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 //

 // Adaptation for C2 of the escape analysis algorithm described in:

 //

 // [Choi99] Jong-Deok Shoi, Manish Gupta, Mauricio Seffano,

 //          Vugranam C. Sreedhar, Sam Midkiff,

 //          "Escape Analysis for Java", Procedings of ACM SIGPLAN

 //          OOPSLA  Conference, November 1, 1999

 //

 // The flow-insensitive analysis described in the paper has been implemented.

 //

 // The analysis requires construction of a "connection graph" (CG) for

 // the method being analyzed.  The nodes of the connection graph are:

 //

 //     -  Java objects (JO)

 //     -  Local variables (LV)

 //     -  Fields of an object (OF),  these also include array elements

 //

 // The CG contains 3 types of edges:

 //

 //   -  PointsTo  (-P>)    {LV, OF} to JO

 //   -  Deferred  (-D>)    from {LV, OF} to {LV, OF}

 //   -  Field     (-F>)    from JO to OF

 //

 // The following  utility functions is used by the algorithm:

 //

 //   PointsTo(n) - n is any CG node, it returns the set of JO that n could

 //                 point to.

 //

 // The algorithm describes how to construct the connection graph

 // in the following 4 cases:

 //

 //          Case                  Edges Created

 //

 // (1)   p   = new T()              LV -P> JO

 // (2)   p   = q                    LV -D> LV

 // (3)   p.f = q                    JO -F> OF,  OF -D> LV

 // (4)   p   = q.f                  JO -F> OF,  LV -D> OF

 //

 // In all these cases, p and q are local variables.  For static field

 // references, we can construct a local variable containing a reference

 // to the static memory.

 //

 // C2 does not have local variables.  However for the purposes of constructing

 // the connection graph, the following IR nodes are treated as local variables:

 //     Phi    (pointer values)

 //     LoadP

 //     Proj#5 (value returned from callnodes including allocations)

 //     CheckCastPP, CastPP

 //

 // The LoadP, Proj and CheckCastPP behave like variables assigned to only once.

 // Only a Phi can have multiple assignments.  Each input to a Phi is treated

 // as an assignment to it.

 //

 // The following node types are JavaObject:

 //

 //     top()

 //     Allocate

 //     AllocateArray

 //     Parm  (for incoming arguments)

 //     CastX2P ("unsafe" operations)

 //     CreateEx

 //     ConP

 //     LoadKlass

 //     ThreadLocal

 //

 // AddP nodes are fields.

 //

 // After building the graph, a pass is made over the nodes, deleting deferred

 // nodes and copying the edges from the target of the deferred edge to the

 // source.  This results in a graph with no deferred edges, only:

 //

 //    LV -P> JO

 //    OF -P> JO (the object whose oop is stored in the field)

 //    JO -F> OF

 //

 // Then, for each node which is GlobalEscape, anything it could point to

 // is marked GlobalEscape.  Finally, for any node marked ArgEscape, anything

 // it could point to is marked ArgEscape.

 //

 class  Compile;

 class  Node;

 class  CallNode;

 class  PhiNode;

 class  PhaseTransform;

 class  Type;

 class  TypePtr;

 class  VectorSet;

 class PointsToNode {

 friend class ConnectionGraph;

 public:

   typedef enum {

     UnknownType = 0,

     JavaObject  = 1,

     LocalVar    = 2,

     Field       = 3

   } NodeType;

   typedef enum {

     UnknownEscape = 0,

     NoEscape      = 1, // A scalar replaceable object with unique type.

     ArgEscape     = 2, // An object passed as argument or referenced by

                        // argument (and not globally escape during call).

     GlobalEscape  = 3  // An object escapes the method and thread.

   } EscapeState;

   typedef enum {

     UnknownEdge   = 0,

     PointsToEdge  = 1,

     DeferredEdge  = 2,

     FieldEdge     = 3

   } EdgeType;

 private:

   enum {

     EdgeMask = 3,

     EdgeShift = 2,

     INITIAL_EDGE_COUNT = 4

   };

   NodeType             _type;

   EscapeState          _escape;

   GrowableArray<uint>* _edges;   // outgoing edges

 public:

   Node* _node;              // Ideal node corresponding to this PointsTo node.

   int   _offset;            // Object fields offsets.

   bool  _scalar_replaceable;// Not escaped object could be replaced with scalar

   bool  _hidden_alias;      // This node is an argument to a function.

