[torque] Replace ReferenceType by generic Torque struct Reference<T>

This CL removes the built-in reference type in favor of a Torque-implemented generic struct, i.e., internal::Reference<T>. It also adds various infrastructure for getting and creating new generic struct instances, as well as matching against them.

R=tebbi@chromium.org

Change-Id: I1e3d6afe355a0603fa9c3ad789c6b8a97d1b3c26
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1718148
Commit-Queue: Georg Schmid <gsps@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62939}

BUILD.gn

@@ -984,6 +984,7 @@ torque_files = [
   "src/builtins/string-slice.tq",
   "src/builtins/string-startswith.tq",
   "src/builtins/string-substring.tq",
+  "src/builtins/torque-internal.tq",
   "src/builtins/typed-array-createtypedarray.tq",
   "src/builtins/typed-array-every.tq",
   "src/builtins/typed-array-filter.tq",

src/builtins/torque-internal.tq

@@ -0,0 +1,12 @@
+// Copyright 2019 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+namespace torque_internal {
+
+  struct Reference<T: type> {
+    const object: HeapObject;
+    const offset: intptr;
+  }
+
+}  // namespace torque_internal

src/codegen/code-stub-assembler.h

@@ -847,6 +847,7 @@ class V8_EXPORT_PRIVATE CodeStubAssembler
 
   // Reference is the CSA-equivalent of a Torque reference value,
   // representing an inner pointer into a HeapObject.
+  // TODO(gsps): Remove in favor of flattened {Load,Store}Reference interface
   struct Reference {
     TNode<HeapObject> object;
     TNode<IntPtrT> offset;

src/torque/ast.h

@@ -46,8 +46,7 @@ namespace torque {
 #define AST_TYPE_EXPRESSION_NODE_KIND_LIST(V) \
   V(BasicTypeExpression)                      \
   V(FunctionTypeExpression)                   \
-  V(UnionTypeExpression)                      \
-  V(ReferenceTypeExpression)
+  V(UnionTypeExpression)
 
 #define AST_STATEMENT_NODE_KIND_LIST(V) \
   V(BlockStatement)                     \
@@ -619,13 +618,6 @@ struct UnionTypeExpression : TypeExpression {
   TypeExpression* b;
 };
 
-struct ReferenceTypeExpression : TypeExpression {
-  DEFINE_AST_NODE_LEAF_BOILERPLATE(ReferenceTypeExpression)
-  ReferenceTypeExpression(SourcePosition pos, TypeExpression* referenced_type)
-      : TypeExpression(kKind, pos), referenced_type(referenced_type) {}
-  TypeExpression* referenced_type;
-};
-
 struct ExpressionStatement : Statement {
   DEFINE_AST_NODE_LEAF_BOILERPLATE(ExpressionStatement)
   ExpressionStatement(SourcePosition pos, Expression* expression)

src/torque/constants.h

@@ -49,6 +49,8 @@ static const char* const FLOAT64_TYPE_STRING = "float64";
 static const char* const CONST_INT31_TYPE_STRING = "constexpr int31";
 static const char* const CONST_INT32_TYPE_STRING = "constexpr int32";
 static const char* const CONST_FLOAT64_TYPE_STRING = "constexpr float64";
+static const char* const TORQUE_INTERNAL_NAMESPACE_STRING = "torque_internal";
+static const char* const REFERENCE_TYPE_STRING = "Reference";
 
 inline bool IsConstexprName(const std::string& name) {
   return name.substr(0, std::strlen(CONSTEXPR_TYPE_PREFIX)) ==

src/torque/csa-generator.cc

@@ -305,8 +305,7 @@ void CSAGenerator::EmitInstruction(const CallCsaMacroInstruction& instruction,
   std::string catch_name =
       PreCallableExceptionPreparation(instruction.catch_block);
   out_ << "    ";
-  bool needs_flattening =
-      return_type->IsStructType() || return_type->IsReferenceType();
+  bool needs_flattening = return_type->IsStructType();
   if (needs_flattening) {
     out_ << "std::tie(";
     PrintCommaSeparatedList(out_, results);
@@ -766,11 +765,6 @@ void CSAGenerator::EmitCSAValue(VisitResult result,
                    out);
     }
     out << "}";
-  } else if (result.type()->IsReferenceType()) {
-    DCHECK_EQ(2, result.stack_range().Size());
-    size_t offset = result.stack_range().begin().offset;
-    out << "CodeStubAssembler::Reference{" << values.Peek(BottomOffset{offset})
-        << ", " << values.Peek(BottomOffset{offset + 1}) << "}";
   } else {
     DCHECK_EQ(1, result.stack_range().Size());
     out << "compiler::TNode<" << result.type()->GetGeneratedTNodeTypeName()

