c, c++: attribute format on a ctor with a vbase [PR101833, PR47634]
[official-gcc.git] / gcc / postreload-gcse.cc
blobfc63f0b5c7708bf5a0fd529cb2a99a5d152184ee
1 /* Post reload partially redundant load elimination
2 Copyright (C) 2004-2022 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
9 version.
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 for more details.
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "backend.h"
24 #include "target.h"
25 #include "rtl.h"
26 #include "tree.h"
27 #include "predict.h"
28 #include "df.h"
29 #include "memmodel.h"
30 #include "tm_p.h"
31 #include "insn-config.h"
32 #include "emit-rtl.h"
33 #include "recog.h"
35 #include "cfgrtl.h"
36 #include "profile.h"
37 #include "expr.h"
38 #include "tree-pass.h"
39 #include "dbgcnt.h"
40 #include "intl.h"
41 #include "gcse-common.h"
42 #include "gcse.h"
43 #include "regs.h"
44 #include "function-abi.h"
46 /* The following code implements gcse after reload, the purpose of this
47 pass is to cleanup redundant loads generated by reload and other
48 optimizations that come after gcse. It searches for simple inter-block
49 redundancies and tries to eliminate them by adding moves and loads
50 in cold places.
52 Perform partially redundant load elimination, try to eliminate redundant
53 loads created by the reload pass. We try to look for full or partial
54 redundant loads fed by one or more loads/stores in predecessor BBs,
55 and try adding loads to make them fully redundant. We also check if
56 it's worth adding loads to be able to delete the redundant load.
58 Algorithm:
59 1. Build available expressions hash table:
60 For each load/store instruction, if the loaded/stored memory didn't
61 change until the end of the basic block add this memory expression to
62 the hash table.
63 2. Perform Redundancy elimination:
64 For each load instruction do the following:
65 perform partial redundancy elimination, check if it's worth adding
66 loads to make the load fully redundant. If so add loads and
67 register copies and delete the load.
68 3. Delete instructions made redundant in step 2.
70 Future enhancement:
71 If the loaded register is used/defined between load and some store,
72 look for some other free register between load and all its stores,
73 and replace the load with a copy from this register to the loaded
74 register.
78 /* Keep statistics of this pass. */
79 static struct
81 int moves_inserted;
82 int copies_inserted;
83 int insns_deleted;
84 } stats;
86 /* We need to keep a hash table of expressions. The table entries are of
87 type 'struct expr', and for each expression there is a single linked
88 list of occurrences. */
90 /* Expression elements in the hash table. */
91 struct expr
93 /* The expression (SET_SRC for expressions, PATTERN for assignments). */
94 rtx expr;
96 /* The same hash for this entry. */
97 hashval_t hash;
99 /* Index in the transparent bitmaps. */
100 unsigned int bitmap_index;
102 /* List of available occurrence in basic blocks in the function. */
103 struct occr *avail_occr;
106 /* Hashtable helpers. */
108 struct expr_hasher : nofree_ptr_hash <expr>
110 static inline hashval_t hash (const expr *);
111 static inline bool equal (const expr *, const expr *);
115 /* Hash expression X.
116 DO_NOT_RECORD_P is a boolean indicating if a volatile operand is found
117 or if the expression contains something we don't want to insert in the
118 table. */
120 static hashval_t
121 hash_expr (rtx x, int *do_not_record_p)
123 *do_not_record_p = 0;
124 return hash_rtx (x, GET_MODE (x), do_not_record_p,
125 NULL, /*have_reg_qty=*/false);
128 /* Callback for hashtab.
129 Return the hash value for expression EXP. We don't actually hash
130 here, we just return the cached hash value. */
132 inline hashval_t
133 expr_hasher::hash (const expr *exp)
135 return exp->hash;
138 /* Callback for hashtab.
139 Return nonzero if exp1 is equivalent to exp2. */
141 inline bool
142 expr_hasher::equal (const expr *exp1, const expr *exp2)
144 int equiv_p = exp_equiv_p (exp1->expr, exp2->expr, 0, true);
146 gcc_assert (!equiv_p || exp1->hash == exp2->hash);
147 return equiv_p;
150 /* The table itself. */
151 static hash_table<expr_hasher> *expr_table;
154 static struct obstack expr_obstack;
156 /* Occurrence of an expression.
157 There is at most one occurrence per basic block. If a pattern appears
158 more than once, the last appearance is used. */
160 struct occr
162 /* Next occurrence of this expression. */
163 struct occr *next;
164 /* The insn that computes the expression. */
165 rtx_insn *insn;
166 /* Nonzero if this [anticipatable] occurrence has been deleted. */
167 char deleted_p;
170 static struct obstack occr_obstack;
172 /* The following structure holds the information about the occurrences of
173 the redundant instructions. */
174 struct unoccr
176 struct unoccr *next;
177 edge pred;
178 rtx_insn *insn;
181 static struct obstack unoccr_obstack;
183 /* Array where each element is the CUID if the insn that last set the hard
184 register with the number of the element, since the start of the current
185 basic block.
187 This array is used during the building of the hash table (step 1) to
188 determine if a reg is killed before the end of a basic block.
190 It is also used when eliminating partial redundancies (step 2) to see
191 if a reg was modified since the start of a basic block. */
192 static int *reg_avail_info;
194 /* A list of insns that may modify memory within the current basic block. */
195 struct modifies_mem
197 rtx_insn *insn;
198 struct modifies_mem *next;
200 static struct modifies_mem *modifies_mem_list;
202 /* The modifies_mem structs also go on an obstack, only this obstack is
203 freed each time after completing the analysis or transformations on
204 a basic block. So we allocate a dummy modifies_mem_obstack_bottom
205 object on the obstack to keep track of the bottom of the obstack. */
206 static struct obstack modifies_mem_obstack;
207 static struct modifies_mem *modifies_mem_obstack_bottom;
209 /* Mapping of insn UIDs to CUIDs.
