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