1/* Interprocedural semantic function equality pass
2 Copyright (C) 2014-2017 Free Software Foundation, Inc.
3
4 Contributed by Jan Hubicka <hubicka@ucw.cz> and Martin Liska <mliska@suse.cz>
5
6This file is part of GCC.
7
8GCC is free software; you can redistribute it and/or modify it under
9the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 3, or (at your option) any later
11version.
12
13GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14WARRANTY; without even the implied warranty of MERCHANTABILITY or
15FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16for more details.
17
18You should have received a copy of the GNU General Public License
19along with GCC; see the file COPYING3. If not see
20<http://www.gnu.org/licenses/>. */
21
22namespace ipa_icf {
23class 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. */
28class congruence_class
29{
30public:
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. */
60enum sem_item_type
61{
62 FUNC,
63 VAR
64};
65
66/* Class is container for address references for a symtab_node. */
67
68class symbol_compare_collection
69{
70public:
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
90struct 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. */
131class sem_usage_pair
132{
133public:
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. */
146class sem_item
147{
148public:
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 sem_item (sem_item_type _type, symtab_node *_node, bitmap_obstack *stack);
156
157 virtual ~sem_item ();
158
159 /* Dump function for debugging purpose. */
160 DEBUG_FUNCTION void dump (void);
161
162 /* Initialize semantic item by info reachable during LTO WPA phase. */
163 virtual void init_wpa (void) = 0;
164
165 /* Semantic item initialization function. */
166 virtual void init (void) = 0;
167
168 /* Add reference to a semantic TARGET. */
169 void add_reference (sem_item *target);
170
171 /* Fast equality function based on knowledge known in WPA. */
172 virtual bool equals_wpa (sem_item *item,
173 hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
174
175 /* Returns true if the item equals to ITEM given as arguemnt. */
176 virtual bool equals (sem_item *item,
177 hash_map <symtab_node *, sem_item *> &ignored_nodes) = 0;
178
179 /* References independent hash function. */
180 virtual hashval_t get_hash (void) = 0;
181
182 /* Set new hash value of the item. */
183 void set_hash (hashval_t hash);
184
185 /* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
186 be applied. */
187 virtual bool merge (sem_item *alias_item) = 0;
188
189 /* Dump symbol to FILE. */
190 virtual void dump_to_file (FILE *file) = 0;
191
192 /* Update hash by address sensitive references. */
193 void update_hash_by_addr_refs (hash_map <symtab_node *,
194 sem_item *> &m_symtab_node_map);
195
196 /* Update hash by computed local hash values taken from different
197 semantic items. */
198 void update_hash_by_local_refs (hash_map <symtab_node *,
199 sem_item *> &m_symtab_node_map);
200
201 /* Return base tree that can be used for compatible_types_p and
202 contains_polymorphic_type_p comparison. */
203 static bool get_base_types (tree *t1, tree *t2);
204
205 /* Return true if target supports alias symbols. */
206 bool target_supports_symbol_aliases_p (void);
207
208 /* Item type. */
209 sem_item_type type;
210
211 /* Symtab node. */
212 symtab_node *node;
213
214 /* Declaration tree node. */
215 tree decl;
216
217 /* Semantic references used that generate congruence groups. */
218 vec <sem_item *> refs;
219
220 /* Pointer to a congruence class the item belongs to. */
221 congruence_class *cls;
222
223 /* Index of the item in a class belonging to. */
224 unsigned int index_in_class;
225
226 /* List of semantic items where the instance is used. */
227 vec <sem_usage_pair *> usages;
228
229 /* A bitmap with indices of all classes referencing this item. */
230 bitmap usage_index_bitmap;
231
232 /* List of tree references (either FUNC_DECL or VAR_DECL). */
233 vec <tree> tree_refs;
234
235 /* A set with symbol table references. */
236 hash_set <symtab_node *> refs_set;
237
238 /* Temporary hash used where hash values of references are added. */
239 hashval_t global_hash;
240protected:
241 /* Cached, once calculated hash for the item. */
242
243 /* Accumulate to HSTATE a hash of expression EXP. */
244 static void add_expr (const_tree exp, inchash::hash &hstate);
245 /* Accumulate to HSTATE a hash of type T. */
246 static void add_type (const_tree t, inchash::hash &hstate);
247
248 /* Compare properties of symbol that does not affect semantics of symbol
249 itself but affects semantics of its references.
