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[official-gcc.git] / gcc / bb-reorder.c
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1 /* Basic block reordering routines for the GNU compiler.
2 Copyright (C) 2000-2014 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it
7 under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
11 GCC is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
14 License for more details.
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/>. */
20 /* This (greedy) algorithm constructs traces in several rounds.
21 The construction starts from "seeds". The seed for the first round
22 is the entry point of the function. When there are more than one seed,
23 the one with the lowest key in the heap is selected first (see bb_to_key).
24 Then the algorithm repeatedly adds the most probable successor to the end
25 of a trace. Finally it connects the traces.
27 There are two parameters: Branch Threshold and Exec Threshold.
28 If the probability of an edge to a successor of the current basic block is
29 lower than Branch Threshold or its frequency is lower than Exec Threshold,
30 then the successor will be the seed in one of the next rounds.
31 Each round has these parameters lower than the previous one.
32 The last round has to have these parameters set to zero so that the
33 remaining blocks are picked up.
35 The algorithm selects the most probable successor from all unvisited
36 successors and successors that have been added to this trace.
37 The other successors (that has not been "sent" to the next round) will be
38 other seeds for this round and the secondary traces will start from them.
39 If the successor has not been visited in this trace, it is added to the
40 trace (however, there is some heuristic for simple branches).
41 If the successor has been visited in this trace, a loop has been found.
42 If the loop has many iterations, the loop is rotated so that the source
43 block of the most probable edge going out of the loop is the last block
44 of the trace.
45 If the loop has few iterations and there is no edge from the last block of
46 the loop going out of the loop, the loop header is duplicated.
48 When connecting traces, the algorithm first checks whether there is an edge
49 from the last block of a trace to the first block of another trace.
50 When there are still some unconnected traces it checks whether there exists
51 a basic block BB such that BB is a successor of the last block of a trace
52 and BB is a predecessor of the first block of another trace. In this case,
53 BB is duplicated, added at the end of the first trace and the traces are
54 connected through it.
55 The rest of traces are simply connected so there will be a jump to the
56 beginning of the rest of traces.
58 The above description is for the full algorithm, which is used when the
59 function is optimized for speed. When the function is optimized for size,
60 in order to reduce long jumps and connect more fallthru edges, the
61 algorithm is modified as follows:
62 (1) Break long traces to short ones. A trace is broken at a block that has
63 multiple predecessors/ successors during trace discovery. When connecting
64 traces, only connect Trace n with Trace n + 1. This change reduces most
65 long jumps compared with the above algorithm.
66 (2) Ignore the edge probability and frequency for fallthru edges.
67 (3) Keep the original order of blocks when there is no chance to fall
68 through. We rely on the results of cfg_cleanup.
70 To implement the change for code size optimization, block's index is
71 selected as the key and all traces are found in one round.
73 References:
75 "Software Trace Cache"
76 A. Ramirez, J. Larriba-Pey, C. Navarro, J. Torrellas and M. Valero; 1999
77 http://citeseer.nj.nec.com/15361.html
81 #include "config.h"
82 #include "system.h"
83 #include "coretypes.h"
84 #include "tm.h"
85 #include "tree.h"
86 #include "rtl.h"
87 #include "regs.h"
88 #include "flags.h"
89 #include "output.h"
90 #include "fibheap.h"
91 #include "target.h"
92 #include "function.h"
93 #include "tm_p.h"
94 #include "obstack.h"
95 #include "expr.h"
96 #include "params.h"
97 #include "diagnostic-core.h"
98 #include "toplev.h" /* user_defined_section_attribute */
99 #include "tree-pass.h"
100 #include "df.h"
101 #include "bb-reorder.h"
102 #include "cgraph.h"
103 #include "except.h"
105 /* The number of rounds. In most cases there will only be 4 rounds, but
106 when partitioning hot and cold basic blocks into separate sections of
107 the object file there will be an extra round. */
108 #define N_ROUNDS 5
110 /* Stubs in case we don't have a return insn.
111 We have to check at run time too, not only compile time. */
113 #ifndef HAVE_return
114 #define HAVE_return 0
115 #define gen_return() NULL_RTX
116 #endif
119 struct target_bb_reorder default_target_bb_reorder;
120 #if SWITCHABLE_TARGET
121 struct target_bb_reorder *this_target_bb_reorder = &default_target_bb_reorder;
122 #endif
124 #define uncond_jump_length \
125 (this_target_bb_reorder->x_uncond_jump_length)
127 /* Branch thresholds in thousandths (per mille) of the REG_BR_PROB_BASE. */
128 static const int branch_threshold[N_ROUNDS] = {400, 200, 100, 0, 0};
130 /* Exec thresholds in thousandths (per mille) of the frequency of bb 0. */
131 static const int exec_threshold[N_ROUNDS] = {500, 200, 50, 0, 0};
133 /* If edge frequency is lower than DUPLICATION_THRESHOLD per mille of entry
134 block the edge destination is not duplicated while connecting traces. */
135 #define DUPLICATION_THRESHOLD 100
137 /* Structure to hold needed information for each basic block. */
138 typedef struct bbro_basic_block_data_def
140 /* Which trace is the bb start of (-1 means it is not a start of any). */
141 int start_of_trace;
143 /* Which trace is the bb end of (-1 means it is not an end of any). */
144 int end_of_trace;
146 /* Which trace is the bb in? */
147 int in_trace;
149 /* Which trace was this bb visited in? */
150 int visited;
152 /* Which heap is BB in (if any)? */
153 fibheap_t heap;
155 /* Which heap node is BB in (if any)? */
156 fibnode_t node;
157 } bbro_basic_block_data;
159 /* The current size of the following dynamic array. */
160 static int array_size;
162 /* The array which holds needed information for basic blocks. */
163 static bbro_basic_block_data *bbd;
165 /* To avoid frequent reallocation the size of arrays is greater than needed,
166 the number of elements is (not less than) 1.25 * size_wanted. */
167 #define GET_ARRAY_SIZE(X) ((((X) / 4) + 1) * 5)
169 /* Free the memory and set the pointer to NULL. */
170 #define FREE(P) (gcc_assert (P), free (P), P = 0)
172 /* Structure for holding information about a trace. */
173 struct trace
175 /* First and last basic block of the trace. */
176 basic_block first, last;
178 /* The round of the STC creation which this trace was found in. */
179 int round;
181 /* The length (i.e. the number of basic blocks) of the trace. */
182 int length;
185 /* Maximum frequency and count of one of the entry blocks. */
186 static int max_entry_frequency;
187 static gcov_type max_entry_count;
189 /* Local function prototypes. */
190 static void find_traces (int *, struct trace *);
191 static basic_block rotate_loop (edge, struct trace *, int);
192 static void mark_bb_visited (basic_block, int);
193 static void find_traces_1_round (int, int, gcov_type, struct trace *, int *,
194 int, fibheap_t *, int);
195 static basic_block copy_bb (basic_block, edge, basic_block, int);
196 static fibheapkey_t bb_to_key (basic_block);
197 static bool better_edge_p (const_basic_block, const_edge, int, int, int, int,
198 const_edge);
199 static bool connect_better_edge_p (const_edge, bool, int, const_edge,
200 struct trace *);
201 static void connect_traces (int, struct trace *);
202 static bool copy_bb_p (const_basic_block, int);
203 static bool push_to_next_round_p (const_basic_block, int, int, int, gcov_type);
205 /* Return the trace number in which BB was visited. */
207 static int
208 bb_visited_trace (const_basic_block bb)
210 gcc_assert (bb->index < array_size);
211 return bbd[bb->index].visited;
214 /* This function marks BB that it was visited in trace number TRACE. */
216 static void
217 mark_bb_visited (basic_block bb, int trace)
219 bbd[bb->index].visited = trace;
220 if (bbd[bb->index].heap)
222 fibheap_delete_node (bbd[bb->index].heap, bbd[bb->index].node);
223 bbd[bb->index].heap = NULL;
224 bbd[bb->index].node = NULL;
228 /* Check to see if bb should be pushed into the next round of trace
229 collections or not. Reasons for pushing the block forward are 1).
230 If the block is cold, we are doing partitioning, and there will be
231 another round (cold partition blocks are not supposed to be
232 collected into traces until the very last round); or 2). There will
233 be another round, and the basic block is not "hot enough" for the
234 current round of trace collection. */
236 static bool
237 push_to_next_round_p (const_basic_block bb, int round, int number_of_rounds,
238 int exec_th, gcov_type count_th)
240 bool there_exists_another_round;
241 bool block_not_hot_enough;
243 there_exists_another_round = round < number_of_rounds - 1;
245 block_not_hot_enough = (bb->frequency < exec_th
246 || bb->count < count_th
247 || probably_never_executed_bb_p (cfun, bb));
249 if (there_exists_another_round
250 && block_not_hot_enough)
251 return true;
252 else
253 return false;
256 /* Find the traces for Software Trace Cache. Chain each trace through
257 RBI()->next. Store the number of traces to N_TRACES and description of
258 traces to TRACES. */
260 static void
261 find_traces (int *n_traces, struct trace *traces)
263 int i;
264 int number_of_rounds;
265 edge e;
266 edge_iterator ei;
267 fibheap_t heap;
269 /* Add one extra round of trace collection when partitioning hot/cold
270 basic blocks into separate sections. The last round is for all the
271 cold blocks (and ONLY the cold blocks). */
273 number_of_rounds = N_ROUNDS - 1;
275 /* Insert entry points of function into heap. */
276 heap = fibheap_new ();
277 max_entry_frequency = 0;
278 max_entry_count = 0;
279 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs)
281 bbd[e->dest->index].heap = heap;
282 bbd[e->dest->index].node = fibheap_insert (heap, bb_to_key (e->dest),
283 e->dest);
284 if (e->dest->frequency > max_entry_frequency)
285 max_entry_frequency = e->dest->frequency;
286 if (e->dest->count > max_entry_count)
287 max_entry_count = e->dest->count;
290 /* Find the traces. */
291 for (i = 0; i < number_of_rounds; i++)
293 gcov_type count_threshold;
295 if (dump_file)
296 fprintf (dump_file, "STC - round %d\n", i + 1);
298 if (max_entry_count < INT_MAX / 1000)
299 count_threshold = max_entry_count * exec_threshold[i] / 1000;
300 else
301 count_threshold = max_entry_count / 1000 * exec_threshold[i];
303 find_traces_1_round (REG_BR_PROB_BASE * branch_threshold[i] / 1000,
304 max_entry_frequency * exec_threshold[i] / 1000,
305 count_threshold, traces, n_traces, i, &heap,
306 number_of_rounds);
308 fibheap_delete (heap);
310 if (dump_file)
312 for (i = 0; i < *n_traces; i++)
314 basic_block bb;
315 fprintf (dump_file, "Trace %d (round %d): ", i + 1,
316 traces[i].round + 1);
317 for (bb = traces[i].first;
318 bb != traces[i].last;
319 bb = (basic_block) bb->aux)
320 fprintf (dump_file, "%d [%d] ", bb->index, bb->frequency);
321 fprintf (dump_file, "%d [%d]\n", bb->index, bb->frequency);
323 fflush (dump_file);
327 /* Rotate loop whose back edge is BACK_EDGE in the tail of trace TRACE
328 (with sequential number TRACE_N). */
330 static basic_block
331 rotate_loop (edge back_edge, struct trace *trace, int trace_n)
333 basic_block bb;
335 /* Information about the best end (end after rotation) of the loop. */
336 basic_block best_bb = NULL;
337 edge best_edge = NULL;
338 int best_freq = -1;
339 gcov_type best_count = -1;
340 /* The best edge is preferred when its destination is not visited yet
341 or is a start block of some trace. */
342 bool is_preferred = false;
344 /* Find the most frequent edge that goes out from current trace. */
345 bb = back_edge->dest;
348 edge e;
349 edge_iterator ei;
351 FOR_EACH_EDGE (e, ei, bb->succs)
352 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
353 && bb_visited_trace (e->dest) != trace_n
354 && (e->flags & EDGE_CAN_FALLTHRU)
355 && !(e->flags & EDGE_COMPLEX))
357 if (is_preferred)
359 /* The best edge is preferred. */
360 if (!bb_visited_trace (e->dest)
361 || bbd[e->dest->index].start_of_trace >= 0)
363 /* The current edge E is also preferred. */
364 int freq = EDGE_FREQUENCY (e);
365 if (freq > best_freq || e->count > best_count)
367 best_freq = freq;
368 best_count = e->count;
369 best_edge = e;
370 best_bb = bb;
374 else
376 if (!bb_visited_trace (e->dest)
377 || bbd[e->dest->index].start_of_trace >= 0)
379 /* The current edge E is preferred. */
380 is_preferred = true;
381 best_freq = EDGE_FREQUENCY (e);
382 best_count = e->count;
383 best_edge = e;
384 best_bb = bb;
386 else
388 int freq = EDGE_FREQUENCY (e);
389 if (!best_edge || freq > best_freq || e->count > best_count)
391 best_freq = freq;
392 best_count = e->count;
393 best_edge = e;
394 best_bb = bb;
399 bb = (basic_block) bb->aux;
401 while (bb != back_edge->dest);
403 if (best_bb)
405 /* Rotate the loop so that the BEST_EDGE goes out from the last block of
406 the trace. */
407 if (back_edge->dest == trace->first)
409 trace->first = (basic_block) best_bb->aux;
411 else
413 basic_block prev_bb;
415 for (prev_bb = trace->first;
416 prev_bb->aux != back_edge->dest;
417 prev_bb = (basic_block) prev_bb->aux)
419 prev_bb->aux = best_bb->aux;
421 /* Try to get rid of uncond jump to cond jump. */
422 if (single_succ_p (prev_bb))
424 basic_block header = single_succ (prev_bb);
426 /* Duplicate HEADER if it is a small block containing cond jump
427 in the end. */
428 if (any_condjump_p (BB_END (header)) && copy_bb_p (header, 0)
429 && !CROSSING_JUMP_P (BB_END (header)))
430 copy_bb (header, single_succ_edge (prev_bb), prev_bb, trace_n);
434 else
436 /* We have not found suitable loop tail so do no rotation. */
437 best_bb = back_edge->src;
439 best_bb->aux = NULL;
440 return best_bb;
443 /* One round of finding traces. Find traces for BRANCH_TH and EXEC_TH i.e. do
444 not include basic blocks whose probability is lower than BRANCH_TH or whose
445 frequency is lower than EXEC_TH into traces (or whose count is lower than
446 COUNT_TH). Store the new traces into TRACES and modify the number of
447 traces *N_TRACES. Set the round (which the trace belongs to) to ROUND.
