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78d140c9 | 1 | /* Post reload partially redundant load elimination |
2b4876d2 | 2 | Copyright (C) 2004, 2005 |
78d140c9 | 3 | Free Software Foundation, Inc. |
4 | ||
5 | This file is part of GCC. | |
6 | ||
7 | GCC is free software; you can redistribute it and/or modify it under | |
8 | the terms of the GNU General Public License as published by the Free | |
9 | Software Foundation; either version 2, or (at your option) any later | |
10 | version. | |
11 | ||
12 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
13 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
14 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
15 | for more details. | |
16 | ||
17 | You should have received a copy of the GNU General Public License | |
18 | along with GCC; see the file COPYING. If not, write to the Free | |
19 | Software Foundation, 59 Temple Place - Suite 330, Boston, MA | |
20 | 02111-1307, USA. */ | |
21 | ||
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
26 | #include "toplev.h" | |
27 | ||
28 | #include "rtl.h" | |
29 | #include "tree.h" | |
30 | #include "tm_p.h" | |
31 | #include "regs.h" | |
32 | #include "hard-reg-set.h" | |
33 | #include "flags.h" | |
34 | #include "real.h" | |
35 | #include "insn-config.h" | |
36 | #include "recog.h" | |
37 | #include "basic-block.h" | |
38 | #include "output.h" | |
39 | #include "function.h" | |
40 | #include "expr.h" | |
41 | #include "except.h" | |
42 | #include "intl.h" | |
43 | #include "obstack.h" | |
44 | #include "hashtab.h" | |
45 | #include "params.h" | |
46 | ||
47 | /* The following code implements gcse after reload, the purpose of this | |
48 | pass is to cleanup redundant loads generated by reload and other | |
49 | optimizations that come after gcse. It searches for simple inter-block | |
50 | redundancies and tries to eliminate them by adding moves and loads | |
51 | in cold places. | |
52 | ||
53 | Perform partially redundant load elimination, try to eliminate redundant | |
54 | loads created by the reload pass. We try to look for full or partial | |
55 | redundant loads fed by one or more loads/stores in predecessor BBs, | |
56 | and try adding loads to make them fully redundant. We also check if | |
57 | it's worth adding loads to be able to delete the redundant load. | |
58 | ||
59 | Algorithm: | |
60 | 1. Build available expressions hash table: | |
61 | For each load/store instruction, if the loaded/stored memory didn't | |
62 | change until the end of the basic block add this memory expression to | |
63 | the hash table. | |
64 | 2. Perform Redundancy elimination: | |
65 | For each load instruction do the following: | |
66 | perform partial redundancy elimination, check if it's worth adding | |
67 | loads to make the load fully redundant. If so add loads and | |
68 | register copies and delete the load. | |
69 | 3. Delete instructions made redundant in step 2. | |
70 | ||
71 | Future enhancement: | |
72 | If the loaded register is used/defined between load and some store, | |
73 | look for some other free register between load and all its stores, | |
74 | and replace the load with a copy from this register to the loaded | |
75 | register. | |
76 | */ | |
77 | \f | |
78 | ||
79 | /* Keep statistics of this pass. */ | |
80 | static struct | |
81 | { | |
82 | int moves_inserted; | |
83 | int copies_inserted; | |
84 | int insns_deleted; | |
85 | } stats; | |
86 | ||
87 | /* We need to keep a hash table of expressions. The table entries are of | |
88 | type 'struct expr', and for each expression there is a single linked | |
91275768 | 89 | list of occurrences. */ |
78d140c9 | 90 | |
91 | /* The table itself. */ | |
92 | static htab_t expr_table; | |
93 | ||
94 | /* Expression elements in the hash table. */ | |
95 | struct expr | |
96 | { | |
97 | /* The expression (SET_SRC for expressions, PATTERN for assignments). */ | |
98 | rtx expr; | |
99 | ||
100 | /* The same hash for this entry. */ | |
101 | hashval_t hash; | |
102 | ||
103 | /* List of available occurrence in basic blocks in the function. */ | |
104 | struct occr *avail_occr; | |
105 | }; | |
106 | ||
107 | static struct obstack expr_obstack; | |
108 | ||
109 | /* Occurrence of an expression. | |
91275768 | 110 | There is at most one occurrence per basic block. If a pattern appears |
78d140c9 | 111 | more than once, the last appearance is used. */ |
112 | ||
113 | struct occr | |
114 | { | |
115 | /* Next occurrence of this expression. */ | |
116 | struct occr *next; | |
117 | /* The insn that computes the expression. */ | |
118 | rtx insn; | |
119 | /* Nonzero if this [anticipatable] occurrence has been deleted. */ | |
120 | char deleted_p; | |
121 | }; | |
122 | ||
123 | static struct obstack occr_obstack; | |
124 | ||
125 | /* The following structure holds the information about the occurrences of | |
126 | the redundant instructions. */ | |
127 | struct unoccr | |
128 | { | |
129 | struct unoccr *next; | |
130 | edge pred; | |
131 | rtx insn; | |
132 | }; | |
133 | ||
134 | static struct obstack unoccr_obstack; | |
135 | ||
136 | /* Array where each element is the CUID if the insn that last set the hard | |
137 | register with the number of the element, since the start of the current | |
d447762f | 138 | basic block. |
139 | ||
140 | This array is used during the building of the hash table (step 1) to | |
141 | determine if a reg is killed before the end of a basic block. | |
142 | ||
143 | It is also used when eliminating partial redundancies (step 2) to see | |
144 | if a reg was modified since the start of a basic block. */ | |
78d140c9 | 145 | static int *reg_avail_info; |
146 | ||
147 | /* A list of insns that may modify memory within the current basic block. */ | |
148 | struct modifies_mem | |
149 | { | |
150 | rtx insn; | |
151 | struct modifies_mem *next; | |
152 | }; | |
153 | static struct modifies_mem *modifies_mem_list; | |
154 | ||
155 | /* The modifies_mem structs also go on an obstack, only this obstack is | |
