1 /*
   2  * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "memory/allocation.inline.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "oops/objArrayKlass.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/arraycopynode.hpp"
  35 #include "opto/cfgnode.hpp"
  36 #include "opto/compile.hpp"
  37 #include "opto/connode.hpp"
  38 #include "opto/convertnode.hpp"
  39 #include "opto/loopnode.hpp"
  40 #include "opto/machnode.hpp"
  41 #include "opto/matcher.hpp"
  42 #include "opto/memnode.hpp"
  43 #include "opto/mulnode.hpp"
  44 #include "opto/narrowptrnode.hpp"
  45 #include "opto/phaseX.hpp"
  46 #include "opto/regmask.hpp"
  47 #include "opto/rootnode.hpp"
  48 #include "utilities/align.hpp"
  49 #include "utilities/copy.hpp"
  50 #include "utilities/macros.hpp"
  51 #include "utilities/vmError.hpp"
  52 
  53 // Portions of code courtesy of Clifford Click
  54 
  55 // Optimization - Graph Style
  56 
  57 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  58 
  59 //=============================================================================
  60 uint MemNode::size_of() const { return sizeof(*this); }
  61 
  62 const TypePtr *MemNode::adr_type() const {
  63   Node* adr = in(Address);
  64   if (adr == NULL)  return NULL; // node is dead
  65   const TypePtr* cross_check = NULL;
  66   DEBUG_ONLY(cross_check = _adr_type);
  67   return calculate_adr_type(adr->bottom_type(), cross_check);
  68 }
  69 
  70 bool MemNode::check_if_adr_maybe_raw(Node* adr) {
  71   if (adr != NULL) {
  72     if (adr->bottom_type()->base() == Type::RawPtr || adr->bottom_type()->base() == Type::AnyPtr) {
  73       return true;
  74     }
  75   }
  76   return false;
  77 }
  78 
  79 #ifndef PRODUCT
  80 void MemNode::dump_spec(outputStream *st) const {
  81   if (in(Address) == NULL)  return; // node is dead
  82 #ifndef ASSERT
  83   // fake the missing field
  84   const TypePtr* _adr_type = NULL;
  85   if (in(Address) != NULL)
  86     _adr_type = in(Address)->bottom_type()->isa_ptr();
  87 #endif
  88   dump_adr_type(this, _adr_type, st);
  89 
  90   Compile* C = Compile::current();
  91   if (C->alias_type(_adr_type)->is_volatile()) {
  92     st->print(" Volatile!");
  93   }
  94   if (_unaligned_access) {
  95     st->print(" unaligned");
  96   }
  97   if (_mismatched_access) {
  98     st->print(" mismatched");
  99   }
 100   if (_unsafe_access) {
 101     st->print(" unsafe");
 102   }
 103 }
 104 
 105 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
 106   st->print(" @");
 107   if (adr_type == NULL) {
 108     st->print("NULL");
 109   } else {
 110     adr_type->dump_on(st);
 111     Compile* C = Compile::current();
 112     Compile::AliasType* atp = NULL;
 113     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
 114     if (atp == NULL)
 115       st->print(", idx=?\?;");
 116     else if (atp->index() == Compile::AliasIdxBot)
 117       st->print(", idx=Bot;");
 118     else if (atp->index() == Compile::AliasIdxTop)
 119       st->print(", idx=Top;");
 120     else if (atp->index() == Compile::AliasIdxRaw)
 121       st->print(", idx=Raw;");
 122     else {
 123       ciField* field = atp->field();
 124       if (field) {
 125         st->print(", name=");
 126         field->print_name_on(st);
 127       }
 128       st->print(", idx=%d;", atp->index());
 129     }
 130   }
 131 }
 132 
 133 extern void print_alias_types();
 134 
 135 #endif
 136 
 137 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 138   assert((t_oop != NULL), "sanity");
 139   bool is_instance = t_oop->is_known_instance_field();
 140   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 141                              (load != NULL) && load->is_Load() &&
 142                              (phase->is_IterGVN() != NULL);
 143   if (!(is_instance || is_boxed_value_load))
 144     return mchain;  // don't try to optimize non-instance types
 145   uint instance_id = t_oop->instance_id();
 146   Node *start_mem = phase->C->start()->proj_out_or_null(TypeFunc::Memory);
 147   Node *prev = NULL;
 148   Node *result = mchain;
 149   while (prev != result) {
 150     prev = result;
 151     if (result == start_mem)
 152       break;  // hit one of our sentinels
 153     // skip over a call which does not affect this memory slice
 154     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 155       Node *proj_in = result->in(0);
 156       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 157         break;  // hit one of our sentinels
 158       } else if (proj_in->is_Call()) {
 159         // ArrayCopyNodes processed here as well
 160         CallNode *call = proj_in->as_Call();
 161         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 162           result = call->in(TypeFunc::Memory);
 163         }
 164       } else if (proj_in->is_Initialize()) {
 165         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 166         // Stop if this is the initialization for the object instance which
 167         // contains this memory slice, otherwise skip over it.
 168         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 169           break;
 170         }
 171         if (is_instance) {
 172           result = proj_in->in(TypeFunc::Memory);
 173         } else if (is_boxed_value_load) {
 174           Node* klass = alloc->in(AllocateNode::KlassNode);
 175           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 176           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 177             result = proj_in->in(TypeFunc::Memory); // not related allocation
 178           }
 179         }
 180       } else if (proj_in->is_MemBar()) {
 181         ArrayCopyNode* ac = NULL;
 182         if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase, ac)) {
 183           break;
 184         }
 185         result = proj_in->in(TypeFunc::Memory);
 186       } else {
 187         assert(false, "unexpected projection");
 188       }
 189     } else if (result->is_ClearArray()) {
 190       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 191         // Can not bypass initialization of the instance
 192         // we are looking for.
 193         break;
 194       }
 195       // Otherwise skip it (the call updated 'result' value).
 196     } else if (result->is_MergeMem()) {
 197       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 198     }
 199   }
 200   return result;
 201 }
 202 
 203 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 204   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 205   if (t_oop == NULL)
 206     return mchain;  // don't try to optimize non-oop types
 207   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 208   bool is_instance = t_oop->is_known_instance_field();
 209   PhaseIterGVN *igvn = phase->is_IterGVN();
 210   if (is_instance && igvn != NULL  && result->is_Phi()) {
 211     PhiNode *mphi = result->as_Phi();
 212     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 213     const TypePtr *t = mphi->adr_type();
 214     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 215         (t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 216          t->is_oopptr()->cast_to_exactness(true)
 217            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 218             ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop)) {
 219       // clone the Phi with our address type
 220       result = mphi->split_out_instance(t_adr, igvn);
 221     } else {
 222       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 223     }
 224   }
 225   return result;
 226 }
 227 
 228 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 229   uint alias_idx = phase->C->get_alias_index(tp);
 230   Node *mem = mmem;
 231 #ifdef ASSERT
 232   {
 233     // Check that current type is consistent with the alias index used during graph construction
 234     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 235     bool consistent =  adr_check == NULL || adr_check->empty() ||
 236                        phase->C->must_alias(adr_check, alias_idx );
 237     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 238     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 239                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 240         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 241         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 242           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 243           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 244       // don't assert if it is dead code.
 245       consistent = true;
 246     }
 247     if( !consistent ) {
 248       st->print("alias_idx==%d, adr_check==", alias_idx);
 249       if( adr_check == NULL ) {
 250         st->print("NULL");
 251       } else {
 252         adr_check->dump();
 253       }
 254       st->cr();
 255       print_alias_types();
 256       assert(consistent, "adr_check must match alias idx");
 257     }
 258   }
 259 #endif
 260   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 261   // means an array I have not precisely typed yet.  Do not do any
 262   // alias stuff with it any time soon.
 263   const TypeOopPtr *toop = tp->isa_oopptr();
 264   if( tp->base() != Type::AnyPtr &&
 265       !(toop &&
 266         toop->klass() != NULL &&
 267         toop->klass()->is_java_lang_Object() &&
 268         toop->offset() == Type::OffsetBot) ) {
 269     // compress paths and change unreachable cycles to TOP
 270     // If not, we can update the input infinitely along a MergeMem cycle
 271     // Equivalent code in PhiNode::Ideal
 272     Node* m  = phase->transform(mmem);
 273     // If transformed to a MergeMem, get the desired slice
 274     // Otherwise the returned node represents memory for every slice
 275     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 276     // Update input if it is progress over what we have now
 277   }
 278   return mem;
 279 }
 280 
 281 //--------------------------Ideal_common---------------------------------------
 282 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 283 // Unhook non-raw memories from complete (macro-expanded) initializations.
 284 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 285   // If our control input is a dead region, kill all below the region
 286   Node *ctl = in(MemNode::Control);
 287   if (ctl && remove_dead_region(phase, can_reshape))
 288     return this;
 289   ctl = in(MemNode::Control);
 290   // Don't bother trying to transform a dead node
 291   if (ctl && ctl->is_top())  return NodeSentinel;
 292 
 293   PhaseIterGVN *igvn = phase->is_IterGVN();
 294   // Wait if control on the worklist.
 295   if (ctl && can_reshape && igvn != NULL) {
 296     Node* bol = NULL;
 297     Node* cmp = NULL;
 298     if (ctl->in(0)->is_If()) {
 299       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 300       bol = ctl->in(0)->in(1);
 301       if (bol->is_Bool())
 302         cmp = ctl->in(0)->in(1)->in(1);
 303     }
 304     if (igvn->_worklist.member(ctl) ||
 305         (bol != NULL && igvn->_worklist.member(bol)) ||
 306         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 307       // This control path may be dead.
 308       // Delay this memory node transformation until the control is processed.
 309       phase->is_IterGVN()->_worklist.push(this);
 310       return NodeSentinel; // caller will return NULL
 311     }
 312   }
 313   // Ignore if memory is dead, or self-loop
 314   Node *mem = in(MemNode::Memory);
 315   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 316   assert(mem != this, "dead loop in MemNode::Ideal");
 317 
 318   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 319     // This memory slice may be dead.
 320     // Delay this mem node transformation until the memory is processed.
 321     phase->is_IterGVN()->_worklist.push(this);
 322     return NodeSentinel; // caller will return NULL
 323   }
 324 
 325   Node *address = in(MemNode::Address);
 326   const Type *t_adr = phase->type(address);
 327   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 328 
 329   if (can_reshape && is_unsafe_access() && (t_adr == TypePtr::NULL_PTR)) {
 330     // Unsafe off-heap access with zero address. Remove access and other control users
 331     // to not confuse optimizations and add a HaltNode to fail if this is ever executed.
 332     assert(ctl != NULL, "unsafe accesses should be control dependent");
 333     for (DUIterator_Fast imax, i = ctl->fast_outs(imax); i < imax; i++) {
 334       Node* u = ctl->fast_out(i);
 335       if (u != ctl) {
 336         igvn->rehash_node_delayed(u);
 337         int nb = u->replace_edge(ctl, phase->C->top());
 338         --i, imax -= nb;
 339       }
 340     }
 341     Node* frame = igvn->transform(new ParmNode(phase->C->start(), TypeFunc::FramePtr));
 342     Node* halt = igvn->transform(new HaltNode(ctl, frame, "unsafe off-heap access with zero address"));
 343     phase->C->root()->add_req(halt);
 344     return this;
 345   }
 346 
 347   if (can_reshape && igvn != NULL &&
 348       (igvn->_worklist.member(address) ||
 349        (igvn->_worklist.size() > 0 && t_adr != adr_type())) ) {
 350     // The address's base and type may change when the address is processed.
 351     // Delay this mem node transformation until the address is processed.
 352     phase->is_IterGVN()->_worklist.push(this);
 353     return NodeSentinel; // caller will return NULL
 354   }
 355 
 356   // Do NOT remove or optimize the next lines: ensure a new alias index
 357   // is allocated for an oop pointer type before Escape Analysis.
 358   // Note: C++ will not remove it since the call has side effect.
 359   if (t_adr->isa_oopptr()) {
 360     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 361   }
 362 
 363   Node* base = NULL;
 364   if (address->is_AddP()) {
 365     base = address->in(AddPNode::Base);
 366   }
 367   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 368       !t_adr->isa_rawptr()) {
 369     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 370     // Skip this node optimization if its address has TOP base.
 371     return NodeSentinel; // caller will return NULL
 372   }
 373 
 374   // Avoid independent memory operations
 375   Node* old_mem = mem;
 376 
 377   // The code which unhooks non-raw memories from complete (macro-expanded)
 378   // initializations was removed. After macro-expansion all stores catched
 379   // by Initialize node became raw stores and there is no information
 380   // which memory slices they modify. So it is unsafe to move any memory
 381   // operation above these stores. Also in most cases hooked non-raw memories
 382   // were already unhooked by using information from detect_ptr_independence()
 383   // and find_previous_store().
 384 
 385   if (mem->is_MergeMem()) {
 386     MergeMemNode* mmem = mem->as_MergeMem();
 387     const TypePtr *tp = t_adr->is_ptr();
 388 
 389     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 390   }
 391 
 392   if (mem != old_mem) {
 393     set_req(MemNode::Memory, mem);
 394     if (can_reshape && old_mem->outcnt() == 0 && igvn != NULL) {
 395       igvn->_worklist.push(old_mem);
 396     }
 397     if (phase->type(mem) == Type::TOP) return NodeSentinel;
 398     return this;
 399   }
 400 
 401   // let the subclass continue analyzing...
 402   return NULL;
 403 }
 404 
 405 // Helper function for proving some simple control dominations.
 406 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 407 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 408 // is not a constant (dominated by the method's StartNode).
 409 // Used by MemNode::find_previous_store to prove that the
 410 // control input of a memory operation predates (dominates)
 411 // an allocation it wants to look past.
 412 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 413   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 414     return false; // Conservative answer for dead code
 415 
 416   // Check 'dom'. Skip Proj and CatchProj nodes.
 417   dom = dom->find_exact_control(dom);
 418   if (dom == NULL || dom->is_top())
 419     return false; // Conservative answer for dead code
 420 
 421   if (dom == sub) {
 422     // For the case when, for example, 'sub' is Initialize and the original
 423     // 'dom' is Proj node of the 'sub'.
 424     return false;
 425   }
 426 
 427   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 428     return true;
 429 
 430   // 'dom' dominates 'sub' if its control edge and control edges
 431   // of all its inputs dominate or equal to sub's control edge.
 432 
 433   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 434   // Or Region for the check in LoadNode::Ideal();
 435   // 'sub' should have sub->in(0) != NULL.
 436   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 437          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 438 
 439   // Get control edge of 'sub'.
 440   Node* orig_sub = sub;
 441   sub = sub->find_exact_control(sub->in(0));
 442   if (sub == NULL || sub->is_top())
 443     return false; // Conservative answer for dead code
 444 
 445   assert(sub->is_CFG(), "expecting control");
 446 
 447   if (sub == dom)
 448     return true;
 449 
 450   if (sub->is_Start() || sub->is_Root())
 451     return false;
 452 
 453   {
 454     // Check all control edges of 'dom'.
 455 
 456     ResourceMark rm;
 457     Arena* arena = Thread::current()->resource_area();
 458     Node_List nlist(arena);
 459     Unique_Node_List dom_list(arena);
 460 
 461     dom_list.push(dom);
 462     bool only_dominating_controls = false;
 463 
 464     for (uint next = 0; next < dom_list.size(); next++) {
 465       Node* n = dom_list.at(next);
 466       if (n == orig_sub)
 467         return false; // One of dom's inputs dominated by sub.
 468       if (!n->is_CFG() && n->pinned()) {
 469         // Check only own control edge for pinned non-control nodes.
 470         n = n->find_exact_control(n->in(0));
 471         if (n == NULL || n->is_top())
 472           return false; // Conservative answer for dead code
 473         assert(n->is_CFG(), "expecting control");
 474         dom_list.push(n);
 475       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 476         only_dominating_controls = true;
 477       } else if (n->is_CFG()) {
 478         if (n->dominates(sub, nlist))
 479           only_dominating_controls = true;
 480         else
 481           return false;
 482       } else {
 483         // First, own control edge.
 484         Node* m = n->find_exact_control(n->in(0));
 485         if (m != NULL) {
 486           if (m->is_top())
 487             return false; // Conservative answer for dead code
 488           dom_list.push(m);
 489         }
 490         // Now, the rest of edges.
 491         uint cnt = n->req();
 492         for (uint i = 1; i < cnt; i++) {
 493           m = n->find_exact_control(n->in(i));
 494           if (m == NULL || m->is_top())
 495             continue;
 496           dom_list.push(m);
 497         }
 498       }
 499     }
 500     return only_dominating_controls;
 501   }
 502 }
 503 
 504 //---------------------detect_ptr_independence---------------------------------
 505 // Used by MemNode::find_previous_store to prove that two base
 506 // pointers are never equal.
 507 // The pointers are accompanied by their associated allocations,
 508 // if any, which have been previously discovered by the caller.
 509 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 510                                       Node* p2, AllocateNode* a2,
 511                                       PhaseTransform* phase) {
 512   // Attempt to prove that these two pointers cannot be aliased.
 513   // They may both manifestly be allocations, and they should differ.
 514   // Or, if they are not both allocations, they can be distinct constants.
 515   // Otherwise, one is an allocation and the other a pre-existing value.
 516   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 517     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 518   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 519     return (a1 != a2);
 520   } else if (a1 != NULL) {                  // one allocation a1
 521     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 522     return all_controls_dominate(p2, a1);
 523   } else { //(a2 != NULL)                   // one allocation a2
 524     return all_controls_dominate(p1, a2);
 525   }
 526   return false;
 527 }
 528 
 529 
 530 // Find an arraycopy that must have set (can_see_stored_value=true) or
 531 // could have set (can_see_stored_value=false) the value for this load
 532 Node* LoadNode::find_previous_arraycopy(PhaseTransform* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
 533   if (mem->is_Proj() && mem->in(0) != NULL && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
 534                                                mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
 535     Node* mb = mem->in(0);
 536     if (mb->in(0) != NULL && mb->in(0)->is_Proj() &&
 537         mb->in(0)->in(0) != NULL && mb->in(0)->in(0)->is_ArrayCopy()) {
 538       ArrayCopyNode* ac = mb->in(0)->in(0)->as_ArrayCopy();
 539       if (ac->is_clonebasic()) {
 540         intptr_t offset;
 541         AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase, offset);
 542         if (alloc != NULL && alloc == ld_alloc) {
 543           return ac;
 544         }
 545       }
 546     }
 547   } else if (mem->is_Proj() && mem->in(0) != NULL && mem->in(0)->is_ArrayCopy()) {
 548     ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
 549 
 550     if (ac->is_arraycopy_validated() ||
 551         ac->is_copyof_validated() ||
 552         ac->is_copyofrange_validated()) {
 553       Node* ld_addp = in(MemNode::Address);
 554       if (ld_addp->is_AddP()) {
 555         Node* ld_base = ld_addp->in(AddPNode::Address);
 556         Node* ld_offs = ld_addp->in(AddPNode::Offset);
 557 
 558         Node* dest = ac->in(ArrayCopyNode::Dest);
 559 
 560         if (dest == ld_base) {
 561           const TypeX *ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 562           if (ac->modifies(ld_offs_t->_lo, ld_offs_t->_hi, phase, can_see_stored_value)) {
 563             return ac;
 564           }
 565           if (!can_see_stored_value) {
 566             mem = ac->in(TypeFunc::Memory);
 567           }
 568         }
 569       }
 570     }
 571   }
 572   return NULL;
 573 }
 574 
 575 // The logic for reordering loads and stores uses four steps:
 576 // (a) Walk carefully past stores and initializations which we
 577 //     can prove are independent of this load.
 578 // (b) Observe that the next memory state makes an exact match
 579 //     with self (load or store), and locate the relevant store.
 580 // (c) Ensure that, if we were to wire self directly to the store,
 581 //     the optimizer would fold it up somehow.
 582 // (d) Do the rewiring, and return, depending on some other part of
 583 //     the optimizer to fold up the load.
 584 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 585 // specific to loads and stores, so they are handled by the callers.
 586 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 587 //
 588 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 589   Node*         ctrl   = in(MemNode::Control);
 590   Node*         adr    = in(MemNode::Address);
 591   intptr_t      offset = 0;
 592   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 593   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 594 
 595   if (offset == Type::OffsetBot)
 596     return NULL;            // cannot unalias unless there are precise offsets
 597 
 598   const bool adr_maybe_raw = check_if_adr_maybe_raw(adr);
 599   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 600 
 601   intptr_t size_in_bytes = memory_size();
 602 
 603   Node* mem = in(MemNode::Memory);   // start searching here...
 604 
 605   int cnt = 50;             // Cycle limiter
 606   for (;;) {                // While we can dance past unrelated stores...
 607     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 608 
 609     Node* prev = mem;
 610     if (mem->is_Store()) {
 611       Node* st_adr = mem->in(MemNode::Address);
 612       intptr_t st_offset = 0;
 613       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 614       if (st_base == NULL)
 615         break;              // inscrutable pointer
 616 
 617       // For raw accesses it's not enough to prove that constant offsets don't intersect.
 618       // We need the bases to be the equal in order for the offset check to make sense.
