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/archiveHeapLoader.hpp"
26 #include "cds/cdsConfig.hpp"
27 #include "cds/heapShared.hpp"
28 #include "classfile/classLoader.hpp"
29 #include "classfile/classLoaderData.inline.hpp"
30 #include "classfile/classLoaderDataGraph.inline.hpp"
31 #include "classfile/javaClasses.inline.hpp"
32 #include "classfile/moduleEntry.hpp"
33 #include "classfile/systemDictionary.hpp"
34 #include "classfile/systemDictionaryShared.hpp"
35 #include "classfile/vmClasses.hpp"
36 #include "classfile/vmSymbols.hpp"
37 #include "gc/shared/collectedHeap.inline.hpp"
38 #include "jvm_io.h"
39 #include "logging/log.hpp"
40 #include "memory/metadataFactory.hpp"
41 #include "memory/metaspaceClosure.hpp"
42 #include "memory/oopFactory.hpp"
43 #include "memory/resourceArea.hpp"
44 #include "memory/universe.hpp"
45 #include "oops/compressedKlass.inline.hpp"
46 #include "oops/compressedOops.inline.hpp"
47 #include "oops/instanceKlass.hpp"
48 #include "oops/klass.inline.hpp"
49 #include "oops/objArrayKlass.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/oopHandle.inline.hpp"
52 #include "prims/jvmtiExport.hpp"
53 #include "runtime/atomic.hpp"
54 #include "runtime/handles.inline.hpp"
55 #include "runtime/perfData.hpp"
56 #include "utilities/macros.hpp"
57 #include "utilities/powerOfTwo.hpp"
58 #include "utilities/rotate_bits.hpp"
59 #include "utilities/stack.inline.hpp"
60
61 void Klass::set_java_mirror(Handle m) {
62 assert(!m.is_null(), "New mirror should never be null.");
63 assert(_java_mirror.is_empty(), "should only be used to initialize mirror");
64 _java_mirror = class_loader_data()->add_handle(m);
65 }
66
67 bool Klass::is_cloneable() const {
68 return _misc_flags.is_cloneable_fast() ||
69 is_subtype_of(vmClasses::Cloneable_klass());
70 }
71
72 void Klass::set_is_cloneable() {
73 if (name() == vmSymbols::java_lang_invoke_MemberName()) {
74 assert(is_final(), "no subclasses allowed");
75 // MemberName cloning should not be intrinsified and always happen in JVM_Clone.
76 } else if (is_instance_klass() && InstanceKlass::cast(this)->reference_type() != REF_NONE) {
77 // Reference cloning should not be intrinsified and always happen in JVM_Clone.
78 } else {
79 _misc_flags.set_is_cloneable_fast(true);
80 }
81 }
82
83 uint8_t Klass::compute_hash_slot(Symbol* n) {
84 uint hash_code;
85 // Special cases for the two superclasses of all Array instances.
86 // Code elsewhere assumes, for all instances of ArrayKlass, that
87 // these two interfaces will be in this order.
88
89 // We ensure there are some empty slots in the hash table between
90 // these two very common interfaces because if they were adjacent
91 // (e.g. Slots 0 and 1), then any other class which hashed to 0 or 1
92 // would result in a probe length of 3.
93 if (n == vmSymbols::java_lang_Cloneable()) {
94 hash_code = 0;
95 } else if (n == vmSymbols::java_io_Serializable()) {
96 hash_code = SECONDARY_SUPERS_TABLE_SIZE / 2;
97 } else {
98 auto s = (const jbyte*) n->bytes();
99 hash_code = java_lang_String::hash_code(s, n->utf8_length());
100 // We use String::hash_code here (rather than e.g.
101 // Symbol::identity_hash()) in order to have a hash code that
102 // does not change from run to run. We want that because the
103 // hash value for a secondary superclass appears in generated
104 // code as a constant.
105
106 // This constant is magic: see Knuth, "Fibonacci Hashing".
107 constexpr uint multiplier
108 = 2654435769; // (uint)(((u8)1 << 32) / ((1 + sqrt(5)) / 2 ))
109 constexpr uint hash_shift = sizeof(hash_code) * 8 - 6;
110 // The leading bits of the least significant half of the product.
111 hash_code = (hash_code * multiplier) >> hash_shift;
112
113 if (StressSecondarySupers) {
114 // Generate many hash collisions in order to stress-test the
115 // linear search fallback.
