1 /*
   2  * Copyright (c) 1997, 2011, 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/loopnode.hpp"
  35 #include "opto/machnode.hpp"
  36 #include "opto/matcher.hpp"
  37 #include "opto/memnode.hpp"
  38 #include "opto/mulnode.hpp"
  39 #include "opto/phaseX.hpp"
  40 #include "opto/regmask.hpp"
  41 
  42 // Portions of code courtesy of Clifford Click
  43 
  44 // Optimization - Graph Style
  45 
  46 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  47 
  48 //=============================================================================
  49 uint MemNode::size_of() const { return sizeof(*this); }
  50 
  51 const TypePtr *MemNode::adr_type() const {
  52   Node* adr = in(Address);
  53   const TypePtr* cross_check = NULL;
  54   DEBUG_ONLY(cross_check = _adr_type);
  55   return calculate_adr_type(adr->bottom_type(), cross_check);
  56 }
  57 
  58 #ifndef PRODUCT
  59 void MemNode::dump_spec(outputStream *st) const {
  60   if (in(Address) == NULL)  return; // node is dead
  61 #ifndef ASSERT
  62   // fake the missing field
  63   const TypePtr* _adr_type = NULL;
  64   if (in(Address) != NULL)
  65     _adr_type = in(Address)->bottom_type()->isa_ptr();
  66 #endif
  67   dump_adr_type(this, _adr_type, st);
  68 
  69   Compile* C = Compile::current();
  70   if( C->alias_type(_adr_type)->is_volatile() )
  71     st->print(" Volatile!");
  72 }
  73 
  74 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
  75   st->print(" @");
  76   if (adr_type == NULL) {
  77     st->print("NULL");
  78   } else {
  79     adr_type->dump_on(st);
  80     Compile* C = Compile::current();
  81     Compile::AliasType* atp = NULL;
  82     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
  83     if (atp == NULL)
  84       st->print(", idx=?\?;");
  85     else if (atp->index() == Compile::AliasIdxBot)
  86       st->print(", idx=Bot;");
  87     else if (atp->index() == Compile::AliasIdxTop)
  88       st->print(", idx=Top;");
  89     else if (atp->index() == Compile::AliasIdxRaw)
  90       st->print(", idx=Raw;");
  91     else {
  92       ciField* field = atp->field();
  93       if (field) {
  94         st->print(", name=");
  95         field->print_name_on(st);
  96       }
  97       st->print(", idx=%d;", atp->index());
  98     }
  99   }
 100 }
 101 
 102 extern void print_alias_types();
 103 
 104 #endif
 105 
 106 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) {
 107   const TypeOopPtr *tinst = t_adr->isa_oopptr();
 108   if (tinst == NULL || !tinst->is_known_instance_field())
 109     return mchain;  // don't try to optimize non-instance types
 110   uint instance_id = tinst->instance_id();
 111   Node *start_mem = phase->C->start()->proj_out(TypeFunc::Memory);
 112   Node *prev = NULL;
 113   Node *result = mchain;
 114   while (prev != result) {
 115     prev = result;
 116     if (result == start_mem)
 117       break;  // hit one of our sentinels
 118     // skip over a call which does not affect this memory slice
 119     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 120       Node *proj_in = result->in(0);
 121       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 122         break;  // hit one of our sentinels
 123       } else if (proj_in->is_Call()) {
 124         CallNode *call = proj_in->as_Call();
 125         if (!call->may_modify(t_adr, phase)) {
 126           result = call->in(TypeFunc::Memory);
 127         }
 128       } else if (proj_in->is_Initialize()) {
 129         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 130         // Stop if this is the initialization for the object instance which
 131         // which contains this memory slice, otherwise skip over it.
 132         if (alloc != NULL && alloc->_idx != instance_id) {
 133           result = proj_in->in(TypeFunc::Memory);
 134         }
 135       } else if (proj_in->is_MemBar()) {
 136         result = proj_in->in(TypeFunc::Memory);
 137       } else {
 138         assert(false, "unexpected projection");
 139       }
 140     } else if (result->is_ClearArray()) {
 141       if (!ClearArrayNode::step_through(&result, instance_id, phase)) {
 142         // Can not bypass initialization of the instance
 143         // we are looking for.
 144         break;
 145       }
 146       // Otherwise skip it (the call updated 'result' value).
 147     } else if (result->is_MergeMem()) {
 148       result = step_through_mergemem(phase, result->as_MergeMem(), t_adr, NULL, tty);
 149     }
 150   }
 151   return result;
 152 }
 153 
 154 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) {
 155   const TypeOopPtr *t_oop = t_adr->isa_oopptr();
 156   bool is_instance = (t_oop != NULL) && t_oop->is_known_instance_field();
 157   PhaseIterGVN *igvn = phase->is_IterGVN();
 158   Node *result = mchain;
 159   result = optimize_simple_memory_chain(result, t_adr, phase);
 160   if (is_instance && igvn != NULL  && result->is_Phi()) {
 161     PhiNode *mphi = result->as_Phi();
 162     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 163     const TypePtr *t = mphi->adr_type();
 164     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 165         t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 166         t->is_oopptr()->cast_to_exactness(true)
 167          ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 168          ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop) {
 169       // clone the Phi with our address type
 170       result = mphi->split_out_instance(t_adr, igvn);
 171     } else {
 172       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 173     }
 174   }
 175   return result;
 176 }
 177 
 178 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 179   uint alias_idx = phase->C->get_alias_index(tp);
 180   Node *mem = mmem;
 181 #ifdef ASSERT
 182   {
 183     // Check that current type is consistent with the alias index used during graph construction
 184     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 185     bool consistent =  adr_check == NULL || adr_check->empty() ||
 186                        phase->C->must_alias(adr_check, alias_idx );
 187     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 188     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 189                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 190         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 191         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 192           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 193           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 194       // don't assert if it is dead code.
 195       consistent = true;
 196     }
 197     if( !consistent ) {
 198       st->print("alias_idx==%d, adr_check==", alias_idx);
 199       if( adr_check == NULL ) {
 200         st->print("NULL");
 201       } else {
 202         adr_check->dump();
 203       }
 204       st->cr();
 205       print_alias_types();
 206       assert(consistent, "adr_check must match alias idx");
 207     }
 208   }
 209 #endif
 210   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 211   // means an array I have not precisely typed yet.  Do not do any
 212   // alias stuff with it any time soon.
 213   const TypeOopPtr *toop = tp->isa_oopptr();
 214   if( tp->base() != Type::AnyPtr &&
 215       !(toop &&
 216         toop->klass() != NULL &&
 217         toop->klass()->is_java_lang_Object() &&
 218         toop->offset() == Type::OffsetBot) ) {
 219     // compress paths and change unreachable cycles to TOP
 220     // If not, we can update the input infinitely along a MergeMem cycle
 221     // Equivalent code in PhiNode::Ideal
 222     Node* m  = phase->transform(mmem);
 223     // If transformed to a MergeMem, get the desired slice
 224     // Otherwise the returned node represents memory for every slice
 225     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 226     // Update input if it is progress over what we have now
 227   }
 228   return mem;
 229 }
 230 
 231 //--------------------------Ideal_common---------------------------------------
 232 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 233 // Unhook non-raw memories from complete (macro-expanded) initializations.
 234 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 235   // If our control input is a dead region, kill all below the region
 236   Node *ctl = in(MemNode::Control);
 237   if (ctl && remove_dead_region(phase, can_reshape))
 238     return this;
 239   ctl = in(MemNode::Control);
 240   // Don't bother trying to transform a dead node
 241   if( ctl && ctl->is_top() )  return NodeSentinel;
 242 
 243   PhaseIterGVN *igvn = phase->is_IterGVN();
 244   // Wait if control on the worklist.
 245   if (ctl && can_reshape && igvn != NULL) {
 246     Node* bol = NULL;
 247     Node* cmp = NULL;
 248     if (ctl->in(0)->is_If()) {
 249       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 250       bol = ctl->in(0)->in(1);
 251       if (bol->is_Bool())
 252         cmp = ctl->in(0)->in(1)->in(1);
 253     }
 254     if (igvn->_worklist.member(ctl) ||
 255         (bol != NULL && igvn->_worklist.member(bol)) ||
 256         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 257       // This control path may be dead.
 258       // Delay this memory node transformation until the control is processed.
 259       phase->is_IterGVN()->_worklist.push(this);
 260       return NodeSentinel; // caller will return NULL
 261     }
 262   }
 263   // Ignore if memory is dead, or self-loop
 264   Node *mem = in(MemNode::Memory);
 265   if( phase->type( mem ) == Type::TOP ) return NodeSentinel; // caller will return NULL
 266   assert( mem != this, "dead loop in MemNode::Ideal" );
 267 
 268   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 269     // This memory slice may be dead.
 270     // Delay this mem node transformation until the memory is processed.
 271     phase->is_IterGVN()->_worklist.push(this);
 272     return NodeSentinel; // caller will return NULL
 273   }
 274 
 275   Node *address = in(MemNode::Address);
 276   const Type *t_adr = phase->type( address );
 277   if( t_adr == Type::TOP )              return NodeSentinel; // caller will return NULL
 278 
 279   if( can_reshape && igvn != NULL &&
 280       (igvn->_worklist.member(address) ||
 281        igvn->_worklist.size() > 0 && (phase->type(address) != adr_type())) ) {
 282     // The address's base and type may change when the address is processed.
 283     // Delay this mem node transformation until the address is processed.
 284     phase->is_IterGVN()->_worklist.push(this);
 285     return NodeSentinel; // caller will return NULL
 286   }
 287 
 288   // Do NOT remove or optimize the next lines: ensure a new alias index
 289   // is allocated for an oop pointer type before Escape Analysis.
 290   // Note: C++ will not remove it since the call has side effect.
 291   if ( t_adr->isa_oopptr() ) {
 292     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 293   }
 294 
 295 #ifdef ASSERT
 296   Node* base = NULL;
 297   if (address->is_AddP())
 298     base = address->in(AddPNode::Base);
 299   assert(base == NULL || t_adr->isa_rawptr() ||
 300         !phase->type(base)->higher_equal(TypePtr::NULL_PTR), "NULL+offs not RAW address?");
 301 #endif
 302 
 303   // Avoid independent memory operations
 304   Node* old_mem = mem;
 305 
 306   // The code which unhooks non-raw memories from complete (macro-expanded)
 307   // initializations was removed. After macro-expansion all stores catched
 308   // by Initialize node became raw stores and there is no information
 309   // which memory slices they modify. So it is unsafe to move any memory
 310   // operation above these stores. Also in most cases hooked non-raw memories
 311   // were already unhooked by using information from detect_ptr_independence()
 312   // and find_previous_store().
 313 
 314   if (mem->is_MergeMem()) {
 315     MergeMemNode* mmem = mem->as_MergeMem();
 316     const TypePtr *tp = t_adr->is_ptr();
 317 
 318     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 319   }
 320 
 321   if (mem != old_mem) {
 322     set_req(MemNode::Memory, mem);
 323     if (phase->type( mem ) == Type::TOP) return NodeSentinel;
 324     return this;
 325   }
 326 
 327   // let the subclass continue analyzing...
 328   return NULL;
 329 }
 330 
 331 // Helper function for proving some simple control dominations.
 332 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 333 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 334 // is not a constant (dominated by the method's StartNode).
 335 // Used by MemNode::find_previous_store to prove that the
 336 // control input of a memory operation predates (dominates)
 337 // an allocation it wants to look past.
 338 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 339   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 340     return false; // Conservative answer for dead code
 341 
 342   // Check 'dom'. Skip Proj and CatchProj nodes.
 343   dom = dom->find_exact_control(dom);
 344   if (dom == NULL || dom->is_top())
 345     return false; // Conservative answer for dead code
 346 
 347   if (dom == sub) {
 348     // For the case when, for example, 'sub' is Initialize and the original
 349     // 'dom' is Proj node of the 'sub'.
 350     return false;
 351   }
 352 
 353   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 354     return true;
 355 
 356   // 'dom' dominates 'sub' if its control edge and control edges
 357   // of all its inputs dominate or equal to sub's control edge.
 358 
 359   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 360   // Or Region for the check in LoadNode::Ideal();
 361   // 'sub' should have sub->in(0) != NULL.
 362   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 363          sub->is_Region(), "expecting only these nodes");
 364 
 365   // Get control edge of 'sub'.
 366   Node* orig_sub = sub;
 367   sub = sub->find_exact_control(sub->in(0));
 368   if (sub == NULL || sub->is_top())
 369     return false; // Conservative answer for dead code
 370 
 371   assert(sub->is_CFG(), "expecting control");
 372 
 373   if (sub == dom)
 374     return true;
 375 
 376   if (sub->is_Start() || sub->is_Root())
 377     return false;
 378 
 379   {
 380     // Check all control edges of 'dom'.
 381 
 382     ResourceMark rm;
 383     Arena* arena = Thread::current()->resource_area();
 384     Node_List nlist(arena);
 385     Unique_Node_List dom_list(arena);
 386 
 387     dom_list.push(dom);
 388     bool only_dominating_controls = false;
 389 
 390     for (uint next = 0; next < dom_list.size(); next++) {
 391       Node* n = dom_list.at(next);
 392       if (n == orig_sub)
 393         return false; // One of dom's inputs dominated by sub.
 394       if (!n->is_CFG() && n->pinned()) {
 395         // Check only own control edge for pinned non-control nodes.
 396         n = n->find_exact_control(n->in(0));
 397         if (n == NULL || n->is_top())
 398           return false; // Conservative answer for dead code
 399         assert(n->is_CFG(), "expecting control");
 400         dom_list.push(n);
 401       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 402         only_dominating_controls = true;
 403       } else if (n->is_CFG()) {
 404         if (n->dominates(sub, nlist))
 405           only_dominating_controls = true;
 406         else
 407           return false;
 408       } else {
 409         // First, own control edge.
 410         Node* m = n->find_exact_control(n->in(0));
 411         if (m != NULL) {
 412           if (m->is_top())
 413             return false; // Conservative answer for dead code
 414           dom_list.push(m);
 415         }
 416         // Now, the rest of edges.
 417         uint cnt = n->req();
 418         for (uint i = 1; i < cnt; i++) {
 419           m = n->find_exact_control(n->in(i));
 420           if (m == NULL || m->is_top())
 421             continue;
 422           dom_list.push(m);
 423         }
 424       }
 425     }
 426     return only_dominating_controls;
 427   }
 428 }
 429 
 430 //---------------------detect_ptr_independence---------------------------------
 431 // Used by MemNode::find_previous_store to prove that two base
 432 // pointers are never equal.
 433 // The pointers are accompanied by their associated allocations,
 434 // if any, which have been previously discovered by the caller.
 435 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 436                                       Node* p2, AllocateNode* a2,
 437                                       PhaseTransform* phase) {
 438   // Attempt to prove that these two pointers cannot be aliased.
 439   // They may both manifestly be allocations, and they should differ.
 440   // Or, if they are not both allocations, they can be distinct constants.
 441   // Otherwise, one is an allocation and the other a pre-existing value.
 442   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 443     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 444   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 445     return (a1 != a2);
 446   } else if (a1 != NULL) {                  // one allocation a1
 447     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 448     return all_controls_dominate(p2, a1);
 449   } else { //(a2 != NULL)                   // one allocation a2
 450     return all_controls_dominate(p1, a2);
 451   }
 452   return false;
 453 }
 454 
 455 
 456 // The logic for reordering loads and stores uses four steps:
 457 // (a) Walk carefully past stores and initializations which we
 458 //     can prove are independent of this load.
 459 // (b) Observe that the next memory state makes an exact match
 460 //     with self (load or store), and locate the relevant store.
 461 // (c) Ensure that, if we were to wire self directly to the store,
 462 //     the optimizer would fold it up somehow.
 463 // (d) Do the rewiring, and return, depending on some other part of
 464 //     the optimizer to fold up the load.
 465 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 466 // specific to loads and stores, so they are handled by the callers.
 467 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 468 //
 469 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 470   Node*         ctrl   = in(MemNode::Control);
 471   Node*         adr    = in(MemNode::Address);
 472   intptr_t      offset = 0;
 473   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 474   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 475 
 476   if (offset == Type::OffsetBot)
 477     return NULL;            // cannot unalias unless there are precise offsets
 478 
 479   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 480 
 481   intptr_t size_in_bytes = memory_size();
 482 
 483   Node* mem = in(MemNode::Memory);   // start searching here...
 484 
 485   int cnt = 50;             // Cycle limiter
 486   for (;;) {                // While we can dance past unrelated stores...
 487     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 488 
 489     if (mem->is_Store()) {
 490       Node* st_adr = mem->in(MemNode::Address);
 491       intptr_t st_offset = 0;
 492       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 493       if (st_base == NULL)
 494         break;              // inscrutable pointer
 495       if (st_offset != offset && st_offset != Type::OffsetBot) {
 496         const int MAX_STORE = BytesPerLong;
 497         if (st_offset >= offset + size_in_bytes ||
 498             st_offset <= offset - MAX_STORE ||
 499             st_offset <= offset - mem->as_Store()->memory_size()) {
 500           // Success:  The offsets are provably independent.
 501           // (You may ask, why not just test st_offset != offset and be done?
 502           // The answer is that stores of different sizes can co-exist
 503           // in the same sequence of RawMem effects.  We sometimes initialize
 504           // a whole 'tile' of array elements with a single jint or jlong.)
 505           mem = mem->in(MemNode::Memory);
 506           continue;           // (a) advance through independent store memory
 507         }
 508       }
 509       if (st_base != base &&
 510           detect_ptr_independence(base, alloc,
 511                                   st_base,
 512                                   AllocateNode::Ideal_allocation(st_base, phase),
 513                                   phase)) {
 514         // Success:  The bases are provably independent.
 515         mem = mem->in(MemNode::Memory);
 516         continue;           // (a) advance through independent store memory
 517       }
 518 
 519       // (b) At this point, if the bases or offsets do not agree, we lose,
 520       // since we have not managed to prove 'this' and 'mem' independent.
 521       if (st_base == base && st_offset == offset) {
 522         return mem;         // let caller handle steps (c), (d)
 523       }
 524 
 525     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 526       InitializeNode* st_init = mem->in(0)->as_Initialize();
 527       AllocateNode*  st_alloc = st_init->allocation();
 528       if (st_alloc == NULL)
 529         break;              // something degenerated
 530       bool known_identical = false;
 531       bool known_independent = false;
 532       if (alloc == st_alloc)
 533         known_identical = true;
 534       else if (alloc != NULL)
 535         known_independent = true;
 536       else if (all_controls_dominate(this, st_alloc))
 537         known_independent = true;
 538 
 539       if (known_independent) {
 540         // The bases are provably independent: Either they are
 541         // manifestly distinct allocations, or else the control
 542         // of this load dominates the store's allocation.
 543         int alias_idx = phase->C->get_alias_index(adr_type());
 544         if (alias_idx == Compile::AliasIdxRaw) {
 545           mem = st_alloc->in(TypeFunc::Memory);
 546         } else {
 547           mem = st_init->memory(alias_idx);
 548         }
 549         continue;           // (a) advance through independent store memory
 550       }
 551 
 552       // (b) at this point, if we are not looking at a store initializing
 553       // the same allocation we are loading from, we lose.
 554       if (known_identical) {
 555         // From caller, can_see_stored_value will consult find_captured_store.
 556         return mem;         // let caller handle steps (c), (d)
 557       }
 558 
 559     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 560       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 561       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 562         CallNode *call = mem->in(0)->as_Call();
 563         if (!call->may_modify(addr_t, phase)) {
 564           mem = call->in(TypeFunc::Memory);
 565           continue;         // (a) advance through independent call memory
 566         }
 567       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 568         mem = mem->in(0)->in(TypeFunc::Memory);
 569         continue;           // (a) advance through independent MemBar memory
 570       } else if (mem->is_ClearArray()) {
 571         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 572           // (the call updated 'mem' value)
 573           continue;         // (a) advance through independent allocation memory
 574         } else {
 575           // Can not bypass initialization of the instance
 576           // we are looking for.
