gccrs: Add get_locus function for abstract class MetaItemInner.
[official-gcc.git] / gcc / tree-ssa-sink.cc
blob87b1d40c174f540d8b1e14956baeb97fbec40852
1 /* Code sinking for trees
2 Copyright (C) 2001-2023 Free Software Foundation, Inc.
3 Contributed by Daniel Berlin <dan@dberlin.org>
5 This file is part of GCC.
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.
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.
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/>. */
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"
39 /* TODO:
40 1. Sinking store only using scalar promotion (IE without moving the RHS):
42 *q = p;
43 p = p + 1;
44 if (something)
45 *q = <not p>;
46 else
47 y = *q;
50 should become
51 sinktemp = p;
52 p = p + 1;
53 if (something)
54 *q = <not p>;
55 else
57 *q = sinktemp;
58 y = *q
60 Store copy propagation will take care of the store elimination above.
63 2. Sinking using Partial Dead Code Elimination. */
66 static struct
68 /* The number of statements sunk down the flowgraph by code sinking. */
69 int sunk;
71 /* The number of stores commoned and sunk down by store commoning. */
72 int commoned;
73 } sink_stats;
76 /* Given a PHI, and one of its arguments (DEF), find the edge for
77 that argument and return it. If the argument occurs twice in the PHI node,
78 we return NULL. */
80 static basic_block
81 find_bb_for_arg (gphi *phi, tree def)
83 size_t i;
84 bool foundone = false;
85 basic_block result = NULL;
86 for (i = 0; i < gimple_phi_num_args (phi); i++)
87 if (PHI_ARG_DEF (phi, i) == def)
89 if (foundone)
90 return NULL;
91 foundone = true;
92 result = gimple_phi_arg_edge (phi, i)->src;
94 return result;
97 /* When the first immediate use is in a statement, then return true if all
98 immediate uses in IMM are in the same statement.
99 We could also do the case where the first immediate use is in a phi node,
100 and all the other uses are in phis in the same basic block, but this
101 requires some expensive checking later (you have to make sure no def/vdef
102 in the statement occurs for multiple edges in the various phi nodes it's
103 used in, so that you only have one place you can sink it to. */
105 static bool
106 all_immediate_uses_same_place (def_operand_p def_p)
108 tree var = DEF_FROM_PTR (def_p);
109 imm_use_iterator imm_iter;
110 use_operand_p use_p;
112 gimple *firstuse = NULL;
113 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
115 if (is_gimple_debug (USE_STMT (use_p)))
116 continue;
117 if (firstuse == NULL)
118 firstuse = USE_STMT (use_p);
119 else
120 if (firstuse != USE_STMT (use_p))
121 return false;
124 return true;
127 /* Find the nearest common dominator of all of the immediate uses in IMM. */
129 static basic_block
130 nearest_common_dominator_of_uses (def_operand_p def_p, bool *debug_stmts)
132 tree var = DEF_FROM_PTR (def_p);
133 auto_bitmap blocks;
134 basic_block commondom;
135 unsigned int j;
136 bitmap_iterator bi;
137 imm_use_iterator imm_iter;
138 use_operand_p use_p;
140 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, var)
142 gimple *usestmt = USE_STMT (use_p);
143 basic_block useblock;
145 if (gphi *phi = dyn_cast <gphi *> (usestmt))
147 int idx = PHI_ARG_INDEX_FROM_USE (use_p);
149 useblock = gimple_phi_arg_edge (phi, idx)->src;
151 else if (is_gimple_debug (usestmt))
153 *debug_stmts = true;
154 continue;
156 else
158 useblock = gimple_bb (usestmt);
161 /* Short circuit. Nothing dominates the entry block. */
162 if (useblock == ENTRY_BLOCK_PTR_FOR_FN (cfun))
163 return NULL;
165 bitmap_set_bit (blocks, useblock->index);
167 commondom = BASIC_BLOCK_FOR_FN (cfun, bitmap_first_set_bit (blocks));
168 EXECUTE_IF_SET_IN_BITMAP (blocks, 0, j, bi)
169 commondom = nearest_common_dominator (CDI_DOMINATORS, commondom,
170 BASIC_BLOCK_FOR_FN (cfun, j));
171 return commondom;
174 /* Given EARLY_BB and LATE_BB, two blocks in a path through the dominator
175 tree, return the best basic block between them (inclusive) to place
176 statements.
