jdk8-mips64-public/hotspot: src/share/vm/opto/memnode.cpp@b130b98db9cf (annotated)

src/share/vm/opto/memnode.cpp@b130b98db9cf (annotated)

src/share/vm/opto/memnode.cpp

Wed, 23 Apr 2008 11:20:36 -0700

author: kvn
date: Wed, 23 Apr 2008 11:20:36 -0700
changeset 559: b130b98db9cf
parent 554: d1a5218d7eaf
child 563: a76240c8b133
permissions: -rw-r--r--

6689060: Escape Analysis does not work with Compressed Oops
Summary: 64-bits VM crashes with -XX:+AggresiveOpts (Escape Analysis + Compressed Oops)
Reviewed-by: never, sgoldman

 /*
  * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
  * CA 95054 USA or visit www.sun.com if you need additional information or
  * have any questions.
  *
  */
 // Portions of code courtesy of Clifford Click
 // Optimization - Graph Style
 #include "incls/_precompiled.incl"
 #include "incls/_memnode.cpp.incl"
 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st);
 //=============================================================================
 uint MemNode::size_of() const { return sizeof(*this); }
 const TypePtr *MemNode::adr_type() const {
   Node* adr = in(Address);
   const TypePtr* cross_check = NULL;
   DEBUG_ONLY(cross_check = _adr_type);
   return calculate_adr_type(adr->bottom_type(), cross_check);
 }
 #ifndef PRODUCT
 void MemNode::dump_spec(outputStream *st) const {
   if (in(Address) == NULL)  return; // node is dead
 #ifndef ASSERT
   // fake the missing field
   const TypePtr* _adr_type = NULL;
   if (in(Address) != NULL)
     _adr_type = in(Address)->bottom_type()->isa_ptr();
 #endif
   dump_adr_type(this, _adr_type, st);
   Compile* C = Compile::current();
   if( C->alias_type(_adr_type)->is_volatile() )
     st->print(" Volatile!");
 }
 void MemNode::dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st) {
   st->print(" @");
   if (adr_type == NULL) {
     st->print("NULL");
   } else {
     adr_type->dump_on(st);
     Compile* C = Compile::current();
     Compile::AliasType* atp = NULL;
     if (C->have_alias_type(adr_type))  atp = C->alias_type(adr_type);
     if (atp == NULL)
       st->print(", idx=?\?;");
     else if (atp->index() == Compile::AliasIdxBot)
       st->print(", idx=Bot;");
     else if (atp->index() == Compile::AliasIdxTop)
       st->print(", idx=Top;");
     else if (atp->index() == Compile::AliasIdxRaw)
       st->print(", idx=Raw;");
     else {
       ciField* field = atp->field();
       if (field) {
         st->print(", name=");
         field->print_name_on(st);
       }
       st->print(", idx=%d;", atp->index());
     }
   }
 }
 extern void print_alias_types();
 #endif
 Node *MemNode::optimize_simple_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) {
   const TypeOopPtr *tinst = t_adr->isa_oopptr();
   if (tinst == NULL || !tinst->is_instance_field())
     return mchain;  // don't try to optimize non-instance types
   uint instance_id = tinst->instance_id();
   Node *prev = NULL;
   Node *result = mchain;
   while (prev != result) {
     prev = result;
     // skip over a call which does not affect this memory slice
     if (result->is_Proj() && result->as_Proj()->_con == TypeFunc::Memory) {
       Node *proj_in = result->in(0);
       if (proj_in->is_Call()) {
         CallNode *call = proj_in->as_Call();
         if (!call->may_modify(t_adr, phase)) {
           result = call->in(TypeFunc::Memory);
         }
       } else if (proj_in->is_Initialize()) {
         AllocateNode* alloc = proj_in->as_Initialize()->allocation();
         // Stop if this is the initialization for the object instance which
         // which contains this memory slice, otherwise skip over it.
         if (alloc != NULL && alloc->_idx != instance_id) {
           result = proj_in->in(TypeFunc::Memory);
         }
       } else if (proj_in->is_MemBar()) {
         result = proj_in->in(TypeFunc::Memory);
       }
     } else if (result->is_MergeMem()) {
       result = step_through_mergemem(phase, result->as_MergeMem(), t_adr, NULL, tty);
     }
   }
   return result;
 }
 Node *MemNode::optimize_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase) {
   const TypeOopPtr *t_oop = t_adr->isa_oopptr();
   bool is_instance = (t_oop != NULL) && t_oop->is_instance_field();
   PhaseIterGVN *igvn = phase->is_IterGVN();
   Node *result = mchain;
   result = optimize_simple_memory_chain(result, t_adr, phase);
   if (is_instance && igvn != NULL  && result->is_Phi()) {
     PhiNode *mphi = result->as_Phi();
     assert(mphi->bottom_type() == Type::MEMORY, "memory phi required");
     const TypePtr *t = mphi->adr_type();
     if (t == TypePtr::BOTTOM || t == TypeRawPtr::BOTTOM) {
       // clone the Phi with our address type
       result = mphi->split_out_instance(t_adr, igvn);
     } else {
       assert(phase->C->get_alias_index(t) == phase->C->get_alias_index(t_adr), "correct memory chain");
     }
   }
   return result;
 }
 static Node *step_through_mergemem(PhaseGVN *phase, MergeMemNode *mmem,  const TypePtr *tp, const TypePtr *adr_check, outputStream *st) {
   uint alias_idx = phase->C->get_alias_index(tp);
   Node *mem = mmem;
 #ifdef ASSERT
   {
     // Check that current type is consistent with the alias index used during graph construction
     assert(alias_idx >= Compile::AliasIdxRaw, "must not be a bad alias_idx");
     bool consistent =  adr_check == NULL || adr_check->empty() ||
                        phase->C->must_alias(adr_check, alias_idx );
     // Sometimes dead array references collapse to a[-1], a[-2], or a[-3]
     if( !consistent && adr_check != NULL && !adr_check->empty() &&
            tp->isa_aryptr() &&    tp->offset() == Type::OffsetBot &&
         adr_check->isa_aryptr() && adr_check->offset() != Type::OffsetBot &&
         ( adr_check->offset() == arrayOopDesc::length_offset_in_bytes() ||
           adr_check->offset() == oopDesc::klass_offset_in_bytes() ||
           adr_check->offset() == oopDesc::mark_offset_in_bytes() ) ) {
       // don't assert if it is dead code.
       consistent = true;
     }
     if( !consistent ) {
       st->print("alias_idx==%d, adr_check==", alias_idx);
       if( adr_check == NULL ) {
         st->print("NULL");
       } else {
         adr_check->dump();
       }
       st->cr();
       print_alias_types();
       assert(consistent, "adr_check must match alias idx");
     }
   }
 #endif
   // TypeInstPtr::NOTNULL+any is an OOP with unknown offset - generally
   // means an array I have not precisely typed yet.  Do not do any
   // alias stuff with it any time soon.
   const TypeOopPtr *tinst = tp->isa_oopptr();
   if( tp->base() != Type::AnyPtr &&
       !(tinst &&
         tinst->klass()->is_java_lang_Object() &&
         tinst->offset() == Type::OffsetBot) ) {
     // compress paths and change unreachable cycles to TOP
     // If not, we can update the input infinitely along a MergeMem cycle
     // Equivalent code in PhiNode::Ideal
     Node* m  = phase->transform(mmem);
     // If tranformed to a MergeMem, get the desired slice
     // Otherwise the returned node represents memory for every slice
     mem = (m->is_MergeMem())? m->as_MergeMem()->memory_at(alias_idx) : m;
     // Update input if it is progress over what we have now
   }
   return mem;
 }
 //--------------------------Ideal_common---------------------------------------
 // Look for degenerate control and memory inputs.  Bypass MergeMem inputs.
 // Unhook non-raw memories from complete (macro-expanded) initializations.
 Node *MemNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
   // If our control input is a dead region, kill all below the region
   Node *ctl = in(MemNode::Control);
   if (ctl && remove_dead_region(phase, can_reshape))
     return this;
   // Ignore if memory is dead, or self-loop
   Node *mem = in(MemNode::Memory);
   if( phase->type( mem ) == Type::TOP ) return NodeSentinel; // caller will return NULL
   assert( mem != this, "dead loop in MemNode::Ideal" );
   Node *address = in(MemNode::Address);
   const Type *t_adr = phase->type( address );
   if( t_adr == Type::TOP )              return NodeSentinel; // caller will return NULL
   // Avoid independent memory operations
   Node* old_mem = mem;
   // The code which unhooks non-raw memories from complete (macro-expanded)
   // initializations was removed. After macro-expansion all stores catched
   // by Initialize node became raw stores and there is no information
   // which memory slices they modify. So it is unsafe to move any memory
   // operation above these stores. Also in most cases hooked non-raw memories
   // were already unhooked by using information from detect_ptr_independence()
   // and find_previous_store().
   if (mem->is_MergeMem()) {
     MergeMemNode* mmem = mem->as_MergeMem();
     const TypePtr *tp = t_adr->is_ptr();
     mem = step_through_mergemem(phase, mmem, tp, adr_type(), tty);
   }
   if (mem != old_mem) {
     set_req(MemNode::Memory, mem);
     return this;
   }
   // let the subclass continue analyzing...
   return NULL;
 }
 // Helper function for proving some simple control dominations.
 // Attempt to prove that all control inputs of 'dom' dominate 'sub'.
 // Already assumes that 'dom' is available at 'sub', and that 'sub'
 // is not a constant (dominated by the method's StartNode).
 // Used by MemNode::find_previous_store to prove that the
 // control input of a memory operation predates (dominates)
 // an allocation it wants to look past.
 bool MemNode::all_controls_dominate(Node* dom, Node* sub) {
   if (dom == NULL || dom->is_top() || sub == NULL || sub->is_top())
     return false; // Conservative answer for dead code
   // Check 'dom'.
   dom = dom->find_exact_control(dom);
   if (dom == NULL || dom->is_top())
     return false; // Conservative answer for dead code
   if (dom->is_Start() || dom->is_Root() || dom == sub)
     return true;
   // 'dom' dominates 'sub' if its control edge and control edges
   // of all its inputs dominate or equal to sub's control edge.
   // Currently 'sub' is either Allocate, Initialize or Start nodes.
   assert(sub->is_Allocate() || sub->is_Initialize() || sub->is_Start(), "expecting only these nodes");
   // Get control edge of 'sub'.
   sub = sub->find_exact_control(sub->in(0));
   if (sub == NULL || sub->is_top())
     return false; // Conservative answer for dead code
   assert(sub->is_CFG(), "expecting control");
   if (sub == dom)
     return true;
   if (sub->is_Start() || sub->is_Root())
     return false;
   {
     // Check all control edges of 'dom'.
     ResourceMark rm;
     Arena* arena = Thread::current()->resource_area();
     Node_List nlist(arena);
     Unique_Node_List dom_list(arena);
     dom_list.push(dom);
     bool only_dominating_controls = false;
     for (uint next = 0; next < dom_list.size(); next++) {
       Node* n = dom_list.at(next);
       if (!n->is_CFG() && n->pinned()) {
         // Check only own control edge for pinned non-control nodes.
         n = n->find_exact_control(n->in(0));
         if (n == NULL || n->is_top())
           return false; // Conservative answer for dead code
         assert(n->is_CFG(), "expecting control");
       }
       if (n->is_Start() || n->is_Root()) {
         only_dominating_controls = true;
       } else if (n->is_CFG()) {
         if (n->dominates(sub, nlist))
           only_dominating_controls = true;
         else
           return false;
       } else {
         // First, own control edge.
         Node* m = n->find_exact_control(n->in(0));
         if (m == NULL)
           continue;
         if (m->is_top())
           return false; // Conservative answer for dead code
         dom_list.push(m);
         // Now, the rest of edges.
         uint cnt = n->req();
         for (uint i = 1; i < cnt; i++) {
           m = n->find_exact_control(n->in(i));
           if (m == NULL || m->is_top())
             continue;
           dom_list.push(m);
         }
       }
     }
     return only_dominating_controls;
   }
 }
 //---------------------detect_ptr_independence---------------------------------
 // Used by MemNode::find_previous_store to prove that two base
 // pointers are never equal.
 // The pointers are accompanied by their associated allocations,
 // if any, which have been previously discovered by the caller.
 bool MemNode::detect_ptr_independence(Node* p1, AllocateNode* a1,
                                       Node* p2, AllocateNode* a2,
                                       PhaseTransform* phase) {
   // Attempt to prove that these two pointers cannot be aliased.
   // They may both manifestly be allocations, and they should differ.
   // Or, if they are not both allocations, they can be distinct constants.
   // Otherwise, one is an allocation and the other a pre-existing value.
   if (a1 == NULL && a2 == NULL) {           // neither an allocation
     return (p1 != p2) && p1->is_Con() && p2->is_Con();
   } else if (a1 != NULL && a2 != NULL) {    // both allocations
     return (a1 != a2);
   } else if (a1 != NULL) {                  // one allocation a1
     // (Note:  p2->is_Con implies p2->in(0)->is_Root, which dominates.)
     return all_controls_dominate(p2, a1);
   } else { //(a2 != NULL)                   // one allocation a2
     return all_controls_dominate(p1, a2);
   }
   return false;
 }
 // The logic for reordering loads and stores uses four steps:
 // (a) Walk carefully past stores and initializations which we
 //     can prove are independent of this load.
 // (b) Observe that the next memory state makes an exact match
 //     with self (load or store), and locate the relevant store.
 // (c) Ensure that, if we were to wire self directly to the store,
 //     the optimizer would fold it up somehow.
 // (d) Do the rewiring, and return, depending on some other part of
 //     the optimizer to fold up the load.
 // This routine handles steps (a) and (b).  Steps (c) and (d) are
 // specific to loads and stores, so they are handled by the callers.
 // (Currently, only LoadNode::Ideal has steps (c), (d).  More later.)
 //
 Node* MemNode::find_previous_store(PhaseTransform* phase) {
   Node*         ctrl   = in(MemNode::Control);
   Node*         adr    = in(MemNode::Address);
   intptr_t      offset = 0;
   Node*         base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
   AllocateNode* alloc  = AllocateNode::Ideal_allocation(base, phase);
   if (offset == Type::OffsetBot)
     return NULL;            // cannot unalias unless there are precise offsets
   const TypeOopPtr *addr_t = adr->bottom_type()->isa_oopptr();
   intptr_t size_in_bytes = memory_size();
   Node* mem = in(MemNode::Memory);   // start searching here...
   int cnt = 50;             // Cycle limiter
   for (;;) {                // While we can dance past unrelated stores...
     if (--cnt < 0)  break;  // Caught in cycle or a complicated dance?
     if (mem->is_Store()) {
       Node* st_adr = mem->in(MemNode::Address);
       intptr_t st_offset = 0;
       Node* st_base = AddPNode::Ideal_base_and_offset(st_adr, phase, st_offset);
       if (st_base == NULL)
         break;              // inscrutable pointer
       if (st_offset != offset && st_offset != Type::OffsetBot) {
         const int MAX_STORE = BytesPerLong;
         if (st_offset >= offset + size_in_bytes ||
             st_offset <= offset - MAX_STORE ||
             st_offset <= offset - mem->as_Store()->memory_size()) {
           // Success:  The offsets are provably independent.
           // (You may ask, why not just test st_offset != offset and be done?
           // The answer is that stores of different sizes can co-exist
           // in the same sequence of RawMem effects.  We sometimes initialize
           // a whole 'tile' of array elements with a single jint or jlong.)
           mem = mem->in(MemNode::Memory);
           continue;           // (a) advance through independent store memory
         }
       }
       if (st_base != base &&
           detect_ptr_independence(base, alloc,
                                   st_base,
                                   AllocateNode::Ideal_allocation(st_base, phase),
                                   phase)) {
         // Success:  The bases are provably independent.
         mem = mem->in(MemNode::Memory);
         continue;           // (a) advance through independent store memory
       }
       // (b) At this point, if the bases or offsets do not agree, we lose,
       // since we have not managed to prove 'this' and 'mem' independent.
       if (st_base == base && st_offset == offset) {
         return mem;         // let caller handle steps (c), (d)
       }
     } else if (mem->is_Proj() && mem->in(0)->is_Initialize()) {
       InitializeNode* st_init = mem->in(0)->as_Initialize();
       AllocateNode*  st_alloc = st_init->allocation();
       if (st_alloc == NULL)
         break;              // something degenerated
       bool known_identical = false;
       bool known_independent = false;
       if (alloc == st_alloc)
         known_identical = true;
       else if (alloc != NULL)
         known_independent = true;
       else if (all_controls_dominate(this, st_alloc))
         known_independent = true;
       if (known_independent) {
         // The bases are provably independent: Either they are
         // manifestly distinct allocations, or else the control
         // of this load dominates the store's allocation.
         int alias_idx = phase->C->get_alias_index(adr_type());
         if (alias_idx == Compile::AliasIdxRaw) {
           mem = st_alloc->in(TypeFunc::Memory);
         } else {
           mem = st_init->memory(alias_idx);
         }
         continue;           // (a) advance through independent store memory
       }
       // (b) at this point, if we are not looking at a store initializing
       // the same allocation we are loading from, we lose.
       if (known_identical) {
         // From caller, can_see_stored_value will consult find_captured_store.
         return mem;         // let caller handle steps (c), (d)
       }
     } else if (addr_t != NULL && addr_t->is_instance_field()) {
       // Can't use optimize_simple_memory_chain() since it needs PhaseGVN.
       if (mem->is_Proj() && mem->in(0)->is_Call()) {
         CallNode *call = mem->in(0)->as_Call();
         if (!call->may_modify(addr_t, phase)) {
           mem = call->in(TypeFunc::Memory);
           continue;         // (a) advance through independent call memory
         }
       } else if (mem->is_Proj() && mem->in(0)->is_MemBar()) {
         mem = mem->in(0)->in(TypeFunc::Memory);
         continue;           // (a) advance through independent MemBar memory
       } else if (mem->is_MergeMem()) {
         int alias_idx = phase->C->get_alias_index(adr_type());
         mem = mem->as_MergeMem()->memory_at(alias_idx);
         continue;           // (a) advance through independent MergeMem memory
       }
     }
     // Unless there is an explicit 'continue', we must bail out here,
     // because 'mem' is an inscrutable memory state (e.g., a call).
     break;
   }
   return NULL;              // bail out
 }
 //----------------------calculate_adr_type-------------------------------------
 // Helper function.  Notices when the given type of address hits top or bottom.
 // Also, asserts a cross-check of the type against the expected address type.
 const TypePtr* MemNode::calculate_adr_type(const Type* t, const TypePtr* cross_check) {
   if (t == Type::TOP)  return NULL; // does not touch memory any more?
   #ifdef PRODUCT
   cross_check = NULL;
   #else
   if (!VerifyAliases || is_error_reported() || Node::in_dump())  cross_check = NULL;
   #endif
   const TypePtr* tp = t->isa_ptr();
   if (tp == NULL) {
     assert(cross_check == NULL || cross_check == TypePtr::BOTTOM, "expected memory type must be wide");
     return TypePtr::BOTTOM;           // touches lots of memory
   } else {
     #ifdef ASSERT
     // %%%% [phh] We don't check the alias index if cross_check is
     //            TypeRawPtr::BOTTOM.  Needs to be investigated.
     if (cross_check != NULL &&
         cross_check != TypePtr::BOTTOM &&
         cross_check != TypeRawPtr::BOTTOM) {
       // Recheck the alias index, to see if it has changed (due to a bug).
