1 | /* Early (pre-RA) rematerialization |
2 | Copyright (C) 2017-2023 Free Software Foundation, Inc. |
3 | |
4 | This file is part of GCC. |
5 | |
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. |
10 | |
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. |
15 | |
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/>. */ |
19 | |
20 | #include "config.h" |
21 | #include "system.h" |
22 | #include "coretypes.h" |
23 | #include "backend.h" |
24 | #include "rtl.h" |
25 | #include "df.h" |
26 | #include "tree-pass.h" |
27 | #include "memmodel.h" |
28 | #include "emit-rtl.h" |
29 | #include "insn-config.h" |
30 | #include "recog.h" |
31 | /* FIXME: The next two are only needed for gen_move_insn. */ |
32 | #include "tree.h" |
33 | #include "expr.h" |
34 | #include "target.h" |
35 | #include "inchash.h" |
36 | #include "rtlhash.h" |
37 | #include "print-rtl.h" |
38 | #include "rtl-iter.h" |
39 | #include "regs.h" |
40 | #include "function-abi.h" |
41 | |
42 | /* This pass runs before register allocation and implements an aggressive |
43 | form of rematerialization. It looks for pseudo registers R of mode M |
44 | for which: |
45 | |
46 | (a) there are no call-preserved registers of mode M; and |
47 | (b) spilling R to the stack is expensive. |
48 | |
49 | The assumption is that it's better to recompute R after each call instead |
50 | of spilling it, even if this extends the live ranges of other registers. |
51 | |
52 | The motivating example for which these conditions hold are AArch64 SVE |
53 | vectors and predicates. Spilling them to the stack makes the frame |
54 | variable-sized, which we'd like to avoid if possible. It's also very |
55 | rare for SVE values to be "naturally" live across a call: usually this |
56 | happens as a result of CSE or other code motion. |
57 | |
58 | The pass is split into the following phases: |
59 | |
60 | Collection phase |
61 | ================ |
62 | |
63 | First we go through all pseudo registers looking for any that meet |
64 | the conditions above. For each such register R, we go through each |
65 | instruction that defines R to see whether any of them are suitable |
66 | rematerialization candidates. If at least one is, we treat all the |
67 | instructions that define R as candidates, but record which ones are |
68 | not in fact suitable. These unsuitable candidates exist only for the |
69 | sake of calculating reaching definitions (see below). |
70 | |
71 | A "candidate" is a single instruction that we want to rematerialize |
72 | and a "candidate register" is a register that is set by at least one |
73 | candidate. |
74 | |
75 | Candidate sorting |
76 | ================= |
77 | |
78 | Next we sort the candidates based on the cfg postorder, so that if |
79 | candidate C1 uses candidate C2, C1 has a lower index than C2. |
80 | This is useful when iterating through candidate bitmaps. |
81 | |
82 | Reaching definition calculation |
83 | =============================== |
84 | |
85 | We then compute standard reaching-definition sets for each candidate. |
86 | Each set specifies which candidates might provide the current definition |
87 | of a live candidate register. |
88 | |
89 | From here on, a candidate C is "live" at a point P if the candidate |
90 | register defined by C is live at P and if C's definition reaches P. |
91 | An instruction I "uses" a candidate C if I takes the register defined by |
92 | C as input and if C is one of the reaching definitions of that register. |
93 | |
94 | Candidate validation and value numbering |
95 | ======================================== |
96 | |
97 | Next we simultaneously decide which candidates are valid and look |
98 | for candidates that are equivalent to each other, assigning numbers |
99 | to each unique candidate value. A candidate C is invalid if: |
100 | |
101 | (a) C uses an invalid candidate; |
102 | |
103 | (b) there is a cycle of candidate uses involving C; or |
104 | |
105 | (c) C takes a candidate register R as input and the reaching |
106 | definitions of R do not have the same value number. |
107 | |
108 | We assign a "representative" candidate C to each value number and from |
109 | here on replace references to other candidates with that value number |
110 | with references to C. It is then only possible to rematerialize a |
111 | register R at point P if (after this replacement) there is a single |
112 | reaching definition of R at P. |
113 | |
114 | Local phase |
115 | =========== |
116 | |
117 | During this phase we go through each block and look for cases in which: |
118 | |
119 | (a) an instruction I comes between two call instructions CI1 and CI2; |
120 | |
121 | (b) I uses a candidate register R; |
122 | |
123 | (c) a candidate C provides the only reaching definition of R; and |
124 | |
125 | (d) C does not come between CI1 and I. |
126 | |
127 | We then emit a copy of C after CI1, as well as the transitive closure |
128 | TC of the candidates used by C. The copies of TC might use the original |
129 | candidate registers or new temporary registers, depending on circumstances. |
130 | |
131 | For example, if elsewhere we have: |
132 | |
133 | C3: R3 <- f3 (...) |
134 | ... |
135 | C2: R2 <- f2 (...) |
136 | ... |
137 | C1: R1 <- f1 (R2, R3, ...) // uses C2 and C3 |
138 | |
139 | then for a block containing: |
140 | |
141 | CI1: call |
142 | ... |
143 | I: use R1 // uses C1 |
144 | ... |
145 | CI2: call |
146 | |
147 | we would emit: |
148 | |
149 | CI1: call |
150 | C3': R3' <- f3 (...) |
151 | C2': R2' <- f2 (...) |
152 | C1': R1 <- f1 (R2', R3', ...) |
153 | ... |
154 | I: use R1 |
155 | ... |
156 | CI2: call |
157 | |
158 | where R2' and R3' might be fresh registers. If instead we had: |
159 | |
160 | CI1: call |
161 | ... |
162 | I1: use R1 // uses C1 |
163 | ... |
164 | I2: use R3 // uses C3 |
165 | ... |
166 | CI2: call |
167 | |
168 | we would keep the original R3: |
169 | |
170 | CI1: call |
171 | C3': R3 <- f3 (...) |
172 | C2': R2' <- f2 (...) |
173 | C1': R1 <- f1 (R2', R3, ...) |
174 | ... |
175 | I1: use R1 // uses C1 |
176 | ... |
177 | I2: use R3 // uses C3 |
178 | ... |
179 | CI2: call |
180 | |
181 | We also record the last call in each block (if any) and compute: |
182 | |
183 | rd_after_call: |
184 | The set of candidates that either (a) are defined outside the block |
185 | and are live after the last call or (b) are defined within the block |
186 | and reach the end of the last call. (We don't track whether the |
187 | latter values are live or not.) |
188 | |
189 | required_after_call: |
190 | The set of candidates that need to be rematerialized after the |
191 | last call in order to satisfy uses in the block itself. |
192 | |
193 | required_in: |
194 | The set of candidates that are live on entry to the block and are |
195 | used without an intervening call. |
196 | |
197 | In addition, we compute the initial values of the sets required by |
198 | the global phase below. |
199 | |
200 | Global phase |
201 | ============ |
202 | |
203 | We next compute a maximal solution to the following availability |
204 | problem: |
205 | |
206 | available_in: |
207 | The set of candidates that are live on entry to a block and can |
208 | be used at that point without rematerialization. |
209 | |
210 | available_out: |
211 | The set of candidates that are live on exit from a block and can |
212 | be used at that point without rematerialization. |
213 | |
214 | available_locally: |
215 | The subset of available_out that is due to code in the block itself. |
216 | It contains candidates that are defined or used in the block and |
217 | not invalidated by a later call. |
218 | |
219 | We then go through each block B and look for an appropriate place |
220 | to insert copies of required_in - available_in. Conceptually we |
221 | start by placing the copies at the head of B, but then move the |
222 | copy of a candidate C to predecessors if: |
223 | |
224 | (a) that seems cheaper; |
225 | |
226 | (b) there is more than one reaching definition of C's register at |
227 | the head of B; or |
228 | |
229 | (c) copying C would clobber a hard register that is live on entry to B. |
230 | |
231 | Moving a copy of C to a predecessor block PB involves: |
232 | |
233 | (1) adding C to PB's required_after_call, if PB contains a call; or |
234 | |
235 | (2) adding C PB's required_in otherwise. |
236 | |
237 | C is then available on output from each PB and on input to B. |
238 | |
239 | Once all this is done, we emit instructions for the final required_in |
240 | and required_after_call sets. */ |
241 | |
242 | namespace { |
243 | |
244 | /* An invalid candidate index, used to indicate that there is more than |
245 | one reaching definition. */ |
246 | const unsigned int MULTIPLE_CANDIDATES = -1U; |
247 | |
248 | /* Pass-specific information about one basic block. */ |
249 | struct remat_block_info { |
250 | /* The last call instruction in the block. */ |
251 | rtx_insn *last_call; |
252 | |
253 | /* The set of candidates that are live on entry to the block. NULL is |
254 | equivalent to an empty set. */ |
255 | bitmap rd_in; |
256 | |
257 | /* The set of candidates that are live on exit from the block. This might |
258 | reuse rd_in. NULL is equivalent to an empty set. */ |
259 | bitmap rd_out; |
260 | |
261 | /* The subset of RD_OUT that comes from local definitions. NULL is |
262 | equivalent to an empty set. */ |
263 | bitmap rd_gen; |
264 | |
265 | /* The set of candidates that the block invalidates (because it defines |
266 | the register to something else, or because the register's value is |
267 | no longer important). NULL is equivalent to an empty set. */ |
268 | bitmap rd_kill; |
269 | |
270 | /* The set of candidates that either (a) are defined outside the block |
271 | and are live after LAST_CALL or (b) are defined within the block |
272 | and reach the instruction after LAST_CALL. (We don't track whether |
273 | the latter values are live or not.) |
274 | |
275 | Only used if LAST_CALL is nonnull. NULL is equivalent to an |
276 | empty set. */ |
277 | bitmap rd_after_call; |
278 | |
279 | /* Candidates that are live and available without rematerialization |
280 | on entry to the block. NULL is equivalent to an empty set. */ |
281 | bitmap available_in; |
282 | |
283 | /* Candidates that become available without rematerialization within the |
284 | block, and remain so on exit. NULL is equivalent to an empty set. */ |
285 | bitmap available_locally; |
286 | |
287 | /* Candidates that are available without rematerialization on exit from |
288 | the block. This might reuse available_in or available_locally. */ |
289 | bitmap available_out; |
290 | |
291 | /* Candidates that need to be rematerialized either at the start of the |
292 | block or before entering the block. */ |
293 | bitmap required_in; |
294 | |
295 | /* Candidates that need to be rematerialized after LAST_CALL. |
296 | Only used if LAST_CALL is nonnull. */ |
297 | bitmap required_after_call; |
298 | |
299 | /* The number of candidates in the block. */ |
300 | unsigned int num_candidates; |
301 | |
302 | /* The earliest candidate in the block (i.e. the one with the |
303 | highest index). Only valid if NUM_CANDIDATES is nonzero. */ |
304 | unsigned int first_candidate; |
305 | |
306 | /* The best (lowest) execution frequency for rematerializing REQUIRED_IN. |
307 | This is the execution frequency of the block if LOCAL_REMAT_CHEAPER_P, |
308 | otherwise it is the sum of the execution frequencies of whichever |
309 | predecessor blocks would do the rematerialization. */ |
310 | int remat_frequency; |
311 | |
312 | /* True if the block ends with an abnormal call. */ |
313 | unsigned int abnormal_call_p : 1; |
314 | |
315 | /* Used to record whether a graph traversal has visited this block. */ |
316 | unsigned int visited_p : 1; |
317 | |
318 | /* True if we have calculated REMAT_FREQUENCY. */ |
319 | unsigned int remat_frequency_valid_p : 1; |
320 | |
321 | /* True if it is cheaper to rematerialize candidates at the start of |
322 | the block, rather than moving them to predecessor blocks. */ |
323 | unsigned int local_remat_cheaper_p : 1; |
324 | }; |
325 | |
326 | /* Information about a group of candidates with the same value number. */ |
327 | struct remat_equiv_class { |
328 | /* The candidates that have the same value number. */ |
