1 /*
  2  * Copyright (c) 1997, 2022, 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 // oopDesc::_mark - the "oop mark word" encoding to be found separately in markWord.hpp
 46 //
 47 // oopDesc::_metadata - encodes the object's klass pointer, as a raw pointer in "_klass"
 48 //                      or compressed pointer in "_compressed_klass"
 49 //
 50 // The overall size of the _metadata field is dependent on "UseCompressedClassPointers",
 51 // hence the terms "narrow" (32 bits) vs "wide" (64 bits).
 52 //
 53 
 54 
 55 // Forward declarations.
 56 class OopClosure;
 57 class FilteringClosure;
 58 
 59 class PSPromotionManager;
 60 class ParCompactionManager;
 61 
 62 class oopDesc {
 63   friend class VMStructs;
 64   friend class JVMCIVMStructs;
 65  private:
 66   volatile markWord _mark;
 67   union _metadata {
 68     Klass*      _klass;
 69     narrowKlass _compressed_klass;
 70   } _metadata;
 71 
 72   // There may be ordering constraints on the initialization of fields that
 73   // make use of the C++ copy/assign incorrect.
 74   NONCOPYABLE(oopDesc);
 75 
 76  public:
 77   // Must be trivial; see verifying static assert after the class.
 78   oopDesc() = default;
 79 
 80   inline markWord  mark()          const;
 81   inline markWord  mark_acquire()  const;
 82   inline markWord* mark_addr() const;
 83 
 84   inline void set_mark(markWord m);
 85   static inline void set_mark(HeapWord* mem, markWord m);
 86 
 87   inline void release_set_mark(markWord m);
 88   inline markWord cas_set_mark(markWord new_mark, markWord old_mark);
 89   inline markWord cas_set_mark(markWord new_mark, markWord old_mark, atomic_memory_order order);
 90 
 91   // Used only to re-initialize the mark word (e.g., of promoted
 92   // objects during a GC) -- requires a valid klass pointer
 93   inline void init_mark();
 94 
 95   inline Klass* klass() const;
 96   inline Klass* klass_or_null() const;
 97   inline Klass* klass_or_null_acquire() const;
 98 
 99   void set_narrow_klass(narrowKlass nk) NOT_CDS_JAVA_HEAP_RETURN;
100   inline void set_klass(Klass* k);
101   static inline void release_set_klass(HeapWord* mem, Klass* k);
102 
103   // For klass field compression
104   static inline void set_klass_gap(HeapWord* mem, int z);
105 
106   // size of object header, aligned to platform wordSize
107   static constexpr int header_size() { return sizeof(oopDesc)/HeapWordSize; }
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_inline_type()      const;
122   inline bool is_instanceRef()      const;
123   inline bool is_stackChunk()       const;
124   inline bool is_array()            const;
125   inline bool is_objArray()         const;
126   inline bool is_typeArray()        const;
127   inline bool is_flatArray()        const;
128   inline bool is_null_free_array()  const;
129 
130   // type test operations that don't require inclusion of oop.inline.hpp.
131   bool is_instance_noinline()         const;
132   bool is_instanceRef_noinline()      const;
133   bool is_stackChunk_noinline()       const;
134   bool is_array_noinline()            const;
135   bool is_objArray_noinline()         const;
136   bool is_typeArray_noinline()        const;
137   bool is_flatArray_noinline()        const;
138   bool is_null_free_array_noinline()  const;
139 
140  protected:
141   inline oop        as_oop() const { return const_cast<oopDesc*>(this); }
142 
143  public:
144   template<typename T>
145   inline T* field_addr(int offset) const;
146 
147   template <typename T> inline size_t field_offset(T* p) const;
148 
149   // Standard compare function returns negative value if o1 < o2
150   //                                   0              if o1 == o2
151   //                                   positive value if o1 > o2
152   inline static int  compare(oop o1, oop o2) {
153     void* o1_addr = (void*)o1;
154     void* o2_addr = (void*)o2;
155     if (o1_addr < o2_addr) {
156       return -1;
157     } else if (o1_addr > o2_addr) {
158       return 1;
159     } else {
160       return 0;
161     }
162   }
163 
164   // Access to fields in a instanceOop through these methods.
