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

   1 /*
   2  * Project:     libFIRM
   3  * File name:   ir/ana/irdom.c
   4  * Purpose:     Construct and access dominator / post dominator tree.
   5  * Author:      Goetz Lindenmaier
   6  * Modified by: Michael Beck, Rubino Geiss
   7  * Created:     2.2002
   8  * CVS-ID:      $Id$
   9  * Copyright:   (c) 2002-2007 Universitaet Karlsruhe
  10  * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
  11  */
  12
  13 #ifdef HAVE_CONFIG_H
  14 #include "config.h"
  15 #endif
  16
  17 #ifdef HAVE_STRING_H
  18 #include <string.h>
  19 #endif
  20
  21 #include "irouts.h"
  22
  23 #include "xmalloc.h"
  24 #include "irgwalk.h"
  25 #include "irdom_t.h"
  26 #include "irgraph_t.h"   /* To access state field. */
  27 #include "irnode_t.h"
  28 #include "ircons_t.h"
  29 #include "array.h"
  30 #include "iredges.h"
  31
  32
  33 #define get_dom_info(bl)  (&(bl)->attr.block.dom)
  34 #define get_pdom_info(bl) (&(bl)->attr.block.pdom)
  35
  36 /*--------------------------------------------------------------------*/
  37 /** Accessing the dominator and post dominator data structures       **/
  38 /*--------------------------------------------------------------------*/
  39
  40 ir_node *get_Block_idom(const ir_node *bl) {
  41         assert(is_Block(bl));
  42         if (get_Block_dom_depth(bl) == -1) {
  43                 /* This block is not reachable from Start */
  44                 return new_Bad();
  45         }
  46         return get_dom_info(bl)->idom;
  47 }
  48
  49 void set_Block_idom(ir_node *bl, ir_node *n) {
  50         ir_dom_info *bli = get_dom_info(bl);
  51
  52         assert(get_irn_op(bl) == op_Block);
  53
  54         /* Set the immediate dominator of bl to n */
  55         bli->idom = n;
  56
  57         /*
  58          * If we don't set the root of the dominator tree
  59          * Append bl to the dominates queue of n.
  60          */
  61         if(n != NULL) {
  62                 ir_dom_info *ni = get_dom_info(n);
  63
  64                 bli->next = ni->first;
  65                 ni->first = bl;
  66         }
  67 }
  68
  69 ir_node *get_Block_ipostdom(const ir_node *bl) {
  70         assert(is_Block(bl));
  71         if (get_Block_postdom_depth(bl) == -1) {
  72                 /* This block is not reachable from Start */
  73                 return new_Bad();
  74         }
  75         return get_pdom_info(bl)->idom;
  76 }
  77
  78 void set_Block_ipostdom(ir_node *bl, ir_node *n) {
  79         ir_dom_info *bli = get_pdom_info(bl);
  80
  81         assert(get_irn_op(bl) == op_Block);
  82
  83         /* Set the immediate post dominator of bl to n */
  84         bli->idom = n;
  85
  86         /*
  87          * If we don't set the root of the post dominator tree
  88          * Append bl to the post dominates queue of n.
