1 /*
2 * Copyright (c) 1997, 2025, 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 "cds/cdsConfig.hpp"
26 #include "cds/heapShared.inline.hpp"
27 #include "classfile/classLoader.hpp"
28 #include "classfile/classLoaderData.inline.hpp"
29 #include "classfile/classLoaderDataGraph.inline.hpp"
30 #include "classfile/javaClasses.inline.hpp"
31 #include "classfile/moduleEntry.hpp"
32 #include "classfile/systemDictionary.hpp"
33 #include "classfile/systemDictionaryShared.hpp"
34 #include "classfile/vmClasses.hpp"
35 #include "classfile/vmSymbols.hpp"
36 #include "gc/shared/collectedHeap.inline.hpp"
37 #include "jvm_io.h"
38 #include "logging/log.hpp"
39 #include "memory/metadataFactory.hpp"
40 #include "memory/metaspaceClosure.hpp"
41 #include "memory/oopFactory.hpp"
42 #include "memory/resourceArea.hpp"
43 #include "memory/universe.hpp"
44 #include "oops/compressedKlass.inline.hpp"
45 #include "oops/compressedOops.inline.hpp"
46 #include "oops/instanceKlass.hpp"
47 #include "oops/klass.inline.hpp"
48 #include "oops/objArrayKlass.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "oops/oopHandle.inline.hpp"
51 #include "prims/jvmtiExport.hpp"
52 #include "runtime/atomicAccess.hpp"
53 #include "runtime/handles.inline.hpp"
54 #include "runtime/perfData.hpp"
55 #include "utilities/macros.hpp"
56 #include "utilities/powerOfTwo.hpp"
57 #include "utilities/rotate_bits.hpp"
58 #include "utilities/stack.inline.hpp"
59
60 #if INCLUDE_JFR
61 #include "jfr/jfr.hpp"
62 #endif
63
64 void Klass::set_java_mirror(Handle m) {
65 assert(!m.is_null(), "New mirror should never be null.");
66 assert(_java_mirror.is_empty(), "should only be used to initialize mirror");
67 _java_mirror = class_loader_data()->add_handle(m);
68 }
69
70 bool Klass::is_cloneable() const {
71 return _misc_flags.is_cloneable_fast() ||
72 is_subtype_of(vmClasses::Cloneable_klass());
73 }
74
75 uint8_t Klass::compute_hash_slot(Symbol* n) {
76 uint hash_code;
77 // Special cases for the two superclasses of all Array instances.
78 // Code elsewhere assumes, for all instances of ArrayKlass, that
79 // these two interfaces will be in this order.
80
81 // We ensure there are some empty slots in the hash table between
82 // these two very common interfaces because if they were adjacent
83 // (e.g. Slots 0 and 1), then any other class which hashed to 0 or 1
84 // would result in a probe length of 3.
85 if (n == vmSymbols::java_lang_Cloneable()) {
86 hash_code = 0;
87 } else if (n == vmSymbols::java_io_Serializable()) {
88 hash_code = SECONDARY_SUPERS_TABLE_SIZE / 2;
89 } else {
90 auto s = (const jbyte*) n->bytes();
91 hash_code = java_lang_String::hash_code(s, n->utf8_length());
92 // We use String::hash_code here (rather than e.g.
93 // Symbol::identity_hash()) in order to have a hash code that
94 // does not change from run to run. We want that because the
95 // hash value for a secondary superclass appears in generated
96 // code as a constant.
97
98 // This constant is magic: see Knuth, "Fibonacci Hashing".
99 constexpr uint multiplier
100 = 2654435769; // (uint)(((u8)1 << 32) / ((1 + sqrt(5)) / 2 ))
101 constexpr uint hash_shift = sizeof(hash_code) * 8 - 6;
102 // The leading bits of the least significant half of the product.
103 hash_code = (hash_code * multiplier) >> hash_shift;
104
105 if (StressSecondarySupers) {
106 // Generate many hash collisions in order to stress-test the
107 // linear search fallback.
108 hash_code = hash_code % 3;
109 hash_code = hash_code * (SECONDARY_SUPERS_TABLE_SIZE / 3);
110 }
111 }
112
113 return (hash_code & SECONDARY_SUPERS_TABLE_MASK);
114 }
115
116 void Klass::set_name(Symbol* n) {
117 _name = n;
118
119 if (_name != nullptr) {
120 _name->increment_refcount();
121 }
122
123 {
124 elapsedTimer selftime;
125 selftime.start();
126
127 _hash_slot = compute_hash_slot(n);
128 assert(_hash_slot < SECONDARY_SUPERS_TABLE_SIZE, "required");
129
130 selftime.stop();
131 if (UsePerfData) {
132 ClassLoader::perf_secondary_hash_time()->inc(selftime.ticks());
133 }
134 }
135
136 if (CDSConfig::is_dumping_archive() && is_instance_klass()) {
137 SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
138 }
139 }
140
141 bool Klass::is_subclass_of(const Klass* k) const {
142 // Run up the super chain and check
143 if (this == k) return true;
144
145 Klass* t = const_cast<Klass*>(this)->super();
146
147 while (t != nullptr) {
148 if (t == k) return true;
149 t = t->super();
150 }
151 return false;
152 }
153
154 void Klass::release_C_heap_structures(bool release_constant_pool) {
155 if (_name != nullptr) _name->decrement_refcount();
156 }
157
158 bool Klass::linear_search_secondary_supers(const Klass* k) const {
159 // Scan the array-of-objects for a match
160 // FIXME: We could do something smarter here, maybe a vectorized
161 // comparison or a binary search, but is that worth any added
162 // complexity?
163 int cnt = secondary_supers()->length();
164 for (int i = 0; i < cnt; i++) {
165 if (secondary_supers()->at(i) == k) {
166 return true;
167 }
168 }
169 return false;
170 }
171
172 // Given a secondary superklass k, an initial array index, and an
173 // occupancy bitmap rotated such that Bit 1 is the next bit to test,
174 // search for k.
175 bool Klass::fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const {
176 // Once the occupancy bitmap is almost full, it's faster to use a
177 // linear search.
