1 /*
   2  * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/systemDictionary.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "memory/allocation.inline.hpp"
  29 #include "oops/objArrayKlass.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/arraycopynode.hpp"
  32 #include "opto/cfgnode.hpp"
  33 #include "opto/compile.hpp"
  34 #include "opto/connode.hpp"
  35 #include "opto/convertnode.hpp"
  36 #include "opto/loopnode.hpp"
  37 #include "opto/machnode.hpp"
  38 #include "opto/matcher.hpp"
  39 #include "opto/memnode.hpp"
  40 #include "opto/mulnode.hpp"
  41 #include "opto/narrowptrnode.hpp"
  42 #include "opto/phaseX.hpp"
  43 #include "opto/regmask.hpp"
  44 #include "utilities/copy.hpp"
  45 
  46 // Portions of code courtesy of Clifford Click
  47 
  48 // Optimization - Graph Style
  49 
  50 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
  51 
  52 //=============================================================================
  53 uint MemNode::size_of() const { return sizeof(*this); }
  54 
  55 const TypePtr *MemNode::adr_type() const {
  56   Node* adr = in(Address);
  57   if (adr == NULL)  return NULL; // node is dead
  58   const TypePtr* cross_check = NULL;
  59   DEBUG_ONLY(cross_check = _adr_type);
  60   return calculate_adr_type(adr->bottom_type(), cross_check);
  61 }
  62 
  63 #ifndef PRODUCT
  64 void MemNode::dump_spec(outputStream *st) const {
  65   if (in(Address) == NULL)  return; // node is dead
  66 #ifndef ASSERT
  67   // fake the missing field
  68   const TypePtr* _adr_type = NULL;
  69   if (in(Address) != NULL)
  70     _adr_type = in(Address)->bottom_type()->isa_ptr();
  71 #endif
  72   dump_adr_type(this, _adr_type, st);
  73 
  74   Compile* C = Compile::current();
  75   if (C->alias_type(_adr_type)->is_volatile()) {
  76     st->print(" Volatile!");
  77   }
  78   if (_unaligned_access) {
  79     st->print(" unaligned");
  80   }
  81   if (_mismatched_access) {
  82     st->print(" mismatched");
  83   }
  84 }
  85 
  86 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
  87   st->print(" @");
  88   if (adr_type == NULL) {
  89     st->print("NULL");
  90   } else {
  91     adr_type->dump_on(st);
  92     Compile* C = Compile::current();
  93     Compile::AliasType* atp = NULL;
  94     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
  95     if (atp == NULL)
  96       st->print(", idx=?\?;");
  97     else if (atp->index() == Compile::AliasIdxBot)
  98       st->print(", idx=Bot;");
  99     else if (atp->index() == Compile::AliasIdxTop)
 100       st->print(", idx=Top;");
 101     else if (atp->index() == Compile::AliasIdxRaw)
 102       st->print(", idx=Raw;");
 103     else {
 104       ciField* field = atp->field();
 105       if (field) {
 106         st->print(", name=");
 107         field->print_name_on(st);
 108       }
 109       st->print(", idx=%d;", atp->index());
 110     }
 111   }
 112 }
 113 
 114 extern void print_alias_types();
 115 
 116 #endif
 117 
 118 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypeOopPtr *t_oop, Node *load, PhaseGVN *phase) {
 119   assert((t_oop != NULL), "sanity");
 120   bool is_instance = t_oop->is_known_instance_field();
 121   bool is_boxed_value_load = t_oop->is_ptr_to_boxed_value() &&
 122                              (load != NULL) && load->is_Load() &&
 123                              (phase->is_IterGVN() != NULL);
 124   if (!(is_instance || is_boxed_value_load))
 125     return mchain;  // don't try to optimize non-instance types
 126   uint instance_id = t_oop->instance_id();
 127   Node *start_mem = phase->C->start()->proj_out(TypeFunc::Memory);
 128   Node *prev = NULL;
 129   Node *result = mchain;
 130   while (prev != result) {
 131     prev = result;
 132     if (result == start_mem)
 133       break;  // hit one of our sentinels
 134     // skip over a call which does not affect this memory slice
 135     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
 136       Node *proj_in = result->in(0);
 137       if (proj_in->is_Allocate() && proj_in->_idx == instance_id) {
 138         break;  // hit one of our sentinels
 139       } else if (proj_in->is_Call()) {
 140         // ArrayCopyNodes processed here as well
 141         CallNode *call = proj_in->as_Call();
 142         if (!call->may_modify(t_oop, phase)) { // returns false for instances
 143           result = call->in(TypeFunc::Memory);
 144         }
 145       } else if (proj_in->is_Initialize()) {
 146         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
 147         // Stop if this is the initialization for the object instance which
 148         // contains this memory slice, otherwise skip over it.
 149         if ((alloc == NULL) || (alloc->_idx == instance_id)) {
 150           break;
 151         }
 152         if (is_instance) {
 153           result = proj_in->in(TypeFunc::Memory);
 154         } else if (is_boxed_value_load) {
 155           Node* klass = alloc->in(AllocateNode::KlassNode);
 156           const TypeKlassPtr* tklass = phase->type(klass)->is_klassptr();
 157           if (tklass->klass_is_exact() && !tklass->klass()->equals(t_oop->klass())) {
 158             result = proj_in->in(TypeFunc::Memory); // not related allocation
 159           }
 160         }
 161       } else if (proj_in->is_MemBar()) {
 162         if (ArrayCopyNode::may_modify(t_oop, proj_in->as_MemBar(), phase)) {
 163           break;
 164         }
 165         result = proj_in->in(TypeFunc::Memory);
 166       } else {
 167         assert(false, "unexpected projection");
 168       }
 169     } else if (result->is_ClearArray()) {
 170       if (!is_instance || !ClearArrayNode::step_through(&result, instance_id, phase)) {
 171         // Can not bypass initialization of the instance
 172         // we are looking for.
 173         break;
 174       }
 175       // Otherwise skip it (the call updated 'result' value).
 176     } else if (result->is_MergeMem()) {
 177       result = step_through_mergemem(phase, result->as_MergeMem(), t_oop, NULL, tty);
 178     }
 179   }
 180   return result;
 181 }
 182 
 183 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, Node *load, PhaseGVN *phase) {
 184   const TypeOopPtr* t_oop = t_adr->isa_oopptr();
 185   if (t_oop == NULL)
 186     return mchain;  // don't try to optimize non-oop types
 187   Node* result = optimize_simple_memory_chain(mchain, t_oop, load, phase);
 188   bool is_instance = t_oop->is_known_instance_field();
 189   PhaseIterGVN *igvn = phase->is_IterGVN();
 190   if (is_instance && igvn != NULL  && result->is_Phi()) {
 191     PhiNode *mphi = result->as_Phi();
 192     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
 193     const TypePtr *t = mphi->adr_type();
 194     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM ||
 195         t->isa_oopptr() && !t->is_oopptr()->is_known_instance() &&
 196         t->is_oopptr()->cast_to_exactness(true)
 197          ->is_oopptr()->cast_to_ptr_type(t_oop->ptr())
 198          ->is_oopptr()->cast_to_instance_id(t_oop->instance_id()) == t_oop) {
 199       // clone the Phi with our address type
 200       result = mphi->split_out_instance(t_adr, igvn);
 201     } else {
 202       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
 203     }
 204   }
 205   return result;
 206 }
 207 
 208 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
 209   uint alias_idx = phase->C->get_alias_index(tp);
 210   Node *mem = mmem;
 211 #ifdef ASSERT
 212   {
 213     // Check that current type is consistent with the alias index used during graph construction
 214     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
 215     bool consistent =  adr_check == NULL || adr_check->empty() ||
 216                        phase->C->must_alias(adr_check, alias_idx );
 217     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
 218     if( !consistent && adr_check != NULL && !adr_check->empty() &&
 219                tp->isa_aryptr() &&        tp->offset() == Type::OffsetBot &&
 220         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
 221         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
 222           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
 223           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
 224       // don't assert if it is dead code.
 225       consistent = true;
 226     }
 227     if( !consistent ) {
 228       st->print("alias_idx==%d, adr_check==", alias_idx);
 229       if( adr_check == NULL ) {
 230         st->print("NULL");
 231       } else {
 232         adr_check->dump();
 233       }
 234       st->cr();
 235       print_alias_types();
 236       assert(consistent, "adr_check must match alias idx");
 237     }
 238   }
 239 #endif
 240   // TypeOopPtr::NOTNULL+any is an OOP with unknown offset - generally
 241   // means an array I have not precisely typed yet.  Do not do any
 242   // alias stuff with it any time soon.
 243   const TypeOopPtr *toop = tp->isa_oopptr();
 244   if( tp->base() != Type::AnyPtr &&
 245       !(toop &&
 246         toop->klass() != NULL &&
 247         toop->klass()->is_java_lang_Object() &&
 248         toop->offset() == Type::OffsetBot) ) {
 249     // compress paths and change unreachable cycles to TOP
 250     // If not, we can update the input infinitely along a MergeMem cycle
 251     // Equivalent code in PhiNode::Ideal
 252     Node* m  = phase->transform(mmem);
 253     // If transformed to a MergeMem, get the desired slice
 254     // Otherwise the returned node represents memory for every slice
 255     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
 256     // Update input if it is progress over what we have now
 257   }
 258   return mem;
 259 }
 260 
 261 //--------------------------Ideal_common---------------------------------------
 262 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 263 // Unhook non-raw memories from complete (macro-expanded) initializations.
 264 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
 265   // If our control input is a dead region, kill all below the region
 266   Node *ctl = in(MemNode::Control);
 267   if (ctl && remove_dead_region(phase, can_reshape))
 268     return this;
 269   ctl = in(MemNode::Control);
 270   // Don't bother trying to transform a dead node
 271   if (ctl && ctl->is_top())  return NodeSentinel;
 272 
 273   PhaseIterGVN *igvn = phase->is_IterGVN();
 274   // Wait if control on the worklist.
 275   if (ctl && can_reshape && igvn != NULL) {
 276     Node* bol = NULL;
 277     Node* cmp = NULL;
 278     if (ctl->in(0)->is_If()) {
 279       assert(ctl->is_IfTrue() || ctl->is_IfFalse(), "sanity");
 280       bol = ctl->in(0)->in(1);
 281       if (bol->is_Bool())
 282         cmp = ctl->in(0)->in(1)->in(1);
 283     }
 284     if (igvn->_worklist.member(ctl) ||
 285         (bol != NULL && igvn->_worklist.member(bol)) ||
 286         (cmp != NULL && igvn->_worklist.member(cmp)) ) {
 287       // This control path may be dead.
 288       // Delay this memory node transformation until the control is processed.
 289       phase->is_IterGVN()->_worklist.push(this);
 290       return NodeSentinel; // caller will return NULL
 291     }
 292   }
 293   // Ignore if memory is dead, or self-loop
 294   Node *mem = in(MemNode::Memory);
 295   if (phase->type( mem ) == Type::TOP) return NodeSentinel; // caller will return NULL
 296   assert(mem != this, "dead loop in MemNode::Ideal");
 297 
 298   if (can_reshape && igvn != NULL && igvn->_worklist.member(mem)) {
 299     // This memory slice may be dead.
 300     // Delay this mem node transformation until the memory is processed.
 301     phase->is_IterGVN()->_worklist.push(this);
 302     return NodeSentinel; // caller will return NULL
 303   }
 304 
 305   Node *address = in(MemNode::Address);
 306   const Type *t_adr = phase->type(address);
 307   if (t_adr == Type::TOP)              return NodeSentinel; // caller will return NULL
 308 
 309   if (can_reshape && igvn != NULL &&
 310       (igvn->_worklist.member(address) ||
 311        igvn->_worklist.size() > 0 && (t_adr != adr_type())) ) {
 312     // The address's base and type may change when the address is processed.
 313     // Delay this mem node transformation until the address is processed.
 314     phase->is_IterGVN()->_worklist.push(this);
 315     return NodeSentinel; // caller will return NULL
 316   }
 317 
 318   // Do NOT remove or optimize the next lines: ensure a new alias index
 319   // is allocated for an oop pointer type before Escape Analysis.
 320   // Note: C++ will not remove it since the call has side effect.
 321   if (t_adr->isa_oopptr()) {
 322     int alias_idx = phase->C->get_alias_index(t_adr->is_ptr());
 323   }
 324 
 325   Node* base = NULL;
 326   if (address->is_AddP()) {
 327     base = address->in(AddPNode::Base);
 328   }
 329   if (base != NULL && phase->type(base)->higher_equal(TypePtr::NULL_PTR) &&
 330       !t_adr->isa_rawptr()) {
 331     // Note: raw address has TOP base and top->higher_equal(TypePtr::NULL_PTR) is true.
 332     // Skip this node optimization if its address has TOP base.
 333     return NodeSentinel; // caller will return NULL
 334   }
 335 
 336   // Avoid independent memory operations
 337   Node* old_mem = mem;
 338 
 339   // The code which unhooks non-raw memories from complete (macro-expanded)
 340   // initializations was removed. After macro-expansion all stores catched
 341   // by Initialize node became raw stores and there is no information
 342   // which memory slices they modify. So it is unsafe to move any memory
 343   // operation above these stores. Also in most cases hooked non-raw memories
 344   // were already unhooked by using information from detect_ptr_independence()
 345   // and find_previous_store().
 346 
 347   if (mem->is_MergeMem()) {
 348     MergeMemNode* mmem = mem->as_MergeMem();
 349     const TypePtr *tp = t_adr->is_ptr();
 350 
 351     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
 352   }
 353 
 354   if (mem != old_mem) {
 355     set_req(MemNode::Memory, mem);
 356     if (can_reshape && old_mem->outcnt() == 0) {
 357         igvn->_worklist.push(old_mem);
 358     }
 359     if (phase->type( mem ) == Type::TOP) return NodeSentinel;
 360     return this;
 361   }
 362 
 363   // let the subclass continue analyzing...
 364   return NULL;
 365 }
 366 
 367 // Helper function for proving some simple control dominations.
 368 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 369 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 370 // is not a constant (dominated by the method's StartNode).
 371 // Used by MemNode::find_previous_store to prove that the
 372 // control input of a memory operation predates (dominates)
 373 // an allocation it wants to look past.
 374 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
 375   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
 376     return false; // Conservative answer for dead code
 377 
 378   // Check 'dom'. Skip Proj and CatchProj nodes.
 379   dom = dom->find_exact_control(dom);
 380   if (dom == NULL || dom->is_top())
 381     return false; // Conservative answer for dead code
 382 
 383   if (dom == sub) {
 384     // For the case when, for example, 'sub' is Initialize and the original
 385     // 'dom' is Proj node of the 'sub'.
 386     return false;
 387   }
 388 
 389   if (dom->is_Con() || dom->is_Start() || dom->is_Root() || dom == sub)
 390     return true;
 391 
 392   // 'dom' dominates 'sub' if its control edge and control edges
 393   // of all its inputs dominate or equal to sub's control edge.
 394 
 395   // Currently 'sub' is either Allocate, Initialize or Start nodes.
 396   // Or Region for the check in LoadNode::Ideal();
 397   // 'sub' should have sub->in(0) != NULL.
 398   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start() ||
 399          sub->is_Region() || sub->is_Call(), "expecting only these nodes");
 400 
 401   // Get control edge of 'sub'.
 402   Node* orig_sub = sub;
 403   sub = sub->find_exact_control(sub->in(0));
 404   if (sub == NULL || sub->is_top())
 405     return false; // Conservative answer for dead code
 406 
 407   assert(sub->is_CFG(), "expecting control");
 408 
 409   if (sub == dom)
 410     return true;
 411 
 412   if (sub->is_Start() || sub->is_Root())
 413     return false;
 414 
 415   {
 416     // Check all control edges of 'dom'.
 417 
 418     ResourceMark rm;
 419     Arena* arena = Thread::current()->resource_area();
 420     Node_List nlist(arena);
 421     Unique_Node_List dom_list(arena);
 422 
 423     dom_list.push(dom);
 424     bool only_dominating_controls = false;
 425 
 426     for (uint next = 0; next < dom_list.size(); next++) {
 427       Node* n = dom_list.at(next);
 428       if (n == orig_sub)
 429         return false; // One of dom's inputs dominated by sub.
 430       if (!n->is_CFG() && n->pinned()) {
 431         // Check only own control edge for pinned non-control nodes.
 432         n = n->find_exact_control(n->in(0));
 433         if (n == NULL || n->is_top())
 434           return false; // Conservative answer for dead code
 435         assert(n->is_CFG(), "expecting control");
 436         dom_list.push(n);
 437       } else if (n->is_Con() || n->is_Start() || n->is_Root()) {
 438         only_dominating_controls = true;
 439       } else if (n->is_CFG()) {
 440         if (n->dominates(sub, nlist))
 441           only_dominating_controls = true;
 442         else
 443           return false;
 444       } else {
 445         // First, own control edge.
 446         Node* m = n->find_exact_control(n->in(0));
 447         if (m != NULL) {
 448           if (m->is_top())
 449             return false; // Conservative answer for dead code
 450           dom_list.push(m);
 451         }
 452         // Now, the rest of edges.
 453         uint cnt = n->req();
 454         for (uint i = 1; i < cnt; i++) {
 455           m = n->find_exact_control(n->in(i));
 456           if (m == NULL || m->is_top())
 457             continue;
 458           dom_list.push(m);
 459         }
 460       }
 461     }
 462     return only_dominating_controls;
 463   }
 464 }
 465 
 466 //---------------------detect_ptr_independence---------------------------------
 467 // Used by MemNode::find_previous_store to prove that two base
 468 // pointers are never equal.
 469 // The pointers are accompanied by their associated allocations,
 470 // if any, which have been previously discovered by the caller.
 471 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
 472                                       Node* p2, AllocateNode* a2,
 473                                       PhaseTransform* phase) {
 474   // Attempt to prove that these two pointers cannot be aliased.
 475   // They may both manifestly be allocations, and they should differ.
 476   // Or, if they are not both allocations, they can be distinct constants.
 477   // Otherwise, one is an allocation and the other a pre-existing value.
 478   if (a1 == NULL && a2 == NULL) {           // neither an allocation
 479     return (p1 != p2) && p1->is_Con() && p2->is_Con();
 480   } else if (a1 != NULL && a2 != NULL) {    // both allocations
 481     return (a1 != a2);
 482   } else if (a1 != NULL) {                  // one allocation a1
 483     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
 484     return all_controls_dominate(p2, a1);
 485   } else { //(a2 != NULL)                   // one allocation a2
 486     return all_controls_dominate(p1, a2);
 487   }
 488   return false;
 489 }
 490 
 491 
 492 // Find an arraycopy that must have set (can_see_stored_value=true) or
 493 // could have set (can_see_stored_value=false) the value for this load
 494 Node* LoadNode::find_previous_arraycopy(PhaseTransform* phase, Node* ld_alloc, Node*& mem, bool can_see_stored_value) const {
 495   if (mem->is_Proj() && mem->in(0) != NULL && (mem->in(0)->Opcode() == Op_MemBarStoreStore ||
 496                                                mem->in(0)->Opcode() == Op_MemBarCPUOrder)) {
 497     Node* mb = mem->in(0);
 498     if (mb->in(0) != NULL && mb->in(0)->is_Proj() &&
 499         mb->in(0)->in(0) != NULL && mb->in(0)->in(0)->is_ArrayCopy()) {
 500       ArrayCopyNode* ac = mb->in(0)->in(0)->as_ArrayCopy();
 501       if (ac->is_clonebasic()) {
 502         intptr_t offset;
 503         AllocateNode* alloc = AllocateNode::Ideal_allocation(ac->in(ArrayCopyNode::Dest), phase, offset);
 504         assert(alloc != NULL && alloc->initialization()->is_complete_with_arraycopy(), "broken allocation");
 505         if (alloc == ld_alloc) {
 506           return ac;
 507         }
 508       }
 509     }
 510   } else if (mem->is_Proj() && mem->in(0) != NULL && mem->in(0)->is_ArrayCopy()) {
 511     ArrayCopyNode* ac = mem->in(0)->as_ArrayCopy();
 512 
 513     if (ac->is_arraycopy_validated() ||
 514         ac->is_copyof_validated() ||
 515         ac->is_copyofrange_validated()) {
 516       Node* ld_addp = in(MemNode::Address);
 517       if (ld_addp->is_AddP()) {
 518         Node* ld_base = ld_addp->in(AddPNode::Address);
 519         Node* ld_offs = ld_addp->in(AddPNode::Offset);
 520 
 521         Node* dest = ac->in(ArrayCopyNode::Dest);
 522 
 523         if (dest == ld_base) {
 524           const TypeX *ld_offs_t = phase->type(ld_offs)->isa_intptr_t();
 525           if (ac->modifies(ld_offs_t->_lo, ld_offs_t->_hi, phase, can_see_stored_value)) {
 526             return ac;
 527           }
 528           if (!can_see_stored_value) {
 529             mem = ac->in(TypeFunc::Memory);
 530           }
 531         }
 532       }
 533     }
 534   }
 535   return NULL;
 536 }
 537 
 538 // The logic for reordering loads and stores uses four steps:
 539 // (a) Walk carefully past stores and initializations which we
 540 //     can prove are independent of this load.
 541 // (b) Observe that the next memory state makes an exact match
 542 //     with self (load or store), and locate the relevant store.
 543 // (c) Ensure that, if we were to wire self directly to the store,
 544 //     the optimizer would fold it up somehow.
 545 // (d) Do the rewiring, and return, depending on some other part of
 546 //     the optimizer to fold up the load.
 547 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 548 // specific to loads and stores, so they are handled by the callers.
 549 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 550 //
 551 Node* MemNode::find_previous_store(PhaseTransform* phase) {
 552   Node*         ctrl   = in(MemNode::Control);
 553   Node*         adr    = in(MemNode::Address);
 554   intptr_t      offset = 0;
 555   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
 556   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
 557 
 558   if (offset == Type::OffsetBot)
 559     return NULL;            // cannot unalias unless there are precise offsets
 560 
 561   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
 562 
 563   intptr_t size_in_bytes = memory_size();
 564 
 565   Node* mem = in(MemNode::Memory);   // start searching here...
 566 
 567   int cnt = 50;             // Cycle limiter
 568   for (;;) {                // While we can dance past unrelated stores...
 569     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
 570 
 571     Node* prev = mem;
 572     if (mem->is_Store()) {
 573       Node* st_adr = mem->in(MemNode::Address);
 574       intptr_t st_offset = 0;
 575       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
 576       if (st_base == NULL)
 577         break;              // inscrutable pointer
 578       if (st_offset != offset && st_offset != Type::OffsetBot) {
 579         const int MAX_STORE = BytesPerLong;
 580         if (st_offset >= offset + size_in_bytes ||
 581             st_offset <= offset - MAX_STORE ||
 582             st_offset <= offset - mem->as_Store()->memory_size()) {
 583           // Success:  The offsets are provably independent.
