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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 : 635741 : find_bb_for_arg (gphi *phi, tree def)
84 : : {
85 : 635741 : size_t i;
86 : 635741 : bool foundone = false;
87 : 635741 : basic_block result = NULL;
88 : 1993242 : for (i = 0; i < gimple_phi_num_args (phi); i++)
89 : 1371418 : if (PHI_ARG_DEF (phi, i) == def)
90 : : {
91 : 649658 : if (foundone)
92 : : return NULL;
93 : 635741 : foundone = true;
94 : 635741 : 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 : 12720868 : all_immediate_uses_same_place (def_operand_p def_p)
109 : : {
110 : 12720868 : tree var = DEF_FROM_PTR (def_p);
111 : 12720868 : imm_use_iterator imm_iter;
112 : 12720868 : use_operand_p use_p;
113 : :
114 : 12720868 : gimple *firstuse = NULL;
115 : 27112975 : FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
116 : : {
117 : 17989262 : if (is_gimple_debug (USE_STMT (use_p)))
118 : 1574525 : continue;
119 : 16414737 : if (firstuse == NULL)
120 : : firstuse = USE_STMT (use_p);
121 : : else
122 : 3693869 : 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 : 12115611 : nearest_common_dominator_of_uses (def_operand_p def_p, bool *debug_stmts)
133 : : {
134 : 12115611 : tree var = DEF_FROM_PTR (def_p);
135 : 12115611 : auto_bitmap blocks;
136 : 12115611 : basic_block commondom;
137 : 12115611 : unsigned int j;
138 : 12115611 : bitmap_iterator bi;
139 : 12115611 : imm_use_iterator imm_iter;
140 : 12115611 : use_operand_p use_p;
141 : :
142 : 41906717 : FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
143 : : {
144 : 29791106 : gimple *usestmt = USE_STMT (use_p);
145 : 29791106 : basic_block useblock;
146 : :
147 : 29791106 : if (gphi *phi = dyn_cast <gphi *> (usestmt))
148 : : {
149 : 3572434 : int idx = PHI_ARG_INDEX_FROM_USE (use_p);
150 : :
151 : 3572434 : useblock = gimple_phi_arg_edge (phi, idx)->src;
152 : : }
153 : 26218672 : else if (is_gimple_debug (usestmt))
154 : : {
155 : 6033309 : *debug_stmts = true;
156 : 6033309 : continue;
157 : : }
158 : : else
159 : : {
160 : 20185363 : useblock = gimple_bb (usestmt);
161 : : }
162 : :
163 : : /* Short circuit. Nothing dominates the entry block. */
164 : 23757797 : if (useblock == ENTRY_BLOCK_PTR_FOR_FN (cfun))
165 : : return NULL;
166 : :
167 : 23757797 : bitmap_set_bit (blocks, useblock->index);
168 : : }
169 : 12115611 : commondom = BASIC_BLOCK_FOR_FN (cfun, bitmap_first_set_bit (blocks));
170 : 33065843 : EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi)
171 : 20950232 : commondom = nearest_common_dominator (CDI_DOMINATORS, commondom,
172 : 20950232 : BASIC_BLOCK_FOR_FN (cfun, j));
173 : : return commondom;
174 : 12115611 : }
175 : :
176 : : /* Return whether sinking STMT from EARLY_BB to BEST_BB should be avoided. */
177 : :
178 : : static bool
179 : 4217260 : 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 : 4217260 : 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 : 4217178 : if (best_bb == early_bb->loop_father->latch
190 : 4217178 : && 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 : 3957017 : if (best_bb->loop_father == early_bb->loop_father
196 : 2820638 : && loop_outer (best_bb->loop_father)
197 : 746938 : && !best_bb->loop_father->inner
198 : 439871 : && gimple_vuse (stmt)
199 : 161523 : && !gimple_vdef (stmt)
200 : 160756 : && flag_tree_loop_vectorize
201 : 153054 : && !(cfun->curr_properties & PROP_loop_opts_done)
202 : 110637 : && dominated_by_p (CDI_DOMINATORS, best_bb->loop_father->latch, early_bb)
203 : 4041964 : && !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 : 9822849 : 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 : 9822849 : while (late_bb != early_bb
