1 /* 2 * Copyright (c) 2018, 2019, 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 "gc/g1/c2/g1BarrierSetC2.hpp" 27 #include "gc/g1/g1BarrierSet.hpp" 28 #include "gc/g1/g1BarrierSetRuntime.hpp" 29 #include "gc/g1/g1CardTable.hpp" 30 #include "gc/g1/g1ThreadLocalData.hpp" 31 #include "gc/g1/heapRegion.hpp" 32 #include "opto/arraycopynode.hpp" 33 #include "opto/compile.hpp" 34 #include "opto/escape.hpp" 35 #include "opto/graphKit.hpp" 36 #include "opto/idealKit.hpp" 37 #include "opto/macro.hpp" 38 #include "opto/rootnode.hpp" 39 #include "opto/type.hpp" 40 #include "utilities/macros.hpp" 41 42 const TypeFunc *G1BarrierSetC2::write_ref_field_pre_entry_Type() { 43 const Type **fields = TypeTuple::fields(2); 44 fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value 45 fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread 46 const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields); 47 48 // create result type (range) 49 fields = TypeTuple::fields(0); 50 const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields); 51 52 return TypeFunc::make(domain, range); 53 } 54 55 const TypeFunc *G1BarrierSetC2::write_ref_field_post_entry_Type() { 56 const Type **fields = TypeTuple::fields(2); 57 fields[TypeFunc::Parms+0] = TypeRawPtr::NOTNULL; // Card addr 58 fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread 59 const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields); 60 61 // create result type (range) 62 fields = TypeTuple::fields(0); 63 const TypeTuple *range = TypeTuple::make(TypeFunc::Parms, fields); 64 65 return TypeFunc::make(domain, range); 66 } 67 68 #define __ ideal. 69 /* 70 * Determine if the G1 pre-barrier can be removed. The pre-barrier is 71 * required by SATB to make sure all objects live at the start of the 72 * marking are kept alive, all reference updates need to any previous 73 * reference stored before writing. 74 * 75 * If the previous value is NULL there is no need to save the old value. 76 * References that are NULL are filtered during runtime by the barrier 77 * code to avoid unnecessary queuing. 78 * 79 * However in the case of newly allocated objects it might be possible to 80 * prove that the reference about to be overwritten is NULL during compile 81 * time and avoid adding the barrier code completely. 82 * 83 * The compiler needs to determine that the object in which a field is about 84 * to be written is newly allocated, and that no prior store to the same field 85 * has happened since the allocation. 86 * 87 * Returns true if the pre-barrier can be removed 88 */ 89 bool G1BarrierSetC2::g1_can_remove_pre_barrier(GraphKit* kit, 90 PhaseTransform* phase, 91 Node* adr, 92 BasicType bt, 93 uint adr_idx) const { 94 intptr_t offset = 0; 95 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); 96 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); 97 98 if (offset == Type::OffsetBot) { 99 return false; // cannot unalias unless there are precise offsets 100 } 101 102 if (alloc == NULL) { 103 return false; // No allocation found 104 } 105 106 intptr_t size_in_bytes = type2aelembytes(bt); 107 108 Node* mem = kit->memory(adr_idx); // start searching here... 109 110 for (int cnt = 0; cnt < 50; cnt++) { 111 112 if (mem->is_Store()) { 113 114 Node* st_adr = mem->in(MemNode::Address); 115 intptr_t st_offset = 0; 116 Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset); 117 118 if (st_base == NULL) { 119 break; // inscrutable pointer 120 } 121 122 // Break we have found a store with same base and offset as ours so break 123 if (st_base == base && st_offset == offset) { 124 break; 125 } 126 127 if (st_offset != offset && st_offset != Type::OffsetBot) { 128 const int MAX_STORE = BytesPerLong; 129 if (st_offset >= offset + size_in_bytes || 130 st_offset <= offset - MAX_STORE || 131 st_offset <= offset - mem->as_Store()->memory_size()) { 132 // Success: The offsets are provably independent. 