1 /*
   2  * Copyright (c) 1998, 2017, 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.
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   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
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  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.
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  24 
  25 #ifndef SHARE_VM_OOPS_CPCACHEOOP_HPP
  26 #define SHARE_VM_OOPS_CPCACHEOOP_HPP
  27 
  28 #include "interpreter/bytecodes.hpp"
  29 #include "memory/allocation.hpp"
  30 #include "oops/array.hpp"
  31 #include "oops/oopHandle.hpp"
  32 #include "runtime/orderAccess.hpp"
  33 #include "utilities/align.hpp"
  34 #include "utilities/constantTag.hpp"
  35 
  36 class PSPromotionManager;
  37 
  38 // The ConstantPoolCache is not a cache! It is the resolution table that the
  39 // interpreter uses to avoid going into the runtime and a way to access resolved
  40 // values.
  41 
  42 // A ConstantPoolCacheEntry describes an individual entry of the constant
  43 // pool cache. There's 2 principal kinds of entries: field entries for in-
  44 // stance & static field access, and method entries for invokes. Some of
  45 // the entry layout is shared and looks as follows:
  46 //
  47 // bit number |31                0|
  48 // bit length |-8--|-8--|---16----|
  49 // --------------------------------
  50 // _indices   [ b2 | b1 |  index  ]  index = constant_pool_index
  51 // _f1        [  entry specific   ]  metadata ptr (method or klass)
  52 // _f2        [  entry specific   ]  vtable or res_ref index, or vfinal method ptr
  53 // _flags     [tos|0|F=1|0|0|0|f|v|0 |0000|field_index] (for field entries)
  54 // bit length [ 4 |1| 1 |1|1|1|1|1|1 |1     |-3-|----16-----]
  55 // _flags     [tos|0|F=0|M|A|I|f|0|vf|indy_rf|000|00000|psize] (for method entries)
  56 // bit length [ 4 |1| 1 |1|1|1|1|1|1 |-4--|--8--|--8--]
  57 
  58 // --------------------------------
  59 //
  60 // with:
  61 // index  = original constant pool index
  62 // b1     = bytecode 1
  63 // b2     = bytecode 2
  64 // psize  = parameters size (method entries only)
  65 // field_index = index into field information in holder InstanceKlass
  66 //          The index max is 0xffff (max number of fields in constant pool)
  67 //          and is multiplied by (InstanceKlass::next_offset) when accessing.
  68 // tos    = TosState
  69 // F      = the entry is for a field (or F=0 for a method)
  70 // A      = call site has an appendix argument (loaded from resolved references)
  71 // I      = interface call is forced virtual (must use a vtable index or vfinal)
  72 // f      = field or method is final
  73 // v      = field is volatile
  74 // vf     = virtual but final (method entries only: is_vfinal())
  75 // indy_rf = call site specifier method resolution failed
  76 //
  77 // The flags after TosState have the following interpretation:
  78 // bit 27: 0 for fields, 1 for methods
  79 // f  flag true if field is marked final
  80 // v  flag true if field is volatile (only for fields)
  81 // f2 flag true if f2 contains an oop (e.g., virtual final method)
  82 // fv flag true if invokeinterface used for method in class Object
  83 //
  84 // The flags 31, 30, 29, 28 together build a 4 bit number 0 to 16 with the
  85 // following mapping to the TosState states:
  86 //
  87 // btos: 0
  88 // ztos: 1
  89 // ctos: 2
  90 // stos: 3
  91 // itos: 4
  92 // ltos: 5
  93 // ftos: 6
  94 // dtos: 7
  95 // atos: 8
  96 // vtos: 9
  97 //
  98 // Entry specific: field entries:
  99 // _indices = get (b1 section) and put (b2 section) bytecodes, original constant pool index
 100 // _f1      = field holder (as a java.lang.Class, not a Klass*)
 101 // _f2      = field offset in bytes
 102 // _flags   = field type information, original FieldInfo index in field holder
 103 //            (field_index section)
 104 //
 105 // Entry specific: method entries:
 106 // _indices = invoke code for f1 (b1 section), invoke code for f2 (b2 section),
 107 //            original constant pool index
 108 // _f1      = Method* for non-virtual calls, unused by virtual calls.
