1 /*
2 * Copyright (c) 2018, 2026, 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 "code/vmreg.inline.hpp"
26 #include "gc/shared/barrierSet.hpp"
27 #include "gc/shared/c2/barrierSetC2.hpp"
28 #include "gc/shared/tlab_globals.hpp"
29 #include "opto/arraycopynode.hpp"
30 #include "opto/block.hpp"
31 #include "opto/convertnode.hpp"
32 #include "opto/graphKit.hpp"
33 #include "opto/idealKit.hpp"
34 #include "opto/macro.hpp"
35 #include "opto/narrowptrnode.hpp"
36 #include "opto/output.hpp"
37 #include "opto/regalloc.hpp"
38 #include "opto/runtime.hpp"
39 #include "utilities/macros.hpp"
40 #include CPU_HEADER(gc/shared/barrierSetAssembler)
41
42 // By default this is a no-op.
43 void BarrierSetC2::resolve_address(C2Access& access) const { }
44
45 void* C2ParseAccess::barrier_set_state() const {
46 return _kit->barrier_set_state();
47 }
48
49 PhaseGVN& C2ParseAccess::gvn() const { return _kit->gvn(); }
50
51 bool C2Access::needs_cpu_membar() const {
52 bool mismatched = (_decorators & C2_MISMATCHED) != 0;
53 bool is_unordered = (_decorators & MO_UNORDERED) != 0;
54
55 bool anonymous = (_decorators & C2_UNSAFE_ACCESS) != 0;
56 bool in_heap = (_decorators & IN_HEAP) != 0;
57 bool in_native = (_decorators & IN_NATIVE) != 0;
58 bool is_mixed = !in_heap && !in_native;
59
60 bool is_write = (_decorators & C2_WRITE_ACCESS) != 0;
61 bool is_read = (_decorators & C2_READ_ACCESS) != 0;
62 bool is_atomic = is_read && is_write;
63
64 if (is_atomic) {
65 // Atomics always need to be wrapped in CPU membars
66 return true;
67 }
68
69 if (anonymous) {
70 // We will need memory barriers unless we can determine a unique
71 // alias category for this reference. (Note: If for some reason
72 // the barriers get omitted and the unsafe reference begins to "pollute"
73 // the alias analysis of the rest of the graph, either Compile::can_alias
74 // or Compile::must_alias will throw a diagnostic assert.)
75 if (is_mixed || !is_unordered || (mismatched && !_addr.type()->isa_aryptr())) {
76 return true;
77 }
78 } else {
79 assert(!is_mixed, "not unsafe");
80 }
81
82 return false;
83 }
84
85 static BarrierSetC2State* barrier_set_state() {
86 return reinterpret_cast<BarrierSetC2State*>(Compile::current()->barrier_set_state());
87 }
88
89 RegMask& BarrierStubC2::live() const {
90 return *barrier_set_state()->live(_node);
91 }
92
93 BarrierStubC2::BarrierStubC2(const MachNode* node)
94 : _node(node),
95 _entry(),
96 _continuation(),
97 _preserve(live()) {}
98
99 Label* BarrierStubC2::entry() {
100 // The _entry will never be bound when in_scratch_emit_size() is true.
101 // However, we still need to return a label that is not bound now, but
102 // will eventually be bound. Any eventually bound label will do, as it
103 // will only act as a placeholder, so we return the _continuation label.
104 return Compile::current()->output()->in_scratch_emit_size() ? &_continuation : &_entry;
105 }
106
107 Label* BarrierStubC2::continuation() {
108 return &_continuation;
109 }
110
111 uint8_t BarrierStubC2::barrier_data() const {
112 return _node->barrier_data();
113 }
114
115 void BarrierStubC2::preserve(Register r) {
116 const VMReg vm_reg = r->as_VMReg();
117 assert(vm_reg->is_Register(), "r must be a general-purpose register");
118 _preserve.insert(OptoReg::as_OptoReg(vm_reg));
119 }
120
121 void BarrierStubC2::dont_preserve(Register r) {
122 VMReg vm_reg = r->as_VMReg();
123 assert(vm_reg->is_Register(), "r must be a general-purpose register");
124 // Subtract the given register and all its sub-registers (e.g. {R11, R11_H}
125 // for r11 in aarch64).
126 do {
127 _preserve.remove(OptoReg::as_OptoReg(vm_reg));
128 vm_reg = vm_reg->next();
129 } while (vm_reg->is_Register() && !vm_reg->is_concrete());
130 }
131
132 const RegMask& BarrierStubC2::preserve_set() const {
133 return _preserve;
134 }
135
136 Node* BarrierSetC2::store_at_resolved(C2Access& access, C2AccessValue& val) const {
137 DecoratorSet decorators = access.decorators();
138
139 bool mismatched = (decorators & C2_MISMATCHED) != 0;
140 bool unaligned = (decorators & C2_UNALIGNED) != 0;
141 bool unsafe = (decorators & C2_UNSAFE_ACCESS) != 0;
142 bool requires_atomic_access = (decorators & MO_UNORDERED) == 0;
143
144 MemNode::MemOrd mo = access.mem_node_mo();
145
146 Node* store;
147 BasicType bt = access.type();
148 if (access.is_parse_access()) {
149 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
150
151 GraphKit* kit = parse_access.kit();
152 store = kit->store_to_memory(kit->control(), access.addr().node(), val.node(), bt,
153 mo, requires_atomic_access, unaligned, mismatched,
154 unsafe, access.barrier_data());
155 } else {
156 assert(access.is_opt_access(), "either parse or opt access");
157 C2OptAccess& opt_access = static_cast<C2OptAccess&>(access);
158 Node* ctl = opt_access.ctl();
159 MergeMemNode* mm = opt_access.mem();
160 PhaseGVN& gvn = opt_access.gvn();
161 const TypePtr* adr_type = access.addr().type();
162 int alias = gvn.C->get_alias_index(adr_type);
163 Node* mem = mm->memory_at(alias);
164
165 StoreNode* st = StoreNode::make(gvn, ctl, mem, access.addr().node(), adr_type, val.node(), bt, mo, requires_atomic_access);
166 if (unaligned) {
167 st->set_unaligned_access();
168 }
169 if (mismatched) {
170 st->set_mismatched_access();
171 }
172 st->set_barrier_data(access.barrier_data());
173 store = gvn.transform(st);
174 if (store == st) {
175 mm->set_memory_at(alias, st);
176 }
177 }
178 access.set_raw_access(store);
179
180 return store;
181 }
182
183 Node* BarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const {
184 DecoratorSet decorators = access.decorators();
185
186 Node* adr = access.addr().node();
187 const TypePtr* adr_type = access.addr().type();
188