 584           // (You may ask, why not just test st_offset != offset and be done?
 585           // The answer is that stores of different sizes can co-exist
 586           // in the same sequence of RawMem effects.  We sometimes initialize
 587           // a whole 'tile' of array elements with a single jint or jlong.)
 588           mem = mem->in(MemNode::Memory);
 589           continue;           // (a) advance through independent store memory
 590         }
 591       }
 592       if (st_base != base &&
 593           detect_ptr_independence(base, alloc,
 594                                   st_base,
 595                                   AllocateNode::Ideal_allocation(st_base, phase),
 596                                   phase)) {
 597         // Success:  The bases are provably independent.
 598         mem = mem->in(MemNode::Memory);
 599         continue;           // (a) advance through independent store memory
 600       }
 601 
 602       // (b) At this point, if the bases or offsets do not agree, we lose,
 603       // since we have not managed to prove 'this' and 'mem' independent.
 604       if (st_base == base && st_offset == offset) {
 605         return mem;         // let caller handle steps (c), (d)
 606       }
 607 
 608     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
 609       InitializeNode* st_init = mem->in(0)->as_Initialize();
 610       AllocateNode*  st_alloc = st_init->allocation();
 611       if (st_alloc == NULL)
 612         break;              // something degenerated
 613       bool known_identical = false;
 614       bool known_independent = false;
 615       if (alloc == st_alloc)
 616         known_identical = true;
 617       else if (alloc != NULL)
 618         known_independent = true;
 619       else if (all_controls_dominate(this, st_alloc))
 620         known_independent = true;
 621 
 622       if (known_independent) {
 623         // The bases are provably independent: Either they are
 624         // manifestly distinct allocations, or else the control
 625         // of this load dominates the store's allocation.
 626         int alias_idx = phase->C->get_alias_index(adr_type());
 627         if (alias_idx == Compile::AliasIdxRaw) {
 628           mem = st_alloc->in(TypeFunc::Memory);
 629         } else {
 630           mem = st_init->memory(alias_idx);
 631         }
 632         continue;           // (a) advance through independent store memory
 633       }
 634 
 635       // (b) at this point, if we are not looking at a store initializing
 636       // the same allocation we are loading from, we lose.
 637       if (known_identical) {
 638         // From caller, can_see_stored_value will consult find_captured_store.
 639         return mem;         // let caller handle steps (c), (d)
 640       }
 641 
 642     } else if (find_previous_arraycopy(phase, alloc, mem, false) != NULL) {
 643       if (prev != mem) {
 644         // Found an arraycopy but it doesn't affect that load
 645         continue;
 646       }
 647       // Found an arraycopy that may affect that load
 648       return mem;
 649     } else if (addr_t != NULL && addr_t->is_known_instance_field()) {
 650       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
 651       if (mem->is_Proj() && mem->in(0)->is_Call()) {
 652         // ArrayCopyNodes processed here as well.
 653         CallNode *call = mem->in(0)->as_Call();
 654         if (!call->may_modify(addr_t, phase)) {
 655           mem = call->in(TypeFunc::Memory);
 656           continue;         // (a) advance through independent call memory
 657         }
 658       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
 659         if (ArrayCopyNode::may_modify(addr_t, mem->in(0)->as_MemBar(), phase)) {
 660           break;
 661         }
 662         mem = mem->in(0)->in(TypeFunc::Memory);
 663         continue;           // (a) advance through independent MemBar memory
 664       } else if (mem->is_ClearArray()) {
 665         if (ClearArrayNode::step_through(&mem, (uint)addr_t->instance_id(), phase)) {
 666           // (the call updated 'mem' value)
 667           continue;         // (a) advance through independent allocation memory
 668         } else {
 669           // Can not bypass initialization of the instance
 670           // we are looking for.
 671           return mem;
 672         }
 673       } else if (mem->is_MergeMem()) {
 674         int alias_idx = phase->C->get_alias_index(adr_type());
 675         mem = mem->as_MergeMem()->memory_at(alias_idx);
 676         continue;           // (a) advance through independent MergeMem memory
 677       }
 678     }
 679 
 680     // Unless there is an explicit 'continue', we must bail out here,
 681     // because 'mem' is an inscrutable memory state (e.g., a call).
 682     break;
 683   }
 684 
 685   return NULL;              // bail out
 686 }
 687 
 688 //----------------------calculate_adr_type-------------------------------------
 689 // Helper function.  Notices when the given type of address hits top or bottom.
 690 // Also, asserts a cross-check of the type against the expected address type.
 691 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
 692   if (t == Type::TOP)  return NULL; // does not touch memory any more?
 693   #ifdef PRODUCT
 694   cross_check = NULL;
 695   #else
 696   if (!VerifyAliases || is_error_reported() || Node::in_dump())  cross_check = NULL;
 697   #endif
 698   const TypePtr* tp = t->isa_ptr();
 699   if (tp == NULL) {
 700     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
 701     return TypePtr::BOTTOM;           // touches lots of memory
 702   } else {
 703     #ifdef ASSERT
 704     // %%%% [phh] We don't check the alias index if cross_check is
 705     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
 706     if (cross_check != NULL &&
 707         cross_check != TypePtr::BOTTOM &&
 708         cross_check != TypeRawPtr::BOTTOM) {
 709       // Recheck the alias index, to see if it has changed (due to a bug).
 710       Compile* C = Compile::current();
 711       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
 712              "must stay in the original alias category");
 713       // The type of the address must be contained in the adr_type,
 714       // disregarding "null"-ness.
 715       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
 716       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
 717       assert(cross_check->meet(tp_notnull) == cross_check->remove_speculative(),
 718              "real address must not escape from expected memory type");
 719     }
 720     #endif
 721     return tp;
 722   }
 723 }
 724 
 725 //=============================================================================
 726 // Should LoadNode::Ideal() attempt to remove control edges?
 727 bool LoadNode::can_remove_control() const {
 728   return true;
 729 }
 730 uint LoadNode::size_of() const { return sizeof(*this); }
 731 uint LoadNode::cmp( const Node &n ) const
 732 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 733 const Type *LoadNode::bottom_type() const { return _type; }
 734 uint LoadNode::ideal_reg() const {
 735   return _type->ideal_reg();
 736 }
 737 
 738 #ifndef PRODUCT
 739 void LoadNode::dump_spec(outputStream *st) const {
 740   MemNode::dump_spec(st);
 741   if( !Verbose && !WizardMode ) {
 742     // standard dump does this in Verbose and WizardMode
 743     st->print(" #"); _type->dump_on(st);
 744   }
 745   if (!_depends_only_on_test) {
 746     st->print(" (does not depend only on test)");
 747   }
 748 }
 749 #endif
 750 
 751 #ifdef ASSERT
 752 //----------------------------is_immutable_value-------------------------------
 753 // Helper function to allow a raw load without control edge for some cases
 754 bool LoadNode::is_immutable_value(Node* adr) {
 755   return (adr->is_AddP() && adr->in(AddPNode::Base)->is_top() &&
 756           adr->in(AddPNode::Address)->Opcode() == Op_ThreadLocal &&
 757           (adr->in(AddPNode::Offset)->find_intptr_t_con(-1) ==
 758            in_bytes(JavaThread::osthread_offset())));
 759 }
 760 #endif
 761 
 762 //----------------------------LoadNode::make-----------------------------------
 763 // Polymorphic factory method:
 764 Node *LoadNode::make(PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt, MemOrd mo,
 765                      ControlDependency control_dependency, bool unaligned, bool mismatched) {
 766   Compile* C = gvn.C;
 767 
 768   // sanity check the alias category against the created node type
 769   assert(!(adr_type->isa_oopptr() &&
 770            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
 771          "use LoadKlassNode instead");
 772   assert(!(adr_type->isa_aryptr() &&
 773            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
 774          "use LoadRangeNode instead");
 775   // Check control edge of raw loads
 776   assert( ctl != NULL || C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
 777           // oop will be recorded in oop map if load crosses safepoint
 778           rt->isa_oopptr() || is_immutable_value(adr),
 779           "raw memory operations should have control edge");
 780   LoadNode* load = NULL;
 781   switch (bt) {
 782   case T_BOOLEAN: load = new LoadUBNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 783   case T_BYTE:    load = new LoadBNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 784   case T_INT:     load = new LoadINode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 785   case T_CHAR:    load = new LoadUSNode(ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 786   case T_SHORT:   load = new LoadSNode (ctl, mem, adr, adr_type, rt->is_int(),  mo, control_dependency); break;
 787   case T_LONG:    load = new LoadLNode (ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency); break;
 788   case T_FLOAT:   load = new LoadFNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 789   case T_DOUBLE:  load = new LoadDNode (ctl, mem, adr, adr_type, rt,            mo, control_dependency); break;
 790   case T_ADDRESS: load = new LoadPNode (ctl, mem, adr, adr_type, rt->is_ptr(),  mo, control_dependency); break;
 791   case T_VALUETYPE:
 792   case T_OBJECT:
 793 #ifdef _LP64
 794     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
 795       load = new LoadNNode(ctl, mem, adr, adr_type, rt->make_narrowoop(), mo, control_dependency);
 796     } else
 797 #endif
 798     {
 799       assert(!adr->bottom_type()->is_ptr_to_narrowoop() && !adr->bottom_type()->is_ptr_to_narrowklass(), "should have got back a narrow oop");
 800       load = new LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr(), mo, control_dependency);
 801     }
 802     break;
 803   }
 804   assert(load != NULL, "LoadNode should have been created");
 805   if (unaligned) {
 806     load->set_unaligned_access();
 807   }
 808   if (mismatched) {
 809     load->set_mismatched_access();
 810   }
 811   if (load->Opcode() == Op_LoadN) {
 812     Node* ld = gvn.transform(load);
 813     return new DecodeNNode(ld, ld->bottom_type()->make_ptr());
 814   }
 815 
 816   return load;
 817 }
 818 
 819 LoadLNode* LoadLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 820                                   ControlDependency control_dependency, bool unaligned, bool mismatched) {
 821   bool require_atomic = true;
 822   LoadLNode* load = new LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), mo, control_dependency, require_atomic);
 823   if (unaligned) {
 824     load->set_unaligned_access();
 825   }
 826   if (mismatched) {
 827     load->set_mismatched_access();
 828   }
 829   return load;
 830 }
 831 
 832 LoadDNode* LoadDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt, MemOrd mo,
 833                                   ControlDependency control_dependency, bool unaligned, bool mismatched) {
 834   bool require_atomic = true;
 835   LoadDNode* load = new LoadDNode(ctl, mem, adr, adr_type, rt, mo, control_dependency, require_atomic);
 836   if (unaligned) {
 837     load->set_unaligned_access();
 838   }
 839   if (mismatched) {
 840     load->set_mismatched_access();
 841   }
 842   return load;
 843 }
 844 
 845 
 846 
 847 //------------------------------hash-------------------------------------------
 848 uint LoadNode::hash() const {
 849   // unroll addition of interesting fields
 850   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 851 }
 852 
 853 static bool skip_through_membars(Compile::AliasType* atp, const TypeInstPtr* tp, bool eliminate_boxing) {
 854   if ((atp != NULL) && (atp->index() >= Compile::AliasIdxRaw)) {
 855     bool non_volatile = (atp->field() != NULL) && !atp->field()->is_volatile();
 856     bool is_stable_ary = FoldStableValues &&
 857                          (tp != NULL) && (tp->isa_aryptr() != NULL) &&
 858                          tp->isa_aryptr()->is_stable();
 859 
 860     return (eliminate_boxing && non_volatile) || is_stable_ary;
 861   }
 862 
 863   return false;
 864 }
 865 
 866 // Is the value loaded previously stored by an arraycopy? If so return
 867 // a load node that reads from the source array so we may be able to
 868 // optimize out the ArrayCopy node later.
 869 Node* LoadNode::can_see_arraycopy_value(Node* st, PhaseTransform* phase) const {
 870   Node* ld_adr = in(MemNode::Address);
 871   intptr_t ld_off = 0;
 872   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 873   Node* ac = find_previous_arraycopy(phase, ld_alloc, st, true);
 874   if (ac != NULL) {
 875     assert(ac->is_ArrayCopy(), "what kind of node can this be?");
 876 
 877     Node* ld = clone();
 878     if (ac->as_ArrayCopy()->is_clonebasic()) {
 879       assert(ld_alloc != NULL, "need an alloc");
 880       Node* addp = in(MemNode::Address)->clone();
 881       assert(addp->is_AddP(), "address must be addp");
 882       assert(addp->in(AddPNode::Base) == ac->in(ArrayCopyNode::Dest)->in(AddPNode::Base), "strange pattern");
 883       assert(addp->in(AddPNode::Address) == ac->in(ArrayCopyNode::Dest)->in(AddPNode::Address), "strange pattern");
 884       addp->set_req(AddPNode::Base, ac->in(ArrayCopyNode::Src)->in(AddPNode::Base));
 885       addp->set_req(AddPNode::Address, ac->in(ArrayCopyNode::Src)->in(AddPNode::Address));
 886       ld->set_req(MemNode::Address, phase->transform(addp));
 887       if (in(0) != NULL) {
 888         assert(ld_alloc->in(0) != NULL, "alloc must have control");
 889         ld->set_req(0, ld_alloc->in(0));
 890       }
 891     } else {
 892       Node* addp = in(MemNode::Address)->clone();
 893       assert(addp->in(AddPNode::Base) == addp->in(AddPNode::Address), "should be");
 894       addp->set_req(AddPNode::Base, ac->in(ArrayCopyNode::Src));
 895       addp->set_req(AddPNode::Address, ac->in(ArrayCopyNode::Src));
 896 
 897       const TypeAryPtr* ary_t = phase->type(in(MemNode::Address))->isa_aryptr();
 898       BasicType ary_elem  = ary_t->klass()->as_array_klass()->element_type()->basic_type();
 899       uint header = arrayOopDesc::base_offset_in_bytes(ary_elem);
 900       uint shift  = exact_log2(type2aelembytes(ary_elem));
 901 
 902       Node* diff = phase->transform(new SubINode(ac->in(ArrayCopyNode::SrcPos), ac->in(ArrayCopyNode::DestPos)));
 903 #ifdef _LP64
 904       diff = phase->transform(new ConvI2LNode(diff));
 905 #endif
 906       diff = phase->transform(new LShiftXNode(diff, phase->intcon(shift)));
 907 
 908       Node* offset = phase->transform(new AddXNode(addp->in(AddPNode::Offset), diff));
 909       addp->set_req(AddPNode::Offset, offset);
 910       ld->set_req(MemNode::Address, phase->transform(addp));
 911 
 912       if (in(0) != NULL) {
 913         assert(ac->in(0) != NULL, "alloc must have control");
 914         ld->set_req(0, ac->in(0));
 915       }
 916     }
 917     // load depends on the tests that validate the arraycopy
 918     ld->as_Load()->_depends_only_on_test = Pinned;
 919     return ld;
 920   }
 921   return NULL;
 922 }
 923 
 924 
 925 //---------------------------can_see_stored_value------------------------------
 926 // This routine exists to make sure this set of tests is done the same
 927 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 928 // will change the graph shape in a way which makes memory alive twice at the
 929 // same time (uses the Oracle model of aliasing), then some
 930 // LoadXNode::Identity will fold things back to the equivalence-class model
 931 // of aliasing.
 932 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
 933   Node* ld_adr = in(MemNode::Address);
 934   intptr_t ld_off = 0;
 935   AllocateNode* ld_alloc = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
 936   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
 937   Compile::AliasType* atp = (tp != NULL) ? phase->C->alias_type(tp) : NULL;
 938   // This is more general than load from boxing objects.
 939   if (skip_through_membars(atp, tp, phase->C->eliminate_boxing())) {
 940     uint alias_idx = atp->index();
 941     bool final = !atp->is_rewritable();
 942     Node* result = NULL;
 943     Node* current = st;
 944     // Skip through chains of MemBarNodes checking the MergeMems for
 945     // new states for the slice of this load.  Stop once any other
 946     // kind of node is encountered.  Loads from final memory can skip
 947     // through any kind of MemBar but normal loads shouldn't skip
 948     // through MemBarAcquire since the could allow them to move out of
 949     // a synchronized region.
 950     while (current->is_Proj()) {
 951       int opc = current->in(0)->Opcode();
 952       if ((final && (opc == Op_MemBarAcquire ||
 953                      opc == Op_MemBarAcquireLock ||
 954                      opc == Op_LoadFence)) ||
 955           opc == Op_MemBarRelease ||
 956           opc == Op_StoreFence ||
 957           opc == Op_MemBarReleaseLock ||
 958           opc == Op_MemBarStoreStore ||
 959           opc == Op_MemBarCPUOrder) {
 960         Node* mem = current->in(0)->in(TypeFunc::Memory);
 961         if (mem->is_MergeMem()) {
 962           MergeMemNode* merge = mem->as_MergeMem();
 963           Node* new_st = merge->memory_at(alias_idx);
 964           if (new_st == merge->base_memory()) {
 965             // Keep searching
 966             current = new_st;
 967             continue;
 968           }
 969           // Save the new memory state for the slice and fall through
 970           // to exit.
 971           result = new_st;
 972         }
 973       }
 974       break;
 975     }
 976     if (result != NULL) {
 977       st = result;
 978     }
 979   }
 980 
 981   // Loop around twice in the case Load -> Initialize -> Store.
 982   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
 983   for (int trip = 0; trip <= 1; trip++) {
 984 
 985     if (st->is_Store()) {
 986       Node* st_adr = st->in(MemNode::Address);
 987       if (!phase->eqv(st_adr, ld_adr)) {
 988         // Try harder before giving up...  Match raw and non-raw pointers.
 989         intptr_t st_off = 0;
 990         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
 991         if (alloc == NULL)       return NULL;
 992         if (alloc != ld_alloc)   return NULL;
 993         if (ld_off != st_off)    return NULL;
 994         // At this point we have proven something like this setup:
 995         //  A = Allocate(...)
 996         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
 997         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
 998         // (Actually, we haven't yet proven the Q's are the same.)
 999         // In other words, we are loading from a casted version of
1000         // the same pointer-and-offset that we stored to.
1001         // Thus, we are able to replace L by V.
1002       }
1003       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
1004       if (store_Opcode() != st->Opcode())
1005         return NULL;
1006       return st->in(MemNode::ValueIn);
1007     }
1008 
1009     // A load from a freshly-created object always returns zero.
1010     // (This can happen after LoadNode::Ideal resets the load's memory input
1011     // to find_captured_store, which returned InitializeNode::zero_memory.)
1012     if (st->is_Proj() && st->in(0)->is_Allocate() &&
1013         (st->in(0) == ld_alloc) &&
1014         (ld_off >= st->in(0)->as_Allocate()->minimum_header_size())) {
1015       // return a zero value for the load's basic type
1016       // (This is one of the few places where a generic PhaseTransform
1017       // can create new nodes.  Think of it as lazily manifesting
1018       // virtually pre-existing constants.)
1019       return phase->zerocon(memory_type());
1020     }
1021 
1022     // A load from an initialization barrier can match a captured store.
1023     if (st->is_Proj() && st->in(0)->is_Initialize()) {
1024       InitializeNode* init = st->in(0)->as_Initialize();
1025       AllocateNode* alloc = init->allocation();
1026       if ((alloc != NULL) && (alloc == ld_alloc)) {
1027         // examine a captured store value
1028         st = init->find_captured_store(ld_off, memory_size(), phase);
1029         if (st != NULL) {
1030           continue;             // take one more trip around
1031         }
1032       }
1033     }
1034 
1035     // Load boxed value from result of valueOf() call is input parameter.
1036     if (this->is_Load() && ld_adr->is_AddP() &&
1037         (tp != NULL) && tp->is_ptr_to_boxed_value()) {
1038       intptr_t ignore = 0;
1039       Node* base = AddPNode::Ideal_base_and_offset(ld_adr, phase, ignore);
1040       if (base != NULL && base->is_Proj() &&
1041           base->as_Proj()->_con == TypeFunc::Parms &&
1042           base->in(0)->is_CallStaticJava() &&
1043           base->in(0)->as_CallStaticJava()->is_boxing_method()) {
1044         return base->in(0)->in(TypeFunc::Parms);
1045       }
1046     }
1047 
1048     break;
1049   }
1050 
1051   return NULL;
1052 }
1053 
1054 //----------------------is_instance_field_load_with_local_phi------------------
1055 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
1056   if( in(Memory)->is_Phi() && in(Memory)->in(0) == ctrl &&
1057       in(Address)->is_AddP() ) {
1058     const TypeOopPtr* t_oop = in(Address)->bottom_type()->isa_oopptr();
1059     // Only instances and boxed values.
1060     if( t_oop != NULL &&
1061         (t_oop->is_ptr_to_boxed_value() ||
1062          t_oop->is_known_instance_field()) &&
1063         t_oop->offset() != Type::OffsetBot &&
1064         t_oop->offset() != Type::OffsetTop) {
1065       return true;
1066     }
1067   }
1068   return false;
1069 }
1070 
1071 //------------------------------Identity---------------------------------------
1072 // Loads are identity if previous store is to same address
1073 Node* LoadNode::Identity(PhaseGVN* phase) {
1074   // If the previous store-maker is the right kind of Store, and the store is
1075   // to the same address, then we are equal to the value stored.
1076   Node* mem = in(Memory);
1077   Node* value = can_see_stored_value(mem, phase);
1078   if( value ) {
1079     // byte, short & char stores truncate naturally.
1080     // A load has to load the truncated value which requires
1081     // some sort of masking operation and that requires an
1082     // Ideal call instead of an Identity call.
1083     if (memory_size() < BytesPerInt) {
1084       // If the input to the store does not fit with the load's result type,
1085       // it must be truncated via an Ideal call.
1086       if (!phase->type(value)->higher_equal(phase->type(this)))
1087         return this;
1088     }
1089     // (This works even when value is a Con, but LoadNode::Value
1090     // usually runs first, producing the singleton type of the Con.)
1091     return value;
1092   }
1093 
1094   // Search for an existing data phi which was generated before for the same
1095   // instance's field to avoid infinite generation of phis in a loop.
1096   Node *region = mem->in(0);
1097   if (is_instance_field_load_with_local_phi(region)) {
1098     const TypeOopPtr *addr_t = in(Address)->bottom_type()->isa_oopptr();
1099     int this_index  = phase->C->get_alias_index(addr_t);
1100     int this_offset = addr_t->offset();
1101     int this_iid    = addr_t->instance_id();
1102     if (!addr_t->is_known_instance() &&
1103          addr_t->is_ptr_to_boxed_value()) {
1104       // Use _idx of address base (could be Phi node) for boxed values.
