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   /* Accumulate to HSTATE a hash of constructor expression EXP.  */
 245   static void add_expr (const_tree exp, inchash::hash &hstate);
 246
 247 private:
 248   /* Initialize internal data structures. Bitmap STACK is used for
 249      bitmap memory allocation process.  */
 250   void setup (bitmap_obstack *stack);
 251 }; // class sem_item
 252
 253 class sem_function: public sem_item
 254 {
 255 public:
 256   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 257   sem_function (bitmap_obstack *stack);
 258
 259   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 260       Bitmap STACK is used for memory allocation.  */
 261   sem_function (cgraph_node *_node, hashval_t _hash, bitmap_obstack *stack);
 262
 263   ~sem_function ();
 264
 265   inline virtual void init_wpa (void)
 266   {
 267     parse_tree_args ();
 268   }
 269
 270   virtual void init (void);
 271   virtual bool equals_wpa (sem_item *item,
 272                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 273   virtual hashval_t get_hash (void);
 274   virtual bool equals (sem_item *item,
 275                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 276   virtual bool merge (sem_item *alias_item);
 277
 278   /* Dump symbol to FILE.  */
 279   virtual void dump_to_file (FILE *file)
 280   {
 281     gcc_assert (file);
 282     dump_function_to_file (decl, file, TDF_DETAILS);
 283   }
 284
 285   /* Parses function arguments and result type.  */
 286   void parse_tree_args (void);
 287
 288   /* Returns cgraph_node.  */
 289   inline cgraph_node *get_node (void)
 290   {
 291     return dyn_cast <cgraph_node *> (node);
 292   }
 293
 294   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 295   void hash_stmt (gimple stmt, inchash::hash &inchash);
 296
 297   /* Return true if polymorphic comparison must be processed.  */
 298   bool compare_polymorphic_p (void);
 299
 300   /* For a given call graph NODE, the function constructs new
 301      semantic function item.  */
 302   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 303
 304   /* Exception handling region tree.  */
 305   eh_region region_tree;
 306
 307   /* Result type tree node.  */
 308   tree result_type;
 309
 310   /* Array of argument tree types.  */
 311   vec <tree> arg_types;
 312
 313   /* Number of function arguments.  */
 314   unsigned int arg_count;
 315
 316   /* Total amount of edges in the function.  */
 317   unsigned int edge_count;
 318
 319   /* Vector of sizes of all basic blocks.  */
 320   vec <unsigned int> bb_sizes;
 321
 322   /* Control flow graph checksum.  */
 323   hashval_t cfg_checksum;
 324
 325   /* GIMPLE codes hash value.  */
 326   hashval_t gcode_hash;
 327
 328   /* Total number of SSA names used in the function.  */
 329   unsigned ssa_names_size;
 330
 331   /* Array of structures for all basic blocks.  */
 332   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 333
 334 private:
 335   /* Calculates hash value based on a BASIC_BLOCK.  */
 336   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 337
 338   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 339      true value is returned if phi nodes are semantically
 340      equivalent in these blocks .  */
 341   bool compare_phi_node (basic_block bb1, basic_block bb2);
 342
 343   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 344      corresponds to TARGET.  */
 345   bool bb_dict_test (vec<int> *bb_dict, int source, int target);
 346
 347   /* Iterates all tree types in T1 and T2 and returns true if all types
 348      are compatible. If COMPARE_POLYMORPHIC is set to true,
 349      more strict comparison is executed.  */
 350   bool compare_type_list (tree t1, tree t2, bool compare_polymorphic);
 351
 352   /* If cgraph edges E1 and E2 are indirect calls, verify that
 353      ICF flags are the same.  */
 354   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 355
 356   /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
 357      point to a same function. Comparison can be skipped if IGNORED_NODES
 358      contains these nodes.  ADDRESS indicate if address is taken.  */
 359   bool compare_cgraph_references (hash_map <symtab_node *, sem_item *>
 360                                   &ignored_nodes,
 361                                   symtab_node *n1, symtab_node *n2,
 362                                   bool address);
 363
 364   /* Processes function equality comparison.  */
 365   bool equals_private (sem_item *item,
 366                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 367
 368   /* Returns true if tree T can be compared as a handled component.  */
 369   static bool icf_handled_component_p (tree t);
 370
 371   /* Function checker stores binding between functions.   */
 372   ipa_icf_gimple::func_checker *m_checker;
 373
 374   /* COMPARED_FUNC is a function that we compare to.  */
