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1 : : /* Code sinking for trees
2 : : Copyright (C) 2001-2025 Free Software Foundation, Inc.
3 : : Contributed by Daniel Berlin <dan@dberlin.org>
4 : :
5 : : This file is part of GCC.
6 : :
7 : : GCC is free software; you can redistribute it and/or modify
8 : : it under the terms of the GNU General Public License as published by
9 : : the Free Software Foundation; either version 3, or (at your option)
10 : : any later version.
11 : :
12 : : GCC is distributed in the hope that it will be useful,
13 : : but WITHOUT ANY WARRANTY; without even the implied warranty of
14 : : MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 : : GNU General Public License for more details.
16 : :
17 : : You should have received a copy of the GNU General Public License
18 : : along with GCC; see the file COPYING3. If not see
19 : : <http://www.gnu.org/licenses/>. */
20 : :
21 : : #include "config.h"
22 : : #include "system.h"
23 : : #include "coretypes.h"
24 : : #include "backend.h"
25 : : #include "tree.h"
26 : : #include "gimple.h"
27 : : #include "cfghooks.h"
28 : : #include "tree-pass.h"
29 : : #include "ssa.h"
30 : : #include "gimple-pretty-print.h"
31 : : #include "fold-const.h"
32 : : #include "stor-layout.h"
33 : : #include "cfganal.h"
34 : : #include "gimple-iterator.h"
35 : : #include "tree-cfg.h"
36 : : #include "cfgloop.h"
37 : : #include "tree-eh.h"
38 : : #include "tree-ssa-live.h"
39 : : #include "tree-dfa.h"
40 : :
41 : : /* TODO:
42 : : 1. Sinking store only using scalar promotion (IE without moving the RHS):
43 : :
44 : : *q = p;
45 : : p = p + 1;
46 : : if (something)
47 : : *q = <not p>;
48 : : else
49 : : y = *q;
50 : :
51 : :
52 : : should become
53 : : sinktemp = p;
54 : : p = p + 1;
55 : : if (something)
56 : : *q = <not p>;
57 : : else
58 : : {
59 : : *q = sinktemp;
60 : : y = *q
61 : : }
62 : : Store copy propagation will take care of the store elimination above.
63 : :
64 : :
65 : : 2. Sinking using Partial Dead Code Elimination. */
66 : :
67 : :
68 : : static struct
69 : : {
70 : : /* The number of statements sunk down the flowgraph by code sinking. */
71 : : int sunk;
72 : :
73 : : /* The number of stores commoned and sunk down by store commoning. */
74 : : int commoned;
75 : : } sink_stats;
76 : :
77 : :
78 : : /* Given a PHI, and one of its arguments (DEF), find the edge for
79 : : that argument and return it. If the argument occurs twice in the PHI node,
80 : : we return NULL. */
81 : :
82 : : static basic_block
83 : 665811 : find_bb_for_arg (gphi *phi, tree def)
84 : : {
85 : 665811 : size_t i;
86 : 665811 : bool foundone = false;
87 : 665811 : basic_block result = NULL;
88 : 2116483 : for (i = 0; i < gimple_phi_num_args (phi); i++)
89 : 1467029 : if (PHI_ARG_DEF (phi, i) == def)
90 : : {
91 : 682168 : if (foundone)
92 : : return NULL;
93 : 665811 : foundone = true;
94 : 665811 : result = gimple_phi_arg_edge (phi, i)->src;
95 : : }
96 : : return result;
97 : : }
98 : :
99 : : /* When the first immediate use is in a statement, then return true if all
100 : : immediate uses in IMM are in the same statement.
