Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2012, 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.

  *

  */

 #include "precompiled.hpp"

 #include "classfile/bytecodeAssembler.hpp"

 #include "classfile/defaultMethods.hpp"

 #include "classfile/symbolTable.hpp"

 #include "memory/allocation.hpp"

 #include "memory/metadataFactory.hpp"

 #include "memory/resourceArea.hpp"

 #include "runtime/signature.hpp"

 #include "runtime/thread.hpp"

 #include "oops/instanceKlass.hpp"

 #include "oops/klass.hpp"

 #include "oops/method.hpp"

 #include "utilities/accessFlags.hpp"

 #include "utilities/exceptions.hpp"

 #include "utilities/ostream.hpp"

 #include "utilities/pair.hpp"

 #include "utilities/resourceHash.hpp"

 typedef enum { QUALIFIED, DISQUALIFIED } QualifiedState;

 // Because we use an iterative algorithm when iterating over the type

 // hierarchy, we can't use traditional scoped objects which automatically do

 // cleanup in the destructor when the scope is exited.  PseudoScope (and

 // PseudoScopeMark) provides a similar functionality, but for when you want a

 // scoped object in non-stack memory (such as in resource memory, as we do

 // here).  You've just got to remember to call 'destroy()' on the scope when

 // leaving it (and marks have to be explicitly added).

 class PseudoScopeMark : public ResourceObj {

  public:

   virtual void destroy() = 0;

 };

 class PseudoScope : public ResourceObj {

  private:

   GrowableArray<PseudoScopeMark*> _marks;

  public:

   static PseudoScope* cast(void* data) {

     return static_cast<PseudoScope*>(data);

   }

   void add_mark(PseudoScopeMark* psm) {

    _marks.append(psm);

   }

   void destroy() {

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

       _marks.at(i)->destroy();

     }

   }

 };

 #ifndef PRODUCT

 static void print_slot(outputStream* str, Symbol* name, Symbol* signature) {

   ResourceMark rm;

   str->print("%s%s", name->as_C_string(), signature->as_C_string());

 }

 static void print_method(outputStream* str, Method* mo, bool with_class=true) {

   ResourceMark rm;

   if (with_class) {

     str->print("%s.", mo->klass_name()->as_C_string());

   }

   print_slot(str, mo->name(), mo->signature());

 }

 #endif // ndef PRODUCT

 /**

  * Perform a depth-first iteration over the class hierarchy, applying

  * algorithmic logic as it goes.

  *

  * This class is one half of the inheritance hierarchy analysis mechanism.

  * It is meant to be used in conjunction with another class, the algorithm,

  * which is indicated by the ALGO template parameter.  This class can be

  * paired with any algorithm class that provides the required methods.

  *

  * This class contains all the mechanics for iterating over the class hierarchy

  * starting at a particular root, without recursing (thus limiting stack growth

  * from this point).  It visits each superclass (if present) and superinterface

  * in a depth-first manner, with callbacks to the ALGO class as each class is

  * encountered (visit()), The algorithm can cut-off further exploration of a

  * particular branch by returning 'false' from a visit() call.

  *

  * The ALGO class, must provide a visit() method, which each of which will be

  * called once for each node in the inheritance tree during the iteration.  In

  * addition, it can provide a memory block via new_node_data(InstanceKlass*),

  * which it can use for node-specific storage (and access via the

  * current_data() and data_at_depth(int) methods).

  *

  * Bare minimum needed to be an ALGO class:

  * class Algo : public HierarchyVisitor<Algo> {

  *   void* new_node_data(InstanceKlass* cls) { return NULL; }

  *   void free_node_data(void* data) { return; }

  *   bool visit() { return true; }

  * };

  */

 template <class ALGO>

 class HierarchyVisitor : StackObj {

  private:

   class Node : public ResourceObj {

    public:

     InstanceKlass* _class;

     bool _super_was_visited;

     int _interface_index;

     void* _algorithm_data;

     Node(InstanceKlass* cls, void* data, bool visit_super)

         : _class(cls), _super_was_visited(!visit_super),

           _interface_index(0), _algorithm_data(data) {}

     int number_of_interfaces() { return _class->local_interfaces()->length(); }

     int interface_index() { return _interface_index; }

     void set_super_visited() { _super_was_visited = true; }

     void increment_visited_interface() { ++_interface_index; }

     void set_all_interfaces_visited() {

       _interface_index = number_of_interfaces();

