1 /* Loop manipulation code for GNU compiler.
2 Copyright (C) 2002-2013 Free Software Foundation, Inc.
4 This file is part of GCC.
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
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
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/>. */
22 #include "coretypes.h"
25 #include "basic-block.h"
27 #include "tree-flow.h"
30 static void copy_loops_to (struct loop **, int,
32 static void loop_redirect_edge (edge, basic_block);
33 static void remove_bbs (basic_block *, int);
34 static bool rpe_enum_p (const_basic_block, const void *);
35 static int find_path (edge, basic_block **);
36 static void fix_loop_placements (struct loop *, bool *);
37 static bool fix_bb_placement (basic_block);
38 static void fix_bb_placements (basic_block, bool *, bitmap);
40 /* Checks whether basic block BB is dominated by DATA. */
42 rpe_enum_p (const_basic_block bb, const void *data)
44 return dominated_by_p (CDI_DOMINATORS, bb, (const_basic_block) data);
47 /* Remove basic blocks BBS. NBBS is the number of the basic blocks. */
50 remove_bbs (basic_block *bbs, int nbbs)
54 for (i = 0; i < nbbs; i++)
55 delete_basic_block (bbs[i]);
58 /* Find path -- i.e. the basic blocks dominated by edge E and put them
59 into array BBS, that will be allocated large enough to contain them.
60 E->dest must have exactly one predecessor for this to work (it is
61 easy to achieve and we do not put it here because we do not want to
62 alter anything by this function). The number of basic blocks in the
65 find_path (edge e, basic_block **bbs)
67 gcc_assert (EDGE_COUNT (e->dest->preds) <= 1);
69 /* Find bbs in the path. */
70 *bbs = XNEWVEC (basic_block, n_basic_blocks);
71 return dfs_enumerate_from (e->dest, 0, rpe_enum_p, *bbs,
72 n_basic_blocks, e->dest);
75 /* Fix placement of basic block BB inside loop hierarchy --
76 Let L be a loop to that BB belongs. Then every successor of BB must either
77 1) belong to some superloop of loop L, or
78 2) be a header of loop K such that K->outer is superloop of L
79 Returns true if we had to move BB into other loop to enforce this condition,
80 false if the placement of BB was already correct (provided that placements
81 of its successors are correct). */
83 fix_bb_placement (basic_block bb)
87 struct loop *loop = current_loops->tree_root, *act;
89 FOR_EACH_EDGE (e, ei, bb->succs)
91 if (e->dest == EXIT_BLOCK_PTR)
94 act = e->dest->loop_father;
95 if (act->header == e->dest)
96 act = loop_outer (act);
98 if (flow_loop_nested_p (loop, act))
102 if (loop == bb->loop_father)
105 remove_bb_from_loops (bb);
106 add_bb_to_loop (bb, loop);
111 /* Fix placement of LOOP inside loop tree, i.e. find the innermost superloop
112 of LOOP to that leads at least one exit edge of LOOP, and set it
113 as the immediate superloop of LOOP. Return true if the immediate superloop
117 fix_loop_placement (struct loop *loop)
121 vec<edge> exits = get_loop_exit_edges (loop);
122 struct loop *father = current_loops->tree_root, *act;
125 FOR_EACH_VEC_ELT (exits, i, e)
127 act = find_common_loop (loop, e->dest->loop_father);
128 if (flow_loop_nested_p (father, act))
132 if (father != loop_outer (loop))
134 for (act = loop_outer (loop); act != father; act = loop_outer (act))
135 act->num_nodes -= loop->num_nodes;
136 flow_loop_tree_node_remove (loop);
137 flow_loop_tree_node_add (father, loop);
139 /* The exit edges of LOOP no longer exits its original immediate
140 superloops; remove them from the appropriate exit lists. */
141 FOR_EACH_VEC_ELT (exits, i, e)
142 rescan_loop_exit (e, false, false);
151 /* Fix placements of basic blocks inside loop hierarchy stored in loops; i.e.
152 enforce condition condition stated in description of fix_bb_placement. We
153 start from basic block FROM that had some of its successors removed, so that
154 his placement no longer has to be correct, and iteratively fix placement of
155 its predecessors that may change if placement of FROM changed. Also fix
156 placement of subloops of FROM->loop_father, that might also be altered due
157 to this change; the condition for them is similar, except that instead of
158 successors we consider edges coming out of the loops.
160 If the changes may invalidate the information about irreducible regions,
161 IRRED_INVALIDATED is set to true.
163 If LOOP_CLOSED_SSA_INVLIDATED is non-zero then all basic blocks with
164 changed loop_father are collected there. */
167 fix_bb_placements (basic_block from,
168 bool *irred_invalidated,
169 bitmap loop_closed_ssa_invalidated)
172 basic_block *queue, *qtop, *qbeg, *qend;
173 struct loop *base_loop, *target_loop;
176 /* We pass through blocks back-reachable from FROM, testing whether some
177 of their successors moved to outer loop. It may be necessary to
178 iterate several times, but it is finite, as we stop unless we move
179 the basic block up the loop structure. The whole story is a bit
180 more complicated due to presence of subloops, those are moved using
181 fix_loop_placement. */
183 base_loop = from->loop_father;
184 /* If we are already in the outermost loop, the basic blocks cannot be moved
185 outside of it. If FROM is the header of the base loop, it cannot be moved
186 outside of it, either. In both cases, we can end now. */
187 if (base_loop == current_loops->tree_root
188 || from == base_loop->header)
191 in_queue = sbitmap_alloc (last_basic_block);
192 bitmap_clear (in_queue);
193 bitmap_set_bit (in_queue, from->index);
194 /* Prevent us from going out of the base_loop. */
195 bitmap_set_bit (in_queue, base_loop->header->index);
197 queue = XNEWVEC (basic_block, base_loop->num_nodes + 1);
198 qtop = queue + base_loop->num_nodes + 1;
210 bitmap_clear_bit (in_queue, from->index);
212 if (from->loop_father->header == from)
214 /* Subloop header, maybe move the loop upward. */
215 if (!fix_loop_placement (from->loop_father))
217 target_loop = loop_outer (from->loop_father);
221 /* Ordinary basic block. */
222 if (!fix_bb_placement (from))
224 if (loop_closed_ssa_invalidated)
225 bitmap_set_bit (loop_closed_ssa_invalidated, from->index);
