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  */
  26 #include "config.h"
  27
  28 #include "irconsconfirm.h"
  29
  30 #include "irgraph_t.h"
  31 #include "irnode_t.h"
  32 #include "ircons_t.h"
  33 #include "irgmod.h"
  34 #include "iropt_dbg.h"
  35 #include "iredges_t.h"
  36 #include "irgwalk.h"
  37 #include "irprintf.h"
  38 #include "irgopt.h"
  39 #include "irpass.h"
  40 #include "irtools.h"
  41 #include "array_t.h"
  42 #include "debug.h"
  43 #include "error.h"
  44 #include "irflag.h"
  45
  46 /**
  47  * Walker environment.
  48  */
  49 typedef struct env_t {
  50         unsigned num_confirms;  /**< Number of inserted Confirm nodes. */
  51         unsigned num_consts;    /**< Number of constants placed. */
  52         unsigned num_eq;        /**< Number of equalities placed. */
  53         unsigned num_non_null;  /**< Number of non-null Confirms. */
  54 } env_t;
  55
  56 /** The debug handle. */
  57 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  58
  59 /**
  60  * Return the effective use block of a node and its predecessor on
  61  * position pos.
  62  *
  63  * @param node  the node
  64  * @param pos   the position of the used input
  65  *
  66  * This handles correctly Phi nodes.
  67  */
  68 static ir_node *get_effective_use_block(ir_node *node, int pos)
  69 {
  70         if (is_Phi(node)) {
  71                 /* the effective use of a Phi argument is in its predecessor block */
  72                 node = get_nodes_block(node);
  73                 return get_Block_cfgpred_block(node, pos);
  74         }
  75         return get_nodes_block(node);
  76 }
  77
  78 static ir_node *get_case_value(ir_node *switchn, long pn)
  79 {
  80         ir_graph              *irg       = get_irn_irg(switchn);
  81         const ir_switch_table *table     = get_Switch_table(switchn);
  82         size_t                 n_entries = ir_switch_table_get_n_entries(table);
  83         ir_tarval             *val       = NULL;
  84         size_t                 e;
  85         for (e = 0; e < n_entries; ++e) {
  86                 const ir_switch_table_entry *entry
  87                         = ir_switch_table_get_entry_const(table, e);
  88                 if (entry->pn != pn)
  89                         continue;
  90                 /* multiple matching entries gets too complicated for a single
  91                  * Confirm */
  92                 if (val != NULL)
  93                         return NULL;
  94                 /* case ranges are too complicated too */
  95                 if (entry->min != entry->max)
  96                         return NULL;
  97                 val = entry->min;
  98         }
  99         assert(val != NULL);
 100         return new_r_Const(irg, val);
 101 }
 102
 103 /**
 104  * Handle a CASE-branch.
 105  *
 106  * Branch labels are a simple case. We can replace the value
 107  * by a Const with the branch label.
 108  */
 109 static void handle_case(ir_node *block, ir_node *switchn, long pn, env_t *env)
 110 {
 111         ir_node *c = NULL;
 112         ir_node *selector = get_Switch_selector(switchn);
 113
 114         /* we can't do usefull things with the default label */
 115         if (pn == pn_Switch_default)
 116                 return;
 117
 118         foreach_out_edge_safe(selector, edge) {
 119                 ir_node *succ = get_edge_src_irn(edge);
 120                 int     pos   = get_edge_src_pos(edge);
 121                 ir_node *blk  = get_effective_use_block(succ, pos);
 122
 123                 if (block_dominates(block, blk)) {
 124                         /*
 125                          * Ok, we found a user of irn that is placed
 126                          * in a block dominated by the branch block.
 127                          * We can replace the input with the Constant
 128                          * branch label.
 129                          */
 130                         if (c == NULL)
 131                                 c = get_case_value(switchn, pn);
 132
 133                         set_irn_n(succ, pos, c);
 134                         DBG_OPT_CONFIRM_C(selector, c);
 135                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 136
 137                         env->num_consts += 1;
 138                 }
 139         }
 140 }
 141
 142 /**
 143  * Handle a mode_b input of Cond nodes.