101 : : We could also do the case where the first immediate use is in a phi node,
102 : : and all the other uses are in phis in the same basic block, but this
103 : : requires some expensive checking later (you have to make sure no def/vdef
104 : : in the statement occurs for multiple edges in the various phi nodes it's
105 : : used in, so that you only have one place you can sink it to. */
106 : :
107 : : static bool
108 : 13037909 : all_immediate_uses_same_place (def_operand_p def_p)
109 : : {
110 : 13037909 : tree var = DEF_FROM_PTR (def_p);
111 : 13037909 : imm_use_iterator imm_iter;
112 : 13037909 : use_operand_p use_p;
113 : :
114 : 13037909 : gimple *firstuse = NULL;
115 : 27871748 : FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
116 : : {
117 : 18589090 : if (is_gimple_debug (USE_STMT (use_p)))
118 : 1699958 : continue;
119 : 16889132 : if (firstuse == NULL)
120 : : firstuse = USE_STMT (use_p);
121 : : else
122 : 3851223 : if (firstuse != USE_STMT (use_p))
123 : : return false;
124 : : }
125 : :
126 : : return true;
127 : : }
128 : :
129 : : /* Find the nearest common dominator of all of the immediate uses in IMM. */
130 : :
131 : : static basic_block
132 : 12543903 : nearest_common_dominator_of_uses (def_operand_p def_p, bool *debug_stmts)
133 : : {
134 : 12543903 : tree var = DEF_FROM_PTR (def_p);
135 : 12543903 : auto_bitmap blocks;
136 : 12543903 : basic_block commondom;
137 : 12543903 : unsigned int j;
138 : 12543903 : bitmap_iterator bi;
139 : 12543903 : imm_use_iterator imm_iter;
140 : 12543903 : use_operand_p use_p;
141 : :
142 : 43873170 : FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
143 : : {
144 : 31329267 : gimple *usestmt = USE_STMT (use_p);
145 : 31329267 : basic_block useblock;
146 : :
147 : 31329267 : if (gphi *phi = dyn_cast <gphi *> (usestmt))
148 : : {
149 : 3739430 : int idx = PHI_ARG_INDEX_FROM_USE (use_p);
150 : :
151 : 3739430 : useblock = gimple_phi_arg_edge (phi, idx)->src;
152 : : }
153 : 27589837 : else if (is_gimple_debug (usestmt))
154 : : {
155 : 6567934 : *debug_stmts = true;
156 : 6567934 : continue;
157 : : }
158 : : else
159 : : {
160 : 21021903 : useblock = gimple_bb (usestmt);
161 : : }
162 : :
163 : : /* Short circuit. Nothing dominates the entry block. */
164 : 24761333 : if (useblock == ENTRY_BLOCK_PTR_FOR_FN (cfun))
165 : : return NULL;
166 : :
167 : 24761333 : bitmap_set_bit (blocks, useblock->index);
168 : : }
169 : 12543903 : commondom = BASIC_BLOCK_FOR_FN (cfun, bitmap_first_set_bit (blocks));
170 : 34353660 : EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi)
171 : 21809757 : commondom = nearest_common_dominator (CDI_DOMINATORS, commondom,
172 : 21809757 : BASIC_BLOCK_FOR_FN (cfun, j));
173 : : return commondom;
174 : 12543903 : }
175 : :
176 : : /* Return whether sinking STMT from EARLY_BB to BEST_BB should be avoided. */
177 : :
178 : : static bool
179 : 4425927 : do_not_sink (gimple *stmt, basic_block early_bb, basic_block best_bb)
180 : : {
181 : : /* Placing a statement before a setjmp-like function would be invalid
182 : : (it cannot be reevaluated when execution follows an abnormal edge).
183 : : If we selected a block with abnormal predecessors, just punt. */
184 : 4425927 : if (bb_has_abnormal_pred (best_bb))
185 : : return true;
186 : :
187 : : /* If the latch block is empty, don't make it non-empty by sinking
188 : : something into it. */
189 : 4425841 : if (best_bb == early_bb->loop_father->latch
190 : 4425841 : && empty_block_p (best_bb))
191 : : return true;
192 : :
193 : : /* Avoid turning an unconditional read into a conditional one when we
194 : : still might want to perform vectorization. */
195 : 4161968 : if (best_bb->loop_father == early_bb->loop_father
196 : 2988978 : && loop_outer (best_bb->loop_father)
197 : 755578 : && !best_bb->loop_father->inner
198 : 450665 : && gimple_vuse (stmt)
199 : 176660 : && !gimple_vdef (stmt)
200 : 163321 : && flag_tree_loop_vectorize
201 : 155561 : && !(cfun->curr_properties & PROP_loop_opts_done)
202 : 111401 : && dominated_by_p (CDI_DOMINATORS, best_bb->loop_father->latch, early_bb)
203 : 4248727 : && !dominated_by_p (CDI_DOMINATORS, best_bb->loop_father->latch, best_bb))
204 : : return true;
205 : :
206 : : return false;
207 : : }
208 : :
209 : : /* Given EARLY_BB and LATE_BB, two blocks in a path through the dominator
210 : : tree, return the best basic block between them (inclusive) to place
211 : : statements.
212 : :
213 : : We want the most control dependent block in the shallowest loop nest.