133 // (You may ask, why not just test st_offset != offset and be done? 134 // The answer is that stores of different sizes can co-exist 135 // in the same sequence of RawMem effects. We sometimes initialize 136 // a whole 'tile' of array elements with a single jint or jlong.) 137 mem = mem->in(MemNode::Memory); 138 continue; // advance through independent store memory 139 } 140 } 141 142 if (st_base != base 143 && MemNode::detect_ptr_independence(base, alloc, st_base, 144 AllocateNode::Ideal_allocation(st_base, phase), 145 phase)) { 146 // Success: The bases are provably independent. 147 mem = mem->in(MemNode::Memory); 148 continue; // advance through independent store memory 149 } 150 } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) { 151 152 InitializeNode* st_init = mem->in(0)->as_Initialize(); 153 AllocateNode* st_alloc = st_init->allocation(); 154 155 // Make sure that we are looking at the same allocation site. 156 // The alloc variable is guaranteed to not be null here from earlier check. 157 if (alloc == st_alloc) { 158 // Check that the initialization is storing NULL so that no previous store 159 // has been moved up and directly write a reference 160 Node* captured_store = st_init->find_captured_store(offset, 161 type2aelembytes(T_OBJECT), 162 phase); 163 if (captured_store == NULL || captured_store == st_init->zero_memory()) { 164 return true; 165 } 166 } 167 } 168 169 // Unless there is an explicit 'continue', we must bail out here, 170 // because 'mem' is an inscrutable memory state (e.g., a call). 171 break; 172 } 173 174 return false; 175 } 176 177 // G1 pre/post barriers 178 void G1BarrierSetC2::pre_barrier(GraphKit* kit, 179 bool do_load, 180 Node* ctl, 181 Node* obj, 182 Node* adr, 183 uint alias_idx, 184 Node* val, 185 const TypeOopPtr* val_type, 186 Node* pre_val, 187 BasicType bt) const { 188 // Some sanity checks 189 // Note: val is unused in this routine. 190 191 if (do_load) { 192 // We need to generate the load of the previous value 193 assert(obj != NULL, "must have a base"); 194 assert(adr != NULL, "where are loading from?"); 195 assert(pre_val == NULL, "loaded already?"); 196 assert(val_type != NULL, "need a type"); 197 198 if (use_ReduceInitialCardMarks() 199 && g1_can_remove_pre_barrier(kit, &kit->gvn(), adr, bt, alias_idx)) { 200 return; 201 } 202 203 } else { 204 // In this case both val_type and alias_idx are unused. 205 assert(pre_val != NULL, "must be loaded already"); 206 // Nothing to be done if pre_val is null. 207 if (pre_val->bottom_type() == TypePtr::NULL_PTR) return; 208 assert(pre_val->bottom_type()->basic_type() == T_OBJECT, "or we shouldn't be here"); 209 } 210 assert(bt == T_OBJECT, "or we shouldn't be here"); 211 212 IdealKit ideal(kit, true); 213 214 Node* tls = __ thread(); // ThreadLocalStorage 215 216 Node* no_base = __ top(); 217 Node* zero = __ ConI(0); 218 Node* zeroX = __ ConX(0); 219 220 float likely = PROB_LIKELY(0.999); 221 float unlikely = PROB_UNLIKELY(0.999); 222 223 BasicType active_type = in_bytes(SATBMarkQueue::byte_width_of_active()) == 4 ? T_INT : T_BYTE; 224 assert(in_bytes(SATBMarkQueue::byte_width_of_active()) == 4 || in_bytes(SATBMarkQueue::byte_width_of_active()) == 1, "flag width"); 225 226 // Offsets into the thread 227 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); 228 const int index_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_index_offset()); 229 const int buffer_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_buffer_offset()); 230 231 // Now the actual pointers into the thread 232 Node* marking_adr = __ AddP(no_base, tls, __ ConX(marking_offset)); 233 Node* buffer_adr = __ AddP(no_base, tls, __ ConX(buffer_offset)); 234 Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset)); 235 236 // Now some of the values 237 Node* marking = __ load(__ ctrl(), marking_adr, TypeInt::INT, active_type, Compile::AliasIdxRaw); 238 239 // if (!marking) 240 __ if_then(marking, BoolTest::ne, zero, unlikely); { 241 BasicType index_bt = TypeX_X->basic_type(); 242 assert(sizeof(size_t) == type2aelembytes(index_bt), "Loading G1 SATBMarkQueue::_index with wrong size."); 243 Node* index = __ load(__ ctrl(), index_adr, TypeX_X, index_bt, Compile::AliasIdxRaw); 244 245 if (do_load) { 246 // load original value 247 // alias_idx correct?? 