[ubsan] Temporarily duplicate Struct and Tuple2

in preparation for incrementally transitioning their subclasses.

Bug: v8:3770
Change-Id: I5ed6adb1969bc1ec7125571fea443834ca255c22
Reviewed-on: https://chromium-review.googlesource.com/c/1377453
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58252}

src/objects-debug.cc

@@ -1762,6 +1762,10 @@ void Tuple2::Tuple2Verify(Isolate* isolate) {
   }
 }
 
+void Tuple2Ptr::Tuple2Verify(Isolate* isolate) {
+  reinterpret_cast<Tuple2*>(ptr())->Tuple2Verify(isolate);
+}
+
 void Tuple3::Tuple3Verify(Isolate* isolate) {
   CHECK(IsTuple3());
   VerifyObjectField(isolate, kValue1Offset);

src/objects-printer.cc

@@ -1725,6 +1725,10 @@ void Tuple2::Tuple2Print(std::ostream& os) {  // NOLINT
   os << "\n";
 }
 
+void Tuple2Ptr::Tuple2Print(std::ostream& os) {  // NOLINT
+  reinterpret_cast<Tuple2*>(ptr())->Tuple2Print(os);
+}
+
 void Tuple3::Tuple3Print(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "Tuple3");
   os << "\n - value1: " << Brief(value1());

src/objects.cc

@@ -3762,10 +3762,16 @@ void HeapObject::HeapObjectShortPrint(std::ostream& os) {  // NOLINT
 
 void Struct::BriefPrintDetails(std::ostream& os) {}
 
+void StructPtr::BriefPrintDetails(std::ostream& os) {}
+
 void Tuple2::BriefPrintDetails(std::ostream& os) {
   os << " " << Brief(value1()) << ", " << Brief(value2());
 }
 
+void Tuple2Ptr::BriefPrintDetails(std::ostream& os) {
+  os << " " << Brief(value1()) << ", " << Brief(value2());
+}
+
 void Tuple3::BriefPrintDetails(std::ostream& os) {
   os << " " << Brief(value1()) << ", " << Brief(value2()) << ", "
      << Brief(value3());

src/objects/struct-inl.h

@@ -15,9 +15,21 @@
 namespace v8 {
 namespace internal {
 
+bool StructPtr::IsStructPtr() const {
+  return reinterpret_cast<Struct*>(ptr())->IsStruct();
+}
+bool Tuple2Ptr::IsTuple2Ptr() const {
+  return reinterpret_cast<Tuple2*>(ptr())->IsTuple2();
+}
+
+OBJECT_CONSTRUCTORS_IMPL(StructPtr, HeapObjectPtr)
+OBJECT_CONSTRUCTORS_IMPL(Tuple2Ptr, StructPtr)
+
 CAST_ACCESSOR(AccessorPair)
 CAST_ACCESSOR(Struct)
+CAST_ACCESSOR2(StructPtr)
 CAST_ACCESSOR(Tuple2)
+CAST_ACCESSOR2(Tuple2Ptr)
 CAST_ACCESSOR(Tuple3)
 
 void Struct::InitializeBody(int object_size) {
@@ -27,8 +39,17 @@ void Struct::InitializeBody(int object_size) {
   }
 }
 
+void StructPtr::InitializeBody(int object_size) {
+  Object* value = GetReadOnlyRoots().undefined_value();
+  for (int offset = kHeaderSize; offset < object_size; offset += kPointerSize) {
+    WRITE_FIELD(this, offset, value);
+  }
+}
+
 ACCESSORS(Tuple2, value1, Object, kValue1Offset)
+ACCESSORS(Tuple2Ptr, value1, Object, kValue1Offset)
 ACCESSORS(Tuple2, value2, Object, kValue2Offset)
+ACCESSORS(Tuple2Ptr, value2, Object, kValue2Offset)
 ACCESSORS(Tuple3, value3, Object, kValue3Offset)
 
 ACCESSORS(AccessorPair, getter, Object, kGetterOffset)

src/objects/struct.h

@@ -24,6 +24,20 @@ class Struct : public HeapObject {
   void BriefPrintDetails(std::ostream& os);
 };
 
+// Replacement for the above, temporarily separate for incremental transition
+// of subclasses.
+class StructPtr : public HeapObjectPtr {
+ public:
+  inline void InitializeBody(int object_size);
+  DECL_CAST2(StructPtr)
+  void BriefPrintDetails(std::ostream& os);
+
+  // TODO(3770): Temporary.
+  inline bool IsStructPtr() const;
+
+  OBJECT_CONSTRUCTORS(StructPtr, HeapObjectPtr);
+};
+
 class Tuple2 : public Struct {
  public:
   DECL_ACCESSORS(value1, Object)
@@ -44,6 +58,30 @@ class Tuple2 : public Struct {
   DISALLOW_IMPLICIT_CONSTRUCTORS(Tuple2);
 };
 
+// Replacement for the above, temporarily separate for incremental transition
+// of subclasses.
+class Tuple2Ptr : public StructPtr {
+ public:
+  DECL_ACCESSORS(value1, Object)
+  DECL_ACCESSORS(value2, Object)
+
+  DECL_CAST2(Tuple2Ptr)
+
+  // Dispatched behavior.
+  DECL_PRINTER(Tuple2)
+  DECL_VERIFIER(Tuple2)
+  void BriefPrintDetails(std::ostream& os);
+
+  // TODO(3770): Temporary.
+  inline bool IsTuple2Ptr() const;
+
+  static const int kValue1Offset = HeapObject::kHeaderSize;
+  static const int kValue2Offset = kValue1Offset + kPointerSize;
+  static const int kSize = kValue2Offset + kPointerSize;
+
+  OBJECT_CONSTRUCTORS(Tuple2Ptr, StructPtr);
+};
+
 class Tuple3 : public Tuple2 {
  public:
   DECL_ACCESSORS(value3, Object)