1 /*
   2  * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "memory/allocation.inline.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "oops/objArrayKlass.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/arraycopynode.hpp"
  35 #include "opto/cfgnode.hpp"
  36 #include "opto/compile.hpp"
  37 #include "opto/connode.hpp"
  38 #include "opto/convertnode.hpp"
  39 #include "opto/loopnode.hpp"
  40 #include "opto/machnode.hpp"
  41 #include "opto/matcher.hpp"
  42 #include "opto/memnode.hpp"
  43 #include "opto/mulnode.hpp"
  44 #include "opto/narrowptrnode.hpp"
  45 #include "opto/phaseX.hpp"
  46 #include "opto/regmask.hpp"
  47 #include "opto/rootnode.hpp"
  48 #include "utilities/align.hpp"
  49 #include "utilities/copy.hpp"
  50 #include "utilities/macros.hpp"
  51 #include "utilities/vmError.hpp"
  52 #if INCLUDE_ZGC
  53 #include "gc/z/c2/zBarrierSetC2.hpp"
  54 #endif
  55 
  56 // Portions of code courtesy of Clifford Click
  57 
  58 // Optimization - Graph Style
  59 
  60 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  61 
  62 //=============================================================================
  63 uint MemNode::size_of() const { return sizeof(*this); }
  64 
  65 const TypePtr *MemNode::adr_type() const {
  66   Node* adr = in(Address);
  67   if (adr == NULL)  return NULL; // node is dead
  68   const TypePtr* cross_check = NULL;
  69   DEBUG_ONLY(cross_check = _adr_type);
  70   return calculate_adr_type(adr->bottom_type(), cross_check);
  71 }
  72 
  73 bool MemNode::check_if_adr_maybe_raw(Node* adr) {
  74   if (adr != NULL) {
  75     if (adr->bottom_type()->base() == Type::RawPtr || adr->bottom_type()->base() == Type::AnyPtr) {
  76       return true;
  77     }
  78   }
  79   return false;
  80 }
  81 
  82 #ifndef PRODUCT
  83 void MemNode::dump_spec(outputStream *st) const {
  84   if (in(Address) == NULL)  return; // node is dead
  85 #ifndef ASSERT
  86   // fake the missing field
  87   const TypePtr* _adr_type = NULL;
  88   if (in(Address) != NULL)
  89     _adr_type = in(Address)->bottom_type()->isa_ptr();
  90 #endif
  91   dump_adr_type(this, _adr_type, st);
  92 
  93   Compile* C = Compile::current();
  94   if (C->alias_type(_adr_type)->is_volatile()) {
  95     st->print(" Volatile!");
  96   }
  97   if (_unaligned_access) {
  98     st->print(" unaligned");
  99   }
 100   if (_mismatched_access) {
 101     st->print(" mismatched");
 102   }
 103   if (_unsafe_access) {
 104     st->print(" unsafe");
 105   }
 106 }
 107 
 108 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
 109   st->print(" @");
 110   if (adr_type == NULL) {
 111     st->print("NULL");
 112   } else {
 113     adr_type->dump_on(st);
 114     Compile* C = Compile::current();
 115     Compile::AliasType* atp = NULL;
 116     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
 117     if (atp == NULL)
 118       st->print(", idx=?\?;");
 119     else if (atp->index() == Compile::AliasIdxBot)
 120       st->print(", idx=Bot;");
 121     else if (atp->index() == Compile::AliasIdxTop)
 122       st->print(", idx=Top;");
 123     else if (atp->index() == Compile::AliasIdxRaw)
 124       st->print(", idx=Raw;");
 125     else {
 126       ciField* field = atp->field();
 127       if (field) {
 128         st->print(", name=");
 129         field->print_name_on(st);
 130       }
 131       st->print(", idx=%d;", atp->index());
 132     }
 133   }
 134 }
 135 
 136 extern void print_alias_types();
 137 
 138 #endif
 139 
 140 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 141   assert((t_oop != NULL), "sanity");
 142   bool is_instance = t_oop->is_known_instance_field();
 143   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 144                              (load != NULL) && load->is_Load() &&
 145                              (phase->is_IterGVN() != NULL);
 146   if (!(is_instance || is_boxed_value_load))
 147     return mchain;  // don't try to optimize non-instance types
 148   uint instance_id = t_oop->instance_id();
 149   Node *start_mem = phase->C->start()->proj_out_or_null(TypeFunc::Memory);
 150   Node *prev = NULL;
 151   Node *result = mchain;
 152   while (prev != result) {
 153     prev = result;
 154     if (result == start_mem)
 155       break;  // hit one of our sentinels
 156     // skip over a call which does not affect this memory slice
 157     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 158       Node *proj_in = result->in(0);
 159       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 160         break;  // hit one of our sentinels
 161       } else if (proj_in->is_Call()) {
 162         // ArrayCopyNodes processed here as well
 163         CallNode *call = proj_in->as_Call();
 164         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 165           result = call->in(TypeFunc::Memory);
 166         }
 167       } else if (proj_in->is_Initialize()) {
 168         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 169         // Stop if this is the initialization for the object instance which
 170         // contains this memory slice, otherwise skip over it.
 171         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 172           break;
 173         }
 174         if (is_instance) {
 175           result = proj_in->in(TypeFunc::Memory);
 176         } else if (is_boxed_value_load) {
 177           Node* klass = alloc->in(AllocateNode::KlassNode);
 178           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 179           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 180             result = proj_in->in(TypeFunc::Memory); // not related allocation
 181           }
 182         }
 183       } else if (proj_in->is_MemBar()) {
 184         ArrayCopyNode* ac = NULL;
 185         if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase, ac)) {
 186           break;
 187         }
 188         result = proj_in->in(TypeFunc::Memory);
 189       } else {
 190         assert(false, "unexpected projection");
 191       }
 192     } else if (result->is_ClearArray()) {
 193       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 194         // Can not bypass initialization of the instance
 195         // we are looking for.
 196         break;
 197       }
 198       // Otherwise skip it (the call updated 'result' value).
 199     } else if (result->is_MergeMem()) {
 200       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 201     }
 202   }
 203   return result;
 204 }
 205 
 206 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 207   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 208   if (t_oop == NULL)
 209     return mchain;  // don't try to optimize non-oop types
 210   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 211   bool is_instance = t_oop->is_known_instance_field();
 212   PhaseIterGVN *igvn = phase->is_IterGVN();
 213   if (is_instance && igvn != NULL  && result->is_Phi()) {
 214     PhiNode *mphi = result->as_Phi();
 215     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 216     const TypePtr *t = mphi->adr_type();
 217     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 218         (t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 219          t->is_oopptr()->cast_to_exactness(true)
 220            ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 221             ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop)) {
 222       // clone the Phi with our address type
 223       result = mphi->split_out_instance(t_adr, igvn);
 224     } else {
 225       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 226     }
 227   }
 228   return result;
 229 }
 230 
 231 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 232   uint alias_idx = phase->C->get_alias_index(tp);
 233   Node *mem = mmem;
 234 #ifdef ASSERT
 235   {
 236     // Check that current type is consistent with the alias index used during graph construction
 237     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 238     bool consistent =  adr_check == NULL || adr_check->empty() ||
 239                        phase->C->must_alias(adr_check, alias_idx );
 240     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 241     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 242                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 243         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 244         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 245           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 246           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 247       // don't assert if it is dead code.
 248       consistent = true;
 249     }
 250     if( !consistent ) {
 251       st->print("alias_idx==%d, adr_check==", alias_idx);
 252       if( adr_check == NULL ) {
 253         st->print("NULL");
 254       } else {
 255         adr_check->dump();
 256       }
 257       st->cr();
 258       print_alias_types();
 259       assert(consistent, "adr_check must match alias idx");
 260     }
 261   }
 262 #endif
 263   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 264   // means an array I have not precisely typed yet.  Do not do any
 265   // alias stuff with it any time soon.
 266   const TypeOopPtr *toop = tp->isa_oopptr();
 267   if( tp->base() != Type::AnyPtr &&
 268       !(toop &&
 269         toop->klass() != NULL &&
 270         toop->klass()->is_java_lang_Object() &&
 271         toop->offset() == Type::OffsetBot) ) {
 272     // compress paths and change unreachable cycles to TOP
 273     // If not, we can update the input infinitely along a MergeMem cycle
 274     // Equivalent code in PhiNode::Ideal
 275     Node* m  = phase->transform(mmem);
 276     // If transformed to a MergeMem, get the desired slice
 277     // Otherwise the returned node represents memory for every slice
 278     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 279     // Update input if it is progress over what we have now
 280   }
 281   return mem;
 282 }
 283 
 284 //--------------------------Ideal_common---------------------------------------
 285 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 286 // Unhook non-raw memories from complete (macro-expanded) initializations.
 287 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 288   // If our control input is a dead region, kill all below the region
 289   Node *ctl = in(MemNode::Control);
 290   if (ctl && remove_dead_region(phase, can_reshape))
 291     return this;
 292   ctl = in(MemNode::Control);
 293   // Don't bother trying to transform a dead node
 294   if (ctl && ctl->is_top())  return NodeSentinel;
 295 
 296   PhaseIterGVN *igvn = phase->is_IterGVN();
 297   // Wait if control on the worklist.
 298   if (ctl && can_reshape && igvn != NULL) {
 299     Node* bol = NULL;
 300     Node* cmp = NULL;
 301     if (ctl->in(0)->is_If()) {
 302       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 303       bol = ctl->in(0)->in(1);
 304       if (bol->is_Bool())
 305         cmp = ctl->in(0)->in(1)->in(1);
 306     }
 307     if (igvn->_worklist.member(ctl) ||
 308         (bol != NULL && igvn->_worklist.member(bol)) ||
 309         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 310       // This control path may be dead.
 311       // Delay this memory node transformation until the control is processed.
 312       phase->is_IterGVN()->_worklist.push(this);
 313       return NodeSentinel; // caller will return NULL
 314     }
 315   }
 316   // Ignore if memory is dead, or self-loop
 317   Node *mem = in(MemNode::Memory);
 318   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 319   assert(mem != this, "dead loop in MemNode::Ideal");
 320 
 321   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 322     // This memory slice may be dead.
 323     // Delay this mem node transformation until the memory is processed.
 324     phase->is_IterGVN()->_worklist.push(this);
 325     return NodeSentinel; // caller will return NULL
 326   }
 327 
 328   Node *address = in(MemNode::Address);
 329   const Type *t_adr = phase->type(address);
 330   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 331 
 332   if (can_reshape && is_unsafe_access() && (t_adr == TypePtr::NULL_PTR)) {
 333     // Unsafe off-heap access with zero address. Remove access and other control users
 334     // to not confuse optimizations and add a HaltNode to fail if this is ever executed.
 335     assert(ctl != NULL, "unsafe accesses should be control dependent");
 336     for (DUIterator_Fast imax, i = ctl->fast_outs(imax); i < imax; i++) {
 337       Node* u = ctl->fast_out(i);
 338       if (u != ctl) {
 339         igvn->rehash_node_delayed(u);
 340         int nb = u->replace_edge(ctl, phase->C->top());
 341         --i, imax -= nb;
 342       }
 343     }
 344     Node* frame = igvn->transform(new ParmNode(phase->C->start(), TypeFunc::FramePtr));
 345     Node* halt = igvn->transform(new HaltNode(ctl, frame));
 346     phase->C->root()->add_req(halt);
 347     return this;
 348   }
 349 
 350   if (can_reshape && igvn != NULL &&
 351       (igvn->_worklist.member(address) ||
 352        (igvn->_worklist.size() > 0 && t_adr != adr_type())) ) {
 353     // The address's base and type may change when the address is processed.
 354     // Delay this mem node transformation until the address is processed.
 355     phase->is_IterGVN()->_worklist.push(this);
 356     return NodeSentinel; // caller will return NULL
 357   }
 358 
 359   // Do NOT remove or optimize the next lines: ensure a new alias index
 360   // is allocated for an oop pointer type before Escape Analysis.
 361   // Note: C++ will not remove it since the call has side effect.
 362   if (t_adr->isa_oopptr()) {
 363     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 364   }
 365 
 366   Node* base = NULL;
 367   if (address->is_AddP()) {
 368     base = address->in(AddPNode::Base);
 369   }
 370   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 371       !t_adr->isa_rawptr()) {
 372     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 373     // Skip this node optimization if its address has TOP base.
 374     return NodeSentinel; // caller will return NULL
 375   }
 376 
 377   // Avoid independent memory operations
 378   Node* old_mem = mem;
 379 
 380   // The code which unhooks non-raw memories from complete (macro-expanded)
 381   // initializations was removed. After macro-expansion all stores catched
 382   // by Initialize node became raw stores and there is no information
 383   // which memory slices they modify. So it is unsafe to move any memory
 384   // operation above these stores. Also in most cases hooked non-raw memories
 385   // were already unhooked by using information from detect_ptr_independence()
 386   // and find_previous_store().
 387 
 388   if (mem->is_MergeMem()) {
 389     MergeMemNode* mmem = mem->as_MergeMem();
 390     const TypePtr *tp = t_adr->is_ptr();
 391 
 392     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 393   }
 394 
 395   if (mem != old_mem) {
 396     set_req(MemNode::Memory, mem);
 397     if (can_reshape && old_mem->outcnt() == 0 && igvn != NULL) {
 398       igvn->_worklist.push(old_mem);
 399     }
 400     if (phase->type(mem) == Type::TOP) return NodeSentinel;
 401     return this;
 402   }
 403 
 404   // let the subclass continue analyzing...
 405   return NULL;
 406 }
 407 
 408 // Helper function for proving some simple control dominations.
 409 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 410 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 411 // is not a constant (dominated by the method's StartNode).
 412 // Used by MemNode::find_previous_store to prove that the
 413 // control input of a memory operation predates (dominates)
 414 // an allocation it wants to look past.
 415 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 416   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 417     return false; // Conservative answer for dead code
 418 
 419   // Check 'dom'. Skip Proj and CatchProj nodes.
 420   dom = dom->find_exact_control(dom);
 421   if (dom == NULL || dom->is_top())
 422     return false; // Conservative answer for dead code
 423 
 424   if (dom == sub) {
 425     // For the case when, for example, 'sub' is Initialize and the original
 426     // 'dom' is Proj node of the 'sub'.
 427     return false;
 428   }
 429 
 430   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 431     return true;
 432 
 433   // 'dom' dominates 'sub' if its control edge and control edges
 434   // of all its inputs dominate or equal to sub's control edge.
 435 
 436   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 437   // Or Region for the check in LoadNode::Ideal();
 438   // 'sub' should have sub->in(0) != NULL.
 439   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 440          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 441 
 442   // Get control edge of 'sub'.
 443   Node* orig_sub = sub;
 444   sub = sub->find_exact_control(sub->in(0));
 445   if (sub == NULL || sub->is_top())
 446     return false; // Conservative answer for dead code
 447 
 448   assert(sub->is_CFG(), "expecting control");
 449 
 450   if (sub == dom)
 451     return true;
 452 
 453   if (sub->is_Start() || sub->is_Root())
 454     return false;
 455 
 456   {
 457     // Check all control edges of 'dom'.
 458 
 459     ResourceMark rm;
 460     Arena* arena = Thread::current()->resource_area();
 461     Node_List nlist(arena);
 462     Unique_Node_List dom_list(arena);
 463 
 464     dom_list.push(dom);
 465     bool only_dominating_controls = false;
 466 
 467     for (uint next = 0; next < dom_list.size(); next++) {
 468       Node* n = dom_list.at(next);
 469       if (n == orig_sub)
 470         return false; // One of dom's inputs dominated by sub.
 471       if (!n->is_CFG() && n->pinned()) {
 472         // Check only own control edge for pinned non-control nodes.
 473         n = n->find_exact_control(n->in(0));
 474         if (n == NULL || n->is_top())
 475           return false; // Conservative answer for dead code
 476         assert(n->is_CFG(), "expecting control");
 477         dom_list.push(n);
 478       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 479         only_dominating_controls = true;
 480       } else if (n->is_CFG()) {
 481         if (n->dominates(sub, nlist))
 482           only_dominating_controls = true;
 483         else
 484           return false;
 485       } else {
 486         // First, own control edge.
 487         Node* m = n->find_exact_control(n->in(0));
 488         if (m != NULL) {
 489           if (m->is_top())
 490             return false; // Conservative answer for dead code
 491           dom_list.push(m);
 492         }
 493         // Now, the rest of edges.
 494         uint cnt = n->req();
 495         for (uint i = 1; i < cnt; i++) {
 496           m = n->find_exact_control(n->in(i));
 497           if (m == NULL || m->is_top())
 498             continue;
 499           dom_list.push(m);
 500         }
 501       }
 502     }
 503     return only_dominating_controls;
 504   }
 505 }
 506 
 507 //---------------------detect_ptr_independence---------------------------------
 508 // Used by MemNode::find_previous_store to prove that two base
 509 // pointers are never equal.
 510 // The pointers are accompanied by their associated allocations,
 511 // if any, which have been previously discovered by the caller.
 512 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 513                                       Node* p2, AllocateNode* a2,
 514                                       PhaseTransform* phase) {
 515   // Attempt to prove that these two pointers cannot be aliased.
 516   // They may both manifestly be allocations, and they should differ.
 517   // Or, if they are not both allocations, they can be distinct constants.
 518   // Otherwise, one is an allocation and the other a pre-existing value.
 519   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 520     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 521   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 522     return (a1 != a2);
 523   } else if (a1 != NULL) {                  // one allocation a1
 524     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 525     return all_controls_dominate(p2, a1);
 526   } else { //(a2 != NULL)                   // one allocation a2
 527     return all_controls_dominate(p1, a2);
 528   }
 529   return false;
 530 }
 531 
 532 
 533 // Find an arraycopy that must have set (can_see_stored_value=true) or
 534 // could have set (can_see_stored_value=false) the value for this load
 535 Node* LoadNode::find_previous_arraycopy(PhaseTransform* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
 536   if (mem->is_Proj() && mem->in(0) != NULL && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
 537                                                mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
 538     Node* mb = mem->in(0);
 539     if (mb->in(0) != NULL && mb->in(0)->is_Proj() &&
 540         mb->in(0)->in(0) != NULL && mb->in(0)->in(0)->is_ArrayCopy()) {
 541       ArrayCopyNode* ac = mb->in(0)->in(0)->as_ArrayCopy();
 542       if (ac->is_clonebasic()) {
 543         intptr_t offset;
 544         AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase, offset);
 545         if (alloc != NULL && alloc == ld_alloc) {
 546           return ac;
 547         }
 548       }
 549     }
 550   } else if (mem->is_Proj() && mem->in(0) != NULL && mem->in(0)->is_ArrayCopy()) {
 551     ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
 552 
 553     if (ac->is_arraycopy_validated() ||
 554         ac->is_copyof_validated() ||
 555         ac->is_copyofrange_validated()) {
 556       Node* ld_addp = in(MemNode::Address);
 557       if (ld_addp->is_AddP()) {
 558         Node* ld_base = ld_addp->in(AddPNode::Address);
 559         Node* ld_offs = ld_addp->in(AddPNode::Offset);
 560 
 561         Node* dest = ac->in(ArrayCopyNode::Dest);
 562 
 563         if (dest == ld_base) {
 564           const TypeX *ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 565           if (ac->modifies(ld_offs_t->_lo, ld_offs_t->_hi, phase, can_see_stored_value)) {
 566             return ac;
 567           }
 568           if (!can_see_stored_value) {
 569             mem = ac->in(TypeFunc::Memory);
 570           }
 571         }
 572       }
 573     }
 574   }
 575   return NULL;
 576 }
 577 
 578 // The logic for reordering loads and stores uses four steps:
 579 // (a) Walk carefully past stores and initializations which we
 580 //     can prove are independent of this load.
 581 // (b) Observe that the next memory state makes an exact match
 582 //     with self (load or store), and locate the relevant store.
 583 // (c) Ensure that, if we were to wire self directly to the store,
 584 //     the optimizer would fold it up somehow.
 585 // (d) Do the rewiring, and return, depending on some other part of
 586 //     the optimizer to fold up the load.
 587 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 588 // specific to loads and stores, so they are handled by the callers.
 589 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 590 //
 591 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 592   Node*         ctrl   = in(MemNode::Control);
 593   Node*         adr    = in(MemNode::Address);
 594   intptr_t      offset = 0;
 595   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 596   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 597 
 598   if (offset == Type::OffsetBot)
 599     return NULL;            // cannot unalias unless there are precise offsets
 600 
 601   const bool adr_maybe_raw = check_if_adr_maybe_raw(adr);
 602   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 603 
 604   intptr_t size_in_bytes = memory_size();
 605 
 606   Node* mem = in(MemNode::Memory);   // start searching here...
 607 
 608   int cnt = 50;             // Cycle limiter
 609   for (;;) {                // While we can dance past unrelated stores...
 610     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 611 
 612     Node* prev = mem;
 613     if (mem->is_Store()) {
 614       Node* st_adr = mem->in(MemNode::Address);
 615       intptr_t st_offset = 0;
 616       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 617       if (st_base == NULL)
 618         break;              // inscrutable pointer
 619 
 620       // For raw accesses it's not enough to prove that constant offsets don't intersect.
