aboutsummaryrefslogtreecommitdiff
path: root/gcc/tree-data-ref.c
diff options
context:
space:
mode:
Diffstat (limited to 'gcc/tree-data-ref.c')
0 files changed, 0 insertions, 0 deletions
generated by cgit v1.1 at 2025-06-05 18:16:24 +0000
href='#n69'>69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 
/* Loop distribution.
   Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011
   Free Software Foundation, Inc.
   Contributed by Georges-Andre Silber <Georges-Andre.Silber@ensmp.fr>
   and Sebastian Pop <sebastian.pop@amd.com>.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 3, or (at your option) any
later version.

GCC is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* This pass performs loop distribution: for example, the loop

   |DO I = 2, N
   |    A(I) = B(I) + C
   |    D(I) = A(I-1)*E
   |ENDDO

   is transformed to

   |DOALL I = 2, N
   |   A(I) = B(I) + C
   |ENDDO
   |
   |DOALL I = 2, N
   |   D(I) = A(I-1)*E
   |ENDDO

   This pass uses an RDG, Reduced Dependence Graph built on top of the
   data dependence relations.  The RDG is then topologically sorted to
   obtain a map of information producers/consumers based on which it
   generates the new loops.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tree-flow.h"
#include "cfgloop.h"
#include "tree-chrec.h"
#include "tree-data-ref.h"
#include "tree-scalar-evolution.h"
#include "tree-pass.h"

/* If bit I is not set, it means that this node represents an
   operation that has already been performed, and that should not be
   performed again.  This is the subgraph of remaining important
   computations that is passed to the DFS algorithm for avoiding to
   include several times the same stores in different loops.  */
static bitmap remaining_stmts;

/* A node of the RDG is marked in this bitmap when it has as a
   predecessor a node that writes to memory.  */
static bitmap upstream_mem_writes;

/* Returns true when DEF is an SSA_NAME defined in LOOP and used after
   the LOOP.  */

static bool
ssa_name_has_uses_outside_loop_p (tree def, loop_p loop)
{
  imm_use_iterator imm_iter;
  use_operand_p use_p;

  FOR_EACH_IMM_USE_FAST (use_p, imm_iter, def)
    if (loop != loop_containing_stmt (USE_STMT (use_p)))
      return true;

  return false;
}

/* Returns true when STMT defines a scalar variable used after the
   loop.  */

static bool
stmt_has_scalar_dependences_outside_loop (gimple stmt)
{
  tree name;

  switch (gimple_code (stmt))
    {
    case GIMPLE_CALL:
    case GIMPLE_ASSIGN:
      name = gimple_get_lhs (stmt);
      break;

    case GIMPLE_PHI:
      name = gimple_phi_result (stmt);
      break;

    default:
      return false;
    }

  return (name
	  && TREE_CODE (name) == SSA_NAME
	  && ssa_name_has_uses_outside_loop_p (name,
					       loop_containing_stmt (stmt)));
}

/* Update the PHI nodes of NEW_LOOP.  NEW_LOOP is a duplicate of
   ORIG_LOOP.  */

static void
update_phis_for_loop_copy (struct loop *orig_loop, struct loop *new_loop)
{
  tree new_ssa_name;
  gimple_stmt_iterator si_new, si_orig;
  edge orig_loop_latch = loop_latch_edge (orig_loop);
  edge orig_entry_e = loop_preheader_edge (orig_loop);
  edge new_loop_entry_e = loop_preheader_edge (new_loop);

  /* Scan the phis in the headers of the old and new loops
     (they are organized in exactly the same order).  */
  for (si_new = gsi_start_phis (new_loop->header),
       si_orig = gsi_start_phis (orig_loop->header);
       !gsi_end_p (si_new) && !gsi_end_p (si_orig);
       gsi_next (&si_new), gsi_next (&si_orig))
    {
      tree def;
      source_location locus;
      gimple phi_new = gsi_stmt (si_new);
      gimple phi_orig = gsi_stmt (si_orig);

      /* Add the first phi argument for the phi in NEW_LOOP (the one
	 associated with the entry of NEW_LOOP)  */
      def = PHI_ARG_DEF_FROM_EDGE (phi_orig, orig_entry_e);
      locus = gimple_phi_arg_location_from_edge (phi_orig, orig_entry_e);
      add_phi_arg (phi_new, def, new_loop_entry_e, locus);