226 target_loop = from->loop_father;
229 FOR_EACH_EDGE (e, ei, from->succs)
231 if (e->flags & EDGE_IRREDUCIBLE_LOOP)
232 *irred_invalidated = true;
235 /* Something has changed, insert predecessors into queue. */
236 FOR_EACH_EDGE (e, ei, from->preds)
238 basic_block pred = e->src;
241 if (e->flags & EDGE_IRREDUCIBLE_LOOP)
242 *irred_invalidated = true;
244 if (bitmap_bit_p (in_queue, pred->index))
247 /* If it is subloop, then it either was not moved, or
248 the path up the loop tree from base_loop do not contain
250 nca = find_common_loop (pred->loop_father, base_loop);
251 if (pred->loop_father != base_loop
253 || nca != pred->loop_father))
254 pred = pred->loop_father->header;
255 else if (!flow_loop_nested_p (target_loop, pred->loop_father))
257 /* If PRED is already higher in the loop hierarchy than the
258 TARGET_LOOP to that we moved FROM, the change of the position
259 of FROM does not affect the position of PRED, so there is no
260 point in processing it. */
264 if (bitmap_bit_p (in_queue, pred->index))
267 /* Schedule the basic block. */
272 bitmap_set_bit (in_queue, pred->index);
279 /* Removes path beginning at edge E, i.e. remove basic blocks dominated by E
280 and update loop structures and dominators. Return true if we were able
281 to remove the path, false otherwise (and nothing is affected then). */
286 basic_block *rem_bbs, *bord_bbs, from, bb;
287 vec<basic_block> dom_bbs;
288 int i, nrem, n_bord_bbs;
290 bool irred_invalidated = false;
294 if (!can_remove_branch_p (e))
297 /* Keep track of whether we need to update information about irreducible
298 regions. This is the case if the removed area is a part of the
299 irreducible region, or if the set of basic blocks that belong to a loop
300 that is inside an irreducible region is changed, or if such a loop is
302 if (e->flags & EDGE_IRREDUCIBLE_LOOP)
303 irred_invalidated = true;
305 /* We need to check whether basic blocks are dominated by the edge
306 e, but we only have basic block dominators. This is easy to
307 fix -- when e->dest has exactly one predecessor, this corresponds
308 to blocks dominated by e->dest, if not, split the edge. */
309 if (!single_pred_p (e->dest))
310 e = single_pred_edge (split_edge (e));
312 /* It may happen that by removing path we remove one or more loops
313 we belong to. In this case first unloop the loops, then proceed
314 normally. We may assume that e->dest is not a header of any loop,
315 as it now has exactly one predecessor. */
316 for (l = e->src->loop_father; loop_outer (l); l = f)
319 if (dominated_by_p (CDI_DOMINATORS, l->latch, e->dest))
320 unloop (l, &irred_invalidated, NULL);
323 /* Identify the path. */
324 nrem = find_path (e, &rem_bbs);
327 bord_bbs = XNEWVEC (basic_block, n_basic_blocks);
328 seen = sbitmap_alloc (last_basic_block);
331 /* Find "border" hexes -- i.e. those with predecessor in removed path. */
332 for (i = 0; i < nrem; i++)
333 bitmap_set_bit (seen, rem_bbs[i]->index);
334 if (!irred_invalidated)
335 FOR_EACH_EDGE (ae, ei, e->src->succs)
336 if (ae != e && ae->dest != EXIT_BLOCK_PTR && !bitmap_bit_p (seen, ae->dest->index)
337 && ae->flags & EDGE_IRREDUCIBLE_LOOP)
338 irred_invalidated = true;
339 for (i = 0; i < nrem; i++)
342 FOR_EACH_EDGE (ae, ei, rem_bbs[i]->succs)
343 if (ae->dest != EXIT_BLOCK_PTR && !bitmap_bit_p (seen, ae->dest->index))
345 bitmap_set_bit (seen, ae->dest->index);
346 bord_bbs[n_bord_bbs++] = ae->dest;
348 if (ae->flags & EDGE_IRREDUCIBLE_LOOP)
349 irred_invalidated = true;
353 /* Remove the path. */
358 /* Cancel loops contained in the path. */
359 for (i = 0; i < nrem; i++)
360 if (rem_bbs[i]->loop_father->header == rem_bbs[i])
361 cancel_loop_tree (rem_bbs[i]->loop_father);
363 remove_bbs (rem_bbs, nrem);
366 /* Find blocks whose dominators may be affected. */
368 for (i = 0; i < n_bord_bbs; i++)
372 bb = get_immediate_dominator (CDI_DOMINATORS, bord_bbs[i]);
373 if (bitmap_bit_p (seen, bb->index))
375 bitmap_set_bit (seen, bb->index);
377 for (ldom = first_dom_son (CDI_DOMINATORS, bb);
379 ldom = next_dom_son (CDI_DOMINATORS, ldom))
380 if (!dominated_by_p (CDI_DOMINATORS, from, ldom))
381 dom_bbs.safe_push (ldom);
386 /* Recount dominators. */
387 iterate_fix_dominators (CDI_DOMINATORS, dom_bbs, true);
391 /* Fix placements of basic blocks inside loops and the placement of
392 loops in the loop tree. */
393 fix_bb_placements (from, &irred_invalidated, NULL);
394 fix_loop_placements (from->loop_father, &irred_invalidated);
396 if (irred_invalidated
397 && loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS))
398 mark_irreducible_loops ();
403 /* Creates place for a new LOOP in loops structure. */
406 place_new_loop (struct loop *loop)
408 loop->num = number_of_loops ();
409 vec_safe_push (current_loops->larray, loop);
412 /* Given LOOP structure with filled header and latch, find the body of the
413 corresponding loop and add it to loops tree. Insert the LOOP as a son of
417 add_loop (struct loop *loop, struct loop *outer)
421 struct loop *subloop;
425 /* Add it to loop structure. */
426 place_new_loop (loop);
427 flow_loop_tree_node_add (outer, loop);
429 /* Find its nodes. */
430 bbs = XNEWVEC (basic_block, n_basic_blocks);
431 n = get_loop_body_with_size (loop, bbs, n_basic_blocks);
433 for (i = 0; i < n; i++)
435 if (bbs[i]->loop_father == outer)
437 remove_bb_from_loops (bbs[i]);
438 add_bb_to_loop (bbs[i], loop);
444 /* If we find a direct subloop of OUTER, move it to LOOP. */
445 subloop = bbs[i]->loop_father;
446 if (loop_outer (subloop) == outer
447 && subloop->header == bbs[i])
449 flow_loop_tree_node_remove (subloop);
450 flow_loop_tree_node_add (loop, subloop);
454 /* Update the information about loop exit edges. */
455 for (i = 0; i < n; i++)
457 FOR_EACH_EDGE (e, ei, bbs[i]->succs)
459 rescan_loop_exit (e, false, false);
466 /* Multiply all frequencies in LOOP by NUM/DEN. */
469 scale_loop_frequencies (struct loop *loop, int num, int den)
473 bbs = get_loop_body (loop);
474 scale_bbs_frequencies_int (bbs, loop->num_nodes, num, den);
478 /* Multiply all frequencies in LOOP by SCALE/REG_BR_PROB_BASE.