224 : 10103545 : && do_not_sink (stmt, early_bb, late_bb))
225 : 280696 : late_bb = get_immediate_dominator (CDI_DOMINATORS, late_bb);
226 : :
227 : 9822849 : basic_block best_bb = late_bb;
228 : 9822849 : basic_block temp_bb = late_bb;
229 : 9822849 : while (temp_bb != early_bb)
230 : : {
231 : : /* Walk up the dominator tree, hopefully we'll find a shallower
232 : : loop nest. */
233 : 3080710 : temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb);
234 : :
235 : : /* Do not consider blocks we do not want to sink to. */
236 : 3080710 : 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 : 3080451 : 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 : 2558410 : else if (bb_loop_depth (temp_bb) > bb_loop_depth (best_bb))
246 : : ;
247 : :
248 : : /* But sink the least distance, if the new candidate on the same
249 : : loop depth is post-dominated by the current best block pick
250 : : the new candidate. */
251 : 2300466 : else if (dominated_by_p (CDI_POST_DOMINATORS, temp_bb, best_bb))
252 : : best_bb = temp_bb;
253 : :
254 : : /* Avoid sinking across a conditional branching to exceptional
255 : : code. In practice this does not reduce the number of dynamic
256 : : executions of the sunk statement (this includes EH and
257 : : branches leading to abort for example). Treat this case as
258 : : post-dominating. */
259 : 14597955 : else if (single_pred_p (best_bb)
260 : 1479638 : && single_pred_edge (best_bb)->src == temp_bb
261 : 2685053 : && (single_pred_edge (best_bb)->flags & EDGE_FALLTHRU
262 : : || (single_pred_edge (best_bb)->probability
263 : 13844387 : >= profile_probability::always ())))
264 : : best_bb = temp_bb;
265 : : }
266 : :
267 : 9822849 : gcc_checking_assert (best_bb == early_bb
268 : : || (!do_not_sink (stmt, early_bb, best_bb)
269 : : && ((bb_loop_depth (best_bb)
270 : : < bb_loop_depth (early_bb))
271 : : || !dominated_by_p (CDI_POST_DOMINATORS,
272 : : early_bb, best_bb))));
273 : :
274 : 9822849 : return best_bb;
275 : : }
276 : :
277 : : /* Given a statement (STMT) and the basic block it is currently in (FROMBB),
278 : : determine the location to sink the statement to, if any.
279 : : Returns true if there is such location; in that case, TOGSI points to the
280 : : statement before that STMT should be moved. */
281 : :
282 : : static bool
283 : 111191191 : statement_sink_location (gimple *stmt, basic_block frombb,
284 : : gimple_stmt_iterator *togsi, bool *zero_uses_p,
285 : : virtual_operand_live &vop_live)
286 : : {
287 : 111191191 : gimple *use;
288 : 111191191 : use_operand_p one_use = NULL_USE_OPERAND_P;
289 : 111191191 : basic_block sinkbb;
290 : 111191191 : use_operand_p use_p;
291 : 111191191 : def_operand_p def_p;
292 : 111191191 : ssa_op_iter iter;
293 : 111191191 : imm_use_iterator imm_iter;
294 : :
295 : 111191191 : *zero_uses_p = false;
296 : :
297 : : /* We only can sink assignments and const/pure calls that are guaranteed
298 : : to return exactly once. */
299 : 111191191 : int cf;
300 : 111191191 : if (!is_gimple_assign (stmt)
301 : 111191191 : && (!is_gimple_call (stmt)
302 : 5254575 : || !((cf = gimple_call_flags (stmt)) & (ECF_CONST|ECF_PURE))
303 : 1030058 : || (cf & (ECF_LOOPING_CONST_OR_PURE|ECF_RETURNS_TWICE))))
304 : 79497601 : return false;
305 : :
306 : : /* We only can sink stmts with a single definition. */
307 : 31693590 : def_p = single_ssa_def_operand (stmt, SSA_OP_ALL_DEFS);
308 : 31693590 : if (def_p == NULL_DEF_OPERAND_P)
309 : : return false;
310 : :
311 : : /* There are a few classes of things we can't or don't move, some because we
312 : : don't have code to handle it, some because it's not profitable and some
313 : : because it's not legal.
