rev 7139 : imported patch 8062258.adr_type

   1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
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  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).
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  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "memory/allocation.inline.hpp"
  29 #include "oops/objArrayKlass.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/cfgnode.hpp"
  32 #include "opto/compile.hpp"
  33 #include "opto/connode.hpp"
  34 #include "opto/convertnode.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/machnode.hpp"
  37 #include "opto/matcher.hpp"
  38 #include "opto/memnode.hpp"
  39 #include "opto/mulnode.hpp"
  40 #include "opto/narrowptrnode.hpp"
  41 #include "opto/phaseX.hpp"
  42 #include "opto/regmask.hpp"
  43 
  44 // Portions of code courtesy of Clifford Click
  45 
  46 // Optimization - Graph Style
  47 
  48 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  49 
  50 //=============================================================================
  51 uint MemNode::size_of() const { return sizeof(*this); }
  52 
  53 const TypePtr *MemNode::adr_type() const {
  54   Node* adr = in(Address);
  55   NOT_PRODUCT(if (adr == NULL)  return NULL;) // node is dead
  56   const TypePtr* cross_check = NULL;
  57   DEBUG_ONLY(cross_check = _adr_type);
  58   return calculate_adr_type(adr->bottom_type(), cross_check);
  59 }
  60 
  61 #ifndef PRODUCT
  62 void MemNode::dump_spec(outputStream *st) const {
  63   if (in(Address) == NULL)  return; // node is dead
  64 #ifndef ASSERT
  65   // fake the missing field
  66   const TypePtr* _adr_type = NULL;
  67   if (in(Address) != NULL)
  68     _adr_type = in(Address)->bottom_type()->isa_ptr();
  69 #endif
  70   dump_adr_type(this, _adr_type, st);
  71 
  72   Compile* C = Compile::current();
  73   if( C->alias_type(_adr_type)->is_volatile() )
  74     st->print(" Volatile!");
  75 }
  76 
  77 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
  78   st->print(" @");
  79   if (adr_type == NULL) {
  80     st->print("NULL");
  81   } else {
  82     adr_type->dump_on(st);
  83     Compile* C = Compile::current();
  84     Compile::AliasType* atp = NULL;
  85     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
  86     if (atp == NULL)
  87       st->print(", idx=?\?;");
  88     else if (atp->index() == Compile::AliasIdxBot)
  89       st->print(", idx=Bot;");
  90     else if (atp->index() == Compile::AliasIdxTop)
  91       st->print(", idx=Top;");
  92     else if (atp->index() == Compile::AliasIdxRaw)
  93       st->print(", idx=Raw;");
  94     else {
  95       ciField* field = atp->field();
  96       if (field) {
  97         st->print(", name=");
  98         field->print_name_on(st);
  99       }
 100       st->print(", idx=%d;", atp->index());
 101     }
 102   }
 103 }
 104 
 105 extern void print_alias_types();
 106 
 107 #endif
 108 
 109 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 110   assert((t_oop != NULL), "sanity");
 111   bool is_instance = t_oop->is_known_instance_field();
 112   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 113                              (load != NULL) && load->is_Load() &&
 114                              (phase->is_IterGVN() != NULL);
 115   if (!(is_instance || is_boxed_value_load))
 116     return mchain;  // don't try to optimize non-instance types
 117   uint instance_id = t_oop->instance_id();
 118   Node *start_mem = phase->C->start()->proj_out(TypeFunc::Memory);
 119   Node *prev = NULL;
 120   Node *result = mchain;
 121   while (prev != result) {
 122     prev = result;
 123     if (result == start_mem)
 124       break;  // hit one of our sentinels
 125     // skip over a call which does not affect this memory slice
 126     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 127       Node *proj_in = result->in(0);
 128       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 129         break;  // hit one of our sentinels
 130       } else if (proj_in->is_Call()) {
 131         CallNode *call = proj_in->as_Call();
 132         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 133           result = call->in(TypeFunc::Memory);
 134         }
 135       } else if (proj_in->is_Initialize()) {
 136         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 137         // Stop if this is the initialization for the object instance which
 138         // which contains this memory slice, otherwise skip over it.
 139         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 140           break;
 141         }
 142         if (is_instance) {
 143           result = proj_in->in(TypeFunc::Memory);
 144         } else if (is_boxed_value_load) {
 145           Node* klass = alloc->in(AllocateNode::KlassNode);
 146           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 147           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 148             result = proj_in->in(TypeFunc::Memory); // not related allocation
 149           }
 150         }
 151       } else if (proj_in->is_MemBar()) {
 152         result = proj_in->in(TypeFunc::Memory);
 153       } else {
 154         assert(false, "unexpected projection");
 155       }
 156     } else if (result->is_ClearArray()) {
 157       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 158         // Can not bypass initialization of the instance
 159         // we are looking for.
 160         break;
 161       }
 162       // Otherwise skip it (the call updated 'result' value).
 163     } else if (result->is_MergeMem()) {
 164       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 165     }
 166   }
 167   return result;
 168 }
 169 
 170 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 171   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 172   if (t_oop == NULL)
 173     return mchain;  // don't try to optimize non-oop types
 174   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 175   bool is_instance = t_oop->is_known_instance_field();
 176   PhaseIterGVN *igvn = phase->is_IterGVN();
 177   if (is_instance && igvn != NULL  && result->is_Phi()) {
 178     PhiNode *mphi = result->as_Phi();
 179     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 180     const TypePtr *t = mphi->adr_type();
 181     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 182         t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 183         t->is_oopptr()->cast_to_exactness(true)
 184          ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 185          ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop) {
 186       // clone the Phi with our address type
 187       result = mphi->split_out_instance(t_adr, igvn);
 188     } else {
 189       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 190     }
 191   }
 192   return result;
 193 }
 194 
 195 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 196   uint alias_idx = phase->C->get_alias_index(tp);
 197   Node *mem = mmem;
 198 #ifdef ASSERT
 199   {
 200     // Check that current type is consistent with the alias index used during graph construction
 201     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 202     bool consistent =  adr_check == NULL || adr_check->empty() ||
 203                        phase->C->must_alias(adr_check, alias_idx );
 204     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 205     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 206                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 207         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 208         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 209           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 210           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 211       // don't assert if it is dead code.
 212       consistent = true;
 213     }
 214     if( !consistent ) {
 215       st->print("alias_idx==%d, adr_check==", alias_idx);
 216       if( adr_check == NULL ) {
 217         st->print("NULL");
 218       } else {
 219         adr_check->dump();
 220       }
 221       st->cr();
 222       print_alias_types();
 223       assert(consistent, "adr_check must match alias idx");
 224     }
 225   }
 226 #endif
 227   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 228   // means an array I have not precisely typed yet.  Do not do any
 229   // alias stuff with it any time soon.
 230   const TypeOopPtr *toop = tp->isa_oopptr();
 231   if( tp->base() != Type::AnyPtr &&
 232       !(toop &&
 233         toop->klass() != NULL &&
 234         toop->klass()->is_java_lang_Object() &&
 235         toop->offset() == Type::OffsetBot) ) {
 236     // compress paths and change unreachable cycles to TOP
 237     // If not, we can update the input infinitely along a MergeMem cycle
 238     // Equivalent code in PhiNode::Ideal
 239     Node* m  = phase->transform(mmem);
 240     // If transformed to a MergeMem, get the desired slice
 241     // Otherwise the returned node represents memory for every slice
 242     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 243     // Update input if it is progress over what we have now
 244   }
 245   return mem;
 246 }
 247 
 248 //--------------------------Ideal_common---------------------------------------
 249 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 250 // Unhook non-raw memories from complete (macro-expanded) initializations.
 251 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 252   // If our control input is a dead region, kill all below the region
 253   Node *ctl = in(MemNode::Control);
 254   if (ctl && remove_dead_region(phase, can_reshape))
 255     return this;
 256   ctl = in(MemNode::Control);
 257   // Don't bother trying to transform a dead node
 258   if (ctl && ctl->is_top())  return NodeSentinel;
 259 
 260   PhaseIterGVN *igvn = phase->is_IterGVN();
 261   // Wait if control on the worklist.
 262   if (ctl && can_reshape && igvn != NULL) {
 263     Node* bol = NULL;
 264     Node* cmp = NULL;
 265     if (ctl->in(0)->is_If()) {
 266       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 267       bol = ctl->in(0)->in(1);
 268       if (bol->is_Bool())
 269         cmp = ctl->in(0)->in(1)->in(1);
 270     }
 271     if (igvn->_worklist.member(ctl) ||
 272         (bol != NULL && igvn->_worklist.member(bol)) ||
 273         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 274       // This control path may be dead.
 275       // Delay this memory node transformation until the control is processed.
 276       phase->is_IterGVN()->_worklist.push(this);
 277       return NodeSentinel; // caller will return NULL
 278     }
 279   }
 280   // Ignore if memory is dead, or self-loop
 281   Node *mem = in(MemNode::Memory);
 282   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 283   assert(mem != this, "dead loop in MemNode::Ideal");
 284 
 285   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 286     // This memory slice may be dead.
 287     // Delay this mem node transformation until the memory is processed.
 288     phase->is_IterGVN()->_worklist.push(this);
 289     return NodeSentinel; // caller will return NULL
 290   }
 291 
 292   Node *address = in(MemNode::Address);
 293   const Type *t_adr = phase->type(address);
 294   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 295 
 296   if (can_reshape && igvn != NULL &&
 297       (igvn->_worklist.member(address) ||
 298        igvn->_worklist.size() > 0 && (t_adr != adr_type())) ) {
 299     // The address's base and type may change when the address is processed.
 300     // Delay this mem node transformation until the address is processed.
 301     phase->is_IterGVN()->_worklist.push(this);
 302     return NodeSentinel; // caller will return NULL
 303   }
 304 
 305   // Do NOT remove or optimize the next lines: ensure a new alias index
 306   // is allocated for an oop pointer type before Escape Analysis.
 307   // Note: C++ will not remove it since the call has side effect.
 308   if (t_adr->isa_oopptr()) {
 309     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 310   }
 311 
 312   Node* base = NULL;
 313   if (address->is_AddP()) {
 314     base = address->in(AddPNode::Base);
 315   }
 316   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 317       !t_adr->isa_rawptr()) {
 318     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 319     // Skip this node optimization if its address has TOP base.
 320     return NodeSentinel; // caller will return NULL
 321   }
 322 
 323   // Avoid independent memory operations
 324   Node* old_mem = mem;
 325 
 326   // The code which unhooks non-raw memories from complete (macro-expanded)
 327   // initializations was removed. After macro-expansion all stores catched
 328   // by Initialize node became raw stores and there is no information
 329   // which memory slices they modify. So it is unsafe to move any memory
 330   // operation above these stores. Also in most cases hooked non-raw memories
 331   // were already unhooked by using information from detect_ptr_independence()
 332   // and find_previous_store().
 333 
 334   if (mem->is_MergeMem()) {
 335     MergeMemNode* mmem = mem->as_MergeMem();
 336     const TypePtr *tp = t_adr->is_ptr();
 337 
 338     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 339   }
 340 
 341   if (mem != old_mem) {
 342     set_req(MemNode::Memory, mem);
 343     if (can_reshape && old_mem->outcnt() == 0) {
 344         igvn->_worklist.push(old_mem);
 345     }
 346     if (phase->type( mem ) == Type::TOP) return NodeSentinel;
 347     return this;
 348   }
 349 
 350   // let the subclass continue analyzing...
 351   return NULL;
 352 }
 353 
 354 // Helper function for proving some simple control dominations.
 355 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 356 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 357 // is not a constant (dominated by the method's StartNode).
 358 // Used by MemNode::find_previous_store to prove that the
 359 // control input of a memory operation predates (dominates)
 360 // an allocation it wants to look past.
 361 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 362   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 363     return false; // Conservative answer for dead code
 364 
 365   // Check 'dom'. Skip Proj and CatchProj nodes.
 366   dom = dom->find_exact_control(dom);
 367   if (dom == NULL || dom->is_top())
 368     return false; // Conservative answer for dead code
 369 
 370   if (dom == sub) {
 371     // For the case when, for example, 'sub' is Initialize and the original
 372     // 'dom' is Proj node of the 'sub'.
 373     return false;
 374   }
 375 
 376   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 377     return true;
 378 
 379   // 'dom' dominates 'sub' if its control edge and control edges
 380   // of all its inputs dominate or equal to sub's control edge.
 381 
 382   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 383   // Or Region for the check in LoadNode::Ideal();
 384   // 'sub' should have sub->in(0) != NULL.
 385   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 386          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 387 
 388   // Get control edge of 'sub'.
 389   Node* orig_sub = sub;
 390   sub = sub->find_exact_control(sub->in(0));
 391   if (sub == NULL || sub->is_top())
 392     return false; // Conservative answer for dead code
 393 
 394   assert(sub->is_CFG(), "expecting control");
 395 
 396   if (sub == dom)
 397     return true;
 398 
 399   if (sub->is_Start() || sub->is_Root())
 400     return false;
 401 
 402   {
 403     // Check all control edges of 'dom'.
 404 
 405     ResourceMark rm;
 406     Arena* arena = Thread::current()->resource_area();
 407     Node_List nlist(arena);
 408     Unique_Node_List dom_list(arena);
 409 
 410     dom_list.push(dom);
 411     bool only_dominating_controls = false;
 412 
 413     for (uint next = 0; next < dom_list.size(); next++) {
 414       Node* n = dom_list.at(next);
 415       if (n == orig_sub)
 416         return false; // One of dom's inputs dominated by sub.
 417       if (!n->is_CFG() && n->pinned()) {
 418         // Check only own control edge for pinned non-control nodes.
 419         n = n->find_exact_control(n->in(0));
 420         if (n == NULL || n->is_top())
 421           return false; // Conservative answer for dead code
 422         assert(n->is_CFG(), "expecting control");
 423         dom_list.push(n);
 424       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 425         only_dominating_controls = true;
 426       } else if (n->is_CFG()) {
 427         if (n->dominates(sub, nlist))
 428           only_dominating_controls = true;
 429         else
 430           return false;
 431       } else {
 432         // First, own control edge.
 433         Node* m = n->find_exact_control(n->in(0));
 434         if (m != NULL) {
 435           if (m->is_top())
 436             return false; // Conservative answer for dead code
 437           dom_list.push(m);
 438         }
 439         // Now, the rest of edges.
 440         uint cnt = n->req();
 441         for (uint i = 1; i < cnt; i++) {
 442           m = n->find_exact_control(n->in(i));
 443           if (m == NULL || m->is_top())
 444             continue;
 445           dom_list.push(m);
 446         }
 447       }
 448     }
 449     return only_dominating_controls;
 450   }
 451 }
 452 
 453 //---------------------detect_ptr_independence---------------------------------
 454 // Used by MemNode::find_previous_store to prove that two base
 455 // pointers are never equal.
 456 // The pointers are accompanied by their associated allocations,
 457 // if any, which have been previously discovered by the caller.
 458 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 459                                       Node* p2, AllocateNode* a2,
 460                                       PhaseTransform* phase) {
 461   // Attempt to prove that these two pointers cannot be aliased.
 462   // They may both manifestly be allocations, and they should differ.
 463   // Or, if they are not both allocations, they can be distinct constants.
 464   // Otherwise, one is an allocation and the other a pre-existing value.
 465   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 466     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 467   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 468     return (a1 != a2);
 469   } else if (a1 != NULL) {                  // one allocation a1
 470     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 471     return all_controls_dominate(p2, a1);
 472   } else { //(a2 != NULL)                   // one allocation a2
 473     return all_controls_dominate(p1, a2);
 474   }
 475   return false;
 476 }
 477 
 478 
 479 // The logic for reordering loads and stores uses four steps:
 480 // (a) Walk carefully past stores and initializations which we
 481 //     can prove are independent of this load.
 482 // (b) Observe that the next memory state makes an exact match
 483 //     with self (load or store), and locate the relevant store.
 484 // (c) Ensure that, if we were to wire self directly to the store,
 485 //     the optimizer would fold it up somehow.
 486 // (d) Do the rewiring, and return, depending on some other part of
 487 //     the optimizer to fold up the load.
 488 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 489 // specific to loads and stores, so they are handled by the callers.
 490 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 491 //
 492 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 493   Node*         ctrl   = in(MemNode::Control);
 494   Node*         adr    = in(MemNode::Address);
 495   intptr_t      offset = 0;
 496   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 497   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 498 
 499   if (offset == Type::OffsetBot)
 500     return NULL;            // cannot unalias unless there are precise offsets
 501 
 502   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 503 
 504   intptr_t size_in_bytes = memory_size();
 505 
 506   Node* mem = in(MemNode::Memory);   // start searching here...
 507 
 508   int cnt = 50;             // Cycle limiter
 509   for (;;) {                // While we can dance past unrelated stores...
 510     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 511 
 512     if (mem->is_Store()) {
 513       Node* st_adr = mem->in(MemNode::Address);
 514       intptr_t st_offset = 0;
 515       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 516       if (st_base == NULL)
 517         break;              // inscrutable pointer
 518       if (st_offset != offset && st_offset != Type::OffsetBot) {
 519         const int MAX_STORE = BytesPerLong;
 520         if (st_offset >= offset + size_in_bytes ||
 521             st_offset <= offset - MAX_STORE ||
 522             st_offset <= offset - mem->as_Store()->memory_size()) {
 523           // Success:  The offsets are provably independent.
 524           // (You may ask, why not just test st_offset != offset and be done?
 525           // The answer is that stores of different sizes can co-exist
 526           // in the same sequence of RawMem effects.  We sometimes initialize
 527           // a whole 'tile' of array elements with a single jint or jlong.)
 528           mem = mem->in(MemNode::Memory);
 529           continue;           // (a) advance through independent store memory
 530         }
 531       }
 532       if (st_base != base &&
 533           detect_ptr_independence(base, alloc,
 534                                   st_base,
 535                                   AllocateNode::Ideal_allocation(st_base, phase),
 536                                   phase)) {
 537         // Success:  The bases are provably independent.
 538         mem = mem->in(MemNode::Memory);
 539         continue;           // (a) advance through independent store memory
 540       }
 541 
 542       // (b) At this point, if the bases or offsets do not agree, we lose,
 543       // since we have not managed to prove 'this' and 'mem' independent.
 544       if (st_base == base && st_offset == offset) {
 545         return mem;         // let caller handle steps (c), (d)
 546       }
 547 
 548     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 549       InitializeNode* st_init = mem->in(0)->as_Initialize();
 550       AllocateNode*  st_alloc = st_init->allocation();
 551       if (st_alloc == NULL)
 552         break;              // something degenerated
 553       bool known_identical = false;
 554       bool known_independent = false;
 555       if (alloc == st_alloc)
 556         known_identical = true;
 557       else if (alloc != NULL)
 558         known_independent = true;
 559       else if (all_controls_dominate(this, st_alloc))
 560         known_independent = true;
 561 
 562       if (known_independent) {
 563         // The bases are provably independent: Either they are
 564         // manifestly distinct allocations, or else the control
 565         // of this load dominates the store's allocation.
 566         int alias_idx = phase->C->get_alias_index(adr_type());
 567         if (alias_idx == Compile::AliasIdxRaw) {
 568           mem = st_alloc->in(TypeFunc::Memory);
 569         } else {
 570           mem = st_init->memory(alias_idx);
 571         }
 572         continue;           // (a) advance through independent store memory
 573       }
 574 
 575       // (b) at this point, if we are not looking at a store initializing
 576       // the same allocation we are loading from, we lose.
 577       if (known_identical) {
 578         // From caller, can_see_stored_value will consult find_captured_store.
 579         return mem;         // let caller handle steps (c), (d)
 580       }
 581 
 582     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 583       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 584       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 585         CallNode *call = mem->in(0)->as_Call();
 586         if (!call->may_modify(addr_t, phase)) {
 587           mem = call->in(TypeFunc::Memory);
 588           continue;         // (a) advance through independent call memory
 589         }
 590       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 591         mem = mem->in(0)->in(TypeFunc::Memory);
 592         continue;           // (a) advance through independent MemBar memory
 593       } else if (mem->is_ClearArray()) {
 594         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 595           // (the call updated 'mem' value)
 596           continue;         // (a) advance through independent allocation memory
 597         } else {
 598           // Can not bypass initialization of the instance
 599           // we are looking for.
