1 /*
   2  * Copyright (c) 1997, 2018, 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/systemDictionary.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "memory/allocation.inline.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "oops/objArrayKlass.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/arraycopynode.hpp"
  35 #include "opto/cfgnode.hpp"
  36 #include "opto/compile.hpp"
  37 #include "opto/connode.hpp"
  38 #include "opto/convertnode.hpp"
  39 #include "opto/loopnode.hpp"
  40 #include "opto/machnode.hpp"
  41 #include "opto/matcher.hpp"
  42 #include "opto/memnode.hpp"
  43 #include "opto/mulnode.hpp"
  44 #include "opto/narrowptrnode.hpp"
  45 #include "opto/phaseX.hpp"
  46 #include "opto/regmask.hpp"
  47 #include "utilities/align.hpp"
  48 #include "utilities/copy.hpp"
  49 #include "utilities/macros.hpp"
  50 #include "utilities/vmError.hpp"
  51 #if INCLUDE_ZGC
  52 #include "gc/z/c2/zBarrierSetC2.hpp"
  53 #endif
  54 
  55 // Portions of code courtesy of Clifford Click
  56 
  57 // Optimization - Graph Style
  58 
  59 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  60 
  61 //=============================================================================
  62 uint MemNode::size_of() const { return sizeof(*this); }
  63 
  64 const TypePtr *MemNode::adr_type() const {
  65   Node* adr = in(Address);
  66   if (adr == NULL)  return NULL; // node is dead
  67   const TypePtr* cross_check = NULL;
  68   DEBUG_ONLY(cross_check = _adr_type);
  69   return calculate_adr_type(adr->bottom_type(), cross_check);
  70 }
  71 
  72 bool MemNode::check_if_adr_maybe_raw(Node* adr) {
  73   if (adr != NULL) {
  74     if (adr->bottom_type()->base() == Type::RawPtr || adr->bottom_type()->base() == Type::AnyPtr) {
  75       return true;
  76     }
  77   }
  78   return false;
  79 }
  80 
  81 #ifndef PRODUCT
  82 void MemNode::dump_spec(outputStream *st) const {
  83   if (in(Address) == NULL)  return; // node is dead
  84 #ifndef ASSERT
  85   // fake the missing field
  86   const TypePtr* _adr_type = NULL;
  87   if (in(Address) != NULL)
  88     _adr_type = in(Address)->bottom_type()->isa_ptr();
  89 #endif
  90   dump_adr_type(this, _adr_type, st);
  91 
  92   Compile* C = Compile::current();
  93   if (C->alias_type(_adr_type)->is_volatile()) {
  94     st->print(" Volatile!");
  95   }
  96   if (_unaligned_access) {
  97     st->print(" unaligned");
  98   }
  99   if (_mismatched_access) {
 100     st->print(" mismatched");
 101   }
 102 }
 103 
 104 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
 105   st->print(" @");
 106   if (adr_type == NULL) {
 107     st->print("NULL");
 108   } else {
 109     adr_type->dump_on(st);
 110     Compile* C = Compile::current();
 111     Compile::AliasType* atp = NULL;
 112     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
 113     if (atp == NULL)
 114       st->print(", idx=?\?;");
 115     else if (atp->index() == Compile::AliasIdxBot)
 116       st->print(", idx=Bot;");
 117     else if (atp->index() == Compile::AliasIdxTop)
 118       st->print(", idx=Top;");
 119     else if (atp->index() == Compile::AliasIdxRaw)
 120       st->print(", idx=Raw;");
 121     else {
 122       ciField* field = atp->field();
 123       if (field) {
 124         st->print(", name=");
 125         field->print_name_on(st);
 126       }
 127       st->print(", idx=%d;", atp->index());
 128     }
 129   }
 130 }
 131 
 132 extern void print_alias_types();
 133 
 134 #endif
 135 
 136 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 137   assert((t_oop != NULL), "sanity");
 138   bool is_instance = t_oop->is_known_instance_field();
 139   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 140                              (load != NULL) && load->is_Load() &&
 141                              (phase->is_IterGVN() != NULL);
 142   if (!(is_instance || is_boxed_value_load))
 143     return mchain;  // don't try to optimize non-instance types
 144   uint instance_id = t_oop->instance_id();
 145   Node *start_mem = phase->C->start()->proj_out_or_null(TypeFunc::Memory);
 146   Node *prev = NULL;
 147   Node *result = mchain;
 148   while (prev != result) {
 149     prev = result;
 150     if (result == start_mem)
 151       break;  // hit one of our sentinels
 152     // skip over a call which does not affect this memory slice
 153     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 154       Node *proj_in = result->in(0);
 155       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 156         break;  // hit one of our sentinels
 157       } else if (proj_in->is_Call()) {
 158         // ArrayCopyNodes processed here as well
 159         CallNode *call = proj_in->as_Call();
 160         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 161           result = call->in(TypeFunc::Memory);
 162         }
 163       } else if (proj_in->is_Initialize()) {
 164         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 165         // Stop if this is the initialization for the object instance which
 166         // contains this memory slice, otherwise skip over it.
 167         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 168           break;
 169         }
 170         if (is_instance) {
 171           result = proj_in->in(TypeFunc::Memory);
 172         } else if (is_boxed_value_load) {
 173           Node* klass = alloc->in(AllocateNode::KlassNode);
 174           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 175           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 176             result = proj_in->in(TypeFunc::Memory); // not related allocation
 177           }
 178         }
 179       } else if (proj_in->is_MemBar()) {
 180         ArrayCopyNode* ac = NULL;
 181         if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase, ac)) {
 182           break;
 183         }
 184         result = proj_in->in(TypeFunc::Memory);
 185       } else {
 186         assert(false, "unexpected projection");
 187       }
 188     } else if (result->is_ClearArray()) {
 189       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 190         // Can not bypass initialization of the instance
 191         // we are looking for.
 192         break;
 193       }
 194       // Otherwise skip it (the call updated 'result' value).
 195     } else if (result->is_MergeMem()) {
 196       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 197     }
 198   }
 199   return result;
 200 }
 201 
 202 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 203   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 204   if (t_oop == NULL)
 205     return mchain;  // don't try to optimize non-oop types
 206   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 207   bool is_instance = t_oop->is_known_instance_field();
 208   PhaseIterGVN *igvn = phase->is_IterGVN();
 209   if (is_instance && igvn != NULL  && result->is_Phi()) {
 210     PhiNode *mphi = result->as_Phi();
 211     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 212     const TypePtr *t = mphi->adr_type();
 213     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 214         (t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 215          t->is_oopptr()->cast_to_exactness(true)
 216            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 217             ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop)) {
 218       // clone the Phi with our address type
 219       result = mphi->split_out_instance(t_adr, igvn);
 220     } else {
 221       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 222     }
 223   }
 224   return result;
 225 }
 226 
 227 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 228   uint alias_idx = phase->C->get_alias_index(tp);
 229   Node *mem = mmem;
 230 #ifdef ASSERT
 231   {
 232     // Check that current type is consistent with the alias index used during graph construction
 233     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 234     bool consistent =  adr_check == NULL || adr_check->empty() ||
 235                        phase->C->must_alias(adr_check, alias_idx );
 236     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 237     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 238                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 239         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 240         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 241           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 242           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 243       // don't assert if it is dead code.
 244       consistent = true;
 245     }
 246     if( !consistent ) {
 247       st->print("alias_idx==%d, adr_check==", alias_idx);
 248       if( adr_check == NULL ) {
 249         st->print("NULL");
 250       } else {
 251         adr_check->dump();
 252       }
 253       st->cr();
 254       print_alias_types();
 255       assert(consistent, "adr_check must match alias idx");
 256     }
 257   }
 258 #endif
 259   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 260   // means an array I have not precisely typed yet.  Do not do any
 261   // alias stuff with it any time soon.
 262   const TypeOopPtr *toop = tp->isa_oopptr();
 263   if( tp->base() != Type::AnyPtr &&
 264       !(toop &&
 265         toop->klass() != NULL &&
 266         toop->klass()->is_java_lang_Object() &&
 267         toop->offset() == Type::OffsetBot) ) {
 268     // compress paths and change unreachable cycles to TOP
 269     // If not, we can update the input infinitely along a MergeMem cycle
 270     // Equivalent code in PhiNode::Ideal
 271     Node* m  = phase->transform(mmem);
 272     // If transformed to a MergeMem, get the desired slice
 273     // Otherwise the returned node represents memory for every slice
 274     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 275     // Update input if it is progress over what we have now
 276   }
 277   return mem;
 278 }
 279 
 280 //--------------------------Ideal_common---------------------------------------
 281 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 282 // Unhook non-raw memories from complete (macro-expanded) initializations.
 283 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 284   // If our control input is a dead region, kill all below the region
 285   Node *ctl = in(MemNode::Control);
 286   if (ctl && remove_dead_region(phase, can_reshape))
 287     return this;
 288   ctl = in(MemNode::Control);
 289   // Don't bother trying to transform a dead node
 290   if (ctl && ctl->is_top())  return NodeSentinel;
 291 
 292   PhaseIterGVN *igvn = phase->is_IterGVN();
 293   // Wait if control on the worklist.
 294   if (ctl && can_reshape && igvn != NULL) {
 295     Node* bol = NULL;
 296     Node* cmp = NULL;
 297     if (ctl->in(0)->is_If()) {
 298       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 299       bol = ctl->in(0)->in(1);
 300       if (bol->is_Bool())
 301         cmp = ctl->in(0)->in(1)->in(1);
 302     }
 303     if (igvn->_worklist.member(ctl) ||
 304         (bol != NULL && igvn->_worklist.member(bol)) ||
 305         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 306       // This control path may be dead.
 307       // Delay this memory node transformation until the control is processed.
 308       phase->is_IterGVN()->_worklist.push(this);
 309       return NodeSentinel; // caller will return NULL
 310     }
 311   }
 312   // Ignore if memory is dead, or self-loop
 313   Node *mem = in(MemNode::Memory);
 314   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 315   assert(mem != this, "dead loop in MemNode::Ideal");
 316 
 317   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 318     // This memory slice may be dead.
 319     // Delay this mem node transformation until the memory is processed.
 320     phase->is_IterGVN()->_worklist.push(this);
 321     return NodeSentinel; // caller will return NULL
 322   }
 323 
 324   Node *address = in(MemNode::Address);
 325   const Type *t_adr = phase->type(address);
 326   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 327 
 328   if (can_reshape && igvn != NULL &&
 329       (igvn->_worklist.member(address) ||
 330        (igvn->_worklist.size() > 0 && t_adr != adr_type())) ) {
 331     // The address's base and type may change when the address is processed.
 332     // Delay this mem node transformation until the address is processed.
 333     phase->is_IterGVN()->_worklist.push(this);
 334     return NodeSentinel; // caller will return NULL
 335   }
 336 
 337   // Do NOT remove or optimize the next lines: ensure a new alias index
 338   // is allocated for an oop pointer type before Escape Analysis.
 339   // Note: C++ will not remove it since the call has side effect.
 340   if (t_adr->isa_oopptr()) {
 341     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 342   }
 343 
 344   Node* base = NULL;
 345   if (address->is_AddP()) {
 346     base = address->in(AddPNode::Base);
 347   }
 348   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 349       !t_adr->isa_rawptr()) {
 350     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 351     // Skip this node optimization if its address has TOP base.
 352     return NodeSentinel; // caller will return NULL
 353   }
 354 
 355   // Avoid independent memory operations
 356   Node* old_mem = mem;
 357 
 358   // The code which unhooks non-raw memories from complete (macro-expanded)
 359   // initializations was removed. After macro-expansion all stores catched
 360   // by Initialize node became raw stores and there is no information
 361   // which memory slices they modify. So it is unsafe to move any memory
 362   // operation above these stores. Also in most cases hooked non-raw memories
 363   // were already unhooked by using information from detect_ptr_independence()
 364   // and find_previous_store().
 365 
 366   if (mem->is_MergeMem()) {
 367     MergeMemNode* mmem = mem->as_MergeMem();
 368     const TypePtr *tp = t_adr->is_ptr();
 369 
 370     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 371   }
 372 
 373   if (mem != old_mem) {
 374     set_req(MemNode::Memory, mem);
 375     if (can_reshape && old_mem->outcnt() == 0 && igvn != NULL) {
 376       igvn->_worklist.push(old_mem);
 377     }
 378     if (phase->type(mem) == Type::TOP) return NodeSentinel;
 379     return this;
 380   }
 381 
 382   // let the subclass continue analyzing...
 383   return NULL;
 384 }
 385 
 386 // Helper function for proving some simple control dominations.
 387 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 388 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 389 // is not a constant (dominated by the method's StartNode).
 390 // Used by MemNode::find_previous_store to prove that the
 391 // control input of a memory operation predates (dominates)
 392 // an allocation it wants to look past.
 393 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 394   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 395     return false; // Conservative answer for dead code
 396 
 397   // Check 'dom'. Skip Proj and CatchProj nodes.
 398   dom = dom->find_exact_control(dom);
 399   if (dom == NULL || dom->is_top())
 400     return false; // Conservative answer for dead code
 401 
 402   if (dom == sub) {
 403     // For the case when, for example, 'sub' is Initialize and the original
 404     // 'dom' is Proj node of the 'sub'.
 405     return false;
 406   }
 407 
 408   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 409     return true;
 410 
 411   // 'dom' dominates 'sub' if its control edge and control edges
 412   // of all its inputs dominate or equal to sub's control edge.
 413 
 414   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 415   // Or Region for the check in LoadNode::Ideal();
 416   // 'sub' should have sub->in(0) != NULL.
 417   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 418          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 419 
 420   // Get control edge of 'sub'.
 421   Node* orig_sub = sub;
 422   sub = sub->find_exact_control(sub->in(0));
 423   if (sub == NULL || sub->is_top())
 424     return false; // Conservative answer for dead code
 425 
 426   assert(sub->is_CFG(), "expecting control");
 427 
 428   if (sub == dom)
 429     return true;
 430 
 431   if (sub->is_Start() || sub->is_Root())
 432     return false;
 433 
 434   {
 435     // Check all control edges of 'dom'.
 436 
 437     ResourceMark rm;
 438     Arena* arena = Thread::current()->resource_area();
 439     Node_List nlist(arena);
 440     Unique_Node_List dom_list(arena);
 441 
 442     dom_list.push(dom);
 443     bool only_dominating_controls = false;
 444 
 445     for (uint next = 0; next < dom_list.size(); next++) {
 446       Node* n = dom_list.at(next);
 447       if (n == orig_sub)
 448         return false; // One of dom's inputs dominated by sub.
 449       if (!n->is_CFG() && n->pinned()) {
 450         // Check only own control edge for pinned non-control nodes.
 451         n = n->find_exact_control(n->in(0));
 452         if (n == NULL || n->is_top())
 453           return false; // Conservative answer for dead code
 454         assert(n->is_CFG(), "expecting control");
 455         dom_list.push(n);
 456       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 457         only_dominating_controls = true;
 458       } else if (n->is_CFG()) {
 459         if (n->dominates(sub, nlist))
 460           only_dominating_controls = true;
 461         else
 462           return false;
 463       } else {
 464         // First, own control edge.
 465         Node* m = n->find_exact_control(n->in(0));
 466         if (m != NULL) {
 467           if (m->is_top())
 468             return false; // Conservative answer for dead code
 469           dom_list.push(m);
 470         }
 471         // Now, the rest of edges.
 472         uint cnt = n->req();
 473         for (uint i = 1; i < cnt; i++) {
 474           m = n->find_exact_control(n->in(i));
 475           if (m == NULL || m->is_top())
 476             continue;
 477           dom_list.push(m);
 478         }
 479       }
 480     }
 481     return only_dominating_controls;
 482   }
 483 }
 484 
 485 //---------------------detect_ptr_independence---------------------------------
 486 // Used by MemNode::find_previous_store to prove that two base
 487 // pointers are never equal.
 488 // The pointers are accompanied by their associated allocations,
 489 // if any, which have been previously discovered by the caller.
 490 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 491                                       Node* p2, AllocateNode* a2,
 492                                       PhaseTransform* phase) {
 493   // Attempt to prove that these two pointers cannot be aliased.
 494   // They may both manifestly be allocations, and they should differ.
 495   // Or, if they are not both allocations, they can be distinct constants.
 496   // Otherwise, one is an allocation and the other a pre-existing value.
 497   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 498     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 499   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 500     return (a1 != a2);
 501   } else if (a1 != NULL) {                  // one allocation a1
 502     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 503     return all_controls_dominate(p2, a1);
 504   } else { //(a2 != NULL)                   // one allocation a2
 505     return all_controls_dominate(p1, a2);
 506   }
 507   return false;
 508 }
 509 
 510 
 511 // Find an arraycopy that must have set (can_see_stored_value=true) or
 512 // could have set (can_see_stored_value=false) the value for this load
 513 Node* LoadNode::find_previous_arraycopy(PhaseTransform* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
 514   if (mem->is_Proj() && mem->in(0) != NULL && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
 515                                                mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
 516     Node* mb = mem->in(0);
 517     if (mb->in(0) != NULL && mb->in(0)->is_Proj() &&
 518         mb->in(0)->in(0) != NULL && mb->in(0)->in(0)->is_ArrayCopy()) {
 519       ArrayCopyNode* ac = mb->in(0)->in(0)->as_ArrayCopy();
 520       if (ac->is_clonebasic()) {
 521         intptr_t offset;
 522         AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase, offset);
 523         if (alloc != NULL && alloc == ld_alloc) {
 524           return ac;
 525         }
 526       }
 527     }
 528   } else if (mem->is_Proj() && mem->in(0) != NULL && mem->in(0)->is_ArrayCopy()) {
 529     ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
 530 
 531     if (ac->is_arraycopy_validated() ||
 532         ac->is_copyof_validated() ||
 533         ac->is_copyofrange_validated()) {
 534       Node* ld_addp = in(MemNode::Address);
 535       if (ld_addp->is_AddP()) {
 536         Node* ld_base = ld_addp->in(AddPNode::Address);
 537         Node* ld_offs = ld_addp->in(AddPNode::Offset);
 538 
 539         Node* dest = ac->in(ArrayCopyNode::Dest);
 540 
 541         if (dest == ld_base) {
 542           const TypeX *ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 543           if (ac->modifies(ld_offs_t->_lo, ld_offs_t->_hi, phase, can_see_stored_value)) {
 544             return ac;
 545           }
 546           if (!can_see_stored_value) {
 547             mem = ac->in(TypeFunc::Memory);
 548           }
 549         }
 550       }
 551     }
 552   }
 553   return NULL;
 554 }
 555 
 556 // The logic for reordering loads and stores uses four steps:
 557 // (a) Walk carefully past stores and initializations which we
 558 //     can prove are independent of this load.
 559 // (b) Observe that the next memory state makes an exact match
 560 //     with self (load or store), and locate the relevant store.
 561 // (c) Ensure that, if we were to wire self directly to the store,
 562 //     the optimizer would fold it up somehow.
 563 // (d) Do the rewiring, and return, depending on some other part of
 564 //     the optimizer to fold up the load.
 565 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 566 // specific to loads and stores, so they are handled by the callers.
 567 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 568 //
 569 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 570   Node*         ctrl   = in(MemNode::Control);
 571   Node*         adr    = in(MemNode::Address);
 572   intptr_t      offset = 0;
 573   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 574   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 575 
 576   if (offset == Type::OffsetBot)
 577     return NULL;            // cannot unalias unless there are precise offsets
 578 
 579   const bool adr_maybe_raw = check_if_adr_maybe_raw(adr);
 580   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 581 
 582   intptr_t size_in_bytes = memory_size();
 583 
 584   Node* mem = in(MemNode::Memory);   // start searching here...
 585 
 586   int cnt = 50;             // Cycle limiter
 587   for (;;) {                // While we can dance past unrelated stores...
 588     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 589 
 590     Node* prev = mem;
 591     if (mem->is_Store()) {
 592       Node* st_adr = mem->in(MemNode::Address);
 593       intptr_t st_offset = 0;
 594       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 595       if (st_base == NULL)
 596         break;              // inscrutable pointer
 597 
 598       // For raw accesses it's not enough to prove that constant offsets don't intersect.
 599       // We need the bases to be the equal in order for the offset check to make sense.
 600       if ((adr_maybe_raw || check_if_adr_maybe_raw(st_adr)) && st_base != base) {
 601         break;
 602       }
 603 
 604       if (st_offset != offset && st_offset != Type::OffsetBot) {
 605         const int MAX_STORE = BytesPerLong;
 606         if (st_offset >= offset + size_in_bytes ||
 607             st_offset <= offset - MAX_STORE ||
 608             st_offset <= offset - mem->as_Store()->memory_size()) {
 609           // Success:  The offsets are provably independent.
 610           // (You may ask, why not just test st_offset != offset and be done?
 611           // The answer is that stores of different sizes can co-exist
 612           // in the same sequence of RawMem effects.  We sometimes initialize
 613           // a whole 'tile' of array elements with a single jint or jlong.)
