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(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(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));
 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);
 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),
 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 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 850 const Type *LoadNode::bottom_type() const { return _type; }
 851 uint LoadNode::ideal_reg() const {
 852   return _type->ideal_reg();
 853 }
 854 
 855 #ifndef PRODUCT
 856 void LoadNode::dump_spec(outputStream *st) const {
 857   MemNode::dump_spec(st);
 858   if( !Verbose && !WizardMode ) {
 859     // standard dump does this in Verbose and WizardMode
 860     st->print(" #"); _type->dump_on(st);
 861   }
 862   if (!depends_only_on_test()) {
 863     st->print(" (does not depend only on test, ");
 864     if (control_dependency() == UnknownControl) {
 865       st->print("unknown control");
 866     } else if (control_dependency() == Pinned) {
 867       st->print("pinned");
 868     } else if (adr_type() == TypeRawPtr::BOTTOM) {
 869       st->print("raw access");
 870     } else {
 871       st->print("unknown reason");
 872     }
 873     st->print(")");
 874   }
 875 }
 876 #endif
 877 
 878 #ifdef ASSERT
 879 //----------------------------is_immutable_value-------------------------------
 880 // Helper function to allow a raw load without control edge for some cases
 881 bool LoadNode::is_immutable_value(Node* adr) {
 882   if (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 883       adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal) {
 884 
 885     jlong offset = adr->in(AddPNode::Offset)->find_intptr_t_con(-1);
 886     int offsets[] = {
 887       in_bytes(JavaThread::osthread_offset()),
 888       in_bytes(JavaThread::threadObj_offset()),
 889       in_bytes(JavaThread::vthread_offset()),
 890       in_bytes(JavaThread::scopedValueCache_offset()),
 891     };
 892 
 893     for (size_t i = 0; i < sizeof offsets / sizeof offsets[0]; i++) {
 894       if (offset == offsets[i]) {
 895         return true;
 896       }
 897     }
 898   }
 899 
 900   return false;
 901 }
 902 #endif
 903 
 904 //----------------------------LoadNode::make-----------------------------------
 905 // Polymorphic factory method:
 906 Node* LoadNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, BasicType bt, MemOrd mo,
 907                      ControlDependency control_dependency, bool require_atomic_access, bool unaligned, bool mismatched, bool unsafe, uint8_t barrier_data) {
 908   Compile* C = gvn.C;
 909 
 910   // sanity check the alias category against the created node type
 911   assert(!(adr_type->isa_oopptr() &&
 912            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 913          "use LoadKlassNode instead");
 914   assert(!(adr_type->isa_aryptr() &&
 915            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 916          "use LoadRangeNode instead");
 917   // Check control edge of raw loads
 918   assert( ctl != nullptr || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 919           // oop will be recorded in oop map if load crosses safepoint
 920           rt->isa_oopptr() || is_immutable_value(adr),
 921           "raw memory operations should have control edge");
 922   LoadNode* load = nullptr;
 923   switch (bt) {
 924   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 925   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 926   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 927   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 928   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 929   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic_access); break;
 930   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 931   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency, require_atomic_access); break;
 932   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 933   case T_OBJECT:
 934 #ifdef _LP64
 935     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 936       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 937     } else
 938 #endif
 939     {
 940       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 941       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr(), mo, control_dependency);
 942     }
 943     break;
 944   default:
 945     ShouldNotReachHere();
 946     break;
 947   }
 948   assert(load != nullptr, "LoadNode should have been created");
 949   if (unaligned) {
 950     load->set_unaligned_access();
 951   }
 952   if (mismatched) {
 953     load->set_mismatched_access();
 954   }
 955   if (unsafe) {
 956     load->set_unsafe_access();
 957   }
 958   load->set_barrier_data(barrier_data);
 959   if (load->Opcode() == Op_LoadN) {
 960     Node* ld = gvn.transform(load);
 961     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 962   }
 963 
 964   return load;
 965 }
 966 
 967 //------------------------------hash-------------------------------------------
 968 uint LoadNode::hash() const {
 969   // unroll addition of interesting fields
 970   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 971 }
 972 
 973 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 974   if ((atp != nullptr) && (atp->index() >= Compile::AliasIdxRaw)) {
 975     bool non_volatile = (atp->field() != nullptr) && !atp->field()->is_volatile();
 976     bool is_stable_ary = FoldStableValues &&
 977                          (tp != nullptr) && (tp->isa_aryptr() != nullptr) &&
 978                          tp->isa_aryptr()->is_stable();
 979 
 980     return (eliminate_boxing && non_volatile) || is_stable_ary;
 981   }
 982 
 983   return false;
 984 }
 985 
 986 // Is the value loaded previously stored by an arraycopy? If so return
 987 // a load node that reads from the source array so we may be able to
 988 // optimize out the ArrayCopy node later.
 989 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseGVN* phase) const {
 990   Node* ld_adr = in(MemNode::Address);
 991   intptr_t ld_off = 0;
 992   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 993   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
 994   if (ac != nullptr) {
 995     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
 996 
 997     Node* mem = ac->in(TypeFunc::Memory);
 998     Node* ctl = ac->in(0);
 999     Node* src = ac->in(ArrayCopyNode::Src);
1000 
1001     if (!ac->as_ArrayCopy()->is_clonebasic() && !phase->type(src)->isa_aryptr()) {
1002       return nullptr;
1003     }
1004 
1005     LoadNode* ld = clone()->as_Load();
1006     Node* addp = in(MemNode::Address)->clone();
1007     if (ac->as_ArrayCopy()->is_clonebasic()) {
1008       assert(ld_alloc != nullptr, "need an alloc");
1009       assert(addp->is_AddP(), "address must be addp");
1010       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1011       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Base)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)), "strange pattern");
1012       assert(bs->step_over_gc_barrier(addp->in(AddPNode::Address)) == bs->step_over_gc_barrier(ac->in(ArrayCopyNode::Dest)), "strange pattern");
1013       addp->set_req(AddPNode::Base, src);
1014       addp->set_req(AddPNode::Address, src);
1015     } else {
1016       assert(ac->as_ArrayCopy()->is_arraycopy_validated() ||
1017              ac->as_ArrayCopy()->is_copyof_validated() ||
1018              ac->as_ArrayCopy()->is_copyofrange_validated(), "only supported cases");
1019       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
1020       addp->set_req(AddPNode::Base, src);
1021       addp->set_req(AddPNode::Address, src);
1022 
1023       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
1024       BasicType ary_elem = ary_t->isa_aryptr()->elem()->array_element_basic_type();
1025       if (is_reference_type(ary_elem, true)) ary_elem = T_OBJECT;
1026 
1027       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
1028       uint shift  = exact_log2(type2aelembytes(ary_elem));
1029 
1030       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
1031 #ifdef _LP64
1032       diff = phase->transform(new ConvI2LNode(diff));
1033 #endif
1034       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
1035 
1036       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
1037       addp->set_req(AddPNode::Offset, offset);
1038     }
1039     addp = phase->transform(addp);
1040 #ifdef ASSERT
1041     const TypePtr* adr_type = phase->type(addp)->is_ptr();
1042     ld->_adr_type = adr_type;
1043 #endif
1044     ld->set_req(MemNode::Address, addp);
1045     ld->set_req(0, ctl);
1046     ld->set_req(MemNode::Memory, mem);
1047     // load depends on the tests that validate the arraycopy
1048     ld->_control_dependency = UnknownControl;
1049     return ld;
1050   }
1051   return nullptr;
1052 }
1053 
1054 
1055 //---------------------------can_see_stored_value------------------------------
1056 // This routine exists to make sure this set of tests is done the same
1057 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
1058 // will change the graph shape in a way which makes memory alive twice at the
1059 // same time (uses the Oracle model of aliasing), then some
1060 // LoadXNode::Identity will fold things back to the equivalence-class model
1061 // of aliasing.
1062 Node* MemNode::can_see_stored_value(Node* st, PhaseValues* phase) const {
1063   Node* ld_adr = in(MemNode::Address);
1064   intptr_t ld_off = 0;
1065   Node* ld_base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ld_off);
1066   Node* ld_alloc = AllocateNode::Ideal_allocation(ld_base);
1067   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
1068   Compile::AliasType* atp = (tp != nullptr) ? phase->C->alias_type(tp) : nullptr;
1069   // This is more general than load from boxing objects.
1070   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
1071     uint alias_idx = atp->index();
1072     Node* result = nullptr;
1073     Node* current = st;
1074     // Skip through chains of MemBarNodes checking the MergeMems for
1075     // new states for the slice of this load.  Stop once any other
1076     // kind of node is encountered.  Loads from final memory can skip
1077     // through any kind of MemBar but normal loads shouldn't skip
1078     // through MemBarAcquire since the could allow them to move out of
1079     // a synchronized region. It is not safe to step over MemBarCPUOrder,
1080     // because alias info above them may be inaccurate (e.g., due to
1081     // mixed/mismatched unsafe accesses).
1082     bool is_final_mem = !atp->is_rewritable();
1083     while (current->is_Proj()) {
1084       int opc = current->in(0)->Opcode();
1085       if ((is_final_mem && (opc == Op_MemBarAcquire ||
1086                             opc == Op_MemBarAcquireLock ||
1087                             opc == Op_LoadFence)) ||
1088           opc == Op_MemBarRelease ||
1089           opc == Op_StoreFence ||
1090           opc == Op_MemBarReleaseLock ||
1091           opc == Op_MemBarStoreStore ||
1092           opc == Op_StoreStoreFence) {
1093         Node* mem = current->in(0)->in(TypeFunc::Memory);
1094         if (mem->is_MergeMem()) {
1095           MergeMemNode* merge = mem->as_MergeMem();
1096           Node* new_st = merge->memory_at(alias_idx);
1097           if (new_st == merge->base_memory()) {
1098             // Keep searching
1099             current = new_st;
1100             continue;
1101           }
1102           // Save the new memory state for the slice and fall through
1103           // to exit.
1104           result = new_st;
1105         }
1106       }
1107       break;
1108     }
1109     if (result != nullptr) {
1110       st = result;
1111     }
1112   }
1113 
1114   // Loop around twice in the case Load -> Initialize -> Store.
1115   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1116   for (int trip = 0; trip <= 1; trip++) {
1117 
1118     if (st->is_Store()) {
1119       Node* st_adr = st->in(MemNode::Address);
1120       if (st_adr != ld_adr) {
1121         // Try harder before giving up. Unify base pointers with casts (e.g., raw/non-raw pointers).
1122         intptr_t st_off = 0;
1123         Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_off);
1124         if (ld_base == nullptr)                                return nullptr;
1125         if (st_base == nullptr)                                return nullptr;
1126         if (!ld_base->eqv_uncast(st_base, /*keep_deps=*/true)) return nullptr;
1127         if (ld_off != st_off)                                  return nullptr;
1128         if (ld_off == Type::OffsetBot)                         return nullptr;
1129         // Same base, same offset.
1130         // Possible improvement for arrays: check index value instead of absolute offset.
1131 
1132         // At this point we have proven something like this setup:
1133         //   B = << base >>
1134         //   L =  LoadQ(AddP(Check/CastPP(B), #Off))
1135         //   S = StoreQ(AddP(             B , #Off), V)
1136         // (Actually, we haven't yet proven the Q's are the same.)
1137         // In other words, we are loading from a casted version of
1138         // the same pointer-and-offset that we stored to.
1139         // Casted version may carry a dependency and it is respected.
1140         // Thus, we are able to replace L by V.
1141       }
1142       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1143       if (store_Opcode() != st->Opcode()) {
1144         return nullptr;
1145       }
1146       // LoadVector/StoreVector needs additional check to ensure the types match.
1147       if (st->is_StoreVector()) {
1148         const TypeVect*  in_vt = st->as_StoreVector()->vect_type();
1149         const TypeVect* out_vt = as_LoadVector()->vect_type();
1150         if (in_vt != out_vt) {
1151           return nullptr;
1152         }
1153       }
1154       return st->in(MemNode::ValueIn);
1155     }
1156 
1157     // A load from a freshly-created object always returns zero.
1158     // (This can happen after LoadNode::Ideal resets the load's memory input
1159     // to find_captured_store, which returned InitializeNode::zero_memory.)
1160     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1161         (st->in(0) == ld_alloc) &&
1162         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1163       // return a zero value for the load's basic type
1164       // (This is one of the few places where a generic PhaseTransform
1165       // can create new nodes.  Think of it as lazily manifesting
1166       // virtually pre-existing constants.)
1167       if (memory_type() != T_VOID) {
1168         if (ReduceBulkZeroing || find_array_copy_clone(ld_alloc, in(MemNode::Memory)) == nullptr) {
1169           // If ReduceBulkZeroing is disabled, we need to check if the allocation does not belong to an
1170           // ArrayCopyNode clone. If it does, then we cannot assume zero since the initialization is done
1171           // by the ArrayCopyNode.
1172           return phase->zerocon(memory_type());
1173         }
1174       } else {
1175         // TODO: materialize all-zero vector constant
1176         assert(!isa_Load() || as_Load()->type()->isa_vect(), "");
1177       }
1178     }
1179 
1180     // A load from an initialization barrier can match a captured store.
1181     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1182       InitializeNode* init = st->in(0)->as_Initialize();
1183       AllocateNode* alloc = init->allocation();
1184       if ((alloc != nullptr) && (alloc == ld_alloc)) {
1185         // examine a captured store value
1186         st = init->find_captured_store(ld_off, memory_size(), phase);
1187         if (st != nullptr) {
1188           continue;             // take one more trip around
1189         }
1190       }
1191     }
1192 
1193     // Load boxed value from result of valueOf() call is input parameter.
1194     if (this->is_Load() && ld_adr->is_AddP() &&
1195         (tp != nullptr) && tp->is_ptr_to_boxed_value()) {
1196       intptr_t ignore = 0;
1197       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1198       BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1199       base = bs->step_over_gc_barrier(base);
1200       if (base != nullptr && base->is_Proj() &&
1201           base->as_Proj()->_con == TypeFunc::Parms &&
1202           base->in(0)->is_CallStaticJava() &&
1203           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1204         return base->in(0)->in(TypeFunc::Parms);
1205       }
1206     }
1207 
1208     break;
1209   }
1210 
1211   return nullptr;
1212 }
1213 
1214 //----------------------is_instance_field_load_with_local_phi------------------
1215 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1216   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1217       in(Address)->is_AddP() ) {
1218     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1219     // Only instances and boxed values.
1220     if( t_oop != nullptr &&
1221         (t_oop->is_ptr_to_boxed_value() ||
1222          t_oop->is_known_instance_field()) &&
1223         t_oop->offset() != Type::OffsetBot &&
1224         t_oop->offset() != Type::OffsetTop) {
1225       return true;
1226     }
1227   }
1228   return false;
1229 }
1230 
1231 //------------------------------Identity---------------------------------------
1232 // Loads are identity if previous store is to same address
1233 Node* LoadNode::Identity(PhaseGVN* phase) {
1234   // If the previous store-maker is the right kind of Store, and the store is
1235   // to the same address, then we are equal to the value stored.
1236   Node* mem = in(Memory);
1237   Node* value = can_see_stored_value(mem, phase);
1238   if( value ) {
1239     // byte, short & char stores truncate naturally.
1240     // A load has to load the truncated value which requires
1241     // some sort of masking operation and that requires an
1242     // Ideal call instead of an Identity call.
1243     if (memory_size() < BytesPerInt) {
1244       // If the input to the store does not fit with the load's result type,
1245       // it must be truncated via an Ideal call.
1246       if (!phase->type(value)->higher_equal(phase->type(this)))
1247         return this;
1248     }
1249     // (This works even when value is a Con, but LoadNode::Value
1250     // usually runs first, producing the singleton type of the Con.)
1251     if (!has_pinned_control_dependency() || value->is_Con()) {
1252       return value;
1253     } else {
1254       return this;
1255     }
1256   }
1257 
1258   if (has_pinned_control_dependency()) {
1259     return this;
1260   }
1261   // Search for an existing data phi which was generated before for the same
1262   // instance's field to avoid infinite generation of phis in a loop.
1263   Node *region = mem->in(0);
1264   if (is_instance_field_load_with_local_phi(region)) {
1265     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1266     int this_index  = phase->C->get_alias_index(addr_t);
1267     int this_offset = addr_t->offset();
1268     int this_iid    = addr_t->instance_id();
1269     if (!addr_t->is_known_instance() &&
1270          addr_t->is_ptr_to_boxed_value()) {
1271       // Use _idx of address base (could be Phi node) for boxed values.
1272       intptr_t   ignore = 0;
1273       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1274       if (base == nullptr) {
1275         return this;
1276       }
1277       this_iid = base->_idx;
1278     }
1279     const Type* this_type = bottom_type();
1280     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1281       Node* phi = region->fast_out(i);
1282       if (phi->is_Phi() && phi != mem &&
1283           phi->as_Phi()->is_same_inst_field(this_type, (int)mem->_idx, this_iid, this_index, this_offset)) {
1284         return phi;
1285       }
1286     }
1287   }
1288 
1289   return this;
1290 }
1291 
1292 // Construct an equivalent unsigned load.
1293 Node* LoadNode::convert_to_unsigned_load(PhaseGVN& gvn) {
1294   BasicType bt = T_ILLEGAL;
1295   const Type* rt = nullptr;
1296   switch (Opcode()) {
1297     case Op_LoadUB: return this;
1298     case Op_LoadUS: return this;
1299     case Op_LoadB: bt = T_BOOLEAN; rt = TypeInt::UBYTE; break;
1300     case Op_LoadS: bt = T_CHAR;    rt = TypeInt::CHAR;  break;
1301     default:
1302       assert(false, "no unsigned variant: %s", Name());
1303       return nullptr;
1304   }
1305   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1306                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1307                         false /*require_atomic_access*/, is_unaligned_access(), is_mismatched_access());
1308 }
1309 
1310 // Construct an equivalent signed load.
1311 Node* LoadNode::convert_to_signed_load(PhaseGVN& gvn) {
1312   BasicType bt = T_ILLEGAL;
1313   const Type* rt = nullptr;
1314   switch (Opcode()) {
1315     case Op_LoadUB: bt = T_BYTE;  rt = TypeInt::BYTE;  break;
1316     case Op_LoadUS: bt = T_SHORT; rt = TypeInt::SHORT; break;
1317     case Op_LoadB: // fall through
1318     case Op_LoadS: // fall through
1319     case Op_LoadI: // fall through
1320     case Op_LoadL: return this;
1321     default:
1322       assert(false, "no signed variant: %s", Name());
1323       return nullptr;
1324   }
1325   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1326                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1327                         false /*require_atomic_access*/, is_unaligned_access(), is_mismatched_access());
1328 }
1329 
1330 bool LoadNode::has_reinterpret_variant(const Type* rt) {
1331   BasicType bt = rt->basic_type();
1332   switch (Opcode()) {
1333     case Op_LoadI: return (bt == T_FLOAT);
1334     case Op_LoadL: return (bt == T_DOUBLE);
1335     case Op_LoadF: return (bt == T_INT);
1336     case Op_LoadD: return (bt == T_LONG);
1337 
1338     default: return false;
1339   }
1340 }
1341 
1342 Node* LoadNode::convert_to_reinterpret_load(PhaseGVN& gvn, const Type* rt) {
1343   BasicType bt = rt->basic_type();
1344   assert(has_reinterpret_variant(rt), "no reinterpret variant: %s %s", Name(), type2name(bt));
1345   bool is_mismatched = is_mismatched_access();
1346   const TypeRawPtr* raw_type = gvn.type(in(MemNode::Memory))->isa_rawptr();
1347   if (raw_type == nullptr) {
1348     is_mismatched = true; // conservatively match all non-raw accesses as mismatched
1349   }
1350   const int op = Opcode();
1351   bool require_atomic_access = (op == Op_LoadL && ((LoadLNode*)this)->require_atomic_access()) ||
1352                                (op == Op_LoadD && ((LoadDNode*)this)->require_atomic_access());
1353   return LoadNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1354                         raw_adr_type(), rt, bt, _mo, _control_dependency,
1355                         require_atomic_access, is_unaligned_access(), is_mismatched);
1356 }
1357 
1358 bool StoreNode::has_reinterpret_variant(const Type* vt) {
1359   BasicType bt = vt->basic_type();
1360   switch (Opcode()) {
1361     case Op_StoreI: return (bt == T_FLOAT);
1362     case Op_StoreL: return (bt == T_DOUBLE);
1363     case Op_StoreF: return (bt == T_INT);
1364     case Op_StoreD: return (bt == T_LONG);
1365 
1366     default: return false;
1367   }
1368 }
1369 
1370 Node* StoreNode::convert_to_reinterpret_store(PhaseGVN& gvn, Node* val, const Type* vt) {
1371   BasicType bt = vt->basic_type();
1372   assert(has_reinterpret_variant(vt), "no reinterpret variant: %s %s", Name(), type2name(bt));
1373   const int op = Opcode();
1374   bool require_atomic_access = (op == Op_StoreL && ((StoreLNode*)this)->require_atomic_access()) ||
1375                                (op == Op_StoreD && ((StoreDNode*)this)->require_atomic_access());
1376   StoreNode* st = StoreNode::make(gvn, in(MemNode::Control), in(MemNode::Memory), in(MemNode::Address),
1377                                   raw_adr_type(), val, bt, _mo, require_atomic_access);
1378 
1379   bool is_mismatched = is_mismatched_access();
1380   const TypeRawPtr* raw_type = gvn.type(in(MemNode::Memory))->isa_rawptr();
1381   if (raw_type == nullptr) {
1382     is_mismatched = true; // conservatively match all non-raw accesses as mismatched
1383   }
1384   if (is_mismatched) {
1385     st->set_mismatched_access();
1386   }
1387   return st;
1388 }
1389 
1390 // We're loading from an object which has autobox behaviour.