189 bool mismatched = (decorators & C2_MISMATCHED) != 0;
190 bool requires_atomic_access = (decorators & MO_UNORDERED) == 0;
191 bool unaligned = (decorators & C2_UNALIGNED) != 0;
192 bool control_dependent = (decorators & C2_CONTROL_DEPENDENT_LOAD) != 0;
193 bool unknown_control = (decorators & C2_UNKNOWN_CONTROL_LOAD) != 0;
194 bool unsafe = (decorators & C2_UNSAFE_ACCESS) != 0;
195 bool immutable = (decorators & C2_IMMUTABLE_MEMORY) != 0;
196
197 MemNode::MemOrd mo = access.mem_node_mo();
198 LoadNode::ControlDependency dep = unknown_control ? LoadNode::UnknownControl : LoadNode::DependsOnlyOnTest;
199
200 Node* load;
201 if (access.is_parse_access()) {
202 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
203 GraphKit* kit = parse_access.kit();
204 Node* control = control_dependent ? kit->control() : nullptr;
205
206 if (immutable) {
207 Compile* C = Compile::current();
208 Node* mem = kit->immutable_memory();
209 load = LoadNode::make(kit->gvn(), control, mem, adr,
210 adr_type, val_type, access.type(), mo, dep, requires_atomic_access,
211 unaligned, mismatched, unsafe, access.barrier_data());
212 load = kit->gvn().transform(load);
213 } else {
214 load = kit->make_load(control, adr, val_type, access.type(), mo,
215 dep, requires_atomic_access, unaligned, mismatched, unsafe,
216 access.barrier_data());
217 }
218 } else {
219 assert(access.is_opt_access(), "either parse or opt access");
220 C2OptAccess& opt_access = static_cast<C2OptAccess&>(access);
221 Node* control = control_dependent ? opt_access.ctl() : nullptr;
222 MergeMemNode* mm = opt_access.mem();
223 PhaseGVN& gvn = opt_access.gvn();
224 Node* mem = mm->memory_at(gvn.C->get_alias_index(adr_type));
225 load = LoadNode::make(gvn, control, mem, adr, adr_type, val_type, access.type(), mo, dep,
226 requires_atomic_access, unaligned, mismatched, unsafe, access.barrier_data());
227 load = gvn.transform(load);
228 }
229 access.set_raw_access(load);
230
231 return load;
232 }
233
234 class C2AccessFence: public StackObj {
235 C2Access& _access;
236 Node* _leading_membar;
237
238 public:
239 C2AccessFence(C2Access& access) :
240 _access(access), _leading_membar(nullptr) {
241 GraphKit* kit = nullptr;
242 if (access.is_parse_access()) {
243 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
244 kit = parse_access.kit();
245 }
246 DecoratorSet decorators = access.decorators();
247
248 bool is_write = (decorators & C2_WRITE_ACCESS) != 0;
249 bool is_read = (decorators & C2_READ_ACCESS) != 0;
250 bool is_atomic = is_read && is_write;
251
252 bool is_volatile = (decorators & MO_SEQ_CST) != 0;
253 bool is_release = (decorators & MO_RELEASE) != 0;
254
255 if (is_atomic) {
256 assert(kit != nullptr, "unsupported at optimization time");
257 // Memory-model-wise, a LoadStore acts like a little synchronized
258 // block, so needs barriers on each side. These don't translate
259 // into actual barriers on most machines, but we still need rest of
260 // compiler to respect ordering.
261 if (is_release) {
262 _leading_membar = kit->insert_mem_bar(Op_MemBarRelease);
263 } else if (is_volatile) {
264 if (support_IRIW_for_not_multiple_copy_atomic_cpu) {
265 _leading_membar = kit->insert_mem_bar(Op_MemBarVolatile);
266 } else {
267 _leading_membar = kit->insert_mem_bar(Op_MemBarRelease);
268 }
269 }
270 } else if (is_write) {
271 // If reference is volatile, prevent following memory ops from
272 // floating down past the volatile write. Also prevents commoning
273 // another volatile read.
274 if (is_volatile || is_release) {
275 assert(kit != nullptr, "unsupported at optimization time");
276 _leading_membar = kit->insert_mem_bar(Op_MemBarRelease);
277 }
278 } else {
279 // Memory barrier to prevent normal and 'unsafe' accesses from
280 // bypassing each other. Happens after null checks, so the
281 // exception paths do not take memory state from the memory barrier,
282 // so there's no problems making a strong assert about mixing users
283 // of safe & unsafe memory.
284 if (is_volatile && support_IRIW_for_not_multiple_copy_atomic_cpu) {
285 assert(kit != nullptr, "unsupported at optimization time");
286 _leading_membar = kit->insert_mem_bar(Op_MemBarVolatile);
287 }
288 }
289
290 if (access.needs_cpu_membar()) {
291 assert(kit != nullptr, "unsupported at optimization time");
292 kit->insert_mem_bar(Op_MemBarCPUOrder);
293 }
294
295 if (is_atomic) {
296 // 4984716: MemBars must be inserted before this
297 // memory node in order to avoid a false
298 // dependency which will confuse the scheduler.
299 access.set_memory();
300 }
301 }
302
303 ~C2AccessFence() {
304 GraphKit* kit = nullptr;
305 if (_access.is_parse_access()) {
306 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(_access);
307 kit = parse_access.kit();
308 }
309 DecoratorSet decorators = _access.decorators();
310
311 bool is_write = (decorators & C2_WRITE_ACCESS) != 0;
312 bool is_read = (decorators & C2_READ_ACCESS) != 0;
313 bool is_atomic = is_read && is_write;
314
315 bool is_volatile = (decorators & MO_SEQ_CST) != 0;
316 bool is_acquire = (decorators & MO_ACQUIRE) != 0;
317
318 // If reference is volatile, prevent following volatiles ops from
319 // floating up before the volatile access.
320 if (_access.needs_cpu_membar()) {
321 kit->insert_mem_bar(Op_MemBarCPUOrder);
322 }
323
324 if (is_atomic) {
325 assert(kit != nullptr, "unsupported at optimization time");
326 if (is_acquire || is_volatile) {
327 Node* n = _access.raw_access();
328 Node* mb = kit->insert_mem_bar(Op_MemBarAcquire, n);
329 if (_leading_membar != nullptr) {
330 MemBarNode::set_load_store_pair(_leading_membar->as_MemBar(), mb->as_MemBar());
331 }
332 }
333 } else if (is_write) {
334 // If not multiple copy atomic, we do the MemBarVolatile before the load.
