Revert "[VM/nnbd] Canonicalize TypeParameter objects in the VM."

This reverts commit 6a98e2719e.

Reason for revert: Unexpected test failures

Original change's description:
> [VM/nnbd] Canonicalize TypeParameter objects in the VM.
> 
> Prior to this CL, type parameters were all assumed canonical, even duplicate ones.
> 
> Per a new convention introduced in this CL, the type parameter array in generic classes and generic functions contains canonical type parameters. As these type parameters get cloned with a different nullability, they are inserted in a new hash table of canonical type parameters.
> 
> This fixes performance issue https://github.com/dart-lang/sdk/issues/41421
> 
> Change-Id: I9086158fa6b6261e9997bb50edec6d7c54abbfa1
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/148223
> Commit-Queue: Régis Crelier <regis@google.com>
> Reviewed-by: Ryan Macnak <rmacnak@google.com>

TBR=rmacnak@google.com,alexmarkov@google.com,asiva@google.com,regis@google.com

Change-Id: I0ca3b6b66e2281c285eba6b564f78c0e6b2f2217
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150265
Reviewed-by: Régis Crelier <regis@google.com>
Commit-Queue: Régis Crelier <regis@google.com>

runtime/vm/class_finalizer.cc

@@ -300,13 +300,13 @@ void ClassFinalizer::VerifyBootstrapClasses() {
 }
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 
-void ClassFinalizer::FinalizeTypeParameters(const Class& cls) {
+void ClassFinalizer::FinalizeTypeParameters(const Class& cls,
+                                            PendingTypes* pending_types) {
   if (FLAG_trace_type_finalization) {
     THR_Print("Finalizing type parameters of '%s'\n",
               String::Handle(cls.Name()).ToCString());
   }
   // The type parameter bounds are not finalized here.
-  const intptr_t offset = cls.NumTypeArguments() - cls.NumTypeParameters();
   const TypeArguments& type_parameters =
       TypeArguments::Handle(cls.type_parameters());
   if (!type_parameters.IsNull()) {
@@ -314,14 +314,9 @@ void ClassFinalizer::FinalizeTypeParameters(const Class& cls) {
     const intptr_t num_types = type_parameters.Length();
     for (intptr_t i = 0; i < num_types; i++) {
       type_parameter ^= type_parameters.TypeAt(i);
-      if (!type_parameter.IsFinalized()) {
-        type_parameter.set_index(type_parameter.index() + offset);
-        type_parameter.SetIsFinalized();
-      }
-      if (!type_parameter.IsCanonical()) {
-        // The declaration of a type parameter is canonical.
-        type_parameter.SetCanonical();
-      }
+      type_parameter ^=
+          FinalizeType(cls, type_parameter, kFinalize, pending_types);
+      type_parameters.SetTypeAt(i, type_parameter);
     }
   }
 }
@@ -430,7 +425,7 @@ intptr_t ClassFinalizer::ExpandAndFinalizeTypeArguments(
   Class& type_class = Class::Handle(zone, type.type_class());
   type_class.EnsureDeclarationLoaded();
   if (!type_class.is_type_finalized()) {
-    FinalizeTypeParameters(type_class);
+    FinalizeTypeParameters(type_class, pending_types);
   }
 
   // The finalized type argument vector needs num_type_arguments types.
@@ -564,7 +559,7 @@ void ClassFinalizer::FinalizeTypeArguments(const Class& cls,
                                            TrailPtr trail) {
   ASSERT(arguments.Length() >= cls.NumTypeArguments());
   if (!cls.is_type_finalized()) {
-    FinalizeTypeParameters(cls);
+    FinalizeTypeParameters(cls, pending_types);
   }
   AbstractType& super_type = AbstractType::Handle(cls.super_type());
   if (!super_type.IsNull()) {
@@ -682,7 +677,8 @@ AbstractTypePtr ClassFinalizer::FinalizeType(const Class& cls,
   ASSERT((pending_types == NULL) || (finalization < kCanonicalize));
   if (type.IsFinalized()) {
     // Ensure type is canonical if canonicalization is requested.
-    if ((finalization >= kCanonicalize) && !type.IsCanonical()) {
+    if ((finalization >= kCanonicalize) && !type.IsCanonical() &&
+        type.IsType()) {
       return type.Canonicalize();
     }
     return type.raw();
@@ -735,7 +731,8 @@ AbstractTypePtr ClassFinalizer::FinalizeType(const Class& cls,
                 type_parameter.index());
     }
 
