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 /*

  * Copyright (c) 1997, 2013, 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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  */

 #ifndef SHARE_VM_OOPS_CONSTANTPOOLOOP_HPP

 #define SHARE_VM_OOPS_CONSTANTPOOLOOP_HPP

 #include "oops/arrayOop.hpp"

 #include "oops/cpCache.hpp"

 #include "oops/objArrayOop.hpp"

 #include "oops/symbol.hpp"

 #include "oops/typeArrayOop.hpp"

 #include "runtime/handles.hpp"

 #include "utilities/constantTag.hpp"

 #ifdef TARGET_ARCH_x86

 # include "bytes_x86.hpp"

 #endif

 #ifdef TARGET_ARCH_sparc

 # include "bytes_sparc.hpp"

 #endif

 #ifdef TARGET_ARCH_zero

 # include "bytes_zero.hpp"

 #endif

 #ifdef TARGET_ARCH_arm

 # include "bytes_arm.hpp"

 #endif

 #ifdef TARGET_ARCH_ppc

 # include "bytes_ppc.hpp"

 #endif

 // A constantPool is an array containing class constants as described in the

 // class file.

 //

 // Most of the constant pool entries are written during class parsing, which

 // is safe.  For klass types, the constant pool entry is

 // modified when the entry is resolved.  If a klass constant pool

 // entry is read without a lock, only the resolved state guarantees that

 // the entry in the constant pool is a klass object and not a Symbol*.

 class SymbolHashMap;

 class CPSlot VALUE_OBJ_CLASS_SPEC {

   intptr_t _ptr;

  public:

   CPSlot(intptr_t ptr): _ptr(ptr) {}

   CPSlot(Klass* ptr): _ptr((intptr_t)ptr) {}

   CPSlot(Symbol* ptr): _ptr((intptr_t)ptr | 1) {}

   intptr_t value()   { return _ptr; }

   bool is_resolved()   { return (_ptr & 1) == 0; }

   bool is_unresolved() { return (_ptr & 1) == 1; }

   Symbol* get_symbol() {

     assert(is_unresolved(), "bad call");

     return (Symbol*)(_ptr & ~1);

   }

   Klass* get_klass() {

     assert(is_resolved(), "bad call");

     return (Klass*)_ptr;

   }

 };

 class KlassSizeStats;

 class ConstantPool : public Metadata {

   friend class VMStructs;

   friend class BytecodeInterpreter;  // Directly extracts an oop in the pool for fast instanceof/checkcast

   friend class Universe;             // For null constructor

  private:

   Array<u1>*           _tags;        // the tag array describing the constant pool's contents

   ConstantPoolCache*   _cache;       // the cache holding interpreter runtime information

   InstanceKlass*       _pool_holder; // the corresponding class

   Array<u2>*           _operands;    // for variable-sized (InvokeDynamic) nodes, usually empty

   // Array of resolved objects from the constant pool and map from resolved

   // object index to original constant pool index

   jobject              _resolved_references;

   Array<u2>*           _reference_map;

   enum {

     _has_invokedynamic = 1,           // Flags

     _has_pseudo_string = 2,

     _has_preresolution = 4,

     _on_stack          = 8

   };

   int                  _flags;  // old fashioned bit twiddling

   int                  _length; // number of elements in the array

   union {

     // set for CDS to restore resolved references

     int                _resolved_reference_length;

     // keeps version number for redefined classes (used in backtrace)

     int                _version;

   } _saved;

   Monitor*             _lock;

   void set_tags(Array<u1>* tags)               { _tags = tags; }

   void tag_at_put(int which, jbyte t)          { tags()->at_put(which, t); }

   void release_tag_at_put(int which, jbyte t)  { tags()->release_at_put(which, t); }

   void set_operands(Array<u2>* operands)       { _operands = operands; }

   int flags() const                            { return _flags; }

   void set_flags(int f)                        { _flags = f; }

  private:

   intptr_t* base() const { return (intptr_t*) (((char*) this) + sizeof(ConstantPool)); }

   CPSlot slot_at(int which) {

     assert(is_within_bounds(which), "index out of bounds");

     // Uses volatile because the klass slot changes without a lock.

     volatile intptr_t adr = (intptr_t)OrderAccess::load_ptr_acquire(obj_at_addr_raw(which));

     assert(adr != 0 || which == 0, "cp entry for klass should not be zero");

     return CPSlot(adr);

   }

   void slot_at_put(int which, CPSlot s) const {

     assert(is_within_bounds(which), "index out of bounds");

     assert(s.value() != 0, "Caught something");

     *(intptr_t*)&base()[which] = s.value();