 577           return mem;
 578         }
 579       } else if (mem->is_MergeMem()) {
 580         int alias_idx = phase->C->get_alias_index(adr_type());
 581         mem = mem->as_MergeMem()->memory_at(alias_idx);
 582         continue;           // (a) advance through independent MergeMem memory
 583       }
 584     }
 585 
 586     // Unless there is an explicit 'continue', we must bail out here,
 587     // because 'mem' is an inscrutable memory state (e.g., a call).
 588     break;
 589   }
 590 
 591   return NULL;              // bail out
 592 }
 593 
 594 //----------------------calculate_adr_type-------------------------------------
 595 // Helper function.  Notices when the given type of address hits top or bottom.
 596 // Also, asserts a cross-check of the type against the expected address type.
 597 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 598   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 599   #ifdef PRODUCT
 600   cross_check = NULL;
 601   #else
 602   if (!VerifyAliases || is_error_reported() || Node::in_dump())  cross_check = NULL;
 603   #endif
 604   const TypePtr* tp = t->isa_ptr();
 605   if (tp == NULL) {
 606     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 607     return TypePtr::BOTTOM;           // touches lots of memory
 608   } else {
 609     #ifdef ASSERT
 610     // %%%% [phh] We don't check the alias index if cross_check is
 611     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 612     if (cross_check != NULL &&
 613         cross_check != TypePtr::BOTTOM &&
 614         cross_check != TypeRawPtr::BOTTOM) {
 615       // Recheck the alias index, to see if it has changed (due to a bug).
 616       Compile* C = Compile::current();
 617       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 618              "must stay in the original alias category");
 619       // The type of the address must be contained in the adr_type,
 620       // disregarding "null"-ness.
 621       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 622       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 623       assert(cross_check->meet(tp_notnull) == cross_check,
 624              "real address must not escape from expected memory type");
 625     }
 626     #endif
 627     return tp;
 628   }
 629 }
 630 
 631 //------------------------adr_phi_is_loop_invariant----------------------------
 632 // A helper function for Ideal_DU_postCCP to check if a Phi in a counted
 633 // loop is loop invariant. Make a quick traversal of Phi and associated
 634 // CastPP nodes, looking to see if they are a closed group within the loop.
 635 bool MemNode::adr_phi_is_loop_invariant(Node* adr_phi, Node* cast) {
 636   // The idea is that the phi-nest must boil down to only CastPP nodes
 637   // with the same data. This implies that any path into the loop already
 638   // includes such a CastPP, and so the original cast, whatever its input,
 639   // must be covered by an equivalent cast, with an earlier control input.
 640   ResourceMark rm;
 641 
 642   // The loop entry input of the phi should be the unique dominating
 643   // node for every Phi/CastPP in the loop.
 644   Unique_Node_List closure;
 645   closure.push(adr_phi->in(LoopNode::EntryControl));
 646 
 647   // Add the phi node and the cast to the worklist.
 648   Unique_Node_List worklist;
 649   worklist.push(adr_phi);
 650   if( cast != NULL ){
 651     if( !cast->is_ConstraintCast() ) return false;
 652     worklist.push(cast);
 653   }
 654 
 655   // Begin recursive walk of phi nodes.
 656   while( worklist.size() ){
 657     // Take a node off the worklist
 658     Node *n = worklist.pop();
 659     if( !closure.member(n) ){
 660       // Add it to the closure.
 661       closure.push(n);
 662       // Make a sanity check to ensure we don't waste too much time here.
 663       if( closure.size() > 20) return false;
 664       // This node is OK if:
 665       //  - it is a cast of an identical value
 666       //  - or it is a phi node (then we add its inputs to the worklist)
 667       // Otherwise, the node is not OK, and we presume the cast is not invariant
 668       if( n->is_ConstraintCast() ){
 669         worklist.push(n->in(1));
 670       } else if( n->is_Phi() ) {
 671         for( uint i = 1; i < n->req(); i++ ) {
 672           worklist.push(n->in(i));
 673         }
 674       } else {
 675         return false;
 676       }
 677     }
 678   }
 679 
 680   // Quit when the worklist is empty, and we've found no offending nodes.
 681   return true;
 682 }
 683 
 684 //------------------------------Ideal_DU_postCCP-------------------------------
 685 // Find any cast-away of null-ness and keep its control.  Null cast-aways are
 686 // going away in this pass and we need to make this memory op depend on the
 687 // gating null check.
 688 Node *MemNode::Ideal_DU_postCCP( PhaseCCP *ccp ) {
 689   return Ideal_common_DU_postCCP(ccp, this, in(MemNode::Address));
 690 }
 691 
 692 // I tried to leave the CastPP's in.  This makes the graph more accurate in
 693 // some sense; we get to keep around the knowledge that an oop is not-null
 694 // after some test.  Alas, the CastPP's interfere with GVN (some values are
 695 // the regular oop, some are the CastPP of the oop, all merge at Phi's which
 696 // cannot collapse, etc).  This cost us 10% on SpecJVM, even when I removed
 697 // some of the more trivial cases in the optimizer.  Removing more useless
 698 // Phi's started allowing Loads to illegally float above null checks.  I gave
 699 // up on this approach.  CNC 10/20/2000
 700 // This static method may be called not from MemNode (EncodePNode calls it).
 701 // Only the control edge of the node 'n' might be updated.
 702 Node *MemNode::Ideal_common_DU_postCCP( PhaseCCP *ccp, Node* n, Node* adr ) {
 703   Node *skipped_cast = NULL;
 704   // Need a null check?  Regular static accesses do not because they are
 705   // from constant addresses.  Array ops are gated by the range check (which
 706   // always includes a NULL check).  Just check field ops.
 707   if( n->in(MemNode::Control) == NULL ) {
 708     // Scan upwards for the highest location we can place this memory op.
 709     while( true ) {
 710       switch( adr->Opcode() ) {
 711 
 712       case Op_AddP:             // No change to NULL-ness, so peek thru AddP's
 713         adr = adr->in(AddPNode::Base);
 714         continue;
 715 
 716       case Op_DecodeN:         // No change to NULL-ness, so peek thru
 717         adr = adr->in(1);
 718         continue;
 719 
 720       case Op_CastPP:
 721         // If the CastPP is useless, just peek on through it.
 722         if( ccp->type(adr) == ccp->type(adr->in(1)) ) {
 723           // Remember the cast that we've peeked though. If we peek
 724           // through more than one, then we end up remembering the highest
 725           // one, that is, if in a loop, the one closest to the top.
 726           skipped_cast = adr;
 727           adr = adr->in(1);
 728           continue;
 729         }
 730         // CastPP is going away in this pass!  We need this memory op to be
 731         // control-dependent on the test that is guarding the CastPP.
 732         ccp->hash_delete(n);
 733         n->set_req(MemNode::Control, adr->in(0));
 734         ccp->hash_insert(n);
 735         return n;
 736 
 737       case Op_Phi:
 738         // Attempt to float above a Phi to some dominating point.
 739         if (adr->in(0) != NULL && adr->in(0)->is_CountedLoop()) {
 740           // If we've already peeked through a Cast (which could have set the
 741           // control), we can't float above a Phi, because the skipped Cast
 742           // may not be loop invariant.
 743           if (adr_phi_is_loop_invariant(adr, skipped_cast)) {
 744             adr = adr->in(1);
 745             continue;
 746           }
 747         }
 748 
 749         // Intentional fallthrough!
 750 
 751         // No obvious dominating point.  The mem op is pinned below the Phi
 752         // by the Phi itself.  If the Phi goes away (no true value is merged)
 753         // then the mem op can float, but not indefinitely.  It must be pinned
 754         // behind the controls leading to the Phi.
 755       case Op_CheckCastPP:
 756         // These usually stick around to change address type, however a
 757         // useless one can be elided and we still need to pick up a control edge
 758         if (adr->in(0) == NULL) {
 759           // This CheckCastPP node has NO control and is likely useless. But we
 760           // need check further up the ancestor chain for a control input to keep
 761           // the node in place. 4959717.
 762           skipped_cast = adr;
 763           adr = adr->in(1);
 764           continue;
 765         }
 766         ccp->hash_delete(n);
 767         n->set_req(MemNode::Control, adr->in(0));
 768         ccp->hash_insert(n);
 769         return n;
 770 
 771         // List of "safe" opcodes; those that implicitly block the memory
 772         // op below any null check.
 773       case Op_CastX2P:          // no null checks on native pointers
 774       case Op_Parm:             // 'this' pointer is not null
 775       case Op_LoadP:            // Loading from within a klass
 776       case Op_LoadN:            // Loading from within a klass
 777       case Op_LoadKlass:        // Loading from within a klass
 778       case Op_LoadNKlass:       // Loading from within a klass
 779       case Op_ConP:             // Loading from a klass
 780       case Op_ConN:             // Loading from a klass
 781       case Op_CreateEx:         // Sucking up the guts of an exception oop
 782       case Op_Con:              // Reading from TLS
 783       case Op_CMoveP:           // CMoveP is pinned
 784       case Op_CMoveN:           // CMoveN is pinned
 785         break;                  // No progress
 786 
 787       case Op_Proj:             // Direct call to an allocation routine
 788       case Op_SCMemProj:        // Memory state from store conditional ops
 789 #ifdef ASSERT
 790         {
 791           assert(adr->as_Proj()->_con == TypeFunc::Parms, "must be return value");
 792           const Node* call = adr->in(0);
 793           if (call->is_CallJava()) {
 794             const CallJavaNode* call_java = call->as_CallJava();
 795             const TypeTuple *r = call_java->tf()->range();
 796             assert(r->cnt() > TypeFunc::Parms, "must return value");
 797             const Type* ret_type = r->field_at(TypeFunc::Parms);
 798             assert(ret_type && ret_type->isa_ptr(), "must return pointer");
 799             // We further presume that this is one of
 800             // new_instance_Java, new_array_Java, or
 801             // the like, but do not assert for this.
 802           } else if (call->is_Allocate()) {
 803             // similar case to new_instance_Java, etc.
 804           } else if (!call->is_CallLeaf()) {
 805             // Projections from fetch_oop (OSR) are allowed as well.
 806             ShouldNotReachHere();
 807           }
 808         }
 809 #endif
 810         break;
 811       default:
 812         ShouldNotReachHere();
 813       }
 814       break;
 815     }
 816   }
 817 
 818   return  NULL;               // No progress
 819 }
 820 
 821 
 822 //=============================================================================
 823 uint LoadNode::size_of() const { return sizeof(*this); }
 824 uint LoadNode::cmp( const Node &n ) const
 825 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 826 const Type *LoadNode::bottom_type() const { return _type; }
 827 uint LoadNode::ideal_reg() const {
 828   return Matcher::base2reg[_type->base()];
 829 }
 830 
 831 #ifndef PRODUCT
 832 void LoadNode::dump_spec(outputStream *st) const {
 833   MemNode::dump_spec(st);
 834   if( !Verbose && !WizardMode ) {
 835     // standard dump does this in Verbose and WizardMode
 836     st->print(" #"); _type->dump_on(st);
 837   }
 838 }
 839 #endif
 840 
 841 #ifdef ASSERT
 842 //----------------------------is_immutable_value-------------------------------
 843 // Helper function to allow a raw load without control edge for some cases
 844 bool LoadNode::is_immutable_value(Node* adr) {
 845   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 846           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 847           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 848            in_bytes(JavaThread::osthread_offset())));
 849 }
 850 #endif
 851 
 852 //----------------------------LoadNode::make-----------------------------------
 853 // Polymorphic factory method:
 854 Node *LoadNode::make( PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt ) {
 855   Compile* C = gvn.C;
 856 
 857   // sanity check the alias category against the created node type
 858   assert(!(adr_type->isa_oopptr() &&
 859            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 860          "use LoadKlassNode instead");
 861   assert(!(adr_type->isa_aryptr() &&
 862            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 863          "use LoadRangeNode instead");
 864   // Check control edge of raw loads
 865   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 866           // oop will be recorded in oop map if load crosses safepoint
 867           rt->isa_oopptr() || is_immutable_value(adr),
 868           "raw memory operations should have control edge");
 869   switch (bt) {
 870   case T_BOOLEAN: return new (C, 3) LoadUBNode(ctl, mem, adr, adr_type, rt->is_int()    );
 871   case T_BYTE:    return new (C, 3) LoadBNode (ctl, mem, adr, adr_type, rt->is_int()    );
 872   case T_INT:     return new (C, 3) LoadINode (ctl, mem, adr, adr_type, rt->is_int()    );
 873   case T_CHAR:    return new (C, 3) LoadUSNode(ctl, mem, adr, adr_type, rt->is_int()    );
 874   case T_SHORT:   return new (C, 3) LoadSNode (ctl, mem, adr, adr_type, rt->is_int()    );
 875   case T_LONG:    return new (C, 3) LoadLNode (ctl, mem, adr, adr_type, rt->is_long()   );
 876   case T_FLOAT:   return new (C, 3) LoadFNode (ctl, mem, adr, adr_type, rt              );
 877   case T_DOUBLE:  return new (C, 3) LoadDNode (ctl, mem, adr, adr_type, rt              );
 878   case T_ADDRESS: return new (C, 3) LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr()    );
 879   case T_OBJECT:
 880 #ifdef _LP64
 881     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 882       Node* load  = gvn.transform(new (C, 3) LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop()));
 883       return new (C, 2) DecodeNNode(load, load->bottom_type()->make_ptr());
 884     } else
 885 #endif
 886     {
 887       assert(!adr->bottom_type()->is_ptr_to_narrowoop(), "should have got back a narrow oop");
 888       return new (C, 3) LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr());
 889     }
 890   }
 891   ShouldNotReachHere();
 892   return (LoadNode*)NULL;
 893 }
 894 
 895 LoadLNode* LoadLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt) {
 896   bool require_atomic = true;
 897   return new (C, 3) LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), require_atomic);
 898 }
 899 
 900 
 901 
 902 
 903 //------------------------------hash-------------------------------------------
 904 uint LoadNode::hash() const {
 905   // unroll addition of interesting fields
 906   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 907 }
 908 
 909 //---------------------------can_see_stored_value------------------------------
 910 // This routine exists to make sure this set of tests is done the same
 911 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 912 // will change the graph shape in a way which makes memory alive twice at the
 913 // same time (uses the Oracle model of aliasing), then some
 914 // LoadXNode::Identity will fold things back to the equivalence-class model
 915 // of aliasing.
 916 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 917   Node* ld_adr = in(MemNode::Address);
 918 
 919   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 920   Compile::AliasType* atp = tp != NULL ? phase->C->alias_type(tp) : NULL;
 921   if (EliminateAutoBox && atp != NULL && atp->index() >= Compile::AliasIdxRaw &&
 922       atp->field() != NULL && !atp->field()->is_volatile()) {
 923     uint alias_idx = atp->index();
 924     bool final = atp->field()->is_final();
 925     Node* result = NULL;
 926     Node* current = st;
 927     // Skip through chains of MemBarNodes checking the MergeMems for
 928     // new states for the slice of this load.  Stop once any other
 929     // kind of node is encountered.  Loads from final memory can skip
 930     // through any kind of MemBar but normal loads shouldn't skip
 931     // through MemBarAcquire since the could allow them to move out of
 932     // a synchronized region.
 933     while (current->is_Proj()) {
 934       int opc = current->in(0)->Opcode();
 935       if ((final && (opc == Op_MemBarAcquire || opc == Op_MemBarAcquireLock)) ||
 936           opc == Op_MemBarRelease || opc == Op_MemBarCPUOrder ||
 937           opc == Op_MemBarReleaseLock) {
 938         Node* mem = current->in(0)->in(TypeFunc::Memory);
 939         if (mem->is_MergeMem()) {
 940           MergeMemNode* merge = mem->as_MergeMem();
 941           Node* new_st = merge->memory_at(alias_idx);
 942           if (new_st == merge->base_memory()) {
 943             // Keep searching
 944             current = merge->base_memory();
 945             continue;
 946           }
 947           // Save the new memory state for the slice and fall through
 948           // to exit.
 949           result = new_st;
 950         }
 951       }
 952       break;
 953     }
 954     if (result != NULL) {
 955       st = result;
 956     }
 957   }
 958 
 959 
 960   // Loop around twice in the case Load -> Initialize -> Store.
 961   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
 962   for (int trip = 0; trip <= 1; trip++) {
 963 
 964     if (st->is_Store()) {
 965       Node* st_adr = st->in(MemNode::Address);
 966       if (!phase->eqv(st_adr, ld_adr)) {
 967         // Try harder before giving up...  Match raw and non-raw pointers.
 968         intptr_t st_off = 0;
 969         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
 970         if (alloc == NULL)       return NULL;
 971         intptr_t ld_off = 0;
 972         AllocateNode* allo2 = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 973         if (alloc != allo2)      return NULL;
 974         if (ld_off != st_off)    return NULL;
 975         // At this point we have proven something like this setup:
 976         //  A = Allocate(...)
 977         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
 978         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
 979         // (Actually, we haven't yet proven the Q's are the same.)
 980         // In other words, we are loading from a casted version of
 981         // the same pointer-and-offset that we stored to.
 982         // Thus, we are able to replace L by V.
 983       }
 984       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
 985       if (store_Opcode() != st->Opcode())
 986         return NULL;
 987       return st->in(MemNode::ValueIn);
 988     }
 989 
 990     intptr_t offset = 0;  // scratch
 991 
 992     // A load from a freshly-created object always returns zero.
 993     // (This can happen after LoadNode::Ideal resets the load's memory input
 994     // to find_captured_store, which returned InitializeNode::zero_memory.)
 995     if (st->is_Proj() && st->in(0)->is_Allocate() &&
 996         st->in(0) == AllocateNode::Ideal_allocation(ld_adr, phase, offset) &&
 997         offset >= st->in(0)->as_Allocate()->minimum_header_size()) {
 998       // return a zero value for the load's basic type
 999       // (This is one of the few places where a generic PhaseTransform
1000       // can create new nodes.  Think of it as lazily manifesting
1001       // virtually pre-existing constants.)
1002       return phase->zerocon(memory_type());
1003     }
1004 
1005     // A load from an initialization barrier can match a captured store.
1006     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1007       InitializeNode* init = st->in(0)->as_Initialize();
1008       AllocateNode* alloc = init->allocation();
1009       if (alloc != NULL &&
1010           alloc == AllocateNode::Ideal_allocation(ld_adr, phase, offset)) {
1011         // examine a captured store value
1012         st = init->find_captured_store(offset, memory_size(), phase);
1013         if (st != NULL)
1014           continue;             // take one more trip around
1015       }
1016     }
1017 
1018     break;
1019   }
1020 
1021   return NULL;
1022 }
1023 
1024 //----------------------is_instance_field_load_with_local_phi------------------
1025 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1026   if( in(MemNode::Memory)->is_Phi() && in(MemNode::Memory)->in(0) == ctrl &&
1027       in(MemNode::Address)->is_AddP() ) {
1028     const TypeOopPtr* t_oop = in(MemNode::Address)->bottom_type()->isa_oopptr();
1029     // Only instances.
1030     if( t_oop != NULL && t_oop->is_known_instance_field() &&
1031         t_oop->offset() != Type::OffsetBot &&
1032         t_oop->offset() != Type::OffsetTop) {
1033       return true;
1034     }
1035   }
1036   return false;
1037 }
1038 
1039 //------------------------------Identity---------------------------------------
1040 // Loads are identity if previous store is to same address
1041 Node *LoadNode::Identity( PhaseTransform *phase ) {
1042   // If the previous store-maker is the right kind of Store, and the store is
1043   // to the same address, then we are equal to the value stored.
1044   Node* mem = in(MemNode::Memory);
1045   Node* value = can_see_stored_value(mem, phase);
1046   if( value ) {
1047     // byte, short & char stores truncate naturally.
1048     // A load has to load the truncated value which requires
1049     // some sort of masking operation and that requires an
1050     // Ideal call instead of an Identity call.
1051     if (memory_size() < BytesPerInt) {
1052       // If the input to the store does not fit with the load's result type,
1053       // it must be truncated via an Ideal call.
1054       if (!phase->type(value)->higher_equal(phase->type(this)))
1055         return this;
1056     }
1057     // (This works even when value is a Con, but LoadNode::Value
1058     // usually runs first, producing the singleton type of the Con.)
1059     return value;
1060   }
1061 
1062   // Search for an existing data phi which was generated before for the same
1063   // instance's field to avoid infinite generation of phis in a loop.
