Mon, 26 Aug 2013 11:35:25 -0400
8012294: remove generic handling for default methods
Reviewed-by: kamg, coleenp
1 /*
2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "classfile/bytecodeAssembler.hpp"
27 #include "classfile/defaultMethods.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "memory/allocation.hpp"
30 #include "memory/metadataFactory.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "runtime/signature.hpp"
33 #include "runtime/thread.hpp"
34 #include "oops/instanceKlass.hpp"
35 #include "oops/klass.hpp"
36 #include "oops/method.hpp"
37 #include "utilities/accessFlags.hpp"
38 #include "utilities/exceptions.hpp"
39 #include "utilities/ostream.hpp"
40 #include "utilities/pair.hpp"
41 #include "utilities/resourceHash.hpp"
43 typedef enum { QUALIFIED, DISQUALIFIED } QualifiedState;
45 // Because we use an iterative algorithm when iterating over the type
46 // hierarchy, we can't use traditional scoped objects which automatically do
47 // cleanup in the destructor when the scope is exited. PseudoScope (and
48 // PseudoScopeMark) provides a similar functionality, but for when you want a
49 // scoped object in non-stack memory (such as in resource memory, as we do
50 // here). You've just got to remember to call 'destroy()' on the scope when
51 // leaving it (and marks have to be explicitly added).
52 class PseudoScopeMark : public ResourceObj {
53 public:
54 virtual void destroy() = 0;
55 };
57 class PseudoScope : public ResourceObj {
58 private:
59 GrowableArray<PseudoScopeMark*> _marks;
60 public:
62 static PseudoScope* cast(void* data) {
63 return static_cast<PseudoScope*>(data);
64 }
66 void add_mark(PseudoScopeMark* psm) {
67 _marks.append(psm);
68 }
70 void destroy() {
71 for (int i = 0; i < _marks.length(); ++i) {
72 _marks.at(i)->destroy();
73 }
74 }
75 };
77 #ifndef PRODUCT
78 static void print_slot(outputStream* str, Symbol* name, Symbol* signature) {
79 ResourceMark rm;
80 str->print("%s%s", name->as_C_string(), signature->as_C_string());
81 }
83 static void print_method(outputStream* str, Method* mo, bool with_class=true) {
84 ResourceMark rm;
85 if (with_class) {
86 str->print("%s.", mo->klass_name()->as_C_string());
87 }
88 print_slot(str, mo->name(), mo->signature());
89 }
90 #endif // ndef PRODUCT
92 /**
93 * Perform a depth-first iteration over the class hierarchy, applying
94 * algorithmic logic as it goes.
95 *
96 * This class is one half of the inheritance hierarchy analysis mechanism.
97 * It is meant to be used in conjunction with another class, the algorithm,
98 * which is indicated by the ALGO template parameter. This class can be
99 * paired with any algorithm class that provides the required methods.
100 *
101 * This class contains all the mechanics for iterating over the class hierarchy
102 * starting at a particular root, without recursing (thus limiting stack growth
103 * from this point). It visits each superclass (if present) and superinterface
104 * in a depth-first manner, with callbacks to the ALGO class as each class is
105 * encountered (visit()), The algorithm can cut-off further exploration of a
106 * particular branch by returning 'false' from a visit() call.
107 *
108 * The ALGO class, must provide a visit() method, which each of which will be
109 * called once for each node in the inheritance tree during the iteration. In
110 * addition, it can provide a memory block via new_node_data(InstanceKlass*),
111 * which it can use for node-specific storage (and access via the
112 * current_data() and data_at_depth(int) methods).
113 *
114 * Bare minimum needed to be an ALGO class:
115 * class Algo : public HierarchyVisitor<Algo> {
116 * void* new_node_data(InstanceKlass* cls) { return NULL; }
117 * void free_node_data(void* data) { return; }
118 * bool visit() { return true; }
119 * };
120 */
121 template <class ALGO>
122 class HierarchyVisitor : StackObj {
123 private:
125 class Node : public ResourceObj {
126 public:
127 InstanceKlass* _class;
128 bool _super_was_visited;
129 int _interface_index;
130 void* _algorithm_data;
132 Node(InstanceKlass* cls, void* data, bool visit_super)
133 : _class(cls), _super_was_visited(!visit_super),
134 _interface_index(0), _algorithm_data(data) {}
136 int number_of_interfaces() { return _class->local_interfaces()->length(); }
137 int interface_index() { return _interface_index; }
138 void set_super_visited() { _super_was_visited = true; }
139 void increment_visited_interface() { ++_interface_index; }
140 void set_all_interfaces_visited() {
141 _interface_index = number_of_interfaces();
142 }
143 bool has_visited_super() { return _super_was_visited; }
144 bool has_visited_all_interfaces() {
145 return interface_index() >= number_of_interfaces();
146 }
147 InstanceKlass* interface_at(int index) {
148 return InstanceKlass::cast(_class->local_interfaces()->at(index));
149 }
150 InstanceKlass* next_super() { return _class->java_super(); }
151 InstanceKlass* next_interface() {
152 return interface_at(interface_index());
153 }
154 };
156 bool _cancelled;
157 GrowableArray<Node*> _path;
159 Node* current_top() const { return _path.top(); }
160 bool has_more_nodes() const { return !_path.is_empty(); }
161 void push(InstanceKlass* cls, void* data) {
162 assert(cls != NULL, "Requires a valid instance class");
163 Node* node = new Node(cls, data, has_super(cls));
164 _path.push(node);
165 }
166 void pop() { _path.pop(); }
168 void reset_iteration() {
169 _cancelled = false;
170 _path.clear();
171 }
172 bool is_cancelled() const { return _cancelled; }
174 static bool has_super(InstanceKlass* cls) {
175 return cls->super() != NULL && !cls->is_interface();
176 }
178 Node* node_at_depth(int i) const {
179 return (i >= _path.length()) ? NULL : _path.at(_path.length() - i - 1);
180 }
182 protected:
184 // Accessors available to the algorithm