329 | bitmap members; |
330 | |
331 | /* The candidate that was first added to MEMBERS. */ |
332 | unsigned int earliest; |
333 | |
334 | /* The candidate that represents the others. This is always the one |
335 | with the highest index. */ |
336 | unsigned int representative; |
337 | }; |
338 | |
339 | /* Information about an instruction that we might want to rematerialize. */ |
340 | struct remat_candidate { |
341 | /* The pseudo register that the instruction sets. */ |
342 | unsigned int regno; |
343 | |
344 | /* A temporary register used when rematerializing uses of this candidate, |
345 | if REGNO doesn't have the right value or isn't worth using. */ |
346 | unsigned int copy_regno; |
347 | |
348 | /* True if we intend to rematerialize this instruction by emitting |
349 | a move of a constant into REGNO, false if we intend to emit a |
350 | copy of the original instruction. */ |
351 | unsigned int constant_p : 1; |
352 | |
353 | /* True if we still think it's possible to rematerialize INSN. */ |
354 | unsigned int can_copy_p : 1; |
355 | |
356 | /* Used to record whether a graph traversal has visited this candidate. */ |
357 | unsigned int visited_p : 1; |
358 | |
359 | /* True if we have verified that it's possible to rematerialize INSN. |
360 | Once this is true, both it and CAN_COPY_P remain true. */ |
361 | unsigned int validated_p : 1; |
362 | |
363 | /* True if we have "stabilized" INSN, i.e. ensured that all non-candidate |
364 | registers read by INSN will have the same value when rematerializing INSN. |
365 | Only ever true if CAN_COPY_P. */ |
366 | unsigned int stabilized_p : 1; |
367 | |
368 | /* Hash value used for value numbering. */ |
369 | hashval_t hash; |
370 | |
371 | /* The instruction that sets REGNO. */ |
372 | rtx_insn *insn; |
373 | |
374 | /* If CONSTANT_P, the value that should be moved into REGNO when |
375 | rematerializing, otherwise the pattern of the instruction that |
376 | should be used. */ |
377 | rtx remat_rtx; |
378 | |
379 | /* The set of candidates that INSN takes as input. NULL is equivalent |
380 | to the empty set. All candidates in this set have a higher index |
381 | than the current candidate. */ |
382 | bitmap uses; |
383 | |
384 | /* The set of hard registers that would be clobbered by rematerializing |
385 | the candidate, including (transitively) all those that would be |
386 | clobbered by rematerializing USES. */ |
387 | bitmap clobbers; |
388 | |
389 | /* The equivalence class to which the candidate belongs, or null if none. */ |
390 | remat_equiv_class *equiv_class; |
391 | }; |
392 | |
393 | /* Hash functions used for value numbering. */ |
394 | struct remat_candidate_hasher : nofree_ptr_hash <remat_candidate> |
395 | { |
396 | typedef value_type compare_type; |
397 | static hashval_t hash (const remat_candidate *); |
398 | static bool equal (const remat_candidate *, const remat_candidate *); |
399 | }; |
400 | |
401 | /* Main class for this pass. */ |
402 | class early_remat { |
403 | public: |
404 | early_remat (function *, sbitmap); |
405 | ~early_remat (); |
406 | |
407 | void run (void); |
408 | |
409 | private: |
410 | bitmap alloc_bitmap (void); |
411 | bitmap get_bitmap (bitmap *); |
412 | void init_temp_bitmap (bitmap *); |
413 | void copy_temp_bitmap (bitmap *, bitmap *); |
414 | |
415 | void dump_insn_id (rtx_insn *); |
416 | void dump_candidate_bitmap (bitmap); |
417 | void dump_all_candidates (void); |
418 | void dump_edge_list (basic_block, bool); |
419 | void dump_block_info (basic_block); |
420 | void dump_all_blocks (void); |
421 | |
422 | bool interesting_regno_p (unsigned int); |
423 | remat_candidate *add_candidate (rtx_insn *, unsigned int, bool); |
424 | bool maybe_add_candidate (rtx_insn *, unsigned int); |
425 | bool collect_candidates (void); |
426 | void init_block_info (void); |
427 | void sort_candidates (void); |
428 | void finalize_candidate_indices (void); |
429 | void record_equiv_candidates (unsigned int, unsigned int); |
430 | static bool rd_confluence_n (edge); |
431 | static bool rd_transfer (int); |
432 | void compute_rd (void); |
433 | unsigned int canon_candidate (unsigned int); |
434 | void canon_bitmap (bitmap *); |
435 | unsigned int resolve_reaching_def (bitmap); |
436 | bool check_candidate_uses (unsigned int); |
437 | void compute_clobbers (unsigned int); |
438 | void assign_value_number (unsigned int); |
439 | void decide_candidate_validity (void); |
440 | void restrict_remat_for_unavail_regs (bitmap, const_bitmap); |
441 | void restrict_remat_for_call (bitmap, rtx_insn *); |
442 | bool stable_use_p (unsigned int); |
443 | void emit_copy_before (unsigned int, rtx, rtx); |
444 | void stabilize_pattern (unsigned int); |
445 | void replace_dest_with_copy (unsigned int); |
446 | void stabilize_candidate_uses (unsigned int, bitmap, bitmap, bitmap, |
447 | bitmap); |
448 | void emit_remat_insns (bitmap, bitmap, bitmap, rtx_insn *); |
449 | bool set_available_out (remat_block_info *); |
450 | void process_block (basic_block); |
451 | void local_phase (void); |
452 | static bool avail_confluence_n (edge); |
453 | static bool avail_transfer (int); |
454 | void compute_availability (void); |
455 | void unshare_available_sets (remat_block_info *); |
456 | bool can_move_across_edge_p (edge); |
457 | bool local_remat_cheaper_p (unsigned int); |
458 | bool need_to_move_candidate_p (unsigned int, unsigned int); |
459 | void compute_minimum_move_set (unsigned int, bitmap); |
460 | void move_to_predecessors (unsigned int, bitmap, bitmap); |
461 | void choose_rematerialization_points (void); |
462 | void emit_remat_insns_for_block (basic_block); |
463 | void global_phase (void); |
464 | |
465 | /* The function that we're optimizing. */ |
466 | function *m_fn; |
467 | |
468 | /* The modes that we want to rematerialize. */ |
469 | sbitmap m_selected_modes; |
470 | |
471 | /* All rematerialization candidates, identified by their index into the |
472 | vector. */ |
473 | auto_vec<remat_candidate> m_candidates; |
474 | |
475 | /* The set of candidate registers. */ |
476 | bitmap_head m_candidate_regnos; |
477 | |
478 | /* Temporary sets. */ |
479 | bitmap_head m_tmp_bitmap; |
480 | bitmap m_available; |
481 | bitmap m_required; |
482 | |
483 | /* Information about each basic block. */ |
484 | auto_vec<remat_block_info> m_block_info; |
485 | |
486 | /* A mapping from register numbers to the set of associated candidates. |
487 | Only valid for registers in M_CANDIDATE_REGNOS. */ |
488 | auto_vec<bitmap> m_regno_to_candidates; |
489 | |
490 | /* An obstack used for allocating bitmaps, so that we can free them all |
491 | in one go. */ |
492 | bitmap_obstack m_obstack; |
493 | |
494 | /* A hash table of candidates used for value numbering. If a candidate |
495 | in the table is in an equivalence class, the candidate is marked as |
496 | the earliest member of the class. */ |
497 | hash_table<remat_candidate_hasher> m_value_table; |
498 | |
499 | /* Used temporarily by callback functions. */ |
500 | static early_remat *er; |
501 | }; |
502 | |
503 | } |
504 | |
505 | early_remat *early_remat::er; |
506 | |
507 | /* rtx_equal_p callback that treats any two SCRATCHes as equal. |
508 | This allows us to compare two copies of a pattern, even though their |
509 | SCRATCHes are always distinct. */ |
510 | |
511 | static bool |
512 | scratch_equal (const_rtx *x, const_rtx *y, rtx *nx, rtx *ny) |
513 | { |
514 | if (GET_CODE (*x) == SCRATCH && GET_CODE (*y) == SCRATCH) |
515 | { |
516 | *nx = const0_rtx; |
517 | *ny = const0_rtx; |
518 | return true; |
519 | } |
520 | return false; |
521 | } |
522 | |
523 | /* Hash callback functions for remat_candidate. */ |
524 | |
525 | hashval_t |
526 | remat_candidate_hasher::hash (const remat_candidate *cand) |
527 | { |
528 | return cand->hash; |
529 | } |
530 | |
531 | bool |
532 | remat_candidate_hasher::equal (const remat_candidate *cand1, |
533 | const remat_candidate *cand2) |
534 | { |
535 | return (cand1->regno == cand2->regno |
536 | && cand1->constant_p == cand2->constant_p |
537 | && rtx_equal_p (cand1->remat_rtx, cand2->remat_rtx, |
538 | cand1->constant_p ? NULL : scratch_equal) |
539 | && (!cand1->uses || bitmap_equal_p (cand1->uses, cand2->uses))); |
540 | } |
541 | |
542 | /* Return true if B is null or empty. */ |
543 | |
544 | inline bool |
545 | empty_p (bitmap b) |
546 | { |
547 | return !b || bitmap_empty_p (map: b); |
548 | } |
549 | |
550 | /* Allocate a new bitmap. It will be automatically freed at the end of |
551 | the pass. */ |
552 | |
553 | inline bitmap |
554 | early_remat::alloc_bitmap (void) |
555 | { |
556 | return bitmap_alloc (obstack: &m_obstack); |
557 | } |
558 | |
559 | /* Initialize *PTR to an empty bitmap if it is currently null. */ |
560 | |
561 | inline bitmap |
562 | early_remat::get_bitmap (bitmap *ptr) |
563 | { |
564 | if (!*ptr) |
565 | *ptr = alloc_bitmap (); |
566 | return *ptr; |
567 | } |
568 | |
569 | /* *PTR is either null or empty. If it is null, initialize it to an |
570 | empty bitmap. */ |
571 | |
572 | inline void |
573 | early_remat::init_temp_bitmap (bitmap *ptr) |
574 | { |
575 | if (!*ptr) |
576 | *ptr = alloc_bitmap (); |
577 | else |
578 | gcc_checking_assert (bitmap_empty_p (*ptr)); |
579 | } |
580 | |
581 | /* Move *SRC to *DEST and leave *SRC empty. */ |
582 | |
583 | inline void |
584 | early_remat::copy_temp_bitmap (bitmap *dest, bitmap *src) |
585 | { |
586 | if (!empty_p (b: *src)) |
587 | { |
588 | *dest = *src; |
589 | *src = NULL; |
590 | } |
591 | else |
592 | *dest = NULL; |
593 | } |
594 | |
595 | /* Print INSN's identifier to the dump file. */ |
596 | |
597 | void |
598 | early_remat::dump_insn_id (rtx_insn *insn) |
599 | { |
600 | fprintf (stream: dump_file, format: "%d[bb:%d]" , INSN_UID (insn), |
601 | BLOCK_FOR_INSN (insn)->index); |
602 | } |
603 | |
604 | /* Print candidate set CANDIDATES to the dump file, with a leading space. */ |
605 | |
606 | void |
607 | early_remat::dump_candidate_bitmap (bitmap candidates) |
608 | { |
609 | if (empty_p (b: candidates)) |
610 | { |
611 | fprintf (stream: dump_file, format: " none" ); |
612 | return; |
613 | } |
614 | |
615 | unsigned int cand_index; |
616 | bitmap_iterator bi; |
617 | EXECUTE_IF_SET_IN_BITMAP (candidates, 0, cand_index, bi) |
618 | fprintf (stream: dump_file, format: " %d" , cand_index); |
619 | } |
620 | |
621 | /* Print information about all candidates to the dump file. */ |
622 | |
623 | void |
624 | early_remat::dump_all_candidates (void) |
625 | { |
626 | fprintf (stream: dump_file, format: "\n;; Candidates:\n;;\n" ); |
627 | fprintf (stream: dump_file, format: ";; %5s %5s %8s %s\n" , "#" , "reg" , "mode" , "insn" ); |
628 | fprintf (stream: dump_file, format: ";; %5s %5s %8s %s\n" , "=" , "===" , "====" , "====" ); |
629 | unsigned int cand_index; |
630 | remat_candidate *cand; |
631 | FOR_EACH_VEC_ELT (m_candidates, cand_index, cand) |
632 | { |
633 | fprintf (stream: dump_file, format: ";; %5d %5d %8s " , cand_index, cand->regno, |
634 | GET_MODE_NAME (GET_MODE (regno_reg_rtx[cand->regno]))); |
635 | dump_insn_id (insn: cand->insn); |
636 | if (!cand->can_copy_p) |
637 | fprintf (stream: dump_file, format: " -- can't copy" ); |
638 | fprintf (stream: dump_file, format: "\n" ); |
639 | } |
640 | |
641 | fprintf (stream: dump_file, format: "\n;; Register-to-candidate mapping:\n;;\n" ); |
642 | unsigned int regno; |
643 | bitmap_iterator bi; |
644 | EXECUTE_IF_SET_IN_BITMAP (&m_candidate_regnos, 0, regno, bi) |
645 | { |
646 | fprintf (stream: dump_file, format: ";; %5d:" , regno); |
647 | dump_candidate_bitmap (candidates: m_regno_to_candidates[regno]); |
648 | fprintf (stream: dump_file, format: "\n" ); |
649 | } |
650 | } |
651 | |
652 | /* Print the predecessors or successors of BB to the dump file, with a |
653 | leading space. DO_SUCC is true to print successors and false to print |
654 | predecessors. */ |
655 | |
656 | void |
657 | early_remat::dump_edge_list (basic_block bb, bool do_succ) |
658 | { |
659 | edge e; |
660 | edge_iterator ei; |
661 | FOR_EACH_EDGE (e, ei, do_succ ? bb->succs : bb->preds) |
662 | dump_edge_info (dump_file, e, TDF_NONE, do_succ); |
663 | } |
664 | |
665 | /* Print information about basic block BB to the dump file. */ |
666 | |
667 | void |
668 | early_remat::dump_block_info (basic_block bb) |
669 | { |