448 The function expects starting basic blocks to be in *HEAP and will delete
449 *HEAP and store starting points for the next round into new *HEAP. */
451 static void
452 find_traces_1_round (int branch_th, int exec_th, gcov_type count_th,
453 struct trace *traces, int *n_traces, int round,
454 fibheap_t *heap, int number_of_rounds)
456 /* Heap for discarded basic blocks which are possible starting points for
457 the next round. */
458 fibheap_t new_heap = fibheap_new ();
459 bool for_size = optimize_function_for_size_p (cfun);
461 while (!fibheap_empty (*heap))
463 basic_block bb;
464 struct trace *trace;
465 edge best_edge, e;
466 fibheapkey_t key;
467 edge_iterator ei;
469 bb = (basic_block) fibheap_extract_min (*heap);
470 bbd[bb->index].heap = NULL;
471 bbd[bb->index].node = NULL;
473 if (dump_file)
474 fprintf (dump_file, "Getting bb %d\n", bb->index);
476 /* If the BB's frequency is too low, send BB to the next round. When
477 partitioning hot/cold blocks into separate sections, make sure all
478 the cold blocks (and ONLY the cold blocks) go into the (extra) final
479 round. When optimizing for size, do not push to next round. */
481 if (!for_size
482 && push_to_next_round_p (bb, round, number_of_rounds, exec_th,
483 count_th))
485 int key = bb_to_key (bb);
486 bbd[bb->index].heap = new_heap;
487 bbd[bb->index].node = fibheap_insert (new_heap, key, bb);
489 if (dump_file)
490 fprintf (dump_file,
491 " Possible start point of next round: %d (key: %d)\n",
492 bb->index, key);
493 continue;
496 trace = traces + *n_traces;
497 trace->first = bb;
498 trace->round = round;
499 trace->length = 0;
500 bbd[bb->index].in_trace = *n_traces;
501 (*n_traces)++;
505 int prob, freq;
506 bool ends_in_call;
508 /* The probability and frequency of the best edge. */
509 int best_prob = INT_MIN / 2;
510 int best_freq = INT_MIN / 2;
512 best_edge = NULL;
513 mark_bb_visited (bb, *n_traces);
514 trace->length++;
516 if (dump_file)
517 fprintf (dump_file, "Basic block %d was visited in trace %d\n",
518 bb->index, *n_traces - 1);
520 ends_in_call = block_ends_with_call_p (bb);
522 /* Select the successor that will be placed after BB. */
523 FOR_EACH_EDGE (e, ei, bb->succs)
525 gcc_assert (!(e->flags & EDGE_FAKE));
527 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
528 continue;
530 if (bb_visited_trace (e->dest)
531 && bb_visited_trace (e->dest) != *n_traces)
532 continue;
534 if (BB_PARTITION (e->dest) != BB_PARTITION (bb))
535 continue;
537 prob = e->probability;
538 freq = e->dest->frequency;
540 /* The only sensible preference for a call instruction is the
541 fallthru edge. Don't bother selecting anything else. */
542 if (ends_in_call)
544 if (e->flags & EDGE_CAN_FALLTHRU)
546 best_edge = e;
547 best_prob = prob;
548 best_freq = freq;
550 continue;
553 /* Edge that cannot be fallthru or improbable or infrequent
554 successor (i.e. it is unsuitable successor). When optimizing
555 for size, ignore the probability and frequency. */
556 if (!(e->flags & EDGE_CAN_FALLTHRU) || (e->flags & EDGE_COMPLEX)
557 || ((prob < branch_th || EDGE_FREQUENCY (e) < exec_th
558 || e->count < count_th) && (!for_size)))
559 continue;
561 /* If partitioning hot/cold basic blocks, don't consider edges
562 that cross section boundaries. */
564 if (better_edge_p (bb, e, prob, freq, best_prob, best_freq,
565 best_edge))
567 best_edge = e;
568 best_prob = prob;
569 best_freq = freq;
573 /* If the best destination has multiple predecessors, and can be
574 duplicated cheaper than a jump, don't allow it to be added
575 to a trace. We'll duplicate it when connecting traces. */
576 if (best_edge && EDGE_COUNT (best_edge->dest->preds) >= 2
577 && copy_bb_p (best_edge->dest, 0))
578 best_edge = NULL;
580 /* If the best destination has multiple successors or predecessors,
581 don't allow it to be added when optimizing for size. This makes
582 sure predecessors with smaller index are handled before the best
583 destinarion. It breaks long trace and reduces long jumps.
585 Take if-then-else as an example.
591 If we do not remove the best edge B->D/C->D, the final order might
592 be A B D ... C. C is at the end of the program. If D's successors
593 and D are complicated, might need long jumps for A->C and C->D.
594 Similar issue for order: A C D ... B.
596 After removing the best edge, the final result will be ABCD/ ACBD.
597 It does not add jump compared with the previous order. But it
598 reduces the possibility of long jumps. */
599 if (best_edge && for_size
600 && (EDGE_COUNT (best_edge->dest->succs) > 1
601 || EDGE_COUNT (best_edge->dest->preds) > 1))
602 best_edge = NULL;
604 /* Add all non-selected successors to the heaps. */
605 FOR_EACH_EDGE (e, ei, bb->succs)
607 if (e == best_edge
608 || e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)
609 || bb_visited_trace (e->dest))
610 continue;
612 key = bb_to_key (e->dest);
614 if (bbd[e->dest->index].heap)
616 /* E->DEST is already in some heap. */
617 if (key != bbd[e->dest->index].node->key)
619 if (dump_file)
621 fprintf (dump_file,
622 "Changing key for bb %d from %ld to %ld.\n",
623 e->dest->index,
624 (long) bbd[e->dest->index].node->key,
625 key);
627 fibheap_replace_key (bbd[e->dest->index].heap,
628 bbd[e->dest->index].node, key);
631 else
633 fibheap_t which_heap = *heap;
635 prob = e->probability;
636 freq = EDGE_FREQUENCY (e);
638 if (!(e->flags & EDGE_CAN_FALLTHRU)
639 || (e->flags & EDGE_COMPLEX)
640 || prob < branch_th || freq < exec_th
641 || e->count < count_th)
643 /* When partitioning hot/cold basic blocks, make sure
644 the cold blocks (and only the cold blocks) all get
645 pushed to the last round of trace collection. When
646 optimizing for size, do not push to next round. */
648 if (!for_size && push_to_next_round_p (e->dest, round,
649 number_of_rounds,
650 exec_th, count_th))
651 which_heap = new_heap;
654 bbd[e->dest->index].heap = which_heap;
655 bbd[e->dest->index].node = fibheap_insert (which_heap,
656 key, e->dest);
658 if (dump_file)
660 fprintf (dump_file,
661 " Possible start of %s round: %d (key: %ld)\n",
662 (which_heap == new_heap) ? "next" : "this",
663 e->dest->index, (long) key);
669 if (best_edge) /* Suitable successor was found. */
671 if (bb_visited_trace (best_edge->dest) == *n_traces)
673 /* We do nothing with one basic block loops. */
674 if (best_edge->dest != bb)
676 if (EDGE_FREQUENCY (best_edge)
677 > 4 * best_edge->dest->frequency / 5)
679 /* The loop has at least 4 iterations. If the loop
680 header is not the first block of the function
681 we can rotate the loop. */
683 if (best_edge->dest
684 != ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb)
686 if (dump_file)
688 fprintf (dump_file,
689 "Rotating loop %d - %d\n",
690 best_edge->dest->index, bb->index);
692 bb->aux = best_edge->dest;
693 bbd[best_edge->dest->index].in_trace =
694 (*n_traces) - 1;
695 bb = rotate_loop (best_edge, trace, *n_traces);
698 else
700 /* The loop has less than 4 iterations. */
702 if (single_succ_p (bb)
703 && copy_bb_p (best_edge->dest,
704 optimize_edge_for_speed_p
705 (best_edge)))
707 bb = copy_bb (best_edge->dest, best_edge, bb,
708 *n_traces);
709 trace->length++;
714 /* Terminate the trace. */
715 break;
717 else
719 /* Check for a situation
727 where
728 EDGE_FREQUENCY (AB) + EDGE_FREQUENCY (BC)
729 >= EDGE_FREQUENCY (AC).