156 | freed each time after completing the analysis or transformations on | |
157 | a basic block. So we allocate a dummy modifies_mem_obstack_bottom | |
158 | object on the obstack to keep track of the bottom of the obstack. */ | |
159 | static struct obstack modifies_mem_obstack; | |
160 | static struct modifies_mem *modifies_mem_obstack_bottom; | |
161 | ||
162 | /* Mapping of insn UIDs to CUIDs. | |
163 | CUIDs are like UIDs except they increase monotonically in each basic | |
164 | block, have no gaps, and only apply to real insns. */ | |
165 | static int *uid_cuid; | |
166 | #define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)]) | |
167 | \f | |
168 | ||
169 | /* Helpers for memory allocation/freeing. */ | |
170 | static void alloc_mem (void); | |
171 | static void free_mem (void); | |
172 | ||
173 | /* Support for hash table construction and transformations. */ | |
174 | static bool oprs_unchanged_p (rtx, rtx, bool); | |
175 | static void record_last_reg_set_info (rtx, int); | |
176 | static void record_last_mem_set_info (rtx); | |
177 | static void record_last_set_info (rtx, rtx, void *); | |
d447762f | 178 | static void record_opr_changes (rtx); |
78d140c9 | 179 | |
180 | static void find_mem_conflicts (rtx, rtx, void *); | |
181 | static int load_killed_in_block_p (int, rtx, bool); | |
182 | static void reset_opr_set_tables (void); | |
183 | ||
184 | /* Hash table support. */ | |
185 | static hashval_t hash_expr (rtx, int *); | |
186 | static hashval_t hash_expr_for_htab (const void *); | |
187 | static int expr_equiv_p (const void *, const void *); | |
188 | static void insert_expr_in_table (rtx, rtx); | |
189 | static struct expr *lookup_expr_in_table (rtx); | |
190 | static int dump_hash_table_entry (void **, void *); | |
191 | static void dump_hash_table (FILE *); | |
192 | ||
193 | /* Helpers for eliminate_partially_redundant_load. */ | |
194 | static bool reg_killed_on_edge (rtx, edge); | |
195 | static bool reg_used_on_edge (rtx, edge); | |
196 | ||
197 | static rtx reg_set_between_after_reload_p (rtx, rtx, rtx); | |
198 | static rtx reg_used_between_after_reload_p (rtx, rtx, rtx); | |
199 | static rtx get_avail_load_store_reg (rtx); | |
200 | ||
201 | static bool bb_has_well_behaved_predecessors (basic_block); | |
202 | static struct occr* get_bb_avail_insn (basic_block, struct occr *); | |
203 | static void hash_scan_set (rtx); | |
204 | static void compute_hash_table (void); | |
205 | ||
206 | /* The work horses of this pass. */ | |
207 | static void eliminate_partially_redundant_load (basic_block, | |
208 | rtx, | |
209 | struct expr *); | |
210 | static void eliminate_partially_redundant_loads (void); | |
211 | \f | |
212 | ||
213 | /* Allocate memory for the CUID mapping array and register/memory | |
214 | tracking tables. */ | |
215 | ||
216 | static void | |
217 | alloc_mem (void) | |
218 | { | |
219 | int i; | |
220 | basic_block bb; | |
221 | rtx insn; | |
222 | ||
223 | /* Find the largest UID and create a mapping from UIDs to CUIDs. */ | |
224 | uid_cuid = xcalloc (get_max_uid () + 1, sizeof (int)); | |
225 | i = 0; | |
226 | FOR_EACH_BB (bb) | |
227 | FOR_BB_INSNS (bb, insn) | |
228 | { | |
229 | if (INSN_P (insn)) | |
230 | uid_cuid[INSN_UID (insn)] = i++; | |
231 | else | |
232 | uid_cuid[INSN_UID (insn)] = i; | |
233 | } | |
234 | ||
235 | /* Allocate the available expressions hash table. We don't want to | |
236 | make the hash table too small, but unnecessarily making it too large | |
237 | also doesn't help. The i/4 is a gcse.c relic, and seems like a | |
238 | reasonable choice. */ | |
239 | expr_table = htab_create (MAX (i / 4, 13), | |
240 | hash_expr_for_htab, expr_equiv_p, NULL); | |
241 | ||
242 | /* We allocate everything on obstacks because we often can roll back | |
243 | the whole obstack to some point. Freeing obstacks is very fast. */ | |
244 | gcc_obstack_init (&expr_obstack); | |
245 | gcc_obstack_init (&occr_obstack); | |
246 | gcc_obstack_init (&unoccr_obstack); | |
247 | gcc_obstack_init (&modifies_mem_obstack); | |
248 | ||
249 | /* Working array used to track the last set for each register | |
250 | in the current block. */ | |
251 | reg_avail_info = (int *) xmalloc (FIRST_PSEUDO_REGISTER * sizeof (int)); | |
252 | ||
253 | /* Put a dummy modifies_mem object on the modifies_mem_obstack, so we | |
254 | can roll it back in reset_opr_set_tables. */ | |
255 | modifies_mem_obstack_bottom = | |
256 | (struct modifies_mem *) obstack_alloc (&modifies_mem_obstack, | |
257 | sizeof (struct modifies_mem)); | |
258 | } | |
259 | ||
260 | /* Free memory allocated by alloc_mem. */ | |
261 | ||
262 | static void | |
263 | free_mem (void) | |
264 | { | |
265 | free (uid_cuid); | |
266 | ||
267 | htab_delete (expr_table); | |
268 | ||
269 | obstack_free (&expr_obstack, NULL); | |
270 | obstack_free (&occr_obstack, NULL); | |
271 | obstack_free (&unoccr_obstack, NULL); | |
272 | obstack_free (&modifies_mem_obstack, NULL); | |
273 | ||
274 | free (reg_avail_info); | |
275 | } | |
276 | \f | |
277 | ||
278 | /* Hash expression X. | |
279 | DO_NOT_RECORD_P is a boolean indicating if a volatile operand is found | |
280 | or if the expression contains something we don't want to insert in the | |
281 | table. */ | |
282 | ||
283 | static hashval_t | |
284 | hash_expr (rtx x, int *do_not_record_p) | |
285 | { | |
286 | *do_not_record_p = 0; | |
287 | return hash_rtx (x, GET_MODE (x), do_not_record_p, | |
288 | NULL, /*have_reg_qty=*/false); | |
289 | } | |
290 | ||
291 | /* Callback for hashtab. | |
292 | Return the hash value for expression EXP. We don't actually hash | |
293 | here, we just return the cached hash value. */ | |
294 | ||
295 | static hashval_t | |
296 | hash_expr_for_htab (const void *expp) | |
297 | { | |
298 | struct expr *exp = (struct expr *) expp; | |
299 | return exp->hash; | |
300 | } | |
301 | ||
302 | /* Callbach for hashtab. | |
303 | Return nonzero if exp1 is equivalent to exp2. */ | |
304 | ||
305 | static int | |