   }

   intptr_t* obj_at_addr_raw(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (intptr_t*) &base()[which];

   }

   jint* int_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jint*) &base()[which];

   }

   jlong* long_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jlong*) &base()[which];

   }

   jfloat* float_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jfloat*) &base()[which];

   }

   jdouble* double_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (jdouble*) &base()[which];

   }

   ConstantPool(Array<u1>* tags);

   ConstantPool() { assert(DumpSharedSpaces || UseSharedSpaces, "only for CDS"); }

  public:

   static ConstantPool* allocate(ClassLoaderData* loader_data, int length, TRAPS);

   bool is_constantPool() const volatile     { return true; }

   Array<u1>* tags() const                   { return _tags; }

   Array<u2>* operands() const               { return _operands; }

   bool has_invokedynamic() const            { return (_flags & _has_invokedynamic) != 0; }

   void set_has_invokedynamic()              { _flags |= _has_invokedynamic; }

   bool has_pseudo_string() const            { return (_flags & _has_pseudo_string) != 0; }

   void set_has_pseudo_string()              { _flags |= _has_pseudo_string; }

   bool has_preresolution() const            { return (_flags & _has_preresolution) != 0; }

   void set_has_preresolution()              { _flags |= _has_preresolution; }

   // Redefine classes support.  If a method refering to this constant pool

   // is on the executing stack, or as a handle in vm code, this constant pool

   // can't be removed from the set of previous versions saved in the instance

   // class.

   bool on_stack() const                      { return (_flags &_on_stack) != 0; }

   void set_on_stack(const bool value);

   // Klass holding pool

   InstanceKlass* pool_holder() const      { return _pool_holder; }

   void set_pool_holder(InstanceKlass* k)  { _pool_holder = k; }

   InstanceKlass** pool_holder_addr()      { return &_pool_holder; }

   // Interpreter runtime support

   ConstantPoolCache* cache() const        { return _cache; }

   void set_cache(ConstantPoolCache* cache){ _cache = cache; }

   // Create object cache in the constant pool

   void initialize_resolved_references(ClassLoaderData* loader_data,

                                       intStack reference_map,

                                       int constant_pool_map_length,

                                       TRAPS);

   // resolved strings, methodHandles and callsite objects from the constant pool

   objArrayOop resolved_references()  const;

   // mapping resolved object array indexes to cp indexes and back.

   int object_to_cp_index(int index)         { return _reference_map->at(index); }

   int cp_to_object_index(int index);

   // Invokedynamic indexes.

   // They must look completely different from normal indexes.

   // The main reason is that byte swapping is sometimes done on normal indexes.

   // Finally, it is helpful for debugging to tell the two apart.

   static bool is_invokedynamic_index(int i) { return (i < 0); }

   static int  decode_invokedynamic_index(int i) { assert(is_invokedynamic_index(i),  ""); return ~i; }

   static int  encode_invokedynamic_index(int i) { assert(!is_invokedynamic_index(i), ""); return ~i; }

   // The invokedynamic points at a CP cache entry.  This entry points back

   // at the original CP entry (CONSTANT_InvokeDynamic) and also (via f2) at an entry

   // in the resolved_references array (which provides the appendix argument).

   int invokedynamic_cp_cache_index(int index) const {

     assert (is_invokedynamic_index(index), "should be a invokedynamic index");

     int cache_index = decode_invokedynamic_index(index);

     return cache_index;

   }

   ConstantPoolCacheEntry* invokedynamic_cp_cache_entry_at(int index) const {

     // decode index that invokedynamic points to.

     int cp_cache_index = invokedynamic_cp_cache_index(index);

     return cache()->entry_at(cp_cache_index);

   }

   // Assembly code support

   static int tags_offset_in_bytes()         { return offset_of(ConstantPool, _tags); }

   static int cache_offset_in_bytes()        { return offset_of(ConstantPool, _cache); }

   static int pool_holder_offset_in_bytes()  { return offset_of(ConstantPool, _pool_holder); }

   static int resolved_references_offset_in_bytes() { return offset_of(ConstantPool, _resolved_references); }

   static int reference_map_offset_in_bytes() { return offset_of(ConstantPool, _reference_map); }

   // Storing constants

   void klass_at_put(int which, Klass* k) {

     assert(k != NULL, "resolved class shouldn't be null");

     assert(is_within_bounds(which), "index out of bounds");

     OrderAccess::release_store_ptr((Klass* volatile *)obj_at_addr_raw(which), k);

     // The interpreter assumes when the tag is stored, the klass is resolved

     // and the Klass* is a klass rather than a Symbol*, so we need

     // hardware store ordering here.

