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 <assert.h>
  32 #include "array.h"
  33 #include "condeval.h"
  34 #include "debug.h"
  35 #include "ircons.h"
  36 #include "irgmod.h"
  37 #include "irgopt.h"
  38 #include "irgwalk.h"
  39 #include "irnode.h"
  40 #include "irnode_t.h"
  41 #include "iredges.h"
  42 #include "iredges_t.h"
  43 #include "irtools.h"
  44 #include "irgraph.h"
  45 #include "tv.h"
  46
  47 DEBUG_ONLY(static firm_dbg_module_t *dbg);
  48
  49 /**
  50  * Add the new predecessor x to node node, which is either a Block or a Phi
  51  */
  52 static void add_pred(ir_node* node, ir_node* x)
  53 {
  54         ir_node** ins;
  55         int n;
  56         int i;
  57
  58         assert(is_Block(node) || is_Phi(node));
  59
  60         n = get_irn_arity(node);
  61         NEW_ARR_A(ir_node*, ins, n + 1);
  62         for (i = 0; i < n; i++)
  63                 ins[i] = get_irn_n(node, i);
  64         ins[n] = x;
  65         set_irn_in(node, n + 1, ins);
  66 }
  67
  68 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
  69 {
  70         int i;
  71         int n_cfgpreds;
  72         ir_graph *irg;
  73         ir_node *phi;
  74         ir_node **in;
  75
  76         // This is needed because we create bads sometimes
  77         if(is_Bad(block))
  78                 return new_Bad();
  79
  80         // already processed this block?
  81         if(irn_visited(block)) {
  82                 ir_node *value = (ir_node*) get_irn_link(block);
  83                 return value;
  84         }
  85
  86         // blocks with only 1 pred need no phi
  87         n_cfgpreds = get_Block_n_cfgpreds(block);
  88         if(n_cfgpreds == 1) {
  89                 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
  90                 ir_node *value = search_def_and_create_phis(pred_block, mode);
  91
  92                 set_irn_link(block, value);
  93                 mark_irn_visited(block);
  94                 return value;
  95         }
  96
  97         // create a new phi
  98         NEW_ARR_A(ir_node*, in, n_cfgpreds);
  99         for(i = 0; i < n_cfgpreds; ++i)
 100                 in[i] = new_Unknown(mode);
 101
 102         irg = get_irn_irg(block);
 103         phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
 104         set_irn_link(block, phi);
 105         mark_irn_visited(block);
 106
 107         // set phi preds
 108         for(i = 0; i < n_cfgpreds; ++i) {
 109                 ir_node *pred_block = get_Block_cfgpred_block(block, i);
 110                 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
 111
 112                 set_irn_n(phi, i, pred_val);
 113         }
 114
 115         return phi;
 116 }
 117
 118 /**
 119  * Given a set of values this function constructs SSA-form for the users of the
 120  * first value (the users are determined through the out-edges of the value).
 121  * Uses the irn_visited flags. Works without using the dominance tree.
