nsz Git - libfirm/blob - ir/opt/ifconv.c

   1 /*
   2  * Copyright (C) 1995-2007 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    ir/opt/ifconv.c
  22  * @brief   If conversion
  23  * @author  Christoph Mallon
  24  * @version $Id$
  25  */
  26
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include <assert.h>
  32 #include "dbginfo.h"
  33 #include "iroptimize.h"
  34 #include "obst.h"
  35 #include "irnode_t.h"
  36 #include "cdep.h"
  37 #include "ircons.h"
  38 #include "irdom.h"
  39 #include "irgmod.h"
  40 #include "irgopt.h"
  41 #include "irgwalk.h"
  42 #include "irtools.h"
  43 #include "array.h"
  44 #include "xmalloc.h"
  45
  46 // debug
  47 #include "irdump.h"
  48 #include "debug.h"
  49
  50 DEBUG_ONLY(firm_dbg_module_t *dbg);
  51
  52 /** allow every Psi to be created. */
  53 static int default_allow_ifconv(ir_node *sel, ir_node* phi_list, int i, int j)
  54 {
  55         (void) sel;
  56         (void) phi_list;
  57         (void) i;
  58         (void) j;
  59         return 1;
  60 }
  61
  62 /**
  63  * Default options.
  64  */
  65 static const opt_if_conv_info_t default_info = {
  66         0,    /* doesn't matter for Psi */
  67         default_allow_ifconv
  68 };
  69
  70 /**
  71  * Additional block info.
  72  */
  73 typedef struct block_info {
  74         ir_node *phi;   /**< head of the Phi list */
  75         int has_pinned; /**< set if the block contains instructions that cannot be moved */
  76 } block_info;
  77
  78
  79 static INLINE block_info* get_block_blockinfo(const ir_node* block)
  80 {
  81         return get_irn_link(block);
  82 }
  83
  84
  85 /**
  86  * Returns non-zero if a Block can be emptied.
  87  */
  88 static int can_empty_block(ir_node *block)
  89 {
  90         return !get_block_blockinfo(block)->has_pinned;
  91 }
  92
  93
  94 static ir_node* walk_to_projx(ir_node* start, const ir_node* dependency)
  95 {
  96         int arity;
  97         int i;
  98
  99         /* No need to find the conditional block if this block cannot be emptied and
 100          * therefore not moved */
 101         if (!can_empty_block(start)) return NULL;
 102
 103         arity = get_irn_arity(start);
 104         for (i = 0; i < arity; ++i) {
 105                 ir_node* pred = get_irn_n(start, i);
 106                 ir_node* pred_block = get_nodes_block(pred);
 107
 108                 if (pred_block == dependency) {
 109                         if (is_Proj(pred)) {
 110                                 assert(get_irn_mode(pred) == mode_X);
 111                                 return pred;
 112                         }
 113                         return NULL;
 114                 }
 115
 116                 if (is_Proj(pred)) {
 117                         assert(get_irn_mode(pred) == mode_X);
 118                         return NULL;
 119                 }
 120
 121                 if (is_cdep_on(pred_block, dependency)) {
 122                         return walk_to_projx(pred_block, dependency);
 123                 }
 124         }
 125         return NULL;
 126 }
 127
 128
 129 /**
 130  * Copies the DAG starting at node to the ith predecessor block of src_block
 131  * -if the node isn't in the src_block, this is a nop and the node is returned
 132  * -if the node is a phi in the src_block, the ith predecessor of the phi is
 133  *   returned
 134  * otherwise returns the copy of the passed node
 135  */
 136 static ir_node* copy_to(ir_node* node, ir_node* src_block, int i)
 137 {
 138         ir_node* dst_block;
 139         ir_node* copy;
 140         int arity;
 141         int j;
 142
 143         if (get_nodes_block(node) != src_block) return node;
 144         if (get_irn_op(node) == op_Phi) return get_irn_n(node, i);
 145
 146         copy = exact_copy(node);
 147         dst_block = get_nodes_block(get_irn_n(src_block, i));
 148         set_nodes_block(copy, dst_block);
 149
 150         DB((dbg, LEVEL_1, "Copying node %+F to block %+F, copy is %+F\n",
 151                 node, dst_block, copy));
 152
 153         arity = get_irn_arity(node);
 154         for (j = 0; j < arity; ++j) {
