1 /* 2 * Copyright (c) 1997, 2025, 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 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 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, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 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/compressedKlass.hpp" 31 #include "oops/accessDecorators.hpp" 32 #include "oops/markWord.hpp" 33 #include "oops/metadata.hpp" 34 #include "oops/objLayout.hpp" 35 #include "runtime/atomic.hpp" 36 #include "utilities/globalDefinitions.hpp" 37 #include "utilities/macros.hpp" 38 #include <type_traits> 39 40 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe 41 // the format of Java objects so the fields can be accessed from C++. 42 // oopDesc is abstract. 43 // (see oopHierarchy for complete oop class hierarchy) 44 // 45 // no virtual functions allowed 46 47 class oopDesc { 48 friend class VMStructs; 49 friend class JVMCIVMStructs; 50 private: 51 volatile markWord _mark; 52 union _metadata { 53 Klass* _klass; 54 narrowKlass _compressed_klass; 55 } _metadata; 56 57 // There may be ordering constraints on the initialization of fields that 58 // make use of the C++ copy/assign incorrect. 59 NONCOPYABLE(oopDesc); 60 61 inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order); 62 63 public: 64 // Must be trivial; see verifying static assert after the class. 65 oopDesc() = default; 66 67 inline markWord mark() const; 68 inline markWord mark_acquire() const; 69 inline markWord* mark_addr() const; 70 71 inline void set_mark(markWord m); 72 static inline void set_mark(HeapWord* mem, markWord m); 73 static inline void release_set_mark(HeapWord* mem, markWord m); 74 75 inline void release_set_mark(markWord m); 76 inline markWord cas_set_mark(markWord new_mark, markWord old_mark); 77 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order); 78 79 // Returns the prototype mark that should be used for this object. 80 inline markWord prototype_mark() const; 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 klass without running any asserts. 90 inline Klass* klass_without_asserts() const; 91 92 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN; 93 inline narrowKlass narrow_klass() const; 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 int header_size() { 102 if (UseCompactObjectHeaders) { 103 return sizeof(markWord) / HeapWordSize; 104 } else { 105 return sizeof(oopDesc) / HeapWordSize; 106 } 107 } 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_instanceRef() const; 122 inline bool is_stackChunk() const; 123 inline bool is_array() const; 124 inline bool is_objArray() const; 125 inline bool is_typeArray() const; 126 127 // type test operations that don't require inclusion of oop.inline.hpp. 128 bool is_instance_noinline() const; 129 bool is_instanceRef_noinline() const; 130 bool is_stackChunk_noinline() const; 131 bool is_array_noinline() const; 132 bool is_objArray_noinline() const; 133 bool is_typeArray_noinline() const; 134 135 protected: 136 inline oop as_oop() const { return const_cast<oopDesc*>(this); } 137 138 public: 139 template<typename T> 140 inline T* field_addr(int offset) const; 141 142 template <typename T> inline size_t field_offset(T* p) const; 143 144 // Standard compare function returns negative value if o1 < o2 145 // 0 if o1 == o2 146 // positive value if o1 > o2 147 inline static int compare(oop o1, oop o2) { 148 void* o1_addr = (void*)o1; 149 void* o2_addr = (void*)o2; 150 if (o1_addr < o2_addr) { 151 return -1; 152 } else if (o1_addr > o2_addr) { 153 return 1; 154 } else { 155 return 0; 156 } 157 } 158 159 // Access to fields in a instanceOop through these methods. 160 template<DecoratorSet decorators> 161 oop obj_field_access(int offset) const; 162 oop obj_field(int offset) const; 163 164 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 template<DecoratorSet decorators> 168 void obj_field_put_access(int offset, oop value); 169 170 Metadata* metadata_field(int offset) const; 171 void metadata_field_put(int offset, Metadata* value); 172 173 Metadata* metadata_field_acquire(int offset) const; 174 void release_metadata_field_put(int offset, Metadata* value); 175 176 jbyte byte_field(int offset) const; 177 void byte_field_put(int offset, jbyte contents); 178 179 jchar char_field(int offset) const; 180 void char_field_put(int offset, jchar contents); 181 182 jboolean bool_field(int offset) const; 183 void bool_field_put(int offset, jboolean contents); 184 jboolean bool_field_volatile(int offset) const; 185 void bool_field_put_volatile(int offset, jboolean contents); 186 187 jint int_field(int offset) const; 188 void int_field_put(int offset, jint contents); 189 190 jshort short_field(int offset) const; 191 void short_field_put(int offset, jshort contents); 192 193 jlong long_field(int offset) const; 194 void long_field_put(int offset, jlong contents); 195 196 jfloat float_field(int offset) const; 197 void float_field_put(int offset, jfloat contents); 198 199 jdouble double_field(int offset) const; 200 void double_field_put(int offset, jdouble contents); 201 202 address address_field(int offset) const; 203 void address_field_put(int offset, address contents); 204 205 oop obj_field_acquire(int offset) const; 206 void release_obj_field_put(int offset, oop value); 207 208 jbyte byte_field_acquire(int offset) const; 209 void release_byte_field_put(int offset, jbyte contents); 210 211 jchar char_field_acquire(int offset) const; 212 void release_char_field_put(int