116 hash_code = hash_code % 3;
117 hash_code = hash_code * (SECONDARY_SUPERS_TABLE_SIZE / 3);
118 }
119 }
120
121 return (hash_code & SECONDARY_SUPERS_TABLE_MASK);
122 }
123
124 void Klass::set_name(Symbol* n) {
125 _name = n;
126
127 if (_name != nullptr) {
128 _name->increment_refcount();
129 }
130
131 {
132 elapsedTimer selftime;
133 selftime.start();
134
135 _hash_slot = compute_hash_slot(n);
136 assert(_hash_slot < SECONDARY_SUPERS_TABLE_SIZE, "required");
137
138 selftime.stop();
139 if (UsePerfData) {
140 ClassLoader::perf_secondary_hash_time()->inc(selftime.ticks());
141 }
142 }
143
144 if (CDSConfig::is_dumping_archive() && is_instance_klass()) {
145 SystemDictionaryShared::init_dumptime_info(InstanceKlass::cast(this));
146 }
147 }
148
149 bool Klass::is_subclass_of(const Klass* k) const {
150 // Run up the super chain and check
151 if (this == k) return true;
152
153 Klass* t = const_cast<Klass*>(this)->super();
154
155 while (t != nullptr) {
156 if (t == k) return true;
157 t = t->super();
158 }
159 return false;
160 }
161
162 void Klass::release_C_heap_structures(bool release_constant_pool) {
163 if (_name != nullptr) _name->decrement_refcount();
164 }
165
166 bool Klass::linear_search_secondary_supers(const Klass* k) const {
167 // Scan the array-of-objects for a match
168 // FIXME: We could do something smarter here, maybe a vectorized
169 // comparison or a binary search, but is that worth any added
170 // complexity?
171 int cnt = secondary_supers()->length();
172 for (int i = 0; i < cnt; i++) {
173 if (secondary_supers()->at(i) == k) {
174 return true;
175 }
176 }
177 return false;
178 }
179
180 // Given a secondary superklass k, an initial array index, and an
181 // occupancy bitmap rotated such that Bit 1 is the next bit to test,
182 // search for k.
183 bool Klass::fallback_search_secondary_supers(const Klass* k, int index, uintx rotated_bitmap) const {
184 // Once the occupancy bitmap is almost full, it's faster to use a
185 // linear search.
186 if (secondary_supers()->length() > SECONDARY_SUPERS_TABLE_SIZE - 2) {
187 return linear_search_secondary_supers(k);
188 }
189
190 // This is conventional linear probing, but instead of terminating
191 // when a null entry is found in the table, we maintain a bitmap
192 // in which a 0 indicates missing entries.
193
194 precond((int)population_count(rotated_bitmap) == secondary_supers()->length());
195
196 // The check for secondary_supers()->length() <= SECONDARY_SUPERS_TABLE_SIZE - 2
197 // at the start of this function guarantees there are 0s in the
198 // bitmap, so this loop eventually terminates.
199 while ((rotated_bitmap & 2) != 0) {
200 if (++index == secondary_supers()->length()) {
201 index = 0;
202 }
203 if (secondary_supers()->at(index) == k) {
204 return true;
205 }
206 rotated_bitmap = rotate_right(rotated_bitmap, 1);
207 }
208 return false;
209 }
210
211 // Return self, except for abstract classes with exactly 1
212 // implementor. Then return the 1 concrete implementation.
213 Klass *Klass::up_cast_abstract() {
214 Klass *r = this;
215 while( r->is_abstract() ) { // Receiver is abstract?
216 Klass *s = r->subklass(); // Check for exactly 1 subklass
217 if (s == nullptr || s->next_sibling() != nullptr) // Oops; wrong count; give up
218 return this; // Return 'this' as a no-progress flag
219 r = s; // Loop till find concrete class
220 }
221 return r; // Return the 1 concrete class
222 }
223
224 // Find LCA in class hierarchy
225 Klass *Klass::LCA( Klass *k2 ) {
226 Klass *k1 = this;
227 while( 1 ) {
228 if( k1->is_subtype_of(k2) ) return k2;
229 if( k2->is_subtype_of(k1) ) return k1;
230 k1 = k1->super();
231 k2 = k2->super();
232 }
233 }
234
235
236 void Klass::check_valid_for_instantiation(bool throwError, TRAPS) {
237 ResourceMark rm(THREAD);
238 THROW_MSG(throwError ? vmSymbols::java_lang_InstantiationError()
239 : vmSymbols::java_lang_InstantiationException(), external_name());
240 }
241
242
243 void Klass::copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS) {
244 ResourceMark rm(THREAD);
245 assert(s != nullptr, "Throw NPE!");
246 THROW_MSG(vmSymbols::java_lang_ArrayStoreException(),
247 err_msg("arraycopy: source type %s is not an array", s->klass()->external_name()));
248 }
249
250
251 void Klass::initialize(TRAPS) {
252 ShouldNotReachHere();
253 }
254
255 Klass* Klass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {
256 #ifdef ASSERT
257 tty->print_cr("Error: find_field called on a klass oop."
258 " Likely error: reflection method does not correctly"
259 " wrap return value in a mirror object.");
260 #endif
261 ShouldNotReachHere();
262 return nullptr;
263 }
264
265 Method* Klass::uncached_lookup_method(const Symbol* name, const Symbol* signature,
266 OverpassLookupMode overpass_mode,
267 PrivateLookupMode private_mode) const {
268 #ifdef ASSERT
269 tty->print_cr("Error: uncached_lookup_method called on a klass oop."
