1 /* Dead-code elimination pass for the GNU compiler. 2 Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc. 3 Written by Jeffrey D. Oldham <oldham@codesourcery.com>. 4 5 This file is part of GCC. 6 7 GCC is free software; you can redistribute it and/or modify it under 8 the terms of the GNU General Public License as published by the Free 9 Software Foundation; either version 2, or (at your option) any later 10 version. 11 12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13 WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GCC; see the file COPYING. If not, write to the Free 19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA 20 02111-1307, USA. */ 21 22 /* Dead-code elimination is the removal of instructions which have no 23 impact on the program's output. "Dead instructions" have no impact 24 on the program's output, while "necessary instructions" may have 25 impact on the output. 26 27 The algorithm consists of three phases: 28 1) marking as necessary all instructions known to be necessary, 29 e.g., writing a value to memory, 30 2) propagating necessary instructions, e.g., the instructions 31 giving values to operands in necessary instructions, and 32 3) removing dead instructions (except replacing dead conditionals 33 with unconditional jumps). 34 35 Side Effects: 36 The last step can require adding labels, deleting insns, and 37 modifying basic block structures. Some conditional jumps may be 38 converted to unconditional jumps so the control-flow graph may be 39 out-of-date. 40 41 Edges from some infinite loops to the exit block can be added to 42 the control-flow graph, but will be removed after this pass is 43 complete. 44 45 It Does Not Perform: 46 We decided to not simultaneously perform jump optimization and dead 47 loop removal during dead-code elimination. Thus, all jump 48 instructions originally present remain after dead-code elimination 49 but 1) unnecessary conditional jump instructions are changed to 50 unconditional jump instructions and 2) all unconditional jump 51 instructions remain. 52 53 Assumptions: 54 1) SSA has been performed. 55 2) The basic block and control-flow graph structures are accurate. 56 3) The flow graph permits constructing an edge_list. 57 4) note rtxes should be saved. 58 59 Unfinished: 60 When replacing unnecessary conditional jumps with unconditional 61 jumps, the control-flow graph is not updated. It should be. 62 63 References: 64 Building an Optimizing Compiler 65 Robert Morgan 66 Butterworth-Heinemann, 1998 67 Section 8.9 68 */ 69 70 #include "config.h" 71 #include "system.h" 72 73 #include "rtl.h" 74 #include "hard-reg-set.h" 75 #include "basic-block.h" 76 #include "ssa.h" 77 #include "insn-config.h" 78 #include "recog.h" 79 #include "output.h" 80 81 82 /* A map from blocks to the edges on which they are control dependent. */ 83 typedef struct { 84 /* An dynamically allocated array. The Nth element corresponds to 85 the block with index N + 2. The Ith bit in the bitmap is set if 86 that block is dependent on the Ith edge. */ 87 bitmap *data; 88 /* The number of elements in the array. */ 89 int length; 90 } control_dependent_block_to_edge_map_s, *control_dependent_block_to_edge_map; 91 92 /* Local function prototypes. */ 93 static control_dependent_block_to_edge_map control_dependent_block_to_edge_map_create 94 PARAMS((size_t num_basic_blocks)); 95 static void set_control_dependent_block_to_edge_map_bit 96 PARAMS ((control_dependent_block_to_edge_map c, basic_block bb, 97 int edge_index)); 98 static void control_dependent_block_to_edge_map_free 99 PARAMS ((control_dependent_block_to_edge_map c)); 100 static void find_all_control_dependences 101 PARAMS ((struct edge_list *el, dominance_info pdom, 