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_ptr (v->m_references[i]->ultimate_alias_target ());
 100
 101     hstate.add_int (v->m_interposables.length ());
 102
 103     for (unsigned i = 0; i < v->m_interposables.length (); i++)
 104       hstate.add_ptr (v->m_interposables[i]->ultimate_alias_target ());
 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   /* Gets symbol name of the item.  */
 175   const char *name (void)
 176   {
 177     return node->name ();
 178   }
 179
 180   /* Gets assembler name of the item.  */
 181   const char *asm_name (void)
 182   {
 183     return node->asm_name ();
 184   }
 185
 186   /* Fast equality function based on knowledge known in WPA.  */
 187   virtual bool equals_wpa (sem_item *item,
 188                            hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 189
 190   /* Returns true if the item equals to ITEM given as arguemnt.  */
 191   virtual bool equals (sem_item *item,
 192                        hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 193
 194   /* References independent hash function.  */
 195   virtual hashval_t get_hash (void) = 0;
 196
 197   /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
 198      be applied.  */
 199   virtual bool merge (sem_item *alias_item) = 0;
 200
 201   /* Dump symbol to FILE.  */
 202   virtual void dump_to_file (FILE *file) = 0;
 203
 204   /* Return base tree that can be used for compatible_types_p and
 205      contains_polymorphic_type_p comparison.  */
 206   static bool get_base_types (tree *t1, tree *t2);
 207
 208   /* Return true if target supports alias symbols.  */
 209   bool target_supports_symbol_aliases_p (void);
 210
 211   /* Item type.  */
 212   sem_item_type type;
 213
 214   /* Symtab node.  */
 215   symtab_node *node;
 216
 217   /* Declaration tree node.  */
 218   tree decl;
 219
 220   /* Semantic references used that generate congruence groups.  */
 221   vec <sem_item *> refs;
 222
 223   /* Pointer to a congruence class the item belongs to.  */
 224   congruence_class *cls;
 225
 226   /* Index of the item in a class belonging to.  */
 227   unsigned int index_in_class;
 228
 229   /* List of semantic items where the instance is used.  */
 230   vec <sem_usage_pair *> usages;
 231
 232   /* A bitmap with indices of all classes referencing this item.  */
 233   bitmap usage_index_bitmap;
 234
 235   /* List of tree references (either FUNC_DECL or VAR_DECL).  */
 236   vec <tree> tree_refs;
 237
 238   /* A set with symbol table references.  */
 239   hash_set <symtab_node *> refs_set;
 240
 241 protected:
 242   /* Cached, once calculated hash for the item.  */
 243   hashval_t hash;
 244
 245   /* Accumulate to HSTATE a hash of constructor expression EXP.  */
 246   static void add_expr (const_tree exp, inchash::hash &hstate);
 247
 248   /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
 249      point to a same function. Comparison can be skipped if IGNORED_NODES
 250      contains these nodes.  ADDRESS indicate if address is taken.  */
 251   bool compare_cgraph_references (hash_map <symtab_node *, sem_item *>
 252                                   &ignored_nodes,
 253                                   symtab_node *n1, symtab_node *n2,
 254                                   bool address);
 255
 256 private:
 257   /* Initialize internal data structures. Bitmap STACK is used for
 258      bitmap memory allocation process.  */
 259   void setup (bitmap_obstack *stack);
 260 }; // class sem_item
 261
 262 class sem_function: public sem_item
 263 {
 264 public:
 265   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 266   sem_function (bitmap_obstack *stack);
 267
 268   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 269       Bitmap STACK is used for memory allocation.  */
 270   sem_function (cgraph_node *_node, hashval_t _hash, bitmap_obstack *stack);
 271
 272   ~sem_function ();
 273
 274   inline virtual void init_wpa (void)
 275   {
 276     parse_tree_args ();
 277   }
 278
 279   virtual void init (void);
 280   virtual bool equals_wpa (sem_item *item,
 281                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 282   virtual hashval_t get_hash (void);
 283   virtual bool equals (sem_item *item,
 284                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 285   virtual bool merge (sem_item *alias_item);
 286
 287   /* Dump symbol to FILE.  */
 288   virtual void dump_to_file (FILE *file)
 289   {
 290     gcc_assert (file);
 291     dump_function_to_file (decl, file, TDF_DETAILS);
 292   }
 293
 294   /* Parses function arguments and result type.  */
 295   void parse_tree_args (void);
 296
 297   /* Returns cgraph_node.  */
 298   inline cgraph_node *get_node (void)
 299   {
 300     return dyn_cast <cgraph_node *> (node);
 301   }
 302
 303   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 304   void hash_stmt (gimple stmt, inchash::hash &inchash);
 305
 306   /* Return true if polymorphic comparison must be processed.  */
 307   bool compare_polymorphic_p (void);
 308
 309   /* For a given call graph NODE, the function constructs new
 310      semantic function item.  */
 311   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 312
 313   /* Exception handling region tree.  */
 314   eh_region region_tree;
 315
 316   /* Result type tree node.  */
 317   tree result_type;
 318
 319   /* Array of argument tree types.  */
 320   vec <tree> arg_types;
 321
 322   /* Number of function arguments.  */
 323   unsigned int arg_count;
 324
 325   /* Total amount of edges in the function.  */
 326   unsigned int edge_count;
 327
 328   /* Vector of sizes of all basic blocks.  */
 329   vec <unsigned int> bb_sizes;
 330
 331   /* Control flow graph checksum.  */
 332   hashval_t cfg_checksum;
 333
 334   /* GIMPLE codes hash value.  */
 335   hashval_t gcode_hash;
 336
 337   /* Total number of SSA names used in the function.  */
 338   unsigned ssa_names_size;
 339
 340   /* Array of structures for all basic blocks.  */
