1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "memory/allocation.inline.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "oops/objArrayKlass.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/arraycopynode.hpp"
  35 #include "opto/cfgnode.hpp"
  36 #include "opto/compile.hpp"
  37 #include "opto/connode.hpp"
  38 #include "opto/convertnode.hpp"
  39 #include "opto/loopnode.hpp"
  40 #include "opto/machnode.hpp"
  41 #include "opto/matcher.hpp"
  42 #include "opto/memnode.hpp"
  43 #include "opto/mulnode.hpp"
  44 #include "opto/narrowptrnode.hpp"
  45 #include "opto/phaseX.hpp"
  46 #include "opto/regmask.hpp"
  47 #include "utilities/align.hpp"
  48 #include "utilities/copy.hpp"
  49 #include "utilities/macros.hpp"
  50 #include "utilities/vmError.hpp"
  51 #if INCLUDE_ZGC
  52 #include "gc/z/c2/zBarrierSetC2.hpp"
  53 #endif
  54 
  55 // Portions of code courtesy of Clifford Click
  56 
  57 // Optimization - Graph Style
  58 
  59 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  60 
  61 //=============================================================================
  62 uint MemNode::size_of() const { return sizeof(*this); }
  63 
  64 const TypePtr *MemNode::adr_type() const {
  65   Node* adr = in(Address);
  66   if (adr == NULL)  return NULL; // node is dead
  67   const TypePtr* cross_check = NULL;
  68   DEBUG_ONLY(cross_check = _adr_type);
  69   return calculate_adr_type(adr->bottom_type(), cross_check);
  70 }
  71 
  72 bool MemNode::check_if_adr_maybe_raw(Node* adr) {
  73   if (adr != NULL) {
  74     if (adr->bottom_type()->base() == Type::RawPtr || adr->bottom_type()->base() == Type::AnyPtr) {
  75       return true;
  76     }
  77   }
  78   return false;
  79 }
  80 
  81 #ifndef PRODUCT
  82 void MemNode::dump_spec(outputStream *st) const {
  83   if (in(Address) == NULL)  return; // node is dead
  84 #ifndef ASSERT
  85   // fake the missing field
  86   const TypePtr* _adr_type = NULL;
  87   if (in(Address) != NULL)
  88     _adr_type = in(Address)->bottom_type()->isa_ptr();
  89 #endif
  90   dump_adr_type(this, _adr_type, st);
  91 
  92   Compile* C = Compile::current();
  93   if (C->alias_type(_adr_type)->is_volatile()) {
  94     st->print(" Volatile!");
  95   }
  96   if (_unaligned_access) {
  97     st->print(" unaligned");
  98   }
  99   if (_mismatched_access) {
 100     st->print(" mismatched");
 101   }
 102   if (_unsafe_access) {
 103     st->print(" unsafe");
 104   }
 105 }
 106 
 107 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
 108   st->print(" @");
 109   if (adr_type == NULL) {
 110     st->print("NULL");
 111   } else {
 112     adr_type->dump_on(st);
 113     Compile* C = Compile::current();
 114     Compile::AliasType* atp = NULL;
 115     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
 116     if (atp == NULL)
 117       st->print(", idx=?\?;");
 118     else if (atp->index() == Compile::AliasIdxBot)
 119       st->print(", idx=Bot;");
 120     else if (atp->index() == Compile::AliasIdxTop)
 121       st->print(", idx=Top;");
 122     else if (atp->index() == Compile::AliasIdxRaw)
 123       st->print(", idx=Raw;");
 124     else {
 125       ciField* field = atp->field();
 126       if (field) {
 127         st->print(", name=");
 128         field->print_name_on(st);
 129       }
 130       st->print(", idx=%d;", atp->index());
 131     }
 132   }
 133 }
 134 
 135 extern void print_alias_types();
 136 
 137 #endif
 138 
 139 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 140   assert((t_oop != NULL), "sanity");
 141   bool is_instance = t_oop->is_known_instance_field();
 142   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 143                              (load != NULL) && load->is_Load() &&
 144                              (phase->is_IterGVN() != NULL);
 145   if (!(is_instance || is_boxed_value_load))
 146     return mchain;  // don't try to optimize non-instance types
 147   uint instance_id = t_oop->instance_id();
 148   Node *start_mem = phase->C->start()->proj_out_or_null(TypeFunc::Memory);
 149   Node *prev = NULL;
 150   Node *result = mchain;
 151   while (prev != result) {
 152     prev = result;
 153     if (result == start_mem)
 154       break;  // hit one of our sentinels
 155     // skip over a call which does not affect this memory slice
 156     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 157       Node *proj_in = result->in(0);
 158       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 159         break;  // hit one of our sentinels
 160       } else if (proj_in->is_Call()) {
 161         // ArrayCopyNodes processed here as well
 162         CallNode *call = proj_in->as_Call();
 163         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 164           result = call->in(TypeFunc::Memory);
 165         }
 166       } else if (proj_in->is_Initialize()) {
 167         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 168         // Stop if this is the initialization for the object instance which
 169         // contains this memory slice, otherwise skip over it.
 170         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 171           break;
 172         }
 173         if (is_instance) {
 174           result = proj_in->in(TypeFunc::Memory);
 175         } else if (is_boxed_value_load) {
 176           Node* klass = alloc->in(AllocateNode::KlassNode);
 177           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 178           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 179             result = proj_in->in(TypeFunc::Memory); // not related allocation
 180           }
 181         }
 182       } else if (proj_in->is_MemBar()) {
 183         ArrayCopyNode* ac = NULL;
 184         if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase, ac)) {
 185           break;
 186         }
 187         result = proj_in->in(TypeFunc::Memory);
 188       } else {
 189         assert(false, "unexpected projection");
 190       }
 191     } else if (result->is_ClearArray()) {
 192       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 193         // Can not bypass initialization of the instance
 194         // we are looking for.
 195         break;
 196       }
 197       // Otherwise skip it (the call updated 'result' value).
 198     } else if (result->is_MergeMem()) {
 199       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 200     }
 201   }
 202   return result;
 203 }
 204 
 205 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 206   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 207   if (t_oop == NULL)
 208     return mchain;  // don't try to optimize non-oop types
 209   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 210   bool is_instance = t_oop->is_known_instance_field();
 211   PhaseIterGVN *igvn = phase->is_IterGVN();
 212   if (is_instance && igvn != NULL  && result->is_Phi()) {
 213     PhiNode *mphi = result->as_Phi();
 214     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 215     const TypePtr *t = mphi->adr_type();
 216     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 217         (t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 218          t->is_oopptr()->cast_to_exactness(true)
 219            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 220             ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop)) {
 221       // clone the Phi with our address type
 222       result = mphi->split_out_instance(t_adr, igvn);
 223     } else {
 224       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 225     }
 226   }
 227   return result;
 228 }
 229 
 230 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 231   uint alias_idx = phase->C->get_alias_index(tp);
 232   Node *mem = mmem;
 233 #ifdef ASSERT
 234   {
 235     // Check that current type is consistent with the alias index used during graph construction
 236     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 237     bool consistent =  adr_check == NULL || adr_check->empty() ||
 238                        phase->C->must_alias(adr_check, alias_idx );
 239     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 240     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 241                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 242         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 243         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 244           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 245           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 246       // don't assert if it is dead code.
 247       consistent = true;
 248     }
 249     if( !consistent ) {
 250       st->print("alias_idx==%d, adr_check==", alias_idx);
 251       if( adr_check == NULL ) {
 252         st->print("NULL");
 253       } else {
 254         adr_check->dump();
 255       }
 256       st->cr();
 257       print_alias_types();
 258       assert(consistent, "adr_check must match alias idx");
 259     }
 260   }
 261 #endif
 262   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 263   // means an array I have not precisely typed yet.  Do not do any
 264   // alias stuff with it any time soon.
 265   const TypeOopPtr *toop = tp->isa_oopptr();
 266   if( tp->base() != Type::AnyPtr &&
 267       !(toop &&
 268         toop->klass() != NULL &&
 269         toop->klass()->is_java_lang_Object() &&
 270         toop->offset() == Type::OffsetBot) ) {
 271     // compress paths and change unreachable cycles to TOP
 272     // If not, we can update the input infinitely along a MergeMem cycle
 273     // Equivalent code in PhiNode::Ideal
 274     Node* m  = phase->transform(mmem);
 275     // If transformed to a MergeMem, get the desired slice
 276     // Otherwise the returned node represents memory for every slice
 277     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 278     // Update input if it is progress over what we have now
 279   }
 280   return mem;
 281 }
 282 
 283 //--------------------------Ideal_common---------------------------------------
 284 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 285 // Unhook non-raw memories from complete (macro-expanded) initializations.
 286 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 287   // If our control input is a dead region, kill all below the region
 288   Node *ctl = in(MemNode::Control);
 289   if (ctl && remove_dead_region(phase, can_reshape))
 290     return this;
 291   ctl = in(MemNode::Control);
 292   // Don't bother trying to transform a dead node
 293   if (ctl && ctl->is_top())  return NodeSentinel;
 294 
 295   PhaseIterGVN *igvn = phase->is_IterGVN();
 296   // Wait if control on the worklist.
 297   if (ctl && can_reshape && igvn != NULL) {
 298     Node* bol = NULL;
 299     Node* cmp = NULL;
 300     if (ctl->in(0)->is_If()) {
 301       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 302       bol = ctl->in(0)->in(1);
 303       if (bol->is_Bool())
 304         cmp = ctl->in(0)->in(1)->in(1);
 305     }
 306     if (igvn->_worklist.member(ctl) ||
 307         (bol != NULL && igvn->_worklist.member(bol)) ||
 308         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 309       // This control path may be dead.
 310       // Delay this memory node transformation until the control is processed.
 311       phase->is_IterGVN()->_worklist.push(this);
 312       return NodeSentinel; // caller will return NULL
 313     }
 314   }
 315   // Ignore if memory is dead, or self-loop
 316   Node *mem = in(MemNode::Memory);
 317   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 318   assert(mem != this, "dead loop in MemNode::Ideal");
 319 
 320   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 321     // This memory slice may be dead.
 322     // Delay this mem node transformation until the memory is processed.
 323     phase->is_IterGVN()->_worklist.push(this);
 324     return NodeSentinel; // caller will return NULL
 325   }
 326 
 327   Node *address = in(MemNode::Address);
 328   const Type *t_adr = phase->type(address);
 329   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 330 
 331   if (can_reshape && igvn != NULL &&
 332       (igvn->_worklist.member(address) ||
 333        (igvn->_worklist.size() > 0 && t_adr != adr_type())) ) {
 334     // The address's base and type may change when the address is processed.
 335     // Delay this mem node transformation until the address is processed.
 336     phase->is_IterGVN()->_worklist.push(this);
 337     return NodeSentinel; // caller will return NULL
 338   }
 339 
 340   // Do NOT remove or optimize the next lines: ensure a new alias index
 341   // is allocated for an oop pointer type before Escape Analysis.
 342   // Note: C++ will not remove it since the call has side effect.
 343   if (t_adr->isa_oopptr()) {
 344     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 345   }
 346 
 347   Node* base = NULL;
 348   if (address->is_AddP()) {
 349     base = address->in(AddPNode::Base);
 350   }
 351   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 352       !t_adr->isa_rawptr()) {
 353     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 354     // Skip this node optimization if its address has TOP base.
 355     return NodeSentinel; // caller will return NULL
 356   }
 357 
 358   // Avoid independent memory operations
 359   Node* old_mem = mem;
 360 
 361   // The code which unhooks non-raw memories from complete (macro-expanded)
 362   // initializations was removed. After macro-expansion all stores catched
 363   // by Initialize node became raw stores and there is no information
 364   // which memory slices they modify. So it is unsafe to move any memory
 365   // operation above these stores. Also in most cases hooked non-raw memories
 366   // were already unhooked by using information from detect_ptr_independence()
 367   // and find_previous_store().
 368 
 369   if (mem->is_MergeMem()) {
 370     MergeMemNode* mmem = mem->as_MergeMem();
 371     const TypePtr *tp = t_adr->is_ptr();
 372 
 373     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 374   }
 375 
 376   if (mem != old_mem) {
 377     set_req(MemNode::Memory, mem);
 378     if (can_reshape && old_mem->outcnt() == 0 && igvn != NULL) {
 379       igvn->_worklist.push(old_mem);
 380     }
 381     if (phase->type(mem) == Type::TOP) return NodeSentinel;
 382     return this;
 383   }
 384 
 385   // let the subclass continue analyzing...
 386   return NULL;
 387 }
 388 
 389 // Helper function for proving some simple control dominations.
 390 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 391 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 392 // is not a constant (dominated by the method's StartNode).
 393 // Used by MemNode::find_previous_store to prove that the
 394 // control input of a memory operation predates (dominates)
 395 // an allocation it wants to look past.
 396 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 397   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 398     return false; // Conservative answer for dead code
 399 
 400   // Check 'dom'. Skip Proj and CatchProj nodes.
 401   dom = dom->find_exact_control(dom);
 402   if (dom == NULL || dom->is_top())
 403     return false; // Conservative answer for dead code
 404 
 405   if (dom == sub) {
 406     // For the case when, for example, 'sub' is Initialize and the original
 407     // 'dom' is Proj node of the 'sub'.
 408     return false;
 409   }
 410 
 411   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 412     return true;
 413 
 414   // 'dom' dominates 'sub' if its control edge and control edges
 415   // of all its inputs dominate or equal to sub's control edge.
 416 
 417   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 418   // Or Region for the check in LoadNode::Ideal();
 419   // 'sub' should have sub->in(0) != NULL.
 420   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 421          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 422 
 423   // Get control edge of 'sub'.
 424   Node* orig_sub = sub;
 425   sub = sub->find_exact_control(sub->in(0));
 426   if (sub == NULL || sub->is_top())
 427     return false; // Conservative answer for dead code
 428 
 429   assert(sub->is_CFG(), "expecting control");
 430 
 431   if (sub == dom)
 432     return true;
 433 
 434   if (sub->is_Start() || sub->is_Root())
 435     return false;
 436 
 437   {
 438     // Check all control edges of 'dom'.
 439 
 440     ResourceMark rm;
 441     Arena* arena = Thread::current()->resource_area();
 442     Node_List nlist(arena);
 443     Unique_Node_List dom_list(arena);
 444 
 445     dom_list.push(dom);
 446     bool only_dominating_controls = false;
 447 
 448     for (uint next = 0; next < dom_list.size(); next++) {
 449       Node* n = dom_list.at(next);
 450       if (n == orig_sub)
 451         return false; // One of dom's inputs dominated by sub.
 452       if (!n->is_CFG() && n->pinned()) {
 453         // Check only own control edge for pinned non-control nodes.
 454         n = n->find_exact_control(n->in(0));
 455         if (n == NULL || n->is_top())
 456           return false; // Conservative answer for dead code
 457         assert(n->is_CFG(), "expecting control");
 458         dom_list.push(n);
 459       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 460         only_dominating_controls = true;
 461       } else if (n->is_CFG()) {
 462         if (n->dominates(sub, nlist))
 463           only_dominating_controls = true;
 464         else
 465           return false;
 466       } else {
 467         // First, own control edge.
 468         Node* m = n->find_exact_control(n->in(0));
 469         if (m != NULL) {
 470           if (m->is_top())
 471             return false; // Conservative answer for dead code
 472           dom_list.push(m);
 473         }
 474         // Now, the rest of edges.
 475         uint cnt = n->req();
 476         for (uint i = 1; i < cnt; i++) {
 477           m = n->find_exact_control(n->in(i));
 478           if (m == NULL || m->is_top())
 479             continue;
 480           dom_list.push(m);
 481         }
 482       }
 483     }
 484     return only_dominating_controls;
 485   }
 486 }
 487 
 488 //---------------------detect_ptr_independence---------------------------------
 489 // Used by MemNode::find_previous_store to prove that two base
 490 // pointers are never equal.
 491 // The pointers are accompanied by their associated allocations,
 492 // if any, which have been previously discovered by the caller.
 493 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 494                                       Node* p2, AllocateNode* a2,
 495                                       PhaseTransform* phase) {
 496   // Attempt to prove that these two pointers cannot be aliased.
 497   // They may both manifestly be allocations, and they should differ.
 498   // Or, if they are not both allocations, they can be distinct constants.
 499   // Otherwise, one is an allocation and the other a pre-existing value.
 500   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 501     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 502   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 503     return (a1 != a2);
 504   } else if (a1 != NULL) {                  // one allocation a1
 505     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 506     return all_controls_dominate(p2, a1);
 507   } else { //(a2 != NULL)                   // one allocation a2
 508     return all_controls_dominate(p1, a2);
 509   }
 510   return false;
 511 }
 512 
 513 
 514 // Find an arraycopy that must have set (can_see_stored_value=true) or
 515 // could have set (can_see_stored_value=false) the value for this load
 516 Node* LoadNode::find_previous_arraycopy(PhaseTransform* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
 517   if (mem->is_Proj() && mem->in(0) != NULL && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
 518                                                mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
 519     Node* mb = mem->in(0);
 520     if (mb->in(0) != NULL && mb->in(0)->is_Proj() &&
 521         mb->in(0)->in(0) != NULL && mb->in(0)->in(0)->is_ArrayCopy()) {
 522       ArrayCopyNode* ac = mb->in(0)->in(0)->as_ArrayCopy();
 523       if (ac->is_clonebasic()) {
 524         intptr_t offset;
 525         AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase, offset);
 526         if (alloc != NULL && alloc == ld_alloc) {
 527           return ac;
 528         }
 529       }
 530     }
 531   } else if (mem->is_Proj() && mem->in(0) != NULL && mem->in(0)->is_ArrayCopy()) {
 532     ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
 533 
 534     if (ac->is_arraycopy_validated() ||
 535         ac->is_copyof_validated() ||
 536         ac->is_copyofrange_validated()) {
 537       Node* ld_addp = in(MemNode::Address);
 538       if (ld_addp->is_AddP()) {
 539         Node* ld_base = ld_addp->in(AddPNode::Address);
 540         Node* ld_offs = ld_addp->in(AddPNode::Offset);
 541 
 542         Node* dest = ac->in(ArrayCopyNode::Dest);
 543 
 544         if (dest == ld_base) {
 545           const TypeX *ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 546           if (ac->modifies(ld_offs_t->_lo, ld_offs_t->_hi, phase, can_see_stored_value)) {
 547             return ac;
 548           }
 549           if (!can_see_stored_value) {
 550             mem = ac->in(TypeFunc::Memory);
 551           }
 552         }
 553       }
 554     }
 555   }
 556   return NULL;
 557 }
 558 
 559 // The logic for reordering loads and stores uses four steps:
 560 // (a) Walk carefully past stores and initializations which we
 561 //     can prove are independent of this load.
 562 // (b) Observe that the next memory state makes an exact match
 563 //     with self (load or store), and locate the relevant store.
 564 // (c) Ensure that, if we were to wire self directly to the store,
 565 //     the optimizer would fold it up somehow.
 566 // (d) Do the rewiring, and return, depending on some other part of
 567 //     the optimizer to fold up the load.
 568 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 569 // specific to loads and stores, so they are handled by the callers.
 570 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 571 //
 572 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 573   Node*         ctrl   = in(MemNode::Control);
 574   Node*         adr    = in(MemNode::Address);
 575   intptr_t      offset = 0;
 576   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 577   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 578 
 579   if (offset == Type::OffsetBot)
 580     return NULL;            // cannot unalias unless there are precise offsets
 581 
 582   const bool adr_maybe_raw = check_if_adr_maybe_raw(adr);
 583   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 584 
 585   intptr_t size_in_bytes = memory_size();
 586 
 587   Node* mem = in(MemNode::Memory);   // start searching here...
 588 
 589   int cnt = 50;             // Cycle limiter
 590   for (;;) {                // While we can dance past unrelated stores...
 591     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 592 
 593     Node* prev = mem;
 594     if (mem->is_Store()) {
 595       Node* st_adr = mem->in(MemNode::Address);
 596       intptr_t st_offset = 0;
 597       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 598       if (st_base == NULL)
 599         break;              // inscrutable pointer
 600 
 601       // For raw accesses it's not enough to prove that constant offsets don't intersect.
 602       // We need the bases to be the equal in order for the offset check to make sense.
 603       if ((adr_maybe_raw || check_if_adr_maybe_raw(st_adr)) && st_base != base) {
 604         break;
 605       }
 606 
 607       if (st_offset != offset && st_offset != Type::OffsetBot) {
 608         const int MAX_STORE = BytesPerLong;
 609         if (st_offset >= offset + size_in_bytes ||
 610             st_offset <= offset - MAX_STORE ||
 611             st_offset <= offset - mem->as_Store()->memory_size()) {
 612           // Success:  The offsets are provably independent.
 613           // (You may ask, why not just test st_offset != offset and be done?
 614           // The answer is that stores of different sizes can co-exist
 615           // in the same sequence of RawMem effects.  We sometimes initialize
 616           // a whole 'tile' of array elements with a single jint or jlong.)
