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

   1 /*
   2  * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
   3  *
   4  * This file is part of libFirm.
   5  *
   6  * This file may be distributed and/or modified under the terms of the
   7  * GNU General Public License version 2 as published by the Free Software
   8  * Foundation and appearing in the file LICENSE.GPL included in the
   9  * packaging of this file.
  10  *
  11  * Licensees holding valid libFirm Professional Edition licenses may use
  12  * this file in accordance with the libFirm Commercial License.
  13  * Agreement provided with the Software.
  14  *
  15  * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
  16  * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  17  * PURPOSE.
  18  */
  19
  20 /**
  21  * @file
  22  * @brief    Construction of Confirm nodes
  23  * @author   Michael Beck
  24  * @date     6.2005
  25  * @version  $Id$
  26  */
  27 #ifdef HAVE_CONFIG_H
  28 # include "config.h"
  29 #endif
  30
  31 #include "irgraph_t.h"
  32 #include "irnode_t.h"
  33 #include "ircons_t.h"
  34 #include "irgmod.h"
  35 #include "iropt_dbg.h"
  36 #include "iredges_t.h"
  37 #include "irgwalk.h"
  38 #include "irprintf.h"
  39 #include "irgopt.h"
  40 #include "irtools.h"
  41 #include "array_t.h"
  42 #include "debug.h"
  43 #include "irflag.h"
  44
  45 /**
  46  * Walker environment.
  47  */
  48 typedef struct _env_t {
  49         unsigned num_confirms;  /**< Number of inserted Confirm nodes. */
  50         unsigned num_consts;    /**< Number of constants placed. */
  51         unsigned num_eq;        /**< Number of equalities placed. */
  52         unsigned num_non_null;  /**< Number of non-null Confirms. */
  53 } env_t;
  54
  55 /** The debug handle. */
  56 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  57
  58 /**
  59  * Return the effective use block of a node and it's predecessor on
  60  * position pos.
  61  *
  62  * @param node  the node
  63  * @param pos   the position of the used input
  64  *
  65  * This handles correctly Phi nodes.
  66  */
  67 static ir_node *get_effective_use_block(ir_node *node, int pos) {
  68         if (is_Phi(node)) {
  69                 /* the effective use of a Phi argument is in its predecessor block */
  70                 node = get_nodes_block(node);
  71                 return get_Block_cfgpred_block(node, pos);
  72         }
  73         return get_nodes_block(node);
  74 }
  75
  76 /**
  77  * Handle a CASE-branch.
  78  *
  79  * @param block   the block which is entered by the branch
  80  * @param irn     the node expressing the switch value
  81  * @param nr      the branch label
  82  * @param env     statistical environment
  83  *
  84  * Branch labels are a simple case. We can replace the value
  85  * by a Const with the branch label.
  86  */
  87 static void handle_case(ir_node *block, ir_node *irn, long nr, env_t *env) {
  88         const ir_edge_t *edge, *next;
  89         ir_node *c = NULL;
  90
  91         if (is_Bad(irn))
  92                 return;
  93
  94         for (edge = get_irn_out_edge_first(irn); edge; edge = next) {
  95                 ir_node *succ = get_edge_src_irn(edge);
  96                 int     pos   = get_edge_src_pos(edge);
  97                 ir_node *blk  = get_effective_use_block(succ, pos);
  98
  99                 next = get_irn_out_edge_next(irn, edge);
 100
 101                 if (block_dominates(block, blk)) {
 102                         /*
 103                          * Ok, we found a user of irn that is placed
 104                          * in a block dominated by the branch block.
 105                          * We can replace the input with the Constant
 106                          * branch label.
 107                          */
 108
 109                         if (! c) {
 110                                 ir_mode *mode = get_irn_mode(irn);
 111                                 ir_type *tp   = get_irn_type(irn);
 112                                 tarval *tv    = new_tarval_from_long(nr, mode);
 113                                 c = new_r_Const_type(current_ir_graph, block, mode, tv, tp);
 114                         }
 115
 116                         set_irn_n(succ, pos, c);
 117                         DBG_OPT_CONFIRM_C(irn, c);
 118                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 119
 120                         env->num_consts += 1;
 121                 }
 122         }
 123 }  /* handle_case */
 124
 125 /**
 126  * Handle a mode_b input of Cond nodes.