 600           return mem;
 601         }
 602       } else if (mem->is_MergeMem()) {
 603         int alias_idx = phase->C->get_alias_index(adr_type());
 604         mem = mem->as_MergeMem()->memory_at(alias_idx);
 605         continue;           // (a) advance through independent MergeMem memory
 606       }
 607     }
 608 
 609     // Unless there is an explicit 'continue', we must bail out here,
 610     // because 'mem' is an inscrutable memory state (e.g., a call).
 611     break;
 612   }
 613 
 614   return NULL;              // bail out
 615 }
 616 
 617 //----------------------calculate_adr_type-------------------------------------
 618 // Helper function.  Notices when the given type of address hits top or bottom.
 619 // Also, asserts a cross-check of the type against the expected address type.
 620 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 621   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 622   #ifdef PRODUCT
 623   cross_check = NULL;
 624   #else
 625   if (!VerifyAliases || is_error_reported() || Node::in_dump())  cross_check = NULL;
 626   #endif
 627   const TypePtr* tp = t->isa_ptr();
 628   if (tp == NULL) {
 629     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 630     return TypePtr::BOTTOM;           // touches lots of memory
 631   } else {
 632     #ifdef ASSERT
 633     // %%%% [phh] We don't check the alias index if cross_check is
 634     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 635     if (cross_check != NULL &&
 636         cross_check != TypePtr::BOTTOM &&
 637         cross_check != TypeRawPtr::BOTTOM) {
 638       // Recheck the alias index, to see if it has changed (due to a bug).
 639       Compile* C = Compile::current();
 640       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 641              "must stay in the original alias category");
 642       // The type of the address must be contained in the adr_type,
 643       // disregarding "null"-ness.
 644       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 645       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 646       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 647              "real address must not escape from expected memory type");
 648     }
 649     #endif
 650     return tp;
 651   }
 652 }
 653 
 654 //------------------------adr_phi_is_loop_invariant----------------------------
 655 // A helper function for Ideal_DU_postCCP to check if a Phi in a counted
 656 // loop is loop invariant. Make a quick traversal of Phi and associated
 657 // CastPP nodes, looking to see if they are a closed group within the loop.
 658 bool MemNode::adr_phi_is_loop_invariant(Node* adr_phi, Node* cast) {
 659   // The idea is that the phi-nest must boil down to only CastPP nodes
 660   // with the same data. This implies that any path into the loop already
 661   // includes such a CastPP, and so the original cast, whatever its input,
 662   // must be covered by an equivalent cast, with an earlier control input.
 663   ResourceMark rm;
 664 
 665   // The loop entry input of the phi should be the unique dominating
 666   // node for every Phi/CastPP in the loop.
 667   Unique_Node_List closure;
 668   closure.push(adr_phi->in(LoopNode::EntryControl));
 669 
 670   // Add the phi node and the cast to the worklist.
 671   Unique_Node_List worklist;
 672   worklist.push(adr_phi);
 673   if( cast != NULL ){
 674     if( !cast->is_ConstraintCast() ) return false;
 675     worklist.push(cast);
 676   }
 677 
 678   // Begin recursive walk of phi nodes.
 679   while( worklist.size() ){
 680     // Take a node off the worklist
 681     Node *n = worklist.pop();
 682     if( !closure.member(n) ){
 683       // Add it to the closure.
 684       closure.push(n);
 685       // Make a sanity check to ensure we don't waste too much time here.
 686       if( closure.size() > 20) return false;
 687       // This node is OK if:
 688       //  - it is a cast of an identical value
 689       //  - or it is a phi node (then we add its inputs to the worklist)
 690       // Otherwise, the node is not OK, and we presume the cast is not invariant
 691       if( n->is_ConstraintCast() ){
 692         worklist.push(n->in(1));
 693       } else if( n->is_Phi() ) {
 694         for( uint i = 1; i < n->req(); i++ ) {
 695           worklist.push(n->in(i));
 696         }
 697       } else {
 698         return false;
 699       }
 700     }
 701   }
 702 
 703   // Quit when the worklist is empty, and we've found no offending nodes.
 704   return true;
 705 }
 706 
 707 //------------------------------Ideal_DU_postCCP-------------------------------
 708 // Find any cast-away of null-ness and keep its control.  Null cast-aways are
 709 // going away in this pass and we need to make this memory op depend on the
 710 // gating null check.
 711 Node *MemNode::Ideal_DU_postCCP( PhaseCCP *ccp ) {
 712   return Ideal_common_DU_postCCP(ccp, this, in(MemNode::Address));
 713 }
 714 
 715 // I tried to leave the CastPP's in.  This makes the graph more accurate in
 716 // some sense; we get to keep around the knowledge that an oop is not-null
 717 // after some test.  Alas, the CastPP's interfere with GVN (some values are
 718 // the regular oop, some are the CastPP of the oop, all merge at Phi's which
 719 // cannot collapse, etc).  This cost us 10% on SpecJVM, even when I removed
 720 // some of the more trivial cases in the optimizer.  Removing more useless
 721 // Phi's started allowing Loads to illegally float above null checks.  I gave
 722 // up on this approach.  CNC 10/20/2000
 723 // This static method may be called not from MemNode (EncodePNode calls it).
 724 // Only the control edge of the node 'n' might be updated.
 725 Node *MemNode::Ideal_common_DU_postCCP( PhaseCCP *ccp, Node* n, Node* adr ) {
 726   Node *skipped_cast = NULL;
 727   // Need a null check?  Regular static accesses do not because they are
 728   // from constant addresses.  Array ops are gated by the range check (which
 729   // always includes a NULL check).  Just check field ops.
 730   if( n->in(MemNode::Control) == NULL ) {
 731     // Scan upwards for the highest location we can place this memory op.
 732     while( true ) {
 733       switch( adr->Opcode() ) {
 734 
 735       case Op_AddP:             // No change to NULL-ness, so peek thru AddP's
 736         adr = adr->in(AddPNode::Base);
 737         continue;
 738 
 739       case Op_DecodeN:         // No change to NULL-ness, so peek thru
 740       case Op_DecodeNKlass:
 741         adr = adr->in(1);
 742         continue;
 743 
 744       case Op_EncodeP:
 745       case Op_EncodePKlass:
 746         // EncodeP node's control edge could be set by this method
 747         // when EncodeP node depends on CastPP node.
 748         //
 749         // Use its control edge for memory op because EncodeP may go away
 750         // later when it is folded with following or preceding DecodeN node.
 751         if (adr->in(0) == NULL) {
 752           // Keep looking for cast nodes.
 753           adr = adr->in(1);
 754           continue;
 755         }
 756         ccp->hash_delete(n);
 757         n->set_req(MemNode::Control, adr->in(0));
 758         ccp->hash_insert(n);
 759         return n;
 760 
 761       case Op_CastPP:
 762         // If the CastPP is useless, just peek on through it.
 763         if( ccp->type(adr) == ccp->type(adr->in(1)) ) {
 764           // Remember the cast that we've peeked though. If we peek
 765           // through more than one, then we end up remembering the highest
 766           // one, that is, if in a loop, the one closest to the top.
 767           skipped_cast = adr;
 768           adr = adr->in(1);
 769           continue;
 770         }
 771         // CastPP is going away in this pass!  We need this memory op to be
 772         // control-dependent on the test that is guarding the CastPP.
 773         ccp->hash_delete(n);
 774         n->set_req(MemNode::Control, adr->in(0));
 775         ccp->hash_insert(n);
 776         return n;
 777 
 778       case Op_Phi:
 779         // Attempt to float above a Phi to some dominating point.
 780         if (adr->in(0) != NULL && adr->in(0)->is_CountedLoop()) {
 781           // If we've already peeked through a Cast (which could have set the
 782           // control), we can't float above a Phi, because the skipped Cast
 783           // may not be loop invariant.
 784           if (adr_phi_is_loop_invariant(adr, skipped_cast)) {
 785             adr = adr->in(1);
 786             continue;
 787           }
 788         }
 789 
 790         // Intentional fallthrough!
 791 
 792         // No obvious dominating point.  The mem op is pinned below the Phi
 793         // by the Phi itself.  If the Phi goes away (no true value is merged)
 794         // then the mem op can float, but not indefinitely.  It must be pinned
 795         // behind the controls leading to the Phi.
 796       case Op_CheckCastPP:
 797         // These usually stick around to change address type, however a
 798         // useless one can be elided and we still need to pick up a control edge
 799         if (adr->in(0) == NULL) {
 800           // This CheckCastPP node has NO control and is likely useless. But we
 801           // need check further up the ancestor chain for a control input to keep
 802           // the node in place. 4959717.
 803           skipped_cast = adr;
 804           adr = adr->in(1);
 805           continue;
 806         }
 807         ccp->hash_delete(n);
 808         n->set_req(MemNode::Control, adr->in(0));
 809         ccp->hash_insert(n);
 810         return n;
 811 
 812         // List of "safe" opcodes; those that implicitly block the memory
 813         // op below any null check.
 814       case Op_CastX2P:          // no null checks on native pointers
 815       case Op_Parm:             // 'this' pointer is not null
 816       case Op_LoadP:            // Loading from within a klass
 817       case Op_LoadN:            // Loading from within a klass
 818       case Op_LoadKlass:        // Loading from within a klass
 819       case Op_LoadNKlass:       // Loading from within a klass
 820       case Op_ConP:             // Loading from a klass
 821       case Op_ConN:             // Loading from a klass
 822       case Op_ConNKlass:        // Loading from a klass
 823       case Op_CreateEx:         // Sucking up the guts of an exception oop
 824       case Op_Con:              // Reading from TLS
 825       case Op_CMoveP:           // CMoveP is pinned
 826       case Op_CMoveN:           // CMoveN is pinned
 827         break;                  // No progress
 828 
 829       case Op_Proj:             // Direct call to an allocation routine
 830       case Op_SCMemProj:        // Memory state from store conditional ops
 831 #ifdef ASSERT
 832         {
 833           assert(adr->as_Proj()->_con == TypeFunc::Parms, "must be return value");
 834           const Node* call = adr->in(0);
 835           if (call->is_CallJava()) {
 836             const CallJavaNode* call_java = call->as_CallJava();
 837             const TypeTuple *r = call_java->tf()->range();
 838             assert(r->cnt() > TypeFunc::Parms, "must return value");
 839             const Type* ret_type = r->field_at(TypeFunc::Parms);
 840             assert(ret_type && ret_type->isa_ptr(), "must return pointer");
 841             // We further presume that this is one of
 842             // new_instance_Java, new_array_Java, or
 843             // the like, but do not assert for this.
 844           } else if (call->is_Allocate()) {
 845             // similar case to new_instance_Java, etc.
 846           } else if (!call->is_CallLeaf()) {
 847             // Projections from fetch_oop (OSR) are allowed as well.
 848             ShouldNotReachHere();
 849           }
 850         }
 851 #endif
 852         break;
 853       default:
 854         ShouldNotReachHere();
 855       }
 856       break;
 857     }
 858   }
 859 
 860   return  NULL;               // No progress
 861 }
 862 
 863 
 864 //=============================================================================
 865 uint LoadNode::size_of() const { return sizeof(*this); }
 866 uint LoadNode::cmp( const Node &n ) const
 867 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 868 const Type *LoadNode::bottom_type() const { return _type; }
 869 uint LoadNode::ideal_reg() const {
 870   return _type->ideal_reg();
 871 }
 872 
 873 #ifndef PRODUCT
 874 void LoadNode::dump_spec(outputStream *st) const {
 875   MemNode::dump_spec(st);
 876   if( !Verbose && !WizardMode ) {
 877     // standard dump does this in Verbose and WizardMode
 878     st->print(" #"); _type->dump_on(st);
 879   }
 880 }
 881 #endif
 882 
 883 #ifdef ASSERT
 884 //----------------------------is_immutable_value-------------------------------
 885 // Helper function to allow a raw load without control edge for some cases
 886 bool LoadNode::is_immutable_value(Node* adr) {
 887   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 888           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 889           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 890            in_bytes(JavaThread::osthread_offset())));
 891 }
 892 #endif
 893 
 894 //----------------------------LoadNode::make-----------------------------------
 895 // Polymorphic factory method:
 896 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo) {
 897   Compile* C = gvn.C;
 898 
 899   // sanity check the alias category against the created node type
 900   assert(!(adr_type->isa_oopptr() &&
 901            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 902          "use LoadKlassNode instead");
 903   assert(!(adr_type->isa_aryptr() &&
 904            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 905          "use LoadRangeNode instead");
 906   // Check control edge of raw loads
 907   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 908           // oop will be recorded in oop map if load crosses safepoint
 909           rt->isa_oopptr() || is_immutable_value(adr),
 910           "raw memory operations should have control edge");
 911   switch (bt) {
 912   case T_BOOLEAN: return new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo);
 913   case T_BYTE:    return new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo);
 914   case T_INT:     return new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo);
 915   case T_CHAR:    return new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo);
 916   case T_SHORT:   return new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo);
 917   case T_LONG:    return new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo);
 918   case T_FLOAT:   return new LoadFNode (ctl, mem, adr, adr_type, rt,            mo);
 919   case T_DOUBLE:  return new LoadDNode (ctl, mem, adr, adr_type, rt,            mo);
 920   case T_ADDRESS: return new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo);
 921   case T_OBJECT:
 922 #ifdef _LP64
 923     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 924       Node* load  = gvn.transform(new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo));
 925       return new DecodeNNode(load, load->bottom_type()->make_ptr());
 926     } else
 927 #endif
 928     {
 929       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 930       return new LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr(), mo);
 931     }
 932   }
 933   ShouldNotReachHere();
 934   return (LoadNode*)NULL;
 935 }
 936 
 937 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo) {
 938   bool require_atomic = true;
 939   return new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, require_atomic);
 940 }
 941 
 942 LoadDNode* LoadDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo) {
 943   bool require_atomic = true;
 944   return new LoadDNode(ctl, mem, adr, adr_type, rt, mo, require_atomic);
 945 }
 946 
 947 
 948 
 949 //------------------------------hash-------------------------------------------
 950 uint LoadNode::hash() const {
 951   // unroll addition of interesting fields
 952   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 953 }
 954 
 955 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 956   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 957     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 958     bool is_stable_ary = FoldStableValues &&
 959                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 960                          tp->isa_aryptr()->is_stable();
 961 
 962     return (eliminate_boxing && non_volatile) || is_stable_ary;
 963   }
 964 
 965   return false;
 966 }
 967 
 968 //---------------------------can_see_stored_value------------------------------
 969 // This routine exists to make sure this set of tests is done the same
 970 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 971 // will change the graph shape in a way which makes memory alive twice at the
 972 // same time (uses the Oracle model of aliasing), then some
 973 // LoadXNode::Identity will fold things back to the equivalence-class model
 974 // of aliasing.
 975 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 976   Node* ld_adr = in(MemNode::Address);
 977   intptr_t ld_off = 0;
 978   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 979   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 980   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
 981   // This is more general than load from boxing objects.
 982   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
 983     uint alias_idx = atp->index();
 984     bool final = !atp->is_rewritable();
 985     Node* result = NULL;
 986     Node* current = st;
 987     // Skip through chains of MemBarNodes checking the MergeMems for
 988     // new states for the slice of this load.  Stop once any other
 989     // kind of node is encountered.  Loads from final memory can skip
 990     // through any kind of MemBar but normal loads shouldn't skip
 991     // through MemBarAcquire since the could allow them to move out of
 992     // a synchronized region.
 993     while (current->is_Proj()) {
 994       int opc = current->in(0)->Opcode();
 995       if ((final && (opc == Op_MemBarAcquire ||
 996                      opc == Op_MemBarAcquireLock ||
 997                      opc == Op_LoadFence)) ||
 998           opc == Op_MemBarRelease ||
 999           opc == Op_StoreFence ||
1000           opc == Op_MemBarReleaseLock ||
1001           opc == Op_MemBarCPUOrder) {
1002         Node* mem = current->in(0)->in(TypeFunc::Memory);
1003         if (mem->is_MergeMem()) {
1004           MergeMemNode* merge = mem->as_MergeMem();
1005           Node* new_st = merge->memory_at(alias_idx);
1006           if (new_st == merge->base_memory()) {
1007             // Keep searching
1008             current = new_st;
1009             continue;
1010           }
1011           // Save the new memory state for the slice and fall through
1012           // to exit.
1013           result = new_st;
1014         }
1015       }
1016       break;
1017     }
1018     if (result != NULL) {
1019       st = result;
1020     }
1021   }
1022 
1023   // Loop around twice in the case Load -> Initialize -> Store.
1024   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1025   for (int trip = 0; trip <= 1; trip++) {
1026 
1027     if (st->is_Store()) {
1028       Node* st_adr = st->in(MemNode::Address);
1029       if (!phase->eqv(st_adr, ld_adr)) {
1030         // Try harder before giving up...  Match raw and non-raw pointers.
1031         intptr_t st_off = 0;
1032         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
1033         if (alloc == NULL)       return NULL;
1034         if (alloc != ld_alloc)   return NULL;
1035         if (ld_off != st_off)    return NULL;
1036         // At this point we have proven something like this setup:
1037         //  A = Allocate(...)
1038         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
1039         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
1040         // (Actually, we haven't yet proven the Q's are the same.)
1041         // In other words, we are loading from a casted version of
1042         // the same pointer-and-offset that we stored to.
1043         // Thus, we are able to replace L by V.
1044       }
1045       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1046       if (store_Opcode() != st->Opcode())
1047         return NULL;
1048       return st->in(MemNode::ValueIn);
1049     }
1050 
1051     // A load from a freshly-created object always returns zero.
1052     // (This can happen after LoadNode::Ideal resets the load's memory input
1053     // to find_captured_store, which returned InitializeNode::zero_memory.)
1054     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1055         (st->in(0) == ld_alloc) &&
1056         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1057       // return a zero value for the load's basic type
1058       // (This is one of the few places where a generic PhaseTransform
1059       // can create new nodes.  Think of it as lazily manifesting
1060       // virtually pre-existing constants.)
1061       return phase->zerocon(memory_type());
1062     }
1063 
1064     // A load from an initialization barrier can match a captured store.
1065     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1066       InitializeNode* init = st->in(0)->as_Initialize();
1067       AllocateNode* alloc = init->allocation();
1068       if ((alloc != NULL) && (alloc == ld_alloc)) {
1069         // examine a captured store value
1070         st = init->find_captured_store(ld_off, memory_size(), phase);
1071         if (st != NULL)
1072           continue;             // take one more trip around
1073       }
1074     }
1075 
1076     // Load boxed value from result of valueOf() call is input parameter.
1077     if (this->is_Load() && ld_adr->is_AddP() &&
1078         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1079       intptr_t ignore = 0;
1080       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1081       if (base != NULL && base->is_Proj() &&
1082           base->as_Proj()->_con == TypeFunc::Parms &&
1083           base->in(0)->is_CallStaticJava() &&
1084           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1085         return base->in(0)->in(TypeFunc::Parms);
1086       }
1087     }
1088 
1089     break;
1090   }
1091 
1092   return NULL;
1093 }
1094 
1095 //----------------------is_instance_field_load_with_local_phi------------------
1096 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1097   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1098       in(Address)->is_AddP() ) {
1099     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1100     // Only instances and boxed values.
1101     if( t_oop != NULL &&
1102         (t_oop->is_ptr_to_boxed_value() ||
1103          t_oop->is_known_instance_field()) &&
1104         t_oop->offset() != Type::OffsetBot &&
1105         t_oop->offset() != Type::OffsetTop) {
1106       return true;
1107     }
1108   }
1109   return false;
1110 }
1111 
1112 //------------------------------Identity---------------------------------------
1113 // Loads are identity if previous store is to same address
1114 Node *LoadNode::Identity( PhaseTransform *phase ) {
1115   // If the previous store-maker is the right kind of Store, and the store is
1116   // to the same address, then we are equal to the value stored.
1117   Node* mem = in(Memory);
1118   Node* value = can_see_stored_value(mem, phase);
1119   if( value ) {
1120     // byte, short & char stores truncate naturally.
1121     // A load has to load the truncated value which requires
1122     // some sort of masking operation and that requires an
1123     // Ideal call instead of an Identity call.
1124     if (memory_size() < BytesPerInt) {
1125       // If the input to the store does not fit with the load's result type,
1126       // it must be truncated via an Ideal call.
1127       if (!phase->type(value)->higher_equal(phase->type(this)))
1128         return this;
1129     }
1130     // (This works even when value is a Con, but LoadNode::Value
1131     // usually runs first, producing the singleton type of the Con.)
1132     return value;
1133   }
1134 
1135   // Search for an existing data phi which was generated before for the same
1136   // instance's field to avoid infinite generation of phis in a loop.
