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.
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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
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
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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 // 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 static inline void set_klass_gap(HeapWord* mem, int z);
105
106 // size of object header, aligned to platform wordSize
107 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
108
109 // Returns whether this is an instance of k or an instance of a subclass of k
110 inline bool is_a(Klass* k) const;
111
112 // Returns the actual oop size of the object in machine words
113 inline size_t size();
114
115 // Sometimes (for complicated concurrency-related reasons), it is useful
116 // to be able to figure out the size of an object knowing its klass.
117 inline size_t size_given_klass(Klass* klass);
118
119 // type test operations (inlined in oop.inline.hpp)
120 inline bool is_instance() const;
121 inline bool is_inline_type() const;
122 inline bool is_instanceRef() const;
123 inline bool is_stackChunk() const;
124 inline bool is_array() const;
125 inline bool is_objArray() const;
126 inline bool is_typeArray() 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_instanceRef_noinline() const;
133 bool is_stackChunk_noinline() const;
134 bool is_array_noinline() const;
135 bool is_objArray_noinline() const;
136 bool is_typeArray_noinline() const;
137 bool is_flatArray_noinline() const;
138 bool is_null_free_array_noinline() const;
139
140 protected:
141 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
142
143 public:
144 template<typename T>
145 inline T* field_addr(int offset) const;
146
147 template <typename T> inline size_t field_offset(T* p) const;
148
149 // Standard compare function returns negative value if o1 < o2
150 // 0 if o1 == o2
151 // positive value if o1 > o2
152 inline static int compare(oop o1, oop o2) {
153 void* o1_addr = (void*)o1;
154 void* o2_addr = (void*)o2;
155 if (o1_addr < o2_addr) {
156 return -1;
157 } else if (o1_addr > o2_addr) {
158 return 1;
159 } else {
160 return 0;
161 }
162 }
163
164 // Access to fields in a instanceOop through these methods.
165 template<DecoratorSet decorators>
166 oop obj_field_access(int offset) const;
167 oop obj_field(int offset) const;
168
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 template<DecoratorSet decorators>
173 void obj_field_put_access(int offset, oop value);
174
175 Metadata* metadata_field(int offset) const;
176 void metadata_field_put(int offset, Metadata* value);
177
178 Metadata* metadata_field_acquire(int offset) const;
179 void release_metadata_field_put(int offset, Metadata* value);
180
181 jbyte byte_field(int offset) const;
182 void byte_field_put(int offset, jbyte contents);
183
184 jchar char_field(int offset) const;
185 void char_field_put(int offset, jchar contents);
186
187 jboolean bool_field(int offset) const;
188 void bool_field_put(int offset, jboolean contents);
189 jboolean bool_field_volatile(int offset) const;
190 void bool_field_put_volatile(int offset, jboolean contents);
191
192 jint int_field(int offset) const;
193 void int_field_put(int offset, jint contents);
194
195 jshort short_field(int offset) const;
196 void short_field_put(int offset, jshort contents);
197
198 jlong long_field(int offset) const;
199 void long_field_put(int offset, jlong contents);
200
201 jfloat float_field(int offset) const;
202 void float_field_put(int offset, jfloat contents);
203
204 jdouble double_field(int offset) const;
205 void double_field_put(int offset, jdouble contents);
206
207 address address_field(int offset) const;
208 void address_field_put(int offset, address contents);
209
210 oop obj_field_acquire(int offset) const;
211 void release_obj_field_put(int offset, oop value);
212
213 jbyte byte_field_acquire(int offset) const;
214 void release_byte_field_put(int offset, jbyte contents);
215
216 jchar char_field_acquire(int offset) const;
217 void release_char_field_put(int offset, jchar contents);
218
219 jboolean bool_field_acquire(int offset) const;
220 void release_bool_field_put(int offset, jboolean contents);
221
222 jint int_field_acquire(int offset) const;
223 void release_int_field_put(int offset, jint contents);
224
225 jshort short_field_acquire(int offset) const;
226 void release_short_field_put(int offset, jshort contents);
227
228 jlong long_field_acquire(int offset) const;
229 void release_long_field_put(int offset, jlong contents);
230
231 jfloat float_field_acquire(int offset) const;
232 void release_float_field_put(int offset, jfloat contents);
233
234 jdouble double_field_acquire(int offset) const;
235 void release_double_field_put(int offset, jdouble contents);
236
237 address address_field_acquire(int offset) const;
238 void release_address_field_put(int offset, address contents);
239
240 // printing functions for VM debugging
241 void print_on(outputStream* st) const; // First level print
242 void print_value_on(outputStream* st) const; // Second level print.
243 void print_address_on(outputStream* st) const; // Address printing
244
245 // printing on default output stream
246 void print();
247 void print_value();
248 void print_address();
249
250 // return the print strings
251 char* print_string();
252 char* print_value_string();
253
254 // verification operations
255 static void verify_on(outputStream* st, oopDesc* oop_desc);
256 static void verify(oopDesc* oopDesc);
257
258 // locking operations
259 inline bool is_locked() const;
260 inline bool is_unlocked() const;
261
262 // asserts and guarantees
263 static bool is_oop(oop obj, bool ignore_mark_word = false);
264 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
265
266 // garbage collection
267 inline bool is_gc_marked() const;
268
269 // Forward pointer operations for scavenge
270 inline bool is_forwarded() const;
271
272 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
273
274 inline void forward_to(oop p);
275
276 // Like "forward_to", but inserts the forwarding pointer atomically.
277 // Exactly one thread succeeds in inserting the forwarding pointer, and
278 // this call returns "NULL" for that thread; any other thread has the
279 // value of the forwarding pointer returned and does not modify "this".
280 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
281
282 inline oop forwardee() const;
283
284 // Age of object during scavenge
285 inline uint age() const;
286 inline void incr_age();
287
288 template <typename OopClosureType>
289 inline void oop_iterate(OopClosureType* cl);
290
291 template <typename OopClosureType>
292 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
293
294 template <typename OopClosureType>
295 inline size_t oop_iterate_size(OopClosureType* cl);
296
297 template <typename OopClosureType>
298 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
299
300 template <typename OopClosureType>
301 inline void oop_iterate_backwards(OopClosureType* cl);
302
303 template <typename OopClosureType>
304 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
305
306 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
307
308 // identity hash; returns the identity hash key (computes it if necessary)
309 inline intptr_t identity_hash();
310 intptr_t slow_identity_hash();
311
312 // marks are forwarded to stack when object is locked
313 inline bool has_displaced_mark() const;
314 inline markWord displaced_mark() const;
315 inline void set_displaced_mark(markWord m);
316
317 // Checks if the mark word needs to be preserved
318 inline bool mark_must_be_preserved() const;
319 inline bool mark_must_be_preserved(markWord m) const;
320
321 static bool has_klass_gap();
322
323 // for code generation
324 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); }
325 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); }
326 static int klass_gap_offset_in_bytes() {
327 assert(has_klass_gap(), "only applicable to compressed klass pointers");
328 return klass_offset_in_bytes() + sizeof(narrowKlass);
329 }
330
331 // for error reporting
332 static void* load_klass_raw(oop obj);
333 static void* load_oop_raw(oop obj, int offset);
334
335 DEBUG_ONLY(bool size_might_change();)
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