102 control_dependent_block_to_edge_map cdbte)); 103 static void find_control_dependence 104 PARAMS ((struct edge_list *el, int edge_index, dominance_info pdom, 105 control_dependent_block_to_edge_map cdbte)); 106 static basic_block find_pdom 107 PARAMS ((dominance_info pdom, basic_block block)); 108 static int inherently_necessary_register_1 109 PARAMS ((rtx *current_rtx, void *data)); 110 static int inherently_necessary_register 111 PARAMS ((rtx current_rtx)); 112 static int find_inherently_necessary 113 PARAMS ((rtx current_rtx)); 114 static int propagate_necessity_through_operand 115 PARAMS ((rtx *current_rtx, void *data)); 116 static void note_inherently_necessary_set 117 PARAMS ((rtx, rtx, void *)); 118 119 /* Unnecessary insns are indicated using insns' in_struct bit. */ 120 121 /* Indicate INSN is dead-code; returns nothing. */ 122 #define KILL_INSN(INSN) INSN_DEAD_CODE_P(INSN) = 1 123 /* Indicate INSN is necessary, i.e., not dead-code; returns nothing. */ 124 #define RESURRECT_INSN(INSN) INSN_DEAD_CODE_P(INSN) = 0 125 /* Return nonzero if INSN is unnecessary. */ 126 #define UNNECESSARY_P(INSN) INSN_DEAD_CODE_P(INSN) 127 static void mark_all_insn_unnecessary 128 PARAMS ((void)); 129 /* Execute CODE with free variable INSN for all unnecessary insns in 130 an unspecified order, producing no output. */ 131 #define EXECUTE_IF_UNNECESSARY(INSN, CODE) \ 132 { \ 133 rtx INSN; \ 134 \ 135 for (INSN = get_insns (); INSN != NULL_RTX; INSN = NEXT_INSN (INSN)) \ 136 if (INSN_DEAD_CODE_P (INSN)) { \ 137 CODE; \ 138 } \ 139 } 140 /* Find the label beginning block BB. */ 141 static rtx find_block_label 142 PARAMS ((basic_block bb)); 143 /* Remove INSN, updating its basic block structure. */ 144 static void delete_insn_bb 145 PARAMS ((rtx insn)); 146 147 /* Recording which blocks are control dependent on which edges. We 148 expect each block to be control dependent on very few edges so we 149 use a bitmap for each block recording its edges. An array holds 150 the bitmap. Its position 0 entry holds the bitmap for block 151 INVALID_BLOCK+1 so that all blocks, including the entry and exit 152 blocks can participate in the data structure. */ 153 154 /* Create a control_dependent_block_to_edge_map, given the number 155 NUM_BASIC_BLOCKS of non-entry, non-exit basic blocks, e.g., 156 n_basic_blocks. This memory must be released using 157 control_dependent_block_to_edge_map_free (). */ 158 159 static control_dependent_block_to_edge_map 160 control_dependent_block_to_edge_map_create (num_basic_blocks) 161 size_t num_basic_blocks; 162 { 163 int i; 164 control_dependent_block_to_edge_map c 165 = xmalloc (sizeof (control_dependent_block_to_edge_map_s)); 166 c->length = num_basic_blocks - (INVALID_BLOCK+1); 167 c->data = xmalloc ((size_t) c->length*sizeof (bitmap)); 168 for (i = 0; i < c->length; ++i) 169 c->data[i] = BITMAP_XMALLOC (); 170 171 return c; 172 } 173 174 /* Indicate block BB is control dependent on an edge with index 175 EDGE_INDEX in the mapping C of blocks to edges on which they are 176 control-dependent. */ 177 178 static void 179 set_control_dependent_block_to_edge_map_bit (c, bb, edge_index) 180 control_dependent_block_to_edge_map c; 181 basic_block bb; 182 int edge_index; 183 { 184 if (bb->index - (INVALID_BLOCK+1) >= c->length) 185 abort (); 186 187 bitmap_set_bit (c->data[bb->index - (INVALID_BLOCK+1)], 188 edge_index); 189 } 190 191 /* Execute CODE for each edge (given number EDGE_NUMBER within the 192 CODE) for which the block containing INSN is control dependent, 193 returning no output. CDBTE is the mapping of blocks to edges on 194 which they are control-dependent. */ 195 196 #define EXECUTE_IF_CONTROL_DEPENDENT(CDBTE, INSN, EDGE_NUMBER, CODE) \ 197 