1 /* Basic block reordering routines for the GNU compiler. 2 Copyright (C) 2000-2018 Free Software Foundation, Inc. 3 4 This file is part of GCC. 5 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. 10 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. 15 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/>. */ 19 20 /* This file contains the "reorder blocks" pass, which changes the control 21 flow of a function to encounter fewer branches; the "partition blocks" 22 pass, which divides the basic blocks into "hot" and "cold" partitions, 23 which are kept separate; and the "duplicate computed gotos" pass, which 24 duplicates blocks ending in an indirect jump. 25 26 There are two algorithms for "reorder blocks": the "simple" algorithm, 27 which just rearranges blocks, trying to minimize the number of executed 28 unconditional branches; and the "software trace cache" algorithm, which 29 also copies code, and in general tries a lot harder to have long linear 30 pieces of machine code executed. This algorithm is described next. */ 31 32 /* This (greedy) algorithm constructs traces in several rounds. 33 The construction starts from "seeds". The seed for the first round 34 is the entry point of the function. When there are more than one seed, 35 the one with the lowest key in the heap is selected first (see bb_to_key). 36 Then the algorithm repeatedly adds the most probable successor to the end 37 of a trace. Finally it connects the traces. 38 39 There are two parameters: Branch Threshold and Exec Threshold. 40 If the probability of an edge to a successor of the current basic block is 41 lower than Branch Threshold or its count is lower than Exec Threshold, 42 then the successor will be the seed in one of the next rounds. 43 Each round has these parameters lower than the previous one. 44 The last round has to have these parameters set to zero so that the 45 remaining blocks are picked up. 46 47 The algorithm selects the most probable successor from all unvisited 48 successors and successors that have been added to this trace. 49 The other successors (that has not been "sent" to the next round) will be 50 other seeds for this round and the secondary traces will start from them. 51 If the successor has not been visited in this trace, it is added to the 52 trace (however, there is some heuristic for simple branches). 53 If the successor has been visited in this trace, a loop has been found. 54 If the loop has many iterations, the loop is rotated so that the source 55 block of the most probable edge going out of the loop is the last block 56 of the trace. 57 If the loop has few iterations and there is no edge from the last block of 58 the loop going out of the loop, the loop header is duplicated. 59 60 When connecting traces, the algorithm first checks whether there is an edge 61 from the last block of a trace to the first block of another trace. 62 When there are still some unconnected traces it checks whether there exists 63 a basic block BB such that BB is a successor of the last block of a trace 64 and BB is a predecessor of the first block of another trace. In this case, 65 BB is duplicated, added at the end of the first trace and the traces are 66 connected through it. 67 The rest of traces are simply connected so there will be a jump to the 68 beginning of the rest of traces. 69 70 The above description is for the full algorithm, which is used when the 71 function is optimized for speed. When the function is optimized for size, 72 in order to reduce long jumps and connect more fallthru edges, the 73 algorithm is modified as follows: 74 (1) Break long traces to short ones. A trace is broken at a block that has 75 multiple predecessors/ successors during trace discovery. When connecting 76 traces, only connect Trace n with Trace n + 1. This change reduces most 77 long jumps compared with the above algorithm. 78 (2) Ignore the edge probability and count for fallthru edges. 79 (3) Keep the original order of blocks when there is no chance to fall 80 through. We rely on the results of cfg_cleanup. 81 82 To implement the change for code size optimization, block's index is 83 selected as the key and all traces are found in one round. 84 85 References: 86 87 "Software Trace Cache" 88 A. Ramirez, J. Larriba-Pey, C. Navarro, J. Torrellas and M. Valero; 1999 89 http://citeseer.nj.nec.com/15361.html 90 91 */ 92 93 #include "config.h" 94 #define INCLUDE_ALGORITHM /* stable_sort */ 95 #include "system.h" 96 #include "coretypes.h" 97 #include "backend.h" 98 #include "target.h" 99 #include "rtl.h" 100 #include "tree.h" 101 #include "cfghooks.h" 102 #include "df.h" 103 #include "memmodel.h" 104 #include "optabs.h" 105 #include "regs.h" 106 #include "emit-rtl.h" 107 #include "output.h" 108 #include "expr.h" 109 #include "params.h" 110 #include "tree-pass.h" 111 #include "cfgrtl.h" 112 #include "cfganal.h" 113 #include "cfgbuild.h" 114 #include "cfgcleanup.h" 115 #include "bb-reorder.h" 116 #include "except.h" 117 #include "fibonacci_heap.h" 118 #include "stringpool.h" 119 #include "attribs.h" 120 #include "common/common-target.h" 121 122 /* The number of rounds. In most cases there will only be 4 rounds, but 123 when partitioning hot and cold basic blocks into separate sections of 124 the object file there will be an extra round. */ 125 #define N_ROUNDS 5 126 127 struct target_bb_reorder default_target_bb_reorder; 128 #if SWITCHABLE_TARGET 129 struct target_bb_reorder *this_target_bb_reorder = &default_target_bb_reorder; 130 #endif 131 132 #define uncond_jump_length \ 133 (this_target_bb_reorder->x_uncond_jump_length) 134 135 /* Branch thresholds in thousandths (per mille) of the REG_BR_PROB_BASE. */ 136 static const int branch_threshold[N_ROUNDS] = {400, 200, 100, 0, 0}; 137 138 /* Exec thresholds in thousandths (per mille) of the count of bb 0. */ 139 static const int exec_threshold[N_ROUNDS] = {500, 200, 50, 0, 0}; 140 141 /* If edge count is lower than DUPLICATION_THRESHOLD per mille of entry 142 block the edge destination is not duplicated while connecting traces. */ 143 #define DUPLICATION_THRESHOLD 100 144 145 typedef fibonacci_heap <long, basic_block_def> bb_heap_t; 146 typedef fibonacci_node <long, basic_block_def> bb_heap_node_t; 147 148 /* Structure to hold needed information for each basic block. */ 149 struct bbro_basic_block_data 150 { 151 /* Which trace is the bb start of (-1 means it is not a start of any). */ 152 int start_of_trace; 153 154 /* Which trace is the bb end of (-1 means it is not an end of any). */ 155 int end_of_trace; 156 157 /* Which trace is the bb in? */ 158 int in_trace; 159 160 /* Which trace was this bb visited in? */ 161 int visited; 162 163 /* Cached maximum frequency of interesting incoming edges. 164 Minus one means not yet computed. */ 165 int priority; 166 167 /* Which heap is BB in (if any)? */ 168 bb_heap_t *heap; 169 170 /* Which heap node is BB in (if any)? */ 171 bb_heap_node_t *node; 172 }; 173 174 /* The current size of the following dynamic array. */ 175 static int array_size; 176 177 /* The array which holds needed information for basic blocks. */ 178 static bbro_basic_block_data *bbd; 179 180 /* To avoid frequent reallocation the size of arrays is greater than needed, 181 the number of elements is (not less than) 1.25 * size_wanted. */ 182 #define GET_ARRAY_SIZE(X) ((((X) / 4) + 1) * 5) 183 184 /* Free the memory and set the pointer to NULL. */ 185 #define FREE(P) (gcc_assert (P), free (P), P = 0) 186 187 /* Structure for holding information about a trace. */ 188 struct trace 189 { 190 /* First and last basic block of the trace. */ 191 basic_block first, last; 192 193 /* The round of the STC creation which this trace was found in. */ 194 int round; 195 196 /* The length (i.e. the number of basic blocks) of the trace. */ 197 int length; 198 }; 199 200 /* Maximum count of one of the entry blocks. */ 201 static profile_count max_entry_count; 202 203 /* Local function prototypes. */ 204 static void find_traces_1_round (int, profile_count, struct trace *, int *, 205 int, bb_heap_t **, int); 206 static basic_block copy_bb (basic_block, edge, basic_block, int); 207 static long bb_to_key (basic_block); 208 static bool better_edge_p (const_basic_block, const_edge, profile_probability, 209 profile_count, profile_probability, profile_count, 210 const_edge); 211 static bool copy_bb_p (const_basic_block, int); 212 213 /* Return the trace number in which BB was visited. */ 214 215 static int 216 bb_visited_trace (const_basic_block bb) 217 { 218 gcc_assert (bb->index < array_size); 219 return bbd[bb->index].visited; 220 } 221 222 /* This function marks BB that it was visited in trace number TRACE. */ 223 224 static void 225 mark_bb_visited (basic_block bb, int trace) 226 { 227 bbd[bb->index].visited = trace; 228 if (bbd[bb->index].heap) 229 { 230 bbd[bb->index].heap->delete_node (bbd[bb->index].node); 231 bbd[bb->index].heap = NULL; 232 bbd[bb->index].node = NULL; 233 } 234 } 235 236 /* Check to see if bb should be pushed into the next round of trace 237 collections or not. Reasons for pushing the block forward are 1). 238 If the block is cold, we are doing partitioning, and there will be 239 another round (cold partition blocks are not supposed to be 240 collected into traces until the very last round); or 2). There will 241 be another round, and the basic block is not "hot enough" for the 242 current round of trace collection. */ 243 244 static bool 245 push_to_next_round_p (const_basic_block bb, int round, int number_of_rounds, 246 profile_count count_th) 247 { 248 bool there_exists_another_round; 249 bool block_not_hot_enough; 250 251 there_exists_another_round = round < number_of_rounds - 1; 252 253 block_not_hot_enough = (bb->count < count_th 254 || probably_never_executed_bb_p (cfun, bb)); 255 256 if (there_exists_another_round 257 && block_not_hot_enough) 258 return true; 259 else 260 return false; 261 } 262 263 /* Find the traces for Software Trace Cache. Chain each trace through 264 RBI()->next. Store the number of traces to N_TRACES and description of 265 traces to TRACES. */ 266 267 static void 268 find_traces (int *n_traces, struct trace *traces) 269 { 270 int i; 271 int number_of_rounds; 272 edge e; 273 edge_iterator ei; 274 bb_heap_t *heap = new bb_heap_t (LONG_MIN); 275 276 /* Add one extra round of trace collection when partitioning hot/cold 277 basic blocks into separate sections. The last round is for all the 278 cold blocks (and ONLY the cold blocks). */ 279 280 number_of_rounds = N_ROUNDS - 1; 281 282 /* Insert entry points of function into heap. */ 283 max_entry_count = profile_count::zero (); 284 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs) 285 { 286 bbd[e->dest->index].heap = heap; 287 bbd[e->dest->index].node = heap->insert (bb_to_key (e->dest), e->dest); 288 if (e->dest->count > max_entry_count) 289 max_entry_count = e->dest->count; 290 } 291 292 /* Find the traces. */ 293 for (i = 0; i < number_of_rounds; i++) 294 { 295 profile_count count_threshold; 296 297 if (dump_file) 298 fprintf (dump_file, "STC - round %d\n", i + 1); 299 300 count_threshold = max_entry_count.apply_scale (exec_threshold[i], 1000); 301 302 find_traces_1_round (REG_BR_PROB_BASE * branch_threshold[i] / 1000, 303 count_threshold, traces, n_traces, i, &heap, 304 number_of_rounds); 305 } 306 delete heap; 307 308 if (dump_file) 309 { 310 for (i = 0; i < *n_traces; i++) 311 { 312 basic_block bb; 313 fprintf (dump_file, "Trace %d (round %d): ", i + 1, 314 traces[i].round + 1); 315 for (bb = traces[i].first; 316 bb != traces[i].last; 317 bb = (basic_block) bb->aux) 318 { 319 fprintf (dump_file, "%d [", bb->index); 320 bb->count.dump (dump_file); 321 fprintf (dump_file, "] "); 322 } 323 fprintf (dump_file, "%d [", bb->index); 324 bb->count.dump (dump_file); 325 fprintf (dump_file, "]\n"); 326 } 327 fflush (dump_file); 328 } 329 } 330 331 /* Rotate loop whose back edge is BACK_EDGE in the tail of trace TRACE 332 (with sequential number TRACE_N). */ 333 334 static basic_block 335 rotate_loop (edge back_edge, struct trace *trace, int trace_n) 336 { 337 basic_block bb; 338 339 /* Information about the best end (end after rotation) of the loop. */ 340 basic_block best_bb = NULL; 341 edge best_edge = NULL; 342 profile_count best_count = profile_count::uninitialized (); 343 /* The best edge is preferred when its destination is not visited yet 344 or is a start block of some trace. */ 345 bool is_preferred = false; 346 347 /* Find the most frequent edge that goes out from current trace. */ 348 bb = back_edge->dest; 349 do 350 { 351 edge e; 352 edge_iterator ei; 353 354 FOR_EACH_EDGE (e, ei, bb->succs) 355 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) 356 && bb_visited_trace (e->dest) != trace_n 357 && (e->flags & EDGE_CAN_FALLTHRU) 358 && !