250 If ADDRESS is true, do extra checking needed for IPA_REF_ADDR. */
251 static bool compare_referenced_symbol_properties (symtab_node *used_by,
252 symtab_node *n1,
253 symtab_node *n2,
254 bool address);
255
256 /* Compare two attribute lists. */
257 static bool compare_attributes (const_tree list1, const_tree list2);
258
259 /* Hash properties compared by compare_referenced_symbol_properties. */
260 void hash_referenced_symbol_properties (symtab_node *ref,
261 inchash::hash &hstate,
262 bool address);
263
264 /* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
265 point to a same function. Comparison can be skipped if IGNORED_NODES
266 contains these nodes. ADDRESS indicate if address is taken. */
267 bool compare_symbol_references (hash_map <symtab_node *, sem_item *>
268 &ignored_nodes,
269 symtab_node *n1, symtab_node *n2,
270 bool address);
271protected:
272 /* Hash of item. */
273 hashval_t m_hash;
274
275 /* Indicated whether a hash value has been set or not. */
276 bool m_hash_set;
277
278private:
279 /* Initialize internal data structures. Bitmap STACK is used for
280 bitmap memory allocation process. */
281 void setup (bitmap_obstack *stack);
282}; // class sem_item
283
284class sem_function: public sem_item
285{
286public:
287 /* Semantic function constructor that uses STACK as bitmap memory stack. */
288 sem_function (bitmap_obstack *stack);
289
290 /* Constructor based on callgraph node _NODE.
291 Bitmap STACK is used for memory allocation. */
292 sem_function (cgraph_node *_node, bitmap_obstack *stack);
293
294 ~sem_function ();
295
296 inline virtual void init_wpa (void)
297 {
298 }
299
300 virtual void init (void);
301 virtual bool equals_wpa (sem_item *item,
302 hash_map <symtab_node *, sem_item *> &ignored_nodes);
303 virtual hashval_t get_hash (void);
304 virtual bool equals (sem_item *item,
305 hash_map <symtab_node *, sem_item *> &ignored_nodes);
306 virtual bool merge (sem_item *alias_item);
307
308 /* Dump symbol to FILE. */
309 virtual void dump_to_file (FILE *file)
310 {
311 gcc_assert (file);
312 dump_function_to_file (decl, file, TDF_DETAILS);
313 }
314
315 /* Returns cgraph_node. */
316 inline cgraph_node *get_node (void)
317 {
318 return dyn_cast <cgraph_node *> (node);
319 }
320
321 /* Improve accumulated hash for HSTATE based on a gimple statement STMT. */
322 void hash_stmt (gimple *stmt, inchash::hash &inchash);
323
324 /* Return true if polymorphic comparison must be processed. */
325 bool compare_polymorphic_p (void);
326
327 /* For a given call graph NODE, the function constructs new
328 semantic function item. */
329 static sem_function *parse (cgraph_node *node, bitmap_obstack *stack);
330
331 /* Perform additional checks needed to match types of used function
332 paramters. */
333 bool compatible_parm_types_p (tree, tree);
334
335 /* Exception handling region tree. */
336 eh_region region_tree;
337
338 /* Number of function arguments. */
339 unsigned int arg_count;
340
341 /* Total amount of edges in the function. */
342 unsigned int edge_count;
343
344 /* Vector of sizes of all basic blocks. */
345 vec <unsigned int> bb_sizes;
346
347 /* Control flow graph checksum. */
348 hashval_t cfg_checksum;
349
350 /* GIMPLE codes hash value. */
351 hashval_t gcode_hash;
352
353 /* Total number of SSA names used in the function. */
354 unsigned ssa_names_size;
355
356 /* Array of structures for all basic blocks. */
357 vec <ipa_icf_gimple::sem_bb *> bb_sorted;
358
359 /* Return true if parameter I may be used. */
360 bool param_used_p (unsigned int i);
361
362private:
363 /* Calculates hash value based on a BASIC_BLOCK. */
364 hashval_t get_bb_hash (const ipa_icf_gimple::sem_bb *basic_block);
365
366 /* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
367 true value is returned if phi nodes are semantically
368 equivalent in these blocks . */
369 bool compare_phi_node (basic_block bb1, basic_block bb2);
370
371 /* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
372 corresponds to TARGET. */
373 bool bb_dict_test (vec<int> *bb_dict, int source, int target);
374
375 /* If cgraph edges E1 and E2 are indirect calls, verify that
376 ICF flags are the same. */
377 bool compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2);
378
379 /* Processes function equality comparison. */
380 bool equals_private (sem_item *item);
381
382 /* Returns true if tree T can be compared as a handled component. */
383 static bool icf_handled_component_p (tree t);
384
385 /* Function checker stores binding between functions. */
386 ipa_icf_gimple::func_checker *m_checker;
387
388 /* COMPARED_FUNC is a function that we compare to. */
389 sem_function *m_compared_func;
390}; // class sem_function
391
392class sem_variable: public sem_item
393{
394public:
395 /* Semantic variable constructor that uses STACK as bitmap memory stack. */
396 sem_variable (bitmap_obstack *stack);
397
398 /* Constructor based on callgraph node _NODE.
