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 /*

  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

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  */

 #include "precompiled.hpp"

 #include "classfile/classLoaderData.hpp"

 #include "classfile/javaClasses.hpp"

 #include "classfile/symbolTable.hpp"

 #include "classfile/systemDictionary.hpp"

 #include "classfile/vmSymbols.hpp"

 #include "interpreter/linkResolver.hpp"

 #include "memory/metadataFactory.hpp"

 #include "memory/oopFactory.hpp"

 #include "oops/constantPool.hpp"

 #include "oops/instanceKlass.hpp"

 #include "oops/objArrayKlass.hpp"

 #include "prims/jvmtiRedefineClasses.hpp"

 #include "runtime/fieldType.hpp"

 #include "runtime/init.hpp"

 #include "runtime/javaCalls.hpp"

 #include "runtime/signature.hpp"

 #include "runtime/vframe.hpp"

 ConstantPool* ConstantPool::allocate(ClassLoaderData* loader_data, int length, TRAPS) {

   // Tags are RW but comment below applies to tags also.

   Array<u1>* tags = MetadataFactory::new_writeable_array<u1>(loader_data, length, 0, CHECK_NULL);

   int size = ConstantPool::size(length);

   // CDS considerations:

   // Allocate read-write but may be able to move to read-only at dumping time

   // if all the klasses are resolved.  The only other field that is writable is

   // the resolved_references array, which is recreated at startup time.

   // But that could be moved to InstanceKlass (although a pain to access from

   // assembly code).  Maybe it could be moved to the cpCache which is RW.

   return new (loader_data, size, false, THREAD) ConstantPool(tags);

 }

 ConstantPool::ConstantPool(Array<u1>* tags) {

   set_length(tags->length());

   set_tags(NULL);

   set_cache(NULL);

   set_reference_map(NULL);

   set_resolved_references(NULL);

   set_operands(NULL);

   set_pool_holder(NULL);

   set_flags(0);

   // only set to non-zero if constant pool is merged by RedefineClasses

   set_orig_length(0);

   set_lock(new Monitor(Monitor::nonleaf + 2, "A constant pool lock"));

   // all fields are initialized; needed for GC

   set_on_stack(false);

   // initialize tag array

   int length = tags->length();

   for (int index = 0; index < length; index++) {

     tags->at_put(index, JVM_CONSTANT_Invalid);

   }

   set_tags(tags);

 }

 void ConstantPool::deallocate_contents(ClassLoaderData* loader_data) {

   MetadataFactory::free_metadata(loader_data, cache());

   set_cache(NULL);

   MetadataFactory::free_array<jushort>(loader_data, operands());

   set_operands(NULL);

   release_C_heap_structures();

   // free tag array

   MetadataFactory::free_array<u1>(loader_data, tags());

   set_tags(NULL);

 }

 void ConstantPool::release_C_heap_structures() {

   // walk constant pool and decrement symbol reference counts

   unreference_symbols();

   delete _lock;

   set_lock(NULL);

 }

 void ConstantPool::set_flag_at(FlagBit fb) {

   const int MAX_STATE_CHANGES = 2;

   for (int i = MAX_STATE_CHANGES + 10; i > 0; i--) {

     int oflags = _flags;

     int nflags = oflags | (1 << (int)fb);

     if (Atomic::cmpxchg(nflags, &_flags, oflags) == oflags)

       return;

   }

   assert(false, "failed to cmpxchg flags");

   _flags |= (1 << (int)fb);     // better than nothing

 }

 objArrayOop ConstantPool::resolved_references() const {

   return (objArrayOop)JNIHandles::resolve(_resolved_references);

 }

 // Create resolved_references array and mapping array for original cp indexes

 // The ldc bytecode was rewritten to have the resolved reference array index so need a way

 // to map it back for resolving and some unlikely miscellaneous uses.

 // The objects created by invokedynamic are appended to this list.

 void ConstantPool::initialize_resolved_references(ClassLoaderData* loader_data,

                                                   intStack reference_map,

                                                   int constant_pool_map_length,

                                                    TRAPS) {

   // Initialized the resolved object cache.

   int map_length = reference_map.length();

   if (map_length > 0) {

     // Only need mapping back to constant pool entries.  The map isn't used for

     // invokedynamic resolved_reference entries.  The constant pool cache index

     // has the mapping back to both the constant pool and to the resolved

     // reference index.

     if (constant_pool_map_length > 0) {

       Array<u2>* om = MetadataFactory::new_array<u2>(loader_data, map_length, CHECK);

       for (int i = 0; i < constant_pool_map_length; i++) {

         int x = reference_map.at(i);

         assert(x == (int)(jushort) x, "klass index is too big");

         om->at_put(i, (jushort)x);

       }

       set_reference_map(om);

     }

     // Create Java array for holding resolved strings, methodHandles,

     // methodTypes, invokedynamic and invokehandle appendix objects, etc.

     objArrayOop stom = oopFactory::new_objArray(SystemDictionary::Object_klass(), map_length, CHECK);

     Handle refs_handle (THREAD, (oop)stom);  // must handleize.

     set_resolved_references(loader_data->add_handle(refs_handle));

   }

 }

 // CDS support. Create a new resolved_references array.

 void ConstantPool::restore_unshareable_info(TRAPS) {

   // restore the C++ vtable from the shared archive

   restore_vtable();

   if (SystemDictionary::Object_klass_loaded()) {

     // Recreate the object array and add to ClassLoaderData.

     int map_length = resolved_reference_length();

     if (map_length > 0) {

       objArrayOop stom = oopFactory::new_objArray(SystemDictionary::Object_klass(), map_length, CHECK);

       Handle refs_handle (THREAD, (oop)stom);  // must handleize.

       ClassLoaderData* loader_data = pool_holder()->class_loader_data();

       set_resolved_references(loader_data->add_handle(refs_handle));

     }

     // Also need to recreate the mutex.  Make sure this matches the constructor

     set_lock(new Monitor(Monitor::nonleaf + 2, "A constant pool lock"));

   }

 }

 void ConstantPool::remove_unshareable_info() {

   // Resolved references are not in the shared archive.

   // Save the length for restoration.  It is not necessarily the same length

   // as reference_map.length() if invokedynamic is saved.

   set_resolved_reference_length(

     resolved_references() != NULL ? resolved_references()->length() : 0);

   set_resolved_references(NULL);

   set_lock(NULL);

 }

 int ConstantPool::cp_to_object_index(int cp_index) {

   // this is harder don't do this so much.

   for (int i = 0; i< reference_map()->length(); i++) {

     if (reference_map()->at(i) == cp_index) return i;

     // Zero entry is divider between constant pool indices for strings,

     // method handles and method types. After that the index is a constant

     // pool cache index for invokedynamic.  Stop when zero (which can never

     // be a constant pool index)

     if (reference_map()->at(i) == 0) break;

   }

   // We might not find the index.

   return _no_index_sentinel;

 }

 Klass* ConstantPool::klass_at_impl(constantPoolHandle this_oop, int which, TRAPS) {

   // A resolved constantPool entry will contain a Klass*, otherwise a Symbol*.

   // It is not safe to rely on the tag bit's here, since we don't have a lock, and the entry and

   // tag is not updated atomicly.

   CPSlot entry = this_oop->slot_at(which);

   if (entry.is_resolved()) {

     assert(entry.get_klass()->is_klass(), "must be");

     // Already resolved - return entry.

     return entry.get_klass();

   }

   // Acquire lock on constant oop while doing update. After we get the lock, we check if another object

   // already has updated the object

   assert(THREAD->is_Java_thread(), "must be a Java thread");

   bool do_resolve = false;

   bool in_error = false;

   // Create a handle for the mirror. This will preserve the resolved class

   // until the loader_data is registered.

   Handle mirror_handle;

   Symbol* name = NULL;

   Handle       loader;

   {  MonitorLockerEx ml(this_oop->lock());

     if (this_oop->tag_at(which).is_unresolved_klass()) {

       if (this_oop->tag_at(which).is_unresolved_klass_in_error()) {

         in_error = true;

       } else {

         do_resolve = true;

         name   = this_oop->unresolved_klass_at(which);

         loader = Handle(THREAD, this_oop->pool_holder()->class_loader());

       }

     }

   } // unlocking constantPool

   // The original attempt to resolve this constant pool entry failed so find the

   // original error and throw it again (JVMS 5.4.3).

   if (in_error) {

     Symbol* error = SystemDictionary::find_resolution_error(this_oop, which);

     guarantee(error != (Symbol*)NULL, "tag mismatch with resolution error table");

     ResourceMark rm;

     // exception text will be the class name

     const char* className = this_oop->unresolved_klass_at(which)->as_C_string();

     THROW_MSG_0(error, className);

   }

   if (do_resolve) {

     // this_oop must be unlocked during resolve_or_fail

     oop protection_domain = this_oop->pool_holder()->protection_domain();

     Handle h_prot (THREAD, protection_domain);

     Klass* k_oop = SystemDictionary::resolve_or_fail(name, loader, h_prot, true, THREAD);

     KlassHandle k;

     if (!HAS_PENDING_EXCEPTION) {

       k = KlassHandle(THREAD, k_oop);

       // preserve the resolved klass.

       mirror_handle = Handle(THREAD, k_oop->java_mirror());

       // Do access check for klasses

       verify_constant_pool_resolve(this_oop, k, THREAD);

     }

     // Failed to resolve class. We must record the errors so that subsequent attempts

     // to resolve this constant pool entry fail with the same error (JVMS 5.4.3).