src/torque/declarable.cc

@@ -74,11 +74,7 @@ base::Optional<const Type*> InferTypeArgument(const std::string& to_infer,
       basic->name == to_infer) {
     return argument;
   }
-  auto* ref = ReferenceTypeExpression::DynamicCast(parameter);
-  if (ref && argument->IsReferenceType()) {
-    return InferTypeArgument(to_infer, ref->referenced_type,
-                             ReferenceType::cast(argument)->referenced_type());
-  }
+  // TODO(gsps): Perform type inference for generic types
   return base::nullopt;
 }
 

src/torque/declarable.h

@@ -505,11 +505,6 @@ class Generic : public Declarable {
   SpecializationMap<Callable> specializations_;
 };
 
-struct SpecializationKey {
-  Generic* generic;
-  TypeVector specialized_types;
-};
-
 class GenericStructType : public Declarable {
  public:
   DECLARE_DECLARABLE_BOILERPLATE(GenericStructType, generic_type)

src/torque/declaration-visitor.cc

@@ -205,7 +205,7 @@ void DeclarationVisitor::Visit(SpecializationDeclaration* decl) {
       TypeVisitor::MakeSignature(decl->signature.get());
   for (Generic* generic : generic_list) {
     Signature generic_signature_with_types =
-        MakeSpecializedSignature(SpecializationKey{
+        MakeSpecializedSignature(SpecializationKey<Generic>{
             generic, TypeVisitor::ComputeTypeVector(decl->generic_parameters)});
     if (signature_with_types.HasSameTypesAs(generic_signature_with_types,
                                             ParameterMode::kIgnoreImplicit)) {
@@ -233,7 +233,7 @@ void DeclarationVisitor::Visit(SpecializationDeclaration* decl) {
     stream << "\ncandidates are:";
     for (Generic* generic : generic_list) {
       stream << "\n  "
-             << MakeSpecializedSignature(SpecializationKey{
+             << MakeSpecializedSignature(SpecializationKey<Generic>{
                     generic,
                     TypeVisitor::ComputeTypeVector(decl->generic_parameters)});
     }
@@ -245,8 +245,9 @@ void DeclarationVisitor::Visit(SpecializationDeclaration* decl) {
                                       matching_generic->IdentifierPosition());
   }
 
-  Specialize(SpecializationKey{matching_generic, TypeVisitor::ComputeTypeVector(
-                                                     decl->generic_parameters)},
+  Specialize(SpecializationKey<Generic>{matching_generic,
+                                        TypeVisitor::ComputeTypeVector(
+                                            decl->generic_parameters)},
              matching_generic->declaration()->callable, decl->signature.get(),
              decl->body, decl->pos);
 }
@@ -267,7 +268,8 @@ void DeclarationVisitor::Visit(CppIncludeDeclaration* decl) {
   GlobalContext::AddCppInclude(decl->include_path);
 }
 
-void DeclarationVisitor::DeclareSpecializedTypes(const SpecializationKey& key) {
+void DeclarationVisitor::DeclareSpecializedTypes(
+    const SpecializationKey<Generic>& key) {
   size_t i = 0;
   const std::size_t generic_parameter_count =
       key.generic->declaration()->generic_parameters.size();
@@ -288,7 +290,7 @@ void DeclarationVisitor::DeclareSpecializedTypes(const SpecializationKey& key) {
 }
 
 Signature DeclarationVisitor::MakeSpecializedSignature(
-    const SpecializationKey& key) {
+    const SpecializationKey<Generic>& key) {
   CurrentScope::Scope generic_scope(key.generic->ParentScope());
   // Create a temporary fake-namespace just to temporarily declare the
   // specialization aliases for the generic types to create a signature.
@@ -299,7 +301,8 @@ Signature DeclarationVisitor::MakeSpecializedSignature(
       key.generic->declaration()->callable->signature.get());
 }
 