1137   Node *region = mem->in(0);
1138   if (is_instance_field_load_with_local_phi(region)) {
1139     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1140     int this_index  = phase->C->get_alias_index(addr_t);
1141     int this_offset = addr_t->offset();
1142     int this_iid    = addr_t->instance_id();
1143     if (!addr_t->is_known_instance() &&
1144          addr_t->is_ptr_to_boxed_value()) {
1145       // Use _idx of address base (could be Phi node) for boxed values.
1146       intptr_t   ignore = 0;
1147       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1148       this_iid = base->_idx;
1149     }
1150     const Type* this_type = bottom_type();
1151     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1152       Node* phi = region->fast_out(i);
1153       if (phi->is_Phi() && phi != mem &&
1154           phi->as_Phi()->is_same_inst_field(this_type, this_iid, this_index, this_offset)) {
1155         return phi;
1156       }
1157     }
1158   }
1159 
1160   return this;
1161 }
1162 
1163 // We're loading from an object which has autobox behaviour.
1164 // If this object is result of a valueOf call we'll have a phi
1165 // merging a newly allocated object and a load from the cache.
1166 // We want to replace this load with the original incoming
1167 // argument to the valueOf call.
1168 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1169   assert(phase->C->eliminate_boxing(), "sanity");
1170   intptr_t ignore = 0;
1171   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1172   if ((base == NULL) || base->is_Phi()) {
1173     // Push the loads from the phi that comes from valueOf up
1174     // through it to allow elimination of the loads and the recovery
1175     // of the original value. It is done in split_through_phi().
1176     return NULL;
1177   } else if (base->is_Load() ||
1178              base->is_DecodeN() && base->in(1)->is_Load()) {
1179     // Eliminate the load of boxed value for integer types from the cache
1180     // array by deriving the value from the index into the array.
1181     // Capture the offset of the load and then reverse the computation.
1182 
1183     // Get LoadN node which loads a boxing object from 'cache' array.
1184     if (base->is_DecodeN()) {
1185       base = base->in(1);
1186     }
1187     if (!base->in(Address)->is_AddP()) {
1188       return NULL; // Complex address
1189     }
1190     AddPNode* address = base->in(Address)->as_AddP();
1191     Node* cache_base = address->in(AddPNode::Base);
1192     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1193       // Get ConP node which is static 'cache' field.
1194       cache_base = cache_base->in(1);
1195     }
1196     if ((cache_base != NULL) && cache_base->is_Con()) {
1197       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1198       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1199         Node* elements[4];
1200         int shift = exact_log2(type2aelembytes(T_OBJECT));
1201         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1202         if ((count >  0) && elements[0]->is_Con() &&
1203             ((count == 1) ||
1204              (count == 2) && elements[1]->Opcode() == Op_LShiftX &&
1205                              elements[1]->in(2) == phase->intcon(shift))) {
1206           ciObjArray* array = base_type->const_oop()->as_obj_array();
1207           // Fetch the box object cache[0] at the base of the array and get its value
1208           ciInstance* box = array->obj_at(0)->as_instance();
1209           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1210           assert(ik->is_box_klass(), "sanity");
1211           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1212           if (ik->nof_nonstatic_fields() == 1) {
1213             // This should be true nonstatic_field_at requires calling
1214             // nof_nonstatic_fields so check it anyway
1215             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1216             BasicType bt = c.basic_type();
1217             // Only integer types have boxing cache.
1218             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1219                    bt == T_BYTE    || bt == T_SHORT ||
1220                    bt == T_INT     || bt == T_LONG, err_msg_res("wrong type = %s", type2name(bt)));
1221             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1222             if (cache_low != (int)cache_low) {
1223               return NULL; // should not happen since cache is array indexed by value
1224             }
1225             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1226             if (offset != (int)offset) {
1227               return NULL; // should not happen since cache is array indexed by value
1228             }
1229            // Add up all the offsets making of the address of the load
1230             Node* result = elements[0];
1231             for (int i = 1; i < count; i++) {
1232               result = phase->transform(new AddXNode(result, elements[i]));
1233             }
1234             // Remove the constant offset from the address and then
1235             result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1236             // remove the scaling of the offset to recover the original index.
1237             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1238               // Peel the shift off directly but wrap it in a dummy node
1239               // since Ideal can't return existing nodes
1240               result = new RShiftXNode(result->in(1), phase->intcon(0));
1241             } else if (result->is_Add() && result->in(2)->is_Con() &&
1242                        result->in(1)->Opcode() == Op_LShiftX &&
1243                        result->in(1)->in(2) == phase->intcon(shift)) {
1244               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1245               // but for boxing cache access we know that X<<Z will not overflow
1246               // (there is range check) so we do this optimizatrion by hand here.
1247               Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1248               result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1249             } else {
1250               result = new RShiftXNode(result, phase->intcon(shift));
1251             }
1252 #ifdef _LP64
1253             if (bt != T_LONG) {
1254               result = new ConvL2INode(phase->transform(result));
1255             }
1256 #else
1257             if (bt == T_LONG) {
1258               result = new ConvI2LNode(phase->transform(result));
1259             }
1260 #endif
1261             return result;
1262           }
1263         }
1264       }
1265     }
1266   }
1267   return NULL;
1268 }
1269 
1270 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1271   Node* region = phi->in(0);
1272   if (region == NULL) {
1273     return false; // Wait stable graph
1274   }
1275   uint cnt = phi->req();
1276   for (uint i = 1; i < cnt; i++) {
1277     Node* rc = region->in(i);
1278     if (rc == NULL || phase->type(rc) == Type::TOP)
1279       return false; // Wait stable graph
1280     Node* in = phi->in(i);
1281     if (in == NULL || phase->type(in) == Type::TOP)
1282       return false; // Wait stable graph
1283   }
1284   return true;
1285 }
1286 //------------------------------split_through_phi------------------------------
1287 // Split instance or boxed field load through Phi.
1288 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1289   Node* mem     = in(Memory);
1290   Node* address = in(Address);
1291   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1292 
1293   assert((t_oop != NULL) &&
1294          (t_oop->is_known_instance_field() ||
1295           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1296 
1297   Compile* C = phase->C;
1298   intptr_t ignore = 0;
1299   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1300   bool base_is_phi = (base != NULL) && base->is_Phi();
1301   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1302                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1303                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1304 
1305   if (!((mem->is_Phi() || base_is_phi) &&
1306         (load_boxed_values || t_oop->is_known_instance_field()))) {
1307     return NULL; // memory is not Phi
1308   }
1309 
1310   if (mem->is_Phi()) {
1311     if (!stable_phi(mem->as_Phi(), phase)) {
1312       return NULL; // Wait stable graph
1313     }
1314     uint cnt = mem->req();
1315     // Check for loop invariant memory.
1316     if (cnt == 3) {
1317       for (uint i = 1; i < cnt; i++) {
1318         Node* in = mem->in(i);
1319         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1320         if (m == mem) {
1321           set_req(Memory, mem->in(cnt - i));
1322           return this; // made change
1323         }
1324       }
1325     }
1326   }
1327   if (base_is_phi) {
1328     if (!stable_phi(base->as_Phi(), phase)) {
1329       return NULL; // Wait stable graph
1330     }
1331     uint cnt = base->req();
1332     // Check for loop invariant memory.
1333     if (cnt == 3) {
1334       for (uint i = 1; i < cnt; i++) {
1335         if (base->in(i) == base) {
1336           return NULL; // Wait stable graph
1337         }
1338       }
1339     }
1340   }
1341 
1342   bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1343 
1344   // Split through Phi (see original code in loopopts.cpp).
1345   assert(C->have_alias_type(t_oop), "instance should have alias type");
1346 
1347   // Do nothing here if Identity will find a value
1348   // (to avoid infinite chain of value phis generation).
1349   if (!phase->eqv(this, this->Identity(phase)))
1350     return NULL;
1351 
1352   // Select Region to split through.
1353   Node* region;
1354   if (!base_is_phi) {
1355     assert(mem->is_Phi(), "sanity");
1356     region = mem->in(0);
1357     // Skip if the region dominates some control edge of the address.
1358     if (!MemNode::all_controls_dominate(address, region))
1359       return NULL;
1360   } else if (!mem->is_Phi()) {
1361     assert(base_is_phi, "sanity");
1362     region = base->in(0);
1363     // Skip if the region dominates some control edge of the memory.
1364     if (!MemNode::all_controls_dominate(mem, region))
1365       return NULL;
1366   } else if (base->in(0) != mem->in(0)) {
1367     assert(base_is_phi && mem->is_Phi(), "sanity");
1368     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1369       region = base->in(0);
1370     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1371       region = mem->in(0);
1372     } else {
1373       return NULL; // complex graph
1374     }
1375   } else {
1376     assert(base->in(0) == mem->in(0), "sanity");
1377     region = mem->in(0);
1378   }
1379 
1380   const Type* this_type = this->bottom_type();
1381   int this_index  = C->get_alias_index(t_oop);
1382   int this_offset = t_oop->offset();
1383   int this_iid    = t_oop->instance_id();
1384   if (!t_oop->is_known_instance() && load_boxed_values) {
1385     // Use _idx of address base for boxed values.
1386     this_iid = base->_idx;
1387   }
1388   PhaseIterGVN* igvn = phase->is_IterGVN();
1389   Node* phi = new PhiNode(region, this_type, NULL, this_iid, this_index, this_offset);
1390   for (uint i = 1; i < region->req(); i++) {
1391     Node* x;
1392     Node* the_clone = NULL;
1393     if (region->in(i) == C->top()) {
1394       x = C->top();      // Dead path?  Use a dead data op
1395     } else {
1396       x = this->clone();        // Else clone up the data op
1397       the_clone = x;            // Remember for possible deletion.
1398       // Alter data node to use pre-phi inputs
1399       if (this->in(0) == region) {
1400         x->set_req(0, region->in(i));
1401       } else {
1402         x->set_req(0, NULL);
1403       }
1404       if (mem->is_Phi() && (mem->in(0) == region)) {
1405         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1406       }
1407       if (address->is_Phi() && address->in(0) == region) {
1408         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1409       }
1410       if (base_is_phi && (base->in(0) == region)) {
1411         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1412         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1413         x->set_req(Address, adr_x);
1414       }
1415     }
1416     // Check for a 'win' on some paths
1417     const Type *t = x->Value(igvn);
1418 
1419     bool singleton = t->singleton();
1420 
1421     // See comments in PhaseIdealLoop::split_thru_phi().
1422     if (singleton && t == Type::TOP) {
1423       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1424     }
1425 
1426     if (singleton) {
1427       x = igvn->makecon(t);
1428     } else {
1429       // We now call Identity to try to simplify the cloned node.
1430       // Note that some Identity methods call phase->type(this).
1431       // Make sure that the type array is big enough for
1432       // our new node, even though we may throw the node away.
1433       // (This tweaking with igvn only works because x is a new node.)
1434       igvn->set_type(x, t);
1435       // If x is a TypeNode, capture any more-precise type permanently into Node
1436       // otherwise it will be not updated during igvn->transform since
1437       // igvn->type(x) is set to x->Value() already.
1438       x->raise_bottom_type(t);
1439       Node *y = x->Identity(igvn);
1440       if (y != x) {
1441         x = y;
1442       } else {
1443         y = igvn->hash_find_insert(x);
1444         if (y) {
1445           x = y;
1446         } else {
1447           // Else x is a new node we are keeping
1448           // We do not need register_new_node_with_optimizer
1449           // because set_type has already been called.
1450           igvn->_worklist.push(x);
1451         }
1452       }
1453     }
1454     if (x != the_clone && the_clone != NULL) {
1455       igvn->remove_dead_node(the_clone);
1456     }
1457     phi->set_req(i, x);
1458   }
1459   // Record Phi
1460   igvn->register_new_node_with_optimizer(phi);
1461   return phi;
1462 }
1463 
1464 //------------------------------Ideal------------------------------------------
1465 // If the load is from Field memory and the pointer is non-null, we can
1466 // zero out the control input.
1467 // If the offset is constant and the base is an object allocation,
1468 // try to hook me up to the exact initializing store.
1469 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1470   Node* p = MemNode::Ideal_common(phase, can_reshape);
1471   if (p)  return (p == NodeSentinel) ? NULL : p;
1472 
1473   Node* ctrl    = in(MemNode::Control);
1474   Node* address = in(MemNode::Address);
1475   bool progress = false;
1476 
1477   // Skip up past a SafePoint control.  Cannot do this for Stores because
1478   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1479   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1480       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
1481     ctrl = ctrl->in(0);
1482     set_req(MemNode::Control,ctrl);
1483     progress = true;
1484   }
1485 
1486   intptr_t ignore = 0;
1487   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1488   if (base != NULL
1489       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1490     // Check for useless control edge in some common special cases
1491     if (in(MemNode::Control) != NULL
1492         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1493         && all_controls_dominate(base, phase->C->start())) {
1494       // A method-invariant, non-null address (constant or 'this' argument).
1495       set_req(MemNode::Control, NULL);
1496       progress = true;
1497     }
1498   }
1499 
1500   Node* mem = in(MemNode::Memory);
1501   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1502 
1503   if (can_reshape && (addr_t != NULL)) {
1504     // try to optimize our memory input
1505     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1506     if (opt_mem != mem) {
1507       set_req(MemNode::Memory, opt_mem);
1508       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1509       return this;
1510     }
1511     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1512     if ((t_oop != NULL) &&
1513         (t_oop->is_known_instance_field() ||
1514          t_oop->is_ptr_to_boxed_value())) {
1515       PhaseIterGVN *igvn = phase->is_IterGVN();
1516       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1517         // Delay this transformation until memory Phi is processed.
1518         phase->is_IterGVN()->_worklist.push(this);
1519         return NULL;
1520       }
1521       // Split instance field load through Phi.
1522       Node* result = split_through_phi(phase);
1523       if (result != NULL) return result;
1524 
1525       if (t_oop->is_ptr_to_boxed_value()) {
1526         Node* result = eliminate_autobox(phase);
1527         if (result != NULL) return result;
1528       }
1529     }
1530   }
1531 
1532   // Check for prior store with a different base or offset; make Load
1533   // independent.  Skip through any number of them.  Bail out if the stores
1534   // are in an endless dead cycle and report no progress.  This is a key
1535   // transform for Reflection.  However, if after skipping through the Stores
1536   // we can't then fold up against a prior store do NOT do the transform as
1537   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1538   // array memory alive twice: once for the hoisted Load and again after the
1539   // bypassed Store.  This situation only works if EVERYBODY who does
1540   // anti-dependence work knows how to bypass.  I.e. we need all
1541   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1542   // the alias index stuff.  So instead, peek through Stores and IFF we can
1543   // fold up, do so.
1544   Node* prev_mem = find_previous_store(phase);
1545   // Steps (a), (b):  Walk past independent stores to find an exact match.
1546   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1547     // (c) See if we can fold up on the spot, but don't fold up here.
1548     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1549     // just return a prior value, which is done by Identity calls.
1550     if (can_see_stored_value(prev_mem, phase)) {
1551       // Make ready for step (d):
1552       set_req(MemNode::Memory, prev_mem);
1553       return this;
1554     }
1555   }
1556 
1557   return progress ? this : NULL;
1558 }
1559 
1560 // Helper to recognize certain Klass fields which are invariant across
1561 // some group of array types (e.g., int[] or all T[] where T < Object).
1562 const Type*
1563 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1564                                  ciKlass* klass) const {
1565   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1566     // The field is Klass::_modifier_flags.  Return its (constant) value.
1567     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1568     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1569     return TypeInt::make(klass->modifier_flags());
1570   }
1571   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1572     // The field is Klass::_access_flags.  Return its (constant) value.
1573     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1574     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1575     return TypeInt::make(klass->access_flags());
1576   }
1577   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1578     // The field is Klass::_layout_helper.  Return its constant value if known.
1579     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1580     return TypeInt::make(klass->layout_helper());
1581   }
1582 
1583   // No match.
1584   return NULL;
1585 }
1586 
1587 // Try to constant-fold a stable array element.
1588 static const Type* fold_stable_ary_elem(const TypeAryPtr* ary, int off, BasicType loadbt) {
1589   assert(ary->const_oop(), "array should be constant");
1590   assert(ary->is_stable(), "array should be stable");
1591 
1592   // Decode the results of GraphKit::array_element_address.
1593   ciArray* aobj = ary->const_oop()->as_array();
1594   ciConstant con = aobj->element_value_by_offset(off);
1595 
1596   if (con.basic_type() != T_ILLEGAL && !con.is_null_or_zero()) {
1597     const Type* con_type = Type::make_from_constant(con);
1598     if (con_type != NULL) {
1599       if (con_type->isa_aryptr()) {
1600         // Join with the array element type, in case it is also stable.
1601         int dim = ary->stable_dimension();
1602         con_type = con_type->is_aryptr()->cast_to_stable(true, dim-1);
1603       }
1604       if (loadbt == T_NARROWOOP && con_type->isa_oopptr()) {
1605         con_type = con_type->make_narrowoop();
1606       }
1607 #ifndef PRODUCT
1608       if (TraceIterativeGVN) {
1609         tty->print("FoldStableValues: array element [off=%d]: con_type=", off);
1610         con_type->dump(); tty->cr();
1611       }
1612 #endif //PRODUCT
1613       return con_type;
1614     }
1615   }
1616   return NULL;
1617 }
1618 
1619 //------------------------------Value-----------------------------------------
1620 const Type *LoadNode::Value( PhaseTransform *phase ) const {
1621   // Either input is TOP ==> the result is TOP
1622   Node* mem = in(MemNode::Memory);
1623   const Type *t1 = phase->type(mem);
1624   if (t1 == Type::TOP)  return Type::TOP;
1625   Node* adr = in(MemNode::Address);
1626   const TypePtr* tp = phase->type(adr)->isa_ptr();
1627   if (tp == NULL || tp->empty())  return Type::TOP;
1628   int off = tp->offset();
1629   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1630   Compile* C = phase->C;
1631 
1632   // Try to guess loaded type from pointer type
1633   if (tp->isa_aryptr()) {
1634     const TypeAryPtr* ary = tp->is_aryptr();
1635     const Type* t = ary->elem();
1636 
1637     // Determine whether the reference is beyond the header or not, by comparing
1638     // the offset against the offset of the start of the array's data.
1639     // Different array types begin at slightly different offsets (12 vs. 16).
1640     // We choose T_BYTE as an example base type that is least restrictive
1641     // as to alignment, which will therefore produce the smallest
1642     // possible base offset.
1643     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1644     const bool off_beyond_header = ((uint)off >= (uint)min_base_off);
1645 
1646     // Try to constant-fold a stable array element.
1647     if (FoldStableValues && ary->is_stable() && ary->const_oop() != NULL) {
1648       // Make sure the reference is not into the header and the offset is constant
1649       if (off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1650         const Type* con_type = fold_stable_ary_elem(ary, off, memory_type());
1651         if (con_type != NULL) {
1652           return con_type;
1653         }
1654       }
1655     }
1656 
1657     // Don't do this for integer types. There is only potential profit if
1658     // the element type t is lower than _type; that is, for int types, if _type is
1659     // more restrictive than t.  This only happens here if one is short and the other
1660     // char (both 16 bits), and in those cases we've made an intentional decision
1661     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1662     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1663     //
1664     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1665     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1666     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1667     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1668     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1669     // In fact, that could have been the original type of p1, and p1 could have
1670     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1671     // expression (LShiftL quux 3) independently optimized to the constant 8.
1672     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1673         && (_type->isa_vect() == NULL)
1674         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1675       // t might actually be lower than _type, if _type is a unique
1676       // concrete subclass of abstract class t.
1677       if (off_beyond_header) {  // is the offset beyond the header?
1678         const Type* jt = t->join_speculative(_type);
1679         // In any case, do not allow the join, per se, to empty out the type.
1680         if (jt->empty() && !t->empty()) {
1681           // This can happen if a interface-typed array narrows to a class type.