  89          */
  90         if(n != NULL) {
  91                 ir_dom_info *ni = get_pdom_info(n);
  92
  93                 bli->next = ni->first;
  94                 ni->first = bl;
  95         }
  96 }
  97
  98 int get_Block_dom_pre_num(const ir_node *bl) {
  99         assert(get_irn_op(bl) == op_Block);
 100         return get_dom_info(bl)->pre_num;
 101 }
 102
 103 void set_Block_dom_pre_num(ir_node *bl, int num) {
 104         assert(get_irn_op(bl) == op_Block);
 105         get_dom_info(bl)->pre_num = num;
 106 }
 107
 108 int get_Block_dom_depth(const ir_node *bl) {
 109         assert(get_irn_op(bl) == op_Block);
 110         return get_dom_info(bl)->dom_depth;
 111 }
 112
 113 void set_Block_dom_depth(ir_node *bl, int depth) {
 114         assert(get_irn_op(bl) == op_Block);
 115         get_dom_info(bl)->dom_depth = depth;
 116 }
 117
 118
 119 int get_Block_postdom_pre_num(const ir_node *bl) {
 120         assert(get_irn_op(bl) == op_Block);
 121         return get_pdom_info(bl)->pre_num;
 122 }
 123
 124 void set_Block_postdom_pre_num(ir_node *bl, int num) {
 125         assert(get_irn_op(bl) == op_Block);
 126         get_pdom_info(bl)->pre_num = num;
 127 }
 128
 129 int get_Block_postdom_depth(const ir_node *bl) {
 130         assert(get_irn_op(bl) == op_Block);
 131         return get_pdom_info(bl)->dom_depth;
 132 }
 133
 134 void set_Block_postdom_depth(ir_node *bl, int depth) {
 135         assert(get_irn_op(bl) == op_Block);
 136         get_pdom_info(bl)->dom_depth = depth;
 137 }
 138
 139 unsigned get_Block_dom_tree_pre_num(const ir_node *bl)
 140 {
 141         assert(is_Block(bl));
 142         return get_dom_info(bl)->tree_pre_num;
 143 }
 144
 145 unsigned get_Block_dom_max_subtree_pre_num(const ir_node *bl)
 146 {
 147         assert(is_Block(bl));
 148         return get_dom_info(bl)->max_subtree_pre_num;
 149 }
 150
 151 unsigned get_Block_pdom_tree_pre_num(const ir_node *bl)
 152 {
 153         assert(is_Block(bl));
 154         return get_pdom_info(bl)->tree_pre_num;
 155 }
 156
 157 unsigned get_Block_pdom_max_subtree_pre_num(const ir_node *bl)
 158 {
 159         assert(is_Block(bl));
 160         return get_pdom_info(bl)->max_subtree_pre_num;
 161 }
 162
 163 /* Check, if a block dominates another block. */
 164 int block_dominates(const ir_node *a, const ir_node *b)
 165 {
 166         const ir_dom_info *ai, *bi;
 167
 168         if (is_Block(a) && is_Block(b)) {
 169                 ai = get_dom_info(a);
 170                 bi = get_dom_info(b);
 171                 return bi->tree_pre_num - ai->tree_pre_num
 172                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 173         }
 174
 175         return 0;
 176 }
 177
 178 /* Returns the smallest common dominator block of two nodes. */
 179 ir_node *node_smallest_common_dominator(ir_node *a, ir_node *b)
 180 {
 181         ir_node *bl_a   = is_Block(a) ? a : get_nodes_block(a);
 182         ir_node *bl_b   = is_Block(b) ? b : get_nodes_block(b);
 183         ir_node *dom_bl = NULL;
 184
 185         /* Check if block of a dominates block of b */
 186         if (block_dominates(bl_a, bl_b))
 187                 dom_bl = bl_a;
 188         /* Check if block of b dominates block of a */
 189         else if (block_dominates(bl_b, bl_a))
 190                 dom_bl = bl_b;
 191         else {
 192                 /* walk up dominator tree and search for first block dominating a and b */
 193                 while (! dom_bl) {
 194                         bl_a = get_Block_idom(bl_a);
 195
 196                         assert(! is_Bad(bl_a) && "block is dead?");
 197
 198                         if (block_dominates(bl_a, bl_b))
 199                                 dom_bl = bl_a;
 200                 }
 201         }
 202
 203         return dom_bl;
 204 }
 205
 206 /* Returns the smallest common dominator block of all users of a node. */
 207 ir_node *node_users_smallest_common_dominator(ir_node *irn, int handle_phi)
 208 {
 209         int n, j, i = 0, success;
 210         ir_node **user_blocks, *dom_bl;
 211         const ir_edge_t *edge;
 212
 213         assert(! is_Block(irn) && "WRONG USAGE of node_users_smallest_common_dominator");
 214         assert(edges_activated(get_irn_irg(irn)) && "need edges activated");
 215
 216         n = get_irn_n_edges(irn);
 217
 218         /* get array to hold all block of the node users */
 219         NEW_ARR_A(ir_node *, user_blocks, n);
 220         foreach_out_edge(irn, edge) {
 221                 ir_node *src = get_edge_src_irn(edge);
 222
 223                 if (is_Phi(src) && handle_phi) {
 224                         /* get the corresponding cfg predecessor block if phi handling requested */
