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 "interpreter/bytecodeStream.hpp"
26 #include "interpreter/oopMapCache.hpp"
27 #include "logging/log.hpp"
28 #include "logging/logStream.hpp"
29 #include "memory/allocation.inline.hpp"
30 #include "memory/resourceArea.hpp"
31 #include "oops/generateOopMap.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/atomic.hpp"
34 #include "runtime/handles.inline.hpp"
35 #include "runtime/safepoint.hpp"
36 #include "runtime/signature.hpp"
37 #include "utilities/globalCounter.inline.hpp"
38
39 class OopMapCacheEntry: private InterpreterOopMap {
40 friend class InterpreterOopMap;
41 friend class OopMapForCacheEntry;
42 friend class OopMapCache;
43 friend class VerifyClosure;
44
45 private:
46 OopMapCacheEntry* _next;
47
48 protected:
49 // Initialization
50 void fill(const methodHandle& method, int bci);
51 // fills the bit mask for native calls
52 void fill_for_native(const methodHandle& method);
53 void set_mask(CellTypeState* vars, CellTypeState* stack, int stack_top);
54
55 // Deallocate bit masks and initialize fields
56 void flush();
57
58 static void deallocate(OopMapCacheEntry* const entry);
59
60 private:
61 void allocate_bit_mask(); // allocates the bit mask on C heap f necessary
62 void deallocate_bit_mask(); // allocates the bit mask on C heap f necessary
63 bool verify_mask(CellTypeState *vars, CellTypeState *stack, int max_locals, int stack_top);
64
65 public:
66 OopMapCacheEntry() : InterpreterOopMap() {
67 _next = nullptr;
68 }
69 };
70
71
72 // Implementation of OopMapForCacheEntry
73 // (subclass of GenerateOopMap, initializes an OopMapCacheEntry for a given method and bci)
74
75 class OopMapForCacheEntry: public GenerateOopMap {
76 OopMapCacheEntry *_entry;
77 int _bci;
78 int _stack_top;
79
80 virtual bool report_results() const { return false; }
81 virtual bool possible_gc_point (BytecodeStream *bcs);
82 virtual void fill_stackmap_prolog (int nof_gc_points);
83 virtual void fill_stackmap_epilog ();
84 virtual void fill_stackmap_for_opcodes (BytecodeStream *bcs,
85 CellTypeState* vars,
86 CellTypeState* stack,
87 int stack_top);
88 virtual void fill_init_vars (GrowableArray<intptr_t> *init_vars);
89
90 public:
91 OopMapForCacheEntry(const methodHandle& method, int bci, OopMapCacheEntry *entry);
92
93 // Computes stack map for (method,bci) and initialize entry
94 bool compute_map(Thread* current);
95 int size();
96 };
97
98
99 OopMapForCacheEntry::OopMapForCacheEntry(const methodHandle& method, int bci, OopMapCacheEntry* entry) : GenerateOopMap(method) {
100 _bci = bci;
101 _entry = entry;
102 _stack_top = -1;
103 }
104
105
106 bool OopMapForCacheEntry::compute_map(Thread* current) {
107 assert(!method()->is_native(), "cannot compute oop map for native methods");
108 // First check if it is a method where the stackmap is always empty
109 if (method()->code_size() == 0 || method()->max_locals() + method()->max_stack() == 0) {
110 _entry->set_mask_size(0);
111 } else {
112 ResourceMark rm;
113 if (!GenerateOopMap::compute_map(current)) {
114 fatal("Unrecoverable verification or out-of-memory error");
115 return false;
116 }
117 result_for_basicblock(_bci);
118 }
119 return true;
120 }
121
122
123 bool OopMapForCacheEntry::possible_gc_point(BytecodeStream *bcs) {
124 return false; // We are not reporting any result. We call result_for_basicblock directly
