nsz Git - libfirm/blob - ir/opt/condeval.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
  22  * @brief   Partial condition evaluation
  23  * @date    10. Sep. 2006
  24  * @author  Christoph Mallon, Matthias Braun
  25  * @version $Id$
  26  */
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include "iroptimize.h"
  32
  33 #include <assert.h>
  34 #include "array.h"
  35 #include "debug.h"
  36 #include "ircons.h"
  37 #include "irgmod.h"
  38 #include "irgopt.h"
  39 #include "irgwalk.h"
  40 #include "irnode.h"
  41 #include "irnode_t.h"
  42 #include "iredges.h"
  43 #include "iredges_t.h"
  44 #include "irtools.h"
  45 #include "irgraph.h"
  46 #include "tv.h"
  47
  48 //#define AVOID_PHIB
  49
  50 DEBUG_ONLY(static firm_dbg_module_t *dbg);
  51
  52 /**
  53  * Add the new predecessor x to node node, which is either a Block or a Phi
  54  */
  55 static void add_pred(ir_node* node, ir_node* x)
  56 {
  57         ir_node** ins;
  58         int n;
  59         int i;
  60
  61         assert(is_Block(node) || is_Phi(node));
  62
  63         n = get_irn_arity(node);
  64         NEW_ARR_A(ir_node*, ins, n + 1);
  65         for (i = 0; i < n; i++)
  66                 ins[i] = get_irn_n(node, i);
  67         ins[n] = x;
  68         set_irn_in(node, n + 1, ins);
  69 }
  70
  71 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
  72 {
  73         int i;
  74         int n_cfgpreds;
  75         ir_graph *irg;
  76         ir_node *phi;
  77         ir_node **in;
  78
  79         // This is needed because we create bads sometimes
  80         if(is_Bad(block))
  81                 return new_Bad();
  82
  83         // already processed this block?
  84         if(irn_visited(block)) {
  85                 ir_node *value = (ir_node*) get_irn_link(block);
  86                 return value;
  87         }
  88
  89         irg = get_irn_irg(block);
  90         assert(block != get_irg_start_block(irg));
  91
  92         // blocks with only 1 pred need no phi
  93         n_cfgpreds = get_Block_n_cfgpreds(block);
  94         if(n_cfgpreds == 1) {
  95                 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
  96                 ir_node *value      = search_def_and_create_phis(pred_block, mode);
  97
  98                 set_irn_link(block, value);
  99                 mark_irn_visited(block);
 100                 return value;
 101         }
 102
 103         // create a new phi
 104         NEW_ARR_A(ir_node*, in, n_cfgpreds);
 105         for(i = 0; i < n_cfgpreds; ++i)
 106                 in[i] = new_Unknown(mode);
 107
 108         phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
 109         set_irn_link(block, phi);
 110         mark_irn_visited(block);
 111
 112         // set phi preds
 113         for(i = 0; i < n_cfgpreds; ++i) {
 114                 ir_node *pred_block = get_Block_cfgpred_block(block, i);
 115                 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
 116
 117                 set_irn_n(phi, i, pred_val);
 118         }
 119
 120         return phi;
 121 }
 122
 123 /**
 124  * Given a set of values this function constructs SSA-form for the users of the
 125  * first value (the users are determined through the out-edges of the value).
 126  * Uses the irn_visited flags. Works without using the dominance tree.