 127  *
 128  * @param block     the block which is entered by the branch
 129  * @param selector  the mode_b node expressing the branch condition
 130  * @param pnc       the true/false condition branch
 131  * @param env       statistical environment
 132  */
 133 static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env) {
 134         ir_node *cond, *old, *cond_block = NULL, *other_blk = NULL, *con = NULL;
 135         ir_node *c_b = NULL, *c_o = NULL;
 136         const ir_edge_t *edge, *next;
 137
 138         for (edge = get_irn_out_edge_first(selector); edge; edge = next) {
 139                 ir_node *user     = get_edge_src_irn(edge);
 140                 int     pos       = get_edge_src_pos(edge);
 141                 ir_node *user_blk = get_effective_use_block(user, pos);
 142
 143                 next = get_irn_out_edge_next(selector, edge);
 144                 if (block_dominates(block, user_blk)) {
 145                         /*
 146                          * Ok, we found a usage of selector in a block
 147                          * dominated by the branch block.
 148                          * We can replace the input with true/false.
 149                          */
 150                         if (con == NULL) {
 151                                 con = new_Const(mode_b, pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
 152                         }
 153                         old = get_irn_n(user, pos);
 154                         set_irn_n(user, pos, con);
 155                         DBG_OPT_CONFIRM_C(old, con);
 156
 157                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, con));
 158
 159                         env->num_consts += 1;
 160                 } else {
 161                         int i, n;
 162
 163                         /* get the other block */
 164                         if (other_blk == NULL) {
 165                                 /* we have already tested, that block has only ONE Cond predecessor */
 166                                 cond = get_Proj_pred(get_Block_cfgpred(block, 0));
 167                                 cond_block = get_nodes_block(cond);
 168                                 foreach_out_edge(cond, edge) {
 169                                         ir_node *proj = get_edge_src_irn(edge);
 170                                         if (get_Proj_proj(proj) == (long)pnc)
 171                                                 continue;
 172                                         edge = get_irn_out_edge_first(proj);
 173                                         other_blk = get_edge_src_irn(edge);
 174                                         break;
 175                                 }
 176                                 assert(other_blk);
 177
 178                                 /*
 179                                  * Note the special case here: if block is a then, there might be no else
 180                                  * block. In that case the other_block is the user_blk itself and pred_block
 181                                  * is the cond_block ...
 182                                  *
 183                                  * Best would be to introduce a block here, removing this critical edge.
 184                                  * For some reasons I cannot repair dominance here, so I have to remove
 185                                  * ALL critical edges...
 186                                  * FIXME: This should not be needed if we could repair dominance ...
 187                                  */
 188                         }
 189
 190                         n = get_Block_n_cfgpreds(user_blk);
 191
 192                         /*
 193                          * We have found a user in a non-dominated block:
 194                          * check, if all its block predecessors are dominated.
 195                          * If yes, place a Phi.
 196                          */
 197                         for (i = n - 1; i >= 0; --i) {
 198                                 ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 199
 200                                 if (!block_dominates(block, pred_blk) &&
 201                                     !block_dominates(other_blk, pred_blk)) {
 202                                         /* can't do anything */
 203                                         break;
 204                                 }
 205                         }
 206                         if (i < 0) {
 207                                 ir_node *phi, **in;
 208
 209                                 NEW_ARR_A(ir_node *, in, n);
 210                                 /* ok, ALL predecessors are either dominated by block OR other block */
 211                                 if (c_b == NULL) {
 212                                         ir_node *c_true  = new_Const(mode_b, tarval_b_true);
 213                                         ir_node *c_false = new_Const(mode_b, tarval_b_false);
 214                                         c_b = new_r_Confirm(current_ir_graph, cond_block, selector,
 215                                                 pnc == pn_Cond_true ? c_true : c_false, pn_Cmp_Eq);
 216                                         c_o = new_r_Confirm(current_ir_graph, cond_block, selector,
 217                                                 pnc == pn_Cond_false ? c_true : c_false, pn_Cmp_Eq);
 218                                 }
 219                                 for (i = n - 1; i >= 0; --i) {
 220                                         ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 221
 222                                         if (block_dominates(block, pred_blk))
 223                                                 in[i] = c_b;
 224                                         else
 225                                                 in[i] = c_o;
 226                                 }
 227                                 phi = new_r_Phi(current_ir_graph, user_blk, n, in, mode_b);
 228                                 set_irn_n(user, pos, phi);
 229                         }
 230                 }
 231         }
 232 }
 233
 234 /**
 235  * Handle an IF-branch.
