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 narrowKlass _compressed_klass;
53
54 // There may be ordering constraints on the initialization of fields that
55 // make use of the C++ copy/assign incorrect.
56 NONCOPYABLE(oopDesc);
57
58 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order);
59
60 public:
61 // Must be trivial; see verifying static assert after the class.
62 oopDesc() = default;
63
64 inline void* base_addr();
65 inline const void* base_addr() const;
66
67 inline markWord mark() const;
68 inline markWord mark_acquire() const;
69
70 inline void set_mark(markWord m);
71 static inline void set_mark(HeapWord* mem, markWord m);
72 inline void set_mark_full(markWord m);
73 static inline void release_set_mark(HeapWord* mem, markWord m);
74
75 inline void release_set_mark(markWord m);
76 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
77 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
78
79 // Returns the prototype mark that should be used for this object.
80 inline markWord prototype_mark() const;
81
82 // Initializes the mark word of an object (typically an object copy)
83 // to the prototype mark -- requires a valid klass pointer.
84 // This completely resets the mark-word, except for the
85 // Klass bits.
86 // This is typically used by clone() routines, where the copy of
87 // the object is a new object identity.
88 inline void init_mark();
89
90 // Re-initializes the mark word of an object (typically an object copy)
91 // to the prototype mark -- requires a valid klass pointer.
92 // This completely resets the mark-word, except for the
93 // Klass bits and the hashcode, which are preserved.
94 // This is typically used by GCs when they copy object to new locations,
95 // where the copy of the object preserves the previous identity.
96 inline void reinit_mark();
97
98 inline Klass* klass() const;
99 inline Klass* klass_or_null() const;
100 inline Klass* klass_or_null_acquire() const;
101 // Get the klass without running any asserts.
102 inline Klass* klass_without_asserts() const;
103
104 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
105 inline narrowKlass narrow_klass() const;
106 inline void set_klass(Klass* k);
107 static inline void release_set_klass(HeapWord* mem, Klass* k);
108
109 // For klass field compression
110 static inline void set_klass_gap(HeapWord* mem, int z);
111
112 // Size of object header, aligned to platform wordSize
113 static int header_size() {
114 if (UseCompactObjectHeaders) {
115 return sizeof(markWord) / HeapWordSize;
116 } else {
117 return sizeof(oopDesc) / HeapWordSize;
118 }
119 }
120
121 // Returns whether this is an instance of k or an instance of a subclass of k
122 inline bool is_a(Klass* k) const;
123
124 // Returns the actual oop size of the object in machine words
125 inline size_t size();
126
127 // Returns the size that a copy of this object requires, in machine words.
128 // It can be 1 word larger than its current size to accomodate
129 // an additional 4-byte-field for the identity hash-code.
130 //
131 // size: the current size of this object, we're passing this here for performance
132 // reasons, because all callers compute this anyway, and we want to avoid
133 // recomputing it.
134 // mark: the mark-word of this object. Some callers (e.g. G1ParScanThreadState::do_copy_to_survivor_space())
135 // need to use a known markWord because of racing GC threads that can change
136 // the markWord at any time.
137 inline size_t copy_size(size_t size, markWord mark) const;
138 // Special version to deal with scratch classes in CDS. There we allocate
139 // temporary scratch classes (which are skeleton versions of InstanceMirrorKlass,
140 // which represent java.lang.Class objects in the CDS archive). At that point, we
141 // don't know whether or not the final archived version will be hashed or expanded,
142 // and therefore we allocate them in the special state not-hashed-but-expanded.
143 // When creating the final copy of those objects, we either populate the hidden hash
144 // field and make the object 'expanded', or we turn it back to 'not-hashed'
145 // and reduce the object's size. We do this by providing a separate method for CDS
146 // so that we don't affect GC performance.
147 inline size_t copy_size_cds(size_t size, markWord mark) const;
148
149 // Sometimes (for complicated concurrency-related reasons), it is useful
150 // to be able to figure out the size of an object knowing its klass.
151 inline size_t base_size_given_klass(markWord m, const Klass* klass);
152 inline size_t size_given_mark_and_klass(markWord mrk, const Klass* kls);
153
154 // Returns the size of a forwarded object in its original (source) space.
155 // Only valid for scavenge-style forwarding (oopDesc::forward_to(/_atomic)).