306 | expr_equiv_p (const void *exp1p, const void *exp2p) | |
307 | { | |
308 | struct expr *exp1 = (struct expr *) exp1p; | |
309 | struct expr *exp2 = (struct expr *) exp2p; | |
310 | int equiv_p = exp_equiv_p (exp1->expr, exp2->expr, 0, true); | |
2045cdd4 | 311 | if (equiv_p |
312 | && exp1->hash != exp2->hash) | |
313 | abort (); | |
78d140c9 | 314 | return equiv_p; |
315 | } | |
316 | \f | |
317 | ||
318 | /* Insert expression X in INSN in the hash TABLE. | |
319 | If it is already present, record it as the last occurrence in INSN's | |
320 | basic block. */ | |
321 | ||
322 | static void | |
323 | insert_expr_in_table (rtx x, rtx insn) | |
324 | { | |
325 | int do_not_record_p; | |
326 | hashval_t hash; | |
327 | struct expr *cur_expr, **slot; | |
328 | struct occr *avail_occr, *last_occr = NULL; | |
329 | ||
330 | hash = hash_expr (x, &do_not_record_p); | |
331 | ||
332 | /* Do not insert expression in the table if it contains volatile operands, | |
333 | or if hash_expr determines the expression is something we don't want | |
334 | to or can't handle. */ | |
335 | if (do_not_record_p) | |
336 | return; | |
337 | ||
338 | /* We anticipate that redundant expressions are rare, so for convenience | |
339 | allocate a new hash table element here already and set its fields. | |
340 | If we don't do this, we need a hack with a static struct expr. Anyway, | |
341 | obstack_free is really fast and one more obstack_alloc doesn't hurt if | |
342 | we're going to see more expressions later on. */ | |
343 | cur_expr = (struct expr *) obstack_alloc (&expr_obstack, | |
344 | sizeof (struct expr)); | |
345 | cur_expr->expr = x; | |
346 | cur_expr->hash = hash; | |
347 | cur_expr->avail_occr = NULL; | |
348 | ||
349 | slot = (struct expr **) htab_find_slot_with_hash (expr_table, cur_expr, | |
350 | hash, INSERT); | |
351 | ||
352 | if (! (*slot)) | |
353 | /* The expression isn't found, so insert it. */ | |
354 | *slot = cur_expr; | |
355 | else | |
356 | { | |
357 | /* The expression is already in the table, so roll back the | |
358 | obstack and use the existing table entry. */ | |
359 | obstack_free (&expr_obstack, cur_expr); | |
360 | cur_expr = *slot; | |
361 | } | |
362 | ||
363 | /* Search for another occurrence in the same basic block. */ | |
364 | avail_occr = cur_expr->avail_occr; | |
365 | while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn)) | |
366 | { | |
367 | /* If an occurrence isn't found, save a pointer to the end of | |
368 | the list. */ | |
369 | last_occr = avail_occr; | |
370 | avail_occr = avail_occr->next; | |
371 | } | |
372 | ||
373 | if (avail_occr) | |
374 | /* Found another instance of the expression in the same basic block. | |
375 | Prefer this occurrence to the currently recorded one. We want | |
376 | the last one in the block and the block is scanned from start | |
377 | to end. */ | |
378 | avail_occr->insn = insn; | |
379 | else | |
380 | { | |
381 | /* First occurrence of this expression in this basic block. */ | |
382 | avail_occr = (struct occr *) obstack_alloc (&occr_obstack, | |
383 | sizeof (struct occr)); | |
384 | ||
385 | /* First occurrence of this expression in any block? */ | |
386 | if (cur_expr->avail_occr == NULL) | |
387 | cur_expr->avail_occr = avail_occr; | |
388 | else | |
389 | last_occr->next = avail_occr; | |
390 | ||
391 | avail_occr->insn = insn; | |
392 | avail_occr->next = NULL; | |
393 | avail_occr->deleted_p = 0; | |
394 | } | |
395 | } | |
396 | \f | |
397 | ||
398 | /* Lookup pattern PAT in the expression hash table. | |
399 | The result is a pointer to the table entry, or NULL if not found. */ | |
400 | ||
401 | static struct expr * | |
402 | lookup_expr_in_table (rtx pat) | |
403 | { | |
404 | int do_not_record_p; | |
405 | struct expr **slot, *tmp_expr; | |
406 | hashval_t hash = hash_expr (pat, &do_not_record_p); | |
407 | ||
408 | if (do_not_record_p) | |
409 | return NULL; | |
410 | ||
411 | tmp_expr = (struct expr *) obstack_alloc (&expr_obstack, | |
412 | sizeof (struct expr)); | |
413 | tmp_expr->expr = pat; | |
414 | tmp_expr->hash = hash; | |
415 | tmp_expr->avail_occr = NULL; | |
416 | ||
417 | slot = (struct expr **) htab_find_slot_with_hash (expr_table, tmp_expr, | |
418 | hash, INSERT); | |
419 | obstack_free (&expr_obstack, tmp_expr); | |
420 | ||
421 | if (!slot) | |
422 | return NULL; | |
423 | else | |
424 | return (*slot); | |
425 | } | |
426 | \f | |
427 | ||
91275768 | 428 | /* Dump all expressions and occurrences that are currently in the |
78d140c9 | 429 | expression hash table to FILE. */ |
430 | ||
431 | /* This helper is called via htab_traverse. */ | |
432 | static int | |
433 | dump_hash_table_entry (void **slot, void *filep) | |
434 | { | |
435 | struct expr *expr = (struct expr *) *slot; | |
436 | FILE *file = (FILE *) filep; | |
437 | struct occr *occr; | |
438 | ||
439 | fprintf (file, "expr: "); | |
440 | print_rtl (file, expr->expr); | |
441 | fprintf (file,"\nhashcode: %u\n", expr->hash); | |
442 | fprintf (file,"list of occurences:\n"); | |
443 | occr = expr->avail_occr; | |
444 | while (occr) | |
445 | { | |
446 | rtx insn = occr->insn; | |
447 | print_rtl_single (file, insn); | |
448 | fprintf (file, "\n"); | |
449 | occr = occr->next; | |
450 | } | |
451 | fprintf (file, "\n"); | |
452 | return 1; | |
453 | } | |
454 | ||
455 | static void | |
456 | dump_hash_table (FILE *file) | |
457 | { | |
458 | fprintf (file, "\n\nexpression hash table\n"); | |
459 | fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n", | |
460 | (long) htab_size (expr_table), | |
461 | (long) htab_elements (expr_table), | |
462 | htab_collisions (expr_table)); | |
463 | if (htab_elements (expr_table) > 0) | |
464 | { | |
465 | fprintf (file, "\n\ntable entries:\n"); | |
466 | htab_traverse (expr_table, dump_hash_table_entry, file); | |
467 | } | |
468 | fprintf (file, "\n"); | |
469 | } | |
470 | \f | |
471 | ||
d447762f | 472 | /* Return nonzero if the operands of expression X are unchanged |
473 | 1) from the start of INSN's basic block up to but not including INSN | |