1064   Node *region = mem->in(0);
1065   if (is_instance_field_load_with_local_phi(region)) {
1066     const TypePtr *addr_t = in(MemNode::Address)->bottom_type()->isa_ptr();
1067     int this_index  = phase->C->get_alias_index(addr_t);
1068     int this_offset = addr_t->offset();
1069     int this_id    = addr_t->is_oopptr()->instance_id();
1070     const Type* this_type = bottom_type();
1071     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1072       Node* phi = region->fast_out(i);
1073       if (phi->is_Phi() && phi != mem &&
1074           phi->as_Phi()->is_same_inst_field(this_type, this_id, this_index, this_offset)) {
1075         return phi;
1076       }
1077     }
1078   }
1079 
1080   return this;
1081 }
1082 
1083 
1084 // Returns true if the AliasType refers to the field that holds the
1085 // cached box array.  Currently only handles the IntegerCache case.
1086 static bool is_autobox_cache(Compile::AliasType* atp) {
1087   if (atp != NULL && atp->field() != NULL) {
1088     ciField* field = atp->field();
1089     ciSymbol* klass = field->holder()->name();
1090     if (field->name() == ciSymbol::cache_field_name() &&
1091         field->holder()->uses_default_loader() &&
1092         klass == ciSymbol::java_lang_Integer_IntegerCache()) {
1093       return true;
1094     }
1095   }
1096   return false;
1097 }
1098 
1099 // Fetch the base value in the autobox array
1100 static bool fetch_autobox_base(Compile::AliasType* atp, int& cache_offset) {
1101   if (atp != NULL && atp->field() != NULL) {
1102     ciField* field = atp->field();
1103     ciSymbol* klass = field->holder()->name();
1104     if (field->name() == ciSymbol::cache_field_name() &&
1105         field->holder()->uses_default_loader() &&
1106         klass == ciSymbol::java_lang_Integer_IntegerCache()) {
1107       assert(field->is_constant(), "what?");
1108       ciObjArray* array = field->constant_value().as_object()->as_obj_array();
1109       // Fetch the box object at the base of the array and get its value
1110       ciInstance* box = array->obj_at(0)->as_instance();
1111       ciInstanceKlass* ik = box->klass()->as_instance_klass();
1112       if (ik->nof_nonstatic_fields() == 1) {
1113         // This should be true nonstatic_field_at requires calling
1114         // nof_nonstatic_fields so check it anyway
1115         ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1116         cache_offset = c.as_int();
1117       }
1118       return true;
1119     }
1120   }
1121   return false;
1122 }
1123 
1124 // Returns true if the AliasType refers to the value field of an
1125 // autobox object.  Currently only handles Integer.
1126 static bool is_autobox_object(Compile::AliasType* atp) {
1127   if (atp != NULL && atp->field() != NULL) {
1128     ciField* field = atp->field();
1129     ciSymbol* klass = field->holder()->name();
1130     if (field->name() == ciSymbol::value_name() &&
1131         field->holder()->uses_default_loader() &&
1132         klass == ciSymbol::java_lang_Integer()) {
1133       return true;
1134     }
1135   }
1136   return false;
1137 }
1138 
1139 
1140 // We're loading from an object which has autobox behaviour.
1141 // If this object is result of a valueOf call we'll have a phi
1142 // merging a newly allocated object and a load from the cache.
1143 // We want to replace this load with the original incoming
1144 // argument to the valueOf call.
1145 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1146   Node* base = in(Address)->in(AddPNode::Base);
1147   if (base->is_Phi() && base->req() == 3) {
1148     AllocateNode* allocation = NULL;
1149     int allocation_index = -1;
1150     int load_index = -1;
1151     for (uint i = 1; i < base->req(); i++) {
1152       allocation = AllocateNode::Ideal_allocation(base->in(i), phase);
1153       if (allocation != NULL) {
1154         allocation_index = i;
1155         load_index = 3 - allocation_index;
1156         break;
1157       }
1158     }
1159     bool has_load = ( allocation != NULL &&
1160                       (base->in(load_index)->is_Load() ||
1161                        base->in(load_index)->is_DecodeN() &&
1162                        base->in(load_index)->in(1)->is_Load()) );
1163     if (has_load && in(Memory)->is_Phi() && in(Memory)->in(0) == base->in(0)) {
1164       // Push the loads from the phi that comes from valueOf up
1165       // through it to allow elimination of the loads and the recovery
1166       // of the original value.
1167       Node* mem_phi = in(Memory);
1168       Node* offset = in(Address)->in(AddPNode::Offset);
1169       Node* region = base->in(0);
1170 
1171       Node* in1 = clone();
1172       Node* in1_addr = in1->in(Address)->clone();
1173       in1_addr->set_req(AddPNode::Base, base->in(allocation_index));
1174       in1_addr->set_req(AddPNode::Address, base->in(allocation_index));
1175       in1_addr->set_req(AddPNode::Offset, offset);
1176       in1->set_req(0, region->in(allocation_index));
1177       in1->set_req(Address, in1_addr);
1178       in1->set_req(Memory, mem_phi->in(allocation_index));
1179 
1180       Node* in2 = clone();
1181       Node* in2_addr = in2->in(Address)->clone();
1182       in2_addr->set_req(AddPNode::Base, base->in(load_index));
1183       in2_addr->set_req(AddPNode::Address, base->in(load_index));
1184       in2_addr->set_req(AddPNode::Offset, offset);
1185       in2->set_req(0, region->in(load_index));
1186       in2->set_req(Address, in2_addr);
1187       in2->set_req(Memory, mem_phi->in(load_index));
1188 
1189       in1_addr = phase->transform(in1_addr);
1190       in1 =      phase->transform(in1);
1191       in2_addr = phase->transform(in2_addr);
1192       in2 =      phase->transform(in2);
1193 
1194       PhiNode* result = PhiNode::make_blank(region, this);
1195       result->set_req(allocation_index, in1);
1196       result->set_req(load_index, in2);
1197       return result;
1198     }
1199   } else if (base->is_Load() ||
1200              base->is_DecodeN() && base->in(1)->is_Load()) {
1201     if (base->is_DecodeN()) {
1202       // Get LoadN node which loads cached Integer object
1203       base = base->in(1);
1204     }
1205     // Eliminate the load of Integer.value for integers from the cache
1206     // array by deriving the value from the index into the array.
1207     // Capture the offset of the load and then reverse the computation.
1208     Node* load_base = base->in(Address)->in(AddPNode::Base);
1209     if (load_base->is_DecodeN()) {
1210       // Get LoadN node which loads IntegerCache.cache field
1211       load_base = load_base->in(1);
1212     }
1213     if (load_base != NULL) {
1214       Compile::AliasType* atp = phase->C->alias_type(load_base->adr_type());
1215       intptr_t cache_offset;
1216       int shift = -1;
1217       Node* cache = NULL;
1218       if (is_autobox_cache(atp)) {
1219         shift  = exact_log2(type2aelembytes(T_OBJECT));
1220         cache = AddPNode::Ideal_base_and_offset(load_base->in(Address), phase, cache_offset);
1221       }
1222       if (cache != NULL && base->in(Address)->is_AddP()) {
1223         Node* elements[4];
1224         int count = base->in(Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
1225         int cache_low;
1226         if (count > 0 && fetch_autobox_base(atp, cache_low)) {
1227           int offset = arrayOopDesc::base_offset_in_bytes(memory_type()) - (cache_low << shift);
1228           // Add up all the offsets making of the address of the load
1229           Node* result = elements[0];
1230           for (int i = 1; i < count; i++) {
1231             result = phase->transform(new (phase->C, 3) AddXNode(result, elements[i]));
1232           }
1233           // Remove the constant offset from the address and then
1234           // remove the scaling of the offset to recover the original index.
1235           result = phase->transform(new (phase->C, 3) AddXNode(result, phase->MakeConX(-offset)));
1236           if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1237             // Peel the shift off directly but wrap it in a dummy node
1238             // since Ideal can't return existing nodes
1239             result = new (phase->C, 3) RShiftXNode(result->in(1), phase->intcon(0));
1240           } else {
1241             result = new (phase->C, 3) RShiftXNode(result, phase->intcon(shift));
1242           }
1243 #ifdef _LP64
1244           result = new (phase->C, 2) ConvL2INode(phase->transform(result));
1245 #endif
1246           return result;
1247         }
1248       }
1249     }
1250   }
1251   return NULL;
1252 }
1253 
1254 //------------------------------split_through_phi------------------------------
1255 // Split instance field load through Phi.
1256 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1257   Node* mem     = in(MemNode::Memory);
1258   Node* address = in(MemNode::Address);
1259   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1260   const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1261 
1262   assert(mem->is_Phi() && (t_oop != NULL) &&
1263          t_oop->is_known_instance_field(), "invalide conditions");
1264 
1265   Node *region = mem->in(0);
1266   if (region == NULL) {
1267     return NULL; // Wait stable graph
1268   }
1269   uint cnt = mem->req();
1270   for (uint i = 1; i < cnt; i++) {
1271     Node* rc = region->in(i);
1272     if (rc == NULL || phase->type(rc) == Type::TOP)
1273       return NULL; // Wait stable graph
1274     Node *in = mem->in(i);
1275     if (in == NULL) {
1276       return NULL; // Wait stable graph
1277     }
1278   }
1279   // Check for loop invariant.
1280   if (cnt == 3) {
1281     for (uint i = 1; i < cnt; i++) {
1282       Node *in = mem->in(i);
1283       Node* m = MemNode::optimize_memory_chain(in, addr_t, phase);
1284       if (m == mem) {
1285         set_req(MemNode::Memory, mem->in(cnt - i)); // Skip this phi.
1286         return this;
1287       }
1288     }
1289   }
1290   // Split through Phi (see original code in loopopts.cpp).
1291   assert(phase->C->have_alias_type(addr_t), "instance should have alias type");
1292 
1293   // Do nothing here if Identity will find a value
1294   // (to avoid infinite chain of value phis generation).
1295   if (!phase->eqv(this, this->Identity(phase)))
1296     return NULL;
1297 
1298   // Skip the split if the region dominates some control edge of the address.
1299   if (!MemNode::all_controls_dominate(address, region))
1300     return NULL;
1301 
1302   const Type* this_type = this->bottom_type();
1303   int this_index  = phase->C->get_alias_index(addr_t);
1304   int this_offset = addr_t->offset();
1305   int this_iid    = addr_t->is_oopptr()->instance_id();
1306   PhaseIterGVN *igvn = phase->is_IterGVN();
1307   Node *phi = new (igvn->C, region->req()) PhiNode(region, this_type, NULL, this_iid, this_index, this_offset);
1308   for (uint i = 1; i < region->req(); i++) {
1309     Node *x;
1310     Node* the_clone = NULL;
1311     if (region->in(i) == phase->C->top()) {
1312       x = phase->C->top();      // Dead path?  Use a dead data op
1313     } else {
1314       x = this->clone();        // Else clone up the data op
1315       the_clone = x;            // Remember for possible deletion.
1316       // Alter data node to use pre-phi inputs
1317       if (this->in(0) == region) {
1318         x->set_req(0, region->in(i));
1319       } else {
1320         x->set_req(0, NULL);
1321       }
1322       for (uint j = 1; j < this->req(); j++) {
1323         Node *in = this->in(j);
1324         if (in->is_Phi() && in->in(0) == region)
1325           x->set_req(j, in->in(i)); // Use pre-Phi input for the clone
1326       }
1327     }
1328     // Check for a 'win' on some paths
1329     const Type *t = x->Value(igvn);
1330 
1331     bool singleton = t->singleton();
1332 
1333     // See comments in PhaseIdealLoop::split_thru_phi().
1334     if (singleton && t == Type::TOP) {
1335       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1336     }
1337 
1338     if (singleton) {
1339       x = igvn->makecon(t);
1340     } else {
1341       // We now call Identity to try to simplify the cloned node.
1342       // Note that some Identity methods call phase->type(this).
1343       // Make sure that the type array is big enough for
1344       // our new node, even though we may throw the node away.
1345       // (This tweaking with igvn only works because x is a new node.)
1346       igvn->set_type(x, t);
1347       // If x is a TypeNode, capture any more-precise type permanently into Node
1348       // otherwise it will be not updated during igvn->transform since
1349       // igvn->type(x) is set to x->Value() already.
1350       x->raise_bottom_type(t);
1351       Node *y = x->Identity(igvn);
1352       if (y != x) {
1353         x = y;
1354       } else {
1355         y = igvn->hash_find(x);
1356         if (y) {
1357           x = y;
1358         } else {
1359           // Else x is a new node we are keeping
1360           // We do not need register_new_node_with_optimizer
1361           // because set_type has already been called.
1362           igvn->_worklist.push(x);
1363         }
1364       }
1365     }
1366     if (x != the_clone && the_clone != NULL)
1367       igvn->remove_dead_node(the_clone);
1368     phi->set_req(i, x);
1369   }
1370   // Record Phi
1371   igvn->register_new_node_with_optimizer(phi);
1372   return phi;
1373 }
1374 
1375 //------------------------------Ideal------------------------------------------
1376 // If the load is from Field memory and the pointer is non-null, we can
1377 // zero out the control input.
1378 // If the offset is constant and the base is an object allocation,
1379 // try to hook me up to the exact initializing store.
1380 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1381   Node* p = MemNode::Ideal_common(phase, can_reshape);
1382   if (p)  return (p == NodeSentinel) ? NULL : p;
1383 
1384   Node* ctrl    = in(MemNode::Control);
1385   Node* address = in(MemNode::Address);
1386 
1387   // Skip up past a SafePoint control.  Cannot do this for Stores because
1388   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1389   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1390       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
1391     ctrl = ctrl->in(0);
1392     set_req(MemNode::Control,ctrl);
1393   }
1394 
1395   intptr_t ignore = 0;
1396   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1397   if (base != NULL
1398       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1399     // Check for useless control edge in some common special cases
1400     if (in(MemNode::Control) != NULL
1401         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1402         && all_controls_dominate(base, phase->C->start())) {
1403       // A method-invariant, non-null address (constant or 'this' argument).
1404       set_req(MemNode::Control, NULL);
1405     }
1406 
1407     if (EliminateAutoBox && can_reshape) {
1408       assert(!phase->type(base)->higher_equal(TypePtr::NULL_PTR), "the autobox pointer should be non-null");
1409       Compile::AliasType* atp = phase->C->alias_type(adr_type());
1410       if (is_autobox_object(atp)) {
1411         Node* result = eliminate_autobox(phase);
1412         if (result != NULL) return result;
1413       }
1414     }
1415   }
1416 
1417   Node* mem = in(MemNode::Memory);
1418   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1419 
1420   if (addr_t != NULL) {
1421     // try to optimize our memory input
1422     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, phase);
1423     if (opt_mem != mem) {
1424       set_req(MemNode::Memory, opt_mem);
1425       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1426       return this;
1427     }
1428     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1429     if (can_reshape && opt_mem->is_Phi() &&
1430         (t_oop != NULL) && t_oop->is_known_instance_field()) {
1431       PhaseIterGVN *igvn = phase->is_IterGVN();
1432       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1433         // Delay this transformation until memory Phi is processed.
1434         phase->is_IterGVN()->_worklist.push(this);
1435         return NULL;
1436       }
1437       // Split instance field load through Phi.
1438       Node* result = split_through_phi(phase);
1439       if (result != NULL) return result;
1440     }
1441   }
1442 
1443   // Check for prior store with a different base or offset; make Load
1444   // independent.  Skip through any number of them.  Bail out if the stores
1445   // are in an endless dead cycle and report no progress.  This is a key
1446   // transform for Reflection.  However, if after skipping through the Stores
1447   // we can't then fold up against a prior store do NOT do the transform as
1448   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1449   // array memory alive twice: once for the hoisted Load and again after the
1450   // bypassed Store.  This situation only works if EVERYBODY who does
1451   // anti-dependence work knows how to bypass.  I.e. we need all
1452   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1453   // the alias index stuff.  So instead, peek through Stores and IFF we can
1454   // fold up, do so.
1455   Node* prev_mem = find_previous_store(phase);
1456   // Steps (a), (b):  Walk past independent stores to find an exact match.
1457   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1458     // (c) See if we can fold up on the spot, but don't fold up here.
1459     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1460     // just return a prior value, which is done by Identity calls.
1461     if (can_see_stored_value(prev_mem, phase)) {
1462       // Make ready for step (d):
1463       set_req(MemNode::Memory, prev_mem);
1464       return this;
1465     }
1466   }
1467 
1468   return NULL;                  // No further progress
1469 }
1470 
1471 // Helper to recognize certain Klass fields which are invariant across
1472 // some group of array types (e.g., int[] or all T[] where T < Object).
1473 const Type*
1474 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1475                                  ciKlass* klass) const {
1476   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1477     // The field is Klass::_modifier_flags.  Return its (constant) value.
1478     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1479     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1480     return TypeInt::make(klass->modifier_flags());
1481   }
1482   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1483     // The field is Klass::_access_flags.  Return its (constant) value.
1484     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1485     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1486     return TypeInt::make(klass->access_flags());
1487   }
1488   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1489     // The field is Klass::_layout_helper.  Return its constant value if known.
1490     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1491     return TypeInt::make(klass->layout_helper());
1492   }
1493 
1494   // No match.
1495   return NULL;
1496 }
1497 
1498 //------------------------------Value-----------------------------------------
1499 const Type *LoadNode::Value( PhaseTransform *phase ) const {
1500   // Either input is TOP ==> the result is TOP
1501   Node* mem = in(MemNode::Memory);
1502   const Type *t1 = phase->type(mem);
1503   if (t1 == Type::TOP)  return Type::TOP;
1504   Node* adr = in(MemNode::Address);
1505   const TypePtr* tp = phase->type(adr)->isa_ptr();
1506   if (tp == NULL || tp->empty())  return Type::TOP;
1507   int off = tp->offset();
1508   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1509   Compile* C = phase->C;
1510 
1511   // Try to guess loaded type from pointer type
1512   if (tp->base() == Type::AryPtr) {
1513     const Type *t = tp->is_aryptr()->elem();
1514     // Don't do this for integer types. There is only potential profit if
1515     // the element type t is lower than _type; that is, for int types, if _type is
1516     // more restrictive than t.  This only happens here if one is short and the other
1517     // char (both 16 bits), and in those cases we've made an intentional decision
1518     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1519     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1520     //
1521     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1522     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1523     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1524     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1525     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1526     // In fact, that could have been the original type of p1, and p1 could have
1527     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1528     // expression (LShiftL quux 3) independently optimized to the constant 8.
1529     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1530         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1531       // t might actually be lower than _type, if _type is a unique
1532       // concrete subclass of abstract class t.
1533       // Make sure the reference is not into the header, by comparing
1534       // the offset against the offset of the start of the array's data.
1535       // Different array types begin at slightly different offsets (12 vs. 16).
1536       // We choose T_BYTE as an example base type that is least restrictive
1537       // as to alignment, which will therefore produce the smallest
1538       // possible base offset.
1539       const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1540       if ((uint)off >= (uint)min_base_off) {  // is the offset beyond the header?
1541         const Type* jt = t->join(_type);
1542         // In any case, do not allow the join, per se, to empty out the type.
1543         if (jt->empty() && !t->empty()) {
1544           // This can happen if a interface-typed array narrows to a class type.
1545           jt = _type;
1546         }
1547 
1548         if (EliminateAutoBox && adr->is_AddP()) {
1549           // The pointers in the autobox arrays are always non-null
1550           Node* base = adr->in(AddPNode::Base);
1551           if (base != NULL &&
1552               !phase->type(base)->higher_equal(TypePtr::NULL_PTR)) {
1553             Compile::AliasType* atp = C->alias_type(base->adr_type());
1554             if (is_autobox_cache(atp)) {
1555               return jt->join(TypePtr::NOTNULL)->is_ptr();
1556             }
1557           }
1558         }
1559         return jt;
1560       }
1561     }
1562   } else if (tp->base() == Type::InstPtr) {
1563     ciEnv* env = C->env();
1564     const TypeInstPtr* tinst = tp->is_instptr();
1565     ciKlass* klass = tinst->klass();
1566     assert( off != Type::OffsetBot ||
1567             // arrays can be cast to Objects
1568             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1569             // unsafe field access may not have a constant offset
1570             C->has_unsafe_access(),
1571             "Field accesses must be precise" );
1572     // For oop loads, we expect the _type to be precise
1573     if (klass == env->String_klass() &&
1574         adr->is_AddP() && off != Type::OffsetBot) {
1575       // For constant Strings treat the final fields as compile time constants.