 619       if ((adr_maybe_raw || check_if_adr_maybe_raw(st_adr)) && st_base != base) {
 620         break;
 621       }
 622 
 623       if (st_offset != offset && st_offset != Type::OffsetBot) {
 624         const int MAX_STORE = BytesPerLong;
 625         if (st_offset >= offset + size_in_bytes ||
 626             st_offset <= offset - MAX_STORE ||
 627             st_offset <= offset - mem->as_Store()->memory_size()) {
 628           // Success:  The offsets are provably independent.
 629           // (You may ask, why not just test st_offset != offset and be done?
 630           // The answer is that stores of different sizes can co-exist
 631           // in the same sequence of RawMem effects.  We sometimes initialize
 632           // a whole 'tile' of array elements with a single jint or jlong.)
 633           mem = mem->in(MemNode::Memory);
 634           continue;           // (a) advance through independent store memory
 635         }
 636       }
 637       if (st_base != base &&
 638           detect_ptr_independence(base, alloc,
 639                                   st_base,
 640                                   AllocateNode::Ideal_allocation(st_base, phase),
 641                                   phase)) {
 642         // Success:  The bases are provably independent.
 643         mem = mem->in(MemNode::Memory);
 644         continue;           // (a) advance through independent store memory
 645       }
 646 
 647       // (b) At this point, if the bases or offsets do not agree, we lose,
 648       // since we have not managed to prove 'this' and 'mem' independent.
 649       if (st_base == base && st_offset == offset) {
 650         return mem;         // let caller handle steps (c), (d)
 651       }
 652 
 653     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 654       InitializeNode* st_init = mem->in(0)->as_Initialize();
 655       AllocateNode*  st_alloc = st_init->allocation();
 656       if (st_alloc == NULL)
 657         break;              // something degenerated
 658       bool known_identical = false;
 659       bool known_independent = false;
 660       if (alloc == st_alloc)
 661         known_identical = true;
 662       else if (alloc != NULL)
 663         known_independent = true;
 664       else if (all_controls_dominate(this, st_alloc))
 665         known_independent = true;
 666 
 667       if (known_independent) {
 668         // The bases are provably independent: Either they are
 669         // manifestly distinct allocations, or else the control
 670         // of this load dominates the store's allocation.
 671         int alias_idx = phase->C->get_alias_index(adr_type());
 672         if (alias_idx == Compile::AliasIdxRaw) {
 673           mem = st_alloc->in(TypeFunc::Memory);
 674         } else {
 675           mem = st_init->memory(alias_idx);
 676         }
 677         continue;           // (a) advance through independent store memory
 678       }
 679 
 680       // (b) at this point, if we are not looking at a store initializing
 681       // the same allocation we are loading from, we lose.
 682       if (known_identical) {
 683         // From caller, can_see_stored_value will consult find_captured_store.
 684         return mem;         // let caller handle steps (c), (d)
 685       }
 686 
 687     } else if (find_previous_arraycopy(phase, alloc, mem, false) != NULL) {
 688       if (prev != mem) {
 689         // Found an arraycopy but it doesn't affect that load
 690         continue;
 691       }
 692       // Found an arraycopy that may affect that load
 693       return mem;
 694     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 695       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 696       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 697         // ArrayCopyNodes processed here as well.
 698         CallNode *call = mem->in(0)->as_Call();
 699         if (!call->may_modify(addr_t, phase)) {
 700           mem = call->in(TypeFunc::Memory);
 701           continue;         // (a) advance through independent call memory
 702         }
 703       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 704         ArrayCopyNode* ac = NULL;
 705         if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase, ac)) {
 706           break;
 707         }
 708         mem = mem->in(0)->in(TypeFunc::Memory);
 709         continue;           // (a) advance through independent MemBar memory
 710       } else if (mem->is_ClearArray()) {
 711         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 712           // (the call updated 'mem' value)
 713           continue;         // (a) advance through independent allocation memory
 714         } else {
 715           // Can not bypass initialization of the instance
 716           // we are looking for.
 717           return mem;
 718         }
 719       } else if (mem->is_MergeMem()) {
 720         int alias_idx = phase->C->get_alias_index(adr_type());
 721         mem = mem->as_MergeMem()->memory_at(alias_idx);
 722         continue;           // (a) advance through independent MergeMem memory
 723       }
 724     }
 725 
 726     // Unless there is an explicit 'continue', we must bail out here,
 727     // because 'mem' is an inscrutable memory state (e.g., a call).
 728     break;
 729   }
 730 
 731   return NULL;              // bail out
 732 }
 733 
 734 //----------------------calculate_adr_type-------------------------------------
 735 // Helper function.  Notices when the given type of address hits top or bottom.
 736 // Also, asserts a cross-check of the type against the expected address type.
 737 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 738   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 739   #ifdef PRODUCT
 740   cross_check = NULL;
 741   #else
 742   if (!VerifyAliases || VMError::is_error_reported() || Node::in_dump())  cross_check = NULL;
 743   #endif
 744   const TypePtr* tp = t->isa_ptr();
 745   if (tp == NULL) {
 746     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 747     return TypePtr::BOTTOM;           // touches lots of memory
 748   } else {
 749     #ifdef ASSERT
 750     // %%%% [phh] We don't check the alias index if cross_check is
 751     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 752     if (cross_check != NULL &&
 753         cross_check != TypePtr::BOTTOM &&
 754         cross_check != TypeRawPtr::BOTTOM) {
 755       // Recheck the alias index, to see if it has changed (due to a bug).
 756       Compile* C = Compile::current();
 757       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 758              "must stay in the original alias category");
 759       // The type of the address must be contained in the adr_type,
 760       // disregarding "null"-ness.
 761       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 762       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 763       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 764              "real address must not escape from expected memory type");
 765     }
 766     #endif
 767     return tp;
 768   }
 769 }
 770 
 771 //=============================================================================
 772 // Should LoadNode::Ideal() attempt to remove control edges?
 773 bool LoadNode::can_remove_control() const {
 774   return true;
 775 }
 776 uint LoadNode::size_of() const { return sizeof(*this); }
 777 bool LoadNode::cmp( const Node &n ) const
 778 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 779 const Type *LoadNode::bottom_type() const { return _type; }
 780 uint LoadNode::ideal_reg() const {
 781   return _type->ideal_reg();
 782 }
 783 
 784 #ifndef PRODUCT
 785 void LoadNode::dump_spec(outputStream *st) const {
 786   MemNode::dump_spec(st);
 787   if( !Verbose && !WizardMode ) {
 788     // standard dump does this in Verbose and WizardMode
 789     st->print(" #"); _type->dump_on(st);
 790   }
 791   if (!depends_only_on_test()) {
 792     st->print(" (does not depend only on test)");
 793   }
 794 }
 795 #endif
 796 
 797 #ifdef ASSERT
 798 //----------------------------is_immutable_value-------------------------------
 799 // Helper function to allow a raw load without control edge for some cases
 800 bool LoadNode::is_immutable_value(Node* adr) {
 801   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 802           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 803           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 804            in_bytes(JavaThread::osthread_offset())));
 805 }
 806 #endif
 807 
 808 //----------------------------LoadNode::make-----------------------------------
 809 // Polymorphic factory method:
 810 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo,
 811                      ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 812   Compile* C = gvn.C;
 813 
 814   // sanity check the alias category against the created node type
 815   assert(!(adr_type->isa_oopptr() &&
 816            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 817          "use LoadKlassNode instead");
 818   assert(!(adr_type->isa_aryptr() &&
 819            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 820          "use LoadRangeNode instead");
 821   // Check control edge of raw loads
 822   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 823           // oop will be recorded in oop map if load crosses safepoint
 824           rt->isa_oopptr() || is_immutable_value(adr),
 825           "raw memory operations should have control edge");
 826   LoadNode* load = NULL;
 827   switch (bt) {
 828   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 829   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 830   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 831   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 832   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 833   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency); break;
 834   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 835   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 836   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 837   case T_OBJECT:
 838 #ifdef _LP64
 839     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 840       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 841     } else
 842 #endif
 843     {
 844       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 845       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
 846     }
 847     break;
 848   default:
 849     ShouldNotReachHere();
 850     break;
 851   }
 852   assert(load != NULL, "LoadNode should have been created");
 853   if (unaligned) {
 854     load->set_unaligned_access();
 855   }
 856   if (mismatched) {
 857     load->set_mismatched_access();
 858   }
 859   if (unsafe) {
 860     load->set_unsafe_access();
 861   }
 862   if (load->Opcode() == Op_LoadN) {
 863     Node* ld = gvn.transform(load);
 864     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 865   }
 866 
 867   return load;
 868 }
 869 
 870 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 871                                   ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 872   bool require_atomic = true;
 873   LoadLNode* load = new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic);
 874   if (unaligned) {
 875     load->set_unaligned_access();
 876   }
 877   if (mismatched) {
 878     load->set_mismatched_access();
 879   }
 880   if (unsafe) {
 881     load->set_unsafe_access();
 882   }
 883   return load;
 884 }
 885 
 886 LoadDNode* LoadDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 887                                   ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 888   bool require_atomic = true;
 889   LoadDNode* load = new LoadDNode(ctl, mem, adr, adr_type, rt, mo, control_dependency, require_atomic);
 890   if (unaligned) {
 891     load->set_unaligned_access();
 892   }
 893   if (mismatched) {
 894     load->set_mismatched_access();
 895   }
 896   if (unsafe) {
 897     load->set_unsafe_access();
 898   }
 899   return load;
 900 }
 901 
 902 
 903 
 904 //------------------------------hash-------------------------------------------
 905 uint LoadNode::hash() const {
 906   // unroll addition of interesting fields
 907   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 908 }
 909 
 910 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 911   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 912     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 913     bool is_stable_ary = FoldStableValues &&
 914                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 915                          tp->isa_aryptr()->is_stable();
 916 
 917     return (eliminate_boxing && non_volatile) || is_stable_ary;
 918   }
 919 
 920   return false;
 921 }
 922 
 923 // Is the value loaded previously stored by an arraycopy? If so return
 924 // a load node that reads from the source array so we may be able to
 925 // optimize out the ArrayCopy node later.
 926 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
 927   Node* ld_adr = in(MemNode::Address);
 928   intptr_t ld_off = 0;
 929   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 930   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
 931   if (ac != NULL) {
 932     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
 933 
 934     Node* mem = ac->in(TypeFunc::Memory);
 935     Node* ctl = ac->in(0);
 936     Node* src = ac->in(ArrayCopyNode::Src);
 937 
 938     if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
 939       return NULL;
 940     }
 941 
 942     LoadNode* ld = clone()->as_Load();
 943     Node* addp = in(MemNode::Address)->clone();
 944     if (ac->as_ArrayCopy()->is_clonebasic()) {
 945       assert(ld_alloc != NULL, "need an alloc");
 946       assert(addp->is_AddP(), "address must be addp");
 947       assert(ac->in(ArrayCopyNode::Dest)->is_AddP(), "dest must be an address");
 948       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
 949       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Base)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base)), "strange pattern");
 950       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Address)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address)), "strange pattern");
 951       addp->set_req(AddPNode::Base, src->in(AddPNode::Base));
 952       addp->set_req(AddPNode::Address, src->in(AddPNode::Address));
 953     } else {
 954       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
 955              ac->as_ArrayCopy()->is_copyof_validated() ||
 956              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
 957       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
 958       addp->set_req(AddPNode::Base, src);
 959       addp->set_req(AddPNode::Address, src);
 960 
 961       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
 962       BasicType ary_elem  = ary_t->klass()->as_array_klass()->element_type()->basic_type();
 963       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 964       uint shift  = exact_log2(type2aelembytes(ary_elem));
 965 
 966       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
 967 #ifdef _LP64
 968       diff = phase->transform(new ConvI2LNode(diff));
 969 #endif
 970       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
 971 
 972       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
 973       addp->set_req(AddPNode::Offset, offset);
 974     }
 975     addp = phase->transform(addp);
 976 #ifdef ASSERT
 977     const TypePtr* adr_type = phase->type(addp)->is_ptr();
 978     ld->_adr_type = adr_type;
 979 #endif
 980     ld->set_req(MemNode::Address, addp);
 981     ld->set_req(0, ctl);
 982     ld->set_req(MemNode::Memory, mem);
 983     // load depends on the tests that validate the arraycopy
 984     ld->_control_dependency = UnknownControl;
 985     return ld;
 986   }
 987   return NULL;
 988 }
 989 
 990 
 991 //---------------------------can_see_stored_value------------------------------
 992 // This routine exists to make sure this set of tests is done the same
 993 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 994 // will change the graph shape in a way which makes memory alive twice at the
 995 // same time (uses the Oracle model of aliasing), then some
 996 // LoadXNode::Identity will fold things back to the equivalence-class model
 997 // of aliasing.
 998 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 999   Node* ld_adr = in(MemNode::Address);
1000   intptr_t ld_off = 0;
1001   Node* ld_base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ld_off);
1002   Node* ld_alloc = AllocateNode::Ideal_allocation(ld_base, phase);
1003   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
1004   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
1005   // This is more general than load from boxing objects.
1006   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
1007     uint alias_idx = atp->index();
1008     bool final = !atp->is_rewritable();
1009     Node* result = NULL;
1010     Node* current = st;
1011     // Skip through chains of MemBarNodes checking the MergeMems for
1012     // new states for the slice of this load.  Stop once any other
1013     // kind of node is encountered.  Loads from final memory can skip
1014     // through any kind of MemBar but normal loads shouldn't skip
1015     // through MemBarAcquire since the could allow them to move out of
1016     // a synchronized region.
1017     while (current->is_Proj()) {
1018       int opc = current->in(0)->Opcode();
1019       if ((final && (opc == Op_MemBarAcquire ||
1020                      opc == Op_MemBarAcquireLock ||
1021                      opc == Op_LoadFence)) ||
1022           opc == Op_MemBarRelease ||
1023           opc == Op_StoreFence ||
1024           opc == Op_MemBarReleaseLock ||
1025           opc == Op_MemBarStoreStore ||
1026           opc == Op_MemBarCPUOrder) {
1027         Node* mem = current->in(0)->in(TypeFunc::Memory);
1028         if (mem->is_MergeMem()) {
1029           MergeMemNode* merge = mem->as_MergeMem();
1030           Node* new_st = merge->memory_at(alias_idx);
1031           if (new_st == merge->base_memory()) {
1032             // Keep searching
1033             current = new_st;
1034             continue;
1035           }
1036           // Save the new memory state for the slice and fall through
1037           // to exit.
1038           result = new_st;
1039         }
1040       }
1041       break;
1042     }
1043     if (result != NULL) {
1044       st = result;
1045     }
1046   }
1047 
1048   // Loop around twice in the case Load -> Initialize -> Store.
1049   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1050   for (int trip = 0; trip <= 1; trip++) {
1051 
1052     if (st->is_Store()) {
1053       Node* st_adr = st->in(MemNode::Address);
1054       if (!phase->eqv(st_adr, ld_adr)) {
1055         // Try harder before giving up. Unify base pointers with casts (e.g., raw/non-raw pointers).
1056         intptr_t st_off = 0;
1057         Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_off);
1058         if (ld_base == NULL)                                   return NULL;
1059         if (st_base == NULL)                                   return NULL;
1060         if (!ld_base->eqv_uncast(st_base, /*keep_deps=*/true)) return NULL;
1061         if (ld_off != st_off)                                  return NULL;
1062         if (ld_off == Type::OffsetBot)                         return NULL;
1063         // Same base, same offset.
1064         // Possible improvement for arrays: check index value instead of absolute offset.
1065 
1066         // At this point we have proven something like this setup:
1067         //   B = << base >>
1068         //   L =  LoadQ(AddP(Check/CastPP(B), #Off))
1069         //   S = StoreQ(AddP(             B , #Off), V)
1070         // (Actually, we haven't yet proven the Q's are the same.)
1071         // In other words, we are loading from a casted version of
1072         // the same pointer-and-offset that we stored to.
1073         // Casted version may carry a dependency and it is respected.
1074         // Thus, we are able to replace L by V.
1075       }
1076       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1077       if (store_Opcode() != st->Opcode())
1078         return NULL;
1079       return st->in(MemNode::ValueIn);
1080     }
1081 
1082     // A load from a freshly-created object always returns zero.
1083     // (This can happen after LoadNode::Ideal resets the load's memory input
1084     // to find_captured_store, which returned InitializeNode::zero_memory.)
1085     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1086         (st->in(0) == ld_alloc) &&
1087         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1088       // return a zero value for the load's basic type
1089       // (This is one of the few places where a generic PhaseTransform
1090       // can create new nodes.  Think of it as lazily manifesting
1091       // virtually pre-existing constants.)
1092       return phase->zerocon(memory_type());
1093     }
1094 
1095     // A load from an initialization barrier can match a captured store.
1096     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1097       InitializeNode* init = st->in(0)->as_Initialize();
1098       AllocateNode* alloc = init->allocation();
1099       if ((alloc != NULL) && (alloc == ld_alloc)) {
1100         // examine a captured store value
1101         st = init->find_captured_store(ld_off, memory_size(), phase);
1102         if (st != NULL) {
1103           continue;             // take one more trip around
1104         }
1105       }
1106     }
1107 
1108     // Load boxed value from result of valueOf() call is input parameter.
1109     if (this->is_Load() && ld_adr->is_AddP() &&
1110         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1111       intptr_t ignore = 0;
1112       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1113       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1114       base = bs->step_over_gc_barrier(base);
1115       if (base != NULL && base->is_Proj() &&
1116           base->as_Proj()->_con == TypeFunc::Parms &&
1117           base->in(0)->is_CallStaticJava() &&
1118           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1119         return base->in(0)->in(TypeFunc::Parms);
1120       }
1121     }
1122 
1123     break;
1124   }
1125 
1126   return NULL;
1127 }
1128 
1129 //----------------------is_instance_field_load_with_local_phi------------------
1130 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1131   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1132       in(Address)->is_AddP() ) {
1133     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1134     // Only instances and boxed values.
1135     if( t_oop != NULL &&
1136         (t_oop->is_ptr_to_boxed_value() ||
1137          t_oop->is_known_instance_field()) &&
1138         t_oop->offset() != Type::OffsetBot &&
1139         t_oop->offset() != Type::OffsetTop) {
1140       return true;
1141     }
1142   }
1143   return false;
1144 }
1145 
1146 //------------------------------Identity---------------------------------------
1147 // Loads are identity if previous store is to same address
1148 Node* LoadNode::Identity(PhaseGVN* phase) {
1149   // If the previous store-maker is the right kind of Store, and the store is
1150   // to the same address, then we are equal to the value stored.
1151   Node* mem = in(Memory);
1152   Node* value = can_see_stored_value(mem, phase);
1153   if( value ) {
1154     // byte, short & char stores truncate naturally.
1155     // A load has to load the truncated value which requires
1156     // some sort of masking operation and that requires an
1157     // Ideal call instead of an Identity call.
1158     if (memory_size() < BytesPerInt) {
1159       // If the input to the store does not fit with the load's result type,
1160       // it must be truncated via an Ideal call.
1161       if (!phase->type(value)->higher_equal(phase->type(this)))
1162         return this;
1163     }
1164     // (This works even when value is a Con, but LoadNode::Value
1165     // usually runs first, producing the singleton type of the Con.)
1166     return value;
1167   }
1168 
1169   // Search for an existing data phi which was generated before for the same
1170   // instance's field to avoid infinite generation of phis in a loop.
1171   Node *region = mem->in(0);
1172   if (is_instance_field_load_with_local_phi(region)) {
1173     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1174     int this_index  = phase->C->get_alias_index(addr_t);
1175     int this_offset = addr_t->offset();
1176     int this_iid    = addr_t->instance_id();
1177     if (!addr_t->is_known_instance() &&
1178          addr_t->is_ptr_to_boxed_value()) {
1179       // Use _idx of address base (could be Phi node) for boxed values.
1180       intptr_t   ignore = 0;
1181       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1182       if (base == NULL) {
1183         return this;
1184       }
1185       this_iid = base->_idx;
1186     }
1187     const Type* this_type = bottom_type();
1188     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1189       Node* phi = region->fast_out(i);
1190       if (phi->is_Phi() && phi != mem &&
1191           phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1192         return phi;
1193       }
1194     }
1195   }
1196 
1197   return this;
1198 }
1199 
1200 // Construct an equivalent unsigned load.
1201 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1202   BasicType bt = T_ILLEGAL;
1203   const Type* rt = NULL;
1204   switch (Opcode()) {
1205     case Op_LoadUB: return this;
1206     case Op_LoadUS: return this;
1207     case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1208     case Op_LoadS: bt = T_CHAR;    rt = TypeInt::CHAR;  break;
1209     default:
1210       assert(false, "no unsigned variant: %s", Name());
1211       return NULL;
1212   }
1213   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1214                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1215                         is_unaligned_access(), is_mismatched_access());
1216 }
1217 
1218 // Construct an equivalent signed load.
1219 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1220   BasicType bt = T_ILLEGAL;
1221   const Type* rt = NULL;
1222   switch (Opcode()) {
1223     case Op_LoadUB: bt = T_BYTE;  rt = TypeInt::BYTE;  break;
1224     case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1225     case Op_LoadB: // fall through
1226     case Op_LoadS: // fall through
1227     case Op_LoadI: // fall through
1228     case Op_LoadL: return this;
1229     default:
1230       assert(false, "no signed variant: %s", Name());
1231       return NULL;
1232   }
1233   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1234                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1235                         is_unaligned_access(), is_mismatched_access());
1236 }
1237 
1238 // We're loading from an object which has autobox behaviour.
