1 /*
2 * Copyright (c) 2018, 2025, Red Hat, Inc. 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
26 #include "gc/shenandoah/shenandoahAsserts.hpp"
27 #include "gc/shenandoah/shenandoahForwarding.hpp"
28 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
29 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
30 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
31 #include "gc/shenandoah/shenandoahUtils.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "runtime/os.hpp"
35 #include "utilities/vmError.hpp"
36
37 void print_raw_memory(ShenandoahMessageBuffer &msg, void* loc) {
38 // Be extra safe. Only access data that is guaranteed to be safe:
39 // should be in heap, in known committed region, within that region.
40
41 ShenandoahHeap* heap = ShenandoahHeap::heap();
42 if (!heap->is_in_reserved(loc)) return;
43
44 ShenandoahHeapRegion* r = heap->heap_region_containing(loc);
45 if (r != nullptr && r->is_committed()) {
46 address start = MAX2((address) r->bottom(), (address) loc - 32);
47 address end = MIN2((address) r->end(), (address) loc + 128);
48 if (start >= end) return;
49
50 stringStream ss;
51 os::print_hex_dump(&ss, start, end, 4);
52 msg.append("\n");
53 msg.append("Raw heap memory:\n%s", ss.freeze());
54 }
55 }
56
57 void ShenandoahAsserts::print_obj(ShenandoahMessageBuffer& msg, oop obj) {
58 ShenandoahHeap* heap = ShenandoahHeap::heap();
59 ShenandoahHeapRegion *r = heap->heap_region_containing(obj);
60
61 ResourceMark rm;
62 stringStream ss;
63 StreamIndentor si(&ss);
64
65 ShenandoahMarkingContext* const ctx = heap->marking_context();
66
67 narrowKlass nk = 0;
68 const Klass* obj_klass = nullptr;
69 const bool klass_valid = extract_klass_safely(obj, nk, obj_klass);
70 const char* klass_text = "(invalid)";
71 if (klass_valid && os::is_readable_pointer(obj_klass) && Metaspace::contains(obj_klass)) {
72 klass_text = obj_klass->external_name();
73 }
74 ss.print_cr(PTR_FORMAT " - nk %u klass " PTR_FORMAT " %s\n", p2i(obj), nk, p2i(obj_klass), klass_text);
75 {
76 StreamIndentor si(&ss);
77 ss.print_cr("%3s allocated after mark start", ctx->allocated_after_mark_start(obj) ? "" : "not");
78 ss.print_cr("%3s after update watermark", cast_from_oop<HeapWord*>(obj) >= r->get_update_watermark() ? "" : "not");
79 ss.print_cr("%3s marked strong", ctx->is_marked_strong(obj) ? "" : "not");
80 ss.print_cr("%3s marked weak", ctx->is_marked_weak(obj) ? "" : "not");
81 ss.print_cr("%3s in collection set", heap->in_collection_set(obj) ? "" : "not");
82 if (heap->mode()->is_generational() && !obj->is_forwarded()) {
83 ss.print_cr("age: %d", obj->age());
84 }
85 ss.print_raw("mark: ");
86 obj->mark().print_on(&ss);
87 ss.cr();
88 ss.print_raw("region: ");
89 r->print_on(&ss);
90 ss.cr();
91 if (obj_klass == vmClasses::Class_klass()) {
92 msg.append(" mirrored klass: " PTR_FORMAT "\n", p2i(obj->metadata_field(java_lang_Class::klass_offset())));
93 msg.append(" mirrored array klass: " PTR_FORMAT "\n", p2i(obj->metadata_field(java_lang_Class::array_klass_offset())));
94 }
95 }
96 const_address loc = cast_from_oop<const_address>(obj);
97 os::print_hex_dump(&ss, loc, loc + 64, 4, true, 32, loc);
98 msg.append("%s", ss.base());
99 }
100
101 void ShenandoahAsserts::print_non_obj(ShenandoahMessageBuffer& msg, void* loc) {
102 ShenandoahHeap* heap = ShenandoahHeap::heap();
103 if (heap->is_in_reserved(loc)) {
104 msg.append(" inside Java heap\n");
105 ShenandoahHeapRegion *r = heap->heap_region_containing(loc);
106 stringStream ss;
107 r->print_on(&ss);
108