     if (HAS_PENDING_EXCEPTION) {

       ResourceMark rm;

       Symbol* error = PENDING_EXCEPTION->klass()->name();

       bool throw_orig_error = false;

       {

         MonitorLockerEx ml(this_oop->lock());

         // some other thread has beaten us and has resolved the class.

         if (this_oop->tag_at(which).is_klass()) {

           CLEAR_PENDING_EXCEPTION;

           entry = this_oop->resolved_klass_at(which);

           return entry.get_klass();

         }

         if (!PENDING_EXCEPTION->

               is_a(SystemDictionary::LinkageError_klass())) {

           // Just throw the exception and don't prevent these classes from

           // being loaded due to virtual machine errors like StackOverflow

           // and OutOfMemoryError, etc, or if the thread was hit by stop()

           // Needs clarification to section 5.4.3 of the VM spec (see 6308271)

         }

         else if (!this_oop->tag_at(which).is_unresolved_klass_in_error()) {

           SystemDictionary::add_resolution_error(this_oop, which, error);

           this_oop->tag_at_put(which, JVM_CONSTANT_UnresolvedClassInError);

         } else {

           // some other thread has put the class in error state.

           error = SystemDictionary::find_resolution_error(this_oop, which);

           assert(error != NULL, "checking");

           throw_orig_error = true;

         }

       } // unlocked

       if (throw_orig_error) {

         CLEAR_PENDING_EXCEPTION;

         ResourceMark rm;

         const char* className = this_oop->unresolved_klass_at(which)->as_C_string();

         THROW_MSG_0(error, className);

       }

       return 0;

     }

     if (TraceClassResolution && !k()->oop_is_array()) {

       // skip resolving the constant pool so that this code get's

       // called the next time some bytecodes refer to this class.

       ResourceMark rm;

       int line_number = -1;

       const char * source_file = NULL;

       if (JavaThread::current()->has_last_Java_frame()) {

         // try to identify the method which called this function.

         vframeStream vfst(JavaThread::current());

         if (!vfst.at_end()) {

           line_number = vfst.method()->line_number_from_bci(vfst.bci());

           Symbol* s = vfst.method()->method_holder()->source_file_name();

           if (s != NULL) {

             source_file = s->as_C_string();

           }

         }

       }

       if (k() != this_oop->pool_holder()) {

         // only print something if the classes are different

         if (source_file != NULL) {

           tty->print("RESOLVE %s %s %s:%d\n",

                      this_oop->pool_holder()->external_name(),

                      InstanceKlass::cast(k())->external_name(), source_file, line_number);

         } else {

           tty->print("RESOLVE %s %s\n",

                      this_oop->pool_holder()->external_name(),

                      InstanceKlass::cast(k())->external_name());

         }

       }

       return k();

     } else {

       MonitorLockerEx ml(this_oop->lock());

       // Only updated constant pool - if it is resolved.

       do_resolve = this_oop->tag_at(which).is_unresolved_klass();

       if (do_resolve) {

         ClassLoaderData* this_key = this_oop->pool_holder()->class_loader_data();

         if (!this_key->is_the_null_class_loader_data()) {

           this_key->record_dependency(k(), CHECK_NULL); // Can throw OOM

         }

         this_oop->klass_at_put(which, k());

       }

     }

   }

   entry = this_oop->resolved_klass_at(which);

   assert(entry.is_resolved() && entry.get_klass()->is_klass(), "must be resolved at this point");

   return entry.get_klass();

 }

 // Does not update ConstantPool* - to avoid any exception throwing. Used

 // by compiler and exception handling.  Also used to avoid classloads for

 // instanceof operations. Returns NULL if the class has not been loaded or

 // if the verification of constant pool failed

 Klass* ConstantPool::klass_at_if_loaded(constantPoolHandle this_oop, int which) {

   CPSlot entry = this_oop->slot_at(which);

   if (entry.is_resolved()) {

     assert(entry.get_klass()->is_klass(), "must be");

     return entry.get_klass();

   } else {

     assert(entry.is_unresolved(), "must be either symbol or klass");

     Thread *thread = Thread::current();

     Symbol* name = entry.get_symbol();

     oop loader = this_oop->pool_holder()->class_loader();

     oop protection_domain = this_oop->pool_holder()->protection_domain();

     Handle h_prot (thread, protection_domain);

     Handle h_loader (thread, loader);

     Klass* k = SystemDictionary::find(name, h_loader, h_prot, thread);

     if (k != NULL) {

       // Make sure that resolving is legal

       EXCEPTION_MARK;

       KlassHandle klass(THREAD, k);

       // return NULL if verification fails

       verify_constant_pool_resolve(this_oop, klass, THREAD);

       if (HAS_PENDING_EXCEPTION) {

         CLEAR_PENDING_EXCEPTION;

         return NULL;

       }

       return klass();

     } else {

       return k;

     }

   }

 }

 Klass* ConstantPool::klass_ref_at_if_loaded(constantPoolHandle this_oop, int which) {

   return klass_at_if_loaded(this_oop, this_oop->klass_ref_index_at(which));

 }

 // This is an interface for the compiler that allows accessing non-resolved entries

 // in the constant pool - but still performs the validations tests. Must be used

 // in a pre-parse of the compiler - to determine what it can do and not do.

 // Note: We cannot update the ConstantPool from the vm_thread.

 Klass* ConstantPool::klass_ref_at_if_loaded_check(constantPoolHandle this_oop, int index, TRAPS) {

   int which = this_oop->klass_ref_index_at(index);

   CPSlot entry = this_oop->slot_at(which);

   if (entry.is_resolved()) {

     assert(entry.get_klass()->is_klass(), "must be");

     return entry.get_klass();

   } else {

     assert(entry.is_unresolved(), "must be either symbol or klass");

     Symbol*  name  = entry.get_symbol();

     oop loader = this_oop->pool_holder()->class_loader();

     oop protection_domain = this_oop->pool_holder()->protection_domain();

     Handle h_loader(THREAD, loader);

     Handle h_prot  (THREAD, protection_domain);

     KlassHandle k(THREAD, SystemDictionary::find(name, h_loader, h_prot, THREAD));

     // Do access check for klasses

     if( k.not_null() ) verify_constant_pool_resolve(this_oop, k, CHECK_NULL);

     return k();

   }

 }

 Method* ConstantPool::method_at_if_loaded(constantPoolHandle cpool,

                                                    int which) {

   if (cpool->cache() == NULL)  return NULL;  // nothing to load yet

   int cache_index = decode_cpcache_index(which, true);

   if (!(cache_index >= 0 && cache_index < cpool->cache()->length())) {

     // FIXME: should be an assert

     if (PrintMiscellaneous && (Verbose||WizardMode)) {

       tty->print_cr("bad operand %d in:", which); cpool->print();

     }

     return NULL;

   }

   ConstantPoolCacheEntry* e = cpool->cache()->entry_at(cache_index);

   return e->method_if_resolved(cpool);

 }

 bool ConstantPool::has_appendix_at_if_loaded(constantPoolHandle cpool, int which) {

   if (cpool->cache() == NULL)  return false;  // nothing to load yet

   int cache_index = decode_cpcache_index(which, true);

   ConstantPoolCacheEntry* e = cpool->cache()->entry_at(cache_index);

   return e->has_appendix();

 }

 oop ConstantPool::appendix_at_if_loaded(constantPoolHandle cpool, int which) {

   if (cpool->cache() == NULL)  return NULL;  // nothing to load yet

   int cache_index = decode_cpcache_index(which, true);

   ConstantPoolCacheEntry* e = cpool->cache()->entry_at(cache_index);

   return e->appendix_if_resolved(cpool);

 }

 bool ConstantPool::has_method_type_at_if_loaded(constantPoolHandle cpool, int which) {

   if (cpool->cache() == NULL)  return false;  // nothing to load yet

   int cache_index = decode_cpcache_index(which, true);

   ConstantPoolCacheEntry* e = cpool->cache()->entry_at(cache_index);

   return e->has_method_type();

 }

 oop ConstantPool::method_type_at_if_loaded(constantPoolHandle cpool, int which) {

   if (cpool->cache() == NULL)  return NULL;  // nothing to load yet

   int cache_index = decode_cpcache_index(which, true);

   ConstantPoolCacheEntry* e = cpool->cache()->entry_at(cache_index);

   return e->method_type_if_resolved(cpool);

 }

 Symbol* ConstantPool::impl_name_ref_at(int which, bool uncached) {

   int name_index = name_ref_index_at(impl_name_and_type_ref_index_at(which, uncached));

   return symbol_at(name_index);

 }

 Symbol* ConstantPool::impl_signature_ref_at(int which, bool uncached) {

   int signature_index = signature_ref_index_at(impl_name_and_type_ref_index_at(which, uncached));

   return symbol_at(signature_index);

 }

 int ConstantPool::impl_name_and_type_ref_index_at(int which, bool uncached) {

   int i = which;

   if (!uncached && cache() != NULL) {

     if (ConstantPool::is_invokedynamic_index(which)) {

       // Invokedynamic index is index into resolved_references

       int pool_index = invokedynamic_cp_cache_entry_at(which)->constant_pool_index();

       pool_index = invoke_dynamic_name_and_type_ref_index_at(pool_index);

       assert(tag_at(pool_index).is_name_and_type(), "");

       return pool_index;

     }

     // change byte-ordering and go via cache

     i = remap_instruction_operand_from_cache(which);