270 " Likely error: reflection method does not correctly"
271 " wrap return value in a mirror object.");
272 #endif
273 ShouldNotReachHere();
274 return nullptr;
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(_shared_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 // superklass links
598 InstanceKlass* Klass::superklass() const {
599 assert(super() == nullptr || super()->is_instance_klass(), "must be instance klass");
600 return _super == nullptr ? nullptr : InstanceKlass::cast(_super);
601 }
602
603 // subklass links. Used by the compiler (and vtable initialization)
604 // May be cleaned concurrently, so must use the Compile_lock.
605 // The log parameter is for clean_weak_klass_links to report unlinked classes.
606 Klass* Klass::subklass(bool log) const {
607 // Need load_acquire on the _subklass, because it races with inserts that
608 // publishes freshly initialized data.
609 for (Klass* chain = Atomic::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 = Atomic::load(&chain->_next_sibling))
614 {
615 if (chain->is_loader_alive()) {
616 return chain;
617 } else if (log) {
618 if (log_is_enabled(Trace, class, unload)) {
619 ResourceMark rm;
620 log_trace(class, unload)("unlinking class (subclass): %s", chain->external_name());
621 }
622 }
623 }
624 return nullptr;
625 }
626
627 Klass* Klass::next_sibling(bool log) const {
628 // Do not need load_acquire on _next_sibling, because inserts never
629 // create _next_sibling edges to dead data.
630 for (Klass* chain = Atomic::load(&_next_sibling);
631 chain != nullptr;
632 chain = Atomic::load(&chain->_next_sibling)) {
633 // Only return alive klass, there may be stale klass
634 // in this chain if cleaned concurrently.
635 if (chain->is_loader_alive()) {
636 return chain;
637 } else if (log) {
638 if (log_is_enabled(Trace, class, unload)) {
639 ResourceMark rm;
640 log_trace(class, unload)("unlinking class (sibling): %s", chain->external_name());
641 }
642 }
643 }
644 return nullptr;
645 }
646
647 void Klass::set_subklass(Klass* s) {
648 assert(s != this, "sanity check");
649 Atomic::release_store(&_subklass, s);
650 }
651
652 void Klass::set_next_sibling(Klass* s) {
653 assert(s != this, "sanity check");
654 // Does not need release semantics. If used by cleanup, it will link to
655 // already safely published data, and if used by inserts, will be published
656 // safely using cmpxchg.
657 Atomic::store(&_next_sibling, s);
658 }
659
660 void Klass::append_to_sibling_list() {
661 if (Universe::is_fully_initialized()) {
662 assert_locked_or_safepoint(Compile_lock);
663 }
664 DEBUG_ONLY(verify();)
665 // add ourselves to superklass' subklass list
666 InstanceKlass* super = superklass();
667 if (super == nullptr) return; // special case: class Object
668 assert((!super->is_interface() // interfaces cannot be supers
669 && (super->superklass() == nullptr || !is_interface())),
670 "an interface can only be a subklass of Object");
671
672 // Make sure there is no stale subklass head
673 super->clean_subklass();
674
675 for (;;) {
676 Klass* prev_first_subklass = Atomic::load_acquire(&_super->_subklass);
677 if (prev_first_subklass != nullptr) {
678 // set our sibling to be the superklass' previous first subklass
679 assert(prev_first_subklass->is_loader_alive(), "May not attach not alive klasses");
680 set_next_sibling(prev_first_subklass);
681 }
682 // Note that the prev_first_subklass is always alive, meaning no sibling_next links
683 // are ever created to not alive klasses. This is an important invariant of the lock-free
684 // cleaning protocol, that allows us to safely unlink dead klasses from the sibling list.
685 if (Atomic::cmpxchg(&super->_subklass, prev_first_subklass, this) == prev_first_subklass) {
686 return;
687 }
688 }
689 DEBUG_ONLY(verify();)
690 }
691
692 void Klass::clean_subklass() {
693 for (;;) {
694 // Need load_acquire, due to contending with concurrent inserts
695 Klass* subklass = Atomic::load_acquire(&_subklass);
696 if (subklass == nullptr || subklass->is_loader_alive()) {
697 return;
698 }
699 // Try to fix _subklass until it points at something not dead.
700 Atomic::cmpxchg(&_subklass, subklass, subklass->next_sibling());
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->subklass(true);
720 current->clean_subklass();
721 if (sub != nullptr) {
722 stack.push(sub);
723 }
724
725 // Find and set the first alive sibling
726 Klass* sibling = current->next_sibling(true);
727 current->set_next_sibling(sibling);
728 if (sibling != nullptr) {
729 stack.push(sibling);
730 }
731
732 // Clean the implementors list and method data.