-    return type_parameter.Canonicalize();
+    // We do not canonicalize type parameters.
+    return type_parameter.raw();
   }
 
   // At this point, we can only have a Type.
@@ -848,12 +845,7 @@ void ClassFinalizer::FinalizeSignature(const Class& cls,
       if (!type_param.IsFinalized()) {
         type_param.set_index(num_parent_type_params + i);
         type_param.SetIsFinalized();
-        // The declaration of a type parameter is canonical.
-        type_param.SetCanonical();
       }
-    }
-    for (intptr_t i = 0; i < num_type_params; i++) {
-      type_param ^= type_params.TypeAt(i);
       type = type_param.bound();
       finalized_type = FinalizeType(cls, type, finalization);
       if (finalized_type.raw() != type.raw()) {
@@ -1594,7 +1586,6 @@ void ClassFinalizer::RemapClassIds(intptr_t* old_to_new_cid) {
 // Usages of canonical hash codes are:
 //
 //   * ObjectStore::canonical_types()
-//   * ObjectStore::canonical_type_parameters()
 //   * ObjectStore::canonical_type_arguments()
 //   * Class::constants()
 //
@@ -1663,33 +1654,6 @@ void ClassFinalizer::RehashTypes() {
   }
   object_store->set_canonical_types(types_table.Release());
 
-  // Rehash the canonical TypeParameters table.
-  Array& typeparams_array = Array::Handle(Z);
-  GrowableObjectArray& typeparams =
-      GrowableObjectArray::Handle(Z, GrowableObjectArray::New());
-  TypeParameter& typeparam = TypeParameter::Handle(Z);
-  {
-    CanonicalTypeParameterSet typeparams_table(
-        Z, object_store->canonical_type_parameters());
-    typeparams_array = HashTables::ToArray(typeparams_table, false);
-    for (intptr_t i = 0; i < typeparams_array.Length(); i++) {
-      typeparam ^= typeparams_array.At(i);
-      typeparams.Add(typeparam);
-    }
-    typeparams_table.Release();
-  }
-
-  dict_size = Utils::RoundUpToPowerOfTwo(typeparams.Length() * 4 / 3);
-  typeparams_array =
-      HashTables::New<CanonicalTypeParameterSet>(dict_size, Heap::kOld);
-  CanonicalTypeParameterSet typeparams_table(Z, typeparams_array.raw());
-  for (intptr_t i = 0; i < typeparams.Length(); i++) {
-    typeparam ^= typeparams.At(i);
-    bool present = typeparams_table.Insert(typeparam);
-    ASSERT(!present);
-  }
-  object_store->set_canonical_type_parameters(typeparams_table.Release());
-
   // Rehash the canonical TypeArguments table.
   Array& typeargs_array = Array::Handle(Z);
   GrowableObjectArray& typeargs =

runtime/vm/class_finalizer.h

@@ -79,7 +79,8 @@ class ClassFinalizer : public AllStatic {
 
  private:
   static void AllocateEnumValues(const Class& enum_cls);
-  static void FinalizeTypeParameters(const Class& cls);
+  static void FinalizeTypeParameters(const Class& cls,
+                                     PendingTypes* pending_types = NULL);
   static intptr_t ExpandAndFinalizeTypeArguments(const Class& cls,
                                                  const AbstractType& type,
                                                  PendingTypes* pending_types);

runtime/vm/clustered_snapshot.cc

@@ -3498,28 +3498,19 @@ class TypeRefDeserializationCluster : public DeserializationCluster {
 class TypeParameterSerializationCluster : public SerializationCluster {
  public:
   TypeParameterSerializationCluster() : SerializationCluster("TypeParameter") {}
+
   ~TypeParameterSerializationCluster() {}
 
   void Trace(Serializer* s, ObjectPtr object) {
     TypeParameterPtr type = TypeParameter::RawCast(object);
-    if (type->ptr()->IsCanonical()) {
-      canonical_objects_.Add(type);
-    } else {
-      objects_.Add(type);
-    }
-
+    objects_.Add(type);
+    ASSERT(!type->ptr()->IsCanonical());
     PushFromTo(type);
   }
 
