gcc/analyzer/constraint-manager.h

   1 /* Tracking equivalence classes and constraints at a point on an execution path.
   2    Copyright (C) 2019-2021 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 /* One of the end-points of a range.  */
  29
  30 struct bound
  31 {
  32   bound () : m_constant (NULL_TREE), m_closed (false) {}
  33   bound (tree constant, bool closed)
  34   : m_constant (constant), m_closed (closed) {}
  35
  36   void ensure_closed (bool is_upper);
  37
  38   const char * get_relation_as_str () const;
  39
  40   tree m_constant;
  41   bool m_closed;
  42 };
  43
  44 /* A range of values, used for determining if a value has been
  45    constrained to just one possible constant value.  */
  46
  47 struct range
  48 {
  49   range () : m_lower_bound (), m_upper_bound () {}
  50   range (const bound &lower, const bound &upper)
  51   : m_lower_bound (lower), m_upper_bound (upper) {}
  52
  53   void dump_to_pp (pretty_printer *pp) const;
  54   void dump () const;
  55
  56   tree constrained_to_single_element ();
  57
  58   tristate eval_condition (enum tree_code op,
  59                            tree rhs_const) const;
  60   bool below_lower_bound (tree rhs_const) const;
  61   bool above_upper_bound (tree rhs_const) const;
  62
  63   bound m_lower_bound;
  64   bound m_upper_bound;
  65 };
  66
  67 /* A closed range of values with constant integer bounds
  68    e.g. [3, 5] for the set {3, 4, 5}.  */
  69
  70 struct bounded_range
  71 {
  72   bounded_range (const_tree lower, const_tree upper);
  73
  74   void dump_to_pp (pretty_printer *pp, bool show_types) const;
  75   void dump (bool show_types) const;
  76
  77   json::object *to_json () const;
  78
  79   bool contains_p (tree cst) const;
  80
  81   bool intersects_p (const bounded_range &other,
  82                      bounded_range *out) const;
  83
  84   bool operator== (const bounded_range &other) const;
  85   bool operator!= (const bounded_range &other) const
  86   {
  87     return !(*this == other);
  88   }
  89
  90   static int cmp (const bounded_range &a, const bounded_range &b);
  91
  92   tree m_lower;
  93   tree m_upper;
  94
  95 private:
  96   static void set_json_attr (json::object *obj, const char *name, tree value);
  97 };
  98
  99 /* A collection of bounded_range instances, suitable
 100    for representing the ranges on a case label within a switch
 101    statement.  */
 102
 103 struct bounded_ranges
 104 {
 105 public:
 106   typedef bounded_ranges key_t;
 107
 108   bounded_ranges (const bounded_range &range);
 109   bounded_ranges (const vec<bounded_range> &ranges);
 110   bounded_ranges (enum tree_code op, tree rhs_const);
 111
 112   bool operator== (const bounded_ranges &other) const;
 113
 114   hashval_t get_hash () const { return m_hash; }
 115
 116   void dump_to_pp (pretty_printer *pp, bool show_types) const;
 117   void dump (bool show_types) const;
 118
 119   json::value *to_json () const;
 120
 121   tristate eval_condition (enum tree_code op,
 122                            tree rhs_const,
 123                            bounded_ranges_manager *mgr) const;
 124
 125   bool contain_p (tree cst) const;
 126   bool empty_p () const { return m_ranges.length () == 0; }
 127
 128   static int cmp (const bounded_ranges *a, const bounded_ranges *b);
 129
 130 private:
 131   void canonicalize ();
 132   void validate () const;
 133
 134   friend class bounded_ranges_manager;
 135
 136   auto_vec<bounded_range> m_ranges;
 137   hashval_t m_hash;
 138 };
 139
 140 } // namespace ana
 141
 142 template <> struct default_hash_traits<bounded_ranges::key_t>
 143 : public member_function_hash_traits<bounded_ranges::key_t>
 144 {
 145   static const bool empty_zero_p = true;
 146 };
 147
 148 namespace ana {
 149
 150 /* An object to own and consolidate bounded_ranges instances.