178 if (secondary_supers()->length() > SECONDARY_SUPERS_TABLE_SIZE - 2) {
179 return linear_search_secondary_supers(k);
180 }
181
182 // This is conventional linear probing, but instead of terminating
183 // when a null entry is found in the table, we maintain a bitmap
184 // in which a 0 indicates missing entries.
185
186 precond((int)population_count(rotated_bitmap) == secondary_supers()->length());
187
188 // The check for secondary_supers()->length() <= SECONDARY_SUPERS_TABLE_SIZE - 2
189 // at the start of this function guarantees there are 0s in the
190 // bitmap, so this loop eventually terminates.
191 while ((rotated_bitmap & 2) != 0) {
192 if (++index == secondary_supers()->length()) {
193 index = 0;
194 }
195 if (secondary_supers()->at(index) == k) {
196 return true;
197 }
198 rotated_bitmap = rotate_right(rotated_bitmap, 1);
199 }
200 return false;
201 }
202
203 // Return self, except for abstract classes with exactly 1
204 // implementor. Then return the 1 concrete implementation.
205 Klass *Klass::up_cast_abstract() {
206 Klass *r = this;
207 while( r->is_abstract() ) { // Receiver is abstract?
208 Klass *s = r->subklass(); // Check for exactly 1 subklass
209 if (s == nullptr || s->next_sibling() != nullptr) // Oops; wrong count; give up
210 return this; // Return 'this' as a no-progress flag
211 r = s; // Loop till find concrete class
212 }
213 return r; // Return the 1 concrete class
214 }
215
216 // Find LCA in class hierarchy
217 Klass *Klass::LCA( Klass *k2 ) {
218 Klass *k1 = this;
219 while( 1 ) {
220 if( k1->is_subtype_of(k2) ) return k2;
221 if( k2->is_subtype_of(k1) ) return k1;
222 k1 = k1->super();
223 k2 = k2->super();
224 }
225 }
226
227
228 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
229 ResourceMark rm(THREAD);
230 THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
231 : vmSymbols::java_lang_InstantiationException(), external_name());
232 }
233
234
235 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
236 ResourceMark rm(THREAD);
237 assert(s != nullptr, "Throw NPE!");
238 THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
239 err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
240 }
241
242
243 void Klass::initialize(TRAPS) {
244 ShouldNotReachHere();
245 }
246
247 void Klass::initialize_preemptable(TRAPS) {
248 ShouldNotReachHere();
249 }
250
251 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
252 #ifdef ASSERT
253 tty->print_cr("Error: find_field called on a klass oop."
254 " Likely error: reflection method does not correctly"
255 " wrap return value in a mirror object.");
256 #endif
257 ShouldNotReachHere();
258 return nullptr;
259 }
260
261 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
262 OverpassLookupMode overpass_mode,
263 PrivateLookupMode private_mode) const {
264 #ifdef ASSERT
265 tty->print_cr("Error: uncached_lookup_method called on a klass oop."
266 " Likely error: reflection method does not correctly"
267 " wrap return value in a mirror object.");
268 #endif
269 ShouldNotReachHere();
270 return nullptr;
271 }
272
273 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
274 return Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);
275 }
276
277 Klass::Klass() : _kind(UnknownKlassKind) {
278 assert(CDSConfig::is_dumping_static_archive() || CDSConfig::is_using_archive(), "only for cds");
279 }
280
281 // "Normal" instantiation is preceded by a MetaspaceObj allocation
282 // which zeros out memory - calloc equivalent.
283 // The constructor is also used from CppVtableCloner,
284 // which doesn't zero out the memory before calling the constructor.
285 Klass::Klass(KlassKind kind, markWord prototype_header) : _kind(kind),
286 _shared_class_path_index(-1) {
287 set_prototype_header(make_prototype_header(this, prototype_header));
288 CDS_ONLY(_aot_class_flags = 0;)
289 CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
290 _primary_supers[0] = this;
291 set_super_check_offset(in_bytes(primary_supers_offset()));
292 }
293
294 jint Klass::array_layout_helper(BasicType etype) {
295 assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
296 // Note that T_ARRAY is not allowed here.
297 int hsize = arrayOopDesc::base_offset_in_bytes(etype);
298 int esize = type2aelembytes(etype);
299 bool isobj = (etype == T_OBJECT);
300 int tag = isobj ? _lh_array_tag_ref_value : _lh_array_tag_type_value;
301 int lh = array_layout_helper(tag, false, hsize, etype, exact_log2(esize));
302
303 assert(lh < (int)_lh_neutral_value, "must look like an array layout");
304 assert(layout_helper_is_array(lh), "correct kind");
305 assert(layout_helper_is_refArray(lh) == isobj, "correct kind");
306 assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
307 assert(layout_helper_header_size(lh) == hsize, "correct decode");
308 assert(layout_helper_element_type(lh) == etype, "correct decode");
309 assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
310
311 return lh;
312 }
313
314 int Klass::modifier_flags() const {
315 int mods = java_lang_Class::modifiers(java_mirror());
316 assert(mods == compute_modifier_flags(), "should be same");
317 return mods;
318 }
319
320 bool Klass::can_be_primary_super_slow() const {
321 if (super() == nullptr)
322 return true;
323 else if (super()->super_depth() >= primary_super_limit()-1)
324 return false;
325 else
326 return true;
327 }
328
329 void Klass::set_secondary_supers(Array<Klass*>* secondaries, uintx bitmap) {
330 #ifdef ASSERT
331 if (secondaries != nullptr) {
332 uintx real_bitmap = compute_secondary_supers_bitmap(secondaries);
333 assert(bitmap == real_bitmap, "must be");
334 assert(secondaries->length() >= (int)population_count(bitmap), "must be");
335 }
336 #endif
337 _secondary_supers_bitmap = bitmap;
338 _secondary_supers = secondaries;
339
340 if (secondaries != nullptr) {
341 LogMessage(class, load) msg;
342 NonInterleavingLogStream log {LogLevel::Debug, msg};
343 if (log.is_enabled()) {
344 ResourceMark rm;
345 log.print_cr("set_secondary_supers: hash_slot: %d; klass: %s", hash_slot(), external_name());
346 print_secondary_supers_on(&log);
347 }
348 }
349 }
350
351 // Hashed secondary superclasses
352 //
353 // We use a compressed 64-entry hash table with linear probing. We
354 // start by creating a hash table in the usual way, followed by a pass
355 // that removes all the null entries. To indicate which entries would
356 // have been null we use a bitmap that contains a 1 in each position
357 // where an entry is present, 0 otherwise. This bitmap also serves as
358 // a kind of Bloom filter, which in many cases allows us quickly to
359 // eliminate the possibility that something is a member of a set of
360 // secondaries.
