1 /*
   2  * Copyright (c) 1997, 2013, 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/cfgnode.hpp"
  32 #include "opto/compile.hpp"
  33 #include "opto/connode.hpp"
  34 #include "opto/convertnode.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/machnode.hpp"
  37 #include "opto/matcher.hpp"
  38 #include "opto/memnode.hpp"
  39 #include "opto/mulnode.hpp"
  40 #include "opto/narrowptrnode.hpp"
  41 #include "opto/phaseX.hpp"
  42 #include "opto/regmask.hpp"
  43 
  44 // Portions of code courtesy of Clifford Click
  45 
  46 // Optimization - Graph Style
  47 
  48 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  49 
  50 //=============================================================================
  51 uint MemNode::size_of() const { return sizeof(*this); }
  52 
  53 const TypePtr *MemNode::adr_type() const {
  54   Node* adr = in(Address);
  55   const TypePtr* cross_check = NULL;
  56   DEBUG_ONLY(cross_check = _adr_type);
  57   return calculate_adr_type(adr->bottom_type(), cross_check);
  58 }
  59 
  60 #ifndef PRODUCT
  61 void MemNode::dump_spec(outputStream *st) const {
  62   if (in(Address) == NULL)  return; // node is dead
  63 #ifndef ASSERT
  64   // fake the missing field
  65   const TypePtr* _adr_type = NULL;
  66   if (in(Address) != NULL)
  67     _adr_type = in(Address)->bottom_type()->isa_ptr();
  68 #endif
  69   dump_adr_type(this, _adr_type, st);
  70 
  71   Compile* C = Compile::current();
  72   if( C->alias_type(_adr_type)->is_volatile() )
  73     st->print(" Volatile!");
  74 }
  75 
  76 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
  77   st->print(" @");
  78   if (adr_type == NULL) {
  79     st->print("NULL");
  80   } else {
  81     adr_type->dump_on(st);
  82     Compile* C = Compile::current();
  83     Compile::AliasType* atp = NULL;
  84     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
  85     if (atp == NULL)
  86       st->print(", idx=?\?;");
  87     else if (atp->index() == Compile::AliasIdxBot)
  88       st->print(", idx=Bot;");
  89     else if (atp->index() == Compile::AliasIdxTop)
  90       st->print(", idx=Top;");
  91     else if (atp->index() == Compile::AliasIdxRaw)
  92       st->print(", idx=Raw;");
  93     else {
  94       ciField* field = atp->field();
  95       if (field) {
  96         st->print(", name=");
  97         field->print_name_on(st);
  98       }
  99       st->print(", idx=%d;", atp->index());
 100     }
 101   }
 102 }
 103 
 104 extern void print_alias_types();
 105 
 106 #endif
 107 
 108 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 109   assert((t_oop != NULL), "sanity");
 110   bool is_instance = t_oop->is_known_instance_field();
 111   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 112                              (load != NULL) && load->is_Load() &&
 113                              (phase->is_IterGVN() != NULL);
 114   if (!(is_instance || is_boxed_value_load))
 115     return mchain;  // don't try to optimize non-instance types
 116   uint instance_id = t_oop->instance_id();
 117   Node *start_mem = phase->C->start()->proj_out(TypeFunc::Memory);
 118   Node *prev = NULL;
 119   Node *result = mchain;
 120   while (prev != result) {
 121     prev = result;
 122     if (result == start_mem)
 123       break;  // hit one of our sentinels
 124     // skip over a call which does not affect this memory slice
 125     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 126       Node *proj_in = result->in(0);
 127       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 128         break;  // hit one of our sentinels
 129       } else if (proj_in->is_Call()) {
 130         CallNode *call = proj_in->as_Call();
 131         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 132           result = call->in(TypeFunc::Memory);
 133         }
 134       } else if (proj_in->is_Initialize()) {
 135         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 136         // Stop if this is the initialization for the object instance which
 137         // which contains this memory slice, otherwise skip over it.
 138         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 139           break;
 140         }
 141         if (is_instance) {
 142           result = proj_in->in(TypeFunc::Memory);
 143         } else if (is_boxed_value_load) {
 144           Node* klass = alloc->in(AllocateNode::KlassNode);
 145           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 146           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 147             result = proj_in->in(TypeFunc::Memory); // not related allocation
 148           }
 149         }
 150       } else if (proj_in->is_MemBar()) {
 151         result = proj_in->in(TypeFunc::Memory);
 152       } else {
 153         assert(false, "unexpected projection");
 154       }
 155     } else if (result->is_ClearArray()) {
 156       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 157         // Can not bypass initialization of the instance
 158         // we are looking for.
 159         break;
 160       }
 161       // Otherwise skip it (the call updated 'result' value).
 162     } else if (result->is_MergeMem()) {
 163       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 164     }
 165   }
 166   return result;
 167 }
 168 
 169 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 170   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 171   if (t_oop == NULL)
 172     return mchain;  // don't try to optimize non-oop types
 173   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 174   bool is_instance = t_oop->is_known_instance_field();
 175   PhaseIterGVN *igvn = phase->is_IterGVN();
 176   if (is_instance && igvn != NULL  && result->is_Phi()) {
 177     PhiNode *mphi = result->as_Phi();
 178     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 179     const TypePtr *t = mphi->adr_type();
 180     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 181         t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 182         t->is_oopptr()->cast_to_exactness(true)
 183          ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 184          ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop) {
 185       // clone the Phi with our address type
 186       result = mphi->split_out_instance(t_adr, igvn);
 187     } else {
 188       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 189     }
 190   }
 191   return result;
 192 }
 193 
 194 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 195   uint alias_idx = phase->C->get_alias_index(tp);
 196   Node *mem = mmem;
 197 #ifdef ASSERT
 198   {
 199     // Check that current type is consistent with the alias index used during graph construction
 200     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 201     bool consistent =  adr_check == NULL || adr_check->empty() ||
 202                        phase->C->must_alias(adr_check, alias_idx );
 203     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 204     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 205                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 206         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 207         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 208           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 209           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 210       // don't assert if it is dead code.
 211       consistent = true;
 212     }
 213     if( !consistent ) {
 214       st->print("alias_idx==%d, adr_check==", alias_idx);
 215       if( adr_check == NULL ) {
 216         st->print("NULL");
 217       } else {
 218         adr_check->dump();
 219       }
 220       st->cr();
 221       print_alias_types();
 222       assert(consistent, "adr_check must match alias idx");
 223     }
 224   }
 225 #endif
 226   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 227   // means an array I have not precisely typed yet.  Do not do any
 228   // alias stuff with it any time soon.
 229   const TypeOopPtr *toop = tp->isa_oopptr();
 230   if( tp->base() != Type::AnyPtr &&
 231       !(toop &&
 232         toop->klass() != NULL &&
 233         toop->klass()->is_java_lang_Object() &&
 234         toop->offset() == Type::OffsetBot) ) {
 235     // compress paths and change unreachable cycles to TOP
 236     // If not, we can update the input infinitely along a MergeMem cycle
 237     // Equivalent code in PhiNode::Ideal
 238     Node* m  = phase->transform(mmem);
 239     // If transformed to a MergeMem, get the desired slice
 240     // Otherwise the returned node represents memory for every slice
 241     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 242     // Update input if it is progress over what we have now
 243   }
 244   return mem;
 245 }
 246 
 247 //--------------------------Ideal_common---------------------------------------
 248 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 249 // Unhook non-raw memories from complete (macro-expanded) initializations.
 250 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 251   // If our control input is a dead region, kill all below the region
 252   Node *ctl = in(MemNode::Control);
 253   if (ctl && remove_dead_region(phase, can_reshape))
 254     return this;
 255   ctl = in(MemNode::Control);
 256   // Don't bother trying to transform a dead node
 257   if (ctl && ctl->is_top())  return NodeSentinel;
 258 
 259   PhaseIterGVN *igvn = phase->is_IterGVN();
 260   // Wait if control on the worklist.
 261   if (ctl && can_reshape && igvn != NULL) {
 262     Node* bol = NULL;
 263     Node* cmp = NULL;
 264     if (ctl->in(0)->is_If()) {
 265       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 266       bol = ctl->in(0)->in(1);
 267       if (bol->is_Bool())
 268         cmp = ctl->in(0)->in(1)->in(1);
 269     }
 270     if (igvn->_worklist.member(ctl) ||
 271         (bol != NULL && igvn->_worklist.member(bol)) ||
 272         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 273       // This control path may be dead.
 274       // Delay this memory node transformation until the control is processed.
 275       phase->is_IterGVN()->_worklist.push(this);
 276       return NodeSentinel; // caller will return NULL
 277     }
 278   }
 279   // Ignore if memory is dead, or self-loop
 280   Node *mem = in(MemNode::Memory);
 281   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 282   assert(mem != this, "dead loop in MemNode::Ideal");
 283 
 284   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 285     // This memory slice may be dead.
 286     // Delay this mem node transformation until the memory is processed.
 287     phase->is_IterGVN()->_worklist.push(this);
 288     return NodeSentinel; // caller will return NULL
 289   }
 290 
 291   Node *address = in(MemNode::Address);
 292   const Type *t_adr = phase->type(address);
 293   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 294 
 295   if (can_reshape && igvn != NULL &&
 296       (igvn->_worklist.member(address) ||
 297        igvn->_worklist.size() > 0 && (t_adr != adr_type())) ) {
 298     // The address's base and type may change when the address is processed.
 299     // Delay this mem node transformation until the address is processed.
 300     phase->is_IterGVN()->_worklist.push(this);
 301     return NodeSentinel; // caller will return NULL
 302   }
 303 
 304   // Do NOT remove or optimize the next lines: ensure a new alias index
 305   // is allocated for an oop pointer type before Escape Analysis.
 306   // Note: C++ will not remove it since the call has side effect.
 307   if (t_adr->isa_oopptr()) {
 308     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 309   }
 310 
 311 #ifdef ASSERT
 312   Node* base = NULL;
 313   if (address->is_AddP())
 314     base = address->in(AddPNode::Base);
 315   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 316       !t_adr->isa_rawptr()) {
 317     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 318     Compile* C = phase->C;
 319     tty->cr();
 320     tty->print_cr("===== NULL+offs not RAW address =====");
 321     if (C->is_dead_node(this->_idx))    tty->print_cr("'this' is dead");
 322     if ((ctl != NULL) && C->is_dead_node(ctl->_idx)) tty->print_cr("'ctl' is dead");
 323     if (C->is_dead_node(mem->_idx))     tty->print_cr("'mem' is dead");
 324     if (C->is_dead_node(address->_idx)) tty->print_cr("'address' is dead");
 325     if (C->is_dead_node(base->_idx))    tty->print_cr("'base' is dead");
 326     tty->cr();
 327     base->dump(1);
 328     tty->cr();
 329     this->dump(2);
 330     tty->print("this->adr_type():     "); adr_type()->dump(); tty->cr();
 331     tty->print("phase->type(address): "); t_adr->dump(); tty->cr();
 332     tty->print("phase->type(base):    "); phase->type(address)->dump(); tty->cr();
 333     tty->cr();
 334   }
 335   assert(base == NULL || t_adr->isa_rawptr() ||
 336         !phase->type(base)->higher_equal(TypePtr::NULL_PTR), "NULL+offs not RAW address?");
 337 #endif
 338 
 339   // Avoid independent memory operations
 340   Node* old_mem = mem;
 341 
 342   // The code which unhooks non-raw memories from complete (macro-expanded)
 343   // initializations was removed. After macro-expansion all stores catched
 344   // by Initialize node became raw stores and there is no information
 345   // which memory slices they modify. So it is unsafe to move any memory
 346   // operation above these stores. Also in most cases hooked non-raw memories
 347   // were already unhooked by using information from detect_ptr_independence()
 348   // and find_previous_store().
 349 
 350   if (mem->is_MergeMem()) {
 351     MergeMemNode* mmem = mem->as_MergeMem();
 352     const TypePtr *tp = t_adr->is_ptr();
 353 
 354     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 355   }
 356 
 357   if (mem != old_mem) {
 358     set_req(MemNode::Memory, mem);
 359     if (can_reshape && old_mem->outcnt() == 0) {
 360         igvn->_worklist.push(old_mem);
 361     }
 362     if (phase->type( mem ) == Type::TOP) return NodeSentinel;
 363     return this;
 364   }
 365 
 366   // let the subclass continue analyzing...
 367   return NULL;
 368 }
 369 
 370 // Helper function for proving some simple control dominations.
 371 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 372 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 373 // is not a constant (dominated by the method's StartNode).
 374 // Used by MemNode::find_previous_store to prove that the
 375 // control input of a memory operation predates (dominates)
 376 // an allocation it wants to look past.
 377 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 378   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 379     return false; // Conservative answer for dead code
 380 
 381   // Check 'dom'. Skip Proj and CatchProj nodes.
 382   dom = dom->find_exact_control(dom);
 383   if (dom == NULL || dom->is_top())
 384     return false; // Conservative answer for dead code
 385 
 386   if (dom == sub) {
 387     // For the case when, for example, 'sub' is Initialize and the original
 388     // 'dom' is Proj node of the 'sub'.
 389     return false;
 390   }
 391 
 392   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 393     return true;
 394 
 395   // 'dom' dominates 'sub' if its control edge and control edges
 396   // of all its inputs dominate or equal to sub's control edge.
 397 
 398   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 399   // Or Region for the check in LoadNode::Ideal();
 400   // 'sub' should have sub->in(0) != NULL.
 401   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 402          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 403 
 404   // Get control edge of 'sub'.
 405   Node* orig_sub = sub;
 406   sub = sub->find_exact_control(sub->in(0));
 407   if (sub == NULL || sub->is_top())
 408     return false; // Conservative answer for dead code
 409 
 410   assert(sub->is_CFG(), "expecting control");
 411 
 412   if (sub == dom)
 413     return true;
 414 
 415   if (sub->is_Start() || sub->is_Root())
 416     return false;
 417 
 418   {
 419     // Check all control edges of 'dom'.
 420 
 421     ResourceMark rm;
 422     Arena* arena = Thread::current()->resource_area();
 423     Node_List nlist(arena);
 424     Unique_Node_List dom_list(arena);
 425 
 426     dom_list.push(dom);
 427     bool only_dominating_controls = false;
 428 
 429     for (uint next = 0; next < dom_list.size(); next++) {
 430       Node* n = dom_list.at(next);
 431       if (n == orig_sub)
 432         return false; // One of dom's inputs dominated by sub.
 433       if (!n->is_CFG() && n->pinned()) {
 434         // Check only own control edge for pinned non-control nodes.
 435         n = n->find_exact_control(n->in(0));
 436         if (n == NULL || n->is_top())
 437           return false; // Conservative answer for dead code
 438         assert(n->is_CFG(), "expecting control");
 439         dom_list.push(n);
 440       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 441         only_dominating_controls = true;
 442       } else if (n->is_CFG()) {
 443         if (n->dominates(sub, nlist))
 444           only_dominating_controls = true;
 445         else
 446           return false;
 447       } else {
 448         // First, own control edge.
 449         Node* m = n->find_exact_control(n->in(0));
 450         if (m != NULL) {
 451           if (m->is_top())
 452             return false; // Conservative answer for dead code
 453           dom_list.push(m);
 454         }
 455         // Now, the rest of edges.
 456         uint cnt = n->req();
 457         for (uint i = 1; i < cnt; i++) {
 458           m = n->find_exact_control(n->in(i));
 459           if (m == NULL || m->is_top())
 460             continue;
 461           dom_list.push(m);
 462         }
 463       }
 464     }
 465     return only_dominating_controls;
 466   }
 467 }
 468 
 469 //---------------------detect_ptr_independence---------------------------------
 470 // Used by MemNode::find_previous_store to prove that two base
 471 // pointers are never equal.
 472 // The pointers are accompanied by their associated allocations,
 473 // if any, which have been previously discovered by the caller.
 474 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 475                                       Node* p2, AllocateNode* a2,
 476                                       PhaseTransform* phase) {
 477   // Attempt to prove that these two pointers cannot be aliased.
 478   // They may both manifestly be allocations, and they should differ.
 479   // Or, if they are not both allocations, they can be distinct constants.
 480   // Otherwise, one is an allocation and the other a pre-existing value.
 481   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 482     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 483   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 484     return (a1 != a2);
 485   } else if (a1 != NULL) {                  // one allocation a1
 486     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 487     return all_controls_dominate(p2, a1);
 488   } else { //(a2 != NULL)                   // one allocation a2
 489     return all_controls_dominate(p1, a2);
 490   }
 491   return false;
 492 }
 493 
 494 
 495 // The logic for reordering loads and stores uses four steps:
 496 // (a) Walk carefully past stores and initializations which we
 497 //     can prove are independent of this load.
 498 // (b) Observe that the next memory state makes an exact match
 499 //     with self (load or store), and locate the relevant store.
 500 // (c) Ensure that, if we were to wire self directly to the store,
 501 //     the optimizer would fold it up somehow.
 502 // (d) Do the rewiring, and return, depending on some other part of
 503 //     the optimizer to fold up the load.
 504 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 505 // specific to loads and stores, so they are handled by the callers.
 506 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 507 //
 508 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 509   Node*         ctrl   = in(MemNode::Control);
 510   Node*         adr    = in(MemNode::Address);
 511   intptr_t      offset = 0;
 512   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 513   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 514 
 515   if (offset == Type::OffsetBot)
 516     return NULL;            // cannot unalias unless there are precise offsets
 517 
 518   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 519 
 520   intptr_t size_in_bytes = memory_size();
 521 
 522   Node* mem = in(MemNode::Memory);   // start searching here...
 523 
 524   int cnt = 50;             // Cycle limiter
 525   for (;;) {                // While we can dance past unrelated stores...
 526     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 527 
 528     if (mem->is_Store()) {
 529       Node* st_adr = mem->in(MemNode::Address);
 530       intptr_t st_offset = 0;
 531       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 532       if (st_base == NULL)
 533         break;              // inscrutable pointer
 534       if (st_offset != offset && st_offset != Type::OffsetBot) {
 535         const int MAX_STORE = BytesPerLong;
 536         if (st_offset >= offset + size_in_bytes ||
 537             st_offset <= offset - MAX_STORE ||
 538             st_offset <= offset - mem->as_Store()->memory_size()) {
 539           // Success:  The offsets are provably independent.
 540           // (You may ask, why not just test st_offset != offset and be done?
 541           // The answer is that stores of different sizes can co-exist
 542           // in the same sequence of RawMem effects.  We sometimes initialize
 543           // a whole 'tile' of array elements with a single jint or jlong.)
 544           mem = mem->in(MemNode::Memory);
 545           continue;           // (a) advance through independent store memory
 546         }
 547       }
 548       if (st_base != base &&
 549           detect_ptr_independence(base, alloc,
 550                                   st_base,
 551                                   AllocateNode::Ideal_allocation(st_base, phase),
 552                                   phase)) {
 553         // Success:  The bases are provably independent.
 554         mem = mem->in(MemNode::Memory);
 555         continue;           // (a) advance through independent store memory
 556       }
 557 
 558       // (b) At this point, if the bases or offsets do not agree, we lose,
 559       // since we have not managed to prove 'this' and 'mem' independent.
 560       if (st_base == base && st_offset == offset) {
 561         return mem;         // let caller handle steps (c), (d)
 562       }
 563 
 564     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 565       InitializeNode* st_init = mem->in(0)->as_Initialize();
 566       AllocateNode*  st_alloc = st_init->allocation();
 567       if (st_alloc == NULL)
 568         break;              // something degenerated
 569       bool known_identical = false;
 570       bool known_independent = false;
 571       if (alloc == st_alloc)
 572         known_identical = true;
 573       else if (alloc != NULL)
 574         known_independent = true;
 575       else if (all_controls_dominate(this, st_alloc))
 576         known_independent = true;
 577 
 578       if (known_independent) {
 579         // The bases are provably independent: Either they are
 580         // manifestly distinct allocations, or else the control
 581         // of this load dominates the store's allocation.
 582         int alias_idx = phase->C->get_alias_index(adr_type());
 583         if (alias_idx == Compile::AliasIdxRaw) {
 584           mem = st_alloc->in(TypeFunc::Memory);
 585         } else {
 586           mem = st_init->memory(alias_idx);
 587         }
 588         continue;           // (a) advance through independent store memory
 589       }
 590 
 591       // (b) at this point, if we are not looking at a store initializing
 592       // the same allocation we are loading from, we lose.
 593       if (known_identical) {
 594         // From caller, can_see_stored_value will consult find_captured_store.
 595         return mem;         // let caller handle steps (c), (d)
 596       }
 597 
 598     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 599       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 600       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 601         CallNode *call = mem->in(0)->as_Call();
 602         if (!call->may_modify(addr_t, phase)) {
 603           mem = call->in(TypeFunc::Memory);
 604           continue;         // (a) advance through independent call memory
 605         }
 606       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 607         mem = mem->in(0)->in(TypeFunc::Memory);
 608         continue;           // (a) advance through independent MemBar memory
 609       } else if (mem->is_ClearArray()) {
 610         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 611           // (the call updated 'mem' value)
 612           continue;         // (a) advance through independent allocation memory
 613         } else {
 614           // Can not bypass initialization of the instance
 615           // we are looking for.
