1 /*
   2  * Copyright (c) 1997, 2011, 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_VM_OOPS_INSTANCEKLASS_HPP
  26 #define SHARE_VM_OOPS_INSTANCEKLASS_HPP
  27 
  28 #include "oops/constMethodOop.hpp"
  29 #include "oops/constantPoolOop.hpp"
  30 #include "oops/fieldInfo.hpp"
  31 #include "oops/instanceOop.hpp"
  32 #include "oops/klassOop.hpp"
  33 #include "oops/klassVtable.hpp"
  34 #include "oops/objArrayOop.hpp"
  35 #include "runtime/handles.hpp"
  36 #include "runtime/os.hpp"
  37 #include "utilities/accessFlags.hpp"
  38 #include "utilities/bitMap.inline.hpp"
  39 
  40 // An instanceKlass is the VM level representation of a Java class.
  41 // It contains all information needed for at class at execution runtime.
  42 
  43 //  instanceKlass layout:
  44 //    [header                     ] klassOop
  45 //    [klass pointer              ] klassOop
  46 //    [C++ vtbl pointer           ] Klass
  47 //    [subtype cache              ] Klass
  48 //    [instance size              ] Klass
  49 //    [java mirror                ] Klass
  50 //    [super                      ] Klass
  51 //    [access_flags               ] Klass
  52 //    [name                       ] Klass
  53 //    [first subklass             ] Klass
  54 //    [next sibling               ] Klass
  55 //    [array klasses              ]
  56 //    [methods                    ]
  57 //    [local interfaces           ]
  58 //    [transitive interfaces      ]
  59 //    [number of implementors     ]
  60 //    [implementors               ] klassOop[2]
  61 //    [fields                     ]
  62 //    [constants                  ]
  63 //    [class loader               ]
  64 //    [protection domain          ]
  65 //    [signers                    ]
  66 //    [source file name           ]
  67 //    [inner classes              ]
  68 //    [static field size          ]
  69 //    [nonstatic field size       ]
  70 //    [static oop fields size     ]
  71 //    [nonstatic oop maps size    ]
  72 //    [has finalize method        ]
  73 //    [deoptimization mark bit    ]
  74 //    [initialization state       ]
  75 //    [initializing thread        ]
  76 //    [Java vtable length         ]
  77 //    [oop map cache (stack maps) ]
  78 //    [EMBEDDED Java vtable             ] size in words = vtable_len
  79 //    [EMBEDDED nonstatic oop-map blocks] size in words = nonstatic_oop_map_size
  80 //
  81 //    The embedded nonstatic oop-map blocks are short pairs (offset, length) indicating
  82 //    where oops are located in instances of this klass.
  83 
  84 
  85 // forward declaration for class -- see below for definition
  86 class SuperTypeClosure;
  87 class JNIid;
  88 class jniIdMapBase;
  89 class BreakpointInfo;
  90 class fieldDescriptor;
  91 class DepChange;
  92 class nmethodBucket;
  93 class PreviousVersionNode;
  94 class JvmtiCachedClassFieldMap;
  95 
  96 // This is used in iterators below.
  97 class FieldClosure: public StackObj {
  98 public:
  99   virtual void do_field(fieldDescriptor* fd) = 0;
 100 };
 101 
 102 #ifndef PRODUCT
 103 // Print fields.
 104 // If "obj" argument to constructor is NULL, prints static fields, otherwise prints non-static fields.
 105 class FieldPrinter: public FieldClosure {
 106    oop _obj;
 107    outputStream* _st;
 108  public:
 109    FieldPrinter(outputStream* st, oop obj = NULL) : _obj(obj), _st(st) {}
 110    void do_field(fieldDescriptor* fd);
 111 };
 112 #endif  // !PRODUCT
 113 
 114 // ValueObjs embedded in klass. Describes where oops are located in instances of
 115 // this klass.
 116 class OopMapBlock VALUE_OBJ_CLASS_SPEC {
 117  public:
 118   // Byte offset of the first oop mapped by this block.
 119   int offset() const          { return _offset; }
 120   void set_offset(int offset) { _offset = offset; }
 121 
 122   // Number of oops in this block.
 123   uint count() const         { return _count; }
 124   void set_count(uint count) { _count = count; }
 125 
 126   // sizeof(OopMapBlock) in HeapWords.
 127   static const int size_in_words() {
 128     return align_size_up(int(sizeof(OopMapBlock)), HeapWordSize) >>
 129       LogHeapWordSize;
 130   }
 131 
 132  private:
 133   int  _offset;
 134   uint _count;
 135 };
 136 
 137 class instanceKlass: public Klass {
 138   friend class VMStructs;
 139  public:
 140   // See "The Java Virtual Machine Specification" section 2.16.2-5 for a detailed description
 141   // of the class loading & initialization procedure, and the use of the states.
 142   enum ClassState {
 143     unparsable_by_gc = 0,               // object is not yet parsable by gc. Value of _init_state at object allocation.
 144     allocated,                          // allocated (but not yet linked)
 145     loaded,                             // loaded and inserted in class hierarchy (but not linked yet)
 146     linked,                             // successfully linked/verified (but not initialized yet)
 147     being_initialized,                  // currently running class initializer
 148     fully_initialized,                  // initialized (successfull final state)
 149     initialization_error                // error happened during initialization
 150   };
 151 
 152  public:
 153   oop* oop_block_beg() const { return adr_array_klasses(); }
 154   oop* oop_block_end() const { return adr_methods_default_annotations() + 1; }
 155 
 156   enum {
 157     implementors_limit = 2              // how many implems can we track?
 158   };
 159 
 160  protected:
 161   //
 162   // The oop block.  See comment in klass.hpp before making changes.
 163   //
 164 
 165   // Array classes holding elements of this class.
 166   klassOop        _array_klasses;
 167   // Method array.
 168   objArrayOop     _methods;
 169   // Int array containing the original order of method in the class file (for
 170   // JVMTI).
 171   typeArrayOop    _method_ordering;
 172   // Interface (klassOops) this class declares locally to implement.
 173   objArrayOop     _local_interfaces;
 174   // Interface (klassOops) this class implements transitively.
 175   objArrayOop     _transitive_interfaces;
 176   // Instance and static variable information, 5-tuples of shorts [access, name
 177   // index, sig index, initval index, offset].
 178   typeArrayOop    _fields;
 179   // Constant pool for this class.
 180   constantPoolOop _constants;
 181   // Class loader used to load this class, NULL if VM loader used.
 182   oop             _class_loader;
 183   // Protection domain.
