gcc/ipa-icf.h

   1 /* Interprocedural semantic function equality pass
   2    Copyright (C) 2014 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 /* Semantic item usage pair.  */
  67 class sem_usage_pair
  68 {
  69 public:
  70   /* Constructor for key value pair, where _ITEM is key and _INDEX is a target.  */
  71   sem_usage_pair (sem_item *_item, unsigned int _index);
  72
  73   /* Target semantic item where an item is used.  */
  74   sem_item *item;
  75
  76   /* Index of usage of such an item.  */
  77   unsigned int index;
  78 };
  79
  80 /* Semantic item is a base class that encapsulates all shared functionality
  81    for both semantic function and variable items.  */
  82 class sem_item
  83 {
  84 public:
  85   /* Semantic item constructor for a node of _TYPE, where STACK is used
  86      for bitmap memory allocation.  */
  87   sem_item (sem_item_type _type, bitmap_obstack *stack);
  88
  89   /* Semantic item constructor for a node of _TYPE, where STACK is used
  90      for bitmap memory allocation. The item is based on symtab node _NODE
  91      with computed _HASH.  */
  92   sem_item (sem_item_type _type, symtab_node *_node, hashval_t _hash,
  93             bitmap_obstack *stack);
  94
  95   virtual ~sem_item ();
  96
  97   /* Dump function for debugging purpose.  */
  98   DEBUG_FUNCTION void dump (void);
  99
 100   /* Initialize semantic item by info reachable during LTO WPA phase.  */
 101   virtual void init_wpa (void) = 0;
 102
 103   /* Semantic item initialization function.  */
 104   virtual void init (void) = 0;
 105
 106   /* Add reference to a semantic TARGET.  */
 107   void add_reference (sem_item *target);
 108
 109   /* Gets symbol name of the item.  */
 110   const char *name (void)
 111   {
 112     return node->name ();
 113   }
 114
 115   /* Gets assembler name of the item.  */
 116   const char *asm_name (void)
 117   {
 118     return node->asm_name ();
 119   }
 120
 121   /* Fast equality function based on knowledge known in WPA.  */
 122   virtual bool equals_wpa (sem_item *item,
 123                            hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 124
 125   /* Returns true if the item equals to ITEM given as arguemnt.  */
 126   virtual bool equals (sem_item *item,
 127                        hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
 128
 129   /* References independent hash function.  */
 130   virtual hashval_t get_hash (void) = 0;
 131
 132   /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
 133      be applied.  */
 134   virtual bool merge (sem_item *alias_item) = 0;
 135
 136   /* Dump symbol to FILE.  */
 137   virtual void dump_to_file (FILE *file) = 0;
 138
 139   /* Return base tree that can be used for compatible_types_p and
 140      contains_polymorphic_type_p comparison.  */
 141
 142   static bool get_base_types (tree *t1, tree *t2);
 143
 144   /* Item type.  */
 145   sem_item_type type;
 146
 147   /* Symtab node.  */
 148   symtab_node *node;
 149
 150   /* Declaration tree node.  */
 151   tree decl;
 152
 153   /* Semantic references used that generate congruence groups.  */
 154   vec <sem_item *> refs;
 155
 156   /* Pointer to a congruence class the item belongs to.  */
 157   congruence_class *cls;
 158
 159   /* Index of the item in a class belonging to.  */
 160   unsigned int index_in_class;
 161
 162   /* List of semantic items where the instance is used.  */
 163   vec <sem_usage_pair *> usages;
 164
 165   /* A bitmap with indices of all classes referencing this item.  */
 166   bitmap usage_index_bitmap;
 167
 168   /* List of tree references (either FUNC_DECL or VAR_DECL).  */
 169   vec <tree> tree_refs;
 170
 171   /* A set with symbol table references.  */
 172   hash_set <symtab_node *> refs_set;
 173
 174 protected:
 175   /* Cached, once calculated hash for the item.  */
 176   hashval_t hash;
 177
 178 private:
 179   /* Initialize internal data structures. Bitmap STACK is used for
 180      bitmap memory allocation process.  */
 181   void setup (bitmap_obstack *stack);
 182 }; // class sem_item
 183
 184 class sem_function: public sem_item
 185 {
 186 public:
 187   /* Semantic function constructor that uses STACK as bitmap memory stack.  */
 188   sem_function (bitmap_obstack *stack);
 189
 190   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 191       Bitmap STACK is used for memory allocation.  */
 192   sem_function (cgraph_node *_node, hashval_t _hash, bitmap_obstack *stack);