1391 // If this object is result of a valueOf call we'll have a phi
1392 // merging a newly allocated object and a load from the cache.
1393 // We want to replace this load with the original incoming
1394 // argument to the valueOf call.
1395 Node* LoadNode::eliminate_autobox(PhaseIterGVN* igvn) {
1396   assert(igvn->C->eliminate_boxing(), "sanity");
1397   intptr_t ignore = 0;
1398   Node* base = AddPNode::Ideal_base_and_offset(in(Address), igvn, ignore);
1399   if ((base == nullptr) || base->is_Phi()) {
1400     // Push the loads from the phi that comes from valueOf up
1401     // through it to allow elimination of the loads and the recovery
1402     // of the original value. It is done in split_through_phi().
1403     return nullptr;
1404   } else if (base->is_Load() ||
1405              (base->is_DecodeN() && base->in(1)->is_Load())) {
1406     // Eliminate the load of boxed value for integer types from the cache
1407     // array by deriving the value from the index into the array.
1408     // Capture the offset of the load and then reverse the computation.
1409 
1410     // Get LoadN node which loads a boxing object from 'cache' array.
1411     if (base->is_DecodeN()) {
1412       base = base->in(1);
1413     }
1414     if (!base->in(Address)->is_AddP()) {
1415       return nullptr; // Complex address
1416     }
1417     AddPNode* address = base->in(Address)->as_AddP();
1418     Node* cache_base = address->in(AddPNode::Base);
1419     if ((cache_base != nullptr) && cache_base->is_DecodeN()) {
1420       // Get ConP node which is static 'cache' field.
1421       cache_base = cache_base->in(1);
1422     }
1423     if ((cache_base != nullptr) && cache_base->is_Con()) {
1424       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1425       if ((base_type != nullptr) && base_type->is_autobox_cache()) {
1426         Node* elements[4];
1427         int shift = exact_log2(type2aelembytes(T_OBJECT));
1428         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1429         if (count > 0 && elements[0]->is_Con() &&
1430             (count == 1 ||
1431              (count == 2 && elements[1]->Opcode() == Op_LShiftX &&
1432                             elements[1]->in(2) == igvn->intcon(shift)))) {
1433           ciObjArray* array = base_type->const_oop()->as_obj_array();
1434           // Fetch the box object cache[0] at the base of the array and get its value
1435           ciInstance* box = array->obj_at(0)->as_instance();
1436           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1437           assert(ik->is_box_klass(), "sanity");
1438           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1439           if (ik->nof_nonstatic_fields() == 1) {
1440             // This should be true nonstatic_field_at requires calling
1441             // nof_nonstatic_fields so check it anyway
1442             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1443             BasicType bt = c.basic_type();
1444             // Only integer types have boxing cache.
1445             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1446                    bt == T_BYTE    || bt == T_SHORT ||
1447                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1448             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1449             if (cache_low != (int)cache_low) {
1450               return nullptr; // should not happen since cache is array indexed by value
1451             }
1452             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1453             if (offset != (int)offset) {
1454               return nullptr; // should not happen since cache is array indexed by value
1455             }
1456            // Add up all the offsets making of the address of the load
1457             Node* result = elements[0];
1458             for (int i = 1; i < count; i++) {
1459               result = igvn->transform(new AddXNode(result, elements[i]));
1460             }
1461             // Remove the constant offset from the address and then
1462             result = igvn->transform(new AddXNode(result, igvn->MakeConX(-(int)offset)));
1463             // remove the scaling of the offset to recover the original index.
1464             if (result->Opcode() == Op_LShiftX && result->in(2) == igvn->intcon(shift)) {
1465               // Peel the shift off directly but wrap it in a dummy node
1466               // since Ideal can't return existing nodes
1467               igvn->_worklist.push(result); // remove dead node later
1468               result = new RShiftXNode(result->in(1), igvn->intcon(0));
1469             } else if (result->is_Add() && result->in(2)->is_Con() &&
1470                        result->in(1)->Opcode() == Op_LShiftX &&
1471                        result->in(1)->in(2) == igvn->intcon(shift)) {
1472               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1473               // but for boxing cache access we know that X<<Z will not overflow
1474               // (there is range check) so we do this optimizatrion by hand here.
1475               igvn->_worklist.push(result); // remove dead node later
1476               Node* add_con = new RShiftXNode(result->in(2), igvn->intcon(shift));
1477               result = new AddXNode(result->in(1)->in(1), igvn->transform(add_con));
1478             } else {
1479               result = new RShiftXNode(result, igvn->intcon(shift));
1480             }
1481 #ifdef _LP64
1482             if (bt != T_LONG) {
1483               result = new ConvL2INode(igvn->transform(result));
1484             }
1485 #else
1486             if (bt == T_LONG) {
1487               result = new ConvI2LNode(igvn->transform(result));
1488             }
1489 #endif
1490             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1491             // Need to preserve unboxing load type if it is unsigned.
1492             switch(this->Opcode()) {
1493               case Op_LoadUB:
1494                 result = new AndINode(igvn->transform(result), igvn->intcon(0xFF));
1495                 break;
1496               case Op_LoadUS:
1497                 result = new AndINode(igvn->transform(result), igvn->intcon(0xFFFF));
1498                 break;
1499             }
1500             return result;
1501           }
1502         }
1503       }
1504     }
1505   }
1506   return nullptr;
1507 }
1508 
1509 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1510   Node* region = phi->in(0);
1511   if (region == nullptr) {
1512     return false; // Wait stable graph
1513   }
1514   uint cnt = phi->req();
1515   for (uint i = 1; i < cnt; i++) {
1516     Node* rc = region->in(i);
1517     if (rc == nullptr || phase->type(rc) == Type::TOP)
1518       return false; // Wait stable graph
1519     Node* in = phi->in(i);
1520     if (in == nullptr || phase->type(in) == Type::TOP)
1521       return false; // Wait stable graph
1522   }
1523   return true;
1524 }
1525 
1526 //------------------------------split_through_phi------------------------------
1527 // Check whether a call to 'split_through_phi' would split this load through the
1528 // Phi *base*. This method is essentially a copy of the validations performed
1529 // by 'split_through_phi'. The first use of this method was in EA code as part
1530 // of simplification of allocation merges.
1531 bool LoadNode::can_split_through_phi_base(PhaseGVN* phase) {
1532   Node* mem        = in(Memory);
1533   Node* address    = in(Address);
1534   intptr_t ignore  = 0;
1535   Node*    base    = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1536   bool base_is_phi = (base != nullptr) && base->is_Phi();
1537 
1538   if (req() > 3 || !base_is_phi) {
1539     return false;
1540   }
1541 
1542   if (!mem->is_Phi()) {
1543     if (!MemNode::all_controls_dominate(mem, base->in(0)))
1544       return false;
1545   } else if (base->in(0) != mem->in(0)) {
1546     if (!MemNode::all_controls_dominate(mem, base->in(0))) {
1547       return false;
1548     }
1549   }
1550 
1551   return true;
1552 }
1553 
1554 //------------------------------split_through_phi------------------------------
1555 // Split instance or boxed field load through Phi.
1556 Node* LoadNode::split_through_phi(PhaseGVN* phase, bool ignore_missing_instance_id) {
1557   if (req() > 3) {
1558     assert(is_LoadVector() && Opcode() != Op_LoadVector, "load has too many inputs");
1559     // LoadVector subclasses such as LoadVectorMasked have extra inputs that the logic below doesn't take into account
1560     return nullptr;
1561   }
1562   Node* mem     = in(Memory);
1563   Node* address = in(Address);
1564   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1565 
1566   assert((t_oop != nullptr) &&
1567          (ignore_missing_instance_id ||
1568           t_oop->is_known_instance_field() ||
1569           t_oop->is_ptr_to_boxed_value()), "invalid conditions");
1570 
1571   Compile* C = phase->C;
1572   intptr_t ignore = 0;
1573   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1574   bool base_is_phi = (base != nullptr) && base->is_Phi();
1575   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1576                            (base != nullptr) && (base == address->in(AddPNode::Base)) &&
1577                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1578 
1579   if (!((mem->is_Phi() || base_is_phi) &&
1580         (ignore_missing_instance_id || load_boxed_values || t_oop->is_known_instance_field()))) {
1581     return nullptr; // Neither memory or base are Phi
1582   }
1583 
1584   if (mem->is_Phi()) {
1585     if (!stable_phi(mem->as_Phi(), phase)) {
1586       return nullptr; // Wait stable graph
1587     }
1588     uint cnt = mem->req();
1589     // Check for loop invariant memory.
1590     if (cnt == 3) {
1591       for (uint i = 1; i < cnt; i++) {
1592         Node* in = mem->in(i);
1593         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1594         if (m == mem) {
1595           if (i == 1) {
1596             // if the first edge was a loop, check second edge too.
1597             // If both are replaceable - we are in an infinite loop
1598             Node *n = optimize_memory_chain(mem->in(2), t_oop, this, phase);
1599             if (n == mem) {
1600               break;
1601             }
1602           }
1603           set_req(Memory, mem->in(cnt - i));
1604           return this; // made change
1605         }
1606       }
1607     }
1608   }
1609   if (base_is_phi) {
1610     if (!stable_phi(base->as_Phi(), phase)) {
1611       return nullptr; // Wait stable graph
1612     }
1613     uint cnt = base->req();
1614     // Check for loop invariant memory.
1615     if (cnt == 3) {
1616       for (uint i = 1; i < cnt; i++) {
1617         if (base->in(i) == base) {
1618           return nullptr; // Wait stable graph
1619         }
1620       }
1621     }
1622   }
1623 
1624   // Split through Phi (see original code in loopopts.cpp).
1625   assert(ignore_missing_instance_id || C->have_alias_type(t_oop), "instance should have alias type");
1626 
1627   // Do nothing here if Identity will find a value
1628   // (to avoid infinite chain of value phis generation).
1629   if (this != Identity(phase)) {
1630     return nullptr;
1631   }
1632 
1633   // Select Region to split through.
1634   Node* region;
1635   if (!base_is_phi) {
1636     assert(mem->is_Phi(), "sanity");
1637     region = mem->in(0);
1638     // Skip if the region dominates some control edge of the address.
1639     if (!MemNode::all_controls_dominate(address, region))
1640       return nullptr;
1641   } else if (!mem->is_Phi()) {
1642     assert(base_is_phi, "sanity");
1643     region = base->in(0);
1644     // Skip if the region dominates some control edge of the memory.
1645     if (!MemNode::all_controls_dominate(mem, region))
1646       return nullptr;
1647   } else if (base->in(0) != mem->in(0)) {
1648     assert(base_is_phi && mem->is_Phi(), "sanity");
1649     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1650       region = base->in(0);
1651     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1652       region = mem->in(0);
1653     } else {
1654       return nullptr; // complex graph
1655     }
1656   } else {
1657     assert(base->in(0) == mem->in(0), "sanity");
1658     region = mem->in(0);
1659   }
1660 
1661   Node* phi = nullptr;
1662   const Type* this_type = this->bottom_type();
1663   PhaseIterGVN* igvn = phase->is_IterGVN();
1664   if (t_oop != nullptr && (t_oop->is_known_instance_field() || load_boxed_values)) {
1665     int this_index = C->get_alias_index(t_oop);
1666     int this_offset = t_oop->offset();
1667     int this_iid = t_oop->is_known_instance_field() ? t_oop->instance_id() : base->_idx;
1668     phi = new PhiNode(region, this_type, nullptr, mem->_idx, this_iid, this_index, this_offset);
1669   } else if (ignore_missing_instance_id) {
1670     phi = new PhiNode(region, this_type, nullptr, mem->_idx);
1671   } else {
1672     return nullptr;
1673   }
1674 
1675   for (uint i = 1; i < region->req(); i++) {
1676     Node* x;
1677     Node* the_clone = nullptr;
1678     Node* in = region->in(i);
1679     if (region->is_CountedLoop() && region->as_Loop()->is_strip_mined() && i == LoopNode::EntryControl &&
1680         in != nullptr && in->is_OuterStripMinedLoop()) {
1681       // No node should go in the outer strip mined loop
1682       in = in->in(LoopNode::EntryControl);
1683     }
1684     if (in == nullptr || in == C->top()) {
1685       x = C->top();      // Dead path?  Use a dead data op
1686     } else {
1687       x = this->clone();        // Else clone up the data op
1688       the_clone = x;            // Remember for possible deletion.
1689       // Alter data node to use pre-phi inputs
1690       if (this->in(0) == region) {
1691         x->set_req(0, in);
1692       } else {
1693         x->set_req(0, nullptr);
1694       }
1695       if (mem->is_Phi() && (mem->in(0) == region)) {
1696         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1697       }
1698       if (address->is_Phi() && address->in(0) == region) {
1699         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1700       }
1701       if (base_is_phi && (base->in(0) == region)) {
1702         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1703         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1704         x->set_req(Address, adr_x);
1705       }
1706     }
1707     // Check for a 'win' on some paths
1708     const Type *t = x->Value(igvn);
1709 
1710     bool singleton = t->singleton();
1711 
1712     // See comments in PhaseIdealLoop::split_thru_phi().
1713     if (singleton && t == Type::TOP) {
1714       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1715     }
1716 
1717     if (singleton) {
1718       x = igvn->makecon(t);
1719     } else {
1720       // We now call Identity to try to simplify the cloned node.
1721       // Note that some Identity methods call phase->type(this).
1722       // Make sure that the type array is big enough for
1723       // our new node, even though we may throw the node away.
1724       // (This tweaking with igvn only works because x is a new node.)
1725       igvn->set_type(x, t);
1726       // If x is a TypeNode, capture any more-precise type permanently into Node
1727       // otherwise it will be not updated during igvn->transform since
1728       // igvn->type(x) is set to x->Value() already.
1729       x->raise_bottom_type(t);
1730       Node* y = x->Identity(igvn);
1731       if (y != x) {
1732         x = y;
1733       } else {
1734         y = igvn->hash_find_insert(x);
1735         if (y) {
1736           x = y;
1737         } else {
1738           // Else x is a new node we are keeping
1739           // We do not need register_new_node_with_optimizer
1740           // because set_type has already been called.
1741           igvn->_worklist.push(x);
1742         }
1743       }
1744     }
1745     if (x != the_clone && the_clone != nullptr) {
1746       igvn->remove_dead_node(the_clone);
1747     }
1748     phi->set_req(i, x);
1749   }
1750   // Record Phi
1751   igvn->register_new_node_with_optimizer(phi);
1752   return phi;
1753 }
1754 
1755 AllocateNode* LoadNode::is_new_object_mark_load() const {
1756   if (Opcode() == Op_LoadX) {
1757     Node* address = in(MemNode::Address);
1758     AllocateNode* alloc = AllocateNode::Ideal_allocation(address);
1759     Node* mem = in(MemNode::Memory);
1760     if (alloc != nullptr && mem->is_Proj() &&
1761         mem->in(0) != nullptr &&
1762         mem->in(0) == alloc->initialization() &&
1763         alloc->initialization()->proj_out_or_null(0) != nullptr) {
1764       return alloc;
1765     }
1766   }
1767   return nullptr;
1768 }
1769 
1770 
1771 //------------------------------Ideal------------------------------------------
1772 // If the load is from Field memory and the pointer is non-null, it might be possible to
1773 // zero out the control input.
1774 // If the offset is constant and the base is an object allocation,
1775 // try to hook me up to the exact initializing store.
1776 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1777   if (has_pinned_control_dependency()) {
1778     return nullptr;
1779   }
1780   Node* p = MemNode::Ideal_common(phase, can_reshape);
1781   if (p)  return (p == NodeSentinel) ? nullptr : p;
1782 
1783   Node* ctrl    = in(MemNode::Control);
1784   Node* address = in(MemNode::Address);
1785   bool progress = false;
1786 
1787   bool addr_mark = ((phase->type(address)->isa_oopptr() || phase->type(address)->isa_narrowoop()) &&
1788          phase->type(address)->is_ptr()->offset() == oopDesc::mark_offset_in_bytes());
1789 
1790   // Skip up past a SafePoint control.  Cannot do this for Stores because
1791   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1792   if( ctrl != nullptr && ctrl->Opcode() == Op_SafePoint &&
1793       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw  &&
1794       !addr_mark &&
1795       (depends_only_on_test() || has_unknown_control_dependency())) {
1796     ctrl = ctrl->in(0);
1797     set_req(MemNode::Control,ctrl);
1798     progress = true;
1799   }
1800 
1801   intptr_t ignore = 0;
1802   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1803   if (base != nullptr
1804       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1805     // Check for useless control edge in some common special cases
1806     if (in(MemNode::Control) != nullptr
1807         && can_remove_control()
1808         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1809         && all_controls_dominate(base, phase->C->start())) {
1810       // A method-invariant, non-null address (constant or 'this' argument).
1811       set_req(MemNode::Control, nullptr);
1812       progress = true;
1813     }
1814   }
1815 
1816   Node* mem = in(MemNode::Memory);
1817   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1818 
1819   if (can_reshape && (addr_t != nullptr)) {
1820     // try to optimize our memory input
1821     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1822     if (opt_mem != mem) {
1823       set_req_X(MemNode::Memory, opt_mem, phase);
1824       if (phase->type( opt_mem ) == Type::TOP) return nullptr;
1825       return this;
1826     }
1827     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1828     if ((t_oop != nullptr) &&
1829         (t_oop->is_known_instance_field() ||
1830          t_oop->is_ptr_to_boxed_value())) {
1831       PhaseIterGVN *igvn = phase->is_IterGVN();
1832       assert(igvn != nullptr, "must be PhaseIterGVN when can_reshape is true");
1833       if (igvn->_worklist.member(opt_mem)) {
1834         // Delay this transformation until memory Phi is processed.
1835         igvn->_worklist.push(this);
1836         return nullptr;
1837       }
1838       // Split instance field load through Phi.
