1 /* Basic block reordering routines for the GNU compiler.
2 Copyright (C) 2000, 2002, 2003 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 2, or (at your option)
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 COPYING. If not, write to the Free
18 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
21 /* This (greedy) algorithm constructs traces in several rounds.
22 The construction starts from "seeds". The seed for the first round
23 is the entry point of function. When there are more than one seed
24 that one is selected first that has the lowest key in the heap
25 (see function bb_to_key). Then the algorithm repeatedly adds the most
26 probable successor to the end of a trace. Finally it connects the traces.
28 There are two parameters: Branch Threshold and Exec Threshold.
29 If the edge to a successor of the actual basic block is lower than
30 Branch Threshold or the frequency of the successor is lower than
31 Exec Threshold the successor will be the seed in one of the next rounds.
32 Each round has these parameters lower than the previous one.
33 The last round has to have these parameters set to zero
34 so that the remaining blocks are picked up.
36 The algorithm selects the most probable successor from all unvisited
37 successors and successors that have been added to this trace.
38 The other successors (that has not been "sent" to the next round) will be
39 other seeds for this round and the secondary traces will start in them.
40 If the successor has not been visited in this trace it is added to the trace
41 (however, there is some heuristic for simple branches).
42 If the successor has been visited in this trace the loop has been found.
43 If the loop has many iterations the loop is rotated so that the
44 source block of the most probable edge going out from the loop
45 is the last block of the trace.
46 If the loop has few iterations and there is no edge from the last block of
47 the loop going out from loop the loop header is duplicated.
48 Finally, the construction of the trace is terminated.
50 When connecting traces it first checks whether there is an edge from the
51 last block of one trace to the first block of another trace.
52 When there are still some unconnected traces it checks whether there exists
53 a basic block BB such that BB is a successor of the last bb of one trace
54 and BB is a predecessor of the first block of another trace. In this case,
55 BB is duplicated and the traces are connected through this duplicate.
56 The rest of traces are simply connected so there will be a jump to the
57 beginning of the rest of trace.
62 "Software Trace Cache"
63 A. Ramirez, J. Larriba-Pey, C. Navarro, J. Torrellas and M. Valero; 1999
64 http://citeseer.nj.nec.com/15361.html
70 #include "coretypes.h"
73 #include "basic-block.h"
76 #include "cfglayout.h"
80 /* The number of rounds. */
83 /* Branch thresholds in thousandths (per mille) of the REG_BR_PROB_BASE. */
84 static int branch_threshold[N_ROUNDS] = {400, 200, 100, 0};
86 /* Exec thresholds in thousandths (per mille) of the frequency of bb 0. */
87 static int exec_threshold[N_ROUNDS] = {500, 200, 50, 0};
89 /* If edge frequency is lower than DUPLICATION_THRESHOLD per mille of entry
90 block the edge destination is not duplicated while connecting traces. */
91 #define DUPLICATION_THRESHOLD 100
93 /* Length of unconditional jump instruction. */
94 static int uncond_jump_length;
96 /* Structure to hold needed information for each basic block. */
97 typedef struct bbro_basic_block_data_def
