1 /* 2 * Copyright (c) 2018, 2020, 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 "precompiled.hpp" 26 #include "classfile/javaClasses.hpp" 27 #include "gc/g1/c2/g1BarrierSetC2.hpp" 28 #include "gc/g1/g1BarrierSet.hpp" 29 #include "gc/g1/g1BarrierSetRuntime.hpp" 30 #include "gc/g1/g1CardTable.hpp" 31 #include "gc/g1/g1ThreadLocalData.hpp" 32 #include "gc/g1/heapRegion.hpp" 33 #include "opto/arraycopynode.hpp" 34 #include "opto/compile.hpp" 35 #include "opto/escape.hpp" 36 #include "opto/graphKit.hpp" 37 #include "opto/idealKit.hpp" 38 #include "opto/macro.hpp" 39 #include "opto/rootnode.hpp" 40 #include "opto/type.hpp" 41 #include "utilities/macros.hpp" 42 43 const TypeFunc *G1BarrierSetC2::write_ref_field_pre_entry_Type() { 44 const Type **fields = TypeTuple::fields(2); 45 fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value 46 fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread 47 const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields); 48 49 // create result type (range) 50 fields = TypeTuple::fields(0); 51 const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields); 52 53 return TypeFunc::make(domain, range); 54 } 55 56 const TypeFunc *G1BarrierSetC2::write_ref_field_post_entry_Type() { 57 const Type **fields = TypeTuple::fields(2); 58 fields[TypeFunc::Parms+0] = TypeRawPtr::NOTNULL; // Card addr 59 fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread 60 const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields); 61 62 // create result type (range) 63 fields = TypeTuple::fields(0); 64 const TypeTuple *range = TypeTuple::make(TypeFunc::Parms, fields); 65 66 return TypeFunc::make(domain, range); 67 } 68 69 #define __ ideal. 70 /* 71 * Determine if the G1 pre-barrier can be removed. The pre-barrier is 72 * required by SATB to make sure all objects live at the start of the 73 * marking are kept alive, all reference updates need to any previous 74 * reference stored before writing. 75 * 76 * If the previous value is NULL there is no need to save the old value. 77 * References that are NULL are filtered during runtime by the barrier 78 * code to avoid unnecessary queuing. 79 * 80 * However in the case of newly allocated objects it might be possible to 81 * prove that the reference about to be overwritten is NULL during compile 82 * time and avoid adding the barrier code completely. 83 * 84 * The compiler needs to determine that the object in which a field is about 85 * to be written is newly allocated, and that no prior store to the same field 86 * has happened since the allocation. 87 * 88 * Returns true if the pre-barrier can be removed 89 */ 90 bool G1BarrierSetC2::g1_can_remove_pre_barrier(GraphKit* kit, 91 PhaseTransform* phase, 92 Node* adr, 93 BasicType bt, 94 uint adr_idx) const { 95 intptr_t offset = 0; 96 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); 97 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); 98 99 if (offset == Type::OffsetBot) { 100 return false; // cannot unalias unless there are precise offsets 101 } 102 103 if (alloc == NULL) { 104 return false; // No allocation found 105 } 106 107 intptr_t size_in_bytes = type2aelembytes(bt); 108 109 Node* mem = kit->memory(adr_idx); // start searching here... 110 111 for (int cnt = 0; cnt < 50; cnt++) { 112 113 if (mem->is_Store()) { 114 115 Node* st_adr = mem->in(MemNode::Address); 116 intptr_t st_offset = 0; 117 Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset); 118 119 if (st_base == NULL) { 120 break; // inscrutable pointer 121 } 122 123 // Break we have found a store with same base and offset as ours so break 124 if (st_base == base && st_offset == offset) { 125 break; 126 } 127 128 if (st_offset != offset && st_offset != Type::OffsetBot) { 129 const int MAX_STORE = BytesPerLong; 130 if (st_offset >= offset + size_in_bytes || 131 st_offset <= offset - MAX_STORE || 132 st_offset <= offset - mem->as_Store()->memory_size()) { 133 // Success: The offsets are provably independent. 