(e->flags & EDGE_COMPLEX)) 359 { 360 if (is_preferred) 361 { 362 /* The best edge is preferred. */ 363 if (!bb_visited_trace (e->dest) 364 || bbd[e->dest->index].start_of_trace >= 0) 365 { 366 /* The current edge E is also preferred. */ 367 if (e->count () > best_count) 368 { 369 best_count = e->count (); 370 best_edge = e; 371 best_bb = bb; 372 } 373 } 374 } 375 else 376 { 377 if (!bb_visited_trace (e->dest) 378 || bbd[e->dest->index].start_of_trace >= 0) 379 { 380 /* The current edge E is preferred. */ 381 is_preferred = true; 382 best_count = e->count (); 383 best_edge = e; 384 best_bb = bb; 385 } 386 else 387 { 388 if (!best_edge || e->count () > best_count) 389 { 390 best_count = e->count (); 391 best_edge = e; 392 best_bb = bb; 393 } 394 } 395 } 396 } 397 bb = (basic_block) bb->aux; 398 } 399 while (bb != back_edge->dest); 400 401 if (best_bb) 402 { 403 /* Rotate the loop so that the BEST_EDGE goes out from the last block of 404 the trace. */ 405 if (back_edge->dest == trace->first) 406 { 407 trace->first = (basic_block) best_bb->aux; 408 } 409 else 410 { 411 basic_block prev_bb; 412 413 for (prev_bb = trace->first; 414 prev_bb->aux != back_edge->dest; 415 prev_bb = (basic_block) prev_bb->aux) 416 ; 417 prev_bb->aux = best_bb->aux; 418 419 /* Try to get rid of uncond jump to cond jump. */ 420 if (single_succ_p (prev_bb)) 421 { 422 basic_block header = single_succ (prev_bb); 423 424 /* Duplicate HEADER if it is a small block containing cond jump 425 in the end. */ 426 if (any_condjump_p (BB_END (header)) && copy_bb_p (header, 0) 427 && !CROSSING_JUMP_P (BB_END (header))) 428 copy_bb (header, single_succ_edge (prev_bb), prev_bb, trace_n); 429 } 430 } 431 } 432 else 433 { 434 /* We have not found suitable loop tail so do no rotation. */ 435 best_bb = back_edge->src; 436 } 437 best_bb->aux = NULL; 438 return best_bb; 439 } 440 441 /* One round of finding traces. Find traces for BRANCH_TH and EXEC_TH i.e. do 442 not include basic blocks whose probability is lower than BRANCH_TH or whose 443 count is lower than EXEC_TH into traces (or whose count is lower than 444 COUNT_TH). Store the new traces into TRACES and modify the number of 445 traces *N_TRACES. Set the round (which the trace belongs to) to ROUND. 446 The function expects starting basic blocks to be in *HEAP and will delete 447 *HEAP and store starting points for the next round into new *HEAP. */ 448 449 static void 450 find_traces_1_round (int branch_th, profile_count count_th, 451 struct trace *traces, int *n_traces, int round, 452 bb_heap_t **heap, int number_of_rounds) 453 { 454 /* Heap for discarded basic blocks which are possible starting points for 455 the next round. */ 456 bb_heap_t *new_heap = new bb_heap_t (LONG_MIN); 457 bool for_size = optimize_function_for_size_p (cfun); 458 459 while (!(*heap)->empty ()) 460 { 461 basic_block bb; 462 struct trace *trace; 463 edge best_edge, e; 464 long key; 465 edge_iterator ei; 466 467 bb = (*heap)->extract_min (); 468 bbd[bb->index].heap = NULL; 469 bbd[bb->index].node = NULL; 470 471 if (dump_file) 472 fprintf (dump_file, "Getting bb %d\n", bb->index); 473 474 /* If the BB's count is too low, send BB to the next round. When 475 partitioning hot/cold blocks into separate sections, make sure all 476 the cold blocks (and ONLY the cold blocks) go into the (extra) final 477 round. When optimizing for size, do not push to next round. */ 478 479 if (!for_size 480 && push_to_next_round_p (bb, round, number_of_rounds, 481 count_th)) 482 { 483 int key = bb_to_key (bb); 484 bbd[bb->index].heap = new_heap; 485 bbd[bb->index].node = new_heap->insert (key, bb); 486 487 if (dump_file) 488 fprintf (dump_file, 489 " Possible start point of next round: %d (key: %d)\n", 490 bb->index, key); 491 continue; 492 } 493 494 trace = traces + *n_traces; 495 trace->first = bb; 496 trace->round = round; 497 trace->length = 0; 498 bbd[bb->index].in_trace = *n_traces; 499 (*n_traces)++; 500 501 do 502 { 503 bool ends_in_call; 504 505 /* The probability and count of the best edge. */ 506 profile_probability best_prob = profile_probability::uninitialized (); 507 profile_count best_count = profile_count::uninitialized (); 508 509 best_edge = NULL; 510 mark_bb_visited (bb, *n_traces); 511 trace->length++; 512 513 if (dump_file) 514 fprintf (dump_file, "Basic block %d was visited in trace %d\n", 515 bb->index, *n_traces); 516 517 ends_in_call = block_ends_with_call_p (bb); 518 519 /* Select the successor that will be placed after BB. */ 520 FOR_EACH_EDGE (e, ei, bb->succs) 521 { 522 gcc_assert (!(e->flags & EDGE_FAKE)); 523 524 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun)) 525 continue; 526 527 if (bb_visited_trace (e->dest) 528 && bb_visited_trace (e->dest) != *n_traces) 529 continue; 530 531 /* If partitioning hot/cold basic blocks, don't consider edges 532 that cross section boundaries. */ 533 if (BB_PARTITION (e->dest) != BB_PARTITION (bb)) 534 continue; 535 536 profile_probability prob = e->probability; 537 profile_count count = e->dest->count; 538 539 /* The only sensible preference for a call instruction is the 540 fallthru edge. Don't bother selecting anything else. */ 541 if (ends_in_call) 542 { 543 if (e->flags & EDGE_CAN_FALLTHRU) 544 { 545 best_edge = e; 546 best_prob = prob; 547 best_count = count; 548 } 549 continue; 550 } 551 552 /* Edge that cannot be fallthru or improbable or infrequent 553 successor (i.e. it is unsuitable successor). When optimizing 554 for size, ignore the probability and count. */ 555 if (!(e->flags & EDGE_CAN_FALLTHRU) || (e->flags & EDGE_COMPLEX) 556 || !prob.initialized_p () 557 || ((prob.to_reg_br_prob_base () < branch_th 558 || e->count () < count_th) && (!for_size))) 559 continue; 560 561 if (better_edge_p (bb, e, prob, count, best_prob, best_count, 562 best_edge)) 563 { 564 best_edge = e; 565 best_prob = prob; 566 best_count = count; 567 } 568 } 569 570 /* If the best destination has multiple predecessors and can be 571 duplicated cheaper than a jump, don't allow it to be added to 572 a trace; we'll duplicate it when connecting the traces later. 573 However, we need to check that this duplication wouldn't leave 574 the best destination with only crossing predecessors, because 575 this would change its effective partition from hot to cold. */ 576 if (best_edge 577 && EDGE_COUNT (best_edge->dest->preds) >= 2 578 && copy_bb_p (best_edge->dest, 0)) 579 { 580 bool only_crossing_preds = true; 581 edge e; 582 edge_iterator ei; 583 FOR_EACH_EDGE (e, ei, best_edge->dest->preds) 584 if (e != best_edge && !(e->flags & EDGE_CROSSING)) 585 { 586 only_crossing_preds = false; 587 break; 588 } 589 if (!only_crossing_preds) 590 best_edge = NULL; 591 } 592 593 /* If the best destination has multiple successors or predecessors, 594 don't allow it to be added when optimizing for size. This makes 595 sure predecessors with smaller index are handled before the best 596 destinarion. It breaks long trace and reduces long jumps. 597 598 Take if-then-else as an example. 599 A 600 / \ 601 B C 602 \ / 603 D 604 If we do not remove the best edge B->D/C->D, the final order might 605 be A B D ... C. C is at the end of the program. If D's successors 606 and D are complicated, might need long jumps for A->C and C->D. 607 Similar issue for order: A C D ... B. 608 609 After removing the best edge, the final result will be ABCD/ ACBD. 610 It does not add jump compared with the previous order. But it 611 reduces the possibility of long jumps. */ 612 if (best_edge && for_size 613 && (EDGE_COUNT (best_edge->dest->succs) > 1 614 || EDGE_COUNT (best_edge->dest->preds) > 1)) 615 best_edge = NULL; 616 617 /* Add all non-selected successors to the heaps. */ 618 FOR_EACH_EDGE (e, ei, bb->succs) 619 { 620 if (e == best_edge 621 || e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun) 622 || bb_visited_trace (e->dest)) 623 continue; 624 625 key = bb_to_key (e->dest); 626 627 if (bbd[e->dest->index].heap) 628 { 629 /* E->DEST is already in some heap. */ 630 if (key != bbd[e->dest->index].node->get_key ()) 631 { 632 if (dump_file) 633 { 634 fprintf (dump_file, 635 "Changing key for bb %d from %ld to %ld.\n", 636 e->dest->index, 637 (long) bbd[e->dest->index].node->get_key (), 638 key); 639 } 640 bbd[e->dest->index].heap->replace_key 641 (bbd[e->dest->index].node, key); 642 } 643 } 644 else 645 { 646 bb_heap_t *which_heap = *heap; 647 648 profile_probability prob = e->probability; 649 650 if (!(e->flags & EDGE_CAN_FALLTHRU) 651 || (e->flags & EDGE_COMPLEX) 652 || !prob.initialized_p () 653 || prob.to_reg_br_prob_base () < branch_th 654 || e->count () < count_th) 655 { 656 /* When partitioning hot/cold basic blocks, make sure 657 the cold blocks (and only the cold blocks) all get 658 pushed to the last round of trace collection. When 659 optimizing for size, do not push to next round. */ 660 661 if (!for_size && push_to_next_round_p (e->dest, round, 662 number_of_rounds, 663 count_th)) 664 which_heap = new_heap; 665 } 666 667 bbd[e->dest->index].heap = which_heap; 668 bbd[e->dest->index].node = which_heap->insert (key, e->dest); 669 670 if (dump_file) 671 { 672 fprintf (dump_file, 673 " Possible start of %s round: %d (key: %ld)\n", 674 (which_heap == new_heap) ? "next" : "this", 675 e->dest->index, (long) key); 676 } 677 678 } 679 } 680 681 if (best_edge) /* Suitable successor was found. */ 682 { 683 if (bb_visited_trace (best_edge->dest) == *n_traces) 684 { 685 /* We do nothing with one basic block loops. */ 686 if (best_edge->dest != bb) 687 { 688 if (best_edge->count () 689 > best_edge->dest->count.apply_scale (4, 5)) 690 { 691 /* The loop has at least 4 iterations. If the loop 692 header is not the first block of the function 693 we can rotate the loop. */ 694 695 if (best_edge->dest 696 != ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb) 697 { 698 if (dump_file) 699 { 700 fprintf (dump_file, 701 "Rotating loop %d - %d\n", 702 best_edge->dest->index, bb->index); 703 } 704 bb->aux = best_edge->dest; 705 bbd[best_edge->dest->index].in_trace = 706 (*n_traces) - 1; 707 bb = rotate_loop (best_edge, trace, *n_traces); 708 } 709 } 710 else 711 { 712 /* The loop has less than 4 iterations. */ 713 714 if (single_succ_p (bb) 715 && copy_bb_p (best_edge->dest, 716 optimize_edge_for_speed_p 717 (best_edge))) 718 { 719 bb = copy_bb (best_edge->dest, best_edge, bb, 720 *n_traces); 721 trace->length++; 722 } 723 } 724 } 725 726 /* Terminate the trace. */ 727 break; 728 } 729 else 730 { 731 /* Check for a situation 732 733 A 734 /| 735 B | 736 \| 737 C 738 739 where 740 AB->count () + BC->count () >= AC->count (). 741 (i.e. 2 * B->count >= AC->count ) 742 Best ordering is then A B C. 743 744 When optimizing for size, A B C is always the best order. 745 746 This situation is created for example by: 747 748 if (A) B; 749 C; 750 751 */ 752 753 FOR_EACH_EDGE (e, ei, bb->succs) 754 if (e != best_edge 755 && (e->flags & EDGE_CAN_FALLTHRU) 756 && !(e->flags & EDGE_COMPLEX) 757 && !bb_visited_trace (e->dest) 758 && single_pred_p (e->dest) 759 && !(e->flags & EDGE_CROSSING) 760 && single_succ_p (e->dest) 761 && (single_succ_edge (e->dest)->flags 762 & EDGE_CAN_FALLTHRU) 763 && !