361 uintx Klass::hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite) {
362 const int length = secondaries->length();
363
364 if (length == 0) {
365 return SECONDARY_SUPERS_BITMAP_EMPTY;
366 }
367
368 if (length == 1) {
369 int hash_slot = secondaries->at(0)->hash_slot();
370 return uintx(1) << hash_slot;
371 }
372
373 // Invariant: _secondary_supers.length >= population_count(_secondary_supers_bitmap)
374
375 // Don't attempt to hash a table that's completely full, because in
376 // the case of an absent interface linear probing would not
377 // terminate.
378 if (length >= SECONDARY_SUPERS_TABLE_SIZE) {
379 return SECONDARY_SUPERS_BITMAP_FULL;
380 }
381
382 {
383 PerfTraceTime ptt(ClassLoader::perf_secondary_hash_time());
384
385 ResourceMark rm;
386 uintx bitmap = SECONDARY_SUPERS_BITMAP_EMPTY;
387 auto hashed_secondaries = new GrowableArray<Klass*>(SECONDARY_SUPERS_TABLE_SIZE,
388 SECONDARY_SUPERS_TABLE_SIZE, nullptr);
389
390 for (int j = 0; j < length; j++) {
391 Klass* k = secondaries->at(j);
392 hash_insert(k, hashed_secondaries, bitmap);
393 }
394
395 // Pack the hashed secondaries array by copying it into the
396 // secondaries array, sans nulls, if modification is allowed.
397 // Otherwise, validate the order.
398 int i = 0;
399 for (int slot = 0; slot < SECONDARY_SUPERS_TABLE_SIZE; slot++) {
400 bool has_element = ((bitmap >> slot) & 1) != 0;
401 assert(has_element == (hashed_secondaries->at(slot) != nullptr), "");
402 if (has_element) {
403 Klass* k = hashed_secondaries->at(slot);
404 if (rewrite) {
405 secondaries->at_put(i, k);
406 } else if (secondaries->at(i) != k) {
407 assert(false, "broken secondary supers hash table");
408 return SECONDARY_SUPERS_BITMAP_FULL;
409 }
410 i++;
411 }
412 }
413 assert(i == secondaries->length(), "mismatch");
414 postcond((int)population_count(bitmap) == secondaries->length());
415
416 return bitmap;
417 }
418 }
419
420 void Klass::hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap) {
421 assert(bitmap != SECONDARY_SUPERS_BITMAP_FULL, "");
422
423 int dist = 0;
424 for (int slot = klass->hash_slot(); true; slot = (slot + 1) & SECONDARY_SUPERS_TABLE_MASK) {
425 Klass* existing = secondaries->at(slot);
426 assert(((bitmap >> slot) & 1) == (existing != nullptr), "mismatch");
427 if (existing == nullptr) { // no conflict
428 secondaries->at_put(slot, klass);
429 bitmap |= uintx(1) << slot;
430 assert(bitmap != SECONDARY_SUPERS_BITMAP_FULL, "");
431 return;
432 } else {
433 // Use Robin Hood hashing to minimize the worst case search.
434 // Also, every permutation of the insertion sequence produces
435 // the same final Robin Hood hash table, provided that a
436 // consistent tie breaker is used.
437 int existing_dist = (slot - existing->hash_slot()) & SECONDARY_SUPERS_TABLE_MASK;
438 if (existing_dist < dist
439 // This tie breaker ensures that the hash order is maintained.
440 || ((existing_dist == dist)
441 && (uintptr_t(existing) < uintptr_t(klass)))) {
442 Klass* tmp = secondaries->at(slot);
443 secondaries->at_put(slot, klass);
444 klass = tmp;
445 dist = existing_dist;
446 }
447 ++dist;
448 }
449 }
450 }
451
452 Array<Klass*>* Klass::pack_secondary_supers(ClassLoaderData* loader_data,
453 GrowableArray<Klass*>* primaries,
454 GrowableArray<Klass*>* secondaries,
455 uintx& bitmap, TRAPS) {
456 int new_length = primaries->length() + secondaries->length();
457 Array<Klass*>* secondary_supers = MetadataFactory::new_array<Klass*>(loader_data, new_length, CHECK_NULL);
458
459 // Combine the two arrays into a metadata object to pack the array.
460 // The primaries are added in the reverse order, then the secondaries.
461 int fill_p = primaries->length();
462 for (int j = 0; j < fill_p; j++) {
463 secondary_supers->at_put(j, primaries->pop()); // add primaries in reverse order.
464 }
465 for( int j = 0; j < secondaries->length(); j++ ) {
466 secondary_supers->at_put(j+fill_p, secondaries->at(j)); // add secondaries on the end.
467 }
468 #ifdef ASSERT
469 // We must not copy any null placeholders left over from bootstrap.