 621       // We need the bases to be the equal in order for the offset check to make sense.
 622       if ((adr_maybe_raw || check_if_adr_maybe_raw(st_adr)) && st_base != base) {
 623         break;
 624       }
 625 
 626       if (st_offset != offset && st_offset != Type::OffsetBot) {
 627         const int MAX_STORE = BytesPerLong;
 628         if (st_offset >= offset + size_in_bytes ||
 629             st_offset <= offset - MAX_STORE ||
 630             st_offset <= offset - mem->as_Store()->memory_size()) {
 631           // Success:  The offsets are provably independent.
 632           // (You may ask, why not just test st_offset != offset and be done?
 633           // The answer is that stores of different sizes can co-exist
 634           // in the same sequence of RawMem effects.  We sometimes initialize
 635           // a whole 'tile' of array elements with a single jint or jlong.)
 636           mem = mem->in(MemNode::Memory);
 637           continue;           // (a) advance through independent store memory
 638         }
 639       }
 640       if (st_base != base &&
 641           detect_ptr_independence(base, alloc,
 642                                   st_base,
 643                                   AllocateNode::Ideal_allocation(st_base, phase),
 644                                   phase)) {
 645         // Success:  The bases are provably independent.
 646         mem = mem->in(MemNode::Memory);
 647         continue;           // (a) advance through independent store memory
 648       }
 649 
 650       // (b) At this point, if the bases or offsets do not agree, we lose,
 651       // since we have not managed to prove 'this' and 'mem' independent.
 652       if (st_base == base && st_offset == offset) {
 653         return mem;         // let caller handle steps (c), (d)
 654       }
 655 
 656     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 657       InitializeNode* st_init = mem->in(0)->as_Initialize();
 658       AllocateNode*  st_alloc = st_init->allocation();
 659       if (st_alloc == NULL)
 660         break;              // something degenerated
 661       bool known_identical = false;
 662       bool known_independent = false;
 663       if (alloc == st_alloc)
 664         known_identical = true;
 665       else if (alloc != NULL)
 666         known_independent = true;
 667       else if (all_controls_dominate(this, st_alloc))
 668         known_independent = true;
 669 
 670       if (known_independent) {
 671         // The bases are provably independent: Either they are
 672         // manifestly distinct allocations, or else the control
 673         // of this load dominates the store's allocation.
 674         int alias_idx = phase->C->get_alias_index(adr_type());
 675         if (alias_idx == Compile::AliasIdxRaw) {
 676           mem = st_alloc->in(TypeFunc::Memory);
 677         } else {
 678           mem = st_init->memory(alias_idx);
 679         }
 680         continue;           // (a) advance through independent store memory
 681       }
 682 
 683       // (b) at this point, if we are not looking at a store initializing
 684       // the same allocation we are loading from, we lose.
 685       if (known_identical) {
 686         // From caller, can_see_stored_value will consult find_captured_store.
 687         return mem;         // let caller handle steps (c), (d)
 688       }
 689 
 690     } else if (find_previous_arraycopy(phase, alloc, mem, false) != NULL) {
 691       if (prev != mem) {
 692         // Found an arraycopy but it doesn't affect that load
 693         continue;
 694       }
 695       // Found an arraycopy that may affect that load
 696       return mem;
 697     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 698       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 699       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 700         // ArrayCopyNodes processed here as well.
 701         CallNode *call = mem->in(0)->as_Call();
 702         if (!call->may_modify(addr_t, phase)) {
 703           mem = call->in(TypeFunc::Memory);
 704           continue;         // (a) advance through independent call memory
 705         }
 706       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 707         ArrayCopyNode* ac = NULL;
 708         if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase, ac)) {
 709           break;
 710         }
 711         mem = mem->in(0)->in(TypeFunc::Memory);
 712         continue;           // (a) advance through independent MemBar memory
 713       } else if (mem->is_ClearArray()) {
 714         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 715           // (the call updated 'mem' value)
 716           continue;         // (a) advance through independent allocation memory
 717         } else {
 718           // Can not bypass initialization of the instance
 719           // we are looking for.
 720           return mem;
 721         }
 722       } else if (mem->is_MergeMem()) {
 723         int alias_idx = phase->C->get_alias_index(adr_type());
 724         mem = mem->as_MergeMem()->memory_at(alias_idx);
 725         continue;           // (a) advance through independent MergeMem memory
 726       }
 727     }
 728 
 729     // Unless there is an explicit 'continue', we must bail out here,
 730     // because 'mem' is an inscrutable memory state (e.g., a call).
 731     break;
 732   }
 733 
 734   return NULL;              // bail out
 735 }
 736 
 737 //----------------------calculate_adr_type-------------------------------------
 738 // Helper function.  Notices when the given type of address hits top or bottom.
 739 // Also, asserts a cross-check of the type against the expected address type.
 740 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 741   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 742   #ifdef PRODUCT
 743   cross_check = NULL;
 744   #else
 745   if (!VerifyAliases || VMError::is_error_reported() || Node::in_dump())  cross_check = NULL;
 746   #endif
 747   const TypePtr* tp = t->isa_ptr();
 748   if (tp == NULL) {
 749     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 750     return TypePtr::BOTTOM;           // touches lots of memory
 751   } else {
 752     #ifdef ASSERT
 753     // %%%% [phh] We don't check the alias index if cross_check is
 754     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 755     if (cross_check != NULL &&
 756         cross_check != TypePtr::BOTTOM &&
 757         cross_check != TypeRawPtr::BOTTOM) {
 758       // Recheck the alias index, to see if it has changed (due to a bug).
 759       Compile* C = Compile::current();
 760       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 761              "must stay in the original alias category");
 762       // The type of the address must be contained in the adr_type,
 763       // disregarding "null"-ness.
 764       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 765       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 766       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 767              "real address must not escape from expected memory type");
 768     }
 769     #endif
 770     return tp;
 771   }
 772 }
 773 
 774 //=============================================================================
 775 // Should LoadNode::Ideal() attempt to remove control edges?
 776 bool LoadNode::can_remove_control() const {
 777   return true;
 778 }
 779 uint LoadNode::size_of() const { return sizeof(*this); }
 780 uint LoadNode::cmp( const Node &n ) const
 781 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 782 const Type *LoadNode::bottom_type() const { return _type; }
 783 uint LoadNode::ideal_reg() const {
 784   return _type->ideal_reg();
 785 }
 786 
 787 #ifndef PRODUCT
 788 void LoadNode::dump_spec(outputStream *st) const {
 789   MemNode::dump_spec(st);
 790   if( !Verbose && !WizardMode ) {
 791     // standard dump does this in Verbose and WizardMode
 792     st->print(" #"); _type->dump_on(st);
 793   }
 794   if (!depends_only_on_test()) {
 795     st->print(" (does not depend only on test)");
 796   }
 797 }
 798 #endif
 799 
 800 #ifdef ASSERT
 801 //----------------------------is_immutable_value-------------------------------
 802 // Helper function to allow a raw load without control edge for some cases
 803 bool LoadNode::is_immutable_value(Node* adr) {
 804   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 805           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 806           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 807            in_bytes(JavaThread::osthread_offset())));
 808 }
 809 #endif
 810 
 811 //----------------------------LoadNode::make-----------------------------------
 812 // Polymorphic factory method:
 813 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo,
 814                      ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 815   Compile* C = gvn.C;
 816 
 817   // sanity check the alias category against the created node type
 818   assert(!(adr_type->isa_oopptr() &&
 819            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 820          "use LoadKlassNode instead");
 821   assert(!(adr_type->isa_aryptr() &&
 822            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 823          "use LoadRangeNode instead");
 824   // Check control edge of raw loads
 825   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 826           // oop will be recorded in oop map if load crosses safepoint
 827           rt->isa_oopptr() || is_immutable_value(adr),
 828           "raw memory operations should have control edge");
 829   LoadNode* load = NULL;
 830   switch (bt) {
 831   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 832   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 833   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 834   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 835   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 836   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency); break;
 837   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 838   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 839   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 840   case T_OBJECT:
 841 #ifdef _LP64
 842     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 843       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 844     } else
 845 #endif
 846     {
 847       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 848       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
 849     }
 850     break;
 851   default:
 852     ShouldNotReachHere();
 853     break;
 854   }
 855   assert(load != NULL, "LoadNode should have been created");
 856   if (unaligned) {
 857     load->set_unaligned_access();
 858   }
 859   if (mismatched) {
 860     load->set_mismatched_access();
 861   }
 862   if (unsafe) {
 863     load->set_unsafe_access();
 864   }
 865   if (load->Opcode() == Op_LoadN) {
 866     Node* ld = gvn.transform(load);
 867     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 868   }
 869 
 870   return load;
 871 }
 872 
 873 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 874                                   ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 875   bool require_atomic = true;
 876   LoadLNode* load = new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic);
 877   if (unaligned) {
 878     load->set_unaligned_access();
 879   }
 880   if (mismatched) {
 881     load->set_mismatched_access();
 882   }
 883   if (unsafe) {
 884     load->set_unsafe_access();
 885   }
 886   return load;
 887 }
 888 
 889 LoadDNode* LoadDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 890                                   ControlDependency control_dependency, bool unaligned, bool mismatched, bool unsafe) {
 891   bool require_atomic = true;
 892   LoadDNode* load = new LoadDNode(ctl, mem, adr, adr_type, rt, mo, control_dependency, require_atomic);
 893   if (unaligned) {
 894     load->set_unaligned_access();
 895   }
 896   if (mismatched) {
 897     load->set_mismatched_access();
 898   }
 899   if (unsafe) {
 900     load->set_unsafe_access();
 901   }
 902   return load;
 903 }
 904 
 905 
 906 
 907 //------------------------------hash-------------------------------------------
 908 uint LoadNode::hash() const {
 909   // unroll addition of interesting fields
 910   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 911 }
 912 
 913 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 914   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 915     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 916     bool is_stable_ary = FoldStableValues &&
 917                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 918                          tp->isa_aryptr()->is_stable();
 919 
 920     return (eliminate_boxing && non_volatile) || is_stable_ary;
 921   }
 922 
 923   return false;
 924 }
 925 
 926 // Is the value loaded previously stored by an arraycopy? If so return
 927 // a load node that reads from the source array so we may be able to
 928 // optimize out the ArrayCopy node later.
 929 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
 930 #if INCLUDE_ZGC
 931   if (UseZGC) {
 932     if (bottom_type()->make_oopptr() != NULL) {
 933       return NULL;
 934     }
 935   }
 936 #endif
 937 
 938   Node* ld_adr = in(MemNode::Address);
 939   intptr_t ld_off = 0;
 940   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 941   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
 942   if (ac != NULL) {
 943     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
 944 
 945     Node* mem = ac->in(TypeFunc::Memory);
 946     Node* ctl = ac->in(0);
 947     Node* src = ac->in(ArrayCopyNode::Src);
 948 
 949     if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
 950       return NULL;
 951     }
 952 
 953     LoadNode* ld = clone()->as_Load();
 954     Node* addp = in(MemNode::Address)->clone();
 955     if (ac->as_ArrayCopy()->is_clonebasic()) {
 956       assert(ld_alloc != NULL, "need an alloc");
 957       assert(addp->is_AddP(), "address must be addp");
 958       assert(addp->in(AddPNode::Base) == ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base), "strange pattern");
 959       assert(addp->in(AddPNode::Address) == ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address), "strange pattern");
 960       addp->set_req(AddPNode::Base, src->in(AddPNode::Base));
 961       addp->set_req(AddPNode::Address, src->in(AddPNode::Address));
 962     } else {
 963       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
 964              ac->as_ArrayCopy()->is_copyof_validated() ||
 965              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
 966       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
 967       addp->set_req(AddPNode::Base, src);
 968       addp->set_req(AddPNode::Address, src);
 969 
 970       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
 971       BasicType ary_elem  = ary_t->klass()->as_array_klass()->element_type()->basic_type();
 972       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 973       uint shift  = exact_log2(type2aelembytes(ary_elem));
 974 
 975       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
 976 #ifdef _LP64
 977       diff = phase->transform(new ConvI2LNode(diff));
 978 #endif
 979       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
 980 
 981       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
 982       addp->set_req(AddPNode::Offset, offset);
 983     }
 984     addp = phase->transform(addp);
 985 #ifdef ASSERT
 986     const TypePtr* adr_type = phase->type(addp)->is_ptr();
 987     ld->_adr_type = adr_type;
 988 #endif
 989     ld->set_req(MemNode::Address, addp);
 990     ld->set_req(0, ctl);
 991     ld->set_req(MemNode::Memory, mem);
 992     // load depends on the tests that validate the arraycopy
 993     ld->_control_dependency = Pinned;
 994     return ld;
 995   }
 996   return NULL;
 997 }
 998 
 999 
1000 //---------------------------can_see_stored_value------------------------------
1001 // This routine exists to make sure this set of tests is done the same
1002 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
1003 // will change the graph shape in a way which makes memory alive twice at the
1004 // same time (uses the Oracle model of aliasing), then some
1005 // LoadXNode::Identity will fold things back to the equivalence-class model
1006 // of aliasing.
1007 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
1008   Node* ld_adr = in(MemNode::Address);
1009   intptr_t ld_off = 0;
1010   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
1011   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
1012   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
1013   // This is more general than load from boxing objects.
1014   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
1015     uint alias_idx = atp->index();
1016     bool final = !atp->is_rewritable();
1017     Node* result = NULL;
1018     Node* current = st;
1019     // Skip through chains of MemBarNodes checking the MergeMems for
1020     // new states for the slice of this load.  Stop once any other
1021     // kind of node is encountered.  Loads from final memory can skip
1022     // through any kind of MemBar but normal loads shouldn't skip
1023     // through MemBarAcquire since the could allow them to move out of
1024     // a synchronized region.
1025     while (current->is_Proj()) {
1026       int opc = current->in(0)->Opcode();
1027       if ((final && (opc == Op_MemBarAcquire ||
1028                      opc == Op_MemBarAcquireLock ||
1029                      opc == Op_LoadFence)) ||
1030           opc == Op_MemBarRelease ||
1031           opc == Op_StoreFence ||
1032           opc == Op_MemBarReleaseLock ||
1033           opc == Op_MemBarStoreStore ||
1034           opc == Op_MemBarCPUOrder) {
1035         Node* mem = current->in(0)->in(TypeFunc::Memory);
1036         if (mem->is_MergeMem()) {
1037           MergeMemNode* merge = mem->as_MergeMem();
1038           Node* new_st = merge->memory_at(alias_idx);
1039           if (new_st == merge->base_memory()) {
1040             // Keep searching
1041             current = new_st;
1042             continue;
1043           }
1044           // Save the new memory state for the slice and fall through
1045           // to exit.
1046           result = new_st;
1047         }
1048       }
1049       break;
1050     }
1051     if (result != NULL) {
1052       st = result;
1053     }
1054   }
1055 
1056   // Loop around twice in the case Load -> Initialize -> Store.
1057   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1058   for (int trip = 0; trip <= 1; trip++) {
1059 
1060     if (st->is_Store()) {
1061       Node* st_adr = st->in(MemNode::Address);
1062       if (!phase->eqv(st_adr, ld_adr)) {
1063         // Try harder before giving up...  Match raw and non-raw pointers.
1064         intptr_t st_off = 0;
1065         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
1066         if (alloc == NULL)       return NULL;
1067         if (alloc != ld_alloc)   return NULL;
1068         if (ld_off != st_off)    return NULL;
1069         // At this point we have proven something like this setup:
1070         //  A = Allocate(...)
1071         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
1072         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
1073         // (Actually, we haven't yet proven the Q's are the same.)
1074         // In other words, we are loading from a casted version of
1075         // the same pointer-and-offset that we stored to.
1076         // Thus, we are able to replace L by V.
1077       }
1078       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1079       if (store_Opcode() != st->Opcode())
1080         return NULL;
1081       return st->in(MemNode::ValueIn);
1082     }
1083 
1084     // A load from a freshly-created object always returns zero.
1085     // (This can happen after LoadNode::Ideal resets the load's memory input
1086     // to find_captured_store, which returned InitializeNode::zero_memory.)
1087     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1088         (st->in(0) == ld_alloc) &&
1089         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1090       // return a zero value for the load's basic type
1091       // (This is one of the few places where a generic PhaseTransform
1092       // can create new nodes.  Think of it as lazily manifesting
1093       // virtually pre-existing constants.)
1094       return phase->zerocon(memory_type());
1095     }
1096 
1097     // A load from an initialization barrier can match a captured store.
1098     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1099       InitializeNode* init = st->in(0)->as_Initialize();
1100       AllocateNode* alloc = init->allocation();
1101       if ((alloc != NULL) && (alloc == ld_alloc)) {
1102         // examine a captured store value
1103         st = init->find_captured_store(ld_off, memory_size(), phase);
1104         if (st != NULL) {
1105           continue;             // take one more trip around
1106         }
1107       }
1108     }
1109 
1110     // Load boxed value from result of valueOf() call is input parameter.
1111     if (this->is_Load() && ld_adr->is_AddP() &&
1112         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1113       intptr_t ignore = 0;
1114       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1115       if (base != NULL && base->is_Proj() &&
1116           base->as_Proj()->_con == TypeFunc::Parms &&
1117           base->in(0)->is_CallStaticJava() &&
1118           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1119         return base->in(0)->in(TypeFunc::Parms);
1120       }
1121     }
1122 
1123     break;
1124   }
1125 
1126   return NULL;
1127 }
1128 
1129 //----------------------is_instance_field_load_with_local_phi------------------
1130 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1131   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1132       in(Address)->is_AddP() ) {
1133     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1134     // Only instances and boxed values.
1135     if( t_oop != NULL &&
1136         (t_oop->is_ptr_to_boxed_value() ||
1137          t_oop->is_known_instance_field()) &&
1138         t_oop->offset() != Type::OffsetBot &&
1139         t_oop->offset() != Type::OffsetTop) {
1140       return true;
1141     }
1142   }
1143   return false;
1144 }
1145 
1146 //------------------------------Identity---------------------------------------
1147 // Loads are identity if previous store is to same address
1148 Node* LoadNode::Identity(PhaseGVN* phase) {
1149   // If the previous store-maker is the right kind of Store, and the store is
1150   // to the same address, then we are equal to the value stored.
1151   Node* mem = in(Memory);
1152   Node* value = can_see_stored_value(mem, phase);
1153   if( value ) {
1154     // byte, short & char stores truncate naturally.
1155     // A load has to load the truncated value which requires
1156     // some sort of masking operation and that requires an
1157     // Ideal call instead of an Identity call.
1158     if (memory_size() < BytesPerInt) {
1159       // If the input to the store does not fit with the load's result type,
1160       // it must be truncated via an Ideal call.
1161       if (!phase->type(value)->higher_equal(phase->type(this)))
1162         return this;
1163     }
1164     // (This works even when value is a Con, but LoadNode::Value
1165     // usually runs first, producing the singleton type of the Con.)
1166     return value;
1167   }
1168 
1169   // Search for an existing data phi which was generated before for the same
1170   // instance's field to avoid infinite generation of phis in a loop.
1171   Node *region = mem->in(0);
1172   if (is_instance_field_load_with_local_phi(region)) {
1173     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1174     int this_index  = phase->C->get_alias_index(addr_t);
1175     int this_offset = addr_t->offset();
1176     int this_iid    = addr_t->instance_id();
1177     if (!addr_t->is_known_instance() &&
1178          addr_t->is_ptr_to_boxed_value()) {
1179       // Use _idx of address base (could be Phi node) for boxed values.
1180       intptr_t   ignore = 0;
1181       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1182       if (base == NULL) {
1183         return this;
1184       }
1185       this_iid = base->_idx;
1186     }
1187     const Type* this_type = bottom_type();
1188     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1189       Node* phi = region->fast_out(i);
1190       if (phi->is_Phi() && phi != mem &&
1191           phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1192         return phi;
1193       }
1194     }
1195   }
1196 
1197   return this;
1198 }
1199 
1200 // Construct an equivalent unsigned load.
1201 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1202   BasicType bt = T_ILLEGAL;
1203   const Type* rt = NULL;
1204   switch (Opcode()) {
1205     case Op_LoadUB: return this;
1206     case Op_LoadUS: return this;
1207     case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1208     case Op_LoadS: bt = T_CHAR;    rt = TypeInt::CHAR;  break;
1209     default:
1210       assert(false, "no unsigned variant: %s", Name());
1211       return NULL;
1212   }
1213   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1214                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1215                         is_unaligned_access(), is_mismatched_access());
1216 }
1217 
1218 // Construct an equivalent signed load.
1219 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1220   BasicType bt = T_ILLEGAL;
1221   const Type* rt = NULL;
1222   switch (Opcode()) {
1223     case Op_LoadUB: bt = T_BYTE;  rt = TypeInt::BYTE;  break;
1224     case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1225     case Op_LoadB: // fall through
1226     case Op_LoadS: // fall through
1227     case Op_LoadI: // fall through
1228     case Op_LoadL: return this;
1229     default:
1230       assert(false, "no signed variant: %s", Name());
1231       return NULL;
1232   }
1233   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1234                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1235                         is_unaligned_access(), is_mismatched_access());
1236 }
1237 
1238 // We're loading from an object which has autobox behaviour.