       Compile* C = Compile::current();
       assert(C->get_alias_index(cross_check) == C->get_alias_index(tp),
              "must stay in the original alias category");
       // The type of the address must be contained in the adr_type,
       // disregarding "null"-ness.
       // (We make an exception for TypeRawPtr::BOTTOM, which is a bit bucket.)
       const TypePtr* tp_notnull = tp->join(TypePtr::NOTNULL)->is_ptr();
       assert(cross_check->meet(tp_notnull) == cross_check,
              "real address must not escape from expected memory type");
     }
     #endif
     return tp;
   }
 }
 //------------------------adr_phi_is_loop_invariant----------------------------
 // A helper function for Ideal_DU_postCCP to check if a Phi in a counted
 // loop is loop invariant. Make a quick traversal of Phi and associated
 // CastPP nodes, looking to see if they are a closed group within the loop.
 bool MemNode::adr_phi_is_loop_invariant(Node* adr_phi, Node* cast) {
   // The idea is that the phi-nest must boil down to only CastPP nodes
   // with the same data. This implies that any path into the loop already
   // includes such a CastPP, and so the original cast, whatever its input,
   // must be covered by an equivalent cast, with an earlier control input.
   ResourceMark rm;
   // The loop entry input of the phi should be the unique dominating
   // node for every Phi/CastPP in the loop.
   Unique_Node_List closure;
   closure.push(adr_phi->in(LoopNode::EntryControl));
   // Add the phi node and the cast to the worklist.
   Unique_Node_List worklist;
   worklist.push(adr_phi);
   if( cast != NULL ){
     if( !cast->is_ConstraintCast() ) return false;
     worklist.push(cast);
   }
   // Begin recursive walk of phi nodes.
   while( worklist.size() ){
     // Take a node off the worklist
     Node *n = worklist.pop();
     if( !closure.member(n) ){
       // Add it to the closure.
       closure.push(n);
       // Make a sanity check to ensure we don't waste too much time here.
       if( closure.size() > 20) return false;
       // This node is OK if:
       //  - it is a cast of an identical value
       //  - or it is a phi node (then we add its inputs to the worklist)
       // Otherwise, the node is not OK, and we presume the cast is not invariant
       if( n->is_ConstraintCast() ){
         worklist.push(n->in(1));
       } else if( n->is_Phi() ) {
         for( uint i = 1; i < n->req(); i++ ) {
           worklist.push(n->in(i));
         }
       } else {
         return false;
       }
     }
   }
   // Quit when the worklist is empty, and we've found no offending nodes.
   return true;
 }
 //------------------------------Ideal_DU_postCCP-------------------------------
 // Find any cast-away of null-ness and keep its control.  Null cast-aways are
 // going away in this pass and we need to make this memory op depend on the
 // gating null check.
 // I tried to leave the CastPP's in.  This makes the graph more accurate in
 // some sense; we get to keep around the knowledge that an oop is not-null
 // after some test.  Alas, the CastPP's interfere with GVN (some values are
 // the regular oop, some are the CastPP of the oop, all merge at Phi's which
 // cannot collapse, etc).  This cost us 10% on SpecJVM, even when I removed
 // some of the more trivial cases in the optimizer.  Removing more useless
 // Phi's started allowing Loads to illegally float above null checks.  I gave
 // up on this approach.  CNC 10/20/2000
 Node *MemNode::Ideal_DU_postCCP( PhaseCCP *ccp ) {
   Node *ctr = in(MemNode::Control);
   Node *mem = in(MemNode::Memory);
   Node *adr = in(MemNode::Address);
   Node *skipped_cast = NULL;
   // Need a null check?  Regular static accesses do not because they are
   // from constant addresses.  Array ops are gated by the range check (which
   // always includes a NULL check).  Just check field ops.
   if( !ctr ) {
     // Scan upwards for the highest location we can place this memory op.
     while( true ) {
       switch( adr->Opcode() ) {
       case Op_AddP:             // No change to NULL-ness, so peek thru AddP's
         adr = adr->in(AddPNode::Base);
         continue;
       case Op_DecodeN:         // No change to NULL-ness, so peek thru
         adr = adr->in(1);
         continue;
       case Op_CastPP:
         // If the CastPP is useless, just peek on through it.
         if( ccp->type(adr) == ccp->type(adr->in(1)) ) {
           // Remember the cast that we've peeked though. If we peek
           // through more than one, then we end up remembering the highest
           // one, that is, if in a loop, the one closest to the top.
           skipped_cast = adr;
           adr = adr->in(1);
           continue;
         }
         // CastPP is going away in this pass!  We need this memory op to be
         // control-dependent on the test that is guarding the CastPP.
         ccp->hash_delete(this);
         set_req(MemNode::Control, adr->in(0));
         ccp->hash_insert(this);
         return this;
       case Op_Phi:
         // Attempt to float above a Phi to some dominating point.
         if (adr->in(0) != NULL && adr->in(0)->is_CountedLoop()) {
           // If we've already peeked through a Cast (which could have set the
           // control), we can't float above a Phi, because the skipped Cast
           // may not be loop invariant.
           if (adr_phi_is_loop_invariant(adr, skipped_cast)) {
             adr = adr->in(1);
             continue;
           }
         }
         // Intentional fallthrough!
         // No obvious dominating point.  The mem op is pinned below the Phi
         // by the Phi itself.  If the Phi goes away (no true value is merged)
         // then the mem op can float, but not indefinitely.  It must be pinned
         // behind the controls leading to the Phi.
       case Op_CheckCastPP:
         // These usually stick around to change address type, however a
         // useless one can be elided and we still need to pick up a control edge
         if (adr->in(0) == NULL) {
           // This CheckCastPP node has NO control and is likely useless. But we
           // need check further up the ancestor chain for a control input to keep
           // the node in place. 4959717.
           skipped_cast = adr;
           adr = adr->in(1);
           continue;
         }
         ccp->hash_delete(this);
         set_req(MemNode::Control, adr->in(0));
         ccp->hash_insert(this);
         return this;
         // List of "safe" opcodes; those that implicitly block the memory
         // op below any null check.
       case Op_CastX2P:          // no null checks on native pointers
       case Op_Parm:             // 'this' pointer is not null
       case Op_LoadP:            // Loading from within a klass
       case Op_LoadN:            // Loading from within a klass
       case Op_LoadKlass:        // Loading from within a klass
       case Op_ConP:             // Loading from a klass
       case Op_CreateEx:         // Sucking up the guts of an exception oop
       case Op_Con:              // Reading from TLS
       case Op_CMoveP:           // CMoveP is pinned
         break;                  // No progress
       case Op_Proj:             // Direct call to an allocation routine
       case Op_SCMemProj:        // Memory state from store conditional ops
 #ifdef ASSERT
         {
           assert(adr->as_Proj()->_con == TypeFunc::Parms, "must be return value");
           const Node* call = adr->in(0);
           if (call->is_CallStaticJava()) {
             const CallStaticJavaNode* call_java = call->as_CallStaticJava();
             const TypeTuple *r = call_java->tf()->range();
             assert(r->cnt() > TypeFunc::Parms, "must return value");
             const Type* ret_type = r->field_at(TypeFunc::Parms);
             assert(ret_type && ret_type->isa_ptr(), "must return pointer");
             // We further presume that this is one of
             // new_instance_Java, new_array_Java, or
             // the like, but do not assert for this.
           } else if (call->is_Allocate()) {
             // similar case to new_instance_Java, etc.
           } else if (!call->is_CallLeaf()) {
             // Projections from fetch_oop (OSR) are allowed as well.
             ShouldNotReachHere();
           }
         }
 #endif
         break;
       default:
         ShouldNotReachHere();
       }
       break;
     }
   }
   return  NULL;               // No progress
 }
 //=============================================================================
 uint LoadNode::size_of() const { return sizeof(*this); }
 uint LoadNode::cmp( const Node &n ) const
 { return !Type::cmp( _type, ((LoadNode&)n)._type ); }
 const Type *LoadNode::bottom_type() const { return _type; }
 uint LoadNode::ideal_reg() const {
   return Matcher::base2reg[_type->base()];
 }
 #ifndef PRODUCT
 void LoadNode::dump_spec(outputStream *st) const {
   MemNode::dump_spec(st);
   if( !Verbose && !WizardMode ) {
     // standard dump does this in Verbose and WizardMode
     st->print(" #"); _type->dump_on(st);
   }
 }
 #endif
 //----------------------------LoadNode::make-----------------------------------
 // Polymorphic factory method:
 Node *LoadNode::make( PhaseGVN& gvn, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt ) {
   Compile* C = gvn.C;
   // sanity check the alias category against the created node type
   assert(!(adr_type->isa_oopptr() &&
            adr_type->offset() == oopDesc::klass_offset_in_bytes()),
          "use LoadKlassNode instead");
   assert(!(adr_type->isa_aryptr() &&
            adr_type->offset() == arrayOopDesc::length_offset_in_bytes()),
          "use LoadRangeNode instead");
   switch (bt) {
   case T_BOOLEAN:
   case T_BYTE:    return new (C, 3) LoadBNode(ctl, mem, adr, adr_type, rt->is_int()    );
   case T_INT:     return new (C, 3) LoadINode(ctl, mem, adr, adr_type, rt->is_int()    );
   case T_CHAR:    return new (C, 3) LoadCNode(ctl, mem, adr, adr_type, rt->is_int()    );
   case T_SHORT:   return new (C, 3) LoadSNode(ctl, mem, adr, adr_type, rt->is_int()    );
   case T_LONG:    return new (C, 3) LoadLNode(ctl, mem, adr, adr_type, rt->is_long()   );
   case T_FLOAT:   return new (C, 3) LoadFNode(ctl, mem, adr, adr_type, rt              );
   case T_DOUBLE:  return new (C, 3) LoadDNode(ctl, mem, adr, adr_type, rt              );
   case T_ADDRESS: return new (C, 3) LoadPNode(ctl, mem, adr, adr_type, rt->is_ptr()    );
   case T_OBJECT:
 #ifdef _LP64
     if (adr->bottom_type()->is_narrow()) {
       const TypeNarrowOop* narrowtype;
       if (rt->isa_narrowoop()) {
         narrowtype = rt->is_narrowoop();
       } else {
         narrowtype = rt->is_oopptr()->make_narrowoop();
       }
       Node* load  = gvn.transform(new (C, 3) LoadNNode(ctl, mem, adr, adr_type, narrowtype));
       return DecodeNNode::decode(&gvn, load);
     } else
 #endif
       {
         assert(!adr->bottom_type()->is_narrow(), "should have got back a narrow oop");
         return new (C, 3) LoadPNode(ctl, mem, adr, adr_type, rt->is_oopptr());
       }
   }
   ShouldNotReachHere();
   return (LoadNode*)NULL;
 }
 LoadLNode* LoadLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt) {
   bool require_atomic = true;
   return new (C, 3) LoadLNode(ctl, mem, adr, adr_type, rt->is_long(), require_atomic);
 }
 //------------------------------hash-------------------------------------------
 uint LoadNode::hash() const {
   // unroll addition of interesting fields
   return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address);
 }
 //---------------------------can_see_stored_value------------------------------
 // This routine exists to make sure this set of tests is done the same
 // everywhere.  We need to make a coordinated change: first LoadNode::Ideal
 // will change the graph shape in a way which makes memory alive twice at the
 // same time (uses the Oracle model of aliasing), then some
 // LoadXNode::Identity will fold things back to the equivalence-class model
 // of aliasing.
 Node* MemNode::can_see_stored_value(Node* st, PhaseTransform* phase) const {
   Node* ld_adr = in(MemNode::Address);
   const TypeInstPtr* tp = phase->type(ld_adr)->isa_instptr();
   Compile::AliasType* atp = tp != NULL ? phase->C->alias_type(tp) : NULL;
   if (EliminateAutoBox && atp != NULL && atp->index() >= Compile::AliasIdxRaw &&
       atp->field() != NULL && !atp->field()->is_volatile()) {
     uint alias_idx = atp->index();
     bool final = atp->field()->is_final();
     Node* result = NULL;
     Node* current = st;
     // Skip through chains of MemBarNodes checking the MergeMems for
     // new states for the slice of this load.  Stop once any other
     // kind of node is encountered.  Loads from final memory can skip
     // through any kind of MemBar but normal loads shouldn't skip
     // through MemBarAcquire since the could allow them to move out of
     // a synchronized region.
     while (current->is_Proj()) {
       int opc = current->in(0)->Opcode();
       if ((final && opc == Op_MemBarAcquire) ||
           opc == Op_MemBarRelease || opc == Op_MemBarCPUOrder) {
         Node* mem = current->in(0)->in(TypeFunc::Memory);
         if (mem->is_MergeMem()) {
           MergeMemNode* merge = mem->as_MergeMem();
           Node* new_st = merge->memory_at(alias_idx);
           if (new_st == merge->base_memory()) {
             // Keep searching
             current = merge->base_memory();
             continue;
           }
           // Save the new memory state for the slice and fall through
           // to exit.
           result = new_st;
         }
       }
       break;
     }
     if (result != NULL) {
       st = result;
     }
   }
   // Loop around twice in the case Load -> Initialize -> Store.
   // (See PhaseIterGVN::add_users_to_worklist, which knows about this case.)
   for (int trip = 0; trip <= 1; trip++) {
     if (st->is_Store()) {
       Node* st_adr = st->in(MemNode::Address);
       if (!phase->eqv(st_adr, ld_adr)) {
         // Try harder before giving up...  Match raw and non-raw pointers.
         intptr_t st_off = 0;
         AllocateNode* alloc = AllocateNode::Ideal_allocation(st_adr, phase, st_off);
         if (alloc == NULL)       return NULL;
         intptr_t ld_off = 0;
         AllocateNode* allo2 = AllocateNode::Ideal_allocation(ld_adr, phase, ld_off);
         if (alloc != allo2)      return NULL;
         if (ld_off != st_off)    return NULL;
         // At this point we have proven something like this setup:
         //  A = Allocate(...)
         //  L = LoadQ(,  AddP(CastPP(, A.Parm),, #Off))
         //  S = StoreQ(, AddP(,        A.Parm  , #Off), V)
         // (Actually, we haven't yet proven the Q's are the same.)
         // In other words, we are loading from a casted version of
         // the same pointer-and-offset that we stored to.
         // Thus, we are able to replace L by V.
       }
       // Now prove that we have a LoadQ matched to a StoreQ, for some Q.
       if (store_Opcode() != st->Opcode())
         return NULL;
       return st->in(MemNode::ValueIn);
     }
     intptr_t offset = 0;  // scratch
     // A load from a freshly-created object always returns zero.
     // (This can happen after LoadNode::Ideal resets the load's memory input
     // to find_captured_store, which returned InitializeNode::zero_memory.)
     if (st->is_Proj() && st->in(0)->is_Allocate() &&
         st->in(0) == AllocateNode::Ideal_allocation(ld_adr, phase, offset) &&
         offset >= st->in(0)->as_Allocate()->minimum_header_size()) {
       // return a zero value for the load's basic type
       // (This is one of the few places where a generic PhaseTransform
       // can create new nodes.  Think of it as lazily manifesting
       // virtually pre-existing constants.)
       return phase->zerocon(memory_type());
     }
     // A load from an initialization barrier can match a captured store.
     if (st->is_Proj() && st->in(0)->is_Initialize()) {
       InitializeNode* init = st->in(0)->as_Initialize();
       AllocateNode* alloc = init->allocation();
       if (alloc != NULL &&
           alloc == AllocateNode::Ideal_allocation(ld_adr, phase, offset)) {
         // examine a captured store value
         st = init->find_captured_store(offset, memory_size(), phase);
         if (st != NULL)
           continue;             // take one more trip around
       }
     }
     break;
   }
   return NULL;
 }
 //----------------------is_instance_field_load_with_local_phi------------------
 bool LoadNode::is_instance_field_load_with_local_phi(Node* ctrl) {
   if( in(MemNode::Memory)->is_Phi() && in(MemNode::Memory)->in(0) == ctrl &&
       in(MemNode::Address)->is_AddP() ) {
     const TypeOopPtr* t_oop = in(MemNode::Address)->bottom_type()->isa_oopptr();
     // Only instances.
     if( t_oop != NULL && t_oop->is_instance_field() &&
         t_oop->offset() != Type::OffsetBot &&
         t_oop->offset() != Type::OffsetTop) {
       return true;
     }
   }
   return false;
 }
 //------------------------------Identity---------------------------------------
 // Loads are identity if previous store is to same address
 Node *LoadNode::Identity( PhaseTransform *phase ) {
   // If the previous store-maker is the right kind of Store, and the store is
   // to the same address, then we are equal to the value stored.
   Node* mem = in(MemNode::Memory);
   Node* value = can_see_stored_value(mem, phase);
   if( value ) {
     // byte, short & char stores truncate naturally.
     // A load has to load the truncated value which requires
     // some sort of masking operation and that requires an
     // Ideal call instead of an Identity call.
     if (memory_size() < BytesPerInt) {
       // If the input to the store does not fit with the load's result type,
       // it must be truncated via an Ideal call.
       if (!phase->type(value)->higher_equal(phase->type(this)))
         return this;
     }
     // (This works even when value is a Con, but LoadNode::Value
     // usually runs first, producing the singleton type of the Con.)
     return value;
   }
   // Search for an existing data phi which was generated before for the same
   // instance's field to avoid infinite genertion of phis in a loop.
   Node *region = mem->in(0);
   if (is_instance_field_load_with_local_phi(region)) {
     const TypePtr *addr_t = in(MemNode::Address)->bottom_type()->isa_ptr();
     int this_index  = phase->C->get_alias_index(addr_t);
     int this_offset = addr_t->offset();
     int this_id    = addr_t->is_oopptr()->instance_id();
     const Type* this_type = bottom_type();
     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
       Node* phi = region->fast_out(i);
       if (phi->is_Phi() && phi != mem &&
           phi->as_Phi()->is_same_inst_field(this_type, this_id, this_index, this_offset)) {
         return phi;
       }
     }
   }
   return this;
 }
 // Returns true if the AliasType refers to the field that holds the
 // cached box array.  Currently only handles the IntegerCache case.
 static bool is_autobox_cache(Compile::AliasType* atp) {
   if (atp != NULL && atp->field() != NULL) {
     ciField* field = atp->field();
     ciSymbol* klass = field->holder()->name();
     if (field->name() == ciSymbol::cache_field_name() &&
         field->holder()->uses_default_loader() &&
         klass == ciSymbol::java_lang_Integer_IntegerCache()) {
       return true;
     }
   }
   return false;
 }
 // Fetch the base value in the autobox array
 static bool fetch_autobox_base(Compile::AliasType* atp, int& cache_offset) {
   if (atp != NULL && atp->field() != NULL) {
     ciField* field = atp->field();
     ciSymbol* klass = field->holder()->name();
     if (field->name() == ciSymbol::cache_field_name() &&
         field->holder()->uses_default_loader() &&
         klass == ciSymbol::java_lang_Integer_IntegerCache()) {
       assert(field->is_constant(), "what?");
       ciObjArray* array = field->constant_value().as_object()->as_obj_array();
       // Fetch the box object at the base of the array and get its value
       ciInstance* box = array->obj_at(0)->as_instance();
       ciInstanceKlass* ik = box->klass()->as_instance_klass();
       if (ik->nof_nonstatic_fields() == 1) {
         // This should be true nonstatic_field_at requires calling
         // nof_nonstatic_fields so check it anyway
         ciConstant c = box->field_value(ik->nonstatic_field_at(0));
         cache_offset = c.as_int();
       }
       return true;
     }
   }
   return false;
 }
 // Returns true if the AliasType refers to the value field of an
 // autobox object.  Currently only handles Integer.
 static bool is_autobox_object(Compile::AliasType* atp) {
   if (atp != NULL && atp->field() != NULL) {
     ciField* field = atp->field();
     ciSymbol* klass = field->holder()->name();
     if (field->name() == ciSymbol::value_name() &&
         field->holder()->uses_default_loader() &&
         klass == ciSymbol::java_lang_Integer()) {
       return true;
     }
   }
   return false;
 }
 // We're loading from an object which has autobox behaviour.