314 : :
315 : : We can't sink things that may be global stores, at least not without
316 : : calculating a lot more information, because we may cause it to no longer
317 : : be seen by an external routine that needs it depending on where it gets
318 : : moved to.
319 : :
320 : : We can't sink statements that end basic blocks without splitting the
321 : : incoming edge for the sink location to place it there.
322 : :
323 : : We can't sink statements that have volatile operands.
324 : :
325 : : We don't want to sink dead code, so anything with 0 immediate uses is not
326 : : sunk.
327 : :
328 : : Don't sink BLKmode assignments if current function has any local explicit
329 : : register variables, as BLKmode assignments may involve memcpy or memset
330 : : calls or, on some targets, inline expansion thereof that sometimes need
331 : : to use specific hard registers.
332 : :
333 : : */
334 : 31693534 : if (stmt_ends_bb_p (stmt)
335 : 31460397 : || gimple_has_side_effects (stmt)
336 : 60844797 : || (cfun->has_local_explicit_reg_vars
337 : 1617 : && TYPE_MODE (TREE_TYPE (gimple_get_lhs (stmt))) == BLKmode))
338 : 2542271 : return false;
339 : :
340 : : /* Return if there are no immediate uses of this stmt. */
341 : 29151263 : if (has_zero_uses (DEF_FROM_PTR (def_p)))
342 : : {
343 : 99940 : *zero_uses_p = true;
344 : 99940 : return false;
345 : : }
346 : :
347 : 29051323 : if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (DEF_FROM_PTR (def_p)))
348 : : return false;
349 : :
350 : 71299671 : FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
351 : : {
352 : 42250398 : tree use = USE_FROM_PTR (use_p);
353 : 42250398 : if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use))
354 : : return false;
355 : : }
356 : :
357 : 29049273 : use = NULL;
358 : :
359 : : /* If stmt is a store the one and only use needs to be the VOP
360 : : merging PHI node. */
361 : 29049273 : if (virtual_operand_p (DEF_FROM_PTR (def_p)))
362 : : {
363 : 8554796 : FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p))
364 : : {
365 : 8473811 : gimple *use_stmt = USE_STMT (use_p);
366 : :
367 : : /* A killing definition is not a use. */
368 : 8473811 : if ((gimple_has_lhs (use_stmt)
369 : 6663605 : && operand_equal_p (gimple_get_lhs (stmt),
370 : 6663605 : gimple_get_lhs (use_stmt), 0))
371 : 9195849 : || stmt_kills_ref_p (use_stmt, gimple_get_lhs (stmt)))
372 : : {
373 : : /* If use_stmt is or might be a nop assignment then USE_STMT
374 : : acts as a use as well as definition. */
375 : 27291 : if (stmt != use_stmt
376 : 27291 : && ref_maybe_used_by_stmt_p (use_stmt,
377 : : gimple_get_lhs (stmt)))
378 : : return false;
379 : 26784 : continue;
380 : : }
381 : :
382 : 8446520 : if (gimple_code (use_stmt) != GIMPLE_PHI)
383 : : return false;
384 : :
385 : 1057355 : if (use
386 : 1057355 : && use != use_stmt)
387 : : return false;
388 : :
389 : : use = use_stmt;
390 : : }
391 : 80985 : if (!use)
392 : : return false;
393 : : }
394 : : /* If all the immediate uses are not in the same place, find the nearest
395 : : common dominator of all the immediate uses. For PHI nodes, we have to
396 : : find the nearest common dominator of all of the predecessor blocks, since
397 : : that is where insertion would have to take place. */
398 : 21239324 : else if (gimple_vuse (stmt)
399 : 21239324 : || !all_immediate_uses_same_place (def_p))
400 : : {
401 : 12115611 : bool debug_stmts = false;
402 : 12115611 : basic_block commondom = nearest_common_dominator_of_uses (def_p,
403 : : &debug_stmts);
404 : :
405 : 12115611 : if (commondom == frombb)
406 : : return false;
407 : :
408 : : /* If this is a load then do not sink past any stores. */