(single_succ_edge (e->dest)->flags & EDGE_COMPLEX) 764 && single_succ (e->dest) == best_edge->dest 765 && (e->dest->count.apply_scale (2, 1) 766 >= best_edge->count () || for_size)) 767 { 768 best_edge = e; 769 if (dump_file) 770 fprintf (dump_file, "Selecting BB %d\n", 771 best_edge->dest->index); 772 break; 773 } 774 775 bb->aux = best_edge->dest; 776 bbd[best_edge->dest->index].in_trace = (*n_traces) - 1; 777 bb = best_edge->dest; 778 } 779 } 780 } 781 while (best_edge); 782 trace->last = bb; 783 bbd[trace->first->index].start_of_trace = *n_traces - 1; 784 if (bbd[trace->last->index].end_of_trace != *n_traces - 1) 785 { 786 bbd[trace->last->index].end_of_trace = *n_traces - 1; 787 /* Update the cached maximum frequency for interesting predecessor 788 edges for successors of the new trace end. */ 789 FOR_EACH_EDGE (e, ei, trace->last->succs) 790 if (EDGE_FREQUENCY (e) > bbd[e->dest->index].priority) 791 bbd[e->dest->index].priority = EDGE_FREQUENCY (e); 792 } 793 794 /* The trace is terminated so we have to recount the keys in heap 795 (some block can have a lower key because now one of its predecessors 796 is an end of the trace). */ 797 FOR_EACH_EDGE (e, ei, bb->succs) 798 { 799 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun) 800 || bb_visited_trace (e->dest)) 801 continue; 802 803 if (bbd[e->dest->index].heap) 804 { 805 key = bb_to_key (e->dest); 806 if (key != bbd[e->dest->index].node->get_key ()) 807 { 808 if (dump_file) 809 { 810 fprintf (dump_file, 811 "Changing key for bb %d from %ld to %ld.\n", 812 e->dest->index, 813 (long) bbd[e->dest->index].node->get_key (), key); 814 } 815 bbd[e->dest->index].heap->replace_key 816 (bbd[e->dest->index].node, key); 817 } 818 } 819 } 820 } 821 822 delete (*heap); 823 824 /* "Return" the new heap. */ 825 *heap = new_heap; 826 } 827 828 /* Create a duplicate of the basic block OLD_BB and redirect edge E to it, add 829 it to trace after BB, mark OLD_BB visited and update pass' data structures 830 (TRACE is a number of trace which OLD_BB is duplicated to). */ 831 832 static basic_block 833 copy_bb (basic_block old_bb, edge e, basic_block bb, int trace) 834 { 835 basic_block new_bb; 836 837 new_bb = duplicate_block (old_bb, e, bb); 838 BB_COPY_PARTITION (new_bb, old_bb); 839 840 gcc_assert (e->dest == new_bb); 841 842 if (dump_file) 843 fprintf (dump_file, 844 "Duplicated bb %d (created bb %d)\n", 845 old_bb->index, new_bb->index); 846 847 if (new_bb->index >= array_size 848 || last_basic_block_for_fn (cfun) > array_size) 849 { 850 int i; 851 int new_size; 852 853 new_size = MAX (last_basic_block_for_fn (cfun), new_bb->index + 1); 854 new_size = GET_ARRAY_SIZE (new_size); 855 bbd = XRESIZEVEC (bbro_basic_block_data, bbd, new_size); 856 for (i = array_size; i < new_size; i++) 857 { 858 bbd[i].start_of_trace = -1; 859 bbd[i].end_of_trace = -1; 860 bbd[i].in_trace = -1; 861 bbd[i].visited = 0; 862 bbd[i].priority = -1; 863 bbd[i].heap = NULL; 864 bbd[i].node = NULL; 865 } 866 array_size = new_size; 867 868 if (dump_file) 869 { 870 fprintf (dump_file, 871 "Growing the dynamic array to %d elements.\n", 872 array_size); 873 } 874 } 875 876 gcc_assert (!bb_visited_trace (e->dest)); 877 mark_bb_visited (new_bb, trace); 878 new_bb->aux = bb->aux; 879 bb->aux = new_bb; 880 881 bbd[new_bb->index].in_trace = trace; 882 883 return new_bb; 884 } 885 886 /* Compute and return the key (for the heap) of the basic block BB. */ 887 888 static long 889 bb_to_key (basic_block bb) 890 { 891 edge e; 892 edge_iterator ei; 893 894 /* Use index as key to align with its original order. */ 895 if (optimize_function_for_size_p (cfun)) 896 return bb->index; 897 898 /* Do not start in probably never executed blocks. */ 899 900 if (BB_PARTITION (bb) == BB_COLD_PARTITION 901 || probably_never_executed_bb_p (cfun, bb)) 902 return BB_FREQ_MAX; 903 904 /* Prefer blocks whose predecessor is an end of some trace 905 or whose predecessor edge is EDGE_DFS_BACK. */ 906 int priority = bbd[bb->index].priority; 907 if (priority == -1) 908 { 909 priority = 0; 910 FOR_EACH_EDGE (e, ei, bb->preds) 911 { 912 if ((e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun) 913 && bbd[e->src->index].end_of_trace >= 0) 914 || (e->flags & EDGE_DFS_BACK)) 915 { 916 int edge_freq = EDGE_FREQUENCY (e); 917 918 if (edge_freq > priority) 919 priority = edge_freq; 920 } 921 } 922 bbd[bb->index].priority = priority; 923 } 924 925 if (priority) 926 /* The block with priority should have significantly lower key. */ 927 return -(100 * BB_FREQ_MAX + 100 * priority + bb->count.to_frequency (cfun)); 928 929 return -bb->count.to_frequency (cfun); 930 } 931 932 /* Return true when the edge E from basic block BB is better than the temporary 933 best edge (details are in function). The probability of edge E is PROB. The 934 count of the successor is COUNT. The current best probability is 935 BEST_PROB, the best count is BEST_COUNT. 936 The edge is considered to be equivalent when PROB does not differ much from 937 BEST_PROB; similarly for count. */ 938 939 static bool 940 better_edge_p (const_basic_block bb, const_edge e, profile_probability prob, 941 profile_count count, profile_probability best_prob, 942 profile_count best_count, const_edge cur_best_edge) 943 { 944 bool is_better_edge; 945 946 /* The BEST_* values do not have to be best, but can be a bit smaller than 947 maximum values. */ 948 profile_probability diff_prob = best_prob.apply_scale (1, 10); 949 950 /* The smaller one is better to keep the original order. */ 951 if (optimize_function_for_size_p (cfun)) 952 return !cur_best_edge 953 || cur_best_edge->dest->index > e->dest->index; 954 955 /* Those edges are so expensive that continuing a trace is not useful 956 performance wise. */ 957 if (e->flags & (EDGE_ABNORMAL | EDGE_EH)) 958 return false; 959 960 if (prob > best_prob + diff_prob 961 || (!best_prob.initialized_p () 962 && prob > profile_probability::guessed_never ())) 963 /* The edge has higher probability than the temporary best edge. */ 964 is_better_edge = true; 965 else if (prob < best_prob - diff_prob) 966 /* The edge has lower probability than the temporary best edge. */ 967 is_better_edge = false; 968 else 969 { 970 profile_count diff_count = best_count.apply_scale (1, 10); 971 if (count < best_count - diff_count 972 || (!best_count.initialized_p () 973 && count.nonzero_p ())) 974 /* The edge and the temporary best edge have almost equivalent 975 probabilities. The higher countuency of a successor now means 976 that there is another edge going into that successor. 977 This successor has lower countuency so it is better. */ 978 is_better_edge = true; 979 else if (count > best_count + diff_count) 980 /* This successor has higher countuency so it is worse. */ 981 is_better_edge = false; 982 else if (e->dest->prev_bb == bb) 983 /* The edges have equivalent probabilities and the successors 984 have equivalent frequencies. Select the previous successor. */ 985 is_better_edge = true; 986 else 987 is_better_edge = false; 988 } 989 990 return is_better_edge; 991 } 992 993 /* Return true when the edge E is better than the temporary best edge 994 CUR_BEST_EDGE. If SRC_INDEX_P is true, the function compares the src bb of 995 E and CUR_BEST_EDGE; otherwise it will compare the dest bb. 996 BEST_LEN is the trace length of src (or dest) bb in CUR_BEST_EDGE. 997 TRACES record the information about traces. 998 When optimizing for size, the edge with smaller index is better. 999 When optimizing for speed, the edge with bigger probability or longer trace 1000 is better. */ 1001 1002 static bool 1003 connect_better_edge_p (const_edge e, bool src_index_p, int best_len, 1004 const_edge cur_best_edge, struct trace *traces) 1005 { 1006 int e_index; 1007 int b_index; 1008 bool is_better_edge; 1009 1010 if (!cur_best_edge) 1011 return true; 1012 1013 if (optimize_function_for_size_p (cfun)) 1014 { 1015 e_index = src_index_p ? e->src->index : e->dest->index; 1016 b_index = src_index_p ? cur_best_edge->src->index 1017 : cur_best_edge->dest->index; 1018 /* The smaller one is better to keep the original order. */ 1019 return b_index > e_index; 1020 } 1021 1022 if (src_index_p) 1023 { 1024 e_index = e->src->index; 1025 1026 /* We are looking for predecessor, so probabilities are not that 1027 informative. We do not want to connect A to B becuse A has 1028 only one sucessor (probablity is 100%) while there is edge 1029 A' to B where probability is 90% but which is much more frequent. */ 1030 if (e->count () > cur_best_edge->count ()) 1031 /* The edge has higher probability than the temporary best edge. */ 1032 is_better_edge = true; 1033 else if (e->count () < cur_best_edge->count ()) 1034 /* The edge has lower probability than the temporary best edge. */ 1035 is_better_edge = false; 1036 if (e->probability > cur_best_edge->probability) 1037 /* The edge has higher probability than the temporary best edge. */ 1038 is_better_edge = true; 1039 else if (e->probability < cur_best_edge->probability) 1040 /* The edge has lower probability than the temporary best edge. */ 1041 is_better_edge = false; 1042 else if (traces[bbd[e_index].end_of_trace].length > best_len) 1043 /* The edge and the temporary best edge have equivalent probabilities. 1044 The edge with longer trace is better. */ 1045 is_better_edge = true; 1046 else 1047 is_better_edge = false; 1048 } 1049 else 1050 { 1051 e_index = e->dest->index; 1052 1053 if (e->probability > cur_best_edge->probability) 1054 /* The edge has higher probability than the temporary best edge. */ 1055 is_better_edge = true; 1056 else if (e->probability < cur_best_edge->probability) 1057 /* The edge has lower probability than the temporary best edge. */ 1058 is_better_edge = false; 1059 else if (traces[bbd[e_index].start_of_trace].length > best_len) 1060 /* The edge and the temporary best edge have equivalent probabilities. 1061 The edge with longer trace is better. */ 1062 is_better_edge = true; 1063 else 1064 is_better_edge = false; 1065 } 1066 1067 return is_better_edge; 1068 } 1069 1070 /* Connect traces in array TRACES, N_TRACES is the count of traces. */ 1071 1072 static void 1073 connect_traces (int n_traces, struct trace *traces) 1074 { 1075 int i; 1076 bool *connected; 1077 bool two_passes; 1078 int last_trace; 1079 int current_pass; 1080 int current_partition; 1081 profile_count count_threshold; 1082 bool for_size = optimize_function_for_size_p (cfun); 1083 1084 count_threshold = max_entry_count.apply_scale (DUPLICATION_THRESHOLD, 1000); 1085 1086 connected = XCNEWVEC (bool, n_traces); 1087 last_trace = -1; 1088 current_pass = 1; 1089 current_partition = BB_PARTITION (traces[0].first); 1090 two_passes = false; 1091 1092 if (crtl->has_bb_partition) 1093 for (i = 0; i < n_traces && !two_passes; i++) 1094 if (BB_PARTITION (traces[0].first) 1095 != BB_PARTITION (traces[i].first)) 1096 two_passes = true; 1097 1098 for (i = 0; i < n_traces || (two_passes && current_pass == 1) ; i++) 1099 { 1100 int t = i; 1101 int t2; 1102 edge e, best; 1103 int best_len; 1104 1105 if (i >= n_traces) 1106 { 1107 gcc_assert (two_passes && current_pass == 1); 1108 i = 0; 1109 t = i; 1110 current_pass = 2; 1111 if (current_partition == BB_HOT_PARTITION) 1112 current_partition = BB_COLD_PARTITION; 1113 else 1114 current_partition = BB_HOT_PARTITION; 1115 } 1116 1117 if (connected[t]) 1118 continue; 1119 1120 if (two_passes 1121 && BB_PARTITION (traces[t].first) != current_partition) 1122 continue; 1123 1124 connected[t] = true; 1125 1126 /* Find the predecessor traces. */ 1127 for (t2 = t; t2 > 0;) 1128 { 1129 edge_iterator ei; 1130 best = NULL; 1131 best_len = 0; 1132 FOR_EACH_EDGE (e, ei, traces[t2].first->preds) 1133 { 1134 int si = e->src->index; 1135 1136 if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun) 1137 && (e->flags & EDGE_CAN_FALLTHRU) 1138 && !