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 void Klass::set_java_mirror(Handle m) {
61 assert(!m.is_null(), "New mirror should never be null.");
62 assert(_java_mirror.is_empty(), "should only be used to initialize mirror");
63 _java_mirror = class_loader_data()->add_handle(m);
64 }
65
66 bool Klass::is_cloneable() const {
67 return _misc_flags.is_cloneable_fast() ||
68 is_subtype_of(vmClasses::Cloneable_klass());
69 }
70
71 void Klass::set_is_cloneable() {
72 if (name() == vmSymbols::java_lang_invoke_MemberName()) {
73 assert(is_final(), "no subclasses allowed");
74 // MemberName cloning should not be intrinsified and always happen in JVM_Clone.
75 } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {
76 // Reference cloning should not be intrinsified and always happen in JVM_Clone.
77 } else {
78 _misc_flags.set_is_cloneable_fast(true);
79 }
80 }
81
82 uint8_t Klass::compute_hash_slot(Symbol* n) {
83 uint hash_code;
84 // Special cases for the two superclasses of all Array instances.
85 // Code elsewhere assumes, for all instances of ArrayKlass, that
86 // these two interfaces will be in this order.
87
88 // We ensure there are some empty slots in the hash table between
89 // these two very common interfaces because if they were adjacent
90 // (e.g. Slots 0 and 1), then any other class which hashed to 0 or 1
91 // would result in a probe length of 3.
92 if (n == vmSymbols::java_lang_Cloneable()) {
93 hash_code = 0;
94 } else if (n == vmSymbols::java_io_Serializable()) {
95 hash_code = SECONDARY_SUPERS_TABLE_SIZE / 2;
96 } else {
97 auto s = (const jbyte*) n->bytes();
98 hash_code = java_lang_String::hash_code(s, n->utf8_length());
99 // We use String::hash_code here (rather than e.g.
100 // Symbol::identity_hash()) in order to have a hash code that
101 // does not change from run to run. We want that because the
102 // hash value for a secondary superclass appears in generated
103 // code as a constant.
104
105 // This constant is magic: see Knuth, "Fibonacci Hashing".
106 constexpr uint multiplier
107 = 2654435769; // (uint)(((u8)1 << 32) / ((1 + sqrt(5)) / 2 ))
108 constexpr uint hash_shift = sizeof(hash_code) * 8 - 6;
109 // The leading bits of the least significant half of the product.
110 hash_code = (hash_code * multiplier) >> hash_shift;
111
112 if (StressSecondarySupers) {
113 // Generate many hash collisions in order to stress-test the
114 // linear search fallback.
115 hash_code = hash_code % 3;
116 hash_code = hash_code * (SECONDARY_SUPERS_TABLE_SIZE / 3);
117 }
118 }
119
120 return (hash_code & SECONDARY_SUPERS_TABLE_MASK);
121 }
122
123 void Klass::set_name(Symbol* n) {
124 _name = n;
125
126 if (_name != nullptr) {
127 _name->increment_refcount();
128 }
129
130 {
131 elapsedTimer selftime;
132 selftime.start();
133
134 _hash_slot = compute_hash_slot(n);
135 assert(_hash_slot < SECONDARY_SUPERS_TABLE_SIZE, "required");
136
137 selftime.stop();
138 if (UsePerfData) {
139 ClassLoader::perf_secondary_hash_time()->inc(selftime.ticks());
140 }
141 }
142
143 if (CDSConfig::is_dumping_archive() && is_instance_klass()) {
144 SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
145 }
146 }
147
148 bool Klass::is_subclass_of(const Klass* k) const {
149 // Run up the super chain and check
150 if (this == k) return true;
151
152 Klass* t = const_cast<Klass*>(this)->super();
153
154 while (t != nullptr) {
155 if (t == k) return true;
156 t = t->super();
157 }
158 return false;
159 }
160
161 void Klass::release_C_heap_structures(bool release_constant_pool) {
162 if (_name != nullptr) _name->decrement_refcount();
163 }
164
165 bool Klass::linear_search_secondary_supers(const Klass* k) const {
166 // Scan the array-of-objects for a match
167 // FIXME: We could do something smarter here, maybe a vectorized
168 // comparison or a binary search, but is that worth any added
169 // complexity?
170 int cnt = secondary_supers()->length();
171 for (int i = 0; i < cnt; i++) {
172 if (secondary_supers()->at(i) == k) {
173 return true;
174 }
175 }
176 return false;
177 }
178
179 // Given a secondary superklass k, an initial array index, and an
180 // occupancy bitmap rotated such that Bit 1 is the next bit to test,
181 // search for k.
182 bool Klass::fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const {
183 // Once the occupancy bitmap is almost full, it's faster to use a
184 // linear search.
185 if (secondary_supers()->length() > SECONDARY_SUPERS_TABLE_SIZE - 2) {
186 return linear_search_secondary_supers(k);
187 }
188
189 // This is conventional linear probing, but instead of terminating
190 // when a null entry is found in the table, we maintain a bitmap
191 // in which a 0 indicates missing entries.
192
193 precond((int)population_count(rotated_bitmap) == secondary_supers()->length());
194
195 // The check for secondary_supers()->length() <= SECONDARY_SUPERS_TABLE_SIZE - 2
196 // at the start of this function guarantees there are 0s in the
197 // bitmap, so this loop eventually terminates.
198 while ((rotated_bitmap & 2) != 0) {
199 if (++index == secondary_supers()->length()) {
200 index = 0;
201 }
202 if (secondary_supers()->at(index) == k) {
203 return true;
204 }
205 rotated_bitmap = rotate_right(rotated_bitmap, 1);
206 }
207 return false;
208 }
209
210 // Return self, except for abstract classes with exactly 1
211 // implementor. Then return the 1 concrete implementation.
212 Klass *Klass::up_cast_abstract() {
213 Klass *r = this;
214 while( r->is_abstract() ) { // Receiver is abstract?