 122  */
 123 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
 124 {
 125         int i;
 126         ir_graph *irg;
 127         ir_mode *mode;
 128         const ir_edge_t *edge;
 129         const ir_edge_t *next;
 130         ir_node *value;
 131
 132         assert(n_vals > 0);
 133
 134         irg = get_irn_irg(vals[0]);
 135         inc_irg_visited(irg);
 136
 137         mode = get_irn_mode(vals[0]);
 138         for(i = 0; i < n_vals; ++i) {
 139                 ir_node *value = vals[i];
 140                 ir_node *value_block = blocks[i];
 141
 142                 assert(get_irn_mode(value) == mode);
 143
 144                 set_irn_link(value_block, value);
 145                 mark_irn_visited(value_block);
 146         }
 147
 148         // Only fix the users of the first, i.e. the original node
 149         value = vals[0];
 150
 151         // this can happen when fixing phi preds, we mustn't fix the users
 152         if(get_nodes_block(value) != blocks[0]) return;
 153
 154         foreach_out_edge_safe(value, edge, next) {
 155                 ir_node *user = get_edge_src_irn(edge);
 156                 int j = get_edge_src_pos(edge);
 157                 ir_node *user_block = get_nodes_block(user);
 158                 ir_node *newval;
 159
 160                 // ignore keeps
 161                 if(get_irn_op(user) == op_End)
 162                         continue;
 163
 164                 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
 165
 166                 if(is_Phi(user)) {
 167                         ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 168                         newval = search_def_and_create_phis(pred_block, mode);
 169                 } else {
 170                         newval = search_def_and_create_phis(user_block, mode);
 171                 }
 172
 173                 // don't fix newly created phis from the SSA construction
 174                 if (newval != user) {
 175                         DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
 176                         set_irn_n(user, j, newval);
 177                 }
 178         }
 179 }
 180
 181 static void split_critical_edge(ir_node *block, int pos) {
 182         ir_graph *irg = get_irn_irg(block);
 183         ir_node *in[1];
 184         ir_node *new_block;
 185         ir_node *new_jmp;
 186
 187         in[0] = get_Block_cfgpred(block, pos);
 188         new_block = new_r_Block(irg, 1, in);
 189         new_jmp = new_r_Jmp(irg, new_block);
 190         set_Block_cfgpred(block, pos, new_jmp);
 191 }
 192
 193 typedef struct _condeval_env_t {
 194         ir_node *true_block;
 195         pn_Cmp pnc;
 196         ir_node *cnst;
 197         unsigned long visited_nr;
 198
 199         ir_node *cnst_pred;     /**< the block before the constant */
 200         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 201 } condeval_env_t;
 202
 203 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 204         const ir_edge_t *edge;
 205
 206         /* Look at all nodes in the cond_block and copy them into pred */
 207         foreach_out_edge(block, edge) {
 208                 ir_node *node = get_edge_src_irn(edge);
 209                 ir_node *copy;
 210                 ir_mode *mode = get_irn_mode(node);
 211
 212                 /* ignore control flow */
 213                 if (mode == mode_X || is_Cond(node))
 214                         continue;
 215                 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
 216                    be handled in all backends. Instead we duplicate the node and move it to it's users */
 217                 if (mode == mode_b) {
 218                         const ir_edge_t *edge, *next;
 219                         ir_node *pred;
 220                         int      pn;
 221
 222                         assert(is_Proj(node));
 223
 224                         pred = get_Proj_pred(node);
 225                         pn   = get_Proj_proj(node);
 226
 227                         foreach_out_edge_safe(node, edge, next) {
 228                                 ir_node *cmp_copy;
 229                                 ir_node *user       = get_edge_src_irn(edge);
 230                                 int pos             = get_edge_src_pos(edge);
 231                                 ir_node *user_block = get_nodes_block(user);
 232
 233                                 if(user_block == block)
 234                                         continue;
 235
 236                                 cmp_copy = exact_copy(pred);
 237                                 set_nodes_block(cmp_copy, user_block);
 238                                 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
 239                                 set_irn_n(user, pos, copy);
 240                         }
 241                         continue;
 242                 }
 243
 244                 /* we can evaluate Phis right now, all other nodes get copied */
 245                 if (is_Phi(node)) {
 246                         copy = get_Phi_pred(node, j);
 247                 } else {
 248                         copy = exact_copy(node);
 249                         set_nodes_block(copy, copy_block);
 250                 }
 251
 252                 set_irn_link(node, copy);
 253                 set_irn_visited(node, env->visited_nr);
 254
 255                 /* we might hit values in blocks that have already been processed by a
 256                  * recursive find_phi_with_const call */
 257                 assert(get_irn_visited(copy) <= env->visited_nr);
 258                 if(get_irn_visited(copy) >= env->visited_nr) {
 259                         ir_node *prev_copy = get_irn_link(copy);
 260                         if(prev_copy != NULL)
 261                                 set_irn_link(node, prev_copy);
 262                 }
 263         }
 264
 265         /* fix data-flow (and reconstruct SSA if needed) */
 266         foreach_out_edge(block, edge) {
 267                 ir_node *vals[2];
 268                 ir_node *blocks[2];
 269                 ir_node *node = get_edge_src_irn(edge);
 270                 ir_mode *mode = get_irn_mode(node);
 271
 272                 if (mode == mode_X || is_Cond(node))
 273                         continue;
 274                 if (mode == mode_b)
 275                         continue;
 276
 277                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 278
 279                 blocks[0] = block;
 280                 vals[0] = node;
 281                 blocks[1] = copy_block;
 282                 vals[1] = get_irn_link(node);
 283                 construct_ssa(blocks, vals, 2);
 284         }
 285 }
 286
 287 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 288         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 289
 290         // does the compare evaluate to true?
