1 /*
   2  * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "precompiled.hpp"
  25 #include "gc/shared/barrierSet.hpp"
  26 #include "gc/shenandoah/shenandoahForwarding.hpp"
  27 #include "gc/shenandoah/shenandoahHeap.hpp"
  28 #include "gc/shenandoah/shenandoahHeuristics.hpp"
  29 #include "gc/shenandoah/shenandoahRuntime.hpp"
  30 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
  31 #include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
  32 #include "gc/shenandoah/c2/shenandoahSupport.hpp"
  33 #include "opto/arraycopynode.hpp"
  34 #include "opto/escape.hpp"
  35 #include "opto/graphKit.hpp"
  36 #include "opto/idealKit.hpp"
  37 #include "opto/macro.hpp"
  38 #include "opto/movenode.hpp"
  39 #include "opto/narrowptrnode.hpp"
  40 #include "opto/rootnode.hpp"
  41 
  42 ShenandoahBarrierSetC2* ShenandoahBarrierSetC2::bsc2() {
  43   return reinterpret_cast<ShenandoahBarrierSetC2*>(BarrierSet::barrier_set()->barrier_set_c2());
  44 }
  45 
  46 ShenandoahBarrierSetC2State::ShenandoahBarrierSetC2State(Arena* comp_arena)
  47   : _enqueue_barriers(new (comp_arena) GrowableArray<ShenandoahEnqueueBarrierNode*>(comp_arena, 8,  0, NULL)),
  48     _load_reference_barriers(new (comp_arena) GrowableArray<ShenandoahLoadReferenceBarrierNode*>(comp_arena, 8,  0, NULL)) {
  49 }
  50 
  51 int ShenandoahBarrierSetC2State::enqueue_barriers_count() const {
  52   return _enqueue_barriers->length();
  53 }
  54 
  55 ShenandoahEnqueueBarrierNode* ShenandoahBarrierSetC2State::enqueue_barrier(int idx) const {
  56   return _enqueue_barriers->at(idx);
  57 }
  58 
  59 void ShenandoahBarrierSetC2State::add_enqueue_barrier(ShenandoahEnqueueBarrierNode * n) {
  60   assert(!_enqueue_barriers->contains(n), "duplicate entry in barrier list");
  61   _enqueue_barriers->append(n);
  62 }
  63 
  64 void ShenandoahBarrierSetC2State::remove_enqueue_barrier(ShenandoahEnqueueBarrierNode * n) {
  65   if (_enqueue_barriers->contains(n)) {
  66     _enqueue_barriers->remove(n);
  67   }
  68 }
  69 
  70 int ShenandoahBarrierSetC2State::load_reference_barriers_count() const {
  71   return _load_reference_barriers->length();
  72 }
  73 
  74 ShenandoahLoadReferenceBarrierNode* ShenandoahBarrierSetC2State::load_reference_barrier(int idx) const {
  75   return _load_reference_barriers->at(idx);
  76 }
  77 
  78 void ShenandoahBarrierSetC2State::add_load_reference_barrier(ShenandoahLoadReferenceBarrierNode * n) {
  79   assert(!_load_reference_barriers->contains(n), "duplicate entry in barrier list");
  80   _load_reference_barriers->append(n);
  81 }
  82 
  83 void ShenandoahBarrierSetC2State::remove_load_reference_barrier(ShenandoahLoadReferenceBarrierNode * n) {
  84   if (_load_reference_barriers->contains(n)) {
  85     _load_reference_barriers->remove(n);
  86   }
  87 }
  88 
  89 Node* ShenandoahBarrierSetC2::shenandoah_storeval_barrier(GraphKit* kit, Node* obj) const {
  90   if (ShenandoahStoreValEnqueueBarrier) {
  91     obj = shenandoah_enqueue_barrier(kit, obj);
  92   }
  93   return obj;
  94 }
  95 
  96 #define __ kit->
  97 
  98 bool ShenandoahBarrierSetC2::satb_can_remove_pre_barrier(GraphKit* kit, PhaseTransform* phase, Node* adr,
  99                                                          BasicType bt, uint adr_idx) const {
 100   intptr_t offset = 0;
 101   Node* base = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 102   AllocateNode* alloc = AllocateNode::Ideal_allocation(base, phase);
 103 
 104   if (offset == Type::OffsetBot) {
 105     return false; // cannot unalias unless there are precise offsets
 106   }
 107 
 108   if (alloc == NULL) {
 109     return false; // No allocation found
 110   }
 111 
 112   intptr_t size_in_bytes = type2aelembytes(bt);
 113 
 114   Node* mem = __ memory(adr_idx); // start searching here...
 115 
 116   for (int cnt = 0; cnt < 50; cnt++) {
 117 
 118     if (mem->is_Store()) {
 119 
 120       Node* st_adr = mem->in(MemNode::Address);
 121       intptr_t st_offset = 0;
 122       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 123 
 124       if (st_base == NULL) {
 125         break; // inscrutable pointer
 126       }
 127 
 128       // Break we have found a store with same base and offset as ours so break
 129       if (st_base == base && st_offset == offset) {
 130         break;
 131       }
 132 
 133       if (st_offset != offset && st_offset != Type::OffsetBot) {
 134         const int MAX_STORE = BytesPerLong;
 135         if (st_offset >= offset + size_in_bytes ||
 136             st_offset <= offset - MAX_STORE ||
 137             st_offset <= offset - mem->as_Store()->memory_size()) {
 138           // Success:  The offsets are provably independent.
 139           // (You may ask, why not just test st_offset != offset and be done?
 140           // The answer is that stores of different sizes can co-exist
 141           // in the same sequence of RawMem effects.  We sometimes initialize
 142           // a whole 'tile' of array elements with a single jint or jlong.)
