nsz Git - libfirm/blob - ir/ana/irdom.c

   1 /*
   2  * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
   3  *
   4  * This file is part of libFirm.
   5  *
   6  * This file may be distributed and/or modified under the terms of the
   7  * GNU General Public License version 2 as published by the Free Software
   8  * Foundation and appearing in the file LICENSE.GPL included in the
   9  * packaging of this file.
  10  *
  11  * Licensees holding valid libFirm Professional Edition licenses may use
  12  * this file in accordance with the libFirm Commercial License.
  13  * Agreement provided with the Software.
  14  *
  15  * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
  16  * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  17  * PURPOSE.
  18  */
  19
  20 /**
  21  * @file
  22  * @brief     Construct and access dominator / post dominator tree.
  23  * @author    Goetz Lindenmaier, Michael Beck, Rubino Geiss
  24  * @date      2.2002
  25  * @version   $Id$
  26  */
  27 #include "config.h"
  28
  29 #include <string.h>
  30
  31 #include "irouts.h"
  32
  33 #include "xmalloc.h"
  34 #include "irgwalk.h"
  35 #include "irdom_t.h"
  36 #include "irgraph_t.h"
  37 #include "irnode_t.h"
  38 #include "ircons_t.h"
  39 #include "array_t.h"
  40 #include "iredges.h"
  41
  42
  43 #define get_dom_info(bl)  (&(bl)->attr.block.dom)
  44 #define get_pdom_info(bl) (&(bl)->attr.block.pdom)
  45
  46 /*--------------------------------------------------------------------*/
  47 /** Accessing the dominator and post dominator data structures       **/
  48 /*--------------------------------------------------------------------*/
  49
  50 ir_node *get_Block_idom(const ir_node *bl)
  51 {
  52         assert(is_Block(bl));
  53         if (get_Block_dom_depth(bl) == -1) {
  54                 /* This block is not reachable from Start */
  55                 ir_graph *irg = get_irn_irg(bl);
  56                 return new_r_Bad(irg, mode_BB);
  57         }
  58         return get_dom_info(bl)->idom;
  59 }
  60
  61 void set_Block_idom(ir_node *bl, ir_node *n)
  62 {
  63         ir_dom_info *bli = get_dom_info(bl);
  64
  65         assert(is_Block(bl));
  66
  67         /* Set the immediate dominator of bl to n */
  68         bli->idom = n;
  69
  70         /*
  71          * If we don't set the root of the dominator tree
  72          * Append bl to the dominates queue of n.
  73          */
  74         if (n != NULL) {
  75                 ir_dom_info *ni = get_dom_info(n);
  76
  77                 bli->next = ni->first;
  78                 ni->first = bl;
  79         }
  80 }
  81
  82 ir_node *get_Block_ipostdom(const ir_node *bl)
  83 {
  84         assert(is_Block(bl));
  85         if (get_Block_postdom_depth(bl) == -1) {
  86                 /* This block is not reachable from Start */
  87                 ir_graph *irg = get_irn_irg(bl);
  88                 return new_r_Bad(irg, mode_BB);
  89         }
  90         return get_pdom_info(bl)->idom;
  91 }
  92
  93 void set_Block_ipostdom(ir_node *bl, ir_node *n)
  94 {
  95         ir_dom_info *bli = get_pdom_info(bl);
  96
  97         assert(is_Block(bl));
  98
  99         /* Set the immediate post dominator of bl to n */
 100         bli->idom = n;
 101
 102         /*
 103          * If we don't set the root of the post dominator tree
 104          * Append bl to the post dominates queue of n.
