call-string.h

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/* Call stacks at program points.
   Copyright (C) 2019-2024 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_CALL_STRING_H
#define GCC_ANALYZER_CALL_STRING_H
 
namespace ana {
 
class supergraph;
class supernode;
class call_superedge;
class return_superedge;
 
 
/* A string of return_superedge pointers, representing a call stack
   at a program point.
 
   This is used to ensure that we generate interprocedurally valid paths
   i.e. that we return to the same callsite that called us.
 
   The class stores returning calls ( which may be represented by a
   returning superedge ). We do so because this is what we need to compare
   against.
 
   Instances of call_string are consolidated by the region_model_manager,
   which effectively owns them: it owns the root/empty call_string, and each
   call_string instance tracks its children, lazily creating them on demand,
   so that the call_string instances form a tree-like hierarchy in memory.  */
 
class call_string
{
public:
  /* A struct representing an element in the call_string.
 
   Each element represents a path from m_callee to m_caller which represents
   returning from function.  */
 
  struct element_t
  {
    element_t (const supernode *caller, const supernode *callee)
    :  m_caller (caller), m_callee (callee)
    {
    }
 
    bool operator== (const element_t &other) const;
    bool operator!= (const element_t &other) const;
 
    /* Accessors */
    function *get_caller_function () const;
    function *get_callee_function () const;
 
    const supernode *m_caller;
    const supernode *m_callee;
  };
 
  void print (pretty_printer *pp) const;
 
  json::value *to_json () const;
 
  bool empty_p () const { return m_elements.is_empty (); }
 
  const call_string *push_call (const supergraph &sg,
                                const call_superedge *sedge) const;
 
  const call_string *push_call (const supernode *src,
                                const supernode *dest) const;
  const call_string *get_parent () const { return m_parent; }
 
  int calc_recursion_depth () const;
 
  static int cmp (const call_string &a,
                  const call_string &b);
 
  static int cmp_ptr_ptr (const void *, const void *);
 
  /* Accessors */
 
  const supernode *get_callee_node () const;
  const supernode *get_caller_node () const;
  unsigned length () const { return m_elements.length (); }
  element_t operator[] (unsigned idx) const
  {
    return m_elements[idx];
  }
  const element_t &get_top_of_stack () const
  {
    gcc_assert (m_elements.length () > 0);
    return m_elements[m_elements.length () - 1];
  }
 
  int count_occurrences_of_function (function *) const;
 
  void validate () const;
 
private:
  struct hashmap_traits_t
  {
    typedef element_t key_type;
    typedef const call_string *value_type;
 
    static const bool maybe_mx = false;
    static inline hashval_t hash (const key_type &k)
    {
      inchash::hash hstate;
      hstate.add_ptr (k.m_caller);
      hstate.add_ptr (k.m_callee);
      return hstate.end ();
    }
    static inline bool equal_keys (const key_type &k1, const key_type &k2)
    {
      return k1 == k2;
    }
    template <typename T> static inline void remove (T &entry)
    {
      entry.m_key = element_t (NULL, NULL);
    }
    static const bool empty_zero_p = true;
    template <typename T> static inline bool is_empty (const T &entry)
    {
      return entry.m_key.m_caller == NULL;
    }
    template <typename T> static inline bool is_deleted (const T &entry)
    {
      return entry.m_key.m_caller == reinterpret_cast<const supernode *> (1);
    }
    template <typename T> static inline void mark_empty (T &entry)
    {
      entry.m_key = element_t (NULL, NULL);
      entry.m_value = NULL;
    }
    template <typename T> static inline void mark_deleted (T &entry)
    {
      entry.m_key.m_caller = reinterpret_cast<const supernode *> (1);
    }
  };
 
  friend class region_model_manager;
 
  DISABLE_COPY_AND_ASSIGN (call_string);
 
  call_string ();
  call_string (const call_string &parent, const element_t &to_push);
  ~call_string ();
 
  void recursive_log (logger *logger) const;
 
  const call_string *m_parent;
  auto_vec<element_t> m_elements;
  mutable hash_map<element_t, const call_string *, hashmap_traits_t> m_children;
};
 
} // namespace ana
 
#endif /* GCC_ANALYZER_CALL_STRING_H */