cfgbuild.c revision 90075
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 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, 59 Temple Place - Suite 330, Boston, MA 2002111-1307, 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 - Local CFG construction 33 find_sub_basic_blocks */ 34 35#include "config.h" 36#include "system.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#include "obstack.h" 49 50static int count_basic_blocks PARAMS ((rtx)); 51static void find_basic_blocks_1 PARAMS ((rtx)); 52static rtx find_label_refs PARAMS ((rtx, rtx)); 53static void make_edges PARAMS ((rtx, int, int, int)); 54static void make_label_edge PARAMS ((sbitmap *, basic_block, 55 rtx, int)); 56static void make_eh_edge PARAMS ((sbitmap *, basic_block, rtx)); 57static void find_bb_boundaries PARAMS ((basic_block)); 58static void compute_outgoing_frequencies PARAMS ((basic_block)); 59static bool inside_basic_block_p PARAMS ((rtx)); 60static bool control_flow_insn_p PARAMS ((rtx)); 61 62/* Return true if insn is something that should be contained inside basic 63 block. */ 64 65static bool 66inside_basic_block_p (insn) 67 rtx insn; 68{ 69 switch (GET_CODE (insn)) 70 { 71 case CODE_LABEL: 72 /* Avoid creating of basic block for jumptables. */ 73 return (NEXT_INSN (insn) == 0 74 || GET_CODE (NEXT_INSN (insn)) != JUMP_INSN 75 || (GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_VEC 76 && GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_DIFF_VEC)); 77 78 case JUMP_INSN: 79 return (GET_CODE (PATTERN (insn)) != ADDR_VEC 80 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC); 81 82 case CALL_INSN: 83 case INSN: 84 return true; 85 86 case BARRIER: 87 case NOTE: 88 return false; 89 90 default: 91 abort (); 92 } 93} 94 95/* Return true if INSN may cause control flow transfer, so it should be last in 96 the basic block. */ 97 98static bool 99control_flow_insn_p (insn) 100 rtx insn; 101{ 102 rtx note; 103 104 switch (GET_CODE (insn)) 105 { 106 case NOTE: 107 case CODE_LABEL: 108 return false; 109 110 case JUMP_INSN: 111 /* Jump insn always causes control transfer except for tablejumps. */ 112 return (GET_CODE (PATTERN (insn)) != ADDR_VEC 113 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC); 114 115 case CALL_INSN: 116 /* Call insn may return to the nonlocal goto handler. */ 117 return ((nonlocal_goto_handler_labels 118 && (0 == (note = find_reg_note (insn, REG_EH_REGION, 119 NULL_RTX)) 120 || INTVAL (XEXP (note, 0)) >= 0)) 121 /* Or may trap. */ 122 || can_throw_internal (insn)); 123 124 case INSN: 125 return (flag_non_call_exceptions && can_throw_internal (insn)); 126 127 case BARRIER: 128 /* It is nonsence to reach barrier when looking for the 129 end of basic block, but before dead code is eliminated 130 this may happen. */ 131 return false; 132 133 default: 134 abort (); 135 } 136} 137 138/* Count the basic blocks of the function. */ 139 140static int 141count_basic_blocks (f) 142 rtx f; 143{ 144 int count = 0; 145 bool saw_insn = false; 146 rtx insn; 147 148 for (insn = f; insn; insn = NEXT_INSN (insn)) 149 { 150 /* Code labels and barriers causes curent basic block to be 151 terminated at previous real insn. */ 152 if ((GET_CODE (insn) == CODE_LABEL || GET_CODE (insn) == BARRIER) 153 && saw_insn) 154 count++, saw_insn = false; 155 156 /* Start basic block if needed. */ 157 if (!saw_insn && inside_basic_block_p (insn)) 158 saw_insn = true; 159 160 /* Control flow insn causes current basic block to be terminated. */ 161 if (saw_insn && control_flow_insn_p (insn)) 162 count++, saw_insn = false; 163 } 164 165 if (saw_insn) 166 count++; 167 168 /* The rest of the compiler works a bit smoother when we don't have to 169 check for the edge case of do-nothing functions with no basic blocks. */ 170 if (count == 0) 171 { 172 emit_insn (gen_rtx_USE (VOIDmode, const0_rtx)); 173 count = 1; 174 } 175 176 return count; 177} 178 179/* Scan a list of insns for labels referred to other than by jumps. 