1 /*
2 * Copyright (c) 1997, 2024, 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 "oops/objLayout.hpp"
35 #include "runtime/atomic.hpp"
36 #include "utilities/globalDefinitions.hpp"
37 #include "utilities/macros.hpp"
38 #include <type_traits>
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 // oopDesc::_mark - the "oop mark word" encoding to be found separately in markWord.hpp
48 //
49 // oopDesc::_metadata - encodes the object's klass pointer, as a raw pointer in "_klass"
50 // or compressed pointer in "_compressed_klass"
51 //
52 // The overall size of the _metadata field is dependent on "UseCompressedClassPointers",
53 // hence the terms "narrow" (32 bits) vs "wide" (64 bits).
54 //
55
56
57 // Forward declarations.
58 class OopClosure;
59 class PSPromotionManager;
60 class ParCompactionManager;
61
62 class oopDesc {
63 friend class VMStructs;
64 friend class JVMCIVMStructs;
65 private:
66 volatile markWord _mark;
67 union _metadata {
68 Klass* _klass;
69 narrowKlass _compressed_klass;
70 } _metadata;
71
72 // There may be ordering constraints on the initialization of fields that
73 // make use of the C++ copy/assign incorrect.
74 NONCOPYABLE(oopDesc);
75
76 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order);
77
78 public:
79 // Must be trivial; see verifying static assert after the class.
80 oopDesc() = default;
81
82 inline markWord mark() const;
83 inline markWord mark_acquire() const;
84 inline markWord* mark_addr() const;
85
86 inline void set_mark(markWord m);
87 static inline void set_mark(HeapWord* mem, markWord m);
88 static inline void release_set_mark(HeapWord* mem, markWord m);
89
90 inline void release_set_mark(markWord m);
91 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
92 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
93
94 // Returns the prototype mark that should be used for this object.
95 inline markWord prototype_mark() const;
96
97 // Used only to re-initialize the mark word (e.g., of promoted
98 // objects during a GC) -- requires a valid klass pointer
99 inline void init_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 void set_klass(Klass* k);
109 static inline void release_set_klass(HeapWord* mem, Klass* k);
110
111 // For klass field compression
112 static inline void set_klass_gap(HeapWord* mem, int z);
113
114 // Size of object header, aligned to platform wordSize
115 static int header_size() {
116 if (UseCompactObjectHeaders) {
117 return sizeof(markWord) / HeapWordSize;
118 } else {
119 return sizeof(oopDesc) / HeapWordSize;
120 }
121 }
122
123 // Returns whether this is an instance of k or an instance of a subclass of k
124 inline bool is_a(Klass* k) const;
125
126 // Returns the actual oop size of the object in machine words
127 inline size_t size();
128
129 // Sometimes (for complicated concurrency-related reasons), it is useful
130 // to be able to figure out the size of an object knowing its klass.
131 inline size_t size_given_klass(Klass* klass);
132
133 // type test operations (inlined in oop.inline.hpp)
134 inline bool is_instance() const;
135 inline bool is_inline_type() const;
136 inline bool is_instanceRef() const;
137 inline bool is_stackChunk() const;
138 inline bool is_array() const;
139 inline bool is_objArray() const;
140 inline bool is_typeArray() const;
141 inline bool is_flatArray() const;
142 inline bool is_null_free_array() const;
143
144 // type test operations that don't require inclusion of oop.inline.hpp.
145 bool is_instance_noinline() const;
146 bool is_instanceRef_noinline() const;
147 bool is_stackChunk_noinline() const;
148 bool is_array_noinline() const;
149 bool is_objArray_noinline() const;
150 bool is_typeArray_noinline() const;
151 bool is_flatArray_noinline() const;
152 bool is_null_free_array_noinline() const;
153
154 protected:
155 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
156
157 public:
158 template<typename T>
159 inline T* field_addr(int offset) const;
160
161 template <typename T> inline size_t field_offset(T* p) const;
162
163 // Standard compare function returns negative value if o1 < o2
164 // 0 if o1 == o2
165 // positive value if o1 > o2
166 inline static int compare(oop o1, oop o2) {
167 void* o1_addr = (void*)o1;
168 void* o2_addr = (void*)o2;
169 if (o1_addr < o2_addr) {
170 return -1;
171 } else if (o1_addr > o2_addr) {
172 return 1;
173 } else {
174 return 0;
175 }
176 }
177
178 // Access to fields in a instanceOop through these methods.