-Callable* DeclarationVisitor::SpecializeImplicit(const SpecializationKey& key) {
+Callable* DeclarationVisitor::SpecializeImplicit(
+    const SpecializationKey<Generic>& key) {
   if (!key.generic->declaration()->body &&
       IntrinsicDeclaration::DynamicCast(key.generic->declaration()->callable) ==
           nullptr) {
@@ -318,7 +321,7 @@ Callable* DeclarationVisitor::SpecializeImplicit(const SpecializationKey& key) {
 }
 
 Callable* DeclarationVisitor::Specialize(
-    const SpecializationKey& key, CallableNode* declaration,
+    const SpecializationKey<Generic>& key, CallableNode* declaration,
     base::Optional<const CallableNodeSignature*> signature,
     base::Optional<Statement*> body, SourcePosition position) {
   CurrentSourcePosition::Scope pos_scope(position);

src/torque/declaration-visitor.h

@@ -107,15 +107,16 @@ class DeclarationVisitor {
   static void Visit(ExternConstDeclaration* decl);
   static void Visit(CppIncludeDeclaration* decl);
 
-  static Signature MakeSpecializedSignature(const SpecializationKey& key);
-  static Callable* SpecializeImplicit(const SpecializationKey& key);
+  static Signature MakeSpecializedSignature(
+      const SpecializationKey<Generic>& key);
+  static Callable* SpecializeImplicit(const SpecializationKey<Generic>& key);
   static Callable* Specialize(
-      const SpecializationKey& key, CallableNode* declaration,
+      const SpecializationKey<Generic>& key, CallableNode* declaration,
       base::Optional<const CallableNodeSignature*> signature,
       base::Optional<Statement*> body, SourcePosition position);
 
  private:
-  static void DeclareSpecializedTypes(const SpecializationKey& key);
+  static void DeclareSpecializedTypes(const SpecializationKey<Generic>& key);
 };
 
 }  // namespace torque

src/torque/implementation-visitor.cc

@@ -1599,7 +1599,7 @@ void FailCallableLookup(const std::string& reason, const QualifiedName& name,
   ReportError(stream.str());
 }
 
-Callable* GetOrCreateSpecialization(const SpecializationKey& key) {
+Callable* GetOrCreateSpecialization(const SpecializationKey<Generic>& key) {
   if (base::Optional<Callable*> specialization =
           key.generic->specializations().Get(key.specialized_types)) {
     return *specialization;
@@ -1664,7 +1664,8 @@ Callable* ImplementationVisitor::LookupCallable(
       overloads.push_back(generic);
       overload_signatures.push_back(
           DeclarationVisitor::MakeSpecializedSignature(
-              SpecializationKey{generic, *inferred_specialization_types}));
+              SpecializationKey<Generic>{generic,
+                                         *inferred_specialization_types}));
     } else if (Callable* callable = Callable::DynamicCast(declarable)) {
       overloads.push_back(callable);
       overload_signatures.push_back(callable->signature());
@@ -1717,9 +1718,9 @@ Callable* ImplementationVisitor::LookupCallable(
   }
 
   if (Generic* generic = Generic::DynamicCast(overloads[best])) {
-    result = GetOrCreateSpecialization(
-        SpecializationKey{generic, *generic->InferSpecializationTypes(
-                                       specialization_types, parameter_types)});
+    result = GetOrCreateSpecialization(SpecializationKey<Generic>{
+        generic, *generic->InferSpecializationTypes(specialization_types,
+                                                    parameter_types)});
   } else {
     result = Callable::cast(overloads[best]);
   }
@@ -1927,8 +1928,9 @@ LocationReference ImplementationVisitor::GetLocationReference(
   }
   if (expr->generic_arguments.size() != 0) {
     Generic* generic = Declarations::LookupUniqueGeneric(name);
-    Callable* specialization = GetOrCreateSpecialization(SpecializationKey{
-        generic, TypeVisitor::ComputeTypeVector(expr->generic_arguments)});
+    Callable* specialization =
+        GetOrCreateSpecialization(SpecializationKey<Generic>{
+            generic, TypeVisitor::ComputeTypeVector(expr->generic_arguments)});
     if (Builtin* builtin = Builtin::DynamicCast(specialization)) {
       DCHECK(!builtin->IsExternal());
       return LocationReference::Temporary(GetBuiltinCode(builtin),
@@ -1963,8 +1965,8 @@ LocationReference ImplementationVisitor::GetLocationReference(
 LocationReference ImplementationVisitor::GetLocationReference(
     DereferenceExpression* expr) {
   VisitResult ref = Visit(expr->reference);
-  const ReferenceType* type = ReferenceType::DynamicCast(ref.type());
-  if (!type) {
+  if (!StructType::MatchUnaryGeneric(ref.type(),
+                                     TypeOracle::GetReferenceGeneric())) {
     ReportError("Operator * expects a reference but found a value of type ",
                 *ref.type());
   }
@@ -2542,10 +2544,6 @@ StackRange ImplementationVisitor::LowerParameter(
       range.Extend(parameter_range);
     }
     return range;
-  } else if (type->IsReferenceType()) {
-    lowered_parameters->Push(parameter_name + ".object");
-    lowered_parameters->Push(parameter_name + ".offset");
-    return lowered_parameters->TopRange(2);
   } else {
     lowered_parameters->Push(parameter_name);
     return lowered_parameters->TopRange(1);