 // If this object is result of a valueOf call we'll have a phi
 // merging a newly allocated object and a load from the cache.
 // We want to replace this load with the original incoming
 // argument to the valueOf call.
 Node* LoadNode::eliminate_autobox(PhaseGVN* phase) {
   Node* base = in(Address)->in(AddPNode::Base);
   if (base->is_Phi() && base->req() == 3) {
     AllocateNode* allocation = NULL;
     int allocation_index = -1;
     int load_index = -1;
     for (uint i = 1; i < base->req(); i++) {
       allocation = AllocateNode::Ideal_allocation(base->in(i), phase);
       if (allocation != NULL) {
         allocation_index = i;
         load_index = 3 - allocation_index;
         break;
       }
     }
     LoadNode* load = NULL;
     if (allocation != NULL && base->in(load_index)->is_Load()) {
       load = base->in(load_index)->as_Load();
     }
     if (load != NULL && in(Memory)->is_Phi() && in(Memory)->in(0) == base->in(0)) {
       // Push the loads from the phi that comes from valueOf up
       // through it to allow elimination of the loads and the recovery
       // of the original value.
       Node* mem_phi = in(Memory);
       Node* offset = in(Address)->in(AddPNode::Offset);
       Node* in1 = clone();
       Node* in1_addr = in1->in(Address)->clone();
       in1_addr->set_req(AddPNode::Base, base->in(allocation_index));
       in1_addr->set_req(AddPNode::Address, base->in(allocation_index));
       in1_addr->set_req(AddPNode::Offset, offset);
       in1->set_req(0, base->in(allocation_index));
       in1->set_req(Address, in1_addr);
       in1->set_req(Memory, mem_phi->in(allocation_index));
       Node* in2 = clone();
       Node* in2_addr = in2->in(Address)->clone();
       in2_addr->set_req(AddPNode::Base, base->in(load_index));
       in2_addr->set_req(AddPNode::Address, base->in(load_index));
       in2_addr->set_req(AddPNode::Offset, offset);
       in2->set_req(0, base->in(load_index));
       in2->set_req(Address, in2_addr);
       in2->set_req(Memory, mem_phi->in(load_index));
       in1_addr = phase->transform(in1_addr);
       in1 =      phase->transform(in1);
       in2_addr = phase->transform(in2_addr);
       in2 =      phase->transform(in2);
       PhiNode* result = PhiNode::make_blank(base->in(0), this);
       result->set_req(allocation_index, in1);
       result->set_req(load_index, in2);
       return result;
     }
   } else if (base->is_Load()) {
     // Eliminate the load of Integer.value for integers from the cache
     // array by deriving the value from the index into the array.
     // Capture the offset of the load and then reverse the computation.
     Node* load_base = base->in(Address)->in(AddPNode::Base);
     if (load_base != NULL) {
       Compile::AliasType* atp = phase->C->alias_type(load_base->adr_type());
       intptr_t cache_offset;
       int shift = -1;
       Node* cache = NULL;
       if (is_autobox_cache(atp)) {
         shift  = exact_log2(type2aelembytes(T_OBJECT));
         cache = AddPNode::Ideal_base_and_offset(load_base->in(Address), phase, cache_offset);
       }
       if (cache != NULL && base->in(Address)->is_AddP()) {
         Node* elements[4];
         int count = base->in(Address)->as_AddP()->unpack_offsets(elements, ARRAY_SIZE(elements));
         int cache_low;
         if (count > 0 && fetch_autobox_base(atp, cache_low)) {
           int offset = arrayOopDesc::base_offset_in_bytes(memory_type()) - (cache_low << shift);
           // Add up all the offsets making of the address of the load
           Node* result = elements[0];
           for (int i = 1; i < count; i++) {
             result = phase->transform(new (phase->C, 3) AddXNode(result, elements[i]));
           }
           // Remove the constant offset from the address and then
           // remove the scaling of the offset to recover the original index.
           result = phase->transform(new (phase->C, 3) AddXNode(result, phase->MakeConX(-offset)));
           if (result->Opcode() == Op_LShiftX && result->in(2) == phase->intcon(shift)) {
             // Peel the shift off directly but wrap it in a dummy node
             // since Ideal can't return existing nodes
             result = new (phase->C, 3) RShiftXNode(result->in(1), phase->intcon(0));
           } else {
             result = new (phase->C, 3) RShiftXNode(result, phase->intcon(shift));
           }
 #ifdef _LP64
           result = new (phase->C, 2) ConvL2INode(phase->transform(result));
 #endif
           return result;
         }
       }
     }
   }
   return NULL;
 }
 //------------------------------Ideal------------------------------------------
 // If the load is from Field memory and the pointer is non-null, we can
 // zero out the control input.
 // If the offset is constant and the base is an object allocation,
 // try to hook me up to the exact initializing store.
 Node *LoadNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   Node* p = MemNode::Ideal_common(phase, can_reshape);
   if (p)  return (p == NodeSentinel) ? NULL : p;
   Node* ctrl    = in(MemNode::Control);
   Node* address = in(MemNode::Address);
   // Skip up past a SafePoint control.  Cannot do this for Stores because
   // pointer stores & cardmarks must stay on the same side of a SafePoint.
   if( ctrl != NULL && ctrl->Opcode() == Op_SafePoint &&
       phase->C->get_alias_index(phase->type(address)->is_ptr()) != Compile::AliasIdxRaw ) {
     ctrl = ctrl->in(0);
     set_req(MemNode::Control,ctrl);
   }
   // Check for useless control edge in some common special cases
   if (in(MemNode::Control) != NULL) {
     intptr_t ignore = 0;
     Node*    base   = AddPNode::Ideal_base_and_offset(address, phase, ignore);
     if (base != NULL
         && phase->type(base)->higher_equal(TypePtr::NOTNULL)
         && all_controls_dominate(base, phase->C->start())) {
       // A method-invariant, non-null address (constant or 'this' argument).
       set_req(MemNode::Control, NULL);
     }
   }
   if (EliminateAutoBox && can_reshape && in(Address)->is_AddP()) {
     Node* base = in(Address)->in(AddPNode::Base);
     if (base != NULL) {
       Compile::AliasType* atp = phase->C->alias_type(adr_type());
       if (is_autobox_object(atp)) {
         Node* result = eliminate_autobox(phase);
         if (result != NULL) return result;
       }
     }
   }
   Node* mem = in(MemNode::Memory);
   const TypePtr *addr_t = phase->type(address)->isa_ptr();
   if (addr_t != NULL) {
     // try to optimize our memory input
     Node* opt_mem = MemNode::optimize_memory_chain(mem, addr_t, phase);
     if (opt_mem != mem) {
       set_req(MemNode::Memory, opt_mem);
       return this;
     }
     const TypeOopPtr *t_oop = addr_t->isa_oopptr();
     if (can_reshape && opt_mem->is_Phi() &&
         (t_oop != NULL) && t_oop->is_instance_field()) {
       assert(t_oop->offset() != Type::OffsetBot && t_oop->offset() != Type::OffsetTop, "");
       Node *region = opt_mem->in(0);
       uint cnt = opt_mem->req();
       for( uint i = 1; i < cnt; i++ ) {
         Node *in = opt_mem->in(i);
         if( in == NULL ) {
           region = NULL; // Wait stable graph
           break;
         }
       }
       if (region != NULL) {
         // Check for loop invariant.
         if (cnt == 3) {
           for( uint i = 1; i < cnt; i++ ) {
             Node *in = opt_mem->in(i);
             Node* m = MemNode::optimize_memory_chain(in, addr_t, phase);
             if (m == opt_mem) {
               set_req(MemNode::Memory, opt_mem->in(cnt - i)); // Skip this phi.
               return this;
             }
           }
         }
         // Split through Phi (see original code in loopopts.cpp).
         assert(phase->C->have_alias_type(addr_t), "instance should have alias type");
         // Do nothing here if Identity will find a value
         // (to avoid infinite chain of value phis generation).
         if ( !phase->eqv(this, this->Identity(phase)) )
           return NULL;
         const Type* this_type = this->bottom_type();
         int this_index  = phase->C->get_alias_index(addr_t);
         int this_offset = addr_t->offset();
         int this_iid    = addr_t->is_oopptr()->instance_id();
         int wins = 0;
         PhaseIterGVN *igvn = phase->is_IterGVN();
         Node *phi = new (igvn->C, region->req()) PhiNode(region, this_type, NULL, this_iid, this_index, this_offset);
         for( uint i = 1; i < region->req(); i++ ) {
           Node *x;
           Node* the_clone = NULL;
           if( region->in(i) == phase->C->top() ) {
             x = phase->C->top();      // Dead path?  Use a dead data op
           } else {
             x = this->clone();        // Else clone up the data op
             the_clone = x;            // Remember for possible deletion.
             // Alter data node to use pre-phi inputs
             if( this->in(0) == region ) {
               x->set_req( 0, region->in(i) );
             } else {
               x->set_req( 0, NULL );
             }
             for( uint j = 1; j < this->req(); j++ ) {
               Node *in = this->in(j);
               if( in->is_Phi() && in->in(0) == region )
                 x->set_req( j, in->in(i) ); // Use pre-Phi input for the clone
             }
           }
           // Check for a 'win' on some paths
           const Type *t = x->Value(igvn);
           bool singleton = t->singleton();
           // See comments in PhaseIdealLoop::split_thru_phi().
           if( singleton && t == Type::TOP ) {
             singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
           }
           if( singleton ) {
             wins++;
             x = igvn->makecon(t);
           } else {
             // We now call Identity to try to simplify the cloned node.
             // Note that some Identity methods call phase->type(this).
             // Make sure that the type array is big enough for
             // our new node, even though we may throw the node away.
             // (This tweaking with igvn only works because x is a new node.)
             igvn->set_type(x, t);
             Node *y = x->Identity(igvn);
             if( y != x ) {
               wins++;
               x = y;
             } else {
               y = igvn->hash_find(x);
               if( y ) {
                 wins++;
                 x = y;
               } else {
                 // Else x is a new node we are keeping
                 // We do not need register_new_node_with_optimizer
                 // because set_type has already been called.
                 igvn->_worklist.push(x);
               }
             }
           }
           if (x != the_clone && the_clone != NULL)
             igvn->remove_dead_node(the_clone);
           phi->set_req(i, x);
         }
         if( wins > 0 ) {
           // Record Phi
           igvn->register_new_node_with_optimizer(phi);
           return phi;
         } else {
           igvn->remove_dead_node(phi);
         }
       }
     }
   }
   // Check for prior store with a different base or offset; make Load
   // independent.  Skip through any number of them.  Bail out if the stores
   // are in an endless dead cycle and report no progress.  This is a key
   // transform for Reflection.  However, if after skipping through the Stores
   // we can't then fold up against a prior store do NOT do the transform as
   // this amounts to using the 'Oracle' model of aliasing.  It leaves the same
   // array memory alive twice: once for the hoisted Load and again after the
   // bypassed Store.  This situation only works if EVERYBODY who does
   // anti-dependence work knows how to bypass.  I.e. we need all
   // anti-dependence checks to ask the same Oracle.  Right now, that Oracle is
   // the alias index stuff.  So instead, peek through Stores and IFF we can
   // fold up, do so.
   Node* prev_mem = find_previous_store(phase);
   // Steps (a), (b):  Walk past independent stores to find an exact match.
   if (prev_mem != NULL && prev_mem != in(MemNode::Memory)) {
     // (c) See if we can fold up on the spot, but don't fold up here.
     // Fold-up might require truncation (for LoadB/LoadS/LoadC) or
     // just return a prior value, which is done by Identity calls.
     if (can_see_stored_value(prev_mem, phase)) {
       // Make ready for step (d):
       set_req(MemNode::Memory, prev_mem);
       return this;
     }
   }
   return NULL;                  // No further progress
 }
 // Helper to recognize certain Klass fields which are invariant across
 // some group of array types (e.g., int[] or all T[] where T < Object).
 const Type*
 LoadNode::load_array_final_field(const TypeKlassPtr *tkls,
                                  ciKlass* klass) const {
   if (tkls->offset() == Klass::modifier_flags_offset_in_bytes() + (int)sizeof(oopDesc)) {
     // The field is Klass::_modifier_flags.  Return its (constant) value.
     // (Folds up the 2nd indirection in aClassConstant.getModifiers().)
     assert(this->Opcode() == Op_LoadI, "must load an int from _modifier_flags");
     return TypeInt::make(klass->modifier_flags());
   }
   if (tkls->offset() == Klass::access_flags_offset_in_bytes() + (int)sizeof(oopDesc)) {
     // The field is Klass::_access_flags.  Return its (constant) value.
     // (Folds up the 2nd indirection in Reflection.getClassAccessFlags(aClassConstant).)
     assert(this->Opcode() == Op_LoadI, "must load an int from _access_flags");
     return TypeInt::make(klass->access_flags());
   }
   if (tkls->offset() == Klass::layout_helper_offset_in_bytes() + (int)sizeof(oopDesc)) {
     // The field is Klass::_layout_helper.  Return its constant value if known.
     assert(this->Opcode() == Op_LoadI, "must load an int from _layout_helper");
     return TypeInt::make(klass->layout_helper());
   }
   // No match.
   return NULL;
 }
 //------------------------------Value-----------------------------------------
 const Type *LoadNode::Value( PhaseTransform *phase ) const {
   // Either input is TOP ==> the result is TOP
   Node* mem = in(MemNode::Memory);
   const Type *t1 = phase->type(mem);
   if (t1 == Type::TOP)  return Type::TOP;
   Node* adr = in(MemNode::Address);
   const TypePtr* tp = phase->type(adr)->isa_ptr();
   if (tp == NULL || tp->empty())  return Type::TOP;
   int off = tp->offset();
   assert(off != Type::OffsetTop, "case covered by TypePtr::empty");
   // Try to guess loaded type from pointer type
   if (tp->base() == Type::AryPtr) {
     const Type *t = tp->is_aryptr()->elem();
     // Don't do this for integer types. There is only potential profit if
     // the element type t is lower than _type; that is, for int types, if _type is
     // more restrictive than t.  This only happens here if one is short and the other
     // char (both 16 bits), and in those cases we've made an intentional decision
     // to use one kind of load over the other. See AndINode::Ideal and 4965907.
     // Also, do not try to narrow the type for a LoadKlass, regardless of offset.
     //
     // Yes, it is possible to encounter an expression like (LoadKlass p1:(AddP x x 8))
     // where the _gvn.type of the AddP is wider than 8.  This occurs when an earlier
     // copy p0 of (AddP x x 8) has been proven equal to p1, and the p0 has been
     // subsumed by p1.  If p1 is on the worklist but has not yet been re-transformed,
     // it is possible that p1 will have a type like Foo*[int+]:NotNull*+any.
     // In fact, that could have been the original type of p1, and p1 could have
     // had an original form like p1:(AddP x x (LShiftL quux 3)), where the
     // expression (LShiftL quux 3) independently optimized to the constant 8.
     if ((t->isa_int() == NULL) && (t->isa_long() == NULL)
         && Opcode() != Op_LoadKlass) {
       // t might actually be lower than _type, if _type is a unique
       // concrete subclass of abstract class t.
       // Make sure the reference is not into the header, by comparing
       // the offset against the offset of the start of the array's data.
       // Different array types begin at slightly different offsets (12 vs. 16).
       // We choose T_BYTE as an example base type that is least restrictive
       // as to alignment, which will therefore produce the smallest
       // possible base offset.
       const int min_base_off = arrayOopDesc::base_offset_in_bytes(T_BYTE);
       if ((uint)off >= (uint)min_base_off) {  // is the offset beyond the header?
         const Type* jt = t->join(_type);
         // In any case, do not allow the join, per se, to empty out the type.
         if (jt->empty() && !t->empty()) {
           // This can happen if a interface-typed array narrows to a class type.
           jt = _type;
         }
         if (EliminateAutoBox) {
           // The pointers in the autobox arrays are always non-null
           Node* base = in(Address)->in(AddPNode::Base);
           if (base != NULL) {
             Compile::AliasType* atp = phase->C->alias_type(base->adr_type());
             if (is_autobox_cache(atp)) {
               return jt->join(TypePtr::NOTNULL)->is_ptr();
             }
           }
         }
         return jt;
       }
     }
   } else if (tp->base() == Type::InstPtr) {
     assert( off != Type::OffsetBot ||
             // arrays can be cast to Objects
             tp->is_oopptr()->klass()->is_java_lang_Object() ||
             // unsafe field access may not have a constant offset
             phase->C->has_unsafe_access(),
             "Field accesses must be precise" );
     // For oop loads, we expect the _type to be precise
   } else if (tp->base() == Type::KlassPtr) {
     assert( off != Type::OffsetBot ||
             // arrays can be cast to Objects
             tp->is_klassptr()->klass()->is_java_lang_Object() ||
             // also allow array-loading from the primary supertype
             // array during subtype checks
             Opcode() == Op_LoadKlass,
             "Field accesses must be precise" );
     // For klass/static loads, we expect the _type to be precise
   }
   const TypeKlassPtr *tkls = tp->isa_klassptr();
   if (tkls != NULL && !StressReflectiveCode) {
     ciKlass* klass = tkls->klass();
     if (klass->is_loaded() && tkls->klass_is_exact()) {
       // We are loading a field from a Klass metaobject whose identity
       // is known at compile time (the type is "exact" or "precise").
       // Check for fields we know are maintained as constants by the VM.
       if (tkls->offset() == Klass::super_check_offset_offset_in_bytes() + (int)sizeof(oopDesc)) {
         // The field is Klass::_super_check_offset.  Return its (constant) value.
         // (Folds up type checking code.)
         assert(Opcode() == Op_LoadI, "must load an int from _super_check_offset");
         return TypeInt::make(klass->super_check_offset());
       }
       // Compute index into primary_supers array
       juint depth = (tkls->offset() - (Klass::primary_supers_offset_in_bytes() + (int)sizeof(oopDesc))) / sizeof(klassOop);
       // Check for overflowing; use unsigned compare to handle the negative case.
       if( depth < ciKlass::primary_super_limit() ) {
         // The field is an element of Klass::_primary_supers.  Return its (constant) value.