 291         if(cmp_result == pn_Cmp_False)
 292                 return 0;
 293         if((cmp_result & pnc) != cmp_result)
 294                 return 0;
 295
 296         return 1;
 297 }
 298
 299 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 300         ir_node *block = get_nodes_block(jump);
 301
 302         if(irn_visited(value))
 303                 return NULL;
 304         mark_irn_visited(value);
 305
 306         if(is_Const(value)) {
 307                 tarval *tv_const = get_Const_tarval(env->cnst);
 308                 tarval *tv = get_Const_tarval(value);
 309
 310                 if(!eval_cmp(env->pnc, tv, tv_const))
 311                         return NULL;
 312
 313                 DB((
 314                         dbg, LEVEL_1,
 315                         "> Found condition evaluation candidate %+F->%+F\n",
 316                         env->true_block, block
 317                 ));
 318
 319                 // adjust true_block to point directly towards our jump
 320                 add_pred(env->true_block, jump);
 321
 322                 split_critical_edge(env->true_block, 0);
 323
 324                 // we need a bigger visited nr when going back
 325                 env->visited_nr++;
 326
 327                 return block;
 328         }
 329
 330         if(is_Phi(value)) {
 331                 int i, arity;
 332
 333                 // the phi has to be in the same block as the jump
 334                 if(get_nodes_block(value) != block)
 335                         return NULL;
 336
 337                 arity = get_irn_arity(value);
 338                 for(i = 0; i < arity; ++i) {
 339                         ir_node *copy_block;
 340                         ir_node *phi_pred = get_Phi_pred(value, i);
 341                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 342
 343                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 344                         if(copy_block == NULL)
 345                                 continue;
 346
 347                         /* copy duplicated nodes in copy_block and fix SSA */
 348                         copy_and_fix(block, copy_block, i, env);
 349
 350                         if(copy_block == get_nodes_block(cfgpred)) {
 351                                 env->cnst_pred = block;
 352                                 env->cnst_pos = i;
 353                         }
 354
 355                         // return now as we can't process more possibilities in 1 run
 356                         return copy_block;
 357                 }
 358         }
 359
 360         return NULL;
 361 }
 362
 363
 364 /**
 365  * Block-walker: searches for the following construct
 366  *
 367  *  Const or Phi with constants
 368  *           |
 369  *          Cmp
 370  *           |
 371  *         Cond
 372  *          /
 373  *       ProjX
 374  *        /
 375  *     Block
 376  */
 377 static void cond_eval(ir_node* block, void* data)
 378 {
 379         condeval_env_t env;
 380         int *changed = data;
 381         ir_graph *irg = current_ir_graph;
 382         ir_node *copy_block;
 383         ir_node *pred;
 384         ir_node *projx;
 385         ir_node *cond;
 386         ir_node *cmp;
 387         ir_node *left;
 388         ir_node *right;
 389         ir_node *cond_block;
 390         pn_Cmp pnc;
 391
 392         if(get_Block_n_cfgpreds(block) != 1)
 393                 return;
 394
 395         projx = get_Block_cfgpred(block, 0);
 396         if (!is_Proj(projx))
 397                 return;
 398         assert(get_irn_mode(projx) == mode_X);
 399
 400         cond = get_Proj_pred(projx);
 401         if (!is_Cond(cond))
 402                 return;
 403
 404         pred = get_Cond_selector(cond);
 405         // TODO handle switches
 406         if (get_irn_mode(pred) != mode_b)
 407                 return;
 408         if (!is_Proj(pred))
 409                 return;
 410         pnc = get_Proj_proj(pred);
 411
 412         cmp = get_Proj_pred(pred);
 413         assert(is_Cmp(cmp));
 414
 415         left  = get_Cmp_left(cmp);
