gcc/analyzer/exploded-graph.h

/* Classes for managing a directed graph of <point, state> pairs.
   Copyright (C) 2019-2020 Free Software Foundation, Inc.
   Contributed by David Malcolm <dmalcolm@redhat.com>.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC 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 for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#ifndef GCC_ANALYZER_EXPLODED_GRAPH_H
#define GCC_ANALYZER_EXPLODED_GRAPH_H

namespace ana {

/* Concrete implementation of region_model_context, wiring it up to the
   rest of the analysis engine.  */

class impl_region_model_context : public region_model_context
{
 public:
  impl_region_model_context (exploded_graph &eg,
			     const exploded_node *enode_for_diag,

			     /* TODO: should we be getting the ECs from the
				old state, rather than the new?  */
			     const program_state *old_state,
			     program_state *new_state,
			     state_change *change,

			     const gimple *stmt,
			     stmt_finder *stmt_finder = NULL);

  impl_region_model_context (program_state *state,
			     state_change *change,
			     const extrinsic_state &ext_state,
			     logger *logger = NULL);

  void warn (pending_diagnostic *d) FINAL OVERRIDE;

  void remap_svalue_ids (const svalue_id_map &map) FINAL OVERRIDE;

  int on_svalue_purge (svalue_id first_unused_sid,
		       const svalue_id_map &map) FINAL OVERRIDE;

  logger *get_logger () FINAL OVERRIDE
  {
    return m_logger.get_logger ();
  }

  void on_state_leak (const state_machine &sm,
		      int sm_idx,
		      svalue_id sid,
		      svalue_id first_unused_sid,
		      const svalue_id_map &map,
		      state_machine::state_t state);

  void on_inherited_svalue (svalue_id parent_sid,
			    svalue_id child_sid) FINAL OVERRIDE;

  void on_cast (svalue_id src_sid,
		svalue_id dst_sid) FINAL OVERRIDE;

  void on_condition (tree lhs, enum tree_code op, tree rhs) FINAL OVERRIDE;

  void on_unknown_change (svalue_id sid ATTRIBUTE_UNUSED) FINAL OVERRIDE;

  void on_phi (const gphi *phi, tree rhs) FINAL OVERRIDE;

  void on_unexpected_tree_code (tree t,
				const dump_location_t &loc) FINAL OVERRIDE;

  exploded_graph *m_eg;
  log_user m_logger;
  const exploded_node *m_enode_for_diag;
  const program_state *m_old_state;
  program_state *m_new_state;
  state_change *m_change;
  const gimple *m_stmt;
  stmt_finder *m_stmt_finder;
  const extrinsic_state &m_ext_state;
};

/* A <program_point, program_state> pair, used internally by
   exploded_node as its immutable data, and as a key for identifying
   exploded_nodes we've already seen in the graph.  */

class point_and_state
{
public:
  point_and_state (const program_point &point,
		   const program_state &state)
  : m_point (point),
    m_state (state),
    m_hash (m_point.hash () ^ m_state.hash ())
  {
    /* We shouldn't be building point_and_states and thus exploded_nodes
       for states that aren't valid.  */
    gcc_assert (state.m_valid);
  }

  hashval_t hash () const
  {
    return m_hash;
  }
  bool operator== (const point_and_state &other) const
  {
    return m_point == other.m_point && m_state == other.m_state;
  }

  const program_point &get_point () const { return m_point; }
  const program_state &get_state () const { return m_state; }

  void set_state (const program_state &state)
  {
    m_state = state;
    m_hash = m_point.hash () ^ m_state.hash ();
  }

  void validate (const extrinsic_state &ext_state) const;

private:
  program_point m_point;
  program_state m_state;
  hashval_t m_hash;
};

/* A traits class for exploded graphs and their nodes and edges.  */

struct eg_traits
{
  typedef exploded_node node_t;
  typedef exploded_edge edge_t;
  typedef exploded_graph graph_t;
  struct dump_args_t
  {
    dump_args_t (const exploded_graph &eg) : m_eg (eg) {}
    const exploded_graph &m_eg;
  };
  typedef exploded_cluster cluster_t;
};