210 CUIDs are like UIDs except they increase monotonically in each basic
211 block, have no gaps, and only apply to real insns. */
212 static int *uid_cuid;
213 #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
215 /* Bitmap of blocks which have memory stores. */
216 static bitmap modify_mem_list_set;
218 /* Bitmap of blocks which have calls. */
219 static bitmap blocks_with_calls;
221 /* Vector indexed by block # with a list of all the insns that
222 modify memory within the block. */
223 static vec<rtx_insn *> *modify_mem_list;
225 /* Vector indexed by block # with a canonicalized list of insns
226 that modify memory in the block. */
227 static vec<modify_pair> *canon_modify_mem_list;
229 /* Vector of simple bitmaps indexed by block number. Each component sbitmap
230 indicates which expressions are transparent through the block. */
231 static sbitmap *transp;
234 /* Helpers for memory allocation/freeing. */
235 static void alloc_mem (void);
236 static void free_mem (void);
238 /* Support for hash table construction and transformations. */
239 static bool oprs_unchanged_p (rtx, rtx_insn *, bool);
240 static void record_last_reg_set_info (rtx_insn *, rtx);
241 static void record_last_reg_set_info_regno (rtx_insn *, int);
242 static void record_last_mem_set_info (rtx_insn *);
243 static void record_last_set_info (rtx, const_rtx, void *);
244 static void record_opr_changes (rtx_insn *);
246 static void find_mem_conflicts (rtx, const_rtx, void *);
247 static int load_killed_in_block_p (int, rtx, bool);
248 static void reset_opr_set_tables (void);
250 /* Hash table support. */
251 static hashval_t hash_expr (rtx, int *);
252 static void insert_expr_in_table (rtx, rtx_insn *);
253 static struct expr *lookup_expr_in_table (rtx);
254 static void dump_hash_table (FILE *);
256 /* Helpers for eliminate_partially_redundant_load. */
257 static bool reg_killed_on_edge (rtx, edge);
258 static bool reg_used_on_edge (rtx, edge);
260 static rtx get_avail_load_store_reg (rtx_insn *);
262 static bool bb_has_well_behaved_predecessors (basic_block);
263 static struct occr* get_bb_avail_insn (basic_block, struct occr *, int);
264 static void hash_scan_set (rtx_insn *);
265 static void compute_hash_table (void);
267 /* The work horses of this pass. */
268 static void eliminate_partially_redundant_load (basic_block,
269 rtx_insn *,
270 struct expr *);
271 static void eliminate_partially_redundant_loads (void);
274 /* Allocate memory for the CUID mapping array and register/memory
275 tracking tables. */
277 static void
278 alloc_mem (void)
280 int i;
281 basic_block bb;
282 rtx_insn *insn;
284 /* Find the largest UID and create a mapping from UIDs to CUIDs. */
285 uid_cuid = XCNEWVEC (int, get_max_uid () + 1);
286 i = 1;
287 FOR_EACH_BB_FN (bb, cfun)
288 FOR_BB_INSNS (bb, insn)
290 if (INSN_P (insn))
291 uid_cuid[INSN_UID (insn)] = i++;
292 else
293 uid_cuid[INSN_UID (insn)] = i;
296 /* Allocate the available expressions hash table. We don't want to
297 make the hash table too small, but unnecessarily making it too large
298 also doesn't help. The i/4 is a gcse.cc relic, and seems like a
299 reasonable choice. */
300 expr_table = new hash_table<expr_hasher> (MAX (i / 4, 13));
302 /* We allocate everything on obstacks because we often can roll back
303 the whole obstack to some point. Freeing obstacks is very fast. */
304 gcc_obstack_init (&expr_obstack);
305 gcc_obstack_init (&occr_obstack);
306 gcc_obstack_init (&unoccr_obstack);
307 gcc_obstack_init (&modifies_mem_obstack);
309 /* Working array used to track the last set for each register
310 in the current block. */
311 reg_avail_info = (int *) xmalloc (FIRST_PSEUDO_REGISTER * sizeof (int));
313 /* Put a dummy modifies_mem object on the modifies_mem_obstack, so we
314 can roll it back in reset_opr_set_tables. */
315 modifies_mem_obstack_bottom =
316 (struct modifies_mem *) obstack_alloc (&modifies_mem_obstack,
317 sizeof (struct modifies_mem));
319 blocks_with_calls = BITMAP_ALLOC (NULL);
320 modify_mem_list_set = BITMAP_ALLOC (NULL);
322 modify_mem_list = (vec_rtx_heap *) xcalloc (last_basic_block_for_fn (cfun),
323 sizeof (vec_rtx_heap));
324 canon_modify_mem_list
325 = (vec_modify_pair_heap *) xcalloc (last_basic_block_for_fn (cfun),
326 sizeof (vec_modify_pair_heap));
329 /* Free memory allocated by alloc_mem. */
331 static void
332 free_mem (void)
334 free (uid_cuid);
336 delete expr_table;
337 expr_table = NULL;
339 obstack_free (&expr_obstack, NULL);
340 obstack_free (&occr_obstack, NULL);
341 obstack_free (&unoccr_obstack, NULL);
342 obstack_free (&modifies_mem_obstack, NULL);
344 unsigned i;
345 bitmap_iterator bi;
346 EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set, 0, i, bi)
348 modify_mem_list[i].release ();
349 canon_modify_mem_list[i].release ();
352 BITMAP_FREE (blocks_with_calls);
353 BITMAP_FREE (modify_mem_list_set);
354 free (reg_avail_info);
355 free (modify_mem_list);
356 free (canon_modify_mem_list);
360 /* Insert expression X in INSN in the hash TABLE.
361 If it is already present, record it as the last occurrence in INSN's
362 basic block. */
364 static void
365 insert_expr_in_table (rtx x, rtx_insn *insn)
367 int do_not_record_p;
368 hashval_t hash;
369 struct expr *cur_expr, **slot;
370 struct occr *avail_occr;
372 hash = hash_expr (x, &do_not_record_p);
374 /* Do not insert expression in the table if it contains volatile operands,
375 or if hash_expr determines the expression is something we don't want
376 to or can't handle. */
377 if (do_not_record_p)
378 return;
380 /* We anticipate that redundant expressions are rare, so for convenience
381 allocate a new hash table element here already and set its fields.