 616           return mem;
 617         }
 618       } else if (mem->is_MergeMem()) {
 619         int alias_idx = phase->C->get_alias_index(adr_type());
 620         mem = mem->as_MergeMem()->memory_at(alias_idx);
 621         continue;           // (a) advance through independent MergeMem memory
 622       }
 623     }
 624 
 625     // Unless there is an explicit 'continue', we must bail out here,
 626     // because 'mem' is an inscrutable memory state (e.g., a call).
 627     break;
 628   }
 629 
 630   return NULL;              // bail out
 631 }
 632 
 633 //----------------------calculate_adr_type-------------------------------------
 634 // Helper function.  Notices when the given type of address hits top or bottom.
 635 // Also, asserts a cross-check of the type against the expected address type.
 636 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 637   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 638   #ifdef PRODUCT
 639   cross_check = NULL;
 640   #else
 641   if (!VerifyAliases || is_error_reported() || Node::in_dump())  cross_check = NULL;
 642   #endif
 643   const TypePtr* tp = t->isa_ptr();
 644   if (tp == NULL) {
 645     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 646     return TypePtr::BOTTOM;           // touches lots of memory
 647   } else {
 648     #ifdef ASSERT
 649     // %%%% [phh] We don't check the alias index if cross_check is
 650     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 651     if (cross_check != NULL &&
 652         cross_check != TypePtr::BOTTOM &&
 653         cross_check != TypeRawPtr::BOTTOM) {
 654       // Recheck the alias index, to see if it has changed (due to a bug).
 655       Compile* C = Compile::current();
 656       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 657              "must stay in the original alias category");
 658       // The type of the address must be contained in the adr_type,
 659       // disregarding "null"-ness.
 660       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 661       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 662       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 663              "real address must not escape from expected memory type");
 664     }
 665     #endif
 666     return tp;
 667   }
 668 }
 669 
 670 //------------------------adr_phi_is_loop_invariant----------------------------
 671 // A helper function for Ideal_DU_postCCP to check if a Phi in a counted
 672 // loop is loop invariant. Make a quick traversal of Phi and associated
 673 // CastPP nodes, looking to see if they are a closed group within the loop.
 674 bool MemNode::adr_phi_is_loop_invariant(Node* adr_phi, Node* cast) {
 675   // The idea is that the phi-nest must boil down to only CastPP nodes
 676   // with the same data. This implies that any path into the loop already
 677   // includes such a CastPP, and so the original cast, whatever its input,
 678   // must be covered by an equivalent cast, with an earlier control input.
 679   ResourceMark rm;
 680 
 681   // The loop entry input of the phi should be the unique dominating
 682   // node for every Phi/CastPP in the loop.
 683   Unique_Node_List closure;
 684   closure.push(adr_phi->in(LoopNode::EntryControl));
 685 
 686   // Add the phi node and the cast to the worklist.
 687   Unique_Node_List worklist;
 688   worklist.push(adr_phi);
 689   if( cast != NULL ){
 690     if( !cast->is_ConstraintCast() ) return false;
 691     worklist.push(cast);
 692   }
 693 
 694   // Begin recursive walk of phi nodes.
 695   while( worklist.size() ){
 696     // Take a node off the worklist
 697     Node *n = worklist.pop();
 698     if( !closure.member(n) ){
 699       // Add it to the closure.
 700       closure.push(n);
 701       // Make a sanity check to ensure we don't waste too much time here.
 702       if( closure.size() > 20) return false;
 703       // This node is OK if:
 704       //  - it is a cast of an identical value
 705       //  - or it is a phi node (then we add its inputs to the worklist)
 706       // Otherwise, the node is not OK, and we presume the cast is not invariant
 707       if( n->is_ConstraintCast() ){
 708         worklist.push(n->in(1));
 709       } else if( n->is_Phi() ) {
 710         for( uint i = 1; i < n->req(); i++ ) {
 711           worklist.push(n->in(i));
 712         }
 713       } else {
 714         return false;
 715       }
 716     }
 717   }
 718 
 719   // Quit when the worklist is empty, and we've found no offending nodes.
 720   return true;
 721 }
 722 
 723 //------------------------------Ideal_DU_postCCP-------------------------------
 724 // Find any cast-away of null-ness and keep its control.  Null cast-aways are
 725 // going away in this pass and we need to make this memory op depend on the
 726 // gating null check.
 727 Node *MemNode::Ideal_DU_postCCP( PhaseCCP *ccp ) {
 728   return Ideal_common_DU_postCCP(ccp, this, in(MemNode::Address));
 729 }
 730 
 731 // I tried to leave the CastPP's in.  This makes the graph more accurate in
 732 // some sense; we get to keep around the knowledge that an oop is not-null
 733 // after some test.  Alas, the CastPP's interfere with GVN (some values are
 734 // the regular oop, some are the CastPP of the oop, all merge at Phi's which
 735 // cannot collapse, etc).  This cost us 10% on SpecJVM, even when I removed
 736 // some of the more trivial cases in the optimizer.  Removing more useless
 737 // Phi's started allowing Loads to illegally float above null checks.  I gave
 738 // up on this approach.  CNC 10/20/2000
 739 // This static method may be called not from MemNode (EncodePNode calls it).
 740 // Only the control edge of the node 'n' might be updated.
 741 Node *MemNode::Ideal_common_DU_postCCP( PhaseCCP *ccp, Node* n, Node* adr ) {
 742   Node *skipped_cast = NULL;
 743   // Need a null check?  Regular static accesses do not because they are
 744   // from constant addresses.  Array ops are gated by the range check (which
 745   // always includes a NULL check).  Just check field ops.
 746   if( n->in(MemNode::Control) == NULL ) {
 747     // Scan upwards for the highest location we can place this memory op.
 748     while( true ) {
 749       switch( adr->Opcode() ) {
 750 
 751       case Op_AddP:             // No change to NULL-ness, so peek thru AddP's
 752         adr = adr->in(AddPNode::Base);
 753         continue;
 754 
 755       case Op_DecodeN:         // No change to NULL-ness, so peek thru
 756       case Op_DecodeNKlass:
 757         adr = adr->in(1);
 758         continue;
 759 
 760       case Op_EncodeP:
 761       case Op_EncodePKlass:
 762         // EncodeP node's control edge could be set by this method
 763         // when EncodeP node depends on CastPP node.
 764         //
 765         // Use its control edge for memory op because EncodeP may go away
 766         // later when it is folded with following or preceding DecodeN node.
 767         if (adr->in(0) == NULL) {
 768           // Keep looking for cast nodes.
 769           adr = adr->in(1);
 770           continue;
 771         }
 772         ccp->hash_delete(n);
 773         n->set_req(MemNode::Control, adr->in(0));
 774         ccp->hash_insert(n);
 775         return n;
 776 
 777       case Op_CastPP:
 778         // If the CastPP is useless, just peek on through it.
 779         if( ccp->type(adr) == ccp->type(adr->in(1)) ) {
 780           // Remember the cast that we've peeked though. If we peek
 781           // through more than one, then we end up remembering the highest
 782           // one, that is, if in a loop, the one closest to the top.
 783           skipped_cast = adr;
 784           adr = adr->in(1);
 785           continue;
 786         }
 787         // CastPP is going away in this pass!  We need this memory op to be
 788         // control-dependent on the test that is guarding the CastPP.
 789         ccp->hash_delete(n);
 790         n->set_req(MemNode::Control, adr->in(0));
 791         ccp->hash_insert(n);
 792         return n;
 793 
 794       case Op_Phi:
 795         // Attempt to float above a Phi to some dominating point.
 796         if (adr->in(0) != NULL && adr->in(0)->is_CountedLoop()) {
 797           // If we've already peeked through a Cast (which could have set the
 798           // control), we can't float above a Phi, because the skipped Cast
 799           // may not be loop invariant.
 800           if (adr_phi_is_loop_invariant(adr, skipped_cast)) {
 801             adr = adr->in(1);
 802             continue;
 803           }
 804         }
 805 
 806         // Intentional fallthrough!
 807 
 808         // No obvious dominating point.  The mem op is pinned below the Phi
 809         // by the Phi itself.  If the Phi goes away (no true value is merged)
 810         // then the mem op can float, but not indefinitely.  It must be pinned
 811         // behind the controls leading to the Phi.
 812       case Op_CheckCastPP:
 813         // These usually stick around to change address type, however a
 814         // useless one can be elided and we still need to pick up a control edge
 815         if (adr->in(0) == NULL) {
 816           // This CheckCastPP node has NO control and is likely useless. But we
 817           // need check further up the ancestor chain for a control input to keep
 818           // the node in place. 4959717.
 819           skipped_cast = adr;
 820           adr = adr->in(1);
 821           continue;
 822         }
 823         ccp->hash_delete(n);
 824         n->set_req(MemNode::Control, adr->in(0));
 825         ccp->hash_insert(n);
 826         return n;
 827 
 828         // List of "safe" opcodes; those that implicitly block the memory
 829         // op below any null check.
 830       case Op_CastX2P:          // no null checks on native pointers
 831       case Op_Parm:             // 'this' pointer is not null
 832       case Op_LoadP:            // Loading from within a klass
 833       case Op_LoadN:            // Loading from within a klass
 834       case Op_LoadKlass:        // Loading from within a klass
 835       case Op_LoadNKlass:       // Loading from within a klass
 836       case Op_ConP:             // Loading from a klass
 837       case Op_ConN:             // Loading from a klass
 838       case Op_ConNKlass:        // Loading from a klass
 839       case Op_CreateEx:         // Sucking up the guts of an exception oop
 840       case Op_Con:              // Reading from TLS
 841       case Op_CMoveP:           // CMoveP is pinned
 842       case Op_CMoveN:           // CMoveN is pinned
 843         break;                  // No progress
 844 
 845       case Op_Proj:             // Direct call to an allocation routine
 846       case Op_SCMemProj:        // Memory state from store conditional ops
 847 #ifdef ASSERT
 848         {
 849           assert(adr->as_Proj()->_con == TypeFunc::Parms, "must be return value");
 850           const Node* call = adr->in(0);
 851           if (call->is_CallJava()) {
 852             const CallJavaNode* call_java = call->as_CallJava();
 853             const TypeTuple *r = call_java->tf()->range();
 854             assert(r->cnt() > TypeFunc::Parms, "must return value");
 855             const Type* ret_type = r->field_at(TypeFunc::Parms);
 856             assert(ret_type && ret_type->isa_ptr(), "must return pointer");
 857             // We further presume that this is one of
 858             // new_instance_Java, new_array_Java, or
 859             // the like, but do not assert for this.
 860           } else if (call->is_Allocate()) {
 861             // similar case to new_instance_Java, etc.
 862           } else if (!call->is_CallLeaf()) {
 863             // Projections from fetch_oop (OSR) are allowed as well.
 864             ShouldNotReachHere();
 865           }
 866         }
 867 #endif
 868         break;
 869       default:
 870         ShouldNotReachHere();
 871       }
 872       break;
 873     }
 874   }
 875 
 876   return  NULL;               // No progress
 877 }
 878 
 879 
 880 //=============================================================================
 881 uint LoadNode::size_of() const { return sizeof(*this); }
 882 uint LoadNode::cmp( const Node &n ) const
 883 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 884 const Type *LoadNode::bottom_type() const { return _type; }
 885 uint LoadNode::ideal_reg() const {
 886   return _type->ideal_reg();
 887 }
 888 
 889 #ifndef PRODUCT
 890 void LoadNode::dump_spec(outputStream *st) const {
 891   MemNode::dump_spec(st);
 892   if( !Verbose && !WizardMode ) {
 893     // standard dump does this in Verbose and WizardMode
 894     st->print(" #"); _type->dump_on(st);
 895   }
 896 }
 897 #endif
 898 
 899 #ifdef ASSERT
 900 //----------------------------is_immutable_value-------------------------------
 901 // Helper function to allow a raw load without control edge for some cases
 902 bool LoadNode::is_immutable_value(Node* adr) {
 903   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 904           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 905           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 906            in_bytes(JavaThread::osthread_offset())));
 907 }
 908 #endif
 909 
 910 //----------------------------LoadNode::make-----------------------------------
 911 // Polymorphic factory method:
 912 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo) {
 913   Compile* C = gvn.C;
 914 
 915   // sanity check the alias category against the created node type
 916   assert(!(adr_type->isa_oopptr() &&
 917            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 918          "use LoadKlassNode instead");
 919   assert(!(adr_type->isa_aryptr() &&
 920            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 921          "use LoadRangeNode instead");
 922   // Check control edge of raw loads
 923   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 924           // oop will be recorded in oop map if load crosses safepoint
 925           rt->isa_oopptr() || is_immutable_value(adr),
 926           "raw memory operations should have control edge");
 927   switch (bt) {
 928   case T_BOOLEAN: return new (C) LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo);
 929   case T_BYTE:    return new (C) LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo);
 930   case T_INT:     return new (C) LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo);
 931   case T_CHAR:    return new (C) LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo);
 932   case T_SHORT:   return new (C) LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo);
 933   case T_LONG:    return new (C) LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo);
 934   case T_FLOAT:   return new (C) LoadFNode (ctl, mem, adr, adr_type, rt,            mo);
 935   case T_DOUBLE:  return new (C) LoadDNode (ctl, mem, adr, adr_type, rt,            mo);
 936   case T_ADDRESS: return new (C) LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo);
 937   case T_OBJECT:
 938 #ifdef _LP64
 939     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 940       Node* load  = gvn.transform(new (C) LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo));
 941       return new (C) DecodeNNode(load, load->bottom_type()->make_ptr());
 942     } else
 943 #endif
 944     {
 945       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 946       return new (C) LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr(), mo);
 947     }
 948   }
 949   ShouldNotReachHere();
 950   return (LoadNode*)NULL;
 951 }
 952 
 953 LoadLNode* LoadLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo) {
 954   bool require_atomic = true;
 955   return new (C) LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, require_atomic);
 956 }
 957 
 958 
 959 
 960 
 961 //------------------------------hash-------------------------------------------
 962 uint LoadNode::hash() const {
 963   // unroll addition of interesting fields
 964   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 965 }
 966 
 967 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 968   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 969     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 970     bool is_stable_ary = FoldStableValues &&
 971                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 972                          tp->isa_aryptr()->is_stable();
 973 
 974     return (eliminate_boxing && non_volatile) || is_stable_ary;
 975   }
 976 
 977   return false;
 978 }
 979 
 980 //---------------------------can_see_stored_value------------------------------
 981 // This routine exists to make sure this set of tests is done the same
 982 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 983 // will change the graph shape in a way which makes memory alive twice at the
 984 // same time (uses the Oracle model of aliasing), then some
 985 // LoadXNode::Identity will fold things back to the equivalence-class model
 986 // of aliasing.
 987 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 988   Node* ld_adr = in(MemNode::Address);
 989   intptr_t ld_off = 0;
 990   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 991   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 992   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
 993   // This is more general than load from boxing objects.
 994   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
 995     uint alias_idx = atp->index();
 996     bool final = !atp->is_rewritable();
 997     Node* result = NULL;
 998     Node* current = st;
 999     // Skip through chains of MemBarNodes checking the MergeMems for
1000     // new states for the slice of this load.  Stop once any other
1001     // kind of node is encountered.  Loads from final memory can skip
1002     // through any kind of MemBar but normal loads shouldn't skip
1003     // through MemBarAcquire since the could allow them to move out of
1004     // a synchronized region.
1005     while (current->is_Proj()) {
1006       int opc = current->in(0)->Opcode();
1007       if ((final && (opc == Op_MemBarAcquire ||
1008                      opc == Op_MemBarAcquireLock ||
1009                      opc == Op_LoadFence)) ||
1010           opc == Op_MemBarRelease ||
1011           opc == Op_StoreFence ||
1012           opc == Op_MemBarReleaseLock ||
1013           opc == Op_MemBarCPUOrder) {
1014         Node* mem = current->in(0)->in(TypeFunc::Memory);
1015         if (mem->is_MergeMem()) {
1016           MergeMemNode* merge = mem->as_MergeMem();
1017           Node* new_st = merge->memory_at(alias_idx);
1018           if (new_st == merge->base_memory()) {
1019             // Keep searching
1020             current = new_st;
1021             continue;
1022           }
1023           // Save the new memory state for the slice and fall through
1024           // to exit.
1025           result = new_st;
1026         }
1027       }
1028       break;
1029     }
1030     if (result != NULL) {
1031       st = result;
1032     }
1033   }
1034 
1035   // Loop around twice in the case Load -> Initialize -> Store.
1036   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
1037   for (int trip = 0; trip <= 1; trip++) {
1038 
1039     if (st->is_Store()) {
1040       Node* st_adr = st->in(MemNode::Address);
1041       if (!phase->eqv(st_adr, ld_adr)) {
1042         // Try harder before giving up...  Match raw and non-raw pointers.
1043         intptr_t st_off = 0;
1044         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
1045         if (alloc == NULL)       return NULL;
1046         if (alloc != ld_alloc)   return NULL;
1047         if (ld_off != st_off)    return NULL;
1048         // At this point we have proven something like this setup:
1049         //  A = Allocate(...)
1050         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
1051         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
1052         // (Actually, we haven't yet proven the Q's are the same.)
1053         // In other words, we are loading from a casted version of
1054         // the same pointer-and-offset that we stored to.
1055         // Thus, we are able to replace L by V.
1056       }
1057       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1058       if (store_Opcode() != st->Opcode())
1059         return NULL;
1060       return st->in(MemNode::ValueIn);
1061     }
1062 
1063     // A load from a freshly-created object always returns zero.
1064     // (This can happen after LoadNode::Ideal resets the load's memory input
1065     // to find_captured_store, which returned InitializeNode::zero_memory.)
1066     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1067         (st->in(0) == ld_alloc) &&
1068         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1069       // return a zero value for the load's basic type
1070       // (This is one of the few places where a generic PhaseTransform
1071       // can create new nodes.  Think of it as lazily manifesting
1072       // virtually pre-existing constants.)
1073       return phase->zerocon(memory_type());
1074     }
1075 
1076     // A load from an initialization barrier can match a captured store.
1077     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1078       InitializeNode* init = st->in(0)->as_Initialize();
1079       AllocateNode* alloc = init->allocation();
1080       if ((alloc != NULL) && (alloc == ld_alloc)) {
1081         // examine a captured store value
1082         st = init->find_captured_store(ld_off, memory_size(), phase);
1083         if (st != NULL)
1084           continue;             // take one more trip around
1085       }
1086     }
1087 
1088     // Load boxed value from result of valueOf() call is input parameter.
1089     if (this->is_Load() && ld_adr->is_AddP() &&
1090         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1091       intptr_t ignore = 0;
1092       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1093       if (base != NULL && base->is_Proj() &&
1094           base->as_Proj()->_con == TypeFunc::Parms &&
1095           base->in(0)->is_CallStaticJava() &&
1096           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1097         return base->in(0)->in(TypeFunc::Parms);
1098       }
1099     }
1100 
1101     break;
1102   }
1103 
1104   return NULL;
1105 }
1106 
1107 //----------------------is_instance_field_load_with_local_phi------------------
1108 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1109   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1110       in(Address)->is_AddP() ) {
1111     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1112     // Only instances and boxed values.
1113     if( t_oop != NULL &&
1114         (t_oop->is_ptr_to_boxed_value() ||
1115          t_oop->is_known_instance_field()) &&
1116         t_oop->offset() != Type::OffsetBot &&
1117         t_oop->offset() != Type::OffsetTop) {
1118       return true;
1119     }
1120   }
1121   return false;
1122 }
1123 
1124 //------------------------------Identity---------------------------------------
1125 // Loads are identity if previous store is to same address
1126 Node *LoadNode::Identity( PhaseTransform *phase ) {
1127   // If the previous store-maker is the right kind of Store, and the store is
1128   // to the same address, then we are equal to the value stored.
1129   Node* mem = in(Memory);
1130   Node* value = can_see_stored_value(mem, phase);
1131   if( value ) {
1132     // byte, short & char stores truncate naturally.
1133     // A load has to load the truncated value which requires
1134     // some sort of masking operation and that requires an
1135     // Ideal call instead of an Identity call.
1136     if (memory_size() < BytesPerInt) {
1137       // If the input to the store does not fit with the load's result type,
1138       // it must be truncated via an Ideal call.
1139       if (!phase->type(value)->higher_equal(phase->type(this)))
1140         return this;
1141     }
1142     // (This works even when value is a Con, but LoadNode::Value
1143     // usually runs first, producing the singleton type of the Con.)
1144     return value;
1145   }
1146 
1147   // Search for an existing data phi which was generated before for the same
1148   // instance's field to avoid infinite generation of phis in a loop.
1149   Node *region = mem->in(0);
1150   if (is_instance_field_load_with_local_phi(region)) {
1151     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1152     int this_index  = phase->C->get_alias_index(addr_t);
1153     int this_offset = addr_t->offset();
1154     int this_iid    = addr_t->instance_id();
1155     if (!addr_t->is_known_instance() &&
1156          addr_t->is_ptr_to_boxed_value()) {
1157       // Use _idx of address base (could be Phi node) for boxed values.