125 }
126
127
128 void OopMapForCacheEntry::fill_stackmap_prolog(int nof_gc_points) {
129 // Do nothing
130 }
131
132
133 void OopMapForCacheEntry::fill_stackmap_epilog() {
134 // Do nothing
135 }
136
137
138 void OopMapForCacheEntry::fill_init_vars(GrowableArray<intptr_t> *init_vars) {
139 // Do nothing
140 }
141
142
143 void OopMapForCacheEntry::fill_stackmap_for_opcodes(BytecodeStream *bcs,
144 CellTypeState* vars,
145 CellTypeState* stack,
146 int stack_top) {
147 // Only interested in one specific bci
148 if (bcs->bci() == _bci) {
149 _entry->set_mask(vars, stack, stack_top);
150 _stack_top = stack_top;
151 }
152 }
153
154
155 int OopMapForCacheEntry::size() {
156 assert(_stack_top != -1, "compute_map must be called first");
157 return ((method()->is_static()) ? 0 : 1) + method()->max_locals() + _stack_top;
158 }
159
160
161 // Implementation of InterpreterOopMap and OopMapCacheEntry
162
163 class VerifyClosure : public OffsetClosure {
164 private:
165 OopMapCacheEntry* _entry;
166 bool _failed;
167
168 public:
169 VerifyClosure(OopMapCacheEntry* entry) { _entry = entry; _failed = false; }
170 void offset_do(int offset) { if (!_entry->is_oop(offset)) _failed = true; }
171 bool failed() const { return _failed; }
172 };
173
174 InterpreterOopMap::InterpreterOopMap() {
175 initialize();
176 }
177
178 InterpreterOopMap::~InterpreterOopMap() {
179 if (has_valid_mask() && mask_size() > small_mask_limit) {
180 assert(_bit_mask[0] != 0, "should have pointer to C heap");
181 FREE_C_HEAP_ARRAY(uintptr_t, _bit_mask[0]);
182 }
183 }
184
185 bool InterpreterOopMap::is_empty() const {
186 bool result = _method == nullptr;
187 assert(_method != nullptr || (_bci == 0 &&
188 (_mask_size == 0 || _mask_size == USHRT_MAX) &&
189 _bit_mask[0] == 0), "Should be completely empty");
190 return result;
191 }
192
193 void InterpreterOopMap::initialize() {
194 _method = nullptr;
195 _mask_size = USHRT_MAX; // This value should cause a failure quickly
196 _bci = 0;
197 _expression_stack_size = 0;
198 _num_oops = 0;
199 for (int i = 0; i < N; i++) _bit_mask[i] = 0;
200 }
201
202 void InterpreterOopMap::iterate_oop(OffsetClosure* oop_closure) const {
203 int n = number_of_entries();
204 int word_index = 0;
205 uintptr_t value = 0;
206 uintptr_t mask = 0;
207 // iterate over entries
208 for (int i = 0; i < n; i++, mask <<= bits_per_entry) {
209 // get current word
210 if (mask == 0) {
211 value = bit_mask()[word_index++];
212 mask = 1;
213 }
214 // test for oop
215 if ((value & (mask << oop_bit_number)) != 0) oop_closure->offset_do(i);
216 }
217 }
218
219 void InterpreterOopMap::print() const {
220 int n = number_of_entries();
221 tty->print("oop map for ");
222 method()->print_value();
223 tty->print(" @ %d = [%d] { ", bci(), n);
224 for (int i = 0; i < n; i++) {
225 if (is_dead(i)) tty->print("%d+ ", i);
226 else
227 if (is_oop(i)) tty->print("%d ", i);
228 }
229 tty->print_cr("}");
230 }
231
232 class MaskFillerForNative: public NativeSignatureIterator {
233 private:
234 uintptr_t * _mask; // the bit mask to be filled
235 int _size; // the mask size in bits
236 int _num_oops;
237
238 void set_one(int i) {
239 _num_oops++;
240 i *= InterpreterOopMap::bits_per_entry;
241 assert(0 <= i && i < _size, "offset out of bounds");
