1 /*
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  6  * under the terms of the GNU General Public License version 2 only, as
  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   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   inline int klass_gap() const;
 95   inline void set_klass_gap(int z);
 96   static inline void set_klass_gap(HeapWord* mem, int z);
 97 
 98   // size of object header, aligned to platform wordSize
 99   static int header_size() { return sizeof(oopDesc)/HeapWordSize; }
100 
101   // Returns whether this is an instance of k or an instance of a subclass of k
102   inline bool is_a(Klass* k) const;
103 
104   // Returns the actual oop size of the object
105   inline int size();
106 
107   // Sometimes (for complicated concurrency-related reasons), it is useful
108   // to be able to figure out the size of an object knowing its klass.
109   inline int size_given_klass(Klass* klass);
110 
111   // type test operations (inlined in oop.inline.hpp)
112   inline bool is_instance()            const;
113   inline bool is_array()               const;
114   inline bool is_objArray()            const;
115   inline bool is_typeArray()           const;
116 
117   // type test operations that don't require inclusion of oop.inline.hpp.
118   bool is_instance_noinline()          const;
119   bool is_array_noinline()             const;
120   bool is_objArray_noinline()          const;
121   bool is_typeArray_noinline()         const;
122 
123  protected:
124   inline oop        as_oop() const { return const_cast<oopDesc*>(this); }
125 
126  public:
127   // field addresses in oop
128   inline void* field_addr(int offset) const;
129 
130   // Need this as public for garbage collection.
131   template <class T> inline T* obj_field_addr(int offset) const;
132 
133   template <typename T> inline size_t field_offset(T* p) const;
134 
135   // Standard compare function returns negative value if o1 < o2
136   //                                   0              if o1 == o2
137   //                                   positive value if o1 > o2
138   inline static int  compare(oop o1, oop o2) {
139     void* o1_addr = (void*)o1;
140     void* o2_addr = (void*)o2;
141     if (o1_addr < o2_addr) {
142       return -1;
143     } else if (o1_addr > o2_addr) {
144       return 1;
145     } else {
146       return 0;
147     }
148   }
149 
150   // Access to fields in a instanceOop through these methods.
151   template <DecoratorSet decorator>
152   oop obj_field_access(int offset) const;
153   oop obj_field(int offset) const;
154   void obj_field_put(int offset, oop value);
155   void obj_field_put_raw(int offset, oop value);
156   void obj_field_put_volatile(int offset, oop value);
157 
158   Metadata* metadata_field(int offset) const;
159   void metadata_field_put(int offset, Metadata* value);
160 
161   Metadata* metadata_field_acquire(int offset) const;
162   void release_metadata_field_put(int offset, Metadata* value);
163 
164   jbyte byte_field(int offset) const;
165   void byte_field_put(int offset, jbyte contents);
166 
167   jchar char_field(int offset) const;
168   void char_field_put(int offset, jchar contents);
169 
170   jboolean bool_field(int offset) const;
171   void bool_field_put(int offset, jboolean contents);
172   jboolean bool_field_volatile(int offset) const;
173   void bool_field_put_volatile(int offset, jboolean contents);
174 
175   jint int_field(int offset) const;
176   void int_field_put(int offset, jint contents);
177 
178   jshort short_field(int offset) const;
179   void short_field_put(int offset, jshort contents);
180 
181   jlong long_field(int offset) const;
182   void long_field_put(int offset, jlong contents);
183 
184   jfloat float_field(int offset) const;
185   void float_field_put(int offset, jfloat contents);
186 
187   jdouble double_field(int offset) const;
188   void double_field_put(int offset, jdouble contents);
189 
190   address address_field(int offset) const;
191   void address_field_put(int offset, address contents);
192 
193   oop obj_field_acquire(int offset) const;
194   void release_obj_field_put(int offset, oop value);
195 
196   jbyte byte_field_acquire(int offset) const;
197   void release_byte_field_put(int offset, jbyte contents);
198 
199   jchar char_field_acquire(int offset) const;
200   void release_char_field_put(int offset, jchar contents);
201 
202   jboolean bool_field_acquire(int offset) const;
203   void release_bool_field_put(int offset, jboolean contents);
204 
205   jint int_field_acquire(int offset) const;
206   void release_int_field_put(int offset, jint contents);
207 
208   jshort short_field_acquire(int offset) const;
209   void release_short_field_put(int offset, jshort contents);
210 
211   jlong long_field_acquire(int offset) const;
212   void release_long_field_put(int offset, jlong contents);
213 
214   jfloat float_field_acquire(int offset) const;
215   void release_float_field_put(int offset, jfloat contents);
216 
217   jdouble double_field_acquire(int offset) const;
218   void release_double_field_put(int offset, jdouble contents);
219 
220   address address_field_acquire(int offset) const;
221   void release_address_field_put(int offset, address contents);
222 
223   // printing functions for VM debugging
224   void print_on(outputStream* st) const;        // First level print
225   void print_value_on(outputStream* st) const;  // Second level print.