1839       Node* result = split_through_phi(phase);
1840       if (result != nullptr) return result;
1841 
1842       if (t_oop->is_ptr_to_boxed_value()) {
1843         Node* result = eliminate_autobox(igvn);
1844         if (result != nullptr) return result;
1845       }
1846     }
1847   }
1848 
1849   // Is there a dominating load that loads the same value?  Leave
1850   // anything that is not a load of a field/array element (like
1851   // barriers etc.) alone
1852   if (in(0) != nullptr && !adr_type()->isa_rawptr() && can_reshape) {
1853     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1854       Node *use = mem->fast_out(i);
1855       if (use != this &&
1856           use->Opcode() == Opcode() &&
1857           use->in(0) != nullptr &&
1858           use->in(0) != in(0) &&
1859           use->in(Address) == in(Address)) {
1860         Node* ctl = in(0);
1861         for (int i = 0; i < 10 && ctl != nullptr; i++) {
1862           ctl = IfNode::up_one_dom(ctl);
1863           if (ctl == use->in(0)) {
1864             set_req(0, use->in(0));
1865             return this;
1866           }
1867         }
1868       }
1869     }
1870   }
1871 
1872   // Check for prior store with a different base or offset; make Load
1873   // independent.  Skip through any number of them.  Bail out if the stores
1874   // are in an endless dead cycle and report no progress.  This is a key
1875   // transform for Reflection.  However, if after skipping through the Stores
1876   // we can't then fold up against a prior store do NOT do the transform as
1877   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1878   // array memory alive twice: once for the hoisted Load and again after the
1879   // bypassed Store.  This situation only works if EVERYBODY who does
1880   // anti-dependence work knows how to bypass.  I.e. we need all
1881   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1882   // the alias index stuff.  So instead, peek through Stores and IFF we can
1883   // fold up, do so.
1884   Node* prev_mem = find_previous_store(phase);
1885   if (prev_mem != nullptr) {
1886     Node* value = can_see_arraycopy_value(prev_mem, phase);
1887     if (value != nullptr) {
1888       return value;
1889     }
1890   }
1891   // Steps (a), (b):  Walk past independent stores to find an exact match.
1892   if (prev_mem != nullptr && prev_mem != in(MemNode::Memory)) {
1893     // (c) See if we can fold up on the spot, but don't fold up here.
1894     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1895     // just return a prior value, which is done by Identity calls.
1896     if (can_see_stored_value(prev_mem, phase)) {
1897       // Make ready for step (d):
1898       set_req_X(MemNode::Memory, prev_mem, phase);
1899       return this;
1900     }
1901   }
1902 
1903   return progress ? this : nullptr;
1904 }
1905 
1906 // Helper to recognize certain Klass fields which are invariant across
1907 // some group of array types (e.g., int[] or all T[] where T < Object).
1908 const Type*
1909 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1910                                  ciKlass* klass) const {
1911   if (UseCompactObjectHeaders) {
1912     if (tkls->offset() == in_bytes(Klass::prototype_header_offset())) {
1913       // The field is Klass::_prototype_header.  Return its (constant) value.
1914       assert(this->Opcode() == Op_LoadX, "must load a proper type from _prototype_header");
1915       return TypeX::make(klass->prototype_header());
1916     }
1917   }
1918   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1919     // The field is Klass::_modifier_flags.  Return its (constant) value.
1920     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1921     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1922     return TypeInt::make(klass->modifier_flags());
1923   }
1924   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1925     // The field is Klass::_access_flags.  Return its (constant) value.
1926     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1927     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1928     return TypeInt::make(klass->access_flags());
1929   }
1930   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1931     // The field is Klass::_layout_helper.  Return its constant value if known.
1932     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1933     return TypeInt::make(klass->layout_helper());
1934   }
1935 
1936   // No match.
1937   return nullptr;
1938 }
1939 
1940 //------------------------------Value-----------------------------------------
1941 const Type* LoadNode::Value(PhaseGVN* phase) const {
1942   // Either input is TOP ==> the result is TOP
1943   Node* mem = in(MemNode::Memory);
1944   const Type *t1 = phase->type(mem);
1945   if (t1 == Type::TOP)  return Type::TOP;
1946   Node* adr = in(MemNode::Address);
1947   const TypePtr* tp = phase->type(adr)->isa_ptr();
1948   if (tp == nullptr || tp->empty())  return Type::TOP;
1949   int off = tp->offset();
1950   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1951   Compile* C = phase->C;
1952 
1953   // Try to guess loaded type from pointer type
1954   if (tp->isa_aryptr()) {
1955     const TypeAryPtr* ary = tp->is_aryptr();
1956     const Type* t = ary->elem();
1957 
1958     // Determine whether the reference is beyond the header or not, by comparing
1959     // the offset against the offset of the start of the array's data.
1960     // Different array types begin at slightly different offsets (12 vs. 16).
1961     // We choose T_BYTE as an example base type that is least restrictive
1962     // as to alignment, which will therefore produce the smallest
1963     // possible base offset.
1964     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1965     const bool off_beyond_header = (off >= min_base_off);
1966 
1967     // Try to constant-fold a stable array element.
1968     if (FoldStableValues && !is_mismatched_access() && ary->is_stable()) {
1969       // Make sure the reference is not into the header and the offset is constant
1970       ciObject* aobj = ary->const_oop();
1971       if (aobj != nullptr && off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1972         int stable_dimension = (ary->stable_dimension() > 0 ? ary->stable_dimension() - 1 : 0);
1973         const Type* con_type = Type::make_constant_from_array_element(aobj->as_array(), off,
1974                                                                       stable_dimension,
1975                                                                       memory_type(), is_unsigned());
1976         if (con_type != nullptr) {
1977           return con_type;
1978         }
1979       }
1980     }
1981 
1982     // Don't do this for integer types. There is only potential profit if
1983     // the element type t is lower than _type; that is, for int types, if _type is
1984     // more restrictive than t.  This only happens here if one is short and the other
1985     // char (both 16 bits), and in those cases we've made an intentional decision
1986     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1987     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1988     //
1989     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1990     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1991     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1992     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1993     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1994     // In fact, that could have been the original type of p1, and p1 could have
1995     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1996     // expression (LShiftL quux 3) independently optimized to the constant 8.
1997     if ((t->isa_int() == nullptr) && (t->isa_long() == nullptr)
1998         && (_type->isa_vect() == nullptr)
1999         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
2000       // t might actually be lower than _type, if _type is a unique
2001       // concrete subclass of abstract class t.
2002       if (off_beyond_header || off == Type::OffsetBot) {  // is the offset beyond the header?
2003         const Type* jt = t->join_speculative(_type);
2004         // In any case, do not allow the join, per se, to empty out the type.
2005         if (jt->empty() && !t->empty()) {
2006           // This can happen if a interface-typed array narrows to a class type.
2007           jt = _type;
2008         }
2009 #ifdef ASSERT
2010         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
2011           // The pointers in the autobox arrays are always non-null
2012           Node* base = adr->in(AddPNode::Base);
2013           if ((base != nullptr) && base->is_DecodeN()) {
2014             // Get LoadN node which loads IntegerCache.cache field
2015             base = base->in(1);
2016           }
2017           if ((base != nullptr) && base->is_Con()) {
2018             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
2019             if ((base_type != nullptr) && base_type->is_autobox_cache()) {
2020               // It could be narrow oop
2021               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
2022             }
2023           }
2024         }
2025 #endif
2026         return jt;
2027       }
2028     }
2029   } else if (tp->base() == Type::InstPtr) {
2030     assert( off != Type::OffsetBot ||
2031             // arrays can be cast to Objects
2032             !tp->isa_instptr() ||
2033             tp->is_instptr()->instance_klass()->is_java_lang_Object() ||
2034             // unsafe field access may not have a constant offset
2035             C->has_unsafe_access(),
2036             "Field accesses must be precise" );
2037     // For oop loads, we expect the _type to be precise.
2038 
2039     // Optimize loads from constant fields.
2040     const TypeInstPtr* tinst = tp->is_instptr();
2041     ciObject* const_oop = tinst->const_oop();
2042     if (!is_mismatched_access() && off != Type::OffsetBot && const_oop != nullptr && const_oop->is_instance()) {
2043       const Type* con_type = Type::make_constant_from_field(const_oop->as_instance(), off, is_unsigned(), memory_type());
2044       if (con_type != nullptr) {
2045         return con_type;
2046       }
2047     }
2048   } else if (tp->base() == Type::KlassPtr || tp->base() == Type::InstKlassPtr || tp->base() == Type::AryKlassPtr) {
2049     assert(off != Type::OffsetBot ||
2050             !tp->isa_instklassptr() ||
2051            // arrays can be cast to Objects
2052            tp->isa_instklassptr()->instance_klass()->is_java_lang_Object() ||
2053            // also allow array-loading from the primary supertype
2054            // array during subtype checks
2055            Opcode() == Op_LoadKlass,
2056            "Field accesses must be precise");
2057     // For klass/static loads, we expect the _type to be precise
2058   } else if (tp->base() == Type::RawPtr && adr->is_Load() && off == 0) {
2059     /* With mirrors being an indirect in the Klass*
2060      * the VM is now using two loads. LoadKlass(LoadP(LoadP(Klass, mirror_offset), zero_offset))
2061      * The LoadP from the Klass has a RawPtr type (see LibraryCallKit::load_mirror_from_klass).
2062      *
2063      * So check the type and klass of the node before the LoadP.
2064      */
2065     Node* adr2 = adr->in(MemNode::Address);
2066     const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2067     if (tkls != nullptr && !StressReflectiveCode) {
2068       if (tkls->is_loaded() && tkls->klass_is_exact() && tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
2069         ciKlass* klass = tkls->exact_klass();
2070         assert(adr->Opcode() == Op_LoadP, "must load an oop from _java_mirror");
2071         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
2072         return TypeInstPtr::make(klass->java_mirror());
2073       }
2074     }
2075   }
2076 
2077   const TypeKlassPtr *tkls = tp->isa_klassptr();
2078   if (tkls != nullptr) {
2079     if (tkls->is_loaded() && tkls->klass_is_exact()) {
2080       ciKlass* klass = tkls->exact_klass();
2081       // We are loading a field from a Klass metaobject whose identity
2082       // is known at compile time (the type is "exact" or "precise").
2083       // Check for fields we know are maintained as constants by the VM.
2084       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
2085         // The field is Klass::_super_check_offset.  Return its (constant) value.
2086         // (Folds up type checking code.)
2087         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
2088         return TypeInt::make(klass->super_check_offset());
2089       }
2090       if (UseCompactObjectHeaders) {
2091         if (tkls->offset() == in_bytes(Klass::prototype_header_offset())) {
2092           // The field is Klass::_prototype_header. Return its (constant) value.
2093           assert(this->Opcode() == Op_LoadX, "must load a proper type from _prototype_header");
2094           return TypeX::make(klass->prototype_header());
2095         }
2096       }
2097       // Compute index into primary_supers array
2098       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
2099       // Check for overflowing; use unsigned compare to handle the negative case.
2100       if( depth < ciKlass::primary_super_limit() ) {
2101         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
2102         // (Folds up type checking code.)
2103         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
2104         ciKlass *ss = klass->super_of_depth(depth);
2105         return ss ? TypeKlassPtr::make(ss, Type::trust_interfaces) : TypePtr::NULL_PTR;
2106       }
2107       const Type* aift = load_array_final_field(tkls, klass);
2108       if (aift != nullptr)  return aift;
2109     }
2110 
2111     // We can still check if we are loading from the primary_supers array at a
2112     // shallow enough depth.  Even though the klass is not exact, entries less
2113     // than or equal to its super depth are correct.
2114     if (tkls->is_loaded()) {
2115       ciKlass* klass = nullptr;
2116       if (tkls->isa_instklassptr()) {
2117         klass = tkls->is_instklassptr()->instance_klass();
2118       } else {
2119         int dims;
2120         const Type* inner = tkls->is_aryklassptr()->base_element_type(dims);
2121         if (inner->isa_instklassptr()) {
2122           klass = inner->is_instklassptr()->instance_klass();
2123           klass = ciObjArrayKlass::make(klass, dims);
2124         }
2125       }
2126       if (klass != nullptr) {
2127         // Compute index into primary_supers array
2128         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
2129         // Check for overflowing; use unsigned compare to handle the negative case.
2130         if (depth < ciKlass::primary_super_limit() &&
2131             depth <= klass->super_depth()) { // allow self-depth checks to handle self-check case
2132           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
2133           // (Folds up type checking code.)
2134           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
2135           ciKlass *ss = klass->super_of_depth(depth);
2136           return ss ? TypeKlassPtr::make(ss, Type::trust_interfaces) : TypePtr::NULL_PTR;
2137         }
2138       }
2139     }
2140 
2141     // If the type is enough to determine that the thing is not an array,
2142     // we can give the layout_helper a positive interval type.
2143     // This will help short-circuit some reflective code.
2144     if (tkls->offset() == in_bytes(Klass::layout_helper_offset()) &&
2145         tkls->isa_instklassptr() && // not directly typed as an array
2146         !tkls->is_instklassptr()->instance_klass()->is_java_lang_Object() // not the supertype of all T[] and specifically not Serializable & Cloneable
2147         ) {
2148       // Note:  When interfaces are reliable, we can narrow the interface
2149       // test to (klass != Serializable && klass != Cloneable).
2150       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
2151       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
2152       // The key property of this type is that it folds up tests
2153       // for array-ness, since it proves that the layout_helper is positive.
2154       // Thus, a generic value like the basic object layout helper works fine.
2155       return TypeInt::make(min_size, max_jint, Type::WidenMin);
2156     }
2157   }
2158 
2159   // If we are loading from a freshly-allocated object, produce a zero,
2160   // if the load is provably beyond the header of the object.
2161   // (Also allow a variable load from a fresh array to produce zero.)
2162   const TypeOopPtr *tinst = tp->isa_oopptr();
2163   bool is_instance = (tinst != nullptr) && tinst->is_known_instance_field();
2164   bool is_boxed_value = (tinst != nullptr) && tinst->is_ptr_to_boxed_value();
2165   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
2166     Node* value = can_see_stored_value(mem,phase);
2167     if (value != nullptr && value->is_Con()) {
2168       assert(value->bottom_type()->higher_equal(_type),"sanity");
2169       return value->bottom_type();
2170     }
2171   }
2172 
2173   bool is_vect = (_type->isa_vect() != nullptr);
2174   if (is_instance && !is_vect) {
2175     // If we have an instance type and our memory input is the
2176     // programs's initial memory state, there is no matching store,
2177     // so just return a zero of the appropriate type -
2178     // except if it is vectorized - then we have no zero constant.
2179     Node *mem = in(MemNode::Memory);
2180     if (mem->is_Parm() && mem->in(0)->is_Start()) {
2181       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
2182       return Type::get_zero_type(_type->basic_type());
2183     }
2184   }
2185 
2186   Node* alloc = is_new_object_mark_load();
2187   if (!UseCompactObjectHeaders && alloc != nullptr) {
2188     return TypeX::make(markWord::prototype().value());
2189   }
2190 
2191   return _type;
2192 }
2193 
2194 //------------------------------match_edge-------------------------------------
2195 // Do we Match on this edge index or not?  Match only the address.
2196 uint LoadNode::match_edge(uint idx) const {
2197   return idx == MemNode::Address;
2198 }
2199 
2200 //--------------------------LoadBNode::Ideal--------------------------------------
2201 //
2202 //  If the previous store is to the same address as this load,
2203 //  and the value stored was larger than a byte, replace this load
2204 //  with the value stored truncated to a byte.  If no truncation is
2205 //  needed, the replacement is done in LoadNode::Identity().
2206 //
2207 Node* LoadBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2208   Node* mem = in(MemNode::Memory);
2209   Node* value = can_see_stored_value(mem,phase);
2210   if (value != nullptr) {
2211     Node* narrow = Compile::narrow_value(T_BYTE, value, _type, phase, false);
2212     if (narrow != value) {
2213       return narrow;
2214     }
2215   }
2216   // Identity call will handle the case where truncation is not needed.
2217   return LoadNode::Ideal(phase, can_reshape);
2218 }
2219 
2220 const Type* LoadBNode::Value(PhaseGVN* phase) const {
2221   Node* mem = in(MemNode::Memory);
2222   Node* value = can_see_stored_value(mem,phase);
2223   if (value != nullptr && value->is_Con() &&
2224       !value->bottom_type()->higher_equal(_type)) {
2225     // If the input to the store does not fit with the load's result type,
2226     // it must be truncated. We can't delay until Ideal call since
2227     // a singleton Value is needed for split_thru_phi optimization.
2228     int con = value->get_int();
2229     return TypeInt::make((con << 24) >> 24);
2230   }
2231   return LoadNode::Value(phase);
2232 }
2233 
2234 //--------------------------LoadUBNode::Ideal-------------------------------------
2235 //
2236 //  If the previous store is to the same address as this load,
2237 //  and the value stored was larger than a byte, replace this load
2238 //  with the value stored truncated to a byte.  If no truncation is
2239 //  needed, the replacement is done in LoadNode::Identity().
2240 //
2241 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2242   Node* mem = in(MemNode::Memory);
2243   Node* value = can_see_stored_value(mem, phase);
2244   if (value != nullptr) {
2245     Node* narrow = Compile::narrow_value(T_BOOLEAN, value, _type, phase, false);
2246     if (narrow != value) {
2247       return narrow;
2248     }
2249   }
2250   // Identity call will handle the case where truncation is not needed.
2251   return LoadNode::Ideal(phase, can_reshape);
2252 }
2253 
2254 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
2255   Node* mem = in(MemNode::Memory);
2256   Node* value = can_see_stored_value(mem,phase);
2257   if (value != nullptr && value->is_Con() &&
2258       !value->bottom_type()->higher_equal(_type)) {
2259     // If the input to the store does not fit with the load's result type,
2260     // it must be truncated. We can't delay until Ideal call since
2261     // a singleton Value is needed for split_thru_phi optimization.
2262     int con = value->get_int();
2263     return TypeInt::make(con & 0xFF);
2264   }
2265   return LoadNode::Value(phase);
2266 }
2267 
2268 //--------------------------LoadUSNode::Ideal-------------------------------------
2269 //
2270 //  If the previous store is to the same address as this load,
2271 //  and the value stored was larger than a char, replace this load
2272 //  with the value stored truncated to a char.  If no truncation is
2273 //  needed, the replacement is done in LoadNode::Identity().
2274 //
2275 Node* LoadUSNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2276   Node* mem = in(MemNode::Memory);
2277   Node* value = can_see_stored_value(mem,phase);
2278   if (value != nullptr) {
2279     Node* narrow = Compile::narrow_value(T_CHAR, value, _type, phase, false);
2280     if (narrow != value) {
2281       return narrow;
2282     }
2283   }
2284   // Identity call will handle the case where truncation is not needed.
2285   return LoadNode::Ideal(phase, can_reshape);
2286 }
2287 
2288 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
2289   Node* mem = in(MemNode::Memory);
2290   Node* value = can_see_stored_value(mem,phase);
2291   if (value != nullptr && value->is_Con() &&
2292       !value->bottom_type()->higher_equal(_type)) {
2293     // If the input to the store does not fit with the load's result type,
2294     // it must be truncated. We can't delay until Ideal call since
2295     // a singleton Value is needed for split_thru_phi optimization.
2296     int con = value->get_int();
2297     return TypeInt::make(con & 0xFFFF);
2298   }
2299   return LoadNode::Value(phase);
2300 }
2301 
2302 //--------------------------LoadSNode::Ideal--------------------------------------
2303 //
2304 //  If the previous store is to the same address as this load,
2305 //  and the value stored was larger than a short, replace this load
2306 //  with the value stored truncated to a short.  If no truncation is
2307 //  needed, the replacement is done in LoadNode::Identity().
2308 //
2309 Node* LoadSNode::Ideal(PhaseGVN* phase, bool can_reshape) {
2310   Node* mem = in(MemNode::Memory);
2311   Node* value = can_see_stored_value(mem,phase);
2312   if (value != nullptr) {
2313     Node* narrow = Compile::narrow_value(T_SHORT, value, _type, phase, false);
2314     if (narrow != value) {
2315       return narrow;
2316     }
2317   }
2318   // Identity call will handle the case where truncation is not needed.
2319   return LoadNode::Ideal(phase, can_reshape);
2320 }
2321 
2322 const Type* LoadSNode::Value(PhaseGVN* phase) const {
2323   Node* mem = in(MemNode::Memory);
2324   Node* value = can_see_stored_value(mem,phase);
2325   if (value != nullptr && value->is_Con() &&
2326       !value->bottom_type()->higher_equal(_type)) {
2327     // If the input to the store does not fit with the load's result type,
2328     // it must be truncated. We can't delay until Ideal call since
2329     // a singleton Value is needed for split_thru_phi optimization.