470 for (int j = 0; j < secondary_supers->length(); j++) {
471 assert(secondary_supers->at(j) != nullptr, "correct bootstrapping order");
472 }
473 #endif
474
475 bitmap = hash_secondary_supers(secondary_supers, /*rewrite=*/true); // rewrites freshly allocated array
476 return secondary_supers;
477 }
478
479 uintx Klass::compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers) {
480 return hash_secondary_supers(secondary_supers, /*rewrite=*/false); // no rewrites allowed
481 }
482
483 uint8_t Klass::compute_home_slot(Klass* k, uintx bitmap) {
484 uint8_t hash = k->hash_slot();
485 if (hash > 0) {
486 return population_count(bitmap << (SECONDARY_SUPERS_TABLE_SIZE - hash));
487 }
488 return 0;
489 }
490
491
492 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
493 if (k == nullptr) {
494 set_super(nullptr);
495 _primary_supers[0] = this;
496 assert(super_depth() == 0, "Object must already be initialized properly");
497 } else if (k != super() || k == vmClasses::Object_klass()) {
498 assert(super() == nullptr || super() == vmClasses::Object_klass(),
499 "initialize this only once to a non-trivial value");
500 set_super(k);
501 Klass* sup = k;
502 int sup_depth = sup->super_depth();
503 juint my_depth = MIN2(sup_depth + 1, (int)primary_super_limit());
504 if (!can_be_primary_super_slow())
505 my_depth = primary_super_limit();
506 for (juint i = 0; i < my_depth; i++) {
507 _primary_supers[i] = sup->_primary_supers[i];
508 }
509 Klass* *super_check_cell;
510 if (my_depth < primary_super_limit()) {
511 _primary_supers[my_depth] = this;
512 super_check_cell = &_primary_supers[my_depth];
513 } else {
514 // Overflow of the primary_supers array forces me to be secondary.
515 super_check_cell = &_secondary_super_cache;
516 }
517 set_super_check_offset(u4((address)super_check_cell - (address) this));
518
519 #ifdef ASSERT
520 {
521 juint j = super_depth();
522 assert(j == my_depth, "computed accessor gets right answer");
523 Klass* t = this;
524 while (!t->can_be_primary_super()) {
525 t = t->super();
526 j = t->super_depth();
527 }
528 for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
529 assert(primary_super_of_depth(j1) == nullptr, "super list padding");
530 }
531 while (t != nullptr) {
532 assert(primary_super_of_depth(j) == t, "super list initialization");
533 t = t->super();
534 --j;
535 }
536 assert(j == (juint)-1, "correct depth count");
537 }
538 #endif
539 }
540
541 if (secondary_supers() == nullptr) {
542
543 // Now compute the list of secondary supertypes.
544 // Secondaries can occasionally be on the super chain,
545 // if the inline "_primary_supers" array overflows.
546 int extras = 0;
547 Klass* p;
548 for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
549 ++extras;
550 }
551
552 ResourceMark rm(THREAD); // need to reclaim GrowableArrays allocated below
553
554 // Compute the "real" non-extra secondaries.
555 GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
556 if (secondaries == nullptr) {
557 // secondary_supers set by compute_secondary_supers
558 return;
559 }
560
561 GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
562
563 for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
564 int i; // Scan for overflow primaries being duplicates of 2nd'arys
565
566 // This happens frequently for very deeply nested arrays: the
567 // primary superclass chain overflows into the secondary. The
568 // secondary list contains the element_klass's secondaries with
569 // an extra array dimension added. If the element_klass's
570 // secondary list already contains some primary overflows, they
571 // (with the extra level of array-ness) will collide with the
572 // normal primary superclass overflows.
573 for( i = 0; i < secondaries->length(); i++ ) {
574 if( secondaries->at(i) == p )
575 break;
576 }
577 if( i < secondaries->length() )
578 continue; // It's a dup, don't put it in
579 primaries->push(p);
580 }
581 // Combine the two arrays into a metadata object to pack the array.
582 uintx bitmap = 0;
583 Array<Klass*>* s2 = pack_secondary_supers(class_loader_data(), primaries, secondaries, bitmap, CHECK);
584 set_secondary_supers(s2, bitmap);
585 }
586 }
587
588 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
589 Array<InstanceKlass*>* transitive_interfaces) {
590 assert(num_extra_slots == 0, "override for complex klasses");
591 assert(transitive_interfaces == nullptr, "sanity");
592 set_secondary_supers(Universe::the_empty_klass_array(), Universe::the_empty_klass_bitmap());
593 return nullptr;
594 }
595
596
597 // subklass links. Used by the compiler (and vtable initialization)
598 // May be cleaned concurrently, so must use the Compile_lock.
599 Klass* Klass::subklass() const {
600 // Need load_acquire on the _subklass, because it races with inserts that
601 // publishes freshly initialized data.
602 for (Klass* chain = AtomicAccess::load_acquire(&_subklass);
603 chain != nullptr;
604 // Do not need load_acquire on _next_sibling, because inserts never
605 // create _next_sibling edges to dead data.
606 chain = AtomicAccess::load(&chain->_next_sibling))
607 {
608 if (chain->is_loader_alive()) {
609 return chain;
610 }
611 }
612 return nullptr;
613 }
614
615 Klass* Klass::next_sibling(bool log) const {
616 // Do not need load_acquire on _next_sibling, because inserts never
617 // create _next_sibling edges to dead data.
618 for (Klass* chain = AtomicAccess::load(&_next_sibling);
619 chain != nullptr;
620 chain = AtomicAccess::load(&chain->_next_sibling)) {
621 // Only return alive klass, there may be stale klass
622 // in this chain if cleaned concurrently.
623 if (chain->is_loader_alive()) {
624 return chain;
625 } else if (log) {
626 if (log_is_enabled(Trace, class, unload)) {
627 ResourceMark rm;
628 log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
629 }
630 }
631 }
632 return nullptr;
633 }
634
635 void Klass::set_subklass(Klass* s) {
636 assert(s != this, "sanity check");
637 AtomicAccess::release_store(&_subklass, s);
638 }
639
640 void Klass::set_next_sibling(Klass* s) {
641 assert(s != this, "sanity check");
642 // Does not need release semantics. If used by cleanup, it will link to
643 // already safely published data, and if used by inserts, will be published
644 // safely using cmpxchg.
645 AtomicAccess::store(&_next_sibling, s);
646 }
647
648 void Klass::append_to_sibling_list() {
649 if (Universe::is_fully_initialized()) {
650 assert_locked_or_safepoint(Compile_lock);
651 }
652 DEBUG_ONLY(verify();)
653 // add ourselves to super' subklass list
654 InstanceKlass* super = java_super();
655 if (super == nullptr) return; // special case: class Object
656 assert((!super->is_interface() // interfaces cannot be supers
657 && (super->java_super() == nullptr || !is_interface())),
658 "an interface can only be a subklass of Object");
659
660 // Make sure there is no stale subklass head
661 super->clean_subklass();
662
663 for (;;) {
664 Klass* prev_first_subklass = AtomicAccess::load_acquire(&_super->_subklass);
665 if (prev_first_subklass != nullptr) {
666 // set our sibling to be the super' previous first subklass
667 assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
668 set_next_sibling(prev_first_subklass);
669 }
670 // Note that the prev_first_subklass is always alive, meaning no sibling_next links
671 // are ever created to not alive klasses. This is an important invariant of the lock-free
672 // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
673 if (AtomicAccess::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
674 return;
675 }
676 }
677 DEBUG_ONLY(verify();)
678 }
679
680 // The log parameter is for clean_weak_klass_links to report unlinked classes.