733 if (clean_alive_klasses && current->is_instance_klass()) {
734 InstanceKlass* ik = InstanceKlass::cast(current);
735 clean_weak_instanceklass_links(ik);
736 }
737 }
738 }
739
740 void Klass::clean_weak_instanceklass_links(InstanceKlass* ik) {
741 ik->clean_weak_instanceklass_links();
742 // JVMTI RedefineClasses creates previous versions that are not in
743 // the class hierarchy, so process them here.
744 while ((ik = ik->previous_versions()) != nullptr) {
745 ik->clean_weak_instanceklass_links();
746 }
747 }
748
749 void Klass::metaspace_pointers_do(MetaspaceClosure* it) {
750 if (log_is_enabled(Trace, aot)) {
751 ResourceMark rm;
752 log_trace(aot)("Iter(Klass): %p (%s)", this, external_name());
753 }
754
755 it->push(&_name);
756 it->push(&_secondary_supers);
757 for (int i = 0; i < _primary_super_limit; i++) {
758 it->push(&_primary_supers[i]);
759 }
760 it->push(&_super);
761 if (!CDSConfig::is_dumping_archive()) {
762 // If dumping archive, these may point to excluded classes. There's no need
763 // to follow these pointers anyway, as they will be set to null in
764 // remove_unshareable_info().
765 it->push((Klass**)&_subklass);
766 it->push((Klass**)&_next_sibling);
767 it->push(&_next_link);
768 }
769
770 vtableEntry* vt = start_of_vtable();
771 for (int i=0; i<vtable_length(); i++) {
772 it->push(vt[i].method_addr());
773 }
774 }
775
776 #if INCLUDE_CDS
777 void Klass::remove_unshareable_info() {
778 assert(CDSConfig::is_dumping_archive(),
779 "only called during CDS dump time");
780 JFR_ONLY(REMOVE_ID(this);)
781 if (log_is_enabled(Trace, aot, unshareable)) {
782 ResourceMark rm;
783 log_trace(aot, unshareable)("remove: %s", external_name());
784 }
785
786 // _secondary_super_cache may be updated by an is_subtype_of() call
787 // while ArchiveBuilder is copying metaspace objects. Let's reset it to
788 // null and let it be repopulated at runtime.
789 set_secondary_super_cache(nullptr);
790
791 set_subklass(nullptr);
792 set_next_sibling(nullptr);
793 set_next_link(nullptr);
794
795 // Null out class_loader_data because we don't share that yet.
796 set_class_loader_data(nullptr);
797 set_is_shared();
798
799 if (CDSConfig::is_dumping_classic_static_archive()) {
800 // "Classic" static archives are required to have deterministic contents.
801 // The elements in _secondary_supers are addresses in the ArchiveBuilder
802 // output buffer, so they should have deterministic values. If we rehash
803 // _secondary_supers, its elements will appear in a deterministic order.
804 //
805 // Note that the bitmap is guaranteed to be deterministic, regardless of the
806 // actual addresses of the elements in _secondary_supers. So rehashing shouldn't
807 // change it.
808 uintx bitmap = hash_secondary_supers(secondary_supers(), true);
809 assert(bitmap == _secondary_supers_bitmap, "bitmap should not be changed due to rehashing");
810 }
811 }
812
813 void Klass::remove_java_mirror() {
814 assert(CDSConfig::is_dumping_archive(), "sanity");
815 if (log_is_enabled(Trace, aot, unshareable)) {
816 ResourceMark rm;
817 log_trace(aot, unshareable)("remove java_mirror: %s", external_name());
818 }
819
820 #if INCLUDE_CDS_JAVA_HEAP
821 _archived_mirror_index = -1;
822 if (CDSConfig::is_dumping_heap()) {
823 Klass* src_k = ArchiveBuilder::current()->get_source_addr(this);
824 oop orig_mirror = src_k->java_mirror();
825 if (orig_mirror == nullptr) {
826 assert(CDSConfig::is_dumping_final_static_archive(), "sanity");
827 if (is_instance_klass()) {
828 assert(InstanceKlass::cast(this)->defined_by_other_loaders(), "sanity");
829 } else {
830 precond(is_objArray_klass());
831 Klass *k = ObjArrayKlass::cast(this)->bottom_klass();
832 precond(k->is_instance_klass());
833 assert(InstanceKlass::cast(k)->defined_by_other_loaders(), "sanity");
834 }
835 } else {
836 oop scratch_mirror = HeapShared::scratch_java_mirror(orig_mirror);
837 if (scratch_mirror != nullptr) {
838 _archived_mirror_index = HeapShared::append_root(scratch_mirror);
839 }
840 }
841 }
842 #endif
843
844 // Just null out the mirror. The class_loader_data() no longer exists.