2330     int con = value->get_int();
2331     return TypeInt::make((con << 16) >> 16);
2332   }
2333   return LoadNode::Value(phase);
2334 }
2335 
2336 //=============================================================================
2337 //----------------------------LoadKlassNode::make------------------------------
2338 // Polymorphic factory method:
2339 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2340   // sanity check the alias category against the created node type
2341   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2342   assert(adr_type != nullptr, "expecting TypeKlassPtr");
2343 #ifdef _LP64
2344   if (adr_type->is_ptr_to_narrowklass()) {
2345     assert(UseCompressedClassPointers, "no compressed klasses");
2346     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2347     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2348   }
2349 #endif
2350   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2351   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2352 }
2353 
2354 //------------------------------Value------------------------------------------
2355 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2356   return klass_value_common(phase);
2357 }
2358 
2359 // In most cases, LoadKlassNode does not have the control input set. If the control
2360 // input is set, it must not be removed (by LoadNode::Ideal()).
2361 bool LoadKlassNode::can_remove_control() const {
2362   return false;
2363 }
2364 
2365 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2366   // Either input is TOP ==> the result is TOP
2367   const Type *t1 = phase->type( in(MemNode::Memory) );
2368   if (t1 == Type::TOP)  return Type::TOP;
2369   Node *adr = in(MemNode::Address);
2370   const Type *t2 = phase->type( adr );
2371   if (t2 == Type::TOP)  return Type::TOP;
2372   const TypePtr *tp = t2->is_ptr();
2373   if (TypePtr::above_centerline(tp->ptr()) ||
2374       tp->ptr() == TypePtr::Null)  return Type::TOP;
2375 
2376   // Return a more precise klass, if possible
2377   const TypeInstPtr *tinst = tp->isa_instptr();
2378   if (tinst != nullptr) {
2379     ciInstanceKlass* ik = tinst->instance_klass();
2380     int offset = tinst->offset();
2381     if (ik == phase->C->env()->Class_klass()
2382         && (offset == java_lang_Class::klass_offset() ||
2383             offset == java_lang_Class::array_klass_offset())) {
2384       // We are loading a special hidden field from a Class mirror object,
2385       // the field which points to the VM's Klass metaobject.
2386       ciType* t = tinst->java_mirror_type();
2387       // java_mirror_type returns non-null for compile-time Class constants.
2388       if (t != nullptr) {
2389         // constant oop => constant klass
2390         if (offset == java_lang_Class::array_klass_offset()) {
2391           if (t->is_void()) {
2392             // We cannot create a void array.  Since void is a primitive type return null
2393             // klass.  Users of this result need to do a null check on the returned klass.
2394             return TypePtr::NULL_PTR;
2395           }
2396           return TypeKlassPtr::make(ciArrayKlass::make(t), Type::trust_interfaces);
2397         }
2398         if (!t->is_klass()) {
2399           // a primitive Class (e.g., int.class) has null for a klass field
2400           return TypePtr::NULL_PTR;
2401         }
2402         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2403         return TypeKlassPtr::make(t->as_klass(), Type::trust_interfaces);
2404       }
2405       // non-constant mirror, so we can't tell what's going on
2406     }
2407     if (!tinst->is_loaded())
2408       return _type;             // Bail out if not loaded
2409     if (offset == oopDesc::klass_offset_in_bytes()) {
2410       return tinst->as_klass_type(true);
2411     }
2412   }
2413 
2414   // Check for loading klass from an array
2415   const TypeAryPtr *tary = tp->isa_aryptr();
2416   if (tary != nullptr &&
2417       tary->offset() == oopDesc::klass_offset_in_bytes()) {
2418     return tary->as_klass_type(true);
2419   }
2420 
2421   // Check for loading klass from an array klass
2422   const TypeKlassPtr *tkls = tp->isa_klassptr();
2423   if (tkls != nullptr && !StressReflectiveCode) {
2424     if (!tkls->is_loaded())
2425      return _type;             // Bail out if not loaded
2426     if (tkls->isa_aryklassptr() && tkls->is_aryklassptr()->elem()->isa_klassptr() &&
2427         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2428       // // Always returning precise element type is incorrect,
2429       // // e.g., element type could be object and array may contain strings
2430       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2431 
2432       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2433       // according to the element type's subclassing.
2434       return tkls->is_aryklassptr()->elem()->isa_klassptr()->cast_to_exactness(tkls->klass_is_exact());
2435     }
2436     if (tkls->isa_instklassptr() != nullptr && tkls->klass_is_exact() &&
2437         tkls->offset() == in_bytes(Klass::super_offset())) {
2438       ciKlass* sup = tkls->is_instklassptr()->instance_klass()->super();
2439       // The field is Klass::_super.  Return its (constant) value.
2440       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2441       return sup ? TypeKlassPtr::make(sup, Type::trust_interfaces) : TypePtr::NULL_PTR;
2442     }
2443   }
2444 
2445   // Bailout case
2446   return LoadNode::Value(phase);
2447 }
2448 
2449 //------------------------------Identity---------------------------------------
2450 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2451 // Also feed through the klass in Allocate(...klass...)._klass.
2452 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2453   return klass_identity_common(phase);
2454 }
2455 
2456 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2457   Node* x = LoadNode::Identity(phase);
2458   if (x != this)  return x;
2459 
2460   // Take apart the address into an oop and offset.
2461   // Return 'this' if we cannot.
2462   Node*    adr    = in(MemNode::Address);
2463   intptr_t offset = 0;
2464   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2465   if (base == nullptr)     return this;
2466   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2467   if (toop == nullptr)     return this;
2468 
2469   // Step over potential GC barrier for OopHandle resolve
2470   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2471   if (bs->is_gc_barrier_node(base)) {
2472     base = bs->step_over_gc_barrier(base);
2473   }
2474 
2475   // We can fetch the klass directly through an AllocateNode.
2476   // This works even if the klass is not constant (clone or newArray).
2477   if (offset == oopDesc::klass_offset_in_bytes()) {
2478     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2479     if (allocated_klass != nullptr) {
2480       return allocated_klass;
2481     }
2482   }
2483 
2484   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2485   // See inline_native_Class_query for occurrences of these patterns.
2486   // Java Example:  x.getClass().isAssignableFrom(y)
2487   //
2488   // This improves reflective code, often making the Class
2489   // mirror go completely dead.  (Current exception:  Class
2490   // mirrors may appear in debug info, but we could clean them out by
2491   // introducing a new debug info operator for Klass.java_mirror).
2492 
2493   if (toop->isa_instptr() && toop->is_instptr()->instance_klass() == phase->C->env()->Class_klass()
2494       && offset == java_lang_Class::klass_offset()) {
2495     if (base->is_Load()) {
2496       Node* base2 = base->in(MemNode::Address);
2497       if (base2->is_Load()) { /* direct load of a load which is the OopHandle */
2498         Node* adr2 = base2->in(MemNode::Address);
2499         const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2500         if (tkls != nullptr && !tkls->empty()
2501             && (tkls->isa_instklassptr() || tkls->isa_aryklassptr())
2502             && adr2->is_AddP()
2503            ) {
2504           int mirror_field = in_bytes(Klass::java_mirror_offset());
2505           if (tkls->offset() == mirror_field) {
2506             return adr2->in(AddPNode::Base);
2507           }
2508         }
2509       }
2510     }
2511   }
2512 
2513   return this;
2514 }
2515 
2516 
2517 //------------------------------Value------------------------------------------
2518 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2519   const Type *t = klass_value_common(phase);
2520   if (t == Type::TOP)
2521     return t;
2522 
2523   return t->make_narrowklass();
2524 }
2525 
2526 //------------------------------Identity---------------------------------------
2527 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2528 // Also feed through the klass in Allocate(...klass...)._klass.
2529 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2530   Node *x = klass_identity_common(phase);
2531 
2532   const Type *t = phase->type( x );
2533   if( t == Type::TOP ) return x;
2534   if( t->isa_narrowklass()) return x;
2535   assert (!t->isa_narrowoop(), "no narrow oop here");
2536 
2537   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2538 }
2539 
2540 //------------------------------Value-----------------------------------------
2541 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2542   // Either input is TOP ==> the result is TOP
2543   const Type *t1 = phase->type( in(MemNode::Memory) );
2544   if( t1 == Type::TOP ) return Type::TOP;
2545   Node *adr = in(MemNode::Address);
2546   const Type *t2 = phase->type( adr );
2547   if( t2 == Type::TOP ) return Type::TOP;
2548   const TypePtr *tp = t2->is_ptr();
2549   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2550   const TypeAryPtr *tap = tp->isa_aryptr();
2551   if( !tap ) return _type;
2552   return tap->size();
2553 }
2554 
2555 //-------------------------------Ideal---------------------------------------
2556 // Feed through the length in AllocateArray(...length...)._length.
2557 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2558   Node* p = MemNode::Ideal_common(phase, can_reshape);
2559   if (p)  return (p == NodeSentinel) ? nullptr : p;
2560 
2561   // Take apart the address into an oop and offset.
2562   // Return 'this' if we cannot.
2563   Node*    adr    = in(MemNode::Address);
2564   intptr_t offset = 0;
2565   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2566   if (base == nullptr)     return nullptr;
2567   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2568   if (tary == nullptr)     return nullptr;
2569 
2570   // We can fetch the length directly through an AllocateArrayNode.
2571   // This works even if the length is not constant (clone or newArray).
2572   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2573     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base);
2574     if (alloc != nullptr) {
2575       Node* allocated_length = alloc->Ideal_length();
2576       Node* len = alloc->make_ideal_length(tary, phase);
2577       if (allocated_length != len) {
2578         // New CastII improves on this.
2579         return len;
2580       }
2581     }
2582   }
2583 
2584   return nullptr;
2585 }
2586 
2587 //------------------------------Identity---------------------------------------
2588 // Feed through the length in AllocateArray(...length...)._length.
2589 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2590   Node* x = LoadINode::Identity(phase);
2591   if (x != this)  return x;
2592 
2593   // Take apart the address into an oop and offset.
2594   // Return 'this' if we cannot.
2595   Node*    adr    = in(MemNode::Address);
2596   intptr_t offset = 0;
2597   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2598   if (base == nullptr)     return this;
2599   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2600   if (tary == nullptr)     return this;
2601 
2602   // We can fetch the length directly through an AllocateArrayNode.
2603   // This works even if the length is not constant (clone or newArray).
2604   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2605     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base);
2606     if (alloc != nullptr) {
2607       Node* allocated_length = alloc->Ideal_length();
2608       // Do not allow make_ideal_length to allocate a CastII node.
2609       Node* len = alloc->make_ideal_length(tary, phase, false);
2610       if (allocated_length == len) {
2611         // Return allocated_length only if it would not be improved by a CastII.
2612         return allocated_length;
2613       }
2614     }
2615   }
2616 
2617   return this;
2618 
2619 }
2620 
2621 //=============================================================================
2622 //---------------------------StoreNode::make-----------------------------------
2623 // Polymorphic factory method:
2624 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) {
2625   assert((mo == unordered || mo == release), "unexpected");
2626   Compile* C = gvn.C;
2627   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2628          ctl != nullptr, "raw memory operations should have control edge");
2629 
2630   switch (bt) {
2631   case T_BOOLEAN: val = gvn.transform(new AndINode(val, gvn.intcon(0x1))); // Fall through to T_BYTE case
2632   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2633   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2634   case T_CHAR:
2635   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2636   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic_access);
2637   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2638   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic_access);
2639   case T_METADATA:
2640   case T_ADDRESS:
2641   case T_OBJECT:
2642 #ifdef _LP64
2643     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2644       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2645       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2646     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2647                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2648                 adr->bottom_type()->isa_rawptr())) {
2649       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2650       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2651     }
2652 #endif
2653     {
2654       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2655     }
2656   default:
2657     ShouldNotReachHere();
2658     return (StoreNode*)nullptr;
2659   }
2660 }
2661 
2662 //--------------------------bottom_type----------------------------------------
2663 const Type *StoreNode::bottom_type() const {
2664   return Type::MEMORY;
2665 }
2666 
2667 //------------------------------hash-------------------------------------------
2668 uint StoreNode::hash() const {
2669   // unroll addition of interesting fields
2670   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2671 
2672   // Since they are not commoned, do not hash them:
2673   return NO_HASH;
2674 }
2675 
2676 //------------------------------Ideal------------------------------------------
2677 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2678 // When a store immediately follows a relevant allocation/initialization,
2679 // try to capture it into the initialization, or hoist it above.
2680 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2681   Node* p = MemNode::Ideal_common(phase, can_reshape);
2682   if (p)  return (p == NodeSentinel) ? nullptr : p;
2683 
2684   Node* mem     = in(MemNode::Memory);
2685   Node* address = in(MemNode::Address);
2686   Node* value   = in(MemNode::ValueIn);
2687   // Back-to-back stores to same address?  Fold em up.  Generally
2688   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2689   // since they must follow each StoreP operation.  Redundant StoreCMs
2690   // are eliminated just before matching in final_graph_reshape.
2691   {
2692     Node* st = mem;
2693     // If Store 'st' has more than one use, we cannot fold 'st' away.
2694     // For example, 'st' might be the final state at a conditional
2695     // return.  Or, 'st' might be used by some node which is live at
2696     // the same time 'st' is live, which might be unschedulable.  So,
2697     // require exactly ONE user until such time as we clone 'mem' for
2698     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2699     // true).
2700     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2701       // Looking at a dead closed cycle of memory?
2702       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2703       assert(Opcode() == st->Opcode() ||
2704              st->Opcode() == Op_StoreVector ||
2705              Opcode() == Op_StoreVector ||
2706              st->Opcode() == Op_StoreVectorScatter ||
2707              Opcode() == Op_StoreVectorScatter ||
2708              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2709              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2710              (Opcode() == Op_StoreI && st->Opcode() == Op_StoreL) || // initialization by arraycopy
2711              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2712              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2713 
2714       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2715           st->as_Store()->memory_size() <= this->memory_size()) {
2716         Node* use = st->raw_out(0);
2717         if (phase->is_IterGVN()) {
2718           phase->is_IterGVN()->rehash_node_delayed(use);
2719         }
2720         // It's OK to do this in the parser, since DU info is always accurate,
2721         // and the parser always refers to nodes via SafePointNode maps.
2722         use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase);
2723         return this;
2724       }
2725       st = st->in(MemNode::Memory);
2726     }
2727   }
2728 
2729 
2730   // Capture an unaliased, unconditional, simple store into an initializer.
2731   // Or, if it is independent of the allocation, hoist it above the allocation.
2732   if (ReduceFieldZeroing && /*can_reshape &&*/
2733       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2734     InitializeNode* init = mem->in(0)->as_Initialize();
2735     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2736     if (offset > 0) {
2737       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2738       // If the InitializeNode captured me, it made a raw copy of me,
2739       // and I need to disappear.
2740       if (moved != nullptr) {
2741         // %%% hack to ensure that Ideal returns a new node:
2742         mem = MergeMemNode::make(mem);
2743         return mem;             // fold me away
2744       }
2745     }
2746   }
2747 
2748   // Fold reinterpret cast into memory operation:
2749   //    StoreX mem (MoveY2X v) => StoreY mem v
2750   if (value->is_Move()) {
2751     const Type* vt = value->in(1)->bottom_type();
2752     if (has_reinterpret_variant(vt)) {
2753       if (phase->C->post_loop_opts_phase()) {
2754         return convert_to_reinterpret_store(*phase, value->in(1), vt);
2755       } else {
2756         phase->C->record_for_post_loop_opts_igvn(this); // attempt the transformation once loop opts are over
2757       }
2758     }
2759   }
2760 
2761   return nullptr;                  // No further progress
2762 }
2763 
2764 //------------------------------Value-----------------------------------------
2765 const Type* StoreNode::Value(PhaseGVN* phase) const {
2766   // Either input is TOP ==> the result is TOP
2767   const Type *t1 = phase->type( in(MemNode::Memory) );
2768   if( t1 == Type::TOP ) return Type::TOP;
2769   const Type *t2 = phase->type( in(MemNode::Address) );
2770   if( t2 == Type::TOP ) return Type::TOP;
2771   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2772   if( t3 == Type::TOP ) return Type::TOP;
2773   return Type::MEMORY;
2774 }
2775 
2776 //------------------------------Identity---------------------------------------
2777 // Remove redundant stores:
2778 //   Store(m, p, Load(m, p)) changes to m.
2779 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2780 Node* StoreNode::Identity(PhaseGVN* phase) {
2781   Node* mem = in(MemNode::Memory);
2782   Node* adr = in(MemNode::Address);
2783   Node* val = in(MemNode::ValueIn);
2784 
2785   Node* result = this;
2786 
2787   // Load then Store?  Then the Store is useless
2788   if (val->is_Load() &&
2789       val->in(MemNode::Address)->eqv_uncast(adr) &&
2790       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2791       val->as_Load()->store_Opcode() == Opcode()) {
2792     result = mem;
2793   }
2794 
2795   // Two stores in a row of the same value?
2796   if (result == this &&
2797       mem->is_Store() &&
2798       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2799       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2800       mem->Opcode() == Opcode()) {
2801     result = mem;
2802   }
2803 
2804   // Store of zero anywhere into a freshly-allocated object?
2805   // Then the store is useless.
2806   // (It must already have been captured by the InitializeNode.)
2807   if (result == this &&
2808       ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2809     // a newly allocated object is already all-zeroes everywhere
2810     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2811       result = mem;
2812     }
2813 
2814     if (result == this) {
2815       // the store may also apply to zero-bits in an earlier object
2816       Node* prev_mem = find_previous_store(phase);
2817       // Steps (a), (b):  Walk past independent stores to find an exact match.
2818       if (prev_mem != nullptr) {
2819         Node* prev_val = can_see_stored_value(prev_mem, phase);
2820         if (prev_val != nullptr && prev_val == val) {
2821           // prev_val and val might differ by a cast; it would be good
2822           // to keep the more informative of the two.
2823           result = mem;
2824         }
2825       }
2826     }
2827   }
2828 
2829   PhaseIterGVN* igvn = phase->is_IterGVN();
2830   if (result != this && igvn != nullptr) {
2831     MemBarNode* trailing = trailing_membar();
2832     if (trailing != nullptr) {
2833 #ifdef ASSERT
2834       const TypeOopPtr* t_oop = phase->type(in(Address))->isa_oopptr();
2835       assert(t_oop == nullptr || t_oop->is_known_instance_field(), "only for non escaping objects");
2836 #endif
2837       trailing->remove(igvn);
2838     }
2839   }
2840 
2841   return result;
2842 }
2843 
2844 //------------------------------match_edge-------------------------------------
2845 // Do we Match on this edge index or not?  Match only memory & value
2846 uint StoreNode::match_edge(uint idx) const {
2847   return idx == MemNode::Address || idx == MemNode::ValueIn;
2848 }
2849 
2850 //------------------------------cmp--------------------------------------------
2851 // Do not common stores up together.  They generally have to be split
2852 // back up anyways, so do not bother.
2853 bool StoreNode::cmp( const Node &n ) const {
2854   return (&n == this);          // Always fail except on self
2855 }
2856 
2857 //------------------------------Ideal_masked_input-----------------------------
2858 // Check for a useless mask before a partial-word store
2859 // (StoreB ... (AndI valIn conIa) )
2860 // If (conIa & mask == mask) this simplifies to
2861 // (StoreB ... (valIn) )
2862 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2863   Node *val = in(MemNode::ValueIn);
2864   if( val->Opcode() == Op_AndI ) {
2865     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2866     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2867       set_req_X(MemNode::ValueIn, val->in(1), phase);
2868       return this;
2869     }
2870   }
2871   return nullptr;
2872 }
2873 
2874 
2875 //------------------------------Ideal_sign_extended_input----------------------
2876 // Check for useless sign-extension before a partial-word store
2877 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2878 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2879 // (StoreB ... (valIn) )
2880 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2881   Node *val = in(MemNode::ValueIn);
2882   if( val->Opcode() == Op_RShiftI ) {
2883     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2884     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2885       Node *shl = val->in(1);
2886       if( shl->Opcode() == Op_LShiftI ) {
2887         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2888         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2889           set_req_X(MemNode::ValueIn, shl->in(1), phase);
2890           return this;
2891         }
2892       }
2893     }
2894   }
2895   return nullptr;
2896 }
2897 
2898 //------------------------------value_never_loaded-----------------------------------
2899 // Determine whether there are any possible loads of the value stored.