180 This is used to scan the alternatives of a call placeholder. */ 181 182static rtx 183find_label_refs (f, lvl) 184 rtx f; 185 rtx lvl; 186{ 187 rtx insn; 188 189 for (insn = f; insn; insn = NEXT_INSN (insn)) 190 if (INSN_P (insn) && GET_CODE (insn) != JUMP_INSN) 191 { 192 rtx note; 193 194 /* Make a list of all labels referred to other than by jumps 195 (which just don't have the REG_LABEL notes). 196 197 Make a special exception for labels followed by an ADDR*VEC, 198 as this would be a part of the tablejump setup code. 199 200 Make a special exception to registers loaded with label 201 values just before jump insns that use them. */ 202 203 for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) 204 if (REG_NOTE_KIND (note) == REG_LABEL) 205 { 206 rtx lab = XEXP (note, 0), next; 207 208 if ((next = next_nonnote_insn (lab)) != NULL 209 && GET_CODE (next) == JUMP_INSN 210 && (GET_CODE (PATTERN (next)) == ADDR_VEC 211 || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC)) 212 ; 213 else if (GET_CODE (lab) == NOTE) 214 ; 215 else if (GET_CODE (NEXT_INSN (insn)) == JUMP_INSN 216 && find_reg_note (NEXT_INSN (insn), REG_LABEL, lab)) 217 ; 218 else 219 lvl = alloc_EXPR_LIST (0, XEXP (note, 0), lvl); 220 } 221 } 222 223 return lvl; 224} 225 226/* Create an edge between two basic blocks. FLAGS are auxiliary information 227 about the edge that is accumulated between calls. */ 228 229/* Create an edge from a basic block to a label. */ 230 231static void 232make_label_edge (edge_cache, src, label, flags) 233 sbitmap *edge_cache; 234 basic_block src; 235 rtx label; 236 int flags; 237{ 238 if (GET_CODE (label) != CODE_LABEL) 239 abort (); 240 241 /* If the label was never emitted, this insn is junk, but avoid a 242 crash trying to refer to BLOCK_FOR_INSN (label). This can happen 243 as a result of a syntax error and a diagnostic has already been 244 printed. */ 245 246 if (INSN_UID (label) == 0) 247 return; 248 249 cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (label), flags); 250} 251 252/* Create the edges generated by INSN in REGION. */ 253 254static void 255make_eh_edge (edge_cache, src, insn) 256 sbitmap *edge_cache; 257 basic_block src; 258 rtx insn; 259{ 260 int is_call = GET_CODE (insn) == CALL_INSN ? EDGE_ABNORMAL_CALL : 0; 261 rtx handlers, i; 262 263 handlers = reachable_handlers (insn); 264 265 for (i = handlers; i; i = XEXP (i, 1)) 266 make_label_edge (edge_cache, src, XEXP (i, 0), 267 EDGE_ABNORMAL | EDGE_EH | is_call); 268 269 free_INSN_LIST_list (&handlers); 270} 271 272/* Identify the edges between basic blocks MIN to MAX. 273 274 NONLOCAL_LABEL_LIST is a list of non-local labels in the function. Blocks 275 that are otherwise unreachable may be reachable with a non-local goto. 276 277 BB_EH_END is an array indexed by basic block number in which we record 278 the list of exception regions active at the end of the basic block. */ 279 280static void 281make_edges (label_value_list, min, max, update_p) 282 rtx label_value_list; 283 int min, max, update_p; 284{ 285 int i; 286 sbitmap *edge_cache = NULL; 287 288 /* Assume no