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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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 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 inline markWord resolve_mark() const;
83
84 // Returns the prototype mark that should be used for this object.
85 inline markWord prototype_mark() const;
86
87 // Used only to re-initialize the mark word (e.g., of promoted
88 // objects during a GC) -- requires a valid klass pointer
89 inline void init_mark();
90
91 inline Klass* klass() const;
92 inline Klass* klass_or_null() const;
93 inline Klass* klass_or_null_acquire() const;
94 // Get the raw value without any checks.
95 inline Klass* klass_raw() const;
96
97 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
98 inline void set_klass(Klass* k);
99 static inline void release_set_klass(HeapWord* mem, Klass* k);
100
101 // For klass field compression
102 static inline void set_klass_gap(HeapWord* mem, int z);
103
104 // size of object header, aligned to platform wordSize
105 static int header_size() {
106 if (UseCompactObjectHeaders) {
107 return sizeof(markWord) / HeapWordSize;
108 } else {
109 return sizeof(oopDesc)/HeapWordSize;
110 }
111 }
112
113 // Returns whether this is an instance of k or an instance of a subclass of k
114 inline bool is_a(Klass* k) const;
115
116 // Returns the actual oop size of the object in machine words
117 inline size_t size();
118
119 // Sometimes (for complicated concurrency-related reasons), it is useful
120 // to be able to figure out the size of an object knowing its klass.
121 inline size_t size_given_klass(Klass* klass);
122
123 // The following set of methods is used to access the mark-word and related
124 // properties when the object may be forwarded. Be careful where and when
125 // using this method. It assumes that the forwardee is installed in
126 // the header as a plain pointer (or self-forwarded). In particular,
127 // those methods can not deal with the sliding-forwarding that is used
128 // in Serial, G1 and Shenandoah full-GCs.
129 private:
130 inline Klass* forward_safe_klass_impl(markWord m) const;
131 public:
132 inline Klass* forward_safe_klass() const;
133 inline Klass* forward_safe_klass(markWord m) const;
134 inline size_t forward_safe_size();
135 inline void forward_safe_init_mark();
136
137 // type test operations (inlined in oop.inline.hpp)
138 inline bool is_instance() const;
139 inline bool is_instanceRef() const;
140 inline bool is_stackChunk() const;
141 inline bool is_array() const;
142 inline bool is_objArray() const;
143 inline bool is_typeArray() const;
144
145 // type test operations that don't require inclusion of oop.inline.hpp.
146 bool is_instance_noinline() const;
147 bool is_instanceRef_noinline() const;
148 bool is_stackChunk_noinline() const;
149 bool is_array_noinline() const;
150 bool is_objArray_noinline() const;
151 bool is_typeArray_noinline() const;
152
153 protected:
154 inline oop as_oop() const { return const_cast<oopDesc*>(this); }
155
156 public:
157 template<typename T>
158 inline T* field_addr(int offset) const;
159
160 template <typename T> inline size_t field_offset(T* p) const;
161
162 // Standard compare function returns negative value if o1 < o2
163 // 0 if o1 == o2
164 // positive value if o1 > o2
165 inline static int compare(oop o1, oop o2) {
166 void* o1_addr = (void*)o1;
167 void* o2_addr = (void*)o2;
168 if (o1_addr < o2_addr) {
169 return -1;
170 } else if (o1_addr > o2_addr) {
171 return 1;
172 } else {
173 return 0;
174 }
175 }
176
177 // Access to fields in a instanceOop through these methods.
178 template<DecoratorSet decorators>
179 oop obj_field_access(int offset) const;
180 oop obj_field(int offset) const;
181
182 void obj_field_put(int offset, oop value);
183 void obj_field_put_raw(int offset, oop value);
184 void obj_field_put_volatile(int offset, oop value);
185 template<DecoratorSet decorators>
186 void obj_field_put_access(int offset, oop value);
187
188 Metadata* metadata_field(int offset) const;
189 void metadata_field_put(int offset, Metadata* value);
190
191 Metadata* metadata_field_acquire(int offset) const;
192 void release_metadata_field_put(int offset, Metadata* value);
193
194 jbyte byte_field(int offset) const;
195 void byte_field_put(int offset, jbyte contents);
196
197 jchar char_field(int offset) const;
198 void char_field_put(int offset, jchar contents);
199
200 jboolean bool_field(int offset) const;
201 void bool_field_put(int offset, jboolean contents);
202 jboolean bool_field_volatile(int offset) const;
203 void bool_field_put_volatile(int offset, jboolean contents);
204
205 jint int_field(int offset) const;
206 void int_field_put(int offset, jint contents);
207
208 jshort short_field(int offset) const;
209 void short_field_put(int offset, jshort contents);
210
211 jlong long_field(int offset) const;
212 void long_field_put(int offset, jlong contents);
213
214 jfloat float_field(int offset) const;
215 void float_field_put(int offset, jfloat contents);
216
217 jdouble double_field(int offset) const;
218 void double_field_put(int offset, jdouble contents);
219
220 address address_field(int offset) const;
221 void address_field_put(int offset, address contents);
222
223 oop obj_field_acquire(int offset) const;
224 void release_obj_field_put(int offset, oop value);
225
226 jbyte byte_field_acquire(int offset) const;
227 void release_byte_field_put(int offset, jbyte contents);
228
229 jchar char_field_acquire(int offset) const;
230 void release_char_field_put(int offset, jchar contents);
231
232 jboolean bool_field_acquire(int offset) const;
233 void release_bool_field_put(int offset, jboolean contents);
234
235 jint int_field_acquire(int offset) const;
236 void release_int_field_put(int offset, jint contents);
237
238 jshort short_field_acquire(int offset) const;
239 void release_short_field_put(int offset, jshort contents);
240
241 jlong long_field_acquire(int offset) const;
242 void release_long_field_put(int offset, jlong contents);
243
244 jfloat float_field_acquire(int offset) const;
245 void release_float_field_put(int offset, jfloat contents);
246
247 jdouble double_field_acquire(int offset) const;
248 void release_double_field_put(int offset, jdouble contents);
249
250 address address_field_acquire(int offset) const;
251 void release_address_field_put(int offset, address contents);
252
253 // printing functions for VM debugging
254 void print_on(outputStream* st) const; // First level print
255 void print_value_on(outputStream* st) const; // Second level print.
