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                 return new_Bad();
  56         }
  57         return get_dom_info(bl)->idom;
  58 }
  59
  60 void set_Block_idom(ir_node *bl, ir_node *n)
  61 {
  62         ir_dom_info *bli = get_dom_info(bl);
  63
  64         assert(is_Block(bl));
  65
  66         /* Set the immediate dominator of bl to n */
  67         bli->idom = n;
  68
  69         /*
  70          * If we don't set the root of the dominator tree
  71          * Append bl to the dominates queue of n.
  72          */
  73         if (n != NULL) {
  74                 ir_dom_info *ni = get_dom_info(n);
  75
  76                 bli->next = ni->first;
  77                 ni->first = bl;
  78         }
  79 }
  80
  81 ir_node *get_Block_ipostdom(const ir_node *bl)
  82 {
  83         assert(is_Block(bl));
  84         if (get_Block_postdom_depth(bl) == -1) {
  85                 /* This block is not reachable from Start */
  86                 return new_Bad();
  87         }
  88         return get_pdom_info(bl)->idom;
  89 }
  90
  91 void set_Block_ipostdom(ir_node *bl, ir_node *n)
  92 {
  93         ir_dom_info *bli = get_pdom_info(bl);
  94
  95         assert(is_Block(bl));
  96
  97         /* Set the immediate post dominator of bl to n */
  98         bli->idom = n;
  99
 100         /*
 101          * If we don't set the root of the post dominator tree
 102          * Append bl to the post dominates queue of n.
 103          */
 104         if (n != NULL) {
 105                 ir_dom_info *ni = get_pdom_info(n);
 106
 107                 bli->next = ni->first;
 108                 ni->first = bl;
 109         }
 110 }
 111
 112 int get_Block_dom_pre_num(const ir_node *bl)
 113 {
 114         assert(is_Block(bl));
 115         return get_dom_info(bl)->pre_num;
 116 }
 117
 118 void set_Block_dom_pre_num(ir_node *bl, int num)
 119 {
 120         assert(is_Block(bl));
 121         get_dom_info(bl)->pre_num = num;
 122 }
 123
 124 int get_Block_dom_depth(const ir_node *bl)
 125 {
 126         assert(is_Block(bl));
 127         return get_dom_info(bl)->dom_depth;
 128 }
 129
 130 void set_Block_dom_depth(ir_node *bl, int depth)
 131 {
 132         assert(is_Block(bl));
 133         get_dom_info(bl)->dom_depth = depth;
 134 }
 135
 136
 137 int get_Block_postdom_pre_num(const ir_node *bl)
 138 {
 139         assert(is_Block(bl));
 140         return get_pdom_info(bl)->pre_num;
 141 }
 142
 143 void set_Block_postdom_pre_num(ir_node *bl, int num)
 144 {
 145         assert(is_Block(bl));
 146         get_pdom_info(bl)->pre_num = num;
 147 }
 148
 149 int get_Block_postdom_depth(const ir_node *bl)
 150 {
 151         assert(is_Block(bl));
 152         return get_pdom_info(bl)->dom_depth;
 153 }
 154
 155 void set_Block_postdom_depth(ir_node *bl, int depth)
 156 {
 157         assert(is_Block(bl));
 158         get_pdom_info(bl)->dom_depth = depth;
 159 }
 160
 161 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
 162 {
 163         assert(is_Block(bl));
 164         return get_dom_info(bl)->tree_pre_num;
 165 }
 166
 167 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
 168 {
 169         assert(is_Block(bl));
 170         return get_dom_info(bl)->max_subtree_pre_num;
 171 }
 172
 173 unsigned get_Block_pdom_tree_pre_num(const ir_node *bl)
 174 {
 175         assert(is_Block(bl));
 176         return get_pdom_info(bl)->tree_pre_num;
 177 }
 178
 179 unsigned get_Block_pdom_max_subtree_pre_num(const ir_node *bl)
 180 {
 181         assert(is_Block(bl));
 182         return get_pdom_info(bl)->max_subtree_pre_num;
 183 }
 184
 185 /* Check, if a block dominates another block. */
 186 int block_dominates(const ir_node *a, const ir_node *b)
 187 {
 188         const ir_dom_info *ai, *bi;
 189
 190         if (is_Block(a) && is_Block(b)) {
 191                 ai = get_dom_info(a);
 192                 bi = get_dom_info(b);
 193                 return bi->tree_pre_num - ai->tree_pre_num
 194                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 195         }
 196
 197         return 0;
 198 }
 199
 200 /* Check, if a block strictly dominates another block. */
 201 int block_strictly_dominates(const ir_node *a, const ir_node *b)
 202 {
 203         return (a != b) && block_dominates(a, b);
 204 }
 205