computed jump; revise as we create edges. */ 289 current_function_has_computed_jump = 0; 290 291 /* Heavy use of computed goto in machine-generated code can lead to 292 nearly fully-connected CFGs. In that case we spend a significant 293 amount of time searching the edge lists for duplicates. */ 294 if (forced_labels || label_value_list) 295 { 296 edge_cache = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks); 297 sbitmap_vector_zero (edge_cache, n_basic_blocks); 298 299 if (update_p) 300 for (i = min; i <= max; ++i) 301 { 302 edge e; 303 304 for (e = BASIC_BLOCK (i)->succ; e ; e = e->succ_next) 305 if (e->dest != EXIT_BLOCK_PTR) 306 SET_BIT (edge_cache[i], e->dest->index); 307 } 308 } 309 310 /* By nature of the way these get numbered, block 0 is always the entry. */ 311 if (min == 0) 312 cached_make_edge (edge_cache, ENTRY_BLOCK_PTR, BASIC_BLOCK (0), 313 EDGE_FALLTHRU); 314 315 for (i = min; i <= max; ++i) 316 { 317 basic_block bb = BASIC_BLOCK (i); 318 rtx insn, x; 319 enum rtx_code code; 320 int force_fallthru = 0; 321 322 if (GET_CODE (bb->head) == CODE_LABEL && LABEL_ALTERNATE_NAME (bb->head)) 323 cached_make_edge (NULL, ENTRY_BLOCK_PTR, bb, 0); 324 325 /* Examine the last instruction of the block, and discover the 326 ways we can leave the block. */ 327 328 insn = bb->end; 329 code = GET_CODE (insn); 330 331 /* A branch. */ 332 if (code == JUMP_INSN) 333 { 334 rtx tmp; 335 336 /* Recognize exception handling placeholders. */ 337 if (GET_CODE (PATTERN (insn)) == RESX) 338 make_eh_edge (edge_cache, bb, insn); 339 340 /* Recognize a non-local goto as a branch outside the 341 current function. */ 342 else if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX)) 343 ; 344 345 /* ??? Recognize a tablejump and do the right thing. */ 346 else if ((tmp = JUMP_LABEL (insn)) != NULL_RTX 347 && (tmp = NEXT_INSN (tmp)) != NULL_RTX 348 && GET_CODE (tmp) == JUMP_INSN 349 && (GET_CODE (PATTERN (tmp)) == ADDR_VEC 350 || GET_CODE (PATTERN (tmp)) == ADDR_DIFF_VEC)) 351 { 352 rtvec vec; 353 int j; 354 355 if (GET_CODE (PATTERN (tmp)) == ADDR_VEC) 356 vec = XVEC (PATTERN (tmp), 0); 357 else 358 vec = XVEC (PATTERN (tmp), 1); 359 360 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j) 361 make_label_edge (edge_cache, bb, 362 XEXP (RTVEC_ELT (vec, j), 0), 0); 363 364 /* Some targets (eg, ARM) emit a conditional jump that also 365 contains the out-of-range target. Scan for these and 366 add an edge if necessary. */ 367 if ((tmp = single_set (insn)) != NULL 368 && SET_DEST (tmp) == pc_rtx 369 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE 370 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF) 371 make_label_edge (edge_cache, bb, 372 XEXP (XEXP (SET_SRC (tmp), 2), 0), 0); 373 374#ifdef CASE_DROPS_THROUGH 375 /* Silly VAXen. The ADDR_VEC is going to be in the way of 376 us naturally detecting fallthru into the next block. */ 377 force_fallthru = 1; 378#endif 379 } 380 381 /* If this is a computed jump, then mark it as reaching 382 everything on the label_value_list and forced_labels list. */ 383 else if (computed_jump_p (insn)) 384 { 385 current_function_has_computed_jump = 1; 386 387 for (x = label_value_list; x; x = XEXP (x, 1)) 388 make_label_edge (edge_cache, bb, XEXP (x, 0), EDGE_ABNORMAL); 389 390 for (x = forced_labels; x; x = XEXP (x, 1)) 391 make_label_edge (edge_cache, bb, XEXP (x, 0), EDGE_ABNORMAL); 392 } 393 394 /* Returns create an exit out. */ 395 else if (returnjump_p (insn)) 396 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 0); 397 398 /* Otherwise, we have a plain conditional or unconditional jump. */ 399 else 400 { 401 if (! JUMP_LABEL (insn)) 402 abort (); 403 make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0); 404 } 405 } 406 407 /* If this is a sibling call insn, then this is in effect a combined call 408 and return, and so we need an edge to the exit block. No need to 409 worry about EH edges, since we wouldn't have created the sibling call 410 in the first place. */ 411 if (code == CALL_INSN && SIBLING_CALL_P (insn)) 412 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 413 EDGE_ABNORMAL | EDGE_ABNORMAL_CALL); 414 415 /* If this is a CALL_INSN, then mark it as reaching the active EH 416 handler for this CALL_INSN. If we're handling non-call 417 exceptions then any insn can reach any of the active handlers. 418 Also mark the CALL_INSN as reaching any nonlocal goto handler. */ 419 else if (code == CALL_INSN || flag_non_call_exceptions) 420 { 421 /* Add any appropriate EH edges. */ 422 make_eh_edge (edge_cache, bb, insn); 423 424 if (code == CALL_INSN && nonlocal_goto_handler_labels) 425 { 426 /* ??? This could be made smarter: in some cases it's possible 427 to tell that certain calls will not do a nonlocal goto. 428 For example, if the nested functions that do the nonlocal 429 gotos do not have their addresses taken, then only calls to 430 those functions or to other nested functions that use them 431 could possibly do nonlocal gotos. */ 432 433 /* We do know that a REG_EH_REGION note with a value less 434 than 0 is guaranteed not to perform a non-local goto. */ 435 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX); 436 437 if (!note || INTVAL (XEXP (note, 0)) >= 0) 438 for (x = nonlocal_goto_handler_labels; x; x = XEXP (x, 1)) 439 make_label_edge (edge_cache, bb, XEXP (x, 0), 440 EDGE_ABNORMAL | EDGE_ABNORMAL_CALL); 441 } 442 } 443 444 /* Find out if we can drop through to the next block. */ 445 insn = next_nonnote_insn (insn); 446 if (!insn || (i + 1 == n_basic_blocks && force_fallthru)) 447 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, EDGE_FALLTHRU); 448 else if (i + 1 < n_basic_blocks) 449 { 450 rtx tmp = BLOCK_HEAD (i + 1); 451 if (GET_CODE (tmp) == NOTE) 452 tmp = next_nonnote_insn (tmp); 453 if (force_fallthru || insn == tmp) 454 cached_make_edge (edge_cache, bb, BASIC_BLOCK (i + 1), 455 EDGE_FALLTHRU); 456 } 457 } 458 459 if (edge_cache) 460 sbitmap_vector_free (edge_cache); 461} 462 463/* Find all basic blocks of the function whose first insn is F. 464 465 Collect and return a list of labels whose addresses are taken. This 466 will be used in make_edges for use with computed gotos. */ 467 468static void 469find_basic_blocks_1 (f) 470 rtx f; 471{ 472 rtx insn, next; 473 int i = 0; 474 rtx bb_note = NULL_RTX; 475 rtx lvl = NULL_RTX; 476 rtx trll = NULL_RTX; 477 rtx head = NULL_RTX; 478 rtx end = NULL_RTX; 479 480 /* We process the instructions in a slightly different way than we did 481 previously. This is so that we see a NOTE_BASIC_BLOCK after we have 482 closed out the previous block, so that it gets attached at the proper 483 place. Since this form should be equivalent to the previous, 484 count_basic_blocks continues to use the old form as a check. */ 485 486 for (insn = f; insn; insn = next) 487 { 488 enum rtx_code code = GET_CODE (insn); 489 490 next = NEXT_INSN (insn); 491 492 if ((GET_CODE (insn) == CODE_LABEL || GET_CODE (insn) == BARRIER) 493 && head) 494 { 495 create_basic_block_structure (i++, head, end, bb_note); 496 head = end = NULL_RTX; 497 