offset, jchar contents); 213 214 jboolean bool_field_acquire(int offset) const; 215 void release_bool_field_put(int offset, jboolean contents); 216 217 jint int_field_relaxed(int offset) const; 218 void int_field_put_relaxed(int offset, jint contents); 219 jint int_field_acquire(int offset) const; 220 void release_int_field_put(int offset, jint contents); 221 222 jshort short_field_acquire(int offset) const; 223 void release_short_field_put(int offset, jshort contents); 224 225 jlong long_field_acquire(int offset) const; 226 void release_long_field_put(int offset, jlong contents); 227 228 jfloat float_field_acquire(int offset) const; 229 void release_float_field_put(int offset, jfloat contents); 230 231 jdouble double_field_acquire(int offset) const; 232 void release_double_field_put(int offset, jdouble contents); 233 234 address address_field_acquire(int offset) const; 235 void release_address_field_put(int offset, address contents); 236 237 // printing functions for VM debugging 238 void print_on(outputStream* st) const; // First level print 239 void print_value_on(outputStream* st) const; // Second level print. 240 void print_address_on(outputStream* st) const; // Address printing 241 void print_name_on(outputStream* st) const; // External name printing. 242 243 // printing on default output stream 244 void print(); 245 void print_value(); 246 void print_address(); 247 248 // return the print strings 249 char* print_string(); 250 char* print_value_string(); 251 252 // verification operations 253 static void verify_on(outputStream* st, oopDesc* oop_desc); 254 static void verify(oopDesc* oopDesc); 255 256 // locking operations 257 inline bool is_locked() const; 258 inline bool is_unlocked() const; 259 260 // asserts and guarantees 261 static bool is_oop(oop obj, bool ignore_mark_word = false); 262 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false); 263 264 // garbage collection 265 inline bool is_gc_marked() const; 266 267 // Forward pointer operations for scavenge 268 inline bool is_forwarded() const; 269 inline bool is_self_forwarded() const; 270 271 inline void forward_to(oop p); 272 inline void forward_to_self(); 273 274 // Like "forward_to", but inserts the forwarding pointer atomically. 275 // Exactly one thread succeeds in inserting the forwarding pointer, and 276 // this call returns null for that thread; any other thread has the 277 // value of the forwarding pointer returned and does not modify "this". 278 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative); 279 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative); 280 281 inline oop forwardee() const; 282 inline oop forwardee(markWord header) const; 283 284 inline void unset_self_forwarded(); 285 286 // Age of object during scavenge 287 inline uint age() const; 288 inline void incr_age(); 289 290 template <typename OopClosureType> 291 inline void oop_iterate(OopClosureType* cl); 292 293 template <typename OopClosureType> 294 inline void oop_iterate(OopClosureType* cl, MemRegion mr); 295 296 template <typename OopClosureType> 297 inline size_t oop_iterate_size(OopClosureType* cl); 298 299 template <typename OopClosureType> 300 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr); 301 302 template <typename OopClosureType> 303 inline void oop_iterate_backwards(OopClosureType* cl); 304 305 template <typename OopClosureType> 306 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass); 307 308 inline static bool is_instanceof_or_null(oop obj, Klass* klass); 309 310 // identity hash; returns the identity hash key (computes it if necessary) 311 inline intptr_t identity_hash(); 312 intptr_t slow_identity_hash(); 313 inline bool fast_no_hash_check(); 314 315 // marks are forwarded to stack when object is locked 316 inline bool has_displaced_mark() const; 317 inline markWord displaced_mark() const; 318 inline void set_displaced_mark(markWord m); 319 320 // Checks if the mark word needs to be preserved 321 inline bool mark_must_be_preserved() const; 322 inline bool mark_must_be_preserved(markWord m) const; 323 324 inline static bool has_klass_gap() { 325 return ObjLayout::oop_has_klass_gap(); 326 } 327 328 // for code generation 329 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); } 330 static int klass_offset_in_bytes() { 331 #ifdef _LP64 332 if (UseCompactObjectHeaders) { 333 // NOTE: The only places where this is used with compact headers are the C2 334 // compiler and JVMCI. 335 return mark_offset_in_bytes() + markWord::klass_offset_in_bytes; 336 } else 337 #endif 338 { 339 return (int)offset_of(oopDesc, _metadata._klass); 340 } 341 } 342 static int klass_gap_offset_in_bytes() { 343 assert(has_klass_gap(), "only applicable to compressed klass pointers"); 344 return klass_offset_in_bytes() + sizeof(narrowKlass); 345 } 346 347 static int base_offset_in_bytes() { 348 return ObjLayout::oop_base_offset_in_bytes(); 349 } 350 351 // for error reporting 352 static void* load_oop_raw(oop obj, int offset); 353 }; 354 355 // An oopDesc is not initialized via a constructor. Space is allocated in 356 // the Java heap, and static functions provided here on HeapWord* are used 357 // to fill in certain parts of that memory. The allocated memory is then 358 // treated as referring to an oopDesc. For that to be valid, the oopDesc 359 // class must have a trivial default constructor (C++14 3.8/1). 360 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required"); 361 362 #endif // SHARE_OOPS_OOP_HPP