Revert of [heap] Remove size specializations in static object visitors.

src/heap/objects-visiting.h

Index: src/heap/objects-visiting.h
diff --git a/src/heap/objects-visiting.h b/src/heap/objects-visiting.h
index abbb27a3267d7fba7618ccddf8930a93da667e50..f10f370314766cebfb8520aa118b899e4440cde0 100644
--- a/src/heap/objects-visiting.h
+++ b/src/heap/objects-visiting.h
@@ -41,11 +41,42 @@
   V(FixedFloat64Array)     \
   V(NativeContext)         \
   V(AllocationSite)        \
-  V(DataObject)            \
-  V(JSObjectFast)          \
-  V(JSObject)              \
-  V(JSApiObject)           \
-  V(Struct)                \
+  V(DataObject2)           \
+  V(DataObject3)           \
+  V(DataObject4)           \
+  V(DataObject5)           \
+  V(DataObject6)           \
+  V(DataObject7)           \
+  V(DataObject8)           \
+  V(DataObject9)           \
+  V(DataObjectGeneric)     \
+  V(JSObject2)             \
+  V(JSObject3)             \
+  V(JSObject4)             \
+  V(JSObject5)             \
+  V(JSObject6)             \
+  V(JSObject7)             \
+  V(JSObject8)             \
+  V(JSObject9)             \
+  V(JSObjectGeneric)       \
+  V(JSApiObject2)          \
+  V(JSApiObject3)          \
+  V(JSApiObject4)          \
+  V(JSApiObject5)          \
+  V(JSApiObject6)          \
+  V(JSApiObject7)          \
+  V(JSApiObject8)          \
+  V(JSApiObject9)          \
+  V(JSApiObjectGeneric)    \
+  V(Struct2)               \
+  V(Struct3)               \
+  V(Struct4)               \
+  V(Struct5)               \
+  V(Struct6)               \
+  V(Struct7)               \
+  V(Struct8)               \
+  V(Struct9)               \
+  V(StructGeneric)         \
   V(ConsString)            \
   V(SlicedString)          \
   V(ThinString)            \
@@ -76,7 +107,11 @@
 #define VISITOR_ID_ENUM_DECL(id) kVisit##id,
     VISITOR_ID_LIST(VISITOR_ID_ENUM_DECL)
 #undef VISITOR_ID_ENUM_DECL
-        kVisitorIdCount
+        kVisitorIdCount,
+    kVisitDataObject = kVisitDataObject2,
+    kVisitJSObject = kVisitJSObject2,
+    kVisitJSApiObject = kVisitJSApiObject2,
+    kVisitStruct = kVisitStruct2,
   };
 
   // Visitor ID should fit in one byte.
@@ -89,6 +124,28 @@
 
   // Determine which specialized visitor should be used for given map.
   static VisitorId GetVisitorId(Map* map);
+
+  // For visitors that allow specialization by size calculate VisitorId based
+  // on size, base visitor id and generic visitor id.
+  static VisitorId GetVisitorIdForSize(VisitorId base, VisitorId generic,
+                                       int object_size,
+                                       bool has_unboxed_fields) {
+    DCHECK((base == kVisitDataObject) || (base == kVisitStruct) ||
+           (base == kVisitJSObject) || (base == kVisitJSApiObject));
+    DCHECK(IsAligned(object_size, kPointerSize));
+    DCHECK(Heap::kMinObjectSizeInWords * kPointerSize <= object_size);
+    DCHECK(object_size <= kMaxRegularHeapObjectSize);
+    DCHECK(!has_unboxed_fields || (base == kVisitJSObject) ||
+           (base == kVisitJSApiObject));
+
+    if (has_unboxed_fields) return generic;
+
+    int visitor_id = Min(
+        base + (object_size >> kPointerSizeLog2) - Heap::kMinObjectSizeInWords,
+        static_cast<int>(generic));
+
+    return static_cast<VisitorId>(visitor_id);
+  }
 };
 
 
@@ -115,6 +172,30 @@
     callbacks_[id] = reinterpret_cast<base::AtomicWord>(callback);
   }
 
