gcc/ipa-icf.h

   1 /* Interprocedural semantic function equality pass
   2    Copyright (C) 2014-2015 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_hashmap_traits: default_hashmap_traits
  91 {
  92   static hashval_t
  93   hash (const symbol_compare_collection *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_keys (const symbol_compare_collection *a,
 111               const symbol_compare_collection *b)
 112   {
 113     if (a->m_references.length () != b->m_references.length ()
 114         || a->m_interposables.length () != b->m_interposables.length ())
 115       return false;
 116
 117     for (unsigned i = 0; i < a->m_references.length (); i++)
 118       if (a->m_references[i]->equal_address_to (b->m_references[i]) != 1)
 119         return false;
 120
 121     for (unsigned i = 0; i < a->m_interposables.length (); i++)
 122       if (!a->m_interposables[i]->semantically_equivalent_p
 123         (b->m_interposables[i]))
 124         return false;
 125
 126     return true;
 127   }
 128 };
 129
 130
 131 /* Semantic item usage pair.  */
 132 class sem_usage_pair
 133 {
 134 public:
 135   /* Constructor for key value pair, where _ITEM is key and _INDEX is a target.  */
 136   sem_usage_pair (sem_item *_item, unsigned int _index);
 137
 138   /* Target semantic item where an item is used.  */
 139   sem_item *item;
 140
 141   /* Index of usage of such an item.  */
 142   unsigned int index;
 143 };
 144
 145 /* Semantic item is a base class that encapsulates all shared functionality
 146    for both semantic function and variable items.  */
 147 class sem_item
 148 {
 149 public:
 150   /* Semantic item constructor for a node of _TYPE, where STACK is used
 151      for bitmap memory allocation.  */
 152   sem_item (sem_item_type _type, bitmap_obstack *stack);
 153
 154   /* Semantic item constructor for a node of _TYPE, where STACK is used
 155      for bitmap memory allocation. The item is based on symtab node _NODE
 156      with computed _HASH.  */
 157   sem_item (sem_item_type _type, symtab_node *_node, hashval_t _hash,
 158             bitmap_obstack *stack);
 159
 160   virtual ~sem_item ();
 161
 162   /* Dump function for debugging purpose.  */
 163   DEBUG_FUNCTION void dump (void);
 164
 165   /* Initialize semantic item by info reachable during LTO WPA phase.  */
 166   virtual void init_wpa (void) = 0;
 167
 168   /* Semantic item initialization function.  */
 169   virtual void init (void) = 0;
 170
 171   /* Add reference to a semantic TARGET.  */
 172   void add_reference (sem_item *target);
 173
 174   /* Fast equality function based on knowledge known in WPA.  */
 175   virtual bool equals_wpa (sem_item *item,
 176                            hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 177
 178   /* Returns true if the item equals to ITEM given as arguemnt.  */
 179   virtual bool equals (sem_item *item,
 180                        hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 181
 182   /* References independent hash function.  */
 183   virtual hashval_t get_hash (void) = 0;
 184
 185   /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
 186      be applied.  */
 187   virtual bool merge (sem_item *alias_item) = 0;
 188
 189   /* Dump symbol to FILE.  */
 190   virtual void dump_to_file (FILE *file) = 0;
 191
 192   /* Update hash by address sensitive references.  */
 193   void update_hash_by_addr_refs (hash_map <symtab_node *,
 194                                  sem_item *> &m_symtab_node_map);
 195
 196   /* Update hash by computed local hash values taken from different
 197      semantic items.  */
 198   void update_hash_by_local_refs (hash_map <symtab_node *,
 199                                   sem_item *> &m_symtab_node_map);
 200
 201   /* Return base tree that can be used for compatible_types_p and
 202      contains_polymorphic_type_p comparison.  */
 203   static bool get_base_types (tree *t1, tree *t2);
 204
 205   /* Return true if target supports alias symbols.  */
 206   bool target_supports_symbol_aliases_p (void);
 207
 208   /* Item type.  */
 209   sem_item_type type;
 210
 211   /* Symtab node.  */
 212   symtab_node *node;
 213
 214   /* Declaration tree node.  */
 215   tree decl;
 216
 217   /* Semantic references used that generate congruence groups.  */
 218   vec <sem_item *> refs;
 219
 220   /* Pointer to a congruence class the item belongs to.  */
 221   congruence_class *cls;
 222
 223   /* Index of the item in a class belonging to.  */
 224   unsigned int index_in_class;
 225
 226   /* List of semantic items where the instance is used.  */
 227   vec <sem_usage_pair *> usages;
 228
 229   /* A bitmap with indices of all classes referencing this item.  */
 230   bitmap usage_index_bitmap;
 231
 232   /* List of tree references (either FUNC_DECL or VAR_DECL).  */
 233   vec <tree> tree_refs;
 234
 235   /* A set with symbol table references.  */
 236   hash_set <symtab_node *> refs_set;
 237
 238   /* Hash of item.  */
 239   hashval_t hash;
 240
 241   /* Temporary hash used where hash values of references are added.  */
 242   hashval_t global_hash;
 243 protected:
 244   /* Cached, once calculated hash for the item.  */
 245
 246   /* Accumulate to HSTATE a hash of expression EXP.  */
 247   static void add_expr (const_tree exp, inchash::hash &hstate);
 248   /* Accumulate to HSTATE a hash of type T.  */
 249   static void add_type (const_tree t, inchash::hash &hstate);
 250
 251   /* Compare properties of symbol that does not affect semantics of symbol
 252      itself but affects semantics of its references.
