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

 /*

  * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

  * CA 95054 USA or visit www.sun.com if you need additional information or

  * have any questions.

  *

  */

 // Portions of code courtesy of Clifford Click

 // Optimization - Graph Style

 class AbstractLockNode;

 class AddNode;

 class AddPNode;

 class AliasInfo;

 class AllocateArrayNode;

 class AllocateNode;

 class Block;

 class Block_Array;

 class BoolNode;

 class BoxLockNode;

 class CMoveNode;

 class CallDynamicJavaNode;

 class CallJavaNode;

 class CallLeafNode;

 class CallNode;

 class CallRuntimeNode;

 class CallStaticJavaNode;

 class CatchNode;

 class CatchProjNode;

 class CheckCastPPNode;

 class CmpNode;

 class CodeBuffer;

 class ConstraintCastNode;

 class ConNode;

 class CountedLoopNode;

 class CountedLoopEndNode;

 class FastLockNode;

 class FastUnlockNode;

 class IfNode;

 class InitializeNode;

 class JVMState;

 class JumpNode;

 class JumpProjNode;

 class LoadNode;

 class LoadStoreNode;

 class LockNode;

 class LoopNode;

 class MachCallDynamicJavaNode;

 class MachCallJavaNode;

 class MachCallLeafNode;

 class MachCallNode;

 class MachCallRuntimeNode;

 class MachCallStaticJavaNode;

 class MachIfNode;

 class MachNode;

 class MachNullCheckNode;

 class MachReturnNode;

 class MachSafePointNode;

 class MachSpillCopyNode;

 class MachTempNode;

 class Matcher;

 class MemBarNode;

 class MemNode;

 class MergeMemNode;

 class MulNode;

 class MultiNode;

 class MultiBranchNode;

 class NeverBranchNode;

 class Node;

 class Node_Array;

 class Node_List;

 class Node_Stack;

 class NullCheckNode;

 class OopMap;

 class ParmNode;

 class PCTableNode;

 class PhaseCCP;

 class PhaseGVN;

 class PhaseIterGVN;

 class PhaseRegAlloc;

 class PhaseTransform;

 class PhaseValues;

 class PhiNode;

 class Pipeline;

 class ProjNode;

 class RegMask;

 class RegionNode;

 class RootNode;

 class SafePointNode;

 class StartNode;

 class State;

 class StoreNode;

 class SubNode;

 class Type;

 class TypeNode;

 class UnlockNode;

 class VectorSet;

 class IfTrueNode;

 class IfFalseNode;

 typedef void (*NFunc)(Node&,void*);

 extern "C" {

   typedef int (*C_sort_func_t)(const void *, const void *);

 }

 // The type of all node counts and indexes.

 // It must hold at least 16 bits, but must also be fast to load and store.

 // This type, if less than 32 bits, could limit the number of possible nodes.

 // (To make this type platform-specific, move to globalDefinitions_xxx.hpp.)

 typedef unsigned int node_idx_t;

 #ifndef OPTO_DU_ITERATOR_ASSERT

 #ifdef ASSERT

 #define OPTO_DU_ITERATOR_ASSERT 1

 #else

 #define OPTO_DU_ITERATOR_ASSERT 0

 #endif

 #endif //OPTO_DU_ITERATOR_ASSERT

 #if OPTO_DU_ITERATOR_ASSERT

 class DUIterator;

 class DUIterator_Fast;

 class DUIterator_Last;

 #else

 typedef uint   DUIterator;

 typedef Node** DUIterator_Fast;

 typedef Node** DUIterator_Last;

 #endif

 // Node Sentinel

 #define NodeSentinel (Node*)-1

 // Unknown count frequency

 #define COUNT_UNKNOWN (-1.0f)

 //------------------------------Node-------------------------------------------

 // Nodes define actions in the program.  They create values, which have types.

 // They are both vertices in a directed graph and program primitives.  Nodes

 // are labeled; the label is the "opcode", the primitive function in the lambda

 // calculus sense that gives meaning to the Node.  Node inputs are ordered (so

 // that "a-b" is different from "b-a").  The inputs to a Node are the inputs to

 // the Node's function.  These inputs also define a Type equation for the Node.

 // Solving these Type equations amounts to doing dataflow analysis.

 // Control and data are uniformly represented in the graph.  Finally, Nodes

 // have a unique dense integer index which is used to index into side arrays

 // whenever I have phase-specific information.

 class Node {

   // Lots of restrictions on cloning Nodes

   Node(const Node&);            // not defined; linker error to use these

   Node &operator=(const Node &rhs);

 public:

   friend class Compile;

   #if OPTO_DU_ITERATOR_ASSERT

   friend class DUIterator_Common;

   friend class DUIterator;

   friend class DUIterator_Fast;

   friend class DUIterator_Last;

   #endif

   // Because Nodes come and go, I define an Arena of Node structures to pull

   // from.  This should allow fast access to node creation & deletion.  This

   // field is a local cache of a value defined in some "program fragment" for

   // which these Nodes are just a part of.

   // New Operator that takes a Compile pointer, this will eventually

   // be the "new" New operator.

   inline void* operator new( size_t x, Compile* C) {

     Node* n = (Node*)C->node_arena()->Amalloc_D(x);

 #ifdef ASSERT

     n->_in = (Node**)n; // magic cookie for assertion check

 #endif

     n->_out = (Node**)C;

     return (void*)n;

   }

   // New Operator that takes a Compile pointer, this will eventually

   // be the "new" New operator.

   inline void* operator new( size_t x, Compile* C, int y) {

     Node* n = (Node*)C->node_arena()->Amalloc_D(x + y*sizeof(void*));

     n->_in = (Node**)(((char*)n) + x);

 #ifdef ASSERT

     n->_in[y-1] = n; // magic cookie for assertion check

 #endif

     n->_out = (Node**)C;

     return (void*)n;

   }

   // Delete is a NOP

   void operator delete( void *ptr ) {}

   // Fancy destructor; eagerly attempt to reclaim Node numberings and storage

   void destruct();

   // Create a new Node.  Required is the number is of inputs required for

   // semantic correctness.

   Node( uint required );

   // Create a new Node with given input edges.

   // This version requires use of the "edge-count" new.

   // E.g.  new (C,3) FooNode( C, NULL, left, right );

   Node( Node *n0 );

   Node( Node *n0, Node *n1 );

   Node( Node *n0, Node *n1, Node *n2 );

   Node( Node *n0, Node *n1, Node *n2, Node *n3 );

   Node( Node *n0, Node *n1, Node *n2, Node *n3, Node *n4 );

   Node( Node *n0, Node *n1, Node *n2, Node *n3, Node *n4, Node *n5 );

   Node( Node *n0, Node *n1, Node *n2, Node *n3,

             Node *n4, Node *n5, Node *n6 );

   // Clone an inherited Node given only the base Node type.

   Node* clone() const;

   // Clone a Node, immediately supplying one or two new edges.

   // The first and second arguments, if non-null, replace in(1) and in(2),

   // respectively.

   Node* clone_with_data_edge(Node* in1, Node* in2 = NULL) const {

     Node* nn = clone();

     if (in1 != NULL)  nn->set_req(1, in1);

     if (in2 != NULL)  nn->set_req(2, in2);

     return nn;

   }

 private:

   // Shared setup for the above constructors.

   // Handles all interactions with Compile::current.

   // Puts initial values in all Node fields except _idx.

