1 /*
2 * Copyright (c) 1997, 2024, 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 */
24
25 #include "precompiled.hpp"
26 #include "cds/archiveHeapLoader.hpp"
27 #include "cds/cdsConfig.hpp"
28 #include "cds/heapShared.hpp"
29 #include "classfile/classLoader.hpp"
30 #include "classfile/classLoaderData.inline.hpp"
31 #include "classfile/classLoaderDataGraph.inline.hpp"
32 #include "classfile/javaClasses.inline.hpp"
33 #include "classfile/moduleEntry.hpp"
34 #include "classfile/systemDictionary.hpp"
35 #include "classfile/systemDictionaryShared.hpp"
36 #include "classfile/vmClasses.hpp"
37 #include "classfile/vmSymbols.hpp"
38 #include "gc/shared/collectedHeap.inline.hpp"
39 #include "jvm_io.h"
40 #include "logging/log.hpp"
41 #include "memory/metadataFactory.hpp"
42 #include "memory/metaspaceClosure.hpp"
43 #include "memory/oopFactory.hpp"
44 #include "memory/resourceArea.hpp"
45 #include "memory/universe.hpp"
46 #include "oops/compressedOops.inline.hpp"
47 #include "oops/instanceKlass.hpp"
48 #include "oops/klass.inline.hpp"
49 #include "oops/objArrayKlass.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/oopHandle.inline.hpp"
52 #include "prims/jvmtiExport.hpp"
53 #include "runtime/atomic.hpp"
54 #include "runtime/handles.inline.hpp"
55 #include "runtime/perfData.hpp"
56 #include "utilities/macros.hpp"
57 #include "utilities/powerOfTwo.hpp"
58 #include "utilities/rotate_bits.hpp"
59 #include "utilities/stack.inline.hpp"
60
61 void Klass::set_java_mirror(Handle m) {
62 assert(!m.is_null(), "New mirror should never be null.");
63 assert(_java_mirror.is_empty(), "should only be used to initialize mirror");
64 _java_mirror = class_loader_data()->add_handle(m);
65 }
66
67 bool Klass::is_cloneable() const {
68 return _access_flags.is_cloneable_fast() ||
69 is_subtype_of(vmClasses::Cloneable_klass());
70 }
71
72 void Klass::set_is_cloneable() {
73 if (name() == vmSymbols::java_lang_invoke_MemberName()) {
74 assert(is_final(), "no subclasses allowed");
75 // MemberName cloning should not be intrinsified and always happen in JVM_Clone.
76 } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {
77 // Reference cloning should not be intrinsified and always happen in JVM_Clone.
78 } else {
79 _access_flags.set_is_cloneable_fast();
80 }
81 }
82
83 uint8_t Klass::compute_hash_slot(Symbol* n) {
84 uint hash_code;
85 // Special cases for the two superclasses of all Array instances.
86 // Code elsewhere assumes, for all instances of ArrayKlass, that
87 // these two interfaces will be in this order.
88
89 // We ensure there are some empty slots in the hash table between
90 // these two very common interfaces because if they were adjacent
91 // (e.g. Slots 0 and 1), then any other class which hashed to 0 or 1
92 // would result in a probe length of 3.
93 if (n == vmSymbols::java_lang_Cloneable()) {
94 hash_code = 0;
95 } else if (n == vmSymbols::java_io_Serializable()) {
96 hash_code = SECONDARY_SUPERS_TABLE_SIZE / 2;
97 } else {
98 auto s = (const jbyte*) n->bytes();
99 hash_code = java_lang_String::hash_code(s, n->utf8_length());
100 // We use String::hash_code here (rather than e.g.
101 // Symbol::identity_hash()) in order to have a hash code that
102 // does not change from run to run. We want that because the
103 // hash value for a secondary superclass appears in generated
104 // code as a constant.
105
106 // This constant is magic: see Knuth, "Fibonacci Hashing".
107 constexpr uint multiplier
108 = 2654435769; // (uint)(((u8)1 << 32) / ((1 + sqrt(5)) / 2 ))
109 constexpr uint hash_shift = sizeof(hash_code) * 8 - 6;
110 // The leading bits of the least significant half of the product.
111 hash_code = (hash_code * multiplier) >> hash_shift;
112
113 if (StressSecondarySupers) {
114 // Generate many hash collisions in order to stress-test the
115 // linear search fallback.
116 hash_code = hash_code % 3;
117 hash_code = hash_code * (SECONDARY_SUPERS_TABLE_SIZE / 3);
118 }
119 }
120
121 return (hash_code & SECONDARY_SUPERS_TABLE_MASK);
122 }
123
124 void Klass::set_name(Symbol* n) {
125 _name = n;
126
127 if (_name != nullptr) {
128 _name->increment_refcount();
129 }
130
131 if (UseSecondarySupersTable) {
132 elapsedTimer selftime;
133 selftime.start();
134
135 _hash_slot = compute_hash_slot(n);
136 assert(_hash_slot < SECONDARY_SUPERS_TABLE_SIZE, "required");
137
138 selftime.stop();
139 if (UsePerfData) {
140 ClassLoader::perf_secondary_hash_time()->inc(selftime.ticks());
141 }
142 }
143
144 if (CDSConfig::is_dumping_archive() && is_instance_klass()) {
145 SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
146 }
147 }
148
149 bool Klass::is_subclass_of(const Klass* k) const {
150 // Run up the super chain and check
151 if (this == k) return true;
152
153 Klass* t = const_cast<Klass*>(this)->super();
154
155 while (t != nullptr) {
156 if (t == k) return true;
157 t = t->super();
158 }
159 return false;
160 }
161
162 void Klass::release_C_heap_structures(bool release_constant_pool) {
163 if (_name != nullptr) _name->decrement_refcount();
164 }
165
166 bool Klass::search_secondary_supers(Klass* k) const {
167 // Put some extra logic here out-of-line, before the search proper.