     }

     bool has_visited_super() { return _super_was_visited; }

     bool has_visited_all_interfaces() {

       return interface_index() >= number_of_interfaces();

     }

     InstanceKlass* interface_at(int index) {

       return InstanceKlass::cast(_class->local_interfaces()->at(index));

     }

     InstanceKlass* next_super() { return _class->java_super(); }

     InstanceKlass* next_interface() {

       return interface_at(interface_index());

     }

   };

   bool _cancelled;

   GrowableArray<Node*> _path;

   Node* current_top() const { return _path.top(); }

   bool has_more_nodes() const { return !_path.is_empty(); }

   void push(InstanceKlass* cls, void* data) {

     assert(cls != NULL, "Requires a valid instance class");

     Node* node = new Node(cls, data, has_super(cls));

     _path.push(node);

   }

   void pop() { _path.pop(); }

   void reset_iteration() {

     _cancelled = false;

     _path.clear();

   }

   bool is_cancelled() const { return _cancelled; }

   static bool has_super(InstanceKlass* cls) {

     return cls->super() != NULL && !cls->is_interface();

   }

   Node* node_at_depth(int i) const {

     return (i >= _path.length()) ? NULL : _path.at(_path.length() - i - 1);

   }

  protected:

   // Accessors available to the algorithm

   int current_depth() const { return _path.length() - 1; }

   InstanceKlass* class_at_depth(int i) {

     Node* n = node_at_depth(i);

     return n == NULL ? NULL : n->_class;

   }

   InstanceKlass* current_class() { return class_at_depth(0); }

   void* data_at_depth(int i) {

     Node* n = node_at_depth(i);

     return n == NULL ? NULL : n->_algorithm_data;

   }

   void* current_data() { return data_at_depth(0); }

   void cancel_iteration() { _cancelled = true; }

  public:

   void run(InstanceKlass* root) {

     ALGO* algo = static_cast<ALGO*>(this);

     reset_iteration();

     void* algo_data = algo->new_node_data(root);

     push(root, algo_data);

     bool top_needs_visit = true;

     do {

       Node* top = current_top();

       if (top_needs_visit) {

         if (algo->visit() == false) {

           // algorithm does not want to continue along this path.  Arrange

           // it so that this state is immediately popped off the stack

           top->set_super_visited();

           top->set_all_interfaces_visited();

         }

         top_needs_visit = false;

       }

       if (top->has_visited_super() && top->has_visited_all_interfaces()) {

         algo->free_node_data(top->_algorithm_data);

         pop();

       } else {

         InstanceKlass* next = NULL;

         if (top->has_visited_super() == false) {

           next = top->next_super();

           top->set_super_visited();

         } else {

           next = top->next_interface();

           top->increment_visited_interface();

         }

         assert(next != NULL, "Otherwise we shouldn't be here");

         algo_data = algo->new_node_data(next);

         push(next, algo_data);

         top_needs_visit = true;

       }

     } while (!is_cancelled() && has_more_nodes());

   }

 };

 #ifndef PRODUCT

 class PrintHierarchy : public HierarchyVisitor<PrintHierarchy> {

  public:

   bool visit() {

     InstanceKlass* cls = current_class();

     streamIndentor si(tty, current_depth() * 2);

     tty->indent().print_cr("%s", cls->name()->as_C_string());

     return true;

   }

   void* new_node_data(InstanceKlass* cls) { return NULL; }

   void free_node_data(void* data) { return; }

 };

 #endif // ndef PRODUCT

 // Used to register InstanceKlass objects and all related metadata structures

 // (Methods, ConstantPools) as "in-use" by the current thread so that they can't

 // be deallocated by class redefinition while we're using them.  The classes are

 // de-registered when this goes out of scope.