 105          */
 106         if (n != NULL) {
 107                 ir_dom_info *ni = get_pdom_info(n);
 108
 109                 bli->next = ni->first;
 110                 ni->first = bl;
 111         }
 112 }
 113
 114 int get_Block_dom_pre_num(const ir_node *bl)
 115 {
 116         assert(is_Block(bl));
 117         return get_dom_info(bl)->pre_num;
 118 }
 119
 120 void set_Block_dom_pre_num(ir_node *bl, int num)
 121 {
 122         assert(is_Block(bl));
 123         get_dom_info(bl)->pre_num = num;
 124 }
 125
 126 int get_Block_dom_depth(const ir_node *bl)
 127 {
 128         assert(is_Block(bl));
 129         return get_dom_info(bl)->dom_depth;
 130 }
 131
 132 void set_Block_dom_depth(ir_node *bl, int depth)
 133 {
 134         assert(is_Block(bl));
 135         get_dom_info(bl)->dom_depth = depth;
 136 }
 137
 138
 139 int get_Block_postdom_pre_num(const ir_node *bl)
 140 {
 141         assert(is_Block(bl));
 142         return get_pdom_info(bl)->pre_num;
 143 }
 144
 145 void set_Block_postdom_pre_num(ir_node *bl, int num)
 146 {
 147         assert(is_Block(bl));
 148         get_pdom_info(bl)->pre_num = num;
 149 }
 150
 151 int get_Block_postdom_depth(const ir_node *bl)
 152 {
 153         assert(is_Block(bl));
 154         return get_pdom_info(bl)->dom_depth;
 155 }
 156
 157 void set_Block_postdom_depth(ir_node *bl, int depth)
 158 {
 159         assert(is_Block(bl));
 160         get_pdom_info(bl)->dom_depth = depth;
 161 }
 162
 163 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
 164 {
 165         assert(is_Block(bl));
 166         return get_dom_info(bl)->tree_pre_num;
 167 }
 168
 169 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
 170 {
 171         assert(is_Block(bl));
 172         return get_dom_info(bl)->max_subtree_pre_num;
 173 }
 174
 175 unsigned get_Block_pdom_tree_pre_num(const ir_node *bl)
 176 {
 177         assert(is_Block(bl));
 178         return get_pdom_info(bl)->tree_pre_num;
 179 }
 180
 181 unsigned get_Block_pdom_max_subtree_pre_num(const ir_node *bl)
 182 {
 183         assert(is_Block(bl));
 184         return get_pdom_info(bl)->max_subtree_pre_num;
 185 }
 186
 187 /* Check, if a block dominates another block. */
 188 int block_dominates(const ir_node *a, const ir_node *b)
 189 {
 190         const ir_dom_info *ai, *bi;
 191
 192         if (is_Block(a) && is_Block(b)) {
 193                 ai = get_dom_info(a);
 194                 bi = get_dom_info(b);
 195                 return bi->tree_pre_num - ai->tree_pre_num
 196                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 197         }
 198
 199         return 0;
 200 }
 201
 202 /* Check, if a block strictly dominates another block. */
 203 int block_strictly_dominates(const ir_node *a, const ir_node *b)
 204 {
 205         return (a != b) && block_dominates(a, b);
 206 }
 207
 208 /* Returns the smallest common dominator block of two nodes. */
 209 ir_node *node_smallest_common_dominator(ir_node *a, ir_node *b)
 210 {
 211         ir_node *bl_a   = is_Block(a) ? a : get_nodes_block(a);
 212         ir_node *bl_b   = is_Block(b) ? b : get_nodes_block(b);
 213         ir_node *dom_bl = NULL;
 214
 215         /* Check if block of a dominates block of b */
 216         if (block_dominates(bl_a, bl_b))
 217                 dom_bl = bl_a;
 218         /* Check if block of b dominates block of a */
 219         else if (block_dominates(bl_b, bl_a))
 220                 dom_bl = bl_b;
 221         else {
 222                 /* walk up dominator tree and search for first block dominating a and b */
 223                 while (! dom_bl) {
 224                         bl_a = get_Block_idom(bl_a);
 225
 226                         assert(! is_Bad(bl_a) && "block is dead?");
 227
 228                         if (block_dominates(bl_a, bl_b))
 229                                 dom_bl = bl_a;
 230                 }
 231         }
 232
 233         return dom_bl;
 234 }
 235
 236 /* Returns the smallest common dominator block of all users of a node. */
 237 ir_node *node_users_smallest_common_dominator(ir_node *irn, int handle_phi)
 238 {
 239         int n, j, i = 0, success;
 240         ir_node **user_blocks, *dom_bl;
 241         const ir_edge_t *edge;
 242