1576       Node* base = adr->in(AddPNode::Base);
1577       const TypeOopPtr* t = phase->type(base)->isa_oopptr();
1578       if (t != NULL && t->singleton()) {
1579         ciField* field = env->String_klass()->get_field_by_offset(off, false);
1580         if (field != NULL && field->is_final()) {
1581           ciObject* string = t->const_oop();
1582           ciConstant constant = string->as_instance()->field_value(field);
1583           if (constant.basic_type() == T_INT) {
1584             return TypeInt::make(constant.as_int());
1585           } else if (constant.basic_type() == T_ARRAY) {
1586             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1587               return TypeNarrowOop::make_from_constant(constant.as_object(), true);
1588             } else {
1589               return TypeOopPtr::make_from_constant(constant.as_object(), true);
1590             }
1591           }
1592         }
1593       }
1594     }
1595     // Optimizations for constant objects
1596     ciObject* const_oop = tinst->const_oop();
1597     if (const_oop != NULL) {
1598       // For constant CallSites treat the target field as a compile time constant.
1599       if (const_oop->is_call_site()) {
1600         ciCallSite* call_site = const_oop->as_call_site();
1601         ciField* field = call_site->klass()->as_instance_klass()->get_field_by_offset(off, /*is_static=*/ false);
1602         if (field != NULL && field->is_call_site_target()) {
1603           ciMethodHandle* target = call_site->get_target();
1604           if (target != NULL) {  // just in case
1605             ciConstant constant(T_OBJECT, target);
1606             const Type* t;
1607             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1608               t = TypeNarrowOop::make_from_constant(constant.as_object(), true);
1609             } else {
1610               t = TypeOopPtr::make_from_constant(constant.as_object(), true);
1611             }
1612             // Add a dependence for invalidation of the optimization.
1613             if (!call_site->is_constant_call_site()) {
1614               C->dependencies()->assert_call_site_target_value(call_site, target);
1615             }
1616             return t;
1617           }
1618         }
1619       }
1620     }
1621   } else if (tp->base() == Type::KlassPtr) {
1622     assert( off != Type::OffsetBot ||
1623             // arrays can be cast to Objects
1624             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1625             // also allow array-loading from the primary supertype
1626             // array during subtype checks
1627             Opcode() == Op_LoadKlass,
1628             "Field accesses must be precise" );
1629     // For klass/static loads, we expect the _type to be precise
1630   }
1631 
1632   const TypeKlassPtr *tkls = tp->isa_klassptr();
1633   if (tkls != NULL && !StressReflectiveCode) {
1634     ciKlass* klass = tkls->klass();
1635     if (klass->is_loaded() && tkls->klass_is_exact()) {
1636       // We are loading a field from a Klass metaobject whose identity
1637       // is known at compile time (the type is "exact" or "precise").
1638       // Check for fields we know are maintained as constants by the VM.
1639       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1640         // The field is Klass::_super_check_offset.  Return its (constant) value.
1641         // (Folds up type checking code.)
1642         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1643         return TypeInt::make(klass->super_check_offset());
1644       }
1645       // Compute index into primary_supers array
1646       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(klassOop);
1647       // Check for overflowing; use unsigned compare to handle the negative case.
1648       if( depth < ciKlass::primary_super_limit() ) {
1649         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1650         // (Folds up type checking code.)
1651         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1652         ciKlass *ss = klass->super_of_depth(depth);
1653         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1654       }
1655       const Type* aift = load_array_final_field(tkls, klass);
1656       if (aift != NULL)  return aift;
1657       if (tkls->offset() == in_bytes(arrayKlass::component_mirror_offset())
1658           && klass->is_array_klass()) {
1659         // The field is arrayKlass::_component_mirror.  Return its (constant) value.
1660         // (Folds up aClassConstant.getComponentType, common in Arrays.copyOf.)
1661         assert(Opcode() == Op_LoadP, "must load an oop from _component_mirror");
1662         return TypeInstPtr::make(klass->as_array_klass()->component_mirror());
1663       }
1664       if (tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1665         // The field is Klass::_java_mirror.  Return its (constant) value.
1666         // (Folds up the 2nd indirection in anObjConstant.getClass().)
1667         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1668         return TypeInstPtr::make(klass->java_mirror());
1669       }
1670     }
1671 
1672     // We can still check if we are loading from the primary_supers array at a
1673     // shallow enough depth.  Even though the klass is not exact, entries less
1674     // than or equal to its super depth are correct.
1675     if (klass->is_loaded() ) {
1676       ciType *inner = klass->klass();
1677       while( inner->is_obj_array_klass() )
1678         inner = inner->as_obj_array_klass()->base_element_type();
1679       if( inner->is_instance_klass() &&
1680           !inner->as_instance_klass()->flags().is_interface() ) {
1681         // Compute index into primary_supers array
1682         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(klassOop);
1683         // Check for overflowing; use unsigned compare to handle the negative case.
1684         if( depth < ciKlass::primary_super_limit() &&
1685             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1686           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1687           // (Folds up type checking code.)
1688           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1689           ciKlass *ss = klass->super_of_depth(depth);
1690           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1691         }
1692       }
1693     }
1694 
1695     // If the type is enough to determine that the thing is not an array,
1696     // we can give the layout_helper a positive interval type.
1697     // This will help short-circuit some reflective code.
1698     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1699         && !klass->is_array_klass() // not directly typed as an array
1700         && !klass->is_interface()  // specifically not Serializable & Cloneable
1701         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1702         ) {
1703       // Note:  When interfaces are reliable, we can narrow the interface
1704       // test to (klass != Serializable && klass != Cloneable).
1705       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1706       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1707       // The key property of this type is that it folds up tests
1708       // for array-ness, since it proves that the layout_helper is positive.
1709       // Thus, a generic value like the basic object layout helper works fine.
1710       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1711     }
1712   }
1713 
1714   // If we are loading from a freshly-allocated object, produce a zero,
1715   // if the load is provably beyond the header of the object.
1716   // (Also allow a variable load from a fresh array to produce zero.)
1717   const TypeOopPtr *tinst = tp->isa_oopptr();
1718   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1719   if (ReduceFieldZeroing || is_instance) {
1720     Node* value = can_see_stored_value(mem,phase);
1721     if (value != NULL && value->is_Con())
1722       return value->bottom_type();
1723   }
1724 
1725   if (is_instance) {
1726     // If we have an instance type and our memory input is the
1727     // programs's initial memory state, there is no matching store,
1728     // so just return a zero of the appropriate type
1729     Node *mem = in(MemNode::Memory);
1730     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1731       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1732       return Type::get_zero_type(_type->basic_type());
1733     }
1734   }
1735   return _type;
1736 }
1737 
1738 //------------------------------match_edge-------------------------------------
1739 // Do we Match on this edge index or not?  Match only the address.
1740 uint LoadNode::match_edge(uint idx) const {
1741   return idx == MemNode::Address;
1742 }
1743 
1744 //--------------------------LoadBNode::Ideal--------------------------------------
1745 //
1746 //  If the previous store is to the same address as this load,
1747 //  and the value stored was larger than a byte, replace this load
1748 //  with the value stored truncated to a byte.  If no truncation is
1749 //  needed, the replacement is done in LoadNode::Identity().
1750 //
1751 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1752   Node* mem = in(MemNode::Memory);
1753   Node* value = can_see_stored_value(mem,phase);
1754   if( value && !phase->type(value)->higher_equal( _type ) ) {
1755     Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(24)) );
1756     return new (phase->C, 3) RShiftINode(result, phase->intcon(24));
1757   }
1758   // Identity call will handle the case where truncation is not needed.
1759   return LoadNode::Ideal(phase, can_reshape);
1760 }
1761 
1762 //--------------------------LoadUBNode::Ideal-------------------------------------
1763 //
1764 //  If the previous store is to the same address as this load,
1765 //  and the value stored was larger than a byte, replace this load
1766 //  with the value stored truncated to a byte.  If no truncation is
1767 //  needed, the replacement is done in LoadNode::Identity().
1768 //
1769 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1770   Node* mem = in(MemNode::Memory);
1771   Node* value = can_see_stored_value(mem, phase);
1772   if (value && !phase->type(value)->higher_equal(_type))
1773     return new (phase->C, 3) AndINode(value, phase->intcon(0xFF));
1774   // Identity call will handle the case where truncation is not needed.
1775   return LoadNode::Ideal(phase, can_reshape);
1776 }
1777 
1778 //--------------------------LoadUSNode::Ideal-------------------------------------
1779 //
1780 //  If the previous store is to the same address as this load,
1781 //  and the value stored was larger than a char, replace this load
1782 //  with the value stored truncated to a char.  If no truncation is
1783 //  needed, the replacement is done in LoadNode::Identity().
1784 //
1785 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1786   Node* mem = in(MemNode::Memory);
1787   Node* value = can_see_stored_value(mem,phase);
1788   if( value && !phase->type(value)->higher_equal( _type ) )
1789     return new (phase->C, 3) AndINode(value,phase->intcon(0xFFFF));
1790   // Identity call will handle the case where truncation is not needed.
1791   return LoadNode::Ideal(phase, can_reshape);
1792 }
1793 
1794 //--------------------------LoadSNode::Ideal--------------------------------------
1795 //
1796 //  If the previous store is to the same address as this load,
1797 //  and the value stored was larger than a short, replace this load
1798 //  with the value stored truncated to a short.  If no truncation is
1799 //  needed, the replacement is done in LoadNode::Identity().
1800 //
1801 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1802   Node* mem = in(MemNode::Memory);
1803   Node* value = can_see_stored_value(mem,phase);
1804   if( value && !phase->type(value)->higher_equal( _type ) ) {
1805     Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(16)) );
1806     return new (phase->C, 3) RShiftINode(result, phase->intcon(16));
1807   }
1808   // Identity call will handle the case where truncation is not needed.
1809   return LoadNode::Ideal(phase, can_reshape);
1810 }
1811 
1812 //=============================================================================
1813 //----------------------------LoadKlassNode::make------------------------------
1814 // Polymorphic factory method:
1815 Node *LoadKlassNode::make( PhaseGVN& gvn, Node *mem, Node *adr, const TypePtr* at, const TypeKlassPtr *tk ) {
1816   Compile* C = gvn.C;
1817   Node *ctl = NULL;
1818   // sanity check the alias category against the created node type
1819   const TypeOopPtr *adr_type = adr->bottom_type()->isa_oopptr();
1820   assert(adr_type != NULL, "expecting TypeOopPtr");
1821 #ifdef _LP64
1822   if (adr_type->is_ptr_to_narrowoop()) {
1823     Node* load_klass = gvn.transform(new (C, 3) LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowoop()));
1824     return new (C, 2) DecodeNNode(load_klass, load_klass->bottom_type()->make_ptr());
1825   }
1826 #endif
1827   assert(!adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
1828   return new (C, 3) LoadKlassNode(ctl, mem, adr, at, tk);
1829 }
1830 
1831 //------------------------------Value------------------------------------------
1832 const Type *LoadKlassNode::Value( PhaseTransform *phase ) const {
1833   return klass_value_common(phase);
1834 }
1835 
1836 const Type *LoadNode::klass_value_common( PhaseTransform *phase ) const {
1837   // Either input is TOP ==> the result is TOP
1838   const Type *t1 = phase->type( in(MemNode::Memory) );
1839   if (t1 == Type::TOP)  return Type::TOP;
1840   Node *adr = in(MemNode::Address);
1841   const Type *t2 = phase->type( adr );
1842   if (t2 == Type::TOP)  return Type::TOP;
1843   const TypePtr *tp = t2->is_ptr();
1844   if (TypePtr::above_centerline(tp->ptr()) ||
1845       tp->ptr() == TypePtr::Null)  return Type::TOP;
1846 
1847   // Return a more precise klass, if possible
1848   const TypeInstPtr *tinst = tp->isa_instptr();
1849   if (tinst != NULL) {
1850     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
1851     int offset = tinst->offset();
1852     if (ik == phase->C->env()->Class_klass()
1853         && (offset == java_lang_Class::klass_offset_in_bytes() ||
1854             offset == java_lang_Class::array_klass_offset_in_bytes())) {
1855       // We are loading a special hidden field from a Class mirror object,
1856       // the field which points to the VM's Klass metaobject.
1857       ciType* t = tinst->java_mirror_type();
1858       // java_mirror_type returns non-null for compile-time Class constants.
1859       if (t != NULL) {
1860         // constant oop => constant klass
1861         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
1862           return TypeKlassPtr::make(ciArrayKlass::make(t));
1863         }
1864         if (!t->is_klass()) {
1865           // a primitive Class (e.g., int.class) has NULL for a klass field
1866           return TypePtr::NULL_PTR;
1867         }
1868         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
1869         return TypeKlassPtr::make(t->as_klass());
1870       }
1871       // non-constant mirror, so we can't tell what's going on
1872     }
1873     if( !ik->is_loaded() )
1874       return _type;             // Bail out if not loaded
1875     if (offset == oopDesc::klass_offset_in_bytes()) {
1876       if (tinst->klass_is_exact()) {
1877         return TypeKlassPtr::make(ik);
1878       }
1879       // See if we can become precise: no subklasses and no interface
1880       // (Note:  We need to support verified interfaces.)
1881       if (!ik->is_interface() && !ik->has_subklass()) {
1882         //assert(!UseExactTypes, "this code should be useless with exact types");
1883         // Add a dependence; if any subclass added we need to recompile
1884         if (!ik->is_final()) {
1885           // %%% should use stronger assert_unique_concrete_subtype instead
1886           phase->C->dependencies()->assert_leaf_type(ik);
1887         }
1888         // Return precise klass
1889         return TypeKlassPtr::make(ik);
1890       }
1891 
1892       // Return root of possible klass
1893       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
1894     }
1895   }
1896 
1897   // Check for loading klass from an array
1898   const TypeAryPtr *tary = tp->isa_aryptr();
1899   if( tary != NULL ) {
1900     ciKlass *tary_klass = tary->klass();
1901     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
1902         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
1903       if (tary->klass_is_exact()) {
1904         return TypeKlassPtr::make(tary_klass);
1905       }
1906       ciArrayKlass *ak = tary->klass()->as_array_klass();
1907       // If the klass is an object array, we defer the question to the
1908       // array component klass.
1909       if( ak->is_obj_array_klass() ) {
1910         assert( ak->is_loaded(), "" );
1911         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
1912         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
1913           ciInstanceKlass* ik = base_k->as_instance_klass();
1914           // See if we can become precise: no subklasses and no interface
1915           if (!ik->is_interface() && !ik->has_subklass()) {
1916             //assert(!UseExactTypes, "this code should be useless with exact types");
1917             // Add a dependence; if any subclass added we need to recompile
1918             if (!ik->is_final()) {
1919               phase->C->dependencies()->assert_leaf_type(ik);
1920             }
1921             // Return precise array klass
1922             return TypeKlassPtr::make(ak);
1923           }
1924         }
1925         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
1926       } else {                  // Found a type-array?
1927         //assert(!UseExactTypes, "this code should be useless with exact types");
1928         assert( ak->is_type_array_klass(), "" );
1929         return TypeKlassPtr::make(ak); // These are always precise
1930       }
1931     }
1932   }
1933 
1934   // Check for loading klass from an array klass
1935   const TypeKlassPtr *tkls = tp->isa_klassptr();
1936   if (tkls != NULL && !StressReflectiveCode) {
1937     ciKlass* klass = tkls->klass();
1938     if( !klass->is_loaded() )
1939       return _type;             // Bail out if not loaded
1940     if( klass->is_obj_array_klass() &&
1941         tkls->offset() == in_bytes(objArrayKlass::element_klass_offset())) {
1942       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
1943       // // Always returning precise element type is incorrect,
1944       // // e.g., element type could be object and array may contain strings
1945       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
1946 
1947       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
1948       // according to the element type's subclassing.
1949       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
1950     }
1951     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
1952         tkls->offset() == in_bytes(Klass::super_offset())) {
1953       ciKlass* sup = klass->as_instance_klass()->super();
1954       // The field is Klass::_super.  Return its (constant) value.
1955       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
1956       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
1957     }
1958   }
1959 
1960   // Bailout case
1961   return LoadNode::Value(phase);
1962 }
1963 
1964 //------------------------------Identity---------------------------------------
1965 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
1966 // Also feed through the klass in Allocate(...klass...)._klass.
1967 Node* LoadKlassNode::Identity( PhaseTransform *phase ) {
1968   return klass_identity_common(phase);
1969 }
1970 
1971 Node* LoadNode::klass_identity_common(PhaseTransform *phase ) {
1972   Node* x = LoadNode::Identity(phase);
1973   if (x != this)  return x;
1974 
1975   // Take apart the address into an oop and and offset.
1976   // Return 'this' if we cannot.
1977   Node*    adr    = in(MemNode::Address);
1978   intptr_t offset = 0;
1979   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
1980   if (base == NULL)     return this;
1981   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
1982   if (toop == NULL)     return this;
1983 
1984   // We can fetch the klass directly through an AllocateNode.
1985   // This works even if the klass is not constant (clone or newArray).
1986   if (offset == oopDesc::klass_offset_in_bytes()) {
1987     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
1988     if (allocated_klass != NULL) {
1989       return allocated_klass;
1990     }
1991   }
1992 
1993   // Simplify k.java_mirror.as_klass to plain k, where k is a klassOop.
1994   // Simplify ak.component_mirror.array_klass to plain ak, ak an arrayKlass.
1995   // See inline_native_Class_query for occurrences of these patterns.
1996   // Java Example:  x.getClass().isAssignableFrom(y)
1997   // Java Example:  Array.newInstance(x.getClass().getComponentType(), n)
1998   //
1999   // This improves reflective code, often making the Class
2000   // mirror go completely dead.  (Current exception:  Class
2001   // mirrors may appear in debug info, but we could clean them out by
2002   // introducing a new debug info operator for klassOop.java_mirror).
2003   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2004       && (offset == java_lang_Class::klass_offset_in_bytes() ||
2005           offset == java_lang_Class::array_klass_offset_in_bytes())) {
2006     // We are loading a special hidden field from a Class mirror,
2007     // the field which points to its Klass or arrayKlass metaobject.
2008     if (base->is_Load()) {
2009       Node* adr2 = base->in(MemNode::Address);
2010       const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2011       if (tkls != NULL && !tkls->empty()
2012           && (tkls->klass()->is_instance_klass() ||
2013               tkls->klass()->is_array_klass())
2014           && adr2->is_AddP()
2015           ) {
2016         int mirror_field = in_bytes(Klass::java_mirror_offset());
2017         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2018           mirror_field = in_bytes(arrayKlass::component_mirror_offset());
2019         }
2020         if (tkls->offset() == mirror_field) {
2021           return adr2->in(AddPNode::Base);
2022         }
2023       }
2024     }
2025   }
2026 
2027   return this;
2028 }
2029 
2030 
2031 //------------------------------Value------------------------------------------
2032 const Type *LoadNKlassNode::Value( PhaseTransform *phase ) const {
2033   const Type *t = klass_value_common(phase);
2034   if (t == Type::TOP)
2035     return t;
2036 
2037   return t->make_narrowoop();
2038 }
2039 
2040 //------------------------------Identity---------------------------------------
2041 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2042 // Also feed through the klass in Allocate(...klass...)._klass.
2043 Node* LoadNKlassNode::Identity( PhaseTransform *phase ) {
2044   Node *x = klass_identity_common(phase);
2045 
2046   const Type *t = phase->type( x );
2047   if( t == Type::TOP ) return x;
2048   if( t->isa_narrowoop()) return x;
2049 
2050   return phase->transform(new (phase->C, 2) EncodePNode(x, t->make_narrowoop()));
2051 }
2052 
2053 //------------------------------Value-----------------------------------------
2054 const Type *LoadRangeNode::Value( PhaseTransform *phase ) const {
2055   // Either input is TOP ==> the result is TOP
2056   const Type *t1 = phase->type( in(MemNode::Memory) );
2057   if( t1 == Type::TOP ) return Type::TOP;
2058   Node *adr = in(MemNode::Address);
2059   const Type *t2 = phase->type( adr );
2060   if( t2 == Type::TOP ) return Type::TOP;
2061   const TypePtr *tp = t2->is_ptr();
2062   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2063   const TypeAryPtr *tap = tp->isa_aryptr();
2064   if( !tap ) return _type;
2065   return tap->size();
2066 }
2067 
2068 //-------------------------------Ideal---------------------------------------
2069 // Feed through the length in AllocateArray(...length...)._length.
