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 }