1682           jt = _type;
1683         }
1684 #ifdef ASSERT
1685         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1686           // The pointers in the autobox arrays are always non-null
1687           Node* base = adr->in(AddPNode::Base);
1688           if ((base != NULL) && base->is_DecodeN()) {
1689             // Get LoadN node which loads IntegerCache.cache field
1690             base = base->in(1);
1691           }
1692           if ((base != NULL) && base->is_Con()) {
1693             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1694             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1695               // It could be narrow oop
1696               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1697             }
1698           }
1699         }
1700 #endif
1701         return jt;
1702       }
1703     }
1704   } else if (tp->base() == Type::InstPtr) {
1705     ciEnv* env = C->env();
1706     const TypeInstPtr* tinst = tp->is_instptr();
1707     ciKlass* klass = tinst->klass();
1708     assert( off != Type::OffsetBot ||
1709             // arrays can be cast to Objects
1710             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1711             // unsafe field access may not have a constant offset
1712             C->has_unsafe_access(),
1713             "Field accesses must be precise" );
1714     // For oop loads, we expect the _type to be precise
1715     if (klass == env->String_klass() &&
1716         adr->is_AddP() && off != Type::OffsetBot) {
1717       // For constant Strings treat the final fields as compile time constants.
1718       Node* base = adr->in(AddPNode::Base);
1719       const TypeOopPtr* t = phase->type(base)->isa_oopptr();
1720       if (t != NULL && t->singleton()) {
1721         ciField* field = env->String_klass()->get_field_by_offset(off, false);
1722         if (field != NULL && field->is_final()) {
1723           ciObject* string = t->const_oop();
1724           ciConstant constant = string->as_instance()->field_value(field);
1725           if (constant.basic_type() == T_INT) {
1726             return TypeInt::make(constant.as_int());
1727           } else if (constant.basic_type() == T_ARRAY) {
1728             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1729               return TypeNarrowOop::make_from_constant(constant.as_object(), true);
1730             } else {
1731               return TypeOopPtr::make_from_constant(constant.as_object(), true);
1732             }
1733           }
1734         }
1735       }
1736     }
1737     // Optimizations for constant objects
1738     ciObject* const_oop = tinst->const_oop();
1739     if (const_oop != NULL) {
1740       // For constant Boxed value treat the target field as a compile time constant.
1741       if (tinst->is_ptr_to_boxed_value()) {
1742         return tinst->get_const_boxed_value();
1743       } else
1744       // For constant CallSites treat the target field as a compile time constant.
1745       if (const_oop->is_call_site()) {
1746         ciCallSite* call_site = const_oop->as_call_site();
1747         ciField* field = call_site->klass()->as_instance_klass()->get_field_by_offset(off, /*is_static=*/ false);
1748         if (field != NULL && field->is_call_site_target()) {
1749           ciMethodHandle* target = call_site->get_target();
1750           if (target != NULL) {  // just in case
1751             ciConstant constant(T_OBJECT, target);
1752             const Type* t;
1753             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1754               t = TypeNarrowOop::make_from_constant(constant.as_object(), true);
1755             } else {
1756               t = TypeOopPtr::make_from_constant(constant.as_object(), true);
1757             }
1758             // Add a dependence for invalidation of the optimization.
1759             if (!call_site->is_constant_call_site()) {
1760               C->dependencies()->assert_call_site_target_value(call_site, target);
1761             }
1762             return t;
1763           }
1764         }
1765       }
1766     }
1767   } else if (tp->base() == Type::KlassPtr) {
1768     assert( off != Type::OffsetBot ||
1769             // arrays can be cast to Objects
1770             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1771             // also allow array-loading from the primary supertype
1772             // array during subtype checks
1773             Opcode() == Op_LoadKlass,
1774             "Field accesses must be precise" );
1775     // For klass/static loads, we expect the _type to be precise
1776   }
1777 
1778   const TypeKlassPtr *tkls = tp->isa_klassptr();
1779   if (tkls != NULL && !StressReflectiveCode) {
1780     ciKlass* klass = tkls->klass();
1781     if (klass->is_loaded() && tkls->klass_is_exact()) {
1782       // We are loading a field from a Klass metaobject whose identity
1783       // is known at compile time (the type is "exact" or "precise").
1784       // Check for fields we know are maintained as constants by the VM.
1785       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1786         // The field is Klass::_super_check_offset.  Return its (constant) value.
1787         // (Folds up type checking code.)
1788         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1789         return TypeInt::make(klass->super_check_offset());
1790       }
1791       // Compute index into primary_supers array
1792       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1793       // Check for overflowing; use unsigned compare to handle the negative case.
1794       if( depth < ciKlass::primary_super_limit() ) {
1795         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1796         // (Folds up type checking code.)
1797         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1798         ciKlass *ss = klass->super_of_depth(depth);
1799         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1800       }
1801       const Type* aift = load_array_final_field(tkls, klass);
1802       if (aift != NULL)  return aift;
1803       if (tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1804         // The field is Klass::_java_mirror.  Return its (constant) value.
1805         // (Folds up the 2nd indirection in anObjConstant.getClass().)
1806         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1807         return TypeInstPtr::make(klass->java_mirror());
1808       }
1809     }
1810 
1811     // We can still check if we are loading from the primary_supers array at a
1812     // shallow enough depth.  Even though the klass is not exact, entries less
1813     // than or equal to its super depth are correct.
1814     if (klass->is_loaded() ) {
1815       ciType *inner = klass;
1816       while( inner->is_obj_array_klass() )
1817         inner = inner->as_obj_array_klass()->base_element_type();
1818       if( inner->is_instance_klass() &&
1819           !inner->as_instance_klass()->flags().is_interface() ) {
1820         // Compute index into primary_supers array
1821         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1822         // Check for overflowing; use unsigned compare to handle the negative case.
1823         if( depth < ciKlass::primary_super_limit() &&
1824             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1825           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1826           // (Folds up type checking code.)
1827           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1828           ciKlass *ss = klass->super_of_depth(depth);
1829           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1830         }
1831       }
1832     }
1833 
1834     // If the type is enough to determine that the thing is not an array,
1835     // we can give the layout_helper a positive interval type.
1836     // This will help short-circuit some reflective code.
1837     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1838         && !klass->is_array_klass() // not directly typed as an array
1839         && !klass->is_interface()  // specifically not Serializable & Cloneable
1840         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1841         ) {
1842       // Note:  When interfaces are reliable, we can narrow the interface
1843       // test to (klass != Serializable && klass != Cloneable).
1844       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1845       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1846       // The key property of this type is that it folds up tests
1847       // for array-ness, since it proves that the layout_helper is positive.
1848       // Thus, a generic value like the basic object layout helper works fine.
1849       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1850     }
1851   }
1852 
1853   // If we are loading from a freshly-allocated object, produce a zero,
1854   // if the load is provably beyond the header of the object.
1855   // (Also allow a variable load from a fresh array to produce zero.)
1856   const TypeOopPtr *tinst = tp->isa_oopptr();
1857   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1858   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1859   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1860     Node* value = can_see_stored_value(mem,phase);
1861     if (value != NULL && value->is_Con()) {
1862       assert(value->bottom_type()->higher_equal(_type),"sanity");
1863       return value->bottom_type();
1864     }
1865   }
1866 
1867   if (is_instance) {
1868     // If we have an instance type and our memory input is the
1869     // programs's initial memory state, there is no matching store,
1870     // so just return a zero of the appropriate type
1871     Node *mem = in(MemNode::Memory);
1872     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1873       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1874       return Type::get_zero_type(_type->basic_type());
1875     }
1876   }
1877   return _type;
1878 }
1879 
1880 //------------------------------match_edge-------------------------------------
1881 // Do we Match on this edge index or not?  Match only the address.
1882 uint LoadNode::match_edge(uint idx) const {
1883   return idx == MemNode::Address;
1884 }
1885 
1886 //--------------------------LoadBNode::Ideal--------------------------------------
1887 //
1888 //  If the previous store is to the same address as this load,
1889 //  and the value stored was larger than a byte, replace this load
1890 //  with the value stored truncated to a byte.  If no truncation is
1891 //  needed, the replacement is done in LoadNode::Identity().
1892 //
1893 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1894   Node* mem = in(MemNode::Memory);
1895   Node* value = can_see_stored_value(mem,phase);
1896   if( value && !phase->type(value)->higher_equal( _type ) ) {
1897     Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1898     return new RShiftINode(result, phase->intcon(24));
1899   }
1900   // Identity call will handle the case where truncation is not needed.
1901   return LoadNode::Ideal(phase, can_reshape);
1902 }
1903 
1904 const Type* LoadBNode::Value(PhaseTransform *phase) const {
1905   Node* mem = in(MemNode::Memory);
1906   Node* value = can_see_stored_value(mem,phase);
1907   if (value != NULL && value->is_Con() &&
1908       !value->bottom_type()->higher_equal(_type)) {
1909     // If the input to the store does not fit with the load's result type,
1910     // it must be truncated. We can't delay until Ideal call since
1911     // a singleton Value is needed for split_thru_phi optimization.
1912     int con = value->get_int();
1913     return TypeInt::make((con << 24) >> 24);
1914   }
1915   return LoadNode::Value(phase);
1916 }
1917 
1918 //--------------------------LoadUBNode::Ideal-------------------------------------
1919 //
1920 //  If the previous store is to the same address as this load,
1921 //  and the value stored was larger than a byte, replace this load
1922 //  with the value stored truncated to a byte.  If no truncation is
1923 //  needed, the replacement is done in LoadNode::Identity().
1924 //
1925 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1926   Node* mem = in(MemNode::Memory);
1927   Node* value = can_see_stored_value(mem, phase);
1928   if (value && !phase->type(value)->higher_equal(_type))
1929     return new AndINode(value, phase->intcon(0xFF));
1930   // Identity call will handle the case where truncation is not needed.
1931   return LoadNode::Ideal(phase, can_reshape);
1932 }
1933 
1934 const Type* LoadUBNode::Value(PhaseTransform *phase) const {
1935   Node* mem = in(MemNode::Memory);
1936   Node* value = can_see_stored_value(mem,phase);
1937   if (value != NULL && value->is_Con() &&
1938       !value->bottom_type()->higher_equal(_type)) {
1939     // If the input to the store does not fit with the load's result type,
1940     // it must be truncated. We can't delay until Ideal call since
1941     // a singleton Value is needed for split_thru_phi optimization.
1942     int con = value->get_int();
1943     return TypeInt::make(con & 0xFF);
1944   }
1945   return LoadNode::Value(phase);
1946 }
1947 
1948 //--------------------------LoadUSNode::Ideal-------------------------------------
1949 //
1950 //  If the previous store is to the same address as this load,
1951 //  and the value stored was larger than a char, replace this load
1952 //  with the value stored truncated to a char.  If no truncation is
1953 //  needed, the replacement is done in LoadNode::Identity().
1954 //
1955 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1956   Node* mem = in(MemNode::Memory);
1957   Node* value = can_see_stored_value(mem,phase);
1958   if( value && !phase->type(value)->higher_equal( _type ) )
1959     return new AndINode(value,phase->intcon(0xFFFF));
1960   // Identity call will handle the case where truncation is not needed.
1961   return LoadNode::Ideal(phase, can_reshape);
1962 }
1963 
1964 const Type* LoadUSNode::Value(PhaseTransform *phase) const {
1965   Node* mem = in(MemNode::Memory);
1966   Node* value = can_see_stored_value(mem,phase);
1967   if (value != NULL && value->is_Con() &&
1968       !value->bottom_type()->higher_equal(_type)) {
1969     // If the input to the store does not fit with the load's result type,
1970     // it must be truncated. We can't delay until Ideal call since
1971     // a singleton Value is needed for split_thru_phi optimization.
1972     int con = value->get_int();
1973     return TypeInt::make(con & 0xFFFF);
1974   }
1975   return LoadNode::Value(phase);
1976 }
1977 
1978 //--------------------------LoadSNode::Ideal--------------------------------------
1979 //
1980 //  If the previous store is to the same address as this load,
1981 //  and the value stored was larger than a short, replace this load
1982 //  with the value stored truncated to a short.  If no truncation is
1983 //  needed, the replacement is done in LoadNode::Identity().
1984 //
1985 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1986   Node* mem = in(MemNode::Memory);
1987   Node* value = can_see_stored_value(mem,phase);
1988   if( value && !phase->type(value)->higher_equal( _type ) ) {
1989     Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
1990     return new RShiftINode(result, phase->intcon(16));
1991   }
1992   // Identity call will handle the case where truncation is not needed.
1993   return LoadNode::Ideal(phase, can_reshape);
1994 }
1995 
1996 const Type* LoadSNode::Value(PhaseTransform *phase) const {
1997   Node* mem = in(MemNode::Memory);
1998   Node* value = can_see_stored_value(mem,phase);
1999   if (value != NULL && value->is_Con() &&
2000       !value->bottom_type()->higher_equal(_type)) {
2001     // If the input to the store does not fit with the load's result type,
2002     // it must be truncated. We can't delay until Ideal call since
2003     // a singleton Value is needed for split_thru_phi optimization.
2004     int con = value->get_int();
2005     return TypeInt::make((con << 16) >> 16);
2006   }
2007   return LoadNode::Value(phase);
2008 }
2009 
2010 //=============================================================================
2011 //----------------------------LoadKlassNode::make------------------------------
2012 // Polymorphic factory method:
2013 Node *LoadKlassNode::make( PhaseGVN& gvn, Node *mem, Node *adr, const TypePtr* at, const TypeKlassPtr *tk ) {
2014   Node *ctl = NULL;
2015   // sanity check the alias category against the created node type
2016   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2017   assert(adr_type != NULL, "expecting TypeKlassPtr");
2018 #ifdef _LP64
2019   if (adr_type->is_ptr_to_narrowklass()) {
2020     assert(UseCompressedClassPointers, "no compressed klasses");
2021     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2022     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2023   }
2024 #endif
2025   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2026   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2027 }
2028 
2029 //------------------------------Value------------------------------------------
2030 const Type *LoadKlassNode::Value( PhaseTransform *phase ) const {
2031   return klass_value_common(phase);
2032 }
2033 
2034 const Type *LoadNode::klass_value_common( PhaseTransform *phase ) const {
2035   // Either input is TOP ==> the result is TOP
2036   const Type *t1 = phase->type( in(MemNode::Memory) );
2037   if (t1 == Type::TOP)  return Type::TOP;
2038   Node *adr = in(MemNode::Address);
2039   const Type *t2 = phase->type( adr );
2040   if (t2 == Type::TOP)  return Type::TOP;
2041   const TypePtr *tp = t2->is_ptr();
2042   if (TypePtr::above_centerline(tp->ptr()) ||
2043       tp->ptr() == TypePtr::Null)  return Type::TOP;
2044 
2045   // Return a more precise klass, if possible
2046   const TypeInstPtr *tinst = tp->isa_instptr();
2047   if (tinst != NULL) {
2048     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2049     int offset = tinst->offset();
2050     if (ik == phase->C->env()->Class_klass()
2051         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2052             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2053       // We are loading a special hidden field from a Class mirror object,
2054       // the field which points to the VM's Klass metaobject.
2055       ciType* t = tinst->java_mirror_type();
2056       // java_mirror_type returns non-null for compile-time Class constants.
2057       if (t != NULL) {
2058         // constant oop => constant klass
2059         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2060           if (t->is_void()) {
2061             // We cannot create a void array.  Since void is a primitive type return null
2062             // klass.  Users of this result need to do a null check on the returned klass.
2063             return TypePtr::NULL_PTR;
2064           }
2065           return TypeKlassPtr::make(ciArrayKlass::make(t));
2066         }
2067         if (!t->is_klass()) {
2068           // a primitive Class (e.g., int.class) has NULL for a klass field
2069           return TypePtr::NULL_PTR;
2070         }
2071         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2072         return TypeKlassPtr::make(t->as_klass());
2073       }
2074       // non-constant mirror, so we can't tell what's going on
2075     }
2076     if( !ik->is_loaded() )
2077       return _type;             // Bail out if not loaded
2078     if (offset == oopDesc::klass_offset_in_bytes()) {
2079       if (tinst->klass_is_exact()) {
2080         return TypeKlassPtr::make(ik);
2081       }
2082       // See if we can become precise: no subklasses and no interface
2083       // (Note:  We need to support verified interfaces.)
2084       if (!ik->is_interface() && !ik->has_subklass()) {
2085         //assert(!UseExactTypes, "this code should be useless with exact types");
2086         // Add a dependence; if any subclass added we need to recompile
2087         if (!ik->is_final()) {
2088           // %%% should use stronger assert_unique_concrete_subtype instead
2089           phase->C->dependencies()->assert_leaf_type(ik);
2090         }
2091         // Return precise klass
2092         return TypeKlassPtr::make(ik);
2093       }
2094 
2095       // Return root of possible klass
2096       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2097     }
2098   }
2099 
2100   // Check for loading klass from an array
2101   const TypeAryPtr *tary = tp->isa_aryptr();
2102   if( tary != NULL ) {
2103     ciKlass *tary_klass = tary->klass();
2104     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2105         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2106       if (tary->klass_is_exact()) {
2107         return TypeKlassPtr::make(tary_klass);
2108       }
2109       ciArrayKlass *ak = tary->klass()->as_array_klass();
2110       // If the klass is an object array, we defer the question to the
2111       // array component klass.
2112       if( ak->is_obj_array_klass() ) {
2113         assert( ak->is_loaded(), "" );
2114         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2115         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2116           ciInstanceKlass* ik = base_k->as_instance_klass();
2117           // See if we can become precise: no subklasses and no interface
2118           if (!ik->is_interface() && !ik->has_subklass()) {
2119             //assert(!UseExactTypes, "this code should be useless with exact types");
2120             // Add a dependence; if any subclass added we need to recompile
2121             if (!ik->is_final()) {
2122               phase->C->dependencies()->assert_leaf_type(ik);
2123             }
2124             // Return precise array klass
2125             return TypeKlassPtr::make(ak);
2126           }
2127         }
2128         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2129       } else {                  // Found a type-array?
2130         //assert(!UseExactTypes, "this code should be useless with exact types");
2131         assert( ak->is_type_array_klass(), "" );
2132         return TypeKlassPtr::make(ak); // These are always precise
2133       }
2134     }
2135   }
2136 
2137   // Check for loading klass from an array klass
2138   const TypeKlassPtr *tkls = tp->isa_klassptr();
2139   if (tkls != NULL && !StressReflectiveCode) {
2140     ciKlass* klass = tkls->klass();
2141     if( !klass->is_loaded() )
2142       return _type;             // Bail out if not loaded
2143     if( klass->is_obj_array_klass() &&
2144         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2145       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2146       // // Always returning precise element type is incorrect,
2147       // // e.g., element type could be object and array may contain strings
2148       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2149 
2150       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2151       // according to the element type's subclassing.
2152       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2153     }
2154     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2155         tkls->offset() == in_bytes(Klass::super_offset())) {
2156       ciKlass* sup = klass->as_instance_klass()->super();
2157       // The field is Klass::_super.  Return its (constant) value.
2158       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2159       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2160     }
2161   }
2162 
2163   // Bailout case
2164   return LoadNode::Value(phase);
2165 }
2166 
2167 //------------------------------Identity---------------------------------------
2168 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2169 // Also feed through the klass in Allocate(...klass...)._klass.
2170 Node* LoadKlassNode::Identity( PhaseTransform *phase ) {
2171   return klass_identity_common(phase);
2172 }
2173 
2174 Node* LoadNode::klass_identity_common(PhaseTransform *phase ) {
2175   Node* x = LoadNode::Identity(phase);
2176   if (x != this)  return x;
2177 
2178   // Take apart the address into an oop and and offset.
2179   // Return 'this' if we cannot.
2180   Node*    adr    = in(MemNode::Address);
2181   intptr_t offset = 0;
2182   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2183   if (base == NULL)     return this;
2184   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2185   if (toop == NULL)     return this;
2186 
2187   // We can fetch the klass directly through an AllocateNode.
2188   // This works even if the klass is not constant (clone or newArray).
2189   if (offset == oopDesc::klass_offset_in_bytes()) {
2190     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2191     if (allocated_klass != NULL) {
2192       return allocated_klass;
2193     }
2194   }
2195 
2196   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2197   // See inline_native_Class_query for occurrences of these patterns.
2198   // Java Example:  x.getClass().isAssignableFrom(y)
2199   //
2200   // This improves reflective code, often making the Class
2201   // mirror go completely dead.  (Current exception:  Class
2202   // mirrors may appear in debug info, but we could clean them out by
2203   // introducing a new debug info operator for Klass*.java_mirror).
2204   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2205       && offset == java_lang_Class::klass_offset_in_bytes()) {
2206     // We are loading a special hidden field from a Class mirror,
2207     // the field which points to its Klass or ArrayKlass metaobject.