 243         assert(! is_Block(irn) && "WRONG USAGE of node_users_smallest_common_dominator");
 244         assert(edges_activated(get_irn_irg(irn)) && "need edges activated");
 245
 246         n = get_irn_n_edges(irn);
 247
 248         /* get array to hold all block of the node users */
 249         NEW_ARR_A(ir_node *, user_blocks, n);
 250         foreach_out_edge(irn, edge) {
 251                 ir_node *src = get_edge_src_irn(edge);
 252
 253                 if (is_Phi(src) && handle_phi) {
 254                         /* get the corresponding cfg predecessor block if phi handling requested */
 255                         j  = get_edge_src_pos(edge);
 256                         assert(j >= 0 && "kaputt");
 257                         user_blocks[i++] = get_Block_cfgpred_block(get_nodes_block(src), j);
 258                 }
 259                 else
 260                         user_blocks[i++] = is_Block(src) ? src : get_nodes_block(src);
 261         }
 262
 263         assert(i == n && "get_irn_n_edges probably broken");
 264
 265         /* in case of only one user: return the block of the user */
 266         if (n == 1)
 267                 return user_blocks[0];
 268
 269         i = 0;
 270         /* search the smallest block dominating all user blocks */
 271         do {
 272                 dom_bl  = node_smallest_common_dominator(user_blocks[i], user_blocks[i + 1]);
 273                 success = 1;
 274
 275                 /* check if this block dominates all remaining blocks as well */
 276                 for (j = i + 2; j < n; j++) {
 277                         if (! block_dominates(dom_bl, user_blocks[j]))
 278                                 success = 0;
 279                 }
 280
 281                 if (success)
 282                         break;
 283
 284                 /* inherit the dominator block of the first (i + 1) users */
 285                 user_blocks[++i] = dom_bl;
 286         } while (i < n - 1);
 287
 288         assert(success && "no block found dominating all users");
 289
 290         return dom_bl;
 291 }
 292
 293
 294 /* Get the first node in the list of nodes dominated by a given block. */
 295 ir_node *get_Block_dominated_first(const ir_node *bl)
 296 {
 297         assert(is_Block(bl));
 298         return get_dom_info(bl)->first;
 299 }
 300
 301 /* Get the next node in a list of nodes which are dominated by some
 302  * other node. */
 303 ir_node *get_Block_dominated_next(const ir_node *bl)
 304 {
 305         assert(is_Block(bl));
 306         return get_dom_info(bl)->next;
 307 }
 308
 309 /* Check, if a block post dominates another block. */
 310 int block_postdominates(const ir_node *a, const ir_node *b)
 311 {
 312         const ir_dom_info *ai, *bi;
 313
 314         if (is_Block(a) && is_Block(b)) {
 315                 ai = get_pdom_info(a);
 316                 bi = get_pdom_info(b);
 317                 return bi->tree_pre_num - ai->tree_pre_num
 318                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 319         }
 320
 321         return 0;
 322 }
 323
 324 /* Check, if a block strictly dominates another block. */
 325 int block_strictly_postdominates(const ir_node *a, const ir_node *b)
 326 {
 327         return (a != b) && block_postdominates(a, b);
 328 }
 329
 330
 331 /* Get the first node in the list of nodes post dominated by a given block. */
 332 ir_node *get_Block_postdominated_first(const ir_node *bl)
 333 {
 334         assert(is_Block(bl));
 335         return get_pdom_info(bl)->first;
 336 }
 337
 338 /* Get the next node in a list of nodes which are post dominated by some
 339  * other node. */
 340 ir_node *get_Block_postdominated_next(const ir_node *bl)
 341 {
 342         assert(is_Block(bl));
 343         return get_pdom_info(bl)->next;
 344 }
 345
 346 /* Visit all nodes in the dominator subtree of a given node. */
 347 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
 348                 irg_walk_func *post, void *env)
 349 {
 350         ir_node *p;
 351
 352         if (pre)
 353                 pre(bl, env);
 354
 355         dominates_for_each(bl, p) {
 356                 dom_tree_walk(p, pre, post, env);
 357         }
 358
 359         if (post)
 360                 post(bl, env);
 361 }
 362
 363 /* Visit all nodes in the post dominator subtree of a given node. */