 193
 194   ~sem_function ();
 195
 196   inline virtual void init_wpa (void)
 197   {
 198     parse_tree_args ();
 199   }
 200
 201   virtual void init (void);
 202   virtual bool equals_wpa (sem_item *item,
 203                            hash_map <symtab_node *, sem_item *> &ignored_nodes);
 204   virtual hashval_t get_hash (void);
 205   virtual bool equals (sem_item *item,
 206                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 207   virtual bool merge (sem_item *alias_item);
 208
 209   /* Dump symbol to FILE.  */
 210   virtual void dump_to_file (FILE *file)
 211   {
 212     gcc_assert (file);
 213     dump_function_to_file (decl, file, TDF_DETAILS);
 214   }
 215
 216   /* Parses function arguments and result type.  */
 217   void parse_tree_args (void);
 218
 219   /* Returns cgraph_node.  */
 220   inline cgraph_node *get_node (void)
 221   {
 222     return dyn_cast <cgraph_node *> (node);
 223   }
 224
 225   /* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */
 226   void hash_stmt (inchash::hash *inchash, gimple stmt);
 227
 228   /* Return true if polymorphic comparison must be processed.  */
 229   bool compare_polymorphic_p (void);
 230
 231   /* For a given call graph NODE, the function constructs new
 232      semantic function item.  */
 233   static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
 234
 235   /* Exception handling region tree.  */
 236   eh_region region_tree;
 237
 238   /* Result type tree node.  */
 239   tree result_type;
 240
 241   /* Array of argument tree types.  */
 242   vec <tree> arg_types;
 243
 244   /* Number of function arguments.  */
 245   unsigned int arg_count;
 246
 247   /* Total amount of edges in the function.  */
 248   unsigned int edge_count;
 249
 250   /* Vector of sizes of all basic blocks.  */
 251   vec <unsigned int> bb_sizes;
 252
 253   /* Control flow graph checksum.  */
 254   hashval_t cfg_checksum;
 255
 256   /* GIMPLE codes hash value.  */
 257   hashval_t gcode_hash;
 258
 259   /* Total number of SSA names used in the function.  */
 260   unsigned ssa_names_size;
 261
 262   /* Array of structures for all basic blocks.  */
 263   vec <ipa_icf_gimple::sem_bb *> bb_sorted;
 264
 265 private:
 266   /* Calculates hash value based on a BASIC_BLOCK.  */
 267   hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
 268
 269   /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
 270      true value is returned if phi nodes are semantically
 271      equivalent in these blocks .  */
 272   bool compare_phi_node (basic_block bb1, basic_block bb2);
 273
 274   /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
 275      corresponds to TARGET.  */
 276   bool bb_dict_test (int* bb_dict, int source, int target);
 277
 278   /* Iterates all tree types in T1 and T2 and returns true if all types
 279      are compatible. If COMPARE_POLYMORPHIC is set to true,
 280      more strict comparison is executed.  */
 281   bool compare_type_list (tree t1, tree t2, bool compare_polymorphic);
 282
 283   /* If cgraph edges E1 and E2 are indirect calls, verify that
 284      ICF flags are the same.  */
 285   bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
 286
 287   /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
 288      point to a same function. Comparison can be skipped if IGNORED_NODES
 289      contains these nodes.  */
 290   bool compare_cgraph_references (hash_map <symtab_node *, sem_item *>
 291                                   &ignored_nodes,
 292                                   symtab_node *n1, symtab_node *n2);
 293
 294   /* Processes function equality comparison.  */
 295   bool equals_private (sem_item *item,
 296                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 297
 298   /* Returns true if tree T can be compared as a handled component.  */
 299   static bool icf_handled_component_p (tree t);
 300
 301   /* Function checker stores binding between functions.   */
 302   ipa_icf_gimple::func_checker *m_checker;
 303
 304   /* COMPARED_FUNC is a function that we compare to.  */
 305   sem_function *m_compared_func;
 306 }; // class sem_function
 307
 308 class sem_variable: public sem_item
 309 {
 310 public:
 311   /* Semantic variable constructor that uses STACK as bitmap memory stack.  */
 312   sem_variable (bitmap_obstack *stack);
 313
 314   /*  Constructor based on callgraph node _NODE with computed hash _HASH.