215 Klass *s = r->subklass(); // Check for exactly 1 subklass
216 if (s == nullptr || s->next_sibling() != nullptr) // Oops; wrong count; give up
217 return this; // Return 'this' as a no-progress flag
218 r = s; // Loop till find concrete class
219 }
220 return r; // Return the 1 concrete class
221 }
222
223 // Find LCA in class hierarchy
224 Klass *Klass::LCA( Klass *k2 ) {
225 Klass *k1 = this;
226 while( 1 ) {
227 if( k1->is_subtype_of(k2) ) return k2;
228 if( k2->is_subtype_of(k1) ) return k1;
229 k1 = k1->super();
230 k2 = k2->super();
231 }
232 }
233
234
235 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
236 ResourceMark rm(THREAD);
237 THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
238 : vmSymbols::java_lang_InstantiationException(), external_name());
239 }
240
241
242 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
243 ResourceMark rm(THREAD);
244 assert(s != nullptr, "Throw NPE!");
245 THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
246 err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
247 }
248
249
250 void Klass::initialize(TRAPS) {
251 ShouldNotReachHere();
252 }
253
254 void Klass::initialize_preemptable(TRAPS) {
255 ShouldNotReachHere();
256 }
257
258 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
259 #ifdef ASSERT
260 tty->print_cr("Error: find_field called on a klass oop."
261 " Likely error: reflection method does not correctly"
262 " wrap return value in a mirror object.");
263 #endif
264 ShouldNotReachHere();
265 return nullptr;
266 }
267
268 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
269 OverpassLookupMode overpass_mode,
270 PrivateLookupMode private_mode) const {
271 #ifdef ASSERT
272 tty->print_cr("Error: uncached_lookup_method called on a klass oop."
273 " Likely error: reflection method does not correctly"
274 " wrap return value in a mirror object.");
275 #endif
276 ShouldNotReachHere();
277 return nullptr;
278 }
279
280 void* Klass::operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw() {
281 return Metaspace::allocate(loader_data, word_size, MetaspaceObj::ClassType, THREAD);
282 }
283
284 Klass::Klass() : _kind(UnknownKlassKind) {
285 assert(CDSConfig::is_dumping_static_archive() || CDSConfig::is_using_archive(), "only for cds");
286 }
287
288 // "Normal" instantiation is preceded by a MetaspaceObj allocation
289 // which zeros out memory - calloc equivalent.
290 // The constructor is also used from CppVtableCloner,
291 // which doesn't zero out the memory before calling the constructor.
292 Klass::Klass(KlassKind kind, markWord prototype_header) : _kind(kind),
293 _shared_class_path_index(-1) {
294 set_prototype_header(make_prototype_header(this, prototype_header));
295 CDS_ONLY(_aot_class_flags = 0;)
296 CDS_JAVA_HEAP_ONLY(_archived_mirror_index = -1;)
297 _primary_supers[0] = this;
298 set_super_check_offset(in_bytes(primary_supers_offset()));
299 }
300
301 jint Klass::array_layout_helper(BasicType etype) {
302 assert(etype >= T_BOOLEAN && etype <= T_OBJECT, "valid etype");
303 // Note that T_ARRAY is not allowed here.
304 int hsize = arrayOopDesc::base_offset_in_bytes(etype);
305 int esize = type2aelembytes(etype);
306 bool isobj = (etype == T_OBJECT);
307 int tag = isobj ? _lh_array_tag_ref_value : _lh_array_tag_type_value;
308 int lh = array_layout_helper(tag, false, hsize, etype, exact_log2(esize));
309
310 assert(lh < (int)_lh_neutral_value, "must look like an array layout");
311 assert(layout_helper_is_array(lh), "correct kind");
312 assert(layout_helper_is_refArray(lh) == isobj, "correct kind");
313 assert(layout_helper_is_typeArray(lh) == !isobj, "correct kind");
314 assert(layout_helper_header_size(lh) == hsize, "correct decode");
315 assert(layout_helper_element_type(lh) == etype, "correct decode");
316 assert(1 << layout_helper_log2_element_size(lh) == esize, "correct decode");
317
318 return lh;
319 }
320
321 int Klass::modifier_flags() const {
322 int mods = java_lang_Class::modifiers(java_mirror());
323 assert(mods == compute_modifier_flags(), "should be same");
324 return mods;
325 }
326
327 bool Klass::can_be_primary_super_slow() const {
328 if (super() == nullptr)
329 return true;
330 else if (super()->super_depth() >= primary_super_limit()-1)
331 return false;
332 else
333 return true;
334 }
335
336 void Klass::set_secondary_supers(Array<Klass*>* secondaries, uintx bitmap) {
337 #ifdef ASSERT
338 if (secondaries != nullptr) {
339 uintx real_bitmap = compute_secondary_supers_bitmap(secondaries);
340 assert(bitmap == real_bitmap, "must be");
341 assert(secondaries->length() >= (int)population_count(bitmap), "must be");
342 }
343 #endif
344 _secondary_supers_bitmap = bitmap;
345 _secondary_supers = secondaries;
346
347 if (secondaries != nullptr) {
348 LogMessage(class, load) msg;
349 NonInterleavingLogStream log {LogLevel::Debug, msg};
350 if (log.is_enabled()) {
351 ResourceMark rm;
352 log.print_cr("set_secondary_supers: hash_slot: %d; klass: %s", hash_slot(), external_name());
353 print_secondary_supers_on(&log);
354 }
355 }
356 }
357
358 // Hashed secondary superclasses
359 //
360 // We use a compressed 64-entry hash table with linear probing. We
361 // start by creating a hash table in the usual way, followed by a pass
362 // that removes all the null entries. To indicate which entries would
363 // have been null we use a bitmap that contains a 1 in each position
364 // where an entry is present, 0 otherwise. This bitmap also serves as
365 // a kind of Bloom filter, which in many cases allows us quickly to
366 // eliminate the possibility that something is a member of a set of
367 // secondaries.
368 uintx Klass::hash_secondary_supers(Array<Klass*>* secondaries, bool rewrite) {
369 const int length = secondaries->length();
370
371 if (length == 0) {
372 return SECONDARY_SUPERS_BITMAP_EMPTY;
373 }
374
375 if (length == 1) {
376 int hash_slot = secondaries->at(0)->hash_slot();
377 return uintx(1) << hash_slot;
378 }
379
380 // Invariant: _secondary_supers.length >= population_count(_secondary_supers_bitmap)
381
382 // Don't attempt to hash a table that's completely full, because in
383 // the case of an absent interface linear probing would not
384 // terminate.