730 (i.e. 2 * B->frequency >= EDGE_FREQUENCY (AC) )
731 Best ordering is then A B C.
733 When optimizing for size, A B C is always the best order.
735 This situation is created for example by:
737 if (A) B;
742 FOR_EACH_EDGE (e, ei, bb->succs)
743 if (e != best_edge
744 && (e->flags & EDGE_CAN_FALLTHRU)
745 && !(e->flags & EDGE_COMPLEX)
746 && !bb_visited_trace (e->dest)
747 && single_pred_p (e->dest)
748 && !(e->flags & EDGE_CROSSING)
749 && single_succ_p (e->dest)
750 && (single_succ_edge (e->dest)->flags
751 & EDGE_CAN_FALLTHRU)
752 && !(single_succ_edge (e->dest)->flags & EDGE_COMPLEX)
753 && single_succ (e->dest) == best_edge->dest
754 && (2 * e->dest->frequency >= EDGE_FREQUENCY (best_edge)
755 || for_size))
757 best_edge = e;
758 if (dump_file)
759 fprintf (dump_file, "Selecting BB %d\n",
760 best_edge->dest->index);
761 break;
764 bb->aux = best_edge->dest;
765 bbd[best_edge->dest->index].in_trace = (*n_traces) - 1;
766 bb = best_edge->dest;
770 while (best_edge);
771 trace->last = bb;
772 bbd[trace->first->index].start_of_trace = *n_traces - 1;
773 bbd[trace->last->index].end_of_trace = *n_traces - 1;
775 /* The trace is terminated so we have to recount the keys in heap
776 (some block can have a lower key because now one of its predecessors
777 is an end of the trace). */
778 FOR_EACH_EDGE (e, ei, bb->succs)
780 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)
781 || bb_visited_trace (e->dest))
782 continue;
784 if (bbd[e->dest->index].heap)
786 key = bb_to_key (e->dest);
787 if (key != bbd[e->dest->index].node->key)
789 if (dump_file)
791 fprintf (dump_file,
792 "Changing key for bb %d from %ld to %ld.\n",
793 e->dest->index,
794 (long) bbd[e->dest->index].node->key, key);
796 fibheap_replace_key (bbd[e->dest->index].heap,
797 bbd[e->dest->index].node,
798 key);
804 fibheap_delete (*heap);
806 /* "Return" the new heap. */
807 *heap = new_heap;
810 /* Create a duplicate of the basic block OLD_BB and redirect edge E to it, add
811 it to trace after BB, mark OLD_BB visited and update pass' data structures
812 (TRACE is a number of trace which OLD_BB is duplicated to). */
814 static basic_block
815 copy_bb (basic_block old_bb, edge e, basic_block bb, int trace)
817 basic_block new_bb;
819 new_bb = duplicate_block (old_bb, e, bb);
820 BB_COPY_PARTITION (new_bb, old_bb);
822 gcc_assert (e->dest == new_bb);
824 if (dump_file)
825 fprintf (dump_file,
826 "Duplicated bb %d (created bb %d)\n",
827 old_bb->index, new_bb->index);
829 if (new_bb->index >= array_size
830 || last_basic_block_for_fn (cfun) > array_size)
832 int i;
833 int new_size;
835 new_size = MAX (last_basic_block_for_fn (cfun), new_bb->index + 1);
836 new_size = GET_ARRAY_SIZE (new_size);
837 bbd = XRESIZEVEC (bbro_basic_block_data, bbd, new_size);
838 for (i = array_size; i < new_size; i++)
840 bbd[i].start_of_trace = -1;
841 bbd[i].end_of_trace = -1;
842 bbd[i].in_trace = -1;
843 bbd[i].visited = 0;
844 bbd[i].heap = NULL;
845 bbd[i].node = NULL;
847 array_size = new_size;
849 if (dump_file)
851 fprintf (dump_file,
852 "Growing the dynamic array to %d elements.\n",
853 array_size);
857 gcc_assert (!bb_visited_trace (e->dest));
858 mark_bb_visited (new_bb, trace);
859 new_bb->aux = bb->aux;
860 bb->aux = new_bb;
862 bbd[new_bb->index].in_trace = trace;
864 return new_bb;
867 /* Compute and return the key (for the heap) of the basic block BB. */
869 static fibheapkey_t
870 bb_to_key (basic_block bb)
872 edge e;
873 edge_iterator ei;
874 int priority = 0;
876 /* Use index as key to align with its original order. */
877 if (optimize_function_for_size_p (cfun))
878 return bb->index;
880 /* Do not start in probably never executed blocks. */
882 if (BB_PARTITION (bb) == BB_COLD_PARTITION
883 || probably_never_executed_bb_p (cfun, bb))
884 return BB_FREQ_MAX;
886 /* Prefer blocks whose predecessor is an end of some trace
887 or whose predecessor edge is EDGE_DFS_BACK. */
888 FOR_EACH_EDGE (e, ei, bb->preds)
890 if ((e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
891 && bbd[e->src->index].end_of_trace >= 0)
892 || (e->flags & EDGE_DFS_BACK))
894 int edge_freq = EDGE_FREQUENCY (e);
896 if (edge_freq > priority)
897 priority = edge_freq;
901 if (priority)
902 /* The block with priority should have significantly lower key. */
903 return -(100 * BB_FREQ_MAX + 100 * priority + bb->frequency);
905 return -bb->frequency;
908 /* Return true when the edge E from basic block BB is better than the temporary
909 best edge (details are in function). The probability of edge E is PROB. The
910 frequency of the successor is FREQ. The current best probability is
911 BEST_PROB, the best frequency is BEST_FREQ.
912 The edge is considered to be equivalent when PROB does not differ much from
913 BEST_PROB; similarly for frequency. */
915 static bool
916 better_edge_p (const_basic_block bb, const_edge e, int prob, int freq,
917 int best_prob, int best_freq, const_edge cur_best_edge)
919 bool is_better_edge;
921 /* The BEST_* values do not have to be best, but can be a bit smaller than
922 maximum values. */
923 int diff_prob = best_prob / 10;
924 int diff_freq = best_freq / 10;
926 /* The smaller one is better to keep the original order. */
927 if (optimize_function_for_size_p (cfun))
928 return !cur_best_edge
929 || cur_best_edge->dest->index > e->dest->index;
931 if (prob > best_prob + diff_prob)
932 /* The edge has higher probability than the temporary best edge. */
933 is_better_edge = true;
934 else if (prob < best_prob - diff_prob)
935 /* The edge has lower probability than the temporary best edge. */
936 is_better_edge = false;
937 else if (freq < best_freq - diff_freq)
938 /* The edge and the temporary best edge have almost equivalent
939 probabilities. The higher frequency of a successor now means
940 that there is another edge going into that successor.
941 This successor has lower frequency so it is better. */
942 is_better_edge = true;
943 else if (freq > best_freq + diff_freq)
944 /* This successor has higher frequency so it is worse. */
945 is_better_edge = false;
946 else if (e->dest->prev_bb == bb)
947 /* The edges have equivalent probabilities and the successors
948 have equivalent frequencies. Select the previous successor. */
949 is_better_edge = true;
950 else
951 is_better_edge = false;
953 /* If we are doing hot/cold partitioning, make sure that we always favor
954 non-crossing edges over crossing edges. */
956 if (!is_better_edge
957 && flag_reorder_blocks_and_partition
958 && cur_best_edge
959 && (cur_best_edge->flags & EDGE_CROSSING)
960 && !(e->flags & EDGE_CROSSING))
961 is_better_edge = true;
963 return is_better_edge;
966 /* Return true when the edge E is better than the temporary best edge
967 CUR_BEST_EDGE. If SRC_INDEX_P is true, the function compares the src bb of
968 E and CUR_BEST_EDGE; otherwise it will compare the dest bb.
969 BEST_LEN is the trace length of src (or dest) bb in CUR_BEST_EDGE.
970 TRACES record the information about traces.
971 When optimizing for size, the edge with smaller index is better.
972 When optimizing for speed, the edge with bigger probability or longer trace
973 is better. */
975 static bool
976 connect_better_edge_p (const_edge e, bool src_index_p, int best_len,
977 const_edge cur_best_edge, struct trace *traces)
979 int e_index;
980 int b_index;
981 bool is_better_edge;
983 if (!cur_best_edge)
984 return true;
986 if (optimize_function_for_size_p (cfun))
988 e_index = src_index_p ? e->src->index : e->dest->index;
989 b_index = src_index_p ? cur_best_edge->src->index
990 : cur_best_edge->dest->index;
991 /* The smaller one is better to keep the original order. */
992 return b_index > e_index;
995 if (src_index_p)
997 e_index = e->src->index;
999 if (e->probability > cur_best_edge->probability)
1000 /* The edge has higher probability than the temporary best edge. */
1001 is_better_edge = true;
1002 else if (e->probability < cur_best_edge->probability)
1003 /* The edge has lower probability than the temporary best edge. */
1004 is_better_edge = false;
1005 else if (traces[bbd[e_index].end_of_trace].length > best_len)
1006 /* The edge and the temporary best edge have equivalent probabilities.
1007 The edge with longer trace is better. */
1008 is_better_edge = true;
1009 else
1010 is_better_edge = false;
1012 else
1014 e_index = e->dest->index;
1016 if (e->probability > cur_best_edge->probability)
1017 /* The edge has higher probability than the temporary best edge. */
1018 is_better_edge = true;
1019 else if (e->probability < cur_best_edge->probability)
1020 /* The edge has lower probability than the temporary best edge. */
1021 is_better_edge = false;
1022 else if (traces[bbd[e_index].start_of_trace].length > best_len)
1023 /* The edge and the temporary best edge have equivalent probabilities.