335 if (is_volatile && !support_IRIW_for_not_multiple_copy_atomic_cpu) {
336 assert(kit != nullptr, "unsupported at optimization time");
337 Node* n = _access.raw_access();
338 Node* mb = kit->insert_mem_bar(Op_MemBarVolatile, n); // Use fat membar
339 if (_leading_membar != nullptr) {
340 MemBarNode::set_store_pair(_leading_membar->as_MemBar(), mb->as_MemBar());
341 }
342 }
343 } else {
344 if (is_volatile || is_acquire) {
345 assert(kit != nullptr, "unsupported at optimization time");
346 Node* n = _access.raw_access();
347 assert(_leading_membar == nullptr || support_IRIW_for_not_multiple_copy_atomic_cpu, "no leading membar expected");
348 Node* mb = kit->insert_mem_bar(Op_MemBarAcquire, n);
349 mb->as_MemBar()->set_trailing_load();
350 }
351 }
352 }
353 };
354
355 Node* BarrierSetC2::store_at(C2Access& access, C2AccessValue& val) const {
356 C2AccessFence fence(access);
357 resolve_address(access);
358 return store_at_resolved(access, val);
359 }
360
361 Node* BarrierSetC2::load_at(C2Access& access, const Type* val_type) const {
362 C2AccessFence fence(access);
363 resolve_address(access);
364 return load_at_resolved(access, val_type);
365 }
366
367 MemNode::MemOrd C2Access::mem_node_mo() const {
368 bool is_write = (_decorators & C2_WRITE_ACCESS) != 0;
369 bool is_read = (_decorators & C2_READ_ACCESS) != 0;
370 if ((_decorators & MO_SEQ_CST) != 0) {
371 if (is_write && is_read) {
372 // For atomic operations
373 return MemNode::seqcst;
374 } else if (is_write) {
375 return MemNode::release;
376 } else {
377 assert(is_read, "what else?");
378 return MemNode::acquire;
379 }
380 } else if ((_decorators & MO_RELEASE) != 0) {
381 return MemNode::release;
382 } else if ((_decorators & MO_ACQUIRE) != 0) {
383 return MemNode::acquire;
384 } else if (is_write) {
385 // Volatile fields need releasing stores.
386 // Non-volatile fields also need releasing stores if they hold an
387 // object reference, because the object reference might point to
388 // a freshly created object.
389 // Conservatively release stores of object references.
390 return StoreNode::release_if_reference(_type);
391 } else {
392 return MemNode::unordered;
393 }
394 }
395
396 void C2Access::fixup_decorators() {
397 bool default_mo = (_decorators & MO_DECORATOR_MASK) == 0;
398 bool anonymous = (_decorators & C2_UNSAFE_ACCESS) != 0;
399
400 bool is_read = (_decorators & C2_READ_ACCESS) != 0;
401 bool is_write = (_decorators & C2_WRITE_ACCESS) != 0;
402
403 _decorators = AccessInternal::decorator_fixup(_decorators, _type);
404
405 if (is_read && !is_write && anonymous) {
406 // To be valid, unsafe loads may depend on other conditions than
407 // the one that guards them: pin the Load node
408 _decorators |= C2_CONTROL_DEPENDENT_LOAD;
409 _decorators |= C2_UNKNOWN_CONTROL_LOAD;
410 const TypePtr* adr_type = _addr.type();
411 Node* adr = _addr.node();
412 if (!needs_cpu_membar() && adr_type->isa_instptr()) {
413 assert(adr_type->meet(TypePtr::NULL_PTR) != adr_type->remove_speculative(), "should be not null");
414 intptr_t offset = Type::OffsetBot;
415 AddPNode::Ideal_base_and_offset(adr, &gvn(), offset);
416 if (offset >= 0) {
417 int s = Klass::layout_helper_size_in_bytes(adr_type->isa_instptr()->instance_klass()->layout_helper());
418 if (offset < s) {
419 // Guaranteed to be a valid access, no need to pin it
420 _decorators ^= C2_CONTROL_DEPENDENT_LOAD;
421 _decorators ^= C2_UNKNOWN_CONTROL_LOAD;
422 }
423 }
424 }
425 }
426 }
427
428 //--------------------------- atomic operations---------------------------------
429
430 void BarrierSetC2::pin_atomic_op(C2AtomicParseAccess& access) const {
431 // SCMemProjNodes represent the memory state of a LoadStore. Their
432 // main role is to prevent LoadStore nodes from being optimized away
433 // when their results aren't used.
434 assert(access.is_parse_access(), "entry not supported at optimization time");
435 C2ParseAccess& parse_access = static_cast<C2ParseAccess&>(access);
436 GraphKit* kit = parse_access.kit();
437 Node* load_store = access.raw_access();
438 assert(load_store != nullptr, "must pin atomic op");
439 Node* proj = kit->gvn().transform(new SCMemProjNode(load_store));
440 kit->set_memory(proj, access.alias_idx());
441 }
442
443 void C2AtomicParseAccess::set_memory() {
444 Node *mem = _kit->memory(_alias_idx);
445 _memory = mem;
446 }
447
448 Node* BarrierSetC2::atomic_cmpxchg_val_at_resolved(C2AtomicParseAccess& access, Node* expected_val,
449 Node* new_val, const Type* value_type) const {
450 GraphKit* kit = access.kit();
451 MemNode::MemOrd mo = access.mem_node_mo();
452 Node* mem = access.memory();
453
454 Node* adr = access.addr().node();
455 const TypePtr* adr_type = access.addr().type();
456
457 Node* load_store = nullptr;
458
459 if (access.is_oop()) {
460 #ifdef _LP64
461 if (adr->bottom_type()->is_ptr_to_narrowoop()) {
462 Node *newval_enc = kit->gvn().transform(new EncodePNode(new_val, new_val->bottom_type()->make_narrowoop()));
463 Node *oldval_enc = kit->gvn().transform(new EncodePNode(expected_val, expected_val->bottom_type()->make_narrowoop()));
464 load_store = new CompareAndExchangeNNode(kit->control(), mem, adr, newval_enc, oldval_enc, adr_type, value_type->make_narrowoop(), mo);
465 } else
466 #endif
467 {
468 load_store = new CompareAndExchangePNode(kit->control(), mem, adr, new_val, expected_val, adr_type, value_type->is_oopptr(), mo);
469 }
470 } else {
471 switch (access.type()) {
472 case T_BYTE: {
473 load_store = new CompareAndExchangeBNode(kit->control(), mem, adr, new_val, expected_val, adr_type, mo);
474 break;
475 }