479 If ITERATION_BOUND is non-zero, scale even further if loop is predicted
480 to iterate too many times. */
483 scale_loop_profile (struct loop *loop, int scale, gcov_type iteration_bound)
485 gcov_type iterations = expected_loop_iterations_unbounded (loop);
489 if (dump_file && (dump_flags & TDF_DETAILS))
490 fprintf (dump_file, ";; Scaling loop %i with scale %f, "
491 "bounding iterations to %i from guessed %i\n",
492 loop->num, (double)scale / REG_BR_PROB_BASE,
493 (int)iteration_bound, (int)iterations);
495 /* See if loop is predicted to iterate too many times. */
496 if (iteration_bound && iterations > 0
497 && RDIV (iterations * scale, REG_BR_PROB_BASE) > iteration_bound)
499 /* Fixing loop profile for different trip count is not trivial; the exit
500 probabilities has to be updated to match and frequencies propagated down
503 We fully update only the simple case of loop with single exit that is
504 either from the latch or BB just before latch and leads from BB with
505 simple conditional jump. This is OK for use in vectorizer. */
506 e = single_exit (loop);
511 gcov_type count_delta;
513 FOR_EACH_EDGE (other_e, ei, e->src->succs)
514 if (!(other_e->flags & (EDGE_ABNORMAL | EDGE_FAKE))
518 /* Probability of exit must be 1/iterations. */
519 freq_delta = EDGE_FREQUENCY (e);
520 e->probability = REG_BR_PROB_BASE / iteration_bound;
521 other_e->probability = inverse_probability (e->probability);
522 freq_delta -= EDGE_FREQUENCY (e);
524 /* Adjust counts accordingly. */
525 count_delta = e->count;
526 e->count = apply_probability (e->src->count, e->probability);
527 other_e->count = apply_probability (e->src->count, other_e->probability);
528 count_delta -= e->count;
530 /* If latch exists, change its frequency and count, since we changed
531 probability of exit. Theoretically we should update everything from
532 source of exit edge to latch, but for vectorizer this is enough. */
534 && loop->latch != e->src)
536 loop->latch->frequency += freq_delta;
537 if (loop->latch->frequency < 0)
538 loop->latch->frequency = 0;
539 loop->latch->count += count_delta;
540 if (loop->latch->count < 0)
541 loop->latch->count = 0;
545 /* Roughly speaking we want to reduce the loop body profile by the
546 the difference of loop iterations. We however can do better if
547 we look at the actual profile, if it is available. */
548 scale = RDIV (iteration_bound * scale, iterations);
549 if (loop->header->count)
551 gcov_type count_in = 0;
553 FOR_EACH_EDGE (e, ei, loop->header->preds)
554 if (e->src != loop->latch)
555 count_in += e->count;
558 scale = RDIV (count_in * iteration_bound * REG_BR_PROB_BASE, loop->header->count);
560 else if (loop->header->frequency)
564 FOR_EACH_EDGE (e, ei, loop->header->preds)
565 if (e->src != loop->latch)
566 freq_in += EDGE_FREQUENCY (e);
569 scale = RDIV (freq_in * iteration_bound * REG_BR_PROB_BASE, loop->header->frequency);
575 if (scale == REG_BR_PROB_BASE)
578 /* Scale the actual probabilities. */
579 scale_loop_frequencies (loop, scale, REG_BR_PROB_BASE);
580 if (dump_file && (dump_flags & TDF_DETAILS))
581 fprintf (dump_file, ";; guessed iterations are now %i\n",
582 (int)expected_loop_iterations_unbounded (loop));
585 /* Recompute dominance information for basic blocks outside LOOP. */
588 update_dominators_in_loop (struct loop *loop)
590 vec<basic_block> dom_bbs = vNULL;
595 seen = sbitmap_alloc (last_basic_block);
597 body = get_loop_body (loop);
599 for (i = 0; i < loop->num_nodes; i++)
600 bitmap_set_bit (seen, body[i]->index);
602 for (i = 0; i < loop->num_nodes; i++)
606 for (ldom = first_dom_son (CDI_DOMINATORS, body[i]);
608 ldom = next_dom_son (CDI_DOMINATORS, ldom))
609 if (!bitmap_bit_p (seen, ldom->index))
611 bitmap_set_bit (seen, ldom->index);
612 dom_bbs.safe_push (ldom);
616 iterate_fix_dominators (CDI_DOMINATORS, dom_bbs, false);
622 /* Creates an if region as shown above. CONDITION is used to create
626 | ------------- -------------
627 | | pred_bb | | pred_bb |
628 | ------------- -------------
632 | | ====> -------------
637 | ------------- e_false / \ e_true
639 | ------------- ----------- -----------
640 | | false_bb | | true_bb |
641 | ----------- -----------
648 | | exit_edge (result)
657 create_empty_if_region_on_edge (edge entry_edge, tree condition)
660 basic_block cond_bb, true_bb, false_bb, join_bb;
661 edge e_true, e_false, exit_edge;
664 gimple_stmt_iterator gsi;
666 cond_bb = split_edge (entry_edge);
668 /* Insert condition in cond_bb. */
669 gsi = gsi_last_bb (cond_bb);
671 force_gimple_operand_gsi (&gsi, condition, true, NULL,
672 false, GSI_NEW_STMT);
673 cond_stmt = gimple_build_cond_from_tree (simple_cond, NULL_TREE, NULL_TREE);
674 gsi = gsi_last_bb (cond_bb);
675 gsi_insert_after (&gsi, cond_stmt, GSI_NEW_STMT);
677 join_bb = split_edge (single_succ_edge (cond_bb));
679 e_true = single_succ_edge (cond_bb);
680 true_bb = split_edge (e_true);
682 e_false = make_edge (cond_bb, join_bb, 0);
683 false_bb = split_edge (e_false);
685 e_true->flags &= ~EDGE_FALLTHRU;
686 e_true->flags |= EDGE_TRUE_VALUE;
687 e_false->flags &= ~EDGE_FALLTHRU;
688 e_false->flags |= EDGE_FALSE_VALUE;
690 set_immediate_dominator (CDI_DOMINATORS, cond_bb, entry_edge->src);
691 set_immediate_dominator (CDI_DOMINATORS, true_bb, cond_bb);
692 set_immediate_dominator (CDI_DOMINATORS, false_bb, cond_bb);
693 set_immediate_dominator (CDI_DOMINATORS, join_bb, cond_bb);
695 exit_edge = single_succ_edge (join_bb);
697 if (single_pred_p (exit_edge->dest))
698 set_immediate_dominator (CDI_DOMINATORS, exit_edge->dest, join_bb);
703 /* create_empty_loop_on_edge
705 | - pred_bb - ------ pred_bb ------
706 | | | | iv0 = initial_value |
707 | -----|----- ---------|-----------
708 | | ______ | entry_edge
710 | | ====> | -V---V- loop_header -------------
711 | V | | iv_before = phi (iv0, iv_after) |
712 | - succ_bb - | ---|-----------------------------
714 | ----------- | ---V--- loop_body ---------------
715 | | | iv_after = iv_before + stride |
716 | | | if (iv_before < upper_bound) |
717 | | ---|--------------\--------------
720 | | - loop_latch - V- succ_bb -
722 | | /------------- -----------
725 Creates an empty loop as shown above, the IV_BEFORE is the SSA_NAME
726 that is used before the increment of IV. IV_BEFORE should be used for
727 adding code to the body that uses the IV. OUTER is the outer loop in
728 which the new loop should be inserted.
