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 } env_t;
  53
  54 /** The debug handle. */
  55 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  56
  57 /**
  58  * Return the effective use block of a node and it's predecessor on
  59  * position pos.
  60  *
  61  * @param node  the node
  62  * @param pos   the position of the used input
  63  *
  64  * This handles correctly Phi nodes.
  65  */
  66 static ir_node *get_effective_use_block(ir_node *node, int pos) {
  67         if (is_Phi(node)) {
  68                 /* the effective use of a Phi argument is in its predecessor block */
  69                 node = get_nodes_block(node);
  70                 return get_Block_cfgpred_block(node, pos);
  71         }
  72         return get_nodes_block(node);
  73 }
  74
  75 /**
  76  * Handle a CASE-branch.
  77  *
  78  * @param block   the block which is entered by the branch
  79  * @param irn     the node expressing the switch value
  80  * @param nr      the branch label
  81  * @param env     statistical environment
  82  *
  83  * Branch labels are a simple case. We can replace the value
  84  * by a Const with the branch label.
  85  */
  86 static void handle_case(ir_node *block, ir_node *irn, long nr, env_t *env) {
  87         const ir_edge_t *edge, *next;
  88         ir_node *c = NULL;
  89
  90         if (is_Bad(irn))
  91                 return;
  92
  93         for (edge = get_irn_out_edge_first(irn); edge; edge = next) {
  94                 ir_node *succ = get_edge_src_irn(edge);
  95                 int     pos   = get_edge_src_pos(edge);
  96                 ir_node *blk  = get_effective_use_block(succ, pos);
  97
  98                 next = get_irn_out_edge_next(irn, edge);
  99
 100                 if (block_dominates(block, blk)) {
 101                         /*
 102                          * Ok, we found a user of irn that is placed
 103                          * in a block dominated by the branch block.
 104                          * We can replace the input with the Constant
 105                          * branch label.
 106                          */
 107
 108                         if (! c) {
 109                                 ir_mode *mode = get_irn_mode(irn);
 110                                 ir_type *tp   = get_irn_type(irn);
 111                                 tarval *tv    = new_tarval_from_long(nr, mode);
 112                                 c = new_r_Const_type(current_ir_graph, block, mode, tv, tp);
 113                         }
 114
 115                         set_irn_n(succ, pos, c);
 116                         DBG_OPT_CONFIRM_C(irn, c);
 117 //                      ir_printf("1 Replacing input %d of node %n with %n\n", pos, succ, c);
 118
 119                         env->num_consts += 1;
 120                 }
 121         }
 122 }  /* handle_case */
 123
 124 /**
 125  * Handle a mode_b input of Cond nodes.
 126  *
 127  * @param block     the block which is entered by the branch
 128  * @param selector  the mode_b node expressing the branch condition
 129  * @param pnc       the true/false condition branch
 130  * @param env       statistical environment
 131  */
 132 static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env) {
 133         ir_node *cond, *old, *cond_block = NULL, *other_blk = NULL, *con = NULL;
 134         ir_node *c_b = NULL, *c_o = NULL;
 135         const ir_edge_t *edge, *next;
 136
 137         for (edge = get_irn_out_edge_first(selector); edge; edge = next) {
 138                 ir_node *user     = get_edge_src_irn(edge);
 139                 int     pos       = get_edge_src_pos(edge);
 140                 ir_node *user_blk = get_effective_use_block(user, pos);
 141
 142                 next = get_irn_out_edge_next(selector, edge);
 143                 if (block_dominates(block, user_blk)) {
 144                         /*
 145                          * Ok, we found a usage of selector in a block
 146                          * dominated by the branch block.
 147                          * We can replace the input with true/false.
