[ptr-compr] Rename XxxSlot classes to FullXxxSlot

and
1) make them represent kSystemPointerSize-sized off-heap slots,
2) reintroduce XxxSlots as an on-heap kTaggedSize-sized slots (for now they
   are just aliases to respective FullXxxSlots).

Bug: v8:8518
Change-Id: I8a9177562308bd9420b1eebca959cc52ceaa628e
Reviewed-on: https://chromium-review.googlesource.com/c/1363144
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58056}

src/contexts.h

@@ -17,7 +17,6 @@ class JSGlobalObject;
 class JSGlobalProxy;
 class MicrotaskQueue;
 class NativeContext;
-class ObjectSlot;
 class RegExpMatchInfo;
 
 enum ContextLookupFlags {

src/globals.h

@@ -574,7 +574,9 @@ class NewSpace;
 class NewLargeObjectSpace;
 class NumberDictionary;
 class Object;
-class ObjectSlot;
+class FullObjectSlot;
+class FullMaybeObjectSlot;
+class FullHeapObjectSlot;
 class OldSpace;
 class ParameterCount;
 class ReadOnlySpace;
@@ -591,6 +593,41 @@ class Struct;
 class Symbol;
 class Variable;
 
+enum class SlotLocation { kOnHeap, kOffHeap };
+
+template <SlotLocation slot_location>
+struct SlotTraits;
+
+// Off-heap slots are always full-pointer slots.
+template <>
+struct SlotTraits<SlotLocation::kOffHeap> {
+  using TObjectSlot = FullObjectSlot;
+  using TMaybeObjectSlot = FullMaybeObjectSlot;
+  using THeapObjectSlot = FullHeapObjectSlot;
+};
+
+// On-heap slots are either full-pointer slots or compressed slots depending
+// on whether the pointer compression is enabled or not.
+template <>
+struct SlotTraits<SlotLocation::kOnHeap> {
+  using TObjectSlot = FullObjectSlot;
+  using TMaybeObjectSlot = FullMaybeObjectSlot;
+  using THeapObjectSlot = FullHeapObjectSlot;
+};
+
+// An ObjectSlot instance describes a kTaggedSize-sized on-heap field ("slot")
+// holding ObjectPtr value (smi or strong heap object).
+using ObjectSlot = SlotTraits<SlotLocation::kOnHeap>::TObjectSlot;
+
+// A MaybeObjectSlot instance describes a kTaggedSize-sized on-heap field
+// ("slot") holding MaybeObject (smi or weak heap object or strong heap object).
+using MaybeObjectSlot = SlotTraits<SlotLocation::kOnHeap>::TMaybeObjectSlot;
+
+// A HeapObjectSlot instance describes a kTaggedSize-sized field ("slot")
+// holding a weak or strong pointer to a heap object (think:
+// HeapObjectReference).
+using HeapObjectSlot = SlotTraits<SlotLocation::kOnHeap>::THeapObjectSlot;
+
 typedef bool (*WeakSlotCallback)(ObjectSlot pointer);
 
 typedef bool (*WeakSlotCallbackWithHeap)(Heap* heap, ObjectSlot pointer);

src/heap/concurrent-marking.cc

@@ -61,9 +61,7 @@ class SlotSnapshot {
   Object* value(int i) const { return snapshot_[i].second; }
   void clear() { number_of_slots_ = 0; }
   void add(ObjectSlot slot, Object* value) {
-    snapshot_[number_of_slots_].first = slot;
-    snapshot_[number_of_slots_].second = value;
-    ++number_of_slots_;
+    snapshot_[number_of_slots_++] = {slot, value};
   }
 
  private:
@@ -158,7 +156,7 @@ class ConcurrentMarkingVisitor final
         // barrier will treat the weak reference as strong, so we won't miss the
         // weak reference.
         ProcessStrongHeapObject(host, ObjectSlot(slot), heap_object);
-      } else if (TSlot::kCanBeWeek &&
+      } else if (TSlot::kCanBeWeak &&
                  object.GetHeapObjectIfWeak(&heap_object)) {
         ProcessWeakHeapObject(host, HeapObjectSlot(slot), heap_object);
       }

