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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.

  bool                    _progress;   // Indicates whether new Graph's edges

                                       // were created.

  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 of the specified type pointing to the specified target.

  // Set _progress if new edge is added.

  void add_edge(PointsToNode *f, uint to_i, PointsToNode::EdgeType et) {

    uint e_cnt = f->edge_count();

    f->add_edge(to_i, et);

    _progress |= (f->edge_count() != e_cnt);

  }

  // 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

};