gcc/ipa-icf.h

   1 /* Interprocedural semantic function equality pass
   2    Copyright (C) 2014-2019 Free Software Foundation, Inc.
   3
   4    Contributed by Jan Hubicka <hubicka@ucw.cz> and Martin Liska <mliska@suse.cz>
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it under
   9 the terms of the GNU General Public License as published by the Free
  10 Software Foundation; either version 3, or (at your option) any later
  11 version.
  12
  13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  16 for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 namespace ipa_icf {
  23 class sem_item;
  24
  25 /* Congruence class encompasses a collection of either functions or
  26    read-only variables. These items are considered to be equivalent
  27    if not proved the oposite.  */
  28 class congruence_class
  29 {
  30 public:
  31   /* Congruence class constructor for a new class with _ID.  */
  32   congruence_class (unsigned int _id): in_worklist (false), id(_id)
  33   {
  34   }
  35
  36   /* Destructor.  */
  37   ~congruence_class ()
  38   {
  39   }
  40
  41   /* Dump function prints all class members to a FILE with an INDENT.  */
  42   void dump (FILE *file, unsigned int indent = 0) const;
  43
  44   /* Returns true if there's a member that is used from another group.  */
  45   bool is_class_used (void);
  46
  47   /* Flag is used in case we want to remove a class from worklist and
  48      delete operation is quite expensive for
  49      the data structure (linked list).  */
  50   bool in_worklist;
  51
  52   /* Vector of all group members.  */
  53   auto_vec <sem_item *> members;
  54
  55   /* Global unique class identifier.  */
  56   unsigned int id;
  57 };
  58
  59 /* Semantic item type enum.  */
  60 enum sem_item_type
  61 {
  62   FUNC,
  63   VAR
  64 };
  65
  66 /* Class is container for address references for a symtab_node.  */
  67
  68 class symbol_compare_collection
  69 {
  70 public:
  71   /* Constructor.  */
  72   symbol_compare_collection (symtab_node *node);
  73
  74   /* Destructor.  */
  75   ~symbol_compare_collection ()
  76   {
  77     m_references.release ();
  78     m_interposables.release ();
  79   }
  80
  81   /* Vector of address references.  */
  82   vec<symtab_node *> m_references;
  83
  84   /* Vector of interposable references.  */
  85   vec<symtab_node *> m_interposables;
  86 };
  87
  88 /* Hash traits for symbol_compare_collection map.  */
  89
  90 struct symbol_compare_hash : nofree_ptr_hash <symbol_compare_collection>
  91 {
  92   static hashval_t
  93   hash (value_type v)
  94   {
  95     inchash::hash hstate;
  96     hstate.add_int (v->m_references.length ());
  97
  98     for (unsigned i = 0; i < v->m_references.length (); i++)
  99       hstate.add_int (v->m_references[i]->ultimate_alias_target ()->order);
 100
 101     hstate.add_int (v->m_interposables.length ());
 102
 103     for (unsigned i = 0; i < v->m_interposables.length (); i++)
 104       hstate.add_int (v->m_interposables[i]->ultimate_alias_target ()->order);
 105
 106     return hstate.end ();
 107   }
 108
 109   static bool
 110   equal (value_type a, value_type b)
 111   {
 112     if (a->m_references.length () != b->m_references.length ()
 113         || a->m_interposables.length () != b->m_interposables.length ())
 114       return false;
 115
 116     for (unsigned i = 0; i < a->m_references.length (); i++)
 117       if (a->m_references[i]->equal_address_to (b->m_references[i]) != 1)
 118         return false;
 119
 120     for (unsigned i = 0; i < a->m_interposables.length (); i++)
 121       if (!a->m_interposables[i]->semantically_equivalent_p
 122         (b->m_interposables[i]))
 123         return false;
 124
 125     return true;
 126   }
 127 };
 128
 129
 130 /* Semantic item usage pair.  */
 131 class sem_usage_pair
 132 {
 133 public:
 134   /* Constructor for key value pair, where _ITEM is key and _INDEX is a target.  */
 135   sem_usage_pair (sem_item *_item, unsigned int _index);
 136
 137   /* Target semantic item where an item is used.  */
 138   sem_item *item;
 139
 140   /* Index of usage of such an item.  */
 141   unsigned int index;
 142 };
 143