/* An exploded_node is a unique, immutable <point, state> pair within the
   exploded_graph.
   Each exploded_node has a unique index within the graph
   (for ease of debugging).  */

class exploded_node : public dnode<eg_traits>
{
 public:
  /* Has this enode had exploded_graph::process_node called on it?
     This allows us to distinguish enodes that were merged during
     worklist-handling, and thus never had process_node called on them
     (in favor of processing the merged node).  */
  enum status
  {
    /* Node is in the worklist.  */
    STATUS_WORKLIST,

    /* Node has had exploded_graph::process_node called on it.  */
    STATUS_PROCESSED,

    /* Node was left unprocessed due to merger; it won't have had
       exploded_graph::process_node called on it.  */
    STATUS_MERGER
  };

  exploded_node (const point_and_state &ps, int index);

  hashval_t hash () const { return m_ps.hash (); }

  const char * get_dot_fillcolor () const;
  void dump_dot (graphviz_out *gv, const dump_args_t &args)
    const FINAL OVERRIDE;
  void dump_dot_id (pretty_printer *pp) const;

  void dump_to_pp (pretty_printer *pp, const extrinsic_state &ext_state) const;
  void dump (FILE *fp, const extrinsic_state &ext_state) const;
  void dump (const extrinsic_state &ext_state) const;

  /* The result of on_stmt.  */
  struct on_stmt_flags
  {
    on_stmt_flags (bool sm_changes)
    : m_sm_changes (sm_changes),
      m_terminate_path (false)
    {}

    static on_stmt_flags terminate_path ()
    {
      return on_stmt_flags (true, true);
    }

    static on_stmt_flags state_change (bool any_sm_changes)
    {
      return on_stmt_flags (any_sm_changes, false);
    }

    /* Did any sm-changes occur handling the stmt.  */
    bool m_sm_changes : 1;

    /* Should we stop analyzing this path (on_stmt may have already
       added nodes/edges, e.g. when handling longjmp).  */
    bool m_terminate_path : 1;

  private:
    on_stmt_flags (bool sm_changes,
		   bool terminate_path)
    : m_sm_changes (sm_changes),
      m_terminate_path (terminate_path)
    {}
  };

  on_stmt_flags on_stmt (exploded_graph &eg,
			 const supernode *snode,
			 const gimple *stmt,
			 program_state *state,
			 state_change *change) const;
  bool on_edge (exploded_graph &eg,
		const superedge *succ,
		program_point *next_point,
		program_state *next_state,
		state_change *change) const;
  void on_longjmp (exploded_graph &eg,
		   const gcall *call,
		   program_state *new_state,
		   region_model_context *ctxt) const;

  void detect_leaks (exploded_graph &eg) const;

  const program_point &get_point () const { return m_ps.get_point (); }
  const supernode *get_supernode () const
  {
    return get_point ().get_supernode ();
  }
  function *get_function () const
  {
    return get_point ().get_function ();
  }
  int get_stack_depth () const
  {
    return get_point ().get_stack_depth ();
  }
  const gimple *get_stmt () const { return get_point ().get_stmt (); }

  const program_state &get_state () const { return m_ps.get_state (); }

  const point_and_state *get_ps_key () const { return &m_ps; }
  const program_point *get_point_key () const { return &m_ps.get_point (); }

  void dump_succs_and_preds (FILE *outf) const;

  enum status get_status () const { return m_status; }
  void set_status (enum status status)
  {
    gcc_assert (m_status == STATUS_WORKLIST);
    m_status = status;
  }

private:
  DISABLE_COPY_AND_ASSIGN (exploded_node);

  /* The <program_point, program_state> pair.  This is const, as it
     is immutable once the exploded_node has been created.  */
  const point_and_state m_ps;

  enum status m_status;

public:
  /* The index of this exploded_node.  */
  const int m_index;
};

/* An edge within the exploded graph.
   Some exploded_edges have an underlying superedge; others don't.  */

class exploded_edge : public dedge<eg_traits>
{
 public:
  /* Abstract base class for associating custom data with an
     exploded_edge, for handling non-standard edges such as
     rewinding from a longjmp, signal handlers, etc.  */
  class custom_info_t
  {
  public:
    virtual ~custom_info_t () {}

    /* Hook for making .dot label more readable .  */
    virtual void print (pretty_printer *pp) = 0;