2070 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2071   Node* p = MemNode::Ideal_common(phase, can_reshape);
2072   if (p)  return (p == NodeSentinel) ? NULL : p;
2073 
2074   // Take apart the address into an oop and and offset.
2075   // Return 'this' if we cannot.
2076   Node*    adr    = in(MemNode::Address);
2077   intptr_t offset = 0;
2078   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2079   if (base == NULL)     return NULL;
2080   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2081   if (tary == NULL)     return NULL;
2082 
2083   // We can fetch the length directly through an AllocateArrayNode.
2084   // This works even if the length is not constant (clone or newArray).
2085   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2086     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2087     if (alloc != NULL) {
2088       Node* allocated_length = alloc->Ideal_length();
2089       Node* len = alloc->make_ideal_length(tary, phase);
2090       if (allocated_length != len) {
2091         // New CastII improves on this.
2092         return len;
2093       }
2094     }
2095   }
2096 
2097   return NULL;
2098 }
2099 
2100 //------------------------------Identity---------------------------------------
2101 // Feed through the length in AllocateArray(...length...)._length.
2102 Node* LoadRangeNode::Identity( PhaseTransform *phase ) {
2103   Node* x = LoadINode::Identity(phase);
2104   if (x != this)  return x;
2105 
2106   // Take apart the address into an oop and and offset.
2107   // Return 'this' if we cannot.
2108   Node*    adr    = in(MemNode::Address);
2109   intptr_t offset = 0;
2110   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2111   if (base == NULL)     return this;
2112   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2113   if (tary == NULL)     return this;
2114 
2115   // We can fetch the length directly through an AllocateArrayNode.
2116   // This works even if the length is not constant (clone or newArray).
2117   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2118     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2119     if (alloc != NULL) {
2120       Node* allocated_length = alloc->Ideal_length();
2121       // Do not allow make_ideal_length to allocate a CastII node.
2122       Node* len = alloc->make_ideal_length(tary, phase, false);
2123       if (allocated_length == len) {
2124         // Return allocated_length only if it would not be improved by a CastII.
2125         return allocated_length;
2126       }
2127     }
2128   }
2129 
2130   return this;
2131 
2132 }
2133 
2134 //=============================================================================
2135 //---------------------------StoreNode::make-----------------------------------
2136 // Polymorphic factory method:
2137 StoreNode* StoreNode::make( PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt ) {
2138   Compile* C = gvn.C;
2139   assert( C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2140           ctl != NULL, "raw memory operations should have control edge");
2141 
2142   switch (bt) {
2143   case T_BOOLEAN:
2144   case T_BYTE:    return new (C, 4) StoreBNode(ctl, mem, adr, adr_type, val);
2145   case T_INT:     return new (C, 4) StoreINode(ctl, mem, adr, adr_type, val);
2146   case T_CHAR:
2147   case T_SHORT:   return new (C, 4) StoreCNode(ctl, mem, adr, adr_type, val);
2148   case T_LONG:    return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val);
2149   case T_FLOAT:   return new (C, 4) StoreFNode(ctl, mem, adr, adr_type, val);
2150   case T_DOUBLE:  return new (C, 4) StoreDNode(ctl, mem, adr, adr_type, val);
2151   case T_ADDRESS:
2152   case T_OBJECT:
2153 #ifdef _LP64
2154     if (adr->bottom_type()->is_ptr_to_narrowoop() ||
2155         (UseCompressedOops && val->bottom_type()->isa_klassptr() &&
2156          adr->bottom_type()->isa_rawptr())) {
2157       val = gvn.transform(new (C, 2) EncodePNode(val, val->bottom_type()->make_narrowoop()));
2158       return new (C, 4) StoreNNode(ctl, mem, adr, adr_type, val);
2159     } else
2160 #endif
2161     {
2162       return new (C, 4) StorePNode(ctl, mem, adr, adr_type, val);
2163     }
2164   }
2165   ShouldNotReachHere();
2166   return (StoreNode*)NULL;
2167 }
2168 
2169 StoreLNode* StoreLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val) {
2170   bool require_atomic = true;
2171   return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val, require_atomic);
2172 }
2173 
2174 
2175 //--------------------------bottom_type----------------------------------------
2176 const Type *StoreNode::bottom_type() const {
2177   return Type::MEMORY;
2178 }
2179 
2180 //------------------------------hash-------------------------------------------
2181 uint StoreNode::hash() const {
2182   // unroll addition of interesting fields
2183   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2184 
2185   // Since they are not commoned, do not hash them:
2186   return NO_HASH;
2187 }
2188 
2189 //------------------------------Ideal------------------------------------------
2190 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2191 // When a store immediately follows a relevant allocation/initialization,
2192 // try to capture it into the initialization, or hoist it above.
2193 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2194   Node* p = MemNode::Ideal_common(phase, can_reshape);
2195   if (p)  return (p == NodeSentinel) ? NULL : p;
2196 
2197   Node* mem     = in(MemNode::Memory);
2198   Node* address = in(MemNode::Address);
2199 
2200   // Back-to-back stores to same address?  Fold em up.  Generally
2201   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2202   // since they must follow each StoreP operation.  Redundant StoreCMs
2203   // are eliminated just before matching in final_graph_reshape.
2204   if (mem->is_Store() && phase->eqv_uncast(mem->in(MemNode::Address), address) &&
2205       mem->Opcode() != Op_StoreCM) {
2206     // Looking at a dead closed cycle of memory?
2207     assert(mem != mem->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
2208 
2209     assert(Opcode() == mem->Opcode() ||
2210            phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw,
2211            "no mismatched stores, except on raw memory");
2212 
2213     if (mem->outcnt() == 1 &&           // check for intervening uses
2214         mem->as_Store()->memory_size() <= this->memory_size()) {
2215       // If anybody other than 'this' uses 'mem', we cannot fold 'mem' away.
2216       // For example, 'mem' might be the final state at a conditional return.
2217       // Or, 'mem' might be used by some node which is live at the same time
2218       // 'this' is live, which might be unschedulable.  So, require exactly
2219       // ONE user, the 'this' store, until such time as we clone 'mem' for
2220       // each of 'mem's uses (thus making the exactly-1-user-rule hold true).
2221       if (can_reshape) {  // (%%% is this an anachronism?)
2222         set_req_X(MemNode::Memory, mem->in(MemNode::Memory),
2223                   phase->is_IterGVN());
2224       } else {
2225         // It's OK to do this in the parser, since DU info is always accurate,
2226         // and the parser always refers to nodes via SafePointNode maps.
2227         set_req(MemNode::Memory, mem->in(MemNode::Memory));
2228       }
2229       return this;
2230     }
2231   }
2232 
2233   // Capture an unaliased, unconditional, simple store into an initializer.
2234   // Or, if it is independent of the allocation, hoist it above the allocation.
2235   if (ReduceFieldZeroing && /*can_reshape &&*/
2236       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2237     InitializeNode* init = mem->in(0)->as_Initialize();
2238     intptr_t offset = init->can_capture_store(this, phase);
2239     if (offset > 0) {
2240       Node* moved = init->capture_store(this, offset, phase);
2241       // If the InitializeNode captured me, it made a raw copy of me,
2242       // and I need to disappear.
2243       if (moved != NULL) {
2244         // %%% hack to ensure that Ideal returns a new node:
2245         mem = MergeMemNode::make(phase->C, mem);
2246         return mem;             // fold me away
2247       }
2248     }
2249   }
2250 
2251   return NULL;                  // No further progress
2252 }
2253 
2254 //------------------------------Value-----------------------------------------
2255 const Type *StoreNode::Value( PhaseTransform *phase ) const {
2256   // Either input is TOP ==> the result is TOP
2257   const Type *t1 = phase->type( in(MemNode::Memory) );
2258   if( t1 == Type::TOP ) return Type::TOP;
2259   const Type *t2 = phase->type( in(MemNode::Address) );
2260   if( t2 == Type::TOP ) return Type::TOP;
2261   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2262   if( t3 == Type::TOP ) return Type::TOP;
2263   return Type::MEMORY;
2264 }
2265 
2266 //------------------------------Identity---------------------------------------
2267 // Remove redundant stores:
2268 //   Store(m, p, Load(m, p)) changes to m.
2269 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2270 Node *StoreNode::Identity( PhaseTransform *phase ) {
2271   Node* mem = in(MemNode::Memory);
2272   Node* adr = in(MemNode::Address);
2273   Node* val = in(MemNode::ValueIn);
2274 
2275   // Load then Store?  Then the Store is useless
2276   if (val->is_Load() &&
2277       phase->eqv_uncast( val->in(MemNode::Address), adr ) &&
2278       phase->eqv_uncast( val->in(MemNode::Memory ), mem ) &&
2279       val->as_Load()->store_Opcode() == Opcode()) {
2280     return mem;
2281   }
2282 
2283   // Two stores in a row of the same value?
2284   if (mem->is_Store() &&
2285       phase->eqv_uncast( mem->in(MemNode::Address), adr ) &&
2286       phase->eqv_uncast( mem->in(MemNode::ValueIn), val ) &&
2287       mem->Opcode() == Opcode()) {
2288     return mem;
2289   }
2290 
2291   // Store of zero anywhere into a freshly-allocated object?
2292   // Then the store is useless.
2293   // (It must already have been captured by the InitializeNode.)
2294   if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2295     // a newly allocated object is already all-zeroes everywhere
2296     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2297       return mem;
2298     }
2299 
2300     // the store may also apply to zero-bits in an earlier object
2301     Node* prev_mem = find_previous_store(phase);
2302     // Steps (a), (b):  Walk past independent stores to find an exact match.
2303     if (prev_mem != NULL) {
2304       Node* prev_val = can_see_stored_value(prev_mem, phase);
2305       if (prev_val != NULL && phase->eqv(prev_val, val)) {
2306         // prev_val and val might differ by a cast; it would be good
2307         // to keep the more informative of the two.
2308         return mem;
2309       }
2310     }
2311   }
2312 
2313   return this;
2314 }
2315 
2316 //------------------------------match_edge-------------------------------------
2317 // Do we Match on this edge index or not?  Match only memory & value
2318 uint StoreNode::match_edge(uint idx) const {
2319   return idx == MemNode::Address || idx == MemNode::ValueIn;
2320 }
2321 
2322 //------------------------------cmp--------------------------------------------
2323 // Do not common stores up together.  They generally have to be split
2324 // back up anyways, so do not bother.
2325 uint StoreNode::cmp( const Node &n ) const {
2326   return (&n == this);          // Always fail except on self
2327 }
2328 
2329 //------------------------------Ideal_masked_input-----------------------------
2330 // Check for a useless mask before a partial-word store
2331 // (StoreB ... (AndI valIn conIa) )
2332 // If (conIa & mask == mask) this simplifies to
2333 // (StoreB ... (valIn) )
2334 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2335   Node *val = in(MemNode::ValueIn);
2336   if( val->Opcode() == Op_AndI ) {
2337     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2338     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2339       set_req(MemNode::ValueIn, val->in(1));
2340       return this;
2341     }
2342   }
2343   return NULL;
2344 }
2345 
2346 
2347 //------------------------------Ideal_sign_extended_input----------------------
2348 // Check for useless sign-extension before a partial-word store
2349 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2350 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2351 // (StoreB ... (valIn) )
2352 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2353   Node *val = in(MemNode::ValueIn);
2354   if( val->Opcode() == Op_RShiftI ) {
2355     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2356     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2357       Node *shl = val->in(1);
2358       if( shl->Opcode() == Op_LShiftI ) {
2359         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2360         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2361           set_req(MemNode::ValueIn, shl->in(1));
2362           return this;
2363         }
2364       }
2365     }
2366   }
2367   return NULL;
2368 }
2369 
2370 //------------------------------value_never_loaded-----------------------------------
2371 // Determine whether there are any possible loads of the value stored.
2372 // For simplicity, we actually check if there are any loads from the
2373 // address stored to, not just for loads of the value stored by this node.
2374 //
2375 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2376   Node *adr = in(Address);
2377   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2378   if (adr_oop == NULL)
2379     return false;
2380   if (!adr_oop->is_known_instance_field())
2381     return false; // if not a distinct instance, there may be aliases of the address
2382   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2383     Node *use = adr->fast_out(i);
2384     int opc = use->Opcode();
2385     if (use->is_Load() || use->is_LoadStore()) {
2386       return false;
2387     }
2388   }
2389   return true;
2390 }
2391 
2392 //=============================================================================
2393 //------------------------------Ideal------------------------------------------
2394 // If the store is from an AND mask that leaves the low bits untouched, then
2395 // we can skip the AND operation.  If the store is from a sign-extension
2396 // (a left shift, then right shift) we can skip both.
2397 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2398   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2399   if( progress != NULL ) return progress;
2400 
2401   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2402   if( progress != NULL ) return progress;
2403 
2404   // Finally check the default case
2405   return StoreNode::Ideal(phase, can_reshape);
2406 }
2407 
2408 //=============================================================================
2409 //------------------------------Ideal------------------------------------------
2410 // If the store is from an AND mask that leaves the low bits untouched, then
2411 // we can skip the AND operation
2412 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2413   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2414   if( progress != NULL ) return progress;
2415 
2416   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2417   if( progress != NULL ) return progress;
2418 
2419   // Finally check the default case
2420   return StoreNode::Ideal(phase, can_reshape);
2421 }
2422 
2423 //=============================================================================
2424 //------------------------------Identity---------------------------------------
2425 Node *StoreCMNode::Identity( PhaseTransform *phase ) {
2426   // No need to card mark when storing a null ptr
2427   Node* my_store = in(MemNode::OopStore);
2428   if (my_store->is_Store()) {
2429     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2430     if( t1 == TypePtr::NULL_PTR ) {
2431       return in(MemNode::Memory);
2432     }
2433   }
2434   return this;
2435 }
2436 
2437 //=============================================================================
2438 //------------------------------Ideal---------------------------------------
2439 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2440   Node* progress = StoreNode::Ideal(phase, can_reshape);
2441   if (progress != NULL) return progress;
2442 
2443   Node* my_store = in(MemNode::OopStore);
2444   if (my_store->is_MergeMem()) {
2445     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2446     set_req(MemNode::OopStore, mem);
2447     return this;
2448   }
2449 
2450   return NULL;
2451 }
2452 
2453 //------------------------------Value-----------------------------------------
2454 const Type *StoreCMNode::Value( PhaseTransform *phase ) const {
2455   // Either input is TOP ==> the result is TOP
2456   const Type *t = phase->type( in(MemNode::Memory) );
2457   if( t == Type::TOP ) return Type::TOP;
2458   t = phase->type( in(MemNode::Address) );
2459   if( t == Type::TOP ) return Type::TOP;
2460   t = phase->type( in(MemNode::ValueIn) );
2461   if( t == Type::TOP ) return Type::TOP;
2462   // If extra input is TOP ==> the result is TOP
2463   t = phase->type( in(MemNode::OopStore) );
2464   if( t == Type::TOP ) return Type::TOP;
2465 
2466   return StoreNode::Value( phase );
2467 }
2468 
2469 
2470 //=============================================================================
2471 //----------------------------------SCMemProjNode------------------------------
2472 const Type * SCMemProjNode::Value( PhaseTransform *phase ) const
2473 {
2474   return bottom_type();
2475 }
2476 
2477 //=============================================================================
2478 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : Node(5) {
2479   init_req(MemNode::Control, c  );
2480   init_req(MemNode::Memory , mem);
2481   init_req(MemNode::Address, adr);
2482   init_req(MemNode::ValueIn, val);
2483   init_req(         ExpectedIn, ex );
2484   init_class_id(Class_LoadStore);
2485 
2486 }
2487 
2488 //=============================================================================
2489 //-------------------------------adr_type--------------------------------------
2490 // Do we Match on this edge index or not?  Do not match memory
2491 const TypePtr* ClearArrayNode::adr_type() const {
2492   Node *adr = in(3);
2493   return MemNode::calculate_adr_type(adr->bottom_type());
2494 }
2495 
2496 //------------------------------match_edge-------------------------------------
2497 // Do we Match on this edge index or not?  Do not match memory
2498 uint ClearArrayNode::match_edge(uint idx) const {
2499   return idx > 1;
2500 }
2501 
2502 //------------------------------Identity---------------------------------------
2503 // Clearing a zero length array does nothing
2504 Node *ClearArrayNode::Identity( PhaseTransform *phase ) {
2505   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2506 }
2507 
2508 //------------------------------Idealize---------------------------------------
2509 // Clearing a short array is faster with stores
2510 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){
2511   const int unit = BytesPerLong;
2512   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2513   if (!t)  return NULL;
2514   if (!t->is_con())  return NULL;
2515   intptr_t raw_count = t->get_con();
2516   intptr_t size = raw_count;
2517   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2518   // Clearing nothing uses the Identity call.
2519   // Negative clears are possible on dead ClearArrays
2520   // (see jck test stmt114.stmt11402.val).
2521   if (size <= 0 || size % unit != 0)  return NULL;
2522   intptr_t count = size / unit;
2523   // Length too long; use fast hardware clear
2524   if (size > Matcher::init_array_short_size)  return NULL;
2525   Node *mem = in(1);
2526   if( phase->type(mem)==Type::TOP ) return NULL;
2527   Node *adr = in(3);
2528   const Type* at = phase->type(adr);
2529   if( at==Type::TOP ) return NULL;
2530   const TypePtr* atp = at->isa_ptr();
2531   // adjust atp to be the correct array element address type
2532   if (atp == NULL)  atp = TypePtr::BOTTOM;
2533   else              atp = atp->add_offset(Type::OffsetBot);
2534   // Get base for derived pointer purposes
2535   if( adr->Opcode() != Op_AddP ) Unimplemented();
2536   Node *base = adr->in(1);
2537 
2538   Node *zero = phase->makecon(TypeLong::ZERO);
2539   Node *off  = phase->MakeConX(BytesPerLong);
2540   mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero);
2541   count--;
2542   while( count-- ) {
2543     mem = phase->transform(mem);
2544     adr = phase->transform(new (phase->C, 4) AddPNode(base,adr,off));
2545     mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero);
2546   }
2547   return mem;
2548 }
2549 
2550 //----------------------------step_through----------------------------------
2551 // Return allocation input memory edge if it is different instance
2552 // or itself if it is the one we are looking for.
2553 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2554   Node* n = *np;
2555   assert(n->is_ClearArray(), "sanity");
2556   intptr_t offset;
2557   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2558   // This method is called only before Allocate nodes are expanded during
2559   // macro nodes expansion. Before that ClearArray nodes are only generated
2560   // in LibraryCallKit::generate_arraycopy() which follows allocations.
2561   assert(alloc != NULL, "should have allocation");
2562   if (alloc->_idx == instance_id) {
2563     // Can not bypass initialization of the instance we are looking for.
2564     return false;
2565   }
2566   // Otherwise skip it.
2567   InitializeNode* init = alloc->initialization();
2568   if (init != NULL)
2569     *np = init->in(TypeFunc::Memory);
2570   else
2571     *np = alloc->in(TypeFunc::Memory);
2572   return true;
2573 }
2574 
2575 //----------------------------clear_memory-------------------------------------
2576 // Generate code to initialize object storage to zero.
2577 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2578                                    intptr_t start_offset,
2579                                    Node* end_offset,
2580                                    PhaseGVN* phase) {
2581   Compile* C = phase->C;
2582   intptr_t offset = start_offset;
2583 
2584   int unit = BytesPerLong;
2585   if ((offset % unit) != 0) {
2586     Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(offset));
2587     adr = phase->transform(adr);
2588     const TypePtr* atp = TypeRawPtr::BOTTOM;
2589     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT);
2590     mem = phase->transform(mem);
2591     offset += BytesPerInt;
2592   }
2593   assert((offset % unit) == 0, "");
2594 
2595   // Initialize the remaining stuff, if any, with a ClearArray.