1239 // If this object is result of a valueOf call we'll have a phi
1240 // merging a newly allocated object and a load from the cache.
1241 // We want to replace this load with the original incoming
1242 // argument to the valueOf call.
1243 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1244   assert(phase->C->eliminate_boxing(), "sanity");
1245   intptr_t ignore = 0;
1246   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1247   if ((base == NULL) || base->is_Phi()) {
1248     // Push the loads from the phi that comes from valueOf up
1249     // through it to allow elimination of the loads and the recovery
1250     // of the original value. It is done in split_through_phi().
1251     return NULL;
1252   } else if (base->is_Load() ||
1253              (base->is_DecodeN() && base->in(1)->is_Load())) {
1254     // Eliminate the load of boxed value for integer types from the cache
1255     // array by deriving the value from the index into the array.
1256     // Capture the offset of the load and then reverse the computation.
1257 
1258     // Get LoadN node which loads a boxing object from 'cache' array.
1259     if (base->is_DecodeN()) {
1260       base = base->in(1);
1261     }
1262     if (!base->in(Address)->is_AddP()) {
1263       return NULL; // Complex address
1264     }
1265     AddPNode* address = base->in(Address)->as_AddP();
1266     Node* cache_base = address->in(AddPNode::Base);
1267     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1268       // Get ConP node which is static 'cache' field.
1269       cache_base = cache_base->in(1);
1270     }
1271     if ((cache_base != NULL) && cache_base->is_Con()) {
1272       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1273       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1274         Node* elements[4];
1275         int shift = exact_log2(type2aelembytes(T_OBJECT));
1276         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1277         if (count > 0 && elements[0]->is_Con() &&
1278             (count == 1 ||
1279              (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1280                             elements[1]->in(2) == phase->intcon(shift)))) {
1281           ciObjArray* array = base_type->const_oop()->as_obj_array();
1282           // Fetch the box object cache[0] at the base of the array and get its value
1283           ciInstance* box = array->obj_at(0)->as_instance();
1284           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1285           assert(ik->is_box_klass(), "sanity");
1286           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1287           if (ik->nof_nonstatic_fields() == 1) {
1288             // This should be true nonstatic_field_at requires calling
1289             // nof_nonstatic_fields so check it anyway
1290             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1291             BasicType bt = c.basic_type();
1292             // Only integer types have boxing cache.
1293             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1294                    bt == T_BYTE    || bt == T_SHORT ||
1295                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1296             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1297             if (cache_low != (int)cache_low) {
1298               return NULL; // should not happen since cache is array indexed by value
1299             }
1300             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1301             if (offset != (int)offset) {
1302               return NULL; // should not happen since cache is array indexed by value
1303             }
1304            // Add up all the offsets making of the address of the load
1305             Node* result = elements[0];
1306             for (int i = 1; i < count; i++) {
1307               result = phase->transform(new AddXNode(result, elements[i]));
1308             }
1309             // Remove the constant offset from the address and then
1310             result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1311             // remove the scaling of the offset to recover the original index.
1312             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1313               // Peel the shift off directly but wrap it in a dummy node
1314               // since Ideal can't return existing nodes
1315               result = new RShiftXNode(result->in(1), phase->intcon(0));
1316             } else if (result->is_Add() && result->in(2)->is_Con() &&
1317                        result->in(1)->Opcode() == Op_LShiftX &&
1318                        result->in(1)->in(2) == phase->intcon(shift)) {
1319               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1320               // but for boxing cache access we know that X<<Z will not overflow
1321               // (there is range check) so we do this optimizatrion by hand here.
1322               Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1323               result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1324             } else {
1325               result = new RShiftXNode(result, phase->intcon(shift));
1326             }
1327 #ifdef _LP64
1328             if (bt != T_LONG) {
1329               result = new ConvL2INode(phase->transform(result));
1330             }
1331 #else
1332             if (bt == T_LONG) {
1333               result = new ConvI2LNode(phase->transform(result));
1334             }
1335 #endif
1336             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1337             // Need to preserve unboxing load type if it is unsigned.
1338             switch(this->Opcode()) {
1339               case Op_LoadUB:
1340                 result = new AndINode(phase->transform(result), phase->intcon(0xFF));
1341                 break;
1342               case Op_LoadUS:
1343                 result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
1344                 break;
1345             }
1346             return result;
1347           }
1348         }
1349       }
1350     }
1351   }
1352   return NULL;
1353 }
1354 
1355 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1356   Node* region = phi->in(0);
1357   if (region == NULL) {
1358     return false; // Wait stable graph
1359   }
1360   uint cnt = phi->req();
1361   for (uint i = 1; i < cnt; i++) {
1362     Node* rc = region->in(i);
1363     if (rc == NULL || phase->type(rc) == Type::TOP)
1364       return false; // Wait stable graph
1365     Node* in = phi->in(i);
1366     if (in == NULL || phase->type(in) == Type::TOP)
1367       return false; // Wait stable graph
1368   }
1369   return true;
1370 }
1371 //------------------------------split_through_phi------------------------------
1372 // Split instance or boxed field load through Phi.
1373 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1374   Node* mem     = in(Memory);
1375   Node* address = in(Address);
1376   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1377 
1378   assert((t_oop != NULL) &&
1379          (t_oop->is_known_instance_field() ||
1380           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1381 
1382   Compile* C = phase->C;
1383   intptr_t ignore = 0;
1384   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1385   bool base_is_phi = (base != NULL) && base->is_Phi();
1386   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1387                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1388                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1389 
1390   if (!((mem->is_Phi() || base_is_phi) &&
1391         (load_boxed_values || t_oop->is_known_instance_field()))) {
1392     return NULL; // memory is not Phi
1393   }
1394 
1395   if (mem->is_Phi()) {
1396     if (!stable_phi(mem->as_Phi(), phase)) {
1397       return NULL; // Wait stable graph
1398     }
1399     uint cnt = mem->req();
1400     // Check for loop invariant memory.
1401     if (cnt == 3) {
1402       for (uint i = 1; i < cnt; i++) {
1403         Node* in = mem->in(i);
1404         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1405         if (m == mem) {
1406           if (i == 1) {
1407             // if the first edge was a loop, check second edge too.
1408             // If both are replaceable - we are in an infinite loop
1409             Node *n = optimize_memory_chain(mem->in(2), t_oop, this, phase);
1410             if (n == mem) {
1411               break;
1412             }
1413           }
1414           set_req(Memory, mem->in(cnt - i));
1415           return this; // made change
1416         }
1417       }
1418     }
1419   }
1420   if (base_is_phi) {
1421     if (!stable_phi(base->as_Phi(), phase)) {
1422       return NULL; // Wait stable graph
1423     }
1424     uint cnt = base->req();
1425     // Check for loop invariant memory.
1426     if (cnt == 3) {
1427       for (uint i = 1; i < cnt; i++) {
1428         if (base->in(i) == base) {
1429           return NULL; // Wait stable graph
1430         }
1431       }
1432     }
1433   }
1434 
1435   bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1436 
1437   // Split through Phi (see original code in loopopts.cpp).
1438   assert(C->have_alias_type(t_oop), "instance should have alias type");
1439 
1440   // Do nothing here if Identity will find a value
1441   // (to avoid infinite chain of value phis generation).
1442   if (!phase->eqv(this, phase->apply_identity(this)))
1443     return NULL;
1444 
1445   // Select Region to split through.
1446   Node* region;
1447   if (!base_is_phi) {
1448     assert(mem->is_Phi(), "sanity");
1449     region = mem->in(0);
1450     // Skip if the region dominates some control edge of the address.
1451     if (!MemNode::all_controls_dominate(address, region))
1452       return NULL;
1453   } else if (!mem->is_Phi()) {
1454     assert(base_is_phi, "sanity");
1455     region = base->in(0);
1456     // Skip if the region dominates some control edge of the memory.
1457     if (!MemNode::all_controls_dominate(mem, region))
1458       return NULL;
1459   } else if (base->in(0) != mem->in(0)) {
1460     assert(base_is_phi && mem->is_Phi(), "sanity");
1461     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1462       region = base->in(0);
1463     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1464       region = mem->in(0);
1465     } else {
1466       return NULL; // complex graph
1467     }
1468   } else {
1469     assert(base->in(0) == mem->in(0), "sanity");
1470     region = mem->in(0);
1471   }
1472 
1473   const Type* this_type = this->bottom_type();
1474   int this_index  = C->get_alias_index(t_oop);
1475   int this_offset = t_oop->offset();
1476   int this_iid    = t_oop->instance_id();
1477   if (!t_oop->is_known_instance() && load_boxed_values) {
1478     // Use _idx of address base for boxed values.
1479     this_iid = base->_idx;
1480   }
1481   PhaseIterGVN* igvn = phase->is_IterGVN();
1482   Node* phi = new PhiNode(region, this_type, NULL, mem->_idx, this_iid, this_index, this_offset);
1483   for (uint i = 1; i < region->req(); i++) {
1484     Node* x;
1485     Node* the_clone = NULL;
1486     if (region->in(i) == C->top()) {
1487       x = C->top();      // Dead path?  Use a dead data op
1488     } else {
1489       x = this->clone();        // Else clone up the data op
1490       the_clone = x;            // Remember for possible deletion.
1491       // Alter data node to use pre-phi inputs
1492       if (this->in(0) == region) {
1493         x->set_req(0, region->in(i));
1494       } else {
1495         x->set_req(0, NULL);
1496       }
1497       if (mem->is_Phi() && (mem->in(0) == region)) {
1498         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1499       }
1500       if (address->is_Phi() && address->in(0) == region) {
1501         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1502       }
1503       if (base_is_phi && (base->in(0) == region)) {
1504         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1505         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1506         x->set_req(Address, adr_x);
1507       }
1508     }
1509     // Check for a 'win' on some paths
1510     const Type *t = x->Value(igvn);
1511 
1512     bool singleton = t->singleton();
1513 
1514     // See comments in PhaseIdealLoop::split_thru_phi().
1515     if (singleton && t == Type::TOP) {
1516       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1517     }
1518 
1519     if (singleton) {
1520       x = igvn->makecon(t);
1521     } else {
1522       // We now call Identity to try to simplify the cloned node.
1523       // Note that some Identity methods call phase->type(this).
1524       // Make sure that the type array is big enough for
1525       // our new node, even though we may throw the node away.
1526       // (This tweaking with igvn only works because x is a new node.)
1527       igvn->set_type(x, t);
1528       // If x is a TypeNode, capture any more-precise type permanently into Node
1529       // otherwise it will be not updated during igvn->transform since
1530       // igvn->type(x) is set to x->Value() already.
1531       x->raise_bottom_type(t);
1532       Node *y = igvn->apply_identity(x);
1533       if (y != x) {
1534         x = y;
1535       } else {
1536         y = igvn->hash_find_insert(x);
1537         if (y) {
1538           x = y;
1539         } else {
1540           // Else x is a new node we are keeping
1541           // We do not need register_new_node_with_optimizer
1542           // because set_type has already been called.
1543           igvn->_worklist.push(x);
1544         }
1545       }
1546     }
1547     if (x != the_clone && the_clone != NULL) {
1548       igvn->remove_dead_node(the_clone);
1549     }
1550     phi->set_req(i, x);
1551   }
1552   // Record Phi
1553   igvn->register_new_node_with_optimizer(phi);
1554   return phi;
1555 }
1556 
1557 //------------------------------Ideal------------------------------------------
1558 // If the load is from Field memory and the pointer is non-null, it might be possible to
1559 // zero out the control input.
1560 // If the offset is constant and the base is an object allocation,
1561 // try to hook me up to the exact initializing store.
1562 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1563   Node* p = MemNode::Ideal_common(phase, can_reshape);
1564   if (p)  return (p == NodeSentinel) ? NULL : p;
1565 
1566   Node* ctrl    = in(MemNode::Control);
1567   Node* address = in(MemNode::Address);
1568   bool progress = false;
1569 
1570   bool addr_mark = ((phase->type(address)->isa_oopptr() || phase->type(address)->isa_narrowoop()) &&
1571          phase->type(address)->is_ptr()->offset() == oopDesc::mark_offset_in_bytes());
1572 
1573   // Skip up past a SafePoint control.  Cannot do this for Stores because
1574   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1575   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1576       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw  &&
1577       !addr_mark ) {
1578     ctrl = ctrl->in(0);
1579     set_req(MemNode::Control,ctrl);
1580     progress = true;
1581   }
1582 
1583   intptr_t ignore = 0;
1584   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1585   if (base != NULL
1586       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1587     // Check for useless control edge in some common special cases
1588     if (in(MemNode::Control) != NULL
1589         && can_remove_control()
1590         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1591         && all_controls_dominate(base, phase->C->start())) {
1592       // A method-invariant, non-null address (constant or 'this' argument).
1593       set_req(MemNode::Control, NULL);
1594       progress = true;
1595     }
1596   }
1597 
1598   Node* mem = in(MemNode::Memory);
1599   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1600 
1601   if (can_reshape && (addr_t != NULL)) {
1602     // try to optimize our memory input
1603     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1604     if (opt_mem != mem) {
1605       set_req(MemNode::Memory, opt_mem);
1606       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1607       return this;
1608     }
1609     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1610     if ((t_oop != NULL) &&
1611         (t_oop->is_known_instance_field() ||
1612          t_oop->is_ptr_to_boxed_value())) {
1613       PhaseIterGVN *igvn = phase->is_IterGVN();
1614       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1615         // Delay this transformation until memory Phi is processed.
1616         phase->is_IterGVN()->_worklist.push(this);
1617         return NULL;
1618       }
1619       // Split instance field load through Phi.
1620       Node* result = split_through_phi(phase);
1621       if (result != NULL) return result;
1622 
1623       if (t_oop->is_ptr_to_boxed_value()) {
1624         Node* result = eliminate_autobox(phase);
1625         if (result != NULL) return result;
1626       }
1627     }
1628   }
1629 
1630   // Is there a dominating load that loads the same value?  Leave
1631   // anything that is not a load of a field/array element (like
1632   // barriers etc.) alone
1633   if (in(0) != NULL && !adr_type()->isa_rawptr() && can_reshape) {
1634     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1635       Node *use = mem->fast_out(i);
1636       if (use != this &&
1637           use->Opcode() == Opcode() &&
1638           use->in(0) != NULL &&
1639           use->in(0) != in(0) &&
1640           use->in(Address) == in(Address)) {
1641         Node* ctl = in(0);
1642         for (int i = 0; i < 10 && ctl != NULL; i++) {
1643           ctl = IfNode::up_one_dom(ctl);
1644           if (ctl == use->in(0)) {
1645             set_req(0, use->in(0));
1646             return this;
1647           }
1648         }
1649       }
1650     }
1651   }
1652 
1653   // Check for prior store with a different base or offset; make Load
1654   // independent.  Skip through any number of them.  Bail out if the stores
1655   // are in an endless dead cycle and report no progress.  This is a key
1656   // transform for Reflection.  However, if after skipping through the Stores
1657   // we can't then fold up against a prior store do NOT do the transform as
1658   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1659   // array memory alive twice: once for the hoisted Load and again after the
1660   // bypassed Store.  This situation only works if EVERYBODY who does
1661   // anti-dependence work knows how to bypass.  I.e. we need all
1662   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1663   // the alias index stuff.  So instead, peek through Stores and IFF we can
1664   // fold up, do so.
1665   Node* prev_mem = find_previous_store(phase);
1666   if (prev_mem != NULL) {
1667     Node* value = can_see_arraycopy_value(prev_mem, phase);
1668     if (value != NULL) {
1669       return value;
1670     }
1671   }
1672   // Steps (a), (b):  Walk past independent stores to find an exact match.
1673   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1674     // (c) See if we can fold up on the spot, but don't fold up here.
1675     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1676     // just return a prior value, which is done by Identity calls.
1677     if (can_see_stored_value(prev_mem, phase)) {
1678       // Make ready for step (d):
1679       set_req(MemNode::Memory, prev_mem);
1680       return this;
1681     }
1682   }
1683 
1684   return progress ? this : NULL;
1685 }
1686 
1687 // Helper to recognize certain Klass fields which are invariant across
1688 // some group of array types (e.g., int[] or all T[] where T < Object).
1689 const Type*
1690 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1691                                  ciKlass* klass) const {
1692   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1693     // The field is Klass::_modifier_flags.  Return its (constant) value.
1694     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1695     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1696     return TypeInt::make(klass->modifier_flags());
1697   }
1698   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1699     // The field is Klass::_access_flags.  Return its (constant) value.
1700     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1701     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1702     return TypeInt::make(klass->access_flags());
1703   }
1704   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1705     // The field is Klass::_layout_helper.  Return its constant value if known.
1706     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1707     return TypeInt::make(klass->layout_helper());
1708   }
1709 
1710   // No match.
1711   return NULL;
1712 }
1713 
1714 //------------------------------Value-----------------------------------------
1715 const Type* LoadNode::Value(PhaseGVN* phase) const {
1716   // Either input is TOP ==> the result is TOP
1717   Node* mem = in(MemNode::Memory);
1718   const Type *t1 = phase->type(mem);
1719   if (t1 == Type::TOP)  return Type::TOP;
1720   Node* adr = in(MemNode::Address);
1721   const TypePtr* tp = phase->type(adr)->isa_ptr();
1722   if (tp == NULL || tp->empty())  return Type::TOP;
1723   int off = tp->offset();
1724   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1725   Compile* C = phase->C;
1726 
1727   // Try to guess loaded type from pointer type
1728   if (tp->isa_aryptr()) {
1729     const TypeAryPtr* ary = tp->is_aryptr();
1730     const Type* t = ary->elem();
1731 
1732     // Determine whether the reference is beyond the header or not, by comparing
1733     // the offset against the offset of the start of the array's data.
1734     // Different array types begin at slightly different offsets (12 vs. 16).
1735     // We choose T_BYTE as an example base type that is least restrictive
1736     // as to alignment, which will therefore produce the smallest
1737     // possible base offset.
1738     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1739     const bool off_beyond_header = ((uint)off >= (uint)min_base_off);
1740 
1741     // Try to constant-fold a stable array element.
1742     if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1743       // Make sure the reference is not into the header and the offset is constant
1744       ciObject* aobj = ary->const_oop();
1745       if (aobj != NULL && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1746         int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1747         const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1748                                                                       stable_dimension,
1749                                                                       memory_type(), is_unsigned());
1750         if (con_type != NULL) {
1751           return con_type;
1752         }
1753       }
1754     }
1755 
1756     // Don't do this for integer types. There is only potential profit if
1757     // the element type t is lower than _type; that is, for int types, if _type is
1758     // more restrictive than t.  This only happens here if one is short and the other
1759     // char (both 16 bits), and in those cases we've made an intentional decision
1760     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1761     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1762     //
1763     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1764     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1765     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1766     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1767     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1768     // In fact, that could have been the original type of p1, and p1 could have
1769     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1770     // expression (LShiftL quux 3) independently optimized to the constant 8.
1771     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1772         && (_type->isa_vect() == NULL)
1773         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1774       // t might actually be lower than _type, if _type is a unique
1775       // concrete subclass of abstract class t.
1776       if (off_beyond_header) {  // is the offset beyond the header?
1777         const Type* jt = t->join_speculative(_type);
1778         // In any case, do not allow the join, per se, to empty out the type.
1779         if (jt->empty() && !t->empty()) {
1780           // This can happen if a interface-typed array narrows to a class type.
1781           jt = _type;
1782         }
1783 #ifdef ASSERT
1784         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1785           // The pointers in the autobox arrays are always non-null
1786           Node* base = adr->in(AddPNode::Base);
1787           if ((base != NULL) && base->is_DecodeN()) {
1788             // Get LoadN node which loads IntegerCache.cache field
1789             base = base->in(1);
1790           }
1791           if ((base != NULL) && base->is_Con()) {
1792             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1793             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1794               // It could be narrow oop
1795               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1796             }
1797           }
1798         }
1799 #endif
1800         return jt;
1801       }
1802     }
1803   } else if (tp->base() == Type::InstPtr) {
1804     assert( off != Type::OffsetBot ||
1805             // arrays can be cast to Objects
1806             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1807             // unsafe field access may not have a constant offset
1808             C->has_unsafe_access(),
1809             "Field accesses must be precise" );
1810     // For oop loads, we expect the _type to be precise.
1811 
1812     // Optimize loads from constant fields.
1813     const TypeInstPtr* tinst = tp->is_instptr();
1814     ciObject* const_oop = tinst->const_oop();
1815     if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != NULL && const_oop->is_instance()) {
1816       const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
1817       if (con_type != NULL) {
1818         return con_type;
1819       }
1820     }
1821   } else if (tp->base() == Type::KlassPtr) {
1822     assert( off != Type::OffsetBot ||
1823             // arrays can be cast to Objects
1824             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1825             // also allow array-loading from the primary supertype
1826             // array during subtype checks
1827             Opcode() == Op_LoadKlass,
1828             "Field accesses must be precise" );
1829     // For klass/static loads, we expect the _type to be precise
1830   } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
1831     /* With mirrors being an indirect in the Klass*
1832      * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
1833      * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
1834      *
1835      * So check the type and klass of the node before the LoadP.
