Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1997, 2009, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 // Portions of code courtesy of Clifford Click

 class MultiNode;

 class PhaseCCP;

 class PhaseTransform;

 //------------------------------MemNode----------------------------------------

 // Load or Store, possibly throwing a NULL pointer exception

 class MemNode : public Node {

 protected:

 #ifdef ASSERT

   const TypePtr* _adr_type;     // What kind of memory is being addressed?

 #endif

   virtual uint size_of() const; // Size is bigger (ASSERT only)

 public:

   enum { Control,               // When is it safe to do this load?

          Memory,                // Chunk of memory is being loaded from

          Address,               // Actually address, derived from base

          ValueIn,               // Value to store

          OopStore               // Preceeding oop store, only in StoreCM

   };

 protected:

   MemNode( Node *c0, Node *c1, Node *c2, const TypePtr* at )

     : Node(c0,c1,c2   ) {

     init_class_id(Class_Mem);

     debug_only(_adr_type=at; adr_type();)

   }

   MemNode( Node *c0, Node *c1, Node *c2, const TypePtr* at, Node *c3 )

     : Node(c0,c1,c2,c3) {

     init_class_id(Class_Mem);

     debug_only(_adr_type=at; adr_type();)

   }

   MemNode( Node *c0, Node *c1, Node *c2, const TypePtr* at, Node *c3, Node *c4)

     : Node(c0,c1,c2,c3,c4) {

     init_class_id(Class_Mem);

     debug_only(_adr_type=at; adr_type();)

   }

 public:

   // Helpers for the optimizer.  Documented in memnode.cpp.

   static bool detect_ptr_independence(Node* p1, AllocateNode* a1,

                                       Node* p2, AllocateNode* a2,

                                       PhaseTransform* phase);

   static bool adr_phi_is_loop_invariant(Node* adr_phi, Node* cast);

   static Node *optimize_simple_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase);

   static Node *optimize_memory_chain(Node *mchain, const TypePtr *t_adr, PhaseGVN *phase);

   // This one should probably be a phase-specific function:

   static bool all_controls_dominate(Node* dom, Node* sub);

   // Find any cast-away of null-ness and keep its control.

   static  Node *Ideal_common_DU_postCCP( PhaseCCP *ccp, Node* n, Node* adr );

   virtual Node *Ideal_DU_postCCP( PhaseCCP *ccp );

   virtual const class TypePtr *adr_type() const;  // returns bottom_type of address

   // Shared code for Ideal methods:

   Node *Ideal_common(PhaseGVN *phase, bool can_reshape);  // Return -1 for short-circuit NULL.

   // Helper function for adr_type() implementations.

   static const TypePtr* calculate_adr_type(const Type* t, const TypePtr* cross_check = NULL);

   // Raw access function, to allow copying of adr_type efficiently in

   // product builds and retain the debug info for debug builds.

   const TypePtr *raw_adr_type() const {

 #ifdef ASSERT

     return _adr_type;

 #else

     return 0;

 #endif

   }

   // Map a load or store opcode to its corresponding store opcode.

   // (Return -1 if unknown.)

   virtual int store_Opcode() const { return -1; }

   // What is the type of the value in memory?  (T_VOID mean "unspecified".)

   virtual BasicType memory_type() const = 0;

   virtual int memory_size() const {

 #ifdef ASSERT

     return type2aelembytes(memory_type(), true);

 #else

     return type2aelembytes(memory_type());

 #endif

   }

   // Search through memory states which precede this node (load or store).

   // Look for an exact match for the address, with no intervening

   // aliased stores.

   Node* find_previous_store(PhaseTransform* phase);

   // Can this node (load or store) accurately see a stored value in

   // the given memory state?  (The state may or may not be in(Memory).)

   Node* can_see_stored_value(Node* st, PhaseTransform* phase) const;

 #ifndef PRODUCT

   static void dump_adr_type(const Node* mem, const TypePtr* adr_type, outputStream *st);

   virtual void dump_spec(outputStream *st) const;

 #endif

 };

 //------------------------------LoadNode---------------------------------------

 // Load value; requires Memory and Address

 class LoadNode : public MemNode {

 protected:

   virtual uint cmp( const Node &n ) const;

   virtual uint size_of() const; // Size is bigger

   const Type* const _type;      // What kind of value is loaded?

 public:

   LoadNode( Node *c, Node *mem, Node *adr, const TypePtr* at, const Type *rt )

     : MemNode(c,mem,adr,at), _type(rt) {

     init_class_id(Class_Load);

   }

   // Polymorphic factory method:

   static Node* make( PhaseGVN& gvn, Node *c, Node *mem, Node *adr,

                      const TypePtr* at, const Type *rt, BasicType bt );

   virtual uint hash()   const;  // Check the type

   // Handle algebraic identities here.  If we have an identity, return the Node

   // we are equivalent to.  We look for Load of a Store.

   virtual Node *Identity( PhaseTransform *phase );

   // If the load is from Field memory and the pointer is non-null, we can

   // zero out the control input.

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   // Split instance field load through Phi.

   Node* split_through_phi(PhaseGVN *phase);

   // Recover original value from boxed values

   Node *eliminate_autobox(PhaseGVN *phase);

   // Compute a new Type for this node.  Basically we just do the pre-check,

   // then call the virtual add() to set the type.

   virtual const Type *Value( PhaseTransform *phase ) const;

   // Common methods for LoadKlass and LoadNKlass nodes.

   const Type *klass_value_common( PhaseTransform *phase ) const;

   Node *klass_identity_common( PhaseTransform *phase );

   virtual uint ideal_reg() const;

   virtual const Type *bottom_type() const;

   // Following method is copied from TypeNode:

   void set_type(const Type* t) {

     assert(t != NULL, "sanity");

     debug_only(uint check_hash = (VerifyHashTableKeys && _hash_lock) ? hash() : NO_HASH);

     *(const Type**)&_type = t;   // cast away const-ness

     // If this node is in the hash table, make sure it doesn't need a rehash.

     assert(check_hash == NO_HASH || check_hash == hash(), "type change must preserve hash code");