409 : 2042230 : if (gimple_vuse (stmt))
410 : : {
411 : : /* Do not sink loads from hard registers. */
412 : 795276 : if (gimple_assign_single_p (stmt)
413 : 791235 : && VAR_P (gimple_assign_rhs1 (stmt))
414 : 817278 : && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt)))
415 : : return false;
416 : :
417 : : /* When the live virtual operand at the intended sink location is
418 : : not the same as the one from the load walk up the dominator tree
419 : : for a new candidate location. */
420 : : while (commondom != frombb
421 : 3481990 : && vop_live.get_live_in (commondom) != gimple_vuse (stmt))
422 : 1137203 : commondom = get_immediate_dominator (CDI_DOMINATORS, commondom);
423 : 795272 : if (commondom == frombb)
424 : : return false;
425 : : }
426 : :
427 : : /* Our common dominator has to be dominated by frombb in order to be a
428 : : trivially safe place to put this statement, since it has multiple
429 : : uses. */
430 : 638151 : if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb))
431 : : return false;
432 : :
433 : 638151 : commondom = select_best_block (frombb, commondom, stmt);
434 : :
435 : 638151 : if (commondom == frombb)
436 : : return false;
437 : :
438 : 390458 : *togsi = gsi_after_labels (commondom);
439 : :
440 : 390458 : return true;
441 : : }
442 : : else
443 : : {
444 : 9407655 : FOR_EACH_IMM_USE_FAST (one_use, imm_iter, DEF_FROM_PTR (def_p))
445 : : {
446 : 9407655 : if (is_gimple_debug (USE_STMT (one_use)))
447 : 283942 : continue;
448 : : break;
449 : : }
450 : 9123713 : use = USE_STMT (one_use);
451 : :
452 : 9123713 : if (gimple_code (use) != GIMPLE_PHI)
453 : : {
454 : 8562874 : sinkbb = select_best_block (frombb, gimple_bb (use), stmt);
455 : :
456 : 8562874 : if (sinkbb == frombb)
457 : : return false;
458 : :
459 : 365626 : *togsi = gsi_after_labels (sinkbb);
460 : :
461 : 365626 : return true;
462 : : }
463 : : }
464 : :
465 : 635741 : sinkbb = find_bb_for_arg (as_a <gphi *> (use), DEF_FROM_PTR (def_p));
466 : :
467 : : /* This can happen if there are multiple uses in a PHI. */
468 : 635741 : if (!sinkbb)
469 : : return false;
470 : :
471 : 621824 : basic_block bestbb = select_best_block (frombb, sinkbb, stmt);
472 : 621824 : if (bestbb == frombb
473 : : /* When we sink a store make sure there's not a path to any of
474 : : the possibly skipped killing defs as that wrecks the virtual
475 : : operand update, requiring inserting of a PHI node. */
476 : 721594 : || (gimple_vdef (stmt)
477 : 2530 : && bestbb != sinkbb
478 : 16 : && !dominated_by_p (CDI_POST_DOMINATORS, bestbb, sinkbb)))
479 : 522069 : return false;
480 : :
481 : 99755 : *togsi = gsi_after_labels (bestbb);
482 : :
483 : 99755 : return true;
484 : : }
485 : :
486 : : /* Very simplistic code to sink common stores from the predecessor through
487 : : our virtual PHI. We do this before sinking stmts from BB as it might
488 : : expose sinking opportunities of the merged stores.
489 : : Once we have partial dead code elimination through sth like SSU-PRE this
490 : : should be moved there. */
491 : :
492 : : static unsigned
493 : 31863222 : sink_common_stores_to_bb (basic_block bb)
494 : : {
495 : 31863222 : unsigned todo = 0;
496 : 31863222 : gphi *phi;
497 : :
498 : 31863222 : if (EDGE_COUNT (bb->preds) > 1
499 : 29823637 : && (phi = get_virtual_phi (bb)))
500 : : {
501 : : /* Repeat until no more common stores are found. */
502 : 3905649 : while (1)
503 : : {
504 : 3812670 : gimple *first_store = NULL;
505 : 3812670 : auto_vec <tree, 5> vdefs;
506 : 3812670 : gimple_stmt_iterator gsi;
507 : :
508 : : /* Search for common stores defined by all virtual PHI args.