 236  *
 237  * @param block   the block which is entered by the branch
 238  * @param cmp     the Cmp node expressing the branch condition
 239  * @param pnc     the Compare relation for taking this branch
 240  * @param env     statistical environment
 241  */
 242 static void handle_if(ir_node *block, ir_node *cmp, pn_Cmp pnc, env_t *env) {
 243         ir_node *left  = get_Cmp_left(cmp);
 244         ir_node *right = get_Cmp_right(cmp);
 245         ir_node *cond_block;
 246         ir_op *op;
 247         const ir_edge_t *edge, *next;
 248
 249         /* Beware of Bads */
 250         if (is_Bad(left) || is_Bad(right))
 251                 return;
 252
 253         op = get_irn_op(left);
 254
 255         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 256            These are removed anyway */
 257         if (op == op_Const && is_Const(right))
 258                 return;
 259
 260         /* try to place the constant on the right side for a Confirm */
 261         if (op == op_Const || op == op_SymConst) {
 262                 ir_node *t = left;
 263
 264                 left  = right;
 265                 right = t;
 266
 267                 pnc = get_inversed_pnc(pnc);
 268         }
 269
 270         /*
 271          * First case: both values are identical.
 272          * replace the left one by the right (potentially const) one.
 273          */
 274         if (pnc == pn_Cmp_Eq) {
 275                 cond_block = get_Block_cfgpred_block(block, 0);
 276                 for (edge = get_irn_out_edge_first(left); edge; edge = next) {
 277                         ir_node *user = get_edge_src_irn(edge);
 278                         int     pos   = get_edge_src_pos(edge);
 279                         ir_node *blk  = get_effective_use_block(user, pos);
 280
 281                         next = get_irn_out_edge_next(left, edge);
 282                         if (block_dominates(block, blk)) {
 283                                 /*
 284                                  * Ok, we found a usage of left in a block
 285                                  * dominated by the branch block.
 286                                  * We can replace the input with right.
 287                                  */
 288                                 set_irn_n(user, pos, right);
 289                                 DBG_OPT_CONFIRM(left, right);
 290
 291                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));
 292
 293                                 env->num_eq += 1;
 294                         } else if (block_dominates(blk, cond_block)) {
 295                                 if (is_Const(right) && get_irn_pinned(user) == op_pin_state_floats) {
 296                                         /*
 297                                          * left == Const and we found a movable user of left in a
 298                                          * dominator of the Cond block
 299                                          */
 300                                         const ir_edge_t *edge, *next;
 301                                         for (edge = get_irn_out_edge_first(user); edge; edge = next) {
 302                                                 ir_node *usr_of_usr = get_edge_src_irn(edge);
 303                                                 int      npos = get_edge_src_pos(edge);
 304                                                 ir_node *blk  = get_effective_use_block(usr_of_usr, npos);
 305
 306                                                 next = get_irn_out_edge_next(user, edge);
 307                                                 if (block_dominates(block, blk)) {
 308                                                         /*
 309                                                          * The user of the user is dominated by our true/false
 310                                                          * block. So, create a copy of user WITH the constant
 311                                                          * replacing it's pos'th input.
 312                                                          *
 313                                                          * This is always good for unop's and might be good
 314                                                          * for binops.
 315                                                          *
 316                                                          * If user has other user in the false/true block, code
 317                                                          * placement will move it down.
 318                                                          * If there are users in cond block or upper, we create
 319                                                          * "redundant ops", because one will have a const op,
 320                                                          * the other no const ...
 321                                                          */
 322                                                         ir_node *new_op = exact_copy(user);
 323                                                         set_nodes_block(new_op, block);
 324                                                         set_irn_n(new_op, pos, right);
 325                                                         set_irn_n(usr_of_usr, npos, new_op);
 326                                                 }
 327                                         }
 328                                 }
 329                         }
 330                 }
 331         } else { /* not pn_Cmp_Eq cases */
 332                 ir_node *c = NULL;
 333
 334                 for (edge = get_irn_out_edge_first(left); edge; edge = next) {
 335                         ir_node *succ = get_edge_src_irn(edge);
 336                         int     pos   = get_edge_src_pos(edge);
 337                         ir_node *blk  = get_effective_use_block(succ, pos);
 338
 339                         next = get_irn_out_edge_next(left, edge);
 340                         if (block_dominates(block, blk)) {
 341                                 /*
 342                                  * Ok, we found a usage of left in a block
 343                                  * dominated by the branch block.