 155                 set_irn_n(copy, j, copy_to(get_irn_n(node, j), src_block, i));
 156                 DB((dbg, LEVEL_2, "-- pred %d is %+F\n", j, get_irn_n(copy, j)));
 157         }
 158         return copy;
 159 }
 160
 161
 162 /**
 163  * Remove predecessors i and j from node and add predecessor new_pred
 164  */
 165 static void rewire(ir_node* node, int i, int j, ir_node* new_pred)
 166 {
 167         int arity = get_irn_arity(node);
 168         ir_node **ins;
 169         int k;
 170         int l;
 171
 172         NEW_ARR_A(ir_node *, ins, arity - 1);
 173
 174         l = 0;
 175         for (k = 0; k < i;     ++k) ins[l++] = get_irn_n(node, k);
 176         for (++k;   k < j;     ++k) ins[l++] = get_irn_n(node, k);
 177         for (++k;   k < arity; ++k) ins[l++] = get_irn_n(node, k);
 178         ins[l++] = new_pred;
 179         assert(l == arity - 1);
 180         set_irn_in(node, l, ins);
 181 }
 182
 183
 184 /**
 185  * Remove the jth predecessors from the ith predecessor of block and add it to block
 186  */
 187 static void split_block(ir_node* block, int i, int j)
 188 {
 189         ir_node* pred_block = get_nodes_block(get_irn_n(block, i));
 190         int arity = get_irn_arity(block);
 191         int new_pred_arity;
 192         ir_node* phi;
 193         ir_node **ins;
 194         ir_node **pred_ins;
 195         int k;
 196
 197         DB((dbg, LEVEL_1, "Splitting predecessor %d of predecessor %d of %+F\n", j, i, block));
 198
 199         NEW_ARR_A(ir_node*, ins, arity + 1);
 200
 201         for (phi = get_block_blockinfo(block)->phi; phi != NULL; phi = get_irn_link(phi)) {
 202                 ir_node* copy = copy_to(get_irn_n(phi, i), pred_block, j);
 203
 204                 for (k = 0; k < i; ++k) ins[k] = get_irn_n(phi, k);
 205                 ins[k++] = copy;
 206                 for (; k < arity; ++k) ins[k] = get_irn_n(phi, k);
 207                 ins[k] = get_irn_n(phi, i);
 208                 assert(k == arity);
 209                 set_irn_in(phi, arity + 1, ins);
 210         }
 211
 212         for (k = 0; k < i; ++k) ins[k] = get_irn_n(block, k);
 213         ins[k++] = get_irn_n(pred_block, j);
 214         for (; k < arity; ++k) ins[k] = get_irn_n(block, k);
 215         ins[k] = get_irn_n(block, i);
 216         assert(k == arity);
 217         set_irn_in(block, arity + 1, ins);
 218
 219         new_pred_arity = get_irn_arity(pred_block) - 1;
 220         NEW_ARR_A(ir_node*, pred_ins, new_pred_arity);
 221
 222         for (phi = get_block_blockinfo(pred_block)->phi; phi != NULL; phi = get_irn_link(phi)) {
 223                 for (k = 0; k < j; ++k) pred_ins[k] = get_irn_n(phi, k);
 224                 for (; k < new_pred_arity; ++k) pred_ins[k] = get_irn_n(phi, k + 1);
 225                 assert(k == new_pred_arity);
 226                 if (new_pred_arity > 1) {
 227                         set_irn_in(phi, new_pred_arity, pred_ins);
 228                 } else {
 229                         exchange(phi, pred_ins[0]);
 230                 }
 231         }
 232
 233         for (k = 0; k < j; ++k) pred_ins[k] = get_irn_n(pred_block, k);
 234         for (; k < new_pred_arity; ++k) pred_ins[k] = get_irn_n(pred_block, k + 1);
 235         assert(k == new_pred_arity);
 236         if (new_pred_arity > 1) {
 237                 set_irn_in(pred_block, new_pred_arity, pred_ins);
 238         } else {
 239                 exchange(pred_block, get_nodes_block(pred_ins[0]));
 240         }
 241 }
 242
 243
 244 static void prepare_path(ir_node* block, int i, const ir_node* dependency)
 245 {
 246         ir_node* pred = get_nodes_block(get_irn_n(block, i));
 247         int pred_arity;
 248         int j;
 249
 250         DB((dbg, LEVEL_1, "Preparing predecessor %d of %+F\n", i, block));
 251
 252         pred_arity = get_irn_arity(pred);
 253         for (j = 0; j < pred_arity; ++j) {
 254                 ir_node* pred_pred = get_nodes_block(get_irn_n(pred, j));
 255
 256                 if (is_cdep_on(pred_pred, dependency)) {
 257                         prepare_path(pred, j, dependency);
