45
46 // Forward declarations.
47 class OopClosure;
48 class PSPromotionManager;
49 class ParCompactionManager;
50
51 class oopDesc {
52 friend class VMStructs;
53 friend class JVMCIVMStructs;
54 private:
55 volatile markWord _mark;
56 union _metadata {
57 Klass* _klass;
58 narrowKlass _compressed_klass;
59 } _metadata;
60
61 // There may be ordering constraints on the initialization of fields that
62 // make use of the C++ copy/assign incorrect.
63 NONCOPYABLE(oopDesc);
64
65 public:
66 // Must be trivial; see verifying static assert after the class.
67 oopDesc() = default;
68
69 inline markWord mark() const;
70 inline markWord mark_acquire() const;
71 inline markWord* mark_addr() const;
72
73 inline void set_mark(markWord m);
74 static inline void set_mark(HeapWord* mem, markWord m);
75 static inline void release_set_mark(HeapWord* mem, markWord m);
76
77 inline void release_set_mark(markWord m);
78 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
79 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
80
81 // Used only to re-initialize the mark word (e.g., of promoted
82 // objects during a GC) -- requires a valid klass pointer
83 inline void init_mark();
84
85 inline Klass* klass() const;
86 inline Klass* klass_or_null() const;
87 inline Klass* klass_or_null_acquire() const;
88 // Get the klass without running any asserts.
89 inline Klass* klass_without_asserts() const;
90
91 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
92 inline void set_klass(Klass* k);
93 static inline void release_set_klass(HeapWord* mem, Klass* k);
94
95 // For klass field compression
96 static inline void set_klass_gap(HeapWord* mem, int z);
97
98 // size of object header, aligned to platform wordSize
99 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
100
101 // Returns whether this is an instance of k or an instance of a subclass of k
102 inline bool is_a(Klass* k) const;
103
104 // Returns the actual oop size of the object in machine words
105 inline size_t size();
106
107 // Sometimes (for complicated concurrency-related reasons), it is useful
108 // to be able to figure out the size of an object knowing its klass.
109 inline size_t size_given_klass(Klass* klass);
110
111 // type test operations (inlined in oop.inline.hpp)
112 inline bool is_instance() const;
113 inline bool is_instanceRef() const;
114 inline bool is_stackChunk() const;
115 inline bool is_array() const;
116 inline bool is_objArray() const;
117 inline bool is_typeArray() const;
118
119 // type test operations that don't require inclusion of oop.inline.hpp.
120 bool is_instance_noinline() const;
121 bool is_instanceRef_noinline() const;
122 bool is_stackChunk_noinline() const;
123 bool is_array_noinline() const;
124 bool is_objArray_noinline() const;
125 bool is_typeArray_noinline() const;
126
127 protected:
128 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
129
130 public:
241 char* print_string();
242 char* print_value_string();
243
244 // verification operations
245 static void verify_on(outputStream* st, oopDesc* oop_desc);
246 static void verify(oopDesc* oopDesc);
247
248 // locking operations
249 inline bool is_locked() const;
250 inline bool is_unlocked() const;
251
252 // asserts and guarantees
253 static bool is_oop(oop obj, bool ignore_mark_word = false);
254 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
255
256 // garbage collection
257 inline bool is_gc_marked() const;
258
259 // Forward pointer operations for scavenge
260 inline bool is_forwarded() const;
261
262 inline void forward_to(oop p);
263
264 // Like "forward_to", but inserts the forwarding pointer atomically.
265 // Exactly one thread succeeds in inserting the forwarding pointer, and
266 // this call returns null for that thread; any other thread has the
267 // value of the forwarding pointer returned and does not modify "this".
