1 /*
2 * Copyright (c) 1997, 2023, 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/compressedKlass.hpp"
31 #include "oops/accessDecorators.hpp"
32 #include "oops/markWord.hpp"
33 #include "oops/metadata.hpp"
34 #include "runtime/atomic.hpp"
35 #include "utilities/globalDefinitions.hpp"
36 #include "utilities/macros.hpp"
37 #include <type_traits>
38
39 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe
40 // the format of Java objects so the fields can be accessed from C++.
41 // oopDesc is abstract.
42 // (see oopHierarchy for complete oop class hierarchy)
43 //
44 // no virtual functions allowed
45
46 // Forward declarations.
47 class OopClosure;
48 class PSPromotionManager;
49 class ParCompactionManager;
50
51 class oopDesc {
52 friend class VMStructs;
53 friend class JVMCIVMStructs;
54 private:
55 volatile markWord _mark;
56 union _metadata {
57 Klass* _klass;
58 narrowKlass _compressed_klass;
59 } _metadata;
60
61 // There may be ordering constraints on the initialization of fields that
62 // make use of the C++ copy/assign incorrect.
63 NONCOPYABLE(oopDesc);
64
65 public:
66 // Must be trivial; see verifying static assert after the class.
67 oopDesc() = default;
68
69 inline markWord mark() const;
70 inline markWord mark_acquire() const;
71 inline markWord* mark_addr() const;
72
73 inline void set_mark(markWord m);
74 static inline void set_mark(HeapWord* mem, markWord m);
75 static inline void release_set_mark(HeapWord* mem, markWord m);
76
77 inline void release_set_mark(markWord m);
78 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
79 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
80
81 // Used only to re-initialize the mark word (e.g., of promoted
82 // objects during a GC) -- requires a valid klass pointer
83 inline void init_mark();
84
85 inline Klass* klass() const;
86 inline Klass* klass_or_null() const;
87 inline Klass* klass_or_null_acquire() const;
88 // Get the raw value without any checks.
89 inline Klass* klass_raw() const;
90
91 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
92 inline void set_klass(Klass* k);
93 static inline void release_set_klass(HeapWord* mem, Klass* k);
94
95 // For klass field compression
96 static inline void set_klass_gap(HeapWord* mem, int z);
97
98 // size of object header, aligned to platform wordSize
99 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
100
101 // Returns whether this is an instance of k or an instance of a subclass of k
102 inline bool is_a(Klass* k) const;
103
104 // Returns the actual oop size of the object in machine words
105 inline size_t size();
106
107 // Sometimes (for complicated concurrency-related reasons), it is useful
108 // to be able to figure out the size of an object knowing its klass.
109 inline size_t size_given_klass(Klass* klass);
110
111 // type test operations (inlined in oop.inline.hpp)
112 inline bool is_instance() const;
113 inline bool is_instanceRef() const;
114 inline bool is_stackChunk() const;
115 inline bool is_array() const;
116 inline bool is_objArray() const;
117 inline bool is_typeArray() const;
118
119 // type test operations that don't require inclusion of oop.inline.hpp.
120 bool is_instance_noinline() const;
121 bool is_instanceRef_noinline() const;
122 bool is_stackChunk_noinline() const;
123 bool is_array_noinline() const;
124 bool is_objArray_noinline() const;
125 bool is_typeArray_noinline() const;
126
127 protected:
128 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
129
130 public:
131 template<typename T>
132 inline T* field_addr(int offset) const;
133
134 template <typename T> inline size_t field_offset(T* p) const;
135
136 // Standard compare function returns negative value if o1 < o2
137 // 0 if o1 == o2
138 // positive value if o1 > o2
139 inline static int compare(oop o1, oop o2) {
140 void* o1_addr = (void*)o1;
141 void* o2_addr = (void*)o2;
142 if (o1_addr < o2_addr) {
143 return -1;
144 } else if (o1_addr > o2_addr) {
145 return 1;
146 } else {
147 return 0;
148 }
149 }
150
151 // Access to fields in a instanceOop through these methods.
