1 /*
2 * Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
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/accessDecorators.hpp"
31 #include "oops/compressedKlass.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
39 #include <type_traits>
40
41 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe
42 // the format of Java objects so the fields can be accessed from C++.
43 // oopDesc is abstract.
44 // (see oopHierarchy for complete oop class hierarchy)
45 //
46 // no virtual functions allowed
47
48 class oopDesc {
49 friend class VMStructs;
50 friend class JVMCIVMStructs;
51 private:
52 volatile markWord _mark;
53 union _metadata {
54 Klass* _klass;
55 narrowKlass _compressed_klass;
56 } _metadata;
57
58 // There may be ordering constraints on the initialization of fields that
59 // make use of the C++ copy/assign incorrect.
60 NONCOPYABLE(oopDesc);
61
62 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order);
63
64 public:
65 // Must be trivial; see verifying static assert after the class.
66 oopDesc() = default;
67
68 inline markWord mark() const;
69 inline markWord mark_acquire() const;
70 inline markWord* mark_addr() const;
71
72 inline void set_mark(markWord m);
73 static inline void set_mark(HeapWord* mem, 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 narrowKlass narrow_klass() const;
95 inline void set_klass(Klass* k);
96 static inline void release_set_klass(HeapWord* mem, Klass* k);
97
98 // For klass field compression
99 static inline void set_klass_gap(HeapWord* mem, int z);
100
101 // Size of object header, aligned to platform wordSize
102 static int header_size() {
103 if (UseCompactObjectHeaders) {
104 return sizeof(markWord) / HeapWordSize;
105 } else {
106 return sizeof(oopDesc) / HeapWordSize;
107 }
108 }
109
110 // Returns whether this is an instance of k or an instance of a subclass of k
111 inline bool is_a(Klass* k) const;
112
113 // Returns the actual oop size of the object in machine words
114 inline size_t size();
115
116 // Sometimes (for complicated concurrency-related reasons), it is useful
117 // to be able to figure out the size of an object knowing its klass.
118 inline size_t size_given_klass(Klass* klass);
119
120 // type test operations (inlined in oop.inline.hpp)
121 inline bool is_instance() const;
122 inline bool is_instanceRef() const;
123 inline bool is_stackChunk() const;
124 inline bool is_array() const;
125 inline bool is_objArray() const;
126 inline bool is_typeArray() const;
127
128 // type test operations that don't require inclusion of oop.inline.hpp.
129 bool is_instance_noinline() const;
130 bool is_instanceRef_noinline() const;
131 bool is_stackChunk_noinline() const;
132 bool is_array_noinline() const;
133 bool is_objArray_noinline() const;
134 bool is_typeArray_noinline() const;
135
136 protected:
137 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
138
139 public:
140 template<typename T>
141 inline T* field_addr(int offset) const;
142
143 template <typename T> inline size_t field_offset(T* p) const;
144
145 // Standard compare function returns negative value if o1 < o2
146 // 0 if o1 == o2
147 // positive value if o1 > o2
148 inline static int compare(oop o1, oop o2) {
149 void* o1_addr = (void*)o1;
150 void* o2_addr = (void*)o2;
151 if (o1_addr < o2_addr) {
152 return -1;
153 } else if (o1_addr > o2_addr) {
154 return 1;
155 } else {
156 return 0;
157 }
158 }
159
160 // Access to fields in a instanceOop through these methods.
161 template<DecoratorSet decorators>
162 oop obj_field_access(int offset) const;
163 oop obj_field(int offset) const;
164
165 void obj_field_put(int offset, oop value);
166 void obj_field_put_raw(int offset, oop value);
167 void obj_field_put_volatile(int offset, oop value);
168 template<DecoratorSet decorators>
169 void obj_field_put_access(int offset, oop value);
170
171 Metadata* metadata_field(int offset) const;
172 void metadata_field_put(int offset, Metadata* value);
173
174 Metadata* metadata_field_acquire(int offset) const;
175 void release_metadata_field_put(int offset, Metadata* value);
176
177 jbyte byte_field(int offset) const;
178 void byte_field_put(int offset, jbyte contents);
179
180 jchar char_field(int offset) const;
181 void char_field_put(int offset, jchar contents);
182
183 jboolean bool_field(int offset) const;
184 void bool_field_put(int offset, jboolean contents);
185 jboolean bool_field_volatile(int offset) const;
186 void bool_field_put_volatile(int offset, jboolean contents);
187
188 jint int_field(int offset) const;
189 void int_field_put(int offset, jint contents);
190
191 jshort short_field(int offset) const;
192 void short_field_put(int offset, jshort contents);
193
194 jlong long_field(int offset) const;
195 void long_field_put(int offset, jlong contents);
196
197 jfloat float_field(int offset) const;
198 void float_field_put(int offset, jfloat contents);
199
200 jdouble double_field(int offset) const;
201 void double_field_put(int offset, jdouble contents);
202
203 address address_field(int offset) const;
204 void address_field_put(int offset, address contents);
205
206 oop obj_field_acquire(int offset) const;
207 void release_obj_field_put(int offset, oop value);
208
209 jbyte byte_field_acquire(int offset) const;
210 void release_byte_field_put(int offset, jbyte contents);
211
212 jchar char_field_acquire(int offset) const;
213 void release_char_field_put(int offset, jchar contents);
214
215 jboolean bool_field_acquire(int offset) const;
216 void release_bool_field_put(int offset, jboolean contents);
217
218 jint int_field_relaxed(int offset) const;
219 void int_field_put_relaxed(int offset, jint contents);
220 jint int_field_acquire(int offset) const;
221 void release_int_field_put(int offset, jint contents);
222
223 jshort short_field_acquire(int offset) const;
224 void release_short_field_put(int offset, jshort contents);
225
226 jlong long_field_acquire(int offset) const;
227 void release_long_field_put(int offset, jlong contents);
228
229 jfloat float_field_acquire(int offset) const;
230 void release_float_field_put(int offset, jfloat contents);
231
232 jdouble double_field_acquire(int offset) const;
233 void release_double_field_put(int offset, jdouble contents);
234
235 address address_field_acquire(int offset) const;
236 void release_address_field_put(int offset, address contents);
237
238 // printing functions for VM debugging
239 void print_on(outputStream* st) const; // First level print
240 void print_value_on(outputStream* st) const; // Second level print.