382 If we don't do this, we need a hack with a static struct expr. Anyway,
383 obstack_free is really fast and one more obstack_alloc doesn't hurt if
384 we're going to see more expressions later on. */
385 cur_expr = (struct expr *) obstack_alloc (&expr_obstack,
386 sizeof (struct expr));
387 cur_expr->expr = x;
388 cur_expr->hash = hash;
389 cur_expr->avail_occr = NULL;
391 slot = expr_table->find_slot_with_hash (cur_expr, hash, INSERT);
393 if (! (*slot))
395 /* The expression isn't found, so insert it. */
396 *slot = cur_expr;
398 /* Anytime we add an entry to the table, record the index
399 of the new entry. The bitmap index starts counting
400 at zero. */
401 cur_expr->bitmap_index = expr_table->elements () - 1;
403 else
405 /* The expression is already in the table, so roll back the
406 obstack and use the existing table entry. */
407 obstack_free (&expr_obstack, cur_expr);
408 cur_expr = *slot;
411 /* Search for another occurrence in the same basic block. We insert
412 insns blockwise from start to end, so keep appending to the
413 start of the list so we have to check only a single element. */
414 avail_occr = cur_expr->avail_occr;
415 if (avail_occr
416 && BLOCK_FOR_INSN (avail_occr->insn) == BLOCK_FOR_INSN (insn))
417 avail_occr->insn = insn;
418 else
420 /* First occurrence of this expression in this basic block. */
421 avail_occr = (struct occr *) obstack_alloc (&occr_obstack,
422 sizeof (struct occr));
423 avail_occr->insn = insn;
424 avail_occr->next = cur_expr->avail_occr;
425 avail_occr->deleted_p = 0;
426 cur_expr->avail_occr = avail_occr;
431 /* Lookup pattern PAT in the expression hash table.
432 The result is a pointer to the table entry, or NULL if not found. */
434 static struct expr *
435 lookup_expr_in_table (rtx pat)
437 int do_not_record_p;
438 struct expr **slot, *tmp_expr;
439 hashval_t hash = hash_expr (pat, &do_not_record_p);
441 if (do_not_record_p)
442 return NULL;
444 tmp_expr = (struct expr *) obstack_alloc (&expr_obstack,
445 sizeof (struct expr));
446 tmp_expr->expr = pat;
447 tmp_expr->hash = hash;
448 tmp_expr->avail_occr = NULL;
450 slot = expr_table->find_slot_with_hash (tmp_expr, hash, INSERT);
451 obstack_free (&expr_obstack, tmp_expr);
453 if (!slot)
454 return NULL;
455 else
456 return (*slot);
460 /* Dump all expressions and occurrences that are currently in the
461 expression hash table to FILE. */
463 /* This helper is called via htab_traverse. */
465 dump_expr_hash_table_entry (expr **slot, FILE *file)
467 struct expr *exprs = *slot;
468 struct occr *occr;
470 fprintf (file, "expr: ");
471 print_rtl (file, exprs->expr);
472 fprintf (file,"\nhashcode: %u\n", exprs->hash);
473 fprintf (file,"list of occurrences:\n");
474 occr = exprs->avail_occr;
475 while (occr)
477 rtx_insn *insn = occr->insn;
478 print_rtl_single (file, insn);
479 fprintf (file, "\n");
480 occr = occr->next;
482 fprintf (file, "\n");
483 return 1;
486 static void
487 dump_hash_table (FILE *file)
489 fprintf (file, "\n\nexpression hash table\n");
490 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
491 (long) expr_table->size (),
492 (long) expr_table->elements (),
493 expr_table->collisions ());
494 if (!expr_table->is_empty ())
496 fprintf (file, "\n\ntable entries:\n");
497 expr_table->traverse <FILE *, dump_expr_hash_table_entry> (file);
499 fprintf (file, "\n");
502 /* Return true if register X is recorded as being set by an instruction
503 whose CUID is greater than the one given. */
505 static bool
506 reg_changed_after_insn_p (rtx x, int cuid)
508 unsigned int regno, end_regno;
510 regno = REGNO (x);
511 end_regno = END_REGNO (x);
513 if (reg_avail_info[regno] > cuid)
514 return true;
515 while (++regno < end_regno);
516 return false;
519 /* Return nonzero if the operands of expression X are unchanged
520 1) from the start of INSN's basic block up to but not including INSN
521 if AFTER_INSN is false, or
522 2) from INSN to the end of INSN's basic block if AFTER_INSN is true. */
524 static bool
525 oprs_unchanged_p (rtx x, rtx_insn *insn, bool after_insn)
527 int i, j;
528 enum rtx_code code;
529 const char *fmt;
531 if (x == 0)
532 return 1;
534 code = GET_CODE (x);
535 switch (code)
537 case REG:
538 /* We are called after register allocation. */
539 gcc_assert (REGNO (x) < FIRST_PSEUDO_REGISTER);
540 if (after_insn)
541 return !reg_changed_after_insn_p (x, INSN_CUID (insn) - 1);
542 else
543 return !reg_changed_after_insn_p (x, 0);
545 case MEM:
546 if (load_killed_in_block_p (INSN_CUID (insn), x, after_insn))
547 return 0;
548 else
549 return oprs_unchanged_p (XEXP (x, 0), insn, after_insn);
551 case PC:
552 case CONST:
553 CASE_CONST_ANY:
554 case SYMBOL_REF:
555 case LABEL_REF:
556 case ADDR_VEC:
557 case ADDR_DIFF_VEC:
558 return 1;
560 case PRE_DEC:
561 case PRE_INC:
562 case POST_DEC:
563 case POST_INC:
564 case PRE_MODIFY:
565 case POST_MODIFY:
566 if (after_insn)
567 return 0;
568 break;
570 default:
571 break;
574 for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--)
576 if (fmt[i] == 'e')
578 if (! oprs_unchanged_p (XEXP (x, i), insn, after_insn))
579 return 0;
581 else if (fmt[i] == 'E')
582 for (j = 0; j < XVECLEN (x, i); j++)
583 if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, after_insn))
584 return 0;
587 return 1;
591 /* Used for communication between find_mem_conflicts and
592 load_killed_in_block_p. Nonzero if find_mem_conflicts finds a
593 conflict between two memory references.
