1 /*
   2  * Copyright (c) 1997, 2023, 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/javaClasses.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "gc/shared/tlab_globals.hpp"
  31 #include "memory/allocation.inline.hpp"
  32 #include "memory/resourceArea.hpp"
  33 #include "oops/objArrayKlass.hpp"
  34 #include "opto/addnode.hpp"
  35 #include "opto/arraycopynode.hpp"
  36 #include "opto/cfgnode.hpp"
  37 #include "opto/regalloc.hpp"
  38 #include "opto/compile.hpp"
  39 #include "opto/connode.hpp"
  40 #include "opto/convertnode.hpp"
  41 #include "opto/loopnode.hpp"
  42 #include "opto/machnode.hpp"
  43 #include "opto/matcher.hpp"
  44 #include "opto/memnode.hpp"
  45 #include "opto/mulnode.hpp"
  46 #include "opto/narrowptrnode.hpp"
  47 #include "opto/phaseX.hpp"
  48 #include "opto/regmask.hpp"
  49 #include "opto/rootnode.hpp"
  50 #include "opto/vectornode.hpp"
  51 #include "utilities/align.hpp"
  52 #include "utilities/copy.hpp"
  53 #include "utilities/macros.hpp"
  54 #include "utilities/powerOfTwo.hpp"
  55 #include "utilities/vmError.hpp"
  56 
  57 // Portions of code courtesy of Clifford Click
  58 
  59 // Optimization - Graph Style
  60 
  61 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  62 
  63 //=============================================================================
  64 uint MemNode::size_of() const { return sizeof(*this); }
  65 
  66 const TypePtr *MemNode::adr_type() const {
  67   Node* adr = in(Address);
  68   if (adr == nullptr)  return nullptr; // node is dead
  69   const TypePtr* cross_check = nullptr;
  70   DEBUG_ONLY(cross_check = _adr_type);
  71   return calculate_adr_type(adr->bottom_type(), cross_check);
  72 }
  73 
  74 bool MemNode::check_if_adr_maybe_raw(Node* adr) {
  75   if (adr != nullptr) {
  76     if (adr->bottom_type()->base() == Type::RawPtr || adr->bottom_type()->base() == Type::AnyPtr) {
  77       return true;
  78     }
  79   }
  80   return false;
  81 }
  82 
  83 #ifndef PRODUCT
  84 void MemNode::dump_spec(outputStream *st) const {
  85   if (in(Address) == nullptr)  return; // node is dead
  86 #ifndef ASSERT
  87   // fake the missing field
  88   const TypePtr* _adr_type = nullptr;
  89   if (in(Address) != nullptr)
  90     _adr_type = in(Address)->bottom_type()->isa_ptr();
  91 #endif
  92   dump_adr_type(this, _adr_type, st);
  93 
  94   Compile* C = Compile::current();
  95   if (C->alias_type(_adr_type)->is_volatile()) {
  96     st->print(" Volatile!");
  97   }
  98   if (_unaligned_access) {
  99     st->print(" unaligned");
 100   }
 101   if (_mismatched_access) {
 102     st->print(" mismatched");
 103   }
 104   if (_unsafe_access) {
 105     st->print(" unsafe");
 106   }
 107 }
 108 
 109 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
 110   st->print(" @");
 111   if (adr_type == nullptr) {
 112     st->print("null");
 113   } else {
 114     adr_type->dump_on(st);
 115     Compile* C = Compile::current();
 116     Compile::AliasType* atp = nullptr;
 117     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
 118     if (atp == nullptr)
 119       st->print(", idx=?\?;");
 120     else if (atp->index() == Compile::AliasIdxBot)
 121       st->print(", idx=Bot;");
 122     else if (atp->index() == Compile::AliasIdxTop)
 123       st->print(", idx=Top;");
 124     else if (atp->index() == Compile::AliasIdxRaw)
 125       st->print(", idx=Raw;");
 126     else {
 127       ciField* field = atp->field();
 128       if (field) {
 129         st->print(", name=");
 130         field->print_name_on(st);
 131       }
 132       st->print(", idx=%d;", atp->index());
 133     }
 134   }
 135 }
 136 
 137 extern void print_alias_types();
 138 
 139 #endif
 140 
 141 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 142   assert((t_oop != nullptr), "sanity");
 143   bool is_instance = t_oop->is_known_instance_field();
 144   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 145                              (load != nullptr) && load->is_Load() &&
 146                              (phase->is_IterGVN() != nullptr);
 147   if (!(is_instance || is_boxed_value_load))
 148     return mchain;  // don't try to optimize non-instance types
 149   uint instance_id = t_oop->instance_id();
 150   Node *start_mem = phase->C->start()->proj_out_or_null(TypeFunc::Memory);
 151   Node *prev = nullptr;
 152   Node *result = mchain;
 153   while (prev != result) {
 154     prev = result;
 155     if (result == start_mem)
 156       break;  // hit one of our sentinels
 157     // skip over a call which does not affect this memory slice
 158     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 159       Node *proj_in = result->in(0);
 160       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 161         break;  // hit one of our sentinels
 162       } else if (proj_in->is_Call()) {
 163         // ArrayCopyNodes processed here as well
 164         CallNode *call = proj_in->as_Call();
 165         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 166           result = call->in(TypeFunc::Memory);
 167         }
 168       } else if (proj_in->is_Initialize()) {
 169         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 170         // Stop if this is the initialization for the object instance which
 171         // contains this memory slice, otherwise skip over it.
 172         if ((alloc == nullptr) || (alloc->_idx == instance_id)) {
 173           break;
 174         }
 175         if (is_instance) {
 176           result = proj_in->in(TypeFunc::Memory);
 177         } else if (is_boxed_value_load) {
 178           Node* klass = alloc->in(AllocateNode::KlassNode);
 179           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 180           if (tklass->klass_is_exact() && !tklass->exact_klass()->equals(t_oop->is_instptr()->exact_klass())) {
 181             result = proj_in->in(TypeFunc::Memory); // not related allocation
 182           }
 183         }
 184       } else if (proj_in->is_MemBar()) {
 185         ArrayCopyNode* ac = nullptr;
 186         if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase, ac)) {
 187           break;
 188         }
 189         result = proj_in->in(TypeFunc::Memory);
 190       } else if (proj_in->is_top()) {
 191         break; // dead code
 192       } else {
 193         assert(false, "unexpected projection");
 194       }
 195     } else if (result->is_ClearArray()) {
 196       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 197         // Can not bypass initialization of the instance
 198         // we are looking for.
 199         break;
 200       }
 201       // Otherwise skip it (the call updated 'result' value).
 202     } else if (result->is_MergeMem()) {
 203       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, nullptr, tty);
 204     }
 205   }
 206   return result;
 207 }
 208 
 209 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 210   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 211   if (t_oop == nullptr)
 212     return mchain;  // don't try to optimize non-oop types
 213   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 214   bool is_instance = t_oop->is_known_instance_field();
 215   PhaseIterGVN *igvn = phase->is_IterGVN();
 216   if (is_instance && igvn != nullptr && result->is_Phi()) {
 217     PhiNode *mphi = result->as_Phi();
 218     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 219     const TypePtr *t = mphi->adr_type();
 220     bool do_split = false;
 221     // In the following cases, Load memory input can be further optimized based on
 222     // its precise address type
 223     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ) {
 224       do_split = true;
 225     } else if (t->isa_oopptr() && !t->is_oopptr()->is_known_instance()) {
 226       const TypeOopPtr* mem_t =
 227         t->is_oopptr()->cast_to_exactness(true)
 228         ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 229         ->is_oopptr()->cast_to_instance_id(t_oop->instance_id());
 230       if (t_oop->is_aryptr()) {
 231         mem_t = mem_t->is_aryptr()
 232                      ->cast_to_stable(t_oop->is_aryptr()->is_stable())
 233                      ->cast_to_size(t_oop->is_aryptr()->size())
 234                      ->with_offset(t_oop->is_aryptr()->offset())
 235                      ->is_aryptr();
 236       }
 237       do_split = mem_t == t_oop;
 238     }
 239     if (do_split) {
 240       // clone the Phi with our address type
 241       result = mphi->split_out_instance(t_adr, igvn);
 242     } else {
 243       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 244     }
 245   }
 246   return result;
 247 }
 248 
 249 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 250   uint alias_idx = phase->C->get_alias_index(tp);
 251   Node *mem = mmem;
 252 #ifdef ASSERT
 253   {
 254     // Check that current type is consistent with the alias index used during graph construction
 255     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 256     bool consistent =  adr_check == nullptr || adr_check->empty() ||
 257                        phase->C->must_alias(adr_check, alias_idx );
 258     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 259     if( !consistent && adr_check != nullptr && !adr_check->empty() &&
 260                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 261         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 262         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 263           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 264           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 265       // don't assert if it is dead code.
 266       consistent = true;
 267     }
 268     if( !consistent ) {
 269       st->print("alias_idx==%d, adr_check==", alias_idx);
 270       if( adr_check == nullptr ) {
 271         st->print("null");
 272       } else {
 273         adr_check->dump();
 274       }
 275       st->cr();
 276       print_alias_types();
 277       assert(consistent, "adr_check must match alias idx");
 278     }
 279   }
 280 #endif
 281   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 282   // means an array I have not precisely typed yet.  Do not do any
 283   // alias stuff with it any time soon.
 284   const TypeOopPtr *toop = tp->isa_oopptr();
 285   if (tp->base() != Type::AnyPtr &&
 286       !(toop &&
 287         toop->isa_instptr() &&
 288         toop->is_instptr()->instance_klass()->is_java_lang_Object() &&
 289         toop->offset() == Type::OffsetBot)) {
 290     // compress paths and change unreachable cycles to TOP
 291     // If not, we can update the input infinitely along a MergeMem cycle
 292     // Equivalent code in PhiNode::Ideal
 293     Node* m  = phase->transform(mmem);
 294     // If transformed to a MergeMem, get the desired slice
 295     // Otherwise the returned node represents memory for every slice
 296     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 297     // Update input if it is progress over what we have now
 298   }
 299   return mem;
 300 }
 301 
 302 //--------------------------Ideal_common---------------------------------------
 303 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 304 // Unhook non-raw memories from complete (macro-expanded) initializations.
 305 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 306   // If our control input is a dead region, kill all below the region
 307   Node *ctl = in(MemNode::Control);
 308   if (ctl && remove_dead_region(phase, can_reshape))
 309     return this;
 310   ctl = in(MemNode::Control);
 311   // Don't bother trying to transform a dead node
 312   if (ctl && ctl->is_top())  return NodeSentinel;
 313 
 314   PhaseIterGVN *igvn = phase->is_IterGVN();
 315   // Wait if control on the worklist.
 316   if (ctl && can_reshape && igvn != nullptr) {
 317     Node* bol = nullptr;
 318     Node* cmp = nullptr;
 319     if (ctl->in(0)->is_If()) {
 320       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 321       bol = ctl->in(0)->in(1);
 322       if (bol->is_Bool())
 323         cmp = ctl->in(0)->in(1)->in(1);
 324     }
 325     if (igvn->_worklist.member(ctl) ||
 326         (bol != nullptr && igvn->_worklist.member(bol)) ||
 327         (cmp != nullptr && igvn->_worklist.member(cmp)) ) {
 328       // This control path may be dead.
 329       // Delay this memory node transformation until the control is processed.
 330       igvn->_worklist.push(this);
 331       return NodeSentinel; // caller will return null
 332     }
 333   }
 334   // Ignore if memory is dead, or self-loop
 335   Node *mem = in(MemNode::Memory);
 336   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return null
 337   assert(mem != this, "dead loop in MemNode::Ideal");
 338 
 339   if (can_reshape && igvn != nullptr && igvn->_worklist.member(mem)) {
 340     // This memory slice may be dead.
 341     // Delay this mem node transformation until the memory is processed.
 342     igvn->_worklist.push(this);
 343     return NodeSentinel; // caller will return null
 344   }
 345 
 346   Node *address = in(MemNode::Address);
 347   const Type *t_adr = phase->type(address);
 348   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return null
 349 
 350   if (can_reshape && is_unsafe_access() && (t_adr == TypePtr::NULL_PTR)) {
 351     // Unsafe off-heap access with zero address. Remove access and other control users
 352     // to not confuse optimizations and add a HaltNode to fail if this is ever executed.
 353     assert(ctl != nullptr, "unsafe accesses should be control dependent");
 354     for (DUIterator_Fast imax, i = ctl->fast_outs(imax); i < imax; i++) {
 355       Node* u = ctl->fast_out(i);
 356       if (u != ctl) {
 357         igvn->rehash_node_delayed(u);
 358         int nb = u->replace_edge(ctl, phase->C->top(), igvn);
 359         --i, imax -= nb;
 360       }
 361     }
 362     Node* frame = igvn->transform(new ParmNode(phase->C->start(), TypeFunc::FramePtr));
 363     Node* halt = igvn->transform(new HaltNode(ctl, frame, "unsafe off-heap access with zero address"));
 364     phase->C->root()->add_req(halt);
 365     return this;
 366   }
 367 
 368   if (can_reshape && igvn != nullptr &&
 369       (igvn->_worklist.member(address) ||
 370        (igvn->_worklist.size() > 0 && t_adr != adr_type())) ) {
 371     // The address's base and type may change when the address is processed.
 372     // Delay this mem node transformation until the address is processed.
 373     igvn->_worklist.push(this);
 374     return NodeSentinel; // caller will return null
 375   }
 376 
 377   // Do NOT remove or optimize the next lines: ensure a new alias index
 378   // is allocated for an oop pointer type before Escape Analysis.
 379   // Note: C++ will not remove it since the call has side effect.
 380   if (t_adr->isa_oopptr()) {
 381     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 382   }
 383 
 384   Node* base = nullptr;
 385   if (address->is_AddP()) {
 386     base = address->in(AddPNode::Base);
 387   }
 388   if (base != nullptr && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 389       !t_adr->isa_rawptr()) {
 390     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 391     // Skip this node optimization if its address has TOP base.
 392     return NodeSentinel; // caller will return null
 393   }
 394 
 395   // Avoid independent memory operations
 396   Node* old_mem = mem;
 397 
 398   // The code which unhooks non-raw memories from complete (macro-expanded)
 399   // initializations was removed. After macro-expansion all stores caught
 400   // by Initialize node became raw stores and there is no information
 401   // which memory slices they modify. So it is unsafe to move any memory
 402   // operation above these stores. Also in most cases hooked non-raw memories
 403   // were already unhooked by using information from detect_ptr_independence()
 404   // and find_previous_store().
 405 
 406   if (mem->is_MergeMem()) {
 407     MergeMemNode* mmem = mem->as_MergeMem();
 408     const TypePtr *tp = t_adr->is_ptr();
 409 
 410     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 411   }
 412 
 413   if (mem != old_mem) {
 414     set_req_X(MemNode::Memory, mem, phase);
 415     if (phase->type(mem) == Type::TOP) return NodeSentinel;
 416     return this;
 417   }
 418 
 419   // let the subclass continue analyzing...
 420   return nullptr;
 421 }
 422 
 423 // Helper function for proving some simple control dominations.
 424 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 425 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 426 // is not a constant (dominated by the method's StartNode).
 427 // Used by MemNode::find_previous_store to prove that the
 428 // control input of a memory operation predates (dominates)
 429 // an allocation it wants to look past.
 430 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 431   if (dom == nullptr || dom->is_top() || sub == nullptr || sub->is_top())
 432     return false; // Conservative answer for dead code
 433 
 434   // Check 'dom'. Skip Proj and CatchProj nodes.
 435   dom = dom->find_exact_control(dom);
 436   if (dom == nullptr || dom->is_top())
 437     return false; // Conservative answer for dead code
 438 
 439   if (dom == sub) {
 440     // For the case when, for example, 'sub' is Initialize and the original
 441     // 'dom' is Proj node of the 'sub'.
 442     return false;
 443   }
 444 
 445   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 446     return true;
 447 
 448   // 'dom' dominates 'sub' if its control edge and control edges
 449   // of all its inputs dominate or equal to sub's control edge.
 450 
 451   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 452   // Or Region for the check in LoadNode::Ideal();
 453   // 'sub' should have sub->in(0) != nullptr.
 454   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 455          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 456 
 457   // Get control edge of 'sub'.
 458   Node* orig_sub = sub;
 459   sub = sub->find_exact_control(sub->in(0));
 460   if (sub == nullptr || sub->is_top())
 461     return false; // Conservative answer for dead code
 462 
 463   assert(sub->is_CFG(), "expecting control");
 464 
 465   if (sub == dom)
 466     return true;
 467 
 468   if (sub->is_Start() || sub->is_Root())
 469     return false;
 470 
 471   {
 472     // Check all control edges of 'dom'.
 473 
 474     ResourceMark rm;
 475     Node_List nlist;
 476     Unique_Node_List dom_list;
 477 
 478     dom_list.push(dom);
 479     bool only_dominating_controls = false;
 480 
 481     for (uint next = 0; next < dom_list.size(); next++) {
 482       Node* n = dom_list.at(next);
 483       if (n == orig_sub)
 484         return false; // One of dom's inputs dominated by sub.
 485       if (!n->is_CFG() && n->pinned()) {
 486         // Check only own control edge for pinned non-control nodes.
 487         n = n->find_exact_control(n->in(0));
 488         if (n == nullptr || n->is_top())
 489           return false; // Conservative answer for dead code
 490         assert(n->is_CFG(), "expecting control");
 491         dom_list.push(n);
 492       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 493         only_dominating_controls = true;
 494       } else if (n->is_CFG()) {
 495         if (n->dominates(sub, nlist))
 496           only_dominating_controls = true;
 497         else
 498           return false;
 499       } else {
 500         // First, own control edge.
 501         Node* m = n->find_exact_control(n->in(0));
 502         if (m != nullptr) {
 503           if (m->is_top())
 504             return false; // Conservative answer for dead code
 505           dom_list.push(m);
 506         }
 507         // Now, the rest of edges.
 508         uint cnt = n->req();
 509         for (uint i = 1; i < cnt; i++) {
 510           m = n->find_exact_control(n->in(i));
 511           if (m == nullptr || m->is_top())
 512             continue;
 513           dom_list.push(m);
 514         }
 515       }
 516     }
 517     return only_dominating_controls;
 518   }
 519 }
 520 
 521 //---------------------detect_ptr_independence---------------------------------
 522 // Used by MemNode::find_previous_store to prove that two base
 523 // pointers are never equal.
 524 // The pointers are accompanied by their associated allocations,
 525 // if any, which have been previously discovered by the caller.
 526 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 527                                       Node* p2, AllocateNode* a2,
 528                                       PhaseTransform* phase) {
 529   // Attempt to prove that these two pointers cannot be aliased.
 530   // They may both manifestly be allocations, and they should differ.
 531   // Or, if they are not both allocations, they can be distinct constants.
 532   // Otherwise, one is an allocation and the other a pre-existing value.
 533   if (a1 == nullptr && a2 == nullptr) {           // neither an allocation
 534     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 535   } else if (a1 != nullptr && a2 != nullptr) {    // both allocations
 536     return (a1 != a2);
 537   } else if (a1 != nullptr) {                  // one allocation a1
 538     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 539     return all_controls_dominate(p2, a1);
 540   } else { //(a2 != null)                   // one allocation a2
 541     return all_controls_dominate(p1, a2);
 542   }
 543   return false;
 544 }
 545 
 546 
 547 // Find an arraycopy ac that produces the memory state represented by parameter mem.
 548 // Return ac if
 549 // (a) can_see_stored_value=true  and ac must have set the value for this load or if
 550 // (b) can_see_stored_value=false and ac could have set the value for this load or if
 551 // (c) can_see_stored_value=false and ac cannot have set the value for this load.
 552 // In case (c) change the parameter mem to the memory input of ac to skip it
 553 // when searching stored value.
 554 // Otherwise return null.
 555 Node* LoadNode::find_previous_arraycopy(PhaseValues* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
 556   ArrayCopyNode* ac = find_array_copy_clone(phase, ld_alloc, mem);
 557   if (ac != nullptr) {
 558     Node* ld_addp = in(MemNode::Address);
 559     Node* src = ac->in(ArrayCopyNode::Src);
 560     const TypeAryPtr* ary_t = phase->type(src)->isa_aryptr();
 561 
 562     // This is a load from a cloned array. The corresponding arraycopy ac must
 563     // have set the value for the load and we can return ac but only if the load
 564     // is known to be within bounds. This is checked below.
 565     if (ary_t != nullptr && ld_addp->is_AddP()) {
 566       Node* ld_offs = ld_addp->in(AddPNode::Offset);
 567       BasicType ary_elem = ary_t->elem()->array_element_basic_type();
 568       jlong header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 569       jlong elemsize = type2aelembytes(ary_elem);
 570 
 571       const TypeX*   ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 572       const TypeInt* sizetype  = ary_t->size();
 573 
 574       if (ld_offs_t->_lo >= header && ld_offs_t->_hi < (sizetype->_lo * elemsize + header)) {
 575         // The load is known to be within bounds. It receives its value from ac.
 576         return ac;
 577       }
 578       // The load is known to be out-of-bounds.
 579     }
 580     // The load could be out-of-bounds. It must not be hoisted but must remain
 581     // dependent on the runtime range check. This is achieved by returning null.
 582   } else if (mem->is_Proj() && mem->in(0) != nullptr && mem->in(0)->is_ArrayCopy()) {
 583     ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
 584 
 585     if (ac->is_arraycopy_validated() ||
 586         ac->is_copyof_validated() ||
 587         ac->is_copyofrange_validated()) {
 588       Node* ld_addp = in(MemNode::Address);
 589       if (ld_addp->is_AddP()) {
 590         Node* ld_base = ld_addp->in(AddPNode::Address);
 591         Node* ld_offs = ld_addp->in(AddPNode::Offset);
 592 
 593         Node* dest = ac->in(ArrayCopyNode::Dest);
 594 
 595         if (dest == ld_base) {
 596           const TypeX* ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 597           assert(!ld_offs_t->empty(), "dead reference should be checked already");
 598           // Take into account vector or unsafe access size
 599           jlong ld_size_in_bytes = (jlong)memory_size();
 600           jlong offset_hi = ld_offs_t->_hi + ld_size_in_bytes - 1;
 601           offset_hi = MIN2(offset_hi, (jlong)(TypeX::MAX->_hi)); // Take care for overflow in 32-bit VM
 602           if (ac->modifies(ld_offs_t->_lo, (intptr_t)offset_hi, phase, can_see_stored_value)) {
 603             return ac;
 604           }
 605           if (!can_see_stored_value) {
 606             mem = ac->in(TypeFunc::Memory);
 607             return ac;
 608           }
 609         }
 610       }
 611     }
 612   }
 613   return nullptr;
 614 }
 615 
 616 ArrayCopyNode* MemNode::find_array_copy_clone(PhaseValues* phase, Node* ld_alloc, Node* mem) const {
 617   if (mem->is_Proj() && mem->in(0) != nullptr && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
 618                                                mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
 619     if (ld_alloc != nullptr) {
 620       // Check if there is an array copy for a clone
 621       Node* mb = mem->in(0);
 622       ArrayCopyNode* ac = nullptr;
 623       if (mb->in(0) != nullptr && mb->in(0)->is_Proj() &&
 624           mb->in(0)->in(0) != nullptr && mb->in(0)->in(0)->is_ArrayCopy()) {
 625         ac = mb->in(0)->in(0)->as_ArrayCopy();
 626       } else {
 627         // Step over GC barrier when ReduceInitialCardMarks is disabled
 628         BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
 629         Node* control_proj_ac = bs->step_over_gc_barrier(mb->in(0));
 630 
 631         if (control_proj_ac->is_Proj() && control_proj_ac->in(0)->is_ArrayCopy()) {
 632           ac = control_proj_ac->in(0)->as_ArrayCopy();
 633         }
 634       }
 635 
 636       if (ac != nullptr && ac->is_clonebasic()) {
 637         AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase);
 638         if (alloc != nullptr && alloc == ld_alloc) {
 639           return ac;
 640         }
 641       }
 642     }
 643   }
 644   return nullptr;
 645 }
 646 
 647 // The logic for reordering loads and stores uses four steps:
 648 // (a) Walk carefully past stores and initializations which we
 649 //     can prove are independent of this load.