185 int current_depth() const { return _path.length() - 1; }
187 InstanceKlass* class_at_depth(int i) {
188 Node* n = node_at_depth(i);
189 return n == NULL ? NULL : n->_class;
190 }
191 InstanceKlass* current_class() { return class_at_depth(0); }
193 void* data_at_depth(int i) {
194 Node* n = node_at_depth(i);
195 return n == NULL ? NULL : n->_algorithm_data;
196 }
197 void* current_data() { return data_at_depth(0); }
199 void cancel_iteration() { _cancelled = true; }
201 public:
203 void run(InstanceKlass* root) {
204 ALGO* algo = static_cast<ALGO*>(this);
206 reset_iteration();
208 void* algo_data = algo->new_node_data(root);
209 push(root, algo_data);
210 bool top_needs_visit = true;
212 do {
213 Node* top = current_top();
214 if (top_needs_visit) {
215 if (algo->visit() == false) {
216 // algorithm does not want to continue along this path. Arrange
217 // it so that this state is immediately popped off the stack
218 top->set_super_visited();
219 top->set_all_interfaces_visited();
220 }
221 top_needs_visit = false;
222 }
224 if (top->has_visited_super() && top->has_visited_all_interfaces()) {
225 algo->free_node_data(top->_algorithm_data);
226 pop();
227 } else {
228 InstanceKlass* next = NULL;
229 if (top->has_visited_super() == false) {
230 next = top->next_super();
231 top->set_super_visited();
232 } else {
233 next = top->next_interface();
234 top->increment_visited_interface();
235 }
236 assert(next != NULL, "Otherwise we shouldn't be here");
237 algo_data = algo->new_node_data(next);
238 push(next, algo_data);
239 top_needs_visit = true;
240 }
241 } while (!is_cancelled() && has_more_nodes());
242 }
243 };
245 #ifndef PRODUCT
246 class PrintHierarchy : public HierarchyVisitor<PrintHierarchy> {
247 public:
249 bool visit() {
250 InstanceKlass* cls = current_class();
251 streamIndentor si(tty, current_depth() * 2);
252 tty->indent().print_cr("%s", cls->name()->as_C_string());
253 return true;
254 }
256 void* new_node_data(InstanceKlass* cls) { return NULL; }
257 void free_node_data(void* data) { return; }
258 };
259 #endif // ndef PRODUCT
261 // Used to register InstanceKlass objects and all related metadata structures
262 // (Methods, ConstantPools) as "in-use" by the current thread so that they can't
263 // be deallocated by class redefinition while we're using them. The classes are
264 // de-registered when this goes out of scope.
265 //
266 // Once a class is registered, we need not bother with methodHandles or
267 // constantPoolHandles for it's associated metadata.
268 class KeepAliveRegistrar : public StackObj {
269 private:
270 Thread* _thread;
271 GrowableArray<ConstantPool*> _keep_alive;
273 public:
274 KeepAliveRegistrar(Thread* thread) : _thread(thread), _keep_alive(20) {
275 assert(thread == Thread::current(), "Must be current thread");
276 }
278 ~KeepAliveRegistrar() {
279 for (int i = _keep_alive.length() - 1; i >= 0; --i) {
280 ConstantPool* cp = _keep_alive.at(i);
281 int idx = _thread->metadata_handles()->find_from_end(cp);
282 assert(idx > 0, "Must be in the list");
283 _thread->metadata_handles()->remove_at(idx);
284 }
285 }
287 // Register a class as 'in-use' by the thread. It's fine to register a class
288 // multiple times (though perhaps inefficient)
289 void register_class(InstanceKlass* ik) {
290 ConstantPool* cp = ik->constants();
291 _keep_alive.push(cp);
292 _thread->metadata_handles()->push(cp);
293 }
294 };
296 class KeepAliveVisitor : public HierarchyVisitor<KeepAliveVisitor> {
297 private:
298 KeepAliveRegistrar* _registrar;
300 public:
301 KeepAliveVisitor(KeepAliveRegistrar* registrar) : _registrar(registrar) {}
303 void* new_node_data(InstanceKlass* cls) { return NULL; }
304 void free_node_data(void* data) { return; }
306 bool visit() {
307 _registrar->register_class(current_class());
308 return true;
309 }
310 };
313 // A method family contains a set of all methods that implement a single
314 // erased method. As members of the set are collected while walking over the
315 // hierarchy, they are tagged with a qualification state. The qualification
316 // state for an erased method is set to disqualified if there exists a path
317 // from the root of hierarchy to the method that contains an interleaving
318 // erased method defined in an interface.
320 class MethodFamily : public ResourceObj {
321 private:
323 GrowableArray<Pair<Method*,QualifiedState> > _members;
324 ResourceHashtable<Method*, int> _member_index;
326 Method* _selected_target; // Filled in later, if a unique target exists
327 Symbol* _exception_message; // If no unique target is found
329 bool contains_method(Method* method) {
330 int* lookup = _member_index.get(method);
331 return lookup != NULL;
332 }
334 void add_method(Method* method, QualifiedState state) {
335 Pair<Method*,QualifiedState> entry(method, state);
336 _member_index.put(method, _members.length());
337 _members.append(entry);
338 }
340 void disqualify_method(Method* method) {
341 int* index = _member_index.get(method);
342 guarantee(index != NULL && *index >= 0 && *index < _members.length(), "bad index");
343 _members.at(*index).second = DISQUALIFIED;
344 }
346 Symbol* generate_no_defaults_message(TRAPS) const;
347 Symbol* generate_abstract_method_message(Method* method, TRAPS) const;
348 Symbol* generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const;
350 public:
352 MethodFamily()
353 : _selected_target(NULL), _exception_message(NULL) {}
355 void set_target_if_empty(Method* m) {
356 if (_selected_target == NULL && !m->is_overpass()) {
357 _selected_target = m;
358 }
359 }
361 void record_qualified_method(Method* m) {
362 // If the method already exists in the set as qualified, this operation is
363 // redundant. If it already exists as disqualified, then we leave it as
364 // disqualfied. Thus we only add to the set if it's not already in the
365 // set.