 144 typedef std::pair<symtab_node *, symtab_node *> symtab_pair;
 145
 146 /* Semantic item is a base class that encapsulates all shared functionality
 147    for both semantic function and variable items.  */
 148 class sem_item
 149 {
 150 public:
 151   /* Semantic item constructor for a node of _TYPE, where STACK is used
 152      for bitmap memory allocation.  */
 153   sem_item (sem_item_type _type, bitmap_obstack *stack);
 154
 155   /* Semantic item constructor for a node of _TYPE, where STACK is used
 156      for bitmap memory allocation.  The item is based on symtab node _NODE.  */
 157   sem_item (sem_item_type _type, symtab_node *_node, bitmap_obstack *stack);
 158
 159   virtual ~sem_item ();
 160
 161   /* Dump function for debugging purpose.  */
 162   DEBUG_FUNCTION void dump (void);
 163
 164   /* Initialize semantic item by info reachable during LTO WPA phase.  */
 165   virtual void init_wpa (void) = 0;
 166
 167   /* Semantic item initialization function.  */
 168   virtual void init (void) = 0;
 169
 170   /* Add reference to a semantic TARGET.  */
 171   void add_reference (sem_item *target);
 172
 173   /* Fast equality function based on knowledge known in WPA.  */
 174   virtual bool equals_wpa (sem_item *item,
 175                            hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 176
 177   /* Returns true if the item equals to ITEM given as arguemnt.  */
 178   virtual bool equals (sem_item *item,
 179                        hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 180
 181   /* References independent hash function.  */
 182   virtual hashval_t get_hash (void) = 0;
 183
 184   /* Set new hash value of the item.  */
 185   void set_hash (hashval_t hash);
 186
 187   /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
 188      be applied.  */
 189   virtual bool merge (sem_item *alias_item) = 0;
 190
 191   /* Dump symbol to FILE.  */
 192   virtual void dump_to_file (FILE *file) = 0;
 193
 194   /* Update hash by address sensitive references.  */
 195   void update_hash_by_addr_refs (hash_map <symtab_node *,
 196                                  sem_item *> &m_symtab_node_map);
 197
 198   /* Update hash by computed local hash values taken from different
 199      semantic items.  */
 200   void update_hash_by_local_refs (hash_map <symtab_node *,
 201                                   sem_item *> &m_symtab_node_map);
 202
 203   /* Return base tree that can be used for compatible_types_p and
 204      contains_polymorphic_type_p comparison.  */
 205   static bool get_base_types (tree *t1, tree *t2);
 206
 207   /* Return true if target supports alias symbols.  */
 208   bool target_supports_symbol_aliases_p (void);
 209
 210   /* Item type.  */
 211   sem_item_type type;
 212
 213   /* Symtab node.  */
 214   symtab_node *node;
 215
 216   /* Declaration tree node.  */
 217   tree decl;
 218
 219   /* Semantic references used that generate congruence groups.  */
 220   vec <sem_item *> refs;
 221
 222   /* Pointer to a congruence class the item belongs to.  */
 223   congruence_class *cls;
 224
 225   /* Index of the item in a class belonging to.  */
 226   unsigned int index_in_class;
 227
 228   /* List of semantic items where the instance is used.  */
 229   vec <sem_usage_pair *> usages;
 230
 231   /* A bitmap with indices of all classes referencing this item.  */
 232   bitmap usage_index_bitmap;
 233
 234   /* List of tree references (either FUNC_DECL or VAR_DECL).  */
 235   vec <tree> tree_refs;
 236
 237   /* A set with symbol table references.  */
 238   hash_set <symtab_node *> refs_set;
 239
 240   /* Temporary hash used where hash values of references are added.  */
 241   hashval_t global_hash;
 242 protected:
 243   /* Cached, once calculated hash for the item.  */
 244
 245   /* Accumulate to HSTATE a hash of expression EXP.  */
 246   static void add_expr (const_tree exp, inchash::hash &hstate);
 247   /* Accumulate to HSTATE a hash of type T.  */
 248   static void add_type (const_tree t, inchash::hash &hstate);
 249
 250   /* Compare properties of symbol that does not affect semantics of symbol
 251      itself but affects semantics of its references.