109 msg.append(" %3s in collection set\n", heap->in_collection_set_loc(loc) ? "" : "not");
110 msg.append(" region: %s", ss.freeze());
111 } else {
112 msg.append(" outside of Java heap\n");
113 stringStream ss;
114 os::print_location(&ss, (intptr_t) loc, false);
115 msg.append(" %s", ss.freeze());
116 }
117 }
118
119 void ShenandoahAsserts::print_obj_safe(ShenandoahMessageBuffer& msg, void* loc) {
120 ShenandoahHeap* heap = ShenandoahHeap::heap();
121 msg.append(" " PTR_FORMAT " - safe print, no details\n", p2i(loc));
122 if (heap->is_in_reserved(loc)) {
123 ShenandoahHeapRegion* r = heap->heap_region_containing(loc);
124 if (r != nullptr) {
125 stringStream ss;
126 r->print_on(&ss);
127 msg.append(" region: %s", ss.freeze());
128 print_raw_memory(msg, loc);
129 }
130 }
131 }
132
133 void ShenandoahAsserts::print_failure(SafeLevel level, oop obj, void* interior_loc, oop loc,
134 const char* phase, const char* label,
135 const char* file, int line) {
136 ShenandoahHeap* heap = ShenandoahHeap::heap();
137 ResourceMark rm;
138
139 if (!os::is_readable_pointer(obj)) {
140 level = _safe_unknown;
141 }
142
143 bool loc_in_heap = (loc != nullptr && heap->is_in_reserved(loc));
144
145 ShenandoahMessageBuffer msg("%s; %s\n\n", phase, label);
146
147 msg.append("Referenced from:\n");
148 if (interior_loc != nullptr) {
149 msg.append(" interior location: " PTR_FORMAT "\n", p2i(interior_loc));
150 if (loc_in_heap && os::is_readable_pointer(loc)) {
151 print_obj(msg, loc);
152 } else {
153 print_non_obj(msg, interior_loc);
154 }
155 } else {
156 msg.append(" no interior location recorded (probably a plain heap scan, or detached oop)\n");
157 }
158 msg.append("\n");
159
160 msg.append("Object:\n");
161 if (level >= _safe_oop) {
162 print_obj(msg, obj);
163 } else {
164 print_obj_safe(msg, obj);
165 }
166 msg.append("\n");
167
168 if (level >= _safe_oop) {
169 oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
170 msg.append("Forwardee:\n");
171 if (obj != fwd) {
172 if (level >= _safe_oop_fwd && os::is_readable_pointer(fwd)) {
173 print_obj(msg, fwd);
174 } else {
175 print_obj_safe(msg, fwd);
176 }
177 } else {
178 msg.append(" (the object itself)");
179 }
180 msg.append("\n");
181 }
182
183 if (level >= _safe_oop_fwd) {
184 oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
185 oop fwd2 = ShenandoahForwarding::get_forwardee_raw_unchecked(fwd);
186 if (fwd != fwd2) {
187 msg.append("Second forwardee:\n");
188 print_obj_safe(msg, fwd2);
189 msg.append("\n");
190 }
191 }
192
193 report_vm_error(file, line, msg.buffer());
194 }
195
196 void ShenandoahAsserts::assert_in_heap_bounds(void* interior_loc, oop obj, const char *file, int line) {
197 ShenandoahHeap* heap = ShenandoahHeap::heap();
198
199 if (!heap->is_in_reserved(obj)) {
200 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_in_heap_bounds failed",
201 "oop must be in heap bounds",
202 file, line);
203 }
204 }
205
206 void ShenandoahAsserts::assert_in_heap_bounds_or_null(void* interior_loc, oop obj, const char *file, int line) {
207 ShenandoahHeap* heap = ShenandoahHeap::heap();
208
209 if (obj != nullptr && !heap->is_in_reserved(obj)) {
210 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_in_heap_bounds_or_null failed",
211 "oop must be in heap bounds",
212 file, line);
213 }
214 }
215
216 void ShenandoahAsserts::assert_correct(void* interior_loc, oop obj, const char* file, int line) {
217 ShenandoahHeap* heap = ShenandoahHeap::heap();
218
219 // Step 1. Check that obj is correct.
220 // After this step, it is safe to call heap_region_containing().