EXECUTE_IF_SET_IN_BITMAP \ 198 (CDBTE->data[BLOCK_NUM (INSN) - (INVALID_BLOCK+1)], 0, \ 199 EDGE_NUMBER, CODE) 200 201 /* Destroy a control_dependent_block_to_edge_map C. */ 202 203 static void 204 control_dependent_block_to_edge_map_free (c) 205 control_dependent_block_to_edge_map c; 206 { 207 int i; 208 for (i = 0; i < c->length; ++i) 209 BITMAP_XFREE (c->data[i]); 210 free ((PTR) c); 211 } 212 213 /* Record all blocks' control dependences on all edges in the edge 214 list EL, ala Morgan, Section 3.6. The mapping PDOM of blocks to 215 their postdominators are used, and results are stored in CDBTE, 216 which should be empty. */ 217 218 static void 219 find_all_control_dependences (el, pdom, cdbte) 220 struct edge_list *el; 221 dominance_info pdom; 222 control_dependent_block_to_edge_map cdbte; 223 { 224 int i; 225 226 for (i = 0; i < NUM_EDGES (el); ++i) 227 find_control_dependence (el, i, pdom, cdbte); 228 } 229 230 /* Determine all blocks' control dependences on the given edge with 231 edge_list EL index EDGE_INDEX, ala Morgan, Section 3.6. The 232 mapping PDOM of blocks to their postdominators are used, and 233 results are stored in CDBTE, which is assumed to be initialized 234 with zeros in each (block b', edge) position. */ 235 236 static void 237 find_control_dependence (el, edge_index, pdom, cdbte) 238 struct edge_list *el; 239 int edge_index; 240 dominance_info pdom; 241 control_dependent_block_to_edge_map cdbte; 242 { 243 basic_block current_block; 244 basic_block ending_block; 245 246 if (INDEX_EDGE_PRED_BB (el, edge_index) == EXIT_BLOCK_PTR) 247 abort (); 248 ending_block = 249 (INDEX_EDGE_PRED_BB (el, edge_index) == ENTRY_BLOCK_PTR) 250 ? ENTRY_BLOCK_PTR->next_bb 251 : find_pdom (pdom, INDEX_EDGE_PRED_BB (el, edge_index)); 252 253 for (current_block = INDEX_EDGE_SUCC_BB (el, edge_index); 254 current_block != ending_block && current_block != EXIT_BLOCK_PTR; 255 current_block = find_pdom (pdom, current_block)) 256 { 257 set_control_dependent_block_to_edge_map_bit (cdbte, 258 current_block, 259 edge_index); 260 } 261 } 262 263 /* Find the immediate postdominator PDOM of the specified basic block 264 BLOCK. This function is necessary because some blocks have 265 negative numbers. */ 266 267 static basic_block 268 find_pdom (pdom, block) 269 dominance_info pdom; 270 basic_block block; 271 { 272 if (!block) 273 abort (); 274 if (block->index == INVALID_BLOCK) 275 abort (); 276 277 if (block == ENTRY_BLOCK_PTR) 278 return ENTRY_BLOCK_PTR->next_bb; 279 else if (block == EXIT_BLOCK_PTR) 280 return EXIT_BLOCK_PTR; 281 else 282 { 283 basic_block bb = get_immediate_dominator (pdom, block); 284 if (!bb) 285 return EXIT_BLOCK_PTR; 286 return bb; 287 } 288 } 289 290 /* Determine if the given CURRENT_RTX uses a hard register not 291 converted to SSA. Returns nonzero only if it uses such a hard 292 register. DATA is not used. 293 294 The program counter (PC) is not considered inherently necessary 295 since code should be position-independent and thus not depend on 296 particular PC values. */ 297 298 static int 299 inherently_necessary_register_1 (current_rtx, data) 300 rtx *current_rtx; 301 void *data ATTRIBUTE_UNUSED; 302 { 303 rtx x = *current_rtx; 304 305 if (x == NULL_RTX) 306 return 0; 307 switch (GET_CODE (x)) 308 { 309 case CLOBBER: 310 /* Do not traverse the rest of the clobber. */ 311 return -1; 312 break; 313 case PC: 314 return 0; 315 break; 316 case REG: 317 if (CONVERT_REGISTER_TO_SSA_P (REGNO (x)) || x == pc_rtx) 318 return 0; 319 else 320 return !0; 321 break; 322 default: 323 return 0; 324 break; 325 } 326 } 327 328 /* Return nonzero if the insn CURRENT_RTX is inherently necessary. */ 329 330 static int 331 inherently_necessary_register (current_rtx) 332 