 315       Bitmap STACK is used for memory allocation.  */
 316
 317   sem_variable (varpool_node *_node, hashval_t _hash, bitmap_obstack *stack);
 318
 319   inline virtual void init_wpa (void) {}
 320
 321   /* Semantic variable initialization function.  */
 322   inline virtual void init (void)
 323   {
 324     decl = get_node ()->decl;
 325     ctor = ctor_for_folding (decl);
 326   }
 327
 328   virtual hashval_t get_hash (void);
 329   virtual bool merge (sem_item *alias_item);
 330   virtual void dump_to_file (FILE *file);
 331   virtual bool equals (sem_item *item,
 332                        hash_map <symtab_node *, sem_item *> &ignored_nodes);
 333
 334   /* Fast equality variable based on knowledge known in WPA.  */
 335   inline virtual bool equals_wpa (sem_item *item,
 336                                   hash_map <symtab_node *, sem_item *> & ARG_UNUSED(ignored_nodes))
 337   {
 338     gcc_assert (item->type == VAR);
 339     return true;
 340   }
 341
 342   /* Returns varpool_node.  */
 343   inline varpool_node *get_node (void)
 344   {
 345     return dyn_cast <varpool_node *> (node);
 346   }
 347
 348   /* Parser function that visits a varpool NODE.  */
 349   static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
 350
 351   /* Variable constructor.  */
 352   tree ctor;
 353
 354 private:
 355   /* Iterates though a constructor and identifies tree references
 356      we are interested in semantic function equality.  */
 357   void parse_tree_refs (tree t);
 358
 359   /* Compares trees T1 and T2 for semantic equality.  */
 360   static bool equals (tree t1, tree t2);
 361
 362   /* Compare that symbol sections are either NULL or have same name.  */
 363   bool compare_sections (sem_variable *alias);
 364
 365 }; // class sem_variable
 366
 367 class sem_item_optimizer;
 368
 369 struct congruence_class_group
 370 {
 371   hashval_t hash;
 372   sem_item_type type;
 373   vec <congruence_class *> classes;
 374 };
 375
 376 /* Congruence class set structure.  */
 377 struct congruence_class_group_hash: typed_noop_remove <congruence_class_group>
 378 {
 379   typedef congruence_class_group value_type;
 380   typedef congruence_class_group compare_type;
 381
 382   static inline hashval_t hash (const value_type *item)
 383   {
 384     return item->hash;
 385   }
 386
 387   static inline int equal (const value_type *item1, const compare_type *item2)
 388   {
 389     return item1->hash == item2->hash && item1->type == item2->type;
 390   }
 391 };
 392
 393 struct traverse_split_pair
 394 {
 395   sem_item_optimizer *optimizer;
 396   class congruence_class *cls;
 397 };
 398
 399 /* Semantic item optimizer includes all top-level logic
 400    related to semantic equality comparison.  */
 401 class sem_item_optimizer
 402 {
 403 public:
 404   sem_item_optimizer ();
 405   ~sem_item_optimizer ();
 406
 407   /* Function responsible for visiting all potential functions and
 408      read-only variables that can be merged.  */
 409   void parse_funcs_and_vars (void);
 410
 411   /* Optimizer entry point.  */
 412   void execute (void);
 413
 414   /* Dump function. */
 415   void dump (void);
 416
 417   /* Verify congruence classes if checking is enabled.  */
 418   void verify_classes (void);
 419
 420   /* Write IPA ICF summary for symbols.  */
 421   void write_summary (void);
 422
 423   /* Read IPA IPA ICF summary for symbols.  */
 424   void read_summary (void);
 425
 426   /* Callgraph removal hook called for a NODE with a custom DATA.  */
 427   static void cgraph_removal_hook (cgraph_node *node, void *data);
 428
 429   /* Varpool removal hook called for a NODE with a custom DATA.  */
 430   static void varpool_removal_hook (varpool_node *node, void *data);
 431
 432   /* Worklist of congruence classes that can potentially
 433      refine classes of congruence.  */
 434   std::list<congruence_class *> worklist;
 435
 436   /* Remove semantic ITEM and release memory.  */
 437   void remove_item (sem_item *item);
 438
 439   /* Remove symtab NODE triggered by symtab removal hooks.  */
 440   void remove_symtab_node (symtab_node *node);
 441
 442   /* Register callgraph and varpool hooks.  */
 443   void register_hooks (void);
 444
 445   /* Unregister callgraph and varpool hooks.  */
 446   void unregister_hooks (void);
 447
 448   /* Adds a CLS to hashtable associated by hash value.  */
 449   void add_class (congruence_class *cls);
 450
 451   /* Gets a congruence class group based on given HASH value and TYPE.  */
 452   congruence_class_group *get_group_by_hash (hashval_t hash,
 453       sem_item_type type);
 454
 455 private:
 456
 457   /* Congruence classes are built by hash value.  */
 458   void build_hash_based_classes (void);
 459
 460   /* Semantic items in classes having more than one element and initialized.