 225                         j  = get_edge_src_pos(edge);
 226                         assert(j >= 0 && "kaputt");
 227                         user_blocks[i++] = get_Block_cfgpred_block(get_nodes_block(src), j);
 228                 }
 229                 else
 230                         user_blocks[i++] = is_Block(src) ? src : get_nodes_block(src);
 231         }
 232
 233         assert(i == n && "get_irn_n_edges probably broken");
 234
 235         /* in case of only one user: return the block of the user */
 236         if (n == 1)
 237                 return user_blocks[0];
 238
 239         i = 0;
 240         /* search the smallest block dominating all user blocks */
 241         do {
 242                 dom_bl  = node_smallest_common_dominator(user_blocks[i], user_blocks[i + 1]);
 243                 success = 1;
 244
 245                 /* check if this block dominates all remaining blocks as well */
 246                 for (j = i + 2; j < n; j++) {
 247                         if (! block_dominates(dom_bl, user_blocks[j]))
 248                                 success = 0;
 249                 }
 250
 251                 if (success)
 252                         break;
 253
 254                 /* inherit the dominator block of the first (i + 1) users */
 255                 user_blocks[++i] = dom_bl;
 256         } while (i < n - 1);
 257
 258         assert(success && "no block found dominating all users");
 259
 260         return dom_bl;
 261 }
 262
 263
 264 /* Get the first node in the list of nodes dominated by a given block. */
 265 ir_node *get_Block_dominated_first(const ir_node *bl)
 266 {
 267         assert(is_Block(bl));
 268         return get_dom_info(bl)->first;
 269 }
 270
 271 /* Get the next node in a list of nodes which are dominated by some
 272  * other node. */
 273 ir_node *get_Block_dominated_next(const ir_node *bl)
 274 {
 275         assert(is_Block(bl));
 276         return get_dom_info(bl)->next;
 277 }
 278
 279 /* Check, if a block post dominates another block. */
 280 int block_postdominates(const ir_node *a, const ir_node *b)
 281 {
 282         const ir_dom_info *ai, *bi;
 283
 284         if (is_Block(a) && is_Block(b)) {
 285                 ai = get_pdom_info(a);
 286                 bi = get_pdom_info(b);
 287                 return bi->tree_pre_num - ai->tree_pre_num
 288                         <= ai->max_subtree_pre_num - ai->tree_pre_num;
 289         }
 290
 291         return 0;
 292 }
 293
 294 /* Get the first node in the list of nodes post dominated by a given block. */
 295 ir_node *get_Block_postdominated_first(const ir_node *bl)
 296 {
 297         assert(is_Block(bl));
 298         return get_pdom_info(bl)->first;
 299 }
 300
 301 /* Get the next node in a list of nodes which are post dominated by some
 302  * other node. */
 303 ir_node *get_Block_postdominated_next(const ir_node *bl)
 304 {
 305         assert(is_Block(bl));
 306         return get_pdom_info(bl)->next;
 307 }
 308
 309 /* Visit all nodes in the dominator subtree of a given node. */
 310 void dom_tree_walk(ir_node *bl, irg_walk_func *pre,
 311                 irg_walk_func *post, void *env)
 312 {
 313         ir_node *p;
 314
 315         if(pre)
 316                 pre(bl, env);
 317
 318         dominates_for_each(bl, p) {
 319                 dom_tree_walk(p, pre, post, env);
 320         }
 321
 322         if(post)
 323                 post(bl, env);
 324 }
 325
 326 /* Visit all nodes in the post dominator subtree of a given node. */
 327 void postdom_tree_walk(ir_node *bl, irg_walk_func *pre,
 328                 irg_walk_func *post, void *env)
 329 {
 330         ir_node *p;
 331
 332         if(pre)
 333                 pre(bl, env);
 334
 335         postdominates_for_each(bl, p) {
 336                 postdom_tree_walk(p, pre, post, env);
 337         }
 338
 339         if(post)
 340                 post(bl, env);
 341 }
 342
 343 /* Walk over the dominator tree of an irg starting at the root. */
 344 void dom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 345                 irg_walk_func *post, void *env)
 346 {
 347         /* The root of the dominator tree should be the Start block. */
 348         ir_node *root = get_irg_start_block(irg);
 349
 350   assert(irg->dom_state == dom_consistent
 351                         && "The dominators of the irg must be consistent");
 352         assert(root && "The start block of the graph is NULL?");
 353         assert(get_dom_info(root)->idom == NULL
 354                         && "The start node in the graph must be the root of the dominator tree");