   // Returns the initial value for _idx, which cannot

   // be initialized by assignment.

   inline int Init(int req, Compile* C);

 //----------------- input edge handling

 protected:

   friend class PhaseCFG;        // Access to address of _in array elements

   Node **_in;                   // Array of use-def references to Nodes

   Node **_out;                  // Array of def-use references to Nodes

   // Input edges are split into two catagories.  Required edges are required

   // for semantic correctness; order is important and NULLs are allowed.

   // Precedence edges are used to help determine execution order and are

   // added, e.g., for scheduling purposes.  They are unordered and not

   // duplicated; they have no embedded NULLs.  Edges from 0 to _cnt-1

   // are required, from _cnt to _max-1 are precedence edges.

   node_idx_t _cnt;              // Total number of required Node inputs.

   node_idx_t _max;              // Actual length of input array.

   // Output edges are an unordered list of def-use edges which exactly

   // correspond to required input edges which point from other nodes

   // to this one.  Thus the count of the output edges is the number of

   // users of this node.

   node_idx_t _outcnt;           // Total number of Node outputs.

   node_idx_t _outmax;           // Actual length of output array.

   // Grow the actual input array to the next larger power-of-2 bigger than len.

   void grow( uint len );

   // Grow the output array to the next larger power-of-2 bigger than len.

   void out_grow( uint len );

  public:

   // Each Node is assigned a unique small/dense number.  This number is used

   // to index into auxiliary arrays of data and bitvectors.

   // It is declared const to defend against inadvertant assignment,

   // since it is used by clients as a naked field.

   const node_idx_t _idx;

   // Get the (read-only) number of input edges

   uint req() const { return _cnt; }

   uint len() const { return _max; }

   // Get the (read-only) number of output edges

   uint outcnt() const { return _outcnt; }

 #if OPTO_DU_ITERATOR_ASSERT

   // Iterate over the out-edges of this node.  Deletions are illegal.

   inline DUIterator outs() const;

   // Use this when the out array might have changed to suppress asserts.

   inline DUIterator& refresh_out_pos(DUIterator& i) const;

   // Does the node have an out at this position?  (Used for iteration.)

   inline bool has_out(DUIterator& i) const;

   inline Node*    out(DUIterator& i) const;

   // Iterate over the out-edges of this node.  All changes are illegal.

   inline DUIterator_Fast fast_outs(DUIterator_Fast& max) const;

   inline Node*    fast_out(DUIterator_Fast& i) const;

   // Iterate over the out-edges of this node, deleting one at a time.

   inline DUIterator_Last last_outs(DUIterator_Last& min) const;

   inline Node*    last_out(DUIterator_Last& i) const;

   // The inline bodies of all these methods are after the iterator definitions.

 #else

   // Iterate over the out-edges of this node.  Deletions are illegal.

   // This iteration uses integral indexes, to decouple from array reallocations.

   DUIterator outs() const  { return 0; }

   // Use this when the out array might have changed to suppress asserts.

   DUIterator refresh_out_pos(DUIterator i) const { return i; }

   // Reference to the i'th output Node.  Error if out of bounds.

   Node*    out(DUIterator i) const { assert(i < _outcnt, "oob"); return _out[i]; }

   // Does the node have an out at this position?  (Used for iteration.)

   bool has_out(DUIterator i) const { return i < _outcnt; }

   // Iterate over the out-edges of this node.  All changes are illegal.

   // This iteration uses a pointer internal to the out array.

   DUIterator_Fast fast_outs(DUIterator_Fast& max) const {

     Node** out = _out;

     // Assign a limit pointer to the reference argument:

     max = out + (ptrdiff_t)_outcnt;

     // Return the base pointer:

     return out;

   }

   Node*    fast_out(DUIterator_Fast i) const  { return *i; }

   // Iterate over the out-edges of this node, deleting one at a time.

   // This iteration uses a pointer internal to the out array.

   DUIterator_Last last_outs(DUIterator_Last& min) const {

     Node** out = _out;

     // Assign a limit pointer to the reference argument:

     min = out;

     // Return the pointer to the start of the iteration:

     return out + (ptrdiff_t)_outcnt - 1;

   }

   Node*    last_out(DUIterator_Last i) const  { return *i; }

 #endif

   // Reference to the i'th input Node.  Error if out of bounds.

   Node* in(uint i) const { assert(i < _max,"oob"); return _in[i]; }

   // Reference to the i'th output Node.  Error if out of bounds.

   // Use this accessor sparingly.  We are going trying to use iterators instead.

   Node* raw_out(uint i) const { assert(i < _outcnt,"oob"); return _out[i]; }

   // Return the unique out edge.

   Node* unique_out() const { assert(_outcnt==1,"not unique"); return _out[0]; }

   // Delete out edge at position 'i' by moving last out edge to position 'i'

   void  raw_del_out(uint i) {

     assert(i < _outcnt,"oob");

     assert(_outcnt > 0,"oob");

     #if OPTO_DU_ITERATOR_ASSERT

     // Record that a change happened here.

     debug_only(_last_del = _out[i]; ++_del_tick);

     #endif

     _out[i] = _out[--_outcnt];

     // Smash the old edge so it can't be used accidentally.

     debug_only(_out[_outcnt] = (Node *)(uintptr_t)0xdeadbeef);

   }

 #ifdef ASSERT

   bool is_dead() const;

 #define is_not_dead(n) ((n) == NULL || !VerifyIterativeGVN || !((n)->is_dead()))

 #endif

   // Set a required input edge, also updates corresponding output edge

   void add_req( Node *n ); // Append a NEW required input

   void add_req_batch( Node* n, uint m ); // Append m NEW required inputs (all n).

   void del_req( uint idx ); // Delete required edge & compact

   void ins_req( uint i, Node *n ); // Insert a NEW required input

   void set_req( uint i, Node *n ) {

     assert( is_not_dead(n), "can not use dead node");

     assert( i < _cnt, "oob");

     assert( !VerifyHashTableKeys || _hash_lock == 0,

             "remove node from hash table before modifying it");

     Node** p = &_in[i];    // cache this._in, across the del_out call

     if (*p != NULL)  (*p)->del_out((Node *)this);

     (*p) = n;

     if (n != NULL)      n->add_out((Node *)this);

   }

   // Light version of set_req() to init inputs after node creation.

   void init_req( uint i, Node *n ) {

     assert( i == 0 && this == n ||

             is_not_dead(n), "can not use dead node");

     assert( i < _cnt, "oob");

     assert( !VerifyHashTableKeys || _hash_lock == 0,

             "remove node from hash table before modifying it");

     assert( _in[i] == NULL, "sanity");

     _in[i] = n;

     if (n != NULL)      n->add_out((Node *)this);

   }

   // Find first occurrence of n among my edges:

   int find_edge(Node* n);

   int replace_edge(Node* old, Node* neww);

   // NULL out all inputs to eliminate incoming Def-Use edges.

   // Return the number of edges between 'n' and 'this'

   int  disconnect_inputs(Node *n);

   // Quickly, return true if and only if I am Compile::current()->top().

   bool is_top() const {

     assert((this == (Node*) Compile::current()->top()) == (_out == NULL), "");

     return (_out == NULL);

   }

   // Reaffirm invariants for is_top.  (Only from Compile::set_cached_top_node.)

   void setup_is_top();

   // Strip away casting.  (It is depth-limited.)