   }

   const Type* type() const { assert(_type != NULL, "sanity"); return _type; };

   // Do not match memory edge

   virtual uint match_edge(uint idx) const;

   // Map a load opcode to its corresponding store opcode.

   virtual int store_Opcode() const = 0;

   // Check if the load's memory input is a Phi node with the same control.

   bool is_instance_field_load_with_local_phi(Node* ctrl);

 #ifndef PRODUCT

   virtual void dump_spec(outputStream *st) const;

 #endif

 #ifdef ASSERT

   // Helper function to allow a raw load without control edge for some cases

   static bool is_immutable_value(Node* adr);

 #endif

 protected:

   const Type* load_array_final_field(const TypeKlassPtr *tkls,

                                      ciKlass* klass) const;

 };

 //------------------------------LoadBNode--------------------------------------

 // Load a byte (8bits signed) from memory

 class LoadBNode : public LoadNode {

 public:

   LoadBNode( Node *c, Node *mem, Node *adr, const TypePtr* at, const TypeInt *ti = TypeInt::BYTE )

     : LoadNode(c,mem,adr,at,ti) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual int store_Opcode() const { return Op_StoreB; }

   virtual BasicType memory_type() const { return T_BYTE; }

 };

 //------------------------------LoadUBNode-------------------------------------

 // Load a unsigned byte (8bits unsigned) from memory

 class LoadUBNode : public LoadNode {

 public:

   LoadUBNode(Node* c, Node* mem, Node* adr, const TypePtr* at, const TypeInt* ti = TypeInt::UBYTE )

     : LoadNode(c, mem, adr, at, ti) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node* Ideal(PhaseGVN *phase, bool can_reshape);

   virtual int store_Opcode() const { return Op_StoreB; }

   virtual BasicType memory_type() const { return T_BYTE; }

 };

 //------------------------------LoadUSNode-------------------------------------

 // Load an unsigned short/char (16bits unsigned) from memory

 class LoadUSNode : public LoadNode {

 public:

   LoadUSNode( Node *c, Node *mem, Node *adr, const TypePtr* at, const TypeInt *ti = TypeInt::CHAR )

     : LoadNode(c,mem,adr,at,ti) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual int store_Opcode() const { return Op_StoreC; }

   virtual BasicType memory_type() const { return T_CHAR; }

 };

 //------------------------------LoadINode--------------------------------------

 // Load an integer from memory

 class LoadINode : public LoadNode {

 public:

   LoadINode( Node *c, Node *mem, Node *adr, const TypePtr* at, const TypeInt *ti = TypeInt::INT )

     : LoadNode(c,mem,adr,at,ti) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual int store_Opcode() const { return Op_StoreI; }

   virtual BasicType memory_type() const { return T_INT; }

 };

 //------------------------------LoadUI2LNode-----------------------------------

 // Load an unsigned integer into long from memory

 class LoadUI2LNode : public LoadNode {

 public:

   LoadUI2LNode(Node* c, Node* mem, Node* adr, const TypePtr* at, const TypeLong* t = TypeLong::UINT)

     : LoadNode(c, mem, adr, at, t) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegL; }

   virtual int store_Opcode() const { return Op_StoreL; }

   virtual BasicType memory_type() const { return T_LONG; }

 };

 //------------------------------LoadRangeNode----------------------------------

 // Load an array length from the array

 class LoadRangeNode : public LoadINode {

 public:

   LoadRangeNode( Node *c, Node *mem, Node *adr, const TypeInt *ti = TypeInt::POS )

     : LoadINode(c,mem,adr,TypeAryPtr::RANGE,ti) {}

   virtual int Opcode() const;

   virtual const Type *Value( PhaseTransform *phase ) const;

   virtual Node *Identity( PhaseTransform *phase );

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

 };

 //------------------------------LoadLNode--------------------------------------

 // Load a long from memory

 class LoadLNode : public LoadNode {

   virtual uint hash() const { return LoadNode::hash() + _require_atomic_access; }

   virtual uint cmp( const Node &n ) const {

     return _require_atomic_access == ((LoadLNode&)n)._require_atomic_access

       && LoadNode::cmp(n);

   }

   virtual uint size_of() const { return sizeof(*this); }

   const bool _require_atomic_access;  // is piecewise load forbidden?

 public:

   LoadLNode( Node *c, Node *mem, Node *adr, const TypePtr* at,

              const TypeLong *tl = TypeLong::LONG,

              bool require_atomic_access = false )

     : LoadNode(c,mem,adr,at,tl)

     , _require_atomic_access(require_atomic_access)

   {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegL; }

   virtual int store_Opcode() const { return Op_StoreL; }

   virtual BasicType memory_type() const { return T_LONG; }

   bool require_atomic_access() { return _require_atomic_access; }

   static LoadLNode* make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, const Type* rt);

 #ifndef PRODUCT

   virtual void dump_spec(outputStream *st) const {

     LoadNode::dump_spec(st);

     if (_require_atomic_access)  st->print(" Atomic!");

   }

 #endif

 };

 //------------------------------LoadL_unalignedNode----------------------------

 // Load a long from unaligned memory

 class LoadL_unalignedNode : public LoadLNode {

 public:

   LoadL_unalignedNode( Node *c, Node *mem, Node *adr, const TypePtr* at )

     : LoadLNode(c,mem,adr,at) {}

   virtual int Opcode() const;

 };

 //------------------------------LoadFNode--------------------------------------

 // Load a float (64 bits) from memory

 class LoadFNode : public LoadNode {

 public:

   LoadFNode( Node *c, Node *mem, Node *adr, const TypePtr* at, const Type *t = Type::FLOAT )

     : LoadNode(c,mem,adr,at,t) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegF; }

   virtual int store_Opcode() const { return Op_StoreF; }

   virtual BasicType memory_type() const { return T_FLOAT; }

 };

 //------------------------------LoadDNode--------------------------------------

 // Load a double (64 bits) from memory

 class LoadDNode : public LoadNode {

 public:

   LoadDNode( Node *c, Node *mem, Node *adr, const TypePtr* at, const Type *t = Type::DOUBLE )