134 // (You may ask, why not just test st_offset != offset and be done? 135 // The answer is that stores of different sizes can co-exist 136 // in the same sequence of RawMem effects. We sometimes initialize 137 // a whole 'tile' of array elements with a single jint or jlong.) 138 mem = mem->in(MemNode::Memory); 139 continue; // advance through independent store memory 140 } 141 } 142 143 if (st_base != base 144 && MemNode::detect_ptr_independence(base, alloc, st_base, 145 AllocateNode::Ideal_allocation(st_base, phase), 146 phase)) { 147 // Success: The bases are provably independent. 148 mem = mem->in(MemNode::Memory); 149 continue; // advance through independent store memory 150 } 151 } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) { 152 153 InitializeNode* st_init = mem->in(0)->as_Initialize(); 154 AllocateNode* st_alloc = st_init->allocation(); 155 156 // Make sure that we are looking at the same allocation site. 157 // The alloc variable is guaranteed to not be null here from earlier check. 158 if (alloc == st_alloc) { 159 // Check that the initialization is storing NULL so that no previous store 160 // has been moved up and directly write a reference 161 Node* captured_store = st_init->find_captured_store(offset, 162 type2aelembytes(T_OBJECT), 163 phase); 164 if (captured_store == NULL || captured_store == st_init->zero_memory()) { 165 return true; 166 } 167 } 168 } 169 170 // Unless there is an explicit 'continue', we must bail out here, 171 // because 'mem' is an inscrutable memory state (e.g., a call). 172 break; 173 } 174 175 return false; 176 } 177 178 // G1 pre/post barriers 179 void G1BarrierSetC2::pre_barrier(GraphKit* kit, 180 bool do_load, 181 Node* ctl, 182 Node* obj, 183 Node* adr, 184 uint alias_idx, 185 Node* val, 186 const TypeOopPtr* val_type, 187 Node* pre_val, 188 BasicType bt) const { 189 // Some sanity checks 190 // Note: val is unused in this routine. 191 192 if (do_load) { 193 // We need to generate the load of the previous value 194 assert(obj != NULL, "must have a base"); 195 assert(adr != NULL, "where are loading from?"); 196 assert(pre_val == NULL, "loaded already?"); 197 assert(val_type != NULL, "need a type"); 198 199 if (use_ReduceInitialCardMarks() 200 && g1_can_remove_pre_barrier(kit, &kit->gvn(), adr, bt, alias_idx)) { 201 return; 202 } 203 204 } else { 205 // In this case both val_type and alias_idx are unused. 206 assert(pre_val != NULL, "must be loaded already"); 207 // Nothing to be done if pre_val is null. 208 if (pre_val->bottom_type() == TypePtr::NULL_PTR) return; 209 assert(pre_val->bottom_type()->basic_type() == T_OBJECT, "or we shouldn't be here"); 210 } 211 assert(bt == T_OBJECT, "or we shouldn't be here"); 212 213 IdealKit ideal(kit, true); 214 215 Node* tls = __ thread(); // ThreadLocalStorage 216 217 Node* no_base = __ top(); 218 Node* zero = __ ConI(0); 219 Node* zeroX = __ ConX(0); 220 221 float likely = PROB_LIKELY(0.999); 222 float unlikely = PROB_UNLIKELY(0.999); 223 224 BasicType active_type = in_bytes(SATBMarkQueue::byte_width_of_active()) == 4 ? T_INT : T_BYTE; 225 assert(in_bytes(SATBMarkQueue::byte_width_of_active()) == 4 || in_bytes(SATBMarkQueue::byte_width_of_active()) == 1, "flag width"); 226 227 // Offsets into the thread 228 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); 229 const int index_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_index_offset()); 230 const int buffer_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_buffer_offset()); 231 232 // Now the actual pointers into the thread 233 Node* marking_adr = __ AddP(no_base, tls, __ ConX(marking_offset)); 234 Node* buffer_adr = __ AddP(no_base, tls, __ ConX(buffer_offset)); 235 Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset)); 236 237 // Now some of the values 238 Node* marking = __ load(__ ctrl(), marking_adr, TypeInt::INT, active_type, Compile::AliasIdxRaw); 239 240 // if (!marking) 241 __ if_then(marking, BoolTest::ne, zero, unlikely); { 242 BasicType index_bt = TypeX_X->basic_type(); 243 assert(sizeof(size_t) == type2aelembytes(index_bt), "Loading G1 SATBMarkQueue::_index with wrong size."); 244 Node* index = __ load(__ ctrl(), index_adr, TypeX_X, index_bt, Compile::AliasIdxRaw); 245 246 if (do_load) { 247 // load original value 248 // alias_idx correct?? 