 650 // (b) Observe that the next memory state makes an exact match
 651 //     with self (load or store), and locate the relevant store.
 652 // (c) Ensure that, if we were to wire self directly to the store,
 653 //     the optimizer would fold it up somehow.
 654 // (d) Do the rewiring, and return, depending on some other part of
 655 //     the optimizer to fold up the load.
 656 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 657 // specific to loads and stores, so they are handled by the callers.
 658 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 659 //
 660 Node* MemNode::find_previous_store(PhaseValues* phase) {
 661   Node*         ctrl   = in(MemNode::Control);
 662   Node*         adr    = in(MemNode::Address);
 663   intptr_t      offset = 0;
 664   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 665   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 666 
 667   if (offset == Type::OffsetBot)
 668     return nullptr;            // cannot unalias unless there are precise offsets
 669 
 670   const bool adr_maybe_raw = check_if_adr_maybe_raw(adr);
 671   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 672 
 673   intptr_t size_in_bytes = memory_size();
 674 
 675   Node* mem = in(MemNode::Memory);   // start searching here...
 676 
 677   int cnt = 50;             // Cycle limiter
 678   for (;;) {                // While we can dance past unrelated stores...
 679     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 680 
 681     Node* prev = mem;
 682     if (mem->is_Store()) {
 683       Node* st_adr = mem->in(MemNode::Address);
 684       intptr_t st_offset = 0;
 685       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 686       if (st_base == nullptr)
 687         break;              // inscrutable pointer
 688 
 689       // For raw accesses it's not enough to prove that constant offsets don't intersect.
 690       // We need the bases to be the equal in order for the offset check to make sense.
 691       if ((adr_maybe_raw || check_if_adr_maybe_raw(st_adr)) && st_base != base) {
 692         break;
 693       }
 694 
 695       if (st_offset != offset && st_offset != Type::OffsetBot) {
 696         const int MAX_STORE = MAX2(BytesPerLong, (int)MaxVectorSize);
 697         assert(mem->as_Store()->memory_size() <= MAX_STORE, "");
 698         if (st_offset >= offset + size_in_bytes ||
 699             st_offset <= offset - MAX_STORE ||
 700             st_offset <= offset - mem->as_Store()->memory_size()) {
 701           // Success:  The offsets are provably independent.
 702           // (You may ask, why not just test st_offset != offset and be done?
 703           // The answer is that stores of different sizes can co-exist
 704           // in the same sequence of RawMem effects.  We sometimes initialize
 705           // a whole 'tile' of array elements with a single jint or jlong.)
 706           mem = mem->in(MemNode::Memory);
 707           continue;           // (a) advance through independent store memory
 708         }
 709       }
 710       if (st_base != base &&
 711           detect_ptr_independence(base, alloc,
 712                                   st_base,
 713                                   AllocateNode::Ideal_allocation(st_base, phase),
 714                                   phase)) {
 715         // Success:  The bases are provably independent.
 716         mem = mem->in(MemNode::Memory);
 717         continue;           // (a) advance through independent store memory
 718       }
 719 
 720       // (b) At this point, if the bases or offsets do not agree, we lose,
 721       // since we have not managed to prove 'this' and 'mem' independent.
 722       if (st_base == base && st_offset == offset) {
 723         return mem;         // let caller handle steps (c), (d)
 724       }
 725 
 726     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 727       InitializeNode* st_init = mem->in(0)->as_Initialize();
 728       AllocateNode*  st_alloc = st_init->allocation();
 729       if (st_alloc == nullptr)
 730         break;              // something degenerated
 731       bool known_identical = false;
 732       bool known_independent = false;
 733       if (alloc == st_alloc)
 734         known_identical = true;
 735       else if (alloc != nullptr)
 736         known_independent = true;
 737       else if (all_controls_dominate(this, st_alloc))
 738         known_independent = true;
 739 
 740       if (known_independent) {
 741         // The bases are provably independent: Either they are
 742         // manifestly distinct allocations, or else the control
 743         // of this load dominates the store's allocation.
 744         int alias_idx = phase->C->get_alias_index(adr_type());
 745         if (alias_idx == Compile::AliasIdxRaw) {
 746           mem = st_alloc->in(TypeFunc::Memory);
 747         } else {
 748           mem = st_init->memory(alias_idx);
 749         }
 750         continue;           // (a) advance through independent store memory
 751       }
 752 
 753       // (b) at this point, if we are not looking at a store initializing
 754       // the same allocation we are loading from, we lose.
 755       if (known_identical) {
 756         // From caller, can_see_stored_value will consult find_captured_store.
 757         return mem;         // let caller handle steps (c), (d)
 758       }
 759 
 760     } else if (find_previous_arraycopy(phase, alloc, mem, false) != nullptr) {
 761       if (prev != mem) {
 762         // Found an arraycopy but it doesn't affect that load
 763         continue;
 764       }
 765       // Found an arraycopy that may affect that load
 766       return mem;
 767     } else if (addr_t != nullptr && addr_t->is_known_instance_field()) {
 768       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 769       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 770         // ArrayCopyNodes processed here as well.
 771         CallNode *call = mem->in(0)->as_Call();
 772         if (!call->may_modify(addr_t, phase)) {
 773           mem = call->in(TypeFunc::Memory);
 774           continue;         // (a) advance through independent call memory
 775         }
 776       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 777         ArrayCopyNode* ac = nullptr;
 778         if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase, ac)) {
 779           break;
 780         }
 781         mem = mem->in(0)->in(TypeFunc::Memory);
 782         continue;           // (a) advance through independent MemBar memory
 783       } else if (mem->is_ClearArray()) {
 784         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 785           // (the call updated 'mem' value)
 786           continue;         // (a) advance through independent allocation memory
 787         } else {
 788           // Can not bypass initialization of the instance
 789           // we are looking for.
 790           return mem;
 791         }
 792       } else if (mem->is_MergeMem()) {
 793         int alias_idx = phase->C->get_alias_index(adr_type());
 794         mem = mem->as_MergeMem()->memory_at(alias_idx);
 795         continue;           // (a) advance through independent MergeMem memory
 796       }
 797     }
 798 
 799     // Unless there is an explicit 'continue', we must bail out here,
 800     // because 'mem' is an inscrutable memory state (e.g., a call).
 801     break;
 802   }
 803 
 804   return nullptr;              // bail out
 805 }
 806 
 807 //----------------------calculate_adr_type-------------------------------------
 808 // Helper function.  Notices when the given type of address hits top or bottom.
 809 // Also, asserts a cross-check of the type against the expected address type.
 810 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 811   if (t == Type::TOP)  return nullptr; // does not touch memory any more?
 812   #ifdef ASSERT
 813   if (!VerifyAliases || VMError::is_error_reported() || Node::in_dump())  cross_check = nullptr;
 814   #endif
 815   const TypePtr* tp = t->isa_ptr();
 816   if (tp == nullptr) {
 817     assert(cross_check == nullptr || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 818     return TypePtr::BOTTOM;           // touches lots of memory
 819   } else {
 820     #ifdef ASSERT
 821     // %%%% [phh] We don't check the alias index if cross_check is
 822     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 823     if (cross_check != nullptr &&
 824         cross_check != TypePtr::BOTTOM &&
 825         cross_check != TypeRawPtr::BOTTOM) {
 826       // Recheck the alias index, to see if it has changed (due to a bug).
 827       Compile* C = Compile::current();
 828       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 829              "must stay in the original alias category");
 830       // The type of the address must be contained in the adr_type,
 831       // disregarding "null"-ness.
 832       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 833       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 834       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 835              "real address must not escape from expected memory type");
 836     }
 837     #endif
 838     return tp;
 839   }
 840 }
 841 
 842 //=============================================================================
 843 // Should LoadNode::Ideal() attempt to remove control edges?
 844 bool LoadNode::can_remove_control() const {
 845   return !has_pinned_control_dependency();
 846 }
 847 uint LoadNode::size_of() const { return sizeof(*this); }
 848 bool LoadNode::cmp(const Node &n) const {
 849   LoadNode& load = (LoadNode &)n;
 850   return !Type::cmp(_type, load._type) &&
 851          _control_dependency == load._control_dependency &&
 852          _mo == load._mo;
 853 }
 854 const Type *LoadNode::bottom_type() const { return _type; }
 855 uint LoadNode::ideal_reg() const {
 856   return _type->ideal_reg();
 857 }
 858 
 859 #ifndef PRODUCT
 860 void LoadNode::dump_spec(outputStream *st) const {
 861   MemNode::dump_spec(st);
 862   if( !Verbose && !WizardMode ) {
 863     // standard dump does this in Verbose and WizardMode
 864     st->print(" #"); _type->dump_on(st);
 865   }
 866   if (!depends_only_on_test()) {
 867     st->print(" (does not depend only on test, ");
 868     if (control_dependency() == UnknownControl) {
 869       st->print("unknown control");
 870     } else if (control_dependency() == Pinned) {
 871       st->print("pinned");
 872     } else if (adr_type() == TypeRawPtr::BOTTOM) {
 873       st->print("raw access");
 874     } else {
 875       st->print("unknown reason");
 876     }
 877     st->print(")");
 878   }
 879 }
 880 #endif
 881 
 882 #ifdef ASSERT
 883 //----------------------------is_immutable_value-------------------------------
 884 // Helper function to allow a raw load without control edge for some cases
 885 bool LoadNode::is_immutable_value(Node* adr) {
 886   if (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 887       adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal) {
 888 
 889     jlong offset = adr->in(AddPNode::Offset)->find_intptr_t_con(-1);
 890     int offsets[] = {
 891       in_bytes(JavaThread::osthread_offset()),
 892       in_bytes(JavaThread::threadObj_offset()),
 893       in_bytes(JavaThread::vthread_offset()),
 894       in_bytes(JavaThread::scopedValueCache_offset()),
 895     };
 896 
 897     for (size_t i = 0; i < sizeof offsets / sizeof offsets[0]; i++) {
 898       if (offset == offsets[i]) {
 899         return true;
 900       }
 901     }
 902   }
 903 
 904   return false;
 905 }
 906 #endif
 907 
 908 //----------------------------LoadNode::make-----------------------------------
 909 // Polymorphic factory method:
 910 Node* LoadNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, BasicType bt, MemOrd mo,
 911                      ControlDependency control_dependency, bool require_atomic_access, bool unaligned, bool mismatched, bool unsafe, uint8_t barrier_data) {
 912   Compile* C = gvn.C;
 913 
 914   // sanity check the alias category against the created node type
 915   assert(!(adr_type->isa_oopptr() &&
 916            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 917          "use LoadKlassNode instead");
 918   assert(!(adr_type->isa_aryptr() &&
 919            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 920          "use LoadRangeNode instead");
 921   // Check control edge of raw loads
 922   assert( ctl != nullptr || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 923           // oop will be recorded in oop map if load crosses safepoint
 924           rt->isa_oopptr() || is_immutable_value(adr),
 925           "raw memory operations should have control edge");
 926   LoadNode* load = nullptr;
 927   switch (bt) {
 928   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 929   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 930   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 931   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 932   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 933   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic_access); break;
 934   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 935   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency, require_atomic_access); break;
 936   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 937   case T_OBJECT:
 938 #ifdef _LP64
 939     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 940       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 941     } else
 942 #endif
 943     {
 944       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 945       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
 946     }
 947     break;
 948   default:
 949     ShouldNotReachHere();
 950     break;
 951   }
 952   assert(load != nullptr, "LoadNode should have been created");
 953   if (unaligned) {
 954     load->set_unaligned_access();
 955   }
 956   if (mismatched) {
 957     load->set_mismatched_access();
 958   }
 959   if (unsafe) {
 960     load->set_unsafe_access();
 961   }
 962   load->set_barrier_data(barrier_data);
 963   if (load->Opcode() == Op_LoadN) {
 964     Node* ld = gvn.transform(load);
 965     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 966   }
 967 
 968   return load;
 969 }
 970 
 971 //------------------------------hash-------------------------------------------
 972 uint LoadNode::hash() const {
 973   // unroll addition of interesting fields
 974   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 975 }
 976 
 977 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 978   if ((atp != nullptr) && (atp->index() >= Compile::AliasIdxRaw)) {
 979     bool non_volatile = (atp->field() != nullptr) && !atp->field()->is_volatile();
 980     bool is_stable_ary = FoldStableValues &&
 981                          (tp != nullptr) && (tp->isa_aryptr() != nullptr) &&
 982                          tp->isa_aryptr()->is_stable();
 983 
 984     return (eliminate_boxing && non_volatile) || is_stable_ary;
 985   }
 986 
 987   return false;
 988 }
 989 
 990 LoadNode* LoadNode::pin_array_access_node() const {
 991   const TypePtr* adr_type = this->adr_type();
 992   if (adr_type != nullptr && adr_type->isa_aryptr()) {
 993     return clone_pinned();
 994   }
 995   return nullptr;
 996 }
 997 
 998 // Is the value loaded previously stored by an arraycopy? If so return
 999 // a load node that reads from the source array so we may be able to
1000 // optimize out the ArrayCopy node later.
1001 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
1002   Node* ld_adr = in(MemNode::Address);
1003   intptr_t ld_off = 0;
1004   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
1005   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
1006   if (ac != nullptr) {
1007     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
1008 
1009     Node* mem = ac->in(TypeFunc::Memory);
1010     Node* ctl = ac->in(0);
1011     Node* src = ac->in(ArrayCopyNode::Src);
1012 
1013     if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
1014       return nullptr;
1015     }
1016 
1017     // load depends on the tests that validate the arraycopy
1018     LoadNode* ld = clone_pinned();
1019     Node* addp = in(MemNode::Address)->clone();
1020     if (ac->as_ArrayCopy()->is_clonebasic()) {
1021       assert(ld_alloc != nullptr, "need an alloc");
1022       assert(addp->is_AddP(), "address must be addp");
1023       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1024       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Base)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)), "strange pattern");
1025       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Address)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)), "strange pattern");
1026       addp->set_req(AddPNode::Base, src);
1027       addp->set_req(AddPNode::Address, src);
1028     } else {
1029       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
1030              ac->as_ArrayCopy()->is_copyof_validated() ||
1031              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
1032       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
1033       addp->set_req(AddPNode::Base, src);
1034       addp->set_req(AddPNode::Address, src);
1035 
1036       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
1037       BasicType ary_elem = ary_t->isa_aryptr()->elem()->array_element_basic_type();
1038       if (is_reference_type(ary_elem, true)) ary_elem = T_OBJECT;
1039 
1040       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
1041       uint shift  = exact_log2(type2aelembytes(ary_elem));
1042 
1043       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
1044 #ifdef _LP64
1045       diff = phase->transform(new ConvI2LNode(diff));
1046 #endif
1047       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
1048 
1049       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
1050       addp->set_req(AddPNode::Offset, offset);
1051     }
1052     addp = phase->transform(addp);
1053 #ifdef ASSERT
1054     const TypePtr* adr_type = phase->type(addp)->is_ptr();
1055     ld->_adr_type = adr_type;
1056 #endif
1057     ld->set_req(MemNode::Address, addp);
1058     ld->set_req(0, ctl);
1059     ld->set_req(MemNode::Memory, mem);
1060     return ld;
1061   }
1062   return nullptr;
1063 }
1064 
1065 
1066 //---------------------------can_see_stored_value------------------------------
1067 // This routine exists to make sure this set of tests is done the same
1068 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
1069 // will change the graph shape in a way which makes memory alive twice at the
1070 // same time (uses the Oracle model of aliasing), then some
1071 // LoadXNode::Identity will fold things back to the equivalence-class model
1072 // of aliasing.
1073 Node* MemNode::can_see_stored_value(Node* st, PhaseValues* phase) const {
1074   Node* ld_adr = in(MemNode::Address);
1075   intptr_t ld_off = 0;
1076   Node* ld_base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ld_off);
1077   Node* ld_alloc = AllocateNode::Ideal_allocation(ld_base, phase);
1078   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
1079   Compile::AliasType* atp = (tp != nullptr) ? phase->C->alias_type(tp) : nullptr;
1080   // This is more general than load from boxing objects.
1081   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
1082     uint alias_idx = atp->index();
1083     Node* result = nullptr;
1084     Node* current = st;
1085     // Skip through chains of MemBarNodes checking the MergeMems for
1086     // new states for the slice of this load.  Stop once any other
1087     // kind of node is encountered.  Loads from final memory can skip
1088     // through any kind of MemBar but normal loads shouldn't skip
1089     // through MemBarAcquire since the could allow them to move out of
1090     // a synchronized region. It is not safe to step over MemBarCPUOrder,
1091     // because alias info above them may be inaccurate (e.g., due to
1092     // mixed/mismatched unsafe accesses).
1093     bool is_final_mem = !atp->is_rewritable();
1094     while (current->is_Proj()) {
1095       int opc = current->in(0)->Opcode();
1096       if ((is_final_mem && (opc == Op_MemBarAcquire ||
1097                             opc == Op_MemBarAcquireLock ||
1098                             opc == Op_LoadFence)) ||
1099           opc == Op_MemBarRelease ||
1100           opc == Op_StoreFence ||
1101           opc == Op_MemBarReleaseLock ||
1102           opc == Op_MemBarStoreStore ||
1103           opc == Op_StoreStoreFence) {
1104         Node* mem = current->in(0)->in(TypeFunc::Memory);
1105         if (mem->is_MergeMem()) {
1106           MergeMemNode* merge = mem->as_MergeMem();
1107           Node* new_st = merge->memory_at(alias_idx);
1108           if (new_st == merge->base_memory()) {
1109             // Keep searching
1110             current = new_st;
1111             continue;
1112           }
1113           // Save the new memory state for the slice and fall through
1114           // to exit.
1115           result = new_st;
1116         }
1117       }
1118       break;
1119     }
1120     if (result != nullptr) {
1121       st = result;
1122     }
1123   }
1124 
1125   // Loop around twice in the case Load -> Initialize -> Store.
1126   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1127   for (int trip = 0; trip <= 1; trip++) {
1128 
1129     if (st->is_Store()) {
1130       Node* st_adr = st->in(MemNode::Address);
1131       if (st_adr != ld_adr) {
1132         // Try harder before giving up. Unify base pointers with casts (e.g., raw/non-raw pointers).
1133         intptr_t st_off = 0;
1134         Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_off);
1135         if (ld_base == nullptr)                                return nullptr;
1136         if (st_base == nullptr)                                return nullptr;
1137         if (!ld_base->eqv_uncast(st_base, /*keep_deps=*/true)) return nullptr;
1138         if (ld_off != st_off)                                  return nullptr;
1139         if (ld_off == Type::OffsetBot)                         return nullptr;
1140         // Same base, same offset.
1141         // Possible improvement for arrays: check index value instead of absolute offset.
1142 
1143         // At this point we have proven something like this setup:
1144         //   B = << base >>
1145         //   L =  LoadQ(AddP(Check/CastPP(B), #Off))
1146         //   S = StoreQ(AddP(             B , #Off), V)
1147         // (Actually, we haven't yet proven the Q's are the same.)
1148         // In other words, we are loading from a casted version of
1149         // the same pointer-and-offset that we stored to.
1150         // Casted version may carry a dependency and it is respected.
1151         // Thus, we are able to replace L by V.
1152       }
1153       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1154       if (store_Opcode() != st->Opcode()) {
1155         return nullptr;
1156       }
1157       // LoadVector/StoreVector needs additional check to ensure the types match.
1158       if (st->is_StoreVector()) {
1159         const TypeVect*  in_vt = st->as_StoreVector()->vect_type();
1160         const TypeVect* out_vt = as_LoadVector()->vect_type();
1161         if (in_vt != out_vt) {
1162           return nullptr;
1163         }
1164       }
1165       return st->in(MemNode::ValueIn);
1166     }
1167 
1168     // A load from a freshly-created object always returns zero.
1169     // (This can happen after LoadNode::Ideal resets the load's memory input
1170     // to find_captured_store, which returned InitializeNode::zero_memory.)
1171     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1172         (st->in(0) == ld_alloc) &&
1173         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1174       // return a zero value for the load's basic type
1175       // (This is one of the few places where a generic PhaseTransform
1176       // can create new nodes.  Think of it as lazily manifesting
1177       // virtually pre-existing constants.)
1178       if (memory_type() != T_VOID) {
1179         if (ReduceBulkZeroing || find_array_copy_clone(phase, ld_alloc, in(MemNode::Memory)) == nullptr) {
1180           // If ReduceBulkZeroing is disabled, we need to check if the allocation does not belong to an
1181           // ArrayCopyNode clone. If it does, then we cannot assume zero since the initialization is done
1182           // by the ArrayCopyNode.
1183           return phase->zerocon(memory_type());
1184         }
1185       } else {
1186         // TODO: materialize all-zero vector constant
1187         assert(!isa_Load() || as_Load()->type()->isa_vect(), "");
1188       }
1189     }
1190 
1191     // A load from an initialization barrier can match a captured store.
1192     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1193       InitializeNode* init = st->in(0)->as_Initialize();
1194       AllocateNode* alloc = init->allocation();
1195       if ((alloc != nullptr) && (alloc == ld_alloc)) {
1196         // examine a captured store value
1197         st = init->find_captured_store(ld_off, memory_size(), phase);
1198         if (st != nullptr) {
1199           continue;             // take one more trip around
1200         }
1201       }
1202     }
1203 
1204     // Load boxed value from result of valueOf() call is input parameter.
1205     if (this->is_Load() && ld_adr->is_AddP() &&
1206         (tp != nullptr) && tp->is_ptr_to_boxed_value()) {
1207       intptr_t ignore = 0;
1208       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1209       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1210       base = bs->step_over_gc_barrier(base);
1211       if (base != nullptr && base->is_Proj() &&
1212           base->as_Proj()->_con == TypeFunc::Parms &&
1213           base->in(0)->is_CallStaticJava() &&
1214           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1215         return base->in(0)->in(TypeFunc::Parms);
1216       }
1217     }
1218 
1219     break;
1220   }
1221 
1222   return nullptr;
1223 }
1224 
1225 //----------------------is_instance_field_load_with_local_phi------------------
1226 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1227   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1228       in(Address)->is_AddP() ) {
1229     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1230     // Only instances and boxed values.
1231     if( t_oop != nullptr &&
1232         (t_oop->is_ptr_to_boxed_value() ||
1233          t_oop->is_known_instance_field()) &&
1234         t_oop->offset() != Type::OffsetBot &&
1235         t_oop->offset() != Type::OffsetTop) {
1236       return true;
1237     }
1238   }
1239   return false;
1240 }
1241 
1242 //------------------------------Identity---------------------------------------
1243 // Loads are identity if previous store is to same address
1244 Node* LoadNode::Identity(PhaseGVN* phase) {
1245   // If the previous store-maker is the right kind of Store, and the store is
1246   // to the same address, then we are equal to the value stored.
