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. 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 // 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 77 inline void release_set_mark(markWord m); 78 inline markWord cas_set_mark(markWord new_mark, markWord old_mark); 79 inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order); 80 81 // Used only to re-initialize the mark word (e.g., of promoted 82 // objects during a GC) -- requires a valid klass pointer 83 inline void init_mark(); 84 85 inline Klass* klass() const; 86 inline Klass* klass_or_null() const; 87 inline Klass* klass_or_null_acquire() const; 88 89 void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN; 90 inline void set_klass(Klass* k); 91 static inline void release_set_klass(HeapWord* mem, Klass* k); 92 93 // For klass field compression 94 static inline void set_klass_gap(HeapWord* mem, int z); 95 96 // size of object header, aligned to platform wordSize 97 static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; } 98 99 // Returns whether this is an instance of k or an instance of a subclass of k 100 inline bool is_a(Klass* k) const; 101 102 // Returns the actual oop size of the object 103 inline size_t size(); 104 105 // Sometimes (for complicated concurrency-related reasons), it is useful 106 // to be able to figure out the size of an object knowing its klass. 107 inline size_t size_given_klass(Klass* klass); 108 109 // type test operations (inlined in oop.inline.hpp) 110 inline bool is_instance() const; 111 inline bool is_array() const; 112 inline bool is_objArray() const; 113 inline bool is_typeArray() const; 114 115 // type test operations that don't require inclusion of oop.inline.hpp. 116 bool is_instance_noinline() const; 117 bool is_array_noinline() const; 118 bool is_objArray_noinline() const; 119 bool is_typeArray_noinline() const; 120 121 protected: 122 inline oop as_oop() const { return const_cast<oopDesc*>(this); } 123 124 public: 125 template<typename T> 126 inline T* field_addr(int offset) const; 127 128 template <typename T> inline size_t field_offset(T* p) const; 129 130 // Standard compare function returns negative value if o1 < o2 131 // 0 if o1 == o2 132 // positive value if o1 > o2 133 inline static int compare(oop o1, oop o2) { 134 void* o1_addr = (void*)o1; 135 void* o2_addr = (void*)o2; 136 if (o1_addr < o2_addr) { 137 return -1; 138 } else if (o1_addr > o2_addr) { 139 return 1; 140 } else { 141 return 0; 142 } 143 } 144 145 // Access to fields in a instanceOop through these methods. 146 template <DecoratorSet decorator> 147 oop obj_field_access(int offset) const; 148 oop obj_field(int offset) const; 149 void obj_field_put(int offset, oop value); 150 void obj_field_put_raw(int offset, oop value); 151 void obj_field_put_volatile(int offset, oop value); 152 153 Metadata* metadata_field(int offset) const; 154 void metadata_field_put(int offset, Metadata* value); 155 156 Metadata* metadata_field_acquire(int offset) const; 157 void release_metadata_field_put(int offset, Metadata* value); 158 159 jbyte byte_field(int offset) const; 160 void byte_field_put(int offset, jbyte contents); 161 162 jchar char_field(int offset) const; 163 void char_field_put(int offset, jchar contents); 164 165 jboolean bool_field(int offset) const; 166 void bool_field_put(int offset, jboolean contents); 167 jboolean bool_field_volatile(int offset) const; 168 void bool_field_put_volatile(int offset, jboolean contents); 169 170 jint int_field(int offset) const; 171 void int_field_put(int offset, jint contents); 172 173 jshort short_field(int offset) const; 174 void short_field_put(int offset, jshort contents); 175 176 jlong long_field(int offset) const; 177 void long_field_put(int offset, jlong contents); 178 179 jfloat float_field(int offset) const; 180 void float_field_put(int offset, jfloat contents); 181 182 jdouble double_field(int offset) const; 183 void double_field_put(int offset, jdouble contents); 184 185 address address_field(int offset) const; 186 void address_field_put(int offset, address contents); 187 188 oop obj_field_acquire(int offset) const; 189 void release_obj_field_put(int offset, oop value); 190 191 jbyte byte_field_acquire(int offset) const; 192 void release_byte_field_put(int offset, jbyte contents); 193 194 jchar char_field_acquire(int offset) const; 195 void release_char_field_put(int offset, jchar contents); 196 197 jboolean bool_field_acquire(int offset) const; 198 void release_bool_field_put(int offset, jboolean contents); 199 200 jint int_field_acquire(int offset) const; 201 void release_int_field_put(int offset, jint