242 _mask[i / BitsPerWord] |= (((uintptr_t) 1 << InterpreterOopMap::oop_bit_number) << (i % BitsPerWord));
243 }
244
245 public:
246 void pass_byte() { /* ignore */ }
247 void pass_short() { /* ignore */ }
248 void pass_int() { /* ignore */ }
249 void pass_long() { /* ignore */ }
250 void pass_float() { /* ignore */ }
251 void pass_double() { /* ignore */ }
252 void pass_object() { set_one(offset()); }
253
254 MaskFillerForNative(const methodHandle& method, uintptr_t* mask, int size) : NativeSignatureIterator(method) {
255 _mask = mask;
256 _size = size;
257 _num_oops = 0;
258 // initialize with 0
259 int i = (size + BitsPerWord - 1) / BitsPerWord;
260 while (i-- > 0) _mask[i] = 0;
261 }
262
263 void generate() {
264 iterate();
265 }
266
267 int num_oops() { return _num_oops; }
268 };
269
270 bool OopMapCacheEntry::verify_mask(CellTypeState* vars, CellTypeState* stack, int max_locals, int stack_top) {
271 // Check mask includes map
272 VerifyClosure blk(this);
273 iterate_oop(&blk);
274 if (blk.failed()) return false;
275
276 // Check if map is generated correctly
277 // (Use ?: operator to make sure all 'true' & 'false' are represented exactly the same so we can use == afterwards)
278 const bool log = log_is_enabled(Trace, interpreter, oopmap);
279 LogStream st(Log(interpreter, oopmap)::trace());
280
281 if (log) st.print("Locals (%d): ", max_locals);
282 for(int i = 0; i < max_locals; i++) {
283 bool v1 = is_oop(i) ? true : false;
284 bool v2 = vars[i].is_reference();
285 assert(v1 == v2, "locals oop mask generation error");
286 if (log) st.print("%d", v1 ? 1 : 0);
287 }
288 if (log) st.cr();
289
290 if (log) st.print("Stack (%d): ", stack_top);
291 for(int j = 0; j < stack_top; j++) {
292 bool v1 = is_oop(max_locals + j) ? true : false;
293 bool v2 = stack[j].is_reference();
294 assert(v1 == v2, "stack oop mask generation error");
295 if (log) st.print("%d", v1 ? 1 : 0);
296 }
297 if (log) st.cr();
298 return true;
299 }
300
301 void OopMapCacheEntry::allocate_bit_mask() {
302 if (mask_size() > small_mask_limit) {
303 assert(_bit_mask[0] == 0, "bit mask should be new or just flushed");
304 _bit_mask[0] = (intptr_t)
305 NEW_C_HEAP_ARRAY(uintptr_t, mask_word_size(), mtClass);
306 }
307 }
308
309 void OopMapCacheEntry::deallocate_bit_mask() {
310 if (mask_size() > small_mask_limit && _bit_mask[0] != 0) {
311 assert(!Thread::current()->resource_area()->contains((void*)_bit_mask[0]),
312 "This bit mask should not be in the resource area");
313 FREE_C_HEAP_ARRAY(uintptr_t, _bit_mask[0]);
314 debug_only(_bit_mask[0] = 0;)
315 }
316 }
317
318
319 void OopMapCacheEntry::fill_for_native(const methodHandle& mh) {
320 assert(mh->is_native(), "method must be native method");
321 set_mask_size(mh->size_of_parameters() * bits_per_entry);
322 allocate_bit_mask();
323 // fill mask for parameters
324 MaskFillerForNative mf(mh, bit_mask(), mask_size());
325 mf.generate();
326 _num_oops = mf.num_oops();
327 }
328
329
330 void OopMapCacheEntry::fill(const methodHandle& method, int bci) {
331 // Flush entry to deallocate an existing entry
332 flush();
333 set_method(method());
334 set_bci(checked_cast<unsigned short>(bci)); // bci is always u2
335 if (method->is_native()) {
336 // Native method activations have oops only among the parameters and one
337 // extra oop following the parameters (the mirror for static native methods).