                             // which may return it creating a hidden alias.

   PointsToNode():

     _type(UnknownType),

     _escape(UnknownEscape),

     _edges(NULL),

     _node(NULL),

     _offset(-1),

     _scalar_replaceable(true),

     _hidden_alias(false) {}

   EscapeState escape_state() const { return _escape; }

   NodeType node_type() const { return _type;}

   int offset() { return _offset;}

   void set_offset(int offs) { _offset = offs;}

   void set_escape_state(EscapeState state) { _escape = state; }

   void set_node_type(NodeType ntype) {

     assert(_type == UnknownType || _type == ntype, "Can't change node type");

     _type = ntype;

   }

   // count of outgoing edges

   uint edge_count() const { return (_edges == NULL) ? 0 : _edges->length(); }

   // node index of target of outgoing edge "e"

   uint edge_target(uint e) const {

     assert(_edges != NULL, "valid edge index");

     return (_edges->at(e) >> EdgeShift);

   }

   // type of outgoing edge "e"

   EdgeType edge_type(uint e) const {

     assert(_edges != NULL, "valid edge index");

     return (EdgeType) (_edges->at(e) & EdgeMask);

   }

   // add a edge of the specified type pointing to the specified target

   void add_edge(uint targIdx, EdgeType et);

   // remove an edge of the specified type pointing to the specified target

   void remove_edge(uint targIdx, EdgeType et);

 #ifndef PRODUCT

   void dump(bool print_state=true) const;

 #endif

 };

 class ConnectionGraph: public ResourceObj {

 private:

   GrowableArray<PointsToNode>  _nodes; // Connection graph nodes indexed

                                        // by ideal node index.

   Unique_Node_List  _delayed_worklist; // Nodes to be processed before

                                        // the call build_connection_graph().

   GrowableArray<MergeMemNode *>  _mergemem_worklist; // List of all MergeMem nodes

   VectorSet                _processed; // Records which nodes have been

                                        // processed.

   bool                    _collecting; // Indicates whether escape information

                                        // is still being collected. If false,

                                        // no new nodes will be processed.

   uint                _phantom_object; // Index of globally escaping object

                                        // that pointer values loaded from

                                        // a field which has not been set

                                        // are assumed to point to.

   uint                      _oop_null; // ConP(#NULL)

   uint                     _noop_null; // ConN(#NULL)

   Compile *                  _compile; // Compile object for current compilation

   PhaseIterGVN *                _igvn; // Value numbering

   // Address of an element in _nodes.  Used when the element is to be modified

   PointsToNode *ptnode_adr(uint idx) const {

     // There should be no new ideal nodes during ConnectionGraph build,

     // growableArray::adr_at() will throw assert otherwise.

     return _nodes.adr_at(idx);

   }

   uint nodes_size() const { return _nodes.length(); }

   // Add node to ConnectionGraph.

   void add_node(Node *n, PointsToNode::NodeType nt, PointsToNode::EscapeState es, bool done);

   // offset of a field reference

   int address_offset(Node* adr, PhaseTransform *phase);

   // compute the escape state for arguments to a call

   void process_call_arguments(CallNode *call, PhaseTransform *phase);

   // compute the escape state for the return value of a call

   void process_call_result(ProjNode *resproj, PhaseTransform *phase);

   // Populate Connection Graph with Ideal nodes.

   void record_for_escape_analysis(Node *n, PhaseTransform *phase);

   // Build Connection Graph and set nodes escape state.

   void build_connection_graph(Node *n, PhaseTransform *phase);

   // walk the connection graph starting at the node corresponding to "n" and

   // add the index of everything it could point to, to "ptset".  This may cause

   // Phi's encountered to get (re)processed  (which requires "phase".)

   void PointsTo(VectorSet &ptset, Node * n);