1024 The edge with longer trace is better. */
1025 is_better_edge = true;
1026 else
1027 is_better_edge = false;
1030 return is_better_edge;
1033 /* Connect traces in array TRACES, N_TRACES is the count of traces. */
1035 static void
1036 connect_traces (int n_traces, struct trace *traces)
1038 int i;
1039 bool *connected;
1040 bool two_passes;
1041 int last_trace;
1042 int current_pass;
1043 int current_partition;
1044 int freq_threshold;
1045 gcov_type count_threshold;
1046 bool for_size = optimize_function_for_size_p (cfun);
1048 freq_threshold = max_entry_frequency * DUPLICATION_THRESHOLD / 1000;
1049 if (max_entry_count < INT_MAX / 1000)
1050 count_threshold = max_entry_count * DUPLICATION_THRESHOLD / 1000;
1051 else
1052 count_threshold = max_entry_count / 1000 * DUPLICATION_THRESHOLD;
1054 connected = XCNEWVEC (bool, n_traces);
1055 last_trace = -1;
1056 current_pass = 1;
1057 current_partition = BB_PARTITION (traces[0].first);
1058 two_passes = false;
1060 if (crtl->has_bb_partition)
1061 for (i = 0; i < n_traces && !two_passes; i++)
1062 if (BB_PARTITION (traces[0].first)
1063 != BB_PARTITION (traces[i].first))
1064 two_passes = true;
1066 for (i = 0; i < n_traces || (two_passes && current_pass == 1) ; i++)
1068 int t = i;
1069 int t2;
1070 edge e, best;
1071 int best_len;
1073 if (i >= n_traces)
1075 gcc_assert (two_passes && current_pass == 1);
1076 i = 0;
1077 t = i;
1078 current_pass = 2;
1079 if (current_partition == BB_HOT_PARTITION)
1080 current_partition = BB_COLD_PARTITION;
1081 else
1082 current_partition = BB_HOT_PARTITION;
1085 if (connected[t])
1086 continue;
1088 if (two_passes
1089 && BB_PARTITION (traces[t].first) != current_partition)
1090 continue;
1092 connected[t] = true;
1094 /* Find the predecessor traces. */
1095 for (t2 = t; t2 > 0;)
1097 edge_iterator ei;
1098 best = NULL;
1099 best_len = 0;
1100 FOR_EACH_EDGE (e, ei, traces[t2].first->preds)
1102 int si = e->src->index;
1104 if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
1105 && (e->flags & EDGE_CAN_FALLTHRU)
1106 && !(e->flags & EDGE_COMPLEX)
1107 && bbd[si].end_of_trace >= 0
1108 && !connected[bbd[si].end_of_trace]
1109 && (BB_PARTITION (e->src) == current_partition)
1110 && connect_better_edge_p (e, true, best_len, best, traces))
1112 best = e;
1113 best_len = traces[bbd[si].end_of_trace].length;
1116 if (best)
1118 best->src->aux = best->dest;
1119 t2 = bbd[best->src->index].end_of_trace;
1120 connected[t2] = true;
1122 if (dump_file)
1124 fprintf (dump_file, "Connection: %d %d\n",
1125 best->src->index, best->dest->index);
1128 else
1129 break;
1132 if (last_trace >= 0)
1133 traces[last_trace].last->aux = traces[t2].first;
1134 last_trace = t;
1136 /* Find the successor traces. */
1137 while (1)
1139 /* Find the continuation of the chain. */
1140 edge_iterator ei;
1141 best = NULL;
1142 best_len = 0;
1143 FOR_EACH_EDGE (e, ei, traces[t].last->succs)
1145 int di = e->dest->index;
1147 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
1148 && (e->flags & EDGE_CAN_FALLTHRU)
1149 && !(e->flags & EDGE_COMPLEX)
1150 && bbd[di].start_of_trace >= 0
1151 && !connected[bbd[di].start_of_trace]
1152 && (BB_PARTITION (e->dest) == current_partition)
1153 && connect_better_edge_p (e, false, best_len, best, traces))
1155 best = e;
1156 best_len = traces[bbd[di].start_of_trace].length;
1160 if (for_size)
1162 if (!best)
1163 /* Stop finding the successor traces. */
1164 break;
1166 /* It is OK to connect block n with block n + 1 or a block
1167 before n. For others, only connect to the loop header. */
1168 if (best->dest->index > (traces[t].last->index + 1))
1170 int count = EDGE_COUNT (best->dest->preds);
1172 FOR_EACH_EDGE (e, ei, best->dest->preds)
1173 if (e->flags & EDGE_DFS_BACK)
1174 count--;
1176 /* If dest has multiple predecessors, skip it. We expect
1177 that one predecessor with smaller index connects with it
1178 later. */
1179 if (count != 1)
1180 break;
1183 /* Only connect Trace n with Trace n + 1. It is conservative
1184 to keep the order as close as possible to the original order.
1185 It also helps to reduce long jumps. */
1186 if (last_trace != bbd[best->dest->index].start_of_trace - 1)
1187 break;
1189 if (dump_file)
1190 fprintf (dump_file, "Connection: %d %d\n",
1191 best->src->index, best->dest->index);
1193 t = bbd[best->dest->index].start_of_trace;
1194 traces[last_trace].last->aux = traces[t].first;
1195 connected[t] = true;
1196 last_trace = t;
1198 else if (best)
1200 if (dump_file)
1202 fprintf (dump_file, "Connection: %d %d\n",
1203 best->src->index, best->dest->index);
1205 t = bbd[best->dest->index].start_of_trace;
1206 traces[last_trace].last->aux = traces[t].first;
1207 connected[t] = true;
1208 last_trace = t;
1210 else
1212 /* Try to connect the traces by duplication of 1 block. */
1213 edge e2;
1214 basic_block next_bb = NULL;
1215 bool try_copy = false;
1217 FOR_EACH_EDGE (e, ei, traces[t].last->succs)
1218 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
1219 && (e->flags & EDGE_CAN_FALLTHRU)
1220 && !(e->flags & EDGE_COMPLEX)
1221 && (!best || e->probability > best->probability))
1223 edge_iterator ei;
1224 edge best2 = NULL;
1225 int best2_len = 0;
1227 /* If the destination is a start of a trace which is only
1228 one block long, then no need to search the successor
1229 blocks of the trace. Accept it. */
1230 if (bbd[e->dest->index].start_of_trace >= 0
1231 && traces[bbd[e->dest->index].start_of_trace].length
1232 == 1)
1234 best = e;
1235 try_copy = true;
1236 continue;
1239 FOR_EACH_EDGE (e2, ei, e->dest->succs)
1241 int di = e2->dest->index;
1243 if (e2->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)
1244 || ((e2->flags & EDGE_CAN_FALLTHRU)
1245 && !(e2->flags & EDGE_COMPLEX)
1246 && bbd[di].start_of_trace >= 0
1247 && !connected[bbd[di].start_of_trace]
1248 && BB_PARTITION (e2->dest) == current_partition
1249 && EDGE_FREQUENCY (e2) >= freq_threshold
1250 && e2->count >= count_threshold
1251 && (!best2
1252 || e2->probability > best2->probability
1253 || (e2->probability == best2->probability
1254 && traces[bbd[di].start_of_trace].length
1255 > best2_len))))
1257 best = e;
1258 best2 = e2;
1259 if (e2->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
1260 best2_len = traces[bbd[di].start_of_trace].length;
1261 else
1262 best2_len = INT_MAX;
1263 next_bb = e2->dest;
1264 try_copy = true;
1269 if (crtl->has_bb_partition)
1270 try_copy = false;
1272 /* Copy tiny blocks always; copy larger blocks only when the
1273 edge is traversed frequently enough. */
1274 if (try_copy
1275 && copy_bb_p (best->dest,
1276 optimize_edge_for_speed_p (best)
1277 && EDGE_FREQUENCY (best) >= freq_threshold
1278 && best->count >= count_threshold))
1280 basic_block new_bb;
1282 if (dump_file)
1284 fprintf (dump_file, "Connection: %d %d ",
1285 traces[t].last->index, best->dest->index);
1286 if (!next_bb)
1287 fputc ('\n', dump_file);
1288 else if (next_bb == EXIT_BLOCK_PTR_FOR_FN (cfun))
1289 fprintf (dump_file, "exit\n");
1290 else
1291 fprintf (dump_file, "%d\n", next_bb->index);
1294 new_bb = copy_bb (best->dest, best, traces[t].last, t);
1295 traces[t].last = new_bb;
1296 if (next_bb && next_bb != EXIT_BLOCK_PTR_FOR_FN (cfun))
1298 t = bbd[next_bb->index].start_of_trace;
1299 traces[last_trace].last->aux = traces[t].first;
1300 connected[t] = true;
1301 last_trace = t;
1303 else
1304 break; /* Stop finding the successor traces. */
1306 else
1307 break; /* Stop finding the successor traces. */
1312 if (dump_file)
1314 basic_block bb;
1316 fprintf (dump_file, "Final order:\n");
1317 for (bb = traces[0].first; bb; bb = (basic_block) bb->aux)
1318 fprintf (dump_file, "%d ", bb->index);
1319 fprintf (dump_file, "\n");
1320 fflush (dump_file);
1323 FREE (connected);
1326 /* Return true when BB can and should be copied. CODE_MAY_GROW is true
1327 when code size is allowed to grow by duplication. */
1329 static bool
1330 copy_bb_p (const_basic_block bb, int code_may_grow)
1332 int size = 0;
1333 int max_size = uncond_jump_length;
1334 rtx_insn *insn;
1336 if (!bb->frequency)
1337 return false;
1338 if (EDGE_COUNT (bb->preds) < 2)
1339 return false;
1340 if (!can_duplicate_block_p (bb))
1341 return false;
1343 /* Avoid duplicating blocks which have many successors (PR/13430). */
1344 if (EDGE_COUNT (bb->succs) > 8)
1345 return false;
1347 if (code_may_grow && optimize_bb_for_speed_p (bb))
1348 max_size *= PARAM_VALUE (PARAM_MAX_GROW_COPY_BB_INSNS);
1350 FOR_BB_INSNS (bb, insn)
1352 if (INSN_P (insn))
1353 size += get_attr_min_length (insn);
1356 if (size <= max_size)
1357 return true;
1359 if (dump_file)
1361 fprintf (dump_file,
1362 "Block %d can't be copied because its size = %d.\n",
1363 bb->index, size);
1366 return false;
1369 /* Return the length of unconditional jump instruction. */
1372 get_uncond_jump_length (void)
1374 rtx_insn *label, *jump;
1375 int length;
1377 label = emit_label_before (gen_label_rtx (), get_insns ());
1378 jump = emit_jump_insn (gen_jump (label));
1380 length = get_attr_min_length (jump);
1382 delete_insn (jump);
1383 delete_insn (label);
1384 return length;
1387 /* The landing pad OLD_LP, in block OLD_BB, has edges from both partitions.
1388 Duplicate the landing pad and split the edges so that no EH edge
1389 crosses partitions. */
1391 static void
1392 fix_up_crossing_landing_pad (eh_landing_pad old_lp, basic_block old_bb)
1394 eh_landing_pad new_lp;
1395 basic_block new_bb, last_bb, post_bb;
1396 rtx_insn *new_label, *jump;
1397 rtx post_label;
1398 unsigned new_partition;
1399 edge_iterator ei;
1400 edge e;
1402 /* Generate the new landing-pad structure. */
1403 new_lp = gen_eh_landing_pad (old_lp->region);
1404 new_lp->post_landing_pad = old_lp->post_landing_pad;
1405 new_lp->landing_pad = gen_label_rtx ();
1406 LABEL_PRESERVE_P (new_lp->landing_pad) = 1;
1408 /* Put appropriate instructions in new bb. */
1409 new_label = emit_label (new_lp->landing_pad);
1411 expand_dw2_landing_pad_for_region (old_lp->region);
1413 post_bb = BLOCK_FOR_INSN (old_lp->landing_pad);
1414 post_bb = single_succ (post_bb);
1415 post_label = block_label (post_bb);
1416 jump = emit_jump_insn (gen_jump (post_label));
1417 JUMP_LABEL (jump) = post_label;
1419 /* Create new basic block to be dest for lp. */
1420 last_bb = EXIT_BLOCK_PTR_FOR_FN (cfun)->prev_bb;
1421 new_bb = create_basic_block (new_label, jump, last_bb);
1422 new_bb->aux = last_bb->aux;
1423 last_bb->aux = new_bb;
1425 emit_barrier_after_bb (new_bb);
1427 make_edge (new_bb, post_bb, 0);
1429 /* Make sure new bb is in the other partition. */
1430 new_partition = BB_PARTITION (old_bb);
1431 new_partition ^= BB_HOT_PARTITION | BB_COLD_PARTITION;
1432 BB_SET_PARTITION (new_bb, new_partition);
1434 /* Fix up the edges. */
1435 for (ei = ei_start (old_bb->preds); (e = ei_safe_edge (ei)) != NULL; )
1436 if (BB_PARTITION (e->src) == new_partition)
1438 rtx_insn *insn = BB_END (e->src);
1439 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
1441 gcc_assert (note != NULL);
1442 gcc_checking_assert (INTVAL (XEXP (note, 0)) == old_lp->index);
1443 XEXP (note, 0) = GEN_INT (new_lp->index);
1445 /* Adjust the edge to the new destination. */
1446 redirect_edge_succ (e, new_bb);
1448 else
1449 ei_next (&ei);
1453 /* Ensure that all hot bbs are included in a hot path through the
1454 procedure. This is done by calling this function twice, once
1455 with WALK_UP true (to look for paths from the entry to hot bbs) and
1456 once with WALK_UP false (to look for paths from hot bbs to the exit).