 617           mem = mem->in(MemNode::Memory);
 618           continue;           // (a) advance through independent store memory
 619         }
 620       }
 621       if (st_base != base &&
 622           detect_ptr_independence(base, alloc,
 623                                   st_base,
 624                                   AllocateNode::Ideal_allocation(st_base, phase),
 625                                   phase)) {
 626         // Success:  The bases are provably independent.
 627         mem = mem->in(MemNode::Memory);
 628         continue;           // (a) advance through independent store memory
 629       }
 630 
 631       // (b) At this point, if the bases or offsets do not agree, we lose,
 632       // since we have not managed to prove 'this' and 'mem' independent.
 633       if (st_base == base && st_offset == offset) {
 634         return mem;         // let caller handle steps (c), (d)
 635       }
 636 
 637     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 638       InitializeNode* st_init = mem->in(0)->as_Initialize();
 639       AllocateNode*  st_alloc = st_init->allocation();
 640       if (st_alloc == NULL)
 641         break;              // something degenerated
 642       bool known_identical = false;
 643       bool known_independent = false;
 644       if (alloc == st_alloc)
 645         known_identical = true;
 646       else if (alloc != NULL)
 647         known_independent = true;
 648       else if (all_controls_dominate(this, st_alloc))
 649         known_independent = true;
 650 
 651       if (known_independent) {
 652         // The bases are provably independent: Either they are
 653         // manifestly distinct allocations, or else the control
 654         // of this load dominates the store's allocation.
 655         int alias_idx = phase->C->get_alias_index(adr_type());
 656         if (alias_idx == Compile::AliasIdxRaw) {
 657           mem = st_alloc->in(TypeFunc::Memory);
 658         } else {
 659           mem = st_init->memory(alias_idx);
 660         }
 661         continue;           // (a) advance through independent store memory
 662       }
 663 
 664       // (b) at this point, if we are not looking at a store initializing
 665       // the same allocation we are loading from, we lose.
 666       if (known_identical) {
 667         // From caller, can_see_stored_value will consult find_captured_store.
 668         return mem;         // let caller handle steps (c), (d)
 669       }
 670 
 671     } else if (find_previous_arraycopy(phase, alloc, mem, false) != NULL) {
 672       if (prev != mem) {
 673         // Found an arraycopy but it doesn't affect that load
 674         continue;
 675       }
 676       // Found an arraycopy that may affect that load
 677       return mem;
 678     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 679       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 680       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 681         // ArrayCopyNodes processed here as well.
 682         CallNode *call = mem->in(0)->as_Call();
 683         if (!call->may_modify(addr_t, phase)) {
 684           mem = call->in(TypeFunc::Memory);
 685           continue;         // (a) advance through independent call memory
 686         }
 687       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 688         ArrayCopyNode* ac = NULL;
 689         if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase, ac)) {
 690           break;
 691         }
 692         mem = mem->in(0)->in(TypeFunc::Memory);
 693         continue;           // (a) advance through independent MemBar memory
 694       } else if (mem->is_ClearArray()) {
 695         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 696           // (the call updated 'mem' value)
 697           continue;         // (a) advance through independent allocation memory
 698         } else {
 699           // Can not bypass initialization of the instance
 700           // we are looking for.
 701           return mem;
 702         }
 703       } else if (mem->is_MergeMem()) {
 704         int alias_idx = phase->C->get_alias_index(adr_type());
 705         mem = mem->as_MergeMem()->memory_at(alias_idx);
 706         continue;           // (a) advance through independent MergeMem memory
 707       }
 708     }
 709 
 710     // Unless there is an explicit 'continue', we must bail out here,
 711     // because 'mem' is an inscrutable memory state (e.g., a call).
 712     break;
 713   }
 714 
 715   return NULL;              // bail out
 716 }
 717 
 718 //----------------------calculate_adr_type-------------------------------------
 719 // Helper function.  Notices when the given type of address hits top or bottom.
 720 // Also, asserts a cross-check of the type against the expected address type.
 721 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 722   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 723   #ifdef PRODUCT
 724   cross_check = NULL;
 725   #else
 726   if (!VerifyAliases || VMError::is_error_reported() || Node::in_dump())  cross_check = NULL;
 727   #endif
 728   const TypePtr* tp = t->isa_ptr();
 729   if (tp == NULL) {
 730     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 731     return TypePtr::BOTTOM;           // touches lots of memory
 732   } else {
 733     #ifdef ASSERT
 734     // %%%% [phh] We don't check the alias index if cross_check is
 735     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 736     if (cross_check != NULL &&
 737         cross_check != TypePtr::BOTTOM &&
 738         cross_check != TypeRawPtr::BOTTOM) {
 739       // Recheck the alias index, to see if it has changed (due to a bug).
 740       Compile* C = Compile::current();
 741       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 742              "must stay in the original alias category");
 743       // The type of the address must be contained in the adr_type,
 744       // disregarding "null"-ness.
 745       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 746       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 747       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 748              "real address must not escape from expected memory type");
 749     }
 750     #endif
 751     return tp;
 752   }
 753 }
 754 
 755 //=============================================================================
 756 // Should LoadNode::Ideal() attempt to remove control edges?
 757 bool LoadNode::can_remove_control() const {
 758   return true;
 759 }
 760 uint LoadNode::size_of() const { return sizeof(*this); }
 761 bool LoadNode::cmp( const Node &n ) const
 762 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 763 const Type *LoadNode::bottom_type() const { return _type; }
 764 uint LoadNode::ideal_reg() const {
 765   return _type->ideal_reg();
 766 }
 767 
 768 #ifndef PRODUCT
 769 void LoadNode::dump_spec(outputStream *st) const {
 770   MemNode::dump_spec(st);
 771   if( !Verbose && !WizardMode ) {
 772     // standard dump does this in Verbose and WizardMode
 773     st->print(" #"); _type->dump_on(st);
 774   }
 775   if (!depends_only_on_test()) {
 776     st->print(" (does not depend only on test)");
 777   }
 778 }
 779 #endif
 780 
 781 #ifdef ASSERT
 782 //----------------------------is_immutable_value-------------------------------
 783 // Helper function to allow a raw load without control edge for some cases
 784 bool LoadNode::is_immutable_value(Node* adr) {
 785   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 786           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 787           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 788            in_bytes(JavaThread::osthread_offset())));
 789 }
 790 #endif
 791 
 792 //----------------------------LoadNode::make-----------------------------------
 793 // Polymorphic factory method:
 794 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo,
 795                      ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 796   Compile* C = gvn.C;
 797 
 798   // sanity check the alias category against the created node type
 799   assert(!(adr_type->isa_oopptr() &&
 800            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 801          "use LoadKlassNode instead");
 802   assert(!(adr_type->isa_aryptr() &&
 803            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 804          "use LoadRangeNode instead");
 805   // Check control edge of raw loads
 806   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 807           // oop will be recorded in oop map if load crosses safepoint
 808           rt->isa_oopptr() || is_immutable_value(adr),
 809           "raw memory operations should have control edge");
 810   LoadNode* load = NULL;
 811   switch (bt) {
 812   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 813   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 814   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 815   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 816   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 817   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency); break;
 818   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 819   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 820   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 821   case T_OBJECT:
 822 #ifdef _LP64
 823     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 824       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 825     } else
 826 #endif
 827     {
 828       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 829       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
 830     }
 831     break;
 832   default:
 833     ShouldNotReachHere();
 834     break;
 835   }
 836   assert(load != NULL, "LoadNode should have been created");
 837   if (unaligned) {
 838     load->set_unaligned_access();
 839   }
 840   if (mismatched) {
 841     load->set_mismatched_access();
 842   }
 843   if (unsafe) {
 844     load->set_unsafe_access();
 845   }
 846   if (load->Opcode() == Op_LoadN) {
 847     Node* ld = gvn.transform(load);
 848     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 849   }
 850 
 851   return load;
 852 }
 853 
 854 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 855                                   ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 856   bool require_atomic = true;
 857   LoadLNode* load = new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic);
 858   if (unaligned) {
 859     load->set_unaligned_access();
 860   }
 861   if (mismatched) {
 862     load->set_mismatched_access();
 863   }
 864   if (unsafe) {
 865     load->set_unsafe_access();
 866   }
 867   return load;
 868 }
 869 
 870 LoadDNode* LoadDNode::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   LoadDNode* load = new LoadDNode(ctl, mem, adr, adr_type, rt, 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 
 887 
 888 //------------------------------hash-------------------------------------------
 889 uint LoadNode::hash() const {
 890   // unroll addition of interesting fields
 891   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 892 }
 893 
 894 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 895   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 896     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 897     bool is_stable_ary = FoldStableValues &&
 898                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 899                          tp->isa_aryptr()->is_stable();
 900 
 901     return (eliminate_boxing && non_volatile) || is_stable_ary;
 902   }
 903 
 904   return false;
 905 }
 906 
 907 // Is the value loaded previously stored by an arraycopy? If so return
 908 // a load node that reads from the source array so we may be able to
 909 // optimize out the ArrayCopy node later.
 910 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
 911   Node* ld_adr = in(MemNode::Address);
 912   intptr_t ld_off = 0;
 913   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 914   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
 915   if (ac != NULL) {
 916     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
 917 
 918     Node* mem = ac->in(TypeFunc::Memory);
 919     Node* ctl = ac->in(0);
 920     Node* src = ac->in(ArrayCopyNode::Src);
 921 
 922     if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
 923       return NULL;
 924     }
 925 
 926     LoadNode* ld = clone()->as_Load();
 927     Node* addp = in(MemNode::Address)->clone();
 928     if (ac->as_ArrayCopy()->is_clonebasic()) {
 929       assert(ld_alloc != NULL, "need an alloc");
 930       assert(addp->is_AddP(), "address must be addp");
 931       assert(ac->in(ArrayCopyNode::Dest)->is_AddP(), "dest must be an address");
 932       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
 933       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Base)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base)), "strange pattern");
 934       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Address)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address)), "strange pattern");
 935       addp->set_req(AddPNode::Base, src->in(AddPNode::Base));
 936       addp->set_req(AddPNode::Address, src->in(AddPNode::Address));
 937     } else {
 938       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
 939              ac->as_ArrayCopy()->is_copyof_validated() ||
 940              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
 941       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
 942       addp->set_req(AddPNode::Base, src);
 943       addp->set_req(AddPNode::Address, src);
 944 
 945       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
 946       BasicType ary_elem  = ary_t->klass()->as_array_klass()->element_type()->basic_type();
 947       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 948       uint shift  = exact_log2(type2aelembytes(ary_elem));
 949 
 950       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
 951 #ifdef _LP64
 952       diff = phase->transform(new ConvI2LNode(diff));
 953 #endif
 954       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
 955 
 956       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
 957       addp->set_req(AddPNode::Offset, offset);
 958     }
 959     addp = phase->transform(addp);
 960 #ifdef ASSERT
 961     const TypePtr* adr_type = phase->type(addp)->is_ptr();
 962     ld->_adr_type = adr_type;
 963 #endif
 964     ld->set_req(MemNode::Address, addp);
 965     ld->set_req(0, ctl);
 966     ld->set_req(MemNode::Memory, mem);
 967     // load depends on the tests that validate the arraycopy
 968     ld->_control_dependency = Pinned;
 969     return ld;
 970   }
 971   return NULL;
 972 }
 973 
 974 
 975 //---------------------------can_see_stored_value------------------------------
 976 // This routine exists to make sure this set of tests is done the same
 977 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 978 // will change the graph shape in a way which makes memory alive twice at the
 979 // same time (uses the Oracle model of aliasing), then some
 980 // LoadXNode::Identity will fold things back to the equivalence-class model
 981 // of aliasing.
 982 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 983   Node* ld_adr = in(MemNode::Address);
 984   intptr_t ld_off = 0;
 985   Node* ld_base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ld_off);
 986   Node* ld_alloc = AllocateNode::Ideal_allocation(ld_base, phase);
 987   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 988   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
 989   // This is more general than load from boxing objects.
 990   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
 991     uint alias_idx = atp->index();
 992     bool final = !atp->is_rewritable();
 993     Node* result = NULL;
 994     Node* current = st;
 995     // Skip through chains of MemBarNodes checking the MergeMems for
 996     // new states for the slice of this load.  Stop once any other
 997     // kind of node is encountered.  Loads from final memory can skip
 998     // through any kind of MemBar but normal loads shouldn't skip
 999     // through MemBarAcquire since the could allow them to move out of
1000     // a synchronized region.
1001     while (current->is_Proj()) {
1002       int opc = current->in(0)->Opcode();
1003       if ((final && (opc == Op_MemBarAcquire ||
1004                      opc == Op_MemBarAcquireLock ||
1005                      opc == Op_LoadFence)) ||
1006           opc == Op_MemBarRelease ||
1007           opc == Op_StoreFence ||
1008           opc == Op_MemBarReleaseLock ||
1009           opc == Op_MemBarStoreStore ||
1010           opc == Op_MemBarCPUOrder) {
1011         Node* mem = current->in(0)->in(TypeFunc::Memory);
1012         if (mem->is_MergeMem()) {
1013           MergeMemNode* merge = mem->as_MergeMem();
1014           Node* new_st = merge->memory_at(alias_idx);
1015           if (new_st == merge->base_memory()) {
1016             // Keep searching
1017             current = new_st;
1018             continue;
1019           }
1020           // Save the new memory state for the slice and fall through
1021           // to exit.
1022           result = new_st;
1023         }
1024       }
1025       break;
1026     }
1027     if (result != NULL) {
1028       st = result;
1029     }
1030   }
1031 
1032   // Loop around twice in the case Load -> Initialize -> Store.
1033   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1034   for (int trip = 0; trip <= 1; trip++) {
1035 
1036     if (st->is_Store()) {
1037       Node* st_adr = st->in(MemNode::Address);
1038       if (!phase->eqv(st_adr, ld_adr)) {
1039         // Try harder before giving up. Unify base pointers with casts (e.g., raw/non-raw pointers).
1040         intptr_t st_off = 0;
1041         Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_off);
1042         if (ld_base == NULL)                                   return NULL;
1043         if (st_base == NULL)                                   return NULL;
1044         if (!ld_base->eqv_uncast(st_base, /*keep_deps=*/true)) return NULL;
1045         if (ld_off != st_off)                                  return NULL;
1046         if (ld_off == Type::OffsetBot)                         return NULL;
1047         // Same base, same offset.
1048         // Possible improvement for arrays: check index value instead of absolute offset.
1049 
1050         // At this point we have proven something like this setup:
1051         //   B = << base >>
1052         //   L =  LoadQ(AddP(Check/CastPP(B), #Off))
1053         //   S = StoreQ(AddP(             B , #Off), V)
1054         // (Actually, we haven't yet proven the Q's are the same.)
1055         // In other words, we are loading from a casted version of
1056         // the same pointer-and-offset that we stored to.
1057         // Casted version may carry a dependency and it is respected.
1058         // Thus, we are able to replace L by V.
1059       }
1060       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1061       if (store_Opcode() != st->Opcode())
1062         return NULL;
1063       return st->in(MemNode::ValueIn);
1064     }
1065 
1066     // A load from a freshly-created object always returns zero.
1067     // (This can happen after LoadNode::Ideal resets the load's memory input
1068     // to find_captured_store, which returned InitializeNode::zero_memory.)
1069     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1070         (st->in(0) == ld_alloc) &&
1071         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1072       // return a zero value for the load's basic type
1073       // (This is one of the few places where a generic PhaseTransform
1074       // can create new nodes.  Think of it as lazily manifesting
1075       // virtually pre-existing constants.)
1076       return phase->zerocon(memory_type());
1077     }
1078 
1079     // A load from an initialization barrier can match a captured store.
1080     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1081       InitializeNode* init = st->in(0)->as_Initialize();
1082       AllocateNode* alloc = init->allocation();
1083       if ((alloc != NULL) && (alloc == ld_alloc)) {
1084         // examine a captured store value
1085         st = init->find_captured_store(ld_off, memory_size(), phase);
1086         if (st != NULL) {
1087           continue;             // take one more trip around
1088         }
1089       }
1090     }
1091 
1092     // Load boxed value from result of valueOf() call is input parameter.
1093     if (this->is_Load() && ld_adr->is_AddP() &&
1094         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1095       intptr_t ignore = 0;
1096       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1097       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1098       base = bs->step_over_gc_barrier(base);
1099       if (base != NULL && base->is_Proj() &&
1100           base->as_Proj()->_con == TypeFunc::Parms &&
1101           base->in(0)->is_CallStaticJava() &&
1102           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1103         return base->in(0)->in(TypeFunc::Parms);
1104       }
1105     }
1106 
1107     break;
1108   }
1109 
1110   return NULL;
1111 }
1112 
1113 //----------------------is_instance_field_load_with_local_phi------------------
1114 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1115   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1116       in(Address)->is_AddP() ) {
1117     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1118     // Only instances and boxed values.
1119     if( t_oop != NULL &&
1120         (t_oop->is_ptr_to_boxed_value() ||
1121          t_oop->is_known_instance_field()) &&
1122         t_oop->offset() != Type::OffsetBot &&
1123         t_oop->offset() != Type::OffsetTop) {
1124       return true;
1125     }
1126   }
1127   return false;
1128 }
1129 
1130 //------------------------------Identity---------------------------------------
1131 // Loads are identity if previous store is to same address
1132 Node* LoadNode::Identity(PhaseGVN* phase) {
1133   // If the previous store-maker is the right kind of Store, and the store is
1134   // to the same address, then we are equal to the value stored.
1135   Node* mem = in(Memory);
1136   Node* value = can_see_stored_value(mem, phase);
1137   if( value ) {
1138     // byte, short & char stores truncate naturally.
1139     // A load has to load the truncated value which requires
1140     // some sort of masking operation and that requires an
1141     // Ideal call instead of an Identity call.
1142     if (memory_size() < BytesPerInt) {
1143       // If the input to the store does not fit with the load's result type,
1144       // it must be truncated via an Ideal call.
1145       if (!phase->type(value)->higher_equal(phase->type(this)))
1146         return this;
1147     }
1148     // (This works even when value is a Con, but LoadNode::Value
1149     // usually runs first, producing the singleton type of the Con.)
1150     return value;
1151   }
1152 
1153   // Search for an existing data phi which was generated before for the same
1154   // instance's field to avoid infinite generation of phis in a loop.
1155   Node *region = mem->in(0);
1156   if (is_instance_field_load_with_local_phi(region)) {
1157     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1158     int this_index  = phase->C->get_alias_index(addr_t);
1159     int this_offset = addr_t->offset();
1160     int this_iid    = addr_t->instance_id();
1161     if (!addr_t->is_known_instance() &&
1162          addr_t->is_ptr_to_boxed_value()) {
1163       // Use _idx of address base (could be Phi node) for boxed values.
1164       intptr_t   ignore = 0;
1165       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1166       if (base == NULL) {
1167         return this;
1168       }
1169       this_iid = base->_idx;
1170     }
1171     const Type* this_type = bottom_type();
1172     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1173       Node* phi = region->fast_out(i);
1174       if (phi->is_Phi() && phi != mem &&
1175           phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1176         return phi;
1177       }
1178     }
1179   }
1180 
1181   return this;
1182 }
1183 
1184 // Construct an equivalent unsigned load.
1185 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1186   BasicType bt = T_ILLEGAL;
1187   const Type* rt = NULL;
1188   switch (Opcode()) {
1189     case Op_LoadUB: return this;
1190     case Op_LoadUS: return this;
1191     case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1192     case Op_LoadS: bt = T_CHAR;    rt = TypeInt::CHAR;  break;
1193     default:
1194       assert(false, "no unsigned variant: %s", Name());
1195       return NULL;
1196   }
1197   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1198                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1199                         is_unaligned_access(), is_mismatched_access());
1200 }
1201 
1202 // Construct an equivalent signed load.
1203 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1204   BasicType bt = T_ILLEGAL;
1205   const Type* rt = NULL;
1206   switch (Opcode()) {
1207     case Op_LoadUB: bt = T_BYTE;  rt = TypeInt::BYTE;  break;
1208     case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1209     case Op_LoadB: // fall through
1210     case Op_LoadS: // fall through
1211     case Op_LoadI: // fall through
1212     case Op_LoadL: return this;
1213     default:
1214       assert(false, "no signed variant: %s", Name());
1215       return NULL;
1216   }
1217   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1218                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1219                         is_unaligned_access(), is_mismatched_access());
1220 }
1221 
1222 // We're loading from an object which has autobox behaviour.
1223 // If this object is result of a valueOf call we'll have a phi
1224 // merging a newly allocated object and a load from the cache.
1225 // We want to replace this load with the original incoming
1226 // argument to the valueOf call.
1227 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1228   assert(phase->C->eliminate_boxing(), "sanity");
1229   intptr_t ignore = 0;
1230   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1231   if ((base == NULL) || base->is_Phi()) {
1232     // Push the loads from the phi that comes from valueOf up
1233     // through it to allow elimination of the loads and the recovery
1234     // of the original value. It is done in split_through_phi().