 355         dom_tree_walk(root, pre, post, env);
 356 }
 357
 358 /* Walk over the post dominator tree of an irg starting at the root. */
 359 void postdom_tree_walk_irg(ir_graph *irg, irg_walk_func *pre,
 360                 irg_walk_func *post, void *env)
 361 {
 362         /* The root of the dominator tree should be the End block. */
 363         ir_node *root = get_irg_end_block(irg);
 364
 365         assert(irg->pdom_state == dom_consistent
 366                         && "The dominators of the irg must be consistent");
 367         assert(root && "The end block of the graph is NULL?");
 368         assert(get_pdom_info(root)->idom == NULL
 369                         && "The End block node in the graph must be the root of the post dominator tree");
 370         postdom_tree_walk(root, pre, post, env);
 371 }
 372
 373
 374 static void assign_tree_dom_pre_order(ir_node *bl, void *data)
 375 {
 376         unsigned *num = data;
 377         ir_dom_info *bi = get_dom_info(bl);
 378
 379         bi->tree_pre_num = (*num)++;
 380 }
 381
 382 static void assign_tree_dom_pre_order_max(ir_node *bl, void *data)
 383 {
 384         ir_dom_info *bi = get_dom_info(bl);
 385         ir_node *p;
 386         unsigned max = 0;
 387         unsigned children = 0;
 388
 389         for(p = bi->first; p; p = get_dom_info(p)->next) {
 390                 unsigned max_p = get_dom_info(p)->max_subtree_pre_num;
 391                 max = max > max_p ? max : max_p;
 392                 children++;
 393         }
 394
 395         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 396         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 397 }
 398
 399 static void assign_tree_postdom_pre_order(ir_node *bl, void *data)
 400 {
 401         unsigned *num = data;
 402         ir_dom_info *bi = get_pdom_info(bl);
 403
 404         bi->tree_pre_num = (*num)++;
 405 }
 406
 407 static void assign_tree_postdom_pre_order_max(ir_node *bl, void *data)
 408 {
 409         ir_dom_info *bi = get_pdom_info(bl);
 410         ir_node *p;
 411         unsigned max = 0;
 412         unsigned children = 0;
 413
 414         for(p = bi->first; p; p = get_pdom_info(p)->next) {
 415                 unsigned max_p = get_pdom_info(p)->max_subtree_pre_num;
 416                 max = max > max_p ? max : max_p;
 417                 children++;
 418         }
 419
 420         bi->max_subtree_pre_num = children > 0 ? max : bi->tree_pre_num;
 421         assert(bi->max_subtree_pre_num >= bi->tree_pre_num);
 422 }
 423
 424 /*--------------------------------------------------------------------*/
 425 /*  Building and Removing the dominator data structure                */
 426 /*--------------------------------------------------------------------*/
 427
 428 /**
 429  * count the number of blocks and clears the post dominance info
 430  */
 431 static void count_and_init_blocks_pdom(ir_node *bl, void *env) {
 432         int *n_blocks = (int *) env;
 433         (*n_blocks) ++;
 434
 435         memset(get_pdom_info(bl), 0, sizeof(ir_dom_info));
 436         set_Block_ipostdom(bl, NULL);
 437         set_Block_postdom_pre_num(bl, -1);
 438         set_Block_postdom_depth(bl, -1);
 439 }
 440
 441 /** temporary type used while constructing the dominator / post dominator tree. */
 442 typedef struct tmp_dom_info {
 443         ir_node *block;               /**< backlink */
 444
 445         struct tmp_dom_info *semi;    /**< semidominator */
 446         struct tmp_dom_info *parent;
 447         struct tmp_dom_info *label;   /**< used for LINK and EVAL */
 448         struct tmp_dom_info *ancestor;/**< used for LINK and EVAL */
 449         struct tmp_dom_info *dom;     /**< After step 3, if the semidominator of w is
 450                                            its immediate dominator, then w->dom is the
 451                                            immediate dominator of w.  Otherwise w->dom
 452                                            is a vertex v whose number is smaller than
 453                                            w and whose immediate dominator is also w's
 454                                            immediate dominator. After step 4, w->dom
 455                                            is the immediate dominator of w.  */
 456         struct tmp_dom_info *bucket;  /**< set of vertices with same semidominator */
 457 } tmp_dom_info;
 458
 459 /** Struct to pass info through walker. */
 460 typedef struct {
 461         tmp_dom_info *d;
 462         int used;
 463 } dom_env;
 464
 465
 466 /**
 467  * Walks Blocks along the out data structure.  If recursion started with
 468  * Start block misses control dead blocks.