   Node* uncast() const;

 private:

   static Node* uncast_helper(const Node* n);

   // Add an output edge to the end of the list

   void add_out( Node *n ) {

     if (is_top())  return;

     if( _outcnt == _outmax ) out_grow(_outcnt);

     _out[_outcnt++] = n;

   }

   // Delete an output edge

   void del_out( Node *n ) {

     if (is_top())  return;

     Node** outp = &_out[_outcnt];

     // Find and remove n

     do {

       assert(outp > _out, "Missing Def-Use edge");

     } while (*--outp != n);

     *outp = _out[--_outcnt];

     // Smash the old edge so it can't be used accidentally.

     debug_only(_out[_outcnt] = (Node *)(uintptr_t)0xdeadbeef);

     // Record that a change happened here.

     #if OPTO_DU_ITERATOR_ASSERT

     debug_only(_last_del = n; ++_del_tick);

     #endif

   }

 public:

   // Globally replace this node by a given new node, updating all uses.

   void replace_by(Node* new_node);

   void set_req_X( uint i, Node *n, PhaseIterGVN *igvn );

   // Find the one non-null required input.  RegionNode only

   Node *nonnull_req() const;

   // Add or remove precedence edges

   void add_prec( Node *n );

   void rm_prec( uint i );

   void set_prec( uint i, Node *n ) {

     assert( is_not_dead(n), "can not use dead node");

     assert( i >= _cnt, "not a precedence edge");

     if (_in[i] != NULL) _in[i]->del_out((Node *)this);

     _in[i] = n;

     if (n != NULL) n->add_out((Node *)this);

   }

   // Set this node's index, used by cisc_version to replace current node

   void set_idx(uint new_idx) {

     const node_idx_t* ref = &_idx;

     *(node_idx_t*)ref = new_idx;

   }

   // Swap input edge order.  (Edge indexes i1 and i2 are usually 1 and 2.)

   void swap_edges(uint i1, uint i2) {

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

     // Def-Use info is unchanged

     Node* n1 = in(i1);

     Node* n2 = in(i2);

     _in[i1] = n2;

     _in[i2] = n1;

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

     assert(check_hash == NO_HASH || check_hash == hash(), "edge swap must preserve hash code");

   }

   // Iterators over input Nodes for a Node X are written as:

   // for( i = 0; i < X.req(); i++ ) ... X[i] ...

   // NOTE: Required edges can contain embedded NULL pointers.

 //----------------- Other Node Properties

   // Generate class id for some ideal nodes to avoid virtual query

   // methods is_<Node>().

   // Class id is the set of bits corresponded to the node class and all its

   // super classes so that queries for super classes are also valid.

   // Subclasses of the same super class have different assigned bit

   // (the third parameter in the macro DEFINE_CLASS_ID).

   // Classes with deeper hierarchy are declared first.

   // Classes with the same hierarchy depth are sorted by usage frequency.

   //

   // The query method masks the bits to cut off bits of subclasses

   // and then compare the result with the class id

   // (see the macro DEFINE_CLASS_QUERY below).

   //

   //  Class_MachCall=30, ClassMask_MachCall=31

   // 12               8               4               0

   //  0   0   0   0   0   0   0   0   1   1   1   1   0

   //                                  |   |   |   |

   //                                  |   |   |   Bit_Mach=2

   //                                  |   |   Bit_MachReturn=4

   //                                  |   Bit_MachSafePoint=8

   //                                  Bit_MachCall=16

   //

   //  Class_CountedLoop=56, ClassMask_CountedLoop=63

   // 12               8               4               0

   //  0   0   0   0   0   0   0   1   1   1   0   0   0

   //                              |   |   |

   //                              |   |   Bit_Region=8

   //                              |   Bit_Loop=16

   //                              Bit_CountedLoop=32

   #define DEFINE_CLASS_ID(cl, supcl, subn) \

   Bit_##cl = (Class_##supcl == 0) ? 1 << subn : (Bit_##supcl) << (1 + subn) , \

   Class_##cl = Class_##supcl + Bit_##cl , \

   ClassMask_##cl = ((Bit_##cl << 1) - 1) ,

   // This enum is used only for C2 ideal and mach nodes with is_<node>() methods

   // so that it's values fits into 16 bits.

   enum NodeClasses {

     Bit_Node   = 0x0000,

     Class_Node = 0x0000,

     ClassMask_Node = 0xFFFF,

     DEFINE_CLASS_ID(Multi, Node, 0)

       DEFINE_CLASS_ID(SafePoint, Multi, 0)

         DEFINE_CLASS_ID(Call,      SafePoint, 0)

           DEFINE_CLASS_ID(CallJava,         Call, 0)

             DEFINE_CLASS_ID(CallStaticJava,   CallJava, 0)

             DEFINE_CLASS_ID(CallDynamicJava,  CallJava, 1)

           DEFINE_CLASS_ID(CallRuntime,      Call, 1)

             DEFINE_CLASS_ID(CallLeaf,         CallRuntime, 0)

           DEFINE_CLASS_ID(Allocate,         Call, 2)

             DEFINE_CLASS_ID(AllocateArray,    Allocate, 0)

           DEFINE_CLASS_ID(AbstractLock,     Call, 3)

             DEFINE_CLASS_ID(Lock,             AbstractLock, 0)

             DEFINE_CLASS_ID(Unlock,           AbstractLock, 1)

       DEFINE_CLASS_ID(MultiBranch, Multi, 1)

         DEFINE_CLASS_ID(PCTable,     MultiBranch, 0)

           DEFINE_CLASS_ID(Catch,       PCTable, 0)

           DEFINE_CLASS_ID(Jump,        PCTable, 1)

         DEFINE_CLASS_ID(If,          MultiBranch, 1)

           DEFINE_CLASS_ID(CountedLoopEnd, If, 0)

         DEFINE_CLASS_ID(NeverBranch, MultiBranch, 2)

       DEFINE_CLASS_ID(Start,       Multi, 2)

       DEFINE_CLASS_ID(MemBar,      Multi, 3)

         DEFINE_CLASS_ID(Initialize,    MemBar, 0)

     DEFINE_CLASS_ID(Mach,  Node, 1)

       DEFINE_CLASS_ID(MachReturn, Mach, 0)

         DEFINE_CLASS_ID(MachSafePoint, MachReturn, 0)

           DEFINE_CLASS_ID(MachCall, MachSafePoint, 0)

             DEFINE_CLASS_ID(MachCallJava,         MachCall, 0)

               DEFINE_CLASS_ID(MachCallStaticJava,   MachCallJava, 0)

               DEFINE_CLASS_ID(MachCallDynamicJava,  MachCallJava, 1)

             DEFINE_CLASS_ID(MachCallRuntime,      MachCall, 1)

               DEFINE_CLASS_ID(MachCallLeaf,         MachCallRuntime, 0)

       DEFINE_CLASS_ID(MachSpillCopy, Mach, 1)

       DEFINE_CLASS_ID(MachNullCheck, Mach, 2)

       DEFINE_CLASS_ID(MachIf,        Mach, 3)

       DEFINE_CLASS_ID(MachTemp,      Mach, 4)

     DEFINE_CLASS_ID(Proj,  Node, 2)

       DEFINE_CLASS_ID(CatchProj, Proj, 0)

       DEFINE_CLASS_ID(JumpProj,  Proj, 1)

       DEFINE_CLASS_ID(IfTrue,    Proj, 2)

       DEFINE_CLASS_ID(IfFalse,   Proj, 3)

       DEFINE_CLASS_ID(Parm,      Proj, 4)