338 fill_for_native(method);
339 } else {
340 OopMapForCacheEntry gen(method, bci, this);
341 if (!gen.compute_map(Thread::current())) {
342 fatal("Unrecoverable verification or out-of-memory error");
343 }
344 }
345 }
346
347
348 void OopMapCacheEntry::set_mask(CellTypeState *vars, CellTypeState *stack, int stack_top) {
349 // compute bit mask size
350 int max_locals = method()->max_locals();
351 int n_entries = max_locals + stack_top;
352 set_mask_size(n_entries * bits_per_entry);
353 allocate_bit_mask();
354 set_expression_stack_size(stack_top);
355
356 // compute bits
357 int word_index = 0;
358 uintptr_t value = 0;
359 uintptr_t mask = 1;
360
361 _num_oops = 0;
362 CellTypeState* cell = vars;
363 for (int entry_index = 0; entry_index < n_entries; entry_index++, mask <<= bits_per_entry, cell++) {
364 // store last word
365 if (mask == 0) {
366 bit_mask()[word_index++] = value;
367 value = 0;
368 mask = 1;
369 }
370
371 // switch to stack when done with locals
372 if (entry_index == max_locals) {
373 cell = stack;
374 }
375
376 // set oop bit
377 if (cell->is_reference()) {
378 value |= (mask << oop_bit_number );
379 _num_oops++;
380 }
381
382 // set dead bit
383 if (!cell->is_live()) {
384 value |= (mask << dead_bit_number);
385 assert(!cell->is_reference(), "dead value marked as oop");
386 }
387 }
388
389 // make sure last word is stored
390 bit_mask()[word_index] = value;
391
392 // verify bit mask
393 assert(verify_mask(vars, stack, max_locals, stack_top), "mask could not be verified");
394 }
395
396 void OopMapCacheEntry::flush() {
397 deallocate_bit_mask();
398 initialize();
399 }
400
401 void OopMapCacheEntry::deallocate(OopMapCacheEntry* const entry) {
402 entry->flush();
403 FREE_C_HEAP_OBJ(entry);
404 }
405
406 // Implementation of OopMapCache
407
408 void InterpreterOopMap::copy_from(const OopMapCacheEntry* src) {
409 // The expectation is that this InterpreterOopMap is recently created
410 // and empty. It is used to get a copy of a cached entry.
411 assert(!has_valid_mask(), "InterpreterOopMap object can only be filled once");
412 assert(src->has_valid_mask(), "Cannot copy entry with an invalid mask");
413
414 set_method(src->method());
415 set_bci(src->bci());
416 set_mask_size(src->mask_size());
417 set_expression_stack_size(src->expression_stack_size());
418 _num_oops = src->num_oops();
419
420 // Is the bit mask contained in the entry?
421 if (src->mask_size() <= small_mask_limit) {
422 memcpy(_bit_mask, src->_bit_mask, mask_word_size() * BytesPerWord);
423 } else {
424 _bit_mask[0] = (uintptr_t) NEW_C_HEAP_ARRAY(uintptr_t, mask_word_size(), mtClass);
425 memcpy((void*) _bit_mask[0], (void*) src->_bit_mask[0], mask_word_size() * BytesPerWord);
426 }
427 }
428
429 inline unsigned int OopMapCache::hash_value_for(const methodHandle& method, int bci) const {
430 // We use method->code_size() rather than method->identity_hash() below since
431 // the mark may not be present if a pointer to the method is already reversed.