1105       intptr_t   ignore = 0;
1106       Node*      base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1107       this_iid = base->_idx;
1108     }
1109     const Type* this_type = bottom_type();
1110     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1111       Node* phi = region->fast_out(i);
1112       if (phi->is_Phi() && phi != mem &&
1113           phi->as_Phi()->is_same_inst_field(this_type, this_iid, this_index, this_offset)) {
1114         return phi;
1115       }
1116     }
1117   }
1118 
1119   return this;
1120 }
1121 
1122 // We're loading from an object which has autobox behaviour.
1123 // If this object is result of a valueOf call we'll have a phi
1124 // merging a newly allocated object and a load from the cache.
1125 // We want to replace this load with the original incoming
1126 // argument to the valueOf call.
1127 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
1128   assert(phase->C->eliminate_boxing(), "sanity");
1129   intptr_t ignore = 0;
1130   Node* base = AddPNode::Ideal_base_and_offset(in(Address), phase, ignore);
1131   if ((base == NULL) || base->is_Phi()) {
1132     // Push the loads from the phi that comes from valueOf up
1133     // through it to allow elimination of the loads and the recovery
1134     // of the original value. It is done in split_through_phi().
1135     return NULL;
1136   } else if (base->is_Load() ||
1137              base->is_DecodeN() && base->in(1)->is_Load()) {
1138     // Eliminate the load of boxed value for integer types from the cache
1139     // array by deriving the value from the index into the array.
1140     // Capture the offset of the load and then reverse the computation.
1141 
1142     // Get LoadN node which loads a boxing object from 'cache' array.
1143     if (base->is_DecodeN()) {
1144       base = base->in(1);
1145     }
1146     if (!base->in(Address)->is_AddP()) {
1147       return NULL; // Complex address
1148     }
1149     AddPNode* address = base->in(Address)->as_AddP();
1150     Node* cache_base = address->in(AddPNode::Base);
1151     if ((cache_base != NULL) && cache_base->is_DecodeN()) {
1152       // Get ConP node which is static 'cache' field.
1153       cache_base = cache_base->in(1);
1154     }
1155     if ((cache_base != NULL) && cache_base->is_Con()) {
1156       const TypeAryPtr* base_type = cache_base->bottom_type()->isa_aryptr();
1157       if ((base_type != NULL) && base_type->is_autobox_cache()) {
1158         Node* elements[4];
1159         int shift = exact_log2(type2aelembytes(T_OBJECT));
1160         int count = address->unpack_offsets(elements, ARRAY_SIZE(elements));
1161         if ((count >  0) && elements[0]->is_Con() &&
1162             ((count == 1) ||
1163              (count == 2) && elements[1]->Opcode() == Op_LShiftX &&
1164                              elements[1]->in(2) == phase->intcon(shift))) {
1165           ciObjArray* array = base_type->const_oop()->as_obj_array();
1166           // Fetch the box object cache[0] at the base of the array and get its value
1167           ciInstance* box = array->obj_at(0)->as_instance();
1168           ciInstanceKlass* ik = box->klass()->as_instance_klass();
1169           assert(ik->is_box_klass(), "sanity");
1170           assert(ik->nof_nonstatic_fields() == 1, "change following code");
1171           if (ik->nof_nonstatic_fields() == 1) {
1172             // This should be true nonstatic_field_at requires calling
1173             // nof_nonstatic_fields so check it anyway
1174             ciConstant c = box->field_value(ik->nonstatic_field_at(0));
1175             BasicType bt = c.basic_type();
1176             // Only integer types have boxing cache.
1177             assert(bt == T_BOOLEAN || bt == T_CHAR  ||
1178                    bt == T_BYTE    || bt == T_SHORT ||
1179                    bt == T_INT     || bt == T_LONG, "wrong type = %s", type2name(bt));
1180             jlong cache_low = (bt == T_LONG) ? c.as_long() : c.as_int();
1181             if (cache_low != (int)cache_low) {
1182               return NULL; // should not happen since cache is array indexed by value
1183             }
1184             jlong offset = arrayOopDesc::base_offset_in_bytes(T_OBJECT) - (cache_low << shift);
1185             if (offset != (int)offset) {
1186               return NULL; // should not happen since cache is array indexed by value
1187             }
1188            // Add up all the offsets making of the address of the load
1189             Node* result = elements[0];
1190             for (int i = 1; i < count; i++) {
1191               result = phase->transform(new AddXNode(result, elements[i]));
1192             }
1193             // Remove the constant offset from the address and then
1194             result = phase->transform(new AddXNode(result, phase->MakeConX(-(int)offset)));
1195             // remove the scaling of the offset to recover the original index.
1196             if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
1197               // Peel the shift off directly but wrap it in a dummy node
1198               // since Ideal can't return existing nodes
1199               result = new RShiftXNode(result->in(1), phase->intcon(0));
1200             } else if (result->is_Add() && result->in(2)->is_Con() &&
1201                        result->in(1)->Opcode() == Op_LShiftX &&
1202                        result->in(1)->in(2) == phase->intcon(shift)) {
1203               // We can't do general optimization: ((X<<Z) + Y) >> Z ==> X + (Y>>Z)
1204               // but for boxing cache access we know that X<<Z will not overflow
1205               // (there is range check) so we do this optimizatrion by hand here.
1206               Node* add_con = new RShiftXNode(result->in(2), phase->intcon(shift));
1207               result = new AddXNode(result->in(1)->in(1), phase->transform(add_con));
1208             } else {
1209               result = new RShiftXNode(result, phase->intcon(shift));
1210             }
1211 #ifdef _LP64
1212             if (bt != T_LONG) {
1213               result = new ConvL2INode(phase->transform(result));
1214             }
1215 #else
1216             if (bt == T_LONG) {
1217               result = new ConvI2LNode(phase->transform(result));
1218             }
1219 #endif
1220             // Boxing/unboxing can be done from signed & unsigned loads (e.g. LoadUB -> ... -> LoadB pair).
1221             // Need to preserve unboxing load type if it is unsigned.
1222             switch(this->Opcode()) {
1223               case Op_LoadUB:
1224                 result = new AndINode(phase->transform(result), phase->intcon(0xFF));
1225                 break;
1226               case Op_LoadUS:
1227                 result = new AndINode(phase->transform(result), phase->intcon(0xFFFF));
1228                 break;
1229             }
1230             return result;
1231           }
1232         }
1233       }
1234     }
1235   }
1236   return NULL;
1237 }
1238 
1239 static bool stable_phi(PhiNode* phi, PhaseGVN *phase) {
1240   Node* region = phi->in(0);
1241   if (region == NULL) {
1242     return false; // Wait stable graph
1243   }
1244   uint cnt = phi->req();
1245   for (uint i = 1; i < cnt; i++) {
1246     Node* rc = region->in(i);
1247     if (rc == NULL || phase->type(rc) == Type::TOP)
1248       return false; // Wait stable graph
1249     Node* in = phi->in(i);
1250     if (in == NULL || phase->type(in) == Type::TOP)
1251       return false; // Wait stable graph
1252   }
1253   return true;
1254 }
1255 //------------------------------split_through_phi------------------------------
1256 // Split instance or boxed field load through Phi.
1257 Node *LoadNode::split_through_phi(PhaseGVN *phase) {
1258   Node* mem     = in(Memory);
1259   Node* address = in(Address);
1260   const TypeOopPtr *t_oop = phase->type(address)->isa_oopptr();
1261 
1262   assert((t_oop != NULL) &&
1263          (t_oop->is_known_instance_field() ||
1264           t_oop->is_ptr_to_boxed_value()), "invalide conditions");
1265 
1266   Compile* C = phase->C;
1267   intptr_t ignore = 0;
1268   Node*    base = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1269   bool base_is_phi = (base != NULL) && base->is_Phi();
1270   bool load_boxed_values = t_oop->is_ptr_to_boxed_value() && C->aggressive_unboxing() &&
1271                            (base != NULL) && (base == address->in(AddPNode::Base)) &&
1272                            phase->type(base)->higher_equal(TypePtr::NOTNULL);
1273 
1274   if (!((mem->is_Phi() || base_is_phi) &&
1275         (load_boxed_values || t_oop->is_known_instance_field()))) {
1276     return NULL; // memory is not Phi
1277   }
1278 
1279   if (mem->is_Phi()) {
1280     if (!stable_phi(mem->as_Phi(), phase)) {
1281       return NULL; // Wait stable graph
1282     }
1283     uint cnt = mem->req();
1284     // Check for loop invariant memory.
1285     if (cnt == 3) {
1286       for (uint i = 1; i < cnt; i++) {
1287         Node* in = mem->in(i);
1288         Node*  m = optimize_memory_chain(in, t_oop, this, phase);
1289         if (m == mem) {
1290           set_req(Memory, mem->in(cnt - i));
1291           return this; // made change
1292         }
1293       }
1294     }
1295   }
1296   if (base_is_phi) {
1297     if (!stable_phi(base->as_Phi(), phase)) {
1298       return NULL; // Wait stable graph
1299     }
1300     uint cnt = base->req();
1301     // Check for loop invariant memory.
1302     if (cnt == 3) {
1303       for (uint i = 1; i < cnt; i++) {
1304         if (base->in(i) == base) {
1305           return NULL; // Wait stable graph
1306         }
1307       }
1308     }
1309   }
1310 
1311   bool load_boxed_phi = load_boxed_values && base_is_phi && (base->in(0) == mem->in(0));
1312 
1313   // Split through Phi (see original code in loopopts.cpp).
1314   assert(C->have_alias_type(t_oop), "instance should have alias type");
1315 
1316   // Do nothing here if Identity will find a value
1317   // (to avoid infinite chain of value phis generation).
1318   if (!phase->eqv(this, this->Identity(phase)))
1319     return NULL;
1320 
1321   // Select Region to split through.
1322   Node* region;
1323   if (!base_is_phi) {
1324     assert(mem->is_Phi(), "sanity");
1325     region = mem->in(0);
1326     // Skip if the region dominates some control edge of the address.
1327     if (!MemNode::all_controls_dominate(address, region))
1328       return NULL;
1329   } else if (!mem->is_Phi()) {
1330     assert(base_is_phi, "sanity");
1331     region = base->in(0);
1332     // Skip if the region dominates some control edge of the memory.
1333     if (!MemNode::all_controls_dominate(mem, region))
1334       return NULL;
1335   } else if (base->in(0) != mem->in(0)) {
1336     assert(base_is_phi && mem->is_Phi(), "sanity");
1337     if (MemNode::all_controls_dominate(mem, base->in(0))) {
1338       region = base->in(0);
1339     } else if (MemNode::all_controls_dominate(address, mem->in(0))) {
1340       region = mem->in(0);
1341     } else {
1342       return NULL; // complex graph
1343     }
1344   } else {
1345     assert(base->in(0) == mem->in(0), "sanity");
1346     region = mem->in(0);
1347   }
1348 
1349   const Type* this_type = this->bottom_type();
1350   int this_index  = C->get_alias_index(t_oop);
1351   int this_offset = t_oop->offset();
1352   int this_iid    = t_oop->instance_id();
1353   if (!t_oop->is_known_instance() && load_boxed_values) {
1354     // Use _idx of address base for boxed values.
1355     this_iid = base->_idx;
1356   }
1357   PhaseIterGVN* igvn = phase->is_IterGVN();
1358   Node* phi = new PhiNode(region, this_type, NULL, this_iid, this_index, this_offset);
1359   for (uint i = 1; i < region->req(); i++) {
1360     Node* x;
1361     Node* the_clone = NULL;
1362     if (region->in(i) == C->top()) {
1363       x = C->top();      // Dead path?  Use a dead data op
1364     } else {
1365       x = this->clone();        // Else clone up the data op
1366       the_clone = x;            // Remember for possible deletion.
1367       // Alter data node to use pre-phi inputs
1368       if (this->in(0) == region) {
1369         x->set_req(0, region->in(i));
1370       } else {
1371         x->set_req(0, NULL);
1372       }
1373       if (mem->is_Phi() && (mem->in(0) == region)) {
1374         x->set_req(Memory, mem->in(i)); // Use pre-Phi input for the clone.
1375       }
1376       if (address->is_Phi() && address->in(0) == region) {
1377         x->set_req(Address, address->in(i)); // Use pre-Phi input for the clone
1378       }
1379       if (base_is_phi && (base->in(0) == region)) {
1380         Node* base_x = base->in(i); // Clone address for loads from boxed objects.
1381         Node* adr_x = phase->transform(new AddPNode(base_x,base_x,address->in(AddPNode::Offset)));
1382         x->set_req(Address, adr_x);
1383       }
1384     }
1385     // Check for a 'win' on some paths
1386     const Type *t = x->Value(igvn);
1387 
1388     bool singleton = t->singleton();
1389 
1390     // See comments in PhaseIdealLoop::split_thru_phi().
1391     if (singleton && t == Type::TOP) {
1392       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
1393     }
1394 
1395     if (singleton) {
1396       x = igvn->makecon(t);
1397     } else {
1398       // We now call Identity to try to simplify the cloned node.
1399       // Note that some Identity methods call phase->type(this).
1400       // Make sure that the type array is big enough for
1401       // our new node, even though we may throw the node away.
1402       // (This tweaking with igvn only works because x is a new node.)
1403       igvn->set_type(x, t);
1404       // If x is a TypeNode, capture any more-precise type permanently into Node
1405       // otherwise it will be not updated during igvn->transform since
1406       // igvn->type(x) is set to x->Value() already.
1407       x->raise_bottom_type(t);
1408       Node *y = x->Identity(igvn);
1409       if (y != x) {
1410         x = y;
1411       } else {
1412         y = igvn->hash_find_insert(x);
1413         if (y) {
1414           x = y;
1415         } else {
1416           // Else x is a new node we are keeping
1417           // We do not need register_new_node_with_optimizer
1418           // because set_type has already been called.
1419           igvn->_worklist.push(x);
1420         }
1421       }
1422     }
1423     if (x != the_clone && the_clone != NULL) {
1424       igvn->remove_dead_node(the_clone);
1425     }
1426     phi->set_req(i, x);
1427   }
1428   // Record Phi
1429   igvn->register_new_node_with_optimizer(phi);
1430   return phi;
1431 }
1432 
1433 //------------------------------Ideal------------------------------------------
1434 // If the load is from Field memory and the pointer is non-null, it might be possible to
1435 // zero out the control input.
1436 // If the offset is constant and the base is an object allocation,
1437 // try to hook me up to the exact initializing store.
1438 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1439   Node* p = MemNode::Ideal_common(phase, can_reshape);
1440   if (p)  return (p == NodeSentinel) ? NULL : p;
1441 
1442   Node* ctrl    = in(MemNode::Control);
1443   Node* address = in(MemNode::Address);
1444   bool progress = false;
1445 
1446   // Skip up past a SafePoint control.  Cannot do this for Stores because
1447   // pointer stores & cardmarks must stay on the same side of a SafePoint.
1448   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
1449       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
1450     ctrl = ctrl->in(0);
1451     set_req(MemNode::Control,ctrl);
1452     progress = true;
1453   }
1454 
1455   intptr_t ignore = 0;
1456   Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
1457   if (base != NULL
1458       && phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw) {
1459     // Check for useless control edge in some common special cases
1460     if (in(MemNode::Control) != NULL
1461         && can_remove_control()
1462         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
1463         && all_controls_dominate(base, phase->C->start())) {
1464       // A method-invariant, non-null address (constant or 'this' argument).
1465       set_req(MemNode::Control, NULL);
1466       progress = true;
1467     }
1468   }
1469 
1470   Node* mem = in(MemNode::Memory);
1471   const TypePtr *addr_t = phase->type(address)->isa_ptr();
1472 
1473   if (can_reshape && (addr_t != NULL)) {
1474     // try to optimize our memory input
1475     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, this, phase);
1476     if (opt_mem != mem) {
1477       set_req(MemNode::Memory, opt_mem);
1478       if (phase->type( opt_mem ) == Type::TOP) return NULL;
1479       return this;
1480     }
1481     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
1482     if ((t_oop != NULL) &&
1483         (t_oop->is_known_instance_field() ||
1484          t_oop->is_ptr_to_boxed_value())) {
1485       PhaseIterGVN *igvn = phase->is_IterGVN();
1486       if (igvn != NULL && igvn->_worklist.member(opt_mem)) {
1487         // Delay this transformation until memory Phi is processed.
1488         phase->is_IterGVN()->_worklist.push(this);
1489         return NULL;
1490       }
1491       // Split instance field load through Phi.
1492       Node* result = split_through_phi(phase);
1493       if (result != NULL) return result;
1494 
1495       if (t_oop->is_ptr_to_boxed_value()) {
1496         Node* result = eliminate_autobox(phase);
1497         if (result != NULL) return result;
1498       }
1499     }
1500   }
1501 
1502   // Is there a dominating load that loads the same value?  Leave
1503   // anything that is not a load of a field/array element (like
1504   // barriers etc.) alone
1505   if (in(0) != NULL && adr_type() != TypeRawPtr::BOTTOM && can_reshape) {
1506     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
1507       Node *use = mem->fast_out(i);
1508       if (use != this &&
1509           use->Opcode() == Opcode() &&
1510           use->in(0) != NULL &&
1511           use->in(0) != in(0) &&
1512           use->in(Address) == in(Address)) {
1513         Node* ctl = in(0);
1514         for (int i = 0; i < 10 && ctl != NULL; i++) {
1515           ctl = IfNode::up_one_dom(ctl);
1516           if (ctl == use->in(0)) {
1517             set_req(0, use->in(0));
1518             return this;
1519           }
1520         }
1521       }
1522     }
1523   }
1524 
1525   // Check for prior store with a different base or offset; make Load
1526   // independent.  Skip through any number of them.  Bail out if the stores
1527   // are in an endless dead cycle and report no progress.  This is a key
1528   // transform for Reflection.  However, if after skipping through the Stores
1529   // we can't then fold up against a prior store do NOT do the transform as
1530   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
1531   // array memory alive twice: once for the hoisted Load and again after the
1532   // bypassed Store.  This situation only works if EVERYBODY who does
1533   // anti-dependence work knows how to bypass.  I.e. we need all
1534   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
1535   // the alias index stuff.  So instead, peek through Stores and IFF we can
1536   // fold up, do so.
1537   Node* prev_mem = find_previous_store(phase);
1538   if (prev_mem != NULL) {
1539     Node* value = can_see_arraycopy_value(prev_mem, phase);
1540     if (value != NULL) {
1541       return value;
1542     }
1543   }
1544   // Steps (a), (b):  Walk past independent stores to find an exact match.
1545   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
1546     // (c) See if we can fold up on the spot, but don't fold up here.
1547     // Fold-up might require truncation (for LoadB/LoadS/LoadUS) or
1548     // just return a prior value, which is done by Identity calls.
1549     if (can_see_stored_value(prev_mem, phase)) {
1550       // Make ready for step (d):
1551       set_req(MemNode::Memory, prev_mem);
1552       return this;
1553     }
1554   }
1555 
1556   return progress ? this : NULL;
1557 }
1558 
1559 // Helper to recognize certain Klass fields which are invariant across
1560 // some group of array types (e.g., int[] or all T[] where T < Object).
1561 const Type*
1562 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
1563                                  ciKlass* klass) const {
1564   if (tkls->offset() == in_bytes(Klass::modifier_flags_offset())) {
1565     // The field is Klass::_modifier_flags.  Return its (constant) value.
1566     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
1567     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
1568     return TypeInt::make(klass->modifier_flags());
1569   }
1570   if (tkls->offset() == in_bytes(Klass::access_flags_offset())) {
1571     // The field is Klass::_access_flags.  Return its (constant) value.
1572     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
1573     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
1574     return TypeInt::make(klass->access_flags());
1575   }
1576   if (tkls->offset() == in_bytes(Klass::layout_helper_offset())) {
1577     // The field is Klass::_layout_helper.  Return its constant value if known.
1578     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
1579     return TypeInt::make(klass->layout_helper());
1580   }
1581 
1582   // No match.
1583   return NULL;
1584 }
1585 
1586 static bool is_mismatched_access(ciConstant con, BasicType loadbt) {
1587   BasicType conbt = con.basic_type();
1588   switch (conbt) {
1589     case T_BOOLEAN: conbt = T_BYTE;   break;
1590     case T_ARRAY:   conbt = T_OBJECT; break;
1591   }
1592   switch (loadbt) {
1593     case T_BOOLEAN:   loadbt = T_BYTE;   break;
1594     case T_NARROWOOP: loadbt = T_OBJECT; break;
1595     case T_ARRAY:     loadbt = T_OBJECT; break;
1596     case T_ADDRESS:   loadbt = T_OBJECT; break;
1597   }
1598   return (conbt != loadbt);
1599 }
1600 
1601 // Try to constant-fold a stable array element.
1602 static const Type* fold_stable_ary_elem(const TypeAryPtr* ary, int off, BasicType loadbt) {
1603   assert(ary->const_oop(), "array should be constant");
1604   assert(ary->is_stable(), "array should be stable");
1605 
1606   // Decode the results of GraphKit::array_element_address.
1607   ciArray* aobj = ary->const_oop()->as_array();
1608   ciConstant con = aobj->element_value_by_offset(off);
1609   if (con.basic_type() != T_ILLEGAL && !con.is_null_or_zero()) {
1610     bool is_mismatched = is_mismatched_access(con, loadbt);
1611     assert(!is_mismatched, "conbt=%s; loadbt=%s", type2name(con.basic_type()), type2name(loadbt));
1612     const Type* con_type = Type::make_from_constant(con);
1613     // Guard against erroneous constant folding.
1614     if (!is_mismatched && con_type != NULL) {
1615       if (con_type->isa_aryptr()) {
1616         // Join with the array element type, in case it is also stable.
1617         int dim = ary->stable_dimension();
1618         con_type = con_type->is_aryptr()->cast_to_stable(true, dim-1);
1619       }
1620       if (loadbt == T_NARROWOOP && con_type->isa_oopptr()) {
1621         con_type = con_type->make_narrowoop();
1622       }
1623 #ifndef PRODUCT
1624       if (TraceIterativeGVN) {
1625         tty->print("FoldStableValues: array element [off=%d]: con_type=", off);
1626         con_type->dump(); tty->cr();
1627       }
1628 #endif //PRODUCT
1629       return con_type;
1630     }
1631   }
1632   return NULL;
1633 }
1634 
1635 //------------------------------Value-----------------------------------------
1636 const Type* LoadNode::Value(PhaseGVN* phase) const {
1637   // Either input is TOP ==> the result is TOP
1638   Node* mem = in(MemNode::Memory);
1639   const Type *t1 = phase->type(mem);
1640   if (t1 == Type::TOP)  return Type::TOP;
1641   Node* adr = in(MemNode::Address);
1642   const TypePtr* tp = phase->type(adr)->isa_ptr();
1643   if (tp == NULL || tp->empty())  return Type::TOP;
1644   int off = tp->offset();
1645   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
1646   Compile* C = phase->C;
1647 
1648   // Try to guess loaded type from pointer type
1649   if (tp->isa_aryptr()) {
1650     const TypeAryPtr* ary = tp->is_aryptr();
1651     const Type* t = ary->elem();
1652 
1653     // Determine whether the reference is beyond the header or not, by comparing
1654     // the offset against the offset of the start of the array's data.