1239 // If this object is result of a valueOf call we'll have a phi
1240 // merging a newly allocated object and a load from the cache.
1241 // We want to replace this load with the original incoming
1242 // argument to the valueOf call.
1243 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1244   assert(phase->C->eliminate_boxing(), "sanity");
1245   intptr_t ignore = 0;
1246   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1247   if ((base == NULL) || base->is_Phi()) {
1248     // Push the loads from the phi that comes from valueOf up
1249     // through it to allow elimination of the loads and the recovery
1250     // of the original value. It is done in split_through_phi().
1251     return NULL;
1252   } else if (base->is_Load() ||
1253              (base->is_DecodeN() && base->in(1)->is_Load())) {
1254     // Eliminate the load of boxed value for integer types from the cache
1255     // array by deriving the value from the index into the array.
1256     // Capture the offset of the load and then reverse the computation.
1257 
1258     // Get LoadN node which loads a boxing object from 'cache' array.
1259     if (base->is_DecodeN()) {
1260       base = base->in(1);
1261     }
1262     if (!base->in(Address)->is_AddP()) {
1263       return NULL; // Complex address
1264     }
1265     AddPNode* address = base->in(Address)->as_AddP();
1266     Node* cache_base = address->in(AddPNode::Base);
1267     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1268       // Get ConP node which is static 'cache' field.
1269       cache_base = cache_base->in(1);
1270     }
1271     if ((cache_base != NULL) && cache_base->is_Con()) {
1272       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1273       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1274         Node* elements[4];
1275         int shift = exact_log2(type2aelembytes(T_OBJECT));
1276         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1277         if (count > 0 && elements[0]->is_Con() &&
1278             (count == 1 ||
1279              (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1280                             elements[1]->in(2) == phase->intcon(shift)))) {
1281           ciObjArray* array = base_type->const_oop()->as_obj_array();
1282           // Fetch the box object cache[0] at the base of the array and get its value
1283           ciInstance* box = array->obj_at(0)->as_instance();
1284           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1285           assert(ik->is_box_klass(), "sanity");
1286           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1287           if (ik->nof_nonstatic_fields() == 1) {
1288             // This should be true nonstatic_field_at requires calling
1289             // nof_nonstatic_fields so check it anyway
1290             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1291             BasicType bt = c.basic_type();
1292             // Only integer types have boxing cache.
1293             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1294                    bt == T_BYTE    || bt == T_SHORT ||
1295                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1296             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1297             if (cache_low != (int)cache_low) {
1298               return NULL; // should not happen since cache is array indexed by value
1299             }
1300             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1301             if (offset != (int)offset) {
1302               return NULL; // should not happen since cache is array indexed by value
1303             }
1304            // Add up all the offsets making of the address of the load
1305             Node* result = elements[0];
1306             for (int i = 1; i < count; i++) {
1307               result = phase->transform(new AddXNode(result, elements[i]));
1308             }
1309             // Remove the constant offset from the address and then
1310             result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1311             // remove the scaling of the offset to recover the original index.
1312             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1313               // Peel the shift off directly but wrap it in a dummy node
1314               // since Ideal can't return existing nodes
1315               result = new RShiftXNode(result->in(1), phase->intcon(0));
1316             } else if (result->is_Add() && result->in(2)->is_Con() &&
1317                        result->in(1)->Opcode() == Op_LShiftX &&
1318                        result->in(1)->in(2) == phase->intcon(shift)) {
1319               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1320               // but for boxing cache access we know that X<<Z will not overflow
1321               // (there is range check) so we do this optimizatrion by hand here.
1322               Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1323               result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1324             } else {
1325               result = new RShiftXNode(result, phase->intcon(shift));
1326             }
1327 #ifdef _LP64
1328             if (bt != T_LONG) {
1329               result = new ConvL2INode(phase->transform(result));
1330             }
1331 #else
1332             if (bt == T_LONG) {
1333               result = new ConvI2LNode(phase->transform(result));
1334             }
1335 #endif
1336             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1337             // Need to preserve unboxing load type if it is unsigned.
1338             switch(this->Opcode()) {
1339               case Op_LoadUB:
1340                 result = new AndINode(phase->transform(result), phase->intcon(0xFF));
1341                 break;
1342               case Op_LoadUS:
1343                 result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
1344                 break;
1345             }
1346             return result;
1347           }
1348         }
1349       }
1350     }
1351   }
1352   return NULL;
1353 }
1354 
1355 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1356   Node* region = phi->in(0);
1357   if (region == NULL) {
1358     return false; // Wait stable graph
1359   }
1360   uint cnt = phi->req();
1361   for (uint i = 1; i < cnt; i++) {
1362     Node* rc = region->in(i);
1363     if (rc == NULL || phase->type(rc) == Type::TOP)
1364       return false; // Wait stable graph
1365     Node* in = phi->in(i);
1366     if (in == NULL || phase->type(in) == Type::TOP)
1367       return false; // Wait stable graph
1368   }
1369   return true;
1370 }
1371 //------------------------------split_through_phi------------------------------
1372 // Split instance or boxed field load through Phi.
1373 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1374   Node* mem     = in(Memory);
1375   Node* address = in(Address);
1376   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1377 
1378   assert((t_oop != NULL) &&
1379          (t_oop->is_known_instance_field() ||
1380           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1381 
1382   Compile* C = phase->C;
1383   intptr_t ignore = 0;
1384   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1385   bool base_is_phi = (base != NULL) && base->is_Phi();
1386   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1387                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1388                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1389 
1390   if (!((mem->is_Phi() || base_is_phi) &&
1391         (load_boxed_values || t_oop->is_known_instance_field()))) {
1392     return NULL; // memory is not Phi
1393   }
1394 
1395   if (mem->is_Phi()) {
1396     if (!stable_phi(mem->as_Phi(), phase)) {
1397       return NULL; // Wait stable graph
1398     }
1399     uint cnt = mem->req();
1400     // Check for loop invariant memory.
1401     if (cnt == 3) {
1402       for (uint i = 1; i < cnt; i++) {
1403         Node* in = mem->in(i);
1404         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1405         if (m == mem) {
1406           if (i == 1) {
1407             // if the first edge was a loop, check second edge too.
1408             // If both are replaceable - we are in an infinite loop
1409             Node *n = optimize_memory_chain(mem->in(2), t_oop, this, phase);
1410             if (n == mem) {
1411               break;
1412             }
1413           }
1414           set_req(Memory, mem->in(cnt - i));
1415           return this; // made change
1416         }
1417       }
1418     }
1419   }
1420   if (base_is_phi) {
1421     if (!stable_phi(base->as_Phi(), phase)) {
1422       return NULL; // Wait stable graph
1423     }
1424     uint cnt = base->req();
1425     // Check for loop invariant memory.
1426     if (cnt == 3) {
1427       for (uint i = 1; i < cnt; i++) {
1428         if (base->in(i) == base) {
1429           return NULL; // Wait stable graph
1430         }
1431       }
1432     }
1433   }
1434 
1435   // Split through Phi (see original code in loopopts.cpp).
1436   assert(C->have_alias_type(t_oop), "instance should have alias type");
1437 
1438   // Do nothing here if Identity will find a value
1439   // (to avoid infinite chain of value phis generation).
1440   if (!phase->eqv(this, phase->apply_identity(this)))
1441     return NULL;
1442 
1443   // Select Region to split through.
1444   Node* region;
1445   if (!base_is_phi) {
1446     assert(mem->is_Phi(), "sanity");
1447     region = mem->in(0);
1448     // Skip if the region dominates some control edge of the address.
1449     if (!MemNode::all_controls_dominate(address, region))
1450       return NULL;
1451   } else if (!mem->is_Phi()) {
1452     assert(base_is_phi, "sanity");
1453     region = base->in(0);
1454     // Skip if the region dominates some control edge of the memory.
1455     if (!MemNode::all_controls_dominate(mem, region))
1456       return NULL;
1457   } else if (base->in(0) != mem->in(0)) {
1458     assert(base_is_phi && mem->is_Phi(), "sanity");
1459     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1460       region = base->in(0);
1461     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1462       region = mem->in(0);
1463     } else {
1464       return NULL; // complex graph
1465     }
1466   } else {
1467     assert(base->in(0) == mem->in(0), "sanity");
1468     region = mem->in(0);
1469   }
1470 
1471   const Type* this_type = this->bottom_type();
1472   int this_index  = C->get_alias_index(t_oop);
1473   int this_offset = t_oop->offset();
1474   int this_iid    = t_oop->instance_id();
1475   if (!t_oop->is_known_instance() && load_boxed_values) {
1476     // Use _idx of address base for boxed values.
1477     this_iid = base->_idx;
1478   }
1479   PhaseIterGVN* igvn = phase->is_IterGVN();
1480   Node* phi = new PhiNode(region, this_type, NULL, mem->_idx, this_iid, this_index, this_offset);
1481   for (uint i = 1; i < region->req(); i++) {
1482     Node* x;
1483     Node* the_clone = NULL;
1484     if (region->in(i) == C->top()) {
1485       x = C->top();      // Dead path?  Use a dead data op
1486     } else {
1487       x = this->clone();        // Else clone up the data op
1488       the_clone = x;            // Remember for possible deletion.
1489       // Alter data node to use pre-phi inputs
1490       if (this->in(0) == region) {
1491         x->set_req(0, region->in(i));
1492       } else {
1493         x->set_req(0, NULL);
1494       }
1495       if (mem->is_Phi() && (mem->in(0) == region)) {
1496         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1497       }
1498       if (address->is_Phi() && address->in(0) == region) {
1499         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1500       }
1501       if (base_is_phi && (base->in(0) == region)) {
1502         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1503         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1504         x->set_req(Address, adr_x);
1505       }
1506     }
1507     // Check for a 'win' on some paths
1508     const Type *t = x->Value(igvn);
1509 
1510     bool singleton = t->singleton();
1511 
1512     // See comments in PhaseIdealLoop::split_thru_phi().
1513     if (singleton && t == Type::TOP) {
1514       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1515     }
1516 
1517     if (singleton) {
1518       x = igvn->makecon(t);
1519     } else {
1520       // We now call Identity to try to simplify the cloned node.
1521       // Note that some Identity methods call phase->type(this).
1522       // Make sure that the type array is big enough for
1523       // our new node, even though we may throw the node away.
1524       // (This tweaking with igvn only works because x is a new node.)
1525       igvn->set_type(x, t);
1526       // If x is a TypeNode, capture any more-precise type permanently into Node
1527       // otherwise it will be not updated during igvn->transform since
1528       // igvn->type(x) is set to x->Value() already.
1529       x->raise_bottom_type(t);
1530       Node *y = igvn->apply_identity(x);
1531       if (y != x) {
1532         x = y;
1533       } else {
1534         y = igvn->hash_find_insert(x);
1535         if (y) {
1536           x = y;
1537         } else {
1538           // Else x is a new node we are keeping
1539           // We do not need register_new_node_with_optimizer
1540           // because set_type has already been called.
1541           igvn->_worklist.push(x);
1542         }
1543       }
1544     }
1545     if (x != the_clone && the_clone != NULL) {
1546       igvn->remove_dead_node(the_clone);
1547     }
1548     phi->set_req(i, x);
1549   }
1550   // Record Phi
1551   igvn->register_new_node_with_optimizer(phi);
1552   return phi;
1553 }
1554 
1555 AllocateNode* LoadNode::is_new_object_mark_load(PhaseGVN *phase) const {
1556   if (Opcode() == Op_LoadX) {
1557     Node* address = in(MemNode::Address);
1558     AllocateNode* alloc = AllocateNode::Ideal_allocation(address, phase);
1559     Node* mem = in(MemNode::Memory);
1560     if (alloc != NULL && mem->is_Proj() &&
1561         mem->in(0) != NULL &&
1562         mem->in(0) == alloc->initialization() &&
1563         alloc->initialization()->proj_out_or_null(0) != NULL) {
1564       return alloc;
1565     }
1566   }
1567   return NULL;
1568 }
1569 
1570 
1571 //------------------------------Ideal------------------------------------------
1572 // If the load is from Field memory and the pointer is non-null, it might be possible to
1573 // zero out the control input.
1574 // If the offset is constant and the base is an object allocation,
1575 // try to hook me up to the exact initializing store.
1576 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1577   Node* p = MemNode::Ideal_common(phase, can_reshape);
1578   if (p)  return (p == NodeSentinel) ? NULL : p;
1579 
1580   Node* ctrl    = in(MemNode::Control);
1581   Node* address = in(MemNode::Address);
1582   bool progress = false;
1583 
1584   bool addr_mark = ((phase->type(address)->isa_oopptr() || phase->type(address)->isa_narrowoop()) &&
1585          phase->type(address)->is_ptr()->offset() == oopDesc::mark_offset_in_bytes());
1586 
1587   // Skip up past a SafePoint control.  Cannot do this for Stores because
1588   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1589   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1590       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw  &&
1591       !addr_mark &&
1592       (depends_only_on_test() || has_unknown_control_dependency())) {
1593     ctrl = ctrl->in(0);
1594     set_req(MemNode::Control,ctrl);
1595     progress = true;
1596   }
1597 
1598   intptr_t ignore = 0;
1599   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1600   if (base != NULL
1601       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1602     // Check for useless control edge in some common special cases
1603     if (in(MemNode::Control) != NULL
1604         && can_remove_control()
1605         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1606         && all_controls_dominate(base, phase->C->start())) {
1607       // A method-invariant, non-null address (constant or 'this' argument).
1608       set_req(MemNode::Control, NULL);
1609       progress = true;
1610     }
1611   }
1612 
1613   Node* mem = in(MemNode::Memory);
1614   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1615 
1616   if (can_reshape && (addr_t != NULL)) {
1617     // try to optimize our memory input
1618     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1619     if (opt_mem != mem) {
1620       set_req(MemNode::Memory, opt_mem);
1621       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1622       return this;
1623     }
1624     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1625     if ((t_oop != NULL) &&
1626         (t_oop->is_known_instance_field() ||
1627          t_oop->is_ptr_to_boxed_value())) {
1628       PhaseIterGVN *igvn = phase->is_IterGVN();
1629       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1630         // Delay this transformation until memory Phi is processed.
1631         phase->is_IterGVN()->_worklist.push(this);
1632         return NULL;
1633       }
1634       // Split instance field load through Phi.
1635       Node* result = split_through_phi(phase);
1636       if (result != NULL) return result;
1637 
1638       if (t_oop->is_ptr_to_boxed_value()) {
1639         Node* result = eliminate_autobox(phase);
1640         if (result != NULL) return result;
1641       }
1642     }
1643   }
1644 
1645   // Is there a dominating load that loads the same value?  Leave
1646   // anything that is not a load of a field/array element (like
1647   // barriers etc.) alone
1648   if (in(0) != NULL && !adr_type()->isa_rawptr() && can_reshape) {
1649     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1650       Node *use = mem->fast_out(i);
1651       if (use != this &&
1652           use->Opcode() == Opcode() &&
1653           use->in(0) != NULL &&
1654           use->in(0) != in(0) &&
1655           use->in(Address) == in(Address)) {
1656         Node* ctl = in(0);
1657         for (int i = 0; i < 10 && ctl != NULL; i++) {
1658           ctl = IfNode::up_one_dom(ctl);
1659           if (ctl == use->in(0)) {
1660             set_req(0, use->in(0));
1661             return this;
1662           }
1663         }
1664       }
1665     }
1666   }
1667 
1668   // Check for prior store with a different base or offset; make Load
1669   // independent.  Skip through any number of them.  Bail out if the stores
1670   // are in an endless dead cycle and report no progress.  This is a key
1671   // transform for Reflection.  However, if after skipping through the Stores
1672   // we can't then fold up against a prior store do NOT do the transform as
1673   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1674   // array memory alive twice: once for the hoisted Load and again after the
1675   // bypassed Store.  This situation only works if EVERYBODY who does
1676   // anti-dependence work knows how to bypass.  I.e. we need all
1677   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1678   // the alias index stuff.  So instead, peek through Stores and IFF we can
1679   // fold up, do so.
1680   Node* prev_mem = find_previous_store(phase);
1681   if (prev_mem != NULL) {
1682     Node* value = can_see_arraycopy_value(prev_mem, phase);
1683     if (value != NULL) {
1684       return value;
1685     }
1686   }
1687   // Steps (a), (b):  Walk past independent stores to find an exact match.
1688   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1689     // (c) See if we can fold up on the spot, but don't fold up here.
1690     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1691     // just return a prior value, which is done by Identity calls.
1692     if (can_see_stored_value(prev_mem, phase)) {
1693       // Make ready for step (d):
1694       set_req(MemNode::Memory, prev_mem);
1695       return this;
1696     }
1697   }
1698 
1699   AllocateNode* alloc = is_new_object_mark_load(phase);
1700   if (alloc != NULL && alloc->Opcode() == Op_Allocate && UseBiasedLocking) {
1701     InitializeNode* init = alloc->initialization();
1702     Node* control = init->proj_out(0);
1703     return alloc->make_ideal_mark(phase, address, control, mem);
1704   }
1705 
1706   return progress ? this : NULL;
1707 }
1708 
1709 // Helper to recognize certain Klass fields which are invariant across
1710 // some group of array types (e.g., int[] or all T[] where T < Object).
1711 const Type*
1712 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1713                                  ciKlass* klass) const {
1714   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1715     // The field is Klass::_modifier_flags.  Return its (constant) value.
1716     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1717     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1718     return TypeInt::make(klass->modifier_flags());
1719   }
1720   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1721     // The field is Klass::_access_flags.  Return its (constant) value.
1722     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1723     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1724     return TypeInt::make(klass->access_flags());
1725   }
1726   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1727     // The field is Klass::_layout_helper.  Return its constant value if known.
1728     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1729     return TypeInt::make(klass->layout_helper());
1730   }
1731 
1732   // No match.
1733   return NULL;
1734 }
1735 
1736 //------------------------------Value-----------------------------------------
1737 const Type* LoadNode::Value(PhaseGVN* phase) const {
1738   // Either input is TOP ==> the result is TOP
1739   Node* mem = in(MemNode::Memory);
1740   const Type *t1 = phase->type(mem);
1741   if (t1 == Type::TOP)  return Type::TOP;
1742   Node* adr = in(MemNode::Address);
1743   const TypePtr* tp = phase->type(adr)->isa_ptr();
1744   if (tp == NULL || tp->empty())  return Type::TOP;
1745   int off = tp->offset();
1746   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1747   Compile* C = phase->C;
1748 
1749   // Try to guess loaded type from pointer type
1750   if (tp->isa_aryptr()) {
1751     const TypeAryPtr* ary = tp->is_aryptr();
1752     const Type* t = ary->elem();
1753 
1754     // Determine whether the reference is beyond the header or not, by comparing
1755     // the offset against the offset of the start of the array's data.
1756     // Different array types begin at slightly different offsets (12 vs. 16).
1757     // We choose T_BYTE as an example base type that is least restrictive
1758     // as to alignment, which will therefore produce the smallest
1759     // possible base offset.
1760     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1761     const bool off_beyond_header = (off >= min_base_off);
1762 
1763     // Try to constant-fold a stable array element.
1764     if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1765       // Make sure the reference is not into the header and the offset is constant
1766       ciObject* aobj = ary->const_oop();
1767       if (aobj != NULL && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1768         int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1769         const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1770                                                                       stable_dimension,
1771                                                                       memory_type(), is_unsigned());
1772         if (con_type != NULL) {
1773           return con_type;
1774         }
1775       }
1776     }
1777 
1778     // Don't do this for integer types. There is only potential profit if
1779     // the element type t is lower than _type; that is, for int types, if _type is
1780     // more restrictive than t.  This only happens here if one is short and the other
1781     // char (both 16 bits), and in those cases we've made an intentional decision
1782     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1783     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1784     //
1785     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1786     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1787     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1788     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1789     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1790     // In fact, that could have been the original type of p1, and p1 could have
1791     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1792     // expression (LShiftL quux 3) independently optimized to the constant 8.
1793     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1794         && (_type->isa_vect() == NULL)
1795         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1796       // t might actually be lower than _type, if _type is a unique
1797       // concrete subclass of abstract class t.
1798       if (off_beyond_header || off == Type::OffsetBot) {  // is the offset beyond the header?
1799         const Type* jt = t->join_speculative(_type);
1800         // In any case, do not allow the join, per se, to empty out the type.
1801         if (jt->empty() && !t->empty()) {
1802           // This can happen if a interface-typed array narrows to a class type.
1803           jt = _type;
1804         }
1805 #ifdef ASSERT
1806         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1807           // The pointers in the autobox arrays are always non-null
1808           Node* base = adr->in(AddPNode::Base);
1809           if ((base != NULL) && base->is_DecodeN()) {
1810             // Get LoadN node which loads IntegerCache.cache field
1811             base = base->in(1);
1812           }
1813           if ((base != NULL) && base->is_Con()) {
1814             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1815             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1816               // It could be narrow oop
1817               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1818             }
1819           }
1820         }
1821 #endif
1822         return jt;
1823       }
1824     }
1825   } else if (tp->base() == Type::InstPtr) {
1826     assert( off != Type::OffsetBot ||
1827             // arrays can be cast to Objects
1828             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1829             // unsafe field access may not have a constant offset
1830             C->has_unsafe_access(),
1831             "Field accesses must be precise" );
1832     // For oop loads, we expect the _type to be precise.