256 void print_address_on(outputStream* st) const; // Address printing
257 void print_name_on(outputStream* st) const; // External name printing.
258
259 // printing on default output stream
260 void print();
261 void print_value();
262 void print_address();
263
264 // return the print strings
265 char* print_string();
266 char* print_value_string();
267
268 // verification operations
269 static void verify_on(outputStream* st, oopDesc* oop_desc);
270 static void verify(oopDesc* oopDesc);
271
272 // locking operations
273 inline bool is_locked() const;
274 inline bool is_unlocked() const;
275
276 // asserts and guarantees
277 static bool is_oop(oop obj, bool ignore_mark_word = false);
278 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
279
280 // garbage collection
281 inline bool is_gc_marked() const;
282
283 // Forward pointer operations for scavenge
284 inline bool is_forwarded() const;
285
286 inline void forward_to(oop p);
287 inline void forward_to_self();
288
289 // Like "forward_to", but inserts the forwarding pointer atomically.
290 // Exactly one thread succeeds in inserting the forwarding pointer, and
291 // this call returns null for that thread; any other thread has the
292 // value of the forwarding pointer returned and does not modify "this".
293 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
294 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
295
296 inline oop forwardee() const;
297 inline oop forwardee(markWord header) const;
298
299 // Age of object during scavenge
300 inline uint age() const;
301 inline void incr_age();
302
303 template <typename OopClosureType>
304 inline void oop_iterate(OopClosureType* cl);
305
306 template <typename OopClosureType>
307 inline void oop_iterate(OopClosureType* cl, MemRegion mr);
308
309 template <typename OopClosureType>
310 inline size_t oop_iterate_size(OopClosureType* cl);
311
312 template <typename OopClosureType>
313 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
314
315 template <typename OopClosureType>
316 inline void oop_iterate_backwards(OopClosureType* cl);
317
318 template <typename OopClosureType>
319 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
320
321 inline static bool is_instanceof_or_null(oop obj, Klass* klass);
322
323 // identity hash; returns the identity hash key (computes it if necessary)
324 inline intptr_t identity_hash();
325 intptr_t slow_identity_hash();
326 inline bool fast_no_hash_check();
327
328 // marks are forwarded to stack when object is locked
329 inline bool has_displaced_mark() const;
330 inline markWord displaced_mark() const;
331 inline void set_displaced_mark(markWord m);
332
333 // Checks if the mark word needs to be preserved
334 inline bool mark_must_be_preserved() const;
335 inline bool mark_must_be_preserved(markWord m) const;
336
337 static bool has_klass_gap();
338
339 // for code generation
340 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); }
341 static int klass_offset_in_bytes() {
342 #ifdef _LP64
343 if (UseCompactObjectHeaders) {
344 STATIC_ASSERT(markWord::klass_shift % 8 == 0);
345 return mark_offset_in_bytes() + markWord::klass_shift / 8;
346 } else
347 #endif
348 {
349 return (int)offset_of(oopDesc, _metadata._klass);
350 }
351 }
352 static int klass_gap_offset_in_bytes() {
353 assert(has_klass_gap(), "only applicable to compressed klass pointers");
354 assert(!UseCompactObjectHeaders, "don't use klass_offset_in_bytes() with compact headers");
355 return klass_offset_in_bytes() + sizeof(narrowKlass);
356 }
357
358 static int base_offset_in_bytes() {
359 #ifdef _LP64
360 if (UseCompactObjectHeaders) {
361 // With compact headers, the Klass* field is not used for the Klass*
362 // and is used for the object fields instead.
363 STATIC_ASSERT(sizeof(markWord) == 8);
364 return sizeof(markWord);
365 } else if (UseCompressedClassPointers) {
366 return sizeof(markWord) + sizeof(narrowKlass);
367 } else
368 #endif
369 {
370 return sizeof(oopDesc);
371 }
372 }
373
374 // for error reporting
375 static void* load_klass_raw(oop obj);
376 static void* load_oop_raw(oop obj, int offset);
377
378 DEBUG_ONLY(bool size_might_change();)
379 };
380
381 // An oopDesc is not initialized via a constructor. Space is allocated in
382 // the Java heap, and static functions provided here on HeapWord* are used
383 // to fill in certain parts of that memory. The allocated memory is then
384 // treated as referring to an oopDesc. For that to be valid, the oopDesc
385 // class must have a trivial default constructor (C++14 3.8/1).
386 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
387
388 #endif // SHARE_OOPS_OOP_HPP