214 : :
215 : : If the resulting block is in a shallower loop nest, then use it. */
216 : :
217 : : static basic_block
218 : 16279186 : select_best_block (basic_block early_bb,
219 : : basic_block late_bb,
220 : : gimple *stmt)
221 : : {
222 : : /* First pick a block we do not disqualify. */
223 : 16279186 : while (late_bb != early_bb
224 : 16564176 : && do_not_sink (stmt, early_bb, late_bb))
225 : 284990 : late_bb = get_immediate_dominator (CDI_DOMINATORS, late_bb);
226 : :
227 : 16279186 : basic_block best_bb = late_bb;
228 : 16279186 : basic_block temp_bb = late_bb;
229 : 19477612 : while (temp_bb != early_bb)
230 : : {
231 : : /* Walk up the dominator tree, hopefully we'll find a shallower
232 : : loop nest. */
233 : 3198426 : temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb);
234 : :
235 : : /* Do not consider blocks we do not want to sink to. */
236 : 3198426 : if (temp_bb != early_bb && do_not_sink (stmt, early_bb, temp_bb))
237 : : ;
238 : :
239 : : /* If we've moved into a lower loop nest, then that becomes
240 : : our best block. */
241 : 3198181 : else if (bb_loop_depth (temp_bb) < bb_loop_depth (best_bb))
242 : : best_bb = temp_bb;
243 : :
244 : : /* A higher loop nest is always worse. */
245 : 2650307 : else if (bb_loop_depth (temp_bb) > bb_loop_depth (best_bb))
246 : : ;
247 : :
248 : : /* Likewise an irreducible region inside an otherwise same loop
249 : : depth. */
250 : 2392684 : else if ((temp_bb->flags & BB_IRREDUCIBLE_LOOP)
251 : 6283 : && !(best_bb->flags & BB_IRREDUCIBLE_LOOP))
252 : : ;
253 : :
254 : : /* But sink the least distance, if the new candidate on the same
255 : : loop depth is post-dominated by the current best block pick
256 : : the new candidate. */
257 : 2392443 : else if (dominated_by_p (CDI_POST_DOMINATORS, temp_bb, best_bb))
258 : : best_bb = temp_bb;
259 : :
260 : : /* Avoid sinking across a conditional branching to exceptional
261 : : code. In practice this does not reduce the number of dynamic
262 : : executions of the sunk statement (this includes EH and
263 : : branches leading to abort for example). Treat this case as
264 : : post-dominating. */
265 : 3624920 : else if (single_pred_p (best_bb)
266 : 1551033 : && single_pred_edge (best_bb)->src == temp_bb
267 : 2799806 : && (single_pred_edge (best_bb)->flags & EDGE_FALLTHRU
268 : 1005156 : || (single_pred_edge (best_bb)->probability
269 : 2885532 : >= profile_probability::always ())))
270 : 1317866 : best_bb = temp_bb;
271 : : }
272 : :
273 : 16279186 : gcc_checking_assert (best_bb == early_bb
274 : : || !do_not_sink (stmt, early_bb, best_bb));
275 : :
276 : 16279186 : return best_bb;
277 : : }
278 : :
279 : : /* Given a statement (STMT) and the basic block it is currently in (FROMBB),
280 : : determine the location to sink the statement to, if any.
281 : : Returns true if there is such location; in that case, TOGSI points to the
282 : : statement before that STMT should be moved. */
283 : :
284 : : static bool
285 : 117169215 : statement_sink_location (gimple *stmt, basic_block frombb,
286 : : gimple_stmt_iterator *togsi, bool *zero_uses_p,
287 : : virtual_operand_live &vop_live)
288 : : {
289 : 117169215 : gimple *use;
290 : 117169215 : use_operand_p one_use = NULL_USE_OPERAND_P;
291 : 117169215 : basic_block sinkbb;
292 : 117169215 : use_operand_p use_p;
293 : 117169215 : def_operand_p def_p;
294 : 117169215 : ssa_op_iter iter;
295 : 117169215 : imm_use_iterator imm_iter;
296 : :
297 : 117169215 : *zero_uses_p = false;
298 : :
299 : : /* We only can sink assignments and const/pure calls that are guaranteed
300 : : to return exactly once. */
301 : 117169215 : int cf;
302 : 117169215 : if (!is_gimple_assign (stmt)
303 : 117169215 : && (!is_gimple_call (stmt)
304 : 5311036 : || !((cf = gimple_call_flags (stmt)) & (ECF_CONST|ECF_PURE))
305 : 1015506 : || (cf & (ECF_LOOPING_CONST_OR_PURE|ECF_RETURNS_TWICE))))
306 : 84556261 : return false;
307 : :
308 : : /* We only can sink stmts with a single definition. */
309 : 32612954 : def_p = single_ssa_def_operand (stmt, SSA_OP_ALL_DEFS);
310 : 32612954 : if (def_p == NULL_DEF_OPERAND_P)
311 : : return false;
312 : :
313 : : /* There are a few classes of things we can't or don't move, some because we
314 : : don't have code to handle it, some because it's not profitable and some
315 : : because it's not legal.
316 : :
317 : : We can't sink things that may be global stores, at least not without
318 : : calculating a lot more information, because we may cause it to no longer
319 : : be seen by an external routine that needs it depending on where it gets
320 : : moved to.
321 : :
322 : : We can't sink statements that end basic blocks without splitting the
323 : : incoming edge for the sink location to place it there.
324 : :
325 : : We can't sink statements that have volatile operands.
326 : :
327 : : We don't want to sink dead code, so anything with 0 immediate uses is not
328 : : sunk.
329 : :
330 : : Don't sink BLKmode assignments if current function has any local explicit
331 : : register variables, as BLKmode assignments may involve memcpy or memset
332 : : calls or, on some targets, inline expansion thereof that sometimes need
333 : : to use specific hard registers.
