gcc/ipa-icf.h

   1 /* Interprocedural semantic function equality pass
   2    Copyright (C) 2014-2016 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   /* Set new hash value of the item.  */
 185   void set_hash (hashval_t hash);
 186
 187   /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
 188      be applied.  */
 189   virtual bool merge (sem_item *alias_item) = 0;
 190
 191   /* Dump symbol to FILE.  */
 192   virtual void dump_to_file (FILE *file) = 0;
 193
 194   /* Update hash by address sensitive references.  */
 195   void update_hash_by_addr_refs (hash_map <symtab_node *,
 196                                  sem_item *> &m_symtab_node_map);
 197
 198   /* Update hash by computed local hash values taken from different
 199      semantic items.  */
 200   void update_hash_by_local_refs (hash_map <symtab_node *,
 201                                   sem_item *> &m_symtab_node_map);
 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   /* 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 protected:
 274   /* Hash of item.  */
 275   hashval_t m_hash;
 276
 277 private:
 278   /* Initialize internal data structures. Bitmap STACK is used for
 279      bitmap memory allocation process.  */
 280   void setup (bitmap_obstack *stack);
 281 }; // class sem_item
 282
 283 class sem_function: public sem_item
 284 {
 285 public:
 286   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 287   sem_function (bitmap_obstack *stack);
 288
 289   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 290       Bitmap STACK is used for memory allocation.  */
 291   sem_function (cgraph_node *_node, hashval_t _hash, bitmap_obstack *stack);
 292
 293   ~sem_function ();
 294
 295   inline virtual void init_wpa (void)
 296   {
 297   }
 298
 299   virtual void init (void);
 300   virtual bool equals_wpa (sem_item *item,
 301                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 302   virtual hashval_t get_hash (void);
 303   virtual bool equals (sem_item *item,
 304                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 305   virtual bool merge (sem_item *alias_item);
 306
 307   /* Dump symbol to FILE.  */
 308   virtual void dump_to_file (FILE *file)
 309   {
 310     gcc_assert (file);
 311     dump_function_to_file (decl, file, TDF_DETAILS);
 312   }
 313
 314   /* Returns cgraph_node.  */
 315   inline cgraph_node *get_node (void)
 316   {
 317     return dyn_cast <cgraph_node *> (node);
 318   }
 319
 320   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 321   void hash_stmt (gimple *stmt, inchash::hash &inchash);
 322
 323   /* Return true if polymorphic comparison must be processed.  */
 324   bool compare_polymorphic_p (void);
 325
 326   /* For a given call graph NODE, the function constructs new
 327      semantic function item.  */
 328   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 329
 330   /* Perform additional checks needed to match types of used function
 331      paramters.  */
 332   bool compatible_parm_types_p (tree, tree);
 333
 334   /* Exception handling region tree.  */
 335   eh_region region_tree;
 336
 337   /* Number of function arguments.  */
 338   unsigned int arg_count;
 339
 340   /* Total amount of edges in the function.  */
 341   unsigned int edge_count;
 342
 343   /* Vector of sizes of all basic blocks.  */
 344   vec <unsigned int> bb_sizes;
 345
 346   /* Control flow graph checksum.  */
 347   hashval_t cfg_checksum;
 348
 349   /* GIMPLE codes hash value.  */
 350   hashval_t gcode_hash;
 351
 352   /* Total number of SSA names used in the function.  */
 353   unsigned ssa_names_size;
 354
 355   /* Array of structures for all basic blocks.  */
 356   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 357
 358   /* Return true if parameter I may be used.  */
 359   bool param_used_p (unsigned int i);
 360
 361 private:
 362   /* Calculates hash value based on a BASIC_BLOCK.  */
 363   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 364
 365   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 366      true value is returned if phi nodes are semantically
 367      equivalent in these blocks .  */
 368   bool compare_phi_node (basic_block bb1, basic_block bb2);
 369
 370   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 371      corresponds to TARGET.  */
 372   bool bb_dict_test (vec<int> *bb_dict, int source, int target);
 373
