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   std::unique_ptr<text_art::widget>
  91   make_dump_widget (const text_art::dump_widget_info &dwi) const;
  92
  93   bool contains_p (tree cst) const;
  94
  95   bool intersects_p (const bounded_range &other,
  96                      bounded_range *out) const;
  97
  98   bool operator== (const bounded_range &other) const;
  99   bool operator!= (const bounded_range &other) const
 100   {
 101     return !(*this == other);
 102   }
 103
 104   static int cmp (const bounded_range &a, const bounded_range &b);
 105
 106   bool singleton_p () const
 107   {
 108     return tree_int_cst_equal (m_lower, m_upper);
 109   }
 110
 111   tree m_lower;
 112   tree m_upper;
 113
 114 private:
 115   static void set_json_attr (json::object *obj, const char *name, tree value);
 116 };
 117
 118 /* A collection of bounded_range instances, suitable
 119    for representing the ranges on a case label within a switch
 120    statement.  */
 121
 122 struct bounded_ranges
 123 {
 124 public:
 125   typedef bounded_ranges key_t;
 126
 127   bounded_ranges (const bounded_range &range);
 128   bounded_ranges (const vec<bounded_range> &ranges);
 129   bounded_ranges (enum tree_code op, tree rhs_const);
 130
 131   bool operator== (const bounded_ranges &other) const;
 132
 133   hashval_t get_hash () const { return m_hash; }
 134
 135   void dump_to_pp (pretty_printer *pp, bool show_types) const;
 136   void dump (bool show_types) const;
 137
 138   json::value *to_json () const;
 139
 140   void add_to_dump_widget (text_art::tree_widget &parent,
 141                            const text_art::dump_widget_info &dwi) const;
 142
 143   tristate eval_condition (enum tree_code op,
 144                            tree rhs_const,
 145                            bounded_ranges_manager *mgr) const;
 146
 147   bool contain_p (tree cst) const;
 148   bool empty_p () const { return m_ranges.length () == 0; }
 149
 150   static int cmp (const bounded_ranges *a, const bounded_ranges *b);
 151
 152   unsigned get_count () const { return m_ranges.length (); }
 153   const bounded_range &get_range (unsigned idx) const { return m_ranges[idx]; }
 154
 155 private:
 156   void canonicalize ();
 157   void validate () const;
 158
 159   friend class bounded_ranges_manager;
 160
 161   auto_vec<bounded_range> m_ranges;
 162   hashval_t m_hash;
 163 };
 164
 165 } // namespace ana
 166
 167 template <> struct default_hash_traits<bounded_ranges::key_t>
 168 : public member_function_hash_traits<bounded_ranges::key_t>
 169 {
 170   static const bool empty_zero_p = true;
 171 };
 172
 173 namespace ana {
 174
 175 /* An object to own and consolidate bounded_ranges instances.