165   template<DecoratorSet decorators>
166   oop obj_field_access(int offset) const;
167   oop obj_field(int offset) const;
168 
169   void obj_field_put(int offset, oop value);
170   void obj_field_put_raw(int offset, oop value);
171   void obj_field_put_volatile(int offset, oop value);
172   template<DecoratorSet decorators>
173   void obj_field_put_access(int offset, oop value);
174 
175   Metadata* metadata_field(int offset) const;
176   void metadata_field_put(int offset, Metadata* value);
177 
178   Metadata* metadata_field_acquire(int offset) const;
179   void release_metadata_field_put(int offset, Metadata* value);
180 
181   jbyte byte_field(int offset) const;
182   void byte_field_put(int offset, jbyte contents);
183 
184   jchar char_field(int offset) const;
185   void char_field_put(int offset, jchar contents);
186 
187   jboolean bool_field(int offset) const;
188   void bool_field_put(int offset, jboolean contents);
189   jboolean bool_field_volatile(int offset) const;
190   void bool_field_put_volatile(int offset, jboolean contents);
191 
192   jint int_field(int offset) const;
193   void int_field_put(int offset, jint contents);
194 
195   jshort short_field(int offset) const;
196   void short_field_put(int offset, jshort contents);
197 
198   jlong long_field(int offset) const;
199   void long_field_put(int offset, jlong contents);
200 
201   jfloat float_field(int offset) const;
202   void float_field_put(int offset, jfloat contents);
203 
204   jdouble double_field(int offset) const;
205   void double_field_put(int offset, jdouble contents);
206 
207   address address_field(int offset) const;
208   void address_field_put(int offset, address contents);
209 
210   oop obj_field_acquire(int offset) const;
211   void release_obj_field_put(int offset, oop value);
212 
213   jbyte byte_field_acquire(int offset) const;
214   void release_byte_field_put(int offset, jbyte contents);
215 
216   jchar char_field_acquire(int offset) const;
217   void release_char_field_put(int offset, jchar contents);
218 
219   jboolean bool_field_acquire(int offset) const;
220   void release_bool_field_put(int offset, jboolean contents);
221 
222   jint int_field_acquire(int offset) const;
223   void release_int_field_put(int offset, jint contents);
224 
225   jshort short_field_acquire(int offset) const;
226   void release_short_field_put(int offset, jshort contents);
227 
228   jlong long_field_acquire(int offset) const;
229   void release_long_field_put(int offset, jlong contents);
230 
231   jfloat float_field_acquire(int offset) const;
232   void release_float_field_put(int offset, jfloat contents);
233 
234   jdouble double_field_acquire(int offset) const;
235   void release_double_field_put(int offset, jdouble contents);
236 
237   address address_field_acquire(int offset) const;
238   void release_address_field_put(int offset, address contents);
239 
240   // printing functions for VM debugging
241   void print_on(outputStream* st) const;        // First level print
242   void print_value_on(outputStream* st) const;  // Second level print.
243   void print_address_on(outputStream* st) const; // Address printing
244 
245   // printing on default output stream
246   void print();
247   void print_value();
248   void print_address();
249 
250   // return the print strings
251   char* print_string();
252   char* print_value_string();
253 
254   // verification operations
255   static void verify_on(outputStream* st, oopDesc* oop_desc);
256   static void verify(oopDesc* oopDesc);
257 
258   // locking operations
259   inline bool is_locked()   const;
260   inline bool is_unlocked() const;
261 
262   // asserts and guarantees
263   static bool is_oop(oop obj, bool ignore_mark_word = false);
264   static bool is_oop_or_null(oop obj, bool ignore_mark_word = false);
265 
266   // garbage collection
267   inline bool is_gc_marked() const;
268 
269   // Forward pointer operations for scavenge
270   inline bool is_forwarded() const;
271 
272   void verify_forwardee(oop forwardee) NOT_DEBUG_RETURN;
273 
274   inline void forward_to(oop p);
275 
276   // Like "forward_to", but inserts the forwarding pointer atomically.
277   // Exactly one thread succeeds in inserting the forwarding pointer, and
278   // this call returns "NULL" for that thread; any other thread has the
279   // value of the forwarding pointer returned and does not modify "this".
280   inline oop forward_to_atomic(oop p, markWord compare, atomic_memory_order order = memory_order_conservative);
281 
282   inline oop forwardee() const;
283 
284   // Age of object during scavenge
285   inline uint age() const;
286   inline void incr_age();
287 
288   template <typename OopClosureType>
289   inline void oop_iterate(OopClosureType* cl);
290 
291   template <typename OopClosureType>
292   inline void oop_iterate(OopClosureType* cl, MemRegion mr);
293 
294   template <typename OopClosureType>
295   inline size_t oop_iterate_size(OopClosureType* cl);
296 
297   template <typename OopClosureType>
298   inline size_t oop_iterate_size(OopClosureType* cl, MemRegion mr);
299 
300   template <typename OopClosureType>
301   inline void oop_iterate_backwards(OopClosureType* cl);
302 
303   template <typename OopClosureType>
304   inline void oop_iterate_backwards(OopClosureType* cl, Klass* klass);
305 
306   inline static bool is_instanceof_or_null(oop obj, Klass* klass);
307 
308   // identity hash; returns the identity hash key (computes it if necessary)
309   inline intptr_t identity_hash();
310   intptr_t slow_identity_hash();
311 
312   // marks are forwarded to stack when object is locked
313   inline bool     has_displaced_mark() const;
314   inline markWord displaced_mark() const;
315   inline void     set_displaced_mark(markWord m);
316 
317   // Checks if the mark word needs to be preserved
318   inline bool mark_must_be_preserved() const;
319   inline bool mark_must_be_preserved(markWord m) const;
320 
321   static bool has_klass_gap();
322 
323   // for code generation
324   static int mark_offset_in_bytes()      { return offset_of(oopDesc, _mark); }
325   static int klass_offset_in_bytes()     { return offset_of(oopDesc, _metadata._klass); }
326   static int klass_gap_offset_in_bytes() {
327     assert(has_klass_gap(), "only applicable to compressed klass pointers");
328     return klass_offset_in_bytes() + sizeof(narrowKlass);
329   }
330 
331   // for error reporting
332   static void* load_klass_raw(oop obj);
333   static void* load_oop_raw(oop obj, int offset);
334 
335   DEBUG_ONLY(bool size_might_change();)
336 };
337 
338 // An oopDesc is not initialized via a constructor.  Space is allocated in
339 // the Java heap, and static functions provided here on HeapWord* are used
340 // to fill in certain parts of that memory.  The allocated memory is then
341 // treated as referring to an oopDesc.  For that to be valid, the oopDesc
342 // class must have a trivial default constructor (C++14 3.8/1).
343 static_assert(std::is_trivially_default_constructible<oopDesc>::value, "required");
344 
345 #endif // SHARE_OOPS_OOP_HPP