99 /* Which trace is the bb start of (-1 means it is not a start of a trace). */
102 /* Which trace is the bb end of (-1 means it is not an end of a trace). */
105 /* Which heap is BB in (if any)? */
108 /* Which heap node is BB in (if any)? */
110 } bbro_basic_block_data;
112 /* The current size of the following dynamic array. */
113 static int array_size;
115 /* The array which holds needed information for basic blocks. */
116 static bbro_basic_block_data *bbd;
118 /* To avoid frequent reallocation the size of arrays is greater than needed,
119 the number of elements is (not less than) 1.25 * size_wanted. */
120 #define GET_ARRAY_SIZE(X) ((((X) / 4) + 1) * 5)
122 /* Free the memory and set the pointer to NULL. */
124 do { if (P) { free (P); P = 0; } else { abort (); } } while (0)
126 /* Structure for holding information about a trace. */
129 /* First and last basic block of the trace. */
130 basic_block first, last;
132 /* The round of the STC creation which this trace was found in. */
135 /* The length (i.e. the number of basic blocks) of the trace. */
139 /* Maximum frequency and count of one of the entry blocks. */
140 int max_entry_frequency;
141 gcov_type max_entry_count;
143 /* Local function prototypes. */
144 static void find_traces PARAMS ((int *, struct trace *));
145 static basic_block rotate_loop PARAMS ((edge, struct trace *, int));
146 static void mark_bb_visited PARAMS ((basic_block, int));
147 static void find_traces_1_round PARAMS ((int, int, gcov_type,
148 struct trace *, int *, int,
150 static basic_block copy_bb PARAMS ((basic_block, edge,
152 static fibheapkey_t bb_to_key PARAMS ((basic_block));
153 static bool better_edge_p PARAMS ((basic_block, edge, int, int,
155 static void connect_traces PARAMS ((int, struct trace *));
156 static bool copy_bb_p PARAMS ((basic_block, int));
157 static int get_uncond_jump_length PARAMS ((void));
159 /* Find the traces for Software Trace Cache. Chain each trace through
160 RBI()->next. Store the number of traces to N_TRACES and description of
164 find_traces (n_traces, traces)
166 struct trace *traces;
172 /* Insert entry points of function into heap. */
173 heap = fibheap_new ();
174 max_entry_frequency = 0;
176 for (e = ENTRY_BLOCK_PTR->succ; e; e = e->succ_next)
178 bbd[e->dest->index].heap = heap;
179 bbd[e->dest->index].node = fibheap_insert (heap, bb_to_key (e->dest),
181 if (e->dest->frequency > max_entry_frequency)
182 max_entry_frequency = e->dest->frequency;
183 if (e->dest->count > max_entry_count)
184 max_entry_count = e->dest->count;
187 /* Find the traces. */
188 for (i = 0; i < N_ROUNDS; i++)
190 gcov_type count_threshold;
193 fprintf (rtl_dump_file, "STC - round %d\n", i + 1);
195 if (max_entry_count < INT_MAX / 1000)
196 count_threshold = max_entry_count * exec_threshold[i] / 1000;
198 count_threshold = max_entry_count / 1000 * exec_threshold[i];
200 find_traces_1_round (REG_BR_PROB_BASE * branch_threshold[i] / 1000,
201 max_entry_frequency * exec_threshold[i] / 1000,
202 count_threshold, traces, n_traces, i, &heap);
204 fibheap_delete (heap);
208 for (i = 0; i < *n_traces; i++)
211 fprintf (rtl_dump_file, "Trace %d (round %d): ", i + 1,
212 traces[i].round + 1);
213 for (bb = traces[i].first; bb != traces[i].last; bb = RBI (bb)->next)
214 fprintf (rtl_dump_file, "%d [%d] ", bb->index, bb->frequency);
215 fprintf (rtl_dump_file, "%d [%d]\n", bb->index, bb->frequency);
217 fflush (rtl_dump_file);
221 /* Rotate loop whose back edge is BACK_EDGE in the tail of trace TRACE
222 (with sequential number TRACE_N). */
225 rotate_loop (back_edge, trace, trace_n)