474 | if AFTER_INSN is false, or | |
475 | 2) from INSN to the end of INSN's basic block if AFTER_INSN is true. */ | |
78d140c9 | 476 | |
477 | static bool | |
478 | oprs_unchanged_p (rtx x, rtx insn, bool after_insn) | |
479 | { | |
480 | int i, j; | |
481 | enum rtx_code code; | |
482 | const char *fmt; | |
483 | ||
484 | if (x == 0) | |
485 | return 1; | |
486 | ||
487 | code = GET_CODE (x); | |
488 | switch (code) | |
489 | { | |
490 | case REG: | |
2045cdd4 | 491 | #ifdef ENABLE_CHECKING |
78d140c9 | 492 | /* We are called after register allocation. */ |
2045cdd4 | 493 | if (REGNO (x) >= FIRST_PSEUDO_REGISTER) |
494 | abort (); | |
495 | #endif | |
78d140c9 | 496 | if (after_insn) |
497 | /* If the last CUID setting the insn is less than the CUID of | |
498 | INSN, then reg X is not changed in or after INSN. */ | |
499 | return reg_avail_info[REGNO (x)] < INSN_CUID (insn); | |
500 | else | |
501 | /* Reg X is not set before INSN in the current basic block if | |
502 | we have not yet recorded the CUID of an insn that touches | |
503 | the reg. */ | |
504 | return reg_avail_info[REGNO (x)] == 0; | |
505 | ||
506 | case MEM: | |
507 | if (load_killed_in_block_p (INSN_CUID (insn), x, after_insn)) | |
508 | return 0; | |
509 | else | |
510 | return oprs_unchanged_p (XEXP (x, 0), insn, after_insn); | |
511 | ||
512 | case PC: | |
513 | case CC0: /*FIXME*/ | |
514 | case CONST: | |
515 | case CONST_INT: | |
516 | case CONST_DOUBLE: | |
517 | case CONST_VECTOR: | |
518 | case SYMBOL_REF: | |
519 | case LABEL_REF: | |
520 | case ADDR_VEC: | |
521 | case ADDR_DIFF_VEC: | |
522 | return 1; | |
523 | ||
524 | case PRE_DEC: | |
525 | case PRE_INC: | |
526 | case POST_DEC: | |
527 | case POST_INC: | |
528 | case PRE_MODIFY: | |
529 | case POST_MODIFY: | |
530 | if (after_insn) | |
531 | return 0; | |
532 | break; | |
533 | ||
534 | default: | |
535 | break; | |
536 | } | |
537 | ||
538 | for (i = GET_RTX_LENGTH (code) - 1, fmt = GET_RTX_FORMAT (code); i >= 0; i--) | |
539 | { | |
540 | if (fmt[i] == 'e') | |
541 | { | |
542 | if (! oprs_unchanged_p (XEXP (x, i), insn, after_insn)) | |
543 | return 0; | |
544 | } | |
545 | else if (fmt[i] == 'E') | |
546 | for (j = 0; j < XVECLEN (x, i); j++) | |
547 | if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, after_insn)) | |
548 | return 0; | |
549 | } | |
550 | ||
551 | return 1; | |
552 | } | |
553 | \f | |
554 | ||
555 | /* Used for communication between find_mem_conflicts and | |
556 | load_killed_in_block_p. Nonzero if find_mem_conflicts finds a | |
557 | conflict between two memory references. | |
558 | This is a bit of a hack to work around the limitations of note_stores. */ | |
559 | static int mems_conflict_p; | |
560 | ||
561 | /* DEST is the output of an instruction. If it is a memory reference, and | |
562 | possibly conflicts with the load found in DATA, then set mems_conflict_p | |
563 | to a nonzero value. */ | |
564 | ||
565 | static void | |
566 | find_mem_conflicts (rtx dest, rtx setter ATTRIBUTE_UNUSED, | |
567 | void *data) | |
568 | { | |
569 | rtx mem_op = (rtx) data; | |
570 | ||
571 | while (GET_CODE (dest) == SUBREG | |
572 | || GET_CODE (dest) == ZERO_EXTRACT | |
78d140c9 | 573 | || GET_CODE (dest) == STRICT_LOW_PART) |
574 | dest = XEXP (dest, 0); | |
575 | ||
576 | /* If DEST is not a MEM, then it will not conflict with the load. Note | |
577 | that function calls are assumed to clobber memory, but are handled | |
578 | elsewhere. */ | |
579 | if (! MEM_P (dest)) | |
580 | return; | |
581 | ||
582 | if (true_dependence (dest, GET_MODE (dest), mem_op, | |
583 | rtx_addr_varies_p)) | |
584 | mems_conflict_p = 1; | |
585 | } | |
586 | \f | |
587 | ||
588 | /* Return nonzero if the expression in X (a memory reference) is killed | |
d447762f | 589 | in the current basic block before (if AFTER_INSN is false) or after |
590 | (if AFTER_INSN is true) the insn with the CUID in UID_LIMIT. | |
591 | ||
592 | This function assumes that the modifies_mem table is flushed when | |
593 | the hash table construction or redundancy elimination phases start | |
594 | processing a new basic block. */ | |
78d140c9 | 595 | |
596 | static int | |
597 | load_killed_in_block_p (int uid_limit, rtx x, bool after_insn) | |
598 | { | |
599 | struct modifies_mem *list_entry = modifies_mem_list; | |
600 | ||
601 | while (list_entry) | |
602 | { | |
603 | rtx setter = list_entry->insn; | |
604 | ||
605 | /* Ignore entries in the list that do not apply. */ | |
606 | if ((after_insn | |
607 | && INSN_CUID (setter) < uid_limit) | |
608 | || (! after_insn | |
609 | && INSN_CUID (setter) > uid_limit)) | |
610 | { | |
611 | list_entry = list_entry->next; | |
612 | continue; | |
613 | } | |
614 | ||
615 | /* If SETTER is a call everything is clobbered. Note that calls | |
616 | to pure functions are never put on the list, so we need not | |
617 | worry about them. */ | |
618 | if (CALL_P (setter)) | |
619 | return 1; | |
620 | ||
621 | /* SETTER must be an insn of some kind that sets memory. Call | |
622 | note_stores to examine each hunk of memory that is modified. | |
623 | It will set mems_conflict_p to nonzero if there may be a | |
624 | conflict between X and SETTER. */ | |
625 | mems_conflict_p = 0; | |
626 | note_stores (PATTERN (setter), find_mem_conflicts, x); | |
627 | if (mems_conflict_p) | |
628 | return 1; | |
629 | ||
630 | list_entry = list_entry->next; | |
631 | } | |
632 | return 0; | |
633 | } | |
634 | \f | |
635 | ||
636 | /* Record register first/last/block set information for REGNO in INSN. */ | |
637 | ||
d447762f | 638 | static inline void |
78d140c9 | 639 | record_last_reg_set_info (rtx insn, int regno) |
640 | { | |
641 | reg_avail_info[regno] = INSN_CUID (insn); | |
642 | } | |
643 | ||
644 | ||
645 | /* Record memory modification information for INSN. We do not actually care | |
646 | about the memory location(s) that are set, or even how they are set (consider | |
647 | a CALL_INSN). We merely need to record which insns modify memory. */ | |