 148                          */
 149                         if (con == NULL) {
 150                                 con = new_Const(mode_b, pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
 151                         }
 152                         old = get_irn_n(user, pos);
 153                         set_irn_n(user, pos, con);
 154                         DBG_OPT_CONFIRM_C(old, con);
 155
 156                         DB((dbg, LEVEL_2, "Replacing input %d of node %n with %n\n", pos, user, con));
 157
 158                         env->num_consts += 1;
 159                 } else {
 160                         int i, n;
 161
 162                         /* get the other block */
 163                         if (other_blk == NULL) {
 164                                 /* we have already tested, that block has only ONE Cond predecessor */
 165                                 cond = get_Proj_pred(get_Block_cfgpred(block, 0));
 166                                 cond_block = get_nodes_block(cond);
 167                                 foreach_out_edge(cond, edge) {
 168                                         ir_node *proj = get_edge_src_irn(edge);
 169                                         if (get_Proj_proj(proj) == (long)pnc)
 170                                                 continue;
 171                                         edge = get_irn_out_edge_first(proj);
 172                                         other_blk = get_edge_src_irn(edge);
 173                                         break;
 174                                 }
 175                                 assert(other_blk);
 176
 177                                 /*
 178                                  * Note the special case here: if block is a then, there might be no else
 179                                  * block. In that case the other_block is the user_blk itself and pred_block
 180                                  * is the cond_block ...
 181                                  *
 182                                  * Best would be to introduce a block here, removing this critical edge.
 183                                  * For some reasons I cannot repair dominance here, so I have to remove
 184                                  * ALL critical edges...
 185                                  * FIXME: This should not be needed if we could repair dominance ...
 186                                  */
 187                         }
 188
 189                         n = get_Block_n_cfgpreds(user_blk);
 190
 191                         /*
 192                          * We have found a user in a non-dominated block:
 193                          * check, if all its block predecessors are dominated.
 194                          * If yes, place a Phi.
 195                          */
 196                         for (i = n - 1; i >= 0; --i) {
 197                                 ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 198
 199                                 if (!block_dominates(block, pred_blk) &&
 200                                     !block_dominates(other_blk, pred_blk)) {
 201                                         /* can't do anything */
 202                                         break;
 203                                 }
 204                         }
 205                         if (i < 0) {
 206                                 ir_node *phi, **in;
 207
 208                                 NEW_ARR_A(ir_node *, in, n);
 209                                 /* ok, ALL predecessors are either dominated by block OR other block */
 210                                 if (c_b == NULL) {
 211                                         ir_node *c_true  = new_Const(mode_b, tarval_b_true);
 212                                         ir_node *c_false = new_Const(mode_b, tarval_b_false);
 213                                         c_b = new_r_Confirm(current_ir_graph, cond_block, selector,
 214                                                 pnc == pn_Cond_true ? c_true : c_false, pn_Cmp_Eq);
 215                                         c_o = new_r_Confirm(current_ir_graph, cond_block, selector,
 216                                                 pnc == pn_Cond_false ? c_true : c_false, pn_Cmp_Eq);
 217                                 }
 218                                 for (i = n - 1; i >= 0; --i) {
 219                                         ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 220
 221                                         if (block_dominates(block, pred_blk))
 222                                                 in[i] = c_b;
 223                                         else
 224                                                 in[i] = c_o;
 225                                 }
 226                                 phi = new_r_Phi(current_ir_graph, user_blk, n, in, mode_b);
 227                                 set_irn_n(user, pos, phi);
 228                         }
 229                 }
 230         }
 231 }
 232
 233 /**
 234  * Handle an IF-branch.
 235  *
 236  * @param block   the block which is entered by the branch
 237  * @param cmp     the Cmp node expressing the branch condition
 238  * @param pnc     the Compare relation for taking this branch
 239  * @param env     statistical environment
 240  */
 241 static void handle_if(ir_node *block, ir_node *cmp, pn_Cmp pnc, env_t *env) {
 242         ir_node *left  = get_Cmp_left(cmp);
 243         ir_node *right = get_Cmp_right(cmp);
 244         ir_node *cond_block;
 245         ir_op *op;
 246         const ir_edge_t *edge, *next;
 247
 248         /* Beware of Bads */
 249         if (is_Bad(left) || is_Bad(right))
 250                 return;
 251
 252         op = get_irn_op(left);
 253
 254         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 255            These are removed anyway */
 256         if (op == op_Const && is_Const(right))
 257                 return;
 258
 259         /* try to place the constant on the right side for a Confirm */
 260         if (op == op_Const || op == op_SymConst) {
 261                 ir_node *t = left;
 262
 263                 left  = right;
 264                 right = t;
 265
 266                 pnc = get_inversed_pnc(pnc);
 267         }
 268
 269         /*
 270          * First case: both values are identical.