178 We want the most control dependent block in the shallowest loop nest.
180 If the resulting block is in a shallower loop nest, then use it. Else
181 only use the resulting block if it has significantly lower execution
182 frequency than EARLY_BB to avoid gratuitous statement movement. We
183 consider statements with VOPS more desirable to move.
185 This pass would obviously benefit from PDO as it utilizes block
186 frequencies. It would also benefit from recomputing frequencies
187 if profile data is not available since frequencies often get out
188 of sync with reality. */
190 static basic_block
191 select_best_block (basic_block early_bb,
192 basic_block late_bb,
193 gimple *stmt)
195 basic_block best_bb = late_bb;
196 basic_block temp_bb = late_bb;
197 int threshold;
199 while (temp_bb != early_bb)
201 /* If we've moved into a lower loop nest, then that becomes
202 our best block. */
203 if (bb_loop_depth (temp_bb) < bb_loop_depth (best_bb))
204 best_bb = temp_bb;
206 /* Walk up the dominator tree, hopefully we'll find a shallower
207 loop nest. */
208 temp_bb = get_immediate_dominator (CDI_DOMINATORS, temp_bb);
211 /* Placing a statement before a setjmp-like function would be invalid
212 (it cannot be reevaluated when execution follows an abnormal edge).
213 If we selected a block with abnormal predecessors, just punt. */
214 if (bb_has_abnormal_pred (best_bb))
215 return early_bb;
217 /* If we found a shallower loop nest, then we always consider that
218 a win. This will always give us the most control dependent block
219 within that loop nest. */
220 if (bb_loop_depth (best_bb) < bb_loop_depth (early_bb))
221 return best_bb;
223 /* Get the sinking threshold. If the statement to be moved has memory
224 operands, then increase the threshold by 7% as those are even more
225 profitable to avoid, clamping at 100%. */
226 threshold = param_sink_frequency_threshold;
227 if (gimple_vuse (stmt) || gimple_vdef (stmt))
229 threshold += 7;
230 if (threshold > 100)
231 threshold = 100;
234 /* If BEST_BB is at the same nesting level, then require it to have
235 significantly lower execution frequency to avoid gratuitous movement. */
236 if (bb_loop_depth (best_bb) == bb_loop_depth (early_bb)
237 /* If result of comparsion is unknown, prefer EARLY_BB.
238 Thus use !(...>=..) rather than (...<...) */
239 && !(best_bb->count * 100 >= early_bb->count * threshold))
240 return best_bb;
242 /* No better block found, so return EARLY_BB, which happens to be the
243 statement's original block. */
244 return early_bb;
247 /* Given a statement (STMT) and the basic block it is currently in (FROMBB),
248 determine the location to sink the statement to, if any.
249 Returns true if there is such location; in that case, TOGSI points to the
250 statement before that STMT should be moved. */
252 static bool
253 statement_sink_location (gimple *stmt, basic_block frombb,
254 gimple_stmt_iterator *togsi, bool *zero_uses_p)
256 gimple *use;
257 use_operand_p one_use = NULL_USE_OPERAND_P;
258 basic_block sinkbb;
259 use_operand_p use_p;
260 def_operand_p def_p;
261 ssa_op_iter iter;
262 imm_use_iterator imm_iter;
264 *zero_uses_p = false;
266 /* We only can sink assignments and const/pure calls that are guaranteed
267 to return exactly once. */
268 int cf;
269 if (!is_gimple_assign (stmt)
270 && (!is_gimple_call (stmt)
271 || !((cf = gimple_call_flags (stmt)) & (ECF_CONST|ECF_PURE))
272 || (cf & (ECF_LOOPING_CONST_OR_PURE|ECF_RETURNS_TWICE))))
273 return false;
275 /* We only can sink stmts with a single definition. */
276 def_p = single_ssa_def_operand (stmt, SSA_OP_ALL_DEFS);
277 if (def_p == NULL_DEF_OPERAND_P)
278 return false;
280 /* There are a few classes of things we can't or don't move, some because we
281 don't have code to handle it, some because it's not profitable and some
282 because it's not legal.