 252      If ADDRESS is true, do extra checking needed for IPA_REF_ADDR.  */
 253   static bool compare_referenced_symbol_properties (symtab_node *used_by,
 254                                                     symtab_node *n1,
 255                                                     symtab_node *n2,
 256                                                     bool address);
 257
 258   /* Hash properties compared by compare_referenced_symbol_properties.  */
 259   void hash_referenced_symbol_properties (symtab_node *ref,
 260                                           inchash::hash &hstate,
 261                                           bool address);
 262
 263   /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
 264      point to a same function. Comparison can be skipped if IGNORED_NODES
 265      contains these nodes.  ADDRESS indicate if address is taken.  */
 266   bool compare_symbol_references (hash_map <symtab_node *, sem_item *>
 267                                   &ignored_nodes,
 268                                   symtab_node *n1, symtab_node *n2,
 269                                   bool address);
 270 protected:
 271   /* Hash of item.  */
 272   hashval_t m_hash;
 273
 274   /* Indicated whether a hash value has been set or not.  */
 275   bool m_hash_set;
 276
 277 private:
 278   /* Initialize internal data structures. Bitmap STACK is used for
 279      bitmap memory allocation process.  */
 280   void setup (bitmap_obstack *stack);
 281
 282   /* Because types can be arbitrarily large, avoid quadratic bottleneck.  */
 283   static hash_map<const_tree, hashval_t> m_type_hash_cache;
 284 }; // class sem_item
 285
 286 class sem_function: public sem_item
 287 {
 288 public:
 289   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 290   sem_function (bitmap_obstack *stack);
 291
 292   /*  Constructor based on callgraph node _NODE.
 293       Bitmap STACK is used for memory allocation.  */
 294   sem_function (cgraph_node *_node, bitmap_obstack *stack);
 295
 296   ~sem_function ();
 297
 298   inline virtual void init_wpa (void)
 299   {
 300   }
 301
 302   virtual void init (void);
 303   virtual bool equals_wpa (sem_item *item,
 304                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 305   virtual hashval_t get_hash (void);
 306   virtual bool equals (sem_item *item,
 307                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 308   virtual bool merge (sem_item *alias_item);
 309
 310   /* Dump symbol to FILE.  */
 311   virtual void dump_to_file (FILE *file)
 312   {
 313     gcc_assert (file);
 314     dump_function_to_file (decl, file, TDF_DETAILS);
 315   }
 316
 317   /* Returns cgraph_node.  */
 318   inline cgraph_node *get_node (void)
 319   {
 320     return dyn_cast <cgraph_node *> (node);
 321   }
 322
 323   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 324   void hash_stmt (gimple *stmt, inchash::hash &inchash);
 325
 326   /* Return true if polymorphic comparison must be processed.  */
 327   bool compare_polymorphic_p (void);
 328
 329   /* For a given call graph NODE, the function constructs new
 330      semantic function item.  */
 331   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 332
 333   /* Perform additional checks needed to match types of used function
 334      paramters.  */
 335   bool compatible_parm_types_p (tree, tree);
 336
 337   /* Exception handling region tree.  */
 338   eh_region region_tree;
 339
 340   /* Number of function arguments.  */
 341   unsigned int arg_count;
 342
 343   /* Total amount of edges in the function.  */
 344   unsigned int edge_count;
 345
 346   /* Vector of sizes of all basic blocks.  */
 347   vec <unsigned int> bb_sizes;
 348
 349   /* Control flow graph checksum.  */
 350   hashval_t cfg_checksum;
 351
 352   /* GIMPLE codes hash value.  */
 353   hashval_t gcode_hash;
 354
 355   /* Total number of SSA names used in the function.  */
 356   unsigned ssa_names_size;
 357
 358   /* Array of structures for all basic blocks.  */
 359   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 360
 361   /* Return true if parameter I may be used.  */
 362   bool param_used_p (unsigned int i);
 363
 364 private:
 365   /* Calculates hash value based on a BASIC_BLOCK.  */
 366   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 367
 368   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 369      true value is returned if phi nodes are semantically
 370      equivalent in these blocks .  */
 371   bool compare_phi_node (basic_block bb1, basic_block bb2);
 372
 373   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 374      corresponds to TARGET.  */
 375   bool bb_dict_test (vec<int> *bb_dict, int source, int target);
 376
 377   /* If cgraph edges E1 and E2 are indirect calls, verify that
 378      ICF flags are the same.  */
 379   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 380
 381   /* Processes function equality comparison.  */
 382   bool equals_private (sem_item *item);
 383
 384   /* Returns true if tree T can be compared as a handled component.  */
 385   static bool icf_handled_component_p (tree t);
 386
 387   /* Function checker stores binding between functions.   */
 388   ipa_icf_gimple::func_checker *m_checker;
 389
 390   /* COMPARED_FUNC is a function that we compare to.  */
 391   sem_function *m_compared_func;
 392 }; // class sem_function
 393
 394 class sem_variable: public sem_item
 395 {
 396 public:
 397   /* Semantic variable constructor that uses STACK as bitmap memory stack.  */
 398   sem_variable (bitmap_obstack *stack);
 399
 400   /*  Constructor based on callgraph node _NODE.
