1/* Control flow graph building code for GNU compiler. 2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 3 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc. 4 5This file is part of GCC. 6 7GCC is free software; you can redistribute it and/or modify it under 8the terms of the GNU General Public License as published by the Free 9Software Foundation; either version 2, or (at your option) any later 10version. 11 12GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13WARRANTY; without even the implied warranty of MERCHANTABILITY or 14FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15for more details. 16 17You should have received a copy of the GNU General Public License 18along with GCC; see the file COPYING. If not, write to the Free 19Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 2002110-1301, USA. */ 21 22/* find_basic_blocks divides the current function's rtl into basic 23 blocks and constructs the CFG. The blocks are recorded in the 24 basic_block_info array; the CFG exists in the edge structures 25 referenced by the blocks. 26 27 find_basic_blocks also finds any unreachable loops and deletes them. 28 29 Available functionality: 30 - CFG construction 31 find_basic_blocks */ 32 33#include "config.h" 34#include "system.h" 35#include "coretypes.h" 36#include "tm.h" 37#include "tree.h" 38#include "rtl.h" 39#include "hard-reg-set.h" 40#include "basic-block.h" 41#include "regs.h" 42#include "flags.h" 43#include "output.h" 44#include "function.h" 45#include "except.h" 46#include "toplev.h" 47#include "timevar.h" 48 49static int count_basic_blocks (rtx); 50static void find_basic_blocks_1 (rtx); 51static void make_edges (basic_block, basic_block, int); 52static void make_label_edge (sbitmap, basic_block, rtx, int); 53static void find_bb_boundaries (basic_block); 54static void compute_outgoing_frequencies (basic_block); 55 56/* Return true if insn is something that should be contained inside basic 57 block. */ 58 59bool 60inside_basic_block_p (rtx insn) 61{ 62 switch (GET_CODE (insn)) 63 { 64 case CODE_LABEL: 65 /* Avoid creating of basic block for jumptables. */ 66 return (NEXT_INSN (insn) == 0 67 || !JUMP_P (NEXT_INSN (insn)) 68 || (GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_VEC 69 && GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_DIFF_VEC)); 70 71 case JUMP_INSN: 72 return (GET_CODE (PATTERN (insn)) != ADDR_VEC 73 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC); 74 75 case CALL_INSN: 76 case INSN: 77 return true; 78 79 case BARRIER: 80 case NOTE: 81 return false; 82 83 default: 84 gcc_unreachable (); 85 } 86} 87 88/* Return true if INSN may cause control flow transfer, so it should be last in 89 the basic block. */ 90 91bool 92control_flow_insn_p (rtx insn) 93{ 94 rtx note; 95 96 switch (GET_CODE (insn)) 97 { 98 case NOTE: 99 case CODE_LABEL: 100 return false; 101 102 case JUMP_INSN: 103 /* Jump insn always causes control transfer except for tablejumps. */ 104 return (GET_CODE (PATTERN (insn)) != ADDR_VEC 105 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC); 106 107 case CALL_INSN: 108 /* Noreturn and sibling call instructions terminate the basic blocks 109 (but only if they happen unconditionally). */ 110 if ((SIBLING_CALL_P (insn) 111 || find_reg_note (insn, REG_NORETURN, 0)) 112 && GET_CODE (PATTERN (insn)) != COND_EXEC) 113 return true; 114 /* Call insn may return to the nonlocal goto