1 /* Basic block reordering routines for the GNU compiler.
2 Copyright (C) 2000, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2010
3 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 GCC is distributed in the hope that it will be useful, but WITHOUT
13 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
15 License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
21 /* 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"
77 #include "cfglayout.h"
85 #include "diagnostic-core.h"
86 #include "toplev.h" /* user_defined_section_attribute */
87 #include "tree-pass.h"
89 #include "bb-reorder.h"
91 /* The number of rounds. In most cases there will only be 4 rounds, but
92 when partitioning hot and cold basic blocks into separate sections of
93 the .o file there will be an extra round.*/
96 /* Stubs in case we don't have a return insn.
97 We have to check at runtime too, not only compiletime. */
100 #define HAVE_return 0
101 #define gen_return() NULL_RTX
105 struct target_bb_reorder default_target_bb_reorder;
106 #if SWITCHABLE_TARGET
107 struct target_bb_reorder *this_target_bb_reorder = &default_target_bb_reorder;
110 #define uncond_jump_length \
111 (this_target_bb_reorder->x_uncond_jump_length)
113 /* Branch thresholds in thousandths (per mille) of the REG_BR_PROB_BASE. */
114 static int branch_threshold[N_ROUNDS] = {400, 200, 100, 0, 0};
116 /* Exec thresholds in thousandths (per mille) of the frequency of bb 0. */
117 static int exec_threshold[N_ROUNDS] = {500, 200, 50, 0, 0};
119 /* If edge frequency is lower than DUPLICATION_THRESHOLD per mille of entry
120 block the edge destination is not duplicated while connecting traces. */
121 #define DUPLICATION_THRESHOLD 100
123 /* Structure to hold needed information for each basic block. */
124 typedef struct bbro_basic_block_data_def
126 /* Which trace is the bb start of (-1 means it is not a start of a trace). */
129 /* Which trace is the bb end of (-1 means it is not an end of a trace). */
132 /* Which trace is the bb in? */
135 /* Which heap is BB in (if any)? */
138 /* Which heap node is BB in (if any)? */
140 } bbro_basic_block_data;
142 /* The current size of the following dynamic array. */
143 static int array_size;
145 /* The array which holds needed information for basic blocks. */
146 static bbro_basic_block_data *bbd;
148 /* To avoid frequent reallocation the size of arrays is greater than needed,
149 the number of elements is (not less than) 1.25 * size_wanted. */
150 #define GET_ARRAY_SIZE(X) ((((X) / 4) + 1) * 5)
152 /* Free the memory and set the pointer to NULL. */
153 #define FREE(P) (gcc_assert (P), free (P), P = 0)
155 /* Structure for holding information about a trace. */
158 /* First and last basic block of the trace. */
159 basic_block first, last;
161 /* The round of the STC creation which this trace was found in. */
164 /* The length (i.e. the number of basic blocks) of the trace. */
168 /* Maximum frequency and count of one of the entry blocks. */
169 static int max_entry_frequency;
170 static gcov_type max_entry_count;
172 /* Local function prototypes. */
173 static void find_traces (int *, struct trace *);
174 static basic_block rotate_loop (edge, struct trace *, int);
175 static void mark_bb_visited (basic_block, int);
176 static void find_traces_1_round (int, int, gcov_type, struct trace *, int *,
177 int, fibheap_t *, int);
178 static basic_block copy_bb (basic_block, edge, basic_block, int);
179 static fibheapkey_t bb_to_key (basic_block);
180 static bool better_edge_p (const_basic_block, const_edge, int, int, int, int, const_edge);
181 static void connect_traces (int, struct trace *);
182 static bool copy_bb_p (const_basic_block, int);
183 static int get_uncond_jump_length (void);
184 static bool push_to_next_round_p (const_basic_block, int, int, int, gcov_type);
186 /* Check to see if bb should be pushed into the next round of trace
187 collections or not. Reasons for pushing the block forward are 1).
188 If the block is cold, we are doing partitioning, and there will be
189 another round (cold partition blocks are not supposed to be
190 collected into traces until the very last round); or 2). There will
191 be another round, and the basic block is not "hot enough" for the
192 current round of trace collection. */
195 push_to_next_round_p (const_basic_block bb, int round, int number_of_rounds,
196 int exec_th, gcov_type count_th)
198 bool there_exists_another_round;
199 bool block_not_hot_enough;
201 there_exists_another_round = round < number_of_rounds - 1;
203 block_not_hot_enough = (bb->frequency < exec_th
204 || bb->count < count_th
205 || probably_never_executed_bb_p (bb));
207 if (there_exists_another_round
208 && block_not_hot_enough)
214 /* Find the traces for Software Trace Cache. Chain each trace through
215 RBI()->next. Store the number of traces to N_TRACES and description of
219 find_traces (int *n_traces, struct trace *traces)
222 int number_of_rounds;
227 /* Add one extra round of trace collection when partitioning hot/cold
228 basic blocks into separate sections. The last round is for all the
229 cold blocks (and ONLY the cold blocks). */
231 number_of_rounds = N_ROUNDS - 1;
233 /* Insert entry points of function into heap. */
234 heap = fibheap_new ();
235 max_entry_frequency = 0;
237 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
239 bbd[e->dest->index].heap = heap;
240 bbd[e->dest->index].node = fibheap_insert (heap, bb_to_key (e->dest),
242 if (e->dest->frequency > max_entry_frequency)
243 max_entry_frequency = e->dest->frequency;
244 if (e->dest->count > max_entry_count)
245 max_entry_count = e->dest->count;
248 /* Find the traces. */
249 for (i = 0; i < number_of_rounds; i++)
251 gcov_type count_threshold;
254 fprintf (dump_file, "STC - round %d\n", i + 1);
256 if (max_entry_count < INT_MAX / 1000)
257 count_threshold = max_entry_count * exec_threshold[i] / 1000;
259 count_threshold = max_entry_count / 1000 * exec_threshold[i];
261 find_traces_1_round (REG_BR_PROB_BASE * branch_threshold[i] / 1000,
262 max_entry_frequency * exec_threshold[i] / 1000,
263 count_threshold, traces, n_traces, i, &heap,
266 fibheap_delete (heap);
270 for (i = 0; i < *n_traces; i++)
273 fprintf (dump_file, "Trace %d (round %d): ", i + 1,
274 traces[i].round + 1);
275 for (bb = traces[i].first; bb != traces[i].last; bb = (basic_block) bb->aux)
276 fprintf (dump_file, "%d [%d] ", bb->index, bb->frequency);
277 fprintf (dump_file, "%d [%d]\n", bb->index, bb->frequency);
283 /* Rotate loop whose back edge is BACK_EDGE in the tail of trace TRACE
284 (with sequential number TRACE_N). */
287 rotate_loop (edge back_edge, struct trace *trace, int trace_n)
291 /* Information about the best end (end after rotation) of the loop. */
292 basic_block best_bb = NULL;
293 edge best_edge = NULL;
295 gcov_type best_count = -1;
296 /* The best edge is preferred when its destination is not visited yet
297 or is a start block of some trace. */
298 bool is_preferred = false;
300 /* Find the most frequent edge that goes out from current trace. */
301 bb = back_edge->dest;
307 FOR_EACH_EDGE (e, ei, bb->succs)
308 if (e->dest != EXIT_BLOCK_PTR
309 && e->dest->il.rtl->visited != trace_n