 127  */
 128 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
 129 {
 130         int i;
 131         ir_graph *irg;
 132         ir_mode *mode;
 133         const ir_edge_t *edge;
 134         const ir_edge_t *next;
 135         ir_node *value;
 136
 137         assert(n_vals == 2);
 138
 139         irg = get_irn_irg(vals[0]);
 140         inc_irg_visited(irg);
 141
 142         mode = get_irn_mode(vals[0]);
 143         for(i = 0; i < n_vals; ++i) {
 144                 ir_node *value = vals[i];
 145                 ir_node *value_block = blocks[i];
 146
 147                 assert(get_irn_mode(value) == mode);
 148
 149                 set_irn_link(value_block, value);
 150                 mark_irn_visited(value_block);
 151         }
 152
 153         // Only fix the users of the first, i.e. the original node
 154         value = vals[0];
 155
 156         foreach_out_edge_safe(value, edge, next) {
 157                 ir_node *user = get_edge_src_irn(edge);
 158                 int j = get_edge_src_pos(edge);
 159                 ir_node *user_block = get_nodes_block(user);
 160                 ir_node *newval;
 161
 162                 // ignore keeps
 163                 if(get_irn_op(user) == op_End)
 164                         continue;
 165
 166                 if (user_block == blocks[1])
 167                         continue;
 168
 169                 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
 170
 171                 if(is_Phi(user)) {
 172                         ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 173                         newval = search_def_and_create_phis(pred_block, mode);
 174                 } else {
 175                         newval = search_def_and_create_phis(user_block, mode);
 176                 }
 177
 178                 // don't fix newly created phis from the SSA construction
 179                 if (newval != user) {
 180                         DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
 181                         set_irn_n(user, j, newval);
 182                 }
 183         }
 184 }
 185
 186 static void split_critical_edge(ir_node *block, int pos) {
 187         ir_graph *irg = get_irn_irg(block);
 188         ir_node *in[1];
 189         ir_node *new_block;
 190         ir_node *new_jmp;
 191
 192         in[0] = get_Block_cfgpred(block, pos);
 193         new_block = new_r_Block(irg, 1, in);
 194         new_jmp = new_r_Jmp(irg, new_block);
 195         set_Block_cfgpred(block, pos, new_jmp);
 196 }
 197
 198 typedef struct condeval_env_t {
 199         ir_node       *true_block;
 200         pn_Cmp         pnc;
 201         ir_node       *cnst;
 202         tarval        *tv;
 203         unsigned long  visited_nr;
 204
 205         ir_node       *cnst_pred;   /**< the block before the constant */
 206         int            cnst_pos;    /**< the pos to the constant block (needed to
 207                                           kill that edge later) */
 208 } condeval_env_t;
 209
 210 static ir_node *copy_and_fix_node(const condeval_env_t *env, ir_node *block,
 211                                   ir_node *copy_block, int j, ir_node *node) {
 212         int      i, arity;
 213         ir_node *copy;
 214
 215         /* we can evaluate Phis right now, all other nodes get copied */
 216         if (is_Phi(node)) {
 217                 copy = get_Phi_pred(node, j);
 218                 /* we might have to evaluate a phi-cascades */
 219                 if(get_irn_visited(copy) >= env->visited_nr) {
 220                         copy = get_irn_link(copy);
 221                 }
 222         } else {
 223                 copy = exact_copy(node);
 224                 set_nodes_block(copy, copy_block);
 225
 226                 assert(get_irn_mode(copy) != mode_X);
 227
 228                 arity = get_irn_arity(copy);
 229                 for(i = 0; i < arity; ++i) {
 230                         ir_node *pred     = get_irn_n(copy, i);
 231                         ir_node *new_pred;
 232
 233                         if(get_nodes_block(pred) != block)
 234                                 continue;
 235
 236                         if(get_irn_visited(pred) >= env->visited_nr) {
 237                                 new_pred = get_irn_link(pred);
 238                         } else {
 239                                 new_pred = copy_and_fix_node(env, block, copy_block, j, pred);
 240                         }
 241                         set_irn_n(copy, i, new_pred);
 242                 }
 243         }
 244
 245         set_irn_link(node, copy);
 246         set_irn_visited(node, env->visited_nr);
 247
 248         return copy;
 249 }
 250
 251 static void copy_and_fix(const condeval_env_t *env, ir_node *block,
 252                          ir_node *copy_block, int j) {
 253         const ir_edge_t *edge;
 254
 255         /* Look at all nodes in the cond_block and copy them into pred */
 256         foreach_out_edge(block, edge) {
 257                 ir_node *node = get_edge_src_irn(edge);
 258                 ir_node *copy;
 259                 ir_mode *mode = get_irn_mode(node);
 260
 261                 /* ignore control flow */
 262                 if (mode == mode_X || is_Cond(node))