1235     return NULL;
1236   } else if (base->is_Load() ||
1237              (base->is_DecodeN() && base->in(1)->is_Load())) {
1238     // Eliminate the load of boxed value for integer types from the cache
1239     // array by deriving the value from the index into the array.
1240     // Capture the offset of the load and then reverse the computation.
1241 
1242     // Get LoadN node which loads a boxing object from 'cache' array.
1243     if (base->is_DecodeN()) {
1244       base = base->in(1);
1245     }
1246     if (!base->in(Address)->is_AddP()) {
1247       return NULL; // Complex address
1248     }
1249     AddPNode* address = base->in(Address)->as_AddP();
1250     Node* cache_base = address->in(AddPNode::Base);
1251     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1252       // Get ConP node which is static 'cache' field.
1253       cache_base = cache_base->in(1);
1254     }
1255     if ((cache_base != NULL) && cache_base->is_Con()) {
1256       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1257       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1258         Node* elements[4];
1259         int shift = exact_log2(type2aelembytes(T_OBJECT));
1260         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1261         if (count > 0 && elements[0]->is_Con() &&
1262             (count == 1 ||
1263              (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1264                             elements[1]->in(2) == phase->intcon(shift)))) {
1265           ciObjArray* array = base_type->const_oop()->as_obj_array();
1266           // Fetch the box object cache[0] at the base of the array and get its value
1267           ciInstance* box = array->obj_at(0)->as_instance();
1268           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1269           assert(ik->is_box_klass(), "sanity");
1270           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1271           if (ik->nof_nonstatic_fields() == 1) {
1272             // This should be true nonstatic_field_at requires calling
1273             // nof_nonstatic_fields so check it anyway
1274             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1275             BasicType bt = c.basic_type();
1276             // Only integer types have boxing cache.
1277             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1278                    bt == T_BYTE    || bt == T_SHORT ||
1279                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1280             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1281             if (cache_low != (int)cache_low) {
1282               return NULL; // should not happen since cache is array indexed by value
1283             }
1284             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1285             if (offset != (int)offset) {
1286               return NULL; // should not happen since cache is array indexed by value
1287             }
1288            // Add up all the offsets making of the address of the load
1289             Node* result = elements[0];
1290             for (int i = 1; i < count; i++) {
1291               result = phase->transform(new AddXNode(result, elements[i]));
1292             }
1293             // Remove the constant offset from the address and then
1294             result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1295             // remove the scaling of the offset to recover the original index.
1296             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1297               // Peel the shift off directly but wrap it in a dummy node
1298               // since Ideal can't return existing nodes
1299               result = new RShiftXNode(result->in(1), phase->intcon(0));
1300             } else if (result->is_Add() && result->in(2)->is_Con() &&
1301                        result->in(1)->Opcode() == Op_LShiftX &&
1302                        result->in(1)->in(2) == phase->intcon(shift)) {
1303               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1304               // but for boxing cache access we know that X<<Z will not overflow
1305               // (there is range check) so we do this optimizatrion by hand here.
1306               Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1307               result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1308             } else {
1309               result = new RShiftXNode(result, phase->intcon(shift));
1310             }
1311 #ifdef _LP64
1312             if (bt != T_LONG) {
1313               result = new ConvL2INode(phase->transform(result));
1314             }
1315 #else
1316             if (bt == T_LONG) {
1317               result = new ConvI2LNode(phase->transform(result));
1318             }
1319 #endif
1320             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1321             // Need to preserve unboxing load type if it is unsigned.
1322             switch(this->Opcode()) {
1323               case Op_LoadUB:
1324                 result = new AndINode(phase->transform(result), phase->intcon(0xFF));
1325                 break;
1326               case Op_LoadUS:
1327                 result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
1328                 break;
1329             }
1330             return result;
1331           }
1332         }
1333       }
1334     }
1335   }
1336   return NULL;
1337 }
1338 
1339 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1340   Node* region = phi->in(0);
1341   if (region == NULL) {
1342     return false; // Wait stable graph
1343   }
1344   uint cnt = phi->req();
1345   for (uint i = 1; i < cnt; i++) {
1346     Node* rc = region->in(i);
1347     if (rc == NULL || phase->type(rc) == Type::TOP)
1348       return false; // Wait stable graph
1349     Node* in = phi->in(i);
1350     if (in == NULL || phase->type(in) == Type::TOP)
1351       return false; // Wait stable graph
1352   }
1353   return true;
1354 }
1355 //------------------------------split_through_phi------------------------------
1356 // Split instance or boxed field load through Phi.
1357 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1358   Node* mem     = in(Memory);
1359   Node* address = in(Address);
1360   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1361 
1362   assert((t_oop != NULL) &&
1363          (t_oop->is_known_instance_field() ||
1364           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1365 
1366   Compile* C = phase->C;
1367   intptr_t ignore = 0;
1368   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1369   bool base_is_phi = (base != NULL) && base->is_Phi();
1370   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1371                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1372                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1373 
1374   if (!((mem->is_Phi() || base_is_phi) &&
1375         (load_boxed_values || t_oop->is_known_instance_field()))) {
1376     return NULL; // memory is not Phi
1377   }
1378 
1379   if (mem->is_Phi()) {
1380     if (!stable_phi(mem->as_Phi(), phase)) {
1381       return NULL; // Wait stable graph
1382     }
1383     uint cnt = mem->req();
1384     // Check for loop invariant memory.
1385     if (cnt == 3) {
1386       for (uint i = 1; i < cnt; i++) {
1387         Node* in = mem->in(i);
1388         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1389         if (m == mem) {
1390           if (i == 1) {
1391             // if the first edge was a loop, check second edge too.
1392             // If both are replaceable - we are in an infinite loop
1393             Node *n = optimize_memory_chain(mem->in(2), t_oop, this, phase);
1394             if (n == mem) {
1395               break;
1396             }
1397           }
1398           set_req(Memory, mem->in(cnt - i));
1399           return this; // made change
1400         }
1401       }
1402     }
1403   }
1404   if (base_is_phi) {
1405     if (!stable_phi(base->as_Phi(), phase)) {
1406       return NULL; // Wait stable graph
1407     }
1408     uint cnt = base->req();
1409     // Check for loop invariant memory.
1410     if (cnt == 3) {
1411       for (uint i = 1; i < cnt; i++) {
1412         if (base->in(i) == base) {
1413           return NULL; // Wait stable graph
1414         }
1415       }
1416     }
1417   }
1418 
1419   bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1420 
1421   // Split through Phi (see original code in loopopts.cpp).
1422   assert(C->have_alias_type(t_oop), "instance should have alias type");
1423 
1424   // Do nothing here if Identity will find a value
1425   // (to avoid infinite chain of value phis generation).
1426   if (!phase->eqv(this, phase->apply_identity(this)))
1427     return NULL;
1428 
1429   // Select Region to split through.
1430   Node* region;
1431   if (!base_is_phi) {
1432     assert(mem->is_Phi(), "sanity");
1433     region = mem->in(0);
1434     // Skip if the region dominates some control edge of the address.
1435     if (!MemNode::all_controls_dominate(address, region))
1436       return NULL;
1437   } else if (!mem->is_Phi()) {
1438     assert(base_is_phi, "sanity");
1439     region = base->in(0);
1440     // Skip if the region dominates some control edge of the memory.
1441     if (!MemNode::all_controls_dominate(mem, region))
1442       return NULL;
1443   } else if (base->in(0) != mem->in(0)) {
1444     assert(base_is_phi && mem->is_Phi(), "sanity");
1445     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1446       region = base->in(0);
1447     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1448       region = mem->in(0);
1449     } else {
1450       return NULL; // complex graph
1451     }
1452   } else {
1453     assert(base->in(0) == mem->in(0), "sanity");
1454     region = mem->in(0);
1455   }
1456 
1457   const Type* this_type = this->bottom_type();
1458   int this_index  = C->get_alias_index(t_oop);
1459   int this_offset = t_oop->offset();
1460   int this_iid    = t_oop->instance_id();
1461   if (!t_oop->is_known_instance() && load_boxed_values) {
1462     // Use _idx of address base for boxed values.
1463     this_iid = base->_idx;
1464   }
1465   PhaseIterGVN* igvn = phase->is_IterGVN();
1466   Node* phi = new PhiNode(region, this_type, NULL, mem->_idx, this_iid, this_index, this_offset);
1467   for (uint i = 1; i < region->req(); i++) {
1468     Node* x;
1469     Node* the_clone = NULL;
1470     if (region->in(i) == C->top()) {
1471       x = C->top();      // Dead path?  Use a dead data op
1472     } else {
1473       x = this->clone();        // Else clone up the data op
1474       the_clone = x;            // Remember for possible deletion.
1475       // Alter data node to use pre-phi inputs
1476       if (this->in(0) == region) {
1477         x->set_req(0, region->in(i));
1478       } else {
1479         x->set_req(0, NULL);
1480       }
1481       if (mem->is_Phi() && (mem->in(0) == region)) {
1482         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1483       }
1484       if (address->is_Phi() && address->in(0) == region) {
1485         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1486       }
1487       if (base_is_phi && (base->in(0) == region)) {
1488         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1489         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1490         x->set_req(Address, adr_x);
1491       }
1492     }
1493     // Check for a 'win' on some paths
1494     const Type *t = x->Value(igvn);
1495 
1496     bool singleton = t->singleton();
1497 
1498     // See comments in PhaseIdealLoop::split_thru_phi().
1499     if (singleton && t == Type::TOP) {
1500       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1501     }
1502 
1503     if (singleton) {
1504       x = igvn->makecon(t);
1505     } else {
1506       // We now call Identity to try to simplify the cloned node.
1507       // Note that some Identity methods call phase->type(this).
1508       // Make sure that the type array is big enough for
1509       // our new node, even though we may throw the node away.
1510       // (This tweaking with igvn only works because x is a new node.)
1511       igvn->set_type(x, t);
1512       // If x is a TypeNode, capture any more-precise type permanently into Node
1513       // otherwise it will be not updated during igvn->transform since
1514       // igvn->type(x) is set to x->Value() already.
1515       x->raise_bottom_type(t);
1516       Node *y = igvn->apply_identity(x);
1517       if (y != x) {
1518         x = y;
1519       } else {
1520         y = igvn->hash_find_insert(x);
1521         if (y) {
1522           x = y;
1523         } else {
1524           // Else x is a new node we are keeping
1525           // We do not need register_new_node_with_optimizer
1526           // because set_type has already been called.
1527           igvn->_worklist.push(x);
1528         }
1529       }
1530     }
1531     if (x != the_clone && the_clone != NULL) {
1532       igvn->remove_dead_node(the_clone);
1533     }
1534     phi->set_req(i, x);
1535   }
1536   // Record Phi
1537   igvn->register_new_node_with_optimizer(phi);
1538   return phi;
1539 }
1540 
1541 //------------------------------Ideal------------------------------------------
1542 // If the load is from Field memory and the pointer is non-null, it might be possible to
1543 // zero out the control input.
1544 // If the offset is constant and the base is an object allocation,
1545 // try to hook me up to the exact initializing store.
1546 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1547   Node* p = MemNode::Ideal_common(phase, can_reshape);
1548   if (p)  return (p == NodeSentinel) ? NULL : p;
1549 
1550   Node* ctrl    = in(MemNode::Control);
1551   Node* address = in(MemNode::Address);
1552   bool progress = false;
1553 
1554   bool addr_mark = ((phase->type(address)->isa_oopptr() || phase->type(address)->isa_narrowoop()) &&
1555          phase->type(address)->is_ptr()->offset() == oopDesc::mark_offset_in_bytes());
1556 
1557   // Skip up past a SafePoint control.  Cannot do this for Stores because
1558   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1559   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1560       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw  &&
1561       !addr_mark ) {
1562     ctrl = ctrl->in(0);
1563     set_req(MemNode::Control,ctrl);
1564     progress = true;
1565   }
1566 
1567   intptr_t ignore = 0;
1568   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1569   if (base != NULL
1570       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1571     // Check for useless control edge in some common special cases
1572     if (in(MemNode::Control) != NULL
1573         && can_remove_control()
1574         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1575         && all_controls_dominate(base, phase->C->start())) {
1576       // A method-invariant, non-null address (constant or 'this' argument).
1577       set_req(MemNode::Control, NULL);
1578       progress = true;
1579     }
1580   }
1581 
1582   Node* mem = in(MemNode::Memory);
1583   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1584 
1585   if (can_reshape && (addr_t != NULL)) {
1586     // try to optimize our memory input
1587     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1588     if (opt_mem != mem) {
1589       set_req(MemNode::Memory, opt_mem);
1590       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1591       return this;
1592     }
1593     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1594     if ((t_oop != NULL) &&
1595         (t_oop->is_known_instance_field() ||
1596          t_oop->is_ptr_to_boxed_value())) {
1597       PhaseIterGVN *igvn = phase->is_IterGVN();
1598       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1599         // Delay this transformation until memory Phi is processed.
1600         phase->is_IterGVN()->_worklist.push(this);
1601         return NULL;
1602       }
1603       // Split instance field load through Phi.
1604       Node* result = split_through_phi(phase);
1605       if (result != NULL) return result;
1606 
1607       if (t_oop->is_ptr_to_boxed_value()) {
1608         Node* result = eliminate_autobox(phase);
1609         if (result != NULL) return result;
1610       }
1611     }
1612   }
1613 
1614   // Is there a dominating load that loads the same value?  Leave
1615   // anything that is not a load of a field/array element (like
1616   // barriers etc.) alone
1617   if (in(0) != NULL && !adr_type()->isa_rawptr() && can_reshape) {
1618     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1619       Node *use = mem->fast_out(i);
1620       if (use != this &&
1621           use->Opcode() == Opcode() &&
1622           use->in(0) != NULL &&
1623           use->in(0) != in(0) &&
1624           use->in(Address) == in(Address)) {
1625         Node* ctl = in(0);
1626         for (int i = 0; i < 10 && ctl != NULL; i++) {
1627           ctl = IfNode::up_one_dom(ctl);
1628           if (ctl == use->in(0)) {
1629             set_req(0, use->in(0));
1630             return this;
1631           }
1632         }
1633       }
1634     }
1635   }
1636 
1637   // Check for prior store with a different base or offset; make Load
1638   // independent.  Skip through any number of them.  Bail out if the stores
1639   // are in an endless dead cycle and report no progress.  This is a key
1640   // transform for Reflection.  However, if after skipping through the Stores
1641   // we can't then fold up against a prior store do NOT do the transform as
1642   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1643   // array memory alive twice: once for the hoisted Load and again after the
1644   // bypassed Store.  This situation only works if EVERYBODY who does
1645   // anti-dependence work knows how to bypass.  I.e. we need all
1646   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1647   // the alias index stuff.  So instead, peek through Stores and IFF we can
1648   // fold up, do so.
1649   Node* prev_mem = find_previous_store(phase);
1650   if (prev_mem != NULL) {
1651     Node* value = can_see_arraycopy_value(prev_mem, phase);
1652     if (value != NULL) {
1653       return value;
1654     }
1655   }
1656   // Steps (a), (b):  Walk past independent stores to find an exact match.
1657   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1658     // (c) See if we can fold up on the spot, but don't fold up here.
1659     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1660     // just return a prior value, which is done by Identity calls.
1661     if (can_see_stored_value(prev_mem, phase)) {
1662       // Make ready for step (d):
1663       set_req(MemNode::Memory, prev_mem);
1664       return this;
1665     }
1666   }
1667 
1668   return progress ? this : NULL;
1669 }
1670 
1671 // Helper to recognize certain Klass fields which are invariant across
1672 // some group of array types (e.g., int[] or all T[] where T < Object).
1673 const Type*
1674 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1675                                  ciKlass* klass) const {
1676   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1677     // The field is Klass::_modifier_flags.  Return its (constant) value.
1678     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1679     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1680     return TypeInt::make(klass->modifier_flags());
1681   }
1682   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1683     // The field is Klass::_access_flags.  Return its (constant) value.
1684     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1685     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1686     return TypeInt::make(klass->access_flags());
1687   }
1688   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1689     // The field is Klass::_layout_helper.  Return its constant value if known.
1690     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1691     return TypeInt::make(klass->layout_helper());
1692   }
1693 
1694   // No match.
1695   return NULL;
1696 }
1697 
1698 //------------------------------Value-----------------------------------------
1699 const Type* LoadNode::Value(PhaseGVN* phase) const {
1700   // Either input is TOP ==> the result is TOP
1701   Node* mem = in(MemNode::Memory);
1702   const Type *t1 = phase->type(mem);
1703   if (t1 == Type::TOP)  return Type::TOP;
1704   Node* adr = in(MemNode::Address);
1705   const TypePtr* tp = phase->type(adr)->isa_ptr();
1706   if (tp == NULL || tp->empty())  return Type::TOP;
1707   int off = tp->offset();
1708   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1709   Compile* C = phase->C;
1710 
1711   // Try to guess loaded type from pointer type
1712   if (tp->isa_aryptr()) {
1713     const TypeAryPtr* ary = tp->is_aryptr();
1714     const Type* t = ary->elem();
1715 
1716     // Determine whether the reference is beyond the header or not, by comparing
1717     // the offset against the offset of the start of the array's data.
1718     // Different array types begin at slightly different offsets (12 vs. 16).
1719     // We choose T_BYTE as an example base type that is least restrictive
1720     // as to alignment, which will therefore produce the smallest
1721     // possible base offset.
1722     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1723     const bool off_beyond_header = (off >= min_base_off);
1724 
1725     // Try to constant-fold a stable array element.
1726     if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1727       // Make sure the reference is not into the header and the offset is constant
1728       ciObject* aobj = ary->const_oop();
1729       if (aobj != NULL && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1730         int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1731         const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1732                                                                       stable_dimension,
1733                                                                       memory_type(), is_unsigned());
1734         if (con_type != NULL) {
1735           return con_type;
1736         }
1737       }
1738     }
1739 
1740     // Don't do this for integer types. There is only potential profit if
1741     // the element type t is lower than _type; that is, for int types, if _type is
1742     // more restrictive than t.  This only happens here if one is short and the other
1743     // char (both 16 bits), and in those cases we've made an intentional decision
1744     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1745     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1746     //
1747     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1748     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1749     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1750     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1751     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1752     // In fact, that could have been the original type of p1, and p1 could have
1753     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1754     // expression (LShiftL quux 3) independently optimized to the constant 8.
1755     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1756         && (_type->isa_vect() == NULL)
1757         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1758       // t might actually be lower than _type, if _type is a unique
1759       // concrete subclass of abstract class t.
1760       if (off_beyond_header || off == Type::OffsetBot) {  // is the offset beyond the header?
1761         const Type* jt = t->join_speculative(_type);
1762         // In any case, do not allow the join, per se, to empty out the type.
1763         if (jt->empty() && !t->empty()) {
1764           // This can happen if a interface-typed array narrows to a class type.
1765           jt = _type;
1766         }
1767 #ifdef ASSERT
1768         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1769           // The pointers in the autobox arrays are always non-null
1770           Node* base = adr->in(AddPNode::Base);
1771           if ((base != NULL) && base->is_DecodeN()) {
1772             // Get LoadN node which loads IntegerCache.cache field
1773             base = base->in(1);
1774           }
1775           if ((base != NULL) && base->is_Con()) {
1776             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1777             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1778               // It could be narrow oop
1779               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1780             }
1781           }
1782         }
1783 #endif
1784         return jt;
1785       }
1786     }
1787   } else if (tp->base() == Type::InstPtr) {
1788     assert( off != Type::OffsetBot ||
1789             // arrays can be cast to Objects
1790             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1791             // unsafe field access may not have a constant offset
1792             C->has_unsafe_access(),
1793             "Field accesses must be precise" );
1794     // For oop loads, we expect the _type to be precise.
1795 
1796     // Optimize loads from constant fields.
1797     const TypeInstPtr* tinst = tp->is_instptr();
1798     ciObject* const_oop = tinst->const_oop();
1799     if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
1800       const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
1801       if (con_type != NULL) {
1802         return con_type;
1803       }
1804     }
1805   } else if (tp->base() == Type::KlassPtr) {
1806     assert( off != Type::OffsetBot ||
1807             // arrays can be cast to Objects
1808             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1809             // also allow array-loading from the primary supertype
1810             // array during subtype checks
1811             Opcode() == Op_LoadKlass,
1812             "Field accesses must be precise" );
1813     // For klass/static loads, we expect the _type to be precise
1814   } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
1815     /* With mirrors being an indirect in the Klass*
1816      * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
1817      * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
1818      *
1819      * So check the type and klass of the node before the LoadP.
