[dart2wasm] Special runtime type classes for special interface types

Adds special representations of runtime types for the interface types
`Object`, `Function` and `Record`. With this change, all types with
non-interface subtypes have special representations, which avoids some
special cases down the line.

Change-Id: I61b4da20fa1cc62d42e1770278a3272028c9e2a0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/318681
Reviewed-by: Joshua Litt <joshualitt@google.com>

pkg/dart2wasm/lib/class_info.dart

@@ -506,6 +506,11 @@ class ClassInfoCollector {
   void collect() {
     _initializeTop();
 
+    // Initialize the record base class early to give enough space for special
+    // values in the type category table before the first masquerade class
+    // (which is `Type`).
+    _initialize(translator.coreTypes.recordClass);
+
     // Subclasses of the `_Closure` class are generated on the fly as fields
     // with function types are encountered. Therefore, `_Closure` class must
     // be early in the initialization order.
@@ -526,11 +531,6 @@ class ClassInfoCollector {
       _initialize(cls);
     }
 
-    // Initialize the record base class if we have record classes.
-    if (translator.recordClasses.isNotEmpty) {
-      _initialize(translator.coreTypes.recordClass);
-    }
-
     for (Library library in translator.component.libraries) {
       for (Class cls in library.classes) {
         if (cls.superclass == translator.coreTypes.recordClass) {

pkg/dart2wasm/lib/constants.dart

@@ -801,7 +801,7 @@ class ConstantCreator extends ConstantVisitor<ConstantInfo?> {
 
     ClassInfo info = translator.classInfo[types.classForType(type)]!;
     translator.functions.allocateClass(info.classId);
-    if (type is InterfaceType) {
+    if (type is InterfaceType && !types.isSpecializedClass(type.classNode)) {
       return _makeInterfaceType(constant, type, info);
     } else if (type is FutureOrType) {
       return _makeFutureOrType(constant, type, info);
@@ -861,7 +861,8 @@ class ConstantCreator extends ConstantVisitor<ConstantInfo?> {
       assert(type is VoidType ||
           type is NeverType ||
           type is NullType ||
-          type is DynamicType);
+          type is DynamicType ||
+          type is InterfaceType && types.isSpecializedClass(type.classNode));
       return createConstant(constant, info.nonNullableType, (function, b) {
         b.i32_const(info.classId);
         b.i32_const(initialIdentityHash);

pkg/dart2wasm/lib/intrinsics.dart

@@ -1149,6 +1149,7 @@ class Intrinsifier {
       w.Label notMasqueraded = b.block();
       w.Label recordType = b.block();
       w.Label functionType = b.block();
+      w.Label objectType = b.block();
       w.Label abstractClass = b.block();
 
       // Look up the type category by class ID and switch on it.
@@ -1161,6 +1162,7 @@ class Intrinsifier {
       b.local_tee(resultClassId);
       b.br_table([
         abstractClass,
+        objectType,
         functionType,
         recordType,
         if (masqueraded) notMasqueraded
@@ -1170,6 +1172,16 @@ class Intrinsifier {
       // We should never see class IDs for abstract types.
       b.unreachable();
 
+      b.end(); // objectType
+      ClassInfo objectTypeInfo =
+          translator.classInfo[translator.objectTypeClass]!;
+      b.i32_const(objectTypeInfo.classId);
+      b.i32_const(initialIdentityHash);
+      // Runtime types are never nullable.
+      b.i32_const(0);
+      b.struct_new(objectTypeInfo.struct);
+      b.return_();
+
       b.end(); // functionType
       w.StructType closureBase = translator.closureLayouter.closureBaseStruct;
       b.local_get(object);

pkg/dart2wasm/lib/kernel_nodes.dart

@@ -68,6 +68,9 @@ mixin KernelNodes {
   late final Class typeClass = index.getClass("dart:core", "_Type");
   late final Class dynamicTypeClass =
       index.getClass("dart:core", "_DynamicType");
+  late final Class objectTypeClass = index.getClass("dart:core", "_ObjectType");
+  late final Class abstractFunctionTypeClass =
+      index.getClass("dart:core", "_AbstractFunctionType");
   late final Class functionTypeClass =
       index.getClass("dart:core", "_FunctionType");
   late final Class functionTypeParameterTypeClass =
@@ -86,6 +89,8 @@ mixin KernelNodes {
   late final Class stackTraceClass = index.getClass("dart:core", "StackTrace");
   late final Class typeUniverseClass =
       index.getClass("dart:core", "_TypeUniverse");
+  late final Class abstractRecordTypeClass =
+      index.getClass("dart:core", "_AbstractRecordType");
   late final Class recordTypeClass = index.getClass("dart:core", "_RecordType");
 