284 We can't sink things that may be global stores, at least not without
285 calculating a lot more information, because we may cause it to no longer
286 be seen by an external routine that needs it depending on where it gets
287 moved to.
289 We can't sink statements that end basic blocks without splitting the
290 incoming edge for the sink location to place it there.
292 We can't sink statements that have volatile operands.
294 We don't want to sink dead code, so anything with 0 immediate uses is not
295 sunk.
297 Don't sink BLKmode assignments if current function has any local explicit
298 register variables, as BLKmode assignments may involve memcpy or memset
299 calls or, on some targets, inline expansion thereof that sometimes need
300 to use specific hard registers.
303 if (stmt_ends_bb_p (stmt)
304 || gimple_has_side_effects (stmt)
305 || (cfun->has_local_explicit_reg_vars
306 && TYPE_MODE (TREE_TYPE (gimple_get_lhs (stmt))) == BLKmode))
307 return false;
309 /* Return if there are no immediate uses of this stmt. */
310 if (has_zero_uses (DEF_FROM_PTR (def_p)))
312 *zero_uses_p = true;
313 return false;
316 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (DEF_FROM_PTR (def_p)))
317 return false;
319 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
321 tree use = USE_FROM_PTR (use_p);
322 if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (use))
323 return false;
326 use = NULL;
328 /* If stmt is a store the one and only use needs to be the VOP
329 merging PHI node. */
330 if (virtual_operand_p (DEF_FROM_PTR (def_p)))
332 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, DEF_FROM_PTR (def_p))
334 gimple *use_stmt = USE_STMT (use_p);
336 /* A killing definition is not a use. */
337 if ((gimple_has_lhs (use_stmt)
338 && operand_equal_p (gimple_get_lhs (stmt),
339 gimple_get_lhs (use_stmt), 0))
340 || stmt_kills_ref_p (use_stmt, gimple_get_lhs (stmt)))
342 /* If use_stmt is or might be a nop assignment then USE_STMT
343 acts as a use as well as definition. */
344 if (stmt != use_stmt
345 && ref_maybe_used_by_stmt_p (use_stmt,
346 gimple_get_lhs (stmt)))
347 return false;
348 continue;
351 if (gimple_code (use_stmt) != GIMPLE_PHI)
352 return false;
354 if (use
355 && use != use_stmt)
356 return false;
358 use = use_stmt;
360 if (!use)
361 return false;
363 /* If all the immediate uses are not in the same place, find the nearest
364 common dominator of all the immediate uses. For PHI nodes, we have to
365 find the nearest common dominator of all of the predecessor blocks, since
366 that is where insertion would have to take place. */
367 else if (gimple_vuse (stmt)
368 || !all_immediate_uses_same_place (def_p))
370 bool debug_stmts = false;
371 basic_block commondom = nearest_common_dominator_of_uses (def_p,
372 &debug_stmts);
374 if (commondom == frombb)
375 return false;
377 /* If this is a load then do not sink past any stores.