 263                         continue;
 264 #ifdef AVOID_PHIB
 265                 /* we may not copy mode_b nodes, because this could produce phi with
 266                  * mode_bs which can't be handled in all backends. Instead we duplicate
 267                  * the node and move it to it's users */
 268                 if (mode == mode_b) {
 269                         const ir_edge_t *edge, *next;
 270                         ir_node *pred;
 271                         int      pn;
 272
 273                         assert(is_Proj(node));
 274
 275                         pred = get_Proj_pred(node);
 276                         pn   = get_Proj_proj(node);
 277
 278                         foreach_out_edge_safe(node, edge, next) {
 279                                 ir_node *cmp_copy;
 280                                 ir_node *user       = get_edge_src_irn(edge);
 281                                 int pos             = get_edge_src_pos(edge);
 282                                 ir_node *user_block = get_nodes_block(user);
 283
 284                                 if(user_block == block)
 285                                         continue;
 286
 287                                 cmp_copy = exact_copy(pred);
 288                                 set_nodes_block(cmp_copy, user_block);
 289                                 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
 290                                 set_irn_n(user, pos, copy);
 291                         }
 292                         continue;
 293                 }
 294 #endif
 295
 296                 copy = copy_and_fix_node(env, block, copy_block, j, node);
 297
 298                 /* we might hit values in blocks that have already been processed by a
 299                  * recursive find_phi_with_const call */
 300                 assert(get_irn_visited(copy) <= env->visited_nr);
 301                 if(get_irn_visited(copy) >= env->visited_nr) {
 302                         ir_node *prev_copy = get_irn_link(copy);
 303                         if(prev_copy != NULL)
 304                                 set_irn_link(node, prev_copy);
 305                 }
 306         }
 307
 308         /* fix data-flow (and reconstruct SSA if needed) */
 309         foreach_out_edge(block, edge) {
 310                 ir_node *vals[2];
 311                 ir_node *blocks[2];
 312                 ir_node *node = get_edge_src_irn(edge);
 313                 ir_mode *mode = get_irn_mode(node);
 314
 315                 if (mode == mode_X || is_Cond(node))
 316                         continue;
 317 #ifdef AVOID_PHIB
 318                 if (mode == mode_b)
 319                         continue;
 320 #endif
 321
 322                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 323
 324                 blocks[0] = block;
 325                 vals[0] = node;
 326                 blocks[1] = copy_block;
 327                 vals[1] = get_irn_link(node);
 328                 construct_ssa(blocks, vals, 2);
 329         }
 330 }
 331
 332 /**
 333  * returns wether the cmp evaluates to true or false, or can't be evaluated!
 334  * 1: true, 0: false, -1: can't evaluate
 335  */
 336 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 337         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 338
 339         // does the compare evaluate to true?
 340         if(cmp_result == pn_Cmp_False)
 341                 return -1;
 342         if((cmp_result & pnc) != cmp_result)
 343                 return 0;
 344
 345         return 1;
 346 }
 347
 348 static ir_node *find_const(condeval_env_t *env, ir_node *jump, ir_node *value)
 349 {
 350         ir_node *block = get_nodes_block(jump);
 351
 352         if(irn_visited(value))
 353                 return NULL;
 354         mark_irn_visited(value);
 355
 356         if(is_Const(value)) {
 357                 tarval *tv_const = get_Const_tarval(env->cnst);
 358                 tarval *tv       = get_Const_tarval(value);
 359
 360                 if(eval_cmp(env->pnc, tv, tv_const) <= 0) {
 361                         return NULL;
 362                 }
 363
 364                 DB((
 365                         dbg, LEVEL_1,
 366                         "> Found condition evaluation candidate %+F->%+F\n",
 367                         env->true_block, block
 368                 ));
 369
 370                 // adjust true_block to point directly towards our jump
 371                 add_pred(env->true_block, jump);
 372
 373                 split_critical_edge(env->true_block, 0);
 374
 375                 // we need a bigger visited nr when going back
 376                 env->visited_nr++;
 377
 378                 return block;
 379         }
 380
 381         if(is_Phi(value)) {
 382                 int i, arity;
 383
 384                 /* the phi has to be in the same block as the jump */
 385                 if(get_nodes_block(value) != block) {
 386                         return NULL;
 387                 }
 388
 389                 arity = get_irn_arity(value);
 390                 for(i = 0; i < arity; ++i) {
 391                         ir_node *copy_block;
 392                         ir_node *phi_pred = get_Phi_pred(value, i);