 //

 // Once a class is registered, we need not bother with methodHandles or

 // constantPoolHandles for it's associated metadata.

 class KeepAliveRegistrar : public StackObj {

  private:

   Thread* _thread;

   GrowableArray<ConstantPool*> _keep_alive;

  public:

   KeepAliveRegistrar(Thread* thread) : _thread(thread), _keep_alive(20) {

     assert(thread == Thread::current(), "Must be current thread");

   }

   ~KeepAliveRegistrar() {

     for (int i = _keep_alive.length() - 1; i >= 0; --i) {

       ConstantPool* cp = _keep_alive.at(i);

       int idx = _thread->metadata_handles()->find_from_end(cp);

       assert(idx > 0, "Must be in the list");

       _thread->metadata_handles()->remove_at(idx);

     }

   }

   // Register a class as 'in-use' by the thread.  It's fine to register a class

   // multiple times (though perhaps inefficient)

   void register_class(InstanceKlass* ik) {

     ConstantPool* cp = ik->constants();

     _keep_alive.push(cp);

     _thread->metadata_handles()->push(cp);

   }

 };

 class KeepAliveVisitor : public HierarchyVisitor<KeepAliveVisitor> {

  private:

   KeepAliveRegistrar* _registrar;

  public:

   KeepAliveVisitor(KeepAliveRegistrar* registrar) : _registrar(registrar) {}

   void* new_node_data(InstanceKlass* cls) { return NULL; }

   void free_node_data(void* data) { return; }

   bool visit() {

     _registrar->register_class(current_class());

     return true;

   }

 };

 // A method family contains a set of all methods that implement a single

 // erased method. As members of the set are collected while walking over the

 // hierarchy, they are tagged with a qualification state.  The qualification

 // state for an erased method is set to disqualified if there exists a path

 // from the root of hierarchy to the method that contains an interleaving

 // erased method defined in an interface.

 class MethodFamily : public ResourceObj {

  private:

   GrowableArray<Pair<Method*,QualifiedState> > _members;

   ResourceHashtable<Method*, int> _member_index;

   Method* _selected_target;  // Filled in later, if a unique target exists

   Symbol* _exception_message; // If no unique target is found

   Symbol* _exception_name;    // If no unique target is found

   bool contains_method(Method* method) {

     int* lookup = _member_index.get(method);

     return lookup != NULL;

   }

   void add_method(Method* method, QualifiedState state) {

     Pair<Method*,QualifiedState> entry(method, state);

     _member_index.put(method, _members.length());

     _members.append(entry);

   }

   void disqualify_method(Method* method) {

     int* index = _member_index.get(method);

     guarantee(index != NULL && *index >= 0 && *index < _members.length(), "bad index");

     _members.at(*index).second = DISQUALIFIED;

   }

   Symbol* generate_no_defaults_message(TRAPS) const;

   Symbol* generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const;

  public:

   MethodFamily()

       : _selected_target(NULL), _exception_message(NULL), _exception_name(NULL) {}

   void set_target_if_empty(Method* m) {

     if (_selected_target == NULL && !m->is_overpass()) {

       _selected_target = m;

     }

   }

   void record_qualified_method(Method* m) {

     // If the method already exists in the set as qualified, this operation is

     // redundant.  If it already exists as disqualified, then we leave it as

     // disqualfied.  Thus we only add to the set if it's not already in the

     // set.

     if (!contains_method(m)) {

       add_method(m, QUALIFIED);

     }

   }

   void record_disqualified_method(Method* m) {

     // If not in the set, add it as disqualified.  If it's already in the set,

     // then set the state to disqualified no matter what the previous state was.

     if (!contains_method(m)) {

       add_method(m, DISQUALIFIED);

     } else {

       disqualify_method(m);

     }

   }

   bool has_target() const { return _selected_target != NULL; }

   bool throws_exception() { return _exception_message != NULL; }

   Method* get_selected_target() { return _selected_target; }

   Symbol* get_exception_message() { return _exception_message; }

   Symbol* get_exception_name() { return _exception_name; }

   // Either sets the target or the exception error message

   void determine_target(InstanceKlass* root, TRAPS) {

     if (has_target() || throws_exception()) {

       return;

     }

     GrowableArray<Method*> qualified_methods;

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

       Pair<Method*,QualifiedState> entry = _members.at(i);

       if (entry.second == QUALIFIED) {

         qualified_methods.append(entry.first);

       }

     }

     if (qualified_methods.length() == 0) {

       _exception_message = generate_no_defaults_message(CHECK);

       _exception_name = vmSymbols::java_lang_AbstractMethodError();

     } else if (qualified_methods.length() == 1) {

       // leave abstract methods alone, they will be found via normal search path

       Method* method = qualified_methods.at(0);

       if (!method->is_abstract()) {

         _selected_target = qualified_methods.at(0);

       }

     } else {

       _exception_message = generate_conflicts_message(&qualified_methods,CHECK);