bb_note = NULL_RTX; 498 } 499 500 if (inside_basic_block_p (insn)) 501 { 502 if (head == NULL_RTX) 503 head = insn; 504 end = insn; 505 } 506 507 if (head && control_flow_insn_p (insn)) 508 { 509 create_basic_block_structure (i++, head, end, bb_note); 510 head = end = NULL_RTX; 511 bb_note = NULL_RTX; 512 } 513 514 switch (code) 515 { 516 case NOTE: 517 { 518 int kind = NOTE_LINE_NUMBER (insn); 519 520 /* Look for basic block notes with which to keep the 521 basic_block_info pointers stable. Unthread the note now; 522 we'll put it back at the right place in create_basic_block. 523 Or not at all if we've already found a note in this block. */ 524 if (kind == NOTE_INSN_BASIC_BLOCK) 525 { 526 if (bb_note == NULL_RTX) 527 bb_note = insn; 528 else 529 next = delete_insn (insn); 530 } 531 break; 532 } 533 534 case CODE_LABEL: 535 case JUMP_INSN: 536 case INSN: 537 case BARRIER: 538 break; 539 540 case CALL_INSN: 541 if (GET_CODE (PATTERN (insn)) == CALL_PLACEHOLDER) 542 { 543 /* Scan each of the alternatives for label refs. */ 544 lvl = find_label_refs (XEXP (PATTERN (insn), 0), lvl); 545 lvl = find_label_refs (XEXP (PATTERN (insn), 1), lvl); 546 lvl = find_label_refs (XEXP (PATTERN (insn), 2), lvl); 547 /* Record its tail recursion label, if any. */ 548 if (XEXP (PATTERN (insn), 3) != NULL_RTX) 549 trll = alloc_EXPR_LIST (0, XEXP (PATTERN (insn), 3), trll); 550 } 551 break; 552 553 default: 554 abort (); 555 } 556 557 if (GET_CODE (insn) == INSN || GET_CODE (insn) == CALL_INSN) 558 { 559 rtx note; 560 561 /* Make a list of all labels referred to other than by jumps. 562 563 Make a special exception for labels followed by an ADDR*VEC, 564 as this would be a part of the tablejump setup code. 565 566 Make a special exception to registers loaded with label 567 values just before jump insns that use them. */ 568 569 for (note = REG_NOTES (insn); note; note = XEXP (note, 1)) 570 if (REG_NOTE_KIND (note) == REG_LABEL) 571 { 572 rtx lab = XEXP (note, 0), next; 573 574 if ((next = next_nonnote_insn (lab)) != NULL 575 && GET_CODE (next) == JUMP_INSN 576 && (GET_CODE (PATTERN (next)) == ADDR_VEC 577 || GET_CODE (PATTERN (next)) == ADDR_DIFF_VEC)) 578 ; 579 else if (GET_CODE (lab) == NOTE) 580 ; 581 else if (GET_CODE (NEXT_INSN (insn)) == JUMP_INSN 582 && find_reg_note (NEXT_INSN (insn), REG_LABEL, lab)) 583 ; 584 else 585 lvl = alloc_EXPR_LIST (0, XEXP (note, 0), lvl); 586 } 587 } 588 } 589 590 if (head != NULL_RTX) 591 create_basic_block_structure (i++, head, end, bb_note); 592 else if (bb_note) 593 delete_insn (bb_note); 594 595 if (i != n_basic_blocks) 596 abort (); 597 598 label_value_list = lvl; 599 tail_recursion_label_list = trll; 600} 601 602 603/* Find basic blocks of the current function. 604 F is the first insn of the function and NREGS the number of register 605 numbers in use. */ 606 607void 608find_basic_blocks (f, nregs, file) 609 rtx f; 610 int nregs ATTRIBUTE_UNUSED; 611 FILE *file ATTRIBUTE_UNUSED; 612{ 613 int max_uid; 614 timevar_push (TV_CFG); 615 616 basic_block_for_insn = 0; 617 618 /* Flush out existing data. */ 619 if (basic_block_info != NULL) 620 { 621 int i; 622 623 clear_edges (); 624 625 /* Clear bb->aux on all extant basic blocks. We'll use this as a 626 tag for reuse during create_basic_block, just in case some pass 627 copies around basic block notes improperly. */ 628 for (i = 0; i < n_basic_blocks; ++i) 629 BASIC_BLOCK (i)->aux = NULL; 630 631 VARRAY_FREE (basic_block_info); 632 } 633 634 n_basic_blocks = count_basic_blocks (f); 635 636 /* Size