 184   oop             _protection_domain;
 185   // Host class, which grants its access privileges to this class also.
 186   // This is only non-null for an anonymous class (JSR 292 enabled).
 187   // The host class is either named, or a previously loaded anonymous class.
 188   klassOop        _host_klass;
 189   // Class signers.
 190   objArrayOop     _signers;
 191   // inner_classes attribute.
 192   typeArrayOop    _inner_classes;
 193   // Implementors of this interface (not valid if it overflows)
 194   klassOop        _implementors[implementors_limit];
 195   // Annotations for this class, or null if none.
 196   typeArrayOop    _class_annotations;
 197   // Annotation objects (byte arrays) for fields, or null if no annotations.
 198   // Indices correspond to entries (not indices) in fields array.
 199   objArrayOop     _fields_annotations;
 200   // Annotation objects (byte arrays) for methods, or null if no annotations.
 201   // Index is the idnum, which is initially the same as the methods array index.
 202   objArrayOop     _methods_annotations;
 203   // Annotation objects (byte arrays) for methods' parameters, or null if no
 204   // such annotations.
 205   // Index is the idnum, which is initially the same as the methods array index.
 206   objArrayOop     _methods_parameter_annotations;
 207   // Annotation objects (byte arrays) for methods' default values, or null if no
 208   // such annotations.
 209   // Index is the idnum, which is initially the same as the methods array index.
 210   objArrayOop     _methods_default_annotations;
 211 
 212   //
 213   // End of the oop block.
 214   //
 215 
 216   // Name of source file containing this klass, NULL if not specified.
 217   Symbol*         _source_file_name;
 218   // the source debug extension for this klass, NULL if not specified.
 219   Symbol*         _source_debug_extension;
 220   // Generic signature, or null if none.
 221   Symbol*         _generic_signature;
 222   // Array name derived from this class which needs unreferencing
 223   // if this class is unloaded.
 224   Symbol*         _array_name;
 225 
 226   // Number of heapOopSize words used by non-static fields in this klass
 227   // (including inherited fields but after header_size()).
 228   int             _nonstatic_field_size;
 229   int             _static_field_size;    // number words used by static fields (oop and non-oop) in this klass
 230   u2              _static_oop_field_count;// number of static oop fields in this klass
 231   u2              _java_fields_count;    // The number of declared Java fields
 232   int             _nonstatic_oop_map_size;// size in words of nonstatic oop map blocks
 233 
 234   bool            _is_marked_dependent;  // used for marking during flushing and deoptimization
 235   bool            _rewritten;            // methods rewritten.
 236   bool            _has_nonstatic_fields; // for sizing with UseCompressedOops
 237   bool            _should_verify_class;  // allow caching of preverification
 238   u2              _minor_version;        // minor version number of class file
 239   u2              _major_version;        // major version number of class file
 240   Thread*         _init_thread;          // Pointer to current thread doing initialization (to handle recusive initialization)
 241   int             _vtable_len;           // length of Java vtable (in words)
 242   int             _itable_len;           // length of Java itable (in words)
 243   OopMapCache*    volatile _oop_map_cache;   // OopMapCache for all methods in the klass (allocated lazily)
 244   JNIid*          _jni_ids;              // First JNI identifier for static fields in this class
 245   jmethodID*      _methods_jmethod_ids;  // jmethodIDs corresponding to method_idnum, or NULL if none
 246   int*            _methods_cached_itable_indices;  // itable_index cache for JNI invoke corresponding to methods idnum, or NULL
 247   nmethodBucket*  _dependencies;         // list of dependent nmethods
 248   nmethod*        _osr_nmethods_head;    // Head of list of on-stack replacement nmethods for this class
 249   BreakpointInfo* _breakpoints;          // bpt lists, managed by methodOop
 250   int             _nof_implementors;     // No of implementors of this interface (zero if not an interface)
 251   // Array of interesting part(s) of the previous version(s) of this
 252   // instanceKlass. See PreviousVersionWalker below.
 253   GrowableArray<PreviousVersionNode *>* _previous_versions;
 254   u2              _enclosing_method_class_index;  // Constant pool index for class of enclosing method, or 0 if none
 255   u2              _enclosing_method_method_index; // Constant pool index for name and type of enclosing method, or 0 if none
 256   // JVMTI fields can be moved to their own structure - see 6315920
 257   unsigned char * _cached_class_file_bytes;       // JVMTI: cached class file, before retransformable agent modified it in CFLH
 258   jint            _cached_class_file_len;         // JVMTI: length of above
 259   JvmtiCachedClassFieldMap* _jvmti_cached_class_field_map;  // JVMTI: used during heap iteration
 260   volatile u2     _idnum_allocated_count;         // JNI/JVMTI: increments with the addition of methods, old ids don't change
 261 
 262   // Class states are defined as ClassState (see above).
 263   // Place the _init_state here to utilize the unused 2-byte after
 264   // _idnum_allocated_count.