385 if (length >= SECONDARY_SUPERS_TABLE_SIZE) {
386 return SECONDARY_SUPERS_BITMAP_FULL;
387 }
388
389 {
390 PerfTraceTime ptt(ClassLoader::perf_secondary_hash_time());
391
392 ResourceMark rm;
393 uintx bitmap = SECONDARY_SUPERS_BITMAP_EMPTY;
394 auto hashed_secondaries = new GrowableArray<Klass*>(SECONDARY_SUPERS_TABLE_SIZE,
395 SECONDARY_SUPERS_TABLE_SIZE, nullptr);
396
397 for (int j = 0; j < length; j++) {
398 Klass* k = secondaries->at(j);
399 hash_insert(k, hashed_secondaries, bitmap);
400 }
401
402 // Pack the hashed secondaries array by copying it into the
403 // secondaries array, sans nulls, if modification is allowed.
404 // Otherwise, validate the order.
405 int i = 0;
406 for (int slot = 0; slot < SECONDARY_SUPERS_TABLE_SIZE; slot++) {
407 bool has_element = ((bitmap >> slot) & 1) != 0;
408 assert(has_element == (hashed_secondaries->at(slot) != nullptr), "");
409 if (has_element) {
410 Klass* k = hashed_secondaries->at(slot);
411 if (rewrite) {
412 secondaries->at_put(i, k);
413 } else if (secondaries->at(i) != k) {
414 assert(false, "broken secondary supers hash table");
415 return SECONDARY_SUPERS_BITMAP_FULL;
416 }
417 i++;
418 }
419 }
420 assert(i == secondaries->length(), "mismatch");
421 postcond((int)population_count(bitmap) == secondaries->length());
422
423 return bitmap;
424 }
425 }
426
427 void Klass::hash_insert(Klass* klass, GrowableArray<Klass*>* secondaries, uintx& bitmap) {
428 assert(bitmap != SECONDARY_SUPERS_BITMAP_FULL, "");
429
430 int dist = 0;
431 for (int slot = klass->hash_slot(); true; slot = (slot + 1) & SECONDARY_SUPERS_TABLE_MASK) {
432 Klass* existing = secondaries->at(slot);
433 assert(((bitmap >> slot) & 1) == (existing != nullptr), "mismatch");
434 if (existing == nullptr) { // no conflict
435 secondaries->at_put(slot, klass);
436 bitmap |= uintx(1) << slot;
437 assert(bitmap != SECONDARY_SUPERS_BITMAP_FULL, "");
438 return;
439 } else {
440 // Use Robin Hood hashing to minimize the worst case search.
441 // Also, every permutation of the insertion sequence produces
442 // the same final Robin Hood hash table, provided that a
443 // consistent tie breaker is used.
444 int existing_dist = (slot - existing->hash_slot()) & SECONDARY_SUPERS_TABLE_MASK;
445 if (existing_dist < dist
446 // This tie breaker ensures that the hash order is maintained.
447 || ((existing_dist == dist)
448 && (uintptr_t(existing) < uintptr_t(klass)))) {
449 Klass* tmp = secondaries->at(slot);
450 secondaries->at_put(slot, klass);
451 klass = tmp;
452 dist = existing_dist;
453 }
454 ++dist;
455 }
456 }
457 }
458
459 Array<Klass*>* Klass::pack_secondary_supers(ClassLoaderData* loader_data,
460 GrowableArray<Klass*>* primaries,
461 GrowableArray<Klass*>* secondaries,
462 uintx& bitmap, TRAPS) {
463 int new_length = primaries->length() + secondaries->length();
464 Array<Klass*>* secondary_supers = MetadataFactory::new_array<Klass*>(loader_data, new_length, CHECK_NULL);
465
466 // Combine the two arrays into a metadata object to pack the array.
467 // The primaries are added in the reverse order, then the secondaries.
468 int fill_p = primaries->length();
469 for (int j = 0; j < fill_p; j++) {
470 secondary_supers->at_put(j, primaries->pop()); // add primaries in reverse order.
471 }
472 for( int j = 0; j < secondaries->length(); j++ ) {
473 secondary_supers->at_put(j+fill_p, secondaries->at(j)); // add secondaries on the end.
474 }
475 #ifdef ASSERT
476 // We must not copy any null placeholders left over from bootstrap.
477 for (int j = 0; j < secondary_supers->length(); j++) {
478 assert(secondary_supers->at(j) != nullptr, "correct bootstrapping order");
479 }
480 #endif
481
482 bitmap = hash_secondary_supers(secondary_supers, /*rewrite=*/true); // rewrites freshly allocated array
483 return secondary_supers;
484 }
485
486 uintx Klass::compute_secondary_supers_bitmap(Array<Klass*>* secondary_supers) {
487 return hash_secondary_supers(secondary_supers, /*rewrite=*/false); // no rewrites allowed
488 }
489
490 uint8_t Klass::compute_home_slot(Klass* k, uintx bitmap) {
491 uint8_t hash = k->hash_slot();
492 if (hash > 0) {
493 return population_count(bitmap << (SECONDARY_SUPERS_TABLE_SIZE - hash));
494 }
495 return 0;
496 }
497
498
499 void Klass::initialize_supers(Klass* k, Array<InstanceKlass*>* transitive_interfaces, TRAPS) {
500 if (k == nullptr) {
501 set_super(nullptr);
502 _primary_supers[0] = this;
503 assert(super_depth() == 0, "Object must already be initialized properly");
504 } else if (k != super() || k == vmClasses::Object_klass()) {
505 assert(super() == nullptr || super() == vmClasses::Object_klass(),
506 "initialize this only once to a non-trivial value");
507 set_super(k);
508 Klass* sup = k;
509 int sup_depth = sup->super_depth();
510 juint my_depth = MIN2(sup_depth + 1, (int)primary_super_limit());
511 if (!can_be_primary_super_slow())
512 my_depth = primary_super_limit();
513 for (juint i = 0; i < my_depth; i++) {
514 _primary_supers[i] = sup->_primary_supers[i];
515 }
516 Klass* *super_check_cell;
517 if (my_depth < primary_super_limit()) {
518 _primary_supers[my_depth] = this;
519 super_check_cell = &_primary_supers[my_depth];
520 } else {
521 // Overflow of the primary_supers array forces me to be secondary.