rtx current_rtx; 333 { 334 return for_each_rtx (¤t_rtx, 335 &inherently_necessary_register_1, NULL); 336 } 337 338 339 /* Called via note_stores for each store in an insn. Note whether 340 or not a particular store is inherently necessary. Store a 341 nonzero value in inherently_necessary_p if such a store is found. */ 342 343 static void 344 note_inherently_necessary_set (dest, set, data) 345 rtx set ATTRIBUTE_UNUSED; 346 rtx dest; 347 void *data; 348 { 349 int *inherently_necessary_set_p = (int *) data; 350 351 while (GET_CODE (dest) == SUBREG 352 || GET_CODE (dest) == STRICT_LOW_PART 353 || GET_CODE (dest) == ZERO_EXTRACT 354 || GET_CODE (dest) == SIGN_EXTRACT) 355 dest = XEXP (dest, 0); 356 357 if (GET_CODE (dest) == MEM 358 || GET_CODE (dest) == UNSPEC 359 || GET_CODE (dest) == UNSPEC_VOLATILE) 360 *inherently_necessary_set_p = 1; 361 } 362 363 /* Mark X as inherently necessary if appropriate. For example, 364 function calls and storing values into memory are inherently 365 necessary. This function is to be used with for_each_rtx (). 366 Return nonzero iff inherently necessary. */ 367 368 static int 369 find_inherently_necessary (x) 370 rtx x; 371 { 372 if (x == NULL_RTX) 373 return 0; 374 else if (inherently_necessary_register (x)) 375 return !0; 376 else 377 switch (GET_CODE (x)) 378 { 379 case CALL_INSN: 380 case BARRIER: 381 case PREFETCH: 382 return !0; 383 case CODE_LABEL: 384 case NOTE: 385 return 0; 386 case JUMP_INSN: 387 return JUMP_TABLE_DATA_P (x) || computed_jump_p (x) != 0; 388 case INSN: 389 { 390 int inherently_necessary_set = 0; 391 note_stores (PATTERN (x), 392 note_inherently_necessary_set, 393 &inherently_necessary_set); 394 395 /* If we found an inherently necessary set or an asm 396 instruction, then we consider this insn inherently 397 necessary. */ 398 return (inherently_necessary_set 399 || GET_CODE (PATTERN (x)) == ASM_INPUT 400 || asm_noperands (PATTERN (x)) >= 0); 401 } 402 default: 403 /* Found an impossible insn type. */ 404 abort (); 405 break; 406 } 407 } 408 409 /* Propagate necessity through REG and SUBREG operands of CURRENT_RTX. 410 This function is called with for_each_rtx () on necessary 411 instructions. The DATA must be a varray of unprocessed 412 instructions. */ 413 414 static int 415 propagate_necessity_through_operand (current_rtx, data) 416 rtx *current_rtx; 417 void *data; 418 { 419 rtx x = *current_rtx; 420 varray_type *unprocessed_instructions = (varray_type *) data; 421 422 if (x == NULL_RTX) 423 return 0; 424 switch ( GET_CODE (x)) 425 { 426 case REG: 427 if (CONVERT_REGISTER_TO_SSA_P (REGNO (x))) 428 { 429 rtx insn = VARRAY_RTX (ssa_definition, REGNO (x)); 430 if (insn != NULL_RTX && UNNECESSARY_P (insn)) 431 { 432 RESURRECT_INSN (insn); 433 VARRAY_PUSH_RTX (*unprocessed_instructions, insn); 434 } 435 } 436 return 0; 437 438 default: 439 return 0; 440 } 441 } 442 443 /* Indicate all insns initially assumed to be unnecessary. */ 444 445 static void 446 mark_all_insn_unnecessary () 447 { 448 rtx insn; 449 for (insn = get_insns (); insn != NULL_RTX; insn = NEXT_INSN (insn)) 450 KILL_INSN (insn); 451 } 452 453 /* Find the label beginning block BB, adding one if necessary. */ 454 455 static rtx 456 find_block_label (bb) 457 basic_block bb; 458 { 459 rtx insn = bb->head; 460 if (LABEL_P (insn)) 461 return insn; 462 else 463 { 464 rtx new_label = emit_label_before (gen_label_rtx (), insn); 465 if (insn == bb->head) 466 bb->head = new_label; 467 return new_label; 468 } 469 } 470 471 /* Remove INSN, updating its basic block structure. */ 472 473 static void 474 delete_insn_bb (insn) 475 rtx insn; 476 { 477 if (!insn) 478 abort (); 479 480 /* Do not actually delete anything that is not an INSN. 481 482 We can get here