 176    This also caches the mapping from switch_cfg_superedge
 177    bounded_ranges instances, so that get_or_create_ranges_for_switch is
 178    memoized.  */
 179
 180 class bounded_ranges_manager
 181 {
 182 public:
 183   ~bounded_ranges_manager ();
 184
 185   const bounded_ranges *
 186   get_or_create_ranges_for_switch (const switch_cfg_superedge *edge,
 187                                    const gswitch *switch_stmt);
 188
 189   const bounded_ranges *get_or_create_empty ();
 190   const bounded_ranges *get_or_create_point (const_tree value);
 191   const bounded_ranges *get_or_create_range (const_tree lower_bound,
 192                                              const_tree upper_bound);
 193   const bounded_ranges *
 194   get_or_create_union (const vec <const bounded_ranges *> &others);
 195   const bounded_ranges *
 196   get_or_create_intersection (const bounded_ranges *a,
 197                               const bounded_ranges *b);
 198   const bounded_ranges *
 199   get_or_create_inverse (const bounded_ranges *other, tree type);
 200
 201   void log_stats (logger *logger, bool show_objs) const;
 202
 203 private:
 204   const bounded_ranges *
 205   create_ranges_for_switch (const switch_cfg_superedge &edge,
 206                             const gswitch *switch_stmt);
 207
 208   const bounded_ranges *
 209   make_case_label_ranges (const gswitch *switch_stmt,
 210                           tree case_label);
 211
 212   const bounded_ranges *consolidate (bounded_ranges *);
 213
 214   struct hash_traits_t : public typed_noop_remove<bounded_ranges *>
 215   {
 216     typedef bounded_ranges *key_type;
 217     typedef bounded_ranges *value_type;
 218
 219     static inline bool
 220     equal (const key_type &k1, const key_type &k2)
 221     {
 222       return *k1 == *k2;
 223     }
 224     static inline hashval_t
 225     hash (const key_type &k)
 226     {
 227       return k->get_hash ();
 228     }
 229     static inline bool is_empty (key_type k) { return k == NULL; }
 230     static inline void mark_empty (key_type &k) { k = NULL; }
 231     static inline bool is_deleted (key_type k)
 232     {
 233       return k == reinterpret_cast<key_type> (1);
 234     }
 235
 236     static const bool empty_zero_p = true;
 237   };
 238   struct traits_t : public simple_hashmap_traits<hash_traits_t,
 239                                                  bounded_ranges *>
 240   {
 241   };
 242   typedef hash_map<bounded_ranges *, bounded_ranges *, traits_t> map_t;
 243   map_t m_map;
 244
 245   typedef hash_map<const switch_cfg_superedge *,
 246                    const bounded_ranges *> edge_cache_t;
 247   edge_cache_t m_edge_cache;
 248 };
 249
 250 /* An equivalence class within a constraint manager: a set of
 251    svalues that are known to all be equal to each other,
 252    together with an optional tree constant that they are equal to.  */
 253
 254 class equiv_class
 255 {
 256 public:
 257   equiv_class ();
 258   equiv_class (const equiv_class &other);
 259
 260   hashval_t hash () const;
 261   bool operator== (const equiv_class &other);
 262
 263   void add (const svalue *sval);
 264   bool del (const svalue *sval);
 265
 266   tree get_any_constant () const { return m_constant; }
 267
 268   const svalue *get_representative () const;
 269
 270   void canonicalize ();
 271
 272   void print (pretty_printer *pp) const;
 273
 274   json::object *to_json () const;
 275
 276   std::unique_ptr<text_art::tree_widget>
 277   make_dump_widget (const text_art::dump_widget_info &dwi,
 278                     unsigned id) const;
 279
 280   bool contains_non_constant_p () const;
 281
 282   /* An equivalence class can contain multiple constants (e.g. multiple
 283      different zeroes, for different types); these are just for the last
 284      constant added.  */
 285   tree m_constant;
 286   const svalue *m_cst_sval;
 287
 288   // TODO: should this be a set rather than a vec?