432 return ((unsigned int) bci)
433 ^ ((unsigned int) method->max_locals() << 2)
434 ^ ((unsigned int) method->code_size() << 4)
435 ^ ((unsigned int) method->size_of_parameters() << 6);
436 }
437
438 OopMapCacheEntry* volatile OopMapCache::_old_entries = nullptr;
439
440 OopMapCache::OopMapCache() {
441 for(int i = 0; i < size; i++) _array[i] = nullptr;
442 }
443
444
445 OopMapCache::~OopMapCache() {
446 // Deallocate oop maps that are allocated out-of-line
447 flush();
448 }
449
450 OopMapCacheEntry* OopMapCache::entry_at(int i) const {
451 return Atomic::load_acquire(&(_array[i % size]));
452 }
453
454 bool OopMapCache::put_at(int i, OopMapCacheEntry* entry, OopMapCacheEntry* old) {
455 return Atomic::cmpxchg(&_array[i % size], old, entry) == old;
456 }
457
458 void OopMapCache::flush() {
459 for (int i = 0; i < size; i++) {
460 OopMapCacheEntry* entry = _array[i];
461 if (entry != nullptr) {
462 _array[i] = nullptr; // no barrier, only called in OopMapCache destructor
463 OopMapCacheEntry::deallocate(entry);
464 }
465 }
466 }
467
468 void OopMapCache::flush_obsolete_entries() {
469 assert(SafepointSynchronize::is_at_safepoint(), "called by RedefineClasses in a safepoint");
470 for (int i = 0; i < size; i++) {
471 OopMapCacheEntry* entry = _array[i];
472 if (entry != nullptr && !entry->is_empty() && entry->method()->is_old()) {
473 // Cache entry is occupied by an old redefined method and we don't want
474 // to pin it down so flush the entry.
475 if (log_is_enabled(Debug, redefine, class, oopmap)) {
476 ResourceMark rm;
477 log_debug(redefine, class, interpreter, oopmap)
478 ("flush: %s(%s): cached entry @%d",
479 entry->method()->name()->as_C_string(), entry->method()->signature()->as_C_string(), i);
480 }
481 _array[i] = nullptr;
482 OopMapCacheEntry::deallocate(entry);
483 }
484 }
485 }
486
487 // Lookup or compute/cache the entry.
488 void OopMapCache::lookup(const methodHandle& method,
489 int bci,
490 InterpreterOopMap* entry_for) {
491 int probe = hash_value_for(method, bci);
492
493 if (log_is_enabled(Debug, interpreter, oopmap)) {
494 static int count = 0;
495 ResourceMark rm;
496 log_debug(interpreter, oopmap)
497 ("%d - Computing oopmap at bci %d for %s at hash %d", ++count, bci,
498 method()->name_and_sig_as_C_string(), probe);
499 }
500
501 // Search hashtable for match.
502 // Need a critical section to avoid race against concurrent reclamation.
503 {
504 GlobalCounter::CriticalSection cs(Thread::current());
505 for (int i = 0; i < probe_depth; i++) {
506 OopMapCacheEntry *entry = entry_at(probe + i);
507 if (entry != nullptr && !entry->is_empty() && entry->match(method, bci)) {
508 entry_for->copy_from(entry);
509 assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
510 log_debug(interpreter, oopmap)("- found at hash %d", probe + i);
511 return;
512 }
513 }
514 }
515
516 // Entry is not in hashtable.
517 // Compute entry
518
519 OopMapCacheEntry* tmp = NEW_C_HEAP_OBJ(OopMapCacheEntry, mtClass);
520 tmp->initialize();
521 tmp->fill(method, bci);
522 entry_for->copy_from(tmp);
523
524 if (method->should_not_be_cached()) {
525 // It is either not safe or not a good idea to cache this Method*
526 // at this time. We give the caller of lookup() a copy of the
527 // interesting info via parameter entry_for, but we don't add it to
528 // the cache. See the gory details in Method*.cpp.