     DEFINE_CLASS_ID(Region, Node, 3)

       DEFINE_CLASS_ID(Loop, Region, 0)

         DEFINE_CLASS_ID(Root,        Loop, 0)

         DEFINE_CLASS_ID(CountedLoop, Loop, 1)

     DEFINE_CLASS_ID(Sub,   Node, 4)

       DEFINE_CLASS_ID(Cmp,   Sub, 0)

         DEFINE_CLASS_ID(FastLock,   Cmp, 0)

         DEFINE_CLASS_ID(FastUnlock, Cmp, 1)

     DEFINE_CLASS_ID(Type,  Node, 5)

       DEFINE_CLASS_ID(Phi,   Type, 0)

       DEFINE_CLASS_ID(ConstraintCast, Type, 1)

       DEFINE_CLASS_ID(CheckCastPP, Type, 2)

       DEFINE_CLASS_ID(CMove, Type, 3)

     DEFINE_CLASS_ID(Mem,   Node, 6)

       DEFINE_CLASS_ID(Load,  Mem, 0)

       DEFINE_CLASS_ID(Store, Mem, 1)

       DEFINE_CLASS_ID(LoadStore, Mem, 2)

     DEFINE_CLASS_ID(MergeMem, Node, 7)

     DEFINE_CLASS_ID(Bool,     Node, 8)

     DEFINE_CLASS_ID(AddP,     Node, 9)

     DEFINE_CLASS_ID(BoxLock,  Node, 10)

     DEFINE_CLASS_ID(Add,      Node, 11)

     DEFINE_CLASS_ID(Mul,      Node, 12)

     _max_classes  = ClassMask_Mul

   };

   #undef DEFINE_CLASS_ID

   // Flags are sorted by usage frequency.

   enum NodeFlags {

     Flag_is_Copy             = 0x01, // should be first bit to avoid shift

     Flag_is_Call             = Flag_is_Copy << 1,

     Flag_rematerialize       = Flag_is_Call << 1,

     Flag_needs_anti_dependence_check = Flag_rematerialize << 1,

     Flag_is_macro            = Flag_needs_anti_dependence_check << 1,

     Flag_is_Con              = Flag_is_macro << 1,

     Flag_is_cisc_alternate   = Flag_is_Con << 1,

     Flag_is_Branch           = Flag_is_cisc_alternate << 1,

     Flag_is_block_start      = Flag_is_Branch << 1,

     Flag_is_Goto             = Flag_is_block_start << 1,

     Flag_is_dead_loop_safe   = Flag_is_Goto << 1,

     Flag_may_be_short_branch = Flag_is_dead_loop_safe << 1,

     Flag_is_safepoint_node   = Flag_may_be_short_branch << 1,

     Flag_is_pc_relative      = Flag_is_safepoint_node << 1,

     Flag_is_Vector           = Flag_is_pc_relative << 1,

     _max_flags = (Flag_is_Vector << 1) - 1 // allow flags combination

   };

 private:

   jushort _class_id;

   jushort _flags;

 protected:

   // These methods should be called from constructors only.

   void init_class_id(jushort c) {

     assert(c <= _max_classes, "invalid node class");

     _class_id = c; // cast out const

   }

   void init_flags(jushort fl) {

     assert(fl <= _max_flags, "invalid node flag");

     _flags |= fl;

   }

   void clear_flag(jushort fl) {

     assert(fl <= _max_flags, "invalid node flag");

     _flags &= ~fl;

   }

 public:

   const jushort class_id() const { return _class_id; }

   const jushort flags() const { return _flags; }

   // Return a dense integer opcode number

   virtual int Opcode() const;

   // Virtual inherited Node size

   virtual uint size_of() const;

   // Other interesting Node properties

   // Special case: is_Call() returns true for both CallNode and MachCallNode.

   bool is_Call() const {

     return (_flags & Flag_is_Call) != 0;

   }

   CallNode *as_Call() const { // Only for CallNode (not for MachCallNode)

     assert((_class_id & ClassMask_Call) == Class_Call, "invalid node class");

     return (CallNode*)this;

   }

   #define DEFINE_CLASS_QUERY(type) \

   bool is_##type() const { \

     return ((_class_id & ClassMask_##type) == Class_##type); \

   } \

   type##Node *as_##type() const { \

     assert(is_##type(), "invalid node class"); \

     return (type##Node*)this; \

   }

   DEFINE_CLASS_QUERY(AbstractLock)

   DEFINE_CLASS_QUERY(Add)

   DEFINE_CLASS_QUERY(AddP)

   DEFINE_CLASS_QUERY(Allocate)

   DEFINE_CLASS_QUERY(AllocateArray)

   DEFINE_CLASS_QUERY(Bool)

   DEFINE_CLASS_QUERY(BoxLock)

   DEFINE_CLASS_QUERY(CallDynamicJava)

   DEFINE_CLASS_QUERY(CallJava)

   DEFINE_CLASS_QUERY(CallLeaf)

   DEFINE_CLASS_QUERY(CallRuntime)

   DEFINE_CLASS_QUERY(CallStaticJava)

   DEFINE_CLASS_QUERY(Catch)

   DEFINE_CLASS_QUERY(CatchProj)

   DEFINE_CLASS_QUERY(CheckCastPP)

   DEFINE_CLASS_QUERY(ConstraintCast)

   DEFINE_CLASS_QUERY(CMove)

   DEFINE_CLASS_QUERY(Cmp)

   DEFINE_CLASS_QUERY(CountedLoop)

   DEFINE_CLASS_QUERY(CountedLoopEnd)

   DEFINE_CLASS_QUERY(FastLock)

   DEFINE_CLASS_QUERY(FastUnlock)

   DEFINE_CLASS_QUERY(If)

   DEFINE_CLASS_QUERY(IfFalse)

   DEFINE_CLASS_QUERY(IfTrue)

   DEFINE_CLASS_QUERY(Initialize)

   DEFINE_CLASS_QUERY(Jump)

   DEFINE_CLASS_QUERY(JumpProj)

   DEFINE_CLASS_QUERY(Load)

   DEFINE_CLASS_QUERY(LoadStore)

   DEFINE_CLASS_QUERY(Lock)

   DEFINE_CLASS_QUERY(Loop)

   DEFINE_CLASS_QUERY(Mach)

   DEFINE_CLASS_QUERY(MachCall)

   DEFINE_CLASS_QUERY(MachCallDynamicJava)

   DEFINE_CLASS_QUERY(MachCallJava)

   DEFINE_CLASS_QUERY(MachCallLeaf)

   DEFINE_CLASS_QUERY(MachCallRuntime)

   DEFINE_CLASS_QUERY(MachCallStaticJava)

   DEFINE_CLASS_QUERY(MachIf)

   DEFINE_CLASS_QUERY(MachNullCheck)

   DEFINE_CLASS_QUERY(MachReturn)

   DEFINE_CLASS_QUERY(MachSafePoint)

   DEFINE_CLASS_QUERY(MachSpillCopy)

   DEFINE_CLASS_QUERY(MachTemp)

   DEFINE_CLASS_QUERY(Mem)

   DEFINE_CLASS_QUERY(MemBar)

   DEFINE_CLASS_QUERY(MergeMem)

   DEFINE_CLASS_QUERY(Mul)

   DEFINE_CLASS_QUERY(Multi)

   DEFINE_CLASS_QUERY(MultiBranch)

   DEFINE_CLASS_QUERY(Parm)