366 if (!contains_method(m)) {
367 add_method(m, QUALIFIED);
368 }
369 }
371 void record_disqualified_method(Method* m) {
372 // If not in the set, add it as disqualified. If it's already in the set,
373 // then set the state to disqualified no matter what the previous state was.
374 if (!contains_method(m)) {
375 add_method(m, DISQUALIFIED);
376 } else {
377 disqualify_method(m);
378 }
379 }
381 bool has_target() const { return _selected_target != NULL; }
382 bool throws_exception() { return _exception_message != NULL; }
384 Method* get_selected_target() { return _selected_target; }
385 Symbol* get_exception_message() { return _exception_message; }
387 // Either sets the target or the exception error message
388 void determine_target(InstanceKlass* root, TRAPS) {
389 if (has_target() || throws_exception()) {
390 return;
391 }
393 GrowableArray<Method*> qualified_methods;
394 for (int i = 0; i < _members.length(); ++i) {
395 Pair<Method*,QualifiedState> entry = _members.at(i);
396 if (entry.second == QUALIFIED) {
397 qualified_methods.append(entry.first);
398 }
399 }
401 if (qualified_methods.length() == 0) {
402 _exception_message = generate_no_defaults_message(CHECK);
403 } else if (qualified_methods.length() == 1) {
404 Method* method = qualified_methods.at(0);
405 if (method->is_abstract()) {
406 _exception_message = generate_abstract_method_message(method, CHECK);
407 } else {
408 _selected_target = qualified_methods.at(0);
409 }
410 } else {
411 _exception_message = generate_conflicts_message(&qualified_methods,CHECK);
412 }
414 assert((has_target() ^ throws_exception()) == 1,
415 "One and only one must be true");
416 }
418 bool contains_signature(Symbol* query) {
419 for (int i = 0; i < _members.length(); ++i) {
420 if (query == _members.at(i).first->signature()) {
421 return true;
422 }
423 }
424 return false;
425 }
427 #ifndef PRODUCT
428 void print_sig_on(outputStream* str, Symbol* signature, int indent) const {
429 streamIndentor si(str, indent * 2);
431 str->indent().print_cr("Logical Method %s:", signature->as_C_string());
433 streamIndentor si2(str);
434 for (int i = 0; i < _members.length(); ++i) {
435 str->indent();
436 print_method(str, _members.at(i).first);
437 if (_members.at(i).second == DISQUALIFIED) {
438 str->print(" (disqualified)");
439 }
440 str->print_cr("");
441 }
443 if (_selected_target != NULL) {
444 print_selected(str, 1);
445 }
446 }
448 void print_selected(outputStream* str, int indent) const {
449 assert(has_target(), "Should be called otherwise");
450 streamIndentor si(str, indent * 2);
451 str->indent().print("Selected method: ");
452 print_method(str, _selected_target);
453 str->print_cr("");
454 }
456 void print_exception(outputStream* str, int indent) {
457 assert(throws_exception(), "Should be called otherwise");
458 streamIndentor si(str, indent * 2);
459 str->indent().print_cr("%s", _exception_message->as_C_string());
460 }
461 #endif // ndef PRODUCT
462 };
464 Symbol* MethodFamily::generate_no_defaults_message(TRAPS) const {
465 return SymbolTable::new_symbol("No qualifying defaults found", CHECK_NULL);
466 }
468 Symbol* MethodFamily::generate_abstract_method_message(Method* method, TRAPS) const {
469 Symbol* klass = method->klass_name();
470 Symbol* name = method->name();
471 Symbol* sig = method->signature();
472 stringStream ss;
473 ss.print("Method ");
474 ss.write((const char*)klass->bytes(), klass->utf8_length());
475 ss.print(".");
476 ss.write((const char*)name->bytes(), name->utf8_length());
477 ss.write((const char*)sig->bytes(), sig->utf8_length());
478 ss.print(" is abstract");
479 return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);
480 }
482 Symbol* MethodFamily::generate_conflicts_message(GrowableArray<Method*>* methods, TRAPS) const {
483 stringStream ss;
484 ss.print("Conflicting default methods:");
485 for (int i = 0; i < methods->length(); ++i) {
486 Method* method = methods->at(i);
487 Symbol* klass = method->klass_name();
488 Symbol* name = method->name();
489 ss.print(" ");
490 ss.write((const char*)klass->bytes(), klass->utf8_length());
491 ss.print(".");
492 ss.write((const char*)name->bytes(), name->utf8_length());
493 }
494 return SymbolTable::new_symbol(ss.base(), (int)ss.size(), CHECK_NULL);
495 }
498 class StateRestorer;
500 // StatefulMethodFamily is a wrapper around a MethodFamily that maintains the
501 // qualification state during hierarchy visitation, and applies that state
502 // when adding members to the MethodFamily