 469  */
 470 static void init_tmp_dom_info(ir_node *bl, tmp_dom_info *parent,
 471                               tmp_dom_info *tdi_list, int *used, int n_blocks) {
 472         tmp_dom_info *tdi;
 473         int i;
 474
 475         assert(is_Block(bl));
 476         if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
 477           return;
 478         mark_Block_block_visited(bl);
 479         set_Block_dom_pre_num(bl, *used);
 480
 481         assert(*used < n_blocks);
 482         tdi = &tdi_list[*used];
 483         ++(*used);
 484
 485         tdi->semi     = tdi;
 486         tdi->label    = tdi;
 487         tdi->ancestor = NULL;
 488         tdi->bucket   = NULL;
 489         tdi->parent   = parent;
 490         tdi->block    = bl;
 491
 492         /* Iterate */
 493         for (i = get_Block_n_cfg_outs_ka(bl) - 1; i >= 0; --i) {
 494                 ir_node *pred = get_Block_cfg_out_ka(bl, i);
 495                 assert(is_Block(pred));
 496                 init_tmp_dom_info(pred, tdi, tdi_list, used, n_blocks);
 497         }
 498 }
 499
 500 /**
 501  * Walks Blocks along the control flow.  If recursion started with
 502  * End block misses blocks in endless loops.
 503  */
 504 static void init_tmp_pdom_info(ir_node *bl, tmp_dom_info *parent,
 505                                tmp_dom_info *tdi_list, int* used, int n_blocks) {
 506         tmp_dom_info *tdi;
 507         int i;
 508
 509         assert(is_Block(bl));
 510         if (get_irg_block_visited(current_ir_graph) == get_Block_block_visited(bl))
 511           return;
 512         mark_Block_block_visited(bl);
 513         set_Block_postdom_pre_num(bl, *used);
 514
 515         assert(*used < n_blocks);
 516         tdi = &tdi_list[*used];
 517         ++(*used);
 518
 519         tdi->semi = tdi;
 520         tdi->label = tdi;
 521         tdi->ancestor = NULL;
 522         tdi->bucket = NULL;
 523         tdi->parent = parent;
 524         tdi->block = bl;
 525
 526         /* Iterate */
 527         for (i = get_Block_n_cfgpreds(bl) - 1; i >= 0; --i) {
 528                 ir_node *pred = get_Block_cfgpred_block(bl, i);
 529                 if (is_Bad(pred))
 530                         continue;
 531                 assert(is_Block(pred));
 532                 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
 533         }
 534
 535         /* Handle keep-alives. Note that the preprocessing
 536            in init_construction() had already killed all
 537            phantom keep-alive edges. All remaining block keep-alives
 538            are really edges to endless loops.
 539          */
 540         if (bl == get_irg_end_block(current_ir_graph)) {
 541                 ir_node *end = get_irg_end(current_ir_graph);
 542
 543                 for (i = get_irn_arity(end) - 1; i >= 0; --i) {
 544                         ir_node *pred = get_irn_n(end, i);
 545
 546                         if (is_Block(pred))
 547                                 init_tmp_pdom_info(pred, tdi, tdi_list, used, n_blocks);
 548                 }
 549         }
 550 }
 551
 552 static void dom_compress(tmp_dom_info *v) {
 553         assert (v->ancestor);
 554         if (v->ancestor->ancestor) {
 555                 dom_compress (v->ancestor);
 556                 if (v->ancestor->label->semi < v->label->semi) {
 557                         v->label = v->ancestor->label;
 558                 }
 559                 v->ancestor = v->ancestor->ancestor;
 560         }
 561 }
 562
 563 /**
 564  * if V is a root, return v, else return the vertex u, not being the
 565  * root, with minimum u->semi on the path from v to its root.