 143           mem = mem->in(MemNode::Memory);
 144           continue; // advance through independent store memory
 145         }
 146       }
 147 
 148       if (st_base != base
 149           && MemNode::detect_ptr_independence(base, alloc, st_base,
 150                                               AllocateNode::Ideal_allocation(st_base, phase),
 151                                               phase)) {
 152         // Success:  The bases are provably independent.
 153         mem = mem->in(MemNode::Memory);
 154         continue; // advance through independent store memory
 155       }
 156     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 157 
 158       InitializeNode* st_init = mem->in(0)->as_Initialize();
 159       AllocateNode* st_alloc = st_init->allocation();
 160 
 161       // Make sure that we are looking at the same allocation site.
 162       // The alloc variable is guaranteed to not be null here from earlier check.
 163       if (alloc == st_alloc) {
 164         // Check that the initialization is storing NULL so that no previous store
 165         // has been moved up and directly write a reference
 166         Node* captured_store = st_init->find_captured_store(offset,
 167                                                             type2aelembytes(T_OBJECT),
 168                                                             phase);
 169         if (captured_store == NULL || captured_store == st_init->zero_memory()) {
 170           return true;
 171         }
 172       }
 173     }
 174 
 175     // Unless there is an explicit 'continue', we must bail out here,
 176     // because 'mem' is an inscrutable memory state (e.g., a call).
 177     break;
 178   }
 179 
 180   return false;
 181 }
 182 
 183 #undef __
 184 #define __ ideal.
 185 
 186 void ShenandoahBarrierSetC2::satb_write_barrier_pre(GraphKit* kit,
 187                                                     bool do_load,
 188                                                     Node* obj,
 189                                                     Node* adr,
 190                                                     uint alias_idx,
 191                                                     Node* val,
 192                                                     const TypeOopPtr* val_type,
 193                                                     Node* pre_val,
 194                                                     BasicType bt) const {
 195   // Some sanity checks
 196   // Note: val is unused in this routine.
 197 
 198   if (do_load) {
 199     // We need to generate the load of the previous value
 200     assert(obj != NULL, "must have a base");
 201     assert(adr != NULL, "where are loading from?");
 202     assert(pre_val == NULL, "loaded already?");
 203     assert(val_type != NULL, "need a type");
 204 
 205     if (ReduceInitialCardMarks
 206         && satb_can_remove_pre_barrier(kit, &kit->gvn(), adr, bt, alias_idx)) {
 207       return;
 208     }
 209 
 210   } else {
 211     // In this case both val_type and alias_idx are unused.
 212     assert(pre_val != NULL, "must be loaded already");
 213     // Nothing to be done if pre_val is null.
 214     if (pre_val->bottom_type() == TypePtr::NULL_PTR) return;
 215     assert(pre_val->bottom_type()->basic_type() == T_OBJECT, "or we shouldn't be here");
 216   }
 217   assert(bt == T_OBJECT, "or we shouldn't be here");
 218 
 219   IdealKit ideal(kit, true);
 220 
 221   Node* tls = __ thread(); // ThreadLocalStorage
 222 
 223   Node* no_base = __ top();
 224   Node* zero  = __ ConI(0);
 225   Node* zeroX = __ ConX(0);
 226 
 227   float likely  = PROB_LIKELY(0.999);
 228   float unlikely  = PROB_UNLIKELY(0.999);
 229 
 230   // Offsets into the thread
 231   const int index_offset   = in_bytes(ShenandoahThreadLocalData::satb_mark_queue_index_offset());
 232   const int buffer_offset  = in_bytes(ShenandoahThreadLocalData::satb_mark_queue_buffer_offset());
 233 
 234   // Now the actual pointers into the thread
 235   Node* buffer_adr  = __ AddP(no_base, tls, __ ConX(buffer_offset));
 236   Node* index_adr   = __ AddP(no_base, tls, __ ConX(index_offset));
 237 
 238   // Now some of the values
 239   Node* marking;
 240   Node* gc_state = __ AddP(no_base, tls, __ ConX(in_bytes(ShenandoahThreadLocalData::gc_state_offset())));
 241   Node* ld = __ load(__ ctrl(), gc_state, TypeInt::BYTE, T_BYTE, Compile::AliasIdxRaw);
 242   marking = __ AndI(ld, __ ConI(ShenandoahHeap::MARKING));
 243   assert(ShenandoahBarrierC2Support::is_gc_state_load(ld), "Should match the shape");
 244 
 245   // if (!marking)
 246   __ if_then(marking, BoolTest::ne, zero, unlikely); {
 247     BasicType index_bt = TypeX_X->basic_type();
 248     assert(sizeof(size_t) == type2aelembytes(index_bt), "Loading G1 SATBMarkQueue::_index with wrong size.");
 249     Node* index   = __ load(__ ctrl(), index_adr, TypeX_X, index_bt, Compile::AliasIdxRaw);
 250 
 251     if (do_load) {
 252       // load original value
 253       // alias_idx correct??
 254       pre_val = __ load(__ ctrl(), adr, val_type, bt, alias_idx);
 255     }
 256 
 257     // if (pre_val != NULL)
 258     __ if_then(pre_val, BoolTest::ne, kit->null()); {
 259       Node* buffer  = __ load(__ ctrl(), buffer_adr, TypeRawPtr::NOTNULL, T_ADDRESS, Compile::AliasIdxRaw);
 260 
 261       // is the queue for this thread full?