2208     if (base->is_Load()) {
2209       Node* adr2 = base->in(MemNode::Address);
2210       const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2211       if (tkls != NULL && !tkls->empty()
2212           && (tkls->klass()->is_instance_klass() ||
2213               tkls->klass()->is_array_klass())
2214           && adr2->is_AddP()
2215           ) {
2216         int mirror_field = in_bytes(Klass::java_mirror_offset());
2217         if (tkls->offset() == mirror_field) {
2218           return adr2->in(AddPNode::Base);
2219         }
2220       }
2221     }
2222   }
2223 
2224   return this;
2225 }
2226 
2227 
2228 //------------------------------Value------------------------------------------
2229 const Type *LoadNKlassNode::Value( PhaseTransform *phase ) const {
2230   const Type *t = klass_value_common(phase);
2231   if (t == Type::TOP)
2232     return t;
2233 
2234   return t->make_narrowklass();
2235 }
2236 
2237 //------------------------------Identity---------------------------------------
2238 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2239 // Also feed through the klass in Allocate(...klass...)._klass.
2240 Node* LoadNKlassNode::Identity( PhaseTransform *phase ) {
2241   Node *x = klass_identity_common(phase);
2242 
2243   const Type *t = phase->type( x );
2244   if( t == Type::TOP ) return x;
2245   if( t->isa_narrowklass()) return x;
2246   assert (!t->isa_narrowoop(), "no narrow oop here");
2247 
2248   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2249 }
2250 
2251 //------------------------------Value-----------------------------------------
2252 const Type *LoadRangeNode::Value( PhaseTransform *phase ) const {
2253   // Either input is TOP ==> the result is TOP
2254   const Type *t1 = phase->type( in(MemNode::Memory) );
2255   if( t1 == Type::TOP ) return Type::TOP;
2256   Node *adr = in(MemNode::Address);
2257   const Type *t2 = phase->type( adr );
2258   if( t2 == Type::TOP ) return Type::TOP;
2259   const TypePtr *tp = t2->is_ptr();
2260   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2261   const TypeAryPtr *tap = tp->isa_aryptr();
2262   if( !tap ) return _type;
2263   return tap->size();
2264 }
2265 
2266 //-------------------------------Ideal---------------------------------------
2267 // Feed through the length in AllocateArray(...length...)._length.
2268 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2269   Node* p = MemNode::Ideal_common(phase, can_reshape);
2270   if (p)  return (p == NodeSentinel) ? NULL : p;
2271 
2272   // Take apart the address into an oop and and offset.
2273   // Return 'this' if we cannot.
2274   Node*    adr    = in(MemNode::Address);
2275   intptr_t offset = 0;
2276   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2277   if (base == NULL)     return NULL;
2278   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2279   if (tary == NULL)     return NULL;
2280 
2281   // We can fetch the length directly through an AllocateArrayNode.
2282   // This works even if the length is not constant (clone or newArray).
2283   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2284     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2285     if (alloc != NULL) {
2286       Node* allocated_length = alloc->Ideal_length();
2287       Node* len = alloc->make_ideal_length(tary, phase);
2288       if (allocated_length != len) {
2289         // New CastII improves on this.
2290         return len;
2291       }
2292     }
2293   }
2294 
2295   return NULL;
2296 }
2297 
2298 //------------------------------Identity---------------------------------------
2299 // Feed through the length in AllocateArray(...length...)._length.
2300 Node* LoadRangeNode::Identity( PhaseTransform *phase ) {
2301   Node* x = LoadINode::Identity(phase);
2302   if (x != this)  return x;
2303 
2304   // Take apart the address into an oop and and offset.
2305   // Return 'this' if we cannot.
2306   Node*    adr    = in(MemNode::Address);
2307   intptr_t offset = 0;
2308   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2309   if (base == NULL)     return this;
2310   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2311   if (tary == NULL)     return this;
2312 
2313   // We can fetch the length directly through an AllocateArrayNode.
2314   // This works even if the length is not constant (clone or newArray).
2315   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2316     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2317     if (alloc != NULL) {
2318       Node* allocated_length = alloc->Ideal_length();
2319       // Do not allow make_ideal_length to allocate a CastII node.
2320       Node* len = alloc->make_ideal_length(tary, phase, false);
2321       if (allocated_length == len) {
2322         // Return allocated_length only if it would not be improved by a CastII.
2323         return allocated_length;
2324       }
2325     }
2326   }
2327 
2328   return this;
2329 
2330 }
2331 
2332 //=============================================================================
2333 //---------------------------StoreNode::make-----------------------------------
2334 // Polymorphic factory method:
2335 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2336   assert((mo == unordered || mo == release), "unexpected");
2337   Compile* C = gvn.C;
2338   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2339          ctl != NULL, "raw memory operations should have control edge");
2340 
2341   switch (bt) {
2342   case T_BOOLEAN:
2343   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2344   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2345   case T_CHAR:
2346   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2347   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2348   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2349   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2350   case T_METADATA:
2351   case T_ADDRESS:
2352   case T_OBJECT:
2353 #ifdef _LP64
2354     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2355       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2356       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2357     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2358                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2359                 adr->bottom_type()->isa_rawptr())) {
2360       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2361       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2362     }
2363 #endif
2364     {
2365       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2366     }
2367   }
2368   ShouldNotReachHere();
2369   return (StoreNode*)NULL;
2370 }
2371 
2372 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2373   bool require_atomic = true;
2374   return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2375 }
2376 
2377 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2378   bool require_atomic = true;
2379   return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2380 }
2381 
2382 
2383 //--------------------------bottom_type----------------------------------------
2384 const Type *StoreNode::bottom_type() const {
2385   return Type::MEMORY;
2386 }
2387 
2388 //------------------------------hash-------------------------------------------
2389 uint StoreNode::hash() const {
2390   // unroll addition of interesting fields
2391   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2392 
2393   // Since they are not commoned, do not hash them:
2394   return NO_HASH;
2395 }
2396 
2397 //------------------------------Ideal------------------------------------------
2398 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2399 // When a store immediately follows a relevant allocation/initialization,
2400 // try to capture it into the initialization, or hoist it above.
2401 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2402   Node* p = MemNode::Ideal_common(phase, can_reshape);
2403   if (p)  return (p == NodeSentinel) ? NULL : p;
2404 
2405   Node* mem     = in(MemNode::Memory);
2406   Node* address = in(MemNode::Address);
2407 
2408   // Back-to-back stores to same address?  Fold em up.  Generally
2409   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2410   // since they must follow each StoreP operation.  Redundant StoreCMs
2411   // are eliminated just before matching in final_graph_reshape.
2412   if (mem->is_Store() && mem->in(MemNode::Address)->eqv_uncast(address) &&
2413       mem->Opcode() != Op_StoreCM) {
2414     // Looking at a dead closed cycle of memory?
2415     assert(mem != mem->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2416 
2417     assert(Opcode() == mem->Opcode() ||
2418            phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw,
2419            "no mismatched stores, except on raw memory");
2420 
2421     if (mem->outcnt() == 1 &&           // check for intervening uses
2422         mem->as_Store()->memory_size() <= this->memory_size()) {
2423       // If anybody other than 'this' uses 'mem', we cannot fold 'mem' away.
2424       // For example, 'mem' might be the final state at a conditional return.
2425       // Or, 'mem' might be used by some node which is live at the same time
2426       // 'this' is live, which might be unschedulable.  So, require exactly
2427       // ONE user, the 'this' store, until such time as we clone 'mem' for
2428       // each of 'mem's uses (thus making the exactly-1-user-rule hold true).
2429       if (can_reshape) {  // (%%% is this an anachronism?)
2430         set_req_X(MemNode::Memory, mem->in(MemNode::Memory),
2431                   phase->is_IterGVN());
2432       } else {
2433         // It's OK to do this in the parser, since DU info is always accurate,
2434         // and the parser always refers to nodes via SafePointNode maps.
2435         set_req(MemNode::Memory, mem->in(MemNode::Memory));
2436       }
2437       return this;
2438     }
2439   }
2440 
2441   // Capture an unaliased, unconditional, simple store into an initializer.
2442   // Or, if it is independent of the allocation, hoist it above the allocation.
2443   if (ReduceFieldZeroing && /*can_reshape &&*/
2444       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2445     InitializeNode* init = mem->in(0)->as_Initialize();
2446     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2447     if (offset > 0) {
2448       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2449       // If the InitializeNode captured me, it made a raw copy of me,
2450       // and I need to disappear.
2451       if (moved != NULL) {
2452         // %%% hack to ensure that Ideal returns a new node:
2453         mem = MergeMemNode::make(mem);
2454         return mem;             // fold me away
2455       }
2456     }
2457   }
2458 
2459   return NULL;                  // No further progress
2460 }
2461 
2462 //------------------------------Value-----------------------------------------
2463 const Type *StoreNode::Value( PhaseTransform *phase ) const {
2464   // Either input is TOP ==> the result is TOP
2465   const Type *t1 = phase->type( in(MemNode::Memory) );
2466   if( t1 == Type::TOP ) return Type::TOP;
2467   const Type *t2 = phase->type( in(MemNode::Address) );
2468   if( t2 == Type::TOP ) return Type::TOP;
2469   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2470   if( t3 == Type::TOP ) return Type::TOP;
2471   return Type::MEMORY;
2472 }
2473 
2474 //------------------------------Identity---------------------------------------
2475 // Remove redundant stores:
2476 //   Store(m, p, Load(m, p)) changes to m.
2477 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2478 Node *StoreNode::Identity( PhaseTransform *phase ) {
2479   Node* mem = in(MemNode::Memory);
2480   Node* adr = in(MemNode::Address);
2481   Node* val = in(MemNode::ValueIn);
2482 
2483   // Load then Store?  Then the Store is useless
2484   if (val->is_Load() &&
2485       val->in(MemNode::Address)->eqv_uncast(adr) &&
2486       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2487       val->as_Load()->store_Opcode() == Opcode()) {
2488     return mem;
2489   }
2490 
2491   // Two stores in a row of the same value?
2492   if (mem->is_Store() &&
2493       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2494       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2495       mem->Opcode() == Opcode()) {
2496     return mem;
2497   }
2498 
2499   // Store of zero anywhere into a freshly-allocated object?
2500   // Then the store is useless.
2501   // (It must already have been captured by the InitializeNode.)
2502   if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2503     // a newly allocated object is already all-zeroes everywhere
2504     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2505       return mem;
2506     }
2507 
2508     // the store may also apply to zero-bits in an earlier object
2509     Node* prev_mem = find_previous_store(phase);
2510     // Steps (a), (b):  Walk past independent stores to find an exact match.
2511     if (prev_mem != NULL) {
2512       Node* prev_val = can_see_stored_value(prev_mem, phase);
2513       if (prev_val != NULL && phase->eqv(prev_val, val)) {
2514         // prev_val and val might differ by a cast; it would be good
2515         // to keep the more informative of the two.
2516         return mem;
2517       }
2518     }
2519   }
2520 
2521   return this;
2522 }
2523 
2524 //------------------------------match_edge-------------------------------------
2525 // Do we Match on this edge index or not?  Match only memory & value
2526 uint StoreNode::match_edge(uint idx) const {
2527   return idx == MemNode::Address || idx == MemNode::ValueIn;
2528 }
2529 
2530 //------------------------------cmp--------------------------------------------
2531 // Do not common stores up together.  They generally have to be split
2532 // back up anyways, so do not bother.
2533 uint StoreNode::cmp( const Node &n ) const {
2534   return (&n == this);          // Always fail except on self
2535 }
2536 
2537 //------------------------------Ideal_masked_input-----------------------------
2538 // Check for a useless mask before a partial-word store
2539 // (StoreB ... (AndI valIn conIa) )
2540 // If (conIa & mask == mask) this simplifies to
2541 // (StoreB ... (valIn) )
2542 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2543   Node *val = in(MemNode::ValueIn);
2544   if( val->Opcode() == Op_AndI ) {
2545     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2546     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2547       set_req(MemNode::ValueIn, val->in(1));
2548       return this;
2549     }
2550   }
2551   return NULL;
2552 }
2553 
2554 
2555 //------------------------------Ideal_sign_extended_input----------------------
2556 // Check for useless sign-extension before a partial-word store
2557 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2558 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2559 // (StoreB ... (valIn) )
2560 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2561   Node *val = in(MemNode::ValueIn);
2562   if( val->Opcode() == Op_RShiftI ) {
2563     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2564     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2565       Node *shl = val->in(1);
2566       if( shl->Opcode() == Op_LShiftI ) {
2567         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2568         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2569           set_req(MemNode::ValueIn, shl->in(1));
2570           return this;
2571         }
2572       }
2573     }
2574   }
2575   return NULL;
2576 }
2577 
2578 //------------------------------value_never_loaded-----------------------------------
2579 // Determine whether there are any possible loads of the value stored.
2580 // For simplicity, we actually check if there are any loads from the
2581 // address stored to, not just for loads of the value stored by this node.
2582 //
2583 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2584   Node *adr = in(Address);
2585   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2586   if (adr_oop == NULL)
2587     return false;
2588   if (!adr_oop->is_known_instance_field())
2589     return false; // if not a distinct instance, there may be aliases of the address
2590   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2591     Node *use = adr->fast_out(i);
2592     int opc = use->Opcode();
2593     if (use->is_Load() || use->is_LoadStore()) {
2594       return false;
2595     }
2596   }
2597   return true;
2598 }
2599 
2600 //=============================================================================
2601 //------------------------------Ideal------------------------------------------
2602 // If the store is from an AND mask that leaves the low bits untouched, then
2603 // we can skip the AND operation.  If the store is from a sign-extension
2604 // (a left shift, then right shift) we can skip both.
2605 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2606   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2607   if( progress != NULL ) return progress;
2608 
2609   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2610   if( progress != NULL ) return progress;
2611 
2612   // Finally check the default case
2613   return StoreNode::Ideal(phase, can_reshape);
2614 }
2615 
2616 //=============================================================================
2617 //------------------------------Ideal------------------------------------------
2618 // If the store is from an AND mask that leaves the low bits untouched, then
2619 // we can skip the AND operation
2620 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2621   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2622   if( progress != NULL ) return progress;
2623 
2624   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2625   if( progress != NULL ) return progress;
2626 
2627   // Finally check the default case
2628   return StoreNode::Ideal(phase, can_reshape);
2629 }
2630 
2631 //=============================================================================
2632 //------------------------------Identity---------------------------------------
2633 Node *StoreCMNode::Identity( PhaseTransform *phase ) {
2634   // No need to card mark when storing a null ptr
2635   Node* my_store = in(MemNode::OopStore);
2636   if (my_store->is_Store()) {
2637     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2638     if( t1 == TypePtr::NULL_PTR ) {
2639       return in(MemNode::Memory);
2640     }
2641   }
2642   return this;
2643 }
2644 
2645 //=============================================================================
2646 //------------------------------Ideal---------------------------------------
2647 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2648   Node* progress = StoreNode::Ideal(phase, can_reshape);
2649   if (progress != NULL) return progress;
2650 
2651   Node* my_store = in(MemNode::OopStore);
2652   if (my_store->is_MergeMem()) {
2653     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2654     set_req(MemNode::OopStore, mem);
2655     return this;
2656   }
2657 
2658   return NULL;
2659 }
2660 
2661 //------------------------------Value-----------------------------------------
2662 const Type *StoreCMNode::Value( PhaseTransform *phase ) const {
2663   // Either input is TOP ==> the result is TOP
2664   const Type *t = phase->type( in(MemNode::Memory) );
2665   if( t == Type::TOP ) return Type::TOP;
2666   t = phase->type( in(MemNode::Address) );
2667   if( t == Type::TOP ) return Type::TOP;
2668   t = phase->type( in(MemNode::ValueIn) );
2669   if( t == Type::TOP ) return Type::TOP;
2670   // If extra input is TOP ==> the result is TOP
2671   t = phase->type( in(MemNode::OopStore) );
2672   if( t == Type::TOP ) return Type::TOP;
2673 
2674   return StoreNode::Value( phase );
2675 }
2676 
2677 
2678 //=============================================================================
2679 //----------------------------------SCMemProjNode------------------------------
2680 const Type * SCMemProjNode::Value( PhaseTransform *phase ) const
2681 {
2682   return bottom_type();
2683 }
2684 
2685 //=============================================================================
2686 //----------------------------------LoadStoreNode------------------------------
2687 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2688   : Node(required),
2689     _type(rt),
2690     _adr_type(at)
2691 {
2692   init_req(MemNode::Control, c  );
2693   init_req(MemNode::Memory , mem);
2694   init_req(MemNode::Address, adr);
2695   init_req(MemNode::ValueIn, val);
2696   init_class_id(Class_LoadStore);
2697 }
2698 
2699 uint LoadStoreNode::ideal_reg() const {
2700   return _type->ideal_reg();
2701 }
2702 
2703 bool LoadStoreNode::result_not_used() const {
2704   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2705     Node *x = fast_out(i);
2706     if (x->Opcode() == Op_SCMemProj) continue;
2707     return false;
2708   }
2709   return true;
2710 }
2711 
2712 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2713 
2714 //=============================================================================
2715 //----------------------------------LoadStoreConditionalNode--------------------
2716 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2717   init_req(ExpectedIn, ex );
2718 }
2719 
2720 //=============================================================================
2721 //-------------------------------adr_type--------------------------------------
2722 // Do we Match on this edge index or not?  Do not match memory
2723 const TypePtr* ClearArrayNode::adr_type() const {
2724   Node *adr = in(3);
2725   return MemNode::calculate_adr_type(adr->bottom_type());
2726 }
2727 
2728 //------------------------------match_edge-------------------------------------
2729 // Do we Match on this edge index or not?  Do not match memory
2730 uint ClearArrayNode::match_edge(uint idx) const {
2731   return idx > 1;
2732 }
2733 
2734 //------------------------------Identity---------------------------------------
2735 // Clearing a zero length array does nothing
2736 Node *ClearArrayNode::Identity( PhaseTransform *phase ) {
2737   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2738 }
2739 
2740 //------------------------------Idealize---------------------------------------
2741 // Clearing a short array is faster with stores
2742 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){
2743   const int unit = BytesPerLong;
2744   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2745   if (!t)  return NULL;
2746   if (!t->is_con())  return NULL;
2747   intptr_t raw_count = t->get_con();
2748   intptr_t size = raw_count;
2749   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2750   // Clearing nothing uses the Identity call.
2751   // Negative clears are possible on dead ClearArrays
2752   // (see jck test stmt114.stmt11402.val).
2753   if (size <= 0 || size % unit != 0)  return NULL;
2754   intptr_t count = size / unit;
2755   // Length too long; use fast hardware clear
2756   if (size > Matcher::init_array_short_size)  return NULL;
2757   Node *mem = in(1);
2758   if( phase->type(mem)==Type::TOP ) return NULL;
2759   Node *adr = in(3);
2760   const Type* at = phase->type(adr);
2761   if( at==Type::TOP ) return NULL;
2762   const TypePtr* atp = at->isa_ptr();
2763   // adjust atp to be the correct array element address type
2764   if (atp == NULL)  atp = TypePtr::BOTTOM;
2765   else              atp = atp->add_offset(Type::OffsetBot);
2766   // Get base for derived pointer purposes
2767   if( adr->Opcode() != Op_AddP ) Unimplemented();
2768   Node *base = adr->in(1);
2769 
2770   Node *zero = phase->makecon(TypeLong::ZERO);
2771   Node *off  = phase->MakeConX(BytesPerLong);
2772   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2773   count--;
2774   while( count-- ) {
2775     mem = phase->transform(mem);
2776     adr = phase->transform(new AddPNode(base,adr,off));
2777     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2778   }
2779   return mem;
2780 }
2781 
2782 //----------------------------step_through----------------------------------
2783 // Return allocation input memory edge if it is different instance
2784 // or itself if it is the one we are looking for.
2785 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2786   Node* n = *np;
2787   assert(n->is_ClearArray(), "sanity");
2788   intptr_t offset;
2789   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2790   // This method is called only before Allocate nodes are expanded
2791   // during macro nodes expansion. Before that ClearArray nodes are
2792   // only generated in PhaseMacroExpand::generate_arraycopy() (before
2793   // Allocate nodes are expanded) which follows allocations.
2794   assert(alloc != NULL, "should have allocation");
2795   if (alloc->_idx == instance_id) {
2796     // Can not bypass initialization of the instance we are looking for.
2797     return false;
2798   }
2799   // Otherwise skip it.
2800   InitializeNode* init = alloc->initialization();
2801   if (init != NULL)
2802     *np = init->in(TypeFunc::Memory);
2803   else
2804     *np = alloc->in(TypeFunc::Memory);
2805   return true;
2806 }
2807 
2808 //----------------------------clear_memory-------------------------------------
2809 // Generate code to initialize object storage to zero.