1820      */
1821     Node* adr2 = adr->in(MemNode::Address);
1822     const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
1823     if (tkls != NULL && !StressReflectiveCode) {
1824       ciKlass* klass = tkls->klass();
1825       if (klass->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1826         assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1827         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1828         return TypeInstPtr::make(klass->java_mirror());
1829       }
1830     }
1831   }
1832 
1833   const TypeKlassPtr *tkls = tp->isa_klassptr();
1834   if (tkls != NULL && !StressReflectiveCode) {
1835     ciKlass* klass = tkls->klass();
1836     if (klass->is_loaded() && tkls->klass_is_exact()) {
1837       // We are loading a field from a Klass metaobject whose identity
1838       // is known at compile time (the type is "exact" or "precise").
1839       // Check for fields we know are maintained as constants by the VM.
1840       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1841         // The field is Klass::_super_check_offset.  Return its (constant) value.
1842         // (Folds up type checking code.)
1843         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1844         return TypeInt::make(klass->super_check_offset());
1845       }
1846       // Compute index into primary_supers array
1847       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1848       // Check for overflowing; use unsigned compare to handle the negative case.
1849       if( depth < ciKlass::primary_super_limit() ) {
1850         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1851         // (Folds up type checking code.)
1852         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1853         ciKlass *ss = klass->super_of_depth(depth);
1854         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1855       }
1856       const Type* aift = load_array_final_field(tkls, klass);
1857       if (aift != NULL)  return aift;
1858     }
1859 
1860     // We can still check if we are loading from the primary_supers array at a
1861     // shallow enough depth.  Even though the klass is not exact, entries less
1862     // than or equal to its super depth are correct.
1863     if (klass->is_loaded() ) {
1864       ciType *inner = klass;
1865       while( inner->is_obj_array_klass() )
1866         inner = inner->as_obj_array_klass()->base_element_type();
1867       if( inner->is_instance_klass() &&
1868           !inner->as_instance_klass()->flags().is_interface() ) {
1869         // Compute index into primary_supers array
1870         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1871         // Check for overflowing; use unsigned compare to handle the negative case.
1872         if( depth < ciKlass::primary_super_limit() &&
1873             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1874           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1875           // (Folds up type checking code.)
1876           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1877           ciKlass *ss = klass->super_of_depth(depth);
1878           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1879         }
1880       }
1881     }
1882 
1883     // If the type is enough to determine that the thing is not an array,
1884     // we can give the layout_helper a positive interval type.
1885     // This will help short-circuit some reflective code.
1886     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1887         && !klass->is_array_klass() // not directly typed as an array
1888         && !klass->is_interface()  // specifically not Serializable & Cloneable
1889         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1890         ) {
1891       // Note:  When interfaces are reliable, we can narrow the interface
1892       // test to (klass != Serializable && klass != Cloneable).
1893       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1894       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1895       // The key property of this type is that it folds up tests
1896       // for array-ness, since it proves that the layout_helper is positive.
1897       // Thus, a generic value like the basic object layout helper works fine.
1898       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1899     }
1900   }
1901 
1902   // If we are loading from a freshly-allocated object, produce a zero,
1903   // if the load is provably beyond the header of the object.
1904   // (Also allow a variable load from a fresh array to produce zero.)
1905   const TypeOopPtr *tinst = tp->isa_oopptr();
1906   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1907   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1908   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1909     Node* value = can_see_stored_value(mem,phase);
1910     if (value != NULL && value->is_Con()) {
1911       assert(value->bottom_type()->higher_equal(_type),"sanity");
1912       return value->bottom_type();
1913     }
1914   }
1915 
1916   if (is_instance) {
1917     // If we have an instance type and our memory input is the
1918     // programs's initial memory state, there is no matching store,
1919     // so just return a zero of the appropriate type
1920     Node *mem = in(MemNode::Memory);
1921     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1922       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1923       return Type::get_zero_type(_type->basic_type());
1924     }
1925   }
1926   return _type;
1927 }
1928 
1929 //------------------------------match_edge-------------------------------------
1930 // Do we Match on this edge index or not?  Match only the address.
1931 uint LoadNode::match_edge(uint idx) const {
1932   return idx == MemNode::Address;
1933 }
1934 
1935 //--------------------------LoadBNode::Ideal--------------------------------------
1936 //
1937 //  If the previous store is to the same address as this load,
1938 //  and the value stored was larger than a byte, replace this load
1939 //  with the value stored truncated to a byte.  If no truncation is
1940 //  needed, the replacement is done in LoadNode::Identity().
1941 //
1942 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1943   Node* mem = in(MemNode::Memory);
1944   Node* value = can_see_stored_value(mem,phase);
1945   if( value && !phase->type(value)->higher_equal( _type ) ) {
1946     Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1947     return new RShiftINode(result, phase->intcon(24));
1948   }
1949   // Identity call will handle the case where truncation is not needed.
1950   return LoadNode::Ideal(phase, can_reshape);
1951 }
1952 
1953 const Type* LoadBNode::Value(PhaseGVN* phase) const {
1954   Node* mem = in(MemNode::Memory);
1955   Node* value = can_see_stored_value(mem,phase);
1956   if (value != NULL && value->is_Con() &&
1957       !value->bottom_type()->higher_equal(_type)) {
1958     // If the input to the store does not fit with the load's result type,
1959     // it must be truncated. We can't delay until Ideal call since
1960     // a singleton Value is needed for split_thru_phi optimization.
1961     int con = value->get_int();
1962     return TypeInt::make((con << 24) >> 24);
1963   }
1964   return LoadNode::Value(phase);
1965 }
1966 
1967 //--------------------------LoadUBNode::Ideal-------------------------------------
1968 //
1969 //  If the previous store is to the same address as this load,
1970 //  and the value stored was larger than a byte, replace this load
1971 //  with the value stored truncated to a byte.  If no truncation is
1972 //  needed, the replacement is done in LoadNode::Identity().
1973 //
1974 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1975   Node* mem = in(MemNode::Memory);
1976   Node* value = can_see_stored_value(mem, phase);
1977   if (value && !phase->type(value)->higher_equal(_type))
1978     return new AndINode(value, phase->intcon(0xFF));
1979   // Identity call will handle the case where truncation is not needed.
1980   return LoadNode::Ideal(phase, can_reshape);
1981 }
1982 
1983 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
1984   Node* mem = in(MemNode::Memory);
1985   Node* value = can_see_stored_value(mem,phase);
1986   if (value != NULL && value->is_Con() &&
1987       !value->bottom_type()->higher_equal(_type)) {
1988     // If the input to the store does not fit with the load's result type,
1989     // it must be truncated. We can't delay until Ideal call since
1990     // a singleton Value is needed for split_thru_phi optimization.
1991     int con = value->get_int();
1992     return TypeInt::make(con & 0xFF);
1993   }
1994   return LoadNode::Value(phase);
1995 }
1996 
1997 //--------------------------LoadUSNode::Ideal-------------------------------------
1998 //
1999 //  If the previous store is to the same address as this load,
2000 //  and the value stored was larger than a char, replace this load
2001 //  with the value stored truncated to a char.  If no truncation is
2002 //  needed, the replacement is done in LoadNode::Identity().
2003 //
2004 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2005   Node* mem = in(MemNode::Memory);
2006   Node* value = can_see_stored_value(mem,phase);
2007   if( value && !phase->type(value)->higher_equal( _type ) )
2008     return new AndINode(value,phase->intcon(0xFFFF));
2009   // Identity call will handle the case where truncation is not needed.
2010   return LoadNode::Ideal(phase, can_reshape);
2011 }
2012 
2013 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
2014   Node* mem = in(MemNode::Memory);
2015   Node* value = can_see_stored_value(mem,phase);
2016   if (value != NULL && value->is_Con() &&
2017       !value->bottom_type()->higher_equal(_type)) {
2018     // If the input to the store does not fit with the load's result type,
2019     // it must be truncated. We can't delay until Ideal call since
2020     // a singleton Value is needed for split_thru_phi optimization.
2021     int con = value->get_int();
2022     return TypeInt::make(con & 0xFFFF);
2023   }
2024   return LoadNode::Value(phase);
2025 }
2026 
2027 //--------------------------LoadSNode::Ideal--------------------------------------
2028 //
2029 //  If the previous store is to the same address as this load,
2030 //  and the value stored was larger than a short, replace this load
2031 //  with the value stored truncated to a short.  If no truncation is
2032 //  needed, the replacement is done in LoadNode::Identity().
2033 //
2034 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2035   Node* mem = in(MemNode::Memory);
2036   Node* value = can_see_stored_value(mem,phase);
2037   if( value && !phase->type(value)->higher_equal( _type ) ) {
2038     Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
2039     return new RShiftINode(result, phase->intcon(16));
2040   }
2041   // Identity call will handle the case where truncation is not needed.
2042   return LoadNode::Ideal(phase, can_reshape);
2043 }
2044 
2045 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2046   Node* mem = in(MemNode::Memory);
2047   Node* value = can_see_stored_value(mem,phase);
2048   if (value != NULL && value->is_Con() &&
2049       !value->bottom_type()->higher_equal(_type)) {
2050     // If the input to the store does not fit with the load's result type,
2051     // it must be truncated. We can't delay until Ideal call since
2052     // a singleton Value is needed for split_thru_phi optimization.
2053     int con = value->get_int();
2054     return TypeInt::make((con << 16) >> 16);
2055   }
2056   return LoadNode::Value(phase);
2057 }
2058 
2059 //=============================================================================
2060 //----------------------------LoadKlassNode::make------------------------------
2061 // Polymorphic factory method:
2062 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2063   // sanity check the alias category against the created node type
2064   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2065   assert(adr_type != NULL, "expecting TypeKlassPtr");
2066 #ifdef _LP64
2067   if (adr_type->is_ptr_to_narrowklass()) {
2068     assert(UseCompressedClassPointers, "no compressed klasses");
2069     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2070     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2071   }
2072 #endif
2073   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2074   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2075 }
2076 
2077 //------------------------------Value------------------------------------------
2078 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2079   return klass_value_common(phase);
2080 }
2081 
2082 // In most cases, LoadKlassNode does not have the control input set. If the control
2083 // input is set, it must not be removed (by LoadNode::Ideal()).
2084 bool LoadKlassNode::can_remove_control() const {
2085   return false;
2086 }
2087 
2088 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2089   // Either input is TOP ==> the result is TOP
2090   const Type *t1 = phase->type( in(MemNode::Memory) );
2091   if (t1 == Type::TOP)  return Type::TOP;
2092   Node *adr = in(MemNode::Address);
2093   const Type *t2 = phase->type( adr );
2094   if (t2 == Type::TOP)  return Type::TOP;
2095   const TypePtr *tp = t2->is_ptr();
2096   if (TypePtr::above_centerline(tp->ptr()) ||
2097       tp->ptr() == TypePtr::Null)  return Type::TOP;
2098 
2099   // Return a more precise klass, if possible
2100   const TypeInstPtr *tinst = tp->isa_instptr();
2101   if (tinst != NULL) {
2102     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2103     int offset = tinst->offset();
2104     if (ik == phase->C->env()->Class_klass()
2105         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2106             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2107       // We are loading a special hidden field from a Class mirror object,
2108       // the field which points to the VM's Klass metaobject.
2109       ciType* t = tinst->java_mirror_type();
2110       // java_mirror_type returns non-null for compile-time Class constants.
2111       if (t != NULL) {
2112         // constant oop => constant klass
2113         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2114           if (t->is_void()) {
2115             // We cannot create a void array.  Since void is a primitive type return null
2116             // klass.  Users of this result need to do a null check on the returned klass.
2117             return TypePtr::NULL_PTR;
2118           }
2119           return TypeKlassPtr::make(ciArrayKlass::make(t));
2120         }
2121         if (!t->is_klass()) {
2122           // a primitive Class (e.g., int.class) has NULL for a klass field
2123           return TypePtr::NULL_PTR;
2124         }
2125         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2126         return TypeKlassPtr::make(t->as_klass());
2127       }
2128       // non-constant mirror, so we can't tell what's going on
2129     }
2130     if( !ik->is_loaded() )
2131       return _type;             // Bail out if not loaded
2132     if (offset == oopDesc::klass_offset_in_bytes()) {
2133       if (tinst->klass_is_exact()) {
2134         return TypeKlassPtr::make(ik);
2135       }
2136       // See if we can become precise: no subklasses and no interface
2137       // (Note:  We need to support verified interfaces.)
2138       if (!ik->is_interface() && !ik->has_subklass()) {
2139         //assert(!UseExactTypes, "this code should be useless with exact types");
2140         // Add a dependence; if any subclass added we need to recompile
2141         if (!ik->is_final()) {
2142           // %%% should use stronger assert_unique_concrete_subtype instead
2143           phase->C->dependencies()->assert_leaf_type(ik);
2144         }
2145         // Return precise klass
2146         return TypeKlassPtr::make(ik);
2147       }
2148 
2149       // Return root of possible klass
2150       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2151     }
2152   }
2153 
2154   // Check for loading klass from an array
2155   const TypeAryPtr *tary = tp->isa_aryptr();
2156   if( tary != NULL ) {
2157     ciKlass *tary_klass = tary->klass();
2158     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2159         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2160       if (tary->klass_is_exact()) {
2161         return TypeKlassPtr::make(tary_klass);
2162       }
2163       ciArrayKlass *ak = tary->klass()->as_array_klass();
2164       // If the klass is an object array, we defer the question to the
2165       // array component klass.
2166       if( ak->is_obj_array_klass() ) {
2167         assert( ak->is_loaded(), "" );
2168         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2169         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2170           ciInstanceKlass* ik = base_k->as_instance_klass();
2171           // See if we can become precise: no subklasses and no interface
2172           if (!ik->is_interface() && !ik->has_subklass()) {
2173             //assert(!UseExactTypes, "this code should be useless with exact types");
2174             // Add a dependence; if any subclass added we need to recompile
2175             if (!ik->is_final()) {
2176               phase->C->dependencies()->assert_leaf_type(ik);
2177             }
2178             // Return precise array klass
2179             return TypeKlassPtr::make(ak);
2180           }
2181         }
2182         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2183       } else {                  // Found a type-array?
2184         //assert(!UseExactTypes, "this code should be useless with exact types");
2185         assert( ak->is_type_array_klass(), "" );
2186         return TypeKlassPtr::make(ak); // These are always precise
2187       }
2188     }
2189   }
2190 
2191   // Check for loading klass from an array klass
2192   const TypeKlassPtr *tkls = tp->isa_klassptr();
2193   if (tkls != NULL && !StressReflectiveCode) {
2194     ciKlass* klass = tkls->klass();
2195     if( !klass->is_loaded() )
2196       return _type;             // Bail out if not loaded
2197     if( klass->is_obj_array_klass() &&
2198         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2199       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2200       // // Always returning precise element type is incorrect,
2201       // // e.g., element type could be object and array may contain strings
2202       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2203 
2204       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2205       // according to the element type's subclassing.
2206       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2207     }
2208     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2209         tkls->offset() == in_bytes(Klass::super_offset())) {
2210       ciKlass* sup = klass->as_instance_klass()->super();
2211       // The field is Klass::_super.  Return its (constant) value.
2212       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2213       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2214     }
2215   }
2216 
2217   // Bailout case
2218   return LoadNode::Value(phase);
2219 }
2220 
2221 //------------------------------Identity---------------------------------------
2222 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2223 // Also feed through the klass in Allocate(...klass...)._klass.
2224 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2225   return klass_identity_common(phase);
2226 }
2227 
2228 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2229   Node* x = LoadNode::Identity(phase);
2230   if (x != this)  return x;
2231 
2232   // Take apart the address into an oop and and offset.
2233   // Return 'this' if we cannot.
2234   Node*    adr    = in(MemNode::Address);
2235   intptr_t offset = 0;
2236   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2237   if (base == NULL)     return this;
2238   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2239   if (toop == NULL)     return this;
2240 
2241   // Step over potential GC barrier for OopHandle resolve
2242   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2243   if (bs->is_gc_barrier_node(base)) {
2244     base = bs->step_over_gc_barrier(base);
2245   }
2246 
2247   // We can fetch the klass directly through an AllocateNode.
2248   // This works even if the klass is not constant (clone or newArray).
2249   if (offset == oopDesc::klass_offset_in_bytes()) {
2250     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2251     if (allocated_klass != NULL) {
2252       return allocated_klass;
2253     }
2254   }
2255 
2256   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2257   // See inline_native_Class_query for occurrences of these patterns.
2258   // Java Example:  x.getClass().isAssignableFrom(y)
2259   //
2260   // This improves reflective code, often making the Class
2261   // mirror go completely dead.  (Current exception:  Class
2262   // mirrors may appear in debug info, but we could clean them out by
2263   // introducing a new debug info operator for Klass.java_mirror).
2264 
2265   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2266       && offset == java_lang_Class::klass_offset_in_bytes()) {
2267     if (base->is_Load()) {
2268       Node* base2 = base->in(MemNode::Address);
2269       if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2270         Node* adr2 = base2->in(MemNode::Address);
2271         const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2272         if (tkls != NULL && !tkls->empty()
2273             && (tkls->klass()->is_instance_klass() ||
2274               tkls->klass()->is_array_klass())
2275             && adr2->is_AddP()
2276            ) {
2277           int mirror_field = in_bytes(Klass::java_mirror_offset());
2278           if (tkls->offset() == mirror_field) {
2279             return adr2->in(AddPNode::Base);
2280           }
2281         }
2282       }
2283     }
2284   }
2285 
2286   return this;
2287 }
2288 
2289 
2290 //------------------------------Value------------------------------------------
2291 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2292   const Type *t = klass_value_common(phase);
2293   if (t == Type::TOP)
2294     return t;
2295 
2296   return t->make_narrowklass();
2297 }
2298 
2299 //------------------------------Identity---------------------------------------
2300 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2301 // Also feed through the klass in Allocate(...klass...)._klass.
2302 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2303   Node *x = klass_identity_common(phase);
2304 
2305   const Type *t = phase->type( x );
2306   if( t == Type::TOP ) return x;
2307   if( t->isa_narrowklass()) return x;
2308   assert (!t->isa_narrowoop(), "no narrow oop here");
2309 
2310   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2311 }
2312 
2313 //------------------------------Value-----------------------------------------
2314 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2315   // Either input is TOP ==> the result is TOP
2316   const Type *t1 = phase->type( in(MemNode::Memory) );
2317   if( t1 == Type::TOP ) return Type::TOP;
2318   Node *adr = in(MemNode::Address);
2319   const Type *t2 = phase->type( adr );
2320   if( t2 == Type::TOP ) return Type::TOP;
2321   const TypePtr *tp = t2->is_ptr();
2322   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2323   const TypeAryPtr *tap = tp->isa_aryptr();
2324   if( !tap ) return _type;
2325   return tap->size();
2326 }
2327 
2328 //-------------------------------Ideal---------------------------------------
2329 // Feed through the length in AllocateArray(...length...)._length.
2330 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2331   Node* p = MemNode::Ideal_common(phase, can_reshape);
2332   if (p)  return (p == NodeSentinel) ? NULL : p;
2333 
2334   // Take apart the address into an oop and and offset.
2335   // Return 'this' if we cannot.
2336   Node*    adr    = in(MemNode::Address);
2337   intptr_t offset = 0;
2338   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2339   if (base == NULL)     return NULL;
2340   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2341   if (tary == NULL)     return NULL;
2342 
2343   // We can fetch the length directly through an AllocateArrayNode.
2344   // This works even if the length is not constant (clone or newArray).
2345   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2346     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2347     if (alloc != NULL) {
2348       Node* allocated_length = alloc->Ideal_length();
2349       Node* len = alloc->make_ideal_length(tary, phase);
2350       if (allocated_length != len) {
2351         // New CastII improves on this.
2352         return len;
2353       }
2354     }
2355   }
2356 
2357   return NULL;
2358 }
2359 
2360 //------------------------------Identity---------------------------------------
2361 // Feed through the length in AllocateArray(...length...)._length.
2362 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2363   Node* x = LoadINode::Identity(phase);
2364   if (x != this)  return x;
2365 
2366   // Take apart the address into an oop and and offset.
2367   // Return 'this' if we cannot.
2368   Node*    adr    = in(MemNode::Address);
2369   intptr_t offset = 0;
2370   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2371   if (base == NULL)     return this;
2372   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2373   if (tary == NULL)     return this;
2374 
2375   // We can fetch the length directly through an AllocateArrayNode.
2376   // This works even if the length is not constant (clone or newArray).
2377   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2378     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2379     if (alloc != NULL) {
2380       Node* allocated_length = alloc->Ideal_length();
2381       // Do not allow make_ideal_length to allocate a CastII node.
2382       Node* len = alloc->make_ideal_length(tary, phase, false);
2383       if (allocated_length == len) {
2384         // Return allocated_length only if it would not be improved by a CastII.