476 case T_SHORT: {
477 load_store = new CompareAndExchangeSNode(kit->control(), mem, adr, new_val, expected_val, adr_type, mo);
478 break;
479 }
480 case T_INT: {
481 load_store = new CompareAndExchangeINode(kit->control(), mem, adr, new_val, expected_val, adr_type, mo);
482 break;
483 }
484 case T_LONG: {
485 load_store = new CompareAndExchangeLNode(kit->control(), mem, adr, new_val, expected_val, adr_type, mo);
486 break;
487 }
488 default:
489 ShouldNotReachHere();
490 }
491 }
492
493 load_store->as_LoadStore()->set_barrier_data(access.barrier_data());
494 load_store = kit->gvn().transform(load_store);
495
496 access.set_raw_access(load_store);
497 pin_atomic_op(access);
498
499 #ifdef _LP64
500 if (access.is_oop() && adr->bottom_type()->is_ptr_to_narrowoop()) {
501 return kit->gvn().transform(new DecodeNNode(load_store, load_store->get_ptr_type()));
502 }
503 #endif
504
505 return load_store;
506 }
507
508 Node* BarrierSetC2::atomic_cmpxchg_bool_at_resolved(C2AtomicParseAccess& access, Node* expected_val,
509 Node* new_val, const Type* value_type) const {
510 GraphKit* kit = access.kit();
511 DecoratorSet decorators = access.decorators();
512 MemNode::MemOrd mo = access.mem_node_mo();
513 Node* mem = access.memory();
514 bool is_weak_cas = (decorators & C2_WEAK_CMPXCHG) != 0;
515 Node* load_store = nullptr;
516 Node* adr = access.addr().node();
517
518 if (access.is_oop()) {
519 #ifdef _LP64
520 if (adr->bottom_type()->is_ptr_to_narrowoop()) {
521 Node *newval_enc = kit->gvn().transform(new EncodePNode(new_val, new_val->bottom_type()->make_narrowoop()));
522 Node *oldval_enc = kit->gvn().transform(new EncodePNode(expected_val, expected_val->bottom_type()->make_narrowoop()));
523 if (is_weak_cas) {
524 load_store = new WeakCompareAndSwapNNode(kit->control(), mem, adr, newval_enc, oldval_enc, mo);
525 } else {
526 load_store = new CompareAndSwapNNode(kit->control(), mem, adr, newval_enc, oldval_enc, mo);
527 }
528 } else
529 #endif
530 {
531 if (is_weak_cas) {
532 load_store = new WeakCompareAndSwapPNode(kit->control(), mem, adr, new_val, expected_val, mo);
533 } else {
534 load_store = new CompareAndSwapPNode(kit->control(), mem, adr, new_val, expected_val, mo);
535 }
536 }
537 } else {
538 switch(access.type()) {
539 case T_BYTE: {
540 if (is_weak_cas) {
541 load_store = new WeakCompareAndSwapBNode(kit->control(), mem, adr, new_val, expected_val, mo);
542 } else {
543 load_store = new CompareAndSwapBNode(kit->control(), mem, adr, new_val, expected_val, mo);
544 }
545 break;
546 }
547 case T_SHORT: {
548 if (is_weak_cas) {
549 load_store = new WeakCompareAndSwapSNode(kit->control(), mem, adr, new_val, expected_val, mo);
550 } else {
551 load_store = new CompareAndSwapSNode(kit->control(), mem, adr, new_val, expected_val, mo);
552 }
553 break;
554 }
555 case T_INT: {
556 if (is_weak_cas) {
557 load_store = new WeakCompareAndSwapINode(kit->control(), mem, adr, new_val, expected_val, mo);
558 } else {
559 load_store = new CompareAndSwapINode(kit->control(), mem, adr, new_val, expected_val, mo);
560 }
561 break;
562 }
563 case T_LONG: {
564 if (is_weak_cas) {
565 load_store = new WeakCompareAndSwapLNode(kit->control(), mem, adr, new_val, expected_val, mo);
566 } else {
567 load_store = new CompareAndSwapLNode(kit->control(), mem, adr, new_val, expected_val, mo);
568 }
569 break;
570 }
571 default:
572 ShouldNotReachHere();
573 }
574 }
575
576 load_store->as_LoadStore()->set_barrier_data(access.barrier_data());
577 load_store = kit->gvn().transform(load_store);
578
579 access.set_raw_access(load_store);
580 pin_atomic_op(access);
581
582 return load_store;
583 }
584
585 Node* BarrierSetC2::atomic_xchg_at_resolved(C2AtomicParseAccess& access, Node* new_val, const Type* value_type) const {
586 GraphKit* kit = access.kit();
587 Node* mem = access.memory();
588 Node* adr = access.addr().node();
589 const TypePtr* adr_type = access.addr().type();
590 Node* load_store = nullptr;
591
592 if (access.is_oop()) {
593 #ifdef _LP64
594 if (adr->bottom_type()->is_ptr_to_narrowoop()) {
595 Node *newval_enc = kit->gvn().transform(new EncodePNode(new_val, new_val->bottom_type()->make_narrowoop()));
596 load_store = kit->gvn().transform(new GetAndSetNNode(kit->control(), mem, adr, newval_enc, adr_type, value_type->make_narrowoop()));
597 } else
598 #endif
599 {
600 load_store = new GetAndSetPNode(kit->control(), mem, adr, new_val, adr_type, value_type->is_oopptr());
601 }
602 } else {
603 switch (access.type()) {
604 case T_BYTE:
605 load_store = new GetAndSetBNode(kit->control(), mem, adr, new_val, adr_type);
606 break;
607 case T_SHORT:
608 load_store = new GetAndSetSNode(kit->control(), mem, adr, new_val, adr_type);
609 break;
610 case T_INT:
611 load_store = new GetAndSetINode(kit->control(), mem, adr, new_val, adr_type);
612 break;
613 case T_LONG:
614 load_store = new GetAndSetLNode(kit->control(), mem, adr, new_val, adr_type);
615 break;
616 default:
617 ShouldNotReachHere();
618 }
619 }
620
621 load_store->as_LoadStore()->set_barrier_data(access.barrier_data());
622 load_store = kit->gvn().transform(load_store);
623
624 access.set_raw_access(load_store);
625 pin_atomic_op(access);
626
627 #ifdef _LP64
628 if (access.is_oop() && adr->bottom_type()->is_ptr_to_narrowoop()) {
629 return kit->gvn().transform(new DecodeNNode(load_store, load_store->get_ptr_type()));
630 }
631 #endif
632
633 return load_store;
634 }
635
636 Node* BarrierSetC2::atomic_add_at_resolved(C2AtomicParseAccess& access, Node* new_val, const Type* value_type) const {
637 Node* load_store = nullptr;
