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