 262       __ if_then(index, BoolTest::ne, zeroX, likely); {
 263 
 264         // decrement the index
 265         Node* next_index = kit->gvn().transform(new SubXNode(index, __ ConX(sizeof(intptr_t))));
 266 
 267         // Now get the buffer location we will log the previous value into and store it
 268         Node *log_addr = __ AddP(no_base, buffer, next_index);
 269         __ store(__ ctrl(), log_addr, pre_val, T_OBJECT, Compile::AliasIdxRaw, MemNode::unordered);
 270         // update the index
 271         __ store(__ ctrl(), index_adr, next_index, index_bt, Compile::AliasIdxRaw, MemNode::unordered);
 272 
 273       } __ else_(); {
 274 
 275         // logging buffer is full, call the runtime
 276         const TypeFunc *tf = ShenandoahBarrierSetC2::write_ref_field_pre_entry_Type();
 277         __ make_leaf_call(tf, CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry), "shenandoah_wb_pre", pre_val, tls);
 278       } __ end_if();  // (!index)
 279     } __ end_if();  // (pre_val != NULL)
 280   } __ end_if();  // (!marking)
 281 
 282   // Final sync IdealKit and GraphKit.
 283   kit->final_sync(ideal);
 284 
 285   if (ShenandoahSATBBarrier && adr != NULL) {
 286     Node* c = kit->control();
 287     Node* call = c->in(1)->in(1)->in(1)->in(0);
 288     assert(is_shenandoah_wb_pre_call(call), "shenandoah_wb_pre call expected");
 289     call->add_req(adr);
 290   }
 291 }
 292 
 293 bool ShenandoahBarrierSetC2::is_shenandoah_wb_pre_call(Node* call) {
 294   return call->is_CallLeaf() &&
 295          call->as_CallLeaf()->entry_point() == CAST_FROM_FN_PTR(address, ShenandoahRuntime::write_ref_field_pre_entry);
 296 }
 297 
 298 bool ShenandoahBarrierSetC2::is_shenandoah_lrb_call(Node* call) {
 299   return call->is_CallLeaf() &&
 300           call->as_CallLeaf()->entry_point() == CAST_FROM_FN_PTR(address, ShenandoahRuntime::load_reference_barrier);
 301 }
 302 
 303 bool ShenandoahBarrierSetC2::is_shenandoah_marking_if(PhaseTransform *phase, Node* n) {
 304   if (n->Opcode() != Op_If) {
 305     return false;
 306   }
 307 
 308   Node* bol = n->in(1);
 309   assert(bol->is_Bool(), "");
 310   Node* cmpx = bol->in(1);
 311   if (bol->as_Bool()->_test._test == BoolTest::ne &&
 312       cmpx->is_Cmp() && cmpx->in(2) == phase->intcon(0) &&
 313       is_shenandoah_state_load(cmpx->in(1)->in(1)) &&
 314       cmpx->in(1)->in(2)->is_Con() &&
 315       cmpx->in(1)->in(2) == phase->intcon(ShenandoahHeap::MARKING)) {
 316     return true;
 317   }
 318 
 319   return false;
 320 }
 321 
 322 bool ShenandoahBarrierSetC2::is_shenandoah_state_load(Node* n) {
 323   if (!n->is_Load()) return false;
 324   const int state_offset = in_bytes(ShenandoahThreadLocalData::gc_state_offset());
 325   return n->in(2)->is_AddP() && n->in(2)->in(2)->Opcode() == Op_ThreadLocal
 326          && n->in(2)->in(3)->is_Con()
 327          && n->in(2)->in(3)->bottom_type()->is_intptr_t()->get_con() == state_offset;
 328 }
 329 
 330 void ShenandoahBarrierSetC2::shenandoah_write_barrier_pre(GraphKit* kit,
 331                                                           bool do_load,
 332                                                           Node* obj,
 333                                                           Node* adr,
 334                                                           uint alias_idx,
 335                                                           Node* val,
 336                                                           const TypeOopPtr* val_type,
 337                                                           Node* pre_val,
 338                                                           BasicType bt) const {
 339   if (ShenandoahSATBBarrier) {
 340     IdealKit ideal(kit);
 341     kit->sync_kit(ideal);
 342 
 343     satb_write_barrier_pre(kit, do_load, obj, adr, alias_idx, val, val_type, pre_val, bt);
 344 
 345     ideal.sync_kit(kit);
 346     kit->final_sync(ideal);
 347   }
 348 }
 349 
 350 Node* ShenandoahBarrierSetC2::shenandoah_enqueue_barrier(GraphKit* kit, Node* pre_val) const {
 351   return kit->gvn().transform(new ShenandoahEnqueueBarrierNode(pre_val));
 352 }
 353 
 354 // Helper that guards and inserts a pre-barrier.
 355 void ShenandoahBarrierSetC2::insert_pre_barrier(GraphKit* kit, Node* base_oop, Node* offset,
 356                                                 Node* pre_val, bool need_mem_bar) const {
 357   // We could be accessing the referent field of a reference object. If so, when G1
 358   // is enabled, we need to log the value in the referent field in an SATB buffer.
 359   // This routine performs some compile time filters and generates suitable
 360   // runtime filters that guard the pre-barrier code.
 361   // Also add memory barrier for non volatile load from the referent field
 362   // to prevent commoning of loads across safepoint.
 363 
 364   // Some compile time checks.
 365 
 366   // If offset is a constant, is it java_lang_ref_Reference::_reference_offset?
 367   const TypeX* otype = offset->find_intptr_t_type();
 368   if (otype != NULL && otype->is_con() &&
 369       otype->get_con() != java_lang_ref_Reference::referent_offset) {
 370     // Constant offset but not the reference_offset so just return
 371     return;
 372   }
 373 
 374   // We only need to generate the runtime guards for instances.