232 /* Information about the best end (end after rotation) of the loop. */
233 basic_block best_bb = NULL;
234 edge best_edge = NULL;
236 gcov_type best_count = -1;
237 /* The best edge is preferred when its destination is not visited yet
238 or is a start block of some trace. */
239 bool is_preferred = false;
241 /* Find the most frequent edge that goes out from current trace. */
242 bb = back_edge->dest;
246 for (e = bb->succ; e; e = e->succ_next)
247 if (e->dest != EXIT_BLOCK_PTR
248 && RBI (e->dest)->visited != trace_n
249 && (e->flags & EDGE_CAN_FALLTHRU)
250 && !(e->flags & EDGE_COMPLEX))
254 /* The best edge is preferred. */
255 if (!RBI (e->dest)->visited
256 || bbd[e->dest->index].start_of_trace >= 0)
258 /* The current edge E is also preferred. */
259 int freq = EDGE_FREQUENCY (e);
260 if (freq > best_freq || e->count > best_count)
263 best_count = e->count;
271 if (!RBI (e->dest)->visited
272 || bbd[e->dest->index].start_of_trace >= 0)
274 /* The current edge E is preferred. */
276 best_freq = EDGE_FREQUENCY (e);
277 best_count = e->count;
283 int freq = EDGE_FREQUENCY (e);
284 if (!best_edge || freq > best_freq || e->count > best_count)
287 best_count = e->count;
296 while (bb != back_edge->dest);
300 /* Rotate the loop so that the BEST_EDGE goes out from the last block of
302 if (back_edge->dest == trace->first)
304 trace->first = RBI (best_bb)->next;
310 for (prev_bb = trace->first;
311 RBI (prev_bb)->next != back_edge->dest;
312 prev_bb = RBI (prev_bb)->next)
314 RBI (prev_bb)->next = RBI (best_bb)->next;
316 /* Try to get rid of uncond jump to cond jump. */
317 if (prev_bb->succ && !prev_bb->succ->succ_next)
319 basic_block header = prev_bb->succ->dest;
321 /* Duplicate HEADER if it is a small block containing cond jump
323 if (any_condjump_p (header->end) && copy_bb_p (header, 0))
325 copy_bb (header, prev_bb->succ, prev_bb, trace_n);
332 /* We have not found suitable loop tail so do no rotation. */
333 best_bb = back_edge->src;
335 RBI (best_bb)->next = NULL;
339 /* This function marks BB that it was visited in trace number TRACE. */
342 mark_bb_visited (bb, trace)
346 RBI (bb)->visited = trace;
347 if (bbd[bb->index].heap)
349 fibheap_delete_node (bbd[bb->index].heap, bbd[bb->index].node);
350 bbd[bb->index].heap = NULL;
351 bbd[bb->index].node = NULL;
355 /* One round of finding traces. Find traces for BRANCH_TH and EXEC_TH i.e. do
356 not include basic blocks their probability is lower than BRANCH_TH or their
357 frequency is lower than EXEC_TH into traces (or count is lower than
358 COUNT_TH). It stores the new traces into TRACES and modifies the number of
359 traces *N_TRACES. Sets the round (which the trace belongs to) to ROUND. It
360 expects that starting basic blocks are in *HEAP and at the end it deletes
361 *HEAP and stores starting points for the next round into new *HEAP. */
364 find_traces_1_round (branch_th, exec_th, count_th, traces, n_traces, round,
369 struct trace *traces;
374 /* Heap for discarded basic blocks which are possible starting points for
376 fibheap_t new_heap = fibheap_new ();
378 while (!fibheap_empty (*heap))
385 bb = fibheap_extract_min (*heap);
386 bbd[bb->index].heap = NULL;
387 bbd[bb->index].node = NULL;
390 fprintf (rtl_dump_file, "Getting bb %d\n", bb->index);
392 /* If the BB's frequency is too low send BB to the next round. */
393 if (bb->frequency < exec_th || bb->count < count_th
394 || ((round < N_ROUNDS - 1) && probably_never_executed_bb_p (bb)))
396 int key = bb_to_key (bb);
397 bbd[bb->index].heap = new_heap;