   // dart:core sync* support classes

pkg/dart2wasm/lib/types.dart

@@ -18,10 +18,11 @@ import 'package:wasm_builder/wasm_builder.dart' as w;
 /// the class ID of the masquerade.
 class TypeCategory {
   static const abstractClass = 0;
-  static const function = 1;
-  static const record = 2;
-  static const notMasqueraded = 3;
-  static const minMasqueradeClassId = 4;
+  static const object = 1;
+  static const function = 2;
+  static const record = 3;
+  static const notMasqueraded = 4;
+  static const minMasqueradeClassId = 5;
   static const maxMasqueradeClassId = 63; // Leaves 2 unused bits for future use
 }
 
@@ -279,6 +280,8 @@ class Types {
       int category;
       if (cls == null || cls.isAbstract) {
         category = TypeCategory.abstractClass;
+      } else if (cls == coreTypes.objectClass) {
+        category = TypeCategory.object;
       } else if (cls == translator.closureClass) {
         category = TypeCategory.function;
       } else if (recordClasses.contains(cls)) {
@@ -355,6 +358,15 @@ class Types {
     } else if (type is FutureOrType) {
       return translator.futureOrTypeClass;
     } else if (type is InterfaceType) {
+      if (type.classNode == coreTypes.objectClass) {
+        return translator.objectTypeClass;
+      }
+      if (type.classNode == coreTypes.functionClass) {
+        return translator.abstractFunctionTypeClass;
+      }
+      if (type.classNode == coreTypes.recordClass) {
+        return translator.abstractRecordTypeClass;
+      }
       return translator.interfaceTypeClass;
     } else if (type is FunctionType) {
       return translator.functionTypeClass;
@@ -372,6 +384,12 @@ class Types {
     throw "Unexpected DartType: $type";
   }
 
+  bool isSpecializedClass(Class cls) {
+    return cls == coreTypes.objectClass ||
+        cls == coreTypes.functionClass ||
+        cls == coreTypes.recordClass;
+  }
+
   /// Allocates a `List<_Type>` from [types] and pushes it to the stack.
   void _makeTypeList(CodeGenerator codeGen, Iterable<DartType> types) {
     if (types.every(_isTypeConstant)) {

sdk/lib/_internal/wasm/lib/class_id.dart

@@ -58,12 +58,18 @@ class ClassID {
   external static int get cidFutureOrType;
   @pragma("wasm:class-id", "dart.core#_InterfaceType")
   external static int get cidInterfaceType;
+  @pragma("wasm:class-id", "dart.core#_ObjectType")
+  external static int get cidObjectType;
+  @pragma("wasm:class-id", "dart.core#_AbstractFunctionType")
+  external static int get cidAbstractFunctionType;
   @pragma("wasm:class-id", "dart.core#_FunctionType")
   external static int get cidFunctionType;
   @pragma("wasm:class-id", "dart.core#_FunctionTypeParameterType")
   external static int get cidFunctionTypeParameterType;
   @pragma("wasm:class-id", "dart.core#_InterfaceTypeParameterType")
   external static int get cidInterfaceTypeParameterType;
+  @pragma("wasm:class-id", "dart.core#_AbstractRecordType")
+  external static int get cidAbstractRecordType;
   @pragma("wasm:class-id", "dart.core#_RecordType")
   external static int get cidRecordType;
 

sdk/lib/_internal/wasm/lib/type.dart

@@ -13,7 +13,6 @@ part of 'core_patch.dart';
 // file:
 //   * [_Type.asNonNullable]
 //   * [_FutureOrType.asFuture].
-// TODO(joshualitt): Make `Function` a canonical type.
 abstract class _Type implements Type {
   final bool isDeclaredNullable;
 
@@ -30,7 +29,10 @@ abstract class _Type implements Type {
       _testID(ClassID.cidInterfaceTypeParameterType);
   bool get isFunctionTypeParameterType =>
       _testID(ClassID.cidFunctionTypeParameterType);
+  bool get isObject => _testID(ClassID.cidObjectType);
+  bool get isAbstractFunction => _testID(ClassID.cidAbstractFunctionType);
   bool get isFunction => _testID(ClassID.cidFunctionType);
+  bool get isAbstractRecord => _testID(ClassID.cidAbstractRecordType);
   bool get isRecord => _testID(ClassID.cidRecordType);
 
   T as<T>() => unsafeCast<T>(this);
@@ -308,6 +310,57 @@ class _NamedParameter {
   }
 }
 