src/heap/heap-write-barrier.h

@@ -6,6 +6,7 @@
 #define V8_HEAP_HEAP_WRITE_BARRIER_H_
 
 #include "include/v8-internal.h"
+#include "src/globals.h"
 
 namespace v8 {
 namespace internal {
@@ -16,9 +17,7 @@ class Heap;
 class HeapObject;
 class HeapObjectPtr;
 class MaybeObject;
-class MaybeObjectSlot;
 class Object;
-class ObjectSlot;
 class RelocInfo;
 
 // Note: In general it is preferred to use the macros defined in

src/heap/mark-compact-inl.h

@@ -213,7 +213,7 @@ void MarkingVisitor<fixed_array_mode, retaining_path_mode,
   if (object.GetHeapObjectIfStrong(&target_object)) {
     collector_->RecordSlot(host, HeapObjectSlot(slot), target_object);
     MarkObject(host, target_object);
-  } else if (TSlot::kCanBeWeek && object.GetHeapObjectIfWeak(&target_object)) {
+  } else if (TSlot::kCanBeWeak && object.GetHeapObjectIfWeak(&target_object)) {
     if (marking_state()->IsBlackOrGrey(target_object)) {
       // Weak references with live values are directly processed here to reduce
       // the processing time of weak cells during the main GC pause.

src/objects.h

@@ -272,7 +272,6 @@ class KeyAccumulator;
 class LayoutDescriptor;
 class LookupIterator;
 class FieldType;
-class MaybeObjectSlot;
 class Module;
 class ModuleInfoEntry;
 class ObjectHashTable;

src/objects/descriptor-array.h

@@ -18,7 +18,6 @@ template <typename T>
 class Handle;
 
 class Isolate;
-class MaybeObjectSlot;
 
 // An EnumCache is a pair used to hold keys and indices caches.
 class EnumCache : public Tuple2 {

src/objects/fixed-array-inl.h

@@ -74,7 +74,7 @@ Object* FixedArrayBase::unchecked_synchronized_length() const {
 ACCESSORS(FixedTypedArrayBase, base_pointer, Object, kBasePointerOffset)
 
 ObjectSlot FixedArray::GetFirstElementAddress() {
-  return ObjectSlot(FIELD_ADDR(this, OffsetOfElementAt(0)));
+  return RawField(OffsetOfElementAt(0));
 }
 
 bool FixedArray::ContainsOnlySmisOrHoles() {

src/objects/heap-object.h

@@ -136,7 +136,7 @@ class ObjectPtr {
   };
 
  private:
-  friend class ObjectSlot;
+  friend class FullObjectSlot;
   Address ptr_;
 };
 

src/objects/ordered-hash-table-inl.h

@@ -156,9 +156,9 @@ template <class Derived>
 void SmallOrderedHashTable<Derived>::SetDataEntry(int entry, int relative_index,
                                                   Object* value) {
   DCHECK_NE(kNotFound, entry);
-  Address entry_offset = GetDataEntryOffset(entry, relative_index);
+  int entry_offset = GetDataEntryOffset(entry, relative_index);
   RELAXED_WRITE_FIELD(this, entry_offset, value);
-  WRITE_BARRIER(this, static_cast<int>(entry_offset), value);
+  WRITE_BARRIER(this, entry_offset, value);
 }
 
 template <class Derived, class TableType>

src/objects/slots-inl.h

@@ -16,80 +16,108 @@
 namespace v8 {
 namespace internal {
 
-ObjectSlot::ObjectSlot(ObjectPtr* object)
+//
+// FullObjectSlot implementation.
+//
+
+FullObjectSlot::FullObjectSlot(ObjectPtr* object)
     : SlotBase(reinterpret_cast<Address>(&object->ptr_)) {}
 