249 pre_val = __ load(__ ctrl(), adr, val_type, bt, alias_idx); 250 } 251 252 // if (pre_val != NULL) 253 __ if_then(pre_val, BoolTest::ne, kit->null()); { 254 Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw); 255 256 // is the queue for this thread full? 257 __ if_then(index, BoolTest::ne, zeroX, likely); { 258 259 // decrement the index 260 Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t)))); 261 262 // Now get the buffer location we will log the previous value into and store it 263 Node *log_addr = __ AddP(no_base, buffer, next_index); 264 __ store(__ ctrl(), log_addr, pre_val, T_OBJECT, Compile::AliasIdxRaw, MemNode::unordered); 265 // update the index 266 __ store(__ ctrl(), index_adr, next_index, index_bt, Compile::AliasIdxRaw, MemNode::unordered); 267 268 } __ else_(); { 269 270 // logging buffer is full, call the runtime 271 const TypeFunc *tf = write_ref_field_pre_entry_Type(); 272 __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_pre_entry), "write_ref_field_pre_entry", pre_val, tls); 273 } __ end_if(); // (!index) 274 } __ end_if(); // (pre_val != NULL) 275 } __ end_if(); // (!marking) 276 277 // Final sync IdealKit and GraphKit. 278 kit->final_sync(ideal); 279 } 280 281 /* 282 * G1 similar to any GC with a Young Generation requires a way to keep track of 283 * references from Old Generation to Young Generation to make sure all live 284 * objects are found. G1 also requires to keep track of object references 285 * between different regions to enable evacuation of old regions, which is done 286 * as part of mixed collections. References are tracked in remembered sets and 287 * is continuously updated as reference are written to with the help of the 288 * post-barrier. 289 * 290 * To reduce the number of updates to the remembered set the post-barrier 291 * filters updates to fields in objects located in the Young Generation, 292 * the same region as the reference, when the NULL is being written or 293 * if the card is already marked as dirty by an earlier write. 294 * 295 * Under certain circumstances it is possible to avoid generating the 296 * post-barrier completely if it is possible during compile time to prove 297 * the object is newly allocated and that no safepoint exists between the 298 * allocation and the store. 299 * 300 * In the case of slow allocation the allocation code must handle the barrier 301 * as part of the allocation in the case the allocated object is not located 302 * in the nursery; this would happen for humongous objects. 303 * 304 * Returns true if the post barrier can be removed 305 */ 306 bool G1BarrierSetC2::g1_can_remove_post_barrier(GraphKit* kit, 307 PhaseTransform* phase, Node* store, 308 Node* adr) const { 309 intptr_t offset = 0; 310 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); 311 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); 312 313 if (offset == Type::OffsetBot) { 314 return false; // cannot unalias unless there are precise offsets 315 } 316 317 if (alloc == NULL) { 318 return false; // No allocation found 319 } 320 321 // Start search from Store node 322 Node* mem = store->in(MemNode::Control); 323 if (mem->is_Proj() && mem->in(0)->is_Initialize()) { 324 325 InitializeNode* st_init = mem->in(0)->as_Initialize(); 326 AllocateNode* st_alloc = st_init->allocation(); 327 328 // Make sure we are looking at the same allocation 329 if (alloc == st_alloc) { 330 return true; 331 } 332 } 333 334 return false; 335 } 336 337 // 338 // Update the card table and add card address to the queue 339 // 340 void G1BarrierSetC2::g1_mark_card(GraphKit* kit, 341 IdealKit& ideal, 342 Node* card_adr, 343 Node* oop_store, 344 uint oop_alias_idx, 345 Node* index, 346 Node* index_adr, 347 Node* buffer, 348 const TypeFunc* tf) const { 349 Node* zero = __ ConI(0); 350 Node* zeroX = __ ConX(0); 351 Node* no_base = __ top(); 352 BasicType card_bt = T_BYTE; 353 // Smash zero into card. MUST BE ORDERED WRT TO STORE 354 __ storeCM(__ ctrl(), card_adr, zero, oop_store, oop_alias_idx, card_bt, Compile::AliasIdxRaw); 355 356 // Now do the queue work 357 __ if_then(index, BoolTest::ne, zeroX); { 358 359 Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t)))); 360 Node* log_addr = __ AddP(no_base, buffer, next_index); 361 362 // Order, see storeCM. 