378 Look for virtual definitions in the path from frombb to the sink
379 location computed from the real uses and if found, adjust
380 that it a common dominator. */
381 if (gimple_vuse (stmt))
383 /* Do not sink loads from hard registers. */
384 if (gimple_assign_single_p (stmt)
385 && TREE_CODE (gimple_assign_rhs1 (stmt)) == VAR_DECL
386 && DECL_HARD_REGISTER (gimple_assign_rhs1 (stmt)))
387 return false;
389 imm_use_iterator imm_iter;
390 use_operand_p use_p;
391 FOR_EACH_IMM_USE_FAST (use_p, imm_iter, gimple_vuse (stmt))
393 gimple *use_stmt = USE_STMT (use_p);
394 basic_block bb = gimple_bb (use_stmt);
395 /* For PHI nodes the block we know sth about is the incoming block
396 with the use. */
397 if (gimple_code (use_stmt) == GIMPLE_PHI)
399 /* If the PHI defines the virtual operand, ignore it. */
400 if (gimple_phi_result (use_stmt) == gimple_vuse (stmt))
401 continue;
402 /* In case the PHI node post-dominates the current insert
403 location we can disregard it. But make sure it is not
404 dominating it as well as can happen in a CFG cycle. */
405 if (commondom != bb
406 && !dominated_by_p (CDI_DOMINATORS, commondom, bb)
407 && dominated_by_p (CDI_POST_DOMINATORS, commondom, bb)
408 /* If the blocks are possibly within the same irreducible
409 cycle the above check breaks down. */
410 && !((bb->flags & commondom->flags & BB_IRREDUCIBLE_LOOP)
411 && bb->loop_father == commondom->loop_father)
412 && !((commondom->flags & BB_IRREDUCIBLE_LOOP)
413 && flow_loop_nested_p (commondom->loop_father,
414 bb->loop_father))
415 && !((bb->flags & BB_IRREDUCIBLE_LOOP)
416 && flow_loop_nested_p (bb->loop_father,
417 commondom->loop_father)))
418 continue;
419 bb = EDGE_PRED (bb, PHI_ARG_INDEX_FROM_USE (use_p))->src;
421 else if (!gimple_vdef (use_stmt))
422 continue;
423 /* If the use is not dominated by the path entry it is not on
424 the path. */
425 if (!dominated_by_p (CDI_DOMINATORS, bb, frombb))
426 continue;
427 /* There is no easy way to disregard defs not on the path from
428 frombb to commondom so just consider them all. */
429 commondom = nearest_common_dominator (CDI_DOMINATORS,
430 bb, commondom);
431 if (commondom == frombb)
432 return false;
436 /* Our common dominator has to be dominated by frombb in order to be a
437 trivially safe place to put this statement, since it has multiple
438 uses. */
439 if (!dominated_by_p (CDI_DOMINATORS, commondom, frombb))
440 return false;
442 commondom = select_best_block (frombb, commondom, stmt);
444 if (commondom == frombb)
445 return false;
447 *togsi = gsi_after_labels (commondom);
449 return true;
451 else
453 FOR_EACH_IMM_USE_FAST (one_use, imm_iter, DEF_FROM_PTR (def_p))
455 if (is_gimple_debug (USE_STMT (one_use)))
456 continue;
457 break;
459 use = USE_STMT (one_use);
461 if (gimple_code (use) != GIMPLE_PHI)
463 sinkbb = select_best_block (frombb, gimple_bb (use), stmt);
465 if (sinkbb == frombb)
466 return false;
468 if (sinkbb == gimple_bb (use))
469 *togsi = gsi_for_stmt (use);
470 else
471 *togsi = gsi_after_labels (sinkbb);
473 return true;
477 sinkbb = find_bb_for_arg (as_a <gphi *> (use), DEF_FROM_PTR (def_p));
479 /* This can happen if there are multiple uses in a PHI. */
480 if (!sinkbb)
481 return false;
483 sinkbb = select_best_block (frombb, sinkbb, stmt);
484 if (!sinkbb || sinkbb == frombb)
485 return false;
487 /* If the latch block is empty, don't make it non-empty by sinking
488 something into it. */
489 if (sinkbb == frombb->loop_father->latch
490 && empty_block_p (sinkbb))
491 return false;
493 *togsi = gsi_after_labels (sinkbb);
495 return true;
498 /* Very simplistic code to sink common stores from the predecessor through
499 our virtual PHI. We do this before sinking stmts from BB as it might
500 expose sinking opportunities of the merged stores.
501 Once we have partial dead code elimination through sth like SSU-PRE this
502 should be moved there. */
504 static unsigned
505 sink_common_stores_to_bb (basic_block bb)
507 unsigned todo = 0;
508 gphi *phi;
510 if (EDGE_COUNT (bb->preds) > 1
511 && (phi = get_virtual_phi (bb)))
513 /* Repeat until no more common stores are found. */
514 while (1)
516 gimple *first_store = NULL;
517 auto_vec <tree, 5> vdefs;
518 gimple_stmt_iterator gsi;
520 /* Search for common stores defined by all virtual PHI args.