845 clear_java_mirror_handle();
846 }
847
848 void Klass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {
849 assert(is_klass(), "ensure C++ vtable is restored");
850 assert(is_shared(), "must be set");
851 assert(secondary_supers()->length() >= (int)population_count(_secondary_supers_bitmap), "must be");
852 JFR_ONLY(RESTORE_ID(this);)
853 if (log_is_enabled(Trace, aot, unshareable)) {
854 ResourceMark rm(THREAD);
855 oop class_loader = loader_data->class_loader();
856 log_trace(aot, unshareable)("restore: %s with class loader: %s", external_name(),
857 class_loader != nullptr ? class_loader->klass()->external_name() : "boot");
858 }
859
860 // If an exception happened during CDS restore, some of these fields may already be
861 // set. We leave the class on the CLD list, even if incomplete so that we don't
862 // modify the CLD list outside a safepoint.
863 if (class_loader_data() == nullptr) {
864 set_class_loader_data(loader_data);
865
866 // Add to class loader list first before creating the mirror
867 // (same order as class file parsing)
868 loader_data->add_class(this);
869 }
870
871 Handle loader(THREAD, loader_data->class_loader());
872 ModuleEntry* module_entry = nullptr;
873 Klass* k = this;
874 if (k->is_objArray_klass()) {
875 k = ObjArrayKlass::cast(k)->bottom_klass();
876 }
877 // Obtain klass' module.
878 if (k->is_instance_klass()) {
879 InstanceKlass* ik = (InstanceKlass*) k;
880 module_entry = ik->module();
881 } else {
882 module_entry = ModuleEntryTable::javabase_moduleEntry();
883 }
884 // Obtain java.lang.Module, if available
885 Handle module_handle(THREAD, ((module_entry != nullptr) ? module_entry->module_oop() : (oop)nullptr));
886
887 if (this->has_archived_mirror_index()) {
888 ResourceMark rm(THREAD);
889 log_debug(aot, mirror)("%s has raw archived mirror", external_name());
890 if (ArchiveHeapLoader::is_in_use()) {
891 bool present = java_lang_Class::restore_archived_mirror(this, loader, module_handle,
892 protection_domain,
893 CHECK);
894 if (present) {
895 return;
896 }
897 }
898
899 // No archived mirror data
900 log_debug(aot, mirror)("No archived mirror data for %s", external_name());
901 clear_java_mirror_handle();
902 this->clear_archived_mirror_index();
903 }
904
905 // Only recreate it if not present. A previous attempt to restore may have
906 // gotten an OOM later but keep the mirror if it was created.
907 if (java_mirror() == nullptr) {
908 ResourceMark rm(THREAD);
909 log_trace(aot, mirror)("Recreate mirror for %s", external_name());
910 java_lang_Class::create_mirror(this, loader, module_handle, protection_domain, Handle(), CHECK);
911 }
912 }
913 #endif // INCLUDE_CDS
914
915 #if INCLUDE_CDS_JAVA_HEAP
916 oop Klass::archived_java_mirror() {
917 assert(has_archived_mirror_index(), "must have archived mirror");
918 return HeapShared::get_root(_archived_mirror_index);
919 }
920
921 void Klass::clear_archived_mirror_index() {
922 if (_archived_mirror_index >= 0) {
923 HeapShared::clear_root(_archived_mirror_index);
924 }
925 _archived_mirror_index = -1;
926 }
927 #endif // INCLUDE_CDS_JAVA_HEAP
928
929 void Klass::check_array_allocation_length(int length, int max_length, TRAPS) {
930 if (length > max_length) {
931 if (!THREAD->is_in_internal_oome_mark()) {
932 report_java_out_of_memory("Requested array size exceeds VM limit");
933 JvmtiExport::post_array_size_exhausted();
934 THROW_OOP(Universe::out_of_memory_error_array_size());
935 } else {
936 THROW_OOP(Universe::out_of_memory_error_java_heap_without_backtrace());
937 }
938 } else if (length < 0) {
939 THROW_MSG(vmSymbols::java_lang_NegativeArraySizeException(), err_msg("%d", length));
940 }
941 }
942
943 // Replace the last '+' char with '/'.
944 static char* convert_hidden_name_to_java(Symbol* name) {
945 size_t name_len = name->utf8_length();
946 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
947 name->as_klass_external_name(result, (int)name_len + 1);
948 for (int index = (int)name_len; index > 0; index--) {
949 if (result[index] == '+') {
950 result[index] = JVM_SIGNATURE_SLASH;
951 break;
952 }
953 }
954 return result;
955 }
956
957 // In product mode, this function doesn't have virtual function calls so
958 // there might be some performance advantage to handling InstanceKlass here.