522 super_check_cell = &_secondary_super_cache;
523 }
524 set_super_check_offset(u4((address)super_check_cell - (address) this));
525
526 #ifdef ASSERT
527 {
528 juint j = super_depth();
529 assert(j == my_depth, "computed accessor gets right answer");
530 Klass* t = this;
531 while (!t->can_be_primary_super()) {
532 t = t->super();
533 j = t->super_depth();
534 }
535 for (juint j1 = j+1; j1 < primary_super_limit(); j1++) {
536 assert(primary_super_of_depth(j1) == nullptr, "super list padding");
537 }
538 while (t != nullptr) {
539 assert(primary_super_of_depth(j) == t, "super list initialization");
540 t = t->super();
541 --j;
542 }
543 assert(j == (juint)-1, "correct depth count");
544 }
545 #endif
546 }
547
548 if (secondary_supers() == nullptr) {
549
550 // Now compute the list of secondary supertypes.
551 // Secondaries can occasionally be on the super chain,
552 // if the inline "_primary_supers" array overflows.
553 int extras = 0;
554 Klass* p;
555 for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
556 ++extras;
557 }
558
559 ResourceMark rm(THREAD); // need to reclaim GrowableArrays allocated below
560
561 // Compute the "real" non-extra secondaries.
562 GrowableArray<Klass*>* secondaries = compute_secondary_supers(extras, transitive_interfaces);
563 if (secondaries == nullptr) {
564 // secondary_supers set by compute_secondary_supers
565 return;
566 }
567
568 GrowableArray<Klass*>* primaries = new GrowableArray<Klass*>(extras);
569
570 for (p = super(); !(p == nullptr || p->can_be_primary_super()); p = p->super()) {
571 int i; // Scan for overflow primaries being duplicates of 2nd'arys
572
573 // This happens frequently for very deeply nested arrays: the
574 // primary superclass chain overflows into the secondary. The
575 // secondary list contains the element_klass's secondaries with
576 // an extra array dimension added. If the element_klass's
577 // secondary list already contains some primary overflows, they
578 // (with the extra level of array-ness) will collide with the
579 // normal primary superclass overflows.
580 for( i = 0; i < secondaries->length(); i++ ) {
581 if( secondaries->at(i) == p )
582 break;
583 }
584 if( i < secondaries->length() )
585 continue; // It's a dup, don't put it in
586 primaries->push(p);
587 }
588 // Combine the two arrays into a metadata object to pack the array.
589 uintx bitmap = 0;
590 Array<Klass*>* s2 = pack_secondary_supers(class_loader_data(), primaries, secondaries, bitmap, CHECK);
591 set_secondary_supers(s2, bitmap);
592 }
593 }
594
595 GrowableArray<Klass*>* Klass::compute_secondary_supers(int num_extra_slots,
596 Array<InstanceKlass*>* transitive_interfaces) {
597 assert(num_extra_slots == 0, "override for complex klasses");
598 assert(transitive_interfaces == nullptr, "sanity");
599 set_secondary_supers(Universe::the_empty_klass_array(), Universe::the_empty_klass_bitmap());
600 return nullptr;
601 }
602
603
604 // subklass links. Used by the compiler (and vtable initialization)
605 // May be cleaned concurrently, so must use the Compile_lock.
606 Klass* Klass::subklass() const {
607 // Need load_acquire on the _subklass, because it races with inserts that
608 // publishes freshly initialized data.
609 for (Klass* chain = AtomicAccess::load_acquire(&_subklass);
610 chain != nullptr;
611 // Do not need load_acquire on _next_sibling, because inserts never
612 // create _next_sibling edges to dead data.
613 chain = AtomicAccess::load(&chain->_next_sibling))
614 {
615 if (chain->is_loader_alive()) {
616 return chain;
617 }
618 }
619 return nullptr;
620 }
621
622 Klass* Klass::next_sibling(bool log) const {
623 // Do not need load_acquire on _next_sibling, because inserts never
624 // create _next_sibling edges to dead data.
625 for (Klass* chain = AtomicAccess::load(&_next_sibling);
626 chain != nullptr;
627 chain = AtomicAccess::load(&chain->_next_sibling)) {
628 // Only return alive klass, there may be stale klass
629 // in this chain if cleaned concurrently.
630 if (chain->is_loader_alive()) {
631 return chain;
632 } else if (log) {
633 if (log_is_enabled(Trace, class, unload)) {
634 ResourceMark rm;
635 log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
636 }
637 }
638 }
639 return nullptr;
640 }
641
642 void Klass::set_subklass(Klass* s) {
643 assert(s != this, "sanity check");
644 AtomicAccess::release_store(&_subklass, s);
645 }
646
647 void Klass::set_next_sibling(Klass* s) {
648 assert(s != this, "sanity check");
649 // Does not need release semantics. If used by cleanup, it will link to
650 // already safely published data, and if used by inserts, will be published
651 // safely using cmpxchg.
652 AtomicAccess::store(&_next_sibling, s);
653 }
654
655 void Klass::append_to_sibling_list() {
656 if (Universe::is_fully_initialized()) {
657 assert_locked_or_safepoint(Compile_lock);
658 }
659 DEBUG_ONLY(verify();)
660 // add ourselves to super' subklass list
661 InstanceKlass* super = java_super();
662 if (super == nullptr) return; // special case: class Object
663 assert((!super->is_interface() // interfaces cannot be supers
664 && (super->java_super() == nullptr || !is_interface())),
665 "an interface can only be a subklass of Object");
666
667 // Make sure there is no stale subklass head
668 super->clean_subklass();
669
670 for (;;) {
671 Klass* prev_first_subklass = AtomicAccess::load_acquire(&_super->_subklass);
672 if (prev_first_subklass != nullptr) {
673 // set our sibling to be the super' previous first subklass
674 assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
675 set_next_sibling(prev_first_subklass);
676 }
677 // Note that the prev_first_subklass is always alive, meaning no sibling_next links
678 // are ever created to not alive klasses. This is an important invariant of the lock-free
679 // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
680 if (AtomicAccess::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
681 return;
682 }
683 }
684 DEBUG_ONLY(verify();)
685 }
686
687 // The log parameter is for clean_weak_klass_links to report unlinked classes.