 364 void postdom_tree_walk(ir_node *bl, irg_walk_func *pre,
 365                 irg_walk_func *post, void *env)
 366 {
 367         ir_node *p;
 368
 369         if (pre)
 370                 pre(bl, env);
 371
 372         postdominates_for_each(bl, p) {
 373                 postdom_tree_walk(p, pre, post, env);
 374         }
 375
 376         if (post)
 377                 post(bl, env);
 378 }
 379
 380 /* Walk over the dominator tree of an irg starting at the root. */
 381 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 382                 irg_walk_func *post, void *env)
 383 {
 384         /* The root of the dominator tree should be the Start block. */
 385         ir_node *root = get_irg_start_block(irg);
 386
 387         assert(irg->dom_state == dom_consistent
 388                         && "The dominators of the irg must be consistent");
 389         assert(root && "The start block of the graph is NULL?");
 390         assert(get_dom_info(root)->idom == NULL
 391                         && "The start node in the graph must be the root of the dominator tree");
 392         dom_tree_walk(root, pre, post, env);
 393 }
 394
 395 /* Walk over the post dominator tree of an irg starting at the root. */
 396 void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 397                 irg_walk_func *post, void *env)
 398 {
 399         /* The root of the dominator tree should be the End block. */
 400         ir_node *root = get_irg_end_block(irg);
 401
 402         assert(irg->pdom_state == dom_consistent
 403                         && "The dominators of the irg must be consistent");
 404         assert(root && "The end block of the graph is NULL?");
 405         assert(get_pdom_info(root)->idom == NULL
 406                         && "The End block node in the graph must be the root of the post dominator tree");
 407         postdom_tree_walk(root, pre, post, env);
 408 }
 409
 410
 411 static void assign_tree_dom_pre_order(ir_node *bl, void *data)
 412 {
 413         unsigned *num = (unsigned*) data;
 414         ir_dom_info *bi = get_dom_info(bl);
 415
 416         bi->tree_pre_num = (*num)++;
 417 }
 418
 419 static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
 420 {
 421         ir_dom_info *bi = get_dom_info(bl);
 422         ir_node *p;
 423         unsigned max = 0;
 424         unsigned children = 0;
 425         (void) data;
 426
 427         for (p = bi->first; p; p = get_dom_info(p)->next) {
 428                 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
 429                 max = max > max_p ? max : max_p;
 430                 children++;
 431         }
 432
 433         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 434         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 435 }
 436
 437 static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
 438 {
 439         unsigned *num = (unsigned*) data;
 440         ir_dom_info *bi = get_pdom_info(bl);
 441
 442         bi->tree_pre_num = (*num)++;
 443 }
 444
 445 static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
 446 {
 447         ir_dom_info *bi = get_pdom_info(bl);
 448         ir_node *p;
 449         unsigned max = 0;
 450         unsigned children = 0;
 451         (void) data;
 452
 453         for (p = bi->first; p; p = get_pdom_info(p)->next) {
 454                 unsigned max_p = get_pdom_info(p)->max_subtree_pre_num;
 455                 max = max > max_p ? max : max_p;
 456                 children++;
 457         }
 458
 459         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 460         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 461 }
 462
 463 /*--------------------------------------------------------------------*/
 464 /*  Building and Removing the dominator data structure                */
 465 /*--------------------------------------------------------------------*/
 466
 467 /**
 468  * count the number of blocks and clears the post dominance info
 469  */
 470 static void count_and_init_blocks_pdom(ir_node *bl, void *env)
 471 {
 472         int *n_blocks = (int *) env;
 473
 474         (*n_blocks) ++;
 475
 476         memset(get_pdom_info(bl), 0, sizeof(ir_dom_info));
 477         set_Block_ipostdom(bl, NULL);