168 // This cuts down the size of the inline method.
169
170 // This is necessary, since I am never in my own secondary_super list.
171 if (this == k)
172 return true;
173 // Scan the array-of-objects for a match
174 int cnt = secondary_supers()->length();
175 for (int i = 0; i < cnt; i++) {
176 if (secondary_supers()->at(i) == k) {
177 ((Klass*)this)->set_secondary_super_cache(k);
178 return true;
179 }
180 }
181 return false;
182 }
183
184 // Return self, except for abstract classes with exactly 1
185 // implementor. Then return the 1 concrete implementation.
186 Klass *Klass::up_cast_abstract() {
187 Klass *r = this;
188 while( r->is_abstract() ) { // Receiver is abstract?
189 Klass *s = r->subklass(); // Check for exactly 1 subklass
190 if (s == nullptr || s->next_sibling() != nullptr) // Oops; wrong count; give up
191 return this; // Return 'this' as a no-progress flag
192 r = s; // Loop till find concrete class
193 }
194 return r; // Return the 1 concrete class
195 }
196
197 // Find LCA in class hierarchy
198 Klass *Klass::LCA( Klass *k2 ) {
199 Klass *k1 = this;
200 while( 1 ) {
201 if( k1->is_subtype_of(k2) ) return k2;
202 if( k2->is_subtype_of(k1) ) return k1;
203 k1 = k1->super();
204 k2 = k2->super();
205 }
206 }
207
208
209 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
210 ResourceMark rm(THREAD);
211 THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
212 : vmSymbols::java_lang_InstantiationException(), external_name());
213 }
214
215
216 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
217 ResourceMark rm(THREAD);
218 assert(s != nullptr, "Throw NPE!");
219 THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
220 err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
221 }
222
223
224 void Klass::initialize(TRAPS) {
225 ShouldNotReachHere();
226 }
227
228 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
229 #ifdef ASSERT
230 tty->print_cr("Error: find_field called on a klass oop."
231 " Likely error: reflection method does not correctly"
232 " wrap return value in a mirror object.");
233 #endif
234 ShouldNotReachHere();
235 return nullptr;
236 }
237
238 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
239 OverpassLookupMode overpass_mode,
240 PrivateLookupMode private_mode) const {
241 #ifdef ASSERT
242 tty->print_cr("Error: uncached_lookup_method called on a klass oop."
243 " Likely error: reflection method does not correctly"
244 " wrap return value in a mirror object.");
245 #endif
246 ShouldNotReachHere();
247 return nullptr;
248 }
249
250 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
251 return Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);
252 }
253
254 static markWord make_prototype(Klass* kls) {
255 markWord prototype = markWord::prototype();
256 #ifdef _LP64
257 if (UseCompactObjectHeaders) {
258 prototype = prototype.set_klass(kls);
259 }
260 #endif
261 return prototype;
262 }
263
264 Klass::Klass() : _kind(UnknownKlassKind) {
265 assert(CDSConfig::is_dumping_static_archive() || CDSConfig::is_using_archive(), "only for cds");
266 }
267
268 // "Normal" instantiation is preceded by a MetaspaceObj allocation
269 // which zeros out memory - calloc equivalent.
270 // The constructor is also used from CppVtableCloner,
271 // which doesn't zero out the memory before calling the constructor.
272 Klass::Klass(KlassKind kind) : _kind(kind),
273 _prototype_header(make_prototype(this)),
274 _shared_class_path_index(-1) {
275 CDS_ONLY(_shared_class_flags = 0;)
276 CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
277 _primary_supers[0] = this;
278 set_super_check_offset(in_bytes(primary_supers_offset()));
279 }
280
281 jint Klass::array_layout_helper(BasicType etype) {
282 assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
283 // Note that T_ARRAY is not allowed here.
284 int hsize = arrayOopDesc::base_offset_in_bytes(etype);
285 int esize = type2aelembytes(etype);
286 bool isobj = (etype == T_OBJECT);
287 int tag = isobj ? _lh_array_tag_obj_value : _lh_array_tag_type_value;
288 int lh = array_layout_helper(tag, hsize, etype, exact_log2(esize));
289
290 assert(lh < (int)_lh_neutral_value, "must look like an array layout");
291 assert(layout_helper_is_array(lh), "correct kind");
292 assert(layout_helper_is_objArray(lh) == isobj, "correct kind");
293 assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
294 assert(layout_helper_header_size(lh) == hsize, "correct decode");
295 assert(layout_helper_element_type(lh) == etype, "correct decode");
296 assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
297
298 return lh;
299 }
300
301 bool Klass::can_be_primary_super_slow() const {
302 if (super() == nullptr)
303 return true;
304 else if (super()->super_depth() >= primary_super_limit()-1)
305 return false;
306 else
307 return true;
308 }
309
310 void Klass::set_secondary_supers(Array<Klass*>* secondaries) {
311 assert(!UseSecondarySupersTable || secondaries == nullptr, "");
312 set_secondary_supers(secondaries, SECONDARY_SUPERS_BITMAP_EMPTY);
313 }
314
315 void Klass::set_secondary_supers(Array<Klass*>* secondaries, uintx bitmap) {
316 #ifdef ASSERT
317 if (UseSecondarySupersTable && secondaries != nullptr) {
318 uintx real_bitmap = compute_secondary_supers_bitmap(secondaries);
319 assert(bitmap == real_bitmap, "must be");
320 }
321 #endif
322 _bitmap = bitmap;
323 _secondary_supers = secondaries;
324
325 if (secondaries != nullptr) {
326 LogMessage(class, load) msg;
327 NonInterleavingLogStream log {LogLevel::Debug, msg};
328 if (log.is_enabled()) {
329 ResourceMark rm;
330 log.print_cr("set_secondary_supers: hash_slot: %d; klass: %s", hash_slot(), external_name());
331 print_secondary_supers_on(&log);
332 }
333 }
334 }
335
336 // Hashed secondary superclasses
337 //
338 // We use a compressed 64-entry hash table with linear probing. We
339 // start by creating a hash table in the usual way, followed by a pass
340 // that removes all the null entries. To indicate which entries would
341 // have been null we use a bitmap that contains a 1 in each position
342 // where an entry is present, 0 otherwise. This bitmap also serves as
343 // a kind of Bloom filter, which in many cases allows us quickly to
344 // eliminate the possibility that something is a member of a set of
345 // secondaries.