 271          * replace the left one by the right (potentially const) one.
 272          */
 273         if (pnc == pn_Cmp_Eq) {
 274                 cond_block = get_Block_cfgpred_block(block, 0);
 275                 for (edge = get_irn_out_edge_first(left); edge; edge = next) {
 276                         ir_node *user = get_edge_src_irn(edge);
 277                         int     pos   = get_edge_src_pos(edge);
 278                         ir_node *blk  = get_effective_use_block(user, pos);
 279
 280                         next = get_irn_out_edge_next(left, edge);
 281                         if (block_dominates(block, blk)) {
 282                                 /*
 283                                  * Ok, we found a usage of left in a block
 284                                  * dominated by the branch block.
 285                                  * We can replace the input with right.
 286                                  */
 287                                 set_irn_n(user, pos, right);
 288                                 DBG_OPT_CONFIRM(left, right);
 289
 290                                 DB((dbg, LEVEL_2, "Replacing input %d of node %n with %n\n", pos, user, right));
 291
 292                                 env->num_eq += 1;
 293                         } else if (block_dominates(blk, cond_block)) {
 294                                 if (is_Const(right) && get_irn_pinned(user) == op_pin_state_floats) {
 295                                         /*
 296                                          * left == Const and we found a movable user of left in a
 297                                          * dominator of the Cond block
 298                                          */
 299                                         const ir_edge_t *edge, *next;
 300                                         for (edge = get_irn_out_edge_first(user); edge; edge = next) {
 301                                                 ir_node *usr_of_usr = get_edge_src_irn(edge);
 302                                                 int      npos = get_edge_src_pos(edge);
 303                                                 ir_node *blk  = get_effective_use_block(usr_of_usr, npos);
 304
 305                                                 next = get_irn_out_edge_next(user, edge);
 306                                                 if (block_dominates(block, blk)) {
 307                                                         /*
 308                                                          * The user of the user is dominated by our true/false
 309                                                          * block. So, create a copy of user WITH the constant
 310                                                          * replacing it's pos'th input.
 311                                                          *
 312                                                          * This is always good for unop's and might be good
 313                                                          * for binops.
 314                                                          *
 315                                                          * If user has other user in the false/true block, code
 316                                                          * placement will move it down.
 317                                                          * If there are users in cond block or upper, we create
 318                                                          * "redundant ops", because one will have a const op,
 319                                                          * the other no const ...
 320                                                          */
 321                                                         ir_node *new_op = exact_copy(user);
 322                                                         set_nodes_block(new_op, block);
 323                                                         set_irn_n(new_op, pos, right);
 324                                                         set_irn_n(usr_of_usr, npos, new_op);
 325                                                 }
 326                                         }
 327                                 }
 328                         }
 329                 }
 330         } else { /* not pn_Cmp_Eq cases */
 331                 ir_node *c = NULL;
 332
 333                 for (edge = get_irn_out_edge_first(left); edge; edge = next) {
 334                         ir_node *succ = get_edge_src_irn(edge);
 335                         int     pos   = get_edge_src_pos(edge);
 336                         ir_node *blk  = get_effective_use_block(succ, pos);
 337
 338                         next = get_irn_out_edge_next(left, edge);
 339                         if (block_dominates(block, blk)) {
 340                                 /*
 341                                  * Ok, we found a usage of left in a block
 342                                  * dominated by the branch block.
 343                                  * We can replace the input with a Confirm(left, pnc, right).
 344                                  */
 345                                 if (! c)
 346                                         c = new_r_Confirm(current_ir_graph, block, left, right, pnc);
 347
 348                                 pos = get_edge_src_pos(edge);
 349                                 set_irn_n(succ, pos, c);
 350                                 DB((dbg, LEVEL_2, "Replacing input %d of node %n with %n\n", pos, succ, c));
 351
 352                                 env->num_confirms += 1;
 353                         }
 354                 }
 355         }
 356 }  /* handle_if */
 357
 358 /**
 359  * Pre-block-walker: Called for every block to insert Confirm nodes
 360  */
 361 static void insert_Confirm_in_block(ir_node *block, void *env) {
 362         ir_node *cond, *proj, *selector;
 363         ir_mode *mode;
 364
 365         /*
 366          * we can only handle blocks with only ONE control flow
 367          * predecessor yet.