     release_tag_at_put(which, JVM_CONSTANT_Class);

   }

   // For temporary use while constructing constant pool

   void klass_index_at_put(int which, int name_index) {

     tag_at_put(which, JVM_CONSTANT_ClassIndex);

     *int_at_addr(which) = name_index;

   }

   // Temporary until actual use

   void unresolved_klass_at_put(int which, Symbol* s) {

     release_tag_at_put(which, JVM_CONSTANT_UnresolvedClass);

     slot_at_put(which, s);

   }

   void method_handle_index_at_put(int which, int ref_kind, int ref_index) {

     tag_at_put(which, JVM_CONSTANT_MethodHandle);

     *int_at_addr(which) = ((jint) ref_index<<16) | ref_kind;

   }

   void method_type_index_at_put(int which, int ref_index) {

     tag_at_put(which, JVM_CONSTANT_MethodType);

     *int_at_addr(which) = ref_index;

   }

   void invoke_dynamic_at_put(int which, int bootstrap_specifier_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_InvokeDynamic);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | bootstrap_specifier_index;

   }

   void unresolved_string_at_put(int which, Symbol* s) {

     release_tag_at_put(which, JVM_CONSTANT_String);

     *symbol_at_addr(which) = s;

   }

   void int_at_put(int which, jint i) {

     tag_at_put(which, JVM_CONSTANT_Integer);

     *int_at_addr(which) = i;

   }

   void long_at_put(int which, jlong l) {

     tag_at_put(which, JVM_CONSTANT_Long);

     // *long_at_addr(which) = l;

     Bytes::put_native_u8((address)long_at_addr(which), *((u8*) &l));

   }

   void float_at_put(int which, jfloat f) {

     tag_at_put(which, JVM_CONSTANT_Float);

     *float_at_addr(which) = f;

   }

   void double_at_put(int which, jdouble d) {

     tag_at_put(which, JVM_CONSTANT_Double);

     // *double_at_addr(which) = d;

     // u8 temp = *(u8*) &d;

     Bytes::put_native_u8((address) double_at_addr(which), *((u8*) &d));

   }

   Symbol** symbol_at_addr(int which) const {

     assert(is_within_bounds(which), "index out of bounds");

     return (Symbol**) &base()[which];

   }

   void symbol_at_put(int which, Symbol* s) {

     assert(s->refcount() != 0, "should have nonzero refcount");

     tag_at_put(which, JVM_CONSTANT_Utf8);

     *symbol_at_addr(which) = s;

   }

   void string_at_put(int which, int obj_index, oop str) {

     resolved_references()->obj_at_put(obj_index, str);

   }

   void set_object_tag_at(int which) {

     release_tag_at_put(which, JVM_CONSTANT_Object);

     }

   void object_at_put(int which, oop obj) {

     resolved_references()->obj_at_put(cp_to_object_index(which), obj);

   }

   // For temporary use while constructing constant pool

   void string_index_at_put(int which, int string_index) {

     tag_at_put(which, JVM_CONSTANT_StringIndex);

     *int_at_addr(which) = string_index;

   }

   void field_at_put(int which, int class_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_Fieldref);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;

   }

   void method_at_put(int which, int class_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_Methodref);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;

   }

   void interface_method_at_put(int which, int class_index, int name_and_type_index) {

     tag_at_put(which, JVM_CONSTANT_InterfaceMethodref);

     *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;  // Not so nice

   }

   void name_and_type_at_put(int which, int name_index, int signature_index) {

     tag_at_put(which, JVM_CONSTANT_NameAndType);

     *int_at_addr(which) = ((jint) signature_index<<16) | name_index;  // Not so nice

   }

   // Tag query

   constantTag tag_at(int which) const { return (constantTag)tags()->at_acquire(which); }

   // Fetching constants

   Klass* klass_at(int which, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return klass_at_impl(h_this, which, CHECK_NULL);

   }

   Symbol* klass_name_at(int which);  // Returns the name, w/o resolving.

