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