    /* Hook for updating MODEL within exploded_path::feasible_p.  */
    virtual void update_model (region_model *model,
			       const exploded_edge &eedge) = 0;

    virtual void add_events_to_path (checker_path *emission_path,
				     const exploded_edge &eedge) = 0;
  };

  exploded_edge (exploded_node *src, exploded_node *dest,
		 const extrinsic_state &ext_state,
		 const superedge *sedge,
		 const state_change &change,
		 custom_info_t *custom_info);
  ~exploded_edge ();
  void dump_dot (graphviz_out *gv, const dump_args_t &args)
    const FINAL OVERRIDE;

  //private:
  const superedge *const m_sedge;

  const state_change m_change;

  /* NULL for most edges; will be non-NULL for special cases
     such as an unwind from a longjmp to a setjmp, or when
     a signal is delivered to a signal-handler.

     Owned by this class.  */
  custom_info_t *m_custom_info;

private:
  DISABLE_COPY_AND_ASSIGN (exploded_edge);
};

/* Extra data for an exploded_edge that represents a rewind from a
   longjmp to a setjmp (or from a siglongjmp to a sigsetjmp).  */

class rewind_info_t : public exploded_edge::custom_info_t
{
public:
  rewind_info_t (const setjmp_record &setjmp_record,
		 const gcall *longjmp_call)
  : m_setjmp_record (setjmp_record),
    m_longjmp_call (longjmp_call)
  {}

  void print (pretty_printer *pp) FINAL OVERRIDE
  {
    pp_string (pp, "rewind");
  }

  void update_model (region_model *model,
		     const exploded_edge &eedge) FINAL OVERRIDE;

  void add_events_to_path (checker_path *emission_path,
			   const exploded_edge &eedge) FINAL OVERRIDE;

  const program_point &get_setjmp_point () const
  {
    const program_point &origin_point = get_enode_origin ()->get_point ();

    /* "origin_point" ought to be before the call to "setjmp".  */
    gcc_assert (origin_point.get_kind () == PK_BEFORE_STMT);

    /* TODO: assert that it's the final stmt in its supernode.  */

    return origin_point;
  }

  const gcall *get_setjmp_call () const
  {
    return m_setjmp_record.m_setjmp_call;
  }

  const gcall *get_longjmp_call () const
  {
    return m_longjmp_call;
  }

  const exploded_node *get_enode_origin () const
  {
    return m_setjmp_record.m_enode;
  }

private:
  setjmp_record m_setjmp_record;
  const gcall *m_longjmp_call;
};

/* Statistics about aspects of an exploded_graph.  */

struct stats
{
  stats (int num_supernodes);
  void log (logger *logger) const;
  void dump (FILE *out) const;

  int get_total_enodes () const;

  int m_num_nodes[NUM_POINT_KINDS];
  int m_node_reuse_count;
  int m_node_reuse_after_merge_count;
  int m_num_supernodes;
};

/* Traits class for ensuring uniqueness of point_and_state data within
   an exploded_graph.  */

struct eg_hash_map_traits
{
  typedef const point_and_state *key_type;
  typedef exploded_node *value_type;
  typedef exploded_node *compare_type;

  static inline hashval_t hash (const key_type &k)
  {
    gcc_assert (k != NULL);
    gcc_assert (k != reinterpret_cast<key_type> (1));
    return k->hash ();
  }
  static inline bool equal_keys (const key_type &k1, const key_type &k2)
  {
    gcc_assert (k1 != NULL);
    gcc_assert (k2 != NULL);
    gcc_assert (k1 != reinterpret_cast<key_type> (1));
    gcc_assert (k2 != reinterpret_cast<key_type> (1));
    if (k1 && k2)
      return *k1 == *k2;
    else
      /* Otherwise they must both be non-NULL.  */
      return k1 == k2;
  }
  template <typename T>
  static inline void remove (T &)
  {
    /* empty; the nodes are handled elsewhere.  */
  }
  template <typename T>
  static inline void mark_deleted (T &entry)
  {
    entry.m_key = reinterpret_cast<key_type> (1);
  }
  template <typename T>
  static inline void mark_empty (T &entry)
  {
    entry.m_key = NULL;
  }
  template <typename T>
  static inline bool is_deleted (const T &entry)
  {
    return entry.m_key == reinterpret_cast<key_type> (1);
  }
  template <typename T>
  static inline bool is_empty (const T &entry)
  {
    return entry.m_key == NULL;
  }
  static const bool empty_zero_p = false;
};

