1 /*
2 * Copyright (c) 1997, 2021, 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/markWord.hpp"
32 #include "oops/metadata.hpp"
33 #include "runtime/atomic.hpp"
34 #include "utilities/globalDefinitions.hpp"
35 #include "utilities/macros.hpp"
36 #include <type_traits>
37
38 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe
39 // the format of Java objects so the fields can be accessed from C++.
40 // oopDesc is abstract.
41 // (see oopHierarchy for complete oop class hierarchy)
42 //
43 // no virtual functions allowed
44 //
45 // oopDesc::_mark - the "oop mark word" encoding to be found separately in markWord.hpp
46 //
47 // oopDesc::_metadata - encodes the object's klass pointer, as a raw pointer in "_klass"
48 // or compressed pointer in "_compressed_klass"
49 //
50 // The overall size of the _metadata field is dependent on "UseCompressedClassPointers",
51 // hence the terms "narrow" (32 bits) vs "wide" (64 bits).
52 //
53
54
55 // Forward declarations.
56 class OopClosure;
57 class FilteringClosure;
58
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 public:
77 // Must be trivial; see verifying static assert after the class.
78 oopDesc() = default;
79
80 inline markWord mark() const;
81 inline markWord mark_acquire() const;
82 inline markWord* mark_addr() const;
83
84 inline void set_mark(markWord m);
85 static inline void set_mark(HeapWord* mem, markWord m);
86
87 inline void release_set_mark(markWord m);
88 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
89 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
90
91 // Used only to re-initialize the mark word (e.g., of promoted
92 // objects during a GC) -- requires a valid klass pointer
93 inline void init_mark();
94
95 inline Klass* klass() const;
96 inline Klass* klass_or_null() const;
97 inline Klass* klass_or_null_acquire() const;
98
99 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
100 inline void set_klass(Klass* k);
101 static inline void release_set_klass(HeapWord* mem, Klass* k);
102
103 // For klass field compression
104 inline int klass_gap() const;
105 inline void set_klass_gap(int z);
106 static inline void set_klass_gap(HeapWord* mem, int z);
107
108 // size of object header, aligned to platform wordSize
109 static int header_size() { return sizeof(oopDesc)/HeapWordSize; }
110
111 // Returns whether this is an instance of k or an instance of a subclass of k
112 inline bool is_a(Klass* k) const;
113
114 // Returns the actual oop size of the object
115 inline int size();
116
117 // Sometimes (for complicated concurrency-related reasons), it is useful
118 // to be able to figure out the size of an object knowing its klass.
119 inline int size_given_klass(Klass* klass);
120
121 // type test operations (inlined in oop.inline.hpp)
122 inline bool is_instance() const;
123 inline bool is_array() const;
124 inline bool is_objArray() const;
125 inline bool is_typeArray() const;
126 inline bool is_inline_type() const;
127 inline bool is_flatArray() const;
128 inline bool is_null_free_array() const;
129
130 // type test operations that don't require inclusion of oop.inline.hpp.
131 bool is_instance_noinline() const;
132 bool is_array_noinline() const;
133 bool is_objArray_noinline() const;
134 bool is_typeArray_noinline() const;
135 bool is_flatArray_noinline() const;
136 bool is_null_free_array_noinline() const;
137
138 protected:
139 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
140
141 public:
142 // field addresses in oop
143 inline void* field_addr(int offset) const;
144
145 // Need this as public for garbage collection.
146 template <class T> inline T* obj_field_addr(int offset) const;
147
148 template <typename T> inline size_t field_offset(T* p) const;
149
150 // Standard compare function returns negative value if o1 < o2
151 // 0 if o1 == o2
152 // positive value if o1 > o2
153 inline static int compare(oop o1, oop o2) {
154 void* o1_addr = (void*)o1;
155 void* o2_addr = (void*)o2;
156 if (o1_addr < o2_addr) {
157 return -1;
158 } else if (o1_addr > o2_addr) {
159 return 1;
160 } else {
161 return 0;
162 }
163 }
164
165 // Access to fields in a instanceOop through these methods.