688 Klass* Klass::clean_subklass(bool log) {
689 for (;;) {
690 // Need load_acquire, due to contending with concurrent inserts
691 Klass* subklass = AtomicAccess::load_acquire(&_subklass);
692 if (subklass == nullptr || subklass->is_loader_alive()) {
693 return subklass;
694 }
695 if (log && log_is_enabled(Trace, class, unload)) {
696 ResourceMark rm;
697 log_trace(class, unload)("unlinking class (subclass): %s", subklass->external_name());
698 }
699 // Try to fix _subklass until it points at something not dead.
700 AtomicAccess::cmpxchg(&_subklass, subklass, subklass->next_sibling(log));
701 }
702 }
703
704 void Klass::clean_weak_klass_links(bool unloading_occurred, bool clean_alive_klasses) {
705 if (!ClassUnloading || !unloading_occurred) {
706 return;
707 }
708
709 Klass* root = vmClasses::Object_klass();
710 Stack<Klass*, mtGC> stack;
711
712 stack.push(root);
713 while (!stack.is_empty()) {
714 Klass* current = stack.pop();
715
716 assert(current->is_loader_alive(), "just checking, this should be live");
717
718 // Find and set the first alive subklass
719 Klass* sub = current->clean_subklass(true);
720 if (sub != nullptr) {
721 stack.push(sub);
722 }
723
724 // Find and set the first alive sibling
725 Klass* sibling = current->next_sibling(true);
726 current->set_next_sibling(sibling);
727 if (sibling != nullptr) {
728 stack.push(sibling);
729 }
730
731 // Clean the implementors list and method data.
732 if (clean_alive_klasses && current->is_instance_klass()) {
733 InstanceKlass* ik = InstanceKlass::cast(current);
734 clean_weak_instanceklass_links(ik);
735 }
736 }
737 }
738
739 void Klass::clean_weak_instanceklass_links(InstanceKlass* ik) {
740 ik->clean_weak_instanceklass_links();
741 // JVMTI RedefineClasses creates previous versions that are not in
742 // the class hierarchy, so process them here.
743 while ((ik = ik->previous_versions()) != nullptr) {
744 ik->clean_weak_instanceklass_links();
745 }
746 }
747
748 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
749 if (log_is_enabled(Trace, aot)) {
750 ResourceMark rm;
751 log_trace(aot)("Iter(Klass): %p (%s)", this, external_name());
752 }
753
754 it->push(&_name);
755 it->push(&_secondary_supers);
756 for (int i = 0; i < _primary_super_limit; i++) {
757 it->push(&_primary_supers[i]);
758 }
759 it->push(&_super);
760 if (!CDSConfig::is_dumping_archive()) {
761 // If dumping archive, these may point to excluded classes. There's no need
762 // to follow these pointers anyway, as they will be set to null in
763 // remove_unshareable_info().
764 it->push((Klass**)&_subklass);
765 it->push((Klass**)&_next_sibling);
766 it->push(&_next_link);
767 }
768
769 vtableEntry* vt = start_of_vtable();
770 for (int i=0; i<vtable_length(); i++) {
771 it->push(vt[i].method_addr());
772 }
773 }
774
775 #if INCLUDE_CDS
776 void Klass::remove_unshareable_info() {
777 assert(CDSConfig::is_dumping_archive(),
778 "only called during CDS dump time");
779 JFR_ONLY(REMOVE_ID(this);)
780 if (log_is_enabled(Trace, aot, unshareable)) {
781 ResourceMark rm;
782 log_trace(aot, unshareable)("remove: %s", external_name());
783 }
784
785 // _secondary_super_cache may be updated by an is_subtype_of() call
786 // while ArchiveBuilder is copying metaspace objects. Let's reset it to
787 // null and let it be repopulated at runtime.
788 set_secondary_super_cache(nullptr);
789
790 set_subklass(nullptr);
791 set_next_sibling(nullptr);
792 set_next_link(nullptr);
793
794 // Null out class_loader_data because we don't share that yet.
795 set_class_loader_data(nullptr);
796 set_in_aot_cache();
797
798 if (CDSConfig::is_dumping_classic_static_archive()) {
799 // "Classic" static archives are required to have deterministic contents.
800 // The elements in _secondary_supers are addresses in the ArchiveBuilder
801 // output buffer, so they should have deterministic values. If we rehash
802 // _secondary_supers, its elements will appear in a deterministic order.
803 //
804 // Note that the bitmap is guaranteed to be deterministic, regardless of the
805 // actual addresses of the elements in _secondary_supers. So rehashing shouldn't
806 // change it.
807 uintx bitmap = hash_secondary_supers(secondary_supers(), true);
808 assert(bitmap == _secondary_supers_bitmap, "bitmap should not be changed due to rehashing");
809 }
810 }
811
812 void Klass::remove_java_mirror() {
813 assert(CDSConfig::is_dumping_archive(), "sanity");
814 if (log_is_enabled(Trace, aot, unshareable)) {
815 ResourceMark rm;
816 log_trace(aot, unshareable)("remove java_mirror: %s", external_name());
817 }
818
819 #if INCLUDE_CDS_JAVA_HEAP
820 _archived_mirror_index = -1;
821 if (CDSConfig::is_dumping_heap()) {
822 Klass* src_k = ArchiveBuilder::current()->get_source_addr(this);
823 oop orig_mirror = src_k->java_mirror();
824 if (orig_mirror == nullptr) {
825 assert(CDSConfig::is_dumping_final_static_archive(), "sanity");
826 if (is_instance_klass()) {
827 assert(InstanceKlass::cast(this)->defined_by_other_loaders(), "sanity");
828 } else {
829 precond(is_objArray_klass());
830 Klass *k = ObjArrayKlass::cast(this)->bottom_klass();
831 precond(k->is_instance_klass());
832 assert(InstanceKlass::cast(k)->defined_by_other_loaders(), "sanity");
833 }
834 } else {
835 oop scratch_mirror = HeapShared::scratch_java_mirror(orig_mirror);
836 if (scratch_mirror != nullptr) {
837 _archived_mirror_index = HeapShared::append_root(scratch_mirror);
838 }
839 }
840 }
841 #endif
842
843 // Just null out the mirror. The class_loader_data() no longer exists.