/* Per-program_point data for an exploded_graph.  */

struct per_program_point_data
{
  per_program_point_data (const program_point &key)
  : m_key (key), m_excess_enodes (0)
  {}

  const program_point m_key;
  auto_vec<exploded_node *> m_enodes;
  /* The number of attempts to create an enode for this point
     after exceeding --param=analyzer-max-enodes-per-program-point.  */
  int m_excess_enodes;
};

/* Traits class for storing per-program_point data within
   an exploded_graph.  */

struct eg_point_hash_map_traits
{
  typedef const program_point *key_type;
  typedef per_program_point_data *value_type;
  typedef per_program_point_data *compare_type;

  static inline hashval_t hash (const key_type &k)
  {
    gcc_assert (k != NULL);
    gcc_assert (k != reinterpret_cast<key_type> (1));
    return k->hash ();
  }
  static inline bool equal_keys (const key_type &k1, const key_type &k2)
  {
    gcc_assert (k1 != NULL);
    gcc_assert (k2 != NULL);
    gcc_assert (k1 != reinterpret_cast<key_type> (1));
    gcc_assert (k2 != reinterpret_cast<key_type> (1));
    if (k1 && k2)
      return *k1 == *k2;
    else
      /* Otherwise they must both be non-NULL.  */
      return k1 == k2;
  }
  template <typename T>
  static inline void remove (T &)
  {
    /* empty; the nodes are handled elsewhere.  */
  }
  template <typename T>
  static inline void mark_deleted (T &entry)
  {
    entry.m_key = reinterpret_cast<key_type> (1);
  }
  template <typename T>
  static inline void mark_empty (T &entry)
  {
    entry.m_key = NULL;
  }
  template <typename T>
  static inline bool is_deleted (const T &entry)
  {
    return entry.m_key == reinterpret_cast<key_type> (1);
  }
  template <typename T>
  static inline bool is_empty (const T &entry)
  {
    return entry.m_key == NULL;
  }
  static const bool empty_zero_p = false;
};

/* Data about a particular call_string within an exploded_graph.  */

struct per_call_string_data
{
  per_call_string_data (const call_string &key, int num_supernodes)
  : m_key (key), m_stats (num_supernodes)
  {}

  const call_string m_key;
  stats m_stats;
};

/* Traits class for storing per-call_string data within
   an exploded_graph.  */

struct eg_call_string_hash_map_traits
{
  typedef const call_string *key_type;
  typedef per_call_string_data *value_type;
  typedef per_call_string_data *compare_type;

  static inline hashval_t hash (const key_type &k)
  {
    gcc_assert (k != NULL);
    gcc_assert (k != reinterpret_cast<key_type> (1));
    return k->hash ();
  }
  static inline bool equal_keys (const key_type &k1, const key_type &k2)
  {
    gcc_assert (k1 != NULL);
    gcc_assert (k2 != NULL);
    gcc_assert (k1 != reinterpret_cast<key_type> (1));
    gcc_assert (k2 != reinterpret_cast<key_type> (1));
    if (k1 && k2)
      return *k1 == *k2;
    else
      /* Otherwise they must both be non-NULL.  */
      return k1 == k2;
  }
  template <typename T>
  static inline void remove (T &)
  {
    /* empty; the nodes are handled elsewhere.  */
  }
  template <typename T>
  static inline void mark_deleted (T &entry)
  {
    entry.m_key = reinterpret_cast<key_type> (1);
  }
  template <typename T>
  static inline void mark_empty (T &entry)
  {
    entry.m_key = NULL;
  }
  template <typename T>
  static inline bool is_deleted (const T &entry)
  {
    return entry.m_key == reinterpret_cast<key_type> (1);
  }
  template <typename T>
  static inline bool is_empty (const T &entry)
  {
    return entry.m_key == NULL;
  }
  static const bool empty_zero_p = false;
};

/* Data about a particular function within an exploded_graph.  */

struct per_function_data
{
  per_function_data () {}

  void add_call_summary (exploded_node *node)
  {
    m_summaries.safe_push (node);
  }

  auto_vec<exploded_node *> m_summaries;
};