(e->flags & EDGE_COMPLEX) 1139 && bbd[si].end_of_trace >= 0 1140 && !connected[bbd[si].end_of_trace] 1141 && (BB_PARTITION (e->src) == current_partition) 1142 && connect_better_edge_p (e, true, best_len, best, traces)) 1143 { 1144 best = e; 1145 best_len = traces[bbd[si].end_of_trace].length; 1146 } 1147 } 1148 if (best) 1149 { 1150 best->src->aux = best->dest; 1151 t2 = bbd[best->src->index].end_of_trace; 1152 connected[t2] = true; 1153 1154 if (dump_file) 1155 { 1156 fprintf (dump_file, "Connection: %d %d\n", 1157 best->src->index, best->dest->index); 1158 } 1159 } 1160 else 1161 break; 1162 } 1163 1164 if (last_trace >= 0) 1165 traces[last_trace].last->aux = traces[t2].first; 1166 last_trace = t; 1167 1168 /* Find the successor traces. */ 1169 while (1) 1170 { 1171 /* Find the continuation of the chain. */ 1172 edge_iterator ei; 1173 best = NULL; 1174 best_len = 0; 1175 FOR_EACH_EDGE (e, ei, traces[t].last->succs) 1176 { 1177 int di = e->dest->index; 1178 1179 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) 1180 && (e->flags & EDGE_CAN_FALLTHRU) 1181 && !(e->flags & EDGE_COMPLEX) 1182 && bbd[di].start_of_trace >= 0 1183 && !connected[bbd[di].start_of_trace] 1184 && (BB_PARTITION (e->dest) == current_partition) 1185 && connect_better_edge_p (e, false, best_len, best, traces)) 1186 { 1187 best = e; 1188 best_len = traces[bbd[di].start_of_trace].length; 1189 } 1190 } 1191 1192 if (for_size) 1193 { 1194 if (!best) 1195 /* Stop finding the successor traces. */ 1196 break; 1197 1198 /* It is OK to connect block n with block n + 1 or a block 1199 before n. For others, only connect to the loop header. */ 1200 if (best->dest->index > (traces[t].last->index + 1)) 1201 { 1202 int count = EDGE_COUNT (best->dest->preds); 1203 1204 FOR_EACH_EDGE (e, ei, best->dest->preds) 1205 if (e->flags & EDGE_DFS_BACK) 1206 count--; 1207 1208 /* If dest has multiple predecessors, skip it. We expect 1209 that one predecessor with smaller index connects with it 1210 later. */ 1211 if (count != 1) 1212 break; 1213 } 1214 1215 /* Only connect Trace n with Trace n + 1. It is conservative 1216 to keep the order as close as possible to the original order. 1217 It also helps to reduce long jumps. */ 1218 if (last_trace != bbd[best->dest->index].start_of_trace - 1) 1219 break; 1220 1221 if (dump_file) 1222 fprintf (dump_file, "Connection: %d %d\n", 1223 best->src->index, best->dest->index); 1224 1225 t = bbd[best->dest->index].start_of_trace; 1226 traces[last_trace].last->aux = traces[t].first; 1227 connected[t] = true; 1228 last_trace = t; 1229 } 1230 else if (best) 1231 { 1232 if (dump_file) 1233 { 1234 fprintf (dump_file, "Connection: %d %d\n", 1235 best->src->index, best->dest->index); 1236 } 1237 t = bbd[best->dest->index].start_of_trace; 1238 traces[last_trace].last->aux = traces[t].first; 1239 connected[t] = true; 1240 last_trace = t; 1241 } 1242 else 1243 { 1244 /* Try to connect the traces by duplication of 1 block. */ 1245 edge e2; 1246 basic_block next_bb = NULL; 1247 bool try_copy = false; 1248 1249 FOR_EACH_EDGE (e, ei, traces[t].last->succs) 1250 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) 1251 && (e->flags & EDGE_CAN_FALLTHRU) 1252 && !(e->flags & EDGE_COMPLEX) 1253 && (!best || e->probability > best->probability)) 1254 { 1255 edge_iterator ei; 1256 edge best2 = NULL; 1257 int best2_len = 0; 1258 1259 /* If the destination is a start of a trace which is only 1260 one block long, then no need to search the successor 1261 blocks of the trace. Accept it. */ 1262 if (bbd[e->dest->index].start_of_trace >= 0 1263 && traces[bbd[e->dest->index].start_of_trace].length 1264 == 1) 1265 { 1266 best = e; 1267 try_copy = true; 1268 continue; 1269 } 1270 1271 FOR_EACH_EDGE (e2, ei, e->dest->succs) 1272 { 1273 int di = e2->dest->index; 1274 1275 if (e2->dest == EXIT_BLOCK_PTR_FOR_FN (cfun) 1276 || ((e2->flags & EDGE_CAN_FALLTHRU) 1277 && !(e2->flags & EDGE_COMPLEX) 1278 && bbd[di].start_of_trace >= 0 1279 && !connected[bbd[di].start_of_trace] 1280 && BB_PARTITION (e2->dest) == current_partition 1281 && e2->count () >= count_threshold 1282 && (!best2 1283 || e2->probability > best2->probability 1284 || (e2->probability == best2->probability 1285 && traces[bbd[di].start_of_trace].length 1286 > best2_len)))) 1287 { 1288 best = e; 1289 best2 = e2; 1290 if (e2->dest != EXIT_BLOCK_PTR_FOR_FN (cfun)) 1291 best2_len = traces[bbd[di].start_of_trace].length; 1292 else 1293 best2_len = INT_MAX; 1294 next_bb = e2->dest; 1295 try_copy = true; 1296 } 1297 } 1298 } 1299 1300 /* Copy tiny blocks always; copy larger blocks only when the 1301 edge is traversed frequently enough. */ 1302 if (try_copy 1303 && BB_PARTITION (best->src) == BB_PARTITION (best->dest) 1304 && copy_bb_p (best->dest, 1305 optimize_edge_for_speed_p (best) 1306 && (!best->count ().initialized_p () 1307 || best->count () >= count_threshold))) 1308 { 1309 basic_block new_bb; 1310 1311 if (dump_file) 1312 { 1313 fprintf (dump_file, "Connection: %d %d ", 1314 traces[t].last->index, best->dest->index); 1315 if (!next_bb) 1316 fputc ('\n', dump_file); 1317 else if (next_bb == EXIT_BLOCK_PTR_FOR_FN (cfun)) 1318 fprintf (dump_file, "exit\n"); 1319 else 1320 fprintf (dump_file, "%d\n", next_bb->index); 1321 } 1322 1323 new_bb = copy_bb (best->dest, best, traces[t].last, t); 1324 traces[t].last = new_bb; 1325 if (next_bb && next_bb != EXIT_BLOCK_PTR_FOR_FN (cfun)) 1326 { 1327 t = bbd[next_bb->index].start_of_trace; 1328 traces[last_trace].last->aux = traces[t].first; 1329 connected[t] = true; 1330 last_trace = t; 1331 } 1332 else 1333 break; /* Stop finding the successor traces. */ 1334 } 1335 else 1336 break; /* Stop finding the successor traces. */ 1337 } 1338 } 1339 } 1340 1341 if (dump_file) 1342 { 1343 basic_block bb; 1344 1345 fprintf (dump_file, "Final order:\n"); 1346 for (bb = traces[0].first; bb; bb = (basic_block) bb->aux) 1347 fprintf (dump_file, "%d ", bb->index); 1348 fprintf (dump_file, "\n"); 1349 fflush (dump_file); 1350 } 1351 1352 FREE (connected); 1353 } 1354 1355 /* Return true when BB can and should be copied. CODE_MAY_GROW is true 1356 when code size is allowed to grow by duplication. */ 1357 1358 static bool 1359 copy_bb_p (const_basic_block bb, int code_may_grow) 1360 { 1361 int size = 0; 1362 int max_size = uncond_jump_length; 1363 rtx_insn *insn; 1364 1365 if (EDGE_COUNT (bb->preds) < 2) 1366 return false; 1367 if (!can_duplicate_block_p (bb)) 1368 return false; 1369 1370 /* Avoid duplicating blocks which have many successors (PR/13430). */ 1371 if (EDGE_COUNT (bb->succs) > 8) 1372 return false; 1373 1374 if (code_may_grow && optimize_bb_for_speed_p (bb)) 1375 max_size *= PARAM_VALUE (PARAM_MAX_GROW_COPY_BB_INSNS); 1376 1377 FOR_BB_INSNS (bb, insn) 1378 { 1379 if (INSN_P (insn)) 1380 size += get_attr_min_length (insn); 1381 } 1382 1383 if (size <= max_size) 1384 return true; 1385 1386 if (dump_file) 1387 { 1388 fprintf (dump_file, 1389 "Block %d can't be copied because its size = %d.\n", 1390 bb->index, size); 1391 } 1392 1393 return false; 1394 } 1395 1396 /* Return the length of unconditional jump instruction. */ 1397 1398 int 1399 get_uncond_jump_length (void) 1400 { 1401 int length; 1402 1403 start_sequence (); 1404 rtx_code_label *label = emit_label (gen_label_rtx ()); 1405 rtx_insn *jump = emit_jump_insn (targetm.gen_jump (label)); 1406 length = get_attr_min_length (jump); 1407 end_sequence (); 1408 1409 return length; 1410 } 1411 1412 /* Create a forwarder block to OLD_BB starting with NEW_LABEL and in the 1413 other partition wrt OLD_BB. */ 1414 1415 static basic_block 1416 create_eh_forwarder_block (rtx_code_label *new_label, basic_block old_bb) 1417 { 1418 /* Split OLD_BB, so that EH pads have always only incoming EH edges, 1419 bb_has_eh_pred bbs are treated specially by DF infrastructure. */ 1420 old_bb = split_block_after_labels (old_bb)->dest; 1421 1422 /* Put the new label and a jump in the new basic block. */ 1423 rtx_insn *label = emit_label (new_label); 1424 rtx_code_label *old_label = block_label (old_bb); 1425 rtx_insn *jump = emit_jump_insn (targetm.gen_jump (old_label)); 1426 JUMP_LABEL (jump) = old_label; 1427 1428 /* Create the new basic block and put it in last position. */ 1429 basic_block last_bb = EXIT_BLOCK_PTR_FOR_FN (cfun)->prev_bb; 1430 basic_block new_bb = create_basic_block (label, jump, last_bb); 1431 new_bb->aux = last_bb->aux; 1432 new_bb->count = old_bb->count; 1433 last_bb->aux = new_bb; 1434 1435 emit_barrier_after_bb (new_bb); 1436 1437 make_single_succ_edge (new_bb, old_bb, 0); 1438 1439 /* Make sure the new basic block is in the other partition. */ 1440 unsigned new_partition = BB_PARTITION (old_bb); 1441 new_partition ^= BB_HOT_PARTITION | BB_COLD_PARTITION; 1442 BB_SET_PARTITION (new_bb, new_partition); 1443 1444 return new_bb; 1445 } 1446 1447 /* The common landing pad in block OLD_BB has edges from both partitions. 1448 Add a new landing pad that will just jump to the old one and split the 1449 edges so that no EH edge crosses partitions. */ 1450 1451 static void 1452 sjlj_fix_up_crossing_landing_pad (basic_block old_bb) 1453 { 1454 const unsigned lp_len = cfun->eh->lp_array->length (); 1455 edge_iterator ei; 1456 edge e; 1457 1458 /* Generate the new common landing-pad label. */ 1459 rtx_code_label *new_label = gen_label_rtx (); 1460 LABEL_PRESERVE_P (new_label) = 1; 1461 1462 /* Create the forwarder block. */ 1463 basic_block new_bb = create_eh_forwarder_block (new_label, old_bb); 1464 1465 /* Create the map from old to new lp index and initialize it. */ 1466 unsigned *index_map = (unsigned *) alloca (lp_len * sizeof (unsigned)); 1467 memset (index_map, 0, lp_len * sizeof (unsigned)); 1468 1469 /* Fix up the edges. */ 1470 for (ei = ei_start (old_bb->preds); (e = ei_safe_edge (ei)) != NULL; ) 1471 if (e->src != new_bb && BB_PARTITION (e->src) == BB_PARTITION (new_bb)) 1472 { 1473 rtx_insn *insn = BB_END (e->src); 1474 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX); 1475 1476 gcc_assert (note != NULL); 1477 const unsigned old_index = INTVAL (XEXP (note, 0)); 1478 1479 /* Generate the new landing-pad structure. */ 1480 if (index_map[old_index] == 0) 1481 { 1482 eh_landing_pad old_lp = (*cfun->eh->lp_array)[old_index]; 1483 eh_landing_pad new_lp = gen_eh_landing_pad (old_lp->region); 1484 new_lp->post_landing_pad = old_lp->post_landing_pad; 1485 new_lp->landing_pad = new_label; 1486 index_map[old_index] = new_lp->index; 1487 } 1488 XEXP (note, 0) = GEN_INT (index_map[old_index]); 1489 1490 /* Adjust the edge to the new destination. */ 1491 redirect_edge_succ (e, new_bb); 1492 } 1493 else 1494 ei_next (&ei); 1495 } 1496 1497 /* The landing pad OLD_LP, in block OLD_BB, has edges from both partitions. 1498 Add a new landing pad that will just jump to the old one and split the 1499 edges so that no EH edge crosses partitions. */ 1500 1501 static void 1502 dw2_fix_up_crossing_landing_pad (eh_landing_pad old_lp, basic_block old_bb) 1503 { 1504 eh_landing_pad new_lp; 1505 edge_iterator ei; 1506 edge e; 1507 1508 /* Generate the new landing-pad structure. */ 1509 new_lp = gen_eh_landing_pad (old_lp->region); 1510 new_lp->post_landing_pad = old_lp->post_landing_pad; 1511 new_lp->landing_pad = gen_label_rtx (); 1512 LABEL_PRESERVE_P (new_lp->landing_pad) = 1; 1513 1514 /* Create the forwarder block. */ 1515 basic_block new_bb = create_eh_forwarder_block (new_lp->landing_pad, old_bb); 1516 1517 /* Fix up the edges. */ 1518 for (ei = ei_start (old_bb->preds); (e = ei_safe_edge (ei)) != NULL; ) 1519 if (e->src != new_bb && BB_PARTITION (e->src) == BB_PARTITION (new_bb)) 1520 { 1521 rtx_insn *insn = BB_END (e->src); 1522 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX); 1523 1524 gcc_assert (note != NULL); 1525 gcc_checking_assert (INTVAL (XEXP (note, 0)) == old_lp->index); 1526 XEXP (note, 0) = GEN_INT (new_lp->index); 1527 1528 /* Adjust the edge to the new destination. */ 1529 redirect_edge_succ (e, new_bb); 1530 } 1531 else 1532 ei_next (&ei); 1533 } 1534 1535 1536 /* Ensure that all hot bbs are included in a hot path through the 1537 procedure. This is done by calling this function twice, once 1538 with WALK_UP true (to look for paths from the entry to hot bbs) and 1539 once with WALK_UP false (to look for paths from hot bbs to the exit). 