1 /*
2 * Copyright (c) 1997, 2022, 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
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7 * published by the Free Software Foundation.
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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,
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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 in machine words
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_instanceRef() const;
112 inline bool is_stackChunk() const;
113 inline bool is_array() const;
114 inline bool is_objArray() const;
115 inline bool is_typeArray() const;
116
117 // type test operations that don't require inclusion of oop.inline.hpp.
118 bool is_instance_noinline() const;
119 bool is_instanceRef_noinline() const;
120 bool is_stackChunk_noinline() const;
121 bool is_array_noinline() const;
122 bool is_objArray_noinline() const;
123 bool is_typeArray_noinline() const;
124
125 protected:
126 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
127
128 public:
129 template<typename T>
130 inline T* field_addr(int offset) const;
131
132 template <typename T> inline size_t field_offset(T* p) const;
133
134 // Standard compare function returns negative value if o1 < o2
135 // 0 if o1 == o2
136 // positive value if o1 > o2
137 inline static int compare(oop o1, oop o2) {
138 void* o1_addr = (void*)o1;
139 void* o2_addr = (void*)o2;
140 if (o1_addr < o2_addr) {
141 return -1;
142 } else if (o1_addr > o2_addr) {
143 return 1;
144 } else {
145 return 0;
146 }
147 }
148
149 // Access to fields in a instanceOop through these methods.
150 template<DecoratorSet decorators>
151 oop obj_field_access(int offset) const;
152 oop obj_field(int offset) const;
153
154 void obj_field_put(int offset, oop value);
155 void obj_field_put_raw(int offset, oop value);
156 void obj_field_put_volatile(int offset, oop value);
157 template<DecoratorSet decorators>
158 void obj_field_put_access(int offset, oop value);
159
160 Metadata* metadata_field(int offset) const;
161 void metadata_field_put(int offset, Metadata* value);
162
163 Metadata* metadata_field_acquire(int offset) const;
164 void release_metadata_field_put(int offset, Metadata* value);
165
166 jbyte byte_field(int offset) const;
167 void byte_field_put(int offset, jbyte contents);
168
169 jchar char_field(int offset) const;
170 void char_field_put(int offset, jchar contents);
171
172 jboolean bool_field(int offset) const;
173 void bool_field_put(int offset, jboolean contents);
174 jboolean bool_field_volatile(int offset) const;
175 void bool_field_put_volatile(int offset, jboolean contents);
176
177 jint int_field(int offset) const;
178 void int_field_put(int offset, jint contents);
179
180 jshort short_field(int offset) const;
181 void short_field_put(int offset, jshort contents);
182
183 jlong long_field(int offset) const;
184 void long_field_put(int offset, jlong contents);
185
186 jfloat float_field(int offset) const;
187 void float_field_put(int offset, jfloat contents);
188
189 jdouble double_field(int offset) const;
190 void double_field_put(int offset, jdouble contents);
191
192 address address_field(int offset) const;
193 void address_field_put(int offset, address contents);
194
195 oop obj_field_acquire(int offset) const;
196 void release_obj_field_put(int offset, oop value);
197
198 jbyte byte_field_acquire(int offset) const;
199 void release_byte_field_put(int offset, jbyte contents);
200
201 jchar char_field_acquire(int offset) const;
202 void release_char_field_put(int offset, jchar contents);
203
204 jboolean bool_field_acquire(int offset) const;
205 void release_bool_field_put(int offset, jboolean contents);
206
207 jint int_field_acquire(int offset) const;
208 void release_int_field_put(int offset, jint contents);
209
210 jshort short_field_acquire(int offset) const;
211 void release_short_field_put(int offset, jshort contents);
212
213 jlong long_field_acquire(int offset) const;
214 void release_long_field_put(int offset, jlong contents);
215
216 jfloat float_field_acquire(int offset) const;
217 void release_float_field_put(int offset, jfloat contents);
218
219 jdouble double_field_acquire(int offset) const;
220 void release_double_field_put(int offset, jdouble contents);
221
222 address address_field_acquire(int offset) const;
223 void release_address_field_put(int offset, address contents);
224
225 // printing functions for VM debugging
226 void print_on(outputStream* st) const; // First level print
227 void print_value_on(outputStream* st) const; // Second level print.
228 void print_address_on(outputStream* st) const; // Address printing
229
230 // printing on default output stream
231 void print();
232 void print_value();
233 void print_address();
234
235 // return the print strings
236 char* print_string();
237 char* print_value_string();
238
239 // verification operations
240 static void verify_on(outputStream* st, oopDesc* oop_desc);
241 static void verify(oopDesc* oopDesc);
242
243 // locking operations
244 inline bool is_locked() const;
245 inline bool is_unlocked() const;
246
247 // asserts and guarantees
248 static bool is_oop(oop obj, bool ignore_mark_word = false);
249 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
250
251 // garbage collection
252 inline bool is_gc_marked() const;
253
254 // Forward pointer operations for scavenge
255 inline bool is_forwarded() const;
256
257 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
258
259 inline void forward_to(oop p);
260
261 // Like "forward_to", but inserts the forwarding pointer atomically.
262 // Exactly one thread succeeds in inserting the forwarding pointer, and
263 // this call returns "NULL" for that thread; any other thread has the
264 // value of the forwarding pointer returned and does not modify "this".
265 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
266
267 inline oop forwardee() const;
268
269 // Age of object during scavenge
270 inline uint age() const;
271 inline void incr_age();
272
273 template <typename OopClosureType>
274 inline void oop_iterate(OopClosureType* cl);
275
276 template <typename OopClosureType>
277 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
278
279 template <typename OopClosureType>
280 inline size_t oop_iterate_size(OopClosureType* cl);
281
282 template <typename OopClosureType>
283 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
284
285 template <typename OopClosureType>
286 inline void oop_iterate_backwards(OopClosureType* cl);
287
288 template <typename OopClosureType>
289 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
290
291 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
292
293 // identity hash; returns the identity hash key (computes it if necessary)
294 inline intptr_t identity_hash();
295 intptr_t slow_identity_hash();
296 inline bool fast_no_hash_check();
297
298 // marks are forwarded to stack when object is locked
299 inline bool has_displaced_mark() const;
300 inline markWord displaced_mark() const;
301 inline void set_displaced_mark(markWord m);
302
303 // Checks if the mark word needs to be preserved
304 inline bool mark_must_be_preserved() const;
305 inline bool mark_must_be_preserved(markWord m) const;
306
307 static bool has_klass_gap();
308
309 // for code generation
310 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); }
311 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); }
312 static int klass_gap_offset_in_bytes() {
313 assert(has_klass_gap(), "only applicable to compressed klass pointers");
314 return klass_offset_in_bytes() + sizeof(narrowKlass);
315 }
316
317 // for error reporting
318 static void* load_klass_raw(oop obj);
319 static void* load_oop_raw(oop obj, int offset);
320
321 DEBUG_ONLY(bool size_might_change();)
322 };
323
324 // An oopDesc is not initialized via a constructor. Space is allocated in
325 // the Java heap, and static functions provided here on HeapWord* are used
326 // to fill in certain parts of that memory. The allocated memory is then
327 // treated as referring to an oopDesc. For that to be valid, the oopDesc
328 // class must have a trivial default constructor (C++14 3.8/1).
329 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
330
331 #endif // SHARE_OOPS_OOP_HPP