363 __ store(__ ctrl(), log_addr, card_adr, T_ADDRESS, Compile::AliasIdxRaw, MemNode::unordered); 364 __ store(__ ctrl(), index_adr, next_index, TypeX_X->basic_type(), Compile::AliasIdxRaw, MemNode::unordered); 365 366 } __ else_(); { 367 __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_post_entry), "write_ref_field_post_entry", card_adr, __ thread()); 368 } __ end_if(); 369 370 } 371 372 void G1BarrierSetC2::post_barrier(GraphKit* kit, 373 Node* ctl, 374 Node* oop_store, 375 Node* obj, 376 Node* adr, 377 uint alias_idx, 378 Node* val, 379 BasicType bt, 380 bool use_precise) const { 381 // If we are writing a NULL then we need no post barrier 382 383 if (val != NULL && val->is_Con() && val->bottom_type() == TypePtr::NULL_PTR) { 384 // Must be NULL 385 const Type* t = val->bottom_type(); 386 assert(t == Type::TOP || t == TypePtr::NULL_PTR, "must be NULL"); 387 // No post barrier if writing NULLx 388 return; 389 } 390 391 if (use_ReduceInitialCardMarks() && obj == kit->just_allocated_object(kit->control())) { 392 // We can skip marks on a freshly-allocated object in Eden. 393 // Keep this code in sync with new_deferred_store_barrier() in runtime.cpp. 394 // That routine informs GC to take appropriate compensating steps, 395 // upon a slow-path allocation, so as to make this card-mark 396 // elision safe. 397 return; 398 } 399 400 if (use_ReduceInitialCardMarks() 401 && g1_can_remove_post_barrier(kit, &kit->gvn(), oop_store, adr)) { 402 return; 403 } 404 405 if (!use_precise) { 406 // All card marks for a (non-array) instance are in one place: 407 adr = obj; 408 } 409 // (Else it's an array (or unknown), and we want more precise card marks.) 410 assert(adr != NULL, ""); 411 412 IdealKit ideal(kit, true); 413 414 Node* tls = __ thread(); // ThreadLocalStorage 415 416 Node* no_base = __ top(); 417 float likely = PROB_LIKELY_MAG(3); 418 float unlikely = PROB_UNLIKELY_MAG(3); 419 Node* young_card = __ ConI((jint)G1CardTable::g1_young_card_val()); 420 Node* dirty_card = __ ConI((jint)G1CardTable::dirty_card_val()); 421 Node* zeroX = __ ConX(0); 422 423 const TypeFunc *tf = write_ref_field_post_entry_Type(); 424 425 // Offsets into the thread 426 const int index_offset = in_bytes(G1ThreadLocalData::dirty_card_queue_index_offset()); 427 const int buffer_offset = in_bytes(G1ThreadLocalData::dirty_card_queue_buffer_offset()); 428 429 // Pointers into the thread 430 431 Node* buffer_adr = __ AddP(no_base, tls, __ ConX(buffer_offset)); 432 Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset)); 433 434 // Now some values 435 // Use ctrl to avoid hoisting these values past a safepoint, which could 436 // potentially reset these fields in the JavaThread. 437 Node* index = __ load(__ ctrl(), index_adr, TypeX_X, TypeX_X->basic_type(), Compile::AliasIdxRaw); 438 Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw); 439 440 // Convert the store obj pointer to an int prior to doing math on it 441 // Must use ctrl to prevent "integerized oop" existing across safepoint 442 Node* cast = __ CastPX(__ ctrl(), adr); 443 444 // Divide pointer by card size 445 Node* card_offset = __ URShiftX( cast, __ ConI(CardTable::card_shift()) ); 446 447 // Combine card table base and card offset 448 Node* card_adr = __ AddP(no_base, byte_map_base_node(kit), card_offset ); 449 450 // If we know the value being stored does it cross regions? 451 452 if (val != NULL) { 453 // Does the store cause us to cross regions? 454 455 // Should be able to do an unsigned compare of region_size instead of 456 // and extra shift. Do we have an unsigned compare?? 