346 uintx Klass::hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite) {
347 const int length = secondaries->length();
348
349 if (length == 0) {
350 return SECONDARY_SUPERS_BITMAP_EMPTY;
351 }
352
353 if (length == 1) {
354 int hash_slot = secondaries->at(0)->hash_slot();
355 return uintx(1) << hash_slot;
356 }
357
358 // For performance reasons we don't use a hashed table unless there
359 // are at least two empty slots in it. If there were only one empty
360 // slot it'd take a long time to create the table and the resulting
361 // search would be no faster than linear probing.
362 if (length > SECONDARY_SUPERS_TABLE_SIZE - 2) {
363 return SECONDARY_SUPERS_BITMAP_FULL;
364 }
365
366 {
367 PerfTraceTime ptt(ClassLoader::perf_secondary_hash_time());
368
369 ResourceMark rm;
370 uintx bitmap = SECONDARY_SUPERS_BITMAP_EMPTY;
371 auto hashed_secondaries = new GrowableArray<Klass*>(SECONDARY_SUPERS_TABLE_SIZE,
372 SECONDARY_SUPERS_TABLE_SIZE, nullptr);
373
374 for (int j = 0; j < length; j++) {
375 Klass* k = secondaries->at(j);
376 hash_insert(k, hashed_secondaries, bitmap);
377 }
378
379 // Pack the hashed secondaries array by copying it into the
380 // secondaries array, sans nulls, if modification is allowed.
381 // Otherwise, validate the order.
382 int i = 0;
383 for (int slot = 0; slot < SECONDARY_SUPERS_TABLE_SIZE; slot++) {
384 bool has_element = ((bitmap >> slot) & 1) != 0;
385 assert(has_element == (hashed_secondaries->at(slot) != nullptr), "");
386 if (has_element) {
387 Klass* k = hashed_secondaries->at(slot);
388 if (rewrite) {
389 secondaries->at_put(i, k);
390 } else if (secondaries->at(i) != k) {
391 assert(false, "broken secondary supers hash table");
392 return SECONDARY_SUPERS_BITMAP_FULL;
393 }
394 i++;
395 }
396 }
397 assert(i == secondaries->length(), "mismatch");
398
399 return bitmap;
400 }
401 }
402
403 void Klass::hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap) {
404 assert(bitmap != SECONDARY_SUPERS_BITMAP_FULL, "");
405
406 int dist = 0;
407 for (int slot = klass->hash_slot(); true; slot = (slot + 1) & SECONDARY_SUPERS_TABLE_MASK) {
408 Klass* existing = secondaries->at(slot);
409 assert(((bitmap >> slot) & 1) == (existing != nullptr), "mismatch");
410 if (existing == nullptr) { // no conflict
411 secondaries->at_put(slot, klass);
412 bitmap |= uintx(1) << slot;
413 assert(bitmap != SECONDARY_SUPERS_BITMAP_FULL, "");
414 return;
415 } else {
416 // Use Robin Hood hashing to minimize the worst case search.
417 // Also, every permutation of the insertion sequence produces
418 // the same final Robin Hood hash table, provided that a
419 // consistent tie breaker is used.
420 int existing_dist = (slot - existing->hash_slot()) & SECONDARY_SUPERS_TABLE_MASK;
421 if (existing_dist < dist
422 // This tie breaker ensures that the hash order is maintained.
423 || ((existing_dist == dist)
424 && (uintptr_t(existing) < uintptr_t(klass)))) {
425 Klass* tmp = secondaries->at(slot);
426 secondaries->at_put(slot, klass);
427 klass = tmp;
428 dist = existing_dist;
429 }
430 ++dist;
431 }
432 }
433 }
434
435 Array<Klass*>* Klass::pack_secondary_supers(ClassLoaderData* loader_data,
436 GrowableArray<Klass*>* primaries,
437 GrowableArray<Klass*>* secondaries,
438 uintx& bitmap, TRAPS) {
439 int new_length = primaries->length() + secondaries->length();
440 Array<Klass*>* secondary_supers = MetadataFactory::new_array<Klass*>(loader_data, new_length, CHECK_NULL);
441
442 // Combine the two arrays into a metadata object to pack the array.
443 // The primaries are added in the reverse order, then the secondaries.
444 int fill_p = primaries->length();
445 for (int j = 0; j < fill_p; j++) {
446 secondary_supers->at_put(j, primaries->pop()); // add primaries in reverse order.
447 }
448 for( int j = 0; j < secondaries->length(); j++ ) {
449 secondary_supers->at_put(j+fill_p, secondaries->at(j)); // add secondaries on the end.
450 }
451 #ifdef ASSERT
452 // We must not copy any null placeholders left over from bootstrap.
