1 /*
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 12  * version 2 for more details (a copy is included in the LICENSE file that
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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/compressedKlass.hpp"
 32 #include "oops/markWord.hpp"
 33 #include "oops/metadata.hpp"
 34 #include "oops/objLayout.hpp"
 35 #include "runtime/atomicAccess.hpp"
 36 #include "utilities/globalDefinitions.hpp"
 37 #include "utilities/macros.hpp"
 38 
 39 #include <type_traits>
 40 
 41 // oopDesc is the top baseclass for objects classes. The {name}Desc classes describe
 42 // the format of Java objects so the fields can be accessed from C++.
 43 // oopDesc is abstract.
 44 // (see oopHierarchy for complete oop class hierarchy)
 45 //
 46 // no virtual functions allowed
 47 //
 48 // oopDesc::_mark - the "oop mark word" encoding to be found separately in markWord.hpp
 49 //
 50 // oopDesc::_metadata - encodes the object's klass pointer, as a raw pointer in "_klass"
 51 //                      or compressed pointer in "_compressed_klass"
 52 //
 53 // The overall size of the _metadata field is dependent on "UseCompressedClassPointers",
 54 // hence the terms "narrow" (32 bits) vs "wide" (64 bits).
 55 //
 56 
 57 
 58 class oopDesc {
 59   friend class VMStructs;
 60   friend class JVMCIVMStructs;
 61  private:
 62   volatile markWord _mark;
 63   union _metadata {
 64     Klass*      _klass;
 65     narrowKlass _compressed_klass;
 66   } _metadata;
 67 
 68   // There may be ordering constraints on the initialization of fields that
 69   // make use of the C++ copy/assign incorrect.
 70   NONCOPYABLE(oopDesc);
 71 
 72   inline oop cas_set_forwardee(markWord new_mark, markWord old_mark, atomic_memory_order order);
 73 
 74  public:
 75   // Must be trivial; see verifying static assert after the class.
 76   oopDesc() = default;
 77 
 78   inline void* base_addr();
 79   inline const void* base_addr() const;
 80 
 81   inline markWord  mark()          const;
 82   inline markWord  mark_acquire()  const;
 83 
 84   inline void set_mark(markWord m);
 85   static inline void set_mark(HeapWord* mem, markWord m);
 86   static inline void release_set_mark(HeapWord* mem, markWord m);
 87 
 88   inline void release_set_mark(markWord m);
 89   inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
 90   inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
 91 
 92   // Returns the prototype mark that should be used for this object.
 93   inline markWord prototype_mark() const;
 94 
 95   // Used only to re-initialize the mark word (e.g., of promoted
 96   // objects during a GC) -- requires a valid klass pointer
 97   inline void init_mark();
 98   inline void reinit_mark(); // special for parallelGC
 99 
100   inline Klass* klass() const;
101   inline Klass* klass_or_null() const;
102   inline Klass* klass_or_null_acquire() const;
103   // Get the klass without running any asserts.
104   inline Klass* klass_without_asserts() const;
105 
106   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
107   inline narrowKlass narrow_klass() const;
108   inline void set_klass(Klass* k);
109   static inline void release_set_klass(HeapWord* mem, Klass* k);
110 
111   // For klass field compression
112   static inline void set_klass_gap(HeapWord* mem, int z);
113 
114   // Size of object header, aligned to platform wordSize
115   static int header_size() {
116     if (UseCompactObjectHeaders) {
117       return sizeof(markWord) / HeapWordSize;
118     } else {
119       return sizeof(oopDesc)  / HeapWordSize;
120     }
121   }
122 
123   // Returns whether this is an instance of k or an instance of a subclass of k
124   inline bool is_a(Klass* k) const;
125 
126   // Returns the actual oop size of the object in machine words
127   inline size_t size();
128 
129   // Sometimes (for complicated concurrency-related reasons), it is useful
130   // to be able to figure out the size of an object knowing its klass.
131   inline size_t size_given_klass(Klass* klass);
132 
133   // type test operations (inlined in oop.inline.hpp)
134   inline bool is_instance()         const;
135   inline bool is_inline_type()      const;
136   inline bool is_instanceRef()      const;
137   inline bool is_stackChunk()       const;
138   inline bool is_array()            const;
139   inline bool is_objArray()         const;
140   inline bool is_typeArray()        const;
141   inline bool is_flatArray()        const;
142   inline bool is_refArray()         const;
143   inline bool is_null_free_array()  const;
144   inline bool is_refined_objArray() const;
145 
146   // type test operations that don't require inclusion of oop.inline.hpp.