 375   const TypeOopPtr* btype = base_oop->bottom_type()->isa_oopptr();
 376   if (btype != NULL) {
 377     if (btype->isa_aryptr()) {
 378       // Array type so nothing to do
 379       return;
 380     }
 381 
 382     const TypeInstPtr* itype = btype->isa_instptr();
 383     if (itype != NULL) {
 384       // Can the klass of base_oop be statically determined to be
 385       // _not_ a sub-class of Reference and _not_ Object?
 386       ciKlass* klass = itype->klass();
 387       if ( klass->is_loaded() &&
 388           !klass->is_subtype_of(kit->env()->Reference_klass()) &&
 389           !kit->env()->Object_klass()->is_subtype_of(klass)) {
 390         return;
 391       }
 392     }
 393   }
 394 
 395   // The compile time filters did not reject base_oop/offset so
 396   // we need to generate the following runtime filters
 397   //
 398   // if (offset == java_lang_ref_Reference::_reference_offset) {
 399   //   if (instance_of(base, java.lang.ref.Reference)) {
 400   //     pre_barrier(_, pre_val, ...);
 401   //   }
 402   // }
 403 
 404   float likely   = PROB_LIKELY(  0.999);
 405   float unlikely = PROB_UNLIKELY(0.999);
 406 
 407   IdealKit ideal(kit);
 408 
 409   Node* referent_off = __ ConX(java_lang_ref_Reference::referent_offset);
 410 
 411   __ if_then(offset, BoolTest::eq, referent_off, unlikely); {
 412       // Update graphKit memory and control from IdealKit.
 413       kit->sync_kit(ideal);
 414 
 415       Node* ref_klass_con = kit->makecon(TypeKlassPtr::make(kit->env()->Reference_klass()));
 416       Node* is_instof = kit->gen_instanceof(base_oop, ref_klass_con);
 417 
 418       // Update IdealKit memory and control from graphKit.
 419       __ sync_kit(kit);
 420 
 421       Node* one = __ ConI(1);
 422       // is_instof == 0 if base_oop == NULL
 423       __ if_then(is_instof, BoolTest::eq, one, unlikely); {
 424 
 425         // Update graphKit from IdeakKit.
 426         kit->sync_kit(ideal);
 427 
 428         // Use the pre-barrier to record the value in the referent field
 429         satb_write_barrier_pre(kit, false /* do_load */,
 430                                NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */,
 431                                pre_val /* pre_val */,
 432                                T_OBJECT);
 433         if (need_mem_bar) {
 434           // Add memory barrier to prevent commoning reads from this field
 435           // across safepoint since GC can change its value.
 436           kit->insert_mem_bar(Op_MemBarCPUOrder);
 437         }
 438         // Update IdealKit from graphKit.
 439         __ sync_kit(kit);
 440 
 441       } __ end_if(); // _ref_type != ref_none
 442   } __ end_if(); // offset == referent_offset
 443 
 444   // Final sync IdealKit and GraphKit.
 445   kit->final_sync(ideal);
 446 }
 447 
 448 #undef __
 449 
 450 const TypeFunc* ShenandoahBarrierSetC2::write_ref_field_pre_entry_Type() {
 451   const Type **fields = TypeTuple::fields(2);
 452   fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value
 453   fields[TypeFunc::Parms+1] = TypeRawPtr::NOTNULL; // thread
 454   const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+2, fields);
 455 
 456   // create result type (range)
 457   fields = TypeTuple::fields(0);
 458   const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields);
 459 
 460   return TypeFunc::make(domain, range);
 461 }
 462 
 463 const TypeFunc* ShenandoahBarrierSetC2::shenandoah_clone_barrier_Type() {
 464   const Type **fields = TypeTuple::fields(1);
 465   fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value
 466   const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+1, fields);
 467 
 468   // create result type (range)
 469   fields = TypeTuple::fields(0);
 470   const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+0, fields);
 471 
 472   return TypeFunc::make(domain, range);
 473 }
 474 
 475 const TypeFunc* ShenandoahBarrierSetC2::shenandoah_load_reference_barrier_Type() {
 476   const Type **fields = TypeTuple::fields(1);
 477   fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL; // original field value
 478   const TypeTuple *domain = TypeTuple::make(TypeFunc::Parms+1, fields);
 479 
 480   // create result type (range)
 481   fields = TypeTuple::fields(1);
 482   fields[TypeFunc::Parms+0] = TypeInstPtr::NOTNULL;
 483   const TypeTuple *range = TypeTuple::make(TypeFunc::Parms+1, fields);
 484 
 485   return TypeFunc::make(domain, range);
 486 }
 487 
 488 Node* ShenandoahBarrierSetC2::store_at_resolved(C2Access& access, C2AccessValue& val) const {
 489   DecoratorSet decorators = access.decorators();
 490 
 491   const TypePtr* adr_type = access.addr().type();
 492   Node* adr = access.addr().node();
 493 
 494   bool anonymous = (decorators & ON_UNKNOWN_OOP_REF) != 0;
 495   bool on_heap = (decorators & IN_HEAP) != 0;
 496 
 497   if (!access.is_oop() || (!on_heap && !anonymous)) {
 498     return BarrierSetC2::store_at_resolved(access, val);
 499   }
 500 
 501   GraphKit* kit = access.kit();
 502 
 503   uint adr_idx = kit->C->get_alias_index(adr_type);
 504   assert(adr_idx != Compile::AliasIdxTop, "use other store_to_memory factory" );
 505   Node* value = val.node();
 506   value = shenandoah_storeval_barrier(kit, value);
 507   val.set_node(value);
 508   shenandoah_write_barrier_pre(kit, true /* do_load */, /*kit->control(),*/ access.base(), adr, adr_idx, val.node(),
 509                                static_cast<const TypeOopPtr*>(val.type()), NULL /* pre_val */, access.type());
 510   return BarrierSetC2::store_at_resolved(access, val);
 511 }
 512 
 513 Node* ShenandoahBarrierSetC2::load_at_resolved(C2Access& access, const Type* val_type) const {
 514   DecoratorSet decorators = access.decorators();
 515 
 516   Node* adr = access.addr().node();
 517   Node* obj = access.base();
 518 
 519   bool mismatched = (decorators & C2_MISMATCHED) != 0;
 520   bool unknown = (decorators & ON_UNKNOWN_OOP_REF) != 0;
 521   bool on_heap = (decorators & IN_HEAP) != 0;
 522   bool on_weak = (decorators & ON_WEAK_OOP_REF) != 0;
 523   bool is_unordered = (decorators & MO_UNORDERED) != 0;
 524   bool need_cpu_mem_bar = !is_unordered || mismatched || !on_heap;
 525 
 526   Node* top = Compile::current()->top();
 527 
 528   Node* offset = adr->is_AddP() ? adr->in(AddPNode::Offset) : top;
 529   Node* load = BarrierSetC2::load_at_resolved(access, val_type);
 530 
 531   if (access.is_oop()) {
 532     if (ShenandoahLoadRefBarrier) {
 533       load = new ShenandoahLoadReferenceBarrierNode(NULL, load);
 534       load = access.kit()->gvn().transform(load);
 535     }
 536   }
 537 
 538   // If we are reading the value of the referent field of a Reference
 539   // object (either by using Unsafe directly or through reflection)
 540   // then, if SATB is enabled, we need to record the referent in an
 541   // SATB log buffer using the pre-barrier mechanism.