the basic block table. The actual structures will be allocated 637 by find_basic_blocks_1, since we want to keep the structure pointers 638 stable across calls to find_basic_blocks. */ 639 /* ??? This whole issue would be much simpler if we called find_basic_blocks 640 exactly once, and thereafter we don't have a single long chain of 641 instructions at all until close to the end of compilation when we 642 actually lay them out. */ 643 644 VARRAY_BB_INIT (basic_block_info, n_basic_blocks, "basic_block_info"); 645 646 find_basic_blocks_1 (f); 647 648 /* Record the block to which an insn belongs. */ 649 /* ??? This should be done another way, by which (perhaps) a label is 650 tagged directly with the basic block that it starts. It is used for 651 more than that currently, but IMO that is the only valid use. */ 652 653 max_uid = get_max_uid (); 654#ifdef AUTO_INC_DEC 655 /* Leave space for insns life_analysis makes in some cases for auto-inc. 656 These cases are rare, so we don't need too much space. */ 657 max_uid += max_uid / 10; 658#endif 659 660 compute_bb_for_insn (max_uid); 661 662 /* Discover the edges of our cfg. */ 663 make_edges (label_value_list, 0, n_basic_blocks - 1, 0); 664 665 /* Do very simple cleanup now, for the benefit of code that runs between 666 here and cleanup_cfg, e.g. thread_prologue_and_epilogue_insns. */ 667 tidy_fallthru_edges (); 668 669#ifdef ENABLE_CHECKING 670 verify_flow_info (); 671#endif 672 timevar_pop (TV_CFG); 673} 674 675/* State of basic block as seen by find_sub_basic_blocks. */ 676enum state {BLOCK_NEW = 0, BLOCK_ORIGINAL, BLOCK_TO_SPLIT}; 677 678#define STATE(BB) (enum state) ((size_t) (BB)->aux) 679#define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE)) 680 681/* Scan basic block BB for possible BB boundaries inside the block 682 and create new basic blocks in the progress. */ 683 684static void 685find_bb_boundaries (bb) 686 basic_block bb; 687{ 688 rtx insn = bb->head; 689 rtx end = bb->end; 690 rtx flow_transfer_insn = NULL_RTX; 691 edge fallthru = NULL; 692 693 if (insn == bb->end) 694 return; 695 696 if (GET_CODE (insn) == CODE_LABEL) 697 insn = NEXT_INSN (insn); 698 699 /* Scan insn chain and try to find new basic block boundaries. */ 700 while (1) 701 { 702 enum rtx_code code = GET_CODE (insn); 703 704 /* On code label, split current basic block. */ 705 if (code == CODE_LABEL) 706 { 707 fallthru = split_block (bb, PREV_INSN (insn)); 708 if (flow_transfer_insn) 709 bb->end = flow_transfer_insn; 710 711 bb = fallthru->dest; 712 remove_edge (fallthru); 713 flow_transfer_insn = NULL_RTX; 714 if (LABEL_ALTERNATE_NAME (insn)) 715 make_edge (ENTRY_BLOCK_PTR, bb, 0); 716 } 717 718 /* In case we've previously seen an insn that effects a control 719 flow transfer, split the block. */ 720 if (flow_transfer_insn && inside_basic_block_p (insn)) 721 { 722 fallthru = split_block (bb, PREV_INSN (insn)); 723 bb->end = flow_transfer_insn; 724 bb = fallthru->dest; 725 remove_edge (fallthru); 726 flow_transfer_insn = NULL_RTX; 727 } 728 729 if (control_flow_insn_p (insn)) 730 flow_transfer_insn = insn; 731 if (insn == end) 732 break; 733 insn = NEXT_INSN (insn); 734 } 735 736 /* In case expander replaced normal insn by sequence terminating by 737 return and barrier, or possibly other sequence not behaving like 738 ordinary jump, we need to take care and move basic block boundary. */ 739 if (flow_transfer_insn) 740 bb->end = flow_transfer_insn; 741 742 /* We've possibly replaced the conditional jump by conditional jump 743 followed