398 bbd[bb->index].node = fibheap_insert (new_heap, key, bb);
401 fprintf (rtl_dump_file,
402 " Possible start point of next round: %d (key: %d)\n",
407 trace = traces + *n_traces;
409 trace->round = round;
417 /* The probability and frequency of the best edge. */
418 int best_prob = INT_MIN / 2;
419 int best_freq = INT_MIN / 2;
422 mark_bb_visited (bb, *n_traces);
426 fprintf (rtl_dump_file, "Basic block %d was visited in trace %d\n",
427 bb->index, *n_traces - 1);
429 /* Select the successor that will be placed after BB. */
430 for (e = bb->succ; e; e = e->succ_next)
432 if (e->flags & EDGE_FAKE)
435 if (e->dest == EXIT_BLOCK_PTR)
438 if (RBI (e->dest)->visited
439 && RBI (e->dest)->visited != *n_traces)
442 prob = e->probability;
443 freq = EDGE_FREQUENCY (e);
445 /* Edge that cannot be fallthru or improbable or infrequent
446 successor (ie. it is unsuitable successor). */
447 if (!(e->flags & EDGE_CAN_FALLTHRU) || (e->flags & EDGE_COMPLEX)
448 || prob < branch_th || freq < exec_th || e->count < count_th)
451 /* If the destination has multiple precessesors, and can be
452 duplicated cheaper than a jump, don't allow it to be added
453 to a trace. We'll duplicate it when connecting traces. */
454 if (e->dest->pred->pred_next && copy_bb_p (e->dest, 0))
457 if (better_edge_p (bb, e, prob, freq, best_prob, best_freq))
465 /* Add all non-selected successors to the heaps. */
466 for (e = bb->succ; e; e = e->succ_next)
469 || e->dest == EXIT_BLOCK_PTR
470 || RBI (e->dest)->visited)
473 key = bb_to_key (e->dest);
475 if (bbd[e->dest->index].heap)
477 /* E->DEST is already in some heap. */
478 if (key != bbd[e->dest->index].node->key)
482 fprintf (rtl_dump_file,
483 "Changing key for bb %d from %ld to %ld.\n",
485 (long) bbd[e->dest->index].node->key,
488 fibheap_replace_key (bbd[e->dest->index].heap,
489 bbd[e->dest->index].node, key);
494 fibheap_t which_heap = *heap;
496 prob = e->probability;
497 freq = EDGE_FREQUENCY (e);
499 if (!(e->flags & EDGE_CAN_FALLTHRU)
500 || (e->flags & EDGE_COMPLEX)
501 || prob < branch_th || freq < exec_th
502 || e->count < count_th)
504 if (round < N_ROUNDS - 1)
505 which_heap = new_heap;
508 bbd[e->dest->index].heap = which_heap;
509 bbd[e->dest->index].node = fibheap_insert (which_heap,
514 fprintf (rtl_dump_file,
515 " Possible start of %s round: %d (key: %ld)\n",
516 (which_heap == new_heap) ? "next" : "this",
517 e->dest->index, (long) key);
523 if (best_edge) /* Suitable successor was found. */
525 if (RBI (best_edge->dest)->visited == *n_traces)
527 /* We do nothing with one basic block loops. */
528 if (best_edge->dest != bb)
530 if (EDGE_FREQUENCY (best_edge)
531 > 4 * best_edge->dest->frequency / 5)
533 /* The loop has at least 4 iterations. If the loop
534 header is not the first block of the function
535 we can rotate the loop. */
537 if (best_edge->dest != ENTRY_BLOCK_PTR->next_bb)
541 fprintf (rtl_dump_file,
542 "Rotating loop %d - %d\n",
543 best_edge->dest->index, bb->index);
545 RBI (bb)->next = best_edge->dest;
546 bb = rotate_loop (best_edge, trace, *n_traces);
551 /* The loop has less than 4 iterations. */
553 /* Check whether there is another edge from BB. */
555 for (another_edge = bb->succ;
557 another_edge = another_edge->succ_next)
558 if (another_edge != best_edge)
561 if (!another_edge && copy_bb_p (best_edge->dest,
564 bb = copy_bb (best_edge->dest, best_edge, bb,
570 /* Terminate the trace. */
575 /* Check for a situation
584 EDGE_FREQUENCY (AB) + EDGE_FREQUENCY (BC)
585 >= EDGE_FREQUENCY (AC).
586 (i.e. 2 * B->frequency >= EDGE_FREQUENCY (AC) )