 109 //            for interface calls, which are essentially virtual but need a klass,
 110 //            contains Klass* for the corresponding interface.
 111 //            for invokedynamic and invokehandle, f1 contains the adapter method which
 112 //            manages the actual call. The appendix is stored in the ConstantPool
 113 //            resolved_references array.
 114 //            (upcoming metadata changes will move the appendix to a separate array)
 115 // _f2      = vtable/itable index (or final Method*) for virtual calls only,
 116 //            unused by non-virtual.  The is_vfinal flag indicates this is a
 117 //            method pointer for a final method, not an index.
 118 // _flags   = method type info (t section),
 119 //            virtual final bit (vfinal),
 120 //            parameter size (psize section)
 121 //
 122 // Note: invokevirtual & invokespecial bytecodes can share the same constant
 123 //       pool entry and thus the same constant pool cache entry. All invoke
 124 //       bytecodes but invokevirtual use only _f1 and the corresponding b1
 125 //       bytecode, while invokevirtual uses only _f2 and the corresponding
 126 //       b2 bytecode.  The value of _flags is shared for both types of entries.
 127 //
 128 // The fields are volatile so that they are stored in the order written in the
 129 // source code.  The _indices field with the bytecode must be written last.
 130 
 131 class CallInfo;
 132 
 133 class ConstantPoolCacheEntry VALUE_OBJ_CLASS_SPEC {
 134   friend class VMStructs;
 135   friend class constantPoolCacheKlass;
 136   friend class ConstantPool;
 137   friend class InterpreterRuntime;
 138 
 139  private:
 140   volatile intx     _indices;  // constant pool index & rewrite bytecodes
 141   Metadata* volatile   _f1;       // entry specific metadata field
 142   volatile intx        _f2;       // entry specific int/metadata field
 143   volatile intx     _flags;    // flags
 144 
 145 
 146   void set_bytecode_1(Bytecodes::Code code);
 147   void set_bytecode_2(Bytecodes::Code code);
 148   void set_f1(Metadata* f1) {
 149     Metadata* existing_f1 = _f1; // read once
 150     assert(existing_f1 == NULL || existing_f1 == f1, "illegal field change");
 151     _f1 = f1;
 152   }
 153   void release_set_f1(Metadata* f1);
 154   void set_f2(intx f2) {
 155     intx existing_f2 = _f2; // read once
 156     assert(existing_f2 == 0 || existing_f2 == f2, "illegal field change");
 157     _f2 = f2;
 158   }
 159   void set_f2_as_vfinal_method(Method* f2) {
 160     assert(is_vfinal(), "flags must be set");
 161     set_f2((intx)f2);
 162   }
 163   int make_flags(TosState state, int option_bits, int field_index_or_method_params);
 164   void set_flags(intx flags)                     { _flags = flags; }
 165   void set_field_flags(TosState field_type, int option_bits, int field_index) {
 166     assert((field_index & field_index_mask) == field_index, "field_index in range");
 167     set_flags(make_flags(field_type, option_bits | (1 << is_field_entry_shift), field_index));
 168   }
 169   void set_method_flags(TosState return_type, int option_bits, int method_params) {
 170     assert((method_params & parameter_size_mask) == method_params, "method_params in range");
 171     set_flags(make_flags(return_type, option_bits, method_params));
 172   }
 173 
 174  public:
 175   // specific bit definitions for the flags field:
 176   // (Note: the interpreter must use these definitions to access the CP cache.)
 177   enum {
 178     // high order bits are the TosState corresponding to field type or method return type
 179     tos_state_bits             = 4,
 180     tos_state_mask             = right_n_bits(tos_state_bits),
 181     tos_state_shift            = BitsPerInt - tos_state_bits,  // see verify_tos_state_shift below
 182     // misc. option bits; can be any bit position in [16..27]
 183     is_field_entry_shift       = 26,  // (F) is it a field or a method?