     : LoadNode(c,mem,adr,at,t) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegD; }

   virtual int store_Opcode() const { return Op_StoreD; }

   virtual BasicType memory_type() const { return T_DOUBLE; }

 };

 //------------------------------LoadD_unalignedNode----------------------------

 // Load a double from unaligned memory

 class LoadD_unalignedNode : public LoadDNode {

 public:

   LoadD_unalignedNode( Node *c, Node *mem, Node *adr, const TypePtr* at )

     : LoadDNode(c,mem,adr,at) {}

   virtual int Opcode() const;

 };

 //------------------------------LoadPNode--------------------------------------

 // Load a pointer from memory (either object or array)

 class LoadPNode : public LoadNode {

 public:

   LoadPNode( Node *c, Node *mem, Node *adr, const TypePtr *at, const TypePtr* t )

     : LoadNode(c,mem,adr,at,t) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegP; }

   virtual int store_Opcode() const { return Op_StoreP; }

   virtual BasicType memory_type() const { return T_ADDRESS; }

   // depends_only_on_test is almost always true, and needs to be almost always

   // true to enable key hoisting & commoning optimizations.  However, for the

   // special case of RawPtr loads from TLS top & end, the control edge carries

   // the dependence preventing hoisting past a Safepoint instead of the memory

   // edge.  (An unfortunate consequence of having Safepoints not set Raw

   // Memory; itself an unfortunate consequence of having Nodes which produce

   // results (new raw memory state) inside of loops preventing all manner of

   // other optimizations).  Basically, it's ugly but so is the alternative.

   // See comment in macro.cpp, around line 125 expand_allocate_common().

   virtual bool depends_only_on_test() const { return adr_type() != TypeRawPtr::BOTTOM; }

 };

 //------------------------------LoadNNode--------------------------------------

 // Load a narrow oop from memory (either object or array)

 class LoadNNode : public LoadNode {

 public:

   LoadNNode( Node *c, Node *mem, Node *adr, const TypePtr *at, const Type* t )

     : LoadNode(c,mem,adr,at,t) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegN; }

   virtual int store_Opcode() const { return Op_StoreN; }

   virtual BasicType memory_type() const { return T_NARROWOOP; }

   // depends_only_on_test is almost always true, and needs to be almost always

   // true to enable key hoisting & commoning optimizations.  However, for the

   // special case of RawPtr loads from TLS top & end, the control edge carries

   // the dependence preventing hoisting past a Safepoint instead of the memory

   // edge.  (An unfortunate consequence of having Safepoints not set Raw

   // Memory; itself an unfortunate consequence of having Nodes which produce

   // results (new raw memory state) inside of loops preventing all manner of

   // other optimizations).  Basically, it's ugly but so is the alternative.

   // See comment in macro.cpp, around line 125 expand_allocate_common().

   virtual bool depends_only_on_test() const { return adr_type() != TypeRawPtr::BOTTOM; }

 };

 //------------------------------LoadKlassNode----------------------------------

 // Load a Klass from an object

 class LoadKlassNode : public LoadPNode {

 public:

   LoadKlassNode( Node *c, Node *mem, Node *adr, const TypePtr *at, const TypeKlassPtr *tk )

     : LoadPNode(c,mem,adr,at,tk) {}

   virtual int Opcode() const;

   virtual const Type *Value( PhaseTransform *phase ) const;

   virtual Node *Identity( PhaseTransform *phase );

   virtual bool depends_only_on_test() const { return true; }

   // Polymorphic factory method:

   static Node* make( PhaseGVN& gvn, Node *mem, Node *adr, const TypePtr* at,

                      const TypeKlassPtr *tk = TypeKlassPtr::OBJECT );

 };

 //------------------------------LoadNKlassNode---------------------------------

 // Load a narrow Klass from an object.

 class LoadNKlassNode : public LoadNNode {

 public:

   LoadNKlassNode( Node *c, Node *mem, Node *adr, const TypePtr *at, const TypeNarrowOop *tk )

     : LoadNNode(c,mem,adr,at,tk) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegN; }

   virtual int store_Opcode() const { return Op_StoreN; }

   virtual BasicType memory_type() const { return T_NARROWOOP; }

   virtual const Type *Value( PhaseTransform *phase ) const;

   virtual Node *Identity( PhaseTransform *phase );

   virtual bool depends_only_on_test() const { return true; }

 };

 //------------------------------LoadSNode--------------------------------------

 // Load a short (16bits signed) from memory

 class LoadSNode : public LoadNode {

 public:

   LoadSNode( Node *c, Node *mem, Node *adr, const TypePtr* at, const TypeInt *ti = TypeInt::SHORT )

     : LoadNode(c,mem,adr,at,ti) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual int store_Opcode() const { return Op_StoreC; }

   virtual BasicType memory_type() const { return T_SHORT; }

 };

 //------------------------------StoreNode--------------------------------------

 // Store value; requires Store, Address and Value

 class StoreNode : public MemNode {

 protected:

   virtual uint cmp( const Node &n ) const;

   virtual bool depends_only_on_test() const { return false; }

   Node *Ideal_masked_input       (PhaseGVN *phase, uint mask);

   Node *Ideal_sign_extended_input(PhaseGVN *phase, int  num_bits);

 public:

   StoreNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val )

     : MemNode(c,mem,adr,at,val) {

     init_class_id(Class_Store);

   }

   StoreNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val, Node *oop_store )

     : MemNode(c,mem,adr,at,val,oop_store) {

     init_class_id(Class_Store);

   }

   // Polymorphic factory method:

   static StoreNode* make( PhaseGVN& gvn, Node *c, Node *mem, Node *adr,

                           const TypePtr* at, Node *val, BasicType bt );

   virtual uint hash() const;    // Check the type

   // If the store is to Field memory and the pointer is non-null, we can

   // zero out the control input.