 566  */
 567 INLINE static tmp_dom_info *dom_eval(tmp_dom_info *v) {
 568         if (!v->ancestor) return v;
 569         dom_compress (v);
 570         return v->label;
 571 }
 572
 573 /** make V W's ancestor */
 574 INLINE static void dom_link(tmp_dom_info *v, tmp_dom_info *w) {
 575         w->ancestor = v;
 576 }
 577
 578 /**
 579  * Walker: count the number of blocks and clears the dominance info
 580  */
 581 static void count_and_init_blocks_dom(ir_node *bl, void *env) {
 582         int *n_blocks = (int *) env;
 583         (*n_blocks) ++;
 584
 585         memset(get_dom_info(bl), 0, sizeof(ir_dom_info));
 586         set_Block_idom(bl, NULL);
 587         set_Block_dom_pre_num(bl, -1);
 588         set_Block_dom_depth(bl, -1);
 589 }
 590
 591 /**
 592  * Initialize the dominance/postdominance construction:
 593  *
 594  * - count the number of blocks
 595  * - clear the dominance info
 596  * - remove Block-keepalives of live blocks to reduce
 597  *   the number of "phantom" block edges
 598  *
 599  * @param irg  the graph
 600  * @param pre  a walker function that will be called for every block in the graph
 601  */
 602 static int init_construction(ir_graph *irg, irg_walk_func *pre) {
 603         ir_graph *rem = current_ir_graph;
 604         ir_node *end;
 605         int arity;
 606         int n_blocks = 0;
 607
 608         current_ir_graph = irg;
 609
 610         /* this visits only the reachable blocks */
 611         irg_block_walk(get_irg_end_block(irg), pre, NULL, &n_blocks);
 612
 613         /* now visit the unreachable (from End) Blocks and remove unnecessary keep-alives */
 614         end   = get_irg_end(irg);
 615         arity = get_End_n_keepalives(end);
 616         if (arity) {    /* we have keep-alives */
 617                 ir_node **in;
 618                 int i, j;
 619
 620                 NEW_ARR_A(ir_node *, in, arity);
 621                 for (i = j = 0; i < arity; i++) {
 622                         ir_node *pred = get_End_keepalive(end, i);
 623
 624                         if (get_irn_op(pred) == op_Block) {
 625                                 if (Block_not_block_visited(pred)) {
 626                                         /* we found a endless loop */
 627                                         dec_irg_block_visited(irg);
 628                                         irg_block_walk(pred, pre, NULL, &n_blocks);
 629                                 }
 630                                 else
 631                                         continue;
 632                         }
 633                         in[j++] = pred;
 634                 }
 635                 if (j != arity) {
 636                         /* we kill some Block keep-alives */
 637                         set_End_keepalives(end, j, in);
 638                         set_irg_outs_inconsistent(irg);
 639                 }
 640         }
 641
 642         current_ir_graph = rem;
 643         return n_blocks;
 644 }
 645
 646
 647 /* Computes the dominator trees.  Sets a flag in irg to "dom_consistent".
 648    If the control flow of the graph is changed this flag must be set to
 649    "dom_inconsistent".  */
 650 void compute_doms(ir_graph *irg) {
 651         ir_graph *rem = current_ir_graph;
 652         int n_blocks, used, i, j;
 653         tmp_dom_info *tdi_list;   /* Ein Golf? */
 654
 655         current_ir_graph = irg;
 656
 657         /* Update graph state */
 658         assert(get_irg_phase_state(irg) != phase_building);
 659         irg->dom_state = dom_consistent;
 660
 661         /* Count the number of blocks in the graph. */
 662         n_blocks = init_construction(irg, count_and_init_blocks_dom);
 663
 664         /* Memory for temporary information. */
 665         tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
 666
 667         /* We need the out data structure. */
 668         assure_irg_outs(irg);
 669
 670         /* this with a standard walker as passing the parent to the sons isn't
 671            simple. */
 672         used = 0;
 673         inc_irg_block_visited(irg);
 674         init_tmp_dom_info(get_irg_start_block(irg), NULL, tdi_list, &used, n_blocks);
 675         /* If not all blocks are reachable from Start by out edges this assertion
 676            fails.