1457 Returns the updated value of COLD_BB_COUNT and adds newly-hot bbs
1458 to BBS_IN_HOT_PARTITION. */
1460 static unsigned int
1461 sanitize_hot_paths (bool walk_up, unsigned int cold_bb_count,
1462 vec<basic_block> *bbs_in_hot_partition)
1464 /* Callers check this. */
1465 gcc_checking_assert (cold_bb_count);
1467 /* Keep examining hot bbs while we still have some left to check
1468 and there are remaining cold bbs. */
1469 vec<basic_block> hot_bbs_to_check = bbs_in_hot_partition->copy ();
1470 while (! hot_bbs_to_check.is_empty ()
1471 && cold_bb_count)
1473 basic_block bb = hot_bbs_to_check.pop ();
1474 vec<edge, va_gc> *edges = walk_up ? bb->preds : bb->succs;
1475 edge e;
1476 edge_iterator ei;
1477 int highest_probability = 0;
1478 int highest_freq = 0;
1479 gcov_type highest_count = 0;
1480 bool found = false;
1482 /* Walk the preds/succs and check if there is at least one already
1483 marked hot. Keep track of the most frequent pred/succ so that we
1484 can mark it hot if we don't find one. */
1485 FOR_EACH_EDGE (e, ei, edges)
1487 basic_block reach_bb = walk_up ? e->src : e->dest;
1489 if (e->flags & EDGE_DFS_BACK)
1490 continue;
1492 if (BB_PARTITION (reach_bb) != BB_COLD_PARTITION)
1494 found = true;
1495 break;
1497 /* The following loop will look for the hottest edge via
1498 the edge count, if it is non-zero, then fallback to the edge
1499 frequency and finally the edge probability. */
1500 if (e->count > highest_count)
1501 highest_count = e->count;
1502 int edge_freq = EDGE_FREQUENCY (e);
1503 if (edge_freq > highest_freq)
1504 highest_freq = edge_freq;
1505 if (e->probability > highest_probability)
1506 highest_probability = e->probability;
1509 /* If bb is reached by (or reaches, in the case of !WALK_UP) another hot
1510 block (or unpartitioned, e.g. the entry block) then it is ok. If not,
1511 then the most frequent pred (or succ) needs to be adjusted. In the
1512 case where multiple preds/succs have the same frequency (e.g. a
1513 50-50 branch), then both will be adjusted. */
1514 if (found)
1515 continue;
1517 FOR_EACH_EDGE (e, ei, edges)
1519 if (e->flags & EDGE_DFS_BACK)
1520 continue;
1521 /* Select the hottest edge using the edge count, if it is non-zero,
1522 then fallback to the edge frequency and finally the edge
1523 probability. */
1524 if (highest_count)
1526 if (e->count < highest_count)
1527 continue;
1529 else if (highest_freq)
1531 if (EDGE_FREQUENCY (e) < highest_freq)
1532 continue;
1534 else if (e->probability < highest_probability)
1535 continue;
1537 basic_block reach_bb = walk_up ? e->src : e->dest;
1539 /* We have a hot bb with an immediate dominator that is cold.
1540 The dominator needs to be re-marked hot. */
1541 BB_SET_PARTITION (reach_bb, BB_HOT_PARTITION);
1542 cold_bb_count--;
1544 /* Now we need to examine newly-hot reach_bb to see if it is also
1545 dominated by a cold bb. */
1546 bbs_in_hot_partition->safe_push (reach_bb);
1547 hot_bbs_to_check.safe_push (reach_bb);
1551 return cold_bb_count;
1555 /* Find the basic blocks that are rarely executed and need to be moved to
1556 a separate section of the .o file (to cut down on paging and improve
1557 cache locality). Return a vector of all edges that cross. */
1559 static vec<edge>
1560 find_rarely_executed_basic_blocks_and_crossing_edges (void)
1562 vec<edge> crossing_edges = vNULL;
1563 basic_block bb;
1564 edge e;
1565 edge_iterator ei;
1566 unsigned int cold_bb_count = 0;
1567 vec<basic_block> bbs_in_hot_partition = vNULL;
1569 /* Mark which partition (hot/cold) each basic block belongs in. */
1570 FOR_EACH_BB_FN (bb, cfun)
1572 bool cold_bb = false;
1574 if (probably_never_executed_bb_p (cfun, bb))
1576 /* Handle profile insanities created by upstream optimizations
1577 by also checking the incoming edge weights. If there is a non-cold
1578 incoming edge, conservatively prevent this block from being split
1579 into the cold section. */
1580 cold_bb = true;
1581 FOR_EACH_EDGE (e, ei, bb->preds)
1582 if (!probably_never_executed_edge_p (cfun, e))
1584 cold_bb = false;
1585 break;
1588 if (cold_bb)
1590 BB_SET_PARTITION (bb, BB_COLD_PARTITION);
1591 cold_bb_count++;
1593 else
1595 BB_SET_PARTITION (bb, BB_HOT_PARTITION);
1596 bbs_in_hot_partition.safe_push (bb);
1600 /* Ensure that hot bbs are included along a hot path from the entry to exit.
1601 Several different possibilities may include cold bbs along all paths
1602 to/from a hot bb. One is that there are edge weight insanities
1603 due to optimization phases that do not properly update basic block profile
1604 counts. The second is that the entry of the function may not be hot, because
1605 it is entered fewer times than the number of profile training runs, but there
1606 is a loop inside the function that causes blocks within the function to be
1607 above the threshold for hotness. This is fixed by walking up from hot bbs
1608 to the entry block, and then down from hot bbs to the exit, performing
1609 partitioning fixups as necessary. */
1610 if (cold_bb_count)
1612 mark_dfs_back_edges ();
1613 cold_bb_count = sanitize_hot_paths (true, cold_bb_count,
1614 &bbs_in_hot_partition);
1615 if (cold_bb_count)
1616 sanitize_hot_paths (false, cold_bb_count, &bbs_in_hot_partition);
1619 /* The format of .gcc_except_table does not allow landing pads to
1620 be in a different partition as the throw. Fix this by either
1621 moving or duplicating the landing pads. */
1622 if (cfun->eh->lp_array)
1624 unsigned i;
1625 eh_landing_pad lp;
1627 FOR_EACH_VEC_ELT (*cfun->eh->lp_array, i, lp)
1629 bool all_same, all_diff;
1631 if (lp == NULL
1632 || lp->landing_pad == NULL_RTX
1633 || !LABEL_P (lp->landing_pad))
1634 continue;
1636 all_same = all_diff = true;
1637 bb = BLOCK_FOR_INSN (lp->landing_pad);
1638 FOR_EACH_EDGE (e, ei, bb->preds)
1640 gcc_assert (e->flags & EDGE_EH);
1641 if (BB_PARTITION (bb) == BB_PARTITION (e->src))
1642 all_diff = false;
1643 else
1644 all_same = false;
1647 if (all_same)
1649 else if (all_diff)
1651 int which = BB_PARTITION (bb);
1652 which ^= BB_HOT_PARTITION | BB_COLD_PARTITION;
1653 BB_SET_PARTITION (bb, which);
1655 else
1656 fix_up_crossing_landing_pad (lp, bb);
1660 /* Mark every edge that crosses between sections. */
1662 FOR_EACH_BB_FN (bb, cfun)
1663 FOR_EACH_EDGE (e, ei, bb->succs)
1665 unsigned int flags = e->flags;
1667 /* We should never have EDGE_CROSSING set yet. */
1668 gcc_checking_assert ((flags & EDGE_CROSSING) == 0);
1670 if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
1671 && e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
1672 && BB_PARTITION (e->src) != BB_PARTITION (e->dest))
1674 crossing_edges.safe_push (e);
1675 flags |= EDGE_CROSSING;
1678 /* Now that we've split eh edges as appropriate, allow landing pads
1679 to be merged with the post-landing pads. */
1680 flags &= ~EDGE_PRESERVE;
1682 e->flags = flags;
1685 return crossing_edges;
1688 /* Set the flag EDGE_CAN_FALLTHRU for edges that can be fallthru. */
1690 static void
1691 set_edge_can_fallthru_flag (void)
1693 basic_block bb;
1695 FOR_EACH_BB_FN (bb, cfun)
1697 edge e;
1698 edge_iterator ei;
1700 FOR_EACH_EDGE (e, ei, bb->succs)
1702 e->flags &= ~EDGE_CAN_FALLTHRU;
1704 /* The FALLTHRU edge is also CAN_FALLTHRU edge. */
1705 if (e->flags & EDGE_FALLTHRU)
1706 e->flags |= EDGE_CAN_FALLTHRU;
1709 /* If the BB ends with an invertible condjump all (2) edges are
1710 CAN_FALLTHRU edges. */
1711 if (EDGE_COUNT (bb->succs) != 2)
1712 continue;
1713 if (!any_condjump_p (BB_END (bb)))
1714 continue;
1715 if (!invert_jump (BB_END (bb), JUMP_LABEL (BB_END (bb)), 0))
1716 continue;
1717 invert_jump (BB_END (bb), JUMP_LABEL (BB_END (bb)), 0);
1718 EDGE_SUCC (bb, 0)->flags |= EDGE_CAN_FALLTHRU;
1719 EDGE_SUCC (bb, 1)->flags |= EDGE_CAN_FALLTHRU;
1723 /* If any destination of a crossing edge does not have a label, add label;
1724 Convert any easy fall-through crossing edges to unconditional jumps. */
1726 static void
1727 add_labels_and_missing_jumps (vec<edge> crossing_edges)
1729 size_t i;
1730 edge e;
1732 FOR_EACH_VEC_ELT (crossing_edges, i, e)
1734 basic_block src = e->src;
1735 basic_block dest = e->dest;
1736 rtx label;
1737 rtx_insn *new_jump;
1739 if (dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
1740 continue;
1742 /* Make sure dest has a label. */
1743 label = block_label (dest);
1745 /* Nothing to do for non-fallthru edges. */
1746 if (src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
1747 continue;
1748 if ((e->flags & EDGE_FALLTHRU) == 0)
1749 continue;
1751 /* If the block does not end with a control flow insn, then we
1752 can trivially add a jump to the end to fixup the crossing.
1753 Otherwise the jump will have to go in a new bb, which will
1754 be handled by fix_up_fall_thru_edges function. */
1755 if (control_flow_insn_p (BB_END (src)))
1756 continue;
1758 /* Make sure there's only one successor. */
1759 gcc_assert (single_succ_p (src));
1761 new_jump = emit_jump_insn_after (gen_jump (label), BB_END (src));
1762 BB_END (src) = new_jump;
1763 JUMP_LABEL (new_jump) = label;
1764 LABEL_NUSES (label) += 1;
1766 emit_barrier_after_bb (src);
1768 /* Mark edge as non-fallthru. */
1769 e->flags &= ~EDGE_FALLTHRU;
1773 /* Find any bb's where the fall-through edge is a crossing edge (note that
1774 these bb's must also contain a conditional jump or end with a call
1775 instruction; we've already dealt with fall-through edges for blocks
1776 that didn't have a conditional jump or didn't end with call instruction
1777 in the call to add_labels_and_missing_jumps). Convert the fall-through
1778 edge to non-crossing edge by inserting a new bb to fall-through into.