844 clear_java_mirror_handle();
845 }
846
847 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
848 assert(is_klass(), "ensure C++ vtable is restored");
849 assert(in_aot_cache(), "must be set");
850 assert(secondary_supers()->length() >= (int)population_count(_secondary_supers_bitmap), "must be");
851 JFR_ONLY(RESTORE_ID(this);)
852 if (log_is_enabled(Trace, aot, unshareable)) {
853 ResourceMark rm(THREAD);
854 oop class_loader = loader_data->class_loader();
855 log_trace(aot, unshareable)("restore: %s with class loader: %s", external_name(),
856 class_loader != nullptr ? class_loader->klass()->external_name() : "boot");
857 }
858
859 // If an exception happened during CDS restore, some of these fields may already be
860 // set. We leave the class on the CLD list, even if incomplete so that we don't
861 // modify the CLD list outside a safepoint.
862 if (class_loader_data() == nullptr) {
863 set_class_loader_data(loader_data);
864 }
865 // Add to class loader list first before creating the mirror
866 // (same order as class file parsing)
867 loader_data->add_class(this);
868
869 Handle loader(THREAD, loader_data->class_loader());
870 ModuleEntry* module_entry = nullptr;
871 Klass* k = this;
872 if (k->is_objArray_klass()) {
873 k = ObjArrayKlass::cast(k)->bottom_klass();
874 }
875 // Obtain klass' module.
876 if (k->is_instance_klass()) {
877 InstanceKlass* ik = (InstanceKlass*) k;
878 module_entry = ik->module();
879 } else {
880 module_entry = ModuleEntryTable::javabase_moduleEntry();
881 }
882 // Obtain java.lang.Module, if available
883 Handle module_handle(THREAD, ((module_entry != nullptr) ? module_entry->module_oop() : (oop)nullptr));
884
885 if (this->has_archived_mirror_index()) {
886 ResourceMark rm(THREAD);
887 log_debug(aot, mirror)("%s has raw archived mirror", external_name());
888 if (HeapShared::is_archived_heap_in_use()) {
889 bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
890 protection_domain,
891 CHECK);
892 if (present) {
893 return;
894 }
895 }
896
897 // No archived mirror data
898 log_debug(aot, mirror)("No archived mirror data for %s", external_name());
899 clear_java_mirror_handle();
900 this->clear_archived_mirror_index();
901 }
902
903 // Only recreate it if not present. A previous attempt to restore may have
904 // gotten an OOM later but keep the mirror if it was created.
905 if (java_mirror() == nullptr) {
906 ResourceMark rm(THREAD);
907 log_trace(aot, mirror)("Recreate mirror for %s", external_name());
908 java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
909 }
910 }
911 #endif // INCLUDE_CDS
912
913 #if INCLUDE_CDS_JAVA_HEAP
914 oop Klass::archived_java_mirror() {
915 assert(has_archived_mirror_index(), "must have archived mirror");
916 return HeapShared::get_root(_archived_mirror_index);
917 }
918
919 void Klass::clear_archived_mirror_index() {
920 if (_archived_mirror_index >= 0) {
921 HeapShared::clear_root(_archived_mirror_index);
922 }
923 _archived_mirror_index = -1;
924 }
925 #endif // INCLUDE_CDS_JAVA_HEAP
926
927 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
928 if (length > max_length) {
929 if (!THREAD->is_in_internal_oome_mark()) {
930 report_java_out_of_memory("Requested array size exceeds VM limit");
931 JvmtiExport::post_array_size_exhausted();
932 THROW_OOP(Universe::out_of_memory_error_array_size());
933 } else {
934 THROW_OOP(Universe::out_of_memory_error_java_heap_without_backtrace());
935 }
936 } else if (length < 0) {
937 THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
938 }
939 }
940
941 // Replace the last '+' char with '/'.
942 static char* convert_hidden_name_to_java(Symbol* name) {
943 size_t name_len = name->utf8_length();
944 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
945 name->as_klass_external_name(result, (int)name_len + 1);
946 for (int index = (int)name_len; index > 0; index--) {
947 if (result[index] == '+') {
948 result[index] = JVM_SIGNATURE_SLASH;
949 break;
950 }
951 }
952 return result;
953 }
954
955 // In product mode, this function doesn't have virtual function calls so
956 // there might be some performance advantage to handling InstanceKlass here.
957 const char* Klass::external_name() const {
958 if (is_instance_klass()) {
959 const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
960 if (ik->is_hidden()) {
961 char* result = convert_hidden_name_to_java(name());
962 return result;
963 }
964 } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
965 char* result = convert_hidden_name_to_java(name());
966 return result;
967 }
968 if (name() == nullptr) return "<unknown>";
969 return name()->as_klass_external_name();
970 }
971
972 const char* Klass::signature_name() const {
973 if (name() == nullptr) return "<unknown>";
974 if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
975 size_t name_len = name()->utf8_length();
976 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
977 name()->as_C_string(result, (int)name_len + 1);
978 for (int index = (int)name_len; index > 0; index--) {
979 if (result[index] == '+') {
980 result[index] = JVM_SIGNATURE_DOT;
981 break;
982 }
983 }
984 return result;
985 }
986 return name()->as_C_string();
987 }
988
989 const char* Klass::external_kind() const {
990 if (is_interface()) return "interface";
991 if (is_abstract()) return "abstract class";
992 return "class";
993 }
994
995 // Unless overridden, jvmti_class_status has no flags set.