457 // Node* region_size = __ ConI(1 << HeapRegion::LogOfHRGrainBytes); 458 Node* xor_res = __ URShiftX ( __ XorX( cast, __ CastPX(__ ctrl(), val)), __ ConI(HeapRegion::LogOfHRGrainBytes)); 459 460 // if (xor_res == 0) same region so skip 461 __ if_then(xor_res, BoolTest::ne, zeroX, likely); { 462 463 // No barrier if we are storing a NULL 464 __ if_then(val, BoolTest::ne, kit->null(), likely); { 465 466 // Ok must mark the card if not already dirty 467 468 // load the original value of the card 469 Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); 470 471 __ if_then(card_val, BoolTest::ne, young_card, unlikely); { 472 kit->sync_kit(ideal); 473 kit->insert_mem_bar(Op_MemBarVolatile, oop_store); 474 __ sync_kit(kit); 475 476 Node* card_val_reload = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); 477 __ if_then(card_val_reload, BoolTest::ne, dirty_card); { 478 g1_mark_card(kit, ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf); 479 } __ end_if(); 480 } __ end_if(); 481 } __ end_if(); 482 } __ end_if(); 483 } else { 484 // The Object.clone() intrinsic uses this path if !ReduceInitialCardMarks. 485 // We don't need a barrier here if the destination is a newly allocated object 486 // in Eden. Otherwise, GC verification breaks because we assume that cards in Eden 487 // are set to 'g1_young_gen' (see G1CardTable::verify_g1_young_region()). 488 assert(!use_ReduceInitialCardMarks(), "can only happen with card marking"); 489 Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); 490 __ if_then(card_val, BoolTest::ne, young_card); { 491 g1_mark_card(kit, ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf); 492 } __ end_if(); 493 } 494 495 // Final sync IdealKit and GraphKit. 496 kit->final_sync(ideal); 497 } 498 499 // Helper that guards and inserts a pre-barrier. 500 void G1BarrierSetC2::insert_pre_barrier(GraphKit* kit, Node* base_oop, Node* offset, 501 Node* pre_val, bool need_mem_bar) const { 502 // We could be accessing the referent field of a reference object. If so, when G1 503 // is enabled, we need to log the value in the referent field in an SATB buffer. 504 // This routine performs some compile time filters and generates suitable 505 // runtime filters that guard the pre-barrier code. 506 // Also add memory barrier for non volatile load from the referent field 507 // to prevent commoning of loads across safepoint. 508 509 // Some compile time checks. 510 511 // If offset is a constant, is it java_lang_ref_Reference::_reference_offset? 512 const TypeX* otype = offset->find_intptr_t_type(); 513 if (otype != NULL && otype->is_con() && 514 otype->get_con() != java_lang_ref_Reference::referent_offset()) { 515 // Constant offset but not the reference_offset so just return 516 return; 517 } 518 519 // We only need to generate the runtime guards for instances. 520 const TypeOopPtr* btype = base_oop->bottom_type()->isa_oopptr(); 521 if (btype != NULL) { 522 if (btype->isa_aryptr()) { 523 // Array type so nothing to do 524 return; 525 } 526 527 const TypeInstPtr* itype = btype->isa_instptr(); 528 if (itype != NULL) { 529 // Can the klass of base_oop be statically determined to be 530 // _not_ a sub-class of Reference and _not_ Object? 531 ciKlass* klass = itype->klass(); 532 if ( klass->is_loaded() && 533 !klass->is_subtype_of(kit->env()->Reference_klass()) && 534 !kit->env()->Object_klass()->is_subtype_of(klass)) { 535 return; 536 } 537 } 538 } 539 540 // The compile time filters did not reject base_oop/offset so 541 // we need to generate the following runtime filters 542 // 543 // if (offset == java_lang_ref_Reference::_reference_offset) { 544 // if (instance_of(base, java.lang.ref.Reference)) { 545 // pre_barrier(_, pre_val, ...); 546 // } 547 // } 548 549 float likely = PROB_LIKELY( 0.999); 550 float unlikely = PROB_UNLIKELY(0.999); 551 552 IdealKit ideal(kit); 553 554 Node* referent_off = __ ConX(java_lang_ref_Reference::referent_offset()); 555 556 __ if_then(offset, BoolTest::eq, referent_off, unlikely); { 557 // Update graphKit memory and control from IdealKit. 