   void WriteAlloc(Serializer* s) {
     s->WriteCid(kTypeParameterCid);
-    intptr_t count = canonical_objects_.length();
-    s->WriteUnsigned(count);
-    for (intptr_t i = 0; i < count; i++) {
-      TypeParameterPtr type = canonical_objects_[i];
-      s->AssignRef(type);
-    }
-    count = objects_.length();
+    const intptr_t count = objects_.length();
     s->WriteUnsigned(count);
     for (intptr_t i = 0; i < count; i++) {
       TypeParameterPtr type = objects_[i];
@@ -3528,21 +3519,7 @@ class TypeParameterSerializationCluster : public SerializationCluster {
   }
 
   void WriteFill(Serializer* s) {
-    intptr_t count = canonical_objects_.length();
-    for (intptr_t i = 0; i < count; i++) {
-      TypeParameterPtr type = canonical_objects_[i];
-      AutoTraceObject(type);
-      WriteFromTo(type);
-      s->Write<int32_t>(type->ptr()->parameterized_class_id_);
-      s->WriteTokenPosition(type->ptr()->token_pos_);
-      s->Write<int16_t>(type->ptr()->index_);
-      const uint8_t combined =
-          (type->ptr()->flags_ << 4) | type->ptr()->nullability_;
-      ASSERT(type->ptr()->flags_ == (combined >> 4));
-      ASSERT(type->ptr()->nullability_ == (combined & 0xf));
-      s->Write<uint8_t>(combined);
-    }
-    count = objects_.length();
+    const intptr_t count = objects_.length();
     for (intptr_t i = 0; i < count; i++) {
       TypeParameterPtr type = objects_[i];
       AutoTraceObject(type);
@@ -3559,7 +3536,6 @@ class TypeParameterSerializationCluster : public SerializationCluster {
   }
 
  private:
-  GrowableArray<TypeParameterPtr> canonical_objects_;
   GrowableArray<TypeParameterPtr> objects_;
 };
 #endif  // !DART_PRECOMPILED_RUNTIME
@@ -3570,17 +3546,9 @@ class TypeParameterDeserializationCluster : public DeserializationCluster {
   ~TypeParameterDeserializationCluster() {}
 
   void ReadAlloc(Deserializer* d) {
-    canonical_start_index_ = d->next_index();
-    PageSpace* old_space = d->heap()->old_space();
-    intptr_t count = d->ReadUnsigned();
-    for (intptr_t i = 0; i < count; i++) {
-      d->AssignRef(
-          AllocateUninitialized(old_space, TypeParameter::InstanceSize()));
-    }
-    canonical_stop_index_ = d->next_index();
-
     start_index_ = d->next_index();
-    count = d->ReadUnsigned();
+    PageSpace* old_space = d->heap()->old_space();
+    const intptr_t count = d->ReadUnsigned();
     for (intptr_t i = 0; i < count; i++) {
       d->AssignRef(
           AllocateUninitialized(old_space, TypeParameter::InstanceSize()));
@@ -3589,26 +3557,10 @@ class TypeParameterDeserializationCluster : public DeserializationCluster {
   }
 
   void ReadFill(Deserializer* d) {
-    for (intptr_t id = canonical_start_index_; id < canonical_stop_index_;
-         id++) {
-      TypeParameterPtr type = static_cast<TypeParameterPtr>(d->Ref(id));
-      bool is_canonical = true;
-      Deserializer::InitializeHeader(
-          type, kTypeParameterCid, TypeParameter::InstanceSize(), is_canonical);
-      ReadFromTo(type);
-      type->ptr()->parameterized_class_id_ = d->Read<int32_t>();
-      type->ptr()->token_pos_ = d->ReadTokenPosition();
-      type->ptr()->index_ = d->Read<int16_t>();
-      const uint8_t combined = d->Read<uint8_t>();
-      type->ptr()->flags_ = combined >> 4;
-      type->ptr()->nullability_ = combined & 0xf;
-    }
-
     for (intptr_t id = start_index_; id < stop_index_; id++) {
       TypeParameterPtr type = static_cast<TypeParameterPtr>(d->Ref(id));
-      bool is_canonical = false;
-      Deserializer::InitializeHeader(
-          type, kTypeParameterCid, TypeParameter::InstanceSize(), is_canonical);
+      Deserializer::InitializeHeader(type, kTypeParameterCid,
+                                     TypeParameter::InstanceSize());
       ReadFromTo(type);
       type->ptr()->parameterized_class_id_ = d->Read<int32_t>();
       type->ptr()->token_pos_ = d->ReadTokenPosition();
@@ -3624,13 +3576,6 @@ class TypeParameterDeserializationCluster : public DeserializationCluster {
     Code& stub = Code::Handle(zone);
 