-ObjectPtr ObjectSlot::load() const { return ObjectPtr(*location()); }
+bool FullObjectSlot::contains_value(Address raw_value) const {
+  return *location() == raw_value;
+}
+
+Object* FullObjectSlot::operator*() const {
+  return reinterpret_cast<Object*>(*location());
+}
+
+ObjectPtr FullObjectSlot::load() const { return ObjectPtr(*location()); }
 
-void ObjectSlot::store(Object* value) const { *location() = value->ptr(); }
+void FullObjectSlot::store(Object* value) const { *location() = value->ptr(); }
+void FullObjectSlot::store(ObjectPtr value) const { *location() = value.ptr(); }
 
-ObjectPtr ObjectSlot::Acquire_Load() const {
-  return ObjectPtr(AsAtomicTagged::Acquire_Load(location()));
+ObjectPtr FullObjectSlot::Acquire_Load() const {
+  return ObjectPtr(base::AsAtomicPointer::Acquire_Load(location()));
 }
 
-Object* ObjectSlot::Acquire_Load1() const {
-  return reinterpret_cast<Object*>(AsAtomicTagged::Acquire_Load(location()));
+Object* FullObjectSlot::Acquire_Load1() const {
+  return reinterpret_cast<Object*>(
+      base::AsAtomicPointer::Acquire_Load(location()));
 }
 
-ObjectPtr ObjectSlot::Relaxed_Load() const {
-  return ObjectPtr(AsAtomicTagged::Relaxed_Load(location()));
+ObjectPtr FullObjectSlot::Relaxed_Load() const {
+  return ObjectPtr(base::AsAtomicPointer::Relaxed_Load(location()));
 }
 
-void ObjectSlot::Relaxed_Store(ObjectPtr value) const {
-  AsAtomicTagged::Relaxed_Store(location(), value->ptr());
+void FullObjectSlot::Relaxed_Store(ObjectPtr value) const {
+  base::AsAtomicPointer::Relaxed_Store(location(), value->ptr());
 }
 
-void ObjectSlot::Relaxed_Store1(Object* value) const {
-  AsAtomicTagged::Relaxed_Store(location(), value->ptr());
+void FullObjectSlot::Relaxed_Store1(Object* value) const {
+  base::AsAtomicPointer::Relaxed_Store(location(), value->ptr());
 }
 
-void ObjectSlot::Release_Store1(Object* value) const {
-  AsAtomicTagged::Release_Store(location(), value->ptr());
+void FullObjectSlot::Release_Store1(Object* value) const {
+  base::AsAtomicPointer::Release_Store(location(), value->ptr());
 }
 
-void ObjectSlot::Release_Store(ObjectPtr value) const {
-  AsAtomicTagged::Release_Store(location(), value->ptr());
+void FullObjectSlot::Release_Store(ObjectPtr value) const {
+  base::AsAtomicPointer::Release_Store(location(), value->ptr());
 }
 
-ObjectPtr ObjectSlot::Release_CompareAndSwap(ObjectPtr old,
+ObjectPtr FullObjectSlot::Release_CompareAndSwap(ObjectPtr old,
                                                  ObjectPtr target) const {
-  Address result = AsAtomicTagged::Release_CompareAndSwap(
+  Address result = base::AsAtomicPointer::Release_CompareAndSwap(
       location(), old->ptr(), target->ptr());
   return ObjectPtr(result);
 }
 
-MaybeObject MaybeObjectSlot::operator*() const {
+//
+// FullMaybeObjectSlot implementation.
+//
+
+MaybeObject FullMaybeObjectSlot::operator*() const {
   return MaybeObject(*location());
 }
 
-MaybeObject MaybeObjectSlot::load() const { return MaybeObject(*location()); }
+MaybeObject FullMaybeObjectSlot::load() const {
+  return MaybeObject(*location());
+}
 
-void MaybeObjectSlot::store(MaybeObject value) const {
+void FullMaybeObjectSlot::store(MaybeObject value) const {
   *location() = value.ptr();
 }
 
