gcc/gimple-iterator.c

   1 /* Iterator routines for GIMPLE statements.
   2    Copyright (C) 2007-2013 Free Software Foundation, Inc.
   3    Contributed by Aldy Hernandez  <aldy@quesejoda.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 3, 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 COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tm.h"
  25 #include "tree.h"
  26 #include "gimple.h"
  27 #include "gimple-iterator.h"
  28 #include "gimple-ssa.h"
  29 #include "cgraph.h"
  30 #include "tree-cfg.h"
  31 #include "tree-phinodes.h"
  32 #include "ssa-iterators.h"
  33 #include "tree-ssa.h"
  34 #include "value-prof.h"
  35
  36
  37 /* Mark the statement STMT as modified, and update it.  */
  38
  39 static inline void
  40 update_modified_stmt (gimple stmt)
  41 {
  42   if (!ssa_operands_active (cfun))
  43     return;
  44   update_stmt_if_modified (stmt);
  45 }
  46
  47
  48 /* Mark the statements in SEQ as modified, and update them.  */
  49
  50 static void
  51 update_modified_stmts (gimple_seq seq)
  52 {
  53   gimple_stmt_iterator gsi;
  54
  55   if (!ssa_operands_active (cfun))
  56     return;
  57   for (gsi = gsi_start (seq); !gsi_end_p (gsi); gsi_next (&gsi))
  58     update_stmt_if_modified (gsi_stmt (gsi));
  59 }
  60
  61
  62 /* Set BB to be the basic block for all the statements in the list
  63    starting at FIRST and LAST.  */
  64
  65 static void
  66 update_bb_for_stmts (gimple_seq_node first, gimple_seq_node last,
  67                      basic_block bb)
  68 {
  69   gimple_seq_node n;
  70
  71   for (n = first; n; n = n->next)
  72     {
  73       gimple_set_bb (n, bb);
  74       if (n == last)
  75         break;
  76     }
  77 }
  78
  79 /* Set the frequencies for the cgraph_edges for each of the calls
  80    starting at FIRST for their new position within BB.  */
  81
  82 static void
  83 update_call_edge_frequencies (gimple_seq_node first, basic_block bb)
  84 {
  85   struct cgraph_node *cfun_node = NULL;
  86   int bb_freq = 0;
  87   gimple_seq_node n;
  88
  89   for (n = first; n ; n = n->next)
  90     if (is_gimple_call (n))
  91       {
  92         struct cgraph_edge *e;
  93
  94         /* These function calls are expensive enough that we want
  95            to avoid calling them if we never see any calls.  */
  96         if (cfun_node == NULL)
  97           {
  98             cfun_node = cgraph_get_node (current_function_decl);
  99             bb_freq = (compute_call_stmt_bb_frequency
 100                        (current_function_decl, bb));
 101           }
 102
 103         e = cgraph_edge (cfun_node, n);
 104         if (e != NULL)
 105           e->frequency = bb_freq;
 106       }
 107 }
 108
 109 /* Insert the sequence delimited by nodes FIRST and LAST before
 110    iterator I.  M specifies how to update iterator I after insertion
 111    (see enum gsi_iterator_update).
 112
 113    This routine assumes that there is a forward and backward path
 114    between FIRST and LAST (i.e., they are linked in a doubly-linked
 115    list).  Additionally, if FIRST == LAST, this routine will properly
 116    insert a single node.  */
 117
 118 static void
 119 gsi_insert_seq_nodes_before (gimple_stmt_iterator *i,
 120                              gimple_seq_node first,
 121                              gimple_seq_node last,
 122                              enum gsi_iterator_update mode)
 123 {
 124   basic_block bb;
 125   gimple_seq_node cur = i->ptr;
 126
 127   gcc_assert (!cur || cur->prev);
 128
 129   if ((bb = gsi_bb (*i)) != NULL)
 130     update_bb_for_stmts (first, last, bb);
 131
 132   /* Link SEQ before CUR in the sequence.  */
 133   if (cur)
 134     {
 135       first->prev = cur->prev;
 136       if (first->prev->next)
 137         first->prev->next = first;
 138       else
 139         gimple_seq_set_first (i->seq, first);
 140       last->next = cur;
 141       cur->prev = last;
 142     }
 143   else
 144     {
 145       gimple_seq_node itlast = gimple_seq_last (*i->seq);
 146
 147       /* If CUR is NULL, we link at the end of the sequence (this case happens
 148          when gsi_after_labels is called for a basic block that contains only
 149          labels, so it returns an iterator after the end of the block, and
 150          we need to insert before it; it might be cleaner to add a flag to the
 151          iterator saying whether we are at the start or end of the list).  */
 152       last->next = NULL;
 153       if (itlast)
 154         {
 155           first->prev = itlast;
 156           itlast->next = first;
 157         }
 158       else
 159         gimple_seq_set_first (i->seq, first);
 160       gimple_seq_set_last (i->seq, last);
 161     }
 162
 163   /* Update the iterator, if requested.  */
 164   switch (mode)
 165     {
 166     case GSI_NEW_STMT:
 167     case GSI_CONTINUE_LINKING:
 168       i->ptr = first;
 169       break;
 170     case GSI_SAME_STMT:
 171       break;
 172     default:
 173       gcc_unreachable ();
 174     }
 175 }
 176
 177
 178 /* Inserts the sequence of statements SEQ before the statement pointed
 179    by iterator I.  MODE indicates what to do with the iterator after
 180    insertion (see enum gsi_iterator_update).