 542   // Also we need to add memory barrier to prevent commoning reads
 543   // from this field across safepoint since GC can change its value.
 544   bool need_read_barrier = ShenandoahKeepAliveBarrier &&
 545     (on_heap && (on_weak || (unknown && offset != top && obj != top)));
 546 
 547   if (!access.is_oop() || !need_read_barrier) {
 548     return load;
 549   }
 550 
 551   GraphKit* kit = access.kit();
 552 
 553   if (on_weak) {
 554     // Use the pre-barrier to record the value in the referent field
 555     satb_write_barrier_pre(kit, false /* do_load */,
 556                            NULL /* obj */, NULL /* adr */, max_juint /* alias_idx */, NULL /* val */, NULL /* val_type */,
 557                            load /* pre_val */, T_OBJECT);
 558     // Add memory barrier to prevent commoning reads from this field
 559     // across safepoint since GC can change its value.
 560     kit->insert_mem_bar(Op_MemBarCPUOrder);
 561   } else if (unknown) {
 562     // We do not require a mem bar inside pre_barrier if need_mem_bar
 563     // is set: the barriers would be emitted by us.
 564     insert_pre_barrier(kit, obj, offset, load, !need_cpu_mem_bar);
 565   }
 566 
 567   return load;
 568 }
 569 
 570 static void pin_atomic_op(C2AtomicAccess& access) {
 571   if (!access.needs_pinning()) {
 572     return;
 573   }
 574   // SCMemProjNodes represent the memory state of a LoadStore. Their
 575   // main role is to prevent LoadStore nodes from being optimized away
 576   // when their results aren't used.
 577   GraphKit* kit = access.kit();
 578   Node* load_store = access.raw_access();
 579   assert(load_store != NULL, "must pin atomic op");
 580   Node* proj = kit->gvn().transform(new SCMemProjNode(load_store));
 581   kit->set_memory(proj, access.alias_idx());
 582 }
 583 
 584 Node* ShenandoahBarrierSetC2::atomic_cmpxchg_val_at_resolved(C2AtomicAccess& access, Node* expected_val,
 585                                                    Node* new_val, const Type* value_type) const {
 586   GraphKit* kit = access.kit();
 587   if (access.is_oop()) {
 588     new_val = shenandoah_storeval_barrier(kit, new_val);
 589     shenandoah_write_barrier_pre(kit, false /* do_load */,
 590                                  NULL, NULL, max_juint, NULL, NULL,
 591                                  expected_val /* pre_val */, T_OBJECT);
 592 
 593     MemNode::MemOrd mo = access.mem_node_mo();
 594     Node* mem = access.memory();
 595     Node* adr = access.addr().node();
 596     const TypePtr* adr_type = access.addr().type();
 597     Node* load_store = NULL;
 598 
 599 #ifdef _LP64
 600     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 601       Node *newval_enc = kit->gvn().transform(new EncodePNode(new_val, new_val->bottom_type()->make_narrowoop()));
 602       Node *oldval_enc = kit->gvn().transform(new EncodePNode(expected_val, expected_val->bottom_type()->make_narrowoop()));
 603       if (ShenandoahCASBarrier) {
 604         load_store = kit->gvn().transform(new ShenandoahCompareAndExchangeNNode(kit->control(), mem, adr, newval_enc, oldval_enc, adr_type, value_type->make_narrowoop(), mo));
 605       } else {
 606         load_store = kit->gvn().transform(new CompareAndExchangeNNode(kit->control(), mem, adr, newval_enc, oldval_enc, adr_type, value_type->make_narrowoop(), mo));
 607       }
 608     } else
 609 #endif
 610     {
 611       if (ShenandoahCASBarrier) {
 612         load_store = kit->gvn().transform(new ShenandoahCompareAndExchangePNode(kit->control(), mem, adr, new_val, expected_val, adr_type, value_type->is_oopptr(), mo));
 613       } else {
 614         load_store = kit->gvn().transform(new CompareAndExchangePNode(kit->control(), mem, adr, new_val, expected_val, adr_type, value_type->is_oopptr(), mo));
 615       }
 616     }
 617 
 618     access.set_raw_access(load_store);
 619     pin_atomic_op(access);
 620 
 621 #ifdef _LP64
 622     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 623       load_store = kit->gvn().transform(new DecodeNNode(load_store, load_store->get_ptr_type()));
 624     }
