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(addp->in(AddPNode::Base) == ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base), "strange pattern");
 928       assert(addp->in(AddPNode::Address) == ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address), "strange pattern");


 929       addp->set_req(AddPNode::Base, src->in(AddPNode::Base));
 930       addp->set_req(AddPNode::Address, src->in(AddPNode::Address));
 931     } else {
 932       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
 933              ac->as_ArrayCopy()->is_copyof_validated() ||
 934              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
 935       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
 936       addp->set_req(AddPNode::Base, src);
 937       addp->set_req(AddPNode::Address, src);
 938 
 939       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
 940       BasicType ary_elem  = ary_t->klass()->as_array_klass()->element_type()->basic_type();
 941       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 942       uint shift  = exact_log2(type2aelembytes(ary_elem));
 943 
 944       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
 945 #ifdef _LP64
 946       diff = phase->transform(new ConvI2LNode(diff));
 947 #endif
 948       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
 949 
 950       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
 951       addp->set_req(AddPNode::Offset, offset);
 952     }
 953     addp = phase->transform(addp);
 954 #ifdef ASSERT
 955     const TypePtr* adr_type = phase->type(addp)->is_ptr();
 956     ld->_adr_type = adr_type;
 957 #endif
 958     ld->set_req(MemNode::Address, addp);
 959     ld->set_req(0, ctl);
 960     ld->set_req(MemNode::Memory, mem);
 961     // load depends on the tests that validate the arraycopy
 962     ld->_control_dependency = Pinned;
 963     return ld;
 964   }
 965   return NULL;
 966 }
 967 
 968 
 969 //---------------------------can_see_stored_value------------------------------
 970 // This routine exists to make sure this set of tests is done the same
 971 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 972 // will change the graph shape in a way which makes memory alive twice at the
 973 // same time (uses the Oracle model of aliasing), then some
 974 // LoadXNode::Identity will fold things back to the equivalence-class model
 975 // of aliasing.
 976 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 977   Node* ld_adr = in(MemNode::Address);
 978   intptr_t ld_off = 0;
 979   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 980   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 981   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
 982   // This is more general than load from boxing objects.
 983   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
 984     uint alias_idx = atp->index();
 985     bool final = !atp->is_rewritable();
 986     Node* result = NULL;
 987     Node* current = st;
 988     // Skip through chains of MemBarNodes checking the MergeMems for
 989     // new states for the slice of this load.  Stop once any other
 990     // kind of node is encountered.  Loads from final memory can skip
 991     // through any kind of MemBar but normal loads shouldn't skip
 992     // through MemBarAcquire since the could allow them to move out of
 993     // a synchronized region.
 994     while (current->is_Proj()) {
 995       int opc = current->in(0)->Opcode();
 996       if ((final && (opc == Op_MemBarAcquire ||
 997                      opc == Op_MemBarAcquireLock ||
 998                      opc == Op_LoadFence)) ||
 999           opc == Op_MemBarRelease ||
1000           opc == Op_StoreFence ||
1001           opc == Op_MemBarReleaseLock ||
1002           opc == Op_MemBarStoreStore ||
1003           opc == Op_MemBarCPUOrder) {
1004         Node* mem = current->in(0)->in(TypeFunc::Memory);
1005         if (mem->is_MergeMem()) {
1006           MergeMemNode* merge = mem->as_MergeMem();
1007           Node* new_st = merge->memory_at(alias_idx);
1008           if (new_st == merge->base_memory()) {
1009             // Keep searching
1010             current = new_st;
1011             continue;
1012           }
1013           // Save the new memory state for the slice and fall through
1014           // to exit.
1015           result = new_st;
1016         }
1017       }
1018       break;
1019     }
1020     if (result != NULL) {
1021       st = result;
1022     }
1023   }
1024 
1025   // Loop around twice in the case Load -> Initialize -> Store.
1026   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1027   for (int trip = 0; trip <= 1; trip++) {
1028 
1029     if (st->is_Store()) {
1030       Node* st_adr = st->in(MemNode::Address);
1031       if (!phase->eqv(st_adr, ld_adr)) {
1032         // Try harder before giving up...  Match raw and non-raw pointers.
1033         intptr_t st_off = 0;
1034         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
1035         if (alloc == NULL)       return NULL;
1036         if (alloc != ld_alloc)   return NULL;
1037         if (ld_off != st_off)    return NULL;
1038         // At this point we have proven something like this setup:
1039         //  A = Allocate(...)
1040         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
1041         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
1042         // (Actually, we haven't yet proven the Q's are the same.)
1043         // In other words, we are loading from a casted version of
1044         // the same pointer-and-offset that we stored to.
1045         // Thus, we are able to replace L by V.
1046       }
1047       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1048       if (store_Opcode() != st->Opcode())
1049         return NULL;
1050       return st->in(MemNode::ValueIn);
1051     }
1052 
1053     // A load from a freshly-created object always returns zero.
1054     // (This can happen after LoadNode::Ideal resets the load's memory input
1055     // to find_captured_store, which returned InitializeNode::zero_memory.)
1056     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1057         (st->in(0) == ld_alloc) &&
1058         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1059       // return a zero value for the load's basic type
1060       // (This is one of the few places where a generic PhaseTransform
1061       // can create new nodes.  Think of it as lazily manifesting
1062       // virtually pre-existing constants.)
1063       return phase->zerocon(memory_type());
1064     }
1065 
1066     // A load from an initialization barrier can match a captured store.
1067     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1068       InitializeNode* init = st->in(0)->as_Initialize();
1069       AllocateNode* alloc = init->allocation();
1070       if ((alloc != NULL) && (alloc == ld_alloc)) {
1071         // examine a captured store value
1072         st = init->find_captured_store(ld_off, memory_size(), phase);
1073         if (st != NULL) {
1074           continue;             // take one more trip around
1075         }
1076       }
1077     }
1078 
1079     // Load boxed value from result of valueOf() call is input parameter.
1080     if (this->is_Load() && ld_adr->is_AddP() &&
1081         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1082       intptr_t ignore = 0;
1083       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);


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