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24
25 #ifndef SHARE_OOPS_OOP_HPP
26 #define SHARE_OOPS_OOP_HPP
27
28 #include "memory/iterator.hpp"
29 #include "memory/memRegion.hpp"
30 #include "oops/compressedKlass.hpp"
31 #include "oops/accessDecorators.hpp"
32 #include "oops/markWord.hpp"
33 #include "oops/metadata.hpp"
34 #include "oops/objLayout.hpp"
35 #include "runtime/atomic.hpp"
36 #include "utilities/globalDefinitions.hpp"
37 #include "utilities/macros.hpp"
38 #include <type_traits>
39
40 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe
41 // the format of Java objects so the fields can be accessed from C++.
42 // oopDesc is abstract.
43 // (see oopHierarchy for complete oop class hierarchy)
44 //
45 // no virtual functions allowed
46
47 class oopDesc {
48 friend class VMStructs;
49 friend class JVMCIVMStructs;
50 private:
51 volatile markWord _mark;
52 union _metadata {
53 Klass* _klass;
54 narrowKlass _compressed_klass;
55 } _metadata;
56
57 // There may be ordering constraints on the initialization of fields that
58 // make use of the C++ copy/assign incorrect.
59 NONCOPYABLE(oopDesc);
60
61 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order);
62
63 public:
64 // Must be trivial; see verifying static assert after the class.
65 oopDesc() = default;
66
67 inline markWord mark() const;
68 inline markWord mark_acquire() const;
69 inline markWord* mark_addr() const;
70
71 inline void set_mark(markWord m);
72 static inline void set_mark(HeapWord* mem, markWord m);
73 inline void set_mark_full(markWord m);
74 static inline void release_set_mark(HeapWord* mem, markWord m);
75
76 inline void release_set_mark(markWord m);
77 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
78 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
79
80 // Returns the prototype mark that should be used for this object.
81 inline markWord prototype_mark() const;
82
83 // Used only to re-initialize the mark word (e.g., of promoted
84 // objects during a GC) -- requires a valid klass pointer
85 inline void init_mark();
86
87 inline Klass* klass() const;
88 inline Klass* klass_or_null() const;
89 inline Klass* klass_or_null_acquire() const;
90 // Get the klass without running any asserts.
91 inline Klass* klass_without_asserts() const;
92
93 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
94 inline void set_klass(Klass* k);
95 static inline void release_set_klass(HeapWord* mem, Klass* k);
96
97 // For klass field compression
98 static inline void set_klass_gap(HeapWord* mem, int z);
99
100 // Size of object header, aligned to platform wordSize
101 static int header_size() {
102 if (UseCompactObjectHeaders) {
103 return sizeof(markWord) / HeapWordSize;
104 } else {
105 return sizeof(oopDesc) / HeapWordSize;
106 }
107 }
108
109 // Returns whether this is an instance of k or an instance of a subclass of k
110 inline bool is_a(Klass* k) const;
111
112 // Returns the actual oop size of the object in machine words
113 inline size_t size();
114
115 // Returns the size that a copy of this object requires, in machine words.
116 // It can be 1 word larger than its current size to accomodate
117 // an additional 4-byte-field for the identity hash-code.
118 //
119 // size: the current size of this object, we're passing this here for performance
120 // reasons, because all callers compute this anyway, and we want to avoid
121 // recomputing it.
122 // mark: the mark-word of this object. Some callers (e.g. G1ParScanThreadState::do_copy_to_survivor_space())
123 // need to use a known markWord because of racing GC threads that can change
124 // the markWord at any time.
125 inline size_t copy_size(size_t size, markWord mark) const;
126 // Special version to deal with scratch classes in CDS. There we allocate
127 // temporary scratch classes (which are skeleton versions of InstanceMirrorKlass,
128 // which represent java.lang.Class objects in the CDS archive). At that point, we
129 // don't know whether or not the final archived version will be hashed or expanded,
130 // and therefore we allocate them in the special state not-hashed-but-expanded.
131 // When creating the final copy of those objects, we either populate the hidden hash
132 // field and make the object 'expanded', or we turn it back to 'not-hashed'
133 // and reduce the object's size. We do this by providing a separate method for CDS
134 // so that we don't affect GC performance.
135 inline size_t copy_size_cds(size_t size, markWord mark) const;
136
137 // Sometimes (for complicated concurrency-related reasons), it is useful
138 // to be able to figure out the size of an object knowing its klass.