 625 #endif
 626     load_store = kit->gvn().transform(new ShenandoahLoadReferenceBarrierNode(NULL, load_store));
 627     return load_store;
 628   }
 629   return BarrierSetC2::atomic_cmpxchg_val_at_resolved(access, expected_val, new_val, value_type);
 630 }
 631 
 632 Node* ShenandoahBarrierSetC2::atomic_cmpxchg_bool_at_resolved(C2AtomicAccess& access, Node* expected_val,
 633                                                               Node* new_val, const Type* value_type) const {
 634   GraphKit* kit = access.kit();
 635   if (access.is_oop()) {
 636     new_val = shenandoah_storeval_barrier(kit, new_val);
 637     shenandoah_write_barrier_pre(kit, false /* do_load */,
 638                                  NULL, NULL, max_juint, NULL, NULL,
 639                                  expected_val /* pre_val */, T_OBJECT);
 640     DecoratorSet decorators = access.decorators();
 641     MemNode::MemOrd mo = access.mem_node_mo();
 642     Node* mem = access.memory();
 643     bool is_weak_cas = (decorators & C2_WEAK_CMPXCHG) != 0;
 644     Node* load_store = NULL;
 645     Node* adr = access.addr().node();
 646 #ifdef _LP64
 647     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 648       Node *newval_enc = kit->gvn().transform(new EncodePNode(new_val, new_val->bottom_type()->make_narrowoop()));
 649       Node *oldval_enc = kit->gvn().transform(new EncodePNode(expected_val, expected_val->bottom_type()->make_narrowoop()));
 650       if (ShenandoahCASBarrier) {
 651         if (is_weak_cas) {
 652           load_store = kit->gvn().transform(new ShenandoahWeakCompareAndSwapNNode(kit->control(), mem, adr, newval_enc, oldval_enc, mo));
 653         } else {
 654           load_store = kit->gvn().transform(new ShenandoahCompareAndSwapNNode(kit->control(), mem, adr, newval_enc, oldval_enc, mo));
 655         }
 656       } else {
 657         if (is_weak_cas) {
 658           load_store = kit->gvn().transform(new WeakCompareAndSwapNNode(kit->control(), mem, adr, newval_enc, oldval_enc, mo));
 659         } else {
 660           load_store = kit->gvn().transform(new CompareAndSwapNNode(kit->control(), mem, adr, newval_enc, oldval_enc, mo));
 661         }
 662       }
 663     } else
 664 #endif
 665     {
 666       if (ShenandoahCASBarrier) {
 667         if (is_weak_cas) {
 668           load_store = kit->gvn().transform(new ShenandoahWeakCompareAndSwapPNode(kit->control(), mem, adr, new_val, expected_val, mo));
 669         } else {
 670           load_store = kit->gvn().transform(new ShenandoahCompareAndSwapPNode(kit->control(), mem, adr, new_val, expected_val, mo));
 671         }
 672       } else {
 673         if (is_weak_cas) {
 674           load_store = kit->gvn().transform(new WeakCompareAndSwapPNode(kit->control(), mem, adr, new_val, expected_val, mo));
 675         } else {
 676           load_store = kit->gvn().transform(new CompareAndSwapPNode(kit->control(), mem, adr, new_val, expected_val, mo));
 677         }
 678       }
 679     }
 680     access.set_raw_access(load_store);
 681     pin_atomic_op(access);
 682     return load_store;
 683   }
 684   return BarrierSetC2::atomic_cmpxchg_bool_at_resolved(access, expected_val, new_val, value_type);
 685 }
 686 
 687 Node* ShenandoahBarrierSetC2::atomic_xchg_at_resolved(C2AtomicAccess& access, Node* val, const Type* value_type) const {
 688   GraphKit* kit = access.kit();
 689   if (access.is_oop()) {
 690     val = shenandoah_storeval_barrier(kit, val);
 691   }
 692   Node* result = BarrierSetC2::atomic_xchg_at_resolved(access, val, value_type);
 693   if (access.is_oop()) {
 694     result = kit->gvn().transform(new ShenandoahLoadReferenceBarrierNode(NULL, result));
 695     shenandoah_write_barrier_pre(kit, false /* do_load */,
 696                                  NULL, NULL, max_juint, NULL, NULL,
 697                                  result /* pre_val */, T_OBJECT);
 698   }
 699   return result;
 700 }
 701 
 702 void ShenandoahBarrierSetC2::clone(GraphKit* kit, Node* src, Node* dst, Node* size, bool is_array) const {
 703   // TODO: Implement using proper barriers.
