gcc/analyzer/constraint-manager.h

   1 /* Tracking equivalence classes and constraints at a point on an execution path.
   2    Copyright (C) 2019-2024 Free Software Foundation, Inc.
   3    Contributed by David Malcolm <dmalcolm@redhat.com>.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it
   8 under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 3, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful, but
  13 WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 General Public License for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #ifndef GCC_ANALYZER_CONSTRAINT_MANAGER_H
  22 #define GCC_ANALYZER_CONSTRAINT_MANAGER_H
  23
  24 namespace ana {
  25
  26 class constraint_manager;
  27
  28 enum bound_kind
  29 {
  30   BK_LOWER,
  31   BK_UPPER
  32 };
  33
  34 /* One of the end-points of a range.  */
  35
  36 struct bound
  37 {
  38   bound () : m_constant (NULL_TREE), m_closed (false) {}
  39   bound (tree constant, bool closed)
  40   : m_constant (constant), m_closed (closed) {}
  41
  42   void ensure_closed (enum bound_kind bound_kind);
  43
  44   const char * get_relation_as_str () const;
  45
  46   tree m_constant;
  47   bool m_closed;
  48 };
  49
  50 /* A range of values, used for determining if a value has been
  51    constrained to just one possible constant value.  */
  52
  53 class range
  54 {
  55 public:
  56   range () : m_lower_bound (), m_upper_bound () {}
  57   range (const bound &lower, const bound &upper)
  58   : m_lower_bound (lower), m_upper_bound (upper) {}
  59
  60   void dump_to_pp (pretty_printer *pp) const;
  61   void dump () const;
  62
  63   tree constrained_to_single_element ();
  64
  65   tristate eval_condition (enum tree_code op,
  66                            tree rhs_const) const;
  67   bool below_lower_bound (tree rhs_const) const;
  68   bool above_upper_bound (tree rhs_const) const;
  69
  70   bool add_bound (bound b, enum bound_kind bound_kind);
  71   bool add_bound (enum tree_code op, tree rhs_const);
  72
  73 private:
  74   bound m_lower_bound;
  75   bound m_upper_bound;
  76 };
  77
  78 /* A closed range of values with constant integer bounds
  79    e.g. [3, 5] for the set {3, 4, 5}.  */
  80
  81 struct bounded_range
  82 {
  83   bounded_range (const_tree lower, const_tree upper);
  84
  85   void dump_to_pp (pretty_printer *pp, bool show_types) const;
  86   void dump (bool show_types) const;
  87
  88   json::object *to_json () const;
  89
  90   bool contains_p (tree cst) const;
  91
  92   bool intersects_p (const bounded_range &other,
  93                      bounded_range *out) const;
  94
  95   bool operator== (const bounded_range &other) const;
  96   bool operator!= (const bounded_range &other) const
  97   {
  98     return !(*this == other);
  99   }
 100
 101   static int cmp (const bounded_range &a, const bounded_range &b);
 102
 103   bool singleton_p () const
 104   {
 105     return tree_int_cst_equal (m_lower, m_upper);
 106   }
 107
 108   tree m_lower;
 109   tree m_upper;
 110
 111 private:
 112   static void set_json_attr (json::object *obj, const char *name, tree value);
 113 };
 114
 115 /* A collection of bounded_range instances, suitable
 116    for representing the ranges on a case label within a switch
 117    statement.  */
 118
 119 struct bounded_ranges
 120 {
 121 public:
 122   typedef bounded_ranges key_t;
 123
 124   bounded_ranges (const bounded_range &range);
 125   bounded_ranges (const vec<bounded_range> &ranges);
 126   bounded_ranges (enum tree_code op, tree rhs_const);
 127
 128   bool operator== (const bounded_ranges &other) const;
 129
 130   hashval_t get_hash () const { return m_hash; }
 131
 132   void dump_to_pp (pretty_printer *pp, bool show_types) const;
 133   void dump (bool show_types) const;
 134
 135   json::value *to_json () const;
 136
 137   tristate eval_condition (enum tree_code op,
 138                            tree rhs_const,
 139                            bounded_ranges_manager *mgr) const;
 140
 141   bool contain_p (tree cst) const;
 142   bool empty_p () const { return m_ranges.length () == 0; }
 143
 144   static int cmp (const bounded_ranges *a, const bounded_ranges *b);
 145
 146   unsigned get_count () const { return m_ranges.length (); }
 147   const bounded_range &get_range (unsigned idx) const { return m_ranges[idx]; }
 148
 149 private:
 150   void canonicalize ();
 151   void validate () const;
 152
 153   friend class bounded_ranges_manager;
 154
 155   auto_vec<bounded_range> m_ranges;
 156   hashval_t m_hash;
 157 };
 158
 159 } // namespace ana
 160
 161 template <> struct default_hash_traits<bounded_ranges::key_t>
 162 : public member_function_hash_traits<bounded_ranges::key_t>
 163 {
 164   static const bool empty_zero_p = true;
 165 };
 166
 167 namespace ana {
 168
 169 /* An object to own and consolidate bounded_ranges instances.