1158       intptr_t   ignore = 0;
1159       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1160       this_iid = base->_idx;
1161     }
1162     const Type* this_type = bottom_type();
1163     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1164       Node* phi = region->fast_out(i);
1165       if (phi->is_Phi() && phi != mem &&
1166           phi->as_Phi()->is_same_inst_field(this_type, this_iid, this_index, this_offset)) {
1167         return phi;
1168       }
1169     }
1170   }
1171 
1172   return this;
1173 }
1174 
1175 // We're loading from an object which has autobox behaviour.
1176 // If this object is result of a valueOf call we'll have a phi
1177 // merging a newly allocated object and a load from the cache.
1178 // We want to replace this load with the original incoming
1179 // argument to the valueOf call.
1180 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1181   assert(phase->C->eliminate_boxing(), "sanity");
1182   intptr_t ignore = 0;
1183   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1184   if ((base == NULL) || base->is_Phi()) {
1185     // Push the loads from the phi that comes from valueOf up
1186     // through it to allow elimination of the loads and the recovery
1187     // of the original value. It is done in split_through_phi().
1188     return NULL;
1189   } else if (base->is_Load() ||
1190              base->is_DecodeN() && base->in(1)->is_Load()) {
1191     // Eliminate the load of boxed value for integer types from the cache
1192     // array by deriving the value from the index into the array.
1193     // Capture the offset of the load and then reverse the computation.
1194 
1195     // Get LoadN node which loads a boxing object from 'cache' array.
1196     if (base->is_DecodeN()) {
1197       base = base->in(1);
1198     }
1199     if (!base->in(Address)->is_AddP()) {
1200       return NULL; // Complex address
1201     }
1202     AddPNode* address = base->in(Address)->as_AddP();
1203     Node* cache_base = address->in(AddPNode::Base);
1204     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1205       // Get ConP node which is static 'cache' field.
1206       cache_base = cache_base->in(1);
1207     }
1208     if ((cache_base != NULL) && cache_base->is_Con()) {
1209       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1210       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1211         Node* elements[4];
1212         int shift = exact_log2(type2aelembytes(T_OBJECT));
1213         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1214         if ((count >  0) && elements[0]->is_Con() &&
1215             ((count == 1) ||
1216              (count == 2) && elements[1]->Opcode() == Op_LShiftX &&
1217                              elements[1]->in(2) == phase->intcon(shift))) {
1218           ciObjArray* array = base_type->const_oop()->as_obj_array();
1219           // Fetch the box object cache[0] at the base of the array and get its value
1220           ciInstance* box = array->obj_at(0)->as_instance();
1221           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1222           assert(ik->is_box_klass(), "sanity");
1223           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1224           if (ik->nof_nonstatic_fields() == 1) {
1225             // This should be true nonstatic_field_at requires calling
1226             // nof_nonstatic_fields so check it anyway
1227             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1228             BasicType bt = c.basic_type();
1229             // Only integer types have boxing cache.
1230             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1231                    bt == T_BYTE    || bt == T_SHORT ||
1232                    bt == T_INT     || bt == T_LONG, err_msg_res("wrong type = %s", type2name(bt)));
1233             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1234             if (cache_low != (int)cache_low) {
1235               return NULL; // should not happen since cache is array indexed by value
1236             }
1237             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1238             if (offset != (int)offset) {
1239               return NULL; // should not happen since cache is array indexed by value
1240             }
1241            // Add up all the offsets making of the address of the load
1242             Node* result = elements[0];
1243             for (int i = 1; i < count; i++) {
1244               result = phase->transform(new (phase->C) AddXNode(result, elements[i]));
1245             }
1246             // Remove the constant offset from the address and then
1247             result = phase->transform(new (phase->C) AddXNode(result, phase->MakeConX(-(int)offset)));
1248             // remove the scaling of the offset to recover the original index.
1249             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1250               // Peel the shift off directly but wrap it in a dummy node
1251               // since Ideal can't return existing nodes
1252               result = new (phase->C) RShiftXNode(result->in(1), phase->intcon(0));
1253             } else if (result->is_Add() && result->in(2)->is_Con() &&
1254                        result->in(1)->Opcode() == Op_LShiftX &&
1255                        result->in(1)->in(2) == phase->intcon(shift)) {
1256               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1257               // but for boxing cache access we know that X<<Z will not overflow
1258               // (there is range check) so we do this optimizatrion by hand here.
1259               Node* add_con = new (phase->C) RShiftXNode(result->in(2), phase->intcon(shift));
1260               result = new (phase->C) AddXNode(result->in(1)->in(1), phase->transform(add_con));
1261             } else {
1262               result = new (phase->C) RShiftXNode(result, phase->intcon(shift));
1263             }
1264 #ifdef _LP64
1265             if (bt != T_LONG) {
1266               result = new (phase->C) ConvL2INode(phase->transform(result));
1267             }
1268 #else
1269             if (bt == T_LONG) {
1270               result = new (phase->C) ConvI2LNode(phase->transform(result));
1271             }
1272 #endif
1273             return result;
1274           }
1275         }
1276       }
1277     }
1278   }
1279   return NULL;
1280 }
1281 
1282 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1283   Node* region = phi->in(0);
1284   if (region == NULL) {
1285     return false; // Wait stable graph
1286   }
1287   uint cnt = phi->req();
1288   for (uint i = 1; i < cnt; i++) {
1289     Node* rc = region->in(i);
1290     if (rc == NULL || phase->type(rc) == Type::TOP)
1291       return false; // Wait stable graph
1292     Node* in = phi->in(i);
1293     if (in == NULL || phase->type(in) == Type::TOP)
1294       return false; // Wait stable graph
1295   }
1296   return true;
1297 }
1298 //------------------------------split_through_phi------------------------------
1299 // Split instance or boxed field load through Phi.
1300 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1301   Node* mem     = in(Memory);
1302   Node* address = in(Address);
1303   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1304 
1305   assert((t_oop != NULL) &&
1306          (t_oop->is_known_instance_field() ||
1307           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1308 
1309   Compile* C = phase->C;
1310   intptr_t ignore = 0;
1311   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1312   bool base_is_phi = (base != NULL) && base->is_Phi();
1313   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1314                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1315                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1316 
1317   if (!((mem->is_Phi() || base_is_phi) &&
1318         (load_boxed_values || t_oop->is_known_instance_field()))) {
1319     return NULL; // memory is not Phi
1320   }
1321 
1322   if (mem->is_Phi()) {
1323     if (!stable_phi(mem->as_Phi(), phase)) {
1324       return NULL; // Wait stable graph
1325     }
1326     uint cnt = mem->req();
1327     // Check for loop invariant memory.
1328     if (cnt == 3) {
1329       for (uint i = 1; i < cnt; i++) {
1330         Node* in = mem->in(i);
1331         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1332         if (m == mem) {
1333           set_req(Memory, mem->in(cnt - i));
1334           return this; // made change
1335         }
1336       }
1337     }
1338   }
1339   if (base_is_phi) {
1340     if (!stable_phi(base->as_Phi(), phase)) {
1341       return NULL; // Wait stable graph
1342     }
1343     uint cnt = base->req();
1344     // Check for loop invariant memory.
1345     if (cnt == 3) {
1346       for (uint i = 1; i < cnt; i++) {
1347         if (base->in(i) == base) {
1348           return NULL; // Wait stable graph
1349         }
1350       }
1351     }
1352   }
1353 
1354   bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1355 
1356   // Split through Phi (see original code in loopopts.cpp).
1357   assert(C->have_alias_type(t_oop), "instance should have alias type");
1358 
1359   // Do nothing here if Identity will find a value
1360   // (to avoid infinite chain of value phis generation).
1361   if (!phase->eqv(this, this->Identity(phase)))
1362     return NULL;
1363 
1364   // Select Region to split through.
1365   Node* region;
1366   if (!base_is_phi) {
1367     assert(mem->is_Phi(), "sanity");
1368     region = mem->in(0);
1369     // Skip if the region dominates some control edge of the address.
1370     if (!MemNode::all_controls_dominate(address, region))
1371       return NULL;
1372   } else if (!mem->is_Phi()) {
1373     assert(base_is_phi, "sanity");
1374     region = base->in(0);
1375     // Skip if the region dominates some control edge of the memory.
1376     if (!MemNode::all_controls_dominate(mem, region))
1377       return NULL;
1378   } else if (base->in(0) != mem->in(0)) {
1379     assert(base_is_phi && mem->is_Phi(), "sanity");
1380     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1381       region = base->in(0);
1382     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1383       region = mem->in(0);
1384     } else {
1385       return NULL; // complex graph
1386     }
1387   } else {
1388     assert(base->in(0) == mem->in(0), "sanity");
1389     region = mem->in(0);
1390   }
1391 
1392   const Type* this_type = this->bottom_type();
1393   int this_index  = C->get_alias_index(t_oop);
1394   int this_offset = t_oop->offset();
1395   int this_iid    = t_oop->instance_id();
1396   if (!t_oop->is_known_instance() && load_boxed_values) {
1397     // Use _idx of address base for boxed values.
1398     this_iid = base->_idx;
1399   }
1400   PhaseIterGVN* igvn = phase->is_IterGVN();
1401   Node* phi = new (C) PhiNode(region, this_type, NULL, this_iid, this_index, this_offset);
1402   for (uint i = 1; i < region->req(); i++) {
1403     Node* x;
1404     Node* the_clone = NULL;
1405     if (region->in(i) == C->top()) {
1406       x = C->top();      // Dead path?  Use a dead data op
1407     } else {
1408       x = this->clone();        // Else clone up the data op
1409       the_clone = x;            // Remember for possible deletion.
1410       // Alter data node to use pre-phi inputs
1411       if (this->in(0) == region) {
1412         x->set_req(0, region->in(i));
1413       } else {
1414         x->set_req(0, NULL);
1415       }
1416       if (mem->is_Phi() && (mem->in(0) == region)) {
1417         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1418       }
1419       if (address->is_Phi() && address->in(0) == region) {
1420         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1421       }
1422       if (base_is_phi && (base->in(0) == region)) {
1423         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1424         Node* adr_x = phase->transform(new (C) AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1425         x->set_req(Address, adr_x);
1426       }
1427     }
1428     // Check for a 'win' on some paths
1429     const Type *t = x->Value(igvn);
1430 
1431     bool singleton = t->singleton();
1432 
1433     // See comments in PhaseIdealLoop::split_thru_phi().
1434     if (singleton && t == Type::TOP) {
1435       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1436     }
1437 
1438     if (singleton) {
1439       x = igvn->makecon(t);
1440     } else {
1441       // We now call Identity to try to simplify the cloned node.
1442       // Note that some Identity methods call phase->type(this).
1443       // Make sure that the type array is big enough for
1444       // our new node, even though we may throw the node away.
1445       // (This tweaking with igvn only works because x is a new node.)
1446       igvn->set_type(x, t);
1447       // If x is a TypeNode, capture any more-precise type permanently into Node
1448       // otherwise it will be not updated during igvn->transform since
1449       // igvn->type(x) is set to x->Value() already.
1450       x->raise_bottom_type(t);
1451       Node *y = x->Identity(igvn);
1452       if (y != x) {
1453         x = y;
1454       } else {
1455         y = igvn->hash_find_insert(x);
1456         if (y) {
1457           x = y;
1458         } else {
1459           // Else x is a new node we are keeping
1460           // We do not need register_new_node_with_optimizer
1461           // because set_type has already been called.
1462           igvn->_worklist.push(x);
1463         }
1464       }
1465     }
1466     if (x != the_clone && the_clone != NULL) {
1467       igvn->remove_dead_node(the_clone);
1468     }
1469     phi->set_req(i, x);
1470   }
1471   // Record Phi
1472   igvn->register_new_node_with_optimizer(phi);
1473   return phi;
1474 }
1475 
1476 //------------------------------Ideal------------------------------------------
1477 // If the load is from Field memory and the pointer is non-null, we can
1478 // zero out the control input.
1479 // If the offset is constant and the base is an object allocation,
1480 // try to hook me up to the exact initializing store.
1481 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1482   Node* p = MemNode::Ideal_common(phase, can_reshape);
1483   if (p)  return (p == NodeSentinel) ? NULL : p;
1484 
1485   Node* ctrl    = in(MemNode::Control);
1486   Node* address = in(MemNode::Address);
1487 
1488   // Skip up past a SafePoint control.  Cannot do this for Stores because
1489   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1490   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1491       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
1492     ctrl = ctrl->in(0);
1493     set_req(MemNode::Control,ctrl);
1494   }
1495 
1496   intptr_t ignore = 0;
1497   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1498   if (base != NULL
1499       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1500     // Check for useless control edge in some common special cases
1501     if (in(MemNode::Control) != NULL
1502         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1503         && all_controls_dominate(base, phase->C->start())) {
1504       // A method-invariant, non-null address (constant or 'this' argument).
1505       set_req(MemNode::Control, NULL);
1506     }
1507   }
1508 
1509   Node* mem = in(MemNode::Memory);
1510   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1511 
1512   if (can_reshape && (addr_t != NULL)) {
1513     // try to optimize our memory input
1514     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1515     if (opt_mem != mem) {
1516       set_req(MemNode::Memory, opt_mem);
1517       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1518       return this;
1519     }
1520     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1521     if ((t_oop != NULL) &&
1522         (t_oop->is_known_instance_field() ||
1523          t_oop->is_ptr_to_boxed_value())) {
1524       PhaseIterGVN *igvn = phase->is_IterGVN();
1525       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1526         // Delay this transformation until memory Phi is processed.
1527         phase->is_IterGVN()->_worklist.push(this);
1528         return NULL;
1529       }
1530       // Split instance field load through Phi.
1531       Node* result = split_through_phi(phase);
1532       if (result != NULL) return result;
1533 
1534       if (t_oop->is_ptr_to_boxed_value()) {
1535         Node* result = eliminate_autobox(phase);
1536         if (result != NULL) return result;
1537       }
1538     }
1539   }
1540 
1541   // Check for prior store with a different base or offset; make Load
1542   // independent.  Skip through any number of them.  Bail out if the stores
1543   // are in an endless dead cycle and report no progress.  This is a key
1544   // transform for Reflection.  However, if after skipping through the Stores
1545   // we can't then fold up against a prior store do NOT do the transform as
1546   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1547   // array memory alive twice: once for the hoisted Load and again after the
1548   // bypassed Store.  This situation only works if EVERYBODY who does
1549   // anti-dependence work knows how to bypass.  I.e. we need all
1550   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1551   // the alias index stuff.  So instead, peek through Stores and IFF we can
1552   // fold up, do so.
1553   Node* prev_mem = find_previous_store(phase);
1554   // Steps (a), (b):  Walk past independent stores to find an exact match.
1555   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1556     // (c) See if we can fold up on the spot, but don't fold up here.
1557     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1558     // just return a prior value, which is done by Identity calls.
1559     if (can_see_stored_value(prev_mem, phase)) {
1560       // Make ready for step (d):
1561       set_req(MemNode::Memory, prev_mem);
1562       return this;
1563     }
1564   }
1565 
1566   return NULL;                  // No further progress
1567 }
1568 
1569 // Helper to recognize certain Klass fields which are invariant across
1570 // some group of array types (e.g., int[] or all T[] where T < Object).
1571 const Type*
1572 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1573                                  ciKlass* klass) const {
1574   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1575     // The field is Klass::_modifier_flags.  Return its (constant) value.
1576     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1577     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1578     return TypeInt::make(klass->modifier_flags());
1579   }
1580   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1581     // The field is Klass::_access_flags.  Return its (constant) value.
1582     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1583     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1584     return TypeInt::make(klass->access_flags());
1585   }
1586   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1587     // The field is Klass::_layout_helper.  Return its constant value if known.
1588     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1589     return TypeInt::make(klass->layout_helper());
1590   }
1591 
1592   // No match.
1593   return NULL;
1594 }
1595 
1596 // Try to constant-fold a stable array element.
1597 static const Type* fold_stable_ary_elem(const TypeAryPtr* ary, int off, BasicType loadbt) {
1598   assert(ary->const_oop(), "array should be constant");
1599   assert(ary->is_stable(), "array should be stable");
1600 
1601   // Decode the results of GraphKit::array_element_address.
1602   ciArray* aobj = ary->const_oop()->as_array();
1603   ciConstant con = aobj->element_value_by_offset(off);
1604 
1605   if (con.basic_type() != T_ILLEGAL && !con.is_null_or_zero()) {
1606     const Type* con_type = Type::make_from_constant(con);
1607     if (con_type != NULL) {
1608       if (con_type->isa_aryptr()) {
1609         // Join with the array element type, in case it is also stable.
1610         int dim = ary->stable_dimension();
1611         con_type = con_type->is_aryptr()->cast_to_stable(true, dim-1);
1612       }
1613       if (loadbt == T_NARROWOOP && con_type->isa_oopptr()) {
1614         con_type = con_type->make_narrowoop();
1615       }
1616 #ifndef PRODUCT
1617       if (TraceIterativeGVN) {
1618         tty->print("FoldStableValues: array element [off=%d]: con_type=", off);
1619         con_type->dump(); tty->cr();
1620       }
1621 #endif //PRODUCT
1622       return con_type;
1623     }
1624   }
1625   return NULL;
1626 }
1627 
1628 //------------------------------Value-----------------------------------------
1629 const Type *LoadNode::Value( PhaseTransform *phase ) const {
1630   // Either input is TOP ==> the result is TOP
1631   Node* mem = in(MemNode::Memory);
1632   const Type *t1 = phase->type(mem);
1633   if (t1 == Type::TOP)  return Type::TOP;
1634   Node* adr = in(MemNode::Address);
1635   const TypePtr* tp = phase->type(adr)->isa_ptr();
1636   if (tp == NULL || tp->empty())  return Type::TOP;
1637   int off = tp->offset();
1638   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1639   Compile* C = phase->C;
1640 
1641   // Try to guess loaded type from pointer type
1642   if (tp->isa_aryptr()) {
1643     const TypeAryPtr* ary = tp->is_aryptr();
1644     const Type* t = ary->elem();
1645 
1646     // Determine whether the reference is beyond the header or not, by comparing
1647     // the offset against the offset of the start of the array's data.
1648     // Different array types begin at slightly different offsets (12 vs. 16).
1649     // We choose T_BYTE as an example base type that is least restrictive
1650     // as to alignment, which will therefore produce the smallest
1651     // possible base offset.
1652     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1653     const bool off_beyond_header = ((uint)off >= (uint)min_base_off);
1654 
1655     // Try to constant-fold a stable array element.
1656     if (FoldStableValues && ary->is_stable() && ary->const_oop() != NULL) {
1657       // Make sure the reference is not into the header and the offset is constant
1658       if (off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1659         const Type* con_type = fold_stable_ary_elem(ary, off, memory_type());
1660         if (con_type != NULL) {
1661           return con_type;
1662         }
1663       }
1664     }
1665 
1666     // Don't do this for integer types. There is only potential profit if
1667     // the element type t is lower than _type; that is, for int types, if _type is
1668     // more restrictive than t.  This only happens here if one is short and the other
1669     // char (both 16 bits), and in those cases we've made an intentional decision
1670     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1671     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1672     //
1673     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1674     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1675     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1676     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1677     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1678     // In fact, that could have been the original type of p1, and p1 could have
1679     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1680     // expression (LShiftL quux 3) independently optimized to the constant 8.
1681     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1682         && (_type->isa_vect() == NULL)
1683         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1684       // t might actually be lower than _type, if _type is a unique
1685       // concrete subclass of abstract class t.
1686       if (off_beyond_header) {  // is the offset beyond the header?
1687         const Type* jt = t->join_speculative(_type);
1688         // In any case, do not allow the join, per se, to empty out the type.
1689         if (jt->empty() && !t->empty()) {
1690           // This can happen if a interface-typed array narrows to a class type.
1691           jt = _type;
1692         }
1693 #ifdef ASSERT
1694         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1695           // The pointers in the autobox arrays are always non-null
1696           Node* base = adr->in(AddPNode::Base);
1697           if ((base != NULL) && base->is_DecodeN()) {
1698             // Get LoadN node which loads IntegerCache.cache field
1699             base = base->in(1);
1700           }
1701           if ((base != NULL) && base->is_Con()) {
1702             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1703             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1704               // It could be narrow oop
1705               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1706             }
1707           }
1708         }
1709 #endif
1710         return jt;
1711       }
1712     }
1713   } else if (tp->base() == Type::InstPtr) {
1714     ciEnv* env = C->env();
1715     const TypeInstPtr* tinst = tp->is_instptr();
1716     ciKlass* klass = tinst->klass();
1717     assert( off != Type::OffsetBot ||
1718             // arrays can be cast to Objects
1719             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1720             // unsafe field access may not have a constant offset
1721             C->has_unsafe_access(),
1722             "Field accesses must be precise" );
1723     // For oop loads, we expect the _type to be precise
1724     if (klass == env->String_klass() &&
1725         adr->is_AddP() && off != Type::OffsetBot) {
1726       // For constant Strings treat the final fields as compile time constants.