648 | ||
649 | static void | |
650 | record_last_mem_set_info (rtx insn) | |
651 | { | |
652 | struct modifies_mem *list_entry; | |
653 | ||
654 | list_entry = (struct modifies_mem *) obstack_alloc (&modifies_mem_obstack, | |
655 | sizeof (struct modifies_mem)); | |
656 | list_entry->insn = insn; | |
657 | list_entry->next = modifies_mem_list; | |
658 | modifies_mem_list = list_entry; | |
659 | } | |
660 | ||
661 | /* Called from compute_hash_table via note_stores to handle one | |
662 | SET or CLOBBER in an insn. DATA is really the instruction in which | |
663 | the SET is taking place. */ | |
664 | ||
665 | static void | |
666 | record_last_set_info (rtx dest, rtx setter ATTRIBUTE_UNUSED, void *data) | |
667 | { | |
668 | rtx last_set_insn = (rtx) data; | |
669 | ||
670 | if (GET_CODE (dest) == SUBREG) | |
671 | dest = SUBREG_REG (dest); | |
672 | ||
673 | if (REG_P (dest)) | |
674 | record_last_reg_set_info (last_set_insn, REGNO (dest)); | |
675 | else if (MEM_P (dest) | |
676 | /* Ignore pushes, they clobber nothing. */ | |
677 | && ! push_operand (dest, GET_MODE (dest))) | |
678 | record_last_mem_set_info (last_set_insn); | |
679 | } | |
d447762f | 680 | |
78d140c9 | 681 | |
682 | /* Reset tables used to keep track of what's still available since the | |
683 | start of the block. */ | |
684 | ||
685 | static void | |
686 | reset_opr_set_tables (void) | |
687 | { | |
688 | memset (reg_avail_info, 0, FIRST_PSEUDO_REGISTER * sizeof (int)); | |
689 | obstack_free (&modifies_mem_obstack, modifies_mem_obstack_bottom); | |
690 | modifies_mem_list = NULL; | |
691 | } | |
d447762f | 692 | \f |
78d140c9 | 693 | |
694 | /* Record things set by INSN. | |
695 | This data is used by oprs_unchanged_p. */ | |
696 | ||
697 | static void | |
d447762f | 698 | record_opr_changes (rtx insn) |
78d140c9 | 699 | { |
d447762f | 700 | rtx note; |
78d140c9 | 701 | |
d447762f | 702 | /* Find all stores and record them. */ |
703 | note_stores (PATTERN (insn), record_last_set_info, insn); | |
78d140c9 | 704 | |
d447762f | 705 | /* Also record autoincremented REGs for this insn as changed. */ |
706 | for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) | |
707 | if (REG_NOTE_KIND (note) == REG_INC) | |
708 | record_last_reg_set_info (insn, REGNO (XEXP (note, 0))); | |
78d140c9 | 709 | |
d447762f | 710 | /* Finally, if this is a call, record all call clobbers. */ |
711 | if (CALL_P (insn)) | |
712 | { | |
713 | unsigned int regno; | |
d447762f | 714 | |
715 | for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++) | |
4fec1d6c | 716 | if (TEST_HARD_REG_BIT (regs_invalidated_by_call, regno)) |
d447762f | 717 | record_last_reg_set_info (insn, regno); |
78d140c9 | 718 | |
d447762f | 719 | if (! CONST_OR_PURE_CALL_P (insn)) |
720 | record_last_mem_set_info (insn); | |
721 | } | |
78d140c9 | 722 | } |
723 | \f | |
724 | ||
725 | /* Scan the pattern of INSN and add an entry to the hash TABLE. | |
726 | After reload we are interested in loads/stores only. */ | |
727 | ||
728 | static void | |
729 | hash_scan_set (rtx insn) | |
730 | { | |
731 | rtx pat = PATTERN (insn); | |
732 | rtx src = SET_SRC (pat); | |
733 | rtx dest = SET_DEST (pat); | |
734 | ||
735 | /* We are only interested in loads and stores. */ | |
736 | if (! MEM_P (src) && ! MEM_P (dest)) | |
737 | return; | |
738 | ||
739 | /* Don't mess with jumps and nops. */ | |
740 | if (JUMP_P (insn) || set_noop_p (pat)) | |
741 | return; | |
742 | ||
743 | #ifdef ENABLE_CHEKCING | |
744 | /* We shouldn't have any EH_REGION notes post reload. */ | |
2045cdd4 | 745 | if (find_reg_note (insn, REG_EH_REGION, NULL_RTX)) |
746 | abort (); | |
78d140c9 | 747 | #endif |
748 | ||
749 | if (REG_P (dest)) | |
750 | { | |
d447762f | 751 | if (/* Don't CSE something if we can't do a reg/reg copy. */ |
78d140c9 | 752 | can_copy_p (GET_MODE (dest)) |
753 | /* Is SET_SRC something we want to gcse? */ | |
754 | && general_operand (src, GET_MODE (src)) | |
755 | /* An expression is not available if its operands are | |
756 | subsequently modified, including this insn. */ | |
757 | && oprs_unchanged_p (src, insn, true)) | |
758 | { | |
759 | insert_expr_in_table (src, insn); | |
760 | } | |
761 | } | |
762 | else if (REG_P (src)) | |
763 | { | |
764 | /* Only record sets of pseudo-regs in the hash table. */ | |
d447762f | 765 | if (/* Don't CSE something if we can't do a reg/reg copy. */ |
78d140c9 | 766 | can_copy_p (GET_MODE (src)) |
767 | /* Is SET_DEST something we want to gcse? */ | |
768 | && general_operand (dest, GET_MODE (dest)) | |
769 | && ! (flag_float_store && FLOAT_MODE_P (GET_MODE (dest))) | |
770 | /* Check if the memory expression is killed after insn. */ | |
771 | && ! load_killed_in_block_p (INSN_CUID (insn) + 1, dest, true) | |
772 | && oprs_unchanged_p (XEXP (dest, 0), insn, true)) | |
773 | { | |
774 | insert_expr_in_table (dest, insn); | |
775 | } | |
776 | } | |
777 | } | |
778 | \f | |
d447762f | 779 | |
78d140c9 | 780 | /* Create hash table of memory expressions available at end of basic |
d447762f | 781 | blocks. Basically you should think of this hash table as the |
782 | representation of AVAIL_OUT. This is the set of expressions that | |
783 | is generated in a basic block and not killed before the end of the | |
784 | same basic block. Notice that this is really a local computation. */ | |
78d140c9 | 785 | |
786 | static void | |
787 | compute_hash_table (void) | |
788 | { | |
789 | basic_block bb; | |
790 | ||
791 | FOR_EACH_BB (bb) | |
792 | { | |
793 | rtx insn; | |
78d140c9 | 794 | |
795 | /* First pass over the instructions records information used to | |
d447762f | 796 | determine when registers and memory are last set. |
797 | Since we compute a "local" AVAIL_OUT, reset the tables that | |
798 | help us keep track of what has been modified since the start | |
799 | of the block. */ | |
800 | reset_opr_set_tables (); | |
78d140c9 | 801 | FOR_BB_INSNS (bb, insn) |
802 | { | |
d447762f | 803 | if (INSN_P (insn)) |
804 | record_opr_changes (insn); | |