1247   Node* mem = in(Memory);
1248   Node* value = can_see_stored_value(mem, phase);
1249   if( value ) {
1250     // byte, short & char stores truncate naturally.
1251     // A load has to load the truncated value which requires
1252     // some sort of masking operation and that requires an
1253     // Ideal call instead of an Identity call.
1254     if (memory_size() < BytesPerInt) {
1255       // If the input to the store does not fit with the load's result type,
1256       // it must be truncated via an Ideal call.
1257       if (!phase->type(value)->higher_equal(phase->type(this)))
1258         return this;
1259     }
1260     // (This works even when value is a Con, but LoadNode::Value
1261     // usually runs first, producing the singleton type of the Con.)
1262     if (!has_pinned_control_dependency() || value->is_Con()) {
1263       return value;
1264     } else {
1265       return this;
1266     }
1267   }
1268 
1269   if (has_pinned_control_dependency()) {
1270     return this;
1271   }
1272   // Search for an existing data phi which was generated before for the same
1273   // instance's field to avoid infinite generation of phis in a loop.
1274   Node *region = mem->in(0);
1275   if (is_instance_field_load_with_local_phi(region)) {
1276     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1277     int this_index  = phase->C->get_alias_index(addr_t);
1278     int this_offset = addr_t->offset();
1279     int this_iid    = addr_t->instance_id();
1280     if (!addr_t->is_known_instance() &&
1281          addr_t->is_ptr_to_boxed_value()) {
1282       // Use _idx of address base (could be Phi node) for boxed values.
1283       intptr_t   ignore = 0;
1284       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1285       if (base == nullptr) {
1286         return this;
1287       }
1288       this_iid = base->_idx;
1289     }
1290     const Type* this_type = bottom_type();
1291     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1292       Node* phi = region->fast_out(i);
1293       if (phi->is_Phi() && phi != mem &&
1294           phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1295         return phi;
1296       }
1297     }
1298   }
1299 
1300   return this;
1301 }
1302 
1303 // Construct an equivalent unsigned load.
1304 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1305   BasicType bt = T_ILLEGAL;
1306   const Type* rt = nullptr;
1307   switch (Opcode()) {
1308     case Op_LoadUB: return this;
1309     case Op_LoadUS: return this;
1310     case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1311     case Op_LoadS: bt = T_CHAR;    rt = TypeInt::CHAR;  break;
1312     default:
1313       assert(false, "no unsigned variant: %s", Name());
1314       return nullptr;
1315   }
1316   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1317                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1318                         false /*require_atomic_access*/, is_unaligned_access(), is_mismatched_access());
1319 }
1320 
1321 // Construct an equivalent signed load.
1322 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1323   BasicType bt = T_ILLEGAL;
1324   const Type* rt = nullptr;
1325   switch (Opcode()) {
1326     case Op_LoadUB: bt = T_BYTE;  rt = TypeInt::BYTE;  break;
1327     case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1328     case Op_LoadB: // fall through
1329     case Op_LoadS: // fall through
1330     case Op_LoadI: // fall through
1331     case Op_LoadL: return this;
1332     default:
1333       assert(false, "no signed variant: %s", Name());
1334       return nullptr;
1335   }
1336   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1337                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1338                         false /*require_atomic_access*/, is_unaligned_access(), is_mismatched_access());
1339 }
1340 
1341 bool LoadNode::has_reinterpret_variant(const Type* rt) {
1342   BasicType bt = rt->basic_type();
1343   switch (Opcode()) {
1344     case Op_LoadI: return (bt == T_FLOAT);
1345     case Op_LoadL: return (bt == T_DOUBLE);
1346     case Op_LoadF: return (bt == T_INT);
1347     case Op_LoadD: return (bt == T_LONG);
1348 
1349     default: return false;
1350   }
1351 }
1352 
1353 Node* LoadNode::convert_to_reinterpret_load(PhaseGVN& gvn, const Type* rt) {
1354   BasicType bt = rt->basic_type();
1355   assert(has_reinterpret_variant(rt), "no reinterpret variant: %s %s", Name(), type2name(bt));
1356   bool is_mismatched = is_mismatched_access();
1357   const TypeRawPtr* raw_type = gvn.type(in(MemNode::Memory))->isa_rawptr();
1358   if (raw_type == nullptr) {
1359     is_mismatched = true; // conservatively match all non-raw accesses as mismatched
1360   }
1361   const int op = Opcode();
1362   bool require_atomic_access = (op == Op_LoadL && ((LoadLNode*)this)->require_atomic_access()) ||
1363                                (op == Op_LoadD && ((LoadDNode*)this)->require_atomic_access());
1364   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1365                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1366                         require_atomic_access, is_unaligned_access(), is_mismatched);
1367 }
1368 
1369 bool StoreNode::has_reinterpret_variant(const Type* vt) {
1370   BasicType bt = vt->basic_type();
1371   switch (Opcode()) {
1372     case Op_StoreI: return (bt == T_FLOAT);
1373     case Op_StoreL: return (bt == T_DOUBLE);
1374     case Op_StoreF: return (bt == T_INT);
1375     case Op_StoreD: return (bt == T_LONG);
1376 
1377     default: return false;
1378   }
1379 }
1380 
1381 Node* StoreNode::convert_to_reinterpret_store(PhaseGVN& gvn, Node* val, const Type* vt) {
1382   BasicType bt = vt->basic_type();
1383   assert(has_reinterpret_variant(vt), "no reinterpret variant: %s %s", Name(), type2name(bt));
1384   const int op = Opcode();
1385   bool require_atomic_access = (op == Op_StoreL && ((StoreLNode*)this)->require_atomic_access()) ||
1386                                (op == Op_StoreD && ((StoreDNode*)this)->require_atomic_access());
1387   StoreNode* st = StoreNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1388                                   raw_adr_type(), val, bt, _mo, require_atomic_access);
1389 
1390   bool is_mismatched = is_mismatched_access();
1391   const TypeRawPtr* raw_type = gvn.type(in(MemNode::Memory))->isa_rawptr();
1392   if (raw_type == nullptr) {
1393     is_mismatched = true; // conservatively match all non-raw accesses as mismatched
1394   }
1395   if (is_mismatched) {
1396     st->set_mismatched_access();
1397   }
1398   return st;
1399 }
1400 
1401 // We're loading from an object which has autobox behaviour.
1402 // If this object is result of a valueOf call we'll have a phi
1403 // merging a newly allocated object and a load from the cache.
1404 // We want to replace this load with the original incoming
1405 // argument to the valueOf call.
1406 Node* LoadNode::eliminate_autobox(PhaseIterGVN* igvn) {
1407   assert(igvn->C->eliminate_boxing(), "sanity");
1408   intptr_t ignore = 0;
1409   Node* base = AddPNode::Ideal_base_and_offset(in(Address), igvn, ignore);
1410   if ((base == nullptr) || base->is_Phi()) {
1411     // Push the loads from the phi that comes from valueOf up
1412     // through it to allow elimination of the loads and the recovery
1413     // of the original value. It is done in split_through_phi().
1414     return nullptr;
1415   } else if (base->is_Load() ||
1416              (base->is_DecodeN() && base->in(1)->is_Load())) {
1417     // Eliminate the load of boxed value for integer types from the cache
1418     // array by deriving the value from the index into the array.
1419     // Capture the offset of the load and then reverse the computation.
1420 
1421     // Get LoadN node which loads a boxing object from 'cache' array.
1422     if (base->is_DecodeN()) {
1423       base = base->in(1);
1424     }
1425     if (!base->in(Address)->is_AddP()) {
1426       return nullptr; // Complex address
1427     }
1428     AddPNode* address = base->in(Address)->as_AddP();
1429     Node* cache_base = address->in(AddPNode::Base);
1430     if ((cache_base != nullptr) && cache_base->is_DecodeN()) {
1431       // Get ConP node which is static 'cache' field.
1432       cache_base = cache_base->in(1);
1433     }
1434     if ((cache_base != nullptr) && cache_base->is_Con()) {
1435       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1436       if ((base_type != nullptr) && base_type->is_autobox_cache()) {
1437         Node* elements[4];
1438         int shift = exact_log2(type2aelembytes(T_OBJECT));
1439         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1440         if (count > 0 && elements[0]->is_Con() &&
1441             (count == 1 ||
1442              (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1443                             elements[1]->in(2) == igvn->intcon(shift)))) {
1444           ciObjArray* array = base_type->const_oop()->as_obj_array();
1445           // Fetch the box object cache[0] at the base of the array and get its value
1446           ciInstance* box = array->obj_at(0)->as_instance();
1447           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1448           assert(ik->is_box_klass(), "sanity");
1449           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1450           if (ik->nof_nonstatic_fields() == 1) {
1451             // This should be true nonstatic_field_at requires calling
1452             // nof_nonstatic_fields so check it anyway
1453             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1454             BasicType bt = c.basic_type();
1455             // Only integer types have boxing cache.
1456             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1457                    bt == T_BYTE    || bt == T_SHORT ||
1458                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1459             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1460             if (cache_low != (int)cache_low) {
1461               return nullptr; // should not happen since cache is array indexed by value
1462             }
1463             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1464             if (offset != (int)offset) {
1465               return nullptr; // should not happen since cache is array indexed by value
1466             }
1467            // Add up all the offsets making of the address of the load
1468             Node* result = elements[0];
1469             for (int i = 1; i < count; i++) {
1470               result = igvn->transform(new AddXNode(result, elements[i]));
1471             }
1472             // Remove the constant offset from the address and then
1473             result = igvn->transform(new AddXNode(result, igvn->MakeConX(-(int)offset)));
1474             // remove the scaling of the offset to recover the original index.
1475             if (result->Opcode() == Op_LShiftX && result->in(2) == igvn->intcon(shift)) {
1476               // Peel the shift off directly but wrap it in a dummy node
1477               // since Ideal can't return existing nodes
1478               igvn->_worklist.push(result); // remove dead node later
1479               result = new RShiftXNode(result->in(1), igvn->intcon(0));
1480             } else if (result->is_Add() && result->in(2)->is_Con() &&
1481                        result->in(1)->Opcode() == Op_LShiftX &&
1482                        result->in(1)->in(2) == igvn->intcon(shift)) {
1483               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1484               // but for boxing cache access we know that X<<Z will not overflow
1485               // (there is range check) so we do this optimizatrion by hand here.
1486               igvn->_worklist.push(result); // remove dead node later
1487               Node* add_con = new RShiftXNode(result->in(2), igvn->intcon(shift));
1488               result = new AddXNode(result->in(1)->in(1), igvn->transform(add_con));
1489             } else {
1490               result = new RShiftXNode(result, igvn->intcon(shift));
1491             }
1492 #ifdef _LP64
1493             if (bt != T_LONG) {
1494               result = new ConvL2INode(igvn->transform(result));
1495             }
1496 #else
1497             if (bt == T_LONG) {
1498               result = new ConvI2LNode(igvn->transform(result));
1499             }
1500 #endif
1501             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1502             // Need to preserve unboxing load type if it is unsigned.
1503             switch(this->Opcode()) {
1504               case Op_LoadUB:
1505                 result = new AndINode(igvn->transform(result), igvn->intcon(0xFF));
1506                 break;
1507               case Op_LoadUS:
1508                 result = new AndINode(igvn->transform(result), igvn->intcon(0xFFFF));
1509                 break;
1510             }
1511             return result;
1512           }
1513         }
1514       }
1515     }
1516   }
1517   return nullptr;
1518 }
1519 
1520 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1521   Node* region = phi->in(0);
1522   if (region == nullptr) {
1523     return false; // Wait stable graph
1524   }
1525   uint cnt = phi->req();
1526   for (uint i = 1; i < cnt; i++) {
1527     Node* rc = region->in(i);
1528     if (rc == nullptr || phase->type(rc) == Type::TOP)
1529       return false; // Wait stable graph
1530     Node* in = phi->in(i);
1531     if (in == nullptr || phase->type(in) == Type::TOP)
1532       return false; // Wait stable graph
1533   }
1534   return true;
1535 }
1536 //------------------------------split_through_phi------------------------------
1537 // Split instance or boxed field load through Phi.
1538 Node* LoadNode::split_through_phi(PhaseGVN* phase) {
1539   if (req() > 3) {
1540     assert(is_LoadVector() && Opcode() != Op_LoadVector, "load has too many inputs");
1541     // LoadVector subclasses such as LoadVectorMasked have extra inputs that the logic below doesn't take into account
1542     return nullptr;
1543   }
1544   Node* mem     = in(Memory);
1545   Node* address = in(Address);
1546   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1547 
1548   assert((t_oop != nullptr) &&
1549          (t_oop->is_known_instance_field() ||
1550           t_oop->is_ptr_to_boxed_value()), "invalid conditions");
1551 
1552   Compile* C = phase->C;
1553   intptr_t ignore = 0;
1554   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1555   bool base_is_phi = (base != nullptr) && base->is_Phi();
1556   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1557                            (base != nullptr) && (base == address->in(AddPNode::Base)) &&
1558                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1559 
1560   if (!((mem->is_Phi() || base_is_phi) &&
1561         (load_boxed_values || t_oop->is_known_instance_field()))) {
1562     return nullptr; // memory is not Phi
1563   }
1564 
1565   if (mem->is_Phi()) {
1566     if (!stable_phi(mem->as_Phi(), phase)) {
1567       return nullptr; // Wait stable graph
1568     }
1569     uint cnt = mem->req();
1570     // Check for loop invariant memory.
1571     if (cnt == 3) {
1572       for (uint i = 1; i < cnt; i++) {
1573         Node* in = mem->in(i);
1574         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1575         if (m == mem) {
1576           if (i == 1) {
1577             // if the first edge was a loop, check second edge too.
1578             // If both are replaceable - we are in an infinite loop
1579             Node *n = optimize_memory_chain(mem->in(2), t_oop, this, phase);
1580             if (n == mem) {
1581               break;
1582             }
1583           }
1584           set_req(Memory, mem->in(cnt - i));
1585           return this; // made change
1586         }
1587       }
1588     }
1589   }
1590   if (base_is_phi) {
1591     if (!stable_phi(base->as_Phi(), phase)) {
1592       return nullptr; // Wait stable graph
1593     }
1594     uint cnt = base->req();
1595     // Check for loop invariant memory.
1596     if (cnt == 3) {
1597       for (uint i = 1; i < cnt; i++) {
1598         if (base->in(i) == base) {
1599           return nullptr; // Wait stable graph
1600         }
1601       }
1602     }
1603   }
1604 
1605   // Split through Phi (see original code in loopopts.cpp).
1606   assert(C->have_alias_type(t_oop), "instance should have alias type");
1607 
1608   // Do nothing here if Identity will find a value
1609   // (to avoid infinite chain of value phis generation).
1610   if (this != Identity(phase)) {
1611     return nullptr;
1612   }
1613 
1614   // Select Region to split through.
1615   Node* region;
1616   if (!base_is_phi) {
1617     assert(mem->is_Phi(), "sanity");
1618     region = mem->in(0);
1619     // Skip if the region dominates some control edge of the address.
1620     if (!MemNode::all_controls_dominate(address, region))
1621       return nullptr;
1622   } else if (!mem->is_Phi()) {
1623     assert(base_is_phi, "sanity");
1624     region = base->in(0);
1625     // Skip if the region dominates some control edge of the memory.
1626     if (!MemNode::all_controls_dominate(mem, region))
1627       return nullptr;
1628   } else if (base->in(0) != mem->in(0)) {
1629     assert(base_is_phi && mem->is_Phi(), "sanity");
1630     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1631       region = base->in(0);
1632     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1633       region = mem->in(0);
1634     } else {
1635       return nullptr; // complex graph
1636     }
1637   } else {
1638     assert(base->in(0) == mem->in(0), "sanity");
1639     region = mem->in(0);
1640   }
1641 
1642   const Type* this_type = this->bottom_type();
1643   int this_index  = C->get_alias_index(t_oop);
1644   int this_offset = t_oop->offset();
1645   int this_iid    = t_oop->instance_id();
1646   if (!t_oop->is_known_instance() && load_boxed_values) {
1647     // Use _idx of address base for boxed values.
1648     this_iid = base->_idx;
1649   }
1650   PhaseIterGVN* igvn = phase->is_IterGVN();
1651   Node* phi = new PhiNode(region, this_type, nullptr, mem->_idx, this_iid, this_index, this_offset);
1652   for (uint i = 1; i < region->req(); i++) {
1653     Node* x;
1654     Node* the_clone = nullptr;
1655     Node* in = region->in(i);
1656     if (region->is_CountedLoop() && region->as_Loop()->is_strip_mined() && i == LoopNode::EntryControl &&
1657         in != nullptr && in->is_OuterStripMinedLoop()) {
1658       // No node should go in the outer strip mined loop
1659       in = in->in(LoopNode::EntryControl);
1660     }
1661     if (in == nullptr || in == C->top()) {
1662       x = C->top();      // Dead path?  Use a dead data op
1663     } else {
1664       x = this->clone();        // Else clone up the data op
1665       the_clone = x;            // Remember for possible deletion.
1666       // Alter data node to use pre-phi inputs
1667       if (this->in(0) == region) {
1668         x->set_req(0, in);
1669       } else {
1670         x->set_req(0, nullptr);
1671       }
1672       if (mem->is_Phi() && (mem->in(0) == region)) {
1673         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1674       }
1675       if (address->is_Phi() && address->in(0) == region) {
1676         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1677       }
1678       if (base_is_phi && (base->in(0) == region)) {
1679         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1680         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1681         x->set_req(Address, adr_x);
1682       }
1683     }
1684     // Check for a 'win' on some paths
1685     const Type *t = x->Value(igvn);
1686 
1687     bool singleton = t->singleton();
1688 
1689     // See comments in PhaseIdealLoop::split_thru_phi().
1690     if (singleton && t == Type::TOP) {
1691       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1692     }
1693 
1694     if (singleton) {
1695       x = igvn->makecon(t);
1696     } else {
1697       // We now call Identity to try to simplify the cloned node.
1698       // Note that some Identity methods call phase->type(this).
1699       // Make sure that the type array is big enough for
1700       // our new node, even though we may throw the node away.
1701       // (This tweaking with igvn only works because x is a new node.)
1702       igvn->set_type(x, t);
1703       // If x is a TypeNode, capture any more-precise type permanently into Node
1704       // otherwise it will be not updated during igvn->transform since
1705       // igvn->type(x) is set to x->Value() already.
1706       x->raise_bottom_type(t);
1707       Node* y = x->Identity(igvn);
1708       if (y != x) {
1709         x = y;
1710       } else {
1711         y = igvn->hash_find_insert(x);
1712         if (y) {
1713           x = y;
1714         } else {
1715           // Else x is a new node we are keeping
1716           // We do not need register_new_node_with_optimizer
1717           // because set_type has already been called.
1718           igvn->_worklist.push(x);
1719         }
1720       }
1721     }
1722     if (x != the_clone && the_clone != nullptr) {
1723       igvn->remove_dead_node(the_clone);
1724     }
1725     phi->set_req(i, x);
1726   }
1727   // Record Phi
1728   igvn->register_new_node_with_optimizer(phi);
1729   return phi;
1730 }
1731 
1732 AllocateNode* LoadNode::is_new_object_mark_load(PhaseGVN *phase) const {
1733   if (Opcode() == Op_LoadX) {
1734     Node* address = in(MemNode::Address);
1735     AllocateNode* alloc = AllocateNode::Ideal_allocation(address, phase);
1736     Node* mem = in(MemNode::Memory);
1737     if (alloc != nullptr && mem->is_Proj() &&
1738         mem->in(0) != nullptr &&
1739         mem->in(0) == alloc->initialization() &&
1740         alloc->initialization()->proj_out_or_null(0) != nullptr) {
1741       return alloc;
1742     }
1743   }
1744   return nullptr;
1745 }
1746 
1747 
1748 //------------------------------Ideal------------------------------------------
1749 // If the load is from Field memory and the pointer is non-null, it might be possible to
1750 // zero out the control input.
1751 // If the offset is constant and the base is an object allocation,
1752 // try to hook me up to the exact initializing store.
1753 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1754   if (has_pinned_control_dependency()) {
1755     return nullptr;
1756   }
1757   Node* p = MemNode::Ideal_common(phase, can_reshape);
1758   if (p)  return (p == NodeSentinel) ? nullptr : p;
1759 
1760   Node* ctrl    = in(MemNode::Control);
1761   Node* address = in(MemNode::Address);
1762   bool progress = false;
1763 
1764   bool addr_mark = ((phase->type(address)->isa_oopptr() || phase->type(address)->isa_narrowoop()) &&
1765          phase->type(address)->is_ptr()->offset() == oopDesc::mark_offset_in_bytes());
1766 
1767   // Skip up past a SafePoint control.  Cannot do this for Stores because
1768   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1769   if( ctrl != nullptr && ctrl->Opcode() == Op_SafePoint &&
1770       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw  &&
1771       !addr_mark &&
1772       (depends_only_on_test() || has_unknown_control_dependency())) {
1773     ctrl = ctrl->in(0);
1774     set_req(MemNode::Control,ctrl);
1775     progress = true;
1776   }
1777 
1778   intptr_t ignore = 0;
1779   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1780   if (base != nullptr
1781       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1782     // Check for useless control edge in some common special cases
1783     if (in(MemNode::Control) != nullptr
1784         && can_remove_control()
1785         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1786         && all_controls_dominate(base, phase->C->start())) {
1787       // A method-invariant, non-null address (constant or 'this' argument).
1788       set_req(MemNode::Control, nullptr);
1789       progress = true;
1790     }
1791   }
1792 
1793   Node* mem = in(MemNode::Memory);
1794   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1795 
1796   if (can_reshape && (addr_t != nullptr)) {
1797     // try to optimize our memory input
1798     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1799     if (opt_mem != mem) {
1800       set_req_X(MemNode::Memory, opt_mem, phase);
1801       if (phase->type( opt_mem ) == Type::TOP) return nullptr;
1802       return this;
1803     }
1804     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1805     if ((t_oop != nullptr) &&
1806         (t_oop->is_known_instance_field() ||
1807          t_oop->is_ptr_to_boxed_value())) {
1808       PhaseIterGVN *igvn = phase->is_IterGVN();
1809       assert(igvn != nullptr, "must be PhaseIterGVN when can_reshape is true");
1810       if (igvn->_worklist.member(opt_mem)) {
1811         // Delay this transformation until memory Phi is processed.
1812         igvn->_worklist.push(this);
1813         return nullptr;
1814       }
1815       // Split instance field load through Phi.
1816       Node* result = split_through_phi(phase);
1817       if (result != nullptr) return result;
1818 
1819       if (t_oop->is_ptr_to_boxed_value()) {
1820         Node* result = eliminate_autobox(igvn);
1821         if (result != nullptr) return result;
1822       }
1823     }
1824   }
1825 
1826   // Is there a dominating load that loads the same value?  Leave
1827   // anything that is not a load of a field/array element (like
1828   // barriers etc.) alone
1829   if (in(0) != nullptr && !adr_type()->isa_rawptr() && can_reshape) {
1830     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1831       Node *use = mem->fast_out(i);
1832       if (use != this &&
1833           use->Opcode() == Opcode() &&
1834           use->in(0) != nullptr &&
1835           use->in(0) != in(0) &&
1836           use->in(Address) == in(Address)) {
1837         Node* ctl = in(0);
1838         for (int i = 0; i < 10 && ctl != nullptr; i++) {
1839           ctl = IfNode::up_one_dom(ctl);
1840           if (ctl == use->in(0)) {
1841             set_req(0, use->in(0));
1842             return this;
1843           }
1844         }
1845       }
1846     }
1847   }
1848 
1849   // Check for prior store with a different base or offset; make Load
1850   // independent.  Skip through any number of them.  Bail out if the stores
1851   // are in an endless dead cycle and report no progress.  This is a key
1852   // transform for Reflection.  However, if after skipping through the Stores
1853   // we can't then fold up against a prior store do NOT do the transform as
1854   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1855   // array memory alive twice: once for the hoisted Load and again after the
1856   // bypassed Store.  This situation only works if EVERYBODY who does
1857   // anti-dependence work knows how to bypass.  I.e. we need all
1858   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1859   // the alias index stuff.  So instead, peek through Stores and IFF we can
1860   // fold up, do so.