248 pre_val = __ load(__ ctrl(), adr, val_type, bt, alias_idx); 249 } 250 251 // if (pre_val != NULL) 252 __ if_then(pre_val, BoolTest::ne, kit->null()); { 253 Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw); 254 255 // is the queue for this thread full? 256 __ if_then(index, BoolTest::ne, zeroX, likely); { 257 258 // decrement the index 259 Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t)))); 260 261 // Now get the buffer location we will log the previous value into and store it 262 Node *log_addr = __ AddP(no_base, buffer, next_index); 263 __ store(__ ctrl(), log_addr, pre_val, T_OBJECT, Compile::AliasIdxRaw, MemNode::unordered); 264 // update the index 265 __ store(__ ctrl(), index_adr, next_index, index_bt, Compile::AliasIdxRaw, MemNode::unordered); 266 267 } __ else_(); { 268 269 // logging buffer is full, call the runtime 270 const TypeFunc *tf = write_ref_field_pre_entry_Type(); 271 __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_pre_entry), "write_ref_field_pre_entry", pre_val, tls); 272 } __ end_if(); // (!index) 273 } __ end_if(); // (pre_val != NULL) 274 } __ end_if(); // (!marking) 275 276 // Final sync IdealKit and GraphKit. 277 kit->final_sync(ideal); 278 } 279 280 /* 281 * G1 similar to any GC with a Young Generation requires a way to keep track of 282 * references from Old Generation to Young Generation to make sure all live 283 * objects are found. G1 also requires to keep track of object references 284 * between different regions to enable evacuation of old regions, which is done 285 * as part of mixed collections. References are tracked in remembered sets and 286 * is continuously updated as reference are written to with the help of the 287 * post-barrier. 288 * 289 * To reduce the number of updates to the remembered set the post-barrier 290 * filters updates to fields in objects located in the Young Generation, 291 * the same region as the reference, when the NULL is being written or 292 * if the card is already marked as dirty by an earlier write. 293 * 294 * Under certain circumstances it is possible to avoid generating the 295 * post-barrier completely if it is possible during compile time to prove 296 * the object is newly allocated and that no safepoint exists between the 297 * allocation and the store. 298 * 299 * In the case of slow allocation the allocation code must handle the barrier 300 * as part of the allocation in the case the allocated object is not located 301 * in the nursery, this would happen for humongous objects. 302 * 303 * Returns true if the post barrier can be removed 304 */ 305 bool G1BarrierSetC2::g1_can_remove_post_barrier(GraphKit* kit, 306 PhaseTransform* phase, Node* store, 307 Node* adr) const { 308 intptr_t offset = 0; 309 Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset); 310 AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase); 311 312 if (offset == Type::OffsetBot) { 313 return false; // cannot unalias unless there are precise offsets 314 } 315 316 if (alloc == NULL) { 317 return false; // No allocation found 318 } 319 320 // Start search from Store node 321 Node* mem = store->in(MemNode::Control); 322 if (mem->is_Proj() && mem->in(0)->is_Initialize()) { 323 324 InitializeNode* st_init = mem->in(0)->as_Initialize(); 325 AllocateNode* st_alloc = st_init->allocation(); 326 327 // Make sure we are looking at the same allocation 328 if (alloc == st_alloc) { 329 return true; 330 } 331 } 332 333 return false; 334 } 335 336 // 337 // Update the card table and add card address to the queue 338 // 339 void G1BarrierSetC2::g1_mark_card(GraphKit* kit, 340 IdealKit& ideal, 341 Node* card_adr, 342 Node* oop_store, 343 uint oop_alias_idx, 344 Node* index, 345 Node* index_adr, 346 Node* buffer, 347 const TypeFunc* tf) const { 348 Node* zero = __ ConI(0); 349 Node* zeroX = __ ConX(0); 350 Node* no_base = __ top(); 351 BasicType card_bt = T_BYTE; 352 // Smash zero into card. MUST BE ORDERED WRT TO STORE 353 __ storeCM(__ ctrl(), card_adr, zero, oop_store, oop_alias_idx, card_bt, Compile::AliasIdxRaw); 354 355 // Now do the queue work 356 __ if_then(index, BoolTest::ne, zeroX); { 357 358 Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t)))); 359 Node* log_addr = __ AddP(no_base, buffer, next_index); 360 361 // Order, see storeCM. 