   DEFINE_CLASS_QUERY(PCTable)

   DEFINE_CLASS_QUERY(Phi)

   DEFINE_CLASS_QUERY(Proj)

   DEFINE_CLASS_QUERY(Region)

   DEFINE_CLASS_QUERY(Root)

   DEFINE_CLASS_QUERY(SafePoint)

   DEFINE_CLASS_QUERY(Start)

   DEFINE_CLASS_QUERY(Store)

   DEFINE_CLASS_QUERY(Sub)

   DEFINE_CLASS_QUERY(Type)

   DEFINE_CLASS_QUERY(Unlock)

   #undef DEFINE_CLASS_QUERY

   // duplicate of is_MachSpillCopy()

   bool is_SpillCopy () const {

     return ((_class_id & ClassMask_MachSpillCopy) == Class_MachSpillCopy);

   }

   bool is_Con () const { return (_flags & Flag_is_Con) != 0; }

   bool is_Goto() const { return (_flags & Flag_is_Goto) != 0; }

   // The data node which is safe to leave in dead loop during IGVN optimization.

   bool is_dead_loop_safe() const {

     return is_Phi() || is_Proj() ||

            (_flags & (Flag_is_dead_loop_safe | Flag_is_Con)) != 0;

   }

   // is_Copy() returns copied edge index (0 or 1)

   uint is_Copy() const { return (_flags & Flag_is_Copy); }

   virtual bool is_CFG() const { return false; }

   // If this node is control-dependent on a test, can it be

   // rerouted to a dominating equivalent test?  This is usually

   // true of non-CFG nodes, but can be false for operations which

   // depend for their correct sequencing on more than one test.

   // (In that case, hoisting to a dominating test may silently

   // skip some other important test.)

   virtual bool depends_only_on_test() const { assert(!is_CFG(), ""); return true; };

   // defined for MachNodes that match 'If' | 'Goto' | 'CountedLoopEnd'

   bool is_Branch() const { return (_flags & Flag_is_Branch) != 0; }

   // When building basic blocks, I need to have a notion of block beginning

   // Nodes, next block selector Nodes (block enders), and next block

   // projections.  These calls need to work on their machine equivalents.  The

   // Ideal beginning Nodes are RootNode, RegionNode and StartNode.

   bool is_block_start() const {

     if ( is_Region() )

       return this == (const Node*)in(0);

     else

       return (_flags & Flag_is_block_start) != 0;

   }

   // The Ideal control projection Nodes are IfTrue/IfFalse, JumpProjNode, Root,

   // Goto and Return.  This call also returns the block ending Node.

   virtual const Node *is_block_proj() const;

   // The node is a "macro" node which needs to be expanded before matching

   bool is_macro() const { return (_flags & Flag_is_macro) != 0; }

   // Value is a vector of primitive values

   bool is_Vector() const { return (_flags & Flag_is_Vector) != 0; }

 //----------------- Optimization

   // Get the worst-case Type output for this Node.

   virtual const class Type *bottom_type() const;

   // If we find a better type for a node, try to record it permanently.

   // Return true if this node actually changed.

   // Be sure to do the hash_delete game in the "rehash" variant.

   void raise_bottom_type(const Type* new_type);

   // Get the address type with which this node uses and/or defs memory,

   // or NULL if none.  The address type is conservatively wide.

   // Returns non-null for calls, membars, loads, stores, etc.

   // Returns TypePtr::BOTTOM if the node touches memory "broadly".

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

   // Return an existing node which computes the same function as this node.

   // The optimistic combined algorithm requires this to return a Node which

   // is a small number of steps away (e.g., one of my inputs).

   virtual Node *Identity( PhaseTransform *phase );

   // Return the set of values this Node can take on at runtime.

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

   // Return a node which is more "ideal" than the current node.

   // The invariants on this call are subtle.  If in doubt, read the

   // treatise in node.cpp above the default implemention AND TEST WITH

   // +VerifyIterativeGVN!

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

   // Some nodes have specific Ideal subgraph transformations only if they are

   // unique users of specific nodes. Such nodes should be put on IGVN worklist

   // for the transformations to happen.

   bool has_special_unique_user() const;

 protected:

   bool remove_dead_region(PhaseGVN *phase, bool can_reshape);

 public:

   // Idealize graph, using DU info.  Done after constant propagation

   virtual Node *Ideal_DU_postCCP( PhaseCCP *ccp );

   // See if there is valid pipeline info

   static  const Pipeline *pipeline_class();

   virtual const Pipeline *pipeline() const;

   // Compute the latency from the def to this instruction of the ith input node

   uint latency(uint i);

   // Hash & compare functions, for pessimistic value numbering

   // If the hash function returns the special sentinel value NO_HASH,

   // the node is guaranteed never to compare equal to any other node.

   // If we accidently generate a hash with value NO_HASH the node

   // won't go into the table and we'll lose a little optimization.

   enum { NO_HASH = 0 };

   virtual uint hash() const;

   virtual uint cmp( const Node &n ) const;

   // Operation appears to be iteratively computed (such as an induction variable)

   // It is possible for this operation to return false for a loop-varying

   // value, if it appears (by local graph inspection) to be computed by a simple conditional.

   bool is_iteratively_computed();

   // Determine if a node is Counted loop induction variable.

   // The method is defined in loopnode.cpp.

   const Node* is_loop_iv() const;

   // Return a node with opcode "opc" and same inputs as "this" if one can

   // be found; Otherwise return NULL;

   Node* find_similar(int opc);

   // Return the unique control out if only one. Null if none or more than one.

   Node* unique_ctrl_out();

 //----------------- Code Generation

   // Ideal register class for Matching.  Zero means unmatched instruction

   // (these are cloned instead of converted to machine nodes).

   virtual uint ideal_reg() const;

   static const uint NotAMachineReg;   // must be > max. machine register

   // Do we Match on this edge index or not?  Generally false for Control

   // and true for everything else.  Weird for calls & returns.

   virtual uint match_edge(uint idx) const;

   // Register class output is returned in

   virtual const RegMask &out_RegMask() const;

   // Register class input is expected in

   virtual const RegMask &in_RegMask(uint) const;

   // Should we clone rather than spill this instruction?

   bool rematerialize() const;

   // Return JVM State Object if this Node carries debug info, or NULL otherwise

   virtual JVMState* jvms() const;

   // Print as assembly

   virtual void format( PhaseRegAlloc *, outputStream* st = tty ) const;

   // Emit bytes starting at parameter 'ptr'

   // Bump 'ptr' by the number of output bytes

   virtual void emit(CodeBuffer &cbuf, PhaseRegAlloc *ra_) const;

   // Size of instruction in bytes

   virtual uint size(PhaseRegAlloc *ra_) const;

   // Convenience function to extract an integer constant from a node.