594 This is a bit of a hack to work around the limitations of note_stores. */
595 static int mems_conflict_p;
597 /* DEST is the output of an instruction. If it is a memory reference, and
598 possibly conflicts with the load found in DATA, then set mems_conflict_p
599 to a nonzero value. */
601 static void
602 find_mem_conflicts (rtx dest, const_rtx setter ATTRIBUTE_UNUSED,
603 void *data)
605 rtx mem_op = (rtx) data;
607 while (GET_CODE (dest) == SUBREG
608 || GET_CODE (dest) == ZERO_EXTRACT
609 || GET_CODE (dest) == STRICT_LOW_PART)
610 dest = XEXP (dest, 0);
612 /* If DEST is not a MEM, then it will not conflict with the load. Note
613 that function calls are assumed to clobber memory, but are handled
614 elsewhere. */
615 if (! MEM_P (dest))
616 return;
618 if (true_dependence (dest, GET_MODE (dest), mem_op))
619 mems_conflict_p = 1;
623 /* Return nonzero if the expression in X (a memory reference) is killed
624 in the current basic block before (if AFTER_INSN is false) or after
625 (if AFTER_INSN is true) the insn with the CUID in UID_LIMIT.
627 This function assumes that the modifies_mem table is flushed when
628 the hash table construction or redundancy elimination phases start
629 processing a new basic block. */
631 static int
632 load_killed_in_block_p (int uid_limit, rtx x, bool after_insn)
634 struct modifies_mem *list_entry = modifies_mem_list;
636 while (list_entry)
638 rtx_insn *setter = list_entry->insn;
640 /* Ignore entries in the list that do not apply. */
641 if ((after_insn
642 && INSN_CUID (setter) < uid_limit)
643 || (! after_insn
644 && INSN_CUID (setter) > uid_limit))
646 list_entry = list_entry->next;
647 continue;
650 /* If SETTER is a call everything is clobbered. Note that calls
651 to pure functions are never put on the list, so we need not
652 worry about them. */
653 if (CALL_P (setter))
654 return 1;
656 /* SETTER must be an insn of some kind that sets memory. Call
657 note_stores to examine each hunk of memory that is modified.
658 It will set mems_conflict_p to nonzero if there may be a
659 conflict between X and SETTER. */
660 mems_conflict_p = 0;
661 note_stores (setter, find_mem_conflicts, x);
662 if (mems_conflict_p)
663 return 1;
665 list_entry = list_entry->next;
667 return 0;
671 /* Record register first/last/block set information for REGNO in INSN. */
673 static inline void
674 record_last_reg_set_info (rtx_insn *insn, rtx reg)
676 unsigned int regno, end_regno;
678 regno = REGNO (reg);
679 end_regno = END_REGNO (reg);
681 reg_avail_info[regno] = INSN_CUID (insn);
682 while (++regno < end_regno);
685 static inline void
686 record_last_reg_set_info_regno (rtx_insn *insn, int regno)
688 reg_avail_info[regno] = INSN_CUID (insn);
692 /* Record memory modification information for INSN. We do not actually care
693 about the memory location(s) that are set, or even how they are set (consider
694 a CALL_INSN). We merely need to record which insns modify memory. */
696 static void
697 record_last_mem_set_info (rtx_insn *insn)
699 struct modifies_mem *list_entry;
701 list_entry = (struct modifies_mem *) obstack_alloc (&modifies_mem_obstack,
702 sizeof (struct modifies_mem));
703 list_entry->insn = insn;
704 list_entry->next = modifies_mem_list;
705 modifies_mem_list = list_entry;
707 record_last_mem_set_info_common (insn, modify_mem_list,
708 canon_modify_mem_list,
709 modify_mem_list_set,
710 blocks_with_calls);
713 /* Called from compute_hash_table via note_stores to handle one
714 SET or CLOBBER in an insn. DATA is really the instruction in which
715 the SET is taking place. */
717 static void
718 record_last_set_info (rtx dest, const_rtx setter ATTRIBUTE_UNUSED, void *data)
720 rtx_insn *last_set_insn = (rtx_insn *) data;
722 if (GET_CODE (dest) == SUBREG)
723 dest = SUBREG_REG (dest);
725 if (REG_P (dest))
726 record_last_reg_set_info (last_set_insn, dest);
727 else if (MEM_P (dest))
729 /* Ignore pushes, they don't clobber memory. They may still
730 clobber the stack pointer though. Some targets do argument
731 pushes without adding REG_INC notes. See e.g. PR25196,
732 where a pushsi2 on i386 doesn't have REG_INC notes. Note
733 such changes here too. */
734 if (! push_operand (dest, GET_MODE (dest)))
735 record_last_mem_set_info (last_set_insn);
736 else
737 record_last_reg_set_info_regno (last_set_insn, STACK_POINTER_REGNUM);
742 /* Reset tables used to keep track of what's still available since the
743 start of the block. */
745 static void
746 reset_opr_set_tables (void)
748 memset (reg_avail_info, 0, FIRST_PSEUDO_REGISTER * sizeof (int));
749 obstack_free (&modifies_mem_obstack, modifies_mem_obstack_bottom);
750 modifies_mem_list = NULL;
754 /* Record things set by INSN.