 144  *
 145  * @param block     the block which is entered by the branch
 146  * @param selector  the mode_b node expressing the branch condition
 147  * @param pnc       the true/false condition branch
 148  * @param env       statistical environment
 149  */
 150 static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env)
 151 {
 152         ir_node *cond, *old, *other_blk = NULL, *con = NULL;
 153         ir_node *c_b = NULL, *c_o = NULL;
 154
 155         foreach_out_edge_safe(selector, edge) {
 156                 ir_node *user     = get_edge_src_irn(edge);
 157                 int     pos       = get_edge_src_pos(edge);
 158                 ir_node *user_blk = get_effective_use_block(user, pos);
 159
 160                 if (block_dominates(block, user_blk)) {
 161                         /*
 162                          * Ok, we found a usage of selector in a block
 163                          * dominated by the branch block.
 164                          * We can replace the input with true/false.
 165                          */
 166                         if (con == NULL) {
 167                                 ir_graph *irg = get_irn_irg(block);
 168                                 con = new_r_Const(irg, pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
 169                         }
 170                         old = get_irn_n(user, pos);
 171                         set_irn_n(user, pos, con);
 172                         DBG_OPT_CONFIRM_C(old, con);
 173
 174                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, con));
 175
 176                         env->num_consts += 1;
 177                 } else {
 178                         int i, n;
 179
 180                         /* get the other block */
 181                         if (other_blk == NULL) {
 182                                 /* we have already tested, that block has only ONE Cond predecessor */
 183                                 cond = get_Proj_pred(get_Block_cfgpred(block, 0));
 184                                 foreach_out_edge(cond, edge) {
 185                                         ir_node *proj = get_edge_src_irn(edge);
 186                                         if (get_Proj_proj(proj) == (long)pnc)
 187                                                 continue;
 188                                         edge = get_irn_out_edge_first(proj);
 189                                         other_blk = get_edge_src_irn(edge);
 190                                         break;
 191                                 }
 192                                 assert(other_blk);
 193
 194                                 /*
 195                                  * Note the special case here: if block is a then, there might be no else
 196                                  * block. In that case the other_block is the user_blk itself and pred_block
 197                                  * is the cond_block ...
 198                                  *
 199                                  * Best would be to introduce a block here, removing this critical edge.
 200                                  * For some reasons I cannot repair dominance here, so I have to remove
 201                                  * ALL critical edges...
 202                                  * FIXME: This should not be needed if we could repair dominance ...
 203                                  */
 204                         }
 205
 206                         n = get_Block_n_cfgpreds(user_blk);
 207
 208                         /*
 209                          * We have found a user in a non-dominated block:
 210                          * check, if all its block predecessors are dominated.
 211                          * If yes, place a Phi.
 212                          */
 213                         for (i = n - 1; i >= 0; --i) {
 214                                 ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 215
 216                                 if (!block_dominates(block, pred_blk) &&
 217                                     !block_dominates(other_blk, pred_blk)) {
 218                                         /* can't do anything */
 219                                         break;
 220                                 }
 221                         }
 222                         if (i < 0) {
 223                                 ir_node *phi, **in;
 224
 225                                 NEW_ARR_A(ir_node *, in, n);
 226                                 /* ok, ALL predecessors are either dominated by block OR other block */
 227                                 if (c_b == NULL) {
 228                                         ir_graph *irg    = get_irn_irg(block);
 229                                         ir_node *c_true  = new_r_Const(irg, tarval_b_true);
 230                                         ir_node *c_false = new_r_Const(irg, tarval_b_false);
 231                                         env->num_consts += 2;
 232                                         if (pnc == pn_Cond_true) {
 233                                                 c_b = c_true;
 234                                                 c_o = c_false;
 235                                         } else {
 236                                                 c_b = c_false;
 237                                                 c_o = c_true;
 238                                         }
 239                                 }
 240                                 for (i = n - 1; i >= 0; --i) {
 241                                         ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 242
 243                                         if (block_dominates(block, pred_blk))
 244                                                 in[i] = c_b;
 245                                         else
 246                                                 in[i] = c_o;
 247                                 }
 248                                 phi = new_r_Phi(user_blk, n, in, mode_b);
 249                                 set_irn_n(user, pos, phi);
 250                                 env->num_eq += 1;
 251                         }
 252                 }
 253         }
 254 }
 255
 256 /**
 257  * Handle an IF-branch.