221 if (!heap->is_in_reserved(obj)) {
222 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
223 "oop must be in heap bounds",
224 file, line);
225 }
226
227 if (!os::is_readable_pointer(obj)) {
228 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
229 "oop within heap bounds but at unreadable location",
230 file, line);
231 }
232
233 if (!heap->is_in(obj)) {
234 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
235 "Object should be in active region area",
236 file, line);
237 }
238
239 oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
240
241 if (obj != fwd) {
242 // When Full GC moves the objects, we cannot trust fwdptrs. If we got here, it means something
243 // tries fwdptr manipulation when Full GC is running. The only exception is using the fwdptr
244 // that still points to the object itself.
245 if (heap->is_full_gc_move_in_progress()) {
246 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
247 "Non-trivial forwarding pointer during Full GC moves, probable bug.",
248 file, line);
249 }
250
251 // Step 2. Check that forwardee is correct
252 if (!heap->is_in_reserved(fwd)) {
253 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
254 "Forwardee must be in heap bounds",
255 file, line);
256 }
257
258 if (!os::is_readable_pointer(fwd)) {
259 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
260 "Forwardee within heap bounds but at unreadable location",
261 file, line);
262 }
263
264 // Step 3. Check that forwardee points to correct region
265 if (!heap->is_in(fwd)) {
266 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
267 "Forwardee should be in active region area",
268 file, line);
269 }
270
271 if (heap->heap_region_index_containing(fwd) == heap->heap_region_index_containing(obj)) {
272 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
273 "Non-trivial forwardee should be in another region",
274 file, line);
275 }
276
277 // Step 4. Check for multiple forwardings
278 oop fwd2 = ShenandoahForwarding::get_forwardee_raw_unchecked(fwd);
279 if (fwd != fwd2) {
280 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
281 "Multiple forwardings",
282 file, line);
283 }
284 }
285
286 const Klass* obj_klass = nullptr;
287 narrowKlass nk = 0;
288 if (!extract_klass_safely(obj, nk, obj_klass)) {
289 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
290 "Object klass pointer invalid",
291 file,line);
292 }
293
294 if (obj_klass == nullptr) {
295 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
296 "Object klass pointer should not be null",
297 file,line);
298 }
299
300 if (!Metaspace::contains(obj_klass)) {
301 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
302 "Object klass pointer must go to metaspace",
303 file,line);
304 }
305
306 if (!UseCompactObjectHeaders && obj_klass != fwd->klass_or_null()) {
307 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
308 "Forwardee klass disagrees with object class",
309 file, line);
310 }
311
312 // Do additional checks for special objects: their fields can hold metadata as well.
313 // We want to check class loading/unloading did not corrupt them. We can only reasonably
314 // trust the forwarded objects, as the from-space object can have the klasses effectively
315 // dead.
316
317 if (Universe::is_fully_initialized() && (obj_klass == vmClasses::Class_klass())) {
318 const Metadata* klass = fwd->metadata_field(java_lang_Class::klass_offset());
319 if (klass != nullptr && !Metaspace::contains(klass)) {
320 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
321 "Mirrored instance class should point to Metaspace",
322 file, line);
323 }
324
325 const Metadata* array_klass = fwd->metadata_field(java_lang_Class::array_klass_offset());
326 if (array_klass != nullptr && !Metaspace::contains(array_klass)) {
327 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_correct failed",
328 "Mirrored array class should point to Metaspace",
329 file, line);
330 }
331 }
332 }
333
334 void ShenandoahAsserts::assert_in_correct_region(void* interior_loc, oop obj, const char* file, int line) {
335 assert_correct(interior_loc, obj, file, line);
336
337 ShenandoahHeap* heap = ShenandoahHeap::heap();
338 ShenandoahHeapRegion* r = heap->heap_region_containing(obj);
339 if (!r->is_active()) {