 289   auto_vec<const svalue *> m_vars;
 290 };
 291
 292 /* The various kinds of constraint.  */
 293
 294 enum constraint_op
 295 {
 296   CONSTRAINT_NE,
 297   CONSTRAINT_LT,
 298   CONSTRAINT_LE
 299 };
 300
 301 const char *constraint_op_code (enum constraint_op c_op);
 302
 303 /* An ID for an equiv_class within a constraint_manager.  Internally, this
 304    is an index into a vector of equiv_class * within the constraint_manager.  */
 305
 306 class equiv_class_id
 307 {
 308 public:
 309   static equiv_class_id null () { return equiv_class_id (-1); }
 310
 311   equiv_class_id (unsigned idx) : m_idx (idx) {}
 312   const equiv_class &get_obj (const constraint_manager &cm) const;
 313   equiv_class &get_obj (constraint_manager &cm) const;
 314
 315   bool operator== (const equiv_class_id &other) const
 316   {
 317     return m_idx == other.m_idx;
 318   }
 319   bool operator!= (const equiv_class_id &other) const
 320   {
 321     return m_idx != other.m_idx;
 322   }
 323
 324   bool null_p () const { return m_idx == -1; }
 325
 326   static equiv_class_id from_int (int idx) { return equiv_class_id (idx); }
 327   int as_int () const { return m_idx; }
 328
 329   void print (pretty_printer *pp) const;
 330
 331   void update_for_removal (equiv_class_id other)
 332   {
 333     if (m_idx > other.m_idx)
 334       m_idx--;
 335   }
 336
 337   int m_idx;
 338 };
 339
 340 /* A relationship between two equivalence classes in a constraint_manager.  */
 341
 342 class constraint
 343 {
 344  public:
 345   constraint (equiv_class_id lhs, enum constraint_op c_op, equiv_class_id rhs)
 346   : m_lhs (lhs), m_op (c_op), m_rhs (rhs)
 347   {
 348     gcc_assert (!lhs.null_p ());
 349     gcc_assert (!rhs.null_p ());
 350   }
 351
 352   void print (pretty_printer *pp, const constraint_manager &cm) const;
 353
 354   json::object *to_json () const;
 355
 356   std::unique_ptr<text_art::widget>
 357   make_dump_widget (const text_art::dump_widget_info &dwi,
 358                     const constraint_manager &cm) const;
 359
 360   hashval_t hash () const;
 361   bool operator== (const constraint &other) const;
 362
 363   /* Is this an ordering, rather than a "!=".  */
 364   bool is_ordering_p () const
 365   {
 366     return m_op != CONSTRAINT_NE;
 367   }
 368
 369   bool implied_by (const constraint &other,
 370                    const constraint_manager &cm) const;
 371
 372   equiv_class_id m_lhs;
 373   enum constraint_op m_op;
 374   equiv_class_id m_rhs;
 375 };
 376
 377 /* An abstract base class for use with constraint_manager::for_each_fact.  */
 378
 379 class fact_visitor
 380 {
 381  public:
 382   virtual ~fact_visitor () {}
 383   virtual void on_fact (const svalue *lhs,
 384                         enum tree_code,
 385                         const svalue *rhs) = 0;
 386   virtual void on_ranges (const svalue *lhs,
 387                           const bounded_ranges *ranges) = 0;
 388 };
 389
 390 class bounded_ranges_constraint
 391 {
 392 public:
 393   bounded_ranges_constraint (equiv_class_id ec_id,
 394                              const bounded_ranges *ranges)
 395   : m_ec_id (ec_id), m_ranges (ranges)
 396   {
 397   }
 398
 399   void print (pretty_printer *pp, const constraint_manager &cm) const;
 400
 401   json::object *to_json () const;
 402
 403   bool operator== (const bounded_ranges_constraint &other) const;
 404   bool operator!= (const bounded_ranges_constraint &other) const
 405   {
 406     return !(*this == other);
 407   }
 408
 409   void add_to_hash (inchash::hash *hstate) const;
 410
 411   std::unique_ptr<text_art::tree_widget>
 412   make_dump_widget (const text_art::dump_widget_info &dwi) const;
 413
 414   equiv_class_id m_ec_id;
 415   const bounded_ranges *m_ranges;
 416 };
 417
 418 /* A collection of equivalence classes and constraints on them.