2596   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2597 }
2598 
2599 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2600                                    Node* start_offset,
2601                                    Node* end_offset,
2602                                    PhaseGVN* phase) {
2603   if (start_offset == end_offset) {
2604     // nothing to do
2605     return mem;
2606   }
2607 
2608   Compile* C = phase->C;
2609   int unit = BytesPerLong;
2610   Node* zbase = start_offset;
2611   Node* zend  = end_offset;
2612 
2613   // Scale to the unit required by the CPU:
2614   if (!Matcher::init_array_count_is_in_bytes) {
2615     Node* shift = phase->intcon(exact_log2(unit));
2616     zbase = phase->transform( new(C,3) URShiftXNode(zbase, shift) );
2617     zend  = phase->transform( new(C,3) URShiftXNode(zend,  shift) );
2618   }
2619 
2620   Node* zsize = phase->transform( new(C,3) SubXNode(zend, zbase) );
2621   Node* zinit = phase->zerocon((unit == BytesPerLong) ? T_LONG : T_INT);
2622 
2623   // Bulk clear double-words
2624   Node* adr = phase->transform( new(C,4) AddPNode(dest, dest, start_offset) );
2625   mem = new (C, 4) ClearArrayNode(ctl, mem, zsize, adr);
2626   return phase->transform(mem);
2627 }
2628 
2629 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2630                                    intptr_t start_offset,
2631                                    intptr_t end_offset,
2632                                    PhaseGVN* phase) {
2633   if (start_offset == end_offset) {
2634     // nothing to do
2635     return mem;
2636   }
2637 
2638   Compile* C = phase->C;
2639   assert((end_offset % BytesPerInt) == 0, "odd end offset");
2640   intptr_t done_offset = end_offset;
2641   if ((done_offset % BytesPerLong) != 0) {
2642     done_offset -= BytesPerInt;
2643   }
2644   if (done_offset > start_offset) {
2645     mem = clear_memory(ctl, mem, dest,
2646                        start_offset, phase->MakeConX(done_offset), phase);
2647   }
2648   if (done_offset < end_offset) { // emit the final 32-bit store
2649     Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(done_offset));
2650     adr = phase->transform(adr);
2651     const TypePtr* atp = TypeRawPtr::BOTTOM;
2652     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT);
2653     mem = phase->transform(mem);
2654     done_offset += BytesPerInt;
2655   }
2656   assert(done_offset == end_offset, "");
2657   return mem;
2658 }
2659 
2660 //=============================================================================
2661 // Do not match memory edge.
2662 uint StrIntrinsicNode::match_edge(uint idx) const {
2663   return idx == 2 || idx == 3;
2664 }
2665 
2666 //------------------------------Ideal------------------------------------------
2667 // Return a node which is more "ideal" than the current node.  Strip out
2668 // control copies
2669 Node *StrIntrinsicNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2670   if (remove_dead_region(phase, can_reshape)) return this;
2671   // Don't bother trying to transform a dead node
2672   if (in(0) && in(0)->is_top())  return NULL;
2673 
2674   if (can_reshape) {
2675     Node* mem = phase->transform(in(MemNode::Memory));
2676     // If transformed to a MergeMem, get the desired slice
2677     uint alias_idx = phase->C->get_alias_index(adr_type());
2678     mem = mem->is_MergeMem() ? mem->as_MergeMem()->memory_at(alias_idx) : mem;
2679     if (mem != in(MemNode::Memory)) {
2680       set_req(MemNode::Memory, mem);
2681       return this;
2682     }
2683   }
2684   return NULL;
2685 }
2686 
2687 //------------------------------Value------------------------------------------
2688 const Type *StrIntrinsicNode::Value( PhaseTransform *phase ) const {
2689   if (in(0) && phase->type(in(0)) == Type::TOP) return Type::TOP;
2690   return bottom_type();
2691 }
2692 
2693 //=============================================================================
2694 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
2695   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
2696     _adr_type(C->get_adr_type(alias_idx))
2697 {
2698   init_class_id(Class_MemBar);
2699   Node* top = C->top();
2700   init_req(TypeFunc::I_O,top);
2701   init_req(TypeFunc::FramePtr,top);
2702   init_req(TypeFunc::ReturnAdr,top);
2703   if (precedent != NULL)
2704     init_req(TypeFunc::Parms, precedent);
2705 }
2706 
2707 //------------------------------cmp--------------------------------------------
2708 uint MemBarNode::hash() const { return NO_HASH; }
2709 uint MemBarNode::cmp( const Node &n ) const {
2710   return (&n == this);          // Always fail except on self
2711 }
2712 
2713 //------------------------------make-------------------------------------------
2714 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
2715   int len = Precedent + (pn == NULL? 0: 1);
2716   switch (opcode) {
2717   case Op_MemBarAcquire:   return new(C, len) MemBarAcquireNode(C,  atp, pn);
2718   case Op_MemBarRelease:   return new(C, len) MemBarReleaseNode(C,  atp, pn);
2719   case Op_MemBarAcquireLock: return new(C, len) MemBarAcquireLockNode(C,  atp, pn);
2720   case Op_MemBarReleaseLock: return new(C, len) MemBarReleaseLockNode(C,  atp, pn);
2721   case Op_MemBarVolatile:  return new(C, len) MemBarVolatileNode(C, atp, pn);
2722   case Op_MemBarCPUOrder:  return new(C, len) MemBarCPUOrderNode(C, atp, pn);
2723   case Op_Initialize:      return new(C, len) InitializeNode(C,     atp, pn);
2724   default:                 ShouldNotReachHere(); return NULL;
2725   }
2726 }
2727 
2728 //------------------------------Ideal------------------------------------------
2729 // Return a node which is more "ideal" than the current node.  Strip out
2730 // control copies
2731 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2732   if (remove_dead_region(phase, can_reshape)) return this;
2733   // Don't bother trying to transform a dead node
2734   if (in(0) && in(0)->is_top())  return NULL;
2735 
2736   // Eliminate volatile MemBars for scalar replaced objects.
2737   if (can_reshape && req() == (Precedent+1) &&
2738       (Opcode() == Op_MemBarAcquire || Opcode() == Op_MemBarVolatile)) {
2739     // Volatile field loads and stores.
2740     Node* my_mem = in(MemBarNode::Precedent);
2741     if (my_mem != NULL && my_mem->is_Mem()) {
2742       const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
2743       // Check for scalar replaced object reference.
2744       if( t_oop != NULL && t_oop->is_known_instance_field() &&
2745           t_oop->offset() != Type::OffsetBot &&
2746           t_oop->offset() != Type::OffsetTop) {
2747         // Replace MemBar projections by its inputs.
2748         PhaseIterGVN* igvn = phase->is_IterGVN();
2749         igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
2750         igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
2751         // Must return either the original node (now dead) or a new node
2752         // (Do not return a top here, since that would break the uniqueness of top.)
2753         return new (phase->C, 1) ConINode(TypeInt::ZERO);
2754       }
2755     }
2756   }
2757   return NULL;
2758 }
2759 
2760 //------------------------------Value------------------------------------------
2761 const Type *MemBarNode::Value( PhaseTransform *phase ) const {
2762   if( !in(0) ) return Type::TOP;
2763   if( phase->type(in(0)) == Type::TOP )
2764     return Type::TOP;
2765   return TypeTuple::MEMBAR;
2766 }
2767 
2768 //------------------------------match------------------------------------------
2769 // Construct projections for memory.
2770 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
2771   switch (proj->_con) {
2772   case TypeFunc::Control:
2773   case TypeFunc::Memory:
2774     return new (m->C, 1) MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
2775   }
2776   ShouldNotReachHere();
2777   return NULL;
2778 }
2779 
2780 //===========================InitializeNode====================================
2781 // SUMMARY:
2782 // This node acts as a memory barrier on raw memory, after some raw stores.
2783 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
2784 // The Initialize can 'capture' suitably constrained stores as raw inits.
2785 // It can coalesce related raw stores into larger units (called 'tiles').
2786 // It can avoid zeroing new storage for memory units which have raw inits.
2787 // At macro-expansion, it is marked 'complete', and does not optimize further.
2788 //
2789 // EXAMPLE:
2790 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
2791 //   ctl = incoming control; mem* = incoming memory
2792 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
2793 // First allocate uninitialized memory and fill in the header:
2794 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
2795 //   ctl := alloc.Control; mem* := alloc.Memory*
2796 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
2797 // Then initialize to zero the non-header parts of the raw memory block:
2798 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
2799 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
2800 // After the initialize node executes, the object is ready for service:
2801 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
2802 // Suppose its body is immediately initialized as {1,2}:
2803 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
2804 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
2805 //   mem.SLICE(#short[*]) := store2
2806 //
2807 // DETAILS:
2808 // An InitializeNode collects and isolates object initialization after
2809 // an AllocateNode and before the next possible safepoint.  As a
2810 // memory barrier (MemBarNode), it keeps critical stores from drifting
2811 // down past any safepoint or any publication of the allocation.
2812 // Before this barrier, a newly-allocated object may have uninitialized bits.
2813 // After this barrier, it may be treated as a real oop, and GC is allowed.
2814 //
2815 // The semantics of the InitializeNode include an implicit zeroing of
2816 // the new object from object header to the end of the object.
2817 // (The object header and end are determined by the AllocateNode.)
2818 //
2819 // Certain stores may be added as direct inputs to the InitializeNode.
2820 // These stores must update raw memory, and they must be to addresses
2821 // derived from the raw address produced by AllocateNode, and with
2822 // a constant offset.  They must be ordered by increasing offset.
2823 // The first one is at in(RawStores), the last at in(req()-1).
2824 // Unlike most memory operations, they are not linked in a chain,
2825 // but are displayed in parallel as users of the rawmem output of
2826 // the allocation.
2827 //
2828 // (See comments in InitializeNode::capture_store, which continue
2829 // the example given above.)
2830 //
2831 // When the associated Allocate is macro-expanded, the InitializeNode
2832 // may be rewritten to optimize collected stores.  A ClearArrayNode
2833 // may also be created at that point to represent any required zeroing.
2834 // The InitializeNode is then marked 'complete', prohibiting further
2835 // capturing of nearby memory operations.
2836 //
2837 // During macro-expansion, all captured initializations which store
2838 // constant values of 32 bits or smaller are coalesced (if advantageous)
2839 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
2840 // initialized in fewer memory operations.  Memory words which are
2841 // covered by neither tiles nor non-constant stores are pre-zeroed
2842 // by explicit stores of zero.  (The code shape happens to do all
2843 // zeroing first, then all other stores, with both sequences occurring
2844 // in order of ascending offsets.)
2845 //
2846 // Alternatively, code may be inserted between an AllocateNode and its
2847 // InitializeNode, to perform arbitrary initialization of the new object.
2848 // E.g., the object copying intrinsics insert complex data transfers here.
2849 // The initialization must then be marked as 'complete' disable the
2850 // built-in zeroing semantics and the collection of initializing stores.
2851 //
2852 // While an InitializeNode is incomplete, reads from the memory state
2853 // produced by it are optimizable if they match the control edge and
2854 // new oop address associated with the allocation/initialization.
2855 // They return a stored value (if the offset matches) or else zero.
2856 // A write to the memory state, if it matches control and address,
2857 // and if it is to a constant offset, may be 'captured' by the
2858 // InitializeNode.  It is cloned as a raw memory operation and rewired
2859 // inside the initialization, to the raw oop produced by the allocation.
2860 // Operations on addresses which are provably distinct (e.g., to
2861 // other AllocateNodes) are allowed to bypass the initialization.
2862 //
2863 // The effect of all this is to consolidate object initialization
2864 // (both arrays and non-arrays, both piecewise and bulk) into a
2865 // single location, where it can be optimized as a unit.
2866 //
2867 // Only stores with an offset less than TrackedInitializationLimit words
2868 // will be considered for capture by an InitializeNode.  This puts a
2869 // reasonable limit on the complexity of optimized initializations.
2870 
2871 //---------------------------InitializeNode------------------------------------
2872 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
2873   : _is_complete(Incomplete),
2874     MemBarNode(C, adr_type, rawoop)
2875 {
2876   init_class_id(Class_Initialize);
2877 
2878   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
2879   assert(in(RawAddress) == rawoop, "proper init");
2880   // Note:  allocation() can be NULL, for secondary initialization barriers
2881 }
2882 
2883 // Since this node is not matched, it will be processed by the
2884 // register allocator.  Declare that there are no constraints
2885 // on the allocation of the RawAddress edge.
2886 const RegMask &InitializeNode::in_RegMask(uint idx) const {
2887   // This edge should be set to top, by the set_complete.  But be conservative.
2888   if (idx == InitializeNode::RawAddress)
2889     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
2890   return RegMask::Empty;
2891 }
2892 
2893 Node* InitializeNode::memory(uint alias_idx) {
2894   Node* mem = in(Memory);
2895   if (mem->is_MergeMem()) {
2896     return mem->as_MergeMem()->memory_at(alias_idx);
2897   } else {
2898     // incoming raw memory is not split
2899     return mem;
2900   }
2901 }
2902 
2903 bool InitializeNode::is_non_zero() {
2904   if (is_complete())  return false;
2905   remove_extra_zeroes();
2906   return (req() > RawStores);
2907 }
2908 
2909 void InitializeNode::set_complete(PhaseGVN* phase) {
2910   assert(!is_complete(), "caller responsibility");
2911   _is_complete = Complete;
2912 
2913   // After this node is complete, it contains a bunch of
2914   // raw-memory initializations.  There is no need for
2915   // it to have anything to do with non-raw memory effects.
2916   // Therefore, tell all non-raw users to re-optimize themselves,
2917   // after skipping the memory effects of this initialization.
2918   PhaseIterGVN* igvn = phase->is_IterGVN();
2919   if (igvn)  igvn->add_users_to_worklist(this);
2920 }
2921 
2922 // convenience function
2923 // return false if the init contains any stores already
2924 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
2925   InitializeNode* init = initialization();
2926   if (init == NULL || init->is_complete())  return false;
2927   init->remove_extra_zeroes();
2928   // for now, if this allocation has already collected any inits, bail:
2929   if (init->is_non_zero())  return false;
2930   init->set_complete(phase);
2931   return true;
2932 }
2933 
2934 void InitializeNode::remove_extra_zeroes() {
2935   if (req() == RawStores)  return;
2936   Node* zmem = zero_memory();
2937   uint fill = RawStores;
2938   for (uint i = fill; i < req(); i++) {
2939     Node* n = in(i);
2940     if (n->is_top() || n == zmem)  continue;  // skip
2941     if (fill < i)  set_req(fill, n);          // compact
2942     ++fill;
2943   }
2944   // delete any empty spaces created:
2945   while (fill < req()) {
2946     del_req(fill);
2947   }
2948 }
2949 
2950 // Helper for remembering which stores go with which offsets.
2951 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
2952   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
2953   intptr_t offset = -1;
2954   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
2955                                                phase, offset);
2956   if (base == NULL)     return -1;  // something is dead,
2957   if (offset < 0)       return -1;  //        dead, dead
2958   return offset;
2959 }
2960 
2961 // Helper for proving that an initialization expression is
2962 // "simple enough" to be folded into an object initialization.
2963 // Attempts to prove that a store's initial value 'n' can be captured
2964 // within the initialization without creating a vicious cycle, such as:
2965 //     { Foo p = new Foo(); p.next = p; }
2966 // True for constants and parameters and small combinations thereof.
2967 bool InitializeNode::detect_init_independence(Node* n,
2968                                               bool st_is_pinned,
2969                                               int& count) {
2970   if (n == NULL)      return true;   // (can this really happen?)
2971   if (n->is_Proj())   n = n->in(0);
2972   if (n == this)      return false;  // found a cycle
2973   if (n->is_Con())    return true;
2974   if (n->is_Start())  return true;   // params, etc., are OK
2975   if (n->is_Root())   return true;   // even better
2976 
2977   Node* ctl = n->in(0);
2978   if (ctl != NULL && !ctl->is_top()) {
2979     if (ctl->is_Proj())  ctl = ctl->in(0);
2980     if (ctl == this)  return false;
2981 
2982     // If we already know that the enclosing memory op is pinned right after
2983     // the init, then any control flow that the store has picked up
2984     // must have preceded the init, or else be equal to the init.
2985     // Even after loop optimizations (which might change control edges)
2986     // a store is never pinned *before* the availability of its inputs.
2987     if (!MemNode::all_controls_dominate(n, this))
2988       return false;                  // failed to prove a good control
2989 
2990   }
2991 
2992   // Check data edges for possible dependencies on 'this'.
2993   if ((count += 1) > 20)  return false;  // complexity limit
2994   for (uint i = 1; i < n->req(); i++) {
2995     Node* m = n->in(i);
2996     if (m == NULL || m == n || m->is_top())  continue;
2997     uint first_i = n->find_edge(m);
2998     if (i != first_i)  continue;  // process duplicate edge just once
2999     if (!detect_init_independence(m, st_is_pinned, count)) {
3000       return false;
3001     }
3002   }
3003 
3004   return true;
3005 }
3006 
3007 // Here are all the checks a Store must pass before it can be moved into
3008 // an initialization.  Returns zero if a check fails.
3009 // On success, returns the (constant) offset to which the store applies,
3010 // within the initialized memory.
3011 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase) {
3012   const int FAIL = 0;
3013   if (st->req() != MemNode::ValueIn + 1)
3014     return FAIL;                // an inscrutable StoreNode (card mark?)
3015   Node* ctl = st->in(MemNode::Control);
3016   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3017     return FAIL;                // must be unconditional after the initialization
3018   Node* mem = st->in(MemNode::Memory);
3019   if (!(mem->is_Proj() && mem->in(0) == this))
3020     return FAIL;                // must not be preceded by other stores
3021   Node* adr = st->in(MemNode::Address);
3022   intptr_t offset;
3023   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3024   if (alloc == NULL)
3025     return FAIL;                // inscrutable address
3026   if (alloc != allocation())
3027     return FAIL;                // wrong allocation!  (store needs to float up)
3028   Node* val = st->in(MemNode::ValueIn);
3029   int complexity_count = 0;
3030   if (!detect_init_independence(val, true, complexity_count))
3031     return FAIL;                // stored value must be 'simple enough'
3032 
3033   return offset;                // success
3034 }
3035 
3036 // Find the captured store in(i) which corresponds to the range
3037 // [start..start+size) in the initialized object.
3038 // If there is one, return its index i.  If there isn't, return the
3039 // negative of the index where it should be inserted.
3040 // Return 0 if the queried range overlaps an initialization boundary
3041 // or if dead code is encountered.
3042 // If size_in_bytes is zero, do not bother with overlap checks.
3043 int InitializeNode::captured_store_insertion_point(intptr_t start,
3044                                                    int size_in_bytes,
3045                                                    PhaseTransform* phase) {
3046   const int FAIL = 0, MAX_STORE = BytesPerLong;
3047 
3048   if (is_complete())
3049     return FAIL;                // arraycopy got here first; punt
3050 
3051   assert(allocation() != NULL, "must be present");
3052 
3053   // no negatives, no header fields:
3054   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3055 
3056   // after a certain size, we bail out on tracking all the stores:
3057   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3058   if (start >= ti_limit)  return FAIL;
3059 
3060   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3061     if (i >= limit)  return -(int)i; // not found; here is where to put it
3062 
3063     Node*    st     = in(i);
3064     intptr_t st_off = get_store_offset(st, phase);
3065     if (st_off < 0) {
3066       if (st != zero_memory()) {
3067         return FAIL;            // bail out if there is dead garbage
3068       }
3069     } else if (st_off > start) {
3070       // ...we are done, since stores are ordered
3071       if (st_off < start + size_in_bytes) {
3072         return FAIL;            // the next store overlaps
3073       }
3074       return -(int)i;           // not found; here is where to put it
3075     } else if (st_off < start) {
3076       if (size_in_bytes != 0 &&
3077           start < st_off + MAX_STORE &&
3078           start < st_off + st->as_Store()->memory_size()) {
3079         return FAIL;            // the previous store overlaps
3080       }
3081     } else {
3082       if (size_in_bytes != 0 &&
3083           st->as_Store()->memory_size() != size_in_bytes) {
3084         return FAIL;            // mismatched store size
3085       }
3086       return i;
3087     }
3088 
3089     ++i;
3090   }
3091 }
3092 
3093 // Look for a captured store which initializes at the offset 'start'
3094 // with the given size.  If there is no such store, and no other
3095 // initialization interferes, then return zero_memory (the memory
3096 // projection of the AllocateNode).