996 jint Klass::jvmti_class_status() const {
997 return 0;
998 }
999
1000
1001 // Printing
1002
1003 void Klass::print_on(outputStream* st) const {
1004 ResourceMark rm;
1005 // print title
1006 st->print("%s", internal_name());
1007 print_address_on(st);
1008 st->cr();
1009 }
1010
1011 #define BULLET " - "
1012
1013 // Caller needs ResourceMark
1014 void Klass::oop_print_on(oop obj, outputStream* st) {
1015 // print title
1016 st->print_cr("%s ", internal_name());
1017 obj->print_address_on(st);
1018
1019 if (WizardMode) {
1020 // print header
1021 obj->mark().print_on(st);
1022 st->cr();
1023 st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
1024 st->cr();
1025 }
1026
1027 // print class
1028 st->print(BULLET"klass: ");
1029 obj->klass()->print_value_on(st);
1030 st->print(BULLET"flags: "); _misc_flags.print_on(st); st->cr();
1031 st->cr();
1032 }
1033
1034 void Klass::oop_print_value_on(oop obj, outputStream* st) {
1035 // print title
1036 ResourceMark rm; // Cannot print in debug mode without this
1037 st->print("%s", internal_name());
1038 obj->print_address_on(st);
1039 }
1040
1041 // Verification
1042
1043 void Klass::verify_on(outputStream* st) {
1044
1045 // This can be expensive, but it is worth checking that this klass is actually
1046 // in the CLD graph but not in production.
1047 #ifdef ASSERT
1048 if (UseCompressedClassPointers) {
1049 // Stricter checks for both correct alignment and placement
1050 CompressedKlassPointers::check_encodable(this);
1051 } else {
1052 assert(Metaspace::contains((address)this), "Should be");
1053 }
1054 #endif // ASSERT
1055
1056 guarantee(this->is_klass(),"should be klass");
1057
1058 if (super() != nullptr) {
1059 guarantee(super()->is_klass(), "should be klass");
1060 }
1061 if (secondary_super_cache() != nullptr) {
1062 Klass* ko = secondary_super_cache();
1063 guarantee(ko->is_klass(), "should be klass");
1064 }
1065 for ( uint i = 0; i < primary_super_limit(); i++ ) {
1066 Klass* ko = _primary_supers[i];
1067 if (ko != nullptr) {
1068 guarantee(ko->is_klass(), "should be klass");
1069 }
1070 }
1071
1072 if (java_mirror_no_keepalive() != nullptr) {
1073 guarantee(java_lang_Class::is_instance(java_mirror_no_keepalive()), "should be instance");
1074 }
1075 }
1076
1077 void Klass::oop_verify_on(oop obj, outputStream* st) {
1078 guarantee(oopDesc::is_oop(obj), "should be oop");
1079 guarantee(obj->klass()->is_klass(), "klass field is not a klass");
1080 }
1081
1082 // Note: this function is called with an address that may or may not be a Klass.
1083 // The point is not to assert it is but to check if it could be.
1084 bool Klass::is_valid(Klass* k) {
1085 if (!is_aligned(k, sizeof(MetaWord))) return false;
1086 if ((size_t)k < os::min_page_size()) return false;
1087
1088 if (!os::is_readable_range(k, k + 1)) return false;
1089 if (!Metaspace::contains(k)) return false;
1090
1091 if (!Symbol::is_valid(k->name())) return false;
1092 return ClassLoaderDataGraph::is_valid(k->class_loader_data());
1093 }
1094
1095 Method* Klass::method_at_vtable(int index) {
1096 #ifndef PRODUCT
1097 assert(index >= 0, "valid vtable index");
1098 if (DebugVtables) {
1099 verify_vtable_index(index);
1100 }
1101 #endif
1102 return start_of_vtable()[index].method();
1103 }
1104
1105
1106 #ifndef PRODUCT
1107
1108 bool Klass::verify_vtable_index(int i) {
1109 int limit = vtable_length()/vtableEntry::size();
1110 assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
1111 return true;
1112 }
1113
1114 #endif // PRODUCT
1115
1116 // Caller needs ResourceMark
1117 // joint_in_module_of_loader provides an optimization if 2 classes are in
1118 // the same module to succinctly print out relevant information about their
1119 // module name and class loader's name_and_id for error messages.
1120 // Format:
1121 // <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
1122 // are in module <module-name>[@<version>]
1123 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1124 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
1125 assert(module() == class2->module(), "classes do not have the same module");
1126 const char* class1_name = external_name();
1127 size_t len = strlen(class1_name) + 1;
1128
1129 const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
1130 len += strlen(class2_description);
1131
1132 len += strlen(" and ");
1133
1134 char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1135
1136 // Just return the FQN if error when allocating string
1137 if (joint_description == nullptr) {
1138 return class1_name;
1139 }
1140
1141 jio_snprintf(joint_description, len, "%s and %s",
1142 class1_name,
1143 class2_description);
1144
1145 return joint_description;
1146 }
1147
1148 // Caller needs ResourceMark
1149 // class_in_module_of_loader provides a standard way to include
1150 // relevant information about a class, such as its module name as
1151 // well as its class loader's name_and_id, in error messages and logging.
1152 // Format:
1153 // <fully-qualified-external-class-name> is in module <module-name>[@<version>]
1154 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1155 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
1156 // 1. fully qualified external name of class
1157 const char* klass_name = external_name();
1158 size_t len = strlen(klass_name) + 1;
1159
1160 // 2. module name + @version
1161 const char* module_name = "";
1162 const char* version = "";
1163 bool has_version = false;
1164 bool module_is_named = false;
1165 const char* module_name_phrase = "";
1166 const Klass* bottom_klass = is_objArray_klass() ?