670 | remat_block_info *info = &m_block_info[bb->index]; |
671 | fprintf (stream: dump_file, format: ";;\n;; Block %d:" , bb->index); |
672 | int width = 25; |
673 | |
674 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "predecessors" ); |
675 | dump_edge_list (bb, do_succ: false); |
676 | |
677 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "successors" ); |
678 | dump_edge_list (bb, do_succ: true); |
679 | |
680 | fprintf (stream: dump_file, format: "\n;;%*s: %d" , width, "frequency" , |
681 | bb->count.to_frequency (fun: m_fn)); |
682 | |
683 | if (info->last_call) |
684 | fprintf (stream: dump_file, format: "\n;;%*s: %d" , width, "last call" , |
685 | INSN_UID (insn: info->last_call)); |
686 | |
687 | if (!empty_p (b: info->rd_in)) |
688 | { |
689 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "RD in" ); |
690 | dump_candidate_bitmap (candidates: info->rd_in); |
691 | } |
692 | if (!empty_p (b: info->rd_kill)) |
693 | { |
694 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "RD kill" ); |
695 | dump_candidate_bitmap (candidates: info->rd_kill); |
696 | } |
697 | if (!empty_p (b: info->rd_gen)) |
698 | { |
699 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "RD gen" ); |
700 | dump_candidate_bitmap (candidates: info->rd_gen); |
701 | } |
702 | if (!empty_p (b: info->rd_after_call)) |
703 | { |
704 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "RD after call" ); |
705 | dump_candidate_bitmap (candidates: info->rd_after_call); |
706 | } |
707 | if (!empty_p (b: info->rd_out)) |
708 | { |
709 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "RD out" ); |
710 | if (info->rd_in == info->rd_out) |
711 | fprintf (stream: dump_file, format: " RD in" ); |
712 | else |
713 | dump_candidate_bitmap (candidates: info->rd_out); |
714 | } |
715 | if (!empty_p (b: info->available_in)) |
716 | { |
717 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "available in" ); |
718 | dump_candidate_bitmap (candidates: info->available_in); |
719 | } |
720 | if (!empty_p (b: info->available_locally)) |
721 | { |
722 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "available locally" ); |
723 | dump_candidate_bitmap (candidates: info->available_locally); |
724 | } |
725 | if (!empty_p (b: info->available_out)) |
726 | { |
727 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "available out" ); |
728 | if (info->available_in == info->available_out) |
729 | fprintf (stream: dump_file, format: " available in" ); |
730 | else if (info->available_locally == info->available_out) |
731 | fprintf (stream: dump_file, format: " available locally" ); |
732 | else |
733 | dump_candidate_bitmap (candidates: info->available_out); |
734 | } |
735 | if (!empty_p (b: info->required_in)) |
736 | { |
737 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "required in" ); |
738 | dump_candidate_bitmap (candidates: info->required_in); |
739 | } |
740 | if (!empty_p (b: info->required_after_call)) |
741 | { |
742 | fprintf (stream: dump_file, format: "\n;;%*s:" , width, "required after call" ); |
743 | dump_candidate_bitmap (candidates: info->required_after_call); |
744 | } |
745 | fprintf (stream: dump_file, format: "\n" ); |
746 | } |
747 | |
748 | /* Print information about all basic blocks to the dump file. */ |
749 | |
750 | void |
751 | early_remat::dump_all_blocks (void) |
752 | { |
753 | basic_block bb; |
754 | FOR_EACH_BB_FN (bb, m_fn) |
755 | dump_block_info (bb); |
756 | } |
757 | |
758 | /* Return true if REGNO is worth rematerializing. */ |
759 | |
760 | bool |
761 | early_remat::interesting_regno_p (unsigned int regno) |
762 | { |
763 | /* Ignore unused registers. */ |
764 | rtx reg = regno_reg_rtx[regno]; |
765 | if (!reg || DF_REG_DEF_COUNT (regno) == 0) |
766 | return false; |
767 | |
768 | /* Make sure the register has a mode that we want to rematerialize. */ |
769 | if (!bitmap_bit_p (map: m_selected_modes, GET_MODE (reg))) |
770 | return false; |
771 | |
772 | /* Ignore values that might sometimes be used uninitialized. We could |
773 | instead add dummy candidates for the entry block definition, and so |
774 | handle uses that are definitely not uninitialized, but the combination |
775 | of the two should be rare in practice. */ |
776 | if (bitmap_bit_p (DF_LR_OUT (ENTRY_BLOCK_PTR_FOR_FN (m_fn)), regno)) |
777 | return false; |
778 | |
779 | return true; |
780 | } |
781 | |
782 | /* Record the set of register REGNO in instruction INSN as a |
783 | rematerialization candidate. CAN_COPY_P is true unless we already |
784 | know that rematerialization is impossible (in which case the candidate |
785 | only exists for the reaching definition calculation). |
786 | |
787 | The candidate's index is not fixed at this stage. */ |
788 | |
789 | remat_candidate * |
790 | early_remat::add_candidate (rtx_insn *insn, unsigned int regno, |
791 | bool can_copy_p) |
792 | { |
793 | remat_candidate cand; |
794 | memset (s: &cand, c: 0, n: sizeof (cand)); |
795 | cand.regno = regno; |
796 | cand.insn = insn; |
797 | cand.remat_rtx = PATTERN (insn); |
798 | cand.can_copy_p = can_copy_p; |
799 | m_candidates.safe_push (obj: cand); |
800 | |
801 | bitmap_set_bit (&m_candidate_regnos, regno); |
802 | |
803 | return &m_candidates.last (); |
804 | } |
805 | |
806 | /* Return true if we can rematerialize the set of register REGNO in |
807 | instruction INSN, and add it as a candidate if so. When returning |
808 | false, print the reason to the dump file. */ |
809 | |
810 | bool |
811 | early_remat::maybe_add_candidate (rtx_insn *insn, unsigned int regno) |
812 | { |
813 | #define FAILURE_FORMAT ";; Can't rematerialize set of reg %d in %d[bb:%d]: " |
814 | #define FAILURE_ARGS regno, INSN_UID (insn), BLOCK_FOR_INSN (insn)->index |
815 | |
816 | /* The definition must come from an ordinary instruction. */ |
817 | basic_block bb = BLOCK_FOR_INSN (insn); |
818 | if (!NONJUMP_INSN_P (insn) |
819 | || (insn == BB_END (bb) |
820 | && has_abnormal_or_eh_outgoing_edge_p (bb))) |
821 | { |
822 | if (dump_file) |
823 | fprintf (stream: dump_file, FAILURE_FORMAT "insn alters control flow\n" , |
824 | FAILURE_ARGS); |
825 | return false; |
826 | } |
827 | |
828 | /* Prefer to rematerialize constants directly -- it's much easier. */ |
829 | machine_mode mode = GET_MODE (regno_reg_rtx[regno]); |
830 | if (rtx note = find_reg_equal_equiv_note (insn)) |
831 | { |
832 | rtx val = XEXP (note, 0); |
833 | if (CONSTANT_P (val) |
834 | && targetm.legitimate_constant_p (mode, val)) |
835 | { |
836 | remat_candidate *cand = add_candidate (insn, regno, can_copy_p: true); |
837 | cand->constant_p = true; |
838 | cand->remat_rtx = val; |
839 | return true; |
840 | } |
841 | } |
842 | |
843 | /* See whether the target has reasons to prevent a copy. */ |
844 | if (targetm.cannot_copy_insn_p && targetm.cannot_copy_insn_p (insn)) |
845 | { |
846 | if (dump_file) |
847 | fprintf (stream: dump_file, FAILURE_FORMAT "target forbids copying\n" , |
848 | FAILURE_ARGS); |
849 | return false; |
850 | } |
851 | |
852 | /* We can't copy trapping instructions. */ |
853 | rtx pat = PATTERN (insn); |
854 | if (may_trap_p (pat)) |
855 | { |
856 | if (dump_file) |
857 | fprintf (stream: dump_file, FAILURE_FORMAT "insn might trap\n" , FAILURE_ARGS); |
858 | return false; |
859 | } |
860 | |
861 | /* We can't copy instructions that read memory, unless we know that |
862 | the contents never change. */ |
863 | subrtx_iterator::array_type array; |
864 | FOR_EACH_SUBRTX (iter, array, pat, ALL) |
865 | if (MEM_P (*iter) && !MEM_READONLY_P (*iter)) |
866 | { |
867 | if (dump_file) |
868 | fprintf (stream: dump_file, FAILURE_FORMAT "insn references non-constant" |
869 | " memory\n" , FAILURE_ARGS); |
870 | return false; |
871 | } |
872 | |
873 | /* Check each defined register. */ |
874 | df_ref ref; |
875 | FOR_EACH_INSN_DEF (ref, insn) |
876 | { |
877 | unsigned int def_regno = DF_REF_REGNO (ref); |
878 | if (def_regno == regno) |
879 | { |
880 | /* Make sure the definition is write-only. (Partial definitions, |
881 | such as setting the low part and clobbering the high part, |
882 | are otherwise OK.) */ |
883 | if (DF_REF_FLAGS_IS_SET (ref, DF_REF_READ_WRITE)) |
884 | { |
885 | if (dump_file) |
886 | fprintf (stream: dump_file, FAILURE_FORMAT "destination is" |
887 | " read-modify-write\n" , FAILURE_ARGS); |
888 | return false; |
889 | } |
890 | } |
891 | else |
892 | { |
893 | /* The instruction can set additional registers, provided that |
894 | they're hard registers. This is useful for instructions |
895 | that alter the condition codes. */ |
896 | if (!HARD_REGISTER_NUM_P (def_regno)) |
897 | { |
898 | if (dump_file) |
899 | fprintf (stream: dump_file, FAILURE_FORMAT "insn also sets" |
900 | " pseudo reg %d\n" , FAILURE_ARGS, def_regno); |
901 | return false; |
902 | } |
903 | } |
904 | } |
905 | |
906 | /* If the instruction uses fixed hard registers, check that those |
907 | registers have the same value throughout the function. If the |
908 | instruction uses non-fixed hard registers, check that we can |
909 | replace them with pseudos. */ |
910 | FOR_EACH_INSN_USE (ref, insn) |
911 | { |
912 | unsigned int use_regno = DF_REF_REGNO (ref); |
913 | if (HARD_REGISTER_NUM_P (use_regno) && fixed_regs[use_regno]) |
914 | { |
915 | if (rtx_unstable_p (DF_REF_REAL_REG (ref))) |
916 | { |
917 | if (dump_file) |
918 | fprintf (stream: dump_file, FAILURE_FORMAT "insn uses fixed hard reg" |
919 | " %d\n" , FAILURE_ARGS, use_regno); |
920 | return false; |
921 | } |
922 | } |
923 | else if (HARD_REGISTER_NUM_P (use_regno)) |
924 | { |
925 | /* Allocate a dummy pseudo register and temporarily install it. |
926 | Make the register number depend on the mode, which should |
927 | provide enough sharing for match_dup while also weeding |
928 | out cases in which operands with different modes are |
929 | explicitly tied. */ |
930 | rtx *loc = DF_REF_REAL_LOC (ref); |
931 | unsigned int size = RTX_CODE_SIZE (REG); |
932 | rtx new_reg = (rtx) alloca (size); |
933 | memset (s: new_reg, c: 0, n: size); |
934 | PUT_CODE (new_reg, REG); |
935 | set_mode_and_regno (new_reg, GET_MODE (*loc), |
936 | LAST_VIRTUAL_REGISTER + 1 + GET_MODE (*loc)); |
937 | validate_change (insn, loc, new_reg, 1); |
938 | } |
939 | } |
940 | bool ok_p = verify_changes (0); |
941 | cancel_changes (0); |
942 | if (!ok_p) |
943 | { |
944 | if (dump_file) |
945 | fprintf (stream: dump_file, FAILURE_FORMAT "insn does not allow hard" |
946 | " register inputs to be replaced\n" , FAILURE_ARGS); |
947 | return false; |
948 | } |
949 | |
950 | #undef FAILURE_ARGS |
951 | #undef FAILURE_FORMAT |
952 | |
953 | add_candidate (insn, regno, can_copy_p: true); |
954 | return true; |
955 | } |
956 | |
957 | /* Calculate the set of rematerialization candidates. Return true if |
958 | we find at least one. */ |
959 | |
960 | bool |
961 | early_remat::collect_candidates (void) |
962 | { |
963 | unsigned int nregs = DF_REG_SIZE (df); |
964 | for (unsigned int regno = FIRST_PSEUDO_REGISTER; regno < nregs; ++regno) |
965 | if (interesting_regno_p (regno)) |
966 | { |
967 | /* Create candidates for all suitable definitions. */ |
968 | bitmap_clear (&m_tmp_bitmap); |
969 | unsigned int bad = 0; |
970 | unsigned int id = 0; |
971 | for (df_ref ref = DF_REG_DEF_CHAIN (regno); ref; |
972 | ref = DF_REF_NEXT_REG (ref)) |
973 | { |
974 | rtx_insn *insn = DF_REF_INSN (ref); |
975 | if (maybe_add_candidate (insn, regno)) |
976 | bitmap_set_bit (&m_tmp_bitmap, id); |
977 | else |
978 | bad += 1; |
979 | id += 1; |
980 | } |
981 | |
982 | /* If we found at least one suitable definition, add dummy |
983 | candidates for the rest, so that we can see which definitions |
984 | are live where. */ |
985 | if (!bitmap_empty_p (map: &m_tmp_bitmap) && bad) |
986 | { |
987 | id = 0; |
988 | for (df_ref ref = DF_REG_DEF_CHAIN (regno); ref; |
989 | ref = DF_REF_NEXT_REG (ref)) |
990 | { |
991 | if (!bitmap_bit_p (&m_tmp_bitmap, id)) |
992 | add_candidate (DF_REF_INSN (ref), regno, can_copy_p: false); |
993 | id += 1; |
994 | } |
995 | } |
996 | } |
997 | |
998 | |
999 | return !m_candidates.is_empty (); |
1000 | } |
1001 | |
1002 | /* Initialize the m_block_info array. */ |
1003 | |
1004 | void |
1005 | early_remat::init_block_info (void) |
1006 | { |
1007 | unsigned int n_blocks = last_basic_block_for_fn (m_fn); |
1008 | m_block_info.safe_grow_cleared (len: n_blocks, exact: true); |