 206 /* Returns the smallest common dominator block of two nodes. */
 207 ir_node *node_smallest_common_dominator(ir_node *a, ir_node *b)
 208 {
 209         ir_node *bl_a   = is_Block(a) ? a : get_nodes_block(a);
 210         ir_node *bl_b   = is_Block(b) ? b : get_nodes_block(b);
 211         ir_node *dom_bl = NULL;
 212
 213         /* Check if block of a dominates block of b */
 214         if (block_dominates(bl_a, bl_b))
 215                 dom_bl = bl_a;
 216         /* Check if block of b dominates block of a */
 217         else if (block_dominates(bl_b, bl_a))
 218                 dom_bl = bl_b;
 219         else {
 220                 /* walk up dominator tree and search for first block dominating a and b */
 221                 while (! dom_bl) {
 222                         bl_a = get_Block_idom(bl_a);
 223
 224                         assert(! is_Bad(bl_a) && "block is dead?");
 225
 226                         if (block_dominates(bl_a, bl_b))
 227                                 dom_bl = bl_a;
 228                 }
 229         }
 230
 231         return dom_bl;
 232 }
 233
 234 /* Returns the smallest common dominator block of all users of a node. */
 235 ir_node *node_users_smallest_common_dominator(ir_node *irn, int handle_phi)
 236 {
 237         int n, j, i = 0, success;
 238         ir_node **user_blocks, *dom_bl;
 239         const ir_edge_t *edge;
 240
 241         assert(! is_Block(irn) && "WRONG USAGE of node_users_smallest_common_dominator");
 242         assert(edges_activated(get_irn_irg(irn)) && "need edges activated");
 243
 244         n = get_irn_n_edges(irn);
 245
 246         /* get array to hold all block of the node users */
 247         NEW_ARR_A(ir_node *, user_blocks, n);
 248         foreach_out_edge(irn, edge) {
 249                 ir_node *src = get_edge_src_irn(edge);
 250
 251                 if (is_Phi(src) && handle_phi) {
 252                         /* get the corresponding cfg predecessor block if phi handling requested */
 253                         j  = get_edge_src_pos(edge);
 254                         assert(j >= 0 && "kaputt");
 255                         user_blocks[i++] = get_Block_cfgpred_block(get_nodes_block(src), j);
 256                 }
 257                 else
 258                         user_blocks[i++] = is_Block(src) ? src : get_nodes_block(src);
 259         }
 260
 261         assert(i == n && "get_irn_n_edges probably broken");
 262
 263         /* in case of only one user: return the block of the user */
 264         if (n == 1)
 265                 return user_blocks[0];
 266
 267         i = 0;
 268         /* search the smallest block dominating all user blocks */
 269         do {
 270                 dom_bl  = node_smallest_common_dominator(user_blocks[i], user_blocks[i + 1]);
 271                 success = 1;
 272
 273                 /* check if this block dominates all remaining blocks as well */
 274                 for (j = i + 2; j < n; j++) {
 275                         if (! block_dominates(dom_bl, user_blocks[j]))
 276                                 success = 0;
 277                 }
 278
 279                 if (success)
 280                         break;
 281
 282                 /* inherit the dominator block of the first (i + 1) users */
 283                 user_blocks[++i] = dom_bl;
 284         } while (i < n - 1);
 285
 286         assert(success && "no block found dominating all users");
 287
 288         return dom_bl;
 289 }
 290
 291
 292 /* Get the first node in the list of nodes dominated by a given block. */
 293 ir_node *get_Block_dominated_first(const ir_node *bl)
 294 {
 295         assert(is_Block(bl));
 296         return get_dom_info(bl)->first;
 297 }
 298
 299 /* Get the next node in a list of nodes which are dominated by some
 300  * other node. */
 301 ir_node *get_Block_dominated_next(const ir_node *bl)
 302 {
 303         assert(is_Block(bl));
 304         return get_dom_info(bl)->next;
 305 }
 306
 307 /* Check, if a block post dominates another block. */
 308 int block_postdominates(const ir_node *a, const ir_node *b)
 309 {
 310         const ir_dom_info *ai, *bi;
 311
 312         if (is_Block(a) && is_Block(b)) {
 313                 ai = get_pdom_info(a);
 314                 bi = get_pdom_info(b);
 315                 return bi->tree_pre_num - ai->tree_pre_num