1167 ObjArrayKlass::cast(this)->bottom_klass() : this;
1168 if (bottom_klass->is_instance_klass()) {
1169 ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
1170 if (module->is_named()) {
1171 module_is_named = true;
1172 module_name_phrase = "module ";
1173 module_name = module->name()->as_C_string();
1174 len += strlen(module_name);
1175 // Use version if exists and is not a jdk module
1176 if (module->should_show_version()) {
1177 has_version = true;
1178 version = module->version()->as_C_string();
1179 // Include stlen(version) + 1 for the "@"
1180 len += strlen(version) + 1;
1181 }
1182 } else {
1183 module_name = UNNAMED_MODULE;
1184 len += UNNAMED_MODULE_LEN;
1185 }
1186 } else {
1187 // klass is an array of primitives, module is java.base
1188 module_is_named = true;
1189 module_name_phrase = "module ";
1190 module_name = JAVA_BASE_NAME;
1191 len += JAVA_BASE_NAME_LEN;
1192 }
1193
1194 // 3. class loader's name_and_id
1195 ClassLoaderData* cld = class_loader_data();
1196 assert(cld != nullptr, "class_loader_data should not be null");
1197 const char* loader_name_and_id = cld->loader_name_and_id();
1198 len += strlen(loader_name_and_id);
1199
1200 // 4. include parent loader information
1201 const char* parent_loader_phrase = "";
1202 const char* parent_loader_name_and_id = "";
1203 if (include_parent_loader &&
1204 !cld->is_builtin_class_loader_data()) {
1205 oop parent_loader = java_lang_ClassLoader::parent(class_loader());
1206 ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
1207 // The parent loader's ClassLoaderData could be null if it is
1208 // a delegating class loader that has never defined a class.
1209 // In this case the loader's name must be obtained via the parent loader's oop.
1210 if (parent_cld == nullptr) {
1211 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
1212 if (cl_name_and_id != nullptr) {
1213 parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
1214 }
1215 } else {
1216 parent_loader_name_and_id = parent_cld->loader_name_and_id();
1217 }
1218 parent_loader_phrase = ", parent loader ";
1219 len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
1220 }
1221
1222 // Start to construct final full class description string
1223 len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
1224 len += strlen(module_name_phrase) + strlen(" of loader ");
1225
1226 char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1227
1228 // Just return the FQN if error when allocating string
1229 if (class_description == nullptr) {
1230 return klass_name;
1231 }
1232
1233 jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
1234 klass_name,
1235 (use_are) ? "are" : "is",
1236 module_name_phrase,
1237 module_name,
1238 (has_version) ? "@" : "",
1239 (has_version) ? version : "",
1240 loader_name_and_id,
1241 parent_loader_phrase,
1242 parent_loader_name_and_id);
1243
1244 return class_description;
1245 }
1246
1247 class LookupStats : StackObj {
1248 private:
1249 uint _no_of_samples;
1250 uint _worst;
1251 uint _worst_count;
1252 uint _average;
1253 uint _best;
1254 uint _best_count;
1255 public:
1256 LookupStats() : _no_of_samples(0), _worst(0), _worst_count(0), _average(0), _best(INT_MAX), _best_count(0) {}
1257
1258 ~LookupStats() {
1259 assert(_best <= _worst || _no_of_samples == 0, "sanity");
1260 }
1261
1262 void sample(uint value) {
1263 ++_no_of_samples;
1264 _average += value;
1265
1266 if (_worst < value) {
1267 _worst = value;
1268 _worst_count = 1;
1269 } else if (_worst == value) {
1270 ++_worst_count;
1271 }
1272
1273 if (_best > value) {
1274 _best = value;
1275 _best_count = 1;
1276 } else if (_best == value) {
1277 ++_best_count;
1278 }
1279 }
1280
1281 void print_on(outputStream* st) const {
1282 st->print("best: %2d (%4.1f%%)", _best, (100.0 * _best_count) / _no_of_samples);
1283 if (_best_count < _no_of_samples) {
1284 st->print("; average: %4.1f; worst: %2d (%4.1f%%)",
1285 (1.0 * _average) / _no_of_samples,
1286 _worst, (100.0 * _worst_count) / _no_of_samples);
1287 }
1288 }
1289 };
1290
1291 static void print_positive_lookup_stats(Array<Klass*>* secondary_supers, uintx bitmap, outputStream* st) {
1292 int num_of_supers = secondary_supers->length();
1293
1294 LookupStats s;
1295 for (int i = 0; i < num_of_supers; i++) {
1296 Klass* secondary_super = secondary_supers->at(i);
1297 int home_slot = Klass::compute_home_slot(secondary_super, bitmap);
1298 uint score = 1 + ((i - home_slot) & Klass::SECONDARY_SUPERS_TABLE_MASK);
1299 s.sample(score);
1300 }
1301 st->print("positive_lookup: "); s.print_on(st);
1302 }
1303
1304 static uint compute_distance_to_nearest_zero(int slot, uintx bitmap) {
1305 assert(~bitmap != 0, "no zeroes");
1306 uintx start = rotate_right(bitmap, slot);
1307 return count_trailing_zeros(~start);
1308 }
1309
1310 static void print_negative_lookup_stats(uintx bitmap, outputStream* st) {
1311 LookupStats s;
1312 for (int slot = 0; slot < Klass::SECONDARY_SUPERS_TABLE_SIZE; slot++) {
1313 uint score = compute_distance_to_nearest_zero(slot, bitmap);
1314 s.sample(score);
1315 }
1316 st->print("negative_lookup: "); s.print_on(st);
1317 }
1318
1319 void Klass::print_secondary_supers_on(outputStream* st) const {
1320 if (secondary_supers() != nullptr) {
1321 st->print(" - "); st->print("%d elements;", _secondary_supers->length());
1322 st->print_cr(" bitmap: " UINTX_FORMAT_X_0, _secondary_supers_bitmap);
1323 if (_secondary_supers_bitmap != SECONDARY_SUPERS_BITMAP_EMPTY &&
1324 _secondary_supers_bitmap != SECONDARY_SUPERS_BITMAP_FULL) {
1325 st->print(" - "); print_positive_lookup_stats(secondary_supers(),
1326 _secondary_supers_bitmap, st); st->cr();
1327 st->print(" - "); print_negative_lookup_stats(_secondary_supers_bitmap, st); st->cr();
1328 }
1329 } else {
1330 st->print("null");
1331 }
1332 }
1333
1334 void Klass::on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg) {
1335 ResourceMark rm;
1336 super->print();
1337 sub->print();
1338 fatal("%s: %s implements %s: linear_search: %d; table_lookup: %d",
1339 msg, sub->external_name(), super->external_name(), linear_result, table_result);
1340 }