       _exception_name = vmSymbols::java_lang_IncompatibleClassChangeError();

       if (TraceDefaultMethods) {

         _exception_message->print_value_on(tty);

         tty->print_cr("");

       }

     }

   }

   bool contains_signature(Symbol* query) {

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

       if (query == _members.at(i).first->signature()) {

         return true;

       }

     }

     return false;

   }

 #ifndef PRODUCT

   void print_sig_on(outputStream* str, Symbol* signature, int indent) const {

     streamIndentor si(str, indent * 2);

     str->indent().print_cr("Logical Method %s:", signature->as_C_string());

     streamIndentor si2(str);

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

       str->indent();

       print_method(str, _members.at(i).first);

       if (_members.at(i).second == DISQUALIFIED) {

         str->print(" (disqualified)");

       }

       str->print_cr("");

     }

     if (_selected_target != NULL) {

       print_selected(str, 1);

     }

   }

   void print_selected(outputStream* str, int indent) const {

     assert(has_target(), "Should be called otherwise");

     streamIndentor si(str, indent * 2);

     str->indent().print("Selected method: ");

     print_method(str, _selected_target);

     Klass* method_holder = _selected_target->method_holder();

     if (!method_holder->is_interface()) {

       tty->print(" : in superclass");

     }

     str->print_cr("");

   }

   void print_exception(outputStream* str, int indent) {

     assert(throws_exception(), "Should be called otherwise");

     assert(_exception_name != NULL, "exception_name should be set");

     streamIndentor si(str, indent * 2);

     str->indent().print_cr("%s: %s", _exception_name->as_C_string(), _exception_message->as_C_string());

   }

 #endif // ndef PRODUCT

 };

 Symbol* MethodFamily::generate_no_defaults_message(TRAPS) const {

   return SymbolTable::new_symbol("No qualifying defaults found", CHECK_NULL);

 }

 Symbol* MethodFamily::generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const {

   stringStream ss;

   ss.print("Conflicting default methods:");

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

     Method* method = methods->at(i);

     Symbol* klass = method->klass_name();

     Symbol* name = method->name();

     ss.print(" ");

     ss.write((const char*)klass->bytes(), klass->utf8_length());

     ss.print(".");

     ss.write((const char*)name->bytes(), name->utf8_length());

   }

   return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);

 }

 class StateRestorer;

 // StatefulMethodFamily is a wrapper around a MethodFamily that maintains the

 // qualification state during hierarchy visitation, and applies that state

 // when adding members to the MethodFamily

 class StatefulMethodFamily : public ResourceObj {

   friend class StateRestorer;

  private:

   QualifiedState _qualification_state;

   void set_qualification_state(QualifiedState state) {

     _qualification_state = state;

   }

  protected:

   MethodFamily* _method_family;

  public:

   StatefulMethodFamily() {

    _method_family = new MethodFamily();

    _qualification_state = QUALIFIED;

   }

   StatefulMethodFamily(MethodFamily* mf) {

    _method_family = mf;

    _qualification_state = QUALIFIED;

   }

   void set_target_if_empty(Method* m) { _method_family->set_target_if_empty(m); }

   MethodFamily* get_method_family() { return _method_family; }

   StateRestorer* record_method_and_dq_further(Method* mo);

 };

 class StateRestorer : public PseudoScopeMark {

  private:

   StatefulMethodFamily* _method;

   QualifiedState _state_to_restore;

  public:

   StateRestorer(StatefulMethodFamily* dm, QualifiedState state)

       : _method(dm), _state_to_restore(state) {}

   ~StateRestorer() { destroy(); }

   void restore_state() { _method->set_qualification_state(_state_to_restore); }

   virtual void destroy() { restore_state(); }

 };

 StateRestorer* StatefulMethodFamily::record_method_and_dq_further(Method* mo) {

   StateRestorer* mark = new StateRestorer(this, _qualification_state);

   if (_qualification_state == QUALIFIED) {

     _method_family->record_qualified_method(mo);

   } else {

     _method_family->record_disqualified_method(mo);

   }

   // Everything found "above"??? this method in the hierarchy walk is set to

   // disqualified

   set_qualification_state(DISQUALIFIED);

   return mark;

 }

 // Represents a location corresponding to a vtable slot for methods that

 // neither the class nor any of it's ancestors provide an implementaion.