 253      If ADDRESS is true, do extra checking needed for IPA_REF_ADDR.  */
 254   static bool compare_referenced_symbol_properties (symtab_node *used_by,
 255                                                     symtab_node *n1,
 256                                                     symtab_node *n2,
 257                                                     bool address);
 258
 259   /* Compare two attribute lists.  */
 260   static bool compare_attributes (const_tree list1, const_tree list2);
 261
 262   /* Hash properties compared by compare_referenced_symbol_properties.  */
 263   void hash_referenced_symbol_properties (symtab_node *ref,
 264                                           inchash::hash &hstate,
 265                                           bool address);
 266
 267   /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
 268      point to a same function. Comparison can be skipped if IGNORED_NODES
 269      contains these nodes.  ADDRESS indicate if address is taken.  */
 270   bool compare_symbol_references (hash_map <symtab_node *, sem_item *>
 271                                   &ignored_nodes,
 272                                   symtab_node *n1, symtab_node *n2,
 273                                   bool address);
 274
 275 private:
 276   /* Initialize internal data structures. Bitmap STACK is used for
 277      bitmap memory allocation process.  */
 278   void setup (bitmap_obstack *stack);
 279 }; // class sem_item
 280
 281 class sem_function: public sem_item
 282 {
 283 public:
 284   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 285   sem_function (bitmap_obstack *stack);
 286
 287   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 288       Bitmap STACK is used for memory allocation.  */
 289   sem_function (cgraph_node *_node, hashval_t _hash, bitmap_obstack *stack);
 290
 291   ~sem_function ();
 292
 293   inline virtual void init_wpa (void)
 294   {
 295   }
 296
 297   virtual void init (void);
 298   virtual bool equals_wpa (sem_item *item,
 299                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 300   virtual hashval_t get_hash (void);
 301   virtual bool equals (sem_item *item,
 302                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 303   virtual bool merge (sem_item *alias_item);
 304
 305   /* Dump symbol to FILE.  */
 306   virtual void dump_to_file (FILE *file)
 307   {
 308     gcc_assert (file);
 309     dump_function_to_file (decl, file, TDF_DETAILS);
 310   }
 311
 312   /* Returns cgraph_node.  */
 313   inline cgraph_node *get_node (void)
 314   {
 315     return dyn_cast <cgraph_node *> (node);
 316   }
 317
 318   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 319   void hash_stmt (gimple stmt, inchash::hash &inchash);
 320
 321   /* Return true if polymorphic comparison must be processed.  */
 322   bool compare_polymorphic_p (void);
 323
 324   /* For a given call graph NODE, the function constructs new
 325      semantic function item.  */
 326   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 327
 328   /* Perform additional checks needed to match types of used function
 329      paramters.  */
 330   bool compatible_parm_types_p (tree, tree);
 331
 332   /* Exception handling region tree.  */
 333   eh_region region_tree;
 334
 335   /* Number of function arguments.  */
 336   unsigned int arg_count;
 337
 338   /* Total amount of edges in the function.  */
 339   unsigned int edge_count;
 340
 341   /* Vector of sizes of all basic blocks.  */
 342   vec <unsigned int> bb_sizes;
 343
 344   /* Control flow graph checksum.  */
 345   hashval_t cfg_checksum;
 346
 347   /* GIMPLE codes hash value.  */
 348   hashval_t gcode_hash;
 349
 350   /* Total number of SSA names used in the function.  */
 351   unsigned ssa_names_size;
 352
 353   /* Array of structures for all basic blocks.  */
 354   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 355
 356   /* Return true if parameter I may be used.  */
 357   bool param_used_p (unsigned int i);
 358
 359 private:
 360   /* Calculates hash value based on a BASIC_BLOCK.  */
 361   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 362
 363   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 364      true value is returned if phi nodes are semantically
 365      equivalent in these blocks .  */
 366   bool compare_phi_node (basic_block bb1, basic_block bb2);
 367
 368   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 369      corresponds to TARGET.  */
 370   bool bb_dict_test (vec<int> *bb_dict, int source, int target);
 371
 372   /* If cgraph edges E1 and E2 are indirect calls, verify that
 373      ICF flags are the same.  */
 374   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 375
 376   /* Processes function equality comparison.  */
 377   bool equals_private (sem_item *item);
 378
 379   /* Returns true if tree T can be compared as a handled component.  */
 380   static bool icf_handled_component_p (tree t);
 381
 382   /* Function checker stores binding between functions.   */
 383   ipa_icf_gimple::func_checker *m_checker;
 384