 265   u1              _init_state;                    // state of class
 266 
 267   u1              _reference_type;                // reference type
 268 
 269   // embedded Java vtable follows here
 270   // embedded Java itables follows here
 271   // embedded static fields follows here
 272   // embedded nonstatic oop-map blocks follows here
 273 
 274   friend class instanceKlassKlass;
 275   friend class SystemDictionary;
 276 
 277  public:
 278   bool has_nonstatic_fields() const        { return _has_nonstatic_fields; }
 279   void set_has_nonstatic_fields(bool b)    { _has_nonstatic_fields = b; }
 280 
 281   // field sizes
 282   int nonstatic_field_size() const         { return _nonstatic_field_size; }
 283   void set_nonstatic_field_size(int size)  { _nonstatic_field_size = size; }
 284 
 285   int static_field_size() const            { return _static_field_size; }
 286   void set_static_field_size(int size)     { _static_field_size = size; }
 287 
 288   int static_oop_field_count() const       { return (int)_static_oop_field_count; }
 289   void set_static_oop_field_count(u2 size) { _static_oop_field_count = size; }
 290 
 291   // Java vtable
 292   int  vtable_length() const               { return _vtable_len; }
 293   void set_vtable_length(int len)          { _vtable_len = len; }
 294 
 295   // Java itable
 296   int  itable_length() const               { return _itable_len; }
 297   void set_itable_length(int len)          { _itable_len = len; }
 298 
 299   // array klasses
 300   klassOop array_klasses() const           { return _array_klasses; }
 301   void set_array_klasses(klassOop k)       { oop_store_without_check((oop*) &_array_klasses, (oop) k); }
 302 
 303   // methods
 304   objArrayOop methods() const              { return _methods; }
 305   void set_methods(objArrayOop a)          { oop_store_without_check((oop*) &_methods, (oop) a); }
 306   methodOop method_with_idnum(int idnum);
 307 
 308   // method ordering
 309   typeArrayOop method_ordering() const     { return _method_ordering; }
 310   void set_method_ordering(typeArrayOop m) { oop_store_without_check((oop*) &_method_ordering, (oop) m); }
 311 
 312   // interfaces
 313   objArrayOop local_interfaces() const          { return _local_interfaces; }
 314   void set_local_interfaces(objArrayOop a)      { oop_store_without_check((oop*) &_local_interfaces, (oop) a); }
 315   objArrayOop transitive_interfaces() const     { return _transitive_interfaces; }
 316   void set_transitive_interfaces(objArrayOop a) { oop_store_without_check((oop*) &_transitive_interfaces, (oop) a); }
 317 
 318  private:
 319   friend class fieldDescriptor;
 320   FieldInfo* field(int index) const { return FieldInfo::from_field_array(_fields, index); }
 321 
 322  public:
 323   int     field_offset      (int index) const { return field(index)->offset(); }
 324   int     field_access_flags(int index) const { return field(index)->access_flags(); }
 325   Symbol* field_name        (int index) const { return field(index)->name(constants()); }
 326   Symbol* field_signature   (int index) const { return field(index)->signature(constants()); }
 327 
 328   // Number of Java declared fields
 329   int java_fields_count() const           { return (int)_java_fields_count; }
 330 
 331   // Number of fields including any injected fields
 332   int all_fields_count() const            { return _fields->length() / sizeof(FieldInfo::field_slots); }
 333 
 334   typeArrayOop fields() const              { return _fields; }
 335 
 336   void set_fields(typeArrayOop f, u2 java_fields_count) {
 337     oop_store_without_check((oop*) &_fields, (oop) f);
 338     _java_fields_count = java_fields_count;
 339   }
 340 
 341   // inner classes
 342   typeArrayOop inner_classes() const       { return _inner_classes; }
 343   void set_inner_classes(typeArrayOop f)   { oop_store_without_check((oop*) &_inner_classes, (oop) f); }
 344 
 345   enum InnerClassAttributeOffset {
 346     // From http://mirror.eng/products/jdk/1.1/docs/guide/innerclasses/spec/innerclasses.doc10.html#18814
 347     inner_class_inner_class_info_offset = 0,
 348     inner_class_outer_class_info_offset = 1,
 349     inner_class_inner_name_offset = 2,
 350     inner_class_access_flags_offset = 3,
 351     inner_class_next_offset = 4
 352   };
 353 
 354   // method override check
 355   bool is_override(methodHandle super_method, Handle targetclassloader, Symbol* targetclassname, TRAPS);
 356 
 357   // package
 358   bool is_same_class_package(klassOop class2);
 359   bool is_same_class_package(oop classloader2, Symbol* classname2);
 360   static bool is_same_class_package(oop class_loader1, Symbol* class_name1, oop class_loader2, Symbol* class_name2);
 361 
 362   // find an enclosing class (defined where original code was, in jvm.cpp!)
 363   klassOop compute_enclosing_class(bool* inner_is_member, TRAPS) {
 364     instanceKlassHandle self(THREAD, this->as_klassOop());
 365     return compute_enclosing_class_impl(self, inner_is_member, THREAD);
 366   }
 367   static klassOop compute_enclosing_class_impl(instanceKlassHandle self,
 368                                                bool* inner_is_member, TRAPS);
 369 
 370   // tell if two classes have the same enclosing class (at package level)
 371   bool is_same_package_member(klassOop class2, TRAPS) {
 372     instanceKlassHandle self(THREAD, this->as_klassOop());
 373     return is_same_package_member_impl(self, class2, THREAD);
 374   }
 375   static bool is_same_package_member_impl(instanceKlassHandle self,
 376                                           klassOop class2, TRAPS);
 377 
 378   // initialization state
 379   bool is_loaded() const                   { return _init_state >= loaded; }
 380   bool is_linked() const                   { return _init_state >= linked; }
 381   bool is_initialized() const              { return _init_state == fully_initialized; }
 382   bool is_not_initialized() const          { return _init_state <  being_initialized; }
 383   bool is_being_initialized() const        { return _init_state == being_initialized; }
 384   bool is_in_error_state() const           { return _init_state == initialization_error; }
 385   bool is_reentrant_initialization(Thread *thread)  { return thread == _init_thread; }
 386   ClassState  init_state()                 { return (ClassState)_init_state; }
 387   bool is_rewritten() const                { return _rewritten; }
 388 
 389   // defineClass specified verification
 390   bool should_verify_class() const         { return _should_verify_class; }
 391   void set_should_verify_class(bool value) { _should_verify_class = value; }
 392 
 393   // marking
 394   bool is_marked_dependent() const         { return _is_marked_dependent; }
 395   void set_is_marked_dependent(bool value) { _is_marked_dependent = value; }
 396 
 397   // initialization (virtuals from Klass)
 398   bool should_be_initialized() const;  // means that initialize should be called
 399   void initialize(TRAPS);
 400   void link_class(TRAPS);
 401   bool link_class_or_fail(TRAPS); // returns false on failure
 402   void unlink_class();
 403   void rewrite_class(TRAPS);
 404   void relocate_and_link_methods(TRAPS);
 405   methodOop class_initializer();
 406 
 407   // set the class to initialized if no static initializer is present
 408   void eager_initialize(Thread *thread);
 409 
 410   // reference type
 411   ReferenceType reference_type() const     { return (ReferenceType)_reference_type; }
 412   void set_reference_type(ReferenceType t) { _reference_type = (u1)t; }
 413 
 414   static ByteSize reference_type_offset() { return in_ByteSize(sizeof(klassOopDesc) + offset_of(instanceKlass, _reference_type)); }
 415 
 416   // find local field, returns true if found
 417   bool find_local_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const;
 418   // find field in direct superinterfaces, returns the interface in which the field is defined
 419   klassOop find_interface_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const;
 420   // find field according to JVM spec 5.4.3.2, returns the klass in which the field is defined
 421   klassOop find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const;
 422   // find instance or static fields according to JVM spec 5.4.3.2, returns the klass in which the field is defined
 423   klassOop find_field(Symbol* name, Symbol* sig, bool is_static, fieldDescriptor* fd) const;
 424 
 425   // find a non-static or static field given its offset within the class.