2385         return allocated_length;
2386       }
2387     }
2388   }
2389 
2390   return this;
2391 
2392 }
2393 
2394 //=============================================================================
2395 //---------------------------StoreNode::make-----------------------------------
2396 // Polymorphic factory method:
2397 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2398   assert((mo == unordered || mo == release), "unexpected");
2399   Compile* C = gvn.C;
2400   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2401          ctl != NULL, "raw memory operations should have control edge");
2402 
2403   switch (bt) {
2404   case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2405   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2406   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2407   case T_CHAR:
2408   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2409   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2410   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2411   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2412   case T_METADATA:
2413   case T_ADDRESS:
2414   case T_OBJECT:
2415 #ifdef _LP64
2416     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2417       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2418       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2419     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2420                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2421                 adr->bottom_type()->isa_rawptr())) {
2422       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2423       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2424     }
2425 #endif
2426     {
2427       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2428     }
2429   default:
2430     ShouldNotReachHere();
2431     return (StoreNode*)NULL;
2432   }
2433 }
2434 
2435 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2436   bool require_atomic = true;
2437   return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2438 }
2439 
2440 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2441   bool require_atomic = true;
2442   return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2443 }
2444 
2445 
2446 //--------------------------bottom_type----------------------------------------
2447 const Type *StoreNode::bottom_type() const {
2448   return Type::MEMORY;
2449 }
2450 
2451 //------------------------------hash-------------------------------------------
2452 uint StoreNode::hash() const {
2453   // unroll addition of interesting fields
2454   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2455 
2456   // Since they are not commoned, do not hash them:
2457   return NO_HASH;
2458 }
2459 
2460 //------------------------------Ideal------------------------------------------
2461 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2462 // When a store immediately follows a relevant allocation/initialization,
2463 // try to capture it into the initialization, or hoist it above.
2464 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2465   Node* p = MemNode::Ideal_common(phase, can_reshape);
2466   if (p)  return (p == NodeSentinel) ? NULL : p;
2467 
2468   Node* mem     = in(MemNode::Memory);
2469   Node* address = in(MemNode::Address);
2470   // Back-to-back stores to same address?  Fold em up.  Generally
2471   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2472   // since they must follow each StoreP operation.  Redundant StoreCMs
2473   // are eliminated just before matching in final_graph_reshape.
2474   {
2475     Node* st = mem;
2476     // If Store 'st' has more than one use, we cannot fold 'st' away.
2477     // For example, 'st' might be the final state at a conditional
2478     // return.  Or, 'st' might be used by some node which is live at
2479     // the same time 'st' is live, which might be unschedulable.  So,
2480     // require exactly ONE user until such time as we clone 'mem' for
2481     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2482     // true).
2483     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2484       // Looking at a dead closed cycle of memory?
2485       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2486       assert(Opcode() == st->Opcode() ||
2487              st->Opcode() == Op_StoreVector ||
2488              Opcode() == Op_StoreVector ||
2489              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2490              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2491              (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2492              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2493              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2494 
2495       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2496           st->as_Store()->memory_size() <= this->memory_size()) {
2497         Node* use = st->raw_out(0);
2498         phase->igvn_rehash_node_delayed(use);
2499         if (can_reshape) {
2500           use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase->is_IterGVN());
2501         } else {
2502           // It's OK to do this in the parser, since DU info is always accurate,
2503           // and the parser always refers to nodes via SafePointNode maps.
2504           use->set_req(MemNode::Memory, st->in(MemNode::Memory));
2505         }
2506         return this;
2507       }
2508       st = st->in(MemNode::Memory);
2509     }
2510   }
2511 
2512 
2513   // Capture an unaliased, unconditional, simple store into an initializer.
2514   // Or, if it is independent of the allocation, hoist it above the allocation.
2515   if (ReduceFieldZeroing && /*can_reshape &&*/
2516       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2517     InitializeNode* init = mem->in(0)->as_Initialize();
2518     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2519     if (offset > 0) {
2520       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2521       // If the InitializeNode captured me, it made a raw copy of me,
2522       // and I need to disappear.
2523       if (moved != NULL) {
2524         // %%% hack to ensure that Ideal returns a new node:
2525         mem = MergeMemNode::make(mem);
2526         return mem;             // fold me away
2527       }
2528     }
2529   }
2530 
2531   return NULL;                  // No further progress
2532 }
2533 
2534 //------------------------------Value-----------------------------------------
2535 const Type* StoreNode::Value(PhaseGVN* phase) const {
2536   // Either input is TOP ==> the result is TOP
2537   const Type *t1 = phase->type( in(MemNode::Memory) );
2538   if( t1 == Type::TOP ) return Type::TOP;
2539   const Type *t2 = phase->type( in(MemNode::Address) );
2540   if( t2 == Type::TOP ) return Type::TOP;
2541   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2542   if( t3 == Type::TOP ) return Type::TOP;
2543   return Type::MEMORY;
2544 }
2545 
2546 //------------------------------Identity---------------------------------------
2547 // Remove redundant stores:
2548 //   Store(m, p, Load(m, p)) changes to m.
2549 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2550 Node* StoreNode::Identity(PhaseGVN* phase) {
2551   Node* mem = in(MemNode::Memory);
2552   Node* adr = in(MemNode::Address);
2553   Node* val = in(MemNode::ValueIn);
2554 
2555   Node* result = this;
2556 
2557   // Load then Store?  Then the Store is useless
2558   if (val->is_Load() &&
2559       val->in(MemNode::Address)->eqv_uncast(adr) &&
2560       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2561       val->as_Load()->store_Opcode() == Opcode()) {
2562     result = mem;
2563   }
2564 
2565   // Two stores in a row of the same value?
2566   if (result == this &&
2567       mem->is_Store() &&
2568       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2569       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2570       mem->Opcode() == Opcode()) {
2571     result = mem;
2572   }
2573 
2574   // Store of zero anywhere into a freshly-allocated object?
2575   // Then the store is useless.
2576   // (It must already have been captured by the InitializeNode.)
2577   if (result == this &&
2578       ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2579     // a newly allocated object is already all-zeroes everywhere
2580     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2581       result = mem;
2582     }
2583 
2584     if (result == this) {
2585       // the store may also apply to zero-bits in an earlier object
2586       Node* prev_mem = find_previous_store(phase);
2587       // Steps (a), (b):  Walk past independent stores to find an exact match.
2588       if (prev_mem != NULL) {
2589         Node* prev_val = can_see_stored_value(prev_mem, phase);
2590         if (prev_val != NULL && phase->eqv(prev_val, val)) {
2591           // prev_val and val might differ by a cast; it would be good
2592           // to keep the more informative of the two.
2593           result = mem;
2594         }
2595       }
2596     }
2597   }
2598 
2599   if (result != this && phase->is_IterGVN() != NULL) {
2600     MemBarNode* trailing = trailing_membar();
2601     if (trailing != NULL) {
2602 #ifdef ASSERT
2603       const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2604       assert(t_oop == NULL || t_oop->is_known_instance_field(), "only for non escaping objects");
2605 #endif
2606       PhaseIterGVN* igvn = phase->is_IterGVN();
2607       trailing->remove(igvn);
2608     }
2609   }
2610 
2611   return result;
2612 }
2613 
2614 //------------------------------match_edge-------------------------------------
2615 // Do we Match on this edge index or not?  Match only memory & value
2616 uint StoreNode::match_edge(uint idx) const {
2617   return idx == MemNode::Address || idx == MemNode::ValueIn;
2618 }
2619 
2620 //------------------------------cmp--------------------------------------------
2621 // Do not common stores up together.  They generally have to be split
2622 // back up anyways, so do not bother.
2623 bool StoreNode::cmp( const Node &n ) const {
2624   return (&n == this);          // Always fail except on self
2625 }
2626 
2627 //------------------------------Ideal_masked_input-----------------------------
2628 // Check for a useless mask before a partial-word store
2629 // (StoreB ... (AndI valIn conIa) )
2630 // If (conIa & mask == mask) this simplifies to
2631 // (StoreB ... (valIn) )
2632 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2633   Node *val = in(MemNode::ValueIn);
2634   if( val->Opcode() == Op_AndI ) {
2635     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2636     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2637       set_req(MemNode::ValueIn, val->in(1));
2638       return this;
2639     }
2640   }
2641   return NULL;
2642 }
2643 
2644 
2645 //------------------------------Ideal_sign_extended_input----------------------
2646 // Check for useless sign-extension before a partial-word store
2647 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2648 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2649 // (StoreB ... (valIn) )
2650 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2651   Node *val = in(MemNode::ValueIn);
2652   if( val->Opcode() == Op_RShiftI ) {
2653     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2654     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2655       Node *shl = val->in(1);
2656       if( shl->Opcode() == Op_LShiftI ) {
2657         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2658         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2659           set_req(MemNode::ValueIn, shl->in(1));
2660           return this;
2661         }
2662       }
2663     }
2664   }
2665   return NULL;
2666 }
2667 
2668 //------------------------------value_never_loaded-----------------------------------
2669 // Determine whether there are any possible loads of the value stored.
2670 // For simplicity, we actually check if there are any loads from the
2671 // address stored to, not just for loads of the value stored by this node.
2672 //
2673 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2674   Node *adr = in(Address);
2675   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2676   if (adr_oop == NULL)
2677     return false;
2678   if (!adr_oop->is_known_instance_field())
2679     return false; // if not a distinct instance, there may be aliases of the address
2680   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2681     Node *use = adr->fast_out(i);
2682     if (use->is_Load() || use->is_LoadStore()) {
2683       return false;
2684     }
2685   }
2686   return true;
2687 }
2688 
2689 MemBarNode* StoreNode::trailing_membar() const {
2690   if (is_release()) {
2691     MemBarNode* trailing_mb = NULL;
2692     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2693       Node* u = fast_out(i);
2694       if (u->is_MemBar()) {
2695         if (u->as_MemBar()->trailing_store()) {
2696           assert(u->Opcode() == Op_MemBarVolatile, "");
2697           assert(trailing_mb == NULL, "only one");
2698           trailing_mb = u->as_MemBar();
2699 #ifdef ASSERT
2700           Node* leading = u->as_MemBar()->leading_membar();
2701           assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2702           assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2703           assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2704 #endif
2705         } else {
2706           assert(u->as_MemBar()->standalone(), "");
2707         }
2708       }
2709     }
2710     return trailing_mb;
2711   }
2712   return NULL;
2713 }
2714 
2715 
2716 //=============================================================================
2717 //------------------------------Ideal------------------------------------------
2718 // If the store is from an AND mask that leaves the low bits untouched, then
2719 // we can skip the AND operation.  If the store is from a sign-extension
2720 // (a left shift, then right shift) we can skip both.
2721 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2722   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2723   if( progress != NULL ) return progress;
2724 
2725   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2726   if( progress != NULL ) return progress;
2727 
2728   // Finally check the default case
2729   return StoreNode::Ideal(phase, can_reshape);
2730 }
2731 
2732 //=============================================================================
2733 //------------------------------Ideal------------------------------------------
2734 // If the store is from an AND mask that leaves the low bits untouched, then
2735 // we can skip the AND operation
2736 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2737   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2738   if( progress != NULL ) return progress;
2739 
2740   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2741   if( progress != NULL ) return progress;
2742 
2743   // Finally check the default case
2744   return StoreNode::Ideal(phase, can_reshape);
2745 }
2746 
2747 //=============================================================================
2748 //------------------------------Identity---------------------------------------
2749 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2750   // No need to card mark when storing a null ptr
2751   Node* my_store = in(MemNode::OopStore);
2752   if (my_store->is_Store()) {
2753     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2754     if( t1 == TypePtr::NULL_PTR ) {
2755       return in(MemNode::Memory);
2756     }
2757   }
2758   return this;
2759 }
2760 
2761 //=============================================================================
2762 //------------------------------Ideal---------------------------------------
2763 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2764   Node* progress = StoreNode::Ideal(phase, can_reshape);
2765   if (progress != NULL) return progress;
2766 
2767   Node* my_store = in(MemNode::OopStore);
2768   if (my_store->is_MergeMem()) {
2769     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2770     set_req(MemNode::OopStore, mem);
2771     return this;
2772   }
2773 
2774   return NULL;
2775 }
2776 
2777 //------------------------------Value-----------------------------------------
2778 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
2779   // Either input is TOP ==> the result is TOP
2780   const Type *t = phase->type( in(MemNode::Memory) );
2781   if( t == Type::TOP ) return Type::TOP;
2782   t = phase->type( in(MemNode::Address) );
2783   if( t == Type::TOP ) return Type::TOP;
2784   t = phase->type( in(MemNode::ValueIn) );
2785   if( t == Type::TOP ) return Type::TOP;
2786   // If extra input is TOP ==> the result is TOP
2787   t = phase->type( in(MemNode::OopStore) );
2788   if( t == Type::TOP ) return Type::TOP;
2789 
2790   return StoreNode::Value( phase );
2791 }
2792 
2793 
2794 //=============================================================================
2795 //----------------------------------SCMemProjNode------------------------------
2796 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
2797 {
2798   return bottom_type();
2799 }
2800 
2801 //=============================================================================
2802 //----------------------------------LoadStoreNode------------------------------
2803 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2804   : Node(required),
2805     _type(rt),
2806     _adr_type(at),
2807     _has_barrier(false)
2808 {
2809   init_req(MemNode::Control, c  );
2810   init_req(MemNode::Memory , mem);
2811   init_req(MemNode::Address, adr);
2812   init_req(MemNode::ValueIn, val);
2813   init_class_id(Class_LoadStore);
2814 }
2815 
2816 uint LoadStoreNode::ideal_reg() const {
2817   return _type->ideal_reg();
2818 }
2819 
2820 bool LoadStoreNode::result_not_used() const {
2821   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2822     Node *x = fast_out(i);
2823     if (x->Opcode() == Op_SCMemProj) continue;
2824     return false;
2825   }
2826   return true;
2827 }
2828 
2829 MemBarNode* LoadStoreNode::trailing_membar() const {
2830   MemBarNode* trailing = NULL;
2831   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2832     Node* u = fast_out(i);
2833     if (u->is_MemBar()) {
2834       if (u->as_MemBar()->trailing_load_store()) {
2835         assert(u->Opcode() == Op_MemBarAcquire, "");
2836         assert(trailing == NULL, "only one");
2837         trailing = u->as_MemBar();
2838 #ifdef ASSERT
2839         Node* leading = trailing->leading_membar();
2840         assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2841         assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
2842         assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
2843 #endif
2844       } else {
2845         assert(u->as_MemBar()->standalone(), "wrong barrier kind");
2846       }
2847     }
2848   }
2849 
2850   return trailing;
2851 }
2852 
2853 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2854 
2855 //=============================================================================
2856 //----------------------------------LoadStoreConditionalNode--------------------
2857 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2858   init_req(ExpectedIn, ex );
2859 }
2860 
2861 //=============================================================================
2862 //-------------------------------adr_type--------------------------------------
2863 const TypePtr* ClearArrayNode::adr_type() const {
2864   Node *adr = in(3);
2865   if (adr == NULL)  return NULL; // node is dead
2866   return MemNode::calculate_adr_type(adr->bottom_type());
2867 }
2868 
2869 //------------------------------match_edge-------------------------------------
2870 // Do we Match on this edge index or not?  Do not match memory
2871 uint ClearArrayNode::match_edge(uint idx) const {
2872   return idx > 1;
2873 }
2874 
2875 //------------------------------Identity---------------------------------------
2876 // Clearing a zero length array does nothing
2877 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
2878   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2879 }
2880 
2881 //------------------------------Idealize---------------------------------------
2882 // Clearing a short array is faster with stores
2883 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2884   // Already know this is a large node, do not try to ideal it
2885   if (!IdealizeClearArrayNode || _is_large) return NULL;
2886 
2887   const int unit = BytesPerLong;
2888   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2889   if (!t)  return NULL;
2890   if (!t->is_con())  return NULL;
2891   intptr_t raw_count = t->get_con();
2892   intptr_t size = raw_count;
2893   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2894   // Clearing nothing uses the Identity call.
2895   // Negative clears are possible on dead ClearArrays
2896   // (see jck test stmt114.stmt11402.val).
2897   if (size <= 0 || size % unit != 0)  return NULL;
2898   intptr_t count = size / unit;
2899   // Length too long; communicate this to matchers and assemblers.
2900   // Assemblers are responsible to produce fast hardware clears for it.
2901   if (size > InitArrayShortSize) {
2902     return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
2903   }
2904   Node *mem = in(1);
2905   if( phase->type(mem)==Type::TOP ) return NULL;
2906   Node *adr = in(3);
2907   const Type* at = phase->type(adr);
2908   if( at==Type::TOP ) return NULL;
2909   const TypePtr* atp = at->isa_ptr();
2910   // adjust atp to be the correct array element address type
2911   if (atp == NULL)  atp = TypePtr::BOTTOM;
2912   else              atp = atp->add_offset(Type::OffsetBot);
2913   // Get base for derived pointer purposes
2914   if( adr->Opcode() != Op_AddP ) Unimplemented();
2915   Node *base = adr->in(1);
2916 
2917   Node *zero = phase->makecon(TypeLong::ZERO);
2918   Node *off  = phase->MakeConX(BytesPerLong);
2919   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2920   count--;
2921   while( count-- ) {
2922     mem = phase->transform(mem);
2923     adr = phase->transform(new AddPNode(base,adr,off));
2924     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2925   }
2926   return mem;
2927 }
2928 
2929 //----------------------------step_through----------------------------------
2930 // Return allocation input memory edge if it is different instance
2931 // or itself if it is the one we are looking for.
2932 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2933   Node* n = *np;
2934   assert(n->is_ClearArray(), "sanity");
2935   intptr_t offset;
2936   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2937   // This method is called only before Allocate nodes are expanded
2938   // during macro nodes expansion. Before that ClearArray nodes are
2939   // only generated in PhaseMacroExpand::generate_arraycopy() (before
2940   // Allocate nodes are expanded) which follows allocations.
2941   assert(alloc != NULL, "should have allocation");
2942   if (alloc->_idx == instance_id) {
2943     // Can not bypass initialization of the instance we are looking for.
2944     return false;
2945   }
2946   // Otherwise skip it.
2947   InitializeNode* init = alloc->initialization();
2948   if (init != NULL)
2949     *np = init->in(TypeFunc::Memory);
2950   else
2951     *np = alloc->in(TypeFunc::Memory);
2952   return true;
2953 }
2954 
2955 //----------------------------clear_memory-------------------------------------
2956 // Generate code to initialize object storage to zero.
2957 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2958                                    intptr_t start_offset,
2959                                    Node* end_offset,
2960                                    PhaseGVN* phase) {
2961   intptr_t offset = start_offset;
2962 
2963   int unit = BytesPerLong;
2964   if ((offset % unit) != 0) {
2965     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
2966     adr = phase->transform(adr);
2967     const TypePtr* atp = TypeRawPtr::BOTTOM;
2968     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2969     mem = phase->transform(mem);
2970     offset += BytesPerInt;
2971   }
2972   assert((offset % unit) == 0, "");
2973 
2974   // Initialize the remaining stuff, if any, with a ClearArray.
2975   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2976 }
2977 
2978 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2979                                    Node* start_offset,
2980                                    Node* end_offset,
2981                                    PhaseGVN* phase) {
2982   if (start_offset == end_offset) {
2983     // nothing to do
2984     return mem;
2985   }
2986 
2987   int unit = BytesPerLong;
2988   Node* zbase = start_offset;
2989   Node* zend  = end_offset;
2990 
2991   // Scale to the unit required by the CPU:
2992   if (!Matcher::init_array_count_is_in_bytes) {
2993     Node* shift = phase->intcon(exact_log2(unit));
2994     zbase = phase->transform(new URShiftXNode(zbase, shift) );
2995     zend  = phase->transform(new URShiftXNode(zend,  shift) );
2996   }
2997 
2998   // Bulk clear double-words
2999   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
3000   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
3001   mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
3002   return phase->transform(mem);
3003 }
3004 
3005 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3006                                    intptr_t start_offset,
3007                                    intptr_t end_offset,
3008                                    PhaseGVN* phase) {
3009   if (start_offset == end_offset) {
3010     // nothing to do
3011     return mem;
3012   }
3013 
3014   assert((end_offset % BytesPerInt) == 0, "odd end offset");
3015   intptr_t done_offset = end_offset;
3016   if ((done_offset % BytesPerLong) != 0) {
3017     done_offset -= BytesPerInt;
3018   }
3019   if (done_offset > start_offset) {
3020     mem = clear_memory(ctl, mem, dest,
3021                        start_offset, phase->MakeConX(done_offset), phase);
3022   }
3023   if (done_offset < end_offset) { // emit the final 32-bit store
3024     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3025     adr = phase->transform(adr);
3026     const TypePtr* atp = TypeRawPtr::BOTTOM;
3027     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3028     mem = phase->transform(mem);
3029     done_offset += BytesPerInt;
3030   }
3031   assert(done_offset == end_offset, "");
3032   return mem;
3033 }
3034 
3035 //=============================================================================
3036 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3037   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
3038     _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3039 #ifdef ASSERT
3040   , _pair_idx(0)
3041 #endif
3042 {
3043   init_class_id(Class_MemBar);
3044   Node* top = C->top();
3045   init_req(TypeFunc::I_O,top);
3046   init_req(TypeFunc::FramePtr,top);
3047   init_req(TypeFunc::ReturnAdr,top);
3048   if (precedent != NULL)
3049     init_req(TypeFunc::Parms, precedent);
3050 }
3051 
3052 //------------------------------cmp--------------------------------------------
3053 uint MemBarNode::hash() const { return NO_HASH; }
3054 bool MemBarNode::cmp( const Node &n ) const {
3055   return (&n == this);          // Always fail except on self
3056 }
3057 
3058 //------------------------------make-------------------------------------------
3059 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3060   switch (opcode) {
3061   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
3062   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
3063   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
3064   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
3065   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3066   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3067   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
3068   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
3069   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
3070   case Op_Initialize:        return new InitializeNode(C, atp, pn);
3071   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
3072   default: ShouldNotReachHere(); return NULL;
3073   }
3074 }
3075 
3076 void MemBarNode::remove(PhaseIterGVN *igvn) {
3077   if (outcnt() != 2) {
3078     return;
3079   }
3080   if (trailing_store() || trailing_load_store()) {
3081     MemBarNode* leading = leading_membar();
3082     if (leading != NULL) {
3083       assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3084       leading->remove(igvn);
3085     }
3086   }
3087   igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3088   igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3089 }
3090 
3091 //------------------------------Ideal------------------------------------------
3092 // Return a node which is more "ideal" than the current node.  Strip out
3093 // control copies
3094 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3095   if (remove_dead_region(phase, can_reshape)) return this;
3096   // Don't bother trying to transform a dead node
3097   if (in(0) && in(0)->is_top()) {
3098     return NULL;
3099   }
3100 
3101   bool progress = false;
3102   // Eliminate volatile MemBars for scalar replaced objects.