 614           mem = mem->in(MemNode::Memory);
 615           continue;           // (a) advance through independent store memory
 616         }
 617       }
 618       if (st_base != base &&
 619           detect_ptr_independence(base, alloc,
 620                                   st_base,
 621                                   AllocateNode::Ideal_allocation(st_base, phase),
 622                                   phase)) {
 623         // Success:  The bases are provably independent.
 624         mem = mem->in(MemNode::Memory);
 625         continue;           // (a) advance through independent store memory
 626       }
 627 
 628       // (b) At this point, if the bases or offsets do not agree, we lose,
 629       // since we have not managed to prove 'this' and 'mem' independent.
 630       if (st_base == base && st_offset == offset) {
 631         return mem;         // let caller handle steps (c), (d)
 632       }
 633 
 634     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 635       InitializeNode* st_init = mem->in(0)->as_Initialize();
 636       AllocateNode*  st_alloc = st_init->allocation();
 637       if (st_alloc == NULL)
 638         break;              // something degenerated
 639       bool known_identical = false;
 640       bool known_independent = false;
 641       if (alloc == st_alloc)
 642         known_identical = true;
 643       else if (alloc != NULL)
 644         known_independent = true;
 645       else if (all_controls_dominate(this, st_alloc))
 646         known_independent = true;
 647 
 648       if (known_independent) {
 649         // The bases are provably independent: Either they are
 650         // manifestly distinct allocations, or else the control
 651         // of this load dominates the store's allocation.
 652         int alias_idx = phase->C->get_alias_index(adr_type());
 653         if (alias_idx == Compile::AliasIdxRaw) {
 654           mem = st_alloc->in(TypeFunc::Memory);
 655         } else {
 656           mem = st_init->memory(alias_idx);
 657         }
 658         continue;           // (a) advance through independent store memory
 659       }
 660 
 661       // (b) at this point, if we are not looking at a store initializing
 662       // the same allocation we are loading from, we lose.
 663       if (known_identical) {
 664         // From caller, can_see_stored_value will consult find_captured_store.
 665         return mem;         // let caller handle steps (c), (d)
 666       }
 667 
 668     } else if (find_previous_arraycopy(phase, alloc, mem, false) != NULL) {
 669       if (prev != mem) {
 670         // Found an arraycopy but it doesn't affect that load
 671         continue;
 672       }
 673       // Found an arraycopy that may affect that load
 674       return mem;
 675     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 676       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 677       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 678         // ArrayCopyNodes processed here as well.
 679         CallNode *call = mem->in(0)->as_Call();
 680         if (!call->may_modify(addr_t, phase)) {
 681           mem = call->in(TypeFunc::Memory);
 682           continue;         // (a) advance through independent call memory
 683         }
 684       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 685         ArrayCopyNode* ac = NULL;
 686         if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase, ac)) {
 687           break;
 688         }
 689         mem = mem->in(0)->in(TypeFunc::Memory);
 690         continue;           // (a) advance through independent MemBar memory
 691       } else if (mem->is_ClearArray()) {
 692         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 693           // (the call updated 'mem' value)
 694           continue;         // (a) advance through independent allocation memory
 695         } else {
 696           // Can not bypass initialization of the instance
 697           // we are looking for.
 698           return mem;
 699         }
 700       } else if (mem->is_MergeMem()) {
 701         int alias_idx = phase->C->get_alias_index(adr_type());
 702         mem = mem->as_MergeMem()->memory_at(alias_idx);
 703         continue;           // (a) advance through independent MergeMem memory
 704       }
 705     }
 706 
 707     // Unless there is an explicit 'continue', we must bail out here,
 708     // because 'mem' is an inscrutable memory state (e.g., a call).
 709     break;
 710   }
 711 
 712   return NULL;              // bail out
 713 }
 714 
 715 //----------------------calculate_adr_type-------------------------------------
 716 // Helper function.  Notices when the given type of address hits top or bottom.
 717 // Also, asserts a cross-check of the type against the expected address type.
 718 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 719   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 720   #ifdef PRODUCT
 721   cross_check = NULL;
 722   #else
 723   if (!VerifyAliases || VMError::is_error_reported() || Node::in_dump())  cross_check = NULL;
 724   #endif
 725   const TypePtr* tp = t->isa_ptr();
 726   if (tp == NULL) {
 727     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 728     return TypePtr::BOTTOM;           // touches lots of memory
 729   } else {
 730     #ifdef ASSERT
 731     // %%%% [phh] We don't check the alias index if cross_check is
 732     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 733     if (cross_check != NULL &&
 734         cross_check != TypePtr::BOTTOM &&
 735         cross_check != TypeRawPtr::BOTTOM) {
 736       // Recheck the alias index, to see if it has changed (due to a bug).
 737       Compile* C = Compile::current();
 738       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 739              "must stay in the original alias category");
 740       // The type of the address must be contained in the adr_type,
 741       // disregarding "null"-ness.
 742       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 743       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 744       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 745              "real address must not escape from expected memory type");
 746     }
 747     #endif
 748     return tp;
 749   }
 750 }
 751 
 752 //=============================================================================
 753 // Should LoadNode::Ideal() attempt to remove control edges?
 754 bool LoadNode::can_remove_control() const {
 755   return true;
 756 }
 757 uint LoadNode::size_of() const { return sizeof(*this); }
 758 uint LoadNode::cmp( const Node &n ) const
 759 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 760 const Type *LoadNode::bottom_type() const { return _type; }
 761 uint LoadNode::ideal_reg() const {
 762   return _type->ideal_reg();
 763 }
 764 
 765 #ifndef PRODUCT
 766 void LoadNode::dump_spec(outputStream *st) const {
 767   MemNode::dump_spec(st);
 768   if( !Verbose && !WizardMode ) {
 769     // standard dump does this in Verbose and WizardMode
 770     st->print(" #"); _type->dump_on(st);
 771   }
 772   if (!depends_only_on_test()) {
 773     st->print(" (does not depend only on test)");
 774   }
 775 }
 776 #endif
 777 
 778 #ifdef ASSERT
 779 //----------------------------is_immutable_value-------------------------------
 780 // Helper function to allow a raw load without control edge for some cases
 781 bool LoadNode::is_immutable_value(Node* adr) {
 782   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 783           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 784           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 785            in_bytes(JavaThread::osthread_offset())));
 786 }
 787 #endif
 788 
 789 //----------------------------LoadNode::make-----------------------------------
 790 // Polymorphic factory method:
 791 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo,
 792                      ControlDependency control_dependency, bool unaligned, bool mismatched) {
 793   Compile* C = gvn.C;
 794 
 795   // sanity check the alias category against the created node type
 796   assert(!(adr_type->isa_oopptr() &&
 797            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 798          "use LoadKlassNode instead");
 799   assert(!(adr_type->isa_aryptr() &&
 800            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 801          "use LoadRangeNode instead");
 802   // Check control edge of raw loads
 803   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 804           // oop will be recorded in oop map if load crosses safepoint
 805           rt->isa_oopptr() || is_immutable_value(adr),
 806           "raw memory operations should have control edge");
 807   LoadNode* load = NULL;
 808   switch (bt) {
 809   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 810   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 811   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 812   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 813   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 814   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency); break;
 815   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 816   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 817   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 818   case T_OBJECT:
 819 #ifdef _LP64
 820     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 821       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 822     } else
 823 #endif
 824     {
 825       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 826       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
 827     }
 828     break;
 829   default:
 830     ShouldNotReachHere();
 831     break;
 832   }
 833   assert(load != NULL, "LoadNode should have been created");
 834   if (unaligned) {
 835     load->set_unaligned_access();
 836   }
 837   if (mismatched) {
 838     load->set_mismatched_access();
 839   }
 840   if (load->Opcode() == Op_LoadN) {
 841     Node* ld = gvn.transform(load);
 842     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 843   }
 844 
 845   return load;
 846 }
 847 
 848 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 849                                   ControlDependency control_dependency, bool unaligned, bool mismatched) {
 850   bool require_atomic = true;
 851   LoadLNode* load = new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic);
 852   if (unaligned) {
 853     load->set_unaligned_access();
 854   }
 855   if (mismatched) {
 856     load->set_mismatched_access();
 857   }
 858   return load;
 859 }
 860 
 861 LoadDNode* LoadDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 862                                   ControlDependency control_dependency, bool unaligned, bool mismatched) {
 863   bool require_atomic = true;
 864   LoadDNode* load = new LoadDNode(ctl, mem, adr, adr_type, rt, mo, control_dependency, require_atomic);
 865   if (unaligned) {
 866     load->set_unaligned_access();
 867   }
 868   if (mismatched) {
 869     load->set_mismatched_access();
 870   }
 871   return load;
 872 }
 873 
 874 
 875 
 876 //------------------------------hash-------------------------------------------
 877 uint LoadNode::hash() const {
 878   // unroll addition of interesting fields
 879   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 880 }
 881 
 882 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 883   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 884     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 885     bool is_stable_ary = FoldStableValues &&
 886                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 887                          tp->isa_aryptr()->is_stable();
 888 
 889     return (eliminate_boxing && non_volatile) || is_stable_ary;
 890   }
 891 
 892   return false;
 893 }
 894 
 895 // Is the value loaded previously stored by an arraycopy? If so return
 896 // a load node that reads from the source array so we may be able to
 897 // optimize out the ArrayCopy node later.
 898 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
 899 #if INCLUDE_ZGC
 900   if (UseZGC) {
 901     if (bottom_type()->make_oopptr() != NULL) {
 902       return NULL;
 903     }
 904   }
 905 #endif
 906 
 907   Node* ld_adr = in(MemNode::Address);
 908   intptr_t ld_off = 0;
 909   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 910   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
 911   if (ac != NULL) {
 912     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
 913 
 914     Node* mem = ac->in(TypeFunc::Memory);
 915     Node* ctl = ac->in(0);
 916     Node* src = ac->in(ArrayCopyNode::Src);
 917 
 918     if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
 919       return NULL;
 920     }
 921 
 922     LoadNode* ld = clone()->as_Load();
 923     Node* addp = in(MemNode::Address)->clone();
 924     if (ac->as_ArrayCopy()->is_clonebasic()) {
 925       assert(ld_alloc != NULL, "need an alloc");
 926       assert(addp->is_AddP(), "address must be addp");
 927       assert(ac->in(ArrayCopyNode::Dest)->is_AddP(), "dest must be an address");
 928       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
 929       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Base)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base)), "strange pattern");
 930       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Address)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address)), "strange pattern");
 931       addp->set_req(AddPNode::Base, src->in(AddPNode::Base));
 932       addp->set_req(AddPNode::Address, src->in(AddPNode::Address));
 933     } else {
 934       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
 935              ac->as_ArrayCopy()->is_copyof_validated() ||
 936              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
 937       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
 938       addp->set_req(AddPNode::Base, src);
 939       addp->set_req(AddPNode::Address, src);
 940 
 941       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
 942       BasicType ary_elem  = ary_t->klass()->as_array_klass()->element_type()->basic_type();
 943       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 944       uint shift  = exact_log2(type2aelembytes(ary_elem));
 945 
 946       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
 947 #ifdef _LP64
 948       diff = phase->transform(new ConvI2LNode(diff));
 949 #endif
 950       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
 951 
 952       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
 953       addp->set_req(AddPNode::Offset, offset);
 954     }
 955     addp = phase->transform(addp);
 956 #ifdef ASSERT
 957     const TypePtr* adr_type = phase->type(addp)->is_ptr();
 958     ld->_adr_type = adr_type;
 959 #endif
 960     ld->set_req(MemNode::Address, addp);
 961     ld->set_req(0, ctl);
 962     ld->set_req(MemNode::Memory, mem);
 963     // load depends on the tests that validate the arraycopy
 964     ld->_control_dependency = Pinned;
 965     return ld;
 966   }
 967   return NULL;
 968 }
 969 
 970 
 971 //---------------------------can_see_stored_value------------------------------
 972 // This routine exists to make sure this set of tests is done the same
 973 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 974 // will change the graph shape in a way which makes memory alive twice at the
 975 // same time (uses the Oracle model of aliasing), then some
 976 // LoadXNode::Identity will fold things back to the equivalence-class model
 977 // of aliasing.
 978 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 979   Node* ld_adr = in(MemNode::Address);
 980   intptr_t ld_off = 0;
 981   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 982   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 983   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
 984   // This is more general than load from boxing objects.
 985   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
 986     uint alias_idx = atp->index();
 987     bool final = !atp->is_rewritable();
 988     Node* result = NULL;
 989     Node* current = st;
 990     // Skip through chains of MemBarNodes checking the MergeMems for
 991     // new states for the slice of this load.  Stop once any other
 992     // kind of node is encountered.  Loads from final memory can skip
 993     // through any kind of MemBar but normal loads shouldn't skip
 994     // through MemBarAcquire since the could allow them to move out of
 995     // a synchronized region.
 996     while (current->is_Proj()) {
 997       int opc = current->in(0)->Opcode();
 998       if ((final && (opc == Op_MemBarAcquire ||
 999                      opc == Op_MemBarAcquireLock ||
1000                      opc == Op_LoadFence)) ||
1001           opc == Op_MemBarRelease ||
1002           opc == Op_StoreFence ||
1003           opc == Op_MemBarReleaseLock ||
1004           opc == Op_MemBarStoreStore ||
1005           opc == Op_MemBarCPUOrder) {
1006         Node* mem = current->in(0)->in(TypeFunc::Memory);
1007         if (mem->is_MergeMem()) {
1008           MergeMemNode* merge = mem->as_MergeMem();
1009           Node* new_st = merge->memory_at(alias_idx);
1010           if (new_st == merge->base_memory()) {
1011             // Keep searching
1012             current = new_st;
1013             continue;
1014           }
1015           // Save the new memory state for the slice and fall through
1016           // to exit.
1017           result = new_st;
1018         }
1019       }
1020       break;
1021     }
1022     if (result != NULL) {
1023       st = result;
1024     }
1025   }
1026 
1027   // Loop around twice in the case Load -> Initialize -> Store.
1028   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1029   for (int trip = 0; trip <= 1; trip++) {
1030 
1031     if (st->is_Store()) {
1032       Node* st_adr = st->in(MemNode::Address);
1033       if (!phase->eqv(st_adr, ld_adr)) {
1034         // Try harder before giving up...  Match raw and non-raw pointers.
1035         intptr_t st_off = 0;
1036         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
1037         if (alloc == NULL)       return NULL;
1038         if (alloc != ld_alloc)   return NULL;
1039         if (ld_off != st_off)    return NULL;
1040         // At this point we have proven something like this setup:
1041         //  A = Allocate(...)
1042         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
1043         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
1044         // (Actually, we haven't yet proven the Q's are the same.)
1045         // In other words, we are loading from a casted version of
1046         // the same pointer-and-offset that we stored to.
1047         // Thus, we are able to replace L by V.
1048       }
1049       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1050       if (store_Opcode() != st->Opcode())
1051         return NULL;
1052       return st->in(MemNode::ValueIn);
1053     }
1054 
1055     // A load from a freshly-created object always returns zero.
1056     // (This can happen after LoadNode::Ideal resets the load's memory input
1057     // to find_captured_store, which returned InitializeNode::zero_memory.)
1058     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1059         (st->in(0) == ld_alloc) &&
1060         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1061       // return a zero value for the load's basic type
1062       // (This is one of the few places where a generic PhaseTransform
1063       // can create new nodes.  Think of it as lazily manifesting
1064       // virtually pre-existing constants.)
1065       return phase->zerocon(memory_type());
1066     }
1067 
1068     // A load from an initialization barrier can match a captured store.
1069     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1070       InitializeNode* init = st->in(0)->as_Initialize();
1071       AllocateNode* alloc = init->allocation();
1072       if ((alloc != NULL) && (alloc == ld_alloc)) {
1073         // examine a captured store value
1074         st = init->find_captured_store(ld_off, memory_size(), phase);
1075         if (st != NULL) {
1076           continue;             // take one more trip around
1077         }
1078       }
1079     }
1080 
1081     // Load boxed value from result of valueOf() call is input parameter.
1082     if (this->is_Load() && ld_adr->is_AddP() &&
1083         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1084       intptr_t ignore = 0;
1085       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1086       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1087       base = bs->step_over_gc_barrier(base);
1088       if (base != NULL && base->is_Proj() &&
1089           base->as_Proj()->_con == TypeFunc::Parms &&
1090           base->in(0)->is_CallStaticJava() &&
1091           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1092         return base->in(0)->in(TypeFunc::Parms);
1093       }
1094     }
1095 
1096     break;
1097   }
1098 
1099   return NULL;
1100 }
1101 
1102 //----------------------is_instance_field_load_with_local_phi------------------
1103 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1104   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1105       in(Address)->is_AddP() ) {
1106     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1107     // Only instances and boxed values.
1108     if( t_oop != NULL &&
1109         (t_oop->is_ptr_to_boxed_value() ||
1110          t_oop->is_known_instance_field()) &&
1111         t_oop->offset() != Type::OffsetBot &&
1112         t_oop->offset() != Type::OffsetTop) {
1113       return true;
1114     }
1115   }
1116   return false;
1117 }
1118 
1119 //------------------------------Identity---------------------------------------
1120 // Loads are identity if previous store is to same address
1121 Node* LoadNode::Identity(PhaseGVN* phase) {
1122   // If the previous store-maker is the right kind of Store, and the store is
1123   // to the same address, then we are equal to the value stored.
1124   Node* mem = in(Memory);
1125   Node* value = can_see_stored_value(mem, phase);
1126   if( value ) {
1127     // byte, short & char stores truncate naturally.
1128     // A load has to load the truncated value which requires
1129     // some sort of masking operation and that requires an
1130     // Ideal call instead of an Identity call.
1131     if (memory_size() < BytesPerInt) {
1132       // If the input to the store does not fit with the load's result type,
1133       // it must be truncated via an Ideal call.
1134       if (!phase->type(value)->higher_equal(phase->type(this)))
1135         return this;
1136     }
1137     // (This works even when value is a Con, but LoadNode::Value
1138     // usually runs first, producing the singleton type of the Con.)
1139     return value;
1140   }
1141 
1142   // Search for an existing data phi which was generated before for the same
1143   // instance's field to avoid infinite generation of phis in a loop.
1144   Node *region = mem->in(0);
1145   if (is_instance_field_load_with_local_phi(region)) {
1146     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1147     int this_index  = phase->C->get_alias_index(addr_t);
1148     int this_offset = addr_t->offset();
1149     int this_iid    = addr_t->instance_id();
1150     if (!addr_t->is_known_instance() &&
1151          addr_t->is_ptr_to_boxed_value()) {
1152       // Use _idx of address base (could be Phi node) for boxed values.
1153       intptr_t   ignore = 0;
1154       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1155       if (base == NULL) {
1156         return this;
1157       }
1158       this_iid = base->_idx;
1159     }
1160     const Type* this_type = bottom_type();
1161     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1162       Node* phi = region->fast_out(i);
1163       if (phi->is_Phi() && phi != mem &&
1164           phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1165         return phi;
1166       }
1167     }
1168   }
1169 
1170   return this;
1171 }
1172 
1173 // Construct an equivalent unsigned load.
1174 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1175   BasicType bt = T_ILLEGAL;
1176   const Type* rt = NULL;
1177   switch (Opcode()) {
1178     case Op_LoadUB: return this;
1179     case Op_LoadUS: return this;
1180     case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1181     case Op_LoadS: bt = T_CHAR;    rt = TypeInt::CHAR;  break;
1182     default:
1183       assert(false, "no unsigned variant: %s", Name());
1184       return NULL;
1185   }
1186   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1187                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1188                         is_unaligned_access(), is_mismatched_access());
1189 }
1190 
1191 // Construct an equivalent signed load.
1192 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1193   BasicType bt = T_ILLEGAL;
1194   const Type* rt = NULL;
1195   switch (Opcode()) {
1196     case Op_LoadUB: bt = T_BYTE;  rt = TypeInt::BYTE;  break;
1197     case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1198     case Op_LoadB: // fall through
1199     case Op_LoadS: // fall through
1200     case Op_LoadI: // fall through
1201     case Op_LoadL: return this;
1202     default:
1203       assert(false, "no signed variant: %s", Name());
1204       return NULL;
1205   }
1206   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1207                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1208                         is_unaligned_access(), is_mismatched_access());
1209 }
1210 
1211 // We're loading from an object which has autobox behaviour.
1212 // If this object is result of a valueOf call we'll have a phi
1213 // merging a newly allocated object and a load from the cache.
1214 // We want to replace this load with the original incoming
1215 // argument to the valueOf call.
1216 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1217   assert(phase->C->eliminate_boxing(), "sanity");
1218   intptr_t ignore = 0;
1219   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1220   if ((base == NULL) || base->is_Phi()) {
1221     // Push the loads from the phi that comes from valueOf up
1222     // through it to allow elimination of the loads and the recovery
1223     // of the original value. It is done in split_through_phi().
