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
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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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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 static inline void release_set_mark(HeapWord* mem, markWord m);
77
78 inline void release_set_mark(markWord m);
79 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
80 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
81
82 // Used only to re-initialize the mark word (e.g., of promoted
83 // objects during a GC) -- requires a valid klass pointer
84 inline void init_mark();
85
86 inline Klass* klass() const;
87 inline Klass* klass_or_null() const;
88 inline Klass* klass_or_null_acquire() const;
89 // Get the raw value without any checks.
90 inline Klass* klass_raw() const;
91
92 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
93 inline void set_klass(Klass* k);
94 static inline void release_set_klass(HeapWord* mem, Klass* k);
95
96 // For klass field compression
97 static inline void set_klass_gap(HeapWord* mem, int z);
98
99 // size of object header, aligned to platform wordSize
100 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
101
102 // Returns whether this is an instance of k or an instance of a subclass of k
103 inline bool is_a(Klass* k) const;
104
105 // Returns the actual oop size of the object in machine words
106 inline size_t size();
107
108 // Sometimes (for complicated concurrency-related reasons), it is useful
109 // to be able to figure out the size of an object knowing its klass.
110 inline size_t size_given_klass(Klass* klass);
111
112 // type test operations (inlined in oop.inline.hpp)
113 inline bool is_instance() const;
114 inline bool is_instanceRef() const;
115 inline bool is_stackChunk() const;
116 inline bool is_array() const;
117 inline bool is_objArray() const;
118 inline bool is_typeArray() const;
119
120 // type test operations that don't require inclusion of oop.inline.hpp.
121 bool is_instance_noinline() const;
122 bool is_instanceRef_noinline() const;
123 bool is_stackChunk_noinline() const;
124 bool is_array_noinline() const;
125 bool is_objArray_noinline() const;
126 bool is_typeArray_noinline() const;
127
128 protected:
129 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
130
131 public:
132 template<typename T>
133 inline T* field_addr(int offset) const;
134
135 template <typename T> inline size_t field_offset(T* p) const;
136
137 // Standard compare function returns negative value if o1 < o2
138 // 0 if o1 == o2
139 // positive value if o1 > o2
140 inline static int compare(oop o1, oop o2) {
141 void* o1_addr = (void*)o1;
142 void* o2_addr = (void*)o2;
143 if (o1_addr < o2_addr) {
144 return -1;
145 } else if (o1_addr > o2_addr) {
146 return 1;
147 } else {
148 return 0;
149 }
150 }
151
152 // Access to fields in a instanceOop through these methods.
153 template<DecoratorSet decorators>
154 oop obj_field_access(int offset) const;
155 oop obj_field(int offset) const;
156
157 void obj_field_put(int offset, oop value);
158 void obj_field_put_raw(int offset, oop value);
159 void obj_field_put_volatile(int offset, oop value);
160 template<DecoratorSet decorators>
161 void obj_field_put_access(int offset, oop value);
162
163 Metadata* metadata_field(int offset) const;
164 void metadata_field_put(int offset, Metadata* value);
165
166 Metadata* metadata_field_acquire(int offset) const;
167 void release_metadata_field_put(int offset, Metadata* value);
168
169 jbyte byte_field(int offset) const;
170 void byte_field_put(int offset, jbyte contents);
171
172 jchar char_field(int offset) const;
173 void char_field_put(int offset, jchar contents);
174
175 jboolean bool_field(int offset) const;
176 void bool_field_put(int offset, jboolean contents);
177 jboolean bool_field_volatile(int offset) const;
178 void bool_field_put_volatile(int offset, jboolean contents);
179
180 jint int_field(int offset) const;
181 void int_field_put(int offset, jint contents);
182
183 jshort short_field(int offset) const;
184 void short_field_put(int offset, jshort contents);
185
186 jlong long_field(int offset) const;
187 void long_field_put(int offset, jlong contents);
188
189 jfloat float_field(int offset) const;
190 void float_field_put(int offset, jfloat contents);
191
192 jdouble double_field(int offset) const;
193 void double_field_put(int offset, jdouble contents);
194
195 address address_field(int offset) const;
196 void address_field_put(int offset, address contents);
197
198 oop obj_field_acquire(int offset) const;
199 void release_obj_field_put(int offset, oop value);
200
201 jbyte byte_field_acquire(int offset) const;
202 void release_byte_field_put(int offset, jbyte contents);
203
204 jchar char_field_acquire(int offset) const;
205 void release_char_field_put(int offset, jchar contents);
206
207 jboolean bool_field_acquire(int offset) const;
208 void release_bool_field_put(int offset, jboolean contents);
209
210 jint int_field_acquire(int offset) const;
211 void release_int_field_put(int offset, jint contents);
212
213 jshort short_field_acquire(int offset) const;
214 void release_short_field_put(int offset, jshort contents);
215
216 jlong long_field_acquire(int offset) const;
217 void release_long_field_put(int offset, jlong contents);
218
219 jfloat float_field_acquire(int offset) const;
220 void release_float_field_put(int offset, jfloat contents);
221
222 jdouble double_field_acquire(int offset) const;
223 void release_double_field_put(int offset, jdouble contents);
224
225 address address_field_acquire(int offset) const;
226 void release_address_field_put(int offset, address contents);
227
228 // printing functions for VM debugging
229 void print_on(outputStream* st) const; // First level print
230 void print_value_on(outputStream* st) const; // Second level print.