 426   bool contains_field_offset(int offset) {
 427     return instanceOopDesc::contains_field_offset(offset, nonstatic_field_size());
 428   }
 429 
 430   bool find_local_field_from_offset(int offset, bool is_static, fieldDescriptor* fd) const;
 431   bool find_field_from_offset(int offset, bool is_static, fieldDescriptor* fd) const;
 432 
 433   // find a local method (returns NULL if not found)
 434   methodOop find_method(Symbol* name, Symbol* signature) const;
 435   static methodOop find_method(objArrayOop methods, Symbol* name, Symbol* signature);
 436 
 437   // lookup operation (returns NULL if not found)
 438   methodOop uncached_lookup_method(Symbol* name, Symbol* signature) const;
 439 
 440   // lookup a method in all the interfaces that this class implements
 441   // (returns NULL if not found)
 442   methodOop lookup_method_in_all_interfaces(Symbol* name, Symbol* signature) const;
 443 
 444   // constant pool
 445   constantPoolOop constants() const        { return _constants; }
 446   void set_constants(constantPoolOop c)    { oop_store_without_check((oop*) &_constants, (oop) c); }
 447 
 448   // class loader
 449   oop class_loader() const                 { return _class_loader; }
 450   void set_class_loader(oop l)             { oop_store((oop*) &_class_loader, l); }
 451 
 452   // protection domain
 453   oop protection_domain()                  { return _protection_domain; }
 454   void set_protection_domain(oop pd)       { oop_store((oop*) &_protection_domain, pd); }
 455 
 456   // host class
 457   oop host_klass() const                   { return _host_klass; }
 458   void set_host_klass(oop host)            { oop_store((oop*) &_host_klass, host); }
 459   bool is_anonymous() const                { return _host_klass != NULL; }
 460 
 461   // signers
 462   objArrayOop signers() const              { return _signers; }
 463   void set_signers(objArrayOop s)          { oop_store((oop*) &_signers, oop(s)); }
 464 
 465   // source file name
 466   Symbol* source_file_name() const         { return _source_file_name; }
 467   void set_source_file_name(Symbol* n);
 468 
 469   // minor and major version numbers of class file
 470   u2 minor_version() const                 { return _minor_version; }
 471   void set_minor_version(u2 minor_version) { _minor_version = minor_version; }
 472   u2 major_version() const                 { return _major_version; }
 473   void set_major_version(u2 major_version) { _major_version = major_version; }
 474 
 475   // source debug extension
 476   Symbol* source_debug_extension() const   { return _source_debug_extension; }
 477   void set_source_debug_extension(Symbol* n);
 478 
 479   // symbol unloading support (refcount already added)
 480   Symbol* array_name()                     { return _array_name; }
 481   void set_array_name(Symbol* name)        { assert(_array_name == NULL, "name already created"); _array_name = name; }
 482 
 483   // nonstatic oop-map blocks
 484   static int nonstatic_oop_map_size(unsigned int oop_map_count) {
 485     return oop_map_count * OopMapBlock::size_in_words();
 486   }
 487   unsigned int nonstatic_oop_map_count() const {
 488     return _nonstatic_oop_map_size / OopMapBlock::size_in_words();
 489   }
 490   int nonstatic_oop_map_size() const { return _nonstatic_oop_map_size; }
 491   void set_nonstatic_oop_map_size(int words) {
 492     _nonstatic_oop_map_size = words;
 493   }
 494 
 495   // RedefineClasses() support for previous versions:
 496   void add_previous_version(instanceKlassHandle ikh, BitMap *emcp_methods,
 497          int emcp_method_count);
 498   // If the _previous_versions array is non-NULL, then this klass
 499   // has been redefined at least once even if we aren't currently
 500   // tracking a previous version.
 501   bool has_been_redefined() const { return _previous_versions != NULL; }
 502   bool has_previous_version() const;
 503   void init_previous_versions() {
 504     _previous_versions = NULL;
 505   }
 506   GrowableArray<PreviousVersionNode *>* previous_versions() const {
 507     return _previous_versions;
 508   }
 509 
 510   // JVMTI: Support for caching a class file before it is modified by an agent that can do retransformation
 511   void set_cached_class_file(unsigned char *class_file_bytes,
 512                              jint class_file_len)     { _cached_class_file_len = class_file_len;
 513                                                         _cached_class_file_bytes = class_file_bytes; }
 514   jint get_cached_class_file_len()                    { return _cached_class_file_len; }
 515   unsigned char * get_cached_class_file_bytes()       { return _cached_class_file_bytes; }
 516 
 517   // JVMTI: Support for caching of field indices, types, and offsets
 518   void set_jvmti_cached_class_field_map(JvmtiCachedClassFieldMap* descriptor) {
 519     _jvmti_cached_class_field_map = descriptor;
 520   }
 521   JvmtiCachedClassFieldMap* jvmti_cached_class_field_map() const {
 522     return _jvmti_cached_class_field_map;
 523   }
 524 
 525   // for adding methods, constMethodOopDesc::UNSET_IDNUM means no more ids available
 526   inline u2 next_method_idnum();
 527   void set_initial_method_idnum(u2 value)             { _idnum_allocated_count = value; }
 528 
 529   // generics support
 530   Symbol* generic_signature() const                   { return _generic_signature; }
 531   void set_generic_signature(Symbol* sig)             { _generic_signature = sig; }
 532 
 533   u2 enclosing_method_class_index() const             { return _enclosing_method_class_index; }
 534   u2 enclosing_method_method_index() const            { return _enclosing_method_method_index; }
 535   void set_enclosing_method_indices(u2 class_index,
 536                                     u2 method_index)  { _enclosing_method_class_index  = class_index;
 537                                                         _enclosing_method_method_index = method_index; }
