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1 : // Copyright 2018 the V8 project authors. All rights reserved.
2 : // Use of this source code is governed by a BSD-style license that can be
3 : // found in the LICENSE file.
4 :
5 : #ifndef V8_OBJECTS_HEAP_OBJECT_H_
6 : #define V8_OBJECTS_HEAP_OBJECT_H_
7 :
8 : #include "src/globals.h"
9 : #include "src/roots.h"
10 :
11 : #include "src/objects.h"
12 :
13 : // Has to be the last include (doesn't have include guards):
14 : #include "src/objects/object-macros.h"
15 :
16 : namespace v8 {
17 : namespace internal {
18 :
19 : class Heap;
20 :
21 : // HeapObject is the superclass for all classes describing heap allocated
22 : // objects.
23 : class HeapObject : public Object {
24 : public:
25 3398171 : bool is_null() const { return ptr() == kNullAddress; }
26 :
27 : // [map]: Contains a map which contains the object's reflective
28 : // information.
29 : inline Map map() const;
30 : inline void set_map(Map value);
31 :
32 : inline MapWordSlot map_slot() const;
33 :
34 : // The no-write-barrier version. This is OK if the object is white and in
35 : // new space, or if the value is an immortal immutable object, like the maps
36 : // of primitive (non-JS) objects like strings, heap numbers etc.
37 : inline void set_map_no_write_barrier(Map value);
38 :
39 : // Get the map using acquire load.
40 : inline Map synchronized_map() const;
41 : inline MapWord synchronized_map_word() const;
42 :
43 : // Set the map using release store
44 : inline void synchronized_set_map(Map value);
45 : inline void synchronized_set_map_word(MapWord map_word);
46 :
47 : // Initialize the map immediately after the object is allocated.
48 : // Do not use this outside Heap.
49 : inline void set_map_after_allocation(
50 : Map value, WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
51 :
52 : // During garbage collection, the map word of a heap object does not
53 : // necessarily contain a map pointer.
54 : inline MapWord map_word() const;
55 : inline void set_map_word(MapWord map_word);
56 :
57 : // TODO(v8:7464): Once RO_SPACE is shared between isolates, this method can be
58 : // removed as ReadOnlyRoots will be accessible from a global variable. For now
59 : // this method exists to help remove GetIsolate/GetHeap from HeapObject, in a
60 : // way that doesn't require passing Isolate/Heap down huge call chains or to
61 : // places where it might not be safe to access it.
62 : inline ReadOnlyRoots GetReadOnlyRoots() const;
63 :
64 : #define IS_TYPE_FUNCTION_DECL(Type) V8_INLINE bool Is##Type() const;
65 : HEAP_OBJECT_TYPE_LIST(IS_TYPE_FUNCTION_DECL)
66 : #undef IS_TYPE_FUNCTION_DECL
67 :
68 : bool IsExternal(Isolate* isolate) const;
69 :
70 : // Oddball checks are faster when they are raw pointer comparisons, so the
71 : // isolate/read-only roots overloads should be preferred where possible.
72 : #define IS_TYPE_FUNCTION_DECL(Type, Value) \
73 : V8_INLINE bool Is##Type(Isolate* isolate) const; \
74 : V8_INLINE bool Is##Type(ReadOnlyRoots roots) const; \
75 : V8_INLINE bool Is##Type() const;
76 : ODDBALL_LIST(IS_TYPE_FUNCTION_DECL)
77 : #undef IS_TYPE_FUNCTION_DECL
78 :
79 : V8_INLINE bool IsNullOrUndefined(Isolate* isolate) const;
80 : V8_INLINE bool IsNullOrUndefined(ReadOnlyRoots roots) const;
81 : V8_INLINE bool IsNullOrUndefined() const;
82 :
83 : #define DECL_STRUCT_PREDICATE(NAME, Name, name) V8_INLINE bool Is##Name() const;
84 : STRUCT_LIST(DECL_STRUCT_PREDICATE)
85 : #undef DECL_STRUCT_PREDICATE
86 :
87 : // Converts an address to a HeapObject pointer.
88 : static inline HeapObject FromAddress(Address address);
89 :
90 : // Returns the address of this HeapObject.
91 1788676956 : inline Address address() const { return ptr() - kHeapObjectTag; }
92 :
93 : // Iterates over pointers contained in the object (including the Map).
94 : // If it's not performance critical iteration use the non-templatized
95 : // version.
96 : void Iterate(ObjectVisitor* v);
97 :
98 : template <typename ObjectVisitor>
99 : inline void IterateFast(ObjectVisitor* v);
100 :
101 : // Iterates over all pointers contained in the object except the
102 : // first map pointer. The object type is given in the first
103 : // parameter. This function does not access the map pointer in the
104 : // object, and so is safe to call while the map pointer is modified.
105 : // If it's not performance critical iteration use the non-templatized
106 : // version.