 258                         split_block(block, i, j);
 259                         break;
 260                 }
 261         }
 262 }
 263
 264
 265 static void if_conv_walker(ir_node* block, void* env)
 266 {
 267         opt_if_conv_info_t* opt_info = env;
 268         int arity;
 269         int i;
 270
 271         /* Bail out, if there are no Phis at all */
 272         if (get_block_blockinfo(block)->phi == NULL) return;
 273
 274 restart:
 275         arity = get_irn_arity(block);
 276         for (i = 0; i < arity; ++i) {
 277                 ir_node* pred0;
 278                 cdep* cdep;
 279
 280                 pred0 = get_nodes_block(get_irn_n(block, i));
 281                 for (cdep = find_cdep(pred0); cdep != NULL; cdep = cdep->next) {
 282                         const ir_node* dependency = cdep->node;
 283                         ir_node* projx0 = walk_to_projx(pred0, dependency);
 284                         ir_node* cond;
 285                         int j;
 286
 287                         if (projx0 == NULL) continue;
 288
 289                         cond = get_Proj_pred(projx0);
 290                         if (get_irn_op(cond) != op_Cond) continue;
 291
 292                         /* We only handle boolean decisions, no switches */
 293                         if (get_irn_mode(get_Cond_selector(cond)) != mode_b) continue;
 294
 295                         for (j = i + 1; j < arity; ++j) {
 296                                 ir_node* projx1;
 297                                 ir_node* conds[1];
 298                                 ir_node* psi_block;
 299                                 ir_node* phi;
 300                                 ir_node* pred1;
 301                                 dbg_info* cond_dbg;
 302
 303                                 pred1 = get_nodes_block(get_irn_n(block, j));
 304
 305                                 if (!is_cdep_on(pred1, dependency)) continue;
 306
 307                                 projx1 = walk_to_projx(pred1, dependency);
 308
 309                                 if (projx1 == NULL) continue;
 310
 311                                 phi = get_block_blockinfo(block)->phi;
 312                                 if (!opt_info->allow_ifconv(get_Cond_selector(cond), phi, i, j)) continue;
 313
 314                                 DB((dbg, LEVEL_1, "Found Cond %+F with proj %+F and %+F\n",
 315                                         cond, projx0, projx1
 316                                 ));
 317
 318                                 prepare_path(block, i, dependency);
 319                                 prepare_path(block, j, dependency);
 320                                 arity = get_irn_arity(block);
 321
 322                                 conds[0] = get_Cond_selector(cond);
 323
 324                                 psi_block = get_nodes_block(cond);
 325                                 cond_dbg = get_irn_dbg_info(cond);
 326                                 do {
 327                                         ir_node* val_i = get_irn_n(phi, i);
 328                                         ir_node* val_j = get_irn_n(phi, j);
 329                                         ir_node* psi;
 330                                         ir_node* next_phi;
 331
 332                                         if (val_i == val_j) {
 333                                                 psi = val_i;
 334                                                 DB((dbg, LEVEL_2,  "Generating no psi, because both values are equal\n"));
 335                                         } else {
 336                                                 ir_node* vals[2];
 337
 338                                                 /* Something is very fishy if two predecessors of a PhiM point into
 339                                                  * one block, but not at the same memory node
 340                                                  */
 341                                                 assert(get_irn_mode(phi) != mode_M);
 342                                                 if (get_Proj_proj(projx0) == pn_Cond_true) {