 375   sem_function *m_compared_func;
 376 }; // class sem_function
 377
 378 class sem_variable: public sem_item
 379 {
 380 public:
 381   /* Semantic variable constructor that uses STACK as bitmap memory stack.  */
 382   sem_variable (bitmap_obstack *stack);
 383
 384   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 385       Bitmap STACK is used for memory allocation.  */
 386
 387   sem_variable (varpool_node *_node, hashval_t _hash, bitmap_obstack *stack);
 388
 389   inline virtual void init_wpa (void) {}
 390
 391   /* Semantic variable initialization function.  */
 392   inline virtual void init (void)
 393   {
 394     decl = get_node ()->decl;
 395     ctor = ctor_for_folding (decl);
 396   }
 397
 398   virtual hashval_t get_hash (void);
 399   virtual bool merge (sem_item *alias_item);
 400   virtual void dump_to_file (FILE *file);
 401   virtual bool equals (sem_item *item,
 402                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 403
 404   /* Fast equality variable based on knowledge known in WPA.  */
 405   inline virtual bool equals_wpa (sem_item *item,
 406                                   hash_map <symtab_node *, sem_item *> & ARG_UNUSED(ignored_nodes))
 407   {
 408     gcc_assert (item->type == VAR);
 409     return true;
 410   }
 411
 412   /* Returns varpool_node.  */
 413   inline varpool_node *get_node (void)
 414   {
 415     return dyn_cast <varpool_node *> (node);
 416   }
 417
 418   /* Parser function that visits a varpool NODE.  */
 419   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 420
 421   /* Variable constructor.  */
 422   tree ctor;
 423
 424 private:
 425   /* Iterates though a constructor and identifies tree references
 426      we are interested in semantic function equality.  */
 427   void parse_tree_refs (tree t);
 428
 429   /* Compares trees T1 and T2 for semantic equality.  */
 430   static bool equals (tree t1, tree t2);
 431
 432   /* Compare that symbol sections are either NULL or have same name.  */
 433   bool compare_sections (sem_variable *alias);
 434
 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_group_hash: typed_noop_remove <congruence_class_group>
 448 {
 449   typedef congruence_class_group value_type;
 450   typedef congruence_class_group compare_type;
 451
 452   static inline hashval_t hash (const value_type *item)
 453   {
 454     return item->hash;
 455   }
 456
 457   static inline int equal (const value_type *item1, const compare_type *item2)
 458   {
 459     return item1->hash == item2->hash && item1->type == item2->type;
 460   }
 461 };
 462
 463 struct traverse_split_pair
 464 {
 465   sem_item_optimizer *optimizer;
 466   class congruence_class *cls;
 467 };
 468
 469 /* Semantic item optimizer includes all top-level logic
 470    related to semantic equality comparison.  */
 471 class sem_item_optimizer
 472 {
 473 public:
 474   sem_item_optimizer ();
 475   ~sem_item_optimizer ();
 476
 477   /* Function responsible for visiting all potential functions and
 478      read-only variables that can be merged.  */
 479   void parse_funcs_and_vars (void);
 480
 481   /* Optimizer entry point.  */
 482   void execute (void);
 483
 484   /* Dump function. */
 485   void dump (void);
 486
 487   /* Verify congruence classes if checking is enabled.  */
 488   void verify_classes (void);
 489
 490   /* Write IPA ICF summary for symbols.  */
 491   void write_summary (void);
 492
 493   /* Read IPA IPA ICF summary for symbols.  */
 494   void read_summary (void);
 495
 496   /* Callgraph removal hook called for a NODE with a custom DATA.  */
 497   static void cgraph_removal_hook (cgraph_node *node, void *data);
 498
 499   /* Varpool removal hook called for a NODE with a custom DATA.  */
 500   static void varpool_removal_hook (varpool_node *node, void *data);
 501
 502   /* Worklist of congruence classes that can potentially
 503      refine classes of congruence.  */
 504   std::list<congruence_class *> worklist;
 505
 506   /* Remove semantic ITEM and release memory.  */
 507   void remove_item (sem_item *item);
 508
 509   /* Remove symtab NODE triggered by symtab removal hooks.  */
 510   void remove_symtab_node (symtab_node *node);
 511
 512   /* Register callgraph and varpool hooks.  */
 513   void register_hooks (void);
 514
 515   /* Unregister callgraph and varpool hooks.  */
 516   void unregister_hooks (void);
 517
 518   /* Adds a CLS to hashtable associated by hash value.  */
 519   void add_class (congruence_class *cls);
 520
 521   /* Gets a congruence class group based on given HASH value and TYPE.  */
 522   congruence_class_group *get_group_by_hash (hashval_t hash,
 523       sem_item_type type);
 524
 525 private:
 526
 527   /* Congruence classes are built by hash value.  */
 528   void build_hash_based_classes (void);
 529
 530   /* Semantic items in classes having more than one element and initialized.