959 const char* Klass::external_name() const {
960 if (is_instance_klass()) {
961 const InstanceKlass* ik = static_cast<const InstanceKlass*>(this);
962 if (ik->is_hidden()) {
963 char* result = convert_hidden_name_to_java(name());
964 return result;
965 }
966 } else if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
967 char* result = convert_hidden_name_to_java(name());
968 return result;
969 }
970 if (name() == nullptr) return "<unknown>";
971 return name()->as_klass_external_name();
972 }
973
974 const char* Klass::signature_name() const {
975 if (name() == nullptr) return "<unknown>";
976 if (is_objArray_klass() && ObjArrayKlass::cast(this)->bottom_klass()->is_hidden()) {
977 size_t name_len = name()->utf8_length();
978 char* result = NEW_RESOURCE_ARRAY(char, name_len + 1);
979 name()->as_C_string(result, (int)name_len + 1);
980 for (int index = (int)name_len; index > 0; index--) {
981 if (result[index] == '+') {
982 result[index] = JVM_SIGNATURE_DOT;
983 break;
984 }
985 }
986 return result;
987 }
988 return name()->as_C_string();
989 }
990
991 const char* Klass::external_kind() const {
992 if (is_interface()) return "interface";
993 if (is_abstract()) return "abstract class";
994 return "class";
995 }
996
997 // Unless overridden, jvmti_class_status has no flags set.
998 jint Klass::jvmti_class_status() const {
999 return 0;
1000 }
1001
1002
1003 // Printing
1004
1005 void Klass::print_on(outputStream* st) const {
1006 ResourceMark rm;
1007 // print title
1008 st->print("%s", internal_name());
1009 print_address_on(st);
1010 st->cr();
1011 }
1012
1013 #define BULLET " - "
1014
1015 // Caller needs ResourceMark
1016 void Klass::oop_print_on(oop obj, outputStream* st) {
1017 // print title
1018 st->print_cr("%s ", internal_name());
1019 obj->print_address_on(st);
1020
1021 if (WizardMode) {
1022 // print header
1023 obj->mark().print_on(st);
1024 st->cr();
1025 st->print(BULLET"prototype_header: " INTPTR_FORMAT, _prototype_header.value());
1026 st->cr();
1027 }
1028
1029 // print class
1030 st->print(BULLET"klass: ");
1031 obj->klass()->print_value_on(st);
1032 st->print(BULLET"flags: "); _misc_flags.print_on(st); st->cr();
1033 st->cr();
1034 }
1035
1036 void Klass::oop_print_value_on(oop obj, outputStream* st) {
1037 // print title
1038 ResourceMark rm; // Cannot print in debug mode without this
1039 st->print("%s", internal_name());
1040 obj->print_address_on(st);
1041 }
1042
1043 // Verification
1044
1045 void Klass::verify_on(outputStream* st) {
1046
1047 // This can be expensive, but it is worth checking that this klass is actually
1048 // in the CLD graph but not in production.
1049 #ifdef ASSERT
1050 if (UseCompressedClassPointers && needs_narrow_id()) {
1051 // Stricter checks for both correct alignment and placement
1052 CompressedKlassPointers::check_encodable(this);
1053 } else {
1054 assert(Metaspace::contains((address)this), "Should be");
1055 }
1056 #endif // ASSERT
1057
1058 guarantee(this->is_klass(),"should be klass");
1059
1060 if (super() != nullptr) {
1061 guarantee(super()->is_klass(), "should be klass");
1062 }
1063 if (secondary_super_cache() != nullptr) {
1064 Klass* ko = secondary_super_cache();
1065 guarantee(ko->is_klass(), "should be klass");
1066 }
1067 for ( uint i = 0; i < primary_super_limit(); i++ ) {
1068 Klass* ko = _primary_supers[i];
1069 if (ko != nullptr) {
1070 guarantee(ko->is_klass(), "should be klass");
1071 }
1072 }
1073
1074 if (java_mirror_no_keepalive() != nullptr) {
1075 guarantee(java_lang_Class::is_instance(java_mirror_no_keepalive()), "should be instance");
1076 }
1077 }
1078
1079 void Klass::oop_verify_on(oop obj, outputStream* st) {
1080 guarantee(oopDesc::is_oop(obj), "should be oop");
1081 guarantee(obj->klass()->is_klass(), "klass field is not a klass");
1082 }
1083
1084 // Note: this function is called with an address that may or may not be a Klass.
1085 // The point is not to assert it is but to check if it could be.
1086 bool Klass::is_valid(Klass* k) {
1087 if (!is_aligned(k, sizeof(MetaWord))) return false;
1088 if ((size_t)k < os::min_page_size()) return false;
1089
1090 if (!os::is_readable_range(k, k + 1)) return false;
1091 if (!Metaspace::contains(k)) return false;
1092
1093 if (!Symbol::is_valid(k->name())) return false;
1094 return ClassLoaderDataGraph::is_valid(k->class_loader_data());
1095 }
1096
1097 Method* Klass::method_at_vtable(int index) {
1098 #ifndef PRODUCT
1099 assert(index >= 0, "valid vtable index");
1100 if (DebugVtables) {
1101 verify_vtable_index(index);
1102 }
1103 #endif
1104 return start_of_vtable()[index].method();
1105 }
1106
1107
1108 #ifndef PRODUCT
1109
1110 bool Klass::verify_vtable_index(int i) {
1111 int limit = vtable_length()/vtableEntry::size();
1112 assert(i >= 0 && i < limit, "index %d out of bounds %d", i, limit);
1113 return true;
1114 }
1115
1116 #endif // PRODUCT
1117
1118 // Caller needs ResourceMark
1119 // joint_in_module_of_loader provides an optimization if 2 classes are in
1120 // the same module to succinctly print out relevant information about their
1121 // module name and class loader's name_and_id for error messages.