   //  Edge manipulation.  The "from_i" and "to_i" arguments are the

   //  node indices of the source and destination of the edge

   void add_pointsto_edge(uint from_i, uint to_i);

   void add_deferred_edge(uint from_i, uint to_i);

   void add_field_edge(uint from_i, uint to_i, int offs);

   // Add an edge to node given by "to_i" from any field of adr_i whose offset

   // matches "offset"  A deferred edge is added if to_i is a LocalVar, and

   // a pointsto edge is added if it is a JavaObject

   void add_edge_from_fields(uint adr, uint to_i, int offs);

   // Add a deferred  edge from node given by "from_i" to any field

   // of adr_i whose offset matches "offset"

   void add_deferred_edge_to_fields(uint from_i, uint adr, int offs);

   // Remove outgoing deferred edges from the node referenced by "ni".

   // Any outgoing edges from the target of the deferred edge are copied

   // to "ni".

   void remove_deferred(uint ni, GrowableArray<uint>* deferred_edges, VectorSet* visited);

   Node_Array _node_map; // used for bookeeping during type splitting

                         // Used for the following purposes:

                         // Memory Phi    - most recent unique Phi split out

                         //                 from this Phi

                         // MemNode       - new memory input for this node

                         // ChecCastPP    - allocation that this is a cast of

                         // allocation    - CheckCastPP of the allocation

   bool split_AddP(Node *addp, Node *base,  PhaseGVN  *igvn);

   PhiNode *create_split_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *>  &orig_phi_worklist, PhaseGVN  *igvn, bool &new_created);

   PhiNode *split_memory_phi(PhiNode *orig_phi, int alias_idx, GrowableArray<PhiNode *>  &orig_phi_worklist, PhaseGVN  *igvn);

   void  move_inst_mem(Node* n, GrowableArray<PhiNode *>  &orig_phis, PhaseGVN *igvn);

   Node *find_inst_mem(Node *mem, int alias_idx,GrowableArray<PhiNode *>  &orig_phi_worklist,  PhaseGVN  *igvn);

   // Propagate unique types created for unescaped allocated objects

   // through the graph

   void split_unique_types(GrowableArray<Node *>  &alloc_worklist);

   // manage entries in _node_map

   void  set_map(int idx, Node *n)        { _node_map.map(idx, n); }

   Node *get_map(int idx)                 { return _node_map[idx]; }

   PhiNode *get_map_phi(int idx) {

     Node *phi = _node_map[idx];

     return (phi == NULL) ? NULL : phi->as_Phi();

   }

   // Notify optimizer that a node has been modified

   // Node:  This assumes that escape analysis is run before

   //        PhaseIterGVN creation

   void record_for_optimizer(Node *n) {

     _igvn->_worklist.push(n);

   }

   // Set the escape state of a node

   void set_escape_state(uint ni, PointsToNode::EscapeState es);

   // Search for objects which are not scalar replaceable.

   void verify_escape_state(int nidx, VectorSet& ptset, PhaseTransform* phase);

 public:

   ConnectionGraph(Compile *C, PhaseIterGVN *igvn);

   // Check for non-escaping candidates

   static bool has_candidates(Compile *C);

   // Perform escape analysis

   static void do_analysis(Compile *C, PhaseIterGVN *igvn);

   // Compute the escape information

   bool compute_escape();

   // escape state of a node

   PointsToNode::EscapeState escape_state(Node *n);

   // other information we have collected

   bool is_scalar_replaceable(Node *n) {

     if (_collecting || (n->_idx >= nodes_size()))

       return false;

     PointsToNode* ptn = ptnode_adr(n->_idx);

     return ptn->escape_state() == PointsToNode::NoEscape && ptn->_scalar_replaceable;

   }

   bool hidden_alias(Node *n) {

     if (_collecting || (n->_idx >= nodes_size()))

       return true;

     PointsToNode* ptn = ptnode_adr(n->_idx);

     return (ptn->escape_state() != PointsToNode::NoEscape) || ptn->_hidden_alias;

   }

 #ifndef PRODUCT

   void dump();

 #endif

 };