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.
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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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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 * accompanied this code).
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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/compressedKlass.hpp"
31 #include "oops/accessDecorators.hpp"
32 #include "oops/markWord.hpp"
33 #include "oops/metadata.hpp"
34 #include "runtime/atomic.hpp"
35 #include "utilities/globalDefinitions.hpp"
36 #include "utilities/macros.hpp"
37 #include <type_traits>
38
39 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe
40 // the format of Java objects so the fields can be accessed from C++.
41 // oopDesc is abstract.
42 // (see oopHierarchy for complete oop class hierarchy)
43 //
44 // no virtual functions allowed
45
46 // Forward declarations.
47 class OopClosure;
48 class FilteringClosure;
49
50 class PSPromotionManager;
51 class ParCompactionManager;
52
53 class oopDesc {
54 friend class VMStructs;
55 friend class JVMCIVMStructs;
56 private:
57 volatile markWord _mark;
58 union _metadata {
59 Klass* _klass;
60 narrowKlass _compressed_klass;
61 } _metadata;
62
63 // There may be ordering constraints on the initialization of fields that
64 // make use of the C++ copy/assign incorrect.
65 NONCOPYABLE(oopDesc);
66
67 public:
68 // Must be trivial; see verifying static assert after the class.
69 oopDesc() = default;
70
71 inline markWord mark() const;
72 inline markWord mark_acquire() const;
73 inline markWord* mark_addr() const;
74
75 inline void set_mark(markWord m);
76 static inline void set_mark(HeapWord* mem, markWord m);
77 static inline void release_set_mark(HeapWord* mem, markWord m);
78
79 inline void release_set_mark(markWord m);
80 inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
81 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
82
83 // Used only to re-initialize the mark word (e.g., of promoted
84 // objects during a GC) -- requires a valid klass pointer
85 inline void init_mark();
86
87 inline Klass* klass() const;
88 inline Klass* klass_or_null() const;
89 inline Klass* klass_or_null_acquire() const;
90 // Get the raw value without any checks.
91 inline Klass* klass_raw() const;
92
93 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
94 inline void set_klass(Klass* k);
95 static inline void release_set_klass(HeapWord* mem, Klass* k);
96
97 // For klass field compression
98 static inline void set_klass_gap(HeapWord* mem, int z);
99
100 // size of object header, aligned to platform wordSize
101 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
102
103 // Returns whether this is an instance of k or an instance of a subclass of k
104 inline bool is_a(Klass* k) const;
105
106 // Returns the actual oop size of the object in machine words
107 inline size_t size();
108
109 // Sometimes (for complicated concurrency-related reasons), it is useful
110 // to be able to figure out the size of an object knowing its klass.
111 inline size_t size_given_klass(Klass* klass);
112
113 // type test operations (inlined in oop.inline.hpp)
114 inline bool is_instance() const;
115 inline bool is_instanceRef() const;
116 inline bool is_stackChunk() const;
117 inline bool is_array() const;
118 inline bool is_objArray() const;
119 inline bool is_typeArray() const;
120
121 // type test operations that don't require inclusion of oop.inline.hpp.
122 bool is_instance_noinline() const;
123 bool is_instanceRef_noinline() const;
124 bool is_stackChunk_noinline() const;
125 bool is_array_noinline() const;
126 bool is_objArray_noinline() const;
127 bool is_typeArray_noinline() const;
128
129 protected:
130 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
131
132 public:
133 template<typename T>
134 inline T* field_addr(int offset) const;
135
136 template <typename T> inline size_t field_offset(T* p) const;
137
138 // Standard compare function returns negative value if o1 < o2
139 // 0 if o1 == o2
140 // positive value if o1 > o2
141 inline static int compare(oop o1, oop o2) {
142 void* o1_addr = (void*)o1;
143 void* o2_addr = (void*)o2;
144 if (o1_addr < o2_addr) {
145 return -1;
146 } else if (o1_addr > o2_addr) {
147 return 1;
148 } else {
149 return 0;
150 }
151 }
152
153 // Access to fields in a instanceOop through these methods.
