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       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   /* Gets symbol name of the item.  */
 174   const char *name (void)
 175   {
 176     return node->name ();
 177   }
 178
 179   /* Gets assembler name of the item.  */
 180   const char *asm_name (void)
 181   {
 182     return node->asm_name ();
 183   }
 184
 185   /* Fast equality function based on knowledge known in WPA.  */
 186   virtual bool equals_wpa (sem_item *item,
 187                            hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 188
 189   /* Returns true if the item equals to ITEM given as arguemnt.  */
 190   virtual bool equals (sem_item *item,
 191                        hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 192
 193   /* References independent hash function.  */
 194   virtual hashval_t get_hash (void) = 0;
 195
 196   /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
 197      be applied.  */
 198   virtual bool merge (sem_item *alias_item) = 0;
 199
 200   /* Dump symbol to FILE.  */
 201   virtual void dump_to_file (FILE *file) = 0;
 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 protected:
 241   /* Cached, once calculated hash for the item.  */
 242   hashval_t hash;
 243
 244 private:
 245   /* Initialize internal data structures. Bitmap STACK is used for
 246      bitmap memory allocation process.  */
 247   void setup (bitmap_obstack *stack);
 248 }; // class sem_item
 249
 250 class sem_function: public sem_item
 251 {
 252 public:
 253   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 254   sem_function (bitmap_obstack *stack);
 255
 256   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 257       Bitmap STACK is used for memory allocation.  */
 258   sem_function (cgraph_node *_node, hashval_t _hash, bitmap_obstack *stack);
 259
 260   ~sem_function ();
 261
 262   inline virtual void init_wpa (void)
 263   {
 264     parse_tree_args ();
 265   }
 266
 267   virtual void init (void);
 268   virtual bool equals_wpa (sem_item *item,
 269                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 270   virtual hashval_t get_hash (void);
 271   virtual bool equals (sem_item *item,
 272                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 273   virtual bool merge (sem_item *alias_item);
 274
 275   /* Dump symbol to FILE.  */
 276   virtual void dump_to_file (FILE *file)
 277   {
 278     gcc_assert (file);
 279     dump_function_to_file (decl, file, TDF_DETAILS);
 280   }
 281
 282   /* Parses function arguments and result type.  */
 283   void parse_tree_args (void);
 284
 285   /* Returns cgraph_node.  */
 286   inline cgraph_node *get_node (void)
 287   {
 288     return dyn_cast <cgraph_node *> (node);
 289   }
 290
 291   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 292   void hash_stmt (inchash::hash *inchash, gimple stmt);
 293
 294   /* Return true if polymorphic comparison must be processed.  */
 295   bool compare_polymorphic_p (void);
 296
 297   /* For a given call graph NODE, the function constructs new
 298      semantic function item.  */
 299   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 300
 301   /* Exception handling region tree.  */
 302   eh_region region_tree;
 303
 304   /* Result type tree node.  */
 305   tree result_type;
 306
 307   /* Array of argument tree types.  */
 308   vec <tree> arg_types;
 309
 310   /* Number of function arguments.  */
 311   unsigned int arg_count;
 312
 313   /* Total amount of edges in the function.  */
 314   unsigned int edge_count;
 315
 316   /* Vector of sizes of all basic blocks.  */
 317   vec <unsigned int> bb_sizes;
 318
 319   /* Control flow graph checksum.  */
 320   hashval_t cfg_checksum;
 321
 322   /* GIMPLE codes hash value.  */
 323   hashval_t gcode_hash;
 324
 325   /* Total number of SSA names used in the function.  */
 326   unsigned ssa_names_size;
 327
 328   /* Array of structures for all basic blocks.  */
 329   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 330
 331 private:
 332   /* Calculates hash value based on a BASIC_BLOCK.  */
 333   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 334
 335   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 336      true value is returned if phi nodes are semantically
 337      equivalent in these blocks .  */
 338   bool compare_phi_node (basic_block bb1, basic_block bb2);
 339
 340   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 341      corresponds to TARGET.  */
 342   bool bb_dict_test (vec<int> *bb_dict, int source, int target);
 343
 344   /* Iterates all tree types in T1 and T2 and returns true if all types