1861   Node* prev_mem = find_previous_store(phase);
1862   if (prev_mem != nullptr) {
1863     Node* value = can_see_arraycopy_value(prev_mem, phase);
1864     if (value != nullptr) {
1865       return value;
1866     }
1867   }
1868   // Steps (a), (b):  Walk past independent stores to find an exact match.
1869   if (prev_mem != nullptr && prev_mem != in(MemNode::Memory)) {
1870     // (c) See if we can fold up on the spot, but don't fold up here.
1871     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1872     // just return a prior value, which is done by Identity calls.
1873     if (can_see_stored_value(prev_mem, phase)) {
1874       // Make ready for step (d):
1875       set_req_X(MemNode::Memory, prev_mem, phase);
1876       return this;
1877     }
1878   }
1879 
1880   return progress ? this : nullptr;
1881 }
1882 
1883 // Helper to recognize certain Klass fields which are invariant across
1884 // some group of array types (e.g., int[] or all T[] where T < Object).
1885 const Type*
1886 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1887                                  ciKlass* klass) const {
1888   if (UseCompactObjectHeaders) {
1889     if (tkls->offset() == in_bytes(Klass::prototype_header_offset())) {
1890       // The field is Klass::_prototype_header.  Return its (constant) value.
1891       assert(this->Opcode() == Op_LoadX, "must load a proper type from _prototype_header");
1892       return TypeX::make(klass->prototype_header());
1893     }
1894   }
1895   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1896     // The field is Klass::_modifier_flags.  Return its (constant) value.
1897     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1898     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1899     return TypeInt::make(klass->modifier_flags());
1900   }
1901   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1902     // The field is Klass::_access_flags.  Return its (constant) value.
1903     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1904     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1905     return TypeInt::make(klass->access_flags());
1906   }
1907   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1908     // The field is Klass::_layout_helper.  Return its constant value if known.
1909     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1910     return TypeInt::make(klass->layout_helper());
1911   }
1912 
1913   // No match.
1914   return nullptr;
1915 }
1916 
1917 //------------------------------Value-----------------------------------------
1918 const Type* LoadNode::Value(PhaseGVN* phase) const {
1919   // Either input is TOP ==> the result is TOP
1920   Node* mem = in(MemNode::Memory);
1921   const Type *t1 = phase->type(mem);
1922   if (t1 == Type::TOP)  return Type::TOP;
1923   Node* adr = in(MemNode::Address);
1924   const TypePtr* tp = phase->type(adr)->isa_ptr();
1925   if (tp == nullptr || tp->empty())  return Type::TOP;
1926   int off = tp->offset();
1927   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1928   Compile* C = phase->C;
1929 
1930   // Try to guess loaded type from pointer type
1931   if (tp->isa_aryptr()) {
1932     const TypeAryPtr* ary = tp->is_aryptr();
1933     const Type* t = ary->elem();
1934 
1935     // Determine whether the reference is beyond the header or not, by comparing
1936     // the offset against the offset of the start of the array's data.
1937     // Different array types begin at slightly different offsets (12 vs. 16).
1938     // We choose T_BYTE as an example base type that is least restrictive
1939     // as to alignment, which will therefore produce the smallest
1940     // possible base offset.
1941     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1942     const bool off_beyond_header = (off >= min_base_off);
1943 
1944     // Try to constant-fold a stable array element.
1945     if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1946       // Make sure the reference is not into the header and the offset is constant
1947       ciObject* aobj = ary->const_oop();
1948       if (aobj != nullptr && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1949         int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1950         const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1951                                                                       stable_dimension,
1952                                                                       memory_type(), is_unsigned());
1953         if (con_type != nullptr) {
1954           return con_type;
1955         }
1956       }
1957     }
1958 
1959     // Don't do this for integer types. There is only potential profit if
1960     // the element type t is lower than _type; that is, for int types, if _type is
1961     // more restrictive than t.  This only happens here if one is short and the other
1962     // char (both 16 bits), and in those cases we've made an intentional decision
1963     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1964     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1965     //
1966     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1967     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1968     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1969     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1970     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1971     // In fact, that could have been the original type of p1, and p1 could have
1972     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1973     // expression (LShiftL quux 3) independently optimized to the constant 8.
1974     if ((t->isa_int() == nullptr) && (t->isa_long() == nullptr)
1975         && (_type->isa_vect() == nullptr)
1976         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1977       // t might actually be lower than _type, if _type is a unique
1978       // concrete subclass of abstract class t.
1979       if (off_beyond_header || off == Type::OffsetBot) {  // is the offset beyond the header?
1980         const Type* jt = t->join_speculative(_type);
1981         // In any case, do not allow the join, per se, to empty out the type.
1982         if (jt->empty() && !t->empty()) {
1983           // This can happen if a interface-typed array narrows to a class type.
1984           jt = _type;
1985         }
1986 #ifdef ASSERT
1987         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1988           // The pointers in the autobox arrays are always non-null
1989           Node* base = adr->in(AddPNode::Base);
1990           if ((base != nullptr) && base->is_DecodeN()) {
1991             // Get LoadN node which loads IntegerCache.cache field
1992             base = base->in(1);
1993           }
1994           if ((base != nullptr) && base->is_Con()) {
1995             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1996             if ((base_type != nullptr) && base_type->is_autobox_cache()) {
1997               // It could be narrow oop
1998               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1999             }
2000           }
2001         }
2002 #endif
2003         return jt;
2004       }
2005     }
2006   } else if (tp->base() == Type::InstPtr) {
2007     assert( off != Type::OffsetBot ||
2008             // arrays can be cast to Objects
2009             !tp->isa_instptr() ||
2010             tp->is_instptr()->instance_klass()->is_java_lang_Object() ||
2011             // unsafe field access may not have a constant offset
2012             C->has_unsafe_access(),
2013             "Field accesses must be precise" );
2014     // For oop loads, we expect the _type to be precise.
2015 
2016     // Optimize loads from constant fields.
2017     const TypeInstPtr* tinst = tp->is_instptr();
2018     ciObject* const_oop = tinst->const_oop();
2019     if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != nullptr && const_oop->is_instance()) {
2020       const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
2021       if (con_type != nullptr) {
2022         return con_type;
2023       }
2024     }
2025   } else if (tp->base() == Type::KlassPtr || tp->base() == Type::InstKlassPtr || tp->base() == Type::AryKlassPtr) {
2026     assert(off != Type::OffsetBot ||
2027             !tp->isa_instklassptr() ||
2028            // arrays can be cast to Objects
2029            tp->isa_instklassptr()->instance_klass()->is_java_lang_Object() ||
2030            // also allow array-loading from the primary supertype
2031            // array during subtype checks
2032            Opcode() == Op_LoadKlass,
2033            "Field accesses must be precise");
2034     // For klass/static loads, we expect the _type to be precise
2035   } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
2036     /* With mirrors being an indirect in the Klass*
2037      * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
2038      * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
2039      *
2040      * So check the type and klass of the node before the LoadP.
2041      */
2042     Node* adr2 = adr->in(MemNode::Address);
2043     const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2044     if (tkls != nullptr && !StressReflectiveCode) {
2045       if (tkls->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
2046         ciKlass* klass = tkls->exact_klass();
2047         assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
2048         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
2049         return TypeInstPtr::make(klass->java_mirror());
2050       }
2051     }
2052   }
2053 
2054   const TypeKlassPtr *tkls = tp->isa_klassptr();
2055   if (tkls != nullptr) {
2056     if (tkls->is_loaded() && tkls->klass_is_exact()) {
2057       ciKlass* klass = tkls->exact_klass();
2058       // We are loading a field from a Klass metaobject whose identity
2059       // is known at compile time (the type is "exact" or "precise").
2060       // Check for fields we know are maintained as constants by the VM.
2061       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
2062         // The field is Klass::_super_check_offset.  Return its (constant) value.
2063         // (Folds up type checking code.)
2064         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
2065         return TypeInt::make(klass->super_check_offset());
2066       }
2067       if (UseCompactObjectHeaders) {
2068         if (tkls->offset() == in_bytes(Klass::prototype_header_offset())) {
2069           // The field is Klass::_prototype_header. Return its (constant) value.
2070           assert(this->Opcode() == Op_LoadX, "must load a proper type from _prototype_header");
2071           return TypeX::make(klass->prototype_header());
2072         }
2073       }
2074       // Compute index into primary_supers array
2075       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
2076       // Check for overflowing; use unsigned compare to handle the negative case.
2077       if( depth < ciKlass::primary_super_limit() ) {
2078         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
2079         // (Folds up type checking code.)
2080         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
2081         ciKlass *ss = klass->super_of_depth(depth);
2082         return ss ? TypeKlassPtr::make(ss, Type::trust_interfaces) : TypePtr::NULL_PTR;
2083       }
2084       const Type* aift = load_array_final_field(tkls, klass);
2085       if (aift != nullptr)  return aift;
2086     }
2087 
2088     // We can still check if we are loading from the primary_supers array at a
2089     // shallow enough depth.  Even though the klass is not exact, entries less
2090     // than or equal to its super depth are correct.
2091     if (tkls->is_loaded()) {
2092       ciKlass* klass = nullptr;
2093       if (tkls->isa_instklassptr()) {
2094         klass = tkls->is_instklassptr()->instance_klass();
2095       } else {
2096         int dims;
2097         const Type* inner = tkls->is_aryklassptr()->base_element_type(dims);
2098         if (inner->isa_instklassptr()) {
2099           klass = inner->is_instklassptr()->instance_klass();
2100           klass = ciObjArrayKlass::make(klass, dims);
2101         }
2102       }
2103       if (klass != nullptr) {
2104         // Compute index into primary_supers array
2105         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
2106         // Check for overflowing; use unsigned compare to handle the negative case.
2107         if (depth < ciKlass::primary_super_limit() &&
2108             depth <= klass->super_depth()) { // allow self-depth checks to handle self-check case
2109           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
2110           // (Folds up type checking code.)
2111           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
2112           ciKlass *ss = klass->super_of_depth(depth);
2113           return ss ? TypeKlassPtr::make(ss, Type::trust_interfaces) : TypePtr::NULL_PTR;
2114         }
2115       }
2116     }
2117 
2118     // If the type is enough to determine that the thing is not an array,
2119     // we can give the layout_helper a positive interval type.
2120     // This will help short-circuit some reflective code.
2121     if (tkls->offset() == in_bytes(Klass::layout_helper_offset()) &&
2122         tkls->isa_instklassptr() && // not directly typed as an array
2123         !tkls->is_instklassptr()->instance_klass()->is_java_lang_Object() // not the supertype of all T[] and specifically not Serializable & Cloneable
2124         ) {
2125       // Note:  When interfaces are reliable, we can narrow the interface
2126       // test to (klass != Serializable && klass != Cloneable).
2127       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
2128       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
2129       // The key property of this type is that it folds up tests
2130       // for array-ness, since it proves that the layout_helper is positive.
2131       // Thus, a generic value like the basic object layout helper works fine.
2132       return TypeInt::make(min_size, max_jint, Type::WidenMin);
2133     }
2134   }
2135 
2136   // If we are loading from a freshly-allocated object, produce a zero,
2137   // if the load is provably beyond the header of the object.
2138   // (Also allow a variable load from a fresh array to produce zero.)
2139   const TypeOopPtr *tinst = tp->isa_oopptr();
2140   bool is_instance = (tinst != nullptr) && tinst->is_known_instance_field();
2141   bool is_boxed_value = (tinst != nullptr) && tinst->is_ptr_to_boxed_value();
2142   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
2143     Node* value = can_see_stored_value(mem,phase);
2144     if (value != nullptr && value->is_Con()) {
2145       assert(value->bottom_type()->higher_equal(_type),"sanity");
2146       return value->bottom_type();
2147     }
2148   }
2149 
2150   bool is_vect = (_type->isa_vect() != nullptr);
2151   if (is_instance && !is_vect) {
2152     // If we have an instance type and our memory input is the
2153     // programs's initial memory state, there is no matching store,
2154     // so just return a zero of the appropriate type -
2155     // except if it is vectorized - then we have no zero constant.
2156     Node *mem = in(MemNode::Memory);
2157     if (mem->is_Parm() && mem->in(0)->is_Start()) {
2158       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
2159       return Type::get_zero_type(_type->basic_type());
2160     }
2161   }
2162 
2163   Node* alloc = is_new_object_mark_load(phase);
2164   if (!UseCompactObjectHeaders && alloc != nullptr) {
2165     return TypeX::make(markWord::prototype().value());
2166   }
2167 
2168   return _type;
2169 }
2170 
2171 //------------------------------match_edge-------------------------------------
2172 // Do we Match on this edge index or not?  Match only the address.
2173 uint LoadNode::match_edge(uint idx) const {
2174   return idx == MemNode::Address;
2175 }
2176 
2177 //--------------------------LoadBNode::Ideal--------------------------------------
2178 //
2179 //  If the previous store is to the same address as this load,
2180 //  and the value stored was larger than a byte, replace this load
2181 //  with the value stored truncated to a byte.  If no truncation is
2182 //  needed, the replacement is done in LoadNode::Identity().
2183 //
2184 Node* LoadBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2185   Node* mem = in(MemNode::Memory);
2186   Node* value = can_see_stored_value(mem,phase);
2187   if (value != nullptr) {
2188     Node* narrow = Compile::narrow_value(T_BYTE, value, _type, phase, false);
2189     if (narrow != value) {
2190       return narrow;
2191     }
2192   }
2193   // Identity call will handle the case where truncation is not needed.
2194   return LoadNode::Ideal(phase, can_reshape);
2195 }
2196 
2197 const Type* LoadBNode::Value(PhaseGVN* phase) const {
2198   Node* mem = in(MemNode::Memory);
2199   Node* value = can_see_stored_value(mem,phase);
2200   if (value != nullptr && value->is_Con() &&
2201       !value->bottom_type()->higher_equal(_type)) {
2202     // If the input to the store does not fit with the load's result type,
2203     // it must be truncated. We can't delay until Ideal call since
2204     // a singleton Value is needed for split_thru_phi optimization.
2205     int con = value->get_int();
2206     return TypeInt::make((con << 24) >> 24);
2207   }
2208   return LoadNode::Value(phase);
2209 }
2210 
2211 //--------------------------LoadUBNode::Ideal-------------------------------------
2212 //
2213 //  If the previous store is to the same address as this load,
2214 //  and the value stored was larger than a byte, replace this load
2215 //  with the value stored truncated to a byte.  If no truncation is
2216 //  needed, the replacement is done in LoadNode::Identity().
2217 //
2218 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2219   Node* mem = in(MemNode::Memory);
2220   Node* value = can_see_stored_value(mem, phase);
2221   if (value != nullptr) {
2222     Node* narrow = Compile::narrow_value(T_BOOLEAN, value, _type, phase, false);
2223     if (narrow != value) {
2224       return narrow;
2225     }
2226   }
2227   // Identity call will handle the case where truncation is not needed.
2228   return LoadNode::Ideal(phase, can_reshape);
2229 }
2230 
2231 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
2232   Node* mem = in(MemNode::Memory);
2233   Node* value = can_see_stored_value(mem,phase);
2234   if (value != nullptr && value->is_Con() &&
2235       !value->bottom_type()->higher_equal(_type)) {
2236     // If the input to the store does not fit with the load's result type,
2237     // it must be truncated. We can't delay until Ideal call since
2238     // a singleton Value is needed for split_thru_phi optimization.
2239     int con = value->get_int();
2240     return TypeInt::make(con & 0xFF);
2241   }
2242   return LoadNode::Value(phase);
2243 }
2244 
2245 //--------------------------LoadUSNode::Ideal-------------------------------------
2246 //
2247 //  If the previous store is to the same address as this load,
2248 //  and the value stored was larger than a char, replace this load
2249 //  with the value stored truncated to a char.  If no truncation is
2250 //  needed, the replacement is done in LoadNode::Identity().
2251 //
2252 Node* LoadUSNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2253   Node* mem = in(MemNode::Memory);
2254   Node* value = can_see_stored_value(mem,phase);
2255   if (value != nullptr) {
2256     Node* narrow = Compile::narrow_value(T_CHAR, value, _type, phase, false);
2257     if (narrow != value) {
2258       return narrow;
2259     }
2260   }
2261   // Identity call will handle the case where truncation is not needed.
2262   return LoadNode::Ideal(phase, can_reshape);
2263 }
2264 
2265 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
2266   Node* mem = in(MemNode::Memory);
2267   Node* value = can_see_stored_value(mem,phase);
2268   if (value != nullptr && value->is_Con() &&
2269       !value->bottom_type()->higher_equal(_type)) {
2270     // If the input to the store does not fit with the load's result type,
2271     // it must be truncated. We can't delay until Ideal call since
2272     // a singleton Value is needed for split_thru_phi optimization.
2273     int con = value->get_int();
2274     return TypeInt::make(con & 0xFFFF);
2275   }
2276   return LoadNode::Value(phase);
2277 }
2278 
2279 //--------------------------LoadSNode::Ideal--------------------------------------
2280 //
2281 //  If the previous store is to the same address as this load,
2282 //  and the value stored was larger than a short, replace this load
2283 //  with the value stored truncated to a short.  If no truncation is
2284 //  needed, the replacement is done in LoadNode::Identity().
2285 //
2286 Node* LoadSNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2287   Node* mem = in(MemNode::Memory);
2288   Node* value = can_see_stored_value(mem,phase);
2289   if (value != nullptr) {
2290     Node* narrow = Compile::narrow_value(T_SHORT, value, _type, phase, false);
2291     if (narrow != value) {
2292       return narrow;
2293     }
2294   }
2295   // Identity call will handle the case where truncation is not needed.
2296   return LoadNode::Ideal(phase, can_reshape);
2297 }
2298 
2299 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2300   Node* mem = in(MemNode::Memory);
2301   Node* value = can_see_stored_value(mem,phase);
2302   if (value != nullptr && value->is_Con() &&
2303       !value->bottom_type()->higher_equal(_type)) {
2304     // If the input to the store does not fit with the load's result type,
2305     // it must be truncated. We can't delay until Ideal call since
2306     // a singleton Value is needed for split_thru_phi optimization.
2307     int con = value->get_int();
2308     return TypeInt::make((con << 16) >> 16);
2309   }
2310   return LoadNode::Value(phase);
2311 }
2312 
2313 //=============================================================================
2314 //----------------------------LoadKlassNode::make------------------------------
2315 // Polymorphic factory method:
2316 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2317   // sanity check the alias category against the created node type
2318   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2319   assert(adr_type != nullptr, "expecting TypeKlassPtr");
2320 #ifdef _LP64
2321   if (adr_type->is_ptr_to_narrowklass()) {
2322     assert(UseCompressedClassPointers, "no compressed klasses");
2323     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2324     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2325   }
2326 #endif
2327   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2328   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2329 }
2330 
2331 //------------------------------Value------------------------------------------
2332 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2333   return klass_value_common(phase);
2334 }
2335 
2336 // In most cases, LoadKlassNode does not have the control input set. If the control
2337 // input is set, it must not be removed (by LoadNode::Ideal()).
2338 bool LoadKlassNode::can_remove_control() const {
2339   return false;
2340 }
2341 
2342 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2343   // Either input is TOP ==> the result is TOP
2344   const Type *t1 = phase->type( in(MemNode::Memory) );
2345   if (t1 == Type::TOP)  return Type::TOP;
2346   Node *adr = in(MemNode::Address);
2347   const Type *t2 = phase->type( adr );
2348   if (t2 == Type::TOP)  return Type::TOP;
2349   const TypePtr *tp = t2->is_ptr();
2350   if (TypePtr::above_centerline(tp->ptr()) ||
2351       tp->ptr() == TypePtr::Null)  return Type::TOP;
2352 
2353   // Return a more precise klass, if possible
2354   const TypeInstPtr *tinst = tp->isa_instptr();
2355   if (tinst != nullptr) {
2356     ciInstanceKlass* ik = tinst->instance_klass();
2357     int offset = tinst->offset();
2358     if (ik == phase->C->env()->Class_klass()
2359         && (offset == java_lang_Class::klass_offset() ||
2360             offset == java_lang_Class::array_klass_offset())) {
2361       // We are loading a special hidden field from a Class mirror object,
2362       // the field which points to the VM's Klass metaobject.
2363       ciType* t = tinst->java_mirror_type();
2364       // java_mirror_type returns non-null for compile-time Class constants.
2365       if (t != nullptr) {
2366         // constant oop => constant klass
2367         if (offset == java_lang_Class::array_klass_offset()) {
2368           if (t->is_void()) {
2369             // We cannot create a void array.  Since void is a primitive type return null
2370             // klass.  Users of this result need to do a null check on the returned klass.
2371             return TypePtr::NULL_PTR;
2372           }
2373           return TypeKlassPtr::make(ciArrayKlass::make(t), Type::trust_interfaces);
2374         }
2375         if (!t->is_klass()) {
2376           // a primitive Class (e.g., int.class) has null for a klass field
2377           return TypePtr::NULL_PTR;
2378         }
2379         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2380         return TypeKlassPtr::make(t->as_klass(), Type::trust_interfaces);
2381       }
2382       // non-constant mirror, so we can't tell what's going on
2383     }
2384     if (!tinst->is_loaded())
2385       return _type;             // Bail out if not loaded
2386     if (offset == oopDesc::klass_offset_in_bytes()) {
2387       return tinst->as_klass_type(true);
2388     }
2389   }
2390 
2391   // Check for loading klass from an array
2392   const TypeAryPtr *tary = tp->isa_aryptr();
2393   if (tary != nullptr &&
2394       tary->offset() == oopDesc::klass_offset_in_bytes()) {
2395     return tary->as_klass_type(true);
2396   }
2397 
2398   // Check for loading klass from an array klass
2399   const TypeKlassPtr *tkls = tp->isa_klassptr();
2400   if (tkls != nullptr && !StressReflectiveCode) {
2401     if (!tkls->is_loaded())
2402      return _type;             // Bail out if not loaded
2403     if (tkls->isa_aryklassptr() && tkls->is_aryklassptr()->elem()->isa_klassptr() &&
2404         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2405       // // Always returning precise element type is incorrect,
2406       // // e.g., element type could be object and array may contain strings
2407       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2408 
2409       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2410       // according to the element type's subclassing.
2411       return tkls->is_aryklassptr()->elem()->isa_klassptr()->cast_to_exactness(tkls->klass_is_exact());
2412     }
2413     if (tkls->isa_instklassptr() != nullptr && tkls->klass_is_exact() &&
2414         tkls->offset() == in_bytes(Klass::super_offset())) {
2415       ciKlass* sup = tkls->is_instklassptr()->instance_klass()->super();
2416       // The field is Klass::_super.  Return its (constant) value.
2417       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2418       return sup ? TypeKlassPtr::make(sup, Type::trust_interfaces) : TypePtr::NULL_PTR;
2419     }
2420   }
2421 
2422   // Bailout case
2423   return LoadNode::Value(phase);
2424 }
2425 
2426 //------------------------------Identity---------------------------------------
2427 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2428 // Also feed through the klass in Allocate(...klass...)._klass.