1540 Returns the updated value of COLD_BB_COUNT and adds newly-hot bbs 1541 to BBS_IN_HOT_PARTITION. */ 1542 1543 static unsigned int 1544 sanitize_hot_paths (bool walk_up, unsigned int cold_bb_count, 1545 vec<basic_block> *bbs_in_hot_partition) 1546 { 1547 /* Callers check this. */ 1548 gcc_checking_assert (cold_bb_count); 1549 1550 /* Keep examining hot bbs while we still have some left to check 1551 and there are remaining cold bbs. */ 1552 vec<basic_block> hot_bbs_to_check = bbs_in_hot_partition->copy (); 1553 while (! hot_bbs_to_check.is_empty () 1554 && cold_bb_count) 1555 { 1556 basic_block bb = hot_bbs_to_check.pop (); 1557 vec<edge, va_gc> *edges = walk_up ? bb->preds : bb->succs; 1558 edge e; 1559 edge_iterator ei; 1560 profile_probability highest_probability 1561 = profile_probability::uninitialized (); 1562 profile_count highest_count = profile_count::uninitialized (); 1563 bool found = false; 1564 1565 /* Walk the preds/succs and check if there is at least one already 1566 marked hot. Keep track of the most frequent pred/succ so that we 1567 can mark it hot if we don't find one. */ 1568 FOR_EACH_EDGE (e, ei, edges) 1569 { 1570 basic_block reach_bb = walk_up ? e->src : e->dest; 1571 1572 if (e->flags & EDGE_DFS_BACK) 1573 continue; 1574 1575 /* Do not expect profile insanities when profile was not adjusted. */ 1576 if (e->probability == profile_probability::never () 1577 || e->count () == profile_count::zero ()) 1578 continue; 1579 1580 if (BB_PARTITION (reach_bb) != BB_COLD_PARTITION) 1581 { 1582 found = true; 1583 break; 1584 } 1585 /* The following loop will look for the hottest edge via 1586 the edge count, if it is non-zero, then fallback to 1587 the edge probability. */ 1588 if (!(e->count () > highest_count)) 1589 highest_count = e->count (); 1590 if (!highest_probability.initialized_p () 1591 || e->probability > highest_probability) 1592 highest_probability = e->probability; 1593 } 1594 1595 /* If bb is reached by (or reaches, in the case of !WALK_UP) another hot 1596 block (or unpartitioned, e.g. the entry block) then it is ok. If not, 1597 then the most frequent pred (or succ) needs to be adjusted. In the 1598 case where multiple preds/succs have the same frequency (e.g. a 1599 50-50 branch), then both will be adjusted. */ 1600 if (found) 1601 continue; 1602 1603 FOR_EACH_EDGE (e, ei, edges) 1604 { 1605 if (e->flags & EDGE_DFS_BACK) 1606 continue; 1607 /* Do not expect profile insanities when profile was not adjusted. */ 1608 if (e->probability == profile_probability::never () 1609 || e->count () == profile_count::zero ()) 1610 continue; 1611 /* Select the hottest edge using the edge count, if it is non-zero, 1612 then fallback to the edge probability. */ 1613 if (highest_count.initialized_p ()) 1614 { 1615 if (!(e->count () >= highest_count)) 1616 continue; 1617 } 1618 else if (!(e->probability >= highest_probability)) 1619 continue; 1620 1621 basic_block reach_bb = walk_up ? e->src : e->dest; 1622 1623 /* We have a hot bb with an immediate dominator that is cold. 1624 The dominator needs to be re-marked hot. */ 1625 BB_SET_PARTITION (reach_bb, BB_HOT_PARTITION); 1626 if (dump_file) 1627 fprintf (dump_file, "Promoting bb %i to hot partition to sanitize " 1628 "profile of bb %i in %s walk\n", reach_bb->index, 1629 bb->index, walk_up ? "backward" : "forward"); 1630 cold_bb_count--; 1631 1632 /* Now we need to examine newly-hot reach_bb to see if it is also 1633 dominated by a cold bb. */ 1634 bbs_in_hot_partition->safe_push (reach_bb); 1635 hot_bbs_to_check.safe_push (reach_bb); 1636 } 1637 } 1638 hot_bbs_to_check.release (); 1639 1640 return cold_bb_count; 1641 } 1642 1643 1644 /* Find the basic blocks that are rarely executed and need to be moved to 1645 a separate section of the .o file (to cut down on paging and improve 1646 cache locality). Return a vector of all edges that cross. */ 1647 1648 static vec<edge> 1649 find_rarely_executed_basic_blocks_and_crossing_edges (void) 1650 { 1651 vec<edge> crossing_edges = vNULL; 1652 basic_block bb; 1653 edge e; 1654 edge_iterator ei; 1655 unsigned int cold_bb_count = 0; 1656 auto_vec<basic_block> bbs_in_hot_partition; 1657 1658 propagate_unlikely_bbs_forward (); 1659 1660 /* Mark which partition (hot/cold) each basic block belongs in. */ 1661 FOR_EACH_BB_FN (bb, cfun) 1662 { 1663 bool cold_bb = false; 1664 1665 if (probably_never_executed_bb_p (cfun, bb)) 1666 { 1667 /* Handle profile insanities created by upstream optimizations 1668 by also checking the incoming edge weights. If there is a non-cold 1669 incoming edge, conservatively prevent this block from being split 1670 into the cold section. */ 1671 cold_bb = true; 1672 FOR_EACH_EDGE (e, ei, bb->preds) 1673 if (!probably_never_executed_edge_p (cfun, e)) 1674 { 1675 cold_bb = false; 1676 break; 1677 } 1678 } 1679 if (cold_bb) 1680 { 1681 BB_SET_PARTITION (bb, BB_COLD_PARTITION); 1682 cold_bb_count++; 1683 } 1684 else 1685 { 1686 BB_SET_PARTITION (bb, BB_HOT_PARTITION); 1687 bbs_in_hot_partition.safe_push (bb); 1688 } 1689 } 1690 1691 /* Ensure that hot bbs are included along a hot path from the entry to exit. 1692 Several different possibilities may include cold bbs along all paths 1693 to/from a hot bb. One is that there are edge weight insanities 1694 due to optimization phases that do not properly update basic block profile 1695 counts. The second is that the entry of the function may not be hot, because 1696 it is entered fewer times than the number of profile training runs, but there 1697 is a loop inside the function that causes blocks within the function to be 1698 above the threshold for hotness. This is fixed by walking up from hot bbs 1699 to the entry block, and then down from hot bbs to the exit, performing 1700 partitioning fixups as necessary. */ 1701 if (cold_bb_count) 1702 { 1703 mark_dfs_back_edges (); 1704 cold_bb_count = sanitize_hot_paths (true, cold_bb_count, 1705 &bbs_in_hot_partition); 1706 if (cold_bb_count) 1707 sanitize_hot_paths (false, cold_bb_count, &bbs_in_hot_partition); 1708 1709 hash_set <basic_block> set; 1710 find_bbs_reachable_by_hot_paths (&set); 1711 FOR_EACH_BB_FN (bb, cfun) 1712 if (!set.contains (bb)) 1713 BB_SET_PARTITION (bb, BB_COLD_PARTITION); 1714 } 1715 1716 /* The format of .gcc_except_table does not allow landing pads to 1717 be in a different partition as the throw. Fix this by either 1718 moving the landing pads or inserting forwarder landing pads. */ 1719 if (cfun->eh->lp_array) 1720 { 1721 const bool sjlj 1722 = (targetm_common.except_unwind_info (&global_options) == UI_SJLJ); 1723 unsigned i; 1724 eh_landing_pad lp; 1725 1726 FOR_EACH_VEC_ELT (*cfun->eh->lp_array, i, lp) 1727 { 1728 bool all_same, all_diff; 1729 1730 if (lp == NULL 1731 || lp->landing_pad == NULL_RTX 1732 || !LABEL_P (lp->landing_pad)) 1733 continue; 1734 1735 all_same = all_diff = true; 1736 bb = BLOCK_FOR_INSN (lp->landing_pad); 1737 FOR_EACH_EDGE (e, ei, bb->preds) 1738 { 1739 gcc_assert (e->flags & EDGE_EH); 1740 if (BB_PARTITION (bb) == BB_PARTITION (e->src)) 1741 all_diff = false; 1742 else 1743 all_same = false; 1744 } 1745 1746 if (all_same) 1747 ; 1748 else if (all_diff) 1749 { 1750 int which = BB_PARTITION (bb); 1751 which ^= BB_HOT_PARTITION | BB_COLD_PARTITION; 1752 BB_SET_PARTITION (bb, which); 1753 } 1754 else if (sjlj) 1755 sjlj_fix_up_crossing_landing_pad (bb); 1756 else 1757 dw2_fix_up_crossing_landing_pad (lp, bb); 1758 1759 /* There is a single, common landing pad in SJLJ mode. */ 1760 if (sjlj) 1761 break; 1762 } 1763 } 1764 1765 /* Mark every edge that crosses between sections. */ 1766 FOR_EACH_BB_FN (bb, cfun) 1767 FOR_EACH_EDGE (e, ei, bb->succs) 1768 { 1769 unsigned int flags = e->flags; 1770 1771 /* We should never have EDGE_CROSSING set yet. */ 1772 gcc_checking_assert ((flags & EDGE_CROSSING) == 0); 1773 1774 if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun) 1775 && e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun) 1776 && BB_PARTITION (e->src) != BB_PARTITION (e->dest)) 1777 { 1778 crossing_edges.safe_push (e); 1779 flags |= EDGE_CROSSING; 1780 } 1781 1782 /* Now that we've split eh edges as appropriate, allow landing pads 1783 to be merged with the post-landing pads. */ 1784 flags &= ~EDGE_PRESERVE; 1785 1786 e->flags = flags; 1787 } 1788 1789 return crossing_edges; 1790 } 1791 1792 /* Set the flag EDGE_CAN_FALLTHRU for edges that can be fallthru. */ 1793 1794 static void 1795 set_edge_can_fallthru_flag (void) 1796 { 1797 basic_block bb; 1798 1799 FOR_EACH_BB_FN (bb, cfun) 1800 { 1801 edge e; 1802 edge_iterator ei; 1803 1804 FOR_EACH_EDGE (e, ei, bb->succs) 1805 { 1806 e->flags &= ~EDGE_CAN_FALLTHRU; 1807 1808 /* The FALLTHRU edge is also CAN_FALLTHRU edge. */ 1809 if (e->flags & EDGE_FALLTHRU) 1810 e->flags |= EDGE_CAN_FALLTHRU; 1811 } 1812 1813 /* If the BB ends with an invertible condjump all (2) edges are 1814 CAN_FALLTHRU edges. */ 1815 if (EDGE_COUNT (bb->succs) != 2) 1816 continue; 1817 if (!any_condjump_p (BB_END (bb))) 1818 continue; 1819 1820 rtx_jump_insn *bb_end_jump = as_a <rtx_jump_insn *> (BB_END (bb)); 1821 if (!invert_jump (bb_end_jump, JUMP_LABEL (bb_end_jump), 0)) 1822 continue; 1823 invert_jump (bb_end_jump, JUMP_LABEL (bb_end_jump), 0); 1824 EDGE_SUCC (bb, 0)->flags |= EDGE_CAN_FALLTHRU; 1825 EDGE_SUCC (bb, 1)->flags |= EDGE_CAN_FALLTHRU; 1826 } 1827 } 1828 1829 /* If any destination of a crossing edge does not have a label, add label; 1830 Convert any easy fall-through crossing edges to unconditional jumps. */ 1831 1832 static void 1833 add_labels_and_missing_jumps (vec<edge> crossing_edges) 1834 { 1835 size_t i; 1836 edge e; 1837 1838 FOR_EACH_VEC_ELT (crossing_edges, i, e) 1839 { 1840 basic_block src = e->src; 1841 basic_block dest = e->dest; 1842 rtx_jump_insn *new_jump; 1843 1844 if (dest == EXIT_BLOCK_PTR_FOR_FN (cfun)) 1845 continue; 1846 1847 /* Make sure dest has a label. */ 1848 rtx_code_label *label = block_label (dest); 1849 1850 /* Nothing to do for non-fallthru edges. */ 1851 if (src == ENTRY_BLOCK_PTR_FOR_FN (cfun)) 1852 continue; 1853 if ((e->flags & EDGE_FALLTHRU) == 0) 1854 continue; 1855 1856 /* If the block does not end with a control flow insn, then we 1857 can trivially add a jump to the end to fixup the crossing. 1858 Otherwise the jump will have to go in a new bb, which will 1859 be handled by fix_up_fall_thru_edges function. */ 1860 if (control_flow_insn_p (BB_END (src))) 1861 continue; 1862 1863 /* Make sure there's only one successor. */ 1864 gcc_assert (single_succ_p (src)); 1865 1866 new_jump = emit_jump_insn_after (targetm.gen_jump (label), BB_END (src)); 1867 BB_END (src) = new_jump; 1868 JUMP_LABEL (new_jump) = label; 1869 LABEL_NUSES (label) += 1; 1870 1871 emit_barrier_after_bb (src); 1872 1873 /* Mark edge as non-fallthru. */ 1874 e->flags &= ~EDGE_FALLTHRU; 1875 } 1876 } 1877 1878 /* Find any bb's where the fall-through edge is a crossing edge (note that 1879 these bb's must also contain a conditional jump or end with a call 1880 instruction; we've already dealt with fall-through edges for blocks 1881 that didn't have a conditional jump or didn't end with call instruction 1882 in the call to add_labels_and_missing_jumps). Convert the fall-through 1883 edge to non-crossing edge by inserting a new bb to fall-through into. 1884 The new bb will contain an unconditional jump (crossing edge) to the 1885 original fall through destination. */ 1886 1887 static void 1888 fix_up_fall_thru_edges (void) 1889 { 1890 basic_block cur_bb; 1891 1892 FOR_EACH_BB_FN (cur_bb, cfun) 1893 { 1894 edge succ1; 1895 edge succ2; 1896 edge fall_thru = NULL; 1897 edge cond_jump = NULL; 1898 1899 fall_thru = NULL; 1900 if (EDGE_COUNT (cur_bb->succs) > 0) 1901 succ1 = EDGE_SUCC (cur_bb, 0); 1902 else 1903 succ1 = NULL; 1904 1905 if (EDGE_COUNT (cur_bb->succs) > 1) 1906 succ2 = EDGE_SUCC (cur_bb, 1); 1907 else 1908 succ2 = NULL; 1909 1910 /* Find the fall-through edge. */ 1911 1912 if (succ1 1913 && (succ1->flags & EDGE_FALLTHRU)) 1914 { 1915 fall_thru = succ1; 1916 cond_jump = succ2; 1917 } 1918 else if (succ2 1919 && (succ2->flags & EDGE_FALLTHRU)) 1920 { 1921 fall_thru = succ2; 1922 cond_jump = succ1; 1923 } 1924 else if (succ2 && EDGE_COUNT (cur_bb->succs) > 2) 1925 fall_thru = find_fallthru_edge (cur_bb->succs); 1926 1927 if (fall_thru && (fall_thru->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))) 1928 { 1929 /* Check to see if the fall-thru edge is a crossing edge. */ 1930 1931 if (fall_thru->flags & EDGE_CROSSING) 1932 { 1933 /* The fall_thru edge crosses; now check the cond jump edge, if 1934 it exists. */ 1935 1936 bool cond_jump_crosses = true; 1937 int invert_worked = 0; 1938 rtx_insn *old_jump = BB_END (cur_bb); 1939 1940 /* Find the jump instruction, if there is one. */ 1941 1942 if (cond_jump) 1943 { 1944 if (!