638 GraphKit* kit = access.kit();
639 Node* adr = access.addr().node();
640 const TypePtr* adr_type = access.addr().type();
641 Node* mem = access.memory();
642
643 switch(access.type()) {
644 case T_BYTE:
645 load_store = new GetAndAddBNode(kit->control(), mem, adr, new_val, adr_type);
646 break;
647 case T_SHORT:
648 load_store = new GetAndAddSNode(kit->control(), mem, adr, new_val, adr_type);
649 break;
650 case T_INT:
651 load_store = new GetAndAddINode(kit->control(), mem, adr, new_val, adr_type);
652 break;
653 case T_LONG:
654 load_store = new GetAndAddLNode(kit->control(), mem, adr, new_val, adr_type);
655 break;
656 default:
657 ShouldNotReachHere();
658 }
659
660 load_store->as_LoadStore()->set_barrier_data(access.barrier_data());
661 load_store = kit->gvn().transform(load_store);
662
663 access.set_raw_access(load_store);
664 pin_atomic_op(access);
665
666 return load_store;
667 }
668
669 Node* BarrierSetC2::atomic_cmpxchg_val_at(C2AtomicParseAccess& access, Node* expected_val,
670 Node* new_val, const Type* value_type) const {
671 C2AccessFence fence(access);
672 resolve_address(access);
673 return atomic_cmpxchg_val_at_resolved(access, expected_val, new_val, value_type);
674 }
675
676 Node* BarrierSetC2::atomic_cmpxchg_bool_at(C2AtomicParseAccess& access, Node* expected_val,
677 Node* new_val, const Type* value_type) const {
678 C2AccessFence fence(access);
679 resolve_address(access);
680 return atomic_cmpxchg_bool_at_resolved(access, expected_val, new_val, value_type);
681 }
682
683 Node* BarrierSetC2::atomic_xchg_at(C2AtomicParseAccess& access, Node* new_val, const Type* value_type) const {
684 C2AccessFence fence(access);
685 resolve_address(access);
686 return atomic_xchg_at_resolved(access, new_val, value_type);
687 }
688
689 Node* BarrierSetC2::atomic_add_at(C2AtomicParseAccess& access, Node* new_val, const Type* value_type) const {
690 C2AccessFence fence(access);
691 resolve_address(access);
692 return atomic_add_at_resolved(access, new_val, value_type);
693 }
694
695 int BarrierSetC2::arraycopy_payload_base_offset(bool is_array) {
696 // Exclude the header but include array length to copy by 8 bytes words.
697 // Can't use base_offset_in_bytes(bt) since basic type is unknown.
698 int base_off = is_array ? arrayOopDesc::length_offset_in_bytes() :
699 instanceOopDesc::base_offset_in_bytes();
700 // base_off:
701 // 8 - 32-bit VM or 64-bit VM, compact headers
702 // 12 - 64-bit VM, compressed klass
703 // 16 - 64-bit VM, normal klass
704 if (base_off % BytesPerLong != 0) {
705 assert(!UseCompactObjectHeaders, "");
706 if (is_array) {
707 // Exclude length to copy by 8 bytes words.
708 base_off += sizeof(int);
709 } else {
710 // Include klass to copy by 8 bytes words.
711 base_off = instanceOopDesc::klass_offset_in_bytes();
712 }
713 assert(base_off % BytesPerLong == 0, "expect 8 bytes alignment");
714 }
715 return base_off;
716 }
717
718 void BarrierSetC2::clone(GraphKit* kit, Node* src_base, Node* dst_base, Node* size, bool is_array) const {
719 int base_off = arraycopy_payload_base_offset(is_array);
720 Node* payload_size = size;
721 Node* offset = kit->MakeConX(base_off);
722 payload_size = kit->gvn().transform(new SubXNode(payload_size, offset));
723 if (is_array) {
724 // Ensure the array payload size is rounded up to the next BytesPerLong
725 // multiple when converting to double-words. This is necessary because array
726 // size does not include object alignment padding, so it might not be a
727 // multiple of BytesPerLong for sub-long element types.
728 payload_size = kit->gvn().transform(new AddXNode(payload_size, kit->MakeConX(BytesPerLong - 1)));
729 }
730 payload_size = kit->gvn().transform(new URShiftXNode(payload_size, kit->intcon(LogBytesPerLong)));
731 ArrayCopyNode* ac = ArrayCopyNode::make(kit, false, src_base, offset, dst_base, offset, payload_size, true, false);
732 if (is_array) {
733 ac->set_clone_array();
734 } else {
735 ac->set_clone_inst();
736 }
737 Node* n = kit->gvn().transform(ac);
738 if (n == ac) {
739 const TypePtr* raw_adr_type = TypeRawPtr::BOTTOM;
740 ac->set_adr_type(TypeRawPtr::BOTTOM);
741 kit->set_predefined_output_for_runtime_call(ac, ac->in(TypeFunc::Memory), raw_adr_type);
742 } else {
743 kit->set_all_memory(n);
744 }
745 }
746
747 Node* BarrierSetC2::obj_allocate(PhaseMacroExpand* macro, Node* mem, Node* toobig_false, Node* size_in_bytes,
748 Node*& i_o, Node*& needgc_ctrl,
749 Node*& fast_oop_ctrl, Node*& fast_oop_rawmem,
750 intx prefetch_lines) const {
751 assert(UseTLAB, "Only for TLAB enabled allocations");
752
753 Node* thread = macro->transform_later(new ThreadLocalNode());
754 Node* tlab_top_adr = macro->off_heap_plus_addr(thread, in_bytes(JavaThread::tlab_top_offset()));
755 Node* tlab_end_adr = macro->off_heap_plus_addr(thread, in_bytes(JavaThread::tlab_end_offset()));
756
757 // Load TLAB end.
758 //
759 // Note: We set the control input on "tlab_end" and "old_tlab_top" to work around
760 // a bug where these values were being moved across
761 // a safepoint. These are not oops, so they cannot be include in the oop
762 // map, but they can be changed by a GC. The proper way to fix this would
763 // be to set the raw memory state when generating a SafepointNode. However
764 // this will require extensive changes to the loop optimization in order to
765 // prevent a degradation of the optimization.
766 // See comment in memnode.hpp, around line 227 in class LoadPNode.
767 Node* tlab_end = macro->make_load_raw(toobig_false, mem, tlab_end_adr, 0, TypeRawPtr::BOTTOM, T_ADDRESS);
768
769 // Load the TLAB top.