2429 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2430   return klass_identity_common(phase);
2431 }
2432 
2433 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2434   Node* x = LoadNode::Identity(phase);
2435   if (x != this)  return x;
2436 
2437   // Take apart the address into an oop and offset.
2438   // Return 'this' if we cannot.
2439   Node*    adr    = in(MemNode::Address);
2440   intptr_t offset = 0;
2441   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2442   if (base == nullptr)     return this;
2443   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2444   if (toop == nullptr)     return this;
2445 
2446   // Step over potential GC barrier for OopHandle resolve
2447   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2448   if (bs->is_gc_barrier_node(base)) {
2449     base = bs->step_over_gc_barrier(base);
2450   }
2451 
2452   // We can fetch the klass directly through an AllocateNode.
2453   // This works even if the klass is not constant (clone or newArray).
2454   if (offset == oopDesc::klass_offset_in_bytes()) {
2455     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2456     if (allocated_klass != nullptr) {
2457       return allocated_klass;
2458     }
2459   }
2460 
2461   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2462   // See inline_native_Class_query for occurrences of these patterns.
2463   // Java Example:  x.getClass().isAssignableFrom(y)
2464   //
2465   // This improves reflective code, often making the Class
2466   // mirror go completely dead.  (Current exception:  Class
2467   // mirrors may appear in debug info, but we could clean them out by
2468   // introducing a new debug info operator for Klass.java_mirror).
2469 
2470   if (toop->isa_instptr() && toop->is_instptr()->instance_klass() == phase->C->env()->Class_klass()
2471       && offset == java_lang_Class::klass_offset()) {
2472     if (base->is_Load()) {
2473       Node* base2 = base->in(MemNode::Address);
2474       if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2475         Node* adr2 = base2->in(MemNode::Address);
2476         const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2477         if (tkls != nullptr && !tkls->empty()
2478             && (tkls->isa_instklassptr() || tkls->isa_aryklassptr())
2479             && adr2->is_AddP()
2480            ) {
2481           int mirror_field = in_bytes(Klass::java_mirror_offset());
2482           if (tkls->offset() == mirror_field) {
2483             return adr2->in(AddPNode::Base);
2484           }
2485         }
2486       }
2487     }
2488   }
2489 
2490   return this;
2491 }
2492 
2493 LoadNode* LoadNode::clone_pinned() const {
2494   LoadNode* ld = clone()->as_Load();
2495   ld->_control_dependency = UnknownControl;
2496   return ld;
2497 }
2498 
2499 
2500 //------------------------------Value------------------------------------------
2501 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2502   const Type *t = klass_value_common(phase);
2503   if (t == Type::TOP)
2504     return t;
2505 
2506   return t->make_narrowklass();
2507 }
2508 
2509 //------------------------------Identity---------------------------------------
2510 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2511 // Also feed through the klass in Allocate(...klass...)._klass.
2512 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2513   Node *x = klass_identity_common(phase);
2514 
2515   const Type *t = phase->type( x );
2516   if( t == Type::TOP ) return x;
2517   if( t->isa_narrowklass()) return x;
2518   assert (!t->isa_narrowoop(), "no narrow oop here");
2519 
2520   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2521 }
2522 
2523 //------------------------------Value-----------------------------------------
2524 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2525   // Either input is TOP ==> the result is TOP
2526   const Type *t1 = phase->type( in(MemNode::Memory) );
2527   if( t1 == Type::TOP ) return Type::TOP;
2528   Node *adr = in(MemNode::Address);
2529   const Type *t2 = phase->type( adr );
2530   if( t2 == Type::TOP ) return Type::TOP;
2531   const TypePtr *tp = t2->is_ptr();
2532   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2533   const TypeAryPtr *tap = tp->isa_aryptr();
2534   if( !tap ) return _type;
2535   return tap->size();
2536 }
2537 
2538 //-------------------------------Ideal---------------------------------------
2539 // Feed through the length in AllocateArray(...length...)._length.
2540 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2541   Node* p = MemNode::Ideal_common(phase, can_reshape);
2542   if (p)  return (p == NodeSentinel) ? nullptr : p;
2543 
2544   // Take apart the address into an oop and offset.
2545   // Return 'this' if we cannot.
2546   Node*    adr    = in(MemNode::Address);
2547   intptr_t offset = 0;
2548   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2549   if (base == nullptr)     return nullptr;
2550   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2551   if (tary == nullptr)     return nullptr;
2552 
2553   // We can fetch the length directly through an AllocateArrayNode.
2554   // This works even if the length is not constant (clone or newArray).
2555   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2556     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2557     if (alloc != nullptr) {
2558       Node* allocated_length = alloc->Ideal_length();
2559       Node* len = alloc->make_ideal_length(tary, phase);
2560       if (allocated_length != len) {
2561         // New CastII improves on this.
2562         return len;
2563       }
2564     }
2565   }
2566 
2567   return nullptr;
2568 }
2569 
2570 //------------------------------Identity---------------------------------------
2571 // Feed through the length in AllocateArray(...length...)._length.
2572 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2573   Node* x = LoadINode::Identity(phase);
2574   if (x != this)  return x;
2575 
2576   // Take apart the address into an oop and offset.
2577   // Return 'this' if we cannot.
2578   Node*    adr    = in(MemNode::Address);
2579   intptr_t offset = 0;
2580   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2581   if (base == nullptr)     return this;
2582   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2583   if (tary == nullptr)     return this;
2584 
2585   // We can fetch the length directly through an AllocateArrayNode.
2586   // This works even if the length is not constant (clone or newArray).
2587   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2588     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2589     if (alloc != nullptr) {
2590       Node* allocated_length = alloc->Ideal_length();
2591       // Do not allow make_ideal_length to allocate a CastII node.
2592       Node* len = alloc->make_ideal_length(tary, phase, false);
2593       if (allocated_length == len) {
2594         // Return allocated_length only if it would not be improved by a CastII.
2595         return allocated_length;
2596       }
2597     }
2598   }
2599 
2600   return this;
2601 
2602 }
2603 
2604 //=============================================================================
2605 //---------------------------StoreNode::make-----------------------------------
2606 // Polymorphic factory method:
2607 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo, bool require_atomic_access) {
2608   assert((mo == unordered || mo == release), "unexpected");
2609   Compile* C = gvn.C;
2610   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2611          ctl != nullptr, "raw memory operations should have control edge");
2612 
2613   switch (bt) {
2614   case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2615   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2616   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2617   case T_CHAR:
2618   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2619   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic_access);
2620   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2621   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic_access);
2622   case T_METADATA:
2623   case T_ADDRESS:
2624   case T_OBJECT:
2625 #ifdef _LP64
2626     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2627       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2628       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2629     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2630                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2631                 adr->bottom_type()->isa_rawptr())) {
2632       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2633       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2634     }
2635 #endif
2636     {
2637       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2638     }
2639   default:
2640     ShouldNotReachHere();
2641     return (StoreNode*)nullptr;
2642   }
2643 }
2644 
2645 //--------------------------bottom_type----------------------------------------
2646 const Type *StoreNode::bottom_type() const {
2647   return Type::MEMORY;
2648 }
2649 
2650 //------------------------------hash-------------------------------------------
2651 uint StoreNode::hash() const {
2652   // unroll addition of interesting fields
2653   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2654 
2655   // Since they are not commoned, do not hash them:
2656   return NO_HASH;
2657 }
2658 
2659 //------------------------------Ideal------------------------------------------
2660 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2661 // When a store immediately follows a relevant allocation/initialization,
2662 // try to capture it into the initialization, or hoist it above.
2663 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2664   Node* p = MemNode::Ideal_common(phase, can_reshape);
2665   if (p)  return (p == NodeSentinel) ? nullptr : p;
2666 
2667   Node* mem     = in(MemNode::Memory);
2668   Node* address = in(MemNode::Address);
2669   Node* value   = in(MemNode::ValueIn);
2670   // Back-to-back stores to same address?  Fold em up.  Generally
2671   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2672   // since they must follow each StoreP operation.  Redundant StoreCMs
2673   // are eliminated just before matching in final_graph_reshape.
2674   {
2675     Node* st = mem;
2676     // If Store 'st' has more than one use, we cannot fold 'st' away.
2677     // For example, 'st' might be the final state at a conditional
2678     // return.  Or, 'st' might be used by some node which is live at
2679     // the same time 'st' is live, which might be unschedulable.  So,
2680     // require exactly ONE user until such time as we clone 'mem' for
2681     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2682     // true).
2683     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2684       // Looking at a dead closed cycle of memory?
2685       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2686       assert(Opcode() == st->Opcode() ||
2687              st->Opcode() == Op_StoreVector ||
2688              Opcode() == Op_StoreVector ||
2689              st->Opcode() == Op_StoreVectorScatter ||
2690              Opcode() == Op_StoreVectorScatter ||
2691              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2692              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2693              (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2694              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2695              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2696 
2697       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2698           st->as_Store()->memory_size() <= this->memory_size()) {
2699         Node* use = st->raw_out(0);
2700         if (phase->is_IterGVN()) {
2701           phase->is_IterGVN()->rehash_node_delayed(use);
2702         }
2703         // It's OK to do this in the parser, since DU info is always accurate,
2704         // and the parser always refers to nodes via SafePointNode maps.
2705         use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase);
2706         return this;
2707       }
2708       st = st->in(MemNode::Memory);
2709     }
2710   }
2711 
2712 
2713   // Capture an unaliased, unconditional, simple store into an initializer.
2714   // Or, if it is independent of the allocation, hoist it above the allocation.
2715   if (ReduceFieldZeroing && /*can_reshape &&*/
2716       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2717     InitializeNode* init = mem->in(0)->as_Initialize();
2718     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2719     if (offset > 0) {
2720       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2721       // If the InitializeNode captured me, it made a raw copy of me,
2722       // and I need to disappear.
2723       if (moved != nullptr) {
2724         // %%% hack to ensure that Ideal returns a new node:
2725         mem = MergeMemNode::make(mem);
2726         return mem;             // fold me away
2727       }
2728     }
2729   }
2730 
2731   // Fold reinterpret cast into memory operation:
2732   //    StoreX mem (MoveY2X v) => StoreY mem v
2733   if (value->is_Move()) {
2734     const Type* vt = value->in(1)->bottom_type();
2735     if (has_reinterpret_variant(vt)) {
2736       if (phase->C->post_loop_opts_phase()) {
2737         return convert_to_reinterpret_store(*phase, value->in(1), vt);
2738       } else {
2739         phase->C->record_for_post_loop_opts_igvn(this); // attempt the transformation once loop opts are over
2740       }
2741     }
2742   }
2743 
2744   return nullptr;                  // No further progress
2745 }
2746 
2747 //------------------------------Value-----------------------------------------
2748 const Type* StoreNode::Value(PhaseGVN* phase) const {
2749   // Either input is TOP ==> the result is TOP
2750   const Type *t1 = phase->type( in(MemNode::Memory) );
2751   if( t1 == Type::TOP ) return Type::TOP;
2752   const Type *t2 = phase->type( in(MemNode::Address) );
2753   if( t2 == Type::TOP ) return Type::TOP;
2754   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2755   if( t3 == Type::TOP ) return Type::TOP;
2756   return Type::MEMORY;
2757 }
2758 
2759 //------------------------------Identity---------------------------------------
2760 // Remove redundant stores:
2761 //   Store(m, p, Load(m, p)) changes to m.
2762 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2763 Node* StoreNode::Identity(PhaseGVN* phase) {
2764   Node* mem = in(MemNode::Memory);
2765   Node* adr = in(MemNode::Address);
2766   Node* val = in(MemNode::ValueIn);
2767 
2768   Node* result = this;
2769 
2770   // Load then Store?  Then the Store is useless
2771   if (val->is_Load() &&
2772       val->in(MemNode::Address)->eqv_uncast(adr) &&
2773       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2774       val->as_Load()->store_Opcode() == Opcode()) {
2775     // Ensure vector type is the same
2776     if (!is_StoreVector() || (mem->is_LoadVector() && as_StoreVector()->vect_type() == mem->as_LoadVector()->vect_type())) {
2777       result = mem;
2778     }
2779   }
2780 
2781   // Two stores in a row of the same value?
2782   if (result == this &&
2783       mem->is_Store() &&
2784       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2785       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2786       mem->Opcode() == Opcode()) {
2787     if (!is_StoreVector()) {
2788       result = mem;
2789     } else {
2790       const StoreVectorNode* store_vector = as_StoreVector();
2791       const StoreVectorNode* mem_vector = mem->as_StoreVector();
2792       const Node* store_indices = store_vector->indices();
2793       const Node* mem_indices = mem_vector->indices();
2794       const Node* store_mask = store_vector->mask();
2795       const Node* mem_mask = mem_vector->mask();
2796       // Ensure types, indices, and masks match
2797       if (store_vector->vect_type() == mem_vector->vect_type() &&
2798           ((store_indices == nullptr) == (mem_indices == nullptr) &&
2799            (store_indices == nullptr || store_indices->eqv_uncast(mem_indices))) &&
2800           ((store_mask == nullptr) == (mem_mask == nullptr) &&
2801            (store_mask == nullptr || store_mask->eqv_uncast(mem_mask)))) {
2802         result = mem;
2803       }
2804     }
2805   }
2806 
2807   // Store of zero anywhere into a freshly-allocated object?
2808   // Then the store is useless.
2809   // (It must already have been captured by the InitializeNode.)
2810   if (result == this &&
2811       ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2812     // a newly allocated object is already all-zeroes everywhere
2813     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2814       result = mem;
2815     }
2816 
2817     if (result == this) {
2818       // the store may also apply to zero-bits in an earlier object
2819       Node* prev_mem = find_previous_store(phase);
2820       // Steps (a), (b):  Walk past independent stores to find an exact match.
2821       if (prev_mem != nullptr) {
2822         Node* prev_val = can_see_stored_value(prev_mem, phase);
2823         if (prev_val != nullptr && prev_val == val) {
2824           // prev_val and val might differ by a cast; it would be good
2825           // to keep the more informative of the two.
2826           result = mem;
2827         }
2828       }
2829     }
2830   }
2831 
2832   PhaseIterGVN* igvn = phase->is_IterGVN();
2833   if (result != this && igvn != nullptr) {
2834     MemBarNode* trailing = trailing_membar();
2835     if (trailing != nullptr) {
2836 #ifdef ASSERT
2837       const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2838       assert(t_oop == nullptr || t_oop->is_known_instance_field(), "only for non escaping objects");
2839 #endif
2840       trailing->remove(igvn);
2841     }
2842   }
2843 
2844   return result;
2845 }
2846 
2847 //------------------------------match_edge-------------------------------------
2848 // Do we Match on this edge index or not?  Match only memory & value
2849 uint StoreNode::match_edge(uint idx) const {
2850   return idx == MemNode::Address || idx == MemNode::ValueIn;
2851 }
2852 
2853 //------------------------------cmp--------------------------------------------
2854 // Do not common stores up together.  They generally have to be split
2855 // back up anyways, so do not bother.
2856 bool StoreNode::cmp( const Node &n ) const {
2857   return (&n == this);          // Always fail except on self
2858 }
2859 
2860 //------------------------------Ideal_masked_input-----------------------------
2861 // Check for a useless mask before a partial-word store
2862 // (StoreB ... (AndI valIn conIa) )
2863 // If (conIa & mask == mask) this simplifies to
2864 // (StoreB ... (valIn) )
2865 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2866   Node *val = in(MemNode::ValueIn);
2867   if( val->Opcode() == Op_AndI ) {
2868     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2869     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2870       set_req_X(MemNode::ValueIn, val->in(1), phase);
2871       return this;
2872     }
2873   }
2874   return nullptr;
2875 }
2876 
2877 
2878 //------------------------------Ideal_sign_extended_input----------------------
2879 // Check for useless sign-extension before a partial-word store
2880 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2881 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2882 // (StoreB ... (valIn) )
2883 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2884   Node *val = in(MemNode::ValueIn);
2885   if( val->Opcode() == Op_RShiftI ) {
2886     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2887     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2888       Node *shl = val->in(1);
2889       if( shl->Opcode() == Op_LShiftI ) {
2890         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2891         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2892           set_req_X(MemNode::ValueIn, shl->in(1), phase);
2893           return this;
2894         }
2895       }
2896     }
2897   }
2898   return nullptr;
2899 }
2900 
2901 //------------------------------value_never_loaded-----------------------------------
2902 // Determine whether there are any possible loads of the value stored.
2903 // For simplicity, we actually check if there are any loads from the
2904 // address stored to, not just for loads of the value stored by this node.
2905 //
2906 bool StoreNode::value_never_loaded(PhaseValues* phase) const {
2907   Node *adr = in(Address);
2908   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2909   if (adr_oop == nullptr)
2910     return false;
2911   if (!adr_oop->is_known_instance_field())
2912     return false; // if not a distinct instance, there may be aliases of the address
2913   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2914     Node *use = adr->fast_out(i);
2915     if (use->is_Load() || use->is_LoadStore()) {
2916       return false;
2917     }
2918   }
2919   return true;
2920 }
2921 
2922 MemBarNode* StoreNode::trailing_membar() const {
2923   if (is_release()) {
2924     MemBarNode* trailing_mb = nullptr;
2925     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2926       Node* u = fast_out(i);
2927       if (u->is_MemBar()) {
2928         if (u->as_MemBar()->trailing_store()) {
2929           assert(u->Opcode() == Op_MemBarVolatile, "");
2930           assert(trailing_mb == nullptr, "only one");
2931           trailing_mb = u->as_MemBar();
2932 #ifdef ASSERT
2933           Node* leading = u->as_MemBar()->leading_membar();
2934           assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2935           assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2936           assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2937 #endif
2938         } else {
2939           assert(u->as_MemBar()->standalone(), "");
2940         }
2941       }
2942     }
2943     return trailing_mb;
2944   }
2945   return nullptr;
2946 }
2947 
2948 
2949 //=============================================================================
2950 //------------------------------Ideal------------------------------------------
2951 // If the store is from an AND mask that leaves the low bits untouched, then
2952 // we can skip the AND operation.  If the store is from a sign-extension
2953 // (a left shift, then right shift) we can skip both.
2954 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2955   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2956   if( progress != nullptr ) return progress;
2957 
2958   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2959   if( progress != nullptr ) return progress;
2960 
2961   // Finally check the default case
2962   return StoreNode::Ideal(phase, can_reshape);
2963 }
2964 
2965 //=============================================================================
2966 //------------------------------Ideal------------------------------------------
2967 // If the store is from an AND mask that leaves the low bits untouched, then
2968 // we can skip the AND operation
2969 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2970   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2971   if( progress != nullptr ) return progress;
2972 
2973   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2974   if( progress != nullptr ) return progress;
2975 
2976   // Finally check the default case
2977   return StoreNode::Ideal(phase, can_reshape);
2978 }
2979 
2980 //=============================================================================
2981 //------------------------------Identity---------------------------------------
2982 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2983   // No need to card mark when storing a null ptr
2984   Node* my_store = in(MemNode::OopStore);
2985   if (my_store->is_Store()) {
2986     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2987     if( t1 == TypePtr::NULL_PTR ) {
2988       return in(MemNode::Memory);
2989     }
2990   }
2991   return this;
2992 }
2993 
2994 //=============================================================================
2995 //------------------------------Ideal---------------------------------------
2996 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2997   Node* progress = StoreNode::Ideal(phase, can_reshape);
2998   if (progress != nullptr) return progress;
2999 
3000   Node* my_store = in(MemNode::OopStore);
3001   if (my_store->is_MergeMem()) {
3002     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
3003     set_req_X(MemNode::OopStore, mem, phase);
3004     return this;
3005   }
3006 
3007   return nullptr;
3008 }
3009 
3010 //------------------------------Value-----------------------------------------
3011 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
3012   // Either input is TOP ==> the result is TOP (checked in StoreNode::Value).
3013   // If extra input is TOP ==> the result is TOP
3014   const Type* t = phase->type(in(MemNode::OopStore));
3015   if (t == Type::TOP) {
3016     return Type::TOP;
3017   }
3018   return StoreNode::Value(phase);
3019 }
3020 
3021 
3022 //=============================================================================
3023 //----------------------------------SCMemProjNode------------------------------
3024 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
3025 {
3026   if (in(0) == nullptr || phase->type(in(0)) == Type::TOP) {
3027     return Type::TOP;
3028   }
3029   return bottom_type();
3030 }
3031 
3032 //=============================================================================
3033 //----------------------------------LoadStoreNode------------------------------
3034 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
3035   : Node(required),
3036     _type(rt),
3037     _adr_type(at),
3038     _barrier_data(0)
3039 {
3040   init_req(MemNode::Control, c  );
3041   init_req(MemNode::Memory , mem);
3042   init_req(MemNode::Address, adr);
3043   init_req(MemNode::ValueIn, val);
3044   init_class_id(Class_LoadStore);
3045 }
3046 
3047 //------------------------------Value-----------------------------------------
3048 const Type* LoadStoreNode::Value(PhaseGVN* phase) const {
3049   // Either input is TOP ==> the result is TOP
3050   if (!in(MemNode::Control) || phase->type(in(MemNode::Control)) == Type::TOP) {
3051     return Type::TOP;
3052   }
3053   const Type* t = phase->type(in(MemNode::Memory));
3054   if (t == Type::TOP) {
3055     return Type::TOP;
3056   }
3057   t = phase->type(in(MemNode::Address));
3058   if (t == Type::TOP) {
3059     return Type::TOP;
3060   }
3061   t = phase->type(in(MemNode::ValueIn));
3062   if (t == Type::TOP) {
3063     return Type::TOP;
3064   }
3065   return bottom_type();
3066 }
3067 
3068 uint LoadStoreNode::ideal_reg() const {
3069   return _type->ideal_reg();
3070 }
3071 
3072 bool LoadStoreNode::result_not_used() const {
3073   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
3074     Node *x = fast_out(i);
3075     if (x->Opcode() == Op_SCMemProj) continue;
3076     return false;
3077   }
3078   return true;
3079 }
3080 
3081 MemBarNode* LoadStoreNode::trailing_membar() const {
3082   MemBarNode* trailing = nullptr;
3083   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
3084     Node* u = fast_out(i);
3085     if (u->is_MemBar()) {
3086       if (u->as_MemBar()->trailing_load_store()) {
3087         assert(u->Opcode() == Op_MemBarAcquire, "");
3088         assert(trailing == nullptr, "only one");
3089         trailing = u->as_MemBar();
3090 #ifdef ASSERT
3091         Node* leading = trailing->leading_membar();
3092         assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
3093         assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
3094         assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
3095 #endif
3096       } else {
3097         assert(u->as_MemBar()->standalone(), "wrong barrier kind");
3098       }
3099     }
3100   }
3101 
3102   return trailing;
3103 }
3104 
3105 uint LoadStoreNode::size_of() const { return sizeof(*this); }
3106 
3107 //=============================================================================
3108 //----------------------------------LoadStoreConditionalNode--------------------
3109 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, nullptr, TypeInt::BOOL, 5) {
3110   init_req(ExpectedIn, ex );
3111 }
3112 
3113 const Type* LoadStoreConditionalNode::Value(PhaseGVN* phase) const {
3114   // Either input is TOP ==> the result is TOP
3115   const Type* t = phase->type(in(ExpectedIn));
3116   if (t == Type::TOP) {
3117     return Type::TOP;
3118   }
3119   return LoadStoreNode::Value(phase);
3120 }
3121 
3122 //=============================================================================
3123 //-------------------------------adr_type--------------------------------------
3124 const TypePtr* ClearArrayNode::adr_type() const {
3125   Node *adr = in(3);
3126   if (adr == nullptr)  return nullptr; // node is dead
3127   return MemNode::calculate_adr_type(adr->bottom_type());
3128 }
3129 
3130 //------------------------------match_edge-------------------------------------
3131 // Do we Match on this edge index or not?  Do not match memory
3132 uint ClearArrayNode::match_edge(uint idx) const {
3133   return idx > 1;
3134 }
3135 
3136 //------------------------------Identity---------------------------------------
3137 // Clearing a zero length array does nothing
3138 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
3139   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
3140 }
3141 
3142 //------------------------------Idealize---------------------------------------
3143 // Clearing a short array is faster with stores
3144 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3145   // Already know this is a large node, do not try to ideal it
3146   if (_is_large) return nullptr;
3147 
3148   const int unit = BytesPerLong;
3149   const TypeX* t = phase->type(in(2))->isa_intptr_t();
3150   if (!t)  return nullptr;
3151   if (!t->is_con())  return nullptr;
3152   intptr_t raw_count = t->get_con();
3153   intptr_t size = raw_count;
3154   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
3155   // Clearing nothing uses the Identity call.