805 | } | |
78d140c9 | 806 | |
d447762f | 807 | /* The next pass actually builds the hash table. */ |
78d140c9 | 808 | FOR_BB_INSNS (bb, insn) |
809 | if (INSN_P (insn) && GET_CODE (PATTERN (insn)) == SET) | |
810 | hash_scan_set (insn); | |
811 | } | |
812 | } | |
813 | \f | |
814 | ||
815 | /* Check if register REG is killed in any insn waiting to be inserted on | |
816 | edge E. This function is required to check that our data flow analysis | |
817 | is still valid prior to commit_edge_insertions. */ | |
818 | ||
819 | static bool | |
820 | reg_killed_on_edge (rtx reg, edge e) | |
821 | { | |
822 | rtx insn; | |
823 | ||
824 | for (insn = e->insns.r; insn; insn = NEXT_INSN (insn)) | |
825 | if (INSN_P (insn) && reg_set_p (reg, insn)) | |
826 | return true; | |
827 | ||
828 | return false; | |
829 | } | |
830 | ||
831 | /* Similar to above - check if register REG is used in any insn waiting | |
832 | to be inserted on edge E. | |
833 | Assumes no such insn can be a CALL_INSN; if so call reg_used_between_p | |
834 | with PREV(insn),NEXT(insn) instead of calling reg_overlap_mentioned_p. */ | |
835 | ||
836 | static bool | |
837 | reg_used_on_edge (rtx reg, edge e) | |
838 | { | |
839 | rtx insn; | |
840 | ||
841 | for (insn = e->insns.r; insn; insn = NEXT_INSN (insn)) | |
842 | if (INSN_P (insn) && reg_overlap_mentioned_p (reg, PATTERN (insn))) | |
843 | return true; | |
844 | ||
845 | return false; | |
846 | } | |
847 | \f | |
848 | ||
849 | /* Return the insn that sets register REG or clobbers it in between | |
850 | FROM_INSN and TO_INSN (exclusive of those two). | |
851 | Just like reg_set_between but for hard registers and not pseudos. */ | |
852 | ||
853 | static rtx | |
854 | reg_set_between_after_reload_p (rtx reg, rtx from_insn, rtx to_insn) | |
855 | { | |
856 | rtx insn; | |
78d140c9 | 857 | |
2045cdd4 | 858 | #ifdef ENABLE_CHECKING |
78d140c9 | 859 | /* We are called after register allocation. */ |
2045cdd4 | 860 | if (!REG_P (reg) || REGNO (reg) >= FIRST_PSEUDO_REGISTER) |
861 | abort (); | |
862 | #endif | |
78d140c9 | 863 | |
864 | if (from_insn == to_insn) | |
865 | return NULL_RTX; | |
866 | ||
78d140c9 | 867 | for (insn = NEXT_INSN (from_insn); |
868 | insn != to_insn; | |
869 | insn = NEXT_INSN (insn)) | |
d447762f | 870 | if (INSN_P (insn)) |
871 | { | |
872 | if (set_of (reg, insn) != NULL_RTX) | |
873 | return insn; | |
874 | if ((CALL_P (insn) | |
875 | && call_used_regs[REGNO (reg)]) | |
876 | || find_reg_fusage (insn, CLOBBER, reg)) | |
877 | return insn; | |
878 | ||
879 | if (FIND_REG_INC_NOTE (insn, reg)) | |
880 | return insn; | |
881 | } | |
78d140c9 | 882 | |
883 | return NULL_RTX; | |
884 | } | |
885 | ||
886 | /* Return the insn that uses register REG in between FROM_INSN and TO_INSN | |
887 | (exclusive of those two). Similar to reg_used_between but for hard | |
888 | registers and not pseudos. */ | |
889 | ||
890 | static rtx | |
891 | reg_used_between_after_reload_p (rtx reg, rtx from_insn, rtx to_insn) | |
892 | { | |
893 | rtx insn; | |
78d140c9 | 894 | |
2045cdd4 | 895 | #ifdef ENABLE_CHECKING |
78d140c9 | 896 | /* We are called after register allocation. */ |
2045cdd4 | 897 | if (!REG_P (reg) || REGNO (reg) >= FIRST_PSEUDO_REGISTER) |
898 | abort (); | |
899 | #endif | |
78d140c9 | 900 | |
901 | if (from_insn == to_insn) | |
902 | return NULL_RTX; | |
903 | ||
78d140c9 | 904 | for (insn = NEXT_INSN (from_insn); |
905 | insn != to_insn; | |
906 | insn = NEXT_INSN (insn)) | |
d447762f | 907 | if (INSN_P (insn)) |
908 | { | |
909 | if (reg_overlap_mentioned_p (reg, PATTERN (insn)) | |
78d140c9 | 910 | || (CALL_P (insn) |
d447762f | 911 | && call_used_regs[REGNO (reg)]) |
78d140c9 | 912 | || find_reg_fusage (insn, USE, reg) |
d447762f | 913 | || find_reg_fusage (insn, CLOBBER, reg)) |
914 | return insn; | |
915 | ||
916 | if (FIND_REG_INC_NOTE (insn, reg)) | |
917 | return insn; | |
918 | } | |
78d140c9 | 919 | |
920 | return NULL_RTX; | |
921 | } | |
922 | ||
923 | /* Return true if REG is used, set, or killed between the beginning of | |
924 | basic block BB and UP_TO_INSN. Caches the result in reg_avail_info. */ | |
925 | ||
926 | static bool | |
927 | reg_set_or_used_since_bb_start (rtx reg, basic_block bb, rtx up_to_insn) | |
928 | { | |
929 | rtx insn, start = PREV_INSN (BB_HEAD (bb)); | |
930 | ||
931 | if (reg_avail_info[REGNO (reg)] != 0) | |
932 | return true; | |
933 | ||
934 | insn = reg_used_between_after_reload_p (reg, start, up_to_insn); | |
935 | if (! insn) | |
936 | insn = reg_set_between_after_reload_p (reg, start, up_to_insn); | |
937 | ||
938 | if (insn) | |
939 | reg_avail_info[REGNO (reg)] = INSN_CUID (insn); | |
940 | ||
941 | return insn != NULL_RTX; | |
942 | } | |
943 | ||
944 | /* Return the loaded/stored register of a load/store instruction. */ | |
945 | ||
946 | static rtx | |
947 | get_avail_load_store_reg (rtx insn) | |
948 | { | |
949 | if (REG_P (SET_DEST (PATTERN (insn)))) /* A load. */ | |
950 | return SET_DEST(PATTERN(insn)); | |
951 | if (REG_P (SET_SRC (PATTERN (insn)))) /* A store. */ | |
952 | return SET_SRC (PATTERN (insn)); | |
2045cdd4 | 953 | abort (); |
78d140c9 | 954 | } |
955 | ||
956 | /* Return nonzero if the predecessors of BB are "well behaved". */ | |
957 | ||
958 | static bool | |
959 | bb_has_well_behaved_predecessors (basic_block bb) | |
960 | { | |
961 | edge pred; | |
cd665a06 | 962 | edge_iterator ei; |
78d140c9 | 963 | |
cd665a06 | 964 | if (EDGE_COUNT (bb->preds) == 0) |
78d140c9 | 965 | return false; |
966 | ||
cd665a06 | 967 | FOR_EACH_EDGE (pred, ei, bb->preds) |
78d140c9 | 968 | { |
969 | if ((pred->flags & EDGE_ABNORMAL) && EDGE_CRITICAL_P (pred)) | |
970 | return false; | |
971 | ||
972 | if (JUMP_TABLE_DATA_P (BB_END (pred->src))) | |
973 | return false; | |
974 | } | |
975 | return true; | |
976 | } | |
977 | ||
978 | ||
979 | /* Search for the occurrences of expression in BB. */ | |
980 | ||
981 | static struct occr* | |
982 | get_bb_avail_insn (basic_block bb, struct occr *occr) | |
983 | { | |