1833 
1834     // Optimize loads from constant fields.
1835     const TypeInstPtr* tinst = tp->is_instptr();
1836     ciObject* const_oop = tinst->const_oop();
1837     if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
1838       const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
1839       if (con_type != NULL) {
1840         return con_type;
1841       }
1842     }
1843   } else if (tp->base() == Type::KlassPtr) {
1844     assert( off != Type::OffsetBot ||
1845             // arrays can be cast to Objects
1846             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1847             // also allow array-loading from the primary supertype
1848             // array during subtype checks
1849             Opcode() == Op_LoadKlass,
1850             "Field accesses must be precise" );
1851     // For klass/static loads, we expect the _type to be precise
1852   } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
1853     /* With mirrors being an indirect in the Klass*
1854      * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
1855      * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
1856      *
1857      * So check the type and klass of the node before the LoadP.
1858      */
1859     Node* adr2 = adr->in(MemNode::Address);
1860     const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
1861     if (tkls != NULL && !StressReflectiveCode) {
1862       ciKlass* klass = tkls->klass();
1863       if (klass->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1864         assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1865         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1866         return TypeInstPtr::make(klass->java_mirror());
1867       }
1868     }
1869   }
1870 
1871   const TypeKlassPtr *tkls = tp->isa_klassptr();
1872   if (tkls != NULL && !StressReflectiveCode) {
1873     ciKlass* klass = tkls->klass();
1874     if (klass->is_loaded() && tkls->klass_is_exact()) {
1875       // We are loading a field from a Klass metaobject whose identity
1876       // is known at compile time (the type is "exact" or "precise").
1877       // Check for fields we know are maintained as constants by the VM.
1878       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1879         // The field is Klass::_super_check_offset.  Return its (constant) value.
1880         // (Folds up type checking code.)
1881         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1882         return TypeInt::make(klass->super_check_offset());
1883       }
1884       // Compute index into primary_supers array
1885       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1886       // Check for overflowing; use unsigned compare to handle the negative case.
1887       if( depth < ciKlass::primary_super_limit() ) {
1888         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1889         // (Folds up type checking code.)
1890         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1891         ciKlass *ss = klass->super_of_depth(depth);
1892         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1893       }
1894       const Type* aift = load_array_final_field(tkls, klass);
1895       if (aift != NULL)  return aift;
1896     }
1897 
1898     // We can still check if we are loading from the primary_supers array at a
1899     // shallow enough depth.  Even though the klass is not exact, entries less
1900     // than or equal to its super depth are correct.
1901     if (klass->is_loaded() ) {
1902       ciType *inner = klass;
1903       while( inner->is_obj_array_klass() )
1904         inner = inner->as_obj_array_klass()->base_element_type();
1905       if( inner->is_instance_klass() &&
1906           !inner->as_instance_klass()->flags().is_interface() ) {
1907         // Compute index into primary_supers array
1908         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1909         // Check for overflowing; use unsigned compare to handle the negative case.
1910         if( depth < ciKlass::primary_super_limit() &&
1911             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1912           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1913           // (Folds up type checking code.)
1914           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1915           ciKlass *ss = klass->super_of_depth(depth);
1916           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1917         }
1918       }
1919     }
1920 
1921     // If the type is enough to determine that the thing is not an array,
1922     // we can give the layout_helper a positive interval type.
1923     // This will help short-circuit some reflective code.
1924     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1925         && !klass->is_array_klass() // not directly typed as an array
1926         && !klass->is_interface()  // specifically not Serializable & Cloneable
1927         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1928         ) {
1929       // Note:  When interfaces are reliable, we can narrow the interface
1930       // test to (klass != Serializable && klass != Cloneable).
1931       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1932       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1933       // The key property of this type is that it folds up tests
1934       // for array-ness, since it proves that the layout_helper is positive.
1935       // Thus, a generic value like the basic object layout helper works fine.
1936       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1937     }
1938   }
1939 
1940   // If we are loading from a freshly-allocated object, produce a zero,
1941   // if the load is provably beyond the header of the object.
1942   // (Also allow a variable load from a fresh array to produce zero.)
1943   const TypeOopPtr *tinst = tp->isa_oopptr();
1944   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1945   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1946   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1947     Node* value = can_see_stored_value(mem,phase);
1948     if (value != NULL && value->is_Con()) {
1949       assert(value->bottom_type()->higher_equal(_type),"sanity");
1950       return value->bottom_type();
1951     }
1952   }
1953 
1954   if (is_instance) {
1955     // If we have an instance type and our memory input is the
1956     // programs's initial memory state, there is no matching store,
1957     // so just return a zero of the appropriate type
1958     Node *mem = in(MemNode::Memory);
1959     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1960       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1961       return Type::get_zero_type(_type->basic_type());
1962     }
1963   }
1964 
1965   Node* alloc = is_new_object_mark_load(phase);
1966   if (alloc != NULL && !(alloc->Opcode() == Op_Allocate && UseBiasedLocking)) {
1967     return TypeX::make(markWord::prototype().value());
1968   }
1969 
1970   return _type;
1971 }
1972 
1973 //------------------------------match_edge-------------------------------------
1974 // Do we Match on this edge index or not?  Match only the address.
1975 uint LoadNode::match_edge(uint idx) const {
1976   return idx == MemNode::Address;
1977 }
1978 
1979 //--------------------------LoadBNode::Ideal--------------------------------------
1980 //
1981 //  If the previous store is to the same address as this load,
1982 //  and the value stored was larger than a byte, replace this load
1983 //  with the value stored truncated to a byte.  If no truncation is
1984 //  needed, the replacement is done in LoadNode::Identity().
1985 //
1986 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1987   Node* mem = in(MemNode::Memory);
1988   Node* value = can_see_stored_value(mem,phase);
1989   if( value && !phase->type(value)->higher_equal( _type ) ) {
1990     Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1991     return new RShiftINode(result, phase->intcon(24));
1992   }
1993   // Identity call will handle the case where truncation is not needed.
1994   return LoadNode::Ideal(phase, can_reshape);
1995 }
1996 
1997 const Type* LoadBNode::Value(PhaseGVN* phase) const {
1998   Node* mem = in(MemNode::Memory);
1999   Node* value = can_see_stored_value(mem,phase);
2000   if (value != NULL && value->is_Con() &&
2001       !value->bottom_type()->higher_equal(_type)) {
2002     // If the input to the store does not fit with the load's result type,
2003     // it must be truncated. We can't delay until Ideal call since
2004     // a singleton Value is needed for split_thru_phi optimization.
2005     int con = value->get_int();
2006     return TypeInt::make((con << 24) >> 24);
2007   }
2008   return LoadNode::Value(phase);
2009 }
2010 
2011 //--------------------------LoadUBNode::Ideal-------------------------------------
2012 //
2013 //  If the previous store is to the same address as this load,
2014 //  and the value stored was larger than a byte, replace this load
2015 //  with the value stored truncated to a byte.  If no truncation is
2016 //  needed, the replacement is done in LoadNode::Identity().
2017 //
2018 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2019   Node* mem = in(MemNode::Memory);
2020   Node* value = can_see_stored_value(mem, phase);
2021   if (value && !phase->type(value)->higher_equal(_type))
2022     return new AndINode(value, phase->intcon(0xFF));
2023   // Identity call will handle the case where truncation is not needed.
2024   return LoadNode::Ideal(phase, can_reshape);
2025 }
2026 
2027 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
2028   Node* mem = in(MemNode::Memory);
2029   Node* value = can_see_stored_value(mem,phase);
2030   if (value != NULL && value->is_Con() &&
2031       !value->bottom_type()->higher_equal(_type)) {
2032     // If the input to the store does not fit with the load's result type,
2033     // it must be truncated. We can't delay until Ideal call since
2034     // a singleton Value is needed for split_thru_phi optimization.
2035     int con = value->get_int();
2036     return TypeInt::make(con & 0xFF);
2037   }
2038   return LoadNode::Value(phase);
2039 }
2040 
2041 //--------------------------LoadUSNode::Ideal-------------------------------------
2042 //
2043 //  If the previous store is to the same address as this load,
2044 //  and the value stored was larger than a char, replace this load
2045 //  with the value stored truncated to a char.  If no truncation is
2046 //  needed, the replacement is done in LoadNode::Identity().
2047 //
2048 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2049   Node* mem = in(MemNode::Memory);
2050   Node* value = can_see_stored_value(mem,phase);
2051   if( value && !phase->type(value)->higher_equal( _type ) )
2052     return new AndINode(value,phase->intcon(0xFFFF));
2053   // Identity call will handle the case where truncation is not needed.
2054   return LoadNode::Ideal(phase, can_reshape);
2055 }
2056 
2057 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
2058   Node* mem = in(MemNode::Memory);
2059   Node* value = can_see_stored_value(mem,phase);
2060   if (value != NULL && value->is_Con() &&
2061       !value->bottom_type()->higher_equal(_type)) {
2062     // If the input to the store does not fit with the load's result type,
2063     // it must be truncated. We can't delay until Ideal call since
2064     // a singleton Value is needed for split_thru_phi optimization.
2065     int con = value->get_int();
2066     return TypeInt::make(con & 0xFFFF);
2067   }
2068   return LoadNode::Value(phase);
2069 }
2070 
2071 //--------------------------LoadSNode::Ideal--------------------------------------
2072 //
2073 //  If the previous store is to the same address as this load,
2074 //  and the value stored was larger than a short, replace this load
2075 //  with the value stored truncated to a short.  If no truncation is
2076 //  needed, the replacement is done in LoadNode::Identity().
2077 //
2078 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2079   Node* mem = in(MemNode::Memory);
2080   Node* value = can_see_stored_value(mem,phase);
2081   if( value && !phase->type(value)->higher_equal( _type ) ) {
2082     Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
2083     return new RShiftINode(result, phase->intcon(16));
2084   }
2085   // Identity call will handle the case where truncation is not needed.
2086   return LoadNode::Ideal(phase, can_reshape);
2087 }
2088 
2089 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2090   Node* mem = in(MemNode::Memory);
2091   Node* value = can_see_stored_value(mem,phase);
2092   if (value != NULL && value->is_Con() &&
2093       !value->bottom_type()->higher_equal(_type)) {
2094     // If the input to the store does not fit with the load's result type,
2095     // it must be truncated. We can't delay until Ideal call since
2096     // a singleton Value is needed for split_thru_phi optimization.
2097     int con = value->get_int();
2098     return TypeInt::make((con << 16) >> 16);
2099   }
2100   return LoadNode::Value(phase);
2101 }
2102 
2103 //=============================================================================
2104 //----------------------------LoadKlassNode::make------------------------------
2105 // Polymorphic factory method:
2106 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2107   // sanity check the alias category against the created node type
2108   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2109   assert(adr_type != NULL, "expecting TypeKlassPtr");
2110 #ifdef _LP64
2111   if (adr_type->is_ptr_to_narrowklass()) {
2112     assert(UseCompressedClassPointers, "no compressed klasses");
2113     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2114     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2115   }
2116 #endif
2117   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2118   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2119 }
2120 
2121 //------------------------------Value------------------------------------------
2122 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2123   return klass_value_common(phase);
2124 }
2125 
2126 // In most cases, LoadKlassNode does not have the control input set. If the control
2127 // input is set, it must not be removed (by LoadNode::Ideal()).
2128 bool LoadKlassNode::can_remove_control() const {
2129   return false;
2130 }
2131 
2132 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2133   // Either input is TOP ==> the result is TOP
2134   const Type *t1 = phase->type( in(MemNode::Memory) );
2135   if (t1 == Type::TOP)  return Type::TOP;
2136   Node *adr = in(MemNode::Address);
2137   const Type *t2 = phase->type( adr );
2138   if (t2 == Type::TOP)  return Type::TOP;
2139   const TypePtr *tp = t2->is_ptr();
2140   if (TypePtr::above_centerline(tp->ptr()) ||
2141       tp->ptr() == TypePtr::Null)  return Type::TOP;
2142 
2143   // Return a more precise klass, if possible
2144   const TypeInstPtr *tinst = tp->isa_instptr();
2145   if (tinst != NULL) {
2146     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2147     int offset = tinst->offset();
2148     if (ik == phase->C->env()->Class_klass()
2149         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2150             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2151       // We are loading a special hidden field from a Class mirror object,
2152       // the field which points to the VM's Klass metaobject.
2153       ciType* t = tinst->java_mirror_type();
2154       // java_mirror_type returns non-null for compile-time Class constants.
2155       if (t != NULL) {
2156         // constant oop => constant klass
2157         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2158           if (t->is_void()) {
2159             // We cannot create a void array.  Since void is a primitive type return null
2160             // klass.  Users of this result need to do a null check on the returned klass.
2161             return TypePtr::NULL_PTR;
2162           }
2163           return TypeKlassPtr::make(ciArrayKlass::make(t));
2164         }
2165         if (!t->is_klass()) {
2166           // a primitive Class (e.g., int.class) has NULL for a klass field
2167           return TypePtr::NULL_PTR;
2168         }
2169         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2170         return TypeKlassPtr::make(t->as_klass());
2171       }
2172       // non-constant mirror, so we can't tell what's going on
2173     }
2174     if( !ik->is_loaded() )
2175       return _type;             // Bail out if not loaded
2176     if (offset == oopDesc::klass_offset_in_bytes()) {
2177       if (tinst->klass_is_exact()) {
2178         return TypeKlassPtr::make(ik);
2179       }
2180       // See if we can become precise: no subklasses and no interface
2181       // (Note:  We need to support verified interfaces.)
2182       if (!ik->is_interface() && !ik->has_subklass()) {
2183         //assert(!UseExactTypes, "this code should be useless with exact types");
2184         // Add a dependence; if any subclass added we need to recompile
2185         if (!ik->is_final()) {
2186           // %%% should use stronger assert_unique_concrete_subtype instead
2187           phase->C->dependencies()->assert_leaf_type(ik);
2188         }
2189         // Return precise klass
2190         return TypeKlassPtr::make(ik);
2191       }
2192 
2193       // Return root of possible klass
2194       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2195     }
2196   }
2197 
2198   // Check for loading klass from an array
2199   const TypeAryPtr *tary = tp->isa_aryptr();
2200   if( tary != NULL ) {
2201     ciKlass *tary_klass = tary->klass();
2202     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2203         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2204       if (tary->klass_is_exact()) {
2205         return TypeKlassPtr::make(tary_klass);
2206       }
2207       ciArrayKlass *ak = tary->klass()->as_array_klass();
2208       // If the klass is an object array, we defer the question to the
2209       // array component klass.
2210       if( ak->is_obj_array_klass() ) {
2211         assert( ak->is_loaded(), "" );
2212         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2213         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2214           ciInstanceKlass* ik = base_k->as_instance_klass();
2215           // See if we can become precise: no subklasses and no interface
2216           if (!ik->is_interface() && !ik->has_subklass()) {
2217             //assert(!UseExactTypes, "this code should be useless with exact types");
2218             // Add a dependence; if any subclass added we need to recompile
2219             if (!ik->is_final()) {
2220               phase->C->dependencies()->assert_leaf_type(ik);
2221             }
2222             // Return precise array klass
2223             return TypeKlassPtr::make(ak);
2224           }
2225         }
2226         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2227       } else {                  // Found a type-array?
2228         //assert(!UseExactTypes, "this code should be useless with exact types");
2229         assert( ak->is_type_array_klass(), "" );
2230         return TypeKlassPtr::make(ak); // These are always precise
2231       }
2232     }
2233   }
2234 
2235   // Check for loading klass from an array klass
2236   const TypeKlassPtr *tkls = tp->isa_klassptr();
2237   if (tkls != NULL && !StressReflectiveCode) {
2238     ciKlass* klass = tkls->klass();
2239     if( !klass->is_loaded() )
2240       return _type;             // Bail out if not loaded
2241     if( klass->is_obj_array_klass() &&
2242         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2243       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2244       // // Always returning precise element type is incorrect,
2245       // // e.g., element type could be object and array may contain strings
2246       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2247 
2248       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2249       // according to the element type's subclassing.
2250       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2251     }
2252     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2253         tkls->offset() == in_bytes(Klass::super_offset())) {
2254       ciKlass* sup = klass->as_instance_klass()->super();
2255       // The field is Klass::_super.  Return its (constant) value.
2256       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2257       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2258     }
2259   }
2260 
2261   // Bailout case
2262   return LoadNode::Value(phase);
2263 }
2264 
2265 //------------------------------Identity---------------------------------------
2266 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2267 // Also feed through the klass in Allocate(...klass...)._klass.
2268 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2269   return klass_identity_common(phase);
2270 }
2271 
2272 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2273   Node* x = LoadNode::Identity(phase);
2274   if (x != this)  return x;
2275 
2276   // Take apart the address into an oop and and offset.
2277   // Return 'this' if we cannot.
2278   Node*    adr    = in(MemNode::Address);
2279   intptr_t offset = 0;
2280   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2281   if (base == NULL)     return this;
2282   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2283   if (toop == NULL)     return this;
2284 
2285   // Step over potential GC barrier for OopHandle resolve
2286   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2287   if (bs->is_gc_barrier_node(base)) {
2288     base = bs->step_over_gc_barrier(base);
2289   }
2290 
2291   // We can fetch the klass directly through an AllocateNode.
2292   // This works even if the klass is not constant (clone or newArray).
2293   if (offset == oopDesc::klass_offset_in_bytes()) {
2294     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2295     if (allocated_klass != NULL) {
2296       return allocated_klass;
2297     }
2298   }
2299 
2300   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2301   // See inline_native_Class_query for occurrences of these patterns.
2302   // Java Example:  x.getClass().isAssignableFrom(y)
2303   //
2304   // This improves reflective code, often making the Class
2305   // mirror go completely dead.  (Current exception:  Class
2306   // mirrors may appear in debug info, but we could clean them out by
2307   // introducing a new debug info operator for Klass.java_mirror).
2308 
2309   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2310       && offset == java_lang_Class::klass_offset_in_bytes()) {
2311     if (base->is_Load()) {
2312       Node* base2 = base->in(MemNode::Address);
2313       if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2314         Node* adr2 = base2->in(MemNode::Address);
2315         const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2316         if (tkls != NULL && !tkls->empty()
2317             && (tkls->klass()->is_instance_klass() ||
2318               tkls->klass()->is_array_klass())
2319             && adr2->is_AddP()
2320            ) {
2321           int mirror_field = in_bytes(Klass::java_mirror_offset());
2322           if (tkls->offset() == mirror_field) {
2323             return adr2->in(AddPNode::Base);
2324           }
2325         }
2326       }
2327     }
2328   }
2329 
2330   return this;
2331 }
2332 
2333 
2334 //------------------------------Value------------------------------------------
2335 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2336   const Type *t = klass_value_common(phase);
2337   if (t == Type::TOP)
2338     return t;
2339 
2340   return t->make_narrowklass();
2341 }
2342 
2343 //------------------------------Identity---------------------------------------
2344 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2345 // Also feed through the klass in Allocate(...klass...)._klass.
2346 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2347   Node *x = klass_identity_common(phase);
2348 
2349   const Type *t = phase->type( x );
2350   if( t == Type::TOP ) return x;
2351   if( t->isa_narrowklass()) return x;
2352   assert (!t->isa_narrowoop(), "no narrow oop here");
2353 
2354   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2355 }
2356 
2357 //------------------------------Value-----------------------------------------
2358 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2359   // Either input is TOP ==> the result is TOP
2360   const Type *t1 = phase->type( in(MemNode::Memory) );
2361   if( t1 == Type::TOP ) return Type::TOP;
2362   Node *adr = in(MemNode::Address);
2363   const Type *t2 = phase->type( adr );
2364   if( t2 == Type::TOP ) return Type::TOP;
2365   const TypePtr *tp = t2->is_ptr();
2366   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2367   const TypeAryPtr *tap = tp->isa_aryptr();
2368   if( !tap ) return _type;
2369   return tap->size();
2370 }
2371 
2372 //-------------------------------Ideal---------------------------------------
2373 // Feed through the length in AllocateArray(...length...)._length.
2374 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2375   Node* p = MemNode::Ideal_common(phase, can_reshape);
2376   if (p)  return (p == NodeSentinel) ? NULL : p;
2377 
2378   // Take apart the address into an oop and and offset.
2379   // Return 'this' if we cannot.
2380   Node*    adr    = in(MemNode::Address);
2381   intptr_t offset = 0;
2382   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2383   if (base == NULL)     return NULL;
2384   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2385   if (tary == NULL)     return NULL;
2386 
2387   // We can fetch the length directly through an AllocateArrayNode.
2388   // This works even if the length is not constant (clone or newArray).
2389   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2390     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2391     if (alloc != NULL) {
2392       Node* allocated_length = alloc->Ideal_length();
2393       Node* len = alloc->make_ideal_length(tary, phase);
2394       if (allocated_length != len) {
2395         // New CastII improves on this.
2396         return len;
2397       }
2398     }
2399   }
2400 
2401   return NULL;
2402 }
2403 
2404 //------------------------------Identity---------------------------------------
2405 // Feed through the length in AllocateArray(...length...)._length.