1836      */
1837     Node* adr2 = adr->in(MemNode::Address);
1838     const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
1839     if (tkls != NULL && !StressReflectiveCode) {
1840       ciKlass* klass = tkls->klass();
1841       if (klass->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1842         assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1843         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1844         return TypeInstPtr::make(klass->java_mirror());
1845       }
1846     }
1847   }
1848 
1849   const TypeKlassPtr *tkls = tp->isa_klassptr();
1850   if (tkls != NULL && !StressReflectiveCode) {
1851     ciKlass* klass = tkls->klass();
1852     if (klass->is_loaded() && tkls->klass_is_exact()) {
1853       // We are loading a field from a Klass metaobject whose identity
1854       // is known at compile time (the type is "exact" or "precise").
1855       // Check for fields we know are maintained as constants by the VM.
1856       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1857         // The field is Klass::_super_check_offset.  Return its (constant) value.
1858         // (Folds up type checking code.)
1859         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1860         return TypeInt::make(klass->super_check_offset());
1861       }
1862       // Compute index into primary_supers array
1863       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1864       // Check for overflowing; use unsigned compare to handle the negative case.
1865       if( depth < ciKlass::primary_super_limit() ) {
1866         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1867         // (Folds up type checking code.)
1868         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1869         ciKlass *ss = klass->super_of_depth(depth);
1870         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1871       }
1872       const Type* aift = load_array_final_field(tkls, klass);
1873       if (aift != NULL)  return aift;
1874     }
1875 
1876     // We can still check if we are loading from the primary_supers array at a
1877     // shallow enough depth.  Even though the klass is not exact, entries less
1878     // than or equal to its super depth are correct.
1879     if (klass->is_loaded() ) {
1880       ciType *inner = klass;
1881       while( inner->is_obj_array_klass() )
1882         inner = inner->as_obj_array_klass()->base_element_type();
1883       if( inner->is_instance_klass() &&
1884           !inner->as_instance_klass()->flags().is_interface() ) {
1885         // Compute index into primary_supers array
1886         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1887         // Check for overflowing; use unsigned compare to handle the negative case.
1888         if( depth < ciKlass::primary_super_limit() &&
1889             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1890           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1891           // (Folds up type checking code.)
1892           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1893           ciKlass *ss = klass->super_of_depth(depth);
1894           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1895         }
1896       }
1897     }
1898 
1899     // If the type is enough to determine that the thing is not an array,
1900     // we can give the layout_helper a positive interval type.
1901     // This will help short-circuit some reflective code.
1902     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1903         && !klass->is_array_klass() // not directly typed as an array
1904         && !klass->is_interface()  // specifically not Serializable & Cloneable
1905         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1906         ) {
1907       // Note:  When interfaces are reliable, we can narrow the interface
1908       // test to (klass != Serializable && klass != Cloneable).
1909       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1910       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1911       // The key property of this type is that it folds up tests
1912       // for array-ness, since it proves that the layout_helper is positive.
1913       // Thus, a generic value like the basic object layout helper works fine.
1914       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1915     }
1916   }
1917 
1918   // If we are loading from a freshly-allocated object, produce a zero,
1919   // if the load is provably beyond the header of the object.
1920   // (Also allow a variable load from a fresh array to produce zero.)
1921   const TypeOopPtr *tinst = tp->isa_oopptr();
1922   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1923   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1924   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1925     Node* value = can_see_stored_value(mem,phase);
1926     if (value != NULL && value->is_Con()) {
1927       assert(value->bottom_type()->higher_equal(_type),"sanity");
1928       return value->bottom_type();
1929     }
1930   }
1931 
1932   if (is_instance) {
1933     // If we have an instance type and our memory input is the
1934     // programs's initial memory state, there is no matching store,
1935     // so just return a zero of the appropriate type
1936     Node *mem = in(MemNode::Memory);
1937     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1938       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1939       return Type::get_zero_type(_type->basic_type());
1940     }
1941   }
1942   return _type;
1943 }
1944 
1945 //------------------------------match_edge-------------------------------------
1946 // Do we Match on this edge index or not?  Match only the address.
1947 uint LoadNode::match_edge(uint idx) const {
1948   return idx == MemNode::Address;
1949 }
1950 
1951 //--------------------------LoadBNode::Ideal--------------------------------------
1952 //
1953 //  If the previous store is to the same address as this load,
1954 //  and the value stored was larger than a byte, replace this load
1955 //  with the value stored truncated to a byte.  If no truncation is
1956 //  needed, the replacement is done in LoadNode::Identity().
1957 //
1958 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1959   Node* mem = in(MemNode::Memory);
1960   Node* value = can_see_stored_value(mem,phase);
1961   if( value && !phase->type(value)->higher_equal( _type ) ) {
1962     Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1963     return new RShiftINode(result, phase->intcon(24));
1964   }
1965   // Identity call will handle the case where truncation is not needed.
1966   return LoadNode::Ideal(phase, can_reshape);
1967 }
1968 
1969 const Type* LoadBNode::Value(PhaseGVN* phase) const {
1970   Node* mem = in(MemNode::Memory);
1971   Node* value = can_see_stored_value(mem,phase);
1972   if (value != NULL && value->is_Con() &&
1973       !value->bottom_type()->higher_equal(_type)) {
1974     // If the input to the store does not fit with the load's result type,
1975     // it must be truncated. We can't delay until Ideal call since
1976     // a singleton Value is needed for split_thru_phi optimization.
1977     int con = value->get_int();
1978     return TypeInt::make((con << 24) >> 24);
1979   }
1980   return LoadNode::Value(phase);
1981 }
1982 
1983 //--------------------------LoadUBNode::Ideal-------------------------------------
1984 //
1985 //  If the previous store is to the same address as this load,
1986 //  and the value stored was larger than a byte, replace this load
1987 //  with the value stored truncated to a byte.  If no truncation is
1988 //  needed, the replacement is done in LoadNode::Identity().
1989 //
1990 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1991   Node* mem = in(MemNode::Memory);
1992   Node* value = can_see_stored_value(mem, phase);
1993   if (value && !phase->type(value)->higher_equal(_type))
1994     return new AndINode(value, phase->intcon(0xFF));
1995   // Identity call will handle the case where truncation is not needed.
1996   return LoadNode::Ideal(phase, can_reshape);
1997 }
1998 
1999 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
2000   Node* mem = in(MemNode::Memory);
2001   Node* value = can_see_stored_value(mem,phase);
2002   if (value != NULL && value->is_Con() &&
2003       !value->bottom_type()->higher_equal(_type)) {
2004     // If the input to the store does not fit with the load's result type,
2005     // it must be truncated. We can't delay until Ideal call since
2006     // a singleton Value is needed for split_thru_phi optimization.
2007     int con = value->get_int();
2008     return TypeInt::make(con & 0xFF);
2009   }
2010   return LoadNode::Value(phase);
2011 }
2012 
2013 //--------------------------LoadUSNode::Ideal-------------------------------------
2014 //
2015 //  If the previous store is to the same address as this load,
2016 //  and the value stored was larger than a char, replace this load
2017 //  with the value stored truncated to a char.  If no truncation is
2018 //  needed, the replacement is done in LoadNode::Identity().
2019 //
2020 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2021   Node* mem = in(MemNode::Memory);
2022   Node* value = can_see_stored_value(mem,phase);
2023   if( value && !phase->type(value)->higher_equal( _type ) )
2024     return new AndINode(value,phase->intcon(0xFFFF));
2025   // Identity call will handle the case where truncation is not needed.
2026   return LoadNode::Ideal(phase, can_reshape);
2027 }
2028 
2029 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
2030   Node* mem = in(MemNode::Memory);
2031   Node* value = can_see_stored_value(mem,phase);
2032   if (value != NULL && value->is_Con() &&
2033       !value->bottom_type()->higher_equal(_type)) {
2034     // If the input to the store does not fit with the load's result type,
2035     // it must be truncated. We can't delay until Ideal call since
2036     // a singleton Value is needed for split_thru_phi optimization.
2037     int con = value->get_int();
2038     return TypeInt::make(con & 0xFFFF);
2039   }
2040   return LoadNode::Value(phase);
2041 }
2042 
2043 //--------------------------LoadSNode::Ideal--------------------------------------
2044 //
2045 //  If the previous store is to the same address as this load,
2046 //  and the value stored was larger than a short, replace this load
2047 //  with the value stored truncated to a short.  If no truncation is
2048 //  needed, the replacement is done in LoadNode::Identity().
2049 //
2050 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2051   Node* mem = in(MemNode::Memory);
2052   Node* value = can_see_stored_value(mem,phase);
2053   if( value && !phase->type(value)->higher_equal( _type ) ) {
2054     Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
2055     return new RShiftINode(result, phase->intcon(16));
2056   }
2057   // Identity call will handle the case where truncation is not needed.
2058   return LoadNode::Ideal(phase, can_reshape);
2059 }
2060 
2061 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2062   Node* mem = in(MemNode::Memory);
2063   Node* value = can_see_stored_value(mem,phase);
2064   if (value != NULL && value->is_Con() &&
2065       !value->bottom_type()->higher_equal(_type)) {
2066     // If the input to the store does not fit with the load's result type,
2067     // it must be truncated. We can't delay until Ideal call since
2068     // a singleton Value is needed for split_thru_phi optimization.
2069     int con = value->get_int();
2070     return TypeInt::make((con << 16) >> 16);
2071   }
2072   return LoadNode::Value(phase);
2073 }
2074 
2075 //=============================================================================
2076 //----------------------------LoadKlassNode::make------------------------------
2077 // Polymorphic factory method:
2078 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2079   // sanity check the alias category against the created node type
2080   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2081   assert(adr_type != NULL, "expecting TypeKlassPtr");
2082 #ifdef _LP64
2083   if (adr_type->is_ptr_to_narrowklass()) {
2084     assert(UseCompressedClassPointers, "no compressed klasses");
2085     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2086     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2087   }
2088 #endif
2089   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2090   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2091 }
2092 
2093 //------------------------------Value------------------------------------------
2094 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2095   return klass_value_common(phase);
2096 }
2097 
2098 // In most cases, LoadKlassNode does not have the control input set. If the control
2099 // input is set, it must not be removed (by LoadNode::Ideal()).
2100 bool LoadKlassNode::can_remove_control() const {
2101   return false;
2102 }
2103 
2104 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2105   // Either input is TOP ==> the result is TOP
2106   const Type *t1 = phase->type( in(MemNode::Memory) );
2107   if (t1 == Type::TOP)  return Type::TOP;
2108   Node *adr = in(MemNode::Address);
2109   const Type *t2 = phase->type( adr );
2110   if (t2 == Type::TOP)  return Type::TOP;
2111   const TypePtr *tp = t2->is_ptr();
2112   if (TypePtr::above_centerline(tp->ptr()) ||
2113       tp->ptr() == TypePtr::Null)  return Type::TOP;
2114 
2115   // Return a more precise klass, if possible
2116   const TypeInstPtr *tinst = tp->isa_instptr();
2117   if (tinst != NULL) {
2118     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2119     int offset = tinst->offset();
2120     if (ik == phase->C->env()->Class_klass()
2121         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2122             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2123       // We are loading a special hidden field from a Class mirror object,
2124       // the field which points to the VM's Klass metaobject.
2125       ciType* t = tinst->java_mirror_type();
2126       // java_mirror_type returns non-null for compile-time Class constants.
2127       if (t != NULL) {
2128         // constant oop => constant klass
2129         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2130           if (t->is_void()) {
2131             // We cannot create a void array.  Since void is a primitive type return null
2132             // klass.  Users of this result need to do a null check on the returned klass.
2133             return TypePtr::NULL_PTR;
2134           }
2135           return TypeKlassPtr::make(ciArrayKlass::make(t));
2136         }
2137         if (!t->is_klass()) {
2138           // a primitive Class (e.g., int.class) has NULL for a klass field
2139           return TypePtr::NULL_PTR;
2140         }
2141         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2142         return TypeKlassPtr::make(t->as_klass());
2143       }
2144       // non-constant mirror, so we can't tell what's going on
2145     }
2146     if( !ik->is_loaded() )
2147       return _type;             // Bail out if not loaded
2148     if (offset == oopDesc::klass_offset_in_bytes()) {
2149       if (tinst->klass_is_exact()) {
2150         return TypeKlassPtr::make(ik);
2151       }
2152       // See if we can become precise: no subklasses and no interface
2153       // (Note:  We need to support verified interfaces.)
2154       if (!ik->is_interface() && !ik->has_subklass()) {
2155         //assert(!UseExactTypes, "this code should be useless with exact types");
2156         // Add a dependence; if any subclass added we need to recompile
2157         if (!ik->is_final()) {
2158           // %%% should use stronger assert_unique_concrete_subtype instead
2159           phase->C->dependencies()->assert_leaf_type(ik);
2160         }
2161         // Return precise klass
2162         return TypeKlassPtr::make(ik);
2163       }
2164 
2165       // Return root of possible klass
2166       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2167     }
2168   }
2169 
2170   // Check for loading klass from an array
2171   const TypeAryPtr *tary = tp->isa_aryptr();
2172   if( tary != NULL ) {
2173     ciKlass *tary_klass = tary->klass();
2174     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2175         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2176       if (tary->klass_is_exact()) {
2177         return TypeKlassPtr::make(tary_klass);
2178       }
2179       ciArrayKlass *ak = tary->klass()->as_array_klass();
2180       // If the klass is an object array, we defer the question to the
2181       // array component klass.
2182       if( ak->is_obj_array_klass() ) {
2183         assert( ak->is_loaded(), "" );
2184         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2185         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2186           ciInstanceKlass* ik = base_k->as_instance_klass();
2187           // See if we can become precise: no subklasses and no interface
2188           if (!ik->is_interface() && !ik->has_subklass()) {
2189             //assert(!UseExactTypes, "this code should be useless with exact types");
2190             // Add a dependence; if any subclass added we need to recompile
2191             if (!ik->is_final()) {
2192               phase->C->dependencies()->assert_leaf_type(ik);
2193             }
2194             // Return precise array klass
2195             return TypeKlassPtr::make(ak);
2196           }
2197         }
2198         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2199       } else {                  // Found a type-array?
2200         //assert(!UseExactTypes, "this code should be useless with exact types");
2201         assert( ak->is_type_array_klass(), "" );
2202         return TypeKlassPtr::make(ak); // These are always precise
2203       }
2204     }
2205   }
2206 
2207   // Check for loading klass from an array klass
2208   const TypeKlassPtr *tkls = tp->isa_klassptr();
2209   if (tkls != NULL && !StressReflectiveCode) {
2210     ciKlass* klass = tkls->klass();
2211     if( !klass->is_loaded() )
2212       return _type;             // Bail out if not loaded
2213     if( klass->is_obj_array_klass() &&
2214         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2215       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2216       // // Always returning precise element type is incorrect,
2217       // // e.g., element type could be object and array may contain strings
2218       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2219 
2220       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2221       // according to the element type's subclassing.
2222       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2223     }
2224     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2225         tkls->offset() == in_bytes(Klass::super_offset())) {
2226       ciKlass* sup = klass->as_instance_klass()->super();
2227       // The field is Klass::_super.  Return its (constant) value.
2228       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2229       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2230     }
2231   }
2232 
2233   // Bailout case
2234   return LoadNode::Value(phase);
2235 }
2236 
2237 //------------------------------Identity---------------------------------------
2238 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2239 // Also feed through the klass in Allocate(...klass...)._klass.
2240 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2241   return klass_identity_common(phase);
2242 }
2243 
2244 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2245   Node* x = LoadNode::Identity(phase);
2246   if (x != this)  return x;
2247 
2248   // Take apart the address into an oop and and offset.
2249   // Return 'this' if we cannot.
2250   Node*    adr    = in(MemNode::Address);
2251   intptr_t offset = 0;
2252   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2253   if (base == NULL)     return this;
2254   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2255   if (toop == NULL)     return this;
2256 
2257   // Step over potential GC barrier for OopHandle resolve
2258   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2259   if (bs->is_gc_barrier_node(base)) {
2260     base = bs->step_over_gc_barrier(base);
2261   }
2262 
2263   // We can fetch the klass directly through an AllocateNode.
2264   // This works even if the klass is not constant (clone or newArray).
2265   if (offset == oopDesc::klass_offset_in_bytes()) {
2266     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2267     if (allocated_klass != NULL) {
2268       return allocated_klass;
2269     }
2270   }
2271 
2272   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2273   // See inline_native_Class_query for occurrences of these patterns.
2274   // Java Example:  x.getClass().isAssignableFrom(y)
2275   //
2276   // This improves reflective code, often making the Class
2277   // mirror go completely dead.  (Current exception:  Class
2278   // mirrors may appear in debug info, but we could clean them out by
2279   // introducing a new debug info operator for Klass.java_mirror).
2280 
2281   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2282       && offset == java_lang_Class::klass_offset_in_bytes()) {
2283     if (base->is_Load()) {
2284       Node* base2 = base->in(MemNode::Address);
2285       if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2286         Node* adr2 = base2->in(MemNode::Address);
2287         const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2288         if (tkls != NULL && !tkls->empty()
2289             && (tkls->klass()->is_instance_klass() ||
2290               tkls->klass()->is_array_klass())
2291             && adr2->is_AddP()
2292            ) {
2293           int mirror_field = in_bytes(Klass::java_mirror_offset());
2294           if (tkls->offset() == mirror_field) {
2295             return adr2->in(AddPNode::Base);
2296           }
2297         }
2298       }
2299     }
2300   }
2301 
2302   return this;
2303 }
2304 
2305 
2306 //------------------------------Value------------------------------------------
2307 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2308   const Type *t = klass_value_common(phase);
2309   if (t == Type::TOP)
2310     return t;
2311 
2312   return t->make_narrowklass();
2313 }
2314 
2315 //------------------------------Identity---------------------------------------
2316 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2317 // Also feed through the klass in Allocate(...klass...)._klass.
2318 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2319   Node *x = klass_identity_common(phase);
2320 
2321   const Type *t = phase->type( x );
2322   if( t == Type::TOP ) return x;
2323   if( t->isa_narrowklass()) return x;
2324   assert (!t->isa_narrowoop(), "no narrow oop here");
2325 
2326   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2327 }
2328 
2329 //------------------------------Value-----------------------------------------
2330 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2331   // Either input is TOP ==> the result is TOP
2332   const Type *t1 = phase->type( in(MemNode::Memory) );
2333   if( t1 == Type::TOP ) return Type::TOP;
2334   Node *adr = in(MemNode::Address);
2335   const Type *t2 = phase->type( adr );
2336   if( t2 == Type::TOP ) return Type::TOP;
2337   const TypePtr *tp = t2->is_ptr();
2338   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2339   const TypeAryPtr *tap = tp->isa_aryptr();
2340   if( !tap ) return _type;
2341   return tap->size();
2342 }
2343 
2344 //-------------------------------Ideal---------------------------------------
2345 // Feed through the length in AllocateArray(...length...)._length.
2346 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2347   Node* p = MemNode::Ideal_common(phase, can_reshape);
2348   if (p)  return (p == NodeSentinel) ? NULL : p;
2349 
2350   // Take apart the address into an oop and and offset.
2351   // Return 'this' if we cannot.
2352   Node*    adr    = in(MemNode::Address);
2353   intptr_t offset = 0;
2354   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2355   if (base == NULL)     return NULL;
2356   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2357   if (tary == NULL)     return NULL;
2358 
2359   // We can fetch the length directly through an AllocateArrayNode.
2360   // This works even if the length is not constant (clone or newArray).
2361   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2362     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2363     if (alloc != NULL) {
2364       Node* allocated_length = alloc->Ideal_length();
2365       Node* len = alloc->make_ideal_length(tary, phase);
2366       if (allocated_length != len) {
2367         // New CastII improves on this.
2368         return len;
2369       }
2370     }
2371   }
2372 
2373   return NULL;
2374 }
2375 
2376 //------------------------------Identity---------------------------------------
2377 // Feed through the length in AllocateArray(...length...)._length.
2378 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2379   Node* x = LoadINode::Identity(phase);
2380   if (x != this)  return x;
2381 
2382   // Take apart the address into an oop and and offset.
2383   // Return 'this' if we cannot.
2384   Node*    adr    = in(MemNode::Address);
2385   intptr_t offset = 0;
2386   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2387   if (base == NULL)     return this;
2388   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2389   if (tary == NULL)     return this;
2390 
2391   // We can fetch the length directly through an AllocateArrayNode.
2392   // This works even if the length is not constant (clone or newArray).
2393   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2394     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2395     if (alloc != NULL) {
2396       Node* allocated_length = alloc->Ideal_length();
2397       // Do not allow make_ideal_length to allocate a CastII node.
2398       Node* len = alloc->make_ideal_length(tary, phase, false);
2399       if (allocated_length == len) {
2400         // Return allocated_length only if it would not be improved by a CastII.
