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