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