1224     return NULL;
1225   } else if (base->is_Load() ||
1226              (base->is_DecodeN() && base->in(1)->is_Load())) {
1227     // Eliminate the load of boxed value for integer types from the cache
1228     // array by deriving the value from the index into the array.
1229     // Capture the offset of the load and then reverse the computation.
1230 
1231     // Get LoadN node which loads a boxing object from 'cache' array.
1232     if (base->is_DecodeN()) {
1233       base = base->in(1);
1234     }
1235     if (!base->in(Address)->is_AddP()) {
1236       return NULL; // Complex address
1237     }
1238     AddPNode* address = base->in(Address)->as_AddP();
1239     Node* cache_base = address->in(AddPNode::Base);
1240     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1241       // Get ConP node which is static 'cache' field.
1242       cache_base = cache_base->in(1);
1243     }
1244     if ((cache_base != NULL) && cache_base->is_Con()) {
1245       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1246       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1247         Node* elements[4];
1248         int shift = exact_log2(type2aelembytes(T_OBJECT));
1249         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1250         if (count > 0 && elements[0]->is_Con() &&
1251             (count == 1 ||
1252              (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1253                             elements[1]->in(2) == phase->intcon(shift)))) {
1254           ciObjArray* array = base_type->const_oop()->as_obj_array();
1255           // Fetch the box object cache[0] at the base of the array and get its value
1256           ciInstance* box = array->obj_at(0)->as_instance();
1257           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1258           assert(ik->is_box_klass(), "sanity");
1259           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1260           if (ik->nof_nonstatic_fields() == 1) {
1261             // This should be true nonstatic_field_at requires calling
1262             // nof_nonstatic_fields so check it anyway
1263             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1264             BasicType bt = c.basic_type();
1265             // Only integer types have boxing cache.
1266             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1267                    bt == T_BYTE    || bt == T_SHORT ||
1268                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1269             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1270             if (cache_low != (int)cache_low) {
1271               return NULL; // should not happen since cache is array indexed by value
1272             }
1273             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1274             if (offset != (int)offset) {
1275               return NULL; // should not happen since cache is array indexed by value
1276             }
1277            // Add up all the offsets making of the address of the load
1278             Node* result = elements[0];
1279             for (int i = 1; i < count; i++) {
1280               result = phase->transform(new AddXNode(result, elements[i]));
1281             }
1282             // Remove the constant offset from the address and then
1283             result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1284             // remove the scaling of the offset to recover the original index.
1285             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1286               // Peel the shift off directly but wrap it in a dummy node
1287               // since Ideal can't return existing nodes
1288               result = new RShiftXNode(result->in(1), phase->intcon(0));
1289             } else if (result->is_Add() && result->in(2)->is_Con() &&
1290                        result->in(1)->Opcode() == Op_LShiftX &&
1291                        result->in(1)->in(2) == phase->intcon(shift)) {
1292               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1293               // but for boxing cache access we know that X<<Z will not overflow
1294               // (there is range check) so we do this optimizatrion by hand here.
1295               Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1296               result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1297             } else {
1298               result = new RShiftXNode(result, phase->intcon(shift));
1299             }
1300 #ifdef _LP64
1301             if (bt != T_LONG) {
1302               result = new ConvL2INode(phase->transform(result));
1303             }
1304 #else
1305             if (bt == T_LONG) {
1306               result = new ConvI2LNode(phase->transform(result));
1307             }
1308 #endif
1309             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1310             // Need to preserve unboxing load type if it is unsigned.
1311             switch(this->Opcode()) {
1312               case Op_LoadUB:
1313                 result = new AndINode(phase->transform(result), phase->intcon(0xFF));
1314                 break;
1315               case Op_LoadUS:
1316                 result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
1317                 break;
1318             }
1319             return result;
1320           }
1321         }
1322       }
1323     }
1324   }
1325   return NULL;
1326 }
1327 
1328 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1329   Node* region = phi->in(0);
1330   if (region == NULL) {
1331     return false; // Wait stable graph
1332   }
1333   uint cnt = phi->req();
1334   for (uint i = 1; i < cnt; i++) {
1335     Node* rc = region->in(i);
1336     if (rc == NULL || phase->type(rc) == Type::TOP)
1337       return false; // Wait stable graph
1338     Node* in = phi->in(i);
1339     if (in == NULL || phase->type(in) == Type::TOP)
1340       return false; // Wait stable graph
1341   }
1342   return true;
1343 }
1344 //------------------------------split_through_phi------------------------------
1345 // Split instance or boxed field load through Phi.
1346 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1347   Node* mem     = in(Memory);
1348   Node* address = in(Address);
1349   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1350 
1351   assert((t_oop != NULL) &&
1352          (t_oop->is_known_instance_field() ||
1353           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1354 
1355   Compile* C = phase->C;
1356   intptr_t ignore = 0;
1357   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1358   bool base_is_phi = (base != NULL) && base->is_Phi();
1359   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1360                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1361                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1362 
1363   if (!((mem->is_Phi() || base_is_phi) &&
1364         (load_boxed_values || t_oop->is_known_instance_field()))) {
1365     return NULL; // memory is not Phi
1366   }
1367 
1368   if (mem->is_Phi()) {
1369     if (!stable_phi(mem->as_Phi(), phase)) {
1370       return NULL; // Wait stable graph
1371     }
1372     uint cnt = mem->req();
1373     // Check for loop invariant memory.
1374     if (cnt == 3) {
1375       for (uint i = 1; i < cnt; i++) {
1376         Node* in = mem->in(i);
1377         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1378         if (m == mem) {
1379           set_req(Memory, mem->in(cnt - i));
1380           return this; // made change
1381         }
1382       }
1383     }
1384   }
1385   if (base_is_phi) {
1386     if (!stable_phi(base->as_Phi(), phase)) {
1387       return NULL; // Wait stable graph
1388     }
1389     uint cnt = base->req();
1390     // Check for loop invariant memory.
1391     if (cnt == 3) {
1392       for (uint i = 1; i < cnt; i++) {
1393         if (base->in(i) == base) {
1394           return NULL; // Wait stable graph
1395         }
1396       }
1397     }
1398   }
1399 
1400   bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1401 
1402   // Split through Phi (see original code in loopopts.cpp).
1403   assert(C->have_alias_type(t_oop), "instance should have alias type");
1404 
1405   // Do nothing here if Identity will find a value
1406   // (to avoid infinite chain of value phis generation).
1407   if (!phase->eqv(this, this->Identity(phase)))
1408     return NULL;
1409 
1410   // Select Region to split through.
1411   Node* region;
1412   if (!base_is_phi) {
1413     assert(mem->is_Phi(), "sanity");
1414     region = mem->in(0);
1415     // Skip if the region dominates some control edge of the address.
1416     if (!MemNode::all_controls_dominate(address, region))
1417       return NULL;
1418   } else if (!mem->is_Phi()) {
1419     assert(base_is_phi, "sanity");
1420     region = base->in(0);
1421     // Skip if the region dominates some control edge of the memory.
1422     if (!MemNode::all_controls_dominate(mem, region))
1423       return NULL;
1424   } else if (base->in(0) != mem->in(0)) {
1425     assert(base_is_phi && mem->is_Phi(), "sanity");
1426     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1427       region = base->in(0);
1428     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1429       region = mem->in(0);
1430     } else {
1431       return NULL; // complex graph
1432     }
1433   } else {
1434     assert(base->in(0) == mem->in(0), "sanity");
1435     region = mem->in(0);
1436   }
1437 
1438   const Type* this_type = this->bottom_type();
1439   int this_index  = C->get_alias_index(t_oop);
1440   int this_offset = t_oop->offset();
1441   int this_iid    = t_oop->instance_id();
1442   if (!t_oop->is_known_instance() && load_boxed_values) {
1443     // Use _idx of address base for boxed values.
1444     this_iid = base->_idx;
1445   }
1446   PhaseIterGVN* igvn = phase->is_IterGVN();
1447   Node* phi = new PhiNode(region, this_type, NULL, mem->_idx, this_iid, this_index, this_offset);
1448   for (uint i = 1; i < region->req(); i++) {
1449     Node* x;
1450     Node* the_clone = NULL;
1451     if (region->in(i) == C->top()) {
1452       x = C->top();      // Dead path?  Use a dead data op
1453     } else {
1454       x = this->clone();        // Else clone up the data op
1455       the_clone = x;            // Remember for possible deletion.
1456       // Alter data node to use pre-phi inputs
1457       if (this->in(0) == region) {
1458         x->set_req(0, region->in(i));
1459       } else {
1460         x->set_req(0, NULL);
1461       }
1462       if (mem->is_Phi() && (mem->in(0) == region)) {
1463         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1464       }
1465       if (address->is_Phi() && address->in(0) == region) {
1466         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1467       }
1468       if (base_is_phi && (base->in(0) == region)) {
1469         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1470         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1471         x->set_req(Address, adr_x);
1472       }
1473     }
1474     // Check for a 'win' on some paths
1475     const Type *t = x->Value(igvn);
1476 
1477     bool singleton = t->singleton();
1478 
1479     // See comments in PhaseIdealLoop::split_thru_phi().
1480     if (singleton && t == Type::TOP) {
1481       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1482     }
1483 
1484     if (singleton) {
1485       x = igvn->makecon(t);
1486     } else {
1487       // We now call Identity to try to simplify the cloned node.
1488       // Note that some Identity methods call phase->type(this).
1489       // Make sure that the type array is big enough for
1490       // our new node, even though we may throw the node away.
1491       // (This tweaking with igvn only works because x is a new node.)
1492       igvn->set_type(x, t);
1493       // If x is a TypeNode, capture any more-precise type permanently into Node
1494       // otherwise it will be not updated during igvn->transform since
1495       // igvn->type(x) is set to x->Value() already.
1496       x->raise_bottom_type(t);
1497       Node *y = x->Identity(igvn);
1498       if (y != x) {
1499         x = y;
1500       } else {
1501         y = igvn->hash_find_insert(x);
1502         if (y) {
1503           x = y;
1504         } else {
1505           // Else x is a new node we are keeping
1506           // We do not need register_new_node_with_optimizer
1507           // because set_type has already been called.
1508           igvn->_worklist.push(x);
1509         }
1510       }
1511     }
1512     if (x != the_clone && the_clone != NULL) {
1513       igvn->remove_dead_node(the_clone);
1514     }
1515     phi->set_req(i, x);
1516   }
1517   // Record Phi
1518   igvn->register_new_node_with_optimizer(phi);
1519   return phi;
1520 }
1521 
1522 //------------------------------Ideal------------------------------------------
1523 // If the load is from Field memory and the pointer is non-null, it might be possible to
1524 // zero out the control input.
1525 // If the offset is constant and the base is an object allocation,
1526 // try to hook me up to the exact initializing store.
1527 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1528   Node* p = MemNode::Ideal_common(phase, can_reshape);
1529   if (p)  return (p == NodeSentinel) ? NULL : p;
1530 
1531   Node* ctrl    = in(MemNode::Control);
1532   Node* address = in(MemNode::Address);
1533   bool progress = false;
1534 
1535   // Skip up past a SafePoint control.  Cannot do this for Stores because
1536   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1537   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1538       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
1539     ctrl = ctrl->in(0);
1540     set_req(MemNode::Control,ctrl);
1541     progress = true;
1542   }
1543 
1544   intptr_t ignore = 0;
1545   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1546   if (base != NULL
1547       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1548     // Check for useless control edge in some common special cases
1549     if (in(MemNode::Control) != NULL
1550         && can_remove_control()
1551         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1552         && all_controls_dominate(base, phase->C->start())) {
1553       // A method-invariant, non-null address (constant or 'this' argument).
1554       set_req(MemNode::Control, NULL);
1555       progress = true;
1556     }
1557   }
1558 
1559   Node* mem = in(MemNode::Memory);
1560   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1561 
1562   if (can_reshape && (addr_t != NULL)) {
1563     // try to optimize our memory input
1564     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1565     if (opt_mem != mem) {
1566       set_req(MemNode::Memory, opt_mem);
1567       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1568       return this;
1569     }
1570     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1571     if ((t_oop != NULL) &&
1572         (t_oop->is_known_instance_field() ||
1573          t_oop->is_ptr_to_boxed_value())) {
1574       PhaseIterGVN *igvn = phase->is_IterGVN();
1575       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1576         // Delay this transformation until memory Phi is processed.
1577         phase->is_IterGVN()->_worklist.push(this);
1578         return NULL;
1579       }
1580       // Split instance field load through Phi.
1581       Node* result = split_through_phi(phase);
1582       if (result != NULL) return result;
1583 
1584       if (t_oop->is_ptr_to_boxed_value()) {
1585         Node* result = eliminate_autobox(phase);
1586         if (result != NULL) return result;
1587       }
1588     }
1589   }
1590 
1591   // Is there a dominating load that loads the same value?  Leave
1592   // anything that is not a load of a field/array element (like
1593   // barriers etc.) alone
1594   if (in(0) != NULL && !adr_type()->isa_rawptr() && can_reshape) {
1595     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1596       Node *use = mem->fast_out(i);
1597       if (use != this &&
1598           use->Opcode() == Opcode() &&
1599           use->in(0) != NULL &&
1600           use->in(0) != in(0) &&
1601           use->in(Address) == in(Address)) {
1602         Node* ctl = in(0);
1603         for (int i = 0; i < 10 && ctl != NULL; i++) {
1604           ctl = IfNode::up_one_dom(ctl);
1605           if (ctl == use->in(0)) {
1606             set_req(0, use->in(0));
1607             return this;
1608           }
1609         }
1610       }
1611     }
1612   }
1613 
1614   // Check for prior store with a different base or offset; make Load
1615   // independent.  Skip through any number of them.  Bail out if the stores
1616   // are in an endless dead cycle and report no progress.  This is a key
1617   // transform for Reflection.  However, if after skipping through the Stores
1618   // we can't then fold up against a prior store do NOT do the transform as
1619   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1620   // array memory alive twice: once for the hoisted Load and again after the
1621   // bypassed Store.  This situation only works if EVERYBODY who does
1622   // anti-dependence work knows how to bypass.  I.e. we need all
1623   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1624   // the alias index stuff.  So instead, peek through Stores and IFF we can
1625   // fold up, do so.
1626   Node* prev_mem = find_previous_store(phase);
1627   if (prev_mem != NULL) {
1628     Node* value = can_see_arraycopy_value(prev_mem, phase);
1629     if (value != NULL) {
1630       return value;
1631     }
1632   }
1633   // Steps (a), (b):  Walk past independent stores to find an exact match.
1634   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1635     // (c) See if we can fold up on the spot, but don't fold up here.
1636     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1637     // just return a prior value, which is done by Identity calls.
1638     if (can_see_stored_value(prev_mem, phase)) {
1639       // Make ready for step (d):
1640       set_req(MemNode::Memory, prev_mem);
1641       return this;
1642     }
1643   }
1644 
1645   return progress ? this : NULL;
1646 }
1647 
1648 // Helper to recognize certain Klass fields which are invariant across
1649 // some group of array types (e.g., int[] or all T[] where T < Object).
1650 const Type*
1651 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1652                                  ciKlass* klass) const {
1653   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1654     // The field is Klass::_modifier_flags.  Return its (constant) value.
1655     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1656     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1657     return TypeInt::make(klass->modifier_flags());
1658   }
1659   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1660     // The field is Klass::_access_flags.  Return its (constant) value.
1661     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1662     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1663     return TypeInt::make(klass->access_flags());
1664   }
1665   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1666     // The field is Klass::_layout_helper.  Return its constant value if known.
1667     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1668     return TypeInt::make(klass->layout_helper());
1669   }
1670 
1671   // No match.
1672   return NULL;
1673 }
1674 
1675 //------------------------------Value-----------------------------------------
1676 const Type* LoadNode::Value(PhaseGVN* phase) const {
1677   // Either input is TOP ==> the result is TOP
1678   Node* mem = in(MemNode::Memory);
1679   const Type *t1 = phase->type(mem);
1680   if (t1 == Type::TOP)  return Type::TOP;
1681   Node* adr = in(MemNode::Address);
1682   const TypePtr* tp = phase->type(adr)->isa_ptr();
1683   if (tp == NULL || tp->empty())  return Type::TOP;
1684   int off = tp->offset();
1685   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1686   Compile* C = phase->C;
1687 
1688   // Try to guess loaded type from pointer type
1689   if (tp->isa_aryptr()) {
1690     const TypeAryPtr* ary = tp->is_aryptr();
1691     const Type* t = ary->elem();
1692 
1693     // Determine whether the reference is beyond the header or not, by comparing
1694     // the offset against the offset of the start of the array's data.
1695     // Different array types begin at slightly different offsets (12 vs. 16).
1696     // We choose T_BYTE as an example base type that is least restrictive
1697     // as to alignment, which will therefore produce the smallest
1698     // possible base offset.
1699     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1700     const bool off_beyond_header = ((uint)off >= (uint)min_base_off);
1701 
1702     // Try to constant-fold a stable array element.
1703     if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1704       // Make sure the reference is not into the header and the offset is constant
1705       ciObject* aobj = ary->const_oop();
1706       if (aobj != NULL && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1707         int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1708         const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1709                                                                       stable_dimension,
1710                                                                       memory_type(), is_unsigned());
1711         if (con_type != NULL) {
1712           return con_type;
1713         }
1714       }
1715     }
1716 
1717     // Don't do this for integer types. There is only potential profit if
1718     // the element type t is lower than _type; that is, for int types, if _type is
1719     // more restrictive than t.  This only happens here if one is short and the other
1720     // char (both 16 bits), and in those cases we've made an intentional decision
1721     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1722     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1723     //
1724     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1725     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1726     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1727     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1728     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1729     // In fact, that could have been the original type of p1, and p1 could have
1730     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1731     // expression (LShiftL quux 3) independently optimized to the constant 8.
1732     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1733         && (_type->isa_vect() == NULL)
1734         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1735       // t might actually be lower than _type, if _type is a unique
1736       // concrete subclass of abstract class t.
1737       if (off_beyond_header) {  // is the offset beyond the header?
1738         const Type* jt = t->join_speculative(_type);
1739         // In any case, do not allow the join, per se, to empty out the type.
1740         if (jt->empty() && !t->empty()) {
1741           // This can happen if a interface-typed array narrows to a class type.
1742           jt = _type;
1743         }
1744 #ifdef ASSERT
1745         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1746           // The pointers in the autobox arrays are always non-null
1747           Node* base = adr->in(AddPNode::Base);
1748           if ((base != NULL) && base->is_DecodeN()) {
1749             // Get LoadN node which loads IntegerCache.cache field
1750             base = base->in(1);
1751           }
1752           if ((base != NULL) && base->is_Con()) {
1753             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1754             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1755               // It could be narrow oop
1756               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1757             }
1758           }
1759         }
1760 #endif
1761         return jt;
1762       }
1763     }
1764   } else if (tp->base() == Type::InstPtr) {
1765     assert( off != Type::OffsetBot ||
1766             // arrays can be cast to Objects
1767             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1768             // unsafe field access may not have a constant offset
1769             C->has_unsafe_access(),
1770             "Field accesses must be precise" );
1771     // For oop loads, we expect the _type to be precise.
1772 
1773     // Optimize loads from constant fields.
1774     const TypeInstPtr* tinst = tp->is_instptr();
1775     ciObject* const_oop = tinst->const_oop();
1776     if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
1777       const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
1778       if (con_type != NULL) {
1779         return con_type;
1780       }
1781     }
1782   } else if (tp->base() == Type::KlassPtr) {
1783     assert( off != Type::OffsetBot ||
1784             // arrays can be cast to Objects
1785             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1786             // also allow array-loading from the primary supertype
1787             // array during subtype checks
1788             Opcode() == Op_LoadKlass,
1789             "Field accesses must be precise" );
1790     // For klass/static loads, we expect the _type to be precise
1791   } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
1792     /* With mirrors being an indirect in the Klass*
1793      * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
1794      * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
1795      *
1796      * So check the type and klass of the node before the LoadP.
1797      */
1798     Node* adr2 = adr->in(MemNode::Address);
1799     const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
1800     if (tkls != NULL && !StressReflectiveCode) {
1801       ciKlass* klass = tkls->klass();
1802       if (klass->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1803         assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1804         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1805         return TypeInstPtr::make(klass->java_mirror());
1806       }
1807     }
1808   }
1809 
1810   const TypeKlassPtr *tkls = tp->isa_klassptr();
1811   if (tkls != NULL && !StressReflectiveCode) {
1812     ciKlass* klass = tkls->klass();
1813     if (klass->is_loaded() && tkls->klass_is_exact()) {
1814       // We are loading a field from a Klass metaobject whose identity
1815       // is known at compile time (the type is "exact" or "precise").
1816       // Check for fields we know are maintained as constants by the VM.
