"
-          "Foo()\n");
-      creator.SetDefaultContext(context);
-    }
-  }
-  v8::StartupData blob =
-      creator.CreateBlob(v8::SnapshotCreator::FunctionCodeHandling::kKeep);
-
-  delete[] blob.data;
-}
-
 }  // namespace internal
 }  // namespace v8