1779 The new bb will contain an unconditional jump (crossing edge) to the
1780 original fall through destination. */
1782 static void
1783 fix_up_fall_thru_edges (void)
1785 basic_block cur_bb;
1786 basic_block new_bb;
1787 edge succ1;
1788 edge succ2;
1789 edge fall_thru;
1790 edge cond_jump = NULL;
1791 edge e;
1792 bool cond_jump_crosses;
1793 int invert_worked;
1794 rtx_insn *old_jump;
1795 rtx fall_thru_label;
1797 FOR_EACH_BB_FN (cur_bb, cfun)
1799 fall_thru = NULL;
1800 if (EDGE_COUNT (cur_bb->succs) > 0)
1801 succ1 = EDGE_SUCC (cur_bb, 0);
1802 else
1803 succ1 = NULL;
1805 if (EDGE_COUNT (cur_bb->succs) > 1)
1806 succ2 = EDGE_SUCC (cur_bb, 1);
1807 else
1808 succ2 = NULL;
1810 /* Find the fall-through edge. */
1812 if (succ1
1813 && (succ1->flags & EDGE_FALLTHRU))
1815 fall_thru = succ1;
1816 cond_jump = succ2;
1818 else if (succ2
1819 && (succ2->flags & EDGE_FALLTHRU))
1821 fall_thru = succ2;
1822 cond_jump = succ1;
1824 else if (succ1
1825 && (block_ends_with_call_p (cur_bb)
1826 || can_throw_internal (BB_END (cur_bb))))
1828 edge e;
1829 edge_iterator ei;
1831 FOR_EACH_EDGE (e, ei, cur_bb->succs)
1832 if (e->flags & EDGE_FALLTHRU)
1834 fall_thru = e;
1835 break;
1839 if (fall_thru && (fall_thru->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)))
1841 /* Check to see if the fall-thru edge is a crossing edge. */
1843 if (fall_thru->flags & EDGE_CROSSING)
1845 /* The fall_thru edge crosses; now check the cond jump edge, if
1846 it exists. */
1848 cond_jump_crosses = true;
1849 invert_worked = 0;
1850 old_jump = BB_END (cur_bb);
1852 /* Find the jump instruction, if there is one. */
1854 if (cond_jump)
1856 if (!(cond_jump->flags & EDGE_CROSSING))
1857 cond_jump_crosses = false;
1859 /* We know the fall-thru edge crosses; if the cond
1860 jump edge does NOT cross, and its destination is the
1861 next block in the bb order, invert the jump
1862 (i.e. fix it so the fall through does not cross and
1863 the cond jump does). */
1865 if (!cond_jump_crosses)
1867 /* Find label in fall_thru block. We've already added
1868 any missing labels, so there must be one. */
1870 fall_thru_label = block_label (fall_thru->dest);
1872 if (old_jump && JUMP_P (old_jump) && fall_thru_label)
1873 invert_worked = invert_jump (old_jump,
1874 fall_thru_label,0);
1875 if (invert_worked)
1877 fall_thru->flags &= ~EDGE_FALLTHRU;
1878 cond_jump->flags |= EDGE_FALLTHRU;
1879 update_br_prob_note (cur_bb);
1880 e = fall_thru;
1881 fall_thru = cond_jump;
1882 cond_jump = e;
1883 cond_jump->flags |= EDGE_CROSSING;
1884 fall_thru->flags &= ~EDGE_CROSSING;
1889 if (cond_jump_crosses || !invert_worked)
1891 /* This is the case where both edges out of the basic
1892 block are crossing edges. Here we will fix up the
1893 fall through edge. The jump edge will be taken care
1894 of later. The EDGE_CROSSING flag of fall_thru edge
1895 is unset before the call to force_nonfallthru
1896 function because if a new basic-block is created
1897 this edge remains in the current section boundary
1898 while the edge between new_bb and the fall_thru->dest
1899 becomes EDGE_CROSSING. */
1901 fall_thru->flags &= ~EDGE_CROSSING;
1902 new_bb = force_nonfallthru (fall_thru);
1904 if (new_bb)
1906 new_bb->aux = cur_bb->aux;
1907 cur_bb->aux = new_bb;
1909 /* This is done by force_nonfallthru_and_redirect. */
1910 gcc_assert (BB_PARTITION (new_bb)
1911 == BB_PARTITION (cur_bb));
1913 single_succ_edge (new_bb)->flags |= EDGE_CROSSING;
1915 else
1917 /* If a new basic-block was not created; restore
1918 the EDGE_CROSSING flag. */
1919 fall_thru->flags |= EDGE_CROSSING;
1922 /* Add barrier after new jump */
1923 emit_barrier_after_bb (new_bb ? new_bb : cur_bb);
1930 /* This function checks the destination block of a "crossing jump" to
1931 see if it has any crossing predecessors that begin with a code label
1932 and end with an unconditional jump. If so, it returns that predecessor
1933 block. (This is to avoid creating lots of new basic blocks that all
1934 contain unconditional jumps to the same destination). */
1936 static basic_block
1937 find_jump_block (basic_block jump_dest)
1939 basic_block source_bb = NULL;
1940 edge e;
1941 rtx_insn *insn;
1942 edge_iterator ei;
1944 FOR_EACH_EDGE (e, ei, jump_dest->preds)
1945 if (e->flags & EDGE_CROSSING)
1947 basic_block src = e->src;
1949 /* Check each predecessor to see if it has a label, and contains
1950 only one executable instruction, which is an unconditional jump.
1951 If so, we can use it. */
1953 if (LABEL_P (BB_HEAD (src)))
1954 for (insn = BB_HEAD (src);
1955 !INSN_P (insn) && insn != NEXT_INSN (BB_END (src));
1956 insn = NEXT_INSN (insn))
1958 if (INSN_P (insn)
1959 && insn == BB_END (src)
1960 && JUMP_P (insn)
1961 && !any_condjump_p (insn))
1963 source_bb = src;
1964 break;
1968 if (source_bb)
1969 break;
1972 return source_bb;
1975 /* Find all BB's with conditional jumps that are crossing edges;
1976 insert a new bb and make the conditional jump branch to the new
1977 bb instead (make the new bb same color so conditional branch won't
1978 be a 'crossing' edge). Insert an unconditional jump from the
1979 new bb to the original destination of the conditional jump. */
1981 static void
1982 fix_crossing_conditional_branches (void)
1984 basic_block cur_bb;
1985 basic_block new_bb;
1986 basic_block dest;
1987 edge succ1;
1988 edge succ2;
1989 edge crossing_edge;
1990 edge new_edge;
1991 rtx_insn *old_jump;
1992 rtx set_src;
1993 rtx old_label = NULL_RTX;
1994 rtx new_label;
1996 FOR_EACH_BB_FN (cur_bb, cfun)
1998 crossing_edge = NULL;
1999 if (EDGE_COUNT (cur_bb->succs) > 0)
2000 succ1 = EDGE_SUCC (cur_bb, 0);
2001 else
2002 succ1 = NULL;
2004 if (EDGE_COUNT (cur_bb->succs) > 1)
2005 succ2 = EDGE_SUCC (cur_bb, 1);
2006 else
2007 succ2 = NULL;
2009 /* We already took care of fall-through edges, so only one successor
2010 can be a crossing edge. */
2012 if (succ1 && (succ1->flags & EDGE_CROSSING))
2013 crossing_edge = succ1;
2014 else if (succ2 && (succ2->flags & EDGE_CROSSING))
2015 crossing_edge = succ2;
2017 if (crossing_edge)
2019 old_jump = BB_END (cur_bb);
2021 /* Check to make sure the jump instruction is a
2022 conditional jump. */
2024 set_src = NULL_RTX;
2026 if (any_condjump_p (old_jump))
2028 if (GET_CODE (PATTERN (old_jump)) == SET)
2029 set_src = SET_SRC (PATTERN (old_jump));
2030 else if (GET_CODE (PATTERN (old_jump)) == PARALLEL)
2032 set_src = XVECEXP (PATTERN (old_jump), 0,0);
2033 if (GET_CODE (set_src) == SET)
2034 set_src = SET_SRC (set_src);
2035 else
2036 set_src = NULL_RTX;
2040 if (set_src && (GET_CODE (set_src) == IF_THEN_ELSE))
2042 if (GET_CODE (XEXP (set_src, 1)) == PC)
2043 old_label = XEXP (set_src, 2);
2044 else if (GET_CODE (XEXP (set_src, 2)) == PC)
2045 old_label = XEXP (set_src, 1);
2047 /* Check to see if new bb for jumping to that dest has
2048 already been created; if so, use it; if not, create
2049 a new one. */
2051 new_bb = find_jump_block (crossing_edge->dest);
2053 if (new_bb)
2054 new_label = block_label (new_bb);
2055 else
2057 basic_block last_bb;
2058 rtx_insn *new_jump;
2060 /* Create new basic block to be dest for
2061 conditional jump. */
2063 /* Put appropriate instructions in new bb. */
2065 new_label = gen_label_rtx ();
2066 emit_label (new_label);
2068 gcc_assert (GET_CODE (old_label) == LABEL_REF);
2069 old_label = JUMP_LABEL (old_jump);
2070 new_jump = emit_jump_insn (gen_jump (old_label));
2071 JUMP_LABEL (new_jump) = old_label;
2073 last_bb = EXIT_BLOCK_PTR_FOR_FN (cfun)->prev_bb;
2074 new_bb = create_basic_block (new_label, new_jump, last_bb);
2075 new_bb->aux = last_bb->aux;
2076 last_bb->aux = new_bb;
2078 emit_barrier_after_bb (new_bb);
2080 /* Make sure new bb is in same partition as source
2081 of conditional branch. */
2082 BB_COPY_PARTITION (new_bb, cur_bb);
2085 /* Make old jump branch to new bb. */
2087 redirect_jump (old_jump, new_label, 0);
2089 /* Remove crossing_edge as predecessor of 'dest'. */
2091 dest = crossing_edge->dest;
2093 redirect_edge_succ (crossing_edge, new_bb);
2095 /* Make a new edge from new_bb to old dest; new edge
2096 will be a successor for new_bb and a predecessor
2097 for 'dest'. */
2099 if (EDGE_COUNT (new_bb->succs) == 0)
2100 new_edge = make_edge (new_bb, dest, 0);
2101 else
2102 new_edge = EDGE_SUCC (new_bb, 0);
2104 crossing_edge->flags &= ~EDGE_CROSSING;
2105 new_edge->flags |= EDGE_CROSSING;
2111 /* Find any unconditional branches that cross between hot and cold
2112 sections. Convert them into indirect jumps instead. */
2114 static void
2115 fix_crossing_unconditional_branches (void)
2117 basic_block cur_bb;
2118 rtx_insn *last_insn;
2119 rtx label;
2120 rtx label_addr;
2121 rtx_insn *indirect_jump_sequence;
2122 rtx_insn *jump_insn = NULL;
2123 rtx new_reg;
2124 rtx_insn *cur_insn;
2125 edge succ;
2127 FOR_EACH_BB_FN (cur_bb, cfun)
2129 last_insn = BB_END (cur_bb);
2131 if (EDGE_COUNT (cur_bb->succs) < 1)
2132 continue;
2134 succ = EDGE_SUCC (cur_bb, 0);
2136 /* Check to see if bb ends in a crossing (unconditional) jump. At
2137 this point, no crossing jumps should be conditional. */
2139 if (JUMP_P (last_insn)
2140 && (succ->flags & EDGE_CROSSING))
2142 gcc_assert (!any_condjump_p (last_insn));
2144 /* Make sure the jump is not already an indirect or table jump. */
2146 if (!computed_jump_p (last_insn)
2147 && !tablejump_p (last_insn, NULL, NULL))
2149 /* We have found a "crossing" unconditional branch. Now
2150 we must convert it to an indirect jump. First create