179 template<DecoratorSet decorators>
180 oop obj_field_access(int offset) const;
181 oop obj_field(int offset) const;
182
183 void obj_field_put(int offset, oop value);
184 void obj_field_put_raw(int offset, oop value);
185 void obj_field_put_volatile(int offset, oop value);
186 template<DecoratorSet decorators>
187 void obj_field_put_access(int offset, oop value);
188
189 Metadata* metadata_field(int offset) const;
190 void metadata_field_put(int offset, Metadata* value);
191
192 Metadata* metadata_field_acquire(int offset) const;
193 void release_metadata_field_put(int offset, Metadata* value);
194
195 jbyte byte_field(int offset) const;
196 void byte_field_put(int offset, jbyte contents);
197
198 jchar char_field(int offset) const;
199 void char_field_put(int offset, jchar contents);
200
201 jboolean bool_field(int offset) const;
202 void bool_field_put(int offset, jboolean contents);
203 jboolean bool_field_volatile(int offset) const;
204 void bool_field_put_volatile(int offset, jboolean contents);
205
206 jint int_field(int offset) const;
207 void int_field_put(int offset, jint contents);
208
209 jshort short_field(int offset) const;
210 void short_field_put(int offset, jshort contents);
211
212 jlong long_field(int offset) const;
213 void long_field_put(int offset, jlong contents);
214
215 jfloat float_field(int offset) const;
216 void float_field_put(int offset, jfloat contents);
217
218 jdouble double_field(int offset) const;
219 void double_field_put(int offset, jdouble contents);
220
221 address address_field(int offset) const;
222 void address_field_put(int offset, address contents);
223
224 oop obj_field_acquire(int offset) const;
225 void release_obj_field_put(int offset, oop value);
226
227 jbyte byte_field_acquire(int offset) const;
228 void release_byte_field_put(int offset, jbyte contents);
229
230 jchar char_field_acquire(int offset) const;
231 void release_char_field_put(int offset, jchar contents);
232
233 jboolean bool_field_acquire(int offset) const;
234 void release_bool_field_put(int offset, jboolean contents);
235
236 jint int_field_relaxed(int offset) const;
237 void int_field_put_relaxed(int offset, jint contents);
238 jint int_field_acquire(int offset) const;
239 void release_int_field_put(int offset, jint contents);
240
241 jshort short_field_acquire(int offset) const;
242 void release_short_field_put(int offset, jshort contents);
243
244 jlong long_field_acquire(int offset) const;
245 void release_long_field_put(int offset, jlong contents);
246
247 jfloat float_field_acquire(int offset) const;
248 void release_float_field_put(int offset, jfloat contents);
249
250 jdouble double_field_acquire(int offset) const;
251 void release_double_field_put(int offset, jdouble contents);
252
253 address address_field_acquire(int offset) const;
254 void release_address_field_put(int offset, address contents);
255
256 // printing functions for VM debugging
257 void print_on(outputStream* st) const; // First level print
258 void print_value_on(outputStream* st) const; // Second level print.
259 void print_address_on(outputStream* st) const; // Address printing
260 void print_name_on(outputStream* st) const; // External name printing.
261
262 // printing on default output stream
263 void print();
264 void print_value();
265 void print_address();
266
267 // return the print strings
268 char* print_string();
269 char* print_value_string();
270
271 // verification operations
272 static void verify_on(outputStream* st, oopDesc* oop_desc);
273 static void verify(oopDesc* oopDesc);
274
275 // locking operations
276 inline bool is_locked() const;
277 inline bool is_unlocked() const;
278
279 // asserts and guarantees
280 static bool is_oop(oop obj, bool ignore_mark_word = false);
281 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
282
283 // garbage collection
284 inline bool is_gc_marked() const;
285
286 // Forward pointer operations for scavenge
287 inline bool is_forwarded() const;
288 inline bool is_self_forwarded() const;
289
290 inline void forward_to(oop p);
291 inline void forward_to_self();
292
293 // Like "forward_to", but inserts the forwarding pointer atomically.
294 // Exactly one thread succeeds in inserting the forwarding pointer, and
295 // this call returns null for that thread; any other thread has the
296 // value of the forwarding pointer returned and does not modify "this".
297 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
298 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
299
300 inline oop forwardee() const;
301 inline oop forwardee(markWord header) const;
302
303 inline void unset_self_forwarded();
304
305 // Age of object during scavenge
306 inline uint age() const;
307 inline void incr_age();
308
309 template <typename OopClosureType>
310 inline void oop_iterate(OopClosureType* cl);
311
312 template <typename OopClosureType>
313 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
314
315 template <typename OopClosureType>
316 inline size_t oop_iterate_size(OopClosureType* cl);
317
318 template <typename OopClosureType>
319 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
320
321 template <typename OopClosureType>
322 inline void oop_iterate_backwards(OopClosureType* cl);
323
324 template <typename OopClosureType>
325 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
326
327 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
328
329 // identity hash; returns the identity hash key (computes it if necessary)
330 inline intptr_t identity_hash();
331 intptr_t slow_identity_hash();
332 inline bool fast_no_hash_check();
333
334 // marks are forwarded to stack when object is locked
335 inline bool has_displaced_mark() const;
336 inline markWord displaced_mark() const;
337 inline void set_displaced_mark(markWord m);
338
339 // Checks if the mark word needs to be preserved
340 inline bool mark_must_be_preserved() const;
341 inline bool mark_must_be_preserved(markWord m) const;
342
343 inline static bool has_klass_gap() {
344 return ObjLayout::oop_has_klass_gap();
345 }
346
347 // for code generation
348 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
349 static int klass_offset_in_bytes() {
350 #ifdef _LP64
351 if (UseCompactObjectHeaders) {
352 // NOTE: The only places where this is used with compact headers are the C2
353 // compiler and JVMCI.
354 return mark_offset_in_bytes() + markWord::klass_offset_in_bytes;
355 } else
356 #endif
357 {
358 return (int)offset_of(oopDesc, _metadata._klass);
359 }
360 }
361 static int klass_gap_offset_in_bytes() {
362 assert(has_klass_gap(), "only applicable to compressed klass pointers");
363 return klass_offset_in_bytes() + sizeof(narrowKlass);
364 }
365
366 static int base_offset_in_bytes() {
367 return ObjLayout::oop_base_offset_in_bytes();
368 }
369
370 // for error reporting
371 static void* load_oop_raw(oop obj, int offset);
372 };
373
374 // An oopDesc is not initialized via a constructor. Space is allocated in
375 // the Java heap, and static functions provided here on HeapWord* are used
376 // to fill in certain parts of that memory. The allocated memory is then
377 // treated as referring to an oopDesc. For that to be valid, the oopDesc
378 // class must have a trivial default constructor (C++14 3.8/1).
379 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
380
381 #endif // SHARE_OOPS_OOP_HPP