503 class StatefulMethodFamily : public ResourceObj {
504 friend class StateRestorer;
505 private:
506 QualifiedState _qualification_state;
508 void set_qualification_state(QualifiedState state) {
509 _qualification_state = state;
510 }
512 protected:
513 MethodFamily* _method_family;
515 public:
516 StatefulMethodFamily() {
517 _method_family = new MethodFamily();
518 _qualification_state = QUALIFIED;
519 }
521 StatefulMethodFamily(MethodFamily* mf) {
522 _method_family = mf;
523 _qualification_state = QUALIFIED;
524 }
526 void set_target_if_empty(Method* m) { _method_family->set_target_if_empty(m); }
528 MethodFamily* get_method_family() { return _method_family; }
530 StateRestorer* record_method_and_dq_further(Method* mo);
531 };
533 class StateRestorer : public PseudoScopeMark {
534 private:
535 StatefulMethodFamily* _method;
536 QualifiedState _state_to_restore;
537 public:
538 StateRestorer(StatefulMethodFamily* dm, QualifiedState state)
539 : _method(dm), _state_to_restore(state) {}
540 ~StateRestorer() { destroy(); }
541 void restore_state() { _method->set_qualification_state(_state_to_restore); }
542 virtual void destroy() { restore_state(); }
543 };
545 StateRestorer* StatefulMethodFamily::record_method_and_dq_further(Method* mo) {
546 StateRestorer* mark = new StateRestorer(this, _qualification_state);
547 if (_qualification_state == QUALIFIED) {
548 _method_family->record_qualified_method(mo);
549 } else {
550 _method_family->record_disqualified_method(mo);
551 }
552 // Everything found "above"??? this method in the hierarchy walk is set to
553 // disqualified
554 set_qualification_state(DISQUALIFIED);
555 return mark;
556 }
558 // Represents a location corresponding to a vtable slot for methods that
559 // neither the class nor any of it's ancestors provide an implementaion.
560 // Default methods may be present to fill this slot.
561 class EmptyVtableSlot : public ResourceObj {
562 private:
563 Symbol* _name;
564 Symbol* _signature;
565 int _size_of_parameters;
566 MethodFamily* _binding;
568 public:
569 EmptyVtableSlot(Method* method)
570 : _name(method->name()), _signature(method->signature()),
571 _size_of_parameters(method->size_of_parameters()), _binding(NULL) {}
573 Symbol* name() const { return _name; }
574 Symbol* signature() const { return _signature; }
575 int size_of_parameters() const { return _size_of_parameters; }
577 void bind_family(MethodFamily* lm) { _binding = lm; }
578 bool is_bound() { return _binding != NULL; }
579 MethodFamily* get_binding() { return _binding; }
581 #ifndef PRODUCT
582 void print_on(outputStream* str) const {
583 print_slot(str, name(), signature());
584 }
585 #endif // ndef PRODUCT
586 };
588 static GrowableArray<EmptyVtableSlot*>* find_empty_vtable_slots(
589 InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {
591 assert(klass != NULL, "Must be valid class");
593 GrowableArray<EmptyVtableSlot*>* slots = new GrowableArray<EmptyVtableSlot*>();
595 // All miranda methods are obvious candidates
596 for (int i = 0; i < mirandas->length(); ++i) {
597 EmptyVtableSlot* slot = new EmptyVtableSlot(mirandas->at(i));
598 slots->append(slot);
599 }
601 // Also any overpasses in our superclasses, that we haven't implemented.
602 // (can't use the vtable because it is not guaranteed to be initialized yet)
603 InstanceKlass* super = klass->java_super();
604 while (super != NULL) {
605 for (int i = 0; i < super->methods()->length(); ++i) {
606 Method* m = super->methods()->at(i);
607 if (m->is_overpass()) {
608 // m is a method that would have been a miranda if not for the
609 // default method processing that occurred on behalf of our superclass,
610 // so it's a method we want to re-examine in this new context. That is,
611 // unless we have a real implementation of it in the current class.
612 Method* impl = klass->lookup_method(m->name(), m->signature());
613 if (impl == NULL || impl->is_overpass()) {
614 slots->append(new EmptyVtableSlot(m));
615 }
616 }
617 }
618 super = super->java_super();
619 }
621 #ifndef PRODUCT
622 if (TraceDefaultMethods) {
623 tty->print_cr("Slots that need filling:");
624 streamIndentor si(tty);
625 for (int i = 0; i < slots->length(); ++i) {
626 tty->indent();
627 slots->at(i)->print_on(tty);
628 tty->print_cr("");
629 }
630 }
631 #endif // ndef PRODUCT
632 return slots;
633 }
635 // Iterates over the superinterface type hierarchy looking for all methods
636 // with a specific erased signature.