+class _ObjectType extends _Type {
+  @pragma("wasm:entry-point")
+  const _ObjectType(super.isDeclaredNullable);
+
+  @override
+  _Type get _asNonNullable => _ObjectType(false);
+
+  @override
+  _Type get _asNullable => _ObjectType(true);
+
+  @override
+  bool operator ==(Object o) {
+    if (!(super == o)) return false;
+    _ObjectType other = unsafeCast<_ObjectType>(o);
+    return isDeclaredNullable == other.isDeclaredNullable;
+  }
+
+  @override
+  int get hashCode {
+    int hash = super.hashCode;
+    return mix64(hash ^ (isDeclaredNullable ? 1 : 0));
+  }
+
+  @override
+  String toString() {
+    StringBuffer s = StringBuffer();
+    s.write("Object");
+    if (isDeclaredNullable) s.write("?");
+    return s.toString();
+  }
+}
+
+class _AbstractFunctionType extends _Type {
+  @pragma("wasm:entry-point")
+  const _AbstractFunctionType(super.isDeclaredNullable);
+
+  @override
+  _Type get _asNonNullable => _AbstractFunctionType(false);
+
+  @override
+  _Type get _asNullable => _AbstractFunctionType(true);
+
+  @override
+  String toString() {
+    StringBuffer s = StringBuffer();
+    s.write("Function");
+    if (isDeclaredNullable) s.write("?");
+    return s.toString();
+  }
+}
+
 class _FunctionType extends _Type {
   // TODO(askesc): The [typeParameterOffset] is 0 except in the rare case where
   // the function type contains a nested generic function type that contains a
@@ -438,6 +491,25 @@ class _FunctionType extends _Type {
   }
 }
 
+class _AbstractRecordType extends _Type {
+  @pragma("wasm:entry-point")
+  const _AbstractRecordType(super.isDeclaredNullable);
+
+  @override
+  _Type get _asNonNullable => _AbstractRecordType(false);
+
+  @override
+  _Type get _asNullable => _AbstractRecordType(true);
+
+  @override
+  String toString() {
+    StringBuffer s = StringBuffer();
+    s.write("Record");
+    if (isDeclaredNullable) s.write("?");
+    return s.toString();
+  }
+}
+
 class _RecordType extends _Type {
   final List<String> names;
   final List<_Type> fieldTypes;
@@ -575,30 +647,20 @@ class _TypeUniverse {
     return _TypeUniverse._(_getTypeRulesSupers(), _getTypeRulesSubstitutions());
   }
 
-  static bool isSpecificInterfaceType(_Type t, int classId) {
-    if (!t.isInterface) return false;
-    _InterfaceType type = t.as<_InterfaceType>();
-    return type.classId == classId;
+  static bool isTopType(_Type type) {
+    return type.isObject && type.isDeclaredNullable ||
+        type.isDynamic ||
+        type.isVoid;
   }
 
-  static bool isObjectQuestionType(_Type t) =>
-      isObjectType(t) && t.isDeclaredNullable;
-
-  static bool isObjectType(_Type t) =>
-      isSpecificInterfaceType(t, ClassID.cidObject);
-
-  static bool isTopType(_Type type) {
-    return isObjectQuestionType(type) || type.isDynamic || type.isVoid;
+  static bool isObjectOrTopType(_Type type) {
+    return type.isObject || type.isDynamic || type.isVoid;
   }
 
   static bool isBottomType(_Type type) {
     return type.isNever;
   }
 
-  static bool isFunctionType(_Type t) =>
-      isSpecificInterfaceType(t, ClassID.cidFunction) ||
-      isSpecificInterfaceType(t, ClassID.cid_Closure);
-
   static _Type substituteInterfaceTypeParameter(
       _InterfaceTypeParameterType typeParameter, List<_Type> substitutions) {
     // If the type parameter is non-nullable, or the substitution type is
@@ -643,7 +705,11 @@ class _TypeUniverse {
   /// substituted.
   static _Type substituteTypeArgument(
       _Type type, List<_Type> substitutions, _FunctionType? rootFunction) {
-    if (type.isNever || type.isDynamic || type.isVoid || type.isNull) {
+    if (type.isNever ||
+        type.isDynamic ||
+        type.isVoid ||
+        type.isNull ||
+        type.isObject) {
       return type;
     } else if (type.isFutureOr) {
       return createNormalizedFutureOrType(
@@ -725,7 +791,7 @@ class _TypeUniverse {
 
   static _Type createNormalizedFutureOrType(
       bool isDeclaredNullable, _Type typeArgument) {
-    if (isTopType(typeArgument) || isObjectType(typeArgument)) {
+    if (isObjectOrTopType(typeArgument)) {
       return typeArgument;
     } else if (typeArgument.isNever) {
       return _InterfaceType(
@@ -940,7 +1006,7 @@ class _TypeUniverse {
     }
 
     // Right Object:
-    if (isObjectType(t)) {
+    if (t.isObject) {
       if (s.isFutureOr) {
         return isSubtype(s.as<_FutureOrType>().typeArgument, sEnv, t, tEnv);
       }
@@ -984,7 +1050,7 @@ class _TypeUniverse {
     // Left Promoted Variable does not apply at runtime.
 
     // Function Type / Function:
-    if (s.isFunction && isFunctionType(t)) {
+    if (s.isFunction && t.isAbstractFunction) {
       return true;
     }
 
@@ -1000,9 +1066,8 @@ class _TypeUniverse {
     }
 
     // Records are subtypes of the `Record` type:
-    if (s.isRecord && t.isInterface) {
-      final tInterfaceType = t.as<_InterfaceType>();
-      return tInterfaceType.classId == ClassID.cidRecord;
+    if (s.isRecord && t.isAbstractRecord) {
+      return true;
     }
 
     // Interface Compositionality + Super-Interface: