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.
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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.
8 *
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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 *
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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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 // 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
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_array() const;
122 inline bool is_objArray() const;
123 inline bool is_typeArray() const;
124 inline bool is_inline_type() const;
125 inline bool is_flatArray() const;
126 inline bool is_null_free_array() const;
127
128 // type test operations that don't require inclusion of oop.inline.hpp.
129 bool is_instance_noinline() const;
130 bool is_array_noinline() const;
131 bool is_objArray_noinline() const;
132 bool is_typeArray_noinline() const;
133 bool is_flatArray_noinline() const;
134 bool is_null_free_array_noinline() const;
135
136 protected:
137 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
138
139 public:
140 template<typename T>
141 inline T* field_addr(int offset) const;
142
143 template <typename T> inline size_t field_offset(T* p) const;
144
145 // Standard compare function returns negative value if o1 < o2
146 // 0 if o1 == o2
147 // positive value if o1 > o2
148 inline static int compare(oop o1, oop o2) {
149 void* o1_addr = (void*)o1;
150 void* o2_addr = (void*)o2;
151 if (o1_addr < o2_addr) {
152 return -1;
153 } else if (o1_addr > o2_addr) {
154 return 1;
155 } else {
156 return 0;
157 }
158 }
159
160 // Access to fields in a instanceOop through these methods.
161 template <DecoratorSet decorator>
162 oop obj_field_access(int offset) const;
163 oop obj_field(int offset) const;
164 void obj_field_put(int offset, oop value);
165 void obj_field_put_raw(int offset, oop value);
166 void obj_field_put_volatile(int offset, oop value);
167
168 Metadata* metadata_field(int offset) const;
169 void metadata_field_put(int offset, Metadata* value);
170
171 Metadata* metadata_field_acquire(int offset) const;
172 void release_metadata_field_put(int offset, Metadata* value);
173
174 jbyte byte_field(int offset) const;
175 void byte_field_put(int offset, jbyte contents);
176
177 jchar char_field(int offset) const;
178 void char_field_put(int offset, jchar contents);
179
180 jboolean bool_field(int offset) const;
181 void bool_field_put(int offset, jboolean contents);
182 jboolean bool_field_volatile(int offset) const;
183 void bool_field_put_volatile(int offset, jboolean contents);
184
185 jint int_field(int offset) const;
186 void int_field_put(int offset, jint contents);
187
188 jshort short_field(int offset) const;
189 void short_field_put(int offset, jshort contents);
190
191 jlong long_field(int offset) const;
192 void long_field_put(int offset, jlong contents);
193
194 jfloat float_field(int offset) const;
195 void float_field_put(int offset, jfloat contents);
196
197 jdouble double_field(int offset) const;
198 void double_field_put(int offset, jdouble contents);
199
200 address address_field(int offset) const;
201 void address_field_put(int offset, address contents);
202
203 oop obj_field_acquire(int offset) const;
204 void release_obj_field_put(int offset, oop value);
205
206 jbyte byte_field_acquire(int offset) const;
207 void release_byte_field_put(int offset, jbyte contents);
208
209 jchar char_field_acquire(int offset) const;
210 void release_char_field_put(int offset, jchar contents);
211
212 jboolean bool_field_acquire(int offset) const;
213 void release_bool_field_put(int offset, jboolean contents);
214
215 jint int_field_acquire(int offset) const;
216 void release_int_field_put(int offset, jint contents);
217
218 jshort short_field_acquire(int offset) const;
219 void release_short_field_put(int offset, jshort contents);
220
221 jlong long_field_acquire(int offset) const;
222 void release_long_field_put(int offset, jlong contents);
223
224 jfloat float_field_acquire(int offset) const;
225 void release_float_field_put(int offset, jfloat contents);
226
227 jdouble double_field_acquire(int offset) const;
228 void release_double_field_put(int offset, jdouble contents);
229
230 address address_field_acquire(int offset) const;
231 void release_address_field_put(int offset, address contents);
232
233 // printing functions for VM debugging
234 void print_on(outputStream* st) const; // First level print
235 void print_value_on(outputStream* st) const; // Second level print.
236 void print_address_on(outputStream* st) const; // Address printing
237
238 // printing on default output stream
239 void print();
240 void print_value();
241 void print_address();
242
243 // return the print strings
244 char* print_string();
245 char* print_value_string();
246
247 // verification operations
248 static void verify_on(outputStream* st, oopDesc* oop_desc);
249 static void verify(oopDesc* oopDesc);
250
251 // locking operations
252 inline bool is_locked() const;
253 inline bool is_unlocked() const;
254
255 // asserts and guarantees
256 static bool is_oop(oop obj, bool ignore_mark_word = false);
257 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
258
259 // garbage collection
260 inline bool is_gc_marked() const;
261
262 // Forward pointer operations for scavenge
263 inline bool is_forwarded() const;
264
265 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
266
267 inline void forward_to(oop p);
268
269 // Like "forward_to", but inserts the forwarding pointer atomically.
270 // Exactly one thread succeeds in inserting the forwarding pointer, and
271 // this call returns "NULL" for that thread; any other thread has the
272 // value of the forwarding pointer returned and does not modify "this".
273 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
274
275 inline oop forwardee() const;
276
277 // Age of object during scavenge
278 inline uint age() const;
279 inline void incr_age();
280
281 template <typename OopClosureType>
282 inline void oop_iterate(OopClosureType* cl);
283
284 template <typename OopClosureType>
285 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
286
287 template <typename OopClosureType>
288 inline size_t oop_iterate_size(OopClosureType* cl);
289
290 template <typename OopClosureType>
291 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
292
293 template <typename OopClosureType>
294 inline void oop_iterate_backwards(OopClosureType* cl);
295
296 template <typename OopClosureType>
297 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
298
299 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
300
301 // identity hash; returns the identity hash key (computes it if necessary)
302 inline intptr_t identity_hash();
303 intptr_t slow_identity_hash();
304
305 // marks are forwarded to stack when object is locked
306 inline bool has_displaced_mark() const;
307 inline markWord displaced_mark() const;
308 inline void set_displaced_mark(markWord m);
309
310 // Checks if the mark word needs to be preserved
311 inline bool mark_must_be_preserved() const;
312 inline bool mark_must_be_preserved(markWord m) const;
313
314 static bool has_klass_gap();
315
316 // for code generation
317 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); }
318 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); }
319 static int klass_gap_offset_in_bytes() {
320 assert(has_klass_gap(), "only applicable to compressed klass pointers");
321 return klass_offset_in_bytes() + sizeof(narrowKlass);
322 }
323
324 // for error reporting
325 static void* load_klass_raw(oop obj);
326 static void* load_oop_raw(oop obj, int offset);
327
328 // Avoid include gc_globals.hpp in oop.inline.hpp
329 DEBUG_ONLY(bool get_UseParallelGC();)
330 DEBUG_ONLY(bool get_UseG1GC();)
331 };
332
333 // An oopDesc is not initialized via a constructor. Space is allocated in
334 // the Java heap, and static functions provided here on HeapWord* are used
335 // to fill in certain parts of that memory. The allocated memory is then
336 // treated as referring to an oopDesc. For that to be valid, the oopDesc
337 // class must have a trivial default constructor (C++14 3.8/1).
338 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
339
340 #endif // SHARE_OOPS_OOP_HPP