      /* Add the second phi argument for the phi in NEW_LOOP (the one
	 associated with the latch of NEW_LOOP)  */
      def = PHI_ARG_DEF_FROM_EDGE (phi_orig, orig_loop_latch);
      locus = gimple_phi_arg_location_from_edge (phi_orig, orig_loop_latch);

      if (TREE_CODE (def) == SSA_NAME)
	{
	  new_ssa_name = get_current_def (def);

	  if (!new_ssa_name)
	    /* This only happens if there are no definitions inside the
	       loop.  Use the the invariant in the new loop as is.  */
	    new_ssa_name = def;
	}
      else
	/* Could be an integer.  */
	new_ssa_name = def;

      add_phi_arg (phi_new, new_ssa_name, loop_latch_edge (new_loop), locus);
    }
}

/* Return a copy of LOOP placed before LOOP.  */

static struct loop *
copy_loop_before (struct loop *loop)
{
  struct loop *res;
  edge preheader = loop_preheader_edge (loop);

  if (!single_exit (loop))
    return NULL;

  initialize_original_copy_tables ();
  res = slpeel_tree_duplicate_loop_to_edge_cfg (loop, preheader);
  free_original_copy_tables ();

  if (!res)
    return NULL;

  update_phis_for_loop_copy (loop, res);
  rename_variables_in_loop (res);

  return res;
}

/* Creates an empty basic block after LOOP.  */

static void
create_bb_after_loop (struct loop *loop)
{
  edge exit = single_exit (loop);

  if (!exit)
    return;

  split_edge (exit);
}

/* Generate code for PARTITION from the code in LOOP.  The loop is
   copied when COPY_P is true.  All the statements not flagged in the
   PARTITION bitmap are removed from the loop or from its copy.  The
   statements are indexed in sequence inside a basic block, and the
   basic blocks of a loop are taken in dom order.  Returns true when
   the code gen succeeded. */

static bool
generate_loops_for_partition (struct loop *loop, bitmap partition, bool copy_p)
{
  unsigned i, x;
  gimple_stmt_iterator bsi;
  basic_block *bbs;

  if (copy_p)
    {
      loop = copy_loop_before (loop);
      create_preheader (loop, CP_SIMPLE_PREHEADERS);
      create_bb_after_loop (loop);
    }

  if (loop == NULL)
    return false;

  /* Remove stmts not in the PARTITION bitmap.  The order in which we
     visit the phi nodes and the statements is exactly as in
     stmts_from_loop.  */
  bbs = get_loop_body_in_dom_order (loop);

  if (MAY_HAVE_DEBUG_STMTS)
    for (x = 0, i = 0; i < loop->num_nodes; i++)
      {
	basic_block bb = bbs[i];

	for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
	  if (!bitmap_bit_p (partition, x++))
	    reset_debug_uses (gsi_stmt (bsi));

	for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
	  {
	    gimple stmt = gsi_stmt (bsi);
	    if (gimple_code (stmt) != GIMPLE_LABEL
		&& !is_gimple_debug (stmt)
		&& !bitmap_bit_p (partition, x++))
	      reset_debug_uses (stmt);
	  }
      }

  for (x = 0, i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = bbs[i];

      for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi);)
	if (!bitmap_bit_p (partition, x++))
	  {
	    gimple phi = gsi_stmt (bsi);
	    if (!is_gimple_reg (gimple_phi_result (phi)))
	      mark_virtual_phi_result_for_renaming (phi);
	    remove_phi_node (&bsi, true);
	  }
	else
	  gsi_next (&bsi);

      for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi);)
	{
	  gimple stmt = gsi_stmt (bsi);
	  if (gimple_code (stmt) != GIMPLE_LABEL
	      && !is_gimple_debug (stmt)
	      && !bitmap_bit_p (partition, x++))
	    {
	      unlink_stmt_vdef (stmt);
	      gsi_remove (&bsi, true);
	      release_defs (stmt);
	    }
	  else
	    gsi_next (&bsi);
	}
    }

  free (bbs);
  return true;
}

/* Build the size argument for a memset call.  */

static inline tree
build_size_arg_loc (location_t loc, tree nb_iter, tree op,
		    gimple_seq *stmt_list)
{
  gimple_seq stmts;
  tree x = fold_build2_loc (loc, MULT_EXPR, size_type_node,
			    fold_convert_loc (loc, size_type_node, nb_iter),
			    fold_convert_loc (loc, size_type_node,
					      TYPE_SIZE_UNIT (TREE_TYPE (op))));
  x = force_gimple_operand (x, &stmts, true, NULL);
  gimple_seq_add_seq (stmt_list, stmts);

  return x;
}

/* Generate a call to memset.  Return true when the operation succeeded.  */

static void
generate_memset_zero (gimple stmt, tree op0, tree nb_iter,
		      gimple_stmt_iterator bsi)
{
  tree addr_base, nb_bytes;
  bool res = false;
  gimple_seq stmt_list = NULL, stmts;
  gimple fn_call;
  tree mem, fn;
  struct data_reference *dr = XCNEW (struct data_reference);
  location_t loc = gimple_location (stmt);