310 && (e->flags & EDGE_CAN_FALLTHRU)
311 && !(e->flags & EDGE_COMPLEX))
315 /* The best edge is preferred. */
316 if (!e->dest->il.rtl->visited
317 || bbd[e->dest->index].start_of_trace >= 0)
319 /* The current edge E is also preferred. */
320 int freq = EDGE_FREQUENCY (e);
321 if (freq > best_freq || e->count > best_count)
324 best_count = e->count;
332 if (!e->dest->il.rtl->visited
333 || bbd[e->dest->index].start_of_trace >= 0)
335 /* The current edge E is preferred. */
337 best_freq = EDGE_FREQUENCY (e);
338 best_count = e->count;
344 int freq = EDGE_FREQUENCY (e);
345 if (!best_edge || freq > best_freq || e->count > best_count)
348 best_count = e->count;
355 bb = (basic_block) bb->aux;
357 while (bb != back_edge->dest);
361 /* Rotate the loop so that the BEST_EDGE goes out from the last block of
363 if (back_edge->dest == trace->first)
365 trace->first = (basic_block) best_bb->aux;
371 for (prev_bb = trace->first;
372 prev_bb->aux != back_edge->dest;
373 prev_bb = (basic_block) prev_bb->aux)
375 prev_bb->aux = best_bb->aux;
377 /* Try to get rid of uncond jump to cond jump. */
378 if (single_succ_p (prev_bb))
380 basic_block header = single_succ (prev_bb);
382 /* Duplicate HEADER if it is a small block containing cond jump
384 if (any_condjump_p (BB_END (header)) && copy_bb_p (header, 0)
385 && !find_reg_note (BB_END (header), REG_CROSSING_JUMP,
387 copy_bb (header, single_succ_edge (prev_bb), prev_bb, trace_n);
393 /* We have not found suitable loop tail so do no rotation. */
394 best_bb = back_edge->src;
400 /* This function marks BB that it was visited in trace number TRACE. */
403 mark_bb_visited (basic_block bb, int trace)
405 bb->il.rtl->visited = trace;
406 if (bbd[bb->index].heap)
408 fibheap_delete_node (bbd[bb->index].heap, bbd[bb->index].node);
409 bbd[bb->index].heap = NULL;
410 bbd[bb->index].node = NULL;
414 /* One round of finding traces. Find traces for BRANCH_TH and EXEC_TH i.e. do
415 not include basic blocks their probability is lower than BRANCH_TH or their
416 frequency is lower than EXEC_TH into traces (or count is lower than
417 COUNT_TH). It stores the new traces into TRACES and modifies the number of
418 traces *N_TRACES. Sets the round (which the trace belongs to) to ROUND. It
419 expects that starting basic blocks are in *HEAP and at the end it deletes
420 *HEAP and stores starting points for the next round into new *HEAP. */
423 find_traces_1_round (int branch_th, int exec_th, gcov_type count_th,
424 struct trace *traces, int *n_traces, int round,
425 fibheap_t *heap, int number_of_rounds)
427 /* Heap for discarded basic blocks which are possible starting points for
429 fibheap_t new_heap = fibheap_new ();
431 while (!fibheap_empty (*heap))
439 bb = (basic_block) fibheap_extract_min (*heap);
440 bbd[bb->index].heap = NULL;
441 bbd[bb->index].node = NULL;
444 fprintf (dump_file, "Getting bb %d\n", bb->index);
446 /* If the BB's frequency is too low send BB to the next round. When
447 partitioning hot/cold blocks into separate sections, make sure all
448 the cold blocks (and ONLY the cold blocks) go into the (extra) final
451 if (push_to_next_round_p (bb, round, number_of_rounds, exec_th,
454 int key = bb_to_key (bb);
455 bbd[bb->index].heap = new_heap;
456 bbd[bb->index].node = fibheap_insert (new_heap, key, bb);
460 " Possible start point of next round: %d (key: %d)\n",
465 trace = traces + *n_traces;
467 trace->round = round;
469 bbd[bb->index].in_trace = *n_traces;
477 /* The probability and frequency of the best edge. */
478 int best_prob = INT_MIN / 2;
479 int best_freq = INT_MIN / 2;
482 mark_bb_visited (bb, *n_traces);
486 fprintf (dump_file, "Basic block %d was visited in trace %d\n",
487 bb->index, *n_traces - 1);
489 ends_in_call = block_ends_with_call_p (bb);
491 /* Select the successor that will be placed after BB. */
492 FOR_EACH_EDGE (e, ei, bb->succs)
494 gcc_assert (!(e->flags & EDGE_FAKE));
496 if (e->dest == EXIT_BLOCK_PTR)
499 if (e->dest->il.rtl->visited
500 && e->dest->il.rtl->visited != *n_traces)
503 if (BB_PARTITION (e->dest) != BB_PARTITION (bb))
506 prob = e->probability;
507 freq = e->dest->frequency;
509 /* The only sensible preference for a call instruction is the
510 fallthru edge. Don't bother selecting anything else. */
513 if (e->flags & EDGE_CAN_FALLTHRU)
522 /* Edge that cannot be fallthru or improbable or infrequent
523 successor (i.e. it is unsuitable successor). */
524 if (!(e->flags & EDGE_CAN_FALLTHRU) || (e->flags & EDGE_COMPLEX)
525 || prob < branch_th || EDGE_FREQUENCY (e) < exec_th
526 || e->count < count_th)
529 /* If partitioning hot/cold basic blocks, don't consider edges
530 that cross section boundaries. */
532 if (better_edge_p (bb, e, prob, freq, best_prob, best_freq,
541 /* If the best destination has multiple predecessors, and can be
542 duplicated cheaper than a jump, don't allow it to be added
543 to a trace. We'll duplicate it when connecting traces. */
544 if (best_edge && EDGE_COUNT (best_edge->dest->preds) >= 2
545 && copy_bb_p (best_edge->dest, 0))
548 /* Add all non-selected successors to the heaps. */
549 FOR_EACH_EDGE (e, ei, bb->succs)
552 || e->dest == EXIT_BLOCK_PTR
553 || e->dest->il.rtl->visited)
556 key = bb_to_key (e->dest);
558 if (bbd[e->dest->index].heap)
560 /* E->DEST is already in some heap. */
561 if (key != bbd[e->dest->index].node->key)
566 "Changing key for bb %d from %ld to %ld.\n",
568 (long) bbd[e->dest->index].node->key,
571 fibheap_replace_key (bbd[e->dest->index].heap,
572 bbd[e->dest->index].node, key);
577 fibheap_t which_heap = *heap;
579 prob = e->probability;
580 freq = EDGE_FREQUENCY (e);
582 if (!(e->flags & EDGE_CAN_FALLTHRU)
583 || (e->flags & EDGE_COMPLEX)
584 || prob < branch_th || freq < exec_th
585 || e->count < count_th)
587 /* When partitioning hot/cold basic blocks, make sure
588 the cold blocks (and only the cold blocks) all get
589 pushed to the last round of trace collection. */
591 if (push_to_next_round_p (e->dest, round,
594 which_heap = new_heap;
597 bbd[e->dest->index].heap = which_heap;
598 bbd[e->dest->index].node = fibheap_insert (which_heap,
604 " Possible start of %s round: %d (key: %ld)\n",
605 (which_heap == new_heap) ? "next" : "this",
606 e->dest->index, (long) key);
612 if (best_edge) /* Suitable successor was found. */
614 if (best_edge->dest->il.rtl->visited == *n_traces)
616 /* We do nothing with one basic block loops. */
617 if (best_edge->dest != bb)
619 if (EDGE_FREQUENCY (best_edge)
620 > 4 * best_edge->dest->frequency / 5)
622 /* The loop has at least 4 iterations. If the loop
623 header is not the first block of the function
624 we can rotate the loop. */
626 if (best_edge->dest != ENTRY_BLOCK_PTR->next_bb)
631 "Rotating loop %d - %d\n",
632 best_edge->dest->index, bb->index);
634 bb->aux = best_edge->dest;
635 bbd[best_edge->dest->index].in_trace =
637 bb = rotate_loop (best_edge, trace, *n_traces);
642 /* The loop has less than 4 iterations. */
644 if (single_succ_p (bb)
645 && copy_bb_p (best_edge->dest,
646 optimize_edge_for_speed_p (best_edge)))
648 bb = copy_bb (best_edge->dest, best_edge, bb,
655 /* Terminate the trace. */
660 /* Check for a situation
669 EDGE_FREQUENCY (AB) + EDGE_FREQUENCY (BC)
670 >= EDGE_FREQUENCY (AC).