730 Both INITIAL_VALUE and UPPER_BOUND expressions are gimplified and
731 inserted on the loop entry edge. This implies that this function
732 should be used only when the UPPER_BOUND expression is a loop
736 create_empty_loop_on_edge (edge entry_edge,
738 tree stride, tree upper_bound,
744 basic_block loop_header, loop_latch, succ_bb, pred_bb;
746 gimple_stmt_iterator gsi;
753 gcc_assert (entry_edge && initial_value && stride && upper_bound && iv);
755 /* Create header, latch and wire up the loop. */
756 pred_bb = entry_edge->src;
757 loop_header = split_edge (entry_edge);
758 loop_latch = split_edge (single_succ_edge (loop_header));
759 succ_bb = single_succ (loop_latch);
760 make_edge (loop_header, succ_bb, 0);
761 redirect_edge_succ_nodup (single_succ_edge (loop_latch), loop_header);
763 /* Set immediate dominator information. */
764 set_immediate_dominator (CDI_DOMINATORS, loop_header, pred_bb);
765 set_immediate_dominator (CDI_DOMINATORS, loop_latch, loop_header);
766 set_immediate_dominator (CDI_DOMINATORS, succ_bb, loop_header);
768 /* Initialize a loop structure and put it in a loop hierarchy. */
769 loop = alloc_loop ();
770 loop->header = loop_header;
771 loop->latch = loop_latch;
772 add_loop (loop, outer);
774 /* TODO: Fix frequencies and counts. */
775 prob = REG_BR_PROB_BASE / 2;
777 scale_loop_frequencies (loop, REG_BR_PROB_BASE - prob, REG_BR_PROB_BASE);
779 /* Update dominators. */
780 update_dominators_in_loop (loop);
782 /* Modify edge flags. */
783 exit_e = single_exit (loop);
784 exit_e->flags = EDGE_LOOP_EXIT | EDGE_FALSE_VALUE;
785 single_pred_edge (loop_latch)->flags = EDGE_TRUE_VALUE;
787 /* Construct IV code in loop. */
788 initial_value = force_gimple_operand (initial_value, &stmts, true, iv);
791 gsi_insert_seq_on_edge (loop_preheader_edge (loop), stmts);
792 gsi_commit_edge_inserts ();
795 upper_bound = force_gimple_operand (upper_bound, &stmts, true, NULL);
798 gsi_insert_seq_on_edge (loop_preheader_edge (loop), stmts);
799 gsi_commit_edge_inserts ();
802 gsi = gsi_last_bb (loop_header);
803 create_iv (initial_value, stride, iv, loop, &gsi, false,
804 iv_before, iv_after);
806 /* Insert loop exit condition. */
807 cond_expr = gimple_build_cond
808 (LT_EXPR, *iv_before, upper_bound, NULL_TREE, NULL_TREE);
810 exit_test = gimple_cond_lhs (cond_expr);
811 exit_test = force_gimple_operand_gsi (&gsi, exit_test, true, NULL,
812 false, GSI_NEW_STMT);
813 gimple_cond_set_lhs (cond_expr, exit_test);
814 gsi = gsi_last_bb (exit_e->src);
815 gsi_insert_after (&gsi, cond_expr, GSI_NEW_STMT);
817 split_block_after_labels (loop_header);
822 /* Make area between HEADER_EDGE and LATCH_EDGE a loop by connecting
823 latch to header and update loop tree and dominators
824 accordingly. Everything between them plus LATCH_EDGE destination must
825 be dominated by HEADER_EDGE destination, and back-reachable from
826 LATCH_EDGE source. HEADER_EDGE is redirected to basic block SWITCH_BB,
827 FALSE_EDGE of SWITCH_BB to original destination of HEADER_EDGE and
828 TRUE_EDGE of SWITCH_BB to original destination of LATCH_EDGE.
829 Returns the newly created loop. Frequencies and counts in the new loop
830 are scaled by FALSE_SCALE and in the old one by TRUE_SCALE. */
833 loopify (edge latch_edge, edge header_edge,
834 basic_block switch_bb, edge true_edge, edge false_edge,
835 bool redirect_all_edges, unsigned true_scale, unsigned false_scale)
837 basic_block succ_bb = latch_edge->dest;
838 basic_block pred_bb = header_edge->src;
839 struct loop *loop = alloc_loop ();
840 struct loop *outer = loop_outer (succ_bb->loop_father);
846 loop->header = header_edge->dest;
847 loop->latch = latch_edge->src;
849 freq = EDGE_FREQUENCY (header_edge);
850 cnt = header_edge->count;
852 /* Redirect edges. */
853 loop_redirect_edge (latch_edge, loop->header);
854 loop_redirect_edge (true_edge, succ_bb);
856 /* During loop versioning, one of the switch_bb edge is already properly
857 set. Do not redirect it again unless redirect_all_edges is true. */
858 if (redirect_all_edges)
860 loop_redirect_edge (header_edge, switch_bb);
861 loop_redirect_edge (false_edge, loop->header);
863 /* Update dominators. */
864 set_immediate_dominator (CDI_DOMINATORS, switch_bb, pred_bb);
865 set_immediate_dominator (CDI_DOMINATORS, loop->header, switch_bb);
868 set_immediate_dominator (CDI_DOMINATORS, succ_bb, switch_bb);
870 /* Compute new loop. */
871 add_loop (loop, outer);
873 /* Add switch_bb to appropriate loop. */
874 if (switch_bb->loop_father)
875 remove_bb_from_loops (switch_bb);
876 add_bb_to_loop (switch_bb, outer);
878 /* Fix frequencies. */
879 if (redirect_all_edges)
881 switch_bb->frequency = freq;
882 switch_bb->count = cnt;
883 FOR_EACH_EDGE (e, ei, switch_bb->succs)
885 e->count = RDIV (switch_bb->count * e->probability, REG_BR_PROB_BASE);
888 scale_loop_frequencies (loop, false_scale, REG_BR_PROB_BASE);
889 scale_loop_frequencies (succ_bb->loop_father, true_scale, REG_BR_PROB_BASE);
890 update_dominators_in_loop (loop);
895 /* Remove the latch edge of a LOOP and update loops to indicate that
896 the LOOP was removed. After this function, original loop latch will
897 have no successor, which caller is expected to fix somehow.
899 If this may cause the information about irreducible regions to become
900 invalid, IRRED_INVALIDATED is set to true.
902 LOOP_CLOSED_SSA_INVALIDATED, if non-NULL, is a bitmap where we store
903 basic blocks that had non-trivial update on their loop_father.*/
906 unloop (struct loop *loop, bool *irred_invalidated,
907 bitmap loop_closed_ssa_invalidated)
912 basic_block latch = loop->latch;
915 if (loop_preheader_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP)
916 *irred_invalidated = true;
918 /* This is relatively straightforward. The dominators are unchanged, as
919 loop header dominates loop latch, so the only thing we have to care of
920 is the placement of loops and basic blocks inside the loop tree. We
921 move them all to the loop->outer, and then let fix_bb_placements do
924 body = get_loop_body (loop);
926 for (i = 0; i < n; i++)
927 if (body[i]->loop_father == loop)
929 remove_bb_from_loops (body[i]);
930 add_bb_to_loop (body[i], loop_outer (loop));
937 flow_loop_tree_node_remove (ploop);
938 flow_loop_tree_node_add (loop_outer (loop), ploop);
941 /* Remove the loop and free its data. */
944 remove_edge (single_succ_edge (latch));
946 /* We do not pass IRRED_INVALIDATED to fix_bb_placements here, as even if
947 there is an irreducible region inside the cancelled loop, the flags will
949 fix_bb_placements (latch, &dummy, loop_closed_ssa_invalidated);
952 /* Fix placement of superloops of LOOP inside loop tree, i.e. ensure that
953 condition stated in description of fix_loop_placement holds for them.
954 It is used in case when we removed some edges coming out of LOOP, which
955 may cause the right placement of LOOP inside loop tree to change.