 478         set_Block_postdom_pre_num(bl, -1);
 479         set_Block_postdom_depth(bl, -1);
 480 }
 481
 482 /** temporary type used while constructing the dominator / post dominator tree. */
 483 typedef struct tmp_dom_info {
 484         ir_node *block;               /**< backlink */
 485
 486         struct tmp_dom_info *semi;    /**< semidominator */
 487         struct tmp_dom_info *parent;
 488         struct tmp_dom_info *label;   /**< used for LINK and EVAL */
 489         struct tmp_dom_info *ancestor;/**< used for LINK and EVAL */
 490         struct tmp_dom_info *dom;     /**< After step 3, if the semidominator of w is
 491                                            its immediate dominator, then w->dom is the
 492                                            immediate dominator of w.  Otherwise w->dom
 493                                            is a vertex v whose number is smaller than
 494                                            w and whose immediate dominator is also w's
 495                                            immediate dominator. After step 4, w->dom
 496                                            is the immediate dominator of w.  */
 497         struct tmp_dom_info *bucket;  /**< set of vertices with same semidominator */
 498 } tmp_dom_info;
 499
 500 /** Struct to pass info through walker. */
 501 typedef struct {
 502         tmp_dom_info *d;
 503         int used;
 504 } dom_env;
 505
 506
 507 /**
 508  * Walks Blocks along the out data structure.  If recursion started with
 509  * Start block misses control dead blocks.
 510  */
 511 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
 512                               tmp_dom_info *tdi_list, int *used, int n_blocks)
 513 {
 514         tmp_dom_info *tdi;
 515         int i;
 516
 517         assert(is_Block(bl));
 518         if (Block_block_visited(bl))
 519           return;
 520         mark_Block_block_visited(bl);
 521         set_Block_dom_pre_num(bl, *used);
 522
 523         assert(*used < n_blocks);
 524         tdi = &tdi_list[*used];
 525         ++(*used);
 526
 527         tdi->semi     = tdi;
 528         tdi->label    = tdi;
 529         tdi->ancestor = NULL;
 530         tdi->bucket   = NULL;
 531         tdi->parent   = parent;
 532         tdi->block    = bl;
 533
 534         /* Iterate */
 535         for (i = get_Block_n_cfg_outs_ka(bl) - 1; i >= 0; --i) {
 536                 ir_node *pred = get_Block_cfg_out_ka(bl, i);
 537                 /* can happen for half-optimized dead code (I've seen this in student
 538                    projects */
 539                 if (!is_Block(pred))
 540                         continue;
 541
 542                 init_tmp_dom_info(pred, tdi, tdi_list, used, n_blocks);
 543         }
 544 }
 545
 546 /**
 547  * Walks Blocks along the control flow.  If recursion started with
 548  * End block misses blocks in endless loops.
 549  */
 550 static void init_tmp_pdom_info(ir_node *bl, tmp_dom_info *parent,
 551                                tmp_dom_info *tdi_list, int* used, int n_blocks)
 552 {
 553         tmp_dom_info *tdi;
 554         int i;
 555
 556         assert(is_Block(bl));
 557         if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
 558           return;
 559         mark_Block_block_visited(bl);
 560         set_Block_postdom_pre_num(bl, *used);
 561
 562         assert(*used < n_blocks);
 563         tdi = &tdi_list[*used];
 564         ++(*used);
 565
 566         tdi->semi = tdi;
 567         tdi->label = tdi;
 568         tdi->ancestor = NULL;
 569         tdi->bucket = NULL;
 570         tdi->parent = parent;
 571         tdi->block = bl;
 572
 573         /* Iterate */
 574         for (i = get_Block_n_cfgpreds(bl) - 1; i >= 0; --i) {
 575                 ir_node *pred = get_Block_cfgpred_block(bl, i);
 576                 if (is_Bad(pred))
 577                         continue;
 578                 assert(is_Block(pred));
 579                 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
 580         }
 581
 582         /* Handle keep-alives. Note that the preprocessing
 583            in init_construction() had already killed all
 584            phantom keep-alive edges. All remaining block keep-alives
 585            are really edges to endless loops.