2401         return allocated_length;
2402       }
2403     }
2404   }
2405 
2406   return this;
2407 
2408 }
2409 
2410 //=============================================================================
2411 //---------------------------StoreNode::make-----------------------------------
2412 // Polymorphic factory method:
2413 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2414   assert((mo == unordered || mo == release), "unexpected");
2415   Compile* C = gvn.C;
2416   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2417          ctl != NULL, "raw memory operations should have control edge");
2418 
2419   switch (bt) {
2420   case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2421   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2422   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2423   case T_CHAR:
2424   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2425   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2426   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2427   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2428   case T_METADATA:
2429   case T_ADDRESS:
2430   case T_OBJECT:
2431 #ifdef _LP64
2432     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2433       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2434       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2435     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2436                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2437                 adr->bottom_type()->isa_rawptr())) {
2438       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2439       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2440     }
2441 #endif
2442     {
2443       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2444     }
2445   default:
2446     ShouldNotReachHere();
2447     return (StoreNode*)NULL;
2448   }
2449 }
2450 
2451 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2452   bool require_atomic = true;
2453   return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2454 }
2455 
2456 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2457   bool require_atomic = true;
2458   return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2459 }
2460 
2461 
2462 //--------------------------bottom_type----------------------------------------
2463 const Type *StoreNode::bottom_type() const {
2464   return Type::MEMORY;
2465 }
2466 
2467 //------------------------------hash-------------------------------------------
2468 uint StoreNode::hash() const {
2469   // unroll addition of interesting fields
2470   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2471 
2472   // Since they are not commoned, do not hash them:
2473   return NO_HASH;
2474 }
2475 
2476 //------------------------------Ideal------------------------------------------
2477 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2478 // When a store immediately follows a relevant allocation/initialization,
2479 // try to capture it into the initialization, or hoist it above.
2480 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2481   Node* p = MemNode::Ideal_common(phase, can_reshape);
2482   if (p)  return (p == NodeSentinel) ? NULL : p;
2483 
2484   Node* mem     = in(MemNode::Memory);
2485   Node* address = in(MemNode::Address);
2486   // Back-to-back stores to same address?  Fold em up.  Generally
2487   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2488   // since they must follow each StoreP operation.  Redundant StoreCMs
2489   // are eliminated just before matching in final_graph_reshape.
2490   {
2491     Node* st = mem;
2492     // If Store 'st' has more than one use, we cannot fold 'st' away.
2493     // For example, 'st' might be the final state at a conditional
2494     // return.  Or, 'st' might be used by some node which is live at
2495     // the same time 'st' is live, which might be unschedulable.  So,
2496     // require exactly ONE user until such time as we clone 'mem' for
2497     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2498     // true).
2499     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2500       // Looking at a dead closed cycle of memory?
2501       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2502       assert(Opcode() == st->Opcode() ||
2503              st->Opcode() == Op_StoreVector ||
2504              Opcode() == Op_StoreVector ||
2505              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2506              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2507              (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2508              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2509              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2510 
2511       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2512           st->as_Store()->memory_size() <= this->memory_size()) {
2513         Node* use = st->raw_out(0);
2514         phase->igvn_rehash_node_delayed(use);
2515         if (can_reshape) {
2516           use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase->is_IterGVN());
2517         } else {
2518           // It's OK to do this in the parser, since DU info is always accurate,
2519           // and the parser always refers to nodes via SafePointNode maps.
2520           use->set_req(MemNode::Memory, st->in(MemNode::Memory));
2521         }
2522         return this;
2523       }
2524       st = st->in(MemNode::Memory);
2525     }
2526   }
2527 
2528 
2529   // Capture an unaliased, unconditional, simple store into an initializer.
2530   // Or, if it is independent of the allocation, hoist it above the allocation.
2531   if (ReduceFieldZeroing && /*can_reshape &&*/
2532       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2533     InitializeNode* init = mem->in(0)->as_Initialize();
2534     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2535     if (offset > 0) {
2536       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2537       // If the InitializeNode captured me, it made a raw copy of me,
2538       // and I need to disappear.
2539       if (moved != NULL) {
2540         // %%% hack to ensure that Ideal returns a new node:
2541         mem = MergeMemNode::make(mem);
2542         return mem;             // fold me away
2543       }
2544     }
2545   }
2546 
2547   return NULL;                  // No further progress
2548 }
2549 
2550 //------------------------------Value-----------------------------------------
2551 const Type* StoreNode::Value(PhaseGVN* phase) const {
2552   // Either input is TOP ==> the result is TOP
2553   const Type *t1 = phase->type( in(MemNode::Memory) );
2554   if( t1 == Type::TOP ) return Type::TOP;
2555   const Type *t2 = phase->type( in(MemNode::Address) );
2556   if( t2 == Type::TOP ) return Type::TOP;
2557   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2558   if( t3 == Type::TOP ) return Type::TOP;
2559   return Type::MEMORY;
2560 }
2561 
2562 //------------------------------Identity---------------------------------------
2563 // Remove redundant stores:
2564 //   Store(m, p, Load(m, p)) changes to m.
2565 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2566 Node* StoreNode::Identity(PhaseGVN* phase) {
2567   Node* mem = in(MemNode::Memory);
2568   Node* adr = in(MemNode::Address);
2569   Node* val = in(MemNode::ValueIn);
2570 
2571   Node* result = this;
2572 
2573   // Load then Store?  Then the Store is useless
2574   if (val->is_Load() &&
2575       val->in(MemNode::Address)->eqv_uncast(adr) &&
2576       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2577       val->as_Load()->store_Opcode() == Opcode()) {
2578     result = mem;
2579   }
2580 
2581   // Two stores in a row of the same value?
2582   if (result == this &&
2583       mem->is_Store() &&
2584       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2585       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2586       mem->Opcode() == Opcode()) {
2587     result = mem;
2588   }
2589 
2590   // Store of zero anywhere into a freshly-allocated object?
2591   // Then the store is useless.
2592   // (It must already have been captured by the InitializeNode.)
2593   if (result == this &&
2594       ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2595     // a newly allocated object is already all-zeroes everywhere
2596     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2597       result = mem;
2598     }
2599 
2600     if (result == this) {
2601       // the store may also apply to zero-bits in an earlier object
2602       Node* prev_mem = find_previous_store(phase);
2603       // Steps (a), (b):  Walk past independent stores to find an exact match.
2604       if (prev_mem != NULL) {
2605         Node* prev_val = can_see_stored_value(prev_mem, phase);
2606         if (prev_val != NULL && phase->eqv(prev_val, val)) {
2607           // prev_val and val might differ by a cast; it would be good
2608           // to keep the more informative of the two.
2609           result = mem;
2610         }
2611       }
2612     }
2613   }
2614 
2615   if (result != this && phase->is_IterGVN() != NULL) {
2616     MemBarNode* trailing = trailing_membar();
2617     if (trailing != NULL) {
2618 #ifdef ASSERT
2619       const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2620       assert(t_oop == NULL || t_oop->is_known_instance_field(), "only for non escaping objects");
2621 #endif
2622       PhaseIterGVN* igvn = phase->is_IterGVN();
2623       trailing->remove(igvn);
2624     }
2625   }
2626 
2627   return result;
2628 }
2629 
2630 //------------------------------match_edge-------------------------------------
2631 // Do we Match on this edge index or not?  Match only memory & value
2632 uint StoreNode::match_edge(uint idx) const {
2633   return idx == MemNode::Address || idx == MemNode::ValueIn;
2634 }
2635 
2636 //------------------------------cmp--------------------------------------------
2637 // Do not common stores up together.  They generally have to be split
2638 // back up anyways, so do not bother.
2639 uint StoreNode::cmp( const Node &n ) const {
2640   return (&n == this);          // Always fail except on self
2641 }
2642 
2643 //------------------------------Ideal_masked_input-----------------------------
2644 // Check for a useless mask before a partial-word store
2645 // (StoreB ... (AndI valIn conIa) )
2646 // If (conIa & mask == mask) this simplifies to
2647 // (StoreB ... (valIn) )
2648 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2649   Node *val = in(MemNode::ValueIn);
2650   if( val->Opcode() == Op_AndI ) {
2651     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2652     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2653       set_req(MemNode::ValueIn, val->in(1));
2654       return this;
2655     }
2656   }
2657   return NULL;
2658 }
2659 
2660 
2661 //------------------------------Ideal_sign_extended_input----------------------
2662 // Check for useless sign-extension before a partial-word store
2663 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2664 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2665 // (StoreB ... (valIn) )
2666 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2667   Node *val = in(MemNode::ValueIn);
2668   if( val->Opcode() == Op_RShiftI ) {
2669     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2670     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2671       Node *shl = val->in(1);
2672       if( shl->Opcode() == Op_LShiftI ) {
2673         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2674         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2675           set_req(MemNode::ValueIn, shl->in(1));
2676           return this;
2677         }
2678       }
2679     }
2680   }
2681   return NULL;
2682 }
2683 
2684 //------------------------------value_never_loaded-----------------------------------
2685 // Determine whether there are any possible loads of the value stored.
2686 // For simplicity, we actually check if there are any loads from the
2687 // address stored to, not just for loads of the value stored by this node.
2688 //
2689 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2690   Node *adr = in(Address);
2691   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2692   if (adr_oop == NULL)
2693     return false;
2694   if (!adr_oop->is_known_instance_field())
2695     return false; // if not a distinct instance, there may be aliases of the address
2696   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2697     Node *use = adr->fast_out(i);
2698     if (use->is_Load() || use->is_LoadStore()) {
2699       return false;
2700     }
2701   }
2702   return true;
2703 }
2704 
2705 MemBarNode* StoreNode::trailing_membar() const {
2706   if (is_release()) {
2707     MemBarNode* trailing_mb = NULL;
2708     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2709       Node* u = fast_out(i);
2710       if (u->is_MemBar()) {
2711         if (u->as_MemBar()->trailing_store()) {
2712           assert(u->Opcode() == Op_MemBarVolatile, "");
2713           assert(trailing_mb == NULL, "only one");
2714           trailing_mb = u->as_MemBar();
2715 #ifdef ASSERT
2716           Node* leading = u->as_MemBar()->leading_membar();
2717           assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2718           assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2719           assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2720 #endif
2721         } else {
2722           assert(u->as_MemBar()->standalone(), "");
2723         }
2724       }
2725     }
2726     return trailing_mb;
2727   }
2728   return NULL;
2729 }
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.  If the store is from a sign-extension
2736 // (a left shift, then right shift) we can skip both.
2737 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2738   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2739   if( progress != NULL ) return progress;
2740 
2741   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2742   if( progress != NULL ) return progress;
2743 
2744   // Finally check the default case
2745   return StoreNode::Ideal(phase, can_reshape);
2746 }
2747 
2748 //=============================================================================
2749 //------------------------------Ideal------------------------------------------
2750 // If the store is from an AND mask that leaves the low bits untouched, then
2751 // we can skip the AND operation
2752 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2753   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2754   if( progress != NULL ) return progress;
2755 
2756   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2757   if( progress != NULL ) return progress;
2758 
2759   // Finally check the default case
2760   return StoreNode::Ideal(phase, can_reshape);
2761 }
2762 
2763 //=============================================================================
2764 //------------------------------Identity---------------------------------------
2765 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2766   // No need to card mark when storing a null ptr
2767   Node* my_store = in(MemNode::OopStore);
2768   if (my_store->is_Store()) {
2769     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2770     if( t1 == TypePtr::NULL_PTR ) {
2771       return in(MemNode::Memory);
2772     }
2773   }
2774   return this;
2775 }
2776 
2777 //=============================================================================
2778 //------------------------------Ideal---------------------------------------
2779 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2780   Node* progress = StoreNode::Ideal(phase, can_reshape);
2781   if (progress != NULL) return progress;
2782 
2783   Node* my_store = in(MemNode::OopStore);
2784   if (my_store->is_MergeMem()) {
2785     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2786     set_req(MemNode::OopStore, mem);
2787     return this;
2788   }
2789 
2790   return NULL;
2791 }
2792 
2793 //------------------------------Value-----------------------------------------
2794 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
2795   // Either input is TOP ==> the result is TOP
2796   const Type *t = phase->type( in(MemNode::Memory) );
2797   if( t == Type::TOP ) return Type::TOP;
2798   t = phase->type( in(MemNode::Address) );
2799   if( t == Type::TOP ) return Type::TOP;
2800   t = phase->type( in(MemNode::ValueIn) );
2801   if( t == Type::TOP ) return Type::TOP;
2802   // If extra input is TOP ==> the result is TOP
2803   t = phase->type( in(MemNode::OopStore) );
2804   if( t == Type::TOP ) return Type::TOP;
2805 
2806   return StoreNode::Value( phase );
2807 }
2808 
2809 
2810 //=============================================================================
2811 //----------------------------------SCMemProjNode------------------------------
2812 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
2813 {
2814   return bottom_type();
2815 }
2816 
2817 //=============================================================================
2818 //----------------------------------LoadStoreNode------------------------------
2819 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2820   : Node(required),
2821     _type(rt),
2822     _adr_type(at)
2823 {
2824   init_req(MemNode::Control, c  );
2825   init_req(MemNode::Memory , mem);
2826   init_req(MemNode::Address, adr);
2827   init_req(MemNode::ValueIn, val);
2828   init_class_id(Class_LoadStore);
2829 }
2830 
2831 uint LoadStoreNode::ideal_reg() const {
2832   return _type->ideal_reg();
2833 }
2834 
2835 bool LoadStoreNode::result_not_used() const {
2836   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2837     Node *x = fast_out(i);
2838     if (x->Opcode() == Op_SCMemProj) continue;
2839     return false;
2840   }
2841   return true;
2842 }
2843 
2844 MemBarNode* LoadStoreNode::trailing_membar() const {
2845   MemBarNode* trailing = NULL;
2846   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2847     Node* u = fast_out(i);
2848     if (u->is_MemBar()) {
2849       if (u->as_MemBar()->trailing_load_store()) {
2850         assert(u->Opcode() == Op_MemBarAcquire, "");
2851         assert(trailing == NULL, "only one");
2852         trailing = u->as_MemBar();
2853 #ifdef ASSERT
2854         Node* leading = trailing->leading_membar();
2855         assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2856         assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
2857         assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
2858 #endif
2859       } else {
2860         assert(u->as_MemBar()->standalone(), "wrong barrier kind");
2861       }
2862     }
2863   }
2864 
2865   return trailing;
2866 }
2867 
2868 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2869 
2870 //=============================================================================
2871 //----------------------------------LoadStoreConditionalNode--------------------
2872 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2873   init_req(ExpectedIn, ex );
2874 }
2875 
2876 //=============================================================================
2877 //-------------------------------adr_type--------------------------------------
2878 const TypePtr* ClearArrayNode::adr_type() const {
2879   Node *adr = in(3);
2880   if (adr == NULL)  return NULL; // node is dead
2881   return MemNode::calculate_adr_type(adr->bottom_type());
2882 }
2883 
2884 //------------------------------match_edge-------------------------------------
2885 // Do we Match on this edge index or not?  Do not match memory
2886 uint ClearArrayNode::match_edge(uint idx) const {
2887   return idx > 1;
2888 }
2889 
2890 //------------------------------Identity---------------------------------------
2891 // Clearing a zero length array does nothing
2892 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
2893   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2894 }
2895 
2896 //------------------------------Idealize---------------------------------------
2897 // Clearing a short array is faster with stores
2898 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2899   // Already know this is a large node, do not try to ideal it
2900   if (!IdealizeClearArrayNode || _is_large) return NULL;
2901 
2902   const int unit = BytesPerLong;
2903   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2904   if (!t)  return NULL;
2905   if (!t->is_con())  return NULL;
2906   intptr_t raw_count = t->get_con();
2907   intptr_t size = raw_count;
2908   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2909   // Clearing nothing uses the Identity call.
2910   // Negative clears are possible on dead ClearArrays
2911   // (see jck test stmt114.stmt11402.val).
2912   if (size <= 0 || size % unit != 0)  return NULL;
2913   intptr_t count = size / unit;
2914   // Length too long; communicate this to matchers and assemblers.
2915   // Assemblers are responsible to produce fast hardware clears for it.
2916   if (size > InitArrayShortSize) {
2917     return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
2918   }
2919   Node *mem = in(1);
2920   if( phase->type(mem)==Type::TOP ) return NULL;
2921   Node *adr = in(3);
2922   const Type* at = phase->type(adr);
2923   if( at==Type::TOP ) return NULL;
2924   const TypePtr* atp = at->isa_ptr();
2925   // adjust atp to be the correct array element address type
2926   if (atp == NULL)  atp = TypePtr::BOTTOM;
2927   else              atp = atp->add_offset(Type::OffsetBot);
2928   // Get base for derived pointer purposes
2929   if( adr->Opcode() != Op_AddP ) Unimplemented();
2930   Node *base = adr->in(1);
2931 
2932   Node *zero = phase->makecon(TypeLong::ZERO);
2933   Node *off  = phase->MakeConX(BytesPerLong);
2934   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2935   count--;
2936   while( count-- ) {
2937     mem = phase->transform(mem);
2938     adr = phase->transform(new AddPNode(base,adr,off));
2939     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2940   }
2941   return mem;
2942 }
2943 
2944 //----------------------------step_through----------------------------------
2945 // Return allocation input memory edge if it is different instance
2946 // or itself if it is the one we are looking for.
2947 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2948   Node* n = *np;
2949   assert(n->is_ClearArray(), "sanity");
2950   intptr_t offset;
2951   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2952   // This method is called only before Allocate nodes are expanded
2953   // during macro nodes expansion. Before that ClearArray nodes are
2954   // only generated in PhaseMacroExpand::generate_arraycopy() (before
2955   // Allocate nodes are expanded) which follows allocations.
2956   assert(alloc != NULL, "should have allocation");
2957   if (alloc->_idx == instance_id) {
2958     // Can not bypass initialization of the instance we are looking for.
2959     return false;
2960   }
2961   // Otherwise skip it.
2962   InitializeNode* init = alloc->initialization();
2963   if (init != NULL)
2964     *np = init->in(TypeFunc::Memory);
2965   else
2966     *np = alloc->in(TypeFunc::Memory);
2967   return true;
2968 }
2969 
2970 //----------------------------clear_memory-------------------------------------
2971 // Generate code to initialize object storage to zero.
2972 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2973                                    intptr_t start_offset,
2974                                    Node* end_offset,
2975                                    PhaseGVN* phase) {
2976   intptr_t offset = start_offset;
2977 
2978   int unit = BytesPerLong;
2979   if ((offset % unit) != 0) {
2980     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
2981     adr = phase->transform(adr);
2982     const TypePtr* atp = TypeRawPtr::BOTTOM;
2983     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2984     mem = phase->transform(mem);
2985     offset += BytesPerInt;
2986   }
2987   assert((offset % unit) == 0, "");
2988 
2989   // Initialize the remaining stuff, if any, with a ClearArray.
2990   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2991 }
2992 
2993 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2994                                    Node* start_offset,
2995                                    Node* end_offset,
2996                                    PhaseGVN* phase) {
2997   if (start_offset == end_offset) {
2998     // nothing to do
2999     return mem;
3000   }
3001 
3002   int unit = BytesPerLong;
3003   Node* zbase = start_offset;
3004   Node* zend  = end_offset;
3005 
3006   // Scale to the unit required by the CPU:
3007   if (!Matcher::init_array_count_is_in_bytes) {
3008     Node* shift = phase->intcon(exact_log2(unit));
3009     zbase = phase->transform(new URShiftXNode(zbase, shift) );
3010     zend  = phase->transform(new URShiftXNode(zend,  shift) );
3011   }
3012 
3013   // Bulk clear double-words
3014   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
3015   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
3016   mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
3017   return phase->transform(mem);
3018 }
3019 
3020 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3021                                    intptr_t start_offset,
3022                                    intptr_t end_offset,
3023                                    PhaseGVN* phase) {
3024   if (start_offset == end_offset) {
3025     // nothing to do
3026     return mem;
3027   }
3028 
3029   assert((end_offset % BytesPerInt) == 0, "odd end offset");
3030   intptr_t done_offset = end_offset;
3031   if ((done_offset % BytesPerLong) != 0) {
3032     done_offset -= BytesPerInt;
3033   }
3034   if (done_offset > start_offset) {
3035     mem = clear_memory(ctl, mem, dest,
3036                        start_offset, phase->MakeConX(done_offset), phase);
3037   }
3038   if (done_offset < end_offset) { // emit the final 32-bit store
3039     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3040     adr = phase->transform(adr);
3041     const TypePtr* atp = TypeRawPtr::BOTTOM;
3042     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3043     mem = phase->transform(mem);
3044     done_offset += BytesPerInt;
3045   }
3046   assert(done_offset == end_offset, "");
3047   return mem;
3048 }
3049 
3050 //=============================================================================
3051 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3052   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
3053     _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3054 #ifdef ASSERT
3055   , _pair_idx(0)
3056 #endif
3057 {
3058   init_class_id(Class_MemBar);
3059   Node* top = C->top();
3060   init_req(TypeFunc::I_O,top);
3061   init_req(TypeFunc::FramePtr,top);
3062   init_req(TypeFunc::ReturnAdr,top);
3063   if (precedent != NULL)
3064     init_req(TypeFunc::Parms, precedent);
3065 }
3066 
3067 //------------------------------cmp--------------------------------------------
3068 uint MemBarNode::hash() const { return NO_HASH; }
3069 uint MemBarNode::cmp( const Node &n ) const {
3070   return (&n == this);          // Always fail except on self
3071 }
3072 
3073 //------------------------------make-------------------------------------------
3074 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3075   switch (opcode) {
3076   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
3077   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
3078   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
3079   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
3080   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3081   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3082   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
3083   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
3084   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
3085   case Op_Initialize:        return new InitializeNode(C, atp, pn);
3086   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
3087   default: ShouldNotReachHere(); return NULL;
3088   }
3089 }
3090 
3091 void MemBarNode::remove(PhaseIterGVN *igvn) {
3092   if (outcnt() != 2) {
3093     return;
3094   }
3095   if (trailing_store() || trailing_load_store()) {
3096     MemBarNode* leading = leading_membar();
3097     if (leading != NULL) {
3098       assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3099       leading->remove(igvn);
3100     }
3101   }
3102   igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3103   igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3104 }
3105 
3106 //------------------------------Ideal------------------------------------------
3107 // Return a node which is more "ideal" than the current node.  Strip out
3108 // control copies
3109 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3110   if (remove_dead_region(phase, can_reshape)) return this;
3111   // Don't bother trying to transform a dead node
3112   if (in(0) && in(0)->is_top()) {
3113     return NULL;
3114   }
3115 
3116 #if INCLUDE_ZGC
3117   if (UseZGC) {
3118     if (req() == (Precedent+1) && in(MemBarNode::Precedent)->in(0) != NULL && in(MemBarNode::Precedent)->in(0)->is_LoadBarrier()) {
3119       Node* load_node = in(MemBarNode::Precedent)->in(0)->in(LoadBarrierNode::Oop);
3120       set_req(MemBarNode::Precedent, load_node);
3121       return this;
3122     }
3123   }
3124 #endif
3125 
3126   bool progress = false;
3127   // Eliminate volatile MemBars for scalar replaced objects.