 416         right = get_Cmp_right(cmp);
 417         assert(get_irn_mode(left) == get_irn_mode(right));
 418
 419         /* we assume that the cond_block is the true case */
 420         if (get_Proj_proj(projx) == pn_Cond_false) {
 421                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 422         }
 423
 424         /* we assume that the constant is on the right side, swap left/right
 425          * if needed */
 426         if(is_Const(left)) {
 427                 ir_node *t = left;
 428                 left = right;
 429                 right = t;
 430
 431                 pnc = get_inversed_pnc(pnc);
 432         }
 433
 434         if(!is_Const(right))
 435                 return;
 436
 437         cond_block = get_nodes_block(cond);
 438
 439         // special case: comparing a constant with a constant
 440         if(is_Const(left)) {
 441                 tarval *tv1 = get_Const_tarval(left);
 442                 tarval *tv2 = get_Const_tarval(right);
 443                 ir_node *pred;
 444                 if(eval_cmp(pnc, tv1, tv2)) {
 445                         pred = new_r_Jmp(irg, cond_block);
 446                 } else {
 447                         pred = new_Bad();
 448                 }
 449                 set_Block_cfgpred(block, 0, pred);
 450                 *changed = 1;
 451                 set_irg_doms_inconsistent(irg);
 452                 set_irg_extblk_inconsistent(irg);
 453                 set_irg_loopinfo_inconsistent(irg);
 454         } else {
 455                 if(get_nodes_block(left) != cond_block)
 456                         return;
 457
 458                 // (recursively) look if a pred of a phi is a constant
 459                 env.true_block = block;
 460                 env.pnc = pnc;
 461                 env.cnst = right;
 462                 inc_irg_visited(current_ir_graph);
 463                 env.visited_nr = get_irg_visited(irg);
 464
 465                 copy_block = find_phi_with_const(projx, left, &env);
 466
 467                 if(copy_block != NULL) {
 468                         /* we have to remove the edge towards the pred as the pred now
 469                          * jumps into the true_block. We also have to shorten phis
 470                          * in our block because of this */
 471                         const ir_edge_t *edge, *next;
 472                         ir_node* bad = new_Bad();
 473                         size_t cnst_pos = env.cnst_pos;
 474
 475                         /* shorten phis */
 476                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 477                                 ir_node *node = get_edge_src_irn(edge);
 478
 479                                 if(is_Phi(node))
 480                                         set_Phi_pred(node, cnst_pos, bad);
 481                         }
 482
 483                         set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
 484
 485                         /* the graph is changed now */
 486                         *changed = 1;
 487                 }
 488         }
 489 }
 490
 491 void opt_cond_eval(ir_graph* irg)
 492 {
 493         int changed, rerun;
 494
 495         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 496
 497         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 498
 499         remove_critical_cf_edges(irg);
 500         normalize_proj_nodes(irg);
 501
 502         edges_assure(irg);
 503         set_using_irn_link(irg);
 504         set_using_visited(irg);
 505
 506         changed = 0;
 507         do {
 508                 rerun = 0;
 509                 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
 510                 changed |= rerun;
 511         } while (rerun);
 512
 513         if (changed) {
 514                 /* control flow changed, some blocks may become dead */
 515                 set_irg_doms_inconsistent(irg);
 516                 set_irg_extblk_inconsistent(irg);
 517                 set_irg_loopinfo_inconsistent(irg);
 518         }
 519
 520         clear_using_visited(irg);
 521         clear_using_irn_link(irg);
 522 }