637 class FindMethodsByErasedSig : public HierarchyVisitor<FindMethodsByErasedSig> {
638 private:
639 // Context data
640 Symbol* _method_name;
641 Symbol* _method_signature;
642 StatefulMethodFamily* _family;
644 public:
645 FindMethodsByErasedSig(Symbol* name, Symbol* signature) :
646 _method_name(name), _method_signature(signature),
647 _family(NULL) {}
649 void get_discovered_family(MethodFamily** family) {
650 if (_family != NULL) {
651 *family = _family->get_method_family();
652 } else {
653 *family = NULL;
654 }
655 }
657 void* new_node_data(InstanceKlass* cls) { return new PseudoScope(); }
658 void free_node_data(void* node_data) {
659 PseudoScope::cast(node_data)->destroy();
660 }
662 // Find all methods on this hierarchy that match this
663 // method's erased (name, signature)
664 bool visit() {
665 PseudoScope* scope = PseudoScope::cast(current_data());
666 InstanceKlass* iklass = current_class();
668 Method* m = iklass->find_method(_method_name, _method_signature);
669 if (m != NULL) {
670 if (_family == NULL) {
671 _family = new StatefulMethodFamily();
672 }
674 if (iklass->is_interface()) {
675 StateRestorer* restorer = _family->record_method_and_dq_further(m);
676 scope->add_mark(restorer);
677 } else {
678 // This is the rule that methods in classes "win" (bad word) over
679 // methods in interfaces. This works because of single inheritance
680 _family->set_target_if_empty(m);
681 }
682 }
683 return true;
684 }
686 };
690 static void create_overpasses(
691 GrowableArray<EmptyVtableSlot*>* slots, InstanceKlass* klass, TRAPS);
693 static void generate_erased_defaults(
694 InstanceKlass* klass, GrowableArray<EmptyVtableSlot*>* empty_slots,
695 EmptyVtableSlot* slot, TRAPS) {
697 // sets up a set of methods with the same exact erased signature
698 FindMethodsByErasedSig visitor(slot->name(), slot->signature());
699 visitor.run(klass);
701 MethodFamily* family;
702 visitor.get_discovered_family(&family);
703 if (family != NULL) {
704 family->determine_target(klass, CHECK);
705 slot->bind_family(family);
706 }
707 }
709 static void merge_in_new_methods(InstanceKlass* klass,
710 GrowableArray<Method*>* new_methods, TRAPS);
712 // This is the guts of the default methods implementation. This is called just
713 // after the classfile has been parsed if some ancestor has default methods.
714 //
715 // First if finds any name/signature slots that need any implementation (either
716 // because they are miranda or a superclass's implementation is an overpass
717 // itself). For each slot, iterate over the hierarchy, to see if they contain a
718 // signature that matches the slot we are looking at.
719 //
720 // For each slot filled, we generate an overpass method that either calls the
721 // unique default method candidate using invokespecial, or throws an exception
722 // (in the case of no default method candidates, or more than one valid
723 // candidate). These methods are then added to the class's method list.
724 // The JVM does not create bridges nor handle generic signatures here.
725 void DefaultMethods::generate_default_methods(
726 InstanceKlass* klass, GrowableArray<Method*>* mirandas, TRAPS) {
728 // This resource mark is the bound for all memory allocation that takes
729 // place during default method processing. After this goes out of scope,
730 // all (Resource) objects' memory will be reclaimed. Be careful if adding an
731 // embedded resource mark under here as that memory can't be used outside
732 // whatever scope it's in.
733 ResourceMark rm(THREAD);
735 // Keep entire hierarchy alive for the duration of the computation
736 KeepAliveRegistrar keepAlive(THREAD);
737 KeepAliveVisitor loadKeepAlive(&keepAlive);
738 loadKeepAlive.run(klass);
740 #ifndef PRODUCT
741 if (TraceDefaultMethods) {
742 ResourceMark rm; // be careful with these!
743 tty->print_cr("Class %s requires default method processing",
744 klass->name()->as_klass_external_name());
745 PrintHierarchy printer;
746 printer.run(klass);
747 }
748 #endif // ndef PRODUCT
750 GrowableArray<EmptyVtableSlot*>* empty_slots =
751 find_empty_vtable_slots(klass, mirandas, CHECK);
753 for (int i = 0; i < empty_slots->length(); ++i) {
754 EmptyVtableSlot* slot = empty_slots->at(i);
755 #ifndef PRODUCT
756 if (TraceDefaultMethods) {
757 streamIndentor si(tty, 2);
758 tty->indent().print("Looking for default methods for slot ");
759 slot->print_on(tty);
760 tty->print_cr("");
761 }
762 #endif // ndef PRODUCT
764 generate_erased_defaults(klass, empty_slots, slot, CHECK);
765 }
766 #ifndef PRODUCT
767 if (TraceDefaultMethods) {
768 tty->print_cr("Creating overpasses...");
769 }
770 #endif // ndef PRODUCT
772 create_overpasses(empty_slots, klass, CHECK);
774 #ifndef PRODUCT
775 if (TraceDefaultMethods) {
776 tty->print_cr("Default method processing complete");
777 }
778 #endif // ndef PRODUCT
779 }
781 /**
782 * Interface inheritance rules were used to find a unique default method
783 * candidate for the resolved class. This
784 * method is only viable if it would also be in the set of default method
785 * candidates if we ran a full analysis on the current class.
786 *
787 * The only reason that the method would not be in the set of candidates for
788 * the current class is if that there's another matching method
789 * which is "more specific" than the found method -- i.e., one could find a
790 * path in the interface hierarchy in which the matching method appears
791 * before we get to '_target'.
792 *
793 * In order to determine this, we examine all of the implemented
794 * interfaces. If we find path that leads to the '_target' interface, then
795 * we examine that path to see if there are any methods that would shadow
796 * the selected method along that path.
797 */
798 class ShadowChecker : public HierarchyVisitor<ShadowChecker> {
799 protected:
800 Thread* THREAD;
802 InstanceKlass* _target;
804 Symbol* _method_name;
805 InstanceKlass* _method_holder;
806 bool _found_shadow;
809 public:
811 ShadowChecker(Thread* thread, Symbol* name, InstanceKlass* holder,
812 InstanceKlass* target)
813 : THREAD(thread), _method_name(name), _method_holder(holder),
814 _target(target), _found_shadow(false) {}
816 void* new_node_data(InstanceKlass* cls) { return NULL; }
817 void free_node_data(void* data) { return; }
819 bool visit() {
820 InstanceKlass* ik = current_class();
821 if (ik == _target && current_depth() == 1) {
822 return false; // This was the specified super -- no need to search it
823 }
824 if (ik == _method_holder || ik == _target) {
825 // We found a path that should be examined to see if it shadows _method
826 if (path_has_shadow()) {
827 _found_shadow = true;
828 cancel_iteration();
829 }
830 return false; // no need to continue up hierarchy
831 }
832 return true;
833 }
835 virtual bool path_has_shadow() = 0;
836 bool found_shadow() { return _found_shadow; }
837 };
839 // Used for Invokespecial.