3128   if (can_reshape && req() == (Precedent+1)) {
3129     bool eliminate = false;
3130     int opc = Opcode();
3131     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3132       // Volatile field loads and stores.
3133       Node* my_mem = in(MemBarNode::Precedent);
3134       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3135       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3136         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3137         // replace this Precedent (decodeN) with the Load instead.
3138         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
3139           Node* load_node = my_mem->in(1);
3140           set_req(MemBarNode::Precedent, load_node);
3141           phase->is_IterGVN()->_worklist.push(my_mem);
3142           my_mem = load_node;
3143         } else {
3144           assert(my_mem->unique_out() == this, "sanity");
3145           del_req(Precedent);
3146           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3147           my_mem = NULL;
3148         }
3149         progress = true;
3150       }
3151       if (my_mem != NULL && my_mem->is_Mem()) {
3152         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3153         // Check for scalar replaced object reference.
3154         if( t_oop != NULL && t_oop->is_known_instance_field() &&
3155             t_oop->offset() != Type::OffsetBot &&
3156             t_oop->offset() != Type::OffsetTop) {
3157           eliminate = true;
3158         }
3159       }
3160     } else if (opc == Op_MemBarRelease) {
3161       // Final field stores.
3162       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
3163       if ((alloc != NULL) && alloc->is_Allocate() &&
3164           alloc->as_Allocate()->does_not_escape_thread()) {
3165         // The allocated object does not escape.
3166         eliminate = true;
3167       }
3168     }
3169     if (eliminate) {
3170       // Replace MemBar projections by its inputs.
3171       PhaseIterGVN* igvn = phase->is_IterGVN();
3172       remove(igvn);
3173       // Must return either the original node (now dead) or a new node
3174       // (Do not return a top here, since that would break the uniqueness of top.)
3175       return new ConINode(TypeInt::ZERO);
3176     }
3177   }
3178   return progress ? this : NULL;
3179 }
3180 
3181 //------------------------------Value------------------------------------------
3182 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3183   if( !in(0) ) return Type::TOP;
3184   if( phase->type(in(0)) == Type::TOP )
3185     return Type::TOP;
3186   return TypeTuple::MEMBAR;
3187 }
3188 
3189 //------------------------------match------------------------------------------
3190 // Construct projections for memory.
3191 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3192   switch (proj->_con) {
3193   case TypeFunc::Control:
3194   case TypeFunc::Memory:
3195     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3196   }
3197   ShouldNotReachHere();
3198   return NULL;
3199 }
3200 
3201 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3202   trailing->_kind = TrailingStore;
3203   leading->_kind = LeadingStore;
3204 #ifdef ASSERT
3205   trailing->_pair_idx = leading->_idx;
3206   leading->_pair_idx = leading->_idx;
3207 #endif
3208 }
3209 
3210 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3211   trailing->_kind = TrailingLoadStore;
3212   leading->_kind = LeadingLoadStore;
3213 #ifdef ASSERT
3214   trailing->_pair_idx = leading->_idx;
3215   leading->_pair_idx = leading->_idx;
3216 #endif
3217 }
3218 
3219 MemBarNode* MemBarNode::trailing_membar() const {
3220   ResourceMark rm;
3221   Node* trailing = (Node*)this;
3222   VectorSet seen(Thread::current()->resource_area());
3223   Node_Stack multis(0);
3224   do {
3225     Node* c = trailing;
3226     uint i = 0;
3227     do {
3228       trailing = NULL;
3229       for (; i < c->outcnt(); i++) {
3230         Node* next = c->raw_out(i);
3231         if (next != c && next->is_CFG()) {
3232           if (c->is_MultiBranch()) {
3233             if (multis.node() == c) {
3234               multis.set_index(i+1);
3235             } else {
3236               multis.push(c, i+1);
3237             }
3238           }
3239           trailing = next;
3240           break;
3241         }
3242       }
3243       if (trailing != NULL && !seen.test_set(trailing->_idx)) {
3244         break;
3245       }
3246       while (multis.size() > 0) {
3247         c = multis.node();
3248         i = multis.index();
3249         if (i < c->req()) {
3250           break;
3251         }
3252         multis.pop();
3253       }
3254     } while (multis.size() > 0);
3255   } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3256 
3257   MemBarNode* mb = trailing->as_MemBar();
3258   assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3259          (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3260   assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3261   return mb;
3262 }
3263 
3264 MemBarNode* MemBarNode::leading_membar() const {
3265   ResourceMark rm;
3266   VectorSet seen(Thread::current()->resource_area());
3267   Node_Stack regions(0);
3268   Node* leading = in(0);
3269   while (leading != NULL && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3270     while (leading == NULL || leading->is_top() || seen.test_set(leading->_idx)) {
3271       leading = NULL;
3272       while (regions.size() > 0 && leading == NULL) {
3273         Node* r = regions.node();
3274         uint i = regions.index();
3275         if (i < r->req()) {
3276           leading = r->in(i);
3277           regions.set_index(i+1);
3278         } else {
3279           regions.pop();
3280         }
3281       }
3282       if (leading == NULL) {
3283         assert(regions.size() == 0, "all paths should have been tried");
3284         return NULL;
3285       }
3286     }
3287     if (leading->is_Region()) {
3288       regions.push(leading, 2);
3289       leading = leading->in(1);
3290     } else {
3291       leading = leading->in(0);
3292     }
3293   }
3294 #ifdef ASSERT
3295   Unique_Node_List wq;
3296   wq.push((Node*)this);
3297   uint found = 0;
3298   for (uint i = 0; i < wq.size(); i++) {
3299     Node* n = wq.at(i);
3300     if (n->is_Region()) {
3301       for (uint j = 1; j < n->req(); j++) {
3302         Node* in = n->in(j);
3303         if (in != NULL && !in->is_top()) {
3304           wq.push(in);
3305         }
3306       }
3307     } else {
3308       if (n->is_MemBar() && n->as_MemBar()->leading()) {
3309         assert(n == leading, "consistency check failed");
3310         found++;
3311       } else {
3312         Node* in = n->in(0);
3313         if (in != NULL && !in->is_top()) {
3314           wq.push(in);
3315         }
3316       }
3317     }
3318   }
3319   assert(found == 1 || (found == 0 && leading == NULL), "consistency check failed");
3320 #endif
3321   if (leading == NULL) {
3322     return NULL;
3323   }
3324   MemBarNode* mb = leading->as_MemBar();
3325   assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3326          (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3327   assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3328   return mb;
3329 }
3330 
3331 //===========================InitializeNode====================================
3332 // SUMMARY:
3333 // This node acts as a memory barrier on raw memory, after some raw stores.
3334 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3335 // The Initialize can 'capture' suitably constrained stores as raw inits.
3336 // It can coalesce related raw stores into larger units (called 'tiles').
3337 // It can avoid zeroing new storage for memory units which have raw inits.
3338 // At macro-expansion, it is marked 'complete', and does not optimize further.
3339 //
3340 // EXAMPLE:
3341 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3342 //   ctl = incoming control; mem* = incoming memory
3343 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3344 // First allocate uninitialized memory and fill in the header:
3345 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3346 //   ctl := alloc.Control; mem* := alloc.Memory*
3347 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3348 // Then initialize to zero the non-header parts of the raw memory block:
3349 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3350 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3351 // After the initialize node executes, the object is ready for service:
3352 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3353 // Suppose its body is immediately initialized as {1,2}:
3354 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3355 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3356 //   mem.SLICE(#short[*]) := store2
3357 //
3358 // DETAILS:
3359 // An InitializeNode collects and isolates object initialization after
3360 // an AllocateNode and before the next possible safepoint.  As a
3361 // memory barrier (MemBarNode), it keeps critical stores from drifting
3362 // down past any safepoint or any publication of the allocation.
3363 // Before this barrier, a newly-allocated object may have uninitialized bits.
3364 // After this barrier, it may be treated as a real oop, and GC is allowed.
3365 //
3366 // The semantics of the InitializeNode include an implicit zeroing of
3367 // the new object from object header to the end of the object.
3368 // (The object header and end are determined by the AllocateNode.)
3369 //
3370 // Certain stores may be added as direct inputs to the InitializeNode.
3371 // These stores must update raw memory, and they must be to addresses
3372 // derived from the raw address produced by AllocateNode, and with
3373 // a constant offset.  They must be ordered by increasing offset.
3374 // The first one is at in(RawStores), the last at in(req()-1).
3375 // Unlike most memory operations, they are not linked in a chain,
3376 // but are displayed in parallel as users of the rawmem output of
3377 // the allocation.
3378 //
3379 // (See comments in InitializeNode::capture_store, which continue
3380 // the example given above.)
3381 //
3382 // When the associated Allocate is macro-expanded, the InitializeNode
3383 // may be rewritten to optimize collected stores.  A ClearArrayNode
3384 // may also be created at that point to represent any required zeroing.
3385 // The InitializeNode is then marked 'complete', prohibiting further
3386 // capturing of nearby memory operations.
3387 //
3388 // During macro-expansion, all captured initializations which store
3389 // constant values of 32 bits or smaller are coalesced (if advantageous)
3390 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3391 // initialized in fewer memory operations.  Memory words which are
3392 // covered by neither tiles nor non-constant stores are pre-zeroed
3393 // by explicit stores of zero.  (The code shape happens to do all
3394 // zeroing first, then all other stores, with both sequences occurring
3395 // in order of ascending offsets.)
3396 //
3397 // Alternatively, code may be inserted between an AllocateNode and its
3398 // InitializeNode, to perform arbitrary initialization of the new object.
3399 // E.g., the object copying intrinsics insert complex data transfers here.
3400 // The initialization must then be marked as 'complete' disable the
3401 // built-in zeroing semantics and the collection of initializing stores.
3402 //
3403 // While an InitializeNode is incomplete, reads from the memory state
3404 // produced by it are optimizable if they match the control edge and
3405 // new oop address associated with the allocation/initialization.
3406 // They return a stored value (if the offset matches) or else zero.
3407 // A write to the memory state, if it matches control and address,
3408 // and if it is to a constant offset, may be 'captured' by the
3409 // InitializeNode.  It is cloned as a raw memory operation and rewired
3410 // inside the initialization, to the raw oop produced by the allocation.
3411 // Operations on addresses which are provably distinct (e.g., to
3412 // other AllocateNodes) are allowed to bypass the initialization.
3413 //
3414 // The effect of all this is to consolidate object initialization
3415 // (both arrays and non-arrays, both piecewise and bulk) into a
3416 // single location, where it can be optimized as a unit.
3417 //
3418 // Only stores with an offset less than TrackedInitializationLimit words
3419 // will be considered for capture by an InitializeNode.  This puts a
3420 // reasonable limit on the complexity of optimized initializations.
3421 
3422 //---------------------------InitializeNode------------------------------------
3423 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3424   : _is_complete(Incomplete), _does_not_escape(false),
3425     MemBarNode(C, adr_type, rawoop)
3426 {
3427   init_class_id(Class_Initialize);
3428 
3429   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3430   assert(in(RawAddress) == rawoop, "proper init");
3431   // Note:  allocation() can be NULL, for secondary initialization barriers
3432 }
3433 
3434 // Since this node is not matched, it will be processed by the
3435 // register allocator.  Declare that there are no constraints
3436 // on the allocation of the RawAddress edge.
3437 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3438   // This edge should be set to top, by the set_complete.  But be conservative.
3439   if (idx == InitializeNode::RawAddress)
3440     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3441   return RegMask::Empty;
3442 }
3443 
3444 Node* InitializeNode::memory(uint alias_idx) {
3445   Node* mem = in(Memory);
3446   if (mem->is_MergeMem()) {
3447     return mem->as_MergeMem()->memory_at(alias_idx);
3448   } else {
3449     // incoming raw memory is not split
3450     return mem;
3451   }
3452 }
3453 
3454 bool InitializeNode::is_non_zero() {
3455   if (is_complete())  return false;
3456   remove_extra_zeroes();
3457   return (req() > RawStores);
3458 }
3459 
3460 void InitializeNode::set_complete(PhaseGVN* phase) {
3461   assert(!is_complete(), "caller responsibility");
3462   _is_complete = Complete;
3463 
3464   // After this node is complete, it contains a bunch of
3465   // raw-memory initializations.  There is no need for
3466   // it to have anything to do with non-raw memory effects.
3467   // Therefore, tell all non-raw users to re-optimize themselves,
3468   // after skipping the memory effects of this initialization.
3469   PhaseIterGVN* igvn = phase->is_IterGVN();
3470   if (igvn)  igvn->add_users_to_worklist(this);
3471 }
3472 
3473 // convenience function
3474 // return false if the init contains any stores already
3475 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3476   InitializeNode* init = initialization();
3477   if (init == NULL || init->is_complete())  return false;
3478   init->remove_extra_zeroes();
3479   // for now, if this allocation has already collected any inits, bail:
3480   if (init->is_non_zero())  return false;
3481   init->set_complete(phase);
3482   return true;
3483 }
3484 
3485 void InitializeNode::remove_extra_zeroes() {
3486   if (req() == RawStores)  return;
3487   Node* zmem = zero_memory();
3488   uint fill = RawStores;
3489   for (uint i = fill; i < req(); i++) {
3490     Node* n = in(i);
3491     if (n->is_top() || n == zmem)  continue;  // skip
3492     if (fill < i)  set_req(fill, n);          // compact
3493     ++fill;
3494   }
3495   // delete any empty spaces created:
3496   while (fill < req()) {
3497     del_req(fill);
3498   }
3499 }
3500 
3501 // Helper for remembering which stores go with which offsets.
3502 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3503   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3504   intptr_t offset = -1;
3505   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3506                                                phase, offset);
3507   if (base == NULL)     return -1;  // something is dead,
3508   if (offset < 0)       return -1;  //        dead, dead
3509   return offset;
3510 }
3511 
3512 // Helper for proving that an initialization expression is
3513 // "simple enough" to be folded into an object initialization.
3514 // Attempts to prove that a store's initial value 'n' can be captured
3515 // within the initialization without creating a vicious cycle, such as:
3516 //     { Foo p = new Foo(); p.next = p; }
3517 // True for constants and parameters and small combinations thereof.
3518 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3519   if (n == NULL)      return true;   // (can this really happen?)
3520   if (n->is_Proj())   n = n->in(0);
3521   if (n == this)      return false;  // found a cycle
3522   if (n->is_Con())    return true;
3523   if (n->is_Start())  return true;   // params, etc., are OK
3524   if (n->is_Root())   return true;   // even better
3525 
3526   Node* ctl = n->in(0);
3527   if (ctl != NULL && !ctl->is_top()) {
3528     if (ctl->is_Proj())  ctl = ctl->in(0);
3529     if (ctl == this)  return false;
3530 
3531     // If we already know that the enclosing memory op is pinned right after
3532     // the init, then any control flow that the store has picked up
3533     // must have preceded the init, or else be equal to the init.
3534     // Even after loop optimizations (which might change control edges)
3535     // a store is never pinned *before* the availability of its inputs.
3536     if (!MemNode::all_controls_dominate(n, this))
3537       return false;                  // failed to prove a good control
3538   }
3539 
3540   // Check data edges for possible dependencies on 'this'.
3541   if ((count += 1) > 20)  return false;  // complexity limit
3542   for (uint i = 1; i < n->req(); i++) {
3543     Node* m = n->in(i);
3544     if (m == NULL || m == n || m->is_top())  continue;
3545     uint first_i = n->find_edge(m);
3546     if (i != first_i)  continue;  // process duplicate edge just once
3547     if (!detect_init_independence(m, count)) {
3548       return false;
3549     }
3550   }
3551 
3552   return true;
3553 }
3554 
3555 // Here are all the checks a Store must pass before it can be moved into
3556 // an initialization.  Returns zero if a check fails.
3557 // On success, returns the (constant) offset to which the store applies,
3558 // within the initialized memory.
3559 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3560   const int FAIL = 0;
3561   if (st->req() != MemNode::ValueIn + 1)
3562     return FAIL;                // an inscrutable StoreNode (card mark?)
3563   Node* ctl = st->in(MemNode::Control);
3564   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3565     return FAIL;                // must be unconditional after the initialization
3566   Node* mem = st->in(MemNode::Memory);
3567   if (!(mem->is_Proj() && mem->in(0) == this))
3568     return FAIL;                // must not be preceded by other stores
3569   Node* adr = st->in(MemNode::Address);
3570   intptr_t offset;
3571   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3572   if (alloc == NULL)
3573     return FAIL;                // inscrutable address
3574   if (alloc != allocation())
3575     return FAIL;                // wrong allocation!  (store needs to float up)
3576   int size_in_bytes = st->memory_size();
3577   if ((size_in_bytes != 0) && (offset % size_in_bytes) != 0) {
3578     return FAIL;                // mismatched access
3579   }
3580   Node* val = st->in(MemNode::ValueIn);
3581   int complexity_count = 0;
3582   if (!detect_init_independence(val, complexity_count))
3583     return FAIL;                // stored value must be 'simple enough'
3584 
3585   // The Store can be captured only if nothing after the allocation
3586   // and before the Store is using the memory location that the store
3587   // overwrites.
3588   bool failed = false;
3589   // If is_complete_with_arraycopy() is true the shape of the graph is
3590   // well defined and is safe so no need for extra checks.
3591   if (!is_complete_with_arraycopy()) {
3592     // We are going to look at each use of the memory state following
3593     // the allocation to make sure nothing reads the memory that the
3594     // Store writes.
3595     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3596     int alias_idx = phase->C->get_alias_index(t_adr);
3597     ResourceMark rm;
3598     Unique_Node_List mems;
3599     mems.push(mem);
3600     Node* unique_merge = NULL;
3601     for (uint next = 0; next < mems.size(); ++next) {
3602       Node *m  = mems.at(next);
3603       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3604         Node *n = m->fast_out(j);
3605         if (n->outcnt() == 0) {
3606           continue;
3607         }
3608         if (n == st) {
3609           continue;
3610         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3611           // If the control of this use is different from the control
3612           // of the Store which is right after the InitializeNode then
3613           // this node cannot be between the InitializeNode and the
3614           // Store.
3615           continue;
3616         } else if (n->is_MergeMem()) {
3617           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3618             // We can hit a MergeMemNode (that will likely go away
3619             // later) that is a direct use of the memory state
3620             // following the InitializeNode on the same slice as the
3621             // store node that we'd like to capture. We need to check
3622             // the uses of the MergeMemNode.
3623             mems.push(n);
3624           }
3625         } else if (n->is_Mem()) {
3626           Node* other_adr = n->in(MemNode::Address);
3627           if (other_adr == adr) {
3628             failed = true;
3629             break;
3630           } else {
3631             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3632             if (other_t_adr != NULL) {
3633               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3634               if (other_alias_idx == alias_idx) {
3635                 // A load from the same memory slice as the store right
3636                 // after the InitializeNode. We check the control of the
3637                 // object/array that is loaded from. If it's the same as
3638                 // the store control then we cannot capture the store.