         // (Folds up type checking code.)
         assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
         ciKlass *ss = klass->super_of_depth(depth);
         return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
       }
       const Type* aift = load_array_final_field(tkls, klass);
       if (aift != NULL)  return aift;
       if (tkls->offset() == in_bytes(arrayKlass::component_mirror_offset()) + (int)sizeof(oopDesc)
           && klass->is_array_klass()) {
         // The field is arrayKlass::_component_mirror.  Return its (constant) value.
         // (Folds up aClassConstant.getComponentType, common in Arrays.copyOf.)
         assert(Opcode() == Op_LoadP, "must load an oop from _component_mirror");
         return TypeInstPtr::make(klass->as_array_klass()->component_mirror());
       }
       if (tkls->offset() == Klass::java_mirror_offset_in_bytes() + (int)sizeof(oopDesc)) {
         // The field is Klass::_java_mirror.  Return its (constant) value.
         // (Folds up the 2nd indirection in anObjConstant.getClass().)
         assert(Opcode() == Op_LoadP, "must load an oop from _java_mirror");
         return TypeInstPtr::make(klass->java_mirror());
       }
     }
     // We can still check if we are loading from the primary_supers array at a
     // shallow enough depth.  Even though the klass is not exact, entries less
     // than or equal to its super depth are correct.
     if (klass->is_loaded() ) {
       ciType *inner = klass->klass();
       while( inner->is_obj_array_klass() )
         inner = inner->as_obj_array_klass()->base_element_type();
       if( inner->is_instance_klass() &&
           !inner->as_instance_klass()->flags().is_interface() ) {
         // Compute index into primary_supers array
         juint depth = (tkls->offset() - (Klass::primary_supers_offset_in_bytes() + (int)sizeof(oopDesc))) / sizeof(klassOop);
         // Check for overflowing; use unsigned compare to handle the negative case.
         if( depth < ciKlass::primary_super_limit() &&
             depth <= klass->super_depth() ) { // allow self-depth checks to handle self-check case
           // The field is an element of Klass::_primary_supers.  Return its (constant) value.
           // (Folds up type checking code.)
           assert(Opcode() == Op_LoadKlass, "must load a klass from _primary_supers");
           ciKlass *ss = klass->super_of_depth(depth);
           return ss ? TypeKlassPtr::make(ss) : TypePtr::NULL_PTR;
         }
       }
     }
     // If the type is enough to determine that the thing is not an array,
     // we can give the layout_helper a positive interval type.
     // This will help short-circuit some reflective code.
     if (tkls->offset() == Klass::layout_helper_offset_in_bytes() + (int)sizeof(oopDesc)
         && !klass->is_array_klass() // not directly typed as an array
         && !klass->is_interface()  // specifically not Serializable & Cloneable
         && !klass->is_java_lang_Object()   // not the supertype of all T[]
         ) {
       // Note:  When interfaces are reliable, we can narrow the interface
       // test to (klass != Serializable && klass != Cloneable).
       assert(Opcode() == Op_LoadI, "must load an int from _layout_helper");
       jint min_size = Klass::instance_layout_helper(oopDesc::header_size(), false);
       // The key property of this type is that it folds up tests
       // for array-ness, since it proves that the layout_helper is positive.
       // Thus, a generic value like the basic object layout helper works fine.
       return TypeInt::make(min_size, max_jint, Type::WidenMin);
     }
   }
   // If we are loading from a freshly-allocated object, produce a zero,
   // if the load is provably beyond the header of the object.
   // (Also allow a variable load from a fresh array to produce zero.)
   if (ReduceFieldZeroing) {
     Node* value = can_see_stored_value(mem,phase);
     if (value != NULL && value->is_Con())
       return value->bottom_type();
   }
   const TypeOopPtr *tinst = tp->isa_oopptr();
   if (tinst != NULL && tinst->is_instance_field()) {
     // If we have an instance type and our memory input is the
     // programs's initial memory state, there is no matching store,
     // so just return a zero of the appropriate type
     Node *mem = in(MemNode::Memory);
     if (mem->is_Parm() && mem->in(0)->is_Start()) {
       assert(mem->as_Parm()->_con == TypeFunc::Memory, "must be memory Parm");
       return Type::get_zero_type(_type->basic_type());
     }
   }
   return _type;
 }
 //------------------------------match_edge-------------------------------------
 // Do we Match on this edge index or not?  Match only the address.
 uint LoadNode::match_edge(uint idx) const {
   return idx == MemNode::Address;
 }
 //--------------------------LoadBNode::Ideal--------------------------------------
 //
 //  If the previous store is to the same address as this load,
 //  and the value stored was larger than a byte, replace this load
 //  with the value stored truncated to a byte.  If no truncation is
 //  needed, the replacement is done in LoadNode::Identity().
 //
 Node *LoadBNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   Node* mem = in(MemNode::Memory);
   Node* value = can_see_stored_value(mem,phase);
   if( value && !phase->type(value)->higher_equal( _type ) ) {
     Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(24)) );
     return new (phase->C, 3) RShiftINode(result, phase->intcon(24));
   }
   // Identity call will handle the case where truncation is not needed.
   return LoadNode::Ideal(phase, can_reshape);
 }
 //--------------------------LoadCNode::Ideal--------------------------------------
 //
 //  If the previous store is to the same address as this load,
 //  and the value stored was larger than a char, replace this load
 //  with the value stored truncated to a char.  If no truncation is
 //  needed, the replacement is done in LoadNode::Identity().
 //
 Node *LoadCNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   Node* mem = in(MemNode::Memory);
   Node* value = can_see_stored_value(mem,phase);
   if( value && !phase->type(value)->higher_equal( _type ) )
     return new (phase->C, 3) AndINode(value,phase->intcon(0xFFFF));
   // Identity call will handle the case where truncation is not needed.
   return LoadNode::Ideal(phase, can_reshape);
 }
 //--------------------------LoadSNode::Ideal--------------------------------------
 //
 //  If the previous store is to the same address as this load,
 //  and the value stored was larger than a short, replace this load
 //  with the value stored truncated to a short.  If no truncation is
 //  needed, the replacement is done in LoadNode::Identity().
 //
 Node *LoadSNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   Node* mem = in(MemNode::Memory);
   Node* value = can_see_stored_value(mem,phase);
   if( value && !phase->type(value)->higher_equal( _type ) ) {
     Node *result = phase->transform( new (phase->C, 3) LShiftINode(value, phase->intcon(16)) );
     return new (phase->C, 3) RShiftINode(result, phase->intcon(16));
   }
   // Identity call will handle the case where truncation is not needed.
   return LoadNode::Ideal(phase, can_reshape);
 }
 //=============================================================================
 //------------------------------Value------------------------------------------
 const Type *LoadKlassNode::Value( PhaseTransform *phase ) const {
   // Either input is TOP ==> the result is TOP
   const Type *t1 = phase->type( in(MemNode::Memory) );
   if (t1 == Type::TOP)  return Type::TOP;
   Node *adr = in(MemNode::Address);
   const Type *t2 = phase->type( adr );
   if (t2 == Type::TOP)  return Type::TOP;
   const TypePtr *tp = t2->is_ptr();
   if (TypePtr::above_centerline(tp->ptr()) ||
       tp->ptr() == TypePtr::Null)  return Type::TOP;
   // Return a more precise klass, if possible
   const TypeInstPtr *tinst = tp->isa_instptr();
   if (tinst != NULL) {
     ciInstanceKlass* ik = tinst->klass()->as_instance_klass();
     int offset = tinst->offset();
     if (ik == phase->C->env()->Class_klass()
         && (offset == java_lang_Class::klass_offset_in_bytes() ||
             offset == java_lang_Class::array_klass_offset_in_bytes())) {
       // We are loading a special hidden field from a Class mirror object,
       // the field which points to the VM's Klass metaobject.
       ciType* t = tinst->java_mirror_type();
       // java_mirror_type returns non-null for compile-time Class constants.
       if (t != NULL) {
         // constant oop => constant klass
         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
           return TypeKlassPtr::make(ciArrayKlass::make(t));
         }
         if (!t->is_klass()) {
           // a primitive Class (e.g., int.class) has NULL for a klass field
           return TypePtr::NULL_PTR;
         }
         // (Folds up the 1st indirection in aClassConstant.getModifiers().)
         return TypeKlassPtr::make(t->as_klass());
       }
       // non-constant mirror, so we can't tell what's going on
     }
     if( !ik->is_loaded() )
       return _type;             // Bail out if not loaded
     if (offset == oopDesc::klass_offset_in_bytes()) {
       if (tinst->klass_is_exact()) {
         return TypeKlassPtr::make(ik);
       }
       // See if we can become precise: no subklasses and no interface
       // (Note:  We need to support verified interfaces.)
       if (!ik->is_interface() && !ik->has_subklass()) {
         //assert(!UseExactTypes, "this code should be useless with exact types");
         // Add a dependence; if any subclass added we need to recompile
         if (!ik->is_final()) {
           // %%% should use stronger assert_unique_concrete_subtype instead
           phase->C->dependencies()->assert_leaf_type(ik);
         }
         // Return precise klass
         return TypeKlassPtr::make(ik);
       }
       // Return root of possible klass
       return TypeKlassPtr::make(TypePtr::NotNull, ik, 0/*offset*/);
     }
   }
   // Check for loading klass from an array
   const TypeAryPtr *tary = tp->isa_aryptr();
   if( tary != NULL ) {
     ciKlass *tary_klass = tary->klass();
     if (tary_klass != NULL   // can be NULL when at BOTTOM or TOP
         && tary->offset() == oopDesc::klass_offset_in_bytes()) {
       if (tary->klass_is_exact()) {
         return TypeKlassPtr::make(tary_klass);
       }
       ciArrayKlass *ak = tary->klass()->as_array_klass();
       // If the klass is an object array, we defer the question to the
       // array component klass.
       if( ak->is_obj_array_klass() ) {
         assert( ak->is_loaded(), "" );
         ciKlass *base_k = ak->as_obj_array_klass()->base_element_klass();
         if( base_k->is_loaded() && base_k->is_instance_klass() ) {
           ciInstanceKlass* ik = base_k->as_instance_klass();
           // See if we can become precise: no subklasses and no interface
           if (!ik->is_interface() && !ik->has_subklass()) {
             //assert(!UseExactTypes, "this code should be useless with exact types");
             // Add a dependence; if any subclass added we need to recompile
             if (!ik->is_final()) {
               phase->C->dependencies()->assert_leaf_type(ik);
             }
             // Return precise array klass
             return TypeKlassPtr::make(ak);
           }
         }
         return TypeKlassPtr::make(TypePtr::NotNull, ak, 0/*offset*/);
       } else {                  // Found a type-array?
         //assert(!UseExactTypes, "this code should be useless with exact types");
         assert( ak->is_type_array_klass(), "" );
         return TypeKlassPtr::make(ak); // These are always precise
       }
     }
   }
   // Check for loading klass from an array klass
   const TypeKlassPtr *tkls = tp->isa_klassptr();
   if (tkls != NULL && !StressReflectiveCode) {
     ciKlass* klass = tkls->klass();
     if( !klass->is_loaded() )
       return _type;             // Bail out if not loaded
     if( klass->is_obj_array_klass() &&
         (uint)tkls->offset() == objArrayKlass::element_klass_offset_in_bytes() + sizeof(oopDesc)) {
       ciKlass* elem = klass->as_obj_array_klass()->element_klass();
       // // Always returning precise element type is incorrect,
       // // e.g., element type could be object and array may contain strings
       // return TypeKlassPtr::make(TypePtr::Constant, elem, 0);
       // The array's TypeKlassPtr was declared 'precise' or 'not precise'
       // according to the element type's subclassing.
       return TypeKlassPtr::make(tkls->ptr(), elem, 0/*offset*/);
     }
     if( klass->is_instance_klass() && tkls->klass_is_exact() &&
         (uint)tkls->offset() == Klass::super_offset_in_bytes() + sizeof(oopDesc)) {
       ciKlass* sup = klass->as_instance_klass()->super();
       // The field is Klass::_super.  Return its (constant) value.
       // (Folds up the 2nd indirection in aClassConstant.getSuperClass().)
       return sup ? TypeKlassPtr::make(sup) : TypePtr::NULL_PTR;
     }
   }
   // Bailout case
   return LoadNode::Value(phase);
 }
 //------------------------------Identity---------------------------------------
 // To clean up reflective code, simplify k.java_mirror.as_klass to plain k.
 // Also feed through the klass in Allocate(...klass...)._klass.
 Node* LoadKlassNode::Identity( PhaseTransform *phase ) {
   Node* x = LoadNode::Identity(phase);
   if (x != this)  return x;
   // Take apart the address into an oop and and offset.
   // Return 'this' if we cannot.
   Node*    adr    = in(MemNode::Address);
   intptr_t offset = 0;
   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
   if (base == NULL)     return this;
   const TypeOopPtr* toop = phase->type(adr)->isa_oopptr();
   if (toop == NULL)     return this;
   // We can fetch the klass directly through an AllocateNode.
   // This works even if the klass is not constant (clone or newArray).
   if (offset == oopDesc::klass_offset_in_bytes()) {
     Node* allocated_klass = AllocateNode::Ideal_klass(base, phase);
     if (allocated_klass != NULL) {
       return allocated_klass;
     }
   }
   // Simplify k.java_mirror.as_klass to plain k, where k is a klassOop.
   // Simplify ak.component_mirror.array_klass to plain ak, ak an arrayKlass.
   // See inline_native_Class_query for occurrences of these patterns.
   // Java Example:  x.getClass().isAssignableFrom(y)
   // Java Example:  Array.newInstance(x.getClass().getComponentType(), n)
   //
   // This improves reflective code, often making the Class
   // mirror go completely dead.  (Current exception:  Class
   // mirrors may appear in debug info, but we could clean them out by
   // introducing a new debug info operator for klassOop.java_mirror).
   if (toop->isa_instptr() && toop->klass() == phase->C->env()->Class_klass()
       && (offset == java_lang_Class::klass_offset_in_bytes() ||
           offset == java_lang_Class::array_klass_offset_in_bytes())) {
     // We are loading a special hidden field from a Class mirror,
     // the field which points to its Klass or arrayKlass metaobject.
     if (base->is_Load()) {
       Node* adr2 = base->in(MemNode::Address);
       const TypeKlassPtr* tkls = phase->type(adr2)->isa_klassptr();
       if (tkls != NULL && !tkls->empty()
           && (tkls->klass()->is_instance_klass() ||
               tkls->klass()->is_array_klass())
           && adr2->is_AddP()
           ) {
         int mirror_field = Klass::java_mirror_offset_in_bytes();
         if (offset == java_lang_Class::array_klass_offset_in_bytes()) {
           mirror_field = in_bytes(arrayKlass::component_mirror_offset());
         }
         if (tkls->offset() == mirror_field + (int)sizeof(oopDesc)) {
           return adr2->in(AddPNode::Base);
         }
       }
     }
   }
   return this;
 }
 //------------------------------Value-----------------------------------------
 const Type *LoadRangeNode::Value( PhaseTransform *phase ) const {
   // Either input is TOP ==> the result is TOP
   const Type *t1 = phase->type( in(MemNode::Memory) );
   if( t1 == Type::TOP ) return Type::TOP;
   Node *adr = in(MemNode::Address);
   const Type *t2 = phase->type( adr );
   if( t2 == Type::TOP ) return Type::TOP;
   const TypePtr *tp = t2->is_ptr();
   if (TypePtr::above_centerline(tp->ptr()))  return Type::TOP;
   const TypeAryPtr *tap = tp->isa_aryptr();
   if( !tap ) return _type;
   return tap->size();
 }
 //------------------------------Identity---------------------------------------
 // Feed through the length in AllocateArray(...length...)._length.
 Node* LoadRangeNode::Identity( PhaseTransform *phase ) {
   Node* x = LoadINode::Identity(phase);
   if (x != this)  return x;
   // Take apart the address into an oop and and offset.
   // Return 'this' if we cannot.
   Node*    adr    = in(MemNode::Address);
   intptr_t offset = 0;
   Node*    base   = AddPNode::Ideal_base_and_offset(adr, phase, offset);
   if (base == NULL)     return this;
   const TypeAryPtr* tary = phase->type(adr)->isa_aryptr();
   if (tary == NULL)     return this;
   // We can fetch the length directly through an AllocateArrayNode.
   // This works even if the length is not constant (clone or newArray).
   if (offset == arrayOopDesc::length_offset_in_bytes()) {
     Node* allocated_length = AllocateArrayNode::Ideal_length(base, phase);
     if (allocated_length != NULL) {
       return allocated_length;
     }
   }
   return this;
 }
 //=============================================================================
 //---------------------------StoreNode::make-----------------------------------
 // Polymorphic factory method:
 StoreNode* StoreNode::make( PhaseGVN& gvn, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt ) {
   Compile* C = gvn.C;
   switch (bt) {
   case T_BOOLEAN:
   case T_BYTE:    return new (C, 4) StoreBNode(ctl, mem, adr, adr_type, val);
   case T_INT:     return new (C, 4) StoreINode(ctl, mem, adr, adr_type, val);
   case T_CHAR:
   case T_SHORT:   return new (C, 4) StoreCNode(ctl, mem, adr, adr_type, val);
   case T_LONG:    return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val);
   case T_FLOAT:   return new (C, 4) StoreFNode(ctl, mem, adr, adr_type, val);
   case T_DOUBLE:  return new (C, 4) StoreDNode(ctl, mem, adr, adr_type, val);
   case T_ADDRESS:
   case T_OBJECT:
 #ifdef _LP64
     if (adr->bottom_type()->is_narrow() ||
         (UseCompressedOops && val->bottom_type()->isa_klassptr() &&
          adr->bottom_type()->isa_rawptr())) {
       const TypePtr* type = val->bottom_type()->is_ptr();
       Node* cp = EncodePNode::encode(&gvn, val);
       return new (C, 4) StoreNNode(ctl, mem, adr, adr_type, cp);
     } else
 #endif
       {
         return new (C, 4) StorePNode(ctl, mem, adr, adr_type, val);
       }
   }
   ShouldNotReachHere();
   return (StoreNode*)NULL;
 }
 StoreLNode* StoreLNode::make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val) {
   bool require_atomic = true;
   return new (C, 4) StoreLNode(ctl, mem, adr, adr_type, val, require_atomic);
 }
 //--------------------------bottom_type----------------------------------------
 const Type *StoreNode::bottom_type() const {
   return Type::MEMORY;
 }
 //------------------------------hash-------------------------------------------
 uint StoreNode::hash() const {
   // unroll addition of interesting fields
   //return (uintptr_t)in(Control) + (uintptr_t)in(Memory) + (uintptr_t)in(Address) + (uintptr_t)in(ValueIn);
   // Since they are not commoned, do not hash them:
   return NO_HASH;
 }
 //------------------------------Ideal------------------------------------------
 // Change back-to-back Store(, p, x) -> Store(m, p, y) to Store(m, p, x).
 // When a store immediately follows a relevant allocation/initialization,
 // try to capture it into the initialization, or hoist it above.
 Node *StoreNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   Node* p = MemNode::Ideal_common(phase, can_reshape);
   if (p)  return (p == NodeSentinel) ? NULL : p;
   Node* mem     = in(MemNode::Memory);
   Node* address = in(MemNode::Address);
   // Back-to-back stores to same address?  Fold em up.