1817       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1818         // The field is Klass::_super_check_offset.  Return its (constant) value.
1819         // (Folds up type checking code.)
1820         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1821         return TypeInt::make(klass->super_check_offset());
1822       }
1823       // Compute index into primary_supers array
1824       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1825       // Check for overflowing; use unsigned compare to handle the negative case.
1826       if( depth < ciKlass::primary_super_limit() ) {
1827         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1828         // (Folds up type checking code.)
1829         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1830         ciKlass *ss = klass->super_of_depth(depth);
1831         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1832       }
1833       const Type* aift = load_array_final_field(tkls, klass);
1834       if (aift != NULL)  return aift;
1835     }
1836 
1837     // We can still check if we are loading from the primary_supers array at a
1838     // shallow enough depth.  Even though the klass is not exact, entries less
1839     // than or equal to its super depth are correct.
1840     if (klass->is_loaded() ) {
1841       ciType *inner = klass;
1842       while( inner->is_obj_array_klass() )
1843         inner = inner->as_obj_array_klass()->base_element_type();
1844       if( inner->is_instance_klass() &&
1845           !inner->as_instance_klass()->flags().is_interface() ) {
1846         // Compute index into primary_supers array
1847         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1848         // Check for overflowing; use unsigned compare to handle the negative case.
1849         if( depth < ciKlass::primary_super_limit() &&
1850             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1851           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1852           // (Folds up type checking code.)
1853           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1854           ciKlass *ss = klass->super_of_depth(depth);
1855           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1856         }
1857       }
1858     }
1859 
1860     // If the type is enough to determine that the thing is not an array,
1861     // we can give the layout_helper a positive interval type.
1862     // This will help short-circuit some reflective code.
1863     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1864         && !klass->is_array_klass() // not directly typed as an array
1865         && !klass->is_interface()  // specifically not Serializable & Cloneable
1866         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1867         ) {
1868       // Note:  When interfaces are reliable, we can narrow the interface
1869       // test to (klass != Serializable && klass != Cloneable).
1870       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1871       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1872       // The key property of this type is that it folds up tests
1873       // for array-ness, since it proves that the layout_helper is positive.
1874       // Thus, a generic value like the basic object layout helper works fine.
1875       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1876     }
1877   }
1878 
1879   // If we are loading from a freshly-allocated object, produce a zero,
1880   // if the load is provably beyond the header of the object.
1881   // (Also allow a variable load from a fresh array to produce zero.)
1882   const TypeOopPtr *tinst = tp->isa_oopptr();
1883   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1884   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1885   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1886     Node* value = can_see_stored_value(mem,phase);
1887     if (value != NULL && value->is_Con()) {
1888       assert(value->bottom_type()->higher_equal(_type),"sanity");
1889       return value->bottom_type();
1890     }
1891   }
1892 
1893   if (is_instance) {
1894     // If we have an instance type and our memory input is the
1895     // programs's initial memory state, there is no matching store,
1896     // so just return a zero of the appropriate type
1897     Node *mem = in(MemNode::Memory);
1898     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1899       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1900       return Type::get_zero_type(_type->basic_type());
1901     }
1902   }
1903   return _type;
1904 }
1905 
1906 //------------------------------match_edge-------------------------------------
1907 // Do we Match on this edge index or not?  Match only the address.
1908 uint LoadNode::match_edge(uint idx) const {
1909   return idx == MemNode::Address;
1910 }
1911 
1912 //--------------------------LoadBNode::Ideal--------------------------------------
1913 //
1914 //  If the previous store is to the same address as this load,
1915 //  and the value stored was larger than a byte, replace this load
1916 //  with the value stored truncated to a byte.  If no truncation is
1917 //  needed, the replacement is done in LoadNode::Identity().
1918 //
1919 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1920   Node* mem = in(MemNode::Memory);
1921   Node* value = can_see_stored_value(mem,phase);
1922   if( value && !phase->type(value)->higher_equal( _type ) ) {
1923     Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1924     return new RShiftINode(result, phase->intcon(24));
1925   }
1926   // Identity call will handle the case where truncation is not needed.
1927   return LoadNode::Ideal(phase, can_reshape);
1928 }
1929 
1930 const Type* LoadBNode::Value(PhaseGVN* phase) const {
1931   Node* mem = in(MemNode::Memory);
1932   Node* value = can_see_stored_value(mem,phase);
1933   if (value != NULL && value->is_Con() &&
1934       !value->bottom_type()->higher_equal(_type)) {
1935     // If the input to the store does not fit with the load's result type,
1936     // it must be truncated. We can't delay until Ideal call since
1937     // a singleton Value is needed for split_thru_phi optimization.
1938     int con = value->get_int();
1939     return TypeInt::make((con << 24) >> 24);
1940   }
1941   return LoadNode::Value(phase);
1942 }
1943 
1944 //--------------------------LoadUBNode::Ideal-------------------------------------
1945 //
1946 //  If the previous store is to the same address as this load,
1947 //  and the value stored was larger than a byte, replace this load
1948 //  with the value stored truncated to a byte.  If no truncation is
1949 //  needed, the replacement is done in LoadNode::Identity().
1950 //
1951 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1952   Node* mem = in(MemNode::Memory);
1953   Node* value = can_see_stored_value(mem, phase);
1954   if (value && !phase->type(value)->higher_equal(_type))
1955     return new AndINode(value, phase->intcon(0xFF));
1956   // Identity call will handle the case where truncation is not needed.
1957   return LoadNode::Ideal(phase, can_reshape);
1958 }
1959 
1960 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
1961   Node* mem = in(MemNode::Memory);
1962   Node* value = can_see_stored_value(mem,phase);
1963   if (value != NULL && value->is_Con() &&
1964       !value->bottom_type()->higher_equal(_type)) {
1965     // If the input to the store does not fit with the load's result type,
1966     // it must be truncated. We can't delay until Ideal call since
1967     // a singleton Value is needed for split_thru_phi optimization.
1968     int con = value->get_int();
1969     return TypeInt::make(con & 0xFF);
1970   }
1971   return LoadNode::Value(phase);
1972 }
1973 
1974 //--------------------------LoadUSNode::Ideal-------------------------------------
1975 //
1976 //  If the previous store is to the same address as this load,
1977 //  and the value stored was larger than a char, replace this load
1978 //  with the value stored truncated to a char.  If no truncation is
1979 //  needed, the replacement is done in LoadNode::Identity().
1980 //
1981 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1982   Node* mem = in(MemNode::Memory);
1983   Node* value = can_see_stored_value(mem,phase);
1984   if( value && !phase->type(value)->higher_equal( _type ) )
1985     return new AndINode(value,phase->intcon(0xFFFF));
1986   // Identity call will handle the case where truncation is not needed.
1987   return LoadNode::Ideal(phase, can_reshape);
1988 }
1989 
1990 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
1991   Node* mem = in(MemNode::Memory);
1992   Node* value = can_see_stored_value(mem,phase);
1993   if (value != NULL && value->is_Con() &&
1994       !value->bottom_type()->higher_equal(_type)) {
1995     // If the input to the store does not fit with the load's result type,
1996     // it must be truncated. We can't delay until Ideal call since
1997     // a singleton Value is needed for split_thru_phi optimization.
1998     int con = value->get_int();
1999     return TypeInt::make(con & 0xFFFF);
2000   }
2001   return LoadNode::Value(phase);
2002 }
2003 
2004 //--------------------------LoadSNode::Ideal--------------------------------------
2005 //
2006 //  If the previous store is to the same address as this load,
2007 //  and the value stored was larger than a short, replace this load
2008 //  with the value stored truncated to a short.  If no truncation is
2009 //  needed, the replacement is done in LoadNode::Identity().
2010 //
2011 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2012   Node* mem = in(MemNode::Memory);
2013   Node* value = can_see_stored_value(mem,phase);
2014   if( value && !phase->type(value)->higher_equal( _type ) ) {
2015     Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
2016     return new RShiftINode(result, phase->intcon(16));
2017   }
2018   // Identity call will handle the case where truncation is not needed.
2019   return LoadNode::Ideal(phase, can_reshape);
2020 }
2021 
2022 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2023   Node* mem = in(MemNode::Memory);
2024   Node* value = can_see_stored_value(mem,phase);
2025   if (value != NULL && value->is_Con() &&
2026       !value->bottom_type()->higher_equal(_type)) {
2027     // If the input to the store does not fit with the load's result type,
2028     // it must be truncated. We can't delay until Ideal call since
2029     // a singleton Value is needed for split_thru_phi optimization.
2030     int con = value->get_int();
2031     return TypeInt::make((con << 16) >> 16);
2032   }
2033   return LoadNode::Value(phase);
2034 }
2035 
2036 //=============================================================================
2037 //----------------------------LoadKlassNode::make------------------------------
2038 // Polymorphic factory method:
2039 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2040   // sanity check the alias category against the created node type
2041   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2042   assert(adr_type != NULL, "expecting TypeKlassPtr");
2043 #ifdef _LP64
2044   if (adr_type->is_ptr_to_narrowklass()) {
2045     assert(UseCompressedClassPointers, "no compressed klasses");
2046     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2047     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2048   }
2049 #endif
2050   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2051   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2052 }
2053 
2054 //------------------------------Value------------------------------------------
2055 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2056   return klass_value_common(phase);
2057 }
2058 
2059 // In most cases, LoadKlassNode does not have the control input set. If the control
2060 // input is set, it must not be removed (by LoadNode::Ideal()).
2061 bool LoadKlassNode::can_remove_control() const {
2062   return false;
2063 }
2064 
2065 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2066   // Either input is TOP ==> the result is TOP
2067   const Type *t1 = phase->type( in(MemNode::Memory) );
2068   if (t1 == Type::TOP)  return Type::TOP;
2069   Node *adr = in(MemNode::Address);
2070   const Type *t2 = phase->type( adr );
2071   if (t2 == Type::TOP)  return Type::TOP;
2072   const TypePtr *tp = t2->is_ptr();
2073   if (TypePtr::above_centerline(tp->ptr()) ||
2074       tp->ptr() == TypePtr::Null)  return Type::TOP;
2075 
2076   // Return a more precise klass, if possible
2077   const TypeInstPtr *tinst = tp->isa_instptr();
2078   if (tinst != NULL) {
2079     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2080     int offset = tinst->offset();
2081     if (ik == phase->C->env()->Class_klass()
2082         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2083             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2084       // We are loading a special hidden field from a Class mirror object,
2085       // the field which points to the VM's Klass metaobject.
2086       ciType* t = tinst->java_mirror_type();
2087       // java_mirror_type returns non-null for compile-time Class constants.
2088       if (t != NULL) {
2089         // constant oop => constant klass
2090         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2091           if (t->is_void()) {
2092             // We cannot create a void array.  Since void is a primitive type return null
2093             // klass.  Users of this result need to do a null check on the returned klass.
2094             return TypePtr::NULL_PTR;
2095           }
2096           return TypeKlassPtr::make(ciArrayKlass::make(t));
2097         }
2098         if (!t->is_klass()) {
2099           // a primitive Class (e.g., int.class) has NULL for a klass field
2100           return TypePtr::NULL_PTR;
2101         }
2102         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2103         return TypeKlassPtr::make(t->as_klass());
2104       }
2105       // non-constant mirror, so we can't tell what's going on
2106     }
2107     if( !ik->is_loaded() )
2108       return _type;             // Bail out if not loaded
2109     if (offset == oopDesc::klass_offset_in_bytes()) {
2110       if (tinst->klass_is_exact()) {
2111         return TypeKlassPtr::make(ik);
2112       }
2113       // See if we can become precise: no subklasses and no interface
2114       // (Note:  We need to support verified interfaces.)
2115       if (!ik->is_interface() && !ik->has_subklass()) {
2116         //assert(!UseExactTypes, "this code should be useless with exact types");
2117         // Add a dependence; if any subclass added we need to recompile
2118         if (!ik->is_final()) {
2119           // %%% should use stronger assert_unique_concrete_subtype instead
2120           phase->C->dependencies()->assert_leaf_type(ik);
2121         }
2122         // Return precise klass
2123         return TypeKlassPtr::make(ik);
2124       }
2125 
2126       // Return root of possible klass
2127       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2128     }
2129   }
2130 
2131   // Check for loading klass from an array
2132   const TypeAryPtr *tary = tp->isa_aryptr();
2133   if( tary != NULL ) {
2134     ciKlass *tary_klass = tary->klass();
2135     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2136         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2137       if (tary->klass_is_exact()) {
2138         return TypeKlassPtr::make(tary_klass);
2139       }
2140       ciArrayKlass *ak = tary->klass()->as_array_klass();
2141       // If the klass is an object array, we defer the question to the
2142       // array component klass.
2143       if( ak->is_obj_array_klass() ) {
2144         assert( ak->is_loaded(), "" );
2145         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2146         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2147           ciInstanceKlass* ik = base_k->as_instance_klass();
2148           // See if we can become precise: no subklasses and no interface
2149           if (!ik->is_interface() && !ik->has_subklass()) {
2150             //assert(!UseExactTypes, "this code should be useless with exact types");
2151             // Add a dependence; if any subclass added we need to recompile
2152             if (!ik->is_final()) {
2153               phase->C->dependencies()->assert_leaf_type(ik);
2154             }
2155             // Return precise array klass
2156             return TypeKlassPtr::make(ak);
2157           }
2158         }
2159         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2160       } else {                  // Found a type-array?
2161         //assert(!UseExactTypes, "this code should be useless with exact types");
2162         assert( ak->is_type_array_klass(), "" );
2163         return TypeKlassPtr::make(ak); // These are always precise
2164       }
2165     }
2166   }
2167 
2168   // Check for loading klass from an array klass
2169   const TypeKlassPtr *tkls = tp->isa_klassptr();
2170   if (tkls != NULL && !StressReflectiveCode) {
2171     ciKlass* klass = tkls->klass();
2172     if( !klass->is_loaded() )
2173       return _type;             // Bail out if not loaded
2174     if( klass->is_obj_array_klass() &&
2175         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2176       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2177       // // Always returning precise element type is incorrect,
2178       // // e.g., element type could be object and array may contain strings
2179       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2180 
2181       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2182       // according to the element type's subclassing.
2183       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2184     }
2185     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2186         tkls->offset() == in_bytes(Klass::super_offset())) {
2187       ciKlass* sup = klass->as_instance_klass()->super();
2188       // The field is Klass::_super.  Return its (constant) value.
2189       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2190       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2191     }
2192   }
2193 
2194   // Bailout case
2195   return LoadNode::Value(phase);
2196 }
2197 
2198 //------------------------------Identity---------------------------------------
2199 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2200 // Also feed through the klass in Allocate(...klass...)._klass.
2201 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2202   return klass_identity_common(phase);
2203 }
2204 
2205 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2206   Node* x = LoadNode::Identity(phase);
2207   if (x != this)  return x;
2208 
2209   // Take apart the address into an oop and and offset.
2210   // Return 'this' if we cannot.
2211   Node*    adr    = in(MemNode::Address);
2212   intptr_t offset = 0;
2213   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2214   if (base == NULL)     return this;
2215   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2216   if (toop == NULL)     return this;
2217 
2218   // Step over potential GC barrier for OopHandle resolve
2219   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2220   if (bs->is_gc_barrier_node(base)) {
2221     base = bs->step_over_gc_barrier(base);
2222   }
2223 
2224   // We can fetch the klass directly through an AllocateNode.
2225   // This works even if the klass is not constant (clone or newArray).
2226   if (offset == oopDesc::klass_offset_in_bytes()) {
2227     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2228     if (allocated_klass != NULL) {
2229       return allocated_klass;
2230     }
2231   }
2232 
2233   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2234   // See inline_native_Class_query for occurrences of these patterns.
2235   // Java Example:  x.getClass().isAssignableFrom(y)
2236   //
2237   // This improves reflective code, often making the Class
2238   // mirror go completely dead.  (Current exception:  Class
2239   // mirrors may appear in debug info, but we could clean them out by
2240   // introducing a new debug info operator for Klass.java_mirror).
2241 
2242   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2243       && offset == java_lang_Class::klass_offset_in_bytes()) {
2244     if (base->is_Load()) {
2245       Node* base2 = base->in(MemNode::Address);
2246       if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2247         Node* adr2 = base2->in(MemNode::Address);
2248         const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2249         if (tkls != NULL && !tkls->empty()
2250             && (tkls->klass()->is_instance_klass() ||
2251               tkls->klass()->is_array_klass())
2252             && adr2->is_AddP()
2253            ) {
2254           int mirror_field = in_bytes(Klass::java_mirror_offset());
2255           if (tkls->offset() == mirror_field) {
2256             return adr2->in(AddPNode::Base);
2257           }
2258         }
2259       }
2260     }
2261   }
2262 
2263   return this;
2264 }
2265 
2266 
2267 //------------------------------Value------------------------------------------
2268 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2269   const Type *t = klass_value_common(phase);
2270   if (t == Type::TOP)
2271     return t;
2272 
2273   return t->make_narrowklass();
2274 }
2275 
2276 //------------------------------Identity---------------------------------------
2277 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2278 // Also feed through the klass in Allocate(...klass...)._klass.
2279 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2280   Node *x = klass_identity_common(phase);
2281 
2282   const Type *t = phase->type( x );
2283   if( t == Type::TOP ) return x;
2284   if( t->isa_narrowklass()) return x;
2285   assert (!t->isa_narrowoop(), "no narrow oop here");
2286 
2287   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2288 }
2289 
2290 //------------------------------Value-----------------------------------------
2291 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2292   // Either input is TOP ==> the result is TOP
2293   const Type *t1 = phase->type( in(MemNode::Memory) );
2294   if( t1 == Type::TOP ) return Type::TOP;
2295   Node *adr = in(MemNode::Address);
2296   const Type *t2 = phase->type( adr );
2297   if( t2 == Type::TOP ) return Type::TOP;
2298   const TypePtr *tp = t2->is_ptr();
2299   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2300   const TypeAryPtr *tap = tp->isa_aryptr();
2301   if( !tap ) return _type;
2302   return tap->size();
2303 }
2304 
2305 //-------------------------------Ideal---------------------------------------
2306 // Feed through the length in AllocateArray(...length...)._length.
2307 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2308   Node* p = MemNode::Ideal_common(phase, can_reshape);
2309   if (p)  return (p == NodeSentinel) ? NULL : p;
2310 
2311   // Take apart the address into an oop and and offset.
2312   // Return 'this' if we cannot.
2313   Node*    adr    = in(MemNode::Address);
2314   intptr_t offset = 0;
2315   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2316   if (base == NULL)     return NULL;
2317   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2318   if (tary == NULL)     return NULL;
2319 
2320   // We can fetch the length directly through an AllocateArrayNode.
2321   // This works even if the length is not constant (clone or newArray).
2322   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2323     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2324     if (alloc != NULL) {
2325       Node* allocated_length = alloc->Ideal_length();
2326       Node* len = alloc->make_ideal_length(tary, phase);
2327       if (allocated_length != len) {
2328         // New CastII improves on this.
2329         return len;
2330       }
2331     }
2332   }
2333 
2334   return NULL;
2335 }
2336 
2337 //------------------------------Identity---------------------------------------
2338 // Feed through the length in AllocateArray(...length...)._length.
2339 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2340   Node* x = LoadINode::Identity(phase);
2341   if (x != this)  return x;
2342 
2343   // Take apart the address into an oop and and offset.
2344   // Return 'this' if we cannot.
2345   Node*    adr    = in(MemNode::Address);
2346   intptr_t offset = 0;
2347   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2348   if (base == NULL)     return this;
2349   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2350   if (tary == NULL)     return this;
2351 
2352   // We can fetch the length directly through an AllocateArrayNode.
2353   // This works even if the length is not constant (clone or newArray).
2354   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2355     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2356     if (alloc != NULL) {
2357       Node* allocated_length = alloc->Ideal_length();
2358       // Do not allow make_ideal_length to allocate a CastII node.
2359       Node* len = alloc->make_ideal_length(tary, phase, false);
2360       if (allocated_length == len) {
2361         // Return allocated_length only if it would not be improved by a CastII.