 374   /* If cgraph edges E1 and E2 are indirect calls, verify that
 375      ICF flags are the same.  */
 376   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 377
 378   /* Processes function equality comparison.  */
 379   bool equals_private (sem_item *item);
 380
 381   /* Returns true if tree T can be compared as a handled component.  */
 382   static bool icf_handled_component_p (tree t);
 383
 384   /* Function checker stores binding between functions.   */
 385   ipa_icf_gimple::func_checker *m_checker;
 386
 387   /* COMPARED_FUNC is a function that we compare to.  */
 388   sem_function *m_compared_func;
 389 }; // class sem_function
 390
 391 class sem_variable: public sem_item
 392 {
 393 public:
 394   /* Semantic variable constructor that uses STACK as bitmap memory stack.  */
 395   sem_variable (bitmap_obstack *stack);
 396
 397   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 398       Bitmap STACK is used for memory allocation.  */
 399
 400   sem_variable (varpool_node *_node, hashval_t _hash, bitmap_obstack *stack);
 401
 402   inline virtual void init_wpa (void) {}
 403
 404   /* Semantic variable initialization function.  */
 405   inline virtual void init (void)
 406   {
 407     decl = get_node ()->decl;
 408   }
 409
 410   virtual hashval_t get_hash (void);
 411   virtual bool merge (sem_item *alias_item);
 412   virtual void dump_to_file (FILE *file);
 413   virtual bool equals (sem_item *item,
 414                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 415
 416   /* Fast equality variable based on knowledge known in WPA.  */
 417   virtual bool equals_wpa (sem_item *item,
 418                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 419
 420   /* Returns varpool_node.  */
 421   inline varpool_node *get_node (void)
 422   {
 423     return dyn_cast <varpool_node *> (node);
 424   }
 425
 426   /* Parser function that visits a varpool NODE.  */
 427   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 428
 429 private:
 430   /* Compares trees T1 and T2 for semantic equality.  */
 431   static bool equals (tree t1, tree t2);
 432 }; // class sem_variable
 433
 434 class sem_item_optimizer;
 435
 436 struct congruence_class_group
 437 {
 438   hashval_t hash;
 439   sem_item_type type;
 440   vec <congruence_class *> classes;
 441 };
 442
 443 /* Congruence class set structure.  */
 444 struct congruence_class_group_hash : nofree_ptr_hash <congruence_class_group>
 445 {
 446   static inline hashval_t hash (const congruence_class_group *item)
 447   {
 448     return item->hash;
 449   }
 450
 451   static inline int equal (const congruence_class_group *item1,
 452                            const congruence_class_group *item2)
 453   {
 454     return item1->hash == item2->hash && item1->type == item2->type;
 455   }
 456 };
 457
 458 struct traverse_split_pair
 459 {
 460   sem_item_optimizer *optimizer;
 461   class congruence_class *cls;
 462 };
 463
 464 /* Semantic item optimizer includes all top-level logic
 465    related to semantic equality comparison.  */
 466 class sem_item_optimizer
 467 {
 468 public:
 469   sem_item_optimizer ();
 470   ~sem_item_optimizer ();
 471
 472   /* Function responsible for visiting all potential functions and
 473      read-only variables that can be merged.  */
 474   void parse_funcs_and_vars (void);
 475
 476   /* Optimizer entry point which returns true in case it processes
 477      a merge operation. True is returned if there's a merge operation
 478      processed.  */
 479   bool execute (void);
 480
 481   /* Dump function. */
 482   void dump (void);
 483
 484   /* Verify congruence classes if checking is enabled.  */
 485   void checking_verify_classes (void);
 486
 487   /* Verify congruence classes.  */
 488   void verify_classes (void);
 489
 490   /* Write IPA ICF summary for symbols.  */
 491   void write_summary (void);
 492
 493   /* Read 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   /* Because types can be arbitrarily large, avoid quadratic bottleneck.  */
 526   hash_map<const_tree, hashval_t> m_type_hash_cache;
 527 private:
 528
 529   /* For each semantic item, append hash values of references.  */
 530   void update_hash_by_addr_refs ();
 531
 532   /* Congruence classes are built by hash value.  */
 533   void build_hash_based_classes (void);
 534
 535   /* Semantic items in classes having more than one element and initialized.