840 // Invokespecial is allowed to invoke a concrete interface method
841 // and can be used to disambuiguate among qualified candidates,
842 // which are methods in immediate superinterfaces,
843 // but may not be used to invoke a candidate that would be shadowed
844 // from the perspective of the caller.
845 // Invokespecial is also used in the overpass generation today
846 // We re-run the shadowchecker because we can't distinguish this case,
847 // but it should return the same answer, since the overpass target
848 // is now the invokespecial caller.
849 class ErasedShadowChecker : public ShadowChecker {
850 private:
851 bool path_has_shadow() {
853 for (int i = current_depth() - 1; i > 0; --i) {
854 InstanceKlass* ik = class_at_depth(i);
856 if (ik->is_interface()) {
857 int end;
858 int start = ik->find_method_by_name(_method_name, &end);
859 if (start != -1) {
860 return true;
861 }
862 }
863 }
864 return false;
865 }
866 public:
868 ErasedShadowChecker(Thread* thread, Symbol* name, InstanceKlass* holder,
869 InstanceKlass* target)
870 : ShadowChecker(thread, name, holder, target) {}
871 };
874 // Find the unique qualified candidate from the perspective of the super_class
875 // which is the resolved_klass, which must be an immediate superinterface
876 // of klass
877 Method* find_erased_super_default(InstanceKlass* current_class, InstanceKlass* super_class, Symbol* method_name, Symbol* sig, TRAPS) {
879 FindMethodsByErasedSig visitor(method_name, sig);
880 visitor.run(super_class); // find candidates from resolved_klass
882 MethodFamily* family;
883 visitor.get_discovered_family(&family);
885 if (family != NULL) {
886 family->determine_target(current_class, CHECK_NULL); // get target from current_class
887 }
889 if (family->has_target()) {
890 Method* target = family->get_selected_target();
891 InstanceKlass* holder = InstanceKlass::cast(target->method_holder());
893 // Verify that the identified method is valid from the context of
894 // the current class, which is the caller class for invokespecial
895 // link resolution, i.e. ensure there it is not shadowed.
896 // You can use invokespecial to disambiguate interface methods, but
897 // you can not use it to skip over an interface method that would shadow it.
898 ErasedShadowChecker checker(THREAD, target->name(), holder, super_class);
899 checker.run(current_class);
901 if (checker.found_shadow()) {
902 #ifndef PRODUCT
903 if (TraceDefaultMethods) {
904 tty->print_cr(" Only candidate found was shadowed.");
905 }
906 #endif // ndef PRODUCT
907 THROW_MSG_(vmSymbols::java_lang_AbstractMethodError(),
908 "Accessible default method not found", NULL);
909 } else {
910 #ifndef PRODUCT
911 if (TraceDefaultMethods) {
912 family->print_sig_on(tty, target->signature(), 1);
913 }
914 #endif // ndef PRODUCT
915 return target;
916 }
917 } else {
918 assert(family->throws_exception(), "must have target or throw");
919 THROW_MSG_(vmSymbols::java_lang_AbstractMethodError(),
920 family->get_exception_message()->as_C_string(), NULL);
921 }
922 }
924 // This is called during linktime when we find an invokespecial call that
925 // refers to a direct superinterface. It indicates that we should find the
926 // default method in the hierarchy of that superinterface, and if that method
927 // would have been a candidate from the point of view of 'this' class, then we
928 // return that method.
929 // This logic assumes that the super is a direct superclass of the caller
930 Method* DefaultMethods::find_super_default(
931 Klass* cls, Klass* super, Symbol* method_name, Symbol* sig, TRAPS) {
933 ResourceMark rm(THREAD);
935 assert(cls != NULL && super != NULL, "Need real classes");
937 InstanceKlass* current_class = InstanceKlass::cast(cls);
938 InstanceKlass* super_class = InstanceKlass::cast(super);
940 // Keep entire hierarchy alive for the duration of the computation
941 KeepAliveRegistrar keepAlive(THREAD);
942 KeepAliveVisitor loadKeepAlive(&keepAlive);
943 loadKeepAlive.run(current_class); // get hierarchy from current class
945 #ifndef PRODUCT
946 if (TraceDefaultMethods) {
947 tty->print_cr("Finding super default method %s.%s%s from %s",
948 super_class->name()->as_C_string(),
949 method_name->as_C_string(), sig->as_C_string(),
950 current_class->name()->as_C_string());
951 }
952 #endif // ndef PRODUCT
954 assert(super_class->is_interface(), "only call for default methods");
956 Method* target = NULL;
957 target = find_erased_super_default(current_class, super_class,
958 method_name, sig, CHECK_NULL);
960 #ifndef PRODUCT
961 if (target != NULL) {
962 if (TraceDefaultMethods) {
963 tty->print(" Returning ");
964 print_method(tty, target, true);
965 tty->print_cr("");
966 }
967 }