755 This data is used by oprs_unchanged_p. */
757 static void
758 record_opr_changes (rtx_insn *insn)
760 rtx note;
762 /* Find all stores and record them. */
763 note_stores (insn, record_last_set_info, insn);
765 /* Also record autoincremented REGs for this insn as changed. */
766 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
767 if (REG_NOTE_KIND (note) == REG_INC)
768 record_last_reg_set_info (insn, XEXP (note, 0));
770 /* Finally, if this is a call, record all call clobbers. */
771 if (CALL_P (insn))
773 unsigned int regno;
774 hard_reg_set_iterator hrsi;
775 /* We don't track modes of hard registers, so we need to be
776 conservative and assume that partial kills are full kills. */
777 HARD_REG_SET callee_clobbers
778 = insn_callee_abi (insn).full_and_partial_reg_clobbers ();
779 EXECUTE_IF_SET_IN_HARD_REG_SET (callee_clobbers, 0, regno, hrsi)
780 record_last_reg_set_info_regno (insn, regno);
782 if (! RTL_CONST_OR_PURE_CALL_P (insn)
783 || RTL_LOOPING_CONST_OR_PURE_CALL_P (insn)
784 || can_throw_external (insn))
785 record_last_mem_set_info (insn);
790 /* Scan the pattern of INSN and add an entry to the hash TABLE.
791 After reload we are interested in loads/stores only. */
793 static void
794 hash_scan_set (rtx_insn *insn)
796 rtx pat = PATTERN (insn);
797 rtx src = SET_SRC (pat);
798 rtx dest = SET_DEST (pat);
800 /* We are only interested in loads and stores. */
801 if (! MEM_P (src) && ! MEM_P (dest))
802 return;
804 /* Don't mess with jumps and nops. */
805 if (JUMP_P (insn) || set_noop_p (pat))
806 return;
808 if (REG_P (dest))
810 if (/* Don't CSE something if we can't do a reg/reg copy. */
811 can_copy_p (GET_MODE (dest))
812 /* Is SET_SRC something we want to gcse? */
813 && general_operand (src, GET_MODE (src))
814 #ifdef STACK_REGS
815 /* Never consider insns touching the register stack. It may
816 create situations that reg-stack cannot handle (e.g. a stack
817 register live across an abnormal edge). */
818 && (REGNO (dest) < FIRST_STACK_REG || REGNO (dest) > LAST_STACK_REG)
819 #endif
820 /* An expression is not available if its operands are
821 subsequently modified, including this insn. */
822 && oprs_unchanged_p (src, insn, true))
824 insert_expr_in_table (src, insn);
827 else if (REG_P (src))
829 /* Only record sets of pseudo-regs in the hash table. */
830 if (/* Don't CSE something if we can't do a reg/reg copy. */
831 can_copy_p (GET_MODE (src))
832 /* Is SET_DEST something we want to gcse? */
833 && general_operand (dest, GET_MODE (dest))
834 #ifdef STACK_REGS
835 /* As above for STACK_REGS. */
836 && (REGNO (src) < FIRST_STACK_REG || REGNO (src) > LAST_STACK_REG)
837 #endif
838 && ! (flag_float_store && FLOAT_MODE_P (GET_MODE (dest)))
839 /* Check if the memory expression is killed after insn. */
840 && ! load_killed_in_block_p (INSN_CUID (insn) + 1, dest, true)
841 && oprs_unchanged_p (XEXP (dest, 0), insn, true))
843 insert_expr_in_table (dest, insn);
849 /* Create hash table of memory expressions available at end of basic
850 blocks. Basically you should think of this hash table as the
851 representation of AVAIL_OUT. This is the set of expressions that
852 is generated in a basic block and not killed before the end of the
853 same basic block. Notice that this is really a local computation. */
855 static void
856 compute_hash_table (void)
858 basic_block bb;
860 FOR_EACH_BB_FN (bb, cfun)
862 rtx_insn *insn;
864 /* First pass over the instructions records information used to
865 determine when registers and memory are last set.
866 Since we compute a "local" AVAIL_OUT, reset the tables that
867 help us keep track of what has been modified since the start
868 of the block. */
869 reset_opr_set_tables ();
870 FOR_BB_INSNS (bb, insn)
872 if (INSN_P (insn))
873 record_opr_changes (insn);
876 /* The next pass actually builds the hash table. */
877 FOR_BB_INSNS (bb, insn)
878 if (INSN_P (insn) && GET_CODE (PATTERN (insn)) == SET)
879 hash_scan_set (insn);
884 /* Check if register REG is killed in any insn waiting to be inserted on
885 edge E. This function is required to check that our data flow analysis
886 is still valid prior to commit_edge_insertions. */
888 static bool
889 reg_killed_on_edge (rtx reg, edge e)
891 rtx_insn *insn;
893 for (insn = e->insns.r; insn; insn = NEXT_INSN (insn))
894 if (INSN_P (insn) && reg_set_p (reg, insn))
895 return true;
897 return false;
900 /* Similar to above - check if register REG is used in any insn waiting
901 to be inserted on edge E.