334 : :
335 : : */
336 : 32612891 : if (stmt_ends_bb_p (stmt)
337 : 32383313 : || gimple_has_side_effects (stmt)
338 : 62601217 : || (cfun->has_local_explicit_reg_vars
339 : 1626 : && TYPE_MODE (TREE_TYPE (gimple_get_lhs (stmt))) == BLKmode))
340 : 2624566 : return false;
341 : :
342 : : /* Return if there are no immediate uses of this stmt. */
343 : 29988325 : if (has_zero_uses (DEF_FROM_PTR (def_p)))
344 : : {
345 : 99676 : *zero_uses_p = true;
346 : 99676 : return false;
347 : : }
348 : :
349 : 29888649 : if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (DEF_FROM_PTR (def_p)))
350 : : return false;
351 : :
352 : 73379966 : FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
353 : : {
354 : 43493370 : tree use = USE_FROM_PTR (use_p);
355 : 43493370 : if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use))
356 : : return false;
357 : : }
358 : :
359 : 29886596 : use = NULL;
360 : :
361 : : /* If stmt is a store the one and only use needs to be a VUSE on
362 : : the live path. */
363 : 29886596 : if (virtual_operand_p (DEF_FROM_PTR (def_p)))
364 : : {
365 : 8060035 : tree lhs = gimple_get_lhs (stmt);
366 : 8060035 : ao_ref ref;
367 : 8060035 : ao_ref_init (&ref, lhs);
368 : 17009783 : FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p))
369 : : {
370 : 10653951 : gimple *use_stmt = USE_STMT (use_p);
371 : :
372 : : /* A killing definition is not a use. */
373 : 10653951 : if (gimple_vdef (use_stmt)
374 : 11155211 : && ((gimple_has_lhs (use_stmt)
375 : 6689683 : && operand_equal_p (lhs,
376 : 6689683 : gimple_get_lhs (use_stmt), 0))
377 : 7784476 : || stmt_kills_ref_p (use_stmt, &ref)))
378 : : {
379 : : /* If use_stmt is or might be a nop assignment then USE_STMT
380 : : acts as a use as well as definition. */
381 : 49926 : if (stmt != use_stmt
382 : 49926 : && ref_maybe_used_by_stmt_p (use_stmt, &ref))
383 : : {
384 : 331 : if (use && use != use_stmt)
385 : 1711292 : return false;
386 : : use = use_stmt;
387 : : }
388 : 49912 : continue;
389 : : }
390 : :
391 : 10604025 : if (is_a <gphi *> (use_stmt)
392 : 10604025 : || ref_maybe_used_by_stmt_p (use_stmt, &ref))
393 : : {
394 : 3432814 : if (use && use != use_stmt)
395 : : return false;
396 : 2381485 : use = use_stmt;
397 : 2381485 : continue;
398 : : }
399 : :
400 : 22107751 : if (gimple_vdef (use_stmt))
401 : : {
402 : 5986792 : if (stmt_may_clobber_ref_p_1 (use_stmt, &ref, false))
403 : : return false;
404 : : /* We do not look past VDEFs, so treat them as sink location. */
405 : 5553626 : if (use && use != use_stmt)
406 : : return false;
407 : : use = use_stmt;
408 : : }
409 : : }
410 : 6355832 : if (!use)
411 : : return false;
412 : : }
413 : : /* If all the immediate uses are not in the same place, find the nearest
414 : : common dominator of all the immediate uses. For PHI nodes, we have to
415 : : find the nearest common dominator of all of the predecessor blocks, since
416 : : that is where insertion would have to take place. */
417 : 21826561 : else if (gimple_vuse (stmt)
418 : 21826561 : || !all_immediate_uses_same_place (def_p))
419 : : {
420 : 12543903 : bool debug_stmts = false;
421 : 12543903 : basic_block commondom = nearest_common_dominator_of_uses (def_p,
422 : : &debug_stmts);
423 : :
424 : 12543903 : if (commondom == frombb)
425 : : return false;
426 : :
427 : : /* If this is a load then do not sink past any stores. */
428 : 2114992 : if (gimple_vuse (stmt))
429 : : {
430 : : /* Do not sink loads from hard registers. */
431 : 820680 : if (gimple_assign_single_p (stmt)
432 : 817579 : && VAR_P (gimple_assign_rhs1 (stmt))
433 : 843528 : && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt)))
434 : : return false;
435 : :
436 : : /* When the live virtual operand at the intended sink location is