362 __ store(__ ctrl(), log_addr, card_adr, T_ADDRESS, Compile::AliasIdxRaw, MemNode::unordered); 363 __ store(__ ctrl(), index_adr, next_index, TypeX_X->basic_type(), Compile::AliasIdxRaw, MemNode::unordered); 364 365 } __ else_(); { 366 __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_post_entry), "write_ref_field_post_entry", card_adr, __ thread()); 367 } __ end_if(); 368 369 } 370 371 void G1BarrierSetC2::post_barrier(GraphKit* kit, 372 Node* ctl, 373 Node* oop_store, 374 Node* obj, 375 Node* adr, 376 uint alias_idx, 377 Node* val, 378 BasicType bt, 379 bool use_precise) const { 380 // If we are writing a NULL then we need no post barrier 381 382 if (val != NULL && val->is_Con() && val->bottom_type() == TypePtr::NULL_PTR) { 383 // Must be NULL 384 const Type* t = val->bottom_type(); 385 assert(t == Type::TOP || t == TypePtr::NULL_PTR, "must be NULL"); 386 // No post barrier if writing NULLx 387 return; 388 } 389 390 if (use_ReduceInitialCardMarks() && obj == kit->just_allocated_object(kit->control())) { 391 // We can skip marks on a freshly-allocated object in Eden. 392 // Keep this code in sync with new_deferred_store_barrier() in runtime.cpp. 393 // That routine informs GC to take appropriate compensating steps, 394 // upon a slow-path allocation, so as to make this card-mark 395 // elision safe. 396 return; 397 } 398 399 if (use_ReduceInitialCardMarks() 400 && g1_can_remove_post_barrier(kit, &kit->gvn(), oop_store, adr)) { 401 return; 402 } 403 404 if (!use_precise) { 405 // All card marks for a (non-array) instance are in one place: 406 adr = obj; 407 } 408 // (Else it's an array (or unknown), and we want more precise card marks.) 409 assert(adr != NULL, ""); 410 411 IdealKit ideal(kit, true); 412 413 Node* tls = __ thread(); // ThreadLocalStorage 414 415 Node* no_base = __ top(); 416 float likely = PROB_LIKELY_MAG(3); 417 float unlikely = PROB_UNLIKELY_MAG(3); 418 Node* young_card = __ ConI((jint)G1CardTable::g1_young_card_val()); 419 Node* dirty_card = __ ConI((jint)G1CardTable::dirty_card_val()); 420 Node* zeroX = __ ConX(0); 421 422 const TypeFunc *tf = write_ref_field_post_entry_Type(); 423 424 // Offsets into the thread 425 const int index_offset = in_bytes(G1ThreadLocalData::dirty_card_queue_index_offset()); 426 const int buffer_offset = in_bytes(G1ThreadLocalData::dirty_card_queue_buffer_offset()); 427 428 // Pointers into the thread 429 430 Node* buffer_adr = __ AddP(no_base, tls, __ ConX(buffer_offset)); 431 Node* index_adr = __ AddP(no_base, tls, __ ConX(index_offset)); 432 433 // Now some values 434 // Use ctrl to avoid hoisting these values past a safepoint, which could 435 // potentially reset these fields in the JavaThread. 436 Node* index = __ load(__ ctrl(), index_adr, TypeX_X, TypeX_X->basic_type(), Compile::AliasIdxRaw); 437 Node* buffer = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw); 438 439 // Convert the store obj pointer to an int prior to doing math on it 440 // Must use ctrl to prevent "integerized oop" existing across safepoint 441 Node* cast = __ CastPX(__ ctrl(), adr); 442 443 // Divide pointer by card size 444 Node* card_offset = __ URShiftX( cast, __ ConI(CardTable::card_shift) ); 445 446 // Combine card table base and card offset 447 Node* card_adr = __ AddP(no_base, byte_map_base_node(kit), card_offset ); 448 449 // If we know the value being stored does it cross regions? 450 451 if (val != NULL) { 452 // Does the store cause us to cross regions? 453 454 // Should be able to do an unsigned compare of region_size instead of 455 // and extra shift. Do we have an unsigned compare?? 