558 kit->sync_kit(ideal); 559 560 Node* ref_klass_con = kit->makecon(TypeKlassPtr::make(kit->env()->Reference_klass())); 561 Node* is_instof = kit->gen_instanceof(base_oop, ref_klass_con); 562 563 // Update IdealKit memory and control from graphKit. 564 __ sync_kit(kit); 565 566 Node* one = __ ConI(1); 567 // is_instof == 0 if base_oop == NULL 568 __ if_then(is_instof, BoolTest::eq, one, unlikely); { 569 570 // Update graphKit from IdeakKit. 571 kit->sync_kit(ideal); 572 573 // Use the pre-barrier to record the value in the referent field 574 pre_barrier(kit, false /* do_load */, 575 __ ctrl(), 576 NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */, 577 pre_val /* pre_val */, 578 T_OBJECT); 579 if (need_mem_bar) { 580 // Add memory barrier to prevent commoning reads from this field 581 // across safepoint since GC can change its value. 582 kit->insert_mem_bar(Op_MemBarCPUOrder); 583 } 584 // Update IdealKit from graphKit. 585 __ sync_kit(kit); 586 587 } __ end_if(); // _ref_type != ref_none 588 } __ end_if(); // offset == referent_offset 589 590 // Final sync IdealKit and GraphKit. 591 kit->final_sync(ideal); 592 } 593 594 #undef __ 595 596 Node* G1BarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const { 597 DecoratorSet decorators = access.decorators(); 598 Node* adr = access.addr().node(); 599 Node* obj = access.base(); 600 601 bool anonymous = (decorators & C2_UNSAFE_ACCESS) != 0; 602 bool mismatched = (decorators & C2_MISMATCHED) != 0; 603 bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0; 604 bool in_heap = (decorators & IN_HEAP) != 0; 605 bool in_native = (decorators & IN_NATIVE) != 0; 606 bool on_weak = (decorators & ON_WEAK_OOP_REF) != 0; 607 bool on_phantom = (decorators & ON_PHANTOM_OOP_REF) != 0; 608 bool is_unordered = (decorators & MO_UNORDERED) != 0; 609 bool no_keepalive = (decorators & AS_NO_KEEPALIVE) != 0; 610 bool is_mixed = !in_heap && !in_native; 611 bool need_cpu_mem_bar = !is_unordered || mismatched || is_mixed; 612 613 Node* top = Compile::current()->top(); 614 Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : top; 615 Node* load = CardTableBarrierSetC2::load_at_resolved(access, val_type); 616 617 // If we are reading the value of the referent field of a Reference 618 // object (either by using Unsafe directly or through reflection) 619 // then, if G1 is enabled, we need to record the referent in an 620 // SATB log buffer using the pre-barrier mechanism. 621 // Also we need to add memory barrier to prevent commoning reads 622 // from this field across safepoint since GC can change its value. 623 bool need_read_barrier = (((on_weak || on_phantom) && !no_keepalive) || 624 (in_heap && unknown && offset != top && obj != top)); 625 626 if (!access.is_oop() || !need_read_barrier) { 627 return load; 628 } 629 630 assert(access.is_parse_access(), "entry not supported at optimization time"); 631 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access); 632 GraphKit* kit = parse_access.kit(); 633 634 if (on_weak || on_phantom) { 635 // Use the pre-barrier to record the value in the referent field 636 pre_barrier(kit, false /* do_load */, 637 kit->control(), 638 NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */, 639 load /* pre_val */, T_OBJECT); 640 // Add memory barrier to prevent commoning reads from this field 641 // across safepoint since GC can change its value. 642 kit->insert_mem_bar(Op_MemBarCPUOrder); 643 } else if (unknown) { 644 // We do not require a mem bar inside pre_barrier if need_mem_bar 645 // is set: the barriers would be emitted by us. 646 insert_pre_barrier(kit, obj, offset, load, !need_cpu_mem_bar); 647 } 648 649 return load; 650 } 651 652 bool G1BarrierSetC2::is_gc_barrier_node(Node* node) const { 653 if (CardTableBarrierSetC2::is_gc_barrier_node(node)) { 654 return true; 655 } 656 if (node->Opcode() != Op_CallLeaf) { 657 return false; 658 } 659 CallLeafNode *call = node->as_CallLeaf(); 660 if (call->_name == NULL) { 661 return false; 662 } 663 664 return strcmp(call->_name, "write_ref_field_pre_entry") == 0 || strcmp(call->_name, "write_ref_field_post_entry") == 0; 665 } 666 667 void G1BarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) const { 668 assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required"); 669 assert(node->outcnt() <= 2, "expects 1 or 2 users: Xor and URShift nodes"); 670 // It could be only one user, URShift node, in Object.clone() intrinsic 671 // but the new allocation is passed to arraycopy stub and it could not 672 // be scalar replaced. So we don't check the case. 673 674 // An other case of only one user (Xor) is when the value check for NULL 675 // in G1 post barrier is folded after CCP so the code which used URShift 676 // is removed. 