 393                         ir_node *cfgpred  = get_Block_cfgpred(block, i);
 394
 395                         copy_block = find_const(env, cfgpred, phi_pred);
 396                         if(copy_block == NULL)
 397                                 continue;
 398
 399                         /* copy duplicated nodes in copy_block and fix SSA */
 400                         copy_and_fix(env, block, copy_block, i);
 401
 402                         if(copy_block == get_nodes_block(cfgpred)) {
 403                                 env->cnst_pred = block;
 404                                 env->cnst_pos  = i;
 405                         }
 406
 407                         /* return now as we can't process more possibilities in 1 run */
 408                         return copy_block;
 409                 }
 410         }
 411
 412         return NULL;
 413 }
 414
 415 static ir_node *find_candidate(condeval_env_t *env, ir_node *jump,
 416                                ir_node *value)
 417 {
 418         ir_node *block = get_nodes_block(jump);
 419
 420         if(irn_visited(value)) {
 421                 return NULL;
 422         }
 423         mark_irn_visited(value);
 424
 425         if(is_Const(value)) {
 426                 tarval *tv = get_Const_tarval(value);
 427
 428                 if(tv != env->tv)
 429                         return NULL;
 430
 431                 DB((
 432                         dbg, LEVEL_1,
 433                         "> Found condition evaluation candidate %+F->%+F\n",
 434                         env->true_block, block
 435                 ));
 436
 437                 // adjust true_block to point directly towards our jump
 438                 add_pred(env->true_block, jump);
 439
 440                 split_critical_edge(env->true_block, 0);
 441
 442                 // we need a bigger visited nr when going back
 443                 env->visited_nr++;
 444
 445                 return block;
 446         }
 447         if(is_Phi(value)) {
 448                 int i, arity;
 449
 450                 // the phi has to be in the same block as the jump
 451                 if(get_nodes_block(value) != block)
 452                         return NULL;
 453
 454                 arity = get_irn_arity(value);
 455                 for(i = 0; i < arity; ++i) {
 456                         ir_node *copy_block;
 457                         ir_node *phi_pred = get_Phi_pred(value, i);
 458                         ir_node *cfgpred  = get_Block_cfgpred(block, i);
 459
 460                         copy_block = find_candidate(env, cfgpred, phi_pred);
 461                         if(copy_block == NULL)
 462                                 continue;
 463
 464                         /* copy duplicated nodes in copy_block and fix SSA */
 465                         copy_and_fix(env, block, copy_block, i);
 466
 467                         if(copy_block == get_nodes_block(cfgpred)) {
 468                                 env->cnst_pred = block;
 469                                 env->cnst_pos  = i;
 470                         }
 471
 472                         // return now as we can't process more possibilities in 1 run
 473                         return copy_block;
 474                 }
 475         }
 476         if(is_Proj(value)) {
 477                 ir_node *left;
 478                 ir_node *right;
 479                 int      pnc;
 480                 ir_node *cmp = get_Proj_pred(value);
 481                 if(!is_Cmp(cmp))
 482                         return NULL;
 483
 484                 left  = get_Cmp_left(cmp);
 485                 right = get_Cmp_right(cmp);
 486                 pnc   = get_Proj_proj(value);
 487
 488                 /* we assume that the constant is on the right side, swap left/right
 489                  * if needed */
 490                 if(is_Const(left)) {
 491                         ir_node *t = left;
 492                         left       = right;
 493                         right      = t;
 494
 495                         pnc        = get_inversed_pnc(pnc);
 496                 }
 497
 498                 if(!is_Const(right))
 499                         return 0;
 500
 501                 if(get_nodes_block(left) != block) {
 502                         return 0;
 503                 }
 504
 505                 /* negate condition when we're looking for the false block */
 506                 if(env->tv == get_tarval_b_false()) {
 507                         pnc = get_negated_pnc(pnc, get_irn_mode(right));
 508                 }
 509
 510                 // (recursively) look if a pred of a phi is a constant
 511                 env->pnc  = pnc;
 512                 env->cnst = right;
 513
 514                 return find_const(env, jump, left);
 515         }
 516
 517         return NULL;
 518 }
 519
 520 /**
 521  * Block-walker: searches for the following construct
 522  *
 523  *  Const or Phi with constants
 524  *           |
 525  *          Cmp
 526  *           |
 527  *         Cond
 528  *          /
 529  *       ProjX
 530  *        /
 531  *     Block
 532  */
 533 static void cond_eval(ir_node* block, void* data)
 534 {
 535         condeval_env_t env;