 341   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 342
 343 private:
 344   /* Calculates hash value based on a BASIC_BLOCK.  */
 345   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 346
 347   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 348      true value is returned if phi nodes are semantically
 349      equivalent in these blocks .  */
 350   bool compare_phi_node (basic_block bb1, basic_block bb2);
 351
 352   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 353      corresponds to TARGET.  */
 354   bool bb_dict_test (vec<int> *bb_dict, int source, int target);
 355
 356   /* If cgraph edges E1 and E2 are indirect calls, verify that
 357      ICF flags are the same.  */
 358   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 359
 360   /* Processes function equality comparison.  */
 361   bool equals_private (sem_item *item,
 362                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 363
 364   /* Returns true if tree T can be compared as a handled component.  */
 365   static bool icf_handled_component_p (tree t);
 366
 367   /* Function checker stores binding between functions.   */
 368   ipa_icf_gimple::func_checker *m_checker;
 369
 370   /* COMPARED_FUNC is a function that we compare to.  */
 371   sem_function *m_compared_func;
 372 }; // class sem_function
 373
 374 class sem_variable: public sem_item
 375 {
 376 public:
 377   /* Semantic variable constructor that uses STACK as bitmap memory stack.  */
 378   sem_variable (bitmap_obstack *stack);
 379
 380   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 381       Bitmap STACK is used for memory allocation.  */
 382
 383   sem_variable (varpool_node *_node, hashval_t _hash, bitmap_obstack *stack);
 384
 385   inline virtual void init_wpa (void) {}
 386
 387   /* Semantic variable initialization function.  */
 388   inline virtual void init (void)
 389   {
 390     decl = get_node ()->decl;
 391   }
 392
 393   virtual hashval_t get_hash (void);
 394   virtual bool merge (sem_item *alias_item);
 395   virtual void dump_to_file (FILE *file);
 396   virtual bool equals (sem_item *item,
 397                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 398
 399   /* Fast equality variable based on knowledge known in WPA.  */
 400   virtual bool equals_wpa (sem_item *item,
 401                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 402
 403   /* Returns varpool_node.  */
 404   inline varpool_node *get_node (void)
 405   {
 406     return dyn_cast <varpool_node *> (node);
 407   }
 408
 409   /* Parser function that visits a varpool NODE.  */
 410   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 411
 412 private:
 413   /* Compares trees T1 and T2 for semantic equality.  */
 414   static bool equals (tree t1, tree t2);
 415 }; // class sem_variable
 416
 417 class sem_item_optimizer;
 418
 419 struct congruence_class_group
 420 {
 421   hashval_t hash;
 422   sem_item_type type;
 423   vec <congruence_class *> classes;
 424 };
 425
 426 /* Congruence class set structure.  */
 427 struct congruence_class_group_hash: typed_noop_remove <congruence_class_group>
 428 {
 429   typedef congruence_class_group value_type;
 430   typedef congruence_class_group compare_type;
 431
 432   static inline hashval_t hash (const value_type *item)
 433   {
 434     return item->hash;
 435   }
 436
 437   static inline int equal (const value_type *item1, const compare_type *item2)
 438   {
 439     return item1->hash == item2->hash && item1->type == item2->type;
 440   }
 441 };
 442
 443 struct traverse_split_pair
 444 {
 445   sem_item_optimizer *optimizer;
 446   class congruence_class *cls;
 447 };
 448
 449 /* Semantic item optimizer includes all top-level logic
 450    related to semantic equality comparison.  */
 451 class sem_item_optimizer
 452 {
 453 public:
 454   sem_item_optimizer ();
 455   ~sem_item_optimizer ();
 456
 457   /* Function responsible for visiting all potential functions and
 458      read-only variables that can be merged.  */
 459   void parse_funcs_and_vars (void);
 460
 461   /* Optimizer entry point which returns true in case it processes
 462      a merge operation. True is returned if there's a merge operation
 463      processed.  */
 464   bool execute (void);
 465
 466   /* Dump function. */
 467   void dump (void);
 468
 469   /* Verify congruence classes if checking is enabled.  */
 470   void verify_classes (void);
 471
 472   /* Write IPA ICF summary for symbols.  */
 473   void write_summary (void);
 474
 475   /* Read IPA IPA ICF summary for symbols.  */
 476   void read_summary (void);
 477
 478   /* Callgraph removal hook called for a NODE with a custom DATA.  */
 479   static void cgraph_removal_hook (cgraph_node *node, void *data);
 480
 481   /* Varpool removal hook called for a NODE with a custom DATA.  */
 482   static void varpool_removal_hook (varpool_node *node, void *data);
 483
 484   /* Worklist of congruence classes that can potentially
 485      refine classes of congruence.  */
 486   std::list<congruence_class *> worklist;
 487
 488   /* Remove semantic ITEM and release memory.  */
 489   void remove_item (sem_item *item);
 490
 491   /* Remove symtab NODE triggered by symtab removal hooks.  */
 492   void remove_symtab_node (symtab_node *node);
 493
 494   /* Register callgraph and varpool hooks.  */
 495   void register_hooks (void);
 496
 497   /* Unregister callgraph and varpool hooks.  */
 498   void unregister_hooks (void);
 499
 500   /* Adds a CLS to hashtable associated by hash value.  */
 501   void add_class (congruence_class *cls);
 502
 503   /* Gets a congruence class group based on given HASH value and TYPE.  */
 504   congruence_class_group *get_group_by_hash (hashval_t hash,
 505       sem_item_type type);
 506
 507 private:
 508
 509   /* Congruence classes are built by hash value.  */
 510   void build_hash_based_classes (void);
 511
 512   /* Semantic items in classes having more than one element and initialized.