509 : : ??? Common stores not present in all predecessors could
510 : : be handled by inserting a forwarder to sink to. Generally
511 : : this involves deciding which stores to do this for if
512 : : multiple common stores are present for different sets of
513 : : predecessors. See PR11832 for an interesting case. */
514 : 4691990 : for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
515 : : {
516 : 4598032 : tree arg = gimple_phi_arg_def (phi, i);
517 : 4598032 : gimple *def = SSA_NAME_DEF_STMT (arg);
518 : 4598032 : if (! is_gimple_assign (def)
519 : 1958233 : || stmt_can_throw_internal (cfun, def)
520 : 1927884 : || (gimple_phi_arg_edge (phi, i)->flags & EDGE_ABNORMAL)
521 : 6525914 : || stmt_references_abnormal_ssa_name (def))
522 : : {
523 : : /* ??? We could handle some cascading with the def being
524 : : another PHI. We'd have to insert multiple PHIs for
525 : : the rhs then though (if they are not all equal). */
526 : : first_store = NULL;
527 : 3718712 : break;
528 : : }
529 : : /* ??? Do not try to do anything fancy with aliasing, thus
530 : : do not sink across non-aliased loads (or even stores,
531 : : so different store order will make the sinking fail). */
532 : 1927867 : bool all_uses_on_phi = true;
533 : 1927867 : imm_use_iterator iter;
534 : 1927867 : use_operand_p use_p;
535 : 3429677 : FOR_EACH_IMM_USE_FAST (use_p, iter, arg)
536 : 2470359 : if (USE_STMT (use_p) != phi)
537 : : {
538 : : all_uses_on_phi = false;
539 : : break;
540 : : }
541 : 1927867 : if (! all_uses_on_phi)
542 : : {
543 : : first_store = NULL;
544 : : break;
545 : : }
546 : : /* Check all stores are to the same LHS. */
547 : 959318 : if (! first_store)
548 : : first_store = def;
549 : : /* ??? We could handle differing SSA uses in the LHS by inserting
550 : : PHIs for them. */
551 : 279937 : else if (! operand_equal_p (gimple_assign_lhs (first_store),
552 : 279937 : gimple_assign_lhs (def), 0)
553 : 479876 : || (gimple_clobber_p (first_store)
554 : 199939 : != gimple_clobber_p (def)))
555 : : {
556 : : first_store = NULL;
557 : : break;
558 : : }
559 : 879320 : vdefs.safe_push (arg);
560 : : }
561 : 3812670 : if (! first_store)
562 : : break;
563 : :
564 : : /* Check if we need a PHI node to merge the stored values. */
565 : 93958 : bool allsame = true;
566 : 93958 : if (!gimple_clobber_p (first_store))
567 : 109861 : for (unsigned i = 1; i < vdefs.length (); ++i)
568 : : {
569 : 101777 : gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
570 : 101777 : if (! operand_equal_p (gimple_assign_rhs1 (first_store),
571 : 101777 : gimple_assign_rhs1 (def), 0))
572 : : {
573 : : allsame = false;
574 : : break;
575 : : }
576 : : }
577 : :
578 : : /* We cannot handle aggregate values if we need to merge them. */
579 : 93958 : tree type = TREE_TYPE (gimple_assign_lhs (first_store));
580 : 93958 : if (! allsame
581 : 93958 : && ! is_gimple_reg_type (type))
582 : : break;
583 : :
584 : 92979 : if (dump_enabled_p ())
585 : : {
586 : 8 : dump_printf_loc (MSG_OPTIMIZED_LOCATIONS,
587 : : first_store,
588 : : "sinking common stores %sto ",
589 : : allsame ? "with same value " : "");
590 : 5 : dump_generic_expr (MSG_OPTIMIZED_LOCATIONS, TDF_SLIM,
591 : : gimple_assign_lhs (first_store));
592 : 5 : dump_printf (MSG_OPTIMIZED_LOCATIONS, "\n");
593 : : }
594 : :
595 : : /* Insert a PHI to merge differing stored values if necessary.