 586          */
 587         if (bl == get_irg_end_block(current_ir_graph)) {
 588                 ir_node *end = get_irg_end(current_ir_graph);
 589
 590                 for (i = get_irn_arity(end) - 1; i >= 0; --i) {
 591                         ir_node *pred = get_irn_n(end, i);
 592
 593                         if (is_Block(pred))
 594                                 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
 595                 }
 596         }
 597 }
 598
 599 static void dom_compress(tmp_dom_info *v)
 600 {
 601         assert (v->ancestor);
 602         if (v->ancestor->ancestor) {
 603                 dom_compress (v->ancestor);
 604                 if (v->ancestor->label->semi < v->label->semi) {
 605                         v->label = v->ancestor->label;
 606                 }
 607                 v->ancestor = v->ancestor->ancestor;
 608         }
 609 }
 610
 611 /**
 612  * if V is a root, return v, else return the vertex u, not being the
 613  * root, with minimum u->semi on the path from v to its root.
 614  */
 615 inline static tmp_dom_info *dom_eval(tmp_dom_info *v)
 616 {
 617         if (!v->ancestor) return v;
 618         dom_compress (v);
 619         return v->label;
 620 }
 621
 622 /** make V W's ancestor */
 623 inline static void dom_link(tmp_dom_info *v, tmp_dom_info *w)
 624 {
 625         w->ancestor = v;
 626 }
 627
 628 /**
 629  * Walker: count the number of blocks and clears the dominance info
 630  */
 631 static void count_and_init_blocks_dom(ir_node *bl, void *env)
 632 {
 633         int *n_blocks = (int *) env;
 634
 635         (*n_blocks) ++;
 636
 637         memset(get_dom_info(bl), 0, sizeof(ir_dom_info));
 638         set_Block_idom(bl, NULL);
 639         set_Block_dom_pre_num(bl, -1);
 640         set_Block_dom_depth(bl, -1);
 641 }
 642
 643 /* Computes the dominator trees.  Sets a flag in irg to "dom_consistent".
 644    If the control flow of the graph is changed this flag must be set to
 645    "dom_inconsistent".  */
 646 void compute_doms(ir_graph *irg)
 647 {
 648         ir_graph *rem = current_ir_graph;
 649         int n_blocks, used, i, j;
 650         tmp_dom_info *tdi_list;   /* Ein Golf? */
 651
 652         current_ir_graph = irg;
 653
 654         /* Update graph state */
 655         assert(get_irg_phase_state(irg) != phase_building);
 656         irg->dom_state = dom_consistent;
 657
 658         /* Count the number of blocks in the graph. */
 659         n_blocks = 0;
 660         irg_block_walk_graph(irg, count_and_init_blocks_dom, NULL, &n_blocks);
 661
 662         /* Memory for temporary information. */
 663         tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);
 664
 665         /* We need the out data structure. */
 666         assure_irg_outs(irg);
 667
 668         /* this with a standard walker as passing the parent to the sons isn't
 669            simple. */
 670         used = 0;
 671         inc_irg_block_visited(irg);
 672         init_tmp_dom_info(get_irg_start_block(irg), NULL, tdi_list, &used, n_blocks);
 673         /* If not all blocks are reachable from Start by out edges this assertion
 674            fails.