107 : void IterateBody(ObjectVisitor* v);
108 : void IterateBody(Map map, int object_size, ObjectVisitor* v);
109 :
110 : template <typename ObjectVisitor>
111 : inline void IterateBodyFast(ObjectVisitor* v);
112 :
113 : template <typename ObjectVisitor>
114 : inline void IterateBodyFast(Map map, int object_size, ObjectVisitor* v);
115 :
116 : // Returns true if the object contains a tagged value at given offset.
117 : // It is used for invalid slots filtering. If the offset points outside
118 : // of the object or to the map word, the result is UNDEFINED (!!!).
119 : V8_EXPORT_PRIVATE bool IsValidSlot(Map map, int offset);
120 :
121 : // Returns the heap object's size in bytes
122 : inline int Size() const;
123 :
124 : // Given a heap object's map pointer, returns the heap size in bytes
125 : // Useful when the map pointer field is used for other purposes.
126 : // GC internal.
127 : V8_EXPORT_PRIVATE int SizeFromMap(Map map) const;
128 :
129 : // Returns the field at offset in obj, as a read/write Object reference.
130 : // Does no checking, and is safe to use during GC, while maps are invalid.
131 : // Does not invoke write barrier, so should only be assigned to
132 : // during marking GC.
133 : inline ObjectSlot RawField(int byte_offset) const;
134 : inline MaybeObjectSlot RawMaybeWeakField(int byte_offset) const;
135 :
136 : DECL_CAST(HeapObject)
137 :
138 : // Return the write barrier mode for this. Callers of this function
139 : // must be able to present a reference to an DisallowHeapAllocation
140 : // object as a sign that they are not going to use this function
141 : // from code that allocates and thus invalidates the returned write
142 : // barrier mode.
143 : inline WriteBarrierMode GetWriteBarrierMode(
144 : const DisallowHeapAllocation& promise);
145 :
146 : // Dispatched behavior.
147 : void HeapObjectShortPrint(std::ostream& os); // NOLINT
148 : #ifdef OBJECT_PRINT
149 : void PrintHeader(std::ostream& os, const char* id); // NOLINT
150 : #endif
151 : DECL_PRINTER(HeapObject)
152 : EXPORT_DECL_VERIFIER(HeapObject)
153 : #ifdef VERIFY_HEAP
154 : inline void VerifyObjectField(Isolate* isolate, int offset);
155 : inline void VerifySmiField(int offset);
156 : inline void VerifyMaybeObjectField(Isolate* isolate, int offset);
157 :
158 : // Verify a pointer is a valid HeapObject pointer that points to object
159 : // areas in the heap.
160 : static void VerifyHeapPointer(Isolate* isolate, Object p);
161 : #endif
162 :
163 : static inline AllocationAlignment RequiredAlignment(Map map);
164 :
165 : // Whether the object needs rehashing. That is the case if the object's
166 : // content depends on FLAG_hash_seed. When the object is deserialized into
167 : // a heap with a different hash seed, these objects need to adapt.
168 : bool NeedsRehashing() const;
169 :
170 : // Rehashing support is not implemented for all objects that need rehashing.
171 : // With objects that need rehashing but cannot be rehashed, rehashing has to
172 : // be disabled.
173 : bool CanBeRehashed() const;
174 :
175 : // Rehash the object based on the layout inferred from its map.
176 : void RehashBasedOnMap(ReadOnlyRoots root);
177 :
178 : // Layout description.
179 : #define HEAP_OBJECT_FIELDS(V) \
180 : V(kMapOffset, kTaggedSize) \
181 : /* Header size. */ \
182 : V(kHeaderSize, 0)
183 :
184 : DEFINE_FIELD_OFFSET_CONSTANTS(Object::kHeaderSize, HEAP_OBJECT_FIELDS)
185 : #undef HEAP_OBJECT_FIELDS
186 :
187 : STATIC_ASSERT(kMapOffset == Internals::kHeapObjectMapOffset);
188 :
189 : inline Address GetFieldAddress(int field_offset) const;
190 :
191 : protected:
192 : // Special-purpose constructor for subclasses that have fast paths where
193 : // their ptr() is a Smi.
194 : enum class AllowInlineSmiStorage { kRequireHeapObjectTag, kAllowBeingASmi };
195 : inline HeapObject(Address ptr, AllowInlineSmiStorage allow_smi);
196 :
197 1998282 : OBJECT_CONSTRUCTORS(HeapObject, Object);
198 : };
199 :
200 : // Helper class for objects that can never be in RO space.
201 : class NeverReadOnlySpaceObject {
202 : public:
203 : // The Heap the object was allocated in. Used also to access Isolate.
204 : static inline Heap* GetHeap(const HeapObject object);
205 :
206 : // Convenience method to get current isolate.
207 : static inline Isolate* GetIsolate(const HeapObject object);
208 : };
209 :
210 : } // namespace internal
211 : } // namespace v8
212 :
213 : #include "src/objects/object-macros-undef.h"
214 :
215 : #endif // V8_OBJECTS_HEAP_OBJECT_H_
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