src/torque/implementation-visitor.h

@@ -12,6 +12,7 @@
 #include "src/torque/cfg.h"
 #include "src/torque/declarations.h"
 #include "src/torque/global-context.h"
+#include "src/torque/type-oracle.h"
 #include "src/torque/types.h"
 #include "src/torque/utils.h"
 
@@ -52,7 +53,8 @@ class LocationReference {
   // pointer.
   static LocationReference HeapReference(VisitResult heap_reference) {
     LocationReference result;
-    DCHECK(heap_reference.type()->IsReferenceType());
+    DCHECK(StructType::MatchUnaryGeneric(heap_reference.type(),
+                                         TypeOracle::GetReferenceGeneric()));
     result.heap_reference_ = std::move(heap_reference);
     return result;
   }
@@ -112,7 +114,8 @@ class LocationReference {
 
   const Type* ReferencedType() const {
     if (IsHeapReference()) {
-      return ReferenceType::cast(heap_reference().type())->referenced_type();
+      return *StructType::MatchUnaryGeneric(heap_reference().type(),
+                                            TypeOracle::GetReferenceGeneric());
     }
     return GetVisitResult().type();
   }

src/torque/instructions.cc

@@ -297,6 +297,7 @@ void CreateFieldReferenceInstruction::TypeInstruction(
   stack->Push(TypeOracle::GetIntPtrType());
 }
 
+// TODO(gsps): Remove in favor of a method on Reference<T>
 void LoadReferenceInstruction::TypeInstruction(Stack<const Type*>* stack,
                                                ControlFlowGraph* cfg) const {
   ExpectType(TypeOracle::GetIntPtrType(), stack->Pop());
@@ -305,6 +306,7 @@ void LoadReferenceInstruction::TypeInstruction(Stack<const Type*>* stack,
   stack->Push(type);
 }
 
+// TODO(gsps): Remove in favor of a method on Reference<T>
 void StoreReferenceInstruction::TypeInstruction(Stack<const Type*>* stack,
                                                 ControlFlowGraph* cfg) const {
   ExpectSubtype(stack->Pop(), type);

src/torque/torque-parser.cc

@@ -879,7 +879,11 @@ base::Optional<ParseResult> MakeFunctionTypeExpression(
 base::Optional<ParseResult> MakeReferenceTypeExpression(
     ParseResultIterator* child_results) {
   auto referenced_type = child_results->NextAs<TypeExpression*>();
-  TypeExpression* result = MakeNode<ReferenceTypeExpression>(referenced_type);
+  std::vector<std::string> namespace_qualification{
+      TORQUE_INTERNAL_NAMESPACE_STRING};
+  std::vector<TypeExpression*> generic_arguments{referenced_type};
+  TypeExpression* result = MakeNode<BasicTypeExpression>(
+      namespace_qualification, REFERENCE_TYPE_STRING, generic_arguments);
   return ParseResult{result};
 }
 

src/torque/type-oracle.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "src/torque/type-oracle.h"
+#include "src/torque/type-visitor.h"
 
 namespace v8 {
 namespace internal {
@@ -23,6 +24,39 @@ void TypeOracle::FinalizeAggregateTypes() {
   }
 }
 