1727       Node* base = adr->in(AddPNode::Base);
1728       const TypeOopPtr* t = phase->type(base)->isa_oopptr();
1729       if (t != NULL && t->singleton()) {
1730         ciField* field = env->String_klass()->get_field_by_offset(off, false);
1731         if (field != NULL && field->is_final()) {
1732           ciObject* string = t->const_oop();
1733           ciConstant constant = string->as_instance()->field_value(field);
1734           if (constant.basic_type() == T_INT) {
1735             return TypeInt::make(constant.as_int());
1736           } else if (constant.basic_type() == T_ARRAY) {
1737             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1738               return TypeNarrowOop::make_from_constant(constant.as_object(), true);
1739             } else {
1740               return TypeOopPtr::make_from_constant(constant.as_object(), true);
1741             }
1742           }
1743         }
1744       }
1745     }
1746     // Optimizations for constant objects
1747     ciObject* const_oop = tinst->const_oop();
1748     if (const_oop != NULL) {
1749       // For constant Boxed value treat the target field as a compile time constant.
1750       if (tinst->is_ptr_to_boxed_value()) {
1751         return tinst->get_const_boxed_value();
1752       } else
1753       // For constant CallSites treat the target field as a compile time constant.
1754       if (const_oop->is_call_site()) {
1755         ciCallSite* call_site = const_oop->as_call_site();
1756         ciField* field = call_site->klass()->as_instance_klass()->get_field_by_offset(off, /*is_static=*/ false);
1757         if (field != NULL && field->is_call_site_target()) {
1758           ciMethodHandle* target = call_site->get_target();
1759           if (target != NULL) {  // just in case
1760             ciConstant constant(T_OBJECT, target);
1761             const Type* t;
1762             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1763               t = TypeNarrowOop::make_from_constant(constant.as_object(), true);
1764             } else {
1765               t = TypeOopPtr::make_from_constant(constant.as_object(), true);
1766             }
1767             // Add a dependence for invalidation of the optimization.
1768             if (!call_site->is_constant_call_site()) {
1769               C->dependencies()->assert_call_site_target_value(call_site, target);
1770             }
1771             return t;
1772           }
1773         }
1774       }
1775     }
1776   } else if (tp->base() == Type::KlassPtr) {
1777     assert( off != Type::OffsetBot ||
1778             // arrays can be cast to Objects
1779             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1780             // also allow array-loading from the primary supertype
1781             // array during subtype checks
1782             Opcode() == Op_LoadKlass,
1783             "Field accesses must be precise" );
1784     // For klass/static loads, we expect the _type to be precise
1785   }
1786 
1787   const TypeKlassPtr *tkls = tp->isa_klassptr();
1788   if (tkls != NULL && !StressReflectiveCode) {
1789     ciKlass* klass = tkls->klass();
1790     if (klass->is_loaded() && tkls->klass_is_exact()) {
1791       // We are loading a field from a Klass metaobject whose identity
1792       // is known at compile time (the type is "exact" or "precise").
1793       // Check for fields we know are maintained as constants by the VM.
1794       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1795         // The field is Klass::_super_check_offset.  Return its (constant) value.
1796         // (Folds up type checking code.)
1797         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1798         return TypeInt::make(klass->super_check_offset());
1799       }
1800       // Compute index into primary_supers array
1801       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1802       // Check for overflowing; use unsigned compare to handle the negative case.
1803       if( depth < ciKlass::primary_super_limit() ) {
1804         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1805         // (Folds up type checking code.)
1806         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1807         ciKlass *ss = klass->super_of_depth(depth);
1808         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1809       }
1810       const Type* aift = load_array_final_field(tkls, klass);
1811       if (aift != NULL)  return aift;
1812       if (tkls->offset() == in_bytes(ArrayKlass::component_mirror_offset())
1813           && klass->is_array_klass()) {
1814         // The field is ArrayKlass::_component_mirror.  Return its (constant) value.
1815         // (Folds up aClassConstant.getComponentType, common in Arrays.copyOf.)
1816         assert(Opcode() == Op_LoadP, "must load an oop from _component_mirror");
1817         return TypeInstPtr::make(klass->as_array_klass()->component_mirror());
1818       }
1819       if (tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1820         // The field is Klass::_java_mirror.  Return its (constant) value.
1821         // (Folds up the 2nd indirection in anObjConstant.getClass().)
1822         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1823         return TypeInstPtr::make(klass->java_mirror());
1824       }
1825     }
1826 
1827     // We can still check if we are loading from the primary_supers array at a
1828     // shallow enough depth.  Even though the klass is not exact, entries less
1829     // than or equal to its super depth are correct.
1830     if (klass->is_loaded() ) {
1831       ciType *inner = klass;
1832       while( inner->is_obj_array_klass() )
1833         inner = inner->as_obj_array_klass()->base_element_type();
1834       if( inner->is_instance_klass() &&
1835           !inner->as_instance_klass()->flags().is_interface() ) {
1836         // Compute index into primary_supers array
1837         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1838         // Check for overflowing; use unsigned compare to handle the negative case.
1839         if( depth < ciKlass::primary_super_limit() &&
1840             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1841           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1842           // (Folds up type checking code.)
1843           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1844           ciKlass *ss = klass->super_of_depth(depth);
1845           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1846         }
1847       }
1848     }
1849 
1850     // If the type is enough to determine that the thing is not an array,
1851     // we can give the layout_helper a positive interval type.
1852     // This will help short-circuit some reflective code.
1853     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1854         && !klass->is_array_klass() // not directly typed as an array
1855         && !klass->is_interface()  // specifically not Serializable & Cloneable
1856         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1857         ) {
1858       // Note:  When interfaces are reliable, we can narrow the interface
1859       // test to (klass != Serializable && klass != Cloneable).
1860       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1861       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1862       // The key property of this type is that it folds up tests
1863       // for array-ness, since it proves that the layout_helper is positive.
1864       // Thus, a generic value like the basic object layout helper works fine.
1865       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1866     }
1867   }
1868 
1869   // If we are loading from a freshly-allocated object, produce a zero,
1870   // if the load is provably beyond the header of the object.
1871   // (Also allow a variable load from a fresh array to produce zero.)
1872   const TypeOopPtr *tinst = tp->isa_oopptr();
1873   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1874   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1875   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1876     Node* value = can_see_stored_value(mem,phase);
1877     if (value != NULL && value->is_Con()) {
1878       assert(value->bottom_type()->higher_equal(_type),"sanity");
1879       return value->bottom_type();
1880     }
1881   }
1882 
1883   if (is_instance) {
1884     // If we have an instance type and our memory input is the
1885     // programs's initial memory state, there is no matching store,
1886     // so just return a zero of the appropriate type
1887     Node *mem = in(MemNode::Memory);
1888     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1889       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1890       return Type::get_zero_type(_type->basic_type());
1891     }
1892   }
1893   return _type;
1894 }
1895 
1896 //------------------------------match_edge-------------------------------------
1897 // Do we Match on this edge index or not?  Match only the address.
1898 uint LoadNode::match_edge(uint idx) const {
1899   return idx == MemNode::Address;
1900 }
1901 
1902 //--------------------------LoadBNode::Ideal--------------------------------------
1903 //
1904 //  If the previous store is to the same address as this load,
1905 //  and the value stored was larger than a byte, replace this load
1906 //  with the value stored truncated to a byte.  If no truncation is
1907 //  needed, the replacement is done in LoadNode::Identity().
1908 //
1909 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1910   Node* mem = in(MemNode::Memory);
1911   Node* value = can_see_stored_value(mem,phase);
1912   if( value && !phase->type(value)->higher_equal( _type ) ) {
1913     Node *result = phase->transform( new (phase->C) LShiftINode(value, phase->intcon(24)) );
1914     return new (phase->C) RShiftINode(result, phase->intcon(24));
1915   }
1916   // Identity call will handle the case where truncation is not needed.
1917   return LoadNode::Ideal(phase, can_reshape);
1918 }
1919 
1920 const Type* LoadBNode::Value(PhaseTransform *phase) const {
1921   Node* mem = in(MemNode::Memory);
1922   Node* value = can_see_stored_value(mem,phase);
1923   if (value != NULL && value->is_Con() &&
1924       !value->bottom_type()->higher_equal(_type)) {
1925     // If the input to the store does not fit with the load's result type,
1926     // it must be truncated. We can't delay until Ideal call since
1927     // a singleton Value is needed for split_thru_phi optimization.
1928     int con = value->get_int();
1929     return TypeInt::make((con << 24) >> 24);
1930   }
1931   return LoadNode::Value(phase);
1932 }
1933 
1934 //--------------------------LoadUBNode::Ideal-------------------------------------
1935 //
1936 //  If the previous store is to the same address as this load,
1937 //  and the value stored was larger than a byte, replace this load
1938 //  with the value stored truncated to a byte.  If no truncation is
1939 //  needed, the replacement is done in LoadNode::Identity().
1940 //
1941 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1942   Node* mem = in(MemNode::Memory);
1943   Node* value = can_see_stored_value(mem, phase);
1944   if (value && !phase->type(value)->higher_equal(_type))
1945     return new (phase->C) AndINode(value, phase->intcon(0xFF));
1946   // Identity call will handle the case where truncation is not needed.
1947   return LoadNode::Ideal(phase, can_reshape);
1948 }
1949 
1950 const Type* LoadUBNode::Value(PhaseTransform *phase) const {
1951   Node* mem = in(MemNode::Memory);
1952   Node* value = can_see_stored_value(mem,phase);
1953   if (value != NULL && value->is_Con() &&
1954       !value->bottom_type()->higher_equal(_type)) {
1955     // If the input to the store does not fit with the load's result type,
1956     // it must be truncated. We can't delay until Ideal call since
1957     // a singleton Value is needed for split_thru_phi optimization.
1958     int con = value->get_int();
1959     return TypeInt::make(con & 0xFF);
1960   }
1961   return LoadNode::Value(phase);
1962 }
1963 
1964 //--------------------------LoadUSNode::Ideal-------------------------------------
1965 //
1966 //  If the previous store is to the same address as this load,
1967 //  and the value stored was larger than a char, replace this load
1968 //  with the value stored truncated to a char.  If no truncation is
1969 //  needed, the replacement is done in LoadNode::Identity().
1970 //
1971 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1972   Node* mem = in(MemNode::Memory);
1973   Node* value = can_see_stored_value(mem,phase);
1974   if( value && !phase->type(value)->higher_equal( _type ) )
1975     return new (phase->C) AndINode(value,phase->intcon(0xFFFF));
1976   // Identity call will handle the case where truncation is not needed.
1977   return LoadNode::Ideal(phase, can_reshape);
1978 }
1979 
1980 const Type* LoadUSNode::Value(PhaseTransform *phase) const {
1981   Node* mem = in(MemNode::Memory);
1982   Node* value = can_see_stored_value(mem,phase);
1983   if (value != NULL && value->is_Con() &&
1984       !value->bottom_type()->higher_equal(_type)) {
1985     // If the input to the store does not fit with the load's result type,
1986     // it must be truncated. We can't delay until Ideal call since
1987     // a singleton Value is needed for split_thru_phi optimization.
1988     int con = value->get_int();
1989     return TypeInt::make(con & 0xFFFF);
1990   }
1991   return LoadNode::Value(phase);
1992 }
1993 
1994 //--------------------------LoadSNode::Ideal--------------------------------------
1995 //
1996 //  If the previous store is to the same address as this load,
1997 //  and the value stored was larger than a short, replace this load
1998 //  with the value stored truncated to a short.  If no truncation is
1999 //  needed, the replacement is done in LoadNode::Identity().
2000 //
2001 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2002   Node* mem = in(MemNode::Memory);
2003   Node* value = can_see_stored_value(mem,phase);
2004   if( value && !phase->type(value)->higher_equal( _type ) ) {
2005     Node *result = phase->transform( new (phase->C) LShiftINode(value, phase->intcon(16)) );
2006     return new (phase->C) RShiftINode(result, phase->intcon(16));
2007   }
2008   // Identity call will handle the case where truncation is not needed.
2009   return LoadNode::Ideal(phase, can_reshape);
2010 }
2011 
2012 const Type* LoadSNode::Value(PhaseTransform *phase) const {
2013   Node* mem = in(MemNode::Memory);
2014   Node* value = can_see_stored_value(mem,phase);
2015   if (value != NULL && value->is_Con() &&
2016       !value->bottom_type()->higher_equal(_type)) {
2017     // If the input to the store does not fit with the load's result type,
2018     // it must be truncated. We can't delay until Ideal call since
2019     // a singleton Value is needed for split_thru_phi optimization.
2020     int con = value->get_int();
2021     return TypeInt::make((con << 16) >> 16);
2022   }
2023   return LoadNode::Value(phase);
2024 }
2025 
2026 //=============================================================================
2027 //----------------------------LoadKlassNode::make------------------------------
2028 // Polymorphic factory method:
2029 Node *LoadKlassNode::make( PhaseGVN& gvn, Node *mem, Node *adr, const TypePtr* at, const TypeKlassPtr *tk ) {
2030   Compile* C = gvn.C;
2031   Node *ctl = NULL;
2032   // sanity check the alias category against the created node type
2033   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2034   assert(adr_type != NULL, "expecting TypeKlassPtr");
2035 #ifdef _LP64
2036   if (adr_type->is_ptr_to_narrowklass()) {
2037     assert(UseCompressedClassPointers, "no compressed klasses");
2038     Node* load_klass = gvn.transform(new (C) LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2039     return new (C) DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2040   }
2041 #endif
2042   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2043   return new (C) LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2044 }
2045 
2046 //------------------------------Value------------------------------------------
2047 const Type *LoadKlassNode::Value( PhaseTransform *phase ) const {
2048   return klass_value_common(phase);
2049 }
2050 
2051 const Type *LoadNode::klass_value_common( PhaseTransform *phase ) const {
2052   // Either input is TOP ==> the result is TOP
2053   const Type *t1 = phase->type( in(MemNode::Memory) );
2054   if (t1 == Type::TOP)  return Type::TOP;
2055   Node *adr = in(MemNode::Address);
2056   const Type *t2 = phase->type( adr );
2057   if (t2 == Type::TOP)  return Type::TOP;
2058   const TypePtr *tp = t2->is_ptr();
2059   if (TypePtr::above_centerline(tp->ptr()) ||
2060       tp->ptr() == TypePtr::Null)  return Type::TOP;
2061 
2062   // Return a more precise klass, if possible
2063   const TypeInstPtr *tinst = tp->isa_instptr();
2064   if (tinst != NULL) {
2065     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2066     int offset = tinst->offset();
2067     if (ik == phase->C->env()->Class_klass()
2068         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2069             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2070       // We are loading a special hidden field from a Class mirror object,
2071       // the field which points to the VM's Klass metaobject.
2072       ciType* t = tinst->java_mirror_type();
2073       // java_mirror_type returns non-null for compile-time Class constants.
2074       if (t != NULL) {
2075         // constant oop => constant klass
2076         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2077           if (t->is_void()) {
2078             // We cannot create a void array.  Since void is a primitive type return null
2079             // klass.  Users of this result need to do a null check on the returned klass.
2080             return TypePtr::NULL_PTR;
2081           }
2082           return TypeKlassPtr::make(ciArrayKlass::make(t));
2083         }
2084         if (!t->is_klass()) {
2085           // a primitive Class (e.g., int.class) has NULL for a klass field
2086           return TypePtr::NULL_PTR;
2087         }
2088         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2089         return TypeKlassPtr::make(t->as_klass());
2090       }
2091       // non-constant mirror, so we can't tell what's going on
2092     }
2093     if( !ik->is_loaded() )
2094       return _type;             // Bail out if not loaded
2095     if (offset == oopDesc::klass_offset_in_bytes()) {
2096       if (tinst->klass_is_exact()) {
2097         return TypeKlassPtr::make(ik);
2098       }
2099       // See if we can become precise: no subklasses and no interface
2100       // (Note:  We need to support verified interfaces.)
2101       if (!ik->is_interface() && !ik->has_subklass()) {
2102         //assert(!UseExactTypes, "this code should be useless with exact types");
2103         // Add a dependence; if any subclass added we need to recompile
2104         if (!ik->is_final()) {
2105           // %%% should use stronger assert_unique_concrete_subtype instead
2106           phase->C->dependencies()->assert_leaf_type(ik);
2107         }
2108         // Return precise klass
2109         return TypeKlassPtr::make(ik);
2110       }
2111 
2112       // Return root of possible klass
2113       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2114     }
2115   }
2116 
2117   // Check for loading klass from an array
2118   const TypeAryPtr *tary = tp->isa_aryptr();
2119   if( tary != NULL ) {
2120     ciKlass *tary_klass = tary->klass();
2121     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2122         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2123       if (tary->klass_is_exact()) {
2124         return TypeKlassPtr::make(tary_klass);
2125       }
2126       ciArrayKlass *ak = tary->klass()->as_array_klass();
2127       // If the klass is an object array, we defer the question to the
2128       // array component klass.
2129       if( ak->is_obj_array_klass() ) {
2130         assert( ak->is_loaded(), "" );
2131         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2132         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2133           ciInstanceKlass* ik = base_k->as_instance_klass();
2134           // See if we can become precise: no subklasses and no interface
2135           if (!ik->is_interface() && !ik->has_subklass()) {
2136             //assert(!UseExactTypes, "this code should be useless with exact types");
2137             // Add a dependence; if any subclass added we need to recompile
2138             if (!ik->is_final()) {
2139               phase->C->dependencies()->assert_leaf_type(ik);
2140             }
2141             // Return precise array klass
2142             return TypeKlassPtr::make(ak);
2143           }
2144         }
2145         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2146       } else {                  // Found a type-array?
2147         //assert(!UseExactTypes, "this code should be useless with exact types");
2148         assert( ak->is_type_array_klass(), "" );
2149         return TypeKlassPtr::make(ak); // These are always precise
2150       }
2151     }
2152   }
2153 
2154   // Check for loading klass from an array klass
2155   const TypeKlassPtr *tkls = tp->isa_klassptr();
2156   if (tkls != NULL && !StressReflectiveCode) {
2157     ciKlass* klass = tkls->klass();
2158     if( !klass->is_loaded() )
2159       return _type;             // Bail out if not loaded
2160     if( klass->is_obj_array_klass() &&
2161         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2162       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2163       // // Always returning precise element type is incorrect,
2164       // // e.g., element type could be object and array may contain strings
2165       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2166 
2167       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2168       // according to the element type's subclassing.
2169       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2170     }
2171     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2172         tkls->offset() == in_bytes(Klass::super_offset())) {
2173       ciKlass* sup = klass->as_instance_klass()->super();
2174       // The field is Klass::_super.  Return its (constant) value.
2175       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2176       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2177     }
2178   }
2179 
2180   // Bailout case
2181   return LoadNode::Value(phase);
2182 }
2183 
2184 //------------------------------Identity---------------------------------------
2185 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2186 // Also feed through the klass in Allocate(...klass...)._klass.
2187 Node* LoadKlassNode::Identity( PhaseTransform *phase ) {
2188   return klass_identity_common(phase);
2189 }
2190 
2191 Node* LoadNode::klass_identity_common(PhaseTransform *phase ) {
2192   Node* x = LoadNode::Identity(phase);
2193   if (x != this)  return x;
2194 
2195   // Take apart the address into an oop and and offset.
2196   // Return 'this' if we cannot.
2197   Node*    adr    = in(MemNode::Address);
2198   intptr_t offset = 0;
2199   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2200   if (base == NULL)     return this;
2201   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2202   if (toop == NULL)     return this;
2203 
2204   // We can fetch the klass directly through an AllocateNode.
2205   // This works even if the klass is not constant (clone or newArray).
2206   if (offset == oopDesc::klass_offset_in_bytes()) {
2207     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2208     if (allocated_klass != NULL) {
2209       return allocated_klass;
2210     }
2211   }
2212 
2213   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2214   // Simplify ak.component_mirror.array_klass to plain ak, ak an ArrayKlass.
2215   // See inline_native_Class_query for occurrences of these patterns.
2216   // Java Example:  x.getClass().isAssignableFrom(y)
2217   // Java Example:  Array.newInstance(x.getClass().getComponentType(), n)
2218   //
2219   // This improves reflective code, often making the Class
2220   // mirror go completely dead.  (Current exception:  Class
2221   // mirrors may appear in debug info, but we could clean them out by
2222   // introducing a new debug info operator for Klass*.java_mirror).
2223   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2224       && (offset == java_lang_Class::klass_offset_in_bytes() ||
2225           offset == java_lang_Class::array_klass_offset_in_bytes())) {
2226     // We are loading a special hidden field from a Class mirror,
2227     // the field which points to its Klass or ArrayKlass metaobject.