/* The strongly connected components of a supergraph.
   In particular, this allows us to compute a partial ordering
   of supernodes.  */

class strongly_connected_components
{
public:
  strongly_connected_components (const supergraph &sg, logger *logger);

  int get_scc_id (int node_index) const
  {
    return m_per_node[node_index].m_lowlink;
  }

  void dump () const;

private:
  struct per_node_data
  {
    per_node_data ()
      : m_index (-1), m_lowlink (-1), m_on_stack (false)
    {}

    int m_index;
    int m_lowlink;
    bool m_on_stack;
  };

  void strong_connect (unsigned index);

  const supergraph &m_sg;
  auto_vec<unsigned> m_stack;
  auto_vec<per_node_data> m_per_node;
};

/* The worklist of exploded_node instances that have been added to
   an exploded_graph, but that haven't yet been processed to find
   their successors (or warnings).

   The enodes are stored in a priority queue, ordered by a topological
   sort of the SCCs in the supergraph, so that enodes for the same
   program_point should appear at the front of the queue together.
   This allows for state-merging at CFG join-points, so that
   sufficiently-similar enodes can be merged into one.  */

class worklist
{
public:
  worklist (const exploded_graph &eg, const analysis_plan &plan);
  unsigned length () const;
  exploded_node *take_next ();
  exploded_node *peek_next ();
  void add_node (exploded_node *enode);

private:
  class key_t
  {
  public:
    key_t (const worklist &w, exploded_node *enode)
    : m_worklist (w), m_enode (enode)
    {}

    bool operator< (const key_t &other) const
    {
      return cmp (*this, other) < 0;
    }

    bool operator== (const key_t &other) const
    {
      return cmp (*this, other) == 0;
    }

    bool operator> (const key_t &other) const
    {
      return !(*this == other || *this < other);
    }

  private:
    static int cmp (const key_t &ka, const key_t &kb);

    int get_scc_id (const exploded_node *enode) const
    {
      const supernode *snode = enode->get_supernode ();
      if (snode == NULL)
	return 0;
      return m_worklist.m_scc.get_scc_id (snode->m_index);
    }

    const worklist &m_worklist;
    exploded_node *m_enode;
  };

  /* The order is important here: m_scc needs to stick around
     until after m_queue has finished being cleaned up (the dtor
     calls the ordering fns).  */
  strongly_connected_components m_scc;
  const analysis_plan &m_plan;

  /* Priority queue, backed by a fibonacci_heap.  */
  typedef fibonacci_heap<key_t, exploded_node> queue_t;
  queue_t m_queue;
};

/* An exploded_graph is a directed graph of unique <point, state> pairs.
   It also has a worklist of nodes that are waiting for their successors
   to be added to the graph.  */

class exploded_graph : public digraph<eg_traits>
{
public:
  typedef hash_map <const call_string *, per_call_string_data *,
		    eg_call_string_hash_map_traits> call_string_data_map_t;

  exploded_graph (const supergraph &sg, logger *logger,
		  const extrinsic_state &ext_state,
		  const state_purge_map *purge_map,
		  const analysis_plan &plan,
		  int verbosity);
  ~exploded_graph ();

  logger *get_logger () const { return m_logger.get_logger (); }

  const supergraph &get_supergraph () const { return m_sg; }
  const extrinsic_state &get_ext_state () const { return m_ext_state; }
  const state_purge_map *get_purge_map () const { return m_purge_map; }
  const analysis_plan &get_analysis_plan () const { return m_plan; }

  exploded_node *get_origin () const { return m_origin; }

  exploded_node *add_function_entry (function *fun);

  void build_initial_worklist ();
  void process_worklist ();
  void process_node (exploded_node *node);

  exploded_node *get_or_create_node (const program_point &point,
				     const program_state &state,
				     state_change *change);
  exploded_edge *add_edge (exploded_node *src, exploded_node *dest,
			   const superedge *sedge,
			   const state_change &change,
			   exploded_edge::custom_info_t *custom = NULL);

  per_program_point_data *
  get_or_create_per_program_point_data (const program_point &);

  per_call_string_data *
  get_or_create_per_call_string_data (const call_string &);

