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 void set_klass(Klass* k); 94 static inline void release_set_klass(HeapWord* mem, Klass* k); 95 96 // For klass field compression 97 static inline void set_klass_gap(HeapWord* mem, int z); 98 99 // Size of object header, aligned to platform wordSize 100 static int header_size() { 101 if (UseCompactObjectHeaders) { 102 return sizeof(markWord) / HeapWordSize; 103 } else { 104 return sizeof(oopDesc) / HeapWordSize; 105 } 106 } 107 108 // Returns whether this is an instance of k or an instance of a subclass of k 109 inline bool is_a(Klass* k) const; 110 111 // Returns the actual oop size of the object in machine words 112 inline size_t size(); 113 114 // Sometimes (for complicated concurrency-related reasons), it is useful 115 // to be able to figure out the size of an object knowing its klass. 116 inline size_t size_given_klass(Klass* klass); 117 118 // type test operations (inlined in oop.inline.hpp) 119 inline bool is_instance() const; 120 inline bool is_instanceRef() const; 121 inline bool is_stackChunk() const; 122 inline bool is_array() const; 123 inline bool is_objArray() const; 124 inline bool is_typeArray() const; 125 126 // type test operations that don't require inclusion of oop.inline.hpp. 127 bool is_instance_noinline() const; 128 bool is_instanceRef_noinline() const; 129 bool is_stackChunk_noinline() const; 130 bool is_array_noinline() const; 131 bool is_objArray_noinline() const; 132 bool is_typeArray_noinline() const; 133 134 protected: 135 inline oop as_oop() const { return const_cast<oopDesc*>(this); } 136 137 public: 138 template<typename T> 139 inline T* field_addr(int offset) const; 140 141 template <typename T> inline size_t field_offset(T* p) const; 142 143 // Standard compare function returns negative value if o1 < o2 144 // 0 if o1 == o2 145 // positive value if o1 > o2 146 inline static int compare(oop o1, oop o2) { 147 void* o1_addr = (void*)o1; 148 void* o2_addr = (void*)o2; 149 if (o1_addr < o2_addr) { 150 return -1; 151 } else if (o1_addr > o2_addr) { 152 return 1; 153 } else { 154 return 0; 155 } 156 } 157 158 // Access to fields in a instanceOop through these methods. 159 template<DecoratorSet decorators> 160 oop obj_field_access(int offset) const; 161 oop obj_field(int offset) const; 162 163 void obj_field_put(int offset, oop value); 164 void obj_field_put_raw(int offset, oop value); 165 void obj_field_put_volatile(int offset, oop value); 166 template<DecoratorSet decorators> 167 void obj_field_put_access(int offset, oop value); 168 169 Metadata* metadata_field(int offset) const; 170 void metadata_field_put(int offset, Metadata* value); 171 172 Metadata* metadata_field_acquire(int offset) const; 173 void release_metadata_field_put(int offset, Metadata* value); 174 175 jbyte byte_field(int offset) const; 176 void byte_field_put(int offset, jbyte contents); 177 178 jchar char_field(int offset) const; 179 void char_field_put(int offset, jchar contents); 180 181 jboolean bool_field(int offset) const; 182 void bool_field_put(int offset, jboolean contents); 183 jboolean bool_field_volatile(int offset) const; 184 void bool_field_put_volatile(int offset, jboolean contents); 185 186 jint int_field(int offset) const; 187 void int_field_put(int offset, jint contents); 188 189 jshort short_field(int offset) const; 190 void short_field_put(int offset, jshort contents); 191 192 jlong long_field(int offset) const; 193 void long_field_put(int offset, jlong contents); 194 195 jfloat float_field(int offset) const; 196 void float_field_put(int offset, jfloat contents); 197 198 jdouble double_field(int offset) const; 199 void double_field_put(int offset, jdouble contents); 200 201 address address_field(int offset) const; 202 void address_field_put(int offset, address contents); 203 204 oop obj_field_acquire(int offset) const; 205 void release_obj_field_put(int offset, oop value); 206 207 jbyte byte_field_acquire(int offset) const; 208 void release_byte_field_put(int offset, jbyte contents); 209 210 jchar char_field_acquire(int offset) const; 211 void release_char_field_put(int offset, jchar contents); 212 213 jboolean bool_field_acquire(int offset) const; 214 void release_bool_field_put(int offset, jboolean contents); 215 216 jint int_field_relaxed(int offset) const; 217 void int_field_put_relaxed(int offset, jint contents); 218 jint int_field_acquire(int offset) const; 219 void release_int_field_put(int offset, jint contents); 220 221 jshort short_field_acquire(int offset) const; 222 void release_short_field_put(int offset, jshort contents); 223 224 jlong long_field_acquire(int offset) const; 225 void release_long_field_put(int offset, jlong contents); 226 227 jfloat float_field_acquire(int offset) const; 228 void release_float_field_put(int offset, jfloat contents); 229 230 jdouble double_field_acquire(int offset) const; 231 void release_double_field_put(int offset, jdouble contents); 232 233 address address_field_acquire(int offset) const; 234 void release_address_field_put(int offset, address contents); 235 236 // printing functions for VM debugging 237 void print_on(outputStream* st) const; // First level print 238 void print_value_on(outputStream* st) const; // Second level print. 