   } else {

     if (tag_at(which).is_invoke_dynamic()) {

       int pool_index = invoke_dynamic_name_and_type_ref_index_at(which);

       assert(tag_at(pool_index).is_name_and_type(), "");

       return pool_index;

     }

   }

   assert(tag_at(i).is_field_or_method(), "Corrupted constant pool");

   assert(!tag_at(i).is_invoke_dynamic(), "Must be handled above");

   jint ref_index = *int_at_addr(i);

   return extract_high_short_from_int(ref_index);

 }

 int ConstantPool::impl_klass_ref_index_at(int which, bool uncached) {

   guarantee(!ConstantPool::is_invokedynamic_index(which),

             "an invokedynamic instruction does not have a klass");

   int i = which;

   if (!uncached && cache() != NULL) {

     // change byte-ordering and go via cache

     i = remap_instruction_operand_from_cache(which);

   }

   assert(tag_at(i).is_field_or_method(), "Corrupted constant pool");

   jint ref_index = *int_at_addr(i);

   return extract_low_short_from_int(ref_index);

 }

 int ConstantPool::remap_instruction_operand_from_cache(int operand) {

   int cpc_index = operand;

   DEBUG_ONLY(cpc_index -= CPCACHE_INDEX_TAG);

   assert((int)(u2)cpc_index == cpc_index, "clean u2");

   int member_index = cache()->entry_at(cpc_index)->constant_pool_index();

   return member_index;

 }

 void ConstantPool::verify_constant_pool_resolve(constantPoolHandle this_oop, KlassHandle k, TRAPS) {

  if (k->oop_is_instance() || k->oop_is_objArray()) {

     instanceKlassHandle holder (THREAD, this_oop->pool_holder());

     Klass* elem_oop = k->oop_is_instance() ? k() : ObjArrayKlass::cast(k())->bottom_klass();

     KlassHandle element (THREAD, elem_oop);

     // The element type could be a typeArray - we only need the access check if it is

     // an reference to another class

     if (element->oop_is_instance()) {

       LinkResolver::check_klass_accessability(holder, element, CHECK);

     }

   }

 }

 int ConstantPool::name_ref_index_at(int which_nt) {

   jint ref_index = name_and_type_at(which_nt);

   return extract_low_short_from_int(ref_index);

 }

 int ConstantPool::signature_ref_index_at(int which_nt) {

   jint ref_index = name_and_type_at(which_nt);

   return extract_high_short_from_int(ref_index);

 }

 Klass* ConstantPool::klass_ref_at(int which, TRAPS) {

   return klass_at(klass_ref_index_at(which), CHECK_NULL);

 }

 Symbol* ConstantPool::klass_name_at(int which) {

   assert(tag_at(which).is_unresolved_klass() || tag_at(which).is_klass(),

          "Corrupted constant pool");

   // A resolved constantPool entry will contain a Klass*, otherwise a Symbol*.

   // It is not safe to rely on the tag bit's here, since we don't have a lock, and the entry and

   // tag is not updated atomicly.

   CPSlot entry = slot_at(which);

   if (entry.is_resolved()) {

     // Already resolved - return entry's name.

     assert(entry.get_klass()->is_klass(), "must be");

     return entry.get_klass()->name();

   } else {

     assert(entry.is_unresolved(), "must be either symbol or klass");

     return entry.get_symbol();

   }

 }

 Symbol* ConstantPool::klass_ref_at_noresolve(int which) {

   jint ref_index = klass_ref_index_at(which);

   return klass_at_noresolve(ref_index);

 }

 Symbol* ConstantPool::uncached_klass_ref_at_noresolve(int which) {

   jint ref_index = uncached_klass_ref_index_at(which);

   return klass_at_noresolve(ref_index);

 }

 char* ConstantPool::string_at_noresolve(int which) {

   Symbol* s = unresolved_string_at(which);

   if (s == NULL) {

     return (char*)"<pseudo-string>";

   } else {

     return unresolved_string_at(which)->as_C_string();

   }

 }

 BasicType ConstantPool::basic_type_for_signature_at(int which) {

   return FieldType::basic_type(symbol_at(which));

 }

 void ConstantPool::resolve_string_constants_impl(constantPoolHandle this_oop, TRAPS) {

   for (int index = 1; index < this_oop->length(); index++) { // Index 0 is unused

     if (this_oop->tag_at(index).is_string()) {

       this_oop->string_at(index, CHECK);

     }

   }

 }

 // Resolve all the classes in the constant pool.  If they are all resolved,

 // the constant pool is read-only.  Enhancement: allocate cp entries to

 // another metaspace, and copy to read-only or read-write space if this

 // bit is set.

 bool ConstantPool::resolve_class_constants(TRAPS) {

   constantPoolHandle cp(THREAD, this);

   for (int index = 1; index < length(); index++) { // Index 0 is unused

     if (tag_at(index).is_unresolved_klass() &&

         klass_at_if_loaded(cp, index) == NULL) {

       return false;

   }

   }

   // set_preresolution(); or some bit for future use

   return true;

 }

 // If resolution for MethodHandle or MethodType fails, save the exception

 // in the resolution error table, so that the same exception is thrown again.

 void ConstantPool::save_and_throw_exception(constantPoolHandle this_oop, int which,

                                      int tag, TRAPS) {

   ResourceMark rm;

   Symbol* error = PENDING_EXCEPTION->klass()->name();

   MonitorLockerEx ml(this_oop->lock());  // lock cpool to change tag.

   int error_tag = (tag == JVM_CONSTANT_MethodHandle) ?

            JVM_CONSTANT_MethodHandleInError : JVM_CONSTANT_MethodTypeInError;

   if (!PENDING_EXCEPTION->

     is_a(SystemDictionary::LinkageError_klass())) {

     // Just throw the exception and don't prevent these classes from

     // being loaded due to virtual machine errors like StackOverflow

     // and OutOfMemoryError, etc, or if the thread was hit by stop()

     // Needs clarification to section 5.4.3 of the VM spec (see 6308271)

   } else if (this_oop->tag_at(which).value() != error_tag) {

     SystemDictionary::add_resolution_error(this_oop, which, error);

     this_oop->tag_at_put(which, error_tag);

   } else {

     // some other thread has put the class in error state.

     error = SystemDictionary::find_resolution_error(this_oop, which);

     assert(error != NULL, "checking");

     CLEAR_PENDING_EXCEPTION;

     THROW_MSG(error, "");

   }

 }

 // Called to resolve constants in the constant pool and return an oop.

 // Some constant pool entries cache their resolved oop. This is also

 // called to create oops from constants to use in arguments for invokedynamic

 oop ConstantPool::resolve_constant_at_impl(constantPoolHandle this_oop, int index, int cache_index, TRAPS) {

   oop result_oop = NULL;

   Handle throw_exception;

   if (cache_index == _possible_index_sentinel) {

     // It is possible that this constant is one which is cached in the objects.

     // We'll do a linear search.  This should be OK because this usage is rare.

     assert(index > 0, "valid index");

     cache_index = this_oop->cp_to_object_index(index);

   }

   assert(cache_index == _no_index_sentinel || cache_index >= 0, "");

   assert(index == _no_index_sentinel || index >= 0, "");

   if (cache_index >= 0) {

     result_oop = this_oop->resolved_references()->obj_at(cache_index);

     if (result_oop != NULL) {

       return result_oop;

       // That was easy...

     }

     index = this_oop->object_to_cp_index(cache_index);

   }

   jvalue prim_value;  // temp used only in a few cases below

   int tag_value = this_oop->tag_at(index).value();

   switch (tag_value) {

   case JVM_CONSTANT_UnresolvedClass:

   case JVM_CONSTANT_UnresolvedClassInError:

   case JVM_CONSTANT_Class:

     {

       assert(cache_index == _no_index_sentinel, "should not have been set");

       Klass* resolved = klass_at_impl(this_oop, index, CHECK_NULL);

       // ldc wants the java mirror.

       result_oop = resolved->java_mirror();

       break;

     }

   case JVM_CONSTANT_String:

     assert(cache_index != _no_index_sentinel, "should have been set");

     if (this_oop->is_pseudo_string_at(index)) {

       result_oop = this_oop->pseudo_string_at(index, cache_index);

       break;

     }

     result_oop = string_at_impl(this_oop, index, cache_index, CHECK_NULL);

     break;

   case JVM_CONSTANT_Object:

     result_oop = this_oop->object_at(index);

     break;

   case JVM_CONSTANT_MethodHandleInError:

   case JVM_CONSTANT_MethodTypeInError:

     {

       Symbol* error = SystemDictionary::find_resolution_error(this_oop, index);

       guarantee(error != (Symbol*)NULL, "tag mismatch with resolution error table");

       ResourceMark rm;

       THROW_MSG_0(error, "");

       break;

     }

   case JVM_CONSTANT_MethodHandle:

     {

       int ref_kind                 = this_oop->method_handle_ref_kind_at(index);

       int callee_index             = this_oop->method_handle_klass_index_at(index);

       Symbol*  name =      this_oop->method_handle_name_ref_at(index);

       Symbol*  signature = this_oop->method_handle_signature_ref_at(index);

       if (PrintMiscellaneous)

         tty->print_cr("resolve JVM_CONSTANT_MethodHandle:%d [%d/%d/%d] %s.%s",

                       ref_kind, index, this_oop->method_handle_index_at(index),

                       callee_index, name->as_C_string(), signature->as_C_string());

       KlassHandle callee;