2900 // For simplicity, we actually check if there are any loads from the
2901 // address stored to, not just for loads of the value stored by this node.
2902 //
2903 bool StoreNode::value_never_loaded(PhaseValues* phase) const {
2904   Node *adr = in(Address);
2905   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2906   if (adr_oop == nullptr)
2907     return false;
2908   if (!adr_oop->is_known_instance_field())
2909     return false; // if not a distinct instance, there may be aliases of the address
2910   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2911     Node *use = adr->fast_out(i);
2912     if (use->is_Load() || use->is_LoadStore()) {
2913       return false;
2914     }
2915   }
2916   return true;
2917 }
2918 
2919 MemBarNode* StoreNode::trailing_membar() const {
2920   if (is_release()) {
2921     MemBarNode* trailing_mb = nullptr;
2922     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2923       Node* u = fast_out(i);
2924       if (u->is_MemBar()) {
2925         if (u->as_MemBar()->trailing_store()) {
2926           assert(u->Opcode() == Op_MemBarVolatile, "");
2927           assert(trailing_mb == nullptr, "only one");
2928           trailing_mb = u->as_MemBar();
2929 #ifdef ASSERT
2930           Node* leading = u->as_MemBar()->leading_membar();
2931           assert(leading->Opcode() == Op_MemBarRelease, "incorrect membar");
2932           assert(leading->as_MemBar()->leading_store(), "incorrect membar pair");
2933           assert(leading->as_MemBar()->trailing_membar() == u, "incorrect membar pair");
2934 #endif
2935         } else {
2936           assert(u->as_MemBar()->standalone(), "");
2937         }
2938       }
2939     }
2940     return trailing_mb;
2941   }
2942   return nullptr;
2943 }
2944 
2945 
2946 //=============================================================================
2947 //------------------------------Ideal------------------------------------------
2948 // If the store is from an AND mask that leaves the low bits untouched, then
2949 // we can skip the AND operation.  If the store is from a sign-extension
2950 // (a left shift, then right shift) we can skip both.
2951 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2952   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2953   if( progress != nullptr ) return progress;
2954 
2955   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2956   if( progress != nullptr ) return progress;
2957 
2958   // Finally check the default case
2959   return StoreNode::Ideal(phase, can_reshape);
2960 }
2961 
2962 //=============================================================================
2963 //------------------------------Ideal------------------------------------------
2964 // If the store is from an AND mask that leaves the low bits untouched, then
2965 // we can skip the AND operation
2966 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2967   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2968   if( progress != nullptr ) return progress;
2969 
2970   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2971   if( progress != nullptr ) return progress;
2972 
2973   // Finally check the default case
2974   return StoreNode::Ideal(phase, can_reshape);
2975 }
2976 
2977 //=============================================================================
2978 //------------------------------Identity---------------------------------------
2979 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2980   // No need to card mark when storing a null ptr
2981   Node* my_store = in(MemNode::OopStore);
2982   if (my_store->is_Store()) {
2983     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2984     if( t1 == TypePtr::NULL_PTR ) {
2985       return in(MemNode::Memory);
2986     }
2987   }
2988   return this;
2989 }
2990 
2991 //=============================================================================
2992 //------------------------------Ideal---------------------------------------
2993 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2994   Node* progress = StoreNode::Ideal(phase, can_reshape);
2995   if (progress != nullptr) return progress;
2996 
2997   Node* my_store = in(MemNode::OopStore);
2998   if (my_store->is_MergeMem()) {
2999     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
3000     set_req_X(MemNode::OopStore, mem, phase);
3001     return this;
3002   }
3003 
3004   return nullptr;
3005 }
3006 
3007 //------------------------------Value-----------------------------------------
3008 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
3009   // Either input is TOP ==> the result is TOP (checked in StoreNode::Value).
3010   // If extra input is TOP ==> the result is TOP
3011   const Type* t = phase->type(in(MemNode::OopStore));
3012   if (t == Type::TOP) {
3013     return Type::TOP;
3014   }
3015   return StoreNode::Value(phase);
3016 }
3017 
3018 
3019 //=============================================================================
3020 //----------------------------------SCMemProjNode------------------------------
3021 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
3022 {
3023   if (in(0) == nullptr || phase->type(in(0)) == Type::TOP) {
3024     return Type::TOP;
3025   }
3026   return bottom_type();
3027 }
3028 
3029 //=============================================================================
3030 //----------------------------------LoadStoreNode------------------------------
3031 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
3032   : Node(required),
3033     _type(rt),
3034     _adr_type(at),
3035     _barrier_data(0)
3036 {
3037   init_req(MemNode::Control, c  );
3038   init_req(MemNode::Memory , mem);
3039   init_req(MemNode::Address, adr);
3040   init_req(MemNode::ValueIn, val);
3041   init_class_id(Class_LoadStore);
3042 }
3043 
3044 //------------------------------Value-----------------------------------------
3045 const Type* LoadStoreNode::Value(PhaseGVN* phase) const {
3046   // Either input is TOP ==> the result is TOP
3047   if (!in(MemNode::Control) || phase->type(in(MemNode::Control)) == Type::TOP) {
3048     return Type::TOP;
3049   }
3050   const Type* t = phase->type(in(MemNode::Memory));
3051   if (t == Type::TOP) {
3052     return Type::TOP;
3053   }
3054   t = phase->type(in(MemNode::Address));
3055   if (t == Type::TOP) {
3056     return Type::TOP;
3057   }
3058   t = phase->type(in(MemNode::ValueIn));
3059   if (t == Type::TOP) {
3060     return Type::TOP;
3061   }
3062   return bottom_type();
3063 }
3064 
3065 uint LoadStoreNode::ideal_reg() const {
3066   return _type->ideal_reg();
3067 }
3068 
3069 // This method conservatively checks if the result of a LoadStoreNode is
3070 // used, that is, if it returns true, then it is definitely the case that
3071 // the result of the node is not needed.
3072 // For example, GetAndAdd can be matched into a lock_add instead of a
3073 // lock_xadd if the result of LoadStoreNode::result_not_used() is true
3074 bool LoadStoreNode::result_not_used() const {
3075   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
3076     Node *x = fast_out(i);
3077     if (x->Opcode() == Op_SCMemProj) {
3078       continue;
3079     }
3080     if (x->bottom_type() == TypeTuple::MEMBAR &&
3081         !x->is_Call() &&
3082         x->Opcode() != Op_Blackhole) {
3083       continue;
3084     }
3085     return false;
3086   }
3087   return true;
3088 }
3089 
3090 MemBarNode* LoadStoreNode::trailing_membar() const {
3091   MemBarNode* trailing = nullptr;
3092   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
3093     Node* u = fast_out(i);
3094     if (u->is_MemBar()) {
3095       if (u->as_MemBar()->trailing_load_store()) {
3096         assert(u->Opcode() == Op_MemBarAcquire, "");
3097         assert(trailing == nullptr, "only one");
3098         trailing = u->as_MemBar();
3099 #ifdef ASSERT
3100         Node* leading = trailing->leading_membar();
3101         assert(support_IRIW_for_not_multiple_copy_atomic_cpu || leading->Opcode() == Op_MemBarRelease, "incorrect membar");
3102         assert(leading->as_MemBar()->leading_load_store(), "incorrect membar pair");
3103         assert(leading->as_MemBar()->trailing_membar() == trailing, "incorrect membar pair");
3104 #endif
3105       } else {
3106         assert(u->as_MemBar()->standalone(), "wrong barrier kind");
3107       }
3108     }
3109   }
3110 
3111   return trailing;
3112 }
3113 
3114 uint LoadStoreNode::size_of() const { return sizeof(*this); }
3115 
3116 //=============================================================================
3117 //----------------------------------LoadStoreConditionalNode--------------------
3118 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, nullptr, TypeInt::BOOL, 5) {
3119   init_req(ExpectedIn, ex );
3120 }
3121 
3122 const Type* LoadStoreConditionalNode::Value(PhaseGVN* phase) const {
3123   // Either input is TOP ==> the result is TOP
3124   const Type* t = phase->type(in(ExpectedIn));
3125   if (t == Type::TOP) {
3126     return Type::TOP;
3127   }
3128   return LoadStoreNode::Value(phase);
3129 }
3130 
3131 //=============================================================================
3132 //-------------------------------adr_type--------------------------------------
3133 const TypePtr* ClearArrayNode::adr_type() const {
3134   Node *adr = in(3);
3135   if (adr == nullptr)  return nullptr; // node is dead
3136   return MemNode::calculate_adr_type(adr->bottom_type());
3137 }
3138 
3139 //------------------------------match_edge-------------------------------------
3140 // Do we Match on this edge index or not?  Do not match memory
3141 uint ClearArrayNode::match_edge(uint idx) const {
3142   return idx > 1;
3143 }
3144 
3145 //------------------------------Identity---------------------------------------
3146 // Clearing a zero length array does nothing
3147 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
3148   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
3149 }
3150 
3151 //------------------------------Idealize---------------------------------------
3152 // Clearing a short array is faster with stores
3153 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3154   // Already know this is a large node, do not try to ideal it
3155   if (_is_large) return nullptr;
3156 
3157   const int unit = BytesPerLong;
3158   const TypeX* t = phase->type(in(2))->isa_intptr_t();
3159   if (!t)  return nullptr;
3160   if (!t->is_con())  return nullptr;
3161   intptr_t raw_count = t->get_con();
3162   intptr_t size = raw_count;
3163   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
3164   // Clearing nothing uses the Identity call.
3165   // Negative clears are possible on dead ClearArrays
3166   // (see jck test stmt114.stmt11402.val).
3167   if (size <= 0 || size % unit != 0)  return nullptr;
3168   intptr_t count = size / unit;
3169   // Length too long; communicate this to matchers and assemblers.
3170   // Assemblers are responsible to produce fast hardware clears for it.
3171   if (size > InitArrayShortSize) {
3172     return new ClearArrayNode(in(0), in(1), in(2), in(3), true);
3173   } else if (size > 2 && Matcher::match_rule_supported_vector(Op_ClearArray, 4, T_LONG)) {
3174     return nullptr;
3175   }
3176   if (!IdealizeClearArrayNode) return nullptr;
3177   Node *mem = in(1);
3178   if( phase->type(mem)==Type::TOP ) return nullptr;
3179   Node *adr = in(3);
3180   const Type* at = phase->type(adr);
3181   if( at==Type::TOP ) return nullptr;
3182   const TypePtr* atp = at->isa_ptr();
3183   // adjust atp to be the correct array element address type
3184   if (atp == nullptr)  atp = TypePtr::BOTTOM;
3185   else              atp = atp->add_offset(Type::OffsetBot);
3186   // Get base for derived pointer purposes
3187   if( adr->Opcode() != Op_AddP ) Unimplemented();
3188   Node *base = adr->in(1);
3189 
3190   Node *zero = phase->makecon(TypeLong::ZERO);
3191   Node *off  = phase->MakeConX(BytesPerLong);
3192   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
3193   count--;
3194   while( count-- ) {
3195     mem = phase->transform(mem);
3196     adr = phase->transform(new AddPNode(base,adr,off));
3197     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
3198   }
3199   return mem;
3200 }
3201 
3202 //----------------------------step_through----------------------------------
3203 // Return allocation input memory edge if it is different instance
3204 // or itself if it is the one we are looking for.
3205 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseValues* phase) {
3206   Node* n = *np;
3207   assert(n->is_ClearArray(), "sanity");
3208   intptr_t offset;
3209   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
3210   // This method is called only before Allocate nodes are expanded
3211   // during macro nodes expansion. Before that ClearArray nodes are
3212   // only generated in PhaseMacroExpand::generate_arraycopy() (before
3213   // Allocate nodes are expanded) which follows allocations.
3214   assert(alloc != nullptr, "should have allocation");
3215   if (alloc->_idx == instance_id) {
3216     // Can not bypass initialization of the instance we are looking for.
3217     return false;
3218   }
3219   // Otherwise skip it.
3220   InitializeNode* init = alloc->initialization();
3221   if (init != nullptr)
3222     *np = init->in(TypeFunc::Memory);
3223   else
3224     *np = alloc->in(TypeFunc::Memory);
3225   return true;
3226 }
3227 
3228 //----------------------------clear_memory-------------------------------------
3229 // Generate code to initialize object storage to zero.
3230 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3231                                    intptr_t start_offset,
3232                                    Node* end_offset,
3233                                    PhaseGVN* phase) {
3234   intptr_t offset = start_offset;
3235 
3236   int unit = BytesPerLong;
3237   if ((offset % unit) != 0) {
3238     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
3239     adr = phase->transform(adr);
3240     const TypePtr* atp = TypeRawPtr::BOTTOM;
3241     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3242     mem = phase->transform(mem);
3243     offset += BytesPerInt;
3244   }
3245   assert((offset % unit) == 0, "");
3246 
3247   // Initialize the remaining stuff, if any, with a ClearArray.
3248   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
3249 }
3250 
3251 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3252                                    Node* start_offset,
3253                                    Node* end_offset,
3254                                    PhaseGVN* phase) {
3255   if (start_offset == end_offset) {
3256     // nothing to do
3257     return mem;
3258   }
3259 
3260   int unit = BytesPerLong;
3261   Node* zbase = start_offset;
3262   Node* zend  = end_offset;
3263 
3264   // Scale to the unit required by the CPU:
3265   if (!Matcher::init_array_count_is_in_bytes) {
3266     Node* shift = phase->intcon(exact_log2(unit));
3267     zbase = phase->transform(new URShiftXNode(zbase, shift) );
3268     zend  = phase->transform(new URShiftXNode(zend,  shift) );
3269   }
3270 
3271   // Bulk clear double-words
3272   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
3273   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
3274   mem = new ClearArrayNode(ctl, mem, zsize, adr, false);
3275   return phase->transform(mem);
3276 }
3277 
3278 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
3279                                    intptr_t start_offset,
3280                                    intptr_t end_offset,
3281                                    PhaseGVN* phase) {
3282   if (start_offset == end_offset) {
3283     // nothing to do
3284     return mem;
3285   }
3286 
3287   assert((end_offset % BytesPerInt) == 0, "odd end offset");
3288   intptr_t done_offset = end_offset;
3289   if ((done_offset % BytesPerLong) != 0) {
3290     done_offset -= BytesPerInt;
3291   }
3292   if (done_offset > start_offset) {
3293     mem = clear_memory(ctl, mem, dest,
3294                        start_offset, phase->MakeConX(done_offset), phase);
3295   }
3296   if (done_offset < end_offset) { // emit the final 32-bit store
3297     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
3298     adr = phase->transform(adr);
3299     const TypePtr* atp = TypeRawPtr::BOTTOM;
3300     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
3301     mem = phase->transform(mem);
3302     done_offset += BytesPerInt;
3303   }
3304   assert(done_offset == end_offset, "");
3305   return mem;
3306 }
3307 
3308 //=============================================================================
3309 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
3310   : MultiNode(TypeFunc::Parms + (precedent == nullptr? 0: 1)),
3311     _adr_type(C->get_adr_type(alias_idx)), _kind(Standalone)
3312 #ifdef ASSERT
3313   , _pair_idx(0)
3314 #endif
3315 {
3316   init_class_id(Class_MemBar);
3317   Node* top = C->top();
3318   init_req(TypeFunc::I_O,top);
3319   init_req(TypeFunc::FramePtr,top);
3320   init_req(TypeFunc::ReturnAdr,top);
3321   if (precedent != nullptr)
3322     init_req(TypeFunc::Parms, precedent);
3323 }
3324 
3325 //------------------------------cmp--------------------------------------------
3326 uint MemBarNode::hash() const { return NO_HASH; }
3327 bool MemBarNode::cmp( const Node &n ) const {
3328   return (&n == this);          // Always fail except on self
3329 }
3330 
3331 //------------------------------make-------------------------------------------
3332 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
3333   switch (opcode) {
3334   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
3335   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
3336   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
3337   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
3338   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
3339   case Op_StoreStoreFence:   return new StoreStoreFenceNode(C, atp, pn);
3340   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
3341   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
3342   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
3343   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
3344   case Op_OnSpinWait:        return new OnSpinWaitNode(C, atp, pn);
3345   case Op_Initialize:        return new InitializeNode(C, atp, pn);
3346   default: ShouldNotReachHere(); return nullptr;
3347   }
3348 }
3349 
3350 void MemBarNode::remove(PhaseIterGVN *igvn) {
3351   if (outcnt() != 2) {
3352     assert(Opcode() == Op_Initialize, "Only seen when there are no use of init memory");
3353     assert(outcnt() == 1, "Only control then");
3354   }
3355   if (trailing_store() || trailing_load_store()) {
3356     MemBarNode* leading = leading_membar();
3357     if (leading != nullptr) {
3358       assert(leading->trailing_membar() == this, "inconsistent leading/trailing membars");
3359       leading->remove(igvn);
3360     }
3361   }
3362   if (proj_out_or_null(TypeFunc::Memory) != nullptr) {
3363     igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3364   }
3365   if (proj_out_or_null(TypeFunc::Control) != nullptr) {
3366     igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3367   }
3368 }
3369 
3370 //------------------------------Ideal------------------------------------------
3371 // Return a node which is more "ideal" than the current node.  Strip out
3372 // control copies
3373 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3374   if (remove_dead_region(phase, can_reshape)) return this;
3375   // Don't bother trying to transform a dead node
3376   if (in(0) && in(0)->is_top()) {
3377     return nullptr;
3378   }
3379 
3380   bool progress = false;
3381   // Eliminate volatile MemBars for scalar replaced objects.
3382   if (can_reshape && req() == (Precedent+1)) {
3383     bool eliminate = false;
3384     int opc = Opcode();
3385     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
3386       // Volatile field loads and stores.
3387       Node* my_mem = in(MemBarNode::Precedent);
3388       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
3389       if ((my_mem != nullptr) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
3390         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
3391         // replace this Precedent (decodeN) with the Load instead.
3392         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
3393           Node* load_node = my_mem->in(1);
3394           set_req(MemBarNode::Precedent, load_node);
3395           phase->is_IterGVN()->_worklist.push(my_mem);
3396           my_mem = load_node;
3397         } else {
3398           assert(my_mem->unique_out() == this, "sanity");
3399           del_req(Precedent);
3400           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
3401           my_mem = nullptr;
3402         }
3403         progress = true;
3404       }
3405       if (my_mem != nullptr && my_mem->is_Mem()) {
3406         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
3407         // Check for scalar replaced object reference.
3408         if( t_oop != nullptr && t_oop->is_known_instance_field() &&
3409             t_oop->offset() != Type::OffsetBot &&
3410             t_oop->offset() != Type::OffsetTop) {
3411           eliminate = true;
3412         }
3413       }
3414     } else if (opc == Op_MemBarRelease) {
3415       // Final field stores.
3416       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent));
3417       if ((alloc != nullptr) && alloc->is_Allocate() &&
3418           alloc->as_Allocate()->does_not_escape_thread()) {
3419         // The allocated object does not escape.
3420         eliminate = true;
3421       }
3422     }
3423     if (eliminate) {
3424       // Replace MemBar projections by its inputs.
3425       PhaseIterGVN* igvn = phase->is_IterGVN();
3426       remove(igvn);
3427       // Must return either the original node (now dead) or a new node
3428       // (Do not return a top here, since that would break the uniqueness of top.)
3429       return new ConINode(TypeInt::ZERO);
3430     }
3431   }
3432   return progress ? this : nullptr;
3433 }
3434 
3435 //------------------------------Value------------------------------------------
3436 const Type* MemBarNode::Value(PhaseGVN* phase) const {
3437   if( !in(0) ) return Type::TOP;
3438   if( phase->type(in(0)) == Type::TOP )
3439     return Type::TOP;
3440   return TypeTuple::MEMBAR;
3441 }
3442 
3443 //------------------------------match------------------------------------------
3444 // Construct projections for memory.