1009 | } |
1010 | |
1011 | /* Maps basic block indices to their position in the forward RPO. */ |
1012 | static unsigned int *rpo_index; |
1013 | |
1014 | /* Order remat_candidates X_IN and Y_IN according to the cfg postorder. */ |
1015 | |
1016 | static int |
1017 | compare_candidates (const void *x_in, const void *y_in) |
1018 | { |
1019 | const remat_candidate *x = (const remat_candidate *) x_in; |
1020 | const remat_candidate *y = (const remat_candidate *) y_in; |
1021 | basic_block x_bb = BLOCK_FOR_INSN (insn: x->insn); |
1022 | basic_block y_bb = BLOCK_FOR_INSN (insn: y->insn); |
1023 | if (x_bb != y_bb) |
1024 | /* Make X and Y follow block postorder. */ |
1025 | return rpo_index[y_bb->index] - rpo_index[x_bb->index]; |
1026 | |
1027 | /* Make X and Y follow a backward traversal of the containing block. */ |
1028 | return DF_INSN_LUID (y->insn) - DF_INSN_LUID (x->insn); |
1029 | } |
1030 | |
1031 | /* Sort the collected rematerialization candidates so that they follow |
1032 | cfg postorder. */ |
1033 | |
1034 | void |
1035 | early_remat::sort_candidates (void) |
1036 | { |
1037 | /* Make sure the DF LUIDs are up-to-date for all the blocks we |
1038 | care about. */ |
1039 | bitmap_clear (&m_tmp_bitmap); |
1040 | unsigned int cand_index; |
1041 | remat_candidate *cand; |
1042 | FOR_EACH_VEC_ELT (m_candidates, cand_index, cand) |
1043 | { |
1044 | basic_block bb = BLOCK_FOR_INSN (insn: cand->insn); |
1045 | if (bitmap_set_bit (&m_tmp_bitmap, bb->index)) |
1046 | df_recompute_luids (bb); |
1047 | } |
1048 | |
1049 | /* Create a mapping from block numbers to their position in the |
1050 | postorder. */ |
1051 | unsigned int n_blocks = last_basic_block_for_fn (m_fn); |
1052 | int *rpo = df_get_postorder (DF_FORWARD); |
1053 | unsigned int rpo_len = df_get_n_blocks (DF_FORWARD); |
1054 | rpo_index = new unsigned int[n_blocks]; |
1055 | for (unsigned int i = 0; i < rpo_len; ++i) |
1056 | rpo_index[rpo[i]] = i; |
1057 | |
1058 | m_candidates.qsort (compare_candidates); |
1059 | |
1060 | delete[] rpo_index; |
1061 | } |
1062 | |
1063 | /* Commit to the current candidate indices and initialize cross-references. */ |
1064 | |
1065 | void |
1066 | early_remat::finalize_candidate_indices (void) |
1067 | { |
1068 | /* Create a bitmap for each candidate register. */ |
1069 | m_regno_to_candidates.safe_grow (len: max_reg_num (), exact: true); |
1070 | unsigned int regno; |
1071 | bitmap_iterator bi; |
1072 | EXECUTE_IF_SET_IN_BITMAP (&m_candidate_regnos, 0, regno, bi) |
1073 | m_regno_to_candidates[regno] = alloc_bitmap (); |
1074 | |
1075 | /* Go through each candidate and record its index. */ |
1076 | unsigned int cand_index; |
1077 | remat_candidate *cand; |
1078 | FOR_EACH_VEC_ELT (m_candidates, cand_index, cand) |
1079 | { |
1080 | basic_block bb = BLOCK_FOR_INSN (insn: cand->insn); |
1081 | remat_block_info *info = &m_block_info[bb->index]; |
1082 | info->num_candidates += 1; |
1083 | info->first_candidate = cand_index; |
1084 | bitmap_set_bit (m_regno_to_candidates[cand->regno], cand_index); |
1085 | } |
1086 | } |
1087 | |
1088 | /* Record that candidates CAND1_INDEX and CAND2_INDEX are equivalent. |
1089 | CAND1_INDEX might already have an equivalence class, but CAND2_INDEX |
1090 | doesn't. */ |
1091 | |
1092 | void |
1093 | early_remat::record_equiv_candidates (unsigned int cand1_index, |
1094 | unsigned int cand2_index) |
1095 | { |
1096 | if (dump_file) |
1097 | fprintf (stream: dump_file, format: ";; Candidate %d is equivalent to candidate %d\n" , |
1098 | cand2_index, cand1_index); |
1099 | |
1100 | remat_candidate *cand1 = &m_candidates[cand1_index]; |
1101 | remat_candidate *cand2 = &m_candidates[cand2_index]; |
1102 | gcc_checking_assert (!cand2->equiv_class); |
1103 | |
1104 | remat_equiv_class *ec = cand1->equiv_class; |
1105 | if (!ec) |
1106 | { |
1107 | ec = XOBNEW (&m_obstack.obstack, remat_equiv_class); |
1108 | ec->members = alloc_bitmap (); |
1109 | bitmap_set_bit (ec->members, cand1_index); |
1110 | ec->earliest = cand1_index; |
1111 | ec->representative = cand1_index; |
1112 | cand1->equiv_class = ec; |
1113 | } |
1114 | cand2->equiv_class = ec; |
1115 | bitmap_set_bit (ec->members, cand2_index); |
1116 | if (cand2_index > ec->representative) |
1117 | ec->representative = cand2_index; |
1118 | } |
1119 | |
1120 | /* Propagate information from the rd_out set of E->src to the rd_in set |
1121 | of E->dest, when computing global reaching definitions. Return true |
1122 | if something changed. */ |
1123 | |
1124 | bool |
1125 | early_remat::rd_confluence_n (edge e) |
1126 | { |
1127 | remat_block_info *src = &er->m_block_info[e->src->index]; |
1128 | remat_block_info *dest = &er->m_block_info[e->dest->index]; |
1129 | |
1130 | /* available_in temporarily contains the set of candidates whose |
1131 | registers are live on entry. */ |
1132 | if (empty_p (b: src->rd_out) || empty_p (b: dest->available_in)) |
1133 | return false; |
1134 | |
1135 | return bitmap_ior_and_into (DST: er->get_bitmap (ptr: &dest->rd_in), |
1136 | B: src->rd_out, C: dest->available_in); |
1137 | } |
1138 | |
1139 | /* Propagate information from the rd_in set of block BB_INDEX to rd_out. |
1140 | Return true if something changed. */ |
1141 | |
1142 | bool |
1143 | early_remat::rd_transfer (int bb_index) |
1144 | { |
1145 | remat_block_info *info = &er->m_block_info[bb_index]; |
1146 | |
1147 | if (empty_p (b: info->rd_in)) |
1148 | return false; |
1149 | |
1150 | if (empty_p (b: info->rd_kill)) |
1151 | { |
1152 | gcc_checking_assert (empty_p (info->rd_gen)); |
1153 | if (!info->rd_out) |
1154 | info->rd_out = info->rd_in; |
1155 | else |
1156 | gcc_checking_assert (info->rd_out == info->rd_in); |
1157 | /* Assume that we only get called if something changed. */ |
1158 | return true; |
1159 | } |
1160 | |
1161 | if (empty_p (b: info->rd_gen)) |
1162 | return bitmap_and_compl (er->get_bitmap (ptr: &info->rd_out), |
1163 | info->rd_in, info->rd_kill); |
1164 | |
1165 | return bitmap_ior_and_compl (DST: er->get_bitmap (ptr: &info->rd_out), A: info->rd_gen, |
1166 | B: info->rd_in, C: info->rd_kill); |
1167 | } |
1168 | |
1169 | /* Calculate the rd_* sets for each block. */ |
1170 | |
1171 | void |
1172 | early_remat::compute_rd (void) |
1173 | { |
1174 | /* First calculate the rd_kill and rd_gen sets, using the fact |
1175 | that m_candidates is sorted in order of decreasing LUID. */ |
1176 | unsigned int cand_index; |
1177 | remat_candidate *cand; |
1178 | FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand_index, cand) |
1179 | { |
1180 | rtx_insn *insn = cand->insn; |
1181 | basic_block bb = BLOCK_FOR_INSN (insn); |
1182 | remat_block_info *info = &m_block_info[bb->index]; |
1183 | bitmap kill = m_regno_to_candidates[cand->regno]; |
1184 | bitmap_ior_into (get_bitmap (ptr: &info->rd_kill), kill); |
1185 | if (bitmap_bit_p (DF_LR_OUT (bb), cand->regno)) |
1186 | { |
1187 | bitmap_and_compl_into (get_bitmap (ptr: &info->rd_gen), kill); |
1188 | bitmap_set_bit (info->rd_gen, cand_index); |
1189 | } |
1190 | } |
1191 | |
1192 | /* Set up the initial values of the other sets. */ |
1193 | basic_block bb; |
1194 | FOR_EACH_BB_FN (bb, m_fn) |
1195 | { |
1196 | remat_block_info *info = &m_block_info[bb->index]; |
1197 | unsigned int regno; |
1198 | bitmap_iterator bi; |
1199 | EXECUTE_IF_AND_IN_BITMAP (DF_LR_IN (bb), &m_candidate_regnos, |
1200 | 0, regno, bi) |
1201 | { |
1202 | /* Use available_in to record the set of candidates whose |
1203 | registers are live on entry (i.e. a maximum bound on rd_in). */ |
1204 | bitmap_ior_into (get_bitmap (ptr: &info->available_in), |
1205 | m_regno_to_candidates[regno]); |
1206 | |
1207 | /* Add registers that die in a block to the block's kill set, |
1208 | so that we don't needlessly propagate them through the rest |
1209 | of the function. */ |
1210 | if (!bitmap_bit_p (DF_LR_OUT (bb), regno)) |
1211 | bitmap_ior_into (get_bitmap (ptr: &info->rd_kill), |
1212 | m_regno_to_candidates[regno]); |
1213 | } |
1214 | |
1215 | /* Initialize each block's rd_out to the minimal set (the set of |
1216 | local definitions). */ |
1217 | if (!empty_p (b: info->rd_gen)) |
1218 | bitmap_copy (get_bitmap (ptr: &info->rd_out), info->rd_gen); |
1219 | } |
1220 | |
1221 | /* Iterate until we reach a fixed point. */ |
1222 | er = this; |
1223 | bitmap_clear (&m_tmp_bitmap); |
1224 | bitmap_set_range (&m_tmp_bitmap, 0, last_basic_block_for_fn (m_fn)); |
1225 | df_simple_dataflow (DF_FORWARD, NULL, NULL, rd_confluence_n, rd_transfer, |
1226 | &m_tmp_bitmap, df_get_postorder (DF_FORWARD), |
1227 | df_get_n_blocks (DF_FORWARD)); |
1228 | er = 0; |
1229 | |
1230 | /* Work out which definitions reach which candidates, again taking |
1231 | advantage of the candidate order. */ |
1232 | bitmap_head reaching; |
1233 | bitmap_initialize (head: &reaching, obstack: &m_obstack); |
1234 | basic_block old_bb = NULL; |
1235 | FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand_index, cand) |
1236 | { |
1237 | bb = BLOCK_FOR_INSN (insn: cand->insn); |
1238 | if (bb != old_bb) |
1239 | { |
1240 | /* Get the definitions that reach the start of the new block. */ |
1241 | remat_block_info *info = &m_block_info[bb->index]; |
1242 | if (info->rd_in) |
1243 | bitmap_copy (&reaching, info->rd_in); |
1244 | else |
1245 | bitmap_clear (&reaching); |
1246 | old_bb = bb; |
1247 | } |
1248 | else |
1249 | { |
1250 | /* Process the definitions of the previous instruction. */ |
1251 | bitmap kill = m_regno_to_candidates[cand[1].regno]; |
1252 | bitmap_and_compl_into (&reaching, kill); |
1253 | bitmap_set_bit (&reaching, cand_index + 1); |
1254 | } |
1255 | |
1256 | if (cand->can_copy_p && !cand->constant_p) |
1257 | { |
1258 | df_ref ref; |
1259 | FOR_EACH_INSN_USE (ref, cand->insn) |
1260 | { |
1261 | unsigned int regno = DF_REF_REGNO (ref); |
1262 | if (bitmap_bit_p (&m_candidate_regnos, regno)) |
1263 | { |
1264 | bitmap defs = m_regno_to_candidates[regno]; |
1265 | bitmap_and (&m_tmp_bitmap, defs, &reaching); |
1266 | bitmap_ior_into (get_bitmap (ptr: &cand->uses), &m_tmp_bitmap); |
1267 | } |
1268 | } |
1269 | } |
1270 | } |
1271 | bitmap_clear (&reaching); |
1272 | } |
1273 | |
1274 | /* If CAND_INDEX is in an equivalence class, return the representative |
1275 | of the class, otherwise return CAND_INDEX. */ |
1276 | |
1277 | inline unsigned int |
1278 | early_remat::canon_candidate (unsigned int cand_index) |
1279 | { |
1280 | if (remat_equiv_class *ec = m_candidates[cand_index].equiv_class) |
1281 | return ec->representative; |
1282 | return cand_index; |
1283 | } |
1284 | |
1285 | /* Make candidate set *PTR refer to candidates using the representative |
1286 | of each equivalence class. */ |
1287 | |
1288 | void |
1289 | early_remat::canon_bitmap (bitmap *ptr) |
1290 | { |
1291 | bitmap old_set = *ptr; |
1292 | if (empty_p (b: old_set)) |
1293 | return; |
1294 | |
1295 | bitmap new_set = NULL; |
1296 | unsigned int old_index; |
1297 | bitmap_iterator bi; |
1298 | EXECUTE_IF_SET_IN_BITMAP (old_set, 0, old_index, bi) |
1299 | { |
1300 | unsigned int new_index = canon_candidate (cand_index: old_index); |
1301 | if (old_index != new_index) |
1302 | { |
1303 | if (!new_set) |
1304 | { |
1305 | new_set = alloc_bitmap (); |
1306 | bitmap_copy (new_set, old_set); |
1307 | } |
1308 | bitmap_clear_bit (new_set, old_index); |
1309 | bitmap_set_bit (new_set, new_index); |
1310 | } |
1311 | } |
1312 | if (new_set) |
1313 | { |
1314 | BITMAP_FREE (*ptr); |
1315 | *ptr = new_set; |
1316 | } |
1317 | } |
1318 | |
1319 | /* If the candidates in REACHING all have the same value, return the |
1320 | earliest instance of that value (i.e. the first one to be added |
1321 | to m_value_table), otherwise return MULTIPLE_CANDIDATES. */ |
1322 | |
1323 | unsigned int |
1324 | early_remat::resolve_reaching_def (bitmap reaching) |
1325 | { |
1326 | unsigned int cand_index = bitmap_first_set_bit (reaching); |
1327 | if (remat_equiv_class *ec = m_candidates[cand_index].equiv_class) |
1328 | { |
1329 | if (!bitmap_intersect_compl_p (reaching, ec->members)) |
1330 | return ec->earliest; |
1331 | } |
1332 | else if (bitmap_single_bit_set_p (reaching)) |
1333 | return cand_index; |
1334 | |
1335 | return MULTIPLE_CANDIDATES; |
1336 | } |
1337 | |
1338 | /* Check whether all candidate registers used by candidate CAND_INDEX have |