437 : : not the same as the one from the load walk up the dominator tree
438 : : for a new candidate location. */
439 : : while (commondom != frombb
440 : 3627994 : && vop_live.get_live_in (commondom) != gimple_vuse (stmt))
441 : 1189997 : commondom = get_immediate_dominator (CDI_DOMINATORS, commondom);
442 : 820674 : if (commondom == frombb)
443 : : return false;
444 : : }
445 : :
446 : : /* Our common dominator has to be dominated by frombb in order to be a
447 : : trivially safe place to put this statement, since it has multiple
448 : : uses. */
449 : 664142 : if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb))
450 : : return false;
451 : :
452 : 664142 : commondom = select_best_block (frombb, commondom, stmt);
453 : :
454 : 664142 : if (commondom == frombb)
455 : : return false;
456 : :
457 : 432740 : *togsi = gsi_after_labels (commondom);
458 : :
459 : 432740 : return true;
460 : : }
461 : : else
462 : : {
463 : 9599846 : FOR_EACH_IMM_USE_FAST (one_use, imm_iter, DEF_FROM_PTR (def_p))
464 : : {
465 : 9599846 : if (is_gimple_debug (USE_STMT (one_use)))
466 : 317188 : continue;
467 : : break;
468 : : }
469 : 9282658 : use = USE_STMT (one_use);
470 : : }
471 : :
472 : 15631401 : if (gimple_code (use) != GIMPLE_PHI)
473 : : {
474 : 14965590 : sinkbb = select_best_block (frombb, gimple_bb (use), stmt);
475 : :
476 : 14965590 : if (sinkbb == frombb)
477 : : return false;
478 : :
479 : : /* The SSA update for sinking of stores cannot insert PHIs, the
480 : : sink location has to lead to exit without crossing any CFG
481 : : merge points to paths not dominated by the sink location. */
482 : 390771 : if (gimple_vdef (stmt)
483 : 104542523 : && (!single_succ_p (sinkbb)
484 : 12924 : || single_succ (sinkbb)->index != EXIT_BLOCK))
485 : : return false;
486 : :
487 : 367518 : *togsi = gsi_after_labels (sinkbb);
488 : :
489 : 367518 : return true;
490 : : }
491 : :
492 : 665811 : sinkbb = find_bb_for_arg (as_a <gphi *> (use), DEF_FROM_PTR (def_p));
493 : :
494 : : /* This can happen if there are multiple uses in a PHI. */
495 : 665811 : if (!sinkbb)
496 : : return false;
497 : :
498 : 649454 : basic_block bestbb = select_best_block (frombb, sinkbb, stmt);
499 : 649454 : if (bestbb == frombb
500 : : /* When we sink a store make sure there's not a path to any of
501 : : the possibly skipped killing defs as that wrecks the virtual
502 : : operand update, requiring inserting of a PHI node. */
503 : 129030 : || (gimple_vdef (stmt)
504 : 10047 : && bestbb != sinkbb
505 : 18 : && !dominated_by_p (CDI_POST_DOMINATORS, bestbb, sinkbb))
506 : : /* Likewise avoid placing VDEFs into an irreducible region. */
507 : 768437 : || (gimple_vdef (stmt)
508 : 10030 : && (bestbb->flags & BB_IRREDUCIBLE_LOOP)))
509 : 530488 : return false;
510 : :
511 : 118966 : *togsi = gsi_after_labels (bestbb);
512 : :
513 : 118966 : return true;
514 : : }
515 : :
516 : : /* Very simplistic code to sink common stores from the predecessor through
517 : : our virtual PHI. We do this before sinking stmts from BB as it might
518 : : expose sinking opportunities of the merged stores.
519 : : Once we have partial dead code elimination through sth like SSU-PRE this
520 : : should be moved there. */
521 : :
522 : : static unsigned
523 : 32922301 : sink_common_stores_to_bb (basic_block bb)
524 : : {
525 : 32922301 : unsigned todo = 0;
526 : 32922301 : gphi *phi;
527 : :
528 : 32922301 : if (EDGE_COUNT (bb->preds) > 1
529 : 30836905 : && (phi = get_virtual_phi (bb)))
530 : : {
531 : : /* Repeat until no more common stores are found. */
532 : 4050150 : while (1)
533 : : {
534 : 3973421 : gimple *first_store = NULL;
535 : 3973421 : auto_vec <tree, 5> vdefs;
536 : 3973421 : gimple_stmt_iterator gsi;
537 : :
538 : : /* Search for common stores defined by all virtual PHI args.