1655     // Different array types begin at slightly different offsets (12 vs. 16).
1656     // We choose T_BYTE as an example base type that is least restrictive
1657     // as to alignment, which will therefore produce the smallest
1658     // possible base offset.
1659     const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
1660     const bool off_beyond_header = ((uint)off >= (uint)min_base_off);
1661 
1662     // Try to constant-fold a stable array element.
1663     if (FoldStableValues && !is_mismatched_access() && ary->is_stable() && ary->const_oop() != NULL) {
1664       // Make sure the reference is not into the header and the offset is constant
1665       if (off_beyond_header && adr->is_AddP() && off != Type::OffsetBot) {
1666         const Type* con_type = fold_stable_ary_elem(ary, off, memory_type());
1667         if (con_type != NULL) {
1668           return con_type;
1669         }
1670       }
1671     }
1672 
1673     // Don't do this for integer types. There is only potential profit if
1674     // the element type t is lower than _type; that is, for int types, if _type is
1675     // more restrictive than t.  This only happens here if one is short and the other
1676     // char (both 16 bits), and in those cases we've made an intentional decision
1677     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
1678     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
1679     //
1680     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
1681     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
1682     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
1683     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
1684     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
1685     // In fact, that could have been the original type of p1, and p1 could have
1686     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
1687     // expression (LShiftL quux 3) independently optimized to the constant 8.
1688     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
1689         && (_type->isa_vect() == NULL)
1690         && Opcode() != Op_LoadKlass && Opcode() != Op_LoadNKlass) {
1691       // t might actually be lower than _type, if _type is a unique
1692       // concrete subclass of abstract class t.
1693       if (off_beyond_header) {  // is the offset beyond the header?
1694         const Type* jt = t->join_speculative(_type);
1695         // In any case, do not allow the join, per se, to empty out the type.
1696         if (jt->empty() && !t->empty()) {
1697           // This can happen if a interface-typed array narrows to a class type.
1698           jt = _type;
1699         }
1700 #ifdef ASSERT
1701         if (phase->C->eliminate_boxing() && adr->is_AddP()) {
1702           // The pointers in the autobox arrays are always non-null
1703           Node* base = adr->in(AddPNode::Base);
1704           if ((base != NULL) && base->is_DecodeN()) {
1705             // Get LoadN node which loads IntegerCache.cache field
1706             base = base->in(1);
1707           }
1708           if ((base != NULL) && base->is_Con()) {
1709             const TypeAryPtr* base_type = base->bottom_type()->isa_aryptr();
1710             if ((base_type != NULL) && base_type->is_autobox_cache()) {
1711               // It could be narrow oop
1712               assert(jt->make_ptr()->ptr() == TypePtr::NotNull,"sanity");
1713             }
1714           }
1715         }
1716 #endif
1717         return jt;
1718       }
1719     }
1720   } else if (tp->base() == Type::InstPtr) {
1721     ciEnv* env = C->env();
1722     const TypeInstPtr* tinst = tp->is_instptr();
1723     ciKlass* klass = tinst->klass();
1724     assert( off != Type::OffsetBot ||
1725             // arrays can be cast to Objects
1726             tp->is_oopptr()->klass()->is_java_lang_Object() ||
1727             // unsafe field access may not have a constant offset
1728             C->has_unsafe_access(),
1729             "Field accesses must be precise" );
1730     // For oop loads, we expect the _type to be precise.
1731     // Optimizations for constant objects
1732     ciObject* const_oop = tinst->const_oop();
1733     if (const_oop != NULL) {
1734       // For constant CallSites treat the target field as a compile time constant.
1735       if (const_oop->is_call_site()) {
1736         ciCallSite* call_site = const_oop->as_call_site();
1737         ciField* field = call_site->klass()->as_instance_klass()->get_field_by_offset(off, /*is_static=*/ false);
1738         if (field != NULL && field->is_call_site_target()) {
1739           ciMethodHandle* target = call_site->get_target();
1740           if (target != NULL) {  // just in case
1741             ciConstant constant(T_OBJECT, target);
1742             const Type* t;
1743             if (adr->bottom_type()->is_ptr_to_narrowoop()) {
1744               t = TypeNarrowOop::make_from_constant(constant.as_object(), true);
1745             } else {
1746               t = TypeOopPtr::make_from_constant(constant.as_object(), true);
1747             }
1748             // Add a dependence for invalidation of the optimization.
1749             if (!call_site->is_constant_call_site()) {
1750               C->dependencies()->assert_call_site_target_value(call_site, target);
1751             }
1752             return t;
1753           }
1754         }
1755       }
1756     }
1757   } else if (tp->base() == Type::KlassPtr) {
1758     assert( off != Type::OffsetBot ||
1759             // arrays can be cast to Objects
1760             tp->is_klassptr()->klass()->is_java_lang_Object() ||
1761             // also allow array-loading from the primary supertype
1762             // array during subtype checks
1763             Opcode() == Op_LoadKlass,
1764             "Field accesses must be precise" );
1765     // For klass/static loads, we expect the _type to be precise
1766   }
1767 
1768   const TypeKlassPtr *tkls = tp->isa_klassptr();
1769   if (tkls != NULL && !StressReflectiveCode) {
1770     ciKlass* klass = tkls->klass();
1771     if (klass->is_loaded() && tkls->klass_is_exact()) {
1772       // We are loading a field from a Klass metaobject whose identity
1773       // is known at compile time (the type is "exact" or "precise").
1774       // Check for fields we know are maintained as constants by the VM.
1775       if (tkls->offset() == in_bytes(Klass::super_check_offset_offset())) {
1776         // The field is Klass::_super_check_offset.  Return its (constant) value.
1777         // (Folds up type checking code.)
1778         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
1779         return TypeInt::make(klass->super_check_offset());
1780       }
1781       // Compute index into primary_supers array
1782       juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1783       // Check for overflowing; use unsigned compare to handle the negative case.
1784       if( depth < ciKlass::primary_super_limit() ) {
1785         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1786         // (Folds up type checking code.)
1787         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1788         ciKlass *ss = klass->super_of_depth(depth);
1789         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1790       }
1791       const Type* aift = load_array_final_field(tkls, klass);
1792       if (aift != NULL)  return aift;
1793       if (tkls->offset() == in_bytes(Klass::java_mirror_offset())) {
1794         // The field is Klass::_java_mirror.  Return its (constant) value.
1795         // (Folds up the 2nd indirection in anObjConstant.getClass().)
1796         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
1797         return TypeInstPtr::make(klass->java_mirror());
1798       }
1799     }
1800 
1801     // We can still check if we are loading from the primary_supers array at a
1802     // shallow enough depth.  Even though the klass is not exact, entries less
1803     // than or equal to its super depth are correct.
1804     if (klass->is_loaded() ) {
1805       ciType *inner = klass;
1806       while( inner->is_obj_array_klass() )
1807         inner = inner->as_obj_array_klass()->base_element_type();
1808       if( inner->is_instance_klass() &&
1809           !inner->as_instance_klass()->flags().is_interface() ) {
1810         // Compute index into primary_supers array
1811         juint depth = (tkls->offset() - in_bytes(Klass::primary_supers_offset())) / sizeof(Klass*);
1812         // Check for overflowing; use unsigned compare to handle the negative case.
1813         if( depth < ciKlass::primary_super_limit() &&
1814             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
1815           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
1816           // (Folds up type checking code.)
1817           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
1818           ciKlass *ss = klass->super_of_depth(depth);
1819           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
1820         }
1821       }
1822     }
1823 
1824     // If the type is enough to determine that the thing is not an array,
1825     // we can give the layout_helper a positive interval type.
1826     // This will help short-circuit some reflective code.
1827     if (tkls->offset() == in_bytes(Klass::layout_helper_offset())
1828         && !klass->is_array_klass() // not directly typed as an array
1829         && !klass->is_interface()  // specifically not Serializable & Cloneable
1830         && !klass->is_java_lang_Object()   // not the supertype of all T[]
1831         ) {
1832       // Note:  When interfaces are reliable, we can narrow the interface
1833       // test to (klass != Serializable && klass != Cloneable).
1834       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
1835       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
1836       // The key property of this type is that it folds up tests
1837       // for array-ness, since it proves that the layout_helper is positive.
1838       // Thus, a generic value like the basic object layout helper works fine.
1839       return TypeInt::make(min_size, max_jint, Type::WidenMin);
1840     }
1841   }
1842 
1843   // If we are loading from a freshly-allocated object, produce a zero,
1844   // if the load is provably beyond the header of the object.
1845   // (Also allow a variable load from a fresh array to produce zero.)
1846   const TypeOopPtr *tinst = tp->isa_oopptr();
1847   bool is_instance = (tinst != NULL) && tinst->is_known_instance_field();
1848   bool is_boxed_value = (tinst != NULL) && tinst->is_ptr_to_boxed_value();
1849   if (ReduceFieldZeroing || is_instance || is_boxed_value) {
1850     Node* value = can_see_stored_value(mem,phase);
1851     if (value != NULL && value->is_Con()) {
1852       assert(value->bottom_type()->higher_equal(_type),"sanity");
1853       return value->bottom_type();
1854     }
1855   }
1856 
1857   if (is_instance) {
1858     // If we have an instance type and our memory input is the
1859     // programs's initial memory state, there is no matching store,
1860     // so just return a zero of the appropriate type
1861     Node *mem = in(MemNode::Memory);
1862     if (mem->is_Parm() && mem->in(0)->is_Start()) {
1863       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
1864       return Type::get_zero_type(_type->basic_type());
1865     }
1866   }
1867   return _type;
1868 }
1869 
1870 //------------------------------match_edge-------------------------------------
1871 // Do we Match on this edge index or not?  Match only the address.
1872 uint LoadNode::match_edge(uint idx) const {
1873   return idx == MemNode::Address;
1874 }
1875 
1876 //--------------------------LoadBNode::Ideal--------------------------------------
1877 //
1878 //  If the previous store is to the same address as this load,
1879 //  and the value stored was larger than a byte, replace this load
1880 //  with the value stored truncated to a byte.  If no truncation is
1881 //  needed, the replacement is done in LoadNode::Identity().
1882 //
1883 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1884   Node* mem = in(MemNode::Memory);
1885   Node* value = can_see_stored_value(mem,phase);
1886   if( value && !phase->type(value)->higher_equal( _type ) ) {
1887     Node *result = phase->transform( new LShiftINode(value, phase->intcon(24)) );
1888     return new RShiftINode(result, phase->intcon(24));
1889   }
1890   // Identity call will handle the case where truncation is not needed.
1891   return LoadNode::Ideal(phase, can_reshape);
1892 }
1893 
1894 const Type* LoadBNode::Value(PhaseGVN* phase) const {
1895   Node* mem = in(MemNode::Memory);
1896   Node* value = can_see_stored_value(mem,phase);
1897   if (value != NULL && value->is_Con() &&
1898       !value->bottom_type()->higher_equal(_type)) {
1899     // If the input to the store does not fit with the load's result type,
1900     // it must be truncated. We can't delay until Ideal call since
1901     // a singleton Value is needed for split_thru_phi optimization.
1902     int con = value->get_int();
1903     return TypeInt::make((con << 24) >> 24);
1904   }
1905   return LoadNode::Value(phase);
1906 }
1907 
1908 //--------------------------LoadUBNode::Ideal-------------------------------------
1909 //
1910 //  If the previous store is to the same address as this load,
1911 //  and the value stored was larger than a byte, replace this load
1912 //  with the value stored truncated to a byte.  If no truncation is
1913 //  needed, the replacement is done in LoadNode::Identity().
1914 //
1915 Node* LoadUBNode::Ideal(PhaseGVN* phase, bool can_reshape) {
1916   Node* mem = in(MemNode::Memory);
1917   Node* value = can_see_stored_value(mem, phase);
1918   if (value && !phase->type(value)->higher_equal(_type))
1919     return new AndINode(value, phase->intcon(0xFF));
1920   // Identity call will handle the case where truncation is not needed.
1921   return LoadNode::Ideal(phase, can_reshape);
1922 }
1923 
1924 const Type* LoadUBNode::Value(PhaseGVN* phase) const {
1925   Node* mem = in(MemNode::Memory);
1926   Node* value = can_see_stored_value(mem,phase);
1927   if (value != NULL && value->is_Con() &&
1928       !value->bottom_type()->higher_equal(_type)) {
1929     // If the input to the store does not fit with the load's result type,
1930     // it must be truncated. We can't delay until Ideal call since
1931     // a singleton Value is needed for split_thru_phi optimization.
1932     int con = value->get_int();
1933     return TypeInt::make(con & 0xFF);
1934   }
1935   return LoadNode::Value(phase);
1936 }
1937 
1938 //--------------------------LoadUSNode::Ideal-------------------------------------
1939 //
1940 //  If the previous store is to the same address as this load,
1941 //  and the value stored was larger than a char, replace this load
1942 //  with the value stored truncated to a char.  If no truncation is
1943 //  needed, the replacement is done in LoadNode::Identity().
1944 //
1945 Node *LoadUSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1946   Node* mem = in(MemNode::Memory);
1947   Node* value = can_see_stored_value(mem,phase);
1948   if( value && !phase->type(value)->higher_equal( _type ) )
1949     return new AndINode(value,phase->intcon(0xFFFF));
1950   // Identity call will handle the case where truncation is not needed.
1951   return LoadNode::Ideal(phase, can_reshape);
1952 }
1953 
1954 const Type* LoadUSNode::Value(PhaseGVN* phase) const {
1955   Node* mem = in(MemNode::Memory);
1956   Node* value = can_see_stored_value(mem,phase);
1957   if (value != NULL && value->is_Con() &&
1958       !value->bottom_type()->higher_equal(_type)) {
1959     // If the input to the store does not fit with the load's result type,
1960     // it must be truncated. We can't delay until Ideal call since
1961     // a singleton Value is needed for split_thru_phi optimization.
1962     int con = value->get_int();
1963     return TypeInt::make(con & 0xFFFF);
1964   }
1965   return LoadNode::Value(phase);
1966 }
1967 
1968 //--------------------------LoadSNode::Ideal--------------------------------------
1969 //
1970 //  If the previous store is to the same address as this load,
1971 //  and the value stored was larger than a short, replace this load
1972 //  with the value stored truncated to a short.  If no truncation is
1973 //  needed, the replacement is done in LoadNode::Identity().
1974 //
1975 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1976   Node* mem = in(MemNode::Memory);
1977   Node* value = can_see_stored_value(mem,phase);
1978   if( value && !phase->type(value)->higher_equal( _type ) ) {
1979     Node *result = phase->transform( new LShiftINode(value, phase->intcon(16)) );
1980     return new RShiftINode(result, phase->intcon(16));
1981   }
1982   // Identity call will handle the case where truncation is not needed.
1983   return LoadNode::Ideal(phase, can_reshape);
1984 }
1985 
1986 const Type* LoadSNode::Value(PhaseGVN* phase) const {
1987   Node* mem = in(MemNode::Memory);
1988   Node* value = can_see_stored_value(mem,phase);
1989   if (value != NULL && value->is_Con() &&
1990       !value->bottom_type()->higher_equal(_type)) {
1991     // If the input to the store does not fit with the load's result type,
1992     // it must be truncated. We can't delay until Ideal call since
1993     // a singleton Value is needed for split_thru_phi optimization.
1994     int con = value->get_int();
1995     return TypeInt::make((con << 16) >> 16);
1996   }
1997   return LoadNode::Value(phase);
1998 }
1999 
2000 //=============================================================================
2001 //----------------------------LoadKlassNode::make------------------------------
2002 // Polymorphic factory method:
2003 Node* LoadKlassNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* at, const TypeKlassPtr* tk) {
2004   // sanity check the alias category against the created node type
2005   const TypePtr *adr_type = adr->bottom_type()->isa_ptr();
2006   assert(adr_type != NULL, "expecting TypeKlassPtr");
2007 #ifdef _LP64
2008   if (adr_type->is_ptr_to_narrowklass()) {
2009     assert(UseCompressedClassPointers, "no compressed klasses");
2010     Node* load_klass = gvn.transform(new LoadNKlassNode(ctl, mem, adr, at, tk->make_narrowklass(), MemNode::unordered));
2011     return new DecodeNKlassNode(load_klass, load_klass->bottom_type()->make_ptr());
2012   }
2013 #endif
2014   assert(!adr_type->is_ptr_to_narrowklass() && !adr_type->is_ptr_to_narrowoop(), "should have got back a narrow oop");
2015   return new LoadKlassNode(ctl, mem, adr, at, tk, MemNode::unordered);
2016 }
2017 
2018 //------------------------------Value------------------------------------------
2019 const Type* LoadKlassNode::Value(PhaseGVN* phase) const {
2020   return klass_value_common(phase);
2021 }
2022 
2023 // In most cases, LoadKlassNode does not have the control input set. If the control
2024 // input is set, it must not be removed (by LoadNode::Ideal()).
2025 bool LoadKlassNode::can_remove_control() const {
2026   return false;
2027 }
2028 
2029 const Type* LoadNode::klass_value_common(PhaseGVN* phase) const {
2030   // Either input is TOP ==> the result is TOP
2031   const Type *t1 = phase->type( in(MemNode::Memory) );
2032   if (t1 == Type::TOP)  return Type::TOP;
2033   Node *adr = in(MemNode::Address);
2034   const Type *t2 = phase->type( adr );
2035   if (t2 == Type::TOP)  return Type::TOP;
2036   const TypePtr *tp = t2->is_ptr();
2037   if (TypePtr::above_centerline(tp->ptr()) ||
2038       tp->ptr() == TypePtr::Null)  return Type::TOP;
2039 
2040   // Return a more precise klass, if possible
2041   const TypeInstPtr *tinst = tp->isa_instptr();
2042   if (tinst != NULL) {
2043     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
2044     int offset = tinst->offset();
2045     if (ik == phase->C->env()->Class_klass()
2046         && (offset == java_lang_Class::klass_offset_in_bytes() ||
2047             offset == java_lang_Class::array_klass_offset_in_bytes())) {
2048       // We are loading a special hidden field from a Class mirror object,
2049       // the field which points to the VM's Klass metaobject.
2050       ciType* t = tinst->java_mirror_type();
2051       // java_mirror_type returns non-null for compile-time Class constants.
2052       if (t != NULL) {
2053         // constant oop => constant klass
2054         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
2055           if (t->is_void()) {
2056             // We cannot create a void array.  Since void is a primitive type return null
2057             // klass.  Users of this result need to do a null check on the returned klass.
2058             return TypePtr::NULL_PTR;
2059           }
2060           return TypeKlassPtr::make(ciArrayKlass::make(t));
2061         }
2062         if (!t->is_klass()) {
2063           // a primitive Class (e.g., int.class) has NULL for a klass field
2064           return TypePtr::NULL_PTR;
2065         }
2066         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
2067         return TypeKlassPtr::make(t->as_klass());
2068       }
2069       // non-constant mirror, so we can't tell what's going on
2070     }
2071     if( !ik->is_loaded() )
2072       return _type;             // Bail out if not loaded
2073     if (offset == oopDesc::klass_offset_in_bytes()) {
2074       if (tinst->klass_is_exact()) {
2075         return TypeKlassPtr::make(ik);
2076       }
2077       // See if we can become precise: no subklasses and no interface
2078       // (Note:  We need to support verified interfaces.)
2079       if (!ik->is_interface() && !ik->has_subklass()) {
2080         //assert(!UseExactTypes, "this code should be useless with exact types");
2081         // Add a dependence; if any subclass added we need to recompile
2082         if (!ik->is_final()) {
2083           // %%% should use stronger assert_unique_concrete_subtype instead
2084           phase->C->dependencies()->assert_leaf_type(ik);
2085         }
2086         // Return precise klass
2087         return TypeKlassPtr::make(ik);
2088       }
2089 
2090       // Return root of possible klass
2091       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
2092     }
2093   }
2094 
2095   // Check for loading klass from an array
2096   const TypeAryPtr *tary = tp->isa_aryptr();
2097   if( tary != NULL ) {
2098     ciKlass *tary_klass = tary->klass();
2099     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
2100         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
2101       if (tary->klass_is_exact()) {
2102         return TypeKlassPtr::make(tary_klass);
2103       }
2104       ciArrayKlass *ak = tary->klass()->as_array_klass();
2105       // If the klass is an object array, we defer the question to the
2106       // array component klass.
2107       if( ak->is_obj_array_klass() ) {
2108         assert( ak->is_loaded(), "" );
2109         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
2110         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
2111           ciInstanceKlass* ik = base_k->as_instance_klass();
2112           // See if we can become precise: no subklasses and no interface
2113           if (!ik->is_interface() && !ik->has_subklass()) {
2114             //assert(!UseExactTypes, "this code should be useless with exact types");
2115             // Add a dependence; if any subclass added we need to recompile
2116             if (!ik->is_final()) {
2117               phase->C->dependencies()->assert_leaf_type(ik);
2118             }
2119             // Return precise array klass
2120             return TypeKlassPtr::make(ak);
2121           }
2122         }
2123         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
2124       } else {                  // Found a type-array?
2125         //assert(!UseExactTypes, "this code should be useless with exact types");
2126         assert( ak->is_type_array_klass(), "" );
2127         return TypeKlassPtr::make(ak); // These are always precise
2128       }
2129     }
2130   }
2131 
2132   // Check for loading klass from an array klass
2133   const TypeKlassPtr *tkls = tp->isa_klassptr();
2134   if (tkls != NULL && !StressReflectiveCode) {
2135     ciKlass* klass = tkls->klass();
2136     if( !klass->is_loaded() )
2137       return _type;             // Bail out if not loaded
2138     if( klass->is_obj_array_klass() &&
2139         tkls->offset() == in_bytes(ObjArrayKlass::element_klass_offset())) {
2140       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
2141       // // Always returning precise element type is incorrect,
2142       // // e.g., element type could be object and array may contain strings
2143       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
2144 
2145       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
2146       // according to the element type's subclassing.
2147       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
2148     }
2149     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
2150         tkls->offset() == in_bytes(Klass::super_offset())) {
2151       ciKlass* sup = klass->as_instance_klass()->super();
2152       // The field is Klass::_super.  Return its (constant) value.
2153       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
2154       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
2155     }
2156   }
2157 
2158   // Bailout case
2159   return LoadNode::Value(phase);
2160 }
2161 
2162 //------------------------------Identity---------------------------------------
2163 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
2164 // Also feed through the klass in Allocate(...klass...)._klass.
2165 Node* LoadKlassNode::Identity(PhaseGVN* phase) {
2166   return klass_identity_common(phase);
2167 }
2168 
2169 Node* LoadNode::klass_identity_common(PhaseGVN* phase) {
2170   Node* x = LoadNode::Identity(phase);
2171   if (x != this)  return x;
2172 
2173   // Take apart the address into an oop and and offset.