   Klass* resolved_klass_at(int which) {  // Used by Compiler

     guarantee(tag_at(which).is_klass(), "Corrupted constant pool");

     // Must do an acquire here in case another thread resolved the klass

     // behind our back, lest we later load stale values thru the oop.

     return CPSlot((Klass*)OrderAccess::load_ptr_acquire(obj_at_addr_raw(which))).get_klass();

   }

   // This method should only be used with a cpool lock or during parsing or gc

   Symbol* unresolved_klass_at(int which) {     // Temporary until actual use

     Symbol* s = CPSlot((Symbol*)OrderAccess::load_ptr_acquire(obj_at_addr_raw(which))).get_symbol();

     // check that the klass is still unresolved.

     assert(tag_at(which).is_unresolved_klass(), "Corrupted constant pool");

     return s;

   }

   // RedefineClasses() API support:

   Symbol* klass_at_noresolve(int which) { return klass_name_at(which); }

   jint int_at(int which) {

     assert(tag_at(which).is_int(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   jlong long_at(int which) {

     assert(tag_at(which).is_long(), "Corrupted constant pool");

     // return *long_at_addr(which);

     u8 tmp = Bytes::get_native_u8((address)&base()[which]);

     return *((jlong*)&tmp);

   }

   jfloat float_at(int which) {

     assert(tag_at(which).is_float(), "Corrupted constant pool");

     return *float_at_addr(which);

   }

   jdouble double_at(int which) {

     assert(tag_at(which).is_double(), "Corrupted constant pool");

     u8 tmp = Bytes::get_native_u8((address)&base()[which]);

     return *((jdouble*)&tmp);

   }

   Symbol* symbol_at(int which) {

     assert(tag_at(which).is_utf8(), "Corrupted constant pool");

     return *symbol_at_addr(which);

   }

   oop string_at(int which, int obj_index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return string_at_impl(h_this, which, obj_index, THREAD);

   }

   oop string_at(int which, TRAPS) {

     int obj_index = cp_to_object_index(which);

     return string_at(which, obj_index, THREAD);

   }

   // Version that can be used before string oop array is created.

   oop uncached_string_at(int which, TRAPS);

   oop object_at(int which) {

     assert(tag_at(which).is_object(), "Corrupted constant pool");

     int obj_index = cp_to_object_index(which);

     return resolved_references()->obj_at(obj_index);

   }

   // A "pseudo-string" is an non-string oop that has found is way into

   // a String entry.

   // Under EnableInvokeDynamic this can happen if the user patches a live

   // object into a CONSTANT_String entry of an anonymous class.

   // Method oops internally created for method handles may also

   // use pseudo-strings to link themselves to related metaobjects.

   bool is_pseudo_string_at(int which) {

     // A pseudo string is a string that doesn't have a symbol in the cpSlot

     return unresolved_string_at(which) == NULL;

   }

   oop pseudo_string_at(int which, int obj_index) {

     assert(tag_at(which).is_string(), "Corrupted constant pool");

     assert(unresolved_string_at(which) == NULL, "shouldn't have symbol");

     oop s = resolved_references()->obj_at(obj_index);

     return s;

   }

   void pseudo_string_at_put(int which, int obj_index, oop x) {

     assert(EnableInvokeDynamic, "");

     set_has_pseudo_string();        // mark header

     assert(tag_at(which).is_string(), "Corrupted constant pool");

     string_at_put(which, obj_index, x);    // this works just fine

   }

   // only called when we are sure a string entry is already resolved (via an

   // earlier string_at call.

   oop resolved_string_at(int which) {

     assert(tag_at(which).is_string(), "Corrupted constant pool");

     // Must do an acquire here in case another thread resolved the klass

     // behind our back, lest we later load stale values thru the oop.

     // we might want a volatile_obj_at in ObjArrayKlass.

     int obj_index = cp_to_object_index(which);

     return resolved_references()->obj_at(obj_index);

   }

   Symbol* unresolved_string_at(int which) {

     assert(tag_at(which).is_string(), "Corrupted constant pool");

     Symbol* s = *symbol_at_addr(which);

     return s;

   }

   // Returns an UTF8 for a CONSTANT_String entry at a given index.

   // UTF8 char* representation was chosen to avoid conversion of

   // java_lang_Strings at resolved entries into Symbol*s

   // or vice versa.

   // Caller is responsible for checking for pseudo-strings.

   char* string_at_noresolve(int which);

   jint name_and_type_at(int which) {

     assert(tag_at(which).is_name_and_type(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   int method_handle_ref_kind_at(int which) {

     assert(tag_at(which).is_method_handle(), "Corrupted constant pool");

     return extract_low_short_from_int(*int_at_addr(which));  // mask out unwanted ref_index bits

   }

   int method_handle_index_at(int which) {

     assert(tag_at(which).is_method_handle(), "Corrupted constant pool");

     return extract_high_short_from_int(*int_at_addr(which));  // shift out unwanted ref_kind bits

   }

   int method_type_index_at(int which) {

     assert(tag_at(which).is_method_type(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   // Derived queries:

   Symbol* method_handle_name_ref_at(int which) {

     int member = method_handle_index_at(which);

     return impl_name_ref_at(member, true);