+  template <typename Visitor, StaticVisitorBase::VisitorId base,
+            StaticVisitorBase::VisitorId generic, int object_size_in_words>
+  void RegisterSpecialization() {
+    static const int size = object_size_in_words * kPointerSize;
+    Register(StaticVisitorBase::GetVisitorIdForSize(base, generic, size, false),
+             &Visitor::template VisitSpecialized<size>);
+  }
+
+
+  template <typename Visitor, StaticVisitorBase::VisitorId base,
+            StaticVisitorBase::VisitorId generic>
+  void RegisterSpecializations() {
+    STATIC_ASSERT((generic - base + Heap::kMinObjectSizeInWords) == 10);
+    RegisterSpecialization<Visitor, base, generic, 2>();
+    RegisterSpecialization<Visitor, base, generic, 3>();
+    RegisterSpecialization<Visitor, base, generic, 4>();
+    RegisterSpecialization<Visitor, base, generic, 5>();
+    RegisterSpecialization<Visitor, base, generic, 6>();
+    RegisterSpecialization<Visitor, base, generic, 7>();
+    RegisterSpecialization<Visitor, base, generic, 8>();
+    RegisterSpecialization<Visitor, base, generic, 9>();
+    Register(generic, &Visitor::Visit);
+  }
+
  private:
   base::AtomicWord callbacks_[StaticVisitorBase::kVisitorIdCount];
 };
@@ -126,6 +207,18 @@
   INLINE(static ReturnType Visit(Map* map, HeapObject* object)) {
     int object_size = BodyDescriptor::SizeOf(map, object);
     BodyDescriptor::template IterateBody<StaticVisitor>(object, object_size);
+    return static_cast<ReturnType>(object_size);
+  }
+
+  // This specialization is only suitable for objects containing pointer fields.
+  template <int object_size>
+  static inline ReturnType VisitSpecialized(Map* map, HeapObject* object) {
+    DCHECK(BodyDescriptor::SizeOf(map, object) == object_size);
+    DCHECK(!FLAG_unbox_double_fields || map->HasFastPointerLayout());
+    StaticVisitor::VisitPointers(
+        object->GetHeap(), object,
+        HeapObject::RawField(object, BodyDescriptor::kStartOffset),
+        HeapObject::RawField(object, object_size));
     return static_cast<ReturnType>(object_size);
   }
 };
@@ -196,6 +289,10 @@
     return FixedDoubleArray::SizeFor(length);
   }
 
+  INLINE(static int VisitJSObject(Map* map, HeapObject* object)) {
+    return JSObjectVisitor::Visit(map, object);
+  }
+
   INLINE(static int VisitSeqOneByteString(Map* map, HeapObject* object)) {
     return SeqOneByteString::cast(object)
         ->SeqOneByteStringSize(map->instance_type());
@@ -227,10 +324,6 @@
 
   typedef FlexibleBodyVisitor<StaticVisitor, JSObject::BodyDescriptor, int>
       JSObjectVisitor;
-
-  // Visitor for JSObjects without unboxed double fields.
-  typedef FlexibleBodyVisitor<StaticVisitor, JSObject::FastBodyDescriptor, int>
-      JSObjectFastVisitor;
 
   typedef int (*Callback)(Map* map, HeapObject* object);
 
@@ -315,13 +408,17 @@
   typedef FlexibleBodyVisitor<StaticVisitor, FixedArray::BodyDescriptor, void>
       FixedArrayVisitor;
 
-  typedef FlexibleBodyVisitor<StaticVisitor, JSObject::FastBodyDescriptor, void>
-      JSObjectFastVisitor;
   typedef FlexibleBodyVisitor<StaticVisitor, JSObject::BodyDescriptor, void>
       JSObjectVisitor;
 
   class JSApiObjectVisitor : AllStatic {
    public:
+    template <int size>
+    static inline void VisitSpecialized(Map* map, HeapObject* object) {
+      TracePossibleWrapper(object);
+      JSObjectVisitor::template VisitSpecialized<size>(map, object);
+    }
+
     INLINE(static void Visit(Map* map, HeapObject* object)) {
       TracePossibleWrapper(object);
       JSObjectVisitor::Visit(map, object);