-MaybeObject MaybeObjectSlot::Relaxed_Load() const {
+MaybeObject FullMaybeObjectSlot::Relaxed_Load() const {
   return MaybeObject(AsAtomicTagged::Relaxed_Load(location()));
 }
 
-void MaybeObjectSlot::Relaxed_Store(MaybeObject value) const {
+void FullMaybeObjectSlot::Relaxed_Store(MaybeObject value) const {
   AsAtomicTagged::Relaxed_Store(location(), value->ptr());
 }
 
-void MaybeObjectSlot::Release_CompareAndSwap(MaybeObject old,
+void FullMaybeObjectSlot::Release_CompareAndSwap(MaybeObject old,
                                                  MaybeObject target) const {
   AsAtomicTagged::Release_CompareAndSwap(location(), old.ptr(), target.ptr());
 }
 
-HeapObjectReference HeapObjectSlot::operator*() const {
+//
+// FullHeapObjectSlot implementation.
+//
+
+HeapObjectReference FullHeapObjectSlot::operator*() const {
   return HeapObjectReference(*location());
 }
 
-void HeapObjectSlot::store(HeapObjectReference value) const {
+void FullHeapObjectSlot::store(HeapObjectReference value) const {
   *location() = value.ptr();
 }
 
-inline void MemsetPointer(ObjectSlot start, Object* value, size_t counter) {
+//
+// Utils.
+//
+
+inline void MemsetPointer(FullObjectSlot start, Object* value, size_t counter) {
   MemsetPointer(start.location(), reinterpret_cast<Address>(value), counter);
 }
 

src/objects/slots.h

@@ -84,32 +84,39 @@ class SlotBase {
   Address ptr_;
 };
 
-// An ObjectSlot instance describes a kTaggedSize-sized field ("slot") holding
-// a tagged pointer (smi or strong heap object).
+// An FullObjectSlot instance describes a kSystemPointerSize-sized field
+// ("slot") holding a tagged pointer (smi or strong heap object).
 // Its address() is the address of the slot.
 // The slot's contents can be read and written using operator* and store().
-class ObjectSlot : public SlotBase<ObjectSlot, Tagged_t, kTaggedSize> {
+class FullObjectSlot
+    : public SlotBase<FullObjectSlot, Address, kSystemPointerSize> {
  public:
   using TObject = ObjectPtr;
+  using THeapObjectSlot = FullHeapObjectSlot;
 
   // Tagged value stored in this slot is guaranteed to never be a weak pointer.
-  static constexpr bool kCanBeWeek = false;
+  static constexpr bool kCanBeWeak = false;
 
-  ObjectSlot() : SlotBase(kNullAddress) {}
-  explicit ObjectSlot(Address ptr) : SlotBase(ptr) {}
-  explicit ObjectSlot(Address* ptr)
+  FullObjectSlot() : SlotBase(kNullAddress) {}
+  explicit FullObjectSlot(Address ptr) : SlotBase(ptr) {}
+  explicit FullObjectSlot(Address* ptr)
       : SlotBase(reinterpret_cast<Address>(ptr)) {}
-  inline explicit ObjectSlot(ObjectPtr* object);
-  explicit ObjectSlot(Object const* const* ptr)
+  inline explicit FullObjectSlot(ObjectPtr* object);
+  explicit FullObjectSlot(Object const* const* ptr)
       : SlotBase(reinterpret_cast<Address>(ptr)) {}
   template <typename T>
-  explicit ObjectSlot(SlotBase<T, TData, kSlotDataSize> slot)
+  explicit FullObjectSlot(SlotBase<T, TData, kSlotDataSize> slot)
       : SlotBase(slot.address()) {}
 
-  Object* operator*() const { return *reinterpret_cast<Object**>(address()); }
+  // Compares memory representation of a value stored in the slot with given
+  // raw value.
+  inline bool contains_value(Address raw_value) const;
+
+  inline Object* operator*() const;
   // TODO(3770): drop this in favor of operator* once migration is complete.
   inline ObjectPtr load() const;
   inline void store(Object* value) const;
+  inline void store(ObjectPtr value) const;
 
   inline ObjectPtr Acquire_Load() const;
   inline ObjectPtr Relaxed_Load() const;
@@ -125,23 +132,29 @@ class ObjectSlot : public SlotBase<ObjectSlot, Tagged_t, kTaggedSize> {
   inline void Release_Store1(Object* value) const;
 };
 