3103   if (can_reshape && req() == (Precedent+1)) {
3104     bool eliminate = false;
3105     int opc = Opcode();
3106     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3107       // Volatile field loads and stores.
3108       Node* my_mem = in(MemBarNode::Precedent);
3109       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3110       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3111         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3112         // replace this Precedent (decodeN) with the Load instead.
3113         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
3114           Node* load_node = my_mem->in(1);
3115           set_req(MemBarNode::Precedent, load_node);
3116           phase->is_IterGVN()->_worklist.push(my_mem);
3117           my_mem = load_node;
3118         } else {
3119           assert(my_mem->unique_out() == this, "sanity");
3120           del_req(Precedent);
3121           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3122           my_mem = NULL;
3123         }
3124         progress = true;
3125       }
3126       if (my_mem != NULL && my_mem->is_Mem()) {
3127         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3128         // Check for scalar replaced object reference.
3129         if( t_oop != NULL && t_oop->is_known_instance_field() &&
3130             t_oop->offset() != Type::OffsetBot &&
3131             t_oop->offset() != Type::OffsetTop) {
3132           eliminate = true;
3133         }
3134       }
3135     } else if (opc == Op_MemBarRelease) {
3136       // Final field stores.
3137       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
3138       if ((alloc != NULL) && alloc->is_Allocate() &&
3139           alloc->as_Allocate()->does_not_escape_thread()) {
3140         // The allocated object does not escape.
3141         eliminate = true;
3142       }
3143     }
3144     if (eliminate) {
3145       // Replace MemBar projections by its inputs.
3146       PhaseIterGVN* igvn = phase->is_IterGVN();
3147       remove(igvn);
3148       // Must return either the original node (now dead) or a new node
3149       // (Do not return a top here, since that would break the uniqueness of top.)
3150       return new ConINode(TypeInt::ZERO);
3151     }
3152   }
3153   return progress ? this : NULL;
3154 }
3155 
3156 //------------------------------Value------------------------------------------
3157 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3158   if( !in(0) ) return Type::TOP;
3159   if( phase->type(in(0)) == Type::TOP )
3160     return Type::TOP;
3161   return TypeTuple::MEMBAR;
3162 }
3163 
3164 //------------------------------match------------------------------------------
3165 // Construct projections for memory.
3166 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3167   switch (proj->_con) {
3168   case TypeFunc::Control:
3169   case TypeFunc::Memory:
3170     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3171   }
3172   ShouldNotReachHere();
3173   return NULL;
3174 }
3175 
3176 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3177   trailing->_kind = TrailingStore;
3178   leading->_kind = LeadingStore;
3179 #ifdef ASSERT
3180   trailing->_pair_idx = leading->_idx;
3181   leading->_pair_idx = leading->_idx;
3182 #endif
3183 }
3184 
3185 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3186   trailing->_kind = TrailingLoadStore;
3187   leading->_kind = LeadingLoadStore;
3188 #ifdef ASSERT
3189   trailing->_pair_idx = leading->_idx;
3190   leading->_pair_idx = leading->_idx;
3191 #endif
3192 }
3193 
3194 MemBarNode* MemBarNode::trailing_membar() const {
3195   ResourceMark rm;
3196   Node* trailing = (Node*)this;
3197   VectorSet seen(Thread::current()->resource_area());
3198   Node_Stack multis(0);
3199   do {
3200     Node* c = trailing;
3201     uint i = 0;
3202     do {
3203       trailing = NULL;
3204       for (; i < c->outcnt(); i++) {
3205         Node* next = c->raw_out(i);
3206         if (next != c && next->is_CFG()) {
3207           if (c->is_MultiBranch()) {
3208             if (multis.node() == c) {
3209               multis.set_index(i+1);
3210             } else {
3211               multis.push(c, i+1);
3212             }
3213           }
3214           trailing = next;
3215           break;
3216         }
3217       }
3218       if (trailing != NULL && !seen.test_set(trailing->_idx)) {
3219         break;
3220       }
3221       while (multis.size() > 0) {
3222         c = multis.node();
3223         i = multis.index();
3224         if (i < c->req()) {
3225           break;
3226         }
3227         multis.pop();
3228       }
3229     } while (multis.size() > 0);
3230   } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3231 
3232   MemBarNode* mb = trailing->as_MemBar();
3233   assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3234          (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3235   assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3236   return mb;
3237 }
3238 
3239 MemBarNode* MemBarNode::leading_membar() const {
3240   ResourceMark rm;
3241   VectorSet seen(Thread::current()->resource_area());
3242   Node_Stack regions(0);
3243   Node* leading = in(0);
3244   while (leading != NULL && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3245     while (leading == NULL || leading->is_top() || seen.test_set(leading->_idx)) {
3246       leading = NULL;
3247       while (regions.size() > 0 && leading == NULL) {
3248         Node* r = regions.node();
3249         uint i = regions.index();
3250         if (i < r->req()) {
3251           leading = r->in(i);
3252           regions.set_index(i+1);
3253         } else {
3254           regions.pop();
3255         }
3256       }
3257       if (leading == NULL) {
3258         assert(regions.size() == 0, "all paths should have been tried");
3259         return NULL;
3260       }
3261     }
3262     if (leading->is_Region()) {
3263       regions.push(leading, 2);
3264       leading = leading->in(1);
3265     } else {
3266       leading = leading->in(0);
3267     }
3268   }
3269 #ifdef ASSERT
3270   Unique_Node_List wq;
3271   wq.push((Node*)this);
3272   uint found = 0;
3273   for (uint i = 0; i < wq.size(); i++) {
3274     Node* n = wq.at(i);
3275     if (n->is_Region()) {
3276       for (uint j = 1; j < n->req(); j++) {
3277         Node* in = n->in(j);
3278         if (in != NULL && !in->is_top()) {
3279           wq.push(in);
3280         }
3281       }
3282     } else {
3283       if (n->is_MemBar() && n->as_MemBar()->leading()) {
3284         assert(n == leading, "consistency check failed");
3285         found++;
3286       } else {
3287         Node* in = n->in(0);
3288         if (in != NULL && !in->is_top()) {
3289           wq.push(in);
3290         }
3291       }
3292     }
3293   }
3294   assert(found == 1 || (found == 0 && leading == NULL), "consistency check failed");
3295 #endif
3296   if (leading == NULL) {
3297     return NULL;
3298   }
3299   MemBarNode* mb = leading->as_MemBar();
3300   assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3301          (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3302   assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3303   return mb;
3304 }
3305 
3306 //===========================InitializeNode====================================
3307 // SUMMARY:
3308 // This node acts as a memory barrier on raw memory, after some raw stores.
3309 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3310 // The Initialize can 'capture' suitably constrained stores as raw inits.
3311 // It can coalesce related raw stores into larger units (called 'tiles').
3312 // It can avoid zeroing new storage for memory units which have raw inits.
3313 // At macro-expansion, it is marked 'complete', and does not optimize further.
3314 //
3315 // EXAMPLE:
3316 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3317 //   ctl = incoming control; mem* = incoming memory
3318 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3319 // First allocate uninitialized memory and fill in the header:
3320 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3321 //   ctl := alloc.Control; mem* := alloc.Memory*
3322 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3323 // Then initialize to zero the non-header parts of the raw memory block:
3324 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3325 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3326 // After the initialize node executes, the object is ready for service:
3327 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3328 // Suppose its body is immediately initialized as {1,2}:
3329 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3330 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3331 //   mem.SLICE(#short[*]) := store2
3332 //
3333 // DETAILS:
3334 // An InitializeNode collects and isolates object initialization after
3335 // an AllocateNode and before the next possible safepoint.  As a
3336 // memory barrier (MemBarNode), it keeps critical stores from drifting
3337 // down past any safepoint or any publication of the allocation.
3338 // Before this barrier, a newly-allocated object may have uninitialized bits.
3339 // After this barrier, it may be treated as a real oop, and GC is allowed.
3340 //
3341 // The semantics of the InitializeNode include an implicit zeroing of
3342 // the new object from object header to the end of the object.
3343 // (The object header and end are determined by the AllocateNode.)
3344 //
3345 // Certain stores may be added as direct inputs to the InitializeNode.
3346 // These stores must update raw memory, and they must be to addresses
3347 // derived from the raw address produced by AllocateNode, and with
3348 // a constant offset.  They must be ordered by increasing offset.
3349 // The first one is at in(RawStores), the last at in(req()-1).
3350 // Unlike most memory operations, they are not linked in a chain,
3351 // but are displayed in parallel as users of the rawmem output of
3352 // the allocation.
3353 //
3354 // (See comments in InitializeNode::capture_store, which continue
3355 // the example given above.)
3356 //
3357 // When the associated Allocate is macro-expanded, the InitializeNode
3358 // may be rewritten to optimize collected stores.  A ClearArrayNode
3359 // may also be created at that point to represent any required zeroing.
3360 // The InitializeNode is then marked 'complete', prohibiting further
3361 // capturing of nearby memory operations.
3362 //
3363 // During macro-expansion, all captured initializations which store
3364 // constant values of 32 bits or smaller are coalesced (if advantageous)
3365 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3366 // initialized in fewer memory operations.  Memory words which are
3367 // covered by neither tiles nor non-constant stores are pre-zeroed
3368 // by explicit stores of zero.  (The code shape happens to do all
3369 // zeroing first, then all other stores, with both sequences occurring
3370 // in order of ascending offsets.)
3371 //
3372 // Alternatively, code may be inserted between an AllocateNode and its
3373 // InitializeNode, to perform arbitrary initialization of the new object.
3374 // E.g., the object copying intrinsics insert complex data transfers here.
3375 // The initialization must then be marked as 'complete' disable the
3376 // built-in zeroing semantics and the collection of initializing stores.
3377 //
3378 // While an InitializeNode is incomplete, reads from the memory state
3379 // produced by it are optimizable if they match the control edge and
3380 // new oop address associated with the allocation/initialization.
3381 // They return a stored value (if the offset matches) or else zero.
3382 // A write to the memory state, if it matches control and address,
3383 // and if it is to a constant offset, may be 'captured' by the
3384 // InitializeNode.  It is cloned as a raw memory operation and rewired
3385 // inside the initialization, to the raw oop produced by the allocation.
3386 // Operations on addresses which are provably distinct (e.g., to
3387 // other AllocateNodes) are allowed to bypass the initialization.
3388 //
3389 // The effect of all this is to consolidate object initialization
3390 // (both arrays and non-arrays, both piecewise and bulk) into a
3391 // single location, where it can be optimized as a unit.
3392 //
3393 // Only stores with an offset less than TrackedInitializationLimit words
3394 // will be considered for capture by an InitializeNode.  This puts a
3395 // reasonable limit on the complexity of optimized initializations.
3396 
3397 //---------------------------InitializeNode------------------------------------
3398 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3399   : MemBarNode(C, adr_type, rawoop),
3400     _is_complete(Incomplete), _does_not_escape(false)
3401 {
3402   init_class_id(Class_Initialize);
3403 
3404   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3405   assert(in(RawAddress) == rawoop, "proper init");
3406   // Note:  allocation() can be NULL, for secondary initialization barriers
3407 }
3408 
3409 // Since this node is not matched, it will be processed by the
3410 // register allocator.  Declare that there are no constraints
3411 // on the allocation of the RawAddress edge.
3412 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3413   // This edge should be set to top, by the set_complete.  But be conservative.
3414   if (idx == InitializeNode::RawAddress)
3415     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3416   return RegMask::Empty;
3417 }
3418 
3419 Node* InitializeNode::memory(uint alias_idx) {
3420   Node* mem = in(Memory);
3421   if (mem->is_MergeMem()) {
3422     return mem->as_MergeMem()->memory_at(alias_idx);
3423   } else {
3424     // incoming raw memory is not split
3425     return mem;
3426   }
3427 }
3428 
3429 bool InitializeNode::is_non_zero() {
3430   if (is_complete())  return false;
3431   remove_extra_zeroes();
3432   return (req() > RawStores);
3433 }
3434 
3435 void InitializeNode::set_complete(PhaseGVN* phase) {
3436   assert(!is_complete(), "caller responsibility");
3437   _is_complete = Complete;
3438 
3439   // After this node is complete, it contains a bunch of
3440   // raw-memory initializations.  There is no need for
3441   // it to have anything to do with non-raw memory effects.
3442   // Therefore, tell all non-raw users to re-optimize themselves,
3443   // after skipping the memory effects of this initialization.
3444   PhaseIterGVN* igvn = phase->is_IterGVN();
3445   if (igvn)  igvn->add_users_to_worklist(this);
3446 }
3447 
3448 // convenience function
3449 // return false if the init contains any stores already
3450 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3451   InitializeNode* init = initialization();
3452   if (init == NULL || init->is_complete())  return false;
3453   init->remove_extra_zeroes();
3454   // for now, if this allocation has already collected any inits, bail:
3455   if (init->is_non_zero())  return false;
3456   init->set_complete(phase);
3457   return true;
3458 }
3459 
3460 void InitializeNode::remove_extra_zeroes() {
3461   if (req() == RawStores)  return;
3462   Node* zmem = zero_memory();
3463   uint fill = RawStores;
3464   for (uint i = fill; i < req(); i++) {
3465     Node* n = in(i);
3466     if (n->is_top() || n == zmem)  continue;  // skip
3467     if (fill < i)  set_req(fill, n);          // compact
3468     ++fill;
3469   }
3470   // delete any empty spaces created:
3471   while (fill < req()) {
3472     del_req(fill);
3473   }
3474 }
3475 
3476 // Helper for remembering which stores go with which offsets.
3477 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3478   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3479   intptr_t offset = -1;
3480   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3481                                                phase, offset);
3482   if (base == NULL)     return -1;  // something is dead,
3483   if (offset < 0)       return -1;  //        dead, dead
3484   return offset;
3485 }
3486 
3487 // Helper for proving that an initialization expression is
3488 // "simple enough" to be folded into an object initialization.
3489 // Attempts to prove that a store's initial value 'n' can be captured
3490 // within the initialization without creating a vicious cycle, such as:
3491 //     { Foo p = new Foo(); p.next = p; }
3492 // True for constants and parameters and small combinations thereof.
3493 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3494   if (n == NULL)      return true;   // (can this really happen?)
3495   if (n->is_Proj())   n = n->in(0);
3496   if (n == this)      return false;  // found a cycle
3497   if (n->is_Con())    return true;
3498   if (n->is_Start())  return true;   // params, etc., are OK
3499   if (n->is_Root())   return true;   // even better
3500 
3501   Node* ctl = n->in(0);
3502   if (ctl != NULL && !ctl->is_top()) {
3503     if (ctl->is_Proj())  ctl = ctl->in(0);
3504     if (ctl == this)  return false;
3505 
3506     // If we already know that the enclosing memory op is pinned right after
3507     // the init, then any control flow that the store has picked up
3508     // must have preceded the init, or else be equal to the init.
3509     // Even after loop optimizations (which might change control edges)
3510     // a store is never pinned *before* the availability of its inputs.
3511     if (!MemNode::all_controls_dominate(n, this))
3512       return false;                  // failed to prove a good control
3513   }
3514 
3515   // Check data edges for possible dependencies on 'this'.
3516   if ((count += 1) > 20)  return false;  // complexity limit
3517   for (uint i = 1; i < n->req(); i++) {
3518     Node* m = n->in(i);
3519     if (m == NULL || m == n || m->is_top())  continue;
3520     uint first_i = n->find_edge(m);
3521     if (i != first_i)  continue;  // process duplicate edge just once
3522     if (!detect_init_independence(m, count)) {
3523       return false;
3524     }
3525   }
3526 
3527   return true;
3528 }
3529 
3530 // Here are all the checks a Store must pass before it can be moved into
3531 // an initialization.  Returns zero if a check fails.
3532 // On success, returns the (constant) offset to which the store applies,
3533 // within the initialized memory.
3534 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3535   const int FAIL = 0;
3536   if (st->req() != MemNode::ValueIn + 1)
3537     return FAIL;                // an inscrutable StoreNode (card mark?)
3538   Node* ctl = st->in(MemNode::Control);
3539   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3540     return FAIL;                // must be unconditional after the initialization
3541   Node* mem = st->in(MemNode::Memory);
3542   if (!(mem->is_Proj() && mem->in(0) == this))
3543     return FAIL;                // must not be preceded by other stores
3544   Node* adr = st->in(MemNode::Address);
3545   intptr_t offset;
3546   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3547   if (alloc == NULL)
3548     return FAIL;                // inscrutable address
3549   if (alloc != allocation())
3550     return FAIL;                // wrong allocation!  (store needs to float up)
3551   int size_in_bytes = st->memory_size();
3552   if ((size_in_bytes != 0) && (offset % size_in_bytes) != 0) {
3553     return FAIL;                // mismatched access
3554   }
3555   Node* val = st->in(MemNode::ValueIn);
3556   int complexity_count = 0;
3557   if (!detect_init_independence(val, complexity_count))
3558     return FAIL;                // stored value must be 'simple enough'
3559 
3560   // The Store can be captured only if nothing after the allocation
3561   // and before the Store is using the memory location that the store
3562   // overwrites.
3563   bool failed = false;
3564   // If is_complete_with_arraycopy() is true the shape of the graph is
3565   // well defined and is safe so no need for extra checks.
3566   if (!is_complete_with_arraycopy()) {
3567     // We are going to look at each use of the memory state following
3568     // the allocation to make sure nothing reads the memory that the
3569     // Store writes.
3570     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3571     int alias_idx = phase->C->get_alias_index(t_adr);
3572     ResourceMark rm;
3573     Unique_Node_List mems;
3574     mems.push(mem);
3575     Node* unique_merge = NULL;
3576     for (uint next = 0; next < mems.size(); ++next) {
3577       Node *m  = mems.at(next);
3578       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3579         Node *n = m->fast_out(j);
3580         if (n->outcnt() == 0) {
3581           continue;
3582         }
3583         if (n == st) {
3584           continue;
3585         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3586           // If the control of this use is different from the control
3587           // of the Store which is right after the InitializeNode then
3588           // this node cannot be between the InitializeNode and the
3589           // Store.
3590           continue;
3591         } else if (n->is_MergeMem()) {
3592           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3593             // We can hit a MergeMemNode (that will likely go away
3594             // later) that is a direct use of the memory state
3595             // following the InitializeNode on the same slice as the
3596             // store node that we'd like to capture. We need to check
3597             // the uses of the MergeMemNode.
3598             mems.push(n);
3599           }
3600         } else if (n->is_Mem()) {
3601           Node* other_adr = n->in(MemNode::Address);
3602           if (other_adr == adr) {
3603             failed = true;
3604             break;
3605           } else {
3606             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3607             if (other_t_adr != NULL) {
3608               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3609               if (other_alias_idx == alias_idx) {
3610                 // A load from the same memory slice as the store right
3611                 // after the InitializeNode. We check the control of the
3612                 // object/array that is loaded from. If it's the same as
3613                 // the store control then we cannot capture the store.