 316                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 317         }
 318
 319         return 0;
 320 }
 321
 322 /* Check, if a block strictly dominates another block. */
 323 int block_strictly_postdominates(const ir_node *a, const ir_node *b)
 324 {
 325         return (a != b) && block_postdominates(a, b);
 326 }
 327
 328
 329 /* Get the first node in the list of nodes post dominated by a given block. */
 330 ir_node *get_Block_postdominated_first(const ir_node *bl)
 331 {
 332         assert(is_Block(bl));
 333         return get_pdom_info(bl)->first;
 334 }
 335
 336 /* Get the next node in a list of nodes which are post dominated by some
 337  * other node. */
 338 ir_node *get_Block_postdominated_next(const ir_node *bl)
 339 {
 340         assert(is_Block(bl));
 341         return get_pdom_info(bl)->next;
 342 }
 343
 344 /* Visit all nodes in the dominator subtree of a given node. */
 345 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
 346                 irg_walk_func *post, void *env)
 347 {
 348         ir_node *p;
 349
 350         if (pre)
 351                 pre(bl, env);
 352
 353         dominates_for_each(bl, p) {
 354                 dom_tree_walk(p, pre, post, env);
 355         }
 356
 357         if (post)
 358                 post(bl, env);
 359 }
 360
 361 /* Visit all nodes in the post dominator subtree of a given node. */
 362 void postdom_tree_walk(ir_node *bl, irg_walk_func *pre,
 363                 irg_walk_func *post, void *env)
 364 {
 365         ir_node *p;
 366
 367         if (pre)
 368                 pre(bl, env);
 369
 370         postdominates_for_each(bl, p) {
 371                 postdom_tree_walk(p, pre, post, env);
 372         }
 373
 374         if (post)
 375                 post(bl, env);
 376 }
 377
 378 /* Walk over the dominator tree of an irg starting at the root. */
 379 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 380                 irg_walk_func *post, void *env)
 381 {
 382         /* The root of the dominator tree should be the Start block. */
 383         ir_node *root = get_irg_start_block(irg);
 384
 385         assert(irg->dom_state == dom_consistent
 386                         && "The dominators of the irg must be consistent");
 387         assert(root && "The start block of the graph is NULL?");
 388         assert(get_dom_info(root)->idom == NULL
 389                         && "The start node in the graph must be the root of the dominator tree");
 390         dom_tree_walk(root, pre, post, env);
 391 }
 392
 393 /* Walk over the post dominator tree of an irg starting at the root. */
 394 void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 395                 irg_walk_func *post, void *env)
 396 {
 397         /* The root of the dominator tree should be the End block. */
 398         ir_node *root = get_irg_end_block(irg);
 399
 400         assert(irg->pdom_state == dom_consistent
 401                         && "The dominators of the irg must be consistent");
 402         assert(root && "The end block of the graph is NULL?");
 403         assert(get_pdom_info(root)->idom == NULL
 404                         && "The End block node in the graph must be the root of the post dominator tree");
 405         postdom_tree_walk(root, pre, post, env);
 406 }
 407
 408
 409 static void assign_tree_dom_pre_order(ir_node *bl, void *data)
 410 {
 411         unsigned *num = data;
 412         ir_dom_info *bi = get_dom_info(bl);
 413
 414         bi->tree_pre_num = (*num)++;
 415 }
 416
 417 static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
 418 {
 419         ir_dom_info *bi = get_dom_info(bl);
 420         ir_node *p;
 421         unsigned max = 0;
 422         unsigned children = 0;
 423         (void) data;
 424
 425         for (p = bi->first; p; p = get_dom_info(p)->next) {
 426                 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
 427                 max = max > max_p ? max : max_p;
 428                 children++;
 429         }
 430
 431         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 432         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 433 }
 434
 435 static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
 436 {
 437         unsigned *num = data;
 438         ir_dom_info *bi = get_pdom_info(bl);
 439