     if (Snapshot::IncludesCode(kind)) {
-      for (intptr_t id = canonical_start_index_; id < canonical_stop_index_;
-           id++) {
-        type_param ^= refs.At(id);
-        stub = type_param.type_test_stub();
-        type_param.SetTypeTestingStub(
-            stub);  // Update type_test_stub_entry_point_
-      }
       for (intptr_t id = start_index_; id < stop_index_; id++) {
         type_param ^= refs.At(id);
         stub = type_param.type_test_stub();
@@ -3638,12 +3583,6 @@ class TypeParameterDeserializationCluster : public DeserializationCluster {
             stub);  // Update type_test_stub_entry_point_
       }
     } else {
-      for (intptr_t id = canonical_start_index_; id < canonical_stop_index_;
-           id++) {
-        type_param ^= refs.At(id);
-        stub = TypeTestingStubGenerator::DefaultCodeForType(type_param);
-        type_param.SetTypeTestingStub(stub);
-      }
       for (intptr_t id = start_index_; id < stop_index_; id++) {
         type_param ^= refs.At(id);
         stub = TypeTestingStubGenerator::DefaultCodeForType(type_param);
@@ -3651,10 +3590,6 @@ class TypeParameterDeserializationCluster : public DeserializationCluster {
       }
     }
   }
-
- private:
-  intptr_t canonical_start_index_;
-  intptr_t canonical_stop_index_;
 };
 
 #if !defined(DART_PRECOMPILED_RUNTIME)

runtime/vm/compiler/aot/precompiler.cc

@@ -384,7 +384,6 @@ void Precompiler::DoCompileAll() {
       DropFields();
       TraceTypesFromRetainedClasses();
       DropTypes();
-      DropTypeParameters();
       DropTypeArguments();
 
       // Clear these before dropping classes as they may hold onto otherwise
@@ -1784,45 +1783,6 @@ void Precompiler::DropTypes() {
   object_store->set_canonical_types(types_table.Release());
 }
 
-void Precompiler::DropTypeParameters() {
-  ObjectStore* object_store = I->object_store();
-  GrowableObjectArray& retained_typeparams =
-      GrowableObjectArray::Handle(Z, GrowableObjectArray::New());
-  Array& typeparams_array = Array::Handle(Z);
-  TypeParameter& typeparam = TypeParameter::Handle(Z);
-  // First drop all the type parameters that are not referenced.
-  {
-    CanonicalTypeParameterSet typeparams_table(
-        Z, object_store->canonical_type_parameters());
-    typeparams_array = HashTables::ToArray(typeparams_table, false);
-    for (intptr_t i = 0; i < typeparams_array.Length(); i++) {
-      typeparam ^= typeparams_array.At(i);
-      bool retain = typeparams_to_retain_.HasKey(&typeparam);
-      if (retain) {
-        retained_typeparams.Add(typeparam);
-      } else {
-        typeparam.ClearCanonical();
-        dropped_typeparam_count_++;
-      }
-    }
-    typeparams_table.Release();
-  }
-
-  // Now construct a new type parameter table and save in the object store.
-  const intptr_t dict_size =
-      Utils::RoundUpToPowerOfTwo(retained_typeparams.Length() * 4 / 3);
-  typeparams_array =
-      HashTables::New<CanonicalTypeParameterSet>(dict_size, Heap::kOld);
-  CanonicalTypeParameterSet typeparams_table(Z, typeparams_array.raw());
-  bool present;
-  for (intptr_t i = 0; i < retained_typeparams.Length(); i++) {
-    typeparam ^= retained_typeparams.At(i);
-    present = typeparams_table.Insert(typeparam);
-    ASSERT(!present);
-  }
-  object_store->set_canonical_type_parameters(typeparams_table.Release());
-}
-
 void Precompiler::DropTypeArguments() {
   ObjectStore* object_store = I->object_store();
   Array& typeargs_array = Array::Handle(Z);

runtime/vm/compiler/aot/precompiler.h

@@ -149,26 +149,6 @@ class AbstractTypeKeyValueTrait {
 
 typedef DirectChainedHashMap<AbstractTypeKeyValueTrait> AbstractTypeSet;
 