2362         return allocated_length;
2363       }
2364     }
2365   }
2366 
2367   return this;
2368 
2369 }
2370 
2371 //=============================================================================
2372 //---------------------------StoreNode::make-----------------------------------
2373 // Polymorphic factory method:
2374 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2375   assert((mo == unordered || mo == release), "unexpected");
2376   Compile* C = gvn.C;
2377   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2378          ctl != NULL, "raw memory operations should have control edge");
2379 
2380   switch (bt) {
2381   case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2382   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2383   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2384   case T_CHAR:
2385   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2386   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2387   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2388   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2389   case T_METADATA:
2390   case T_ADDRESS:
2391   case T_OBJECT:
2392 #ifdef _LP64
2393     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2394       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2395       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2396     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2397                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2398                 adr->bottom_type()->isa_rawptr())) {
2399       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2400       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2401     }
2402 #endif
2403     {
2404       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2405     }
2406   default:
2407     ShouldNotReachHere();
2408     return (StoreNode*)NULL;
2409   }
2410 }
2411 
2412 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2413   bool require_atomic = true;
2414   return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2415 }
2416 
2417 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2418   bool require_atomic = true;
2419   return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2420 }
2421 
2422 
2423 //--------------------------bottom_type----------------------------------------
2424 const Type *StoreNode::bottom_type() const {
2425   return Type::MEMORY;
2426 }
2427 
2428 //------------------------------hash-------------------------------------------
2429 uint StoreNode::hash() const {
2430   // unroll addition of interesting fields
2431   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2432 
2433   // Since they are not commoned, do not hash them:
2434   return NO_HASH;
2435 }
2436 
2437 //------------------------------Ideal------------------------------------------
2438 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2439 // When a store immediately follows a relevant allocation/initialization,
2440 // try to capture it into the initialization, or hoist it above.
2441 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2442   Node* p = MemNode::Ideal_common(phase, can_reshape);
2443   if (p)  return (p == NodeSentinel) ? NULL : p;
2444 
2445   Node* mem     = in(MemNode::Memory);
2446   Node* address = in(MemNode::Address);
2447   // Back-to-back stores to same address?  Fold em up.  Generally
2448   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2449   // since they must follow each StoreP operation.  Redundant StoreCMs
2450   // are eliminated just before matching in final_graph_reshape.
2451   {
2452     Node* st = mem;
2453     // If Store 'st' has more than one use, we cannot fold 'st' away.
2454     // For example, 'st' might be the final state at a conditional
2455     // return.  Or, 'st' might be used by some node which is live at
2456     // the same time 'st' is live, which might be unschedulable.  So,
2457     // require exactly ONE user until such time as we clone 'mem' for
2458     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2459     // true).
2460     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2461       // Looking at a dead closed cycle of memory?
2462       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2463       assert(Opcode() == st->Opcode() ||
2464              st->Opcode() == Op_StoreVector ||
2465              Opcode() == Op_StoreVector ||
2466              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2467              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2468              (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2469              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2470              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2471 
2472       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2473           st->as_Store()->memory_size() <= this->memory_size()) {
2474         Node* use = st->raw_out(0);
2475         phase->igvn_rehash_node_delayed(use);
2476         if (can_reshape) {
2477           use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase->is_IterGVN());
2478         } else {
2479           // It's OK to do this in the parser, since DU info is always accurate,
2480           // and the parser always refers to nodes via SafePointNode maps.
2481           use->set_req(MemNode::Memory, st->in(MemNode::Memory));
2482         }
2483         return this;
2484       }
2485       st = st->in(MemNode::Memory);
2486     }
2487   }
2488 
2489 
2490   // Capture an unaliased, unconditional, simple store into an initializer.
2491   // Or, if it is independent of the allocation, hoist it above the allocation.
2492   if (ReduceFieldZeroing && /*can_reshape &&*/
2493       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2494     InitializeNode* init = mem->in(0)->as_Initialize();
2495     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2496     if (offset > 0) {
2497       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2498       // If the InitializeNode captured me, it made a raw copy of me,
2499       // and I need to disappear.
2500       if (moved != NULL) {
2501         // %%% hack to ensure that Ideal returns a new node:
2502         mem = MergeMemNode::make(mem);
2503         return mem;             // fold me away
2504       }
2505     }
2506   }
2507 
2508   return NULL;                  // No further progress
2509 }
2510 
2511 //------------------------------Value-----------------------------------------
2512 const Type* StoreNode::Value(PhaseGVN* phase) const {
2513   // Either input is TOP ==> the result is TOP
2514   const Type *t1 = phase->type( in(MemNode::Memory) );
2515   if( t1 == Type::TOP ) return Type::TOP;
2516   const Type *t2 = phase->type( in(MemNode::Address) );
2517   if( t2 == Type::TOP ) return Type::TOP;
2518   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2519   if( t3 == Type::TOP ) return Type::TOP;
2520   return Type::MEMORY;
2521 }
2522 
2523 //------------------------------Identity---------------------------------------
2524 // Remove redundant stores:
2525 //   Store(m, p, Load(m, p)) changes to m.
2526 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2527 Node* StoreNode::Identity(PhaseGVN* phase) {
2528   Node* mem = in(MemNode::Memory);
2529   Node* adr = in(MemNode::Address);
2530   Node* val = in(MemNode::ValueIn);
2531 
2532   Node* result = this;
2533 
2534   // Load then Store?  Then the Store is useless
2535   if (val->is_Load() &&
2536       val->in(MemNode::Address)->eqv_uncast(adr) &&
2537       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2538       val->as_Load()->store_Opcode() == Opcode()) {
2539     result = mem;
2540   }
2541 
2542   // Two stores in a row of the same value?
2543   if (result == this &&
2544       mem->is_Store() &&
2545       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2546       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2547       mem->Opcode() == Opcode()) {
2548     result = mem;
2549   }
2550 
2551   // Store of zero anywhere into a freshly-allocated object?
2552   // Then the store is useless.
2553   // (It must already have been captured by the InitializeNode.)
2554   if (result == this &&
2555       ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2556     // a newly allocated object is already all-zeroes everywhere
2557     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2558       result = mem;
2559     }
2560 
2561     if (result == this) {
2562       // the store may also apply to zero-bits in an earlier object
2563       Node* prev_mem = find_previous_store(phase);
2564       // Steps (a), (b):  Walk past independent stores to find an exact match.
2565       if (prev_mem != NULL) {
2566         Node* prev_val = can_see_stored_value(prev_mem, phase);
2567         if (prev_val != NULL && phase->eqv(prev_val, val)) {
2568           // prev_val and val might differ by a cast; it would be good
2569           // to keep the more informative of the two.
2570           result = mem;
2571         }
2572       }
2573     }
2574   }
2575 
2576   if (result != this && phase->is_IterGVN() != NULL) {
2577     MemBarNode* trailing = trailing_membar();
2578     if (trailing != NULL) {
2579 #ifdef ASSERT
2580       const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2581       assert(t_oop == NULL || t_oop->is_known_instance_field(), "only for non escaping objects");
2582 #endif
2583       PhaseIterGVN* igvn = phase->is_IterGVN();
2584       trailing->remove(igvn);
2585     }
2586   }
2587 
2588   return result;
2589 }
2590 
2591 //------------------------------match_edge-------------------------------------
2592 // Do we Match on this edge index or not?  Match only memory & value
2593 uint StoreNode::match_edge(uint idx) const {
2594   return idx == MemNode::Address || idx == MemNode::ValueIn;
2595 }
2596 
2597 //------------------------------cmp--------------------------------------------
2598 // Do not common stores up together.  They generally have to be split
2599 // back up anyways, so do not bother.
2600 uint StoreNode::cmp( const Node &n ) const {
2601   return (&n == this);          // Always fail except on self
2602 }
2603 
2604 //------------------------------Ideal_masked_input-----------------------------
2605 // Check for a useless mask before a partial-word store
2606 // (StoreB ... (AndI valIn conIa) )
2607 // If (conIa & mask == mask) this simplifies to
2608 // (StoreB ... (valIn) )
2609 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2610   Node *val = in(MemNode::ValueIn);
2611   if( val->Opcode() == Op_AndI ) {
2612     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2613     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2614       set_req(MemNode::ValueIn, val->in(1));
2615       return this;
2616     }
2617   }
2618   return NULL;
2619 }
2620 
2621 
2622 //------------------------------Ideal_sign_extended_input----------------------
2623 // Check for useless sign-extension before a partial-word store
2624 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2625 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2626 // (StoreB ... (valIn) )
2627 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2628   Node *val = in(MemNode::ValueIn);
2629   if( val->Opcode() == Op_RShiftI ) {
2630     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2631     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2632       Node *shl = val->in(1);
2633       if( shl->Opcode() == Op_LShiftI ) {
2634         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2635         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2636           set_req(MemNode::ValueIn, shl->in(1));
2637           return this;
2638         }
2639       }
2640     }
2641   }
2642   return NULL;
2643 }
2644 
2645 //------------------------------value_never_loaded-----------------------------------
2646 // Determine whether there are any possible loads of the value stored.
2647 // For simplicity, we actually check if there are any loads from the
2648 // address stored to, not just for loads of the value stored by this node.
2649 //
2650 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2651   Node *adr = in(Address);
2652   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2653   if (adr_oop == NULL)
2654     return false;
2655   if (!adr_oop->is_known_instance_field())
2656     return false; // if not a distinct instance, there may be aliases of the address
2657   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2658     Node *use = adr->fast_out(i);
2659     if (use->is_Load() || use->is_LoadStore()) {
2660       return false;
2661     }
2662   }
2663   return true;
2664 }
2665 
2666 MemBarNode* StoreNode::trailing_membar() const {
2667   if (is_release()) {
2668     MemBarNode* trailing_mb = NULL;
2669     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2670       Node* u = fast_out(i);
2671       if (u->is_MemBar()) {
2672         if (u->as_MemBar()->trailing_store()) {
2673           assert(u->Opcode() == Op_MemBarVolatile, "");
2674           assert(trailing_mb == NULL, "only one");
2675           trailing_mb = u->as_MemBar();
2676 #ifdef ASSERT
2677           Node* leading = u->as_MemBar()->leading_membar();
2678           assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2679           assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2680           assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2681 #endif
2682         } else {
2683           assert(u->as_MemBar()->standalone(), "");
2684         }
2685       }
2686     }
2687     return trailing_mb;
2688   }
2689   return NULL;
2690 }
2691 
2692 
2693 //=============================================================================
2694 //------------------------------Ideal------------------------------------------
2695 // If the store is from an AND mask that leaves the low bits untouched, then
2696 // we can skip the AND operation.  If the store is from a sign-extension
2697 // (a left shift, then right shift) we can skip both.
2698 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2699   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2700   if( progress != NULL ) return progress;
2701 
2702   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2703   if( progress != NULL ) return progress;
2704 
2705   // Finally check the default case
2706   return StoreNode::Ideal(phase, can_reshape);
2707 }
2708 
2709 //=============================================================================
2710 //------------------------------Ideal------------------------------------------
2711 // If the store is from an AND mask that leaves the low bits untouched, then
2712 // we can skip the AND operation
2713 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2714   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2715   if( progress != NULL ) return progress;
2716 
2717   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2718   if( progress != NULL ) return progress;
2719 
2720   // Finally check the default case
2721   return StoreNode::Ideal(phase, can_reshape);
2722 }
2723 
2724 //=============================================================================
2725 //------------------------------Identity---------------------------------------
2726 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2727   // No need to card mark when storing a null ptr
2728   Node* my_store = in(MemNode::OopStore);
2729   if (my_store->is_Store()) {
2730     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2731     if( t1 == TypePtr::NULL_PTR ) {
2732       return in(MemNode::Memory);
2733     }
2734   }
2735   return this;
2736 }
2737 
2738 //=============================================================================
2739 //------------------------------Ideal---------------------------------------
2740 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2741   Node* progress = StoreNode::Ideal(phase, can_reshape);
2742   if (progress != NULL) return progress;
2743 
2744   Node* my_store = in(MemNode::OopStore);
2745   if (my_store->is_MergeMem()) {
2746     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2747     set_req(MemNode::OopStore, mem);
2748     return this;
2749   }
2750 
2751   return NULL;
2752 }
2753 
2754 //------------------------------Value-----------------------------------------
2755 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
2756   // Either input is TOP ==> the result is TOP
2757   const Type *t = phase->type( in(MemNode::Memory) );
2758   if( t == Type::TOP ) return Type::TOP;
2759   t = phase->type( in(MemNode::Address) );
2760   if( t == Type::TOP ) return Type::TOP;
2761   t = phase->type( in(MemNode::ValueIn) );
2762   if( t == Type::TOP ) return Type::TOP;
2763   // If extra input is TOP ==> the result is TOP
2764   t = phase->type( in(MemNode::OopStore) );
2765   if( t == Type::TOP ) return Type::TOP;
2766 
2767   return StoreNode::Value( phase );
2768 }
2769 
2770 
2771 //=============================================================================
2772 //----------------------------------SCMemProjNode------------------------------
2773 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
2774 {
2775   return bottom_type();
2776 }
2777 
2778 //=============================================================================
2779 //----------------------------------LoadStoreNode------------------------------
2780 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2781   : Node(required),
2782     _type(rt),
2783     _adr_type(at)
2784 {
2785   init_req(MemNode::Control, c  );
2786   init_req(MemNode::Memory , mem);
2787   init_req(MemNode::Address, adr);
2788   init_req(MemNode::ValueIn, val);
2789   init_class_id(Class_LoadStore);
2790 }
2791 
2792 uint LoadStoreNode::ideal_reg() const {
2793   return _type->ideal_reg();
2794 }
2795 
2796 bool LoadStoreNode::result_not_used() const {
2797   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2798     Node *x = fast_out(i);
2799     if (x->Opcode() == Op_SCMemProj) continue;
2800     return false;
2801   }
2802   return true;
2803 }
2804 
2805 MemBarNode* LoadStoreNode::trailing_membar() const {
2806   MemBarNode* trailing = NULL;
2807   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2808     Node* u = fast_out(i);
2809     if (u->is_MemBar()) {
2810       if (u->as_MemBar()->trailing_load_store()) {
2811         assert(u->Opcode() == Op_MemBarAcquire, "");
2812         assert(trailing == NULL, "only one");
2813         trailing = u->as_MemBar();
2814 #ifdef ASSERT
2815         Node* leading = trailing->leading_membar();
2816         assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2817         assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
2818         assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
2819 #endif
2820       } else {
2821         assert(u->as_MemBar()->standalone(), "wrong barrier kind");
2822       }
2823     }
2824   }
2825 
2826   return trailing;
2827 }
2828 
2829 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2830 
2831 //=============================================================================
2832 //----------------------------------LoadStoreConditionalNode--------------------
2833 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2834   init_req(ExpectedIn, ex );
2835 }
2836 
2837 //=============================================================================
2838 //-------------------------------adr_type--------------------------------------
2839 const TypePtr* ClearArrayNode::adr_type() const {
2840   Node *adr = in(3);
2841   if (adr == NULL)  return NULL; // node is dead
2842   return MemNode::calculate_adr_type(adr->bottom_type());
2843 }
2844 
2845 //------------------------------match_edge-------------------------------------
2846 // Do we Match on this edge index or not?  Do not match memory
2847 uint ClearArrayNode::match_edge(uint idx) const {
2848   return idx > 1;
2849 }
2850 
2851 //------------------------------Identity---------------------------------------
2852 // Clearing a zero length array does nothing
2853 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
2854   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2855 }
2856 
2857 //------------------------------Idealize---------------------------------------
2858 // Clearing a short array is faster with stores
2859 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2860   // Already know this is a large node, do not try to ideal it
2861   if (!IdealizeClearArrayNode || _is_large) return NULL;
2862 
2863   const int unit = BytesPerLong;
2864   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2865   if (!t)  return NULL;
2866   if (!t->is_con())  return NULL;
2867   intptr_t raw_count = t->get_con();
2868   intptr_t size = raw_count;
2869   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2870   // Clearing nothing uses the Identity call.
2871   // Negative clears are possible on dead ClearArrays
2872   // (see jck test stmt114.stmt11402.val).
2873   if (size <= 0 || size % unit != 0)  return NULL;
2874   intptr_t count = size / unit;
2875   // Length too long; communicate this to matchers and assemblers.
2876   // Assemblers are responsible to produce fast hardware clears for it.
2877   if (size > InitArrayShortSize) {
2878     return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
2879   }
2880   Node *mem = in(1);
2881   if( phase->type(mem)==Type::TOP ) return NULL;
2882   Node *adr = in(3);
2883   const Type* at = phase->type(adr);
2884   if( at==Type::TOP ) return NULL;
2885   const TypePtr* atp = at->isa_ptr();
2886   // adjust atp to be the correct array element address type
2887   if (atp == NULL)  atp = TypePtr::BOTTOM;
2888   else              atp = atp->add_offset(Type::OffsetBot);
2889   // Get base for derived pointer purposes
2890   if( adr->Opcode() != Op_AddP ) Unimplemented();
2891   Node *base = adr->in(1);
2892 
2893   Node *zero = phase->makecon(TypeLong::ZERO);
2894   Node *off  = phase->MakeConX(BytesPerLong);
2895   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2896   count--;
2897   while( count-- ) {
2898     mem = phase->transform(mem);
2899     adr = phase->transform(new AddPNode(base,adr,off));
2900     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2901   }
2902   return mem;
2903 }
2904 
2905 //----------------------------step_through----------------------------------
2906 // Return allocation input memory edge if it is different instance
2907 // or itself if it is the one we are looking for.
2908 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2909   Node* n = *np;
2910   assert(n->is_ClearArray(), "sanity");
2911   intptr_t offset;
2912   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2913   // This method is called only before Allocate nodes are expanded
2914   // during macro nodes expansion. Before that ClearArray nodes are
2915   // only generated in PhaseMacroExpand::generate_arraycopy() (before
2916   // Allocate nodes are expanded) which follows allocations.
2917   assert(alloc != NULL, "should have allocation");
2918   if (alloc->_idx == instance_id) {
2919     // Can not bypass initialization of the instance we are looking for.
2920     return false;
2921   }
2922   // Otherwise skip it.
2923   InitializeNode* init = alloc->initialization();
2924   if (init != NULL)
2925     *np = init->in(TypeFunc::Memory);
2926   else
2927     *np = alloc->in(TypeFunc::Memory);
2928   return true;
2929 }
2930 
2931 //----------------------------clear_memory-------------------------------------
2932 // Generate code to initialize object storage to zero.
2933 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2934                                    intptr_t start_offset,
2935                                    Node* end_offset,
2936                                    PhaseGVN* phase) {
2937   intptr_t offset = start_offset;
2938 
2939   int unit = BytesPerLong;
2940   if ((offset % unit) != 0) {
2941     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
2942     adr = phase->transform(adr);
2943     const TypePtr* atp = TypeRawPtr::BOTTOM;
2944     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2945     mem = phase->transform(mem);
2946     offset += BytesPerInt;
2947   }
2948   assert((offset % unit) == 0, "");
2949 
2950   // Initialize the remaining stuff, if any, with a ClearArray.
2951   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2952 }
2953 
2954 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2955                                    Node* start_offset,
2956                                    Node* end_offset,
2957                                    PhaseGVN* phase) {
2958   if (start_offset == end_offset) {
2959     // nothing to do
2960     return mem;
2961   }
2962 
2963   int unit = BytesPerLong;
2964   Node* zbase = start_offset;
2965   Node* zend  = end_offset;
2966 
2967   // Scale to the unit required by the CPU:
2968   if (!Matcher::init_array_count_is_in_bytes) {
2969     Node* shift = phase->intcon(exact_log2(unit));
2970     zbase = phase->transform(new URShiftXNode(zbase, shift) );
2971     zend  = phase->transform(new URShiftXNode(zend,  shift) );
2972   }
2973 
2974   // Bulk clear double-words
2975   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
2976   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
2977   mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
2978   return phase->transform(mem);
2979 }
2980 
2981 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2982                                    intptr_t start_offset,
2983                                    intptr_t end_offset,
2984                                    PhaseGVN* phase) {
2985   if (start_offset == end_offset) {
2986     // nothing to do
2987     return mem;
2988   }
2989 
2990   assert((end_offset % BytesPerInt) == 0, "odd end offset");
2991   intptr_t done_offset = end_offset;
2992   if ((done_offset % BytesPerLong) != 0) {
2993     done_offset -= BytesPerInt;
2994   }
2995   if (done_offset > start_offset) {
2996     mem = clear_memory(ctl, mem, dest,
2997                        start_offset, phase->MakeConX(done_offset), phase);
2998   }
2999   if (done_offset < end_offset) { // emit the final 32-bit store
3000     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3001     adr = phase->transform(adr);
3002     const TypePtr* atp = TypeRawPtr::BOTTOM;
3003     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3004     mem = phase->transform(mem);
3005     done_offset += BytesPerInt;
3006   }
3007   assert(done_offset == end_offset, "");
3008   return mem;
3009 }
3010 
3011 //=============================================================================
3012 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3013   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
3014     _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3015 #ifdef ASSERT
3016   , _pair_idx(0)
3017 #endif
3018 {
3019   init_class_id(Class_MemBar);
3020   Node* top = C->top();
3021   init_req(TypeFunc::I_O,top);
3022   init_req(TypeFunc::FramePtr,top);
3023   init_req(TypeFunc::ReturnAdr,top);
3024   if (precedent != NULL)
3025     init_req(TypeFunc::Parms, precedent);
3026 }
3027 
3028 //------------------------------cmp--------------------------------------------
3029 uint MemBarNode::hash() const { return NO_HASH; }
3030 uint MemBarNode::cmp( const Node &n ) const {
3031   return (&n == this);          // Always fail except on self
3032 }
3033 
3034 //------------------------------make-------------------------------------------
3035 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3036   switch (opcode) {
3037   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
3038   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
3039   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
3040   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
3041   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3042   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3043   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
3044   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
3045   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
3046   case Op_Initialize:        return new InitializeNode(C, atp, pn);
3047   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
3048   default: ShouldNotReachHere(); return NULL;
3049   }
3050 }
3051 
3052 void MemBarNode::remove(PhaseIterGVN *igvn) {
3053   if (outcnt() != 2) {
3054     return;
3055   }
3056   if (trailing_store() || trailing_load_store()) {
3057     MemBarNode* leading = leading_membar();
3058     if (leading != NULL) {
3059       assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3060       leading->remove(igvn);
3061     }
3062   }
3063   igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3064   igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3065 }
3066 
3067 //------------------------------Ideal------------------------------------------
3068 // Return a node which is more "ideal" than the current node.  Strip out
3069 // control copies
3070 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3071   if (remove_dead_region(phase, can_reshape)) return this;
3072   // Don't bother trying to transform a dead node
3073   if (in(0) && in(0)->is_top()) {
3074     return NULL;
3075   }
3076 
3077 #if INCLUDE_ZGC
3078   if (UseZGC) {
3079     if (req() == (Precedent+1) && in(MemBarNode::Precedent)->in(0) != NULL && in(MemBarNode::Precedent)->in(0)->is_LoadBarrier()) {
3080       Node* load_node = in(MemBarNode::Precedent)->in(0)->in(LoadBarrierNode::Oop);
3081       set_req(MemBarNode::Precedent, load_node);
3082       return this;
3083     }
3084   }
3085 #endif
3086 
3087   bool progress = false;
3088   // Eliminate volatile MemBars for scalar replaced objects.