268 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
269
270 inline oop forwardee() const;
271
272 // Age of object during scavenge
273 inline uint age() const;
274 inline void incr_age();
275
276 template <typename OopClosureType>
277 inline void oop_iterate(OopClosureType* cl);
278
279 template <typename OopClosureType>
280 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
281
282 template <typename OopClosureType>
283 inline size_t oop_iterate_size(OopClosureType* cl);
284
285 template <typename OopClosureType>
286 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
287
288 template <typename OopClosureType>
289 inline void oop_iterate_backwards(OopClosureType* cl);
290
294 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
295
296 // identity hash; returns the identity hash key (computes it if necessary)
297 inline intptr_t identity_hash();
298 intptr_t slow_identity_hash();
299 inline bool fast_no_hash_check();
300
301 // marks are forwarded to stack when object is locked
302 inline bool has_displaced_mark() const;
303 inline markWord displaced_mark() const;
304 inline void set_displaced_mark(markWord m);
305
306 // Checks if the mark word needs to be preserved
307 inline bool mark_must_be_preserved() const;
308 inline bool mark_must_be_preserved(markWord m) const;
309
310 static bool has_klass_gap();
311
312 // for code generation
313 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
314 static int klass_offset_in_bytes() { return (int)offset_of(oopDesc, _metadata._klass); }
315 static int klass_gap_offset_in_bytes() {
316 assert(has_klass_gap(), "only applicable to compressed klass pointers");
317 return klass_offset_in_bytes() + sizeof(narrowKlass);
318 }
319
320 // for error reporting
321 static void* load_oop_raw(oop obj, int offset);
322
323 DEBUG_ONLY(bool size_might_change();)
324 };
325
326 // An oopDesc is not initialized via a constructor. Space is allocated in
327 // the Java heap, and static functions provided here on HeapWord* are used
328 // to fill in certain parts of that memory. The allocated memory is then
329 // treated as referring to an oopDesc. For that to be valid, the oopDesc
330 // class must have a trivial default constructor (C++14 3.8/1).
331 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
332
333 #endif // SHARE_OOPS_OOP_HPP
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45
46 // Forward declarations.
47 class OopClosure;
48 class PSPromotionManager;
49 class ParCompactionManager;
50
51 class oopDesc {
52 friend class VMStructs;
53 friend class JVMCIVMStructs;
54 private:
55 volatile markWord _mark;
56 union _metadata {
57 Klass* _klass;
58 narrowKlass _compressed_klass;
59 } _metadata;
60
61 // There may be ordering constraints on the initialization of fields that
62 // make use of the C++ copy/assign incorrect.
63 NONCOPYABLE(oopDesc);
64
65 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order);
66
67 public:
68 // Must be trivial; see verifying static assert after the class.
69 oopDesc() = default;
70
71 inline markWord mark() const;
72 inline markWord mark_acquire() const;
73 inline markWord* mark_addr() const;
74
75 inline void set_mark(markWord m);
76 static inline void set_mark(HeapWord* mem, markWord m);
77 static inline void release_set_mark(HeapWord* mem, markWord m);
78
79 inline void release_set_mark(markWord m);
80 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
81 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
82
83 inline markWord resolve_mark() const;
84
85 // Returns the prototype mark that should be used for this object.
86 inline markWord prototype_mark() const;
87
88 // Used only to re-initialize the mark word (e.g., of promoted
89 // objects during a GC) -- requires a valid klass pointer
90 inline void init_mark();
91
92 inline Klass* klass() const;
93 inline Klass* klass_or_null() const;
94 inline Klass* klass_or_null_acquire() const;
95 // Get the klass without running any asserts.
96 inline Klass* klass_without_asserts() const;
97
98 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
99 inline void set_klass(Klass* k);
100 static inline void release_set_klass(HeapWord* mem, Klass* k);
101
102 // For klass field compression
103 static inline void set_klass_gap(HeapWord* mem, int z);
104
105 // size of object header, aligned to platform wordSize
106 static int header_size() {
107 if (UseCompactObjectHeaders) {
108 return sizeof(markWord) / HeapWordSize;
109 } else {
110 return sizeof(oopDesc)/HeapWordSize;
111 }
112 }
113
114 // Returns whether this is an instance of k or an instance of a subclass of k
115 inline bool is_a(Klass* k) const;
116
117 // Returns the actual oop size of the object in machine words
118 inline size_t size();
119
120 // Sometimes (for complicated concurrency-related reasons), it is useful
121 // to be able to figure out the size of an object knowing its klass.
122 inline size_t size_given_klass(Klass* klass);
123
124 // The following set of methods is used to access the mark-word and related
125 // properties when the object may be forwarded. Be careful where and when
126 // using this method. It assumes that the forwardee is installed in
127 // the header as a plain pointer (or self-forwarded). In particular,
128 // those methods can not deal with the sliding-forwarding that is used
129 // in Serial, G1 and Shenandoah full-GCs.
130 private:
131 inline Klass* forward_safe_klass_impl(markWord m) const;
132 public:
133 inline Klass* forward_safe_klass() const;
134 inline Klass* forward_safe_klass(markWord m) const;
135 inline size_t forward_safe_size();
136 inline void forward_safe_init_mark();
137
138 // type test operations (inlined in oop.inline.hpp)
139 inline bool is_instance() const;
140 inline bool is_instanceRef() const;
141 inline bool is_stackChunk() const;
142 inline bool is_array() const;
143 inline bool is_objArray() const;
144 inline bool is_typeArray() const;
145
146 // type test operations that don't require inclusion of oop.inline.hpp.