 368          */
 369         if (get_Block_n_cfgpreds(block) != 1)
 370                 return;
 371
 372         proj = get_Block_cfgpred(block, 0);
 373         if (! is_Proj(proj))
 374                 return;
 375
 376         cond = get_Proj_pred(proj);
 377         if (! is_Cond(cond))
 378                 return;
 379
 380         selector = get_Cond_selector(cond);
 381         mode = get_irn_mode(selector);
 382
 383         if (mode == mode_b) {
 384                 ir_node *cmp;
 385                 pn_Cmp pnc;
 386
 387                 handle_modeb(block, selector, get_Proj_proj(proj), env);
 388
 389                 /* this should be an IF, check this */
 390                 if (! is_Proj(selector))
 391                         return;
 392
 393                 cmp = get_Proj_pred(selector);
 394                 if (! is_Cmp(cmp))
 395                         return;
 396
 397                 pnc = get_Proj_proj(selector);
 398
 399                 if (get_Proj_proj(proj) != pn_Cond_true) {
 400                         /* it's the false branch */
 401                         pnc = get_negated_pnc(pnc, mode);
 402                 }
 403                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, cmp, pnc));
 404
 405                 handle_if(block, cmp, pnc, env);
 406         } else if (mode_is_int(mode)) {
 407                 long proj_nr = get_Proj_proj(proj);
 408
 409                 /* this is a CASE, but we cannot handle the default case */
 410                 if (proj_nr == get_Cond_defaultProj(cond))
 411                         return;
 412
 413                 handle_case(block, get_Cond_selector(cond), proj_nr, env);
 414         }
 415 }  /* insert_Confirm_in_block */
 416
 417 /**
 418  * Checks if a node is a non-null Confirm.
 419  */
 420 static int is_non_null_Confirm(const ir_node *ptr) {
 421         /*
 422          * While a SymConst is not a Confirm, it is non-null
 423          * anyway. This helps to reduce the number of
 424          * constructed Confirms.
 425          */
 426         if (is_SymConst_addr_ent(ptr))
 427                 return 1;
 428         for (;;) {
 429                 if (! is_Confirm(ptr))
 430                         return 0;
 431                 if (get_Confirm_cmp(ptr) == pn_Cmp_Lg) {
 432                         ir_node *bound = get_Confirm_bound(ptr);
 433
 434                         if (is_Const(bound) && is_Const_null(bound))
 435                                 return 1;
 436                 }
 437                 ptr = get_Confirm_value(ptr);
 438         }
 439 }  /* is_non_null_Confirm */
 440
 441 /**
 442  * The given pointer will be dereferenced, add non-null Confirms.
 443  *
 444  * @param ptr    a node representing an address
 445  * @param block  the block of the dereferencing instruction
 446  * @param env    environment
 447  */
 448 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env) {
 449         const ir_edge_t *edge, *next;
 450         ir_node         *c = NULL;
 451
 452         foreach_out_edge_safe(ptr, edge, next) {
 453                 ir_node *succ = get_edge_src_irn(edge);
 454                 int     pos;
 455                 ir_node *blk;
 456
 457
 458                 if (is_Confirm(succ)) {
 459                         /* beware of loops */
 460                         continue;
 461                 }
 462
 463                 if ((is_Load(succ) || is_Store(succ)) &&
 464                         get_nodes_block(succ) == block) {
 465                         /* Ignore Loads and Store in the same block for now,
 466                            because we are not sure if they are dominated.
 467                            This is not a bad restriction: if exception flow is
 468                            present, they are in other blocks either. */
 469                         continue;
 470                 }
 471
 472                 pos = get_edge_src_pos(edge);
 473                 blk = get_effective_use_block(succ, pos);
 474
 475                 if (block_dominates(block, blk) && !is_non_null_Confirm(get_irn_n(succ, pos))) {
 476                         /*
 477                          * Ok, we found a usage of ptr in a block
 478                          * dominated by the Load/Store block.