 258  *
 259  * @param block   the block which is entered by the branch
 260  * @param cmp     the Cmp node expressing the branch condition
 261  * @param rel     the Compare relation for taking this branch
 262  * @param env     statistical environment
 263  */
 264 static void handle_if(ir_node *block, ir_node *cmp, ir_relation rel, env_t *env)
 265 {
 266         ir_node *left  = get_Cmp_left(cmp);
 267         ir_node *right = get_Cmp_right(cmp);
 268         ir_node *cond_block;
 269
 270         /* Beware of Bads */
 271         if (is_Bad(left) || is_Bad(right))
 272                 return;
 273
 274         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 275            These are removed anyway */
 276         if (is_Const(left) && is_Const(right))
 277                 return;
 278
 279         /* try to place the constant on the right side for a Confirm */
 280         if (is_Const(left) || is_SymConst(left)) {
 281                 ir_node *t = left;
 282
 283                 left  = right;
 284                 right = t;
 285
 286                 rel = get_inversed_relation(rel);
 287         }
 288
 289         /*
 290          * First case: both values are identical.
 291          * replace the left one by the right (potentially const) one.
 292          */
 293         if (rel == ir_relation_equal) {
 294                 cond_block = get_Block_cfgpred_block(block, 0);
 295                 foreach_out_edge_safe(left, edge) {
 296                         ir_node *user = get_edge_src_irn(edge);
 297                         int     pos   = get_edge_src_pos(edge);
 298                         ir_node *blk  = get_effective_use_block(user, pos);
 299
 300                         if (block_dominates(block, blk)) {
 301                                 /*
 302                                  * Ok, we found a usage of left in a block
 303                                  * dominated by the branch block.
 304                                  * We can replace the input with right.
 305                                  */
 306                                 set_irn_n(user, pos, right);
 307                                 DBG_OPT_CONFIRM(left, right);
 308
 309                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));
 310
 311                                 env->num_eq += 1;
 312                         } else if (block_dominates(blk, cond_block)
 313                                         && is_Const(right)
 314                                         && get_irn_pinned(user) == op_pin_state_floats) {
 315                                 /*
 316                                  * left == Const and we found a movable user of left in a
 317                                  * dominator of the Cond block
 318                                  */
 319                                 foreach_out_edge_safe(user, user_edge) {
 320                                         ir_node *usr_of_usr = get_edge_src_irn(user_edge);
 321                                         int      npos       = get_edge_src_pos(user_edge);
 322                                         ir_node *user_blk   = get_effective_use_block(usr_of_usr, npos);
 323
 324                                         if (block_dominates(block, user_blk)) {
 325                                                 /*
 326                                                  * The user of the user is dominated by our true/false
 327                                                  * block. So, create a copy of user WITH the constant
 328                                                  * replacing its pos'th input.
 329                                                  *
 330                                                  * This is always good for unop's and might be good
 331                                                  * for binops.
 332                                                  *
 333                                                  * If user has other user in the false/true block, code
 334                                                  * placement will move it down.
 335                                                  * If there are users in cond block or upper, we create
 336                                                  * "redundant ops", because one will have a const op,
 337                                                  * the other no const ...
 338                                                  */
 339                                                 ir_node *new_op = exact_copy(user);
 340                                                 set_nodes_block(new_op, block);
 341                                                 set_irn_n(new_op, pos, right);
 342                                                 set_irn_n(usr_of_usr, npos, new_op);
 343                                                 env->num_eq += 1;
 344                                         }
 345                                 }
 346                         }
 347                 }
 348         } else { /* not ir_relation_equal cases */
 349                 ir_node *c = NULL;
 350
 351                 foreach_out_edge_safe(left, edge) {
 352                         ir_node *succ = get_edge_src_irn(edge);
 353                         int     pos   = get_edge_src_pos(edge);
 354                         ir_node *blk  = get_effective_use_block(succ, pos);
 355
 356                         if (block_dominates(block, blk)) {
 357                                 /*
 358                                  * Ok, we found a usage of left in a block
 359                                  * dominated by the branch block.
 360                                  * We can replace the input with a Confirm(left, pnc, right).
 361                                  */
 362                                 if (! c)
 363                                         c = new_r_Confirm(block, left, right, rel);
 364
 365                                 pos = get_edge_src_pos(edge);
 366                                 set_irn_n(succ, pos, c);
 367                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 368
 369                                 env->num_confirms += 1;
 370                         }
 371                 }
 372
 373                 if (! is_Const(right)) {
 374                         /* also construct inverse Confirms */
 375                         ir_node *rc = NULL;
 376
 377                         rel = get_inversed_relation(rel);
 378                         foreach_out_edge_safe(right, edge) {
 379                                 ir_node *succ = get_edge_src_irn(edge);
 380                                 int     pos;
 381                                 ir_node *blk;
 382
 383                                 if (succ == c)
 384                                         continue;
 385
 386                                 pos  = get_edge_src_pos(edge);
 387                                 blk  = get_effective_use_block(succ, pos);
 388
 389                                 if (block_dominates(block, blk)) {
 390                                         /*
 391                                          * Ok, we found a usage of right in a block
 392                                          * dominated by the branch block.
