1 /*
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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).
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 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   narrowKlass narrow_klass_legacy() const { return _metadata._compressed_klass; }
 90   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
 91   inline void set_klass(Klass* k);
 92   static inline void release_set_klass(HeapWord* mem, Klass* k);
 93 
 94   // For klass field compression
 95   inline int klass_gap() const;
 96   inline void set_klass_gap(int z);
 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() { return sizeof(oopDesc)/HeapWordSize; }
101 
102   // Returns whether this is an instance of k or an instance of a subclass of k
103   inline bool is_a(Klass* k) const;
104 
105   // Returns the actual oop size of the object
106   inline size_t size();
107 
108   // Sometimes (for complicated concurrency-related reasons), it is useful
109   // to be able to figure out the size of an object knowing its klass.
110   inline size_t size_given_klass(Klass* klass);
111 
112   // type test operations (inlined in oop.inline.hpp)
113   inline bool is_instance()            const;
114   inline bool is_array()               const;
115   inline bool is_objArray()            const;
116   inline bool is_typeArray()           const;
117 
118   // type test operations that don't require inclusion of oop.inline.hpp.
119   bool is_instance_noinline()          const;
120   bool is_array_noinline()             const;
121   bool is_objArray_noinline()          const;
122   bool is_typeArray_noinline()         const;
123 
124  protected:
125   inline oop        as_oop() const { return const_cast<oopDesc*>(this); }
126 
127  public:
128   template<typename T>
129   inline T* field_addr(int offset) const;
130 
131   template <typename T> inline size_t field_offset(T* p) const;
132 
133   // Standard compare function returns negative value if o1 < o2
134   //                                   0              if o1 == o2
135   //                                   positive value if o1 > o2
136   inline static int  compare(oop o1, oop o2) {
137     void* o1_addr = (void*)o1;
138     void* o2_addr = (void*)o2;
139     if (o1_addr < o2_addr) {
140       return -1;
141     } else if (o1_addr > o2_addr) {
142       return 1;
143     } else {
144       return 0;
145     }
146   }
147 
148   // Access to fields in a instanceOop through these methods.
149   template <DecoratorSet decorator>
150   oop obj_field_access(int offset) const;
151   oop obj_field(int offset) const;
152   void obj_field_put(int offset, oop value);
153   void obj_field_put_raw(int offset, oop value);
154   void obj_field_put_volatile(int offset, oop value);
155 
156   Metadata* metadata_field(int offset) const;
157   void metadata_field_put(int offset, Metadata* value);
158 
159   Metadata* metadata_field_acquire(int offset) const;
160   void release_metadata_field_put(int offset, Metadata* value);
161 
162   jbyte byte_field(int offset) const;
163   void byte_field_put(int offset, jbyte contents);
164 
165   jchar char_field(int offset) const;
166   void char_field_put(int offset, jchar contents);
167 
168   jboolean bool_field(int offset) const;
169   void bool_field_put(int offset, jboolean contents);
170   jboolean bool_field_volatile(int offset) const;
171   void bool_field_put_volatile(int offset, jboolean contents);
172 
173   jint int_field(int offset) const;
174   void int_field_put(int offset, jint contents);
175 
176   jshort short_field(int offset) const;
177   void short_field_put(int offset, jshort contents);
178 
179   jlong long_field(int offset) const;
180   void long_field_put(int offset, jlong contents);
181 
182   jfloat float_field(int offset) const;
183   void float_field_put(int offset, jfloat contents);
184 
185   jdouble double_field(int offset) const;
186   void double_field_put(int offset, jdouble contents);
187 
188   address address_field(int offset) const;
189   void address_field_put(int offset, address contents);
190 
191   oop obj_field_acquire(int offset) const;
192   void release_obj_field_put(int offset, oop value);
193 
194   jbyte byte_field_acquire(int offset) const;
195   void release_byte_field_put(int offset, jbyte contents);
196 
197   jchar char_field_acquire(int offset) const;
198   void release_char_field_put(int offset, jchar contents);
199 
200   jboolean bool_field_acquire(int offset) const;
201   void release_bool_field_put(int offset, jboolean contents);
202 
203   jint int_field_acquire(int offset) const;
204   void release_int_field_put(int offset, jint contents);
205 
206   jshort short_field_acquire(int offset) const;
207   void release_short_field_put(int offset, jshort contents);
208 
209   jlong long_field_acquire(int offset) const;
210   void release_long_field_put(int offset, jlong contents);
211 
212   jfloat float_field_acquire(int offset) const;
213   void release_float_field_put(int offset, jfloat contents);
214 
215   jdouble double_field_acquire(int offset) const;
216   void release_double_field_put(int offset, jdouble contents);
217 
218   address address_field_acquire(int offset) const;
219   void release_address_field_put(int offset, address contents);
220 
221   // printing functions for VM debugging
222   void print_on(outputStream* st) const;        // First level print
223   void print_value_on(outputStream* st) const;  // Second level print.