399 Bitmap STACK is used for memory allocation. */
400
401 sem_variable (varpool_node *_node, bitmap_obstack *stack);
402
403 inline virtual void init_wpa (void) {}
404
405 /* Semantic variable initialization function. */
406 inline virtual void init (void)
407 {
408 decl = get_node ()->decl;
409 }
410
411 virtual hashval_t get_hash (void);
412 virtual bool merge (sem_item *alias_item);
413 virtual void dump_to_file (FILE *file);
414 virtual bool equals (sem_item *item,
415 hash_map <symtab_node *, sem_item *> &ignored_nodes);
416
417 /* Fast equality variable based on knowledge known in WPA. */
418 virtual bool equals_wpa (sem_item *item,
419 hash_map <symtab_node *, sem_item *> &ignored_nodes);
420
421 /* Returns varpool_node. */
422 inline varpool_node *get_node (void)
423 {
424 return dyn_cast <varpool_node *> (node);
425 }
426
427 /* Parser function that visits a varpool NODE. */
428 static sem_variable *parse (varpool_node *node, bitmap_obstack *stack);
429
430private:
431 /* Compares trees T1 and T2 for semantic equality. */
432 static bool equals (tree t1, tree t2);
433}; // class sem_variable
434
435class sem_item_optimizer;
436
437struct congruence_class_group
438{
439 hashval_t hash;
440 sem_item_type type;
441 vec <congruence_class *> classes;
442};
443
444/* Congruence class set structure. */
445struct congruence_class_hash : nofree_ptr_hash <congruence_class_group>
446{
447 static inline hashval_t hash (const congruence_class_group *item)
448 {
449 return item->hash;
450 }
451
452 static inline int equal (const congruence_class_group *item1,
453 const congruence_class_group *item2)
454 {
455 return item1->hash == item2->hash && item1->type == item2->type;
456 }
457};
458
459struct 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. */
467class sem_item_optimizer
468{
469public:
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 which returns true in case it processes
478 a merge operation. True is returned if there's a merge operation
479 processed. */
480 bool execute (void);
481
482 /* Dump function. */
483 void dump (void);
484
485 /* Verify congruence classes if checking is enabled. */
486 void checking_verify_classes (void);
487
488 /* Verify congruence classes. */
489 void verify_classes (void);
490
491 /* Write IPA ICF summary for symbols. */
492 void write_summary (void);
493
494 /* Read IPA ICF summary for symbols. */
495 void read_summary (void);
496
497 /* Callgraph removal hook called for a NODE with a custom DATA. */
498 static void cgraph_removal_hook (cgraph_node *node, void *data);
499
500 /* Varpool removal hook called for a NODE with a custom DATA. */
501 static void varpool_removal_hook (varpool_node *node, void *data);
502
503 /* Worklist of congruence classes that can potentially
504 refine classes of congruence. */
505 std::list<congruence_class *> worklist;
506
507 /* Remove semantic ITEM and release memory. */
508 void remove_item (sem_item *item);
509
510 /* Remove symtab NODE triggered by symtab removal hooks. */
511 void remove_symtab_node (symtab_node *node);
512
513 /* Register callgraph and varpool hooks. */
514 void register_hooks (void);
515
516 /* Unregister callgraph and varpool hooks. */
517 void unregister_hooks (void);
518
519 /* Adds a CLS to hashtable associated by hash value. */
520 void add_class (congruence_class *cls);
521
522 /* Gets a congruence class group based on given HASH value and TYPE. */
523 congruence_class_group *get_group_by_hash (hashval_t hash,
524 sem_item_type type);
525
526 /* Because types can be arbitrarily large, avoid quadratic bottleneck. */
527 hash_map<const_tree, hashval_t> m_type_hash_cache;
528private:
529
530 /* For each semantic item, append hash values of references. */
531 void update_hash_by_addr_refs ();
532
533 /* Congruence classes are built by hash value. */
534 void build_hash_based_classes (void);
535
536 /* Semantic items in classes having more than one element and initialized.