1339 | unique definitions. Return true if so, replacing the candidate's uses |
1340 | set with the appropriate form for value numbering. */ |
1341 | |
1342 | bool |
1343 | early_remat::check_candidate_uses (unsigned int cand_index) |
1344 | { |
1345 | remat_candidate *cand = &m_candidates[cand_index]; |
1346 | |
1347 | /* Process the uses for each register in turn. */ |
1348 | bitmap_head uses; |
1349 | bitmap_initialize (head: &uses, obstack: &m_obstack); |
1350 | bitmap_copy (&uses, cand->uses); |
1351 | bitmap uses_ec = alloc_bitmap (); |
1352 | while (!bitmap_empty_p (map: &uses)) |
1353 | { |
1354 | /* Get the register for the lowest-indexed candidate remaining, |
1355 | and the reaching definitions of that register. */ |
1356 | unsigned int first = bitmap_first_set_bit (&uses); |
1357 | unsigned int regno = m_candidates[first].regno; |
1358 | bitmap_and (&m_tmp_bitmap, &uses, m_regno_to_candidates[regno]); |
1359 | |
1360 | /* See whether all reaching definitions have the same value and if |
1361 | so get the index of the first candidate we saw with that value. */ |
1362 | unsigned int def = resolve_reaching_def (reaching: &m_tmp_bitmap); |
1363 | if (def == MULTIPLE_CANDIDATES) |
1364 | { |
1365 | if (dump_file) |
1366 | fprintf (stream: dump_file, format: ";; Removing candidate %d because there is" |
1367 | " more than one reaching definition of reg %d\n" , |
1368 | cand_index, regno); |
1369 | cand->can_copy_p = false; |
1370 | break; |
1371 | } |
1372 | bitmap_set_bit (uses_ec, def); |
1373 | bitmap_and_compl_into (&uses, &m_tmp_bitmap); |
1374 | } |
1375 | BITMAP_FREE (cand->uses); |
1376 | cand->uses = uses_ec; |
1377 | return cand->can_copy_p; |
1378 | } |
1379 | |
1380 | /* Calculate the set of hard registers that would be clobbered by |
1381 | rematerializing candidate CAND_INDEX. At this point the candidate's |
1382 | set of uses is final. */ |
1383 | |
1384 | void |
1385 | early_remat::compute_clobbers (unsigned int cand_index) |
1386 | { |
1387 | remat_candidate *cand = &m_candidates[cand_index]; |
1388 | if (cand->uses) |
1389 | { |
1390 | unsigned int use_index; |
1391 | bitmap_iterator bi; |
1392 | EXECUTE_IF_SET_IN_BITMAP (cand->uses, 0, use_index, bi) |
1393 | if (bitmap clobbers = m_candidates[use_index].clobbers) |
1394 | bitmap_ior_into (get_bitmap (ptr: &cand->clobbers), clobbers); |
1395 | } |
1396 | |
1397 | df_ref ref; |
1398 | FOR_EACH_INSN_DEF (ref, cand->insn) |
1399 | { |
1400 | unsigned int def_regno = DF_REF_REGNO (ref); |
1401 | if (def_regno != cand->regno) |
1402 | bitmap_set_bit (get_bitmap (ptr: &cand->clobbers), def_regno); |
1403 | } |
1404 | } |
1405 | |
1406 | /* Mark candidate CAND_INDEX as validated and add it to the value table. */ |
1407 | |
1408 | void |
1409 | early_remat::assign_value_number (unsigned int cand_index) |
1410 | { |
1411 | remat_candidate *cand = &m_candidates[cand_index]; |
1412 | gcc_checking_assert (cand->can_copy_p && !cand->validated_p); |
1413 | |
1414 | compute_clobbers (cand_index); |
1415 | cand->validated_p = true; |
1416 | |
1417 | inchash::hash h; |
1418 | h.add_int (v: cand->regno); |
1419 | inchash::add_rtx (cand->remat_rtx, h); |
1420 | cand->hash = h.end (); |
1421 | |
1422 | remat_candidate **slot |
1423 | = m_value_table.find_slot_with_hash (comparable: cand, hash: cand->hash, insert: INSERT); |
1424 | if (!*slot) |
1425 | { |
1426 | *slot = cand; |
1427 | if (dump_file) |
1428 | fprintf (stream: dump_file, format: ";; Candidate %d is not equivalent to" |
1429 | " others seen so far\n" , cand_index); |
1430 | } |
1431 | else |
1432 | record_equiv_candidates (cand1_index: *slot - m_candidates.address (), cand2_index: cand_index); |
1433 | } |
1434 | |
1435 | /* Make a final decision about which candidates are valid and assign |
1436 | value numbers to those that are. */ |
1437 | |
1438 | void |
1439 | early_remat::decide_candidate_validity (void) |
1440 | { |
1441 | auto_vec<unsigned int, 16> stack; |
1442 | unsigned int cand1_index; |
1443 | remat_candidate *cand1; |
1444 | FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand1_index, cand1) |
1445 | { |
1446 | if (!cand1->can_copy_p || cand1->validated_p) |
1447 | continue; |
1448 | |
1449 | if (empty_p (b: cand1->uses)) |
1450 | { |
1451 | assign_value_number (cand_index: cand1_index); |
1452 | continue; |
1453 | } |
1454 | |
1455 | stack.safe_push (obj: cand1_index); |
1456 | while (!stack.is_empty ()) |
1457 | { |
1458 | unsigned int cand2_index = stack.last (); |
1459 | unsigned int watermark = stack.length (); |
1460 | remat_candidate *cand2 = &m_candidates[cand2_index]; |
1461 | if (!cand2->can_copy_p || cand2->validated_p) |
1462 | { |
1463 | stack.pop (); |
1464 | continue; |
1465 | } |
1466 | cand2->visited_p = true; |
1467 | unsigned int cand3_index; |
1468 | bitmap_iterator bi; |
1469 | EXECUTE_IF_SET_IN_BITMAP (cand2->uses, 0, cand3_index, bi) |
1470 | { |
1471 | remat_candidate *cand3 = &m_candidates[cand3_index]; |
1472 | if (!cand3->can_copy_p) |
1473 | { |
1474 | if (dump_file) |
1475 | fprintf (stream: dump_file, format: ";; Removing candidate %d because" |
1476 | " it uses removed candidate %d\n" , cand2_index, |
1477 | cand3_index); |
1478 | cand2->can_copy_p = false; |
1479 | break; |
1480 | } |
1481 | if (!cand3->validated_p) |
1482 | { |
1483 | if (empty_p (b: cand3->uses)) |
1484 | assign_value_number (cand_index: cand3_index); |
1485 | else if (cand3->visited_p) |
1486 | { |
1487 | if (dump_file) |
1488 | fprintf (stream: dump_file, format: ";; Removing candidate %d" |
1489 | " because its definition is cyclic\n" , |
1490 | cand2_index); |
1491 | cand2->can_copy_p = false; |
1492 | break; |
1493 | } |
1494 | else |
1495 | stack.safe_push (obj: cand3_index); |
1496 | } |
1497 | } |
1498 | if (!cand2->can_copy_p) |
1499 | { |
1500 | cand2->visited_p = false; |
1501 | stack.truncate (size: watermark - 1); |
1502 | } |
1503 | else if (watermark == stack.length ()) |
1504 | { |
1505 | cand2->visited_p = false; |
1506 | if (check_candidate_uses (cand_index: cand2_index)) |
1507 | assign_value_number (cand_index: cand2_index); |
1508 | stack.pop (); |
1509 | } |
1510 | } |
1511 | } |
1512 | |
1513 | /* Ensure that the candidates always use the same candidate index |
1514 | to refer to an equivalence class. */ |
1515 | FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand1_index, cand1) |
1516 | if (cand1->can_copy_p && !empty_p (b: cand1->uses)) |
1517 | { |
1518 | canon_bitmap (ptr: &cand1->uses); |
1519 | gcc_checking_assert (bitmap_first_set_bit (cand1->uses) > cand1_index); |
1520 | } |
1521 | } |
1522 | |
1523 | /* Remove any candidates in CANDIDATES that would clobber a register in |
1524 | UNAVAIL_REGS. */ |
1525 | |
1526 | void |
1527 | early_remat::restrict_remat_for_unavail_regs (bitmap candidates, |
1528 | const_bitmap unavail_regs) |
1529 | { |
1530 | bitmap_clear (&m_tmp_bitmap); |
1531 | unsigned int cand_index; |
1532 | bitmap_iterator bi; |
1533 | EXECUTE_IF_SET_IN_BITMAP (candidates, 0, cand_index, bi) |
1534 | { |
1535 | remat_candidate *cand = &m_candidates[cand_index]; |
1536 | if (cand->clobbers |
1537 | && bitmap_intersect_p (cand->clobbers, unavail_regs)) |
1538 | bitmap_set_bit (&m_tmp_bitmap, cand_index); |
1539 | } |
1540 | bitmap_and_compl_into (candidates, &m_tmp_bitmap); |
1541 | } |
1542 | |
1543 | /* Remove any candidates in CANDIDATES that would clobber a register |
1544 | that is potentially live across CALL. */ |
1545 | |
1546 | void |
1547 | early_remat::restrict_remat_for_call (bitmap candidates, rtx_insn *call) |
1548 | { |
1549 | /* We don't know whether partially-clobbered registers are live |
1550 | across the call or not, so assume that they are. */ |
1551 | bitmap_view<HARD_REG_SET> call_preserved_regs |
1552 | (~insn_callee_abi (call).full_reg_clobbers ()); |
1553 | restrict_remat_for_unavail_regs (candidates, unavail_regs: call_preserved_regs); |
1554 | } |
1555 | |
1556 | /* Assuming that every path reaching a point P contains a copy of a |
1557 | use U of REGNO, return true if another copy of U at P would have |
1558 | access to the same value of REGNO. */ |
1559 | |
1560 | bool |
1561 | early_remat::stable_use_p (unsigned int regno) |
1562 | { |
1563 | /* Conservatively assume not for hard registers. */ |
1564 | if (HARD_REGISTER_NUM_P (regno)) |
1565 | return false; |
1566 | |
1567 | /* See if REGNO has a single definition and is never used uninitialized. |
1568 | In this case the definition of REGNO dominates the common dominator |
1569 | of the uses U, which in turn dominates P. */ |
1570 | if (DF_REG_DEF_COUNT (regno) == 1 |
1571 | && !bitmap_bit_p (DF_LR_OUT (ENTRY_BLOCK_PTR_FOR_FN (m_fn)), regno)) |
1572 | return true; |
1573 | |
1574 | return false; |
1575 | } |
1576 | |
1577 | /* Emit a copy from register DEST to register SRC before candidate |
1578 | CAND_INDEX's instruction. */ |
1579 | |
1580 | void |
1581 | early_remat::emit_copy_before (unsigned int cand_index, rtx dest, rtx src) |
1582 | { |
1583 | remat_candidate *cand = &m_candidates[cand_index]; |
1584 | if (dump_file) |
1585 | { |
1586 | fprintf (stream: dump_file, format: ";; Stabilizing insn " ); |
1587 | dump_insn_id (insn: cand->insn); |
1588 | fprintf (stream: dump_file, format: " by copying source reg %d:%s to temporary reg %d\n" , |
1589 | REGNO (src), GET_MODE_NAME (GET_MODE (src)), REGNO (dest)); |
1590 | } |
1591 | emit_insn_before (gen_move_insn (dest, src), cand->insn); |
1592 | } |
1593 | |
1594 | /* Check whether any inputs to candidate CAND_INDEX's instruction could |
1595 | change at rematerialization points and replace them with new pseudo |
1596 | registers if so. */ |
1597 | |
1598 | void |
1599 | early_remat::stabilize_pattern (unsigned int cand_index) |
1600 | { |
1601 | remat_candidate *cand = &m_candidates[cand_index]; |
1602 | if (cand->stabilized_p) |
1603 | return; |
1604 | |
1605 | remat_equiv_class *ec = cand->equiv_class; |
1606 | gcc_checking_assert (!ec || cand_index == ec->representative); |
1607 | |
1608 | /* Record the replacements we've made so far, so that we don't |
1609 | create two separate registers for match_dups. Lookup is O(n), |
1610 | but the n is very small. */ |
1611 | typedef std::pair<rtx, rtx> reg_pair; |
1612 | auto_vec<reg_pair, 16> reg_map; |
1613 | |
1614 | rtx_insn *insn = cand->insn; |
1615 | df_ref ref; |
1616 | FOR_EACH_INSN_USE (ref, insn) |
1617 | { |
1618 | unsigned int old_regno = DF_REF_REGNO (ref); |
1619 | rtx *loc = DF_REF_REAL_LOC (ref); |
1620 | |
1621 | if (HARD_REGISTER_NUM_P (old_regno) && fixed_regs[old_regno]) |
1622 | { |
1623 | /* We checked when adding the candidate that the value is stable. */ |
1624 | gcc_checking_assert (!rtx_unstable_p (*loc)); |
1625 | continue; |
1626 | } |
1627 | |
1628 | if (bitmap_bit_p (&m_candidate_regnos, old_regno)) |
1629 | /* We already know which candidate provides the definition |
1630 | and will handle it during copying. */ |
1631 | continue; |
1632 | |
1633 | if (stable_use_p (regno: old_regno)) |
1634 | /* We can continue to use the existing register. */ |
1635 | continue; |
1636 | |
1637 | /* We need to replace the register. See whether we've already |
1638 | created a suitable copy. */ |
1639 | rtx old_reg = *loc; |
1640 | rtx new_reg = NULL_RTX; |
1641 | machine_mode mode = GET_MODE (old_reg); |
1642 | reg_pair *p; |
1643 | unsigned int pi; |
1644 | FOR_EACH_VEC_ELT (reg_map, pi, p) |
1645 | if (REGNO (p->first) == old_regno |
1646 | && GET_MODE (p->first) == mode) |
1647 | { |
1648 | new_reg = p->second; |
1649 | break; |
1650 | } |
1651 | |
1652 | if (!new_reg) |
1653 | { |
1654 | /* Create a new register and initialize it just before |
1655 | the instruction. */ |
1656 | new_reg = gen_reg_rtx (mode); |
1657 | reg_map.safe_push (obj: reg_pair (old_reg, new_reg)); |
1658 | if (ec) |
1659 | { |
1660 | unsigned int member_index; |
1661 | bitmap_iterator bi; |
1662 | EXECUTE_IF_SET_IN_BITMAP (ec->members, 0, member_index, bi) |
1663 | emit_copy_before (cand_index: member_index, dest: new_reg, src: old_reg); |
1664 | } |
1665 | else |
1666 | emit_copy_before (cand_index, dest: new_reg, src: old_reg); |
1667 | } |
1668 | validate_change (insn, loc, new_reg, true); |
1669 | } |
1670 | if (num_changes_pending ()) |
1671 | { |
1672 | if (!apply_change_group ()) |
1673 | /* We checked when adding the candidates that the pattern allows |