   }

   Symbol* method_handle_signature_ref_at(int which) {

     int member = method_handle_index_at(which);

     return impl_signature_ref_at(member, true);

   }

   int method_handle_klass_index_at(int which) {

     int member = method_handle_index_at(which);

     return impl_klass_ref_index_at(member, true);

   }

   Symbol* method_type_signature_at(int which) {

     int sym = method_type_index_at(which);

     return symbol_at(sym);

   }

   int invoke_dynamic_name_and_type_ref_index_at(int which) {

     assert(tag_at(which).is_invoke_dynamic(), "Corrupted constant pool");

     return extract_high_short_from_int(*int_at_addr(which));

   }

   int invoke_dynamic_bootstrap_specifier_index(int which) {

     assert(tag_at(which).value() == JVM_CONSTANT_InvokeDynamic, "Corrupted constant pool");

     return extract_low_short_from_int(*int_at_addr(which));

   }

   int invoke_dynamic_operand_base(int which) {

     int bootstrap_specifier_index = invoke_dynamic_bootstrap_specifier_index(which);

     return operand_offset_at(operands(), bootstrap_specifier_index);

   }

   // The first part of the operands array consists of an index into the second part.

   // Extract a 32-bit index value from the first part.

   static int operand_offset_at(Array<u2>* operands, int bootstrap_specifier_index) {

     int n = (bootstrap_specifier_index * 2);

     assert(n >= 0 && n+2 <= operands->length(), "oob");

     // The first 32-bit index points to the beginning of the second part

     // of the operands array.  Make sure this index is in the first part.

     DEBUG_ONLY(int second_part = build_int_from_shorts(operands->at(0),

                                                        operands->at(1)));

     assert(second_part == 0 || n+2 <= second_part, "oob (2)");

     int offset = build_int_from_shorts(operands->at(n+0),

                                        operands->at(n+1));

     // The offset itself must point into the second part of the array.

     assert(offset == 0 || offset >= second_part && offset <= operands->length(), "oob (3)");

     return offset;

   }

   static void operand_offset_at_put(Array<u2>* operands, int bootstrap_specifier_index, int offset) {

     int n = bootstrap_specifier_index * 2;

     assert(n >= 0 && n+2 <= operands->length(), "oob");

     operands->at_put(n+0, extract_low_short_from_int(offset));

     operands->at_put(n+1, extract_high_short_from_int(offset));

   }

   static int operand_array_length(Array<u2>* operands) {

     if (operands == NULL || operands->length() == 0)  return 0;

     int second_part = operand_offset_at(operands, 0);

     return (second_part / 2);

   }

 #ifdef ASSERT

   // operand tuples fit together exactly, end to end

   static int operand_limit_at(Array<u2>* operands, int bootstrap_specifier_index) {

     int nextidx = bootstrap_specifier_index + 1;

     if (nextidx == operand_array_length(operands))

       return operands->length();

     else

       return operand_offset_at(operands, nextidx);

   }

   int invoke_dynamic_operand_limit(int which) {

     int bootstrap_specifier_index = invoke_dynamic_bootstrap_specifier_index(which);

     return operand_limit_at(operands(), bootstrap_specifier_index);

   }

 #endif //ASSERT

   // layout of InvokeDynamic bootstrap method specifier (in second part of operands array):

   enum {

          _indy_bsm_offset  = 0,  // CONSTANT_MethodHandle bsm

          _indy_argc_offset = 1,  // u2 argc

          _indy_argv_offset = 2   // u2 argv[argc]

   };

   int invoke_dynamic_bootstrap_method_ref_index_at(int which) {

     assert(tag_at(which).is_invoke_dynamic(), "Corrupted constant pool");

     int op_base = invoke_dynamic_operand_base(which);

     return operands()->at(op_base + _indy_bsm_offset);

   }

   int invoke_dynamic_argument_count_at(int which) {

     assert(tag_at(which).is_invoke_dynamic(), "Corrupted constant pool");

     int op_base = invoke_dynamic_operand_base(which);

     int argc = operands()->at(op_base + _indy_argc_offset);

     DEBUG_ONLY(int end_offset = op_base + _indy_argv_offset + argc;

                int next_offset = invoke_dynamic_operand_limit(which));

     assert(end_offset == next_offset, "matched ending");

     return argc;

   }

   int invoke_dynamic_argument_index_at(int which, int j) {

     int op_base = invoke_dynamic_operand_base(which);

     DEBUG_ONLY(int argc = operands()->at(op_base + _indy_argc_offset));

     assert((uint)j < (uint)argc, "oob");

     return operands()->at(op_base + _indy_argv_offset + j);

   }

   // The following methods (name/signature/klass_ref_at, klass_ref_at_noresolve,

   // name_and_type_ref_index_at) all expect to be passed indices obtained

   // directly from the bytecode.