587 Best ordering is then A B C.
589 This situation is created for example by:
596 for (e = bb->succ; e; e = e->succ_next)
598 && (e->flags & EDGE_CAN_FALLTHRU)
599 && !(e->flags & EDGE_COMPLEX)
600 && !RBI (e->dest)->visited
601 && !e->dest->pred->pred_next
603 && (e->dest->succ->flags & EDGE_CAN_FALLTHRU)
604 && !(e->dest->succ->flags & EDGE_COMPLEX)
605 && !e->dest->succ->succ_next
606 && e->dest->succ->dest == best_edge->dest
607 && 2 * e->dest->frequency >= EDGE_FREQUENCY (best_edge))
611 fprintf (rtl_dump_file, "Selecting BB %d\n",
612 best_edge->dest->index);
616 RBI (bb)->next = best_edge->dest;
617 bb = best_edge->dest;
623 bbd[trace->first->index].start_of_trace = *n_traces - 1;
624 bbd[trace->last->index].end_of_trace = *n_traces - 1;
626 /* The trace is terminated so we have to recount the keys in heap
627 (some block can have a lower key because now one of its predecessors
628 is an end of the trace). */
629 for (e = bb->succ; e; e = e->succ_next)
631 if (e->dest == EXIT_BLOCK_PTR
632 || RBI (e->dest)->visited)
635 if (bbd[e->dest->index].heap)
637 key = bb_to_key (e->dest);
638 if (key != bbd[e->dest->index].node->key)
642 fprintf (rtl_dump_file,
643 "Changing key for bb %d from %ld to %ld.\n",
645 (long) bbd[e->dest->index].node->key, key);
647 fibheap_replace_key (bbd[e->dest->index].heap,
648 bbd[e->dest->index].node,
655 fibheap_delete (*heap);
657 /* "Return" the new heap. */
661 /* Create a duplicate of the basic block OLD_BB and redirect edge E to it, add
662 it to trace after BB, mark OLD_BB visited and update pass' data structures
663 (TRACE is a number of trace which OLD_BB is duplicated to). */
666 copy_bb (old_bb, e, bb, trace)
674 new_bb = cfg_layout_duplicate_bb (old_bb, e);
675 if (e->dest != new_bb)
677 if (RBI (e->dest)->visited)
680 fprintf (rtl_dump_file,
681 "Duplicated bb %d (created bb %d)\n",
682 old_bb->index, new_bb->index);
683 RBI (new_bb)->visited = trace;
684 RBI (new_bb)->next = RBI (bb)->next;
685 RBI (bb)->next = new_bb;
687 if (new_bb->index >= array_size || last_basic_block > array_size)
692 new_size = MAX (last_basic_block, new_bb->index + 1);
693 new_size = GET_ARRAY_SIZE (new_size);
694 bbd = xrealloc (bbd, new_size * sizeof (bbro_basic_block_data));
695 for (i = array_size; i < new_size; i++)
697 bbd[i].start_of_trace = -1;
698 bbd[i].end_of_trace = -1;
702 array_size = new_size;
706 fprintf (rtl_dump_file,
707 "Growing the dynamic array to %d elements.\n",
715 /* Compute and return the key (for the heap) of the basic block BB. */
725 /* Do not start in probably never executed blocks. */
726 if (probably_never_executed_bb_p (bb))
729 /* Prefer blocks whose predecessor is an end of some trace
730 or whose predecessor edge is EDGE_DFS_BACK. */
731 for (e = bb->pred; e; e = e->pred_next)
733 if ((e->src != ENTRY_BLOCK_PTR && bbd[e->src->index].end_of_trace >= 0)
734 || (e->flags & EDGE_DFS_BACK))
736 int edge_freq = EDGE_FREQUENCY (e);
738 if (edge_freq > priority)
739 priority = edge_freq;
744 /* The block with priority should have significantly lower key. */
745 return -(100 * BB_FREQ_MAX + 100 * priority + bb->frequency);
746 return -bb->frequency;
749 /* Return true when the edge E from basic block BB is better than the temporary
750 best edge (details are in function). The probability of edge E is PROB. The
751 frequency of the successor is FREQ. The current best probability is
752 BEST_PROB, the best frequency is BEST_FREQ.
753 The edge is considered to be equivalent when PROB does not differ much from
754 BEST_PROB; similarly for frequency. */
757 better_edge_p (bb, e, prob, freq, best_prob, best_freq)
767 /* The BEST_* values do not have to be best, but can be a bit smaller than
769 int diff_prob = best_prob / 10;
770 int diff_freq = best_freq / 10;
772 if (prob > best_prob + diff_prob)
773 /* The edge has higher probability than the temporary best edge. */
774 is_better_edge = true;
775 else if (prob < best_prob - diff_prob)
776 /* The edge has lower probability than the temporary best edge. */
777 is_better_edge = false;
778 else if (freq < best_freq - diff_freq)
779 /* The edge and the temporary best edge have almost equivalent
780 probabilities. The higher frequency of a successor now means
781 that there is another edge going into that successor.