2406 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2407   Node* x = LoadINode::Identity(phase);
2408   if (x != this)  return x;
2409 
2410   // Take apart the address into an oop and and offset.
2411   // Return 'this' if we cannot.
2412   Node*    adr    = in(MemNode::Address);
2413   intptr_t offset = 0;
2414   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2415   if (base == NULL)     return this;
2416   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2417   if (tary == NULL)     return this;
2418 
2419   // We can fetch the length directly through an AllocateArrayNode.
2420   // This works even if the length is not constant (clone or newArray).
2421   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2422     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2423     if (alloc != NULL) {
2424       Node* allocated_length = alloc->Ideal_length();
2425       // Do not allow make_ideal_length to allocate a CastII node.
2426       Node* len = alloc->make_ideal_length(tary, phase, false);
2427       if (allocated_length == len) {
2428         // Return allocated_length only if it would not be improved by a CastII.
2429         return allocated_length;
2430       }
2431     }
2432   }
2433 
2434   return this;
2435 
2436 }
2437 
2438 //=============================================================================
2439 //---------------------------StoreNode::make-----------------------------------
2440 // Polymorphic factory method:
2441 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2442   assert((mo == unordered || mo == release), "unexpected");
2443   Compile* C = gvn.C;
2444   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2445          ctl != NULL, "raw memory operations should have control edge");
2446 
2447   switch (bt) {
2448   case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2449   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2450   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2451   case T_CHAR:
2452   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2453   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2454   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2455   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2456   case T_METADATA:
2457   case T_ADDRESS:
2458   case T_OBJECT:
2459 #ifdef _LP64
2460     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2461       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2462       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2463     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2464                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2465                 adr->bottom_type()->isa_rawptr())) {
2466       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2467       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2468     }
2469 #endif
2470     {
2471       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2472     }
2473   default:
2474     ShouldNotReachHere();
2475     return (StoreNode*)NULL;
2476   }
2477 }
2478 
2479 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2480   bool require_atomic = true;
2481   return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2482 }
2483 
2484 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2485   bool require_atomic = true;
2486   return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2487 }
2488 
2489 
2490 //--------------------------bottom_type----------------------------------------
2491 const Type *StoreNode::bottom_type() const {
2492   return Type::MEMORY;
2493 }
2494 
2495 //------------------------------hash-------------------------------------------
2496 uint StoreNode::hash() const {
2497   // unroll addition of interesting fields
2498   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2499 
2500   // Since they are not commoned, do not hash them:
2501   return NO_HASH;
2502 }
2503 
2504 //------------------------------Ideal------------------------------------------
2505 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2506 // When a store immediately follows a relevant allocation/initialization,
2507 // try to capture it into the initialization, or hoist it above.
2508 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2509   Node* p = MemNode::Ideal_common(phase, can_reshape);
2510   if (p)  return (p == NodeSentinel) ? NULL : p;
2511 
2512   Node* mem     = in(MemNode::Memory);
2513   Node* address = in(MemNode::Address);
2514   // Back-to-back stores to same address?  Fold em up.  Generally
2515   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2516   // since they must follow each StoreP operation.  Redundant StoreCMs
2517   // are eliminated just before matching in final_graph_reshape.
2518   {
2519     Node* st = mem;
2520     // If Store 'st' has more than one use, we cannot fold 'st' away.
2521     // For example, 'st' might be the final state at a conditional
2522     // return.  Or, 'st' might be used by some node which is live at
2523     // the same time 'st' is live, which might be unschedulable.  So,
2524     // require exactly ONE user until such time as we clone 'mem' for
2525     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2526     // true).
2527     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2528       // Looking at a dead closed cycle of memory?
2529       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2530       assert(Opcode() == st->Opcode() ||
2531              st->Opcode() == Op_StoreVector ||
2532              Opcode() == Op_StoreVector ||
2533              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2534              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2535              (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2536              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2537              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2538 
2539       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2540           st->as_Store()->memory_size() <= this->memory_size()) {
2541         Node* use = st->raw_out(0);
2542         phase->igvn_rehash_node_delayed(use);
2543         if (can_reshape) {
2544           use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase->is_IterGVN());
2545         } else {
2546           // It's OK to do this in the parser, since DU info is always accurate,
2547           // and the parser always refers to nodes via SafePointNode maps.
2548           use->set_req(MemNode::Memory, st->in(MemNode::Memory));
2549         }
2550         return this;
2551       }
2552       st = st->in(MemNode::Memory);
2553     }
2554   }
2555 
2556 
2557   // Capture an unaliased, unconditional, simple store into an initializer.
2558   // Or, if it is independent of the allocation, hoist it above the allocation.
2559   if (ReduceFieldZeroing && /*can_reshape &&*/
2560       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2561     InitializeNode* init = mem->in(0)->as_Initialize();
2562     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2563     if (offset > 0) {
2564       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2565       // If the InitializeNode captured me, it made a raw copy of me,
2566       // and I need to disappear.
2567       if (moved != NULL) {
2568         // %%% hack to ensure that Ideal returns a new node:
2569         mem = MergeMemNode::make(mem);
2570         return mem;             // fold me away
2571       }
2572     }
2573   }
2574 
2575   return NULL;                  // No further progress
2576 }
2577 
2578 //------------------------------Value-----------------------------------------
2579 const Type* StoreNode::Value(PhaseGVN* phase) const {
2580   // Either input is TOP ==> the result is TOP
2581   const Type *t1 = phase->type( in(MemNode::Memory) );
2582   if( t1 == Type::TOP ) return Type::TOP;
2583   const Type *t2 = phase->type( in(MemNode::Address) );
2584   if( t2 == Type::TOP ) return Type::TOP;
2585   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2586   if( t3 == Type::TOP ) return Type::TOP;
2587   return Type::MEMORY;
2588 }
2589 
2590 //------------------------------Identity---------------------------------------
2591 // Remove redundant stores:
2592 //   Store(m, p, Load(m, p)) changes to m.
2593 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2594 Node* StoreNode::Identity(PhaseGVN* phase) {
2595   Node* mem = in(MemNode::Memory);
2596   Node* adr = in(MemNode::Address);
2597   Node* val = in(MemNode::ValueIn);
2598 
2599   Node* result = this;
2600 
2601   // Load then Store?  Then the Store is useless
2602   if (val->is_Load() &&
2603       val->in(MemNode::Address)->eqv_uncast(adr) &&
2604       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2605       val->as_Load()->store_Opcode() == Opcode()) {
2606     result = mem;
2607   }
2608 
2609   // Two stores in a row of the same value?
2610   if (result == this &&
2611       mem->is_Store() &&
2612       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2613       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2614       mem->Opcode() == Opcode()) {
2615     result = mem;
2616   }
2617 
2618   // Store of zero anywhere into a freshly-allocated object?
2619   // Then the store is useless.
2620   // (It must already have been captured by the InitializeNode.)
2621   if (result == this &&
2622       ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2623     // a newly allocated object is already all-zeroes everywhere
2624     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2625       result = mem;
2626     }
2627 
2628     if (result == this) {
2629       // the store may also apply to zero-bits in an earlier object
2630       Node* prev_mem = find_previous_store(phase);
2631       // Steps (a), (b):  Walk past independent stores to find an exact match.
2632       if (prev_mem != NULL) {
2633         Node* prev_val = can_see_stored_value(prev_mem, phase);
2634         if (prev_val != NULL && phase->eqv(prev_val, val)) {
2635           // prev_val and val might differ by a cast; it would be good
2636           // to keep the more informative of the two.
2637           result = mem;
2638         }
2639       }
2640     }
2641   }
2642 
2643   if (result != this && phase->is_IterGVN() != NULL) {
2644     MemBarNode* trailing = trailing_membar();
2645     if (trailing != NULL) {
2646 #ifdef ASSERT
2647       const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2648       assert(t_oop == NULL || t_oop->is_known_instance_field(), "only for non escaping objects");
2649 #endif
2650       PhaseIterGVN* igvn = phase->is_IterGVN();
2651       trailing->remove(igvn);
2652     }
2653   }
2654 
2655   return result;
2656 }
2657 
2658 //------------------------------match_edge-------------------------------------
2659 // Do we Match on this edge index or not?  Match only memory & value
2660 uint StoreNode::match_edge(uint idx) const {
2661   return idx == MemNode::Address || idx == MemNode::ValueIn;
2662 }
2663 
2664 //------------------------------cmp--------------------------------------------
2665 // Do not common stores up together.  They generally have to be split
2666 // back up anyways, so do not bother.
2667 bool StoreNode::cmp( const Node &n ) const {
2668   return (&n == this);          // Always fail except on self
2669 }
2670 
2671 //------------------------------Ideal_masked_input-----------------------------
2672 // Check for a useless mask before a partial-word store
2673 // (StoreB ... (AndI valIn conIa) )
2674 // If (conIa & mask == mask) this simplifies to
2675 // (StoreB ... (valIn) )
2676 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2677   Node *val = in(MemNode::ValueIn);
2678   if( val->Opcode() == Op_AndI ) {
2679     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2680     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2681       set_req(MemNode::ValueIn, val->in(1));
2682       return this;
2683     }
2684   }
2685   return NULL;
2686 }
2687 
2688 
2689 //------------------------------Ideal_sign_extended_input----------------------
2690 // Check for useless sign-extension before a partial-word store
2691 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2692 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2693 // (StoreB ... (valIn) )
2694 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2695   Node *val = in(MemNode::ValueIn);
2696   if( val->Opcode() == Op_RShiftI ) {
2697     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2698     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2699       Node *shl = val->in(1);
2700       if( shl->Opcode() == Op_LShiftI ) {
2701         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2702         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2703           set_req(MemNode::ValueIn, shl->in(1));
2704           return this;
2705         }
2706       }
2707     }
2708   }
2709   return NULL;
2710 }
2711 
2712 //------------------------------value_never_loaded-----------------------------------
2713 // Determine whether there are any possible loads of the value stored.
2714 // For simplicity, we actually check if there are any loads from the
2715 // address stored to, not just for loads of the value stored by this node.
2716 //
2717 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2718   Node *adr = in(Address);
2719   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2720   if (adr_oop == NULL)
2721     return false;
2722   if (!adr_oop->is_known_instance_field())
2723     return false; // if not a distinct instance, there may be aliases of the address
2724   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2725     Node *use = adr->fast_out(i);
2726     if (use->is_Load() || use->is_LoadStore()) {
2727       return false;
2728     }
2729   }
2730   return true;
2731 }
2732 
2733 MemBarNode* StoreNode::trailing_membar() const {
2734   if (is_release()) {
2735     MemBarNode* trailing_mb = NULL;
2736     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2737       Node* u = fast_out(i);
2738       if (u->is_MemBar()) {
2739         if (u->as_MemBar()->trailing_store()) {
2740           assert(u->Opcode() == Op_MemBarVolatile, "");
2741           assert(trailing_mb == NULL, "only one");
2742           trailing_mb = u->as_MemBar();
2743 #ifdef ASSERT
2744           Node* leading = u->as_MemBar()->leading_membar();
2745           assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2746           assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2747           assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2748 #endif
2749         } else {
2750           assert(u->as_MemBar()->standalone(), "");
2751         }
2752       }
2753     }
2754     return trailing_mb;
2755   }
2756   return NULL;
2757 }
2758 
2759 
2760 //=============================================================================
2761 //------------------------------Ideal------------------------------------------
2762 // If the store is from an AND mask that leaves the low bits untouched, then
2763 // we can skip the AND operation.  If the store is from a sign-extension
2764 // (a left shift, then right shift) we can skip both.
2765 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2766   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2767   if( progress != NULL ) return progress;
2768 
2769   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2770   if( progress != NULL ) return progress;
2771 
2772   // Finally check the default case
2773   return StoreNode::Ideal(phase, can_reshape);
2774 }
2775 
2776 //=============================================================================
2777 //------------------------------Ideal------------------------------------------
2778 // If the store is from an AND mask that leaves the low bits untouched, then
2779 // we can skip the AND operation
2780 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2781   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2782   if( progress != NULL ) return progress;
2783 
2784   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2785   if( progress != NULL ) return progress;
2786 
2787   // Finally check the default case
2788   return StoreNode::Ideal(phase, can_reshape);
2789 }
2790 
2791 //=============================================================================
2792 //------------------------------Identity---------------------------------------
2793 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2794   // No need to card mark when storing a null ptr
2795   Node* my_store = in(MemNode::OopStore);
2796   if (my_store->is_Store()) {
2797     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2798     if( t1 == TypePtr::NULL_PTR ) {
2799       return in(MemNode::Memory);
2800     }
2801   }
2802   return this;
2803 }
2804 
2805 //=============================================================================
2806 //------------------------------Ideal---------------------------------------
2807 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2808   Node* progress = StoreNode::Ideal(phase, can_reshape);
2809   if (progress != NULL) return progress;
2810 
2811   Node* my_store = in(MemNode::OopStore);
2812   if (my_store->is_MergeMem()) {
2813     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2814     set_req(MemNode::OopStore, mem);
2815     return this;
2816   }
2817 
2818   return NULL;
2819 }
2820 
2821 //------------------------------Value-----------------------------------------
2822 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
2823   // Either input is TOP ==> the result is TOP
2824   const Type *t = phase->type( in(MemNode::Memory) );
2825   if( t == Type::TOP ) return Type::TOP;
2826   t = phase->type( in(MemNode::Address) );
2827   if( t == Type::TOP ) return Type::TOP;
2828   t = phase->type( in(MemNode::ValueIn) );
2829   if( t == Type::TOP ) return Type::TOP;
2830   // If extra input is TOP ==> the result is TOP
2831   t = phase->type( in(MemNode::OopStore) );
2832   if( t == Type::TOP ) return Type::TOP;
2833 
2834   return StoreNode::Value( phase );
2835 }
2836 
2837 
2838 //=============================================================================
2839 //----------------------------------SCMemProjNode------------------------------
2840 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
2841 {
2842   return bottom_type();
2843 }
2844 
2845 //=============================================================================
2846 //----------------------------------LoadStoreNode------------------------------
2847 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2848   : Node(required),
2849     _type(rt),
2850     _adr_type(at),
2851     _barrier(0)
2852 {
2853   init_req(MemNode::Control, c  );
2854   init_req(MemNode::Memory , mem);
2855   init_req(MemNode::Address, adr);
2856   init_req(MemNode::ValueIn, val);
2857   init_class_id(Class_LoadStore);
2858 }
2859 
2860 uint LoadStoreNode::ideal_reg() const {
2861   return _type->ideal_reg();
2862 }
2863 
2864 bool LoadStoreNode::result_not_used() const {
2865   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2866     Node *x = fast_out(i);
2867     if (x->Opcode() == Op_SCMemProj) continue;
2868     return false;
2869   }
2870   return true;
2871 }
2872 
2873 MemBarNode* LoadStoreNode::trailing_membar() const {
2874   MemBarNode* trailing = NULL;
2875   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2876     Node* u = fast_out(i);
2877     if (u->is_MemBar()) {
2878       if (u->as_MemBar()->trailing_load_store()) {
2879         assert(u->Opcode() == Op_MemBarAcquire, "");
2880         assert(trailing == NULL, "only one");
2881         trailing = u->as_MemBar();
2882 #ifdef ASSERT
2883         Node* leading = trailing->leading_membar();
2884         assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2885         assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
2886         assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
2887 #endif
2888       } else {
2889         assert(u->as_MemBar()->standalone(), "wrong barrier kind");
2890       }
2891     }
2892   }
2893 
2894   return trailing;
2895 }
2896 
2897 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2898 
2899 //=============================================================================
2900 //----------------------------------LoadStoreConditionalNode--------------------
2901 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2902   init_req(ExpectedIn, ex );
2903 }
2904 
2905 //=============================================================================
2906 //-------------------------------adr_type--------------------------------------
2907 const TypePtr* ClearArrayNode::adr_type() const {
2908   Node *adr = in(3);
2909   if (adr == NULL)  return NULL; // node is dead
2910   return MemNode::calculate_adr_type(adr->bottom_type());
2911 }
2912 
2913 //------------------------------match_edge-------------------------------------
2914 // Do we Match on this edge index or not?  Do not match memory
2915 uint ClearArrayNode::match_edge(uint idx) const {
2916   return idx > 1;
2917 }
2918 
2919 //------------------------------Identity---------------------------------------
2920 // Clearing a zero length array does nothing
2921 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
2922   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2923 }
2924 
2925 //------------------------------Idealize---------------------------------------
2926 // Clearing a short array is faster with stores
2927 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2928   // Already know this is a large node, do not try to ideal it
2929   if (!IdealizeClearArrayNode || _is_large) return NULL;
2930 
2931   const int unit = BytesPerLong;
2932   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2933   if (!t)  return NULL;
2934   if (!t->is_con())  return NULL;
2935   intptr_t raw_count = t->get_con();
2936   intptr_t size = raw_count;
2937   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2938   // Clearing nothing uses the Identity call.
2939   // Negative clears are possible on dead ClearArrays
2940   // (see jck test stmt114.stmt11402.val).
2941   if (size <= 0 || size % unit != 0)  return NULL;
2942   intptr_t count = size / unit;
2943   // Length too long; communicate this to matchers and assemblers.
2944   // Assemblers are responsible to produce fast hardware clears for it.
2945   if (size > InitArrayShortSize) {
2946     return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
2947   }
2948   Node *mem = in(1);
2949   if( phase->type(mem)==Type::TOP ) return NULL;
2950   Node *adr = in(3);
2951   const Type* at = phase->type(adr);
2952   if( at==Type::TOP ) return NULL;
2953   const TypePtr* atp = at->isa_ptr();
2954   // adjust atp to be the correct array element address type
2955   if (atp == NULL)  atp = TypePtr::BOTTOM;
2956   else              atp = atp->add_offset(Type::OffsetBot);
2957   // Get base for derived pointer purposes
2958   if( adr->Opcode() != Op_AddP ) Unimplemented();
2959   Node *base = adr->in(1);
2960 
2961   Node *zero = phase->makecon(TypeLong::ZERO);
2962   Node *off  = phase->MakeConX(BytesPerLong);
2963   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2964   count--;
2965   while( count-- ) {
2966     mem = phase->transform(mem);
2967     adr = phase->transform(new AddPNode(base,adr,off));
2968     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2969   }
2970   return mem;
2971 }
2972 
2973 //----------------------------step_through----------------------------------
2974 // Return allocation input memory edge if it is different instance
2975 // or itself if it is the one we are looking for.
2976 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2977   Node* n = *np;
2978   assert(n->is_ClearArray(), "sanity");
2979   intptr_t offset;
2980   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2981   // This method is called only before Allocate nodes are expanded
2982   // during macro nodes expansion. Before that ClearArray nodes are
2983   // only generated in PhaseMacroExpand::generate_arraycopy() (before
2984   // Allocate nodes are expanded) which follows allocations.
2985   assert(alloc != NULL, "should have allocation");
2986   if (alloc->_idx == instance_id) {
2987     // Can not bypass initialization of the instance we are looking for.
2988     return false;
2989   }
2990   // Otherwise skip it.
2991   InitializeNode* init = alloc->initialization();
2992   if (init != NULL)
2993     *np = init->in(TypeFunc::Memory);
2994   else
2995     *np = alloc->in(TypeFunc::Memory);
2996   return true;
2997 }
2998 
2999 //----------------------------clear_memory-------------------------------------
3000 // Generate code to initialize object storage to zero.
3001 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3002                                    intptr_t start_offset,
3003                                    Node* end_offset,
3004                                    PhaseGVN* phase) {
3005   intptr_t offset = start_offset;
3006 
3007   int unit = BytesPerLong;
3008   if ((offset % unit) != 0) {
3009     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
3010     adr = phase->transform(adr);
3011     const TypePtr* atp = TypeRawPtr::BOTTOM;
3012     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3013     mem = phase->transform(mem);
3014     offset += BytesPerInt;
3015   }
3016   assert((offset % unit) == 0, "");
3017 
3018   // Initialize the remaining stuff, if any, with a ClearArray.