handler. */ 115 return ((nonlocal_goto_handler_labels 116 && (0 == (note = find_reg_note (insn, REG_EH_REGION, 117 NULL_RTX)) 118 || INTVAL (XEXP (note, 0)) >= 0)) 119 /* Or may trap. */ 120 || can_throw_internal (insn)); 121 122 case INSN: 123 /* Treat trap instructions like noreturn calls (same provision). */ 124 if (GET_CODE (PATTERN (insn)) == TRAP_IF 125 && XEXP (PATTERN (insn), 0) == const1_rtx) 126 return true; 127 128 return (flag_non_call_exceptions && can_throw_internal (insn)); 129 130 case BARRIER: 131 /* It is nonsense to reach barrier when looking for the 132 end of basic block, but before dead code is eliminated 133 this may happen. */ 134 return false; 135 136 default: 137 gcc_unreachable (); 138 } 139} 140 141/* Count the basic blocks of the function. */ 142 143static int 144count_basic_blocks (rtx f) 145{ 146 int count = NUM_FIXED_BLOCKS; 147 bool saw_insn = false; 148 rtx insn; 149 150 for (insn = f; insn; insn = NEXT_INSN (insn)) 151 { 152 /* Code labels and barriers causes current basic block to be 153 terminated at previous real insn. */ 154 if ((LABEL_P (insn) || BARRIER_P (insn)) 155 && saw_insn) 156 count++, saw_insn = false; 157 158 /* Start basic block if needed. */ 159 if (!saw_insn && inside_basic_block_p (insn)) 160 saw_insn = true; 161 162 /* Control flow insn causes current basic block to be terminated. */ 163 if (saw_insn && control_flow_insn_p (insn)) 164 count++, saw_insn = false; 165 } 166 167 if (saw_insn) 168 count++; 169 170 /* The rest of the compiler works a bit smoother when we don't have to 171 check for the edge case of do-nothing functions with no basic blocks. */ 172 if (count == NUM_FIXED_BLOCKS) 173 { 174 emit_insn (gen_rtx_USE (VOIDmode, const0_rtx)); 175 count = NUM_FIXED_BLOCKS + 1; 176 } 177 178 return count; 179} 180 181/* Create an edge between two basic blocks. FLAGS are auxiliary information 182 about the edge that is accumulated between calls. */ 183 184/* Create an edge from a basic block to a label. */ 185 186static void 187make_label_edge (sbitmap edge_cache, basic_block src, rtx label, int flags) 188{ 189 gcc_assert (LABEL_P (label)); 190 191 /* If the label was never emitted, this insn is junk, but avoid a 192 crash trying to refer to BLOCK_FOR_INSN (label). This can happen 193 as a result of a syntax error and a diagnostic has already been 194 printed. */ 195 196 if (INSN_UID (label) == 0) 197 return; 198 199 cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (label), flags); 200} 201 202/* Create the edges generated by INSN in REGION. */ 203 204void 205rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn) 206{ 207 int is_call = CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0; 208 rtx handlers, i; 209 210 handlers = reachable_handlers (insn); 211 212 for (i = handlers; i; i = XEXP (i, 1)) 213 make_label_edge (edge_cache, src, XEXP (i, 0), 214 EDGE_ABNORMAL | EDGE_EH | is_call); 215 216 free_INSN_LIST_list (&handlers); 217} 218 219/* States of basic block as seen by find_many_sub_basic_blocks. */ 220enum state { 221 /* Basic blocks created via split_block belong to this state. 222 make_edges will examine these basic blocks to see if we need to 223 create edges going out of them. */ 224 BLOCK_NEW = 0, 225 226 /* Basic blocks that do not need examining belong to this state. 