 184     has_method_type_shift      = 25,  // (M) does the call site have a MethodType?
 185     has_appendix_shift         = 24,  // (A) does the call site have an appendix argument?
 186     is_forced_virtual_shift    = 23,  // (I) is the interface reference forced to virtual mode?
 187     is_final_shift             = 22,  // (f) is the field or method final?
 188     is_volatile_shift          = 21,  // (v) is the field volatile?
 189     is_vfinal_shift            = 20,  // (vf) did the call resolve to a final method?
 190     indy_resolution_failed_shift= 19, // (indy_rf) did call site specifier resolution fail ?
 191     // low order bits give field index (for FieldInfo) or method parameter size:
 192     field_index_bits           = 16,
 193     field_index_mask           = right_n_bits(field_index_bits),
 194     parameter_size_bits        = 8,  // subset of field_index_mask, range is 0..255
 195     parameter_size_mask        = right_n_bits(parameter_size_bits),
 196     option_bits_mask           = ~(((~0u) << tos_state_shift) | (field_index_mask | parameter_size_mask))
 197   };
 198 
 199   // specific bit definitions for the indices field:
 200   enum {
 201     cp_index_bits              = 2*BitsPerByte,
 202     cp_index_mask              = right_n_bits(cp_index_bits),
 203     bytecode_1_shift           = cp_index_bits,
 204     bytecode_1_mask            = right_n_bits(BitsPerByte), // == (u1)0xFF
 205     bytecode_2_shift           = cp_index_bits + BitsPerByte,
 206     bytecode_2_mask            = right_n_bits(BitsPerByte)  // == (u1)0xFF
 207   };
 208 
 209 
 210   // Initialization
 211   void initialize_entry(int original_index);     // initialize primary entry
 212   void initialize_resolved_reference_index(int ref_index) {
 213     assert(_f2 == 0, "set once");  // note: ref_index might be zero also
 214     _f2 = ref_index;
 215   }
 216 
 217   void set_field(                                // sets entry to resolved field state
 218     Bytecodes::Code get_code,                    // the bytecode used for reading the field
 219     Bytecodes::Code put_code,                    // the bytecode used for writing the field
 220     Klass*          field_holder,                // the object/klass holding the field
 221     int             orig_field_index,            // the original field index in the field holder
 222     int             field_offset,                // the field offset in words in the field holder
 223     TosState        field_type,                  // the (machine) field type
 224     bool            is_final,                    // the field is final
 225     bool            is_volatile,                 // the field is volatile
 226     Klass*          root_klass                   // needed by the GC to dirty the klass
 227   );
 228 
 229  private:
 230   void set_direct_or_vtable_call(
 231     Bytecodes::Code invoke_code,                 // the bytecode used for invoking the method
 232     const methodHandle& method,                  // the method/prototype if any (NULL, otherwise)
 233     int             vtable_index,                // the vtable index if any, else negative
 234     bool            sender_is_interface
 235   );
 236 
 237  public:
 238   void set_direct_call(                          // sets entry to exact concrete method entry
 239     Bytecodes::Code invoke_code,                 // the bytecode used for invoking the method
 240     const methodHandle& method,                  // the method to call
 241     bool            sender_is_interface
 242   );
 243 
 244   void set_vtable_call(                          // sets entry to vtable index
 245     Bytecodes::Code invoke_code,                 // the bytecode used for invoking the method
 246     const methodHandle& method,                  // resolved method which declares the vtable index
 247     int             vtable_index                 // the vtable index
 248   );
 249 
 250   void set_itable_call(
 251     Bytecodes::Code invoke_code,                 // the bytecode used; must be invokeinterface
 252     Klass* referenced_klass,                     // the referenced klass in the InterfaceMethodref
 253     const methodHandle& method,                  // the resolved interface method
 254     int itable_index                             // index into itable for the method
 255   );
 256 
 257   void set_method_handle(
 258     const constantPoolHandle& cpool,             // holding constant pool (required for locking)
 259     const CallInfo &call_info                    // Call link information
 260   );
 261 
 262   void set_dynamic_call(
 263     const constantPoolHandle& cpool,             // holding constant pool (required for locking)
 264     const CallInfo &call_info                    // Call link information
 265   );
 266 
 267   // Common code for invokedynamic and MH invocations.