539 : : ??? Common stores not present in all predecessors could
540 : : be handled by inserting a forwarder to sink to. Generally
541 : : this involves deciding which stores to do this for if
542 : : multiple common stores are present for different sets of
543 : : predecessors. See PR11832 for an interesting case. */
544 : 4845036 : for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
545 : : {
546 : 4765304 : tree arg = gimple_phi_arg_def (phi, i);
547 : 4765304 : gimple *def = SSA_NAME_DEF_STMT (arg);
548 : 4765304 : if (! is_gimple_assign (def)
549 : 2008628 : || stmt_can_throw_internal (cfun, def)
550 : 1978799 : || (gimple_phi_arg_edge (phi, i)->flags & EDGE_ABNORMAL)
551 : 6744101 : || stmt_references_abnormal_ssa_name (def))
552 : : {
553 : : /* ??? We could handle some cascading with the def being
554 : : another PHI. We'd have to insert multiple PHIs for
555 : : the rhs then though (if they are not all equal). */
556 : : first_store = NULL;
557 : 3893689 : break;
558 : : }
559 : : /* ??? Do not try to do anything fancy with aliasing, thus
560 : : do not sink across non-aliased loads (or even stores,
561 : : so different store order will make the sinking fail). */
562 : 1978782 : bool all_uses_on_phi = true;
563 : 1978782 : imm_use_iterator iter;
564 : 1978782 : use_operand_p use_p;
565 : 3487902 : FOR_EACH_IMM_USE_FAST (use_p, iter, arg)
566 : 2524959 : if (USE_STMT (use_p) != phi)
567 : : {
568 : : all_uses_on_phi = false;
569 : : break;
570 : : }
571 : 1978782 : if (! all_uses_on_phi)
572 : : {
573 : : first_store = NULL;
574 : : break;
575 : : }
576 : : /* Check all stores are to the same LHS. */
577 : 962943 : if (! first_store)
578 : : first_store = def;
579 : : /* ??? We could handle differing SSA uses in the LHS by inserting
580 : : PHIs for them. */
581 : 265138 : else if (! operand_equal_p (gimple_assign_lhs (first_store),
582 : 265138 : gimple_assign_lhs (def), 0)
583 : 438948 : || (gimple_clobber_p (first_store)
584 : 173810 : != gimple_clobber_p (def)))
585 : : {
586 : : first_store = NULL;
587 : : break;
588 : : }
589 : 871615 : vdefs.safe_push (arg);
590 : : }
591 : 3973421 : if (! first_store)
592 : : break;
593 : :
594 : : /* Check if we need a PHI node to merge the stored values. */
595 : 79732 : bool allsame = true;
596 : 79732 : if (!gimple_clobber_p (first_store))
597 : 99878 : for (unsigned i = 1; i < vdefs.length (); ++i)
598 : : {
599 : 91996 : gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
600 : 91996 : if (! operand_equal_p (gimple_assign_rhs1 (first_store),
601 : 91996 : gimple_assign_rhs1 (def), 0))
602 : : {
603 : : allsame = false;
604 : : break;
605 : : }
606 : : }
607 : :
608 : : /* We cannot handle aggregate values if we need to merge them. */
609 : 79732 : tree type = TREE_TYPE (gimple_assign_lhs (first_store));
610 : 79732 : if (! allsame
611 : 79732 : && ! is_gimple_reg_type (type))
612 : : break;
613 : :
614 : 76729 : if (dump_enabled_p ())
615 : : {
616 : 10 : dump_printf_loc (MSG_OPTIMIZED_LOCATIONS,
617 : 5 : first_store,
618 : : "sinking common stores %sto ",
619 : : allsame ? "with same value " : "");
620 : 5 : dump_generic_expr (MSG_OPTIMIZED_LOCATIONS, TDF_SLIM,
621 : : gimple_assign_lhs (first_store));
622 : 5 : dump_printf (MSG_OPTIMIZED_LOCATIONS, "\n");
623 : : }
624 : :
625 : : /* Insert a PHI to merge differing stored values if necessary.
626 : : Note that in general inserting PHIs isn't a very good idea as
627 : : it makes the job of coalescing and register allocation harder.
628 : : Even common SSA uses on the rhs/lhs might extend their lifetime
629 : : across multiple edges by this code motion which makes
630 : : register allocation harder. */
631 : 76729 : tree from;
632 : 76729 : if (! allsame)
633 : : {
634 : 60205 : from = make_ssa_name (type);
635 : 60205 : gphi *newphi = create_phi_node (from, bb);
636 : 240924 : for (unsigned i = 0; i < vdefs.length (); ++i)
637 : : {
638 : 180719 : gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
639 : 180719 : add_phi_arg (newphi, gimple_assign_rhs1 (def),
640 : 180719 : EDGE_PRED (bb, i), UNKNOWN_LOCATION);
641 : : }
642 : : }
643 : : else
644 : 16524 : from = gimple_assign_rhs1 (first_store);
645 : :
646 : : /* Remove all stores. */
647 : 601748 : for (unsigned i = 0; i < vdefs.length (); ++i)
648 : 224145 : TREE_VISITED (vdefs[i]) = 1;
649 : 300874 : for (unsigned i = 0; i < vdefs.length (); ++i)
650 : : /* If we have more than one use of a VDEF on the PHI make sure
651 : : we remove the defining stmt only once. */
652 : 224145 : if (TREE_VISITED (vdefs[i]))
653 : : {
654 : 220945 : TREE_VISITED (vdefs[i]) = 0;
655 : 220945 : gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
656 : 220945 : gsi = gsi_for_stmt (def);
657 : 220945 : unlink_stmt_vdef (def);
658 : 220945 : gsi_remove (&gsi, true);
659 : 220945 : release_defs (def);
660 : : }
661 : :
662 : : /* Insert the first store at the beginning of the merge BB. */
663 : 76729 : gimple_set_vdef (first_store, gimple_phi_result (phi));
664 : 153458 : SSA_NAME_DEF_STMT (gimple_vdef (first_store)) = first_store;
665 : 76729 : gimple_phi_set_result (phi, make_ssa_name (gimple_vop (cfun)));
666 : 76729 : gimple_set_vuse (first_store, gimple_phi_result (phi));
667 : 76729 : gimple_assign_set_rhs1 (first_store, from);
668 : : /* ??? Should we reset first_stores location? */
669 : 76729 : gsi = gsi_after_labels (bb);
670 : 76729 : gsi_insert_before (&gsi, first_store, GSI_SAME_STMT);
671 : 76729 : sink_stats.commoned++;
672 : :
673 : 76729 : todo |= TODO_cleanup_cfg;
674 : 3973421 : }
675 : :
676 : : /* We could now have empty predecessors that we could remove,
677 : : forming a proper CFG for further sinking. Note that even
678 : : CFG cleanup doesn't do this fully at the moment and it
679 : : doesn't preserve post-dominators in the process either.