3089   if (can_reshape && req() == (Precedent+1)) {
3090     bool eliminate = false;
3091     int opc = Opcode();
3092     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3093       // Volatile field loads and stores.
3094       Node* my_mem = in(MemBarNode::Precedent);
3095       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3096       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3097         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3098         // replace this Precedent (decodeN) with the Load instead.
3099         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
3100           Node* load_node = my_mem->in(1);
3101           set_req(MemBarNode::Precedent, load_node);
3102           phase->is_IterGVN()->_worklist.push(my_mem);
3103           my_mem = load_node;
3104         } else {
3105           assert(my_mem->unique_out() == this, "sanity");
3106           del_req(Precedent);
3107           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3108           my_mem = NULL;
3109         }
3110         progress = true;
3111       }
3112       if (my_mem != NULL && my_mem->is_Mem()) {
3113         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3114         // Check for scalar replaced object reference.
3115         if( t_oop != NULL && t_oop->is_known_instance_field() &&
3116             t_oop->offset() != Type::OffsetBot &&
3117             t_oop->offset() != Type::OffsetTop) {
3118           eliminate = true;
3119         }
3120       }
3121     } else if (opc == Op_MemBarRelease) {
3122       // Final field stores.
3123       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
3124       if ((alloc != NULL) && alloc->is_Allocate() &&
3125           alloc->as_Allocate()->does_not_escape_thread()) {
3126         // The allocated object does not escape.
3127         eliminate = true;
3128       }
3129     }
3130     if (eliminate) {
3131       // Replace MemBar projections by its inputs.
3132       PhaseIterGVN* igvn = phase->is_IterGVN();
3133       remove(igvn);
3134       // Must return either the original node (now dead) or a new node
3135       // (Do not return a top here, since that would break the uniqueness of top.)
3136       return new ConINode(TypeInt::ZERO);
3137     }
3138   }
3139   return progress ? this : NULL;
3140 }
3141 
3142 //------------------------------Value------------------------------------------
3143 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3144   if( !in(0) ) return Type::TOP;
3145   if( phase->type(in(0)) == Type::TOP )
3146     return Type::TOP;
3147   return TypeTuple::MEMBAR;
3148 }
3149 
3150 //------------------------------match------------------------------------------
3151 // Construct projections for memory.
3152 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3153   switch (proj->_con) {
3154   case TypeFunc::Control:
3155   case TypeFunc::Memory:
3156     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3157   }
3158   ShouldNotReachHere();
3159   return NULL;
3160 }
3161 
3162 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3163   trailing->_kind = TrailingStore;
3164   leading->_kind = LeadingStore;
3165 #ifdef ASSERT
3166   trailing->_pair_idx = leading->_idx;
3167   leading->_pair_idx = leading->_idx;
3168 #endif
3169 }
3170 
3171 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3172   trailing->_kind = TrailingLoadStore;
3173   leading->_kind = LeadingLoadStore;
3174 #ifdef ASSERT
3175   trailing->_pair_idx = leading->_idx;
3176   leading->_pair_idx = leading->_idx;
3177 #endif
3178 }
3179 
3180 MemBarNode* MemBarNode::trailing_membar() const {
3181   ResourceMark rm;
3182   Node* trailing = (Node*)this;
3183   VectorSet seen(Thread::current()->resource_area());
3184   Node_Stack multis(0);
3185   do {
3186     Node* c = trailing;
3187     uint i = 0;
3188     do {
3189       trailing = NULL;
3190       for (; i < c->outcnt(); i++) {
3191         Node* next = c->raw_out(i);
3192         if (next != c && next->is_CFG()) {
3193           if (c->is_MultiBranch()) {
3194             if (multis.node() == c) {
3195               multis.set_index(i+1);
3196             } else {
3197               multis.push(c, i+1);
3198             }
3199           }
3200           trailing = next;
3201           break;
3202         }
3203       }
3204       if (trailing != NULL && !seen.test_set(trailing->_idx)) {
3205         break;
3206       }
3207       while (multis.size() > 0) {
3208         c = multis.node();
3209         i = multis.index();
3210         if (i < c->req()) {
3211           break;
3212         }
3213         multis.pop();
3214       }
3215     } while (multis.size() > 0);
3216   } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3217 
3218   MemBarNode* mb = trailing->as_MemBar();
3219   assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3220          (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3221   assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3222   return mb;
3223 }
3224 
3225 MemBarNode* MemBarNode::leading_membar() const {
3226   ResourceMark rm;
3227   VectorSet seen(Thread::current()->resource_area());
3228   Node_Stack regions(0);
3229   Node* leading = in(0);
3230   while (leading != NULL && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3231     while (leading == NULL || leading->is_top() || seen.test_set(leading->_idx)) {
3232       leading = NULL;
3233       while (regions.size() > 0) {
3234         Node* r = regions.node();
3235         uint i = regions.index();
3236         if (i < r->req()) {
3237           leading = r->in(i);
3238           regions.set_index(i+1);
3239         } else {
3240           regions.pop();
3241         }
3242       }
3243       if (leading == NULL) {
3244         assert(regions.size() == 0, "all paths should have been tried");
3245         return NULL;
3246       }
3247     }
3248     if (leading->is_Region()) {
3249       regions.push(leading, 2);
3250       leading = leading->in(1);
3251     } else {
3252       leading = leading->in(0);
3253     }
3254   }
3255 #ifdef ASSERT
3256   Unique_Node_List wq;
3257   wq.push((Node*)this);
3258   uint found = 0;
3259   for (uint i = 0; i < wq.size(); i++) {
3260     Node* n = wq.at(i);
3261     if (n->is_Region()) {
3262       for (uint j = 1; j < n->req(); j++) {
3263         Node* in = n->in(j);
3264         if (in != NULL && !in->is_top()) {
3265           wq.push(in);
3266         }
3267       }
3268     } else {
3269       if (n->is_MemBar() && n->as_MemBar()->leading()) {
3270         assert(n == leading, "consistency check failed");
3271         found++;
3272       } else {
3273         Node* in = n->in(0);
3274         if (in != NULL && !in->is_top()) {
3275           wq.push(in);
3276         }
3277       }
3278     }
3279   }
3280   assert(found == 1 || (found == 0 && leading == NULL), "consistency check failed");
3281 #endif
3282   if (leading == NULL) {
3283     return NULL;
3284   }
3285   MemBarNode* mb = leading->as_MemBar();
3286   assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3287          (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3288   assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3289   return mb;
3290 }
3291 
3292 //===========================InitializeNode====================================
3293 // SUMMARY:
3294 // This node acts as a memory barrier on raw memory, after some raw stores.
3295 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3296 // The Initialize can 'capture' suitably constrained stores as raw inits.
3297 // It can coalesce related raw stores into larger units (called 'tiles').
3298 // It can avoid zeroing new storage for memory units which have raw inits.
3299 // At macro-expansion, it is marked 'complete', and does not optimize further.
3300 //
3301 // EXAMPLE:
3302 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3303 //   ctl = incoming control; mem* = incoming memory
3304 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3305 // First allocate uninitialized memory and fill in the header:
3306 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3307 //   ctl := alloc.Control; mem* := alloc.Memory*
3308 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3309 // Then initialize to zero the non-header parts of the raw memory block:
3310 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3311 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3312 // After the initialize node executes, the object is ready for service:
3313 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3314 // Suppose its body is immediately initialized as {1,2}:
3315 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3316 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3317 //   mem.SLICE(#short[*]) := store2
3318 //
3319 // DETAILS:
3320 // An InitializeNode collects and isolates object initialization after
3321 // an AllocateNode and before the next possible safepoint.  As a
3322 // memory barrier (MemBarNode), it keeps critical stores from drifting
3323 // down past any safepoint or any publication of the allocation.
3324 // Before this barrier, a newly-allocated object may have uninitialized bits.
3325 // After this barrier, it may be treated as a real oop, and GC is allowed.
3326 //
3327 // The semantics of the InitializeNode include an implicit zeroing of
3328 // the new object from object header to the end of the object.
3329 // (The object header and end are determined by the AllocateNode.)
3330 //
3331 // Certain stores may be added as direct inputs to the InitializeNode.
3332 // These stores must update raw memory, and they must be to addresses
3333 // derived from the raw address produced by AllocateNode, and with
3334 // a constant offset.  They must be ordered by increasing offset.
3335 // The first one is at in(RawStores), the last at in(req()-1).
3336 // Unlike most memory operations, they are not linked in a chain,
3337 // but are displayed in parallel as users of the rawmem output of
3338 // the allocation.
3339 //
3340 // (See comments in InitializeNode::capture_store, which continue
3341 // the example given above.)
3342 //
3343 // When the associated Allocate is macro-expanded, the InitializeNode
3344 // may be rewritten to optimize collected stores.  A ClearArrayNode
3345 // may also be created at that point to represent any required zeroing.
3346 // The InitializeNode is then marked 'complete', prohibiting further
3347 // capturing of nearby memory operations.
3348 //
3349 // During macro-expansion, all captured initializations which store
3350 // constant values of 32 bits or smaller are coalesced (if advantageous)
3351 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3352 // initialized in fewer memory operations.  Memory words which are
3353 // covered by neither tiles nor non-constant stores are pre-zeroed
3354 // by explicit stores of zero.  (The code shape happens to do all
3355 // zeroing first, then all other stores, with both sequences occurring
3356 // in order of ascending offsets.)
3357 //
3358 // Alternatively, code may be inserted between an AllocateNode and its
3359 // InitializeNode, to perform arbitrary initialization of the new object.
3360 // E.g., the object copying intrinsics insert complex data transfers here.
3361 // The initialization must then be marked as 'complete' disable the
3362 // built-in zeroing semantics and the collection of initializing stores.
3363 //
3364 // While an InitializeNode is incomplete, reads from the memory state
3365 // produced by it are optimizable if they match the control edge and
3366 // new oop address associated with the allocation/initialization.
3367 // They return a stored value (if the offset matches) or else zero.
3368 // A write to the memory state, if it matches control and address,
3369 // and if it is to a constant offset, may be 'captured' by the
3370 // InitializeNode.  It is cloned as a raw memory operation and rewired
3371 // inside the initialization, to the raw oop produced by the allocation.
3372 // Operations on addresses which are provably distinct (e.g., to
3373 // other AllocateNodes) are allowed to bypass the initialization.
3374 //
3375 // The effect of all this is to consolidate object initialization
3376 // (both arrays and non-arrays, both piecewise and bulk) into a
3377 // single location, where it can be optimized as a unit.
3378 //
3379 // Only stores with an offset less than TrackedInitializationLimit words
3380 // will be considered for capture by an InitializeNode.  This puts a
3381 // reasonable limit on the complexity of optimized initializations.
3382 
3383 //---------------------------InitializeNode------------------------------------
3384 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3385   : MemBarNode(C, adr_type, rawoop),
3386     _is_complete(Incomplete), _does_not_escape(false)
3387 {
3388   init_class_id(Class_Initialize);
3389 
3390   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3391   assert(in(RawAddress) == rawoop, "proper init");
3392   // Note:  allocation() can be NULL, for secondary initialization barriers
3393 }
3394 
3395 // Since this node is not matched, it will be processed by the
3396 // register allocator.  Declare that there are no constraints
3397 // on the allocation of the RawAddress edge.
3398 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3399   // This edge should be set to top, by the set_complete.  But be conservative.
3400   if (idx == InitializeNode::RawAddress)
3401     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3402   return RegMask::Empty;
3403 }
3404 
3405 Node* InitializeNode::memory(uint alias_idx) {
3406   Node* mem = in(Memory);
3407   if (mem->is_MergeMem()) {
3408     return mem->as_MergeMem()->memory_at(alias_idx);
3409   } else {
3410     // incoming raw memory is not split
3411     return mem;
3412   }
3413 }
3414 
3415 bool InitializeNode::is_non_zero() {
3416   if (is_complete())  return false;
3417   remove_extra_zeroes();
3418   return (req() > RawStores);
3419 }
3420 
3421 void InitializeNode::set_complete(PhaseGVN* phase) {
3422   assert(!is_complete(), "caller responsibility");
3423   _is_complete = Complete;
3424 
3425   // After this node is complete, it contains a bunch of
3426   // raw-memory initializations.  There is no need for
3427   // it to have anything to do with non-raw memory effects.
3428   // Therefore, tell all non-raw users to re-optimize themselves,
3429   // after skipping the memory effects of this initialization.
3430   PhaseIterGVN* igvn = phase->is_IterGVN();
3431   if (igvn)  igvn->add_users_to_worklist(this);
3432 }
3433 
3434 // convenience function
3435 // return false if the init contains any stores already
3436 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3437   InitializeNode* init = initialization();
3438   if (init == NULL || init->is_complete())  return false;
3439   init->remove_extra_zeroes();
3440   // for now, if this allocation has already collected any inits, bail:
3441   if (init->is_non_zero())  return false;
3442   init->set_complete(phase);
3443   return true;
3444 }
3445 
3446 void InitializeNode::remove_extra_zeroes() {
3447   if (req() == RawStores)  return;
3448   Node* zmem = zero_memory();
3449   uint fill = RawStores;
3450   for (uint i = fill; i < req(); i++) {
3451     Node* n = in(i);
3452     if (n->is_top() || n == zmem)  continue;  // skip
3453     if (fill < i)  set_req(fill, n);          // compact
3454     ++fill;
3455   }
3456   // delete any empty spaces created:
3457   while (fill < req()) {
3458     del_req(fill);
3459   }
3460 }
3461 
3462 // Helper for remembering which stores go with which offsets.
3463 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3464   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3465   intptr_t offset = -1;
3466   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3467                                                phase, offset);
3468   if (base == NULL)     return -1;  // something is dead,
3469   if (offset < 0)       return -1;  //        dead, dead
3470   return offset;
3471 }
3472 
3473 // Helper for proving that an initialization expression is
3474 // "simple enough" to be folded into an object initialization.
3475 // Attempts to prove that a store's initial value 'n' can be captured
3476 // within the initialization without creating a vicious cycle, such as:
3477 //     { Foo p = new Foo(); p.next = p; }
3478 // True for constants and parameters and small combinations thereof.
3479 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3480   if (n == NULL)      return true;   // (can this really happen?)
3481   if (n->is_Proj())   n = n->in(0);
3482   if (n == this)      return false;  // found a cycle
3483   if (n->is_Con())    return true;
3484   if (n->is_Start())  return true;   // params, etc., are OK
3485   if (n->is_Root())   return true;   // even better
3486 
3487   Node* ctl = n->in(0);
3488   if (ctl != NULL && !ctl->is_top()) {
3489     if (ctl->is_Proj())  ctl = ctl->in(0);
3490     if (ctl == this)  return false;
3491 
3492     // If we already know that the enclosing memory op is pinned right after
3493     // the init, then any control flow that the store has picked up
3494     // must have preceded the init, or else be equal to the init.
3495     // Even after loop optimizations (which might change control edges)
3496     // a store is never pinned *before* the availability of its inputs.
3497     if (!MemNode::all_controls_dominate(n, this))
3498       return false;                  // failed to prove a good control
3499   }
3500 
3501   // Check data edges for possible dependencies on 'this'.
3502   if ((count += 1) > 20)  return false;  // complexity limit
3503   for (uint i = 1; i < n->req(); i++) {
3504     Node* m = n->in(i);
3505     if (m == NULL || m == n || m->is_top())  continue;
3506     uint first_i = n->find_edge(m);
3507     if (i != first_i)  continue;  // process duplicate edge just once
3508     if (!detect_init_independence(m, count)) {
3509       return false;
3510     }
3511   }
3512 
3513   return true;
3514 }
3515 
3516 // Here are all the checks a Store must pass before it can be moved into
3517 // an initialization.  Returns zero if a check fails.
3518 // On success, returns the (constant) offset to which the store applies,
3519 // within the initialized memory.
3520 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3521   const int FAIL = 0;
3522   if (st->is_unaligned_access()) {
3523     return FAIL;
3524   }
3525   if (st->req() != MemNode::ValueIn + 1)
3526     return FAIL;                // an inscrutable StoreNode (card mark?)
3527   Node* ctl = st->in(MemNode::Control);
3528   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3529     return FAIL;                // must be unconditional after the initialization
3530   Node* mem = st->in(MemNode::Memory);
3531   if (!(mem->is_Proj() && mem->in(0) == this))
3532     return FAIL;                // must not be preceded by other stores
3533   Node* adr = st->in(MemNode::Address);
3534   intptr_t offset;
3535   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3536   if (alloc == NULL)
3537     return FAIL;                // inscrutable address
3538   if (alloc != allocation())
3539     return FAIL;                // wrong allocation!  (store needs to float up)
3540   Node* val = st->in(MemNode::ValueIn);
3541   int complexity_count = 0;
3542   if (!detect_init_independence(val, complexity_count))
3543     return FAIL;                // stored value must be 'simple enough'
3544 
3545   // The Store can be captured only if nothing after the allocation
3546   // and before the Store is using the memory location that the store
3547   // overwrites.
3548   bool failed = false;
3549   // If is_complete_with_arraycopy() is true the shape of the graph is
3550   // well defined and is safe so no need for extra checks.
3551   if (!is_complete_with_arraycopy()) {
3552     // We are going to look at each use of the memory state following
3553     // the allocation to make sure nothing reads the memory that the
3554     // Store writes.
3555     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3556     int alias_idx = phase->C->get_alias_index(t_adr);
3557     ResourceMark rm;
3558     Unique_Node_List mems;
3559     mems.push(mem);
3560     Node* unique_merge = NULL;
3561     for (uint next = 0; next < mems.size(); ++next) {
3562       Node *m  = mems.at(next);
3563       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3564         Node *n = m->fast_out(j);
3565         if (n->outcnt() == 0) {
3566           continue;
3567         }
3568         if (n == st) {
3569           continue;
3570         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3571           // If the control of this use is different from the control
3572           // of the Store which is right after the InitializeNode then
3573           // this node cannot be between the InitializeNode and the
3574           // Store.
3575           continue;
3576         } else if (n->is_MergeMem()) {
3577           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3578             // We can hit a MergeMemNode (that will likely go away
3579             // later) that is a direct use of the memory state
3580             // following the InitializeNode on the same slice as the
3581             // store node that we'd like to capture. We need to check
3582             // the uses of the MergeMemNode.
3583             mems.push(n);
3584           }
3585         } else if (n->is_Mem()) {
3586           Node* other_adr = n->in(MemNode::Address);
3587           if (other_adr == adr) {
3588             failed = true;
3589             break;
3590           } else {
3591             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3592             if (other_t_adr != NULL) {
3593               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3594               if (other_alias_idx == alias_idx) {
3595                 // A load from the same memory slice as the store right
3596                 // after the InitializeNode. We check the control of the
3597                 // object/array that is loaded from. If it's the same as
3598                 // the store control then we cannot capture the store.
3599                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3600                 Node* base = other_adr;
3601                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3602                 base = base->in(AddPNode::Base);
3603                 if (base != NULL) {
3604                   base = base->uncast();
3605                   if (base->is_Proj() && base->in(0) == alloc) {
3606                     failed = true;
3607                     break;
3608                   }
3609                 }
3610               }
3611             }
3612           }
3613         } else {
3614           failed = true;
3615           break;
3616         }
3617       }
3618     }
3619   }
3620   if (failed) {
3621     if (!can_reshape) {
3622       // We decided we couldn't capture the store during parsing. We
3623       // should try again during the next IGVN once the graph is
3624       // cleaner.