2174   // Return 'this' if we cannot.
2175   Node*    adr    = in(MemNode::Address);
2176   intptr_t offset = 0;
2177   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2178   if (base == NULL)     return this;
2179   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
2180   if (toop == NULL)     return this;
2181 
2182   // We can fetch the klass directly through an AllocateNode.
2183   // This works even if the klass is not constant (clone or newArray).
2184   if (offset == oopDesc::klass_offset_in_bytes()) {
2185     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
2186     if (allocated_klass != NULL) {
2187       return allocated_klass;
2188     }
2189   }
2190 
2191   // Simplify k.java_mirror.as_klass to plain k, where k is a Klass*.
2192   // See inline_native_Class_query for occurrences of these patterns.
2193   // Java Example:  x.getClass().isAssignableFrom(y)
2194   //
2195   // This improves reflective code, often making the Class
2196   // mirror go completely dead.  (Current exception:  Class
2197   // mirrors may appear in debug info, but we could clean them out by
2198   // introducing a new debug info operator for Klass*.java_mirror).
2199   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
2200       && offset == java_lang_Class::klass_offset_in_bytes()) {
2201     // We are loading a special hidden field from a Class mirror,
2202     // the field which points to its Klass or ArrayKlass metaobject.
2203     if (base->is_Load()) {
2204       Node* adr2 = base->in(MemNode::Address);
2205       const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
2206       if (tkls != NULL && !tkls->empty()
2207           && (tkls->klass()->is_instance_klass() ||
2208               tkls->klass()->is_array_klass())
2209           && adr2->is_AddP()
2210           ) {
2211         int mirror_field = in_bytes(Klass::java_mirror_offset());
2212         if (tkls->offset() == mirror_field) {
2213           return adr2->in(AddPNode::Base);
2214         }
2215       }
2216     }
2217   }
2218 
2219   return this;
2220 }
2221 
2222 
2223 //------------------------------Value------------------------------------------
2224 const Type* LoadNKlassNode::Value(PhaseGVN* phase) const {
2225   const Type *t = klass_value_common(phase);
2226   if (t == Type::TOP)
2227     return t;
2228 
2229   return t->make_narrowklass();
2230 }
2231 
2232 //------------------------------Identity---------------------------------------
2233 // To clean up reflective code, simplify k.java_mirror.as_klass to narrow k.
2234 // Also feed through the klass in Allocate(...klass...)._klass.
2235 Node* LoadNKlassNode::Identity(PhaseGVN* phase) {
2236   Node *x = klass_identity_common(phase);
2237 
2238   const Type *t = phase->type( x );
2239   if( t == Type::TOP ) return x;
2240   if( t->isa_narrowklass()) return x;
2241   assert (!t->isa_narrowoop(), "no narrow oop here");
2242 
2243   return phase->transform(new EncodePKlassNode(x, t->make_narrowklass()));
2244 }
2245 
2246 //------------------------------Value-----------------------------------------
2247 const Type* LoadRangeNode::Value(PhaseGVN* phase) const {
2248   // Either input is TOP ==> the result is TOP
2249   const Type *t1 = phase->type( in(MemNode::Memory) );
2250   if( t1 == Type::TOP ) return Type::TOP;
2251   Node *adr = in(MemNode::Address);
2252   const Type *t2 = phase->type( adr );
2253   if( t2 == Type::TOP ) return Type::TOP;
2254   const TypePtr *tp = t2->is_ptr();
2255   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
2256   const TypeAryPtr *tap = tp->isa_aryptr();
2257   if( !tap ) return _type;
2258   return tap->size();
2259 }
2260 
2261 //-------------------------------Ideal---------------------------------------
2262 // Feed through the length in AllocateArray(...length...)._length.
2263 Node *LoadRangeNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2264   Node* p = MemNode::Ideal_common(phase, can_reshape);
2265   if (p)  return (p == NodeSentinel) ? NULL : p;
2266 
2267   // Take apart the address into an oop and and offset.
2268   // Return 'this' if we cannot.
2269   Node*    adr    = in(MemNode::Address);
2270   intptr_t offset = 0;
2271   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase,  offset);
2272   if (base == NULL)     return NULL;
2273   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2274   if (tary == NULL)     return NULL;
2275 
2276   // We can fetch the length directly through an AllocateArrayNode.
2277   // This works even if the length is not constant (clone or newArray).
2278   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2279     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2280     if (alloc != NULL) {
2281       Node* allocated_length = alloc->Ideal_length();
2282       Node* len = alloc->make_ideal_length(tary, phase);
2283       if (allocated_length != len) {
2284         // New CastII improves on this.
2285         return len;
2286       }
2287     }
2288   }
2289 
2290   return NULL;
2291 }
2292 
2293 //------------------------------Identity---------------------------------------
2294 // Feed through the length in AllocateArray(...length...)._length.
2295 Node* LoadRangeNode::Identity(PhaseGVN* phase) {
2296   Node* x = LoadINode::Identity(phase);
2297   if (x != this)  return x;
2298 
2299   // Take apart the address into an oop and and offset.
2300   // Return 'this' if we cannot.
2301   Node*    adr    = in(MemNode::Address);
2302   intptr_t offset = 0;
2303   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
2304   if (base == NULL)     return this;
2305   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
2306   if (tary == NULL)     return this;
2307 
2308   // We can fetch the length directly through an AllocateArrayNode.
2309   // This works even if the length is not constant (clone or newArray).
2310   if (offset == arrayOopDesc::length_offset_in_bytes()) {
2311     AllocateArrayNode* alloc = AllocateArrayNode::Ideal_array_allocation(base, phase);
2312     if (alloc != NULL) {
2313       Node* allocated_length = alloc->Ideal_length();
2314       // Do not allow make_ideal_length to allocate a CastII node.
2315       Node* len = alloc->make_ideal_length(tary, phase, false);
2316       if (allocated_length == len) {
2317         // Return allocated_length only if it would not be improved by a CastII.
2318         return allocated_length;
2319       }
2320     }
2321   }
2322 
2323   return this;
2324 
2325 }
2326 
2327 //=============================================================================
2328 //---------------------------StoreNode::make-----------------------------------
2329 // Polymorphic factory method:
2330 StoreNode* StoreNode::make(PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt, MemOrd mo) {
2331   assert((mo == unordered || mo == release), "unexpected");
2332   Compile* C = gvn.C;
2333   assert(C->get_alias_index(adr_type) != Compile::AliasIdxRaw ||
2334          ctl != NULL, "raw memory operations should have control edge");
2335 
2336   switch (bt) {
2337   case T_BOOLEAN:
2338   case T_BYTE:    return new StoreBNode(ctl, mem, adr, adr_type, val, mo);
2339   case T_INT:     return new StoreINode(ctl, mem, adr, adr_type, val, mo);
2340   case T_CHAR:
2341   case T_SHORT:   return new StoreCNode(ctl, mem, adr, adr_type, val, mo);
2342   case T_LONG:    return new StoreLNode(ctl, mem, adr, adr_type, val, mo);
2343   case T_FLOAT:   return new StoreFNode(ctl, mem, adr, adr_type, val, mo);
2344   case T_DOUBLE:  return new StoreDNode(ctl, mem, adr, adr_type, val, mo);
2345   case T_METADATA:
2346   case T_ADDRESS:
2347   case T_VALUETYPE:
2348   case T_OBJECT:
2349 #ifdef _LP64
2350     if (adr->bottom_type()->is_ptr_to_narrowoop()) {
2351       val = gvn.transform(new EncodePNode(val, val->bottom_type()->make_narrowoop()));
2352       return new StoreNNode(ctl, mem, adr, adr_type, val, mo);
2353     } else if (adr->bottom_type()->is_ptr_to_narrowklass() ||
2354                (UseCompressedClassPointers && val->bottom_type()->isa_klassptr() &&
2355                 adr->bottom_type()->isa_rawptr())) {
2356       val = gvn.transform(new EncodePKlassNode(val, val->bottom_type()->make_narrowklass()));
2357       return new StoreNKlassNode(ctl, mem, adr, adr_type, val, mo);
2358     }
2359 #endif
2360     {
2361       return new StorePNode(ctl, mem, adr, adr_type, val, mo);
2362     }
2363   }
2364   ShouldNotReachHere();
2365   return (StoreNode*)NULL;
2366 }
2367 
2368 StoreLNode* StoreLNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2369   bool require_atomic = true;
2370   return new StoreLNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2371 }
2372 
2373 StoreDNode* StoreDNode::make_atomic(Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, MemOrd mo) {
2374   bool require_atomic = true;
2375   return new StoreDNode(ctl, mem, adr, adr_type, val, mo, require_atomic);
2376 }
2377 
2378 
2379 //--------------------------bottom_type----------------------------------------
2380 const Type *StoreNode::bottom_type() const {
2381   return Type::MEMORY;
2382 }
2383 
2384 //------------------------------hash-------------------------------------------
2385 uint StoreNode::hash() const {
2386   // unroll addition of interesting fields
2387   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
2388 
2389   // Since they are not commoned, do not hash them:
2390   return NO_HASH;
2391 }
2392 
2393 //------------------------------Ideal------------------------------------------
2394 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
2395 // When a store immediately follows a relevant allocation/initialization,
2396 // try to capture it into the initialization, or hoist it above.
2397 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2398   Node* p = MemNode::Ideal_common(phase, can_reshape);
2399   if (p)  return (p == NodeSentinel) ? NULL : p;
2400 
2401   Node* mem     = in(MemNode::Memory);
2402   Node* address = in(MemNode::Address);
2403   // Back-to-back stores to same address?  Fold em up.  Generally
2404   // unsafe if I have intervening uses...  Also disallowed for StoreCM
2405   // since they must follow each StoreP operation.  Redundant StoreCMs
2406   // are eliminated just before matching in final_graph_reshape.
2407   {
2408     Node* st = mem;
2409     // If Store 'st' has more than one use, we cannot fold 'st' away.
2410     // For example, 'st' might be the final state at a conditional
2411     // return.  Or, 'st' might be used by some node which is live at
2412     // the same time 'st' is live, which might be unschedulable.  So,
2413     // require exactly ONE user until such time as we clone 'mem' for
2414     // each of 'mem's uses (thus making the exactly-1-user-rule hold
2415     // true).
2416     while (st->is_Store() && st->outcnt() == 1 && st->Opcode() != Op_StoreCM) {
2417       // Looking at a dead closed cycle of memory?
2418       assert(st != st->in(MemNode::Memory), "dead loop in StoreNode::Ideal");


2419       assert(Opcode() == st->Opcode() ||
2420              st->Opcode() == Op_StoreVector ||
2421              Opcode() == Op_StoreVector ||
2422              phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw ||
2423              (Opcode() == Op_StoreL && st->Opcode() == Op_StoreI) || // expanded ClearArrayNode
2424              (is_mismatched_access() || st->as_Store()->is_mismatched_access()),
2425              "no mismatched stores, except on raw memory: %s %s", NodeClassNames[Opcode()], NodeClassNames[st->Opcode()]);
2426 
2427       if (st->in(MemNode::Address)->eqv_uncast(address) &&
2428           st->as_Store()->memory_size() <= this->memory_size()) {
2429         Node* use = st->raw_out(0);
2430         phase->igvn_rehash_node_delayed(use);
2431         if (can_reshape) {
2432           use->set_req_X(MemNode::Memory, st->in(MemNode::Memory), phase->is_IterGVN());
2433         } else {
2434           // It's OK to do this in the parser, since DU info is always accurate,
2435           // and the parser always refers to nodes via SafePointNode maps.
2436           use->set_req(MemNode::Memory, st->in(MemNode::Memory));
2437         }
2438         return this;
2439       }
2440       st = st->in(MemNode::Memory);
2441     }
2442   }
2443 
2444 
2445   // Capture an unaliased, unconditional, simple store into an initializer.
2446   // Or, if it is independent of the allocation, hoist it above the allocation.
2447   if (ReduceFieldZeroing && /*can_reshape &&*/
2448       mem->is_Proj() && mem->in(0)->is_Initialize()) {
2449     InitializeNode* init = mem->in(0)->as_Initialize();
2450     intptr_t offset = init->can_capture_store(this, phase, can_reshape);
2451     if (offset > 0) {
2452       Node* moved = init->capture_store(this, offset, phase, can_reshape);
2453       // If the InitializeNode captured me, it made a raw copy of me,
2454       // and I need to disappear.
2455       if (moved != NULL) {
2456         // %%% hack to ensure that Ideal returns a new node:
2457         mem = MergeMemNode::make(mem);
2458         return mem;             // fold me away
2459       }
2460     }
2461   }
2462 
2463   return NULL;                  // No further progress
2464 }
2465 
2466 //------------------------------Value-----------------------------------------
2467 const Type* StoreNode::Value(PhaseGVN* phase) const {
2468   // Either input is TOP ==> the result is TOP
2469   const Type *t1 = phase->type( in(MemNode::Memory) );
2470   if( t1 == Type::TOP ) return Type::TOP;
2471   const Type *t2 = phase->type( in(MemNode::Address) );
2472   if( t2 == Type::TOP ) return Type::TOP;
2473   const Type *t3 = phase->type( in(MemNode::ValueIn) );
2474   if( t3 == Type::TOP ) return Type::TOP;
2475   return Type::MEMORY;
2476 }
2477 
2478 //------------------------------Identity---------------------------------------
2479 // Remove redundant stores:
2480 //   Store(m, p, Load(m, p)) changes to m.
2481 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
2482 Node* StoreNode::Identity(PhaseGVN* phase) {
2483   Node* mem = in(MemNode::Memory);
2484   Node* adr = in(MemNode::Address);
2485   Node* val = in(MemNode::ValueIn);
2486 
2487   // Load then Store?  Then the Store is useless
2488   if (val->is_Load() &&
2489       val->in(MemNode::Address)->eqv_uncast(adr) &&
2490       val->in(MemNode::Memory )->eqv_uncast(mem) &&
2491       val->as_Load()->store_Opcode() == Opcode()) {
2492     return mem;
2493   }
2494 
2495   // Two stores in a row of the same value?
2496   if (mem->is_Store() &&
2497       mem->in(MemNode::Address)->eqv_uncast(adr) &&
2498       mem->in(MemNode::ValueIn)->eqv_uncast(val) &&
2499       mem->Opcode() == Opcode()) {
2500     return mem;
2501   }
2502 
2503   // Store of zero anywhere into a freshly-allocated object?
2504   // Then the store is useless.
2505   // (It must already have been captured by the InitializeNode.)
2506   if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
2507     // a newly allocated object is already all-zeroes everywhere
2508     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
2509       return mem;
2510     }
2511 
2512     // the store may also apply to zero-bits in an earlier object
2513     Node* prev_mem = find_previous_store(phase);
2514     // Steps (a), (b):  Walk past independent stores to find an exact match.
2515     if (prev_mem != NULL) {
2516       Node* prev_val = can_see_stored_value(prev_mem, phase);
2517       if (prev_val != NULL && phase->eqv(prev_val, val)) {
2518         // prev_val and val might differ by a cast; it would be good
2519         // to keep the more informative of the two.
2520         return mem;
2521       }
2522     }
2523   }
2524 
2525   return this;
2526 }
2527 
2528 //------------------------------match_edge-------------------------------------
2529 // Do we Match on this edge index or not?  Match only memory & value
2530 uint StoreNode::match_edge(uint idx) const {
2531   return idx == MemNode::Address || idx == MemNode::ValueIn;
2532 }
2533 
2534 //------------------------------cmp--------------------------------------------
2535 // Do not common stores up together.  They generally have to be split
2536 // back up anyways, so do not bother.
2537 uint StoreNode::cmp( const Node &n ) const {
2538   return (&n == this);          // Always fail except on self
2539 }
2540 
2541 //------------------------------Ideal_masked_input-----------------------------
2542 // Check for a useless mask before a partial-word store
2543 // (StoreB ... (AndI valIn conIa) )
2544 // If (conIa & mask == mask) this simplifies to
2545 // (StoreB ... (valIn) )
2546 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
2547   Node *val = in(MemNode::ValueIn);
2548   if( val->Opcode() == Op_AndI ) {
2549     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2550     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
2551       set_req(MemNode::ValueIn, val->in(1));
2552       return this;
2553     }
2554   }
2555   return NULL;
2556 }
2557 
2558 
2559 //------------------------------Ideal_sign_extended_input----------------------
2560 // Check for useless sign-extension before a partial-word store
2561 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
2562 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
2563 // (StoreB ... (valIn) )
2564 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
2565   Node *val = in(MemNode::ValueIn);
2566   if( val->Opcode() == Op_RShiftI ) {
2567     const TypeInt *t = phase->type( val->in(2) )->isa_int();
2568     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
2569       Node *shl = val->in(1);
2570       if( shl->Opcode() == Op_LShiftI ) {
2571         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
2572         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
2573           set_req(MemNode::ValueIn, shl->in(1));
2574           return this;
2575         }
2576       }
2577     }
2578   }
2579   return NULL;
2580 }
2581 
2582 //------------------------------value_never_loaded-----------------------------------
2583 // Determine whether there are any possible loads of the value stored.
2584 // For simplicity, we actually check if there are any loads from the
2585 // address stored to, not just for loads of the value stored by this node.
2586 //
2587 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
2588   Node *adr = in(Address);
2589   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
2590   if (adr_oop == NULL)
2591     return false;
2592   if (!adr_oop->is_known_instance_field())
2593     return false; // if not a distinct instance, there may be aliases of the address
2594   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
2595     Node *use = adr->fast_out(i);
2596     if (use->is_Load() || use->is_LoadStore()) {
2597       return false;
2598     }
2599   }
2600   return true;
2601 }
2602 
2603 //=============================================================================
2604 //------------------------------Ideal------------------------------------------
2605 // If the store is from an AND mask that leaves the low bits untouched, then
2606 // we can skip the AND operation.  If the store is from a sign-extension
2607 // (a left shift, then right shift) we can skip both.
2608 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
2609   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
2610   if( progress != NULL ) return progress;
2611 
2612   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
2613   if( progress != NULL ) return progress;
2614 
2615   // Finally check the default case
2616   return StoreNode::Ideal(phase, can_reshape);
2617 }
2618 
2619 //=============================================================================
2620 //------------------------------Ideal------------------------------------------
2621 // If the store is from an AND mask that leaves the low bits untouched, then
2622 // we can skip the AND operation
2623 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
2624   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
2625   if( progress != NULL ) return progress;
2626 
2627   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
2628   if( progress != NULL ) return progress;
2629 
2630   // Finally check the default case
2631   return StoreNode::Ideal(phase, can_reshape);
2632 }
2633 
2634 //=============================================================================
2635 //------------------------------Identity---------------------------------------
2636 Node* StoreCMNode::Identity(PhaseGVN* phase) {
2637   // No need to card mark when storing a null ptr
2638   Node* my_store = in(MemNode::OopStore);
2639   if (my_store->is_Store()) {
2640     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
2641     if( t1 == TypePtr::NULL_PTR ) {
2642       return in(MemNode::Memory);
2643     }
2644   }
2645   return this;
2646 }
2647 
2648 //=============================================================================
2649 //------------------------------Ideal---------------------------------------
2650 Node *StoreCMNode::Ideal(PhaseGVN *phase, bool can_reshape){
2651   Node* progress = StoreNode::Ideal(phase, can_reshape);
2652   if (progress != NULL) return progress;
2653 
2654   Node* my_store = in(MemNode::OopStore);
2655   if (my_store->is_MergeMem()) {
2656     Node* mem = my_store->as_MergeMem()->memory_at(oop_alias_idx());
2657     set_req(MemNode::OopStore, mem);
2658     return this;
2659   }
2660 
2661   return NULL;
2662 }
2663 
2664 //------------------------------Value-----------------------------------------
2665 const Type* StoreCMNode::Value(PhaseGVN* phase) const {
2666   // Either input is TOP ==> the result is TOP
2667   const Type *t = phase->type( in(MemNode::Memory) );
2668   if( t == Type::TOP ) return Type::TOP;
2669   t = phase->type( in(MemNode::Address) );
2670   if( t == Type::TOP ) return Type::TOP;
2671   t = phase->type( in(MemNode::ValueIn) );
2672   if( t == Type::TOP ) return Type::TOP;
2673   // If extra input is TOP ==> the result is TOP
2674   t = phase->type( in(MemNode::OopStore) );
2675   if( t == Type::TOP ) return Type::TOP;
2676 
2677   return StoreNode::Value( phase );
2678 }
2679 
2680 
2681 //=============================================================================
2682 //----------------------------------SCMemProjNode------------------------------
2683 const Type* SCMemProjNode::Value(PhaseGVN* phase) const
2684 {
2685   return bottom_type();
2686 }
2687 
2688 //=============================================================================
2689 //----------------------------------LoadStoreNode------------------------------
2690 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, const TypePtr* at, const Type* rt, uint required )
2691   : Node(required),
2692     _type(rt),
2693     _adr_type(at)
2694 {
2695   init_req(MemNode::Control, c  );
2696   init_req(MemNode::Memory , mem);
2697   init_req(MemNode::Address, adr);
2698   init_req(MemNode::ValueIn, val);
2699   init_class_id(Class_LoadStore);
2700 }
2701 
2702 uint LoadStoreNode::ideal_reg() const {
2703   return _type->ideal_reg();
2704 }
2705 
2706 bool LoadStoreNode::result_not_used() const {
2707   for( DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++ ) {
2708     Node *x = fast_out(i);
2709     if (x->Opcode() == Op_SCMemProj) continue;
2710     return false;
2711   }
2712   return true;
2713 }
2714 
2715 uint LoadStoreNode::size_of() const { return sizeof(*this); }
2716 
2717 //=============================================================================
2718 //----------------------------------LoadStoreConditionalNode--------------------
2719 LoadStoreConditionalNode::LoadStoreConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : LoadStoreNode(c, mem, adr, val, NULL, TypeInt::BOOL, 5) {
2720   init_req(ExpectedIn, ex );
2721 }
2722 
2723 //=============================================================================
2724 //-------------------------------adr_type--------------------------------------
2725 const TypePtr* ClearArrayNode::adr_type() const {
2726   Node *adr = in(3);
2727   if (adr == NULL)  return NULL; // node is dead
2728   return MemNode::calculate_adr_type(adr->bottom_type());
2729 }
2730 
2731 //------------------------------match_edge-------------------------------------
2732 // Do we Match on this edge index or not?  Do not match memory
2733 uint ClearArrayNode::match_edge(uint idx) const {
2734   return idx > 1;
2735 }
2736 
2737 //------------------------------Identity---------------------------------------
2738 // Clearing a zero length array does nothing
2739 Node* ClearArrayNode::Identity(PhaseGVN* phase) {
2740   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
2741 }
2742 
2743 //------------------------------Idealize---------------------------------------
2744 // Clearing a short array is faster with stores
2745 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){
2746   const int unit = BytesPerLong;
2747   const TypeX* t = phase->type(in(2))->isa_intptr_t();
2748   if (!t)  return NULL;
2749   if (!t->is_con())  return NULL;
2750   intptr_t raw_count = t->get_con();
2751   intptr_t size = raw_count;
2752   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
2753   // Clearing nothing uses the Identity call.