596 : : Note that in general inserting PHIs isn't a very good idea as
597 : : it makes the job of coalescing and register allocation harder.
598 : : Even common SSA uses on the rhs/lhs might extend their lifetime
599 : : across multiple edges by this code motion which makes
600 : : register allocation harder. */
601 : 92979 : tree from;
602 : 92979 : if (! allsame)
603 : : {
604 : 72357 : from = make_ssa_name (type);
605 : 72357 : gphi *newphi = create_phi_node (from, bb);
606 : 289807 : for (unsigned i = 0; i < vdefs.length (); ++i)
607 : : {
608 : 217450 : gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
609 : 217450 : add_phi_arg (newphi, gimple_assign_rhs1 (def),
610 : 217450 : EDGE_PRED (bb, i), UNKNOWN_LOCATION);
611 : : }
612 : : }
613 : : else
614 : 20622 : from = gimple_assign_rhs1 (first_store);
615 : :
616 : : /* Remove all stores. */
617 : 730074 : for (unsigned i = 0; i < vdefs.length (); ++i)
618 : 272058 : TREE_VISITED (vdefs[i]) = 1;
619 : 365037 : for (unsigned i = 0; i < vdefs.length (); ++i)
620 : : /* If we have more than one use of a VDEF on the PHI make sure
621 : : we remove the defining stmt only once. */
622 : 272058 : if (TREE_VISITED (vdefs[i]))
623 : : {
624 : 265820 : TREE_VISITED (vdefs[i]) = 0;
625 : 265820 : gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
626 : 265820 : gsi = gsi_for_stmt (def);
627 : 265820 : unlink_stmt_vdef (def);
628 : 265820 : gsi_remove (&gsi, true);
629 : 265820 : release_defs (def);
630 : : }
631 : :
632 : : /* Insert the first store at the beginning of the merge BB. */
633 : 92979 : gimple_set_vdef (first_store, gimple_phi_result (phi));
634 : 185958 : SSA_NAME_DEF_STMT (gimple_vdef (first_store)) = first_store;
635 : 92979 : gimple_phi_set_result (phi, make_ssa_name (gimple_vop (cfun)));
636 : 92979 : gimple_set_vuse (first_store, gimple_phi_result (phi));
637 : 92979 : gimple_assign_set_rhs1 (first_store, from);
638 : : /* ??? Should we reset first_stores location? */
639 : 92979 : gsi = gsi_after_labels (bb);
640 : 92979 : gsi_insert_before (&gsi, first_store, GSI_SAME_STMT);
641 : 92979 : sink_stats.commoned++;
642 : :
643 : 92979 : todo |= TODO_cleanup_cfg;
644 : 3812670 : }
645 : :
646 : : /* We could now have empty predecessors that we could remove,
647 : : forming a proper CFG for further sinking. Note that even
648 : : CFG cleanup doesn't do this fully at the moment and it
649 : : doesn't preserve post-dominators in the process either.