154 template<DecoratorSet decorators>
155 oop obj_field_access(int offset) const;
156 oop obj_field(int offset) const;
157
158 void obj_field_put(int offset, oop value);
159 void obj_field_put_raw(int offset, oop value);
160 void obj_field_put_volatile(int offset, oop value);
161 template<DecoratorSet decorators>
162 void obj_field_put_access(int offset, oop value);
163
164 Metadata* metadata_field(int offset) const;
165 void metadata_field_put(int offset, Metadata* value);
166
167 Metadata* metadata_field_acquire(int offset) const;
168 void release_metadata_field_put(int offset, Metadata* value);
169
170 jbyte byte_field(int offset) const;
171 void byte_field_put(int offset, jbyte contents);
172
173 jchar char_field(int offset) const;
174 void char_field_put(int offset, jchar contents);
175
176 jboolean bool_field(int offset) const;
177 void bool_field_put(int offset, jboolean contents);
178 jboolean bool_field_volatile(int offset) const;
179 void bool_field_put_volatile(int offset, jboolean contents);
180
181 jint int_field(int offset) const;
182 void int_field_put(int offset, jint contents);
183
184 jshort short_field(int offset) const;
185 void short_field_put(int offset, jshort contents);
186
187 jlong long_field(int offset) const;
188 void long_field_put(int offset, jlong contents);
189
190 jfloat float_field(int offset) const;
191 void float_field_put(int offset, jfloat contents);
192
193 jdouble double_field(int offset) const;
194 void double_field_put(int offset, jdouble contents);
195
196 address address_field(int offset) const;
197 void address_field_put(int offset, address contents);
198
199 oop obj_field_acquire(int offset) const;
200 void release_obj_field_put(int offset, oop value);
201
202 jbyte byte_field_acquire(int offset) const;
203 void release_byte_field_put(int offset, jbyte contents);
204
205 jchar char_field_acquire(int offset) const;
206 void release_char_field_put(int offset, jchar contents);
207
208 jboolean bool_field_acquire(int offset) const;
209 void release_bool_field_put(int offset, jboolean contents);
210
211 jint int_field_acquire(int offset) const;
212 void release_int_field_put(int offset, jint contents);
213
214 jshort short_field_acquire(int offset) const;
215 void release_short_field_put(int offset, jshort contents);
216
217 jlong long_field_acquire(int offset) const;
218 void release_long_field_put(int offset, jlong contents);
219
220 jfloat float_field_acquire(int offset) const;
221 void release_float_field_put(int offset, jfloat contents);
222
223 jdouble double_field_acquire(int offset) const;
224 void release_double_field_put(int offset, jdouble contents);
225
226 address address_field_acquire(int offset) const;
227 void release_address_field_put(int offset, address contents);
228
229 // printing functions for VM debugging
230 void print_on(outputStream* st) const; // First level print
231 void print_value_on(outputStream* st) const; // Second level print.
232 void print_address_on(outputStream* st) const; // Address printing
233 void print_name_on(outputStream* st) const; // External name printing.
234
235 // printing on default output stream
236 void print();
237 void print_value();
238 void print_address();
239
240 // return the print strings
241 char* print_string();
242 char* print_value_string();
243
244 // verification operations
245 static void verify_on(outputStream* st, oopDesc* oop_desc);
246 static void verify(oopDesc* oopDesc);
247
248 // locking operations
249 inline bool is_locked() const;
250 inline bool is_unlocked() const;
251
252 // asserts and guarantees
253 static bool is_oop(oop obj, bool ignore_mark_word = false);
254 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
255
256 // garbage collection
257 inline bool is_gc_marked() const;
258
259 // Forward pointer operations for scavenge
260 inline bool is_forwarded() const;
261
262 inline void forward_to(oop p);
263
264 // Like "forward_to", but inserts the forwarding pointer atomically.
265 // Exactly one thread succeeds in inserting the forwarding pointer, and
266 // this call returns null for that thread; any other thread has the
267 // value of the forwarding pointer returned and does not modify "this".
268 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
269
270 inline oop forwardee() const;
271
272 // Age of object during scavenge
273 inline uint age() const;
274 inline void incr_age();
275
276 template <typename OopClosureType>
277 inline void oop_iterate(OopClosureType* cl);
278
279 template <typename OopClosureType>
280 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
281
282 template <typename OopClosureType>
283 inline size_t oop_iterate_size(OopClosureType* cl);
284
285 template <typename OopClosureType>
286 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
287
288 template <typename OopClosureType>
289 inline void oop_iterate_backwards(OopClosureType* cl);
290
291 template <typename OopClosureType>
292 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
293
294 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
295
296 // identity hash; returns the identity hash key (computes it if necessary)
297 inline intptr_t identity_hash();
298 intptr_t slow_identity_hash();
299 inline bool fast_no_hash_check();
300
301 // marks are forwarded to stack when object is locked
302 inline bool has_displaced_mark() const;
303 inline markWord displaced_mark() const;
304 inline void set_displaced_mark(markWord m);
305
306 // Checks if the mark word needs to be preserved
307 inline bool mark_must_be_preserved() const;
308 inline bool mark_must_be_preserved(markWord m) const;
309
310 static bool has_klass_gap();
311
312 // for code generation
313 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
314 static int klass_offset_in_bytes() { return (int)offset_of(oopDesc, _metadata._klass); }
315 static int klass_gap_offset_in_bytes() {
316 assert(has_klass_gap(), "only applicable to compressed klass pointers");
317 return klass_offset_in_bytes() + sizeof(narrowKlass);
318 }
319
320 // for error reporting
321 static void* load_klass_raw(oop obj);
322 static void* load_oop_raw(oop obj, int offset);
323
324 DEBUG_ONLY(bool size_might_change();)
325 };
326
327 // An oopDesc is not initialized via a constructor. Space is allocated in
328 // the Java heap, and static functions provided here on HeapWord* are used
329 // to fill in certain parts of that memory. The allocated memory is then
330 // treated as referring to an oopDesc. For that to be valid, the oopDesc
331 // class must have a trivial default constructor (C++14 3.8/1).
332 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
333
334 #endif // SHARE_OOPS_OOP_HPP