 268 
 269   // The "appendix" is an optional call-site-specific parameter which is
 270   // pushed by the JVM at the end of the argument list.  This argument may
 271   // be a MethodType for the MH.invokes and a CallSite for an invokedynamic
 272   // instruction.  However, its exact type and use depends on the Java upcall,
 273   // which simply returns a compiled LambdaForm along with any reference
 274   // that LambdaForm needs to complete the call.  If the upcall returns a
 275   // null appendix, the argument is not passed at all.
 276   //
 277   // The appendix is *not* represented in the signature of the symbolic
 278   // reference for the call site, but (if present) it *is* represented in
 279   // the Method* bound to the site.  This means that static and dynamic
 280   // resolution logic needs to make slightly different assessments about the
 281   // number and types of arguments.
 282   void set_method_handle_common(
 283     const constantPoolHandle& cpool,                    // holding constant pool (required for locking)
 284     Bytecodes::Code invoke_code,                 // _invokehandle or _invokedynamic
 285     const CallInfo &call_info                    // Call link information
 286   );
 287 
 288   // Return TRUE if resolution failed and this thread got to record the failure
 289   // status.  Return FALSE if another thread succeeded or failed in resolving
 290   // the method and recorded the success or failure before this thread had a
 291   // chance to record its failure.
 292   bool save_and_throw_indy_exc(const constantPoolHandle& cpool, int cpool_index,
 293                                int index, constantTag tag, TRAPS);
 294 
 295   // invokedynamic and invokehandle call sites have two entries in the
 296   // resolved references array:
 297   //   appendix   (at index+0)
 298   //   MethodType (at index+1)
 299   enum {
 300     _indy_resolved_references_appendix_offset    = 0,
 301     _indy_resolved_references_method_type_offset = 1,
 302     _indy_resolved_references_entries
 303   };
 304 
 305   Method*      method_if_resolved(const constantPoolHandle& cpool);
 306   oop        appendix_if_resolved(const constantPoolHandle& cpool);
 307   oop     method_type_if_resolved(const constantPoolHandle& cpool);
 308 
 309   void set_parameter_size(int value);
 310 
 311   // Which bytecode number (1 or 2) in the index field is valid for this bytecode?
 312   // Returns -1 if neither is valid.
 313   static int bytecode_number(Bytecodes::Code code) {
 314     switch (code) {
 315       case Bytecodes::_getstatic       :    // fall through
 316       case Bytecodes::_getfield        :    // fall through
 317       case Bytecodes::_invokespecial   :    // fall through
 318       case Bytecodes::_invokestatic    :    // fall through
 319       case Bytecodes::_invokehandle    :    // fall through
 320       case Bytecodes::_invokedynamic   :    // fall through
 321       case Bytecodes::_invokeinterface : return 1;
 322       case Bytecodes::_putstatic       :    // fall through
 323       case Bytecodes::_putfield        :    // fall through
 324       case Bytecodes::_invokevirtual   : return 2;
 325       default                          : break;
 326     }
 327     return -1;
 328   }
 329 
 330   // Has this bytecode been resolved? Only valid for invokes and get/put field/static.