   // If it is not an integer constant (either Con, CastII, or Mach),

   // return value_if_unknown.

   jint find_int_con(jint value_if_unknown) const {

     const TypeInt* t = find_int_type();

     return (t != NULL && t->is_con()) ? t->get_con() : value_if_unknown;

   }

   // Return the constant, knowing it is an integer constant already

   jint get_int() const {

     const TypeInt* t = find_int_type();

     guarantee(t != NULL, "must be con");

     return t->get_con();

   }

   // Here's where the work is done.  Can produce non-constant int types too.

   const TypeInt* find_int_type() const;

   // Same thing for long (and intptr_t, via type.hpp):

   jlong get_long() const {

     const TypeLong* t = find_long_type();

     guarantee(t != NULL, "must be con");

     return t->get_con();

   }

   jlong find_long_con(jint value_if_unknown) const {

     const TypeLong* t = find_long_type();

     return (t != NULL && t->is_con()) ? t->get_con() : value_if_unknown;

   }

   const TypeLong* find_long_type() const;

   // These guys are called by code generated by ADLC:

   intptr_t get_ptr() const;

   jdouble getd() const;

   jfloat getf() const;

   // Nodes which are pinned into basic blocks

   virtual bool pinned() const { return false; }

   // Nodes which use memory without consuming it, hence need antidependences

   // More specifically, needs_anti_dependence_check returns true iff the node

   // (a) does a load, and (b) does not perform a store (except perhaps to a

   // stack slot or some other unaliased location).

   bool needs_anti_dependence_check() const;

   // Return which operand this instruction may cisc-spill. In other words,

   // return operand position that can convert from reg to memory access

   virtual int cisc_operand() const { return AdlcVMDeps::Not_cisc_spillable; }

   bool is_cisc_alternate() const { return (_flags & Flag_is_cisc_alternate) != 0; }

 //----------------- Graph walking

 public:

   // Walk and apply member functions recursively.

   // Supplied (this) pointer is root.

   void walk(NFunc pre, NFunc post, void *env);

   static void nop(Node &, void*); // Dummy empty function

   static void packregion( Node &n, void* );

 private:

   void walk_(NFunc pre, NFunc post, void *env, VectorSet &visited);

 //----------------- Printing, etc

 public:

 #ifndef PRODUCT

   Node* find(int idx) const;         // Search the graph for the given idx.

   Node* find_ctrl(int idx) const;    // Search control ancestors for the given idx.

   void dump() const;                 // Print this node,

   void dump(int depth) const;        // Print this node, recursively to depth d

   void dump_ctrl(int depth) const;   // Print control nodes, to depth d

   virtual void dump_req() const;     // Print required-edge info

   virtual void dump_prec() const;    // Print precedence-edge info

   virtual void dump_out() const;     // Print the output edge info

   virtual void dump_spec(outputStream *st) const {}; // Print per-node info

   void verify_edges(Unique_Node_List &visited); // Verify bi-directional edges

   void verify() const;               // Check Def-Use info for my subgraph

   static void verify_recur(const Node *n, int verify_depth, VectorSet &old_space, VectorSet &new_space);

   // This call defines a class-unique string used to identify class instances

   virtual const char *Name() const;

   void dump_format(PhaseRegAlloc *ra) const; // debug access to MachNode::format(...)

   // RegMask Print Functions

   void dump_in_regmask(int idx) { in_RegMask(idx).dump(); }

   void dump_out_regmask() { out_RegMask().dump(); }

   static int _in_dump_cnt;

   static bool in_dump() { return _in_dump_cnt > 0; }

   void fast_dump() const {

     tty->print("%4d: %-17s", _idx, Name());

     for (uint i = 0; i < len(); i++)

       if (in(i))

         tty->print(" %4d", in(i)->_idx);

       else

         tty->print(" NULL");

     tty->print("\n");

   }

 #endif

 #ifdef ASSERT

   void verify_construction();

   bool verify_jvms(const JVMState* jvms) const;

   int  _debug_idx;                     // Unique value assigned to every node.

   int   debug_idx() const              { return _debug_idx; }

   void  set_debug_idx( int debug_idx ) { _debug_idx = debug_idx; }

   Node* _debug_orig;                   // Original version of this, if any.

   Node*  debug_orig() const            { return _debug_orig; }

   void   set_debug_orig(Node* orig);   // _debug_orig = orig

   int        _hash_lock;               // Barrier to modifications of nodes in the hash table

   void  enter_hash_lock() { ++_hash_lock; assert(_hash_lock < 99, "in too many hash tables?"); }

   void   exit_hash_lock() { --_hash_lock; assert(_hash_lock >= 0, "mispaired hash locks"); }

   static void init_NodeProperty();

   #if OPTO_DU_ITERATOR_ASSERT

   const Node* _last_del;               // The last deleted node.

   uint        _del_tick;               // Bumped when a deletion happens..

   #endif

 #endif

 };

 //-----------------------------------------------------------------------------

 // Iterators over DU info, and associated Node functions.

 #if OPTO_DU_ITERATOR_ASSERT

 // Common code for assertion checking on DU iterators.

 class DUIterator_Common VALUE_OBJ_CLASS_SPEC {

 #ifdef ASSERT

  protected:

   bool         _vdui;               // cached value of VerifyDUIterators

   const Node*  _node;               // the node containing the _out array

   uint         _outcnt;             // cached node->_outcnt

   uint         _del_tick;           // cached node->_del_tick

   Node*        _last;               // last value produced by the iterator

   void sample(const Node* node);    // used by c'tor to set up for verifies

   void verify(const Node* node, bool at_end_ok = false);

   void verify_resync();

   void reset(const DUIterator_Common& that);

 // The VDUI_ONLY macro protects code conditionalized on VerifyDUIterators

   #define I_VDUI_ONLY(i,x) { if ((i)._vdui) { x; } }

 #else

   #define I_VDUI_ONLY(i,x) { }

 #endif //ASSERT

 };

 #define VDUI_ONLY(x)     I_VDUI_ONLY(*this, x)

 // Default DU iterator.  Allows appends onto the out array.

 // Allows deletion from the out array only at the current point.

 // Usage:

 //  for (DUIterator i = x->outs(); x->has_out(i); i++) {

 //    Node* y = x->out(i);

 //    ...

 //  }

 // Compiles in product mode to a unsigned integer index, which indexes

 // onto a repeatedly reloaded base pointer of x->_out.  The loop predicate

 // also reloads x->_outcnt.  If you delete, you must perform "--i" just

 // before continuing the loop.  You must delete only the last-produced

 // edge.  You must delete only a single copy of the last-produced edge,

 // or else you must delete all copies at once (the first time the edge

 // is produced by the iterator).

 class DUIterator : public DUIterator_Common {

   friend class Node;

   // This is the index which provides the product-mode behavior.

   // Whatever the product-mode version of the system does to the

   // DUI index is done to this index.  All other fields in

   // this class are used only for assertion checking.

   uint         _idx;

   #ifdef ASSERT

   uint         _refresh_tick;    // Records the refresh activity.

   void sample(const Node* node); // Initialize _refresh_tick etc.

   void verify(const Node* node, bool at_end_ok = false);

   void verify_increment();       // Verify an increment operation.

   void verify_resync();          // Verify that we can back up over a deletion.

   void verify_finish();          // Verify that the loop terminated properly.

   void refresh();                // Resample verification info.

   void reset(const DUIterator& that);  // Resample after assignment.

   #endif

   DUIterator(const Node* node, int dummy_to_avoid_conversion)

     { _idx = 0;                         debug_only(sample(node)); }

  public:

   // initialize to garbage; clear _vdui to disable asserts

   DUIterator()

     { /*initialize to garbage*/         debug_only(_vdui = false); }

   void operator++(int dummy_to_specify_postfix_op)

     { _idx++;                           VDUI_ONLY(verify_increment()); }

   void operator--()

     { VDUI_ONLY(verify_resync());       --_idx; }

   ~DUIterator()

     { VDUI_ONLY(verify_finish()); }

   void operator=(const DUIterator& that)

     { _idx = that._idx;                 debug_only(reset(that)); }

 };

 DUIterator Node::outs() const

   { return DUIterator(this, 0); }

 DUIterator& Node::refresh_out_pos(DUIterator& i) const

   { I_VDUI_ONLY(i, i.refresh());        return i; }

 bool Node::has_out(DUIterator& i) const

   { I_VDUI_ONLY(i, i.verify(this,true));return i._idx < _outcnt; }

 Node*    Node::out(DUIterator& i) const

   { I_VDUI_ONLY(i, i.verify(this));     return debug_only(i._last=) _out[i._idx]; }

 // Faster DU iterator.  Disallows insertions into the out array.