770 Node* old_tlab_top = new LoadPNode(toobig_false, mem, tlab_top_adr, TypeRawPtr::BOTTOM, TypeRawPtr::BOTTOM, MemNode::unordered);
771 macro->transform_later(old_tlab_top);
772
773 // Add to heap top to get a new TLAB top
774 Node* new_tlab_top = AddPNode::make_off_heap(old_tlab_top, size_in_bytes);
775 macro->transform_later(new_tlab_top);
776
777 // Check against TLAB end
778 Node* tlab_full = new CmpPNode(new_tlab_top, tlab_end);
779 macro->transform_later(tlab_full);
780
781 Node* needgc_bol = new BoolNode(tlab_full, BoolTest::ge);
782 macro->transform_later(needgc_bol);
783 IfNode* needgc_iff = new IfNode(toobig_false, needgc_bol, PROB_UNLIKELY_MAG(4), COUNT_UNKNOWN);
784 macro->transform_later(needgc_iff);
785
786 // Plug the failing-heap-space-need-gc test into the slow-path region
787 Node* needgc_true = new IfTrueNode(needgc_iff);
788 macro->transform_later(needgc_true);
789 needgc_ctrl = needgc_true;
790
791 // No need for a GC.
792 Node* needgc_false = new IfFalseNode(needgc_iff);
793 macro->transform_later(needgc_false);
794
795 // Fast path:
796 i_o = macro->prefetch_allocation(i_o, needgc_false, mem,
797 old_tlab_top, new_tlab_top, prefetch_lines);
798
799 // Store the modified TLAB top back down.
800 Node* store_tlab_top = new StorePNode(needgc_false, mem, tlab_top_adr,
801 TypeRawPtr::BOTTOM, new_tlab_top, MemNode::unordered);
802 macro->transform_later(store_tlab_top);
803
804 fast_oop_ctrl = needgc_false;
805 fast_oop_rawmem = store_tlab_top;
806 return old_tlab_top;
807 }
808
809 const TypeFunc* BarrierSetC2::_clone_type_Type = nullptr;
810
811 void BarrierSetC2::make_clone_type() {
812 assert(BarrierSetC2::_clone_type_Type == nullptr, "should be");
813 // Create input type (domain)
814 int argcnt = NOT_LP64(3) LP64_ONLY(4);
815 const Type** const domain_fields = TypeTuple::fields(argcnt);
816 int argp = TypeFunc::Parms;
817 domain_fields[argp++] = TypeInstPtr::NOTNULL; // src
818 domain_fields[argp++] = TypeInstPtr::NOTNULL; // dst
819 domain_fields[argp++] = TypeX_X; // size lower
820 LP64_ONLY(domain_fields[argp++] = Type::HALF); // size upper
821 assert(argp == TypeFunc::Parms+argcnt, "correct decoding");
822 const TypeTuple* const domain = TypeTuple::make(TypeFunc::Parms + argcnt, domain_fields);
823
824 // Create result type (range)
825 const Type** const range_fields = TypeTuple::fields(0);
826 const TypeTuple* const range = TypeTuple::make(TypeFunc::Parms + 0, range_fields);
827
828 BarrierSetC2::_clone_type_Type = TypeFunc::make(domain, range);
829 }
830
831 inline const TypeFunc* BarrierSetC2::clone_type() {
832 assert(BarrierSetC2::_clone_type_Type != nullptr, "should be initialized");
833 return BarrierSetC2::_clone_type_Type;
834 }
835
836 #define XTOP LP64_ONLY(COMMA phase->top())
837
838 void BarrierSetC2::clone_in_runtime(PhaseMacroExpand* phase, ArrayCopyNode* ac,
839 address clone_addr, const char* clone_name) const {
840 Node* const ctrl = ac->in(TypeFunc::Control);
841 Node* const mem = ac->in(TypeFunc::Memory);
842 Node* const src = ac->in(ArrayCopyNode::Src);
843 Node* const dst = ac->in(ArrayCopyNode::Dest);
844 Node* const size = ac->in(ArrayCopyNode::Length);
845
846 assert(size->bottom_type()->base() == Type_X,
847 "Should be of object size type (int for 32 bits, long for 64 bits)");
848
849 // The native clone we are calling here expects the object size in words.
850 // Add header/offset size to payload size to get object size.
851 Node* const base_offset = phase->MakeConX(arraycopy_payload_base_offset(ac->is_clone_array()) >> LogBytesPerLong);
852 Node* const full_size = phase->transform_later(new AddXNode(size, base_offset));
853 // HeapAccess<>::clone expects size in heap words.
854 // For 64-bits platforms, this is a no-operation.
855 // For 32-bits platforms, we need to multiply full_size by HeapWordsPerLong (2).
856 Node* const full_size_in_heap_words = phase->transform_later(new LShiftXNode(full_size, phase->intcon(LogHeapWordsPerLong)));
857
858 Node* const call = phase->make_leaf_call(ctrl,
859 mem,
860 clone_type(),
861 clone_addr,
862 clone_name,
863 TypeRawPtr::BOTTOM,
864 src, dst, full_size_in_heap_words XTOP);
865 phase->transform_later(call);
866 phase->igvn().replace_node(ac, call);
867 }
868
869 void BarrierSetC2::clone_at_expansion(PhaseMacroExpand* phase, ArrayCopyNode* ac) const {
870 Node* ctrl = ac->in(TypeFunc::Control);
871 Node* mem = ac->in(TypeFunc::Memory);
872 Node* src = ac->in(ArrayCopyNode::Src);
873 Node* src_offset = ac->in(ArrayCopyNode::SrcPos);
874 Node* dest = ac->in(ArrayCopyNode::Dest);
875 Node* dest_offset = ac->in(ArrayCopyNode::DestPos);
876 Node* length = ac->in(ArrayCopyNode::Length);
877
878 Node* payload_src = phase->basic_plus_adr(src, src_offset);
879 Node* payload_dst = phase->basic_plus_adr(dest, dest_offset);
880
881 const char* copyfunc_name = "arraycopy";
882 address copyfunc_addr = phase->basictype2arraycopy(T_LONG, nullptr, nullptr, true, copyfunc_name, true);
883
884 const TypePtr* raw_adr_type = TypeRawPtr::BOTTOM;
885 const TypeFunc* call_type = OptoRuntime::fast_arraycopy_Type();
886
887 Node* call = phase->make_leaf_call(ctrl, mem, call_type, copyfunc_addr, copyfunc_name, raw_adr_type, payload_src, payload_dst, length XTOP);
888 phase->transform_later(call);
889
890 phase->igvn().replace_node(ac, call);
891 }
892
893 #undef XTOP
894
895 static bool block_has_safepoint(const Block* block, uint from, uint to) {
896 for (uint i = from; i < to; i++) {
897 if (block->get_node(i)->is_MachSafePoint()) {
898 // Safepoint found
899 return true;
900 }
901 }
902
903 // Safepoint not found
904 return false;
905 }
906
907 static bool block_has_safepoint(const Block* block) {
908 return block_has_safepoint(block, 0, block->number_of_nodes());
909 }
910
911 static uint block_index(const Block* block, const Node* node) {
912 for (uint j = 0; j < block->number_of_nodes(); ++j) {
913 if (block->get_node(j) == node) {
914 return j;
915 }
916 }
917 ShouldNotReachHere();
918 return 0;
919 }
920
921 // Look through various node aliases
922 static const Node* look_through_node(const Node* node) {
923 while (node != nullptr) {
924 const Node* new_node = node;
925 if (node->is_Mach()) {
926 const MachNode* const node_mach = node->as_Mach();
927 if (node_mach->ideal_Opcode() == Op_CheckCastPP) {
928 new_node = node->in(1);
929 }
930 if (node_mach->is_SpillCopy()) {
931 new_node = node->in(1);
932 }
933 }
934 if (new_node == node || new_node == nullptr) {
935 break;
936 } else {
937 node = new_node;
938 }
939 }
940
941 return node;
942 }
943
944 // Whether the given offset is undefined.