 343                                                         vals[0] = val_i;
 344                                                         vals[1] = val_j;
 345                                                 } else {
 346                                                         vals[0] = val_j;
 347                                                         vals[1] = val_i;
 348                                                 }
 349
 350                                                 psi = new_rd_Psi(cond_dbg, current_ir_graph, psi_block, 1, conds, vals, get_irn_mode(phi));
 351                                                 DB((dbg, LEVEL_2, "Generating %+F for %+F\n", psi, phi));
 352                                         }
 353
 354                                         next_phi = get_irn_link(phi);
 355
 356                                         if (arity == 2) {
 357                                                 exchange(phi, psi);
 358                                         } else {
 359                                                 rewire(phi, i, j, psi);
 360                                         }
 361
 362                                         phi = next_phi;
 363                                 } while (phi != NULL);
 364
 365                                 exchange(get_nodes_block(get_irn_n(block, i)), psi_block);
 366                                 exchange(get_nodes_block(get_irn_n(block, j)), psi_block);
 367
 368                                 if (arity == 2) {
 369 #if 1
 370                                         DB((dbg, LEVEL_1,  "Welding block %+F and %+F\n", block, psi_block));
 371                                         /* copy the block-info from the Psi-block to the block before merging */
 372                                         get_block_blockinfo(psi_block)->has_pinned |= get_block_blockinfo(block)->has_pinned;
 373                                         set_irn_link(block, get_irn_link(psi_block));
 374
 375                                         set_irn_in(block, get_irn_arity(psi_block), get_irn_in(psi_block) + 1);
 376                                         exchange_cdep(psi_block, block);
 377                                         exchange(psi_block, block);
 378 #else
 379                                         DB((dbg, LEVEL_1,  "Welding block %+F to %+F\n", block, psi_block));
 380                                         get_block_blockinfo(psi_block)->has_pinned |=   get_block_blockinfo(block)->has_pinned;
 381                                         exchange(block, psi_block);
 382 #endif
 383                                         return;
 384                                 } else {
 385                                         rewire(block, i, j, new_r_Jmp(current_ir_graph, psi_block));
 386                                         goto restart;
 387                                 }
 388                         }
 389                 }
 390         }
 391 }
 392
 393 /**
 394  * Block walker: add additional data
 395  */
 396 static void init_block_link(ir_node *block, void *env)
 397 {
 398         struct obstack *obst = env;
 399         block_info *bi = obstack_alloc(obst, sizeof(*bi));
 400
 401         bi->phi = NULL;
 402         bi->has_pinned = 0;
 403         set_irn_link(block, bi);
 404 }
 405
 406
 407 /**
 408  * Daisy-chain all phis in a block
 409  * If a non-movable node is encountered set the has_pinned flag
 410  */
 411 static void collect_phis(ir_node *node, void *env)
 412 {
 413         (void) env;
 414
 415         if (is_Phi(node)) {
 416                 ir_node *block = get_nodes_block(node);
 417                 block_info *bi = get_block_blockinfo(block);
 418
 419                 set_irn_link(node, bi->phi);
 420                 bi->phi = node;
 421         } else {
 422                 if (is_no_Block(node) && get_irn_pinned(node) == op_pin_state_pinned) {
 423                         /*
 424                          * Ignore control flow nodes, these will be removed.
 425                          * This ignores Raise. That is surely bad. FIXME.