 536         int *changed = data;
 537         ir_node *selector;
 538         ir_node *projx;
 539         ir_node *cond;
 540         ir_node *copy_block;
 541         int      selector_evaluated;
 542         const ir_edge_t *edge, *next;
 543         ir_node* bad;
 544         size_t   cnst_pos;
 545
 546         if(get_Block_n_cfgpreds(block) != 1)
 547                 return;
 548
 549         projx = get_Block_cfgpred(block, 0);
 550         if (!is_Proj(projx))
 551                 return;
 552         assert(get_irn_mode(projx) == mode_X);
 553
 554         cond = get_Proj_pred(projx);
 555         if (!is_Cond(cond))
 556                 return;
 557
 558         selector = get_Cond_selector(cond);
 559         // TODO handle switch Conds
 560         if (get_irn_mode(selector) != mode_b)
 561                 return;
 562
 563         /* handle cases that can be immediately evalutated */
 564         selector_evaluated = -1;
 565         if(is_Proj(selector)) {
 566                 ir_node *cmp = get_Proj_pred(selector);
 567                 if(is_Cmp(cmp)) {
 568                         ir_node *left  = get_Cmp_left(cmp);
 569                         ir_node *right = get_Cmp_right(cmp);
 570                         if(is_Const(left) && is_Const(right)) {
 571                                 int     pnc      = get_Proj_proj(selector);
 572                                 tarval *tv_left  = get_Const_tarval(left);
 573                                 tarval *tv_right = get_Const_tarval(right);
 574
 575                                 selector_evaluated = eval_cmp(pnc, tv_left, tv_right);
 576                                 if(selector_evaluated < 0)
 577                                         return;
 578                         }
 579                 }
 580         } else if(is_Const(selector)) {
 581                 tarval *tv = get_Const_tarval(selector);
 582                 if(tv == get_tarval_b_true()) {
 583                         selector_evaluated = 1;
 584                 } else {
 585                         assert(tv == get_tarval_b_false());
 586                         selector_evaluated = 0;
 587                 }
 588         }
 589
 590         env.cnst_pred = NULL;
 591         if (get_Proj_proj(projx) == pn_Cond_false) {
 592                 env.tv = get_tarval_b_false();
 593                 if(selector_evaluated >= 0)
 594                         selector_evaluated = !selector_evaluated;
 595         } else {
 596                 env.tv = get_tarval_b_true();
 597         }
 598
 599         if(selector_evaluated == 0) {
 600                 bad = new_Bad();
 601                 exchange(projx, bad);
 602                 *changed = 1;
 603                 return;
 604         } else if(selector_evaluated == 1) {
 605                 dbg_info *dbgi = get_irn_dbg_info(selector);
 606                 ir_node  *jmp  = new_rd_Jmp(dbgi, current_ir_graph, get_nodes_block(projx));
 607                 exchange(projx, jmp);
 608                 *changed = 1;
 609                 return;
 610         }
 611
 612         // (recursively) look if a pred of a phi is a constant
 613         env.true_block = block;
 614         inc_irg_visited(current_ir_graph);
 615         env.visited_nr = get_irg_visited(current_ir_graph);
 616
 617         copy_block = find_candidate(&env, projx, selector);
 618         if (copy_block == NULL)
 619                 return;
 620
 621         /* we have to remove the edge towards the pred as the pred now
 622          * jumps into the true_block. We also have to shorten phis
 623          * in our block because of this */
 624         bad      = new_Bad();
 625         cnst_pos = env.cnst_pos;
 626
 627         /* shorten phis */
 628         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 629                 ir_node *node = get_edge_src_irn(edge);
 630
 631                 if(is_Phi(node))
 632                         set_Phi_pred(node, cnst_pos, bad);
 633         }
 634
 635         set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
 636
 637         /* the graph is changed now */
 638         *changed = 1;
 639 }
 640
 641 void opt_cond_eval(ir_graph* irg)
 642 {
 643         int changed, rerun;
 644
 645         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 646
 647         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 648
 649         remove_critical_cf_edges(irg);
 650         normalize_proj_nodes(irg);
 651
 652         edges_assure(irg);
 653         set_using_irn_link(irg);
 654         set_using_visited(irg);
 655
 656         changed = 0;
 657         do {
 658                 rerun = 0;
 659                 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
 660                 changed |= rerun;
 661         } while (rerun);
 662
 663         if (changed) {
 664                 /* control flow changed, some blocks may become dead */
 665                 set_irg_outs_inconsistent(irg);
 666                 set_irg_doms_inconsistent(irg);
 667                 set_irg_extblk_inconsistent(irg);
 668                 set_irg_loopinfo_inconsistent(irg);
 669         }
 670
 671         clear_using_visited(irg);
 672         clear_using_irn_link(irg);
 673 }