 // Default methods may be present to fill this slot.

 class EmptyVtableSlot : public ResourceObj {

  private:

   Symbol* _name;

   Symbol* _signature;

   int _size_of_parameters;

   MethodFamily* _binding;

  public:

   EmptyVtableSlot(Method* method)

       : _name(method->name()), _signature(method->signature()),

         _size_of_parameters(method->size_of_parameters()), _binding(NULL) {}

   Symbol* name() const { return _name; }

   Symbol* signature() const { return _signature; }

   int size_of_parameters() const { return _size_of_parameters; }

   void bind_family(MethodFamily* lm) { _binding = lm; }

   bool is_bound() { return _binding != NULL; }

   MethodFamily* get_binding() { return _binding; }

 #ifndef PRODUCT

   void print_on(outputStream* str) const {

     print_slot(str, name(), signature());

   }

 #endif // ndef PRODUCT

 };

 static bool already_in_vtable_slots(GrowableArray<EmptyVtableSlot*>* slots, Method* m) {

   bool found = false;

   for (int j = 0; j < slots->length(); ++j) {

     if (slots->at(j)->name() == m->name() &&

         slots->at(j)->signature() == m->signature() ) {

       found = true;

       break;

     }

   }

   return found;

 }

 static GrowableArray<EmptyVtableSlot*>* find_empty_vtable_slots(

     InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {

   assert(klass != NULL, "Must be valid class");

   GrowableArray<EmptyVtableSlot*>* slots = new GrowableArray<EmptyVtableSlot*>();

   // All miranda methods are obvious candidates

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

     Method* m = mirandas->at(i);

     if (!already_in_vtable_slots(slots, m)) {

       slots->append(new EmptyVtableSlot(m));

     }

   }

   // Also any overpasses in our superclasses, that we haven't implemented.

   // (can't use the vtable because it is not guaranteed to be initialized yet)

   InstanceKlass* super = klass->java_super();

   while (super != NULL) {

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

       Method* m = super->methods()->at(i);

       if (m->is_overpass()) {

         // m is a method that would have been a miranda if not for the

         // default method processing that occurred on behalf of our superclass,

         // so it's a method we want to re-examine in this new context.  That is,

         // unless we have a real implementation of it in the current class.

         Method* impl = klass->lookup_method(m->name(), m->signature());

         if (impl == NULL || impl->is_overpass()) {

           if (!already_in_vtable_slots(slots, m)) {

             slots->append(new EmptyVtableSlot(m));

           }

         }

       }

     }

     // also any default methods in our superclasses

     if (super->default_methods() != NULL) {

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

         Method* m = super->default_methods()->at(i);

         // m is a method that would have been a miranda if not for the

         // default method processing that occurred on behalf of our superclass,

         // so it's a method we want to re-examine in this new context.  That is,

         // unless we have a real implementation of it in the current class.

         Method* impl = klass->lookup_method(m->name(), m->signature());

         if (impl == NULL || impl->is_overpass()) {

           if (!already_in_vtable_slots(slots, m)) {

             slots->append(new EmptyVtableSlot(m));

           }

         }

       }

     }

     super = super->java_super();

   }

 #ifndef PRODUCT

   if (TraceDefaultMethods) {

     tty->print_cr("Slots that need filling:");

     streamIndentor si(tty);

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

       tty->indent();

       slots->at(i)->print_on(tty);

       tty->print_cr("");

     }

   }

 #endif // ndef PRODUCT

   return slots;

 }

 // Iterates over the superinterface type hierarchy looking for all methods

 // with a specific erased signature.

 class FindMethodsByErasedSig : public HierarchyVisitor<FindMethodsByErasedSig> {

  private:

   // Context data

   Symbol* _method_name;

   Symbol* _method_signature;

   StatefulMethodFamily*  _family;

  public:

   FindMethodsByErasedSig(Symbol* name, Symbol* signature) :

       _method_name(name), _method_signature(signature),

       _family(NULL) {}

   void get_discovered_family(MethodFamily** family) {

       if (_family != NULL) {

         *family = _family->get_method_family();

       } else {

         *family = NULL;

       }

   }

   void* new_node_data(InstanceKlass* cls) { return new PseudoScope(); }

   void free_node_data(void* node_data) {

     PseudoScope::cast(node_data)->destroy();

   }

   // Find all methods on this hierarchy that match this

   // method's erased (name, signature)

   bool visit() {

     PseudoScope* scope = PseudoScope::cast(current_data());