 704   BarrierSetC2::clone(kit, src, dst, size, is_array);
 705 }
 706 
 707 // Support for GC barriers emitted during parsing
 708 bool ShenandoahBarrierSetC2::is_gc_barrier_node(Node* node) const {
 709   if (node->Opcode() == Op_ShenandoahLoadReferenceBarrier) return true;
 710   if (node->Opcode() != Op_CallLeaf && node->Opcode() != Op_CallLeafNoFP) {
 711     return false;
 712   }
 713   CallLeafNode *call = node->as_CallLeaf();
 714   if (call->_name == NULL) {
 715     return false;
 716   }
 717 
 718   return strcmp(call->_name, "shenandoah_clone_barrier") == 0 ||
 719          strcmp(call->_name, "shenandoah_cas_obj") == 0 ||
 720          strcmp(call->_name, "shenandoah_wb_pre") == 0;
 721 }
 722 
 723 Node* ShenandoahBarrierSetC2::step_over_gc_barrier(Node* c) const {
 724   if (c->Opcode() == Op_ShenandoahLoadReferenceBarrier) {
 725     return c->in(ShenandoahLoadReferenceBarrierNode::ValueIn);
 726   }
 727   if (c->Opcode() == Op_ShenandoahEnqueueBarrier) {
 728     c = c->in(1);
 729   }
 730   return c;
 731 }
 732 
 733 bool ShenandoahBarrierSetC2::expand_barriers(Compile* C, PhaseIterGVN& igvn) const {
 734   return !ShenandoahBarrierC2Support::expand(C, igvn);
 735 }
 736 
 737 bool ShenandoahBarrierSetC2::optimize_loops(PhaseIdealLoop* phase, LoopOptsMode mode, VectorSet& visited, Node_Stack& nstack, Node_List& worklist) const {
 738   if (mode == LoopOptsShenandoahExpand) {
 739     assert(UseShenandoahGC, "only for shenandoah");
 740     ShenandoahBarrierC2Support::pin_and_expand(phase);
 741     return true;
 742   } else if (mode == LoopOptsShenandoahPostExpand) {
 743     assert(UseShenandoahGC, "only for shenandoah");
 744     visited.Clear();
 745     ShenandoahBarrierC2Support::optimize_after_expansion(visited, nstack, worklist, phase);
 746     return true;
 747   }
 748   return false;
 749 }
 750 
 751 bool ShenandoahBarrierSetC2::array_copy_requires_gc_barriers(BasicType type) const {
 752   return false;
 753 }
 754 
 755 bool ShenandoahBarrierSetC2::clone_needs_postbarrier(ArrayCopyNode *ac, PhaseIterGVN& igvn) {
 756   Node* src = ac->in(ArrayCopyNode::Src);
 757   const TypeOopPtr* src_type = igvn.type(src)->is_oopptr();
 758   if (src_type->isa_instptr() != NULL) {
 759     ciInstanceKlass* ik = src_type->klass()->as_instance_klass();
 760     if ((src_type->klass_is_exact() || (!ik->is_interface() && !ik->has_subklass())) && !ik->has_injected_fields()) {
 761       if (ik->has_object_fields()) {
 762         return true;
 763       } else {
 764         if (!src_type->klass_is_exact()) {
 765           igvn.C->dependencies()->assert_leaf_type(ik);
 766         }
 767       }
 768     } else {
 769       return true;
 770         }
 771   } else if (src_type->isa_aryptr()) {
 772     BasicType src_elem  = src_type->klass()->as_array_klass()->element_type()->basic_type();
 773     if (src_elem == T_OBJECT || src_elem == T_ARRAY) {
 774       return true;
 775     }
 776   } else {
 777     return true;
 778   }
 779   return false;
 780 }
 781 
 782 // Support for macro expanded GC barriers
 783 void ShenandoahBarrierSetC2::register_potential_barrier_node(Node* node) const {
 784   if (node->Opcode() == Op_ShenandoahEnqueueBarrier) {
 785     state()->add_enqueue_barrier((ShenandoahEnqueueBarrierNode*) node);
 786   }
 787   if (node->Opcode() == Op_ShenandoahLoadReferenceBarrier) {
 788     state()->add_load_reference_barrier((ShenandoahLoadReferenceBarrierNode*) node);
 789   }
 790 }
 791 
 792 void ShenandoahBarrierSetC2::unregister_potential_barrier_node(Node* node) const {
 793   if (node->Opcode() == Op_ShenandoahEnqueueBarrier) {
 794     state()->remove_enqueue_barrier((ShenandoahEnqueueBarrierNode*) node);
 795   }
 796   if (node->Opcode() == Op_ShenandoahLoadReferenceBarrier) {
 797     state()->remove_load_reference_barrier((ShenandoahLoadReferenceBarrierNode*) node);
 798   }
 799 }
 800 
 801 void ShenandoahBarrierSetC2::eliminate_gc_barrier(PhaseMacroExpand* macro, Node* n) const {
 802   if (is_shenandoah_wb_pre_call(n)) {
 803     shenandoah_eliminate_wb_pre(n, &macro->igvn());
 804   }
 805 }
 806 
 807 void ShenandoahBarrierSetC2::shenandoah_eliminate_wb_pre(Node* call, PhaseIterGVN* igvn) const {
 808   assert(UseShenandoahGC && is_shenandoah_wb_pre_call(call), "");
 809   Node* c = call->as_Call()->proj_out(TypeFunc::Control);
 810   c = c->unique_ctrl_out();
 811   assert(c->is_Region() && c->req() == 3, "where's the pre barrier control flow?");
 812   c = c->unique_ctrl_out();
 813   assert(c->is_Region() && c->req() == 3, "where's the pre barrier control flow?");
 814   Node* iff = c->in(1)->is_IfProj() ? c->in(1)->in(0) : c->in(2)->in(0);
 815   assert(iff->is_If(), "expect test");
 816   if (!is_shenandoah_marking_if(igvn, iff)) {
 817     c = c->unique_ctrl_out();
 818     assert(c->is_Region() && c->req() == 3, "where's the pre barrier control flow?");
 819     iff = c->in(1)->is_IfProj() ? c->in(1)->in(0) : c->in(2)->in(0);
 820     assert(is_shenandoah_marking_if(igvn, iff), "expect marking test");
 821   }
 822   Node* cmpx = iff->in(1)->in(1);