 170    This also caches the mapping from switch_cfg_superedge
 171    bounded_ranges instances, so that get_or_create_ranges_for_switch is
 172    memoized.  */
 173
 174 class bounded_ranges_manager
 175 {
 176 public:
 177   ~bounded_ranges_manager ();
 178
 179   const bounded_ranges *
 180   get_or_create_ranges_for_switch (const switch_cfg_superedge *edge,
 181                                    const gswitch *switch_stmt);
 182
 183   const bounded_ranges *get_or_create_empty ();
 184   const bounded_ranges *get_or_create_point (const_tree value);
 185   const bounded_ranges *get_or_create_range (const_tree lower_bound,
 186                                              const_tree upper_bound);
 187   const bounded_ranges *
 188   get_or_create_union (const vec <const bounded_ranges *> &others);
 189   const bounded_ranges *
 190   get_or_create_intersection (const bounded_ranges *a,
 191                               const bounded_ranges *b);
 192   const bounded_ranges *
 193   get_or_create_inverse (const bounded_ranges *other, tree type);
 194
 195   void log_stats (logger *logger, bool show_objs) const;
 196
 197 private:
 198   const bounded_ranges *
 199   create_ranges_for_switch (const switch_cfg_superedge &edge,
 200                             const gswitch *switch_stmt);
 201
 202   const bounded_ranges *
 203   make_case_label_ranges (const gswitch *switch_stmt,
 204                           tree case_label);
 205
 206   const bounded_ranges *consolidate (bounded_ranges *);
 207
 208   struct hash_traits_t : public typed_noop_remove<bounded_ranges *>
 209   {
 210     typedef bounded_ranges *key_type;
 211     typedef bounded_ranges *value_type;
 212
 213     static inline bool
 214     equal (const key_type &k1, const key_type &k2)
 215     {
 216       return *k1 == *k2;
 217     }
 218     static inline hashval_t
 219     hash (const key_type &k)
 220     {
 221       return k->get_hash ();
 222     }
 223     static inline bool is_empty (key_type k) { return k == NULL; }
 224     static inline void mark_empty (key_type &k) { k = NULL; }
 225     static inline bool is_deleted (key_type k)
 226     {
 227       return k == reinterpret_cast<key_type> (1);
 228     }
 229
 230     static const bool empty_zero_p = true;
 231   };
 232   struct traits_t : public simple_hashmap_traits<hash_traits_t,
 233                                                  bounded_ranges *>
 234   {
 235   };
 236   typedef hash_map<bounded_ranges *, bounded_ranges *, traits_t> map_t;
 237   map_t m_map;
 238
 239   typedef hash_map<const switch_cfg_superedge *,
 240                    const bounded_ranges *> edge_cache_t;
 241   edge_cache_t m_edge_cache;
 242 };
 243
 244 /* An equivalence class within a constraint manager: a set of
 245    svalues that are known to all be equal to each other,
 246    together with an optional tree constant that they are equal to.  */
 247
 248 class equiv_class
 249 {
 250 public:
 251   equiv_class ();
 252   equiv_class (const equiv_class &other);
 253
 254   hashval_t hash () const;
 255   bool operator== (const equiv_class &other);
 256
 257   void add (const svalue *sval);
 258   bool del (const svalue *sval);
 259
 260   tree get_any_constant () const { return m_constant; }
 261
 262   const svalue *get_representative () const;
 263
 264   void canonicalize ();
 265
 266   void print (pretty_printer *pp) const;
 267
 268   json::object *to_json () const;
 269
 270   bool contains_non_constant_p () const;
 271
 272   /* An equivalence class can contain multiple constants (e.g. multiple
 273      different zeroes, for different types); these are just for the last
 274      constant added.  */
 275   tree m_constant;
 276   const svalue *m_cst_sval;
 277
 278   // TODO: should this be a set rather than a vec?