     InstanceKlass* iklass = current_class();

     Method* m = iklass->find_method(_method_name, _method_signature);

     // private interface methods are not candidates for default methods

     // invokespecial to private interface methods doesn't use default method logic

     // future: take access controls into account for superclass methods

     if (m != NULL && !m->is_static() && (!iklass->is_interface() || m->is_public())) {

       if (_family == NULL) {

         _family = new StatefulMethodFamily();

       }

       if (iklass->is_interface()) {

         StateRestorer* restorer = _family->record_method_and_dq_further(m);

         scope->add_mark(restorer);

       } else {

         // This is the rule that methods in classes "win" (bad word) over

         // methods in interfaces. This works because of single inheritance

         _family->set_target_if_empty(m);

       }

     }

     return true;

   }

 };

 static void create_defaults_and_exceptions(

     GrowableArray<EmptyVtableSlot*>* slots, InstanceKlass* klass, TRAPS);

 static void generate_erased_defaults(

      InstanceKlass* klass, GrowableArray<EmptyVtableSlot*>* empty_slots,

      EmptyVtableSlot* slot, TRAPS) {

   // sets up a set of methods with the same exact erased signature

   FindMethodsByErasedSig visitor(slot->name(), slot->signature());

   visitor.run(klass);

   MethodFamily* family;

   visitor.get_discovered_family(&family);

   if (family != NULL) {

     family->determine_target(klass, CHECK);

     slot->bind_family(family);

   }

 }

 static void merge_in_new_methods(InstanceKlass* klass,

     GrowableArray<Method*>* new_methods, TRAPS);

 static void create_default_methods( InstanceKlass* klass,

     GrowableArray<Method*>* new_methods, TRAPS);

 // This is the guts of the default methods implementation.  This is called just

 // after the classfile has been parsed if some ancestor has default methods.

 //

 // First if finds any name/signature slots that need any implementation (either

 // because they are miranda or a superclass's implementation is an overpass

 // itself).  For each slot, iterate over the hierarchy, to see if they contain a

 // signature that matches the slot we are looking at.

 //

 // For each slot filled, we generate an overpass method that either calls the

 // unique default method candidate using invokespecial, or throws an exception

 // (in the case of no default method candidates, or more than one valid

 // candidate).  These methods are then added to the class's method list.

 // The JVM does not create bridges nor handle generic signatures here.

 void DefaultMethods::generate_default_methods(

     InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {

   // This resource mark is the bound for all memory allocation that takes

   // place during default method processing.  After this goes out of scope,

   // all (Resource) objects' memory will be reclaimed.  Be careful if adding an

   // embedded resource mark under here as that memory can't be used outside

   // whatever scope it's in.

   ResourceMark rm(THREAD);

   // Keep entire hierarchy alive for the duration of the computation

   KeepAliveRegistrar keepAlive(THREAD);

   KeepAliveVisitor loadKeepAlive(&keepAlive);

   loadKeepAlive.run(klass);

 #ifndef PRODUCT

   if (TraceDefaultMethods) {

     ResourceMark rm;  // be careful with these!

     tty->print_cr("Class %s requires default method processing",

         klass->name()->as_klass_external_name());

     PrintHierarchy printer;

     printer.run(klass);

   }

 #endif // ndef PRODUCT

   GrowableArray<EmptyVtableSlot*>* empty_slots =

       find_empty_vtable_slots(klass, mirandas, CHECK);

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

     EmptyVtableSlot* slot = empty_slots->at(i);

 #ifndef PRODUCT

     if (TraceDefaultMethods) {

       streamIndentor si(tty, 2);

       tty->indent().print("Looking for default methods for slot ");

       slot->print_on(tty);

       tty->print_cr("");

     }

 #endif // ndef PRODUCT

     generate_erased_defaults(klass, empty_slots, slot, CHECK);

  }

 #ifndef PRODUCT

   if (TraceDefaultMethods) {

     tty->print_cr("Creating overpasses...");

   }

 #endif // ndef PRODUCT

   create_defaults_and_exceptions(empty_slots, klass, CHECK);

 #ifndef PRODUCT

   if (TraceDefaultMethods) {

     tty->print_cr("Default method processing complete");

   }

 #endif // ndef PRODUCT

 }

 static int assemble_method_error(

     BytecodeConstantPool* cp, BytecodeBuffer* buffer, Symbol* errorName, Symbol* message, TRAPS) {