 513      In case of WPA, we load function body.  */
 514   void parse_nonsingleton_classes (void);
 515
 516   /* Equality function for semantic items is used to subdivide existing
 517      classes. If IN_WPA, fast equality function is invoked.  */
 518   void subdivide_classes_by_equality (bool in_wpa = false);
 519
 520   /* Subdivide classes by address and interposable references
 521      that members of the class reference.
 522      Example can be a pair of functions that have an address
 523      taken from a function. If these addresses are different the class
 524      is split.  */
 525   unsigned subdivide_classes_by_sensitive_refs();
 526
 527   /* Debug function prints all informations about congruence classes.  */
 528   void dump_cong_classes (void);
 529
 530   /* Build references according to call graph.  */
 531   void build_graph (void);
 532
 533   /* Iterative congruence reduction function.  */
 534   void process_cong_reduction (void);
 535
 536   /* After reduction is done, we can declare all items in a group
 537      to be equal. PREV_CLASS_COUNT is start number of classes
 538      before reduction. True is returned if there's a merge operation
 539      processed.  */
 540   bool merge_classes (unsigned int prev_class_count);
 541
 542   /* Adds a newly created congruence class CLS to worklist.  */
 543   void worklist_push (congruence_class *cls);
 544
 545   /* Pops a class from worklist. */
 546   congruence_class *worklist_pop ();
 547
 548   /* Every usage of a congruence class CLS is a candidate that can split the
 549      collection of classes. Bitmap stack BMSTACK is used for bitmap
 550      allocation.  */
 551   void do_congruence_step (congruence_class *cls);
 552
 553   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 554      Bitmap stack BMSTACK is used for bitmap allocation.  */
 555   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 556
 557   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 558   static void add_item_to_class (congruence_class *cls, sem_item *item);
 559
 560   /* Disposes split map traverse function. CLS is congruence
 561      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 562      but unused argument.  */
 563   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 564                                  traverse_split_pair *pair);
 565
 566   /* Process split operation for a cognruence class CLS,
 567      where bitmap B splits congruence class members. DATA is used
 568      as argument of split pair.  */
 569   static bool traverse_congruence_split (congruence_class * const &cls,
 570                                          bitmap const &b,
 571                                          traverse_split_pair *pair);
 572
 573   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 574      contains LEN bytes.  */
 575   void read_section (lto_file_decl_data *file_data, const char *data,
 576                      size_t len);
 577
 578   /* Removes all callgraph and varpool nodes that are marked by symtab
 579      as deleted.  */
 580   void filter_removed_items (void);
 581
 582   /* Vector of semantic items.  */
 583   vec <sem_item *> m_items;
 584
 585   /* A set containing all items removed by hooks.  */
 586   hash_set <symtab_node *> m_removed_items_set;
 587
 588   /* Hashtable of congruence classes */
 589   hash_table <congruence_class_group_hash> m_classes;
 590
 591   /* Count of congruence classes.  */
 592   unsigned int m_classes_count;
 593
 594   /* Map data structure maps symtab nodes to semantic items.  */
 595   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 596
 597   /* Set to true if a splitter class is removed.  */
 598   bool splitter_class_removed;
 599
 600   /* Global unique class id counter.  */
 601   static unsigned int class_id;
 602
 603   /* Callgraph node removal hook holder.  */
 604   cgraph_node_hook_list *m_cgraph_node_hooks;
 605
 606   /* Varpool node removal hook holder.  */
 607   varpool_node_hook_list *m_varpool_node_hooks;
 608
 609   /* Bitmap stack.  */
 610   bitmap_obstack m_bmstack;
 611 }; // class sem_item_optimizer
 612
 613 } // ipa_icf namespace