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