 // Allows deletion from the out array only at the current point.

 // Usage:

 //  for (DUIterator_Fast imax, i = x->fast_outs(imax); i < imax; i++) {

 //    Node* y = x->fast_out(i);

 //    ...

 //  }

 // Compiles in product mode to raw Node** pointer arithmetic, with

 // no reloading of pointers from the original node x.  If you delete,

 // you must perform "--i; --imax" just before continuing the loop.

 // If you delete multiple copies of the same edge, you must decrement

 // imax, but not i, multiple times:  "--i, imax -= num_edges".

 class DUIterator_Fast : public DUIterator_Common {

   friend class Node;

   friend class DUIterator_Last;

   // This is the pointer which provides the product-mode behavior.

   // Whatever the product-mode version of the system does to the

   // DUI pointer is done to this pointer.  All other fields in

   // this class are used only for assertion checking.

   Node**       _outp;

   #ifdef ASSERT

   void verify(const Node* node, bool at_end_ok = false);

   void verify_limit();

   void verify_resync();

   void verify_relimit(uint n);

   void reset(const DUIterator_Fast& that);

   #endif

   // Note:  offset must be signed, since -1 is sometimes passed

   DUIterator_Fast(const Node* node, ptrdiff_t offset)

     { _outp = node->_out + offset;      debug_only(sample(node)); }

  public:

   // initialize to garbage; clear _vdui to disable asserts

   DUIterator_Fast()

     { /*initialize to garbage*/         debug_only(_vdui = false); }

   void operator++(int dummy_to_specify_postfix_op)

     { _outp++;                          VDUI_ONLY(verify(_node, true)); }

   void operator--()

     { VDUI_ONLY(verify_resync());       --_outp; }

   void operator-=(uint n)   // applied to the limit only

     { _outp -= n;           VDUI_ONLY(verify_relimit(n));  }

   bool operator<(DUIterator_Fast& limit) {

     I_VDUI_ONLY(*this, this->verify(_node, true));

     I_VDUI_ONLY(limit, limit.verify_limit());

     return _outp < limit._outp;

   }

   void operator=(const DUIterator_Fast& that)

     { _outp = that._outp;               debug_only(reset(that)); }

 };

 DUIterator_Fast Node::fast_outs(DUIterator_Fast& imax) const {

   // Assign a limit pointer to the reference argument:

   imax = DUIterator_Fast(this, (ptrdiff_t)_outcnt);

   // Return the base pointer:

   return DUIterator_Fast(this, 0);

 }

 Node* Node::fast_out(DUIterator_Fast& i) const {

   I_VDUI_ONLY(i, i.verify(this));

   return debug_only(i._last=) *i._outp;

 }

 // Faster DU iterator.  Requires each successive edge to be removed.

 // Does not allow insertion of any edges.

 // Usage:

 //  for (DUIterator_Last imin, i = x->last_outs(imin); i >= imin; i -= num_edges) {

 //    Node* y = x->last_out(i);

 //    ...

 //  }

 // Compiles in product mode to raw Node** pointer arithmetic, with

 // no reloading of pointers from the original node x.

 class DUIterator_Last : private DUIterator_Fast {

   friend class Node;

   #ifdef ASSERT

   void verify(const Node* node, bool at_end_ok = false);

   void verify_limit();

   void verify_step(uint num_edges);

   #endif

   // Note:  offset must be signed, since -1 is sometimes passed

   DUIterator_Last(const Node* node, ptrdiff_t offset)

     : DUIterator_Fast(node, offset) { }

   void operator++(int dummy_to_specify_postfix_op) {} // do not use

   void operator<(int)                              {} // do not use

  public:

   DUIterator_Last() { }

   // initialize to garbage

   void operator--()

     { _outp--;              VDUI_ONLY(verify_step(1));  }

   void operator-=(uint n)

     { _outp -= n;           VDUI_ONLY(verify_step(n));  }

   bool operator>=(DUIterator_Last& limit) {

     I_VDUI_ONLY(*this, this->verify(_node, true));

     I_VDUI_ONLY(limit, limit.verify_limit());

     return _outp >= limit._outp;

   }

   void operator=(const DUIterator_Last& that)

     { DUIterator_Fast::operator=(that); }

 };

 DUIterator_Last Node::last_outs(DUIterator_Last& imin) const {

   // Assign a limit pointer to the reference argument:

   imin = DUIterator_Last(this, 0);

   // Return the initial pointer:

   return DUIterator_Last(this, (ptrdiff_t)_outcnt - 1);

 }

 Node* Node::last_out(DUIterator_Last& i) const {

   I_VDUI_ONLY(i, i.verify(this));

   return debug_only(i._last=) *i._outp;

 }

 #endif //OPTO_DU_ITERATOR_ASSERT

 #undef I_VDUI_ONLY

 #undef VDUI_ONLY

 //-----------------------------------------------------------------------------

 // Map dense integer indices to Nodes.  Uses classic doubling-array trick.

 // Abstractly provides an infinite array of Node*'s, initialized to NULL.

 // Note that the constructor just zeros things, and since I use Arena

 // allocation I do not need a destructor to reclaim storage.

 class Node_Array : public ResourceObj {

 protected:

   Arena *_a;                    // Arena to allocate in

   uint   _max;

   Node **_nodes;

   void   grow( uint i );        // Grow array node to fit

 public:

   Node_Array(Arena *a) : _a(a), _max(OptoNodeListSize) {

     _nodes = NEW_ARENA_ARRAY( a, Node *, OptoNodeListSize );

     for( int i = 0; i < OptoNodeListSize; i++ ) {

       _nodes[i] = NULL;

     }

   }

   Node_Array(Node_Array *na) : _a(na->_a), _max(na->_max), _nodes(na->_nodes) {}

   Node *operator[] ( uint i ) const // Lookup, or NULL for not mapped

   { return (i<_max) ? _nodes[i] : (Node*)NULL; }

   Node *at( uint i ) const { assert(i<_max,"oob"); return _nodes[i]; }

   Node **adr() { return _nodes; }

   // Extend the mapping: index i maps to Node *n.

   void map( uint i, Node *n ) { if( i>=_max ) grow(i); _nodes[i] = n; }

   void insert( uint i, Node *n );

   void remove( uint i );        // Remove, preserving order

   void sort( C_sort_func_t func);

   void reset( Arena *new_a );   // Zap mapping to empty; reclaim storage

   void clear();                 // Set all entries to NULL, keep storage

   uint Size() const { return _max; }

   void dump() const;

 };

 class Node_List : public Node_Array {

   uint _cnt;

 public:

   Node_List() : Node_Array(Thread::current()->resource_area()), _cnt(0) {}

   Node_List(Arena *a) : Node_Array(a), _cnt(0) {}

   void insert( uint i, Node *n ) { Node_Array::insert(i,n); _cnt++; }

   void remove( uint i ) { Node_Array::remove(i); _cnt--; }

   void push( Node *b ) { map(_cnt++,b); }

   void yank( Node *n );         // Find and remove

   Node *pop() { return _nodes[--_cnt]; }

   Node *rpop() { Node *b = _nodes[0]; _nodes[0]=_nodes[--_cnt]; return b;}

   void clear() { _cnt = 0; Node_Array::clear(); } // retain storage

   uint size() const { return _cnt; }

   void dump() const;

 };

 //------------------------------Unique_Node_List-------------------------------

 class Unique_Node_List : public Node_List {

   VectorSet _in_worklist;

   uint _clock_index;            // Index in list where to pop from next

 public:

   Unique_Node_List() : Node_List(), _in_worklist(Thread::current()->resource_area()), _clock_index(0) {}

   Unique_Node_List(Arena *a) : Node_List(a), _in_worklist(a), _clock_index(0) {}

   void remove( Node *n );

   bool member( Node *n ) { return _in_worklist.test(n->_idx) != 0; }

   VectorSet &member_set(){ return _in_worklist; }

   void push( Node *b ) {

     if( !_in_worklist.test_set(b->_idx) )

       Node_List::push(b);

   }

   Node *pop() {

     if( _clock_index >= size() ) _clock_index = 0;

     Node *b = at(_clock_index);

     map( _clock_index++, Node_List::pop());

     _in_worklist >>= b->_idx;

     return b;

   }

   Node *remove( uint i ) {

     Node *b = Node_List::at(i);

     _in_worklist >>= b->_idx;

     map(i,Node_List::pop());

     return b;

   }

   void yank( Node *n ) { _in_worklist >>= n->_idx; Node_List::yank(n); }

   void  clear() {

     _in_worklist.Clear();        // Discards storage but grows automatically

     Node_List::clear();

     _clock_index = 0;

   }

   // Used after parsing to remove useless nodes before Iterative GVN

   void remove_useless_nodes(VectorSet &useful);

 #ifndef PRODUCT

   void print_set() const { _in_worklist.print(); }

 #endif

 };

 // Inline definition of Compile::record_for_igvn must be deferred to this point.

 inline void Compile::record_for_igvn(Node* n) {

   _for_igvn->push(n);

   record_for_escape_analysis(n);

 }

 //------------------------------Node_Stack-------------------------------------

 class Node_Stack {

 protected:

   struct INode {

     Node *node; // Processed node

     uint  indx; // Index of next node's child

   };

   INode *_inode_top; // tos, stack grows up

   INode *_inode_max; // End of _inodes == _inodes + _max

   INode *_inodes;    // Array storage for the stack

   Arena *_a;         // Arena to allocate in

   void grow();

 public:

   Node_Stack(int size) {

     size_t max = (size > OptoNodeListSize) ? size : OptoNodeListSize;

     _a = Thread::current()->resource_area();

     _inodes = NEW_ARENA_ARRAY( _a, INode, max );

     _inode_max = _inodes + max;

     _inode_top = _inodes - 1; // stack is empty

   }

   Node_Stack(Arena *a, int size) : _a(a) {

     size_t max = (size > OptoNodeListSize) ? size : OptoNodeListSize;

     _inodes = NEW_ARENA_ARRAY( _a, INode, max );

     _inode_max = _inodes + max;

     _inode_top = _inodes - 1; // stack is empty

   }

   void pop() {

     assert(_inode_top >= _inodes, "node stack underflow");

     --_inode_top;

   }

   void push(Node *n, uint i) {

     ++_inode_top;

     if (_inode_top >= _inode_max) grow();

     INode *top = _inode_top; // optimization

     top->node = n;

     top->indx = i;

   }

   Node *node() const {

     return _inode_top->node;

   }

   Node* node_at(uint i) const {

     assert(_inodes + i <= _inode_top, "in range");

     return _inodes[i].node;

   }

   uint index() const {

     return _inode_top->indx;

   }

   void set_node(Node *n) {

     _inode_top->node = n;

   }

   void set_index(uint i) {

     _inode_top->indx = i;

   }

   uint size_max() const { return (uint)pointer_delta(_inode_max, _inodes,  sizeof(INode)); } // Max size

   uint size() const { return (uint)pointer_delta((_inode_top+1), _inodes,  sizeof(INode)); } // Current size

   bool is_nonempty() const { return (_inode_top >= _inodes); }

   bool is_empty() const { return (_inode_top < _inodes); }

   void clear() { _inode_top = _inodes - 1; } // retain storage

 };

 //-----------------------------Node_Notes--------------------------------------

 // Debugging or profiling annotations loosely and sparsely associated

 // with some nodes.  See Compile::node_notes_at for the accessor.

 class Node_Notes VALUE_OBJ_CLASS_SPEC {

   JVMState* _jvms;

 public:

   Node_Notes(JVMState* jvms = NULL) {

     _jvms = jvms;

   }

   JVMState* jvms()            { return _jvms; }

   void  set_jvms(JVMState* x) {        _jvms = x; }

   // True if there is nothing here.

   bool is_clear() {

     return (_jvms == NULL);

   }

   // Make there be nothing here.

   void clear() {

     _jvms = NULL;

   }

   // Make a new, clean node notes.

   static Node_Notes* make(Compile* C) {

     Node_Notes* nn = NEW_ARENA_ARRAY(C->comp_arena(), Node_Notes, 1);

     nn->clear();

     return nn;

   }

   Node_Notes* clone(Compile* C) {

     Node_Notes* nn = NEW_ARENA_ARRAY(C->comp_arena(), Node_Notes, 1);

     (*nn) = (*this);

     return nn;

   }

   // Absorb any information from source.

   bool update_from(Node_Notes* source) {

     bool changed = false;

     if (source != NULL) {

       if (source->jvms() != NULL) {

         set_jvms(source->jvms());

         changed = true;

       }

     }

     return changed;

   }

 };

 // Inlined accessors for Compile::node_nodes that require the preceding class:

 inline Node_Notes*

 Compile::locate_node_notes(GrowableArray<Node_Notes*>* arr,

                            int idx, bool can_grow) {

   assert(idx >= 0, "oob");

   int block_idx = (idx >> _log2_node_notes_block_size);

   int grow_by = (block_idx - (arr == NULL? 0: arr->length()));

   if (grow_by >= 0) {

     if (!can_grow)  return NULL;

     grow_node_notes(arr, grow_by + 1);

   }

   // (Every element of arr is a sub-array of length _node_notes_block_size.)

   return arr->at(block_idx) + (idx & (_node_notes_block_size-1));

 }

 inline bool

 Compile::set_node_notes_at(int idx, Node_Notes* value) {

   if (value == NULL || value->is_clear())

     return false;  // nothing to write => write nothing

   Node_Notes* loc = locate_node_notes(_node_note_array, idx, true);

   assert(loc != NULL, "");

   return loc->update_from(value);

 }

 //------------------------------TypeNode---------------------------------------

 // Node with a Type constant.

 class TypeNode : public Node {

 protected:

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

   virtual uint cmp( const Node &n ) const;

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

   const Type* const _type;

 public:

   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; };

   TypeNode( const Type *t, uint required ) : Node(required), _type(t) {

     init_class_id(Class_Type);

   }

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

   virtual const Type *bottom_type() const;

   virtual       uint  ideal_reg() const;

 #ifndef PRODUCT

   virtual void dump_spec(outputStream *st) const;

 #endif

 };