 426                          */
 427                         if (!is_cfop(node)) {
 428                                 ir_node *block = get_nodes_block(node);
 429                                 block_info *bi = get_block_blockinfo(block);
 430
 431                                 DB((dbg, LEVEL_2, "Node %+F in block %+F is unmovable\n", node, block));
 432                                 bi->has_pinned = 1;
 433                         }
 434                 }
 435         }
 436 }
 437
 438
 439 /*
 440  * Transform multiple cascaded Psis into one Psi
 441  */
 442 static ir_node* fold_psi(ir_node* psi)
 443 {
 444         int arity = get_Psi_n_conds(psi);
 445         int new_arity = 0;
 446         int i;
 447         ir_node* n;
 448         ir_node** conds;
 449         ir_node** vals;
 450         int j;
 451         ir_node* new_psi;
 452
 453         for (i = 0; i < arity; ++i) {
 454                 n = get_Psi_val(psi, i);
 455                 if (get_irn_op(n) == op_Psi) {
 456                         new_arity += get_Psi_n_conds(n) + 1;
 457                 } else {
 458                         ++new_arity;
 459                 }
 460         }
 461         n = get_Psi_default(psi);
 462         if (get_irn_op(n) == op_Psi) {
 463                 new_arity += get_Psi_n_conds(n);
 464         }
 465
 466         if (arity == new_arity) return psi; // no attached Psis found
 467         DB((dbg, LEVEL_1, "Folding %+F from %d to %d conds\n", psi, arity, new_arity));
 468
 469         NEW_ARR_A(ir_node *, conds, new_arity);
 470         NEW_ARR_A(ir_node *, vals, new_arity + 1);
 471         j = 0;
 472         for (i = 0; i < arity; ++i) {
 473                 ir_node* c = get_Psi_cond(psi, i);
 474
 475                 n = get_Psi_val(psi, i);
 476                 if (get_irn_op(n) == op_Psi) {
 477                         int a = get_Psi_n_conds(n);
 478                         int k;
 479
 480                         for (k = 0; k < a; ++k) {
 481                                 conds[j] = new_r_And(
 482                                         current_ir_graph, get_nodes_block(psi),
 483                                         c, get_Psi_cond(n, k), mode_b
 484                                 );
 485                                 vals[j] = get_Psi_val(n, k);
 486                                 ++j;
 487                         }
 488                         conds[j] = c;
 489                         vals[j] = get_Psi_default(n);
 490                 } else {
 491                         conds[j] = c;
 492                         vals[j] = n;
 493                 }
 494                 ++j;
 495         }
 496         n = get_Psi_default(psi);
 497         if (get_irn_op(n) == op_Psi) {
 498                 int a = get_Psi_n_conds(n);
 499                 int k;
 500
 501                 for (k = 0; k < a; ++k) {
 502                         conds[j] = get_Psi_cond(n, k);
 503                         vals[j] = get_Psi_val(n, k);
 504                         ++j;
 505                 }
 506                 vals[j] = get_Psi_default(n);
 507         } else {
 508                 vals[j] = n;
 509         }
 510         assert(j == new_arity);
 511         new_psi = new_r_Psi(
 512                 current_ir_graph, get_nodes_block(psi),
 513                 new_arity, conds, vals, get_irn_mode(psi)
 514         );
 515         DB((dbg, LEVEL_1, "Folded %+F into new %+F\n", psi, new_psi));
 516         exchange(psi, new_psi);
 517         return new_psi;
 518 }
 519
 520
 521 /*
 522  * Merge consecutive psi inputs if the data inputs are the same
 523  */
 524 static ir_node* meld_psi(ir_node* psi)
 525 {
 526         int arity = get_Psi_n_conds(psi);
 527         int new_arity;
 528         ir_node** conds;
 529         ir_node** vals;
 530         ir_node* cond;
 531         ir_node* val;
 532         int i;
 533         int j;
 534         ir_node* new_psi;
 535
 536         new_arity = 1;
 537         val = get_Psi_val(psi, 0);
 538         DB((dbg, LEVEL_1, "Pred  0 of %+F is %+F\n", psi, val));
 539         for (i = 1; i < arity; ++i) {
 540                 ir_node* v = get_Psi_val(psi, i);
 541                 DB((dbg, LEVEL_1, "Pred %2d of %+F is %+F\n", i, psi, v));
 542                 if (val != v) {
 543                         val = v;
 544                         ++new_arity;
 545                 }