2754   // Negative clears are possible on dead ClearArrays
2755   // (see jck test stmt114.stmt11402.val).
2756   if (size <= 0 || size % unit != 0)  return NULL;
2757   intptr_t count = size / unit;
2758   // Length too long; use fast hardware clear
2759   if (size > Matcher::init_array_short_size)  return NULL;
2760   Node *mem = in(1);
2761   if( phase->type(mem)==Type::TOP ) return NULL;
2762   Node *adr = in(3);
2763   const Type* at = phase->type(adr);
2764   if( at==Type::TOP ) return NULL;
2765   const TypePtr* atp = at->isa_ptr();
2766   // adjust atp to be the correct array element address type
2767   if (atp == NULL)  atp = TypePtr::BOTTOM;
2768   else              atp = atp->add_offset(Type::OffsetBot);
2769   // Get base for derived pointer purposes
2770   if( adr->Opcode() != Op_AddP ) Unimplemented();
2771   Node *base = adr->in(1);
2772 
2773   Node *zero = phase->makecon(TypeLong::ZERO);
2774   Node *off  = phase->MakeConX(BytesPerLong);
2775   mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2776   count--;
2777   while( count-- ) {
2778     mem = phase->transform(mem);
2779     adr = phase->transform(new AddPNode(base,adr,off));
2780     mem = new StoreLNode(in(0),mem,adr,atp,zero,MemNode::unordered,false);
2781   }
2782   return mem;
2783 }
2784 
2785 //----------------------------step_through----------------------------------
2786 // Return allocation input memory edge if it is different instance
2787 // or itself if it is the one we are looking for.
2788 bool ClearArrayNode::step_through(Node** np, uint instance_id, PhaseTransform* phase) {
2789   Node* n = *np;
2790   assert(n->is_ClearArray(), "sanity");
2791   intptr_t offset;
2792   AllocateNode* alloc = AllocateNode::Ideal_allocation(n->in(3), phase, offset);
2793   // This method is called only before Allocate nodes are expanded
2794   // during macro nodes expansion. Before that ClearArray nodes are
2795   // only generated in PhaseMacroExpand::generate_arraycopy() (before
2796   // Allocate nodes are expanded) which follows allocations.
2797   assert(alloc != NULL, "should have allocation");
2798   if (alloc->_idx == instance_id) {
2799     // Can not bypass initialization of the instance we are looking for.
2800     return false;
2801   }
2802   // Otherwise skip it.
2803   InitializeNode* init = alloc->initialization();
2804   if (init != NULL)
2805     *np = init->in(TypeFunc::Memory);
2806   else
2807     *np = alloc->in(TypeFunc::Memory);
2808   return true;
2809 }
2810 
2811 //----------------------------clear_memory-------------------------------------
2812 // Generate code to initialize object storage to zero.
2813 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2814                                    intptr_t start_offset,
2815                                    Node* end_offset,
2816                                    PhaseGVN* phase) {
2817   intptr_t offset = start_offset;
2818 
2819   int unit = BytesPerLong;
2820   if ((offset % unit) != 0) {
2821     Node* adr = new AddPNode(dest, dest, phase->MakeConX(offset));
2822     adr = phase->transform(adr);
2823     const TypePtr* atp = TypeRawPtr::BOTTOM;
2824     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2825     mem = phase->transform(mem);
2826     offset += BytesPerInt;
2827   }
2828   assert((offset % unit) == 0, "");
2829 
2830   // Initialize the remaining stuff, if any, with a ClearArray.
2831   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
2832 }
2833 
2834 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2835                                    Node* start_offset,
2836                                    Node* end_offset,
2837                                    PhaseGVN* phase) {
2838   if (start_offset == end_offset) {
2839     // nothing to do
2840     return mem;
2841   }
2842 
2843   int unit = BytesPerLong;
2844   Node* zbase = start_offset;
2845   Node* zend  = end_offset;
2846 
2847   // Scale to the unit required by the CPU:
2848   if (!Matcher::init_array_count_is_in_bytes) {
2849     Node* shift = phase->intcon(exact_log2(unit));
2850     zbase = phase->transform(new URShiftXNode(zbase, shift) );
2851     zend  = phase->transform(new URShiftXNode(zend,  shift) );
2852   }
2853 
2854   // Bulk clear double-words
2855   Node* zsize = phase->transform(new SubXNode(zend, zbase) );
2856   Node* adr = phase->transform(new AddPNode(dest, dest, start_offset) );
2857   mem = new ClearArrayNode(ctl, mem, zsize, adr);
2858   return phase->transform(mem);
2859 }
2860 
2861 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
2862                                    intptr_t start_offset,
2863                                    intptr_t end_offset,
2864                                    PhaseGVN* phase) {
2865   if (start_offset == end_offset) {
2866     // nothing to do
2867     return mem;
2868   }
2869 
2870   assert((end_offset % BytesPerInt) == 0, "odd end offset");
2871   intptr_t done_offset = end_offset;
2872   if ((done_offset % BytesPerLong) != 0) {
2873     done_offset -= BytesPerInt;
2874   }
2875   if (done_offset > start_offset) {
2876     mem = clear_memory(ctl, mem, dest,
2877                        start_offset, phase->MakeConX(done_offset), phase);
2878   }
2879   if (done_offset < end_offset) { // emit the final 32-bit store
2880     Node* adr = new AddPNode(dest, dest, phase->MakeConX(done_offset));
2881     adr = phase->transform(adr);
2882     const TypePtr* atp = TypeRawPtr::BOTTOM;
2883     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT, MemNode::unordered);
2884     mem = phase->transform(mem);
2885     done_offset += BytesPerInt;
2886   }
2887   assert(done_offset == end_offset, "");
2888   return mem;
2889 }
2890 
2891 //=============================================================================
2892 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
2893   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
2894     _adr_type(C->get_adr_type(alias_idx))
2895 {
2896   init_class_id(Class_MemBar);
2897   Node* top = C->top();
2898   init_req(TypeFunc::I_O,top);
2899   init_req(TypeFunc::FramePtr,top);
2900   init_req(TypeFunc::ReturnAdr,top);
2901   if (precedent != NULL)
2902     init_req(TypeFunc::Parms, precedent);
2903 }
2904 
2905 //------------------------------cmp--------------------------------------------
2906 uint MemBarNode::hash() const { return NO_HASH; }
2907 uint MemBarNode::cmp( const Node &n ) const {
2908   return (&n == this);          // Always fail except on self
2909 }
2910 
2911 //------------------------------make-------------------------------------------
2912 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
2913   switch (opcode) {
2914   case Op_MemBarAcquire:     return new MemBarAcquireNode(C, atp, pn);
2915   case Op_LoadFence:         return new LoadFenceNode(C, atp, pn);
2916   case Op_MemBarRelease:     return new MemBarReleaseNode(C, atp, pn);
2917   case Op_StoreFence:        return new StoreFenceNode(C, atp, pn);
2918   case Op_MemBarAcquireLock: return new MemBarAcquireLockNode(C, atp, pn);
2919   case Op_MemBarReleaseLock: return new MemBarReleaseLockNode(C, atp, pn);
2920   case Op_MemBarVolatile:    return new MemBarVolatileNode(C, atp, pn);
2921   case Op_MemBarCPUOrder:    return new MemBarCPUOrderNode(C, atp, pn);
2922   case Op_Initialize:        return new InitializeNode(C, atp, pn);
2923   case Op_MemBarStoreStore:  return new MemBarStoreStoreNode(C, atp, pn);
2924   default: ShouldNotReachHere(); return NULL;
2925   }
2926 }
2927 
2928 //------------------------------Ideal------------------------------------------
2929 // Return a node which is more "ideal" than the current node.  Strip out
2930 // control copies
2931 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2932   if (remove_dead_region(phase, can_reshape)) return this;
2933   // Don't bother trying to transform a dead node
2934   if (in(0) && in(0)->is_top()) {
2935     return NULL;
2936   }
2937 
2938   bool progress = false;
2939   // Eliminate volatile MemBars for scalar replaced objects.
2940   if (can_reshape && req() == (Precedent+1)) {
2941     bool eliminate = false;
2942     int opc = Opcode();
2943     if ((opc == Op_MemBarAcquire || opc == Op_MemBarVolatile)) {
2944       // Volatile field loads and stores.
2945       Node* my_mem = in(MemBarNode::Precedent);
2946       // The MembarAquire may keep an unused LoadNode alive through the Precedent edge
2947       if ((my_mem != NULL) && (opc == Op_MemBarAcquire) && (my_mem->outcnt() == 1)) {
2948         // if the Precedent is a decodeN and its input (a Load) is used at more than one place,
2949         // replace this Precedent (decodeN) with the Load instead.
2950         if ((my_mem->Opcode() == Op_DecodeN) && (my_mem->in(1)->outcnt() > 1))  {
2951           Node* load_node = my_mem->in(1);
2952           set_req(MemBarNode::Precedent, load_node);
2953           phase->is_IterGVN()->_worklist.push(my_mem);
2954           my_mem = load_node;
2955         } else {
2956           assert(my_mem->unique_out() == this, "sanity");
2957           del_req(Precedent);
2958           phase->is_IterGVN()->_worklist.push(my_mem); // remove dead node later
2959           my_mem = NULL;
2960         }
2961         progress = true;
2962       }
2963       if (my_mem != NULL && my_mem->is_Mem()) {
2964         const TypeOopPtr* t_oop = my_mem->in(MemNode::Address)->bottom_type()->isa_oopptr();
2965         // Check for scalar replaced object reference.
2966         if( t_oop != NULL && t_oop->is_known_instance_field() &&
2967             t_oop->offset() != Type::OffsetBot &&
2968             t_oop->offset() != Type::OffsetTop) {
2969           eliminate = true;
2970         }
2971       }
2972     } else if (opc == Op_MemBarRelease) {
2973       // Final field stores.
2974       Node* alloc = AllocateNode::Ideal_allocation(in(MemBarNode::Precedent), phase);
2975       if ((alloc != NULL) && alloc->is_Allocate() &&
2976           alloc->as_Allocate()->does_not_escape_thread()) {
2977         // The allocated object does not escape.
2978         eliminate = true;
2979       }
2980     }
2981     if (eliminate) {
2982       // Replace MemBar projections by its inputs.
2983       PhaseIterGVN* igvn = phase->is_IterGVN();
2984       igvn->replace_node(proj_out(TypeFunc::Memory), in(TypeFunc::Memory));
2985       igvn->replace_node(proj_out(TypeFunc::Control), in(TypeFunc::Control));
2986       // Must return either the original node (now dead) or a new node
2987       // (Do not return a top here, since that would break the uniqueness of top.)
2988       return new ConINode(TypeInt::ZERO);
2989     }
2990   }
2991   return progress ? this : NULL;
2992 }
2993 
2994 //------------------------------Value------------------------------------------
2995 const Type* MemBarNode::Value(PhaseGVN* phase) const {
2996   if( !in(0) ) return Type::TOP;
2997   if( phase->type(in(0)) == Type::TOP )
2998     return Type::TOP;
2999   return TypeTuple::MEMBAR;
3000 }
3001 
3002 //------------------------------match------------------------------------------
3003 // Construct projections for memory.
3004 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
3005   switch (proj->_con) {
3006   case TypeFunc::Control:
3007   case TypeFunc::Memory:
3008     return new MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
3009   }
3010   ShouldNotReachHere();
3011   return NULL;
3012 }
3013 
3014 //===========================InitializeNode====================================
3015 // SUMMARY:
3016 // This node acts as a memory barrier on raw memory, after some raw stores.
3017 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
3018 // The Initialize can 'capture' suitably constrained stores as raw inits.
3019 // It can coalesce related raw stores into larger units (called 'tiles').
3020 // It can avoid zeroing new storage for memory units which have raw inits.
3021 // At macro-expansion, it is marked 'complete', and does not optimize further.
3022 //
3023 // EXAMPLE:
3024 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
3025 //   ctl = incoming control; mem* = incoming memory
3026 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
3027 // First allocate uninitialized memory and fill in the header:
3028 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
3029 //   ctl := alloc.Control; mem* := alloc.Memory*
3030 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
3031 // Then initialize to zero the non-header parts of the raw memory block:
3032 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
3033 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
3034 // After the initialize node executes, the object is ready for service:
3035 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
3036 // Suppose its body is immediately initialized as {1,2}:
3037 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3038 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3039 //   mem.SLICE(#short[*]) := store2
3040 //
3041 // DETAILS:
3042 // An InitializeNode collects and isolates object initialization after
3043 // an AllocateNode and before the next possible safepoint.  As a
3044 // memory barrier (MemBarNode), it keeps critical stores from drifting
3045 // down past any safepoint or any publication of the allocation.
3046 // Before this barrier, a newly-allocated object may have uninitialized bits.
3047 // After this barrier, it may be treated as a real oop, and GC is allowed.
3048 //
3049 // The semantics of the InitializeNode include an implicit zeroing of
3050 // the new object from object header to the end of the object.
3051 // (The object header and end are determined by the AllocateNode.)
3052 //
3053 // Certain stores may be added as direct inputs to the InitializeNode.
3054 // These stores must update raw memory, and they must be to addresses
3055 // derived from the raw address produced by AllocateNode, and with
3056 // a constant offset.  They must be ordered by increasing offset.
3057 // The first one is at in(RawStores), the last at in(req()-1).
3058 // Unlike most memory operations, they are not linked in a chain,
3059 // but are displayed in parallel as users of the rawmem output of
3060 // the allocation.
3061 //
3062 // (See comments in InitializeNode::capture_store, which continue
3063 // the example given above.)
3064 //
3065 // When the associated Allocate is macro-expanded, the InitializeNode
3066 // may be rewritten to optimize collected stores.  A ClearArrayNode
3067 // may also be created at that point to represent any required zeroing.
3068 // The InitializeNode is then marked 'complete', prohibiting further
3069 // capturing of nearby memory operations.
3070 //
3071 // During macro-expansion, all captured initializations which store
3072 // constant values of 32 bits or smaller are coalesced (if advantageous)
3073 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
3074 // initialized in fewer memory operations.  Memory words which are
3075 // covered by neither tiles nor non-constant stores are pre-zeroed
3076 // by explicit stores of zero.  (The code shape happens to do all
3077 // zeroing first, then all other stores, with both sequences occurring
3078 // in order of ascending offsets.)
3079 //
3080 // Alternatively, code may be inserted between an AllocateNode and its
3081 // InitializeNode, to perform arbitrary initialization of the new object.
3082 // E.g., the object copying intrinsics insert complex data transfers here.
3083 // The initialization must then be marked as 'complete' disable the
3084 // built-in zeroing semantics and the collection of initializing stores.
3085 //
3086 // While an InitializeNode is incomplete, reads from the memory state
3087 // produced by it are optimizable if they match the control edge and
3088 // new oop address associated with the allocation/initialization.
3089 // They return a stored value (if the offset matches) or else zero.
3090 // A write to the memory state, if it matches control and address,
3091 // and if it is to a constant offset, may be 'captured' by the
3092 // InitializeNode.  It is cloned as a raw memory operation and rewired
3093 // inside the initialization, to the raw oop produced by the allocation.
3094 // Operations on addresses which are provably distinct (e.g., to
3095 // other AllocateNodes) are allowed to bypass the initialization.
3096 //
3097 // The effect of all this is to consolidate object initialization
3098 // (both arrays and non-arrays, both piecewise and bulk) into a
3099 // single location, where it can be optimized as a unit.
3100 //
3101 // Only stores with an offset less than TrackedInitializationLimit words
3102 // will be considered for capture by an InitializeNode.  This puts a
3103 // reasonable limit on the complexity of optimized initializations.
3104 
3105 //---------------------------InitializeNode------------------------------------
3106 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
3107   : _is_complete(Incomplete), _does_not_escape(false),
3108     MemBarNode(C, adr_type, rawoop)
3109 {
3110   init_class_id(Class_Initialize);
3111 
3112   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
3113   assert(in(RawAddress) == rawoop, "proper init");
3114   // Note:  allocation() can be NULL, for secondary initialization barriers
3115 }
3116 
3117 // Since this node is not matched, it will be processed by the
3118 // register allocator.  Declare that there are no constraints
3119 // on the allocation of the RawAddress edge.
3120 const RegMask &InitializeNode::in_RegMask(uint idx) const {
3121   // This edge should be set to top, by the set_complete.  But be conservative.
3122   if (idx == InitializeNode::RawAddress)
3123     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
3124   return RegMask::Empty;
3125 }
3126 
3127 Node* InitializeNode::memory(uint alias_idx) {
3128   Node* mem = in(Memory);
3129   if (mem->is_MergeMem()) {
3130     return mem->as_MergeMem()->memory_at(alias_idx);
3131   } else {
3132     // incoming raw memory is not split
3133     return mem;
3134   }
3135 }
3136 
3137 bool InitializeNode::is_non_zero() {
3138   if (is_complete())  return false;
3139   remove_extra_zeroes();
3140   return (req() > RawStores);
3141 }
3142 
3143 void InitializeNode::set_complete(PhaseGVN* phase) {
3144   assert(!is_complete(), "caller responsibility");
3145   _is_complete = Complete;
3146 
3147   // After this node is complete, it contains a bunch of
3148   // raw-memory initializations.  There is no need for
3149   // it to have anything to do with non-raw memory effects.
3150   // Therefore, tell all non-raw users to re-optimize themselves,
3151   // after skipping the memory effects of this initialization.
3152   PhaseIterGVN* igvn = phase->is_IterGVN();
3153   if (igvn)  igvn->add_users_to_worklist(this);
3154 }
3155 
3156 // convenience function
3157 // return false if the init contains any stores already
3158 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
3159   InitializeNode* init = initialization();
3160   if (init == NULL || init->is_complete())  return false;
3161   init->remove_extra_zeroes();
3162   // for now, if this allocation has already collected any inits, bail:
3163   if (init->is_non_zero())  return false;
3164   init->set_complete(phase);
3165   return true;
3166 }
3167 
3168 void InitializeNode::remove_extra_zeroes() {
3169   if (req() == RawStores)  return;
3170   Node* zmem = zero_memory();
3171   uint fill = RawStores;
3172   for (uint i = fill; i < req(); i++) {
3173     Node* n = in(i);
3174     if (n->is_top() || n == zmem)  continue;  // skip
3175     if (fill < i)  set_req(fill, n);          // compact
3176     ++fill;
3177   }
3178   // delete any empty spaces created:
3179   while (fill < req()) {
3180     del_req(fill);
3181   }
3182 }
3183 
3184 // Helper for remembering which stores go with which offsets.
3185 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
3186   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
3187   intptr_t offset = -1;
3188   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
3189                                                phase, offset);
3190   if (base == NULL)     return -1;  // something is dead,
3191   if (offset < 0)       return -1;  //        dead, dead
3192   return offset;
3193 }
3194 
3195 // Helper for proving that an initialization expression is
3196 // "simple enough" to be folded into an object initialization.
3197 // Attempts to prove that a store's initial value 'n' can be captured
3198 // within the initialization without creating a vicious cycle, such as:
3199 //     { Foo p = new Foo(); p.next = p; }
3200 // True for constants and parameters and small combinations thereof.
3201 bool InitializeNode::detect_init_independence(Node* n, int& count) {
3202   if (n == NULL)      return true;   // (can this really happen?)
3203   if (n->is_Proj())   n = n->in(0);
3204   if (n == this)      return false;  // found a cycle
3205   if (n->is_Con())    return true;
3206   if (n->is_Start())  return true;   // params, etc., are OK
3207   if (n->is_Root())   return true;   // even better
3208 
3209   Node* ctl = n->in(0);
3210   if (ctl != NULL && !ctl->is_top()) {
3211     if (ctl->is_Proj())  ctl = ctl->in(0);
3212     if (ctl == this)  return false;
3213 
3214     // If we already know that the enclosing memory op is pinned right after
3215     // the init, then any control flow that the store has picked up
3216     // must have preceded the init, or else be equal to the init.
3217     // Even after loop optimizations (which might change control edges)
3218     // a store is never pinned *before* the availability of its inputs.
3219     if (!MemNode::all_controls_dominate(n, this))
3220       return false;                  // failed to prove a good control
3221   }
3222 
3223   // Check data edges for possible dependencies on 'this'.
3224   if ((count += 1) > 20)  return false;  // complexity limit
3225   for (uint i = 1; i < n->req(); i++) {
3226     Node* m = n->in(i);
3227     if (m == NULL || m == n || m->is_top())  continue;
3228     uint first_i = n->find_edge(m);
3229     if (i != first_i)  continue;  // process duplicate edge just once
3230     if (!detect_init_independence(m, count)) {
3231       return false;
3232     }
3233   }
3234 
3235   return true;
3236 }
3237 
3238 // Here are all the checks a Store must pass before it can be moved into
3239 // an initialization.  Returns zero if a check fails.
3240 // On success, returns the (constant) offset to which the store applies,
3241 // within the initialized memory.
3242 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase, bool can_reshape) {
3243   const int FAIL = 0;
3244   if (st->is_unaligned_access()) {
3245     return FAIL;
3246   }
3247   if (st->req() != MemNode::ValueIn + 1)
3248     return FAIL;                // an inscrutable StoreNode (card mark?)
3249   Node* ctl = st->in(MemNode::Control);
3250   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
3251     return FAIL;                // must be unconditional after the initialization
3252   Node* mem = st->in(MemNode::Memory);
3253   if (!(mem->is_Proj() && mem->in(0) == this))
3254     return FAIL;                // must not be preceded by other stores
3255   Node* adr = st->in(MemNode::Address);
3256   intptr_t offset;
3257   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
3258   if (alloc == NULL)
3259     return FAIL;                // inscrutable address
3260   if (alloc != allocation())
3261     return FAIL;                // wrong allocation!  (store needs to float up)
3262   Node* val = st->in(MemNode::ValueIn);
3263   int complexity_count = 0;
3264   if (!detect_init_independence(val, complexity_count))
3265     return FAIL;                // stored value must be 'simple enough'
3266 
3267   // The Store can be captured only if nothing after the allocation
3268   // and before the Store is using the memory location that the store
3269   // overwrites.
3270   bool failed = false;
3271   // If is_complete_with_arraycopy() is true the shape of the graph is
3272   // well defined and is safe so no need for extra checks.
3273   if (!is_complete_with_arraycopy()) {
3274     // We are going to look at each use of the memory state following
3275     // the allocation to make sure nothing reads the memory that the
3276     // Store writes.