 440         bi->tree_pre_num = (*num)++;
 441 }
 442
 443 static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
 444 {
 445         ir_dom_info *bi = get_pdom_info(bl);
 446         ir_node *p;
 447         unsigned max = 0;
 448         unsigned children = 0;
 449         (void) data;
 450
 451         for (p = bi->first; p; p = get_pdom_info(p)->next) {
 452                 unsigned max_p = get_pdom_info(p)->max_subtree_pre_num;
 453                 max = max > max_p ? max : max_p;
 454                 children++;
 455         }
 456
 457         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 458         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 459 }
 460
 461 /*--------------------------------------------------------------------*/
 462 /*  Building and Removing the dominator data structure                */
 463 /*--------------------------------------------------------------------*/
 464
 465 /**
 466  * count the number of blocks and clears the post dominance info
 467  */
 468 static void count_and_init_blocks_pdom(ir_node *bl, void *env)
 469 {
 470         int *n_blocks = (int *) env;
 471
 472         if (is_Block_dead(bl))
 473                 return;
 474
 475         (*n_blocks) ++;
 476
 477         memset(get_pdom_info(bl), 0, sizeof(ir_dom_info));
 478         set_Block_ipostdom(bl, NULL);
 479         set_Block_postdom_pre_num(bl, -1);
 480         set_Block_postdom_depth(bl, -1);
 481 }
 482
 483 /** temporary type used while constructing the dominator / post dominator tree. */
 484 typedef struct tmp_dom_info {
 485         ir_node *block;               /**< backlink */
 486
 487         struct tmp_dom_info *semi;    /**< semidominator */
 488         struct tmp_dom_info *parent;
 489         struct tmp_dom_info *label;   /**< used for LINK and EVAL */
 490         struct tmp_dom_info *ancestor;/**< used for LINK and EVAL */
 491         struct tmp_dom_info *dom;     /**< After step 3, if the semidominator of w is
 492                                            its immediate dominator, then w->dom is the
 493                                            immediate dominator of w.  Otherwise w->dom
 494                                            is a vertex v whose number is smaller than
 495                                            w and whose immediate dominator is also w's
 496                                            immediate dominator. After step 4, w->dom
 497                                            is the immediate dominator of w.  */
 498         struct tmp_dom_info *bucket;  /**< set of vertices with same semidominator */
 499 } tmp_dom_info;
 500
 501 /** Struct to pass info through walker. */
 502 typedef struct {
 503         tmp_dom_info *d;
 504         int used;
 505 } dom_env;
 506
 507
 508 /**
 509  * Walks Blocks along the out data structure.  If recursion started with
 510  * Start block misses control dead blocks.
 511  */
 512 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
 513                               tmp_dom_info *tdi_list, int *used, int n_blocks)
 514 {
 515         tmp_dom_info *tdi;
 516         int i;
 517
 518         if (is_Block_dead(bl))
 519                 return;
 520
 521         assert(is_Block(bl));
 522         if (Block_block_visited(bl))
 523           return;
 524         mark_Block_block_visited(bl);
 525         set_Block_dom_pre_num(bl, *used);
 526
 527         assert(*used < n_blocks);
 528         tdi = &tdi_list[*used];
 529         ++(*used);
 530
 531         tdi->semi     = tdi;
 532         tdi->label    = tdi;
 533         tdi->ancestor = NULL;
 534         tdi->bucket   = NULL;
 535         tdi->parent   = parent;
 536         tdi->block    = bl;
 537
 538         /* Iterate */
 539         for (i = get_Block_n_cfg_outs_ka(bl) - 1; i >= 0; --i) {
 540                 ir_node *pred = get_Block_cfg_out_ka(bl, i);
 541                 /* can happen for half-optimized dead code (I've seen this in student
 542                    projects */
 543                 if (!is_Block(pred))
 544                         continue;
 545
 546                 init_tmp_dom_info(pred, tdi, tdi_list, used, n_blocks);
 547         }
 548 }
 549
 550 /**
 551  * Walks Blocks along the control flow.  If recursion started with
 552  * End block misses blocks in endless loops.