 531      In case of WPA, we load function body.  */
 532   void parse_nonsingleton_classes (void);
 533
 534   /* Equality function for semantic items is used to subdivide existing
 535      classes. If IN_WPA, fast equality function is invoked.  */
 536   void subdivide_classes_by_equality (bool in_wpa = false);
 537
 538   /* Subdivide classes by address and interposable references
 539      that members of the class reference.
 540      Example can be a pair of functions that have an address
 541      taken from a function. If these addresses are different the class
 542      is split.  */
 543   unsigned subdivide_classes_by_sensitive_refs();
 544
 545   /* Debug function prints all informations about congruence classes.  */
 546   void dump_cong_classes (void);
 547
 548   /* Build references according to call graph.  */
 549   void build_graph (void);
 550
 551   /* Iterative congruence reduction function.  */
 552   void process_cong_reduction (void);
 553
 554   /* After reduction is done, we can declare all items in a group
 555      to be equal. PREV_CLASS_COUNT is start number of classes
 556      before reduction.  */
 557   void merge_classes (unsigned int prev_class_count);
 558
 559   /* Adds a newly created congruence class CLS to worklist.  */
 560   void worklist_push (congruence_class *cls);
 561
 562   /* Pops a class from worklist. */
 563   congruence_class *worklist_pop ();
 564
 565   /* Every usage of a congruence class CLS is a candidate that can split the
 566      collection of classes. Bitmap stack BMSTACK is used for bitmap
 567      allocation.  */
 568   void do_congruence_step (congruence_class *cls);
 569
 570   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 571      Bitmap stack BMSTACK is used for bitmap allocation.  */
 572   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 573
 574   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 575   static void add_item_to_class (congruence_class *cls, sem_item *item);
 576
 577   /* Disposes split map traverse function. CLS is congruence
 578      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 579      but unused argument.  */
 580   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 581                                  traverse_split_pair *pair);
 582
 583   /* Process split operation for a cognruence class CLS,
 584      where bitmap B splits congruence class members. DATA is used
 585      as argument of split pair.  */
 586   static bool traverse_congruence_split (congruence_class * const &cls,
 587                                          bitmap const &b,
 588                                          traverse_split_pair *pair);
 589
 590   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 591      contains LEN bytes.  */
 592   void read_section (lto_file_decl_data *file_data, const char *data,
 593                      size_t len);
 594
 595   /* Removes all callgraph and varpool nodes that are marked by symtab
 596      as deleted.  */
 597   void filter_removed_items (void);
 598
 599   /* Vector of semantic items.  */
 600   vec <sem_item *> m_items;
 601
 602   /* A set containing all items removed by hooks.  */
 603   hash_set <symtab_node *> m_removed_items_set;
 604
 605   /* Hashtable of congruence classes */
 606   hash_table <congruence_class_group_hash> m_classes;
 607
 608   /* Count of congruence classes.  */
 609   unsigned int m_classes_count;
 610
 611   /* Map data structure maps symtab nodes to semantic items.  */
 612   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 613
 614   /* Set to true if a splitter class is removed.  */
 615   bool splitter_class_removed;
 616
 617   /* Global unique class id counter.  */
 618   static unsigned int class_id;
 619
 620   /* Callgraph node removal hook holder.  */
 621   cgraph_node_hook_list *m_cgraph_node_hooks;
 622
 623   /* Varpool node removal hook holder.  */
 624   varpool_node_hook_list *m_varpool_node_hooks;
 625
 626   /* Bitmap stack.  */
 627   bitmap_obstack m_bmstack;
 628 }; // class sem_item_optimizer
 629
 630 } // ipa_icf namespace