  per_function_data *
  get_or_create_per_function_data (function *);
  per_function_data *get_per_function_data (function *) const;

  void save_diagnostic (const state_machine &sm,
			const exploded_node *enode,
			const supernode *node, const gimple *stmt,
			stmt_finder *finder,
			tree var, state_machine::state_t state,
			pending_diagnostic *d);

  diagnostic_manager &get_diagnostic_manager ()
  {
    return m_diagnostic_manager;
  }
  const diagnostic_manager &get_diagnostic_manager () const
  {
    return m_diagnostic_manager;
  }

  stats *get_global_stats () { return &m_global_stats; }
  stats *get_or_create_function_stats (function *fn);
  void log_stats () const;
  void dump_stats (FILE *) const;
  void dump_states_for_supernode (FILE *, const supernode *snode) const;
  void dump_exploded_nodes () const;

  const call_string_data_map_t *get_per_call_string_data () const
  { return &m_per_call_string_data; }

private:
  void print_bar_charts (pretty_printer *pp) const;

  DISABLE_COPY_AND_ASSIGN (exploded_graph);

  const supergraph &m_sg;

  log_user m_logger;

  /* Map from point/state to exploded node.
     To avoid duplication we store point_and_state
     *pointers* as keys, rather than point_and_state, using the
     instance from within the exploded_node, with a custom hasher.  */
  typedef hash_map <const point_and_state *, exploded_node *,
		    eg_hash_map_traits> map_t;
  map_t m_point_and_state_to_node;

  /* Map from program_point to per-program_point data.  */
  typedef hash_map <const program_point *, per_program_point_data *,
		    eg_point_hash_map_traits> point_map_t;
  point_map_t m_per_point_data;

  worklist m_worklist;

  exploded_node *m_origin;

  const extrinsic_state &m_ext_state;

  const state_purge_map *const m_purge_map;

  const analysis_plan &m_plan;

  typedef hash_map<function *, per_function_data *> per_function_data_t;
  per_function_data_t m_per_function_data;

  diagnostic_manager m_diagnostic_manager;

  /* Stats.  */
  stats m_global_stats;
  typedef ordered_hash_map<function *, stats *> function_stat_map_t;
  function_stat_map_t m_per_function_stats;
  stats m_functionless_stats;

  call_string_data_map_t m_per_call_string_data;

  auto_vec<int> m_PK_AFTER_SUPERNODE_per_snode;
};

/* A path within an exploded_graph: a sequence of edges.  */

class exploded_path
{
public:
  exploded_path () : m_edges () {}
  exploded_path (const exploded_path &other);
  exploded_path & operator= (const exploded_path &other);

  unsigned length () const { return m_edges.length (); }

  bool find_stmt_backwards (const gimple *search_stmt,
			    int *out_idx) const;

  exploded_node *get_final_enode () const;

  void dump_to_pp (pretty_printer *pp) const;
  void dump (FILE *fp) const;
  void dump () const;

  bool feasible_p (logger *logger, feasibility_problem **out) const;

  auto_vec<const exploded_edge *> m_edges;
};

/* A reason why a particular exploded_path is infeasible.  */

class feasibility_problem
{
public:
  feasibility_problem (unsigned eedge_idx,
		       const region_model &model,
		       const exploded_edge &eedge,
		       const gimple *last_stmt)
  : m_eedge_idx (eedge_idx), m_model (model), m_eedge (eedge),
    m_last_stmt (last_stmt)
  {}

  unsigned m_eedge_idx;
  region_model m_model;
  const exploded_edge &m_eedge;
  const gimple *m_last_stmt;
};

/* Finding the shortest exploded_path within an exploded_graph.  */

typedef shortest_paths<eg_traits, exploded_path> shortest_exploded_paths;

/* Abstract base class for use when passing NULL as the stmt for
   a possible warning, allowing the choice of stmt to be deferred
   until after we have an emission path (and know we're emitting a
   warning).  */

class stmt_finder
{
public:
  virtual ~stmt_finder () {}
  virtual stmt_finder *clone () const = 0;
  virtual const gimple *find_stmt (const exploded_path &epath) = 0;
};

// TODO: split the above up?

} // namespace ana

#endif /* GCC_ANALYZER_EXPLODED_GRAPH_H */