 181
 182    This function does not scan for new operands.  It is provided for
 183    the use of the gimplifier, which manipulates statements for which
 184    def/use information has not yet been constructed.  Most callers
 185    should use gsi_insert_seq_before.  */
 186
 187 void
 188 gsi_insert_seq_before_without_update (gimple_stmt_iterator *i, gimple_seq seq,
 189                                       enum gsi_iterator_update mode)
 190 {
 191   gimple_seq_node first, last;
 192
 193   if (seq == NULL)
 194     return;
 195
 196   /* Don't allow inserting a sequence into itself.  */
 197   gcc_assert (seq != *i->seq);
 198
 199   first = gimple_seq_first (seq);
 200   last = gimple_seq_last (seq);
 201
 202   /* Empty sequences need no work.  */
 203   if (!first || !last)
 204     {
 205       gcc_assert (first == last);
 206       return;
 207     }
 208
 209   gsi_insert_seq_nodes_before (i, first, last, mode);
 210 }
 211
 212
 213 /* Inserts the sequence of statements SEQ before the statement pointed
 214    by iterator I.  MODE indicates what to do with the iterator after
 215    insertion (see enum gsi_iterator_update). Scan the statements in SEQ
 216    for new operands.  */
 217
 218 void
 219 gsi_insert_seq_before (gimple_stmt_iterator *i, gimple_seq seq,
 220                        enum gsi_iterator_update mode)
 221 {
 222   update_modified_stmts (seq);
 223   gsi_insert_seq_before_without_update (i, seq, mode);
 224 }
 225
 226
 227 /* Insert the sequence delimited by nodes FIRST and LAST after
 228    iterator I.  M specifies how to update iterator I after insertion
 229    (see enum gsi_iterator_update).
 230
 231    This routine assumes that there is a forward and backward path
 232    between FIRST and LAST (i.e., they are linked in a doubly-linked
 233    list).  Additionally, if FIRST == LAST, this routine will properly
 234    insert a single node.  */
 235
 236 static void
 237 gsi_insert_seq_nodes_after (gimple_stmt_iterator *i,
 238                             gimple_seq_node first,
 239                             gimple_seq_node last,
 240                             enum gsi_iterator_update m)
 241 {
 242   basic_block bb;
 243   gimple_seq_node cur = i->ptr;
 244
 245   gcc_assert (!cur || cur->prev);
 246
 247   /* If the iterator is inside a basic block, we need to update the
 248      basic block information for all the nodes between FIRST and LAST.  */
 249   if ((bb = gsi_bb (*i)) != NULL)
 250     update_bb_for_stmts (first, last, bb);
 251
 252   /* Link SEQ after CUR.  */
 253   if (cur)
 254     {
 255       last->next = cur->next;
 256       if (last->next)
 257         {
 258           last->next->prev = last;
 259         }
 260       else
 261         gimple_seq_set_last (i->seq, last);
 262       first->prev = cur;
 263       cur->next = first;
 264     }
 265   else
 266     {
 267       gcc_assert (!gimple_seq_last (*i->seq));
 268       last->next = NULL;
 269       gimple_seq_set_first (i->seq, first);
 270       gimple_seq_set_last (i->seq, last);
 271     }
 272
 273   /* Update the iterator, if requested.  */
 274   switch (m)
 275     {
 276     case GSI_NEW_STMT:
 277       i->ptr = first;
 278       break;
 279     case GSI_CONTINUE_LINKING:
 280       i->ptr = last;
 281       break;
 282     case GSI_SAME_STMT:
 283       gcc_assert (cur);
 284       break;
 285     default:
 286       gcc_unreachable ();
 287     }
 288 }
 289
 290
 291 /* Links sequence SEQ after the statement pointed-to by iterator I.