680 : : The mergephi pass might do it though. gcc.dg/tree-ssa/ssa-sink-13.c
681 : : shows this nicely if you disable tail merging or (same effect)
682 : : make the stored values unequal. */
683 : : }
684 : :
685 : 32922301 : return todo;
686 : : }
687 : :
688 : : /* Perform code sinking on BB */
689 : :
690 : : static unsigned
691 : 32922301 : sink_code_in_bb (basic_block bb, virtual_operand_live &vop_live)
692 : : {
693 : 32922301 : gimple_stmt_iterator gsi;
694 : 32922301 : edge_iterator ei;
695 : 32922301 : edge e;
696 : 32922301 : bool last = true;
697 : 32922301 : unsigned todo = 0;
698 : :
699 : : /* Sink common stores from the predecessor through our virtual PHI. */
700 : 32922301 : todo |= sink_common_stores_to_bb (bb);
701 : :
702 : : /* If this block doesn't dominate anything, there can't be any place to sink
703 : : the statements to. */
704 : 32922301 : if (first_dom_son (CDI_DOMINATORS, bb) == NULL)
705 : : return todo;
706 : :
707 : : /* We can't move things across abnormal edges, so don't try. */
708 : 38676938 : FOR_EACH_EDGE (e, ei, bb->succs)
709 : 24542443 : if (e->flags & EDGE_ABNORMAL)
710 : : return todo;
711 : :
712 : 145438205 : for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
713 : : {
714 : 117169215 : gimple *stmt = gsi_stmt (gsi);
715 : 117169215 : gimple_stmt_iterator togsi;
716 : 117169215 : bool zero_uses_p;
717 : :
718 : 117169215 : if (!statement_sink_location (stmt, bb, &togsi, &zero_uses_p, vop_live))
719 : : {
720 : 116249991 : gimple_stmt_iterator saved = gsi;
721 : 116249991 : if (!gsi_end_p (gsi))
722 : 116249991 : gsi_prev (&gsi);
723 : : /* If we face a dead stmt remove it as it possibly blocks
724 : : sinking of uses. */
725 : 116249991 : if (zero_uses_p
726 : 99676 : && !gimple_vdef (stmt)
727 : 116345863 : && (cfun->can_delete_dead_exceptions
728 : 73714 : || !stmt_could_throw_p (cfun, stmt)))
729 : : {
730 : 50777 : gsi_remove (&saved, true);
731 : 50777 : release_defs (stmt);
732 : : }
733 : : else
734 : : last = false;
735 : 116249991 : continue;
736 : 116249991 : }
737 : 919224 : if (dump_file)
738 : : {
739 : 37 : fprintf (dump_file, "Sinking ");
740 : 37 : print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS);
741 : 37 : fprintf (dump_file, " from bb %d to bb %d\n",
742 : 37 : bb->index, (gsi_bb (togsi))->index);
743 : : }
744 : :
745 : : /* Update virtual operands of statements in the path we
746 : : do not sink to. */
747 : 1838448 : if (gimple_vdef (stmt))
748 : : {
749 : 10779 : imm_use_iterator iter;
750 : 10779 : use_operand_p use_p;
751 : 10779 : gimple *vuse_stmt;
752 : :
753 : 39417 : FOR_EACH_IMM_USE_STMT (vuse_stmt, iter, gimple_vdef (stmt))
754 : 28638 : if (gimple_code (vuse_stmt) != GIMPLE_PHI
755 : 28638 : && !dominated_by_p (CDI_DOMINATORS, gimple_bb (vuse_stmt),
756 : 18625 : gsi_bb (togsi)))
757 : 44349 : FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
758 : 40345 : SET_USE (use_p, gimple_vuse (stmt));
759 : : }
760 : :
761 : : /* If this is the end of the basic block, we need to insert at the end
762 : : of the basic block. */
763 : 919224 : if (gsi_end_p (togsi))
764 : 141371 : gsi_move_to_bb_end (&gsi, gsi_bb (togsi));
765 : : else
766 : 777853 : gsi_move_before (&gsi, &togsi);
767 : :
768 : 919224 : sink_stats.sunk++;
769 : :
770 : : /* If we've just removed the last statement of the BB, the
771 : : gsi_end_p() test below would fail, but gsi_prev() would have
772 : : succeeded, and we want it to succeed. So we keep track of
773 : : whether we're at the last statement and pick up the new last
774 : : statement. */
775 : 919224 : if (last)
776 : : {
777 : 1042 : gsi = gsi_last_bb (bb);
778 : 1042 : continue;
779 : : }
780 : :
781 : 918182 : last = false;
782 : 918182 : if (!gsi_end_p (gsi))
783 : 1836364 : gsi_prev (&gsi);
784 : :
785 : : }
786 : :
787 : : return todo;
788 : : }
789 : :
790 : : /* Perform code sinking.