 401       Bitmap STACK is used for memory allocation.  */
 402
 403   sem_variable (varpool_node *_node, bitmap_obstack *stack);
 404
 405   inline virtual void init_wpa (void) {}
 406
 407   /* Semantic variable initialization function.  */
 408   inline virtual void init (void)
 409   {
 410     decl = get_node ()->decl;
 411   }
 412
 413   virtual hashval_t get_hash (void);
 414   virtual bool merge (sem_item *alias_item);
 415   virtual void dump_to_file (FILE *file);
 416   virtual bool equals (sem_item *item,
 417                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 418
 419   /* Fast equality variable based on knowledge known in WPA.  */
 420   virtual bool equals_wpa (sem_item *item,
 421                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 422
 423   /* Returns varpool_node.  */
 424   inline varpool_node *get_node (void)
 425   {
 426     return dyn_cast <varpool_node *> (node);
 427   }
 428
 429   /* Parser function that visits a varpool NODE.  */
 430   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 431
 432 private:
 433   /* Compares trees T1 and T2 for semantic equality.  */
 434   static bool equals (tree t1, tree t2);
 435 }; // class sem_variable
 436
 437 class sem_item_optimizer;
 438
 439 struct congruence_class_group
 440 {
 441   hashval_t hash;
 442   sem_item_type type;
 443   vec <congruence_class *> classes;
 444 };
 445
 446 /* Congruence class set structure.  */
 447 struct congruence_class_hash : nofree_ptr_hash <congruence_class_group>
 448 {
 449   static inline hashval_t hash (const congruence_class_group *item)
 450   {
 451     return item->hash;
 452   }
 453
 454   static inline int equal (const congruence_class_group *item1,
 455                            const congruence_class_group *item2)
 456   {
 457     return item1->hash == item2->hash && item1->type == item2->type;
 458   }
 459 };
 460
 461 struct traverse_split_pair
 462 {
 463   sem_item_optimizer *optimizer;
 464   class congruence_class *cls;
 465 };
 466
 467 /* Semantic item optimizer includes all top-level logic
 468    related to semantic equality comparison.  */
 469 class sem_item_optimizer
 470 {
 471 public:
 472   sem_item_optimizer ();
 473   ~sem_item_optimizer ();
 474
 475   /* Function responsible for visiting all potential functions and
 476      read-only variables that can be merged.  */
 477   void parse_funcs_and_vars (void);
 478
 479   /* Optimizer entry point which returns true in case it processes
 480      a merge operation. True is returned if there's a merge operation
 481      processed.  */
 482   bool execute (void);
 483
 484   /* Dump function. */
 485   void dump (void);
 486
 487   /* Verify congruence classes if checking is enabled.  */
 488   void checking_verify_classes (void);
 489
 490   /* Verify congruence classes.  */
 491   void verify_classes (void);
 492
 493   /* Write IPA ICF summary for symbols.  */
 494   void write_summary (void);
 495
 496   /* Read IPA ICF summary for symbols.  */
 497   void read_summary (void);
 498
 499   /* Callgraph removal hook called for a NODE with a custom DATA.  */
 500   static void cgraph_removal_hook (cgraph_node *node, void *data);
 501
 502   /* Varpool removal hook called for a NODE with a custom DATA.  */
 503   static void varpool_removal_hook (varpool_node *node, void *data);
 504
 505   /* Worklist of congruence classes that can potentially
 506      refine classes of congruence.  */
 507   std::list<congruence_class *> worklist;
 508
 509   /* Remove semantic ITEM and release memory.  */
 510   void remove_item (sem_item *item);
 511
 512   /* Remove symtab NODE triggered by symtab removal hooks.  */
 513   void remove_symtab_node (symtab_node *node);
 514
 515   /* Register callgraph and varpool hooks.  */
 516   void register_hooks (void);
 517
 518   /* Unregister callgraph and varpool hooks.  */
 519   void unregister_hooks (void);
 520
 521   /* Adds a CLS to hashtable associated by hash value.  */
 522   void add_class (congruence_class *cls);
 523
 524   /* Gets a congruence class group based on given HASH value and TYPE.  */
 525   congruence_class_group *get_group_by_hash (hashval_t hash,
 526       sem_item_type type);
 527 private:
 528
 529   /* For each semantic item, append hash values of references.  */
 530   void update_hash_by_addr_refs ();
 531
 532   /* Congruence classes are built by hash value.  */
 533   void build_hash_based_classes (void);
 534
 535   /* Semantic items in classes having more than one element and initialized.