650 : : The mergephi pass might do it though. gcc.dg/tree-ssa/ssa-sink-13.c
651 : : shows this nicely if you disable tail merging or (same effect)
652 : : make the stored values unequal. */
653 : : }
654 : :
655 : 31863222 : return todo;
656 : : }
657 : :
658 : : /* Perform code sinking on BB */
659 : :
660 : : static unsigned
661 : 31863222 : sink_code_in_bb (basic_block bb, virtual_operand_live &vop_live)
662 : : {
663 : 31863222 : gimple_stmt_iterator gsi;
664 : 31863222 : edge_iterator ei;
665 : 31863222 : edge e;
666 : 31863222 : bool last = true;
667 : 31863222 : unsigned todo = 0;
668 : :
669 : : /* Sink common stores from the predecessor through our virtual PHI. */
670 : 31863222 : todo |= sink_common_stores_to_bb (bb);
671 : :
672 : : /* If this block doesn't dominate anything, there can't be any place to sink
673 : : the statements to. */
674 : 31863222 : if (first_dom_son (CDI_DOMINATORS, bb) == NULL)
675 : : return todo;
676 : :
677 : : /* We can't move things across abnormal edges, so don't try. */
678 : 37437006 : FOR_EACH_EDGE (e, ei, bb->succs)
679 : 23756204 : if (e->flags & EDGE_ABNORMAL)
680 : : return todo;
681 : :
682 : 138552795 : for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
683 : : {
684 : 111191191 : gimple *stmt = gsi_stmt (gsi);
685 : 111191191 : gimple_stmt_iterator togsi;
686 : 111191191 : bool zero_uses_p;
687 : :
688 : 111191191 : if (!statement_sink_location (stmt, bb, &togsi, &zero_uses_p, vop_live))
689 : : {
690 : 110335352 : gimple_stmt_iterator saved = gsi;
691 : 110335352 : if (!gsi_end_p (gsi))
692 : 110335352 : gsi_prev (&gsi);
693 : : /* If we face a dead stmt remove it as it possibly blocks
694 : : sinking of uses. */
695 : 110335352 : if (zero_uses_p
696 : 99940 : && !gimple_vdef (stmt)
697 : 110431509 : && (cfun->can_delete_dead_exceptions
698 : 76039 : || !stmt_could_throw_p (cfun, stmt)))
699 : : {
700 : 48100 : gsi_remove (&saved, true);
701 : 48100 : release_defs (stmt);
702 : : }
703 : : else
704 : : last = false;
705 : 110335352 : continue;
706 : 110335352 : }
707 : 855839 : if (dump_file)
708 : : {
709 : 39 : fprintf (dump_file, "Sinking ");
710 : 39 : print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS);
711 : 39 : fprintf (dump_file, " from bb %d to bb %d\n",
712 : 39 : bb->index, (gsi_bb (togsi))->index);
713 : : }
714 : :
715 : : /* Update virtual operands of statements in the path we
716 : : do not sink to. */
717 : 1711678 : if (gimple_vdef (stmt))
718 : : {
719 : 2515 : imm_use_iterator iter;
720 : 2515 : use_operand_p use_p;
721 : 2515 : gimple *vuse_stmt;
722 : :
723 : 7847 : FOR_EACH_IMM_USE_STMT (vuse_stmt, iter, gimple_vdef (stmt))
724 : 5332 : if (gimple_code (vuse_stmt) != GIMPLE_PHI
725 : 5332 : && !dominated_by_p (CDI_DOMINATORS, gimple_bb (vuse_stmt),
726 : 2817 : gsi_bb (togsi)))
727 : 8451 : FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
728 : 8149 : SET_USE (use_p, gimple_vuse (stmt));
729 : : }
730 : :
731 : : /* If this is the end of the basic block, we need to insert at the end
732 : : of the basic block. */
733 : 855839 : if (gsi_end_p (togsi))
734 : 123067 : gsi_move_to_bb_end (&gsi, gsi_bb (togsi));
735 : : else
736 : 732772 : gsi_move_before (&gsi, &togsi);
737 : :
738 : 855839 : sink_stats.sunk++;
739 : :
740 : : /* If we've just removed the last statement of the BB, the
741 : : gsi_end_p() test below would fail, but gsi_prev() would have
742 : : succeeded, and we want it to succeed. So we keep track of
743 : : whether we're at the last statement and pick up the new last
744 : : statement. */
745 : 855839 : if (last)
746 : : {
747 : 11241 : gsi = gsi_last_bb (bb);
748 : 11241 : continue;
749 : : }
750 : :
751 : 844598 : last = false;
752 : 844598 : if (!gsi_end_p (gsi))
753 : 1689196 : gsi_prev (&gsi);
754 : :
755 : : }
756 : :
757 : : return todo;
758 : : }
759 : :
760 : : /* Perform code sinking.
761 : : This moves code down the flowgraph when we know it would be
762 : : profitable to do so, or it wouldn't increase the number of
763 : : executions of the statement.
764 : :
765 : : IE given
766 : :
767 : : a_1 = b + c;
768 : : if (<something>)
769 : : {
770 : : }
771 : : else
772 : : {
773 : : foo (&b, &c);
774 : : a_5 = b + c;
775 : : }
776 : : a_6 = PHI (a_5, a_1);
777 : : USE a_6.