681 Klass* Klass::clean_subklass(bool log) {
682 for (;;) {
683 // Need load_acquire, due to contending with concurrent inserts
684 Klass* subklass = AtomicAccess::load_acquire(&_subklass);
685 if (subklass == nullptr || subklass->is_loader_alive()) {
686 return subklass;
687 }
688 if (log && log_is_enabled(Trace, class, unload)) {
689 ResourceMark rm;
690 log_trace(class, unload)("unlinking class (subclass): %s", subklass->external_name());
691 }
692 // Try to fix _subklass until it points at something not dead.
693 AtomicAccess::cmpxchg(&_subklass, subklass, subklass->next_sibling(log));
694 }
695 }
696
697 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
698 if (!ClassUnloading || !unloading_occurred) {
699 return;
700 }
701
702 Klass* root = vmClasses::Object_klass();
703 Stack<Klass*, mtGC> stack;
704
705 stack.push(root);
706 while (!stack.is_empty()) {
707 Klass* current = stack.pop();
708
709 assert(current->is_loader_alive(), "just checking, this should be live");
710
711 // Find and set the first alive subklass
712 Klass* sub = current->clean_subklass(true);
713 if (sub != nullptr) {
714 stack.push(sub);
715 }
716
717 // Find and set the first alive sibling
718 Klass* sibling = current->next_sibling(true);
719 current->set_next_sibling(sibling);
720 if (sibling != nullptr) {
721 stack.push(sibling);
722 }
723
724 // Clean the implementors list and method data.
725 if (clean_alive_klasses && current->is_instance_klass()) {
726 InstanceKlass* ik = InstanceKlass::cast(current);
727 clean_weak_instanceklass_links(ik);
728 }
729 }
730 }
731
732 void Klass::clean_weak_instanceklass_links(InstanceKlass* ik) {
733 ik->clean_weak_instanceklass_links();
734 // JVMTI RedefineClasses creates previous versions that are not in
735 // the class hierarchy, so process them here.
736 while ((ik = ik->previous_versions()) != nullptr) {
737 ik->clean_weak_instanceklass_links();
738 }
739 }
740
741 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
742 if (log_is_enabled(Trace, aot)) {
743 ResourceMark rm;
744 log_trace(aot)("Iter(Klass): %p (%s)", this, external_name());
745 }
746
747 it->push(&_name);
748 it->push(&_secondary_supers);
749 for (int i = 0; i < _primary_super_limit; i++) {
750 it->push(&_primary_supers[i]);
751 }
752 it->push(&_super);
753 if (!CDSConfig::is_dumping_archive()) {
754 // If dumping archive, these may point to excluded classes. There's no need
755 // to follow these pointers anyway, as they will be set to null in
756 // remove_unshareable_info().
757 it->push((Klass**)&_subklass);
758 it->push((Klass**)&_next_sibling);
759 it->push(&_next_link);
760 }
761
762 vtableEntry* vt = start_of_vtable();
763 for (int i=0; i<vtable_length(); i++) {
764 it->push(vt[i].method_addr());
765 }
766 }
767
768 #if INCLUDE_CDS
769 void Klass::remove_unshareable_info() {
770 assert(CDSConfig::is_dumping_archive(),
771 "only called during CDS dump time");
772 JFR_ONLY(REMOVE_ID(this);)
773 if (log_is_enabled(Trace, aot, unshareable)) {
774 ResourceMark rm;
775 log_trace(aot, unshareable)("remove: %s", external_name());
776 }
777
778 // _secondary_super_cache may be updated by an is_subtype_of() call
779 // while ArchiveBuilder is copying metaspace objects. Let's reset it to
780 // null and let it be repopulated at runtime.
781 set_secondary_super_cache(nullptr);
782
783 set_subklass(nullptr);
784 set_next_sibling(nullptr);
785 set_next_link(nullptr);
786
787 // Null out class_loader_data because we don't share that yet.
788 set_class_loader_data(nullptr);
789 set_in_aot_cache();
790
791 if (CDSConfig::is_dumping_classic_static_archive()) {
792 // "Classic" static archives are required to have deterministic contents.
793 // The elements in _secondary_supers are addresses in the ArchiveBuilder
794 // output buffer, so they should have deterministic values. If we rehash
795 // _secondary_supers, its elements will appear in a deterministic order.
796 //
797 // Note that the bitmap is guaranteed to be deterministic, regardless of the
798 // actual addresses of the elements in _secondary_supers. So rehashing shouldn't
799 // change it.
800 uintx bitmap = hash_secondary_supers(secondary_supers(), true);
801 assert(bitmap == _secondary_supers_bitmap, "bitmap should not be changed due to rehashing");
802 }
803 }
804
805 void Klass::remove_java_mirror() {
806 assert(CDSConfig::is_dumping_archive(), "sanity");
807 if (log_is_enabled(Trace, aot, unshareable)) {
808 ResourceMark rm;
809 log_trace(aot, unshareable)("remove java_mirror: %s", external_name());
810 }
811
812 #if INCLUDE_CDS_JAVA_HEAP
813 _archived_mirror_index = -1;
814 if (CDSConfig::is_dumping_heap()) {
815 Klass* src_k = ArchiveBuilder::current()->get_source_addr(this);
816 oop orig_mirror = src_k->java_mirror();
817 if (orig_mirror == nullptr) {
818 assert(CDSConfig::is_dumping_final_static_archive(), "sanity");
819 if (is_instance_klass()) {
820 assert(InstanceKlass::cast(this)->defined_by_other_loaders(), "sanity");
821 } else {
822 precond(is_objArray_klass());
823 Klass *k = ObjArrayKlass::cast(this)->bottom_klass();
824 precond(k->is_instance_klass());
825 assert(InstanceKlass::cast(k)->defined_by_other_loaders(), "sanity");
826 }
827 } else {
828 oop scratch_mirror = HeapShared::scratch_java_mirror(orig_mirror);
829 if (scratch_mirror != nullptr) {
830 _archived_mirror_index = HeapShared::append_root(scratch_mirror);
831 }
832 }
833 }
834 #endif
835
836 // Just null out the mirror. The class_loader_data() no longer exists.