3625       phase->C->record_for_igvn(st);
3626     }
3627     return FAIL;
3628   }
3629 
3630   return offset;                // success
3631 }
3632 
3633 // Find the captured store in(i) which corresponds to the range
3634 // [start..start+size) in the initialized object.
3635 // If there is one, return its index i.  If there isn't, return the
3636 // negative of the index where it should be inserted.
3637 // Return 0 if the queried range overlaps an initialization boundary
3638 // or if dead code is encountered.
3639 // If size_in_bytes is zero, do not bother with overlap checks.
3640 int InitializeNode::captured_store_insertion_point(intptr_t start,
3641                                                    int size_in_bytes,
3642                                                    PhaseTransform* phase) {
3643   const int FAIL = 0, MAX_STORE = BytesPerLong;
3644 
3645   if (is_complete())
3646     return FAIL;                // arraycopy got here first; punt
3647 
3648   assert(allocation() != NULL, "must be present");
3649 
3650   // no negatives, no header fields:
3651   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3652 
3653   // after a certain size, we bail out on tracking all the stores:
3654   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3655   if (start >= ti_limit)  return FAIL;
3656 
3657   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3658     if (i >= limit)  return -(int)i; // not found; here is where to put it
3659 
3660     Node*    st     = in(i);
3661     intptr_t st_off = get_store_offset(st, phase);
3662     if (st_off < 0) {
3663       if (st != zero_memory()) {
3664         return FAIL;            // bail out if there is dead garbage
3665       }
3666     } else if (st_off > start) {
3667       // ...we are done, since stores are ordered
3668       if (st_off < start + size_in_bytes) {
3669         return FAIL;            // the next store overlaps
3670       }
3671       return -(int)i;           // not found; here is where to put it
3672     } else if (st_off < start) {
3673       if (size_in_bytes != 0 &&
3674           start < st_off + MAX_STORE &&
3675           start < st_off + st->as_Store()->memory_size()) {
3676         return FAIL;            // the previous store overlaps
3677       }
3678     } else {
3679       if (size_in_bytes != 0 &&
3680           st->as_Store()->memory_size() != size_in_bytes) {
3681         return FAIL;            // mismatched store size
3682       }
3683       return i;
3684     }
3685 
3686     ++i;
3687   }
3688 }
3689 
3690 // Look for a captured store which initializes at the offset 'start'
3691 // with the given size.  If there is no such store, and no other
3692 // initialization interferes, then return zero_memory (the memory
3693 // projection of the AllocateNode).
3694 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3695                                           PhaseTransform* phase) {
3696   assert(stores_are_sane(phase), "");
3697   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3698   if (i == 0) {
3699     return NULL;                // something is dead
3700   } else if (i < 0) {
3701     return zero_memory();       // just primordial zero bits here
3702   } else {
3703     Node* st = in(i);           // here is the store at this position
3704     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3705     return st;
3706   }
3707 }
3708 
3709 // Create, as a raw pointer, an address within my new object at 'offset'.
3710 Node* InitializeNode::make_raw_address(intptr_t offset,
3711                                        PhaseTransform* phase) {
3712   Node* addr = in(RawAddress);
3713   if (offset != 0) {
3714     Compile* C = phase->C;
3715     addr = phase->transform( new AddPNode(C->top(), addr,
3716                                                  phase->MakeConX(offset)) );
3717   }
3718   return addr;
3719 }
3720 
3721 // Clone the given store, converting it into a raw store
3722 // initializing a field or element of my new object.
3723 // Caller is responsible for retiring the original store,
3724 // with subsume_node or the like.
3725 //
3726 // From the example above InitializeNode::InitializeNode,
3727 // here are the old stores to be captured:
3728 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3729 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3730 //
3731 // Here is the changed code; note the extra edges on init:
3732 //   alloc = (Allocate ...)
3733 //   rawoop = alloc.RawAddress
3734 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3735 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3736 //   init = (Initialize alloc.Control alloc.Memory rawoop
3737 //                      rawstore1 rawstore2)
3738 //
3739 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3740                                     PhaseTransform* phase, bool can_reshape) {
3741   assert(stores_are_sane(phase), "");
3742 
3743   if (start < 0)  return NULL;
3744   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3745 
3746   Compile* C = phase->C;
3747   int size_in_bytes = st->memory_size();
3748   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3749   if (i == 0)  return NULL;     // bail out
3750   Node* prev_mem = NULL;        // raw memory for the captured store
3751   if (i > 0) {
3752     prev_mem = in(i);           // there is a pre-existing store under this one
3753     set_req(i, C->top());       // temporarily disconnect it
3754     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3755   } else {
3756     i = -i;                     // no pre-existing store
3757     prev_mem = zero_memory();   // a slice of the newly allocated object
3758     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3759       set_req(--i, C->top());   // reuse this edge; it has been folded away
3760     else
3761       ins_req(i, C->top());     // build a new edge
3762   }
3763   Node* new_st = st->clone();
3764   new_st->set_req(MemNode::Control, in(Control));
3765   new_st->set_req(MemNode::Memory,  prev_mem);
3766   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3767   new_st = phase->transform(new_st);
3768 
3769   // At this point, new_st might have swallowed a pre-existing store
3770   // at the same offset, or perhaps new_st might have disappeared,
3771   // if it redundantly stored the same value (or zero to fresh memory).
3772 
3773   // In any case, wire it in:
3774   phase->igvn_rehash_node_delayed(this);
3775   set_req(i, new_st);
3776 
3777   // The caller may now kill the old guy.
3778   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3779   assert(check_st == new_st || check_st == NULL, "must be findable");
3780   assert(!is_complete(), "");
3781   return new_st;
3782 }
3783 
3784 static bool store_constant(jlong* tiles, int num_tiles,
3785                            intptr_t st_off, int st_size,
3786                            jlong con) {
3787   if ((st_off & (st_size-1)) != 0)
3788     return false;               // strange store offset (assume size==2**N)
3789   address addr = (address)tiles + st_off;
3790   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3791   switch (st_size) {
3792   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3793   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3794   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3795   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3796   default: return false;        // strange store size (detect size!=2**N here)
3797   }
3798   return true;                  // return success to caller
3799 }
3800 
3801 // Coalesce subword constants into int constants and possibly
3802 // into long constants.  The goal, if the CPU permits,
3803 // is to initialize the object with a small number of 64-bit tiles.
3804 // Also, convert floating-point constants to bit patterns.
3805 // Non-constants are not relevant to this pass.
3806 //
3807 // In terms of the running example on InitializeNode::InitializeNode
3808 // and InitializeNode::capture_store, here is the transformation
3809 // of rawstore1 and rawstore2 into rawstore12:
3810 //   alloc = (Allocate ...)
3811 //   rawoop = alloc.RawAddress
3812 //   tile12 = 0x00010002
3813 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3814 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3815 //
3816 void
3817 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3818                                         Node* size_in_bytes,
3819                                         PhaseGVN* phase) {
3820   Compile* C = phase->C;
3821 
3822   assert(stores_are_sane(phase), "");
3823   // Note:  After this pass, they are not completely sane,
3824   // since there may be some overlaps.
3825 
3826   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3827 
3828   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3829   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3830   size_limit = MIN2(size_limit, ti_limit);
3831   size_limit = align_up(size_limit, BytesPerLong);
3832   int num_tiles = size_limit / BytesPerLong;
3833 
3834   // allocate space for the tile map:
3835   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3836   jlong  tiles_buf[small_len];
3837   Node*  nodes_buf[small_len];
3838   jlong  inits_buf[small_len];
3839   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3840                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3841   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3842                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3843   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3844                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3845   // tiles: exact bitwise model of all primitive constants
3846   // nodes: last constant-storing node subsumed into the tiles model
3847   // inits: which bytes (in each tile) are touched by any initializations
3848 
3849   //// Pass A: Fill in the tile model with any relevant stores.
3850 
3851   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3852   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3853   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3854   Node* zmem = zero_memory(); // initially zero memory state
3855   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3856     Node* st = in(i);
3857     intptr_t st_off = get_store_offset(st, phase);
3858 
3859     // Figure out the store's offset and constant value:
3860     if (st_off < header_size)             continue; //skip (ignore header)
3861     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3862     int st_size = st->as_Store()->memory_size();
3863     if (st_off + st_size > size_limit)    break;
3864 
3865     // Record which bytes are touched, whether by constant or not.
3866     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3867       continue;                 // skip (strange store size)
3868 
3869     const Type* val = phase->type(st->in(MemNode::ValueIn));
3870     if (!val->singleton())                continue; //skip (non-con store)
3871     BasicType type = val->basic_type();
3872 
3873     jlong con = 0;
3874     switch (type) {
3875     case T_INT:    con = val->is_int()->get_con();  break;
3876     case T_LONG:   con = val->is_long()->get_con(); break;
3877     case T_FLOAT:  con = jint_cast(val->getf());    break;
3878     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3879     default:                              continue; //skip (odd store type)
3880     }
3881 
3882     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3883         st->Opcode() == Op_StoreL) {
3884       continue;                 // This StoreL is already optimal.
3885     }
3886 
3887     // Store down the constant.
3888     store_constant(tiles, num_tiles, st_off, st_size, con);
3889 
3890     intptr_t j = st_off >> LogBytesPerLong;
3891 
3892     if (type == T_INT && st_size == BytesPerInt
3893         && (st_off & BytesPerInt) == BytesPerInt) {
3894       jlong lcon = tiles[j];
3895       if (!Matcher::isSimpleConstant64(lcon) &&
3896           st->Opcode() == Op_StoreI) {
3897         // This StoreI is already optimal by itself.
3898         jint* intcon = (jint*) &tiles[j];
3899         intcon[1] = 0;  // undo the store_constant()
3900 
3901         // If the previous store is also optimal by itself, back up and
3902         // undo the action of the previous loop iteration... if we can.
3903         // But if we can't, just let the previous half take care of itself.
3904         st = nodes[j];
3905         st_off -= BytesPerInt;
3906         con = intcon[0];
3907         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3908           assert(st_off >= header_size, "still ignoring header");
3909           assert(get_store_offset(st, phase) == st_off, "must be");
3910           assert(in(i-1) == zmem, "must be");
3911           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3912           assert(con == tcon->is_int()->get_con(), "must be");
3913           // Undo the effects of the previous loop trip, which swallowed st:
3914           intcon[0] = 0;        // undo store_constant()
3915           set_req(i-1, st);     // undo set_req(i, zmem)
3916           nodes[j] = NULL;      // undo nodes[j] = st
3917           --old_subword;        // undo ++old_subword
3918         }
3919         continue;               // This StoreI is already optimal.
3920       }
3921     }
3922 
3923     // This store is not needed.
3924     set_req(i, zmem);
3925     nodes[j] = st;              // record for the moment
3926     if (st_size < BytesPerLong) // something has changed
3927           ++old_subword;        // includes int/float, but who's counting...
3928     else  ++old_long;
3929   }
3930 
3931   if ((old_subword + old_long) == 0)
3932     return;                     // nothing more to do
3933 
3934   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3935   // Be sure to insert them before overlapping non-constant stores.
3936   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3937   for (int j = 0; j < num_tiles; j++) {
3938     jlong con  = tiles[j];
3939     jlong init = inits[j];
3940     if (con == 0)  continue;
3941     jint con0,  con1;           // split the constant, address-wise
3942     jint init0, init1;          // split the init map, address-wise
3943     { union { jlong con; jint intcon[2]; } u;
3944       u.con = con;
3945       con0  = u.intcon[0];
3946       con1  = u.intcon[1];
3947       u.con = init;
3948       init0 = u.intcon[0];
3949       init1 = u.intcon[1];
3950     }
3951 
3952     Node* old = nodes[j];
3953     assert(old != NULL, "need the prior store");
3954     intptr_t offset = (j * BytesPerLong);
3955 
3956     bool split = !Matcher::isSimpleConstant64(con);
3957 
3958     if (offset < header_size) {
3959       assert(offset + BytesPerInt >= header_size, "second int counts");
3960       assert(*(jint*)&tiles[j] == 0, "junk in header");
3961       split = true;             // only the second word counts
3962       // Example:  int a[] = { 42 ... }
3963     } else if (con0 == 0 && init0 == -1) {
3964       split = true;             // first word is covered by full inits
3965       // Example:  int a[] = { ... foo(), 42 ... }
3966     } else if (con1 == 0 && init1 == -1) {
3967       split = true;             // second word is covered by full inits
3968       // Example:  int a[] = { ... 42, foo() ... }
3969     }
3970 
3971     // Here's a case where init0 is neither 0 nor -1:
3972     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
3973     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3974     // In this case the tile is not split; it is (jlong)42.
3975     // The big tile is stored down, and then the foo() value is inserted.
3976     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3977 
3978     Node* ctl = old->in(MemNode::Control);
3979     Node* adr = make_raw_address(offset, phase);
3980     const TypePtr* atp = TypeRawPtr::BOTTOM;
3981 
3982     // One or two coalesced stores to plop down.
3983     Node*    st[2];
3984     intptr_t off[2];
3985     int  nst = 0;
3986     if (!split) {
3987       ++new_long;
3988       off[nst] = offset;
3989       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3990                                   phase->longcon(con), T_LONG, MemNode::unordered);
3991     } else {
3992       // Omit either if it is a zero.
3993       if (con0 != 0) {
3994         ++new_int;
3995         off[nst]  = offset;
3996         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3997                                     phase->intcon(con0), T_INT, MemNode::unordered);
3998       }
3999       if (con1 != 0) {
4000         ++new_int;
4001         offset += BytesPerInt;
4002         adr = make_raw_address(offset, phase);
4003         off[nst]  = offset;
4004         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4005                                     phase->intcon(con1), T_INT, MemNode::unordered);
4006       }
4007     }
4008 
4009     // Insert second store first, then the first before the second.
4010     // Insert each one just before any overlapping non-constant stores.
4011     while (nst > 0) {
4012       Node* st1 = st[--nst];
4013       C->copy_node_notes_to(st1, old);
4014       st1 = phase->transform(st1);
4015       offset = off[nst];
4016       assert(offset >= header_size, "do not smash header");
4017       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4018       guarantee(ins_idx != 0, "must re-insert constant store");
4019       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
4020       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4021         set_req(--ins_idx, st1);
4022       else
4023         ins_req(ins_idx, st1);
4024     }
4025   }
4026 
4027   if (PrintCompilation && WizardMode)
4028     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4029                   old_subword, old_long, new_int, new_long);
4030   if (C->log() != NULL)
4031     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4032                    old_subword, old_long, new_int, new_long);
4033 
4034   // Clean up any remaining occurrences of zmem:
4035   remove_extra_zeroes();
4036 }
4037 
4038 // Explore forward from in(start) to find the first fully initialized
4039 // word, and return its offset.  Skip groups of subword stores which
4040 // together initialize full words.  If in(start) is itself part of a
4041 // fully initialized word, return the offset of in(start).  If there
4042 // are no following full-word stores, or if something is fishy, return
4043 // a negative value.
4044 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4045   int       int_map = 0;
4046   intptr_t  int_map_off = 0;
4047   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
4048 
4049   for (uint i = start, limit = req(); i < limit; i++) {
4050     Node* st = in(i);
4051 
4052     intptr_t st_off = get_store_offset(st, phase);
4053     if (st_off < 0)  break;  // return conservative answer
4054 
4055     int st_size = st->as_Store()->memory_size();
4056     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4057       return st_off;            // we found a complete word init
4058     }
4059 
4060     // update the map:
4061 
4062     intptr_t this_int_off = align_down(st_off, BytesPerInt);
4063     if (this_int_off != int_map_off) {
4064       // reset the map:
4065       int_map = 0;
4066       int_map_off = this_int_off;
4067     }
4068 
4069     int subword_off = st_off - this_int_off;
4070     int_map |= right_n_bits(st_size) << subword_off;
4071     if ((int_map & FULL_MAP) == FULL_MAP) {
4072       return this_int_off;      // we found a complete word init
4073     }
4074 
4075     // Did this store hit or cross the word boundary?
4076     intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4077     if (next_int_off == this_int_off + BytesPerInt) {
4078       // We passed the current int, without fully initializing it.
4079       int_map_off = next_int_off;
4080       int_map >>= BytesPerInt;
4081     } else if (next_int_off > this_int_off + BytesPerInt) {
4082       // We passed the current and next int.
4083       return this_int_off + BytesPerInt;
4084     }
4085   }
4086 
4087   return -1;
4088 }
4089 
4090 
4091 // Called when the associated AllocateNode is expanded into CFG.
4092 // At this point, we may perform additional optimizations.
4093 // Linearize the stores by ascending offset, to make memory
4094 // activity as coherent as possible.
4095 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4096                                       intptr_t header_size,
4097                                       Node* size_in_bytes,
4098                                       PhaseGVN* phase) {
4099   assert(!is_complete(), "not already complete");
4100   assert(stores_are_sane(phase), "");
4101   assert(allocation() != NULL, "must be present");
4102 
4103   remove_extra_zeroes();
4104 
4105   if (ReduceFieldZeroing || ReduceBulkZeroing)
4106     // reduce instruction count for common initialization patterns
4107     coalesce_subword_stores(header_size, size_in_bytes, phase);
4108 
4109   Node* zmem = zero_memory();   // initially zero memory state
4110   Node* inits = zmem;           // accumulating a linearized chain of inits
4111   #ifdef ASSERT
4112   intptr_t first_offset = allocation()->minimum_header_size();
4113   intptr_t last_init_off = first_offset;  // previous init offset
4114   intptr_t last_init_end = first_offset;  // previous init offset+size
4115   intptr_t last_tile_end = first_offset;  // previous tile offset+size
4116   #endif
4117   intptr_t zeroes_done = header_size;
4118 
4119   bool do_zeroing = true;       // we might give up if inits are very sparse
4120   int  big_init_gaps = 0;       // how many large gaps have we seen?
4121 
4122   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
4123   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
4124 
4125   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4126     Node* st = in(i);
4127     intptr_t st_off = get_store_offset(st, phase);
4128     if (st_off < 0)
4129       break;                    // unknown junk in the inits
4130     if (st->in(MemNode::Memory) != zmem)
4131       break;                    // complicated store chains somehow in list
4132 
4133     int st_size = st->as_Store()->memory_size();
4134     intptr_t next_init_off = st_off + st_size;
4135 
4136     if (do_zeroing && zeroes_done < next_init_off) {
4137       // See if this store needs a zero before it or under it.
4138       intptr_t zeroes_needed = st_off;
4139 
4140       if (st_size < BytesPerInt) {
4141         // Look for subword stores which only partially initialize words.
4142         // If we find some, we must lay down some word-level zeroes first,
4143         // underneath the subword stores.
4144         //
4145         // Examples:
4146         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
4147         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
4148         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
4149         //
4150         // Note:  coalesce_subword_stores may have already done this,
4151         // if it was prompted by constant non-zero subword initializers.
4152         // But this case can still arise with non-constant stores.
4153 
4154         intptr_t next_full_store = find_next_fullword_store(i, phase);
4155 
4156         // In the examples above:
4157         //   in(i)          p   q   r   s     x   y     z
4158         //   st_off        12  13  14  15    12  13    14
4159         //   st_size        1   1   1   1     1   1     1
4160         //   next_full_s.  12  16  16  16    16  16    16
4161         //   z's_done      12  16  16  16    12  16    12
4162         //   z's_needed    12  16  16  16    16  16    16
4163         //   zsize          0   0   0   0     4   0     4
4164         if (next_full_store < 0) {
4165           // Conservative tack:  Zero to end of current word.
4166           zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4167         } else {
4168           // Zero to beginning of next fully initialized word.
4169           // Or, don't zero at all, if we are already in that word.
4170           assert(next_full_store >= zeroes_needed, "must go forward");
4171           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4172           zeroes_needed = next_full_store;
4173         }
4174       }
4175 
4176       if (zeroes_needed > zeroes_done) {
4177         intptr_t zsize = zeroes_needed - zeroes_done;
4178         // Do some incremental zeroing on rawmem, in parallel with inits.
4179         zeroes_done = align_down(zeroes_done, BytesPerInt);
4180         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4181                                               zeroes_done, zeroes_needed,
4182                                               phase);
4183         zeroes_done = zeroes_needed;
4184         if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4185           do_zeroing = false;   // leave the hole, next time
4186       }
4187     }
4188 
4189     // Collect the store and move on:
4190     st->set_req(MemNode::Memory, inits);
4191     inits = st;                 // put it on the linearized chain
4192     set_req(i, zmem);           // unhook from previous position
4193 
4194     if (zeroes_done == st_off)
4195       zeroes_done = next_init_off;
4196 
4197     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4198 
4199     #ifdef ASSERT
4200     // Various order invariants.  Weaker than stores_are_sane because
4201     // a large constant tile can be filled in by smaller non-constant stores.