147 bool is_instance_noinline() const;
148 bool is_instanceRef_noinline() const;
149 bool is_stackChunk_noinline() const;
150 bool is_array_noinline() const;
151 bool is_objArray_noinline() const;
152 bool is_typeArray_noinline() const;
153
154 protected:
155 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
156
157 public:
268 char* print_string();
269 char* print_value_string();
270
271 // verification operations
272 static void verify_on(outputStream* st, oopDesc* oop_desc);
273 static void verify(oopDesc* oopDesc);
274
275 // locking operations
276 inline bool is_locked() const;
277 inline bool is_unlocked() const;
278
279 // asserts and guarantees
280 static bool is_oop(oop obj, bool ignore_mark_word = false);
281 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
282
283 // garbage collection
284 inline bool is_gc_marked() const;
285
286 // Forward pointer operations for scavenge
287 inline bool is_forwarded() const;
288 inline bool is_self_forwarded() const;
289
290 inline void forward_to(oop p);
291 inline void forward_to_self();
292
293 // Like "forward_to", but inserts the forwarding pointer atomically.
294 // Exactly one thread succeeds in inserting the forwarding pointer, and
295 // this call returns null for that thread; any other thread has the
296 // value of the forwarding pointer returned and does not modify "this".
297 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
298 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
299
300 inline oop forwardee() const;
301 inline oop forwardee(markWord header) const;
302
303 inline void unset_self_forwarded();
304
305 // Age of object during scavenge
306 inline uint age() const;
307 inline void incr_age();
308
309 template <typename OopClosureType>
310 inline void oop_iterate(OopClosureType* cl);
311
312 template <typename OopClosureType>
313 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
314
315 template <typename OopClosureType>
316 inline size_t oop_iterate_size(OopClosureType* cl);
317
318 template <typename OopClosureType>
319 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
320
321 template <typename OopClosureType>
322 inline void oop_iterate_backwards(OopClosureType* cl);
323
327 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
328
329 // identity hash; returns the identity hash key (computes it if necessary)
330 inline intptr_t identity_hash();
331 intptr_t slow_identity_hash();
332 inline bool fast_no_hash_check();
333
334 // marks are forwarded to stack when object is locked
335 inline bool has_displaced_mark() const;
336 inline markWord displaced_mark() const;
337 inline void set_displaced_mark(markWord m);
338
339 // Checks if the mark word needs to be preserved
340 inline bool mark_must_be_preserved() const;
341 inline bool mark_must_be_preserved(markWord m) const;
342
343 static bool has_klass_gap();
344
345 // for code generation
346 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
347 static int klass_offset_in_bytes() {
348 #ifdef _LP64
349 if (UseCompactObjectHeaders) {
350 constexpr int load_shift = markWord::klass_load_shift;
351 STATIC_ASSERT(load_shift % 8 == 0);
352 return mark_offset_in_bytes() + load_shift / 8;
353 } else
354 #endif
355 {
356 return (int)offset_of(oopDesc, _metadata._klass);
357 }
358 }
359 static int klass_gap_offset_in_bytes() {
360 assert(has_klass_gap(), "only applicable to compressed klass pointers");
361 assert(!UseCompactObjectHeaders, "don't use klass_offset_in_bytes() with compact headers");
362 return klass_offset_in_bytes() + sizeof(narrowKlass);
363 }
364
365 static int base_offset_in_bytes() {
366 #ifdef _LP64
367 if (UseCompactObjectHeaders) {
368 // With compact headers, the Klass* field is not used for the Klass*
369 // and is used for the object fields instead.
370 STATIC_ASSERT(sizeof(markWord) == 8);
371 return sizeof(markWord);
372 } else if (UseCompressedClassPointers) {
373 return sizeof(markWord) + sizeof(narrowKlass);
374 } else
375 #endif
376 {
377 return sizeof(oopDesc);
378 }
379 }
380
381 // for error reporting
382 static void* load_oop_raw(oop obj, int offset);
383
384 DEBUG_ONLY(bool size_might_change(Klass* klass);)
385 };
386
387 // An oopDesc is not initialized via a constructor. Space is allocated in
388 // the Java heap, and static functions provided here on HeapWord* are used
389 // to fill in certain parts of that memory. The allocated memory is then
390 // treated as referring to an oopDesc. For that to be valid, the oopDesc
391 // class must have a trivial default constructor (C++14 3.8/1).
392 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
393
394 #endif // SHARE_OOPS_OOP_HPP
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