3277     const TypePtr* t_adr = phase->type(adr)->isa_ptr();
3278     int alias_idx = phase->C->get_alias_index(t_adr);
3279     ResourceMark rm;
3280     Unique_Node_List mems;
3281     mems.push(mem);
3282     Node* unique_merge = NULL;
3283     for (uint next = 0; next < mems.size(); ++next) {
3284       Node *m  = mems.at(next);
3285       for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3286         Node *n = m->fast_out(j);
3287         if (n->outcnt() == 0) {
3288           continue;
3289         }
3290         if (n == st) {
3291           continue;
3292         } else if (n->in(0) != NULL && n->in(0) != ctl) {
3293           // If the control of this use is different from the control
3294           // of the Store which is right after the InitializeNode then
3295           // this node cannot be between the InitializeNode and the
3296           // Store.
3297           continue;
3298         } else if (n->is_MergeMem()) {
3299           if (n->as_MergeMem()->memory_at(alias_idx) == m) {
3300             // We can hit a MergeMemNode (that will likely go away
3301             // later) that is a direct use of the memory state
3302             // following the InitializeNode on the same slice as the
3303             // store node that we'd like to capture. We need to check
3304             // the uses of the MergeMemNode.
3305             mems.push(n);
3306           }
3307         } else if (n->is_Mem()) {
3308           Node* other_adr = n->in(MemNode::Address);
3309           if (other_adr == adr) {
3310             failed = true;
3311             break;
3312           } else {
3313             const TypePtr* other_t_adr = phase->type(other_adr)->isa_ptr();
3314             if (other_t_adr != NULL) {
3315               int other_alias_idx = phase->C->get_alias_index(other_t_adr);
3316               if (other_alias_idx == alias_idx) {
3317                 // A load from the same memory slice as the store right
3318                 // after the InitializeNode. We check the control of the
3319                 // object/array that is loaded from. If it's the same as
3320                 // the store control then we cannot capture the store.
3321                 assert(!n->is_Store(), "2 stores to same slice on same control?");
3322                 Node* base = other_adr;
3323                 assert(base->is_AddP(), "should be addp but is %s", base->Name());
3324                 base = base->in(AddPNode::Base);
3325                 if (base != NULL) {
3326                   base = base->uncast();
3327                   if (base->is_Proj() && base->in(0) == alloc) {
3328                     failed = true;
3329                     break;
3330                   }
3331                 }
3332               }
3333             }
3334           }
3335         } else {
3336           failed = true;
3337           break;
3338         }
3339       }
3340     }
3341   }
3342   if (failed) {
3343     if (!can_reshape) {
3344       // We decided we couldn't capture the store during parsing. We
3345       // should try again during the next IGVN once the graph is
3346       // cleaner.
3347       phase->C->record_for_igvn(st);
3348     }
3349     return FAIL;
3350   }
3351 
3352   return offset;                // success
3353 }
3354 
3355 // Find the captured store in(i) which corresponds to the range
3356 // [start..start+size) in the initialized object.
3357 // If there is one, return its index i.  If there isn't, return the
3358 // negative of the index where it should be inserted.
3359 // Return 0 if the queried range overlaps an initialization boundary
3360 // or if dead code is encountered.
3361 // If size_in_bytes is zero, do not bother with overlap checks.
3362 int InitializeNode::captured_store_insertion_point(intptr_t start,
3363                                                    int size_in_bytes,
3364                                                    PhaseTransform* phase) {
3365   const int FAIL = 0, MAX_STORE = BytesPerLong;
3366 
3367   if (is_complete())
3368     return FAIL;                // arraycopy got here first; punt
3369 
3370   assert(allocation() != NULL, "must be present");
3371 
3372   // no negatives, no header fields:
3373   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
3374 
3375   // after a certain size, we bail out on tracking all the stores:
3376   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3377   if (start >= ti_limit)  return FAIL;
3378 
3379   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
3380     if (i >= limit)  return -(int)i; // not found; here is where to put it
3381 
3382     Node*    st     = in(i);
3383     intptr_t st_off = get_store_offset(st, phase);
3384     if (st_off < 0) {
3385       if (st != zero_memory()) {
3386         return FAIL;            // bail out if there is dead garbage
3387       }
3388     } else if (st_off > start) {
3389       // ...we are done, since stores are ordered
3390       if (st_off < start + size_in_bytes) {
3391         return FAIL;            // the next store overlaps
3392       }
3393       return -(int)i;           // not found; here is where to put it
3394     } else if (st_off < start) {
3395       if (size_in_bytes != 0 &&
3396           start < st_off + MAX_STORE &&
3397           start < st_off + st->as_Store()->memory_size()) {
3398         return FAIL;            // the previous store overlaps
3399       }
3400     } else {
3401       if (size_in_bytes != 0 &&
3402           st->as_Store()->memory_size() != size_in_bytes) {
3403         return FAIL;            // mismatched store size
3404       }
3405       return i;
3406     }
3407 
3408     ++i;
3409   }
3410 }
3411 
3412 // Look for a captured store which initializes at the offset 'start'
3413 // with the given size.  If there is no such store, and no other
3414 // initialization interferes, then return zero_memory (the memory
3415 // projection of the AllocateNode).
3416 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
3417                                           PhaseTransform* phase) {
3418   assert(stores_are_sane(phase), "");
3419   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3420   if (i == 0) {
3421     return NULL;                // something is dead
3422   } else if (i < 0) {
3423     return zero_memory();       // just primordial zero bits here
3424   } else {
3425     Node* st = in(i);           // here is the store at this position
3426     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
3427     return st;
3428   }
3429 }
3430 
3431 // Create, as a raw pointer, an address within my new object at 'offset'.
3432 Node* InitializeNode::make_raw_address(intptr_t offset,
3433                                        PhaseTransform* phase) {
3434   Node* addr = in(RawAddress);
3435   if (offset != 0) {
3436     Compile* C = phase->C;
3437     addr = phase->transform( new AddPNode(C->top(), addr,
3438                                                  phase->MakeConX(offset)) );
3439   }
3440   return addr;
3441 }
3442 
3443 // Clone the given store, converting it into a raw store
3444 // initializing a field or element of my new object.
3445 // Caller is responsible for retiring the original store,
3446 // with subsume_node or the like.
3447 //
3448 // From the example above InitializeNode::InitializeNode,
3449 // here are the old stores to be captured:
3450 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
3451 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
3452 //
3453 // Here is the changed code; note the extra edges on init:
3454 //   alloc = (Allocate ...)
3455 //   rawoop = alloc.RawAddress
3456 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
3457 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
3458 //   init = (Initialize alloc.Control alloc.Memory rawoop
3459 //                      rawstore1 rawstore2)
3460 //
3461 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
3462                                     PhaseTransform* phase, bool can_reshape) {
3463   assert(stores_are_sane(phase), "");
3464 
3465   if (start < 0)  return NULL;
3466   assert(can_capture_store(st, phase, can_reshape) == start, "sanity");
3467 
3468   Compile* C = phase->C;
3469   int size_in_bytes = st->memory_size();
3470   int i = captured_store_insertion_point(start, size_in_bytes, phase);
3471   if (i == 0)  return NULL;     // bail out
3472   Node* prev_mem = NULL;        // raw memory for the captured store
3473   if (i > 0) {
3474     prev_mem = in(i);           // there is a pre-existing store under this one
3475     set_req(i, C->top());       // temporarily disconnect it
3476     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
3477   } else {
3478     i = -i;                     // no pre-existing store
3479     prev_mem = zero_memory();   // a slice of the newly allocated object
3480     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
3481       set_req(--i, C->top());   // reuse this edge; it has been folded away
3482     else
3483       ins_req(i, C->top());     // build a new edge
3484   }
3485   Node* new_st = st->clone();
3486   new_st->set_req(MemNode::Control, in(Control));
3487   new_st->set_req(MemNode::Memory,  prev_mem);
3488   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
3489   new_st = phase->transform(new_st);
3490 
3491   // At this point, new_st might have swallowed a pre-existing store
3492   // at the same offset, or perhaps new_st might have disappeared,
3493   // if it redundantly stored the same value (or zero to fresh memory).
3494 
3495   // In any case, wire it in:
3496   phase->igvn_rehash_node_delayed(this);
3497   set_req(i, new_st);
3498 
3499   // The caller may now kill the old guy.
3500   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
3501   assert(check_st == new_st || check_st == NULL, "must be findable");
3502   assert(!is_complete(), "");
3503   return new_st;
3504 }
3505 
3506 static bool store_constant(jlong* tiles, int num_tiles,
3507                            intptr_t st_off, int st_size,
3508                            jlong con) {
3509   if ((st_off & (st_size-1)) != 0)
3510     return false;               // strange store offset (assume size==2**N)
3511   address addr = (address)tiles + st_off;
3512   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
3513   switch (st_size) {
3514   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
3515   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
3516   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
3517   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
3518   default: return false;        // strange store size (detect size!=2**N here)
3519   }
3520   return true;                  // return success to caller
3521 }
3522 
3523 // Coalesce subword constants into int constants and possibly
3524 // into long constants.  The goal, if the CPU permits,
3525 // is to initialize the object with a small number of 64-bit tiles.
3526 // Also, convert floating-point constants to bit patterns.
3527 // Non-constants are not relevant to this pass.
3528 //
3529 // In terms of the running example on InitializeNode::InitializeNode
3530 // and InitializeNode::capture_store, here is the transformation
3531 // of rawstore1 and rawstore2 into rawstore12:
3532 //   alloc = (Allocate ...)
3533 //   rawoop = alloc.RawAddress
3534 //   tile12 = 0x00010002
3535 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
3536 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
3537 //
3538 void
3539 InitializeNode::coalesce_subword_stores(intptr_t header_size,
3540                                         Node* size_in_bytes,
3541                                         PhaseGVN* phase) {
3542   Compile* C = phase->C;
3543 
3544   assert(stores_are_sane(phase), "");
3545   // Note:  After this pass, they are not completely sane,
3546   // since there may be some overlaps.
3547 
3548   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
3549 
3550   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
3551   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
3552   size_limit = MIN2(size_limit, ti_limit);
3553   size_limit = align_size_up(size_limit, BytesPerLong);
3554   int num_tiles = size_limit / BytesPerLong;
3555 
3556   // allocate space for the tile map:
3557   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
3558   jlong  tiles_buf[small_len];
3559   Node*  nodes_buf[small_len];
3560   jlong  inits_buf[small_len];
3561   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
3562                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3563   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
3564                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
3565   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
3566                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
3567   // tiles: exact bitwise model of all primitive constants
3568   // nodes: last constant-storing node subsumed into the tiles model
3569   // inits: which bytes (in each tile) are touched by any initializations
3570 
3571   //// Pass A: Fill in the tile model with any relevant stores.
3572 
3573   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
3574   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
3575   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
3576   Node* zmem = zero_memory(); // initially zero memory state
3577   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3578     Node* st = in(i);
3579     intptr_t st_off = get_store_offset(st, phase);
3580 
3581     // Figure out the store's offset and constant value:
3582     if (st_off < header_size)             continue; //skip (ignore header)
3583     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
3584     int st_size = st->as_Store()->memory_size();
3585     if (st_off + st_size > size_limit)    break;
3586 
3587     // Record which bytes are touched, whether by constant or not.
3588     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
3589       continue;                 // skip (strange store size)
3590 
3591     const Type* val = phase->type(st->in(MemNode::ValueIn));
3592     if (!val->singleton())                continue; //skip (non-con store)
3593     BasicType type = val->basic_type();
3594 
3595     jlong con = 0;
3596     switch (type) {
3597     case T_INT:    con = val->is_int()->get_con();  break;
3598     case T_LONG:   con = val->is_long()->get_con(); break;
3599     case T_FLOAT:  con = jint_cast(val->getf());    break;
3600     case T_DOUBLE: con = jlong_cast(val->getd());   break;
3601     default:                              continue; //skip (odd store type)
3602     }
3603 
3604     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
3605         st->Opcode() == Op_StoreL) {
3606       continue;                 // This StoreL is already optimal.
3607     }
3608 
3609     // Store down the constant.
3610     store_constant(tiles, num_tiles, st_off, st_size, con);
3611 
3612     intptr_t j = st_off >> LogBytesPerLong;
3613 
3614     if (type == T_INT && st_size == BytesPerInt
3615         && (st_off & BytesPerInt) == BytesPerInt) {
3616       jlong lcon = tiles[j];
3617       if (!Matcher::isSimpleConstant64(lcon) &&
3618           st->Opcode() == Op_StoreI) {
3619         // This StoreI is already optimal by itself.
3620         jint* intcon = (jint*) &tiles[j];
3621         intcon[1] = 0;  // undo the store_constant()
3622 
3623         // If the previous store is also optimal by itself, back up and
3624         // undo the action of the previous loop iteration... if we can.
3625         // But if we can't, just let the previous half take care of itself.
3626         st = nodes[j];
3627         st_off -= BytesPerInt;
3628         con = intcon[0];
3629         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
3630           assert(st_off >= header_size, "still ignoring header");
3631           assert(get_store_offset(st, phase) == st_off, "must be");
3632           assert(in(i-1) == zmem, "must be");
3633           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
3634           assert(con == tcon->is_int()->get_con(), "must be");
3635           // Undo the effects of the previous loop trip, which swallowed st:
3636           intcon[0] = 0;        // undo store_constant()
3637           set_req(i-1, st);     // undo set_req(i, zmem)
3638           nodes[j] = NULL;      // undo nodes[j] = st
3639           --old_subword;        // undo ++old_subword
3640         }
3641         continue;               // This StoreI is already optimal.
3642       }
3643     }
3644 
3645     // This store is not needed.
3646     set_req(i, zmem);
3647     nodes[j] = st;              // record for the moment
3648     if (st_size < BytesPerLong) // something has changed
3649           ++old_subword;        // includes int/float, but who's counting...
3650     else  ++old_long;
3651   }
3652 
3653   if ((old_subword + old_long) == 0)
3654     return;                     // nothing more to do
3655 
3656   //// Pass B: Convert any non-zero tiles into optimal constant stores.
3657   // Be sure to insert them before overlapping non-constant stores.
3658   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
3659   for (int j = 0; j < num_tiles; j++) {
3660     jlong con  = tiles[j];
3661     jlong init = inits[j];
3662     if (con == 0)  continue;
3663     jint con0,  con1;           // split the constant, address-wise
3664     jint init0, init1;          // split the init map, address-wise
3665     { union { jlong con; jint intcon[2]; } u;
3666       u.con = con;
3667       con0  = u.intcon[0];
3668       con1  = u.intcon[1];
3669       u.con = init;
3670       init0 = u.intcon[0];
3671       init1 = u.intcon[1];
3672     }
3673 
3674     Node* old = nodes[j];
3675     assert(old != NULL, "need the prior store");
3676     intptr_t offset = (j * BytesPerLong);
3677 
3678     bool split = !Matcher::isSimpleConstant64(con);
3679 
3680     if (offset < header_size) {
3681       assert(offset + BytesPerInt >= header_size, "second int counts");
3682       assert(*(jint*)&tiles[j] == 0, "junk in header");
3683       split = true;             // only the second word counts
3684       // Example:  int a[] = { 42 ... }
3685     } else if (con0 == 0 && init0 == -1) {
3686       split = true;             // first word is covered by full inits
3687       // Example:  int a[] = { ... foo(), 42 ... }
3688     } else if (con1 == 0 && init1 == -1) {
3689       split = true;             // second word is covered by full inits
3690       // Example:  int a[] = { ... 42, foo() ... }
3691     }
3692 
3693     // Here's a case where init0 is neither 0 nor -1:
3694     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
3695     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
3696     // In this case the tile is not split; it is (jlong)42.
3697     // The big tile is stored down, and then the foo() value is inserted.
3698     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
3699 
3700     Node* ctl = old->in(MemNode::Control);
3701     Node* adr = make_raw_address(offset, phase);
3702     const TypePtr* atp = TypeRawPtr::BOTTOM;
3703 
3704     // One or two coalesced stores to plop down.
3705     Node*    st[2];
3706     intptr_t off[2];
3707     int  nst = 0;
3708     if (!split) {
3709       ++new_long;
3710       off[nst] = offset;
3711       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3712                                   phase->longcon(con), T_LONG, MemNode::unordered);
3713     } else {
3714       // Omit either if it is a zero.
3715       if (con0 != 0) {
3716         ++new_int;
3717         off[nst]  = offset;
3718         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3719                                     phase->intcon(con0), T_INT, MemNode::unordered);
3720       }
3721       if (con1 != 0) {
3722         ++new_int;
3723         offset += BytesPerInt;
3724         adr = make_raw_address(offset, phase);
3725         off[nst]  = offset;
3726         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
3727                                     phase->intcon(con1), T_INT, MemNode::unordered);
3728       }
3729     }
3730 
3731     // Insert second store first, then the first before the second.
3732     // Insert each one just before any overlapping non-constant stores.
3733     while (nst > 0) {
3734       Node* st1 = st[--nst];
3735       C->copy_node_notes_to(st1, old);
3736       st1 = phase->transform(st1);
3737       offset = off[nst];
3738       assert(offset >= header_size, "do not smash header");
3739       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
3740       guarantee(ins_idx != 0, "must re-insert constant store");
3741       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
3742       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
3743         set_req(--ins_idx, st1);
3744       else
3745         ins_req(ins_idx, st1);
3746     }
3747   }
3748 
3749   if (PrintCompilation && WizardMode)
3750     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
3751                   old_subword, old_long, new_int, new_long);
3752   if (C->log() != NULL)
3753     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
3754                    old_subword, old_long, new_int, new_long);
3755 
3756   // Clean up any remaining occurrences of zmem:
3757   remove_extra_zeroes();
3758 }
3759 
3760 // Explore forward from in(start) to find the first fully initialized
3761 // word, and return its offset.  Skip groups of subword stores which
3762 // together initialize full words.  If in(start) is itself part of a
3763 // fully initialized word, return the offset of in(start).  If there
3764 // are no following full-word stores, or if something is fishy, return
3765 // a negative value.
3766 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
3767   int       int_map = 0;
3768   intptr_t  int_map_off = 0;
3769   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
3770 
3771   for (uint i = start, limit = req(); i < limit; i++) {
3772     Node* st = in(i);
3773 
3774     intptr_t st_off = get_store_offset(st, phase);
3775     if (st_off < 0)  break;  // return conservative answer
3776 
3777     int st_size = st->as_Store()->memory_size();
3778     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
3779       return st_off;            // we found a complete word init
3780     }
3781 
3782     // update the map:
3783 
3784     intptr_t this_int_off = align_size_down(st_off, BytesPerInt);
3785     if (this_int_off != int_map_off) {
3786       // reset the map:
3787       int_map = 0;
3788       int_map_off = this_int_off;
3789     }
3790 
3791     int subword_off = st_off - this_int_off;
3792     int_map |= right_n_bits(st_size) << subword_off;
3793     if ((int_map & FULL_MAP) == FULL_MAP) {
3794       return this_int_off;      // we found a complete word init
3795     }
3796 
3797     // Did this store hit or cross the word boundary?
3798     intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt);
3799     if (next_int_off == this_int_off + BytesPerInt) {
3800       // We passed the current int, without fully initializing it.
3801       int_map_off = next_int_off;
3802       int_map >>= BytesPerInt;
3803     } else if (next_int_off > this_int_off + BytesPerInt) {
3804       // We passed the current and next int.
3805       return this_int_off + BytesPerInt;
3806     }
3807   }
3808 
3809   return -1;
3810 }
3811 
3812 
3813 // Called when the associated AllocateNode is expanded into CFG.
3814 // At this point, we may perform additional optimizations.
3815 // Linearize the stores by ascending offset, to make memory
3816 // activity as coherent as possible.
3817 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
3818                                       intptr_t header_size,
3819                                       Node* size_in_bytes,
3820                                       PhaseGVN* phase) {
3821   assert(!is_complete(), "not already complete");
3822   assert(stores_are_sane(phase), "");
3823   assert(allocation() != NULL, "must be present");
3824 
3825   remove_extra_zeroes();
3826 
3827   if (ReduceFieldZeroing || ReduceBulkZeroing)
3828     // reduce instruction count for common initialization patterns
3829     coalesce_subword_stores(header_size, size_in_bytes, phase);
3830 
3831   Node* zmem = zero_memory();   // initially zero memory state
3832   Node* inits = zmem;           // accumulating a linearized chain of inits
3833   #ifdef ASSERT
3834   intptr_t first_offset = allocation()->minimum_header_size();
3835   intptr_t last_init_off = first_offset;  // previous init offset
3836   intptr_t last_init_end = first_offset;  // previous init offset+size
3837   intptr_t last_tile_end = first_offset;  // previous tile offset+size
3838   #endif
3839   intptr_t zeroes_done = header_size;
3840 
3841   bool do_zeroing = true;       // we might give up if inits are very sparse
3842   int  big_init_gaps = 0;       // how many large gaps have we seen?
3843 
3844   if (UseTLAB && ZeroTLAB)  do_zeroing = false;
3845   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
3846 
3847   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
3848     Node* st = in(i);
3849     intptr_t st_off = get_store_offset(st, phase);
3850     if (st_off < 0)
3851       break;                    // unknown junk in the inits
3852     if (st->in(MemNode::Memory) != zmem)
3853       break;                    // complicated store chains somehow in list
3854 
3855     int st_size = st->as_Store()->memory_size();
3856     intptr_t next_init_off = st_off + st_size;
3857 
3858     if (do_zeroing && zeroes_done < next_init_off) {
3859       // See if this store needs a zero before it or under it.
3860       intptr_t zeroes_needed = st_off;
3861 
3862       if (st_size < BytesPerInt) {
3863         // Look for subword stores which only partially initialize words.
3864         // If we find some, we must lay down some word-level zeroes first,
3865         // underneath the subword stores.
3866         //
3867         // Examples:
3868         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
3869         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
3870         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
3871         //
3872         // Note:  coalesce_subword_stores may have already done this,
3873         // if it was prompted by constant non-zero subword initializers.
3874         // But this case can still arise with non-constant stores.
3875 
3876         intptr_t next_full_store = find_next_fullword_store(i, phase);
3877 
3878         // In the examples above:
3879         //   in(i)          p   q   r   s     x   y     z
3880         //   st_off        12  13  14  15    12  13    14
3881         //   st_size        1   1   1   1     1   1     1
3882         //   next_full_s.  12  16  16  16    16  16    16
3883         //   z's_done      12  16  16  16    12  16    12
3884         //   z's_needed    12  16  16  16    16  16    16
3885         //   zsize          0   0   0   0     4   0     4
3886         if (next_full_store < 0) {
3887           // Conservative tack:  Zero to end of current word.
3888           zeroes_needed = align_size_up(zeroes_needed, BytesPerInt);
3889         } else {
3890           // Zero to beginning of next fully initialized word.
3891           // Or, don't zero at all, if we are already in that word.