 345      are compatible. If COMPARE_POLYMORPHIC is set to true,
 346      more strict comparison is executed.  */
 347   bool compare_type_list (tree t1, tree t2, bool compare_polymorphic);
 348
 349   /* If cgraph edges E1 and E2 are indirect calls, verify that
 350      ICF flags are the same.  */
 351   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 352
 353   /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
 354      point to a same function. Comparison can be skipped if IGNORED_NODES
 355      contains these nodes.  */
 356   bool compare_cgraph_references (hash_map <symtab_node *, sem_item *>
 357                                   &ignored_nodes,
 358                                   symtab_node *n1, symtab_node *n2);
 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     ctor = ctor_for_folding (decl);
 392   }
 393
 394   virtual hashval_t get_hash (void);
 395   virtual bool merge (sem_item *alias_item);
 396   virtual void dump_to_file (FILE *file);
 397   virtual bool equals (sem_item *item,
 398                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 399
 400   /* Fast equality variable based on knowledge known in WPA.  */
 401   inline virtual bool equals_wpa (sem_item *item,
 402                                   hash_map <symtab_node *, sem_item *> & ARG_UNUSED(ignored_nodes))
 403   {
 404     gcc_assert (item->type == VAR);
 405     return true;
 406   }
 407
 408   /* Returns varpool_node.  */
 409   inline varpool_node *get_node (void)
 410   {
 411     return dyn_cast <varpool_node *> (node);
 412   }
 413
 414   /* Parser function that visits a varpool NODE.  */
 415   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 416
 417   /* Variable constructor.  */
 418   tree ctor;
 419
 420 private:
 421   /* Iterates though a constructor and identifies tree references
 422      we are interested in semantic function equality.  */
 423   void parse_tree_refs (tree t);
 424
 425   /* Compares trees T1 and T2 for semantic equality.  */
 426   static bool equals (tree t1, tree t2);
 427
 428   /* Compare that symbol sections are either NULL or have same name.  */
 429   bool compare_sections (sem_variable *alias);
 430
 431 }; // class sem_variable
 432
 433 class sem_item_optimizer;
 434
 435 struct congruence_class_group
 436 {
 437   hashval_t hash;
 438   sem_item_type type;
 439   vec <congruence_class *> classes;
 440 };
 441
 442 /* Congruence class set structure.  */
 443 struct congruence_class_group_hash: typed_noop_remove <congruence_class_group>
 444 {
 445   typedef congruence_class_group value_type;
 446   typedef congruence_class_group compare_type;
 447
 448   static inline hashval_t hash (const value_type *item)
 449   {
 450     return item->hash;
 451   }
 452
 453   static inline int equal (const value_type *item1, const compare_type *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.  */
 478   void execute (void);
 479
 480   /* Dump function. */
 481   void dump (void);
 482
 483   /* Verify congruence classes if checking is enabled.  */
 484   void verify_classes (void);
 485
 486   /* Write IPA ICF summary for symbols.  */
 487   void write_summary (void);
 488
 489   /* Read IPA IPA ICF summary for symbols.  */
 490   void read_summary (void);
 491
 492   /* Callgraph removal hook called for a NODE with a custom DATA.  */
 493   static void cgraph_removal_hook (cgraph_node *node, void *data);
 494
 495   /* Varpool removal hook called for a NODE with a custom DATA.  */
 496   static void varpool_removal_hook (varpool_node *node, void *data);
 497
 498   /* Worklist of congruence classes that can potentially
 499      refine classes of congruence.  */
 500   std::list<congruence_class *> worklist;
 501
 502   /* Remove semantic ITEM and release memory.  */
 503   void remove_item (sem_item *item);
 504
 505   /* Remove symtab NODE triggered by symtab removal hooks.  */
 506   void remove_symtab_node (symtab_node *node);
 507
 508   /* Register callgraph and varpool hooks.  */
 509   void register_hooks (void);
 510
 511   /* Unregister callgraph and varpool hooks.  */
 512   void unregister_hooks (void);
 513
 514   /* Adds a CLS to hashtable associated by hash value.  */
 515   void add_class (congruence_class *cls);
 516
 517   /* Gets a congruence class group based on given HASH value and TYPE.  */
 518   congruence_class_group *get_group_by_hash (hashval_t hash,
 519       sem_item_type type);
 520
 521 private:
 522
 523   /* Congruence classes are built by hash value.  */
 524   void build_hash_based_classes (void);
 525
 526   /* Semantic items in classes having more than one element and initialized.