  DR_STMT (dr) = stmt;
  DR_REF (dr) = op0;
  res = dr_analyze_innermost (dr, loop_containing_stmt (stmt));
  gcc_assert (res && stride_of_unit_type_p (DR_STEP (dr), TREE_TYPE (op0)));

  nb_bytes = build_size_arg_loc (loc, nb_iter, op0, &stmt_list);
  addr_base = size_binop_loc (loc, PLUS_EXPR, DR_OFFSET (dr), DR_INIT (dr));
  addr_base = fold_convert_loc (loc, sizetype, addr_base);

  /* Test for a negative stride, iterating over every element.  */
  if (tree_int_cst_sgn (DR_STEP (dr)) == -1)
    {
      addr_base = size_binop_loc (loc, MINUS_EXPR, addr_base,
				  fold_convert_loc (loc, sizetype, nb_bytes));
      addr_base = size_binop_loc (loc, PLUS_EXPR, addr_base,
				  TYPE_SIZE_UNIT (TREE_TYPE (op0)));
    }

  addr_base = fold_build_pointer_plus_loc (loc,
					   DR_BASE_ADDRESS (dr), addr_base);
  mem = force_gimple_operand (addr_base, &stmts, true, NULL);
  gimple_seq_add_seq (&stmt_list, stmts);

  fn = build_fold_addr_expr (builtin_decl_implicit (BUILT_IN_MEMSET));
  fn_call = gimple_build_call (fn, 3, mem, integer_zero_node, nb_bytes);
  gimple_seq_add_stmt (&stmt_list, fn_call);
  gsi_insert_seq_after (&bsi, stmt_list, GSI_CONTINUE_LINKING);

  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "generated memset zero\n");

  free_data_ref (dr);
}

/* Tries to generate a builtin function for the instructions of LOOP
   pointed to by the bits set in PARTITION.  Returns true when the
   operation succeeded.  */

static bool
generate_builtin (struct loop *loop, bitmap partition, bool copy_p)
{
  bool res = false;
  unsigned i, x = 0;
  basic_block *bbs;
  gimple write = NULL;
  gimple_stmt_iterator bsi;
  tree nb_iter = number_of_exit_cond_executions (loop);

  if (!nb_iter || nb_iter == chrec_dont_know)
    return false;

  bbs = get_loop_body_in_dom_order (loop);

  for (i = 0; i < loop->num_nodes; i++)
    {
      basic_block bb = bbs[i];

      for (bsi = gsi_start_phis (bb); !gsi_end_p (bsi); gsi_next (&bsi))
	x++;

      for (bsi = gsi_start_bb (bb); !gsi_end_p (bsi); gsi_next (&bsi))
	{
	  gimple stmt = gsi_stmt (bsi);

	  if (gimple_code (stmt) == GIMPLE_LABEL
	      || is_gimple_debug (stmt))
	    continue;

	  if (!bitmap_bit_p (partition, x++))
	    continue;

	  /* If the stmt has uses outside of the loop fail.  */
	  if (stmt_has_scalar_dependences_outside_loop (stmt))
	    goto end;

	  if (is_gimple_assign (stmt)
	      && !is_gimple_reg (gimple_assign_lhs (stmt)))
	    {
	      /* Don't generate the builtins when there are more than
		 one memory write.  */
	      if (write != NULL)
		goto end;

	      write = stmt;
	      if (bb == loop->latch)
		nb_iter = number_of_latch_executions (loop);
	    }
	}
    }

  if (!stmt_with_adjacent_zero_store_dr_p (write))
    goto end;

  /* The new statements will be placed before LOOP.  */
  bsi = gsi_last_bb (loop_preheader_edge (loop)->src);
  generate_memset_zero (write, gimple_assign_lhs (write), nb_iter, bsi);
  res = true;