241 void print_address_on(outputStream* st) const; // Address printing
242 void print_name_on(outputStream* st) const; // External name printing.
243
244 // printing on default output stream
245 void print();
246 void print_value();
247 void print_address();
248
249 // return the print strings
250 char* print_string();
251 char* print_value_string();
252
253 // verification operations
254 static void verify_on(outputStream* st, oopDesc* oop_desc);
255 static void verify(oopDesc* oopDesc);
256
257 // locking operations
258 inline bool is_locked() const;
259 inline bool is_unlocked() const;
260
261 // asserts and guarantees
262 static bool is_oop(oop obj, bool ignore_mark_word = false);
263 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
264
265 // garbage collection
266 inline bool is_gc_marked() const;
267
268 // Forward pointer operations for scavenge
269 inline bool is_forwarded() const;
270 inline bool is_self_forwarded() const;
271
272 inline void forward_to(oop p);
273 inline void forward_to_self();
274
275 // Like "forward_to", but inserts the forwarding pointer atomically.
276 // Exactly one thread succeeds in inserting the forwarding pointer, and
277 // this call returns null for that thread; any other thread has the
278 // value of the forwarding pointer returned and does not modify "this".
279 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
280 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
281
282 inline oop forwardee() const;
283 inline oop forwardee(markWord header) const;
284
285 inline void unset_self_forwarded();
286
287 // Age of object during scavenge
288 inline uint age() const;
289 inline void incr_age();
290
291 template <typename OopClosureType>
292 inline void oop_iterate(OopClosureType* cl);
293
294 template <typename OopClosureType>
295 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
296
297 template <typename OopClosureType>
298 inline size_t oop_iterate_size(OopClosureType* cl);
299
300 template <typename OopClosureType>
301 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
302
303 template <typename OopClosureType>
304 inline void oop_iterate_backwards(OopClosureType* cl);
305
306 template <typename OopClosureType>
307 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
308
309 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
310
311 // identity hash; returns the identity hash key (computes it if necessary)
312 inline intptr_t identity_hash();
313 intptr_t slow_identity_hash();
314 inline bool fast_no_hash_check();
315
316 // marks are forwarded to stack when object is locked
317 inline bool has_displaced_mark() const;
318 inline markWord displaced_mark() const;
319 inline void set_displaced_mark(markWord m);
320
321 // Checks if the mark word needs to be preserved
322 inline bool mark_must_be_preserved() const;
323 inline bool mark_must_be_preserved(markWord m) const;
324
325 inline static bool has_klass_gap() {
326 return ObjLayout::oop_has_klass_gap();
327 }
328
329 // for code generation
330 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
331 static int klass_offset_in_bytes() {
332 #ifdef _LP64
333 if (UseCompactObjectHeaders) {
334 // NOTE: The only places where this is used with compact headers are the C2
335 // compiler and JVMCI.
336 return mark_offset_in_bytes() + markWord::klass_offset_in_bytes;
337 } else
338 #endif
339 {
340 return (int)offset_of(oopDesc, _metadata._klass);
341 }
342 }
343 static int klass_gap_offset_in_bytes() {
344 assert(has_klass_gap(), "only applicable to compressed klass pointers");
345 return klass_offset_in_bytes() + sizeof(narrowKlass);
346 }
347
348 static int base_offset_in_bytes() {
349 return ObjLayout::oop_base_offset_in_bytes();
350 }
351
352 // for error reporting
353 static void* load_oop_raw(oop obj, int offset);
354 };
355
356 // An oopDesc is not initialized via a constructor. Space is allocated in
357 // the Java heap, and static functions provided here on HeapWord* are used
358 // to fill in certain parts of that memory. The allocated memory is then
359 // treated as referring to an oopDesc. For that to be valid, the oopDesc
360 // class must have a trivial default constructor (C++14 3.8/1).
361 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
362
363 #endif // SHARE_OOPS_OOP_HPP