contents); 202 203 jshort short_field_acquire(int offset) const; 204 void release_short_field_put(int offset, jshort contents); 205 206 jlong long_field_acquire(int offset) const; 207 void release_long_field_put(int offset, jlong contents); 208 209 jfloat float_field_acquire(int offset) const; 210 void release_float_field_put(int offset, jfloat contents); 211 212 jdouble double_field_acquire(int offset) const; 213 void release_double_field_put(int offset, jdouble contents); 214 215 address address_field_acquire(int offset) const; 216 void release_address_field_put(int offset, address contents); 217 218 // printing functions for VM debugging 219 void print_on(outputStream* st) const; // First level print 220 void print_value_on(outputStream* st) const; // Second level print. 221 void print_address_on(outputStream* st) const; // Address printing 222 223 // printing on default output stream 224 void print(); 225 void print_value(); 226 void print_address(); 227 228 // return the print strings 229 char* print_string(); 230 char* print_value_string(); 231 232 // verification operations 233 static void verify_on(outputStream* st, oopDesc* oop_desc); 234 static void verify(oopDesc* oopDesc); 235 236 // locking operations 237 inline bool is_locked() const; 238 inline bool is_unlocked() const; 239 240 // asserts and guarantees 241 static bool is_oop(oop obj, bool ignore_mark_word = false); 242 static bool is_oop_or_null(oop obj, bool ignore_mark_word = false); 243 244 // garbage collection 245 inline bool is_gc_marked() const; 246 247 // Forward pointer operations for scavenge 248 inline bool is_forwarded() const; 249 250 void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN; 251 252 inline void forward_to(oop p); 253 254 // Like "forward_to", but inserts the forwarding pointer atomically. 255 // Exactly one thread succeeds in inserting the forwarding pointer, and 256 // this call returns "NULL" for that thread; any other thread has the 257 // value of the forwarding pointer returned and does not modify "this". 258 inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative); 259 260 inline oop forwardee() const; 261 262 // Age of object during scavenge 263 inline uint age() const; 264 inline void incr_age(); 265 266 template <typename OopClosureType> 267 inline void oop_iterate(OopClosureType* cl); 268 269 template <typename OopClosureType> 270 inline void oop_iterate(OopClosureType* cl, MemRegion mr); 271 272 template <typename OopClosureType> 273 inline size_t oop_iterate_size(OopClosureType* cl); 274 275 template <typename OopClosureType> 276 inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr); 277 278 template <typename OopClosureType> 279 inline void oop_iterate_backwards(OopClosureType* cl); 280 281 template <typename OopClosureType> 282 inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass); 283 284 inline static bool is_instanceof_or_null(oop obj, Klass* klass); 285 286 // identity hash; returns the identity hash key (computes it if necessary) 287 inline intptr_t identity_hash(); 288 intptr_t slow_identity_hash(); 289 290 // marks are forwarded to stack when object is locked 291 inline bool has_displaced_mark() const; 292 inline markWord displaced_mark() const; 293 inline void set_displaced_mark(markWord m); 294 295 // Checks if the mark word needs to be preserved 296 inline bool mark_must_be_preserved() const; 297 inline bool mark_must_be_preserved(markWord m) const; 298 299 static bool has_klass_gap(); 300 301 // for code generation 302 static int mark_offset_in_bytes() { return offset_of(oopDesc, _mark); } 303 static int klass_offset_in_bytes() { return offset_of(oopDesc, _metadata._klass); } 304 static int klass_gap_offset_in_bytes() { 305 assert(has_klass_gap(), "only applicable to compressed klass pointers"); 306 return klass_offset_in_bytes() + sizeof(narrowKlass); 307 } 308 309 // for error reporting 310 static void* load_klass_raw(oop obj); 311 static void* load_oop_raw(oop obj, int offset); 312 313 // Avoid include gc_globals.hpp in oop.inline.hpp 314 DEBUG_ONLY(bool get_UseParallelGC();) 315 DEBUG_ONLY(bool get_UseG1GC();) 316 }; 317 318 // An oopDesc is not initialized via a constructor. Space is allocated in 319 // the Java heap, and static functions provided here on HeapWord* are used 320 // to fill in certain parts of that memory. The allocated memory is then 321 // treated as referring to an oopDesc. For that to be valid, the oopDesc 322 // class must have a trivial default constructor (C++14 3.8/1). 323 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required"); 324 325 #endif // SHARE_OOPS_OOP_HPP