 292    MODE is as in gsi_insert_after.
 293
 294    This function does not scan for new operands.  It is provided for
 295    the use of the gimplifier, which manipulates statements for which
 296    def/use information has not yet been constructed.  Most callers
 297    should use gsi_insert_seq_after.  */
 298
 299 void
 300 gsi_insert_seq_after_without_update (gimple_stmt_iterator *i, gimple_seq seq,
 301                                      enum gsi_iterator_update mode)
 302 {
 303   gimple_seq_node first, last;
 304
 305   if (seq == NULL)
 306     return;
 307
 308   /* Don't allow inserting a sequence into itself.  */
 309   gcc_assert (seq != *i->seq);
 310
 311   first = gimple_seq_first (seq);
 312   last = gimple_seq_last (seq);
 313
 314   /* Empty sequences need no work.  */
 315   if (!first || !last)
 316     {
 317       gcc_assert (first == last);
 318       return;
 319     }
 320
 321   gsi_insert_seq_nodes_after (i, first, last, mode);
 322 }
 323
 324
 325 /* Links sequence SEQ after the statement pointed-to by iterator I.
 326    MODE is as in gsi_insert_after.  Scan the statements in SEQ
 327    for new operands.  */
 328
 329 void
 330 gsi_insert_seq_after (gimple_stmt_iterator *i, gimple_seq seq,
 331                       enum gsi_iterator_update mode)
 332 {
 333   update_modified_stmts (seq);
 334   gsi_insert_seq_after_without_update (i, seq, mode);
 335 }
 336
 337
 338 /* Move all statements in the sequence after I to a new sequence.
 339    Return this new sequence.  */
 340
 341 gimple_seq
 342 gsi_split_seq_after (gimple_stmt_iterator i)
 343 {
 344   gimple_seq_node cur, next;
 345   gimple_seq *pold_seq, new_seq;
 346
 347   cur = i.ptr;
 348
 349   /* How can we possibly split after the end, or before the beginning?  */
 350   gcc_assert (cur && cur->next);
 351   next = cur->next;
 352
 353   pold_seq = i.seq;
 354
 355   gimple_seq_set_first (&new_seq, next);
 356   gimple_seq_set_last (&new_seq, gimple_seq_last (*pold_seq));
 357   gimple_seq_set_last (pold_seq, cur);
 358   cur->next = NULL;
 359
 360   return new_seq;
 361 }
 362
 363
 364 /* Set the statement to which GSI points to STMT.  This only updates
 365    the iterator and the gimple sequence, it doesn't do the bookkeeping
 366    of gsi_replace.  */
 367
 368 void
 369 gsi_set_stmt (gimple_stmt_iterator *gsi, gimple stmt)
 370 {
 371   gimple orig_stmt = gsi_stmt (*gsi);
 372   gimple prev, next;
 373
 374   stmt->next = next = orig_stmt->next;
 375   stmt->prev = prev = orig_stmt->prev;
 376   /* Note how we don't clear next/prev of orig_stmt.  This is so that
 377      copies of *GSI our callers might still hold (to orig_stmt)
 378      can be advanced as if they too were replaced.  */
 379   if (prev->next)
 380     prev->next = stmt;
 381   else
 382     gimple_seq_set_first (gsi->seq, stmt);
 383   if (next)
 384     next->prev = stmt;
 385   else
 386     gimple_seq_set_last (gsi->seq, stmt);
 387
 388   gsi->ptr = stmt;
 389 }
 390
 391
 392 /* Move all statements in the sequence before I to a new sequence.