 527      In case of WPA, we load function body.  */
 528   void parse_nonsingleton_classes (void);
 529
 530   /* Equality function for semantic items is used to subdivide existing
 531      classes. If IN_WPA, fast equality function is invoked.  */
 532   void subdivide_classes_by_equality (bool in_wpa = false);
 533
 534   /* Subdivide classes by address and interposable references
 535      that members of the class reference.
 536      Example can be a pair of functions that have an address
 537      taken from a function. If these addresses are different the class
 538      is split.  */
 539   unsigned subdivide_classes_by_sensitive_refs();
 540
 541   /* Debug function prints all informations about congruence classes.  */
 542   void dump_cong_classes (void);
 543
 544   /* Build references according to call graph.  */
 545   void build_graph (void);
 546
 547   /* Iterative congruence reduction function.  */
 548   void process_cong_reduction (void);
 549
 550   /* After reduction is done, we can declare all items in a group
 551      to be equal. PREV_CLASS_COUNT is start number of classes
 552      before reduction.  */
 553   void merge_classes (unsigned int prev_class_count);
 554
 555   /* Adds a newly created congruence class CLS to worklist.  */
 556   void worklist_push (congruence_class *cls);
 557
 558   /* Pops a class from worklist. */
 559   congruence_class *worklist_pop ();
 560
 561   /* Every usage of a congruence class CLS is a candidate that can split the
 562      collection of classes. Bitmap stack BMSTACK is used for bitmap
 563      allocation.  */
 564   void do_congruence_step (congruence_class *cls);
 565
 566   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 567      Bitmap stack BMSTACK is used for bitmap allocation.  */
 568   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 569
 570   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 571   static void add_item_to_class (congruence_class *cls, sem_item *item);
 572
 573   /* Disposes split map traverse function. CLS is congruence
 574      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 575      but unused argument.  */
 576   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 577                                  traverse_split_pair *pair);
 578
 579   /* Process split operation for a cognruence class CLS,
 580      where bitmap B splits congruence class members. DATA is used
 581      as argument of split pair.  */
 582   static bool traverse_congruence_split (congruence_class * const &cls,
 583                                          bitmap const &b,
 584                                          traverse_split_pair *pair);
 585
 586   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 587      contains LEN bytes.  */
 588   void read_section (lto_file_decl_data *file_data, const char *data,
 589                      size_t len);
 590
 591   /* Removes all callgraph and varpool nodes that are marked by symtab
 592      as deleted.  */
 593   void filter_removed_items (void);
 594
 595   /* Vector of semantic items.  */
 596   vec <sem_item *> m_items;
 597
 598   /* A set containing all items removed by hooks.  */
 599   hash_set <symtab_node *> m_removed_items_set;
 600
 601   /* Hashtable of congruence classes */
 602   hash_table <congruence_class_group_hash> m_classes;
 603
 604   /* Count of congruence classes.  */
 605   unsigned int m_classes_count;
 606
 607   /* Map data structure maps symtab nodes to semantic items.  */
 608   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 609
 610   /* Set to true if a splitter class is removed.  */
 611   bool splitter_class_removed;
 612
 613   /* Global unique class id counter.  */
 614   static unsigned int class_id;
 615
 616   /* Callgraph node removal hook holder.  */
 617   cgraph_node_hook_list *m_cgraph_node_hooks;
 618
 619   /* Varpool node removal hook holder.  */
 620   varpool_node_hook_list *m_varpool_node_hooks;
 621
 622   /* Bitmap stack.  */
 623   bitmap_obstack m_bmstack;
 624 }; // class sem_item_optimizer
 625
 626 } // ipa_icf namespace