3445 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3446   switch (proj->_con) {
3447   case TypeFunc::Control:
3448   case TypeFunc::Memory:
3449     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3450   }
3451   ShouldNotReachHere();
3452   return nullptr;
3453 }
3454 
3455 void MemBarNode::set_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3456   trailing->_kind = TrailingStore;
3457   leading->_kind = LeadingStore;
3458 #ifdef ASSERT
3459   trailing->_pair_idx = leading->_idx;
3460   leading->_pair_idx = leading->_idx;
3461 #endif
3462 }
3463 
3464 void MemBarNode::set_load_store_pair(MemBarNode* leading, MemBarNode* trailing) {
3465   trailing->_kind = TrailingLoadStore;
3466   leading->_kind = LeadingLoadStore;
3467 #ifdef ASSERT
3468   trailing->_pair_idx = leading->_idx;
3469   leading->_pair_idx = leading->_idx;
3470 #endif
3471 }
3472 
3473 MemBarNode* MemBarNode::trailing_membar() const {
3474   ResourceMark rm;
3475   Node* trailing = (Node*)this;
3476   VectorSet seen;
3477   Node_Stack multis(0);
3478   do {
3479     Node* c = trailing;
3480     uint i = 0;
3481     do {
3482       trailing = nullptr;
3483       for (; i < c->outcnt(); i++) {
3484         Node* next = c->raw_out(i);
3485         if (next != c && next->is_CFG()) {
3486           if (c->is_MultiBranch()) {
3487             if (multis.node() == c) {
3488               multis.set_index(i+1);
3489             } else {
3490               multis.push(c, i+1);
3491             }
3492           }
3493           trailing = next;
3494           break;
3495         }
3496       }
3497       if (trailing != nullptr && !seen.test_set(trailing->_idx)) {
3498         break;
3499       }
3500       while (multis.size() > 0) {
3501         c = multis.node();
3502         i = multis.index();
3503         if (i < c->req()) {
3504           break;
3505         }
3506         multis.pop();
3507       }
3508     } while (multis.size() > 0);
3509   } while (!trailing->is_MemBar() || !trailing->as_MemBar()->trailing());
3510 
3511   MemBarNode* mb = trailing->as_MemBar();
3512   assert((mb->_kind == TrailingStore && _kind == LeadingStore) ||
3513          (mb->_kind == TrailingLoadStore && _kind == LeadingLoadStore), "bad trailing membar");
3514   assert(mb->_pair_idx == _pair_idx, "bad trailing membar");
3515   return mb;
3516 }
3517 
3518 MemBarNode* MemBarNode::leading_membar() const {
3519   ResourceMark rm;
3520   VectorSet seen;
3521   Node_Stack regions(0);
3522   Node* leading = in(0);
3523   while (leading != nullptr && (!leading->is_MemBar() || !leading->as_MemBar()->leading())) {
3524     while (leading == nullptr || leading->is_top() || seen.test_set(leading->_idx)) {
3525       leading = nullptr;
3526       while (regions.size() > 0 && leading == nullptr) {
3527         Node* r = regions.node();
3528         uint i = regions.index();
3529         if (i < r->req()) {
3530           leading = r->in(i);
3531           regions.set_index(i+1);
3532         } else {
3533           regions.pop();
3534         }
3535       }
3536       if (leading == nullptr) {
3537         assert(regions.size() == 0, "all paths should have been tried");
3538         return nullptr;
3539       }
3540     }
3541     if (leading->is_Region()) {
3542       regions.push(leading, 2);
3543       leading = leading->in(1);
3544     } else {
3545       leading = leading->in(0);
3546     }
3547   }
3548 #ifdef ASSERT
3549   Unique_Node_List wq;
3550   wq.push((Node*)this);
3551   uint found = 0;
3552   for (uint i = 0; i < wq.size(); i++) {
3553     Node* n = wq.at(i);
3554     if (n->is_Region()) {
3555       for (uint j = 1; j < n->req(); j++) {
3556         Node* in = n->in(j);
3557         if (in != nullptr && !in->is_top()) {
3558           wq.push(in);
3559         }
3560       }
3561     } else {
3562       if (n->is_MemBar() && n->as_MemBar()->leading()) {
3563         assert(n == leading, "consistency check failed");
3564         found++;
3565       } else {
3566         Node* in = n->in(0);
3567         if (in != nullptr && !in->is_top()) {
3568           wq.push(in);
3569         }
3570       }
3571     }
3572   }
3573   assert(found == 1 || (found == 0 && leading == nullptr), "consistency check failed");
3574 #endif
3575   if (leading == nullptr) {
3576     return nullptr;
3577   }
3578   MemBarNode* mb = leading->as_MemBar();
3579   assert((mb->_kind == LeadingStore && _kind == TrailingStore) ||
3580          (mb->_kind == LeadingLoadStore && _kind == TrailingLoadStore), "bad leading membar");
3581   assert(mb->_pair_idx == _pair_idx, "bad leading membar");
3582   return mb;
3583 }
3584 
3585 
3586 //===========================InitializeNode====================================
3587 // SUMMARY:
3588 // This node acts as a memory barrier on raw memory, after some raw stores.
3589 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3590 // The Initialize can 'capture' suitably constrained stores as raw inits.
3591 // It can coalesce related raw stores into larger units (called 'tiles').
3592 // It can avoid zeroing new storage for memory units which have raw inits.
3593 // At macro-expansion, it is marked 'complete', and does not optimize further.
3594 //
3595 // EXAMPLE:
3596 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3597 //   ctl = incoming control; mem* = incoming memory
3598 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3599 // First allocate uninitialized memory and fill in the header:
3600 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3601 //   ctl := alloc.Control; mem* := alloc.Memory*
3602 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3603 // Then initialize to zero the non-header parts of the raw memory block:
3604 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3605 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3606 // After the initialize node executes, the object is ready for service:
3607 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3608 // Suppose its body is immediately initialized as {1,2}:
3609 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3610 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3611 //   mem.SLICE(#short[*]) := store2
3612 //
3613 // DETAILS:
3614 // An InitializeNode collects and isolates object initialization after
3615 // an AllocateNode and before the next possible safepoint.  As a
3616 // memory barrier (MemBarNode), it keeps critical stores from drifting
3617 // down past any safepoint or any publication of the allocation.
3618 // Before this barrier, a newly-allocated object may have uninitialized bits.
3619 // After this barrier, it may be treated as a real oop, and GC is allowed.
3620 //
3621 // The semantics of the InitializeNode include an implicit zeroing of
3622 // the new object from object header to the end of the object.
3623 // (The object header and end are determined by the AllocateNode.)
3624 //
3625 // Certain stores may be added as direct inputs to the InitializeNode.
3626 // These stores must update raw memory, and they must be to addresses
3627 // derived from the raw address produced by AllocateNode, and with
3628 // a constant offset.  They must be ordered by increasing offset.
3629 // The first one is at in(RawStores), the last at in(req()-1).
3630 // Unlike most memory operations, they are not linked in a chain,
3631 // but are displayed in parallel as users of the rawmem output of
3632 // the allocation.
3633 //
3634 // (See comments in InitializeNode::capture_store, which continue
3635 // the example given above.)
3636 //
3637 // When the associated Allocate is macro-expanded, the InitializeNode
3638 // may be rewritten to optimize collected stores.  A ClearArrayNode
3639 // may also be created at that point to represent any required zeroing.
3640 // The InitializeNode is then marked 'complete', prohibiting further
3641 // capturing of nearby memory operations.
3642 //
3643 // During macro-expansion, all captured initializations which store
3644 // constant values of 32 bits or smaller are coalesced (if advantageous)
3645 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3646 // initialized in fewer memory operations.  Memory words which are
3647 // covered by neither tiles nor non-constant stores are pre-zeroed
3648 // by explicit stores of zero.  (The code shape happens to do all
3649 // zeroing first, then all other stores, with both sequences occurring
3650 // in order of ascending offsets.)
3651 //
3652 // Alternatively, code may be inserted between an AllocateNode and its
3653 // InitializeNode, to perform arbitrary initialization of the new object.
3654 // E.g., the object copying intrinsics insert complex data transfers here.
3655 // The initialization must then be marked as 'complete' disable the
3656 // built-in zeroing semantics and the collection of initializing stores.
3657 //
3658 // While an InitializeNode is incomplete, reads from the memory state
3659 // produced by it are optimizable if they match the control edge and
3660 // new oop address associated with the allocation/initialization.
3661 // They return a stored value (if the offset matches) or else zero.
3662 // A write to the memory state, if it matches control and address,
3663 // and if it is to a constant offset, may be 'captured' by the
3664 // InitializeNode.  It is cloned as a raw memory operation and rewired
3665 // inside the initialization, to the raw oop produced by the allocation.
3666 // Operations on addresses which are provably distinct (e.g., to
3667 // other AllocateNodes) are allowed to bypass the initialization.
3668 //
3669 // The effect of all this is to consolidate object initialization
3670 // (both arrays and non-arrays, both piecewise and bulk) into a
3671 // single location, where it can be optimized as a unit.
3672 //
3673 // Only stores with an offset less than TrackedInitializationLimit words
3674 // will be considered for capture by an InitializeNode.  This puts a
3675 // reasonable limit on the complexity of optimized initializations.
3676 
3677 //---------------------------InitializeNode------------------------------------
3678 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3679   : MemBarNode(C, adr_type, rawoop),
3680     _is_complete(Incomplete), _does_not_escape(false)
3681 {
3682   init_class_id(Class_Initialize);
3683 
3684   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3685   assert(in(RawAddress) == rawoop, "proper init");
3686   // Note:  allocation() can be null, for secondary initialization barriers
3687 }
3688 
3689 // Since this node is not matched, it will be processed by the
3690 // register allocator.  Declare that there are no constraints
3691 // on the allocation of the RawAddress edge.
3692 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3693   // This edge should be set to top, by the set_complete.  But be conservative.
3694   if (idx == InitializeNode::RawAddress)
3695     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3696   return RegMask::Empty;
3697 }
3698 
3699 Node* InitializeNode::memory(uint alias_idx) {
3700   Node* mem = in(Memory);
3701   if (mem->is_MergeMem()) {
3702     return mem->as_MergeMem()->memory_at(alias_idx);
3703   } else {
3704     // incoming raw memory is not split
3705     return mem;
3706   }
3707 }
3708 
3709 bool InitializeNode::is_non_zero() {
3710   if (is_complete())  return false;
3711   remove_extra_zeroes();
3712   return (req() > RawStores);
3713 }
3714 
3715 void InitializeNode::set_complete(PhaseGVN* phase) {
3716   assert(!is_complete(), "caller responsibility");
3717   _is_complete = Complete;
3718 
3719   // After this node is complete, it contains a bunch of
3720   // raw-memory initializations.  There is no need for
3721   // it to have anything to do with non-raw memory effects.
3722   // Therefore, tell all non-raw users to re-optimize themselves,
3723   // after skipping the memory effects of this initialization.
3724   PhaseIterGVN* igvn = phase->is_IterGVN();
3725   if (igvn)  igvn->add_users_to_worklist(this);
3726 }
3727 
3728 // convenience function
3729 // return false if the init contains any stores already
3730 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3731   InitializeNode* init = initialization();
3732   if (init == nullptr || init->is_complete())  return false;
3733   init->remove_extra_zeroes();
3734   // for now, if this allocation has already collected any inits, bail:
3735   if (init->is_non_zero())  return false;
3736   init->set_complete(phase);
3737   return true;
3738 }
3739 
3740 void InitializeNode::remove_extra_zeroes() {
3741   if (req() == RawStores)  return;
3742   Node* zmem = zero_memory();
3743   uint fill = RawStores;
3744   for (uint i = fill; i < req(); i++) {
3745     Node* n = in(i);
3746     if (n->is_top() || n == zmem)  continue;  // skip
3747     if (fill < i)  set_req(fill, n);          // compact
3748     ++fill;
3749   }
3750   // delete any empty spaces created:
3751   while (fill < req()) {
3752     del_req(fill);
3753   }
3754 }
3755 
3756 // Helper for remembering which stores go with which offsets.
3757 intptr_t InitializeNode::get_store_offset(Node* st, PhaseValues* phase) {
3758   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3759   intptr_t offset = -1;
3760   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3761                                                phase, offset);
3762   if (base == nullptr)  return -1;  // something is dead,
3763   if (offset < 0)       return -1;  //        dead, dead
3764   return offset;
3765 }
3766 
3767 // Helper for proving that an initialization expression is
3768 // "simple enough" to be folded into an object initialization.
3769 // Attempts to prove that a store's initial value 'n' can be captured
3770 // within the initialization without creating a vicious cycle, such as:
3771 //     { Foo p = new Foo(); p.next = p; }
3772 // True for constants and parameters and small combinations thereof.
3773 bool InitializeNode::detect_init_independence(Node* value, PhaseGVN* phase) {
3774   ResourceMark rm;
3775   Unique_Node_List worklist;
3776   worklist.push(value);
3777 
3778   uint complexity_limit = 20;
3779   for (uint j = 0; j < worklist.size(); j++) {
3780     if (j >= complexity_limit) {
3781       return false;  // Bail out if processed too many nodes
3782     }
3783 
3784     Node* n = worklist.at(j);
3785     if (n == nullptr)   continue;   // (can this really happen?)
3786     if (n->is_Proj())   n = n->in(0);
3787     if (n == this)      return false;  // found a cycle
3788     if (n->is_Con())    continue;
3789     if (n->is_Start())  continue;   // params, etc., are OK
3790     if (n->is_Root())   continue;   // even better
3791 
3792     // There cannot be any dependency if 'n' is a CFG node that dominates the current allocation
3793     if (n->is_CFG() && phase->is_dominator(n, allocation())) {
3794       continue;
3795     }
3796 
3797     Node* ctl = n->in(0);
3798     if (ctl != nullptr && !ctl->is_top()) {
3799       if (ctl->is_Proj())  ctl = ctl->in(0);
3800       if (ctl == this)  return false;
3801 
3802       // If we already know that the enclosing memory op is pinned right after
3803       // the init, then any control flow that the store has picked up
3804       // must have preceded the init, or else be equal to the init.
3805       // Even after loop optimizations (which might change control edges)
3806       // a store is never pinned *before* the availability of its inputs.
3807       if (!MemNode::all_controls_dominate(n, this))
3808         return false;                  // failed to prove a good control
3809     }
3810 
3811     // Check data edges for possible dependencies on 'this'.
3812     for (uint i = 1; i < n->req(); i++) {
3813       Node* m = n->in(i);
3814       if (m == nullptr || m == n || m->is_top())  continue;
3815 
3816       // Only process data inputs once
3817       worklist.push(m);
3818     }
3819   }
3820 
3821   return true;
3822 }
3823 
3824 // Here are all the checks a Store must pass before it can be moved into
3825 // an initialization.  Returns zero if a check fails.
3826 // On success, returns the (constant) offset to which the store applies,
3827 // within the initialized memory.
3828 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseGVN* phase, bool can_reshape) {
3829   const int FAIL = 0;
3830   if (st->req() != MemNode::ValueIn + 1)
3831     return FAIL;                // an inscrutable StoreNode (card mark?)
3832   Node* ctl = st->in(MemNode::Control);
3833   if (!(ctl != nullptr && ctl->is_Proj() && ctl->in(0) == this))
3834     return FAIL;                // must be unconditional after the initialization
3835   Node* mem = st->in(MemNode::Memory);
3836   if (!(mem->is_Proj() && mem->in(0) == this))
3837     return FAIL;                // must not be preceded by other stores
3838   Node* adr = st->in(MemNode::Address);
3839   intptr_t offset;
3840   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3841   if (alloc == nullptr)
3842     return FAIL;                // inscrutable address
3843   if (alloc != allocation())
3844     return FAIL;                // wrong allocation!  (store needs to float up)
3845   int size_in_bytes = st->memory_size();
3846   if ((size_in_bytes != 0) && (offset % size_in_bytes) != 0) {
3847     return FAIL;                // mismatched access
3848   }
3849   Node* val = st->in(MemNode::ValueIn);
3850 
3851   if (!detect_init_independence(val, phase))
3852     return FAIL;                // stored value must be 'simple enough'
3853 
3854   // The Store can be captured only if nothing after the allocation
3855   // and before the Store is using the memory location that the store
3856   // overwrites.
3857   bool failed = false;
3858   // If is_complete_with_arraycopy() is true the shape of the graph is
3859   // well defined and is safe so no need for extra checks.
3860   if (!is_complete_with_arraycopy()) {
3861     // We are going to look at each use of the memory state following
3862     // the allocation to make sure nothing reads the memory that the
3863     // Store writes.
3864     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3865     int alias_idx = phase->C->get_alias_index(t_adr);
3866     ResourceMark rm;
3867     Unique_Node_List mems;
3868     mems.push(mem);
3869     Node* unique_merge = nullptr;
3870     for (uint next = 0; next < mems.size(); ++next) {
3871       Node *m  = mems.at(next);
3872       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3873         Node *n = m->fast_out(j);
3874         if (n->outcnt() == 0) {
3875           continue;
3876         }
3877         if (n == st) {
3878           continue;
3879         } else if (n->in(0) != nullptr && n->in(0) != ctl) {
3880           // If the control of this use is different from the control
3881           // of the Store which is right after the InitializeNode then
3882           // this node cannot be between the InitializeNode and the
3883           // Store.
3884           continue;
3885         } else if (n->is_MergeMem()) {
3886           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3887             // We can hit a MergeMemNode (that will likely go away
3888             // later) that is a direct use of the memory state
3889             // following the InitializeNode on the same slice as the
3890             // store node that we'd like to capture. We need to check
3891             // the uses of the MergeMemNode.
3892             mems.push(n);
3893           }
3894         } else if (n->is_Mem()) {
3895           Node* other_adr = n->in(MemNode::Address);
3896           if (other_adr == adr) {
3897             failed = true;
3898             break;
3899           } else {
3900             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3901             if (other_t_adr != nullptr) {
3902               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3903               if (other_alias_idx == alias_idx) {
3904                 // A load from the same memory slice as the store right
3905                 // after the InitializeNode. We check the control of the
3906                 // object/array that is loaded from. If it's the same as
3907                 // the store control then we cannot capture the store.
3908                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3909                 Node* base = other_adr;
3910                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3911                 base = base->in(AddPNode::Base);
3912                 if (base != nullptr) {
3913                   base = base->uncast();
3914                   if (base->is_Proj() && base->in(0) == alloc) {
3915                     failed = true;
3916                     break;
3917                   }
3918                 }
3919               }
3920             }
3921           }
3922         } else {
3923           failed = true;
3924           break;
3925         }
3926       }
3927     }
3928   }
3929   if (failed) {
3930     if (!can_reshape) {
3931       // We decided we couldn't capture the store during parsing. We
3932       // should try again during the next IGVN once the graph is
3933       // cleaner.
3934       phase->C->record_for_igvn(st);
3935     }
3936     return FAIL;
3937   }
3938 
3939   return offset;                // success
3940 }
3941 
3942 // Find the captured store in(i) which corresponds to the range
3943 // [start..start+size) in the initialized object.
3944 // If there is one, return its index i.  If there isn't, return the
3945 // negative of the index where it should be inserted.
3946 // Return 0 if the queried range overlaps an initialization boundary
3947 // or if dead code is encountered.
3948 // If size_in_bytes is zero, do not bother with overlap checks.