-class TypeParameterKeyValueTrait {
- public:
-  // Typedefs needed for the DirectChainedHashMap template.
-  typedef const TypeParameter* Key;
-  typedef const TypeParameter* Value;
-  typedef const TypeParameter* Pair;
-
-  static Key KeyOf(Pair kv) { return kv; }
-
-  static Value ValueOf(Pair kv) { return kv; }
-
-  static inline intptr_t Hashcode(Key key) { return key->Hash(); }
-
-  static inline bool IsKeyEqual(Pair pair, Key key) {
-    return pair->raw() == key->raw();
-  }
-};
-
-typedef DirectChainedHashMap<TypeParameterKeyValueTrait> TypeParameterSet;
-
 class TypeArgumentsKeyValueTrait {
  public:
   // Typedefs needed for the DirectChainedHashMap template.
@@ -290,7 +270,6 @@ class Precompiler : public ValueObject {
   void DropFields();
   void TraceTypesFromRetainedClasses();
   void DropTypes();
-  void DropTypeParameters();
   void DropTypeArguments();
   void DropMetadata();
   void DropLibraryEntries();
@@ -330,7 +309,6 @@ class Precompiler : public ValueObject {
   intptr_t dropped_class_count_;
   intptr_t dropped_typearg_count_;
   intptr_t dropped_type_count_;
-  intptr_t dropped_typeparam_count_;
   intptr_t dropped_library_count_;
 
   compiler::ObjectPoolBuilder global_object_pool_builder_;
@@ -344,7 +322,6 @@ class Precompiler : public ValueObject {
   ClassSet classes_to_retain_;
   TypeArgumentsSet typeargs_to_retain_;
   AbstractTypeSet types_to_retain_;
-  TypeParameterSet typeparams_to_retain_;
   InstanceSet consts_to_retain_;
   TableSelectorSet seen_table_selectors_;
   Error& error_;

runtime/vm/compiler/frontend/bytecode_reader.cc

@@ -671,7 +671,6 @@ void BytecodeReaderHelper::ReadTypeParametersDeclaration(
                                    nullability, TokenPosition::kNoSource);
     parameter.set_index(offset + i);
     parameter.SetIsFinalized();
-    parameter.SetCanonical();
     type_parameters.SetTypeAt(i, parameter);
   }
 

runtime/vm/object.cc

@@ -1661,12 +1661,6 @@ ErrorPtr Object::Init(Isolate* isolate,
                                               Heap::kOld);
     object_store->set_canonical_types(array);
 
-    // Initialize hash set for canonical type parameters.
-    const intptr_t kInitialCanonicalTypeParameterSize = 4;
-    array = HashTables::New<CanonicalTypeParameterSet>(
-        kInitialCanonicalTypeParameterSize, Heap::kOld);
-    object_store->set_canonical_type_parameters(array);
-
     // Initialize hash set for canonical_type_arguments_.
     const intptr_t kInitialCanonicalTypeArgumentsSize = 4;
     array = HashTables::New<CanonicalTypeArgumentsSet>(
@@ -4894,8 +4888,9 @@ TypePtr Class::DeclarationType() const {
   }
   // For efficiency, the runtimeType intrinsic returns the type cached by
   // DeclarationType without checking its nullability. Therefore, we
-  // consistently cache the kNonNullable version of the type.
-  // The exception is type Null which is stored as kNullable.
+  // consistently cache the kLegacy version of a type, unless the non-nullable
+  // experiment is enabled, in which case we store the kNonNullable version.
+  // In either cases, the exception is type Null which is stored as kNullable.
   Type& type =
       Type::Handle(Type::New(*this, TypeArguments::Handle(type_parameters()),
                              token_pos(), Nullability::kNonNullable));
@@ -7934,13 +7929,11 @@ FunctionPtr Function::InstantiateSignatureFrom(
           cls = type_param.parameterized_class();
           param_name = type_param.name();
           ASSERT(type_param.IsFinalized());
-          ASSERT(type_param.IsCanonical());
           type_param = TypeParameter::New(
               cls, sig, type_param.index(), param_name, type,
               type_param.IsGenericCovariantImpl(), type_param.nullability(),
               type_param.token_pos());
           type_param.SetIsFinalized();
-          type_param.SetCanonical();
           if (instantiated_type_params.IsNull()) {
             instantiated_type_params = TypeArguments::New(type_params.Length());
             for (intptr_t j = 0; j < i; ++j) {
@@ -19268,6 +19261,7 @@ TypePtr Type::ToNullability(Nullability value, Heap::Space space) const {
     ASSERT(!type.IsCanonical());
     type ^= type.Canonicalize();
   }
+  // TODO(regis): Should we link canonical types of different nullability?
   return type.raw();
 }
 