677 678 // Take Region node before eliminating post barrier since it also 679 // eliminates CastP2X node when it has only one user. 680 Node* this_region = node->in(0); 681 assert(this_region != NULL, ""); 682 683 // Remove G1 post barrier. 684 685 // Search for CastP2X->Xor->URShift->Cmp path which 686 // checks if the store done to a different from the value's region. 687 // And replace Cmp with #0 (false) to collapse G1 post barrier. 688 Node* xorx = node->find_out_with(Op_XorX); 689 if (xorx != NULL) { 690 Node* shift = xorx->unique_out(); 691 Node* cmpx = shift->unique_out(); 692 assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() && 693 cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne, 694 "missing region check in G1 post barrier"); 695 macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); 696 697 // Remove G1 pre barrier. 698 699 // Search "if (marking != 0)" check and set it to "false". 700 // There is no G1 pre barrier if previous stored value is NULL 701 // (for example, after initialization). 702 if (this_region->is_Region() && this_region->req() == 3) { 703 int ind = 1; 704 if (!this_region->in(ind)->is_IfFalse()) { 705 ind = 2; 706 } 707 if (this_region->in(ind)->is_IfFalse() && 708 this_region->in(ind)->in(0)->Opcode() == Op_If) { 709 Node* bol = this_region->in(ind)->in(0)->in(1); 710 assert(bol->is_Bool(), ""); 711 cmpx = bol->in(1); 712 if (bol->as_Bool()->_test._test == BoolTest::ne && 713 cmpx->is_Cmp() && cmpx->in(2) == macro->intcon(0) && 714 cmpx->in(1)->is_Load()) { 715 Node* adr = cmpx->in(1)->as_Load()->in(MemNode::Address); 716 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); 717 if (adr->is_AddP() && adr->in(AddPNode::Base) == macro->top() && 718 adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal && 719 adr->in(AddPNode::Offset) == macro->MakeConX(marking_offset)) { 720 macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); 721 } 722 } 723 } 724 } 725 } else { 726 assert(!use_ReduceInitialCardMarks(), "can only happen with card marking"); 727 // This is a G1 post barrier emitted by the Object.clone() intrinsic. 728 // Search for the CastP2X->URShiftX->AddP->LoadB->Cmp path which checks if the card 729 // is marked as young_gen and replace the Cmp with 0 (false) to collapse the barrier. 730 Node* shift = node->find_out_with(Op_URShiftX); 731 assert(shift != NULL, "missing G1 post barrier"); 732 Node* addp = shift->unique_out(); 733 Node* load = addp->find_out_with(Op_LoadB); 734 assert(load != NULL, "missing G1 post barrier"); 735 Node* cmpx = load->unique_out(); 736 assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() && 737 cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne, 738 "missing card value check in G1 post barrier"); 739 macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); 740 // There is no G1 pre barrier in this case 741 } 742 // Now CastP2X can be removed since it is used only on dead path 743 // which currently still alive until igvn optimize it. 744 assert(node->outcnt() == 0 || node->unique_out()->Opcode() == Op_URShiftX, ""); 745 macro->replace_node(node, macro->top()); 746 } 747 748 Node* G1BarrierSetC2::step_over_gc_barrier(Node* c) const { 749 if (!use_ReduceInitialCardMarks() && 750 c != NULL && c->is_Region() && c->req() == 3) { 751 for (uint i = 1; i < c->req(); i++) { 752 if (c->in(i) != NULL && c->in(i)->is_Region() && 753 c->in(i)->req() == 3) { 754 Node* r = c->in(i); 755 for (uint j = 1; j < r->req(); j++) { 756 if (r->in(j) != NULL && r->in(j)->is_Proj() && 757 r->in(j)->in(0) != NULL && 758 r->in(j)->in(0)->Opcode() == Op_CallLeaf && 759 r->in(j)->in(0)->as_Call()->entry_point() == CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_post_entry)) { 760 Node* call = r->in(j)->in(0); 761 c = c->in(i == 1 ? 