152 template<DecoratorSet decorators>
153 oop obj_field_access(int offset) const;
154 oop obj_field(int offset) const;
155
156 void obj_field_put(int offset, oop value);
157 void obj_field_put_raw(int offset, oop value);
158 void obj_field_put_volatile(int offset, oop value);
159 template<DecoratorSet decorators>
160 void obj_field_put_access(int offset, oop value);
161
162 Metadata* metadata_field(int offset) const;
163 void metadata_field_put(int offset, Metadata* value);
164
165 Metadata* metadata_field_acquire(int offset) const;
166 void release_metadata_field_put(int offset, Metadata* value);
167
168 jbyte byte_field(int offset) const;
169 void byte_field_put(int offset, jbyte contents);
170
171 jchar char_field(int offset) const;
172 void char_field_put(int offset, jchar contents);
173
174 jboolean bool_field(int offset) const;
175 void bool_field_put(int offset, jboolean contents);
176 jboolean bool_field_volatile(int offset) const;
177 void bool_field_put_volatile(int offset, jboolean contents);
178
179 jint int_field(int offset) const;
180 void int_field_put(int offset, jint contents);
181
182 jshort short_field(int offset) const;
183 void short_field_put(int offset, jshort contents);
184
185 jlong long_field(int offset) const;
186 void long_field_put(int offset, jlong contents);
187
188 jfloat float_field(int offset) const;
189 void float_field_put(int offset, jfloat contents);
190
191 jdouble double_field(int offset) const;
192 void double_field_put(int offset, jdouble contents);
193
194 address address_field(int offset) const;
195 void address_field_put(int offset, address contents);
196
197 oop obj_field_acquire(int offset) const;
198 void release_obj_field_put(int offset, oop value);
199
200 jbyte byte_field_acquire(int offset) const;
201 void release_byte_field_put(int offset, jbyte contents);
202
203 jchar char_field_acquire(int offset) const;
204 void release_char_field_put(int offset, jchar contents);
205
206 jboolean bool_field_acquire(int offset) const;
207 void release_bool_field_put(int offset, jboolean contents);
208
209 jint int_field_acquire(int offset) const;
210 void release_int_field_put(int offset, jint contents);
211
212 jshort short_field_acquire(int offset) const;
213 void release_short_field_put(int offset, jshort contents);
214
215 jlong long_field_acquire(int offset) const;
216 void release_long_field_put(int offset, jlong contents);
217
218 jfloat float_field_acquire(int offset) const;
219 void release_float_field_put(int offset, jfloat contents);
220
221 jdouble double_field_acquire(int offset) const;
222 void release_double_field_put(int offset, jdouble contents);
223
224 address address_field_acquire(int offset) const;
225 void release_address_field_put(int offset, address contents);
226
227 // printing functions for VM debugging
228 void print_on(outputStream* st) const; // First level print
229 void print_value_on(outputStream* st) const; // Second level print.
230 void print_address_on(outputStream* st) const; // Address printing
231 void print_name_on(outputStream* st) const; // External name printing.
232
233 // printing on default output stream
234 void print();
235 void print_value();
236 void print_address();
237
238 // return the print strings
239 char* print_string();
240 char* print_value_string();
241
242 // verification operations
243 static void verify_on(outputStream* st, oopDesc* oop_desc);
244 static void verify(oopDesc* oopDesc);
245
246 // locking operations
247 inline bool is_locked() const;
248 inline bool is_unlocked() const;
249
250 // asserts and guarantees
251 static bool is_oop(oop obj, bool ignore_mark_word = false);
252 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
253
254 // garbage collection
255 inline bool is_gc_marked() const;
256
257 // Forward pointer operations for scavenge
258 inline bool is_forwarded() const;
259
260 inline void forward_to(oop p);
261
262 // Like "forward_to", but inserts the forwarding pointer atomically.
263 // Exactly one thread succeeds in inserting the forwarding pointer, and
264 // this call returns null for that thread; any other thread has the
265 // value of the forwarding pointer returned and does not modify "this".
266 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
267
268 inline oop forwardee() const;
269
270 // Age of object during scavenge
271 inline uint age() const;
272 inline void incr_age();
273
274 template <typename OopClosureType>
275 inline void oop_iterate(OopClosureType* cl);
276
277 template <typename OopClosureType>
278 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
279
280 template <typename OopClosureType>
281 inline size_t oop_iterate_size(OopClosureType* cl);
282
283 template <typename OopClosureType>
284 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
285
286 template <typename OopClosureType>
287 inline void oop_iterate_backwards(OopClosureType* cl);
288
289 template <typename OopClosureType>
290 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
291
292 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
293
294 // identity hash; returns the identity hash key (computes it if necessary)
295 inline intptr_t identity_hash();
296 intptr_t slow_identity_hash();
297 inline bool fast_no_hash_check();
298
299 // marks are forwarded to stack when object is locked
300 inline bool has_displaced_mark() const;
301 inline markWord displaced_mark() const;
302 inline void set_displaced_mark(markWord m);
303
304 // Checks if the mark word needs to be preserved
305 inline bool mark_must_be_preserved() const;
306 inline bool mark_must_be_preserved(markWord m) const;
307
308 static bool has_klass_gap();
309
310 // for code generation
311 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
312 static int klass_offset_in_bytes() { return (int)offset_of(oopDesc, _metadata._klass); }
313 static int klass_gap_offset_in_bytes() {
314 assert(has_klass_gap(), "only applicable to compressed klass pointers");
315 return klass_offset_in_bytes() + sizeof(narrowKlass);
316 }
317
318 // for error reporting
319 static void* load_klass_raw(oop obj);
320 static void* load_oop_raw(oop obj, int offset);
321
322 DEBUG_ONLY(bool size_might_change();)
323 };
324
325 // An oopDesc is not initialized via a constructor. Space is allocated in
326 // the Java heap, and static functions provided here on HeapWord* are used
327 // to fill in certain parts of that memory. The allocated memory is then
328 // treated as referring to an oopDesc. For that to be valid, the oopDesc
329 // class must have a trivial default constructor (C++14 3.8/1).
330 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
331
332 #endif // SHARE_OOPS_OOP_HPP