3156   // Negative clears are possible on dead ClearArrays
3157   // (see jck test stmt114.stmt11402.val).
3158   if (size <= 0 || size % unit != 0)  return nullptr;
3159   intptr_t count = size / unit;
3160   // Length too long; communicate this to matchers and assemblers.
3161   // Assemblers are responsible to produce fast hardware clears for it.
3162   if (size > InitArrayShortSize) {
3163     return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
3164   } else if (size > 2 && Matcher::match_rule_supported_vector(Op_ClearArray, 4, T_LONG)) {
3165     return nullptr;
3166   }
3167   if (!IdealizeClearArrayNode) return nullptr;
3168   Node *mem = in(1);
3169   if( phase->type(mem)==Type::TOP ) return nullptr;
3170   Node *adr = in(3);
3171   const Type* at = phase->type(adr);
3172   if( at==Type::TOP ) return nullptr;
3173   const TypePtr* atp = at->isa_ptr();
3174   // adjust atp to be the correct array element address type
3175   if (atp == nullptr)  atp = TypePtr::BOTTOM;
3176   else              atp = atp->add_offset(Type::OffsetBot);
3177   // Get base for derived pointer purposes
3178   if( adr->Opcode() != Op_AddP ) Unimplemented();
3179   Node *base = adr->in(1);
3180 
3181   Node *zero = phase->makecon(TypeLong::ZERO);
3182   Node *off  = phase->MakeConX(BytesPerLong);
3183   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
3184   count--;
3185   while( count-- ) {
3186     mem = phase->transform(mem);
3187     adr = phase->transform(new AddPNode(base,adr,off));
3188     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
3189   }
3190   return mem;
3191 }
3192 
3193 //----------------------------step_through----------------------------------
3194 // Return allocation input memory edge if it is different instance
3195 // or itself if it is the one we are looking for.
3196 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseValues* phase) {
3197   Node* n = *np;
3198   assert(n->is_ClearArray(), "sanity");
3199   intptr_t offset;
3200   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
3201   // This method is called only before Allocate nodes are expanded
3202   // during macro nodes expansion. Before that ClearArray nodes are
3203   // only generated in PhaseMacroExpand::generate_arraycopy() (before
3204   // Allocate nodes are expanded) which follows allocations.
3205   assert(alloc != nullptr, "should have allocation");
3206   if (alloc->_idx == instance_id) {
3207     // Can not bypass initialization of the instance we are looking for.
3208     return false;
3209   }
3210   // Otherwise skip it.
3211   InitializeNode* init = alloc->initialization();
3212   if (init != nullptr)
3213     *np = init->in(TypeFunc::Memory);
3214   else
3215     *np = alloc->in(TypeFunc::Memory);
3216   return true;
3217 }
3218 
3219 //----------------------------clear_memory-------------------------------------
3220 // Generate code to initialize object storage to zero.
3221 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3222                                    intptr_t start_offset,
3223                                    Node* end_offset,
3224                                    PhaseGVN* phase) {
3225   intptr_t offset = start_offset;
3226 
3227   int unit = BytesPerLong;
3228   if ((offset % unit) != 0) {
3229     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
3230     adr = phase->transform(adr);
3231     const TypePtr* atp = TypeRawPtr::BOTTOM;
3232     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3233     mem = phase->transform(mem);
3234     offset += BytesPerInt;
3235   }
3236   assert((offset % unit) == 0, "");
3237 
3238   // Initialize the remaining stuff, if any, with a ClearArray.
3239   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
3240 }
3241 
3242 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3243                                    Node* start_offset,
3244                                    Node* end_offset,
3245                                    PhaseGVN* phase) {
3246   if (start_offset == end_offset) {
3247     // nothing to do
3248     return mem;
3249   }
3250 
3251   int unit = BytesPerLong;
3252   Node* zbase = start_offset;
3253   Node* zend  = end_offset;
3254 
3255   // Scale to the unit required by the CPU:
3256   if (!Matcher::init_array_count_is_in_bytes) {
3257     Node* shift = phase->intcon(exact_log2(unit));
3258     zbase = phase->transform(new URShiftXNode(zbase, shift) );
3259     zend  = phase->transform(new URShiftXNode(zend,  shift) );
3260   }
3261 
3262   // Bulk clear double-words
3263   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
3264   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
3265   mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
3266   return phase->transform(mem);
3267 }
3268 
3269 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3270                                    intptr_t start_offset,
3271                                    intptr_t end_offset,
3272                                    PhaseGVN* phase) {
3273   if (start_offset == end_offset) {
3274     // nothing to do
3275     return mem;
3276   }
3277 
3278   assert((end_offset % BytesPerInt) == 0, "odd end offset");
3279   intptr_t done_offset = end_offset;
3280   if ((done_offset % BytesPerLong) != 0) {
3281     done_offset -= BytesPerInt;
3282   }
3283   if (done_offset > start_offset) {
3284     mem = clear_memory(ctl, mem, dest,
3285                        start_offset, phase->MakeConX(done_offset), phase);
3286   }
3287   if (done_offset < end_offset) { // emit the final 32-bit store
3288     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3289     adr = phase->transform(adr);
3290     const TypePtr* atp = TypeRawPtr::BOTTOM;
3291     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3292     mem = phase->transform(mem);
3293     done_offset += BytesPerInt;
3294   }
3295   assert(done_offset == end_offset, "");
3296   return mem;
3297 }
3298 
3299 //=============================================================================
3300 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3301   : MultiNode(TypeFunc::Parms + (precedent == nullptr? 0: 1)),
3302     _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3303 #ifdef ASSERT
3304   , _pair_idx(0)
3305 #endif
3306 {
3307   init_class_id(Class_MemBar);
3308   Node* top = C->top();
3309   init_req(TypeFunc::I_O,top);
3310   init_req(TypeFunc::FramePtr,top);
3311   init_req(TypeFunc::ReturnAdr,top);
3312   if (precedent != nullptr)
3313     init_req(TypeFunc::Parms, precedent);
3314 }
3315 
3316 //------------------------------cmp--------------------------------------------
3317 uint MemBarNode::hash() const { return NO_HASH; }
3318 bool MemBarNode::cmp( const Node &n ) const {
3319   return (&n == this);          // Always fail except on self
3320 }
3321 
3322 //------------------------------make-------------------------------------------
3323 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3324   switch (opcode) {
3325   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
3326   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
3327   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
3328   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
3329   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
3330   case Op_StoreStoreFence:   return new StoreStoreFenceNode(C, atp, pn);
3331   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3332   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3333   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
3334   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
3335   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
3336   case Op_Initialize:        return new InitializeNode(C, atp, pn);
3337   default: ShouldNotReachHere(); return nullptr;
3338   }
3339 }
3340 
3341 void MemBarNode::remove(PhaseIterGVN *igvn) {
3342   if (outcnt() != 2) {
3343     assert(Opcode() == Op_Initialize, "Only seen when there are no use of init memory");
3344     assert(outcnt() == 1, "Only control then");
3345   }
3346   if (trailing_store() || trailing_load_store()) {
3347     MemBarNode* leading = leading_membar();
3348     if (leading != nullptr) {
3349       assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3350       leading->remove(igvn);
3351     }
3352   }
3353   if (proj_out_or_null(TypeFunc::Memory) != nullptr) {
3354     igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3355   }
3356   if (proj_out_or_null(TypeFunc::Control) != nullptr) {
3357     igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3358   }
3359 }
3360 
3361 //------------------------------Ideal------------------------------------------
3362 // Return a node which is more "ideal" than the current node.  Strip out
3363 // control copies
3364 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3365   if (remove_dead_region(phase, can_reshape)) return this;
3366   // Don't bother trying to transform a dead node
3367   if (in(0) && in(0)->is_top()) {
3368     return nullptr;
3369   }
3370 
3371   bool progress = false;
3372   // Eliminate volatile MemBars for scalar replaced objects.
3373   if (can_reshape && req() == (Precedent+1)) {
3374     bool eliminate = false;
3375     int opc = Opcode();
3376     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3377       // Volatile field loads and stores.
3378       Node* my_mem = in(MemBarNode::Precedent);
3379       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3380       if ((my_mem != nullptr) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3381         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3382         // replace this Precedent (decodeN) with the Load instead.
3383         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
3384           Node* load_node = my_mem->in(1);
3385           set_req(MemBarNode::Precedent, load_node);
3386           phase->is_IterGVN()->_worklist.push(my_mem);
3387           my_mem = load_node;
3388         } else {
3389           assert(my_mem->unique_out() == this, "sanity");
3390           assert(!trailing_load_store(), "load store node can't be eliminated");
3391           del_req(Precedent);
3392           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3393           my_mem = nullptr;
3394         }
3395         progress = true;
3396       }
3397       if (my_mem != nullptr && my_mem->is_Mem()) {
3398         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3399         // Check for scalar replaced object reference.
3400         if( t_oop != nullptr && t_oop->is_known_instance_field() &&
3401             t_oop->offset() != Type::OffsetBot &&
3402             t_oop->offset() != Type::OffsetTop) {
3403           eliminate = true;
3404         }
3405       }
3406     } else if (opc == Op_MemBarRelease) {
3407       // Final field stores.
3408       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
3409       if ((alloc != nullptr) && alloc->is_Allocate() &&
3410           alloc->as_Allocate()->does_not_escape_thread()) {
3411         // The allocated object does not escape.
3412         eliminate = true;
3413       }
3414     }
3415     if (eliminate) {
3416       // Replace MemBar projections by its inputs.
3417       PhaseIterGVN* igvn = phase->is_IterGVN();
3418       remove(igvn);
3419       // Must return either the original node (now dead) or a new node
3420       // (Do not return a top here, since that would break the uniqueness of top.)
3421       return new ConINode(TypeInt::ZERO);
3422     }
3423   }
3424   return progress ? this : nullptr;
3425 }
3426 
3427 //------------------------------Value------------------------------------------
3428 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3429   if( !in(0) ) return Type::TOP;
3430   if( phase->type(in(0)) == Type::TOP )
3431     return Type::TOP;
3432   return TypeTuple::MEMBAR;
3433 }
3434 
3435 //------------------------------match------------------------------------------
3436 // Construct projections for memory.
3437 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3438   switch (proj->_con) {
3439   case TypeFunc::Control:
3440   case TypeFunc::Memory:
3441     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3442   }
3443   ShouldNotReachHere();
3444   return nullptr;
3445 }
3446 
3447 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3448   trailing->_kind = TrailingStore;
3449   leading->_kind = LeadingStore;
3450 #ifdef ASSERT
3451   trailing->_pair_idx = leading->_idx;
3452   leading->_pair_idx = leading->_idx;
3453 #endif
3454 }
3455 
3456 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3457   trailing->_kind = TrailingLoadStore;
3458   leading->_kind = LeadingLoadStore;
3459 #ifdef ASSERT
3460   trailing->_pair_idx = leading->_idx;
3461   leading->_pair_idx = leading->_idx;
3462 #endif
3463 }
3464 
3465 MemBarNode* MemBarNode::trailing_membar() const {
3466   ResourceMark rm;
3467   Node* trailing = (Node*)this;
3468   VectorSet seen;
3469   Node_Stack multis(0);
3470   do {
3471     Node* c = trailing;
3472     uint i = 0;
3473     do {
3474       trailing = nullptr;
3475       for (; i < c->outcnt(); i++) {
3476         Node* next = c->raw_out(i);
3477         if (next != c && next->is_CFG()) {
3478           if (c->is_MultiBranch()) {
3479             if (multis.node() == c) {
3480               multis.set_index(i+1);
3481             } else {
3482               multis.push(c, i+1);
3483             }
3484           }
3485           trailing = next;
3486           break;
3487         }
3488       }
3489       if (trailing != nullptr && !seen.test_set(trailing->_idx)) {
3490         break;
3491       }
3492       while (multis.size() > 0) {
3493         c = multis.node();
3494         i = multis.index();
3495         if (i < c->req()) {
3496           break;
3497         }
3498         multis.pop();
3499       }
3500     } while (multis.size() > 0);
3501   } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3502 
3503   MemBarNode* mb = trailing->as_MemBar();
3504   assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3505          (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3506   assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3507   return mb;
3508 }
3509 
3510 MemBarNode* MemBarNode::leading_membar() const {
3511   ResourceMark rm;
3512   VectorSet seen;
3513   Node_Stack regions(0);
3514   Node* leading = in(0);
3515   while (leading != nullptr && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3516     while (leading == nullptr || leading->is_top() || seen.test_set(leading->_idx)) {
3517       leading = nullptr;
3518       while (regions.size() > 0 && leading == nullptr) {
3519         Node* r = regions.node();
3520         uint i = regions.index();
3521         if (i < r->req()) {
3522           leading = r->in(i);
3523           regions.set_index(i+1);
3524         } else {
3525           regions.pop();
3526         }
3527       }
3528       if (leading == nullptr) {
3529         assert(regions.size() == 0, "all paths should have been tried");
3530         return nullptr;
3531       }
3532     }
3533     if (leading->is_Region()) {
3534       regions.push(leading, 2);
3535       leading = leading->in(1);
3536     } else {
3537       leading = leading->in(0);
3538     }
3539   }
3540 #ifdef ASSERT
3541   Unique_Node_List wq;
3542   wq.push((Node*)this);
3543   uint found = 0;
3544   for (uint i = 0; i < wq.size(); i++) {
3545     Node* n = wq.at(i);
3546     if (n->is_Region()) {
3547       for (uint j = 1; j < n->req(); j++) {
3548         Node* in = n->in(j);
3549         if (in != nullptr && !in->is_top()) {
3550           wq.push(in);
3551         }
3552       }
3553     } else {
3554       if (n->is_MemBar() && n->as_MemBar()->leading()) {
3555         assert(n == leading, "consistency check failed");
3556         found++;
3557       } else {
3558         Node* in = n->in(0);
3559         if (in != nullptr && !in->is_top()) {
3560           wq.push(in);
3561         }
3562       }
3563     }
3564   }
3565   assert(found == 1 || (found == 0 && leading == nullptr), "consistency check failed");
3566 #endif
3567   if (leading == nullptr) {
3568     return nullptr;
3569   }
3570   MemBarNode* mb = leading->as_MemBar();
3571   assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3572          (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3573   assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3574   return mb;
3575 }
3576 
3577 
3578 //===========================InitializeNode====================================
3579 // SUMMARY:
3580 // This node acts as a memory barrier on raw memory, after some raw stores.
3581 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3582 // The Initialize can 'capture' suitably constrained stores as raw inits.
3583 // It can coalesce related raw stores into larger units (called 'tiles').
3584 // It can avoid zeroing new storage for memory units which have raw inits.
3585 // At macro-expansion, it is marked 'complete', and does not optimize further.
3586 //
3587 // EXAMPLE:
3588 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3589 //   ctl = incoming control; mem* = incoming memory
3590 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3591 // First allocate uninitialized memory and fill in the header:
3592 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3593 //   ctl := alloc.Control; mem* := alloc.Memory*
3594 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3595 // Then initialize to zero the non-header parts of the raw memory block:
3596 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3597 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3598 // After the initialize node executes, the object is ready for service:
3599 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3600 // Suppose its body is immediately initialized as {1,2}:
3601 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3602 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3603 //   mem.SLICE(#short[*]) := store2
3604 //
3605 // DETAILS:
3606 // An InitializeNode collects and isolates object initialization after
3607 // an AllocateNode and before the next possible safepoint.  As a
3608 // memory barrier (MemBarNode), it keeps critical stores from drifting
3609 // down past any safepoint or any publication of the allocation.
3610 // Before this barrier, a newly-allocated object may have uninitialized bits.
3611 // After this barrier, it may be treated as a real oop, and GC is allowed.
3612 //
3613 // The semantics of the InitializeNode include an implicit zeroing of
3614 // the new object from object header to the end of the object.
3615 // (The object header and end are determined by the AllocateNode.)
3616 //
3617 // Certain stores may be added as direct inputs to the InitializeNode.
3618 // These stores must update raw memory, and they must be to addresses
3619 // derived from the raw address produced by AllocateNode, and with
3620 // a constant offset.  They must be ordered by increasing offset.
3621 // The first one is at in(RawStores), the last at in(req()-1).
3622 // Unlike most memory operations, they are not linked in a chain,
3623 // but are displayed in parallel as users of the rawmem output of
3624 // the allocation.
3625 //
3626 // (See comments in InitializeNode::capture_store, which continue
3627 // the example given above.)
3628 //
3629 // When the associated Allocate is macro-expanded, the InitializeNode
3630 // may be rewritten to optimize collected stores.  A ClearArrayNode
3631 // may also be created at that point to represent any required zeroing.
3632 // The InitializeNode is then marked 'complete', prohibiting further
3633 // capturing of nearby memory operations.
3634 //
3635 // During macro-expansion, all captured initializations which store
3636 // constant values of 32 bits or smaller are coalesced (if advantageous)
3637 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3638 // initialized in fewer memory operations.  Memory words which are
3639 // covered by neither tiles nor non-constant stores are pre-zeroed
3640 // by explicit stores of zero.  (The code shape happens to do all
3641 // zeroing first, then all other stores, with both sequences occurring
3642 // in order of ascending offsets.)
3643 //
3644 // Alternatively, code may be inserted between an AllocateNode and its
3645 // InitializeNode, to perform arbitrary initialization of the new object.
3646 // E.g., the object copying intrinsics insert complex data transfers here.
3647 // The initialization must then be marked as 'complete' disable the
3648 // built-in zeroing semantics and the collection of initializing stores.
3649 //
3650 // While an InitializeNode is incomplete, reads from the memory state
3651 // produced by it are optimizable if they match the control edge and
3652 // new oop address associated with the allocation/initialization.
3653 // They return a stored value (if the offset matches) or else zero.
3654 // A write to the memory state, if it matches control and address,
3655 // and if it is to a constant offset, may be 'captured' by the
3656 // InitializeNode.  It is cloned as a raw memory operation and rewired
3657 // inside the initialization, to the raw oop produced by the allocation.
3658 // Operations on addresses which are provably distinct (e.g., to
3659 // other AllocateNodes) are allowed to bypass the initialization.
3660 //
3661 // The effect of all this is to consolidate object initialization
3662 // (both arrays and non-arrays, both piecewise and bulk) into a
3663 // single location, where it can be optimized as a unit.
3664 //
3665 // Only stores with an offset less than TrackedInitializationLimit words
3666 // will be considered for capture by an InitializeNode.  This puts a
3667 // reasonable limit on the complexity of optimized initializations.
3668 
3669 //---------------------------InitializeNode------------------------------------
3670 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3671   : MemBarNode(C, adr_type, rawoop),
3672     _is_complete(Incomplete), _does_not_escape(false)
3673 {
3674   init_class_id(Class_Initialize);
3675 
3676   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3677   assert(in(RawAddress) == rawoop, "proper init");
3678   // Note:  allocation() can be null, for secondary initialization barriers
3679 }
3680 
3681 // Since this node is not matched, it will be processed by the
3682 // register allocator.  Declare that there are no constraints
3683 // on the allocation of the RawAddress edge.
3684 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3685   // This edge should be set to top, by the set_complete.  But be conservative.
3686   if (idx == InitializeNode::RawAddress)
3687     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3688   return RegMask::Empty;
3689 }
3690 
3691 Node* InitializeNode::memory(uint alias_idx) {
3692   Node* mem = in(Memory);
3693   if (mem->is_MergeMem()) {
3694     return mem->as_MergeMem()->memory_at(alias_idx);
3695   } else {
3696     // incoming raw memory is not split
3697     return mem;
3698   }
3699 }
3700 
3701 bool InitializeNode::is_non_zero() {
3702   if (is_complete())  return false;
3703   remove_extra_zeroes();
3704   return (req() > RawStores);
3705 }
3706 
3707 void InitializeNode::set_complete(PhaseGVN* phase) {
3708   assert(!is_complete(), "caller responsibility");
3709   _is_complete = Complete;
3710 
3711   // After this node is complete, it contains a bunch of
3712   // raw-memory initializations.  There is no need for
3713   // it to have anything to do with non-raw memory effects.
3714   // Therefore, tell all non-raw users to re-optimize themselves,
3715   // after skipping the memory effects of this initialization.
3716   PhaseIterGVN* igvn = phase->is_IterGVN();
3717   if (igvn)  igvn->add_users_to_worklist(this);
3718 }
3719 
3720 // convenience function
3721 // return false if the init contains any stores already
3722 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3723   InitializeNode* init = initialization();
3724   if (init == nullptr || init->is_complete())  return false;
3725   init->remove_extra_zeroes();
3726   // for now, if this allocation has already collected any inits, bail:
3727   if (init->is_non_zero())  return false;
3728   init->set_complete(phase);
3729   return true;
3730 }
3731 
3732 void InitializeNode::remove_extra_zeroes() {
3733   if (req() == RawStores)  return;
3734   Node* zmem = zero_memory();
3735   uint fill = RawStores;
3736   for (uint i = fill; i < req(); i++) {
3737     Node* n = in(i);
3738     if (n->is_top() || n == zmem)  continue;  // skip
3739     if (fill < i)  set_req(fill, n);          // compact
3740     ++fill;
3741   }
3742   // delete any empty spaces created:
3743   while (fill < req()) {
3744     del_req(fill);
3745   }
3746 }
3747 
3748 // Helper for remembering which stores go with which offsets.
3749 intptr_t InitializeNode::get_store_offset(Node* st, PhaseValues* phase) {
3750   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3751   intptr_t offset = -1;
3752   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3753                                                phase, offset);
3754   if (base == nullptr)  return -1;  // something is dead,
3755   if (offset < 0)       return -1;  //        dead, dead
3756   return offset;
3757 }
3758 
3759 // Helper for proving that an initialization expression is
3760 // "simple enough" to be folded into an object initialization.
3761 // Attempts to prove that a store's initial value 'n' can be captured
3762 // within the initialization without creating a vicious cycle, such as:
3763 //     { Foo p = new Foo(); p.next = p; }
3764 // True for constants and parameters and small combinations thereof.