 538 
 539   // jmethodID support
 540   static jmethodID get_jmethod_id(instanceKlassHandle ik_h,
 541                      methodHandle method_h);
 542   static jmethodID get_jmethod_id_fetch_or_update(instanceKlassHandle ik_h,
 543                      size_t idnum, jmethodID new_id, jmethodID* new_jmeths,
 544                      jmethodID* to_dealloc_id_p,
 545                      jmethodID** to_dealloc_jmeths_p);
 546   static void get_jmethod_id_length_value(jmethodID* cache, size_t idnum,
 547                 size_t *length_p, jmethodID* id_p);
 548   jmethodID jmethod_id_or_null(methodOop method);
 549 
 550   // cached itable index support
 551   void set_cached_itable_index(size_t idnum, int index);
 552   int cached_itable_index(size_t idnum);
 553 
 554   // annotations support
 555   typeArrayOop class_annotations() const              { return _class_annotations; }
 556   objArrayOop fields_annotations() const              { return _fields_annotations; }
 557   objArrayOop methods_annotations() const             { return _methods_annotations; }
 558   objArrayOop methods_parameter_annotations() const   { return _methods_parameter_annotations; }
 559   objArrayOop methods_default_annotations() const     { return _methods_default_annotations; }
 560   void set_class_annotations(typeArrayOop md)            { oop_store_without_check((oop*)&_class_annotations, (oop)md); }
 561   void set_fields_annotations(objArrayOop md)            { set_annotations(md, &_fields_annotations); }
 562   void set_methods_annotations(objArrayOop md)           { set_annotations(md, &_methods_annotations); }
 563   void set_methods_parameter_annotations(objArrayOop md) { set_annotations(md, &_methods_parameter_annotations); }
 564   void set_methods_default_annotations(objArrayOop md)   { set_annotations(md, &_methods_default_annotations); }
 565   typeArrayOop get_method_annotations_of(int idnum)
 566                                                 { return get_method_annotations_from(idnum, _methods_annotations); }
 567   typeArrayOop get_method_parameter_annotations_of(int idnum)
 568                                                 { return get_method_annotations_from(idnum, _methods_parameter_annotations); }
 569   typeArrayOop get_method_default_annotations_of(int idnum)
 570                                                 { return get_method_annotations_from(idnum, _methods_default_annotations); }
 571   void set_method_annotations_of(int idnum, typeArrayOop anno)
 572                                                 { set_methods_annotations_of(idnum, anno, &_methods_annotations); }
 573   void set_method_parameter_annotations_of(int idnum, typeArrayOop anno)
 574                                                 { set_methods_annotations_of(idnum, anno, &_methods_annotations); }
 575   void set_method_default_annotations_of(int idnum, typeArrayOop anno)
 576                                                 { set_methods_annotations_of(idnum, anno, &_methods_annotations); }
 577 
 578   // allocation
 579   DEFINE_ALLOCATE_PERMANENT(instanceKlass);
 580   instanceOop allocate_instance(TRAPS);
 581   instanceOop allocate_permanent_instance(TRAPS);
 582 
 583   // additional member function to return a handle
 584   instanceHandle allocate_instance_handle(TRAPS)      { return instanceHandle(THREAD, allocate_instance(THREAD)); }
 585 
 586   objArrayOop allocate_objArray(int n, int length, TRAPS);
 587   // Helper function
 588   static instanceOop register_finalizer(instanceOop i, TRAPS);
 589 
 590   // Check whether reflection/jni/jvm code is allowed to instantiate this class;
 591   // if not, throw either an Error or an Exception.
 592   virtual void check_valid_for_instantiation(bool throwError, TRAPS);
 593 
 594   // initialization
 595   void call_class_initializer(TRAPS);
 596   void set_initialization_state_and_notify(ClassState state, TRAPS);
 597 
 598   // OopMapCache support
 599   OopMapCache* oop_map_cache()               { return _oop_map_cache; }
 600   void set_oop_map_cache(OopMapCache *cache) { _oop_map_cache = cache; }
 601   void mask_for(methodHandle method, int bci, InterpreterOopMap* entry);
 602 
 603   // JNI identifier support (for static fields - for jni performance)
 604   JNIid* jni_ids()                               { return _jni_ids; }
 605   void set_jni_ids(JNIid* ids)                   { _jni_ids = ids; }
 606   JNIid* jni_id_for(int offset);
 607 
 608   // maintenance of deoptimization dependencies
 609   int mark_dependent_nmethods(DepChange& changes);
 610   void add_dependent_nmethod(nmethod* nm);
 611   void remove_dependent_nmethod(nmethod* nm);
 612 
 613   // On-stack replacement support
 614   nmethod* osr_nmethods_head() const         { return _osr_nmethods_head; };
 615   void set_osr_nmethods_head(nmethod* h)     { _osr_nmethods_head = h; };
 616   void add_osr_nmethod(nmethod* n);
 617   void remove_osr_nmethod(nmethod* n);
 618   nmethod* lookup_osr_nmethod(const methodOop m, int bci, int level, bool match_level) const;
 619 
 620   // Breakpoint support (see methods on methodOop for details)
 621   BreakpointInfo* breakpoints() const       { return _breakpoints; };
 622   void set_breakpoints(BreakpointInfo* bps) { _breakpoints = bps; };
 623 
 624   // support for stub routines
 625   static ByteSize init_state_offset()  { return in_ByteSize(sizeof(klassOopDesc) + offset_of(instanceKlass, _init_state)); }
 626   static ByteSize init_thread_offset() { return in_ByteSize(sizeof(klassOopDesc) + offset_of(instanceKlass, _init_thread)); }
 627 
 628   // subclass/subinterface checks
 629   bool implements_interface(klassOop k) const;
 630 
 631   // Access to implementors of an interface. We only store the count
 632   // of implementors, and in case, there are only a few
 633   // implementors, we store them in a short list.
 634   // This accessor returns NULL if we walk off the end of the list.