-// A MaybeObjectSlot instance describes a kTaggedSize-sized field ("slot")
-// holding a possibly-weak tagged pointer (think: MaybeObject).
+// A FullMaybeObjectSlot instance describes a kSystemPointerSize-sized field
+// ("slot") holding a possibly-weak tagged pointer (think: MaybeObject).
 // Its address() is the address of the slot.
 // The slot's contents can be read and written using operator* and store().
-class MaybeObjectSlot
-    : public SlotBase<MaybeObjectSlot, Tagged_t, kTaggedSize> {
+class FullMaybeObjectSlot
+    : public SlotBase<FullMaybeObjectSlot, Address, kSystemPointerSize> {
  public:
   using TObject = MaybeObject;
+  using THeapObjectSlot = FullHeapObjectSlot;
 
   // Tagged value stored in this slot can be a weak pointer.
-  static constexpr bool kCanBeWeek = true;
+  static constexpr bool kCanBeWeak = true;
 
-  explicit MaybeObjectSlot(Address ptr) : SlotBase(ptr) {}
-  explicit MaybeObjectSlot(Object** ptr)
+  FullMaybeObjectSlot() : SlotBase(kNullAddress) {}
+  explicit FullMaybeObjectSlot(Address ptr) : SlotBase(ptr) {}
+  explicit FullMaybeObjectSlot(ObjectPtr* ptr)
+      : SlotBase(reinterpret_cast<Address>(ptr)) {}
+  explicit FullMaybeObjectSlot(Object** ptr)
+      : SlotBase(reinterpret_cast<Address>(ptr)) {}
+  explicit FullMaybeObjectSlot(HeapObject** ptr)
       : SlotBase(reinterpret_cast<Address>(ptr)) {}
   template <typename T>
-  explicit MaybeObjectSlot(SlotBase<T, TData, kSlotDataSize> slot)
+  explicit FullMaybeObjectSlot(SlotBase<T, TData, kSlotDataSize> slot)
       : SlotBase(slot.address()) {}
 
   inline MaybeObject operator*() const;
@@ -154,19 +167,20 @@ class MaybeObjectSlot
   inline void Release_CompareAndSwap(MaybeObject old, MaybeObject target) const;
 };
 
-// A HeapObjectSlot instance describes a kTaggedSize-sized field ("slot")
-// holding a weak or strong pointer to a heap object (think:
+// A FullHeapObjectSlot instance describes a kSystemPointerSize-sized field
+// ("slot") holding a weak or strong pointer to a heap object (think:
 // HeapObjectReference).
 // Its address() is the address of the slot.
 // The slot's contents can be read and written using operator* and store().
 // In case it is known that that slot contains a strong heap object pointer,
 // ToHeapObject() can be used to retrieve that heap object.
-class HeapObjectSlot : public SlotBase<HeapObjectSlot, Tagged_t, kTaggedSize> {
+class FullHeapObjectSlot
+    : public SlotBase<HeapObjectSlot, Address, kSystemPointerSize> {
  public:
-  HeapObjectSlot() : SlotBase(kNullAddress) {}
-  explicit HeapObjectSlot(Address ptr) : SlotBase(ptr) {}
+  FullHeapObjectSlot() : SlotBase(kNullAddress) {}
+  explicit FullHeapObjectSlot(Address ptr) : SlotBase(ptr) {}
   template <typename T>
-  explicit HeapObjectSlot(SlotBase<T, TData, kSlotDataSize> slot)
+  explicit FullHeapObjectSlot(SlotBase<T, TData, kSlotDataSize> slot)
       : SlotBase(slot.address()) {}
 
   inline HeapObjectReference operator*() const;