521 ??? Common stores not present in all predecessors could
522 be handled by inserting a forwarder to sink to. Generally
523 this involves deciding which stores to do this for if
524 multiple common stores are present for different sets of
525 predecessors. See PR11832 for an interesting case. */
526 for (unsigned i = 0; i < gimple_phi_num_args (phi); ++i)
528 tree arg = gimple_phi_arg_def (phi, i);
529 gimple *def = SSA_NAME_DEF_STMT (arg);
530 if (! is_gimple_assign (def)
531 || stmt_can_throw_internal (cfun, def)
532 || (gimple_phi_arg_edge (phi, i)->flags & EDGE_ABNORMAL))
534 /* ??? We could handle some cascading with the def being
535 another PHI. We'd have to insert multiple PHIs for
536 the rhs then though (if they are not all equal). */
537 first_store = NULL;
538 break;
540 /* ??? Do not try to do anything fancy with aliasing, thus
541 do not sink across non-aliased loads (or even stores,
542 so different store order will make the sinking fail). */
543 bool all_uses_on_phi = true;
544 imm_use_iterator iter;
545 use_operand_p use_p;
546 FOR_EACH_IMM_USE_FAST (use_p, iter, arg)
547 if (USE_STMT (use_p) != phi)
549 all_uses_on_phi = false;
550 break;
552 if (! all_uses_on_phi)
554 first_store = NULL;
555 break;
557 /* Check all stores are to the same LHS. */
558 if (! first_store)
559 first_store = def;
560 /* ??? We could handle differing SSA uses in the LHS by inserting
561 PHIs for them. */
562 else if (! operand_equal_p (gimple_assign_lhs (first_store),
563 gimple_assign_lhs (def), 0)
564 || (gimple_clobber_p (first_store)
565 != gimple_clobber_p (def)))
567 first_store = NULL;
568 break;
570 vdefs.safe_push (arg);
572 if (! first_store)
573 break;
575 /* Check if we need a PHI node to merge the stored values. */
576 bool allsame = true;
577 if (!gimple_clobber_p (first_store))
578 for (unsigned i = 1; i < vdefs.length (); ++i)
580 gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
581 if (! operand_equal_p (gimple_assign_rhs1 (first_store),
582 gimple_assign_rhs1 (def), 0))
584 allsame = false;
585 break;
589 /* We cannot handle aggregate values if we need to merge them. */
590 tree type = TREE_TYPE (gimple_assign_lhs (first_store));
591 if (! allsame
592 && ! is_gimple_reg_type (type))
593 break;
595 if (dump_enabled_p ())
597 dump_printf_loc (MSG_OPTIMIZED_LOCATIONS,
598 first_store,
599 "sinking common stores %sto ",
600 allsame ? "with same value " : "");
601 dump_generic_expr (MSG_OPTIMIZED_LOCATIONS, TDF_SLIM,
602 gimple_assign_lhs (first_store));
603 dump_printf (MSG_OPTIMIZED_LOCATIONS, "\n");
606 /* Insert a PHI to merge differing stored values if necessary.
607 Note that in general inserting PHIs isn't a very good idea as
608 it makes the job of coalescing and register allocation harder.