3019   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
3020 }
3021 
3022 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3023                                    Node* start_offset,
3024                                    Node* end_offset,
3025                                    PhaseGVN* phase) {
3026   if (start_offset == end_offset) {
3027     // nothing to do
3028     return mem;
3029   }
3030 
3031   int unit = BytesPerLong;
3032   Node* zbase = start_offset;
3033   Node* zend  = end_offset;
3034 
3035   // Scale to the unit required by the CPU:
3036   if (!Matcher::init_array_count_is_in_bytes) {
3037     Node* shift = phase->intcon(exact_log2(unit));
3038     zbase = phase->transform(new URShiftXNode(zbase, shift) );
3039     zend  = phase->transform(new URShiftXNode(zend,  shift) );
3040   }
3041 
3042   // Bulk clear double-words
3043   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
3044   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
3045   mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
3046   return phase->transform(mem);
3047 }
3048 
3049 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3050                                    intptr_t start_offset,
3051                                    intptr_t end_offset,
3052                                    PhaseGVN* phase) {
3053   if (start_offset == end_offset) {
3054     // nothing to do
3055     return mem;
3056   }
3057 
3058   assert((end_offset % BytesPerInt) == 0, "odd end offset");
3059   intptr_t done_offset = end_offset;
3060   if ((done_offset % BytesPerLong) != 0) {
3061     done_offset -= BytesPerInt;
3062   }
3063   if (done_offset > start_offset) {
3064     mem = clear_memory(ctl, mem, dest,
3065                        start_offset, phase->MakeConX(done_offset), phase);
3066   }
3067   if (done_offset < end_offset) { // emit the final 32-bit store
3068     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3069     adr = phase->transform(adr);
3070     const TypePtr* atp = TypeRawPtr::BOTTOM;
3071     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3072     mem = phase->transform(mem);
3073     done_offset += BytesPerInt;
3074   }
3075   assert(done_offset == end_offset, "");
3076   return mem;
3077 }
3078 
3079 //=============================================================================
3080 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3081   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
3082     _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3083 #ifdef ASSERT
3084   , _pair_idx(0)
3085 #endif
3086 {
3087   init_class_id(Class_MemBar);
3088   Node* top = C->top();
3089   init_req(TypeFunc::I_O,top);
3090   init_req(TypeFunc::FramePtr,top);
3091   init_req(TypeFunc::ReturnAdr,top);
3092   if (precedent != NULL)
3093     init_req(TypeFunc::Parms, precedent);
3094 }
3095 
3096 //------------------------------cmp--------------------------------------------
3097 uint MemBarNode::hash() const { return NO_HASH; }
3098 bool MemBarNode::cmp( const Node &n ) const {
3099   return (&n == this);          // Always fail except on self
3100 }
3101 
3102 //------------------------------make-------------------------------------------
3103 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3104   switch (opcode) {
3105   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
3106   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
3107   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
3108   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
3109   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3110   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3111   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
3112   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
3113   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
3114   case Op_Initialize:        return new InitializeNode(C, atp, pn);
3115   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
3116   default: ShouldNotReachHere(); return NULL;
3117   }
3118 }
3119 
3120 void MemBarNode::remove(PhaseIterGVN *igvn) {
3121   if (outcnt() != 2) {
3122     return;
3123   }
3124   if (trailing_store() || trailing_load_store()) {
3125     MemBarNode* leading = leading_membar();
3126     if (leading != NULL) {
3127       assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3128       leading->remove(igvn);
3129     }
3130   }
3131   igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3132   igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3133 }
3134 
3135 //------------------------------Ideal------------------------------------------
3136 // Return a node which is more "ideal" than the current node.  Strip out
3137 // control copies
3138 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3139   if (remove_dead_region(phase, can_reshape)) return this;
3140   // Don't bother trying to transform a dead node
3141   if (in(0) && in(0)->is_top()) {
3142     return NULL;
3143   }
3144 
3145   bool progress = false;
3146   // Eliminate volatile MemBars for scalar replaced objects.
3147   if (can_reshape && req() == (Precedent+1)) {
3148     bool eliminate = false;
3149     int opc = Opcode();
3150     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3151       // Volatile field loads and stores.
3152       Node* my_mem = in(MemBarNode::Precedent);
3153       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3154       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3155         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3156         // replace this Precedent (decodeN) with the Load instead.
3157         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
3158           Node* load_node = my_mem->in(1);
3159           set_req(MemBarNode::Precedent, load_node);
3160           phase->is_IterGVN()->_worklist.push(my_mem);
3161           my_mem = load_node;
3162         } else {
3163           assert(my_mem->unique_out() == this, "sanity");
3164           del_req(Precedent);
3165           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3166           my_mem = NULL;
3167         }
3168         progress = true;
3169       }
3170       if (my_mem != NULL && my_mem->is_Mem()) {
3171         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3172         // Check for scalar replaced object reference.
3173         if( t_oop != NULL && t_oop->is_known_instance_field() &&
3174             t_oop->offset() != Type::OffsetBot &&
3175             t_oop->offset() != Type::OffsetTop) {
3176           eliminate = true;
3177         }
3178       }
3179     } else if (opc == Op_MemBarRelease) {
3180       // Final field stores.
3181       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
3182       if ((alloc != NULL) && alloc->is_Allocate() &&
3183           alloc->as_Allocate()->does_not_escape_thread()) {
3184         // The allocated object does not escape.
3185         eliminate = true;
3186       }
3187     }
3188     if (eliminate) {
3189       // Replace MemBar projections by its inputs.
3190       PhaseIterGVN* igvn = phase->is_IterGVN();
3191       remove(igvn);
3192       // Must return either the original node (now dead) or a new node
3193       // (Do not return a top here, since that would break the uniqueness of top.)
3194       return new ConINode(TypeInt::ZERO);
3195     }
3196   }
3197   return progress ? this : NULL;
3198 }
3199 
3200 //------------------------------Value------------------------------------------
3201 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3202   if( !in(0) ) return Type::TOP;
3203   if( phase->type(in(0)) == Type::TOP )
3204     return Type::TOP;
3205   return TypeTuple::MEMBAR;
3206 }
3207 
3208 //------------------------------match------------------------------------------
3209 // Construct projections for memory.
3210 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3211   switch (proj->_con) {
3212   case TypeFunc::Control:
3213   case TypeFunc::Memory:
3214     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3215   }
3216   ShouldNotReachHere();
3217   return NULL;
3218 }
3219 
3220 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3221   trailing->_kind = TrailingStore;
3222   leading->_kind = LeadingStore;
3223 #ifdef ASSERT
3224   trailing->_pair_idx = leading->_idx;
3225   leading->_pair_idx = leading->_idx;
3226 #endif
3227 }
3228 
3229 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3230   trailing->_kind = TrailingLoadStore;
3231   leading->_kind = LeadingLoadStore;
3232 #ifdef ASSERT
3233   trailing->_pair_idx = leading->_idx;
3234   leading->_pair_idx = leading->_idx;
3235 #endif
3236 }
3237 
3238 MemBarNode* MemBarNode::trailing_membar() const {
3239   ResourceMark rm;
3240   Node* trailing = (Node*)this;
3241   VectorSet seen(Thread::current()->resource_area());
3242   Node_Stack multis(0);
3243   do {
3244     Node* c = trailing;
3245     uint i = 0;
3246     do {
3247       trailing = NULL;
3248       for (; i < c->outcnt(); i++) {
3249         Node* next = c->raw_out(i);
3250         if (next != c && next->is_CFG()) {
3251           if (c->is_MultiBranch()) {
3252             if (multis.node() == c) {
3253               multis.set_index(i+1);
3254             } else {
3255               multis.push(c, i+1);
3256             }
3257           }
3258           trailing = next;
3259           break;
3260         }
3261       }
3262       if (trailing != NULL && !seen.test_set(trailing->_idx)) {
3263         break;
3264       }
3265       while (multis.size() > 0) {
3266         c = multis.node();
3267         i = multis.index();
3268         if (i < c->req()) {
3269           break;
3270         }
3271         multis.pop();
3272       }
3273     } while (multis.size() > 0);
3274   } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3275 
3276   MemBarNode* mb = trailing->as_MemBar();
3277   assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3278          (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3279   assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3280   return mb;
3281 }
3282 
3283 MemBarNode* MemBarNode::leading_membar() const {
3284   ResourceMark rm;
3285   VectorSet seen(Thread::current()->resource_area());
3286   Node_Stack regions(0);
3287   Node* leading = in(0);
3288   while (leading != NULL && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3289     while (leading == NULL || leading->is_top() || seen.test_set(leading->_idx)) {
3290       leading = NULL;
3291       while (regions.size() > 0 && leading == NULL) {
3292         Node* r = regions.node();
3293         uint i = regions.index();
3294         if (i < r->req()) {
3295           leading = r->in(i);
3296           regions.set_index(i+1);
3297         } else {
3298           regions.pop();
3299         }
3300       }
3301       if (leading == NULL) {
3302         assert(regions.size() == 0, "all paths should have been tried");
3303         return NULL;
3304       }
3305     }
3306     if (leading->is_Region()) {
3307       regions.push(leading, 2);
3308       leading = leading->in(1);
3309     } else {
3310       leading = leading->in(0);
3311     }
3312   }
3313 #ifdef ASSERT
3314   Unique_Node_List wq;
3315   wq.push((Node*)this);
3316   uint found = 0;
3317   for (uint i = 0; i < wq.size(); i++) {
3318     Node* n = wq.at(i);
3319     if (n->is_Region()) {
3320       for (uint j = 1; j < n->req(); j++) {
3321         Node* in = n->in(j);
3322         if (in != NULL && !in->is_top()) {
3323           wq.push(in);
3324         }
3325       }
3326     } else {
3327       if (n->is_MemBar() && n->as_MemBar()->leading()) {
3328         assert(n == leading, "consistency check failed");
3329         found++;
3330       } else {
3331         Node* in = n->in(0);
3332         if (in != NULL && !in->is_top()) {
3333           wq.push(in);
3334         }
3335       }
3336     }
3337   }
3338   assert(found == 1 || (found == 0 && leading == NULL), "consistency check failed");
3339 #endif
3340   if (leading == NULL) {
3341     return NULL;
3342   }
3343   MemBarNode* mb = leading->as_MemBar();
3344   assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3345          (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3346   assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3347   return mb;
3348 }
3349 
3350 //===========================InitializeNode====================================
3351 // SUMMARY:
3352 // This node acts as a memory barrier on raw memory, after some raw stores.
3353 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3354 // The Initialize can 'capture' suitably constrained stores as raw inits.
3355 // It can coalesce related raw stores into larger units (called 'tiles').
3356 // It can avoid zeroing new storage for memory units which have raw inits.
3357 // At macro-expansion, it is marked 'complete', and does not optimize further.
3358 //
3359 // EXAMPLE:
3360 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3361 //   ctl = incoming control; mem* = incoming memory
3362 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3363 // First allocate uninitialized memory and fill in the header:
3364 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3365 //   ctl := alloc.Control; mem* := alloc.Memory*
3366 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3367 // Then initialize to zero the non-header parts of the raw memory block:
3368 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3369 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3370 // After the initialize node executes, the object is ready for service:
3371 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3372 // Suppose its body is immediately initialized as {1,2}:
3373 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3374 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3375 //   mem.SLICE(#short[*]) := store2
3376 //
3377 // DETAILS:
3378 // An InitializeNode collects and isolates object initialization after
3379 // an AllocateNode and before the next possible safepoint.  As a
3380 // memory barrier (MemBarNode), it keeps critical stores from drifting
3381 // down past any safepoint or any publication of the allocation.
3382 // Before this barrier, a newly-allocated object may have uninitialized bits.
3383 // After this barrier, it may be treated as a real oop, and GC is allowed.
3384 //
3385 // The semantics of the InitializeNode include an implicit zeroing of
3386 // the new object from object header to the end of the object.
3387 // (The object header and end are determined by the AllocateNode.)
3388 //
3389 // Certain stores may be added as direct inputs to the InitializeNode.
3390 // These stores must update raw memory, and they must be to addresses
3391 // derived from the raw address produced by AllocateNode, and with
3392 // a constant offset.  They must be ordered by increasing offset.
3393 // The first one is at in(RawStores), the last at in(req()-1).
3394 // Unlike most memory operations, they are not linked in a chain,
3395 // but are displayed in parallel as users of the rawmem output of
3396 // the allocation.
3397 //
3398 // (See comments in InitializeNode::capture_store, which continue
3399 // the example given above.)
3400 //
3401 // When the associated Allocate is macro-expanded, the InitializeNode
3402 // may be rewritten to optimize collected stores.  A ClearArrayNode
3403 // may also be created at that point to represent any required zeroing.
3404 // The InitializeNode is then marked 'complete', prohibiting further
3405 // capturing of nearby memory operations.
3406 //
3407 // During macro-expansion, all captured initializations which store
3408 // constant values of 32 bits or smaller are coalesced (if advantageous)
3409 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3410 // initialized in fewer memory operations.  Memory words which are
3411 // covered by neither tiles nor non-constant stores are pre-zeroed
3412 // by explicit stores of zero.  (The code shape happens to do all
3413 // zeroing first, then all other stores, with both sequences occurring
3414 // in order of ascending offsets.)
3415 //
3416 // Alternatively, code may be inserted between an AllocateNode and its
3417 // InitializeNode, to perform arbitrary initialization of the new object.
3418 // E.g., the object copying intrinsics insert complex data transfers here.
3419 // The initialization must then be marked as 'complete' disable the
3420 // built-in zeroing semantics and the collection of initializing stores.
3421 //
3422 // While an InitializeNode is incomplete, reads from the memory state
3423 // produced by it are optimizable if they match the control edge and
3424 // new oop address associated with the allocation/initialization.
3425 // They return a stored value (if the offset matches) or else zero.
3426 // A write to the memory state, if it matches control and address,
3427 // and if it is to a constant offset, may be 'captured' by the
3428 // InitializeNode.  It is cloned as a raw memory operation and rewired
3429 // inside the initialization, to the raw oop produced by the allocation.
3430 // Operations on addresses which are provably distinct (e.g., to
3431 // other AllocateNodes) are allowed to bypass the initialization.
3432 //
3433 // The effect of all this is to consolidate object initialization
3434 // (both arrays and non-arrays, both piecewise and bulk) into a
3435 // single location, where it can be optimized as a unit.
3436 //
3437 // Only stores with an offset less than TrackedInitializationLimit words
3438 // will be considered for capture by an InitializeNode.  This puts a
3439 // reasonable limit on the complexity of optimized initializations.
3440 
3441 //---------------------------InitializeNode------------------------------------
3442 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3443   : MemBarNode(C, adr_type, rawoop),
3444     _is_complete(Incomplete), _does_not_escape(false)
3445 {
3446   init_class_id(Class_Initialize);
3447 
3448   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3449   assert(in(RawAddress) == rawoop, "proper init");
3450   // Note:  allocation() can be NULL, for secondary initialization barriers
3451 }
3452 
3453 // Since this node is not matched, it will be processed by the
3454 // register allocator.  Declare that there are no constraints
3455 // on the allocation of the RawAddress edge.
3456 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3457   // This edge should be set to top, by the set_complete.  But be conservative.
3458   if (idx == InitializeNode::RawAddress)
3459     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3460   return RegMask::Empty;
3461 }
3462 
3463 Node* InitializeNode::memory(uint alias_idx) {
3464   Node* mem = in(Memory);
3465   if (mem->is_MergeMem()) {
3466     return mem->as_MergeMem()->memory_at(alias_idx);
3467   } else {
3468     // incoming raw memory is not split
3469     return mem;
3470   }
3471 }
3472 
3473 bool InitializeNode::is_non_zero() {
3474   if (is_complete())  return false;
3475   remove_extra_zeroes();
3476   return (req() > RawStores);
3477 }
3478 
3479 void InitializeNode::set_complete(PhaseGVN* phase) {
3480   assert(!is_complete(), "caller responsibility");
3481   _is_complete = Complete;
3482 
3483   // After this node is complete, it contains a bunch of
3484   // raw-memory initializations.  There is no need for
3485   // it to have anything to do with non-raw memory effects.
3486   // Therefore, tell all non-raw users to re-optimize themselves,
3487   // after skipping the memory effects of this initialization.
3488   PhaseIterGVN* igvn = phase->is_IterGVN();
3489   if (igvn)  igvn->add_users_to_worklist(this);
3490 }
3491 
3492 // convenience function
3493 // return false if the init contains any stores already
3494 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3495   InitializeNode* init = initialization();
3496   if (init == NULL || init->is_complete())  return false;
3497   init->remove_extra_zeroes();
3498   // for now, if this allocation has already collected any inits, bail:
3499   if (init->is_non_zero())  return false;
3500   init->set_complete(phase);
3501   return true;
3502 }
3503 
3504 void InitializeNode::remove_extra_zeroes() {
3505   if (req() == RawStores)  return;
3506   Node* zmem = zero_memory();
3507   uint fill = RawStores;
3508   for (uint i = fill; i < req(); i++) {
3509     Node* n = in(i);
3510     if (n->is_top() || n == zmem)  continue;  // skip
3511     if (fill < i)  set_req(fill, n);          // compact
3512     ++fill;
3513   }
3514   // delete any empty spaces created:
3515   while (fill < req()) {
3516     del_req(fill);
3517   }
3518 }
3519 
3520 // Helper for remembering which stores go with which offsets.
3521 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3522   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3523   intptr_t offset = -1;
3524   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3525                                                phase, offset);
3526   if (base == NULL)     return -1;  // something is dead,
3527   if (offset < 0)       return -1;  //        dead, dead
3528   return offset;
3529 }
3530 
3531 // Helper for proving that an initialization expression is
3532 // "simple enough" to be folded into an object initialization.
3533 // Attempts to prove that a store's initial value 'n' can be captured
3534 // within the initialization without creating a vicious cycle, such as:
3535 //     { Foo p = new Foo(); p.next = p; }
3536 // True for constants and parameters and small combinations thereof.
3537 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3538   if (n == NULL)      return true;   // (can this really happen?)
3539   if (n->is_Proj())   n = n->in(0);
3540   if (n == this)      return false;  // found a cycle
3541   if (n->is_Con())    return true;
3542   if (n->is_Start())  return true;   // params, etc., are OK
3543   if (n->is_Root())   return true;   // even better
3544 
3545   Node* ctl = n->in(0);
3546   if (ctl != NULL && !ctl->is_top()) {
3547     if (ctl->is_Proj())  ctl = ctl->in(0);
3548     if (ctl == this)  return false;
3549 
3550     // If we already know that the enclosing memory op is pinned right after
3551     // the init, then any control flow that the store has picked up
3552     // must have preceded the init, or else be equal to the init.
3553     // Even after loop optimizations (which might change control edges)
3554     // a store is never pinned *before* the availability of its inputs.
3555     if (!MemNode::all_controls_dominate(n, this))
3556       return false;                  // failed to prove a good control
3557   }
3558 
3559   // Check data edges for possible dependencies on 'this'.
3560   if ((count += 1) > 20)  return false;  // complexity limit
3561   for (uint i = 1; i < n->req(); i++) {
3562     Node* m = n->in(i);
3563     if (m == NULL || m == n || m->is_top())  continue;
3564     uint first_i = n->find_edge(m);
3565     if (i != first_i)  continue;  // process duplicate edge just once
3566     if (!detect_init_independence(m, count)) {
3567       return false;
3568     }
3569   }
3570 
3571   return true;
3572 }
3573 
3574 // Here are all the checks a Store must pass before it can be moved into
3575 // an initialization.  Returns zero if a check fails.
3576 // On success, returns the (constant) offset to which the store applies,
3577 // within the initialized memory.
3578 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3579   const int FAIL = 0;
3580   if (st->req() != MemNode::ValueIn + 1)
3581     return FAIL;                // an inscrutable StoreNode (card mark?)
3582   Node* ctl = st->in(MemNode::Control);
3583   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3584     return FAIL;                // must be unconditional after the initialization
3585   Node* mem = st->in(MemNode::Memory);
3586   if (!(mem->is_Proj() && mem->in(0) == this))
3587     return FAIL;                // must not be preceded by other stores
3588   Node* adr = st->in(MemNode::Address);
3589   intptr_t offset;
3590   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3591   if (alloc == NULL)
3592     return FAIL;                // inscrutable address
3593   if (alloc != allocation())
3594     return FAIL;                // wrong allocation!  (store needs to float up)
3595   int size_in_bytes = st->memory_size();
3596   if ((size_in_bytes != 0) && (offset % size_in_bytes) != 0) {
3597     return FAIL;                // mismatched access
3598   }
3599   Node* val = st->in(MemNode::ValueIn);
3600   int complexity_count = 0;
3601   if (!detect_init_independence(val, complexity_count))
3602     return FAIL;                // stored value must be 'simple enough'
3603 
3604   // The Store can be captured only if nothing after the allocation
3605   // and before the Store is using the memory location that the store
3606   // overwrites.
3607   bool failed = false;
3608   // If is_complete_with_arraycopy() is true the shape of the graph is
3609   // well defined and is safe so no need for extra checks.
3610   if (!is_complete_with_arraycopy()) {
3611     // We are going to look at each use of the memory state following
3612     // the allocation to make sure nothing reads the memory that the
3613     // Store writes.
3614     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3615     int alias_idx = phase->C->get_alias_index(t_adr);
3616     ResourceMark rm;
3617     Unique_Node_List mems;
3618     mems.push(mem);
3619     Node* unique_merge = NULL;
3620     for (uint next = 0; next < mems.size(); ++next) {
3621       Node *m  = mems.at(next);
3622       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3623         Node *n = m->fast_out(j);
3624         if (n->outcnt() == 0) {
3625           continue;
3626         }
3627         if (n == st) {
3628           continue;
3629         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3630           // If the control of this use is different from the control
3631           // of the Store which is right after the InitializeNode then
3632           // this node cannot be between the InitializeNode and the
3633           // Store.
3634           continue;
3635         } else if (n->is_MergeMem()) {
3636           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3637             // We can hit a MergeMemNode (that will likely go away
3638             // later) that is a direct use of the memory state
3639             // following the InitializeNode on the same slice as the
3640             // store node that we'd like to capture. We need to check
3641             // the uses of the MergeMemNode.