 344                                  * We can replace the input with a Confirm(left, pnc, right).
 345                                  */
 346                                 if (! c)
 347                                         c = new_r_Confirm(current_ir_graph, block, left, right, pnc);
 348
 349                                 pos = get_edge_src_pos(edge);
 350                                 set_irn_n(succ, pos, c);
 351                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 352
 353                                 env->num_confirms += 1;
 354                         }
 355                 }
 356         }
 357 }  /* handle_if */
 358
 359 /**
 360  * Pre-block-walker: Called for every block to insert Confirm nodes
 361  */
 362 static void insert_Confirm_in_block(ir_node *block, void *env) {
 363         ir_node *cond, *proj, *selector;
 364         ir_mode *mode;
 365
 366         /*
 367          * we can only handle blocks with only ONE control flow
 368          * predecessor yet.
 369          */
 370         if (get_Block_n_cfgpreds(block) != 1)
 371                 return;
 372
 373         proj = get_Block_cfgpred(block, 0);
 374         if (! is_Proj(proj))
 375                 return;
 376
 377         cond = get_Proj_pred(proj);
 378         if (! is_Cond(cond))
 379                 return;
 380
 381         selector = get_Cond_selector(cond);
 382         mode = get_irn_mode(selector);
 383
 384         if (mode == mode_b) {
 385                 ir_node *cmp;
 386                 pn_Cmp pnc;
 387
 388                 handle_modeb(block, selector, get_Proj_proj(proj), env);
 389
 390                 /* this should be an IF, check this */
 391                 if (! is_Proj(selector))
 392                         return;
 393
 394                 cmp = get_Proj_pred(selector);
 395                 if (! is_Cmp(cmp))
 396                         return;
 397
 398                 pnc = get_Proj_proj(selector);
 399
 400                 if (get_Proj_proj(proj) != pn_Cond_true) {
 401                         /* it's the false branch */
 402                         pnc = get_negated_pnc(pnc, mode);
 403                 }
 404                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, cmp, pnc));
 405
 406                 handle_if(block, cmp, pnc, env);
 407         } else if (mode_is_int(mode)) {
 408                 long proj_nr = get_Proj_proj(proj);
 409
 410                 /* this is a CASE, but we cannot handle the default case */
 411                 if (proj_nr == get_Cond_defaultProj(cond))
 412                         return;
 413
 414                 handle_case(block, get_Cond_selector(cond), proj_nr, env);
 415         }
 416 }  /* insert_Confirm_in_block */
 417
 418 /**
 419  * Checks if a node is a non-null Confirm.
 420  */
 421 static int is_non_null_Confirm(const ir_node *ptr) {
 422         for (;;) {
 423                 if (! is_Confirm(ptr))
 424                         break;
 425                 if (get_Confirm_cmp(ptr) == pn_Cmp_Lg) {
 426                         ir_node *bound = get_Confirm_bound(ptr);
 427
 428                         if (is_Const(bound) && is_Const_null(bound))
 429                                 return 1;
 430                 }
 431                 ptr = get_Confirm_value(ptr);
 432         }
 433         /*
 434          * While a SymConst is not a Confirm, it is non-null
 435          * anyway. This helps to reduce the number of
 436          * constructed Confirms.
 437          */
 438         if (is_SymConst_addr_ent(ptr))
 439                 return 1;
 440         return 0;
 441 }  /* is_non_null_Confirm */
 442
 443 /**
 444  * The given pointer will be dereferenced, add non-null Confirms.
 445  *
 446  * @param ptr    a node representing an address
 447  * @param block  the block of the dereferencing instruction
 448  * @param env    environment
 449  */
 450 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env) {
 451         const ir_edge_t *edge, *next;
 452         ir_node         *c = NULL;
 453
 454         foreach_out_edge_safe(ptr, edge, next) {
 455                 ir_node *succ = get_edge_src_irn(edge);
 456                 int     pos;
 457                 ir_node *blk;
 458
 459
 460                 /* for now, we place a Confirm only in front of a Cmp */
 461                 if (! is_Cmp(succ))
 462                         continue;
 463
 464                 pos = get_edge_src_pos(edge);
 465                 blk = get_effective_use_block(succ, pos);
 466
 467                 if (block_dominates(block, blk)) {
 468                         /*
 469                          * Ok, we found a usage of ptr in a block
 470                          * dominated by the Load/Store block.