968 #endif // ndef PRODUCT
969 return target;
970 }
972 #ifndef PRODUCT
973 // Return true is broad type is a covariant return of narrow type
974 static bool covariant_return_type(BasicType narrow, BasicType broad) {
975 if (narrow == broad) {
976 return true;
977 }
978 if (broad == T_OBJECT) {
979 return true;
980 }
981 return false;
982 }
983 #endif // ndef PRODUCT
985 static int assemble_redirect(
986 BytecodeConstantPool* cp, BytecodeBuffer* buffer,
987 Symbol* incoming, Method* target, TRAPS) {
989 BytecodeAssembler assem(buffer, cp);
991 SignatureStream in(incoming, true);
992 SignatureStream out(target->signature(), true);
993 u2 parameter_count = 0;
995 assem.aload(parameter_count++); // load 'this'
997 while (!in.at_return_type()) {
998 assert(!out.at_return_type(), "Parameter counts do not match");
999 BasicType bt = in.type();
1000 assert(out.type() == bt, "Parameter types are not compatible");
1001 assem.load(bt, parameter_count);
1002 if (in.is_object() && in.as_symbol(THREAD) != out.as_symbol(THREAD)) {
1003 assem.checkcast(out.as_symbol(THREAD));
1004 } else if (bt == T_LONG || bt == T_DOUBLE) {
1005 ++parameter_count; // longs and doubles use two slots
1006 }
1007 ++parameter_count;
1008 in.next();
1009 out.next();
1010 }
1011 assert(out.at_return_type(), "Parameter counts do not match");
1012 assert(covariant_return_type(out.type(), in.type()), "Return types are not compatible");
1014 if (parameter_count == 1 && (in.type() == T_LONG || in.type() == T_DOUBLE)) {
1015 ++parameter_count; // need room for return value
1016 }
1017 if (target->method_holder()->is_interface()) {
1018 assem.invokespecial(target);
1019 } else {
1020 assem.invokevirtual(target);
1021 }
1023 if (in.is_object() && in.as_symbol(THREAD) != out.as_symbol(THREAD)) {
1024 assem.checkcast(in.as_symbol(THREAD));
1025 }
1026 assem._return(in.type());
1027 return parameter_count;
1028 }
1030 static int assemble_abstract_method_error(
1031 BytecodeConstantPool* cp, BytecodeBuffer* buffer, Symbol* message, TRAPS) {
1033 Symbol* errorName = vmSymbols::java_lang_AbstractMethodError();
1034 Symbol* init = vmSymbols::object_initializer_name();
1035 Symbol* sig = vmSymbols::string_void_signature();
1037 BytecodeAssembler assem(buffer, cp);
1039 assem._new(errorName);
1040 assem.dup();
1041 assem.load_string(message);
1042 assem.invokespecial(errorName, init, sig);
1043 assem.athrow();
1045 return 3; // max stack size: [ exception, exception, string ]
1046 }
1048 static Method* new_method(
1049 BytecodeConstantPool* cp, BytecodeBuffer* bytecodes, Symbol* name,
1050 Symbol* sig, AccessFlags flags, int max_stack, int params,
1051 ConstMethod::MethodType mt, TRAPS) {
1053 address code_start = 0;
1054 int code_length = 0;
1055 InlineTableSizes sizes;
1057 if (bytecodes != NULL && bytecodes->length() > 0) {
1058 code_start = static_cast<address>(bytecodes->adr_at(0));
1059 code_length = bytecodes->length();
1060 }
1062 Method* m = Method::allocate(cp->pool_holder()->class_loader_data(),
1063 code_length, flags, &sizes,
1064 mt, CHECK_NULL);
1066 m->set_constants(NULL); // This will get filled in later
1067 m->set_name_index(cp->utf8(name));
1068 m->set_signature_index(cp->utf8(sig));
1069 #ifdef CC_INTERP
1070 ResultTypeFinder rtf(sig);
1071 m->set_result_index(rtf.type());
1072 #endif
1073 m->set_size_of_parameters(params);
1074 m->set_max_stack(max_stack);
1075 m->set_max_locals(params);
1076 m->constMethod()->set_stackmap_data(NULL);
1077 m->set_code(code_start);
1078 m->set_force_inline(true);
1080 return m;
1081 }
1083 static void switchover_constant_pool(BytecodeConstantPool* bpool,
1084 InstanceKlass* klass, GrowableArray<Method*>* new_methods, TRAPS) {
1086 if (new_methods->length() > 0) {
1087 ConstantPool* cp = bpool->create_constant_pool(CHECK);
1088 if (cp != klass->constants()) {
1089 klass->class_loader_data()->add_to_deallocate_list(klass->constants());
1090 klass->set_constants(cp);
1091 cp->set_pool_holder(klass);
1093 for (int i = 0; i < new_methods->length(); ++i) {
1094 new_methods->at(i)->set_constants(cp);
1095 }
1096 for (int i = 0; i < klass->methods()->length(); ++i) {
1097 Method* mo = klass->methods()->at(i);
1098 mo->set_constants(cp);
1099 }
1100 }
1101 }
1102 }
1104 // A "bridge" is a method created by javac to bridge the gap between
1105 // an implementation and a generically-compatible, but different, signature.
1106 // Bridges have actual bytecode implementation in classfiles.
1107 // An "overpass", on the other hand, performs the same function as a bridge
1108 // but does not occur in a classfile; the VM creates overpass itself,
1109 // when it needs a path to get from a call site to an default method, and
1110 // a bridge doesn't exist.