 385   /* COMPARED_FUNC is a function that we compare to.  */
 386   sem_function *m_compared_func;
 387 }; // class sem_function
 388
 389 class sem_variable: public sem_item
 390 {
 391 public:
 392   /* Semantic variable constructor that uses STACK as bitmap memory stack.  */
 393   sem_variable (bitmap_obstack *stack);
 394
 395   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 396       Bitmap STACK is used for memory allocation.  */
 397
 398   sem_variable (varpool_node *_node, hashval_t _hash, bitmap_obstack *stack);
 399
 400   inline virtual void init_wpa (void) {}
 401
 402   /* Semantic variable initialization function.  */
 403   inline virtual void init (void)
 404   {
 405     decl = get_node ()->decl;
 406   }
 407
 408   virtual hashval_t get_hash (void);
 409   virtual bool merge (sem_item *alias_item);
 410   virtual void dump_to_file (FILE *file);
 411   virtual bool equals (sem_item *item,
 412                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 413
 414   /* Fast equality variable based on knowledge known in WPA.  */
 415   virtual bool equals_wpa (sem_item *item,
 416                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 417
 418   /* Returns varpool_node.  */
 419   inline varpool_node *get_node (void)
 420   {
 421     return dyn_cast <varpool_node *> (node);
 422   }
 423
 424   /* Parser function that visits a varpool NODE.  */
 425   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 426
 427 private:
 428   /* Compares trees T1 and T2 for semantic equality.  */
 429   static bool equals (tree t1, tree t2);
 430 }; // class sem_variable
 431
 432 class sem_item_optimizer;
 433
 434 struct congruence_class_group
 435 {
 436   hashval_t hash;
 437   sem_item_type type;
 438   vec <congruence_class *> classes;
 439 };
 440
 441 /* Congruence class set structure.  */
 442 struct congruence_class_group_hash: typed_noop_remove <congruence_class_group>
 443 {
 444   typedef congruence_class_group *value_type;
 445   typedef congruence_class_group *compare_type;
 446
 447   static inline hashval_t hash (const congruence_class_group *item)
 448   {
 449     return item->hash;
 450   }
 451
 452   static inline int equal (const congruence_class_group *item1,
 453                            const congruence_class_group *item2)
 454   {
 455     return item1->hash == item2->hash && item1->type == item2->type;
 456   }
 457 };
 458
 459 struct traverse_split_pair
 460 {
 461   sem_item_optimizer *optimizer;
 462   class congruence_class *cls;
 463 };
 464
 465 /* Semantic item optimizer includes all top-level logic
 466    related to semantic equality comparison.  */
 467 class sem_item_optimizer
 468 {
 469 public:
 470   sem_item_optimizer ();
 471   ~sem_item_optimizer ();
 472
 473   /* Function responsible for visiting all potential functions and
 474      read-only variables that can be merged.  */
 475   void parse_funcs_and_vars (void);
 476
 477   /* Optimizer entry point which returns true in case it processes
 478      a merge operation. True is returned if there's a merge operation
 479      processed.  */
 480   bool execute (void);
 481
 482   /* Dump function. */
 483   void dump (void);
 484
 485   /* Verify congruence classes if checking is enabled.  */
 486   void verify_classes (void);
 487
 488   /* Write IPA ICF summary for symbols.  */
 489   void write_summary (void);
 490
 491   /* Read IPA IPA ICF summary for symbols.  */
 492   void read_summary (void);
 493
 494   /* Callgraph removal hook called for a NODE with a custom DATA.  */
 495   static void cgraph_removal_hook (cgraph_node *node, void *data);
 496
 497   /* Varpool removal hook called for a NODE with a custom DATA.  */
 498   static void varpool_removal_hook (varpool_node *node, void *data);
 499
 500   /* Worklist of congruence classes that can potentially
 501      refine classes of congruence.  */
 502   std::list<congruence_class *> worklist;
 503
 504   /* Remove semantic ITEM and release memory.  */
 505   void remove_item (sem_item *item);
 506
 507   /* Remove symtab NODE triggered by symtab removal hooks.  */
 508   void remove_symtab_node (symtab_node *node);
 509
 510   /* Register callgraph and varpool hooks.  */
 511   void register_hooks (void);
 512
 513   /* Unregister callgraph and varpool hooks.  */
 514   void unregister_hooks (void);
 515
 516   /* Adds a CLS to hashtable associated by hash value.  */
 517   void add_class (congruence_class *cls);
 518
 519   /* Gets a congruence class group based on given HASH value and TYPE.  */
 520   congruence_class_group *get_group_by_hash (hashval_t hash,
 521       sem_item_type type);
 522
 523   /* Because types can be arbitrarily large, avoid quadratic bottleneck.  */
 524   hash_map<const_tree, hashval_t> m_type_hash_cache;
 525 private:
 526
 527   /* For each semantic item, append hash values of references.  */
 528   void update_hash_by_addr_refs ();
 529
 530   /* Congruence classes are built by hash value.  */
 531   void build_hash_based_classes (void);
 532
 533   /* Semantic items in classes having more than one element and initialized.