671 (i.e. 2 * B->frequency >= EDGE_FREQUENCY (AC) )
672 Best ordering is then A B C.
674 This situation is created for example by:
681 FOR_EACH_EDGE (e, ei, bb->succs)
683 && (e->flags & EDGE_CAN_FALLTHRU)
684 && !(e->flags & EDGE_COMPLEX)
685 && !e->dest->il.rtl->visited
686 && single_pred_p (e->dest)
687 && !(e->flags & EDGE_CROSSING)
688 && single_succ_p (e->dest)
689 && (single_succ_edge (e->dest)->flags
691 && !(single_succ_edge (e->dest)->flags & EDGE_COMPLEX)
692 && single_succ (e->dest) == best_edge->dest
693 && 2 * e->dest->frequency >= EDGE_FREQUENCY (best_edge))
697 fprintf (dump_file, "Selecting BB %d\n",
698 best_edge->dest->index);
702 bb->aux = best_edge->dest;
703 bbd[best_edge->dest->index].in_trace = (*n_traces) - 1;
704 bb = best_edge->dest;
710 bbd[trace->first->index].start_of_trace = *n_traces - 1;
711 bbd[trace->last->index].end_of_trace = *n_traces - 1;
713 /* The trace is terminated so we have to recount the keys in heap
714 (some block can have a lower key because now one of its predecessors
715 is an end of the trace). */
716 FOR_EACH_EDGE (e, ei, bb->succs)
718 if (e->dest == EXIT_BLOCK_PTR
719 || e->dest->il.rtl->visited)
722 if (bbd[e->dest->index].heap)
724 key = bb_to_key (e->dest);
725 if (key != bbd[e->dest->index].node->key)
730 "Changing key for bb %d from %ld to %ld.\n",
732 (long) bbd[e->dest->index].node->key, key);
734 fibheap_replace_key (bbd[e->dest->index].heap,
735 bbd[e->dest->index].node,
742 fibheap_delete (*heap);
744 /* "Return" the new heap. */
748 /* Create a duplicate of the basic block OLD_BB and redirect edge E to it, add
749 it to trace after BB, mark OLD_BB visited and update pass' data structures
750 (TRACE is a number of trace which OLD_BB is duplicated to). */
753 copy_bb (basic_block old_bb, edge e, basic_block bb, int trace)
757 new_bb = duplicate_block (old_bb, e, bb);
758 BB_COPY_PARTITION (new_bb, old_bb);
760 gcc_assert (e->dest == new_bb);
761 gcc_assert (!e->dest->il.rtl->visited);
765 "Duplicated bb %d (created bb %d)\n",
766 old_bb->index, new_bb->index);
767 new_bb->il.rtl->visited = trace;
768 new_bb->aux = bb->aux;
771 if (new_bb->index >= array_size || last_basic_block > array_size)
776 new_size = MAX (last_basic_block, new_bb->index + 1);
777 new_size = GET_ARRAY_SIZE (new_size);
778 bbd = XRESIZEVEC (bbro_basic_block_data, bbd, new_size);
779 for (i = array_size; i < new_size; i++)
781 bbd[i].start_of_trace = -1;
782 bbd[i].in_trace = -1;
783 bbd[i].end_of_trace = -1;
787 array_size = new_size;
792 "Growing the dynamic array to %d elements.\n",
797 bbd[new_bb->index].in_trace = trace;
802 /* Compute and return the key (for the heap) of the basic block BB. */
805 bb_to_key (basic_block bb)
811 /* Do not start in probably never executed blocks. */
813 if (BB_PARTITION (bb) == BB_COLD_PARTITION
814 || probably_never_executed_bb_p (bb))
817 /* Prefer blocks whose predecessor is an end of some trace
818 or whose predecessor edge is EDGE_DFS_BACK. */
819 FOR_EACH_EDGE (e, ei, bb->preds)
821 if ((e->src != ENTRY_BLOCK_PTR && bbd[e->src->index].end_of_trace >= 0)
822 || (e->flags & EDGE_DFS_BACK))
824 int edge_freq = EDGE_FREQUENCY (e);
826 if (edge_freq > priority)
827 priority = edge_freq;
832 /* The block with priority should have significantly lower key. */
833 return -(100 * BB_FREQ_MAX + 100 * priority + bb->frequency);
834 return -bb->frequency;
837 /* Return true when the edge E from basic block BB is better than the temporary
838 best edge (details are in function). The probability of edge E is PROB. The
839 frequency of the successor is FREQ. The current best probability is
840 BEST_PROB, the best frequency is BEST_FREQ.
841 The edge is considered to be equivalent when PROB does not differ much from
842 BEST_PROB; similarly for frequency. */
845 better_edge_p (const_basic_block bb, const_edge e, int prob, int freq, int best_prob,
846 int best_freq, const_edge cur_best_edge)
850 /* The BEST_* values do not have to be best, but can be a bit smaller than
852 int diff_prob = best_prob / 10;
853 int diff_freq = best_freq / 10;
855 if (prob > best_prob + diff_prob)
856 /* The edge has higher probability than the temporary best edge. */
857 is_better_edge = true;
858 else if (prob < best_prob - diff_prob)
859 /* The edge has lower probability than the temporary best edge. */
860 is_better_edge = false;
861 else if (freq < best_freq - diff_freq)
862 /* The edge and the temporary best edge have almost equivalent
863 probabilities. The higher frequency of a successor now means
864 that there is another edge going into that successor.