by cleanup at fallthru edge, so the outgoing edges may 744 be dead. */ 745 purge_dead_edges (bb); 746} 747 748/* Assume that frequency of basic block B is known. Compute frequencies 749 and probabilities of outgoing edges. */ 750 751static void 752compute_outgoing_frequencies (b) 753 basic_block b; 754{ 755 edge e, f; 756 757 if (b->succ && b->succ->succ_next && !b->succ->succ_next->succ_next) 758 { 759 rtx note = find_reg_note (b->end, REG_BR_PROB, NULL); 760 int probability; 761 762 if (!note) 763 return; 764 765 probability = INTVAL (XEXP (find_reg_note (b->end, 766 REG_BR_PROB, NULL), 767 0)); 768 e = BRANCH_EDGE (b); 769 e->probability = probability; 770 e->count = ((b->count * probability + REG_BR_PROB_BASE / 2) 771 / REG_BR_PROB_BASE); 772 f = FALLTHRU_EDGE (b); 773 f->probability = REG_BR_PROB_BASE - probability; 774 f->count = b->count - e->count; 775 } 776 777 if (b->succ && !b->succ->succ_next) 778 { 779 e = b->succ; 780 e->probability = REG_BR_PROB_BASE; 781 e->count = b->count; 782 } 783} 784 785/* Assume that someone emitted code with control flow instructions to the 786 basic block. Update the data structure. */ 787 788void 789find_many_sub_basic_blocks (blocks) 790 sbitmap blocks; 791{ 792 int i; 793 int min, max; 794 795 for (i = 0; i < n_basic_blocks; i++) 796 SET_STATE (BASIC_BLOCK (i), 797 TEST_BIT (blocks, i) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL); 798 799 for (i = 0; i < n_basic_blocks; i++) 800 if (STATE (BASIC_BLOCK (i)) == BLOCK_TO_SPLIT) 801 find_bb_boundaries (BASIC_BLOCK (i)); 802 803 for (i = 0; i < n_basic_blocks; i++) 804 if (STATE (BASIC_BLOCK (i)) != BLOCK_ORIGINAL) 805 break; 806 807 min = max = i; 808 for (; i < n_basic_blocks; i++) 809 if (STATE (BASIC_BLOCK (i)) != BLOCK_ORIGINAL) 810 max = i; 811 812 /* Now re-scan and wire in all edges. This expect simple (conditional) 813 jumps at the end of each new basic blocks. */ 814 make_edges (NULL, min, max, 1); 815 816 /* Update branch probabilities. Expect only (un)conditional jumps 817 to be created with only the forward edges. */ 818 for (i = min; i <= max; i++) 819 { 820 edge e; 821 basic_block b = BASIC_BLOCK (i); 822 823 if (STATE (b) == BLOCK_ORIGINAL) 824 continue; 825 if (STATE (b) == BLOCK_NEW) 826 { 827 b->count = 0; 828 b->frequency = 0; 829 for (e = b->pred; e; e=e->pred_next) 830 { 831 b->count += e->count; 832 b->frequency += EDGE_FREQUENCY (e); 833 } 834 } 835 836 compute_outgoing_frequencies (b); 837 } 838 839 for (i = 0; i < n_basic_blocks; i++) 840 SET_STATE (BASIC_BLOCK (i), 0); 841} 842 843/* Like above but for single basic block only. */ 844 845void 846find_sub_basic_blocks (bb) 847 basic_block bb; 848{ 849 int i; 850 int min, max; 851 basic_block next = (bb->index == n_basic_blocks - 1 852 ? NULL : BASIC_BLOCK (bb->index + 1)); 853 854 min = bb->index; 855 find_bb_boundaries (bb); 856 max = (next ? next->index : n_basic_blocks) - 1; 857 858 /* Now re-scan and wire in all edges. This expect simple (conditional) 859 jumps at the end of each new basic blocks. */ 860 make_edges (NULL, min, max, 1); 861 862 /* Update branch probabilities. Expect only (un)conditional jumps 863 to be created with only the forward edges. */ 864 for (i = min; i <= max; i++) 865 { 866 edge e; 867 basic_block b = BASIC_BLOCK (i); 868 869 if (i != min) 870 { 871 b->count = 0; 872 b->frequency = 0; 873 for (e = b->pred; e; e=e->pred_next) 874 { 875 b->count += e->count; 876 b->frequency += EDGE_FREQUENCY (e); 877 } 878 } 879 880 compute_outgoing_frequencies (b); 881 } 882} 883