 461      In case of WPA, we load function body.  */
 462   void parse_nonsingleton_classes (void);
 463
 464   /* Equality function for semantic items is used to subdivide existing
 465      classes. If IN_WPA, fast equality function is invoked.  */
 466   void subdivide_classes_by_equality (bool in_wpa = false);
 467
 468   /* Debug function prints all informations about congruence classes.  */
 469   void dump_cong_classes (void);
 470
 471   /* Build references according to call graph.  */
 472   void build_graph (void);
 473
 474   /* Iterative congruence reduction function.  */
 475   void process_cong_reduction (void);
 476
 477   /* After reduction is done, we can declare all items in a group
 478      to be equal. PREV_CLASS_COUNT is start number of classes
 479      before reduction.  */
 480   void merge_classes (unsigned int prev_class_count);
 481
 482   /* Adds a newly created congruence class CLS to worklist.  */
 483   void worklist_push (congruence_class *cls);
 484
 485   /* Pops a class from worklist. */
 486   congruence_class *worklist_pop ();
 487
 488   /* Every usage of a congruence class CLS is a candidate that can split the
 489      collection of classes. Bitmap stack BMSTACK is used for bitmap
 490      allocation.  */
 491   void do_congruence_step (congruence_class *cls);
 492
 493   /* Tests if a class CLS used as INDEXth splits any congruence classes.
 494      Bitmap stack BMSTACK is used for bitmap allocation.  */
 495   void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
 496
 497   /* Makes pairing between a congruence class CLS and semantic ITEM.  */
 498   static void add_item_to_class (congruence_class *cls, sem_item *item);
 499
 500   /* Disposes split map traverse function. CLS is congruence
 501      class, BSLOT is bitmap slot we want to release. DATA is mandatory,
 502      but unused argument.  */
 503   static bool release_split_map (congruence_class * const &cls, bitmap const &b,
 504                                  traverse_split_pair *pair);
 505
 506   /* Process split operation for a cognruence class CLS,
 507      where bitmap B splits congruence class members. DATA is used
 508      as argument of split pair.  */
 509   static bool traverse_congruence_split (congruence_class * const &cls,
 510                                          bitmap const &b,
 511                                          traverse_split_pair *pair);
 512
 513   /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
 514      contains LEN bytes.  */
 515   void read_section (lto_file_decl_data *file_data, const char *data,
 516                      size_t len);
 517
 518   /* Removes all callgraph and varpool nodes that are marked by symtab
 519      as deleted.  */
 520   void filter_removed_items (void);
 521
 522   /* Vector of semantic items.  */
 523   vec <sem_item *> m_items;
 524
 525   /* A set containing all items removed by hooks.  */
 526   hash_set <symtab_node *> m_removed_items_set;
 527
 528   /* Hashtable of congruence classes */
 529   hash_table <congruence_class_group_hash> m_classes;
 530
 531   /* Count of congruence classes.  */
 532   unsigned int m_classes_count;
 533
 534   /* Map data structure maps symtab nodes to semantic items.  */
 535   hash_map <symtab_node *, sem_item *> m_symtab_node_map;
 536
 537   /* Set to true if a splitter class is removed.  */
 538   bool splitter_class_removed;
 539
 540   /* Global unique class id counter.  */
 541   static unsigned int class_id;
 542
 543   /* Callgraph node removal hook holder.  */
 544   cgraph_node_hook_list *m_cgraph_node_hooks;
 545
 546   /* Varpool node removal hook holder.  */
 547   varpool_node_hook_list *m_varpool_node_hooks;
 548
 549   /* Bitmap stack.  */
 550   bitmap_obstack m_bmstack;
 551 }; // class sem_item_optimizer
 552
 553 } // ipa_icf namespace