865 This successor has lower frequency so it is better. */
866 is_better_edge = true;
867 else if (freq > best_freq + diff_freq)
868 /* This successor has higher frequency so it is worse. */
869 is_better_edge = false;
870 else if (e->dest->prev_bb == bb)
871 /* The edges have equivalent probabilities and the successors
872 have equivalent frequencies. Select the previous successor. */
873 is_better_edge = true;
875 is_better_edge = false;
877 /* If we are doing hot/cold partitioning, make sure that we always favor
878 non-crossing edges over crossing edges. */
881 && flag_reorder_blocks_and_partition
883 && (cur_best_edge->flags & EDGE_CROSSING)
884 && !(e->flags & EDGE_CROSSING))
885 is_better_edge = true;
887 return is_better_edge;
890 /* Connect traces in array TRACES, N_TRACES is the count of traces. */
893 connect_traces (int n_traces, struct trace *traces)
900 int current_partition;
902 gcov_type count_threshold;
904 freq_threshold = max_entry_frequency * DUPLICATION_THRESHOLD / 1000;
905 if (max_entry_count < INT_MAX / 1000)
906 count_threshold = max_entry_count * DUPLICATION_THRESHOLD / 1000;
908 count_threshold = max_entry_count / 1000 * DUPLICATION_THRESHOLD;
910 connected = XCNEWVEC (bool, n_traces);
913 current_partition = BB_PARTITION (traces[0].first);
916 if (flag_reorder_blocks_and_partition)
917 for (i = 0; i < n_traces && !two_passes; i++)
918 if (BB_PARTITION (traces[0].first)
919 != BB_PARTITION (traces[i].first))
922 for (i = 0; i < n_traces || (two_passes && current_pass == 1) ; i++)
931 gcc_assert (two_passes && current_pass == 1);
935 if (current_partition == BB_HOT_PARTITION)
936 current_partition = BB_COLD_PARTITION;
938 current_partition = BB_HOT_PARTITION;
945 && BB_PARTITION (traces[t].first) != current_partition)
950 /* Find the predecessor traces. */
951 for (t2 = t; t2 > 0;)
956 FOR_EACH_EDGE (e, ei, traces[t2].first->preds)
958 int si = e->src->index;
960 if (e->src != ENTRY_BLOCK_PTR
961 && (e->flags & EDGE_CAN_FALLTHRU)
962 && !(e->flags & EDGE_COMPLEX)
963 && bbd[si].end_of_trace >= 0
964 && !connected[bbd[si].end_of_trace]
965 && (BB_PARTITION (e->src) == current_partition)
967 || e->probability > best->probability
968 || (e->probability == best->probability
969 && traces[bbd[si].end_of_trace].length > best_len)))
972 best_len = traces[bbd[si].end_of_trace].length;
977 best->src->aux = best->dest;
978 t2 = bbd[best->src->index].end_of_trace;
979 connected[t2] = true;
983 fprintf (dump_file, "Connection: %d %d\n",
984 best->src->index, best->dest->index);
992 traces[last_trace].last->aux = traces[t2].first;
995 /* Find the successor traces. */
998 /* Find the continuation of the chain. */
1002 FOR_EACH_EDGE (e, ei, traces[t].last->succs)
1004 int di = e->dest->index;
1006 if (e->dest != EXIT_BLOCK_PTR
1007 && (e->flags & EDGE_CAN_FALLTHRU)
1008 && !(e->flags & EDGE_COMPLEX)
1009 && bbd[di].start_of_trace >= 0
1010 && !connected[bbd[di].start_of_trace]
1011 && (BB_PARTITION (e->dest) == current_partition)
1013 || e->probability > best->probability
1014 || (e->probability == best->probability
1015 && traces[bbd[di].start_of_trace].length > best_len)))
1018 best_len = traces[bbd[di].start_of_trace].length;
1026 fprintf (dump_file, "Connection: %d %d\n",
1027 best->src->index, best->dest->index);
1029 t = bbd[best->dest->index].start_of_trace;
1030 traces[last_trace].last->aux = traces[t].first;
1031 connected[t] = true;
1036 /* Try to connect the traces by duplication of 1 block. */
1038 basic_block next_bb = NULL;
1039 bool try_copy = false;
1041 FOR_EACH_EDGE (e, ei, traces[t].last->succs)
1042 if (e->dest != EXIT_BLOCK_PTR
1043 && (e->flags & EDGE_CAN_FALLTHRU)
1044 && !(e->flags & EDGE_COMPLEX)
1045 && (!best || e->probability > best->probability))
1051 /* If the destination is a start of a trace which is only
1052 one block long, then no need to search the successor
1053 blocks of the trace. Accept it. */
1054 if (bbd[e->dest->index].start_of_trace >= 0
1055 && traces[bbd[e->dest->index].start_of_trace].length
1063 FOR_EACH_EDGE (e2, ei, e->dest->succs)
1065 int di = e2->dest->index;
1067 if (e2->dest == EXIT_BLOCK_PTR
1068 || ((e2->flags & EDGE_CAN_FALLTHRU)
1069 && !(e2->flags & EDGE_COMPLEX)
1070 && bbd[di].start_of_trace >= 0
1071 && !connected[bbd[di].start_of_trace]
1072 && (BB_PARTITION (e2->dest) == current_partition)
1073 && (EDGE_FREQUENCY (e2) >= freq_threshold)
1074 && (e2->count >= count_threshold)
1076 || e2->probability > best2->probability
1077 || (e2->probability == best2->probability
1078 && traces[bbd[di].start_of_trace].length
1083 if (e2->dest != EXIT_BLOCK_PTR)
1084 best2_len = traces[bbd[di].start_of_trace].length;
1086 best2_len = INT_MAX;
1093 if (flag_reorder_blocks_and_partition)
1096 /* Copy tiny blocks always; copy larger blocks only when the
1097 edge is traversed frequently enough. */
1099 && copy_bb_p (best->dest,
1100 optimize_edge_for_speed_p (best)
1101 && EDGE_FREQUENCY (best) >= freq_threshold
1102 && best->count >= count_threshold))
1108 fprintf (dump_file, "Connection: %d %d ",
1109 traces[t].last->index, best->dest->index);
1111 fputc ('\n', dump_file);
1112 else if (next_bb == EXIT_BLOCK_PTR)
1113 fprintf (dump_file, "exit\n");
1115 fprintf (dump_file, "%d\n", next_bb->index);
1118 new_bb = copy_bb (best->dest, best, traces[t].last, t);
1119 traces[t].last = new_bb;
1120 if (next_bb && next_bb != EXIT_BLOCK_PTR)
1122 t = bbd[next_bb->index].start_of_trace;
1123 traces[last_trace].last->aux = traces[t].first;
1124 connected[t] = true;
1128 break; /* Stop finding the successor traces. */
1131 break; /* Stop finding the successor traces. */
1140 fprintf (dump_file, "Final order:\n");
1141 for (bb = traces[0].first; bb; bb = (basic_block) bb->aux)
1142 fprintf (dump_file, "%d ", bb->index);
1143 fprintf (dump_file, "\n");
1150 /* Return true when BB can and should be copied. CODE_MAY_GROW is true
1151 when code size is allowed to grow by duplication. */
1154 copy_bb_p (const_basic_block bb, int code_may_grow)
1157 int max_size = uncond_jump_length;
1162 if (EDGE_COUNT (bb->preds) < 2)
1164 if (!can_duplicate_block_p (bb))
1167 /* Avoid duplicating blocks which have many successors (PR/13430). */
1168 if (EDGE_COUNT (bb->succs) > 8)
1171 if (code_may_grow && optimize_bb_for_speed_p (bb))
1172 max_size *= PARAM_VALUE (PARAM_MAX_GROW_COPY_BB_INSNS);
1174 FOR_BB_INSNS (bb, insn)
1177 size += get_attr_min_length (insn);
1180 if (size <= max_size)
1186 "Block %d can't be copied because its size = %d.\n",
1193 /* Return the length of unconditional jump instruction. */
1196 get_uncond_jump_length (void)
1201 label = emit_label_before (gen_label_rtx (), get_insns ());
1202 jump = emit_jump_insn (gen_jump (label));
1204 length = get_attr_min_length (jump);
1207 delete_insn (label);
1211 /* Find the basic blocks that are rarely executed and need to be moved to
1212 a separate section of the .o file (to cut down on paging and improve
1213 cache locality). Return a vector of all edges that cross. */
1215 static VEC(edge, heap) *
1216 find_rarely_executed_basic_blocks_and_crossing_edges (void)
1218 VEC(edge, heap) *crossing_edges = NULL;
1223 /* Mark which partition (hot/cold) each basic block belongs in. */
1227 if (probably_never_executed_bb_p (bb))
1228 BB_SET_PARTITION (bb, BB_COLD_PARTITION);
1230 BB_SET_PARTITION (bb, BB_HOT_PARTITION);
1233 /* Mark every edge that crosses between sections. */
1236 FOR_EACH_EDGE (e, ei, bb->succs)
1238 if (e->src != ENTRY_BLOCK_PTR
1239 && e->dest != EXIT_BLOCK_PTR
1240 && BB_PARTITION (e->src) != BB_PARTITION (e->dest))
1242 e->flags |= EDGE_CROSSING;
1243 VEC_safe_push (edge, heap, crossing_edges, e);
1246 e->flags &= ~EDGE_CROSSING;
1249 return crossing_edges;
1252 /* If any destination of a crossing edge does not have a label, add label;
1253 Convert any easy fall-through crossing edges to unconditional jumps. */
1256 add_labels_and_missing_jumps (VEC(edge, heap) *crossing_edges)
1261 FOR_EACH_VEC_ELT (edge, crossing_edges, i, e)
1263 basic_block src = e->src;
1264 basic_block dest = e->dest;
1265 rtx label, barrier, new_jump;
1267 if (dest == EXIT_BLOCK_PTR)
1270 /* Make sure dest has a label. */
1271 label = block_label (dest);
1273 /* Nothing to do for non-fallthru edges. */
1274 if (src == ENTRY_BLOCK_PTR)
1276 if ((e->flags & EDGE_FALLTHRU) == 0)
1279 /* If the block does not end with a control flow insn, then we
1280 can trivially add a jump to the end to fixup the crossing.