       { Klass* k = klass_at_impl(this_oop, callee_index, CHECK_NULL);

         callee = KlassHandle(THREAD, k);

       }

       KlassHandle klass(THREAD, this_oop->pool_holder());

       Handle value = SystemDictionary::link_method_handle_constant(klass, ref_kind,

                                                                    callee, name, signature,

                                                                    THREAD);

       result_oop = value();

       if (HAS_PENDING_EXCEPTION) {

         save_and_throw_exception(this_oop, index, tag_value, CHECK_NULL);

       }

       break;

     }

   case JVM_CONSTANT_MethodType:

     {

       Symbol*  signature = this_oop->method_type_signature_at(index);

       if (PrintMiscellaneous)

         tty->print_cr("resolve JVM_CONSTANT_MethodType [%d/%d] %s",

                       index, this_oop->method_type_index_at(index),

                       signature->as_C_string());

       KlassHandle klass(THREAD, this_oop->pool_holder());

       Handle value = SystemDictionary::find_method_handle_type(signature, klass, THREAD);

       result_oop = value();

       if (HAS_PENDING_EXCEPTION) {

         save_and_throw_exception(this_oop, index, tag_value, CHECK_NULL);

       }

       break;

     }

   case JVM_CONSTANT_Integer:

     assert(cache_index == _no_index_sentinel, "should not have been set");

     prim_value.i = this_oop->int_at(index);

     result_oop = java_lang_boxing_object::create(T_INT, &prim_value, CHECK_NULL);

     break;

   case JVM_CONSTANT_Float:

     assert(cache_index == _no_index_sentinel, "should not have been set");

     prim_value.f = this_oop->float_at(index);

     result_oop = java_lang_boxing_object::create(T_FLOAT, &prim_value, CHECK_NULL);

     break;

   case JVM_CONSTANT_Long:

     assert(cache_index == _no_index_sentinel, "should not have been set");

     prim_value.j = this_oop->long_at(index);

     result_oop = java_lang_boxing_object::create(T_LONG, &prim_value, CHECK_NULL);

     break;

   case JVM_CONSTANT_Double:

     assert(cache_index == _no_index_sentinel, "should not have been set");

     prim_value.d = this_oop->double_at(index);

     result_oop = java_lang_boxing_object::create(T_DOUBLE, &prim_value, CHECK_NULL);

     break;

   default:

     DEBUG_ONLY( tty->print_cr("*** %p: tag at CP[%d/%d] = %d",

                               this_oop(), index, cache_index, tag_value) );

     assert(false, "unexpected constant tag");

     break;

   }

   if (cache_index >= 0) {

     // Cache the oop here also.

     Handle result_handle(THREAD, result_oop);

     MonitorLockerEx ml(this_oop->lock());  // don't know if we really need this

     oop result = this_oop->resolved_references()->obj_at(cache_index);

     // Benign race condition:  resolved_references may already be filled in while we were trying to lock.

     // The important thing here is that all threads pick up the same result.

     // It doesn't matter which racing thread wins, as long as only one

     // result is used by all threads, and all future queries.

     // That result may be either a resolved constant or a failure exception.

     if (result == NULL) {

       this_oop->resolved_references()->obj_at_put(cache_index, result_handle());

       return result_handle();

     } else {

       // Return the winning thread's result.  This can be different than

       // result_handle() for MethodHandles.

       return result;

     }

   } else {

     return result_oop;

   }

 }

 oop ConstantPool::uncached_string_at(int which, TRAPS) {

   Symbol* sym = unresolved_string_at(which);

   oop str = StringTable::intern(sym, CHECK_(NULL));

   assert(java_lang_String::is_instance(str), "must be string");

   return str;

 }

 oop ConstantPool::resolve_bootstrap_specifier_at_impl(constantPoolHandle this_oop, int index, TRAPS) {

   assert(this_oop->tag_at(index).is_invoke_dynamic(), "Corrupted constant pool");

   Handle bsm;

   int argc;

   {

     // JVM_CONSTANT_InvokeDynamic is an ordered pair of [bootm, name&type], plus optional arguments

     // The bootm, being a JVM_CONSTANT_MethodHandle, has its own cache entry.

     // It is accompanied by the optional arguments.

     int bsm_index = this_oop->invoke_dynamic_bootstrap_method_ref_index_at(index);

     oop bsm_oop = this_oop->resolve_possibly_cached_constant_at(bsm_index, CHECK_NULL);

     if (!java_lang_invoke_MethodHandle::is_instance(bsm_oop)) {

       THROW_MSG_NULL(vmSymbols::java_lang_LinkageError(), "BSM not an MethodHandle");

     }

     // Extract the optional static arguments.

     argc = this_oop->invoke_dynamic_argument_count_at(index);

     if (argc == 0)  return bsm_oop;

     bsm = Handle(THREAD, bsm_oop);

   }

   objArrayHandle info;

   {

     objArrayOop info_oop = oopFactory::new_objArray(SystemDictionary::Object_klass(), 1+argc, CHECK_NULL);

     info = objArrayHandle(THREAD, info_oop);

   }

   info->obj_at_put(0, bsm());

   for (int i = 0; i < argc; i++) {

     int arg_index = this_oop->invoke_dynamic_argument_index_at(index, i);

     oop arg_oop = this_oop->resolve_possibly_cached_constant_at(arg_index, CHECK_NULL);

     info->obj_at_put(1+i, arg_oop);

   }

   return info();

 }

 oop ConstantPool::string_at_impl(constantPoolHandle this_oop, int which, int obj_index, TRAPS) {

   // If the string has already been interned, this entry will be non-null

   oop str = this_oop->resolved_references()->obj_at(obj_index);

   if (str != NULL) return str;

       Symbol* sym = this_oop->unresolved_string_at(which);

   str = StringTable::intern(sym, CHECK_(NULL));

   this_oop->string_at_put(which, obj_index, str);

   assert(java_lang_String::is_instance(str), "must be string");

   return str;

 }

 bool ConstantPool::klass_name_at_matches(instanceKlassHandle k,

                                                 int which) {

   // Names are interned, so we can compare Symbol*s directly

   Symbol* cp_name = klass_name_at(which);

   return (cp_name == k->name());

 }

 // Iterate over symbols and decrement ones which are Symbol*s.

 // This is done during GC so do not need to lock constantPool unless we

 // have per-thread safepoints.

 // Only decrement the UTF8 symbols. Unresolved classes and strings point to

 // these symbols but didn't increment the reference count.

 void ConstantPool::unreference_symbols() {

   for (int index = 1; index < length(); index++) { // Index 0 is unused

     constantTag tag = tag_at(index);

     if (tag.is_symbol()) {

       symbol_at(index)->decrement_refcount();

     }

   }

 }

 // Compare this constant pool's entry at index1 to the constant pool

 // cp2's entry at index2.

 bool ConstantPool::compare_entry_to(int index1, constantPoolHandle cp2,

        int index2, TRAPS) {

   jbyte t1 = tag_at(index1).value();

   jbyte t2 = cp2->tag_at(index2).value();

   // JVM_CONSTANT_UnresolvedClassInError is equal to JVM_CONSTANT_UnresolvedClass

   // when comparing

   if (t1 == JVM_CONSTANT_UnresolvedClassInError) {

     t1 = JVM_CONSTANT_UnresolvedClass;

   }

   if (t2 == JVM_CONSTANT_UnresolvedClassInError) {

     t2 = JVM_CONSTANT_UnresolvedClass;

   }

   if (t1 != t2) {

     // Not the same entry type so there is nothing else to check. Note

     // that this style of checking will consider resolved/unresolved

     // class pairs as different.

     // From the ConstantPool* API point of view, this is correct

     // behavior. See VM_RedefineClasses::merge_constant_pools() to see how this

     // plays out in the context of ConstantPool* merging.

     return false;

   }

   switch (t1) {

   case JVM_CONSTANT_Class:

   {

     Klass* k1 = klass_at(index1, CHECK_false);

     Klass* k2 = cp2->klass_at(index2, CHECK_false);

     if (k1 == k2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_ClassIndex:

   {

     int recur1 = klass_index_at(index1);

     int recur2 = cp2->klass_index_at(index2);

     bool match = compare_entry_to(recur1, cp2, recur2, CHECK_false);

     if (match) {

       return true;

     }

   } break;

   case JVM_CONSTANT_Double:

   {

     jdouble d1 = double_at(index1);

     jdouble d2 = cp2->double_at(index2);

     if (d1 == d2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_Fieldref:

   case JVM_CONSTANT_InterfaceMethodref:

   case JVM_CONSTANT_Methodref:

   {

     int recur1 = uncached_klass_ref_index_at(index1);

     int recur2 = cp2->uncached_klass_ref_index_at(index2);

     bool match = compare_entry_to(recur1, cp2, recur2, CHECK_false);

     if (match) {

       recur1 = uncached_name_and_type_ref_index_at(index1);

       recur2 = cp2->uncached_name_and_type_ref_index_at(index2);

       match = compare_entry_to(recur1, cp2, recur2, CHECK_false);

       if (match) {

         return true;

       }

     }

   } break;

   case JVM_CONSTANT_Float:

   {

     jfloat f1 = float_at(index1);

     jfloat f2 = cp2->float_at(index2);

     if (f1 == f2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_Integer:

   {

     jint i1 = int_at(index1);

     jint i2 = cp2->int_at(index2);

     if (i1 == i2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_Long:

   {

     jlong l1 = long_at(index1);

     jlong l2 = cp2->long_at(index2);

     if (l1 == l2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_NameAndType:

   {

     int recur1 = name_ref_index_at(index1);

     int recur2 = cp2->name_ref_index_at(index2);

     bool match = compare_entry_to(recur1, cp2, recur2, CHECK_false);

     if (match) {

       recur1 = signature_ref_index_at(index1);

       recur2 = cp2->signature_ref_index_at(index2);

       match = compare_entry_to(recur1, cp2, recur2, CHECK_false);

       if (match) {

         return true;

       }

     }

   } break;

   case JVM_CONSTANT_StringIndex:

   {

     int recur1 = string_index_at(index1);

     int recur2 = cp2->string_index_at(index2);

     bool match = compare_entry_to(recur1, cp2, recur2, CHECK_false);

     if (match) {

       return true;

     }

   } break;

   case JVM_CONSTANT_UnresolvedClass:

   {

     Symbol* k1 = unresolved_klass_at(index1);

     Symbol* k2 = cp2->unresolved_klass_at(index2);

     if (k1 == k2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_MethodType:

   {

     int k1 = method_type_index_at(index1);

     int k2 = cp2->method_type_index_at(index2);

     bool match = compare_entry_to(k1, cp2, k2, CHECK_false);

     if (match) {

       return true;

     }

   } break;

   case JVM_CONSTANT_MethodHandle:

   {

     int k1 = method_handle_ref_kind_at(index1);

     int k2 = cp2->method_handle_ref_kind_at(index2);

     if (k1 == k2) {

       int i1 = method_handle_index_at(index1);

       int i2 = cp2->method_handle_index_at(index2);

       bool match = compare_entry_to(i1, cp2, i2, CHECK_false);

       if (match) {

         return true;

       }

     }

   } break;

   case JVM_CONSTANT_InvokeDynamic:

   {

     int k1 = invoke_dynamic_bootstrap_method_ref_index_at(index1);

     int k2 = cp2->invoke_dynamic_bootstrap_method_ref_index_at(index2);

     bool match = compare_entry_to(k1, cp2, k2, CHECK_false);

     if (!match)  return false;

     k1 = invoke_dynamic_name_and_type_ref_index_at(index1);

     k2 = cp2->invoke_dynamic_name_and_type_ref_index_at(index2);

     match = compare_entry_to(k1, cp2, k2, CHECK_false);

     if (!match)  return false;

     int argc = invoke_dynamic_argument_count_at(index1);

     if (argc == cp2->invoke_dynamic_argument_count_at(index2)) {

       for (int j = 0; j < argc; j++) {

         k1 = invoke_dynamic_argument_index_at(index1, j);

         k2 = cp2->invoke_dynamic_argument_index_at(index2, j);

         match = compare_entry_to(k1, cp2, k2, CHECK_false);

         if (!match)  return false;

       }

       return true;           // got through loop; all elements equal

     }

   } break;

   case JVM_CONSTANT_String:

   {

     Symbol* s1 = unresolved_string_at(index1);

     Symbol* s2 = cp2->unresolved_string_at(index2);

     if (s1 == s2) {

       return true;

     }

   } break;

   case JVM_CONSTANT_Utf8:

   {

     Symbol* s1 = symbol_at(index1);

     Symbol* s2 = cp2->symbol_at(index2);

     if (s1 == s2) {

       return true;

     }

   } break;

   // Invalid is used as the tag for the second constant pool entry

   // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should

   // not be seen by itself.

   case JVM_CONSTANT_Invalid: // fall through

   default:

     ShouldNotReachHere();

     break;

   }

   return false;

 } // end compare_entry_to()

 // Copy this constant pool's entries at start_i to end_i (inclusive)

 // to the constant pool to_cp's entries starting at to_i. A total of

 // (end_i - start_i) + 1 entries are copied.

 void ConstantPool::copy_cp_to_impl(constantPoolHandle from_cp, int start_i, int end_i,

        constantPoolHandle to_cp, int to_i, TRAPS) {

   int dest_i = to_i;  // leave original alone for debug purposes

   for (int src_i = start_i; src_i <= end_i; /* see loop bottom */ ) {

     copy_entry_to(from_cp, src_i, to_cp, dest_i, CHECK);

     switch (from_cp->tag_at(src_i).value()) {

     case JVM_CONSTANT_Double:

     case JVM_CONSTANT_Long:

       // double and long take two constant pool entries

       src_i += 2;

       dest_i += 2;

       break;

     default:

       // all others take one constant pool entry

       src_i++;

       dest_i++;

       break;

     }

   }

   int from_oplen = operand_array_length(from_cp->operands());

   int old_oplen  = operand_array_length(to_cp->operands());

   if (from_oplen != 0) {

     ClassLoaderData* loader_data = to_cp->pool_holder()->class_loader_data();

     // append my operands to the target's operands array

     if (old_oplen == 0) {

       // Can't just reuse from_cp's operand list because of deallocation issues

       int len = from_cp->operands()->length();

       Array<u2>* new_ops = MetadataFactory::new_array<u2>(loader_data, len, CHECK);

       Copy::conjoint_memory_atomic(

           from_cp->operands()->adr_at(0), new_ops->adr_at(0), len * sizeof(u2));

       to_cp->set_operands(new_ops);

     } else {

       int old_len  = to_cp->operands()->length();

       int from_len = from_cp->operands()->length();

       int old_off  = old_oplen * sizeof(u2);

       int from_off = from_oplen * sizeof(u2);

       // Use the metaspace for the destination constant pool

       Array<u2>* new_operands = MetadataFactory::new_array<u2>(loader_data, old_len + from_len, CHECK);

       int fillp = 0, len = 0;

       // first part of dest

       Copy::conjoint_memory_atomic(to_cp->operands()->adr_at(0),

                                    new_operands->adr_at(fillp),

                                    (len = old_off) * sizeof(u2));

       fillp += len;

       // first part of src

       Copy::conjoint_memory_atomic(to_cp->operands()->adr_at(0),

                                    new_operands->adr_at(fillp),

                                    (len = from_off) * sizeof(u2));

       fillp += len;

       // second part of dest

       Copy::conjoint_memory_atomic(to_cp->operands()->adr_at(old_off),

                                    new_operands->adr_at(fillp),

                                    (len = old_len - old_off) * sizeof(u2));

       fillp += len;

       // second part of src

       Copy::conjoint_memory_atomic(to_cp->operands()->adr_at(from_off),

                                    new_operands->adr_at(fillp),

                                    (len = from_len - from_off) * sizeof(u2));

       fillp += len;

       assert(fillp == new_operands->length(), "");

       // Adjust indexes in the first part of the copied operands array.

       for (int j = 0; j < from_oplen; j++) {

         int offset = operand_offset_at(new_operands, old_oplen + j);

         assert(offset == operand_offset_at(from_cp->operands(), j), "correct copy");

         offset += old_len;  // every new tuple is preceded by old_len extra u2's

         operand_offset_at_put(new_operands, old_oplen + j, offset);

       }

       // replace target operands array with combined array

       to_cp->set_operands(new_operands);

     }

   }

 } // end copy_cp_to()

 // Copy this constant pool's entry at from_i to the constant pool

 // to_cp's entry at to_i.

 void ConstantPool::copy_entry_to(constantPoolHandle from_cp, int from_i,

                                         constantPoolHandle to_cp, int to_i,

                                         TRAPS) {

   int tag = from_cp->tag_at(from_i).value();

   switch (tag) {

   case JVM_CONSTANT_Class:

   {

     Klass* k = from_cp->klass_at(from_i, CHECK);

     to_cp->klass_at_put(to_i, k);

   } break;

   case JVM_CONSTANT_ClassIndex:

   {

     jint ki = from_cp->klass_index_at(from_i);

     to_cp->klass_index_at_put(to_i, ki);

   } break;

   case JVM_CONSTANT_Double:

   {

     jdouble d = from_cp->double_at(from_i);

     to_cp->double_at_put(to_i, d);

     // double takes two constant pool entries so init second entry's tag

     to_cp->tag_at_put(to_i + 1, JVM_CONSTANT_Invalid);

   } break;

   case JVM_CONSTANT_Fieldref:

   {

     int class_index = from_cp->uncached_klass_ref_index_at(from_i);

     int name_and_type_index = from_cp->uncached_name_and_type_ref_index_at(from_i);

     to_cp->field_at_put(to_i, class_index, name_and_type_index);

   } break;

   case JVM_CONSTANT_Float:

   {

     jfloat f = from_cp->float_at(from_i);

     to_cp->float_at_put(to_i, f);

   } break;

   case JVM_CONSTANT_Integer:

   {

     jint i = from_cp->int_at(from_i);

     to_cp->int_at_put(to_i, i);

   } break;

   case JVM_CONSTANT_InterfaceMethodref:

   {

     int class_index = from_cp->uncached_klass_ref_index_at(from_i);

     int name_and_type_index = from_cp->uncached_name_and_type_ref_index_at(from_i);

     to_cp->interface_method_at_put(to_i, class_index, name_and_type_index);

   } break;

   case JVM_CONSTANT_Long:

   {

     jlong l = from_cp->long_at(from_i);

     to_cp->long_at_put(to_i, l);

     // long takes two constant pool entries so init second entry's tag

     to_cp->tag_at_put(to_i + 1, JVM_CONSTANT_Invalid);

   } break;

   case JVM_CONSTANT_Methodref:

   {

     int class_index = from_cp->uncached_klass_ref_index_at(from_i);

     int name_and_type_index = from_cp->uncached_name_and_type_ref_index_at(from_i);

     to_cp->method_at_put(to_i, class_index, name_and_type_index);

   } break;

   case JVM_CONSTANT_NameAndType:

   {

     int name_ref_index = from_cp->name_ref_index_at(from_i);

     int signature_ref_index = from_cp->signature_ref_index_at(from_i);

     to_cp->name_and_type_at_put(to_i, name_ref_index, signature_ref_index);

   } break;

   case JVM_CONSTANT_StringIndex:

   {

     jint si = from_cp->string_index_at(from_i);

     to_cp->string_index_at_put(to_i, si);

   } break;

   case JVM_CONSTANT_UnresolvedClass:

   {

     // Can be resolved after checking tag, so check the slot first.