+// static
+const StructType* TypeOracle::GetGenericStructTypeInstance(
+    GenericStructType* generic_struct, TypeVector arg_types) {
+  auto& params = generic_struct->generic_parameters();
+  auto& specializations = generic_struct->specializations();
+
+  if (params.size() != arg_types.size()) {
+    ReportError("Generic struct takes ", params.size(), " parameters, but ",
+                arg_types.size(), " were given");
+  }
+
+  if (auto specialization = specializations.Get(arg_types)) {
+    return *specialization;
+  } else {
+    CurrentScope::Scope generic_scope(generic_struct->ParentScope());
+    // Create a temporary fake-namespace just to temporarily declare the
+    // specialization aliases for the generic types to create a signature.
+    Namespace tmp_namespace("_tmp");
+    CurrentScope::Scope tmp_namespace_scope(&tmp_namespace);
+    auto arg_types_iterator = arg_types.begin();
+    for (auto param : params) {
+      TypeAlias* alias = Declarations::DeclareType(param, *arg_types_iterator);
+      alias->SetIsUserDefined(false);
+      arg_types_iterator++;
+    }
+
+    auto struct_type = TypeVisitor::ComputeType(generic_struct->declaration(),
+                                                {{generic_struct, arg_types}});
+    specializations.Add(arg_types, struct_type);
+    return struct_type;
+  }
+}
+
 }  // namespace torque
 }  // namespace internal
 }  // namespace v8

src/torque/type-oracle.h

@@ -30,8 +30,11 @@ class TypeOracle : public ContextualClass<TypeOracle> {
     return result;
   }
 
-  static StructType* GetStructType(const std::string& name) {
-    StructType* result = new StructType(CurrentNamespace(), name);
+  static StructType* GetStructType(
+      const std::string& basename,
+      StructType::MaybeSpecializationKey specialized_from) {
+    StructType* result =
+        new StructType(CurrentNamespace(), basename, specialized_from);
     Get().aggregate_types_.push_back(std::unique_ptr<StructType>(result));
     return result;
   }
@@ -60,8 +63,17 @@ class TypeOracle : public ContextualClass<TypeOracle> {
     return result;
   }
 
-  static const ReferenceType* GetReferenceType(const Type* referenced_type) {
-    return Get().reference_types_.Add(ReferenceType(referenced_type));
+  static const StructType* GetGenericStructTypeInstance(
+      GenericStructType* generic_struct, TypeVector arg_types);
+
+  static GenericStructType* GetReferenceGeneric() {
+    return Declarations::LookupUniqueGenericStructType(QualifiedName(
+        {TORQUE_INTERNAL_NAMESPACE_STRING}, REFERENCE_TYPE_STRING));
+  }
+
+  static const StructType* GetReferenceType(const Type* referenced_type) {
+    return GetGenericStructTypeInstance(GetReferenceGeneric(),
+                                        {referenced_type});
   }
 
   static const std::vector<const BuiltinPointerType*>&
@@ -245,7 +257,6 @@ class TypeOracle : public ContextualClass<TypeOracle> {
   Deduplicator<BuiltinPointerType> function_pointer_types_;
   std::vector<const BuiltinPointerType*> all_builtin_pointer_types_;
   Deduplicator<UnionType> union_types_;
-  Deduplicator<ReferenceType> reference_types_;
   std::vector<std::unique_ptr<Type>> nominal_types_;
   std::vector<std::unique_ptr<AggregateType>> aggregate_types_;
   std::vector<std::unique_ptr<Type>> top_types_;