945 static bool is_undefined(intptr_t offset) {
946 return offset == Type::OffsetTop;
947 }
948
949 // Whether the given offset is unknown.
950 static bool is_unknown(intptr_t offset) {
951 return offset == Type::OffsetBot;
952 }
953
954 // Whether the given offset is concrete (defined and compile-time known).
955 static bool is_concrete(intptr_t offset) {
956 return !is_undefined(offset) && !is_unknown(offset);
957 }
958
959 // Compute base + offset components of the memory address accessed by mach.
960 // Return a node representing the base address, or null if the base cannot be
961 // found or the offset is undefined or a concrete negative value. If a non-null
962 // base is returned, the offset is a concrete, nonnegative value or unknown.
963 static const Node* get_base_and_offset(const MachNode* mach, intptr_t& offset) {
964 const TypePtr* adr_type = nullptr;
965 offset = 0;
966 const Node* base = mach->get_base_and_disp(offset, adr_type);
967
968 if (base == nullptr || base == NodeSentinel) {
969 return nullptr;
970 }
971
972 if (offset == 0 && base->is_Mach() && base->as_Mach()->ideal_Opcode() == Op_AddP) {
973 // The memory address is computed by 'base' and fed to 'mach' via an
974 // indirect memory operand (indicated by offset == 0). The ultimate base and
975 // offset can be fetched directly from the inputs and Ideal type of 'base'.
976 const TypeOopPtr* oopptr = base->bottom_type()->isa_oopptr();
977 if (oopptr == nullptr) return nullptr;
978 offset = oopptr->offset();
979 // Even if 'base' is not an Ideal AddP node anymore, Matcher::ReduceInst()
980 // guarantees that the base address is still available at the same slot.
981 base = base->in(AddPNode::Base);
982 assert(base != nullptr, "");
983 }
984
985 if (is_undefined(offset) || (is_concrete(offset) && offset < 0)) {
986 return nullptr;
987 }
988
989 return look_through_node(base);
990 }
991
992 // Whether a phi node corresponds to an array allocation.
993 // This test is incomplete: in some edge cases, it might return false even
994 // though the node does correspond to an array allocation.
995 static bool is_array_allocation(const Node* phi) {
996 precond(phi->is_Phi());
997 // Check whether phi has a successor cast (CheckCastPP) to Java array pointer,
998 // possibly below spill copies and other cast nodes. Limit the exploration to
999 // a single path from the phi node consisting of these node types.
1000 const Node* current = phi;
1001 while (true) {
1002 const Node* next = nullptr;
1003 for (DUIterator_Fast imax, i = current->fast_outs(imax); i < imax; i++) {
1004 if (!current->fast_out(i)->isa_Mach()) {
1005 continue;
1006 }
1007 const MachNode* succ = current->fast_out(i)->as_Mach();
1008 if (succ->ideal_Opcode() == Op_CheckCastPP) {
1009 if (succ->get_ptr_type()->isa_aryptr()) {
1010 // Cast to Java array pointer: phi corresponds to an array allocation.
1011 return true;
1012 }
1013 // Other cast: record as candidate for further exploration.
1014 next = succ;
1015 } else if (succ->is_SpillCopy() && next == nullptr) {
1016 // Spill copy, and no better candidate found: record as candidate.
1017 next = succ;
1018 }
1019 }
1020 if (next == nullptr) {
1021 // No evidence found that phi corresponds to an array allocation, and no
1022 // candidates available to continue exploring.
1023 return false;
1024 }
1025 // Continue exploring from the best candidate found.
1026 current = next;
1027 }
1028 ShouldNotReachHere();
1029 }
1030
1031 bool BarrierSetC2::is_allocation(const Node* node) {
1032 assert(node->is_Phi(), "expected phi node");
1033 if (node->req() != 3) {
1034 return false;
1035 }
1036 const Node* const fast_node = node->in(2);
1037 if (!fast_node->is_Mach()) {
1038 return false;
1039 }
1040 const MachNode* const fast_mach = fast_node->as_Mach();
1041 if (fast_mach->ideal_Opcode() != Op_LoadP) {
1042 return false;
1043 }
1044 intptr_t offset;
1045 const Node* const base = get_base_and_offset(fast_mach, offset);
1046 if (base == nullptr || !base->is_Mach() || !is_concrete(offset)) {
1047 return false;
1048 }
1049 const MachNode* const base_mach = base->as_Mach();
1050 if (base_mach->ideal_Opcode() != Op_ThreadLocal) {
1051 return false;
1052 }
1053 return offset == in_bytes(Thread::tlab_top_offset());
1054 }
1055
1056 void BarrierSetC2::elide_dominated_barriers(Node_List& accesses, Node_List& access_dominators) const {
1057 Compile* const C = Compile::current();
1058 PhaseCFG* const cfg = C->cfg();
1059
1060 for (uint i = 0; i < accesses.size(); i++) {
1061 MachNode* const access = accesses.at(i)->as_Mach();
1062 intptr_t access_offset;
1063 const Node* const access_obj = get_base_and_offset(access, access_offset);
1064 Block* const access_block = cfg->get_block_for_node(access);
1065 const uint access_index = block_index(access_block, access);
1066
1067 if (access_obj == nullptr) {
1068 // No information available
1069 continue;
1070 }
1071
1072 for (uint j = 0; j < access_dominators.size(); j++) {
1073 const Node* const mem = access_dominators.at(j);
1074 if (mem->is_Phi()) {
1075 assert(is_allocation(mem), "expected allocation phi node");
1076 if (mem != access_obj) {
1077 continue;
1078 }
1079 if (is_unknown(access_offset) && !is_array_allocation(mem)) {
1080 // The accessed address has an unknown offset, but the allocated
1081 // object cannot be determined to be an array. Avoid eliding in this
1082 // case, to be on the safe side.