2228     if (base->is_Load()) {
2229       Node* adr2 = base->in(MemNode::Address);
2230       const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2231       if (tkls != NULL && !tkls->empty()
2232           && (tkls->klass()->is_instance_klass() ||
2233               tkls->klass()->is_array_klass())
2234           && adr2->is_AddP()
2235           ) {
2236         int mirror_field = in_bytes(Klass::java_mirror_offset());
2237         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2238           mirror_field = in_bytes(ArrayKlass::component_mirror_offset());
2239         }
2240         if (tkls->offset() == mirror_field) {
2241           return adr2->in(AddPNode::Base);
2242         }
2243       }
2244     }
2245   }
2246 
2247   return this;
2248 }
2249 
2250 
2251 //------------------------------Value------------------------------------------
2252 const Type *LoadNKlassNode::Value( PhaseTransform *phase ) const {
2253   const Type *t = klass_value_common(phase);
2254   if (t == Type::TOP)
2255     return t;
2256 
2257   return t->make_narrowklass();
2258 }
2259 
2260 //------------------------------Identity---------------------------------------
2261 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2262 // Also feed through the klass in Allocate(...klass...)._klass.
2263 Node* LoadNKlassNode::Identity( PhaseTransform *phase ) {
2264   Node *x = klass_identity_common(phase);
2265 
2266   const Type *t = phase->type( x );
2267   if( t == Type::TOP ) return x;
2268   if( t->isa_narrowklass()) return x;
2269   assert (!t->isa_narrowoop(), "no narrow oop here");
2270 
2271   return phase->transform(new (phase->C) EncodePKlassNode(x, t->make_narrowklass()));
2272 }
2273 
2274 //------------------------------Value-----------------------------------------
2275 const Type *LoadRangeNode::Value( PhaseTransform *phase ) const {
2276   // Either input is TOP ==> the result is TOP
2277   const Type *t1 = phase->type( in(MemNode::Memory) );
2278   if( t1 == Type::TOP ) return Type::TOP;
2279   Node *adr = in(MemNode::Address);
2280   const Type *t2 = phase->type( adr );
2281   if( t2 == Type::TOP ) return Type::TOP;
2282   const TypePtr *tp = t2->is_ptr();
2283   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2284   const TypeAryPtr *tap = tp->isa_aryptr();
2285   if( !tap ) return _type;
2286   return tap->size();
2287 }
2288 
2289 //-------------------------------Ideal---------------------------------------
2290 // Feed through the length in AllocateArray(...length...)._length.
2291 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2292   Node* p = MemNode::Ideal_common(phase, can_reshape);
2293   if (p)  return (p == NodeSentinel) ? NULL : p;
2294 
2295   // Take apart the address into an oop and and offset.
2296   // Return 'this' if we cannot.
2297   Node*    adr    = in(MemNode::Address);
2298   intptr_t offset = 0;
2299   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2300   if (base == NULL)     return NULL;
2301   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2302   if (tary == NULL)     return NULL;
2303 
2304   // We can fetch the length directly through an AllocateArrayNode.
2305   // This works even if the length is not constant (clone or newArray).
2306   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2307     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2308     if (alloc != NULL) {
2309       Node* allocated_length = alloc->Ideal_length();
2310       Node* len = alloc->make_ideal_length(tary, phase);
2311       if (allocated_length != len) {
2312         // New CastII improves on this.
2313         return len;
2314       }
2315     }
2316   }
2317 
2318   return NULL;
2319 }
2320 
2321 //------------------------------Identity---------------------------------------
2322 // Feed through the length in AllocateArray(...length...)._length.
2323 Node* LoadRangeNode::Identity( PhaseTransform *phase ) {
2324   Node* x = LoadINode::Identity(phase);
2325   if (x != this)  return x;
2326 
2327   // Take apart the address into an oop and and offset.
2328   // Return 'this' if we cannot.
2329   Node*    adr    = in(MemNode::Address);
2330   intptr_t offset = 0;
2331   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2332   if (base == NULL)     return this;
2333   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2334   if (tary == NULL)     return this;
2335 
2336   // We can fetch the length directly through an AllocateArrayNode.
2337   // This works even if the length is not constant (clone or newArray).
2338   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2339     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2340     if (alloc != NULL) {
2341       Node* allocated_length = alloc->Ideal_length();
2342       // Do not allow make_ideal_length to allocate a CastII node.
2343       Node* len = alloc->make_ideal_length(tary, phase, false);
2344       if (allocated_length == len) {
2345         // Return allocated_length only if it would not be improved by a CastII.
2346         return allocated_length;
2347       }
2348     }
2349   }
2350 
2351   return this;
2352 
2353 }
2354 
2355 //=============================================================================
2356 //---------------------------StoreNode::make-----------------------------------
2357 // Polymorphic factory method:
2358 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2359   assert((mo == unordered || mo == release), "unexpected");
2360   Compile* C = gvn.C;
2361   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2362          ctl != NULL, "raw memory operations should have control edge");
2363 
2364   switch (bt) {
2365   case T_BOOLEAN:
2366   case T_BYTE:    return new (C) StoreBNode(ctl, mem, adr, adr_type, val, mo);
2367   case T_INT:     return new (C) StoreINode(ctl, mem, adr, adr_type, val, mo);
2368   case T_CHAR:
2369   case T_SHORT:   return new (C) StoreCNode(ctl, mem, adr, adr_type, val, mo);
2370   case T_LONG:    return new (C) StoreLNode(ctl, mem, adr, adr_type, val, mo);
2371   case T_FLOAT:   return new (C) StoreFNode(ctl, mem, adr, adr_type, val, mo);
2372   case T_DOUBLE:  return new (C) StoreDNode(ctl, mem, adr, adr_type, val, mo);
2373   case T_METADATA:
2374   case T_ADDRESS:
2375   case T_OBJECT:
2376 #ifdef _LP64
2377     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2378       val = gvn.transform(new (C) EncodePNode(val, val->bottom_type()->make_narrowoop()));
2379       return new (C) StoreNNode(ctl, mem, adr, adr_type, val, mo);
2380     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2381                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2382                 adr->bottom_type()->isa_rawptr())) {
2383       val = gvn.transform(new (C) EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2384       return new (C) StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2385     }
2386 #endif
2387     {
2388       return new (C) StorePNode(ctl, mem, adr, adr_type, val, mo);
2389     }
2390   }
2391   ShouldNotReachHere();
2392   return (StoreNode*)NULL;
2393 }
2394 
2395 StoreLNode* StoreLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2396   bool require_atomic = true;
2397   return new (C) StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2398 }
2399 
2400 
2401 //--------------------------bottom_type----------------------------------------
2402 const Type *StoreNode::bottom_type() const {
2403   return Type::MEMORY;
2404 }
2405 
2406 //------------------------------hash-------------------------------------------
2407 uint StoreNode::hash() const {
2408   // unroll addition of interesting fields
2409   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2410 
2411   // Since they are not commoned, do not hash them:
2412   return NO_HASH;
2413 }
2414 
2415 //------------------------------Ideal------------------------------------------
2416 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2417 // When a store immediately follows a relevant allocation/initialization,
2418 // try to capture it into the initialization, or hoist it above.
2419 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2420   Node* p = MemNode::Ideal_common(phase, can_reshape);
2421   if (p)  return (p == NodeSentinel) ? NULL : p;
2422 
2423   Node* mem     = in(MemNode::Memory);
2424   Node* address = in(MemNode::Address);
2425 
2426   // Back-to-back stores to same address?  Fold em up.  Generally
2427   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2428   // since they must follow each StoreP operation.  Redundant StoreCMs
2429   // are eliminated just before matching in final_graph_reshape.
2430   if (mem->is_Store() && mem->in(MemNode::Address)->eqv_uncast(address) &&
2431       mem->Opcode() != Op_StoreCM) {
2432     // Looking at a dead closed cycle of memory?
2433     assert(mem != mem->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2434 
2435     assert(Opcode() == mem->Opcode() ||
2436            phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw,
2437            "no mismatched stores, except on raw memory");
2438 
2439     if (mem->outcnt() == 1 &&           // check for intervening uses
2440         mem->as_Store()->memory_size() <= this->memory_size()) {
2441       // If anybody other than 'this' uses 'mem', we cannot fold 'mem' away.
2442       // For example, 'mem' might be the final state at a conditional return.
2443       // Or, 'mem' might be used by some node which is live at the same time
2444       // 'this' is live, which might be unschedulable.  So, require exactly
2445       // ONE user, the 'this' store, until such time as we clone 'mem' for
2446       // each of 'mem's uses (thus making the exactly-1-user-rule hold true).
2447       if (can_reshape) {  // (%%% is this an anachronism?)
2448         set_req_X(MemNode::Memory, mem->in(MemNode::Memory),
2449                   phase->is_IterGVN());
2450       } else {
2451         // It's OK to do this in the parser, since DU info is always accurate,
2452         // and the parser always refers to nodes via SafePointNode maps.
2453         set_req(MemNode::Memory, mem->in(MemNode::Memory));
2454       }
2455       return this;
2456     }
2457   }
2458 
2459   // Capture an unaliased, unconditional, simple store into an initializer.
2460   // Or, if it is independent of the allocation, hoist it above the allocation.
2461   if (ReduceFieldZeroing && /*can_reshape &&*/
2462       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2463     InitializeNode* init = mem->in(0)->as_Initialize();
2464     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2465     if (offset > 0) {
2466       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2467       // If the InitializeNode captured me, it made a raw copy of me,
2468       // and I need to disappear.
2469       if (moved != NULL) {
2470         // %%% hack to ensure that Ideal returns a new node:
2471         mem = MergeMemNode::make(phase->C, mem);
2472         return mem;             // fold me away
2473       }
2474     }
2475   }
2476 
2477   return NULL;                  // No further progress
2478 }
2479 
2480 //------------------------------Value-----------------------------------------
2481 const Type *StoreNode::Value( PhaseTransform *phase ) const {
2482   // Either input is TOP ==> the result is TOP
2483   const Type *t1 = phase->type( in(MemNode::Memory) );
2484   if( t1 == Type::TOP ) return Type::TOP;
2485   const Type *t2 = phase->type( in(MemNode::Address) );
2486   if( t2 == Type::TOP ) return Type::TOP;
2487   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2488   if( t3 == Type::TOP ) return Type::TOP;
2489   return Type::MEMORY;
2490 }
2491 
2492 //------------------------------Identity---------------------------------------
2493 // Remove redundant stores:
2494 //   Store(m, p, Load(m, p)) changes to m.
2495 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2496 Node *StoreNode::Identity( PhaseTransform *phase ) {
2497   Node* mem = in(MemNode::Memory);
2498   Node* adr = in(MemNode::Address);
2499   Node* val = in(MemNode::ValueIn);
2500 
2501   // Load then Store?  Then the Store is useless
2502   if (val->is_Load() &&
2503       val->in(MemNode::Address)->eqv_uncast(adr) &&
2504       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2505       val->as_Load()->store_Opcode() == Opcode()) {
2506     return mem;
2507   }
2508 
2509   // Two stores in a row of the same value?
2510   if (mem->is_Store() &&
2511       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2512       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2513       mem->Opcode() == Opcode()) {
2514     return mem;
2515   }
2516 
2517   // Store of zero anywhere into a freshly-allocated object?
2518   // Then the store is useless.
2519   // (It must already have been captured by the InitializeNode.)
2520   if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2521     // a newly allocated object is already all-zeroes everywhere
2522     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2523       return mem;
2524     }
2525 
2526     // the store may also apply to zero-bits in an earlier object
2527     Node* prev_mem = find_previous_store(phase);
2528     // Steps (a), (b):  Walk past independent stores to find an exact match.
2529     if (prev_mem != NULL) {
2530       Node* prev_val = can_see_stored_value(prev_mem, phase);
2531       if (prev_val != NULL && phase->eqv(prev_val, val)) {
2532         // prev_val and val might differ by a cast; it would be good
2533         // to keep the more informative of the two.
2534         return mem;
2535       }
2536     }
2537   }
2538 
2539   return this;
2540 }
2541 
2542 //------------------------------match_edge-------------------------------------
2543 // Do we Match on this edge index or not?  Match only memory & value
2544 uint StoreNode::match_edge(uint idx) const {
2545   return idx == MemNode::Address || idx == MemNode::ValueIn;
2546 }
2547 
2548 //------------------------------cmp--------------------------------------------
2549 // Do not common stores up together.  They generally have to be split
2550 // back up anyways, so do not bother.
2551 uint StoreNode::cmp( const Node &n ) const {
2552   return (&n == this);          // Always fail except on self
2553 }
2554 
2555 //------------------------------Ideal_masked_input-----------------------------
2556 // Check for a useless mask before a partial-word store
2557 // (StoreB ... (AndI valIn conIa) )
2558 // If (conIa & mask == mask) this simplifies to
2559 // (StoreB ... (valIn) )
2560 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2561   Node *val = in(MemNode::ValueIn);
2562   if( val->Opcode() == Op_AndI ) {
2563     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2564     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2565       set_req(MemNode::ValueIn, val->in(1));
2566       return this;
2567     }
2568   }
2569   return NULL;
2570 }
2571 
2572 
2573 //------------------------------Ideal_sign_extended_input----------------------
2574 // Check for useless sign-extension before a partial-word store
2575 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2576 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2577 // (StoreB ... (valIn) )
2578 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2579   Node *val = in(MemNode::ValueIn);
2580   if( val->Opcode() == Op_RShiftI ) {
2581     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2582     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2583       Node *shl = val->in(1);
2584       if( shl->Opcode() == Op_LShiftI ) {
2585         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2586         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2587           set_req(MemNode::ValueIn, shl->in(1));
2588           return this;
2589         }
2590       }
2591     }
2592   }
2593   return NULL;
2594 }
2595 
2596 //------------------------------value_never_loaded-----------------------------------
2597 // Determine whether there are any possible loads of the value stored.
2598 // For simplicity, we actually check if there are any loads from the
2599 // address stored to, not just for loads of the value stored by this node.
2600 //
2601 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2602   Node *adr = in(Address);
2603   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2604   if (adr_oop == NULL)
2605     return false;
2606   if (!adr_oop->is_known_instance_field())
2607     return false; // if not a distinct instance, there may be aliases of the address
2608   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2609     Node *use = adr->fast_out(i);
2610     int opc = use->Opcode();
2611     if (use->is_Load() || use->is_LoadStore()) {
2612       return false;
2613     }
2614   }
2615   return true;
2616 }
2617 
2618 //=============================================================================
2619 //------------------------------Ideal------------------------------------------
2620 // If the store is from an AND mask that leaves the low bits untouched, then
2621 // we can skip the AND operation.  If the store is from a sign-extension
2622 // (a left shift, then right shift) we can skip both.
2623 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2624   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2625   if( progress != NULL ) return progress;
2626 
2627   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2628   if( progress != NULL ) return progress;
2629 
2630   // Finally check the default case
2631   return StoreNode::Ideal(phase, can_reshape);
2632 }
2633 
2634 //=============================================================================
2635 //------------------------------Ideal------------------------------------------
2636 // If the store is from an AND mask that leaves the low bits untouched, then
2637 // we can skip the AND operation
2638 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2639   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2640   if( progress != NULL ) return progress;
2641 
2642   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2643   if( progress != NULL ) return progress;
2644 
2645   // Finally check the default case
2646   return StoreNode::Ideal(phase, can_reshape);
2647 }
2648 
2649 //=============================================================================
2650 //------------------------------Identity---------------------------------------
2651 Node *StoreCMNode::Identity( PhaseTransform *phase ) {
2652   // No need to card mark when storing a null ptr
2653   Node* my_store = in(MemNode::OopStore);
2654   if (my_store->is_Store()) {
2655     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2656     if( t1 == TypePtr::NULL_PTR ) {
2657       return in(MemNode::Memory);
2658     }
2659   }
2660   return this;
2661 }
2662 
2663 //=============================================================================
2664 //------------------------------Ideal---------------------------------------
2665 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2666   Node* progress = StoreNode::Ideal(phase, can_reshape);
2667   if (progress != NULL) return progress;
2668 
2669   Node* my_store = in(MemNode::OopStore);
2670   if (my_store->is_MergeMem()) {
2671     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2672     set_req(MemNode::OopStore, mem);
2673     return this;
2674   }
2675 
2676   return NULL;
2677 }
2678 
2679 //------------------------------Value-----------------------------------------
2680 const Type *StoreCMNode::Value( PhaseTransform *phase ) const {
2681   // Either input is TOP ==> the result is TOP
2682   const Type *t = phase->type( in(MemNode::Memory) );
2683   if( t == Type::TOP ) return Type::TOP;
2684   t = phase->type( in(MemNode::Address) );
2685   if( t == Type::TOP ) return Type::TOP;
2686   t = phase->type( in(MemNode::ValueIn) );
2687   if( t == Type::TOP ) return Type::TOP;
2688   // If extra input is TOP ==> the result is TOP
2689   t = phase->type( in(MemNode::OopStore) );
2690   if( t == Type::TOP ) return Type::TOP;
2691 
2692   return StoreNode::Value( phase );
2693 }
2694 
2695 
2696 //=============================================================================
2697 //----------------------------------SCMemProjNode------------------------------
2698 const Type * SCMemProjNode::Value( PhaseTransform *phase ) const
2699 {
2700   return bottom_type();
2701 }
2702 
2703 //=============================================================================
2704 //----------------------------------LoadStoreNode------------------------------
2705 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2706   : Node(required),
2707     _type(rt),
2708     _adr_type(at)
2709 {
2710   init_req(MemNode::Control, c  );
2711   init_req(MemNode::Memory , mem);
2712   init_req(MemNode::Address, adr);
2713   init_req(MemNode::ValueIn, val);
2714   init_class_id(Class_LoadStore);
2715 }
2716 
2717 uint LoadStoreNode::ideal_reg() const {
2718   return _type->ideal_reg();
2719 }
2720 
2721 bool LoadStoreNode::result_not_used() const {
2722   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2723     Node *x = fast_out(i);
2724     if (x->Opcode() == Op_SCMemProj) continue;
2725     return false;
2726   }
2727   return true;
2728 }
2729 
2730 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2731 
2732 //=============================================================================
2733 //----------------------------------LoadStoreConditionalNode--------------------
2734 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2735   init_req(ExpectedIn, ex );
2736 }
2737 
2738 //=============================================================================
2739 //-------------------------------adr_type--------------------------------------
2740 // Do we Match on this edge index or not?  Do not match memory
2741 const TypePtr* ClearArrayNode::adr_type() const {
2742   Node *adr = in(3);
2743   return MemNode::calculate_adr_type(adr->bottom_type());
2744 }
2745 
2746 //------------------------------match_edge-------------------------------------
2747 // Do we Match on this edge index or not?  Do not match memory
2748 uint ClearArrayNode::match_edge(uint idx) const {
2749   return idx > 1;
2750 }
2751 
2752 //------------------------------Identity---------------------------------------
2753 // Clearing a zero length array does nothing
2754 Node *ClearArrayNode::Identity( PhaseTransform *phase ) {
2755   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2756 }
2757 
2758 //------------------------------Idealize---------------------------------------
2759 // Clearing a short array is faster with stores
2760 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){
2761   const int unit = BytesPerLong;
2762   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2763   if (!t)  return NULL;
2764   if (!t->is_con())  return NULL;
2765   intptr_t raw_count = t->get_con();
2766   intptr_t size = raw_count;
2767   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2768   // Clearing nothing uses the Identity call.
2769   // Negative clears are possible on dead ClearArrays
2770   // (see jck test stmt114.stmt11402.val).
2771   if (size <= 0 || size % unit != 0)  return NULL;
2772   intptr_t count = size / unit;
2773   // Length too long; use fast hardware clear
2774   if (size > Matcher::init_array_short_size)  return NULL;
2775   Node *mem = in(1);
2776   if( phase->type(mem)==Type::TOP ) return NULL;
2777   Node *adr = in(3);
2778   const Type* at = phase->type(adr);
2779   if( at==Type::TOP ) return NULL;
2780   const TypePtr* atp = at->isa_ptr();
2781   // adjust atp to be the correct array element address type
2782   if (atp == NULL)  atp = TypePtr::BOTTOM;
2783   else              atp = atp->add_offset(Type::OffsetBot);
2784   // Get base for derived pointer purposes
2785   if( adr->Opcode() != Op_AddP ) Unimplemented();
2786   Node *base = adr->in(1);
2787 
2788   Node *zero = phase->makecon(TypeLong::ZERO);
2789   Node *off  = phase->MakeConX(BytesPerLong);
2790   mem = new (phase->C) StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2791   count--;
2792   while( count-- ) {
2793     mem = phase->transform(mem);
2794     adr = phase->transform(new (phase->C) AddPNode(base,adr,off));
2795     mem = new (phase->C) StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2796   }
2797   return mem;
2798 }
2799 
2800 //----------------------------step_through----------------------------------
2801 // Return allocation input memory edge if it is different instance
2802 // or itself if it is the one we are looking for.
2803 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2804   Node* n = *np;
2805   assert(n->is_ClearArray(), "sanity");
2806   intptr_t offset;
2807   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2808   // This method is called only before Allocate nodes are expanded during
2809   // macro nodes expansion. Before that ClearArray nodes are only generated
2810   // in LibraryCallKit::generate_arraycopy() which follows allocations.