227 These blocks will be left intact. In particular, make_edges will 228 not create edges going out of these basic blocks. */ 229 BLOCK_ORIGINAL, 230 231 /* Basic blocks that may need splitting (due to a label appearing in 232 the middle, etc) belong to this state. After splitting them, 233 make_edges will create edges going out of them as needed. */ 234 BLOCK_TO_SPLIT 235}; 236 237#define STATE(BB) (enum state) ((size_t) (BB)->aux) 238#define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE)) 239 240/* Used internally by purge_dead_tablejump_edges, ORed into state. */ 241#define BLOCK_USED_BY_TABLEJUMP 32 242#define FULL_STATE(BB) ((size_t) (BB)->aux) 243 244/* Identify the edges going out of basic blocks between MIN and MAX, 245 inclusive, that have their states set to BLOCK_NEW or 246 BLOCK_TO_SPLIT. 247 248 UPDATE_P should be nonzero if we are updating CFG and zero if we 249 are building CFG from scratch. */ 250 251static void 252make_edges (basic_block min, basic_block max, int update_p) 253{ 254 basic_block bb; 255 sbitmap edge_cache = NULL; 256 257 /* Heavy use of computed goto in machine-generated code can lead to 258 nearly fully-connected CFGs. In that case we spend a significant 259 amount of time searching the edge lists for duplicates. */ 260 if (forced_labels || cfun->max_jumptable_ents > 100) 261 edge_cache = sbitmap_alloc (last_basic_block); 262 263 /* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block 264 is always the entry. */ 265 if (min == ENTRY_BLOCK_PTR->next_bb) 266 make_edge (ENTRY_BLOCK_PTR, min, EDGE_FALLTHRU); 267 268 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb) 269 { 270 rtx insn, x; 271 enum rtx_code code; 272 edge e; 273 edge_iterator ei; 274 275 if (STATE (bb) == BLOCK_ORIGINAL) 276 continue; 277 278 /* If we have an edge cache, cache edges going out of BB. */ 279 if (edge_cache) 280 { 281 sbitmap_zero (edge_cache); 282 if (update_p) 283 { 284 FOR_EACH_EDGE (e, ei, bb->succs) 285 if (e->dest != EXIT_BLOCK_PTR) 286 SET_BIT (edge_cache, e->dest->index); 287 } 288 } 289 290 if (LABEL_P (BB_HEAD (bb)) 291 && LABEL_ALT_ENTRY_P (BB_HEAD (bb))) 292 cached_make_edge (NULL, ENTRY_BLOCK_PTR, bb, 0); 293 294 /* Examine the last instruction of the block, and discover the 295 ways we can leave the block. */ 296 297 insn = BB_END (bb); 298 code = GET_CODE (insn); 299 300 /* A branch. */ 301 if (code == JUMP_INSN) 302 { 303 rtx tmp; 304 305 /* Recognize exception handling placeholders. */ 306 if (GET_CODE (PATTERN (insn)) == RESX) 307 rtl_make_eh_edge (edge_cache, bb, insn); 308 309 /* Recognize a non-local goto as a branch outside the 310 current function. */ 311 else if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX)) 312 ; 313 314 /* Recognize a tablejump and do the right thing. */ 315 else if (tablejump_p (insn, NULL, &tmp)) 316 { 317 rtvec vec; 318 int j; 319 320 if (GET_CODE (PATTERN (tmp)) == ADDR_VEC) 321 vec = XVEC (PATTERN (tmp), 0); 322 else 323 vec = XVEC (PATTERN (tmp), 1); 324 325 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j) 326 make_label_edge (edge_cache, bb, 327 XEXP (RTVEC_ELT (vec, j), 0), 0); 328 329 /* Some targets (eg, ARM) emit a conditional jump that also 330 contains the out-of-range target. Scan for these and 331 add an edge if necessary. */ 332 if ((tmp = single_set (insn)) != NULL 333 && SET_DEST (tmp) == pc_rtx 334 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE 335 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF) 336 make_label_edge (edge_cache, bb, 