1 /*
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24
25 #ifndef SHARE_OOPS_OOP_HPP
26 #define SHARE_OOPS_OOP_HPP
27
28 #include "cppstdlib/type_traits.hpp"
29 #include "memory/iterator.hpp"
30 #include "memory/memRegion.hpp"
31 #include "oops/accessDecorators.hpp"
32 #include "oops/compressedKlass.hpp"
33 #include "oops/markWord.hpp"
34 #include "oops/metadata.hpp"
35 #include "oops/objLayout.hpp"
36 #include "runtime/atomicAccess.hpp"
37 #include "utilities/globalDefinitions.hpp"
38 #include "utilities/macros.hpp"
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 void* base_addr();
68 inline const void* base_addr() const;
69
70 inline markWord mark() const;
71 inline markWord mark_acquire() const;
72
73 inline void set_mark(markWord m);
74 static inline void set_mark(HeapWord* mem, markWord m);
75 inline void set_mark_full(markWord m);
76 static inline void release_set_mark(HeapWord* mem, markWord m);
77
78 inline void release_set_mark(markWord m);
79 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
80 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
81
82 // Returns the prototype mark that should be used for this object.
83 inline markWord prototype_mark() const;
84
85 // Initializes the mark word of an object (typically an object copy)
86 // to the prototype mark -- requires a valid klass pointer.
87 // This completely resets the mark-word, except for the
88 // Klass bits.
89 // This is typically used by clone() routines, where the copy of
90 // the object is a new object identity.
91 inline void init_mark();
92
93 // Re-initializes the mark word of an object (typically an object copy)
94 // to the prototype mark -- requires a valid klass pointer.
95 // This completely resets the mark-word, except for the
96 // Klass bits and the hashcode, which are preserved.
97 // This is typically used by GCs when they copy object to new locations,
98 // where the copy of the object preserves the previous identity.
99 inline void reinit_mark();
100
101 inline Klass* klass() const;
102 inline Klass* klass_or_null() const;
103 inline Klass* klass_or_null_acquire() const;
104 // Get the klass without running any asserts.
105 inline Klass* klass_without_asserts() const;
106
107 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
108 inline narrowKlass narrow_klass() const;
109 inline void set_klass(Klass* k);
110 static inline void release_set_klass(HeapWord* mem, Klass* k);
111
112 // For klass field compression
113 static inline void set_klass_gap(HeapWord* mem, int z);
114
115 // Size of object header, aligned to platform wordSize
116 static int header_size() {
117 if (UseCompactObjectHeaders) {
118 return sizeof(markWord) / HeapWordSize;
119 } else {
120 return sizeof(oopDesc) / HeapWordSize;
121 }
122 }
123
124 // Returns whether this is an instance of k or an instance of a subclass of k
125 inline bool is_a(Klass* k) const;
126
127 // Returns the actual oop size of the object in machine words
128 inline size_t size();
129
130 // Returns the size that a copy of this object requires, in machine words.
131 // It can be 1 word larger than its current size to accomodate
132 // an additional 4-byte-field for the identity hash-code.
133 //
134 // size: the current size of this object, we're passing this here for performance
135 // reasons, because all callers compute this anyway, and we want to avoid
136 // recomputing it.
137 // mark: the mark-word of this object. Some callers (e.g. G1ParScanThreadState::do_copy_to_survivor_space())
138 // need to use a known markWord because of racing GC threads that can change
139 // the markWord at any time.
140 inline size_t copy_size(size_t size, markWord mark) const;
141 // Special version to deal with scratch classes in CDS. There we allocate
142 // temporary scratch classes (which are skeleton versions of InstanceMirrorKlass,
143 // which represent java.lang.Class objects in the CDS archive). At that point, we
144 // don't know whether or not the final archived version will be hashed or expanded,
145 // and therefore we allocate them in the special state not-hashed-but-expanded.
146 // When creating the final copy of those objects, we either populate the hidden hash
147 // field and make the object 'expanded', or we turn it back to 'not-hashed'
148 // and reduce the object's size. We do this by providing a separate method for CDS
149 // so that we don't affect GC performance.
150 inline size_t copy_size_cds(size_t size, markWord mark) const;
151
152 // Sometimes (for complicated concurrency-related reasons), it is useful
153 // to be able to figure out the size of an object knowing its klass.