 393    Return this new sequence.  I is set to the head of the new list.  */
 394
 395 void
 396 gsi_split_seq_before (gimple_stmt_iterator *i, gimple_seq *pnew_seq)
 397 {
 398   gimple_seq_node cur, prev;
 399   gimple_seq old_seq;
 400
 401   cur = i->ptr;
 402
 403   /* How can we possibly split after the end?  */
 404   gcc_assert (cur);
 405   prev = cur->prev;
 406
 407   old_seq = *i->seq;
 408   if (!prev->next)
 409     *i->seq = NULL;
 410   i->seq = pnew_seq;
 411
 412   /* Set the limits on NEW_SEQ.  */
 413   gimple_seq_set_first (pnew_seq, cur);
 414   gimple_seq_set_last (pnew_seq, gimple_seq_last (old_seq));
 415
 416   /* Cut OLD_SEQ before I.  */
 417   gimple_seq_set_last (&old_seq, prev);
 418   if (prev->next)
 419     prev->next = NULL;
 420 }
 421
 422
 423 /* Replace the statement pointed-to by GSI to STMT.  If UPDATE_EH_INFO
 424    is true, the exception handling information of the original
 425    statement is moved to the new statement.  Assignments must only be
 426    replaced with assignments to the same LHS.  */
 427
 428 void
 429 gsi_replace (gimple_stmt_iterator *gsi, gimple stmt, bool update_eh_info)
 430 {
 431   gimple orig_stmt = gsi_stmt (*gsi);
 432
 433   if (stmt == orig_stmt)
 434     return;
 435
 436   gcc_assert (!gimple_has_lhs (orig_stmt) || !gimple_has_lhs (stmt)
 437               || gimple_get_lhs (orig_stmt) == gimple_get_lhs (stmt));
 438
 439   gimple_set_location (stmt, gimple_location (orig_stmt));
 440   gimple_set_bb (stmt, gsi_bb (*gsi));
 441
 442   /* Preserve EH region information from the original statement, if
 443      requested by the caller.  */
 444   if (update_eh_info)
 445     maybe_clean_or_replace_eh_stmt (orig_stmt, stmt);
 446
 447   gimple_duplicate_stmt_histograms (cfun, stmt, cfun, orig_stmt);
 448
 449   /* Free all the data flow information for ORIG_STMT.  */
 450   gimple_set_bb (orig_stmt, NULL);
 451   gimple_remove_stmt_histograms (cfun, orig_stmt);
 452   delink_stmt_imm_use (orig_stmt);
 453
 454   gsi_set_stmt (gsi, stmt);
 455   gimple_set_modified (stmt, true);
 456   update_modified_stmt (stmt);
 457 }
 458
 459
 460 /* Replace the statement pointed-to by GSI with the sequence SEQ.
 461    If UPDATE_EH_INFO is true, the exception handling information of
 462    the original statement is moved to the last statement of the new
 463    sequence.  If the old statement is an assignment, then so must
 464    be the last statement of the new sequence, and they must have the
 465    same LHS.  */
 466
 467 void
 468 gsi_replace_with_seq (gimple_stmt_iterator *gsi, gimple_seq seq,
 469                       bool update_eh_info)
 470 {
 471   gimple_stmt_iterator seqi;
 472   gimple last;
 473   if (gimple_seq_empty_p (seq))
 474     {
 475       gsi_remove (gsi, true);
 476       return;
 477     }
 478   seqi = gsi_last (seq);
 479   last = gsi_stmt (seqi);
 480   gsi_remove (&seqi, false);
 481   gsi_insert_seq_before (gsi, seq, GSI_SAME_STMT);
 482   gsi_replace (gsi, last, update_eh_info);
 483 }
 484
 485
 486 /* Insert statement STMT before the statement pointed-to by iterator I.
 487    M specifies how to update iterator I after insertion (see enum
 488    gsi_iterator_update).
 489
 490    This function does not scan for new operands.  It is provided for
 491    the use of the gimplifier, which manipulates statements for which
 492    def/use information has not yet been constructed.  Most callers
 493    should use gsi_insert_before.  */
 494
 495 void
 496 gsi_insert_before_without_update (gimple_stmt_iterator *i, gimple stmt,
 497                                   enum gsi_iterator_update m)
 498 {
 499   gsi_insert_seq_nodes_before (i, stmt, stmt, m);
 500 }
 501
 502 /* Insert statement STMT before the statement pointed-to by iterator I.
 503    Update STMT's basic block and scan it for new operands.  M
 504    specifies how to update iterator I after insertion (see enum
 505    gsi_iterator_update).  */
 506
 507 void
 508 gsi_insert_before (gimple_stmt_iterator *i, gimple stmt,
 509                    enum gsi_iterator_update m)
 510 {
 511   update_modified_stmt (stmt);
 512   gsi_insert_before_without_update (i, stmt, m);
 513 }
 514
 515
 516 /* Insert statement STMT after the statement pointed-to by iterator I.