3614                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3615                 Node* base = other_adr;
3616                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3617                 base = base->in(AddPNode::Base);
3618                 if (base != NULL) {
3619                   base = base->uncast();
3620                   if (base->is_Proj() && base->in(0) == alloc) {
3621                     failed = true;
3622                     break;
3623                   }
3624                 }
3625               }
3626             }
3627           }
3628         } else {
3629           failed = true;
3630           break;
3631         }
3632       }
3633     }
3634   }
3635   if (failed) {
3636     if (!can_reshape) {
3637       // We decided we couldn't capture the store during parsing. We
3638       // should try again during the next IGVN once the graph is
3639       // cleaner.
3640       phase->C->record_for_igvn(st);
3641     }
3642     return FAIL;
3643   }
3644 
3645   return offset;                // success
3646 }
3647 
3648 // Find the captured store in(i) which corresponds to the range
3649 // [start..start+size) in the initialized object.
3650 // If there is one, return its index i.  If there isn't, return the
3651 // negative of the index where it should be inserted.
3652 // Return 0 if the queried range overlaps an initialization boundary
3653 // or if dead code is encountered.
3654 // If size_in_bytes is zero, do not bother with overlap checks.
3655 int InitializeNode::captured_store_insertion_point(intptr_t start,
3656                                                    int size_in_bytes,
3657                                                    PhaseTransform* phase) {
3658   const int FAIL = 0, MAX_STORE = BytesPerLong;
3659 
3660   if (is_complete())
3661     return FAIL;                // arraycopy got here first; punt
3662 
3663   assert(allocation() != NULL, "must be present");
3664 
3665   // no negatives, no header fields:
3666   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3667 
3668   // after a certain size, we bail out on tracking all the stores:
3669   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3670   if (start >= ti_limit)  return FAIL;
3671 
3672   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3673     if (i >= limit)  return -(int)i; // not found; here is where to put it
3674 
3675     Node*    st     = in(i);
3676     intptr_t st_off = get_store_offset(st, phase);
3677     if (st_off < 0) {
3678       if (st != zero_memory()) {
3679         return FAIL;            // bail out if there is dead garbage
3680       }
3681     } else if (st_off > start) {
3682       // ...we are done, since stores are ordered
3683       if (st_off < start + size_in_bytes) {
3684         return FAIL;            // the next store overlaps
3685       }
3686       return -(int)i;           // not found; here is where to put it
3687     } else if (st_off < start) {
3688       if (size_in_bytes != 0 &&
3689           start < st_off + MAX_STORE &&
3690           start < st_off + st->as_Store()->memory_size()) {
3691         return FAIL;            // the previous store overlaps
3692       }
3693     } else {
3694       if (size_in_bytes != 0 &&
3695           st->as_Store()->memory_size() != size_in_bytes) {
3696         return FAIL;            // mismatched store size
3697       }
3698       return i;
3699     }
3700 
3701     ++i;
3702   }
3703 }
3704 
3705 // Look for a captured store which initializes at the offset 'start'
3706 // with the given size.  If there is no such store, and no other
3707 // initialization interferes, then return zero_memory (the memory
3708 // projection of the AllocateNode).
3709 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3710                                           PhaseTransform* phase) {
3711   assert(stores_are_sane(phase), "");
3712   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3713   if (i == 0) {
3714     return NULL;                // something is dead
3715   } else if (i < 0) {
3716     return zero_memory();       // just primordial zero bits here
3717   } else {
3718     Node* st = in(i);           // here is the store at this position
3719     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3720     return st;
3721   }
3722 }
3723 
3724 // Create, as a raw pointer, an address within my new object at 'offset'.
3725 Node* InitializeNode::make_raw_address(intptr_t offset,
3726                                        PhaseTransform* phase) {
3727   Node* addr = in(RawAddress);
3728   if (offset != 0) {
3729     Compile* C = phase->C;
3730     addr = phase->transform( new AddPNode(C->top(), addr,
3731                                                  phase->MakeConX(offset)) );
3732   }
3733   return addr;
3734 }
3735 
3736 // Clone the given store, converting it into a raw store
3737 // initializing a field or element of my new object.
3738 // Caller is responsible for retiring the original store,
3739 // with subsume_node or the like.
3740 //
3741 // From the example above InitializeNode::InitializeNode,
3742 // here are the old stores to be captured:
3743 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3744 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3745 //
3746 // Here is the changed code; note the extra edges on init:
3747 //   alloc = (Allocate ...)
3748 //   rawoop = alloc.RawAddress
3749 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3750 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3751 //   init = (Initialize alloc.Control alloc.Memory rawoop
3752 //                      rawstore1 rawstore2)
3753 //
3754 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3755                                     PhaseTransform* phase, bool can_reshape) {
3756   assert(stores_are_sane(phase), "");
3757 
3758   if (start < 0)  return NULL;
3759   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3760 
3761   Compile* C = phase->C;
3762   int size_in_bytes = st->memory_size();
3763   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3764   if (i == 0)  return NULL;     // bail out
3765   Node* prev_mem = NULL;        // raw memory for the captured store
3766   if (i > 0) {
3767     prev_mem = in(i);           // there is a pre-existing store under this one
3768     set_req(i, C->top());       // temporarily disconnect it
3769     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3770   } else {
3771     i = -i;                     // no pre-existing store
3772     prev_mem = zero_memory();   // a slice of the newly allocated object
3773     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3774       set_req(--i, C->top());   // reuse this edge; it has been folded away
3775     else
3776       ins_req(i, C->top());     // build a new edge
3777   }
3778   Node* new_st = st->clone();
3779   new_st->set_req(MemNode::Control, in(Control));
3780   new_st->set_req(MemNode::Memory,  prev_mem);
3781   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3782   new_st = phase->transform(new_st);
3783 
3784   // At this point, new_st might have swallowed a pre-existing store
3785   // at the same offset, or perhaps new_st might have disappeared,
3786   // if it redundantly stored the same value (or zero to fresh memory).
3787 
3788   // In any case, wire it in:
3789   phase->igvn_rehash_node_delayed(this);
3790   set_req(i, new_st);
3791 
3792   // The caller may now kill the old guy.
3793   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3794   assert(check_st == new_st || check_st == NULL, "must be findable");
3795   assert(!is_complete(), "");
3796   return new_st;
3797 }
3798 
3799 static bool store_constant(jlong* tiles, int num_tiles,
3800                            intptr_t st_off, int st_size,
3801                            jlong con) {
3802   if ((st_off & (st_size-1)) != 0)
3803     return false;               // strange store offset (assume size==2**N)
3804   address addr = (address)tiles + st_off;
3805   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3806   switch (st_size) {
3807   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3808   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3809   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3810   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3811   default: return false;        // strange store size (detect size!=2**N here)
3812   }
3813   return true;                  // return success to caller
3814 }
3815 
3816 // Coalesce subword constants into int constants and possibly
3817 // into long constants.  The goal, if the CPU permits,
3818 // is to initialize the object with a small number of 64-bit tiles.
3819 // Also, convert floating-point constants to bit patterns.
3820 // Non-constants are not relevant to this pass.
3821 //
3822 // In terms of the running example on InitializeNode::InitializeNode
3823 // and InitializeNode::capture_store, here is the transformation
3824 // of rawstore1 and rawstore2 into rawstore12:
3825 //   alloc = (Allocate ...)
3826 //   rawoop = alloc.RawAddress
3827 //   tile12 = 0x00010002
3828 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3829 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3830 //
3831 void
3832 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3833                                         Node* size_in_bytes,
3834                                         PhaseGVN* phase) {
3835   Compile* C = phase->C;
3836 
3837   assert(stores_are_sane(phase), "");
3838   // Note:  After this pass, they are not completely sane,
3839   // since there may be some overlaps.
3840 
3841   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3842 
3843   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3844   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3845   size_limit = MIN2(size_limit, ti_limit);
3846   size_limit = align_up(size_limit, BytesPerLong);
3847   int num_tiles = size_limit / BytesPerLong;
3848 
3849   // allocate space for the tile map:
3850   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3851   jlong  tiles_buf[small_len];
3852   Node*  nodes_buf[small_len];
3853   jlong  inits_buf[small_len];
3854   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3855                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3856   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3857                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3858   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3859                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3860   // tiles: exact bitwise model of all primitive constants
3861   // nodes: last constant-storing node subsumed into the tiles model
3862   // inits: which bytes (in each tile) are touched by any initializations
3863 
3864   //// Pass A: Fill in the tile model with any relevant stores.
3865 
3866   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3867   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3868   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3869   Node* zmem = zero_memory(); // initially zero memory state
3870   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3871     Node* st = in(i);
3872     intptr_t st_off = get_store_offset(st, phase);
3873 
3874     // Figure out the store's offset and constant value:
3875     if (st_off < header_size)             continue; //skip (ignore header)
3876     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3877     int st_size = st->as_Store()->memory_size();
3878     if (st_off + st_size > size_limit)    break;
3879 
3880     // Record which bytes are touched, whether by constant or not.
3881     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3882       continue;                 // skip (strange store size)
3883 
3884     const Type* val = phase->type(st->in(MemNode::ValueIn));
3885     if (!val->singleton())                continue; //skip (non-con store)
3886     BasicType type = val->basic_type();
3887 
3888     jlong con = 0;
3889     switch (type) {
3890     case T_INT:    con = val->is_int()->get_con();  break;
3891     case T_LONG:   con = val->is_long()->get_con(); break;
3892     case T_FLOAT:  con = jint_cast(val->getf());    break;
3893     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3894     default:                              continue; //skip (odd store type)
3895     }
3896 
3897     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3898         st->Opcode() == Op_StoreL) {
3899       continue;                 // This StoreL is already optimal.
3900     }
3901 
3902     // Store down the constant.
3903     store_constant(tiles, num_tiles, st_off, st_size, con);
3904 
3905     intptr_t j = st_off >> LogBytesPerLong;
3906 
3907     if (type == T_INT && st_size == BytesPerInt
3908         && (st_off & BytesPerInt) == BytesPerInt) {
3909       jlong lcon = tiles[j];
3910       if (!Matcher::isSimpleConstant64(lcon) &&
3911           st->Opcode() == Op_StoreI) {
3912         // This StoreI is already optimal by itself.
3913         jint* intcon = (jint*) &tiles[j];
3914         intcon[1] = 0;  // undo the store_constant()
3915 
3916         // If the previous store is also optimal by itself, back up and
3917         // undo the action of the previous loop iteration... if we can.
3918         // But if we can't, just let the previous half take care of itself.
3919         st = nodes[j];
3920         st_off -= BytesPerInt;
3921         con = intcon[0];
3922         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3923           assert(st_off >= header_size, "still ignoring header");
3924           assert(get_store_offset(st, phase) == st_off, "must be");
3925           assert(in(i-1) == zmem, "must be");
3926           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3927           assert(con == tcon->is_int()->get_con(), "must be");
3928           // Undo the effects of the previous loop trip, which swallowed st:
3929           intcon[0] = 0;        // undo store_constant()
3930           set_req(i-1, st);     // undo set_req(i, zmem)
3931           nodes[j] = NULL;      // undo nodes[j] = st
3932           --old_subword;        // undo ++old_subword
3933         }
3934         continue;               // This StoreI is already optimal.
3935       }
3936     }
3937 
3938     // This store is not needed.
3939     set_req(i, zmem);
3940     nodes[j] = st;              // record for the moment
3941     if (st_size < BytesPerLong) // something has changed
3942           ++old_subword;        // includes int/float, but who's counting...
3943     else  ++old_long;
3944   }
3945 
3946   if ((old_subword + old_long) == 0)
3947     return;                     // nothing more to do
3948 
3949   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3950   // Be sure to insert them before overlapping non-constant stores.
3951   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3952   for (int j = 0; j < num_tiles; j++) {
3953     jlong con  = tiles[j];
3954     jlong init = inits[j];
3955     if (con == 0)  continue;
3956     jint con0,  con1;           // split the constant, address-wise
3957     jint init0, init1;          // split the init map, address-wise
3958     { union { jlong con; jint intcon[2]; } u;
3959       u.con = con;
3960       con0  = u.intcon[0];
3961       con1  = u.intcon[1];
3962       u.con = init;
3963       init0 = u.intcon[0];
3964       init1 = u.intcon[1];
3965     }
3966 
3967     Node* old = nodes[j];
3968     assert(old != NULL, "need the prior store");
3969     intptr_t offset = (j * BytesPerLong);
3970 
3971     bool split = !Matcher::isSimpleConstant64(con);
3972 
3973     if (offset < header_size) {
3974       assert(offset + BytesPerInt >= header_size, "second int counts");
3975       assert(*(jint*)&tiles[j] == 0, "junk in header");
3976       split = true;             // only the second word counts
3977       // Example:  int a[] = { 42 ... }
3978     } else if (con0 == 0 && init0 == -1) {
3979       split = true;             // first word is covered by full inits
3980       // Example:  int a[] = { ... foo(), 42 ... }
3981     } else if (con1 == 0 && init1 == -1) {
3982       split = true;             // second word is covered by full inits
3983       // Example:  int a[] = { ... 42, foo() ... }
3984     }
3985 
3986     // Here's a case where init0 is neither 0 nor -1:
3987     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
3988     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3989     // In this case the tile is not split; it is (jlong)42.
3990     // The big tile is stored down, and then the foo() value is inserted.
3991     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3992 
3993     Node* ctl = old->in(MemNode::Control);
3994     Node* adr = make_raw_address(offset, phase);
3995     const TypePtr* atp = TypeRawPtr::BOTTOM;
3996 
3997     // One or two coalesced stores to plop down.
3998     Node*    st[2];
3999     intptr_t off[2];
4000     int  nst = 0;
4001     if (!split) {
4002       ++new_long;
4003       off[nst] = offset;
4004       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4005                                   phase->longcon(con), T_LONG, MemNode::unordered);
4006     } else {
4007       // Omit either if it is a zero.
4008       if (con0 != 0) {
4009         ++new_int;
4010         off[nst]  = offset;
4011         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4012                                     phase->intcon(con0), T_INT, MemNode::unordered);
4013       }
4014       if (con1 != 0) {
4015         ++new_int;
4016         offset += BytesPerInt;
4017         adr = make_raw_address(offset, phase);
4018         off[nst]  = offset;
4019         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4020                                     phase->intcon(con1), T_INT, MemNode::unordered);
4021       }
4022     }
4023 
4024     // Insert second store first, then the first before the second.
4025     // Insert each one just before any overlapping non-constant stores.
4026     while (nst > 0) {
4027       Node* st1 = st[--nst];
4028       C->copy_node_notes_to(st1, old);
4029       st1 = phase->transform(st1);
4030       offset = off[nst];
4031       assert(offset >= header_size, "do not smash header");
4032       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4033       guarantee(ins_idx != 0, "must re-insert constant store");
4034       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
4035       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4036         set_req(--ins_idx, st1);
4037       else
4038         ins_req(ins_idx, st1);
4039     }
4040   }
4041 
4042   if (PrintCompilation && WizardMode)
4043     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4044                   old_subword, old_long, new_int, new_long);
4045   if (C->log() != NULL)
4046     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4047                    old_subword, old_long, new_int, new_long);
4048 
4049   // Clean up any remaining occurrences of zmem:
4050   remove_extra_zeroes();
4051 }
4052 
4053 // Explore forward from in(start) to find the first fully initialized
4054 // word, and return its offset.  Skip groups of subword stores which
4055 // together initialize full words.  If in(start) is itself part of a
4056 // fully initialized word, return the offset of in(start).  If there
4057 // are no following full-word stores, or if something is fishy, return
4058 // a negative value.
4059 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4060   int       int_map = 0;
4061   intptr_t  int_map_off = 0;
4062   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
4063 
4064   for (uint i = start, limit = req(); i < limit; i++) {
4065     Node* st = in(i);
4066 
4067     intptr_t st_off = get_store_offset(st, phase);
4068     if (st_off < 0)  break;  // return conservative answer
4069 
4070     int st_size = st->as_Store()->memory_size();
4071     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4072       return st_off;            // we found a complete word init
4073     }
4074 
4075     // update the map:
4076 
4077     intptr_t this_int_off = align_down(st_off, BytesPerInt);
4078     if (this_int_off != int_map_off) {
4079       // reset the map:
4080       int_map = 0;
4081       int_map_off = this_int_off;
4082     }
4083 
4084     int subword_off = st_off - this_int_off;
4085     int_map |= right_n_bits(st_size) << subword_off;
4086     if ((int_map & FULL_MAP) == FULL_MAP) {
4087       return this_int_off;      // we found a complete word init
4088     }
4089 
4090     // Did this store hit or cross the word boundary?
4091     intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4092     if (next_int_off == this_int_off + BytesPerInt) {
4093       // We passed the current int, without fully initializing it.
4094       int_map_off = next_int_off;
4095       int_map >>= BytesPerInt;
4096     } else if (next_int_off > this_int_off + BytesPerInt) {
4097       // We passed the current and next int.
4098       return this_int_off + BytesPerInt;
4099     }
4100   }
4101 
4102   return -1;
4103 }
4104 
4105 
4106 // Called when the associated AllocateNode is expanded into CFG.
4107 // At this point, we may perform additional optimizations.
4108 // Linearize the stores by ascending offset, to make memory
4109 // activity as coherent as possible.
4110 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4111                                       intptr_t header_size,
4112                                       Node* size_in_bytes,
4113                                       PhaseGVN* phase) {
4114   assert(!is_complete(), "not already complete");
4115   assert(stores_are_sane(phase), "");
4116   assert(allocation() != NULL, "must be present");
4117 
4118   remove_extra_zeroes();
4119 
4120   if (ReduceFieldZeroing || ReduceBulkZeroing)
4121     // reduce instruction count for common initialization patterns
4122     coalesce_subword_stores(header_size, size_in_bytes, phase);
4123 
4124   Node* zmem = zero_memory();   // initially zero memory state
4125   Node* inits = zmem;           // accumulating a linearized chain of inits
4126   #ifdef ASSERT
4127   intptr_t first_offset = allocation()->minimum_header_size();
4128   intptr_t last_init_off = first_offset;  // previous init offset
4129   intptr_t last_init_end = first_offset;  // previous init offset+size
4130   intptr_t last_tile_end = first_offset;  // previous tile offset+size
4131   #endif
4132   intptr_t zeroes_done = header_size;
4133 
4134   bool do_zeroing = true;       // we might give up if inits are very sparse
4135   int  big_init_gaps = 0;       // how many large gaps have we seen?
4136 
4137   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
4138   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
4139 
4140   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4141     Node* st = in(i);
4142     intptr_t st_off = get_store_offset(st, phase);
4143     if (st_off < 0)
4144       break;                    // unknown junk in the inits
4145     if (st->in(MemNode::Memory) != zmem)
4146       break;                    // complicated store chains somehow in list
4147 
4148     int st_size = st->as_Store()->memory_size();
4149     intptr_t next_init_off = st_off + st_size;
4150 
4151     if (do_zeroing && zeroes_done < next_init_off) {
4152       // See if this store needs a zero before it or under it.
4153       intptr_t zeroes_needed = st_off;
4154 
4155       if (st_size < BytesPerInt) {
4156         // Look for subword stores which only partially initialize words.
4157         // If we find some, we must lay down some word-level zeroes first,
4158         // underneath the subword stores.
4159         //
4160         // Examples:
4161         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
4162         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
4163         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
4164         //
4165         // Note:  coalesce_subword_stores may have already done this,
4166         // if it was prompted by constant non-zero subword initializers.
4167         // But this case can still arise with non-constant stores.
4168 
4169         intptr_t next_full_store = find_next_fullword_store(i, phase);
4170 
4171         // In the examples above:
4172         //   in(i)          p   q   r   s     x   y     z
4173         //   st_off        12  13  14  15    12  13    14
4174         //   st_size        1   1   1   1     1   1     1
4175         //   next_full_s.  12  16  16  16    16  16    16
4176         //   z's_done      12  16  16  16    12  16    12
4177         //   z's_needed    12  16  16  16    16  16    16
4178         //   zsize          0   0   0   0     4   0     4
4179         if (next_full_store < 0) {
4180           // Conservative tack:  Zero to end of current word.
4181           zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4182         } else {
4183           // Zero to beginning of next fully initialized word.
4184           // Or, don't zero at all, if we are already in that word.
4185           assert(next_full_store >= zeroes_needed, "must go forward");
4186           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4187           zeroes_needed = next_full_store;
4188         }
4189       }
4190 
4191       if (zeroes_needed > zeroes_done) {
4192         intptr_t zsize = zeroes_needed - zeroes_done;
4193         // Do some incremental zeroing on rawmem, in parallel with inits.
4194         zeroes_done = align_down(zeroes_done, BytesPerInt);
4195         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4196                                               zeroes_done, zeroes_needed,
4197                                               phase);
4198         zeroes_done = zeroes_needed;
4199         if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4200           do_zeroing = false;   // leave the hole, next time
4201       }
4202     }
4203 
4204     // Collect the store and move on:
4205     st->set_req(MemNode::Memory, inits);
4206     inits = st;                 // put it on the linearized chain
4207     set_req(i, zmem);           // unhook from previous position
4208 
4209     if (zeroes_done == st_off)
4210       zeroes_done = next_init_off;
4211 
4212     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4213 
4214     #ifdef ASSERT
4215     // Various order invariants.  Weaker than stores_are_sane because
4216     // a large constant tile can be filled in by smaller non-constant stores.