154 inline size_t base_size_given_klass(markWord m, const Klass* klass);
155 inline size_t size_given_mark_and_klass(markWord mrk, const Klass* kls);
156
157 // Returns the size of a forwarded object in its original (source) space.
158 // Only valid for scavenge-style forwarding (oopDesc::forward_to(/_atomic)).
159 inline size_t size_forwarded();
160
161 // type test operations (inlined in oop.inline.hpp)
162 inline bool is_instance() const;
163 inline bool is_instanceRef() const;
164 inline bool is_stackChunk() const;
165 inline bool is_array() const;
166 inline bool is_objArray() const;
167 inline bool is_typeArray() const;
168
169 // type test operations that don't require inclusion of oop.inline.hpp.
170 bool is_instance_noinline() const;
171 bool is_instanceRef_noinline() const;
172 bool is_stackChunk_noinline() const;
173 bool is_array_noinline() const;
174 bool is_objArray_noinline() const;
175 bool is_typeArray_noinline() const;
176
177 protected:
178 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
179
180 public:
181 template<typename T>
182 inline T* field_addr(int offset) const;
183
184 template <typename T> inline size_t field_offset(T* p) const;
185
186 // Standard compare function returns negative value if o1 < o2
187 // 0 if o1 == o2
188 // positive value if o1 > o2
189 inline static int compare(oop o1, oop o2) {
190 void* o1_addr = (void*)o1;
191 void* o2_addr = (void*)o2;
192 if (o1_addr < o2_addr) {
193 return -1;
194 } else if (o1_addr > o2_addr) {
195 return 1;
196 } else {
197 return 0;
198 }
199 }
200
201 // Access to fields in a instanceOop through these methods.
202 template<DecoratorSet decorators>
203 oop obj_field_access(int offset) const;
204 oop obj_field(int offset) const;
205
206 void obj_field_put(int offset, oop value);
207 void obj_field_put_raw(int offset, oop value);
208 void obj_field_put_volatile(int offset, oop value);
209 template<DecoratorSet decorators>
210 void obj_field_put_access(int offset, oop value);
211
212 Metadata* metadata_field(int offset) const;
213 void metadata_field_put(int offset, Metadata* value);
214
215 Metadata* metadata_field_acquire(int offset) const;
216 void release_metadata_field_put(int offset, Metadata* value);
217
218 jbyte byte_field(int offset) const;
219 void byte_field_put(int offset, jbyte contents);
220
221 jchar char_field(int offset) const;
222 void char_field_put(int offset, jchar contents);
223
224 jboolean bool_field(int offset) const;
225 void bool_field_put(int offset, jboolean contents);
226 jboolean bool_field_volatile(int offset) const;
227 void bool_field_put_volatile(int offset, jboolean contents);
228
229 jint int_field(int offset) const;
230 void int_field_put(int offset, jint contents);
231
232 jshort short_field(int offset) const;
233 void short_field_put(int offset, jshort contents);
234
235 jlong long_field(int offset) const;
236 void long_field_put(int offset, jlong contents);
237
238 jfloat float_field(int offset) const;
239 void float_field_put(int offset, jfloat contents);
240
241 jdouble double_field(int offset) const;
242 void double_field_put(int offset, jdouble contents);
243
244 address address_field(int offset) const;
245 void address_field_put(int offset, address contents);
246
247 oop obj_field_acquire(int offset) const;
248 void release_obj_field_put(int offset, oop value);
249
250 jbyte byte_field_acquire(int offset) const;
251 void release_byte_field_put(int offset, jbyte contents);
252
253 jchar char_field_acquire(int offset) const;
254 void release_char_field_put(int offset, jchar contents);
255
256 jboolean bool_field_acquire(int offset) const;
257 void release_bool_field_put(int offset, jboolean contents);
258
259 jint int_field_relaxed(int offset) const;
260 void int_field_put_relaxed(int offset, jint contents);
261 jint int_field_acquire(int offset) const;
262 void release_int_field_put(int offset, jint contents);
263
264 jshort short_field_acquire(int offset) const;
265 void release_short_field_put(int offset, jshort contents);
266
267 jlong long_field_acquire(int offset) const;
268 void release_long_field_put(int offset, jlong contents);
269
270 jfloat float_field_acquire(int offset) const;
271 void release_float_field_put(int offset, jfloat contents);
272
273 jdouble double_field_acquire(int offset) const;
274 void release_double_field_put(int offset, jdouble contents);
275
276 address address_field_acquire(int offset) const;
277 void release_address_field_put(int offset, address contents);
278
279 // printing functions for VM debugging
280 void print_on(outputStream* st) const; // First level print
281 void print_value_on(outputStream* st) const; // Second level print.