2151 reference of label, as target for jump. */
2153 label = JUMP_LABEL (last_insn);
2154 label_addr = gen_rtx_LABEL_REF (Pmode, label);
2155 LABEL_NUSES (label) += 1;
2157 /* Get a register to use for the indirect jump. */
2159 new_reg = gen_reg_rtx (Pmode);
2161 /* Generate indirect the jump sequence. */
2163 start_sequence ();
2164 emit_move_insn (new_reg, label_addr);
2165 emit_indirect_jump (new_reg);
2166 indirect_jump_sequence = get_insns ();
2167 end_sequence ();
2169 /* Make sure every instruction in the new jump sequence has
2170 its basic block set to be cur_bb. */
2172 for (cur_insn = indirect_jump_sequence; cur_insn;
2173 cur_insn = NEXT_INSN (cur_insn))
2175 if (!BARRIER_P (cur_insn))
2176 BLOCK_FOR_INSN (cur_insn) = cur_bb;
2177 if (JUMP_P (cur_insn))
2178 jump_insn = cur_insn;
2181 /* Insert the new (indirect) jump sequence immediately before
2182 the unconditional jump, then delete the unconditional jump. */
2184 emit_insn_before (indirect_jump_sequence, last_insn);
2185 delete_insn (last_insn);
2187 JUMP_LABEL (jump_insn) = label;
2188 LABEL_NUSES (label)++;
2190 /* Make BB_END for cur_bb be the jump instruction (NOT the
2191 barrier instruction at the end of the sequence...). */
2193 BB_END (cur_bb) = jump_insn;
2199 /* Update CROSSING_JUMP_P flags on all jump insns. */
2201 static void
2202 update_crossing_jump_flags (void)
2204 basic_block bb;
2205 edge e;
2206 edge_iterator ei;
2208 FOR_EACH_BB_FN (bb, cfun)
2209 FOR_EACH_EDGE (e, ei, bb->succs)
2210 if (e->flags & EDGE_CROSSING)
2212 if (JUMP_P (BB_END (bb))
2213 /* Some flags were added during fix_up_fall_thru_edges, via
2214 force_nonfallthru_and_redirect. */
2215 && !CROSSING_JUMP_P (BB_END (bb)))
2216 CROSSING_JUMP_P (BB_END (bb)) = 1;
2217 break;
2221 /* Reorder basic blocks. The main entry point to this file. FLAGS is
2222 the set of flags to pass to cfg_layout_initialize(). */
2224 static void
2225 reorder_basic_blocks (void)
2227 int n_traces;
2228 int i;
2229 struct trace *traces;
2231 gcc_assert (current_ir_type () == IR_RTL_CFGLAYOUT);
2233 if (n_basic_blocks_for_fn (cfun) <= NUM_FIXED_BLOCKS + 1)
2234 return;
2236 set_edge_can_fallthru_flag ();
2237 mark_dfs_back_edges ();
2239 /* We are estimating the length of uncond jump insn only once since the code
2240 for getting the insn length always returns the minimal length now. */
2241 if (uncond_jump_length == 0)
2242 uncond_jump_length = get_uncond_jump_length ();
2244 /* We need to know some information for each basic block. */
2245 array_size = GET_ARRAY_SIZE (last_basic_block_for_fn (cfun));
2246 bbd = XNEWVEC (bbro_basic_block_data, array_size);
2247 for (i = 0; i < array_size; i++)
2249 bbd[i].start_of_trace = -1;
2250 bbd[i].end_of_trace = -1;
2251 bbd[i].in_trace = -1;
2252 bbd[i].visited = 0;
2253 bbd[i].heap = NULL;
2254 bbd[i].node = NULL;
2257 traces = XNEWVEC (struct trace, n_basic_blocks_for_fn (cfun));
2258 n_traces = 0;
2259 find_traces (&n_traces, traces);
2260 connect_traces (n_traces, traces);
2261 FREE (traces);
2262 FREE (bbd);
2264 relink_block_chain (/*stay_in_cfglayout_mode=*/true);
2266 if (dump_file)
2268 if (dump_flags & TDF_DETAILS)
2269 dump_reg_info (dump_file);
2270 dump_flow_info (dump_file, dump_flags);
2273 /* Signal that rtl_verify_flow_info_1 can now verify that there
2274 is at most one switch between hot/cold sections. */
2275 crtl->bb_reorder_complete = true;
2278 /* Determine which partition the first basic block in the function
2279 belongs to, then find the first basic block in the current function
2280 that belongs to a different section, and insert a
2281 NOTE_INSN_SWITCH_TEXT_SECTIONS note immediately before it in the
2282 instruction stream. When writing out the assembly code,
2283 encountering this note will make the compiler switch between the
2284 hot and cold text sections. */
2286 void
2287 insert_section_boundary_note (void)
2289 basic_block bb;
2290 bool switched_sections = false;
2291 int current_partition = 0;
2293 if (!crtl->has_bb_partition)
2294 return;
2296 FOR_EACH_BB_FN (bb, cfun)
2298 if (!current_partition)
2299 current_partition = BB_PARTITION (bb);
2300 if (BB_PARTITION (bb) != current_partition)
2302 gcc_assert (!switched_sections);
2303 switched_sections = true;
2304 emit_note_before (NOTE_INSN_SWITCH_TEXT_SECTIONS, BB_HEAD (bb));
2305 current_partition = BB_PARTITION (bb);
2310 namespace {
2312 const pass_data pass_data_reorder_blocks =
2314 RTL_PASS, /* type */
2315 "bbro", /* name */
2316 OPTGROUP_NONE, /* optinfo_flags */
2317 TV_REORDER_BLOCKS, /* tv_id */
2318 0, /* properties_required */
2319 0, /* properties_provided */
2320 0, /* properties_destroyed */
2321 0, /* todo_flags_start */
2322 0, /* todo_flags_finish */
2325 class pass_reorder_blocks : public rtl_opt_pass
2327 public:
2328 pass_reorder_blocks (gcc::context *ctxt)
2329 : rtl_opt_pass (pass_data_reorder_blocks, ctxt)
2332 /* opt_pass methods: */
2333 virtual bool gate (function *)
2335 if (targetm.cannot_modify_jumps_p ())
2336 return false;
2337 return (optimize > 0
2338 && (flag_reorder_blocks || flag_reorder_blocks_and_partition));
2341 virtual unsigned int execute (function *);
2343 }; // class pass_reorder_blocks
2345 unsigned int
2346 pass_reorder_blocks::execute (function *fun)
2348 basic_block bb;
2350 /* Last attempt to optimize CFG, as scheduling, peepholing and insn
2351 splitting possibly introduced more crossjumping opportunities. */
2352 cfg_layout_initialize (CLEANUP_EXPENSIVE);
2354 reorder_basic_blocks ();
2355 cleanup_cfg (CLEANUP_EXPENSIVE);
2357 FOR_EACH_BB_FN (bb, fun)
2358 if (bb->next_bb != EXIT_BLOCK_PTR_FOR_FN (fun))
2359 bb->aux = bb->next_bb;
2360 cfg_layout_finalize ();
2362 return 0;
2365 } // anon namespace
2367 rtl_opt_pass *
2368 make_pass_reorder_blocks (gcc::context *ctxt)
2370 return new pass_reorder_blocks (ctxt);
2373 /* Duplicate the blocks containing computed gotos. This basically unfactors
2374 computed gotos that were factored early on in the compilation process to
2375 speed up edge based data flow. We used to not unfactoring them again,
2376 which can seriously pessimize code with many computed jumps in the source
2377 code, such as interpreters. See e.g. PR15242. */
2379 namespace {
2381 const pass_data pass_data_duplicate_computed_gotos =
2383 RTL_PASS, /* type */
2384 "compgotos", /* name */
2385 OPTGROUP_NONE, /* optinfo_flags */
2386 TV_REORDER_BLOCKS, /* tv_id */
2387 0, /* properties_required */
2388 0, /* properties_provided */
2389 0, /* properties_destroyed */
2390 0, /* todo_flags_start */
2391 0, /* todo_flags_finish */
2394 class pass_duplicate_computed_gotos : public rtl_opt_pass
2396 public:
2397 pass_duplicate_computed_gotos (gcc::context *ctxt)
2398 : rtl_opt_pass (pass_data_duplicate_computed_gotos, ctxt)
2401 /* opt_pass methods: */
2402 virtual bool gate (function *);
2403 virtual unsigned int execute (function *);
2405 }; // class pass_duplicate_computed_gotos
2407 bool
2408 pass_duplicate_computed_gotos::gate (function *fun)
2410 if (targetm.cannot_modify_jumps_p ())
2411 return false;
2412 return (optimize > 0
2413 && flag_expensive_optimizations
2414 && ! optimize_function_for_size_p (fun));
2417 unsigned int
2418 pass_duplicate_computed_gotos::execute (function *fun)
2420 basic_block bb, new_bb;
2421 bitmap candidates;
2422 int max_size;
2423 bool changed = false;
2425 if (n_basic_blocks_for_fn (fun) <= NUM_FIXED_BLOCKS + 1)
2426 return 0;
2428 clear_bb_flags ();
2429 cfg_layout_initialize (0);
2431 /* We are estimating the length of uncond jump insn only once
2432 since the code for getting the insn length always returns
2433 the minimal length now. */
2434 if (uncond_jump_length == 0)
2435 uncond_jump_length = get_uncond_jump_length ();
2437 max_size
2438 = uncond_jump_length * PARAM_VALUE (PARAM_MAX_GOTO_DUPLICATION_INSNS);
2439 candidates = BITMAP_ALLOC (NULL);
2441 /* Look for blocks that end in a computed jump, and see if such blocks
2442 are suitable for unfactoring. If a block is a candidate for unfactoring,
2443 mark it in the candidates. */
2444 FOR_EACH_BB_FN (bb, fun)
2446 rtx_insn *insn;
2447 edge e;
2448 edge_iterator ei;
2449 int size, all_flags;
2451 /* Build the reorder chain for the original order of blocks. */
2452 if (bb->next_bb != EXIT_BLOCK_PTR_FOR_FN (fun))
2453 bb->aux = bb->next_bb;
2455 /* Obviously the block has to end in a computed jump. */
2456 if (!computed_jump_p (BB_END (bb)))
2457 continue;
2459 /* Only consider blocks that can be duplicated. */
2460 if (CROSSING_JUMP_P (BB_END (bb))
2461 || !can_duplicate_block_p (bb))
2462 continue;
2464 /* Make sure that the block is small enough. */
2465 size = 0;
2466 FOR_BB_INSNS (bb, insn)
2467 if (INSN_P (insn))
2469 size += get_attr_min_length (insn);
2470 if (size > max_size)
2471 break;
2473 if (size > max_size)
2474 continue;
2476 /* Final check: there must not be any incoming abnormal edges. */
2477 all_flags = 0;
2478 FOR_EACH_EDGE (e, ei, bb->preds)
2479 all_flags |= e->flags;
2480 if (all_flags & EDGE_COMPLEX)
2481 continue;
2483 bitmap_set_bit (candidates, bb->index);
2486 /* Nothing to do if there is no computed jump here. */
2487 if (bitmap_empty_p (candidates))
2488 goto done;
2490 /* Duplicate computed gotos. */
2491 FOR_EACH_BB_FN (bb, fun)
2493 if (bb->flags & BB_VISITED)
2494 continue;
2496 bb->flags |= BB_VISITED;
2498 /* BB must have one outgoing edge. That edge must not lead to
2499 the exit block or the next block.