537 In case of WPA, we load function body. */
538 void parse_nonsingleton_classes (void);
539
540 /* Equality function for semantic items is used to subdivide existing
541 classes. If IN_WPA, fast equality function is invoked. */
542 void subdivide_classes_by_equality (bool in_wpa = false);
543
544 /* Subdivide classes by address and interposable references
545 that members of the class reference.
546 Example can be a pair of functions that have an address
547 taken from a function. If these addresses are different the class
548 is split. */
549 unsigned subdivide_classes_by_sensitive_refs();
550
551 /* Debug function prints all informations about congruence classes. */
552 void dump_cong_classes (void);
553
554 /* Build references according to call graph. */
555 void build_graph (void);
556
557 /* Iterative congruence reduction function. */
558 void process_cong_reduction (void);
559
560 /* After reduction is done, we can declare all items in a group
561 to be equal. PREV_CLASS_COUNT is start number of classes
562 before reduction. True is returned if there's a merge operation
563 processed. */
564 bool merge_classes (unsigned int prev_class_count);
565
566 /* Adds a newly created congruence class CLS to worklist. */
567 void worklist_push (congruence_class *cls);
568
569 /* Pops a class from worklist. */
570 congruence_class *worklist_pop ();
571
572 /* Every usage of a congruence class CLS is a candidate that can split the
573 collection of classes. Bitmap stack BMSTACK is used for bitmap
574 allocation. */
575 void do_congruence_step (congruence_class *cls);
576
577 /* Tests if a class CLS used as INDEXth splits any congruence classes.
578 Bitmap stack BMSTACK is used for bitmap allocation. */
579 void do_congruence_step_for_index (congruence_class *cls, unsigned int index);
580
581 /* Makes pairing between a congruence class CLS and semantic ITEM. */
582 static void add_item_to_class (congruence_class *cls, sem_item *item);
583
584 /* Disposes split map traverse function. CLS is congruence
585 class, BSLOT is bitmap slot we want to release. DATA is mandatory,
586 but unused argument. */
587 static bool release_split_map (congruence_class * const &cls, bitmap const &b,
588 traverse_split_pair *pair);
589
590 /* Process split operation for a cognruence class CLS,
591 where bitmap B splits congruence class members. DATA is used
592 as argument of split pair. */
593 static bool traverse_congruence_split (congruence_class * const &cls,
594 bitmap const &b,
595 traverse_split_pair *pair);
596
597 /* Reads a section from LTO stream file FILE_DATA. Input block for DATA
598 contains LEN bytes. */
599 void read_section (lto_file_decl_data *file_data, const char *data,
600 size_t len);
601
602 /* Removes all callgraph and varpool nodes that are marked by symtab
603 as deleted. */
604 void filter_removed_items (void);
605
606 /* Vector of semantic items. */
607 vec <sem_item *> m_items;
608
609 /* A set containing all items removed by hooks. */
610 hash_set <symtab_node *> m_removed_items_set;
611
612 /* Hashtable of congruence classes. */
613 hash_table <congruence_class_hash> m_classes;
614
615 /* Count of congruence classes. */
616 unsigned int m_classes_count;
617
618 /* Map data structure maps symtab nodes to semantic items. */
619 hash_map <symtab_node *, sem_item *> m_symtab_node_map;
620
621 /* Set to true if a splitter class is removed. */
622 bool splitter_class_removed;
623
624 /* Global unique class id counter. */
625 static unsigned int class_id;
626
627 /* Callgraph node removal hook holder. */
628 cgraph_node_hook_list *m_cgraph_node_hooks;
629
630 /* Varpool node removal hook holder. */
631 varpool_node_hook_list *m_varpool_node_hooks;
632
633 /* Bitmap stack. */
634 bitmap_obstack m_bmstack;
635}; // class sem_item_optimizer
636
637} // ipa_icf namespace
638