957 IRRED_INVALIDATED is set to true if a change in the loop structures might
958 invalidate the information about irreducible regions. */
961 fix_loop_placements (struct loop *loop, bool *irred_invalidated)
965 while (loop_outer (loop))
967 outer = loop_outer (loop);
968 if (!fix_loop_placement (loop))
971 /* Changing the placement of a loop in the loop tree may alter the
972 validity of condition 2) of the description of fix_bb_placement
973 for its preheader, because the successor is the header and belongs
974 to the loop. So call fix_bb_placements to fix up the placement
975 of the preheader and (possibly) of its predecessors. */
976 fix_bb_placements (loop_preheader_edge (loop)->src,
977 irred_invalidated, NULL);
982 /* Duplicate loop bounds and other information we store about
983 the loop into its duplicate. */
986 copy_loop_info (struct loop *loop, struct loop *target)
988 gcc_checking_assert (!target->any_upper_bound && !target->any_estimate);
989 target->any_upper_bound = loop->any_upper_bound;
990 target->nb_iterations_upper_bound = loop->nb_iterations_upper_bound;
991 target->any_estimate = loop->any_estimate;
992 target->nb_iterations_estimate = loop->nb_iterations_estimate;
993 target->estimate_state = loop->estimate_state;
996 /* Copies copy of LOOP as subloop of TARGET loop, placing newly
997 created loop into loops structure. */
999 duplicate_loop (struct loop *loop, struct loop *target)
1002 cloop = alloc_loop ();
1003 place_new_loop (cloop);
1005 copy_loop_info (loop, cloop);
1007 /* Mark the new loop as copy of LOOP. */
1008 set_loop_copy (loop, cloop);
1010 /* Add it to target. */
1011 flow_loop_tree_node_add (target, cloop);
1016 /* Copies structure of subloops of LOOP into TARGET loop, placing
1017 newly created loops into loop tree. */
1019 duplicate_subloops (struct loop *loop, struct loop *target)
1021 struct loop *aloop, *cloop;
1023 for (aloop = loop->inner; aloop; aloop = aloop->next)
1025 cloop = duplicate_loop (aloop, target);
1026 duplicate_subloops (aloop, cloop);
1030 /* Copies structure of subloops of N loops, stored in array COPIED_LOOPS,
1031 into TARGET loop, placing newly created loops into loop tree. */
1033 copy_loops_to (struct loop **copied_loops, int n, struct loop *target)
1038 for (i = 0; i < n; i++)
1040 aloop = duplicate_loop (copied_loops[i], target);
1041 duplicate_subloops (copied_loops[i], aloop);
1045 /* Redirects edge E to basic block DEST. */
1047 loop_redirect_edge (edge e, basic_block dest)
1049 if (e->dest == dest)
1052 redirect_edge_and_branch_force (e, dest);
1055 /* Check whether LOOP's body can be duplicated. */
1057 can_duplicate_loop_p (const struct loop *loop)
1060 basic_block *bbs = get_loop_body (loop);
1062 ret = can_copy_bbs_p (bbs, loop->num_nodes);
1068 /* Sets probability and count of edge E to zero. The probability and count
1069 is redistributed evenly to the remaining edges coming from E->src. */
1072 set_zero_probability (edge e)
1074 basic_block bb = e->src;
1076 edge ae, last = NULL;
1077 unsigned n = EDGE_COUNT (bb->succs);
1078 gcov_type cnt = e->count, cnt1;
1079 unsigned prob = e->probability, prob1;
1082 cnt1 = cnt / (n - 1);
1083 prob1 = prob / (n - 1);
1085 FOR_EACH_EDGE (ae, ei, bb->succs)
1090 ae->probability += prob1;
1095 /* Move the rest to one of the edges. */
1096 last->probability += prob % (n - 1);
1097 last->count += cnt % (n - 1);
1103 /* Duplicates body of LOOP to given edge E NDUPL times. Takes care of updating
1104 loop structure and dominators. E's destination must be LOOP header for
1105 this to work, i.e. it must be entry or latch edge of this loop; these are
1106 unique, as the loops must have preheaders for this function to work
1107 correctly (in case E is latch, the function unrolls the loop, if E is entry
1108 edge, it peels the loop). Store edges created by copying ORIG edge from
1109 copies corresponding to set bits in WONT_EXIT bitmap (bit 0 corresponds to
1110 original LOOP body, the other copies are numbered in order given by control
1111 flow through them) into TO_REMOVE array. Returns false if duplication is
1115 duplicate_loop_to_header_edge (struct loop *loop, edge e,
1116 unsigned int ndupl, sbitmap wont_exit,
1117 edge orig, vec<edge> *to_remove,
1120 struct loop *target, *aloop;
1121 struct loop **orig_loops;
1122 unsigned n_orig_loops;
1123 basic_block header = loop->header, latch = loop->latch;
1124 basic_block *new_bbs, *bbs, *first_active;
1125 basic_block new_bb, bb, first_active_latch = NULL;
1126 edge ae, latch_edge;
1127 edge spec_edges[2], new_spec_edges[2];
1131 int is_latch = (latch == e->src);
1132 int scale_act = 0, *scale_step = NULL, scale_main = 0;
1133 int scale_after_exit = 0;
1134 int p, freq_in, freq_le, freq_out_orig;
1135 int prob_pass_thru, prob_pass_wont_exit, prob_pass_main;
1136 int add_irreducible_flag;
1137 basic_block place_after;
1138 bitmap bbs_to_scale = NULL;
1141 gcc_assert (e->dest == loop->header);
1142 gcc_assert (ndupl > 0);
1146 /* Orig must be edge out of the loop. */
1147 gcc_assert (flow_bb_inside_loop_p (loop, orig->src));
1148 gcc_assert (!flow_bb_inside_loop_p (loop, orig->dest));
1151 n = loop->num_nodes;
1152 bbs = get_loop_body_in_dom_order (loop);
1153 gcc_assert (bbs[0] == loop->header);
1154 gcc_assert (bbs[n - 1] == loop->latch);
1156 /* Check whether duplication is possible. */
1157 if (!can_copy_bbs_p (bbs, loop->num_nodes))
1162 new_bbs = XNEWVEC (basic_block, loop->num_nodes);
1164 /* In case we are doing loop peeling and the loop is in the middle of
1165 irreducible region, the peeled copies will be inside it too. */
1166 add_irreducible_flag = e->flags & EDGE_IRREDUCIBLE_LOOP;
1167 gcc_assert (!is_latch || !add_irreducible_flag);
1169 /* Find edge from latch. */
1170 latch_edge = loop_latch_edge (loop);
1172 if (flags & DLTHE_FLAG_UPDATE_FREQ)
1174 /* Calculate coefficients by that we have to scale frequencies
1175 of duplicated loop bodies. */
1176 freq_in = header->frequency;
1177 freq_le = EDGE_FREQUENCY (latch_edge);
1180 if (freq_in < freq_le)
1182 freq_out_orig = orig ? EDGE_FREQUENCY (orig) : freq_in - freq_le;
1183 if (freq_out_orig > freq_in - freq_le)
1184 freq_out_orig = freq_in - freq_le;
1185 prob_pass_thru = RDIV (REG_BR_PROB_BASE * freq_le, freq_in);
1186 prob_pass_wont_exit =
1187 RDIV (REG_BR_PROB_BASE * (freq_le + freq_out_orig), freq_in);
1190 && REG_BR_PROB_BASE - orig->probability != 0)
1192 /* The blocks that are dominated by a removed exit edge ORIG have
1193 frequencies scaled by this. */
1194 scale_after_exit = RDIV (REG_BR_PROB_BASE * REG_BR_PROB_BASE,
1195 REG_BR_PROB_BASE - orig->probability);
1196 bbs_to_scale = BITMAP_ALLOC (NULL);