337 XEXP (XEXP (SET_SRC (tmp), 2), 0), 0); 338 } 339 340 /* If this is a computed jump, then mark it as reaching 341 everything on the forced_labels list. */ 342 else if (computed_jump_p (insn)) 343 { 344 for (x = forced_labels; x; x = XEXP (x, 1)) 345 make_label_edge (edge_cache, bb, XEXP (x, 0), EDGE_ABNORMAL); 346 } 347 348 /* Returns create an exit out. */ 349 else if (returnjump_p (insn)) 350 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 0); 351 352 /* Otherwise, we have a plain conditional or unconditional jump. */ 353 else 354 { 355 gcc_assert (JUMP_LABEL (insn)); 356 make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0); 357 } 358 } 359 360 /* If this is a sibling call insn, then this is in effect a combined call 361 and return, and so we need an edge to the exit block. No need to 362 worry about EH edges, since we wouldn't have created the sibling call 363 in the first place. */ 364 if (code == CALL_INSN && SIBLING_CALL_P (insn)) 365 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 366 EDGE_SIBCALL | EDGE_ABNORMAL); 367 368 /* If this is a CALL_INSN, then mark it as reaching the active EH 369 handler for this CALL_INSN. If we're handling non-call 370 exceptions then any insn can reach any of the active handlers. 371 Also mark the CALL_INSN as reaching any nonlocal goto handler. */ 372 else if (code == CALL_INSN || flag_non_call_exceptions) 373 { 374 /* Add any appropriate EH edges. */ 375 rtl_make_eh_edge (edge_cache, bb, insn); 376 377 if (code == CALL_INSN && nonlocal_goto_handler_labels) 378 { 379 /* ??? This could be made smarter: in some cases it's possible 380 to tell that certain calls will not do a nonlocal goto. 381 For example, if the nested functions that do the nonlocal 382 gotos do not have their addresses taken, then only calls to 383 those functions or to other nested functions that use them 384 could possibly do nonlocal gotos. */ 385 386 /* We do know that a REG_EH_REGION note with a value less 387 than 0 is guaranteed not to perform a non-local goto. */ 388 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX); 389 390 if (!note || INTVAL (XEXP (note, 0)) >= 0) 391 for (x = nonlocal_goto_handler_labels; x; x = XEXP (x, 1)) 392 make_label_edge (edge_cache, bb, XEXP (x, 0), 393 EDGE_ABNORMAL | EDGE_ABNORMAL_CALL); 394 } 395 } 396 397 /* Find out if we can drop through to the next block. */ 398 insn = NEXT_INSN (insn); 399 e = find_edge (bb, EXIT_BLOCK_PTR); 400 if (e && e->flags & EDGE_FALLTHRU) 401 insn = NULL; 402 403 while (insn 404 && NOTE_P (insn) 405 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK) 406 insn = NEXT_INSN (insn); 407 408 if (!insn) 409 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, EDGE_FALLTHRU); 410 else if (bb->next_bb != EXIT_BLOCK_PTR) 411 { 412 if (insn == BB_HEAD (bb->next_bb)) 413 cached_make_edge (edge_cache, bb, bb->next_bb, EDGE_FALLTHRU); 414 } 415 } 416 417 if (edge_cache) 418 sbitmap_vector_free (edge_cache); 419} 420 421/* Find all basic blocks of the function whose first insn is F. 422 423 Collect and return a list of labels whose addresses are taken. This 424 will be used in make_edges for use with computed gotos. */ 425 426static void 427find_basic_blocks_1 (rtx f) 428{ 429 rtx insn, next; 430 rtx bb_note = NULL_RTX; 431 rtx head = NULL_RTX; 432 rtx end = NULL_RTX; 433 basic_block prev = ENTRY_BLOCK_PTR; 434 435 /* We process the instructions