 151    This also caches the mapping from switch_cfg_superedge
 152    bounded_ranges instances, so that get_or_create_ranges_for_switch is
 153    memoized.  */
 154
 155 class bounded_ranges_manager
 156 {
 157 public:
 158   ~bounded_ranges_manager ();
 159
 160   const bounded_ranges *
 161   get_or_create_ranges_for_switch (const switch_cfg_superedge *edge,
 162                                    const gswitch *switch_stmt);
 163
 164   const bounded_ranges *get_or_create_empty ();
 165   const bounded_ranges *get_or_create_point (const_tree value);
 166   const bounded_ranges *get_or_create_range (const_tree lower_bound,
 167                                              const_tree upper_bound);
 168   const bounded_ranges *
 169   get_or_create_union (const vec <const bounded_ranges *> &others);
 170   const bounded_ranges *
 171   get_or_create_intersection (const bounded_ranges *a,
 172                               const bounded_ranges *b);
 173   const bounded_ranges *
 174   get_or_create_inverse (const bounded_ranges *other, tree type);
 175
 176   void log_stats (logger *logger, bool show_objs) const;
 177
 178 private:
 179   const bounded_ranges *
 180   create_ranges_for_switch (const switch_cfg_superedge &edge,
 181                             const gswitch *switch_stmt);
 182
 183   const bounded_ranges *
 184   make_case_label_ranges (const gswitch *switch_stmt,
 185                           tree case_label);
 186
 187   const bounded_ranges *consolidate (bounded_ranges *);
 188
 189   struct hash_traits_t : public typed_noop_remove<bounded_ranges *>
 190   {
 191     typedef bounded_ranges *key_type;
 192     typedef bounded_ranges *value_type;
 193
 194     static inline bool
 195     equal (const key_type &k1, const key_type &k2)
 196     {
 197       return *k1 == *k2;
 198     }
 199     static inline hashval_t
 200     hash (const key_type &k)
 201     {
 202       return k->get_hash ();
 203     }
 204     static inline bool is_empty (key_type k) { return k == NULL; }
 205     static inline void mark_empty (key_type &k) { k = NULL; }
 206     static inline bool is_deleted (key_type k)
 207     {
 208       return k == reinterpret_cast<key_type> (1);
 209     }
 210
 211     static const bool empty_zero_p = true;
 212   };
 213   struct traits_t : public simple_hashmap_traits<hash_traits_t,
 214                                                  bounded_ranges *>
 215   {
 216   };
 217   typedef hash_map<bounded_ranges *, bounded_ranges *, traits_t> map_t;
 218   map_t m_map;
 219
 220   typedef hash_map<const switch_cfg_superedge *,
 221                    const bounded_ranges *> edge_cache_t;
 222   edge_cache_t m_edge_cache;
 223 };
 224
 225 /* An equivalence class within a constraint manager: a set of
 226    svalues that are known to all be equal to each other,
 227    together with an optional tree constant that they are equal to.  */
 228
 229 class equiv_class
 230 {
 231 public:
 232   equiv_class ();
 233   equiv_class (const equiv_class &other);
 234
 235   hashval_t hash () const;
 236   bool operator== (const equiv_class &other);
 237
 238   void add (const svalue *sval);
 239   bool del (const svalue *sval);
 240
 241   tree get_any_constant () const { return m_constant; }
 242
 243   const svalue *get_representative () const;
 244
 245   void canonicalize ();
 246
 247   void print (pretty_printer *pp) const;
 248
 249   json::object *to_json () const;
 250
 251   /* An equivalence class can contain multiple constants (e.g. multiple
 252      different zeroes, for different types); these are just for the last
 253      constant added.  */
 254   tree m_constant;
 255   const svalue *m_cst_sval;
 256
 257   // TODO: should this be a set rather than a vec?