because we only consider INSNs as 483 potentially necessary. We leave it to later passes 484 to remove unnecessary notes, unused labels, etc. */ 485 if (! INSN_P (insn)) 486 return; 487 488 delete_insn (insn); 489 } 490 491 /* Perform the dead-code elimination. */ 492 493 void 494 ssa_eliminate_dead_code () 495 { 496 rtx insn; 497 basic_block bb; 498 /* Necessary instructions with operands to explore. */ 499 varray_type unprocessed_instructions; 500 /* Map element (b,e) is nonzero if the block is control dependent on 501 edge. "cdbte" abbreviates control dependent block to edge. */ 502 control_dependent_block_to_edge_map cdbte; 503 /* Element I is the immediate postdominator of block I. */ 504 dominance_info pdom; 505 struct edge_list *el; 506 507 /* Initialize the data structures. */ 508 mark_all_insn_unnecessary (); 509 VARRAY_RTX_INIT (unprocessed_instructions, 64, 510 "unprocessed instructions"); 511 cdbte = control_dependent_block_to_edge_map_create (last_basic_block); 512 513 /* Prepare for use of BLOCK_NUM (). */ 514 connect_infinite_loops_to_exit (); 515 516 /* Compute control dependence. */ 517 pdom = calculate_dominance_info (CDI_POST_DOMINATORS); 518 el = create_edge_list (); 519 find_all_control_dependences (el, pdom, cdbte); 520 521 /* Find inherently necessary instructions. */ 522 for (insn = get_insns (); insn != NULL_RTX; insn = NEXT_INSN (insn)) 523 if (find_inherently_necessary (insn)) 524 { 525 RESURRECT_INSN (insn); 526 VARRAY_PUSH_RTX (unprocessed_instructions, insn); 527 } 528 529 /* Propagate necessity using the operands of necessary instructions. */ 530 while (VARRAY_ACTIVE_SIZE (unprocessed_instructions) > 0) 531 { 532 rtx current_instruction; 533 int edge_number; 534 535 current_instruction = VARRAY_TOP_RTX (unprocessed_instructions); 536 VARRAY_POP (unprocessed_instructions); 537 538 /* Make corresponding control dependent edges necessary. */ 539 /* Assume the only JUMP_INSN is the block's last insn. It appears 540 that the last instruction of the program need not be a 541 JUMP_INSN. */ 542 543 if (INSN_P (current_instruction) 544 && !JUMP_TABLE_DATA_P (current_instruction)) 545 { 546 /* Notes and labels contain no interesting operands. */ 547 EXECUTE_IF_CONTROL_DEPENDENT 548 (cdbte, current_instruction, edge_number, 549 { 550 rtx jump_insn = (INDEX_EDGE_PRED_BB (el, edge_number))->end; 551 if (GET_CODE (jump_insn) == JUMP_INSN 552 && UNNECESSARY_P (jump_insn)) 553 { 554 RESURRECT_INSN (jump_insn); 555 VARRAY_PUSH_RTX (unprocessed_instructions, jump_insn); 556 } 557 }); 558 559 /* Propagate through the operands. */ 560 for_each_rtx (¤t_instruction, 561 &propagate_necessity_through_operand, 562 (PTR) &unprocessed_instructions); 563 564 /* PHI nodes are somewhat special in that each PHI alternative 565 has data and control dependencies. The data dependencies 566 are handled via propagate_necessity_through_operand. We 567 handle the control dependency here. 568 569 We consider the control dependent edges leading to the 570 predecessor block associated with each PHI alternative 571 as necessary. */ 572 if (PHI_NODE_P (current_instruction)) 573 { 574 rtvec phi_vec = XVEC (SET_SRC (PATTERN (current_instruction)), 0); 575 int num_elem = GET_NUM_ELEM (phi_vec); 576 int v; 577 578 for (v = num_elem - 2; v >= 0; v -= 2) 579 { 580 basic_block bb; 581 582 bb = BASIC_BLOCK (INTVAL (RTVEC_ELT (phi_vec, v + 1))); 583 EXECUTE_IF_CONTROL_DEPENDENT 584 (cdbte, bb->end, edge_number, 585 { 586 rtx jump_insn; 587 588 jump_insn = (INDEX_EDGE_PRED_BB (el, edge_number))->end; 589 if (((GET_CODE (jump_insn) == JUMP_INSN)) 590 && UNNECESSARY_P (jump_insn)) 591 { 592 RESURRECT_INSN (jump_insn); 593 VARRAY_PUSH_RTX (unprocessed_instructions, jump_insn); 594 } 