456 // Node* region_size = __ ConI(1 << HeapRegion::LogOfHRGrainBytes); 457 Node* xor_res = __ URShiftX ( __ XorX( cast, __ CastPX(__ ctrl(), val)), __ ConI(HeapRegion::LogOfHRGrainBytes)); 458 459 // if (xor_res == 0) same region so skip 460 __ if_then(xor_res, BoolTest::ne, zeroX, likely); { 461 462 // No barrier if we are storing a NULL 463 __ if_then(val, BoolTest::ne, kit->null(), likely); { 464 465 // Ok must mark the card if not already dirty 466 467 // load the original value of the card 468 Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); 469 470 __ if_then(card_val, BoolTest::ne, young_card, unlikely); { 471 kit->sync_kit(ideal); 472 kit->insert_mem_bar(Op_MemBarVolatile, oop_store); 473 __ sync_kit(kit); 474 475 Node* card_val_reload = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); 476 __ if_then(card_val_reload, BoolTest::ne, dirty_card); { 477 g1_mark_card(kit, ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf); 478 } __ end_if(); 479 } __ end_if(); 480 } __ end_if(); 481 } __ end_if(); 482 } else { 483 // The Object.clone() intrinsic uses this path if !ReduceInitialCardMarks. 484 // We don't need a barrier here if the destination is a newly allocated object 485 // in Eden. Otherwise, GC verification breaks because we assume that cards in Eden 486 // are set to 'g1_young_gen' (see G1CardTable::verify_g1_young_region()). 487 assert(!use_ReduceInitialCardMarks(), "can only happen with card marking"); 488 Node* card_val = __ load(__ ctrl(), card_adr, TypeInt::INT, T_BYTE, Compile::AliasIdxRaw); 489 __ if_then(card_val, BoolTest::ne, young_card); { 490 g1_mark_card(kit, ideal, card_adr, oop_store, alias_idx, index, index_adr, buffer, tf); 491 } __ end_if(); 492 } 493 494 // Final sync IdealKit and GraphKit. 495 kit->final_sync(ideal); 496 } 497 498 // Helper that guards and inserts a pre-barrier. 499 void G1BarrierSetC2::insert_pre_barrier(GraphKit* kit, Node* base_oop, Node* offset, 500 Node* pre_val, bool need_mem_bar) const { 501 // We could be accessing the referent field of a reference object. If so, when G1 502 // is enabled, we need to log the value in the referent field in an SATB buffer. 503 // This routine performs some compile time filters and generates suitable 504 // runtime filters that guard the pre-barrier code. 505 // Also add memory barrier for non volatile load from the referent field 506 // to prevent commoning of loads across safepoint. 507 508 // Some compile time checks. 509 510 // If offset is a constant, is it java_lang_ref_Reference::_reference_offset? 511 const TypeX* otype = offset->find_intptr_t_type(); 512 if (otype != NULL && otype->is_con() && 513 otype->get_con() != java_lang_ref_Reference::referent_offset) { 514 // Constant offset but not the reference_offset so just return 515 return; 516 } 517 518 // We only need to generate the runtime guards for instances. 519 const TypeOopPtr* btype = base_oop->bottom_type()->isa_oopptr(); 520 if (btype != NULL) { 521 if (btype->isa_aryptr()) { 522 // Array type so nothing to do 523 return; 524 } 525 526 const TypeInstPtr* itype = btype->isa_instptr(); 527 if (itype != NULL) { 528 // Can the klass of base_oop be statically determined to be 529 // _not_ a sub-class of Reference and _not_ Object? 530 ciKlass* klass = itype->klass(); 531 if ( klass->is_loaded() && 532 !klass->is_subtype_of(kit->env()->Reference_klass()) && 533 !kit->env()->Object_klass()->is_subtype_of(klass)) { 534 return; 535 } 536 } 537 } 538 539 // The compile time filters did not reject base_oop/offset so 540 // we need to generate the following runtime filters 541 // 542 // if (offset == java_lang_ref_Reference::_reference_offset) { 543 // if (instance_of(base, java.lang.ref.Reference)) { 544 // pre_barrier(_, pre_val, ...); 545 // } 546 // } 547 548 float likely = PROB_LIKELY( 0.999); 549 float unlikely = PROB_UNLIKELY(0.999); 550 551 IdealKit ideal(kit); 552 553 Node* referent_off = __ ConX(java_lang_ref_Reference::referent_offset); 554 555 __ if_then(offset, BoolTest::eq, referent_off, unlikely); { 556 // Update graphKit memory and control from IdealKit. 