1 /*
2 * Copyright (c) 2018, 2023, 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 PhaseValues* 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);
98
99 if (offset == Type::OffsetBot) {
100 return false; // cannot unalias unless there are precise offsets
101 }
102
103 if (alloc == nullptr) {
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 == nullptr) {
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),
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 == nullptr || 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 != nullptr, "must have a base");
195 assert(adr != nullptr, "where are loading from?");
196 assert(pre_val == nullptr, "loaded already?");
197 assert(val_type != nullptr, "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 != nullptr, "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 pre_val = __ load(__ ctrl(), adr, val_type, bt, alias_idx, false, MemNode::unordered, LoadNode::Pinned);
249 }
250
251 // if (pre_val != nullptr)
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 != nullptr)
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 PhaseValues* 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);
311
312 if (offset == Type::OffsetBot) {
313 return false; // cannot unalias unless there are precise offsets
314 }
315
316 if (alloc == nullptr) {
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 != nullptr && 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 null
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 != nullptr, "");
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 != nullptr) {
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(checked_cast<jint>(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 != nullptr && 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 != nullptr) {
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 != nullptr) {
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->instance_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 == nullptr
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 nullptr /* obj */, nullptr /* adr */, max_juint /* alias_idx */, nullptr /* val */, nullptr /* 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 anonymous = (decorators & C2_UNSAFE_ACCESS) != 0;
601 bool mismatched = (decorators & C2_MISMATCHED) != 0;
602 bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
603 bool in_heap = (decorators & IN_HEAP) != 0;
604 bool in_native = (decorators & IN_NATIVE) != 0;
605 bool on_weak = (decorators & ON_WEAK_OOP_REF) != 0;
606 bool on_phantom = (decorators & ON_PHANTOM_OOP_REF) != 0;
607 bool is_unordered = (decorators & MO_UNORDERED) != 0;
608 bool no_keepalive = (decorators & AS_NO_KEEPALIVE) != 0;
609 bool is_mixed = !in_heap && !in_native;
610 bool need_cpu_mem_bar = !is_unordered || mismatched || is_mixed;
611
612 Node* top = Compile::current()->top();
613 Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : top;
614
615 // If we are reading the value of the referent field of a Reference
616 // object (either by using Unsafe directly or through reflection)
617 // then, if G1 is enabled, we need to record the referent in an
618 // SATB log buffer using the pre-barrier mechanism.
619 // Also we need to add memory barrier to prevent commoning reads
620 // from this field across safepoint since GC can change its value.
621 bool need_read_barrier = (((on_weak || on_phantom) && !no_keepalive) ||
622 (in_heap && unknown && offset != top && obj != top));
623
624 if (!access.is_oop() || !need_read_barrier) {
625 return CardTableBarrierSetC2::load_at_resolved(access, val_type);
626 }
627
628 assert(access.is_parse_access(), "entry not supported at optimization time");
629
630 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
631 GraphKit* kit = parse_access.kit();
632 Node* load;
633
634 Node* control = kit->control();
635 const TypePtr* adr_type = access.addr().type();
636 MemNode::MemOrd mo = access.mem_node_mo();
637 bool requires_atomic_access = (decorators & MO_UNORDERED) == 0;
638 bool unaligned = (decorators & C2_UNALIGNED) != 0;
639 bool unsafe = (decorators & C2_UNSAFE_ACCESS) != 0;
640 // Pinned control dependency is the strictest. So it's ok to substitute it for any other.
641 load = kit->make_load(control, adr, val_type, access.type(), adr_type, mo,
642 LoadNode::Pinned, requires_atomic_access, unaligned, mismatched, unsafe,
643 access.barrier_data());
644
645
646 if (on_weak || on_phantom) {
647 // Use the pre-barrier to record the value in the referent field
648 pre_barrier(kit, false /* do_load */,
649 kit->control(),
650 nullptr /* obj */, nullptr /* adr */, max_juint /* alias_idx */, nullptr /* val */, nullptr /* val_type */,
651 load /* pre_val */, T_OBJECT);
652 // Add memory barrier to prevent commoning reads from this field
653 // across safepoint since GC can change its value.