453 for (int j = 0; j < secondary_supers->length(); j++) {
454 assert(secondary_supers->at(j) != nullptr, "correct bootstrapping order");
455 }
456 #endif
457
458 if (UseSecondarySupersTable) {
459 bitmap = hash_secondary_supers(secondary_supers, /*rewrite=*/true); // rewrites freshly allocated array
460 } else {
461 bitmap = SECONDARY_SUPERS_BITMAP_EMPTY;
462 }
463 return secondary_supers;
464 }
465
466 uintx Klass::compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers) {
467 return hash_secondary_supers(secondary_supers, /*rewrite=*/false); // no rewrites allowed
468 }
469
470 uint8_t Klass::compute_home_slot(Klass* k, uintx bitmap) {
471 uint8_t hash = k->hash_slot();
472 if (hash > 0) {
473 return population_count(bitmap << (SECONDARY_SUPERS_TABLE_SIZE - hash));
474 }
475 return 0;
476 }
477
478
479 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
480 if (k == nullptr) {
481 set_super(nullptr);
482 _primary_supers[0] = this;
483 assert(super_depth() == 0, "Object must already be initialized properly");
484 } else if (k != super() || k == vmClasses::Object_klass()) {
485 assert(super() == nullptr || super() == vmClasses::Object_klass(),
486 "initialize this only once to a non-trivial value");
487 set_super(k);
488 Klass* sup = k;
489 int sup_depth = sup->super_depth();
490 juint my_depth = MIN2(sup_depth + 1, (int)primary_super_limit());
491 if (!can_be_primary_super_slow())
492 my_depth = primary_super_limit();
493 for (juint i = 0; i < my_depth; i++) {
494 _primary_supers[i] = sup->_primary_supers[i];
495 }
496 Klass* *super_check_cell;
497 if (my_depth < primary_super_limit()) {
498 _primary_supers[my_depth] = this;
499 super_check_cell = &_primary_supers[my_depth];
500 } else {
501 // Overflow of the primary_supers array forces me to be secondary.
502 super_check_cell = &_secondary_super_cache;
503 }
504 set_super_check_offset(u4((address)super_check_cell - (address) this));
505
506 #ifdef ASSERT
507 {
508 juint j = super_depth();
509 assert(j == my_depth, "computed accessor gets right answer");
510 Klass* t = this;
511 while (!t->can_be_primary_super()) {
512 t = t->super();
513 j = t->super_depth();
514 }
515 for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
516 assert(primary_super_of_depth(j1) == nullptr, "super list padding");
517 }
518 while (t != nullptr) {
519 assert(primary_super_of_depth(j) == t, "super list initialization");
520 t = t->super();
521 --j;
522 }
523 assert(j == (juint)-1, "correct depth count");
524 }
525 #endif
526 }
527
528 if (secondary_supers() == nullptr) {
529
530 // Now compute the list of secondary supertypes.
531 // Secondaries can occasionally be on the super chain,
532 // if the inline "_primary_supers" array overflows.
533 int extras = 0;
534 Klass* p;
535 for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
536 ++extras;
537 }
538
539 ResourceMark rm(THREAD); // need to reclaim GrowableArrays allocated below
540
541 // Compute the "real" non-extra secondaries.
542 GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
543 if (secondaries == nullptr) {
544 // secondary_supers set by compute_secondary_supers
545 return;
546 }
547
548 GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
549
550 for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
551 int i; // Scan for overflow primaries being duplicates of 2nd'arys
552
553 // This happens frequently for very deeply nested arrays: the
554 // primary superclass chain overflows into the secondary. The
555 // secondary list contains the element_klass's secondaries with
556 // an extra array dimension added. If the element_klass's
557 // secondary list already contains some primary overflows, they
558 // (with the extra level of array-ness) will collide with the
559 // normal primary superclass overflows.
560 for( i = 0; i < secondaries->length(); i++ ) {
561 if( secondaries->at(i) == p )
562 break;
563 }
564 if( i < secondaries->length() )
565 continue; // It's a dup, don't put it in
566 primaries->push(p);
567 }
568 // Combine the two arrays into a metadata object to pack the array.
569 uintx bitmap = 0;
570 Array<Klass*>* s2 = pack_secondary_supers(class_loader_data(), primaries, secondaries, bitmap, CHECK);
571 set_secondary_supers(s2, bitmap);
572 }
573 }
574
575 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
576 Array<InstanceKlass*>* transitive_interfaces) {
577 assert(num_extra_slots == 0, "override for complex klasses");
578 assert(transitive_interfaces == nullptr, "sanity");
579 set_secondary_supers(Universe::the_empty_klass_array(), Universe::the_empty_klass_bitmap());
580 return nullptr;
581 }
582
583
584 // superklass links
585 InstanceKlass* Klass::superklass() const {
586 assert(super() == nullptr || super()->is_instance_klass(), "must be instance klass");
587 return _super == nullptr ? nullptr : InstanceKlass::cast(_super);
588 }
589
590 // subklass links. Used by the compiler (and vtable initialization)
591 // May be cleaned concurrently, so must use the Compile_lock.
592 // The log parameter is for clean_weak_klass_links to report unlinked classes.
593 Klass* Klass::subklass(bool log) const {
594 // Need load_acquire on the _subklass, because it races with inserts that
595 // publishes freshly initialized data.
596 for (Klass* chain = Atomic::load_acquire(&_subklass);
597 chain != nullptr;
598 // Do not need load_acquire on _next_sibling, because inserts never
599 // create _next_sibling edges to dead data.
600 chain = Atomic::load(&chain->_next_sibling))
601 {
602 if (chain->is_loader_alive()) {
603 return chain;
604 } else if (log) {
605 if (log_is_enabled(Trace, class, unload)) {
606 ResourceMark rm;
607 log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());
608 }
609 }
610 }
611 return nullptr;
612 }
613
614 Klass* Klass::next_sibling(bool log) const {
615 // Do not need load_acquire on _next_sibling, because inserts never
616 // create _next_sibling edges to dead data.
617 for (Klass* chain = Atomic::load(&_next_sibling);
618 chain != nullptr;
619 chain = Atomic::load(&chain->_next_sibling)) {
620 // Only return alive klass, there may be stale klass
621 // in this chain if cleaned concurrently.