 553  */
 554 static void init_tmp_pdom_info(ir_node *bl, tmp_dom_info *parent,
 555                                tmp_dom_info *tdi_list, int* used, int n_blocks)
 556 {
 557         tmp_dom_info *tdi;
 558         int i;
 559
 560         if (is_Block_dead(bl))
 561                 return;
 562
 563         assert(is_Block(bl));
 564         if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
 565           return;
 566         mark_Block_block_visited(bl);
 567         set_Block_postdom_pre_num(bl, *used);
 568
 569         assert(*used < n_blocks);
 570         tdi = &tdi_list[*used];
 571         ++(*used);
 572
 573         tdi->semi = tdi;
 574         tdi->label = tdi;
 575         tdi->ancestor = NULL;
 576         tdi->bucket = NULL;
 577         tdi->parent = parent;
 578         tdi->block = bl;
 579
 580         /* Iterate */
 581         for (i = get_Block_n_cfgpreds(bl) - 1; i >= 0; --i) {
 582                 ir_node *pred = get_Block_cfgpred_block(bl, i);
 583                 if (is_Bad(pred))
 584                         continue;
 585                 assert(is_Block(pred));
 586                 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
 587         }
 588
 589         /* Handle keep-alives. Note that the preprocessing
 590            in init_construction() had already killed all
 591            phantom keep-alive edges. All remaining block keep-alives
 592            are really edges to endless loops.
 593          */
 594         if (bl == get_irg_end_block(current_ir_graph)) {
 595                 ir_node *end = get_irg_end(current_ir_graph);
 596
 597                 for (i = get_irn_arity(end) - 1; i >= 0; --i) {
 598                         ir_node *pred = get_irn_n(end, i);
 599
 600                         if (is_Block(pred))
 601                                 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
 602                 }
 603         }
 604 }
 605
 606 static void dom_compress(tmp_dom_info *v)
 607 {
 608         assert (v->ancestor);
 609         if (v->ancestor->ancestor) {
 610                 dom_compress (v->ancestor);
 611                 if (v->ancestor->label->semi < v->label->semi) {
 612                         v->label = v->ancestor->label;
 613                 }
 614                 v->ancestor = v->ancestor->ancestor;
 615         }
 616 }
 617
 618 /**
 619  * if V is a root, return v, else return the vertex u, not being the
 620  * root, with minimum u->semi on the path from v to its root.
 621  */
 622 inline static tmp_dom_info *dom_eval(tmp_dom_info *v)
 623 {
 624         if (!v->ancestor) return v;
 625         dom_compress (v);
 626         return v->label;
 627 }
 628
 629 /** make V W's ancestor */
 630 inline static void dom_link(tmp_dom_info *v, tmp_dom_info *w)
 631 {
 632         w->ancestor = v;
 633 }
 634
 635 /**
 636  * Walker: count the number of blocks and clears the dominance info
 637  */
 638 static void count_and_init_blocks_dom(ir_node *bl, void *env)
 639 {
 640         int *n_blocks = (int *) env;
 641         if (is_Block_dead(bl))
 642                 return;
 643
 644         (*n_blocks) ++;
 645
 646         memset(get_dom_info(bl), 0, sizeof(ir_dom_info));
 647         set_Block_idom(bl, NULL);
 648         set_Block_dom_pre_num(bl, -1);
 649         set_Block_dom_depth(bl, -1);
 650 }
 651
 652 /* Computes the dominator trees.  Sets a flag in irg to "dom_consistent".
 653    If the control flow of the graph is changed this flag must be set to
 654    "dom_inconsistent".  */
 655 void compute_doms(ir_graph *irg)
 656 {
 657         ir_graph *rem = current_ir_graph;
 658         int n_blocks, used, i, j;
 659         tmp_dom_info *tdi_list;   /* Ein Golf? */
 660
 661         current_ir_graph = irg;
 662
 663         /* Update graph state */
 664         assert(get_irg_phase_state(irg) != phase_building);
 665         irg->dom_state = dom_consistent;
 666
 667         /* Count the number of blocks in the graph. */
 668         n_blocks = 0;
 669         irg_block_walk_graph(irg, count_and_init_blocks_dom, NULL, &n_blocks);
 670
 671         /* Memory for temporary information. */
 672         tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);
 673
 674         /* We need the out data structure. */
 675         assure_irg_outs(irg);
 676
 677         /* this with a standard walker as passing the parent to the sons isn't
 678            simple. */
 679         used = 0;
 680         inc_irg_block_visited(irg);
 681         init_tmp_dom_info(get_irg_start_block(irg), NULL, tdi_list, &used, n_blocks);
 682         /* If not all blocks are reachable from Start by out edges this assertion
 683            fails.