139 inline size_t base_size_given_klass(markWord m, const Klass* klass);
140 inline size_t size_given_mark_and_klass(markWord mrk, const Klass* kls);
141
142 // type test operations (inlined in oop.inline.hpp)
143 inline bool is_instance() const;
144 inline bool is_instanceRef() const;
145 inline bool is_stackChunk() const;
146 inline bool is_array() const;
147 inline bool is_objArray() const;
148 inline bool is_typeArray() const;
149
150 // type test operations that don't require inclusion of oop.inline.hpp.
151 bool is_instance_noinline() const;
152 bool is_instanceRef_noinline() const;
153 bool is_stackChunk_noinline() const;
154 bool is_array_noinline() const;
155 bool is_objArray_noinline() const;
156 bool is_typeArray_noinline() const;
157
158 protected:
159 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
160
161 public:
162 template<typename T>
163 inline T* field_addr(int offset) const;
164
165 template <typename T> inline size_t field_offset(T* p) const;
166
167 // Standard compare function returns negative value if o1 < o2
168 // 0 if o1 == o2
169 // positive value if o1 > o2
170 inline static int compare(oop o1, oop o2) {
171 void* o1_addr = (void*)o1;
172 void* o2_addr = (void*)o2;
173 if (o1_addr < o2_addr) {
174 return -1;
175 } else if (o1_addr > o2_addr) {
176 return 1;
177 } else {
178 return 0;
179 }
180 }
181
182 // Access to fields in a instanceOop through these methods.
183 template<DecoratorSet decorators>
184 oop obj_field_access(int offset) const;
185 oop obj_field(int offset) const;
186
187 void obj_field_put(int offset, oop value);
188 void obj_field_put_raw(int offset, oop value);
189 void obj_field_put_volatile(int offset, oop value);
190 template<DecoratorSet decorators>
191 void obj_field_put_access(int offset, oop value);
192
193 Metadata* metadata_field(int offset) const;
194 void metadata_field_put(int offset, Metadata* value);
195
196 Metadata* metadata_field_acquire(int offset) const;
197 void release_metadata_field_put(int offset, Metadata* value);
198
199 jbyte byte_field(int offset) const;
200 void byte_field_put(int offset, jbyte contents);
201
202 jchar char_field(int offset) const;
203 void char_field_put(int offset, jchar contents);
204
205 jboolean bool_field(int offset) const;
206 void bool_field_put(int offset, jboolean contents);
207 jboolean bool_field_volatile(int offset) const;
208 void bool_field_put_volatile(int offset, jboolean contents);
209
210 jint int_field(int offset) const;
211 void int_field_put(int offset, jint contents);
212
213 jshort short_field(int offset) const;
214 void short_field_put(int offset, jshort contents);
215
216 jlong long_field(int offset) const;
217 void long_field_put(int offset, jlong contents);
218
219 jfloat float_field(int offset) const;
220 void float_field_put(int offset, jfloat contents);
221
222 jdouble double_field(int offset) const;
223 void double_field_put(int offset, jdouble contents);
224
225 address address_field(int offset) const;
226 void address_field_put(int offset, address contents);
227
228 oop obj_field_acquire(int offset) const;
229 void release_obj_field_put(int offset, oop value);
230
231 jbyte byte_field_acquire(int offset) const;
232 void release_byte_field_put(int offset, jbyte contents);
233
234 jchar char_field_acquire(int offset) const;
235 void release_char_field_put(int offset, jchar contents);
236
237 jboolean bool_field_acquire(int offset) const;
238 void release_bool_field_put(int offset, jboolean contents);
239
240 jint int_field_relaxed(int offset) const;
241 void int_field_put_relaxed(int offset, jint contents);
242 jint int_field_acquire(int offset) const;
243 void release_int_field_put(int offset, jint contents);
244
245 jshort short_field_acquire(int offset) const;
246 void release_short_field_put(int offset, jshort contents);
247
248 jlong long_field_acquire(int offset) const;
249 void release_long_field_put(int offset, jlong contents);
250
251 jfloat float_field_acquire(int offset) const;
252 void release_float_field_put(int offset, jfloat contents);
253
254 jdouble double_field_acquire(int offset) const;
255 void release_double_field_put(int offset, jdouble contents);
256
257 address address_field_acquire(int offset) const;
258 void release_address_field_put(int offset, address contents);
259
260 // printing functions for VM debugging
261 void print_on(outputStream* st) const; // First level print
262 void print_value_on(outputStream* st) const; // Second level print.