 258   auto_vec<const svalue *> m_vars;
 259 };
 260
 261 /* The various kinds of constraint.  */
 262
 263 enum constraint_op
 264 {
 265   CONSTRAINT_NE,
 266   CONSTRAINT_LT,
 267   CONSTRAINT_LE
 268 };
 269
 270 const char *constraint_op_code (enum constraint_op c_op);
 271
 272 /* An ID for an equiv_class within a constraint_manager.  Internally, this
 273    is an index into a vector of equiv_class * within the constraint_manager.  */
 274
 275 class equiv_class_id
 276 {
 277 public:
 278   static equiv_class_id null () { return equiv_class_id (-1); }
 279
 280   equiv_class_id (unsigned idx) : m_idx (idx) {}
 281   const equiv_class &get_obj (const constraint_manager &cm) const;
 282   equiv_class &get_obj (constraint_manager &cm) const;
 283
 284   bool operator== (const equiv_class_id &other) const
 285   {
 286     return m_idx == other.m_idx;
 287   }
 288   bool operator!= (const equiv_class_id &other) const
 289   {
 290     return m_idx != other.m_idx;
 291   }
 292
 293   bool null_p () const { return m_idx == -1; }
 294
 295   static equiv_class_id from_int (int idx) { return equiv_class_id (idx); }
 296   int as_int () const { return m_idx; }
 297
 298   void print (pretty_printer *pp) const;
 299
 300   void update_for_removal (equiv_class_id other)
 301   {
 302     if (m_idx > other.m_idx)
 303       m_idx--;
 304   }
 305
 306   int m_idx;
 307 };
 308
 309 /* A relationship between two equivalence classes in a constraint_manager.  */
 310
 311 class constraint
 312 {
 313  public:
 314   constraint (equiv_class_id lhs, enum constraint_op c_op, equiv_class_id rhs)
 315   : m_lhs (lhs), m_op (c_op), m_rhs (rhs)
 316   {
 317     gcc_assert (!lhs.null_p ());
 318     gcc_assert (!rhs.null_p ());
 319   }
 320
 321   void print (pretty_printer *pp, const constraint_manager &cm) const;
 322
 323   json::object *to_json () const;
 324
 325   hashval_t hash () const;
 326   bool operator== (const constraint &other) const;
 327
 328   /* Is this an ordering, rather than a "!=".  */
 329   bool is_ordering_p () const
 330   {
 331     return m_op != CONSTRAINT_NE;
 332   }
 333
 334   bool implied_by (const constraint &other,
 335                    const constraint_manager &cm) const;
 336
 337   equiv_class_id m_lhs;
 338   enum constraint_op m_op;
 339   equiv_class_id m_rhs;
 340 };
 341
 342 /* An abstract base class for use with constraint_manager::for_each_fact.  */
 343
 344 class fact_visitor
 345 {
 346  public:
 347   virtual ~fact_visitor () {}
 348   virtual void on_fact (const svalue *lhs,
 349                         enum tree_code,
 350                         const svalue *rhs) = 0;
 351   virtual void on_ranges (const svalue *lhs,
 352                           const bounded_ranges *ranges) = 0;
 353 };
 354
 355 class bounded_ranges_constraint
 356 {
 357 public:
 358   bounded_ranges_constraint (equiv_class_id ec_id,
 359                              const bounded_ranges *ranges)
 360   : m_ec_id (ec_id), m_ranges (ranges)
 361   {
 362   }
 363
 364   void print (pretty_printer *pp, const constraint_manager &cm) const;
 365
 366   json::object *to_json () const;
 367
 368   bool operator== (const bounded_ranges_constraint &other) const;
 369   bool operator!= (const bounded_ranges_constraint &other) const
 370   {
 371     return !(*this == other);
 372   }
 373
 374   void add_to_hash (inchash::hash *hstate) const;
 375
 376   equiv_class_id m_ec_id;
 377   const bounded_ranges *m_ranges;
 378 };
 379
 380 /* A collection of equivalence classes and constraints on them.