837 clear_java_mirror_handle();
838 }
839
840 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
841 assert(is_klass(), "ensure C++ vtable is restored");
842 assert(in_aot_cache(), "must be set");
843 assert(secondary_supers()->length() >= (int)population_count(_secondary_supers_bitmap), "must be");
844 if (log_is_enabled(Trace, aot, unshareable)) {
845 ResourceMark rm(THREAD);
846 oop class_loader = loader_data->class_loader();
847 log_trace(aot, unshareable)("restore: %s with class loader: %s", external_name(),
848 class_loader != nullptr ? class_loader->klass()->external_name() : "boot");
849 }
850
851 // If an exception happened during CDS restore, some of these fields may already be
852 // set. We leave the class on the CLD list, even if incomplete so that we don't
853 // modify the CLD list outside a safepoint.
854 if (class_loader_data() == nullptr) {
855 set_class_loader_data(loader_data);
856 }
857
858 // Add to class loader list first before creating the mirror
859 // (same order as class file parsing)
860 loader_data->add_class(this);
861
862 JFR_ONLY(Jfr::on_restoration(this, THREAD);)
863
864 Handle loader(THREAD, loader_data->class_loader());
865 ModuleEntry* module_entry = nullptr;
866 Klass* k = this;
867 if (k->is_objArray_klass()) {
868 k = ObjArrayKlass::cast(k)->bottom_klass();
869 }
870 // Obtain klass' module.
871 if (k->is_instance_klass()) {
872 InstanceKlass* ik = (InstanceKlass*) k;
873 module_entry = ik->module();
874 } else {
875 module_entry = ModuleEntryTable::javabase_moduleEntry();
876 }
877 // Obtain java.lang.Module, if available
878 Handle module_handle(THREAD, ((module_entry != nullptr) ? module_entry->module_oop() : (oop)nullptr));
879
880 if (this->has_archived_mirror_index()) {
881 ResourceMark rm(THREAD);
882 log_debug(aot, mirror)("%s has raw archived mirror", external_name());
883 if (HeapShared::is_archived_heap_in_use()) {
884 bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
885 protection_domain,
886 CHECK);
887 if (present) {
888 return;
889 }
890 }
891
892 // No archived mirror data
893 log_debug(aot, mirror)("No archived mirror data for %s", external_name());
894 clear_java_mirror_handle();
895 this->clear_archived_mirror_index();
896 }
897
898 // Only recreate it if not present. A previous attempt to restore may have
899 // gotten an OOM later but keep the mirror if it was created.
900 if (java_mirror() == nullptr) {
901 ResourceMark rm(THREAD);
902 log_trace(aot, mirror)("Recreate mirror for %s", external_name());
903 java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
904 }
905 }
906 #endif // INCLUDE_CDS
907
908 #if INCLUDE_CDS_JAVA_HEAP
909 oop Klass::archived_java_mirror() {
910 assert(has_archived_mirror_index(), "must have archived mirror");
911 return HeapShared::get_root(_archived_mirror_index);
912 }
913
914 void Klass::clear_archived_mirror_index() {
915 if (_archived_mirror_index >= 0) {
916 HeapShared::clear_root(_archived_mirror_index);
917 }
918 _archived_mirror_index = -1;
919 }
920 #endif // INCLUDE_CDS_JAVA_HEAP
921
922 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
923 if (length > max_length) {
924 if (!THREAD->is_in_internal_oome_mark()) {
925 report_java_out_of_memory("Requested array size exceeds VM limit");
926 JvmtiExport::post_array_size_exhausted();
927 THROW_OOP(Universe::out_of_memory_error_array_size());
928 } else {
929 THROW_OOP(Universe::out_of_memory_error_java_heap_without_backtrace());
930 }
931 } else if (length < 0) {
932 THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
933 }
934 }
935
936 // Replace the last '+' char with '/'.
937 static char* convert_hidden_name_to_java(Symbol* name) {
938 size_t name_len = name->utf8_length();
939 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
940 name->as_klass_external_name(result, (int)name_len + 1);
941 for (int index = (int)name_len; index > 0; index--) {
942 if (result[index] == '+') {
943 result[index] = JVM_SIGNATURE_SLASH;
944 break;
945 }
946 }
947 return result;
948 }
949
950 // In product mode, this function doesn't have virtual function calls so
951 // there might be some performance advantage to handling InstanceKlass here.
952 const char* Klass::external_name() const {
953 if (is_instance_klass()) {
954 const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
955 if (ik->is_hidden()) {
956 char* result = convert_hidden_name_to_java(name());
957 return result;
958 }
959 } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
960 char* result = convert_hidden_name_to_java(name());
961 return result;
962 }
963 if (name() == nullptr) return "<unknown>";
964 return name()->as_klass_external_name();
965 }
966
967 const char* Klass::signature_name() const {
968 if (name() == nullptr) return "<unknown>";
969 if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
970 size_t name_len = name()->utf8_length();
971 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
972 name()->as_C_string(result, (int)name_len + 1);
973 for (int index = (int)name_len; index > 0; index--) {
974 if (result[index] == '+') {
975 result[index] = JVM_SIGNATURE_DOT;
976 break;
977 }
978 }
979 return result;
980 }
981 return name()->as_C_string();
982 }
983
984 const char* Klass::external_kind() const {
985 if (is_interface()) return "interface";
986 if (is_abstract()) return "abstract class";
987 return "class";
988 }
989
990 // Unless overridden, jvmti_class_status has no flags set.