3097 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3098                                           PhaseTransform* phase) {
3099   assert(stores_are_sane(phase), "");
3100   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3101   if (i == 0) {
3102     return NULL;                // something is dead
3103   } else if (i < 0) {
3104     return zero_memory();       // just primordial zero bits here
3105   } else {
3106     Node* st = in(i);           // here is the store at this position
3107     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3108     return st;
3109   }
3110 }
3111 
3112 // Create, as a raw pointer, an address within my new object at 'offset'.
3113 Node* InitializeNode::make_raw_address(intptr_t offset,
3114                                        PhaseTransform* phase) {
3115   Node* addr = in(RawAddress);
3116   if (offset != 0) {
3117     Compile* C = phase->C;
3118     addr = phase->transform( new (C, 4) AddPNode(C->top(), addr,
3119                                                  phase->MakeConX(offset)) );
3120   }
3121   return addr;
3122 }
3123 
3124 // Clone the given store, converting it into a raw store
3125 // initializing a field or element of my new object.
3126 // Caller is responsible for retiring the original store,
3127 // with subsume_node or the like.
3128 //
3129 // From the example above InitializeNode::InitializeNode,
3130 // here are the old stores to be captured:
3131 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3132 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3133 //
3134 // Here is the changed code; note the extra edges on init:
3135 //   alloc = (Allocate ...)
3136 //   rawoop = alloc.RawAddress
3137 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3138 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3139 //   init = (Initialize alloc.Control alloc.Memory rawoop
3140 //                      rawstore1 rawstore2)
3141 //
3142 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3143                                     PhaseTransform* phase) {
3144   assert(stores_are_sane(phase), "");
3145 
3146   if (start < 0)  return NULL;
3147   assert(can_capture_store(st, phase) == start, "sanity");
3148 
3149   Compile* C = phase->C;
3150   int size_in_bytes = st->memory_size();
3151   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3152   if (i == 0)  return NULL;     // bail out
3153   Node* prev_mem = NULL;        // raw memory for the captured store
3154   if (i > 0) {
3155     prev_mem = in(i);           // there is a pre-existing store under this one
3156     set_req(i, C->top());       // temporarily disconnect it
3157     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3158   } else {
3159     i = -i;                     // no pre-existing store
3160     prev_mem = zero_memory();   // a slice of the newly allocated object
3161     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3162       set_req(--i, C->top());   // reuse this edge; it has been folded away
3163     else
3164       ins_req(i, C->top());     // build a new edge
3165   }
3166   Node* new_st = st->clone();
3167   new_st->set_req(MemNode::Control, in(Control));
3168   new_st->set_req(MemNode::Memory,  prev_mem);
3169   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3170   new_st = phase->transform(new_st);
3171 
3172   // At this point, new_st might have swallowed a pre-existing store
3173   // at the same offset, or perhaps new_st might have disappeared,
3174   // if it redundantly stored the same value (or zero to fresh memory).
3175 
3176   // In any case, wire it in:
3177   set_req(i, new_st);
3178 
3179   // The caller may now kill the old guy.
3180   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3181   assert(check_st == new_st || check_st == NULL, "must be findable");
3182   assert(!is_complete(), "");
3183   return new_st;
3184 }
3185 
3186 static bool store_constant(jlong* tiles, int num_tiles,
3187                            intptr_t st_off, int st_size,
3188                            jlong con) {
3189   if ((st_off & (st_size-1)) != 0)
3190     return false;               // strange store offset (assume size==2**N)
3191   address addr = (address)tiles + st_off;
3192   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3193   switch (st_size) {
3194   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3195   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3196   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3197   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3198   default: return false;        // strange store size (detect size!=2**N here)
3199   }
3200   return true;                  // return success to caller
3201 }
3202 
3203 // Coalesce subword constants into int constants and possibly
3204 // into long constants.  The goal, if the CPU permits,
3205 // is to initialize the object with a small number of 64-bit tiles.
3206 // Also, convert floating-point constants to bit patterns.
3207 // Non-constants are not relevant to this pass.
3208 //
3209 // In terms of the running example on InitializeNode::InitializeNode
3210 // and InitializeNode::capture_store, here is the transformation
3211 // of rawstore1 and rawstore2 into rawstore12:
3212 //   alloc = (Allocate ...)
3213 //   rawoop = alloc.RawAddress
3214 //   tile12 = 0x00010002
3215 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3216 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3217 //
3218 void
3219 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3220                                         Node* size_in_bytes,
3221                                         PhaseGVN* phase) {
3222   Compile* C = phase->C;
3223 
3224   assert(stores_are_sane(phase), "");
3225   // Note:  After this pass, they are not completely sane,
3226   // since there may be some overlaps.
3227 
3228   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3229 
3230   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3231   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3232   size_limit = MIN2(size_limit, ti_limit);
3233   size_limit = align_size_up(size_limit, BytesPerLong);
3234   int num_tiles = size_limit / BytesPerLong;
3235 
3236   // allocate space for the tile map:
3237   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3238   jlong  tiles_buf[small_len];
3239   Node*  nodes_buf[small_len];
3240   jlong  inits_buf[small_len];
3241   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3242                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3243   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3244                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3245   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3246                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3247   // tiles: exact bitwise model of all primitive constants
3248   // nodes: last constant-storing node subsumed into the tiles model
3249   // inits: which bytes (in each tile) are touched by any initializations
3250 
3251   //// Pass A: Fill in the tile model with any relevant stores.
3252 
3253   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3254   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3255   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3256   Node* zmem = zero_memory(); // initially zero memory state
3257   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3258     Node* st = in(i);
3259     intptr_t st_off = get_store_offset(st, phase);
3260 
3261     // Figure out the store's offset and constant value:
3262     if (st_off < header_size)             continue; //skip (ignore header)
3263     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3264     int st_size = st->as_Store()->memory_size();
3265     if (st_off + st_size > size_limit)    break;
3266 
3267     // Record which bytes are touched, whether by constant or not.
3268     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3269       continue;                 // skip (strange store size)
3270 
3271     const Type* val = phase->type(st->in(MemNode::ValueIn));
3272     if (!val->singleton())                continue; //skip (non-con store)
3273     BasicType type = val->basic_type();
3274 
3275     jlong con = 0;
3276     switch (type) {
3277     case T_INT:    con = val->is_int()->get_con();  break;
3278     case T_LONG:   con = val->is_long()->get_con(); break;
3279     case T_FLOAT:  con = jint_cast(val->getf());    break;
3280     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3281     default:                              continue; //skip (odd store type)
3282     }
3283 
3284     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3285         st->Opcode() == Op_StoreL) {
3286       continue;                 // This StoreL is already optimal.
3287     }
3288 
3289     // Store down the constant.
3290     store_constant(tiles, num_tiles, st_off, st_size, con);
3291 
3292     intptr_t j = st_off >> LogBytesPerLong;
3293 
3294     if (type == T_INT && st_size == BytesPerInt
3295         && (st_off & BytesPerInt) == BytesPerInt) {
3296       jlong lcon = tiles[j];
3297       if (!Matcher::isSimpleConstant64(lcon) &&
3298           st->Opcode() == Op_StoreI) {
3299         // This StoreI is already optimal by itself.
3300         jint* intcon = (jint*) &tiles[j];
3301         intcon[1] = 0;  // undo the store_constant()
3302 
3303         // If the previous store is also optimal by itself, back up and
3304         // undo the action of the previous loop iteration... if we can.
3305         // But if we can't, just let the previous half take care of itself.
3306         st = nodes[j];
3307         st_off -= BytesPerInt;
3308         con = intcon[0];
3309         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3310           assert(st_off >= header_size, "still ignoring header");
3311           assert(get_store_offset(st, phase) == st_off, "must be");
3312           assert(in(i-1) == zmem, "must be");
3313           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3314           assert(con == tcon->is_int()->get_con(), "must be");
3315           // Undo the effects of the previous loop trip, which swallowed st:
3316           intcon[0] = 0;        // undo store_constant()
3317           set_req(i-1, st);     // undo set_req(i, zmem)
3318           nodes[j] = NULL;      // undo nodes[j] = st
3319           --old_subword;        // undo ++old_subword
3320         }
3321         continue;               // This StoreI is already optimal.
3322       }
3323     }
3324 
3325     // This store is not needed.
3326     set_req(i, zmem);
3327     nodes[j] = st;              // record for the moment
3328     if (st_size < BytesPerLong) // something has changed
3329           ++old_subword;        // includes int/float, but who's counting...
3330     else  ++old_long;
3331   }
3332 
3333   if ((old_subword + old_long) == 0)
3334     return;                     // nothing more to do
3335 
3336   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3337   // Be sure to insert them before overlapping non-constant stores.
3338   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3339   for (int j = 0; j < num_tiles; j++) {
3340     jlong con  = tiles[j];
3341     jlong init = inits[j];
3342     if (con == 0)  continue;
3343     jint con0,  con1;           // split the constant, address-wise
3344     jint init0, init1;          // split the init map, address-wise
3345     { union { jlong con; jint intcon[2]; } u;
3346       u.con = con;
3347       con0  = u.intcon[0];
3348       con1  = u.intcon[1];
3349       u.con = init;
3350       init0 = u.intcon[0];
3351       init1 = u.intcon[1];
3352     }
3353 
3354     Node* old = nodes[j];
3355     assert(old != NULL, "need the prior store");
3356     intptr_t offset = (j * BytesPerLong);
3357 
3358     bool split = !Matcher::isSimpleConstant64(con);
3359 
3360     if (offset < header_size) {
3361       assert(offset + BytesPerInt >= header_size, "second int counts");
3362       assert(*(jint*)&tiles[j] == 0, "junk in header");
3363       split = true;             // only the second word counts
3364       // Example:  int a[] = { 42 ... }
3365     } else if (con0 == 0 && init0 == -1) {
3366       split = true;             // first word is covered by full inits
3367       // Example:  int a[] = { ... foo(), 42 ... }
3368     } else if (con1 == 0 && init1 == -1) {
3369       split = true;             // second word is covered by full inits
3370       // Example:  int a[] = { ... 42, foo() ... }
3371     }
3372 
3373     // Here's a case where init0 is neither 0 nor -1:
3374     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
3375     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3376     // In this case the tile is not split; it is (jlong)42.
3377     // The big tile is stored down, and then the foo() value is inserted.
3378     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3379 
3380     Node* ctl = old->in(MemNode::Control);
3381     Node* adr = make_raw_address(offset, phase);
3382     const TypePtr* atp = TypeRawPtr::BOTTOM;
3383 
3384     // One or two coalesced stores to plop down.
3385     Node*    st[2];
3386     intptr_t off[2];
3387     int  nst = 0;
3388     if (!split) {
3389       ++new_long;
3390       off[nst] = offset;
3391       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3392                                   phase->longcon(con), T_LONG);
3393     } else {
3394       // Omit either if it is a zero.
3395       if (con0 != 0) {
3396         ++new_int;
3397         off[nst]  = offset;
3398         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3399                                     phase->intcon(con0), T_INT);
3400       }
3401       if (con1 != 0) {
3402         ++new_int;
3403         offset += BytesPerInt;
3404         adr = make_raw_address(offset, phase);
3405         off[nst]  = offset;
3406         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3407                                     phase->intcon(con1), T_INT);
3408       }
3409     }
3410 
3411     // Insert second store first, then the first before the second.
3412     // Insert each one just before any overlapping non-constant stores.
3413     while (nst > 0) {
3414       Node* st1 = st[--nst];
3415       C->copy_node_notes_to(st1, old);
3416       st1 = phase->transform(st1);
3417       offset = off[nst];
3418       assert(offset >= header_size, "do not smash header");
3419       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
3420       guarantee(ins_idx != 0, "must re-insert constant store");
3421       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
3422       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
3423         set_req(--ins_idx, st1);
3424       else
3425         ins_req(ins_idx, st1);
3426     }
3427   }
3428 
3429   if (PrintCompilation && WizardMode)
3430     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
3431                   old_subword, old_long, new_int, new_long);
3432   if (C->log() != NULL)
3433     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
3434                    old_subword, old_long, new_int, new_long);
3435 
3436   // Clean up any remaining occurrences of zmem:
3437   remove_extra_zeroes();
3438 }
3439 
3440 // Explore forward from in(start) to find the first fully initialized
3441 // word, and return its offset.  Skip groups of subword stores which
3442 // together initialize full words.  If in(start) is itself part of a
3443 // fully initialized word, return the offset of in(start).  If there
3444 // are no following full-word stores, or if something is fishy, return
3445 // a negative value.
3446 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
3447   int       int_map = 0;
3448   intptr_t  int_map_off = 0;
3449   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
3450 
3451   for (uint i = start, limit = req(); i < limit; i++) {
3452     Node* st = in(i);
3453 
3454     intptr_t st_off = get_store_offset(st, phase);
3455     if (st_off < 0)  break;  // return conservative answer
3456 
3457     int st_size = st->as_Store()->memory_size();
3458     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
3459       return st_off;            // we found a complete word init
3460     }
3461 
3462     // update the map:
3463 
3464     intptr_t this_int_off = align_size_down(st_off, BytesPerInt);
3465     if (this_int_off != int_map_off) {
3466       // reset the map:
3467       int_map = 0;
3468       int_map_off = this_int_off;
3469     }
3470 
3471     int subword_off = st_off - this_int_off;
3472     int_map |= right_n_bits(st_size) << subword_off;
3473     if ((int_map & FULL_MAP) == FULL_MAP) {
3474       return this_int_off;      // we found a complete word init
3475     }
3476 
3477     // Did this store hit or cross the word boundary?
3478     intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt);
3479     if (next_int_off == this_int_off + BytesPerInt) {
3480       // We passed the current int, without fully initializing it.
3481       int_map_off = next_int_off;
3482       int_map >>= BytesPerInt;
3483     } else if (next_int_off > this_int_off + BytesPerInt) {
3484       // We passed the current and next int.
3485       return this_int_off + BytesPerInt;
3486     }
3487   }
3488 
3489   return -1;
3490 }
3491 
3492 
3493 // Called when the associated AllocateNode is expanded into CFG.
3494 // At this point, we may perform additional optimizations.
3495 // Linearize the stores by ascending offset, to make memory
3496 // activity as coherent as possible.
3497 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
3498                                       intptr_t header_size,
3499                                       Node* size_in_bytes,
3500                                       PhaseGVN* phase) {
3501   assert(!is_complete(), "not already complete");
3502   assert(stores_are_sane(phase), "");
3503   assert(allocation() != NULL, "must be present");
3504 
3505   remove_extra_zeroes();
3506 
3507   if (ReduceFieldZeroing || ReduceBulkZeroing)
3508     // reduce instruction count for common initialization patterns
3509     coalesce_subword_stores(header_size, size_in_bytes, phase);
3510 
3511   Node* zmem = zero_memory();   // initially zero memory state
3512   Node* inits = zmem;           // accumulating a linearized chain of inits
3513   #ifdef ASSERT
3514   intptr_t first_offset = allocation()->minimum_header_size();
3515   intptr_t last_init_off = first_offset;  // previous init offset
3516   intptr_t last_init_end = first_offset;  // previous init offset+size
3517   intptr_t last_tile_end = first_offset;  // previous tile offset+size
3518   #endif
3519   intptr_t zeroes_done = header_size;
3520 
3521   bool do_zeroing = true;       // we might give up if inits are very sparse
3522   int  big_init_gaps = 0;       // how many large gaps have we seen?
3523 
3524   if (ZeroTLAB)  do_zeroing = false;
3525   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
3526 
3527   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3528     Node* st = in(i);
3529     intptr_t st_off = get_store_offset(st, phase);
3530     if (st_off < 0)
3531       break;                    // unknown junk in the inits
3532     if (st->in(MemNode::Memory) != zmem)
3533       break;                    // complicated store chains somehow in list
3534 
3535     int st_size = st->as_Store()->memory_size();
3536     intptr_t next_init_off = st_off + st_size;
3537 
3538     if (do_zeroing && zeroes_done < next_init_off) {
3539       // See if this store needs a zero before it or under it.
3540       intptr_t zeroes_needed = st_off;
3541 
3542       if (st_size < BytesPerInt) {
3543         // Look for subword stores which only partially initialize words.
3544         // If we find some, we must lay down some word-level zeroes first,
3545         // underneath the subword stores.
3546         //
3547         // Examples:
3548         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
3549         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
3550         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
3551         //
3552         // Note:  coalesce_subword_stores may have already done this,
3553         // if it was prompted by constant non-zero subword initializers.
3554         // But this case can still arise with non-constant stores.
3555 
3556         intptr_t next_full_store = find_next_fullword_store(i, phase);
3557 
3558         // In the examples above:
3559         //   in(i)          p   q   r   s     x   y     z
3560         //   st_off        12  13  14  15    12  13    14
3561         //   st_size        1   1   1   1     1   1     1
3562         //   next_full_s.  12  16  16  16    16  16    16
3563         //   z's_done      12  16  16  16    12  16    12
3564         //   z's_needed    12  16  16  16    16  16    16
3565         //   zsize          0   0   0   0     4   0     4
3566         if (next_full_store < 0) {
3567           // Conservative tack:  Zero to end of current word.
3568           zeroes_needed = align_size_up(zeroes_needed, BytesPerInt);
3569         } else {
3570           // Zero to beginning of next fully initialized word.
3571           // Or, don't zero at all, if we are already in that word.
3572           assert(next_full_store >= zeroes_needed, "must go forward");
3573           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
3574           zeroes_needed = next_full_store;
3575         }
3576       }
3577 
3578       if (zeroes_needed > zeroes_done) {
3579         intptr_t zsize = zeroes_needed - zeroes_done;
3580         // Do some incremental zeroing on rawmem, in parallel with inits.
3581         zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3582         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3583                                               zeroes_done, zeroes_needed,
3584                                               phase);
3585         zeroes_done = zeroes_needed;
3586         if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2)
3587           do_zeroing = false;   // leave the hole, next time
3588       }
3589     }
3590 
3591     // Collect the store and move on:
3592     st->set_req(MemNode::Memory, inits);
3593     inits = st;                 // put it on the linearized chain
3594     set_req(i, zmem);           // unhook from previous position
3595 
3596     if (zeroes_done == st_off)
3597       zeroes_done = next_init_off;
3598 
3599     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
3600 
3601     #ifdef ASSERT
3602     // Various order invariants.  Weaker than stores_are_sane because
3603     // a large constant tile can be filled in by smaller non-constant stores.
3604     assert(st_off >= last_init_off, "inits do not reverse");
3605     last_init_off = st_off;
3606     const Type* val = NULL;
3607     if (st_size >= BytesPerInt &&
3608         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
3609         (int)val->basic_type() < (int)T_OBJECT) {
3610       assert(st_off >= last_tile_end, "tiles do not overlap");
3611       assert(st_off >= last_init_end, "tiles do not overwrite inits");
3612       last_tile_end = MAX2(last_tile_end, next_init_off);
3613     } else {
3614       intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong);
3615       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
3616       assert(st_off      >= last_init_end, "inits do not overlap");
3617       last_init_end = next_init_off;  // it's a non-tile
3618     }
3619     #endif //ASSERT
3620   }
3621 
3622   remove_extra_zeroes();        // clear out all the zmems left over
3623   add_req(inits);
3624 
3625   if (!ZeroTLAB) {
3626     // If anything remains to be zeroed, zero it all now.
