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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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 // Forward declarations.
46 class OopClosure;
47 class FilteringClosure;
48
49 class PSPromotionManager;
50 class ParCompactionManager;
51
52 class oopDesc {
53 friend class VMStructs;
54 friend class JVMCIVMStructs;
55 private:
56 volatile markWord _mark;
57 union _metadata {
58 Klass* _klass;
59 narrowKlass _compressed_klass;
60 } _metadata;
61
62 // There may be ordering constraints on the initialization of fields that
63 // make use of the C++ copy/assign incorrect.
64 NONCOPYABLE(oopDesc);
65
66 public:
67 // Must be trivial; see verifying static assert after the class.
68 oopDesc() = default;
69
70 inline markWord mark() const;
71 inline markWord mark_acquire() const;
72 inline markWord* mark_addr() const;
73
74 inline void set_mark(markWord m);
75 static inline void 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
89 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
90 inline void set_klass(Klass* k);
91 static inline void release_set_klass(HeapWord* mem, Klass* k);
92
93 // For klass field compression
94 static inline void set_klass_gap(HeapWord* mem, int z);
95
96 // size of object header, aligned to platform wordSize
97 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
98
99 // Returns whether this is an instance of k or an instance of a subclass of k
100 inline bool is_a(Klass* k) const;
101
102 // Returns the actual oop size of the object
103 inline size_t size();
104
105 // Sometimes (for complicated concurrency-related reasons), it is useful
106 // to be able to figure out the size of an object knowing its klass.
107 inline size_t size_given_klass(Klass* klass);
108
109 // type test operations (inlined in oop.inline.hpp)
110 inline bool is_instance() const;
111 inline bool is_array() const;
112 inline bool is_objArray() const;
113 inline bool is_typeArray() const;
114
115 // type test operations that don't require inclusion of oop.inline.hpp.
116 bool is_instance_noinline() const;
117 bool is_array_noinline() const;
118 bool is_objArray_noinline() const;
119 bool is_typeArray_noinline() const;
120
121 protected:
122 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
123
124 public:
125 template<typename T>
126 inline T* field_addr(int offset) const;
127
128 template <typename T> inline size_t field_offset(T* p) const;
129
130 // Standard compare function returns negative value if o1 < o2
131 // 0 if o1 == o2
132 // positive value if o1 > o2
133 inline static int compare(oop o1, oop o2) {
134 void* o1_addr = (void*)o1;
135 void* o2_addr = (void*)o2;
136 if (o1_addr < o2_addr) {
137 return -1;
138 } else if (o1_addr > o2_addr) {
139 return 1;
140 } else {
141 return 0;
142 }
143 }
144
145 // Access to fields in a instanceOop through these methods.
146 template <DecoratorSet decorator>
147 oop obj_field_access(int offset) const;
148 oop obj_field(int offset) const;
149 void obj_field_put(int offset, oop value);
150 void obj_field_put_raw(int offset, oop value);
151 void obj_field_put_volatile(int offset, oop value);
152
153 Metadata* metadata_field(int offset) const;
154 void metadata_field_put(int offset, Metadata* value);
155
156 Metadata* metadata_field_acquire(int offset) const;
157 void release_metadata_field_put(int offset, Metadata* value);
158
159 jbyte byte_field(int offset) const;
160 void byte_field_put(int offset, jbyte contents);
161
162 jchar char_field(int offset) const;
163 void char_field_put(int offset, jchar contents);
164
165 jboolean bool_field(int offset) const;
166 void bool_field_put(int offset, jboolean contents);
167 jboolean bool_field_volatile(int offset) const;
168 void bool_field_put_volatile(int offset, jboolean contents);
169
170 jint int_field(int offset) const;
171 void int_field_put(int offset, jint contents);
172
173 jshort short_field(int offset) const;
174 void short_field_put(int offset, jshort contents);
175
176 jlong long_field(int offset) const;
177 void long_field_put(int offset, jlong contents);
178
179 jfloat float_field(int offset) const;
180 void float_field_put(int offset, jfloat contents);
181
182 jdouble double_field(int offset) const;
183 void double_field_put(int offset, jdouble contents);
184
185 address address_field(int offset) const;
186 void address_field_put(int offset, address contents);
187
188 oop obj_field_acquire(int offset) const;
189 void release_obj_field_put(int offset, oop value);
190
191 jbyte byte_field_acquire(int offset) const;
192 void release_byte_field_put(int offset, jbyte contents);
193
194 jchar char_field_acquire(int offset) const;
195 void release_char_field_put(int offset, jchar contents);
196
197 jboolean bool_field_acquire(int offset) const;
198 void release_bool_field_put(int offset, jboolean contents);
199
200 jint int_field_acquire(int offset) const;
201 void release_int_field_put(int offset, jint contents);
202
203 jshort short_field_acquire(int offset) const;
204 void release_short_field_put(int offset, jshort contents);
205
206 jlong long_field_acquire(int offset) const;
207 void release_long_field_put(int offset, jlong contents);
208
209 jfloat float_field_acquire(int offset) const;
210 void release_float_field_put(int offset, jfloat contents);
211
212 jdouble double_field_acquire(int offset) const;
213 void release_double_field_put(int offset, jdouble contents);
214
215 address address_field_acquire(int offset) const;
216 void release_address_field_put(int offset, address contents);
217
218 // printing functions for VM debugging
219 void print_on(outputStream* st) const; // First level print
220 void print_value_on(outputStream* st) const; // Second level print.