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   // Compute a new Type for this node.  Basically we just do the pre-check,

   // then call the virtual add() to set the type.

   virtual const Type *Value( PhaseTransform *phase ) const;

   // Check for identity function on memory (Load then Store at same address)

   virtual Node *Identity( PhaseTransform *phase );

   // Do not match memory edge

   virtual uint match_edge(uint idx) const;

   virtual const Type *bottom_type() const;  // returns Type::MEMORY

   // Map a store opcode to its corresponding own opcode, trivially.

   virtual int store_Opcode() const { return Opcode(); }

   // have all possible loads of the value stored been optimized away?

   bool value_never_loaded(PhaseTransform *phase) const;

 };

 //------------------------------StoreBNode-------------------------------------

 // Store byte to memory

 class StoreBNode : public StoreNode {

 public:

   StoreBNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual BasicType memory_type() const { return T_BYTE; }

 };

 //------------------------------StoreCNode-------------------------------------

 // Store char/short to memory

 class StoreCNode : public StoreNode {

 public:

   StoreCNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual BasicType memory_type() const { return T_CHAR; }

 };

 //------------------------------StoreINode-------------------------------------

 // Store int to memory

 class StoreINode : public StoreNode {

 public:

   StoreINode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual BasicType memory_type() const { return T_INT; }

 };

 //------------------------------StoreLNode-------------------------------------

 // Store long to memory

 class StoreLNode : public StoreNode {

   virtual uint hash() const { return StoreNode::hash() + _require_atomic_access; }

   virtual uint cmp( const Node &n ) const {

     return _require_atomic_access == ((StoreLNode&)n)._require_atomic_access

       && StoreNode::cmp(n);

   }

   virtual uint size_of() const { return sizeof(*this); }

   const bool _require_atomic_access;  // is piecewise store forbidden?

 public:

   StoreLNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val,

               bool require_atomic_access = false )

     : StoreNode(c,mem,adr,at,val)

     , _require_atomic_access(require_atomic_access)

   {}

   virtual int Opcode() const;

   virtual BasicType memory_type() const { return T_LONG; }

   bool require_atomic_access() { return _require_atomic_access; }

   static StoreLNode* make_atomic(Compile *C, Node* ctl, Node* mem, Node* adr, const TypePtr* adr_type, Node* val);

 #ifndef PRODUCT

   virtual void dump_spec(outputStream *st) const {

     StoreNode::dump_spec(st);

     if (_require_atomic_access)  st->print(" Atomic!");

   }

 #endif

 };

 //------------------------------StoreFNode-------------------------------------

 // Store float to memory

 class StoreFNode : public StoreNode {

 public:

   StoreFNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual BasicType memory_type() const { return T_FLOAT; }

 };

 //------------------------------StoreDNode-------------------------------------

 // Store double to memory

 class StoreDNode : public StoreNode {

 public:

   StoreDNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual BasicType memory_type() const { return T_DOUBLE; }

 };

 //------------------------------StorePNode-------------------------------------

 // Store pointer to memory

 class StorePNode : public StoreNode {

 public:

   StorePNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual BasicType memory_type() const { return T_ADDRESS; }

 };

 //------------------------------StoreNNode-------------------------------------

 // Store narrow oop to memory

 class StoreNNode : public StoreNode {

 public:

   StoreNNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val ) : StoreNode(c,mem,adr,at,val) {}

   virtual int Opcode() const;

   virtual BasicType memory_type() const { return T_NARROWOOP; }

 };

 //------------------------------StoreCMNode-----------------------------------

 // Store card-mark byte to memory for CM

 // The last StoreCM before a SafePoint must be preserved and occur after its "oop" store

 // Preceeding equivalent StoreCMs may be eliminated.

 class StoreCMNode : public StoreNode {

  private:

   virtual uint hash() const { return StoreNode::hash() + _oop_alias_idx; }

   virtual uint cmp( const Node &n ) const {

     return _oop_alias_idx == ((StoreCMNode&)n)._oop_alias_idx

       && StoreNode::cmp(n);

   }

   virtual uint size_of() const { return sizeof(*this); }

   int _oop_alias_idx;   // The alias_idx of OopStore

 public:

   StoreCMNode( Node *c, Node *mem, Node *adr, const TypePtr* at, Node *val, Node *oop_store, int oop_alias_idx ) :

     StoreNode(c,mem,adr,at,val,oop_store),

     _oop_alias_idx(oop_alias_idx) {

     assert(_oop_alias_idx >= Compile::AliasIdxRaw ||

            _oop_alias_idx == Compile::AliasIdxBot && Compile::current()->AliasLevel() == 0,

            "bad oop alias idx");

   }

   virtual int Opcode() const;

   virtual Node *Identity( PhaseTransform *phase );

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual const Type *Value( PhaseTransform *phase ) const;

   virtual BasicType memory_type() const { return T_VOID; } // unspecific

   int oop_alias_idx() const { return _oop_alias_idx; }

 };

 //------------------------------LoadPLockedNode---------------------------------

 // Load-locked a pointer from memory (either object or array).

 // On Sparc & Intel this is implemented as a normal pointer load.

 // On PowerPC and friends it's a real load-locked.

 class LoadPLockedNode : public LoadPNode {

 public:

   LoadPLockedNode( Node *c, Node *mem, Node *adr )

     : LoadPNode(c,mem,adr,TypeRawPtr::BOTTOM, TypeRawPtr::BOTTOM) {}

   virtual int Opcode() const;

   virtual int store_Opcode() const { return Op_StorePConditional; }

   virtual bool depends_only_on_test() const { return true; }

 };

 //------------------------------LoadLLockedNode---------------------------------

 // Load-locked a pointer from memory (either object or array).

 // On Sparc & Intel this is implemented as a normal long load.

 class LoadLLockedNode : public LoadLNode {

 public:

   LoadLLockedNode( Node *c, Node *mem, Node *adr )

     : LoadLNode(c,mem,adr,TypeRawPtr::BOTTOM, TypeLong::LONG) {}

   virtual int Opcode() const;

   virtual int store_Opcode() const { return Op_StoreLConditional; }

 };

 //------------------------------SCMemProjNode---------------------------------------

 // This class defines a projection of the memory  state of a store conditional node.