 536      In case of WPA, we load function body.  */
 537   void parse_nonsingleton_classes (void);
 538
 539   /* Equality function for semantic items is used to subdivide existing
 540      classes. If IN_WPA, fast equality function is invoked.  */
 541   void subdivide_classes_by_equality (bool in_wpa = false);
 542
 543   /* Subdivide classes by address and interposable references
 544      that members of the class reference.
 545      Example can be a pair of functions that have an address
 546      taken from a function. If these addresses are different the class
 547      is split.  */
 548   unsigned subdivide_classes_by_sensitive_refs();
 549
 550   /* Debug function prints all informations about congruence classes.  */
 551   void dump_cong_classes (void);
 552
 553   /* Build references according to call graph.  */
 554   void build_graph (void);
 555
 556   /* Iterative congruence reduction function.  */
 557   void process_cong_reduction (void);
 558
 559   /* After reduction is done, we can declare all items in a group
 560      to be equal. PREV_CLASS_COUNT is start number of classes
 561      before reduction. True is returned if there's a merge operation
 562      processed.  */
 563   bool merge_classes (unsigned int prev_class_count);
 564
 565   /* Fixup points to analysis info.  */
 566   void fixup_points_to_sets (void);
 567
 568   /* Fixup points to set PT.  */
 569   void fixup_pt_set (struct pt_solution *pt);
 570
 571   /* Adds a newly created congruence class CLS to worklist.  */
 572   void worklist_push (congruence_class *cls);
 573
 574   /* Pops a class from worklist. */
 575   congruence_class *worklist_pop ();
 576
 577   /* Every usage of a congruence class CLS is a candidate that can split the
 578      collection of classes. Bitmap stack BMSTACK is used for bitmap
 579      allocation.  */
 580   void do_congruence_step (congruence_class *cls);
 581
 582   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 583      Bitmap stack BMSTACK is used for bitmap allocation.  */
 584   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 585
 586   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 587   static void add_item_to_class (congruence_class *cls, sem_item *item);
 588
 589   /* Disposes split map traverse function. CLS is congruence
 590      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 591      but unused argument.  */
 592   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 593                                  traverse_split_pair *pair);
 594
 595   /* Process split operation for a cognruence class CLS,
 596      where bitmap B splits congruence class members. DATA is used
 597      as argument of split pair.  */
 598   static bool traverse_congruence_split (congruence_class * const &cls,
 599                                          bitmap const &b,
 600                                          traverse_split_pair *pair);
 601
 602   /* Compare function for sorting pairs in do_congruence_step_f.  */
 603   static int sort_congruence_split (const void *, const void *);
 604
 605   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 606      contains LEN bytes.  */
 607   void read_section (lto_file_decl_data *file_data, const char *data,
 608                      size_t len);
 609
 610   /* Removes all callgraph and varpool nodes that are marked by symtab
 611      as deleted.  */
 612   void filter_removed_items (void);
 613
 614   /* Vector of semantic items.  */
 615   vec <sem_item *> m_items;
 616
 617   /* A set containing all items removed by hooks.  */
 618   hash_set <symtab_node *> m_removed_items_set;
 619
 620   /* Hashtable of congruence classes.  */
 621   hash_table <congruence_class_hash> m_classes;
 622
 623   /* Count of congruence classes.  */
 624   unsigned int m_classes_count;
 625
 626   /* Map data structure maps symtab nodes to semantic items.  */
 627   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 628
 629   /* Set to true if a splitter class is removed.  */
 630   bool splitter_class_removed;
 631
 632   /* Global unique class id counter.  */
 633   static unsigned int class_id;
 634
 635   /* Callgraph node removal hook holder.  */
 636   cgraph_node_hook_list *m_cgraph_node_hooks;
 637
 638   /* Varpool node removal hook holder.  */
 639   varpool_node_hook_list *m_varpool_node_hooks;
 640
 641   /* Bitmap stack.  */
 642   bitmap_obstack m_bmstack;
 643
 644   /* Vector of merged variables.  Needed for fixup of points-to-analysis
 645      info.  */
 646   vec <symtab_pair> m_merged_variables;
 647 }; // class sem_item_optimizer
 648
 649 } // ipa_icf namespace