   // Generally unsafe if I have intervening uses...
   if (mem->is_Store() && phase->eqv_uncast(mem->in(MemNode::Address), address)) {
     // Looking at a dead closed cycle of memory?
     assert(mem != mem->in(MemNode::Memory), "dead loop in StoreNode::Ideal");
     assert(Opcode() == mem->Opcode() ||
            phase->C->get_alias_index(adr_type()) == Compile::AliasIdxRaw,
            "no mismatched stores, except on raw memory");
     if (mem->outcnt() == 1 &&           // check for intervening uses
         mem->as_Store()->memory_size() <= this->memory_size()) {
       // If anybody other than 'this' uses 'mem', we cannot fold 'mem' away.
       // For example, 'mem' might be the final state at a conditional return.
       // Or, 'mem' might be used by some node which is live at the same time
       // 'this' is live, which might be unschedulable.  So, require exactly
       // ONE user, the 'this' store, until such time as we clone 'mem' for
       // each of 'mem's uses (thus making the exactly-1-user-rule hold true).
       if (can_reshape) {  // (%%% is this an anachronism?)
         set_req_X(MemNode::Memory, mem->in(MemNode::Memory),
                   phase->is_IterGVN());
       } else {
         // It's OK to do this in the parser, since DU info is always accurate,
         // and the parser always refers to nodes via SafePointNode maps.
         set_req(MemNode::Memory, mem->in(MemNode::Memory));
       }
       return this;
     }
   }
   // Capture an unaliased, unconditional, simple store into an initializer.
   // Or, if it is independent of the allocation, hoist it above the allocation.
   if (ReduceFieldZeroing && /*can_reshape &&*/
       mem->is_Proj() && mem->in(0)->is_Initialize()) {
     InitializeNode* init = mem->in(0)->as_Initialize();
     intptr_t offset = init->can_capture_store(this, phase);
     if (offset > 0) {
       Node* moved = init->capture_store(this, offset, phase);
       // If the InitializeNode captured me, it made a raw copy of me,
       // and I need to disappear.
       if (moved != NULL) {
         // %%% hack to ensure that Ideal returns a new node:
         mem = MergeMemNode::make(phase->C, mem);
         return mem;             // fold me away
       }
     }
   }
   return NULL;                  // No further progress
 }
 //------------------------------Value-----------------------------------------
 const Type *StoreNode::Value( PhaseTransform *phase ) const {
   // Either input is TOP ==> the result is TOP
   const Type *t1 = phase->type( in(MemNode::Memory) );
   if( t1 == Type::TOP ) return Type::TOP;
   const Type *t2 = phase->type( in(MemNode::Address) );
   if( t2 == Type::TOP ) return Type::TOP;
   const Type *t3 = phase->type( in(MemNode::ValueIn) );
   if( t3 == Type::TOP ) return Type::TOP;
   return Type::MEMORY;
 }
 //------------------------------Identity---------------------------------------
 // Remove redundant stores:
 //   Store(m, p, Load(m, p)) changes to m.
 //   Store(, p, x) -> Store(m, p, x) changes to Store(m, p, x).
 Node *StoreNode::Identity( PhaseTransform *phase ) {
   Node* mem = in(MemNode::Memory);
   Node* adr = in(MemNode::Address);
   Node* val = in(MemNode::ValueIn);
   // Load then Store?  Then the Store is useless
   if (val->is_Load() &&
       phase->eqv_uncast( val->in(MemNode::Address), adr ) &&
       phase->eqv_uncast( val->in(MemNode::Memory ), mem ) &&
       val->as_Load()->store_Opcode() == Opcode()) {
     return mem;
   }
   // Two stores in a row of the same value?
   if (mem->is_Store() &&
       phase->eqv_uncast( mem->in(MemNode::Address), adr ) &&
       phase->eqv_uncast( mem->in(MemNode::ValueIn), val ) &&
       mem->Opcode() == Opcode()) {
     return mem;
   }
   // Store of zero anywhere into a freshly-allocated object?
   // Then the store is useless.
   // (It must already have been captured by the InitializeNode.)
   if (ReduceFieldZeroing && phase->type(val)->is_zero_type()) {
     // a newly allocated object is already all-zeroes everywhere
     if (mem->is_Proj() && mem->in(0)->is_Allocate()) {
       return mem;
     }
     // the store may also apply to zero-bits in an earlier object
     Node* prev_mem = find_previous_store(phase);
     // Steps (a), (b):  Walk past independent stores to find an exact match.
     if (prev_mem != NULL) {
       Node* prev_val = can_see_stored_value(prev_mem, phase);
       if (prev_val != NULL && phase->eqv(prev_val, val)) {
         // prev_val and val might differ by a cast; it would be good
         // to keep the more informative of the two.
         return mem;
       }
     }
   }
   return this;
 }
 //------------------------------match_edge-------------------------------------
 // Do we Match on this edge index or not?  Match only memory & value
 uint StoreNode::match_edge(uint idx) const {
   return idx == MemNode::Address || idx == MemNode::ValueIn;
 }
 //------------------------------cmp--------------------------------------------
 // Do not common stores up together.  They generally have to be split
 // back up anyways, so do not bother.
 uint StoreNode::cmp( const Node &n ) const {
   return (&n == this);          // Always fail except on self
 }
 //------------------------------Ideal_masked_input-----------------------------
 // Check for a useless mask before a partial-word store
 // (StoreB ... (AndI valIn conIa) )
 // If (conIa & mask == mask) this simplifies to
 // (StoreB ... (valIn) )
 Node *StoreNode::Ideal_masked_input(PhaseGVN *phase, uint mask) {
   Node *val = in(MemNode::ValueIn);
   if( val->Opcode() == Op_AndI ) {
     const TypeInt *t = phase->type( val->in(2) )->isa_int();
     if( t && t->is_con() && (t->get_con() & mask) == mask ) {
       set_req(MemNode::ValueIn, val->in(1));
       return this;
     }
   }
   return NULL;
 }
 //------------------------------Ideal_sign_extended_input----------------------
 // Check for useless sign-extension before a partial-word store
 // (StoreB ... (RShiftI _ (LShiftI _ valIn conIL ) conIR) )
 // If (conIL == conIR && conIR <= num_bits)  this simplifies to
 // (StoreB ... (valIn) )
 Node *StoreNode::Ideal_sign_extended_input(PhaseGVN *phase, int num_bits) {
   Node *val = in(MemNode::ValueIn);
   if( val->Opcode() == Op_RShiftI ) {
     const TypeInt *t = phase->type( val->in(2) )->isa_int();
     if( t && t->is_con() && (t->get_con() <= num_bits) ) {
       Node *shl = val->in(1);
       if( shl->Opcode() == Op_LShiftI ) {
         const TypeInt *t2 = phase->type( shl->in(2) )->isa_int();
         if( t2 && t2->is_con() && (t2->get_con() == t->get_con()) ) {
           set_req(MemNode::ValueIn, shl->in(1));
           return this;
         }
       }
     }
   }
   return NULL;
 }
 //------------------------------value_never_loaded-----------------------------------
 // Determine whether there are any possible loads of the value stored.
 // For simplicity, we actually check if there are any loads from the
 // address stored to, not just for loads of the value stored by this node.
 //
 bool StoreNode::value_never_loaded( PhaseTransform *phase) const {
   Node *adr = in(Address);
   const TypeOopPtr *adr_oop = phase->type(adr)->isa_oopptr();
   if (adr_oop == NULL)
     return false;
   if (!adr_oop->is_instance_field())
     return false; // if not a distinct instance, there may be aliases of the address
   for (DUIterator_Fast imax, i = adr->fast_outs(imax); i < imax; i++) {
     Node *use = adr->fast_out(i);
     int opc = use->Opcode();
     if (use->is_Load() || use->is_LoadStore()) {
       return false;
     }
   }
   return true;
 }
 //=============================================================================
 //------------------------------Ideal------------------------------------------
 // If the store is from an AND mask that leaves the low bits untouched, then
 // we can skip the AND operation.  If the store is from a sign-extension
 // (a left shift, then right shift) we can skip both.
 Node *StoreBNode::Ideal(PhaseGVN *phase, bool can_reshape){
   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFF);
   if( progress != NULL ) return progress;
   progress = StoreNode::Ideal_sign_extended_input(phase, 24);
   if( progress != NULL ) return progress;
   // Finally check the default case
   return StoreNode::Ideal(phase, can_reshape);
 }
 //=============================================================================
 //------------------------------Ideal------------------------------------------
 // If the store is from an AND mask that leaves the low bits untouched, then
 // we can skip the AND operation
 Node *StoreCNode::Ideal(PhaseGVN *phase, bool can_reshape){
   Node *progress = StoreNode::Ideal_masked_input(phase, 0xFFFF);
   if( progress != NULL ) return progress;
   progress = StoreNode::Ideal_sign_extended_input(phase, 16);
   if( progress != NULL ) return progress;
   // Finally check the default case
   return StoreNode::Ideal(phase, can_reshape);
 }
 //=============================================================================
 //------------------------------Identity---------------------------------------
 Node *StoreCMNode::Identity( PhaseTransform *phase ) {
   // No need to card mark when storing a null ptr
   Node* my_store = in(MemNode::OopStore);
   if (my_store->is_Store()) {
     const Type *t1 = phase->type( my_store->in(MemNode::ValueIn) );
     if( t1 == TypePtr::NULL_PTR ) {
       return in(MemNode::Memory);
     }
   }
   return this;
 }
 //------------------------------Value-----------------------------------------
 const Type *StoreCMNode::Value( PhaseTransform *phase ) const {
   // Either input is TOP ==> the result is TOP
   const Type *t = phase->type( in(MemNode::Memory) );
   if( t == Type::TOP ) return Type::TOP;
   t = phase->type( in(MemNode::Address) );
   if( t == Type::TOP ) return Type::TOP;
   t = phase->type( in(MemNode::ValueIn) );
   if( t == Type::TOP ) return Type::TOP;
   // If extra input is TOP ==> the result is TOP
   t = phase->type( in(MemNode::OopStore) );
   if( t == Type::TOP ) return Type::TOP;
   return StoreNode::Value( phase );
 }
 //=============================================================================
 //----------------------------------SCMemProjNode------------------------------
 const Type * SCMemProjNode::Value( PhaseTransform *phase ) const
 {
   return bottom_type();
 }
 //=============================================================================
 LoadStoreNode::LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex ) : Node(5) {
   init_req(MemNode::Control, c  );
   init_req(MemNode::Memory , mem);
   init_req(MemNode::Address, adr);
   init_req(MemNode::ValueIn, val);
   init_req(         ExpectedIn, ex );
   init_class_id(Class_LoadStore);
 }
 //=============================================================================
 //-------------------------------adr_type--------------------------------------
 // Do we Match on this edge index or not?  Do not match memory
 const TypePtr* ClearArrayNode::adr_type() const {
   Node *adr = in(3);
   return MemNode::calculate_adr_type(adr->bottom_type());
 }
 //------------------------------match_edge-------------------------------------
 // Do we Match on this edge index or not?  Do not match memory
 uint ClearArrayNode::match_edge(uint idx) const {
   return idx > 1;
 }
 //------------------------------Identity---------------------------------------
 // Clearing a zero length array does nothing
 Node *ClearArrayNode::Identity( PhaseTransform *phase ) {
   return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
 }
 //------------------------------Idealize---------------------------------------
 // Clearing a short array is faster with stores
 Node *ClearArrayNode::Ideal(PhaseGVN *phase, bool can_reshape){
   const int unit = BytesPerLong;
   const TypeX* t = phase->type(in(2))->isa_intptr_t();
   if (!t)  return NULL;
   if (!t->is_con())  return NULL;
   intptr_t raw_count = t->get_con();
   intptr_t size = raw_count;
   if (!Matcher::init_array_count_is_in_bytes) size *= unit;
   // Clearing nothing uses the Identity call.
   // Negative clears are possible on dead ClearArrays
   // (see jck test stmt114.stmt11402.val).
   if (size <= 0 || size % unit != 0)  return NULL;
   intptr_t count = size / unit;
   // Length too long; use fast hardware clear
   if (size > Matcher::init_array_short_size)  return NULL;
   Node *mem = in(1);
   if( phase->type(mem)==Type::TOP ) return NULL;
   Node *adr = in(3);
   const Type* at = phase->type(adr);
   if( at==Type::TOP ) return NULL;
   const TypePtr* atp = at->isa_ptr();
   // adjust atp to be the correct array element address type
   if (atp == NULL)  atp = TypePtr::BOTTOM;
   else              atp = atp->add_offset(Type::OffsetBot);
   // Get base for derived pointer purposes
   if( adr->Opcode() != Op_AddP ) Unimplemented();
   Node *base = adr->in(1);
   Node *zero = phase->makecon(TypeLong::ZERO);
   Node *off  = phase->MakeConX(BytesPerLong);
   mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero);
   count--;
   while( count-- ) {
     mem = phase->transform(mem);
     adr = phase->transform(new (phase->C, 4) AddPNode(base,adr,off));
     mem = new (phase->C, 4) StoreLNode(in(0),mem,adr,atp,zero);
   }
   return mem;
 }
 //----------------------------clear_memory-------------------------------------
 // Generate code to initialize object storage to zero.
 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
                                    intptr_t start_offset,
                                    Node* end_offset,
                                    PhaseGVN* phase) {
   Compile* C = phase->C;
   intptr_t offset = start_offset;
   int unit = BytesPerLong;
   if ((offset % unit) != 0) {
     Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(offset));
     adr = phase->transform(adr);
     const TypePtr* atp = TypeRawPtr::BOTTOM;
     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT);
     mem = phase->transform(mem);
     offset += BytesPerInt;
   }
   assert((offset % unit) == 0, "");
   // Initialize the remaining stuff, if any, with a ClearArray.
   return clear_memory(ctl, mem, dest, phase->MakeConX(offset), end_offset, phase);
 }
 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
                                    Node* start_offset,
                                    Node* end_offset,
                                    PhaseGVN* phase) {
   if (start_offset == end_offset) {
     // nothing to do
     return mem;
   }
   Compile* C = phase->C;
   int unit = BytesPerLong;
   Node* zbase = start_offset;
   Node* zend  = end_offset;
   // Scale to the unit required by the CPU:
   if (!Matcher::init_array_count_is_in_bytes) {
     Node* shift = phase->intcon(exact_log2(unit));
     zbase = phase->transform( new(C,3) URShiftXNode(zbase, shift) );
     zend  = phase->transform( new(C,3) URShiftXNode(zend,  shift) );
   }
   Node* zsize = phase->transform( new(C,3) SubXNode(zend, zbase) );
   Node* zinit = phase->zerocon((unit == BytesPerLong) ? T_LONG : T_INT);
   // Bulk clear double-words
   Node* adr = phase->transform( new(C,4) AddPNode(dest, dest, start_offset) );
   mem = new (C, 4) ClearArrayNode(ctl, mem, zsize, adr);
   return phase->transform(mem);
 }
 Node* ClearArrayNode::clear_memory(Node* ctl, Node* mem, Node* dest,
                                    intptr_t start_offset,
                                    intptr_t end_offset,
                                    PhaseGVN* phase) {
   if (start_offset == end_offset) {
     // nothing to do
     return mem;
   }
   Compile* C = phase->C;
   assert((end_offset % BytesPerInt) == 0, "odd end offset");
   intptr_t done_offset = end_offset;
   if ((done_offset % BytesPerLong) != 0) {
     done_offset -= BytesPerInt;
   }
   if (done_offset > start_offset) {
     mem = clear_memory(ctl, mem, dest,
                        start_offset, phase->MakeConX(done_offset), phase);
   }
   if (done_offset < end_offset) { // emit the final 32-bit store
     Node* adr = new (C, 4) AddPNode(dest, dest, phase->MakeConX(done_offset));
     adr = phase->transform(adr);
     const TypePtr* atp = TypeRawPtr::BOTTOM;
     mem = StoreNode::make(*phase, ctl, mem, adr, atp, phase->zerocon(T_INT), T_INT);
     mem = phase->transform(mem);
     done_offset += BytesPerInt;
   }
   assert(done_offset == end_offset, "");
   return mem;
 }
 //=============================================================================
 // Do we match on this edge? No memory edges
 uint StrCompNode::match_edge(uint idx) const {
   return idx == 5 || idx == 6;
 }
 //------------------------------Ideal------------------------------------------
 // Return a node which is more "ideal" than the current node.  Strip out
 // control copies
 Node *StrCompNode::Ideal(PhaseGVN *phase, bool can_reshape){
   return remove_dead_region(phase, can_reshape) ? this : NULL;
 }
 //=============================================================================
 MemBarNode::MemBarNode(Compile* C, int alias_idx, Node* precedent)
   : MultiNode(TypeFunc::Parms + (precedent == NULL? 0: 1)),
     _adr_type(C->get_adr_type(alias_idx))
 {
   init_class_id(Class_MemBar);
   Node* top = C->top();
   init_req(TypeFunc::I_O,top);
   init_req(TypeFunc::FramePtr,top);
   init_req(TypeFunc::ReturnAdr,top);
   if (precedent != NULL)
     init_req(TypeFunc::Parms, precedent);
 }
 //------------------------------cmp--------------------------------------------
 uint MemBarNode::hash() const { return NO_HASH; }
 uint MemBarNode::cmp( const Node &n ) const {
   return (&n == this);          // Always fail except on self
 }
 //------------------------------make-------------------------------------------
 MemBarNode* MemBarNode::make(Compile* C, int opcode, int atp, Node* pn) {
   int len = Precedent + (pn == NULL? 0: 1);
   switch (opcode) {
   case Op_MemBarAcquire:   return new(C, len) MemBarAcquireNode(C,  atp, pn);
   case Op_MemBarRelease:   return new(C, len) MemBarReleaseNode(C,  atp, pn);
   case Op_MemBarVolatile:  return new(C, len) MemBarVolatileNode(C, atp, pn);
   case Op_MemBarCPUOrder:  return new(C, len) MemBarCPUOrderNode(C, atp, pn);
   case Op_Initialize:      return new(C, len) InitializeNode(C,     atp, pn);
   default:                 ShouldNotReachHere(); return NULL;
   }
 }
 //------------------------------Ideal------------------------------------------
 // Return a node which is more "ideal" than the current node.  Strip out
 // control copies
 Node *MemBarNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   if (remove_dead_region(phase, can_reshape))  return this;
   return NULL;
 }
 //------------------------------Value------------------------------------------
 const Type *MemBarNode::Value( PhaseTransform *phase ) const {
   if( !in(0) ) return Type::TOP;
   if( phase->type(in(0)) == Type::TOP )
     return Type::TOP;
   return TypeTuple::MEMBAR;
 }
 //------------------------------match------------------------------------------
 // Construct projections for memory.
 Node *MemBarNode::match( const ProjNode *proj, const Matcher *m ) {
   switch (proj->_con) {
   case TypeFunc::Control:
   case TypeFunc::Memory:
     return new (m->C, 1) MachProjNode(this,proj->_con,RegMask::Empty,MachProjNode::unmatched_proj);
   }
   ShouldNotReachHere();
   return NULL;
 }
 //===========================InitializeNode====================================
 // SUMMARY:
 // This node acts as a memory barrier on raw memory, after some raw stores.