1281 Otherwise the jump will have to go in a new bb, which will
1282 be handled by fix_up_fall_thru_edges function. */
1283 if (control_flow_insn_p (BB_END (src)))
1286 /* Make sure there's only one successor. */
1287 gcc_assert (single_succ_p (src));
1289 new_jump = emit_jump_insn_after (gen_jump (label), BB_END (src));
1290 BB_END (src) = new_jump;
1291 barrier = emit_barrier_after (new_jump);
1292 JUMP_LABEL (new_jump) = label;
1293 LABEL_NUSES (label) += 1;
1294 src->il.rtl->footer = unlink_insn_chain (barrier, barrier);
1296 /* Mark edge as non-fallthru. */
1297 e->flags &= ~EDGE_FALLTHRU;
1301 /* Find any bb's where the fall-through edge is a crossing edge (note that
1302 these bb's must also contain a conditional jump or end with a call
1303 instruction; we've already dealt with fall-through edges for blocks
1304 that didn't have a conditional jump or didn't end with call instruction
1305 in the call to add_labels_and_missing_jumps). Convert the fall-through
1306 edge to non-crossing edge by inserting a new bb to fall-through into.
1307 The new bb will contain an unconditional jump (crossing edge) to the
1308 original fall through destination. */
1311 fix_up_fall_thru_edges (void)
1318 edge cond_jump = NULL;
1320 bool cond_jump_crosses;
1323 rtx fall_thru_label;
1326 FOR_EACH_BB (cur_bb)
1329 if (EDGE_COUNT (cur_bb->succs) > 0)
1330 succ1 = EDGE_SUCC (cur_bb, 0);
1334 if (EDGE_COUNT (cur_bb->succs) > 1)
1335 succ2 = EDGE_SUCC (cur_bb, 1);
1339 /* Find the fall-through edge. */
1342 && (succ1->flags & EDGE_FALLTHRU))
1348 && (succ2->flags & EDGE_FALLTHRU))
1354 && (block_ends_with_call_p (cur_bb)
1355 || can_throw_internal (BB_END (cur_bb))))
1360 /* Find EDGE_CAN_FALLTHRU edge. */
1361 FOR_EACH_EDGE (e, ei, cur_bb->succs)
1362 if (e->flags & EDGE_CAN_FALLTHRU)
1369 if (fall_thru && (fall_thru->dest != EXIT_BLOCK_PTR))
1371 /* Check to see if the fall-thru edge is a crossing edge. */
1373 if (fall_thru->flags & EDGE_CROSSING)
1375 /* The fall_thru edge crosses; now check the cond jump edge, if
1378 cond_jump_crosses = true;
1380 old_jump = BB_END (cur_bb);
1382 /* Find the jump instruction, if there is one. */
1386 if (!(cond_jump->flags & EDGE_CROSSING))
1387 cond_jump_crosses = false;
1389 /* We know the fall-thru edge crosses; if the cond
1390 jump edge does NOT cross, and its destination is the
1391 next block in the bb order, invert the jump
1392 (i.e. fix it so the fall thru does not cross and
1393 the cond jump does). */
1395 if (!cond_jump_crosses
1396 && cur_bb->aux == cond_jump->dest)
1398 /* Find label in fall_thru block. We've already added
1399 any missing labels, so there must be one. */
1401 fall_thru_label = block_label (fall_thru->dest);
1403 if (old_jump && JUMP_P (old_jump) && fall_thru_label)
1404 invert_worked = invert_jump (old_jump,
1408 fall_thru->flags &= ~EDGE_FALLTHRU;
1409 cond_jump->flags |= EDGE_FALLTHRU;
1410 update_br_prob_note (cur_bb);
1412 fall_thru = cond_jump;
1414 cond_jump->flags |= EDGE_CROSSING;
1415 fall_thru->flags &= ~EDGE_CROSSING;
1420 if (cond_jump_crosses || !invert_worked)
1422 /* This is the case where both edges out of the basic
1423 block are crossing edges. Here we will fix up the
1424 fall through edge. The jump edge will be taken care
1425 of later. The EDGE_CROSSING flag of fall_thru edge
1426 is unset before the call to force_nonfallthru
1427 function because if a new basic-block is created
1428 this edge remains in the current section boundary
1429 while the edge between new_bb and the fall_thru->dest
1430 becomes EDGE_CROSSING. */
1432 fall_thru->flags &= ~EDGE_CROSSING;
1433 new_bb = force_nonfallthru (fall_thru);
1437 new_bb->aux = cur_bb->aux;
1438 cur_bb->aux = new_bb;
1440 /* Make sure new fall-through bb is in same
1441 partition as bb it's falling through from. */
1443 BB_COPY_PARTITION (new_bb, cur_bb);
1444 single_succ_edge (new_bb)->flags |= EDGE_CROSSING;
1448 /* If a new basic-block was not created; restore
1449 the EDGE_CROSSING flag. */
1450 fall_thru->flags |= EDGE_CROSSING;
1453 /* Add barrier after new jump */
1457 barrier = emit_barrier_after (BB_END (new_bb));
1458 new_bb->il.rtl->footer = unlink_insn_chain (barrier,
1463 barrier = emit_barrier_after (BB_END (cur_bb));
1464 cur_bb->il.rtl->footer = unlink_insn_chain (barrier,
1473 /* This function checks the destination block of a "crossing jump" to
1474 see if it has any crossing predecessors that begin with a code label
1475 and end with an unconditional jump. If so, it returns that predecessor
1476 block. (This is to avoid creating lots of new basic blocks that all
1477 contain unconditional jumps to the same destination). */
1480 find_jump_block (basic_block jump_dest)
1482 basic_block source_bb = NULL;
1487 FOR_EACH_EDGE (e, ei, jump_dest->preds)
1488 if (e->flags & EDGE_CROSSING)
1490 basic_block src = e->src;
1492 /* Check each predecessor to see if it has a label, and contains
1493 only one executable instruction, which is an unconditional jump.