 675            assert(used == n_blocks && "Precondition for dom construction violated"); */
 676         assert(used <= n_blocks && "Precondition for dom construction violated");
 677         n_blocks = used;
 678
 679
 680         for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 681                 int irn_arity;
 682                 tmp_dom_info *w = &tdi_list[i];
 683                 tmp_dom_info *v;
 684
 685                 /* Step 2 */
 686                 irn_arity = get_irn_arity(w->block);
 687                 for (j = 0; j < irn_arity;  j++) {
 688                         ir_node *pred = get_Block_cfgpred_block(w->block, j);
 689                         tmp_dom_info *u;
 690
 691                         if (is_Bad(pred) || (get_Block_dom_pre_num (pred) == -1))
 692                                 continue;    /* control-dead */
 693
 694                         u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
 695                         if (u->semi < w->semi) w->semi = u->semi;
 696                 }
 697
 698                 /* handle keep-alives if we are at the end block */
 699                 if (w->block == get_irg_end_block(irg)) {
 700                         ir_node *end = get_irg_end(irg);
 701
 702                         irn_arity = get_irn_arity(end);
 703                         for (j = 0; j < irn_arity;  j++) {
 704                                 ir_node *pred = get_irn_n(end, j);
 705                                 tmp_dom_info *u;
 706
 707                                 if (!is_Block(pred) || get_Block_dom_pre_num(pred) == -1)
 708                                         continue;   /* control-dead */
 709
 710                                 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
 711                                 if (u->semi < w->semi) w->semi = u->semi;
 712                         }
 713                 }
 714
 715                 /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 716                    buckets can been implemented as linked lists. */
 717                 w->bucket = w->semi->bucket;
 718                 w->semi->bucket = w;
 719
 720                 dom_link (w->parent, w);
 721
 722                 /* Step 3 */
 723                 while (w->parent->bucket) {
 724                         tmp_dom_info *u;
 725                         v = w->parent->bucket;
 726                         /* remove v from w->parent->bucket */
 727                         w->parent->bucket = v->bucket;
 728                         v->bucket = NULL;
 729
 730                         u = dom_eval (v);
 731                         if (u->semi < v->semi)
 732                                 v->dom = u;
 733                         else
 734                                 v->dom = w->parent;
 735                 }
 736         }
 737         /* Step 4 */
 738         tdi_list[0].dom = NULL;
 739         set_Block_idom(tdi_list[0].block, NULL);
 740         set_Block_dom_depth(tdi_list[0].block, 1);
 741         for (i = 1; i < n_blocks;  i++) {
 742                 tmp_dom_info *w = &tdi_list[i];
 743                 int depth;
 744
 745                 if (! w->dom)
 746                         continue; /* control dead */
 747
 748                 if (w->dom != w->semi) w->dom = w->dom->dom;
 749                 set_Block_idom(w->block, w->dom->block);
 750
 751                 /* blocks dominated by dead one's are still dead */
 752                 depth = get_Block_dom_depth(w->dom->block);
 753                 if (depth > 0)
 754                         ++depth;
 755                 set_Block_dom_depth(w->block, depth);
 756         }
 757
 758         /* clean up */
 759         free(tdi_list);
 760
 761         /* Do a walk over the tree and assign the tree pre orders. */
 762         {
 763                 unsigned tree_pre_order = 0;
 764                 dom_tree_walk_irg(irg, assign_tree_dom_pre_order,
 765                         assign_tree_dom_pre_order_max, &tree_pre_order);
 766         }
 767         current_ir_graph = rem;
 768 }
 769
 770 void assure_doms(ir_graph *irg)
 771 {
 772         if (get_irg_dom_state(irg) != dom_consistent)
 773                 compute_doms(irg);
 774 }
 775
 776 void free_dom(ir_graph *irg)
 777 {
 778         /* Update graph state */
 779         assert(get_irg_phase_state(irg) != phase_building);
 780         irg->dom_state = dom_none;
 781
 782         /* With the implementation right now there is nothing to free,
 783            but better call it anyways... */
 784 }
 785
 786 /* Computes the post dominator trees.  Sets a flag in irg to "dom_consistent".