src/torque/type-visitor.cc

@@ -110,25 +110,12 @@ void DeclareMethods(AggregateType* container_type,
   }
 }
 
-namespace {
-std::string ComputeStructName(StructDeclaration* decl) {
-  TypeVector args;
-  if (decl->IsGeneric()) {
-    args.resize(decl->generic_parameters.size());
-    std::transform(
-        decl->generic_parameters.begin(), decl->generic_parameters.end(),
-        args.begin(), [](Identifier* parameter) {
-          return Declarations::LookupTypeAlias(QualifiedName(parameter->value))
-              ->type();
-        });
-  }
-  return StructType::ComputeName(decl->name->value, args);
-}
-}  // namespace
-
-const StructType* TypeVisitor::ComputeType(StructDeclaration* decl) {
+const StructType* TypeVisitor::ComputeType(
+    StructDeclaration* decl,
+    StructType::MaybeSpecializationKey specialized_from) {
   CurrentSourcePosition::Scope position_activator(decl->pos);
-  StructType* struct_type = TypeOracle::GetStructType(ComputeStructName(decl));
+  StructType* struct_type =
+      TypeOracle::GetStructType(decl->name->value, specialized_from);
   size_t offset = 0;
   for (auto& field : decl->fields) {
     CurrentSourcePosition::Scope position_activator(
@@ -214,34 +201,8 @@ const Type* TypeVisitor::ComputeType(TypeExpression* type_expression) {
     } else {
       auto* generic_struct =
           Declarations::LookupUniqueGenericStructType(qualified_name);
-      auto& params = generic_struct->generic_parameters();
-      auto& specializations = generic_struct->specializations();
-      if (params.size() != args.size()) {
-        ReportError("Generic struct takes ", params.size(),
-                    " parameters, but only ", args.size(), " were given");
-      }
-
-      std::vector<const Type*> arg_types = ComputeTypeVector(args);
-      if (auto specialization = specializations.Get(arg_types)) {
-        type = *specialization;
-      } else {
-        CurrentScope::Scope generic_scope(generic_struct->ParentScope());
-        // Create a temporary fake-namespace just to temporarily declare the
-        // specialization aliases for the generic types to create a signature.
-        Namespace tmp_namespace("_tmp");
-        CurrentScope::Scope tmp_namespace_scope(&tmp_namespace);
-        auto arg_types_iterator = arg_types.begin();
-        for (auto param : params) {
-          TypeAlias* alias =
-              Declarations::DeclareType(param, *arg_types_iterator);
-          alias->SetIsUserDefined(false);
-          arg_types_iterator++;
-        }
-
-        auto struct_type = ComputeType(generic_struct->declaration());
-        specializations.Add(arg_types, struct_type);
-        type = struct_type;
-      }
+      type = TypeOracle::GetGenericStructTypeInstance(generic_struct,
+                                                      ComputeTypeVector(args));
       pos = generic_struct->declaration()->name->pos;
     }
 
@@ -254,10 +215,6 @@ const Type* TypeVisitor::ComputeType(TypeExpression* type_expression) {
                  UnionTypeExpression::DynamicCast(type_expression)) {
     return TypeOracle::GetUnionType(ComputeType(union_type->a),
                                     ComputeType(union_type->b));
-  } else if (auto* reference_type =
-                 ReferenceTypeExpression::DynamicCast(type_expression)) {
-    return TypeOracle::GetReferenceType(
-        ComputeType(reference_type->referenced_type));
   } else {
     auto* function_type_exp = FunctionTypeExpression::cast(type_expression);
     TypeVector argument_types;

src/torque/type-visitor.h

@@ -31,10 +31,13 @@ class TypeVisitor {
 
  private:
   friend class TypeAlias;
+  friend class TypeOracle;
   static const Type* ComputeType(TypeDeclaration* decl);
   static const AbstractType* ComputeType(AbstractTypeDeclaration* decl);
   static const Type* ComputeType(TypeAliasDeclaration* decl);
-  static const StructType* ComputeType(StructDeclaration* decl);
+  static const StructType* ComputeType(
+      StructDeclaration* decl,
+      StructType::MaybeSpecializationKey specialized_from = base::nullopt);
   static const ClassType* ComputeType(ClassDeclaration* decl);
 };
 

src/torque/types.cc

@@ -276,13 +276,14 @@ std::string StructType::GetGeneratedTypeNameImpl() const {
 }
 
 // static
-std::string StructType::ComputeName(const std::string& basename,
-                                    const std::vector<const Type*>& args) {
-  if (args.size() == 0) return basename;
+std::string StructType::ComputeName(
+    const std::string& basename,
+    StructType::MaybeSpecializationKey specialized_from) {
+  if (!specialized_from) return basename;
   std::stringstream s;
   s << basename << "<";
   bool first = true;
-  for (auto t : args) {
+  for (auto t : specialized_from->specialized_types) {
     if (!first) {
       s << ", ";
     }
@@ -293,6 +294,43 @@ std::string StructType::ComputeName(const std::string& basename,
   return s.str();
 }
 