622 if (chain->is_loader_alive()) {
623 return chain;
624 } else if (log) {
625 if (log_is_enabled(Trace, class, unload)) {
626 ResourceMark rm;
627 log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
628 }
629 }
630 }
631 return nullptr;
632 }
633
634 void Klass::set_subklass(Klass* s) {
635 assert(s != this, "sanity check");
636 Atomic::release_store(&_subklass, s);
637 }
638
639 void Klass::set_next_sibling(Klass* s) {
640 assert(s != this, "sanity check");
641 // Does not need release semantics. If used by cleanup, it will link to
642 // already safely published data, and if used by inserts, will be published
643 // safely using cmpxchg.
644 Atomic::store(&_next_sibling, s);
645 }
646
647 void Klass::append_to_sibling_list() {
648 if (Universe::is_fully_initialized()) {
649 assert_locked_or_safepoint(Compile_lock);
650 }
651 debug_only(verify();)
652 // add ourselves to superklass' subklass list
653 InstanceKlass* super = superklass();
654 if (super == nullptr) return; // special case: class Object
655 assert((!super->is_interface() // interfaces cannot be supers
656 && (super->superklass() == nullptr || !is_interface())),
657 "an interface can only be a subklass of Object");
658
659 // Make sure there is no stale subklass head
660 super->clean_subklass();
661
662 for (;;) {
663 Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);
664 if (prev_first_subklass != nullptr) {
665 // set our sibling to be the superklass' previous first subklass
666 assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
667 set_next_sibling(prev_first_subklass);
668 }
669 // Note that the prev_first_subklass is always alive, meaning no sibling_next links
670 // are ever created to not alive klasses. This is an important invariant of the lock-free
671 // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
672 if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
673 return;
674 }
675 }
676 debug_only(verify();)
677 }
678
679 void Klass::clean_subklass() {
680 for (;;) {
681 // Need load_acquire, due to contending with concurrent inserts
682 Klass* subklass = Atomic::load_acquire(&_subklass);
683 if (subklass == nullptr || subklass->is_loader_alive()) {
684 return;
685 }
686 // Try to fix _subklass until it points at something not dead.
687 Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());
688 }
689 }
690
691 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
692 if (!ClassUnloading || !unloading_occurred) {
693 return;
694 }
695
696 Klass* root = vmClasses::Object_klass();
697 Stack<Klass*, mtGC> stack;
698
699 stack.push(root);
700 while (!stack.is_empty()) {
701 Klass* current = stack.pop();
702
703 assert(current->is_loader_alive(), "just checking, this should be live");
704
705 // Find and set the first alive subklass
706 Klass* sub = current->subklass(true);
707 current->clean_subklass();
708 if (sub != nullptr) {
709 stack.push(sub);
710 }
711
712 // Find and set the first alive sibling
713 Klass* sibling = current->next_sibling(true);
714 current->set_next_sibling(sibling);
715 if (sibling != nullptr) {
716 stack.push(sibling);
717 }
718
719 // Clean the implementors list and method data.
720 if (clean_alive_klasses && current->is_instance_klass()) {
721 InstanceKlass* ik = InstanceKlass::cast(current);
722 ik->clean_weak_instanceklass_links();
723
724 // JVMTI RedefineClasses creates previous versions that are not in
725 // the class hierarchy, so process them here.
726 while ((ik = ik->previous_versions()) != nullptr) {
727 ik->clean_weak_instanceklass_links();
728 }
729 }
730 }
731 }
732
733 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
734 if (log_is_enabled(Trace, cds)) {
735 ResourceMark rm;
736 log_trace(cds)("Iter(Klass): %p (%s)", this, external_name());
737 }
738
739 it->push(&_name);
740 it->push(&_secondary_supers);
741 for (int i = 0; i < _primary_super_limit; i++) {
742 it->push(&_primary_supers[i]);
743 }
744 it->push(&_super);
745 if (!CDSConfig::is_dumping_archive()) {
746 // If dumping archive, these may point to excluded classes. There's no need
747 // to follow these pointers anyway, as they will be set to null in
748 // remove_unshareable_info().
749 it->push((Klass**)&_subklass);
750 it->push((Klass**)&_next_sibling);
751 it->push(&_next_link);
752 }
753
754 vtableEntry* vt = start_of_vtable();
755 for (int i=0; i<vtable_length(); i++) {
756 it->push(vt[i].method_addr());
757 }
758 }
759
760 #if INCLUDE_CDS
761 void Klass::remove_unshareable_info() {
762 assert(CDSConfig::is_dumping_archive(),
763 "only called during CDS dump time");
764 JFR_ONLY(REMOVE_ID(this);)
765 if (log_is_enabled(Trace, cds, unshareable)) {
766 ResourceMark rm;
767 log_trace(cds, unshareable)("remove: %s", external_name());
768 }
769
770 // _secondary_super_cache may be updated by an is_subtype_of() call
771 // while ArchiveBuilder is copying metaspace objects. Let's reset it to
772 // null and let it be repopulated at runtime.
773 set_secondary_super_cache(nullptr);
774
775 set_subklass(nullptr);
776 set_next_sibling(nullptr);
777 set_next_link(nullptr);
778
779 // Null out class_loader_data because we don't share that yet.
780 set_class_loader_data(nullptr);
781 set_is_shared();
782
783 // FIXME: validation in Klass::hash_secondary_supers() may fail for shared klasses.
784 // Even though the bitmaps always match, the canonical order of elements in the table
785 // is not guaranteed to stay the same (see tie breaker during Robin Hood hashing in Klass::hash_insert).
786 //assert(compute_secondary_supers_bitmap(secondary_supers()) == _bitmap, "broken table");
787 }
788
789 void Klass::remove_java_mirror() {
790 assert(CDSConfig::is_dumping_archive(), "sanity");
791 if (log_is_enabled(Trace, cds, unshareable)) {
792 ResourceMark rm;
793 log_trace(cds, unshareable)("remove java_mirror: %s", external_name());
794 }
795 // Just null out the mirror. The class_loader_data() no longer exists.