 787    If the control flow of the graph is changed this flag must be set to
 788    "dom_inconsistent".  */
 789 void compute_postdoms(ir_graph *irg)
 790 {
 791         ir_graph *rem = current_ir_graph;
 792         int n_blocks, used, i, j;
 793         tmp_dom_info *tdi_list;
 794
 795         current_ir_graph = irg;
 796
 797         /* Update graph state */
 798         assert(get_irg_phase_state(irg) != phase_building);
 799         irg->pdom_state = dom_consistent;
 800
 801         /* Count the number of blocks in the graph. */
 802         n_blocks = 0;
 803         irg_block_walk_graph(irg, count_and_init_blocks_pdom, NULL, &n_blocks);
 804
 805         /* Memory for temporary information. */
 806         tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);
 807
 808         /* We need the out data structure. */
 809         assure_irg_outs(irg);
 810
 811         /* this with a standard walker as passing the parent to the sons isn't
 812            simple. */
 813         used = 0;
 814         inc_irg_block_visited(irg);
 815         init_tmp_pdom_info(get_irg_end_block(irg), NULL, tdi_list, &used, n_blocks);
 816         /* If not all blocks are reachable from End by cfg edges this assertion
 817            fails.
 818            assert(used == n_blocks && "Precondition for dom construction violated"); */
 819         n_blocks = used;
 820
 821
 822         for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 823                 int irn_arity;
 824                 tmp_dom_info *w = &tdi_list[i];
 825                 tmp_dom_info *v;
 826
 827                 /* Step 2 */
 828                 irn_arity = get_Block_n_cfg_outs_ka(w->block);
 829                 for (j = 0;  j < irn_arity;  j++) {
 830                         ir_node *succ = get_Block_cfg_out_ka(w->block, j);
 831                         tmp_dom_info *u;
 832
 833                         if (get_Block_postdom_pre_num (succ) == -1)
 834                                 continue;    /* endless-loop */
 835
 836                         u = dom_eval (&tdi_list[get_Block_postdom_pre_num(succ)]);
 837                         if (u->semi < w->semi) w->semi = u->semi;
 838                 }
 839                 /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 840                    buckets can be implemented as linked lists. */
 841                 w->bucket = w->semi->bucket;
 842                 w->semi->bucket = w;
 843
 844                 dom_link (w->parent, w);
 845
 846                 /* Step 3 */
 847                 while (w->parent->bucket) {
 848                         tmp_dom_info *u;
 849                         v = w->parent->bucket;
 850                         /* remove v from w->parent->bucket */
 851                         w->parent->bucket = v->bucket;
 852                         v->bucket = NULL;
 853
 854                         u = dom_eval(v);
 855                         if (u->semi < v->semi)
 856                                 v->dom = u;
 857                         else
 858                                 v->dom = w->parent;
 859                 }
 860         }
 861         /* Step 4 */
 862         tdi_list[0].dom = NULL;
 863         set_Block_ipostdom(tdi_list[0].block, NULL);
 864         set_Block_postdom_depth(tdi_list[0].block, 1);
 865         for (i = 1;  i < n_blocks;  i++) {
 866                 tmp_dom_info *w = &tdi_list[i];
 867
 868                 if (w->dom != w->semi) w->dom = w->dom->dom;
 869                 set_Block_ipostdom(w->block, w->dom->block);
 870                 set_Block_postdom_depth(w->block, get_Block_postdom_depth(w->dom->block) + 1);
 871         }
 872
 873         /* clean up */
 874         free(tdi_list);
 875
 876         /* Do a walk over the tree and assign the tree pre orders. */
 877         {
 878                 unsigned tree_pre_order = 0;
 879                 postdom_tree_walk_irg(irg, assign_tree_postdom_pre_order,
 880                         assign_tree_postdom_pre_order_max, &tree_pre_order);
 881         }
 882         current_ir_graph = rem;
 883 }
 884
 885 void assure_postdoms(ir_graph *irg)
 886 {
 887         if (get_irg_postdom_state(irg) != dom_consistent)
 888                 compute_postdoms(irg);
 889 }
 890
 891 void free_postdom(ir_graph *irg)
 892 {
 893         /* Update graph state */
 894         assert(get_irg_phase_state(irg) != phase_building);
 895         irg->pdom_state = dom_none;
 896
 897         /* With the implementation right now there is nothing to free,
 898            but better call it anyways... */
 899 }