in a slightly different way than we did 436 previously. This is so that we see a NOTE_BASIC_BLOCK after we have 437 closed out the previous block, so that it gets attached at the proper 438 place. Since this form should be equivalent to the previous, 439 count_basic_blocks continues to use the old form as a check. */ 440 441 for (insn = f; insn; insn = next) 442 { 443 enum rtx_code code = GET_CODE (insn); 444 445 next = NEXT_INSN (insn); 446 447 if ((LABEL_P (insn) || BARRIER_P (insn)) 448 && head) 449 { 450 prev = create_basic_block_structure (head, end, bb_note, prev); 451 head = end = NULL_RTX; 452 bb_note = NULL_RTX; 453 } 454 455 if (inside_basic_block_p (insn)) 456 { 457 if (head == NULL_RTX) 458 head = insn; 459 end = insn; 460 } 461 462 if (head && control_flow_insn_p (insn)) 463 { 464 prev = create_basic_block_structure (head, end, bb_note, prev); 465 head = end = NULL_RTX; 466 bb_note = NULL_RTX; 467 } 468 469 switch (code) 470 { 471 case NOTE: 472 { 473 int kind = NOTE_LINE_NUMBER (insn); 474 475 /* Look for basic block notes with which to keep the 476 basic_block_info pointers stable. Unthread the note now; 477 we'll put it back at the right place in create_basic_block. 478 Or not at all if we've already found a note in this block. */ 479 if (kind == NOTE_INSN_BASIC_BLOCK) 480 { 481 if (bb_note == NULL_RTX) 482 bb_note = insn; 483 else 484 next = delete_insn (insn); 485 } 486 break; 487 } 488 489 case CODE_LABEL: 490 case JUMP_INSN: 491 case CALL_INSN: 492 case INSN: 493 case BARRIER: 494 break; 495 496 default: 497 gcc_unreachable (); 498 } 499 } 500 501 if (head != NULL_RTX) 502 create_basic_block_structure (head, end, bb_note, prev); 503 else if (bb_note) 504 delete_insn (bb_note); 505 506 gcc_assert (last_basic_block == n_basic_blocks); 507 508 clear_aux_for_blocks (); 509} 510 511 512/* Find basic blocks of the current function. 513 F is the first insn of the function. */ 514 515void 516find_basic_blocks (rtx f) 517{ 518 basic_block bb; 519 520 timevar_push (TV_CFG); 521 522 /* Flush out existing data. */ 523 if (basic_block_info != NULL) 524 { 525 clear_edges (); 526 527 /* Clear bb->aux on all extant basic blocks. We'll use this as a 528 tag for reuse during create_basic_block, just in case some pass 529 copies around basic block notes improperly. */ 530 FOR_EACH_BB (bb) 531 bb->aux = NULL; 532 533 basic_block_info = NULL; 534 } 535 536 n_basic_blocks = count_basic_blocks (f); 537 last_basic_block = NUM_FIXED_BLOCKS; 538 ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR; 539 EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR; 540 541 542 /* Size the basic block table. The actual structures will be allocated 543 by find_basic_blocks_1, since we want to keep the structure pointers 544 stable across calls to find_basic_blocks. */ 545 /* ??? This whole issue would be much simpler if we called find_basic_blocks 546 exactly once, and thereafter we don't have a single long chain of 547 instructions at all until close to the end of compilation when we 548 actually lay them out. */ 549 550 basic_block_info = VEC_alloc (basic_block, gc, n_basic_blocks); 551 VEC_safe_grow (basic_block, gc, basic_block_info, n_basic_blocks); 552 memset (VEC_address (basic_block, basic_block_info), 0, 553 sizeof (basic_block) * n_basic_blocks); 554 SET_BASIC_BLOCK (ENTRY_BLOCK, ENTRY_BLOCK_PTR); 555 SET_BASIC_BLOCK (EXIT_BLOCK, EXIT_BLOCK_PTR); 556 