 517    M specifies how to update iterator I after insertion (see enum
 518    gsi_iterator_update).
 519
 520    This function does not scan for new operands.  It is provided for
 521    the use of the gimplifier, which manipulates statements for which
 522    def/use information has not yet been constructed.  Most callers
 523    should use gsi_insert_after.  */
 524
 525 void
 526 gsi_insert_after_without_update (gimple_stmt_iterator *i, gimple stmt,
 527                                  enum gsi_iterator_update m)
 528 {
 529   gsi_insert_seq_nodes_after (i, stmt, stmt, m);
 530 }
 531
 532
 533 /* Insert statement STMT after the statement pointed-to by iterator I.
 534    Update STMT's basic block and scan it for new operands.  M
 535    specifies how to update iterator I after insertion (see enum
 536    gsi_iterator_update).  */
 537
 538 void
 539 gsi_insert_after (gimple_stmt_iterator *i, gimple stmt,
 540                   enum gsi_iterator_update m)
 541 {
 542   update_modified_stmt (stmt);
 543   gsi_insert_after_without_update (i, stmt, m);
 544 }
 545
 546
 547 /* Remove the current stmt from the sequence.  The iterator is updated
 548    to point to the next statement.
 549
 550    REMOVE_PERMANENTLY is true when the statement is going to be removed
 551    from the IL and not reinserted elsewhere.  In that case we remove the
 552    statement pointed to by iterator I from the EH tables, and free its
 553    operand caches.  Otherwise we do not modify this information.  Returns
 554    true whether EH edge cleanup is required.  */
 555
 556 bool
 557 gsi_remove (gimple_stmt_iterator *i, bool remove_permanently)
 558 {
 559   gimple_seq_node cur, next, prev;
 560   gimple stmt = gsi_stmt (*i);
 561   bool require_eh_edge_purge = false;
 562
 563   if (gimple_code (stmt) != GIMPLE_PHI)
 564     insert_debug_temps_for_defs (i);
 565
 566   /* Free all the data flow information for STMT.  */
 567   gimple_set_bb (stmt, NULL);
 568   delink_stmt_imm_use (stmt);
 569   gimple_set_modified (stmt, true);
 570
 571   if (remove_permanently)
 572     {
 573       require_eh_edge_purge = remove_stmt_from_eh_lp (stmt);
 574       gimple_remove_stmt_histograms (cfun, stmt);
 575     }
 576
 577   /* Update the iterator and re-wire the links in I->SEQ.  */
 578   cur = i->ptr;
 579   next = cur->next;
 580   prev = cur->prev;
 581   /* See gsi_set_stmt for why we don't reset prev/next of STMT.  */
 582
 583   if (next)
 584     /* Cur is not last.  */
 585     next->prev = prev;
 586   else if (prev->next)
 587     /* Cur is last but not first.  */
 588     gimple_seq_set_last (i->seq, prev);
 589
 590   if (prev->next)
 591     /* Cur is not first.  */
 592     prev->next = next;
 593   else
 594     /* Cur is first.  */
 595     *i->seq = next;
 596
 597   i->ptr = next;
 598
 599   return require_eh_edge_purge;
 600 }
 601
 602
 603 /* Finds iterator for STMT.  */
 604
 605 gimple_stmt_iterator
 606 gsi_for_stmt (gimple stmt)
 607 {
 608   gimple_stmt_iterator i;
 609   basic_block bb = gimple_bb (stmt);
 610
 611   if (gimple_code (stmt) == GIMPLE_PHI)
 612     i = gsi_start_phis (bb);
 613   else
 614     i = gsi_start_bb (bb);
 615
 616   i.ptr = stmt;
 617   return i;
 618 }
 619
 620
 621 /* Move the statement at FROM so it comes right after the statement at TO.  */
 622
 623 void
 624 gsi_move_after (gimple_stmt_iterator *from, gimple_stmt_iterator *to)
 625 {
 626   gimple stmt = gsi_stmt (*from);
 627   gsi_remove (from, false);
 628
 629   /* We must have GSI_NEW_STMT here, as gsi_move_after is sometimes used to
 630      move statements to an empty block.  */
 631   gsi_insert_after (to, stmt, GSI_NEW_STMT);
 632 }
 633
 634