(cond_jump->flags & EDGE_CROSSING)) 1945 cond_jump_crosses = false; 1946 1947 /* We know the fall-thru edge crosses; if the cond 1948 jump edge does NOT cross, and its destination is the 1949 next block in the bb order, invert the jump 1950 (i.e. fix it so the fall through does not cross and 1951 the cond jump does). */ 1952 1953 if (!cond_jump_crosses) 1954 { 1955 /* Find label in fall_thru block. We've already added 1956 any missing labels, so there must be one. */ 1957 1958 rtx_code_label *fall_thru_label 1959 = block_label (fall_thru->dest); 1960 1961 if (old_jump && fall_thru_label) 1962 { 1963 rtx_jump_insn *old_jump_insn 1964 = dyn_cast <rtx_jump_insn *> (old_jump); 1965 if (old_jump_insn) 1966 invert_worked = invert_jump (old_jump_insn, 1967 fall_thru_label, 0); 1968 } 1969 1970 if (invert_worked) 1971 { 1972 fall_thru->flags &= ~EDGE_FALLTHRU; 1973 cond_jump->flags |= EDGE_FALLTHRU; 1974 update_br_prob_note (cur_bb); 1975 std::swap (fall_thru, cond_jump); 1976 cond_jump->flags |= EDGE_CROSSING; 1977 fall_thru->flags &= ~EDGE_CROSSING; 1978 } 1979 } 1980 } 1981 1982 if (cond_jump_crosses || !invert_worked) 1983 { 1984 /* This is the case where both edges out of the basic 1985 block are crossing edges. Here we will fix up the 1986 fall through edge. The jump edge will be taken care 1987 of later. The EDGE_CROSSING flag of fall_thru edge 1988 is unset before the call to force_nonfallthru 1989 function because if a new basic-block is created 1990 this edge remains in the current section boundary 1991 while the edge between new_bb and the fall_thru->dest 1992 becomes EDGE_CROSSING. */ 1993 1994 fall_thru->flags &= ~EDGE_CROSSING; 1995 basic_block new_bb = force_nonfallthru (fall_thru); 1996 1997 if (new_bb) 1998 { 1999 new_bb->aux = cur_bb->aux; 2000 cur_bb->aux = new_bb; 2001 2002 /* This is done by force_nonfallthru_and_redirect. */ 2003 gcc_assert (BB_PARTITION (new_bb) 2004 == BB_PARTITION (cur_bb)); 2005 2006 single_succ_edge (new_bb)->flags |= EDGE_CROSSING; 2007 } 2008 else 2009 { 2010 /* If a new basic-block was not created; restore 2011 the EDGE_CROSSING flag. */ 2012 fall_thru->flags |= EDGE_CROSSING; 2013 } 2014 2015 /* Add barrier after new jump */ 2016 emit_barrier_after_bb (new_bb ? new_bb : cur_bb); 2017 } 2018 } 2019 } 2020 } 2021 } 2022 2023 /* This function checks the destination block of a "crossing jump" to 2024 see if it has any crossing predecessors that begin with a code label 2025 and end with an unconditional jump. If so, it returns that predecessor 2026 block. (This is to avoid creating lots of new basic blocks that all 2027 contain unconditional jumps to the same destination). */ 2028 2029 static basic_block 2030 find_jump_block (basic_block jump_dest) 2031 { 2032 basic_block source_bb = NULL; 2033 edge e; 2034 rtx_insn *insn; 2035 edge_iterator ei; 2036 2037 FOR_EACH_EDGE (e, ei, jump_dest->preds) 2038 if (e->flags & EDGE_CROSSING) 2039 { 2040 basic_block src = e->src; 2041 2042 /* Check each predecessor to see if it has a label, and contains 2043 only one executable instruction, which is an unconditional jump. 2044 If so, we can use it. */ 2045 2046 if (LABEL_P (BB_HEAD (src))) 2047 for (insn = BB_HEAD (src); 2048 !INSN_P (insn) && insn != NEXT_INSN (BB_END (src)); 2049 insn = NEXT_INSN (insn)) 2050 { 2051 if (INSN_P (insn) 2052 && insn == BB_END (src) 2053 && JUMP_P (insn) 2054 && !any_condjump_p (insn)) 2055 { 2056 source_bb = src; 2057 break; 2058 } 2059 } 2060 2061 if (source_bb) 2062 break; 2063 } 2064 2065 return source_bb; 2066 } 2067 2068 /* Find all BB's with conditional jumps that are crossing edges; 2069 insert a new bb and make the conditional jump branch to the new 2070 bb instead (make the new bb same color so conditional branch won't 2071 be a 'crossing' edge). Insert an unconditional jump from the 2072 new bb to the original destination of the conditional jump. */ 2073 2074 static void 2075 fix_crossing_conditional_branches (void) 2076 { 2077 basic_block cur_bb; 2078 basic_block new_bb; 2079 basic_block dest; 2080 edge succ1; 2081 edge succ2; 2082 edge crossing_edge; 2083 edge new_edge; 2084 rtx set_src; 2085 rtx old_label = NULL_RTX; 2086 rtx_code_label *new_label; 2087 2088 FOR_EACH_BB_FN (cur_bb, cfun) 2089 { 2090 crossing_edge = NULL; 2091 if (EDGE_COUNT (cur_bb->succs) > 0) 2092 succ1 = EDGE_SUCC (cur_bb, 0); 2093 else 2094 succ1 = NULL; 2095 2096 if (EDGE_COUNT (cur_bb->succs) > 1) 2097 succ2 = EDGE_SUCC (cur_bb, 1); 2098 else 2099 succ2 = NULL; 2100 2101 /* We already took care of fall-through edges, so only one successor 2102 can be a crossing edge. */ 2103 2104 if (succ1 && (succ1->flags & EDGE_CROSSING)) 2105 crossing_edge = succ1; 2106 else if (succ2 && (succ2->flags & EDGE_CROSSING)) 2107 crossing_edge = succ2; 2108 2109 if (crossing_edge) 2110 { 2111 rtx_insn *old_jump = BB_END (cur_bb); 2112 2113 /* Check to make sure the jump instruction is a 2114 conditional jump. */ 2115 2116 set_src = NULL_RTX; 2117 2118 if (any_condjump_p (old_jump)) 2119 { 2120 if (GET_CODE (PATTERN (old_jump)) == SET) 2121 set_src = SET_SRC (PATTERN (old_jump)); 2122 else if (GET_CODE (PATTERN (old_jump)) == PARALLEL) 2123 { 2124 set_src = XVECEXP (PATTERN (old_jump), 0,0); 2125 if (GET_CODE (set_src) == SET) 2126 set_src = SET_SRC (set_src); 2127 else 2128 set_src = NULL_RTX; 2129 } 2130 } 2131 2132 if (set_src && (GET_CODE (set_src) == IF_THEN_ELSE)) 2133 { 2134 rtx_jump_insn *old_jump_insn = 2135 as_a <rtx_jump_insn *> (old_jump); 2136 2137 if (GET_CODE (XEXP (set_src, 1)) == PC) 2138 old_label = XEXP (set_src, 2); 2139 else if (GET_CODE (XEXP (set_src, 2)) == PC) 2140 old_label = XEXP (set_src, 1); 2141 2142 /* Check to see if new bb for jumping to that dest has 2143 already been created; if so, use it; if not, create 2144 a new one. */ 2145 2146 new_bb = find_jump_block (crossing_edge->dest); 2147 2148 if (new_bb) 2149 new_label = block_label (new_bb); 2150 else 2151 { 2152 basic_block last_bb; 2153 rtx_code_label *old_jump_target; 2154 rtx_jump_insn *new_jump; 2155 2156 /* Create new basic block to be dest for 2157 conditional jump. */ 2158 2159 /* Put appropriate instructions in new bb. */ 2160 2161 new_label = gen_label_rtx (); 2162 emit_label (new_label); 2163 2164 gcc_assert (GET_CODE (old_label) == LABEL_REF); 2165 old_jump_target = old_jump_insn->jump_target (); 2166 new_jump = as_a <rtx_jump_insn *> 2167 (emit_jump_insn (targetm.gen_jump (old_jump_target))); 2168 new_jump->set_jump_target (old_jump_target); 2169 2170 last_bb = EXIT_BLOCK_PTR_FOR_FN (cfun)->prev_bb; 2171 new_bb = create_basic_block (new_label, new_jump, last_bb); 2172 new_bb->aux = last_bb->aux; 2173 last_bb->aux = new_bb; 2174 2175 emit_barrier_after_bb (new_bb); 2176 2177 /* Make sure new bb is in same partition as source 2178 of conditional branch. */ 2179 BB_COPY_PARTITION (new_bb, cur_bb); 2180 } 2181 2182 /* Make old jump branch to new bb. */ 2183 2184 redirect_jump (old_jump_insn, new_label, 0); 2185 2186 /* Remove crossing_edge as predecessor of 'dest'. */ 2187 2188 dest = crossing_edge->dest; 2189 2190 redirect_edge_succ (crossing_edge, new_bb); 2191 2192 /* Make a new edge from new_bb to old dest; new edge 2193 will be a successor for new_bb and a predecessor 2194 for 'dest'. */ 2195 2196 if (EDGE_COUNT (new_bb->succs) == 0) 2197 new_edge = make_single_succ_edge (new_bb, dest, 0); 2198 else 2199 new_edge = EDGE_SUCC (new_bb, 0); 2200 2201 crossing_edge->flags &= ~EDGE_CROSSING; 2202 new_edge->flags |= EDGE_CROSSING; 2203 } 2204 } 2205 } 2206 } 2207 2208 /* Find any unconditional branches that cross between hot and cold 2209 sections. Convert them into indirect jumps instead. */ 2210 2211 static void 2212 fix_crossing_unconditional_branches (void) 2213 { 2214 basic_block cur_bb; 2215 rtx_insn *last_insn; 2216 rtx label; 2217 rtx label_addr; 2218 rtx_insn *indirect_jump_sequence; 2219 rtx_insn *jump_insn = NULL; 2220 rtx new_reg; 2221 rtx_insn *cur_insn; 2222 edge succ; 2223 2224 FOR_EACH_BB_FN (cur_bb, cfun) 2225 { 2226 last_insn = BB_END (cur_bb); 2227 2228 if (EDGE_COUNT (cur_bb->succs) < 1) 2229 continue; 2230 2231 succ = EDGE_SUCC (cur_bb, 0); 2232 2233 /* Check to see if bb ends in a crossing (unconditional) jump. At 2234 this point, no crossing jumps should be conditional. */ 2235 2236 if (JUMP_P (last_insn) 2237 && (succ->flags & EDGE_CROSSING)) 2238 { 2239 gcc_assert (!any_condjump_p (last_insn)); 2240 2241 /* Make sure the jump is not already an indirect or table jump. */ 2242 2243 if (!computed_jump_p (last_insn) 2244 && !tablejump_p (last_insn, NULL, NULL)) 2245 { 2246 /* We have found a "crossing" unconditional branch. Now 2247 we must convert it to an indirect jump. First create 2248 reference of label, as target for jump. */ 2249 2250 label = JUMP_LABEL (last_insn); 2251 label_addr = gen_rtx_LABEL_REF (Pmode, label); 2252 LABEL_NUSES (label) += 1; 2253 2254 /* Get a register to use for the indirect jump. */ 2255 2256 new_reg = gen_reg_rtx (Pmode); 2257 2258 /* Generate indirect the jump sequence. */ 2259 2260 start_sequence (); 2261 emit_move_insn (new_reg, label_addr); 2262 emit_indirect_jump (new_reg); 2263 indirect_jump_sequence = get_insns (); 2264 end_sequence (); 2265 2266 /* Make sure every instruction in the new jump sequence has 2267 its basic block set to be cur_bb. */ 2268 2269 for (cur_insn = indirect_jump_sequence; cur_insn; 2270 cur_insn = NEXT_INSN (cur_insn)) 2271 { 2272 if (!BARRIER_P (cur_insn)) 2273 BLOCK_FOR_INSN (cur_insn) = cur_bb; 2274 if (JUMP_P (cur_insn)) 2275 jump_insn = cur_insn; 2276 } 2277 2278 /* Insert the new (indirect) jump sequence immediately before 2279 the unconditional jump, then delete the unconditional jump. */ 2280 2281 emit_insn_before (indirect_jump_sequence, last_insn); 2282 delete_insn (last_insn); 2283 2284 JUMP_LABEL (jump_insn) = label; 2285 LABEL_NUSES (label)++; 2286 2287 /* Make BB_END for cur_bb be the jump instruction (NOT the 2288 barrier instruction at the end of the sequence...). */ 2289 2290 BB_END (cur_bb) = jump_insn; 2291 } 2292 } 2293 } 2294 } 2295 2296 /* Update CROSSING_JUMP_P flags on all jump insns. */ 2297 2298 static void 2299 update_crossing_jump_flags (void) 2300 { 2301 basic_block bb; 2302 edge e; 2303 edge_iterator ei; 2304 2305 FOR_EACH_BB_FN (bb, cfun) 2306 FOR_EACH_EDGE (e, ei, bb->succs) 2307 if (e->flags & EDGE_CROSSING) 2308 { 2309 if (JUMP_P (BB_END (bb))) 2310 CROSSING_JUMP_P (BB_END (bb)) = 1; 2311 break; 2312 } 2313 } 2314 2315 /* Reorder basic blocks using the software trace cache (STC) algorithm. */ 2316 2317 static void 2318 reorder_basic_blocks_software_trace_cache (void) 2319 { 2320 if (dump_file) 2321 fprintf (dump_file, "\nReordering with the STC algorithm.\n\n"); 2322 2323 int n_traces; 2324 int i; 2325 struct trace *traces; 2326 2327 /* We are estimating the length of uncond jump insn only once since the code 2328 for getting the insn length always returns the minimal length now. */ 2329 if (uncond_jump_length == 0) 2330 uncond_jump_length = get_uncond_jump_length (); 2331 2332 /* We need to know some information for each basic block. */ 2333 array_size = GET_ARRAY_SIZE (last_basic_block_for_fn (cfun)); 2334 bbd = XNEWVEC (bbro_basic_block_data, array_size); 2335 for (i = 0; i < array_size; i++) 2336 { 2337 bbd[i].start_of_trace = -1; 2338 bbd[i].end_of_trace = -1; 2339 bbd[i].in_trace = -1; 2340 bbd[i].visited = 0; 2341 bbd[i].priority = -1; 2342 bbd[i].heap = NULL; 2343 bbd[i].node = NULL; 2344 } 2345 2346 traces = XNEWVEC (struct trace, n_basic_blocks_for_fn (cfun)); 2347 n_traces = 0; 2348 find_traces (&n_traces, traces); 2349 connect_traces (n_traces, traces); 2350 FREE (traces); 2351 FREE (bbd); 2352 } 2353 2354 /* Return true if edge E1 is more desirable as a fallthrough edge than 2355 edge E2 is. */ 2356 2357 static bool 2358 edge_order (edge e1, edge e2) 2359 { 2360 return e1->count () > e2->count (); 2361 } 2362 2363 /* Reorder basic blocks using the "simple" algorithm. This tries to 2364 maximize the dynamic number of branches that are fallthrough, without 2365 copying instructions. The algorithm is greedy, looking at the most 2366 frequently executed branch first. */ 2367 2368 static void 2369 reorder_basic_blocks_simple (void) 2370 { 2371 if (dump_file) 2372 fprintf (dump_file, "\nReordering with the \"simple\" algorithm.