 // These nodes return a value, but also update memory.

 class SCMemProjNode : public ProjNode {

 public:

   enum {SCMEMPROJCON = (uint)-2};

   SCMemProjNode( Node *src) : ProjNode( src, SCMEMPROJCON) { }

   virtual int Opcode() const;

   virtual bool      is_CFG() const  { return false; }

   virtual const Type *bottom_type() const {return Type::MEMORY;}

   virtual const TypePtr *adr_type() const { return in(0)->in(MemNode::Memory)->adr_type();}

   virtual uint ideal_reg() const { return 0;} // memory projections don't have a register

   virtual const Type *Value( PhaseTransform *phase ) const;

 #ifndef PRODUCT

   virtual void dump_spec(outputStream *st) const {};

 #endif

 };

 //------------------------------LoadStoreNode---------------------------

 // Note: is_Mem() method returns 'true' for this class.

 class LoadStoreNode : public Node {

 public:

   enum {

     ExpectedIn = MemNode::ValueIn+1 // One more input than MemNode

   };

   LoadStoreNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex);

   virtual bool depends_only_on_test() const { return false; }

   virtual const Type *bottom_type() const { return TypeInt::BOOL; }

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual uint match_edge(uint idx) const { return idx == MemNode::Address || idx == MemNode::ValueIn; }

 };

 //------------------------------StorePConditionalNode---------------------------

 // Conditionally store pointer to memory, if no change since prior

 // load-locked.  Sets flags for success or failure of the store.

 class StorePConditionalNode : public LoadStoreNode {

 public:

   StorePConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ll ) : LoadStoreNode(c, mem, adr, val, ll) { }

   virtual int Opcode() const;

   // Produces flags

   virtual uint ideal_reg() const { return Op_RegFlags; }

 };

 //------------------------------StoreIConditionalNode---------------------------

 // Conditionally store int to memory, if no change since prior

 // load-locked.  Sets flags for success or failure of the store.

 class StoreIConditionalNode : public LoadStoreNode {

 public:

   StoreIConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ii ) : LoadStoreNode(c, mem, adr, val, ii) { }

   virtual int Opcode() const;

   // Produces flags

   virtual uint ideal_reg() const { return Op_RegFlags; }

 };

 //------------------------------StoreLConditionalNode---------------------------

 // Conditionally store long to memory, if no change since prior

 // load-locked.  Sets flags for success or failure of the store.

 class StoreLConditionalNode : public LoadStoreNode {

 public:

   StoreLConditionalNode( Node *c, Node *mem, Node *adr, Node *val, Node *ll ) : LoadStoreNode(c, mem, adr, val, ll) { }

   virtual int Opcode() const;

   // Produces flags

   virtual uint ideal_reg() const { return Op_RegFlags; }

 };

 //------------------------------CompareAndSwapLNode---------------------------

 class CompareAndSwapLNode : public LoadStoreNode {

 public:

   CompareAndSwapLNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex) : LoadStoreNode(c, mem, adr, val, ex) { }

   virtual int Opcode() const;

 };

 //------------------------------CompareAndSwapINode---------------------------

 class CompareAndSwapINode : public LoadStoreNode {

 public:

   CompareAndSwapINode( Node *c, Node *mem, Node *adr, Node *val, Node *ex) : LoadStoreNode(c, mem, adr, val, ex) { }

   virtual int Opcode() const;

 };

 //------------------------------CompareAndSwapPNode---------------------------

 class CompareAndSwapPNode : public LoadStoreNode {

 public:

   CompareAndSwapPNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex) : LoadStoreNode(c, mem, adr, val, ex) { }

   virtual int Opcode() const;

 };

 //------------------------------CompareAndSwapNNode---------------------------

 class CompareAndSwapNNode : public LoadStoreNode {

 public:

   CompareAndSwapNNode( Node *c, Node *mem, Node *adr, Node *val, Node *ex) : LoadStoreNode(c, mem, adr, val, ex) { }

   virtual int Opcode() const;

 };

 //------------------------------ClearArray-------------------------------------

 class ClearArrayNode: public Node {

 public:

   ClearArrayNode( Node *ctrl, Node *arymem, Node *word_cnt, Node *base )

     : Node(ctrl,arymem,word_cnt,base) {

     init_class_id(Class_ClearArray);

   }

   virtual int         Opcode() const;

   virtual const Type *bottom_type() const { return Type::MEMORY; }

   // ClearArray modifies array elements, and so affects only the

   // array memory addressed by the bottom_type of its base address.

   virtual const class TypePtr *adr_type() const;

   virtual Node *Identity( PhaseTransform *phase );

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual uint match_edge(uint idx) const;

   // Clear the given area of an object or array.

   // The start offset must always be aligned mod BytesPerInt.

   // The end offset must always be aligned mod BytesPerLong.

   // Return the new memory.

   static Node* clear_memory(Node* control, Node* mem, Node* dest,

                             intptr_t start_offset,

                             intptr_t end_offset,

                             PhaseGVN* phase);

   static Node* clear_memory(Node* control, Node* mem, Node* dest,

                             intptr_t start_offset,

                             Node* end_offset,

                             PhaseGVN* phase);

   static Node* clear_memory(Node* control, Node* mem, Node* dest,

                             Node* start_offset,

                             Node* end_offset,

                             PhaseGVN* phase);

   // Return allocation input memory edge if it is different instance

   // or itself if it is the one we are looking for.

   static bool step_through(Node** np, uint instance_id, PhaseTransform* phase);

 };

 //------------------------------StrComp-------------------------------------

 class StrCompNode: public Node {

 public:

   StrCompNode(Node* control, Node* char_array_mem,

               Node* s1, Node* c1,

               Node* s2, Node* c2): Node(control, char_array_mem,

                                         s1, c1,

                                         s2, c2) {};

   virtual int Opcode() const;

   virtual bool depends_only_on_test() const { return false; }

   virtual const Type* bottom_type() const { return TypeInt::INT; }

   virtual const TypePtr* adr_type() const { return TypeAryPtr::CHARS; }

   virtual uint match_edge(uint idx) const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

 };

 //------------------------------StrEquals-------------------------------------

 class StrEqualsNode: public Node {

 public:

   StrEqualsNode(Node* control, Node* char_array_mem,

                 Node* s1, Node* s2, Node* c): Node(control, char_array_mem,

                                                    s1, s2, c) {};

   virtual int Opcode() const;

   virtual bool depends_only_on_test() const { return false; }

   virtual const Type* bottom_type() const { return TypeInt::BOOL; }

   virtual const TypePtr* adr_type() const { return TypeAryPtr::CHARS; }

   virtual uint match_edge(uint idx) const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

 };

 //------------------------------StrIndexOf-------------------------------------

 class StrIndexOfNode: public Node {

 public:

   StrIndexOfNode(Node* control, Node* char_array_mem,

                  Node* s1, Node* c1,

                  Node* s2, Node* c2): Node(control, char_array_mem,

                                            s1, c1,

                                            s2, c2) {};

   virtual int Opcode() const;

   virtual bool depends_only_on_test() const { return false; }

   virtual const Type* bottom_type() const { return TypeInt::INT; }

   virtual const TypePtr* adr_type() const { return TypeAryPtr::CHARS; }

   virtual uint match_edge(uint idx) const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

 };

 //------------------------------AryEq---------------------------------------

 class AryEqNode: public Node {

 public:

   AryEqNode(Node* control, Node* char_array_mem,

             Node* s1, Node* s2): Node(control, char_array_mem, s1, s2) {};

   virtual int Opcode() const;

   virtual bool depends_only_on_test() const { return false; }

   virtual const Type* bottom_type() const { return TypeInt::BOOL; }

   virtual const TypePtr* adr_type() const { return TypeAryPtr::CHARS; }

   virtual uint match_edge(uint idx) const;

   virtual uint ideal_reg() const { return Op_RegI; }

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

 };

 //------------------------------MemBar-----------------------------------------

 // There are different flavors of Memory Barriers to match the Java Memory

 // Model.  Monitor-enter and volatile-load act as Aquires: no following ref

 // can be moved to before them.  We insert a MemBar-Acquire after a FastLock or

 // volatile-load.  Monitor-exit and volatile-store act as Release: no

 // preceding ref can be moved to after them.  We insert a MemBar-Release

 // before a FastUnlock or volatile-store.  All volatiles need to be

 // serialized, so we follow all volatile-stores with a MemBar-Volatile to

 // separate it from any following volatile-load.

 class MemBarNode: public MultiNode {

   virtual uint hash() const ;                  // { return NO_HASH; }

   virtual uint cmp( const Node &n ) const ;    // Always fail, except on self

   virtual uint size_of() const { return sizeof(*this); }

   // Memory type this node is serializing.  Usually either rawptr or bottom.

   const TypePtr* _adr_type;

 public:

   enum {

     Precedent = TypeFunc::Parms  // optional edge to force precedence

   };

   MemBarNode(Compile* C, int alias_idx, Node* precedent);

   virtual int Opcode() const = 0;

   virtual const class TypePtr *adr_type() const { return _adr_type; }

   virtual const Type *Value( PhaseTransform *phase ) const;

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual uint match_edge(uint idx) const { return 0; }

   virtual const Type *bottom_type() const { return TypeTuple::MEMBAR; }

   virtual Node *match( const ProjNode *proj, const Matcher *m );

   // Factory method.  Builds a wide or narrow membar.

   // Optional 'precedent' becomes an extra edge if not null.

   static MemBarNode* make(Compile* C, int opcode,

                           int alias_idx = Compile::AliasIdxBot,

                           Node* precedent = NULL);

 };

 // "Acquire" - no following ref can move before (but earlier refs can

 // follow, like an early Load stalled in cache).  Requires multi-cpu

 // visibility.  Inserted after a volatile load or FastLock.

 class MemBarAcquireNode: public MemBarNode {

 public:

   MemBarAcquireNode(Compile* C, int alias_idx, Node* precedent)

     : MemBarNode(C, alias_idx, precedent) {}

   virtual int Opcode() const;

 };

 // "Release" - no earlier ref can move after (but later refs can move

 // up, like a speculative pipelined cache-hitting Load).  Requires

 // multi-cpu visibility.  Inserted before a volatile store or FastUnLock.

 class MemBarReleaseNode: public MemBarNode {

 public:

   MemBarReleaseNode(Compile* C, int alias_idx, Node* precedent)

     : MemBarNode(C, alias_idx, precedent) {}

   virtual int Opcode() const;

 };

 // Ordering between a volatile store and a following volatile load.

 // Requires multi-CPU visibility?

 class MemBarVolatileNode: public MemBarNode {

 public:

   MemBarVolatileNode(Compile* C, int alias_idx, Node* precedent)

     : MemBarNode(C, alias_idx, precedent) {}

   virtual int Opcode() const;

 };

 // Ordering within the same CPU.  Used to order unsafe memory references

 // inside the compiler when we lack alias info.  Not needed "outside" the

 // compiler because the CPU does all the ordering for us.

 class MemBarCPUOrderNode: public MemBarNode {

 public:

   MemBarCPUOrderNode(Compile* C, int alias_idx, Node* precedent)

     : MemBarNode(C, alias_idx, precedent) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return 0; } // not matched in the AD file

 };

 // Isolation of object setup after an AllocateNode and before next safepoint.

 // (See comment in memnode.cpp near InitializeNode::InitializeNode for semantics.)

 class InitializeNode: public MemBarNode {

   friend class AllocateNode;

   bool _is_complete;

 public:

   enum {

     Control    = TypeFunc::Control,

     Memory     = TypeFunc::Memory,     // MergeMem for states affected by this op

     RawAddress = TypeFunc::Parms+0,    // the newly-allocated raw address

     RawStores  = TypeFunc::Parms+1     // zero or more stores (or TOP)

   };

   InitializeNode(Compile* C, int adr_type, Node* rawoop);

   virtual int Opcode() const;

   virtual uint size_of() const { return sizeof(*this); }

   virtual uint ideal_reg() const { return 0; } // not matched in the AD file

   virtual const RegMask &in_RegMask(uint) const;  // mask for RawAddress

   // Manage incoming memory edges via a MergeMem on in(Memory):

   Node* memory(uint alias_idx);

   // The raw memory edge coming directly from the Allocation.