 546         }
 547         DB((dbg, LEVEL_1, "Default of %+F is %+F\n", psi, get_Psi_default(psi)));
 548         if (val == get_Psi_default(psi)) --new_arity;
 549
 550         DB((dbg, LEVEL_1, "Melding Psi %+F from %d conds to %d\n", psi, arity, new_arity));
 551
 552         if (new_arity == arity) return psi;
 553
 554         /* If all data inputs of the Psi are equal, exchange the Psi with that value */
 555         if (new_arity == 0) {
 556                 exchange(psi, val);
 557                 return val;
 558         }
 559
 560         NEW_ARR_A(ir_node *, conds, new_arity);
 561         NEW_ARR_A(ir_node *, vals, new_arity + 1);
 562         cond = get_Psi_cond(psi, 0);
 563         val = get_Psi_val(psi, 0);
 564         j = 0;
 565         for (i = 1; i < arity; ++i) {
 566                 ir_node* v = get_Psi_val(psi, i);
 567
 568                 if (v == val) {
 569                         cond = new_r_Or(
 570                                 current_ir_graph, get_nodes_block(psi),
 571                                 cond, get_Psi_cond(psi, i), mode_b
 572                         );
 573                 } else {
 574                         conds[j] = cond;
 575                         vals[j] = val;
 576                         ++j;
 577                         cond = get_Psi_cond(psi, i)
 578                         val = v;
 579                 }
 580         }
 581         if (val != get_Psi_default(psi)) {
 582                 conds[j] = cond;
 583                 vals[j] = val;
 584                 ++j;
 585         }
 586         vals[j] = get_Psi_default(psi);
 587         assert(j == new_arity);
 588         new_psi = new_r_Psi(
 589                 current_ir_graph, get_nodes_block(psi),
 590                 new_arity, conds, vals, get_irn_mode(psi)
 591         );
 592         DB((dbg, LEVEL_1, "Molded %+F into %+F\n", psi, new_psi));
 593         exchange(psi, new_psi);
 594         return new_psi;
 595 }
 596
 597
 598 /**
 599  * Split a Psi with multiple conditions into multiple Psis with one condtition
 600  * each
 601  */
 602 static ir_node* split_psi(ir_node* psi)
 603 {
 604         int arity = get_Psi_n_conds(psi);
 605         ir_mode* mode;
 606         ir_node* block;
 607         ir_node* rval;
 608         int i;
 609
 610         if (arity == 1) return psi;
 611
 612         mode  = get_irn_mode(psi);
 613         block = get_nodes_block(psi);
 614         rval  = get_Psi_default(psi);
 615         for (i = arity - 1; i >= 0; --i) {
 616                 ir_node* conds[1];
 617                 ir_node* vals[2];
 618
 619                 conds[0] = get_Psi_cond(psi, i);
 620                 vals[0]  = get_Psi_val(psi, i);
 621                 vals[1]  = rval;
 622                 rval     = new_r_Psi(
 623                         current_ir_graph, block, 1, conds, vals, mode
 624                 );
 625         }
 626         exchange(psi, rval);
 627         return rval;
 628 }
 629
 630
 631 static void optimise_psis(ir_node* node, void* env)
 632 {
 633         (void) env;
 634
 635         if (get_irn_op(node) != op_Psi) return;
 636 #if 1
 637         node = fold_psi(node);
 638 #endif
 639 #if 1
 640         node = meld_psi(node);
 641 #endif
 642 #if 1
 643         node = split_psi(node);
 644 #endif
 645 }
 646
 647
 648 void opt_if_conv(ir_graph *irg, const opt_if_conv_info_t *params)
 649 {
 650         struct obstack obst;
 651         opt_if_conv_info_t p;
 652
 653         if (! get_opt_if_conversion())
 654                 return;
 655
 656         /* get the parameters */
 657         p = (params != NULL ? *params : default_info);
 658
 659         FIRM_DBG_REGISTER(dbg, "firm.opt.ifconv");
 660
 661         DB((dbg, LEVEL_1, "Running if-conversion on %+F\n", irg));
 662
 663         normalize_one_return(irg);
 664         remove_critical_cf_edges(irg);
 665
 666         compute_cdep(irg);
 667         assure_doms(irg);
 668
 669         obstack_init(&obst);
 670         irg_block_walk_graph(irg, init_block_link, NULL, &obst);
 671         irg_walk_graph(irg, collect_phis, NULL, NULL);
 672         irg_block_walk_graph(irg, NULL, if_conv_walker, &p);
 673
 674         local_optimize_graph(irg);
 675
 676         irg_walk_graph(irg, NULL, optimise_psis, NULL);
 677
 678         obstack_free(&obst, NULL);
 679
 680         free_dom(irg);
 681         free_cdep(irg);
 682 }