791 : : This moves code down the flowgraph when we know it would be
792 : : profitable to do so, or it wouldn't increase the number of
793 : : executions of the statement.
794 : :
795 : : IE given
796 : :
797 : : a_1 = b + c;
798 : : if (<something>)
799 : : {
800 : : }
801 : : else
802 : : {
803 : : foo (&b, &c);
804 : : a_5 = b + c;
805 : : }
806 : : a_6 = PHI (a_5, a_1);
807 : : USE a_6.
808 : :
809 : : we'll transform this into:
810 : :
811 : : if (<something>)
812 : : {
813 : : a_1 = b + c;
814 : : }
815 : : else
816 : : {
817 : : foo (&b, &c);
818 : : a_5 = b + c;
819 : : }
820 : : a_6 = PHI (a_5, a_1);
821 : : USE a_6.
822 : :
823 : : Note that this reduces the number of computations of a = b + c to 1
824 : : when we take the else edge, instead of 2.
825 : : */
826 : : namespace {
827 : :
828 : : const pass_data pass_data_sink_code =
829 : : {
830 : : GIMPLE_PASS, /* type */
831 : : "sink", /* name */
832 : : OPTGROUP_NONE, /* optinfo_flags */
833 : : TV_TREE_SINK, /* tv_id */
834 : : /* PROP_no_crit_edges is ensured by running split_edges_for_insertion in
835 : : pass_data_sink_code::execute (). */
836 : : ( PROP_cfg | PROP_ssa ), /* properties_required */
837 : : 0, /* properties_provided */
838 : : 0, /* properties_destroyed */
839 : : 0, /* todo_flags_start */
840 : : TODO_update_ssa, /* todo_flags_finish */
841 : : };
842 : :
843 : : class pass_sink_code : public gimple_opt_pass
844 : : {
845 : : public:
846 : 571378 : pass_sink_code (gcc::context *ctxt)
847 : 1142756 : : gimple_opt_pass (pass_data_sink_code, ctxt), unsplit_edges (false)
848 : : {}
849 : :
850 : : /* opt_pass methods: */
851 : 2085556 : bool gate (function *) final override { return flag_tree_sink != 0; }
852 : : unsigned int execute (function *) final override;
853 : 285689 : opt_pass *clone (void) final override { return new pass_sink_code (m_ctxt); }
854 : 571378 : void set_pass_param (unsigned n, bool param) final override
855 : : {
856 : 571378 : gcc_assert (n == 0);
857 : 571378 : unsplit_edges = param;
858 : 571378 : }
859 : :
860 : : private:
861 : : bool unsplit_edges;
862 : : }; // class pass_sink_code
863 : :
864 : : unsigned int
865 : 2085396 : pass_sink_code::execute (function *fun)
866 : : {
867 : 2085396 : loop_optimizer_init (LOOPS_NORMAL);
868 : 2085396 : split_edges_for_insertion ();
869 : : /* Arrange for the critical edge splitting to be undone if requested. */
870 : 2085396 : unsigned todo = unsplit_edges ? TODO_cleanup_cfg : 0;
871 : 2085396 : connect_infinite_loops_to_exit ();
872 : 2085396 : mark_dfs_back_edges (fun);
873 : 2085396 : memset (&sink_stats, 0, sizeof (sink_stats));
874 : 2085396 : calculate_dominance_info (CDI_DOMINATORS);
875 : 2085396 : calculate_dominance_info (CDI_POST_DOMINATORS);
876 : :
877 : 2085396 : virtual_operand_live vop_live;
878 : :
879 : 2085396 : int *rpo = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
880 : 2085396 : int n = inverted_rev_post_order_compute (fun, rpo);
881 : 35007697 : for (int i = 0; i < n; ++i)
882 : 32922301 : todo |= sink_code_in_bb (BASIC_BLOCK_FOR_FN (fun, rpo[i]), vop_live);
883 : 2085396 : free (rpo);
884 : :
885 : 2085396 : statistics_counter_event (fun, "Sunk statements", sink_stats.sunk);
886 : 2085396 : statistics_counter_event (fun, "Commoned stores", sink_stats.commoned);
887 : 2085396 : free_dominance_info (CDI_POST_DOMINATORS);
888 : 2085396 : remove_fake_exit_edges ();
889 : 2085396 : loop_optimizer_finalize ();
890 : :
891 : 2085396 : return todo;
892 : 2085396 : }
893 : :
894 : : } // anon namespace
895 : :
896 : : gimple_opt_pass *
897 : 285689 : make_pass_sink_code (gcc::context *ctxt)
898 : : {
899 : 285689 : return new pass_sink_code (ctxt);
900 : : }
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