3627     zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3628     // if it is the last unused 4 bytes of an instance, forget about it
3629     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
3630     if (zeroes_done + BytesPerLong >= size_limit) {
3631       assert(allocation() != NULL, "");
3632       if (allocation()->Opcode() == Op_Allocate) {
3633         Node* klass_node = allocation()->in(AllocateNode::KlassNode);
3634         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
3635         if (zeroes_done == k->layout_helper())
3636           zeroes_done = size_limit;
3637       }
3638     }
3639     if (zeroes_done < size_limit) {
3640       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3641                                             zeroes_done, size_in_bytes, phase);
3642     }
3643   }
3644 
3645   set_complete(phase);
3646   return rawmem;
3647 }
3648 
3649 
3650 #ifdef ASSERT
3651 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
3652   if (is_complete())
3653     return true;                // stores could be anything at this point
3654   assert(allocation() != NULL, "must be present");
3655   intptr_t last_off = allocation()->minimum_header_size();
3656   for (uint i = InitializeNode::RawStores; i < req(); i++) {
3657     Node* st = in(i);
3658     intptr_t st_off = get_store_offset(st, phase);
3659     if (st_off < 0)  continue;  // ignore dead garbage
3660     if (last_off > st_off) {
3661       tty->print_cr("*** bad store offset at %d: %d > %d", i, last_off, st_off);
3662       this->dump(2);
3663       assert(false, "ascending store offsets");
3664       return false;
3665     }
3666     last_off = st_off + st->as_Store()->memory_size();
3667   }
3668   return true;
3669 }
3670 #endif //ASSERT
3671 
3672 
3673 
3674 
3675 //============================MergeMemNode=====================================
3676 //
3677 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
3678 // contributing store or call operations.  Each contributor provides the memory
3679 // state for a particular "alias type" (see Compile::alias_type).  For example,
3680 // if a MergeMem has an input X for alias category #6, then any memory reference
3681 // to alias category #6 may use X as its memory state input, as an exact equivalent
3682 // to using the MergeMem as a whole.
3683 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
3684 //
3685 // (Here, the <N> notation gives the index of the relevant adr_type.)
3686 //
3687 // In one special case (and more cases in the future), alias categories overlap.
3688 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
3689 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
3690 // it is exactly equivalent to that state W:
3691 //   MergeMem(<Bot>: W) <==> W
3692 //
3693 // Usually, the merge has more than one input.  In that case, where inputs
3694 // overlap (i.e., one is Bot), the narrower alias type determines the memory
3695 // state for that type, and the wider alias type (Bot) fills in everywhere else:
3696 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
3697 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
3698 //
3699 // A merge can take a "wide" memory state as one of its narrow inputs.
3700 // This simply means that the merge observes out only the relevant parts of
3701 // the wide input.  That is, wide memory states arriving at narrow merge inputs
3702 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
3703 //
3704 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
3705 // and that memory slices "leak through":
3706 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
3707 //
3708 // But, in such a cascade, repeated memory slices can "block the leak":
3709 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
3710 //
3711 // In the last example, Y is not part of the combined memory state of the
3712 // outermost MergeMem.  The system must, of course, prevent unschedulable
3713 // memory states from arising, so you can be sure that the state Y is somehow
3714 // a precursor to state Y'.
3715 //
3716 //
3717 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
3718 // of each MergeMemNode array are exactly the numerical alias indexes, including
3719 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
3720 // Compile::alias_type (and kin) produce and manage these indexes.
3721 //
3722 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
3723 // (Note that this provides quick access to the top node inside MergeMem methods,
3724 // without the need to reach out via TLS to Compile::current.)
3725 //
3726 // As a consequence of what was just described, a MergeMem that represents a full
3727 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
3728 // containing all alias categories.
3729 //
3730 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
3731 //
3732 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
3733 // a memory state for the alias type <N>, or else the top node, meaning that
3734 // there is no particular input for that alias type.  Note that the length of
3735 // a MergeMem is variable, and may be extended at any time to accommodate new
3736 // memory states at larger alias indexes.  When merges grow, they are of course
3737 // filled with "top" in the unused in() positions.
3738 //
3739 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
3740 // (Top was chosen because it works smoothly with passes like GCM.)
3741 //
3742 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
3743 // the type of random VM bits like TLS references.)  Since it is always the
3744 // first non-Bot memory slice, some low-level loops use it to initialize an
3745 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
3746 //
3747 //
3748 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
3749 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
3750 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
3751 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
3752 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
3753 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
3754 //
3755 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
3756 // really that different from the other memory inputs.  An abbreviation called
3757 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
3758 //
3759 //
3760 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
3761 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
3762 // that "emerges though" the base memory will be marked as excluding the alias types
3763 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
3764 //
3765 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
3766 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
3767 //
3768 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
3769 // (It is currently unimplemented.)  As you can see, the resulting merge is
3770 // actually a disjoint union of memory states, rather than an overlay.
3771 //
3772 
3773 //------------------------------MergeMemNode-----------------------------------
3774 Node* MergeMemNode::make_empty_memory() {
3775   Node* empty_memory = (Node*) Compile::current()->top();
3776   assert(empty_memory->is_top(), "correct sentinel identity");
3777   return empty_memory;
3778 }
3779 
3780 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
3781   init_class_id(Class_MergeMem);
3782   // all inputs are nullified in Node::Node(int)
3783   // set_input(0, NULL);  // no control input
3784 
3785   // Initialize the edges uniformly to top, for starters.
3786   Node* empty_mem = make_empty_memory();
3787   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
3788     init_req(i,empty_mem);
3789   }
3790   assert(empty_memory() == empty_mem, "");
3791 
3792   if( new_base != NULL && new_base->is_MergeMem() ) {
3793     MergeMemNode* mdef = new_base->as_MergeMem();
3794     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
3795     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
3796       mms.set_memory(mms.memory2());
3797     }
3798     assert(base_memory() == mdef->base_memory(), "");
3799   } else {
3800     set_base_memory(new_base);
3801   }
3802 }
3803 
3804 // Make a new, untransformed MergeMem with the same base as 'mem'.
3805 // If mem is itself a MergeMem, populate the result with the same edges.
3806 MergeMemNode* MergeMemNode::make(Compile* C, Node* mem) {
3807   return new(C, 1+Compile::AliasIdxRaw) MergeMemNode(mem);
3808 }
3809 
3810 //------------------------------cmp--------------------------------------------
3811 uint MergeMemNode::hash() const { return NO_HASH; }
3812 uint MergeMemNode::cmp( const Node &n ) const {
3813   return (&n == this);          // Always fail except on self
3814 }
3815 
3816 //------------------------------Identity---------------------------------------
3817 Node* MergeMemNode::Identity(PhaseTransform *phase) {
3818   // Identity if this merge point does not record any interesting memory
3819   // disambiguations.
3820   Node* base_mem = base_memory();
3821   Node* empty_mem = empty_memory();
3822   if (base_mem != empty_mem) {  // Memory path is not dead?
3823     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3824       Node* mem = in(i);
3825       if (mem != empty_mem && mem != base_mem) {
3826         return this;            // Many memory splits; no change
3827       }
3828     }
3829   }
3830   return base_mem;              // No memory splits; ID on the one true input
3831 }
3832 
3833 //------------------------------Ideal------------------------------------------
3834 // This method is invoked recursively on chains of MergeMem nodes
3835 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3836   // Remove chain'd MergeMems
3837   //
3838   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
3839   // relative to the "in(Bot)".  Since we are patching both at the same time,
3840   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
3841   // but rewrite each "in(i)" relative to the new "in(Bot)".
3842   Node *progress = NULL;
3843 
3844 
3845   Node* old_base = base_memory();
3846   Node* empty_mem = empty_memory();
3847   if (old_base == empty_mem)
3848     return NULL; // Dead memory path.
3849 
3850   MergeMemNode* old_mbase;
3851   if (old_base != NULL && old_base->is_MergeMem())
3852     old_mbase = old_base->as_MergeMem();
3853   else
3854     old_mbase = NULL;
3855   Node* new_base = old_base;
3856 
3857   // simplify stacked MergeMems in base memory
3858   if (old_mbase)  new_base = old_mbase->base_memory();
3859 
3860   // the base memory might contribute new slices beyond my req()
3861   if (old_mbase)  grow_to_match(old_mbase);
3862 
3863   // Look carefully at the base node if it is a phi.
3864   PhiNode* phi_base;
3865   if (new_base != NULL && new_base->is_Phi())
3866     phi_base = new_base->as_Phi();
3867   else
3868     phi_base = NULL;
3869 
3870   Node*    phi_reg = NULL;
3871   uint     phi_len = (uint)-1;
3872   if (phi_base != NULL && !phi_base->is_copy()) {
3873     // do not examine phi if degraded to a copy
3874     phi_reg = phi_base->region();
3875     phi_len = phi_base->req();
3876     // see if the phi is unfinished
3877     for (uint i = 1; i < phi_len; i++) {
3878       if (phi_base->in(i) == NULL) {
3879         // incomplete phi; do not look at it yet!
3880         phi_reg = NULL;
3881         phi_len = (uint)-1;
3882         break;
3883       }
3884     }
3885   }
3886 
3887   // Note:  We do not call verify_sparse on entry, because inputs
3888   // can normalize to the base_memory via subsume_node or similar
3889   // mechanisms.  This method repairs that damage.
3890 
3891   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
3892 
3893   // Look at each slice.
3894   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3895     Node* old_in = in(i);
3896     // calculate the old memory value
3897     Node* old_mem = old_in;
3898     if (old_mem == empty_mem)  old_mem = old_base;
3899     assert(old_mem == memory_at(i), "");
3900 
3901     // maybe update (reslice) the old memory value
3902 
3903     // simplify stacked MergeMems
3904     Node* new_mem = old_mem;
3905     MergeMemNode* old_mmem;
3906     if (old_mem != NULL && old_mem->is_MergeMem())
3907       old_mmem = old_mem->as_MergeMem();
3908     else
3909       old_mmem = NULL;
3910     if (old_mmem == this) {
3911       // This can happen if loops break up and safepoints disappear.
3912       // A merge of BotPtr (default) with a RawPtr memory derived from a
3913       // safepoint can be rewritten to a merge of the same BotPtr with
3914       // the BotPtr phi coming into the loop.  If that phi disappears
3915       // also, we can end up with a self-loop of the mergemem.
3916       // In general, if loops degenerate and memory effects disappear,
3917       // a mergemem can be left looking at itself.  This simply means
3918       // that the mergemem's default should be used, since there is
3919       // no longer any apparent effect on this slice.
3920       // Note: If a memory slice is a MergeMem cycle, it is unreachable
3921       //       from start.  Update the input to TOP.
3922       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
3923     }
3924     else if (old_mmem != NULL) {
3925       new_mem = old_mmem->memory_at(i);
3926     }
3927     // else preceding memory was not a MergeMem
3928 
3929     // replace equivalent phis (unfortunately, they do not GVN together)
3930     if (new_mem != NULL && new_mem != new_base &&
3931         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
3932       if (new_mem->is_Phi()) {
3933         PhiNode* phi_mem = new_mem->as_Phi();
3934         for (uint i = 1; i < phi_len; i++) {
3935           if (phi_base->in(i) != phi_mem->in(i)) {
3936             phi_mem = NULL;
3937             break;
3938           }
3939         }
3940         if (phi_mem != NULL) {
3941           // equivalent phi nodes; revert to the def
3942           new_mem = new_base;
3943         }
3944       }
3945     }
3946 
3947     // maybe store down a new value
3948     Node* new_in = new_mem;
3949     if (new_in == new_base)  new_in = empty_mem;
3950 
3951     if (new_in != old_in) {
3952       // Warning:  Do not combine this "if" with the previous "if"
3953       // A memory slice might have be be rewritten even if it is semantically
3954       // unchanged, if the base_memory value has changed.
3955       set_req(i, new_in);
3956       progress = this;          // Report progress
3957     }
3958   }
3959 
3960   if (new_base != old_base) {
3961     set_req(Compile::AliasIdxBot, new_base);
3962     // Don't use set_base_memory(new_base), because we need to update du.
3963     assert(base_memory() == new_base, "");
3964     progress = this;
3965   }
3966 
3967   if( base_memory() == this ) {
3968     // a self cycle indicates this memory path is dead
3969     set_req(Compile::AliasIdxBot, empty_mem);
3970   }
3971 
3972   // Resolve external cycles by calling Ideal on a MergeMem base_memory
3973   // Recursion must occur after the self cycle check above
3974   if( base_memory()->is_MergeMem() ) {
3975     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
3976     Node *m = phase->transform(new_mbase);  // Rollup any cycles
3977     if( m != NULL && (m->is_top() ||
3978         m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) {
3979       // propagate rollup of dead cycle to self
3980       set_req(Compile::AliasIdxBot, empty_mem);
3981     }
3982   }
3983 
3984   if( base_memory() == empty_mem ) {
3985     progress = this;
3986     // Cut inputs during Parse phase only.
3987     // During Optimize phase a dead MergeMem node will be subsumed by Top.
3988     if( !can_reshape ) {
3989       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
3990         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
3991       }
3992     }
3993   }
3994 
3995   if( !progress && base_memory()->is_Phi() && can_reshape ) {
3996     // Check if PhiNode::Ideal's "Split phis through memory merges"
3997     // transform should be attempted. Look for this->phi->this cycle.
3998     uint merge_width = req();
3999     if (merge_width > Compile::AliasIdxRaw) {
4000       PhiNode* phi = base_memory()->as_Phi();
4001       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4002         if (phi->in(i) == this) {
4003           phase->is_IterGVN()->_worklist.push(phi);
4004           break;
4005         }
4006       }
4007     }
4008   }
4009 
4010   assert(progress || verify_sparse(), "please, no dups of base");
4011   return progress;
4012 }
4013 
4014 //-------------------------set_base_memory-------------------------------------
4015 void MergeMemNode::set_base_memory(Node *new_base) {
4016   Node* empty_mem = empty_memory();
4017   set_req(Compile::AliasIdxBot, new_base);
4018   assert(memory_at(req()) == new_base, "must set default memory");
4019   // Clear out other occurrences of new_base:
4020   if (new_base != empty_mem) {
4021     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4022       if (in(i) == new_base)  set_req(i, empty_mem);
4023     }
4024   }
4025 }
4026 
4027 //------------------------------out_RegMask------------------------------------
4028 const RegMask &MergeMemNode::out_RegMask() const {
4029   return RegMask::Empty;
4030 }
4031 
4032 //------------------------------dump_spec--------------------------------------
4033 #ifndef PRODUCT
4034 void MergeMemNode::dump_spec(outputStream *st) const {
4035   st->print(" {");
4036   Node* base_mem = base_memory();
4037   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4038     Node* mem = memory_at(i);
4039     if (mem == base_mem) { st->print(" -"); continue; }
4040     st->print( " N%d:", mem->_idx );
4041     Compile::current()->get_adr_type(i)->dump_on(st);
4042   }
4043   st->print(" }");
4044 }
4045 #endif // !PRODUCT
4046 
4047 
4048 #ifdef ASSERT
4049 static bool might_be_same(Node* a, Node* b) {
4050   if (a == b)  return true;
4051   if (!(a->is_Phi() || b->is_Phi()))  return false;
4052   // phis shift around during optimization
4053   return true;  // pretty stupid...
4054 }
4055 
4056 // verify a narrow slice (either incoming or outgoing)
4057 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4058   if (!VerifyAliases)       return;  // don't bother to verify unless requested
4059   if (is_error_reported())  return;  // muzzle asserts when debugging an error
4060   if (Node::in_dump())      return;  // muzzle asserts when printing
4061   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4062   assert(n != NULL, "");
4063   // Elide intervening MergeMem's
4064   while (n->is_MergeMem()) {
4065     n = n->as_MergeMem()->memory_at(alias_idx);
4066   }
4067   Compile* C = Compile::current();
4068   const TypePtr* n_adr_type = n->adr_type();
4069   if (n == m->empty_memory()) {
4070     // Implicit copy of base_memory()
4071   } else if (n_adr_type != TypePtr::BOTTOM) {
4072     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4073     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4074   } else {
4075     // A few places like make_runtime_call "know" that VM calls are narrow,
4076     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4077     bool expected_wide_mem = false;
4078     if (n == m->base_memory()) {
4079       expected_wide_mem = true;
4080     } else if (alias_idx == Compile::AliasIdxRaw ||
4081                n == m->memory_at(Compile::AliasIdxRaw)) {
4082       expected_wide_mem = true;
4083     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4084       // memory can "leak through" calls on channels that
4085       // are write-once.  Allow this also.
4086       expected_wide_mem = true;
4087     }
4088     assert(expected_wide_mem, "expected narrow slice replacement");
4089   }
4090 }
4091 #else // !ASSERT
4092 #define verify_memory_slice(m,i,n) (0)  // PRODUCT version is no-op
4093 #endif
4094 
4095 
4096 //-----------------------------memory_at---------------------------------------
4097 Node* MergeMemNode::memory_at(uint alias_idx) const {
4098   assert(alias_idx >= Compile::AliasIdxRaw ||
4099          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4100          "must avoid base_memory and AliasIdxTop");
4101 
4102   // Otherwise, it is a narrow slice.
4103   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4104   Compile *C = Compile::current();
4105   if (is_empty_memory(n)) {
4106     // the array is sparse; empty slots are the "top" node
4107     n = base_memory();
4108     assert(Node::in_dump()
4109            || n == NULL || n->bottom_type() == Type::TOP
4110            || n->adr_type() == NULL // address is TOP
4111            || n->adr_type() == TypePtr::BOTTOM
4112            || n->adr_type() == TypeRawPtr::BOTTOM
4113            || Compile::current()->AliasLevel() == 0,
4114            "must be a wide memory");
4115     // AliasLevel == 0 if we are organizing the memory states manually.
4116     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4117   } else {
4118     // make sure the stored slice is sane
4119     #ifdef ASSERT
4120     if (is_error_reported() || Node::in_dump()) {
4121     } else if (might_be_same(n, base_memory())) {
4122       // Give it a pass:  It is a mostly harmless repetition of the base.
4123       // This can arise normally from node subsumption during optimization.
4124     } else {
4125       verify_memory_slice(this, alias_idx, n);
4126     }
4127     #endif
4128   }
4129   return n;
4130 }
4131 
4132 //---------------------------set_memory_at-------------------------------------
4133 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4134   verify_memory_slice(this, alias_idx, n);
4135   Node* empty_mem = empty_memory();
4136   if (n == base_memory())  n = empty_mem;  // collapse default
4137   uint need_req = alias_idx+1;
4138   if (req() < need_req) {
4139     if (n == empty_mem)  return;  // already the default, so do not grow me
4140     // grow the sparse array
4141     do {
4142       add_req(empty_mem);
4143     } while (req() < need_req);
4144   }
4145   set_req( alias_idx, n );
4146 }
4147 
4148 
4149 
4150 //--------------------------iteration_setup------------------------------------
4151 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4152   if (other != NULL) {
4153     grow_to_match(other);
4154     // invariant:  the finite support of mm2 is within mm->req()
4155     #ifdef ASSERT
4156     for (uint i = req(); i < other->req(); i++) {
4157       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4158     }
4159     #endif
4160   }
4161   // Replace spurious copies of base_memory by top.
4162   Node* base_mem = base_memory();
4163   if (base_mem != NULL && !base_mem->is_top()) {
4164     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4165       if (in(i) == base_mem)
4166         set_req(i, empty_memory());
4167     }
4168   }
4169 }
4170 
4171 //---------------------------grow_to_match-------------------------------------
4172 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4173   Node* empty_mem = empty_memory();
4174   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4175   // look for the finite support of the other memory
4176   for (uint i = other->req(); --i >= req(); ) {
4177     if (other->in(i) != empty_mem) {
4178       uint new_len = i+1;
4179       while (req() < new_len)  add_req(empty_mem);
4180       break;
4181     }
4182   }
4183 }
4184 
4185 //---------------------------verify_sparse-------------------------------------
4186 #ifndef PRODUCT
4187 bool MergeMemNode::verify_sparse() const {
4188   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4189   Node* base_mem = base_memory();
4190   // The following can happen in degenerate cases, since empty==top.
4191   if (is_empty_memory(base_mem))  return true;
4192   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4193     assert(in(i) != NULL, "sane slice");
4194     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4195   }
4196   return true;
4197 }
4198 
4199 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4200   Node* n;
4201   n = mm->in(idx);
4202   if (mem == n)  return true;  // might be empty_memory()
4203   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4204   if (mem == n)  return true;
4205   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4206     if (mem == n)  return true;
4207     if (n == NULL)  break;
4208   }
4209   return false;
4210 }
4211 #endif // !PRODUCT