557 kit->sync_kit(ideal); 558 559 Node* ref_klass_con = kit->makecon(TypeKlassPtr::make(kit->env()->Reference_klass())); 560 Node* is_instof = kit->gen_instanceof(base_oop, ref_klass_con); 561 562 // Update IdealKit memory and control from graphKit. 563 __ sync_kit(kit); 564 565 Node* one = __ ConI(1); 566 // is_instof == 0 if base_oop == NULL 567 __ if_then(is_instof, BoolTest::eq, one, unlikely); { 568 569 // Update graphKit from IdeakKit. 570 kit->sync_kit(ideal); 571 572 // Use the pre-barrier to record the value in the referent field 573 pre_barrier(kit, false /* do_load */, 574 __ ctrl(), 575 NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */, 576 pre_val /* pre_val */, 577 T_OBJECT); 578 if (need_mem_bar) { 579 // Add memory barrier to prevent commoning reads from this field 580 // across safepoint since GC can change its value. 581 kit->insert_mem_bar(Op_MemBarCPUOrder); 582 } 583 // Update IdealKit from graphKit. 584 __ sync_kit(kit); 585 586 } __ end_if(); // _ref_type != ref_none 587 } __ end_if(); // offset == referent_offset 588 589 // Final sync IdealKit and GraphKit. 590 kit->final_sync(ideal); 591 } 592 593 #undef __ 594 595 Node* G1BarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const { 596 DecoratorSet decorators = access.decorators(); 597 Node* adr = access.addr().node(); 598 Node* obj = access.base(); 599 600 bool mismatched = (decorators & C2_MISMATCHED) != 0; 601 bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0; 602 bool in_heap = (decorators & IN_HEAP) != 0; 603 bool on_weak = (decorators & ON_WEAK_OOP_REF) != 0; 604 bool is_unordered = (decorators & MO_UNORDERED) != 0; 605 bool need_cpu_mem_bar = !is_unordered || mismatched || !in_heap; 606 607 Node* top = Compile::current()->top(); 608 Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : top; 609 Node* load = CardTableBarrierSetC2::load_at_resolved(access, val_type); 610 611 // If we are reading the value of the referent field of a Reference 612 // object (either by using Unsafe directly or through reflection) 613 // then, if G1 is enabled, we need to record the referent in an 614 // SATB log buffer using the pre-barrier mechanism. 615 // Also we need to add memory barrier to prevent commoning reads 616 // from this field across safepoint since GC can change its value. 617 bool need_read_barrier = in_heap && (on_weak || 618 (unknown && offset != top && obj != top)); 619 620 if (!access.is_oop() || !need_read_barrier) { 621 return load; 622 } 623 624 assert(access.is_parse_access(), "entry not supported at optimization time"); 625 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access); 626 GraphKit* kit = parse_access.kit(); 627 628 if (on_weak) { 629 // Use the pre-barrier to record the value in the referent field 630 pre_barrier(kit, false /* do_load */, 631 kit->control(), 632 NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */, 633 load /* pre_val */, T_OBJECT); 634 // Add memory barrier to prevent commoning reads from this field 635 // across safepoint since GC can change its value. 636 kit->insert_mem_bar(Op_MemBarCPUOrder); 637 } else if (unknown) { 638 // We do not require a mem bar inside pre_barrier if need_mem_bar 639 // is set: the barriers would be emitted by us. 640 insert_pre_barrier(kit, obj, offset, load, !need_cpu_mem_bar); 641 } 642 643 return load; 644 } 645 646 bool G1BarrierSetC2::is_gc_barrier_node(Node* node) const { 647 if (CardTableBarrierSetC2::is_gc_barrier_node(node)) { 648 return true; 649 } 650 if (node->Opcode() != Op_CallLeaf) { 651 return false; 652 } 653 CallLeafNode *call = node->as_CallLeaf(); 654 if (call->_name == NULL) { 655 return false; 656 } 657 658 return strcmp(call->_name, "write_ref_field_pre_entry") == 0 || strcmp(call->_name, "write_ref_field_post_entry") == 0; 659 } 660 661 void G1BarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* node) const { 662 assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required"); 663 assert(node->outcnt() <= 2, "expects 1 or 2 users: Xor and URShift nodes"); 664 // It could be only one user, URShift node, in Object.clone() intrinsic 665 // but the new allocation is passed to arraycopy stub and it could not 666 // be scalar replaced. So we don't check the case. 667 668 // An other case of only one user (Xor) is when the value check for NULL 669 // in G1 post barrier is folded after CCP so the code which used URShift 670 // is removed. 