3949 int InitializeNode::captured_store_insertion_point(intptr_t start,
3950                                                    int size_in_bytes,
3951                                                    PhaseValues* phase) {
3952   const int FAIL = 0, MAX_STORE = MAX2(BytesPerLong, (int)MaxVectorSize);
3953 
3954   if (is_complete())
3955     return FAIL;                // arraycopy got here first; punt
3956 
3957   assert(allocation() != nullptr, "must be present");
3958 
3959   // no negatives, no header fields:
3960   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3961 
3962   // after a certain size, we bail out on tracking all the stores:
3963   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3964   if (start >= ti_limit)  return FAIL;
3965 
3966   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3967     if (i >= limit)  return -(int)i; // not found; here is where to put it
3968 
3969     Node*    st     = in(i);
3970     intptr_t st_off = get_store_offset(st, phase);
3971     if (st_off < 0) {
3972       if (st != zero_memory()) {
3973         return FAIL;            // bail out if there is dead garbage
3974       }
3975     } else if (st_off > start) {
3976       // ...we are done, since stores are ordered
3977       if (st_off < start + size_in_bytes) {
3978         return FAIL;            // the next store overlaps
3979       }
3980       return -(int)i;           // not found; here is where to put it
3981     } else if (st_off < start) {
3982       assert(st->as_Store()->memory_size() <= MAX_STORE, "");
3983       if (size_in_bytes != 0 &&
3984           start < st_off + MAX_STORE &&
3985           start < st_off + st->as_Store()->memory_size()) {
3986         return FAIL;            // the previous store overlaps
3987       }
3988     } else {
3989       if (size_in_bytes != 0 &&
3990           st->as_Store()->memory_size() != size_in_bytes) {
3991         return FAIL;            // mismatched store size
3992       }
3993       return i;
3994     }
3995 
3996     ++i;
3997   }
3998 }
3999 
4000 // Look for a captured store which initializes at the offset 'start'
4001 // with the given size.  If there is no such store, and no other
4002 // initialization interferes, then return zero_memory (the memory
4003 // projection of the AllocateNode).
4004 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
4005                                           PhaseValues* phase) {
4006   assert(stores_are_sane(phase), "");
4007   int i = captured_store_insertion_point(start, size_in_bytes, phase);
4008   if (i == 0) {
4009     return nullptr;              // something is dead
4010   } else if (i < 0) {
4011     return zero_memory();       // just primordial zero bits here
4012   } else {
4013     Node* st = in(i);           // here is the store at this position
4014     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
4015     return st;
4016   }
4017 }
4018 
4019 // Create, as a raw pointer, an address within my new object at 'offset'.
4020 Node* InitializeNode::make_raw_address(intptr_t offset,
4021                                        PhaseGVN* phase) {
4022   Node* addr = in(RawAddress);
4023   if (offset != 0) {
4024     Compile* C = phase->C;
4025     addr = phase->transform( new AddPNode(C->top(), addr,
4026                                                  phase->MakeConX(offset)) );
4027   }
4028   return addr;
4029 }
4030 
4031 // Clone the given store, converting it into a raw store
4032 // initializing a field or element of my new object.
4033 // Caller is responsible for retiring the original store,
4034 // with subsume_node or the like.
4035 //
4036 // From the example above InitializeNode::InitializeNode,
4037 // here are the old stores to be captured:
4038 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
4039 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
4040 //
4041 // Here is the changed code; note the extra edges on init:
4042 //   alloc = (Allocate ...)
4043 //   rawoop = alloc.RawAddress
4044 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
4045 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
4046 //   init = (Initialize alloc.Control alloc.Memory rawoop
4047 //                      rawstore1 rawstore2)
4048 //
4049 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
4050                                     PhaseGVN* phase, bool can_reshape) {
4051   assert(stores_are_sane(phase), "");
4052 
4053   if (start < 0)  return nullptr;
4054   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
4055 
4056   Compile* C = phase->C;
4057   int size_in_bytes = st->memory_size();
4058   int i = captured_store_insertion_point(start, size_in_bytes, phase);
4059   if (i == 0)  return nullptr;  // bail out
4060   Node* prev_mem = nullptr;     // raw memory for the captured store
4061   if (i > 0) {
4062     prev_mem = in(i);           // there is a pre-existing store under this one
4063     set_req(i, C->top());       // temporarily disconnect it
4064     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
4065   } else {
4066     i = -i;                     // no pre-existing store
4067     prev_mem = zero_memory();   // a slice of the newly allocated object
4068     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
4069       set_req(--i, C->top());   // reuse this edge; it has been folded away
4070     else
4071       ins_req(i, C->top());     // build a new edge
4072   }
4073   Node* new_st = st->clone();
4074   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4075   new_st->set_req(MemNode::Control, in(Control));
4076   new_st->set_req(MemNode::Memory,  prev_mem);
4077   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
4078   bs->eliminate_gc_barrier_data(new_st);
4079   new_st = phase->transform(new_st);
4080 
4081   // At this point, new_st might have swallowed a pre-existing store
4082   // at the same offset, or perhaps new_st might have disappeared,
4083   // if it redundantly stored the same value (or zero to fresh memory).
4084 
4085   // In any case, wire it in:
4086   PhaseIterGVN* igvn = phase->is_IterGVN();
4087   if (igvn) {
4088     igvn->rehash_node_delayed(this);
4089   }
4090   set_req(i, new_st);
4091 
4092   // The caller may now kill the old guy.
4093   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
4094   assert(check_st == new_st || check_st == nullptr, "must be findable");
4095   assert(!is_complete(), "");
4096   return new_st;
4097 }
4098 
4099 static bool store_constant(jlong* tiles, int num_tiles,
4100                            intptr_t st_off, int st_size,
4101                            jlong con) {
4102   if ((st_off & (st_size-1)) != 0)
4103     return false;               // strange store offset (assume size==2**N)
4104   address addr = (address)tiles + st_off;
4105   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
4106   switch (st_size) {
4107   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
4108   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
4109   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
4110   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
4111   default: return false;        // strange store size (detect size!=2**N here)
4112   }
4113   return true;                  // return success to caller
4114 }
4115 
4116 // Coalesce subword constants into int constants and possibly
4117 // into long constants.  The goal, if the CPU permits,
4118 // is to initialize the object with a small number of 64-bit tiles.
4119 // Also, convert floating-point constants to bit patterns.
4120 // Non-constants are not relevant to this pass.
4121 //
4122 // In terms of the running example on InitializeNode::InitializeNode
4123 // and InitializeNode::capture_store, here is the transformation
4124 // of rawstore1 and rawstore2 into rawstore12:
4125 //   alloc = (Allocate ...)
4126 //   rawoop = alloc.RawAddress
4127 //   tile12 = 0x00010002
4128 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
4129 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
4130 //
4131 void
4132 InitializeNode::coalesce_subword_stores(intptr_t header_size,
4133                                         Node* size_in_bytes,
4134                                         PhaseGVN* phase) {
4135   Compile* C = phase->C;
4136 
4137   assert(stores_are_sane(phase), "");
4138   // Note:  After this pass, they are not completely sane,
4139   // since there may be some overlaps.
4140 
4141   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
4142 
4143   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
4144   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
4145   size_limit = MIN2(size_limit, ti_limit);
4146   size_limit = align_up(size_limit, BytesPerLong);
4147   int num_tiles = size_limit / BytesPerLong;
4148 
4149   // allocate space for the tile map:
4150   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
4151   jlong  tiles_buf[small_len];
4152   Node*  nodes_buf[small_len];
4153   jlong  inits_buf[small_len];
4154   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
4155                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
4156   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
4157                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
4158   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
4159                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
4160   // tiles: exact bitwise model of all primitive constants
4161   // nodes: last constant-storing node subsumed into the tiles model
4162   // inits: which bytes (in each tile) are touched by any initializations
4163 
4164   //// Pass A: Fill in the tile model with any relevant stores.
4165 
4166   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
4167   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
4168   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
4169   Node* zmem = zero_memory(); // initially zero memory state
4170   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4171     Node* st = in(i);
4172     intptr_t st_off = get_store_offset(st, phase);
4173 
4174     // Figure out the store's offset and constant value:
4175     if (st_off < header_size)             continue; //skip (ignore header)
4176     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
4177     int st_size = st->as_Store()->memory_size();
4178     if (st_off + st_size > size_limit)    break;
4179 
4180     // Record which bytes are touched, whether by constant or not.
4181     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
4182       continue;                 // skip (strange store size)
4183 
4184     const Type* val = phase->type(st->in(MemNode::ValueIn));
4185     if (!val->singleton())                continue; //skip (non-con store)
4186     BasicType type = val->basic_type();
4187 
4188     jlong con = 0;
4189     switch (type) {
4190     case T_INT:    con = val->is_int()->get_con();  break;
4191     case T_LONG:   con = val->is_long()->get_con(); break;
4192     case T_FLOAT:  con = jint_cast(val->getf());    break;
4193     case T_DOUBLE: con = jlong_cast(val->getd());   break;
4194     default:                              continue; //skip (odd store type)
4195     }
4196 
4197     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
4198         st->Opcode() == Op_StoreL) {
4199       continue;                 // This StoreL is already optimal.
4200     }
4201 
4202     // Store down the constant.
4203     store_constant(tiles, num_tiles, st_off, st_size, con);
4204 
4205     intptr_t j = st_off >> LogBytesPerLong;
4206 
4207     if (type == T_INT && st_size == BytesPerInt
4208         && (st_off & BytesPerInt) == BytesPerInt) {
4209       jlong lcon = tiles[j];
4210       if (!Matcher::isSimpleConstant64(lcon) &&
4211           st->Opcode() == Op_StoreI) {
4212         // This StoreI is already optimal by itself.
4213         jint* intcon = (jint*) &tiles[j];
4214         intcon[1] = 0;  // undo the store_constant()
4215 
4216         // If the previous store is also optimal by itself, back up and
4217         // undo the action of the previous loop iteration... if we can.
4218         // But if we can't, just let the previous half take care of itself.
4219         st = nodes[j];
4220         st_off -= BytesPerInt;
4221         con = intcon[0];
4222         if (con != 0 && st != nullptr && st->Opcode() == Op_StoreI) {
4223           assert(st_off >= header_size, "still ignoring header");
4224           assert(get_store_offset(st, phase) == st_off, "must be");
4225           assert(in(i-1) == zmem, "must be");
4226           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
4227           assert(con == tcon->is_int()->get_con(), "must be");
4228           // Undo the effects of the previous loop trip, which swallowed st:
4229           intcon[0] = 0;        // undo store_constant()
4230           set_req(i-1, st);     // undo set_req(i, zmem)
4231           nodes[j] = nullptr;   // undo nodes[j] = st
4232           --old_subword;        // undo ++old_subword
4233         }
4234         continue;               // This StoreI is already optimal.
4235       }
4236     }
4237 
4238     // This store is not needed.
4239     set_req(i, zmem);
4240     nodes[j] = st;              // record for the moment
4241     if (st_size < BytesPerLong) // something has changed
4242           ++old_subword;        // includes int/float, but who's counting...
4243     else  ++old_long;
4244   }
4245 
4246   if ((old_subword + old_long) == 0)
4247     return;                     // nothing more to do
4248 
4249   //// Pass B: Convert any non-zero tiles into optimal constant stores.
4250   // Be sure to insert them before overlapping non-constant stores.
4251   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
4252   for (int j = 0; j < num_tiles; j++) {
4253     jlong con  = tiles[j];
4254     jlong init = inits[j];
4255     if (con == 0)  continue;
4256     jint con0,  con1;           // split the constant, address-wise
4257     jint init0, init1;          // split the init map, address-wise
4258     { union { jlong con; jint intcon[2]; } u;
4259       u.con = con;
4260       con0  = u.intcon[0];
4261       con1  = u.intcon[1];
4262       u.con = init;
4263       init0 = u.intcon[0];
4264       init1 = u.intcon[1];
4265     }
4266 
4267     Node* old = nodes[j];
4268     assert(old != nullptr, "need the prior store");
4269     intptr_t offset = (j * BytesPerLong);
4270 
4271     bool split = !Matcher::isSimpleConstant64(con);
4272 
4273     if (offset < header_size) {
4274       assert(offset + BytesPerInt >= header_size, "second int counts");
4275       assert(*(jint*)&tiles[j] == 0, "junk in header");
4276       split = true;             // only the second word counts
4277       // Example:  int a[] = { 42 ... }
4278     } else if (con0 == 0 && init0 == -1) {
4279       split = true;             // first word is covered by full inits
4280       // Example:  int a[] = { ... foo(), 42 ... }
4281     } else if (con1 == 0 && init1 == -1) {
4282       split = true;             // second word is covered by full inits
4283       // Example:  int a[] = { ... 42, foo() ... }
4284     }
4285 
4286     // Here's a case where init0 is neither 0 nor -1:
4287     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
4288     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
4289     // In this case the tile is not split; it is (jlong)42.
4290     // The big tile is stored down, and then the foo() value is inserted.
4291     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
4292 
4293     Node* ctl = old->in(MemNode::Control);
4294     Node* adr = make_raw_address(offset, phase);
4295     const TypePtr* atp = TypeRawPtr::BOTTOM;
4296 
4297     // One or two coalesced stores to plop down.
4298     Node*    st[2];
4299     intptr_t off[2];
4300     int  nst = 0;
4301     if (!split) {
4302       ++new_long;
4303       off[nst] = offset;
4304       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4305                                   phase->longcon(con), T_LONG, MemNode::unordered);
4306     } else {
4307       // Omit either if it is a zero.
4308       if (con0 != 0) {
4309         ++new_int;
4310         off[nst]  = offset;
4311         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4312                                     phase->intcon(con0), T_INT, MemNode::unordered);
4313       }
4314       if (con1 != 0) {
4315         ++new_int;
4316         offset += BytesPerInt;
4317         adr = make_raw_address(offset, phase);
4318         off[nst]  = offset;
4319         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
4320                                     phase->intcon(con1), T_INT, MemNode::unordered);
4321       }
4322     }
4323 
4324     // Insert second store first, then the first before the second.
4325     // Insert each one just before any overlapping non-constant stores.
4326     while (nst > 0) {
4327       Node* st1 = st[--nst];
4328       C->copy_node_notes_to(st1, old);
4329       st1 = phase->transform(st1);
4330       offset = off[nst];
4331       assert(offset >= header_size, "do not smash header");
4332       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
4333       guarantee(ins_idx != 0, "must re-insert constant store");
4334       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
4335       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
4336         set_req(--ins_idx, st1);
4337       else
4338         ins_req(ins_idx, st1);
4339     }
4340   }
4341 
4342   if (PrintCompilation && WizardMode)
4343     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
4344                   old_subword, old_long, new_int, new_long);
4345   if (C->log() != nullptr)
4346     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
4347                    old_subword, old_long, new_int, new_long);
4348 
4349   // Clean up any remaining occurrences of zmem:
4350   remove_extra_zeroes();
4351 }
4352 
4353 // Explore forward from in(start) to find the first fully initialized
4354 // word, and return its offset.  Skip groups of subword stores which
4355 // together initialize full words.  If in(start) is itself part of a
4356 // fully initialized word, return the offset of in(start).  If there
4357 // are no following full-word stores, or if something is fishy, return
4358 // a negative value.
4359 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
4360   int       int_map = 0;
4361   intptr_t  int_map_off = 0;
4362   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
4363 
4364   for (uint i = start, limit = req(); i < limit; i++) {
4365     Node* st = in(i);
4366 
4367     intptr_t st_off = get_store_offset(st, phase);
4368     if (st_off < 0)  break;  // return conservative answer
4369 
4370     int st_size = st->as_Store()->memory_size();
4371     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
4372       return st_off;            // we found a complete word init
4373     }
4374 
4375     // update the map:
4376 
4377     intptr_t this_int_off = align_down(st_off, BytesPerInt);
4378     if (this_int_off != int_map_off) {
4379       // reset the map:
4380       int_map = 0;
4381       int_map_off = this_int_off;
4382     }
4383 
4384     int subword_off = st_off - this_int_off;
4385     int_map |= right_n_bits(st_size) << subword_off;
4386     if ((int_map & FULL_MAP) == FULL_MAP) {
4387       return this_int_off;      // we found a complete word init
4388     }
4389 
4390     // Did this store hit or cross the word boundary?
4391     intptr_t next_int_off = align_down(st_off + st_size, BytesPerInt);
4392     if (next_int_off == this_int_off + BytesPerInt) {
4393       // We passed the current int, without fully initializing it.
4394       int_map_off = next_int_off;
4395       int_map >>= BytesPerInt;
4396     } else if (next_int_off > this_int_off + BytesPerInt) {
4397       // We passed the current and next int.
4398       return this_int_off + BytesPerInt;
4399     }
4400   }
4401 
4402   return -1;
4403 }
4404 
4405 
4406 // Called when the associated AllocateNode is expanded into CFG.
4407 // At this point, we may perform additional optimizations.
4408 // Linearize the stores by ascending offset, to make memory
4409 // activity as coherent as possible.
4410 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
4411                                       intptr_t header_size,
4412                                       Node* size_in_bytes,
4413                                       PhaseIterGVN* phase) {
4414   assert(!is_complete(), "not already complete");
4415   assert(stores_are_sane(phase), "");
4416   assert(allocation() != nullptr, "must be present");
4417 
4418   remove_extra_zeroes();
4419 
4420   if (ReduceFieldZeroing || ReduceBulkZeroing)
4421     // reduce instruction count for common initialization patterns
4422     coalesce_subword_stores(header_size, size_in_bytes, phase);
4423 
4424   Node* zmem = zero_memory();   // initially zero memory state
4425   Node* inits = zmem;           // accumulating a linearized chain of inits
4426   #ifdef ASSERT
4427   intptr_t first_offset = allocation()->minimum_header_size();
4428   intptr_t last_init_off = first_offset;  // previous init offset
4429   intptr_t last_init_end = first_offset;  // previous init offset+size
4430   intptr_t last_tile_end = first_offset;  // previous tile offset+size
4431   #endif
4432   intptr_t zeroes_done = header_size;
4433 
4434   bool do_zeroing = true;       // we might give up if inits are very sparse
4435   int  big_init_gaps = 0;       // how many large gaps have we seen?
4436 
4437   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
4438   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
4439 
4440   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
4441     Node* st = in(i);
4442     intptr_t st_off = get_store_offset(st, phase);
4443     if (st_off < 0)
4444       break;                    // unknown junk in the inits
4445     if (st->in(MemNode::Memory) != zmem)
4446       break;                    // complicated store chains somehow in list
4447 
4448     int st_size = st->as_Store()->memory_size();
4449     intptr_t next_init_off = st_off + st_size;
4450 
4451     if (do_zeroing && zeroes_done < next_init_off) {
4452       // See if this store needs a zero before it or under it.
4453       intptr_t zeroes_needed = st_off;
4454 
4455       if (st_size < BytesPerInt) {
4456         // Look for subword stores which only partially initialize words.
4457         // If we find some, we must lay down some word-level zeroes first,
4458         // underneath the subword stores.
4459         //
4460         // Examples:
4461         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
4462         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
4463         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
4464         //
4465         // Note:  coalesce_subword_stores may have already done this,
4466         // if it was prompted by constant non-zero subword initializers.
4467         // But this case can still arise with non-constant stores.
4468 
4469         intptr_t next_full_store = find_next_fullword_store(i, phase);
4470 
4471         // In the examples above:
4472         //   in(i)          p   q   r   s     x   y     z
4473         //   st_off        12  13  14  15    12  13    14
4474         //   st_size        1   1   1   1     1   1     1
4475         //   next_full_s.  12  16  16  16    16  16    16
4476         //   z's_done      12  16  16  16    12  16    12
4477         //   z's_needed    12  16  16  16    16  16    16
4478         //   zsize          0   0   0   0     4   0     4
4479         if (next_full_store < 0) {
4480           // Conservative tack:  Zero to end of current word.
4481           zeroes_needed = align_up(zeroes_needed, BytesPerInt);
4482         } else {
4483           // Zero to beginning of next fully initialized word.
4484           // Or, don't zero at all, if we are already in that word.
4485           assert(next_full_store >= zeroes_needed, "must go forward");
4486           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
4487           zeroes_needed = next_full_store;
4488         }
4489       }
4490 
4491       if (zeroes_needed > zeroes_done) {
4492         intptr_t zsize = zeroes_needed - zeroes_done;
4493         // Do some incremental zeroing on rawmem, in parallel with inits.
4494         zeroes_done = align_down(zeroes_done, BytesPerInt);
4495         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4496                                               zeroes_done, zeroes_needed,
4497                                               phase);
4498         zeroes_done = zeroes_needed;
4499         if (zsize > InitArrayShortSize && ++big_init_gaps > 2)
4500           do_zeroing = false;   // leave the hole, next time
4501       }
4502     }
4503 
4504     // Collect the store and move on:
4505     phase->replace_input_of(st, MemNode::Memory, inits);
4506     inits = st;                 // put it on the linearized chain
4507     set_req(i, zmem);           // unhook from previous position
4508 
4509     if (zeroes_done == st_off)
4510       zeroes_done = next_init_off;
4511 
4512     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
4513 
4514     #ifdef ASSERT
4515     // Various order invariants.  Weaker than stores_are_sane because
4516     // a large constant tile can be filled in by smaller non-constant stores.