  /* If this is the last partition for which we generate code, we have
     to destroy the loop.  */
  if (!copy_p)
    {
      unsigned nbbs = loop->num_nodes;
      edge exit = single_exit (loop);
      basic_block src = loop_preheader_edge (loop)->src, dest = exit->dest;
      redirect_edge_pred (exit, src);
      exit->flags &= ~(EDGE_TRUE_VALUE|EDGE_FALSE_VALUE);
      exit->flags |= EDGE_FALLTHRU;
      cancel_loop_tree (loop);
      rescan_loop_exit (exit, false, true);

      for (i = 0; i < nbbs; i++)
	delete_basic_block (bbs[i]);

      set_immediate_dominator (CDI_DOMINATORS, dest,
			       recompute_dominator (CDI_DOMINATORS, dest));
    }

 end:
  free (bbs);
  return res;
}

/* Generates code for PARTITION.  For simple loops, this function can
   generate a built-in.  */

static bool
generate_code_for_partition (struct loop *loop, bitmap partition, bool copy_p)
{
  if (generate_builtin (loop, partition, copy_p))
    return true;

  return generate_loops_for_partition (loop, partition, copy_p);
}


/* Returns true if the node V of RDG cannot be recomputed.  */

static bool
rdg_cannot_recompute_vertex_p (struct graph *rdg, int v)
{
  if (RDG_MEM_WRITE_STMT (rdg, v))
    return true;

  return false;
}

/* Returns true when the vertex V has already been generated in the
   current partition (V is in PROCESSED), or when V belongs to another
   partition and cannot be recomputed (V is not in REMAINING_STMTS).  */

static inline bool
already_processed_vertex_p (bitmap processed, int v)
{
  return (bitmap_bit_p (processed, v)
	  || !bitmap_bit_p (remaining_stmts, v));
}

/* Returns NULL when there is no anti-dependence among the successors
   of vertex V, otherwise returns the edge with the anti-dep.  */

static struct graph_edge *
has_anti_dependence (struct vertex *v)
{
  struct graph_edge *e;

  if (v->succ)
    for (e = v->succ; e; e = e->succ_next)
      if (RDGE_TYPE (e) == anti_dd)
	return e;

  return NULL;
}

/* Returns true when V has an anti-dependence edge among its successors.  */

static bool
predecessor_has_mem_write (struct graph *rdg, struct vertex *v)
{
  struct graph_edge *e;

  if (v->pred)
    for (e = v->pred; e; e = e->pred_next)
      if (bitmap_bit_p (upstream_mem_writes, e->src)
	  /* Don't consider flow channels: a write to memory followed
	     by a read from memory.  These channels allow the split of
	     the RDG in different partitions.  */
	  && !RDG_MEM_WRITE_STMT (rdg, e->src))
	return true;

  return false;
}

/* Initializes the upstream_mem_writes bitmap following the
   information from RDG.  */

static void
mark_nodes_having_upstream_mem_writes (struct graph *rdg)
{
  int v, x;
  bitmap seen = BITMAP_ALLOC (NULL);

  for (v = rdg->n_vertices - 1; v >= 0; v--)
    if (!bitmap_bit_p (seen, v))
      {
	unsigned i;
	VEC (int, heap) *nodes = VEC_alloc (int, heap, 3);

	graphds_dfs (rdg, &v, 1, &nodes, false, NULL);

	FOR_EACH_VEC_ELT (int, nodes, i, x)
	  {
	    if (!bitmap_set_bit (seen, x))
	      continue;

	    if (RDG_MEM_WRITE_STMT (rdg, x)
		|| predecessor_has_mem_write (rdg, &(rdg->vertices[x]))
		/* In anti dependences the read should occur before
		   the write, this is why both the read and the write
		   should be placed in the same partition.  */
		|| has_anti_dependence (&(rdg->vertices[x])))
	      {
		bitmap_set_bit (upstream_mem_writes, x);
	      }
	  }

	VEC_free (int, heap, nodes);
      }
}

/* Returns true when vertex u has a memory write node as a predecessor
   in RDG.  */

static bool
has_upstream_mem_writes (int u)
{
  return bitmap_bit_p (upstream_mem_writes, u);
}

static void rdg_flag_vertex_and_dependent (struct graph *, int, bitmap, bitmap,
					   bitmap, bool *);

/* Flag the uses of U stopping following the information from
   upstream_mem_writes.  */

static void
rdg_flag_uses (struct graph *rdg, int u, bitmap partition, bitmap loops,
	       bitmap processed, bool *part_has_writes)
{
  use_operand_p use_p;
  struct vertex *x = &(rdg->vertices[u]);
  gimple stmt = RDGV_STMT (x);
  struct graph_edge *anti_dep = has_anti_dependence (x);