   // If the indices are meant to refer to fields or methods, they are

   // actually rewritten constant pool cache indices.

   // The routine remap_instruction_operand_from_cache manages the adjustment

   // of these values back to constant pool indices.

   // There are also "uncached" versions which do not adjust the operand index; see below.

   // FIXME: Consider renaming these with a prefix "cached_" to make the distinction clear.

   // In a few cases (the verifier) there are uses before a cpcache has been built,

   // which are handled by a dynamic check in remap_instruction_operand_from_cache.

   // FIXME: Remove the dynamic check, and adjust all callers to specify the correct mode.

   // Lookup for entries consisting of (klass_index, name_and_type index)

   Klass* klass_ref_at(int which, TRAPS);

   Symbol* klass_ref_at_noresolve(int which);

   Symbol* name_ref_at(int which)                { return impl_name_ref_at(which, false); }

   Symbol* signature_ref_at(int which)           { return impl_signature_ref_at(which, false); }

   int klass_ref_index_at(int which)               { return impl_klass_ref_index_at(which, false); }

   int name_and_type_ref_index_at(int which)       { return impl_name_and_type_ref_index_at(which, false); }

   // Lookup for entries consisting of (name_index, signature_index)

   int name_ref_index_at(int which_nt);            // ==  low-order jshort of name_and_type_at(which_nt)

   int signature_ref_index_at(int which_nt);       // == high-order jshort of name_and_type_at(which_nt)

   BasicType basic_type_for_signature_at(int which);

   // Resolve string constants (to prevent allocation during compilation)

   void resolve_string_constants(TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     resolve_string_constants_impl(h_this, CHECK);

   }

   // CDS support

   void remove_unshareable_info();

   void restore_unshareable_info(TRAPS);

   bool resolve_class_constants(TRAPS);

   // The ConstantPool vtable is restored by this call when the ConstantPool is

   // in the shared archive.  See patch_klass_vtables() in metaspaceShared.cpp for

   // all the gory details.  SA, dtrace and pstack helpers distinguish metadata

   // by their vtable.

   void restore_vtable() { guarantee(is_constantPool(), "vtable restored by this call"); }

  private:

   enum { _no_index_sentinel = -1, _possible_index_sentinel = -2 };

  public:

   // Resolve late bound constants.

   oop resolve_constant_at(int index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return resolve_constant_at_impl(h_this, index, _no_index_sentinel, THREAD);

   }

   oop resolve_cached_constant_at(int cache_index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return resolve_constant_at_impl(h_this, _no_index_sentinel, cache_index, THREAD);

   }

   oop resolve_possibly_cached_constant_at(int pool_index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return resolve_constant_at_impl(h_this, pool_index, _possible_index_sentinel, THREAD);

   }

   oop resolve_bootstrap_specifier_at(int index, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     return resolve_bootstrap_specifier_at_impl(h_this, index, THREAD);

   }

   // Klass name matches name at offset

   bool klass_name_at_matches(instanceKlassHandle k, int which);

   // Sizing

   int length() const                   { return _length; }

   void set_length(int length)          { _length = length; }

   // Tells whether index is within bounds.

   bool is_within_bounds(int index) const {

     return 0 <= index && index < length();

   }

   // Sizing (in words)

   static int header_size()             { return sizeof(ConstantPool)/HeapWordSize; }

   static int size(int length)          { return align_object_size(header_size() + length); }

   int size() const                     { return size(length()); }

 #if INCLUDE_SERVICES

   void collect_statistics(KlassSizeStats *sz) const;

 #endif

   friend class ClassFileParser;

   friend class SystemDictionary;

   // Used by compiler to prevent classloading.

   static Method*          method_at_if_loaded      (constantPoolHandle this_oop, int which);

   static bool       has_appendix_at_if_loaded      (constantPoolHandle this_oop, int which);

   static oop            appendix_at_if_loaded      (constantPoolHandle this_oop, int which);

   static bool    has_method_type_at_if_loaded      (constantPoolHandle this_oop, int which);

   static oop         method_type_at_if_loaded      (constantPoolHandle this_oop, int which);

   static Klass*            klass_at_if_loaded      (constantPoolHandle this_oop, int which);

   static Klass*        klass_ref_at_if_loaded      (constantPoolHandle this_oop, int which);

   // Same as above - but does LinkResolving.

   static Klass*        klass_ref_at_if_loaded_check(constantPoolHandle this_oop, int which, TRAPS);

   // Routines currently used for annotations (only called by jvm.cpp) but which might be used in the

   // future by other Java code. These take constant pool indices rather than

   // constant pool cache indices as do the peer methods above.