282 void print_address_on(outputStream* st) const; // Address printing
283 void print_name_on(outputStream* st) const; // External name printing.
284
285 // printing on default output stream
286 void print();
287 void print_value();
288 void print_address();
289
290 // return the print strings
291 char* print_string();
292 char* print_value_string();
293
294 // verification operations
295 static void verify_on(outputStream* st, oopDesc* oop_desc);
296 static void verify(oopDesc* oopDesc);
297
298 // locking operations
299 inline bool is_locked() const;
300 inline bool is_unlocked() const;
301
302 // asserts and guarantees
303 static bool is_oop(oop obj);
304 static bool is_oop_or_null(oop obj);
305
306 // garbage collection
307 inline bool is_gc_marked() const;
308
309 // Forward pointer operations for scavenge
310 inline bool is_forwarded() const;
311 inline bool is_self_forwarded() const;
312
313 inline void forward_to(oop p);
314 inline void forward_to_self();
315
316 // Like "forward_to", but inserts the forwarding pointer atomically.
317 // Exactly one thread succeeds in inserting the forwarding pointer, and
318 // this call returns null for that thread; any other thread has the
319 // value of the forwarding pointer returned and does not modify "this".
320 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
321 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
322
323 inline oop forwardee() const;
324 inline oop forwardee(markWord header) const;
325
326 inline void unset_self_forwarded();
327 inline void reset_forwarded();
328
329 // Age of object during scavenge
330 inline uint age() const;
331 inline void incr_age();
332
333 template <typename OopClosureType>
334 inline void oop_iterate(OopClosureType* cl);
335
336 template <typename OopClosureType>
337 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
338
339 template <typename OopClosureType>
340 inline size_t oop_iterate_size(OopClosureType* cl);
341
342 template <typename OopClosureType>
343 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
344
345 template <typename OopClosureType>
346 inline void oop_iterate_backwards(OopClosureType* cl);
347
348 template <typename OopClosureType>
349 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
350
351 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
352
353 // identity hash; returns the identity hash key (computes it if necessary)
354 inline intptr_t identity_hash();
355 intptr_t slow_identity_hash();
356 inline bool fast_no_hash_check();
357
358 // Initialize identity hash code in hash word of object copy from original object.
359 // Returns true if the object has been expanded, false otherwise.
360 inline void initialize_hash_if_necessary(oop obj);
361 // For CDS only.
362 markWord initialize_hash_if_necessary(oop obj, Klass* k, markWord m);
363
364 // marks are forwarded to stack when object is locked
365 inline bool has_displaced_mark() const;
366 inline markWord displaced_mark() const;
367 inline void set_displaced_mark(markWord m);
368
369 // Checks if the mark word needs to be preserved
370 inline bool mark_must_be_preserved() const;
371 inline bool mark_must_be_preserved(markWord m) const;
372
373 inline static bool has_klass_gap() {
374 return ObjLayout::oop_has_klass_gap();
375 }
376
377 // for code generation
378 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
379 static int klass_offset_in_bytes() {
380 assert(!UseCompactObjectHeaders, "don't use this with compact headers");
381 return (int)offset_of(oopDesc, _metadata._klass);
382 }
383 static int klass_gap_offset_in_bytes() {
384 assert(has_klass_gap(), "only applicable to compressed klass pointers");
385 if (UseCompactObjectHeaders) {
386 return base_offset_in_bytes();
387 } else {
388 return klass_offset_in_bytes() + sizeof(narrowKlass);
389 }
390 }
391
392 static int base_offset_in_bytes() {
393 return ObjLayout::oop_base_offset_in_bytes();
394 }
395
396 // for error reporting
397 static void* load_oop_raw(oop obj, int offset);
398 };
399
400 // An oopDesc is not initialized via a constructor. Space is allocated in
401 // the Java heap, and static functions provided here on HeapWord* are used
402 // to fill in certain parts of that memory. The allocated memory is then
403 // treated as referring to an oopDesc. For that to be valid, the oopDesc
404 // class must have a trivial default constructor (C++14 3.8/1).
405 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
406
407 #endif // SHARE_OOPS_OOP_HPP