 534      In case of WPA, we load function body.  */
 535   void parse_nonsingleton_classes (void);
 536
 537   /* Equality function for semantic items is used to subdivide existing
 538      classes. If IN_WPA, fast equality function is invoked.  */
 539   void subdivide_classes_by_equality (bool in_wpa = false);
 540
 541   /* Subdivide classes by address and interposable references
 542      that members of the class reference.
 543      Example can be a pair of functions that have an address
 544      taken from a function. If these addresses are different the class
 545      is split.  */
 546   unsigned subdivide_classes_by_sensitive_refs();
 547
 548   /* Debug function prints all informations about congruence classes.  */
 549   void dump_cong_classes (void);
 550
 551   /* Build references according to call graph.  */
 552   void build_graph (void);
 553
 554   /* Iterative congruence reduction function.  */
 555   void process_cong_reduction (void);
 556
 557   /* After reduction is done, we can declare all items in a group
 558      to be equal. PREV_CLASS_COUNT is start number of classes
 559      before reduction. True is returned if there's a merge operation
 560      processed.  */
 561   bool merge_classes (unsigned int prev_class_count);
 562
 563   /* Adds a newly created congruence class CLS to worklist.  */
 564   void worklist_push (congruence_class *cls);
 565
 566   /* Pops a class from worklist. */
 567   congruence_class *worklist_pop ();
 568
 569   /* Every usage of a congruence class CLS is a candidate that can split the
 570      collection of classes. Bitmap stack BMSTACK is used for bitmap
 571      allocation.  */
 572   void do_congruence_step (congruence_class *cls);
 573
 574   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 575      Bitmap stack BMSTACK is used for bitmap allocation.  */
 576   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 577
 578   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 579   static void add_item_to_class (congruence_class *cls, sem_item *item);
 580
 581   /* Disposes split map traverse function. CLS is congruence
 582      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 583      but unused argument.  */
 584   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 585                                  traverse_split_pair *pair);
 586
 587   /* Process split operation for a cognruence class CLS,
 588      where bitmap B splits congruence class members. DATA is used
 589      as argument of split pair.  */
 590   static bool traverse_congruence_split (congruence_class * const &cls,
 591                                          bitmap const &b,
 592                                          traverse_split_pair *pair);
 593
 594   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 595      contains LEN bytes.  */
 596   void read_section (lto_file_decl_data *file_data, const char *data,
 597                      size_t len);
 598
 599   /* Removes all callgraph and varpool nodes that are marked by symtab
 600      as deleted.  */
 601   void filter_removed_items (void);
 602
 603   /* Vector of semantic items.  */
 604   vec <sem_item *> m_items;
 605
 606   /* A set containing all items removed by hooks.  */
 607   hash_set <symtab_node *> m_removed_items_set;
 608
 609   /* Hashtable of congruence classes */
 610   hash_table <congruence_class_group_hash> m_classes;
 611
 612   /* Count of congruence classes.  */
 613   unsigned int m_classes_count;
 614
 615   /* Map data structure maps symtab nodes to semantic items.  */
 616   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 617
 618   /* Set to true if a splitter class is removed.  */
 619   bool splitter_class_removed;
 620
 621   /* Global unique class id counter.  */
 622   static unsigned int class_id;
 623
 624   /* Callgraph node removal hook holder.  */
 625   cgraph_node_hook_list *m_cgraph_node_hooks;
 626
 627   /* Varpool node removal hook holder.  */
 628   varpool_node_hook_list *m_varpool_node_hooks;
 629
 630   /* Bitmap stack.  */
 631   bitmap_obstack m_bmstack;
 632 }; // class sem_item_optimizer
 633
 634 } // ipa_icf namespace