902 Assumes no such insn can be a CALL_INSN; if so call reg_used_between_p
903 with PREV(insn),NEXT(insn) instead of calling reg_overlap_mentioned_p. */
905 static bool
906 reg_used_on_edge (rtx reg, edge e)
908 rtx_insn *insn;
910 for (insn = e->insns.r; insn; insn = NEXT_INSN (insn))
911 if (INSN_P (insn) && reg_overlap_mentioned_p (reg, PATTERN (insn)))
912 return true;
914 return false;
917 /* Return the loaded/stored register of a load/store instruction. */
919 static rtx
920 get_avail_load_store_reg (rtx_insn *insn)
922 if (REG_P (SET_DEST (PATTERN (insn))))
923 /* A load. */
924 return SET_DEST (PATTERN (insn));
925 else
927 /* A store. */
928 gcc_assert (REG_P (SET_SRC (PATTERN (insn))));
929 return SET_SRC (PATTERN (insn));
933 /* Return nonzero if the predecessors of BB are "well behaved". */
935 static bool
936 bb_has_well_behaved_predecessors (basic_block bb)
938 edge pred;
939 edge_iterator ei;
941 if (EDGE_COUNT (bb->preds) == 0)
942 return false;
944 FOR_EACH_EDGE (pred, ei, bb->preds)
946 /* commit_one_edge_insertion refuses to insert on abnormal edges even if
947 the source has only one successor so EDGE_CRITICAL_P is too weak. */
948 if ((pred->flags & EDGE_ABNORMAL) && !single_pred_p (pred->dest))
949 return false;
951 if ((pred->flags & EDGE_ABNORMAL_CALL) && cfun->has_nonlocal_label)
952 return false;
954 if (tablejump_p (BB_END (pred->src), NULL, NULL))
955 return false;
957 return true;
961 /* Search for the occurrences of expression in BB. */
963 static struct occr*
964 get_bb_avail_insn (basic_block bb, struct occr *orig_occr, int bitmap_index)
966 struct occr *occr = orig_occr;
968 for (; occr != NULL; occr = occr->next)
969 if (BLOCK_FOR_INSN (occr->insn) == bb)
970 return occr;
972 /* If we could not find an occurrence in BB, see if BB
973 has a single predecessor with an occurrence that is
974 transparent through BB. */
975 if (transp
976 && single_pred_p (bb)
977 && bitmap_bit_p (transp[bb->index], bitmap_index)
978 && (occr = get_bb_avail_insn (single_pred (bb), orig_occr, bitmap_index)))
980 rtx avail_reg = get_avail_load_store_reg (occr->insn);
981 if (!reg_set_between_p (avail_reg,
982 PREV_INSN (BB_HEAD (bb)),
983 NEXT_INSN (BB_END (bb)))
984 && !reg_killed_on_edge (avail_reg, single_pred_edge (bb)))
985 return occr;
988 return NULL;
992 /* This helper is called via htab_traverse. */
994 compute_expr_transp (expr **slot, FILE *dump_file ATTRIBUTE_UNUSED)
996 struct expr *expr = *slot;
998 compute_transp (expr->expr, expr->bitmap_index, transp,
999 blocks_with_calls, modify_mem_list_set,
1000 canon_modify_mem_list);
1001 return 1;
1004 /* This handles the case where several stores feed a partially redundant
1005 load. It checks if the redundancy elimination is possible and if it's
1006 worth it.
1008 Redundancy elimination is possible if,
1009 1) None of the operands of an insn have been modified since the start
1010 of the current basic block.
1011 2) In any predecessor of the current basic block, the same expression
1012 is generated.
1014 See the function body for the heuristics that determine if eliminating
1015 a redundancy is also worth doing, assuming it is possible. */
1017 static void
1018 eliminate_partially_redundant_load (basic_block bb, rtx_insn *insn,
1019 struct expr *expr)
1021 edge pred;
1022 rtx_insn *avail_insn = NULL;
1023 rtx avail_reg;
1024 rtx dest, pat;
1025 struct occr *a_occr;
1026 struct unoccr *occr, *avail_occrs = NULL;
1027 struct unoccr *unoccr, *unavail_occrs = NULL, *rollback_unoccr = NULL;
1028 int npred_ok = 0;
1029 profile_count ok_count = profile_count::zero ();
1030 /* Redundant load execution count. */
1031 profile_count critical_count = profile_count::zero ();
1032 /* Execution count of critical edges. */
1033 edge_iterator ei;
1034 bool critical_edge_split = false;
1036 /* The execution count of the loads to be added to make the
1037 load fully redundant. */
1038 profile_count not_ok_count = profile_count::zero ();
1039 basic_block pred_bb;
1041 pat = PATTERN (insn);
1042 dest = SET_DEST (pat);
1044 /* Check that the loaded register is not used, set, or killed from the
1045 beginning of the block. */
1046 if (reg_changed_after_insn_p (dest, 0)
1047 || reg_used_between_p (dest, PREV_INSN (BB_HEAD (bb)), insn))
1048 return;
1050 /* Check potential for replacing load with copy for predecessors. */
1051 FOR_EACH_EDGE (pred, ei, bb->preds)
1053 rtx_insn *next_pred_bb_end;
1055 avail_insn = NULL;
1056 avail_reg = NULL_RTX;
1057 pred_bb = pred->src;
1058 for (a_occr = get_bb_avail_insn (pred_bb,
1059 expr->avail_occr,
1060 expr->bitmap_index);
1061 a_occr;
1062 a_occr = get_bb_avail_insn (pred_bb,
1063 a_occr->next,
1064 expr->bitmap_index))
1066 /* Check if the loaded register is not used. */
1067 avail_insn = a_occr->insn;
1068 avail_reg = get_avail_load_store_reg (avail_insn);
1069 gcc_assert (avail_reg);
1071 /* Make sure we can generate a move from register avail_reg to
1072 dest. */
1073 rtx_insn *move = gen_move_insn (copy_rtx (dest),
1074 copy_rtx (avail_reg));
1075 extract_insn (move);
1076 if (! constrain_operands (1, get_preferred_alternatives (insn,
1077 pred_bb))
1078 || reg_killed_on_edge (avail_reg, pred)
1079 || reg_used_on_edge (dest, pred))
1081 avail_insn = NULL;
1082 continue;