984 | for (; occr != NULL; occr = occr->next) | |
985 | if (BLOCK_FOR_INSN (occr->insn) == bb) | |
986 | return occr; | |
987 | return NULL; | |
988 | } | |
989 | ||
990 | ||
991 | /* This handles the case where several stores feed a partially redundant | |
992 | load. It checks if the redundancy elimination is possible and if it's | |
d447762f | 993 | worth it. |
994 | ||
995 | Redundancy elimination is possible if, | |
996 | 1) None of the operands of an insn have been modified since the start | |
997 | of the current basic block. | |
998 | 2) In any predecessor of the current basic block, the same expression | |
999 | is generated. | |
1000 | ||
1001 | See the function body for the heuristics that determine if eliminating | |
1002 | a redundancy is also worth doing, assuming it is possible. */ | |
78d140c9 | 1003 | |
1004 | static void | |
1005 | eliminate_partially_redundant_load (basic_block bb, rtx insn, | |
1006 | struct expr *expr) | |
1007 | { | |
1008 | edge pred; | |
1009 | rtx avail_insn = NULL_RTX; | |
1010 | rtx avail_reg; | |
1011 | rtx dest, pat; | |
1012 | struct occr *a_occr; | |
1013 | struct unoccr *occr, *avail_occrs = NULL; | |
1014 | struct unoccr *unoccr, *unavail_occrs = NULL, *rollback_unoccr = NULL; | |
1015 | int npred_ok = 0; | |
1016 | gcov_type ok_count = 0; /* Redundant load execution count. */ | |
1017 | gcov_type critical_count = 0; /* Execution count of critical edges. */ | |
cd665a06 | 1018 | edge_iterator ei; |
78d140c9 | 1019 | |
1020 | /* The execution count of the loads to be added to make the | |
1021 | load fully redundant. */ | |
1022 | gcov_type not_ok_count = 0; | |
1023 | basic_block pred_bb; | |
1024 | ||
1025 | pat = PATTERN (insn); | |
1026 | dest = SET_DEST (pat); | |
1027 | ||
1028 | /* Check that the loaded register is not used, set, or killed from the | |
1029 | beginning of the block. */ | |
1030 | if (reg_set_or_used_since_bb_start (dest, bb, insn)) | |
1031 | return; | |
1032 | ||
1033 | /* Check potential for replacing load with copy for predecessors. */ | |
cd665a06 | 1034 | FOR_EACH_EDGE (pred, ei, bb->preds) |
78d140c9 | 1035 | { |
1036 | rtx next_pred_bb_end; | |
1037 | ||
1038 | avail_insn = NULL_RTX; | |
1039 | pred_bb = pred->src; | |
1040 | next_pred_bb_end = NEXT_INSN (BB_END (pred_bb)); | |
1041 | for (a_occr = get_bb_avail_insn (pred_bb, expr->avail_occr); a_occr; | |
1042 | a_occr = get_bb_avail_insn (pred_bb, a_occr->next)) | |
1043 | { | |
1044 | /* Check if the loaded register is not used. */ | |
1045 | avail_insn = a_occr->insn; | |
2045cdd4 | 1046 | if (! (avail_reg = get_avail_load_store_reg (avail_insn))) |
1047 | abort (); | |
78d140c9 | 1048 | /* Make sure we can generate a move from register avail_reg to |
1049 | dest. */ | |
1050 | extract_insn (gen_move_insn (copy_rtx (dest), | |
1051 | copy_rtx (avail_reg))); | |
1052 | if (! constrain_operands (1) | |
1053 | || reg_killed_on_edge (avail_reg, pred) | |
1054 | || reg_used_on_edge (dest, pred)) | |
1055 | { | |
1056 | avail_insn = NULL; | |
1057 | continue; | |
1058 | } | |
1059 | if (! reg_set_between_after_reload_p (avail_reg, avail_insn, | |
1060 | next_pred_bb_end)) | |
1061 | /* AVAIL_INSN remains non-null. */ | |
1062 | break; | |
1063 | else | |
1064 | avail_insn = NULL; | |
1065 | } | |
1066 | ||
1067 | if (EDGE_CRITICAL_P (pred)) | |
1068 | critical_count += pred->count; | |
1069 | ||
1070 | if (avail_insn != NULL_RTX) | |
1071 | { | |
1072 | npred_ok++; | |
1073 | ok_count += pred->count; | |
1074 | occr = (struct unoccr *) obstack_alloc (&unoccr_obstack, | |
1075 | sizeof (struct occr)); | |
1076 | occr->insn = avail_insn; | |
1077 | occr->pred = pred; | |
1078 | occr->next = avail_occrs; | |
1079 | avail_occrs = occr; | |
1080 | if (! rollback_unoccr) | |
1081 | rollback_unoccr = occr; | |
1082 | } | |
1083 | else | |
1084 | { | |
1085 | not_ok_count += pred->count; | |
1086 | unoccr = (struct unoccr *) obstack_alloc (&unoccr_obstack, | |
1087 | sizeof (struct unoccr)); | |
1088 | unoccr->insn = NULL_RTX; | |
1089 | unoccr->pred = pred; | |
1090 | unoccr->next = unavail_occrs; | |
1091 | unavail_occrs = unoccr; | |
1092 | if (! rollback_unoccr) | |
1093 | rollback_unoccr = unoccr; | |
1094 | } | |
1095 | } | |
1096 | ||
1097 | if (/* No load can be replaced by copy. */ | |
1098 | npred_ok == 0 | |
1099 | /* Prevent exploding the code. */ | |
1100 | || (optimize_size && npred_ok > 1)) | |
1101 | goto cleanup; | |
1102 | ||
1103 | /* Check if it's worth applying the partial redundancy elimination. */ | |
1104 | if (ok_count < GCSE_AFTER_RELOAD_PARTIAL_FRACTION * not_ok_count) | |
1105 | goto cleanup; | |
1106 | if (ok_count < GCSE_AFTER_RELOAD_CRITICAL_FRACTION * critical_count) | |
1107 | goto cleanup; | |
1108 | ||
1109 | /* Generate moves to the loaded register from where | |
1110 | the memory is available. */ | |
1111 | for (occr = avail_occrs; occr; occr = occr->next) | |
1112 | { | |
1113 | avail_insn = occr->insn; | |
1114 | pred = occr->pred; | |
1115 | /* Set avail_reg to be the register having the value of the | |
1116 | memory. */ | |
1117 | avail_reg = get_avail_load_store_reg (avail_insn); | |
2045cdd4 | 1118 | if (! avail_reg) |
1119 | abort (); | |
78d140c9 | 1120 | |
1121 | insert_insn_on_edge (gen_move_insn (copy_rtx (dest), | |
1122 | copy_rtx (avail_reg)), | |
1123 | pred); | |
1124 | stats.moves_inserted++; | |
1125 | ||
1126 | if (dump_file) | |
1127 | fprintf (dump_file, | |
1128 | "generating move from %d to %d on edge from %d to %d\n", | |
1129 | REGNO (avail_reg), | |
1130 | REGNO (dest), | |
1131 | pred->src->index, | |
1132 | pred->dest->index); | |
1133 | } | |
1134 | ||
1135 | /* Regenerate loads where the memory is unavailable. */ | |
1136 | for (unoccr = unavail_occrs; unoccr; unoccr = unoccr->next) | |
1137 | { | |
1138 | pred = unoccr->pred; | |
1139 | insert_insn_on_edge (copy_insn (PATTERN (insn)), pred); | |
1140 | stats.copies_inserted++; | |
1141 | ||
1142 | if (dump_file) | |
1143 | { | |
1144 | fprintf (dump_file, | |