156 inline size_t size_forwarded();
157
158 // type test operations (inlined in oop.inline.hpp)
159 inline bool is_instance() const;
160 inline bool is_instanceRef() const;
161 inline bool is_stackChunk() const;
162 inline bool is_array() const;
163 inline bool is_objArray() const;
164 inline bool is_typeArray() const;
165
166 // type test operations that don't require inclusion of oop.inline.hpp.
167 bool is_instance_noinline() const;
168 bool is_instanceRef_noinline() const;
169 bool is_stackChunk_noinline() const;
170 bool is_array_noinline() const;
171 bool is_objArray_noinline() const;
172 bool is_typeArray_noinline() const;
173
174 protected:
175 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
176
177 public:
178 template<typename T>
179 inline T* field_addr(int offset) const;
180
181 template <typename T> inline size_t field_offset(T* p) const;
182
183 // Standard compare function returns negative value if o1 < o2
184 // 0 if o1 == o2
185 // positive value if o1 > o2
186 inline static int compare(oop o1, oop o2) {
187 void* o1_addr = (void*)o1;
188 void* o2_addr = (void*)o2;
189 if (o1_addr < o2_addr) {
190 return -1;
191 } else if (o1_addr > o2_addr) {
192 return 1;
193 } else {
194 return 0;
195 }
196 }
197
198 // Access to fields in a instanceOop through these methods.
199 template<DecoratorSet decorators>
200 oop obj_field_access(int offset) const;
201 oop obj_field(int offset) const;
202
203 void obj_field_put(int offset, oop value);
204 void obj_field_put_raw(int offset, oop value);
205 void obj_field_put_volatile(int offset, oop value);
206 template<DecoratorSet decorators>
207 void obj_field_put_access(int offset, oop value);
208
209 Metadata* metadata_field(int offset) const;
210 void metadata_field_put(int offset, Metadata* value);
211
212 Metadata* metadata_field_acquire(int offset) const;
213 void release_metadata_field_put(int offset, Metadata* value);
214
215 jbyte byte_field(int offset) const;
216 void byte_field_put(int offset, jbyte contents);
217
218 jchar char_field(int offset) const;
219 void char_field_put(int offset, jchar contents);
220
221 jboolean bool_field(int offset) const;
222 void bool_field_put(int offset, jboolean contents);
223 jboolean bool_field_volatile(int offset) const;
224 void bool_field_put_volatile(int offset, jboolean contents);
225
226 jint int_field(int offset) const;
227 void int_field_put(int offset, jint contents);
228
229 jshort short_field(int offset) const;
230 void short_field_put(int offset, jshort contents);
231
232 jlong long_field(int offset) const;
233 void long_field_put(int offset, jlong contents);
234
235 jfloat float_field(int offset) const;
236 void float_field_put(int offset, jfloat contents);
237
238 jdouble double_field(int offset) const;
239 void double_field_put(int offset, jdouble contents);
240
241 address address_field(int offset) const;
242 void address_field_put(int offset, address contents);
243
244 oop obj_field_acquire(int offset) const;
245 void release_obj_field_put(int offset, oop value);
246
247 jbyte byte_field_acquire(int offset) const;
248 void release_byte_field_put(int offset, jbyte contents);
249
250 jchar char_field_acquire(int offset) const;
251 void release_char_field_put(int offset, jchar contents);
252
253 jboolean bool_field_acquire(int offset) const;
254 void release_bool_field_put(int offset, jboolean contents);
255
256 jint int_field_relaxed(int offset) const;
257 void int_field_put_relaxed(int offset, jint contents);
258 jint int_field_acquire(int offset) const;
259 void release_int_field_put(int offset, jint contents);
260
261 jshort short_field_acquire(int offset) const;
262 void release_short_field_put(int offset, jshort contents);
263
264 jlong long_field_acquire(int offset) const;
265 void release_long_field_put(int offset, jlong contents);
266
267 jfloat float_field_acquire(int offset) const;
268 void release_float_field_put(int offset, jfloat contents);
269
270 jdouble double_field_acquire(int offset) const;
271 void release_double_field_put(int offset, jdouble contents);
272
273 address address_field_acquire(int offset) const;
274 void release_address_field_put(int offset, address contents);
275
276 // printing functions for VM debugging
277 void print_on(outputStream* st) const; // First level print
278 void print_value_on(outputStream* st) const; // Second level print.