1197 for (i = 0; i < n; i++)
1199 if (bbs[i] != orig->src
1200 && dominated_by_p (CDI_DOMINATORS, bbs[i], orig->src))
1201 bitmap_set_bit (bbs_to_scale, i);
1205 scale_step = XNEWVEC (int, ndupl);
1207 for (i = 1; i <= ndupl; i++)
1208 scale_step[i - 1] = bitmap_bit_p (wont_exit, i)
1209 ? prob_pass_wont_exit
1212 /* Complete peeling is special as the probability of exit in last
1214 if (flags & DLTHE_FLAG_COMPLETTE_PEEL)
1216 int wanted_freq = EDGE_FREQUENCY (e);
1218 if (wanted_freq > freq_in)
1219 wanted_freq = freq_in;
1221 gcc_assert (!is_latch);
1222 /* First copy has frequency of incoming edge. Each subsequent
1223 frequency should be reduced by prob_pass_wont_exit. Caller
1224 should've managed the flags so all except for original loop
1225 has won't exist set. */
1226 scale_act = RDIV (wanted_freq * REG_BR_PROB_BASE, freq_in);
1227 /* Now simulate the duplication adjustments and compute header
1228 frequency of the last copy. */
1229 for (i = 0; i < ndupl; i++)
1230 wanted_freq = RDIV (wanted_freq * scale_step[i], REG_BR_PROB_BASE);
1231 scale_main = RDIV (wanted_freq * REG_BR_PROB_BASE, freq_in);
1235 prob_pass_main = bitmap_bit_p (wont_exit, 0)
1236 ? prob_pass_wont_exit
1239 scale_main = REG_BR_PROB_BASE;
1240 for (i = 0; i < ndupl; i++)
1243 p = RDIV (p * scale_step[i], REG_BR_PROB_BASE);
1245 scale_main = RDIV (REG_BR_PROB_BASE * REG_BR_PROB_BASE, scale_main);
1246 scale_act = RDIV (scale_main * prob_pass_main, REG_BR_PROB_BASE);
1250 scale_main = REG_BR_PROB_BASE;
1251 for (i = 0; i < ndupl; i++)
1252 scale_main = RDIV (scale_main * scale_step[i], REG_BR_PROB_BASE);
1253 scale_act = REG_BR_PROB_BASE - prob_pass_thru;
1255 for (i = 0; i < ndupl; i++)
1256 gcc_assert (scale_step[i] >= 0 && scale_step[i] <= REG_BR_PROB_BASE);
1257 gcc_assert (scale_main >= 0 && scale_main <= REG_BR_PROB_BASE
1258 && scale_act >= 0 && scale_act <= REG_BR_PROB_BASE);
1261 /* Loop the new bbs will belong to. */
1262 target = e->src->loop_father;
1264 /* Original loops. */
1266 for (aloop = loop->inner; aloop; aloop = aloop->next)
1268 orig_loops = XNEWVEC (struct loop *, n_orig_loops);
1269 for (aloop = loop->inner, i = 0; aloop; aloop = aloop->next, i++)
1270 orig_loops[i] = aloop;
1272 set_loop_copy (loop, target);
1274 first_active = XNEWVEC (basic_block, n);
1277 memcpy (first_active, bbs, n * sizeof (basic_block));
1278 first_active_latch = latch;
1281 spec_edges[SE_ORIG] = orig;
1282 spec_edges[SE_LATCH] = latch_edge;
1284 place_after = e->src;
1285 for (j = 0; j < ndupl; j++)
1288 copy_loops_to (orig_loops, n_orig_loops, target);
1291 copy_bbs (bbs, n, new_bbs, spec_edges, 2, new_spec_edges, loop,
1293 place_after = new_spec_edges[SE_LATCH]->src;
1295 if (flags & DLTHE_RECORD_COPY_NUMBER)
1296 for (i = 0; i < n; i++)
1298 gcc_assert (!new_bbs[i]->aux);
1299 new_bbs[i]->aux = (void *)(size_t)(j + 1);
1302 /* Note whether the blocks and edges belong to an irreducible loop. */
1303 if (add_irreducible_flag)
1305 for (i = 0; i < n; i++)
1306 new_bbs[i]->flags |= BB_DUPLICATED;
1307 for (i = 0; i < n; i++)
1310 new_bb = new_bbs[i];
1311 if (new_bb->loop_father == target)
1312 new_bb->flags |= BB_IRREDUCIBLE_LOOP;
1314 FOR_EACH_EDGE (ae, ei, new_bb->succs)
1315 if ((ae->dest->flags & BB_DUPLICATED)
1316 && (ae->src->loop_father == target
1317 || ae->dest->loop_father == target))
1318 ae->flags |= EDGE_IRREDUCIBLE_LOOP;
1320 for (i = 0; i < n; i++)
1321 new_bbs[i]->flags &= ~BB_DUPLICATED;
1324 /* Redirect the special edges. */
1327 redirect_edge_and_branch_force (latch_edge, new_bbs[0]);
1328 redirect_edge_and_branch_force (new_spec_edges[SE_LATCH],
1330 set_immediate_dominator (CDI_DOMINATORS, new_bbs[0], latch);
1331 latch = loop->latch = new_bbs[n - 1];
1332 e = latch_edge = new_spec_edges[SE_LATCH];
1336 redirect_edge_and_branch_force (new_spec_edges[SE_LATCH],
1338 redirect_edge_and_branch_force (e, new_bbs[0]);
1339 set_immediate_dominator (CDI_DOMINATORS, new_bbs[0], e->src);
1340 e = new_spec_edges[SE_LATCH];
1343 /* Record exit edge in this copy. */
1344 if (orig && bitmap_bit_p (wont_exit, j + 1))
1347 to_remove->safe_push (new_spec_edges[SE_ORIG]);
1348 set_zero_probability (new_spec_edges[SE_ORIG]);
1350 /* Scale the frequencies of the blocks dominated by the exit. */
1353 EXECUTE_IF_SET_IN_BITMAP (bbs_to_scale, 0, i, bi)
1355 scale_bbs_frequencies_int (new_bbs + i, 1, scale_after_exit,
1361 /* Record the first copy in the control flow order if it is not
1362 the original loop (i.e. in case of peeling). */
1363 if (!first_active_latch)
1365 memcpy (first_active, new_bbs, n * sizeof (basic_block));
1366 first_active_latch = new_bbs[n - 1];
1369 /* Set counts and frequencies. */
1370 if (flags & DLTHE_FLAG_UPDATE_FREQ)
1372 scale_bbs_frequencies_int (new_bbs, n, scale_act, REG_BR_PROB_BASE);
1373 scale_act = RDIV (scale_act * scale_step[j], REG_BR_PROB_BASE);
1379 /* Record the exit edge in the original loop body, and update the frequencies. */
1380 if (orig && bitmap_bit_p (wont_exit, 0))
1383 to_remove->safe_push (orig);
1384 set_zero_probability (orig);
1386 /* Scale the frequencies of the blocks dominated by the exit. */
1389 EXECUTE_IF_SET_IN_BITMAP (bbs_to_scale, 0, i, bi)
1391 scale_bbs_frequencies_int (bbs + i, 1, scale_after_exit,
1397 /* Update the original loop. */
1399 set_immediate_dominator (CDI_DOMINATORS, e->dest, e->src);
1400 if (flags & DLTHE_FLAG_UPDATE_FREQ)
1402 scale_bbs_frequencies_int (bbs, n, scale_main, REG_BR_PROB_BASE);
1406 /* Update dominators of outer blocks if affected. */
1407 for (i = 0; i < n; i++)
1409 basic_block dominated, dom_bb;
1410 vec<basic_block> dom_bbs;
1416 dom_bbs = get_dominated_by (CDI_DOMINATORS, bb);
1417 FOR_EACH_VEC_ELT (dom_bbs, j, dominated)
1419 if (flow_bb_inside_loop_p (loop, dominated))
1421 dom_bb = nearest_common_dominator (
1422 CDI_DOMINATORS, first_active[i], first_active_latch);
1423 set_immediate_dominator (CDI_DOMINATORS, dominated, dom_bb);
1427 free (first_active);
1430 BITMAP_FREE (bbs_to_scale);
1435 /* A callback for make_forwarder block, to redirect all edges except for
1436 MFB_KJ_EDGE to the entry part. E is the edge for that we should decide
1437 whether to redirect it. */
1441 mfb_keep_just (edge e)
1443 return e != mfb_kj_edge;
1446 /* True when a candidate preheader BLOCK has predecessors from LOOP. */
1449 has_preds_from_loop (basic_block block, struct loop *loop)
1454 FOR_EACH_EDGE (e, ei, block->preds)
1455 if (e->src->loop_father == loop)
1460 /* Creates a pre-header for a LOOP. Returns newly created block. Unless
1461 CP_SIMPLE_PREHEADERS is set in FLAGS, we only force LOOP to have single
1462 entry; otherwise we also force preheader block to have only one successor.