 635   klassOop implementor(int i) const {
 636     return (i < implementors_limit)? _implementors[i]: (klassOop) NULL;
 637   }
 638   int  nof_implementors() const       { return _nof_implementors; }
 639   void add_implementor(klassOop k);  // k is a new class that implements this interface
 640   void init_implementor();           // initialize
 641 
 642   // link this class into the implementors list of every interface it implements
 643   void process_interfaces(Thread *thread);
 644 
 645   // virtual operations from Klass
 646   bool is_leaf_class() const               { return _subklass == NULL; }
 647   objArrayOop compute_secondary_supers(int num_extra_slots, TRAPS);
 648   bool compute_is_subtype_of(klassOop k);
 649   bool can_be_primary_super_slow() const;
 650   klassOop java_super() const              { return super(); }
 651   int oop_size(oop obj)  const             { return size_helper(); }
 652   int klass_oop_size() const               { return object_size(); }
 653   bool oop_is_instance_slow() const        { return true; }
 654 
 655   // Iterators
 656   void do_local_static_fields(FieldClosure* cl);
 657   void do_nonstatic_fields(FieldClosure* cl); // including inherited fields
 658   void do_local_static_fields(void f(fieldDescriptor*, TRAPS), TRAPS);
 659 
 660   void methods_do(void f(methodOop method));
 661   void array_klasses_do(void f(klassOop k));
 662   void with_array_klasses_do(void f(klassOop k));
 663   bool super_types_do(SuperTypeClosure* blk);
 664 
 665   // Casting from klassOop
 666   static instanceKlass* cast(klassOop k) {
 667     assert(k->is_klass(), "must be");
 668     Klass* kp = k->klass_part();
 669     assert(kp->null_vtbl() || kp->oop_is_instance_slow(), "cast to instanceKlass");
 670     return (instanceKlass*) kp;
 671   }
 672 
 673   // Sizing (in words)
 674   static int header_size()            { return align_object_offset(oopDesc::header_size() + sizeof(instanceKlass)/HeapWordSize); }
 675   int object_size() const             { return object_size(align_object_offset(vtable_length()) + align_object_offset(itable_length()) + nonstatic_oop_map_size()); }
 676   static int vtable_start_offset()    { return header_size(); }
 677   static int vtable_length_offset()   { return oopDesc::header_size() + offset_of(instanceKlass, _vtable_len) / HeapWordSize; }
 678   static int object_size(int extra)   { return align_object_size(header_size() + extra); }
 679 
 680   intptr_t* start_of_vtable() const        { return ((intptr_t*)as_klassOop()) + vtable_start_offset(); }
 681   intptr_t* start_of_itable() const        { return start_of_vtable() + align_object_offset(vtable_length()); }
 682   int  itable_offset_in_words() const { return start_of_itable() - (intptr_t*)as_klassOop(); }
 683 
 684   intptr_t* end_of_itable() const          { return start_of_itable() + itable_length(); }
 685 
 686   address static_field_addr(int offset);
 687 
 688   OopMapBlock* start_of_nonstatic_oop_maps() const {
 689     return (OopMapBlock*)(start_of_itable() + align_object_offset(itable_length()));
 690   }
 691 
 692   // Allocation profiling support
 693   juint alloc_size() const            { return _alloc_count * size_helper(); }
 694   void set_alloc_size(juint n)        {}
 695 
 696   // Use this to return the size of an instance in heap words:
 697   int size_helper() const {
 698     return layout_helper_to_size_helper(layout_helper());
 699   }
 700 
 701   // This bit is initialized in classFileParser.cpp.
 702   // It is false under any of the following conditions:
 703   //  - the class is abstract (including any interface)
 704   //  - the class has a finalizer (if !RegisterFinalizersAtInit)
 705   //  - the class size is larger than FastAllocateSizeLimit
 706   //  - the class is java/lang/Class, which cannot be allocated directly
 707   bool can_be_fastpath_allocated() const {
 708     return !layout_helper_needs_slow_path(layout_helper());
 709   }
 710 
 711   // Java vtable/itable
 712   klassVtable* vtable() const;        // return new klassVtable wrapper
 713   inline methodOop method_at_vtable(int index);
 714   klassItable* itable() const;        // return new klassItable wrapper
 715   methodOop method_at_itable(klassOop holder, int index, TRAPS);
 716 
 717   // Garbage collection
 718   void oop_follow_contents(oop obj);
 719   int  oop_adjust_pointers(oop obj);
 720   bool object_is_parsable() const { return _init_state != unparsable_by_gc; }
 721        // Value of _init_state must be zero (unparsable_by_gc) when klass field is set.
 722 
 723   void follow_weak_klass_links(
 724     BoolObjectClosure* is_alive, OopClosure* keep_alive);
 725   void release_C_heap_structures();
 726 
 727   // Parallel Scavenge and Parallel Old
 728   PARALLEL_GC_DECLS
 729 
 730   // Naming
 731   const char* signature_name() const;
 732 
 733   // Iterators
 734   int oop_oop_iterate(oop obj, OopClosure* blk) {
 735     return oop_oop_iterate_v(obj, blk);
 736   }
 737 
 738   int oop_oop_iterate_m(oop obj, OopClosure* blk, MemRegion mr) {
 739     return oop_oop_iterate_v_m(obj, blk, mr);
 740   }
 741 
 742 #define InstanceKlass_OOP_OOP_ITERATE_DECL(OopClosureType, nv_suffix)      \
 743   int  oop_oop_iterate##nv_suffix(oop obj, OopClosureType* blk);           \
 744   int  oop_oop_iterate##nv_suffix##_m(oop obj, OopClosureType* blk,        \
 745                                       MemRegion mr);
 746 
 747   ALL_OOP_OOP_ITERATE_CLOSURES_1(InstanceKlass_OOP_OOP_ITERATE_DECL)
 748   ALL_OOP_OOP_ITERATE_CLOSURES_2(InstanceKlass_OOP_OOP_ITERATE_DECL)
 749 
 750 #ifndef SERIALGC
 751 #define InstanceKlass_OOP_OOP_ITERATE_BACKWARDS_DECL(OopClosureType, nv_suffix) \
 752   int  oop_oop_iterate_backwards##nv_suffix(oop obj, OopClosureType* blk);
 753 
 754   ALL_OOP_OOP_ITERATE_CLOSURES_1(InstanceKlass_OOP_OOP_ITERATE_BACKWARDS_DECL)
 755   ALL_OOP_OOP_ITERATE_CLOSURES_2(InstanceKlass_OOP_OOP_ITERATE_BACKWARDS_DECL)
 756 #endif // !SERIALGC
 757 
 758 private:
 759   // initialization state
 760 #ifdef ASSERT
 761   void set_init_state(ClassState state);
 762 #else
 763   void set_init_state(ClassState state) { _init_state = (u1)state; }
 764 #endif
 765   void set_rewritten()                  { _rewritten = true; }
 766   void set_init_thread(Thread *thread)  { _init_thread = thread; }
 767 
 768   u2 idnum_allocated_count() const      { return _idnum_allocated_count; }
 769   // The RedefineClasses() API can cause new method idnums to be needed
 770   // which will cause the caches to grow. Safety requires different
 771   // cache management logic if the caches can grow instead of just
 772   // going from NULL to non-NULL.