   // The contents of this memory are *always* all-zero-bits.

   Node* zero_memory() { return memory(Compile::AliasIdxRaw); }

   // Return the corresponding allocation for this initialization (or null if none).

   // (Note: Both InitializeNode::allocation and AllocateNode::initialization

   // are defined in graphKit.cpp, which sets up the bidirectional relation.)

   AllocateNode* allocation();

   // Anything other than zeroing in this init?

   bool is_non_zero();

   // An InitializeNode must completed before macro expansion is done.

   // Completion requires that the AllocateNode must be followed by

   // initialization of the new memory to zero, then to any initializers.

   bool is_complete() { return _is_complete; }

   // Mark complete.  (Must not yet be complete.)

   void set_complete(PhaseGVN* phase);

 #ifdef ASSERT

   // ensure all non-degenerate stores are ordered and non-overlapping

   bool stores_are_sane(PhaseTransform* phase);

 #endif //ASSERT

   // See if this store can be captured; return offset where it initializes.

   // Return 0 if the store cannot be moved (any sort of problem).

   intptr_t can_capture_store(StoreNode* st, PhaseTransform* phase);

   // Capture another store; reformat it to write my internal raw memory.

   // Return the captured copy, else NULL if there is some sort of problem.

   Node* capture_store(StoreNode* st, intptr_t start, PhaseTransform* phase);

   // Find captured store which corresponds to the range [start..start+size).

   // Return my own memory projection (meaning the initial zero bits)

   // if there is no such store.  Return NULL if there is a problem.

   Node* find_captured_store(intptr_t start, int size_in_bytes, PhaseTransform* phase);

   // Called when the associated AllocateNode is expanded into CFG.

   Node* complete_stores(Node* rawctl, Node* rawmem, Node* rawptr,

                         intptr_t header_size, Node* size_in_bytes,

                         PhaseGVN* phase);

  private:

   void remove_extra_zeroes();

   // Find out where a captured store should be placed (or already is placed).

   int captured_store_insertion_point(intptr_t start, int size_in_bytes,

                                      PhaseTransform* phase);

   static intptr_t get_store_offset(Node* st, PhaseTransform* phase);

   Node* make_raw_address(intptr_t offset, PhaseTransform* phase);

   bool detect_init_independence(Node* n, bool st_is_pinned, int& count);

   void coalesce_subword_stores(intptr_t header_size, Node* size_in_bytes,

                                PhaseGVN* phase);

   intptr_t find_next_fullword_store(uint i, PhaseGVN* phase);

 };

 //------------------------------MergeMem---------------------------------------

 // (See comment in memnode.cpp near MergeMemNode::MergeMemNode for semantics.)

 class MergeMemNode: public Node {

   virtual uint hash() const ;                  // { return NO_HASH; }

   virtual uint cmp( const Node &n ) const ;    // Always fail, except on self

   friend class MergeMemStream;

   MergeMemNode(Node* def);  // clients use MergeMemNode::make

 public:

   // If the input is a whole memory state, clone it with all its slices intact.

   // Otherwise, make a new memory state with just that base memory input.

   // In either case, the result is a newly created MergeMem.

   static MergeMemNode* make(Compile* C, Node* base_memory);

   virtual int Opcode() const;

   virtual Node *Identity( PhaseTransform *phase );

   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

   virtual uint ideal_reg() const { return NotAMachineReg; }

   virtual uint match_edge(uint idx) const { return 0; }

   virtual const RegMask &out_RegMask() const;

   virtual const Type *bottom_type() const { return Type::MEMORY; }

   virtual const TypePtr *adr_type() const { return TypePtr::BOTTOM; }

   // sparse accessors

   // Fetch the previously stored "set_memory_at", or else the base memory.

   // (Caller should clone it if it is a phi-nest.)

   Node* memory_at(uint alias_idx) const;

   // set the memory, regardless of its previous value

   void set_memory_at(uint alias_idx, Node* n);

   // the "base" is the memory that provides the non-finite support

   Node* base_memory() const       { return in(Compile::AliasIdxBot); }

   // warning: setting the base can implicitly set any of the other slices too

   void set_base_memory(Node* def);

   // sentinel value which denotes a copy of the base memory:

   Node*   empty_memory() const    { return in(Compile::AliasIdxTop); }

   static Node* make_empty_memory(); // where the sentinel comes from

   bool is_empty_memory(Node* n) const { assert((n == empty_memory()) == n->is_top(), "sanity"); return n->is_top(); }

   // hook for the iterator, to perform any necessary setup

   void iteration_setup(const MergeMemNode* other = NULL);

   // push sentinels until I am at least as long as the other (semantic no-op)

   void grow_to_match(const MergeMemNode* other);

   bool verify_sparse() const PRODUCT_RETURN0;

 #ifndef PRODUCT

   virtual void dump_spec(outputStream *st) const;

 #endif

 };

 class MergeMemStream : public StackObj {

  private:

   MergeMemNode*       _mm;

   const MergeMemNode* _mm2;  // optional second guy, contributes non-empty iterations

   Node*               _mm_base;  // loop-invariant base memory of _mm

   int                 _idx;

   int                 _cnt;

   Node*               _mem;

   Node*               _mem2;

   int                 _cnt2;

   void init(MergeMemNode* mm, const MergeMemNode* mm2 = NULL) {

     // subsume_node will break sparseness at times, whenever a memory slice

     // folds down to a copy of the base ("fat") memory.  In such a case,

     // the raw edge will update to base, although it should be top.

     // This iterator will recognize either top or base_memory as an

     // "empty" slice.  See is_empty, is_empty2, and next below.

     //

     // The sparseness property is repaired in MergeMemNode::Ideal.

     // As long as access to a MergeMem goes through this iterator

     // or the memory_at accessor, flaws in the sparseness will

     // never be observed.