 684            assert(used == n_blocks && "Precondition for dom construction violated"); */
 685         assert(used <= n_blocks && "Precondition for dom construction violated");
 686         n_blocks = used;
 687
 688
 689         for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 690                 int irn_arity;
 691                 tmp_dom_info *w = &tdi_list[i];
 692                 tmp_dom_info *v;
 693
 694                 /* Step 2 */
 695                 irn_arity = get_irn_arity(w->block);
 696                 for (j = 0; j < irn_arity;  j++) {
 697                         ir_node *pred = get_Block_cfgpred_block(w->block, j);
 698                         tmp_dom_info *u;
 699
 700                         if (is_Bad(pred) || (get_Block_dom_pre_num (pred) == -1))
 701                                 continue;       /* control-dead */
 702
 703                         u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
 704                         if (u->semi < w->semi) w->semi = u->semi;
 705                 }
 706
 707                 /* handle keep-alives if we are at the end block */
 708                 if (w->block == get_irg_end_block(irg)) {
 709                         ir_node *end = get_irg_end(irg);
 710
 711                         irn_arity = get_irn_arity(end);
 712                         for (j = 0; j < irn_arity;  j++) {
 713                                 ir_node *pred = get_irn_n(end, j);
 714                                 tmp_dom_info *u;
 715
 716                                 if (is_no_Block(pred) || get_Block_dom_pre_num(pred) == -1)
 717                                         continue;       /* control-dead */
 718
 719                                 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
 720                                 if (u->semi < w->semi) w->semi = u->semi;
 721                         }
 722                 }
 723
 724                 /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 725                    buckets can been implemented as linked lists. */
 726                 w->bucket = w->semi->bucket;
 727                 w->semi->bucket = w;
 728
 729                 dom_link (w->parent, w);
 730
 731                 /* Step 3 */
 732                 while (w->parent->bucket) {
 733                         tmp_dom_info *u;
 734                         v = w->parent->bucket;
 735                         /* remove v from w->parent->bucket */
 736                         w->parent->bucket = v->bucket;
 737                         v->bucket = NULL;
 738
 739                         u = dom_eval (v);
 740                         if (u->semi < v->semi)
 741                                 v->dom = u;
 742                         else
 743                                 v->dom = w->parent;
 744                 }
 745         }
 746         /* Step 4 */
 747         tdi_list[0].dom = NULL;
 748         set_Block_idom(tdi_list[0].block, NULL);
 749         set_Block_dom_depth(tdi_list[0].block, 1);
 750         for (i = 1; i < n_blocks;  i++) {
 751                 tmp_dom_info *w = &tdi_list[i];
 752                 int depth;
 753
 754                 if (! w->dom)
 755                         continue; /* control dead */
 756
 757                 if (w->dom != w->semi) w->dom = w->dom->dom;
 758                 set_Block_idom(w->block, w->dom->block);
 759
 760                 /* blocks dominated by dead one's are still dead */
 761                 depth = get_Block_dom_depth(w->dom->block);
 762                 if (depth > 0)
 763                         ++depth;
 764                 set_Block_dom_depth(w->block, depth);
 765         }
 766
 767         /* clean up */
 768         free(tdi_list);
 769
 770         /* Do a walk over the tree and assign the tree pre orders. */
 771         {
 772                 unsigned tree_pre_order = 0;
 773                 dom_tree_walk_irg(irg, assign_tree_dom_pre_order,
 774                         assign_tree_dom_pre_order_max, &tree_pre_order);
 775         }
 776         current_ir_graph = rem;
 777 }
 778
 779 void assure_doms(ir_graph *irg)
 780 {
 781         if (get_irg_dom_state(irg) != dom_consistent)
 782                 compute_doms(irg);
 783 }
 784
 785 void free_dom(ir_graph *irg)
 786 {
 787         /* Update graph state */
 788         assert(get_irg_phase_state(irg) != phase_building);
 789         irg->dom_state = dom_none;
 790
 791         /* With the implementation right now there is nothing to free,
 792            but better call it anyways... */
 793 }
 794
 795 /* Computes the post dominator trees.  Sets a flag in irg to "dom_consistent".