 381
 382    Given N svalues, this can be thought of as representing a subset of
 383    N-dimensional space.  When we call add_constraint,
 384    we are effectively taking an intersection with that constraint.  */
 385
 386 class constraint_manager
 387 {
 388 public:
 389   constraint_manager (region_model_manager *mgr) : m_mgr (mgr) {}
 390   constraint_manager (const constraint_manager &other);
 391   virtual ~constraint_manager () {}
 392
 393   constraint_manager& operator= (const constraint_manager &other);
 394
 395   hashval_t hash () const;
 396   bool operator== (const constraint_manager &other) const;
 397   bool operator!= (const constraint_manager &other) const
 398   {
 399     return !(*this == other);
 400   }
 401
 402   void print (pretty_printer *pp) const;
 403   void dump_to_pp (pretty_printer *pp, bool multiline) const;
 404   void dump (FILE *fp) const;
 405   void dump () const;
 406
 407   json::object *to_json () const;
 408
 409   const equiv_class &get_equiv_class_by_index (unsigned idx) const
 410   {
 411     return *m_equiv_classes[idx];
 412   }
 413   equiv_class &get_equiv_class_by_index (unsigned idx)
 414   {
 415     return *m_equiv_classes[idx];
 416   }
 417
 418   equiv_class &get_equiv_class (const svalue *sval)
 419   {
 420     equiv_class_id ec_id = get_or_add_equiv_class (sval);
 421     return ec_id.get_obj (*this);
 422   }
 423
 424   bool add_constraint (const svalue *lhs,
 425                        enum tree_code op,
 426                        const svalue *rhs);
 427
 428   bool add_constraint (equiv_class_id lhs_ec_id,
 429                        enum tree_code op,
 430                        equiv_class_id rhs_ec_id);
 431
 432   void add_unknown_constraint (equiv_class_id lhs_ec_id,
 433                                enum tree_code op,
 434                                equiv_class_id rhs_ec_id);
 435
 436   bool add_bounded_ranges (const svalue *sval,
 437                            const bounded_ranges *ranges);
 438
 439   bool get_equiv_class_by_svalue (const svalue *sval,
 440                                     equiv_class_id *out) const;
 441   equiv_class_id get_or_add_equiv_class (const svalue *sval);
 442   tristate eval_condition (equiv_class_id lhs,
 443                            enum tree_code op,
 444                            equiv_class_id rhs) const;
 445   tristate eval_condition (equiv_class_id lhs_ec,
 446                            enum tree_code op,
 447                            tree rhs_const) const;
 448   tristate eval_condition (const svalue *lhs,
 449                            enum tree_code op,
 450                            const svalue *rhs) const;
 451   range get_ec_bounds (equiv_class_id ec_id) const;
 452
 453   /* PurgeCriteria should have:
 454      bool should_purge_p (const svalue *sval) const.  */
 455   template <typename PurgeCriteria>
 456   void purge (const PurgeCriteria &p, purge_stats *stats);
 457
 458   void on_liveness_change (const svalue_set &live_svalues,
 459                            const region_model *model);
 460   void purge_state_involving (const svalue *sval);
 461
 462   void canonicalize ();
 463
 464   static void merge (const constraint_manager &cm_a,
 465                      const constraint_manager &cm_b,
 466                      constraint_manager *out);
 467
 468   void for_each_fact (fact_visitor *) const;
 469
 470   void validate () const;
 471
 472   bounded_ranges_manager *get_range_manager () const;
 473
 474   auto_delete_vec<equiv_class> m_equiv_classes;
 475   auto_vec<constraint> m_constraints;
 476   auto_vec<bounded_ranges_constraint> m_bounded_ranges_constraints;
 477
 478  private:
 479   void add_constraint_internal (equiv_class_id lhs_id,
 480                                 enum constraint_op c_op,
 481                                 equiv_class_id rhs_id);
 482
 483   region_model_manager *m_mgr;
 484 };
 485
 486 } // namespace ana
 487
 488 #endif /* GCC_ANALYZER_CONSTRAINT_MANAGER_H */