 419
 420    Given N svalues, this can be thought of as representing a subset of
 421    N-dimensional space.  When we call add_constraint,
 422    we are effectively taking an intersection with that constraint.  */
 423
 424 class constraint_manager
 425 {
 426 public:
 427   constraint_manager (region_model_manager *mgr) : m_mgr (mgr) {}
 428   constraint_manager (const constraint_manager &other);
 429   virtual ~constraint_manager () {}
 430
 431   constraint_manager& operator= (const constraint_manager &other);
 432
 433   hashval_t hash () const;
 434   bool operator== (const constraint_manager &other) const;
 435   bool operator!= (const constraint_manager &other) const
 436   {
 437     return !(*this == other);
 438   }
 439
 440   void print (pretty_printer *pp) const;
 441   void dump_to_pp (pretty_printer *pp, bool multiline) const;
 442   void dump (FILE *fp) const;
 443   void dump () const;
 444
 445   json::object *to_json () const;
 446
 447   std::unique_ptr<text_art::tree_widget>
 448   make_dump_widget (const text_art::dump_widget_info &dwi) const;
 449
 450   const equiv_class &get_equiv_class_by_index (unsigned idx) const
 451   {
 452     return *m_equiv_classes[idx];
 453   }
 454   equiv_class &get_equiv_class_by_index (unsigned idx)
 455   {
 456     return *m_equiv_classes[idx];
 457   }
 458
 459   equiv_class &get_equiv_class (const svalue *sval)
 460   {
 461     equiv_class_id ec_id = get_or_add_equiv_class (sval);
 462     return ec_id.get_obj (*this);
 463   }
 464
 465   bool add_constraint (const svalue *lhs,
 466                        enum tree_code op,
 467                        const svalue *rhs);
 468
 469   bool add_constraint (equiv_class_id lhs_ec_id,
 470                        enum tree_code op,
 471                        equiv_class_id rhs_ec_id);
 472
 473   void add_unknown_constraint (equiv_class_id lhs_ec_id,
 474                                enum tree_code op,
 475                                equiv_class_id rhs_ec_id);
 476
 477   bool add_bounded_ranges (const svalue *sval,
 478                            const bounded_ranges *ranges);
 479
 480   bool get_equiv_class_by_svalue (const svalue *sval,
 481                                     equiv_class_id *out) const;
 482   bool sval_constrained_p (const svalue *sval) const;
 483   equiv_class_id get_or_add_equiv_class (const svalue *sval);
 484   tristate eval_condition (equiv_class_id lhs,
 485                            enum tree_code op,
 486                            equiv_class_id rhs) const;
 487   tristate eval_condition (equiv_class_id lhs_ec,
 488                            enum tree_code op,
 489                            tree rhs_const) const;
 490   tristate eval_condition (const svalue *lhs,
 491                            enum tree_code op,
 492                            const svalue *rhs) const;
 493   range get_ec_bounds (equiv_class_id ec_id) const;
 494
 495   /* PurgeCriteria should have:
 496      bool should_purge_p (const svalue *sval) const.  */
 497   template <typename PurgeCriteria>
 498   void purge (const PurgeCriteria &p, purge_stats *stats);
 499
 500   void on_liveness_change (const svalue_set &live_svalues,
 501                            const region_model *model);
 502   void purge_state_involving (const svalue *sval);
 503
 504   void canonicalize ();
 505
 506   static void merge (const constraint_manager &cm_a,
 507                      const constraint_manager &cm_b,
 508                      constraint_manager *out);
 509
 510   void for_each_fact (fact_visitor *) const;
 511
 512   void validate () const;
 513
 514   bounded_ranges_manager *get_range_manager () const;
 515
 516   bool replay_call_summary (call_summary_replay &r,
 517                             const constraint_manager &summary);
 518
 519   auto_delete_vec<equiv_class> m_equiv_classes;
 520   auto_vec<constraint> m_constraints;
 521   auto_vec<bounded_ranges_constraint> m_bounded_ranges_constraints;
 522
 523  private:
 524   void add_constraint_internal (equiv_class_id lhs_id,
 525                                 enum constraint_op c_op,
 526                                 equiv_class_id rhs_id);
 527   bool impossible_derived_conditions_p (const svalue *lhs,
 528                                         const svalue *rhs) const;
 529
 530   region_model_manager *m_mgr;
 531 };
 532
 533 } // namespace ana
 534
 535 #endif /* GCC_ANALYZER_CONSTRAINT_MANAGER_H */