\n\n"); 2373 2374 edge *edges = new edge[2 * n_basic_blocks_for_fn (cfun)]; 2375 2376 /* First, collect all edges that can be optimized by reordering blocks: 2377 simple jumps and conditional jumps, as well as the function entry edge. */ 2378 2379 int n = 0; 2380 edges[n++] = EDGE_SUCC (ENTRY_BLOCK_PTR_FOR_FN (cfun), 0); 2381 2382 basic_block bb; 2383 FOR_EACH_BB_FN (bb, cfun) 2384 { 2385 rtx_insn *end = BB_END (bb); 2386 2387 if (computed_jump_p (end) || tablejump_p (end, NULL, NULL)) 2388 continue; 2389 2390 /* We cannot optimize asm goto. */ 2391 if (JUMP_P (end) && extract_asm_operands (end)) 2392 continue; 2393 2394 if (single_succ_p (bb)) 2395 edges[n++] = EDGE_SUCC (bb, 0); 2396 else if (any_condjump_p (end)) 2397 { 2398 edge e0 = EDGE_SUCC (bb, 0); 2399 edge e1 = EDGE_SUCC (bb, 1); 2400 /* When optimizing for size it is best to keep the original 2401 fallthrough edges. */ 2402 if (e1->flags & EDGE_FALLTHRU) 2403 std::swap (e0, e1); 2404 edges[n++] = e0; 2405 edges[n++] = e1; 2406 } 2407 } 2408 2409 /* Sort the edges, the most desirable first. When optimizing for size 2410 all edges are equally desirable. */ 2411 2412 if (optimize_function_for_speed_p (cfun)) 2413 std::stable_sort (edges, edges + n, edge_order); 2414 2415 /* Now decide which of those edges to make fallthrough edges. We set 2416 BB_VISITED if a block already has a fallthrough successor assigned 2417 to it. We make ->AUX of an endpoint point to the opposite endpoint 2418 of a sequence of blocks that fall through, and ->AUX will be NULL 2419 for a block that is in such a sequence but not an endpoint anymore. 2420 2421 To start with, everything points to itself, nothing is assigned yet. */ 2422 2423 FOR_ALL_BB_FN (bb, cfun) 2424 { 2425 bb->aux = bb; 2426 bb->flags &= ~BB_VISITED; 2427 } 2428 2429 EXIT_BLOCK_PTR_FOR_FN (cfun)->aux = 0; 2430 2431 /* Now for all edges, the most desirable first, see if that edge can 2432 connect two sequences. If it can, update AUX and BB_VISITED; if it 2433 cannot, zero out the edge in the table. */ 2434 2435 for (int j = 0; j < n; j++) 2436 { 2437 edge e = edges[j]; 2438 2439 basic_block tail_a = e->src; 2440 basic_block head_b = e->dest; 2441 basic_block head_a = (basic_block) tail_a->aux; 2442 basic_block tail_b = (basic_block) head_b->aux; 2443 2444 /* An edge cannot connect two sequences if: 2445 - it crosses partitions; 2446 - its src is not a current endpoint; 2447 - its dest is not a current endpoint; 2448 - or, it would create a loop. */ 2449 2450 if (e->flags & EDGE_CROSSING 2451 || tail_a->flags & BB_VISITED 2452 || !tail_b 2453 || (!(head_b->flags & BB_VISITED) && head_b != tail_b) 2454 || tail_a == tail_b) 2455 { 2456 edges[j] = 0; 2457 continue; 2458 } 2459 2460 tail_a->aux = 0; 2461 head_b->aux = 0; 2462 head_a->aux = tail_b; 2463 tail_b->aux = head_a; 2464 tail_a->flags |= BB_VISITED; 2465 } 2466 2467 /* Put the pieces together, in the same order that the start blocks of 2468 the sequences already had. The hot/cold partitioning gives a little 2469 complication: as a first pass only do this for blocks in the same 2470 partition as the start block, and (if there is anything left to do) 2471 in a second pass handle the other partition. */ 2472 2473 basic_block last_tail = (basic_block) ENTRY_BLOCK_PTR_FOR_FN (cfun)->aux; 2474 2475 int current_partition 2476 = BB_PARTITION (last_tail == ENTRY_BLOCK_PTR_FOR_FN (cfun) 2477 ? EDGE_SUCC (ENTRY_BLOCK_PTR_FOR_FN (cfun), 0)->dest 2478 : last_tail); 2479 bool need_another_pass = true; 2480 2481 for (int pass = 0; pass < 2 && need_another_pass; pass++) 2482 { 2483 need_another_pass = false; 2484 2485 FOR_EACH_BB_FN (bb, cfun) 2486 if ((bb->flags & BB_VISITED && bb->aux) || bb->aux == bb) 2487 { 2488 if (BB_PARTITION (bb) != current_partition) 2489 { 2490 need_another_pass = true; 2491 continue; 2492 } 2493 2494 last_tail->aux = bb; 2495 last_tail = (basic_block) bb->aux; 2496 } 2497 2498 current_partition ^= BB_HOT_PARTITION | BB_COLD_PARTITION; 2499 } 2500 2501 last_tail->aux = 0; 2502 2503 /* Finally, link all the chosen fallthrough edges. */ 2504 2505 for (int j = 0; j < n; j++) 2506 if (edges[j]) 2507 edges[j]->src->aux = edges[j]->dest; 2508 2509 delete[] edges; 2510 2511 /* If the entry edge no longer falls through we have to make a new 2512 block so it can do so again. */ 2513 2514 edge e = EDGE_SUCC (ENTRY_BLOCK_PTR_FOR_FN (cfun), 0); 2515 if (e->dest != ENTRY_BLOCK_PTR_FOR_FN (cfun)->aux) 2516 { 2517 force_nonfallthru (e); 2518 e->src->aux = ENTRY_BLOCK_PTR_FOR_FN (cfun)->aux; 2519 } 2520 } 2521 2522 /* Reorder basic blocks. The main entry point to this file. */ 2523 2524 static void 2525 reorder_basic_blocks (void) 2526 { 2527 gcc_assert (current_ir_type () == IR_RTL_CFGLAYOUT); 2528 2529 if (n_basic_blocks_for_fn (cfun) <= NUM_FIXED_BLOCKS + 1) 2530 return; 2531 2532 set_edge_can_fallthru_flag (); 2533 mark_dfs_back_edges (); 2534 2535 switch (flag_reorder_blocks_algorithm) 2536 { 2537 case REORDER_BLOCKS_ALGORITHM_SIMPLE: 2538 reorder_basic_blocks_simple (); 2539 break; 2540 2541 case REORDER_BLOCKS_ALGORITHM_STC: 2542 reorder_basic_blocks_software_trace_cache (); 2543 break; 2544 2545 default: 2546 gcc_unreachable (); 2547 } 2548 2549 relink_block_chain (/*stay_in_cfglayout_mode=*/true); 2550 2551 if (dump_file) 2552 { 2553 if (dump_flags & TDF_DETAILS) 2554 dump_reg_info (dump_file); 2555 dump_flow_info (dump_file, dump_flags); 2556 } 2557 2558 /* Signal that rtl_verify_flow_info_1 can now verify that there 2559 is at most one switch between hot/cold sections. */ 2560 crtl->bb_reorder_complete = true; 2561 } 2562 2563 /* Determine which partition the first basic block in the function 2564 belongs to, then find the first basic block in the current function 2565 that belongs to a different section, and insert a 2566 NOTE_INSN_SWITCH_TEXT_SECTIONS note immediately before it in the 2567 instruction stream. When writing out the assembly code, 2568 encountering this note will make the compiler switch between the 2569 hot and cold text sections. */ 2570 2571 void 2572 insert_section_boundary_note (void) 2573 { 2574 basic_block bb; 2575 bool switched_sections = false; 2576 int current_partition = 0; 2577 2578 if (!crtl->has_bb_partition) 2579 return; 2580 2581 FOR_EACH_BB_FN (bb, cfun) 2582 { 2583 if (!current_partition) 2584 current_partition = BB_PARTITION (bb); 2585 if (BB_PARTITION (bb) != current_partition) 2586 { 2587 gcc_assert (!switched_sections); 2588 switched_sections = true; 2589 emit_note_before (NOTE_INSN_SWITCH_TEXT_SECTIONS, BB_HEAD (bb)); 2590 current_partition = BB_PARTITION (bb); 2591 } 2592 } 2593 2594 /* Make sure crtl->has_bb_partition matches reality even if bbpart finds 2595 some hot and some cold basic blocks, but later one of those kinds is 2596 optimized away. */ 2597 crtl->has_bb_partition = switched_sections; 2598 } 2599 2600 namespace { 2601 2602 const pass_data pass_data_reorder_blocks = 2603 { 2604 RTL_PASS, /* type */ 2605 "bbro", /* name */ 2606 OPTGROUP_NONE, /* optinfo_flags */ 2607 TV_REORDER_BLOCKS, /* tv_id */ 2608 0, /* properties_required */ 2609 0, /* properties_provided */ 2610 0, /* properties_destroyed */ 2611 0, /* todo_flags_start */ 2612 0, /* todo_flags_finish */ 2613 }; 2614 2615 class pass_reorder_blocks : public rtl_opt_pass 2616 { 2617 public: 2618 pass_reorder_blocks (gcc::context *ctxt) 2619 : rtl_opt_pass (pass_data_reorder_blocks, ctxt) 2620 {} 2621 2622 /* opt_pass methods: */ 2623 virtual bool gate (function *) 2624 { 2625 if (targetm.cannot_modify_jumps_p ()) 2626 return false; 2627 return (optimize > 0 2628 && (flag_reorder_blocks || flag_reorder_blocks_and_partition)); 2629 } 2630 2631 virtual unsigned int execute (function *); 2632 2633 }; // class pass_reorder_blocks 2634 2635 unsigned int 2636 pass_reorder_blocks::execute (function *fun) 2637 { 2638 basic_block bb; 2639 2640 /* Last attempt to optimize CFG, as scheduling, peepholing and insn 2641 splitting possibly introduced more crossjumping opportunities. */ 2642 cfg_layout_initialize (CLEANUP_EXPENSIVE); 2643 2644 reorder_basic_blocks (); 2645 cleanup_cfg (CLEANUP_EXPENSIVE | CLEANUP_NO_PARTITIONING); 2646 2647 FOR_EACH_BB_FN (bb, fun) 2648 if (bb->next_bb != EXIT_BLOCK_PTR_FOR_FN (fun)) 2649 bb->aux = bb->next_bb; 2650 cfg_layout_finalize (); 2651 2652 return 0; 2653 } 2654 2655 } // anon namespace 2656 2657 rtl_opt_pass * 2658 make_pass_reorder_blocks (gcc::context *ctxt) 2659 { 2660 return new pass_reorder_blocks (ctxt); 2661 } 2662 2663 /* Duplicate a block (that we already know ends in a computed jump) into its 2664 predecessors, where possible. Return whether anything is changed. */ 2665 static bool 2666 maybe_duplicate_computed_goto (basic_block bb, int max_size) 2667 { 2668 if (single_pred_p (bb)) 2669 return false; 2670 2671 /* Make sure that the block is small enough. */ 2672 rtx_insn *insn; 2673 FOR_BB_INSNS (bb, insn) 2674 if (INSN_P (insn)) 2675 { 2676 max_size -= get_attr_min_length (insn); 2677 if (max_size < 0) 2678 return false; 2679 } 2680 2681 bool changed = false; 2682 edge e; 2683 edge_iterator ei; 2684 for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); ) 2685 { 2686 basic_block pred = e->src; 2687 2688 /* Do not duplicate BB into PRED if that is the last predecessor, or if 2689 we cannot merge a copy of BB with PRED. */ 2690 if (single_pred_p (bb) 2691 || !single_succ_p (pred) 2692 || e->flags & EDGE_COMPLEX 2693 || pred->index < NUM_FIXED_BLOCKS 2694 || (JUMP_P (BB_END (pred)) && !simplejump_p (BB_END (pred))) 2695 || (JUMP_P (BB_END (pred)) && CROSSING_JUMP_P (BB_END (pred)))) 2696 { 2697 ei_next (&ei); 2698 continue; 2699 } 2700 2701 if (dump_file) 2702 fprintf (dump_file, "Duplicating computed goto bb %d into bb %d\n", 2703 bb->index, e->src->index); 2704 2705 /* Remember if PRED can be duplicated; if so, the copy of BB merged 2706 with PRED can be duplicated as well. */ 2707 bool can_dup_more = can_duplicate_block_p (pred); 2708 2709 /* Make a copy of BB, merge it into PRED. */ 2710 basic_block copy = duplicate_block (bb, e, NULL); 2711 emit_barrier_after_bb (copy); 2712 reorder_insns_nobb (BB_HEAD (copy), BB_END (copy), BB_END (pred)); 2713 merge_blocks (pred, copy); 2714 2715 changed = true; 2716 2717 /* Try to merge the resulting merged PRED into further predecessors. */ 2718 if (can_dup_more) 2719 maybe_duplicate_computed_goto (pred, max_size); 2720 } 2721 2722 return changed; 2723 } 2724 2725 /* Duplicate the blocks containing computed gotos. This basically unfactors 2726 computed gotos that were factored early on in the compilation process to 2727 speed up edge based data flow. We used to not unfactor them again, which 2728 can seriously pessimize code with many computed jumps in the source code, 2729 such as interpreters. See e.g. PR15242. */ 2730 static void 2731 duplicate_computed_gotos (function *fun) 2732 { 2733 /* We are estimating the length of uncond jump insn only once 2734 since the code for getting the insn length always returns 2735 the minimal length now. */ 2736 if (uncond_jump_length == 0) 2737 uncond_jump_length = get_uncond_jump_length (); 2738 2739 /* Never copy a block larger than this. */ 2740 int max_size 2741 = uncond_jump_length * PARAM_VALUE (PARAM_MAX_GOTO_DUPLICATION_INSNS); 2742 2743 bool changed = false; 2744 2745 /* Try to duplicate all blocks that end in a computed jump and that 2746 can be