1494 If so, we can use it. */
1496 if (LABEL_P (BB_HEAD (src)))
1497 for (insn = BB_HEAD (src);
1498 !INSN_P (insn) && insn != NEXT_INSN (BB_END (src));
1499 insn = NEXT_INSN (insn))
1502 && insn == BB_END (src)
1504 && !any_condjump_p (insn))
1518 /* Find all BB's with conditional jumps that are crossing edges;
1519 insert a new bb and make the conditional jump branch to the new
1520 bb instead (make the new bb same color so conditional branch won't
1521 be a 'crossing' edge). Insert an unconditional jump from the
1522 new bb to the original destination of the conditional jump. */
1525 fix_crossing_conditional_branches (void)
1529 basic_block last_bb;
1537 rtx old_label = NULL_RTX;
1542 last_bb = EXIT_BLOCK_PTR->prev_bb;
1544 FOR_EACH_BB (cur_bb)
1546 crossing_edge = NULL;
1547 if (EDGE_COUNT (cur_bb->succs) > 0)
1548 succ1 = EDGE_SUCC (cur_bb, 0);
1552 if (EDGE_COUNT (cur_bb->succs) > 1)
1553 succ2 = EDGE_SUCC (cur_bb, 1);
1557 /* We already took care of fall-through edges, so only one successor
1558 can be a crossing edge. */
1560 if (succ1 && (succ1->flags & EDGE_CROSSING))
1561 crossing_edge = succ1;
1562 else if (succ2 && (succ2->flags & EDGE_CROSSING))
1563 crossing_edge = succ2;
1567 old_jump = BB_END (cur_bb);
1569 /* Check to make sure the jump instruction is a
1570 conditional jump. */
1574 if (any_condjump_p (old_jump))
1576 if (GET_CODE (PATTERN (old_jump)) == SET)
1577 set_src = SET_SRC (PATTERN (old_jump));
1578 else if (GET_CODE (PATTERN (old_jump)) == PARALLEL)
1580 set_src = XVECEXP (PATTERN (old_jump), 0,0);
1581 if (GET_CODE (set_src) == SET)
1582 set_src = SET_SRC (set_src);
1588 if (set_src && (GET_CODE (set_src) == IF_THEN_ELSE))
1590 if (GET_CODE (XEXP (set_src, 1)) == PC)
1591 old_label = XEXP (set_src, 2);
1592 else if (GET_CODE (XEXP (set_src, 2)) == PC)
1593 old_label = XEXP (set_src, 1);
1595 /* Check to see if new bb for jumping to that dest has
1596 already been created; if so, use it; if not, create
1599 new_bb = find_jump_block (crossing_edge->dest);
1602 new_label = block_label (new_bb);
1605 /* Create new basic block to be dest for
1606 conditional jump. */
1608 new_bb = create_basic_block (NULL, NULL, last_bb);
1609 new_bb->aux = last_bb->aux;
1610 last_bb->aux = new_bb;
1612 /* Put appropriate instructions in new bb. */
1614 new_label = gen_label_rtx ();
1615 emit_label_before (new_label, BB_HEAD (new_bb));
1616 BB_HEAD (new_bb) = new_label;
1618 if (GET_CODE (old_label) == LABEL_REF)
1620 old_label = JUMP_LABEL (old_jump);
1621 new_jump = emit_jump_insn_after (gen_jump
1627 gcc_assert (HAVE_return
1628 && GET_CODE (old_label) == RETURN);
1629 new_jump = emit_jump_insn_after (gen_return (),
1633 barrier = emit_barrier_after (new_jump);
1634 JUMP_LABEL (new_jump) = old_label;
1635 new_bb->il.rtl->footer = unlink_insn_chain (barrier,
1638 /* Make sure new bb is in same partition as source
1639 of conditional branch. */
1640 BB_COPY_PARTITION (new_bb, cur_bb);
1643 /* Make old jump branch to new bb. */
1645 redirect_jump (old_jump, new_label, 0);
1647 /* Remove crossing_edge as predecessor of 'dest'. */
1649 dest = crossing_edge->dest;
1651 redirect_edge_succ (crossing_edge, new_bb);
1653 /* Make a new edge from new_bb to old dest; new edge
1654 will be a successor for new_bb and a predecessor
1657 if (EDGE_COUNT (new_bb->succs) == 0)
1658 new_edge = make_edge (new_bb, dest, 0);
1660 new_edge = EDGE_SUCC (new_bb, 0);
1662 crossing_edge->flags &= ~EDGE_CROSSING;
1663 new_edge->flags |= EDGE_CROSSING;
1669 /* Find any unconditional branches that cross between hot and cold
1670 sections. Convert them into indirect jumps instead. */
1673 fix_crossing_unconditional_branches (void)
1679 rtx indirect_jump_sequence;
1680 rtx jump_insn = NULL_RTX;
1685 FOR_EACH_BB (cur_bb)
1687 last_insn = BB_END (cur_bb);
1689 if (EDGE_COUNT (cur_bb->succs) < 1)
1692 succ = EDGE_SUCC (cur_bb, 0);
1694 /* Check to see if bb ends in a crossing (unconditional) jump. At
1695 this point, no crossing jumps should be conditional. */
1697 if (JUMP_P (last_insn)
1698 && (succ->flags & EDGE_CROSSING))
1702 gcc_assert (!any_condjump_p (last_insn));
1704 /* Make sure the jump is not already an indirect or table jump. */
1706 if (!computed_jump_p (last_insn)
1707 && !tablejump_p (last_insn, &label2, &table))
1709 /* We have found a "crossing" unconditional branch. Now
1710 we must convert it to an indirect jump. First create
1711 reference of label, as target for jump. */
1713 label = JUMP_LABEL (last_insn);
1714 label_addr = gen_rtx_LABEL_REF (Pmode, label);
1715 LABEL_NUSES (label) += 1;
1717 /* Get a register to use for the indirect jump. */
1719 new_reg = gen_reg_rtx (Pmode);
1721 /* Generate indirect the jump sequence. */
1724 emit_move_insn (new_reg, label_addr);
1725 emit_indirect_jump (new_reg);
1726 indirect_jump_sequence = get_insns ();
1729 /* Make sure every instruction in the new jump sequence has
1730 its basic block set to be cur_bb. */
1732 for (cur_insn = indirect_jump_sequence; cur_insn;
1733 cur_insn = NEXT_INSN (cur_insn))
1735 if (!BARRIER_P (cur_insn))
1736 BLOCK_FOR_INSN (cur_insn) = cur_bb;
1737 if (JUMP_P (cur_insn))
1738 jump_insn = cur_insn;
1741 /* Insert the new (indirect) jump sequence immediately before
1742 the unconditional jump, then delete the unconditional jump. */
1744 emit_insn_before (indirect_jump_sequence, last_insn);
1745 delete_insn (last_insn);
1747 /* Make BB_END for cur_bb be the jump instruction (NOT the
1748 barrier instruction at the end of the sequence...). */
1750 BB_END (cur_bb) = jump_insn;
1756 /* Add REG_CROSSING_JUMP note to all crossing jump insns. */
1759 add_reg_crossing_jump_notes (void)
1766 FOR_EACH_EDGE (e, ei, bb->succs)
1767 if ((e->flags & EDGE_CROSSING)
1768 && JUMP_P (BB_END (e->src)))
1769 add_reg_note (BB_END (e->src), REG_CROSSING_JUMP, NULL_RTX);
1772 /* Verify, in the basic block chain, that there is at most one switch
1773 between hot/cold partitions. This is modelled on
1774 rtl_verify_flow_info_1, but it cannot go inside that function
1775 because this condition will not be true until after
1776 reorder_basic_blocks is called. */
1779 verify_hot_cold_block_grouping (void)
1783 bool switched_sections = false;
1784 int current_partition = 0;
1788 if (!current_partition)
1789 current_partition = BB_PARTITION (bb);
1790 if (BB_PARTITION (bb) != current_partition)
1792 if (switched_sections)
1794 error ("multiple hot/cold transitions found (bb %i)",
1800 switched_sections = true;
1801 current_partition = BB_PARTITION (bb);
1809 /* Reorder basic blocks. The main entry point to this file. FLAGS is