 479                          * We can replace the input with a Confirm(ptr, !=, NULL).
 480                          */
 481                         if (c == NULL) {
 482                                 ir_mode *mode = get_irn_mode(ptr);
 483                                 c = new_Const(mode, get_mode_null(mode));
 484
 485                                 c = new_r_Confirm(current_ir_graph, block, ptr, c, pn_Cmp_Lg);
 486                         }
 487
 488                         set_irn_n(succ, pos, c);
 489                         DB((dbg, LEVEL_2, "Replacing input %d of node %n with %n\n", pos, succ, c));
 490
 491
 492                         env->num_confirms += 1;
 493                 }
 494         }
 495 }  /* insert_non_null */
 496
 497 /**
 498  * Pre-walker: Called for every node to insert Confirm nodes
 499  */
 500 static void insert_Confirm(ir_node *node, void *env) {
 501         ir_node *ptr;
 502
 503         switch (get_irn_opcode(node)) {
 504         case iro_Block:
 505                 insert_Confirm_in_block(node, env);
 506                 break;
 507         case iro_Load:
 508                 ptr = get_Load_ptr(node);
 509                 if (! is_non_null_Confirm(ptr))
 510                         insert_non_null(ptr, get_nodes_block(node), env);
 511                 break;
 512         case iro_Store:
 513                 ptr = get_Store_ptr(node);
 514                 if (! is_non_null_Confirm(ptr))
 515                         insert_non_null(ptr, get_nodes_block(node), env);
 516                 break;
 517         default:
 518                 break;
 519         }
 520 }  /* insert_Confirm */
 521
 522 /*
 523  * Construct Confirm nodes
 524  */
 525 void construct_confirms(ir_graph *irg) {
 526         env_t env;
 527         int edges_active = edges_activated(irg);
 528
 529
 530         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 531
 532         remove_critical_cf_edges(irg);
 533
 534         /* we need dominance info */
 535         assure_doms(irg);
 536
 537         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 538                "Nodes must be placed to insert Confirms");
 539
 540         if (! edges_active) {
 541                 /* We need edges */
 542                 edges_activate(irg);
 543         }
 544
 545         env.num_confirms = 0;
 546         env.num_consts   = 0;
 547         env.num_eq       = 0;
 548
 549         if (get_opt_global_null_ptr_elimination()) {
 550                 /* do global NULL test elimination */
 551                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 552         } else {
 553                 /* now, visit all blocks and add Confirms where possible */
 554                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 555         }
 556
 557         if (env.num_confirms | env.num_consts | env.num_eq) {
 558                 /* we have add nodes or changed DF edges */
 559                 set_irg_outs_inconsistent(irg);
 560
 561                 /* the new nodes are not in the loop info */
 562                 set_irg_loopinfo_inconsistent(irg);
 563         }
 564
 565         DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
 566         DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
 567         DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
 568
 569         /* deactivate edges if they where off */
 570         if (! edges_active)
 571                 edges_deactivate(irg);
 572 }  /* construct_confirms */
 573
 574 #if 0
 575 /**
 576  * Post-walker: Remove Confirm nodes
 577  */
 578 static void rem_Confirm(ir_node *n, void *env) {
 579         (void) env;
 580         if (is_Confirm(n)) {
 581                 ir_node *value = get_Confirm_value(n);
 582                 if (value != n)
 583                         exchange(n, value);
 584                 else {
 585                         /*
 586                          * Strange: a Confirm is its own bound. This can happen
 587                          * in dead blocks when Phi nodes are already removed.
 588                          */
 589                         exchange(n, new_Bad());
 590                 }
 591         }
 592 }  /* rem_Confirm */
 593 #endif
 594
 595 /*
 596  * Remove all Confirm nodes from a graph.
 597  */
 598 void remove_confirms(ir_graph *irg) {
 599         int rem = get_opt_remove_confirm();
 600
 601         set_opt_remove_confirm(1);
 602         optimize_graph_df(irg);
 603         set_opt_remove_confirm(rem);
 604 }  /* remove_confirms */