1084 next_pred_bb_end = NEXT_INSN (BB_END (BLOCK_FOR_INSN (avail_insn)));
1085 if (!reg_set_between_p (avail_reg, avail_insn, next_pred_bb_end))
1086 /* AVAIL_INSN remains non-null. */
1087 break;
1088 else
1089 avail_insn = NULL;
1092 if (EDGE_CRITICAL_P (pred) && pred->count ().initialized_p ())
1093 critical_count += pred->count ();
1095 if (avail_insn != NULL_RTX)
1097 npred_ok++;
1098 if (pred->count ().initialized_p ())
1099 ok_count = ok_count + pred->count ();
1100 if (! set_noop_p (PATTERN (gen_move_insn (copy_rtx (dest),
1101 copy_rtx (avail_reg)))))
1103 /* Check if there is going to be a split. */
1104 if (EDGE_CRITICAL_P (pred))
1105 critical_edge_split = true;
1107 else /* Its a dead move no need to generate. */
1108 continue;
1109 occr = (struct unoccr *) obstack_alloc (&unoccr_obstack,
1110 sizeof (struct unoccr));
1111 occr->insn = avail_insn;
1112 occr->pred = pred;
1113 occr->next = avail_occrs;
1114 avail_occrs = occr;
1115 if (! rollback_unoccr)
1116 rollback_unoccr = occr;
1118 else
1120 /* Adding a load on a critical edge will cause a split. */
1121 if (EDGE_CRITICAL_P (pred))
1122 critical_edge_split = true;
1123 if (pred->count ().initialized_p ())
1124 not_ok_count = not_ok_count + pred->count ();
1125 unoccr = (struct unoccr *) obstack_alloc (&unoccr_obstack,
1126 sizeof (struct unoccr));
1127 unoccr->insn = NULL;
1128 unoccr->pred = pred;
1129 unoccr->next = unavail_occrs;
1130 unavail_occrs = unoccr;
1131 if (! rollback_unoccr)
1132 rollback_unoccr = unoccr;
1136 if (/* No load can be replaced by copy. */
1137 npred_ok == 0
1138 /* Prevent exploding the code. */
1139 || (optimize_bb_for_size_p (bb) && npred_ok > 1)
1140 /* If we don't have profile information we cannot tell if splitting
1141 a critical edge is profitable or not so don't do it. */
1142 || ((!profile_info || profile_status_for_fn (cfun) != PROFILE_READ
1143 || targetm.cannot_modify_jumps_p ())
1144 && critical_edge_split))
1145 goto cleanup;
1147 /* Check if it's worth applying the partial redundancy elimination. */
1148 if (ok_count.to_gcov_type ()
1149 < param_gcse_after_reload_partial_fraction * not_ok_count.to_gcov_type ())
1150 goto cleanup;
1152 gcov_type threshold;
1153 #if (GCC_VERSION >= 5000)
1154 if (__builtin_mul_overflow (param_gcse_after_reload_critical_fraction,
1155 critical_count.to_gcov_type (), &threshold))
1156 threshold = profile_count::max_count;
1157 #else
1158 threshold
1159 = (param_gcse_after_reload_critical_fraction
1160 * critical_count.to_gcov_type ());
1161 #endif
1163 if (ok_count.to_gcov_type () < threshold)
1164 goto cleanup;
1166 /* Generate moves to the loaded register from where
1167 the memory is available. */
1168 for (occr = avail_occrs; occr; occr = occr->next)
1170 avail_insn = occr->insn;
1171 pred = occr->pred;
1172 /* Set avail_reg to be the register having the value of the
1173 memory. */
1174 avail_reg = get_avail_load_store_reg (avail_insn);
1175 gcc_assert (avail_reg);
1177 insert_insn_on_edge (gen_move_insn (copy_rtx (dest),
1178 copy_rtx (avail_reg)),
1179 pred);
1180 stats.moves_inserted++;
1182 if (dump_file)
1183 fprintf (dump_file,
1184 "generating move from %d to %d on edge from %d to %d\n",
1185 REGNO (avail_reg),
1186 REGNO (dest),
1187 pred->src->index,
1188 pred->dest->index);
1191 /* Regenerate loads where the memory is unavailable. */
1192 for (unoccr = unavail_occrs; unoccr; unoccr = unoccr->next)
1194 pred = unoccr->pred;
1195 insert_insn_on_edge (copy_insn (PATTERN (insn)), pred);
1196 stats.copies_inserted++;
1198 if (dump_file)
1200 fprintf (dump_file,
1201 "generating on edge from %d to %d a copy of load: ",
1202 pred->src->index,
1203 pred->dest->index);
1204 print_rtl (dump_file, PATTERN (insn));
1205 fprintf (dump_file, "\n");
1209 /* Delete the insn if it is not available in this block and mark it
1210 for deletion if it is available. If insn is available it may help
1211 discover additional redundancies, so mark it for later deletion. */
1212 for (a_occr = get_bb_avail_insn (bb, expr->avail_occr, expr->bitmap_index);
1213 a_occr && (a_occr->insn != insn);
1214 a_occr = get_bb_avail_insn (bb, a_occr->next, expr->bitmap_index))
1217 if (!a_occr)
1219 stats.insns_deleted++;
1221 if (dump_file)
1223 fprintf (dump_file, "deleting insn:\n");
1224 print_rtl_single (dump_file, insn);
1225 fprintf (dump_file, "\n");
1227 delete_insn (insn);
1229 else
1230 a_occr->deleted_p = 1;
1232 cleanup:
1233 if (rollback_unoccr)
1234 obstack_free (&unoccr_obstack, rollback_unoccr);
1237 /* Performing the redundancy elimination as described before. */
1239 static void
1240 eliminate_partially_redundant_loads (void)
1242 rtx_insn *insn;
1243 basic_block bb;
1245 /* Note we start at block 1. */
1247 if (ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
1248 return;
1250 FOR_BB_BETWEEN (bb,
1251 ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb->next_bb,
1252 EXIT_BLOCK_PTR_FOR_FN (cfun),
1253 next_bb)
1255 /* Don't try anything on basic blocks with strange predecessors. */
1256 if (! bb_has_well_behaved_predecessors (bb))
1257 continue;
1259 /* Do not try anything on cold basic blocks. */
1260 if (optimize_bb_for_size_p (bb))
1261 continue;
1263 /* Reset the table of things changed since the start of the current
1264 basic block. */
1265 reset_opr_set_tables ();