4517     assert(st_off >= last_init_off, "inits do not reverse");
4518     last_init_off = st_off;
4519     const Type* val = nullptr;
4520     if (st_size >= BytesPerInt &&
4521         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
4522         (int)val->basic_type() < (int)T_OBJECT) {
4523       assert(st_off >= last_tile_end, "tiles do not overlap");
4524       assert(st_off >= last_init_end, "tiles do not overwrite inits");
4525       last_tile_end = MAX2(last_tile_end, next_init_off);
4526     } else {
4527       intptr_t st_tile_end = align_up(next_init_off, BytesPerLong);
4528       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
4529       assert(st_off      >= last_init_end, "inits do not overlap");
4530       last_init_end = next_init_off;  // it's a non-tile
4531     }
4532     #endif //ASSERT
4533   }
4534 
4535   remove_extra_zeroes();        // clear out all the zmems left over
4536   add_req(inits);
4537 
4538   if (!(UseTLAB && ZeroTLAB)) {
4539     // If anything remains to be zeroed, zero it all now.
4540     zeroes_done = align_down(zeroes_done, BytesPerInt);
4541     // if it is the last unused 4 bytes of an instance, forget about it
4542     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
4543     if (zeroes_done + BytesPerLong >= size_limit) {
4544       AllocateNode* alloc = allocation();
4545       assert(alloc != nullptr, "must be present");
4546       if (alloc != nullptr && alloc->Opcode() == Op_Allocate) {
4547         Node* klass_node = alloc->in(AllocateNode::KlassNode);
4548         ciKlass* k = phase->type(klass_node)->is_instklassptr()->instance_klass();
4549         if (zeroes_done == k->layout_helper())
4550           zeroes_done = size_limit;
4551       }
4552     }
4553     if (zeroes_done < size_limit) {
4554       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
4555                                             zeroes_done, size_in_bytes, phase);
4556     }
4557   }
4558 
4559   set_complete(phase);
4560   return rawmem;
4561 }
4562 
4563 
4564 #ifdef ASSERT
4565 bool InitializeNode::stores_are_sane(PhaseValues* phase) {
4566   if (is_complete())
4567     return true;                // stores could be anything at this point
4568   assert(allocation() != nullptr, "must be present");
4569   intptr_t last_off = allocation()->minimum_header_size();
4570   for (uint i = InitializeNode::RawStores; i < req(); i++) {
4571     Node* st = in(i);
4572     intptr_t st_off = get_store_offset(st, phase);
4573     if (st_off < 0)  continue;  // ignore dead garbage
4574     if (last_off > st_off) {
4575       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
4576       this->dump(2);
4577       assert(false, "ascending store offsets");
4578       return false;
4579     }
4580     last_off = st_off + st->as_Store()->memory_size();
4581   }
4582   return true;
4583 }
4584 #endif //ASSERT
4585 
4586 
4587 
4588 
4589 //============================MergeMemNode=====================================
4590 //
4591 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4592 // contributing store or call operations.  Each contributor provides the memory
4593 // state for a particular "alias type" (see Compile::alias_type).  For example,
4594 // if a MergeMem has an input X for alias category #6, then any memory reference
4595 // to alias category #6 may use X as its memory state input, as an exact equivalent
4596 // to using the MergeMem as a whole.
4597 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4598 //
4599 // (Here, the <N> notation gives the index of the relevant adr_type.)
4600 //
4601 // In one special case (and more cases in the future), alias categories overlap.
4602 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4603 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4604 // it is exactly equivalent to that state W:
4605 //   MergeMem(<Bot>: W) <==> W
4606 //
4607 // Usually, the merge has more than one input.  In that case, where inputs
4608 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4609 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4610 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4611 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4612 //
4613 // A merge can take a "wide" memory state as one of its narrow inputs.
4614 // This simply means that the merge observes out only the relevant parts of
4615 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4616 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4617 //
4618 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4619 // and that memory slices "leak through":
4620 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4621 //
4622 // But, in such a cascade, repeated memory slices can "block the leak":
4623 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4624 //
4625 // In the last example, Y is not part of the combined memory state of the
4626 // outermost MergeMem.  The system must, of course, prevent unschedulable
4627 // memory states from arising, so you can be sure that the state Y is somehow
4628 // a precursor to state Y'.
4629 //
4630 //
4631 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4632 // of each MergeMemNode array are exactly the numerical alias indexes, including
4633 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4634 // Compile::alias_type (and kin) produce and manage these indexes.
4635 //
4636 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4637 // (Note that this provides quick access to the top node inside MergeMem methods,
4638 // without the need to reach out via TLS to Compile::current.)
4639 //
4640 // As a consequence of what was just described, a MergeMem that represents a full
4641 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4642 // containing all alias categories.
4643 //
4644 // MergeMem nodes never (?) have control inputs, so in(0) is null.
4645 //
4646 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4647 // a memory state for the alias type <N>, or else the top node, meaning that
4648 // there is no particular input for that alias type.  Note that the length of
4649 // a MergeMem is variable, and may be extended at any time to accommodate new
4650 // memory states at larger alias indexes.  When merges grow, they are of course
4651 // filled with "top" in the unused in() positions.
4652 //
4653 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4654 // (Top was chosen because it works smoothly with passes like GCM.)
4655 //
4656 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4657 // the type of random VM bits like TLS references.)  Since it is always the
4658 // first non-Bot memory slice, some low-level loops use it to initialize an
4659 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4660 //
4661 //
4662 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4663 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4664 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4665 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4666 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4667 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4668 //
4669 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4670 // really that different from the other memory inputs.  An abbreviation called
4671 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4672 //
4673 //
4674 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4675 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4676 // that "emerges though" the base memory will be marked as excluding the alias types
4677 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4678 //
4679 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4680 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4681 //
4682 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4683 // (It is currently unimplemented.)  As you can see, the resulting merge is
4684 // actually a disjoint union of memory states, rather than an overlay.
4685 //
4686 
4687 //------------------------------MergeMemNode-----------------------------------
4688 Node* MergeMemNode::make_empty_memory() {
4689   Node* empty_memory = (Node*) Compile::current()->top();
4690   assert(empty_memory->is_top(), "correct sentinel identity");
4691   return empty_memory;
4692 }
4693 
4694 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4695   init_class_id(Class_MergeMem);
4696   // all inputs are nullified in Node::Node(int)
4697   // set_input(0, nullptr);  // no control input
4698 
4699   // Initialize the edges uniformly to top, for starters.
4700   Node* empty_mem = make_empty_memory();
4701   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4702     init_req(i,empty_mem);
4703   }
4704   assert(empty_memory() == empty_mem, "");
4705 
4706   if( new_base != nullptr && new_base->is_MergeMem() ) {
4707     MergeMemNode* mdef = new_base->as_MergeMem();
4708     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4709     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4710       mms.set_memory(mms.memory2());
4711     }
4712     assert(base_memory() == mdef->base_memory(), "");
4713   } else {
4714     set_base_memory(new_base);
4715   }
4716 }
4717 
4718 // Make a new, untransformed MergeMem with the same base as 'mem'.
4719 // If mem is itself a MergeMem, populate the result with the same edges.
4720 MergeMemNode* MergeMemNode::make(Node* mem) {
4721   return new MergeMemNode(mem);
4722 }
4723 
4724 //------------------------------cmp--------------------------------------------
4725 uint MergeMemNode::hash() const { return NO_HASH; }
4726 bool MergeMemNode::cmp( const Node &n ) const {
4727   return (&n == this);          // Always fail except on self
4728 }
4729 
4730 //------------------------------Identity---------------------------------------
4731 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4732   // Identity if this merge point does not record any interesting memory
4733   // disambiguations.
4734   Node* base_mem = base_memory();
4735   Node* empty_mem = empty_memory();
4736   if (base_mem != empty_mem) {  // Memory path is not dead?
4737     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4738       Node* mem = in(i);
4739       if (mem != empty_mem && mem != base_mem) {
4740         return this;            // Many memory splits; no change
4741       }
4742     }
4743   }
4744   return base_mem;              // No memory splits; ID on the one true input
4745 }
4746 
4747 //------------------------------Ideal------------------------------------------
4748 // This method is invoked recursively on chains of MergeMem nodes
4749 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4750   // Remove chain'd MergeMems
4751   //
4752   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4753   // relative to the "in(Bot)".  Since we are patching both at the same time,
4754   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4755   // but rewrite each "in(i)" relative to the new "in(Bot)".
4756   Node *progress = nullptr;
4757 
4758 
4759   Node* old_base = base_memory();
4760   Node* empty_mem = empty_memory();
4761   if (old_base == empty_mem)
4762     return nullptr; // Dead memory path.
4763 
4764   MergeMemNode* old_mbase;
4765   if (old_base != nullptr && old_base->is_MergeMem())
4766     old_mbase = old_base->as_MergeMem();
4767   else
4768     old_mbase = nullptr;
4769   Node* new_base = old_base;
4770 
4771   // simplify stacked MergeMems in base memory
4772   if (old_mbase)  new_base = old_mbase->base_memory();
4773 
4774   // the base memory might contribute new slices beyond my req()
4775   if (old_mbase)  grow_to_match(old_mbase);
4776 
4777   // Note:  We do not call verify_sparse on entry, because inputs
4778   // can normalize to the base_memory via subsume_node or similar
4779   // mechanisms.  This method repairs that damage.
4780 
4781   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4782 
4783   // Look at each slice.
4784   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4785     Node* old_in = in(i);
4786     // calculate the old memory value
4787     Node* old_mem = old_in;
4788     if (old_mem == empty_mem)  old_mem = old_base;
4789     assert(old_mem == memory_at(i), "");
4790 
4791     // maybe update (reslice) the old memory value
4792 
4793     // simplify stacked MergeMems
4794     Node* new_mem = old_mem;
4795     MergeMemNode* old_mmem;
4796     if (old_mem != nullptr && old_mem->is_MergeMem())
4797       old_mmem = old_mem->as_MergeMem();
4798     else
4799       old_mmem = nullptr;
4800     if (old_mmem == this) {
4801       // This can happen if loops break up and safepoints disappear.
4802       // A merge of BotPtr (default) with a RawPtr memory derived from a
4803       // safepoint can be rewritten to a merge of the same BotPtr with
4804       // the BotPtr phi coming into the loop.  If that phi disappears
4805       // also, we can end up with a self-loop of the mergemem.
4806       // In general, if loops degenerate and memory effects disappear,
4807       // a mergemem can be left looking at itself.  This simply means
4808       // that the mergemem's default should be used, since there is
4809       // no longer any apparent effect on this slice.
4810       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4811       //       from start.  Update the input to TOP.
4812       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4813     }
4814     else if (old_mmem != nullptr) {
4815       new_mem = old_mmem->memory_at(i);
4816     }
4817     // else preceding memory was not a MergeMem
4818 
4819     // maybe store down a new value
4820     Node* new_in = new_mem;
4821     if (new_in == new_base)  new_in = empty_mem;
4822 
4823     if (new_in != old_in) {
4824       // Warning:  Do not combine this "if" with the previous "if"
4825       // A memory slice might have be be rewritten even if it is semantically
4826       // unchanged, if the base_memory value has changed.
4827       set_req_X(i, new_in, phase);
4828       progress = this;          // Report progress
4829     }
4830   }
4831 
4832   if (new_base != old_base) {
4833     set_req_X(Compile::AliasIdxBot, new_base, phase);
4834     // Don't use set_base_memory(new_base), because we need to update du.
4835     assert(base_memory() == new_base, "");
4836     progress = this;
4837   }
4838 
4839   if( base_memory() == this ) {
4840     // a self cycle indicates this memory path is dead
4841     set_req(Compile::AliasIdxBot, empty_mem);
4842   }
4843 
4844   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4845   // Recursion must occur after the self cycle check above
4846   if( base_memory()->is_MergeMem() ) {
4847     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4848     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4849     if( m != nullptr &&
4850         (m->is_top() ||
4851          (m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem)) ) {
4852       // propagate rollup of dead cycle to self
4853       set_req(Compile::AliasIdxBot, empty_mem);
4854     }
4855   }
4856 
4857   if( base_memory() == empty_mem ) {
4858     progress = this;
4859     // Cut inputs during Parse phase only.
4860     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4861     if( !can_reshape ) {
4862       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4863         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4864       }
4865     }
4866   }
4867 
4868   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4869     // Check if PhiNode::Ideal's "Split phis through memory merges"
4870     // transform should be attempted. Look for this->phi->this cycle.
4871     uint merge_width = req();
4872     if (merge_width > Compile::AliasIdxRaw) {
4873       PhiNode* phi = base_memory()->as_Phi();
4874       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4875         if (phi->in(i) == this) {
4876           phase->is_IterGVN()->_worklist.push(phi);
4877           break;
4878         }
4879       }
4880     }
4881   }
4882 
4883   assert(progress || verify_sparse(), "please, no dups of base");
4884   return progress;
4885 }
4886 
4887 //-------------------------set_base_memory-------------------------------------
4888 void MergeMemNode::set_base_memory(Node *new_base) {
4889   Node* empty_mem = empty_memory();
4890   set_req(Compile::AliasIdxBot, new_base);
4891   assert(memory_at(req()) == new_base, "must set default memory");
4892   // Clear out other occurrences of new_base:
4893   if (new_base != empty_mem) {
4894     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4895       if (in(i) == new_base)  set_req(i, empty_mem);
4896     }
4897   }
4898 }
4899 
4900 //------------------------------out_RegMask------------------------------------
4901 const RegMask &MergeMemNode::out_RegMask() const {
4902   return RegMask::Empty;
4903 }
4904 
4905 //------------------------------dump_spec--------------------------------------
4906 #ifndef PRODUCT
4907 void MergeMemNode::dump_spec(outputStream *st) const {
4908   st->print(" {");
4909   Node* base_mem = base_memory();
4910   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4911     Node* mem = (in(i) != nullptr) ? memory_at(i) : base_mem;
4912     if (mem == base_mem) { st->print(" -"); continue; }
4913     st->print( " N%d:", mem->_idx );
4914     Compile::current()->get_adr_type(i)->dump_on(st);
4915   }
4916   st->print(" }");
4917 }
4918 #endif // !PRODUCT
4919 
4920 
4921 #ifdef ASSERT
4922 static bool might_be_same(Node* a, Node* b) {
4923   if (a == b)  return true;
4924   if (!(a->is_Phi() || b->is_Phi()))  return false;
4925   // phis shift around during optimization
4926   return true;  // pretty stupid...
4927 }
4928 
4929 // verify a narrow slice (either incoming or outgoing)
4930 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4931   if (!VerifyAliases)                return;  // don't bother to verify unless requested
4932   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
4933   if (Node::in_dump())               return;  // muzzle asserts when printing
4934   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4935   assert(n != nullptr, "");
4936   // Elide intervening MergeMem's
4937   while (n->is_MergeMem()) {
4938     n = n->as_MergeMem()->memory_at(alias_idx);
4939   }
4940   Compile* C = Compile::current();
4941   const TypePtr* n_adr_type = n->adr_type();
4942   if (n == m->empty_memory()) {
4943     // Implicit copy of base_memory()
4944   } else if (n_adr_type != TypePtr::BOTTOM) {
4945     assert(n_adr_type != nullptr, "new memory must have a well-defined adr_type");
4946     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4947   } else {
4948     // A few places like make_runtime_call "know" that VM calls are narrow,
4949     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4950     bool expected_wide_mem = false;
4951     if (n == m->base_memory()) {
4952       expected_wide_mem = true;
4953     } else if (alias_idx == Compile::AliasIdxRaw ||
4954                n == m->memory_at(Compile::AliasIdxRaw)) {
4955       expected_wide_mem = true;
4956     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4957       // memory can "leak through" calls on channels that
4958       // are write-once.  Allow this also.
4959       expected_wide_mem = true;
4960     }
4961     assert(expected_wide_mem, "expected narrow slice replacement");
4962   }
4963 }
4964 #else // !ASSERT
4965 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4966 #endif
4967 
4968 
4969 //-----------------------------memory_at---------------------------------------
4970 Node* MergeMemNode::memory_at(uint alias_idx) const {
4971   assert(alias_idx >= Compile::AliasIdxRaw ||
4972          alias_idx == Compile::AliasIdxBot && !Compile::current()->do_aliasing(),
4973          "must avoid base_memory and AliasIdxTop");
4974 
4975   // Otherwise, it is a narrow slice.
4976   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4977   if (is_empty_memory(n)) {
4978     // the array is sparse; empty slots are the "top" node
4979     n = base_memory();
4980     assert(Node::in_dump()
4981            || n == nullptr || n->bottom_type() == Type::TOP
4982            || n->adr_type() == nullptr // address is TOP
4983            || n->adr_type() == TypePtr::BOTTOM
4984            || n->adr_type() == TypeRawPtr::BOTTOM
4985            || !Compile::current()->do_aliasing(),
4986            "must be a wide memory");
4987     // do_aliasing == false if we are organizing the memory states manually.
4988     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4989   } else {
4990     // make sure the stored slice is sane
4991     #ifdef ASSERT
4992     if (VMError::is_error_reported() || Node::in_dump()) {
4993     } else if (might_be_same(n, base_memory())) {
4994       // Give it a pass:  It is a mostly harmless repetition of the base.
4995       // This can arise normally from node subsumption during optimization.
4996     } else {
4997       verify_memory_slice(this, alias_idx, n);
4998     }
4999     #endif
5000   }
5001   return n;
5002 }
5003 
5004 //---------------------------set_memory_at-------------------------------------
5005 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
5006   verify_memory_slice(this, alias_idx, n);
5007   Node* empty_mem = empty_memory();
5008   if (n == base_memory())  n = empty_mem;  // collapse default
5009   uint need_req = alias_idx+1;
5010   if (req() < need_req) {
5011     if (n == empty_mem)  return;  // already the default, so do not grow me
5012     // grow the sparse array
5013     do {
5014       add_req(empty_mem);
5015     } while (req() < need_req);
5016   }
5017   set_req( alias_idx, n );
5018 }
5019 
5020 
5021 
5022 //--------------------------iteration_setup------------------------------------
5023 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
5024   if (other != nullptr) {
5025     grow_to_match(other);
5026     // invariant:  the finite support of mm2 is within mm->req()
5027     #ifdef ASSERT
5028     for (uint i = req(); i < other->req(); i++) {
5029       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
5030     }
5031     #endif
5032   }
5033   // Replace spurious copies of base_memory by top.
5034   Node* base_mem = base_memory();
5035   if (base_mem != nullptr && !base_mem->is_top()) {
5036     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
5037       if (in(i) == base_mem)
5038         set_req(i, empty_memory());
5039     }
5040   }
5041 }
5042 
5043 //---------------------------grow_to_match-------------------------------------
5044 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
5045   Node* empty_mem = empty_memory();
5046   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
5047   // look for the finite support of the other memory
5048   for (uint i = other->req(); --i >= req(); ) {
5049     if (other->in(i) != empty_mem) {
5050       uint new_len = i+1;
5051       while (req() < new_len)  add_req(empty_mem);
5052       break;
5053     }
5054   }
5055 }
5056 
5057 //---------------------------verify_sparse-------------------------------------
5058 #ifndef PRODUCT
5059 bool MergeMemNode::verify_sparse() const {
5060   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
5061   Node* base_mem = base_memory();
5062   // The following can happen in degenerate cases, since empty==top.
5063   if (is_empty_memory(base_mem))  return true;
5064   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
5065     assert(in(i) != nullptr, "sane slice");
5066     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
5067   }
5068   return true;
5069 }
5070 
5071 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
5072   Node* n;
5073   n = mm->in(idx);
5074   if (mem == n)  return true;  // might be empty_memory()
5075   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
5076   if (mem == n)  return true;
5077   return false;
5078 }
5079 #endif // !PRODUCT