2811   assert(alloc != NULL, "should have allocation");
2812   if (alloc->_idx == instance_id) {
2813     // Can not bypass initialization of the instance we are looking for.
2814     return false;
2815   }
2816   // Otherwise skip it.
2817   InitializeNode* init = alloc->initialization();
2818   if (init != NULL)
2819     *np = init->in(TypeFunc::Memory);
2820   else
2821     *np = alloc->in(TypeFunc::Memory);
2822   return true;
2823 }
2824 
2825 //----------------------------clear_memory-------------------------------------
2826 // Generate code to initialize object storage to zero.
2827 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2828                                    intptr_t start_offset,
2829                                    Node* end_offset,
2830                                    PhaseGVN* phase) {
2831   Compile* C = phase->C;
2832   intptr_t offset = start_offset;
2833 
2834   int unit = BytesPerLong;
2835   if ((offset % unit) != 0) {
2836     Node* adr = new (C) AddPNode(dest, dest, phase->MakeConX(offset));
2837     adr = phase->transform(adr);
2838     const TypePtr* atp = TypeRawPtr::BOTTOM;
2839     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2840     mem = phase->transform(mem);
2841     offset += BytesPerInt;
2842   }
2843   assert((offset % unit) == 0, "");
2844 
2845   // Initialize the remaining stuff, if any, with a ClearArray.
2846   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2847 }
2848 
2849 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2850                                    Node* start_offset,
2851                                    Node* end_offset,
2852                                    PhaseGVN* phase) {
2853   if (start_offset == end_offset) {
2854     // nothing to do
2855     return mem;
2856   }
2857 
2858   Compile* C = phase->C;
2859   int unit = BytesPerLong;
2860   Node* zbase = start_offset;
2861   Node* zend  = end_offset;
2862 
2863   // Scale to the unit required by the CPU:
2864   if (!Matcher::init_array_count_is_in_bytes) {
2865     Node* shift = phase->intcon(exact_log2(unit));
2866     zbase = phase->transform( new(C) URShiftXNode(zbase, shift) );
2867     zend  = phase->transform( new(C) URShiftXNode(zend,  shift) );
2868   }
2869 
2870   // Bulk clear double-words
2871   Node* zsize = phase->transform( new(C) SubXNode(zend, zbase) );
2872   Node* adr = phase->transform( new(C) AddPNode(dest, dest, start_offset) );
2873   mem = new (C) ClearArrayNode(ctl, mem, zsize, adr);
2874   return phase->transform(mem);
2875 }
2876 
2877 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2878                                    intptr_t start_offset,
2879                                    intptr_t end_offset,
2880                                    PhaseGVN* phase) {
2881   if (start_offset == end_offset) {
2882     // nothing to do
2883     return mem;
2884   }
2885 
2886   Compile* C = phase->C;
2887   assert((end_offset % BytesPerInt) == 0, "odd end offset");
2888   intptr_t done_offset = end_offset;
2889   if ((done_offset % BytesPerLong) != 0) {
2890     done_offset -= BytesPerInt;
2891   }
2892   if (done_offset > start_offset) {
2893     mem = clear_memory(ctl, mem, dest,
2894                        start_offset, phase->MakeConX(done_offset), phase);
2895   }
2896   if (done_offset < end_offset) { // emit the final 32-bit store
2897     Node* adr = new (C) AddPNode(dest, dest, phase->MakeConX(done_offset));
2898     adr = phase->transform(adr);
2899     const TypePtr* atp = TypeRawPtr::BOTTOM;
2900     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2901     mem = phase->transform(mem);
2902     done_offset += BytesPerInt;
2903   }
2904   assert(done_offset == end_offset, "");
2905   return mem;
2906 }
2907 
2908 //=============================================================================
2909 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
2910   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
2911     _adr_type(C->get_adr_type(alias_idx))
2912 {
2913   init_class_id(Class_MemBar);
2914   Node* top = C->top();
2915   init_req(TypeFunc::I_O,top);
2916   init_req(TypeFunc::FramePtr,top);
2917   init_req(TypeFunc::ReturnAdr,top);
2918   if (precedent != NULL)
2919     init_req(TypeFunc::Parms, precedent);
2920 }
2921 
2922 //------------------------------cmp--------------------------------------------
2923 uint MemBarNode::hash() const { return NO_HASH; }
2924 uint MemBarNode::cmp( const Node &n ) const {
2925   return (&n == this);          // Always fail except on self
2926 }
2927 
2928 //------------------------------make-------------------------------------------
2929 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
2930   switch (opcode) {
2931   case Op_MemBarAcquire:     return new(C) MemBarAcquireNode(C, atp, pn);
2932   case Op_LoadFence:         return new(C) LoadFenceNode(C, atp, pn);
2933   case Op_MemBarRelease:     return new(C) MemBarReleaseNode(C, atp, pn);
2934   case Op_StoreFence:        return new(C) StoreFenceNode(C, atp, pn);
2935   case Op_MemBarAcquireLock: return new(C) MemBarAcquireLockNode(C, atp, pn);
2936   case Op_MemBarReleaseLock: return new(C) MemBarReleaseLockNode(C, atp, pn);
2937   case Op_MemBarVolatile:    return new(C) MemBarVolatileNode(C, atp, pn);
2938   case Op_MemBarCPUOrder:    return new(C) MemBarCPUOrderNode(C, atp, pn);
2939   case Op_Initialize:        return new(C) InitializeNode(C, atp, pn);
2940   case Op_MemBarStoreStore:  return new(C) MemBarStoreStoreNode(C, atp, pn);
2941   default: ShouldNotReachHere(); return NULL;
2942   }
2943 }
2944 
2945 //------------------------------Ideal------------------------------------------
2946 // Return a node which is more "ideal" than the current node.  Strip out
2947 // control copies
2948 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2949   if (remove_dead_region(phase, can_reshape)) return this;
2950   // Don't bother trying to transform a dead node
2951   if (in(0) && in(0)->is_top()) {
2952     return NULL;
2953   }
2954 
2955   // Eliminate volatile MemBars for scalar replaced objects.
2956   if (can_reshape && req() == (Precedent+1)) {
2957     bool eliminate = false;
2958     int opc = Opcode();
2959     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
2960       // Volatile field loads and stores.
2961       Node* my_mem = in(MemBarNode::Precedent);
2962       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
2963       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
2964         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
2965         // replace this Precedent (decodeN) with the Load instead.
2966         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
2967           Node* load_node = my_mem->in(1);
2968           set_req(MemBarNode::Precedent, load_node);
2969           phase->is_IterGVN()->_worklist.push(my_mem);
2970           my_mem = load_node;
2971         } else {
2972           assert(my_mem->unique_out() == this, "sanity");
2973           del_req(Precedent);
2974           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
2975           my_mem = NULL;
2976         }
2977       }
2978       if (my_mem != NULL && my_mem->is_Mem()) {
2979         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
2980         // Check for scalar replaced object reference.
2981         if( t_oop != NULL && t_oop->is_known_instance_field() &&
2982             t_oop->offset() != Type::OffsetBot &&
2983             t_oop->offset() != Type::OffsetTop) {
2984           eliminate = true;
2985         }
2986       }
2987     } else if (opc == Op_MemBarRelease) {
2988       // Final field stores.
2989       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
2990       if ((alloc != NULL) && alloc->is_Allocate() &&
2991           alloc->as_Allocate()->_is_non_escaping) {
2992         // The allocated object does not escape.
2993         eliminate = true;
2994       }
2995     }
2996     if (eliminate) {
2997       // Replace MemBar projections by its inputs.
2998       PhaseIterGVN* igvn = phase->is_IterGVN();
2999       igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
3000       igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
3001       // Must return either the original node (now dead) or a new node
3002       // (Do not return a top here, since that would break the uniqueness of top.)
3003       return new (phase->C) ConINode(TypeInt::ZERO);
3004     }
3005   }
3006   return NULL;
3007 }
3008 
3009 //------------------------------Value------------------------------------------
3010 const Type *MemBarNode::Value( PhaseTransform *phase ) const {
3011   if( !in(0) ) return Type::TOP;
3012   if( phase->type(in(0)) == Type::TOP )
3013     return Type::TOP;
3014   return TypeTuple::MEMBAR;
3015 }
3016 
3017 //------------------------------match------------------------------------------
3018 // Construct projections for memory.
3019 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3020   switch (proj->_con) {
3021   case TypeFunc::Control:
3022   case TypeFunc::Memory:
3023     return new (m->C) MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3024   }
3025   ShouldNotReachHere();
3026   return NULL;
3027 }
3028 
3029 //===========================InitializeNode====================================
3030 // SUMMARY:
3031 // This node acts as a memory barrier on raw memory, after some raw stores.
3032 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3033 // The Initialize can 'capture' suitably constrained stores as raw inits.
3034 // It can coalesce related raw stores into larger units (called 'tiles').
3035 // It can avoid zeroing new storage for memory units which have raw inits.
3036 // At macro-expansion, it is marked 'complete', and does not optimize further.
3037 //
3038 // EXAMPLE:
3039 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3040 //   ctl = incoming control; mem* = incoming memory
3041 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3042 // First allocate uninitialized memory and fill in the header:
3043 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3044 //   ctl := alloc.Control; mem* := alloc.Memory*
3045 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3046 // Then initialize to zero the non-header parts of the raw memory block:
3047 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3048 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3049 // After the initialize node executes, the object is ready for service:
3050 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3051 // Suppose its body is immediately initialized as {1,2}:
3052 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3053 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3054 //   mem.SLICE(#short[*]) := store2
3055 //
3056 // DETAILS:
3057 // An InitializeNode collects and isolates object initialization after
3058 // an AllocateNode and before the next possible safepoint.  As a
3059 // memory barrier (MemBarNode), it keeps critical stores from drifting
3060 // down past any safepoint or any publication of the allocation.
3061 // Before this barrier, a newly-allocated object may have uninitialized bits.
3062 // After this barrier, it may be treated as a real oop, and GC is allowed.
3063 //
3064 // The semantics of the InitializeNode include an implicit zeroing of
3065 // the new object from object header to the end of the object.
3066 // (The object header and end are determined by the AllocateNode.)
3067 //
3068 // Certain stores may be added as direct inputs to the InitializeNode.
3069 // These stores must update raw memory, and they must be to addresses
3070 // derived from the raw address produced by AllocateNode, and with
3071 // a constant offset.  They must be ordered by increasing offset.
3072 // The first one is at in(RawStores), the last at in(req()-1).
3073 // Unlike most memory operations, they are not linked in a chain,
3074 // but are displayed in parallel as users of the rawmem output of
3075 // the allocation.
3076 //
3077 // (See comments in InitializeNode::capture_store, which continue
3078 // the example given above.)
3079 //
3080 // When the associated Allocate is macro-expanded, the InitializeNode
3081 // may be rewritten to optimize collected stores.  A ClearArrayNode
3082 // may also be created at that point to represent any required zeroing.
3083 // The InitializeNode is then marked 'complete', prohibiting further
3084 // capturing of nearby memory operations.
3085 //
3086 // During macro-expansion, all captured initializations which store
3087 // constant values of 32 bits or smaller are coalesced (if advantageous)
3088 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3089 // initialized in fewer memory operations.  Memory words which are
3090 // covered by neither tiles nor non-constant stores are pre-zeroed
3091 // by explicit stores of zero.  (The code shape happens to do all
3092 // zeroing first, then all other stores, with both sequences occurring
3093 // in order of ascending offsets.)
3094 //
3095 // Alternatively, code may be inserted between an AllocateNode and its
3096 // InitializeNode, to perform arbitrary initialization of the new object.
3097 // E.g., the object copying intrinsics insert complex data transfers here.
3098 // The initialization must then be marked as 'complete' disable the
3099 // built-in zeroing semantics and the collection of initializing stores.
3100 //
3101 // While an InitializeNode is incomplete, reads from the memory state
3102 // produced by it are optimizable if they match the control edge and
3103 // new oop address associated with the allocation/initialization.
3104 // They return a stored value (if the offset matches) or else zero.
3105 // A write to the memory state, if it matches control and address,
3106 // and if it is to a constant offset, may be 'captured' by the
3107 // InitializeNode.  It is cloned as a raw memory operation and rewired
3108 // inside the initialization, to the raw oop produced by the allocation.
3109 // Operations on addresses which are provably distinct (e.g., to
3110 // other AllocateNodes) are allowed to bypass the initialization.
3111 //
3112 // The effect of all this is to consolidate object initialization
3113 // (both arrays and non-arrays, both piecewise and bulk) into a
3114 // single location, where it can be optimized as a unit.
3115 //
3116 // Only stores with an offset less than TrackedInitializationLimit words
3117 // will be considered for capture by an InitializeNode.  This puts a
3118 // reasonable limit on the complexity of optimized initializations.
3119 
3120 //---------------------------InitializeNode------------------------------------
3121 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3122   : _is_complete(Incomplete), _does_not_escape(false),
3123     MemBarNode(C, adr_type, rawoop)
3124 {
3125   init_class_id(Class_Initialize);
3126 
3127   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3128   assert(in(RawAddress) == rawoop, "proper init");
3129   // Note:  allocation() can be NULL, for secondary initialization barriers
3130 }
3131 
3132 // Since this node is not matched, it will be processed by the
3133 // register allocator.  Declare that there are no constraints
3134 // on the allocation of the RawAddress edge.
3135 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3136   // This edge should be set to top, by the set_complete.  But be conservative.
3137   if (idx == InitializeNode::RawAddress)
3138     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3139   return RegMask::Empty;
3140 }
3141 
3142 Node* InitializeNode::memory(uint alias_idx) {
3143   Node* mem = in(Memory);
3144   if (mem->is_MergeMem()) {
3145     return mem->as_MergeMem()->memory_at(alias_idx);
3146   } else {
3147     // incoming raw memory is not split
3148     return mem;
3149   }
3150 }
3151 
3152 bool InitializeNode::is_non_zero() {
3153   if (is_complete())  return false;
3154   remove_extra_zeroes();
3155   return (req() > RawStores);
3156 }
3157 
3158 void InitializeNode::set_complete(PhaseGVN* phase) {
3159   assert(!is_complete(), "caller responsibility");
3160   _is_complete = Complete;
3161 
3162   // After this node is complete, it contains a bunch of
3163   // raw-memory initializations.  There is no need for
3164   // it to have anything to do with non-raw memory effects.
3165   // Therefore, tell all non-raw users to re-optimize themselves,
3166   // after skipping the memory effects of this initialization.
3167   PhaseIterGVN* igvn = phase->is_IterGVN();
3168   if (igvn)  igvn->add_users_to_worklist(this);
3169 }
3170 
3171 // convenience function
3172 // return false if the init contains any stores already
3173 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3174   InitializeNode* init = initialization();
3175   if (init == NULL || init->is_complete())  return false;
3176   init->remove_extra_zeroes();
3177   // for now, if this allocation has already collected any inits, bail:
3178   if (init->is_non_zero())  return false;
3179   init->set_complete(phase);
3180   return true;
3181 }
3182 
3183 void InitializeNode::remove_extra_zeroes() {
3184   if (req() == RawStores)  return;
3185   Node* zmem = zero_memory();
3186   uint fill = RawStores;
3187   for (uint i = fill; i < req(); i++) {
3188     Node* n = in(i);
3189     if (n->is_top() || n == zmem)  continue;  // skip
3190     if (fill < i)  set_req(fill, n);          // compact
3191     ++fill;
3192   }
3193   // delete any empty spaces created:
3194   while (fill < req()) {
3195     del_req(fill);
3196   }
3197 }
3198 
3199 // Helper for remembering which stores go with which offsets.
3200 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3201   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3202   intptr_t offset = -1;
3203   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3204                                                phase, offset);
3205   if (base == NULL)     return -1;  // something is dead,
3206   if (offset < 0)       return -1;  //        dead, dead
3207   return offset;
3208 }
3209 
3210 // Helper for proving that an initialization expression is
3211 // "simple enough" to be folded into an object initialization.
3212 // Attempts to prove that a store's initial value 'n' can be captured
3213 // within the initialization without creating a vicious cycle, such as:
3214 //     { Foo p = new Foo(); p.next = p; }
3215 // True for constants and parameters and small combinations thereof.
3216 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3217   if (n == NULL)      return true;   // (can this really happen?)
3218   if (n->is_Proj())   n = n->in(0);
3219   if (n == this)      return false;  // found a cycle
3220   if (n->is_Con())    return true;
3221   if (n->is_Start())  return true;   // params, etc., are OK
3222   if (n->is_Root())   return true;   // even better
3223 
3224   Node* ctl = n->in(0);
3225   if (ctl != NULL && !ctl->is_top()) {
3226     if (ctl->is_Proj())  ctl = ctl->in(0);
3227     if (ctl == this)  return false;
3228 
3229     // If we already know that the enclosing memory op is pinned right after
3230     // the init, then any control flow that the store has picked up
3231     // must have preceded the init, or else be equal to the init.
3232     // Even after loop optimizations (which might change control edges)
3233     // a store is never pinned *before* the availability of its inputs.
3234     if (!MemNode::all_controls_dominate(n, this))
3235       return false;                  // failed to prove a good control
3236   }
3237 
3238   // Check data edges for possible dependencies on 'this'.
3239   if ((count += 1) > 20)  return false;  // complexity limit
3240   for (uint i = 1; i < n->req(); i++) {
3241     Node* m = n->in(i);
3242     if (m == NULL || m == n || m->is_top())  continue;
3243     uint first_i = n->find_edge(m);
3244     if (i != first_i)  continue;  // process duplicate edge just once
3245     if (!detect_init_independence(m, count)) {
3246       return false;
3247     }
3248   }
3249 
3250   return true;
3251 }
3252 
3253 // Here are all the checks a Store must pass before it can be moved into
3254 // an initialization.  Returns zero if a check fails.
3255 // On success, returns the (constant) offset to which the store applies,
3256 // within the initialized memory.
3257 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3258   const int FAIL = 0;
3259   if (st->req() != MemNode::ValueIn + 1)
3260     return FAIL;                // an inscrutable StoreNode (card mark?)
3261   Node* ctl = st->in(MemNode::Control);
3262   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3263     return FAIL;                // must be unconditional after the initialization
3264   Node* mem = st->in(MemNode::Memory);
3265   if (!(mem->is_Proj() && mem->in(0) == this))
3266     return FAIL;                // must not be preceded by other stores
3267   Node* adr = st->in(MemNode::Address);
3268   intptr_t offset;
3269   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3270   if (alloc == NULL)
3271     return FAIL;                // inscrutable address
3272   if (alloc != allocation())
3273     return FAIL;                // wrong allocation!  (store needs to float up)
3274   Node* val = st->in(MemNode::ValueIn);
3275   int complexity_count = 0;
3276   if (!detect_init_independence(val, complexity_count))
3277     return FAIL;                // stored value must be 'simple enough'
3278 
3279   // The Store can be captured only if nothing after the allocation
3280   // and before the Store is using the memory location that the store
3281   // overwrites.
3282   bool failed = false;
3283   // If is_complete_with_arraycopy() is true the shape of the graph is
3284   // well defined and is safe so no need for extra checks.
3285   if (!is_complete_with_arraycopy()) {
3286     // We are going to look at each use of the memory state following
3287     // the allocation to make sure nothing reads the memory that the
3288     // Store writes.
3289     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3290     int alias_idx = phase->C->get_alias_index(t_adr);
3291     ResourceMark rm;
3292     Unique_Node_List mems;
3293     mems.push(mem);
3294     Node* unique_merge = NULL;
3295     for (uint next = 0; next < mems.size(); ++next) {
3296       Node *m  = mems.at(next);
3297       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3298         Node *n = m->fast_out(j);
3299         if (n->outcnt() == 0) {
3300           continue;
3301         }
3302         if (n == st) {
3303           continue;
3304         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3305           // If the control of this use is different from the control
3306           // of the Store which is right after the InitializeNode then
3307           // this node cannot be between the InitializeNode and the
3308           // Store.
3309           continue;
3310         } else if (n->is_MergeMem()) {
3311           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3312             // We can hit a MergeMemNode (that will likely go away
3313             // later) that is a direct use of the memory state
3314             // following the InitializeNode on the same slice as the
3315             // store node that we'd like to capture. We need to check
3316             // the uses of the MergeMemNode.
3317             mems.push(n);
3318           }
3319         } else if (n->is_Mem()) {
3320           Node* other_adr = n->in(MemNode::Address);
3321           if (other_adr == adr) {
3322             failed = true;
3323             break;
3324           } else {
3325             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3326             if (other_t_adr != NULL) {
3327               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3328               if (other_alias_idx == alias_idx) {
3329                 // A load from the same memory slice as the store right
3330                 // after the InitializeNode. We check the control of the
3331                 // object/array that is loaded from. If it's the same as
3332                 // the store control then we cannot capture the store.