654 kit->insert_mem_bar(Op_MemBarCPUOrder);
655 } else if (unknown) {
656 // We do not require a mem bar inside pre_barrier if need_mem_bar
657 // is set: the barriers would be emitted by us.
658 insert_pre_barrier(kit, obj, offset, load, !need_cpu_mem_bar);
659 }
660
661 return load;
662 }
663
664 bool G1BarrierSetC2::is_gc_barrier_node(Node* node) const {
665 if (CardTableBarrierSetC2::is_gc_barrier_node(node)) {
666 return true;
667 }
668 if (node->Opcode() != Op_CallLeaf) {
669 return false;
670 }
671 CallLeafNode *call = node->as_CallLeaf();
672 if (call->_name == nullptr) {
673 return false;
674 }
675
676 return strcmp(call->_name, "write_ref_field_pre_entry") == 0 || strcmp(call->_name, "write_ref_field_post_entry") == 0;
677 }
678
679 bool G1BarrierSetC2::is_g1_pre_val_load(Node* n) {
680 if (n->is_Load() && n->as_Load()->has_pinned_control_dependency()) {
681 // Make sure the only users of it are: CmpP, StoreP, and a call to write_ref_field_pre_entry
682
683 // Skip possible decode
684 if (n->outcnt() == 1 && n->unique_out()->is_DecodeN()) {
685 n = n->unique_out();
686 }
687
688 if (n->outcnt() == 3) {
689 int found = 0;
690 for (SimpleDUIterator iter(n); iter.has_next(); iter.next()) {
691 Node* use = iter.get();
692 if (use->is_Cmp() || use->is_Store()) {
693 ++found;
694 } else if (use->is_CallLeaf()) {
695 CallLeafNode* call = use->as_CallLeaf();
696 if (strcmp(call->_name, "write_ref_field_pre_entry") == 0) {
697 ++found;
698 }
699 }
700 }
701 if (found == 3) {
702 return true;
703 }
704 }
705 }
706 return false;
707 }
708
709 bool G1BarrierSetC2::is_gc_pre_barrier_node(Node *node) const {
710 return is_g1_pre_val_load(node);
711 }
712
713 void G1BarrierSetC2::eliminate_gc_barrier(PhaseIterGVN* igvn, Node* node) const {
714 if (is_g1_pre_val_load(node)) {
715 igvn->replace_node(node, igvn->zerocon(node->as_Load()->bottom_type()->basic_type()));
716 } else {
717 assert(node->Opcode() == Op_CastP2X, "ConvP2XNode required");
718 assert(node->outcnt() <= 2, "expects 1 or 2 users: Xor and URShift nodes");
719 // It could be only one user, URShift node, in Object.clone() intrinsic
720 // but the new allocation is passed to arraycopy stub and it could not
721 // be scalar replaced. So we don't check the case.
722
723 // An other case of only one user (Xor) is when the value check for null
724 // in G1 post barrier is folded after CCP so the code which used URShift
725 // is removed.
726
727 // Take Region node before eliminating post barrier since it also
728 // eliminates CastP2X node when it has only one user.
729 Node* this_region = node->in(0);
730 assert(this_region != nullptr, "");
731
732 // Remove G1 post barrier.
733
734 // Search for CastP2X->Xor->URShift->Cmp path which
735 // checks if the store done to a different from the value's region.
736 // And replace Cmp with #0 (false) to collapse G1 post barrier.
737 Node* xorx = node->find_out_with(Op_XorX);
738 if (xorx != nullptr) {
739 Node* shift = xorx->unique_out();
740 Node* cmpx = shift->unique_out();
741 assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() &&
742 cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne,
743 "missing region check in G1 post barrier");
744 igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
745
746 // Remove G1 pre barrier.
747
748 // Search "if (marking != 0)" check and set it to "false".
749 // There is no G1 pre barrier if previous stored value is null
750 // (for example, after initialization).