221 void print_address_on(outputStream* st) const; // Address printing
222
223 // printing on default output stream
224 void print();
225 void print_value();
226 void print_address();
227
228 // return the print strings
229 char* print_string();
230 char* print_value_string();
231
232 // verification operations
233 static void verify_on(outputStream* st, oopDesc* oop_desc);
234 static void verify(oopDesc* oopDesc);
235
236 // locking operations
237 inline bool is_locked() const;
238 inline bool is_unlocked() const;
239
240 // asserts and guarantees
241 static bool is_oop(oop obj, bool ignore_mark_word = false);
242 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
243
244 // garbage collection
245 inline bool is_gc_marked() const;
246
247 // Forward pointer operations for scavenge
248 inline bool is_forwarded() const;
249
250 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
251
252 inline void forward_to(oop p);
253
254 // Like "forward_to", but inserts the forwarding pointer atomically.
255 // Exactly one thread succeeds in inserting the forwarding pointer, and
256 // this call returns "NULL" for that thread; any other thread has the
257 // value of the forwarding pointer returned and does not modify "this".
258 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
259
260 inline oop forwardee() const;
261
262 // Age of object during scavenge
263 inline uint age() const;
264 inline void incr_age();
265
266 template <typename OopClosureType>
267 inline void oop_iterate(OopClosureType* cl);
268
269 template <typename OopClosureType>
270 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
271
272 template <typename OopClosureType>
273 inline size_t oop_iterate_size(OopClosureType* cl);
274
275 template <typename OopClosureType>
276 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
277
278 template <typename OopClosureType>
279 inline void oop_iterate_backwards(OopClosureType* cl);
280
281 template <typename OopClosureType>
282 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
283
284 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
285
286 // identity hash; returns the identity hash key (computes it if necessary)
287 inline intptr_t identity_hash();
288 intptr_t slow_identity_hash();
289
290 // marks are forwarded to stack when object is locked
291 inline bool has_displaced_mark() const;
292 inline markWord displaced_mark() const;
293 inline void set_displaced_mark(markWord m);
294
295 // Checks if the mark word needs to be preserved
296 inline bool mark_must_be_preserved() const;
297 inline bool mark_must_be_preserved(markWord m) const;
298
299 static bool has_klass_gap();
300
301 // for code generation
302 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); }
303 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); }
304 static int klass_gap_offset_in_bytes() {
305 assert(has_klass_gap(), "only applicable to compressed klass pointers");
306 return klass_offset_in_bytes() + sizeof(narrowKlass);
307 }
308
309 // for error reporting
310 static void* load_klass_raw(oop obj);
311 static void* load_oop_raw(oop obj, int offset);
312
313 // Avoid include gc_globals.hpp in oop.inline.hpp
314 DEBUG_ONLY(bool get_UseParallelGC();)
315 DEBUG_ONLY(bool get_UseG1GC();)
316 };
317
318 // An oopDesc is not initialized via a constructor. Space is allocated in
319 // the Java heap, and static functions provided here on HeapWord* are used
320 // to fill in certain parts of that memory. The allocated memory is then
321 // treated as referring to an oopDesc. For that to be valid, the oopDesc
322 // class must have a trivial default constructor (C++14 3.8/1).
323 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
324
325 #endif // SHARE_OOPS_OOP_HPP