3892           assert(next_full_store >= zeroes_needed, "must go forward");
3893           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
3894           zeroes_needed = next_full_store;
3895         }
3896       }
3897 
3898       if (zeroes_needed > zeroes_done) {
3899         intptr_t zsize = zeroes_needed - zeroes_done;
3900         // Do some incremental zeroing on rawmem, in parallel with inits.
3901         zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3902         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3903                                               zeroes_done, zeroes_needed,
3904                                               phase);
3905         zeroes_done = zeroes_needed;
3906         if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2)
3907           do_zeroing = false;   // leave the hole, next time
3908       }
3909     }
3910 
3911     // Collect the store and move on:
3912     st->set_req(MemNode::Memory, inits);
3913     inits = st;                 // put it on the linearized chain
3914     set_req(i, zmem);           // unhook from previous position
3915 
3916     if (zeroes_done == st_off)
3917       zeroes_done = next_init_off;
3918 
3919     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
3920 
3921     #ifdef ASSERT
3922     // Various order invariants.  Weaker than stores_are_sane because
3923     // a large constant tile can be filled in by smaller non-constant stores.
3924     assert(st_off >= last_init_off, "inits do not reverse");
3925     last_init_off = st_off;
3926     const Type* val = NULL;
3927     if (st_size >= BytesPerInt &&
3928         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
3929         (int)val->basic_type() < (int)T_OBJECT) {
3930       assert(st_off >= last_tile_end, "tiles do not overlap");
3931       assert(st_off >= last_init_end, "tiles do not overwrite inits");
3932       last_tile_end = MAX2(last_tile_end, next_init_off);
3933     } else {
3934       intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong);
3935       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
3936       assert(st_off      >= last_init_end, "inits do not overlap");
3937       last_init_end = next_init_off;  // it's a non-tile
3938     }
3939     #endif //ASSERT
3940   }
3941 
3942   remove_extra_zeroes();        // clear out all the zmems left over
3943   add_req(inits);
3944 
3945   if (!(UseTLAB && ZeroTLAB)) {
3946     // If anything remains to be zeroed, zero it all now.
3947     zeroes_done = align_size_down(zeroes_done, BytesPerInt);
3948     // if it is the last unused 4 bytes of an instance, forget about it
3949     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
3950     if (zeroes_done + BytesPerLong >= size_limit) {
3951       assert(allocation() != NULL, "");
3952       if (allocation()->Opcode() == Op_Allocate) {
3953         Node* klass_node = allocation()->in(AllocateNode::KlassNode);
3954         ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
3955         if (zeroes_done == k->layout_helper())
3956           zeroes_done = size_limit;
3957       }
3958     }
3959     if (zeroes_done < size_limit) {
3960       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
3961                                             zeroes_done, size_in_bytes, phase);
3962     }
3963   }
3964 
3965   set_complete(phase);
3966   return rawmem;
3967 }
3968 
3969 
3970 #ifdef ASSERT
3971 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
3972   if (is_complete())
3973     return true;                // stores could be anything at this point
3974   assert(allocation() != NULL, "must be present");
3975   intptr_t last_off = allocation()->minimum_header_size();
3976   for (uint i = InitializeNode::RawStores; i < req(); i++) {
3977     Node* st = in(i);
3978     intptr_t st_off = get_store_offset(st, phase);
3979     if (st_off < 0)  continue;  // ignore dead garbage
3980     if (last_off > st_off) {
3981       tty->print_cr("*** bad store offset at %d: " INTX_FORMAT " > " INTX_FORMAT, i, last_off, st_off);
3982       this->dump(2);
3983       assert(false, "ascending store offsets");
3984       return false;
3985     }
3986     last_off = st_off + st->as_Store()->memory_size();
3987   }
3988   return true;
3989 }
3990 #endif //ASSERT
3991 
3992 
3993 
3994 
3995 //============================MergeMemNode=====================================
3996 //
3997 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
3998 // contributing store or call operations.  Each contributor provides the memory
3999 // state for a particular "alias type" (see Compile::alias_type).  For example,
4000 // if a MergeMem has an input X for alias category #6, then any memory reference
4001 // to alias category #6 may use X as its memory state input, as an exact equivalent
4002 // to using the MergeMem as a whole.
4003 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
4004 //
4005 // (Here, the <N> notation gives the index of the relevant adr_type.)
4006 //
4007 // In one special case (and more cases in the future), alias categories overlap.
4008 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
4009 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
4010 // it is exactly equivalent to that state W:
4011 //   MergeMem(<Bot>: W) <==> W
4012 //
4013 // Usually, the merge has more than one input.  In that case, where inputs
4014 // overlap (i.e., one is Bot), the narrower alias type determines the memory
4015 // state for that type, and the wider alias type (Bot) fills in everywhere else:
4016 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
4017 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
4018 //
4019 // A merge can take a "wide" memory state as one of its narrow inputs.
4020 // This simply means that the merge observes out only the relevant parts of
4021 // the wide input.  That is, wide memory states arriving at narrow merge inputs
4022 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
4023 //
4024 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
4025 // and that memory slices "leak through":
4026 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
4027 //
4028 // But, in such a cascade, repeated memory slices can "block the leak":
4029 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
4030 //
4031 // In the last example, Y is not part of the combined memory state of the
4032 // outermost MergeMem.  The system must, of course, prevent unschedulable
4033 // memory states from arising, so you can be sure that the state Y is somehow
4034 // a precursor to state Y'.
4035 //
4036 //
4037 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
4038 // of each MergeMemNode array are exactly the numerical alias indexes, including
4039 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
4040 // Compile::alias_type (and kin) produce and manage these indexes.
4041 //
4042 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
4043 // (Note that this provides quick access to the top node inside MergeMem methods,
4044 // without the need to reach out via TLS to Compile::current.)
4045 //
4046 // As a consequence of what was just described, a MergeMem that represents a full
4047 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
4048 // containing all alias categories.
4049 //
4050 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
4051 //
4052 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
4053 // a memory state for the alias type <N>, or else the top node, meaning that
4054 // there is no particular input for that alias type.  Note that the length of
4055 // a MergeMem is variable, and may be extended at any time to accommodate new
4056 // memory states at larger alias indexes.  When merges grow, they are of course
4057 // filled with "top" in the unused in() positions.
4058 //
4059 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
4060 // (Top was chosen because it works smoothly with passes like GCM.)
4061 //
4062 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
4063 // the type of random VM bits like TLS references.)  Since it is always the
4064 // first non-Bot memory slice, some low-level loops use it to initialize an
4065 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
4066 //
4067 //
4068 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
4069 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
4070 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
4071 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
4072 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
4073 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
4074 //
4075 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
4076 // really that different from the other memory inputs.  An abbreviation called
4077 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
4078 //
4079 //
4080 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
4081 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
4082 // that "emerges though" the base memory will be marked as excluding the alias types
4083 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
4084 //
4085 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
4086 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
4087 //
4088 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
4089 // (It is currently unimplemented.)  As you can see, the resulting merge is
4090 // actually a disjoint union of memory states, rather than an overlay.
4091 //
4092 
4093 //------------------------------MergeMemNode-----------------------------------
4094 Node* MergeMemNode::make_empty_memory() {
4095   Node* empty_memory = (Node*) Compile::current()->top();
4096   assert(empty_memory->is_top(), "correct sentinel identity");
4097   return empty_memory;
4098 }
4099 
4100 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
4101   init_class_id(Class_MergeMem);
4102   // all inputs are nullified in Node::Node(int)
4103   // set_input(0, NULL);  // no control input
4104 
4105   // Initialize the edges uniformly to top, for starters.
4106   Node* empty_mem = make_empty_memory();
4107   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
4108     init_req(i,empty_mem);
4109   }
4110   assert(empty_memory() == empty_mem, "");
4111 
4112   if( new_base != NULL && new_base->is_MergeMem() ) {
4113     MergeMemNode* mdef = new_base->as_MergeMem();
4114     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
4115     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
4116       mms.set_memory(mms.memory2());
4117     }
4118     assert(base_memory() == mdef->base_memory(), "");
4119   } else {
4120     set_base_memory(new_base);
4121   }
4122 }
4123 
4124 // Make a new, untransformed MergeMem with the same base as 'mem'.
4125 // If mem is itself a MergeMem, populate the result with the same edges.
4126 MergeMemNode* MergeMemNode::make(Node* mem) {
4127   return new MergeMemNode(mem);
4128 }
4129 
4130 //------------------------------cmp--------------------------------------------
4131 uint MergeMemNode::hash() const { return NO_HASH; }
4132 uint MergeMemNode::cmp( const Node &n ) const {
4133   return (&n == this);          // Always fail except on self
4134 }
4135 
4136 //------------------------------Identity---------------------------------------
4137 Node* MergeMemNode::Identity(PhaseGVN* phase) {
4138   // Identity if this merge point does not record any interesting memory
4139   // disambiguations.
4140   Node* base_mem = base_memory();
4141   Node* empty_mem = empty_memory();
4142   if (base_mem != empty_mem) {  // Memory path is not dead?
4143     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4144       Node* mem = in(i);
4145       if (mem != empty_mem && mem != base_mem) {
4146         return this;            // Many memory splits; no change
4147       }
4148     }
4149   }
4150   return base_mem;              // No memory splits; ID on the one true input
4151 }
4152 
4153 //------------------------------Ideal------------------------------------------
4154 // This method is invoked recursively on chains of MergeMem nodes
4155 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
4156   // Remove chain'd MergeMems
4157   //
4158   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
4159   // relative to the "in(Bot)".  Since we are patching both at the same time,
4160   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
4161   // but rewrite each "in(i)" relative to the new "in(Bot)".
4162   Node *progress = NULL;
4163 
4164 
4165   Node* old_base = base_memory();
4166   Node* empty_mem = empty_memory();
4167   if (old_base == empty_mem)
4168     return NULL; // Dead memory path.
4169 
4170   MergeMemNode* old_mbase;
4171   if (old_base != NULL && old_base->is_MergeMem())
4172     old_mbase = old_base->as_MergeMem();
4173   else
4174     old_mbase = NULL;
4175   Node* new_base = old_base;
4176 
4177   // simplify stacked MergeMems in base memory
4178   if (old_mbase)  new_base = old_mbase->base_memory();
4179 
4180   // the base memory might contribute new slices beyond my req()
4181   if (old_mbase)  grow_to_match(old_mbase);
4182 
4183   // Look carefully at the base node if it is a phi.
4184   PhiNode* phi_base;
4185   if (new_base != NULL && new_base->is_Phi())
4186     phi_base = new_base->as_Phi();
4187   else
4188     phi_base = NULL;
4189 
4190   Node*    phi_reg = NULL;
4191   uint     phi_len = (uint)-1;
4192   if (phi_base != NULL && !phi_base->is_copy()) {
4193     // do not examine phi if degraded to a copy
4194     phi_reg = phi_base->region();
4195     phi_len = phi_base->req();
4196     // see if the phi is unfinished
4197     for (uint i = 1; i < phi_len; i++) {
4198       if (phi_base->in(i) == NULL) {
4199         // incomplete phi; do not look at it yet!
4200         phi_reg = NULL;
4201         phi_len = (uint)-1;
4202         break;
4203       }
4204     }
4205   }
4206 
4207   // Note:  We do not call verify_sparse on entry, because inputs
4208   // can normalize to the base_memory via subsume_node or similar
4209   // mechanisms.  This method repairs that damage.
4210 
4211   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
4212 
4213   // Look at each slice.
4214   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4215     Node* old_in = in(i);
4216     // calculate the old memory value
4217     Node* old_mem = old_in;
4218     if (old_mem == empty_mem)  old_mem = old_base;
4219     assert(old_mem == memory_at(i), "");
4220 
4221     // maybe update (reslice) the old memory value
4222 
4223     // simplify stacked MergeMems
4224     Node* new_mem = old_mem;
4225     MergeMemNode* old_mmem;
4226     if (old_mem != NULL && old_mem->is_MergeMem())
4227       old_mmem = old_mem->as_MergeMem();
4228     else
4229       old_mmem = NULL;
4230     if (old_mmem == this) {
4231       // This can happen if loops break up and safepoints disappear.
4232       // A merge of BotPtr (default) with a RawPtr memory derived from a
4233       // safepoint can be rewritten to a merge of the same BotPtr with
4234       // the BotPtr phi coming into the loop.  If that phi disappears
4235       // also, we can end up with a self-loop of the mergemem.
4236       // In general, if loops degenerate and memory effects disappear,
4237       // a mergemem can be left looking at itself.  This simply means
4238       // that the mergemem's default should be used, since there is
4239       // no longer any apparent effect on this slice.
4240       // Note: If a memory slice is a MergeMem cycle, it is unreachable
4241       //       from start.  Update the input to TOP.
4242       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
4243     }
4244     else if (old_mmem != NULL) {
4245       new_mem = old_mmem->memory_at(i);
4246     }
4247     // else preceding memory was not a MergeMem
4248 
4249     // replace equivalent phis (unfortunately, they do not GVN together)
4250     if (new_mem != NULL && new_mem != new_base &&
4251         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
4252       if (new_mem->is_Phi()) {
4253         PhiNode* phi_mem = new_mem->as_Phi();
4254         for (uint i = 1; i < phi_len; i++) {
4255           if (phi_base->in(i) != phi_mem->in(i)) {
4256             phi_mem = NULL;
4257             break;
4258           }
4259         }
4260         if (phi_mem != NULL) {
4261           // equivalent phi nodes; revert to the def
4262           new_mem = new_base;
4263         }
4264       }
4265     }
4266 
4267     // maybe store down a new value
4268     Node* new_in = new_mem;
4269     if (new_in == new_base)  new_in = empty_mem;
4270 
4271     if (new_in != old_in) {
4272       // Warning:  Do not combine this "if" with the previous "if"
4273       // A memory slice might have be be rewritten even if it is semantically
4274       // unchanged, if the base_memory value has changed.
4275       set_req(i, new_in);
4276       progress = this;          // Report progress
4277     }
4278   }
4279 
4280   if (new_base != old_base) {
4281     set_req(Compile::AliasIdxBot, new_base);
4282     // Don't use set_base_memory(new_base), because we need to update du.
4283     assert(base_memory() == new_base, "");
4284     progress = this;
4285   }
4286 
4287   if( base_memory() == this ) {
4288     // a self cycle indicates this memory path is dead
4289     set_req(Compile::AliasIdxBot, empty_mem);
4290   }
4291 
4292   // Resolve external cycles by calling Ideal on a MergeMem base_memory
4293   // Recursion must occur after the self cycle check above
4294   if( base_memory()->is_MergeMem() ) {
4295     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
4296     Node *m = phase->transform(new_mbase);  // Rollup any cycles
4297     if( m != NULL && (m->is_top() ||
4298         m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) {
4299       // propagate rollup of dead cycle to self
4300       set_req(Compile::AliasIdxBot, empty_mem);
4301     }
4302   }
4303 
4304   if( base_memory() == empty_mem ) {
4305     progress = this;
4306     // Cut inputs during Parse phase only.
4307     // During Optimize phase a dead MergeMem node will be subsumed by Top.
4308     if( !can_reshape ) {
4309       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4310         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
4311       }
4312     }
4313   }
4314 
4315   if( !progress && base_memory()->is_Phi() && can_reshape ) {
4316     // Check if PhiNode::Ideal's "Split phis through memory merges"
4317     // transform should be attempted. Look for this->phi->this cycle.
4318     uint merge_width = req();
4319     if (merge_width > Compile::AliasIdxRaw) {
4320       PhiNode* phi = base_memory()->as_Phi();
4321       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
4322         if (phi->in(i) == this) {
4323           phase->is_IterGVN()->_worklist.push(phi);
4324           break;
4325         }
4326       }
4327     }
4328   }
4329 
4330   assert(progress || verify_sparse(), "please, no dups of base");
4331   return progress;
4332 }
4333 
4334 //-------------------------set_base_memory-------------------------------------
4335 void MergeMemNode::set_base_memory(Node *new_base) {
4336   Node* empty_mem = empty_memory();
4337   set_req(Compile::AliasIdxBot, new_base);
4338   assert(memory_at(req()) == new_base, "must set default memory");
4339   // Clear out other occurrences of new_base:
4340   if (new_base != empty_mem) {
4341     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4342       if (in(i) == new_base)  set_req(i, empty_mem);
4343     }
4344   }
4345 }
4346 
4347 //------------------------------out_RegMask------------------------------------
4348 const RegMask &MergeMemNode::out_RegMask() const {
4349   return RegMask::Empty;
4350 }
4351 
4352 //------------------------------dump_spec--------------------------------------
4353 #ifndef PRODUCT
4354 void MergeMemNode::dump_spec(outputStream *st) const {
4355   st->print(" {");
4356   Node* base_mem = base_memory();
4357   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
4358     Node* mem = (in(i) != NULL) ? memory_at(i) : base_mem;
4359     if (mem == base_mem) { st->print(" -"); continue; }
4360     st->print( " N%d:", mem->_idx );
4361     Compile::current()->get_adr_type(i)->dump_on(st);
4362   }
4363   st->print(" }");
4364 }
4365 #endif // !PRODUCT
4366 
4367 
4368 #ifdef ASSERT
4369 static bool might_be_same(Node* a, Node* b) {
4370   if (a == b)  return true;
4371   if (!(a->is_Phi() || b->is_Phi()))  return false;
4372   // phis shift around during optimization
4373   return true;  // pretty stupid...
4374 }
4375 
4376 // verify a narrow slice (either incoming or outgoing)
4377 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
4378   if (!VerifyAliases)       return;  // don't bother to verify unless requested
4379   if (is_error_reported())  return;  // muzzle asserts when debugging an error
4380   if (Node::in_dump())      return;  // muzzle asserts when printing
4381   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
4382   assert(n != NULL, "");
4383   // Elide intervening MergeMem's
4384   while (n->is_MergeMem()) {
4385     n = n->as_MergeMem()->memory_at(alias_idx);
4386   }
4387   Compile* C = Compile::current();
4388   const TypePtr* n_adr_type = n->adr_type();
4389   if (n == m->empty_memory()) {
4390     // Implicit copy of base_memory()
4391   } else if (n_adr_type != TypePtr::BOTTOM) {
4392     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
4393     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
4394   } else {
4395     // A few places like make_runtime_call "know" that VM calls are narrow,
4396     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
4397     bool expected_wide_mem = false;
4398     if (n == m->base_memory()) {
4399       expected_wide_mem = true;
4400     } else if (alias_idx == Compile::AliasIdxRaw ||
4401                n == m->memory_at(Compile::AliasIdxRaw)) {
4402       expected_wide_mem = true;
4403     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
4404       // memory can "leak through" calls on channels that
4405       // are write-once.  Allow this also.
4406       expected_wide_mem = true;
4407     }
4408     assert(expected_wide_mem, "expected narrow slice replacement");
4409   }
4410 }
4411 #else // !ASSERT
4412 #define verify_memory_slice(m,i,n) (void)(0)  // PRODUCT version is no-op
4413 #endif
4414 
4415 
4416 //-----------------------------memory_at---------------------------------------
4417 Node* MergeMemNode::memory_at(uint alias_idx) const {
4418   assert(alias_idx >= Compile::AliasIdxRaw ||
4419          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
4420          "must avoid base_memory and AliasIdxTop");
4421 
4422   // Otherwise, it is a narrow slice.
4423   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
4424   Compile *C = Compile::current();
4425   if (is_empty_memory(n)) {
4426     // the array is sparse; empty slots are the "top" node
4427     n = base_memory();
4428     assert(Node::in_dump()
4429            || n == NULL || n->bottom_type() == Type::TOP
4430            || n->adr_type() == NULL // address is TOP
4431            || n->adr_type() == TypePtr::BOTTOM
4432            || n->adr_type() == TypeRawPtr::BOTTOM
4433            || Compile::current()->AliasLevel() == 0,
4434            "must be a wide memory");
4435     // AliasLevel == 0 if we are organizing the memory states manually.
4436     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
4437   } else {
4438     // make sure the stored slice is sane
4439     #ifdef ASSERT
4440     if (is_error_reported() || Node::in_dump()) {
4441     } else if (might_be_same(n, base_memory())) {
4442       // Give it a pass:  It is a mostly harmless repetition of the base.
4443       // This can arise normally from node subsumption during optimization.
4444     } else {
4445       verify_memory_slice(this, alias_idx, n);
4446     }
4447     #endif
4448   }
4449   return n;
4450 }
4451 
4452 //---------------------------set_memory_at-------------------------------------
4453 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
4454   verify_memory_slice(this, alias_idx, n);
4455   Node* empty_mem = empty_memory();
4456   if (n == base_memory())  n = empty_mem;  // collapse default
4457   uint need_req = alias_idx+1;
4458   if (req() < need_req) {
4459     if (n == empty_mem)  return;  // already the default, so do not grow me
4460     // grow the sparse array
4461     do {
4462       add_req(empty_mem);
4463     } while (req() < need_req);
4464   }
4465   set_req( alias_idx, n );
4466 }
4467 
4468 
4469 
4470 //--------------------------iteration_setup------------------------------------
4471 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
4472   if (other != NULL) {
4473     grow_to_match(other);
4474     // invariant:  the finite support of mm2 is within mm->req()
4475     #ifdef ASSERT
4476     for (uint i = req(); i < other->req(); i++) {
4477       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
4478     }
4479     #endif
4480   }
4481   // Replace spurious copies of base_memory by top.
4482   Node* base_mem = base_memory();
4483   if (base_mem != NULL && !base_mem->is_top()) {
4484     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
4485       if (in(i) == base_mem)
4486         set_req(i, empty_memory());
4487     }
4488   }
4489 }
4490 
4491 //---------------------------grow_to_match-------------------------------------
4492 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
4493   Node* empty_mem = empty_memory();
4494   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
4495   // look for the finite support of the other memory
4496   for (uint i = other->req(); --i >= req(); ) {
4497     if (other->in(i) != empty_mem) {
4498       uint new_len = i+1;
4499       while (req() < new_len)  add_req(empty_mem);
4500       break;
4501     }
4502   }
4503 }
4504 
4505 //---------------------------verify_sparse-------------------------------------
4506 #ifndef PRODUCT
4507 bool MergeMemNode::verify_sparse() const {
4508   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
4509   Node* base_mem = base_memory();
4510   // The following can happen in degenerate cases, since empty==top.
4511   if (is_empty_memory(base_mem))  return true;
4512   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
4513     assert(in(i) != NULL, "sane slice");
4514     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
4515   }
4516   return true;
4517 }
4518 
4519 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
4520   Node* n;
4521   n = mm->in(idx);
4522   if (mem == n)  return true;  // might be empty_memory()
4523   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
4524   if (mem == n)  return true;
4525   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
4526     if (mem == n)  return true;
4527     if (n == NULL)  break;
4528   }
4529   return false;
4530 }
4531 #endif // !PRODUCT
--- EOF ---