751 if (this_region->is_Region() && this_region->req() == 3) {
752 for (int i = 1; i < 3; ++i) {
753 if (this_region->in(i)->is_IfFalse() &&
754 this_region->in(i)->in(0)->is_If() &&
755 this_region->in(i)->in(0)->in(1)->is_Bool()) {
756 Node* bol = this_region->in(i)->in(0)->in(1);
757 cmpx = bol->in(1);
758 if (bol->as_Bool()->_test._test == BoolTest::ne &&
759 cmpx->is_Cmp() && cmpx->in(2) == igvn->intcon(0) &&
760 cmpx->in(1)->is_Load()) {
761 Node* adr = cmpx->in(1)->as_Load()->in(MemNode::Address);
762 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset());
763 if (adr->is_AddP() && adr->in(AddPNode::Base) == igvn->C->top() &&
764 adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
765 adr->in(AddPNode::Offset) == igvn->MakeConX(marking_offset)) {
766 igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
767 }
768 }
769 }
770 }
771 }
772 } else {
773 assert(!use_ReduceInitialCardMarks(), "can only happen with card marking");
774 // This is a G1 post barrier emitted by the Object.clone() intrinsic.
775 // Search for the CastP2X->URShiftX->AddP->LoadB->Cmp path which checks if the card
776 // is marked as young_gen and replace the Cmp with 0 (false) to collapse the barrier.
777 Node* shift = node->find_out_with(Op_URShiftX);
778 assert(shift != nullptr, "missing G1 post barrier");
779 Node* addp = shift->unique_out();
780 Node* load = addp->find_out_with(Op_LoadB);
781 assert(load != nullptr, "missing G1 post barrier");
782 Node* cmpx = load->unique_out();
783 assert(cmpx->is_Cmp() && cmpx->unique_out()->is_Bool() &&
784 cmpx->unique_out()->as_Bool()->_test._test == BoolTest::ne,
785 "missing card value check in G1 post barrier");
786 igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
787 // There is no G1 pre barrier in this case
788 }
789 // Now CastP2X can be removed since it is used only on dead path
790 // which currently still alive until igvn optimize it.
791 assert(node->outcnt() == 0 || node->unique_out()->Opcode() == Op_URShiftX, "");
792 igvn->replace_node(node, igvn->C->top());
793 }
794 }
795
796 Node* G1BarrierSetC2::step_over_gc_barrier(Node* c) const {
797 if (!use_ReduceInitialCardMarks() &&
798 c != nullptr && c->is_Region() && c->req() == 3) {
799 for (uint i = 1; i < c->req(); i++) {
800 if (c->in(i) != nullptr && c->in(i)->is_Region() &&
801 c->in(i)->req() == 3) {
802 Node* r = c->in(i);
803 for (uint j = 1; j < r->req(); j++) {
804 if (r->in(j) != nullptr && r->in(j)->is_Proj() &&
805 r->in(j)->in(0) != nullptr &&
806 r->in(j)->in(0)->Opcode() == Op_CallLeaf &&
807 r->in(j)->in(0)->as_Call()->entry_point() == CAST_FROM_FN_PTR(address, G1BarrierSetRuntime::write_ref_field_post_entry)) {
808 Node* call = r->in(j)->in(0);
809 c = c->in(i == 1 ? 2 : 1);
810 if (c != nullptr && c->Opcode() != Op_Parm) {
811 c = c->in(0);
812 if (c != nullptr) {
813 c = c->in(0);
814 assert(call->in(0) == nullptr ||
815 call->in(0)->in(0) == nullptr ||
816 call->in(0)->in(0)->in(0) == nullptr ||
817 call->in(0)->in(0)->in(0)->in(0) == nullptr ||
818 call->in(0)->in(0)->in(0)->in(0)->in(0) == nullptr ||
819 c == call->in(0)->in(0)->in(0)->in(0)->in(0), "bad barrier shape");
820 return c;
821 }
822 }
823 }
824 }
825 }
826 }
827 }
828 return c;
829 }
830
831 #ifdef ASSERT
832 bool G1BarrierSetC2::has_cas_in_use_chain(Node *n) const {
833 Unique_Node_List visited;
834 Node_List worklist;