1122 // Format:
1123 // <fully-qualified-external-class-name1> and <fully-qualified-external-class-name2>
1124 // are in module <module-name>[@<version>]
1125 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1126 const char* Klass::joint_in_module_of_loader(const Klass* class2, bool include_parent_loader) const {
1127 assert(module() == class2->module(), "classes do not have the same module");
1128 const char* class1_name = external_name();
1129 size_t len = strlen(class1_name) + 1;
1130
1131 const char* class2_description = class2->class_in_module_of_loader(true, include_parent_loader);
1132 len += strlen(class2_description);
1133
1134 len += strlen(" and ");
1135
1136 char* joint_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1137
1138 // Just return the FQN if error when allocating string
1139 if (joint_description == nullptr) {
1140 return class1_name;
1141 }
1142
1143 jio_snprintf(joint_description, len, "%s and %s",
1144 class1_name,
1145 class2_description);
1146
1147 return joint_description;
1148 }
1149
1150 // Caller needs ResourceMark
1151 // class_in_module_of_loader provides a standard way to include
1152 // relevant information about a class, such as its module name as
1153 // well as its class loader's name_and_id, in error messages and logging.
1154 // Format:
1155 // <fully-qualified-external-class-name> is in module <module-name>[@<version>]
1156 // of loader <loader-name_and_id>[, parent loader <parent-loader-name_and_id>]
1157 const char* Klass::class_in_module_of_loader(bool use_are, bool include_parent_loader) const {
1158 // 1. fully qualified external name of class
1159 const char* klass_name = external_name();
1160 size_t len = strlen(klass_name) + 1;
1161
1162 // 2. module name + @version
1163 const char* module_name = "";
1164 const char* version = "";
1165 bool has_version = false;
1166 bool module_is_named = false;
1167 const char* module_name_phrase = "";
1168 const Klass* bottom_klass = is_objArray_klass() ?
1169 ObjArrayKlass::cast(this)->bottom_klass() : this;
1170 if (bottom_klass->is_instance_klass()) {
1171 ModuleEntry* module = InstanceKlass::cast(bottom_klass)->module();
1172 if (module->is_named()) {
1173 module_is_named = true;
1174 module_name_phrase = "module ";
1175 module_name = module->name()->as_C_string();
1176 len += strlen(module_name);
1177 // Use version if exists and is not a jdk module
1178 if (module->should_show_version()) {
1179 has_version = true;
1180 version = module->version()->as_C_string();
1181 // Include stlen(version) + 1 for the "@"
1182 len += strlen(version) + 1;
1183 }
1184 } else {
1185 module_name = UNNAMED_MODULE;
1186 len += UNNAMED_MODULE_LEN;
1187 }
1188 } else {
1189 // klass is an array of primitives, module is java.base
1190 module_is_named = true;
1191 module_name_phrase = "module ";
1192 module_name = JAVA_BASE_NAME;
1193 len += JAVA_BASE_NAME_LEN;
1194 }
1195
1196 // 3. class loader's name_and_id
1197 ClassLoaderData* cld = class_loader_data();
1198 assert(cld != nullptr, "class_loader_data should not be null");
1199 const char* loader_name_and_id = cld->loader_name_and_id();
1200 len += strlen(loader_name_and_id);
1201
1202 // 4. include parent loader information
1203 const char* parent_loader_phrase = "";
1204 const char* parent_loader_name_and_id = "";
1205 if (include_parent_loader &&
1206 !cld->is_builtin_class_loader_data()) {
1207 oop parent_loader = java_lang_ClassLoader::parent(class_loader());
1208 ClassLoaderData *parent_cld = ClassLoaderData::class_loader_data_or_null(parent_loader);
1209 // The parent loader's ClassLoaderData could be null if it is
1210 // a delegating class loader that has never defined a class.
1211 // In this case the loader's name must be obtained via the parent loader's oop.