     CPSlot entry = from_cp->slot_at(from_i);

     if (entry.is_resolved()) {

       assert(entry.get_klass()->is_klass(), "must be");

       // Already resolved

       to_cp->klass_at_put(to_i, entry.get_klass());

     } else {

       to_cp->unresolved_klass_at_put(to_i, entry.get_symbol());

     }

   } break;

   case JVM_CONSTANT_UnresolvedClassInError:

   {

     Symbol* k = from_cp->unresolved_klass_at(from_i);

     to_cp->unresolved_klass_at_put(to_i, k);

     to_cp->tag_at_put(to_i, JVM_CONSTANT_UnresolvedClassInError);

   } break;

   case JVM_CONSTANT_String:

   {

     Symbol* s = from_cp->unresolved_string_at(from_i);

     to_cp->unresolved_string_at_put(to_i, s);

   } break;

   case JVM_CONSTANT_Utf8:

   {

     Symbol* s = from_cp->symbol_at(from_i);

     // Need to increase refcount, the old one will be thrown away and deferenced

     s->increment_refcount();

     to_cp->symbol_at_put(to_i, s);

   } break;

   case JVM_CONSTANT_MethodType:

   {

     jint k = from_cp->method_type_index_at(from_i);

     to_cp->method_type_index_at_put(to_i, k);

   } break;

   case JVM_CONSTANT_MethodHandle:

   {

     int k1 = from_cp->method_handle_ref_kind_at(from_i);

     int k2 = from_cp->method_handle_index_at(from_i);

     to_cp->method_handle_index_at_put(to_i, k1, k2);

   } break;

   case JVM_CONSTANT_InvokeDynamic:

   {

     int k1 = from_cp->invoke_dynamic_bootstrap_specifier_index(from_i);

     int k2 = from_cp->invoke_dynamic_name_and_type_ref_index_at(from_i);

     k1 += operand_array_length(to_cp->operands());  // to_cp might already have operands

     to_cp->invoke_dynamic_at_put(to_i, k1, k2);

   } break;

   // Invalid is used as the tag for the second constant pool entry

   // occupied by JVM_CONSTANT_Double or JVM_CONSTANT_Long. It should

   // not be seen by itself.

   case JVM_CONSTANT_Invalid: // fall through

   default:

   {

     ShouldNotReachHere();

   } break;

   }

 } // end copy_entry_to()

 // Search constant pool search_cp for an entry that matches this

 // constant pool's entry at pattern_i. Returns the index of a

 // matching entry or zero (0) if there is no matching entry.

 int ConstantPool::find_matching_entry(int pattern_i,

       constantPoolHandle search_cp, TRAPS) {

   // index zero (0) is not used

   for (int i = 1; i < search_cp->length(); i++) {

     bool found = compare_entry_to(pattern_i, search_cp, i, CHECK_0);

     if (found) {

       return i;

     }

   }

   return 0;  // entry not found; return unused index zero (0)

 } // end find_matching_entry()

 #ifndef PRODUCT

 const char* ConstantPool::printable_name_at(int which) {

   constantTag tag = tag_at(which);

   if (tag.is_string()) {

     return string_at_noresolve(which);

   } else if (tag.is_klass() || tag.is_unresolved_klass()) {

     return klass_name_at(which)->as_C_string();

   } else if (tag.is_symbol()) {

     return symbol_at(which)->as_C_string();

   }

   return "";

 }

 #endif // PRODUCT

 // JVMTI GetConstantPool support

 // For temporary use until code is stable.

 #define DBG(code)

 static const char* WARN_MSG = "Must not be such entry!";

 static void print_cpool_bytes(jint cnt, u1 *bytes) {

   jint size = 0;

   u2   idx1, idx2;

   for (jint idx = 1; idx < cnt; idx++) {

     jint ent_size = 0;

     u1   tag  = *bytes++;

     size++;                       // count tag

     printf("const #%03d, tag: %02d ", idx, tag);

     switch(tag) {

       case JVM_CONSTANT_Invalid: {

         printf("Invalid");

         break;

       }

       case JVM_CONSTANT_Unicode: {

         printf("Unicode      %s", WARN_MSG);

         break;

       }

       case JVM_CONSTANT_Utf8: {

         u2 len = Bytes::get_Java_u2(bytes);

         char str[128];

         if (len > 127) {

            len = 127;

         }

         strncpy(str, (char *) (bytes+2), len);

         str[len] = '\0';

         printf("Utf8          \"%s\"", str);

         ent_size = 2 + len;

         break;

       }

       case JVM_CONSTANT_Integer: {

         u4 val = Bytes::get_Java_u4(bytes);

         printf("int          %d", *(int *) &val);

         ent_size = 4;

         break;

       }

       case JVM_CONSTANT_Float: {

         u4 val = Bytes::get_Java_u4(bytes);

         printf("float        %5.3ff", *(float *) &val);

         ent_size = 4;

         break;

       }

       case JVM_CONSTANT_Long: {

         u8 val = Bytes::get_Java_u8(bytes);

         printf("long         "INT64_FORMAT, (int64_t) *(jlong *) &val);

         ent_size = 8;

         idx++; // Long takes two cpool slots

         break;

       }

       case JVM_CONSTANT_Double: {

         u8 val = Bytes::get_Java_u8(bytes);

         printf("double       %5.3fd", *(jdouble *)&val);

         ent_size = 8;

         idx++; // Double takes two cpool slots

         break;

       }

       case JVM_CONSTANT_Class: {

         idx1 = Bytes::get_Java_u2(bytes);

         printf("class        #%03d", idx1);

         ent_size = 2;

         break;

       }

       case JVM_CONSTANT_String: {

         idx1 = Bytes::get_Java_u2(bytes);

         printf("String       #%03d", idx1);

         ent_size = 2;

         break;

       }

       case JVM_CONSTANT_Fieldref: {

         idx1 = Bytes::get_Java_u2(bytes);

         idx2 = Bytes::get_Java_u2(bytes+2);

         printf("Field        #%03d, #%03d", (int) idx1, (int) idx2);

         ent_size = 4;

         break;

       }

       case JVM_CONSTANT_Methodref: {

         idx1 = Bytes::get_Java_u2(bytes);

         idx2 = Bytes::get_Java_u2(bytes+2);

         printf("Method       #%03d, #%03d", idx1, idx2);

         ent_size = 4;

         break;

       }

       case JVM_CONSTANT_InterfaceMethodref: {

         idx1 = Bytes::get_Java_u2(bytes);

         idx2 = Bytes::get_Java_u2(bytes+2);

         printf("InterfMethod #%03d, #%03d", idx1, idx2);

         ent_size = 4;

         break;

       }

       case JVM_CONSTANT_NameAndType: {

         idx1 = Bytes::get_Java_u2(bytes);

         idx2 = Bytes::get_Java_u2(bytes+2);

         printf("NameAndType  #%03d, #%03d", idx1, idx2);

         ent_size = 4;

         break;

       }

       case JVM_CONSTANT_ClassIndex: {

         printf("ClassIndex  %s", WARN_MSG);

         break;

       }

       case JVM_CONSTANT_UnresolvedClass: {

         printf("UnresolvedClass: %s", WARN_MSG);

         break;

       }

       case JVM_CONSTANT_UnresolvedClassInError: {

         printf("UnresolvedClassInErr: %s", WARN_MSG);

         break;

       }

       case JVM_CONSTANT_StringIndex: {

         printf("StringIndex: %s", WARN_MSG);

         break;

       }

     }

     printf(";\n");

     bytes += ent_size;

     size  += ent_size;

   }

   printf("Cpool size: %d\n", size);

   fflush(0);

   return;

 } /* end print_cpool_bytes */

 // Returns size of constant pool entry.

 jint ConstantPool::cpool_entry_size(jint idx) {

   switch(tag_at(idx).value()) {

     case JVM_CONSTANT_Invalid:

     case JVM_CONSTANT_Unicode:

       return 1;

     case JVM_CONSTANT_Utf8:

       return 3 + symbol_at(idx)->utf8_length();

     case JVM_CONSTANT_Class:

     case JVM_CONSTANT_String:

     case JVM_CONSTANT_ClassIndex:

     case JVM_CONSTANT_UnresolvedClass:

     case JVM_CONSTANT_UnresolvedClassInError:

     case JVM_CONSTANT_StringIndex:

     case JVM_CONSTANT_MethodType:

       return 3;

     case JVM_CONSTANT_MethodHandle:

       return 4; //tag, ref_kind, ref_index

     case JVM_CONSTANT_Integer:

     case JVM_CONSTANT_Float:

     case JVM_CONSTANT_Fieldref:

     case JVM_CONSTANT_Methodref:

     case JVM_CONSTANT_InterfaceMethodref:

     case JVM_CONSTANT_NameAndType:

       return 5;

     case JVM_CONSTANT_InvokeDynamic:

       // u1 tag, u2 bsm, u2 nt

       return 5;

     case JVM_CONSTANT_Long:

     case JVM_CONSTANT_Double:

       return 9;

   }

   assert(false, "cpool_entry_size: Invalid constant pool entry tag");

   return 1;

 } /* end cpool_entry_size */

 // SymbolHashMap is used to find a constant pool index from a string.