 331   bool is_resolved(Bytecodes::Code code) const {
 332     switch (bytecode_number(code)) {
 333       case 1:  return (bytecode_1() == code);
 334       case 2:  return (bytecode_2() == code);
 335     }
 336     return false;      // default: not resolved
 337   }
 338 
 339   // Accessors
 340   int indices() const                            { return _indices; }
 341   int indices_ord() const                        { return OrderAccess::load_acquire(&_indices); }
 342   int constant_pool_index() const                { return (indices() & cp_index_mask); }
 343   Bytecodes::Code bytecode_1() const             { return Bytecodes::cast((indices_ord() >> bytecode_1_shift) & bytecode_1_mask); }
 344   Bytecodes::Code bytecode_2() const             { return Bytecodes::cast((indices_ord() >> bytecode_2_shift) & bytecode_2_mask); }
 345   Metadata* f1_ord() const                       { return (Metadata *)OrderAccess::load_acquire(&_f1); }
 346   Method*   f1_as_method() const                 { Metadata* f1 = f1_ord(); assert(f1 == NULL || f1->is_method(), ""); return (Method*)f1; }
 347   Klass*    f1_as_klass() const                  { Metadata* f1 = f1_ord(); assert(f1 == NULL || f1->is_klass(), ""); return (Klass*)f1; }
 348   // Use the accessor f1() to acquire _f1's value. This is needed for
 349   // example in BytecodeInterpreter::run(), where is_f1_null() is
 350   // called to check if an invokedynamic call is resolved. This load
 351   // of _f1 must be ordered with the loads performed by
 352   // cache->main_entry_index().
 353   bool      is_f1_null() const                   { Metadata* f1 = f1_ord(); return f1 == NULL; }  // classifies a CPC entry as unbound
 354   int       f2_as_index() const                  { assert(!is_vfinal(), ""); return (int) _f2; }
 355   Method*   f2_as_vfinal_method() const          { assert(is_vfinal(), ""); return (Method*)_f2; }
 356   Method*   f2_as_interface_method() const       { assert(bytecode_1() == Bytecodes::_invokeinterface, ""); return (Method*)_f2; }
 357   intx flags_ord() const                         { return (intx)OrderAccess::load_acquire(&_flags); }
 358   int  field_index() const                       { assert(is_field_entry(),  ""); return (_flags & field_index_mask); }
 359   int  parameter_size() const                    { assert(is_method_entry(), ""); return (_flags & parameter_size_mask); }
 360   bool is_volatile() const                       { return (_flags & (1 << is_volatile_shift))       != 0; }
 361   bool is_final() const                          { return (_flags & (1 << is_final_shift))          != 0; }
 362   bool is_forced_virtual() const                 { return (_flags & (1 << is_forced_virtual_shift)) != 0; }
 363   bool is_vfinal() const                         { return (_flags & (1 << is_vfinal_shift))         != 0; }
 364   bool indy_resolution_failed() const            { intx flags = flags_ord(); return (flags & (1 << indy_resolution_failed_shift)) != 0; }
 365   bool has_appendix() const                      { return (!is_f1_null()) && (_flags & (1 << has_appendix_shift))      != 0; }
 366   bool has_method_type() const                   { return (!is_f1_null()) && (_flags & (1 << has_method_type_shift))   != 0; }
 367   bool is_method_entry() const                   { return (_flags & (1 << is_field_entry_shift))    == 0; }
 368   bool is_field_entry() const                    { return (_flags & (1 << is_field_entry_shift))    != 0; }
 369   bool is_long() const                           { return flag_state() == ltos; }
 370   bool is_double() const                         { return flag_state() == dtos; }
 371   TosState flag_state() const                    { assert((uint)number_of_states <= (uint)tos_state_mask+1, "");
 372                                                    return (TosState)((_flags >> tos_state_shift) & tos_state_mask); }
 373   void set_indy_resolution_failed();
 374 
 375   // Code generation support
 376   static WordSize size()                         {
 377     return in_WordSize(align_up((int)sizeof(ConstantPoolCacheEntry), wordSize) / wordSize);
 378   }
 379   static ByteSize size_in_bytes()                { return in_ByteSize(sizeof(ConstantPoolCacheEntry)); }
 380   static ByteSize indices_offset()               { return byte_offset_of(ConstantPoolCacheEntry, _indices); }
 381   static ByteSize f1_offset()                    { return byte_offset_of(ConstantPoolCacheEntry, _f1); }
 382   static ByteSize f2_offset()                    { return byte_offset_of(ConstantPoolCacheEntry, _f2); }
 383   static ByteSize flags_offset()                 { return byte_offset_of(ConstantPoolCacheEntry, _flags); }
 384 
 385 #if INCLUDE_JVMTI
 386   // RedefineClasses() API support:
 387   // If this ConstantPoolCacheEntry refers to old_method then update it
 388   // to refer to new_method.