796 clear_java_mirror_handle();
797 }
798
799 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
800 assert(is_klass(), "ensure C++ vtable is restored");
801 assert(is_shared(), "must be set");
802 JFR_ONLY(RESTORE_ID(this);)
803 if (log_is_enabled(Trace, cds, unshareable)) {
804 ResourceMark rm(THREAD);
805 oop class_loader = loader_data->class_loader();
806 log_trace(cds, unshareable)("restore: %s with class loader: %s", external_name(),
807 class_loader != nullptr ? class_loader->klass()->external_name() : "boot");
808 }
809
810 // If an exception happened during CDS restore, some of these fields may already be
811 // set. We leave the class on the CLD list, even if incomplete so that we don't
812 // modify the CLD list outside a safepoint.
813 if (class_loader_data() == nullptr) {
814 set_class_loader_data(loader_data);
815
816 // Add to class loader list first before creating the mirror
817 // (same order as class file parsing)
818 loader_data->add_class(this);
819 }
820
821 Handle loader(THREAD, loader_data->class_loader());
822 ModuleEntry* module_entry = nullptr;
823 Klass* k = this;
824 if (k->is_objArray_klass()) {
825 k = ObjArrayKlass::cast(k)->bottom_klass();
826 }
827 // Obtain klass' module.
828 if (k->is_instance_klass()) {
829 InstanceKlass* ik = (InstanceKlass*) k;
830 module_entry = ik->module();
831 } else {
832 module_entry = ModuleEntryTable::javabase_moduleEntry();
833 }
834 // Obtain java.lang.Module, if available
835 Handle module_handle(THREAD, ((module_entry != nullptr) ? module_entry->module() : (oop)nullptr));
836
837 if (this->has_archived_mirror_index()) {
838 ResourceMark rm(THREAD);
839 log_debug(cds, mirror)("%s has raw archived mirror", external_name());
840 if (ArchiveHeapLoader::is_in_use()) {
841 bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
842 protection_domain,
843 CHECK);
844 if (present) {
845 return;
846 }
847 }
848
849 // No archived mirror data
850 log_debug(cds, mirror)("No archived mirror data for %s", external_name());
851 clear_java_mirror_handle();
852 this->clear_archived_mirror_index();
853 }
854
855 // Only recreate it if not present. A previous attempt to restore may have
856 // gotten an OOM later but keep the mirror if it was created.
857 if (java_mirror() == nullptr) {
858 ResourceMark rm(THREAD);
859 log_trace(cds, mirror)("Recreate mirror for %s", external_name());
860 java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
861 }
862 }
863 #endif // INCLUDE_CDS
864
865 #if INCLUDE_CDS_JAVA_HEAP
866 oop Klass::archived_java_mirror() {
867 assert(has_archived_mirror_index(), "must have archived mirror");
868 return HeapShared::get_root(_archived_mirror_index);
869 }
870
871 void Klass::clear_archived_mirror_index() {
872 if (_archived_mirror_index >= 0) {
873 HeapShared::clear_root(_archived_mirror_index);
874 }
875 _archived_mirror_index = -1;
876 }
877
878 // No GC barrier
879 void Klass::set_archived_java_mirror(int mirror_index) {
880 assert(CDSConfig::is_dumping_heap(), "sanity");
881 _archived_mirror_index = mirror_index;
882 }
883 #endif // INCLUDE_CDS_JAVA_HEAP
884
885 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
886 if (length > max_length) {
887 if (!THREAD->is_in_internal_oome_mark()) {
888 report_java_out_of_memory("Requested array size exceeds VM limit");
889 JvmtiExport::post_array_size_exhausted();
890 THROW_OOP(Universe::out_of_memory_error_array_size());
891 } else {
892 THROW_OOP(Universe::out_of_memory_error_java_heap_without_backtrace());
893 }
894 } else if (length < 0) {
895 THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
896 }
897 }
898
899 // Replace the last '+' char with '/'.
900 static char* convert_hidden_name_to_java(Symbol* name) {
901 size_t name_len = name->utf8_length();
902 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
903 name->as_klass_external_name(result, (int)name_len + 1);
904 for (int index = (int)name_len; index > 0; index--) {
905 if (result[index] == '+') {
906 result[index] = JVM_SIGNATURE_SLASH;
907 break;
908 }
909 }
910 return result;
911 }
912
913 // In product mode, this function doesn't have virtual function calls so
914 // there might be some performance advantage to handling InstanceKlass here.
915 const char* Klass::external_name() const {
916 if (is_instance_klass()) {
917 const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
918 if (ik->is_hidden()) {
919 char* result = convert_hidden_name_to_java(name());
920 return result;
921 }
922 } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
923 char* result = convert_hidden_name_to_java(name());
924 return result;
925 }
926 if (name() == nullptr) return "<unknown>";
927 return name()->as_klass_external_name();
928 }
929
930 const char* Klass::signature_name() const {
931 if (name() == nullptr) return "<unknown>";
932 if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
933 size_t name_len = name()->utf8_length();
934 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
935 name()->as_C_string(result, (int)name_len + 1);
936 for (int index = (int)name_len; index > 0; index--) {
937 if (result[index] == '+') {
938 result[index] = JVM_SIGNATURE_DOT;
939 break;
940 }
941 }
942 return result;
943 }
944 return name()->as_C_string();
945 }
946
947 const char* Klass::external_kind() const {
948 if (is_interface()) return "interface";
949 if (is_abstract()) return "abstract class";
950 return "class";
951 }
952
953 // Unless overridden, jvmti_class_status has no flags set.