147   bool is_instance_noinline()         const;
148   bool is_instanceRef_noinline()      const;
149   bool is_stackChunk_noinline()       const;
150   bool is_array_noinline()            const;
151   bool is_objArray_noinline()         const;
152   bool is_refArray_noinline()         const;
153   bool is_typeArray_noinline()        const;
154   bool is_flatArray_noinline()        const;
155   bool is_null_free_array_noinline()  const;
156 
157  protected:
158   inline oop        as_oop() const { return const_cast<oopDesc*>(this); }
159 
160  public:
161   template<typename T>
162   inline T* field_addr(int offset) const;
163 
164   template <typename T> inline size_t field_offset(T* p) const;
165 
166   // Standard compare function returns negative value if o1 < o2
167   //                                   0              if o1 == o2
168   //                                   positive value if o1 > o2
169   inline static int  compare(oop o1, oop o2) {
170     void* o1_addr = (void*)o1;
171     void* o2_addr = (void*)o2;
172     if (o1_addr < o2_addr) {
173       return -1;
174     } else if (o1_addr > o2_addr) {
175       return 1;
176     } else {
177       return 0;
178     }
179   }
180 
181   // Access to fields in a instanceOop through these methods.
182   template<DecoratorSet decorators>
183   oop obj_field_access(int offset) const;
184   oop obj_field(int offset) const;
185 
186   void obj_field_put(int offset, oop value);
187   void obj_field_put_raw(int offset, oop value);
188   void obj_field_put_volatile(int offset, oop value);
189   template<DecoratorSet decorators>
190   void obj_field_put_access(int offset, oop value);
191 
192   Metadata* metadata_field(int offset) const;
193   void metadata_field_put(int offset, Metadata* value);
194 
195   Metadata* metadata_field_acquire(int offset) const;
196   void release_metadata_field_put(int offset, Metadata* value);
197 
198   jbyte byte_field(int offset) const;
199   void byte_field_put(int offset, jbyte contents);
200 
201   jchar char_field(int offset) const;
202   void char_field_put(int offset, jchar contents);
203 
204   jboolean bool_field(int offset) const;
205   void bool_field_put(int offset, jboolean contents);
206   jboolean bool_field_volatile(int offset) const;
207   void bool_field_put_volatile(int offset, jboolean contents);
208 
209   jint int_field(int offset) const;
210   void int_field_put(int offset, jint contents);
211 
212   jshort short_field(int offset) const;
213   void short_field_put(int offset, jshort contents);
214 
215   jlong long_field(int offset) const;
216   void long_field_put(int offset, jlong contents);
217 
218   jfloat float_field(int offset) const;
219   void float_field_put(int offset, jfloat contents);
220 
221   jdouble double_field(int offset) const;
222   void double_field_put(int offset, jdouble contents);
223 
224   address address_field(int offset) const;
225   void address_field_put(int offset, address contents);
226 
227   oop obj_field_acquire(int offset) const;
228   void release_obj_field_put(int offset, oop value);
229 
230   jbyte byte_field_acquire(int offset) const;
231   void release_byte_field_put(int offset, jbyte contents);
232 
233   jchar char_field_acquire(int offset) const;
234   void release_char_field_put(int offset, jchar contents);
235 
236   jboolean bool_field_acquire(int offset) const;
237   void release_bool_field_put(int offset, jboolean contents);
238 
239   jint int_field_relaxed(int offset) const;
240   void int_field_put_relaxed(int offset, jint contents);
241   jint int_field_acquire(int offset) const;
242   void release_int_field_put(int offset, jint contents);
243 
244   jshort short_field_acquire(int offset) const;
245   void release_short_field_put(int offset, jshort contents);
246 
247   jlong long_field_acquire(int offset) const;
248   void release_long_field_put(int offset, jlong contents);
249 
250   jfloat float_field_acquire(int offset) const;
251   void release_float_field_put(int offset, jfloat contents);
252 
253   jdouble double_field_acquire(int offset) const;
254   void release_double_field_put(int offset, jdouble contents);
255 
256   address address_field_acquire(int offset) const;
257   void release_address_field_put(int offset, address contents);
258 
259   // printing functions for VM debugging
260   void print_on(outputStream* st) const;         // First level print
261   void print_value_on(outputStream* st) const;   // Second level print.