 // The 'cooked' oop value feeds from the Initialize, not the Allocation.
 // The Initialize can 'capture' suitably constrained stores as raw inits.
 // It can coalesce related raw stores into larger units (called 'tiles').
 // It can avoid zeroing new storage for memory units which have raw inits.
 // At macro-expansion, it is marked 'complete', and does not optimize further.
 //
 // EXAMPLE:
 // The object 'new short[2]' occupies 16 bytes in a 32-bit machine.
 //   ctl = incoming control; mem* = incoming memory
 // (Note:  A star * on a memory edge denotes I/O and other standard edges.)
 // First allocate uninitialized memory and fill in the header:
 //   alloc = (Allocate ctl mem* 16 #short[].klass ...)
 //   ctl := alloc.Control; mem* := alloc.Memory*
 //   rawmem = alloc.Memory; rawoop = alloc.RawAddress
 // Then initialize to zero the non-header parts of the raw memory block:
 //   init = (Initialize alloc.Control alloc.Memory* alloc.RawAddress)
 //   ctl := init.Control; mem.SLICE(#short[*]) := init.Memory
 // After the initialize node executes, the object is ready for service:
 //   oop := (CheckCastPP init.Control alloc.RawAddress #short[])
 // Suppose its body is immediately initialized as {1,2}:
 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
 //   mem.SLICE(#short[*]) := store2
 //
 // DETAILS:
 // An InitializeNode collects and isolates object initialization after
 // an AllocateNode and before the next possible safepoint.  As a
 // memory barrier (MemBarNode), it keeps critical stores from drifting
 // down past any safepoint or any publication of the allocation.
 // Before this barrier, a newly-allocated object may have uninitialized bits.
 // After this barrier, it may be treated as a real oop, and GC is allowed.
 //
 // The semantics of the InitializeNode include an implicit zeroing of
 // the new object from object header to the end of the object.
 // (The object header and end are determined by the AllocateNode.)
 //
 // Certain stores may be added as direct inputs to the InitializeNode.
 // These stores must update raw memory, and they must be to addresses
 // derived from the raw address produced by AllocateNode, and with
 // a constant offset.  They must be ordered by increasing offset.
 // The first one is at in(RawStores), the last at in(req()-1).
 // Unlike most memory operations, they are not linked in a chain,
 // but are displayed in parallel as users of the rawmem output of
 // the allocation.
 //
 // (See comments in InitializeNode::capture_store, which continue
 // the example given above.)
 //
 // When the associated Allocate is macro-expanded, the InitializeNode
 // may be rewritten to optimize collected stores.  A ClearArrayNode
 // may also be created at that point to represent any required zeroing.
 // The InitializeNode is then marked 'complete', prohibiting further
 // capturing of nearby memory operations.
 //
 // During macro-expansion, all captured initializations which store
 // constant values of 32 bits or smaller are coalesced (if advantagous)
 // into larger 'tiles' 32 or 64 bits.  This allows an object to be
 // initialized in fewer memory operations.  Memory words which are
 // covered by neither tiles nor non-constant stores are pre-zeroed
 // by explicit stores of zero.  (The code shape happens to do all
 // zeroing first, then all other stores, with both sequences occurring
 // in order of ascending offsets.)
 //
 // Alternatively, code may be inserted between an AllocateNode and its
 // InitializeNode, to perform arbitrary initialization of the new object.
 // E.g., the object copying intrinsics insert complex data transfers here.
 // The initialization must then be marked as 'complete' disable the
 // built-in zeroing semantics and the collection of initializing stores.
 //
 // While an InitializeNode is incomplete, reads from the memory state
 // produced by it are optimizable if they match the control edge and
 // new oop address associated with the allocation/initialization.
 // They return a stored value (if the offset matches) or else zero.
 // A write to the memory state, if it matches control and address,
 // and if it is to a constant offset, may be 'captured' by the
 // InitializeNode.  It is cloned as a raw memory operation and rewired
 // inside the initialization, to the raw oop produced by the allocation.
 // Operations on addresses which are provably distinct (e.g., to
 // other AllocateNodes) are allowed to bypass the initialization.
 //
 // The effect of all this is to consolidate object initialization
 // (both arrays and non-arrays, both piecewise and bulk) into a
 // single location, where it can be optimized as a unit.
 //
 // Only stores with an offset less than TrackedInitializationLimit words
 // will be considered for capture by an InitializeNode.  This puts a
 // reasonable limit on the complexity of optimized initializations.
 //---------------------------InitializeNode------------------------------------
 InitializeNode::InitializeNode(Compile* C, int adr_type, Node* rawoop)
   : _is_complete(false),
     MemBarNode(C, adr_type, rawoop)
 {
   init_class_id(Class_Initialize);
   assert(adr_type == Compile::AliasIdxRaw, "only valid atp");
   assert(in(RawAddress) == rawoop, "proper init");
   // Note:  allocation() can be NULL, for secondary initialization barriers
 }
 // Since this node is not matched, it will be processed by the
 // register allocator.  Declare that there are no constraints
 // on the allocation of the RawAddress edge.
 const RegMask &InitializeNode::in_RegMask(uint idx) const {
   // This edge should be set to top, by the set_complete.  But be conservative.
   if (idx == InitializeNode::RawAddress)
     return *(Compile::current()->matcher()->idealreg2spillmask[in(idx)->ideal_reg()]);
   return RegMask::Empty;
 }
 Node* InitializeNode::memory(uint alias_idx) {
   Node* mem = in(Memory);
   if (mem->is_MergeMem()) {
     return mem->as_MergeMem()->memory_at(alias_idx);
   } else {
     // incoming raw memory is not split
     return mem;
   }
 }
 bool InitializeNode::is_non_zero() {
   if (is_complete())  return false;
   remove_extra_zeroes();
   return (req() > RawStores);
 }
 void InitializeNode::set_complete(PhaseGVN* phase) {
   assert(!is_complete(), "caller responsibility");
   _is_complete = true;
   // After this node is complete, it contains a bunch of
   // raw-memory initializations.  There is no need for
   // it to have anything to do with non-raw memory effects.
   // Therefore, tell all non-raw users to re-optimize themselves,
   // after skipping the memory effects of this initialization.
   PhaseIterGVN* igvn = phase->is_IterGVN();
   if (igvn)  igvn->add_users_to_worklist(this);
 }
 // convenience function
 // return false if the init contains any stores already
 bool AllocateNode::maybe_set_complete(PhaseGVN* phase) {
   InitializeNode* init = initialization();
   if (init == NULL || init->is_complete())  return false;
   init->remove_extra_zeroes();
   // for now, if this allocation has already collected any inits, bail:
   if (init->is_non_zero())  return false;
   init->set_complete(phase);
   return true;
 }
 void InitializeNode::remove_extra_zeroes() {
   if (req() == RawStores)  return;
   Node* zmem = zero_memory();
   uint fill = RawStores;
   for (uint i = fill; i < req(); i++) {
     Node* n = in(i);
     if (n->is_top() || n == zmem)  continue;  // skip
     if (fill < i)  set_req(fill, n);          // compact
     ++fill;
   }
   // delete any empty spaces created:
   while (fill < req()) {
     del_req(fill);
   }
 }
 // Helper for remembering which stores go with which offsets.
 intptr_t InitializeNode::get_store_offset(Node* st, PhaseTransform* phase) {
   if (!st->is_Store())  return -1;  // can happen to dead code via subsume_node
   intptr_t offset = -1;
   Node* base = AddPNode::Ideal_base_and_offset(st->in(MemNode::Address),
                                                phase, offset);
   if (base == NULL)     return -1;  // something is dead,
   if (offset < 0)       return -1;  //        dead, dead
   return offset;
 }
 // Helper for proving that an initialization expression is
 // "simple enough" to be folded into an object initialization.
 // Attempts to prove that a store's initial value 'n' can be captured
 // within the initialization without creating a vicious cycle, such as:
 //     { Foo p = new Foo(); p.next = p; }
 // True for constants and parameters and small combinations thereof.
 bool InitializeNode::detect_init_independence(Node* n,
                                               bool st_is_pinned,
                                               int& count) {
   if (n == NULL)      return true;   // (can this really happen?)
   if (n->is_Proj())   n = n->in(0);
   if (n == this)      return false;  // found a cycle
   if (n->is_Con())    return true;
   if (n->is_Start())  return true;   // params, etc., are OK
   if (n->is_Root())   return true;   // even better
   Node* ctl = n->in(0);
   if (ctl != NULL && !ctl->is_top()) {
     if (ctl->is_Proj())  ctl = ctl->in(0);
     if (ctl == this)  return false;
     // If we already know that the enclosing memory op is pinned right after
     // the init, then any control flow that the store has picked up
     // must have preceded the init, or else be equal to the init.
     // Even after loop optimizations (which might change control edges)
     // a store is never pinned *before* the availability of its inputs.
     if (!MemNode::all_controls_dominate(n, this))
       return false;                  // failed to prove a good control
   }
   // Check data edges for possible dependencies on 'this'.
   if ((count += 1) > 20)  return false;  // complexity limit
   for (uint i = 1; i < n->req(); i++) {
     Node* m = n->in(i);
     if (m == NULL || m == n || m->is_top())  continue;
     uint first_i = n->find_edge(m);
     if (i != first_i)  continue;  // process duplicate edge just once
     if (!detect_init_independence(m, st_is_pinned, count)) {
       return false;
     }
   }
   return true;
 }
 // Here are all the checks a Store must pass before it can be moved into
 // an initialization.  Returns zero if a check fails.
 // On success, returns the (constant) offset to which the store applies,
 // within the initialized memory.
 intptr_t InitializeNode::can_capture_store(StoreNode* st, PhaseTransform* phase) {
   const int FAIL = 0;
   if (st->req() != MemNode::ValueIn + 1)
     return FAIL;                // an inscrutable StoreNode (card mark?)
   Node* ctl = st->in(MemNode::Control);
   if (!(ctl != NULL && ctl->is_Proj() && ctl->in(0) == this))
     return FAIL;                // must be unconditional after the initialization
   Node* mem = st->in(MemNode::Memory);
   if (!(mem->is_Proj() && mem->in(0) == this))
     return FAIL;                // must not be preceded by other stores
   Node* adr = st->in(MemNode::Address);
   intptr_t offset;
   AllocateNode* alloc = AllocateNode::Ideal_allocation(adr, phase, offset);
   if (alloc == NULL)
     return FAIL;                // inscrutable address
   if (alloc != allocation())
     return FAIL;                // wrong allocation!  (store needs to float up)
   Node* val = st->in(MemNode::ValueIn);
   int complexity_count = 0;
   if (!detect_init_independence(val, true, complexity_count))
     return FAIL;                // stored value must be 'simple enough'
   return offset;                // success
 }
 // Find the captured store in(i) which corresponds to the range
 // [start..start+size) in the initialized object.
 // If there is one, return its index i.  If there isn't, return the
 // negative of the index where it should be inserted.
 // Return 0 if the queried range overlaps an initialization boundary
 // or if dead code is encountered.
 // If size_in_bytes is zero, do not bother with overlap checks.
 int InitializeNode::captured_store_insertion_point(intptr_t start,
                                                    int size_in_bytes,
                                                    PhaseTransform* phase) {
   const int FAIL = 0, MAX_STORE = BytesPerLong;
   if (is_complete())
     return FAIL;                // arraycopy got here first; punt
   assert(allocation() != NULL, "must be present");
   // no negatives, no header fields:
   if (start < (intptr_t) allocation()->minimum_header_size())  return FAIL;
   // after a certain size, we bail out on tracking all the stores:
   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
   if (start >= ti_limit)  return FAIL;
   for (uint i = InitializeNode::RawStores, limit = req(); ; ) {
     if (i >= limit)  return -(int)i; // not found; here is where to put it
     Node*    st     = in(i);
     intptr_t st_off = get_store_offset(st, phase);
     if (st_off < 0) {
       if (st != zero_memory()) {
         return FAIL;            // bail out if there is dead garbage
       }
     } else if (st_off > start) {
       // ...we are done, since stores are ordered
       if (st_off < start + size_in_bytes) {
         return FAIL;            // the next store overlaps
       }
       return -(int)i;           // not found; here is where to put it
     } else if (st_off < start) {
       if (size_in_bytes != 0 &&
           start < st_off + MAX_STORE &&
           start < st_off + st->as_Store()->memory_size()) {
         return FAIL;            // the previous store overlaps
       }
     } else {
       if (size_in_bytes != 0 &&
           st->as_Store()->memory_size() != size_in_bytes) {
         return FAIL;            // mismatched store size
       }
       return i;
     }
     ++i;
   }
 }
 // Look for a captured store which initializes at the offset 'start'
 // with the given size.  If there is no such store, and no other
 // initialization interferes, then return zero_memory (the memory
 // projection of the AllocateNode).
 Node* InitializeNode::find_captured_store(intptr_t start, int size_in_bytes,
                                           PhaseTransform* phase) {
   assert(stores_are_sane(phase), "");
   int i = captured_store_insertion_point(start, size_in_bytes, phase);
   if (i == 0) {
     return NULL;                // something is dead
   } else if (i < 0) {
     return zero_memory();       // just primordial zero bits here
   } else {
     Node* st = in(i);           // here is the store at this position
     assert(get_store_offset(st->as_Store(), phase) == start, "sanity");
     return st;
   }
 }
 // Create, as a raw pointer, an address within my new object at 'offset'.
 Node* InitializeNode::make_raw_address(intptr_t offset,
                                        PhaseTransform* phase) {
   Node* addr = in(RawAddress);
   if (offset != 0) {
     Compile* C = phase->C;
     addr = phase->transform( new (C, 4) AddPNode(C->top(), addr,
                                                  phase->MakeConX(offset)) );
   }
   return addr;
 }
 // Clone the given store, converting it into a raw store
 // initializing a field or element of my new object.
 // Caller is responsible for retiring the original store,
 // with subsume_node or the like.
 //
 // From the example above InitializeNode::InitializeNode,
 // here are the old stores to be captured:
 //   store1 = (StoreC init.Control init.Memory (+ oop 12) 1)
 //   store2 = (StoreC init.Control store1      (+ oop 14) 2)
 //
 // Here is the changed code; note the extra edges on init:
 //   alloc = (Allocate ...)
 //   rawoop = alloc.RawAddress
 //   rawstore1 = (StoreC alloc.Control alloc.Memory (+ rawoop 12) 1)
 //   rawstore2 = (StoreC alloc.Control alloc.Memory (+ rawoop 14) 2)
 //   init = (Initialize alloc.Control alloc.Memory rawoop
 //                      rawstore1 rawstore2)
 //
 Node* InitializeNode::capture_store(StoreNode* st, intptr_t start,
                                     PhaseTransform* phase) {
   assert(stores_are_sane(phase), "");
   if (start < 0)  return NULL;
   assert(can_capture_store(st, phase) == start, "sanity");
   Compile* C = phase->C;
   int size_in_bytes = st->memory_size();
   int i = captured_store_insertion_point(start, size_in_bytes, phase);
   if (i == 0)  return NULL;     // bail out
   Node* prev_mem = NULL;        // raw memory for the captured store
   if (i > 0) {
     prev_mem = in(i);           // there is a pre-existing store under this one
     set_req(i, C->top());       // temporarily disconnect it
     // See StoreNode::Ideal 'st->outcnt() == 1' for the reason to disconnect.
   } else {
     i = -i;                     // no pre-existing store
     prev_mem = zero_memory();   // a slice of the newly allocated object
     if (i > InitializeNode::RawStores && in(i-1) == prev_mem)
       set_req(--i, C->top());   // reuse this edge; it has been folded away
     else
       ins_req(i, C->top());     // build a new edge
   }
   Node* new_st = st->clone();
   new_st->set_req(MemNode::Control, in(Control));
   new_st->set_req(MemNode::Memory,  prev_mem);
   new_st->set_req(MemNode::Address, make_raw_address(start, phase));
   new_st = phase->transform(new_st);
   // At this point, new_st might have swallowed a pre-existing store
   // at the same offset, or perhaps new_st might have disappeared,
   // if it redundantly stored the same value (or zero to fresh memory).
   // In any case, wire it in:
   set_req(i, new_st);
   // The caller may now kill the old guy.
   DEBUG_ONLY(Node* check_st = find_captured_store(start, size_in_bytes, phase));
   assert(check_st == new_st || check_st == NULL, "must be findable");
   assert(!is_complete(), "");
   return new_st;
 }
 static bool store_constant(jlong* tiles, int num_tiles,
                            intptr_t st_off, int st_size,
                            jlong con) {
   if ((st_off & (st_size-1)) != 0)
     return false;               // strange store offset (assume size==2**N)
   address addr = (address)tiles + st_off;
   assert(st_off >= 0 && addr+st_size <= (address)&tiles[num_tiles], "oob");
   switch (st_size) {
   case sizeof(jbyte):  *(jbyte*) addr = (jbyte) con; break;
   case sizeof(jchar):  *(jchar*) addr = (jchar) con; break;
   case sizeof(jint):   *(jint*)  addr = (jint)  con; break;
   case sizeof(jlong):  *(jlong*) addr = (jlong) con; break;
   default: return false;        // strange store size (detect size!=2**N here)
   }
   return true;                  // return success to caller
 }
 // Coalesce subword constants into int constants and possibly
 // into long constants.  The goal, if the CPU permits,
 // is to initialize the object with a small number of 64-bit tiles.
 // Also, convert floating-point constants to bit patterns.
 // Non-constants are not relevant to this pass.
 //
 // In terms of the running example on InitializeNode::InitializeNode
 // and InitializeNode::capture_store, here is the transformation
 // of rawstore1 and rawstore2 into rawstore12:
 //   alloc = (Allocate ...)
 //   rawoop = alloc.RawAddress
 //   tile12 = 0x00010002
 //   rawstore12 = (StoreI alloc.Control alloc.Memory (+ rawoop 12) tile12)
 //   init = (Initialize alloc.Control alloc.Memory rawoop rawstore12)
 //
 void
 InitializeNode::coalesce_subword_stores(intptr_t header_size,
                                         Node* size_in_bytes,
                                         PhaseGVN* phase) {
   Compile* C = phase->C;
   assert(stores_are_sane(phase), "");
   // Note:  After this pass, they are not completely sane,
   // since there may be some overlaps.
   int old_subword = 0, old_long = 0, new_int = 0, new_long = 0;
   intptr_t ti_limit = (TrackedInitializationLimit * HeapWordSize);
   intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, ti_limit);
   size_limit = MIN2(size_limit, ti_limit);
   size_limit = align_size_up(size_limit, BytesPerLong);
   int num_tiles = size_limit / BytesPerLong;
   // allocate space for the tile map:
   const int small_len = DEBUG_ONLY(true ? 3 :) 30; // keep stack frames small
   jlong  tiles_buf[small_len];
   Node*  nodes_buf[small_len];
   jlong  inits_buf[small_len];
   jlong* tiles = ((num_tiles <= small_len) ? &tiles_buf[0]
                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
   Node** nodes = ((num_tiles <= small_len) ? &nodes_buf[0]
                   : NEW_RESOURCE_ARRAY(Node*, num_tiles));
   jlong* inits = ((num_tiles <= small_len) ? &inits_buf[0]
                   : NEW_RESOURCE_ARRAY(jlong, num_tiles));
   // tiles: exact bitwise model of all primitive constants
   // nodes: last constant-storing node subsumed into the tiles model
   // inits: which bytes (in each tile) are touched by any initializations
   //// Pass A: Fill in the tile model with any relevant stores.