1674 | hard registers to be replaced. Nothing else should make the |
1675 | changes invalid. */ |
1676 | gcc_unreachable (); |
1677 | |
1678 | if (ec) |
1679 | { |
1680 | /* Copy the new pattern to other members of the equivalence |
1681 | class. */ |
1682 | unsigned int member_index; |
1683 | bitmap_iterator bi; |
1684 | EXECUTE_IF_SET_IN_BITMAP (ec->members, 0, member_index, bi) |
1685 | if (cand_index != member_index) |
1686 | { |
1687 | rtx_insn *other_insn = m_candidates[member_index].insn; |
1688 | if (!validate_change (other_insn, &PATTERN (insn: other_insn), |
1689 | copy_insn (PATTERN (insn)), 0)) |
1690 | /* If the original instruction was valid then the copy |
1691 | should be too. */ |
1692 | gcc_unreachable (); |
1693 | } |
1694 | } |
1695 | } |
1696 | |
1697 | cand->stabilized_p = true; |
1698 | } |
1699 | |
1700 | /* Change CAND's instruction so that it sets CAND->copy_regno instead |
1701 | of CAND->regno. */ |
1702 | |
1703 | void |
1704 | early_remat::replace_dest_with_copy (unsigned int cand_index) |
1705 | { |
1706 | remat_candidate *cand = &m_candidates[cand_index]; |
1707 | df_ref def; |
1708 | FOR_EACH_INSN_DEF (def, cand->insn) |
1709 | if (DF_REF_REGNO (def) == cand->regno) |
1710 | validate_change (cand->insn, DF_REF_REAL_LOC (def), |
1711 | regno_reg_rtx[cand->copy_regno], 1); |
1712 | } |
1713 | |
1714 | /* Make sure that the candidates used by candidate CAND_INDEX are available. |
1715 | There are two ways of doing this for an input candidate I: |
1716 | |
1717 | (1) Using the existing register number and ensuring that I is available. |
1718 | |
1719 | (2) Using a new register number (recorded in copy_regno) and adding I |
1720 | to VIA_COPY. This guarantees that making I available does not |
1721 | conflict with other uses of the original register. |
1722 | |
1723 | REQUIRED is the set of candidates that are required but not available |
1724 | before the copy of CAND_INDEX. AVAILABLE is the set of candidates |
1725 | that are already available before the copy of CAND_INDEX. REACHING |
1726 | is the set of candidates that reach the copy of CAND_INDEX. VIA_COPY |
1727 | is the set of candidates that will use new register numbers recorded |
1728 | in copy_regno instead of the original ones. */ |
1729 | |
1730 | void |
1731 | early_remat::stabilize_candidate_uses (unsigned int cand_index, |
1732 | bitmap required, bitmap available, |
1733 | bitmap reaching, bitmap via_copy) |
1734 | { |
1735 | remat_candidate *cand = &m_candidates[cand_index]; |
1736 | df_ref use; |
1737 | FOR_EACH_INSN_USE (use, cand->insn) |
1738 | { |
1739 | unsigned int regno = DF_REF_REGNO (use); |
1740 | if (!bitmap_bit_p (&m_candidate_regnos, regno)) |
1741 | continue; |
1742 | |
1743 | /* Work out which candidate provides the definition. */ |
1744 | bitmap defs = m_regno_to_candidates[regno]; |
1745 | bitmap_and (&m_tmp_bitmap, cand->uses, defs); |
1746 | gcc_checking_assert (bitmap_single_bit_set_p (&m_tmp_bitmap)); |
1747 | unsigned int def_index = bitmap_first_set_bit (&m_tmp_bitmap); |
1748 | |
1749 | /* First see if DEF_INDEX is the only reaching definition of REGNO |
1750 | at this point too and if it is or will become available. We can |
1751 | continue to use REGNO if so. */ |
1752 | bitmap_and (&m_tmp_bitmap, reaching, defs); |
1753 | if (bitmap_single_bit_set_p (&m_tmp_bitmap) |
1754 | && bitmap_first_set_bit (&m_tmp_bitmap) == def_index |
1755 | && ((available && bitmap_bit_p (available, def_index)) |
1756 | || bitmap_bit_p (required, def_index))) |
1757 | { |
1758 | if (dump_file) |
1759 | fprintf (stream: dump_file, format: ";; Keeping reg %d for use of candidate %d" |
1760 | " in candidate %d\n" , regno, def_index, cand_index); |
1761 | continue; |
1762 | } |
1763 | |
1764 | /* Otherwise fall back to using a copy. There are other cases |
1765 | in which we *could* continue to use REGNO, but there's not |
1766 | really much point. Using a separate register ought to make |
1767 | things easier for the register allocator. */ |
1768 | remat_candidate *def_cand = &m_candidates[def_index]; |
1769 | rtx *loc = DF_REF_REAL_LOC (use); |
1770 | rtx new_reg; |
1771 | if (bitmap_set_bit (via_copy, def_index)) |
1772 | { |
1773 | new_reg = gen_reg_rtx (GET_MODE (*loc)); |
1774 | def_cand->copy_regno = REGNO (new_reg); |
1775 | if (dump_file) |
1776 | fprintf (stream: dump_file, format: ";; Creating reg %d for use of candidate %d" |
1777 | " in candidate %d\n" , REGNO (new_reg), def_index, |
1778 | cand_index); |
1779 | } |
1780 | else |
1781 | new_reg = regno_reg_rtx[def_cand->copy_regno]; |
1782 | validate_change (cand->insn, loc, new_reg, 1); |
1783 | } |
1784 | } |
1785 | |
1786 | /* Rematerialize the candidates in REQUIRED after instruction INSN, |
1787 | given that the candidates in AVAILABLE are already available |
1788 | and that REACHING is the set of candidates live after INSN. |
1789 | REQUIRED and AVAILABLE are disjoint on entry. |
1790 | |
1791 | Clear REQUIRED on exit. */ |
1792 | |
1793 | void |
1794 | early_remat::emit_remat_insns (bitmap required, bitmap available, |
1795 | bitmap reaching, rtx_insn *insn) |
1796 | { |
1797 | /* Quick exit if there's nothing to do. */ |
1798 | if (empty_p (b: required)) |
1799 | return; |
1800 | |
1801 | /* Only reaching definitions should be available or required. */ |
1802 | gcc_checking_assert (!bitmap_intersect_compl_p (required, reaching)); |
1803 | if (available) |
1804 | gcc_checking_assert (!bitmap_intersect_compl_p (available, reaching)); |
1805 | |
1806 | bitmap_head via_copy; |
1807 | bitmap_initialize (head: &via_copy, obstack: &m_obstack); |
1808 | while (!bitmap_empty_p (map: required) || !bitmap_empty_p (map: &via_copy)) |
1809 | { |
1810 | /* Pick the lowest-indexed candidate left. */ |
1811 | unsigned int required_index = (bitmap_empty_p (map: required) |
1812 | ? ~0U : bitmap_first_set_bit (required)); |
1813 | unsigned int via_copy_index = (bitmap_empty_p (map: &via_copy) |
1814 | ? ~0U : bitmap_first_set_bit (&via_copy)); |
1815 | unsigned int cand_index = MIN (required_index, via_copy_index); |
1816 | remat_candidate *cand = &m_candidates[cand_index]; |
1817 | |
1818 | bool via_copy_p = (cand_index == via_copy_index); |
1819 | if (via_copy_p) |
1820 | bitmap_clear_bit (&via_copy, cand_index); |
1821 | else |
1822 | { |
1823 | /* Remove all candidates for the same register from REQUIRED. */ |
1824 | bitmap_and (&m_tmp_bitmap, reaching, |
1825 | m_regno_to_candidates[cand->regno]); |
1826 | bitmap_and_compl_into (required, &m_tmp_bitmap); |
1827 | gcc_checking_assert (!bitmap_bit_p (required, cand_index)); |
1828 | |
1829 | /* Only rematerialize if we have a single reaching definition |
1830 | of the register. */ |
1831 | if (!bitmap_single_bit_set_p (&m_tmp_bitmap)) |
1832 | { |
1833 | if (dump_file) |
1834 | { |
1835 | fprintf (stream: dump_file, format: ";; Can't rematerialize reg %d after " , |
1836 | cand->regno); |
1837 | dump_insn_id (insn); |
1838 | fprintf (stream: dump_file, format: ": more than one reaching definition\n" ); |
1839 | } |
1840 | continue; |
1841 | } |
1842 | |
1843 | /* Skip candidates that can't be rematerialized. */ |
1844 | if (!cand->can_copy_p) |
1845 | continue; |
1846 | |
1847 | /* Check the function precondition. */ |
1848 | gcc_checking_assert (!available |
1849 | || !bitmap_bit_p (available, cand_index)); |
1850 | } |
1851 | |
1852 | /* Invalid candidates should have been weeded out by now. */ |
1853 | gcc_assert (cand->can_copy_p); |
1854 | |
1855 | rtx new_pattern; |
1856 | if (cand->constant_p) |
1857 | { |
1858 | /* Emit a simple move. */ |
1859 | unsigned int regno = via_copy_p ? cand->copy_regno : cand->regno; |
1860 | new_pattern = gen_move_insn (regno_reg_rtx[regno], cand->remat_rtx); |
1861 | } |
1862 | else |
1863 | { |
1864 | /* If this is the first time we've copied the instruction, make |
1865 | sure that any inputs will have the same value after INSN. */ |
1866 | stabilize_pattern (cand_index); |
1867 | |
1868 | /* Temporarily adjust the original instruction so that it has |
1869 | the right form for the copy. */ |
1870 | if (via_copy_p) |
1871 | replace_dest_with_copy (cand_index); |
1872 | if (cand->uses) |
1873 | stabilize_candidate_uses (cand_index, required, available, |
1874 | reaching, via_copy: &via_copy); |
1875 | |
1876 | /* Get the new instruction pattern. */ |
1877 | new_pattern = copy_insn (cand->remat_rtx); |
1878 | |
1879 | /* Undo the temporary changes. */ |
1880 | cancel_changes (0); |
1881 | } |
1882 | |
1883 | /* Emit the new instruction. */ |
1884 | rtx_insn *new_insn = emit_insn_after (new_pattern, insn); |
1885 | |
1886 | if (dump_file) |
1887 | { |
1888 | fprintf (stream: dump_file, format: ";; Rematerializing candidate %d after " , |
1889 | cand_index); |
1890 | dump_insn_id (insn); |
1891 | if (via_copy_p) |
1892 | fprintf (stream: dump_file, format: " with new destination reg %d" , |
1893 | cand->copy_regno); |
1894 | fprintf (stream: dump_file, format: ":\n\n" ); |
1895 | print_rtl_single (dump_file, new_insn); |
1896 | fprintf (stream: dump_file, format: "\n" ); |
1897 | } |
1898 | } |
1899 | } |
1900 | |
1901 | /* Recompute INFO's available_out set, given that it's distinct from |
1902 | available_in and available_locally. */ |
1903 | |
1904 | bool |
1905 | early_remat::set_available_out (remat_block_info *info) |
1906 | { |
1907 | if (empty_p (b: info->available_locally)) |
1908 | return bitmap_and_compl (get_bitmap (ptr: &info->available_out), |
1909 | info->available_in, info->rd_kill); |
1910 | |
1911 | if (empty_p (b: info->rd_kill)) |
1912 | return bitmap_ior (get_bitmap (ptr: &info->available_out), |
1913 | info->available_locally, info->available_in); |
1914 | |
1915 | return bitmap_ior_and_compl (DST: get_bitmap (ptr: &info->available_out), |
1916 | A: info->available_locally, B: info->available_in, |
1917 | C: info->rd_kill); |
1918 | } |
1919 | |
1920 | /* If BB has more than one call, decide which candidates should be |
1921 | rematerialized after the non-final calls and emit the associated |
1922 | instructions. Record other information about the block in preparation |
1923 | for the global phase. */ |
1924 | |
1925 | void |
1926 | early_remat::process_block (basic_block bb) |
1927 | { |
1928 | remat_block_info *info = &m_block_info[bb->index]; |
1929 | rtx_insn *last_call = NULL; |
1930 | rtx_insn *insn; |
1931 | |
1932 | /* Ensure that we always use the same candidate index to refer to an |
1933 | equivalence class. */ |
1934 | if (info->rd_out == info->rd_in) |
1935 | { |
1936 | canon_bitmap (ptr: &info->rd_in); |
1937 | info->rd_out = info->rd_in; |
1938 | } |
1939 | else |
1940 | { |
1941 | canon_bitmap (ptr: &info->rd_in); |
1942 | canon_bitmap (ptr: &info->rd_out); |
1943 | } |
1944 | canon_bitmap (ptr: &info->rd_kill); |
1945 | canon_bitmap (ptr: &info->rd_gen); |
1946 | |
1947 | /* The set of candidates that should be rematerialized on entry to the |
1948 | block or after the previous call (whichever is more recent). */ |
1949 | init_temp_bitmap (ptr: &m_required); |
1950 | |
1951 | /* The set of candidates that reach the current instruction (i.e. are |
1952 | live just before the instruction). */ |
1953 | bitmap_head reaching; |
1954 | bitmap_initialize (head: &reaching, obstack: &m_obstack); |
1955 | if (info->rd_in) |
1956 | bitmap_copy (&reaching, info->rd_in); |
1957 | |
1958 | /* The set of candidates that are live and available without |
1959 | rematerialization just before the current instruction. This only |
1960 | accounts for earlier candidates in the block, or those that become |
1961 | available by being added to M_REQUIRED. */ |
1962 | init_temp_bitmap (ptr: &m_available); |
1963 | |
1964 | /* Get the range of candidates in the block. */ |
1965 | unsigned int next_candidate = info->first_candidate; |
1966 | unsigned int num_candidates = info->num_candidates; |
1967 | remat_candidate *next_def = (num_candidates > 0 |
1968 | ? &m_candidates[next_candidate] |
1969 | : NULL); |
1970 | |
1971 | FOR_BB_INSNS (bb, insn) |
1972 | { |
1973 | if (!NONDEBUG_INSN_P (insn)) |
1974 | continue; |
1975 | |
1976 | /* First process uses, since this is a forward walk. */ |
1977 | df_ref ref; |
1978 | FOR_EACH_INSN_USE (ref, insn) |
1979 | { |
1980 | unsigned int regno = DF_REF_REGNO (ref); |