 389   // trace_name_printed is set to true if the current call has
 390   // printed the klass name so that other routines in the adjust_*
 391   // group don't print the klass name.
 392   void adjust_method_entry(Method* old_method, Method* new_method,
 393          bool* trace_name_printed);
 394   bool check_no_old_or_obsolete_entries();
 395   Method* get_interesting_method_entry(Klass* k);
 396 #endif // INCLUDE_JVMTI
 397 
 398   // Debugging & Printing
 399   void print (outputStream* st, int index) const;
 400   void verify(outputStream* st) const;
 401 
 402   static void verify_tos_state_shift() {
 403     // When shifting flags as a 32-bit int, make sure we don't need an extra mask for tos_state:
 404     assert((((u4)-1 >> tos_state_shift) & ~tos_state_mask) == 0, "no need for tos_state mask");
 405   }
 406 
 407   void verify_just_initialized(bool f2_used);
 408   void reinitialize(bool f2_used);
 409 };
 410 
 411 
 412 // A constant pool cache is a runtime data structure set aside to a constant pool. The cache
 413 // holds interpreter runtime information for all field access and invoke bytecodes. The cache
 414 // is created and initialized before a class is actively used (i.e., initialized), the indivi-
 415 // dual cache entries are filled at resolution (i.e., "link") time (see also: rewriter.*).
 416 
 417 class ConstantPoolCache: public MetaspaceObj {
 418   friend class VMStructs;
 419   friend class MetadataFactory;
 420  private:
 421   // If you add a new field that points to any metaspace object, you
 422   // must add this field to ConstantPoolCache::metaspace_pointers_do().
 423   int             _length;
 424   ConstantPool*   _constant_pool;          // the corresponding constant pool
 425 
 426   // The following fields need to be modified at runtime, so they cannot be
 427   // stored in the ConstantPool, which is read-only.
 428   // Array of resolved objects from the constant pool and map from resolved
 429   // object index to original constant pool index
 430   OopHandle            _resolved_references;
 431   Array<u2>*           _reference_map;
 432   // The narrowOop pointer to the archived resolved_references. Set at CDS dump
 433   // time when caching java heap object is supported.
 434   CDS_JAVA_HEAP_ONLY(narrowOop _archived_references;)
 435 
 436   // Sizing
 437   debug_only(friend class ClassVerifier;)
 438 
 439   // Constructor
 440   ConstantPoolCache(int length,
 441                     const intStack& inverse_index_map,
 442                     const intStack& invokedynamic_inverse_index_map,
 443                     const intStack& invokedynamic_references_map) :
 444                           _length(length),
 445                           _constant_pool(NULL) {
 446     CDS_JAVA_HEAP_ONLY(_archived_references = 0;)
 447     initialize(inverse_index_map, invokedynamic_inverse_index_map,
 448                invokedynamic_references_map);
 449     for (int i = 0; i < length; i++) {
 450       assert(entry_at(i)->is_f1_null(), "Failed to clear?");
 451     }
 452   }
 453 
 454   // Initialization
 455   void initialize(const intArray& inverse_index_map,
 456                   const intArray& invokedynamic_inverse_index_map,
 457                   const intArray& invokedynamic_references_map);
 458  public:
 459   static ConstantPoolCache* allocate(ClassLoaderData* loader_data,
 460                                      const intStack& cp_cache_map,
 461                                      const intStack& invokedynamic_cp_cache_map,
 462                                      const intStack& invokedynamic_references_map, TRAPS);
 463   bool is_constantPoolCache() const { return true; }