954 jint Klass::jvmti_class_status() const {
955 return 0;
956 }
957
958
959 // Printing
960
961 void Klass::print_on(outputStream* st) const {
962 ResourceMark rm;
963 // print title
964 st->print("%s", internal_name());
965 print_address_on(st);
966 st->cr();
967 }
968
969 #define BULLET " - "
970
971 // Caller needs ResourceMark
972 void Klass::oop_print_on(oop obj, outputStream* st) {
973 // print title
974 st->print_cr("%s ", internal_name());
975 obj->print_address_on(st);
976
977 if (WizardMode) {
978 // print header
979 obj->mark().print_on(st);
980 st->cr();
981 if (UseCompactObjectHeaders) {
982 st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
983 st->cr();
984 }
985 }
986
987 // print class
988 st->print(BULLET"klass: ");
989 obj->klass()->print_value_on(st);
990 st->cr();
991 }
992
993 void Klass::oop_print_value_on(oop obj, outputStream* st) {
994 // print title
995 ResourceMark rm; // Cannot print in debug mode without this
996 st->print("%s", internal_name());
997 obj->print_address_on(st);
998 }
999
1000 // Verification
1001
1002 void Klass::verify_on(outputStream* st) {
1003
1004 // This can be expensive, but it is worth checking that this klass is actually
1005 // in the CLD graph but not in production.
1006 assert(Metaspace::contains((address)this), "Should be");
1007
1008 guarantee(this->is_klass(),"should be klass");
1009
1010 if (super() != nullptr) {
1011 guarantee(super()->is_klass(), "should be klass");
1012 }
1013 if (secondary_super_cache() != nullptr) {
1014 Klass* ko = secondary_super_cache();
1015 guarantee(ko->is_klass(), "should be klass");
1016 }
1017 for ( uint i = 0; i < primary_super_limit(); i++ ) {
1018 Klass* ko = _primary_supers[i];
1019 if (ko != nullptr) {
1020 guarantee(ko->is_klass(), "should be klass");
1021 }
1022 }
1023
1024 if (java_mirror_no_keepalive() != nullptr) {
1025 guarantee(java_lang_Class::is_instance(java_mirror_no_keepalive()), "should be instance");
1026 }
1027 }
1028
1029 void Klass::oop_verify_on(oop obj, outputStream* st) {
1030 guarantee(oopDesc::is_oop(obj), "should be oop");
1031 guarantee(obj->klass()->is_klass(), "klass field is not a klass");
1032 }
1033
1034 bool Klass::is_valid(Klass* k) {
1035 if (!is_aligned(k, sizeof(MetaWord))) return false;
1036 if ((size_t)k < os::min_page_size()) return false;
1037
1038 if (!os::is_readable_range(k, k + 1)) return false;
1039 if (!Metaspace::contains(k)) return false;
1040
1041 if (!Symbol::is_valid(k->name())) return false;
1042 return ClassLoaderDataGraph::is_valid(k->class_loader_data());
1043 }
1044
1045 Method* Klass::method_at_vtable(int index) {
1046 #ifndef PRODUCT
1047 assert(index >= 0, "valid vtable index");
1048 if (DebugVtables) {
1049 verify_vtable_index(index);
1050 }
1051 #endif
1052 return start_of_vtable()[index].method();
1053 }
1054
1055
1056 #ifndef PRODUCT
1057
1058 bool Klass::verify_vtable_index(int i) {
1059 int limit = vtable_length()/vtableEntry::size();
1060 assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
1061 return true;
1062 }
1063
1064 #endif // PRODUCT
1065
1066 // Caller needs ResourceMark
1067 // joint_in_module_of_loader provides an optimization if 2 classes are in
1068 // the same module to succinctly print out relevant information about their
1069 // module name and class loader's name_and_id for error messages.
1070 // Format:
1071 // <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
1072 // are in module <module-name>[@<version>]
1073 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1074 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
1075 assert(module() == class2->module(), "classes do not have the same module");
1076 const char* class1_name = external_name();
1077 size_t len = strlen(class1_name) + 1;
1078
1079 const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
1080 len += strlen(class2_description);
1081
1082 len += strlen(" and ");
1083
1084 char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1085
1086 // Just return the FQN if error when allocating string
1087 if (joint_description == nullptr) {
1088 return class1_name;
1089 }
1090
1091 jio_snprintf(joint_description, len, "%s and %s",
1092 class1_name,
1093 class2_description);
1094
1095 return joint_description;
1096 }
1097
1098 // Caller needs ResourceMark
1099 // class_in_module_of_loader provides a standard way to include
1100 // relevant information about a class, such as its module name as
1101 // well as its class loader's name_and_id, in error messages and logging.
1102 // Format:
1103 // <fully-qualified-external-class-name> is in module <module-name>[@<version>]
1104 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1105 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
1106 // 1. fully qualified external name of class
1107 const char* klass_name = external_name();
1108 size_t len = strlen(klass_name) + 1;
1109
1110 // 2. module name + @version
1111 const char* module_name = "";
1112 const char* version = "";
1113 bool has_version = false;
1114 bool module_is_named = false;
1115 const char* module_name_phrase = "";
1116 const Klass* bottom_klass = is_objArray_klass() ?
1117 ObjArrayKlass::cast(this)->bottom_klass() : this;
1118 if (bottom_klass->is_instance_klass()) {
1119 ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
1120 if (module->is_named()) {
1121 module_is_named = true;
1122 module_name_phrase = "module ";
1123 module_name = module->name()->as_C_string();
1124 len += strlen(module_name);
1125 // Use version if exists and is not a jdk module
1126 if (module->should_show_version()) {
1127 has_version = true;
1128 version = module->version()->as_C_string();
1129 // Include stlen(version) + 1 for the "@"
1130 len += strlen(version) + 1;
1131 }
1132 } else {
1133 module_name = UNNAMED_MODULE;
1134 len += UNNAMED_MODULE_LEN;
1135 }
1136 } else {
1137 // klass is an array of primitives, module is java.base
1138 module_is_named = true;
1139 module_name_phrase = "module ";
1140 module_name = JAVA_BASE_NAME;
1141 len += JAVA_BASE_NAME_LEN;
1142 }
1143
1144 // 3. class loader's name_and_id
1145 ClassLoaderData* cld = class_loader_data();
1146 assert(cld != nullptr, "class_loader_data should not be null");
1147 const char* loader_name_and_id = cld->loader_name_and_id();
1148 len += strlen(loader_name_and_id);
1149
1150 // 4. include parent loader information
1151 const char* parent_loader_phrase = "";
1152 const char* parent_loader_name_and_id = "";
1153 if (include_parent_loader &&
1154 !cld->is_builtin_class_loader_data()) {
1155 oop parent_loader = java_lang_ClassLoader::parent(class_loader());
1156 ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
1157 // The parent loader's ClassLoaderData could be null if it is
1158 // a delegating class loader that has never defined a class.