duplicated at all. */ 2747 basic_block bb; 2748 FOR_EACH_BB_FN (bb, fun) 2749 if (computed_jump_p (BB_END (bb)) && can_duplicate_block_p (bb)) 2750 changed |= maybe_duplicate_computed_goto (bb, max_size); 2751 2752 /* Duplicating blocks will redirect edges and may cause hot blocks 2753 previously reached by both hot and cold blocks to become dominated 2754 only by cold blocks. */ 2755 if (changed) 2756 fixup_partitions (); 2757 } 2758 2759 namespace { 2760 2761 const pass_data pass_data_duplicate_computed_gotos = 2762 { 2763 RTL_PASS, /* type */ 2764 "compgotos", /* name */ 2765 OPTGROUP_NONE, /* optinfo_flags */ 2766 TV_REORDER_BLOCKS, /* tv_id */ 2767 0, /* properties_required */ 2768 0, /* properties_provided */ 2769 0, /* properties_destroyed */ 2770 0, /* todo_flags_start */ 2771 0, /* todo_flags_finish */ 2772 }; 2773 2774 class pass_duplicate_computed_gotos : public rtl_opt_pass 2775 { 2776 public: 2777 pass_duplicate_computed_gotos (gcc::context *ctxt) 2778 : rtl_opt_pass (pass_data_duplicate_computed_gotos, ctxt) 2779 {} 2780 2781 /* opt_pass methods: */ 2782 virtual bool gate (function *); 2783 virtual unsigned int execute (function *); 2784 2785 }; // class pass_duplicate_computed_gotos 2786 2787 bool 2788 pass_duplicate_computed_gotos::gate (function *fun) 2789 { 2790 if (targetm.cannot_modify_jumps_p ()) 2791 return false; 2792 return (optimize > 0 2793 && flag_expensive_optimizations 2794 && ! optimize_function_for_size_p (fun)); 2795 } 2796 2797 unsigned int 2798 pass_duplicate_computed_gotos::execute (function *fun) 2799 { 2800 duplicate_computed_gotos (fun); 2801 2802 return 0; 2803 } 2804 2805 } // anon namespace 2806 2807 rtl_opt_pass * 2808 make_pass_duplicate_computed_gotos (gcc::context *ctxt) 2809 { 2810 return new pass_duplicate_computed_gotos (ctxt); 2811 } 2812 2813 /* This function is the main 'entrance' for the optimization that 2814 partitions hot and cold basic blocks into separate sections of the 2815 .o file (to improve performance and cache locality). Ideally it 2816 would be called after all optimizations that rearrange the CFG have 2817 been called. However part of this optimization may introduce new 2818 register usage, so it must be called before register allocation has 2819 occurred. This means that this optimization is actually called 2820 well before the optimization that reorders basic blocks (see 2821 function above). 2822 2823 This optimization checks the feedback information to determine 2824 which basic blocks are hot/cold, updates flags on the basic blocks 2825 to indicate which section they belong in. This information is 2826 later used for writing out sections in the .o file. Because hot 2827 and cold sections can be arbitrarily large (within the bounds of 2828 memory), far beyond the size of a single function, it is necessary 2829 to fix up all edges that cross section boundaries, to make sure the 2830 instructions used can actually span the required distance. The 2831 fixes are described below. 2832 2833 Fall-through edges must be changed into jumps; it is not safe or 2834 legal to fall through across a section boundary. Whenever a 2835 fall-through edge crossing a section boundary is encountered, a new 2836 basic block is inserted (in the same section as the fall-through 2837 source), and the fall through edge is redirected to the new basic 2838 block. The new basic block contains an unconditional jump to the 2839 original fall-through target. (If the unconditional jump is 2840 insufficient to cross section boundaries, that is dealt with a 2841 little later, see below). 2842 2843 In order to deal with architectures that have short conditional 2844 branches (which cannot span all of memory) we take any conditional 2845 jump that attempts to cross a section boundary and add a level of 2846 indirection: it becomes a conditional jump to a new basic block, in 2847 the same section. The new basic block contains an unconditional 2848 jump to the original target, in the other section. 2849 2850 For those architectures whose unconditional branch is also 2851 incapable of reaching all of memory, those unconditional jumps are 2852 converted into indirect jumps, through a register. 2853 2854 IMPORTANT NOTE: This optimization causes some messy interactions 2855 with the cfg cleanup optimizations; those optimizations want to 2856 merge blocks wherever possible, and to collapse indirect jump 2857 sequences (change "A jumps to B jumps to C" directly into "A jumps 2858 to C"). Those optimizations can undo the jump fixes that 2859 partitioning is required to make (see above), in order to ensure 2860 that jumps attempting to cross section boundaries are really able 2861 to cover whatever distance the jump requires (on many architectures 2862 conditional or unconditional jumps are not able to reach all of 2863 memory). Therefore tests have to be inserted into each such 2864 optimization to make sure that it does not undo stuff necessary to 2865 cross partition boundaries. This would be much less of a problem 2866 if we could perform this optimization later in the compilation, but 2867 unfortunately the fact that we may need to create indirect jumps 2868 (through registers) requires that this optimization be performed 2869 before register allocation. 2870 2871 Hot and cold basic blocks are partitioned and put in separate 2872 sections of the .o file, to reduce paging and improve cache 2873 performance (hopefully). This can result in bits of code from the 2874 same function being widely separated in the .o file. However this 2875 is not obvious to the current bb structure. Therefore we must take 2876 care to ensure that: 1). There are no fall_thru edges that cross 2877 between sections; 2). For those architectures which have "short" 2878 conditional branches, all conditional branches that attempt to 2879 cross between sections are converted to unconditional branches; 2880 and, 3). For those architectures which have "short" unconditional 2881 branches, all unconditional branches that attempt to cross between 2882 sections are converted to indirect jumps. 2883 2884 The code for fixing up fall_thru edges that cross between hot and 2885 cold basic blocks does so by creating new basic blocks containing 2886 unconditional branches to the appropriate label in the "other" 2887 section. The new basic block is then put in the same (hot or cold) 2888 section as the original conditional branch, and the fall_thru edge 2889 is modified to fall into the new basic block instead. By adding 2890 this level of indirection we end up with only unconditional branches 2891 crossing between hot and cold sections. 2892 2893 Conditional branches are dealt with by adding a level of indirection. 2894 A new basic block is added in the same (hot/cold) section as the 2895 conditional branch, and the conditional branch is retargeted to the 2896 new basic block. The new basic block contains an unconditional branch 2897 to the original target of the conditional branch (in the other section). 2898 2899 Unconditional branches are dealt with by converting them into 2900 indirect jumps. */ 2901 2902 namespace { 2903 2904 const pass_data pass_data_partition_blocks = 2905 { 2906 RTL_PASS, /* type */ 2907 "bbpart", /* name */ 2908 OPTGROUP_NONE, /* optinfo_flags */ 2909 TV_REORDER_BLOCKS, /* tv_id */ 2910 PROP_cfglayout, /* properties_required */ 2911 0, /* properties_provided */ 2912 0, /* properties_destroyed */ 2913 0, /* todo_flags_start */ 2914 0, /* todo_flags_finish */ 2915 }; 2916 2917 class pass_partition_blocks : public rtl_opt_pass 2918 { 2919 public: 2920 pass_partition_blocks (gcc::context *ctxt) 2921 : rtl_opt_pass (pass_data_partition_blocks, ctxt) 2922 {} 2923 2924 /* opt_pass methods: */ 2925 virtual bool gate (function *); 2926 virtual unsigned int execute (function *); 2927 2928 }; // class pass_partition_blocks 2929 2930 bool 2931 pass_partition_blocks::gate (function *fun) 2932 { 2933 /* The optimization to partition hot/cold basic blocks into separate 2934 sections of the .o file does not work well with linkonce or with 2935 user defined section attributes or with naked attribute. Don't call 2936 it if either case arises. */ 2937 return (flag_reorder_blocks_and_partition 2938 && optimize 2939 /* See pass_reorder_blocks::gate. We should not partition if 2940 we are going to omit the reordering. */ 2941 && optimize_function_for_speed_p (fun) 2942 && !DECL_COMDAT_GROUP (current_function_decl) 2943 && !lookup_attribute ("section", DECL_ATTRIBUTES (fun->decl)) 2944 && !lookup_attribute ("naked", DECL_ATTRIBUTES (fun->decl)) 2945 /* Workaround a bug in GDB where read_partial_die doesn't cope 2946 with DIEs with DW_AT_ranges, see PR81115. */ 2947 && !(in_lto_p && MAIN_NAME_P (DECL_NAME (fun->decl)))); 2948 } 2949 2950 unsigned 2951 pass_partition_blocks::execute (function *fun) 2952 { 2953 vec<edge> crossing_edges; 2954 2955 if (n_basic_blocks_for_fn (fun) <= NUM_FIXED_BLOCKS + 1) 2956 return 0; 2957 2958 df_set_flags (DF_DEFER_INSN_RESCAN); 2959 2960 crossing_edges = find_rarely_executed_basic_blocks_and_crossing_edges (); 2961 if (!crossing_edges.exists ()) 2962 /* Make sure to process deferred rescans and clear changeable df flags. */ 2963 return TODO_df_finish; 2964 2965 crtl->has_bb_partition = true; 2966 2967 /* Make sure the source of any crossing edge ends in a jump and the 2968 destination of any crossing edge has a label. */ 2969 add_labels_and_missing_jumps (crossing_edges); 2970 2971 /* Convert all crossing fall_thru edges to non-crossing fall 2972 thrus to unconditional jumps (that jump to the original fall 2973 through dest). */ 2974 fix_up_fall_thru_edges (); 2975 2976 /* If the architecture does not have conditional branches that can 2977 span all of memory, convert crossing conditional branches into 2978 crossing unconditional branches. */ 2979 if (!HAS_LONG_COND_BRANCH) 2980 fix_crossing_conditional_branches (); 2981 2982 /* If the architecture does not have unconditional branches that 2983 can span all of memory, convert crossing unconditional branches 2984 into indirect jumps. Since adding an indirect jump also adds 2985 a new register usage, update the register usage information as 2986 well. */ 2987 if (!HAS_LONG_UNCOND_BRANCH) 2988 fix_crossing_unconditional_branches (); 2989 2990 update_crossing_jump_flags (); 2991 2992 /* Clear bb->aux fields that the above routines were using. */ 2993 clear_aux_for_blocks (); 2994 2995 crossing_edges.release (); 2996 2997 /* ??? FIXME: DF generates the bb info for a block immediately. 2998 And by immediately, I mean *during* creation of the block. 2999 3000 #0 df_bb_refs_collect 3001 #1 in df_bb_refs_record 3002 #2 in create_basic_block_structure 3003 3004 Which means that the bb_has_eh_pred test in df_bb_refs_collect 3005 will *always* fail, because no edges can have been added to the 3006 block yet. Which of course means we don't add the right 3007 artificial refs, which means we fail df_verify (much) later. 3008 3009 Cleanest solution would seem to make DF_DEFER_INSN_RESCAN imply 3010 that we also shouldn't grab data from the new blocks those new 3011 insns are in either. In this way one can create the block, link 3012 it up properly, and have everything Just Work later, when deferred 3013 insns are processed. 3014 3015 In the meantime, we have no other option but to throw away all 3016 of the DF data and recompute it all. */ 3017 if (fun->eh->lp_array) 3018 { 3019 df_finish_pass (true); 3020 df_scan_alloc (NULL); 3021 df_scan_blocks (); 3022 /* Not all post-landing pads use all of the EH_RETURN_DATA_REGNO 3023 data. We blindly generated all of them when creating the new 3024 landing pad. Delete those assignments we don't use. */ 3025 df_set_flags (DF_LR_RUN_DCE); 3026 df_analyze (); 3027 } 3028 3029 /* Make sure to process deferred rescans and clear changeable df flags. */ 3030 return TODO_df_finish; 3031 } 3032 3033 } // anon namespace 3034 3035 rtl_opt_pass * 3036 make_pass_partition_blocks (gcc::context *ctxt) 3037 { 3038 return new pass_partition_blocks (ctxt); 3039 } 3040