226   void print_address_on(outputStream* st) const; // Address printing
227 
228   // printing on default output stream
229   void print();
230   void print_value();
231   void print_address();
232 
233   // return the print strings
234   char* print_string();
235   char* print_value_string();
236 
237   // verification operations
238   static void verify_on(outputStream* st, oopDesc* oop_desc);
239   static void verify(oopDesc* oopDesc);
240 
241   // locking operations
242   inline bool is_locked()   const;
243   inline bool is_unlocked() const;
244 
245   // asserts and guarantees
246   static bool is_oop(oop obj, bool ignore_mark_word = false);
247   static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
248 
249   // garbage collection
250   inline bool is_gc_marked() const;
251 
252   // Forward pointer operations for scavenge
253   inline bool is_forwarded() const;
254 
255   void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
256 
257   inline void forward_to(oop p);
258 
259   // Like "forward_to", but inserts the forwarding pointer atomically.
260   // Exactly one thread succeeds in inserting the forwarding pointer, and
261   // this call returns "NULL" for that thread; any other thread has the
262   // value of the forwarding pointer returned and does not modify "this".
263   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
264 
265   inline oop forwardee() const;
266 
267   // Age of object during scavenge
268   inline uint age() const;
269   inline void incr_age();
270 
271   template <typename OopClosureType>
272   inline void oop_iterate(OopClosureType* cl);
273 
274   template <typename OopClosureType>
275   inline void oop_iterate(OopClosureType* cl, MemRegion mr);
276 
277   template <typename OopClosureType>
278   inline int oop_iterate_size(OopClosureType* cl);
279 
280   template <typename OopClosureType>
281   inline int oop_iterate_size(OopClosureType* cl, MemRegion mr);
282 
283   template <typename OopClosureType>
284   inline void oop_iterate_backwards(OopClosureType* cl);
285 
286   template <typename OopClosureType>
287   inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
288 
289   inline static bool is_instanceof_or_null(oop obj, Klass* klass);
290 
291   // identity hash; returns the identity hash key (computes it if necessary)
292   inline intptr_t identity_hash();
293   intptr_t slow_identity_hash();
294 
295   // marks are forwarded to stack when object is locked
296   inline bool     has_displaced_mark() const;
297   inline markWord displaced_mark() const;
298   inline void     set_displaced_mark(markWord m);
299 
300   // Checks if the mark word needs to be preserved
301   inline bool mark_must_be_preserved() const;
302   inline bool mark_must_be_preserved(markWord m) const;
303 
304   static bool has_klass_gap();
305 
306   // for code generation
307   static int mark_offset_in_bytes()      { return offset_of(oopDesc, _mark); }
308   static int klass_offset_in_bytes()     { return offset_of(oopDesc, _metadata._klass); }
309   static int klass_gap_offset_in_bytes() {
310     assert(has_klass_gap(), "only applicable to compressed klass pointers");
311     return klass_offset_in_bytes() + sizeof(narrowKlass);
312   }
313 
314   // for error reporting
315   static void* load_klass_raw(oop obj);
316   static void* load_oop_raw(oop obj, int offset);
317 
318   // Avoid include gc_globals.hpp in oop.inline.hpp
319   DEBUG_ONLY(bool get_UseParallelGC();)
320   DEBUG_ONLY(bool get_UseG1GC();)
321 };
322 
323 // An oopDesc is not initialized via a constructor.  Space is allocated in
324 // the Java heap, and static functions provided here on HeapWord* are used
325 // to fill in certain parts of that memory.  The allocated memory is then
326 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
327 // class must have a trivial default constructor (C++14 3.8/1).
328 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
329 
330 #endif // SHARE_OOPS_OOP_HPP