3642             mems.push(n);
3643           }
3644         } else if (n->is_Mem()) {
3645           Node* other_adr = n->in(MemNode::Address);
3646           if (other_adr == adr) {
3647             failed = true;
3648             break;
3649           } else {
3650             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3651             if (other_t_adr != NULL) {
3652               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3653               if (other_alias_idx == alias_idx) {
3654                 // A load from the same memory slice as the store right
3655                 // after the InitializeNode. We check the control of the
3656                 // object/array that is loaded from. If it's the same as
3657                 // the store control then we cannot capture the store.
3658                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3659                 Node* base = other_adr;
3660                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3661                 base = base->in(AddPNode::Base);
3662                 if (base != NULL) {
3663                   base = base->uncast();
3664                   if (base->is_Proj() && base->in(0) == alloc) {
3665                     failed = true;
3666                     break;
3667                   }
3668                 }
3669               }
3670             }
3671           }
3672         } else {
3673           failed = true;
3674           break;
3675         }
3676       }
3677     }
3678   }
3679   if (failed) {
3680     if (!can_reshape) {
3681       // We decided we couldn't capture the store during parsing. We
3682       // should try again during the next IGVN once the graph is
3683       // cleaner.
3684       phase->C->record_for_igvn(st);
3685     }
3686     return FAIL;
3687   }
3688 
3689   return offset;                // success
3690 }
3691 
3692 // Find the captured store in(i) which corresponds to the range
3693 // [start..start+size) in the initialized object.
3694 // If there is one, return its index i.  If there isn't, return the
3695 // negative of the index where it should be inserted.
3696 // Return 0 if the queried range overlaps an initialization boundary
3697 // or if dead code is encountered.
3698 // If size_in_bytes is zero, do not bother with overlap checks.
3699 int InitializeNode::captured_store_insertion_point(intptr_t start,
3700                                                    int size_in_bytes,
3701                                                    PhaseTransform* phase) {
3702   const int FAIL = 0, MAX_STORE = BytesPerLong;
3703 
3704   if (is_complete())
3705     return FAIL;                // arraycopy got here first; punt
3706 
3707   assert(allocation() != NULL, "must be present");
3708 
3709   // no negatives, no header fields:
3710   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3711 
3712   // after a certain size, we bail out on tracking all the stores:
3713   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3714   if (start >= ti_limit)  return FAIL;
3715 
3716   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3717     if (i >= limit)  return -(int)i; // not found; here is where to put it
3718 
3719     Node*    st     = in(i);
3720     intptr_t st_off = get_store_offset(st, phase);
3721     if (st_off < 0) {
3722       if (st != zero_memory()) {
3723         return FAIL;            // bail out if there is dead garbage
3724       }
3725     } else if (st_off > start) {
3726       // ...we are done, since stores are ordered
3727       if (st_off < start + size_in_bytes) {
3728         return FAIL;            // the next store overlaps
3729       }
3730       return -(int)i;           // not found; here is where to put it
3731     } else if (st_off < start) {
3732       if (size_in_bytes != 0 &&
3733           start < st_off + MAX_STORE &&
3734           start < st_off + st->as_Store()->memory_size()) {
3735         return FAIL;            // the previous store overlaps
3736       }
3737     } else {
3738       if (size_in_bytes != 0 &&
3739           st->as_Store()->memory_size() != size_in_bytes) {
3740         return FAIL;            // mismatched store size
3741       }
3742       return i;
3743     }
3744 
3745     ++i;
3746   }
3747 }
3748 
3749 // Look for a captured store which initializes at the offset 'start'
3750 // with the given size.  If there is no such store, and no other
3751 // initialization interferes, then return zero_memory (the memory
3752 // projection of the AllocateNode).
3753 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3754                                           PhaseTransform* phase) {
3755   assert(stores_are_sane(phase), "");
3756   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3757   if (i == 0) {
3758     return NULL;                // something is dead
3759   } else if (i < 0) {
3760     return zero_memory();       // just primordial zero bits here
3761   } else {
3762     Node* st = in(i);           // here is the store at this position
3763     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3764     return st;
3765   }
3766 }
3767 
3768 // Create, as a raw pointer, an address within my new object at 'offset'.
3769 Node* InitializeNode::make_raw_address(intptr_t offset,
3770                                        PhaseTransform* phase) {
3771   Node* addr = in(RawAddress);
3772   if (offset != 0) {
3773     Compile* C = phase->C;
3774     addr = phase->transform( new AddPNode(C->top(), addr,
3775                                                  phase->MakeConX(offset)) );
3776   }
3777   return addr;
3778 }
3779 
3780 // Clone the given store, converting it into a raw store
3781 // initializing a field or element of my new object.
3782 // Caller is responsible for retiring the original store,
3783 // with subsume_node or the like.
3784 //
3785 // From the example above InitializeNode::InitializeNode,
3786 // here are the old stores to be captured:
3787 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3788 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3789 //
3790 // Here is the changed code; note the extra edges on init:
3791 //   alloc = (Allocate ...)
3792 //   rawoop = alloc.RawAddress
3793 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3794 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3795 //   init = (Initialize alloc.Control alloc.Memory rawoop
3796 //                      rawstore1 rawstore2)
3797 //
3798 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3799                                     PhaseTransform* phase, bool can_reshape) {
3800   assert(stores_are_sane(phase), "");
3801 
3802   if (start < 0)  return NULL;
3803   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3804 
3805   Compile* C = phase->C;
3806   int size_in_bytes = st->memory_size();
3807   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3808   if (i == 0)  return NULL;     // bail out
3809   Node* prev_mem = NULL;        // raw memory for the captured store
3810   if (i > 0) {
3811     prev_mem = in(i);           // there is a pre-existing store under this one
3812     set_req(i, C->top());       // temporarily disconnect it
3813     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3814   } else {
3815     i = -i;                     // no pre-existing store
3816     prev_mem = zero_memory();   // a slice of the newly allocated object
3817     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3818       set_req(--i, C->top());   // reuse this edge; it has been folded away
3819     else
3820       ins_req(i, C->top());     // build a new edge
3821   }
3822   Node* new_st = st->clone();
3823   new_st->set_req(MemNode::Control, in(Control));
3824   new_st->set_req(MemNode::Memory,  prev_mem);
3825   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3826   new_st = phase->transform(new_st);
3827 
3828   // At this point, new_st might have swallowed a pre-existing store
3829   // at the same offset, or perhaps new_st might have disappeared,
3830   // if it redundantly stored the same value (or zero to fresh memory).
3831 
3832   // In any case, wire it in:
3833   phase->igvn_rehash_node_delayed(this);
3834   set_req(i, new_st);
3835 
3836   // The caller may now kill the old guy.
3837   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3838   assert(check_st == new_st || check_st == NULL, "must be findable");
3839   assert(!is_complete(), "");
3840   return new_st;
3841 }
3842 
3843 static bool store_constant(jlong* tiles, int num_tiles,
3844                            intptr_t st_off, int st_size,
3845                            jlong con) {
3846   if ((st_off & (st_size-1)) != 0)
3847     return false;               // strange store offset (assume size==2**N)
3848   address addr = (address)tiles + st_off;
3849   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3850   switch (st_size) {
3851   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3852   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3853   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3854   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3855   default: return false;        // strange store size (detect size!=2**N here)
3856   }
3857   return true;                  // return success to caller
3858 }
3859 
3860 // Coalesce subword constants into int constants and possibly
3861 // into long constants.  The goal, if the CPU permits,
3862 // is to initialize the object with a small number of 64-bit tiles.
3863 // Also, convert floating-point constants to bit patterns.
3864 // Non-constants are not relevant to this pass.
3865 //
3866 // In terms of the running example on InitializeNode::InitializeNode
3867 // and InitializeNode::capture_store, here is the transformation
3868 // of rawstore1 and rawstore2 into rawstore12:
3869 //   alloc = (Allocate ...)
3870 //   rawoop = alloc.RawAddress
3871 //   tile12 = 0x00010002
3872 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3873 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3874 //
3875 void
3876 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3877                                         Node* size_in_bytes,
3878                                         PhaseGVN* phase) {
3879   Compile* C = phase->C;
3880 
3881   assert(stores_are_sane(phase), "");
3882   // Note:  After this pass, they are not completely sane,
3883   // since there may be some overlaps.
3884 
3885   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3886 
3887   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3888   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3889   size_limit = MIN2(size_limit, ti_limit);
3890   size_limit = align_up(size_limit, BytesPerLong);
3891   int num_tiles = size_limit / BytesPerLong;
3892 
3893   // allocate space for the tile map:
3894   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3895   jlong  tiles_buf[small_len];
3896   Node*  nodes_buf[small_len];
3897   jlong  inits_buf[small_len];
3898   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3899                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3900   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3901                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3902   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3903                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3904   // tiles: exact bitwise model of all primitive constants
3905   // nodes: last constant-storing node subsumed into the tiles model
3906   // inits: which bytes (in each tile) are touched by any initializations
3907 
3908   //// Pass A: Fill in the tile model with any relevant stores.
3909 
3910   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3911   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3912   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3913   Node* zmem = zero_memory(); // initially zero memory state
3914   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3915     Node* st = in(i);
3916     intptr_t st_off = get_store_offset(st, phase);
3917 
3918     // Figure out the store's offset and constant value:
3919     if (st_off < header_size)             continue; //skip (ignore header)
3920     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3921     int st_size = st->as_Store()->memory_size();
3922     if (st_off + st_size > size_limit)    break;
3923 
3924     // Record which bytes are touched, whether by constant or not.
3925     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3926       continue;                 // skip (strange store size)
3927 
3928     const Type* val = phase->type(st->in(MemNode::ValueIn));
3929     if (!val->singleton())                continue; //skip (non-con store)
3930     BasicType type = val->basic_type();
3931 
3932     jlong con = 0;
3933     switch (type) {
3934     case T_INT:    con = val->is_int()->get_con();  break;
3935     case T_LONG:   con = val->is_long()->get_con(); break;
3936     case T_FLOAT:  con = jint_cast(val->getf());    break;
3937     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3938     default:                              continue; //skip (odd store type)
3939     }
3940 
3941     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3942         st->Opcode() == Op_StoreL) {
3943       continue;                 // This StoreL is already optimal.
3944     }
3945 
3946     // Store down the constant.
3947     store_constant(tiles, num_tiles, st_off, st_size, con);
3948 
3949     intptr_t j = st_off >> LogBytesPerLong;
3950 
3951     if (type == T_INT && st_size == BytesPerInt
3952         && (st_off & BytesPerInt) == BytesPerInt) {
3953       jlong lcon = tiles[j];
3954       if (!Matcher::isSimpleConstant64(lcon) &&
3955           st->Opcode() == Op_StoreI) {
3956         // This StoreI is already optimal by itself.
3957         jint* intcon = (jint*) &tiles[j];
3958         intcon[1] = 0;  // undo the store_constant()
3959 
3960         // If the previous store is also optimal by itself, back up and
3961         // undo the action of the previous loop iteration... if we can.
3962         // But if we can't, just let the previous half take care of itself.
3963         st = nodes[j];
3964         st_off -= BytesPerInt;
3965         con = intcon[0];
3966         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3967           assert(st_off >= header_size, "still ignoring header");
3968           assert(get_store_offset(st, phase) == st_off, "must be");
3969           assert(in(i-1) == zmem, "must be");
3970           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3971           assert(con == tcon->is_int()->get_con(), "must be");
3972           // Undo the effects of the previous loop trip, which swallowed st:
3973           intcon[0] = 0;        // undo store_constant()
3974           set_req(i-1, st);     // undo set_req(i, zmem)
3975           nodes[j] = NULL;      // undo nodes[j] = st
3976           --old_subword;        // undo ++old_subword
3977         }
3978         continue;               // This StoreI is already optimal.
3979       }
3980     }
3981 
3982     // This store is not needed.
3983     set_req(i, zmem);
3984     nodes[j] = st;              // record for the moment
3985     if (st_size < BytesPerLong) // something has changed
3986           ++old_subword;        // includes int/float, but who's counting...
3987     else  ++old_long;
3988   }
3989 
3990   if ((old_subword + old_long) == 0)
3991     return;                     // nothing more to do
3992 
3993   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3994   // Be sure to insert them before overlapping non-constant stores.
3995   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3996   for (int j = 0; j < num_tiles; j++) {
3997     jlong con  = tiles[j];
3998     jlong init = inits[j];
3999     if (con == 0)  continue;
4000     jint con0,  con1;           // split the constant, address-wise
4001     jint init0, init1;          // split the init map, address-wise
4002     { union { jlong con; jint intcon[2]; } u;
4003       u.con = con;
4004       con0  = u.intcon[0];
4005       con1  = u.intcon[1];
4006       u.con = init;
4007       init0 = u.intcon[0];
4008       init1 = u.intcon[1];
4009     }
4010 
4011     Node* old = nodes[j];
4012     assert(old != NULL, "need the prior store");
4013     intptr_t offset = (j * BytesPerLong);
4014 
4015     bool split = !Matcher::isSimpleConstant64(con);
4016 
4017     if (offset < header_size) {
4018       assert(offset + BytesPerInt >= header_size, "second int counts");
4019       assert(*(jint*)&tiles[j] == 0, "junk in header");
4020       split = true;             // only the second word counts
4021       // Example:  int a[] = { 42 ... }
4022     } else if (con0 == 0 && init0 == -1) {
4023       split = true;             // first word is covered by full inits
4024       // Example:  int a[] = { ... foo(), 42 ... }
4025     } else if (con1 == 0 && init1 == -1) {
4026       split = true;             // second word is covered by full inits
4027       // Example:  int a[] = { ... 42, foo() ... }
4028     }
4029 
4030     // Here's a case where init0 is neither 0 nor -1:
4031     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
4032     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
4033     // In this case the tile is not split; it is (jlong)42.
4034     // The big tile is stored down, and then the foo() value is inserted.
4035     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
4036 
4037     Node* ctl = old->in(MemNode::Control);
4038     Node* adr = make_raw_address(offset, phase);
4039     const TypePtr* atp = TypeRawPtr::BOTTOM;
4040 
4041     // One or two coalesced stores to plop down.
4042     Node*    st[2];
4043     intptr_t off[2];
4044     int  nst = 0;
4045     if (!split) {
4046       ++new_long;
4047       off[nst] = offset;
4048       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4049                                   phase->longcon(con), T_LONG, MemNode::unordered);
4050     } else {
4051       // Omit either if it is a zero.
4052       if (con0 != 0) {
4053         ++new_int;
4054         off[nst]  = offset;
4055         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4056                                     phase->intcon(con0), T_INT, MemNode::unordered);
4057       }
4058       if (con1 != 0) {
4059         ++new_int;
4060         offset += BytesPerInt;
4061         adr = make_raw_address(offset, phase);
4062         off[nst]  = offset;
4063         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4064                                     phase->intcon(con1), T_INT, MemNode::unordered);
4065       }
4066     }
4067 
4068     // Insert second store first, then the first before the second.
4069     // Insert each one just before any overlapping non-constant stores.
4070     while (nst > 0) {
4071       Node* st1 = st[--nst];
4072       C->copy_node_notes_to(st1, old);
4073       st1 = phase->transform(st1);
4074       offset = off[nst];
4075       assert(offset >= header_size, "do not smash header");
4076       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4077       guarantee(ins_idx != 0, "must re-insert constant store");
4078       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
4079       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4080         set_req(--ins_idx, st1);
4081       else
4082         ins_req(ins_idx, st1);
4083     }
4084   }
4085 
4086   if (PrintCompilation && WizardMode)
4087     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4088                   old_subword, old_long, new_int, new_long);
4089   if (C->log() != NULL)
4090     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4091                    old_subword, old_long, new_int, new_long);
4092 
4093   // Clean up any remaining occurrences of zmem:
4094   remove_extra_zeroes();
4095 }
4096 
4097 // Explore forward from in(start) to find the first fully initialized
4098 // word, and return its offset.  Skip groups of subword stores which
4099 // together initialize full words.  If in(start) is itself part of a
4100 // fully initialized word, return the offset of in(start).  If there
4101 // are no following full-word stores, or if something is fishy, return
4102 // a negative value.
4103 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4104   int       int_map = 0;
4105   intptr_t  int_map_off = 0;
4106   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
4107 
4108   for (uint i = start, limit = req(); i < limit; i++) {
4109     Node* st = in(i);
4110 
4111     intptr_t st_off = get_store_offset(st, phase);
4112     if (st_off < 0)  break;  // return conservative answer
4113 
4114     int st_size = st->as_Store()->memory_size();
4115     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4116       return st_off;            // we found a complete word init
4117     }
4118 
4119     // update the map:
4120 
4121     intptr_t this_int_off = align_down(st_off, BytesPerInt);
4122     if (this_int_off != int_map_off) {
4123       // reset the map:
4124       int_map = 0;
4125       int_map_off = this_int_off;
4126     }
4127 
4128     int subword_off = st_off - this_int_off;
4129     int_map |= right_n_bits(st_size) << subword_off;
4130     if ((int_map & FULL_MAP) == FULL_MAP) {
4131       return this_int_off;      // we found a complete word init
4132     }
4133 
4134     // Did this store hit or cross the word boundary?
4135     intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4136     if (next_int_off == this_int_off + BytesPerInt) {
4137       // We passed the current int, without fully initializing it.
4138       int_map_off = next_int_off;
4139       int_map >>= BytesPerInt;
4140     } else if (next_int_off > this_int_off + BytesPerInt) {
4141       // We passed the current and next int.
4142       return this_int_off + BytesPerInt;
4143     }
4144   }
4145 
4146   return -1;
4147 }
4148 
4149 
4150 // Called when the associated AllocateNode is expanded into CFG.
4151 // At this point, we may perform additional optimizations.
4152 // Linearize the stores by ascending offset, to make memory
4153 // activity as coherent as possible.
4154 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4155                                       intptr_t header_size,
4156                                       Node* size_in_bytes,
4157                                       PhaseGVN* phase) {
4158   assert(!is_complete(), "not already complete");
4159   assert(stores_are_sane(phase), "");
4160   assert(allocation() != NULL, "must be present");
4161 
4162   remove_extra_zeroes();
4163 
4164   if (ReduceFieldZeroing || ReduceBulkZeroing)
4165     // reduce instruction count for common initialization patterns
4166     coalesce_subword_stores(header_size, size_in_bytes, phase);
4167 
4168   Node* zmem = zero_memory();   // initially zero memory state
4169   Node* inits = zmem;           // accumulating a linearized chain of inits
4170   #ifdef ASSERT
4171   intptr_t first_offset = allocation()->minimum_header_size();
4172   intptr_t last_init_off = first_offset;  // previous init offset
4173   intptr_t last_init_end = first_offset;  // previous init offset+size
4174   intptr_t last_tile_end = first_offset;  // previous tile offset+size
4175   #endif
4176   intptr_t zeroes_done = header_size;
4177 
4178   bool do_zeroing = true;       // we might give up if inits are very sparse
4179   int  big_init_gaps = 0;       // how many large gaps have we seen?
4180 
4181   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
4182   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
4183 
4184   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4185     Node* st = in(i);
4186     intptr_t st_off = get_store_offset(st, phase);
4187     if (st_off < 0)
4188       break;                    // unknown junk in the inits
4189     if (st->in(MemNode::Memory) != zmem)
4190       break;                    // complicated store chains somehow in list
4191 
4192     int st_size = st->as_Store()->memory_size();
4193     intptr_t next_init_off = st_off + st_size;
4194 
4195     if (do_zeroing && zeroes_done < next_init_off) {
4196       // See if this store needs a zero before it or under it.
4197       intptr_t zeroes_needed = st_off;
4198 
4199       if (st_size < BytesPerInt) {
4200         // Look for subword stores which only partially initialize words.
4201         // If we find some, we must lay down some word-level zeroes first,
4202         // underneath the subword stores.
4203         //
4204         // Examples:
4205         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
4206         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
4207         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
4208         //
4209         // Note:  coalesce_subword_stores may have already done this,
4210         // if it was prompted by constant non-zero subword initializers.
4211         // But this case can still arise with non-constant stores.
4212 
4213         intptr_t next_full_store = find_next_fullword_store(i, phase);
4214 
4215         // In the examples above:
4216         //   in(i)          p   q   r   s     x   y     z
4217         //   st_off        12  13  14  15    12  13    14
4218         //   st_size        1   1   1   1     1   1     1
4219         //   next_full_s.  12  16  16  16    16  16    16
4220         //   z's_done      12  16  16  16    12  16    12
4221         //   z's_needed    12  16  16  16    16  16    16
4222         //   zsize          0   0   0   0     4   0     4
4223         if (next_full_store < 0) {
4224           // Conservative tack:  Zero to end of current word.
4225           zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4226         } else {
4227           // Zero to beginning of next fully initialized word.
4228           // Or, don't zero at all, if we are already in that word.
4229           assert(next_full_store >= zeroes_needed, "must go forward");
4230           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4231           zeroes_needed = next_full_store;
4232         }
4233       }
4234 
4235       if (zeroes_needed > zeroes_done) {
4236         intptr_t zsize = zeroes_needed - zeroes_done;
4237         // Do some incremental zeroing on rawmem, in parallel with inits.