3333                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3334                 Node* base = other_adr;
3335                 assert(base->is_AddP(), err_msg_res("should be addp but is %s", base->Name()));
3336                 base = base->in(AddPNode::Base);
3337                 if (base != NULL) {
3338                   base = base->uncast();
3339                   if (base->is_Proj() && base->in(0) == alloc) {
3340                     failed = true;
3341                     break;
3342                   }
3343                 }
3344               }
3345             }
3346           }
3347         } else {
3348           failed = true;
3349           break;
3350         }
3351       }
3352     }
3353   }
3354   if (failed) {
3355     if (!can_reshape) {
3356       // We decided we couldn't capture the store during parsing. We
3357       // should try again during the next IGVN once the graph is
3358       // cleaner.
3359       phase->C->record_for_igvn(st);
3360     }
3361     return FAIL;
3362   }
3363 
3364   return offset;                // success
3365 }
3366 
3367 // Find the captured store in(i) which corresponds to the range
3368 // [start..start+size) in the initialized object.
3369 // If there is one, return its index i.  If there isn't, return the
3370 // negative of the index where it should be inserted.
3371 // Return 0 if the queried range overlaps an initialization boundary
3372 // or if dead code is encountered.
3373 // If size_in_bytes is zero, do not bother with overlap checks.
3374 int InitializeNode::captured_store_insertion_point(intptr_t start,
3375                                                    int size_in_bytes,
3376                                                    PhaseTransform* phase) {
3377   const int FAIL = 0, MAX_STORE = BytesPerLong;
3378 
3379   if (is_complete())
3380     return FAIL;                // arraycopy got here first; punt
3381 
3382   assert(allocation() != NULL, "must be present");
3383 
3384   // no negatives, no header fields:
3385   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3386 
3387   // after a certain size, we bail out on tracking all the stores:
3388   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3389   if (start >= ti_limit)  return FAIL;
3390 
3391   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3392     if (i >= limit)  return -(int)i; // not found; here is where to put it
3393 
3394     Node*    st     = in(i);
3395     intptr_t st_off = get_store_offset(st, phase);
3396     if (st_off < 0) {
3397       if (st != zero_memory()) {
3398         return FAIL;            // bail out if there is dead garbage
3399       }
3400     } else if (st_off > start) {
3401       // ...we are done, since stores are ordered
3402       if (st_off < start + size_in_bytes) {
3403         return FAIL;            // the next store overlaps
3404       }
3405       return -(int)i;           // not found; here is where to put it
3406     } else if (st_off < start) {
3407       if (size_in_bytes != 0 &&
3408           start < st_off + MAX_STORE &&
3409           start < st_off + st->as_Store()->memory_size()) {
3410         return FAIL;            // the previous store overlaps
3411       }
3412     } else {
3413       if (size_in_bytes != 0 &&
3414           st->as_Store()->memory_size() != size_in_bytes) {
3415         return FAIL;            // mismatched store size
3416       }
3417       return i;
3418     }
3419 
3420     ++i;
3421   }
3422 }
3423 
3424 // Look for a captured store which initializes at the offset 'start'
3425 // with the given size.  If there is no such store, and no other
3426 // initialization interferes, then return zero_memory (the memory
3427 // projection of the AllocateNode).
3428 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3429                                           PhaseTransform* phase) {
3430   assert(stores_are_sane(phase), "");
3431   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3432   if (i == 0) {
3433     return NULL;                // something is dead
3434   } else if (i < 0) {
3435     return zero_memory();       // just primordial zero bits here
3436   } else {
3437     Node* st = in(i);           // here is the store at this position
3438     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3439     return st;
3440   }
3441 }
3442 
3443 // Create, as a raw pointer, an address within my new object at 'offset'.
3444 Node* InitializeNode::make_raw_address(intptr_t offset,
3445                                        PhaseTransform* phase) {
3446   Node* addr = in(RawAddress);
3447   if (offset != 0) {
3448     Compile* C = phase->C;
3449     addr = phase->transform( new (C) AddPNode(C->top(), addr,
3450                                                  phase->MakeConX(offset)) );
3451   }
3452   return addr;
3453 }
3454 
3455 // Clone the given store, converting it into a raw store
3456 // initializing a field or element of my new object.
3457 // Caller is responsible for retiring the original store,
3458 // with subsume_node or the like.
3459 //
3460 // From the example above InitializeNode::InitializeNode,
3461 // here are the old stores to be captured:
3462 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3463 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3464 //
3465 // Here is the changed code; note the extra edges on init:
3466 //   alloc = (Allocate ...)
3467 //   rawoop = alloc.RawAddress
3468 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3469 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3470 //   init = (Initialize alloc.Control alloc.Memory rawoop
3471 //                      rawstore1 rawstore2)
3472 //
3473 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3474                                     PhaseTransform* phase, bool can_reshape) {
3475   assert(stores_are_sane(phase), "");
3476 
3477   if (start < 0)  return NULL;
3478   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3479 
3480   Compile* C = phase->C;
3481   int size_in_bytes = st->memory_size();
3482   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3483   if (i == 0)  return NULL;     // bail out
3484   Node* prev_mem = NULL;        // raw memory for the captured store
3485   if (i > 0) {
3486     prev_mem = in(i);           // there is a pre-existing store under this one
3487     set_req(i, C->top());       // temporarily disconnect it
3488     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3489   } else {
3490     i = -i;                     // no pre-existing store
3491     prev_mem = zero_memory();   // a slice of the newly allocated object
3492     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3493       set_req(--i, C->top());   // reuse this edge; it has been folded away
3494     else
3495       ins_req(i, C->top());     // build a new edge
3496   }
3497   Node* new_st = st->clone();
3498   new_st->set_req(MemNode::Control, in(Control));
3499   new_st->set_req(MemNode::Memory,  prev_mem);
3500   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3501   new_st = phase->transform(new_st);
3502 
3503   // At this point, new_st might have swallowed a pre-existing store
3504   // at the same offset, or perhaps new_st might have disappeared,
3505   // if it redundantly stored the same value (or zero to fresh memory).
3506 
3507   // In any case, wire it in:
3508   set_req(i, new_st);
3509 
3510   // The caller may now kill the old guy.
3511   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3512   assert(check_st == new_st || check_st == NULL, "must be findable");
3513   assert(!is_complete(), "");
3514   return new_st;
3515 }
3516 
3517 static bool store_constant(jlong* tiles, int num_tiles,
3518                            intptr_t st_off, int st_size,
3519                            jlong con) {
3520   if ((st_off & (st_size-1)) != 0)
3521     return false;               // strange store offset (assume size==2**N)
3522   address addr = (address)tiles + st_off;
3523   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3524   switch (st_size) {
3525   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3526   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3527   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3528   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3529   default: return false;        // strange store size (detect size!=2**N here)
3530   }
3531   return true;                  // return success to caller
3532 }
3533 
3534 // Coalesce subword constants into int constants and possibly
3535 // into long constants.  The goal, if the CPU permits,
3536 // is to initialize the object with a small number of 64-bit tiles.
3537 // Also, convert floating-point constants to bit patterns.
3538 // Non-constants are not relevant to this pass.
3539 //
3540 // In terms of the running example on InitializeNode::InitializeNode
3541 // and InitializeNode::capture_store, here is the transformation
3542 // of rawstore1 and rawstore2 into rawstore12:
3543 //   alloc = (Allocate ...)
3544 //   rawoop = alloc.RawAddress
3545 //   tile12 = 0x00010002
3546 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3547 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3548 //
3549 void
3550 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3551                                         Node* size_in_bytes,
3552                                         PhaseGVN* phase) {
3553   Compile* C = phase->C;
3554 
3555   assert(stores_are_sane(phase), "");
3556   // Note:  After this pass, they are not completely sane,
3557   // since there may be some overlaps.
3558 
3559   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3560 
3561   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3562   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3563   size_limit = MIN2(size_limit, ti_limit);
3564   size_limit = align_size_up(size_limit, BytesPerLong);
3565   int num_tiles = size_limit / BytesPerLong;
3566 
3567   // allocate space for the tile map:
3568   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3569   jlong  tiles_buf[small_len];
3570   Node*  nodes_buf[small_len];
3571   jlong  inits_buf[small_len];
3572   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3573                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3574   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3575                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3576   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3577                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3578   // tiles: exact bitwise model of all primitive constants
3579   // nodes: last constant-storing node subsumed into the tiles model
3580   // inits: which bytes (in each tile) are touched by any initializations
3581 
3582   //// Pass A: Fill in the tile model with any relevant stores.
3583 
3584   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3585   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3586   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3587   Node* zmem = zero_memory(); // initially zero memory state
3588   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3589     Node* st = in(i);
3590     intptr_t st_off = get_store_offset(st, phase);
3591 
3592     // Figure out the store's offset and constant value:
3593     if (st_off < header_size)             continue; //skip (ignore header)
3594     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3595     int st_size = st->as_Store()->memory_size();
3596     if (st_off + st_size > size_limit)    break;
3597 
3598     // Record which bytes are touched, whether by constant or not.
3599     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3600       continue;                 // skip (strange store size)
3601 
3602     const Type* val = phase->type(st->in(MemNode::ValueIn));
3603     if (!val->singleton())                continue; //skip (non-con store)
3604     BasicType type = val->basic_type();
3605 
3606     jlong con = 0;
3607     switch (type) {
3608     case T_INT:    con = val->is_int()->get_con();  break;
3609     case T_LONG:   con = val->is_long()->get_con(); break;
3610     case T_FLOAT:  con = jint_cast(val->getf());    break;
3611     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3612     default:                              continue; //skip (odd store type)
3613     }
3614 
3615     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3616         st->Opcode() == Op_StoreL) {
3617       continue;                 // This StoreL is already optimal.
3618     }
3619 
3620     // Store down the constant.
3621     store_constant(tiles, num_tiles, st_off, st_size, con);
3622 
3623     intptr_t j = st_off >> LogBytesPerLong;
3624 
3625     if (type == T_INT && st_size == BytesPerInt
3626         && (st_off & BytesPerInt) == BytesPerInt) {
3627       jlong lcon = tiles[j];
3628       if (!Matcher::isSimpleConstant64(lcon) &&
3629           st->Opcode() == Op_StoreI) {
3630         // This StoreI is already optimal by itself.
3631         jint* intcon = (jint*) &tiles[j];
3632         intcon[1] = 0;  // undo the store_constant()
3633 
3634         // If the previous store is also optimal by itself, back up and
3635         // undo the action of the previous loop iteration... if we can.
3636         // But if we can't, just let the previous half take care of itself.
3637         st = nodes[j];
3638         st_off -= BytesPerInt;
3639         con = intcon[0];
3640         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3641           assert(st_off >= header_size, "still ignoring header");
3642           assert(get_store_offset(st, phase) == st_off, "must be");
3643           assert(in(i-1) == zmem, "must be");
3644           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3645           assert(con == tcon->is_int()->get_con(), "must be");
3646           // Undo the effects of the previous loop trip, which swallowed st:
3647           intcon[0] = 0;        // undo store_constant()
3648           set_req(i-1, st);     // undo set_req(i, zmem)
3649           nodes[j] = NULL;      // undo nodes[j] = st
3650           --old_subword;        // undo ++old_subword
3651         }
3652         continue;               // This StoreI is already optimal.
3653       }
3654     }
3655 
3656     // This store is not needed.
3657     set_req(i, zmem);
3658     nodes[j] = st;              // record for the moment
3659     if (st_size < BytesPerLong) // something has changed
3660           ++old_subword;        // includes int/float, but who's counting...
3661     else  ++old_long;
3662   }
3663 
3664   if ((old_subword + old_long) == 0)
3665     return;                     // nothing more to do
3666 
3667   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3668   // Be sure to insert them before overlapping non-constant stores.
3669   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3670   for (int j = 0; j < num_tiles; j++) {
3671     jlong con  = tiles[j];
3672     jlong init = inits[j];
3673     if (con == 0)  continue;
3674     jint con0,  con1;           // split the constant, address-wise
3675     jint init0, init1;          // split the init map, address-wise
3676     { union { jlong con; jint intcon[2]; } u;
3677       u.con = con;
3678       con0  = u.intcon[0];
3679       con1  = u.intcon[1];
3680       u.con = init;
3681       init0 = u.intcon[0];
3682       init1 = u.intcon[1];
3683     }
3684 
3685     Node* old = nodes[j];
3686     assert(old != NULL, "need the prior store");
3687     intptr_t offset = (j * BytesPerLong);
3688 
3689     bool split = !Matcher::isSimpleConstant64(con);
3690 
3691     if (offset < header_size) {
3692       assert(offset + BytesPerInt >= header_size, "second int counts");
3693       assert(*(jint*)&tiles[j] == 0, "junk in header");
3694       split = true;             // only the second word counts
3695       // Example:  int a[] = { 42 ... }
3696     } else if (con0 == 0 && init0 == -1) {
3697       split = true;             // first word is covered by full inits
3698       // Example:  int a[] = { ... foo(), 42 ... }
3699     } else if (con1 == 0 && init1 == -1) {
3700       split = true;             // second word is covered by full inits
3701       // Example:  int a[] = { ... 42, foo() ... }
3702     }
3703 
3704     // Here's a case where init0 is neither 0 nor -1:
3705     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
3706     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3707     // In this case the tile is not split; it is (jlong)42.
3708     // The big tile is stored down, and then the foo() value is inserted.
3709     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3710 
3711     Node* ctl = old->in(MemNode::Control);
3712     Node* adr = make_raw_address(offset, phase);
3713     const TypePtr* atp = TypeRawPtr::BOTTOM;
3714 
3715     // One or two coalesced stores to plop down.
3716     Node*    st[2];
3717     intptr_t off[2];
3718     int  nst = 0;
3719     if (!split) {
3720       ++new_long;
3721       off[nst] = offset;
3722       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3723                                   phase->longcon(con), T_LONG, MemNode::unordered);
3724     } else {
3725       // Omit either if it is a zero.
3726       if (con0 != 0) {
3727         ++new_int;
3728         off[nst]  = offset;
3729         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3730                                     phase->intcon(con0), T_INT, MemNode::unordered);
3731       }
3732       if (con1 != 0) {
3733         ++new_int;
3734         offset += BytesPerInt;
3735         adr = make_raw_address(offset, phase);
3736         off[nst]  = offset;
3737         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3738                                     phase->intcon(con1), T_INT, MemNode::unordered);
3739       }
3740     }
3741 
3742     // Insert second store first, then the first before the second.
3743     // Insert each one just before any overlapping non-constant stores.
3744     while (nst > 0) {
3745       Node* st1 = st[--nst];
3746       C->copy_node_notes_to(st1, old);
3747       st1 = phase->transform(st1);
3748       offset = off[nst];
3749       assert(offset >= header_size, "do not smash header");
3750       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
3751       guarantee(ins_idx != 0, "must re-insert constant store");
3752       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
3753       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
3754         set_req(--ins_idx, st1);
3755       else
3756         ins_req(ins_idx, st1);
3757     }
3758   }
3759 
3760   if (PrintCompilation && WizardMode)
3761     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
3762                   old_subword, old_long, new_int, new_long);
3763   if (C->log() != NULL)
3764     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
3765                    old_subword, old_long, new_int, new_long);
3766 
3767   // Clean up any remaining occurrences of zmem:
3768   remove_extra_zeroes();
3769 }
3770 
3771 // Explore forward from in(start) to find the first fully initialized
3772 // word, and return its offset.  Skip groups of subword stores which
3773 // together initialize full words.  If in(start) is itself part of a
3774 // fully initialized word, return the offset of in(start).  If there
3775 // are no following full-word stores, or if something is fishy, return
3776 // a negative value.
3777 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
3778   int       int_map = 0;
3779   intptr_t  int_map_off = 0;
3780   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
3781 
3782   for (uint i = start, limit = req(); i < limit; i++) {
3783     Node* st = in(i);
3784 
3785     intptr_t st_off = get_store_offset(st, phase);
3786     if (st_off < 0)  break;  // return conservative answer
3787 
3788     int st_size = st->as_Store()->memory_size();
3789     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
3790       return st_off;            // we found a complete word init
3791     }
3792 
3793     // update the map:
3794 
3795     intptr_t this_int_off = align_size_down(st_off, BytesPerInt);
3796     if (this_int_off != int_map_off) {
3797       // reset the map:
3798       int_map = 0;
3799       int_map_off = this_int_off;
3800     }
3801 
3802     int subword_off = st_off - this_int_off;
3803     int_map |= right_n_bits(st_size) << subword_off;
3804     if ((int_map & FULL_MAP) == FULL_MAP) {
3805       return this_int_off;      // we found a complete word init
3806     }
3807 
3808     // Did this store hit or cross the word boundary?
3809     intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt);
3810     if (next_int_off == this_int_off + BytesPerInt) {
3811       // We passed the current int, without fully initializing it.
3812       int_map_off = next_int_off;
3813       int_map >>= BytesPerInt;
3814     } else if (next_int_off > this_int_off + BytesPerInt) {
3815       // We passed the current and next int.
3816       return this_int_off + BytesPerInt;
3817     }
3818   }
3819 
3820   return -1;
3821 }
3822 
3823 
3824 // Called when the associated AllocateNode is expanded into CFG.
3825 // At this point, we may perform additional optimizations.
3826 // Linearize the stores by ascending offset, to make memory
3827 // activity as coherent as possible.
3828 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
3829                                       intptr_t header_size,
3830                                       Node* size_in_bytes,
3831                                       PhaseGVN* phase) {
3832   assert(!is_complete(), "not already complete");
3833   assert(stores_are_sane(phase), "");
3834   assert(allocation() != NULL, "must be present");
3835 
3836   remove_extra_zeroes();
3837 
3838   if (ReduceFieldZeroing || ReduceBulkZeroing)
3839     // reduce instruction count for common initialization patterns
3840     coalesce_subword_stores(header_size, size_in_bytes, phase);
3841 
3842   Node* zmem = zero_memory();   // initially zero memory state
3843   Node* inits = zmem;           // accumulating a linearized chain of inits
3844   #ifdef ASSERT
3845   intptr_t first_offset = allocation()->minimum_header_size();
3846   intptr_t last_init_off = first_offset;  // previous init offset
3847   intptr_t last_init_end = first_offset;  // previous init offset+size
3848   intptr_t last_tile_end = first_offset;  // previous tile offset+size
3849   #endif
3850   intptr_t zeroes_done = header_size;
3851 
3852   bool do_zeroing = true;       // we might give up if inits are very sparse
3853   int  big_init_gaps = 0;       // how many large gaps have we seen?
3854 
3855   if (ZeroTLAB)  do_zeroing = false;
3856   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
3857 
3858   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3859     Node* st = in(i);
3860     intptr_t st_off = get_store_offset(st, phase);
3861     if (st_off < 0)
3862       break;                    // unknown junk in the inits
3863     if (st->in(MemNode::Memory) != zmem)
3864       break;                    // complicated store chains somehow in list
3865 
3866     int st_size = st->as_Store()->memory_size();
3867     intptr_t next_init_off = st_off + st_size;
3868 
3869     if (do_zeroing && zeroes_done < next_init_off) {
3870       // See if this store needs a zero before it or under it.
3871       intptr_t zeroes_needed = st_off;
3872 
3873       if (st_size < BytesPerInt) {
3874         // Look for subword stores which only partially initialize words.
3875         // If we find some, we must lay down some word-level zeroes first,
3876         // underneath the subword stores.
3877         //
3878         // Examples:
3879         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
3880         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
3881         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
3882         //
3883         // Note:  coalesce_subword_stores may have already done this,
3884         // if it was prompted by constant non-zero subword initializers.
3885         // But this case can still arise with non-constant stores.
3886 
3887         intptr_t next_full_store = find_next_fullword_store(i, phase);
3888 
3889         // In the examples above:
3890         //   in(i)          p   q   r   s     x   y     z
3891         //   st_off        12  13  14  15    12  13    14
3892         //   st_size        1   1   1   1     1   1     1
3893         //   next_full_s.  12  16  16  16    16  16    16
3894         //   z's_done      12  16  16  16    12  16    12
3895         //   z's_needed    12  16  16  16    16  16    16
3896         //   zsize          0   0   0   0     4   0     4
3897         if (next_full_store < 0) {
3898           // Conservative tack:  Zero to end of current word.
3899           zeroes_needed = align_size_up(zeroes_needed, BytesPerInt);
3900         } else {
3901           // Zero to beginning of next fully initialized word.
3902           // Or, don't zero at all, if we are already in that word.
3903           assert(next_full_store >= zeroes_needed, "must go forward");
3904           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
3905           zeroes_needed = next_full_store;
3906         }
3907       }
3908 
3909       if (zeroes_needed > zeroes_done) {
3910         intptr_t zsize = zeroes_needed - zeroes_done;
3911         // Do some incremental zeroing on rawmem, in parallel with inits.
3912         zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3913         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3914                                               zeroes_done, zeroes_needed,
3915                                               phase);
3916         zeroes_done = zeroes_needed;
3917         if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2)
3918           do_zeroing = false;   // leave the hole, next time
3919       }
3920     }
3921 
3922     // Collect the store and move on:
3923     st->set_req(MemNode::Memory, inits);
3924     inits = st;                 // put it on the linearized chain
3925     set_req(i, zmem);           // unhook from previous position
3926 
3927     if (zeroes_done == st_off)
3928       zeroes_done = next_init_off;
3929 
3930     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
3931 
3932     #ifdef ASSERT
3933     // Various order invariants.  Weaker than stores_are_sane because
3934     // a large constant tile can be filled in by smaller non-constant stores.