1463 When CP_FALLTHRU_PREHEADERS is set in FLAGS, we force the preheader block
1464 to be a fallthru predecessor to the loop header and to have only
1465 predecessors from outside of the loop.
1466 The function also updates dominators. */
1469 create_preheader (struct loop *loop, int flags)
1475 bool latch_edge_was_fallthru;
1476 edge one_succ_pred = NULL, single_entry = NULL;
1479 FOR_EACH_EDGE (e, ei, loop->header->preds)
1481 if (e->src == loop->latch)
1483 irred |= (e->flags & EDGE_IRREDUCIBLE_LOOP) != 0;
1486 if (single_succ_p (e->src))
1489 gcc_assert (nentry);
1492 bool need_forwarder_block = false;
1494 /* We do not allow entry block to be the loop preheader, since we
1495 cannot emit code there. */
1496 if (single_entry->src == ENTRY_BLOCK_PTR)
1497 need_forwarder_block = true;
1500 /* If we want simple preheaders, also force the preheader to have
1501 just a single successor. */
1502 if ((flags & CP_SIMPLE_PREHEADERS)
1503 && !single_succ_p (single_entry->src))
1504 need_forwarder_block = true;
1505 /* If we want fallthru preheaders, also create forwarder block when
1506 preheader ends with a jump or has predecessors from loop. */
1507 else if ((flags & CP_FALLTHRU_PREHEADERS)
1508 && (JUMP_P (BB_END (single_entry->src))
1509 || has_preds_from_loop (single_entry->src, loop)))
1510 need_forwarder_block = true;
1512 if (! need_forwarder_block)
1516 mfb_kj_edge = loop_latch_edge (loop);
1517 latch_edge_was_fallthru = (mfb_kj_edge->flags & EDGE_FALLTHRU) != 0;
1518 fallthru = make_forwarder_block (loop->header, mfb_keep_just, NULL);
1519 dummy = fallthru->src;
1520 loop->header = fallthru->dest;
1522 /* Try to be clever in placing the newly created preheader. The idea is to
1523 avoid breaking any "fallthruness" relationship between blocks.
1525 The preheader was created just before the header and all incoming edges
1526 to the header were redirected to the preheader, except the latch edge.
1527 So the only problematic case is when this latch edge was a fallthru
1528 edge: it is not anymore after the preheader creation so we have broken
1529 the fallthruness. We're therefore going to look for a better place. */
1530 if (latch_edge_was_fallthru)
1535 e = EDGE_PRED (dummy, 0);
1537 move_block_after (dummy, e->src);
1542 dummy->flags |= BB_IRREDUCIBLE_LOOP;
1543 single_succ_edge (dummy)->flags |= EDGE_IRREDUCIBLE_LOOP;
1547 fprintf (dump_file, "Created preheader block for loop %i\n",
1550 if (flags & CP_FALLTHRU_PREHEADERS)
1551 gcc_assert ((single_succ_edge (dummy)->flags & EDGE_FALLTHRU)
1552 && !JUMP_P (BB_END (dummy)));
1557 /* Create preheaders for each loop; for meaning of FLAGS see create_preheader. */
1560 create_preheaders (int flags)
1568 FOR_EACH_LOOP (li, loop, 0)
1569 create_preheader (loop, flags);
1570 loops_state_set (LOOPS_HAVE_PREHEADERS);
1573 /* Forces all loop latches to have only single successor. */
1576 force_single_succ_latches (void)
1582 FOR_EACH_LOOP (li, loop, 0)
1584 if (loop->latch != loop->header && single_succ_p (loop->latch))
1587 e = find_edge (loop->latch, loop->header);
1588 gcc_checking_assert (e != NULL);
1592 loops_state_set (LOOPS_HAVE_SIMPLE_LATCHES);
1595 /* This function is called from loop_version. It splits the entry edge
1596 of the loop we want to version, adds the versioning condition, and
1597 adjust the edges to the two versions of the loop appropriately.
1598 e is an incoming edge. Returns the basic block containing the
1601 --- edge e ---- > [second_head]
1603 Split it and insert new conditional expression and adjust edges.
1605 --- edge e ---> [cond expr] ---> [first_head]
1607 +---------> [second_head]
1609 THEN_PROB is the probability of then branch of the condition. */
1612 lv_adjust_loop_entry_edge (basic_block first_head, basic_block second_head,
1613 edge e, void *cond_expr, unsigned then_prob)
1615 basic_block new_head = NULL;
1618 gcc_assert (e->dest == second_head);
1620 /* Split edge 'e'. This will create a new basic block, where we can
1621 insert conditional expr. */
1622 new_head = split_edge (e);
1624 lv_add_condition_to_bb (first_head, second_head, new_head,
1627 /* Don't set EDGE_TRUE_VALUE in RTL mode, as it's invalid there. */
1628 e = single_succ_edge (new_head);
1629 e1 = make_edge (new_head, first_head,
1630 current_ir_type () == IR_GIMPLE ? EDGE_TRUE_VALUE : 0);
1631 e1->probability = then_prob;
1632 e->probability = REG_BR_PROB_BASE - then_prob;
1633 e1->count = RDIV (e->count * e1->probability, REG_BR_PROB_BASE);
1634 e->count = RDIV (e->count * e->probability, REG_BR_PROB_BASE);
1636 set_immediate_dominator (CDI_DOMINATORS, first_head, new_head);
1637 set_immediate_dominator (CDI_DOMINATORS, second_head, new_head);
1639 /* Adjust loop header phi nodes. */
1640 lv_adjust_loop_header_phi (first_head, second_head, new_head, e1);
1645 /* Main entry point for Loop Versioning transformation.
1647 This transformation given a condition and a loop, creates
1648 -if (condition) { loop_copy1 } else { loop_copy2 },
1649 where loop_copy1 is the loop transformed in one way, and loop_copy2
1650 is the loop transformed in another way (or unchanged). 'condition'
1651 may be a run time test for things that were not resolved by static
1652 analysis (overlapping ranges (anti-aliasing), alignment, etc.).
1654 THEN_PROB is the probability of the then edge of the if. THEN_SCALE
1655 is the ratio by that the frequencies in the original loop should
1656 be scaled. ELSE_SCALE is the ratio by that the frequencies in the
1657 new loop should be scaled.