340 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_in_correct_region failed",
341 "Object must reside in active region",
342 file, line);
343 }
344
345 size_t alloc_size = obj->size();
346 HeapWord* obj_end = cast_from_oop<HeapWord*>(obj) + alloc_size;
347
348 if (ShenandoahHeapRegion::requires_humongous(alloc_size)) {
349 size_t idx = r->index();
350 size_t end_idx = heap->heap_region_index_containing(obj_end - 1);
351 for (size_t i = idx; i < end_idx; i++) {
352 ShenandoahHeapRegion* chain_reg = heap->get_region(i);
353 if (i == idx && !chain_reg->is_humongous_start()) {
354 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_in_correct_region failed",
355 "Object must reside in humongous start",
356 file, line);
357 }
358 if (i != idx && !chain_reg->is_humongous_continuation()) {
359 print_failure(_safe_oop, obj, interior_loc, nullptr, "Shenandoah assert_in_correct_region failed",
360 "Humongous continuation should be of proper size",
361 file, line);
362 }
363 }
364 } else {
365 if (obj_end > r->top()) {
366 print_failure(_safe_unknown, obj, interior_loc, nullptr, "Shenandoah assert_in_correct_region failed",
367 "Object end should be within the active area of the region",
368 file, line);
369 }
370 }
371 }
372
373 void ShenandoahAsserts::assert_forwarded(void* interior_loc, oop obj, const char* file, int line) {
374 assert_correct(interior_loc, obj, file, line);
375 oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
376
377 if (obj == fwd) {
378 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_forwarded failed",
379 "Object should be forwarded",
380 file, line);
381 }
382 }
383
384 void ShenandoahAsserts::assert_not_forwarded(void* interior_loc, oop obj, const char* file, int line) {
385 assert_correct(interior_loc, obj, file, line);
386 oop fwd = ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
387
388 if (obj != fwd) {
389 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_not_forwarded failed",
390 "Object should not be forwarded",
391 file, line);
392 }
393 }
394
395 void ShenandoahAsserts::assert_marked(void *interior_loc, oop obj, const char *file, int line) {
396 assert_correct(interior_loc, obj, file, line);
397
398 ShenandoahHeap* heap = ShenandoahHeap::heap();
399 if (!heap->marking_context()->is_marked(obj)) {
400 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_marked failed",
401 "Object should be marked",
402 file, line);
403 }
404 }
405
406 void ShenandoahAsserts::assert_marked_weak(void *interior_loc, oop obj, const char *file, int line) {
407 assert_correct(interior_loc, obj, file, line);
408
409 ShenandoahHeap* heap = ShenandoahHeap::heap();
410 if (!heap->marking_context()->is_marked_weak(obj)) {
411 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_marked_weak failed",
412 "Object should be marked weakly",
413 file, line);
414 }
415 }
416
417 void ShenandoahAsserts::assert_marked_strong(void *interior_loc, oop obj, const char *file, int line) {
418 assert_correct(interior_loc, obj, file, line);
419
420 ShenandoahHeap* heap = ShenandoahHeap::heap();
421 if (!heap->marking_context()->is_marked_strong(obj)) {
422 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_marked_strong failed",
423 "Object should be marked strongly",
424 file, line);
425 }
426 }
427
428 void ShenandoahAsserts::assert_in_cset(void* interior_loc, oop obj, const char* file, int line) {
429 assert_correct(interior_loc, obj, file, line);
430
431 ShenandoahHeap* heap = ShenandoahHeap::heap();
432 if (!heap->in_collection_set(obj)) {
433 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_in_cset failed",
434 "Object should be in collection set",
435 file, line);
436 }
437 }
438
439 void ShenandoahAsserts::assert_not_in_cset(void* interior_loc, oop obj, const char* file, int line) {
440 assert_correct(interior_loc, obj, file, line);
441
442 ShenandoahHeap* heap = ShenandoahHeap::heap();
443 if (heap->in_collection_set(obj)) {
444 print_failure(_safe_all, obj, interior_loc, nullptr, "Shenandoah assert_not_in_cset failed",
445 "Object should not be in collection set",
446 file, line);
447 }
448 }
449
450 void ShenandoahAsserts::assert_not_in_cset_loc(void* interior_loc, const char* file, int line) {
451 ShenandoahHeap* heap = ShenandoahHeap::heap();