2810 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2811                                    intptr_t start_offset,
2812                                    Node* end_offset,
2813                                    PhaseGVN* phase) {
2814   intptr_t offset = start_offset;
2815 
2816   int unit = BytesPerLong;
2817   if ((offset % unit) != 0) {
2818     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
2819     adr = phase->transform(adr);
2820     const TypePtr* atp = TypeRawPtr::BOTTOM;
2821     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2822     mem = phase->transform(mem);
2823     offset += BytesPerInt;
2824   }
2825   assert((offset % unit) == 0, "");
2826 
2827   // Initialize the remaining stuff, if any, with a ClearArray.
2828   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2829 }
2830 
2831 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2832                                    Node* start_offset,
2833                                    Node* end_offset,
2834                                    PhaseGVN* phase) {
2835   if (start_offset == end_offset) {
2836     // nothing to do
2837     return mem;
2838   }
2839 
2840   int unit = BytesPerLong;
2841   Node* zbase = start_offset;
2842   Node* zend  = end_offset;
2843 
2844   // Scale to the unit required by the CPU:
2845   if (!Matcher::init_array_count_is_in_bytes) {
2846     Node* shift = phase->intcon(exact_log2(unit));
2847     zbase = phase->transform(new URShiftXNode(zbase, shift) );
2848     zend  = phase->transform(new URShiftXNode(zend,  shift) );
2849   }
2850 
2851   // Bulk clear double-words
2852   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
2853   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
2854   mem = new ClearArrayNode(ctl, mem, zsize, adr);
2855   return phase->transform(mem);
2856 }
2857 
2858 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2859                                    intptr_t start_offset,
2860                                    intptr_t end_offset,
2861                                    PhaseGVN* phase) {
2862   if (start_offset == end_offset) {
2863     // nothing to do
2864     return mem;
2865   }
2866 
2867   assert((end_offset % BytesPerInt) == 0, "odd end offset");
2868   intptr_t done_offset = end_offset;
2869   if ((done_offset % BytesPerLong) != 0) {
2870     done_offset -= BytesPerInt;
2871   }
2872   if (done_offset > start_offset) {
2873     mem = clear_memory(ctl, mem, dest,
2874                        start_offset, phase->MakeConX(done_offset), phase);
2875   }
2876   if (done_offset < end_offset) { // emit the final 32-bit store
2877     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
2878     adr = phase->transform(adr);
2879     const TypePtr* atp = TypeRawPtr::BOTTOM;
2880     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2881     mem = phase->transform(mem);
2882     done_offset += BytesPerInt;
2883   }
2884   assert(done_offset == end_offset, "");
2885   return mem;
2886 }
2887 
2888 //=============================================================================
2889 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
2890   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
2891     _adr_type(C->get_adr_type(alias_idx))
2892 {
2893   init_class_id(Class_MemBar);
2894   Node* top = C->top();
2895   init_req(TypeFunc::I_O,top);
2896   init_req(TypeFunc::FramePtr,top);
2897   init_req(TypeFunc::ReturnAdr,top);
2898   if (precedent != NULL)
2899     init_req(TypeFunc::Parms, precedent);
2900 }
2901 
2902 //------------------------------cmp--------------------------------------------
2903 uint MemBarNode::hash() const { return NO_HASH; }
2904 uint MemBarNode::cmp( const Node &n ) const {
2905   return (&n == this);          // Always fail except on self
2906 }
2907 
2908 //------------------------------make-------------------------------------------
2909 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
2910   switch (opcode) {
2911   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
2912   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
2913   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
2914   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
2915   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
2916   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
2917   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
2918   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
2919   case Op_Initialize:        return new InitializeNode(C, atp, pn);
2920   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
2921   default: ShouldNotReachHere(); return NULL;
2922   }
2923 }
2924 
2925 //------------------------------Ideal------------------------------------------
2926 // Return a node which is more "ideal" than the current node.  Strip out
2927 // control copies
2928 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2929   if (remove_dead_region(phase, can_reshape)) return this;
2930   // Don't bother trying to transform a dead node
2931   if (in(0) && in(0)->is_top()) {
2932     return NULL;
2933   }
2934 
2935   bool progress = false;
2936   // Eliminate volatile MemBars for scalar replaced objects.
2937   if (can_reshape && req() == (Precedent+1)) {
2938     bool eliminate = false;
2939     int opc = Opcode();
2940     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
2941       // Volatile field loads and stores.
2942       Node* my_mem = in(MemBarNode::Precedent);
2943       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
2944       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
2945         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
2946         // replace this Precedent (decodeN) with the Load instead.
2947         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
2948           Node* load_node = my_mem->in(1);
2949           set_req(MemBarNode::Precedent, load_node);
2950           phase->is_IterGVN()->_worklist.push(my_mem);
2951           my_mem = load_node;
2952         } else {
2953           assert(my_mem->unique_out() == this, "sanity");
2954           del_req(Precedent);
2955           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
2956           my_mem = NULL;
2957         }
2958         progress = true;
2959       }
2960       if (my_mem != NULL && my_mem->is_Mem()) {
2961         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
2962         // Check for scalar replaced object reference.
2963         if( t_oop != NULL && t_oop->is_known_instance_field() &&
2964             t_oop->offset() != Type::OffsetBot &&
2965             t_oop->offset() != Type::OffsetTop) {
2966           eliminate = true;
2967         }
2968       }
2969     } else if (opc == Op_MemBarRelease) {
2970       // Final field stores.
2971       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
2972       if ((alloc != NULL) && alloc->is_Allocate() &&
2973           alloc->as_Allocate()->_is_non_escaping) {
2974         // The allocated object does not escape.
2975         eliminate = true;
2976       }
2977     }
2978     if (eliminate) {
2979       // Replace MemBar projections by its inputs.
2980       PhaseIterGVN* igvn = phase->is_IterGVN();
2981       igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
2982       igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
2983       // Must return either the original node (now dead) or a new node
2984       // (Do not return a top here, since that would break the uniqueness of top.)
2985       return new ConINode(TypeInt::ZERO);
2986     }
2987   }
2988   return progress ? this : NULL;
2989 }
2990 
2991 //------------------------------Value------------------------------------------
2992 const Type *MemBarNode::Value( PhaseTransform *phase ) const {
2993   if( !in(0) ) return Type::TOP;
2994   if( phase->type(in(0)) == Type::TOP )
2995     return Type::TOP;
2996   return TypeTuple::MEMBAR;
2997 }
2998 
2999 //------------------------------match------------------------------------------
3000 // Construct projections for memory.
3001 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3002   switch (proj->_con) {
3003   case TypeFunc::Control:
3004   case TypeFunc::Memory:
3005     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3006   }
3007   ShouldNotReachHere();
3008   return NULL;
3009 }
3010 
3011 //===========================InitializeNode====================================
3012 // SUMMARY:
3013 // This node acts as a memory barrier on raw memory, after some raw stores.
3014 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3015 // The Initialize can 'capture' suitably constrained stores as raw inits.
3016 // It can coalesce related raw stores into larger units (called 'tiles').
3017 // It can avoid zeroing new storage for memory units which have raw inits.
3018 // At macro-expansion, it is marked 'complete', and does not optimize further.
3019 //
3020 // EXAMPLE:
3021 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3022 //   ctl = incoming control; mem* = incoming memory
3023 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3024 // First allocate uninitialized memory and fill in the header:
3025 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3026 //   ctl := alloc.Control; mem* := alloc.Memory*
3027 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3028 // Then initialize to zero the non-header parts of the raw memory block:
3029 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3030 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3031 // After the initialize node executes, the object is ready for service:
3032 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3033 // Suppose its body is immediately initialized as {1,2}:
3034 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3035 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3036 //   mem.SLICE(#short[*]) := store2
3037 //
3038 // DETAILS:
3039 // An InitializeNode collects and isolates object initialization after
3040 // an AllocateNode and before the next possible safepoint.  As a
3041 // memory barrier (MemBarNode), it keeps critical stores from drifting
3042 // down past any safepoint or any publication of the allocation.
3043 // Before this barrier, a newly-allocated object may have uninitialized bits.
3044 // After this barrier, it may be treated as a real oop, and GC is allowed.
3045 //
3046 // The semantics of the InitializeNode include an implicit zeroing of
3047 // the new object from object header to the end of the object.
3048 // (The object header and end are determined by the AllocateNode.)
3049 //
3050 // Certain stores may be added as direct inputs to the InitializeNode.
3051 // These stores must update raw memory, and they must be to addresses
3052 // derived from the raw address produced by AllocateNode, and with
3053 // a constant offset.  They must be ordered by increasing offset.
3054 // The first one is at in(RawStores), the last at in(req()-1).
3055 // Unlike most memory operations, they are not linked in a chain,
3056 // but are displayed in parallel as users of the rawmem output of
3057 // the allocation.
3058 //
3059 // (See comments in InitializeNode::capture_store, which continue
3060 // the example given above.)
3061 //
3062 // When the associated Allocate is macro-expanded, the InitializeNode
3063 // may be rewritten to optimize collected stores.  A ClearArrayNode
3064 // may also be created at that point to represent any required zeroing.
3065 // The InitializeNode is then marked 'complete', prohibiting further
3066 // capturing of nearby memory operations.
3067 //
3068 // During macro-expansion, all captured initializations which store
3069 // constant values of 32 bits or smaller are coalesced (if advantageous)
3070 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3071 // initialized in fewer memory operations.  Memory words which are
3072 // covered by neither tiles nor non-constant stores are pre-zeroed
3073 // by explicit stores of zero.  (The code shape happens to do all
3074 // zeroing first, then all other stores, with both sequences occurring
3075 // in order of ascending offsets.)
3076 //
3077 // Alternatively, code may be inserted between an AllocateNode and its
3078 // InitializeNode, to perform arbitrary initialization of the new object.
3079 // E.g., the object copying intrinsics insert complex data transfers here.
3080 // The initialization must then be marked as 'complete' disable the
3081 // built-in zeroing semantics and the collection of initializing stores.
3082 //
3083 // While an InitializeNode is incomplete, reads from the memory state
3084 // produced by it are optimizable if they match the control edge and
3085 // new oop address associated with the allocation/initialization.
3086 // They return a stored value (if the offset matches) or else zero.
3087 // A write to the memory state, if it matches control and address,
3088 // and if it is to a constant offset, may be 'captured' by the
3089 // InitializeNode.  It is cloned as a raw memory operation and rewired
3090 // inside the initialization, to the raw oop produced by the allocation.
3091 // Operations on addresses which are provably distinct (e.g., to
3092 // other AllocateNodes) are allowed to bypass the initialization.
3093 //
3094 // The effect of all this is to consolidate object initialization
3095 // (both arrays and non-arrays, both piecewise and bulk) into a
3096 // single location, where it can be optimized as a unit.
3097 //
3098 // Only stores with an offset less than TrackedInitializationLimit words
3099 // will be considered for capture by an InitializeNode.  This puts a
3100 // reasonable limit on the complexity of optimized initializations.
3101 
3102 //---------------------------InitializeNode------------------------------------
3103 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3104   : _is_complete(Incomplete), _does_not_escape(false),
3105     MemBarNode(C, adr_type, rawoop)
3106 {
3107   init_class_id(Class_Initialize);
3108 
3109   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3110   assert(in(RawAddress) == rawoop, "proper init");
3111   // Note:  allocation() can be NULL, for secondary initialization barriers
3112 }
3113 
3114 // Since this node is not matched, it will be processed by the
3115 // register allocator.  Declare that there are no constraints
3116 // on the allocation of the RawAddress edge.
3117 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3118   // This edge should be set to top, by the set_complete.  But be conservative.
3119   if (idx == InitializeNode::RawAddress)
3120     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3121   return RegMask::Empty;
3122 }
3123 
3124 Node* InitializeNode::memory(uint alias_idx) {
3125   Node* mem = in(Memory);
3126   if (mem->is_MergeMem()) {
3127     return mem->as_MergeMem()->memory_at(alias_idx);
3128   } else {
3129     // incoming raw memory is not split
3130     return mem;
3131   }
3132 }
3133 
3134 bool InitializeNode::is_non_zero() {
3135   if (is_complete())  return false;
3136   remove_extra_zeroes();
3137   return (req() > RawStores);
3138 }
3139 
3140 void InitializeNode::set_complete(PhaseGVN* phase) {
3141   assert(!is_complete(), "caller responsibility");
3142   _is_complete = Complete;
3143 
3144   // After this node is complete, it contains a bunch of
3145   // raw-memory initializations.  There is no need for
3146   // it to have anything to do with non-raw memory effects.
3147   // Therefore, tell all non-raw users to re-optimize themselves,
3148   // after skipping the memory effects of this initialization.
3149   PhaseIterGVN* igvn = phase->is_IterGVN();
3150   if (igvn)  igvn->add_users_to_worklist(this);
3151 }
3152 
3153 // convenience function
3154 // return false if the init contains any stores already
3155 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3156   InitializeNode* init = initialization();
3157   if (init == NULL || init->is_complete())  return false;
3158   init->remove_extra_zeroes();
3159   // for now, if this allocation has already collected any inits, bail:
3160   if (init->is_non_zero())  return false;
3161   init->set_complete(phase);
3162   return true;
3163 }
3164 
3165 void InitializeNode::remove_extra_zeroes() {
3166   if (req() == RawStores)  return;
3167   Node* zmem = zero_memory();
3168   uint fill = RawStores;
3169   for (uint i = fill; i < req(); i++) {
3170     Node* n = in(i);
3171     if (n->is_top() || n == zmem)  continue;  // skip
3172     if (fill < i)  set_req(fill, n);          // compact
3173     ++fill;
3174   }
3175   // delete any empty spaces created:
3176   while (fill < req()) {
3177     del_req(fill);
3178   }
3179 }
3180 
3181 // Helper for remembering which stores go with which offsets.
3182 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3183   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3184   intptr_t offset = -1;
3185   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3186                                                phase, offset);
3187   if (base == NULL)     return -1;  // something is dead,
3188   if (offset < 0)       return -1;  //        dead, dead
3189   return offset;
3190 }
3191 
3192 // Helper for proving that an initialization expression is
3193 // "simple enough" to be folded into an object initialization.
3194 // Attempts to prove that a store's initial value 'n' can be captured
3195 // within the initialization without creating a vicious cycle, such as:
3196 //     { Foo p = new Foo(); p.next = p; }
3197 // True for constants and parameters and small combinations thereof.
3198 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3199   if (n == NULL)      return true;   // (can this really happen?)
3200   if (n->is_Proj())   n = n->in(0);
3201   if (n == this)      return false;  // found a cycle
3202   if (n->is_Con())    return true;
3203   if (n->is_Start())  return true;   // params, etc., are OK
3204   if (n->is_Root())   return true;   // even better
3205 
3206   Node* ctl = n->in(0);
3207   if (ctl != NULL && !ctl->is_top()) {
3208     if (ctl->is_Proj())  ctl = ctl->in(0);
3209     if (ctl == this)  return false;
3210 
3211     // If we already know that the enclosing memory op is pinned right after
3212     // the init, then any control flow that the store has picked up
3213     // must have preceded the init, or else be equal to the init.
3214     // Even after loop optimizations (which might change control edges)
3215     // a store is never pinned *before* the availability of its inputs.
3216     if (!MemNode::all_controls_dominate(n, this))
3217       return false;                  // failed to prove a good control
3218   }
3219 
3220   // Check data edges for possible dependencies on 'this'.
3221   if ((count += 1) > 20)  return false;  // complexity limit
3222   for (uint i = 1; i < n->req(); i++) {
3223     Node* m = n->in(i);
3224     if (m == NULL || m == n || m->is_top())  continue;
3225     uint first_i = n->find_edge(m);
3226     if (i != first_i)  continue;  // process duplicate edge just once
3227     if (!detect_init_independence(m, count)) {
3228       return false;
3229     }
3230   }
3231 
3232   return true;
3233 }
3234 
3235 // Here are all the checks a Store must pass before it can be moved into
3236 // an initialization.  Returns zero if a check fails.
3237 // On success, returns the (constant) offset to which the store applies,
3238 // within the initialized memory.
3239 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3240   const int FAIL = 0;
3241   if (st->req() != MemNode::ValueIn + 1)
3242     return FAIL;                // an inscrutable StoreNode (card mark?)
3243   Node* ctl = st->in(MemNode::Control);
3244   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3245     return FAIL;                // must be unconditional after the initialization
3246   Node* mem = st->in(MemNode::Memory);
3247   if (!(mem->is_Proj() && mem->in(0) == this))
3248     return FAIL;                // must not be preceded by other stores
3249   Node* adr = st->in(MemNode::Address);
3250   intptr_t offset;
3251   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3252   if (alloc == NULL)
3253     return FAIL;                // inscrutable address
3254   if (alloc != allocation())
3255     return FAIL;                // wrong allocation!  (store needs to float up)
3256   Node* val = st->in(MemNode::ValueIn);
3257   int complexity_count = 0;
3258   if (!detect_init_independence(val, complexity_count))
3259     return FAIL;                // stored value must be 'simple enough'
3260 
3261   // The Store can be captured only if nothing after the allocation
3262   // and before the Store is using the memory location that the store
3263   // overwrites.
3264   bool failed = false;
3265   // If is_complete_with_arraycopy() is true the shape of the graph is
3266   // well defined and is safe so no need for extra checks.
3267   if (!is_complete_with_arraycopy()) {
3268     // We are going to look at each use of the memory state following
3269     // the allocation to make sure nothing reads the memory that the
3270     // Store writes.
3271     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3272     int alias_idx = phase->C->get_alias_index(t_adr);
3273     ResourceMark rm;
3274     Unique_Node_List mems;
3275     mems.push(mem);
3276     Node* unique_merge = NULL;
3277     for (uint next = 0; next < mems.size(); ++next) {
3278       Node *m  = mems.at(next);
3279       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3280         Node *n = m->fast_out(j);
3281         if (n->outcnt() == 0) {
3282           continue;
3283         }
3284         if (n == st) {
3285           continue;
3286         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3287           // If the control of this use is different from the control
3288           // of the Store which is right after the InitializeNode then
3289           // this node cannot be between the InitializeNode and the
3290           // Store.
3291           continue;
3292         } else if (n->is_MergeMem()) {
3293           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3294             // We can hit a MergeMemNode (that will likely go away
3295             // later) that is a direct use of the memory state
3296             // following the InitializeNode on the same slice as the
3297             // store node that we'd like to capture. We need to check
3298             // the uses of the MergeMemNode.
3299             mems.push(n);
3300           }
3301         } else if (n->is_Mem()) {
3302           Node* other_adr = n->in(MemNode::Address);
3303           if (other_adr == adr) {
3304             failed = true;
3305             break;
3306           } else {
3307             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3308             if (other_t_adr != NULL) {
3309               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3310               if (other_alias_idx == alias_idx) {
3311                 // A load from the same memory slice as the store right
3312                 // after the InitializeNode. We check the control of the
3313                 // object/array that is loaded from. If it's the same as
3314                 // the store control then we cannot capture the store.
3315                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3316                 Node* base = other_adr;
3317                 assert(base->is_AddP(), err_msg_res("should be addp but is %s", base->Name()));
3318                 base = base->in(AddPNode::Base);
3319                 if (base != NULL) {
3320                   base = base->uncast();
3321                   if (base->is_Proj() && base->in(0) == alloc) {
3322                     failed = true;
3323                     break;
3324                   }
3325                 }
3326               }
3327             }
3328           }
3329         } else {
3330           failed = true;
3331           break;
3332         }
3333       }
3334     }
3335   }
3336   if (failed) {
3337     if (!can_reshape) {
3338       // We decided we couldn't capture the store during parsing. We
3339       // should try again during the next IGVN once the graph is
3340       // cleaner.
3341       phase->C->record_for_igvn(st);
3342     }
3343     return FAIL;
3344   }
3345 
3346   return offset;                // success
3347 }
3348 
3349 // Find the captured store in(i) which corresponds to the range
3350 // [start..start+size) in the initialized object.
3351 // If there is one, return its index i.  If there isn't, return the
3352 // negative of the index where it should be inserted.
3353 // Return 0 if the queried range overlaps an initialization boundary
3354 // or if dead code is encountered.
3355 // If size_in_bytes is zero, do not bother with overlap checks.