+std::string StructType::MangledName() const {
+  std::stringstream result;
+  // TODO(gsps): Add 'ST' as a prefix once we can control the generated type
+  // name from Torque code
+  result << basename_;
+  if (specialized_from_) {
+    for (const Type* t : specialized_from_->specialized_types) {
+      std::string arg_type_string = t->MangledName();
+      result << arg_type_string.size() << arg_type_string;
+    }
+  }
+  return result.str();
+}
+
+// static
+base::Optional<const Type*> StructType::MatchUnaryGeneric(
+    const Type* type, GenericStructType* generic) {
+  if (auto* struct_type = StructType::DynamicCast(type)) {
+    return MatchUnaryGeneric(struct_type, generic);
+  }
+  return base::nullopt;
+}
+
+// static
+base::Optional<const Type*> StructType::MatchUnaryGeneric(
+    const StructType* type, GenericStructType* generic) {
+  DCHECK_EQ(generic->generic_parameters().size(), 1);
+  if (!type->specialized_from_) {
+    return base::nullopt;
+  }
+  auto& key = type->specialized_from_.value();
+  if (key.generic != generic || key.specialized_types.size() != 1) {
+    return base::nullopt;
+  }
+  return {key.specialized_types[0]};
+}
+
 std::vector<Method*> AggregateType::Methods(const std::string& name) const {
   if (!is_finalized_) Finalize();
   std::vector<Method*> result;
@@ -560,9 +598,6 @@ void AppendLoweredTypes(const Type* type, std::vector<const Type*>* result) {
     for (const Field& field : s->fields()) {
       AppendLoweredTypes(field.name_and_type.type, result);
     }
-  } else if (type->IsReferenceType()) {
-    result->push_back(TypeOracle::GetHeapObjectType());
-    result->push_back(TypeOracle::GetIntPtrType());
   } else {
     result->push_back(type);
   }

src/torque/types.h

@@ -25,6 +25,7 @@ class AggregateType;
 struct Identifier;
 class Macro;
 class Method;
+class GenericStructType;
 class StructType;
 class ClassType;
 class Value;
@@ -36,7 +37,6 @@ class TypeBase {
     kTopType,
     kAbstractType,
     kBuiltinPointerType,
-    kReferenceType,
     kUnionType,
     kStructType,
     kClassType
@@ -47,7 +47,6 @@ class TypeBase {
   bool IsBuiltinPointerType() const {
     return kind() == Kind::kBuiltinPointerType;
   }
-  bool IsReferenceType() const { return kind() == Kind::kReferenceType; }
   bool IsUnionType() const { return kind() == Kind::kUnionType; }
   bool IsStructType() const { return kind() == Kind::kStructType; }
   bool IsClassType() const { return kind() == Kind::kClassType; }
@@ -143,6 +142,12 @@ struct NameAndType {
 
 std::ostream& operator<<(std::ostream& os, const NameAndType& name_and_type);
 
+template <typename T>
+struct SpecializationKey {
+  T* generic;
+  TypeVector specialized_types;
+};
+
 struct Field {
   // TODO(danno): This likely should be refactored, the handling of the types
   // using the universal grab-bag utility with std::tie, as well as the
@@ -298,43 +303,6 @@ class V8_EXPORT_PRIVATE BuiltinPointerType final : public Type {
   const size_t function_pointer_type_id_;
 };
 