2500 The destination must have more than one predecessor. */
2501 if (!single_succ_p (bb)
2502 || single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (fun)
2503 || single_succ (bb) == bb->next_bb
2504 || single_pred_p (single_succ (bb)))
2505 continue;
2507 /* The successor block has to be a duplication candidate. */
2508 if (!bitmap_bit_p (candidates, single_succ (bb)->index))
2509 continue;
2511 /* Don't duplicate a partition crossing edge, which requires difficult
2512 fixup. */
2513 if (JUMP_P (BB_END (bb)) && CROSSING_JUMP_P (BB_END (bb)))
2514 continue;
2516 new_bb = duplicate_block (single_succ (bb), single_succ_edge (bb), bb);
2517 new_bb->aux = bb->aux;
2518 bb->aux = new_bb;
2519 new_bb->flags |= BB_VISITED;
2520 changed = true;
2523 done:
2524 if (changed)
2526 /* Duplicating blocks above will redirect edges and may cause hot
2527 blocks previously reached by both hot and cold blocks to become
2528 dominated only by cold blocks. */
2529 fixup_partitions ();
2531 /* Merge the duplicated blocks into predecessors, when possible. */
2532 cfg_layout_finalize ();
2533 cleanup_cfg (0);
2535 else
2536 cfg_layout_finalize ();
2538 BITMAP_FREE (candidates);
2539 return 0;
2542 } // anon namespace
2544 rtl_opt_pass *
2545 make_pass_duplicate_computed_gotos (gcc::context *ctxt)
2547 return new pass_duplicate_computed_gotos (ctxt);
2550 /* This function is the main 'entrance' for the optimization that
2551 partitions hot and cold basic blocks into separate sections of the
2552 .o file (to improve performance and cache locality). Ideally it
2553 would be called after all optimizations that rearrange the CFG have
2554 been called. However part of this optimization may introduce new
2555 register usage, so it must be called before register allocation has
2556 occurred. This means that this optimization is actually called
2557 well before the optimization that reorders basic blocks (see
2558 function above).
2560 This optimization checks the feedback information to determine
2561 which basic blocks are hot/cold, updates flags on the basic blocks
2562 to indicate which section they belong in. This information is
2563 later used for writing out sections in the .o file. Because hot
2564 and cold sections can be arbitrarily large (within the bounds of
2565 memory), far beyond the size of a single function, it is necessary
2566 to fix up all edges that cross section boundaries, to make sure the
2567 instructions used can actually span the required distance. The
2568 fixes are described below.
2570 Fall-through edges must be changed into jumps; it is not safe or
2571 legal to fall through across a section boundary. Whenever a
2572 fall-through edge crossing a section boundary is encountered, a new
2573 basic block is inserted (in the same section as the fall-through
2574 source), and the fall through edge is redirected to the new basic
2575 block. The new basic block contains an unconditional jump to the
2576 original fall-through target. (If the unconditional jump is
2577 insufficient to cross section boundaries, that is dealt with a
2578 little later, see below).
2580 In order to deal with architectures that have short conditional
2581 branches (which cannot span all of memory) we take any conditional
2582 jump that attempts to cross a section boundary and add a level of
2583 indirection: it becomes a conditional jump to a new basic block, in
2584 the same section. The new basic block contains an unconditional
2585 jump to the original target, in the other section.
2587 For those architectures whose unconditional branch is also
2588 incapable of reaching all of memory, those unconditional jumps are
2589 converted into indirect jumps, through a register.
2591 IMPORTANT NOTE: This optimization causes some messy interactions
2592 with the cfg cleanup optimizations; those optimizations want to
2593 merge blocks wherever possible, and to collapse indirect jump
2594 sequences (change "A jumps to B jumps to C" directly into "A jumps
2595 to C"). Those optimizations can undo the jump fixes that
2596 partitioning is required to make (see above), in order to ensure
2597 that jumps attempting to cross section boundaries are really able
2598 to cover whatever distance the jump requires (on many architectures
2599 conditional or unconditional jumps are not able to reach all of
2600 memory). Therefore tests have to be inserted into each such
2601 optimization to make sure that it does not undo stuff necessary to
2602 cross partition boundaries. This would be much less of a problem
2603 if we could perform this optimization later in the compilation, but
2604 unfortunately the fact that we may need to create indirect jumps
2605 (through registers) requires that this optimization be performed
2606 before register allocation.
2608 Hot and cold basic blocks are partitioned and put in separate
2609 sections of the .o file, to reduce paging and improve cache
2610 performance (hopefully). This can result in bits of code from the
2611 same function being widely separated in the .o file. However this
2612 is not obvious to the current bb structure. Therefore we must take
2613 care to ensure that: 1). There are no fall_thru edges that cross
2614 between sections; 2). For those architectures which have "short"
2615 conditional branches, all conditional branches that attempt to
2616 cross between sections are converted to unconditional branches;
2617 and, 3). For those architectures which have "short" unconditional
2618 branches, all unconditional branches that attempt to cross between
2619 sections are converted to indirect jumps.
2621 The code for fixing up fall_thru edges that cross between hot and
2622 cold basic blocks does so by creating new basic blocks containing
2623 unconditional branches to the appropriate label in the "other"
2624 section. The new basic block is then put in the same (hot or cold)
2625 section as the original conditional branch, and the fall_thru edge
2626 is modified to fall into the new basic block instead. By adding
2627 this level of indirection we end up with only unconditional branches
2628 crossing between hot and cold sections.
2630 Conditional branches are dealt with by adding a level of indirection.
2631 A new basic block is added in the same (hot/cold) section as the
2632 conditional branch, and the conditional branch is retargeted to the
2633 new basic block. The new basic block contains an unconditional branch
2634 to the original target of the conditional branch (in the other section).
2636 Unconditional branches are dealt with by converting them into
2637 indirect jumps. */
2639 namespace {
2641 const pass_data pass_data_partition_blocks =
2643 RTL_PASS, /* type */
2644 "bbpart", /* name */
2645 OPTGROUP_NONE, /* optinfo_flags */
2646 TV_REORDER_BLOCKS, /* tv_id */
2647 PROP_cfglayout, /* properties_required */
2648 0, /* properties_provided */
2649 0, /* properties_destroyed */
2650 0, /* todo_flags_start */
2651 0, /* todo_flags_finish */
2654 class pass_partition_blocks : public rtl_opt_pass
2656 public:
2657 pass_partition_blocks (gcc::context *ctxt)
2658 : rtl_opt_pass (pass_data_partition_blocks, ctxt)
2661 /* opt_pass methods: */
2662 virtual bool gate (function *);
2663 virtual unsigned int execute (function *);
2665 }; // class pass_partition_blocks
2667 bool
2668 pass_partition_blocks::gate (function *fun)
2670 /* The optimization to partition hot/cold basic blocks into separate
2671 sections of the .o file does not work well with linkonce or with
2672 user defined section attributes. Don't call it if either case
2673 arises. */
2674 return (flag_reorder_blocks_and_partition
2675 && optimize
2676 /* See gate_handle_reorder_blocks. We should not partition if
2677 we are going to omit the reordering. */
2678 && optimize_function_for_speed_p (fun)
2679 && !DECL_COMDAT_GROUP (current_function_decl)
2680 && !user_defined_section_attribute);
2683 unsigned
2684 pass_partition_blocks::execute (function *fun)
2686 vec<edge> crossing_edges;
2688 if (n_basic_blocks_for_fn (fun) <= NUM_FIXED_BLOCKS + 1)
2689 return 0;
2691 df_set_flags (DF_DEFER_INSN_RESCAN);
2693 crossing_edges = find_rarely_executed_basic_blocks_and_crossing_edges ();
2694 if (!crossing_edges.exists ())
2695 return 0;
2697 crtl->has_bb_partition = true;
2699 /* Make sure the source of any crossing edge ends in a jump and the
2700 destination of any crossing edge has a label. */
2701 add_labels_and_missing_jumps (crossing_edges);
2703 /* Convert all crossing fall_thru edges to non-crossing fall
2704 thrus to unconditional jumps (that jump to the original fall
2705 through dest). */
2706 fix_up_fall_thru_edges ();
2708 /* If the architecture does not have conditional branches that can
2709 span all of memory, convert crossing conditional branches into
2710 crossing unconditional branches. */
2711 if (!HAS_LONG_COND_BRANCH)
2712 fix_crossing_conditional_branches ();
2714 /* If the architecture does not have unconditional branches that
2715 can span all of memory, convert crossing unconditional branches
2716 into indirect jumps. Since adding an indirect jump also adds
2717 a new register usage, update the register usage information as
2718 well. */
2719 if (!HAS_LONG_UNCOND_BRANCH)
2720 fix_crossing_unconditional_branches ();
2722 update_crossing_jump_flags ();
2724 /* Clear bb->aux fields that the above routines were using. */
2725 clear_aux_for_blocks ();
2727 crossing_edges.release ();
2729 /* ??? FIXME: DF generates the bb info for a block immediately.
2730 And by immediately, I mean *during* creation of the block.
2732 #0 df_bb_refs_collect
2733 #1 in df_bb_refs_record
2734 #2 in create_basic_block_structure
2736 Which means that the bb_has_eh_pred test in df_bb_refs_collect
2737 will *always* fail, because no edges can have been added to the
2738 block yet. Which of course means we don't add the right
2739 artificial refs, which means we fail df_verify (much) later.
2741 Cleanest solution would seem to make DF_DEFER_INSN_RESCAN imply
2742 that we also shouldn't grab data from the new blocks those new
2743 insns are in either. In this way one can create the block, link
2744 it up properly, and have everything Just Work later, when deferred
2745 insns are processed.
2747 In the meantime, we have no other option but to throw away all
2748 of the DF data and recompute it all. */
2749 if (fun->eh->lp_array)
2751 df_finish_pass (true);
2752 df_scan_alloc (NULL);
2753 df_scan_blocks ();
2754 /* Not all post-landing pads use all of the EH_RETURN_DATA_REGNO
2755 data. We blindly generated all of them when creating the new
2756 landing pad. Delete those assignments we don't use. */
2757 df_set_flags (DF_LR_RUN_DCE);
2758 df_analyze ();
2761 return 0;
2764 } // anon namespace
2766 rtl_opt_pass *
2767 make_pass_partition_blocks (gcc::context *ctxt)
2769 return new pass_partition_blocks (ctxt);