1659 If PLACE_AFTER is true, we place the new loop after LOOP in the
1660 instruction stream, otherwise it is placed before LOOP. */
1663 loop_version (struct loop *loop,
1664 void *cond_expr, basic_block *condition_bb,
1665 unsigned then_prob, unsigned then_scale, unsigned else_scale,
1668 basic_block first_head, second_head;
1669 edge entry, latch_edge, true_edge, false_edge;
1672 basic_block cond_bb;
1674 /* Record entry and latch edges for the loop */
1675 entry = loop_preheader_edge (loop);
1676 irred_flag = entry->flags & EDGE_IRREDUCIBLE_LOOP;
1677 entry->flags &= ~EDGE_IRREDUCIBLE_LOOP;
1679 /* Note down head of loop as first_head. */
1680 first_head = entry->dest;
1682 /* Duplicate loop. */
1683 if (!cfg_hook_duplicate_loop_to_header_edge (loop, entry, 1,
1684 NULL, NULL, NULL, 0))
1686 entry->flags |= irred_flag;
1690 /* After duplication entry edge now points to new loop head block.
1691 Note down new head as second_head. */
1692 second_head = entry->dest;
1694 /* Split loop entry edge and insert new block with cond expr. */
1695 cond_bb = lv_adjust_loop_entry_edge (first_head, second_head,
1696 entry, cond_expr, then_prob);
1698 *condition_bb = cond_bb;
1702 entry->flags |= irred_flag;
1706 latch_edge = single_succ_edge (get_bb_copy (loop->latch));
1708 extract_cond_bb_edges (cond_bb, &true_edge, &false_edge);
1709 nloop = loopify (latch_edge,
1710 single_pred_edge (get_bb_copy (loop->header)),
1711 cond_bb, true_edge, false_edge,
1712 false /* Do not redirect all edges. */,
1713 then_scale, else_scale);
1715 copy_loop_info (loop, nloop);
1717 /* loopify redirected latch_edge. Update its PENDING_STMTS. */
1718 lv_flush_pending_stmts (latch_edge);
1720 /* loopify redirected condition_bb's succ edge. Update its PENDING_STMTS. */
1721 extract_cond_bb_edges (cond_bb, &true_edge, &false_edge);
1722 lv_flush_pending_stmts (false_edge);
1723 /* Adjust irreducible flag. */
1726 cond_bb->flags |= BB_IRREDUCIBLE_LOOP;
1727 loop_preheader_edge (loop)->flags |= EDGE_IRREDUCIBLE_LOOP;
1728 loop_preheader_edge (nloop)->flags |= EDGE_IRREDUCIBLE_LOOP;
1729 single_pred_edge (cond_bb)->flags |= EDGE_IRREDUCIBLE_LOOP;
1734 basic_block *bbs = get_loop_body_in_dom_order (nloop), after;
1737 after = loop->latch;
1739 for (i = 0; i < nloop->num_nodes; i++)
1741 move_block_after (bbs[i], after);
1747 /* At this point condition_bb is loop preheader with two successors,
1748 first_head and second_head. Make sure that loop preheader has only
1750 split_edge (loop_preheader_edge (loop));
1751 split_edge (loop_preheader_edge (nloop));
1756 /* The structure of loops might have changed. Some loops might get removed
1757 (and their headers and latches were set to NULL), loop exists might get
1758 removed (thus the loop nesting may be wrong), and some blocks and edges
1759 were changed (so the information about bb --> loop mapping does not have
1760 to be correct). But still for the remaining loops the header dominates
1761 the latch, and loops did not get new subloops (new loops might possibly
1762 get created, but we are not interested in them). Fix up the mess.
1764 If CHANGED_BBS is not NULL, basic blocks whose loop has changed are
1768 fix_loop_structure (bitmap changed_bbs)
1771 struct loop *loop, *ploop;
1773 bool record_exits = false;
1774 struct loop **superloop = XNEWVEC (struct loop *, number_of_loops ());
1776 /* We need exact and fast dominance info to be available. */
1777 gcc_assert (dom_info_state (CDI_DOMINATORS) == DOM_OK);
1779 /* Remove the old bb -> loop mapping. Remember the depth of the blocks in
1780 the loop hierarchy, so that we can recognize blocks whose loop nesting
1781 relationship has changed. */
1785 bb->aux = (void *) (size_t) loop_depth (bb->loop_father);
1786 bb->loop_father = current_loops->tree_root;
1789 if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
1791 release_recorded_exits ();
1792 record_exits = true;
1795 /* First re-compute loop latches. */
1796 FOR_EACH_LOOP (li, loop, 0)
1799 edge e, first_latch = NULL, latch = NULL;
1804 FOR_EACH_EDGE (e, ei, loop->header->preds)
1805 if (dominated_by_p (CDI_DOMINATORS, e->src, loop->header))
1808 first_latch = latch = e;
1815 /* If there was no latch, schedule the loop for removal. */
1817 loop->header = NULL;
1818 /* If there was a single latch and it belongs to the loop of the
1819 header, record it. */
1821 && latch->src->loop_father == loop)
1822 loop->latch = latch->src;
1823 /* Otherwise there are multiple latches which are eventually
1824 disambiguated below. */
1829 /* Remove the dead loops from structures. We start from the innermost
1830 loops, so that when we remove the loops, we know that the loops inside
1831 are preserved, and do not waste time relinking loops that will be
1833 FOR_EACH_LOOP (li, loop, LI_FROM_INNERMOST)
1840 ploop = loop->inner;
1841 flow_loop_tree_node_remove (ploop);
1842 flow_loop_tree_node_add (loop_outer (loop), ploop);
1845 /* Remove the loop and free its data. */
1849 /* Rescan the bodies of loops, starting from the outermost ones. We assume
1850 that no optimization interchanges the order of the loops, i.e., it cannot
1851 happen that L1 was superloop of L2 before and it is subloop of L2 now
1852 (without explicitly updating loop information). At the same time, we also
1853 determine the new loop structure. */
1854 current_loops->tree_root->num_nodes = n_basic_blocks;
1855 FOR_EACH_LOOP (li, loop, 0)
1857 superloop[loop->num] = loop->header->loop_father;
1858 loop->num_nodes = flow_loop_nodes_find (loop->header, loop);
1861 /* Now fix the loop nesting. */
1862 FOR_EACH_LOOP (li, loop, 0)
1864 ploop = superloop[loop->num];
1865 if (ploop != loop_outer (loop))
1867 flow_loop_tree_node_remove (loop);
1868 flow_loop_tree_node_add (ploop, loop);
1873 /* Mark the blocks whose loop has changed. */
1878 if ((void *) (size_t) loop_depth (bb->loop_father) != bb->aux)
1879 bitmap_set_bit (changed_bbs, bb->index);
1885 if (!loops_state_satisfies_p (LOOPS_MAY_HAVE_MULTIPLE_LATCHES))
1886 disambiguate_loops_with_multiple_latches ();
1888 if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS))
1890 int cp_flags = CP_SIMPLE_PREHEADERS;
1892 if (loops_state_satisfies_p (LOOPS_HAVE_FALLTHRU_PREHEADERS))
1893 cp_flags |= CP_FALLTHRU_PREHEADERS;
1895 create_preheaders (cp_flags);
1898 if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
1899 force_single_succ_latches ();
1901 if (loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS))
1902 mark_irreducible_loops ();
1905 record_loop_exits ();
1907 loops_state_clear (LOOPS_NEED_FIXUP);
1909 #ifdef ENABLE_CHECKING
1910 verify_loop_structure ();