@@ -20116,11 +20110,7 @@ TypeParameterPtr TypeParameter::ToNullability(Nullability value,
   type_parameter.SetHash(0);
   type_parameter.SetTypeTestingStub(Code::Handle(
       TypeTestingStubGenerator::DefaultCodeForType(type_parameter)));
-  if (IsCanonical()) {
-    // Object::Clone does not clone canonical bit.
-    ASSERT(!type_parameter.IsCanonical());
-    type_parameter ^= type_parameter.Canonicalize();
-  }
+  // TODO(regis): Should we link type parameters of different nullability?
   return type_parameter.raw();
 }
 
@@ -20306,90 +20296,6 @@ AbstractTypePtr TypeParameter::InstantiateFrom(
   // not only happens at run time, but also during type finalization.
 }
 
-AbstractTypePtr TypeParameter::Canonicalize(TrailPtr trail) const {
-  ASSERT(IsFinalized());
-  if (IsCanonical()) {
-    return this->raw();
-  }
-  Thread* thread = Thread::Current();
-  Zone* zone = thread->zone();
-  Isolate* isolate = thread->isolate();
-
-  const Class& cls = Class::Handle(zone, parameterized_class());
-  const Function& function = Function::Handle(
-      zone, cls.IsNull() ? parameterized_function() : Function::null());
-  const TypeArguments& type_params = TypeArguments::Handle(
-      zone, cls.IsNull() ? function.type_parameters() : cls.type_parameters());
-  const intptr_t offset =
-      cls.IsNull() ? function.NumParentTypeParameters()
-                   : (cls.NumTypeArguments() - cls.NumTypeParameters());
-  TypeParameter& type_parameter = TypeParameter::Handle(zone);
-  type_parameter ^= type_params.TypeAt(index() - offset);
-  ASSERT(!type_parameter.IsNull());
-  if (type_parameter.nullability() == nullability()) {
-    ASSERT(this->Equals(type_parameter));
-    ASSERT(type_parameter.IsCanonical());
-    ASSERT(type_parameter.IsOld());
-    return type_parameter.raw();
-  }
-
-  ObjectStore* object_store = isolate->object_store();
-  {
-    SafepointMutexLocker ml(isolate->group()->type_canonicalization_mutex());
-    CanonicalTypeParameterSet table(zone,
-                                    object_store->canonical_type_parameters());
-    type_parameter ^= table.GetOrNull(CanonicalTypeParameterKey(*this));
-    if (type_parameter.IsNull()) {
-      // The type parameter was not found in the table. It is not canonical yet.
-      // Add this type parameter into the canonical list of type parameters.
-      if (this->IsNew()) {
-        type_parameter ^= Object::Clone(*this, Heap::kOld);
-      } else {
-        type_parameter = this->raw();
-      }
-      ASSERT(type_parameter.IsOld());
-      type_parameter.SetCanonical();  // Mark object as being canonical.
-      bool present = table.Insert(type_parameter);
-      ASSERT(!present);
-    }
-    object_store->set_canonical_type_parameters(table.Release());
-  }
-  return type_parameter.raw();
-}
-
-#if defined(DEBUG)
-bool TypeParameter::CheckIsCanonical(Thread* thread) const {
-  Zone* zone = thread->zone();
-  Isolate* isolate = thread->isolate();
-
-  const Class& cls = Class::Handle(zone, parameterized_class());
-  const Function& function = Function::Handle(
-      zone, cls.IsNull() ? parameterized_function() : Function::null());
-  const TypeArguments& type_params = TypeArguments::Handle(
-      zone, cls.IsNull() ? function.type_parameters() : cls.type_parameters());
-  const intptr_t offset =
-      cls.IsNull() ? function.NumParentTypeParameters()
-                   : (cls.NumTypeArguments() - cls.NumTypeParameters());
-  TypeParameter& type_parameter = TypeParameter::Handle(zone);
-  type_parameter ^= type_params.TypeAt(index() - offset);
-  ASSERT(!type_parameter.IsNull());
-  if (type_parameter.nullability() == nullability()) {
-    ASSERT(type_parameter.IsCanonical());
-    return (raw() == type_parameter.raw());
-  }
-
-  ObjectStore* object_store = isolate->object_store();
-  {
-    SafepointMutexLocker ml(isolate->group()->type_canonicalization_mutex());
-    CanonicalTypeParameterSet table(zone,
-                                    object_store->canonical_type_parameters());
-    type_parameter ^= table.GetOrNull(CanonicalTypeParameterKey(*this));
-    object_store->set_canonical_type_parameters(table.Release());
-  }
-  return (raw() == type_parameter.raw());
-}
-#endif  // DEBUG
-
 void TypeParameter::EnumerateURIs(URIs* uris) const {
   Thread* thread = Thread::Current();
   Zone* zone = thread->zone();
@@ -24366,14 +24272,6 @@ void DumpTypeTable(Isolate* isolate) {
   table.Release();
 }
 