1981 | if (bitmap_bit_p (&m_candidate_regnos, regno)) |
1982 | { |
1983 | bitmap defs = m_regno_to_candidates[regno]; |
1984 | bitmap_and (&m_tmp_bitmap, defs, &reaching); |
1985 | gcc_checking_assert (!bitmap_empty_p (&m_tmp_bitmap)); |
1986 | if (!bitmap_intersect_p (defs, m_available)) |
1987 | { |
1988 | /* There has been no definition of the register since |
1989 | the last call or the start of the block (whichever |
1990 | is most recent). Mark the reaching definitions |
1991 | as required at that point and thus available here. */ |
1992 | bitmap_ior_into (m_required, &m_tmp_bitmap); |
1993 | bitmap_ior_into (m_available, &m_tmp_bitmap); |
1994 | } |
1995 | } |
1996 | } |
1997 | |
1998 | if (CALL_P (insn)) |
1999 | { |
2000 | if (!last_call) |
2001 | { |
2002 | /* The first call in the block. Record which candidates are |
2003 | required at the start of the block. */ |
2004 | copy_temp_bitmap (dest: &info->required_in, src: &m_required); |
2005 | init_temp_bitmap (ptr: &m_required); |
2006 | } |
2007 | else |
2008 | { |
2009 | /* The fully-local case: candidates that need to be |
2010 | rematerialized after a previous call in the block. */ |
2011 | restrict_remat_for_call (candidates: m_required, call: last_call); |
2012 | emit_remat_insns (required: m_required, NULL, reaching: info->rd_after_call, |
2013 | insn: last_call); |
2014 | } |
2015 | last_call = insn; |
2016 | bitmap_clear (m_available); |
2017 | gcc_checking_assert (empty_p (m_required)); |
2018 | } |
2019 | |
2020 | /* Now process definitions. */ |
2021 | while (next_def && insn == next_def->insn) |
2022 | { |
2023 | unsigned int gen = canon_candidate (cand_index: next_candidate); |
2024 | |
2025 | /* Other candidates with the same regno are not available |
2026 | any more. */ |
2027 | bitmap kill = m_regno_to_candidates[next_def->regno]; |
2028 | bitmap_and_compl_into (m_available, kill); |
2029 | bitmap_and_compl_into (&reaching, kill); |
2030 | |
2031 | /* Record that this candidate is available without |
2032 | rematerialization. */ |
2033 | bitmap_set_bit (m_available, gen); |
2034 | bitmap_set_bit (&reaching, gen); |
2035 | |
2036 | /* Find the next candidate in the block. */ |
2037 | num_candidates -= 1; |
2038 | next_candidate -= 1; |
2039 | if (num_candidates > 0) |
2040 | next_def -= 1; |
2041 | else |
2042 | next_def = NULL; |
2043 | } |
2044 | |
2045 | if (insn == last_call) |
2046 | bitmap_copy (get_bitmap (ptr: &info->rd_after_call), &reaching); |
2047 | } |
2048 | bitmap_clear (&reaching); |
2049 | gcc_checking_assert (num_candidates == 0); |
2050 | |
2051 | /* Remove values from the available set if they aren't live (and so |
2052 | aren't interesting to successor blocks). */ |
2053 | if (info->rd_out) |
2054 | bitmap_and_into (m_available, info->rd_out); |
2055 | |
2056 | /* Record the accumulated information. */ |
2057 | info->last_call = last_call; |
2058 | info->abnormal_call_p = (last_call |
2059 | && last_call == BB_END (bb) |
2060 | && has_abnormal_or_eh_outgoing_edge_p (bb)); |
2061 | copy_temp_bitmap (dest: &info->available_locally, src: &m_available); |
2062 | if (last_call) |
2063 | copy_temp_bitmap (dest: &info->required_after_call, src: &m_required); |
2064 | else |
2065 | copy_temp_bitmap (dest: &info->required_in, src: &m_required); |
2066 | |
2067 | /* Assume at first that all live-in values are available without |
2068 | rematerialization (i.e. start with the most optimistic assumption). */ |
2069 | if (info->available_in) |
2070 | { |
2071 | if (info->rd_in) |
2072 | bitmap_copy (info->available_in, info->rd_in); |
2073 | else |
2074 | BITMAP_FREE (info->available_in); |
2075 | } |
2076 | |
2077 | if (last_call || empty_p (b: info->available_in)) |
2078 | /* The values available on exit from the block are exactly those that |
2079 | are available locally. This set doesn't change. */ |
2080 | info->available_out = info->available_locally; |
2081 | else if (empty_p (b: info->available_locally) && empty_p (b: info->rd_kill)) |
2082 | /* The values available on exit are the same as those available on entry. |
2083 | Updating one updates the other. */ |
2084 | info->available_out = info->available_in; |
2085 | else |
2086 | set_available_out (info); |
2087 | } |
2088 | |
2089 | /* Process each block as for process_block, visiting dominators before |
2090 | the blocks they dominate. */ |
2091 | |
2092 | void |
2093 | early_remat::local_phase (void) |
2094 | { |
2095 | if (dump_file) |
2096 | fprintf (stream: dump_file, format: "\n;; Local phase:\n" ); |
2097 | |
2098 | int *rpo = df_get_postorder (DF_FORWARD); |
2099 | unsigned int rpo_len = df_get_n_blocks (DF_FORWARD); |
2100 | for (unsigned int i = 0; i < rpo_len; ++i) |
2101 | if (rpo[i] >= NUM_FIXED_BLOCKS) |
2102 | process_block (BASIC_BLOCK_FOR_FN (m_fn, rpo[i])); |
2103 | } |
2104 | |
2105 | /* Return true if available values survive across edge E. */ |
2106 | |
2107 | static inline bool |
2108 | available_across_edge_p (edge e) |
2109 | { |
2110 | return (e->flags & EDGE_EH) == 0; |
2111 | } |
2112 | |
2113 | /* Propagate information from the available_out set of E->src to the |
2114 | available_in set of E->dest, when computing global availability. |
2115 | Return true if something changed. */ |
2116 | |
2117 | bool |
2118 | early_remat::avail_confluence_n (edge e) |
2119 | { |
2120 | remat_block_info *src = &er->m_block_info[e->src->index]; |
2121 | remat_block_info *dest = &er->m_block_info[e->dest->index]; |
2122 | |
2123 | if (!available_across_edge_p (e)) |
2124 | return false; |
2125 | |
2126 | if (empty_p (b: dest->available_in)) |
2127 | return false; |
2128 | |
2129 | if (!src->available_out) |
2130 | { |
2131 | bitmap_clear (dest->available_in); |
2132 | return true; |
2133 | } |
2134 | |
2135 | return bitmap_and_into (dest->available_in, src->available_out); |
2136 | } |
2137 | |
2138 | /* Propagate information from the available_in set of block BB_INDEX |
2139 | to available_out. Return true if something changed. */ |
2140 | |
2141 | bool |
2142 | early_remat::avail_transfer (int bb_index) |
2143 | { |
2144 | remat_block_info *info = &er->m_block_info[bb_index]; |
2145 | |
2146 | if (info->available_out == info->available_locally) |
2147 | return false; |
2148 | |
2149 | if (info->available_out == info->available_in) |
2150 | /* Assume that we are only called if the input changed. */ |
2151 | return true; |
2152 | |
2153 | return er->set_available_out (info); |
2154 | } |
2155 | |
2156 | /* Compute global availability for the function, starting with the local |
2157 | information computed by local_phase. */ |
2158 | |
2159 | void |
2160 | early_remat::compute_availability (void) |
2161 | { |
2162 | /* We use df_simple_dataflow instead of the lcm routines for three reasons: |
2163 | |
2164 | (1) it avoids recomputing the traversal order; |
2165 | (2) many of the sets are likely to be sparse, so we don't necessarily |
2166 | want to use sbitmaps; and |
2167 | (3) it means we can avoid creating an explicit kill set for the call. */ |
2168 | er = this; |
2169 | bitmap_clear (&m_tmp_bitmap); |
2170 | bitmap_set_range (&m_tmp_bitmap, 0, last_basic_block_for_fn (m_fn)); |
2171 | df_simple_dataflow (DF_FORWARD, NULL, NULL, |
2172 | avail_confluence_n, avail_transfer, |
2173 | &m_tmp_bitmap, df_get_postorder (DF_FORWARD), |
2174 | df_get_n_blocks (DF_FORWARD)); |
2175 | er = 0; |
2176 | |
2177 | /* Restrict the required_in sets to values that aren't available. */ |
2178 | basic_block bb; |
2179 | FOR_EACH_BB_FN (bb, m_fn) |
2180 | { |
2181 | remat_block_info *info = &m_block_info[bb->index]; |
2182 | if (info->required_in && info->available_in) |
2183 | bitmap_and_compl_into (info->required_in, info->available_in); |
2184 | } |
2185 | } |
2186 | |
2187 | /* Make sure that INFO's available_out and available_in sets are unique. */ |
2188 | |
2189 | inline void |
2190 | early_remat::unshare_available_sets (remat_block_info *info) |
2191 | { |
2192 | if (info->available_in && info->available_in == info->available_out) |
2193 | { |
2194 | info->available_in = alloc_bitmap (); |
2195 | bitmap_copy (info->available_in, info->available_out); |
2196 | } |
2197 | } |
2198 | |
2199 | /* Return true if it is possible to move rematerializations from the |
2200 | destination of E to the source of E. */ |
2201 | |
2202 | inline bool |
2203 | early_remat::can_move_across_edge_p (edge e) |
2204 | { |
2205 | return (available_across_edge_p (e) |
2206 | && !m_block_info[e->src->index].abnormal_call_p); |
2207 | } |
2208 | |
2209 | /* Return true if it is cheaper to rematerialize values at the head of |
2210 | block QUERY_BB_INDEX instead of rematerializing in its predecessors. */ |
2211 | |
2212 | bool |
2213 | early_remat::local_remat_cheaper_p (unsigned int query_bb_index) |
2214 | { |
2215 | if (m_block_info[query_bb_index].remat_frequency_valid_p) |
2216 | return m_block_info[query_bb_index].local_remat_cheaper_p; |
2217 | |
2218 | /* Iteratively compute the cost of rematerializing values in the |
2219 | predecessor blocks, then compare that with the cost of |
2220 | rematerializing at the head of the block. |
2221 | |
2222 | A cycle indicates that there is no call on that execution path, |
2223 | so it isn't necessary to rematerialize on that path. */ |
2224 | auto_vec<basic_block, 16> stack; |
2225 | stack.quick_push (BASIC_BLOCK_FOR_FN (m_fn, query_bb_index)); |
2226 | while (!stack.is_empty ()) |
2227 | { |
2228 | basic_block bb = stack.last (); |
2229 | remat_block_info *info = &m_block_info[bb->index]; |
2230 | if (info->remat_frequency_valid_p) |
2231 | { |
2232 | stack.pop (); |
2233 | continue; |
2234 | } |
2235 | |
2236 | info->visited_p = true; |
2237 | int frequency = 0; |
2238 | bool can_move_p = true; |
2239 | edge e; |
2240 | edge_iterator ei; |
2241 | FOR_EACH_EDGE (e, ei, bb->preds) |
2242 | if (!can_move_across_edge_p (e)) |
2243 | { |
2244 | can_move_p = false; |
2245 | break; |
2246 | } |
2247 | else if (m_block_info[e->src->index].last_call) |
2248 | /* We'll rematerialize after the call. */ |
2249 | frequency += e->src->count.to_frequency (fun: m_fn); |
2250 | else if (m_block_info[e->src->index].remat_frequency_valid_p) |
2251 | /* Add the cost of rematerializing at the head of E->src |
2252 | or in its predecessors (whichever is cheaper). */ |
2253 | frequency += m_block_info[e->src->index].remat_frequency; |
2254 | else if (!m_block_info[e->src->index].visited_p) |
2255 | /* Queue E->src and then revisit this block again. */ |
2256 | stack.safe_push (obj: e->src); |
2257 | |
2258 | /* Come back to this block later if we need to process some of |
2259 | its predecessors. */ |
2260 | if (stack.last () != bb) |
2261 | continue; |
2262 | |
2263 | /* If rematerializing in and before the block have equal cost, prefer |
2264 | rematerializing in the block. This should shorten the live range. */ |
2265 | int bb_frequency = bb->count.to_frequency (fun: m_fn); |
2266 | if (!can_move_p || frequency >= bb_frequency) |
2267 | { |
2268 | info->local_remat_cheaper_p = true; |
2269 | info->remat_frequency = bb_frequency; |
2270 | } |
2271 | else |
2272 | info->remat_frequency = frequency; |
2273 | info->remat_frequency_valid_p = true; |
2274 | info->visited_p = false; |
2275 | if (dump_file) |
2276 | { |
2277 | if (!can_move_p) |
2278 | fprintf (stream: dump_file, format: ";; Need to rematerialize at the head of" |
2279 | " block %d; cannot move to predecessors.\n" , bb->index); |
2280 | else |
2281 | { |
2282 | fprintf (stream: dump_file, format: ";; Block %d has frequency %d," |
2283 | " rematerializing in predecessors has frequency %d" , |
2284 | bb->index, bb_frequency, frequency); |
2285 | if (info->local_remat_cheaper_p) |
2286 | fprintf (stream: dump_file, format: "; prefer to rematerialize" |
2287 | " in the block\n" ); |
2288 | else |
2289 | fprintf (stream: dump_file, format: "; prefer to rematerialize" |
2290 | " in predecessors\n" ); |
2291 | } |
2292 | } |
2293 | stack.pop (); |
2294 | } |
2295 | return m_block_info[query_bb_index].local_remat_cheaper_p; |
2296 | } |
2297 | |
2298 | /* Return true if we cannot rematerialize candidate CAND_INDEX at the head of |
2299 | block BB_INDEX. */ |
2300 | |
2301 | bool |
2302 | early_remat::need_to_move_candidate_p (unsigned int bb_index, |
2303 | unsigned int cand_index) |
2304 | { |
2305 | remat_block_info *info = &m_block_info[bb_index]; |