3935     assert(st_off >= last_init_off, "inits do not reverse");
3936     last_init_off = st_off;
3937     const Type* val = NULL;
3938     if (st_size >= BytesPerInt &&
3939         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
3940         (int)val->basic_type() < (int)T_OBJECT) {
3941       assert(st_off >= last_tile_end, "tiles do not overlap");
3942       assert(st_off >= last_init_end, "tiles do not overwrite inits");
3943       last_tile_end = MAX2(last_tile_end, next_init_off);
3944     } else {
3945       intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong);
3946       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
3947       assert(st_off      >= last_init_end, "inits do not overlap");
3948       last_init_end = next_init_off;  // it's a non-tile
3949     }
3950     #endif //ASSERT
3951   }
3952 
3953   remove_extra_zeroes();        // clear out all the zmems left over
3954   add_req(inits);
3955 
3956   if (!ZeroTLAB) {
3957     // If anything remains to be zeroed, zero it all now.
3958     zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3959     // if it is the last unused 4 bytes of an instance, forget about it
3960     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
3961     if (zeroes_done + BytesPerLong >= size_limit) {
3962       assert(allocation() != NULL, "");
3963       if (allocation()->Opcode() == Op_Allocate) {
3964         Node* klass_node = allocation()->in(AllocateNode::KlassNode);
3965         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
3966         if (zeroes_done == k->layout_helper())
3967           zeroes_done = size_limit;
3968       }
3969     }
3970     if (zeroes_done < size_limit) {
3971       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3972                                             zeroes_done, size_in_bytes, phase);
3973     }
3974   }
3975 
3976   set_complete(phase);
3977   return rawmem;
3978 }
3979 
3980 
3981 #ifdef ASSERT
3982 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
3983   if (is_complete())
3984     return true;                // stores could be anything at this point
3985   assert(allocation() != NULL, "must be present");
3986   intptr_t last_off = allocation()->minimum_header_size();
3987   for (uint i = InitializeNode::RawStores; i < req(); i++) {
3988     Node* st = in(i);
3989     intptr_t st_off = get_store_offset(st, phase);
3990     if (st_off < 0)  continue;  // ignore dead garbage
3991     if (last_off > st_off) {
3992       tty->print_cr("*** bad store offset at %d: %d > %d", i, last_off, st_off);
3993       this->dump(2);
3994       assert(false, "ascending store offsets");
3995       return false;
3996     }
3997     last_off = st_off + st->as_Store()->memory_size();
3998   }
3999   return true;
4000 }
4001 #endif //ASSERT
4002 
4003 
4004 
4005 
4006 //============================MergeMemNode=====================================
4007 //
4008 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
4009 // contributing store or call operations.  Each contributor provides the memory
4010 // state for a particular "alias type" (see Compile::alias_type).  For example,
4011 // if a MergeMem has an input X for alias category #6, then any memory reference
4012 // to alias category #6 may use X as its memory state input, as an exact equivalent
4013 // to using the MergeMem as a whole.
4014 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4015 //
4016 // (Here, the <N> notation gives the index of the relevant adr_type.)
4017 //
4018 // In one special case (and more cases in the future), alias categories overlap.
4019 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4020 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4021 // it is exactly equivalent to that state W:
4022 //   MergeMem(<Bot>: W) <==> W
4023 //
4024 // Usually, the merge has more than one input.  In that case, where inputs
4025 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4026 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4027 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4028 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4029 //
4030 // A merge can take a "wide" memory state as one of its narrow inputs.
4031 // This simply means that the merge observes out only the relevant parts of
4032 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4033 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4034 //
4035 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4036 // and that memory slices "leak through":
4037 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4038 //
4039 // But, in such a cascade, repeated memory slices can "block the leak":
4040 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4041 //
4042 // In the last example, Y is not part of the combined memory state of the
4043 // outermost MergeMem.  The system must, of course, prevent unschedulable
4044 // memory states from arising, so you can be sure that the state Y is somehow
4045 // a precursor to state Y'.
4046 //
4047 //
4048 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4049 // of each MergeMemNode array are exactly the numerical alias indexes, including
4050 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4051 // Compile::alias_type (and kin) produce and manage these indexes.
4052 //
4053 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4054 // (Note that this provides quick access to the top node inside MergeMem methods,
4055 // without the need to reach out via TLS to Compile::current.)
4056 //
4057 // As a consequence of what was just described, a MergeMem that represents a full
4058 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4059 // containing all alias categories.
4060 //
4061 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4062 //
4063 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4064 // a memory state for the alias type <N>, or else the top node, meaning that
4065 // there is no particular input for that alias type.  Note that the length of
4066 // a MergeMem is variable, and may be extended at any time to accommodate new
4067 // memory states at larger alias indexes.  When merges grow, they are of course
4068 // filled with "top" in the unused in() positions.
4069 //
4070 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4071 // (Top was chosen because it works smoothly with passes like GCM.)
4072 //
4073 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4074 // the type of random VM bits like TLS references.)  Since it is always the
4075 // first non-Bot memory slice, some low-level loops use it to initialize an
4076 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4077 //
4078 //
4079 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4080 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4081 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4082 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4083 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4084 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4085 //
4086 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4087 // really that different from the other memory inputs.  An abbreviation called
4088 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4089 //
4090 //
4091 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4092 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4093 // that "emerges though" the base memory will be marked as excluding the alias types
4094 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4095 //
4096 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4097 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4098 //
4099 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4100 // (It is currently unimplemented.)  As you can see, the resulting merge is
4101 // actually a disjoint union of memory states, rather than an overlay.
4102 //
4103 
4104 //------------------------------MergeMemNode-----------------------------------
4105 Node* MergeMemNode::make_empty_memory() {
4106   Node* empty_memory = (Node*) Compile::current()->top();
4107   assert(empty_memory->is_top(), "correct sentinel identity");
4108   return empty_memory;
4109 }
4110 
4111 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4112   init_class_id(Class_MergeMem);
4113   // all inputs are nullified in Node::Node(int)
4114   // set_input(0, NULL);  // no control input
4115 
4116   // Initialize the edges uniformly to top, for starters.
4117   Node* empty_mem = make_empty_memory();
4118   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4119     init_req(i,empty_mem);
4120   }
4121   assert(empty_memory() == empty_mem, "");
4122 
4123   if( new_base != NULL && new_base->is_MergeMem() ) {
4124     MergeMemNode* mdef = new_base->as_MergeMem();
4125     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4126     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4127       mms.set_memory(mms.memory2());
4128     }
4129     assert(base_memory() == mdef->base_memory(), "");
4130   } else {
4131     set_base_memory(new_base);
4132   }
4133 }
4134 
4135 // Make a new, untransformed MergeMem with the same base as 'mem'.
4136 // If mem is itself a MergeMem, populate the result with the same edges.
4137 MergeMemNode* MergeMemNode::make(Compile* C, Node* mem) {
4138   return new(C) MergeMemNode(mem);
4139 }
4140 
4141 //------------------------------cmp--------------------------------------------
4142 uint MergeMemNode::hash() const { return NO_HASH; }
4143 uint MergeMemNode::cmp( const Node &n ) const {
4144   return (&n == this);          // Always fail except on self
4145 }
4146 
4147 //------------------------------Identity---------------------------------------
4148 Node* MergeMemNode::Identity(PhaseTransform *phase) {
4149   // Identity if this merge point does not record any interesting memory
4150   // disambiguations.
4151   Node* base_mem = base_memory();
4152   Node* empty_mem = empty_memory();
4153   if (base_mem != empty_mem) {  // Memory path is not dead?
4154     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4155       Node* mem = in(i);
4156       if (mem != empty_mem && mem != base_mem) {
4157         return this;            // Many memory splits; no change
4158       }
4159     }
4160   }
4161   return base_mem;              // No memory splits; ID on the one true input
4162 }
4163 
4164 //------------------------------Ideal------------------------------------------
4165 // This method is invoked recursively on chains of MergeMem nodes
4166 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4167   // Remove chain'd MergeMems
4168   //
4169   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4170   // relative to the "in(Bot)".  Since we are patching both at the same time,
4171   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4172   // but rewrite each "in(i)" relative to the new "in(Bot)".
4173   Node *progress = NULL;
4174 
4175 
4176   Node* old_base = base_memory();
4177   Node* empty_mem = empty_memory();
4178   if (old_base == empty_mem)
4179     return NULL; // Dead memory path.
4180 
4181   MergeMemNode* old_mbase;
4182   if (old_base != NULL && old_base->is_MergeMem())
4183     old_mbase = old_base->as_MergeMem();
4184   else
4185     old_mbase = NULL;
4186   Node* new_base = old_base;
4187 
4188   // simplify stacked MergeMems in base memory
4189   if (old_mbase)  new_base = old_mbase->base_memory();
4190 
4191   // the base memory might contribute new slices beyond my req()
4192   if (old_mbase)  grow_to_match(old_mbase);
4193 
4194   // Look carefully at the base node if it is a phi.
4195   PhiNode* phi_base;
4196   if (new_base != NULL && new_base->is_Phi())
4197     phi_base = new_base->as_Phi();
4198   else
4199     phi_base = NULL;
4200 
4201   Node*    phi_reg = NULL;
4202   uint     phi_len = (uint)-1;
4203   if (phi_base != NULL && !phi_base->is_copy()) {
4204     // do not examine phi if degraded to a copy
4205     phi_reg = phi_base->region();
4206     phi_len = phi_base->req();
4207     // see if the phi is unfinished
4208     for (uint i = 1; i < phi_len; i++) {
4209       if (phi_base->in(i) == NULL) {
4210         // incomplete phi; do not look at it yet!
4211         phi_reg = NULL;
4212         phi_len = (uint)-1;
4213         break;
4214       }
4215     }
4216   }
4217 
4218   // Note:  We do not call verify_sparse on entry, because inputs
4219   // can normalize to the base_memory via subsume_node or similar
4220   // mechanisms.  This method repairs that damage.
4221 
4222   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4223 
4224   // Look at each slice.
4225   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4226     Node* old_in = in(i);
4227     // calculate the old memory value
4228     Node* old_mem = old_in;
4229     if (old_mem == empty_mem)  old_mem = old_base;
4230     assert(old_mem == memory_at(i), "");
4231 
4232     // maybe update (reslice) the old memory value
4233 
4234     // simplify stacked MergeMems
4235     Node* new_mem = old_mem;
4236     MergeMemNode* old_mmem;
4237     if (old_mem != NULL && old_mem->is_MergeMem())
4238       old_mmem = old_mem->as_MergeMem();
4239     else
4240       old_mmem = NULL;
4241     if (old_mmem == this) {
4242       // This can happen if loops break up and safepoints disappear.
4243       // A merge of BotPtr (default) with a RawPtr memory derived from a
4244       // safepoint can be rewritten to a merge of the same BotPtr with
4245       // the BotPtr phi coming into the loop.  If that phi disappears
4246       // also, we can end up with a self-loop of the mergemem.
4247       // In general, if loops degenerate and memory effects disappear,
4248       // a mergemem can be left looking at itself.  This simply means
4249       // that the mergemem's default should be used, since there is
4250       // no longer any apparent effect on this slice.
4251       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4252       //       from start.  Update the input to TOP.
4253       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4254     }
4255     else if (old_mmem != NULL) {
4256       new_mem = old_mmem->memory_at(i);
4257     }
4258     // else preceding memory was not a MergeMem
4259 
4260     // replace equivalent phis (unfortunately, they do not GVN together)
4261     if (new_mem != NULL && new_mem != new_base &&
4262         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4263       if (new_mem->is_Phi()) {
4264         PhiNode* phi_mem = new_mem->as_Phi();
4265         for (uint i = 1; i < phi_len; i++) {
4266           if (phi_base->in(i) != phi_mem->in(i)) {
4267             phi_mem = NULL;
4268             break;
4269           }
4270         }
4271         if (phi_mem != NULL) {
4272           // equivalent phi nodes; revert to the def
4273           new_mem = new_base;
4274         }
4275       }
4276     }
4277 
4278     // maybe store down a new value
4279     Node* new_in = new_mem;
4280     if (new_in == new_base)  new_in = empty_mem;
4281 
4282     if (new_in != old_in) {
4283       // Warning:  Do not combine this "if" with the previous "if"
4284       // A memory slice might have be be rewritten even if it is semantically
4285       // unchanged, if the base_memory value has changed.
4286       set_req(i, new_in);
4287       progress = this;          // Report progress
4288     }
4289   }
4290 
4291   if (new_base != old_base) {
4292     set_req(Compile::AliasIdxBot, new_base);
4293     // Don't use set_base_memory(new_base), because we need to update du.
4294     assert(base_memory() == new_base, "");
4295     progress = this;
4296   }
4297 
4298   if( base_memory() == this ) {
4299     // a self cycle indicates this memory path is dead
4300     set_req(Compile::AliasIdxBot, empty_mem);
4301   }
4302 
4303   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4304   // Recursion must occur after the self cycle check above
4305   if( base_memory()->is_MergeMem() ) {
4306     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4307     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4308     if( m != NULL && (m->is_top() ||
4309         m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) {
4310       // propagate rollup of dead cycle to self
4311       set_req(Compile::AliasIdxBot, empty_mem);
4312     }
4313   }
4314 
4315   if( base_memory() == empty_mem ) {
4316     progress = this;
4317     // Cut inputs during Parse phase only.
4318     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4319     if( !can_reshape ) {
4320       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4321         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4322       }
4323     }
4324   }
4325 
4326   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4327     // Check if PhiNode::Ideal's "Split phis through memory merges"
4328     // transform should be attempted. Look for this->phi->this cycle.
4329     uint merge_width = req();
4330     if (merge_width > Compile::AliasIdxRaw) {
4331       PhiNode* phi = base_memory()->as_Phi();
4332       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4333         if (phi->in(i) == this) {
4334           phase->is_IterGVN()->_worklist.push(phi);
4335           break;
4336         }
4337       }
4338     }
4339   }
4340 
4341   assert(progress || verify_sparse(), "please, no dups of base");
4342   return progress;
4343 }
4344 
4345 //-------------------------set_base_memory-------------------------------------
4346 void MergeMemNode::set_base_memory(Node *new_base) {
4347   Node* empty_mem = empty_memory();
4348   set_req(Compile::AliasIdxBot, new_base);
4349   assert(memory_at(req()) == new_base, "must set default memory");
4350   // Clear out other occurrences of new_base:
4351   if (new_base != empty_mem) {
4352     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4353       if (in(i) == new_base)  set_req(i, empty_mem);
4354     }
4355   }
4356 }
4357 
4358 //------------------------------out_RegMask------------------------------------
4359 const RegMask &MergeMemNode::out_RegMask() const {
4360   return RegMask::Empty;
4361 }
4362 
4363 //------------------------------dump_spec--------------------------------------
4364 #ifndef PRODUCT
4365 void MergeMemNode::dump_spec(outputStream *st) const {
4366   st->print(" {");
4367   Node* base_mem = base_memory();
4368   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4369     Node* mem = memory_at(i);
4370     if (mem == base_mem) { st->print(" -"); continue; }
4371     st->print( " N%d:", mem->_idx );
4372     Compile::current()->get_adr_type(i)->dump_on(st);
4373   }
4374   st->print(" }");
4375 }
4376 #endif // !PRODUCT
4377 
4378 
4379 #ifdef ASSERT
4380 static bool might_be_same(Node* a, Node* b) {
4381   if (a == b)  return true;
4382   if (!(a->is_Phi() || b->is_Phi()))  return false;
4383   // phis shift around during optimization
4384   return true;  // pretty stupid...
4385 }
4386 
4387 // verify a narrow slice (either incoming or outgoing)
4388 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4389   if (!VerifyAliases)       return;  // don't bother to verify unless requested
4390   if (is_error_reported())  return;  // muzzle asserts when debugging an error
4391   if (Node::in_dump())      return;  // muzzle asserts when printing
4392   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4393   assert(n != NULL, "");
4394   // Elide intervening MergeMem's
4395   while (n->is_MergeMem()) {
4396     n = n->as_MergeMem()->memory_at(alias_idx);
4397   }
4398   Compile* C = Compile::current();
4399   const TypePtr* n_adr_type = n->adr_type();
4400   if (n == m->empty_memory()) {
4401     // Implicit copy of base_memory()
4402   } else if (n_adr_type != TypePtr::BOTTOM) {
4403     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4404     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4405   } else {
4406     // A few places like make_runtime_call "know" that VM calls are narrow,
4407     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4408     bool expected_wide_mem = false;
4409     if (n == m->base_memory()) {
4410       expected_wide_mem = true;
4411     } else if (alias_idx == Compile::AliasIdxRaw ||
4412                n == m->memory_at(Compile::AliasIdxRaw)) {
4413       expected_wide_mem = true;
4414     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4415       // memory can "leak through" calls on channels that
4416       // are write-once.  Allow this also.
4417       expected_wide_mem = true;
4418     }
4419     assert(expected_wide_mem, "expected narrow slice replacement");
4420   }
4421 }
4422 #else // !ASSERT
4423 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4424 #endif
4425 
4426 
4427 //-----------------------------memory_at---------------------------------------
4428 Node* MergeMemNode::memory_at(uint alias_idx) const {
4429   assert(alias_idx >= Compile::AliasIdxRaw ||
4430          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4431          "must avoid base_memory and AliasIdxTop");
4432 
4433   // Otherwise, it is a narrow slice.
4434   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4435   Compile *C = Compile::current();
4436   if (is_empty_memory(n)) {
4437     // the array is sparse; empty slots are the "top" node
4438     n = base_memory();
4439     assert(Node::in_dump()
4440            || n == NULL || n->bottom_type() == Type::TOP
4441            || n->adr_type() == NULL // address is TOP
4442            || n->adr_type() == TypePtr::BOTTOM
4443            || n->adr_type() == TypeRawPtr::BOTTOM
4444            || Compile::current()->AliasLevel() == 0,
4445            "must be a wide memory");
4446     // AliasLevel == 0 if we are organizing the memory states manually.
4447     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4448   } else {
4449     // make sure the stored slice is sane
4450     #ifdef ASSERT
4451     if (is_error_reported() || Node::in_dump()) {
4452     } else if (might_be_same(n, base_memory())) {
4453       // Give it a pass:  It is a mostly harmless repetition of the base.
4454       // This can arise normally from node subsumption during optimization.
4455     } else {
4456       verify_memory_slice(this, alias_idx, n);
4457     }
4458     #endif
4459   }
4460   return n;
4461 }
4462 
4463 //---------------------------set_memory_at-------------------------------------
4464 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4465   verify_memory_slice(this, alias_idx, n);
4466   Node* empty_mem = empty_memory();
4467   if (n == base_memory())  n = empty_mem;  // collapse default
4468   uint need_req = alias_idx+1;
4469   if (req() < need_req) {
4470     if (n == empty_mem)  return;  // already the default, so do not grow me
4471     // grow the sparse array
4472     do {
4473       add_req(empty_mem);
4474     } while (req() < need_req);
4475   }
4476   set_req( alias_idx, n );
4477 }
4478 
4479 
4480 
4481 //--------------------------iteration_setup------------------------------------
4482 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4483   if (other != NULL) {
4484     grow_to_match(other);
4485     // invariant:  the finite support of mm2 is within mm->req()
4486     #ifdef ASSERT
4487     for (uint i = req(); i < other->req(); i++) {
4488       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4489     }
4490     #endif
4491   }
4492   // Replace spurious copies of base_memory by top.
4493   Node* base_mem = base_memory();
4494   if (base_mem != NULL && !base_mem->is_top()) {
4495     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4496       if (in(i) == base_mem)
4497         set_req(i, empty_memory());
4498     }
4499   }
4500 }
4501 
4502 //---------------------------grow_to_match-------------------------------------
4503 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4504   Node* empty_mem = empty_memory();
4505   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4506   // look for the finite support of the other memory
4507   for (uint i = other->req(); --i >= req(); ) {
4508     if (other->in(i) != empty_mem) {
4509       uint new_len = i+1;
4510       while (req() < new_len)  add_req(empty_mem);
4511       break;
4512     }
4513   }
4514 }
4515 
4516 //---------------------------verify_sparse-------------------------------------
4517 #ifndef PRODUCT
4518 bool MergeMemNode::verify_sparse() const {
4519   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4520   Node* base_mem = base_memory();
4521   // The following can happen in degenerate cases, since empty==top.
4522   if (is_empty_memory(base_mem))  return true;
4523   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4524     assert(in(i) != NULL, "sane slice");
4525     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4526   }
4527   return true;
4528 }
4529 
4530 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4531   Node* n;
4532   n = mm->in(idx);
4533   if (mem == n)  return true;  // might be empty_memory()
4534   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4535   if (mem == n)  return true;
4536   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4537     if (mem == n)  return true;
4538     if (n == NULL)  break;
4539   }
4540   return false;
4541 }
4542 #endif // !PRODUCT