1810 the set of flags to pass to cfg_layout_initialize(). */
1813 reorder_basic_blocks (void)
1817 struct trace *traces;
1819 gcc_assert (current_ir_type () == IR_RTL_CFGLAYOUT);
1821 if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1)
1824 set_edge_can_fallthru_flag ();
1825 mark_dfs_back_edges ();
1827 /* We are estimating the length of uncond jump insn only once since the code
1828 for getting the insn length always returns the minimal length now. */
1829 if (uncond_jump_length == 0)
1830 uncond_jump_length = get_uncond_jump_length ();
1832 /* We need to know some information for each basic block. */
1833 array_size = GET_ARRAY_SIZE (last_basic_block);
1834 bbd = XNEWVEC (bbro_basic_block_data, array_size);
1835 for (i = 0; i < array_size; i++)
1837 bbd[i].start_of_trace = -1;
1838 bbd[i].in_trace = -1;
1839 bbd[i].end_of_trace = -1;
1844 traces = XNEWVEC (struct trace, n_basic_blocks);
1846 find_traces (&n_traces, traces);
1847 connect_traces (n_traces, traces);
1851 relink_block_chain (/*stay_in_cfglayout_mode=*/true);
1854 dump_flow_info (dump_file, dump_flags);
1856 if (flag_reorder_blocks_and_partition)
1857 verify_hot_cold_block_grouping ();
1860 /* Determine which partition the first basic block in the function
1861 belongs to, then find the first basic block in the current function
1862 that belongs to a different section, and insert a
1863 NOTE_INSN_SWITCH_TEXT_SECTIONS note immediately before it in the
1864 instruction stream. When writing out the assembly code,
1865 encountering this note will make the compiler switch between the
1866 hot and cold text sections. */
1869 insert_section_boundary_note (void)
1873 int first_partition = 0;
1875 if (flag_reorder_blocks_and_partition)
1878 if (!first_partition)
1879 first_partition = BB_PARTITION (bb);
1880 if (BB_PARTITION (bb) != first_partition)
1882 new_note = emit_note_before (NOTE_INSN_SWITCH_TEXT_SECTIONS,
1884 /* ??? This kind of note always lives between basic blocks,
1885 but add_insn_before will set BLOCK_FOR_INSN anyway. */
1886 BLOCK_FOR_INSN (new_note) = NULL;
1892 /* Duplicate the blocks containing computed gotos. This basically unfactors
1893 computed gotos that were factored early on in the compilation process to
1894 speed up edge based data flow. We used to not unfactoring them again,
1895 which can seriously pessimize code with many computed jumps in the source
1896 code, such as interpreters. See e.g. PR15242. */
1899 gate_duplicate_computed_gotos (void)
1901 if (targetm.cannot_modify_jumps_p ())
1903 return (optimize > 0
1904 && flag_expensive_optimizations
1905 && ! optimize_function_for_size_p (cfun));
1910 duplicate_computed_gotos (void)
1912 basic_block bb, new_bb;
1916 if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1)
1919 cfg_layout_initialize (0);
1921 /* We are estimating the length of uncond jump insn only once
1922 since the code for getting the insn length always returns
1923 the minimal length now. */
1924 if (uncond_jump_length == 0)
1925 uncond_jump_length = get_uncond_jump_length ();
1927 max_size = uncond_jump_length * PARAM_VALUE (PARAM_MAX_GOTO_DUPLICATION_INSNS);
1928 candidates = BITMAP_ALLOC (NULL);
1930 /* Look for blocks that end in a computed jump, and see if such blocks
1931 are suitable for unfactoring. If a block is a candidate for unfactoring,
1932 mark it in the candidates. */
1938 int size, all_flags;
1940 /* Build the reorder chain for the original order of blocks. */
1941 if (bb->next_bb != EXIT_BLOCK_PTR)
1942 bb->aux = bb->next_bb;
1944 /* Obviously the block has to end in a computed jump. */
1945 if (!computed_jump_p (BB_END (bb)))
1948 /* Only consider blocks that can be duplicated. */
1949 if (find_reg_note (BB_END (bb), REG_CROSSING_JUMP, NULL_RTX)
1950 || !can_duplicate_block_p (bb))
1953 /* Make sure that the block is small enough. */
1955 FOR_BB_INSNS (bb, insn)
1958 size += get_attr_min_length (insn);
1959 if (size > max_size)
1962 if (size > max_size)
1965 /* Final check: there must not be any incoming abnormal edges. */
1967 FOR_EACH_EDGE (e, ei, bb->preds)
1968 all_flags |= e->flags;
1969 if (all_flags & EDGE_COMPLEX)
1972 bitmap_set_bit (candidates, bb->index);
1975 /* Nothing to do if there is no computed jump here. */
1976 if (bitmap_empty_p (candidates))
1979 /* Duplicate computed gotos. */
1982 if (bb->il.rtl->visited)
1985 bb->il.rtl->visited = 1;
1987 /* BB must have one outgoing edge. That edge must not lead to
1988 the exit block or the next block.
1989 The destination must have more than one predecessor. */
1990 if (!single_succ_p (bb)
1991 || single_succ (bb) == EXIT_BLOCK_PTR
1992 || single_succ (bb) == bb->next_bb
1993 || single_pred_p (single_succ (bb)))
1996 /* The successor block has to be a duplication candidate. */
1997 if (!bitmap_bit_p (candidates, single_succ (bb)->index))
2000 new_bb = duplicate_block (single_succ (bb), single_succ_edge (bb), bb);
2001 new_bb->aux = bb->aux;
2003 new_bb->il.rtl->visited = 1;
2007 cfg_layout_finalize ();
2009 BITMAP_FREE (candidates);
2013 struct rtl_opt_pass pass_duplicate_computed_gotos =
2017 "compgotos", /* name */
2018 gate_duplicate_computed_gotos, /* gate */
2019 duplicate_computed_gotos, /* execute */
2022 0, /* static_pass_number */
2023 TV_REORDER_BLOCKS, /* tv_id */
2024 0, /* properties_required */
2025 0, /* properties_provided */
2026 0, /* properties_destroyed */
2027 0, /* todo_flags_start */
2028 TODO_verify_rtl_sharing,/* todo_flags_finish */
2033 /* This function is the main 'entrance' for the optimization that
2034 partitions hot and cold basic blocks into separate sections of the
2035 .o file (to improve performance and cache locality). Ideally it
2036 would be called after all optimizations that rearrange the CFG have
2037 been called. However part of this optimization may introduce new
2038 register usage, so it must be called before register allocation has
2039 occurred. This means that this optimization is actually called
2040 well before the optimization that reorders basic blocks (see
2043 This optimization checks the feedback information to determine
2044 which basic blocks are hot/cold, updates flags on the basic blocks
2045 to indicate which section they belong in. This information is
2046 later used for writing out sections in the .o file. Because hot
2047 and cold sections can be arbitrarily large (within the bounds of
2048 memory), far beyond the size of a single function, it is necessary
2049 to fix up all edges that cross section boundaries, to make sure the
2050 instructions used can actually span the required distance. The
2051 fixes are described below.