609 Even common SSA uses on the rhs/lhs might extend their lifetime
610 across multiple edges by this code motion which makes
611 register allocation harder. */
612 tree from;
613 if (! allsame)
615 from = make_ssa_name (type);
616 gphi *newphi = create_phi_node (from, bb);
617 for (unsigned i = 0; i < vdefs.length (); ++i)
619 gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
620 add_phi_arg (newphi, gimple_assign_rhs1 (def),
621 EDGE_PRED (bb, i), UNKNOWN_LOCATION);
624 else
625 from = gimple_assign_rhs1 (first_store);
627 /* Remove all stores. */
628 for (unsigned i = 0; i < vdefs.length (); ++i)
629 TREE_VISITED (vdefs[i]) = 1;
630 for (unsigned i = 0; i < vdefs.length (); ++i)
631 /* If we have more than one use of a VDEF on the PHI make sure
632 we remove the defining stmt only once. */
633 if (TREE_VISITED (vdefs[i]))
635 TREE_VISITED (vdefs[i]) = 0;
636 gimple *def = SSA_NAME_DEF_STMT (vdefs[i]);
637 gsi = gsi_for_stmt (def);
638 unlink_stmt_vdef (def);
639 gsi_remove (&gsi, true);
640 release_defs (def);
643 /* Insert the first store at the beginning of the merge BB. */
644 gimple_set_vdef (first_store, gimple_phi_result (phi));
645 SSA_NAME_DEF_STMT (gimple_vdef (first_store)) = first_store;
646 gimple_phi_set_result (phi, make_ssa_name (gimple_vop (cfun)));
647 gimple_set_vuse (first_store, gimple_phi_result (phi));
648 gimple_assign_set_rhs1 (first_store, from);
649 /* ??? Should we reset first_stores location? */
650 gsi = gsi_after_labels (bb);
651 gsi_insert_before (&gsi, first_store, GSI_SAME_STMT);
652 sink_stats.commoned++;
654 todo |= TODO_cleanup_cfg;
657 /* We could now have empty predecessors that we could remove,
658 forming a proper CFG for further sinking. Note that even
659 CFG cleanup doesn't do this fully at the moment and it
660 doesn't preserve post-dominators in the process either.
661 The mergephi pass might do it though. gcc.dg/tree-ssa/ssa-sink-13.c
662 shows this nicely if you disable tail merging or (same effect)
663 make the stored values unequal. */
666 return todo;
669 /* Perform code sinking on BB */
671 static unsigned
672 sink_code_in_bb (basic_block bb)
674 basic_block son;
675 gimple_stmt_iterator gsi;
676 edge_iterator ei;
677 edge e;
678 bool last = true;
679 unsigned todo = 0;
681 /* Sink common stores from the predecessor through our virtual PHI. */
682 todo |= sink_common_stores_to_bb (bb);
684 /* If this block doesn't dominate anything, there can't be any place to sink
685 the statements to. */
686 if (first_dom_son (CDI_DOMINATORS, bb) == NULL)
687 goto earlyout;
689 /* We can't move things across abnormal edges, so don't try. */
690 FOR_EACH_EDGE (e, ei, bb->succs)
691 if (e->flags & EDGE_ABNORMAL)
692 goto earlyout;
694 for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
696 gimple *stmt = gsi_stmt (gsi);
697 gimple_stmt_iterator togsi;
698 bool zero_uses_p;
700 if (!statement_sink_location (stmt, bb, &togsi, &zero_uses_p))
702 gimple_stmt_iterator saved = gsi;
703 if (!gsi_end_p (gsi))
704 gsi_prev (&gsi);
705 /* If we face a dead stmt remove it as it possibly blocks
706 sinking of uses. */
707 if (zero_uses_p
708 && !gimple_vdef (stmt)
709 && (cfun->can_delete_dead_exceptions
710 || !stmt_could_throw_p (cfun, stmt)))
712 gsi_remove (&saved, true);
713 release_defs (stmt);
715 else
716 last = false;
717 continue;
719 if (dump_file)
721 fprintf (dump_file, "Sinking ");
722 print_gimple_stmt (dump_file, stmt, 0, TDF_VOPS);
723 fprintf (dump_file, " from bb %d to bb %d\n",
724 bb->index, (gsi_bb (togsi))->index);
727 /* Update virtual operands of statements in the path we
728 do not sink to. */
729 if (gimple_vdef (stmt))
731 imm_use_iterator iter;
732 use_operand_p use_p;
733 gimple *vuse_stmt;
735 FOR_EACH_IMM_USE_STMT (vuse_stmt, iter, gimple_vdef (stmt))
736 if (gimple_code (vuse_stmt) != GIMPLE_PHI)
737 FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
738 SET_USE (use_p, gimple_vuse (stmt));
741 /* If this is the end of the basic block, we need to insert at the end
742 of the basic block. */
743 if (gsi_end_p (togsi))
744 gsi_move_to_bb_end (&gsi, gsi_bb (togsi));
745 else
746 gsi_move_before (&gsi, &togsi);
748 sink_stats.sunk++;
750 /* If we've just removed the last statement of the BB, the
751 gsi_end_p() test below would fail, but gsi_prev() would have
752 succeeded, and we want it to succeed. So we keep track of
753 whether we're at the last statement and pick up the new last
754 statement. */
755 if (last)
757 gsi = gsi_last_bb (bb);
758 continue;
761 last = false;
762 if (!gsi_end_p (gsi))
763 gsi_prev (&gsi);
766 earlyout:
767 for (son = first_dom_son (CDI_POST_DOMINATORS, bb);
768 son;
769 son = next_dom_son (CDI_POST_DOMINATORS, son))
771 todo |= sink_code_in_bb (son);
774 return todo;
777 /* Perform code sinking.