3356 int InitializeNode::captured_store_insertion_point(intptr_t start,
3357                                                    int size_in_bytes,
3358                                                    PhaseTransform* phase) {
3359   const int FAIL = 0, MAX_STORE = BytesPerLong;
3360 
3361   if (is_complete())
3362     return FAIL;                // arraycopy got here first; punt
3363 
3364   assert(allocation() != NULL, "must be present");
3365 
3366   // no negatives, no header fields:
3367   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3368 
3369   // after a certain size, we bail out on tracking all the stores:
3370   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3371   if (start >= ti_limit)  return FAIL;
3372 
3373   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3374     if (i >= limit)  return -(int)i; // not found; here is where to put it
3375 
3376     Node*    st     = in(i);
3377     intptr_t st_off = get_store_offset(st, phase);
3378     if (st_off < 0) {
3379       if (st != zero_memory()) {
3380         return FAIL;            // bail out if there is dead garbage
3381       }
3382     } else if (st_off > start) {
3383       // ...we are done, since stores are ordered
3384       if (st_off < start + size_in_bytes) {
3385         return FAIL;            // the next store overlaps
3386       }
3387       return -(int)i;           // not found; here is where to put it
3388     } else if (st_off < start) {
3389       if (size_in_bytes != 0 &&
3390           start < st_off + MAX_STORE &&
3391           start < st_off + st->as_Store()->memory_size()) {
3392         return FAIL;            // the previous store overlaps
3393       }
3394     } else {
3395       if (size_in_bytes != 0 &&
3396           st->as_Store()->memory_size() != size_in_bytes) {
3397         return FAIL;            // mismatched store size
3398       }
3399       return i;
3400     }
3401 
3402     ++i;
3403   }
3404 }
3405 
3406 // Look for a captured store which initializes at the offset 'start'
3407 // with the given size.  If there is no such store, and no other
3408 // initialization interferes, then return zero_memory (the memory
3409 // projection of the AllocateNode).
3410 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3411                                           PhaseTransform* phase) {
3412   assert(stores_are_sane(phase), "");
3413   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3414   if (i == 0) {
3415     return NULL;                // something is dead
3416   } else if (i < 0) {
3417     return zero_memory();       // just primordial zero bits here
3418   } else {
3419     Node* st = in(i);           // here is the store at this position
3420     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3421     return st;
3422   }
3423 }
3424 
3425 // Create, as a raw pointer, an address within my new object at 'offset'.
3426 Node* InitializeNode::make_raw_address(intptr_t offset,
3427                                        PhaseTransform* phase) {
3428   Node* addr = in(RawAddress);
3429   if (offset != 0) {
3430     Compile* C = phase->C;
3431     addr = phase->transform( new AddPNode(C->top(), addr,
3432                                                  phase->MakeConX(offset)) );
3433   }
3434   return addr;
3435 }
3436 
3437 // Clone the given store, converting it into a raw store
3438 // initializing a field or element of my new object.
3439 // Caller is responsible for retiring the original store,
3440 // with subsume_node or the like.
3441 //
3442 // From the example above InitializeNode::InitializeNode,
3443 // here are the old stores to be captured:
3444 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3445 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3446 //
3447 // Here is the changed code; note the extra edges on init:
3448 //   alloc = (Allocate ...)
3449 //   rawoop = alloc.RawAddress
3450 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3451 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3452 //   init = (Initialize alloc.Control alloc.Memory rawoop
3453 //                      rawstore1 rawstore2)
3454 //
3455 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3456                                     PhaseTransform* phase, bool can_reshape) {
3457   assert(stores_are_sane(phase), "");
3458 
3459   if (start < 0)  return NULL;
3460   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3461 
3462   Compile* C = phase->C;
3463   int size_in_bytes = st->memory_size();
3464   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3465   if (i == 0)  return NULL;     // bail out
3466   Node* prev_mem = NULL;        // raw memory for the captured store
3467   if (i > 0) {
3468     prev_mem = in(i);           // there is a pre-existing store under this one
3469     set_req(i, C->top());       // temporarily disconnect it
3470     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3471   } else {
3472     i = -i;                     // no pre-existing store
3473     prev_mem = zero_memory();   // a slice of the newly allocated object
3474     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3475       set_req(--i, C->top());   // reuse this edge; it has been folded away
3476     else
3477       ins_req(i, C->top());     // build a new edge
3478   }
3479   Node* new_st = st->clone();
3480   new_st->set_req(MemNode::Control, in(Control));
3481   new_st->set_req(MemNode::Memory,  prev_mem);
3482   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3483   new_st = phase->transform(new_st);
3484 
3485   // At this point, new_st might have swallowed a pre-existing store
3486   // at the same offset, or perhaps new_st might have disappeared,
3487   // if it redundantly stored the same value (or zero to fresh memory).
3488 
3489   // In any case, wire it in:
3490   phase->igvn_rehash_node_delayed(this);
3491   set_req(i, new_st);
3492 
3493   // The caller may now kill the old guy.
3494   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3495   assert(check_st == new_st || check_st == NULL, "must be findable");
3496   assert(!is_complete(), "");
3497   return new_st;
3498 }
3499 
3500 static bool store_constant(jlong* tiles, int num_tiles,
3501                            intptr_t st_off, int st_size,
3502                            jlong con) {
3503   if ((st_off & (st_size-1)) != 0)
3504     return false;               // strange store offset (assume size==2**N)
3505   address addr = (address)tiles + st_off;
3506   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3507   switch (st_size) {
3508   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3509   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3510   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3511   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3512   default: return false;        // strange store size (detect size!=2**N here)
3513   }
3514   return true;                  // return success to caller
3515 }
3516 
3517 // Coalesce subword constants into int constants and possibly
3518 // into long constants.  The goal, if the CPU permits,
3519 // is to initialize the object with a small number of 64-bit tiles.
3520 // Also, convert floating-point constants to bit patterns.
3521 // Non-constants are not relevant to this pass.
3522 //
3523 // In terms of the running example on InitializeNode::InitializeNode
3524 // and InitializeNode::capture_store, here is the transformation
3525 // of rawstore1 and rawstore2 into rawstore12:
3526 //   alloc = (Allocate ...)
3527 //   rawoop = alloc.RawAddress
3528 //   tile12 = 0x00010002
3529 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3530 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3531 //
3532 void
3533 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3534                                         Node* size_in_bytes,
3535                                         PhaseGVN* phase) {
3536   Compile* C = phase->C;
3537 
3538   assert(stores_are_sane(phase), "");
3539   // Note:  After this pass, they are not completely sane,
3540   // since there may be some overlaps.
3541 
3542   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3543 
3544   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3545   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3546   size_limit = MIN2(size_limit, ti_limit);
3547   size_limit = align_size_up(size_limit, BytesPerLong);
3548   int num_tiles = size_limit / BytesPerLong;
3549 
3550   // allocate space for the tile map:
3551   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3552   jlong  tiles_buf[small_len];
3553   Node*  nodes_buf[small_len];
3554   jlong  inits_buf[small_len];
3555   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3556                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3557   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3558                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3559   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3560                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3561   // tiles: exact bitwise model of all primitive constants
3562   // nodes: last constant-storing node subsumed into the tiles model
3563   // inits: which bytes (in each tile) are touched by any initializations
3564 
3565   //// Pass A: Fill in the tile model with any relevant stores.
3566 
3567   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3568   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3569   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3570   Node* zmem = zero_memory(); // initially zero memory state
3571   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3572     Node* st = in(i);
3573     intptr_t st_off = get_store_offset(st, phase);
3574 
3575     // Figure out the store's offset and constant value:
3576     if (st_off < header_size)             continue; //skip (ignore header)
3577     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3578     int st_size = st->as_Store()->memory_size();
3579     if (st_off + st_size > size_limit)    break;
3580 
3581     // Record which bytes are touched, whether by constant or not.
3582     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3583       continue;                 // skip (strange store size)
3584 
3585     const Type* val = phase->type(st->in(MemNode::ValueIn));
3586     if (!val->singleton())                continue; //skip (non-con store)
3587     BasicType type = val->basic_type();
3588 
3589     jlong con = 0;
3590     switch (type) {
3591     case T_INT:    con = val->is_int()->get_con();  break;
3592     case T_LONG:   con = val->is_long()->get_con(); break;
3593     case T_FLOAT:  con = jint_cast(val->getf());    break;
3594     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3595     default:                              continue; //skip (odd store type)
3596     }
3597 
3598     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3599         st->Opcode() == Op_StoreL) {
3600       continue;                 // This StoreL is already optimal.
3601     }
3602 
3603     // Store down the constant.
3604     store_constant(tiles, num_tiles, st_off, st_size, con);
3605 
3606     intptr_t j = st_off >> LogBytesPerLong;
3607 
3608     if (type == T_INT && st_size == BytesPerInt
3609         && (st_off & BytesPerInt) == BytesPerInt) {
3610       jlong lcon = tiles[j];
3611       if (!Matcher::isSimpleConstant64(lcon) &&
3612           st->Opcode() == Op_StoreI) {
3613         // This StoreI is already optimal by itself.
3614         jint* intcon = (jint*) &tiles[j];
3615         intcon[1] = 0;  // undo the store_constant()
3616 
3617         // If the previous store is also optimal by itself, back up and
3618         // undo the action of the previous loop iteration... if we can.
3619         // But if we can't, just let the previous half take care of itself.
3620         st = nodes[j];
3621         st_off -= BytesPerInt;
3622         con = intcon[0];
3623         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3624           assert(st_off >= header_size, "still ignoring header");
3625           assert(get_store_offset(st, phase) == st_off, "must be");
3626           assert(in(i-1) == zmem, "must be");
3627           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3628           assert(con == tcon->is_int()->get_con(), "must be");
3629           // Undo the effects of the previous loop trip, which swallowed st:
3630           intcon[0] = 0;        // undo store_constant()
3631           set_req(i-1, st);     // undo set_req(i, zmem)
3632           nodes[j] = NULL;      // undo nodes[j] = st
3633           --old_subword;        // undo ++old_subword
3634         }
3635         continue;               // This StoreI is already optimal.
3636       }
3637     }
3638 
3639     // This store is not needed.
3640     set_req(i, zmem);
3641     nodes[j] = st;              // record for the moment
3642     if (st_size < BytesPerLong) // something has changed
3643           ++old_subword;        // includes int/float, but who's counting...
3644     else  ++old_long;
3645   }
3646 
3647   if ((old_subword + old_long) == 0)
3648     return;                     // nothing more to do
3649 
3650   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3651   // Be sure to insert them before overlapping non-constant stores.
3652   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3653   for (int j = 0; j < num_tiles; j++) {
3654     jlong con  = tiles[j];
3655     jlong init = inits[j];
3656     if (con == 0)  continue;
3657     jint con0,  con1;           // split the constant, address-wise
3658     jint init0, init1;          // split the init map, address-wise
3659     { union { jlong con; jint intcon[2]; } u;
3660       u.con = con;
3661       con0  = u.intcon[0];
3662       con1  = u.intcon[1];
3663       u.con = init;
3664       init0 = u.intcon[0];
3665       init1 = u.intcon[1];
3666     }
3667 
3668     Node* old = nodes[j];
3669     assert(old != NULL, "need the prior store");
3670     intptr_t offset = (j * BytesPerLong);
3671 
3672     bool split = !Matcher::isSimpleConstant64(con);
3673 
3674     if (offset < header_size) {
3675       assert(offset + BytesPerInt >= header_size, "second int counts");
3676       assert(*(jint*)&tiles[j] == 0, "junk in header");
3677       split = true;             // only the second word counts
3678       // Example:  int a[] = { 42 ... }
3679     } else if (con0 == 0 && init0 == -1) {
3680       split = true;             // first word is covered by full inits
3681       // Example:  int a[] = { ... foo(), 42 ... }
3682     } else if (con1 == 0 && init1 == -1) {
3683       split = true;             // second word is covered by full inits
3684       // Example:  int a[] = { ... 42, foo() ... }
3685     }
3686 
3687     // Here's a case where init0 is neither 0 nor -1:
3688     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
3689     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3690     // In this case the tile is not split; it is (jlong)42.
3691     // The big tile is stored down, and then the foo() value is inserted.
3692     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3693 
3694     Node* ctl = old->in(MemNode::Control);
3695     Node* adr = make_raw_address(offset, phase);
3696     const TypePtr* atp = TypeRawPtr::BOTTOM;
3697 
3698     // One or two coalesced stores to plop down.
3699     Node*    st[2];
3700     intptr_t off[2];
3701     int  nst = 0;
3702     if (!split) {
3703       ++new_long;
3704       off[nst] = offset;
3705       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3706                                   phase->longcon(con), T_LONG, MemNode::unordered);
3707     } else {
3708       // Omit either if it is a zero.
3709       if (con0 != 0) {
3710         ++new_int;
3711         off[nst]  = offset;
3712         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3713                                     phase->intcon(con0), T_INT, MemNode::unordered);
3714       }
3715       if (con1 != 0) {
3716         ++new_int;
3717         offset += BytesPerInt;
3718         adr = make_raw_address(offset, phase);
3719         off[nst]  = offset;
3720         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3721                                     phase->intcon(con1), T_INT, MemNode::unordered);
3722       }
3723     }
3724 
3725     // Insert second store first, then the first before the second.
3726     // Insert each one just before any overlapping non-constant stores.
3727     while (nst > 0) {
3728       Node* st1 = st[--nst];
3729       C->copy_node_notes_to(st1, old);
3730       st1 = phase->transform(st1);
3731       offset = off[nst];
3732       assert(offset >= header_size, "do not smash header");
3733       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
3734       guarantee(ins_idx != 0, "must re-insert constant store");
3735       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
3736       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
3737         set_req(--ins_idx, st1);
3738       else
3739         ins_req(ins_idx, st1);
3740     }
3741   }
3742 
3743   if (PrintCompilation && WizardMode)
3744     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
3745                   old_subword, old_long, new_int, new_long);
3746   if (C->log() != NULL)
3747     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
3748                    old_subword, old_long, new_int, new_long);
3749 
3750   // Clean up any remaining occurrences of zmem:
3751   remove_extra_zeroes();
3752 }
3753 
3754 // Explore forward from in(start) to find the first fully initialized
3755 // word, and return its offset.  Skip groups of subword stores which
3756 // together initialize full words.  If in(start) is itself part of a
3757 // fully initialized word, return the offset of in(start).  If there
3758 // are no following full-word stores, or if something is fishy, return
3759 // a negative value.
3760 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
3761   int       int_map = 0;
3762   intptr_t  int_map_off = 0;
3763   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
3764 
3765   for (uint i = start, limit = req(); i < limit; i++) {
3766     Node* st = in(i);
3767 
3768     intptr_t st_off = get_store_offset(st, phase);
3769     if (st_off < 0)  break;  // return conservative answer
3770 
3771     int st_size = st->as_Store()->memory_size();
3772     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
3773       return st_off;            // we found a complete word init
3774     }
3775 
3776     // update the map:
3777 
3778     intptr_t this_int_off = align_size_down(st_off, BytesPerInt);
3779     if (this_int_off != int_map_off) {
3780       // reset the map:
3781       int_map = 0;
3782       int_map_off = this_int_off;
3783     }
3784 
3785     int subword_off = st_off - this_int_off;
3786     int_map |= right_n_bits(st_size) << subword_off;
3787     if ((int_map & FULL_MAP) == FULL_MAP) {
3788       return this_int_off;      // we found a complete word init
3789     }
3790 
3791     // Did this store hit or cross the word boundary?
3792     intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt);
3793     if (next_int_off == this_int_off + BytesPerInt) {
3794       // We passed the current int, without fully initializing it.
3795       int_map_off = next_int_off;
3796       int_map >>= BytesPerInt;
3797     } else if (next_int_off > this_int_off + BytesPerInt) {
3798       // We passed the current and next int.
3799       return this_int_off + BytesPerInt;
3800     }
3801   }
3802 
3803   return -1;
3804 }
3805 
3806 
3807 // Called when the associated AllocateNode is expanded into CFG.
3808 // At this point, we may perform additional optimizations.
3809 // Linearize the stores by ascending offset, to make memory
3810 // activity as coherent as possible.
3811 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
3812                                       intptr_t header_size,
3813                                       Node* size_in_bytes,
3814                                       PhaseGVN* phase) {
3815   assert(!is_complete(), "not already complete");
3816   assert(stores_are_sane(phase), "");
3817   assert(allocation() != NULL, "must be present");
3818 
3819   remove_extra_zeroes();
3820 
3821   if (ReduceFieldZeroing || ReduceBulkZeroing)
3822     // reduce instruction count for common initialization patterns
3823     coalesce_subword_stores(header_size, size_in_bytes, phase);
3824 
3825   Node* zmem = zero_memory();   // initially zero memory state
3826   Node* inits = zmem;           // accumulating a linearized chain of inits
3827   #ifdef ASSERT
3828   intptr_t first_offset = allocation()->minimum_header_size();
3829   intptr_t last_init_off = first_offset;  // previous init offset
3830   intptr_t last_init_end = first_offset;  // previous init offset+size
3831   intptr_t last_tile_end = first_offset;  // previous tile offset+size
3832   #endif
3833   intptr_t zeroes_done = header_size;
3834 
3835   bool do_zeroing = true;       // we might give up if inits are very sparse
3836   int  big_init_gaps = 0;       // how many large gaps have we seen?
3837 
3838   if (ZeroTLAB)  do_zeroing = false;
3839   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
3840 
3841   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3842     Node* st = in(i);
3843     intptr_t st_off = get_store_offset(st, phase);
3844     if (st_off < 0)
3845       break;                    // unknown junk in the inits
3846     if (st->in(MemNode::Memory) != zmem)
3847       break;                    // complicated store chains somehow in list
3848 
3849     int st_size = st->as_Store()->memory_size();
3850     intptr_t next_init_off = st_off + st_size;
3851 
3852     if (do_zeroing && zeroes_done < next_init_off) {
3853       // See if this store needs a zero before it or under it.
3854       intptr_t zeroes_needed = st_off;
3855 
3856       if (st_size < BytesPerInt) {
3857         // Look for subword stores which only partially initialize words.
3858         // If we find some, we must lay down some word-level zeroes first,
3859         // underneath the subword stores.
3860         //
3861         // Examples:
3862         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
3863         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
3864         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
3865         //
3866         // Note:  coalesce_subword_stores may have already done this,
3867         // if it was prompted by constant non-zero subword initializers.
3868         // But this case can still arise with non-constant stores.
3869 
3870         intptr_t next_full_store = find_next_fullword_store(i, phase);
3871 
3872         // In the examples above:
3873         //   in(i)          p   q   r   s     x   y     z
3874         //   st_off        12  13  14  15    12  13    14
3875         //   st_size        1   1   1   1     1   1     1
3876         //   next_full_s.  12  16  16  16    16  16    16
3877         //   z's_done      12  16  16  16    12  16    12
3878         //   z's_needed    12  16  16  16    16  16    16
3879         //   zsize          0   0   0   0     4   0     4
3880         if (next_full_store < 0) {
3881           // Conservative tack:  Zero to end of current word.
3882           zeroes_needed = align_size_up(zeroes_needed, BytesPerInt);
3883         } else {
3884           // Zero to beginning of next fully initialized word.
3885           // Or, don't zero at all, if we are already in that word.
3886           assert(next_full_store >= zeroes_needed, "must go forward");
3887           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
3888           zeroes_needed = next_full_store;
3889         }
3890       }
3891 
3892       if (zeroes_needed > zeroes_done) {
3893         intptr_t zsize = zeroes_needed - zeroes_done;
3894         // Do some incremental zeroing on rawmem, in parallel with inits.
3895         zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3896         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3897                                               zeroes_done, zeroes_needed,
3898                                               phase);
3899         zeroes_done = zeroes_needed;
3900         if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2)
3901           do_zeroing = false;   // leave the hole, next time
3902       }
3903     }
3904 
3905     // Collect the store and move on:
3906     st->set_req(MemNode::Memory, inits);
3907     inits = st;                 // put it on the linearized chain
3908     set_req(i, zmem);           // unhook from previous position
3909 
3910     if (zeroes_done == st_off)
3911       zeroes_done = next_init_off;
3912 
3913     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
3914 
3915     #ifdef ASSERT
3916     // Various order invariants.  Weaker than stores_are_sane because
3917     // a large constant tile can be filled in by smaller non-constant stores.