224   void print_address_on(outputStream* st) const; // Address printing
225 
226   // printing on default output stream
227   void print();
228   void print_value();
229   void print_address();
230 
231   // return the print strings
232   char* print_string();
233   char* print_value_string();
234 
235   // verification operations
236   static void verify_on(outputStream* st, oopDesc* oop_desc);
237   static void verify(oopDesc* oopDesc);
238 
239   // locking operations
240   inline bool is_locked()   const;
241   inline bool is_unlocked() const;
242 
243   // asserts and guarantees
244   static bool is_oop(oop obj, bool ignore_mark_word = false);
245   static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
246 
247   // garbage collection
248   inline bool is_gc_marked() const;
249 
250   // Forward pointer operations for scavenge
251   inline bool is_forwarded() const;
252 
253   void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
254 
255   inline void forward_to(oop p);
256   inline void forward_to_self();
257 
258   // Like "forward_to", but inserts the forwarding pointer atomically.
259   // Exactly one thread succeeds in inserting the forwarding pointer, and
260   // this call returns "NULL" for that thread; any other thread has the
261   // value of the forwarding pointer returned and does not modify "this".
262   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
263   inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
264 
265   inline oop forwardee() const;
266   inline oop forwardee(markWord header) const;
267 
268   // Age of object during scavenge
269   inline uint age() const;
270   inline void incr_age();
271 
272   template <typename OopClosureType>
273   inline void oop_iterate(OopClosureType* cl);
274 
275   template <typename OopClosureType>
276   inline void oop_iterate(OopClosureType* cl, MemRegion mr);
277 
278   template <typename OopClosureType>
279   inline size_t oop_iterate_size(OopClosureType* cl);
280 
281   template <typename OopClosureType>
282   inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
283 
284   template <typename OopClosureType>
285   inline void oop_iterate_backwards(OopClosureType* cl);
286 
287   template <typename OopClosureType>
288   inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
289 
290   inline static bool is_instanceof_or_null(oop obj, Klass* klass);
291 
292   // identity hash; returns the identity hash key (computes it if necessary)
293   inline intptr_t identity_hash();
294   intptr_t slow_identity_hash();
295 
296   // marks are forwarded to stack when object is locked
297   inline bool     has_displaced_mark() const;
298   inline markWord displaced_mark() const;
299   inline void     set_displaced_mark(markWord m);
300 
301   // Checks if the mark word needs to be preserved
302   inline bool mark_must_be_preserved() const;
303   inline bool mark_must_be_preserved(markWord m) const;
304 
305   static bool has_klass_gap();
306 
307   // for code generation
308   static int mark_offset_in_bytes()      { return offset_of(oopDesc, _mark); }
309   static int klass_offset_in_bytes()     { return offset_of(oopDesc, _metadata._klass); }
310   static int klass_gap_offset_in_bytes() {
311     assert(has_klass_gap(), "only applicable to compressed klass pointers");
312     return klass_offset_in_bytes() + sizeof(narrowKlass);
313   }
314 
315   // for error reporting
316   static void* load_klass_raw(oop obj);
317   static void* load_oop_raw(oop obj, int offset);
318 
319   // Runtime entry
320   static Klass* load_klass_runtime(oopDesc* o);
321 
322   // Avoid include gc_globals.hpp in oop.inline.hpp
323   DEBUG_ONLY(bool get_UseParallelGC();)
324   DEBUG_ONLY(bool get_UseG1GC();)
325 };
326 
327 // An oopDesc is not initialized via a constructor.  Space is allocated in
328 // the Java heap, and static functions provided here on HeapWord* are used
329 // to fill in certain parts of that memory.  The allocated memory is then
330 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
331 // class must have a trivial default constructor (C++14 3.8/1).
332 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
333 
334 #endif // SHARE_OOPS_OOP_HPP