778 This moves code down the flowgraph when we know it would be
779 profitable to do so, or it wouldn't increase the number of
780 executions of the statement.
782 IE given
784 a_1 = b + c;
785 if (<something>)
788 else
790 foo (&b, &c);
791 a_5 = b + c;
793 a_6 = PHI (a_5, a_1);
794 USE a_6.
796 we'll transform this into:
798 if (<something>)
800 a_1 = b + c;
802 else
804 foo (&b, &c);
805 a_5 = b + c;
807 a_6 = PHI (a_5, a_1);
808 USE a_6.
810 Note that this reduces the number of computations of a = b + c to 1
811 when we take the else edge, instead of 2.
813 namespace {
815 const pass_data pass_data_sink_code =
817 GIMPLE_PASS, /* type */
818 "sink", /* name */
819 OPTGROUP_NONE, /* optinfo_flags */
820 TV_TREE_SINK, /* tv_id */
821 /* PROP_no_crit_edges is ensured by running split_edges_for_insertion in
822 pass_data_sink_code::execute (). */
823 ( PROP_cfg | PROP_ssa ), /* properties_required */
824 0, /* properties_provided */
825 0, /* properties_destroyed */
826 0, /* todo_flags_start */
827 TODO_update_ssa, /* todo_flags_finish */
830 class pass_sink_code : public gimple_opt_pass
832 public:
833 pass_sink_code (gcc::context *ctxt)
834 : gimple_opt_pass (pass_data_sink_code, ctxt), unsplit_edges (false)
837 /* opt_pass methods: */
838 bool gate (function *) final override { return flag_tree_sink != 0; }
839 unsigned int execute (function *) final override;
840 opt_pass *clone (void) final override { return new pass_sink_code (m_ctxt); }
841 void set_pass_param (unsigned n, bool param) final override
843 gcc_assert (n == 0);
844 unsplit_edges = param;
847 private:
848 bool unsplit_edges;
849 }; // class pass_sink_code
851 unsigned int
852 pass_sink_code::execute (function *fun)
854 loop_optimizer_init (LOOPS_NORMAL);
855 split_edges_for_insertion ();
856 /* Arrange for the critical edge splitting to be undone if requested. */
857 unsigned todo = unsplit_edges ? TODO_cleanup_cfg : 0;
858 connect_infinite_loops_to_exit ();
859 memset (&sink_stats, 0, sizeof (sink_stats));
860 calculate_dominance_info (CDI_DOMINATORS);
861 calculate_dominance_info (CDI_POST_DOMINATORS);
862 todo |= sink_code_in_bb (EXIT_BLOCK_PTR_FOR_FN (fun));
863 statistics_counter_event (fun, "Sunk statements", sink_stats.sunk);
864 statistics_counter_event (fun, "Commoned stores", sink_stats.commoned);
865 free_dominance_info (CDI_POST_DOMINATORS);
866 remove_fake_exit_edges ();
867 loop_optimizer_finalize ();
869 return todo;
872 } // anon namespace
874 gimple_opt_pass *
875 make_pass_sink_code (gcc::context *ctxt)
877 return new pass_sink_code (ctxt);