782 This successor has lower frequency so it is better. */
783 is_better_edge = true;
784 else if (freq > best_freq + diff_freq)
785 /* This successor has higher frequency so it is worse. */
786 is_better_edge = false;
787 else if (e->dest->prev_bb == bb)
788 /* The edges have equivalent probabilities and the successors
789 have equivalent frequencies. Select the previous successor. */
790 is_better_edge = true;
792 is_better_edge = false;
794 return is_better_edge;
797 /* Connect traces in array TRACES, N_TRACES is the count of traces. */
800 connect_traces (n_traces, traces)
802 struct trace *traces;
808 gcov_type count_threshold;
810 freq_threshold = max_entry_frequency * DUPLICATION_THRESHOLD / 1000;
811 if (max_entry_count < INT_MAX / 1000)
812 count_threshold = max_entry_count * DUPLICATION_THRESHOLD / 1000;
814 count_threshold = max_entry_count / 1000 * DUPLICATION_THRESHOLD;
816 connected = xcalloc (n_traces, sizeof (bool));
818 for (i = 0; i < n_traces; i++)
830 /* Find the predecessor traces. */
831 for (t2 = t; t2 > 0;)
835 for (e = traces[t2].first->pred; e; e = e->pred_next)
837 int si = e->src->index;
839 if (e->src != ENTRY_BLOCK_PTR
840 && (e->flags & EDGE_CAN_FALLTHRU)
841 && !(e->flags & EDGE_COMPLEX)
842 && bbd[si].end_of_trace >= 0
843 && !connected[bbd[si].end_of_trace]
845 || e->probability > best->probability
846 || (e->probability == best->probability
847 && traces[bbd[si].end_of_trace].length > best_len)))
850 best_len = traces[bbd[si].end_of_trace].length;
855 RBI (best->src)->next = best->dest;
856 t2 = bbd[best->src->index].end_of_trace;
857 connected[t2] = true;
860 fprintf (rtl_dump_file, "Connection: %d %d\n",
861 best->src->index, best->dest->index);
869 RBI (traces[last_trace].last)->next = traces[t2].first;
872 /* Find the successor traces. */
875 /* Find the continuation of the chain. */
878 for (e = traces[t].last->succ; e; e = e->succ_next)
880 int di = e->dest->index;
882 if (e->dest != EXIT_BLOCK_PTR
883 && (e->flags & EDGE_CAN_FALLTHRU)
884 && !(e->flags & EDGE_COMPLEX)
885 && bbd[di].start_of_trace >= 0
886 && !connected[bbd[di].start_of_trace]
888 || e->probability > best->probability
889 || (e->probability == best->probability
890 && traces[bbd[di].start_of_trace].length > best_len)))
893 best_len = traces[bbd[di].start_of_trace].length;
901 fprintf (rtl_dump_file, "Connection: %d %d\n",
902 best->src->index, best->dest->index);
904 t = bbd[best->dest->index].start_of_trace;
905 RBI (traces[last_trace].last)->next = traces[t].first;
911 /* Try to connect the traces by duplication of 1 block. */
913 basic_block next_bb = NULL;
914 bool try_copy = false;
916 for (e = traces[t].last->succ; e; e = e->succ_next)
917 if (e->dest != EXIT_BLOCK_PTR
918 && (e->flags & EDGE_CAN_FALLTHRU)
919 && !(e->flags & EDGE_COMPLEX)
920 && (!best || e->probability > best->probability))
925 /* If the destination trace is only one block
926 long, then no need to search the successor
927 blocks of the trace. Accept it. */
928 if (traces[bbd[e->dest->index].start_of_trace].length == 1)
935 for (e2 = e->dest->succ; e2; e2 = e2->succ_next)
937 int di = e2->dest->index;
939 if (e2->dest == EXIT_BLOCK_PTR
940 || ((e2->flags & EDGE_CAN_FALLTHRU)
941 && !(e2->flags & EDGE_COMPLEX)
942 && bbd[di].start_of_trace >= 0