991 jint Klass::jvmti_class_status() const {
992 return 0;
993 }
994
995
996 // Printing
997
998 void Klass::print_on(outputStream* st) const {
999 ResourceMark rm;
1000 // print title
1001 st->print("%s", internal_name());
1002 print_address_on(st);
1003 st->cr();
1004 }
1005
1006 #define BULLET " - "
1007
1008 // Caller needs ResourceMark
1009 void Klass::oop_print_on(oop obj, outputStream* st) {
1010 // print title
1011 st->print_cr("%s ", internal_name());
1012 obj->print_address_on(st);
1013
1014 if (WizardMode) {
1015 // print header
1016 obj->mark().print_on(st);
1017 st->cr();
1018 st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
1019 st->cr();
1020 }
1021
1022 // print class
1023 st->print(BULLET"klass: ");
1024 obj->klass()->print_value_on(st);
1025 st->print(BULLET"flags: "); _misc_flags.print_on(st); st->cr();
1026 st->cr();
1027 }
1028
1029 void Klass::oop_print_value_on(oop obj, outputStream* st) {
1030 // print title
1031 ResourceMark rm; // Cannot print in debug mode without this
1032 st->print("%s", internal_name());
1033 obj->print_address_on(st);
1034 }
1035
1036 // Verification
1037
1038 void Klass::verify_on(outputStream* st) {
1039
1040 // This can be expensive, but it is worth checking that this klass is actually
1041 // in the CLD graph but not in production.
1042 #ifdef ASSERT
1043 if (UseCompressedClassPointers) {
1044 // Stricter checks for both correct alignment and placement
1045 CompressedKlassPointers::check_encodable(this);
1046 } else {
1047 assert(Metaspace::contains((address)this), "Should be");
1048 }
1049 #endif // ASSERT
1050
1051 guarantee(this->is_klass(),"should be klass");
1052
1053 if (super() != nullptr) {
1054 guarantee(super()->is_klass(), "should be klass");
1055 }
1056 if (secondary_super_cache() != nullptr) {
1057 Klass* ko = secondary_super_cache();
1058 guarantee(ko->is_klass(), "should be klass");
1059 }
1060 for ( uint i = 0; i < primary_super_limit(); i++ ) {
1061 Klass* ko = _primary_supers[i];
1062 if (ko != nullptr) {
1063 guarantee(ko->is_klass(), "should be klass");
1064 }
1065 }
1066
1067 if (java_mirror_no_keepalive() != nullptr) {
1068 guarantee(java_lang_Class::is_instance(java_mirror_no_keepalive()), "should be instance");
1069 }
1070 }
1071
1072 void Klass::oop_verify_on(oop obj, outputStream* st) {
1073 guarantee(oopDesc::is_oop(obj), "should be oop");
1074 guarantee(obj->klass()->is_klass(), "klass field is not a klass");
1075 }
1076
1077 // Note: this function is called with an address that may or may not be a Klass.
1078 // The point is not to assert it is but to check if it could be.
1079 bool Klass::is_valid(Klass* k) {
1080 if (!is_aligned(k, sizeof(MetaWord))) return false;
1081 if ((size_t)k < os::min_page_size()) return false;
1082
1083 if (!os::is_readable_range(k, k + 1)) return false;
1084 if (!Metaspace::contains(k)) return false;
1085
1086 if (!Symbol::is_valid(k->name())) return false;
1087 return ClassLoaderDataGraph::is_valid(k->class_loader_data());
1088 }
1089
1090 Method* Klass::method_at_vtable(int index) {
1091 #ifndef PRODUCT
1092 assert(index >= 0, "valid vtable index");
1093 if (DebugVtables) {
1094 verify_vtable_index(index);
1095 }
1096 #endif
1097 return start_of_vtable()[index].method();
1098 }
1099
1100
1101 #ifndef PRODUCT
1102
1103 bool Klass::verify_vtable_index(int i) {
1104 int limit = vtable_length()/vtableEntry::size();
1105 assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
1106 return true;
1107 }
1108
1109 #endif // PRODUCT
1110
1111 // Caller needs ResourceMark
1112 // joint_in_module_of_loader provides an optimization if 2 classes are in
1113 // the same module to succinctly print out relevant information about their
1114 // module name and class loader's name_and_id for error messages.
1115 // Format:
1116 // <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
1117 // are in module <module-name>[@<version>]
1118 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1119 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
1120 assert(module() == class2->module(), "classes do not have the same module");
1121 const char* class1_name = external_name();
1122 size_t len = strlen(class1_name) + 1;
1123
1124 const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
1125 len += strlen(class2_description);
1126
1127 len += strlen(" and ");
1128
1129 char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1130
1131 // Just return the FQN if error when allocating string
1132 if (joint_description == nullptr) {
1133 return class1_name;
1134 }
1135
1136 jio_snprintf(joint_description, len, "%s and %s",
1137 class1_name,
1138 class2_description);
1139
1140 return joint_description;
1141 }
1142
1143 // Caller needs ResourceMark
1144 // class_in_module_of_loader provides a standard way to include
1145 // relevant information about a class, such as its module name as
1146 // well as its class loader's name_and_id, in error messages and logging.
1147 // Format:
1148 // <fully-qualified-external-class-name> is in module <module-name>[@<version>]
1149 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1150 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
1151 // 1. fully qualified external name of class
1152 const char* klass_name = external_name();
1153 size_t len = strlen(klass_name) + 1;
1154
1155 // 2. module name + @version
1156 const char* module_name = "";
1157 const char* version = "";
1158 bool has_version = false;
1159 bool module_is_named = false;
1160 const char* module_name_phrase = "";
1161 const Klass* bottom_klass = is_objArray_klass() ?