 796    If the control flow of the graph is changed this flag must be set to
 797    "dom_inconsistent".  */
 798 void compute_postdoms(ir_graph *irg)
 799 {
 800         ir_graph *rem = current_ir_graph;
 801         int n_blocks, used, i, j;
 802         tmp_dom_info *tdi_list;
 803
 804         current_ir_graph = irg;
 805
 806         /* Update graph state */
 807         assert(get_irg_phase_state(irg) != phase_building);
 808         irg->pdom_state = dom_consistent;
 809
 810         /* Count the number of blocks in the graph. */
 811         n_blocks = 0;
 812         irg_block_walk_graph(irg, count_and_init_blocks_pdom, NULL, &n_blocks);
 813
 814         /* Memory for temporary information. */
 815         tdi_list = XMALLOCNZ(tmp_dom_info, n_blocks);
 816
 817         /* We need the out data structure. */
 818         assure_irg_outs(irg);
 819
 820         /* this with a standard walker as passing the parent to the sons isn't
 821            simple. */
 822         used = 0;
 823         inc_irg_block_visited(irg);
 824         init_tmp_pdom_info(get_irg_end_block(irg), NULL, tdi_list, &used, n_blocks);
 825         /* If not all blocks are reachable from End by cfg edges this assertion
 826            fails.
 827            assert(used == n_blocks && "Precondition for dom construction violated"); */
 828         n_blocks = used;
 829
 830
 831         for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 832                 int irn_arity;
 833                 tmp_dom_info *w = &tdi_list[i];
 834                 tmp_dom_info *v;
 835
 836                 /* Step 2 */
 837                 irn_arity = get_Block_n_cfg_outs_ka(w->block);
 838                 for (j = 0;  j < irn_arity;  j++) {
 839                         ir_node *succ = get_Block_cfg_out_ka(w->block, j);
 840                         tmp_dom_info *u;
 841
 842                         if (get_Block_postdom_pre_num (succ) == -1)
 843                                 continue;       /* endless-loop */
 844
 845                         u = dom_eval (&tdi_list[get_Block_postdom_pre_num(succ)]);
 846                         if (u->semi < w->semi) w->semi = u->semi;
 847                 }
 848                 /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 849                    buckets can be implemented as linked lists. */
 850                 w->bucket = w->semi->bucket;
 851                 w->semi->bucket = w;
 852
 853                 dom_link (w->parent, w);
 854
 855                 /* Step 3 */
 856                 while (w->parent->bucket) {
 857                         tmp_dom_info *u;
 858                         v = w->parent->bucket;
 859                         /* remove v from w->parent->bucket */
 860                         w->parent->bucket = v->bucket;
 861                         v->bucket = NULL;
 862
 863                         u = dom_eval(v);
 864                         if (u->semi < v->semi)
 865                                 v->dom = u;
 866                         else
 867                                 v->dom = w->parent;
 868                 }
 869         }
 870         /* Step 4 */
 871         tdi_list[0].dom = NULL;
 872         set_Block_ipostdom(tdi_list[0].block, NULL);
 873         set_Block_postdom_depth(tdi_list[0].block, 1);
 874         for (i = 1;  i < n_blocks;  i++) {
 875                 tmp_dom_info *w = &tdi_list[i];
 876
 877                 if (w->dom != w->semi) w->dom = w->dom->dom;
 878                 set_Block_ipostdom(w->block, w->dom->block);
 879                 set_Block_postdom_depth(w->block, get_Block_postdom_depth(w->dom->block) + 1);
 880         }
 881
 882         /* clean up */
 883         free(tdi_list);
 884
 885         /* Do a walk over the tree and assign the tree pre orders. */
 886         {
 887                 unsigned tree_pre_order = 0;
 888                 postdom_tree_walk_irg(irg, assign_tree_postdom_pre_order,
 889                         assign_tree_postdom_pre_order_max, &tree_pre_order);
 890         }
 891         current_ir_graph = rem;
 892 }
 893
 894 void assure_postdoms(ir_graph *irg)
 895 {
 896         if (get_irg_postdom_state(irg) != dom_consistent)
 897                 compute_postdoms(irg);
 898 }
 899
 900 void free_postdom(ir_graph *irg)
 901 {
 902         /* Update graph state */
 903         assert(get_irg_phase_state(irg) != phase_building);
 904         irg->pdom_state = dom_none;
 905
 906         /* With the implementation right now there is nothing to free,
 907            but better call it anyways... */
 908 }