239 void print_address_on(outputStream* st) const; // Address printing 240 void print_name_on(outputStream* st) const; // External name printing. 241 242 // printing on default output stream 243 void print(); 244 void print_value(); 245 void print_address(); 246 247 // return the print strings 248 char* print_string(); 249 char* print_value_string(); 250 251 // verification operations 252 static void verify_on(outputStream* st, oopDesc* oop_desc); 253 static void verify(oopDesc* oopDesc); 254 255 // locking operations 256 inline bool is_locked() const; 257 inline bool is_unlocked() const; 258 259 // asserts and guarantees 260 static bool is_oop(oop obj, bool ignore_mark_word = false); 261 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false); 262 263 // garbage collection 264 inline bool is_gc_marked() const; 265 266 // Forward pointer operations for scavenge 267 inline bool is_forwarded() const; 268 inline bool is_self_forwarded() const; 269 270 inline void forward_to(oop p); 271 inline void forward_to_self(); 272 273 // Like "forward_to", but inserts the forwarding pointer atomically. 274 // Exactly one thread succeeds in inserting the forwarding pointer, and 275 // this call returns null for that thread; any other thread has the 276 // value of the forwarding pointer returned and does not modify "this". 277 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative); 278 inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative); 279 280 inline oop forwardee() const; 281 inline oop forwardee(markWord header) const; 282 283 inline void unset_self_forwarded(); 284 285 // Age of object during scavenge 286 inline uint age() const; 287 inline void incr_age(); 288 289 template <typename OopClosureType> 290 inline void oop_iterate(OopClosureType* cl); 291 292 template <typename OopClosureType> 293 inline void oop_iterate(OopClosureType* cl, MemRegion mr); 294 295 template <typename OopClosureType> 296 inline size_t oop_iterate_size(OopClosureType* cl); 297 298 template <typename OopClosureType> 299 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr); 300 301 template <typename OopClosureType> 302 inline void oop_iterate_backwards(OopClosureType* cl); 303 304 template <typename OopClosureType> 305 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass); 306 307 inline static bool is_instanceof_or_null(oop obj, Klass* klass); 308 309 // identity hash; returns the identity hash key (computes it if necessary) 310 inline intptr_t identity_hash(); 311 intptr_t slow_identity_hash(); 312 inline bool fast_no_hash_check(); 313 314 // marks are forwarded to stack when object is locked 315 inline bool has_displaced_mark() const; 316 inline markWord displaced_mark() const; 317 inline void set_displaced_mark(markWord m); 318 319 // Checks if the mark word needs to be preserved 320 inline bool mark_must_be_preserved() const; 321 inline bool mark_must_be_preserved(markWord m) const; 322 323 inline static bool has_klass_gap() { 324 return ObjLayout::oop_has_klass_gap(); 325 } 326 327 // for code generation 328 static int mark_offset_in_bytes() { return (int)offset_of(oopDesc, _mark); } 329 static int klass_offset_in_bytes() { 330 #ifdef _LP64 331 if (UseCompactObjectHeaders) { 332 // NOTE: The only places where this is used with compact headers are the C2 333 // compiler and JVMCI. 334 return mark_offset_in_bytes() + markWord::klass_offset_in_bytes; 335 } else 336 #endif 337 { 338 return (int)offset_of(oopDesc, _metadata._klass); 339 } 340 } 341 static int klass_gap_offset_in_bytes() { 342 assert(has_klass_gap(), "only applicable to compressed klass pointers"); 343 return klass_offset_in_bytes() + sizeof(narrowKlass); 344 } 345 346 static int base_offset_in_bytes() { 347 return ObjLayout::oop_base_offset_in_bytes(); 348 } 349 350 // for error reporting 351 static void* load_oop_raw(oop obj, int offset); 352 }; 353 354 // An oopDesc is not initialized via a constructor. Space is allocated in 355 // the Java heap, and static functions provided here on HeapWord* are used 356 // to fill in certain parts of that memory. The allocated memory is then 357 // treated as referring to an oopDesc. For that to be valid, the oopDesc 358 // class must have a trivial default constructor (C++14 3.8/1). 359 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required"); 360 361 #endif // SHARE_OOPS_OOP_HPP