1083 continue;
1084 }
1085 assert((is_concrete(access_offset) && access_offset >= 0) || (is_unknown(access_offset) && is_array_allocation(mem)),
1086 "candidate allocation-dominated access offsets must be either concrete and nonnegative, or unknown (for array allocations only)");
1087 } else {
1088 // Access node
1089 const MachNode* const mem_mach = mem->as_Mach();
1090 intptr_t mem_offset;
1091 const Node* const mem_obj = get_base_and_offset(mem_mach, mem_offset);
1092
1093 if (mem_obj == nullptr ||
1094 !is_concrete(access_offset) ||
1095 !is_concrete(mem_offset)) {
1096 // No information available
1097 continue;
1098 }
1099
1100 if (mem_obj != access_obj || mem_offset != access_offset) {
1101 // Not the same addresses, not a candidate
1102 continue;
1103 }
1104 assert(is_concrete(access_offset) && access_offset >= 0,
1105 "candidate non-allocation-dominated access offsets must be concrete and nonnegative");
1106 }
1107
1108 Block* mem_block = cfg->get_block_for_node(mem);
1109 const uint mem_index = block_index(mem_block, mem);
1110
1111 if (access_block == mem_block) {
1112 // Earlier accesses in the same block
1113 if (mem_index < access_index && !block_has_safepoint(mem_block, mem_index + 1, access_index)) {
1114 elide_dominated_barrier(access);
1115 }
1116 } else if (mem_block->dominates(access_block)) {
1117 // Dominating block? Look around for safepoints
1118 ResourceMark rm;
1119 Block_List stack;
1120 VectorSet visited;
1121 stack.push(access_block);
1122 bool safepoint_found = block_has_safepoint(access_block);
1123 while (!safepoint_found && stack.size() > 0) {
1124 const Block* const block = stack.pop();
1125 if (visited.test_set(block->_pre_order)) {
1126 continue;
1127 }
1128 if (block_has_safepoint(block)) {
1129 safepoint_found = true;
1130 break;
1131 }
1132 if (block == mem_block) {
1133 continue;
1134 }
1135
1136 // Push predecessor blocks
1137 for (uint p = 1; p < block->num_preds(); ++p) {
1138 Block* const pred = cfg->get_block_for_node(block->pred(p));
1139 stack.push(pred);
1140 }
1141 }
1142
1143 if (!safepoint_found) {
1144 elide_dominated_barrier(access);
1145 }
1146 }
1147 }
1148 }
1149 }
1150
1151 void BarrierSetC2::compute_liveness_at_stubs() const {
1152 ResourceMark rm;
1153 Compile* const C = Compile::current();
1154 Arena* const A = Thread::current()->resource_area();
1155 PhaseCFG* const cfg = C->cfg();
1156 PhaseRegAlloc* const regalloc = C->regalloc();
1157 RegMask* const live = NEW_ARENA_ARRAY(A, RegMask, cfg->number_of_blocks() * sizeof(RegMask));
1158 BarrierSetAssembler* const bs = BarrierSet::barrier_set()->barrier_set_assembler();
1159 BarrierSetC2State* bs_state = barrier_set_state();
1160 Block_List worklist;
1161
1162 for (uint i = 0; i < cfg->number_of_blocks(); ++i) {
1163 new ((void*)(live + i)) RegMask();
1164 worklist.push(cfg->get_block(i));
1165 }
1166
1167 while (worklist.size() > 0) {
1168 const Block* const block = worklist.pop();
1169 RegMask& old_live = live[block->_pre_order];
1170 RegMask new_live;
1171
1172 // Initialize to union of successors
1173 for (uint i = 0; i < block->_num_succs; i++) {
1174 const uint succ_id = block->_succs[i]->_pre_order;
1175 new_live.or_with(live[succ_id]);
1176 }
1177
1178 // Walk block backwards, computing liveness
1179 for (int i = block->number_of_nodes() - 1; i >= 0; --i) {
1180 const Node* const node = block->get_node(i);
1181
1182 // If this node tracks out-liveness, update it
1183 if (!bs_state->needs_livein_data()) {
1184 RegMask* const regs = bs_state->live(node);
1185 if (regs != nullptr) {
1186 regs->or_with(new_live);
1187 }
1188 }
1189
1190 // Remove def bits
1191 const OptoReg::Name first = bs->refine_register(node, regalloc->get_reg_first(node));
1192 const OptoReg::Name second = bs->refine_register(node, regalloc->get_reg_second(node));
1193 if (first != OptoReg::Bad) {
1194 new_live.remove(first);
1195 }
1196 if (second != OptoReg::Bad) {
1197 new_live.remove(second);
1198 }
1199
1200 // Add use bits
1201 for (uint j = 1; j < node->req(); ++j) {
1202 const Node* const use = node->in(j);
1203 const OptoReg::Name first = bs->refine_register(use, regalloc->get_reg_first(use));
1204 const OptoReg::Name second = bs->refine_register(use, regalloc->get_reg_second(use));
1205 if (first != OptoReg::Bad) {
1206 new_live.insert(first);
1207 }
1208 if (second != OptoReg::Bad) {
1209 new_live.insert(second);
1210 }
1211 }
1212
1213 // If this node tracks in-liveness, update it
1214 if (bs_state->needs_livein_data()) {
1215 RegMask* const regs = bs_state->live(node);
1216 if (regs != nullptr) {
1217 regs->or_with(new_live);
1218 }
1219 }
1220 }
1221
1222 // Now at block top, see if we have any changes
1223 new_live.subtract(old_live);
1224 if (!new_live.is_empty()) {
1225 // Liveness has refined, update and propagate to prior blocks
1226 old_live.or_with(new_live);
1227 for (uint i = 1; i < block->num_preds(); ++i) {
1228 Block* const pred = cfg->get_block_for_node(block->pred(i));
1229 worklist.push(pred);
1230 }
1231 }
1232 }
1233 }