4238         zeroes_done = align_down(zeroes_done, BytesPerInt);
4239         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4240                                               zeroes_done, zeroes_needed,
4241                                               phase);
4242         zeroes_done = zeroes_needed;
4243         if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4244           do_zeroing = false;   // leave the hole, next time
4245       }
4246     }
4247 
4248     // Collect the store and move on:
4249     st->set_req(MemNode::Memory, inits);
4250     inits = st;                 // put it on the linearized chain
4251     set_req(i, zmem);           // unhook from previous position
4252 
4253     if (zeroes_done == st_off)
4254       zeroes_done = next_init_off;
4255 
4256     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4257 
4258     #ifdef ASSERT
4259     // Various order invariants.  Weaker than stores_are_sane because
4260     // a large constant tile can be filled in by smaller non-constant stores.
4261     assert(st_off >= last_init_off, "inits do not reverse");
4262     last_init_off = st_off;
4263     const Type* val = NULL;
4264     if (st_size >= BytesPerInt &&
4265         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4266         (int)val->basic_type() < (int)T_OBJECT) {
4267       assert(st_off >= last_tile_end, "tiles do not overlap");
4268       assert(st_off >= last_init_end, "tiles do not overwrite inits");
4269       last_tile_end = MAX2(last_tile_end, next_init_off);
4270     } else {
4271       intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4272       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4273       assert(st_off      >= last_init_end, "inits do not overlap");
4274       last_init_end = next_init_off;  // it's a non-tile
4275     }
4276     #endif //ASSERT
4277   }
4278 
4279   remove_extra_zeroes();        // clear out all the zmems left over
4280   add_req(inits);
4281 
4282   if (!(UseTLAB && ZeroTLAB)) {
4283     // If anything remains to be zeroed, zero it all now.
4284     zeroes_done = align_down(zeroes_done, BytesPerInt);
4285     // if it is the last unused 4 bytes of an instance, forget about it
4286     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4287     if (zeroes_done + BytesPerLong >= size_limit) {
4288       AllocateNode* alloc = allocation();
4289       assert(alloc != NULL, "must be present");
4290       if (alloc != NULL && alloc->Opcode() == Op_Allocate) {
4291         Node* klass_node = alloc->in(AllocateNode::KlassNode);
4292         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
4293         if (zeroes_done == k->layout_helper())
4294           zeroes_done = size_limit;
4295       }
4296     }
4297     if (zeroes_done < size_limit) {
4298       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4299                                             zeroes_done, size_in_bytes, phase);
4300     }
4301   }
4302 
4303   set_complete(phase);
4304   return rawmem;
4305 }
4306 
4307 
4308 #ifdef ASSERT
4309 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
4310   if (is_complete())
4311     return true;                // stores could be anything at this point
4312   assert(allocation() != NULL, "must be present");
4313   intptr_t last_off = allocation()->minimum_header_size();
4314   for (uint i = InitializeNode::RawStores; i < req(); i++) {
4315     Node* st = in(i);
4316     intptr_t st_off = get_store_offset(st, phase);
4317     if (st_off < 0)  continue;  // ignore dead garbage
4318     if (last_off > st_off) {
4319       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4320       this->dump(2);
4321       assert(false, "ascending store offsets");
4322       return false;
4323     }
4324     last_off = st_off + st->as_Store()->memory_size();
4325   }
4326   return true;
4327 }
4328 #endif //ASSERT
4329 
4330 
4331 
4332 
4333 //============================MergeMemNode=====================================
4334 //
4335 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4336 // contributing store or call operations.  Each contributor provides the memory
4337 // state for a particular "alias type" (see Compile::alias_type).  For example,
4338 // if a MergeMem has an input X for alias category #6, then any memory reference
4339 // to alias category #6 may use X as its memory state input, as an exact equivalent
4340 // to using the MergeMem as a whole.
4341 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4342 //
4343 // (Here, the <N> notation gives the index of the relevant adr_type.)
4344 //
4345 // In one special case (and more cases in the future), alias categories overlap.
4346 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4347 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4348 // it is exactly equivalent to that state W:
4349 //   MergeMem(<Bot>: W) <==> W
4350 //
4351 // Usually, the merge has more than one input.  In that case, where inputs
4352 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4353 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4354 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4355 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4356 //
4357 // A merge can take a "wide" memory state as one of its narrow inputs.
4358 // This simply means that the merge observes out only the relevant parts of
4359 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4360 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4361 //
4362 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4363 // and that memory slices "leak through":
4364 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4365 //
4366 // But, in such a cascade, repeated memory slices can "block the leak":
4367 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4368 //
4369 // In the last example, Y is not part of the combined memory state of the
4370 // outermost MergeMem.  The system must, of course, prevent unschedulable
4371 // memory states from arising, so you can be sure that the state Y is somehow
4372 // a precursor to state Y'.
4373 //
4374 //
4375 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4376 // of each MergeMemNode array are exactly the numerical alias indexes, including
4377 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4378 // Compile::alias_type (and kin) produce and manage these indexes.
4379 //
4380 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4381 // (Note that this provides quick access to the top node inside MergeMem methods,
4382 // without the need to reach out via TLS to Compile::current.)
4383 //
4384 // As a consequence of what was just described, a MergeMem that represents a full
4385 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4386 // containing all alias categories.
4387 //
4388 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4389 //
4390 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4391 // a memory state for the alias type <N>, or else the top node, meaning that
4392 // there is no particular input for that alias type.  Note that the length of
4393 // a MergeMem is variable, and may be extended at any time to accommodate new
4394 // memory states at larger alias indexes.  When merges grow, they are of course
4395 // filled with "top" in the unused in() positions.
4396 //
4397 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4398 // (Top was chosen because it works smoothly with passes like GCM.)
4399 //
4400 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4401 // the type of random VM bits like TLS references.)  Since it is always the
4402 // first non-Bot memory slice, some low-level loops use it to initialize an
4403 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4404 //
4405 //
4406 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4407 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4408 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4409 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4410 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4411 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4412 //
4413 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4414 // really that different from the other memory inputs.  An abbreviation called
4415 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4416 //
4417 //
4418 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4419 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4420 // that "emerges though" the base memory will be marked as excluding the alias types
4421 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4422 //
4423 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4424 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4425 //
4426 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4427 // (It is currently unimplemented.)  As you can see, the resulting merge is
4428 // actually a disjoint union of memory states, rather than an overlay.
4429 //
4430 
4431 //------------------------------MergeMemNode-----------------------------------
4432 Node* MergeMemNode::make_empty_memory() {
4433   Node* empty_memory = (Node*) Compile::current()->top();
4434   assert(empty_memory->is_top(), "correct sentinel identity");
4435   return empty_memory;
4436 }
4437 
4438 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4439   init_class_id(Class_MergeMem);
4440   // all inputs are nullified in Node::Node(int)
4441   // set_input(0, NULL);  // no control input
4442 
4443   // Initialize the edges uniformly to top, for starters.
4444   Node* empty_mem = make_empty_memory();
4445   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4446     init_req(i,empty_mem);
4447   }
4448   assert(empty_memory() == empty_mem, "");
4449 
4450   if( new_base != NULL && new_base->is_MergeMem() ) {
4451     MergeMemNode* mdef = new_base->as_MergeMem();
4452     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4453     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4454       mms.set_memory(mms.memory2());
4455     }
4456     assert(base_memory() == mdef->base_memory(), "");
4457   } else {
4458     set_base_memory(new_base);
4459   }
4460 }
4461 
4462 // Make a new, untransformed MergeMem with the same base as 'mem'.
4463 // If mem is itself a MergeMem, populate the result with the same edges.
4464 MergeMemNode* MergeMemNode::make(Node* mem) {
4465   return new MergeMemNode(mem);
4466 }
4467 
4468 //------------------------------cmp--------------------------------------------
4469 uint MergeMemNode::hash() const { return NO_HASH; }
4470 bool MergeMemNode::cmp( const Node &n ) const {
4471   return (&n == this);          // Always fail except on self
4472 }
4473 
4474 //------------------------------Identity---------------------------------------
4475 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4476   // Identity if this merge point does not record any interesting memory
4477   // disambiguations.
4478   Node* base_mem = base_memory();
4479   Node* empty_mem = empty_memory();
4480   if (base_mem != empty_mem) {  // Memory path is not dead?
4481     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4482       Node* mem = in(i);
4483       if (mem != empty_mem && mem != base_mem) {
4484         return this;            // Many memory splits; no change
4485       }
4486     }
4487   }
4488   return base_mem;              // No memory splits; ID on the one true input
4489 }
4490 
4491 //------------------------------Ideal------------------------------------------
4492 // This method is invoked recursively on chains of MergeMem nodes
4493 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4494   // Remove chain'd MergeMems
4495   //
4496   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4497   // relative to the "in(Bot)".  Since we are patching both at the same time,
4498   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4499   // but rewrite each "in(i)" relative to the new "in(Bot)".
4500   Node *progress = NULL;
4501 
4502 
4503   Node* old_base = base_memory();
4504   Node* empty_mem = empty_memory();
4505   if (old_base == empty_mem)
4506     return NULL; // Dead memory path.
4507 
4508   MergeMemNode* old_mbase;
4509   if (old_base != NULL && old_base->is_MergeMem())
4510     old_mbase = old_base->as_MergeMem();
4511   else
4512     old_mbase = NULL;
4513   Node* new_base = old_base;
4514 
4515   // simplify stacked MergeMems in base memory
4516   if (old_mbase)  new_base = old_mbase->base_memory();
4517 
4518   // the base memory might contribute new slices beyond my req()
4519   if (old_mbase)  grow_to_match(old_mbase);
4520 
4521   // Look carefully at the base node if it is a phi.
4522   PhiNode* phi_base;
4523   if (new_base != NULL && new_base->is_Phi())
4524     phi_base = new_base->as_Phi();
4525   else
4526     phi_base = NULL;
4527 
4528   Node*    phi_reg = NULL;
4529   uint     phi_len = (uint)-1;
4530   if (phi_base != NULL && !phi_base->is_copy()) {
4531     // do not examine phi if degraded to a copy
4532     phi_reg = phi_base->region();
4533     phi_len = phi_base->req();
4534     // see if the phi is unfinished
4535     for (uint i = 1; i < phi_len; i++) {
4536       if (phi_base->in(i) == NULL) {
4537         // incomplete phi; do not look at it yet!
4538         phi_reg = NULL;
4539         phi_len = (uint)-1;
4540         break;
4541       }
4542     }
4543   }
4544 
4545   // Note:  We do not call verify_sparse on entry, because inputs
4546   // can normalize to the base_memory via subsume_node or similar
4547   // mechanisms.  This method repairs that damage.
4548 
4549   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4550 
4551   // Look at each slice.
4552   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4553     Node* old_in = in(i);
4554     // calculate the old memory value
4555     Node* old_mem = old_in;
4556     if (old_mem == empty_mem)  old_mem = old_base;
4557     assert(old_mem == memory_at(i), "");
4558 
4559     // maybe update (reslice) the old memory value
4560 
4561     // simplify stacked MergeMems
4562     Node* new_mem = old_mem;
4563     MergeMemNode* old_mmem;
4564     if (old_mem != NULL && old_mem->is_MergeMem())
4565       old_mmem = old_mem->as_MergeMem();
4566     else
4567       old_mmem = NULL;
4568     if (old_mmem == this) {
4569       // This can happen if loops break up and safepoints disappear.
4570       // A merge of BotPtr (default) with a RawPtr memory derived from a
4571       // safepoint can be rewritten to a merge of the same BotPtr with
4572       // the BotPtr phi coming into the loop.  If that phi disappears
4573       // also, we can end up with a self-loop of the mergemem.
4574       // In general, if loops degenerate and memory effects disappear,
4575       // a mergemem can be left looking at itself.  This simply means
4576       // that the mergemem's default should be used, since there is
4577       // no longer any apparent effect on this slice.
4578       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4579       //       from start.  Update the input to TOP.
4580       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4581     }
4582     else if (old_mmem != NULL) {
4583       new_mem = old_mmem->memory_at(i);
4584     }
4585     // else preceding memory was not a MergeMem
4586 
4587     // replace equivalent phis (unfortunately, they do not GVN together)
4588     if (new_mem != NULL && new_mem != new_base &&
4589         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4590       if (new_mem->is_Phi()) {
4591         PhiNode* phi_mem = new_mem->as_Phi();
4592         for (uint i = 1; i < phi_len; i++) {
4593           if (phi_base->in(i) != phi_mem->in(i)) {
4594             phi_mem = NULL;
4595             break;
4596           }
4597         }
4598         if (phi_mem != NULL) {
4599           // equivalent phi nodes; revert to the def
4600           new_mem = new_base;
4601         }
4602       }
4603     }
4604 
4605     // maybe store down a new value
4606     Node* new_in = new_mem;
4607     if (new_in == new_base)  new_in = empty_mem;
4608 
4609     if (new_in != old_in) {
4610       // Warning:  Do not combine this "if" with the previous "if"
4611       // A memory slice might have be be rewritten even if it is semantically
4612       // unchanged, if the base_memory value has changed.
4613       set_req(i, new_in);
4614       progress = this;          // Report progress
4615     }
4616   }
4617 
4618   if (new_base != old_base) {
4619     set_req(Compile::AliasIdxBot, new_base);
4620     // Don't use set_base_memory(new_base), because we need to update du.
4621     assert(base_memory() == new_base, "");
4622     progress = this;
4623   }
4624 
4625   if( base_memory() == this ) {
4626     // a self cycle indicates this memory path is dead
4627     set_req(Compile::AliasIdxBot, empty_mem);
4628   }
4629 
4630   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4631   // Recursion must occur after the self cycle check above
4632   if( base_memory()->is_MergeMem() ) {
4633     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4634     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4635     if( m != NULL &&
4636         (m->is_top() ||
4637          (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4638       // propagate rollup of dead cycle to self
4639       set_req(Compile::AliasIdxBot, empty_mem);
4640     }
4641   }
4642 
4643   if( base_memory() == empty_mem ) {
4644     progress = this;
4645     // Cut inputs during Parse phase only.
4646     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4647     if( !can_reshape ) {
4648       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4649         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4650       }
4651     }
4652   }
4653 
4654   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4655     // Check if PhiNode::Ideal's "Split phis through memory merges"
4656     // transform should be attempted. Look for this->phi->this cycle.
4657     uint merge_width = req();
4658     if (merge_width > Compile::AliasIdxRaw) {
4659       PhiNode* phi = base_memory()->as_Phi();
4660       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4661         if (phi->in(i) == this) {
4662           phase->is_IterGVN()->_worklist.push(phi);
4663           break;
4664         }
4665       }
4666     }
4667   }
4668 
4669   assert(progress || verify_sparse(), "please, no dups of base");
4670   return progress;
4671 }
4672 
4673 //-------------------------set_base_memory-------------------------------------
4674 void MergeMemNode::set_base_memory(Node *new_base) {
4675   Node* empty_mem = empty_memory();
4676   set_req(Compile::AliasIdxBot, new_base);
4677   assert(memory_at(req()) == new_base, "must set default memory");
4678   // Clear out other occurrences of new_base:
4679   if (new_base != empty_mem) {
4680     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4681       if (in(i) == new_base)  set_req(i, empty_mem);
4682     }
4683   }
4684 }
4685 
4686 //------------------------------out_RegMask------------------------------------
4687 const RegMask &MergeMemNode::out_RegMask() const {
4688   return RegMask::Empty;
4689 }
4690 
4691 //------------------------------dump_spec--------------------------------------
4692 #ifndef PRODUCT
4693 void MergeMemNode::dump_spec(outputStream *st) const {
4694   st->print(" {");
4695   Node* base_mem = base_memory();
4696   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4697     Node* mem = (in(i) != NULL) ? memory_at(i) : base_mem;
4698     if (mem == base_mem) { st->print(" -"); continue; }
4699     st->print( " N%d:", mem->_idx );
4700     Compile::current()->get_adr_type(i)->dump_on(st);
4701   }
4702   st->print(" }");
4703 }
4704 #endif // !PRODUCT
4705 
4706 
4707 #ifdef ASSERT
4708 static bool might_be_same(Node* a, Node* b) {
4709   if (a == b)  return true;
4710   if (!(a->is_Phi() || b->is_Phi()))  return false;
4711   // phis shift around during optimization
4712   return true;  // pretty stupid...
4713 }
4714 
4715 // verify a narrow slice (either incoming or outgoing)
4716 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4717   if (!VerifyAliases)                return;  // don't bother to verify unless requested
4718   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
4719   if (Node::in_dump())               return;  // muzzle asserts when printing
4720   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4721   assert(n != NULL, "");
4722   // Elide intervening MergeMem's
4723   while (n->is_MergeMem()) {
4724     n = n->as_MergeMem()->memory_at(alias_idx);
4725   }
4726   Compile* C = Compile::current();
4727   const TypePtr* n_adr_type = n->adr_type();
4728   if (n == m->empty_memory()) {
4729     // Implicit copy of base_memory()
4730   } else if (n_adr_type != TypePtr::BOTTOM) {
4731     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4732     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4733   } else {
4734     // A few places like make_runtime_call "know" that VM calls are narrow,
4735     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4736     bool expected_wide_mem = false;
4737     if (n == m->base_memory()) {
4738       expected_wide_mem = true;
4739     } else if (alias_idx == Compile::AliasIdxRaw ||
4740                n == m->memory_at(Compile::AliasIdxRaw)) {
4741       expected_wide_mem = true;
4742     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4743       // memory can "leak through" calls on channels that
4744       // are write-once.  Allow this also.
4745       expected_wide_mem = true;
4746     }
4747     assert(expected_wide_mem, "expected narrow slice replacement");
4748   }
4749 }
4750 #else // !ASSERT
4751 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4752 #endif
4753 
4754 
4755 //-----------------------------memory_at---------------------------------------
4756 Node* MergeMemNode::memory_at(uint alias_idx) const {
4757   assert(alias_idx >= Compile::AliasIdxRaw ||
4758          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4759          "must avoid base_memory and AliasIdxTop");
4760 
4761   // Otherwise, it is a narrow slice.
4762   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4763   Compile *C = Compile::current();
4764   if (is_empty_memory(n)) {
4765     // the array is sparse; empty slots are the "top" node
4766     n = base_memory();
4767     assert(Node::in_dump()
4768            || n == NULL || n->bottom_type() == Type::TOP
4769            || n->adr_type() == NULL // address is TOP
4770            || n->adr_type() == TypePtr::BOTTOM
4771            || n->adr_type() == TypeRawPtr::BOTTOM
4772            || Compile::current()->AliasLevel() == 0,
4773            "must be a wide memory");
4774     // AliasLevel == 0 if we are organizing the memory states manually.
4775     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4776   } else {
4777     // make sure the stored slice is sane
4778     #ifdef ASSERT
4779     if (VMError::is_error_reported() || Node::in_dump()) {
4780     } else if (might_be_same(n, base_memory())) {
4781       // Give it a pass:  It is a mostly harmless repetition of the base.
4782       // This can arise normally from node subsumption during optimization.
4783     } else {
4784       verify_memory_slice(this, alias_idx, n);
4785     }
4786     #endif
4787   }
4788   return n;
4789 }
4790 
4791 //---------------------------set_memory_at-------------------------------------
4792 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4793   verify_memory_slice(this, alias_idx, n);
4794   Node* empty_mem = empty_memory();
4795   if (n == base_memory())  n = empty_mem;  // collapse default
4796   uint need_req = alias_idx+1;
4797   if (req() < need_req) {
4798     if (n == empty_mem)  return;  // already the default, so do not grow me
4799     // grow the sparse array
4800     do {
4801       add_req(empty_mem);
4802     } while (req() < need_req);
4803   }
4804   set_req( alias_idx, n );
4805 }
4806 
4807 
4808 
4809 //--------------------------iteration_setup------------------------------------
4810 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4811   if (other != NULL) {
4812     grow_to_match(other);
4813     // invariant:  the finite support of mm2 is within mm->req()
4814     #ifdef ASSERT
4815     for (uint i = req(); i < other->req(); i++) {
4816       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4817     }
4818     #endif
4819   }
4820   // Replace spurious copies of base_memory by top.
4821   Node* base_mem = base_memory();
4822   if (base_mem != NULL && !base_mem->is_top()) {
4823     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4824       if (in(i) == base_mem)
4825         set_req(i, empty_memory());
4826     }
4827   }
4828 }
4829 
4830 //---------------------------grow_to_match-------------------------------------
4831 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4832   Node* empty_mem = empty_memory();
4833   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4834   // look for the finite support of the other memory
4835   for (uint i = other->req(); --i >= req(); ) {
4836     if (other->in(i) != empty_mem) {
4837       uint new_len = i+1;
4838       while (req() < new_len)  add_req(empty_mem);
4839       break;
4840     }
4841   }
4842 }
4843 
4844 //---------------------------verify_sparse-------------------------------------
4845 #ifndef PRODUCT
4846 bool MergeMemNode::verify_sparse() const {
4847   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4848   Node* base_mem = base_memory();
4849   // The following can happen in degenerate cases, since empty==top.
4850   if (is_empty_memory(base_mem))  return true;
4851   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4852     assert(in(i) != NULL, "sane slice");
4853     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4854   }
4855   return true;
4856 }
4857 
4858 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4859   Node* n;
4860   n = mm->in(idx);
4861   if (mem == n)  return true;  // might be empty_memory()
4862   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4863   if (mem == n)  return true;
4864   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4865     if (mem == n)  return true;
4866     if (n == NULL)  break;
4867   }
4868   return false;
4869 }
4870 #endif // !PRODUCT