1162 ObjArrayKlass::cast(this)->bottom_klass() : this;
1163 if (bottom_klass->is_instance_klass()) {
1164 ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
1165 if (module->is_named()) {
1166 module_is_named = true;
1167 module_name_phrase = "module ";
1168 module_name = module->name()->as_C_string();
1169 len += strlen(module_name);
1170 // Use version if exists and is not a jdk module
1171 if (module->should_show_version()) {
1172 has_version = true;
1173 version = module->version()->as_C_string();
1174 // Include stlen(version) + 1 for the "@"
1175 len += strlen(version) + 1;
1176 }
1177 } else {
1178 module_name = UNNAMED_MODULE;
1179 len += UNNAMED_MODULE_LEN;
1180 }
1181 } else {
1182 // klass is an array of primitives, module is java.base
1183 module_is_named = true;
1184 module_name_phrase = "module ";
1185 module_name = JAVA_BASE_NAME;
1186 len += JAVA_BASE_NAME_LEN;
1187 }
1188
1189 // 3. class loader's name_and_id
1190 ClassLoaderData* cld = class_loader_data();
1191 assert(cld != nullptr, "class_loader_data should not be null");
1192 const char* loader_name_and_id = cld->loader_name_and_id();
1193 len += strlen(loader_name_and_id);
1194
1195 // 4. include parent loader information
1196 const char* parent_loader_phrase = "";
1197 const char* parent_loader_name_and_id = "";
1198 if (include_parent_loader &&
1199 !cld->is_builtin_class_loader_data()) {
1200 oop parent_loader = java_lang_ClassLoader::parent(class_loader());
1201 ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
1202 // The parent loader's ClassLoaderData could be null if it is
1203 // a delegating class loader that has never defined a class.
1204 // In this case the loader's name must be obtained via the parent loader's oop.
1205 if (parent_cld == nullptr) {
1206 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
1207 if (cl_name_and_id != nullptr) {
1208 parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
1209 }
1210 } else {
1211 parent_loader_name_and_id = parent_cld->loader_name_and_id();
1212 }
1213 parent_loader_phrase = ", parent loader ";
1214 len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
1215 }
1216
1217 // Start to construct final full class description string
1218 len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
1219 len += strlen(module_name_phrase) + strlen(" of loader ");
1220
1221 char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1222
1223 // Just return the FQN if error when allocating string
1224 if (class_description == nullptr) {
1225 return klass_name;
1226 }
1227
1228 jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
1229 klass_name,
1230 (use_are) ? "are" : "is",
1231 module_name_phrase,
1232 module_name,
1233 (has_version) ? "@" : "",
1234 (has_version) ? version : "",
1235 loader_name_and_id,
1236 parent_loader_phrase,
1237 parent_loader_name_and_id);
1238
1239 return class_description;
1240 }
1241
1242 class LookupStats : StackObj {
1243 private:
1244 uint _no_of_samples;
1245 uint _worst;
1246 uint _worst_count;
1247 uint _average;
1248 uint _best;
1249 uint _best_count;
1250 public:
1251 LookupStats() : _no_of_samples(0), _worst(0), _worst_count(0), _average(0), _best(INT_MAX), _best_count(0) {}
1252
1253 ~LookupStats() {
1254 assert(_best <= _worst || _no_of_samples == 0, "sanity");
1255 }
1256
1257 void sample(uint value) {
1258 ++_no_of_samples;
1259 _average += value;
1260
1261 if (_worst < value) {
1262 _worst = value;
1263 _worst_count = 1;
1264 } else if (_worst == value) {
1265 ++_worst_count;
1266 }
1267
1268 if (_best > value) {
1269 _best = value;
1270 _best_count = 1;
1271 } else if (_best == value) {
1272 ++_best_count;
1273 }
1274 }
1275
1276 void print_on(outputStream* st) const {
1277 st->print("best: %2d (%4.1f%%)", _best, (100.0 * _best_count) / _no_of_samples);
1278 if (_best_count < _no_of_samples) {
1279 st->print("; average: %4.1f; worst: %2d (%4.1f%%)",
1280 (1.0 * _average) / _no_of_samples,
1281 _worst, (100.0 * _worst_count) / _no_of_samples);
1282 }
1283 }
1284 };
1285
1286 static void print_positive_lookup_stats(Array<Klass*>* secondary_supers, uintx bitmap, outputStream* st) {
1287 int num_of_supers = secondary_supers->length();
1288
1289 LookupStats s;
1290 for (int i = 0; i < num_of_supers; i++) {
1291 Klass* secondary_super = secondary_supers->at(i);
1292 int home_slot = Klass::compute_home_slot(secondary_super, bitmap);
1293 uint score = 1 + ((i - home_slot) & Klass::SECONDARY_SUPERS_TABLE_MASK);
1294 s.sample(score);
1295 }
1296 st->print("positive_lookup: "); s.print_on(st);
1297 }
1298
1299 static uint compute_distance_to_nearest_zero(int slot, uintx bitmap) {
1300 assert(~bitmap != 0, "no zeroes");
1301 uintx start = rotate_right(bitmap, slot);
1302 return count_trailing_zeros(~start);
1303 }
1304
1305 static void print_negative_lookup_stats(uintx bitmap, outputStream* st) {
1306 LookupStats s;
1307 for (int slot = 0; slot < Klass::SECONDARY_SUPERS_TABLE_SIZE; slot++) {
1308 uint score = compute_distance_to_nearest_zero(slot, bitmap);
1309 s.sample(score);
1310 }
1311 st->print("negative_lookup: "); s.print_on(st);
1312 }
1313
1314 void Klass::print_secondary_supers_on(outputStream* st) const {
1315 if (secondary_supers() != nullptr) {
1316 st->print(" - "); st->print("%d elements;", _secondary_supers->length());
1317 st->print_cr(" bitmap: " UINTX_FORMAT_X_0, _secondary_supers_bitmap);
1318 if (_secondary_supers_bitmap != SECONDARY_SUPERS_BITMAP_EMPTY &&
1319 _secondary_supers_bitmap != SECONDARY_SUPERS_BITMAP_FULL) {
1320 st->print(" - "); print_positive_lookup_stats(secondary_supers(),
1321 _secondary_supers_bitmap, st); st->cr();
1322 st->print(" - "); print_negative_lookup_stats(_secondary_supers_bitmap, st); st->cr();
1323 }
1324 } else {
1325 st->print("null");
1326 }
1327 }
1328
1329 void Klass::on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg) {
1330 ResourceMark rm;
1331 super->print();
1332 sub->print();
1333 fatal("%s: %s implements %s: linear_search: %d; table_lookup: %d",
1334 msg, sub->external_name(), super->external_name(), linear_result, table_result);
1335 }