 635 /* Move the statement at FROM so it comes right before the statement
 636    at TO.  */
 637
 638 void
 639 gsi_move_before (gimple_stmt_iterator *from, gimple_stmt_iterator *to)
 640 {
 641   gimple stmt = gsi_stmt (*from);
 642   gsi_remove (from, false);
 643
 644   /* For consistency with gsi_move_after, it might be better to have
 645      GSI_NEW_STMT here; however, that breaks several places that expect
 646      that TO does not change.  */
 647   gsi_insert_before (to, stmt, GSI_SAME_STMT);
 648 }
 649
 650
 651 /* Move the statement at FROM to the end of basic block BB.  */
 652
 653 void
 654 gsi_move_to_bb_end (gimple_stmt_iterator *from, basic_block bb)
 655 {
 656   gimple_stmt_iterator last = gsi_last_bb (bb);
 657   gcc_checking_assert (gsi_bb (last) == bb);
 658
 659   /* Have to check gsi_end_p because it could be an empty block.  */
 660   if (!gsi_end_p (last) && is_ctrl_stmt (gsi_stmt (last)))
 661     gsi_move_before (from, &last);
 662   else
 663     gsi_move_after (from, &last);
 664 }
 665
 666
 667 /* Add STMT to the pending list of edge E.  No actual insertion is
 668    made until a call to gsi_commit_edge_inserts () is made.  */
 669
 670 void
 671 gsi_insert_on_edge (edge e, gimple stmt)
 672 {
 673   gimple_seq_add_stmt (&PENDING_STMT (e), stmt);
 674 }
 675
 676 /* Add the sequence of statements SEQ to the pending list of edge E.
 677    No actual insertion is made until a call to gsi_commit_edge_inserts
 678    is made.  */
 679
 680 void
 681 gsi_insert_seq_on_edge (edge e, gimple_seq seq)
 682 {
 683   gimple_seq_add_seq (&PENDING_STMT (e), seq);
 684 }
 685
 686
 687 /* Insert the statement pointed-to by GSI into edge E.  Every attempt
 688    is made to place the statement in an existing basic block, but
 689    sometimes that isn't possible.  When it isn't possible, the edge is
 690    split and the statement is added to the new block.
 691
 692    In all cases, the returned *GSI points to the correct location.  The
 693    return value is true if insertion should be done after the location,
 694    or false if it should be done before the location.  If a new basic block
 695    has to be created, it is stored in *NEW_BB.  */
 696
 697 static bool
 698 gimple_find_edge_insert_loc (edge e, gimple_stmt_iterator *gsi,
 699                              basic_block *new_bb)
 700 {
 701   basic_block dest, src;
 702   gimple tmp;
 703
 704   dest = e->dest;
 705
 706   /* If the destination has one predecessor which has no PHI nodes,
 707      insert there.  Except for the exit block.
 708
 709      The requirement for no PHI nodes could be relaxed.  Basically we
 710      would have to examine the PHIs to prove that none of them used
 711      the value set by the statement we want to insert on E.  That
 712      hardly seems worth the effort.  */
 713  restart:
 714   if (single_pred_p (dest)
 715       && gimple_seq_empty_p (phi_nodes (dest))
 716       && dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
 717     {
 718       *gsi = gsi_start_bb (dest);
 719       if (gsi_end_p (*gsi))
 720         return true;
 721
 722       /* Make sure we insert after any leading labels.  */
 723       tmp = gsi_stmt (*gsi);
 724       while (gimple_code (tmp) == GIMPLE_LABEL)
 725         {
 726           gsi_next (gsi);
 727           if (gsi_end_p (*gsi))
 728             break;
 729           tmp = gsi_stmt (*gsi);
 730         }
 731
 732       if (gsi_end_p (*gsi))
 733         {
 734           *gsi = gsi_last_bb (dest);
 735           return true;
 736         }
 737       else
 738         return false;
 739     }
 740
 741   /* If the source has one successor, the edge is not abnormal and
 742      the last statement does not end a basic block, insert there.