671 672 // Take Region node before eliminating post barrier since it also 673 // eliminates CastP2X node when it has only one user. 674 Node* this_region = node->in(0); 675 assert(this_region != NULL, ""); 676 677 // Remove G1 post barrier. 678 679 // Search for CastP2X->Xor->URShift->Cmp path which 680 // checks if the store done to a different from the value's region. 681 // And replace Cmp with #0 (false) to collapse G1 post barrier. 682 Node* xorx = node->find_out_with(Op_XorX); 683 if (xorx != NULL) { 684 Node* shift = xorx->unique_out(); 685 Node* cmpx = shift->unique_out(); 686 assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() && 687 cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne, 688 "missing region check in G1 post barrier"); 689 macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); 690 691 // Remove G1 pre barrier. 692 693 // Search "if (marking != 0)" check and set it to "false". 694 // There is no G1 pre barrier if previous stored value is NULL 695 // (for example, after initialization). 696 if (this_region->is_Region() && this_region->req() == 3) { 697 int ind = 1; 698 if (!this_region->in(ind)->is_IfFalse()) { 699 ind = 2; 700 } 701 if (this_region->in(ind)->is_IfFalse() && 702 this_region->in(ind)->in(0)->Opcode() == Op_If) { 703 Node* bol = this_region->in(ind)->in(0)->in(1); 704 assert(bol->is_Bool(), ""); 705 cmpx = bol->in(1); 706 if (bol->as_Bool()->_test._test == BoolTest::ne && 707 cmpx->is_Cmp() && cmpx->in(2) == macro->intcon(0) && 708 cmpx->in(1)->is_Load()) { 709 Node* adr = cmpx->in(1)->as_Load()->in(MemNode::Address); 710 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); 711 if (adr->is_AddP() && adr->in(AddPNode::Base) == macro->top() && 712 adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal && 713 adr->in(AddPNode::Offset) == macro->MakeConX(marking_offset)) { 714 macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); 715 } 716 } 717 } 718 } 719 } else { 720 assert(!use_ReduceInitialCardMarks(), "can only happen with card marking"); 721 // This is a G1 post barrier emitted by the Object.clone() intrinsic. 722 // Search for the CastP2X->URShiftX->AddP->LoadB->Cmp path which checks if the card 723 // is marked as young_gen and replace the Cmp with 0 (false) to collapse the barrier. 724 Node* shift = node->find_out_with(Op_URShiftX); 725 assert(shift != NULL, "missing G1 post barrier"); 726 Node* addp = shift->unique_out(); 727 Node* load = addp->find_out_with(Op_LoadB); 728 assert(load != NULL, "missing G1 post barrier"); 729 Node* cmpx = load->unique_out(); 730 assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() && 731 cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne, 732 "missing card value check in G1 post barrier"); 733 macro->replace_node(cmpx, macro->makecon(TypeInt::CC_EQ)); 734 // There is no G1 pre barrier in this case 735 } 736 // Now CastP2X can be removed since it is used only on dead path 737 // which currently still alive until igvn optimize it. 738 assert(node->outcnt() == 0 || node->unique_out()->Opcode() == Op_URShiftX, ""); 739 macro->replace_node(node, macro->top()); 740 } 741 742 Node* G1BarrierSetC2::step_over_gc_barrier(Node* c) const { 743 if (!use_ReduceInitialCardMarks() && 744 c != NULL && c->is_Region() && c->req() == 3) { 745 for (uint i = 1; i < c->req(); i++) { 746 if (c->in(i) != NULL && c->in(i)->is_Region() && 747 c->in(i)->req() == 3) { 748 Node* r = c->in(i); 749 for (uint j = 1; j < r->req(); j++) { 750 if (r->in(j) != NULL && r->in(j)->is_Proj() && 751 r->in(j)->in(0) != NULL && 752 r->in(j)->in(0)->Opcode() == Op_CallLeaf && 753 r->in(j)->in(0)->as_Call()->entry_point() == CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_post_entry)) { 754 Node* call = r->in(j)->in(0); 755 c = c->in(i == 1 ? 