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. 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/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 inline bool fast_no_hash_check(); 312 313 // marks are forwarded to stack when object is locked 314 inline bool has_displaced_mark() const; 315 inline markWord displaced_mark() const; 316 inline void set_displaced_mark(markWord m); 317 318 // Checks if the mark word needs to be preserved 319 inline bool mark_must_be_preserved() const; 320 inline bool mark_must_be_preserved(markWord m) const; 321 322 static bool has_klass_gap(); 323 324 // for code generation 325 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); } 326 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); } 327 static int klass_gap_offset_in_bytes() { 328 assert(has_klass_gap(), "only applicable to compressed klass pointers"); 329 return klass_offset_in_bytes() + sizeof(narrowKlass); 330 } 331 332 // for error reporting 333 static void* load_klass_raw(oop obj); 334 static void* load_oop_raw(oop obj, int offset); 335 336 DEBUG_ONLY(bool size_might_change();) 337 }; 338 339 // An oopDesc is not initialized via a constructor. Space is allocated in 340 // the Java heap, and static functions provided here on HeapWord* are used 341 // to fill in certain parts of that memory. The allocated memory is then 342 // treated as referring to an oopDesc. For that to be valid, the oopDesc 343 // class must have a trivial default constructor (C++14 3.8/1). 344 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required"); 345 346 #endif // SHARE_OOPS_OOP_HPP