3765 bool InitializeNode::detect_init_independence(Node* value, PhaseGVN* phase) {
3766   ResourceMark rm;
3767   Unique_Node_List worklist;
3768   worklist.push(value);
3769 
3770   uint complexity_limit = 20;
3771   for (uint j = 0; j < worklist.size(); j++) {
3772     if (j >= complexity_limit) {
3773       return false;  // Bail out if processed too many nodes
3774     }
3775 
3776     Node* n = worklist.at(j);
3777     if (n == nullptr)   continue;   // (can this really happen?)
3778     if (n->is_Proj())   n = n->in(0);
3779     if (n == this)      return false;  // found a cycle
3780     if (n->is_Con())    continue;
3781     if (n->is_Start())  continue;   // params, etc., are OK
3782     if (n->is_Root())   continue;   // even better
3783 
3784     // There cannot be any dependency if 'n' is a CFG node that dominates the current allocation
3785     if (n->is_CFG() && phase->is_dominator(n, allocation())) {
3786       continue;
3787     }
3788 
3789     Node* ctl = n->in(0);
3790     if (ctl != nullptr && !ctl->is_top()) {
3791       if (ctl->is_Proj())  ctl = ctl->in(0);
3792       if (ctl == this)  return false;
3793 
3794       // If we already know that the enclosing memory op is pinned right after
3795       // the init, then any control flow that the store has picked up
3796       // must have preceded the init, or else be equal to the init.
3797       // Even after loop optimizations (which might change control edges)
3798       // a store is never pinned *before* the availability of its inputs.
3799       if (!MemNode::all_controls_dominate(n, this))
3800         return false;                  // failed to prove a good control
3801     }
3802 
3803     // Check data edges for possible dependencies on 'this'.
3804     for (uint i = 1; i < n->req(); i++) {
3805       Node* m = n->in(i);
3806       if (m == nullptr || m == n || m->is_top())  continue;
3807 
3808       // Only process data inputs once
3809       worklist.push(m);
3810     }
3811   }
3812 
3813   return true;
3814 }
3815 
3816 // Here are all the checks a Store must pass before it can be moved into
3817 // an initialization.  Returns zero if a check fails.
3818 // On success, returns the (constant) offset to which the store applies,
3819 // within the initialized memory.
3820 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseGVN* phase, bool can_reshape) {
3821   const int FAIL = 0;
3822   if (st->req() != MemNode::ValueIn + 1)
3823     return FAIL;                // an inscrutable StoreNode (card mark?)
3824   Node* ctl = st->in(MemNode::Control);
3825   if (!(ctl != nullptr && ctl->is_Proj() && ctl->in(0) == this))
3826     return FAIL;                // must be unconditional after the initialization
3827   Node* mem = st->in(MemNode::Memory);
3828   if (!(mem->is_Proj() && mem->in(0) == this))
3829     return FAIL;                // must not be preceded by other stores
3830   Node* adr = st->in(MemNode::Address);
3831   intptr_t offset;
3832   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3833   if (alloc == nullptr)
3834     return FAIL;                // inscrutable address
3835   if (alloc != allocation())
3836     return FAIL;                // wrong allocation!  (store needs to float up)
3837   int size_in_bytes = st->memory_size();
3838   if ((size_in_bytes != 0) && (offset % size_in_bytes) != 0) {
3839     return FAIL;                // mismatched access
3840   }
3841   Node* val = st->in(MemNode::ValueIn);
3842 
3843   if (!detect_init_independence(val, phase))
3844     return FAIL;                // stored value must be 'simple enough'
3845 
3846   // The Store can be captured only if nothing after the allocation
3847   // and before the Store is using the memory location that the store
3848   // overwrites.
3849   bool failed = false;
3850   // If is_complete_with_arraycopy() is true the shape of the graph is
3851   // well defined and is safe so no need for extra checks.
3852   if (!is_complete_with_arraycopy()) {
3853     // We are going to look at each use of the memory state following
3854     // the allocation to make sure nothing reads the memory that the
3855     // Store writes.
3856     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3857     int alias_idx = phase->C->get_alias_index(t_adr);
3858     ResourceMark rm;
3859     Unique_Node_List mems;
3860     mems.push(mem);
3861     Node* unique_merge = nullptr;
3862     for (uint next = 0; next < mems.size(); ++next) {
3863       Node *m  = mems.at(next);
3864       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3865         Node *n = m->fast_out(j);
3866         if (n->outcnt() == 0) {
3867           continue;
3868         }
3869         if (n == st) {
3870           continue;
3871         } else if (n->in(0) != nullptr && n->in(0) != ctl) {
3872           // If the control of this use is different from the control
3873           // of the Store which is right after the InitializeNode then
3874           // this node cannot be between the InitializeNode and the
3875           // Store.
3876           continue;
3877         } else if (n->is_MergeMem()) {
3878           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3879             // We can hit a MergeMemNode (that will likely go away
3880             // later) that is a direct use of the memory state
3881             // following the InitializeNode on the same slice as the
3882             // store node that we'd like to capture. We need to check
3883             // the uses of the MergeMemNode.
3884             mems.push(n);
3885           }
3886         } else if (n->is_Mem()) {
3887           Node* other_adr = n->in(MemNode::Address);
3888           if (other_adr == adr) {
3889             failed = true;
3890             break;
3891           } else {
3892             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3893             if (other_t_adr != nullptr) {
3894               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3895               if (other_alias_idx == alias_idx) {
3896                 // A load from the same memory slice as the store right
3897                 // after the InitializeNode. We check the control of the
3898                 // object/array that is loaded from. If it's the same as
3899                 // the store control then we cannot capture the store.
3900                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3901                 Node* base = other_adr;
3902                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3903                 base = base->in(AddPNode::Base);
3904                 if (base != nullptr) {
3905                   base = base->uncast();
3906                   if (base->is_Proj() && base->in(0) == alloc) {
3907                     failed = true;
3908                     break;
3909                   }
3910                 }
3911               }
3912             }
3913           }
3914         } else {
3915           failed = true;
3916           break;
3917         }
3918       }
3919     }
3920   }
3921   if (failed) {
3922     if (!can_reshape) {
3923       // We decided we couldn't capture the store during parsing. We
3924       // should try again during the next IGVN once the graph is
3925       // cleaner.
3926       phase->C->record_for_igvn(st);
3927     }
3928     return FAIL;
3929   }
3930 
3931   return offset;                // success
3932 }
3933 
3934 // Find the captured store in(i) which corresponds to the range
3935 // [start..start+size) in the initialized object.
3936 // If there is one, return its index i.  If there isn't, return the
3937 // negative of the index where it should be inserted.
3938 // Return 0 if the queried range overlaps an initialization boundary
3939 // or if dead code is encountered.
3940 // If size_in_bytes is zero, do not bother with overlap checks.
3941 int InitializeNode::captured_store_insertion_point(intptr_t start,
3942                                                    int size_in_bytes,
3943                                                    PhaseValues* phase) {
3944   const int FAIL = 0, MAX_STORE = MAX2(BytesPerLong, (int)MaxVectorSize);
3945 
3946   if (is_complete())
3947     return FAIL;                // arraycopy got here first; punt
3948 
3949   assert(allocation() != nullptr, "must be present");
3950 
3951   // no negatives, no header fields:
3952   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3953 
3954   // after a certain size, we bail out on tracking all the stores:
3955   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3956   if (start >= ti_limit)  return FAIL;
3957 
3958   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3959     if (i >= limit)  return -(int)i; // not found; here is where to put it
3960 
3961     Node*    st     = in(i);
3962     intptr_t st_off = get_store_offset(st, phase);
3963     if (st_off < 0) {
3964       if (st != zero_memory()) {
3965         return FAIL;            // bail out if there is dead garbage
3966       }
3967     } else if (st_off > start) {
3968       // ...we are done, since stores are ordered
3969       if (st_off < start + size_in_bytes) {
3970         return FAIL;            // the next store overlaps
3971       }
3972       return -(int)i;           // not found; here is where to put it
3973     } else if (st_off < start) {
3974       assert(st->as_Store()->memory_size() <= MAX_STORE, "");
3975       if (size_in_bytes != 0 &&
3976           start < st_off + MAX_STORE &&
3977           start < st_off + st->as_Store()->memory_size()) {
3978         return FAIL;            // the previous store overlaps
3979       }
3980     } else {
3981       if (size_in_bytes != 0 &&
3982           st->as_Store()->memory_size() != size_in_bytes) {
3983         return FAIL;            // mismatched store size
3984       }
3985       return i;
3986     }
3987 
3988     ++i;
3989   }
3990 }
3991 
3992 // Look for a captured store which initializes at the offset 'start'
3993 // with the given size.  If there is no such store, and no other
3994 // initialization interferes, then return zero_memory (the memory
3995 // projection of the AllocateNode).
3996 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3997                                           PhaseValues* phase) {
3998   assert(stores_are_sane(phase), "");
3999   int i = captured_store_insertion_point(start, size_in_bytes, phase);
4000   if (i == 0) {
4001     return nullptr;              // something is dead
4002   } else if (i < 0) {
4003     return zero_memory();       // just primordial zero bits here
4004   } else {
4005     Node* st = in(i);           // here is the store at this position
4006     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
4007     return st;
4008   }
4009 }
4010 
4011 // Create, as a raw pointer, an address within my new object at 'offset'.
4012 Node* InitializeNode::make_raw_address(intptr_t offset,
4013                                        PhaseGVN* phase) {
4014   Node* addr = in(RawAddress);
4015   if (offset != 0) {
4016     Compile* C = phase->C;
4017     addr = phase->transform( new AddPNode(C->top(), addr,
4018                                                  phase->MakeConX(offset)) );
4019   }
4020   return addr;
4021 }
4022 
4023 // Clone the given store, converting it into a raw store
4024 // initializing a field or element of my new object.
4025 // Caller is responsible for retiring the original store,
4026 // with subsume_node or the like.
4027 //
4028 // From the example above InitializeNode::InitializeNode,
4029 // here are the old stores to be captured:
4030 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
4031 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
4032 //
4033 // Here is the changed code; note the extra edges on init:
4034 //   alloc = (Allocate ...)
4035 //   rawoop = alloc.RawAddress
4036 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
4037 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
4038 //   init = (Initialize alloc.Control alloc.Memory rawoop
4039 //                      rawstore1 rawstore2)
4040 //
4041 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
4042                                     PhaseGVN* phase, bool can_reshape) {
4043   assert(stores_are_sane(phase), "");
4044 
4045   if (start < 0)  return nullptr;
4046   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
4047 
4048   Compile* C = phase->C;
4049   int size_in_bytes = st->memory_size();
4050   int i = captured_store_insertion_point(start, size_in_bytes, phase);
4051   if (i == 0)  return nullptr;  // bail out
4052   Node* prev_mem = nullptr;     // raw memory for the captured store
4053   if (i > 0) {
4054     prev_mem = in(i);           // there is a pre-existing store under this one
4055     set_req(i, C->top());       // temporarily disconnect it
4056     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
4057   } else {
4058     i = -i;                     // no pre-existing store
4059     prev_mem = zero_memory();   // a slice of the newly allocated object
4060     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
4061       set_req(--i, C->top());   // reuse this edge; it has been folded away
4062     else
4063       ins_req(i, C->top());     // build a new edge
4064   }
4065   Node* new_st = st->clone();
4066   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4067   new_st->set_req(MemNode::Control, in(Control));
4068   new_st->set_req(MemNode::Memory,  prev_mem);
4069   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
4070   bs->eliminate_gc_barrier_data(new_st);
4071   new_st = phase->transform(new_st);
4072 
4073   // At this point, new_st might have swallowed a pre-existing store
4074   // at the same offset, or perhaps new_st might have disappeared,
4075   // if it redundantly stored the same value (or zero to fresh memory).
4076 
4077   // In any case, wire it in:
4078   PhaseIterGVN* igvn = phase->is_IterGVN();
4079   if (igvn) {
4080     igvn->rehash_node_delayed(this);
4081   }
4082   set_req(i, new_st);
4083 
4084   // The caller may now kill the old guy.
4085   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
4086   assert(check_st == new_st || check_st == nullptr, "must be findable");
4087   assert(!is_complete(), "");
4088   return new_st;
4089 }
4090 
4091 static bool store_constant(jlong* tiles, int num_tiles,
4092                            intptr_t st_off, int st_size,
4093                            jlong con) {
4094   if ((st_off & (st_size-1)) != 0)
4095     return false;               // strange store offset (assume size==2**N)
4096   address addr = (address)tiles + st_off;
4097   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
4098   switch (st_size) {
4099   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
4100   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
4101   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
4102   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
4103   default: return false;        // strange store size (detect size!=2**N here)
4104   }
4105   return true;                  // return success to caller
4106 }
4107 
4108 // Coalesce subword constants into int constants and possibly
4109 // into long constants.  The goal, if the CPU permits,
4110 // is to initialize the object with a small number of 64-bit tiles.
4111 // Also, convert floating-point constants to bit patterns.
4112 // Non-constants are not relevant to this pass.
4113 //
4114 // In terms of the running example on InitializeNode::InitializeNode
4115 // and InitializeNode::capture_store, here is the transformation
4116 // of rawstore1 and rawstore2 into rawstore12:
4117 //   alloc = (Allocate ...)
4118 //   rawoop = alloc.RawAddress
4119 //   tile12 = 0x00010002
4120 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
4121 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
4122 //
4123 void
4124 InitializeNode::coalesce_subword_stores(intptr_t header_size,
4125                                         Node* size_in_bytes,
4126                                         PhaseGVN* phase) {
4127   Compile* C = phase->C;
4128 
4129   assert(stores_are_sane(phase), "");
4130   // Note:  After this pass, they are not completely sane,
4131   // since there may be some overlaps.
4132 
4133   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
4134 
4135   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
4136   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
4137   size_limit = MIN2(size_limit, ti_limit);
4138   size_limit = align_up(size_limit, BytesPerLong);
4139   int num_tiles = size_limit / BytesPerLong;
4140 
4141   // allocate space for the tile map:
4142   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
4143   jlong  tiles_buf[small_len];
4144   Node*  nodes_buf[small_len];
4145   jlong  inits_buf[small_len];
4146   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
4147                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
4148   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
4149                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
4150   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
4151                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
4152   // tiles: exact bitwise model of all primitive constants
4153   // nodes: last constant-storing node subsumed into the tiles model
4154   // inits: which bytes (in each tile) are touched by any initializations
4155 
4156   //// Pass A: Fill in the tile model with any relevant stores.
4157 
4158   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
4159   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
4160   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
4161   Node* zmem = zero_memory(); // initially zero memory state
4162   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4163     Node* st = in(i);
4164     intptr_t st_off = get_store_offset(st, phase);
4165 
4166     // Figure out the store's offset and constant value:
4167     if (st_off < header_size)             continue; //skip (ignore header)
4168     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
4169     int st_size = st->as_Store()->memory_size();
4170     if (st_off + st_size > size_limit)    break;
4171 
4172     // Record which bytes are touched, whether by constant or not.
4173     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
4174       continue;                 // skip (strange store size)
4175 
4176     const Type* val = phase->type(st->in(MemNode::ValueIn));
4177     if (!val->singleton())                continue; //skip (non-con store)
4178     BasicType type = val->basic_type();
4179 
4180     jlong con = 0;
4181     switch (type) {
4182     case T_INT:    con = val->is_int()->get_con();  break;
4183     case T_LONG:   con = val->is_long()->get_con(); break;
4184     case T_FLOAT:  con = jint_cast(val->getf());    break;
4185     case T_DOUBLE: con = jlong_cast(val->getd());   break;
4186     default:                              continue; //skip (odd store type)
4187     }
4188 
4189     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
4190         st->Opcode() == Op_StoreL) {
4191       continue;                 // This StoreL is already optimal.
4192     }
4193 
4194     // Store down the constant.
4195     store_constant(tiles, num_tiles, st_off, st_size, con);
4196 
4197     intptr_t j = st_off >> LogBytesPerLong;
4198 
4199     if (type == T_INT && st_size == BytesPerInt
4200         && (st_off & BytesPerInt) == BytesPerInt) {
4201       jlong lcon = tiles[j];
4202       if (!Matcher::isSimpleConstant64(lcon) &&
4203           st->Opcode() == Op_StoreI) {
4204         // This StoreI is already optimal by itself.
4205         jint* intcon = (jint*) &tiles[j];
4206         intcon[1] = 0;  // undo the store_constant()
4207 
4208         // If the previous store is also optimal by itself, back up and
4209         // undo the action of the previous loop iteration... if we can.
4210         // But if we can't, just let the previous half take care of itself.
4211         st = nodes[j];
4212         st_off -= BytesPerInt;
4213         con = intcon[0];
4214         if (con != 0 && st != nullptr && st->Opcode() == Op_StoreI) {
4215           assert(st_off >= header_size, "still ignoring header");
4216           assert(get_store_offset(st, phase) == st_off, "must be");
4217           assert(in(i-1) == zmem, "must be");
4218           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
4219           assert(con == tcon->is_int()->get_con(), "must be");
4220           // Undo the effects of the previous loop trip, which swallowed st:
4221           intcon[0] = 0;        // undo store_constant()
4222           set_req(i-1, st);     // undo set_req(i, zmem)
4223           nodes[j] = nullptr;   // undo nodes[j] = st
4224           --old_subword;        // undo ++old_subword
4225         }
4226         continue;               // This StoreI is already optimal.
4227       }
4228     }
4229 
4230     // This store is not needed.
4231     set_req(i, zmem);
4232     nodes[j] = st;              // record for the moment
4233     if (st_size < BytesPerLong) // something has changed
4234           ++old_subword;        // includes int/float, but who's counting...
4235     else  ++old_long;
4236   }
4237 
4238   if ((old_subword + old_long) == 0)
4239     return;                     // nothing more to do
4240 
4241   //// Pass B: Convert any non-zero tiles into optimal constant stores.
4242   // Be sure to insert them before overlapping non-constant stores.
4243   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
4244   for (int j = 0; j < num_tiles; j++) {
4245     jlong con  = tiles[j];
4246     jlong init = inits[j];
4247     if (con == 0)  continue;
4248     jint con0,  con1;           // split the constant, address-wise
4249     jint init0, init1;          // split the init map, address-wise
4250     { union { jlong con; jint intcon[2]; } u;
4251       u.con = con;
4252       con0  = u.intcon[0];
4253       con1  = u.intcon[1];
4254       u.con = init;
4255       init0 = u.intcon[0];
4256       init1 = u.intcon[1];
4257     }
4258 
4259     Node* old = nodes[j];
4260     assert(old != nullptr, "need the prior store");
4261     intptr_t offset = (j * BytesPerLong);
4262 
4263     bool split = !Matcher::isSimpleConstant64(con);
4264 
4265     if (offset < header_size) {
4266       assert(offset + BytesPerInt >= header_size, "second int counts");
4267       assert(*(jint*)&tiles[j] == 0, "junk in header");
4268       split = true;             // only the second word counts
4269       // Example:  int a[] = { 42 ... }
4270     } else if (con0 == 0 && init0 == -1) {
4271       split = true;             // first word is covered by full inits
4272       // Example:  int a[] = { ... foo(), 42 ... }
4273     } else if (con1 == 0 && init1 == -1) {
4274       split = true;             // second word is covered by full inits
4275       // Example:  int a[] = { ... 42, foo() ... }
4276     }
4277 
4278     // Here's a case where init0 is neither 0 nor -1:
4279     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
4280     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
4281     // In this case the tile is not split; it is (jlong)42.
4282     // The big tile is stored down, and then the foo() value is inserted.
4283     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
4284 
4285     Node* ctl = old->in(MemNode::Control);
4286     Node* adr = make_raw_address(offset, phase);
4287     const TypePtr* atp = TypeRawPtr::BOTTOM;
4288 
4289     // One or two coalesced stores to plop down.
4290     Node*    st[2];
4291     intptr_t off[2];
4292     int  nst = 0;
4293     if (!split) {
4294       ++new_long;
4295       off[nst] = offset;
4296       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4297                                   phase->longcon(con), T_LONG, MemNode::unordered);
4298     } else {
4299       // Omit either if it is a zero.
4300       if (con0 != 0) {
4301         ++new_int;
4302         off[nst]  = offset;
4303         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4304                                     phase->intcon(con0), T_INT, MemNode::unordered);
4305       }
4306       if (con1 != 0) {
4307         ++new_int;
4308         offset += BytesPerInt;
4309         adr = make_raw_address(offset, phase);
4310         off[nst]  = offset;
4311         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4312                                     phase->intcon(con1), T_INT, MemNode::unordered);
4313       }
4314     }
4315 
4316     // Insert second store first, then the first before the second.
4317     // Insert each one just before any overlapping non-constant stores.
4318     while (nst > 0) {
4319       Node* st1 = st[--nst];
4320       C->copy_node_notes_to(st1, old);
4321       st1 = phase->transform(st1);
4322       offset = off[nst];
4323       assert(offset >= header_size, "do not smash header");
4324       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4325       guarantee(ins_idx != 0, "must re-insert constant store");
4326       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
4327       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4328         set_req(--ins_idx, st1);
4329       else
4330         ins_req(ins_idx, st1);
4331     }
4332   }
4333 
4334   if (PrintCompilation && WizardMode)
4335     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4336                   old_subword, old_long, new_int, new_long);
4337   if (C->log() != nullptr)
4338     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4339                    old_subword, old_long, new_int, new_long);
4340 
4341   // Clean up any remaining occurrences of zmem:
4342   remove_extra_zeroes();
4343 }
4344 
4345 // Explore forward from in(start) to find the first fully initialized
4346 // word, and return its offset.  Skip groups of subword stores which
4347 // together initialize full words.  If in(start) is itself part of a
4348 // fully initialized word, return the offset of in(start).  If there
4349 // are no following full-word stores, or if something is fishy, return
4350 // a negative value.
4351 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4352   int       int_map = 0;
4353   intptr_t  int_map_off = 0;
4354   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
4355 
4356   for (uint i = start, limit = req(); i < limit; i++) {
4357     Node* st = in(i);
4358 
4359     intptr_t st_off = get_store_offset(st, phase);
4360     if (st_off < 0)  break;  // return conservative answer
4361 
4362     int st_size = st->as_Store()->memory_size();
4363     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4364       return st_off;            // we found a complete word init
4365     }
4366 
4367     // update the map:
4368 
4369     intptr_t this_int_off = align_down(st_off, BytesPerInt);
4370     if (this_int_off != int_map_off) {
4371       // reset the map:
4372       int_map = 0;
4373       int_map_off = this_int_off;
4374     }
4375 
4376     int subword_off = st_off - this_int_off;
4377     int_map |= right_n_bits(st_size) << subword_off;
4378     if ((int_map & FULL_MAP) == FULL_MAP) {
4379       return this_int_off;      // we found a complete word init
4380     }
4381 
4382     // Did this store hit or cross the word boundary?
4383     intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4384     if (next_int_off == this_int_off + BytesPerInt) {
4385       // We passed the current int, without fully initializing it.
4386       int_map_off = next_int_off;
4387       int_map >>= BytesPerInt;
4388     } else if (next_int_off > this_int_off + BytesPerInt) {
4389       // We passed the current and next int.
4390       return this_int_off + BytesPerInt;
4391     }
4392   }
4393 
4394   return -1;
4395 }
4396 
4397 
4398 // Called when the associated AllocateNode is expanded into CFG.
4399 // At this point, we may perform additional optimizations.
4400 // Linearize the stores by ascending offset, to make memory
4401 // activity as coherent as possible.