     //

     // Also, iteration_setup repairs sparseness.

     assert(mm->verify_sparse(), "please, no dups of base");

     assert(mm2==NULL || mm2->verify_sparse(), "please, no dups of base");

     _mm  = mm;

     _mm_base = mm->base_memory();

     _mm2 = mm2;

     _cnt = mm->req();

     _idx = Compile::AliasIdxBot-1; // start at the base memory

     _mem = NULL;

     _mem2 = NULL;

   }

 #ifdef ASSERT

   Node* check_memory() const {

     if (at_base_memory())

       return _mm->base_memory();

     else if ((uint)_idx < _mm->req() && !_mm->in(_idx)->is_top())

       return _mm->memory_at(_idx);

     else

       return _mm_base;

   }

   Node* check_memory2() const {

     return at_base_memory()? _mm2->base_memory(): _mm2->memory_at(_idx);

   }

 #endif

   static bool match_memory(Node* mem, const MergeMemNode* mm, int idx) PRODUCT_RETURN0;

   void assert_synch() const {

     assert(!_mem || _idx >= _cnt || match_memory(_mem, _mm, _idx),

            "no side-effects except through the stream");

   }

  public:

   // expected usages:

   // for (MergeMemStream mms(mem->is_MergeMem()); next_non_empty(); ) { ... }

   // for (MergeMemStream mms(mem1, mem2); next_non_empty2(); ) { ... }

   // iterate over one merge

   MergeMemStream(MergeMemNode* mm) {

     mm->iteration_setup();

     init(mm);

     debug_only(_cnt2 = 999);

   }

   // iterate in parallel over two merges

   // only iterates through non-empty elements of mm2

   MergeMemStream(MergeMemNode* mm, const MergeMemNode* mm2) {

     assert(mm2, "second argument must be a MergeMem also");

     ((MergeMemNode*)mm2)->iteration_setup();  // update hidden state

     mm->iteration_setup(mm2);

     init(mm, mm2);

     _cnt2 = mm2->req();

   }

 #ifdef ASSERT

   ~MergeMemStream() {

     assert_synch();

   }

 #endif

   MergeMemNode* all_memory() const {

     return _mm;

   }

   Node* base_memory() const {

     assert(_mm_base == _mm->base_memory(), "no update to base memory, please");

     return _mm_base;

   }

   const MergeMemNode* all_memory2() const {

     assert(_mm2 != NULL, "");

     return _mm2;

   }

   bool at_base_memory() const {

     return _idx == Compile::AliasIdxBot;

   }

   int alias_idx() const {

     assert(_mem, "must call next 1st");

     return _idx;

   }

   const TypePtr* adr_type() const {

     return Compile::current()->get_adr_type(alias_idx());

   }

   const TypePtr* adr_type(Compile* C) const {

     return C->get_adr_type(alias_idx());

   }

   bool is_empty() const {

     assert(_mem, "must call next 1st");

     assert(_mem->is_top() == (_mem==_mm->empty_memory()), "correct sentinel");

     return _mem->is_top();

   }

   bool is_empty2() const {

     assert(_mem2, "must call next 1st");

     assert(_mem2->is_top() == (_mem2==_mm2->empty_memory()), "correct sentinel");

     return _mem2->is_top();

   }

   Node* memory() const {

     assert(!is_empty(), "must not be empty");

     assert_synch();

     return _mem;

   }

   // get the current memory, regardless of empty or non-empty status

   Node* force_memory() const {

     assert(!is_empty() || !at_base_memory(), "");

     // Use _mm_base to defend against updates to _mem->base_memory().

     Node *mem = _mem->is_top() ? _mm_base : _mem;

     assert(mem == check_memory(), "");

     return mem;

   }

   Node* memory2() const {

     assert(_mem2 == check_memory2(), "");

     return _mem2;

   }

   void set_memory(Node* mem) {

     if (at_base_memory()) {

       // Note that this does not change the invariant _mm_base.

       _mm->set_base_memory(mem);

     } else {

       _mm->set_memory_at(_idx, mem);

     }

     _mem = mem;

     assert_synch();

   }

   // Recover from a side effect to the MergeMemNode.

   void set_memory() {

     _mem = _mm->in(_idx);

   }

   bool next()  { return next(false); }

   bool next2() { return next(true); }

   bool next_non_empty()  { return next_non_empty(false); }

   bool next_non_empty2() { return next_non_empty(true); }

   // next_non_empty2 can yield states where is_empty() is true

  private:

   // find the next item, which might be empty

   bool next(bool have_mm2) {

     assert((_mm2 != NULL) == have_mm2, "use other next");

     assert_synch();

     if (++_idx < _cnt) {

       // Note:  This iterator allows _mm to be non-sparse.

       // It behaves the same whether _mem is top or base_memory.

       _mem = _mm->in(_idx);

       if (have_mm2)

         _mem2 = _mm2->in((_idx < _cnt2) ? _idx : Compile::AliasIdxTop);

       return true;

     }

     return false;

   }

   // find the next non-empty item

   bool next_non_empty(bool have_mm2) {

     while (next(have_mm2)) {

       if (!is_empty()) {

         // make sure _mem2 is filled in sensibly

         if (have_mm2 && _mem2->is_top())  _mem2 = _mm2->base_memory();

         return true;

       } else if (have_mm2 && !is_empty2()) {

         return true;   // is_empty() == true

       }

     }

     return false;

   }

 };

 //------------------------------Prefetch---------------------------------------

 // Non-faulting prefetch load.  Prefetch for many reads.

 class PrefetchReadNode : public Node {

 public:

   PrefetchReadNode(Node *abio, Node *adr) : Node(0,abio,adr) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return NotAMachineReg; }

   virtual uint match_edge(uint idx) const { return idx==2; }

   virtual const Type *bottom_type() const { return Type::ABIO; }

 };

 // Non-faulting prefetch load.  Prefetch for many reads & many writes.

 class PrefetchWriteNode : public Node {

 public:

   PrefetchWriteNode(Node *abio, Node *adr) : Node(0,abio,adr) {}

   virtual int Opcode() const;

   virtual uint ideal_reg() const { return NotAMachineReg; }

   virtual uint match_edge(uint idx) const { return idx==2; }

   virtual const Type *bottom_type() const { return ( AllocatePrefetchStyle == 3 ) ? Type::MEMORY : Type::ABIO; }

 };