595 }); 596 597 } 598 } 599 } 600 } 601 602 /* Remove the unnecessary instructions. */ 603 EXECUTE_IF_UNNECESSARY (insn, 604 { 605 if (any_condjump_p (insn)) 606 { 607 basic_block bb = BLOCK_FOR_INSN (insn); 608 basic_block pdom_bb = find_pdom (pdom, bb); 609 rtx lbl; 610 edge e; 611 612 /* Egad. The immediate post dominator is the exit block. We 613 would like to optimize this conditional jump to jump directly 614 to the exit block. That can be difficult as we may not have 615 a suitable CODE_LABEL that allows us to fall unmolested into 616 the exit block. 617 618 So, we just delete the conditional branch by turning it into 619 a deleted note. That is safe, but just not as optimal as 620 it could be. */ 621 if (pdom_bb == EXIT_BLOCK_PTR) 622 { 623 /* Since we're going to just delete the branch, we need 624 look at all the edges and remove all those which are not 625 a fallthru edge. */ 626 e = bb->succ; 627 while (e) 628 { 629 edge temp = e; 630 631 e = e->succ_next; 632 if ((temp->flags & EDGE_FALLTHRU) == 0) 633 { 634 /* We've found a non-fallthru edge, find any PHI nodes 635 at the target and clean them up. */ 636 if (temp->dest != EXIT_BLOCK_PTR) 637 { 638 rtx insn 639 = first_insn_after_basic_block_note (temp->dest); 640 641 while (PHI_NODE_P (insn)) 642 { 643 remove_phi_alternative (PATTERN (insn), temp->src); 644 insn = NEXT_INSN (insn); 645 } 646 } 647 648 remove_edge (temp); 649 } 650 } 651 652 /* Now "delete" the conditional jump. */ 653 PUT_CODE (insn, NOTE); 654 NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED; 655 continue; 656 } 657 658 /* We've found a conditional branch that is unnecessary. 659 660 First, remove all outgoing edges from this block, updating 661 PHI nodes as appropriate. */ 662 e = bb->succ; 663 while (e) 664 { 665 edge temp = e; 666 667 e = e->succ_next; 668 669 if (temp->flags & EDGE_ABNORMAL) 670 continue; 671 672 /* We found an edge that is not executable. First simplify 673 the PHI nodes in the target block. */ 674 if (temp->dest != EXIT_BLOCK_PTR) 675 { 676 rtx insn = first_insn_after_basic_block_note (temp->dest); 677 678 while (PHI_NODE_P (insn)) 679 { 680 remove_phi_alternative (PATTERN (insn), temp->src); 681 insn = NEXT_INSN (insn); 682 } 683 } 684 685 remove_edge (temp); 686 } 687 688 /* Create an edge from this block to the post dominator. 689 What about the PHI nodes at the target? */ 690 make_edge (bb, pdom_bb, 0); 691 692 /* Third, transform this insn into an unconditional 693 jump to the label for the immediate postdominator. */ 694 lbl = find_block_label (pdom_bb); 695 SET_SRC (PATTERN (insn)) = gen_rtx_LABEL_REF (VOIDmode, lbl); 696 INSN_CODE (insn) = -1; 697 JUMP_LABEL (insn) = lbl; 698 LABEL_NUSES (lbl)++; 699 700 /* A barrier must follow any unconditional jump. Barriers 701 are not in basic blocks so this must occur after 702 deleting the conditional jump. */ 703 emit_barrier_after (insn); 704 } 705 else if (!JUMP_P (insn)) 706 delete_insn_bb (insn); 707 }); 708 709 /* Remove fake edges from the CFG. */ 710 remove_fake_edges (); 711 712 /* Find any blocks with no successors and ensure they are followed 713 by a BARRIER. delete_insn has the nasty habit of deleting barriers 714 when deleting insns. */ 715 FOR_EACH_BB (bb) 716 { 717 if (bb->succ == NULL) 718 { 719 rtx next = NEXT_INSN (bb->end); 720 721 if (!next || GET_CODE (next) != BARRIER) 722 emit_barrier_after (bb->end); 723 } 724 } 725 /* Release allocated memory. */ 726 for (insn = get_insns (); insn != NULL_RTX; insn = NEXT_INSN (insn)) 727 RESURRECT_INSN (insn); 728 if (VARRAY_ACTIVE_SIZE (unprocessed_instructions) != 0) 729 abort (); 730 control_dependent_block_to_edge_map_free (cdbte); 731 free ((PTR) pdom); 732 free_edge_list (el); 733 } 734