1267 /* Look at all insns in the current basic block and see if there are
1268 any loads in it that we can record. */
1269 FOR_BB_INSNS (bb, insn)
1271 /* Is it a load - of the form (set (reg) (mem))? */
1272 if (NONJUMP_INSN_P (insn)
1273 && GET_CODE (PATTERN (insn)) == SET
1274 && REG_P (SET_DEST (PATTERN (insn)))
1275 && MEM_P (SET_SRC (PATTERN (insn))))
1277 rtx pat = PATTERN (insn);
1278 rtx src = SET_SRC (pat);
1279 struct expr *expr;
1281 if (!MEM_VOLATILE_P (src)
1282 && GET_MODE (src) != BLKmode
1283 && general_operand (src, GET_MODE (src))
1284 /* Are the operands unchanged since the start of the
1285 block? */
1286 && oprs_unchanged_p (src, insn, false)
1287 && !(cfun->can_throw_non_call_exceptions && may_trap_p (src))
1288 && !side_effects_p (src)
1289 /* Is the expression recorded? */
1290 && (expr = lookup_expr_in_table (src)) != NULL)
1292 /* We now have a load (insn) and an available memory at
1293 its BB start (expr). Try to remove the loads if it is
1294 redundant. */
1295 eliminate_partially_redundant_load (bb, insn, expr);
1299 /* Keep track of everything modified by this insn, so that we
1300 know what has been modified since the start of the current
1301 basic block. */
1302 if (INSN_P (insn))
1303 record_opr_changes (insn);
1307 commit_edge_insertions ();
1310 /* Go over the expression hash table and delete insns that were
1311 marked for later deletion. */
1313 /* This helper is called via htab_traverse. */
1315 delete_redundant_insns_1 (expr **slot, void *data ATTRIBUTE_UNUSED)
1317 struct expr *exprs = *slot;
1318 struct occr *occr;
1320 for (occr = exprs->avail_occr; occr != NULL; occr = occr->next)
1322 if (occr->deleted_p && dbg_cnt (gcse2_delete))
1324 delete_insn (occr->insn);
1325 stats.insns_deleted++;
1327 if (dump_file)
1329 fprintf (dump_file, "deleting insn:\n");
1330 print_rtl_single (dump_file, occr->insn);
1331 fprintf (dump_file, "\n");
1336 return 1;
1339 static void
1340 delete_redundant_insns (void)
1342 expr_table->traverse <void *, delete_redundant_insns_1> (NULL);
1343 if (dump_file)
1344 fprintf (dump_file, "\n");
1347 /* Main entry point of the GCSE after reload - clean some redundant loads
1348 due to spilling. */
1350 static void
1351 gcse_after_reload_main (rtx f ATTRIBUTE_UNUSED)
1353 /* Disable computing transparentness if it is too expensive. */
1354 bool do_transp
1355 = !gcse_or_cprop_is_too_expensive (_("using simple load CSE after register "
1356 "allocation"));
1358 memset (&stats, 0, sizeof (stats));
1360 /* Allocate memory for this pass.
1361 Also computes and initializes the insns' CUIDs. */
1362 alloc_mem ();
1364 /* We need alias analysis. */
1365 init_alias_analysis ();
1367 compute_hash_table ();
1369 if (dump_file)
1370 dump_hash_table (dump_file);
1372 if (!expr_table->is_empty ())
1374 /* Knowing which MEMs are transparent through a block can signifiantly
1375 increase the number of redundant loads found. So compute transparency
1376 information for each memory expression in the hash table. */
1377 df_analyze ();
1378 if (do_transp)
1380 /* This cannot be part of the normal allocation routine because
1381 we have to know the number of elements in the hash table. */
1382 transp = sbitmap_vector_alloc (last_basic_block_for_fn (cfun),
1383 expr_table->elements ());
1384 bitmap_vector_ones (transp, last_basic_block_for_fn (cfun));
1385 expr_table->traverse <FILE *, compute_expr_transp> (dump_file);
1387 else
1388 transp = NULL;
1389 eliminate_partially_redundant_loads ();
1390 delete_redundant_insns ();
1391 if (do_transp)
1392 sbitmap_vector_free (transp);
1394 if (dump_file)
1396 fprintf (dump_file, "GCSE AFTER RELOAD stats:\n");
1397 fprintf (dump_file, "copies inserted: %d\n", stats.copies_inserted);
1398 fprintf (dump_file, "moves inserted: %d\n", stats.moves_inserted);
1399 fprintf (dump_file, "insns deleted: %d\n", stats.insns_deleted);
1400 fprintf (dump_file, "\n\n");
1403 statistics_counter_event (cfun, "copies inserted",
1404 stats.copies_inserted);
1405 statistics_counter_event (cfun, "moves inserted",
1406 stats.moves_inserted);
1407 statistics_counter_event (cfun, "insns deleted",
1408 stats.insns_deleted);
1411 /* We are finished with alias. */
1412 end_alias_analysis ();
1414 free_mem ();
1419 static unsigned int
1420 rest_of_handle_gcse2 (void)
1422 gcse_after_reload_main (get_insns ());
1423 rebuild_jump_labels (get_insns ());
1424 return 0;
1427 namespace {
1429 const pass_data pass_data_gcse2 =
1431 RTL_PASS, /* type */
1432 "gcse2", /* name */
1433 OPTGROUP_NONE, /* optinfo_flags */
1434 TV_GCSE_AFTER_RELOAD, /* tv_id */
1435 0, /* properties_required */
1436 0, /* properties_provided */
1437 0, /* properties_destroyed */
1438 0, /* todo_flags_start */
1439 0, /* todo_flags_finish */
1442 class pass_gcse2 : public rtl_opt_pass
1444 public:
1445 pass_gcse2 (gcc::context *ctxt)
1446 : rtl_opt_pass (pass_data_gcse2, ctxt)
1449 /* opt_pass methods: */
1450 virtual bool gate (function *fun)
1452 return (optimize > 0 && flag_gcse_after_reload
1453 && optimize_function_for_speed_p (fun));
1456 virtual unsigned int execute (function *) { return rest_of_handle_gcse2 (); }
1458 }; // class pass_gcse2
1460 } // anon namespace
1462 rtl_opt_pass *
1463 make_pass_gcse2 (gcc::context *ctxt)
1465 return new pass_gcse2 (ctxt);