557 find_basic_blocks_1 (f); 558 559 profile_status = PROFILE_ABSENT; 560 561 /* Tell make_edges to examine every block for out-going edges. */ 562 FOR_EACH_BB (bb) 563 SET_STATE (bb, BLOCK_NEW); 564 565 /* Discover the edges of our cfg. */ 566 make_edges (ENTRY_BLOCK_PTR->next_bb, EXIT_BLOCK_PTR->prev_bb, 0); 567 568 /* Do very simple cleanup now, for the benefit of code that runs between 569 here and cleanup_cfg, e.g. thread_prologue_and_epilogue_insns. */ 570 tidy_fallthru_edges (); 571 572#ifdef ENABLE_CHECKING 573 verify_flow_info (); 574#endif 575 timevar_pop (TV_CFG); 576} 577 578static void 579mark_tablejump_edge (rtx label) 580{ 581 basic_block bb; 582 583 gcc_assert (LABEL_P (label)); 584 /* See comment in make_label_edge. */ 585 if (INSN_UID (label) == 0) 586 return; 587 bb = BLOCK_FOR_INSN (label); 588 SET_STATE (bb, FULL_STATE (bb) | BLOCK_USED_BY_TABLEJUMP); 589} 590 591static void 592purge_dead_tablejump_edges (basic_block bb, rtx table) 593{ 594 rtx insn = BB_END (bb), tmp; 595 rtvec vec; 596 int j; 597 edge_iterator ei; 598 edge e; 599 600 if (GET_CODE (PATTERN (table)) == ADDR_VEC) 601 vec = XVEC (PATTERN (table), 0); 602 else 603 vec = XVEC (PATTERN (table), 1); 604 605 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j) 606 mark_tablejump_edge (XEXP (RTVEC_ELT (vec, j), 0)); 607 608 /* Some targets (eg, ARM) emit a conditional jump that also 609 contains the out-of-range target. Scan for these and 610 add an edge if necessary. */ 611 if ((tmp = single_set (insn)) != NULL 612 && SET_DEST (tmp) == pc_rtx 613 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE 614 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF) 615 mark_tablejump_edge (XEXP (XEXP (SET_SRC (tmp), 2), 0)); 616 617 for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); ) 618 { 619 if (FULL_STATE (e->dest) & BLOCK_USED_BY_TABLEJUMP) 620 SET_STATE (e->dest, FULL_STATE (e->dest) 621 & ~(size_t) BLOCK_USED_BY_TABLEJUMP); 622 else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH))) 623 { 624 remove_edge (e); 625 continue; 626 } 627 ei_next (&ei); 628 } 629} 630 631/* Scan basic block BB for possible BB boundaries inside the block 632 and create new basic blocks in the progress. */ 633 634static void 635find_bb_boundaries (basic_block bb) 636{ 637 basic_block orig_bb = bb; 638 rtx insn = BB_HEAD (bb); 639 rtx end = BB_END (bb); 640 rtx table; 641 rtx flow_transfer_insn = NULL_RTX; 642 edge fallthru = NULL; 643 644 if (insn == BB_END (bb)) 645 return; 646 647 if (LABEL_P (insn)) 648 insn = NEXT_INSN (insn); 649 650 /* Scan insn chain and try to find new basic block boundaries. */ 651 while (1) 652 { 653 enum rtx_code code = GET_CODE (insn); 654 655 /* On code label, split current basic block. */ 656 if (code == CODE_LABEL) 657 { 658 fallthru = split_block (bb, PREV_INSN (insn)); 659 if (flow_transfer_insn) 660 BB_END (bb) = flow_transfer_insn; 661 662 bb = fallthru->dest; 663 remove_edge (fallthru); 664 flow_transfer_insn = NULL_RTX; 665 if (LABEL_ALT_ENTRY_P (insn)) 666 make_edge (ENTRY_BLOCK_PTR, bb, 0); 667 } 668 669 /* In case we've previously seen an insn that effects a control 670 flow transfer, split the block. */ 671 if (flow_transfer_insn && inside_basic_block_p (insn)) 672 { 673 fallthru = split_block (bb, PREV_INSN (insn)); 674 BB_END (bb) = flow_transfer_insn; 675 bb = fallthru->dest; 676 remove_edge (fallthru); 677 flow_transfer_insn = NULL_RTX; 678 } 679 680 if (control_flow_insn_p (insn)) 681 flow_transfer_insn = insn; 682 if (insn == end) 683 break; 684 insn = NEXT_INSN (insn); 685 } 686 687 /* In case expander replaced normal insn by sequence terminating by 688 return and barrier, or possibly other sequence not behaving like 689 ordinary jump, we need to take care and move basic block boundary. */ 690 if (flow_transfer_insn) 691 BB_END (bb) = flow_transfer_insn; 692 693 /* We've possibly replaced the conditional jump by conditional jump 694 followed by cleanup at fallthru edge, so the outgoing edges may 695 be dead. */ 696 purge_dead_edges (bb); 697 698 /* purge_dead_edges doesn't handle tablejump's, but if we have split the 699 basic block, we might need to kill some edges. */ 700 if (bb != orig_bb && tablejump_p (BB_END (bb), NULL, &table)) 701 purge_dead_tablejump_edges (bb, table); 702} 703 704/* Assume that frequency of basic block B is known. Compute frequencies 705 and probabilities of outgoing edges. */ 706 707static void 708compute_outgoing_frequencies (basic_block b) 709{ 710 edge e, f; 711 edge_iterator ei; 712 713 if (EDGE_COUNT (b->succs) == 2) 714 { 715 rtx note = find_reg_note (BB_END (b), REG_BR_PROB, NULL); 716 int probability; 717 718 if (note) 719 { 720 probability = INTVAL (XEXP (note, 0)); 721 e = BRANCH_EDGE (b); 722 e->probability = probability; 723 e->count = ((b->count * probability + REG_BR_PROB_BASE / 2) 724 / REG_BR_PROB_BASE); 725 f = FALLTHRU_EDGE (b); 726 f->probability = REG_BR_PROB_BASE - probability; 727 f->count = b->count - e->count; 728 return; 729 } 730 } 731 732 if (single_succ_p (b)) 733 { 734 e = single_succ_edge (b); 735 e->probability = REG_BR_PROB_BASE; 736 e->count = b->count; 737 return; 738 } 739 guess_outgoing_edge_probabilities (b); 740 if (b->count) 741 FOR_EACH_EDGE (e, ei, b->succs) 742 e->count = ((b->count * e->probability + REG_BR_PROB_BASE / 2) 743 / REG_BR_PROB_BASE); 744} 745 746/* Assume that some pass has inserted labels or control flow 747 instructions within a basic block. Split basic blocks as needed 748 and create edges. */ 749 750void 751find_many_sub_basic_blocks (sbitmap blocks) 752{ 753 basic_block bb, min, max; 754 755 FOR_EACH_BB (bb) 756 SET_STATE (bb, 757 TEST_BIT (blocks, bb->index) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL); 758 759 FOR_EACH_BB (bb) 760 if (STATE (bb) == BLOCK_TO_SPLIT) 761 find_bb_boundaries (bb); 762 763 FOR_EACH_BB (bb) 764 if (STATE (bb) != BLOCK_ORIGINAL) 765 break; 766 767 min = max = bb; 768 for (; bb != EXIT_BLOCK_PTR; bb = bb->next_bb) 769 if (STATE (bb) != BLOCK_ORIGINAL) 770 max = bb; 771 772 /* Now re-scan and wire in all edges. This expect simple (conditional) 773 jumps at the end of each new basic blocks. */ 774 make_edges (min, max, 1); 775 776 /* Update branch probabilities. Expect only (un)conditional jumps 777 to be created with only the forward edges. */ 778 if (profile_status != PROFILE_ABSENT) 779 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb) 780 { 781 edge e; 782 edge_iterator ei; 783 784 if (STATE (bb) == BLOCK_ORIGINAL) 785 continue; 786 if (STATE (bb) == BLOCK_NEW) 787 { 788 bb->count = 0; 789 bb->frequency = 0; 790 FOR_EACH_EDGE (e, ei, bb->preds) 791 { 792 bb->count += e->count; 793 bb->frequency += EDGE_FREQUENCY (e); 794 } 795 } 796 797 compute_outgoing_frequencies (bb); 798 } 799 800 FOR_EACH_BB (bb) 801 SET_STATE (bb, 0); 802} 803