166 template <DecoratorSet decorator>
167 oop obj_field_access(int offset) const;
168 oop obj_field(int offset) const;
169 void obj_field_put(int offset, oop value);
170 void obj_field_put_raw(int offset, oop value);
171 void obj_field_put_volatile(int offset, oop value);
172
173 Metadata* metadata_field(int offset) const;
174 void metadata_field_put(int offset, Metadata* value);
175
176 Metadata* metadata_field_acquire(int offset) const;
177 void release_metadata_field_put(int offset, Metadata* value);
178
179 jbyte byte_field(int offset) const;
180 void byte_field_put(int offset, jbyte contents);
181
182 jchar char_field(int offset) const;
183 void char_field_put(int offset, jchar contents);
184
185 jboolean bool_field(int offset) const;
186 void bool_field_put(int offset, jboolean contents);
187 jboolean bool_field_volatile(int offset) const;
188 void bool_field_put_volatile(int offset, jboolean contents);
189
190 jint int_field(int offset) const;
191 void int_field_put(int offset, jint contents);
192
193 jshort short_field(int offset) const;
194 void short_field_put(int offset, jshort contents);
195
196 jlong long_field(int offset) const;
197 void long_field_put(int offset, jlong contents);
198
199 jfloat float_field(int offset) const;
200 void float_field_put(int offset, jfloat contents);
201
202 jdouble double_field(int offset) const;
203 void double_field_put(int offset, jdouble contents);
204
205 address address_field(int offset) const;
206 void address_field_put(int offset, address contents);
207
208 oop obj_field_acquire(int offset) const;
209 void release_obj_field_put(int offset, oop value);
210
211 jbyte byte_field_acquire(int offset) const;
212 void release_byte_field_put(int offset, jbyte contents);
213
214 jchar char_field_acquire(int offset) const;
215 void release_char_field_put(int offset, jchar contents);
216
217 jboolean bool_field_acquire(int offset) const;
218 void release_bool_field_put(int offset, jboolean contents);
219
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
243 // printing on default output stream
244 void print();
245 void print_value();
246 void print_address();
247
248 // return the print strings
249 char* print_string();
250 char* print_value_string();
251
252 // verification operations
253 static void verify_on(outputStream* st, oopDesc* oop_desc);
254 static void verify(oopDesc* oopDesc);
255
256 // locking operations
257 inline bool is_locked() const;
258 inline bool is_unlocked() const;
259
260 // asserts and guarantees
261 static bool is_oop(oop obj, bool ignore_mark_word = false);
262 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
263
264 // garbage collection
265 inline bool is_gc_marked() const;
266
267 // Forward pointer operations for scavenge
268 inline bool is_forwarded() const;
269
270 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
271
272 inline void forward_to(oop p);
273
274 // Like "forward_to", but inserts the forwarding pointer atomically.
275 // Exactly one thread succeeds in inserting the forwarding pointer, and
276 // this call returns "NULL" for that thread; any other thread has the
277 // value of the forwarding pointer returned and does not modify "this".
278 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
279
280 inline oop forwardee() const;
281
282 // Age of object during scavenge
283 inline uint age() const;
284 inline void incr_age();
285
286 template <typename OopClosureType>
287 inline void oop_iterate(OopClosureType* cl);
288
289 template <typename OopClosureType>
290 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
291
292 template <typename OopClosureType>
293 inline int oop_iterate_size(OopClosureType* cl);
294
295 template <typename OopClosureType>
296 inline int oop_iterate_size(OopClosureType* cl, MemRegion mr);
297
298 template <typename OopClosureType>
299 inline void oop_iterate_backwards(OopClosureType* cl);
300
301 template <typename OopClosureType>
302 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
303
304 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
305
306 // identity hash; returns the identity hash key (computes it if necessary)
307 inline intptr_t identity_hash();
308 intptr_t slow_identity_hash();
309
310 // marks are forwarded to stack when object is locked
311 inline bool has_displaced_mark() const;
312 inline markWord displaced_mark() const;
313 inline void set_displaced_mark(markWord m);
314
315 // Checks if the mark word needs to be preserved
316 inline bool mark_must_be_preserved() const;
317 inline bool mark_must_be_preserved(markWord m) const;
318
319 static bool has_klass_gap();
320
321 // for code generation
322 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); }
323 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); }
324 static int klass_gap_offset_in_bytes() {
325 assert(has_klass_gap(), "only applicable to compressed klass pointers");
326 return klass_offset_in_bytes() + sizeof(narrowKlass);
327 }
328
329 // for error reporting
330 static void* load_klass_raw(oop obj);
331 static void* load_oop_raw(oop obj, int offset);
332
333 // Avoid include gc_globals.hpp in oop.inline.hpp
334 DEBUG_ONLY(bool get_UseParallelGC();)
335 DEBUG_ONLY(bool get_UseG1GC();)
336 };
337
338 // An oopDesc is not initialized via a constructor. Space is allocated in
339 // the Java heap, and static functions provided here on HeapWord* are used
340 // to fill in certain parts of that memory. The allocated memory is then
341 // treated as referring to an oopDesc. For that to be valid, the oopDesc
342 // class must have a trivial default constructor (C++14 3.8/1).
343 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
344
345 #endif // SHARE_OOPS_OOP_HPP