2 : 1); 756 if (c != NULL) { 757 c = c->in(0); 758 if (c != NULL) { 759 c = c->in(0); 760 assert(call->in(0) == NULL || 761 call->in(0)->in(0) == NULL || 762 call->in(0)->in(0)->in(0) == NULL || 763 call->in(0)->in(0)->in(0)->in(0) == NULL || 764 call->in(0)->in(0)->in(0)->in(0)->in(0) == NULL || 765 c == call->in(0)->in(0)->in(0)->in(0)->in(0), "bad barrier shape"); 766 return c; 767 } 768 } 769 } 770 } 771 } 772 } 773 } 774 return c; 775 } 776 777 #ifdef ASSERT 778 void G1BarrierSetC2::verify_gc_barriers(Compile* compile, CompilePhase phase) const { 779 if (phase != BarrierSetC2::BeforeCodeGen) { 780 return; 781 } 782 // Verify G1 pre-barriers 783 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset()); 784 785 ResourceArea *area = Thread::current()->resource_area(); 786 Unique_Node_List visited(area); 787 Node_List worklist(area); 788 // We're going to walk control flow backwards starting from the Root 789 worklist.push(compile->root()); 790 while (worklist.size() > 0) { 791 Node* x = worklist.pop(); 792 if (x == NULL || x == compile->top()) continue; 793 if (visited.member(x)) { 794 continue; 795 } else { 796 visited.push(x); 797 } 798 799 if (x->is_Region()) { 800 for (uint i = 1; i < x->req(); i++) { 801 worklist.push(x->in(i)); 802 } 803 } else { 804 worklist.push(x->in(0)); 805 // We are looking for the pattern: 806 // /->ThreadLocal 807 // If->Bool->CmpI->LoadB->AddP->ConL(marking_offset) 808 // \->ConI(0) 809 // We want to verify that the If and the LoadB have the same control 810 // See GraphKit::g1_write_barrier_pre() 811 if (x->is_If()) { 812 IfNode *iff = x->as_If(); 813 if (iff->in(1)->is_Bool() && iff->in(1)->in(1)->is_Cmp()) { 814 CmpNode *cmp = iff->in(1)->in(1)->as_Cmp(); 815 if (cmp->Opcode() == Op_CmpI && cmp->in(2)->is_Con() && cmp->in(2)->bottom_type()->is_int()->get_con() == 0 816 && cmp->in(1)->is_Load()) { 817 LoadNode* load = cmp->in(1)->as_Load(); 818 if (load->Opcode() == Op_LoadB && load->in(2)->is_AddP() && load->in(2)->in(2)->Opcode() == Op_ThreadLocal 819 && load->in(2)->in(3)->is_Con() 820 && load->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == marking_offset) { 821 822 Node* if_ctrl = iff->in(0); 823 Node* load_ctrl = load->in(0); 824 825 if (if_ctrl != load_ctrl) { 826 // Skip possible CProj->NeverBranch in infinite loops 827 if ((if_ctrl->is_Proj() && if_ctrl->Opcode() == Op_CProj) 828 && (if_ctrl->in(0)->is_MultiBranch() && if_ctrl->in(0)->Opcode() == Op_NeverBranch)) { 829 if_ctrl = if_ctrl->in(0)->in(0); 830 } 831 } 832 assert(load_ctrl != NULL && if_ctrl == load_ctrl, "controls must match"); 833 } 834 } 835 } 836 } 837 } 838 } 839 } 840 #endif 841 842 bool G1BarrierSetC2::escape_add_to_con_graph(ConnectionGraph* conn_graph, PhaseGVN* gvn, Unique_Node_List* delayed_worklist, Node* n, uint opcode) const { 843 if (opcode == Op_StoreP) { 844 Node* adr = n->in(MemNode::Address); 845 const Type* adr_type = gvn->type(adr); 846 // Pointer stores in G1 barriers looks like unsafe access. 847 // Ignore such stores to be able scalar replace non-escaping 848 // allocations. 849 if (adr_type->isa_rawptr() && adr->is_AddP()) { 850 Node* base = conn_graph->get_addp_base(adr); 851 if (base->Opcode() == Op_LoadP && 852 base->in(MemNode::Address)->is_AddP()) { 853 adr = base->in(MemNode::Address); 854 Node* tls = conn_graph->get_addp_base(adr); 855 if (tls->Opcode() == Op_ThreadLocal) { 856 int offs = (int) gvn->find_intptr_t_con(adr->in(AddPNode::Offset), Type::OffsetBot); 857 const int buf_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_buffer_offset()); 858 if (offs == buf_offset) { 859 return true; // G1 pre barrier previous oop value store. 860 } 861 if (offs == in_bytes(G1ThreadLocalData::dirty_card_queue_buffer_offset())) { 862 return true; // G1 post barrier card address store. 863 } 864 } 865 } 866 } 867 } 868 return false; 869 }