-class ReferenceType final : public Type {
- public:
-  DECLARE_TYPE_BOILERPLATE(ReferenceType)
-  std::string MangledName() const override {
-    return "RT" + referenced_type_->MangledName();
-  }
-  std::string ToExplicitString() const override {
-    std::string s = referenced_type_->ToString();
-    if (s.find(' ') != std::string::npos) {
-      s = "(" + s + ")";
-    }
-    return "&" + s;
-  }
-  std::string GetGeneratedTypeNameImpl() const override {
-    return "CodeStubAssembler::Reference";
-  }
-  std::string GetGeneratedTNodeTypeNameImpl() const override { UNREACHABLE(); }
-
-  const Type* referenced_type() const { return referenced_type_; }
-
-  friend size_t hash_value(const ReferenceType& p) {
-    return base::hash_combine(static_cast<size_t>(Kind::kReferenceType),
-                              p.referenced_type_);
-  }
-  bool operator==(const ReferenceType& other) const {
-    return referenced_type_ == other.referenced_type_;
-  }
-
- private:
-  friend class TypeOracle;
-  explicit ReferenceType(const Type* referenced_type)
-      : Type(Kind::kReferenceType, nullptr),
-        referenced_type_(referenced_type) {}
-
-  const Type* const referenced_type_;
-};
-
 bool operator<(const Type& a, const Type& b);
 struct TypeLess {
   bool operator()(const Type* const a, const Type* const b) const {
@@ -500,32 +468,38 @@ class AggregateType : public Type {
 class StructType final : public AggregateType {
  public:
   DECLARE_TYPE_BOILERPLATE(StructType)
+
+  using MaybeSpecializationKey =
+      base::Optional<SpecializationKey<GenericStructType>>;
+
   std::string ToExplicitString() const override;
   std::string GetGeneratedTypeNameImpl() const override;
-  std::string MangledName() const override {
-    // TODO(gsps): Generate more readable mangled names
-    std::string str(name());
-    std::replace(str.begin(), str.end(), ',', '_');
-    std::replace(str.begin(), str.end(), ' ', '_');
-    std::replace(str.begin(), str.end(), '<', '_');
-    std::replace(str.begin(), str.end(), '>', '_');
-    return str;
-  }
+  std::string MangledName() const override;
 
-  static std::string ComputeName(const std::string& basename,
-                                 const std::vector<const Type*>& args);
+  static base::Optional<const Type*> MatchUnaryGeneric(
+      const Type* type, GenericStructType* generic);
+  static base::Optional<const Type*> MatchUnaryGeneric(
+      const StructType* type, GenericStructType* generic);
 
  private:
   friend class TypeOracle;
-  StructType(Namespace* nspace, const std::string& name)
-      : AggregateType(Kind::kStructType, nullptr, nspace, name) {}
+  StructType(Namespace* nspace, const std::string& basename,
+             MaybeSpecializationKey specialized_from = base::nullopt)
+      : AggregateType(Kind::kStructType, nullptr, nspace,
+                      ComputeName(basename, specialized_from)),
+        basename_(basename),
+        specialized_from_(specialized_from) {}
 
   void Finalize() const override {
     is_finalized_ = true;
     CheckForDuplicateFields();
   }
 
-  const std::string& GetStructName() const { return name(); }
+  static std::string ComputeName(const std::string& basename,
+                                 MaybeSpecializationKey specialized_from);
+
+  std::string basename_;
+  MaybeSpecializationKey specialized_from_;
 };
 
 class TypeAlias;

test/torque/test-torque.tq

@@ -898,7 +898,8 @@ namespace test {
     const ref:&Smi = & array.a;
     * ref = 3 + * ref;
     -- * ref;
-    Swap(& array.b, array.GetA());
+    // TODO(gsps): Remove explicit type arg once inference works
+    Swap<Smi>(& array.b, array.GetA());
     check(array.a == 2);
     check(array.b == 9);
   }
@@ -993,7 +994,7 @@ namespace test {
     const snd: T2;
   }
 
-  macro Swap<T1: type, T2: type>(tuple: TestTuple<T1, T2>):
+  macro TupleSwap<T1: type, T2: type>(tuple: TestTuple<T1, T2>):
       TestTuple<T2, T1> {
     return TestTuple<T2, T1>{fst: tuple.snd, snd: tuple.fst};
   }
@@ -1001,7 +1002,7 @@ namespace test {
   @export
   macro TestGenericStruct2(): TestTuple<Smi, intptr> {
     const intptrAndSmi = TestTuple<intptr, Smi>{fst: 1, snd: 2};
-    const smiAndIntptr = Swap<intptr, Smi>(intptrAndSmi);
+    const smiAndIntptr = TupleSwap<intptr, Smi>(intptrAndSmi);
     check(intptrAndSmi.fst == smiAndIntptr.snd);
     check(intptrAndSmi.snd == smiAndIntptr.fst);
     return smiAndIntptr;

test/unittests/torque/torque-unittest.cc

@@ -20,6 +20,13 @@ constexpr const char* kTestTorquePrelude = R"(
 type void;
 type never;
 
+namespace torque_internal {
+  struct Reference<T: type> {
+    const object: HeapObject;
+    const offset: intptr;
+  }
+}
+
 type Tagged generates 'TNode<Object>' constexpr 'ObjectPtr';
 type Smi extends Tagged generates 'TNode<Smi>' constexpr 'Smi';