1145 | "generating on edge from %d to %d a copy of load: ", | |
1146 | pred->src->index, | |
1147 | pred->dest->index); | |
1148 | print_rtl (dump_file, PATTERN (insn)); | |
1149 | fprintf (dump_file, "\n"); | |
1150 | } | |
1151 | } | |
1152 | ||
1153 | /* Delete the insn if it is not available in this block and mark it | |
1154 | for deletion if it is available. If insn is available it may help | |
1155 | discover additional redundancies, so mark it for later deletion. */ | |
1156 | for (a_occr = get_bb_avail_insn (bb, expr->avail_occr); | |
1157 | a_occr && (a_occr->insn != insn); | |
1158 | a_occr = get_bb_avail_insn (bb, a_occr->next)); | |
1159 | ||
1160 | if (!a_occr) | |
1161 | delete_insn (insn); | |
1162 | else | |
1163 | a_occr->deleted_p = 1; | |
1164 | ||
1165 | cleanup: | |
1166 | if (rollback_unoccr) | |
1167 | obstack_free (&unoccr_obstack, rollback_unoccr); | |
1168 | } | |
1169 | ||
1170 | /* Performing the redundancy elimination as described before. */ | |
1171 | ||
1172 | static void | |
1173 | eliminate_partially_redundant_loads (void) | |
1174 | { | |
1175 | rtx insn; | |
1176 | basic_block bb; | |
1177 | ||
1178 | /* Note we start at block 1. */ | |
1179 | ||
1180 | if (ENTRY_BLOCK_PTR->next_bb == EXIT_BLOCK_PTR) | |
1181 | return; | |
1182 | ||
1183 | FOR_BB_BETWEEN (bb, | |
1184 | ENTRY_BLOCK_PTR->next_bb->next_bb, | |
1185 | EXIT_BLOCK_PTR, | |
1186 | next_bb) | |
1187 | { | |
d447762f | 1188 | /* Don't try anything on basic blocks with strange predecessors. */ |
78d140c9 | 1189 | if (! bb_has_well_behaved_predecessors (bb)) |
1190 | continue; | |
1191 | ||
d447762f | 1192 | /* Do not try anything on cold basic blocks. */ |
78d140c9 | 1193 | if (probably_cold_bb_p (bb)) |
1194 | continue; | |
1195 | ||
d447762f | 1196 | /* Reset the table of things changed since the start of the current |
1197 | basic block. */ | |
78d140c9 | 1198 | reset_opr_set_tables (); |
1199 | ||
d447762f | 1200 | /* Look at all insns in the current basic block and see if there are |
1201 | any loads in it that we can record. */ | |
78d140c9 | 1202 | FOR_BB_INSNS (bb, insn) |
1203 | { | |
1204 | /* Is it a load - of the form (set (reg) (mem))? */ | |
1205 | if (NONJUMP_INSN_P (insn) | |
1206 | && GET_CODE (PATTERN (insn)) == SET | |
1207 | && REG_P (SET_DEST (PATTERN (insn))) | |
1208 | && MEM_P (SET_SRC (PATTERN (insn)))) | |
1209 | { | |
1210 | rtx pat = PATTERN (insn); | |
1211 | rtx src = SET_SRC (pat); | |
1212 | struct expr *expr; | |
1213 | ||
1214 | if (!MEM_VOLATILE_P (src) | |
1215 | && GET_MODE (src) != BLKmode | |
1216 | && general_operand (src, GET_MODE (src)) | |
1217 | /* Are the operands unchanged since the start of the | |
1218 | block? */ | |
1219 | && oprs_unchanged_p (src, insn, false) | |
1220 | && !(flag_non_call_exceptions && may_trap_p (src)) | |
1221 | && !side_effects_p (src) | |
1222 | /* Is the expression recorded? */ | |
1223 | && (expr = lookup_expr_in_table (src)) != NULL) | |
1224 | { | |
1225 | /* We now have a load (insn) and an available memory at | |
1226 | its BB start (expr). Try to remove the loads if it is | |
1227 | redundant. */ | |
1228 | eliminate_partially_redundant_load (bb, insn, expr); | |
1229 | } | |
1230 | } | |
1231 | ||
d447762f | 1232 | /* Keep track of everything modified by this insn, so that we |
1233 | know what has been modified since the start of the current | |
1234 | basic block. */ | |
78d140c9 | 1235 | if (INSN_P (insn)) |
d447762f | 1236 | record_opr_changes (insn); |
78d140c9 | 1237 | } |
1238 | } | |
1239 | ||
1240 | commit_edge_insertions (); | |
1241 | } | |
1242 | ||
1243 | /* Go over the expression hash table and delete insns that were | |
1244 | marked for later deletion. */ | |
1245 | ||
1246 | /* This helper is called via htab_traverse. */ | |
1247 | static int | |
1248 | delete_redundant_insns_1 (void **slot, void *data ATTRIBUTE_UNUSED) | |
1249 | { | |
1250 | struct expr *expr = (struct expr *) *slot; | |
1251 | struct occr *occr; | |
1252 | ||
1253 | for (occr = expr->avail_occr; occr != NULL; occr = occr->next) | |
1254 | { | |
1255 | if (occr->deleted_p) | |
1256 | { | |
1257 | delete_insn (occr->insn); | |
1258 | stats.insns_deleted++; | |
1259 | ||
1260 | if (dump_file) | |
1261 | { | |
1262 | fprintf (dump_file, "deleting insn:\n"); | |
1263 | print_rtl_single (dump_file, occr->insn); | |
1264 | fprintf (dump_file, "\n"); | |
1265 | } | |
1266 | } | |
1267 | } | |
1268 | ||
1269 | return 1; | |
1270 | } | |
1271 | ||
1272 | static void | |
1273 | delete_redundant_insns (void) | |
1274 | { | |
1275 | htab_traverse (expr_table, delete_redundant_insns_1, NULL); | |
1276 | if (dump_file) | |
1277 | fprintf (dump_file, "\n"); | |
1278 | } | |
1279 | ||
1280 | /* Main entry point of the GCSE after reload - clean some redundant loads | |
1281 | due to spilling. */ | |
1282 | ||
1283 | void | |
1284 | gcse_after_reload_main (rtx f ATTRIBUTE_UNUSED) | |
1285 | { | |
1286 | memset (&stats, 0, sizeof (stats)); | |
1287 | ||
1288 | /* Allocate ememory for this pass. | |
1289 | Also computes and initializes the insns' CUIDs. */ | |
1290 | alloc_mem (); | |
1291 | ||
1292 | /* We need alias analysis. */ | |
1293 | init_alias_analysis (); | |
1294 | ||
1295 | compute_hash_table (); | |
1296 | ||
1297 | if (dump_file) | |
1298 | dump_hash_table (dump_file); | |
1299 | ||
1300 | if (htab_elements (expr_table) > 0) | |
1301 | { | |
1302 | eliminate_partially_redundant_loads (); | |
1303 | delete_redundant_insns (); | |
1304 | ||
1305 | if (dump_file) | |
1306 | { | |
1307 | fprintf (dump_file, "GCSE AFTER RELOAD stats:\n"); | |
1308 | fprintf (dump_file, "copies inserted: %d\n", stats.copies_inserted); | |
1309 | fprintf (dump_file, "moves inserted: %d\n", stats.moves_inserted); | |
1310 | fprintf (dump_file, "insns deleted: %d\n", stats.insns_deleted); | |
1311 | fprintf (dump_file, "\n\n"); | |
1312 | } | |
1313 | } | |
1314 | ||
1315 | /* We are finished with alias. */ | |
1316 | end_alias_analysis (); | |
1317 | ||
1318 | free_mem (); | |
1319 | } | |
1320 |