   Symbol* uncached_klass_ref_at_noresolve(int which);

   Symbol* uncached_name_ref_at(int which)                 { return impl_name_ref_at(which, true); }

   Symbol* uncached_signature_ref_at(int which)            { return impl_signature_ref_at(which, true); }

   int       uncached_klass_ref_index_at(int which)          { return impl_klass_ref_index_at(which, true); }

   int       uncached_name_and_type_ref_index_at(int which)  { return impl_name_and_type_ref_index_at(which, true); }

   // Sharing

   int pre_resolve_shared_klasses(TRAPS);

   // Debugging

   const char* printable_name_at(int which) PRODUCT_RETURN0;

 #ifdef ASSERT

   enum { CPCACHE_INDEX_TAG = 0x10000 };  // helps keep CP cache indices distinct from CP indices

 #else

   enum { CPCACHE_INDEX_TAG = 0 };        // in product mode, this zero value is a no-op

 #endif //ASSERT

   static int decode_cpcache_index(int raw_index, bool invokedynamic_ok = false) {

     if (invokedynamic_ok && is_invokedynamic_index(raw_index))

       return decode_invokedynamic_index(raw_index);

     else

       return raw_index - CPCACHE_INDEX_TAG;

   }

  private:

   void set_resolved_references(jobject s) { _resolved_references = s; }

   Array<u2>* reference_map() const        { return _reference_map; }

   void set_reference_map(Array<u2>* o)    { _reference_map = o; }

   // patch JSR 292 resolved references after the class is linked.

   void patch_resolved_references(GrowableArray<Handle>* cp_patches);

   Symbol* impl_name_ref_at(int which, bool uncached);

   Symbol* impl_signature_ref_at(int which, bool uncached);

   int       impl_klass_ref_index_at(int which, bool uncached);

   int       impl_name_and_type_ref_index_at(int which, bool uncached);

   int remap_instruction_operand_from_cache(int operand);  // operand must be biased by CPCACHE_INDEX_TAG

   // Used while constructing constant pool (only by ClassFileParser)

   jint klass_index_at(int which) {

     assert(tag_at(which).is_klass_index(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   jint string_index_at(int which) {

     assert(tag_at(which).is_string_index(), "Corrupted constant pool");

     return *int_at_addr(which);

   }

   // Performs the LinkResolver checks

   static void verify_constant_pool_resolve(constantPoolHandle this_oop, KlassHandle klass, TRAPS);

   // Implementation of methods that needs an exposed 'this' pointer, in order to

   // handle GC while executing the method

   static Klass* klass_at_impl(constantPoolHandle this_oop, int which, TRAPS);

   static oop string_at_impl(constantPoolHandle this_oop, int which, int obj_index, TRAPS);

   // Resolve string constants (to prevent allocation during compilation)

   static void resolve_string_constants_impl(constantPoolHandle this_oop, TRAPS);

   static oop resolve_constant_at_impl(constantPoolHandle this_oop, int index, int cache_index, TRAPS);

   static void save_and_throw_exception(constantPoolHandle this_oop, int which, int tag_value, TRAPS);

   static oop resolve_bootstrap_specifier_at_impl(constantPoolHandle this_oop, int index, TRAPS);

  public:

   // Merging ConstantPool* support:

   bool compare_entry_to(int index1, constantPoolHandle cp2, int index2, TRAPS);

   void copy_cp_to(int start_i, int end_i, constantPoolHandle to_cp, int to_i, TRAPS) {

     constantPoolHandle h_this(THREAD, this);

     copy_cp_to_impl(h_this, start_i, end_i, to_cp, to_i, THREAD);

   }

   static void copy_cp_to_impl(constantPoolHandle from_cp, int start_i, int end_i, constantPoolHandle to_cp, int to_i, TRAPS);

   static void copy_entry_to(constantPoolHandle from_cp, int from_i, constantPoolHandle to_cp, int to_i, TRAPS);

   static void copy_operands(constantPoolHandle from_cp, constantPoolHandle to_cp, TRAPS);

   int  find_matching_entry(int pattern_i, constantPoolHandle search_cp, TRAPS);

   int  version() const                    { return _saved._version; }

   void set_version(int version)           { _saved._version = version; }

   void increment_and_save_version(int version) {

     _saved._version = version >= 0 ? (version + 1) : version;  // keep overflow

   }

   void set_resolved_reference_length(int length) { _saved._resolved_reference_length = length; }

   int  resolved_reference_length() const  { return _saved._resolved_reference_length; }

   void set_lock(Monitor* lock)            { _lock = lock; }

   Monitor* lock()                         { return _lock; }

   // Decrease ref counts of symbols that are in the constant pool

   // when the holder class is unloaded

   void unreference_symbols();