778 : :
779 : : we'll transform this into:
780 : :
781 : : if (<something>)
782 : : {
783 : : a_1 = b + c;
784 : : }
785 : : else
786 : : {
787 : : foo (&b, &c);
788 : : a_5 = b + c;
789 : : }
790 : : a_6 = PHI (a_5, a_1);
791 : : USE a_6.
792 : :
793 : : Note that this reduces the number of computations of a = b + c to 1
794 : : when we take the else edge, instead of 2.
795 : : */
796 : : namespace {
797 : :
798 : : const pass_data pass_data_sink_code =
799 : : {
800 : : GIMPLE_PASS, /* type */
801 : : "sink", /* name */
802 : : OPTGROUP_NONE, /* optinfo_flags */
803 : : TV_TREE_SINK, /* tv_id */
804 : : /* PROP_no_crit_edges is ensured by running split_edges_for_insertion in
805 : : pass_data_sink_code::execute (). */
806 : : ( PROP_cfg | PROP_ssa ), /* properties_required */
807 : : 0, /* properties_provided */
808 : : 0, /* properties_destroyed */
809 : : 0, /* todo_flags_start */
810 : : TODO_update_ssa, /* todo_flags_finish */
811 : : };
812 : :
813 : : class pass_sink_code : public gimple_opt_pass
814 : : {
815 : : public:
816 : 555834 : pass_sink_code (gcc::context *ctxt)
817 : 1111668 : : gimple_opt_pass (pass_data_sink_code, ctxt), unsplit_edges (false)
818 : : {}
819 : :
820 : : /* opt_pass methods: */
821 : 2039738 : bool gate (function *) final override { return flag_tree_sink != 0; }
822 : : unsigned int execute (function *) final override;
823 : 277917 : opt_pass *clone (void) final override { return new pass_sink_code (m_ctxt); }
824 : 555834 : void set_pass_param (unsigned n, bool param) final override
825 : : {
826 : 555834 : gcc_assert (n == 0);
827 : 555834 : unsplit_edges = param;
828 : 555834 : }
829 : :
830 : : private:
831 : : bool unsplit_edges;
832 : : }; // class pass_sink_code
833 : :
834 : : unsigned int
835 : 2039585 : pass_sink_code::execute (function *fun)
836 : : {
837 : 2039585 : loop_optimizer_init (LOOPS_NORMAL);
838 : 2039585 : split_edges_for_insertion ();
839 : : /* Arrange for the critical edge splitting to be undone if requested. */
840 : 2039585 : unsigned todo = unsplit_edges ? TODO_cleanup_cfg : 0;
841 : 2039585 : connect_infinite_loops_to_exit ();
842 : 2039585 : mark_dfs_back_edges (fun);
843 : 2039585 : memset (&sink_stats, 0, sizeof (sink_stats));
844 : 2039585 : calculate_dominance_info (CDI_DOMINATORS);
845 : 2039585 : calculate_dominance_info (CDI_POST_DOMINATORS);
846 : :
847 : 2039585 : virtual_operand_live vop_live;
848 : :
849 : 2039585 : int *rpo = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
850 : 2039585 : int n = inverted_rev_post_order_compute (fun, rpo);
851 : 33902807 : for (int i = 0; i < n; ++i)
852 : 31863222 : todo |= sink_code_in_bb (BASIC_BLOCK_FOR_FN (fun, rpo[i]), vop_live);
853 : 2039585 : free (rpo);
854 : :
855 : 2039585 : statistics_counter_event (fun, "Sunk statements", sink_stats.sunk);
856 : 2039585 : statistics_counter_event (fun, "Commoned stores", sink_stats.commoned);
857 : 2039585 : free_dominance_info (CDI_POST_DOMINATORS);
858 : 2039585 : remove_fake_exit_edges ();
859 : 2039585 : loop_optimizer_finalize ();
860 : :
861 : 2039585 : return todo;
862 : 2039585 : }
863 : :
864 : : } // anon namespace
865 : :
866 : : gimple_opt_pass *
867 : 277917 : make_pass_sink_code (gcc::context *ctxt)
868 : : {
869 : 277917 : return new pass_sink_code (ctxt);
870 : : }
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