 773   bool idnum_can_increment() const      { return has_been_redefined(); }
 774   jmethodID* methods_jmethod_ids_acquire() const
 775          { return (jmethodID*)OrderAccess::load_ptr_acquire(&_methods_jmethod_ids); }
 776   void release_set_methods_jmethod_ids(jmethodID* jmeths)
 777          { OrderAccess::release_store_ptr(&_methods_jmethod_ids, jmeths); }
 778 
 779   int* methods_cached_itable_indices_acquire() const
 780          { return (int*)OrderAccess::load_ptr_acquire(&_methods_cached_itable_indices); }
 781   void release_set_methods_cached_itable_indices(int* indices)
 782          { OrderAccess::release_store_ptr(&_methods_cached_itable_indices, indices); }
 783 
 784   inline typeArrayOop get_method_annotations_from(int idnum, objArrayOop annos);
 785   void set_annotations(objArrayOop md, objArrayOop* md_p)  { oop_store_without_check((oop*)md_p, (oop)md); }
 786   void set_methods_annotations_of(int idnum, typeArrayOop anno, objArrayOop* md_p);
 787 
 788   // Offsets for memory management
 789   oop* adr_array_klasses() const     { return (oop*)&this->_array_klasses;}
 790   oop* adr_methods() const           { return (oop*)&this->_methods;}
 791   oop* adr_method_ordering() const   { return (oop*)&this->_method_ordering;}
 792   oop* adr_local_interfaces() const  { return (oop*)&this->_local_interfaces;}
 793   oop* adr_transitive_interfaces() const  { return (oop*)&this->_transitive_interfaces;}
 794   oop* adr_fields() const            { return (oop*)&this->_fields;}
 795   oop* adr_constants() const         { return (oop*)&this->_constants;}
 796   oop* adr_class_loader() const      { return (oop*)&this->_class_loader;}
 797   oop* adr_protection_domain() const { return (oop*)&this->_protection_domain;}
 798   oop* adr_host_klass() const        { return (oop*)&this->_host_klass;}
 799   oop* adr_signers() const           { return (oop*)&this->_signers;}
 800   oop* adr_inner_classes() const     { return (oop*)&this->_inner_classes;}
 801   oop* adr_implementors() const      { return (oop*)&this->_implementors[0];}
 802   oop* adr_methods_jmethod_ids() const             { return (oop*)&this->_methods_jmethod_ids;}
 803   oop* adr_methods_cached_itable_indices() const   { return (oop*)&this->_methods_cached_itable_indices;}
 804   oop* adr_class_annotations() const   { return (oop*)&this->_class_annotations;}
 805   oop* adr_fields_annotations() const  { return (oop*)&this->_fields_annotations;}
 806   oop* adr_methods_annotations() const { return (oop*)&this->_methods_annotations;}
 807   oop* adr_methods_parameter_annotations() const { return (oop*)&this->_methods_parameter_annotations;}
 808   oop* adr_methods_default_annotations() const { return (oop*)&this->_methods_default_annotations;}
 809 
 810   // Static methods that are used to implement member methods where an exposed this pointer
 811   // is needed due to possible GCs
 812   static bool link_class_impl                           (instanceKlassHandle this_oop, bool throw_verifyerror, TRAPS);
 813   static bool verify_code                               (instanceKlassHandle this_oop, bool throw_verifyerror, TRAPS);
 814   static void initialize_impl                           (instanceKlassHandle this_oop, TRAPS);
 815   static void eager_initialize_impl                     (instanceKlassHandle this_oop);
 816   static void set_initialization_state_and_notify_impl  (instanceKlassHandle this_oop, ClassState state, TRAPS);
 817   static void call_class_initializer_impl               (instanceKlassHandle this_oop, TRAPS);
 818   static klassOop array_klass_impl                      (instanceKlassHandle this_oop, bool or_null, int n, TRAPS);
 819   static void do_local_static_fields_impl               (instanceKlassHandle this_oop, void f(fieldDescriptor* fd, TRAPS), TRAPS);
 820   /* jni_id_for_impl for jfieldID only */
 821   static JNIid* jni_id_for_impl                         (instanceKlassHandle this_oop, int offset);
 822 
 823   // Returns the array class for the n'th dimension
 824   klassOop array_klass_impl(bool or_null, int n, TRAPS);
 825 
 826   // Returns the array class with this class as element type
 827   klassOop array_klass_impl(bool or_null, TRAPS);
 828 
 829 public:
 830   // sharing support
 831   virtual void remove_unshareable_info();
 832   virtual void shared_symbols_iterate(SymbolClosure* closure);
 833 
 834   // jvm support
 835   jint compute_modifier_flags(TRAPS) const;
 836 
 837 public:
 838   // JVMTI support
 839   jint jvmti_class_status() const;
 840 
 841  public:
 842   // Printing
 843   void oop_print_value_on(oop obj, outputStream* st);
 844 #ifndef PRODUCT
 845   void oop_print_on      (oop obj, outputStream* st);
 846 
 847   void print_dependent_nmethods(bool verbose = false);
 848   bool is_dependent_nmethod(nmethod* nm);
 849 #endif
 850 
 851   // Verification
 852   const char* internal_name() const;
 853   void oop_verify_on(oop obj, outputStream* st);
 854 };
 855 
 856 inline methodOop instanceKlass::method_at_vtable(int index)  {
 857 #ifndef PRODUCT
 858   assert(index >= 0, "valid vtable index");
 859   if (DebugVtables) {
 860     verify_vtable_index(index);
 861   }
 862 #endif
 863   vtableEntry* ve = (vtableEntry*)start_of_vtable();
 864   return ve[index].method();
 865 }
 866 
 867 inline typeArrayOop instanceKlass::get_method_annotations_from(int idnum, objArrayOop annos) {
 868   if (annos == NULL || annos->length() <= idnum) {
 869     return NULL;
 870   }
 871   return typeArrayOop(annos->obj_at(idnum));
 872 }
 873 
 874 // for adding methods
 875 // UNSET_IDNUM return means no more ids available
 876 inline u2 instanceKlass::next_method_idnum() {
 877   if (_idnum_allocated_count == constMethodOopDesc::MAX_IDNUM) {
 878     return constMethodOopDesc::UNSET_IDNUM; // no more ids available
 879   } else {
 880     return _idnum_allocated_count++;
 881   }
 882 }
 883 
 884 
 885 /* JNIid class for jfieldIDs only */
 886 class JNIid: public CHeapObj {
 887   friend class VMStructs;
 888  private:
 889   klassOop           _holder;
 890   JNIid*             _next;
 891   int                _offset;
 892 #ifdef ASSERT
 893   bool               _is_static_field_id;
 894 #endif
 895 
 896  public:
 897   // Accessors
 898   klassOop holder() const         { return _holder; }
 899   int offset() const              { return _offset; }
 900   JNIid* next()                   { return _next; }
 901   // Constructor
 902   JNIid(klassOop holder, int offset, JNIid* next);
 903   // Identifier lookup
 904   JNIid* find(int offset);
 905 
 906   bool find_local_field(fieldDescriptor* fd) {
 907     return instanceKlass::cast(holder())->find_local_field_from_offset(offset(), true, fd);
 908   }
 909 
 910   // Garbage collection support
 911   oop* holder_addr() { return (oop*)&_holder; }
 912   void oops_do(OopClosure* f);
 913   static void deallocate(JNIid* id);
 914   // Debugging
 915 #ifdef ASSERT
 916   bool is_static_field_id() const { return _is_static_field_id; }
 917   void set_is_static_field_id()   { _is_static_field_id = true; }
 918 #endif
 919   void verify(klassOop holder);
 920 };
 921 
 922 
 923 // If breakpoints are more numerous than just JVMTI breakpoints,
 924 // consider compressing this data structure.