-void DumpTypeParameterTable(Isolate* isolate) {
-  OS::PrintErr("canonical type parameters (cloned from declarations):\n");
-  CanonicalTypeParameterSet table(
-      isolate->object_store()->canonical_type_parameters());
-  table.Dump();
-  table.Release();
-}
-
 void DumpTypeArgumentsTable(Isolate* isolate) {
   OS::PrintErr("canonical type arguments:\n");
   CanonicalTypeArgumentsSet table(

runtime/vm/object.h

@@ -1097,6 +1097,9 @@ class Class : public Object {
   intptr_t NumTypeParameters() const {
     return NumTypeParameters(Thread::Current());
   }
+  static intptr_t type_parameters_offset() {
+    return OFFSET_OF(ClassLayout, type_parameters_);
+  }
 
   // Return a TypeParameter if the type_name is a type parameter of this class.
   // Return null otherwise.
@@ -8173,10 +8176,12 @@ class TypeParameter : public AbstractType {
       intptr_t num_free_fun_type_params,
       Heap::Space space,
       TrailPtr trail = nullptr) const;
-  virtual AbstractTypePtr Canonicalize(TrailPtr trail = nullptr) const;
+  virtual AbstractTypePtr Canonicalize(TrailPtr trail = nullptr) const {
+    return raw();
+  }
 #if defined(DEBUG)
   // Check if type parameter is canonical.
-  virtual bool CheckIsCanonical(Thread* thread) const;
+  virtual bool CheckIsCanonical(Thread* thread) const { return true; }
 #endif  // DEBUG
   virtual void EnumerateURIs(URIs* uris) const;
 

runtime/vm/object_store.h

@@ -130,7 +130,6 @@ class ObjectPointerVisitor;
   RW(Class, weak_property_class)                                               \
   RW(Array, symbol_table)                                                      \
   RW(Array, canonical_types)                                                   \
-  RW(Array, canonical_type_parameters)                                         \
   RW(Array, canonical_type_arguments)                                          \
   RW(Library, async_library)                                                   \
   RW(Library, builtin_library)                                                 \

runtime/vm/raw_object_snapshot.cc

@@ -229,7 +229,6 @@ TypeParameterPtr TypeParameter::ReadFrom(SnapshotReader* reader,
   // Allocate type parameter object.
   TypeParameter& type_parameter =
       TypeParameter::ZoneHandle(reader->zone(), TypeParameter::New());
-  bool is_canonical = ObjectLayout::IsCanonical(tags);
   reader->AddBackRef(object_id, &type_parameter, kIsDeserialized);
 
   // Set all non object fields.
@@ -257,10 +256,6 @@ TypeParameterPtr TypeParameter::ReadFrom(SnapshotReader* reader,
   code = TypeTestingStubGenerator::DefaultCodeForType(type_parameter);
   type_parameter.SetTypeTestingStub(code);
 
-  if (is_canonical) {
-    type_parameter ^= type_parameter.Canonicalize();
-  }
-
   return type_parameter.raw();
 }
 

runtime/vm/symbols.cc

@@ -312,25 +312,21 @@ void Symbols::Compact() {
   // 1. Drop the tables and do a full garbage collection.
   object_store->set_symbol_table(Object::empty_array());
   object_store->set_canonical_types(Object::empty_array());
-  object_store->set_canonical_type_parameters(Object::empty_array());
   object_store->set_canonical_type_arguments(Object::empty_array());
   thread->heap()->CollectAllGarbage();
 
   // 2. Walk the heap to find surviving canonical objects.
   GrowableArray<String*> symbols;
   GrowableArray<class Type*> types;
-  GrowableArray<class TypeParameter*> type_params;
   GrowableArray<class TypeArguments*> type_args;
   class SymbolCollector : public ObjectVisitor {
    public:
     SymbolCollector(Thread* thread,
                     GrowableArray<String*>* symbols,
                     GrowableArray<class Type*>* types,
-                    GrowableArray<class TypeParameter*>* type_params,
                     GrowableArray<class TypeArguments*>* type_args)
         : symbols_(symbols),
           types_(types),
-          type_params_(type_params),
           type_args_(type_args),
           zone_(thread->zone()) {}
 