1159 // In this case the loader's name must be obtained via the parent loader's oop.
1160 if (parent_cld == nullptr) {
1161 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
1162 if (cl_name_and_id != nullptr) {
1163 parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
1164 }
1165 } else {
1166 parent_loader_name_and_id = parent_cld->loader_name_and_id();
1167 }
1168 parent_loader_phrase = ", parent loader ";
1169 len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
1170 }
1171
1172 // Start to construct final full class description string
1173 len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
1174 len += strlen(module_name_phrase) + strlen(" of loader ");
1175
1176 char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1177
1178 // Just return the FQN if error when allocating string
1179 if (class_description == nullptr) {
1180 return klass_name;
1181 }
1182
1183 jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
1184 klass_name,
1185 (use_are) ? "are" : "is",
1186 module_name_phrase,
1187 module_name,
1188 (has_version) ? "@" : "",
1189 (has_version) ? version : "",
1190 loader_name_and_id,
1191 parent_loader_phrase,
1192 parent_loader_name_and_id);
1193
1194 return class_description;
1195 }
1196
1197 class LookupStats : StackObj {
1198 private:
1199 uint _no_of_samples;
1200 uint _worst;
1201 uint _worst_count;
1202 uint _average;
1203 uint _best;
1204 uint _best_count;
1205 public:
1206 LookupStats() : _no_of_samples(0), _worst(0), _worst_count(0), _average(0), _best(INT_MAX), _best_count(0) {}
1207
1208 ~LookupStats() {
1209 assert(_best <= _worst || _no_of_samples == 0, "sanity");
1210 }
1211
1212 void sample(uint value) {
1213 ++_no_of_samples;
1214 _average += value;
1215
1216 if (_worst < value) {
1217 _worst = value;
1218 _worst_count = 1;
1219 } else if (_worst == value) {
1220 ++_worst_count;
1221 }
1222
1223 if (_best > value) {
1224 _best = value;
1225 _best_count = 1;
1226 } else if (_best == value) {
1227 ++_best_count;
1228 }
1229 }
1230
1231 void print_on(outputStream* st) const {
1232 st->print("best: %2d (%4.1f%%)", _best, (100.0 * _best_count) / _no_of_samples);
1233 if (_best_count < _no_of_samples) {
1234 st->print("; average: %4.1f; worst: %2d (%4.1f%%)",
1235 (1.0 * _average) / _no_of_samples,
1236 _worst, (100.0 * _worst_count) / _no_of_samples);
1237 }
1238 }
1239 };
1240
1241 static void print_positive_lookup_stats(Array<Klass*>* secondary_supers, uintx bitmap, outputStream* st) {
1242 int num_of_supers = secondary_supers->length();
1243
1244 LookupStats s;
1245 for (int i = 0; i < num_of_supers; i++) {
1246 Klass* secondary_super = secondary_supers->at(i);
1247 int home_slot = Klass::compute_home_slot(secondary_super, bitmap);
1248 uint score = 1 + ((i - home_slot) & Klass::SECONDARY_SUPERS_TABLE_MASK);
1249 s.sample(score);
1250 }
1251 st->print("positive_lookup: "); s.print_on(st);
1252 }
1253
1254 static uint compute_distance_to_nearest_zero(int slot, uintx bitmap) {
1255 assert(~bitmap != 0, "no zeroes");
1256 uintx start = rotate_right(bitmap, slot);
1257 return count_trailing_zeros(~start);
1258 }
1259
1260 static void print_negative_lookup_stats(uintx bitmap, outputStream* st) {
1261 LookupStats s;
1262 for (int slot = 0; slot < Klass::SECONDARY_SUPERS_TABLE_SIZE; slot++) {
1263 uint score = compute_distance_to_nearest_zero(slot, bitmap);
1264 s.sample(score);
1265 }
1266 st->print("negative_lookup: "); s.print_on(st);
1267 }
1268
1269 void Klass::print_secondary_supers_on(outputStream* st) const {
1270 if (secondary_supers() != nullptr) {
1271 if (UseSecondarySupersTable) {
1272 st->print(" - "); st->print("%d elements;", _secondary_supers->length());
1273 st->print_cr(" bitmap: " UINTX_FORMAT_X_0 ";", _bitmap);
1274 if (_bitmap != SECONDARY_SUPERS_BITMAP_EMPTY &&
1275 _bitmap != SECONDARY_SUPERS_BITMAP_FULL) {
1276 st->print(" - "); print_positive_lookup_stats(secondary_supers(), _bitmap, st); st->cr();
1277 st->print(" - "); print_negative_lookup_stats(_bitmap, st); st->cr();
1278 }
1279 }
1280 } else {
1281 st->print("null");
1282 }
1283 }
1284
1285 void Klass::on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg) {
1286 ResourceMark rm;
1287 super->print();
1288 sub->print();
1289 fatal("%s: %s implements %s: is_subtype_of: %d; linear_search: %d; table_lookup: %d",
1290 msg, sub->external_name(), super->external_name(),
1291 sub->is_subtype_of(super), linear_result, table_result);
1292 }