3639                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3640                 Node* base = other_adr;
3641                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3642                 base = base->in(AddPNode::Base);
3643                 if (base != NULL) {
3644                   base = base->uncast();
3645                   if (base->is_Proj() && base->in(0) == alloc) {
3646                     failed = true;
3647                     break;
3648                   }
3649                 }
3650               }
3651             }
3652           }
3653         } else {
3654           failed = true;
3655           break;
3656         }
3657       }
3658     }
3659   }
3660   if (failed) {
3661     if (!can_reshape) {
3662       // We decided we couldn't capture the store during parsing. We
3663       // should try again during the next IGVN once the graph is
3664       // cleaner.
3665       phase->C->record_for_igvn(st);
3666     }
3667     return FAIL;
3668   }
3669 
3670   return offset;                // success
3671 }
3672 
3673 // Find the captured store in(i) which corresponds to the range
3674 // [start..start+size) in the initialized object.
3675 // If there is one, return its index i.  If there isn't, return the
3676 // negative of the index where it should be inserted.
3677 // Return 0 if the queried range overlaps an initialization boundary
3678 // or if dead code is encountered.
3679 // If size_in_bytes is zero, do not bother with overlap checks.
3680 int InitializeNode::captured_store_insertion_point(intptr_t start,
3681                                                    int size_in_bytes,
3682                                                    PhaseTransform* phase) {
3683   const int FAIL = 0, MAX_STORE = BytesPerLong;
3684 
3685   if (is_complete())
3686     return FAIL;                // arraycopy got here first; punt
3687 
3688   assert(allocation() != NULL, "must be present");
3689 
3690   // no negatives, no header fields:
3691   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3692 
3693   // after a certain size, we bail out on tracking all the stores:
3694   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3695   if (start >= ti_limit)  return FAIL;
3696 
3697   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3698     if (i >= limit)  return -(int)i; // not found; here is where to put it
3699 
3700     Node*    st     = in(i);
3701     intptr_t st_off = get_store_offset(st, phase);
3702     if (st_off < 0) {
3703       if (st != zero_memory()) {
3704         return FAIL;            // bail out if there is dead garbage
3705       }
3706     } else if (st_off > start) {
3707       // ...we are done, since stores are ordered
3708       if (st_off < start + size_in_bytes) {
3709         return FAIL;            // the next store overlaps
3710       }
3711       return -(int)i;           // not found; here is where to put it
3712     } else if (st_off < start) {
3713       if (size_in_bytes != 0 &&
3714           start < st_off + MAX_STORE &&
3715           start < st_off + st->as_Store()->memory_size()) {
3716         return FAIL;            // the previous store overlaps
3717       }
3718     } else {
3719       if (size_in_bytes != 0 &&
3720           st->as_Store()->memory_size() != size_in_bytes) {
3721         return FAIL;            // mismatched store size
3722       }
3723       return i;
3724     }
3725 
3726     ++i;
3727   }
3728 }
3729 
3730 // Look for a captured store which initializes at the offset 'start'
3731 // with the given size.  If there is no such store, and no other
3732 // initialization interferes, then return zero_memory (the memory
3733 // projection of the AllocateNode).
3734 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3735                                           PhaseTransform* phase) {
3736   assert(stores_are_sane(phase), "");
3737   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3738   if (i == 0) {
3739     return NULL;                // something is dead
3740   } else if (i < 0) {
3741     return zero_memory();       // just primordial zero bits here
3742   } else {
3743     Node* st = in(i);           // here is the store at this position
3744     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3745     return st;
3746   }
3747 }
3748 
3749 // Create, as a raw pointer, an address within my new object at 'offset'.
3750 Node* InitializeNode::make_raw_address(intptr_t offset,
3751                                        PhaseTransform* phase) {
3752   Node* addr = in(RawAddress);
3753   if (offset != 0) {
3754     Compile* C = phase->C;
3755     addr = phase->transform( new AddPNode(C->top(), addr,
3756                                                  phase->MakeConX(offset)) );
3757   }
3758   return addr;
3759 }
3760 
3761 // Clone the given store, converting it into a raw store
3762 // initializing a field or element of my new object.
3763 // Caller is responsible for retiring the original store,
3764 // with subsume_node or the like.
3765 //
3766 // From the example above InitializeNode::InitializeNode,
3767 // here are the old stores to be captured:
3768 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3769 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3770 //
3771 // Here is the changed code; note the extra edges on init:
3772 //   alloc = (Allocate ...)
3773 //   rawoop = alloc.RawAddress
3774 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3775 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3776 //   init = (Initialize alloc.Control alloc.Memory rawoop
3777 //                      rawstore1 rawstore2)
3778 //
3779 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3780                                     PhaseTransform* phase, bool can_reshape) {
3781   assert(stores_are_sane(phase), "");
3782 
3783   if (start < 0)  return NULL;
3784   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3785 
3786   Compile* C = phase->C;
3787   int size_in_bytes = st->memory_size();
3788   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3789   if (i == 0)  return NULL;     // bail out
3790   Node* prev_mem = NULL;        // raw memory for the captured store
3791   if (i > 0) {
3792     prev_mem = in(i);           // there is a pre-existing store under this one
3793     set_req(i, C->top());       // temporarily disconnect it
3794     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3795   } else {
3796     i = -i;                     // no pre-existing store
3797     prev_mem = zero_memory();   // a slice of the newly allocated object
3798     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3799       set_req(--i, C->top());   // reuse this edge; it has been folded away
3800     else
3801       ins_req(i, C->top());     // build a new edge
3802   }
3803   Node* new_st = st->clone();
3804   new_st->set_req(MemNode::Control, in(Control));
3805   new_st->set_req(MemNode::Memory,  prev_mem);
3806   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3807   new_st = phase->transform(new_st);
3808 
3809   // At this point, new_st might have swallowed a pre-existing store
3810   // at the same offset, or perhaps new_st might have disappeared,
3811   // if it redundantly stored the same value (or zero to fresh memory).
3812 
3813   // In any case, wire it in:
3814   phase->igvn_rehash_node_delayed(this);
3815   set_req(i, new_st);
3816 
3817   // The caller may now kill the old guy.
3818   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3819   assert(check_st == new_st || check_st == NULL, "must be findable");
3820   assert(!is_complete(), "");
3821   return new_st;
3822 }
3823 
3824 static bool store_constant(jlong* tiles, int num_tiles,
3825                            intptr_t st_off, int st_size,
3826                            jlong con) {
3827   if ((st_off & (st_size-1)) != 0)
3828     return false;               // strange store offset (assume size==2**N)
3829   address addr = (address)tiles + st_off;
3830   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3831   switch (st_size) {
3832   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3833   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3834   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3835   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3836   default: return false;        // strange store size (detect size!=2**N here)
3837   }
3838   return true;                  // return success to caller
3839 }
3840 
3841 // Coalesce subword constants into int constants and possibly
3842 // into long constants.  The goal, if the CPU permits,
3843 // is to initialize the object with a small number of 64-bit tiles.
3844 // Also, convert floating-point constants to bit patterns.
3845 // Non-constants are not relevant to this pass.
3846 //
3847 // In terms of the running example on InitializeNode::InitializeNode
3848 // and InitializeNode::capture_store, here is the transformation
3849 // of rawstore1 and rawstore2 into rawstore12:
3850 //   alloc = (Allocate ...)
3851 //   rawoop = alloc.RawAddress
3852 //   tile12 = 0x00010002
3853 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3854 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3855 //
3856 void
3857 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3858                                         Node* size_in_bytes,
3859                                         PhaseGVN* phase) {
3860   Compile* C = phase->C;
3861 
3862   assert(stores_are_sane(phase), "");
3863   // Note:  After this pass, they are not completely sane,
3864   // since there may be some overlaps.
3865 
3866   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3867 
3868   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3869   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3870   size_limit = MIN2(size_limit, ti_limit);
3871   size_limit = align_up(size_limit, BytesPerLong);
3872   int num_tiles = size_limit / BytesPerLong;
3873 
3874   // allocate space for the tile map:
3875   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3876   jlong  tiles_buf[small_len];
3877   Node*  nodes_buf[small_len];
3878   jlong  inits_buf[small_len];
3879   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3880                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3881   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3882                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3883   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3884                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3885   // tiles: exact bitwise model of all primitive constants
3886   // nodes: last constant-storing node subsumed into the tiles model
3887   // inits: which bytes (in each tile) are touched by any initializations
3888 
3889   //// Pass A: Fill in the tile model with any relevant stores.
3890 
3891   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3892   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3893   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3894   Node* zmem = zero_memory(); // initially zero memory state
3895   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3896     Node* st = in(i);
3897     intptr_t st_off = get_store_offset(st, phase);
3898 
3899     // Figure out the store's offset and constant value:
3900     if (st_off < header_size)             continue; //skip (ignore header)
3901     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3902     int st_size = st->as_Store()->memory_size();
3903     if (st_off + st_size > size_limit)    break;
3904 
3905     // Record which bytes are touched, whether by constant or not.
3906     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3907       continue;                 // skip (strange store size)
3908 
3909     const Type* val = phase->type(st->in(MemNode::ValueIn));
3910     if (!val->singleton())                continue; //skip (non-con store)
3911     BasicType type = val->basic_type();
3912 
3913     jlong con = 0;
3914     switch (type) {
3915     case T_INT:    con = val->is_int()->get_con();  break;
3916     case T_LONG:   con = val->is_long()->get_con(); break;
3917     case T_FLOAT:  con = jint_cast(val->getf());    break;
3918     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3919     default:                              continue; //skip (odd store type)
3920     }
3921 
3922     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3923         st->Opcode() == Op_StoreL) {
3924       continue;                 // This StoreL is already optimal.
3925     }
3926 
3927     // Store down the constant.
3928     store_constant(tiles, num_tiles, st_off, st_size, con);
3929 
3930     intptr_t j = st_off >> LogBytesPerLong;
3931 
3932     if (type == T_INT && st_size == BytesPerInt
3933         && (st_off & BytesPerInt) == BytesPerInt) {
3934       jlong lcon = tiles[j];
3935       if (!Matcher::isSimpleConstant64(lcon) &&
3936           st->Opcode() == Op_StoreI) {
3937         // This StoreI is already optimal by itself.
3938         jint* intcon = (jint*) &tiles[j];
3939         intcon[1] = 0;  // undo the store_constant()
3940 
3941         // If the previous store is also optimal by itself, back up and
3942         // undo the action of the previous loop iteration... if we can.
3943         // But if we can't, just let the previous half take care of itself.
3944         st = nodes[j];
3945         st_off -= BytesPerInt;
3946         con = intcon[0];
3947         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3948           assert(st_off >= header_size, "still ignoring header");
3949           assert(get_store_offset(st, phase) == st_off, "must be");
3950           assert(in(i-1) == zmem, "must be");
3951           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3952           assert(con == tcon->is_int()->get_con(), "must be");
3953           // Undo the effects of the previous loop trip, which swallowed st:
3954           intcon[0] = 0;        // undo store_constant()
3955           set_req(i-1, st);     // undo set_req(i, zmem)
3956           nodes[j] = NULL;      // undo nodes[j] = st
3957           --old_subword;        // undo ++old_subword
3958         }
3959         continue;               // This StoreI is already optimal.
3960       }
3961     }
3962 
3963     // This store is not needed.
3964     set_req(i, zmem);
3965     nodes[j] = st;              // record for the moment
3966     if (st_size < BytesPerLong) // something has changed
3967           ++old_subword;        // includes int/float, but who's counting...
3968     else  ++old_long;
3969   }
3970 
3971   if ((old_subword + old_long) == 0)
3972     return;                     // nothing more to do
3973 
3974   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3975   // Be sure to insert them before overlapping non-constant stores.
3976   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3977   for (int j = 0; j < num_tiles; j++) {
3978     jlong con  = tiles[j];
3979     jlong init = inits[j];
3980     if (con == 0)  continue;
3981     jint con0,  con1;           // split the constant, address-wise
3982     jint init0, init1;          // split the init map, address-wise
3983     { union { jlong con; jint intcon[2]; } u;
3984       u.con = con;
3985       con0  = u.intcon[0];
3986       con1  = u.intcon[1];
3987       u.con = init;
3988       init0 = u.intcon[0];
3989       init1 = u.intcon[1];
3990     }
3991 
3992     Node* old = nodes[j];
3993     assert(old != NULL, "need the prior store");
3994     intptr_t offset = (j * BytesPerLong);
3995 
3996     bool split = !Matcher::isSimpleConstant64(con);
3997 
3998     if (offset < header_size) {
3999       assert(offset + BytesPerInt >= header_size, "second int counts");
4000       assert(*(jint*)&tiles[j] == 0, "junk in header");
4001       split = true;             // only the second word counts
4002       // Example:  int a[] = { 42 ... }
4003     } else if (con0 == 0 && init0 == -1) {
4004       split = true;             // first word is covered by full inits
4005       // Example:  int a[] = { ... foo(), 42 ... }
4006     } else if (con1 == 0 && init1 == -1) {
4007       split = true;             // second word is covered by full inits
4008       // Example:  int a[] = { ... 42, foo() ... }
4009     }
4010 
4011     // Here's a case where init0 is neither 0 nor -1:
4012     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
4013     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
4014     // In this case the tile is not split; it is (jlong)42.
4015     // The big tile is stored down, and then the foo() value is inserted.
4016     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
4017 
4018     Node* ctl = old->in(MemNode::Control);
4019     Node* adr = make_raw_address(offset, phase);
4020     const TypePtr* atp = TypeRawPtr::BOTTOM;
4021 
4022     // One or two coalesced stores to plop down.
4023     Node*    st[2];
4024     intptr_t off[2];
4025     int  nst = 0;
4026     if (!split) {
4027       ++new_long;
4028       off[nst] = offset;
4029       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4030                                   phase->longcon(con), T_LONG, MemNode::unordered);
4031     } else {
4032       // Omit either if it is a zero.
4033       if (con0 != 0) {
4034         ++new_int;
4035         off[nst]  = offset;
4036         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4037                                     phase->intcon(con0), T_INT, MemNode::unordered);
4038       }
4039       if (con1 != 0) {
4040         ++new_int;
4041         offset += BytesPerInt;
4042         adr = make_raw_address(offset, phase);
4043         off[nst]  = offset;
4044         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4045                                     phase->intcon(con1), T_INT, MemNode::unordered);
4046       }
4047     }
4048 
4049     // Insert second store first, then the first before the second.
4050     // Insert each one just before any overlapping non-constant stores.
4051     while (nst > 0) {
4052       Node* st1 = st[--nst];
4053       C->copy_node_notes_to(st1, old);
4054       st1 = phase->transform(st1);
4055       offset = off[nst];
4056       assert(offset >= header_size, "do not smash header");
4057       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4058       guarantee(ins_idx != 0, "must re-insert constant store");
4059       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
4060       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4061         set_req(--ins_idx, st1);
4062       else
4063         ins_req(ins_idx, st1);
4064     }
4065   }
4066 
4067   if (PrintCompilation && WizardMode)
4068     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4069                   old_subword, old_long, new_int, new_long);
4070   if (C->log() != NULL)
4071     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4072                    old_subword, old_long, new_int, new_long);
4073 
4074   // Clean up any remaining occurrences of zmem:
4075   remove_extra_zeroes();
4076 }
4077 
4078 // Explore forward from in(start) to find the first fully initialized
4079 // word, and return its offset.  Skip groups of subword stores which
4080 // together initialize full words.  If in(start) is itself part of a
4081 // fully initialized word, return the offset of in(start).  If there
4082 // are no following full-word stores, or if something is fishy, return
4083 // a negative value.
4084 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4085   int       int_map = 0;
4086   intptr_t  int_map_off = 0;
4087   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
4088 
4089   for (uint i = start, limit = req(); i < limit; i++) {
4090     Node* st = in(i);
4091 
4092     intptr_t st_off = get_store_offset(st, phase);
4093     if (st_off < 0)  break;  // return conservative answer
4094 
4095     int st_size = st->as_Store()->memory_size();
4096     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4097       return st_off;            // we found a complete word init
4098     }
4099 
4100     // update the map:
4101 
4102     intptr_t this_int_off = align_down(st_off, BytesPerInt);
4103     if (this_int_off != int_map_off) {
4104       // reset the map:
4105       int_map = 0;
4106       int_map_off = this_int_off;
4107     }
4108 
4109     int subword_off = st_off - this_int_off;
4110     int_map |= right_n_bits(st_size) << subword_off;
4111     if ((int_map & FULL_MAP) == FULL_MAP) {
4112       return this_int_off;      // we found a complete word init
4113     }
4114 
4115     // Did this store hit or cross the word boundary?
4116     intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4117     if (next_int_off == this_int_off + BytesPerInt) {
4118       // We passed the current int, without fully initializing it.
4119       int_map_off = next_int_off;
4120       int_map >>= BytesPerInt;
4121     } else if (next_int_off > this_int_off + BytesPerInt) {
4122       // We passed the current and next int.
4123       return this_int_off + BytesPerInt;
4124     }
4125   }
4126 
4127   return -1;
4128 }
4129 
4130 
4131 // Called when the associated AllocateNode is expanded into CFG.
4132 // At this point, we may perform additional optimizations.
4133 // Linearize the stores by ascending offset, to make memory
4134 // activity as coherent as possible.
4135 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4136                                       intptr_t header_size,
4137                                       Node* size_in_bytes,
4138                                       PhaseIterGVN* phase) {
4139   assert(!is_complete(), "not already complete");
4140   assert(stores_are_sane(phase), "");
4141   assert(allocation() != NULL, "must be present");
4142 
4143   remove_extra_zeroes();
4144 
4145   if (ReduceFieldZeroing || ReduceBulkZeroing)
4146     // reduce instruction count for common initialization patterns
4147     coalesce_subword_stores(header_size, size_in_bytes, phase);
4148 
4149   Node* zmem = zero_memory();   // initially zero memory state
4150   Node* inits = zmem;           // accumulating a linearized chain of inits
4151   #ifdef ASSERT
4152   intptr_t first_offset = allocation()->minimum_header_size();
4153   intptr_t last_init_off = first_offset;  // previous init offset
4154   intptr_t last_init_end = first_offset;  // previous init offset+size
4155   intptr_t last_tile_end = first_offset;  // previous tile offset+size
4156   #endif
4157   intptr_t zeroes_done = header_size;
4158 
4159   bool do_zeroing = true;       // we might give up if inits are very sparse
4160   int  big_init_gaps = 0;       // how many large gaps have we seen?
4161 
4162   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
4163   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
4164 
4165   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4166     Node* st = in(i);
4167     intptr_t st_off = get_store_offset(st, phase);
4168     if (st_off < 0)
4169       break;                    // unknown junk in the inits
4170     if (st->in(MemNode::Memory) != zmem)
4171       break;                    // complicated store chains somehow in list
4172 
4173     int st_size = st->as_Store()->memory_size();
4174     intptr_t next_init_off = st_off + st_size;
4175 
4176     if (do_zeroing && zeroes_done < next_init_off) {
4177       // See if this store needs a zero before it or under it.
4178       intptr_t zeroes_needed = st_off;
4179 
4180       if (st_size < BytesPerInt) {
4181         // Look for subword stores which only partially initialize words.
4182         // If we find some, we must lay down some word-level zeroes first,
4183         // underneath the subword stores.
4184         //
4185         // Examples:
4186         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
4187         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
4188         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
4189         //
4190         // Note:  coalesce_subword_stores may have already done this,
4191         // if it was prompted by constant non-zero subword initializers.
4192         // But this case can still arise with non-constant stores.
4193 
4194         intptr_t next_full_store = find_next_fullword_store(i, phase);
4195 
4196         // In the examples above:
4197         //   in(i)          p   q   r   s     x   y     z
4198         //   st_off        12  13  14  15    12  13    14
4199         //   st_size        1   1   1   1     1   1     1
4200         //   next_full_s.  12  16  16  16    16  16    16
4201         //   z's_done      12  16  16  16    12  16    12
4202         //   z's_needed    12  16  16  16    16  16    16
4203         //   zsize          0   0   0   0     4   0     4
4204         if (next_full_store < 0) {
4205           // Conservative tack:  Zero to end of current word.
4206           zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4207         } else {
4208           // Zero to beginning of next fully initialized word.
4209           // Or, don't zero at all, if we are already in that word.
4210           assert(next_full_store >= zeroes_needed, "must go forward");
4211           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4212           zeroes_needed = next_full_store;
4213         }
4214       }
4215 
4216       if (zeroes_needed > zeroes_done) {
4217         intptr_t zsize = zeroes_needed - zeroes_done;
4218         // Do some incremental zeroing on rawmem, in parallel with inits.
4219         zeroes_done = align_down(zeroes_done, BytesPerInt);
4220         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4221                                               zeroes_done, zeroes_needed,
4222                                               phase);
4223         zeroes_done = zeroes_needed;
4224         if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4225           do_zeroing = false;   // leave the hole, next time
4226       }
4227     }
4228 
4229     // Collect the store and move on:
4230     phase->replace_input_of(st, MemNode::Memory, inits);
4231     inits = st;                 // put it on the linearized chain
4232     set_req(i, zmem);           // unhook from previous position
4233 
4234     if (zeroes_done == st_off)
4235       zeroes_done = next_init_off;
4236 
4237     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4238 
4239     #ifdef ASSERT
4240     // Various order invariants.  Weaker than stores_are_sane because
4241     // a large constant tile can be filled in by smaller non-constant stores.