835 worklist.push(n);
836 while (worklist.size() > 0) {
837 Node* x = worklist.pop();
838 if (visited.member(x)) {
839 continue;
840 } else {
841 visited.push(x);
842 }
843
844 if (x->is_LoadStore()) {
845 int op = x->Opcode();
846 if (op == Op_CompareAndExchangeP || op == Op_CompareAndExchangeN ||
847 op == Op_CompareAndSwapP || op == Op_CompareAndSwapN ||
848 op == Op_WeakCompareAndSwapP || op == Op_WeakCompareAndSwapN) {
849 return true;
850 }
851 }
852 if (!x->is_CFG()) {
853 for (SimpleDUIterator iter(x); iter.has_next(); iter.next()) {
854 Node* use = iter.get();
855 worklist.push(use);
856 }
857 }
858 }
859 return false;
860 }
861
862 void G1BarrierSetC2::verify_pre_load(Node* marking_if, Unique_Node_List& loads /*output*/) const {
863 assert(loads.size() == 0, "Loads list should be empty");
864 Node* pre_val_if = marking_if->find_out_with(Op_IfTrue)->find_out_with(Op_If);
865 if (pre_val_if != nullptr) {
866 Unique_Node_List visited;
867 Node_List worklist;
868 Node* pre_val = pre_val_if->in(1)->in(1)->in(1);
869
870 worklist.push(pre_val);
871 while (worklist.size() > 0) {
872 Node* x = worklist.pop();
873 if (visited.member(x)) {
874 continue;
875 } else {
876 visited.push(x);
877 }
878
879 if (has_cas_in_use_chain(x)) {
880 loads.clear();
881 return;
882 }
883
884 if (x->is_Con()) {
885 continue;
886 }
887 if (x->is_EncodeP() || x->is_DecodeN()) {
888 worklist.push(x->in(1));
889 continue;
890 }
891 if (x->is_Load() || x->is_LoadStore()) {
892 assert(x->in(0) != nullptr, "Pre-val load has to have a control");
893 loads.push(x);
894 continue;
895 }
896 if (x->is_Phi()) {
897 for (uint i = 1; i < x->req(); i++) {
898 worklist.push(x->in(i));
899 }
900 continue;
901 }
902 assert(false, "Pre-val anomaly");
903 }
904 }
905 }
906
907 void G1BarrierSetC2::verify_no_safepoints(Compile* compile, Node* marking_check_if, const Unique_Node_List& loads) const {
908 if (loads.size() == 0) {
909 return;
910 }
911
912 if (loads.size() == 1) { // Handle the typical situation when there a single pre-value load
913 // that is dominated by the marking_check_if, that's true when the
914 // barrier itself does the pre-val load.
915 Node *pre_val = loads.at(0);
916 if (pre_val->in(0)->in(0) == marking_check_if) { // IfTrue->If
917 return;
918 }
919 }
920
921 // All other cases are when pre-value loads dominate the marking check.
922 Unique_Node_List controls;
923 for (uint i = 0; i < loads.size(); i++) {
924 Node *c = loads.at(i)->in(0);
925 controls.push(c);
926 }
927
928 Unique_Node_List visited;
929 Unique_Node_List safepoints;
930 Node_List worklist;
931 uint found = 0;
932
933 worklist.push(marking_check_if);
934 while (worklist.size() > 0 && found < controls.size()) {
935 Node* x = worklist.pop();
936 if (x == nullptr || x == compile->top()) continue;
937 if (visited.member(x)) {
938 continue;
939 } else {
940 visited.push(x);
941 }
942
943 if (controls.member(x)) {
944 found++;
945 }
946 if (x->is_Region()) {
947 for (uint i = 1; i < x->req(); i++) {
948 worklist.push(x->in(i));
949 }
950 } else {
951 if (!x->is_SafePoint()) {
952 worklist.push(x->in(0));
953 } else {
954 safepoints.push(x);
955 }
956 }
957 }
958 assert(found == controls.size(), "Pre-barrier structure anomaly or possible safepoint");
959 }
960
961 void G1BarrierSetC2::verify_gc_barriers(Compile* compile, CompilePhase phase) const {