1111 static void create_overpasses(
1112 GrowableArray<EmptyVtableSlot*>* slots,
1113 InstanceKlass* klass, TRAPS) {
1115 GrowableArray<Method*> overpasses;
1116 BytecodeConstantPool bpool(klass->constants());
1118 for (int i = 0; i < slots->length(); ++i) {
1119 EmptyVtableSlot* slot = slots->at(i);
1121 if (slot->is_bound()) {
1122 MethodFamily* method = slot->get_binding();
1123 int max_stack = 0;
1124 BytecodeBuffer buffer;
1126 #ifndef PRODUCT
1127 if (TraceDefaultMethods) {
1128 tty->print("for slot: ");
1129 slot->print_on(tty);
1130 tty->print_cr("");
1131 if (method->has_target()) {
1132 method->print_selected(tty, 1);
1133 } else {
1134 method->print_exception(tty, 1);
1135 }
1136 }
1137 #endif // ndef PRODUCT
1138 if (method->has_target()) {
1139 Method* selected = method->get_selected_target();
1140 max_stack = assemble_redirect(
1141 &bpool, &buffer, slot->signature(), selected, CHECK);
1142 } else if (method->throws_exception()) {
1143 max_stack = assemble_abstract_method_error(
1144 &bpool, &buffer, method->get_exception_message(), CHECK);
1145 }
1146 AccessFlags flags = accessFlags_from(
1147 JVM_ACC_PUBLIC | JVM_ACC_SYNTHETIC | JVM_ACC_BRIDGE);
1148 Method* m = new_method(&bpool, &buffer, slot->name(), slot->signature(),
1149 flags, max_stack, slot->size_of_parameters(),
1150 ConstMethod::OVERPASS, CHECK);
1151 if (m != NULL) {
1152 overpasses.push(m);
1153 }
1154 }
1155 }
1157 #ifndef PRODUCT
1158 if (TraceDefaultMethods) {
1159 tty->print_cr("Created %d overpass methods", overpasses.length());
1160 }
1161 #endif // ndef PRODUCT
1163 switchover_constant_pool(&bpool, klass, &overpasses, CHECK);
1164 merge_in_new_methods(klass, &overpasses, CHECK);
1165 }
1167 static void sort_methods(GrowableArray<Method*>* methods) {
1168 // Note that this must sort using the same key as is used for sorting
1169 // methods in InstanceKlass.
1170 bool sorted = true;
1171 for (int i = methods->length() - 1; i > 0; --i) {
1172 for (int j = 0; j < i; ++j) {
1173 Method* m1 = methods->at(j);
1174 Method* m2 = methods->at(j + 1);
1175 if ((uintptr_t)m1->name() > (uintptr_t)m2->name()) {
1176 methods->at_put(j, m2);
1177 methods->at_put(j + 1, m1);
1178 sorted = false;
1179 }
1180 }
1181 if (sorted) break;
1182 sorted = true;
1183 }
1184 #ifdef ASSERT
1185 uintptr_t prev = 0;
1186 for (int i = 0; i < methods->length(); ++i) {
1187 Method* mh = methods->at(i);
1188 uintptr_t nv = (uintptr_t)mh->name();
1189 assert(nv >= prev, "Incorrect overpass method ordering");
1190 prev = nv;
1191 }
1192 #endif
1193 }
1195 static void merge_in_new_methods(InstanceKlass* klass,
1196 GrowableArray<Method*>* new_methods, TRAPS) {
1198 enum { ANNOTATIONS, PARAMETERS, DEFAULTS, NUM_ARRAYS };
1200 Array<Method*>* original_methods = klass->methods();
1201 Array<int>* original_ordering = klass->method_ordering();
1202 Array<int>* merged_ordering = Universe::the_empty_int_array();
1204 int new_size = klass->methods()->length() + new_methods->length();
1206 Array<Method*>* merged_methods = MetadataFactory::new_array<Method*>(
1207 klass->class_loader_data(), new_size, NULL, CHECK);
1209 if (original_ordering != NULL && original_ordering->length() > 0) {
1210 merged_ordering = MetadataFactory::new_array<int>(
1211 klass->class_loader_data(), new_size, CHECK);
1212 }
1213 int method_order_index = klass->methods()->length();
1215 sort_methods(new_methods);
1217 // Perform grand merge of existing methods and new methods
1218 int orig_idx = 0;
1219 int new_idx = 0;
1221 for (int i = 0; i < new_size; ++i) {
1222 Method* orig_method = NULL;
1223 Method* new_method = NULL;
1224 if (orig_idx < original_methods->length()) {
1225 orig_method = original_methods->at(orig_idx);
1226 }
1227 if (new_idx < new_methods->length()) {
1228 new_method = new_methods->at(new_idx);
1229 }
1231 if (orig_method != NULL &&
1232 (new_method == NULL || orig_method->name() < new_method->name())) {
1233 merged_methods->at_put(i, orig_method);
1234 original_methods->at_put(orig_idx, NULL);
1235 if (merged_ordering->length() > 0) {
1236 merged_ordering->at_put(i, original_ordering->at(orig_idx));
1237 }
1238 ++orig_idx;
1239 } else {
1240 merged_methods->at_put(i, new_method);
1241 if (merged_ordering->length() > 0) {
1242 merged_ordering->at_put(i, method_order_index++);
1243 }
1244 ++new_idx;
1245 }
1246 // update idnum for new location
1247 merged_methods->at(i)->set_method_idnum(i);
1248 }
1250 // Verify correct order
1251 #ifdef ASSERT
1252 uintptr_t prev = 0;
1253 for (int i = 0; i < merged_methods->length(); ++i) {
1254 Method* mo = merged_methods->at(i);
1255 uintptr_t nv = (uintptr_t)mo->name();
1256 assert(nv >= prev, "Incorrect method ordering");
1257 prev = nv;
1258 }
1259 #endif
1261 // Replace klass methods with new merged lists
1262 klass->set_methods(merged_methods);
1263 klass->set_initial_method_idnum(new_size);
1265 ClassLoaderData* cld = klass->class_loader_data();
1266 MetadataFactory::free_array(cld, original_methods);
1267 if (original_ordering->length() > 0) {
1268 klass->set_method_ordering(merged_ordering);
1269 MetadataFactory::free_array(cld, original_ordering);
1270 }
1271 }