@@ -340,9 +336,6 @@ void Symbols::Compact() {
           symbols_->Add(&String::Handle(zone_, String::RawCast(obj)));
         } else if (obj->IsType()) {
           types_->Add(&Type::Handle(zone_, Type::RawCast(obj)));
-        } else if (obj->IsTypeParameter()) {
-          type_params_->Add(
-              &TypeParameter::Handle(zone_, TypeParameter::RawCast(obj)));
         } else if (obj->IsTypeArguments()) {
           type_args_->Add(
               &TypeArguments::Handle(zone_, TypeArguments::RawCast(obj)));
@@ -353,14 +346,13 @@ void Symbols::Compact() {
    private:
     GrowableArray<String*>* symbols_;
     GrowableArray<class Type*>* types_;
-    GrowableArray<class TypeParameter*>* type_params_;
     GrowableArray<class TypeArguments*>* type_args_;
     Zone* zone_;
   };
 
   {
     HeapIterationScope iteration(thread);
-    SymbolCollector visitor(thread, &symbols, &types, &type_params, &type_args);
+    SymbolCollector visitor(thread, &symbols, &types, &type_args);
     iteration.IterateObjects(&visitor);
   }
 
@@ -395,21 +387,6 @@ void Symbols::Compact() {
     object_store->set_canonical_types(table.Release());
   }
 
-  {
-    Array& array =
-        Array::Handle(zone, HashTables::New<CanonicalTypeParameterSet>(
-                                type_params.length() * 4 / 3, Heap::kOld));
-    CanonicalTypeParameterSet table(zone, array.raw());
-    for (intptr_t i = 0; i < type_params.length(); i++) {
-      class TypeParameter& type_param = *type_params[i];
-      ASSERT(type_param.IsTypeParameter());
-      ASSERT(type_param.IsCanonical());
-      bool present = table.Insert(type_param);
-      ASSERT(!present);
-    }
-    object_store->set_canonical_type_parameters(table.Release());
-  }
-
   {
     Array& array =
         Array::Handle(zone, HashTables::New<CanonicalTypeArgumentsSet>(

runtime/vm/type_table.h

@@ -50,46 +50,6 @@ class CanonicalTypeTraits {
 };
 typedef UnorderedHashSet<CanonicalTypeTraits> CanonicalTypeSet;
 
-class CanonicalTypeParameterKey {
- public:
-  explicit CanonicalTypeParameterKey(const TypeParameter& key) : key_(key) {}
-  bool Matches(const TypeParameter& arg) const { return key_.Equals(arg); }
-  uword Hash() const { return key_.Hash(); }
-  const TypeParameter& key_;
-
- private:
-  DISALLOW_ALLOCATION();
-};
-
-// Traits for looking up Canonical TypeParameter based on its hash.
-class CanonicalTypeParameterTraits {
- public:
-  static const char* Name() { return "CanonicalTypeParameterTraits"; }
-  static bool ReportStats() { return false; }
-
-  // Called when growing the table.
-  static bool IsMatch(const Object& a, const Object& b) {
-    ASSERT(a.IsTypeParameter() && b.IsTypeParameter());
-    const TypeParameter& arg1 = TypeParameter::Cast(a);
-    const TypeParameter& arg2 = TypeParameter::Cast(b);
-    return arg1.Equals(arg2) && (arg1.Hash() == arg2.Hash());
-  }
-  static bool IsMatch(const CanonicalTypeParameterKey& a, const Object& b) {
-    ASSERT(b.IsTypeParameter());
-    return a.Matches(TypeParameter::Cast(b));
-  }
-  static uword Hash(const Object& key) {
-    ASSERT(key.IsTypeParameter());
-    return TypeParameter::Cast(key).Hash();
-  }
-  static uword Hash(const CanonicalTypeParameterKey& key) { return key.Hash(); }
-  static ObjectPtr NewKey(const CanonicalTypeParameterKey& obj) {
-    return obj.key_.raw();
-  }
-};
-typedef UnorderedHashSet<CanonicalTypeParameterTraits>
-    CanonicalTypeParameterSet;
-
 class CanonicalTypeArgumentsKey {
  public:
   explicit CanonicalTypeArgumentsKey(const TypeArguments& key) : key_(key) {}