 677            assert(used == n_blocks && "Precondition for dom construction violated"); */
 678         assert(used <= n_blocks && "Precondition for dom construction violated");
 679         n_blocks = used;
 680
 681
 682         for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 683                 int irn_arity;
 684                 tmp_dom_info *w = &tdi_list[i];
 685                 tmp_dom_info *v;
 686
 687                 /* Step 2 */
 688                 irn_arity = get_irn_arity(w->block);
 689                 for (j = 0; j < irn_arity;  j++) {
 690                         ir_node *pred = get_Block_cfgpred_block(w->block, j);
 691                         tmp_dom_info *u;
 692
 693                         if (is_Bad(pred) || (get_Block_dom_pre_num (pred) == -1))
 694                                 continue;       /* control-dead */
 695
 696                         u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
 697                         if (u->semi < w->semi) w->semi = u->semi;
 698                 }
 699
 700                 /* handle keep-alives if we are at the end block */
 701                 if (w->block == get_irg_end_block(irg)) {
 702                         ir_node *end = get_irg_end(irg);
 703
 704                         irn_arity = get_irn_arity(end);
 705                         for (j = 0; j < irn_arity;  j++) {
 706                                 ir_node *pred = get_irn_n(end, j);
 707                                 tmp_dom_info *u;
 708
 709                                 if (is_no_Block(pred) || get_Block_dom_pre_num(pred) == -1)
 710                                         continue;       /* control-dead */
 711
 712                                 u = dom_eval (&tdi_list[get_Block_dom_pre_num(pred)]);
 713                                 if (u->semi < w->semi) w->semi = u->semi;
 714                         }
 715                 }
 716
 717                 /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 718                    buckets can been implemented as linked lists. */
 719                 w->bucket = w->semi->bucket;
 720                 w->semi->bucket = w;
 721
 722                 dom_link (w->parent, w);
 723
 724                 /* Step 3 */
 725                 while (w->parent->bucket) {
 726                         tmp_dom_info *u;
 727                         v = w->parent->bucket;
 728                         /* remove v from w->parent->bucket */
 729                         w->parent->bucket = v->bucket;
 730                         v->bucket = NULL;
 731
 732                         u = dom_eval (v);
 733                         if (u->semi < v->semi)
 734                                 v->dom = u;
 735                         else
 736                                 v->dom = w->parent;
 737                 }
 738         }
 739         /* Step 4 */
 740         tdi_list[0].dom = NULL;
 741         set_Block_idom(tdi_list[0].block, NULL);
 742         set_Block_dom_depth(tdi_list[0].block, 1);
 743         for (i = 1; i < n_blocks;  i++) {
 744                 tmp_dom_info *w = &tdi_list[i];
 745                 int depth;
 746
 747                 if (! w->dom)
 748                         continue; /* control dead */
 749
 750                 if (w->dom != w->semi) w->dom = w->dom->dom;
 751                 set_Block_idom(w->block, w->dom->block);
 752
 753                 /* blocks dominated by dead one's are still dead */
 754                 depth = get_Block_dom_depth(w->dom->block);
 755                 if (depth > 0)
 756                         ++depth;
 757                 set_Block_dom_depth(w->block, depth);
 758         }
 759
 760         /* clean up */
 761         free(tdi_list);
 762
 763         /* Do a walk over the tree and assign the tree pre orders. */
 764         {
 765                 unsigned tree_pre_order = 0;
 766                 dom_tree_walk_irg(irg, assign_tree_dom_pre_order,
 767                         assign_tree_dom_pre_order_max, &tree_pre_order);
 768         }
 769         current_ir_graph = rem;
 770 }
 771
 772 void assure_doms(ir_graph *irg) {
 773         if (get_irg_dom_state(irg) != dom_consistent)
 774                 compute_doms(irg);
 775 }
 776
 777 void free_dom(ir_graph *irg) {
 778         /* Update graph state */
 779         assert(get_irg_phase_state(current_ir_graph) != phase_building);
 780         current_ir_graph->dom_state = dom_none;
 781
 782         /* With the implementation right now there is nothing to free,
 783            but better call it anyways... */
 784 }
 785
 786 /* Computes the post dominator trees.  Sets a flag in irg to "dom_consistent".