962 if (phase != BarrierSetC2::BeforeCodeGen) {
963 return;
964 }
965 // Verify G1 pre-barriers
966 const int marking_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_active_offset());
967
968 Unique_Node_List visited;
969 Node_List worklist;
970 // We're going to walk control flow backwards starting from the Root
971 worklist.push(compile->root());
972 while (worklist.size() > 0) {
973 Node* x = worklist.pop();
974 if (x == nullptr || x == compile->top()) continue;
975 if (visited.member(x)) {
976 continue;
977 } else {
978 visited.push(x);
979 }
980
981 if (x->is_Region()) {
982 for (uint i = 1; i < x->req(); i++) {
983 worklist.push(x->in(i));
984 }
985 } else {
986 worklist.push(x->in(0));
987 // We are looking for the pattern:
988 // /->ThreadLocal
989 // If->Bool->CmpI->LoadB->AddP->ConL(marking_offset)
990 // \->ConI(0)
991 // We want to verify that the If and the LoadB have the same control
992 // See GraphKit::g1_write_barrier_pre()
993 if (x->is_If()) {
994 IfNode *iff = x->as_If();
995 if (iff->in(1)->is_Bool() && iff->in(1)->in(1)->is_Cmp()) {
996 CmpNode *cmp = iff->in(1)->in(1)->as_Cmp();
997 if (cmp->Opcode() == Op_CmpI && cmp->in(2)->is_Con() && cmp->in(2)->bottom_type()->is_int()->get_con() == 0
998 && cmp->in(1)->is_Load()) {
999 LoadNode* load = cmp->in(1)->as_Load();
1000 if (load->Opcode() == Op_LoadB && load->in(2)->is_AddP() && load->in(2)->in(2)->Opcode() == Op_ThreadLocal
1001 && load->in(2)->in(3)->is_Con()
1002 && load->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == marking_offset) {
1003
1004 Node* if_ctrl = iff->in(0);
1005 Node* load_ctrl = load->in(0);
1006
1007 if (if_ctrl != load_ctrl) {
1008 // Skip possible CProj->NeverBranch in infinite loops
1009 if ((if_ctrl->is_Proj() && if_ctrl->Opcode() == Op_CProj)
1010 && if_ctrl->in(0)->is_NeverBranch()) {
1011 if_ctrl = if_ctrl->in(0)->in(0);
1012 }
1013 }
1014 assert(load_ctrl != nullptr && if_ctrl == load_ctrl, "controls must match");
1015
1016 Unique_Node_List loads;
1017 verify_pre_load(iff, loads);
1018 verify_no_safepoints(compile, iff, loads);
1019 }
1020 }
1021 }
1022 }
1023 }
1024 }
1025 }
1026 #endif
1027
1028 bool G1BarrierSetC2::escape_add_to_con_graph(ConnectionGraph* conn_graph, PhaseGVN* gvn, Unique_Node_List* delayed_worklist, Node* n, uint opcode) const {
1029 if (opcode == Op_StoreP) {
1030 Node* adr = n->in(MemNode::Address);
1031 const Type* adr_type = gvn->type(adr);
1032 // Pointer stores in G1 barriers looks like unsafe access.
1033 // Ignore such stores to be able scalar replace non-escaping
1034 // allocations.
1035 if (adr_type->isa_rawptr() && adr->is_AddP()) {
1036 Node* base = conn_graph->get_addp_base(adr);
1037 if (base->Opcode() == Op_LoadP &&
1038 base->in(MemNode::Address)->is_AddP()) {
1039 adr = base->in(MemNode::Address);
1040 Node* tls = conn_graph->get_addp_base(adr);
1041 if (tls->Opcode() == Op_ThreadLocal) {
1042 int offs = (int) gvn->find_intptr_t_con(adr->in(AddPNode::Offset), Type::OffsetBot);
1043 const int buf_offset = in_bytes(G1ThreadLocalData::satb_mark_queue_buffer_offset());
1044 if (offs == buf_offset) {
1045 return true; // G1 pre barrier previous oop value store.
1046 }
1047 if (offs == in_bytes(G1ThreadLocalData::dirty_card_queue_buffer_offset())) {
1048 return true; // G1 post barrier card address store.
1049 }
1050 }
1051 }
1052 }
1053 }
1054 return false;
1055 }