 823   igvn->replace_node(cmpx, igvn->makecon(TypeInt::CC_EQ));
 824   igvn->rehash_node_delayed(call);
 825   call->del_req(call->req()-1);
 826 }
 827 
 828 void ShenandoahBarrierSetC2::enqueue_useful_gc_barrier(PhaseIterGVN* igvn, Node* node) const {
 829   if (node->Opcode() == Op_AddP && ShenandoahBarrierSetC2::has_only_shenandoah_wb_pre_uses(node)) {
 830     igvn->add_users_to_worklist(node);
 831   }
 832 }
 833 
 834 void ShenandoahBarrierSetC2::eliminate_useless_gc_barriers(Unique_Node_List &useful) const {
 835   for (uint i = 0; i < useful.size(); i++) {
 836     Node* n = useful.at(i);
 837     if (n->Opcode() == Op_AddP && ShenandoahBarrierSetC2::has_only_shenandoah_wb_pre_uses(n)) {
 838       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 839         Compile::current()->record_for_igvn(n->fast_out(i));
 840       }
 841     }
 842   }
 843   for (int i = state()->enqueue_barriers_count() - 1; i >= 0; i--) {
 844     ShenandoahEnqueueBarrierNode* n = state()->enqueue_barrier(i);
 845     if (!useful.member(n)) {
 846       state()->remove_enqueue_barrier(n);
 847     }
 848   }
 849   for (int i = state()->load_reference_barriers_count() - 1; i >= 0; i--) {
 850     ShenandoahLoadReferenceBarrierNode* n = state()->load_reference_barrier(i);
 851     if (!useful.member(n)) {
 852       state()->remove_load_reference_barrier(n);
 853     }
 854   }
 855 }
 856 
 857 void ShenandoahBarrierSetC2::add_users_to_worklist(Unique_Node_List* worklist) const {}
 858 
 859 void* ShenandoahBarrierSetC2::create_barrier_state(Arena* comp_arena) const {
 860   return new(comp_arena) ShenandoahBarrierSetC2State(comp_arena);
 861 }
 862 
 863 ShenandoahBarrierSetC2State* ShenandoahBarrierSetC2::state() const {
 864   return reinterpret_cast<ShenandoahBarrierSetC2State*>(Compile::current()->barrier_set_state());
 865 }
 866 
 867 // If the BarrierSetC2 state has kept macro nodes in its compilation unit state to be
 868 // expanded later, then now is the time to do so.
 869 bool ShenandoahBarrierSetC2::expand_macro_nodes(PhaseMacroExpand* macro) const { return false; }
 870 
 871 #ifdef ASSERT
 872 void ShenandoahBarrierSetC2::verify_gc_barriers(bool post_parse) const {
 873   if (ShenandoahVerifyOptoBarriers && !post_parse) {
 874     ShenandoahBarrierC2Support::verify(Compile::current()->root());
 875   }
 876 }
 877 #endif
 878 
 879 Node* ShenandoahBarrierSetC2::ideal_node(PhaseGVN* phase, Node* n, bool can_reshape) const {
 880   if (is_shenandoah_wb_pre_call(n)) {
 881     uint cnt = ShenandoahBarrierSetC2::write_ref_field_pre_entry_Type()->domain()->cnt();
 882     if (n->req() > cnt) {
 883       Node* addp = n->in(cnt);
 884       if (has_only_shenandoah_wb_pre_uses(addp)) {
 885         n->del_req(cnt);
 886         if (can_reshape) {
 887           phase->is_IterGVN()->_worklist.push(addp);
 888         }
 889         return n;
 890       }
 891     }
 892   }
 893   if (n->Opcode() == Op_CmpP) {
 894     Node* in1 = n->in(1);
 895     Node* in2 = n->in(2);
 896     if (in1->bottom_type() == TypePtr::NULL_PTR) {
 897       in2 = step_over_gc_barrier(in2);
 898     }
 899     if (in2->bottom_type() == TypePtr::NULL_PTR) {
 900       in1 = step_over_gc_barrier(in1);
 901     }
 902     PhaseIterGVN* igvn = phase->is_IterGVN();
 903     if (in1 != n->in(1)) {
 904       if (igvn != NULL) {
 905         n->set_req_X(1, in1, igvn);
 906       } else {
 907         n->set_req(1, in1);
 908       }
 909       assert(in2 == n->in(2), "only one change");
 910       return n;
 911     }
 912     if (in2 != n->in(2)) {
 913       if (igvn != NULL) {
 914         n->set_req_X(2, in2, igvn);
 915       } else {
 916         n->set_req(2, in2);
 917       }
 918       return n;
 919     }
 920   } else if (can_reshape &&
 921              n->Opcode() == Op_If &&
 922              ShenandoahBarrierC2Support::is_heap_stable_test(n) &&
 923              n->in(0) != NULL) {
 924     Node* dom = n->in(0);
 925     Node* prev_dom = n;
 926     int op = n->Opcode();
 927     int dist = 16;
 928     // Search up the dominator tree for another heap stable test
 929     while (dom->Opcode() != op    ||  // Not same opcode?
 930            !ShenandoahBarrierC2Support::is_heap_stable_test(dom) ||  // Not same input 1?
 931            prev_dom->in(0) != dom) {  // One path of test does not dominate?
 932       if (dist < 0) return NULL;
 933 
 934       dist--;
 935       prev_dom = dom;
 936       dom = IfNode::up_one_dom(dom);
 937       if (!dom) return NULL;
 938     }
 939 
 940     // Check that we did not follow a loop back to ourselves
 941     if (n == dom) {
 942       return NULL;
 943     }
 944 
 945     return n->as_If()->dominated_by(prev_dom, phase->is_IterGVN());
 946   }
 947   return NULL;
 948 }
 949 
 950 bool ShenandoahBarrierSetC2::has_only_shenandoah_wb_pre_uses(Node* n) {
 951   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 952     Node* u = n->fast_out(i);
 953     if (!is_shenandoah_wb_pre_call(u)) {
 954       return false;
 955     }
 956   }
 957   return n->outcnt() > 0;
 958 }