1212 if (parent_cld == nullptr) {
1213 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(parent_loader);
1214 if (cl_name_and_id != nullptr) {
1215 parent_loader_name_and_id = java_lang_String::as_utf8_string(cl_name_and_id);
1216 }
1217 } else {
1218 parent_loader_name_and_id = parent_cld->loader_name_and_id();
1219 }
1220 parent_loader_phrase = ", parent loader ";
1221 len += strlen(parent_loader_phrase) + strlen(parent_loader_name_and_id);
1222 }
1223
1224 // Start to construct final full class description string
1225 len += ((use_are) ? strlen(" are in ") : strlen(" is in "));
1226 len += strlen(module_name_phrase) + strlen(" of loader ");
1227
1228 char* class_description = NEW_RESOURCE_ARRAY_RETURN_NULL(char, len);
1229
1230 // Just return the FQN if error when allocating string
1231 if (class_description == nullptr) {
1232 return klass_name;
1233 }
1234
1235 jio_snprintf(class_description, len, "%s %s in %s%s%s%s of loader %s%s%s",
1236 klass_name,
1237 (use_are) ? "are" : "is",
1238 module_name_phrase,
1239 module_name,
1240 (has_version) ? "@" : "",
1241 (has_version) ? version : "",
1242 loader_name_and_id,
1243 parent_loader_phrase,
1244 parent_loader_name_and_id);
1245
1246 return class_description;
1247 }
1248
1249 class LookupStats : StackObj {
1250 private:
1251 uint _no_of_samples;
1252 uint _worst;
1253 uint _worst_count;
1254 uint _average;
1255 uint _best;
1256 uint _best_count;
1257 public:
1258 LookupStats() : _no_of_samples(0), _worst(0), _worst_count(0), _average(0), _best(INT_MAX), _best_count(0) {}
1259
1260 ~LookupStats() {
1261 assert(_best <= _worst || _no_of_samples == 0, "sanity");
1262 }
1263
1264 void sample(uint value) {
1265 ++_no_of_samples;
1266 _average += value;
1267
1268 if (_worst < value) {
1269 _worst = value;
1270 _worst_count = 1;
1271 } else if (_worst == value) {
1272 ++_worst_count;
1273 }
1274
1275 if (_best > value) {
1276 _best = value;
1277 _best_count = 1;
1278 } else if (_best == value) {
1279 ++_best_count;
1280 }
1281 }
1282
1283 void print_on(outputStream* st) const {
1284 st->print("best: %2d (%4.1f%%)", _best, (100.0 * _best_count) / _no_of_samples);
1285 if (_best_count < _no_of_samples) {
1286 st->print("; average: %4.1f; worst: %2d (%4.1f%%)",
1287 (1.0 * _average) / _no_of_samples,
1288 _worst, (100.0 * _worst_count) / _no_of_samples);
1289 }
1290 }
1291 };
1292
1293 static void print_positive_lookup_stats(Array<Klass*>* secondary_supers, uintx bitmap, outputStream* st) {
1294 int num_of_supers = secondary_supers->length();
1295
1296 LookupStats s;
1297 for (int i = 0; i < num_of_supers; i++) {
1298 Klass* secondary_super = secondary_supers->at(i);
1299 int home_slot = Klass::compute_home_slot(secondary_super, bitmap);
1300 uint score = 1 + ((i - home_slot) & Klass::SECONDARY_SUPERS_TABLE_MASK);
1301 s.sample(score);
1302 }
1303 st->print("positive_lookup: "); s.print_on(st);
1304 }
1305
1306 static uint compute_distance_to_nearest_zero(int slot, uintx bitmap) {
1307 assert(~bitmap != 0, "no zeroes");
1308 uintx start = rotate_right(bitmap, slot);
1309 return count_trailing_zeros(~start);
1310 }
1311
1312 static void print_negative_lookup_stats(uintx bitmap, outputStream* st) {
1313 LookupStats s;
1314 for (int slot = 0; slot < Klass::SECONDARY_SUPERS_TABLE_SIZE; slot++) {
1315 uint score = compute_distance_to_nearest_zero(slot, bitmap);
1316 s.sample(score);
1317 }
1318 st->print("negative_lookup: "); s.print_on(st);
1319 }
1320
1321 void Klass::print_secondary_supers_on(outputStream* st) const {
1322 if (secondary_supers() != nullptr) {
1323 st->print(" - "); st->print("%d elements;", _secondary_supers->length());
1324 st->print_cr(" bitmap: " UINTX_FORMAT_X_0, _secondary_supers_bitmap);
1325 if (_secondary_supers_bitmap != SECONDARY_SUPERS_BITMAP_EMPTY &&
1326 _secondary_supers_bitmap != SECONDARY_SUPERS_BITMAP_FULL) {
1327 st->print(" - "); print_positive_lookup_stats(secondary_supers(),
1328 _secondary_supers_bitmap, st); st->cr();
1329 st->print(" - "); print_negative_lookup_stats(_secondary_supers_bitmap, st); st->cr();
1330 }
1331 } else {
1332 st->print("null");
1333 }
1334 }
1335
1336 void Klass::on_secondary_supers_verification_failure(Klass* super, Klass* sub, bool linear_result, bool table_result, const char* msg) {
1337 ResourceMark rm;
1338 super->print();
1339 sub->print();
1340 fatal("%s: %s implements %s: linear_search: %d; table_lookup: %d",
1341 msg, sub->external_name(), super->external_name(), linear_result, table_result);
1342 }