2 : 1); 762 if (c != NULL && c->Opcode() != Op_Parm) { 763 c = c->in(0); 764 if (c != NULL) { 765 c = c->in(0); 766 assert(call->in(0) == NULL || 767 call->in(0)->in(0) == NULL || 768 call->in(0)->in(0)->in(0) == NULL || 769 call->in(0)->in(0)->in(0)->in(0) == NULL || 770 call->in(0)->in(0)->in(0)->in(0)->in(0) == NULL || 771 c == call->in(0)->in(0)->in(0)->in(0)->in(0), "bad barrier shape"); 772 return c; 773 } 774 } 775 } 776 } 777 } 778 } 779 } 780 return c; 781 } 782 783 #ifdef ASSERT 784 void G1BarrierSetC2::verify_gc_barriers(Compile* compile, CompilePhase phase) const { 785 if (phase != BarrierSetC2::BeforeCodeGen) { 786 return; 787 } 788 // Verify G1 pre-barriers 789 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); 790 791 Unique_Node_List visited; 792 Node_List worklist; 793 // We're going to walk control flow backwards starting from the Root 794 worklist.push(compile->root()); 795 while (worklist.size() > 0) { 796 Node* x = worklist.pop(); 797 if (x == NULL || x == compile->top()) continue; 798 if (visited.member(x)) { 799 continue; 800 } else { 801 visited.push(x); 802 } 803 804 if (x->is_Region()) { 805 for (uint i = 1; i < x->req(); i++) { 806 worklist.push(x->in(i)); 807 } 808 } else { 809 worklist.push(x->in(0)); 810 // We are looking for the pattern: 811 // /->ThreadLocal 812 // If->Bool->CmpI->LoadB->AddP->ConL(marking_offset) 813 // \->ConI(0) 814 // We want to verify that the If and the LoadB have the same control 815 // See GraphKit::g1_write_barrier_pre() 816 if (x->is_If()) { 817 IfNode *iff = x->as_If(); 818 if (iff->in(1)->is_Bool() && iff->in(1)->in(1)->is_Cmp()) { 819 CmpNode *cmp = iff->in(1)->in(1)->as_Cmp(); 820 if (cmp->Opcode() == Op_CmpI && cmp->in(2)->is_Con() && cmp->in(2)->bottom_type()->is_int()->get_con() == 0 821 && cmp->in(1)->is_Load()) { 822 LoadNode* load = cmp->in(1)->as_Load(); 823 if (load->Opcode() == Op_LoadB && load->in(2)->is_AddP() && load->in(2)->in(2)->Opcode() == Op_ThreadLocal 824 && load->in(2)->in(3)->is_Con() 825 && load->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == marking_offset) { 826 827 Node* if_ctrl = iff->in(0); 828 Node* load_ctrl = load->in(0); 829 830 if (if_ctrl != load_ctrl) { 831 // Skip possible CProj->NeverBranch in infinite loops 832 if ((if_ctrl->is_Proj() && if_ctrl->Opcode() == Op_CProj) 833 && (if_ctrl->in(0)->is_MultiBranch() && if_ctrl->in(0)->Opcode() == Op_NeverBranch)) { 834 if_ctrl = if_ctrl->in(0)->in(0); 835 } 836 } 837 assert(load_ctrl != NULL && if_ctrl == load_ctrl, "controls must match"); 838 } 839 } 840 } 841 } 842 } 843 } 844 } 845 #endif 846 847 bool G1BarrierSetC2::escape_add_to_con_graph(ConnectionGraph* conn_graph, PhaseGVN* gvn, Unique_Node_List* delayed_worklist, Node* n, uint opcode) const { 848 if (opcode == Op_StoreP) { 849 Node* adr = n->in(MemNode::Address); 850 const Type* adr_type = gvn->type(adr); 851 // Pointer stores in G1 barriers looks like unsafe access. 852 // Ignore such stores to be able scalar replace non-escaping 853 // allocations. 854 if (adr_type->isa_rawptr() && adr->is_AddP()) { 855 Node* base = conn_graph->get_addp_base(adr); 856 if (base->Opcode() == Op_LoadP && 857 base->in(MemNode::Address)->is_AddP()) { 858 adr = base->in(MemNode::Address); 859 Node* tls = conn_graph->get_addp_base(adr); 860 if (tls->Opcode() == Op_ThreadLocal) { 861 int offs = (int) gvn->find_intptr_t_con(adr->in(AddPNode::Offset), Type::OffsetBot); 862 const int buf_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_buffer_offset()); 863 if (offs == buf_offset) { 864 return true; // G1 pre barrier previous oop value store. 865 } 866 if (offs == in_bytes(G1ThreadLocalData::dirty_card_queue_buffer_offset())) { 867 return true; // G1 post barrier card address store. 868 } 869 } 870 } 871 } 872 } 873 return false; 874 }