4242     assert(st_off >= last_init_off, "inits do not reverse");
4243     last_init_off = st_off;
4244     const Type* val = NULL;
4245     if (st_size >= BytesPerInt &&
4246         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4247         (int)val->basic_type() < (int)T_OBJECT) {
4248       assert(st_off >= last_tile_end, "tiles do not overlap");
4249       assert(st_off >= last_init_end, "tiles do not overwrite inits");
4250       last_tile_end = MAX2(last_tile_end, next_init_off);
4251     } else {
4252       intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4253       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4254       assert(st_off      >= last_init_end, "inits do not overlap");
4255       last_init_end = next_init_off;  // it's a non-tile
4256     }
4257     #endif //ASSERT
4258   }
4259 
4260   remove_extra_zeroes();        // clear out all the zmems left over
4261   add_req(inits);
4262 
4263   if (!(UseTLAB && ZeroTLAB)) {
4264     // If anything remains to be zeroed, zero it all now.
4265     zeroes_done = align_down(zeroes_done, BytesPerInt);
4266     // if it is the last unused 4 bytes of an instance, forget about it
4267     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4268     if (zeroes_done + BytesPerLong >= size_limit) {
4269       AllocateNode* alloc = allocation();
4270       assert(alloc != NULL, "must be present");
4271       if (alloc != NULL && alloc->Opcode() == Op_Allocate) {
4272         Node* klass_node = alloc->in(AllocateNode::KlassNode);
4273         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
4274         if (zeroes_done == k->layout_helper())
4275           zeroes_done = size_limit;
4276       }
4277     }
4278     if (zeroes_done < size_limit) {
4279       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4280                                             zeroes_done, size_in_bytes, phase);
4281     }
4282   }
4283 
4284   set_complete(phase);
4285   return rawmem;
4286 }
4287 
4288 
4289 #ifdef ASSERT
4290 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
4291   if (is_complete())
4292     return true;                // stores could be anything at this point
4293   assert(allocation() != NULL, "must be present");
4294   intptr_t last_off = allocation()->minimum_header_size();
4295   for (uint i = InitializeNode::RawStores; i < req(); i++) {
4296     Node* st = in(i);
4297     intptr_t st_off = get_store_offset(st, phase);
4298     if (st_off < 0)  continue;  // ignore dead garbage
4299     if (last_off > st_off) {
4300       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4301       this->dump(2);
4302       assert(false, "ascending store offsets");
4303       return false;
4304     }
4305     last_off = st_off + st->as_Store()->memory_size();
4306   }
4307   return true;
4308 }
4309 #endif //ASSERT
4310 
4311 
4312 
4313 
4314 //============================MergeMemNode=====================================
4315 //
4316 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4317 // contributing store or call operations.  Each contributor provides the memory
4318 // state for a particular "alias type" (see Compile::alias_type).  For example,
4319 // if a MergeMem has an input X for alias category #6, then any memory reference
4320 // to alias category #6 may use X as its memory state input, as an exact equivalent
4321 // to using the MergeMem as a whole.
4322 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4323 //
4324 // (Here, the <N> notation gives the index of the relevant adr_type.)
4325 //
4326 // In one special case (and more cases in the future), alias categories overlap.
4327 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4328 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4329 // it is exactly equivalent to that state W:
4330 //   MergeMem(<Bot>: W) <==> W
4331 //
4332 // Usually, the merge has more than one input.  In that case, where inputs
4333 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4334 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4335 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4336 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4337 //
4338 // A merge can take a "wide" memory state as one of its narrow inputs.
4339 // This simply means that the merge observes out only the relevant parts of
4340 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4341 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4342 //
4343 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4344 // and that memory slices "leak through":
4345 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4346 //
4347 // But, in such a cascade, repeated memory slices can "block the leak":
4348 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4349 //
4350 // In the last example, Y is not part of the combined memory state of the
4351 // outermost MergeMem.  The system must, of course, prevent unschedulable
4352 // memory states from arising, so you can be sure that the state Y is somehow
4353 // a precursor to state Y'.
4354 //
4355 //
4356 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4357 // of each MergeMemNode array are exactly the numerical alias indexes, including
4358 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4359 // Compile::alias_type (and kin) produce and manage these indexes.
4360 //
4361 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4362 // (Note that this provides quick access to the top node inside MergeMem methods,
4363 // without the need to reach out via TLS to Compile::current.)
4364 //
4365 // As a consequence of what was just described, a MergeMem that represents a full
4366 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4367 // containing all alias categories.
4368 //
4369 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4370 //
4371 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4372 // a memory state for the alias type <N>, or else the top node, meaning that
4373 // there is no particular input for that alias type.  Note that the length of
4374 // a MergeMem is variable, and may be extended at any time to accommodate new
4375 // memory states at larger alias indexes.  When merges grow, they are of course
4376 // filled with "top" in the unused in() positions.
4377 //
4378 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4379 // (Top was chosen because it works smoothly with passes like GCM.)
4380 //
4381 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4382 // the type of random VM bits like TLS references.)  Since it is always the
4383 // first non-Bot memory slice, some low-level loops use it to initialize an
4384 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4385 //
4386 //
4387 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4388 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4389 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4390 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4391 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4392 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4393 //
4394 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4395 // really that different from the other memory inputs.  An abbreviation called
4396 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4397 //
4398 //
4399 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4400 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4401 // that "emerges though" the base memory will be marked as excluding the alias types
4402 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4403 //
4404 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4405 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4406 //
4407 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4408 // (It is currently unimplemented.)  As you can see, the resulting merge is
4409 // actually a disjoint union of memory states, rather than an overlay.
4410 //
4411 
4412 //------------------------------MergeMemNode-----------------------------------
4413 Node* MergeMemNode::make_empty_memory() {
4414   Node* empty_memory = (Node*) Compile::current()->top();
4415   assert(empty_memory->is_top(), "correct sentinel identity");
4416   return empty_memory;
4417 }
4418 
4419 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4420   init_class_id(Class_MergeMem);
4421   // all inputs are nullified in Node::Node(int)
4422   // set_input(0, NULL);  // no control input
4423 
4424   // Initialize the edges uniformly to top, for starters.
4425   Node* empty_mem = make_empty_memory();
4426   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4427     init_req(i,empty_mem);
4428   }
4429   assert(empty_memory() == empty_mem, "");
4430 
4431   if( new_base != NULL && new_base->is_MergeMem() ) {
4432     MergeMemNode* mdef = new_base->as_MergeMem();
4433     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4434     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4435       mms.set_memory(mms.memory2());
4436     }
4437     assert(base_memory() == mdef->base_memory(), "");
4438   } else {
4439     set_base_memory(new_base);
4440   }
4441 }
4442 
4443 // Make a new, untransformed MergeMem with the same base as 'mem'.
4444 // If mem is itself a MergeMem, populate the result with the same edges.
4445 MergeMemNode* MergeMemNode::make(Node* mem) {
4446   return new MergeMemNode(mem);
4447 }
4448 
4449 //------------------------------cmp--------------------------------------------
4450 uint MergeMemNode::hash() const { return NO_HASH; }
4451 uint MergeMemNode::cmp( const Node &n ) const {
4452   return (&n == this);          // Always fail except on self
4453 }
4454 
4455 //------------------------------Identity---------------------------------------
4456 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4457   // Identity if this merge point does not record any interesting memory
4458   // disambiguations.
4459   Node* base_mem = base_memory();
4460   Node* empty_mem = empty_memory();
4461   if (base_mem != empty_mem) {  // Memory path is not dead?
4462     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4463       Node* mem = in(i);
4464       if (mem != empty_mem && mem != base_mem) {
4465         return this;            // Many memory splits; no change
4466       }
4467     }
4468   }
4469   return base_mem;              // No memory splits; ID on the one true input
4470 }
4471 
4472 //------------------------------Ideal------------------------------------------
4473 // This method is invoked recursively on chains of MergeMem nodes
4474 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4475   // Remove chain'd MergeMems
4476   //
4477   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4478   // relative to the "in(Bot)".  Since we are patching both at the same time,
4479   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4480   // but rewrite each "in(i)" relative to the new "in(Bot)".
4481   Node *progress = NULL;
4482 
4483 
4484   Node* old_base = base_memory();
4485   Node* empty_mem = empty_memory();
4486   if (old_base == empty_mem)
4487     return NULL; // Dead memory path.
4488 
4489   MergeMemNode* old_mbase;
4490   if (old_base != NULL && old_base->is_MergeMem())
4491     old_mbase = old_base->as_MergeMem();
4492   else
4493     old_mbase = NULL;
4494   Node* new_base = old_base;
4495 
4496   // simplify stacked MergeMems in base memory
4497   if (old_mbase)  new_base = old_mbase->base_memory();
4498 
4499   // the base memory might contribute new slices beyond my req()
4500   if (old_mbase)  grow_to_match(old_mbase);
4501 
4502   // Look carefully at the base node if it is a phi.
4503   PhiNode* phi_base;
4504   if (new_base != NULL && new_base->is_Phi())
4505     phi_base = new_base->as_Phi();
4506   else
4507     phi_base = NULL;
4508 
4509   Node*    phi_reg = NULL;
4510   uint     phi_len = (uint)-1;
4511   if (phi_base != NULL && !phi_base->is_copy()) {
4512     // do not examine phi if degraded to a copy
4513     phi_reg = phi_base->region();
4514     phi_len = phi_base->req();
4515     // see if the phi is unfinished
4516     for (uint i = 1; i < phi_len; i++) {
4517       if (phi_base->in(i) == NULL) {
4518         // incomplete phi; do not look at it yet!
4519         phi_reg = NULL;
4520         phi_len = (uint)-1;
4521         break;
4522       }
4523     }
4524   }
4525 
4526   // Note:  We do not call verify_sparse on entry, because inputs
4527   // can normalize to the base_memory via subsume_node or similar
4528   // mechanisms.  This method repairs that damage.
4529 
4530   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4531 
4532   // Look at each slice.
4533   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4534     Node* old_in = in(i);
4535     // calculate the old memory value
4536     Node* old_mem = old_in;
4537     if (old_mem == empty_mem)  old_mem = old_base;
4538     assert(old_mem == memory_at(i), "");
4539 
4540     // maybe update (reslice) the old memory value
4541 
4542     // simplify stacked MergeMems
4543     Node* new_mem = old_mem;
4544     MergeMemNode* old_mmem;
4545     if (old_mem != NULL && old_mem->is_MergeMem())
4546       old_mmem = old_mem->as_MergeMem();
4547     else
4548       old_mmem = NULL;
4549     if (old_mmem == this) {
4550       // This can happen if loops break up and safepoints disappear.
4551       // A merge of BotPtr (default) with a RawPtr memory derived from a
4552       // safepoint can be rewritten to a merge of the same BotPtr with
4553       // the BotPtr phi coming into the loop.  If that phi disappears
4554       // also, we can end up with a self-loop of the mergemem.
4555       // In general, if loops degenerate and memory effects disappear,
4556       // a mergemem can be left looking at itself.  This simply means
4557       // that the mergemem's default should be used, since there is
4558       // no longer any apparent effect on this slice.
4559       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4560       //       from start.  Update the input to TOP.
4561       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4562     }
4563     else if (old_mmem != NULL) {
4564       new_mem = old_mmem->memory_at(i);
4565     }
4566     // else preceding memory was not a MergeMem
4567 
4568     // replace equivalent phis (unfortunately, they do not GVN together)
4569     if (new_mem != NULL && new_mem != new_base &&
4570         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4571       if (new_mem->is_Phi()) {
4572         PhiNode* phi_mem = new_mem->as_Phi();
4573         for (uint i = 1; i < phi_len; i++) {
4574           if (phi_base->in(i) != phi_mem->in(i)) {
4575             phi_mem = NULL;
4576             break;
4577           }
4578         }
4579         if (phi_mem != NULL) {
4580           // equivalent phi nodes; revert to the def
4581           new_mem = new_base;
4582         }
4583       }
4584     }
4585 
4586     // maybe store down a new value
4587     Node* new_in = new_mem;
4588     if (new_in == new_base)  new_in = empty_mem;
4589 
4590     if (new_in != old_in) {
4591       // Warning:  Do not combine this "if" with the previous "if"
4592       // A memory slice might have be be rewritten even if it is semantically
4593       // unchanged, if the base_memory value has changed.
4594       set_req(i, new_in);
4595       progress = this;          // Report progress
4596     }
4597   }
4598 
4599   if (new_base != old_base) {
4600     set_req(Compile::AliasIdxBot, new_base);
4601     // Don't use set_base_memory(new_base), because we need to update du.
4602     assert(base_memory() == new_base, "");
4603     progress = this;
4604   }
4605 
4606   if( base_memory() == this ) {
4607     // a self cycle indicates this memory path is dead
4608     set_req(Compile::AliasIdxBot, empty_mem);
4609   }
4610 
4611   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4612   // Recursion must occur after the self cycle check above
4613   if( base_memory()->is_MergeMem() ) {
4614     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4615     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4616     if( m != NULL &&
4617         (m->is_top() ||
4618          (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4619       // propagate rollup of dead cycle to self
4620       set_req(Compile::AliasIdxBot, empty_mem);
4621     }
4622   }
4623 
4624   if( base_memory() == empty_mem ) {
4625     progress = this;
4626     // Cut inputs during Parse phase only.
4627     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4628     if( !can_reshape ) {
4629       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4630         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4631       }
4632     }
4633   }
4634 
4635   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4636     // Check if PhiNode::Ideal's "Split phis through memory merges"
4637     // transform should be attempted. Look for this->phi->this cycle.
4638     uint merge_width = req();
4639     if (merge_width > Compile::AliasIdxRaw) {
4640       PhiNode* phi = base_memory()->as_Phi();
4641       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4642         if (phi->in(i) == this) {
4643           phase->is_IterGVN()->_worklist.push(phi);
4644           break;
4645         }
4646       }
4647     }
4648   }
4649 
4650   assert(progress || verify_sparse(), "please, no dups of base");
4651   return progress;
4652 }
4653 
4654 //-------------------------set_base_memory-------------------------------------
4655 void MergeMemNode::set_base_memory(Node *new_base) {
4656   Node* empty_mem = empty_memory();
4657   set_req(Compile::AliasIdxBot, new_base);
4658   assert(memory_at(req()) == new_base, "must set default memory");
4659   // Clear out other occurrences of new_base:
4660   if (new_base != empty_mem) {
4661     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4662       if (in(i) == new_base)  set_req(i, empty_mem);
4663     }
4664   }
4665 }
4666 
4667 //------------------------------out_RegMask------------------------------------
4668 const RegMask &MergeMemNode::out_RegMask() const {
4669   return RegMask::Empty;
4670 }
4671 
4672 //------------------------------dump_spec--------------------------------------
4673 #ifndef PRODUCT
4674 void MergeMemNode::dump_spec(outputStream *st) const {
4675   st->print(" {");
4676   Node* base_mem = base_memory();
4677   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4678     Node* mem = (in(i) != NULL) ? memory_at(i) : base_mem;
4679     if (mem == base_mem) { st->print(" -"); continue; }
4680     st->print( " N%d:", mem->_idx );
4681     Compile::current()->get_adr_type(i)->dump_on(st);
4682   }
4683   st->print(" }");
4684 }
4685 #endif // !PRODUCT
4686 
4687 
4688 #ifdef ASSERT
4689 static bool might_be_same(Node* a, Node* b) {
4690   if (a == b)  return true;
4691   if (!(a->is_Phi() || b->is_Phi()))  return false;
4692   // phis shift around during optimization
4693   return true;  // pretty stupid...
4694 }
4695 
4696 // verify a narrow slice (either incoming or outgoing)
4697 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4698   if (!VerifyAliases)                return;  // don't bother to verify unless requested
4699   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
4700   if (Node::in_dump())               return;  // muzzle asserts when printing
4701   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4702   assert(n != NULL, "");
4703   // Elide intervening MergeMem's
4704   while (n->is_MergeMem()) {
4705     n = n->as_MergeMem()->memory_at(alias_idx);
4706   }
4707   Compile* C = Compile::current();
4708   const TypePtr* n_adr_type = n->adr_type();
4709   if (n == m->empty_memory()) {
4710     // Implicit copy of base_memory()
4711   } else if (n_adr_type != TypePtr::BOTTOM) {
4712     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4713     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4714   } else {
4715     // A few places like make_runtime_call "know" that VM calls are narrow,
4716     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4717     bool expected_wide_mem = false;
4718     if (n == m->base_memory()) {
4719       expected_wide_mem = true;
4720     } else if (alias_idx == Compile::AliasIdxRaw ||
4721                n == m->memory_at(Compile::AliasIdxRaw)) {
4722       expected_wide_mem = true;
4723     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4724       // memory can "leak through" calls on channels that
4725       // are write-once.  Allow this also.
4726       expected_wide_mem = true;
4727     }
4728     assert(expected_wide_mem, "expected narrow slice replacement");
4729   }
4730 }
4731 #else // !ASSERT
4732 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4733 #endif
4734 
4735 
4736 //-----------------------------memory_at---------------------------------------
4737 Node* MergeMemNode::memory_at(uint alias_idx) const {
4738   assert(alias_idx >= Compile::AliasIdxRaw ||
4739          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4740          "must avoid base_memory and AliasIdxTop");
4741 
4742   // Otherwise, it is a narrow slice.
4743   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4744   Compile *C = Compile::current();
4745   if (is_empty_memory(n)) {
4746     // the array is sparse; empty slots are the "top" node
4747     n = base_memory();
4748     assert(Node::in_dump()
4749            || n == NULL || n->bottom_type() == Type::TOP
4750            || n->adr_type() == NULL // address is TOP
4751            || n->adr_type() == TypePtr::BOTTOM
4752            || n->adr_type() == TypeRawPtr::BOTTOM
4753            || Compile::current()->AliasLevel() == 0,
4754            "must be a wide memory");
4755     // AliasLevel == 0 if we are organizing the memory states manually.
4756     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4757   } else {
4758     // make sure the stored slice is sane
4759     #ifdef ASSERT
4760     if (VMError::is_error_reported() || Node::in_dump()) {
4761     } else if (might_be_same(n, base_memory())) {
4762       // Give it a pass:  It is a mostly harmless repetition of the base.
4763       // This can arise normally from node subsumption during optimization.
4764     } else {
4765       verify_memory_slice(this, alias_idx, n);
4766     }
4767     #endif
4768   }
4769   return n;
4770 }
4771 
4772 //---------------------------set_memory_at-------------------------------------
4773 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4774   verify_memory_slice(this, alias_idx, n);
4775   Node* empty_mem = empty_memory();
4776   if (n == base_memory())  n = empty_mem;  // collapse default
4777   uint need_req = alias_idx+1;
4778   if (req() < need_req) {
4779     if (n == empty_mem)  return;  // already the default, so do not grow me
4780     // grow the sparse array
4781     do {
4782       add_req(empty_mem);
4783     } while (req() < need_req);
4784   }
4785   set_req( alias_idx, n );
4786 }
4787 
4788 
4789 
4790 //--------------------------iteration_setup------------------------------------
4791 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4792   if (other != NULL) {
4793     grow_to_match(other);
4794     // invariant:  the finite support of mm2 is within mm->req()
4795     #ifdef ASSERT
4796     for (uint i = req(); i < other->req(); i++) {
4797       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4798     }
4799     #endif
4800   }
4801   // Replace spurious copies of base_memory by top.
4802   Node* base_mem = base_memory();
4803   if (base_mem != NULL && !base_mem->is_top()) {
4804     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4805       if (in(i) == base_mem)
4806         set_req(i, empty_memory());
4807     }
4808   }
4809 }
4810 
4811 //---------------------------grow_to_match-------------------------------------
4812 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4813   Node* empty_mem = empty_memory();
4814   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4815   // look for the finite support of the other memory
4816   for (uint i = other->req(); --i >= req(); ) {
4817     if (other->in(i) != empty_mem) {
4818       uint new_len = i+1;
4819       while (req() < new_len)  add_req(empty_mem);
4820       break;
4821     }
4822   }
4823 }
4824 
4825 //---------------------------verify_sparse-------------------------------------
4826 #ifndef PRODUCT
4827 bool MergeMemNode::verify_sparse() const {
4828   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4829   Node* base_mem = base_memory();
4830   // The following can happen in degenerate cases, since empty==top.
4831   if (is_empty_memory(base_mem))  return true;
4832   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4833     assert(in(i) != NULL, "sane slice");
4834     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4835   }
4836   return true;
4837 }
4838 
4839 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4840   Node* n;
4841   n = mm->in(idx);
4842   if (mem == n)  return true;  // might be empty_memory()
4843   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4844   if (mem == n)  return true;
4845   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4846     if (mem == n)  return true;
4847     if (n == NULL)  break;
4848   }
4849   return false;
4850 }
4851 #endif // !PRODUCT