943 && !connected[bbd[di].start_of_trace]
944 && (EDGE_FREQUENCY (e2) >= freq_threshold)
945 && (e2->count >= count_threshold)
947 || e2->probability > best2->probability
948 || (e2->probability == best2->probability
949 && traces[bbd[di].start_of_trace].length
954 if (e2->dest != EXIT_BLOCK_PTR)
955 best2_len = traces[bbd[di].start_of_trace].length;
964 /* Copy tiny blocks always; copy larger blocks only when the
965 edge is traversed frequently enough. */
967 && copy_bb_p (best->dest,
969 && EDGE_FREQUENCY (best) >= freq_threshold
970 && best->count >= count_threshold))
976 fprintf (rtl_dump_file, "Connection: %d %d ",
977 traces[t].last->index, best->dest->index);
979 fputc ('\n', rtl_dump_file);
980 else if (next_bb == EXIT_BLOCK_PTR)
981 fprintf (rtl_dump_file, "exit\n");
983 fprintf (rtl_dump_file, "%d\n", next_bb->index);
986 new_bb = copy_bb (best->dest, best, traces[t].last, t);
987 traces[t].last = new_bb;
988 if (next_bb && next_bb != EXIT_BLOCK_PTR)
990 t = bbd[next_bb->index].start_of_trace;
991 RBI (traces[last_trace].last)->next = traces[t].first;
996 break; /* Stop finding the successor traces. */
999 break; /* Stop finding the successor traces. */
1008 fprintf (rtl_dump_file, "Final order:\n");
1009 for (bb = traces[0].first; bb; bb = RBI (bb)->next)
1010 fprintf (rtl_dump_file, "%d ", bb->index);
1011 fprintf (rtl_dump_file, "\n");
1012 fflush (rtl_dump_file);
1018 /* Return true when BB can and should be copied. CODE_MAY_GROW is true
1019 when code size is allowed to grow by duplication. */
1022 copy_bb_p (bb, code_may_grow)
1027 int max_size = uncond_jump_length;
1032 if (!bb->pred || !bb->pred->pred_next)
1034 if (!cfg_layout_can_duplicate_bb_p (bb))
1037 if (code_may_grow && maybe_hot_bb_p (bb))
1040 for (insn = bb->head; insn != NEXT_INSN (bb->end);
1041 insn = NEXT_INSN (insn))
1044 size += get_attr_length (insn);
1047 if (size <= max_size)
1052 fprintf (rtl_dump_file,
1053 "Block %d can't be copied because its size = %d.\n",
1060 /* Return the length of unconditional jump instruction. */
1063 get_uncond_jump_length ()
1068 label = emit_label_before (gen_label_rtx (), get_insns ());
1069 jump = emit_jump_insn (gen_jump (label));
1071 length = get_attr_length (jump);
1074 delete_insn (label);
1078 /* Reorder basic blocks. The main entry point to this file. */
1081 reorder_basic_blocks ()
1085 struct trace *traces;
1087 if (n_basic_blocks <= 1)
1090 if ((* targetm.cannot_modify_jumps_p) ())
1093 cfg_layout_initialize (NULL);
1095 set_edge_can_fallthru_flag ();
1096 mark_dfs_back_edges ();
1098 /* We are estimating the lenght of uncond jump insn only once since the code
1099 for getting the insn lenght always returns the minimal length now. */
1100 if (uncond_jump_length == 0)
1101 uncond_jump_length = get_uncond_jump_length ();
1103 /* We need to know some information for each basic block. */
1104 array_size = GET_ARRAY_SIZE (last_basic_block);
1105 bbd = xmalloc (array_size * sizeof (bbro_basic_block_data));
1106 for (i = 0; i < array_size; i++)
1108 bbd[i].start_of_trace = -1;
1109 bbd[i].end_of_trace = -1;
1114 traces = xmalloc (n_basic_blocks * sizeof (struct trace));
1116 find_traces (&n_traces, traces);
1117 connect_traces (n_traces, traces);
1122 dump_flow_info (rtl_dump_file);
1124 cfg_layout_finalize ();