   Symbol* init = vmSymbols::object_initializer_name();

   Symbol* sig = vmSymbols::string_void_signature();

   BytecodeAssembler assem(buffer, cp);

   assem._new(errorName);

   assem.dup();

   assem.load_string(message);

   assem.invokespecial(errorName, init, sig);

   assem.athrow();

   return 3; // max stack size: [ exception, exception, string ]

 }

 static Method* new_method(

     BytecodeConstantPool* cp, BytecodeBuffer* bytecodes, Symbol* name,

     Symbol* sig, AccessFlags flags, int max_stack, int params,

     ConstMethod::MethodType mt, TRAPS) {

   address code_start = 0;

   int code_length = 0;

   InlineTableSizes sizes;

   if (bytecodes != NULL && bytecodes->length() > 0) {

     code_start = static_cast<address>(bytecodes->adr_at(0));

     code_length = bytecodes->length();

   }

   Method* m = Method::allocate(cp->pool_holder()->class_loader_data(),

                                code_length, flags, &sizes,

                                mt, CHECK_NULL);

   m->set_constants(NULL); // This will get filled in later

   m->set_name_index(cp->utf8(name));

   m->set_signature_index(cp->utf8(sig));

 #ifdef CC_INTERP

   ResultTypeFinder rtf(sig);

   m->set_result_index(rtf.type());

 #endif

   m->set_size_of_parameters(params);

   m->set_max_stack(max_stack);

   m->set_max_locals(params);

   m->constMethod()->set_stackmap_data(NULL);

   m->set_code(code_start);

   return m;

 }

 static void switchover_constant_pool(BytecodeConstantPool* bpool,

     InstanceKlass* klass, GrowableArray<Method*>* new_methods, TRAPS) {

   if (new_methods->length() > 0) {

     ConstantPool* cp = bpool->create_constant_pool(CHECK);

     if (cp != klass->constants()) {

       klass->class_loader_data()->add_to_deallocate_list(klass->constants());

       klass->set_constants(cp);

       cp->set_pool_holder(klass);

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

         new_methods->at(i)->set_constants(cp);

       }

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

         Method* mo = klass->methods()->at(i);

         mo->set_constants(cp);

       }

     }

   }

 }

 // Create default_methods list for the current class.

 // With the VM only processing erased signatures, the VM only

 // creates an overpass in a conflict case or a case with no candidates.

 // This allows virtual methods to override the overpass, but ensures

 // that a local method search will find the exception rather than an abstract

 // or default method that is not a valid candidate.

 static void create_defaults_and_exceptions(

     GrowableArray<EmptyVtableSlot*>* slots,

     InstanceKlass* klass, TRAPS) {

   GrowableArray<Method*> overpasses;

   GrowableArray<Method*> defaults;

   BytecodeConstantPool bpool(klass->constants());

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

     EmptyVtableSlot* slot = slots->at(i);

     if (slot->is_bound()) {

       MethodFamily* method = slot->get_binding();

       BytecodeBuffer buffer;

 #ifndef PRODUCT

       if (TraceDefaultMethods) {

         tty->print("for slot: ");

         slot->print_on(tty);

         tty->print_cr("");

         if (method->has_target()) {

           method->print_selected(tty, 1);

         } else if (method->throws_exception()) {

           method->print_exception(tty, 1);

         }

       }

 #endif // ndef PRODUCT

       if (method->has_target()) {

         Method* selected = method->get_selected_target();

         if (selected->method_holder()->is_interface()) {

           defaults.push(selected);

         }

       } else if (method->throws_exception()) {

         int max_stack = assemble_method_error(&bpool, &buffer,

            method->get_exception_name(), method->get_exception_message(), CHECK);

         AccessFlags flags = accessFlags_from(

           JVM_ACC_PUBLIC | JVM_ACC_SYNTHETIC | JVM_ACC_BRIDGE);

          Method* m = new_method(&bpool, &buffer, slot->name(), slot->signature(),

           flags, max_stack, slot->size_of_parameters(),

           ConstMethod::OVERPASS, CHECK);

         // We push to the methods list:

         // overpass methods which are exception throwing methods

         if (m != NULL) {

           overpasses.push(m);

         }

       }

     }

   }

 #ifndef PRODUCT

   if (TraceDefaultMethods) {

     tty->print_cr("Created %d overpass methods", overpasses.length());

     tty->print_cr("Created %d default  methods", defaults.length());