2053 Fall-through edges must be changed into jumps; it is not safe or
2054 legal to fall through across a section boundary. Whenever a
2055 fall-through edge crossing a section boundary is encountered, a new
2056 basic block is inserted (in the same section as the fall-through
2057 source), and the fall through edge is redirected to the new basic
2058 block. The new basic block contains an unconditional jump to the
2059 original fall-through target. (If the unconditional jump is
2060 insufficient to cross section boundaries, that is dealt with a
2061 little later, see below).
2063 In order to deal with architectures that have short conditional
2064 branches (which cannot span all of memory) we take any conditional
2065 jump that attempts to cross a section boundary and add a level of
2066 indirection: it becomes a conditional jump to a new basic block, in
2067 the same section. The new basic block contains an unconditional
2068 jump to the original target, in the other section.
2070 For those architectures whose unconditional branch is also
2071 incapable of reaching all of memory, those unconditional jumps are
2072 converted into indirect jumps, through a register.
2074 IMPORTANT NOTE: This optimization causes some messy interactions
2075 with the cfg cleanup optimizations; those optimizations want to
2076 merge blocks wherever possible, and to collapse indirect jump
2077 sequences (change "A jumps to B jumps to C" directly into "A jumps
2078 to C"). Those optimizations can undo the jump fixes that
2079 partitioning is required to make (see above), in order to ensure
2080 that jumps attempting to cross section boundaries are really able
2081 to cover whatever distance the jump requires (on many architectures
2082 conditional or unconditional jumps are not able to reach all of
2083 memory). Therefore tests have to be inserted into each such
2084 optimization to make sure that it does not undo stuff necessary to
2085 cross partition boundaries. This would be much less of a problem
2086 if we could perform this optimization later in the compilation, but
2087 unfortunately the fact that we may need to create indirect jumps
2088 (through registers) requires that this optimization be performed
2089 before register allocation.
2091 Hot and cold basic blocks are partitioned and put in separate
2092 sections of the .o file, to reduce paging and improve cache
2093 performance (hopefully). This can result in bits of code from the
2094 same function being widely separated in the .o file. However this
2095 is not obvious to the current bb structure. Therefore we must take
2096 care to ensure that: 1). There are no fall_thru edges that cross
2097 between sections; 2). For those architectures which have "short"
2098 conditional branches, all conditional branches that attempt to
2099 cross between sections are converted to unconditional branches;
2100 and, 3). For those architectures which have "short" unconditional
2101 branches, all unconditional branches that attempt to cross between
2102 sections are converted to indirect jumps.
2104 The code for fixing up fall_thru edges that cross between hot and
2105 cold basic blocks does so by creating new basic blocks containing
2106 unconditional branches to the appropriate label in the "other"
2107 section. The new basic block is then put in the same (hot or cold)
2108 section as the original conditional branch, and the fall_thru edge
2109 is modified to fall into the new basic block instead. By adding
2110 this level of indirection we end up with only unconditional branches
2111 crossing between hot and cold sections.
2113 Conditional branches are dealt with by adding a level of indirection.
2114 A new basic block is added in the same (hot/cold) section as the
2115 conditional branch, and the conditional branch is retargeted to the
2116 new basic block. The new basic block contains an unconditional branch
2117 to the original target of the conditional branch (in the other section).
2119 Unconditional branches are dealt with by converting them into
2123 partition_hot_cold_basic_blocks (void)
2125 VEC(edge, heap) *crossing_edges;
2127 if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1)
2130 crossing_edges = find_rarely_executed_basic_blocks_and_crossing_edges ();
2131 if (crossing_edges == NULL)
2134 /* Make sure the source of any crossing edge ends in a jump and the
2135 destination of any crossing edge has a label. */
2136 add_labels_and_missing_jumps (crossing_edges);
2138 /* Convert all crossing fall_thru edges to non-crossing fall
2139 thrus to unconditional jumps (that jump to the original fall
2141 fix_up_fall_thru_edges ();
2143 /* If the architecture does not have conditional branches that can
2144 span all of memory, convert crossing conditional branches into
2145 crossing unconditional branches. */
2146 if (!HAS_LONG_COND_BRANCH)
2147 fix_crossing_conditional_branches ();
2149 /* If the architecture does not have unconditional branches that
2150 can span all of memory, convert crossing unconditional branches
2151 into indirect jumps. Since adding an indirect jump also adds
2152 a new register usage, update the register usage information as
2154 if (!HAS_LONG_UNCOND_BRANCH)
2155 fix_crossing_unconditional_branches ();
2157 add_reg_crossing_jump_notes ();
2159 VEC_free (edge, heap, crossing_edges);
2161 return TODO_verify_flow | TODO_verify_rtl_sharing;
2165 gate_handle_reorder_blocks (void)
2167 if (targetm.cannot_modify_jumps_p ())
2169 return (optimize > 0);
2173 /* Reorder basic blocks. */
2175 rest_of_handle_reorder_blocks (void)
2179 /* Last attempt to optimize CFG, as scheduling, peepholing and insn
2180 splitting possibly introduced more crossjumping opportunities. */
2181 cfg_layout_initialize (CLEANUP_EXPENSIVE);
2183 if ((flag_reorder_blocks || flag_reorder_blocks_and_partition)
2184 /* Don't reorder blocks when optimizing for size because extra jump insns may
2185 be created; also barrier may create extra padding.
2187 More correctly we should have a block reordering mode that tried to
2188 minimize the combined size of all the jumps. This would more or less
2189 automatically remove extra jumps, but would also try to use more short
2190 jumps instead of long jumps. */
2191 && optimize_function_for_speed_p (cfun))
2193 reorder_basic_blocks ();
2194 cleanup_cfg (CLEANUP_EXPENSIVE);
2198 if (bb->next_bb != EXIT_BLOCK_PTR)
2199 bb->aux = bb->next_bb;
2200 cfg_layout_finalize ();
2202 /* Add NOTE_INSN_SWITCH_TEXT_SECTIONS notes. */
2203 insert_section_boundary_note ();
2207 struct rtl_opt_pass pass_reorder_blocks =
2212 gate_handle_reorder_blocks, /* gate */
2213 rest_of_handle_reorder_blocks, /* execute */
2216 0, /* static_pass_number */
2217 TV_REORDER_BLOCKS, /* tv_id */
2218 0, /* properties_required */
2219 0, /* properties_provided */
2220 0, /* properties_destroyed */
2221 0, /* todo_flags_start */
2222 TODO_verify_rtl_sharing, /* todo_flags_finish */
2227 gate_handle_partition_blocks (void)
2229 /* The optimization to partition hot/cold basic blocks into separate
2230 sections of the .o file does not work well with linkonce or with
2231 user defined section attributes. Don't call it if either case
2233 return (flag_reorder_blocks_and_partition
2234 && !DECL_ONE_ONLY (current_function_decl)
2235 && !user_defined_section_attribute);
2238 struct rtl_opt_pass pass_partition_blocks =
2242 "bbpart", /* name */
2243 gate_handle_partition_blocks, /* gate */
2244 partition_hot_cold_basic_blocks, /* execute */
2247 0, /* static_pass_number */
2248 TV_REORDER_BLOCKS, /* tv_id */
2249 PROP_cfglayout, /* properties_required */
2250 0, /* properties_provided */
2251 0, /* properties_destroyed */
2252 0, /* todo_flags_start */
2253 0 /* todo_flags_finish */