4402 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4403                                       intptr_t header_size,
4404                                       Node* size_in_bytes,
4405                                       PhaseIterGVN* phase) {
4406   assert(!is_complete(), "not already complete");
4407   assert(stores_are_sane(phase), "");
4408   assert(allocation() != nullptr, "must be present");
4409 
4410   remove_extra_zeroes();
4411 
4412   if (ReduceFieldZeroing || ReduceBulkZeroing)
4413     // reduce instruction count for common initialization patterns
4414     coalesce_subword_stores(header_size, size_in_bytes, phase);
4415 
4416   Node* zmem = zero_memory();   // initially zero memory state
4417   Node* inits = zmem;           // accumulating a linearized chain of inits
4418   #ifdef ASSERT
4419   intptr_t first_offset = allocation()->minimum_header_size();
4420   intptr_t last_init_off = first_offset;  // previous init offset
4421   intptr_t last_init_end = first_offset;  // previous init offset+size
4422   intptr_t last_tile_end = first_offset;  // previous tile offset+size
4423   #endif
4424   intptr_t zeroes_done = header_size;
4425 
4426   bool do_zeroing = true;       // we might give up if inits are very sparse
4427   int  big_init_gaps = 0;       // how many large gaps have we seen?
4428 
4429   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
4430   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
4431 
4432   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4433     Node* st = in(i);
4434     intptr_t st_off = get_store_offset(st, phase);
4435     if (st_off < 0)
4436       break;                    // unknown junk in the inits
4437     if (st->in(MemNode::Memory) != zmem)
4438       break;                    // complicated store chains somehow in list
4439 
4440     int st_size = st->as_Store()->memory_size();
4441     intptr_t next_init_off = st_off + st_size;
4442 
4443     if (do_zeroing && zeroes_done < next_init_off) {
4444       // See if this store needs a zero before it or under it.
4445       intptr_t zeroes_needed = st_off;
4446 
4447       if (st_size < BytesPerInt) {
4448         // Look for subword stores which only partially initialize words.
4449         // If we find some, we must lay down some word-level zeroes first,
4450         // underneath the subword stores.
4451         //
4452         // Examples:
4453         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
4454         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
4455         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
4456         //
4457         // Note:  coalesce_subword_stores may have already done this,
4458         // if it was prompted by constant non-zero subword initializers.
4459         // But this case can still arise with non-constant stores.
4460 
4461         intptr_t next_full_store = find_next_fullword_store(i, phase);
4462 
4463         // In the examples above:
4464         //   in(i)          p   q   r   s     x   y     z
4465         //   st_off        12  13  14  15    12  13    14
4466         //   st_size        1   1   1   1     1   1     1
4467         //   next_full_s.  12  16  16  16    16  16    16
4468         //   z's_done      12  16  16  16    12  16    12
4469         //   z's_needed    12  16  16  16    16  16    16
4470         //   zsize          0   0   0   0     4   0     4
4471         if (next_full_store < 0) {
4472           // Conservative tack:  Zero to end of current word.
4473           zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4474         } else {
4475           // Zero to beginning of next fully initialized word.
4476           // Or, don't zero at all, if we are already in that word.
4477           assert(next_full_store >= zeroes_needed, "must go forward");
4478           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4479           zeroes_needed = next_full_store;
4480         }
4481       }
4482 
4483       if (zeroes_needed > zeroes_done) {
4484         intptr_t zsize = zeroes_needed - zeroes_done;
4485         // Do some incremental zeroing on rawmem, in parallel with inits.
4486         zeroes_done = align_down(zeroes_done, BytesPerInt);
4487         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4488                                               zeroes_done, zeroes_needed,
4489                                               phase);
4490         zeroes_done = zeroes_needed;
4491         if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4492           do_zeroing = false;   // leave the hole, next time
4493       }
4494     }
4495 
4496     // Collect the store and move on:
4497     phase->replace_input_of(st, MemNode::Memory, inits);
4498     inits = st;                 // put it on the linearized chain
4499     set_req(i, zmem);           // unhook from previous position
4500 
4501     if (zeroes_done == st_off)
4502       zeroes_done = next_init_off;
4503 
4504     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4505 
4506     #ifdef ASSERT
4507     // Various order invariants.  Weaker than stores_are_sane because
4508     // a large constant tile can be filled in by smaller non-constant stores.
4509     assert(st_off >= last_init_off, "inits do not reverse");
4510     last_init_off = st_off;
4511     const Type* val = nullptr;
4512     if (st_size >= BytesPerInt &&
4513         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4514         (int)val->basic_type() < (int)T_OBJECT) {
4515       assert(st_off >= last_tile_end, "tiles do not overlap");
4516       assert(st_off >= last_init_end, "tiles do not overwrite inits");
4517       last_tile_end = MAX2(last_tile_end, next_init_off);
4518     } else {
4519       intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4520       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4521       assert(st_off      >= last_init_end, "inits do not overlap");
4522       last_init_end = next_init_off;  // it's a non-tile
4523     }
4524     #endif //ASSERT
4525   }
4526 
4527   remove_extra_zeroes();        // clear out all the zmems left over
4528   add_req(inits);
4529 
4530   if (!(UseTLAB && ZeroTLAB)) {
4531     // If anything remains to be zeroed, zero it all now.
4532     zeroes_done = align_down(zeroes_done, BytesPerInt);
4533     // if it is the last unused 4 bytes of an instance, forget about it
4534     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4535     if (zeroes_done + BytesPerLong >= size_limit) {
4536       AllocateNode* alloc = allocation();
4537       assert(alloc != nullptr, "must be present");
4538       if (alloc != nullptr && alloc->Opcode() == Op_Allocate) {
4539         Node* klass_node = alloc->in(AllocateNode::KlassNode);
4540         ciKlass* k = phase->type(klass_node)->is_instklassptr()->instance_klass();
4541         if (zeroes_done == k->layout_helper())
4542           zeroes_done = size_limit;
4543       }
4544     }
4545     if (zeroes_done < size_limit) {
4546       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4547                                             zeroes_done, size_in_bytes, phase);
4548     }
4549   }
4550 
4551   set_complete(phase);
4552   return rawmem;
4553 }
4554 
4555 
4556 #ifdef ASSERT
4557 bool InitializeNode::stores_are_sane(PhaseValues* phase) {
4558   if (is_complete())
4559     return true;                // stores could be anything at this point
4560   assert(allocation() != nullptr, "must be present");
4561   intptr_t last_off = allocation()->minimum_header_size();
4562   for (uint i = InitializeNode::RawStores; i < req(); i++) {
4563     Node* st = in(i);
4564     intptr_t st_off = get_store_offset(st, phase);
4565     if (st_off < 0)  continue;  // ignore dead garbage
4566     if (last_off > st_off) {
4567       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4568       this->dump(2);
4569       assert(false, "ascending store offsets");
4570       return false;
4571     }
4572     last_off = st_off + st->as_Store()->memory_size();
4573   }
4574   return true;
4575 }
4576 #endif //ASSERT
4577 
4578 
4579 
4580 
4581 //============================MergeMemNode=====================================
4582 //
4583 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4584 // contributing store or call operations.  Each contributor provides the memory
4585 // state for a particular "alias type" (see Compile::alias_type).  For example,
4586 // if a MergeMem has an input X for alias category #6, then any memory reference
4587 // to alias category #6 may use X as its memory state input, as an exact equivalent
4588 // to using the MergeMem as a whole.
4589 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4590 //
4591 // (Here, the <N> notation gives the index of the relevant adr_type.)
4592 //
4593 // In one special case (and more cases in the future), alias categories overlap.
4594 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4595 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4596 // it is exactly equivalent to that state W:
4597 //   MergeMem(<Bot>: W) <==> W
4598 //
4599 // Usually, the merge has more than one input.  In that case, where inputs
4600 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4601 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4602 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4603 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4604 //
4605 // A merge can take a "wide" memory state as one of its narrow inputs.
4606 // This simply means that the merge observes out only the relevant parts of
4607 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4608 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4609 //
4610 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4611 // and that memory slices "leak through":
4612 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4613 //
4614 // But, in such a cascade, repeated memory slices can "block the leak":
4615 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4616 //
4617 // In the last example, Y is not part of the combined memory state of the
4618 // outermost MergeMem.  The system must, of course, prevent unschedulable
4619 // memory states from arising, so you can be sure that the state Y is somehow
4620 // a precursor to state Y'.
4621 //
4622 //
4623 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4624 // of each MergeMemNode array are exactly the numerical alias indexes, including
4625 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4626 // Compile::alias_type (and kin) produce and manage these indexes.
4627 //
4628 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4629 // (Note that this provides quick access to the top node inside MergeMem methods,
4630 // without the need to reach out via TLS to Compile::current.)
4631 //
4632 // As a consequence of what was just described, a MergeMem that represents a full
4633 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4634 // containing all alias categories.
4635 //
4636 // MergeMem nodes never (?) have control inputs, so in(0) is null.
4637 //
4638 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4639 // a memory state for the alias type <N>, or else the top node, meaning that
4640 // there is no particular input for that alias type.  Note that the length of
4641 // a MergeMem is variable, and may be extended at any time to accommodate new
4642 // memory states at larger alias indexes.  When merges grow, they are of course
4643 // filled with "top" in the unused in() positions.
4644 //
4645 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4646 // (Top was chosen because it works smoothly with passes like GCM.)
4647 //
4648 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4649 // the type of random VM bits like TLS references.)  Since it is always the
4650 // first non-Bot memory slice, some low-level loops use it to initialize an
4651 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4652 //
4653 //
4654 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4655 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4656 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4657 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4658 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4659 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4660 //
4661 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4662 // really that different from the other memory inputs.  An abbreviation called
4663 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4664 //
4665 //
4666 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4667 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4668 // that "emerges though" the base memory will be marked as excluding the alias types
4669 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4670 //
4671 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4672 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4673 //
4674 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4675 // (It is currently unimplemented.)  As you can see, the resulting merge is
4676 // actually a disjoint union of memory states, rather than an overlay.
4677 //
4678 
4679 //------------------------------MergeMemNode-----------------------------------
4680 Node* MergeMemNode::make_empty_memory() {
4681   Node* empty_memory = (Node*) Compile::current()->top();
4682   assert(empty_memory->is_top(), "correct sentinel identity");
4683   return empty_memory;
4684 }
4685 
4686 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4687   init_class_id(Class_MergeMem);
4688   // all inputs are nullified in Node::Node(int)
4689   // set_input(0, nullptr);  // no control input
4690 
4691   // Initialize the edges uniformly to top, for starters.
4692   Node* empty_mem = make_empty_memory();
4693   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4694     init_req(i,empty_mem);
4695   }
4696   assert(empty_memory() == empty_mem, "");
4697 
4698   if( new_base != nullptr && new_base->is_MergeMem() ) {
4699     MergeMemNode* mdef = new_base->as_MergeMem();
4700     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4701     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4702       mms.set_memory(mms.memory2());
4703     }
4704     assert(base_memory() == mdef->base_memory(), "");
4705   } else {
4706     set_base_memory(new_base);
4707   }
4708 }
4709 
4710 // Make a new, untransformed MergeMem with the same base as 'mem'.
4711 // If mem is itself a MergeMem, populate the result with the same edges.
4712 MergeMemNode* MergeMemNode::make(Node* mem) {
4713   return new MergeMemNode(mem);
4714 }
4715 
4716 //------------------------------cmp--------------------------------------------
4717 uint MergeMemNode::hash() const { return NO_HASH; }
4718 bool MergeMemNode::cmp( const Node &n ) const {
4719   return (&n == this);          // Always fail except on self
4720 }
4721 
4722 //------------------------------Identity---------------------------------------
4723 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4724   // Identity if this merge point does not record any interesting memory
4725   // disambiguations.
4726   Node* base_mem = base_memory();
4727   Node* empty_mem = empty_memory();
4728   if (base_mem != empty_mem) {  // Memory path is not dead?
4729     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4730       Node* mem = in(i);
4731       if (mem != empty_mem && mem != base_mem) {
4732         return this;            // Many memory splits; no change
4733       }
4734     }
4735   }
4736   return base_mem;              // No memory splits; ID on the one true input
4737 }
4738 
4739 //------------------------------Ideal------------------------------------------
4740 // This method is invoked recursively on chains of MergeMem nodes
4741 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4742   // Remove chain'd MergeMems
4743   //
4744   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4745   // relative to the "in(Bot)".  Since we are patching both at the same time,
4746   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4747   // but rewrite each "in(i)" relative to the new "in(Bot)".
4748   Node *progress = nullptr;
4749 
4750 
4751   Node* old_base = base_memory();
4752   Node* empty_mem = empty_memory();
4753   if (old_base == empty_mem)
4754     return nullptr; // Dead memory path.
4755 
4756   MergeMemNode* old_mbase;
4757   if (old_base != nullptr && old_base->is_MergeMem())
4758     old_mbase = old_base->as_MergeMem();
4759   else
4760     old_mbase = nullptr;
4761   Node* new_base = old_base;
4762 
4763   // simplify stacked MergeMems in base memory
4764   if (old_mbase)  new_base = old_mbase->base_memory();
4765 
4766   // the base memory might contribute new slices beyond my req()
4767   if (old_mbase)  grow_to_match(old_mbase);
4768 
4769   // Note:  We do not call verify_sparse on entry, because inputs
4770   // can normalize to the base_memory via subsume_node or similar
4771   // mechanisms.  This method repairs that damage.
4772 
4773   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4774 
4775   // Look at each slice.
4776   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4777     Node* old_in = in(i);
4778     // calculate the old memory value
4779     Node* old_mem = old_in;
4780     if (old_mem == empty_mem)  old_mem = old_base;
4781     assert(old_mem == memory_at(i), "");
4782 
4783     // maybe update (reslice) the old memory value
4784 
4785     // simplify stacked MergeMems
4786     Node* new_mem = old_mem;
4787     MergeMemNode* old_mmem;
4788     if (old_mem != nullptr && old_mem->is_MergeMem())
4789       old_mmem = old_mem->as_MergeMem();
4790     else
4791       old_mmem = nullptr;
4792     if (old_mmem == this) {
4793       // This can happen if loops break up and safepoints disappear.
4794       // A merge of BotPtr (default) with a RawPtr memory derived from a
4795       // safepoint can be rewritten to a merge of the same BotPtr with
4796       // the BotPtr phi coming into the loop.  If that phi disappears
4797       // also, we can end up with a self-loop of the mergemem.
4798       // In general, if loops degenerate and memory effects disappear,
4799       // a mergemem can be left looking at itself.  This simply means
4800       // that the mergemem's default should be used, since there is
4801       // no longer any apparent effect on this slice.
4802       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4803       //       from start.  Update the input to TOP.
4804       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4805     }
4806     else if (old_mmem != nullptr) {
4807       new_mem = old_mmem->memory_at(i);
4808     }
4809     // else preceding memory was not a MergeMem
4810 
4811     // maybe store down a new value
4812     Node* new_in = new_mem;
4813     if (new_in == new_base)  new_in = empty_mem;
4814 
4815     if (new_in != old_in) {
4816       // Warning:  Do not combine this "if" with the previous "if"
4817       // A memory slice might have be be rewritten even if it is semantically
4818       // unchanged, if the base_memory value has changed.
4819       set_req_X(i, new_in, phase);
4820       progress = this;          // Report progress
4821     }
4822   }
4823 
4824   if (new_base != old_base) {
4825     set_req_X(Compile::AliasIdxBot, new_base, phase);
4826     // Don't use set_base_memory(new_base), because we need to update du.
4827     assert(base_memory() == new_base, "");
4828     progress = this;
4829   }
4830 
4831   if( base_memory() == this ) {
4832     // a self cycle indicates this memory path is dead
4833     set_req(Compile::AliasIdxBot, empty_mem);
4834   }
4835 
4836   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4837   // Recursion must occur after the self cycle check above
4838   if( base_memory()->is_MergeMem() ) {
4839     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4840     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4841     if( m != nullptr &&
4842         (m->is_top() ||
4843          (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4844       // propagate rollup of dead cycle to self
4845       set_req(Compile::AliasIdxBot, empty_mem);
4846     }
4847   }
4848 
4849   if( base_memory() == empty_mem ) {
4850     progress = this;
4851     // Cut inputs during Parse phase only.
4852     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4853     if( !can_reshape ) {
4854       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4855         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4856       }
4857     }
4858   }
4859 
4860   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4861     // Check if PhiNode::Ideal's "Split phis through memory merges"
4862     // transform should be attempted. Look for this->phi->this cycle.
4863     uint merge_width = req();
4864     if (merge_width > Compile::AliasIdxRaw) {
4865       PhiNode* phi = base_memory()->as_Phi();
4866       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4867         if (phi->in(i) == this) {
4868           phase->is_IterGVN()->_worklist.push(phi);
4869           break;
4870         }
4871       }
4872     }
4873   }
4874 
4875   assert(progress || verify_sparse(), "please, no dups of base");
4876   return progress;
4877 }
4878 
4879 //-------------------------set_base_memory-------------------------------------
4880 void MergeMemNode::set_base_memory(Node *new_base) {
4881   Node* empty_mem = empty_memory();
4882   set_req(Compile::AliasIdxBot, new_base);
4883   assert(memory_at(req()) == new_base, "must set default memory");
4884   // Clear out other occurrences of new_base:
4885   if (new_base != empty_mem) {
4886     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4887       if (in(i) == new_base)  set_req(i, empty_mem);
4888     }
4889   }
4890 }
4891 
4892 //------------------------------out_RegMask------------------------------------
4893 const RegMask &MergeMemNode::out_RegMask() const {
4894   return RegMask::Empty;
4895 }
4896 
4897 //------------------------------dump_spec--------------------------------------
4898 #ifndef PRODUCT
4899 void MergeMemNode::dump_spec(outputStream *st) const {
4900   st->print(" {");
4901   Node* base_mem = base_memory();
4902   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4903     Node* mem = (in(i) != nullptr) ? memory_at(i) : base_mem;
4904     if (mem == base_mem) { st->print(" -"); continue; }
4905     st->print( " N%d:", mem->_idx );
4906     Compile::current()->get_adr_type(i)->dump_on(st);
4907   }
4908   st->print(" }");
4909 }
4910 #endif // !PRODUCT
4911 
4912 
4913 #ifdef ASSERT
4914 static bool might_be_same(Node* a, Node* b) {
4915   if (a == b)  return true;
4916   if (!(a->is_Phi() || b->is_Phi()))  return false;
4917   // phis shift around during optimization
4918   return true;  // pretty stupid...
4919 }
4920 
4921 // verify a narrow slice (either incoming or outgoing)
4922 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4923   if (!VerifyAliases)                return;  // don't bother to verify unless requested
4924   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
4925   if (Node::in_dump())               return;  // muzzle asserts when printing
4926   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4927   assert(n != nullptr, "");
4928   // Elide intervening MergeMem's
4929   while (n->is_MergeMem()) {
4930     n = n->as_MergeMem()->memory_at(alias_idx);
4931   }
4932   Compile* C = Compile::current();
4933   const TypePtr* n_adr_type = n->adr_type();
4934   if (n == m->empty_memory()) {
4935     // Implicit copy of base_memory()
4936   } else if (n_adr_type != TypePtr::BOTTOM) {
4937     assert(n_adr_type != nullptr, "new memory must have a well-defined adr_type");
4938     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4939   } else {
4940     // A few places like make_runtime_call "know" that VM calls are narrow,
4941     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4942     bool expected_wide_mem = false;
4943     if (n == m->base_memory()) {
4944       expected_wide_mem = true;
4945     } else if (alias_idx == Compile::AliasIdxRaw ||
4946                n == m->memory_at(Compile::AliasIdxRaw)) {
4947       expected_wide_mem = true;
4948     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4949       // memory can "leak through" calls on channels that
4950       // are write-once.  Allow this also.
4951       expected_wide_mem = true;
4952     }
4953     assert(expected_wide_mem, "expected narrow slice replacement");
4954   }
4955 }
4956 #else // !ASSERT
4957 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4958 #endif
4959 
4960 
4961 //-----------------------------memory_at---------------------------------------
4962 Node* MergeMemNode::memory_at(uint alias_idx) const {
4963   assert(alias_idx >= Compile::AliasIdxRaw ||
4964          alias_idx == Compile::AliasIdxBot && !Compile::current()->do_aliasing(),
4965          "must avoid base_memory and AliasIdxTop");
4966 
4967   // Otherwise, it is a narrow slice.
4968   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4969   if (is_empty_memory(n)) {
4970     // the array is sparse; empty slots are the "top" node
4971     n = base_memory();
4972     assert(Node::in_dump()
4973            || n == nullptr || n->bottom_type() == Type::TOP
4974            || n->adr_type() == nullptr // address is TOP
4975            || n->adr_type() == TypePtr::BOTTOM
4976            || n->adr_type() == TypeRawPtr::BOTTOM
4977            || !Compile::current()->do_aliasing(),
4978            "must be a wide memory");
4979     // do_aliasing == false if we are organizing the memory states manually.
4980     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4981   } else {
4982     // make sure the stored slice is sane
4983     #ifdef ASSERT
4984     if (VMError::is_error_reported() || Node::in_dump()) {
4985     } else if (might_be_same(n, base_memory())) {
4986       // Give it a pass:  It is a mostly harmless repetition of the base.
4987       // This can arise normally from node subsumption during optimization.
4988     } else {
4989       verify_memory_slice(this, alias_idx, n);
4990     }
4991     #endif
4992   }
4993   return n;
4994 }
4995 
4996 //---------------------------set_memory_at-------------------------------------
4997 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4998   verify_memory_slice(this, alias_idx, n);
4999   Node* empty_mem = empty_memory();
5000   if (n == base_memory())  n = empty_mem;  // collapse default
5001   uint need_req = alias_idx+1;
5002   if (req() < need_req) {
5003     if (n == empty_mem)  return;  // already the default, so do not grow me
5004     // grow the sparse array
5005     do {
5006       add_req(empty_mem);
5007     } while (req() < need_req);
5008   }
5009   set_req( alias_idx, n );
5010 }
5011 
5012 
5013 
5014 //--------------------------iteration_setup------------------------------------
5015 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
5016   if (other != nullptr) {
5017     grow_to_match(other);
5018     // invariant:  the finite support of mm2 is within mm->req()
5019     #ifdef ASSERT
5020     for (uint i = req(); i < other->req(); i++) {
5021       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
5022     }
5023     #endif
5024   }
5025   // Replace spurious copies of base_memory by top.
5026   Node* base_mem = base_memory();
5027   if (base_mem != nullptr && !base_mem->is_top()) {
5028     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
5029       if (in(i) == base_mem)
5030         set_req(i, empty_memory());
5031     }
5032   }
5033 }
5034 
5035 //---------------------------grow_to_match-------------------------------------
5036 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
5037   Node* empty_mem = empty_memory();
5038   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
5039   // look for the finite support of the other memory
5040   for (uint i = other->req(); --i >= req(); ) {
5041     if (other->in(i) != empty_mem) {
5042       uint new_len = i+1;
5043       while (req() < new_len)  add_req(empty_mem);
5044       break;
5045     }
5046   }
5047 }
5048 
5049 //---------------------------verify_sparse-------------------------------------
5050 #ifndef PRODUCT
5051 bool MergeMemNode::verify_sparse() const {
5052   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
5053   Node* base_mem = base_memory();
5054   // The following can happen in degenerate cases, since empty==top.
5055   if (is_empty_memory(base_mem))  return true;
5056   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
5057     assert(in(i) != nullptr, "sane slice");
5058     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
5059   }
5060   return true;
5061 }
5062 
5063 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
5064   Node* n;
5065   n = mm->in(idx);
5066   if (mem == n)  return true;  // might be empty_memory()
5067   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
5068   if (mem == n)  return true;
5069   return false;
5070 }
5071 #endif // !PRODUCT
--- EOF ---