  /* Keep in the same partition the destination of an antidependence,
     because this is a store to the exact same location.  Putting this
     in another partition is bad for cache locality.  */
  if (anti_dep)
    {
      int v = anti_dep->dest;

      if (!already_processed_vertex_p (processed, v))
	rdg_flag_vertex_and_dependent (rdg, v, partition, loops,
				       processed, part_has_writes);
    }

  if (gimple_code (stmt) != GIMPLE_PHI)
    {
      if ((use_p = gimple_vuse_op (stmt)) != NULL_USE_OPERAND_P)
	{
	  tree use = USE_FROM_PTR (use_p);

	  if (TREE_CODE (use) == SSA_NAME)
	    {
	      gimple def_stmt = SSA_NAME_DEF_STMT (use);
	      int v = rdg_vertex_for_stmt (rdg, def_stmt);

	      if (v >= 0
		  && !already_processed_vertex_p (processed, v))
		rdg_flag_vertex_and_dependent (rdg, v, partition, loops,
					       processed, part_has_writes);
	    }
	}
    }

  if (is_gimple_assign (stmt) && has_upstream_mem_writes (u))
    {
      tree op0 = gimple_assign_lhs (stmt);

      /* Scalar channels don't have enough space for transmitting data
	 between tasks, unless we add more storage by privatizing.  */
      if (is_gimple_reg (op0))
	{
	  use_operand_p use_p;
	  imm_use_iterator iter;

	  FOR_EACH_IMM_USE_FAST (use_p, iter, op0)
	    {
	      int v = rdg_vertex_for_stmt (rdg, USE_STMT (use_p));

	      if (!already_processed_vertex_p (processed, v))
		rdg_flag_vertex_and_dependent (rdg, v, partition, loops,
					       processed, part_has_writes);
	    }
	}
    }
}

/* Flag V from RDG as part of PARTITION, and also flag its loop number
   in LOOPS.  */

static void
rdg_flag_vertex (struct graph *rdg, int v, bitmap partition, bitmap loops,
		 bool *part_has_writes)
{
  struct loop *loop;

  if (!bitmap_set_bit (partition, v))
    return;

  loop = loop_containing_stmt (RDG_STMT (rdg, v));
  bitmap_set_bit (loops, loop->num);

  if (rdg_cannot_recompute_vertex_p (rdg, v))
    {
      *part_has_writes = true;
      bitmap_clear_bit (remaining_stmts, v);
    }
}

/* Flag in the bitmap PARTITION the vertex V and all its predecessors.
   Also flag their loop number in LOOPS.  */

static void
rdg_flag_vertex_and_dependent (struct graph *rdg, int v, bitmap partition,
			       bitmap loops, bitmap processed,
			       bool *part_has_writes)
{
  unsigned i;
  VEC (int, heap) *nodes = VEC_alloc (int, heap, 3);
  int x;

  bitmap_set_bit (processed, v);
  rdg_flag_uses (rdg, v, partition, loops, processed, part_has_writes);
  graphds_dfs (rdg, &v, 1, &nodes, false, remaining_stmts);
  rdg_flag_vertex (rdg, v, partition, loops, part_has_writes);

  FOR_EACH_VEC_ELT (int, nodes, i, x)
    if (!already_processed_vertex_p (processed, x))
      rdg_flag_vertex_and_dependent (rdg, x, partition, loops, processed,
				     part_has_writes);

  VEC_free (int, heap, nodes);
}

/* Initialize CONDS with all the condition statements from the basic
   blocks of LOOP.  */

static void
collect_condition_stmts (struct loop *loop, VEC (gimple, heap) **conds)
{
  unsigned i;
  edge e;
  VEC (edge, heap) *exits = get_loop_exit_edges (loop);

  FOR_EACH_VEC_ELT (edge, exits, i, e)
    {
      gimple cond = last_stmt (e->src);

      if (cond)
	VEC_safe_push (gimple, heap, *conds, cond);
    }

  VEC_free (edge, heap, exits);
}

/* Add to PARTITION all the exit condition statements for LOOPS
   together with all their dependent statements determined from
   RDG.  */

static void
rdg_flag_loop_exits (struct graph *rdg, bitmap loops, bitmap partition,
		     bitmap processed, bool *part_has_writes)
{
  unsigned i;
  bitmap_iterator bi;
  VEC (gimple, heap) *conds = VEC_alloc (gimple, heap, 3);

  EXECUTE_IF_SET_IN_BITMAP (loops, 0, i, bi)
    collect_condition_stmts (get_loop (i), &conds);

  while (!VEC_empty (gimple, conds))
    {
      gimple cond = VEC_pop (gimple, conds);
      int v = rdg_vertex_for_stmt (rdg, cond);
      bitmap new_loops = BITMAP_ALLOC (NULL);

      if (!already_processed_vertex_p (processed, v))