 743      Except for the entry block.  */
 744   src = e->src;
 745   if ((e->flags & EDGE_ABNORMAL) == 0
 746       && single_succ_p (src)
 747       && src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
 748     {
 749       *gsi = gsi_last_bb (src);
 750       if (gsi_end_p (*gsi))
 751         return true;
 752
 753       tmp = gsi_stmt (*gsi);
 754       if (!stmt_ends_bb_p (tmp))
 755         return true;
 756
 757       switch (gimple_code (tmp))
 758         {
 759         case GIMPLE_RETURN:
 760         case GIMPLE_RESX:
 761           return false;
 762         default:
 763           break;
 764         }
 765     }
 766
 767   /* Otherwise, create a new basic block, and split this edge.  */
 768   dest = split_edge (e);
 769   if (new_bb)
 770     *new_bb = dest;
 771   e = single_pred_edge (dest);
 772   goto restart;
 773 }
 774
 775
 776 /* Similar to gsi_insert_on_edge+gsi_commit_edge_inserts.  If a new
 777    block has to be created, it is returned.  */
 778
 779 basic_block
 780 gsi_insert_on_edge_immediate (edge e, gimple stmt)
 781 {
 782   gimple_stmt_iterator gsi;
 783   basic_block new_bb = NULL;
 784   bool ins_after;
 785
 786   gcc_assert (!PENDING_STMT (e));
 787
 788   ins_after = gimple_find_edge_insert_loc (e, &gsi, &new_bb);
 789
 790   update_call_edge_frequencies (stmt, gsi.bb);
 791
 792   if (ins_after)
 793     gsi_insert_after (&gsi, stmt, GSI_NEW_STMT);
 794   else
 795     gsi_insert_before (&gsi, stmt, GSI_NEW_STMT);
 796
 797   return new_bb;
 798 }
 799
 800 /* Insert STMTS on edge E.  If a new block has to be created, it
 801    is returned.  */
 802
 803 basic_block
 804 gsi_insert_seq_on_edge_immediate (edge e, gimple_seq stmts)
 805 {
 806   gimple_stmt_iterator gsi;
 807   basic_block new_bb = NULL;
 808   bool ins_after;
 809
 810   gcc_assert (!PENDING_STMT (e));
 811
 812   ins_after = gimple_find_edge_insert_loc (e, &gsi, &new_bb);
 813   update_call_edge_frequencies (gimple_seq_first (stmts), gsi.bb);
 814
 815   if (ins_after)
 816     gsi_insert_seq_after (&gsi, stmts, GSI_NEW_STMT);
 817   else
 818     gsi_insert_seq_before (&gsi, stmts, GSI_NEW_STMT);
 819
 820   return new_bb;
 821 }
 822
 823 /* This routine will commit all pending edge insertions, creating any new
 824    basic blocks which are necessary.  */
 825
 826 void
 827 gsi_commit_edge_inserts (void)
 828 {
 829   basic_block bb;
 830   edge e;
 831   edge_iterator ei;
 832
 833   gsi_commit_one_edge_insert (single_succ_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun)),
 834                               NULL);
 835
 836   FOR_EACH_BB (bb)
 837     FOR_EACH_EDGE (e, ei, bb->succs)
 838       gsi_commit_one_edge_insert (e, NULL);
 839 }
 840
 841
 842 /* Commit insertions pending at edge E. If a new block is created, set NEW_BB
 843    to this block, otherwise set it to NULL.  */
 844
 845 void
 846 gsi_commit_one_edge_insert (edge e, basic_block *new_bb)
 847 {
 848   if (new_bb)
 849     *new_bb = NULL;
 850
 851   if (PENDING_STMT (e))
 852     {
 853       gimple_stmt_iterator gsi;
 854       gimple_seq seq = PENDING_STMT (e);
 855       bool ins_after;
 856
 857       PENDING_STMT (e) = NULL;
 858
 859       ins_after = gimple_find_edge_insert_loc (e, &gsi, new_bb);
 860       update_call_edge_frequencies (gimple_seq_first (seq), gsi.bb);
 861
 862       if (ins_after)
 863         gsi_insert_seq_after (&gsi, seq, GSI_NEW_STMT);
 864       else
 865         gsi_insert_seq_before (&gsi, seq, GSI_NEW_STMT);
 866     }
 867 }
 868
 869 /* Returns iterator at the start of the list of phi nodes of BB.  */
 870
 871 gimple_stmt_iterator
 872 gsi_start_phis (basic_block bb)
 873 {
 874   gimple_seq *pseq = phi_nodes_ptr (bb);
 875   return gsi_start_1 (pseq);
 876 }