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 /*

  * 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

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  */

 // 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 control input 'dom' dominates (or equals) '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::detect_dominating_control(Node* dom, Node* sub) {

   if (dom == NULL)      return false;

   if (dom->is_Proj())   dom = dom->in(0);

   if (dom->is_Start())  return true; // anything inside the method

   if (dom->is_Root())   return true; // dom 'controls' a constant

   int cnt = 20;                      // detect cycle or too much effort

   while (sub != NULL) {              // walk 'sub' up the chain to 'dom'

     if (--cnt < 0)   return false;   // in a cycle or too complex

     if (sub == dom)  return true;

     if (sub->is_Start())  return false;

     if (sub->is_Root())   return false;

     Node* up = sub->in(0);

     if (sub == up && sub->is_Region()) {

       for (uint i = 1; i < sub->req(); i++) {

         Node* in = sub->in(i);

         if (in != NULL && !in->is_top() && in != sub) {

           up = in; break;            // take any path on the way up to 'dom'

         }

       }

     }

     if (sub == up)  return false;    // some kind of tight cycle

     sub = up;

   }

   return false;

 }

 //---------------------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 detect_dominating_control(p2->in(0), a1->in(0));

   } else { //(a2 != NULL)                   // one allocation a2

     return detect_dominating_control(p1->in(0), a2->in(0));

   }

   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 (ctrl != NULL &&

                detect_dominating_control(ctrl, st_alloc->in(0)))

         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_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_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:

 LoadNode *LoadNode::make( Compile *C, Node *ctl, Node *mem, Node *adr, const TypePtr* adr_type, const Type *rt, BasicType bt ) {

   // 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:  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)

         && detect_dominating_control(base->in(0), 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( Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val, BasicType bt ) {

   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:  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(C, 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(C, 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::detect_dominating_control(ctl, this->in(0)))

       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) sizeof(oopDesc))  return FAIL;

   if (start < (intptr_t) sizeof(arrayOopDesc) &&

       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)