 // This function fills in SymbolHashMaps, one for utf8s and one for

 // class names, returns size of the cpool raw bytes.

 jint ConstantPool::hash_entries_to(SymbolHashMap *symmap,

                                           SymbolHashMap *classmap) {

   jint size = 0;

   for (u2 idx = 1; idx < length(); idx++) {

     u2 tag = tag_at(idx).value();

     size += cpool_entry_size(idx);

     switch(tag) {

       case JVM_CONSTANT_Utf8: {

         Symbol* sym = symbol_at(idx);

         symmap->add_entry(sym, idx);

         DBG(printf("adding symbol entry %s = %d\n", sym->as_utf8(), idx));

         break;

       }

       case JVM_CONSTANT_Class:

       case JVM_CONSTANT_UnresolvedClass:

       case JVM_CONSTANT_UnresolvedClassInError: {

         Symbol* sym = klass_name_at(idx);

         classmap->add_entry(sym, idx);

         DBG(printf("adding class entry %s = %d\n", sym->as_utf8(), idx));

         break;

       }

       case JVM_CONSTANT_Long:

       case JVM_CONSTANT_Double: {

         idx++; // Both Long and Double take two cpool slots

         break;

       }

     }

   }

   return size;

 } /* end hash_utf8_entries_to */

 // Copy cpool bytes.

 // Returns:

 //    0, in case of OutOfMemoryError

 //   -1, in case of internal error

 //  > 0, count of the raw cpool bytes that have been copied

 int ConstantPool::copy_cpool_bytes(int cpool_size,

                                           SymbolHashMap* tbl,

                                           unsigned char *bytes) {

   u2   idx1, idx2;

   jint size  = 0;

   jint cnt   = length();

   unsigned char *start_bytes = bytes;

   for (jint idx = 1; idx < cnt; idx++) {

     u1   tag      = tag_at(idx).value();

     jint ent_size = cpool_entry_size(idx);

     assert(size + ent_size <= cpool_size, "Size mismatch");

     *bytes = tag;

     DBG(printf("#%03hd tag=%03hd, ", idx, tag));

     switch(tag) {

       case JVM_CONSTANT_Invalid: {

         DBG(printf("JVM_CONSTANT_Invalid"));

         break;

       }

       case JVM_CONSTANT_Unicode: {

         assert(false, "Wrong constant pool tag: JVM_CONSTANT_Unicode");

         DBG(printf("JVM_CONSTANT_Unicode"));

         break;

       }

       case JVM_CONSTANT_Utf8: {

         Symbol* sym = symbol_at(idx);

         char*     str = sym->as_utf8();

         // Warning! It's crashing on x86 with len = sym->utf8_length()

         int       len = (int) strlen(str);

         Bytes::put_Java_u2((address) (bytes+1), (u2) len);

         for (int i = 0; i < len; i++) {

             bytes[3+i] = (u1) str[i];

         }

         DBG(printf("JVM_CONSTANT_Utf8: %s ", str));

         break;

       }

       case JVM_CONSTANT_Integer: {

         jint val = int_at(idx);

         Bytes::put_Java_u4((address) (bytes+1), *(u4*)&val);

         break;

       }

       case JVM_CONSTANT_Float: {

         jfloat val = float_at(idx);

         Bytes::put_Java_u4((address) (bytes+1), *(u4*)&val);

         break;

       }

       case JVM_CONSTANT_Long: {

         jlong val = long_at(idx);

         Bytes::put_Java_u8((address) (bytes+1), *(u8*)&val);

         idx++;             // Long takes two cpool slots

         break;

       }

       case JVM_CONSTANT_Double: {

         jdouble val = double_at(idx);

         Bytes::put_Java_u8((address) (bytes+1), *(u8*)&val);

         idx++;             // Double takes two cpool slots

         break;

       }

       case JVM_CONSTANT_Class:

       case JVM_CONSTANT_UnresolvedClass:

       case JVM_CONSTANT_UnresolvedClassInError: {

         *bytes = JVM_CONSTANT_Class;

         Symbol* sym = klass_name_at(idx);

         idx1 = tbl->symbol_to_value(sym);

         assert(idx1 != 0, "Have not found a hashtable entry");

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         DBG(printf("JVM_CONSTANT_Class: idx=#%03hd, %s", idx1, sym->as_utf8()));

         break;

       }

       case JVM_CONSTANT_String: {

         *bytes = JVM_CONSTANT_String;

         Symbol* sym = unresolved_string_at(idx);

         idx1 = tbl->symbol_to_value(sym);

         assert(idx1 != 0, "Have not found a hashtable entry");

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         DBG(char *str = sym->as_utf8());

         DBG(printf("JVM_CONSTANT_String: idx=#%03hd, %s", idx1, str));

         break;

       }

       case JVM_CONSTANT_Fieldref:

       case JVM_CONSTANT_Methodref:

       case JVM_CONSTANT_InterfaceMethodref: {

         idx1 = uncached_klass_ref_index_at(idx);

         idx2 = uncached_name_and_type_ref_index_at(idx);

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         Bytes::put_Java_u2((address) (bytes+3), idx2);

         DBG(printf("JVM_CONSTANT_Methodref: %hd %hd", idx1, idx2));

         break;

       }

       case JVM_CONSTANT_NameAndType: {

         idx1 = name_ref_index_at(idx);

         idx2 = signature_ref_index_at(idx);

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         Bytes::put_Java_u2((address) (bytes+3), idx2);

         DBG(printf("JVM_CONSTANT_NameAndType: %hd %hd", idx1, idx2));

         break;

       }

       case JVM_CONSTANT_ClassIndex: {

         *bytes = JVM_CONSTANT_Class;

         idx1 = klass_index_at(idx);

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         DBG(printf("JVM_CONSTANT_ClassIndex: %hd", idx1));

         break;

       }

       case JVM_CONSTANT_StringIndex: {

         *bytes = JVM_CONSTANT_String;

         idx1 = string_index_at(idx);

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         DBG(printf("JVM_CONSTANT_StringIndex: %hd", idx1));

         break;

       }

       case JVM_CONSTANT_MethodHandle:

       case JVM_CONSTANT_MethodHandleInError: {

         *bytes = JVM_CONSTANT_MethodHandle;

         int kind = method_handle_ref_kind_at(idx);

         idx1 = method_handle_index_at(idx);

         *(bytes+1) = (unsigned char) kind;

         Bytes::put_Java_u2((address) (bytes+2), idx1);

         DBG(printf("JVM_CONSTANT_MethodHandle: %d %hd", kind, idx1));

         break;

       }

       case JVM_CONSTANT_MethodType:

       case JVM_CONSTANT_MethodTypeInError: {

         *bytes = JVM_CONSTANT_MethodType;

         idx1 = method_type_index_at(idx);

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         DBG(printf("JVM_CONSTANT_MethodType: %hd", idx1));

         break;

       }

       case JVM_CONSTANT_InvokeDynamic: {

         *bytes = tag;

         idx1 = extract_low_short_from_int(*int_at_addr(idx));

         idx2 = extract_high_short_from_int(*int_at_addr(idx));

         assert(idx2 == invoke_dynamic_name_and_type_ref_index_at(idx), "correct half of u4");

         Bytes::put_Java_u2((address) (bytes+1), idx1);

         Bytes::put_Java_u2((address) (bytes+3), idx2);

         DBG(printf("JVM_CONSTANT_InvokeDynamic: %hd %hd", idx1, idx2));

         break;

       }

     }

     DBG(printf("\n"));

     bytes += ent_size;

     size  += ent_size;

   }

   assert(size == cpool_size, "Size mismatch");

   // Keep temorarily for debugging until it's stable.

   DBG(print_cpool_bytes(cnt, start_bytes));

   return (int)(bytes - start_bytes);

 } /* end copy_cpool_bytes */

 void ConstantPool::set_on_stack(const bool value) {

   _on_stack = value;

   if (value) MetadataOnStackMark::record(this);

 }

 // JSR 292 support for patching constant pool oops after the class is linked and

 // the oop array for resolved references are created.

 // We can't do this during classfile parsing, which is how the other indexes are

 // patched.  The other patches are applied early for some error checking

 // so only defer the pseudo_strings.

 void ConstantPool::patch_resolved_references(

                                             GrowableArray<Handle>* cp_patches) {

   assert(EnableInvokeDynamic, "");

   for (int index = 1; index < cp_patches->length(); index++) { // Index 0 is unused

     Handle patch = cp_patches->at(index);

     if (patch.not_null()) {

       assert (tag_at(index).is_string(), "should only be string left");

       // Patching a string means pre-resolving it.

       // The spelling in the constant pool is ignored.

       // The constant reference may be any object whatever.