 464 
 465   int length() const                      { return _length; }
 466   void metaspace_pointers_do(MetaspaceClosure* it);
 467   MetaspaceObj::Type type() const         { return ConstantPoolCacheType; }
 468 
 469   oop  archived_references() NOT_CDS_JAVA_HEAP_RETURN_(NULL);
 470   void set_archived_references(oop o) NOT_CDS_JAVA_HEAP_RETURN;
 471 
 472   oop resolved_references()                 { return _resolved_references.resolve(); }
 473   void set_resolved_references(OopHandle s) { _resolved_references = s; }
 474   Array<u2>* reference_map() const        { return _reference_map; }
 475   void set_reference_map(Array<u2>* o)    { _reference_map = o; }
 476 
 477   // Assembly code support
 478   static int resolved_references_offset_in_bytes() { return offset_of(ConstantPoolCache, _resolved_references); }
 479 
 480   // CDS support
 481   void remove_unshareable_info();
 482   void verify_just_initialized();
 483  private:
 484   void walk_entries_for_initialization(bool check_only);
 485   void set_length(int length)                    { _length = length; }
 486 
 487   static int header_size()                       { return sizeof(ConstantPoolCache) / wordSize; }
 488   static int size(int length)                    { return align_metadata_size(header_size() + length * in_words(ConstantPoolCacheEntry::size())); }
 489  public:
 490   int size() const                               { return size(length()); }
 491  private:
 492 
 493   // Helpers
 494   ConstantPool**        constant_pool_addr()     { return &_constant_pool; }
 495   ConstantPoolCacheEntry* base() const           { return (ConstantPoolCacheEntry*)((address)this + in_bytes(base_offset())); }
 496 
 497   friend class constantPoolCacheKlass;
 498   friend class ConstantPoolCacheEntry;
 499 
 500  public:
 501   // Accessors
 502   void set_constant_pool(ConstantPool* pool)   { _constant_pool = pool; }
 503   ConstantPool* constant_pool() const          { return _constant_pool; }
 504   // Fetches the entry at the given index.
 505   // In either case the index must not be encoded or byte-swapped in any way.
 506   ConstantPoolCacheEntry* entry_at(int i) const {
 507     assert(0 <= i && i < length(), "index out of bounds");
 508     return base() + i;
 509   }
 510 
 511   // Code generation
 512   static ByteSize base_offset()                  { return in_ByteSize(sizeof(ConstantPoolCache)); }
 513   static ByteSize entry_offset(int raw_index) {
 514     int index = raw_index;
 515     return (base_offset() + ConstantPoolCacheEntry::size_in_bytes() * index);
 516   }
 517 
 518 #if INCLUDE_JVMTI
 519   // RedefineClasses() API support:
 520   // If any entry of this ConstantPoolCache points to any of
 521   // old_methods, replace it with the corresponding new_method.
 522   // trace_name_printed is set to true if the current call has
 523   // printed the klass name so that other routines in the adjust_*
 524   // group don't print the klass name.
 525   void adjust_method_entries(InstanceKlass* holder, bool* trace_name_printed);
 526   bool check_no_old_or_obsolete_entries();
 527   void dump_cache();
 528 #endif // INCLUDE_JVMTI
 529 
 530   // RedefineClasses support
 531   DEBUG_ONLY(bool on_stack() { return false; })
 532   void deallocate_contents(ClassLoaderData* data);
 533   bool is_klass() const { return false; }
 534 
 535   // Printing
 536   void print_on(outputStream* st) const;
 537   void print_value_on(outputStream* st) const;
 538 
 539   const char* internal_name() const { return "{constant pool cache}"; }
 540 
 541   // Verify
 542   void verify_on(outputStream* st);
 543 };
 544 
 545 #endif // SHARE_VM_OOPS_CPCACHEOOP_HPP