231 void print_address_on(outputStream* st) const; // Address printing
232 void print_name_on(outputStream* st) const; // External name printing.
233
234 // printing on default output stream
235 void print();
236 void print_value();
237 void print_address();
238
239 // return the print strings
240 char* print_string();
241 char* print_value_string();
242
243 // verification operations
244 static void verify_on(outputStream* st, oopDesc* oop_desc);
245 static void verify(oopDesc* oopDesc);
246
247 // locking operations
248 inline bool is_locked() const;
249 inline bool is_unlocked() const;
250
251 // asserts and guarantees
252 static bool is_oop(oop obj, bool ignore_mark_word = false);
253 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
254
255 // garbage collection
256 inline bool is_gc_marked() const;
257
258 // Forward pointer operations for scavenge
259 inline bool is_forwarded() const;
260
261 inline void forward_to(oop p);
262
263 // Like "forward_to", but inserts the forwarding pointer atomically.
264 // Exactly one thread succeeds in inserting the forwarding pointer, and
265 // this call returns null for that thread; any other thread has the
266 // value of the forwarding pointer returned and does not modify "this".
267 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
268
269 inline oop forwardee() const;
270
271 // Age of object during scavenge
272 inline uint age() const;
273 inline void incr_age();
274
275 template <typename OopClosureType>
276 inline void oop_iterate(OopClosureType* cl);
277
278 template <typename OopClosureType>
279 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
280
281 template <typename OopClosureType>
282 inline size_t oop_iterate_size(OopClosureType* cl);
283
284 template <typename OopClosureType>
285 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
286
287 template <typename OopClosureType>
288 inline void oop_iterate_backwards(OopClosureType* cl);
289
290 template <typename OopClosureType>
291 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
292
293 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
294
295 // identity hash; returns the identity hash key (computes it if necessary)
296 inline intptr_t identity_hash();
297 intptr_t slow_identity_hash();
298 inline bool fast_no_hash_check();
299
300 // marks are forwarded to stack when object is locked
301 inline bool has_displaced_mark() const;
302 inline markWord displaced_mark() const;
303 inline void set_displaced_mark(markWord m);
304
305 // Checks if the mark word needs to be preserved
306 inline bool mark_must_be_preserved() const;
307 inline bool mark_must_be_preserved(markWord m) const;
308
309 static bool has_klass_gap();
310
311 // for code generation
312 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
313 static int klass_offset_in_bytes() { return (int)offset_of(oopDesc, _metadata._klass); }
314 static int klass_gap_offset_in_bytes() {
315 assert(has_klass_gap(), "only applicable to compressed klass pointers");
316 return klass_offset_in_bytes() + sizeof(narrowKlass);
317 }
318
319 // for error reporting
320 static void* load_klass_raw(oop obj);
321 static void* load_oop_raw(oop obj, int offset);
322
323 DEBUG_ONLY(bool size_might_change();)
324 };
325
326 // An oopDesc is not initialized via a constructor. Space is allocated in
327 // the Java heap, and static functions provided here on HeapWord* are used
328 // to fill in certain parts of that memory. The allocated memory is then
329 // treated as referring to an oopDesc. For that to be valid, the oopDesc
330 // class must have a trivial default constructor (C++14 3.8/1).
331 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
332
333 #endif // SHARE_OOPS_OOP_HPP