 279   auto_vec<const svalue *> m_vars;
 280 };
 281
 282 /* The various kinds of constraint.  */
 283
 284 enum constraint_op
 285 {
 286   CONSTRAINT_NE,
 287   CONSTRAINT_LT,
 288   CONSTRAINT_LE
 289 };
 290
 291 const char *constraint_op_code (enum constraint_op c_op);
 292
 293 /* An ID for an equiv_class within a constraint_manager.  Internally, this
 294    is an index into a vector of equiv_class * within the constraint_manager.  */
 295
 296 class equiv_class_id
 297 {
 298 public:
 299   static equiv_class_id null () { return equiv_class_id (-1); }
 300
 301   equiv_class_id (unsigned idx) : m_idx (idx) {}
 302   const equiv_class &get_obj (const constraint_manager &cm) const;
 303   equiv_class &get_obj (constraint_manager &cm) const;
 304
 305   bool operator== (const equiv_class_id &other) const
 306   {
 307     return m_idx == other.m_idx;
 308   }
 309   bool operator!= (const equiv_class_id &other) const
 310   {
 311     return m_idx != other.m_idx;
 312   }
 313
 314   bool null_p () const { return m_idx == -1; }
 315
 316   static equiv_class_id from_int (int idx) { return equiv_class_id (idx); }
 317   int as_int () const { return m_idx; }
 318
 319   void print (pretty_printer *pp) const;
 320
 321   void update_for_removal (equiv_class_id other)
 322   {
 323     if (m_idx > other.m_idx)
 324       m_idx--;
 325   }
 326
 327   int m_idx;
 328 };
 329
 330 /* A relationship between two equivalence classes in a constraint_manager.  */
 331
 332 class constraint
 333 {
 334  public:
 335   constraint (equiv_class_id lhs, enum constraint_op c_op, equiv_class_id rhs)
 336   : m_lhs (lhs), m_op (c_op), m_rhs (rhs)
 337   {
 338     gcc_assert (!lhs.null_p ());
 339     gcc_assert (!rhs.null_p ());
 340   }
 341
 342   void print (pretty_printer *pp, const constraint_manager &cm) const;
 343
 344   json::object *to_json () const;
 345
 346   hashval_t hash () const;
 347   bool operator== (const constraint &other) const;
 348
 349   /* Is this an ordering, rather than a "!=".  */
 350   bool is_ordering_p () const
 351   {
 352     return m_op != CONSTRAINT_NE;
 353   }
 354
 355   bool implied_by (const constraint &other,
 356                    const constraint_manager &cm) const;
 357
 358   equiv_class_id m_lhs;
 359   enum constraint_op m_op;
 360   equiv_class_id m_rhs;
 361 };
 362
 363 /* An abstract base class for use with constraint_manager::for_each_fact.  */
 364
 365 class fact_visitor
 366 {
 367  public:
 368   virtual ~fact_visitor () {}
 369   virtual void on_fact (const svalue *lhs,
 370                         enum tree_code,
 371                         const svalue *rhs) = 0;
 372   virtual void on_ranges (const svalue *lhs,
 373                           const bounded_ranges *ranges) = 0;
 374 };
 375
 376 class bounded_ranges_constraint
 377 {
 378 public:
 379   bounded_ranges_constraint (equiv_class_id ec_id,
 380                              const bounded_ranges *ranges)
 381   : m_ec_id (ec_id), m_ranges (ranges)
 382   {
 383   }
 384
 385   void print (pretty_printer *pp, const constraint_manager &cm) const;
 386
 387   json::object *to_json () const;
 388
 389   bool operator== (const bounded_ranges_constraint &other) const;
 390   bool operator!= (const bounded_ranges_constraint &other) const
 391   {
 392     return !(*this == other);
 393   }
 394
 395   void add_to_hash (inchash::hash *hstate) const;
 396
 397   equiv_class_id m_ec_id;
 398   const bounded_ranges *m_ranges;
 399 };
 400
 401 /* A collection of equivalence classes and constraints on them.