279 void print_address_on(outputStream* st) const; // Address printing
280 void print_name_on(outputStream* st) const; // External name printing.
281
282 // printing on default output stream
283 void print();
284 void print_value();
285 void print_address();
286
287 // return the print strings
288 char* print_string();
289 char* print_value_string();
290
291 // verification operations
292 static void verify_on(outputStream* st, oopDesc* oop_desc);
293 static void verify(oopDesc* oopDesc);
294
295 // locking operations
296 inline bool is_locked() const;
297 inline bool is_unlocked() const;
298
299 // asserts and guarantees
300 static bool is_oop(oop obj);
301 static bool is_oop_or_null(oop obj);
302
303 // garbage collection
304 inline bool is_gc_marked() const;
305
306 // Forward pointer operations for scavenge
307 inline bool is_forwarded() const;
308 inline bool is_self_forwarded() const;
309
310 inline void forward_to(oop p);
311 inline void forward_to_self();
312
313 // Like "forward_to", but inserts the forwarding pointer atomically.
314 // Exactly one thread succeeds in inserting the forwarding pointer, and
315 // this call returns null for that thread; any other thread has the
316 // value of the forwarding pointer returned and does not modify "this".
317 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
318 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
319
320 inline oop forwardee() const;
321 inline oop forwardee(markWord header) const;
322
323 inline void unset_self_forwarded();
324 inline void reset_forwarded();
325
326 // Age of object during scavenge
327 inline uint age() const;
328 inline void incr_age();
329
330 template <typename OopClosureType>
331 inline void oop_iterate(OopClosureType* cl);
332
333 template <typename OopClosureType>
334 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
335
336 template <typename OopClosureType>
337 inline size_t oop_iterate_size(OopClosureType* cl);
338
339 template <typename OopClosureType>
340 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
341
342 template <typename OopClosureType>
343 inline void oop_iterate_backwards(OopClosureType* cl);
344
345 template <typename OopClosureType>
346 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
347
348 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
349
350 // identity hash; returns the identity hash key (computes it if necessary)
351 inline intptr_t identity_hash();
352 intptr_t slow_identity_hash();
353 inline bool fast_no_hash_check();
354
355 // Initialize identity hash code in hash word of object copy from original object.
356 // Returns true if the object has been expanded, false otherwise.
357 inline void initialize_hash_if_necessary(oop obj);
358 // For CDS only.
359 markWord initialize_hash_if_necessary(oop obj, Klass* k, markWord m);
360
361 // marks are forwarded to stack when object is locked
362 inline bool has_displaced_mark() const;
363 inline markWord displaced_mark() const;
364 inline void set_displaced_mark(markWord m);
365
366 // Checks if the mark word needs to be preserved
367 inline bool mark_must_be_preserved() const;
368 inline bool mark_must_be_preserved(markWord m) const;
369
370 inline static bool has_klass_gap() {
371 return ObjLayout::oop_has_klass_gap();
372 }
373
374 // for code generation
375 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
376 static int klass_offset_in_bytes() {
377 assert(!UseCompactObjectHeaders, "don't use this with compact headers");
378 return (int)offset_of(oopDesc, _compressed_klass);
379 }
380 static int klass_gap_offset_in_bytes() {
381 assert(has_klass_gap(), "only applicable to compressed klass pointers");
382 if (UseCompactObjectHeaders) {
383 return base_offset_in_bytes();
384 } else {
385 return klass_offset_in_bytes() + sizeof(narrowKlass);
386 }
387 }
388
389 static int base_offset_in_bytes() {
390 return ObjLayout::oop_base_offset_in_bytes();
391 }
392
393 // for error reporting
394 static void* load_oop_raw(oop obj, int offset);
395 };
396
397 // An oopDesc is not initialized via a constructor. Space is allocated in
398 // the Java heap, and static functions provided here on HeapWord* are used
399 // to fill in certain parts of that memory. The allocated memory is then
400 // treated as referring to an oopDesc. For that to be valid, the oopDesc
401 // class must have a trivial default constructor (C++14 3.8/1).
402 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
403
404 #endif // SHARE_OOPS_OOP_HPP