2306 | remat_candidate *cand = &m_candidates[cand_index]; |
2307 | basic_block bb = BASIC_BLOCK_FOR_FN (m_fn, bb_index); |
2308 | |
2309 | /* If there is more than one reaching definition of REGNO, |
2310 | we'll need to rematerialize in predecessors instead. */ |
2311 | bitmap_and (&m_tmp_bitmap, info->rd_in, m_regno_to_candidates[cand->regno]); |
2312 | if (!bitmap_single_bit_set_p (&m_tmp_bitmap)) |
2313 | { |
2314 | if (dump_file) |
2315 | fprintf (stream: dump_file, format: ";; Cannot rematerialize %d at the" |
2316 | " head of block %d because there is more than one" |
2317 | " reaching definition of reg %d\n" , cand_index, |
2318 | bb_index, cand->regno); |
2319 | return true; |
2320 | } |
2321 | |
2322 | /* Likewise if rematerializing CAND here would clobber a live register. */ |
2323 | if (cand->clobbers |
2324 | && bitmap_intersect_p (cand->clobbers, DF_LR_IN (bb))) |
2325 | { |
2326 | if (dump_file) |
2327 | fprintf (stream: dump_file, format: ";; Cannot rematerialize %d at the" |
2328 | " head of block %d because it would clobber live" |
2329 | " registers\n" , cand_index, bb_index); |
2330 | return true; |
2331 | } |
2332 | |
2333 | return false; |
2334 | } |
2335 | |
2336 | /* Set REQUIRED to the minimum set of candidates that must be rematerialized |
2337 | in predecessors of block BB_INDEX instead of at the start of the block. */ |
2338 | |
2339 | void |
2340 | early_remat::compute_minimum_move_set (unsigned int bb_index, |
2341 | bitmap required) |
2342 | { |
2343 | remat_block_info *info = &m_block_info[bb_index]; |
2344 | bitmap_head remaining; |
2345 | |
2346 | bitmap_clear (required); |
2347 | bitmap_initialize (head: &remaining, obstack: &m_obstack); |
2348 | bitmap_copy (&remaining, info->required_in); |
2349 | while (!bitmap_empty_p (map: &remaining)) |
2350 | { |
2351 | unsigned int cand_index = bitmap_first_set_bit (&remaining); |
2352 | remat_candidate *cand = &m_candidates[cand_index]; |
2353 | bitmap_clear_bit (&remaining, cand_index); |
2354 | |
2355 | /* Leave invalid candidates where they are. */ |
2356 | if (!cand->can_copy_p) |
2357 | continue; |
2358 | |
2359 | /* Decide whether to move this candidate. */ |
2360 | if (!bitmap_bit_p (required, cand_index)) |
2361 | { |
2362 | if (!need_to_move_candidate_p (bb_index, cand_index)) |
2363 | continue; |
2364 | bitmap_set_bit (required, cand_index); |
2365 | } |
2366 | |
2367 | /* Also move values used by the candidate, so that we don't |
2368 | rematerialize them twice. */ |
2369 | if (cand->uses) |
2370 | { |
2371 | bitmap_ior_and_into (DST: required, B: cand->uses, C: info->required_in); |
2372 | bitmap_ior_and_into (DST: &remaining, B: cand->uses, C: info->required_in); |
2373 | } |
2374 | } |
2375 | } |
2376 | |
2377 | /* Make the predecessors of BB_INDEX rematerialize the candidates in |
2378 | REQUIRED. Add any blocks whose required_in set changes to |
2379 | PENDING_BLOCKS. */ |
2380 | |
2381 | void |
2382 | early_remat::move_to_predecessors (unsigned int bb_index, bitmap required, |
2383 | bitmap pending_blocks) |
2384 | { |
2385 | if (empty_p (b: required)) |
2386 | return; |
2387 | remat_block_info *dest_info = &m_block_info[bb_index]; |
2388 | basic_block bb = BASIC_BLOCK_FOR_FN (m_fn, bb_index); |
2389 | edge e; |
2390 | edge_iterator ei; |
2391 | FOR_EACH_EDGE (e, ei, bb->preds) |
2392 | { |
2393 | remat_block_info *src_info = &m_block_info[e->src->index]; |
2394 | |
2395 | /* Restrict the set we add to the reaching definitions. */ |
2396 | bitmap_and (&m_tmp_bitmap, required, src_info->rd_out); |
2397 | if (bitmap_empty_p (map: &m_tmp_bitmap)) |
2398 | continue; |
2399 | |
2400 | if (!can_move_across_edge_p (e)) |
2401 | { |
2402 | /* We can't move the rematerialization and we can't do it at |
2403 | the start of the block either. In this case we just give up |
2404 | and rely on spilling to make the values available across E. */ |
2405 | if (dump_file) |
2406 | { |
2407 | fprintf (stream: dump_file, format: ";; Cannot rematerialize the following" |
2408 | " candidates in block %d:" , e->src->index); |
2409 | dump_candidate_bitmap (candidates: required); |
2410 | fprintf (stream: dump_file, format: "\n" ); |
2411 | } |
2412 | continue; |
2413 | } |
2414 | |
2415 | /* Remove candidates that are already available. */ |
2416 | if (src_info->available_out) |
2417 | { |
2418 | bitmap_and_compl_into (&m_tmp_bitmap, src_info->available_out); |
2419 | if (bitmap_empty_p (map: &m_tmp_bitmap)) |
2420 | continue; |
2421 | } |
2422 | |
2423 | /* Add the remaining candidates to the appropriate required set. */ |
2424 | if (dump_file) |
2425 | { |
2426 | fprintf (stream: dump_file, format: ";; Moving this set from block %d" |
2427 | " to block %d:" , bb_index, e->src->index); |
2428 | dump_candidate_bitmap (candidates: &m_tmp_bitmap); |
2429 | fprintf (stream: dump_file, format: "\n" ); |
2430 | } |
2431 | /* If the source block contains a call, we want to rematerialize |
2432 | after the call, otherwise we want to rematerialize at the start |
2433 | of the block. */ |
2434 | bitmap src_required = get_bitmap (ptr: src_info->last_call |
2435 | ? &src_info->required_after_call |
2436 | : &src_info->required_in); |
2437 | if (bitmap_ior_into (src_required, &m_tmp_bitmap)) |
2438 | { |
2439 | if (!src_info->last_call) |
2440 | bitmap_set_bit (pending_blocks, e->src->index); |
2441 | unshare_available_sets (info: src_info); |
2442 | bitmap_ior_into (get_bitmap (ptr: &src_info->available_out), |
2443 | &m_tmp_bitmap); |
2444 | } |
2445 | } |
2446 | |
2447 | /* The candidates are now available on entry to the block. */ |
2448 | bitmap_and_compl_into (dest_info->required_in, required); |
2449 | unshare_available_sets (info: dest_info); |
2450 | bitmap_ior_into (get_bitmap (ptr: &dest_info->available_in), required); |
2451 | } |
2452 | |
2453 | /* Go through the candidates that are currently marked as being |
2454 | rematerialized at the beginning of a block. Decide in each case |
2455 | whether that's valid and profitable; if it isn't, move the |
2456 | rematerialization to predecessor blocks instead. */ |
2457 | |
2458 | void |
2459 | early_remat::choose_rematerialization_points (void) |
2460 | { |
2461 | bitmap_head required; |
2462 | bitmap_head pending_blocks; |
2463 | |
2464 | int *postorder = df_get_postorder (DF_BACKWARD); |
2465 | unsigned int postorder_len = df_get_n_blocks (DF_BACKWARD); |
2466 | bitmap_initialize (head: &required, obstack: &m_obstack); |
2467 | bitmap_initialize (head: &pending_blocks, obstack: &m_obstack); |
2468 | do |
2469 | /* Process the blocks in postorder, to reduce the number of iterations |
2470 | of the outer loop. */ |
2471 | for (unsigned int i = 0; i < postorder_len; ++i) |
2472 | { |
2473 | unsigned int bb_index = postorder[i]; |
2474 | remat_block_info *info = &m_block_info[bb_index]; |
2475 | bitmap_clear_bit (&pending_blocks, bb_index); |
2476 | |
2477 | if (empty_p (b: info->required_in)) |
2478 | continue; |
2479 | |
2480 | if (info->available_in) |
2481 | gcc_checking_assert (!bitmap_intersect_p (info->required_in, |
2482 | info->available_in)); |
2483 | |
2484 | if (local_remat_cheaper_p (query_bb_index: bb_index)) |
2485 | { |
2486 | /* We'd prefer to rematerialize at the head of the block. |
2487 | Only move candidates if we need to. */ |
2488 | compute_minimum_move_set (bb_index, required: &required); |
2489 | move_to_predecessors (bb_index, required: &required, pending_blocks: &pending_blocks); |
2490 | } |
2491 | else |
2492 | move_to_predecessors (bb_index, required: info->required_in, |
2493 | pending_blocks: &pending_blocks); |
2494 | } |
2495 | while (!bitmap_empty_p (map: &pending_blocks)); |
2496 | bitmap_clear (&required); |
2497 | } |
2498 | |
2499 | /* Emit all rematerialization instructions queued for BB. */ |
2500 | |
2501 | void |
2502 | early_remat::emit_remat_insns_for_block (basic_block bb) |
2503 | { |
2504 | remat_block_info *info = &m_block_info[bb->index]; |
2505 | |
2506 | if (info->last_call && !empty_p (b: info->required_after_call)) |
2507 | { |
2508 | restrict_remat_for_call (candidates: info->required_after_call, call: info->last_call); |
2509 | emit_remat_insns (required: info->required_after_call, NULL, |
2510 | reaching: info->rd_after_call, insn: info->last_call); |
2511 | } |
2512 | |
2513 | if (!empty_p (b: info->required_in)) |
2514 | { |
2515 | rtx_insn *insn = BB_HEAD (bb); |
2516 | while (insn != BB_END (bb) |
2517 | && !INSN_P (NEXT_INSN (insn))) |
2518 | insn = NEXT_INSN (insn); |
2519 | restrict_remat_for_unavail_regs (candidates: info->required_in, DF_LR_IN (bb)); |
2520 | emit_remat_insns (required: info->required_in, available: info->available_in, |
2521 | reaching: info->rd_in, insn); |
2522 | } |
2523 | } |
2524 | |
2525 | /* Decide which candidates in each block's REQUIRED_IN set need to be |
2526 | rematerialized and decide where the rematerialization instructions |
2527 | should go. Emit queued rematerialization instructions at the start |
2528 | of blocks and after the last calls in blocks. */ |
2529 | |
2530 | void |
2531 | early_remat::global_phase (void) |
2532 | { |
2533 | compute_availability (); |
2534 | if (dump_file) |
2535 | { |
2536 | fprintf (stream: dump_file, format: "\n;; Blocks after computing global" |
2537 | " availability:\n" ); |
2538 | dump_all_blocks (); |
2539 | } |
2540 | |
2541 | choose_rematerialization_points (); |
2542 | if (dump_file) |
2543 | { |
2544 | fprintf (stream: dump_file, format: "\n;; Blocks after choosing rematerialization" |
2545 | " points:\n" ); |
2546 | dump_all_blocks (); |
2547 | } |
2548 | |
2549 | basic_block bb; |
2550 | FOR_EACH_BB_FN (bb, m_fn) |
2551 | emit_remat_insns_for_block (bb); |
2552 | } |
2553 | |
2554 | /* Main function for the pass. */ |
2555 | |
2556 | void |
2557 | early_remat::run (void) |
2558 | { |
2559 | df_analyze (); |
2560 | |
2561 | if (!collect_candidates ()) |
2562 | return; |
2563 | |
2564 | init_block_info (); |
2565 | sort_candidates (); |
2566 | finalize_candidate_indices (); |
2567 | if (dump_file) |
2568 | dump_all_candidates (); |
2569 | |
2570 | compute_rd (); |
2571 | decide_candidate_validity (); |
2572 | local_phase (); |
2573 | global_phase (); |
2574 | } |
2575 | |
2576 | early_remat::early_remat (function *fn, sbitmap selected_modes) |
2577 | : m_fn (fn), |
2578 | m_selected_modes (selected_modes), |
2579 | m_available (0), |
2580 | m_required (0), |
2581 | m_value_table (63) |
2582 | { |
2583 | bitmap_obstack_initialize (&m_obstack); |
2584 | bitmap_initialize (head: &m_candidate_regnos, obstack: &m_obstack); |
2585 | bitmap_initialize (head: &m_tmp_bitmap, obstack: &m_obstack); |
2586 | } |
2587 | |
2588 | early_remat::~early_remat () |
2589 | { |
2590 | bitmap_obstack_release (&m_obstack); |
2591 | } |
2592 | |
2593 | namespace { |
2594 | |
2595 | const pass_data pass_data_early_remat = |
2596 | { |
2597 | .type: RTL_PASS, /* type */ |
2598 | .name: "early_remat" , /* name */ |
2599 | .optinfo_flags: OPTGROUP_NONE, /* optinfo_flags */ |
2600 | .tv_id: TV_EARLY_REMAT, /* tv_id */ |
2601 | .properties_required: 0, /* properties_required */ |
2602 | .properties_provided: 0, /* properties_provided */ |
2603 | .properties_destroyed: 0, /* properties_destroyed */ |
2604 | .todo_flags_start: 0, /* todo_flags_start */ |
2605 | TODO_df_finish, /* todo_flags_finish */ |
2606 | }; |
2607 | |
2608 | class pass_early_remat : public rtl_opt_pass |
2609 | { |
2610 | public: |
2611 | pass_early_remat (gcc::context *ctxt) |
2612 | : rtl_opt_pass (pass_data_early_remat, ctxt) |
2613 | {} |
2614 | |
2615 | /* opt_pass methods: */ |
2616 | bool gate (function *) final override |
2617 | { |
2618 | return optimize > 1 && NUM_POLY_INT_COEFFS > 1; |
2619 | } |
2620 | |
2621 | unsigned int execute (function *f) final override |
2622 | { |
2623 | auto_sbitmap selected_modes (NUM_MACHINE_MODES); |
2624 | bitmap_clear (selected_modes); |
2625 | targetm.select_early_remat_modes (selected_modes); |
2626 | if (!bitmap_empty_p (selected_modes)) |
2627 | early_remat (f, selected_modes).run (); |
2628 | return 0; |
2629 | } |
2630 | }; // class pass_early_remat |
2631 | |
2632 | } // anon namespace |
2633 | |
2634 | rtl_opt_pass * |
2635 | make_pass_early_remat (gcc::context *ctxt) |
2636 | { |
2637 | return new pass_early_remat (ctxt); |
2638 | } |
2639 | |