529 OopMapCacheEntry::deallocate(tmp);
530 return;
531 }
532
533 // First search for an empty slot
534 for (int i = 0; i < probe_depth; i++) {
535 OopMapCacheEntry* entry = entry_at(probe + i);
536 if (entry == nullptr) {
537 if (put_at(probe + i, tmp, nullptr)) {
538 assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
539 return;
540 }
541 }
542 }
543
544 log_debug(interpreter, oopmap)("*** collision in oopmap cache - flushing item ***");
545
546 // No empty slot (uncommon case). Use (some approximation of a) LRU algorithm
547 // where the first entry in the collision array is replaced with the new one.
548 OopMapCacheEntry* old = entry_at(probe + 0);
549 if (put_at(probe + 0, tmp, old)) {
550 // Cannot deallocate old entry on the spot: it can still be used by readers
551 // that got a reference to it before we were able to replace it in the map.
552 // Instead of synchronizing on GlobalCounter here and incurring heavy thread
553 // walk, we do this clean up out of band.
554 enqueue_for_cleanup(old);
555 } else {
556 OopMapCacheEntry::deallocate(tmp);
557 }
558
559 assert(!entry_for->is_empty(), "A non-empty oop map should be returned");
560 return;
561 }
562
563 void OopMapCache::enqueue_for_cleanup(OopMapCacheEntry* entry) {
564 while (true) {
565 OopMapCacheEntry* head = Atomic::load(&_old_entries);
566 entry->_next = head;
567 if (Atomic::cmpxchg(&_old_entries, head, entry) == head) {
568 // Enqueued successfully.
569 break;
570 }
571 }
572
573 if (log_is_enabled(Debug, interpreter, oopmap)) {
574 ResourceMark rm;
575 log_debug(interpreter, oopmap)("enqueue %s at bci %d for cleanup",
576 entry->method()->name_and_sig_as_C_string(), entry->bci());
577 }
578 }
579
580 bool OopMapCache::has_cleanup_work() {
581 return Atomic::load(&_old_entries) != nullptr;
582 }
583
584 void OopMapCache::try_trigger_cleanup() {
585 // See we can take the lock for the notification without blocking.
586 // This allows triggering the cleanup from GC paths, that can hold
587 // the service lock for e.g. oop iteration in service thread.
588 if (has_cleanup_work() && Service_lock->try_lock_without_rank_check()) {
589 Service_lock->notify_all();
590 Service_lock->unlock();
591 }
592 }
593
594 void OopMapCache::cleanup() {
595 OopMapCacheEntry* entry = Atomic::xchg(&_old_entries, (OopMapCacheEntry*)nullptr);
596 if (entry == nullptr) {
597 // No work.
598 return;
599 }
600
601 // About to delete the entries than might still be accessed by other threads
602 // on lookup path. Need to sync up with them before proceeding.
603 GlobalCounter::write_synchronize();
604
605 while (entry != nullptr) {
606 if (log_is_enabled(Debug, interpreter, oopmap)) {
607 ResourceMark rm;
608 log_debug(interpreter, oopmap)("cleanup entry %s at bci %d",
609 entry->method()->name_and_sig_as_C_string(), entry->bci());
610 }
611 OopMapCacheEntry* next = entry->_next;
612 OopMapCacheEntry::deallocate(entry);
613 entry = next;
614 }
615 }
616
617 void OopMapCache::compute_one_oop_map(const methodHandle& method, int bci, InterpreterOopMap* entry) {
618 // Due to the invariants above it's tricky to allocate a temporary OopMapCacheEntry on the stack
619 OopMapCacheEntry* tmp = NEW_C_HEAP_OBJ(OopMapCacheEntry, mtClass);
620 tmp->initialize();
621 tmp->fill(method, bci);
622 if (tmp->has_valid_mask()) {
623 entry->copy_from(tmp);
624 }
625 OopMapCacheEntry::deallocate(tmp);
626 }