       // If it is not a real interned string, the constant is referred

       // to as a "pseudo-string", and must be presented to the CP

       // explicitly, because it may require scavenging.

       int obj_index = cp_to_object_index(index);

       pseudo_string_at_put(index, obj_index, patch());

       DEBUG_ONLY(cp_patches->at_put(index, Handle());)

     }

   }

 #ifdef ASSERT

   // Ensure that all the patches have been used.

   for (int index = 0; index < cp_patches->length(); index++) {

     assert(cp_patches->at(index).is_null(),

            err_msg("Unused constant pool patch at %d in class file %s",

                    index,

                    pool_holder()->external_name()));

   }

 #endif // ASSERT

 }

 #ifndef PRODUCT

 // CompileTheWorld support. Preload all classes loaded references in the passed in constantpool

 void ConstantPool::preload_and_initialize_all_classes(ConstantPool* obj, TRAPS) {

   guarantee(obj->is_constantPool(), "object must be constant pool");

   constantPoolHandle cp(THREAD, (ConstantPool*)obj);

   guarantee(cp->pool_holder() != NULL, "must be fully loaded");

   for (int i = 0; i< cp->length();  i++) {

     if (cp->tag_at(i).is_unresolved_klass()) {

       // This will force loading of the class

       Klass* klass = cp->klass_at(i, CHECK);

       if (klass->oop_is_instance()) {

         // Force initialization of class

         InstanceKlass::cast(klass)->initialize(CHECK);

       }

     }

   }

 }

 #endif

 // Printing

 void ConstantPool::print_on(outputStream* st) const {

   EXCEPTION_MARK;

   assert(is_constantPool(), "must be constantPool");

   st->print_cr(internal_name());

   if (flags() != 0) {

     st->print(" - flags: 0x%x", flags());

     if (has_pseudo_string()) st->print(" has_pseudo_string");

     if (has_invokedynamic()) st->print(" has_invokedynamic");

     if (has_preresolution()) st->print(" has_preresolution");

     st->cr();

   }

   if (pool_holder() != NULL) {

     st->print_cr(" - holder: " INTPTR_FORMAT, pool_holder());

   }

   st->print_cr(" - cache: " INTPTR_FORMAT, cache());

   st->print_cr(" - resolved_references: " INTPTR_FORMAT, resolved_references());

   st->print_cr(" - reference_map: " INTPTR_FORMAT, reference_map());

   for (int index = 1; index < length(); index++) {      // Index 0 is unused

     ((ConstantPool*)this)->print_entry_on(index, st);

     switch (tag_at(index).value()) {

       case JVM_CONSTANT_Long :

       case JVM_CONSTANT_Double :

         index++;   // Skip entry following eigth-byte constant

     }

   }

   st->cr();

 }

 // Print one constant pool entry

 void ConstantPool::print_entry_on(const int index, outputStream* st) {

   EXCEPTION_MARK;

   st->print(" - %3d : ", index);

   tag_at(index).print_on(st);

   st->print(" : ");

   switch (tag_at(index).value()) {

     case JVM_CONSTANT_Class :

       { Klass* k = klass_at(index, CATCH);

         k->print_value_on(st);

         st->print(" {0x%lx}", (address)k);

       }

       break;

     case JVM_CONSTANT_Fieldref :

     case JVM_CONSTANT_Methodref :

     case JVM_CONSTANT_InterfaceMethodref :

       st->print("klass_index=%d", uncached_klass_ref_index_at(index));

       st->print(" name_and_type_index=%d", uncached_name_and_type_ref_index_at(index));

       break;

     case JVM_CONSTANT_String :

       unresolved_string_at(index)->print_value_on(st);

       break;

     case JVM_CONSTANT_Object : {

       oop anObj = object_at(index);

       anObj->print_value_on(st);

       st->print(" {0x%lx}", (address)anObj);

       } break;

     case JVM_CONSTANT_Integer :

       st->print("%d", int_at(index));

       break;

     case JVM_CONSTANT_Float :

       st->print("%f", float_at(index));

       break;

     case JVM_CONSTANT_Long :

       st->print_jlong(long_at(index));

       break;

     case JVM_CONSTANT_Double :

       st->print("%lf", double_at(index));

       break;

     case JVM_CONSTANT_NameAndType :

       st->print("name_index=%d", name_ref_index_at(index));

       st->print(" signature_index=%d", signature_ref_index_at(index));

       break;

     case JVM_CONSTANT_Utf8 :

       symbol_at(index)->print_value_on(st);

       break;

     case JVM_CONSTANT_UnresolvedClass :               // fall-through

     case JVM_CONSTANT_UnresolvedClassInError: {

       // unresolved_klass_at requires lock or safe world.

       CPSlot entry = slot_at(index);

       if (entry.is_resolved()) {

         entry.get_klass()->print_value_on(st);

       } else {

         entry.get_symbol()->print_value_on(st);

       }

       }

       break;

     case JVM_CONSTANT_MethodHandle :

     case JVM_CONSTANT_MethodHandleInError :

       st->print("ref_kind=%d", method_handle_ref_kind_at(index));

       st->print(" ref_index=%d", method_handle_index_at(index));

       break;

     case JVM_CONSTANT_MethodType :

     case JVM_CONSTANT_MethodTypeInError :

       st->print("signature_index=%d", method_type_index_at(index));

       break;

     case JVM_CONSTANT_InvokeDynamic :

       {

         st->print("bootstrap_method_index=%d", invoke_dynamic_bootstrap_method_ref_index_at(index));

         st->print(" name_and_type_index=%d", invoke_dynamic_name_and_type_ref_index_at(index));

         int argc = invoke_dynamic_argument_count_at(index);

         if (argc > 0) {

           for (int arg_i = 0; arg_i < argc; arg_i++) {

             int arg = invoke_dynamic_argument_index_at(index, arg_i);

             st->print((arg_i == 0 ? " arguments={%d" : ", %d"), arg);

           }

           st->print("}");

         }

       }

       break;

     default:

       ShouldNotReachHere();

       break;

   }

   st->cr();

 }

 void ConstantPool::print_value_on(outputStream* st) const {

   assert(is_constantPool(), "must be constantPool");

   st->print("constant pool [%d]", length());

   if (has_pseudo_string()) st->print("/pseudo_string");

   if (has_invokedynamic()) st->print("/invokedynamic");

   if (has_preresolution()) st->print("/preresolution");

   if (operands() != NULL)  st->print("/operands[%d]", operands()->length());

   print_address_on(st);

   st->print(" for ");

   pool_holder()->print_value_on(st);

   if (pool_holder() != NULL) {

     bool extra = (pool_holder()->constants() != this);

     if (extra)  st->print(" (extra)");

   }

   if (cache() != NULL) {

     st->print(" cache=" PTR_FORMAT, cache());

   }

 }

 // Verification

 void ConstantPool::verify_on(outputStream* st) {

   guarantee(is_constantPool(), "object must be constant pool");

   for (int i = 0; i< length();  i++) {

     constantTag tag = tag_at(i);

     CPSlot entry = slot_at(i);

     if (tag.is_klass()) {

       if (entry.is_resolved()) {

         guarantee(entry.get_klass()->is_metadata(), "should be metadata");

         guarantee(entry.get_klass()->is_klass(),    "should be klass");

       }

     } else if (tag.is_unresolved_klass()) {

       if (entry.is_resolved()) {

         guarantee(entry.get_klass()->is_metadata(), "should be metadata");

         guarantee(entry.get_klass()->is_klass(),    "should be klass");

       }

     } else if (tag.is_symbol()) {

       guarantee(entry.get_symbol()->refcount() != 0, "should have nonzero reference count");

     } else if (tag.is_string()) {

       guarantee(entry.get_symbol()->refcount() != 0, "should have nonzero reference count");

     }

   }

   if (cache() != NULL) {

     // Note: cache() can be NULL before a class is completely setup or

     // in temporary constant pools used during constant pool merging

     guarantee(cache()->is_metadata(),          "should be metadata");

     guarantee(cache()->is_constantPoolCache(), "should be constant pool cache");

   }

   if (pool_holder() != NULL) {

     // Note: pool_holder() can be NULL in temporary constant pools

     // used during constant pool merging

     guarantee(pool_holder()->is_metadata(), "should be metadata");

     guarantee(pool_holder()->is_klass(),    "should be klass");

   }

 }

 void SymbolHashMap::add_entry(Symbol* sym, u2 value) {

   char *str = sym->as_utf8();

   unsigned int hash = compute_hash(str, sym->utf8_length());

   unsigned int index = hash % table_size();

   // check if already in map

   // we prefer the first entry since it is more likely to be what was used in

   // the class file

   for (SymbolHashMapEntry *en = bucket(index); en != NULL; en = en->next()) {

     assert(en->symbol() != NULL, "SymbolHashMapEntry symbol is NULL");

     if (en->hash() == hash && en->symbol() == sym) {

         return;  // already there

     }

   }

   SymbolHashMapEntry* entry = new SymbolHashMapEntry(hash, sym, value);

   entry->set_next(bucket(index));

   _buckets[index].set_entry(entry);

   assert(entry->symbol() != NULL, "SymbolHashMapEntry symbol is NULL");

 }

 SymbolHashMapEntry* SymbolHashMap::find_entry(Symbol* sym) {

   assert(sym != NULL, "SymbolHashMap::find_entry - symbol is NULL");

   char *str = sym->as_utf8();

   int   len = sym->utf8_length();

   unsigned int hash = SymbolHashMap::compute_hash(str, len);

   unsigned int index = hash % table_size();

   for (SymbolHashMapEntry *en = bucket(index); en != NULL; en = en->next()) {

     assert(en->symbol() != NULL, "SymbolHashMapEntry symbol is NULL");

     if (en->hash() == hash && en->symbol() == sym) {

       return en;

     }

   }

   return NULL;

 }