 471                          * We can replace the input with a Confirm(ptr, !=, NULL).
 472                          */
 473                         if (c == NULL) {
 474                                 ir_mode *mode = get_irn_mode(ptr);
 475                                 c = new_Const(mode, get_mode_null(mode));
 476
 477                                 c = new_r_Confirm(current_ir_graph, block, ptr, c, pn_Cmp_Lg);
 478                         }
 479
 480                         set_irn_n(succ, pos, c);
 481                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 482
 483                         env->num_non_null += 1;
 484                         env->num_confirms += 1;
 485                 }
 486         }
 487 }  /* insert_non_null */
 488
 489 /**
 490  * Pre-walker: Called for every node to insert Confirm nodes
 491  */
 492 static void insert_Confirm(ir_node *node, void *env) {
 493         ir_node *ptr;
 494
 495         switch (get_irn_opcode(node)) {
 496         case iro_Block:
 497                 insert_Confirm_in_block(node, env);
 498                 break;
 499         case iro_Load:
 500                 ptr = get_Load_ptr(node);
 501                 if (! is_non_null_Confirm(ptr))
 502                         insert_non_null(ptr, get_nodes_block(node), env);
 503                 break;
 504         case iro_Store:
 505                 ptr = get_Store_ptr(node);
 506                 if (! is_non_null_Confirm(ptr))
 507                         insert_non_null(ptr, get_nodes_block(node), env);
 508                 break;
 509         default:
 510                 break;
 511         }
 512 }  /* insert_Confirm */
 513
 514 /*
 515  * Construct Confirm nodes
 516  */
 517 void construct_confirms(ir_graph *irg) {
 518         env_t env;
 519         int edges_active = edges_activated(irg);
 520
 521
 522         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 523
 524         remove_critical_cf_edges(irg);
 525
 526         /* we need dominance info */
 527         assure_doms(irg);
 528
 529         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 530                "Nodes must be placed to insert Confirms");
 531
 532         if (! edges_active) {
 533                 /* We need edges */
 534                 edges_activate(irg);
 535         }
 536
 537         env.num_confirms = 0;
 538         env.num_consts   = 0;
 539         env.num_eq       = 0;
 540         env.num_non_null = 0;
 541
 542         if (get_opt_global_null_ptr_elimination()) {
 543                 /* do global NULL test elimination */
 544                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 545         } else {
 546                 /* now, visit all blocks and add Confirms where possible */
 547                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 548         }
 549
 550         if (env.num_confirms | env.num_consts | env.num_eq) {
 551                 /* we have add nodes or changed DF edges */
 552                 set_irg_outs_inconsistent(irg);
 553
 554                 /* the new nodes are not in the loop info */
 555                 set_irg_loopinfo_inconsistent(irg);
 556         }
 557
 558         DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
 559         DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
 560         DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
 561         DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));
 562
 563         /* deactivate edges if they where off */
 564         if (! edges_active)
 565                 edges_deactivate(irg);
 566 }  /* construct_confirms */
 567
 568 #if 0
 569 /**
 570  * Post-walker: Remove Confirm nodes
 571  */
 572 static void rem_Confirm(ir_node *n, void *env) {
 573         (void) env;
 574         if (is_Confirm(n)) {
 575                 ir_node *value = get_Confirm_value(n);
 576                 if (value != n)
 577                         exchange(n, value);
 578                 else {
 579                         /*
 580                          * Strange: a Confirm is its own bound. This can happen
 581                          * in dead blocks when Phi nodes are already removed.
 582                          */
 583                         exchange(n, new_Bad());
 584                 }
 585         }
 586 }  /* rem_Confirm */
 587 #endif
 588
 589 /*
 590  * Remove all Confirm nodes from a graph.
 591  */
 592 void remove_confirms(ir_graph *irg) {
 593         int rem = get_opt_remove_confirm();
 594
 595         set_opt_remove_confirm(1);
 596         optimize_graph_df(irg);
 597         set_opt_remove_confirm(rem);
 598 }  /* remove_confirms */