 787    If the control flow of the graph is changed this flag must be set to
 788    "dom_inconsistent".  */
 789 void compute_postdoms(ir_graph *irg) {
 790         ir_graph *rem = current_ir_graph;
 791         int n_blocks, used, i, j;
 792         tmp_dom_info *tdi_list;
 793
 794         current_ir_graph = irg;
 795
 796         /* Update graph state */
 797         assert(get_irg_phase_state(irg) != phase_building);
 798         irg->pdom_state = dom_consistent;
 799
 800         /* Count the number of blocks in the graph. */
 801         n_blocks = init_construction(irg, count_and_init_blocks_pdom);
 802
 803         /* Memory for temporary information. */
 804         tdi_list = xcalloc(n_blocks, sizeof(tdi_list[0]));
 805
 806         /* We need the out data structure. */
 807         assure_irg_outs(irg);
 808
 809         /* this with a standard walker as passing the parent to the sons isn't
 810            simple. */
 811         used = 0;
 812         inc_irg_block_visited(irg);
 813         init_tmp_pdom_info(get_irg_end_block(irg), NULL, tdi_list, &used, n_blocks);
 814         /* If not all blocks are reachable from End by cfg edges this assertion
 815            fails.
 816            assert(used == n_blocks && "Precondition for dom construction violated"); */
 817         n_blocks = used;
 818
 819
 820         for (i = n_blocks-1; i > 0; i--) {  /* Don't iterate the root, it's done. */
 821                 int irn_arity;
 822                 tmp_dom_info *w = &tdi_list[i];
 823                 tmp_dom_info *v;
 824
 825                 /* Step 2 */
 826                 irn_arity = get_Block_n_cfg_outs_ka(w->block);
 827                 for (j = 0;  j < irn_arity;  j++) {
 828                         ir_node *succ = get_Block_cfg_out_ka(w->block, j);
 829                         tmp_dom_info *u;
 830
 831                         if (get_Block_postdom_pre_num (succ) == -1)
 832                                 continue;       /* endless-loop */
 833
 834                         u = dom_eval (&tdi_list[get_Block_postdom_pre_num(succ)]);
 835                         if (u->semi < w->semi) w->semi = u->semi;
 836                 }
 837                 /* Add w to w->semi's bucket.  w is in exactly one bucket, so
 838                    buckets can be implemented as linked lists. */
 839                 w->bucket = w->semi->bucket;
 840                 w->semi->bucket = w;
 841
 842                 dom_link (w->parent, w);
 843
 844                 /* Step 3 */
 845                 while (w->parent->bucket) {
 846                         tmp_dom_info *u;
 847                         v = w->parent->bucket;
 848                         /* remove v from w->parent->bucket */
 849                         w->parent->bucket = v->bucket;
 850                         v->bucket = NULL;
 851
 852                         u = dom_eval(v);
 853                         if (u->semi < v->semi)
 854                                 v->dom = u;
 855                         else
 856                                 v->dom = w->parent;
 857                 }
 858         }
 859         /* Step 4 */
 860         tdi_list[0].dom = NULL;
 861         set_Block_ipostdom(tdi_list[0].block, NULL);
 862         set_Block_postdom_depth(tdi_list[0].block, 1);
 863         for (i = 1;  i < n_blocks;  i++) {
 864                 tmp_dom_info *w = &tdi_list[i];
 865
 866                 if (w->dom != w->semi) w->dom = w->dom->dom;
 867                 set_Block_ipostdom(w->block, w->dom->block);
 868                 set_Block_postdom_depth(w->block, get_Block_postdom_depth(w->dom->block) + 1);
 869         }
 870
 871         /* clean up */
 872         free(tdi_list);
 873
 874         /* Do a walk over the tree and assign the tree pre orders. */
 875         {
 876                 unsigned tree_pre_order = 0;
 877                 postdom_tree_walk_irg(irg, assign_tree_postdom_pre_order,
 878                         assign_tree_postdom_pre_order_max, &tree_pre_order);
 879         }
 880         current_ir_graph = rem;
 881 }
 882
 883 void assure_postdoms(ir_graph *irg) {
 884         if (get_irg_postdom_state(irg) != dom_consistent)
 885                 compute_postdoms(irg);
 886 }
 887
 888 void free_postdom(ir_graph *irg) {
 889         /* Update graph state */
 890         assert(get_irg_phase_state(current_ir_graph) != phase_building);
 891         current_ir_graph->pdom_state = dom_none;
 892
 893         /* With the implementation right now there is nothing to free,
 894            but better call it anyways... */
 895 }