   Copy::zero_to_bytes(tiles, sizeof(tiles[0]) * num_tiles);
   Copy::zero_to_bytes(nodes, sizeof(nodes[0]) * num_tiles);
   Copy::zero_to_bytes(inits, sizeof(inits[0]) * num_tiles);
   Node* zmem = zero_memory(); // initially zero memory state
   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
     Node* st = in(i);
     intptr_t st_off = get_store_offset(st, phase);
     // Figure out the store's offset and constant value:
     if (st_off < header_size)             continue; //skip (ignore header)
     if (st->in(MemNode::Memory) != zmem)  continue; //skip (odd store chain)
     int st_size = st->as_Store()->memory_size();
     if (st_off + st_size > size_limit)    break;
     // Record which bytes are touched, whether by constant or not.
     if (!store_constant(inits, num_tiles, st_off, st_size, (jlong) -1))
       continue;                 // skip (strange store size)
     const Type* val = phase->type(st->in(MemNode::ValueIn));
     if (!val->singleton())                continue; //skip (non-con store)
     BasicType type = val->basic_type();
     jlong con = 0;
     switch (type) {
     case T_INT:    con = val->is_int()->get_con();  break;
     case T_LONG:   con = val->is_long()->get_con(); break;
     case T_FLOAT:  con = jint_cast(val->getf());    break;
     case T_DOUBLE: con = jlong_cast(val->getd());   break;
     default:                              continue; //skip (odd store type)
     }
     if (type == T_LONG && Matcher::isSimpleConstant64(con) &&
         st->Opcode() == Op_StoreL) {
       continue;                 // This StoreL is already optimal.
     }
     // Store down the constant.
     store_constant(tiles, num_tiles, st_off, st_size, con);
     intptr_t j = st_off >> LogBytesPerLong;
     if (type == T_INT && st_size == BytesPerInt
         && (st_off & BytesPerInt) == BytesPerInt) {
       jlong lcon = tiles[j];
       if (!Matcher::isSimpleConstant64(lcon) &&
           st->Opcode() == Op_StoreI) {
         // This StoreI is already optimal by itself.
         jint* intcon = (jint*) &tiles[j];
         intcon[1] = 0;  // undo the store_constant()
         // If the previous store is also optimal by itself, back up and
         // undo the action of the previous loop iteration... if we can.
         // But if we can't, just let the previous half take care of itself.
         st = nodes[j];
         st_off -= BytesPerInt;
         con = intcon[0];
         if (con != 0 && st != NULL && st->Opcode() == Op_StoreI) {
           assert(st_off >= header_size, "still ignoring header");
           assert(get_store_offset(st, phase) == st_off, "must be");
           assert(in(i-1) == zmem, "must be");
           DEBUG_ONLY(const Type* tcon = phase->type(st->in(MemNode::ValueIn)));
           assert(con == tcon->is_int()->get_con(), "must be");
           // Undo the effects of the previous loop trip, which swallowed st:
           intcon[0] = 0;        // undo store_constant()
           set_req(i-1, st);     // undo set_req(i, zmem)
           nodes[j] = NULL;      // undo nodes[j] = st
           --old_subword;        // undo ++old_subword
         }
         continue;               // This StoreI is already optimal.
       }
     }
     // This store is not needed.
     set_req(i, zmem);
     nodes[j] = st;              // record for the moment
     if (st_size < BytesPerLong) // something has changed
           ++old_subword;        // includes int/float, but who's counting...
     else  ++old_long;
   }
   if ((old_subword + old_long) == 0)
     return;                     // nothing more to do
   //// Pass B: Convert any non-zero tiles into optimal constant stores.
   // Be sure to insert them before overlapping non-constant stores.
   // (E.g., byte[] x = { 1,2,y,4 }  =>  x[int 0] = 0x01020004, x[2]=y.)
   for (int j = 0; j < num_tiles; j++) {
     jlong con  = tiles[j];
     jlong init = inits[j];
     if (con == 0)  continue;
     jint con0,  con1;           // split the constant, address-wise
     jint init0, init1;          // split the init map, address-wise
     { union { jlong con; jint intcon[2]; } u;
       u.con = con;
       con0  = u.intcon[0];
       con1  = u.intcon[1];
       u.con = init;
       init0 = u.intcon[0];
       init1 = u.intcon[1];
     }
     Node* old = nodes[j];
     assert(old != NULL, "need the prior store");
     intptr_t offset = (j * BytesPerLong);
     bool split = !Matcher::isSimpleConstant64(con);
     if (offset < header_size) {
       assert(offset + BytesPerInt >= header_size, "second int counts");
       assert(*(jint*)&tiles[j] == 0, "junk in header");
       split = true;             // only the second word counts
       // Example:  int a[] = { 42 ... }
     } else if (con0 == 0 && init0 == -1) {
       split = true;             // first word is covered by full inits
       // Example:  int a[] = { ... foo(), 42 ... }
     } else if (con1 == 0 && init1 == -1) {
       split = true;             // second word is covered by full inits
       // Example:  int a[] = { ... 42, foo() ... }
     }
     // Here's a case where init0 is neither 0 nor -1:
     //   byte a[] = { ... 0,0,foo(),0,  0,0,0,42 ... }
     // Assuming big-endian memory, init0, init1 are 0x0000FF00, 0x000000FF.
     // In this case the tile is not split; it is (jlong)42.
     // The big tile is stored down, and then the foo() value is inserted.
     // (If there were foo(),foo() instead of foo(),0, init0 would be -1.)
     Node* ctl = old->in(MemNode::Control);
     Node* adr = make_raw_address(offset, phase);
     const TypePtr* atp = TypeRawPtr::BOTTOM;
     // One or two coalesced stores to plop down.
     Node*    st[2];
     intptr_t off[2];
     int  nst = 0;
     if (!split) {
       ++new_long;
       off[nst] = offset;
       st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
                                   phase->longcon(con), T_LONG);
     } else {
       // Omit either if it is a zero.
       if (con0 != 0) {
         ++new_int;
         off[nst]  = offset;
         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
                                     phase->intcon(con0), T_INT);
       }
       if (con1 != 0) {
         ++new_int;
         offset += BytesPerInt;
         adr = make_raw_address(offset, phase);
         off[nst]  = offset;
         st[nst++] = StoreNode::make(*phase, ctl, zmem, adr, atp,
                                     phase->intcon(con1), T_INT);
       }
     }
     // Insert second store first, then the first before the second.
     // Insert each one just before any overlapping non-constant stores.
     while (nst > 0) {
       Node* st1 = st[--nst];
       C->copy_node_notes_to(st1, old);
       st1 = phase->transform(st1);
       offset = off[nst];
       assert(offset >= header_size, "do not smash header");
       int ins_idx = captured_store_insertion_point(offset, /*size:*/0, phase);
       guarantee(ins_idx != 0, "must re-insert constant store");
       if (ins_idx < 0)  ins_idx = -ins_idx;  // never overlap
       if (ins_idx > InitializeNode::RawStores && in(ins_idx-1) == zmem)
         set_req(--ins_idx, st1);
       else
         ins_req(ins_idx, st1);
     }
   }
   if (PrintCompilation && WizardMode)
     tty->print_cr("Changed %d/%d subword/long constants into %d/%d int/long",
                   old_subword, old_long, new_int, new_long);
   if (C->log() != NULL)
     C->log()->elem("comment that='%d/%d subword/long to %d/%d int/long'",
                    old_subword, old_long, new_int, new_long);
   // Clean up any remaining occurrences of zmem:
   remove_extra_zeroes();
 }
 // Explore forward from in(start) to find the first fully initialized
 // word, and return its offset.  Skip groups of subword stores which
 // together initialize full words.  If in(start) is itself part of a
 // fully initialized word, return the offset of in(start).  If there
 // are no following full-word stores, or if something is fishy, return
 // a negative value.
 intptr_t InitializeNode::find_next_fullword_store(uint start, PhaseGVN* phase) {
   int       int_map = 0;
   intptr_t  int_map_off = 0;
   const int FULL_MAP = right_n_bits(BytesPerInt);  // the int_map we hope for
   for (uint i = start, limit = req(); i < limit; i++) {
     Node* st = in(i);
     intptr_t st_off = get_store_offset(st, phase);
     if (st_off < 0)  break;  // return conservative answer
     int st_size = st->as_Store()->memory_size();
     if (st_size >= BytesPerInt && (st_off % BytesPerInt) == 0) {
       return st_off;            // we found a complete word init
     }
     // update the map:
     intptr_t this_int_off = align_size_down(st_off, BytesPerInt);
     if (this_int_off != int_map_off) {
       // reset the map:
       int_map = 0;
       int_map_off = this_int_off;
     }
     int subword_off = st_off - this_int_off;
     int_map |= right_n_bits(st_size) << subword_off;
     if ((int_map & FULL_MAP) == FULL_MAP) {
       return this_int_off;      // we found a complete word init
     }
     // Did this store hit or cross the word boundary?
     intptr_t next_int_off = align_size_down(st_off + st_size, BytesPerInt);
     if (next_int_off == this_int_off + BytesPerInt) {
       // We passed the current int, without fully initializing it.
       int_map_off = next_int_off;
       int_map >>= BytesPerInt;
     } else if (next_int_off > this_int_off + BytesPerInt) {
       // We passed the current and next int.
       return this_int_off + BytesPerInt;
     }
   }
   return -1;
 }
 // Called when the associated AllocateNode is expanded into CFG.
 // At this point, we may perform additional optimizations.
 // Linearize the stores by ascending offset, to make memory
 // activity as coherent as possible.
 Node* InitializeNode::complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,
                                       intptr_t header_size,
                                       Node* size_in_bytes,
                                       PhaseGVN* phase) {
   assert(!is_complete(), "not already complete");
   assert(stores_are_sane(phase), "");
   assert(allocation() != NULL, "must be present");
   remove_extra_zeroes();
   if (ReduceFieldZeroing || ReduceBulkZeroing)
     // reduce instruction count for common initialization patterns
     coalesce_subword_stores(header_size, size_in_bytes, phase);
   Node* zmem = zero_memory();   // initially zero memory state
   Node* inits = zmem;           // accumulating a linearized chain of inits
   #ifdef ASSERT
   intptr_t first_offset = allocation()->minimum_header_size();
   intptr_t last_init_off = first_offset;  // previous init offset
   intptr_t last_init_end = first_offset;  // previous init offset+size
   intptr_t last_tile_end = first_offset;  // previous tile offset+size
   #endif
   intptr_t zeroes_done = header_size;
   bool do_zeroing = true;       // we might give up if inits are very sparse
   int  big_init_gaps = 0;       // how many large gaps have we seen?
   if (ZeroTLAB)  do_zeroing = false;
   if (!ReduceFieldZeroing && !ReduceBulkZeroing)  do_zeroing = false;
   for (uint i = InitializeNode::RawStores, limit = req(); i < limit; i++) {
     Node* st = in(i);
     intptr_t st_off = get_store_offset(st, phase);
     if (st_off < 0)
       break;                    // unknown junk in the inits
     if (st->in(MemNode::Memory) != zmem)
       break;                    // complicated store chains somehow in list
     int st_size = st->as_Store()->memory_size();
     intptr_t next_init_off = st_off + st_size;
     if (do_zeroing && zeroes_done < next_init_off) {
       // See if this store needs a zero before it or under it.
       intptr_t zeroes_needed = st_off;
       if (st_size < BytesPerInt) {
         // Look for subword stores which only partially initialize words.
         // If we find some, we must lay down some word-level zeroes first,
         // underneath the subword stores.
         //
         // Examples:
         //   byte[] a = { p,q,r,s }  =>  a[0]=p,a[1]=q,a[2]=r,a[3]=s
         //   byte[] a = { x,y,0,0 }  =>  a[0..3] = 0, a[0]=x,a[1]=y
         //   byte[] a = { 0,0,z,0 }  =>  a[0..3] = 0, a[2]=z
         //
         // Note:  coalesce_subword_stores may have already done this,
         // if it was prompted by constant non-zero subword initializers.
         // But this case can still arise with non-constant stores.
         intptr_t next_full_store = find_next_fullword_store(i, phase);
         // In the examples above:
         //   in(i)          p   q   r   s     x   y     z
         //   st_off        12  13  14  15    12  13    14
         //   st_size        1   1   1   1     1   1     1
         //   next_full_s.  12  16  16  16    16  16    16
         //   z's_done      12  16  16  16    12  16    12
         //   z's_needed    12  16  16  16    16  16    16
         //   zsize          0   0   0   0     4   0     4
         if (next_full_store < 0) {
           // Conservative tack:  Zero to end of current word.
           zeroes_needed = align_size_up(zeroes_needed, BytesPerInt);
         } else {
           // Zero to beginning of next fully initialized word.
           // Or, don't zero at all, if we are already in that word.
           assert(next_full_store >= zeroes_needed, "must go forward");
           assert((next_full_store & (BytesPerInt-1)) == 0, "even boundary");
           zeroes_needed = next_full_store;
         }
       }
       if (zeroes_needed > zeroes_done) {
         intptr_t zsize = zeroes_needed - zeroes_done;
         // Do some incremental zeroing on rawmem, in parallel with inits.
         zeroes_done = align_size_down(zeroes_done, BytesPerInt);
         rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
                                               zeroes_done, zeroes_needed,
                                               phase);
         zeroes_done = zeroes_needed;
         if (zsize > Matcher::init_array_short_size && ++big_init_gaps > 2)
           do_zeroing = false;   // leave the hole, next time
       }
     }
     // Collect the store and move on:
     st->set_req(MemNode::Memory, inits);
     inits = st;                 // put it on the linearized chain
     set_req(i, zmem);           // unhook from previous position
     if (zeroes_done == st_off)
       zeroes_done = next_init_off;
     assert(!do_zeroing || zeroes_done >= next_init_off, "don't miss any");
     #ifdef ASSERT
     // Various order invariants.  Weaker than stores_are_sane because
     // a large constant tile can be filled in by smaller non-constant stores.
     assert(st_off >= last_init_off, "inits do not reverse");
     last_init_off = st_off;
     const Type* val = NULL;
     if (st_size >= BytesPerInt &&
         (val = phase->type(st->in(MemNode::ValueIn)))->singleton() &&
         (int)val->basic_type() < (int)T_OBJECT) {
       assert(st_off >= last_tile_end, "tiles do not overlap");
       assert(st_off >= last_init_end, "tiles do not overwrite inits");
       last_tile_end = MAX2(last_tile_end, next_init_off);
     } else {
       intptr_t st_tile_end = align_size_up(next_init_off, BytesPerLong);
       assert(st_tile_end >= last_tile_end, "inits stay with tiles");
       assert(st_off      >= last_init_end, "inits do not overlap");
       last_init_end = next_init_off;  // it's a non-tile
     }
     #endif //ASSERT
   }
   remove_extra_zeroes();        // clear out all the zmems left over
   add_req(inits);
   if (!ZeroTLAB) {
     // If anything remains to be zeroed, zero it all now.
     zeroes_done = align_size_down(zeroes_done, BytesPerInt);
     // if it is the last unused 4 bytes of an instance, forget about it
     intptr_t size_limit = phase->find_intptr_t_con(size_in_bytes, max_jint);
     if (zeroes_done + BytesPerLong >= size_limit) {
       assert(allocation() != NULL, "");
       Node* klass_node = allocation()->in(AllocateNode::KlassNode);
       ciKlass* k = phase->type(klass_node)->is_klassptr()->klass();
       if (zeroes_done == k->layout_helper())
         zeroes_done = size_limit;
     }
     if (zeroes_done < size_limit) {
       rawmem = ClearArrayNode::clear_memory(rawctl, rawmem, rawptr,
                                             zeroes_done, size_in_bytes, phase);
     }
   }
   set_complete(phase);
   return rawmem;
 }
 #ifdef ASSERT
 bool InitializeNode::stores_are_sane(PhaseTransform* phase) {
   if (is_complete())
     return true;                // stores could be anything at this point
   assert(allocation() != NULL, "must be present");
   intptr_t last_off = allocation()->minimum_header_size();
   for (uint i = InitializeNode::RawStores; i < req(); i++) {
     Node* st = in(i);
     intptr_t st_off = get_store_offset(st, phase);
     if (st_off < 0)  continue;  // ignore dead garbage
     if (last_off > st_off) {
       tty->print_cr("*** bad store offset at %d: %d > %d", i, last_off, st_off);
       this->dump(2);
       assert(false, "ascending store offsets");
       return false;
     }
     last_off = st_off + st->as_Store()->memory_size();
   }
   return true;
 }
 #endif //ASSERT
 //============================MergeMemNode=====================================
 //
 // SEMANTICS OF MEMORY MERGES:  A MergeMem is a memory state assembled from several
 // contributing store or call operations.  Each contributor provides the memory
 // state for a particular "alias type" (see Compile::alias_type).  For example,
 // if a MergeMem has an input X for alias category #6, then any memory reference
 // to alias category #6 may use X as its memory state input, as an exact equivalent
 // to using the MergeMem as a whole.
 //   Load<6>( MergeMem(<6>: X, ...), p ) <==> Load<6>(X,p)
 //
 // (Here, the <N> notation gives the index of the relevant adr_type.)
 //
 // In one special case (and more cases in the future), alias categories overlap.
 // The special alias category "Bot" (Compile::AliasIdxBot) includes all memory
 // states.  Therefore, if a MergeMem has only one contributing input W for Bot,
 // it is exactly equivalent to that state W:
 //   MergeMem(<Bot>: W) <==> W
 //
 // Usually, the merge has more than one input.  In that case, where inputs
 // overlap (i.e., one is Bot), the narrower alias type determines the memory
 // state for that type, and the wider alias type (Bot) fills in everywhere else:
 //   Load<5>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<5>(W,p)
 //   Load<6>( MergeMem(<Bot>: W, <6>: X), p ) <==> Load<6>(X,p)
 //
 // A merge can take a "wide" memory state as one of its narrow inputs.
 // This simply means that the merge observes out only the relevant parts of
 // the wide input.  That is, wide memory states arriving at narrow merge inputs
 // are implicitly "filtered" or "sliced" as necessary.  (This is rare.)
 //
 // These rules imply that MergeMem nodes may cascade (via their <Bot> links),
 // and that memory slices "leak through":
 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y)) <==> MergeMem(<Bot>: W, <7>: Y)
 //
 // But, in such a cascade, repeated memory slices can "block the leak":
 //   MergeMem(<Bot>: MergeMem(<Bot>: W, <7>: Y), <7>: Y') <==> MergeMem(<Bot>: W, <7>: Y')
 //
 // In the last example, Y is not part of the combined memory state of the
 // outermost MergeMem.  The system must, of course, prevent unschedulable
 // memory states from arising, so you can be sure that the state Y is somehow
 // a precursor to state Y'.
 //
 //
 // REPRESENTATION OF MEMORY MERGES: The indexes used to address the Node::in array
 // of each MergeMemNode array are exactly the numerical alias indexes, including
 // but not limited to AliasIdxTop, AliasIdxBot, and AliasIdxRaw.  The functions
 // Compile::alias_type (and kin) produce and manage these indexes.