4217     assert(st_off >= last_init_off, "inits do not reverse");
4218     last_init_off = st_off;
4219     const Type* val = NULL;
4220     if (st_size >= BytesPerInt &&
4221         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4222         (int)val->basic_type() < (int)T_OBJECT) {
4223       assert(st_off >= last_tile_end, "tiles do not overlap");
4224       assert(st_off >= last_init_end, "tiles do not overwrite inits");
4225       last_tile_end = MAX2(last_tile_end, next_init_off);
4226     } else {
4227       intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4228       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4229       assert(st_off      >= last_init_end, "inits do not overlap");
4230       last_init_end = next_init_off;  // it's a non-tile
4231     }
4232     #endif //ASSERT
4233   }
4234 
4235   remove_extra_zeroes();        // clear out all the zmems left over
4236   add_req(inits);
4237 
4238   if (!(UseTLAB && ZeroTLAB)) {
4239     // If anything remains to be zeroed, zero it all now.
4240     zeroes_done = align_down(zeroes_done, BytesPerInt);
4241     // if it is the last unused 4 bytes of an instance, forget about it
4242     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4243     if (zeroes_done + BytesPerLong >= size_limit) {
4244       AllocateNode* alloc = allocation();
4245       assert(alloc != NULL, "must be present");
4246       if (alloc != NULL && alloc->Opcode() == Op_Allocate) {
4247         Node* klass_node = alloc->in(AllocateNode::KlassNode);
4248         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
4249         if (zeroes_done == k->layout_helper())
4250           zeroes_done = size_limit;
4251       }
4252     }
4253     if (zeroes_done < size_limit) {
4254       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4255                                             zeroes_done, size_in_bytes, phase);
4256     }
4257   }
4258 
4259   set_complete(phase);
4260   return rawmem;
4261 }
4262 
4263 
4264 #ifdef ASSERT
4265 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
4266   if (is_complete())
4267     return true;                // stores could be anything at this point
4268   assert(allocation() != NULL, "must be present");
4269   intptr_t last_off = allocation()->minimum_header_size();
4270   for (uint i = InitializeNode::RawStores; i < req(); i++) {
4271     Node* st = in(i);
4272     intptr_t st_off = get_store_offset(st, phase);
4273     if (st_off < 0)  continue;  // ignore dead garbage
4274     if (last_off > st_off) {
4275       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4276       this->dump(2);
4277       assert(false, "ascending store offsets");
4278       return false;
4279     }
4280     last_off = st_off + st->as_Store()->memory_size();
4281   }
4282   return true;
4283 }
4284 #endif //ASSERT
4285 
4286 
4287 
4288 
4289 //============================MergeMemNode=====================================
4290 //
4291 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4292 // contributing store or call operations.  Each contributor provides the memory
4293 // state for a particular "alias type" (see Compile::alias_type).  For example,
4294 // if a MergeMem has an input X for alias category #6, then any memory reference
4295 // to alias category #6 may use X as its memory state input, as an exact equivalent
4296 // to using the MergeMem as a whole.
4297 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4298 //
4299 // (Here, the <N> notation gives the index of the relevant adr_type.)
4300 //
4301 // In one special case (and more cases in the future), alias categories overlap.
4302 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4303 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4304 // it is exactly equivalent to that state W:
4305 //   MergeMem(<Bot>: W) <==> W
4306 //
4307 // Usually, the merge has more than one input.  In that case, where inputs
4308 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4309 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4310 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4311 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4312 //
4313 // A merge can take a "wide" memory state as one of its narrow inputs.
4314 // This simply means that the merge observes out only the relevant parts of
4315 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4316 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4317 //
4318 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4319 // and that memory slices "leak through":
4320 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4321 //
4322 // But, in such a cascade, repeated memory slices can "block the leak":
4323 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4324 //
4325 // In the last example, Y is not part of the combined memory state of the
4326 // outermost MergeMem.  The system must, of course, prevent unschedulable
4327 // memory states from arising, so you can be sure that the state Y is somehow
4328 // a precursor to state Y'.
4329 //
4330 //
4331 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4332 // of each MergeMemNode array are exactly the numerical alias indexes, including
4333 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4334 // Compile::alias_type (and kin) produce and manage these indexes.
4335 //
4336 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4337 // (Note that this provides quick access to the top node inside MergeMem methods,
4338 // without the need to reach out via TLS to Compile::current.)
4339 //
4340 // As a consequence of what was just described, a MergeMem that represents a full
4341 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4342 // containing all alias categories.
4343 //
4344 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4345 //
4346 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4347 // a memory state for the alias type <N>, or else the top node, meaning that
4348 // there is no particular input for that alias type.  Note that the length of
4349 // a MergeMem is variable, and may be extended at any time to accommodate new
4350 // memory states at larger alias indexes.  When merges grow, they are of course
4351 // filled with "top" in the unused in() positions.
4352 //
4353 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4354 // (Top was chosen because it works smoothly with passes like GCM.)
4355 //
4356 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4357 // the type of random VM bits like TLS references.)  Since it is always the
4358 // first non-Bot memory slice, some low-level loops use it to initialize an
4359 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4360 //
4361 //
4362 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4363 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4364 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4365 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4366 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4367 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4368 //
4369 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4370 // really that different from the other memory inputs.  An abbreviation called
4371 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4372 //
4373 //
4374 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4375 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4376 // that "emerges though" the base memory will be marked as excluding the alias types
4377 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4378 //
4379 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4380 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4381 //
4382 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4383 // (It is currently unimplemented.)  As you can see, the resulting merge is
4384 // actually a disjoint union of memory states, rather than an overlay.
4385 //
4386 
4387 //------------------------------MergeMemNode-----------------------------------
4388 Node* MergeMemNode::make_empty_memory() {
4389   Node* empty_memory = (Node*) Compile::current()->top();
4390   assert(empty_memory->is_top(), "correct sentinel identity");
4391   return empty_memory;
4392 }
4393 
4394 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4395   init_class_id(Class_MergeMem);
4396   // all inputs are nullified in Node::Node(int)
4397   // set_input(0, NULL);  // no control input
4398 
4399   // Initialize the edges uniformly to top, for starters.
4400   Node* empty_mem = make_empty_memory();
4401   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4402     init_req(i,empty_mem);
4403   }
4404   assert(empty_memory() == empty_mem, "");
4405 
4406   if( new_base != NULL && new_base->is_MergeMem() ) {
4407     MergeMemNode* mdef = new_base->as_MergeMem();
4408     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4409     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4410       mms.set_memory(mms.memory2());
4411     }
4412     assert(base_memory() == mdef->base_memory(), "");
4413   } else {
4414     set_base_memory(new_base);
4415   }
4416 }
4417 
4418 // Make a new, untransformed MergeMem with the same base as 'mem'.
4419 // If mem is itself a MergeMem, populate the result with the same edges.
4420 MergeMemNode* MergeMemNode::make(Node* mem) {
4421   return new MergeMemNode(mem);
4422 }
4423 
4424 //------------------------------cmp--------------------------------------------
4425 uint MergeMemNode::hash() const { return NO_HASH; }
4426 bool MergeMemNode::cmp( const Node &n ) const {
4427   return (&n == this);          // Always fail except on self
4428 }
4429 
4430 //------------------------------Identity---------------------------------------
4431 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4432   // Identity if this merge point does not record any interesting memory
4433   // disambiguations.
4434   Node* base_mem = base_memory();
4435   Node* empty_mem = empty_memory();
4436   if (base_mem != empty_mem) {  // Memory path is not dead?
4437     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4438       Node* mem = in(i);
4439       if (mem != empty_mem && mem != base_mem) {
4440         return this;            // Many memory splits; no change
4441       }
4442     }
4443   }
4444   return base_mem;              // No memory splits; ID on the one true input
4445 }
4446 
4447 //------------------------------Ideal------------------------------------------
4448 // This method is invoked recursively on chains of MergeMem nodes
4449 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4450   // Remove chain'd MergeMems
4451   //
4452   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4453   // relative to the "in(Bot)".  Since we are patching both at the same time,
4454   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4455   // but rewrite each "in(i)" relative to the new "in(Bot)".
4456   Node *progress = NULL;
4457 
4458 
4459   Node* old_base = base_memory();
4460   Node* empty_mem = empty_memory();
4461   if (old_base == empty_mem)
4462     return NULL; // Dead memory path.
4463 
4464   MergeMemNode* old_mbase;
4465   if (old_base != NULL && old_base->is_MergeMem())
4466     old_mbase = old_base->as_MergeMem();
4467   else
4468     old_mbase = NULL;
4469   Node* new_base = old_base;
4470 
4471   // simplify stacked MergeMems in base memory
4472   if (old_mbase)  new_base = old_mbase->base_memory();
4473 
4474   // the base memory might contribute new slices beyond my req()
4475   if (old_mbase)  grow_to_match(old_mbase);
4476 
4477   // Look carefully at the base node if it is a phi.
4478   PhiNode* phi_base;
4479   if (new_base != NULL && new_base->is_Phi())
4480     phi_base = new_base->as_Phi();
4481   else
4482     phi_base = NULL;
4483 
4484   Node*    phi_reg = NULL;
4485   uint     phi_len = (uint)-1;
4486   if (phi_base != NULL && !phi_base->is_copy()) {
4487     // do not examine phi if degraded to a copy
4488     phi_reg = phi_base->region();
4489     phi_len = phi_base->req();
4490     // see if the phi is unfinished
4491     for (uint i = 1; i < phi_len; i++) {
4492       if (phi_base->in(i) == NULL) {
4493         // incomplete phi; do not look at it yet!
4494         phi_reg = NULL;
4495         phi_len = (uint)-1;
4496         break;
4497       }
4498     }
4499   }
4500 
4501   // Note:  We do not call verify_sparse on entry, because inputs
4502   // can normalize to the base_memory via subsume_node or similar
4503   // mechanisms.  This method repairs that damage.
4504 
4505   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4506 
4507   // Look at each slice.
4508   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4509     Node* old_in = in(i);
4510     // calculate the old memory value
4511     Node* old_mem = old_in;
4512     if (old_mem == empty_mem)  old_mem = old_base;
4513     assert(old_mem == memory_at(i), "");
4514 
4515     // maybe update (reslice) the old memory value
4516 
4517     // simplify stacked MergeMems
4518     Node* new_mem = old_mem;
4519     MergeMemNode* old_mmem;
4520     if (old_mem != NULL && old_mem->is_MergeMem())
4521       old_mmem = old_mem->as_MergeMem();
4522     else
4523       old_mmem = NULL;
4524     if (old_mmem == this) {
4525       // This can happen if loops break up and safepoints disappear.
4526       // A merge of BotPtr (default) with a RawPtr memory derived from a
4527       // safepoint can be rewritten to a merge of the same BotPtr with
4528       // the BotPtr phi coming into the loop.  If that phi disappears
4529       // also, we can end up with a self-loop of the mergemem.
4530       // In general, if loops degenerate and memory effects disappear,
4531       // a mergemem can be left looking at itself.  This simply means
4532       // that the mergemem's default should be used, since there is
4533       // no longer any apparent effect on this slice.
4534       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4535       //       from start.  Update the input to TOP.
4536       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4537     }
4538     else if (old_mmem != NULL) {
4539       new_mem = old_mmem->memory_at(i);
4540     }
4541     // else preceding memory was not a MergeMem
4542 
4543     // replace equivalent phis (unfortunately, they do not GVN together)
4544     if (new_mem != NULL && new_mem != new_base &&
4545         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4546       if (new_mem->is_Phi()) {
4547         PhiNode* phi_mem = new_mem->as_Phi();
4548         for (uint i = 1; i < phi_len; i++) {
4549           if (phi_base->in(i) != phi_mem->in(i)) {
4550             phi_mem = NULL;
4551             break;
4552           }
4553         }
4554         if (phi_mem != NULL) {
4555           // equivalent phi nodes; revert to the def
4556           new_mem = new_base;
4557         }
4558       }
4559     }
4560 
4561     // maybe store down a new value
4562     Node* new_in = new_mem;
4563     if (new_in == new_base)  new_in = empty_mem;
4564 
4565     if (new_in != old_in) {
4566       // Warning:  Do not combine this "if" with the previous "if"
4567       // A memory slice might have be be rewritten even if it is semantically
4568       // unchanged, if the base_memory value has changed.
4569       set_req(i, new_in);
4570       progress = this;          // Report progress
4571     }
4572   }
4573 
4574   if (new_base != old_base) {
4575     set_req(Compile::AliasIdxBot, new_base);
4576     // Don't use set_base_memory(new_base), because we need to update du.
4577     assert(base_memory() == new_base, "");
4578     progress = this;
4579   }
4580 
4581   if( base_memory() == this ) {
4582     // a self cycle indicates this memory path is dead
4583     set_req(Compile::AliasIdxBot, empty_mem);
4584   }
4585 
4586   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4587   // Recursion must occur after the self cycle check above
4588   if( base_memory()->is_MergeMem() ) {
4589     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4590     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4591     if( m != NULL &&
4592         (m->is_top() ||
4593          (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4594       // propagate rollup of dead cycle to self
4595       set_req(Compile::AliasIdxBot, empty_mem);
4596     }
4597   }
4598 
4599   if( base_memory() == empty_mem ) {
4600     progress = this;
4601     // Cut inputs during Parse phase only.
4602     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4603     if( !can_reshape ) {
4604       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4605         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4606       }
4607     }
4608   }
4609 
4610   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4611     // Check if PhiNode::Ideal's "Split phis through memory merges"
4612     // transform should be attempted. Look for this->phi->this cycle.
4613     uint merge_width = req();
4614     if (merge_width > Compile::AliasIdxRaw) {
4615       PhiNode* phi = base_memory()->as_Phi();
4616       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4617         if (phi->in(i) == this) {
4618           phase->is_IterGVN()->_worklist.push(phi);
4619           break;
4620         }
4621       }
4622     }
4623   }
4624 
4625   assert(progress || verify_sparse(), "please, no dups of base");
4626   return progress;
4627 }
4628 
4629 //-------------------------set_base_memory-------------------------------------
4630 void MergeMemNode::set_base_memory(Node *new_base) {
4631   Node* empty_mem = empty_memory();
4632   set_req(Compile::AliasIdxBot, new_base);
4633   assert(memory_at(req()) == new_base, "must set default memory");
4634   // Clear out other occurrences of new_base:
4635   if (new_base != empty_mem) {
4636     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4637       if (in(i) == new_base)  set_req(i, empty_mem);
4638     }
4639   }
4640 }
4641 
4642 //------------------------------out_RegMask------------------------------------
4643 const RegMask &MergeMemNode::out_RegMask() const {
4644   return RegMask::Empty;
4645 }
4646 
4647 //------------------------------dump_spec--------------------------------------
4648 #ifndef PRODUCT
4649 void MergeMemNode::dump_spec(outputStream *st) const {
4650   st->print(" {");
4651   Node* base_mem = base_memory();
4652   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4653     Node* mem = (in(i) != NULL) ? memory_at(i) : base_mem;
4654     if (mem == base_mem) { st->print(" -"); continue; }
4655     st->print( " N%d:", mem->_idx );
4656     Compile::current()->get_adr_type(i)->dump_on(st);
4657   }
4658   st->print(" }");
4659 }
4660 #endif // !PRODUCT
4661 
4662 
4663 #ifdef ASSERT
4664 static bool might_be_same(Node* a, Node* b) {
4665   if (a == b)  return true;
4666   if (!(a->is_Phi() || b->is_Phi()))  return false;
4667   // phis shift around during optimization
4668   return true;  // pretty stupid...
4669 }
4670 
4671 // verify a narrow slice (either incoming or outgoing)
4672 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4673   if (!VerifyAliases)                return;  // don't bother to verify unless requested
4674   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
4675   if (Node::in_dump())               return;  // muzzle asserts when printing
4676   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4677   assert(n != NULL, "");
4678   // Elide intervening MergeMem's
4679   while (n->is_MergeMem()) {
4680     n = n->as_MergeMem()->memory_at(alias_idx);
4681   }
4682   Compile* C = Compile::current();
4683   const TypePtr* n_adr_type = n->adr_type();
4684   if (n == m->empty_memory()) {
4685     // Implicit copy of base_memory()
4686   } else if (n_adr_type != TypePtr::BOTTOM) {
4687     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4688     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4689   } else {
4690     // A few places like make_runtime_call "know" that VM calls are narrow,
4691     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4692     bool expected_wide_mem = false;
4693     if (n == m->base_memory()) {
4694       expected_wide_mem = true;
4695     } else if (alias_idx == Compile::AliasIdxRaw ||
4696                n == m->memory_at(Compile::AliasIdxRaw)) {
4697       expected_wide_mem = true;
4698     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4699       // memory can "leak through" calls on channels that
4700       // are write-once.  Allow this also.
4701       expected_wide_mem = true;
4702     }
4703     assert(expected_wide_mem, "expected narrow slice replacement");
4704   }
4705 }
4706 #else // !ASSERT
4707 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4708 #endif
4709 
4710 
4711 //-----------------------------memory_at---------------------------------------
4712 Node* MergeMemNode::memory_at(uint alias_idx) const {
4713   assert(alias_idx >= Compile::AliasIdxRaw ||
4714          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4715          "must avoid base_memory and AliasIdxTop");
4716 
4717   // Otherwise, it is a narrow slice.
4718   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4719   Compile *C = Compile::current();
4720   if (is_empty_memory(n)) {
4721     // the array is sparse; empty slots are the "top" node
4722     n = base_memory();
4723     assert(Node::in_dump()
4724            || n == NULL || n->bottom_type() == Type::TOP
4725            || n->adr_type() == NULL // address is TOP
4726            || n->adr_type() == TypePtr::BOTTOM
4727            || n->adr_type() == TypeRawPtr::BOTTOM
4728            || Compile::current()->AliasLevel() == 0,
4729            "must be a wide memory");
4730     // AliasLevel == 0 if we are organizing the memory states manually.
4731     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4732   } else {
4733     // make sure the stored slice is sane
4734     #ifdef ASSERT
4735     if (VMError::is_error_reported() || Node::in_dump()) {
4736     } else if (might_be_same(n, base_memory())) {
4737       // Give it a pass:  It is a mostly harmless repetition of the base.
4738       // This can arise normally from node subsumption during optimization.
4739     } else {
4740       verify_memory_slice(this, alias_idx, n);
4741     }
4742     #endif
4743   }
4744   return n;
4745 }
4746 
4747 //---------------------------set_memory_at-------------------------------------
4748 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4749   verify_memory_slice(this, alias_idx, n);
4750   Node* empty_mem = empty_memory();
4751   if (n == base_memory())  n = empty_mem;  // collapse default
4752   uint need_req = alias_idx+1;
4753   if (req() < need_req) {
4754     if (n == empty_mem)  return;  // already the default, so do not grow me
4755     // grow the sparse array
4756     do {
4757       add_req(empty_mem);
4758     } while (req() < need_req);
4759   }
4760   set_req( alias_idx, n );
4761 }
4762 
4763 
4764 
4765 //--------------------------iteration_setup------------------------------------
4766 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4767   if (other != NULL) {
4768     grow_to_match(other);
4769     // invariant:  the finite support of mm2 is within mm->req()
4770     #ifdef ASSERT
4771     for (uint i = req(); i < other->req(); i++) {
4772       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4773     }
4774     #endif
4775   }
4776   // Replace spurious copies of base_memory by top.
4777   Node* base_mem = base_memory();
4778   if (base_mem != NULL && !base_mem->is_top()) {
4779     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4780       if (in(i) == base_mem)
4781         set_req(i, empty_memory());
4782     }
4783   }
4784 }
4785 
4786 //---------------------------grow_to_match-------------------------------------
4787 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4788   Node* empty_mem = empty_memory();
4789   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4790   // look for the finite support of the other memory
4791   for (uint i = other->req(); --i >= req(); ) {
4792     if (other->in(i) != empty_mem) {
4793       uint new_len = i+1;
4794       while (req() < new_len)  add_req(empty_mem);
4795       break;
4796     }
4797   }
4798 }
4799 
4800 //---------------------------verify_sparse-------------------------------------
4801 #ifndef PRODUCT
4802 bool MergeMemNode::verify_sparse() const {
4803   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4804   Node* base_mem = base_memory();
4805   // The following can happen in degenerate cases, since empty==top.
4806   if (is_empty_memory(base_mem))  return true;
4807   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4808     assert(in(i) != NULL, "sane slice");
4809     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4810   }
4811   return true;
4812 }
4813 
4814 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4815   Node* n;
4816   n = mm->in(idx);
4817   if (mem == n)  return true;  // might be empty_memory()
4818   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4819   if (mem == n)  return true;
4820   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4821     if (mem == n)  return true;
4822     if (n == NULL)  break;
4823   }
4824   return false;
4825 }
4826 #endif // !PRODUCT