   // Deallocate constant pool for RedefineClasses

   void deallocate_contents(ClassLoaderData* loader_data);

   void release_C_heap_structures();

   // JVMTI accesss - GetConstantPool, RetransformClasses, ...

   friend class JvmtiConstantPoolReconstituter;

  private:

   jint cpool_entry_size(jint idx);

   jint hash_entries_to(SymbolHashMap *symmap, SymbolHashMap *classmap);

   // Copy cpool bytes into byte array.

   // Returns:

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

   //        0, OutOfMemory error

   //       -1, Internal error

   int  copy_cpool_bytes(int cpool_size,

                         SymbolHashMap* tbl,

                         unsigned char *bytes);

  public:

   // Verify

   void verify_on(outputStream* st);

   // Printing

   void print_on(outputStream* st) const;

   void print_value_on(outputStream* st) const;

   void print_entry_on(int index, outputStream* st);

   const char* internal_name() const { return "{constant pool}"; }

 #ifndef PRODUCT

   // Compile the world support

   static void preload_and_initialize_all_classes(ConstantPool* constant_pool, TRAPS);

 #endif

 };

 class SymbolHashMapEntry : public CHeapObj<mtSymbol> {

  private:

   unsigned int        _hash;   // 32-bit hash for item

   SymbolHashMapEntry* _next;   // Next element in the linked list for this bucket

   Symbol*             _symbol; // 1-st part of the mapping: symbol => value

   u2                  _value;  // 2-nd part of the mapping: symbol => value

  public:

   unsigned   int hash() const             { return _hash;   }

   void       set_hash(unsigned int hash)  { _hash = hash;   }

   SymbolHashMapEntry* next() const        { return _next;   }

   void set_next(SymbolHashMapEntry* next) { _next = next;   }

   Symbol*    symbol() const               { return _symbol; }

   void       set_symbol(Symbol* sym)      { _symbol = sym;  }

   u2         value() const                {  return _value; }

   void       set_value(u2 value)          { _value = value; }

   SymbolHashMapEntry(unsigned int hash, Symbol* symbol, u2 value)

     : _hash(hash), _symbol(symbol), _value(value), _next(NULL) {}

 }; // End SymbolHashMapEntry class

 class SymbolHashMapBucket : public CHeapObj<mtSymbol> {

 private:

   SymbolHashMapEntry*    _entry;

 public:

   SymbolHashMapEntry* entry() const         {  return _entry; }

   void set_entry(SymbolHashMapEntry* entry) { _entry = entry; }

   void clear()                              { _entry = NULL;  }

 }; // End SymbolHashMapBucket class

 class SymbolHashMap: public CHeapObj<mtSymbol> {

  private:

   // Default number of entries in the table

   enum SymbolHashMap_Constants {

     _Def_HashMap_Size = 256

   };

   int                   _table_size;

   SymbolHashMapBucket*  _buckets;

   void initialize_table(int table_size) {

     _table_size = table_size;

     _buckets = NEW_C_HEAP_ARRAY(SymbolHashMapBucket, table_size, mtSymbol);

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

       _buckets[index].clear();

     }

   }

  public:

   int table_size() const        { return _table_size; }

   SymbolHashMap()               { initialize_table(_Def_HashMap_Size); }

   SymbolHashMap(int table_size) { initialize_table(table_size); }

   // hash P(31) from Kernighan & Ritchie

   static unsigned int compute_hash(const char* str, int len) {

     unsigned int hash = 0;

     while (len-- > 0) {

       hash = 31*hash + (unsigned) *str;

       str++;

     }

     return hash;

   }

   SymbolHashMapEntry* bucket(int i) {

     return _buckets[i].entry();

   }

   void add_entry(Symbol* sym, u2 value);

   SymbolHashMapEntry* find_entry(Symbol* sym);

   u2 symbol_to_value(Symbol* sym) {

     SymbolHashMapEntry *entry = find_entry(sym);

     return (entry == NULL) ? 0 : entry->value();

   }

   ~SymbolHashMap() {

     SymbolHashMapEntry* next;

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

       for (SymbolHashMapEntry* cur = bucket(i); cur != NULL; cur = next) {

         next = cur->next();

         delete(cur);

       }

     }

     delete _buckets;

   }

 }; // End SymbolHashMap class

 #endif // SHARE_VM_OOPS_CONSTANTPOOLOOP_HPP