 //
 // By convention, the value of in(AliasIdxTop) (i.e., in(1)) is always the top node.
 // (Note that this provides quick access to the top node inside MergeMem methods,
 // without the need to reach out via TLS to Compile::current.)
 //
 // As a consequence of what was just described, a MergeMem that represents a full
 // memory state has an edge in(AliasIdxBot) which is a "wide" memory state,
 // containing all alias categories.
 //
 // MergeMem nodes never (?) have control inputs, so in(0) is NULL.
 //
 // All other edges in(N) (including in(AliasIdxRaw), which is in(3)) are either
 // a memory state for the alias type <N>, or else the top node, meaning that
 // there is no particular input for that alias type.  Note that the length of
 // a MergeMem is variable, and may be extended at any time to accommodate new
 // memory states at larger alias indexes.  When merges grow, they are of course
 // filled with "top" in the unused in() positions.
 //
 // This use of top is named "empty_memory()", or "empty_mem" (no-memory) as a variable.
 // (Top was chosen because it works smoothly with passes like GCM.)
 //
 // For convenience, we hardwire the alias index for TypeRawPtr::BOTTOM.  (It is
 // the type of random VM bits like TLS references.)  Since it is always the
 // first non-Bot memory slice, some low-level loops use it to initialize an
 // index variable:  for (i = AliasIdxRaw; i < req(); i++).
 //
 //
 // ACCESSORS:  There is a special accessor MergeMemNode::base_memory which returns
 // the distinguished "wide" state.  The accessor MergeMemNode::memory_at(N) returns
 // the memory state for alias type <N>, or (if there is no particular slice at <N>,
 // it returns the base memory.  To prevent bugs, memory_at does not accept <Top>
 // or <Bot> indexes.  The iterator MergeMemStream provides robust iteration over
 // MergeMem nodes or pairs of such nodes, ensuring that the non-top edges are visited.
 //
 // %%%% We may get rid of base_memory as a separate accessor at some point; it isn't
 // really that different from the other memory inputs.  An abbreviation called
 // "bot_memory()" for "memory_at(AliasIdxBot)" would keep code tidy.
 //
 //
 // PARTIAL MEMORY STATES:  During optimization, MergeMem nodes may arise that represent
 // partial memory states.  When a Phi splits through a MergeMem, the copy of the Phi
 // that "emerges though" the base memory will be marked as excluding the alias types
 // of the other (narrow-memory) copies which "emerged through" the narrow edges:
 //
 //   Phi<Bot>(U, MergeMem(<Bot>: W, <8>: Y))
 //     ==Ideal=>  MergeMem(<Bot>: Phi<Bot-8>(U, W), Phi<8>(U, Y))
 //
 // This strange "subtraction" effect is necessary to ensure IGVN convergence.
 // (It is currently unimplemented.)  As you can see, the resulting merge is
 // actually a disjoint union of memory states, rather than an overlay.
 //
 //------------------------------MergeMemNode-----------------------------------
 Node* MergeMemNode::make_empty_memory() {
   Node* empty_memory = (Node*) Compile::current()->top();
   assert(empty_memory->is_top(), "correct sentinel identity");
   return empty_memory;
 }
 MergeMemNode::MergeMemNode(Node *new_base) : Node(1+Compile::AliasIdxRaw) {
   init_class_id(Class_MergeMem);
   // all inputs are nullified in Node::Node(int)
   // set_input(0, NULL);  // no control input
   // Initialize the edges uniformly to top, for starters.
   Node* empty_mem = make_empty_memory();
   for (uint i = Compile::AliasIdxTop; i < req(); i++) {
     init_req(i,empty_mem);
   }
   assert(empty_memory() == empty_mem, "");
   if( new_base != NULL && new_base->is_MergeMem() ) {
     MergeMemNode* mdef = new_base->as_MergeMem();
     assert(mdef->empty_memory() == empty_mem, "consistent sentinels");
     for (MergeMemStream mms(this, mdef); mms.next_non_empty2(); ) {
       mms.set_memory(mms.memory2());
     }
     assert(base_memory() == mdef->base_memory(), "");
   } else {
     set_base_memory(new_base);
   }
 }
 // Make a new, untransformed MergeMem with the same base as 'mem'.
 // If mem is itself a MergeMem, populate the result with the same edges.
 MergeMemNode* MergeMemNode::make(Compile* C, Node* mem) {
   return new(C, 1+Compile::AliasIdxRaw) MergeMemNode(mem);
 }
 //------------------------------cmp--------------------------------------------
 uint MergeMemNode::hash() const { return NO_HASH; }
 uint MergeMemNode::cmp( const Node &n ) const {
   return (&n == this);          // Always fail except on self
 }
 //------------------------------Identity---------------------------------------
 Node* MergeMemNode::Identity(PhaseTransform *phase) {
   // Identity if this merge point does not record any interesting memory
   // disambiguations.
   Node* base_mem = base_memory();
   Node* empty_mem = empty_memory();
   if (base_mem != empty_mem) {  // Memory path is not dead?
     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
       Node* mem = in(i);
       if (mem != empty_mem && mem != base_mem) {
         return this;            // Many memory splits; no change
       }
     }
   }
   return base_mem;              // No memory splits; ID on the one true input
 }
 //------------------------------Ideal------------------------------------------
 // This method is invoked recursively on chains of MergeMem nodes
 Node *MergeMemNode::Ideal(PhaseGVN *phase, bool can_reshape) {
   // Remove chain'd MergeMems
   //
   // This is delicate, because the each "in(i)" (i >= Raw) is interpreted
   // relative to the "in(Bot)".  Since we are patching both at the same time,
   // we have to be careful to read each "in(i)" relative to the old "in(Bot)",
   // but rewrite each "in(i)" relative to the new "in(Bot)".
   Node *progress = NULL;
   Node* old_base = base_memory();
   Node* empty_mem = empty_memory();
   if (old_base == empty_mem)
     return NULL; // Dead memory path.
   MergeMemNode* old_mbase;
   if (old_base != NULL && old_base->is_MergeMem())
     old_mbase = old_base->as_MergeMem();
   else
     old_mbase = NULL;
   Node* new_base = old_base;
   // simplify stacked MergeMems in base memory
   if (old_mbase)  new_base = old_mbase->base_memory();
   // the base memory might contribute new slices beyond my req()
   if (old_mbase)  grow_to_match(old_mbase);
   // Look carefully at the base node if it is a phi.
   PhiNode* phi_base;
   if (new_base != NULL && new_base->is_Phi())
     phi_base = new_base->as_Phi();
   else
     phi_base = NULL;
   Node*    phi_reg = NULL;
   uint     phi_len = (uint)-1;
   if (phi_base != NULL && !phi_base->is_copy()) {
     // do not examine phi if degraded to a copy
     phi_reg = phi_base->region();
     phi_len = phi_base->req();
     // see if the phi is unfinished
     for (uint i = 1; i < phi_len; i++) {
       if (phi_base->in(i) == NULL) {
         // incomplete phi; do not look at it yet!
         phi_reg = NULL;
         phi_len = (uint)-1;
         break;
       }
     }
   }
   // Note:  We do not call verify_sparse on entry, because inputs
   // can normalize to the base_memory via subsume_node or similar
   // mechanisms.  This method repairs that damage.
   assert(!old_mbase || old_mbase->is_empty_memory(empty_mem), "consistent sentinels");
   // Look at each slice.
   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
     Node* old_in = in(i);
     // calculate the old memory value
     Node* old_mem = old_in;
     if (old_mem == empty_mem)  old_mem = old_base;
     assert(old_mem == memory_at(i), "");
     // maybe update (reslice) the old memory value
     // simplify stacked MergeMems
     Node* new_mem = old_mem;
     MergeMemNode* old_mmem;
     if (old_mem != NULL && old_mem->is_MergeMem())
       old_mmem = old_mem->as_MergeMem();
     else
       old_mmem = NULL;
     if (old_mmem == this) {
       // This can happen if loops break up and safepoints disappear.
       // A merge of BotPtr (default) with a RawPtr memory derived from a
       // safepoint can be rewritten to a merge of the same BotPtr with
       // the BotPtr phi coming into the loop.  If that phi disappears
       // also, we can end up with a self-loop of the mergemem.
       // In general, if loops degenerate and memory effects disappear,
       // a mergemem can be left looking at itself.  This simply means
       // that the mergemem's default should be used, since there is
       // no longer any apparent effect on this slice.
       // Note: If a memory slice is a MergeMem cycle, it is unreachable
       //       from start.  Update the input to TOP.
       new_mem = (new_base == this || new_base == empty_mem)? empty_mem : new_base;
     }
     else if (old_mmem != NULL) {
       new_mem = old_mmem->memory_at(i);
     }
     // else preceeding memory was not a MergeMem
     // replace equivalent phis (unfortunately, they do not GVN together)
     if (new_mem != NULL && new_mem != new_base &&
         new_mem->req() == phi_len && new_mem->in(0) == phi_reg) {
       if (new_mem->is_Phi()) {
         PhiNode* phi_mem = new_mem->as_Phi();
         for (uint i = 1; i < phi_len; i++) {
           if (phi_base->in(i) != phi_mem->in(i)) {
             phi_mem = NULL;
             break;
           }
         }
         if (phi_mem != NULL) {
           // equivalent phi nodes; revert to the def
           new_mem = new_base;
         }
       }
     }
     // maybe store down a new value
     Node* new_in = new_mem;
     if (new_in == new_base)  new_in = empty_mem;
     if (new_in != old_in) {
       // Warning:  Do not combine this "if" with the previous "if"
       // A memory slice might have be be rewritten even if it is semantically
       // unchanged, if the base_memory value has changed.
       set_req(i, new_in);
       progress = this;          // Report progress
     }
   }
   if (new_base != old_base) {
     set_req(Compile::AliasIdxBot, new_base);
     // Don't use set_base_memory(new_base), because we need to update du.
     assert(base_memory() == new_base, "");
     progress = this;
   }
   if( base_memory() == this ) {
     // a self cycle indicates this memory path is dead
     set_req(Compile::AliasIdxBot, empty_mem);
   }
   // Resolve external cycles by calling Ideal on a MergeMem base_memory
   // Recursion must occur after the self cycle check above
   if( base_memory()->is_MergeMem() ) {
     MergeMemNode *new_mbase = base_memory()->as_MergeMem();
     Node *m = phase->transform(new_mbase);  // Rollup any cycles
     if( m != NULL && (m->is_top() ||
         m->is_MergeMem() && m->as_MergeMem()->base_memory() == empty_mem) ) {
       // propagate rollup of dead cycle to self
       set_req(Compile::AliasIdxBot, empty_mem);
     }
   }
   if( base_memory() == empty_mem ) {
     progress = this;
     // Cut inputs during Parse phase only.
     // During Optimize phase a dead MergeMem node will be subsumed by Top.
     if( !can_reshape ) {
       for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
         if( in(i) != empty_mem ) { set_req(i, empty_mem); }
       }
     }
   }
   if( !progress && base_memory()->is_Phi() && can_reshape ) {
     // Check if PhiNode::Ideal's "Split phis through memory merges"
     // transform should be attempted. Look for this->phi->this cycle.
     uint merge_width = req();
     if (merge_width > Compile::AliasIdxRaw) {
       PhiNode* phi = base_memory()->as_Phi();
       for( uint i = 1; i < phi->req(); ++i ) {// For all paths in
         if (phi->in(i) == this) {
           phase->is_IterGVN()->_worklist.push(phi);
           break;
         }
       }
     }
   }
   assert(progress || verify_sparse(), "please, no dups of base");
   return progress;
 }
 //-------------------------set_base_memory-------------------------------------
 void MergeMemNode::set_base_memory(Node *new_base) {
   Node* empty_mem = empty_memory();
   set_req(Compile::AliasIdxBot, new_base);
   assert(memory_at(req()) == new_base, "must set default memory");
   // Clear out other occurrences of new_base:
   if (new_base != empty_mem) {
     for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
       if (in(i) == new_base)  set_req(i, empty_mem);
     }
   }
 }
 //------------------------------out_RegMask------------------------------------
 const RegMask &MergeMemNode::out_RegMask() const {
   return RegMask::Empty;
 }
 //------------------------------dump_spec--------------------------------------
 #ifndef PRODUCT
 void MergeMemNode::dump_spec(outputStream *st) const {
   st->print(" {");
   Node* base_mem = base_memory();
   for( uint i = Compile::AliasIdxRaw; i < req(); i++ ) {
     Node* mem = memory_at(i);
     if (mem == base_mem) { st->print(" -"); continue; }
     st->print( " N%d:", mem->_idx );
     Compile::current()->get_adr_type(i)->dump_on(st);
   }
   st->print(" }");
 }
 #endif // !PRODUCT
 #ifdef ASSERT
 static bool might_be_same(Node* a, Node* b) {
   if (a == b)  return true;
   if (!(a->is_Phi() || b->is_Phi()))  return false;
   // phis shift around during optimization
   return true;  // pretty stupid...
 }
 // verify a narrow slice (either incoming or outgoing)
 static void verify_memory_slice(const MergeMemNode* m, int alias_idx, Node* n) {
   if (!VerifyAliases)       return;  // don't bother to verify unless requested
   if (is_error_reported())  return;  // muzzle asserts when debugging an error
   if (Node::in_dump())      return;  // muzzle asserts when printing
   assert(alias_idx >= Compile::AliasIdxRaw, "must not disturb base_memory or sentinel");
   assert(n != NULL, "");
   // Elide intervening MergeMem's
   while (n->is_MergeMem()) {
     n = n->as_MergeMem()->memory_at(alias_idx);
   }
   Compile* C = Compile::current();
   const TypePtr* n_adr_type = n->adr_type();
   if (n == m->empty_memory()) {
     // Implicit copy of base_memory()
   } else if (n_adr_type != TypePtr::BOTTOM) {
     assert(n_adr_type != NULL, "new memory must have a well-defined adr_type");
     assert(C->must_alias(n_adr_type, alias_idx), "new memory must match selected slice");
   } else {
     // A few places like make_runtime_call "know" that VM calls are narrow,
     // and can be used to update only the VM bits stored as TypeRawPtr::BOTTOM.
     bool expected_wide_mem = false;
     if (n == m->base_memory()) {
       expected_wide_mem = true;
     } else if (alias_idx == Compile::AliasIdxRaw ||
                n == m->memory_at(Compile::AliasIdxRaw)) {
       expected_wide_mem = true;
     } else if (!C->alias_type(alias_idx)->is_rewritable()) {
       // memory can "leak through" calls on channels that
       // are write-once.  Allow this also.
       expected_wide_mem = true;
     }
     assert(expected_wide_mem, "expected narrow slice replacement");
   }
 }
 #else // !ASSERT
 #define verify_memory_slice(m,i,n) (0)  // PRODUCT version is no-op
 #endif
 //-----------------------------memory_at---------------------------------------
 Node* MergeMemNode::memory_at(uint alias_idx) const {
   assert(alias_idx >= Compile::AliasIdxRaw ||
          alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,
          "must avoid base_memory and AliasIdxTop");
   // Otherwise, it is a narrow slice.
   Node* n = alias_idx < req() ? in(alias_idx) : empty_memory();
   Compile *C = Compile::current();
   if (is_empty_memory(n)) {
     // the array is sparse; empty slots are the "top" node
     n = base_memory();
     assert(Node::in_dump()
            || n == NULL || n->bottom_type() == Type::TOP
            || n->adr_type() == TypePtr::BOTTOM
            || n->adr_type() == TypeRawPtr::BOTTOM
            || Compile::current()->AliasLevel() == 0,
            "must be a wide memory");
     // AliasLevel == 0 if we are organizing the memory states manually.
     // See verify_memory_slice for comments on TypeRawPtr::BOTTOM.
   } else {
     // make sure the stored slice is sane
     #ifdef ASSERT
     if (is_error_reported() || Node::in_dump()) {
     } else if (might_be_same(n, base_memory())) {
       // Give it a pass:  It is a mostly harmless repetition of the base.
       // This can arise normally from node subsumption during optimization.
     } else {
       verify_memory_slice(this, alias_idx, n);
     }
     #endif
   }
   return n;
 }
 //---------------------------set_memory_at-------------------------------------
 void MergeMemNode::set_memory_at(uint alias_idx, Node *n) {
   verify_memory_slice(this, alias_idx, n);
   Node* empty_mem = empty_memory();
   if (n == base_memory())  n = empty_mem;  // collapse default
   uint need_req = alias_idx+1;
   if (req() < need_req) {
     if (n == empty_mem)  return;  // already the default, so do not grow me
     // grow the sparse array
     do {
       add_req(empty_mem);
     } while (req() < need_req);
   }
   set_req( alias_idx, n );
 }
 //--------------------------iteration_setup------------------------------------
 void MergeMemNode::iteration_setup(const MergeMemNode* other) {
   if (other != NULL) {
     grow_to_match(other);
     // invariant:  the finite support of mm2 is within mm->req()
     #ifdef ASSERT
     for (uint i = req(); i < other->req(); i++) {
       assert(other->is_empty_memory(other->in(i)), "slice left uncovered");
     }
     #endif
   }
   // Replace spurious copies of base_memory by top.
   Node* base_mem = base_memory();
   if (base_mem != NULL && !base_mem->is_top()) {
     for (uint i = Compile::AliasIdxBot+1, imax = req(); i < imax; i++) {
       if (in(i) == base_mem)
         set_req(i, empty_memory());
     }
   }
 }
 //---------------------------grow_to_match-------------------------------------
 void MergeMemNode::grow_to_match(const MergeMemNode* other) {
   Node* empty_mem = empty_memory();
   assert(other->is_empty_memory(empty_mem), "consistent sentinels");
   // look for the finite support of the other memory
   for (uint i = other->req(); --i >= req(); ) {
     if (other->in(i) != empty_mem) {
       uint new_len = i+1;
       while (req() < new_len)  add_req(empty_mem);
       break;
     }
   }
 }
 //---------------------------verify_sparse-------------------------------------
 #ifndef PRODUCT
 bool MergeMemNode::verify_sparse() const {
   assert(is_empty_memory(make_empty_memory()), "sane sentinel");
   Node* base_mem = base_memory();
   // The following can happen in degenerate cases, since empty==top.
   if (is_empty_memory(base_mem))  return true;
   for (uint i = Compile::AliasIdxRaw; i < req(); i++) {
     assert(in(i) != NULL, "sane slice");
     if (in(i) == base_mem)  return false;  // should have been the sentinel value!
   }
   return true;
 }
 bool MergeMemStream::match_memory(Node* mem, const MergeMemNode* mm, int idx) {
   Node* n;
   n = mm->in(idx);
   if (mem == n)  return true;  // might be empty_memory()
   n = (idx == Compile::AliasIdxBot)? mm->base_memory(): mm->memory_at(idx);
   if (mem == n)  return true;
   while (n->is_Phi() && (n = n->as_Phi()->is_copy()) != NULL) {
     if (mem == n)  return true;
     if (n == NULL)  break;
   }
   return false;
 }
 #endif // !PRODUCT

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/memnode.cpp@b130b98db9cf (annotated)

src/share/vm/opto/memnode.cpp