 536      In case of WPA, we load function body.  */
 537   void parse_nonsingleton_classes (void);
 538
 539   /* Equality function for semantic items is used to subdivide existing
 540      classes. If IN_WPA, fast equality function is invoked.  */
 541   void subdivide_classes_by_equality (bool in_wpa = false);
 542
 543   /* Subdivide classes by address and interposable references
 544      that members of the class reference.
 545      Example can be a pair of functions that have an address
 546      taken from a function. If these addresses are different the class
 547      is split.  */
 548   unsigned subdivide_classes_by_sensitive_refs();
 549
 550   /* Debug function prints all informations about congruence classes.  */
 551   void dump_cong_classes (void);
 552
 553   /* Build references according to call graph.  */
 554   void build_graph (void);
 555
 556   /* Iterative congruence reduction function.  */
 557   void process_cong_reduction (void);
 558
 559   /* After reduction is done, we can declare all items in a group
 560      to be equal. PREV_CLASS_COUNT is start number of classes
 561      before reduction. True is returned if there's a merge operation
 562      processed.  */
 563   bool merge_classes (unsigned int prev_class_count);
 564
 565   /* Adds a newly created congruence class CLS to worklist.  */
 566   void worklist_push (congruence_class *cls);
 567
 568   /* Pops a class from worklist. */
 569   congruence_class *worklist_pop ();
 570
 571   /* Every usage of a congruence class CLS is a candidate that can split the
 572      collection of classes. Bitmap stack BMSTACK is used for bitmap
 573      allocation.  */
 574   void do_congruence_step (congruence_class *cls);
 575
 576   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 577      Bitmap stack BMSTACK is used for bitmap allocation.  */
 578   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 579
 580   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 581   static void add_item_to_class (congruence_class *cls, sem_item *item);
 582
 583   /* Disposes split map traverse function. CLS is congruence
 584      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 585      but unused argument.  */
 586   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 587                                  traverse_split_pair *pair);
 588
 589   /* Process split operation for a cognruence class CLS,
 590      where bitmap B splits congruence class members. DATA is used
 591      as argument of split pair.  */
 592   static bool traverse_congruence_split (congruence_class * const &cls,
 593                                          bitmap const &b,
 594                                          traverse_split_pair *pair);
 595
 596   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 597      contains LEN bytes.  */
 598   void read_section (lto_file_decl_data *file_data, const char *data,
 599                      size_t len);
 600
 601   /* Removes all callgraph and varpool nodes that are marked by symtab
 602      as deleted.  */
 603   void filter_removed_items (void);
 604
 605   /* Vector of semantic items.  */
 606   vec <sem_item *> m_items;
 607
 608   /* A set containing all items removed by hooks.  */
 609   hash_set <symtab_node *> m_removed_items_set;
 610
 611   /* Hashtable of congruence classes */
 612   hash_table <congruence_class_group_hash> m_classes;
 613
 614   /* Count of congruence classes.  */
 615   unsigned int m_classes_count;
 616
 617   /* Map data structure maps symtab nodes to semantic items.  */
 618   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 619
 620   /* Set to true if a splitter class is removed.  */
 621   bool splitter_class_removed;
 622
 623   /* Global unique class id counter.  */
 624   static unsigned int class_id;
 625
 626   /* Callgraph node removal hook holder.  */
 627   cgraph_node_hook_list *m_cgraph_node_hooks;
 628
 629   /* Varpool node removal hook holder.  */
 630   varpool_node_hook_list *m_varpool_node_hooks;
 631
 632   /* Bitmap stack.  */
 633   bitmap_obstack m_bmstack;
 634 }; // class sem_item_optimizer
 635
 636 } // ipa_icf namespace