   }

 #endif // ndef PRODUCT

   if (overpasses.length() > 0) {

     switchover_constant_pool(&bpool, klass, &overpasses, CHECK);

     merge_in_new_methods(klass, &overpasses, CHECK);

   }

   if (defaults.length() > 0) {

     create_default_methods(klass, &defaults, CHECK);

   }

 }

 static void create_default_methods( InstanceKlass* klass,

     GrowableArray<Method*>* new_methods, TRAPS) {

   int new_size = new_methods->length();

   Array<Method*>* total_default_methods = MetadataFactory::new_array<Method*>(

       klass->class_loader_data(), new_size, NULL, CHECK);

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

     total_default_methods->at_put(index, new_methods->at(index));

   }

   Method::sort_methods(total_default_methods, false, false);

   klass->set_default_methods(total_default_methods);

 }

 static void sort_methods(GrowableArray<Method*>* methods) {

   // Note that this must sort using the same key as is used for sorting

   // methods in InstanceKlass.

   bool sorted = true;

   for (int i = methods->length() - 1; i > 0; --i) {

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

       Method* m1 = methods->at(j);

       Method* m2 = methods->at(j + 1);

       if ((uintptr_t)m1->name() > (uintptr_t)m2->name()) {

         methods->at_put(j, m2);

         methods->at_put(j + 1, m1);

         sorted = false;

       }

     }

     if (sorted) break;

     sorted = true;

   }

 #ifdef ASSERT

   uintptr_t prev = 0;

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

     Method* mh = methods->at(i);

     uintptr_t nv = (uintptr_t)mh->name();

     assert(nv >= prev, "Incorrect overpass method ordering");

     prev = nv;

   }

 #endif

 }

 static void merge_in_new_methods(InstanceKlass* klass,

     GrowableArray<Method*>* new_methods, TRAPS) {

   enum { ANNOTATIONS, PARAMETERS, DEFAULTS, NUM_ARRAYS };

   Array<Method*>* original_methods = klass->methods();

   Array<int>* original_ordering = klass->method_ordering();

   Array<int>* merged_ordering = Universe::the_empty_int_array();

   int new_size = klass->methods()->length() + new_methods->length();

   Array<Method*>* merged_methods = MetadataFactory::new_array<Method*>(

       klass->class_loader_data(), new_size, NULL, CHECK);

   if (original_ordering != NULL && original_ordering->length() > 0) {

     merged_ordering = MetadataFactory::new_array<int>(

         klass->class_loader_data(), new_size, CHECK);

   }

   int method_order_index = klass->methods()->length();

   sort_methods(new_methods);

   // Perform grand merge of existing methods and new methods

   int orig_idx = 0;

   int new_idx = 0;

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

     Method* orig_method = NULL;

     Method* new_method = NULL;

     if (orig_idx < original_methods->length()) {

       orig_method = original_methods->at(orig_idx);

     }

     if (new_idx < new_methods->length()) {

       new_method = new_methods->at(new_idx);

     }

     if (orig_method != NULL &&

         (new_method == NULL || orig_method->name() < new_method->name())) {

       merged_methods->at_put(i, orig_method);

       original_methods->at_put(orig_idx, NULL);

       if (merged_ordering->length() > 0) {

         merged_ordering->at_put(i, original_ordering->at(orig_idx));

       }

       ++orig_idx;

     } else {

       merged_methods->at_put(i, new_method);

       if (merged_ordering->length() > 0) {

         merged_ordering->at_put(i, method_order_index++);

       }

       ++new_idx;

     }

     // update idnum for new location

     merged_methods->at(i)->set_method_idnum(i);

   }

   // Verify correct order

 #ifdef ASSERT

   uintptr_t prev = 0;

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

     Method* mo = merged_methods->at(i);

     uintptr_t nv = (uintptr_t)mo->name();

     assert(nv >= prev, "Incorrect method ordering");

     prev = nv;

   }

 #endif

   // Replace klass methods with new merged lists

   klass->set_methods(merged_methods);

   klass->set_initial_method_idnum(new_size);

   ClassLoaderData* cld = klass->class_loader_data();

   MetadataFactory::free_array(cld, original_methods);

   if (original_ordering->length() > 0) {

     klass->set_method_ordering(merged_ordering);

     MetadataFactory::free_array(cld, original_ordering);

   }

 }