4202     assert(st_off >= last_init_off, "inits do not reverse");
4203     last_init_off = st_off;
4204     const Type* val = NULL;
4205     if (st_size >= BytesPerInt &&
4206         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4207         (int)val->basic_type() < (int)T_OBJECT) {
4208       assert(st_off >= last_tile_end, "tiles do not overlap");
4209       assert(st_off >= last_init_end, "tiles do not overwrite inits");
4210       last_tile_end = MAX2(last_tile_end, next_init_off);
4211     } else {
4212       intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4213       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4214       assert(st_off      >= last_init_end, "inits do not overlap");
4215       last_init_end = next_init_off;  // it's a non-tile
4216     }
4217     #endif //ASSERT
4218   }
4219 
4220   remove_extra_zeroes();        // clear out all the zmems left over
4221   add_req(inits);
4222 
4223   if (!(UseTLAB && ZeroTLAB)) {
4224     // If anything remains to be zeroed, zero it all now.
4225     zeroes_done = align_down(zeroes_done, BytesPerInt);
4226     // if it is the last unused 4 bytes of an instance, forget about it
4227     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4228     if (zeroes_done + BytesPerLong >= size_limit) {
4229       AllocateNode* alloc = allocation();
4230       assert(alloc != NULL, "must be present");
4231       if (alloc != NULL && alloc->Opcode() == Op_Allocate) {
4232         Node* klass_node = alloc->in(AllocateNode::KlassNode);
4233         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
4234         if (zeroes_done == k->layout_helper())
4235           zeroes_done = size_limit;
4236       }
4237     }
4238     if (zeroes_done < size_limit) {
4239       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4240                                             zeroes_done, size_in_bytes, phase);
4241     }
4242   }
4243 
4244   set_complete(phase);
4245   return rawmem;
4246 }
4247 
4248 
4249 #ifdef ASSERT
4250 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
4251   if (is_complete())
4252     return true;                // stores could be anything at this point
4253   assert(allocation() != NULL, "must be present");
4254   intptr_t last_off = allocation()->minimum_header_size();
4255   for (uint i = InitializeNode::RawStores; i < req(); i++) {
4256     Node* st = in(i);
4257     intptr_t st_off = get_store_offset(st, phase);
4258     if (st_off < 0)  continue;  // ignore dead garbage
4259     if (last_off > st_off) {
4260       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4261       this->dump(2);
4262       assert(false, "ascending store offsets");
4263       return false;
4264     }
4265     last_off = st_off + st->as_Store()->memory_size();
4266   }
4267   return true;
4268 }
4269 #endif //ASSERT
4270 
4271 
4272 
4273 
4274 //============================MergeMemNode=====================================
4275 //
4276 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4277 // contributing store or call operations.  Each contributor provides the memory
4278 // state for a particular "alias type" (see Compile::alias_type).  For example,
4279 // if a MergeMem has an input X for alias category #6, then any memory reference
4280 // to alias category #6 may use X as its memory state input, as an exact equivalent
4281 // to using the MergeMem as a whole.
4282 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4283 //
4284 // (Here, the <N> notation gives the index of the relevant adr_type.)
4285 //
4286 // In one special case (and more cases in the future), alias categories overlap.
4287 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4288 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4289 // it is exactly equivalent to that state W:
4290 //   MergeMem(<Bot>: W) <==> W
4291 //
4292 // Usually, the merge has more than one input.  In that case, where inputs
4293 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4294 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4295 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4296 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4297 //
4298 // A merge can take a "wide" memory state as one of its narrow inputs.
4299 // This simply means that the merge observes out only the relevant parts of
4300 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4301 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4302 //
4303 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4304 // and that memory slices "leak through":
4305 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4306 //
4307 // But, in such a cascade, repeated memory slices can "block the leak":
4308 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4309 //
4310 // In the last example, Y is not part of the combined memory state of the
4311 // outermost MergeMem.  The system must, of course, prevent unschedulable
4312 // memory states from arising, so you can be sure that the state Y is somehow
4313 // a precursor to state Y'.
4314 //
4315 //
4316 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4317 // of each MergeMemNode array are exactly the numerical alias indexes, including
4318 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4319 // Compile::alias_type (and kin) produce and manage these indexes.
4320 //
4321 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4322 // (Note that this provides quick access to the top node inside MergeMem methods,
4323 // without the need to reach out via TLS to Compile::current.)
4324 //
4325 // As a consequence of what was just described, a MergeMem that represents a full
4326 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4327 // containing all alias categories.
4328 //
4329 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4330 //
4331 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4332 // a memory state for the alias type <N>, or else the top node, meaning that
4333 // there is no particular input for that alias type.  Note that the length of
4334 // a MergeMem is variable, and may be extended at any time to accommodate new
4335 // memory states at larger alias indexes.  When merges grow, they are of course
4336 // filled with "top" in the unused in() positions.
4337 //
4338 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4339 // (Top was chosen because it works smoothly with passes like GCM.)
4340 //
4341 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4342 // the type of random VM bits like TLS references.)  Since it is always the
4343 // first non-Bot memory slice, some low-level loops use it to initialize an
4344 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4345 //
4346 //
4347 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4348 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4349 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4350 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4351 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4352 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4353 //
4354 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4355 // really that different from the other memory inputs.  An abbreviation called
4356 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4357 //
4358 //
4359 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4360 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4361 // that "emerges though" the base memory will be marked as excluding the alias types
4362 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4363 //
4364 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4365 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4366 //
4367 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4368 // (It is currently unimplemented.)  As you can see, the resulting merge is
4369 // actually a disjoint union of memory states, rather than an overlay.
4370 //
4371 
4372 //------------------------------MergeMemNode-----------------------------------
4373 Node* MergeMemNode::make_empty_memory() {
4374   Node* empty_memory = (Node*) Compile::current()->top();
4375   assert(empty_memory->is_top(), "correct sentinel identity");
4376   return empty_memory;
4377 }
4378 
4379 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4380   init_class_id(Class_MergeMem);
4381   // all inputs are nullified in Node::Node(int)
4382   // set_input(0, NULL);  // no control input
4383 
4384   // Initialize the edges uniformly to top, for starters.
4385   Node* empty_mem = make_empty_memory();
4386   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4387     init_req(i,empty_mem);
4388   }
4389   assert(empty_memory() == empty_mem, "");
4390 
4391   if( new_base != NULL && new_base->is_MergeMem() ) {
4392     MergeMemNode* mdef = new_base->as_MergeMem();
4393     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4394     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4395       mms.set_memory(mms.memory2());
4396     }
4397     assert(base_memory() == mdef->base_memory(), "");
4398   } else {
4399     set_base_memory(new_base);
4400   }
4401 }
4402 
4403 // Make a new, untransformed MergeMem with the same base as 'mem'.
4404 // If mem is itself a MergeMem, populate the result with the same edges.
4405 MergeMemNode* MergeMemNode::make(Node* mem) {
4406   return new MergeMemNode(mem);
4407 }
4408 
4409 //------------------------------cmp--------------------------------------------
4410 uint MergeMemNode::hash() const { return NO_HASH; }
4411 uint MergeMemNode::cmp( const Node &n ) const {
4412   return (&n == this);          // Always fail except on self
4413 }
4414 
4415 //------------------------------Identity---------------------------------------
4416 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4417   // Identity if this merge point does not record any interesting memory
4418   // disambiguations.
4419   Node* base_mem = base_memory();
4420   Node* empty_mem = empty_memory();
4421   if (base_mem != empty_mem) {  // Memory path is not dead?
4422     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4423       Node* mem = in(i);
4424       if (mem != empty_mem && mem != base_mem) {
4425         return this;            // Many memory splits; no change
4426       }
4427     }
4428   }
4429   return base_mem;              // No memory splits; ID on the one true input
4430 }
4431 
4432 //------------------------------Ideal------------------------------------------
4433 // This method is invoked recursively on chains of MergeMem nodes
4434 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4435   // Remove chain'd MergeMems
4436   //
4437   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4438   // relative to the "in(Bot)".  Since we are patching both at the same time,
4439   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4440   // but rewrite each "in(i)" relative to the new "in(Bot)".
4441   Node *progress = NULL;
4442 
4443 
4444   Node* old_base = base_memory();
4445   Node* empty_mem = empty_memory();
4446   if (old_base == empty_mem)
4447     return NULL; // Dead memory path.
4448 
4449   MergeMemNode* old_mbase;
4450   if (old_base != NULL && old_base->is_MergeMem())
4451     old_mbase = old_base->as_MergeMem();
4452   else
4453     old_mbase = NULL;
4454   Node* new_base = old_base;
4455 
4456   // simplify stacked MergeMems in base memory
4457   if (old_mbase)  new_base = old_mbase->base_memory();
4458 
4459   // the base memory might contribute new slices beyond my req()
4460   if (old_mbase)  grow_to_match(old_mbase);
4461 
4462   // Look carefully at the base node if it is a phi.
4463   PhiNode* phi_base;
4464   if (new_base != NULL && new_base->is_Phi())
4465     phi_base = new_base->as_Phi();
4466   else
4467     phi_base = NULL;
4468 
4469   Node*    phi_reg = NULL;
4470   uint     phi_len = (uint)-1;
4471   if (phi_base != NULL && !phi_base->is_copy()) {
4472     // do not examine phi if degraded to a copy
4473     phi_reg = phi_base->region();
4474     phi_len = phi_base->req();
4475     // see if the phi is unfinished
4476     for (uint i = 1; i < phi_len; i++) {
4477       if (phi_base->in(i) == NULL) {
4478         // incomplete phi; do not look at it yet!
4479         phi_reg = NULL;
4480         phi_len = (uint)-1;
4481         break;
4482       }
4483     }
4484   }
4485 
4486   // Note:  We do not call verify_sparse on entry, because inputs
4487   // can normalize to the base_memory via subsume_node or similar
4488   // mechanisms.  This method repairs that damage.
4489 
4490   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4491 
4492   // Look at each slice.
4493   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4494     Node* old_in = in(i);
4495     // calculate the old memory value
4496     Node* old_mem = old_in;
4497     if (old_mem == empty_mem)  old_mem = old_base;
4498     assert(old_mem == memory_at(i), "");
4499 
4500     // maybe update (reslice) the old memory value
4501 
4502     // simplify stacked MergeMems
4503     Node* new_mem = old_mem;
4504     MergeMemNode* old_mmem;
4505     if (old_mem != NULL && old_mem->is_MergeMem())
4506       old_mmem = old_mem->as_MergeMem();
4507     else
4508       old_mmem = NULL;
4509     if (old_mmem == this) {
4510       // This can happen if loops break up and safepoints disappear.
4511       // A merge of BotPtr (default) with a RawPtr memory derived from a
4512       // safepoint can be rewritten to a merge of the same BotPtr with
4513       // the BotPtr phi coming into the loop.  If that phi disappears
4514       // also, we can end up with a self-loop of the mergemem.
4515       // In general, if loops degenerate and memory effects disappear,
4516       // a mergemem can be left looking at itself.  This simply means
4517       // that the mergemem's default should be used, since there is
4518       // no longer any apparent effect on this slice.
4519       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4520       //       from start.  Update the input to TOP.
4521       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4522     }
4523     else if (old_mmem != NULL) {
4524       new_mem = old_mmem->memory_at(i);
4525     }
4526     // else preceding memory was not a MergeMem
4527 
4528     // replace equivalent phis (unfortunately, they do not GVN together)
4529     if (new_mem != NULL && new_mem != new_base &&
4530         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4531       if (new_mem->is_Phi()) {
4532         PhiNode* phi_mem = new_mem->as_Phi();
4533         for (uint i = 1; i < phi_len; i++) {
4534           if (phi_base->in(i) != phi_mem->in(i)) {
4535             phi_mem = NULL;
4536             break;
4537           }
4538         }
4539         if (phi_mem != NULL) {
4540           // equivalent phi nodes; revert to the def
4541           new_mem = new_base;
4542         }
4543       }
4544     }
4545 
4546     // maybe store down a new value
4547     Node* new_in = new_mem;
4548     if (new_in == new_base)  new_in = empty_mem;
4549 
4550     if (new_in != old_in) {
4551       // Warning:  Do not combine this "if" with the previous "if"
4552       // A memory slice might have be be rewritten even if it is semantically
4553       // unchanged, if the base_memory value has changed.
4554       set_req(i, new_in);
4555       progress = this;          // Report progress
4556     }
4557   }
4558 
4559   if (new_base != old_base) {
4560     set_req(Compile::AliasIdxBot, new_base);
4561     // Don't use set_base_memory(new_base), because we need to update du.
4562     assert(base_memory() == new_base, "");
4563     progress = this;
4564   }
4565 
4566   if( base_memory() == this ) {
4567     // a self cycle indicates this memory path is dead
4568     set_req(Compile::AliasIdxBot, empty_mem);
4569   }
4570 
4571   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4572   // Recursion must occur after the self cycle check above
4573   if( base_memory()->is_MergeMem() ) {
4574     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4575     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4576     if( m != NULL &&
4577         (m->is_top() ||
4578          (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4579       // propagate rollup of dead cycle to self
4580       set_req(Compile::AliasIdxBot, empty_mem);
4581     }
4582   }
4583 
4584   if( base_memory() == empty_mem ) {
4585     progress = this;
4586     // Cut inputs during Parse phase only.
4587     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4588     if( !can_reshape ) {
4589       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4590         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4591       }
4592     }
4593   }
4594 
4595   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4596     // Check if PhiNode::Ideal's "Split phis through memory merges"
4597     // transform should be attempted. Look for this->phi->this cycle.
4598     uint merge_width = req();
4599     if (merge_width > Compile::AliasIdxRaw) {
4600       PhiNode* phi = base_memory()->as_Phi();
4601       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4602         if (phi->in(i) == this) {
4603           phase->is_IterGVN()->_worklist.push(phi);
4604           break;
4605         }
4606       }
4607     }
4608   }
4609 
4610   assert(progress || verify_sparse(), "please, no dups of base");
4611   return progress;
4612 }
4613 
4614 //-------------------------set_base_memory-------------------------------------
4615 void MergeMemNode::set_base_memory(Node *new_base) {
4616   Node* empty_mem = empty_memory();
4617   set_req(Compile::AliasIdxBot, new_base);
4618   assert(memory_at(req()) == new_base, "must set default memory");
4619   // Clear out other occurrences of new_base:
4620   if (new_base != empty_mem) {
4621     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4622       if (in(i) == new_base)  set_req(i, empty_mem);
4623     }
4624   }
4625 }
4626 
4627 //------------------------------out_RegMask------------------------------------
4628 const RegMask &MergeMemNode::out_RegMask() const {
4629   return RegMask::Empty;
4630 }
4631 
4632 //------------------------------dump_spec--------------------------------------
4633 #ifndef PRODUCT
4634 void MergeMemNode::dump_spec(outputStream *st) const {
4635   st->print(" {");
4636   Node* base_mem = base_memory();
4637   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4638     Node* mem = (in(i) != NULL) ? memory_at(i) : base_mem;
4639     if (mem == base_mem) { st->print(" -"); continue; }
4640     st->print( " N%d:", mem->_idx );
4641     Compile::current()->get_adr_type(i)->dump_on(st);
4642   }
4643   st->print(" }");
4644 }
4645 #endif // !PRODUCT
4646 
4647 
4648 #ifdef ASSERT
4649 static bool might_be_same(Node* a, Node* b) {
4650   if (a == b)  return true;
4651   if (!(a->is_Phi() || b->is_Phi()))  return false;
4652   // phis shift around during optimization
4653   return true;  // pretty stupid...
4654 }
4655 
4656 // verify a narrow slice (either incoming or outgoing)
4657 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4658   if (!VerifyAliases)                return;  // don't bother to verify unless requested
4659   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
4660   if (Node::in_dump())               return;  // muzzle asserts when printing
4661   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4662   assert(n != NULL, "");
4663   // Elide intervening MergeMem's
4664   while (n->is_MergeMem()) {
4665     n = n->as_MergeMem()->memory_at(alias_idx);
4666   }
4667   Compile* C = Compile::current();
4668   const TypePtr* n_adr_type = n->adr_type();
4669   if (n == m->empty_memory()) {
4670     // Implicit copy of base_memory()
4671   } else if (n_adr_type != TypePtr::BOTTOM) {
4672     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4673     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4674   } else {
4675     // A few places like make_runtime_call "know" that VM calls are narrow,
4676     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4677     bool expected_wide_mem = false;
4678     if (n == m->base_memory()) {
4679       expected_wide_mem = true;
4680     } else if (alias_idx == Compile::AliasIdxRaw ||
4681                n == m->memory_at(Compile::AliasIdxRaw)) {
4682       expected_wide_mem = true;
4683     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4684       // memory can "leak through" calls on channels that
4685       // are write-once.  Allow this also.
4686       expected_wide_mem = true;
4687     }
4688     assert(expected_wide_mem, "expected narrow slice replacement");
4689   }
4690 }
4691 #else // !ASSERT
4692 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4693 #endif
4694 
4695 
4696 //-----------------------------memory_at---------------------------------------
4697 Node* MergeMemNode::memory_at(uint alias_idx) const {
4698   assert(alias_idx >= Compile::AliasIdxRaw ||
4699          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4700          "must avoid base_memory and AliasIdxTop");
4701 
4702   // Otherwise, it is a narrow slice.
4703   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4704   Compile *C = Compile::current();
4705   if (is_empty_memory(n)) {
4706     // the array is sparse; empty slots are the "top" node
4707     n = base_memory();
4708     assert(Node::in_dump()
4709            || n == NULL || n->bottom_type() == Type::TOP
4710            || n->adr_type() == NULL // address is TOP
4711            || n->adr_type() == TypePtr::BOTTOM
4712            || n->adr_type() == TypeRawPtr::BOTTOM
4713            || Compile::current()->AliasLevel() == 0,
4714            "must be a wide memory");
4715     // AliasLevel == 0 if we are organizing the memory states manually.
4716     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4717   } else {
4718     // make sure the stored slice is sane
4719     #ifdef ASSERT
4720     if (VMError::is_error_reported() || Node::in_dump()) {
4721     } else if (might_be_same(n, base_memory())) {
4722       // Give it a pass:  It is a mostly harmless repetition of the base.
4723       // This can arise normally from node subsumption during optimization.
4724     } else {
4725       verify_memory_slice(this, alias_idx, n);
4726     }
4727     #endif
4728   }
4729   return n;
4730 }
4731 
4732 //---------------------------set_memory_at-------------------------------------
4733 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4734   verify_memory_slice(this, alias_idx, n);
4735   Node* empty_mem = empty_memory();
4736   if (n == base_memory())  n = empty_mem;  // collapse default
4737   uint need_req = alias_idx+1;
4738   if (req() < need_req) {
4739     if (n == empty_mem)  return;  // already the default, so do not grow me
4740     // grow the sparse array
4741     do {
4742       add_req(empty_mem);
4743     } while (req() < need_req);
4744   }
4745   set_req( alias_idx, n );
4746 }
4747 
4748 
4749 
4750 //--------------------------iteration_setup------------------------------------
4751 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4752   if (other != NULL) {
4753     grow_to_match(other);
4754     // invariant:  the finite support of mm2 is within mm->req()
4755     #ifdef ASSERT
4756     for (uint i = req(); i < other->req(); i++) {
4757       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4758     }
4759     #endif
4760   }
4761   // Replace spurious copies of base_memory by top.
4762   Node* base_mem = base_memory();
4763   if (base_mem != NULL && !base_mem->is_top()) {
4764     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4765       if (in(i) == base_mem)
4766         set_req(i, empty_memory());
4767     }
4768   }
4769 }
4770 
4771 //---------------------------grow_to_match-------------------------------------
4772 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4773   Node* empty_mem = empty_memory();
4774   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4775   // look for the finite support of the other memory
4776   for (uint i = other->req(); --i >= req(); ) {
4777     if (other->in(i) != empty_mem) {
4778       uint new_len = i+1;
4779       while (req() < new_len)  add_req(empty_mem);
4780       break;
4781     }
4782   }
4783 }
4784 
4785 //---------------------------verify_sparse-------------------------------------
4786 #ifndef PRODUCT
4787 bool MergeMemNode::verify_sparse() const {
4788   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4789   Node* base_mem = base_memory();
4790   // The following can happen in degenerate cases, since empty==top.
4791   if (is_empty_memory(base_mem))  return true;
4792   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4793     assert(in(i) != NULL, "sane slice");
4794     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4795   }
4796   return true;
4797 }
4798 
4799 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4800   Node* n;
4801   n = mm->in(idx);
4802   if (mem == n)  return true;  // might be empty_memory()
4803   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4804   if (mem == n)  return true;
4805   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4806     if (mem == n)  return true;
4807     if (n == NULL)  break;
4808   }
4809   return false;
4810 }
4811 #endif // !PRODUCT
--- EOF ---