263 void print_address_on(outputStream* st) const; // Address printing
264 void print_name_on(outputStream* st) const; // External name printing.
265
266 // printing on default output stream
267 void print();
268 void print_value();
269 void print_address();
270
271 // return the print strings
272 char* print_string();
273 char* print_value_string();
274
275 // verification operations
276 static void verify_on(outputStream* st, oopDesc* oop_desc);
277 static void verify(oopDesc* oopDesc);
278
279 // locking operations
280 inline bool is_locked() const;
281 inline bool is_unlocked() const;
282
283 // asserts and guarantees
284 static bool is_oop(oop obj, bool ignore_mark_word = false);
285 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
286
287 // garbage collection
288 inline bool is_gc_marked() const;
289
290 // Forward pointer operations for scavenge
291 inline bool is_forwarded() const;
292 inline bool is_self_forwarded() const;
293
294 inline void forward_to(oop p);
295 inline void forward_to_self();
296
297 // Like "forward_to", but inserts the forwarding pointer atomically.
298 // Exactly one thread succeeds in inserting the forwarding pointer, and
299 // this call returns null for that thread; any other thread has the
300 // value of the forwarding pointer returned and does not modify "this".
301 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
302 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
303
304 inline oop forwardee() const;
305 inline oop forwardee(markWord header) const;
306
307 inline void unset_self_forwarded();
308 inline void reset_forwarded();
309
310 // Age of object during scavenge
311 inline uint age() const;
312 inline void incr_age();
313
314 template <typename OopClosureType>
315 inline void oop_iterate(OopClosureType* cl);
316
317 template <typename OopClosureType>
318 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
319
320 template <typename OopClosureType>
321 inline size_t oop_iterate_size(OopClosureType* cl);
322
323 template <typename OopClosureType>
324 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
325
326 template <typename OopClosureType>
327 inline void oop_iterate_backwards(OopClosureType* cl);
328
329 template <typename OopClosureType>
330 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
331
332 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
333
334 // identity hash; returns the identity hash key (computes it if necessary)
335 inline intptr_t identity_hash();
336 intptr_t slow_identity_hash();
337 inline bool fast_no_hash_check();
338
339 // Initialize identity hash code in hash word of object copy from original object.
340 // Returns true if the object has been expanded, false otherwise.
341 inline void initialize_hash_if_necessary(oop obj);
342 // For CDS only.
343 void initialize_hash_if_necessary(oop obj, Klass* k, markWord m);
344
345 // marks are forwarded to stack when object is locked
346 inline bool has_displaced_mark() const;
347 inline markWord displaced_mark() const;
348 inline void set_displaced_mark(markWord m);
349
350 // Checks if the mark word needs to be preserved
351 inline bool mark_must_be_preserved() const;
352 inline bool mark_must_be_preserved(markWord m) const;
353
354 inline static bool has_klass_gap() {
355 return ObjLayout::oop_has_klass_gap();
356 }
357
358 // for code generation
359 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
360 static int klass_offset_in_bytes() {
361 assert(!UseCompactObjectHeaders, "don't use this with compact headers");
362 return (int)offset_of(oopDesc, _metadata._klass);
363 }
364 static int klass_gap_offset_in_bytes() {
365 assert(has_klass_gap(), "only applicable to compressed klass pointers");
366 if (UseCompactObjectHeaders) {
367 return base_offset_in_bytes();
368 } else {
369 return klass_offset_in_bytes() + sizeof(narrowKlass);
370 }
371 }
372
373 static int base_offset_in_bytes() {
374 return ObjLayout::oop_base_offset_in_bytes();
375 }
376
377 // for error reporting
378 static void* load_oop_raw(oop obj, int offset);
379 };
380
381 // An oopDesc is not initialized via a constructor. Space is allocated in
382 // the Java heap, and static functions provided here on HeapWord* are used
383 // to fill in certain parts of that memory. The allocated memory is then
384 // treated as referring to an oopDesc. For that to be valid, the oopDesc
385 // class must have a trivial default constructor (C++14 3.8/1).
386 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
387
388 #endif // SHARE_OOPS_OOP_HPP