452 if (heap->in_collection_set_loc(interior_loc)) {
453 print_failure(_safe_unknown, nullptr, interior_loc, nullptr, "Shenandoah assert_not_in_cset_loc failed",
454 "Interior location should not be in collection set",
455 file, line);
456 }
457 }
458
459 void ShenandoahAsserts::print_rp_failure(const char *label, BoolObjectClosure* actual,
460 const char *file, int line) {
461 ShenandoahMessageBuffer msg("%s\n", label);
462 msg.append(" Actual: " PTR_FORMAT "\n", p2i(actual));
463 report_vm_error(file, line, msg.buffer());
464 }
465
466 void ShenandoahAsserts::assert_locked_or_shenandoah_safepoint(Mutex* lock, const char* file, int line) {
467 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
468 return;
469 }
470
471 if (lock->owned_by_self()) {
472 return;
473 }
474
475 ShenandoahMessageBuffer msg("Must be at a Shenandoah safepoint or held %s lock", lock->name());
476 report_vm_error(file, line, msg.buffer());
477 }
478
479 void ShenandoahAsserts::assert_heaplocked(const char* file, int line) {
480 ShenandoahHeap* heap = ShenandoahHeap::heap();
481
482 if (heap->lock()->owned_by_self()) {
483 return;
484 }
485
486 ShenandoahMessageBuffer msg("Heap lock must be owned by current thread");
487 report_vm_error(file, line, msg.buffer());
488 }
489
490 void ShenandoahAsserts::assert_not_heaplocked(const char* file, int line) {
491 ShenandoahHeap* heap = ShenandoahHeap::heap();
492
493 if (!heap->lock()->owned_by_self()) {
494 return;
495 }
496
497 ShenandoahMessageBuffer msg("Heap lock must not be owned by current thread");
498 report_vm_error(file, line, msg.buffer());
499 }
500
501 void ShenandoahAsserts::assert_heaplocked_or_safepoint(const char* file, int line) {
502 ShenandoahHeap* heap = ShenandoahHeap::heap();
503
504 if (heap->lock()->owned_by_self()) {
505 return;
506 }
507
508 if (ShenandoahSafepoint::is_at_shenandoah_safepoint()) {
509 return;
510 }
511
512 ShenandoahMessageBuffer msg("Heap lock must be owned by current thread, or be at safepoint");
513 report_vm_error(file, line, msg.buffer());
514 }
515
516 void ShenandoahAsserts::assert_generational(const char* file, int line) {
517 if (ShenandoahHeap::heap()->mode()->is_generational()) {
518 return;
519 }
520
521 ShenandoahMessageBuffer msg("Must be in generational mode");
522 report_vm_error(file, line, msg.buffer());
523 }
524
525 void ShenandoahAsserts::assert_control_or_vm_thread_at_safepoint(bool at_safepoint, const char* file, int line) {
526 Thread* thr = Thread::current();
527 if (thr == ShenandoahHeap::heap()->control_thread()) {
528 return;
529 }
530 if (thr->is_VM_thread()) {
531 if (!at_safepoint) {
532 return;
533 } else if (SafepointSynchronize::is_at_safepoint()) {
534 return;
535 }
536 }
537
538 ShenandoahMessageBuffer msg("Must be either control thread, or vm thread");
539 if (at_safepoint) {
540 msg.append(" at a safepoint");
541 }
542 report_vm_error(file, line, msg.buffer());
543 }
544
545 void ShenandoahAsserts::assert_generations_reconciled(const char* file, int line) {
546 if (!SafepointSynchronize::is_at_safepoint()) {
547 return;
548 }
549
550 ShenandoahHeap* heap = ShenandoahHeap::heap();
551 ShenandoahGeneration* ggen = heap->gc_generation();
552 ShenandoahGeneration* agen = heap->active_generation();
553 if (agen == ggen) {
554 return;
555 }
556
557 ShenandoahMessageBuffer msg("Active(%d) & GC(%d) Generations aren't reconciled", agen->type(), ggen->type());
558 report_vm_error(file, line, msg.buffer());
559 }
560
561 bool ShenandoahAsserts::extract_klass_safely(oop obj, narrowKlass& nk, const Klass*& k) {
562 nk = 0;
563 k = nullptr;
564
565 if (!os::is_readable_pointer(obj)) {
566 return false;
567 }
568 if (UseCompressedClassPointers) {
569 if (UseCompactObjectHeaders) { // look in forwardee
570 markWord mark = obj->mark();
571 if (mark.is_marked()) {
572 oop fwd = cast_to_oop(mark.clear_lock_bits().to_pointer());
573 if (!os::is_readable_pointer(fwd)) {
574 return false;
575 }
576 mark = fwd->mark();
577 }
578 nk = mark.narrow_klass();
579 } else {
580 nk = obj->narrow_klass();
581 }
582 if (!CompressedKlassPointers::is_valid_narrow_klass_id(nk)) {
583 return false;
584 }
585 k = CompressedKlassPointers::decode_not_null_without_asserts(nk);
586 } else {
587 k = obj->klass();
588 }
589 return k != nullptr;
590 }