 925 // It is currently a simple linked list defined in methodOop.hpp.
 926 
 927 class BreakpointInfo;
 928 
 929 
 930 // A collection point for interesting information about the previous
 931 // version(s) of an instanceKlass. This class uses weak references to
 932 // the information so that the information may be collected as needed
 933 // by the system. If the information is shared, then a regular
 934 // reference must be used because a weak reference would be seen as
 935 // collectible. A GrowableArray of PreviousVersionNodes is attached
 936 // to the instanceKlass as needed. See PreviousVersionWalker below.
 937 class PreviousVersionNode : public CHeapObj {
 938  private:
 939   // A shared ConstantPool is never collected so we'll always have
 940   // a reference to it so we can update items in the cache. We'll
 941   // have a weak reference to a non-shared ConstantPool until all
 942   // of the methods (EMCP or obsolete) have been collected; the
 943   // non-shared ConstantPool becomes collectible at that point.
 944   jobject _prev_constant_pool;  // regular or weak reference
 945   bool    _prev_cp_is_weak;     // true if not a shared ConstantPool
 946 
 947   // If the previous version of the instanceKlass doesn't have any
 948   // EMCP methods, then _prev_EMCP_methods will be NULL. If all the
 949   // EMCP methods have been collected, then _prev_EMCP_methods can
 950   // have a length of zero.
 951   GrowableArray<jweak>* _prev_EMCP_methods;
 952 
 953 public:
 954   PreviousVersionNode(jobject prev_constant_pool, bool prev_cp_is_weak,
 955     GrowableArray<jweak>* prev_EMCP_methods);
 956   ~PreviousVersionNode();
 957   jobject prev_constant_pool() const {
 958     return _prev_constant_pool;
 959   }
 960   GrowableArray<jweak>* prev_EMCP_methods() const {
 961     return _prev_EMCP_methods;
 962   }
 963 };
 964 
 965 
 966 // A Handle-ized version of PreviousVersionNode.
 967 class PreviousVersionInfo : public ResourceObj {
 968  private:
 969   constantPoolHandle   _prev_constant_pool_handle;
 970   // If the previous version of the instanceKlass doesn't have any
 971   // EMCP methods, then _prev_EMCP_methods will be NULL. Since the
 972   // methods cannot be collected while we hold a handle,
 973   // _prev_EMCP_methods should never have a length of zero.
 974   GrowableArray<methodHandle>* _prev_EMCP_method_handles;
 975 
 976 public:
 977   PreviousVersionInfo(PreviousVersionNode *pv_node);
 978   ~PreviousVersionInfo();
 979   constantPoolHandle prev_constant_pool_handle() const {
 980     return _prev_constant_pool_handle;
 981   }
 982   GrowableArray<methodHandle>* prev_EMCP_method_handles() const {
 983     return _prev_EMCP_method_handles;
 984   }
 985 };
 986 
 987 
 988 // Helper object for walking previous versions. This helper cleans up
 989 // the Handles that it allocates when the helper object is destroyed.
 990 // The PreviousVersionInfo object returned by next_previous_version()
 991 // is only valid until a subsequent call to next_previous_version() or
 992 // the helper object is destroyed.
 993 class PreviousVersionWalker : public StackObj {
 994  private:
 995   GrowableArray<PreviousVersionNode *>* _previous_versions;
 996   int                                   _current_index;
 997   // Fields for cleaning up when we are done walking the previous versions:
 998   // A HandleMark for the PreviousVersionInfo handles:
 999   HandleMark                            _hm;
1000 
1001   // It would be nice to have a ResourceMark field in this helper also,
1002   // but the ResourceMark code says to be careful to delete handles held
1003   // in GrowableArrays _before_ deleting the GrowableArray. Since we
1004   // can't guarantee the order in which the fields are destroyed, we
1005   // have to let the creator of the PreviousVersionWalker object do
1006   // the right thing. Also, adding a ResourceMark here causes an
1007   // include loop.
1008 
1009   // A pointer to the current info object so we can handle the deletes.
1010   PreviousVersionInfo *                 _current_p;
1011 
1012  public:
1013   PreviousVersionWalker(instanceKlass *ik);
1014   ~PreviousVersionWalker();
1015 
1016   // Return the interesting information for the next previous version
1017   // of the klass. Returns NULL if there are no more previous versions.
1018   PreviousVersionInfo* next_previous_version();
1019 };
1020 
1021 
1022 //
1023 // nmethodBucket is used to record dependent nmethods for
1024 // deoptimization.  nmethod dependencies are actually <klass, method>
1025 // pairs but we really only care about the klass part for purposes of
1026 // finding nmethods which might need to be deoptimized.  Instead of
1027 // recording the method, a count of how many times a particular nmethod
1028 // was recorded is kept.  This ensures that any recording errors are
1029 // noticed since an nmethod should be removed as many times are it's
1030 // added.
1031 //
1032 class nmethodBucket: public CHeapObj {
1033   friend class VMStructs;
1034  private:
1035   nmethod*       _nmethod;
1036   int            _count;
1037   nmethodBucket* _next;
1038 
1039  public:
1040   nmethodBucket(nmethod* nmethod, nmethodBucket* next) {
1041     _nmethod = nmethod;
1042     _next = next;
1043     _count = 1;
1044   }
1045   int count()                             { return _count; }
1046   int increment()                         { _count += 1; return _count; }
1047   int decrement()                         { _count -= 1; assert(_count >= 0, "don't underflow"); return _count; }
1048   nmethodBucket* next()                   { return _next; }
1049   void set_next(nmethodBucket* b)         { _next = b; }
1050   nmethod* get_nmethod()                  { return _nmethod; }
1051 };
1052 
1053 #endif // SHARE_VM_OOPS_INSTANCEKLASS_HPP