262   void print_address_on(outputStream* st) const; // Address printing
263   void print_name_on(outputStream* st) const;    // External name printing.
264 
265   // printing on default output stream
266   void print();
267   void print_value();
268   void print_address();
269 
270   // return the print strings
271   char* print_string();
272   char* print_value_string();
273 
274   // verification operations
275   static void verify_on(outputStream* st, oopDesc* oop_desc);
276   static void verify(oopDesc* oopDesc);
277 
278   // locking operations
279   inline bool is_locked()   const;
280   inline bool is_unlocked() const;
281 
282   // asserts and guarantees
283   static bool is_oop(oop obj);
284   static bool is_oop_or_null(oop obj);
285 
286   // garbage collection
287   inline bool is_gc_marked() const;
288 
289   // Forward pointer operations for scavenge
290   inline bool is_forwarded() const;
291   inline bool is_self_forwarded() const;
292 
293   inline void forward_to(oop p);
294   inline void forward_to_self();
295 
296   // Like "forward_to", but inserts the forwarding pointer atomically.
297   // Exactly one thread succeeds in inserting the forwarding pointer, and
298   // this call returns null for that thread; any other thread has the
299   // value of the forwarding pointer returned and does not modify "this".
300   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
301   inline oop forward_to_self_atomic(markWord compare, atomic_memory_order order = memory_order_conservative);
302 
303   inline oop forwardee() const;
304   inline oop forwardee(markWord header) const;
305 
306   inline void unset_self_forwarded();
307 
308   // Age of object during scavenge
309   inline uint age() const;
310   inline void incr_age();
311 
312   template <typename OopClosureType>
313   inline void oop_iterate(OopClosureType* cl);
314 
315   template <typename OopClosureType>
316   inline void oop_iterate(OopClosureType* cl, MemRegion mr);
317 
318   template <typename OopClosureType>
319   inline size_t oop_iterate_size(OopClosureType* cl);
320 
321   template <typename OopClosureType>
322   inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
323 
324   template <typename OopClosureType>
325   inline void oop_iterate_backwards(OopClosureType* cl);
326 
327   template <typename OopClosureType>
328   inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
329 
330   inline static bool is_instanceof_or_null(oop obj, Klass* klass);
331 
332   // identity hash; returns the identity hash key (computes it if necessary)
333   inline intptr_t identity_hash();
334   intptr_t slow_identity_hash();
335   inline bool fast_no_hash_check();
336 
337   // marks are forwarded to stack when object is locked
338   inline bool     has_displaced_mark() const;
339   inline markWord displaced_mark() const;
340   inline void     set_displaced_mark(markWord m);
341 
342   // Checks if the mark word needs to be preserved
343   inline bool mark_must_be_preserved() const;
344   inline bool mark_must_be_preserved(markWord m) const;
345 
346   inline static bool has_klass_gap() {
347     return ObjLayout::oop_has_klass_gap();
348   }
349 
350   // for code generation
351   static int mark_offset_in_bytes()      { return (int)offset_of(oopDesc, _mark); }
352   static int klass_offset_in_bytes()     {
353 #ifdef _LP64
354     if (UseCompactObjectHeaders) {
355       // NOTE: The only places where this is used with compact headers are the C2
356       // compiler and JVMCI.
357       return mark_offset_in_bytes() + markWord::klass_offset_in_bytes;
358     } else
359 #endif
360     {
361       return (int)offset_of(oopDesc, _metadata._klass);
362     }
363   }
364   static int klass_gap_offset_in_bytes() {
365     assert(has_klass_gap(), "only applicable to compressed klass pointers");
366     return klass_offset_in_bytes() + sizeof(narrowKlass);
367   }
368 
369   static int base_offset_in_bytes() {
370     return ObjLayout::oop_base_offset_in_bytes();
371   }
372 
373   // for error reporting
374   static void* load_oop_raw(oop obj, int offset);
375 };
376 
377 // An oopDesc is not initialized via a constructor.  Space is allocated in
378 // the Java heap, and static functions provided here on HeapWord* are used
379 // to fill in certain parts of that memory.  The allocated memory is then
380 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
381 // class must have a trivial default constructor (C++14 3.8/1).
382 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
383 
384 #endif // SHARE_OOPS_OOP_HPP