3918     assert(st_off >= last_init_off, "inits do not reverse");
3919     last_init_off = st_off;
3920     const Type* val = NULL;
3921     if (st_size >= BytesPerInt &&
3922         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
3923         (int)val->basic_type() < (int)T_OBJECT) {
3924       assert(st_off >= last_tile_end, "tiles do not overlap");
3925       assert(st_off >= last_init_end, "tiles do not overwrite inits");
3926       last_tile_end = MAX2(last_tile_end, next_init_off);
3927     } else {
3928       intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong);
3929       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
3930       assert(st_off      >= last_init_end, "inits do not overlap");
3931       last_init_end = next_init_off;  // it's a non-tile
3932     }
3933     #endif //ASSERT
3934   }
3935 
3936   remove_extra_zeroes();        // clear out all the zmems left over
3937   add_req(inits);
3938 
3939   if (!ZeroTLAB) {
3940     // If anything remains to be zeroed, zero it all now.
3941     zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3942     // if it is the last unused 4 bytes of an instance, forget about it
3943     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
3944     if (zeroes_done + BytesPerLong >= size_limit) {
3945       assert(allocation() != NULL, "");
3946       if (allocation()->Opcode() == Op_Allocate) {
3947         Node* klass_node = allocation()->in(AllocateNode::KlassNode);
3948         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
3949         if (zeroes_done == k->layout_helper())
3950           zeroes_done = size_limit;
3951       }
3952     }
3953     if (zeroes_done < size_limit) {
3954       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3955                                             zeroes_done, size_in_bytes, phase);
3956     }
3957   }
3958 
3959   set_complete(phase);
3960   return rawmem;
3961 }
3962 
3963 
3964 #ifdef ASSERT
3965 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
3966   if (is_complete())
3967     return true;                // stores could be anything at this point
3968   assert(allocation() != NULL, "must be present");
3969   intptr_t last_off = allocation()->minimum_header_size();
3970   for (uint i = InitializeNode::RawStores; i < req(); i++) {
3971     Node* st = in(i);
3972     intptr_t st_off = get_store_offset(st, phase);
3973     if (st_off < 0)  continue;  // ignore dead garbage
3974     if (last_off > st_off) {
3975       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
3976       this->dump(2);
3977       assert(false, "ascending store offsets");
3978       return false;
3979     }
3980     last_off = st_off + st->as_Store()->memory_size();
3981   }
3982   return true;
3983 }
3984 #endif //ASSERT
3985 
3986 
3987 
3988 
3989 //============================MergeMemNode=====================================
3990 //
3991 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
3992 // contributing store or call operations.  Each contributor provides the memory
3993 // state for a particular "alias type" (see Compile::alias_type).  For example,
3994 // if a MergeMem has an input X for alias category #6, then any memory reference
3995 // to alias category #6 may use X as its memory state input, as an exact equivalent
3996 // to using the MergeMem as a whole.
3997 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
3998 //
3999 // (Here, the <N> notation gives the index of the relevant adr_type.)
4000 //
4001 // In one special case (and more cases in the future), alias categories overlap.
4002 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4003 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4004 // it is exactly equivalent to that state W:
4005 //   MergeMem(<Bot>: W) <==> W
4006 //
4007 // Usually, the merge has more than one input.  In that case, where inputs
4008 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4009 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4010 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4011 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4012 //
4013 // A merge can take a "wide" memory state as one of its narrow inputs.
4014 // This simply means that the merge observes out only the relevant parts of
4015 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4016 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4017 //
4018 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4019 // and that memory slices "leak through":
4020 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4021 //
4022 // But, in such a cascade, repeated memory slices can "block the leak":
4023 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4024 //
4025 // In the last example, Y is not part of the combined memory state of the
4026 // outermost MergeMem.  The system must, of course, prevent unschedulable
4027 // memory states from arising, so you can be sure that the state Y is somehow
4028 // a precursor to state Y'.
4029 //
4030 //
4031 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4032 // of each MergeMemNode array are exactly the numerical alias indexes, including
4033 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4034 // Compile::alias_type (and kin) produce and manage these indexes.
4035 //
4036 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4037 // (Note that this provides quick access to the top node inside MergeMem methods,
4038 // without the need to reach out via TLS to Compile::current.)
4039 //
4040 // As a consequence of what was just described, a MergeMem that represents a full
4041 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4042 // containing all alias categories.
4043 //
4044 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4045 //
4046 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4047 // a memory state for the alias type <N>, or else the top node, meaning that
4048 // there is no particular input for that alias type.  Note that the length of
4049 // a MergeMem is variable, and may be extended at any time to accommodate new
4050 // memory states at larger alias indexes.  When merges grow, they are of course
4051 // filled with "top" in the unused in() positions.
4052 //
4053 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4054 // (Top was chosen because it works smoothly with passes like GCM.)
4055 //
4056 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4057 // the type of random VM bits like TLS references.)  Since it is always the
4058 // first non-Bot memory slice, some low-level loops use it to initialize an
4059 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4060 //
4061 //
4062 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4063 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4064 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4065 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4066 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4067 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4068 //
4069 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4070 // really that different from the other memory inputs.  An abbreviation called
4071 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4072 //
4073 //
4074 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4075 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4076 // that "emerges though" the base memory will be marked as excluding the alias types
4077 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4078 //
4079 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4080 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4081 //
4082 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4083 // (It is currently unimplemented.)  As you can see, the resulting merge is
4084 // actually a disjoint union of memory states, rather than an overlay.
4085 //
4086 
4087 //------------------------------MergeMemNode-----------------------------------
4088 Node* MergeMemNode::make_empty_memory() {
4089   Node* empty_memory = (Node*) Compile::current()->top();
4090   assert(empty_memory->is_top(), "correct sentinel identity");
4091   return empty_memory;
4092 }
4093 
4094 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4095   init_class_id(Class_MergeMem);
4096   // all inputs are nullified in Node::Node(int)
4097   // set_input(0, NULL);  // no control input
4098 
4099   // Initialize the edges uniformly to top, for starters.
4100   Node* empty_mem = make_empty_memory();
4101   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4102     init_req(i,empty_mem);
4103   }
4104   assert(empty_memory() == empty_mem, "");
4105 
4106   if( new_base != NULL && new_base->is_MergeMem() ) {
4107     MergeMemNode* mdef = new_base->as_MergeMem();
4108     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4109     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4110       mms.set_memory(mms.memory2());
4111     }
4112     assert(base_memory() == mdef->base_memory(), "");
4113   } else {
4114     set_base_memory(new_base);
4115   }
4116 }
4117 
4118 // Make a new, untransformed MergeMem with the same base as 'mem'.
4119 // If mem is itself a MergeMem, populate the result with the same edges.
4120 MergeMemNode* MergeMemNode::make(Node* mem) {
4121   return new MergeMemNode(mem);
4122 }
4123 
4124 //------------------------------cmp--------------------------------------------
4125 uint MergeMemNode::hash() const { return NO_HASH; }
4126 uint MergeMemNode::cmp( const Node &n ) const {
4127   return (&n == this);          // Always fail except on self
4128 }
4129 
4130 //------------------------------Identity---------------------------------------
4131 Node* MergeMemNode::Identity(PhaseTransform *phase) {
4132   // Identity if this merge point does not record any interesting memory
4133   // disambiguations.
4134   Node* base_mem = base_memory();
4135   Node* empty_mem = empty_memory();
4136   if (base_mem != empty_mem) {  // Memory path is not dead?
4137     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4138       Node* mem = in(i);
4139       if (mem != empty_mem && mem != base_mem) {
4140         return this;            // Many memory splits; no change
4141       }
4142     }
4143   }
4144   return base_mem;              // No memory splits; ID on the one true input
4145 }
4146 
4147 //------------------------------Ideal------------------------------------------
4148 // This method is invoked recursively on chains of MergeMem nodes
4149 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4150   // Remove chain'd MergeMems
4151   //
4152   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4153   // relative to the "in(Bot)".  Since we are patching both at the same time,
4154   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4155   // but rewrite each "in(i)" relative to the new "in(Bot)".
4156   Node *progress = NULL;
4157 
4158 
4159   Node* old_base = base_memory();
4160   Node* empty_mem = empty_memory();
4161   if (old_base == empty_mem)
4162     return NULL; // Dead memory path.
4163 
4164   MergeMemNode* old_mbase;
4165   if (old_base != NULL && old_base->is_MergeMem())
4166     old_mbase = old_base->as_MergeMem();
4167   else
4168     old_mbase = NULL;
4169   Node* new_base = old_base;
4170 
4171   // simplify stacked MergeMems in base memory
4172   if (old_mbase)  new_base = old_mbase->base_memory();
4173 
4174   // the base memory might contribute new slices beyond my req()
4175   if (old_mbase)  grow_to_match(old_mbase);
4176 
4177   // Look carefully at the base node if it is a phi.
4178   PhiNode* phi_base;
4179   if (new_base != NULL && new_base->is_Phi())
4180     phi_base = new_base->as_Phi();
4181   else
4182     phi_base = NULL;
4183 
4184   Node*    phi_reg = NULL;
4185   uint     phi_len = (uint)-1;
4186   if (phi_base != NULL && !phi_base->is_copy()) {
4187     // do not examine phi if degraded to a copy
4188     phi_reg = phi_base->region();
4189     phi_len = phi_base->req();
4190     // see if the phi is unfinished
4191     for (uint i = 1; i < phi_len; i++) {
4192       if (phi_base->in(i) == NULL) {
4193         // incomplete phi; do not look at it yet!
4194         phi_reg = NULL;
4195         phi_len = (uint)-1;
4196         break;
4197       }
4198     }
4199   }
4200 
4201   // Note:  We do not call verify_sparse on entry, because inputs
4202   // can normalize to the base_memory via subsume_node or similar
4203   // mechanisms.  This method repairs that damage.
4204 
4205   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4206 
4207   // Look at each slice.
4208   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4209     Node* old_in = in(i);
4210     // calculate the old memory value
4211     Node* old_mem = old_in;
4212     if (old_mem == empty_mem)  old_mem = old_base;
4213     assert(old_mem == memory_at(i), "");
4214 
4215     // maybe update (reslice) the old memory value
4216 
4217     // simplify stacked MergeMems
4218     Node* new_mem = old_mem;
4219     MergeMemNode* old_mmem;
4220     if (old_mem != NULL && old_mem->is_MergeMem())
4221       old_mmem = old_mem->as_MergeMem();
4222     else
4223       old_mmem = NULL;
4224     if (old_mmem == this) {
4225       // This can happen if loops break up and safepoints disappear.
4226       // A merge of BotPtr (default) with a RawPtr memory derived from a
4227       // safepoint can be rewritten to a merge of the same BotPtr with
4228       // the BotPtr phi coming into the loop.  If that phi disappears
4229       // also, we can end up with a self-loop of the mergemem.
4230       // In general, if loops degenerate and memory effects disappear,
4231       // a mergemem can be left looking at itself.  This simply means
4232       // that the mergemem's default should be used, since there is
4233       // no longer any apparent effect on this slice.
4234       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4235       //       from start.  Update the input to TOP.
4236       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4237     }
4238     else if (old_mmem != NULL) {
4239       new_mem = old_mmem->memory_at(i);
4240     }
4241     // else preceding memory was not a MergeMem
4242 
4243     // replace equivalent phis (unfortunately, they do not GVN together)
4244     if (new_mem != NULL && new_mem != new_base &&
4245         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4246       if (new_mem->is_Phi()) {
4247         PhiNode* phi_mem = new_mem->as_Phi();
4248         for (uint i = 1; i < phi_len; i++) {
4249           if (phi_base->in(i) != phi_mem->in(i)) {
4250             phi_mem = NULL;
4251             break;
4252           }
4253         }
4254         if (phi_mem != NULL) {
4255           // equivalent phi nodes; revert to the def
4256           new_mem = new_base;
4257         }
4258       }
4259     }
4260 
4261     // maybe store down a new value
4262     Node* new_in = new_mem;
4263     if (new_in == new_base)  new_in = empty_mem;
4264 
4265     if (new_in != old_in) {
4266       // Warning:  Do not combine this "if" with the previous "if"
4267       // A memory slice might have be be rewritten even if it is semantically
4268       // unchanged, if the base_memory value has changed.
4269       set_req(i, new_in);
4270       progress = this;          // Report progress
4271     }
4272   }
4273 
4274   if (new_base != old_base) {
4275     set_req(Compile::AliasIdxBot, new_base);
4276     // Don't use set_base_memory(new_base), because we need to update du.
4277     assert(base_memory() == new_base, "");
4278     progress = this;
4279   }
4280 
4281   if( base_memory() == this ) {
4282     // a self cycle indicates this memory path is dead
4283     set_req(Compile::AliasIdxBot, empty_mem);
4284   }
4285 
4286   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4287   // Recursion must occur after the self cycle check above
4288   if( base_memory()->is_MergeMem() ) {
4289     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4290     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4291     if( m != NULL && (m->is_top() ||
4292         m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) {
4293       // propagate rollup of dead cycle to self
4294       set_req(Compile::AliasIdxBot, empty_mem);
4295     }
4296   }
4297 
4298   if( base_memory() == empty_mem ) {
4299     progress = this;
4300     // Cut inputs during Parse phase only.
4301     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4302     if( !can_reshape ) {
4303       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4304         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4305       }
4306     }
4307   }
4308 
4309   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4310     // Check if PhiNode::Ideal's "Split phis through memory merges"
4311     // transform should be attempted. Look for this->phi->this cycle.
4312     uint merge_width = req();
4313     if (merge_width > Compile::AliasIdxRaw) {
4314       PhiNode* phi = base_memory()->as_Phi();
4315       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4316         if (phi->in(i) == this) {
4317           phase->is_IterGVN()->_worklist.push(phi);
4318           break;
4319         }
4320       }
4321     }
4322   }
4323 
4324   assert(progress || verify_sparse(), "please, no dups of base");
4325   return progress;
4326 }
4327 
4328 //-------------------------set_base_memory-------------------------------------
4329 void MergeMemNode::set_base_memory(Node *new_base) {
4330   Node* empty_mem = empty_memory();
4331   set_req(Compile::AliasIdxBot, new_base);
4332   assert(memory_at(req()) == new_base, "must set default memory");
4333   // Clear out other occurrences of new_base:
4334   if (new_base != empty_mem) {
4335     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4336       if (in(i) == new_base)  set_req(i, empty_mem);
4337     }
4338   }
4339 }
4340 
4341 //------------------------------out_RegMask------------------------------------
4342 const RegMask &MergeMemNode::out_RegMask() const {
4343   return RegMask::Empty;
4344 }
4345 
4346 //------------------------------dump_spec--------------------------------------
4347 #ifndef PRODUCT
4348 void MergeMemNode::dump_spec(outputStream *st) const {
4349   st->print(" {");
4350   Node* base_mem = base_memory();
4351   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4352     Node* mem = memory_at(i);
4353     if (mem == base_mem) { st->print(" -"); continue; }
4354     st->print( " N%d:", mem->_idx );
4355     Compile::current()->get_adr_type(i)->dump_on(st);
4356   }
4357   st->print(" }");
4358 }
4359 #endif // !PRODUCT
4360 
4361 
4362 #ifdef ASSERT
4363 static bool might_be_same(Node* a, Node* b) {
4364   if (a == b)  return true;
4365   if (!(a->is_Phi() || b->is_Phi()))  return false;
4366   // phis shift around during optimization
4367   return true;  // pretty stupid...
4368 }
4369 
4370 // verify a narrow slice (either incoming or outgoing)
4371 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4372   if (!VerifyAliases)       return;  // don't bother to verify unless requested
4373   if (is_error_reported())  return;  // muzzle asserts when debugging an error
4374   if (Node::in_dump())      return;  // muzzle asserts when printing
4375   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4376   assert(n != NULL, "");
4377   // Elide intervening MergeMem's
4378   while (n->is_MergeMem()) {
4379     n = n->as_MergeMem()->memory_at(alias_idx);
4380   }
4381   Compile* C = Compile::current();
4382   const TypePtr* n_adr_type = n->adr_type();
4383   if (n == m->empty_memory()) {
4384     // Implicit copy of base_memory()
4385   } else if (n_adr_type != TypePtr::BOTTOM) {
4386     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4387     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4388   } else {
4389     // A few places like make_runtime_call "know" that VM calls are narrow,
4390     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4391     bool expected_wide_mem = false;
4392     if (n == m->base_memory()) {
4393       expected_wide_mem = true;
4394     } else if (alias_idx == Compile::AliasIdxRaw ||
4395                n == m->memory_at(Compile::AliasIdxRaw)) {
4396       expected_wide_mem = true;
4397     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4398       // memory can "leak through" calls on channels that
4399       // are write-once.  Allow this also.
4400       expected_wide_mem = true;
4401     }
4402     assert(expected_wide_mem, "expected narrow slice replacement");
4403   }
4404 }
4405 #else // !ASSERT
4406 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4407 #endif
4408 
4409 
4410 //-----------------------------memory_at---------------------------------------
4411 Node* MergeMemNode::memory_at(uint alias_idx) const {
4412   assert(alias_idx >= Compile::AliasIdxRaw ||
4413          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4414          "must avoid base_memory and AliasIdxTop");
4415 
4416   // Otherwise, it is a narrow slice.
4417   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4418   Compile *C = Compile::current();
4419   if (is_empty_memory(n)) {
4420     // the array is sparse; empty slots are the "top" node
4421     n = base_memory();
4422     assert(Node::in_dump()
4423            || n == NULL || n->bottom_type() == Type::TOP
4424            || n->adr_type() == NULL // address is TOP
4425            || n->adr_type() == TypePtr::BOTTOM
4426            || n->adr_type() == TypeRawPtr::BOTTOM
4427            || Compile::current()->AliasLevel() == 0,
4428            "must be a wide memory");
4429     // AliasLevel == 0 if we are organizing the memory states manually.
4430     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4431   } else {
4432     // make sure the stored slice is sane
4433     #ifdef ASSERT
4434     if (is_error_reported() || Node::in_dump()) {
4435     } else if (might_be_same(n, base_memory())) {
4436       // Give it a pass:  It is a mostly harmless repetition of the base.
4437       // This can arise normally from node subsumption during optimization.
4438     } else {
4439       verify_memory_slice(this, alias_idx, n);
4440     }
4441     #endif
4442   }
4443   return n;
4444 }
4445 
4446 //---------------------------set_memory_at-------------------------------------
4447 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4448   verify_memory_slice(this, alias_idx, n);
4449   Node* empty_mem = empty_memory();
4450   if (n == base_memory())  n = empty_mem;  // collapse default
4451   uint need_req = alias_idx+1;
4452   if (req() < need_req) {
4453     if (n == empty_mem)  return;  // already the default, so do not grow me
4454     // grow the sparse array
4455     do {
4456       add_req(empty_mem);
4457     } while (req() < need_req);
4458   }
4459   set_req( alias_idx, n );
4460 }
4461 
4462 
4463 
4464 //--------------------------iteration_setup------------------------------------
4465 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4466   if (other != NULL) {
4467     grow_to_match(other);
4468     // invariant:  the finite support of mm2 is within mm->req()
4469     #ifdef ASSERT
4470     for (uint i = req(); i < other->req(); i++) {
4471       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4472     }
4473     #endif
4474   }
4475   // Replace spurious copies of base_memory by top.
4476   Node* base_mem = base_memory();
4477   if (base_mem != NULL && !base_mem->is_top()) {
4478     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4479       if (in(i) == base_mem)
4480         set_req(i, empty_memory());
4481     }
4482   }
4483 }
4484 
4485 //---------------------------grow_to_match-------------------------------------
4486 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4487   Node* empty_mem = empty_memory();
4488   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4489   // look for the finite support of the other memory
4490   for (uint i = other->req(); --i >= req(); ) {
4491     if (other->in(i) != empty_mem) {
4492       uint new_len = i+1;
4493       while (req() < new_len)  add_req(empty_mem);
4494       break;
4495     }
4496   }
4497 }
4498 
4499 //---------------------------verify_sparse-------------------------------------
4500 #ifndef PRODUCT
4501 bool MergeMemNode::verify_sparse() const {
4502   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4503   Node* base_mem = base_memory();
4504   // The following can happen in degenerate cases, since empty==top.
4505   if (is_empty_memory(base_mem))  return true;
4506   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4507     assert(in(i) != NULL, "sane slice");
4508     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4509   }
4510   return true;
4511 }
4512 
4513 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4514   Node* n;
4515   n = mm->in(idx);
4516   if (mem == n)  return true;  // might be empty_memory()
4517   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4518   if (mem == n)  return true;
4519   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4520     if (mem == n)  return true;
4521     if (n == NULL)  break;
4522   }
4523   return false;
4524 }
4525 #endif // !PRODUCT
--- EOF ---