 402
 403    Given N svalues, this can be thought of as representing a subset of
 404    N-dimensional space.  When we call add_constraint,
 405    we are effectively taking an intersection with that constraint.  */
 406
 407 class constraint_manager
 408 {
 409 public:
 410   constraint_manager (region_model_manager *mgr) : m_mgr (mgr) {}
 411   constraint_manager (const constraint_manager &other);
 412   virtual ~constraint_manager () {}
 413
 414   constraint_manager& operator= (const constraint_manager &other);
 415
 416   hashval_t hash () const;
 417   bool operator== (const constraint_manager &other) const;
 418   bool operator!= (const constraint_manager &other) const
 419   {
 420     return !(*this == other);
 421   }
 422
 423   void print (pretty_printer *pp) const;
 424   void dump_to_pp (pretty_printer *pp, bool multiline) const;
 425   void dump (FILE *fp) const;
 426   void dump () const;
 427
 428   json::object *to_json () const;
 429
 430   const equiv_class &get_equiv_class_by_index (unsigned idx) const
 431   {
 432     return *m_equiv_classes[idx];
 433   }
 434   equiv_class &get_equiv_class_by_index (unsigned idx)
 435   {
 436     return *m_equiv_classes[idx];
 437   }
 438
 439   equiv_class &get_equiv_class (const svalue *sval)
 440   {
 441     equiv_class_id ec_id = get_or_add_equiv_class (sval);
 442     return ec_id.get_obj (*this);
 443   }
 444
 445   bool add_constraint (const svalue *lhs,
 446                        enum tree_code op,
 447                        const svalue *rhs);
 448
 449   bool add_constraint (equiv_class_id lhs_ec_id,
 450                        enum tree_code op,
 451                        equiv_class_id rhs_ec_id);
 452
 453   void add_unknown_constraint (equiv_class_id lhs_ec_id,
 454                                enum tree_code op,
 455                                equiv_class_id rhs_ec_id);
 456
 457   bool add_bounded_ranges (const svalue *sval,
 458                            const bounded_ranges *ranges);
 459
 460   bool get_equiv_class_by_svalue (const svalue *sval,
 461                                     equiv_class_id *out) const;
 462   bool sval_constrained_p (const svalue *sval) const;
 463   equiv_class_id get_or_add_equiv_class (const svalue *sval);
 464   tristate eval_condition (equiv_class_id lhs,
 465                            enum tree_code op,
 466                            equiv_class_id rhs) const;
 467   tristate eval_condition (equiv_class_id lhs_ec,
 468                            enum tree_code op,
 469                            tree rhs_const) const;
 470   tristate eval_condition (const svalue *lhs,
 471                            enum tree_code op,
 472                            const svalue *rhs) const;
 473   range get_ec_bounds (equiv_class_id ec_id) const;
 474
 475   /* PurgeCriteria should have:
 476      bool should_purge_p (const svalue *sval) const.  */
 477   template <typename PurgeCriteria>
 478   void purge (const PurgeCriteria &p, purge_stats *stats);
 479
 480   void on_liveness_change (const svalue_set &live_svalues,
 481                            const region_model *model);
 482   void purge_state_involving (const svalue *sval);
 483
 484   void canonicalize ();
 485
 486   static void merge (const constraint_manager &cm_a,
 487                      const constraint_manager &cm_b,
 488                      constraint_manager *out);
 489
 490   void for_each_fact (fact_visitor *) const;
 491
 492   void validate () const;
 493
 494   bounded_ranges_manager *get_range_manager () const;
 495
 496   bool replay_call_summary (call_summary_replay &r,
 497                             const constraint_manager &summary);
 498
 499   auto_delete_vec<equiv_class> m_equiv_classes;
 500   auto_vec<constraint> m_constraints;
 501   auto_vec<bounded_ranges_constraint> m_bounded_ranges_constraints;
 502
 503  private:
 504   void add_constraint_internal (equiv_class_id lhs_id,
 505                                 enum constraint_op c_op,
 506                                 equiv_class_id rhs_id);
 507   bool impossible_derived_conditions_p (const svalue *lhs,
 508                                         const svalue *rhs) const;
 509
 510   region_model_manager *m_mgr;
 511 };
 512
 513 } // namespace ana
 514
 515 #endif /* GCC_ANALYZER_CONSTRAINT_MANAGER_H */