 393                                          * We can replace the input with a Confirm(right, rel^-1, left).
 394                                          */
 395                                         if (! rc)
 396                                                 rc = new_r_Confirm(block, right, left, rel);
 397
 398                                         pos = get_edge_src_pos(edge);
 399                                         set_irn_n(succ, pos, rc);
 400                                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, rc));
 401
 402                                         env->num_confirms += 1;
 403                                 }
 404                         }
 405                 }
 406         }
 407 }
 408
 409 /**
 410  * Pre-block-walker: Called for every block to insert Confirm nodes
 411  */
 412 static void insert_Confirm_in_block(ir_node *block, void *data)
 413 {
 414         env_t   *env = (env_t*) data;
 415         ir_node *cond;
 416         ir_node *proj;
 417
 418         /*
 419          * we can only handle blocks with only ONE control flow
 420          * predecessor yet.
 421          */
 422         if (get_Block_n_cfgpreds(block) != 1)
 423                 return;
 424
 425         proj = get_Block_cfgpred(block, 0);
 426         if (! is_Proj(proj))
 427                 return;
 428
 429         cond = get_Proj_pred(proj);
 430         if (is_Switch(cond)) {
 431                 long proj_nr = get_Proj_proj(proj);
 432                 handle_case(block, cond, proj_nr, env);
 433         } else if (is_Cond(cond)) {
 434                 ir_node *selector = get_Cond_selector(cond);
 435                 ir_relation rel;
 436
 437                 handle_modeb(block, selector, (pn_Cond) get_Proj_proj(proj), env);
 438
 439                 if (! is_Cmp(selector))
 440                         return;
 441
 442                 rel = get_Cmp_relation(selector);
 443
 444                 if (get_Proj_proj(proj) != pn_Cond_true) {
 445                         /* it's the false branch */
 446                         rel = get_negated_relation(rel);
 447                 }
 448                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, selector, rel));
 449
 450                 handle_if(block, selector, rel, env);
 451         }
 452 }
 453
 454 /**
 455  * Checks if a node is a non-null Confirm.
 456  */
 457 static int is_non_null_Confirm(const ir_node *ptr)
 458 {
 459         for (;;) {
 460                 if (! is_Confirm(ptr))
 461                         break;
 462                 if (get_Confirm_relation(ptr) == ir_relation_less_greater) {
 463                         ir_node *bound = get_Confirm_bound(ptr);
 464
 465                         if (is_Const(bound) && is_Const_null(bound))
 466                                 return 1;
 467                 }
 468                 ptr = get_Confirm_value(ptr);
 469         }
 470         /*
 471          * While a SymConst is not a Confirm, it is non-null
 472          * anyway. This helps to reduce the number of
 473          * constructed Confirms.
 474          */
 475         if (is_SymConst_addr_ent(ptr))
 476                 return 1;
 477         return 0;
 478 }
 479
 480 /**
 481  * The given pointer will be dereferenced, add non-null Confirms.
 482  *
 483  * @param ptr    a node representing an address
 484  * @param block  the block of the dereferencing instruction
 485  * @param env    environment
 486  */
 487 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env)
 488 {
 489         ir_node *c = NULL;
 490
 491         foreach_out_edge_safe(ptr, edge) {
 492                 ir_node *succ = get_edge_src_irn(edge);
 493                 int     pos;
 494                 ir_node *blk;
 495
 496
 497                 /* for now, we place a Confirm only in front of a Cmp */
 498                 if (! is_Cmp(succ))
 499                         continue;
 500
 501                 pos = get_edge_src_pos(edge);
 502                 blk = get_effective_use_block(succ, pos);
 503
 504                 if (block_dominates(block, blk)) {
 505                         /*
 506                          * Ok, we found a usage of ptr in a block
 507                          * dominated by the Load/Store block.
 508                          * We can replace the input with a Confirm(ptr, !=, NULL).
 509                          */
 510                         if (c == NULL) {
 511                                 ir_mode  *mode = get_irn_mode(ptr);
 512                                 ir_graph *irg  = get_irn_irg(block);
 513                                 c = new_r_Const(irg, get_mode_null(mode));
 514                                 c = new_r_Confirm(block, ptr, c, ir_relation_less_greater);
 515                         }
 516
 517                         set_irn_n(succ, pos, c);
 518                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 519
 520                         env->num_non_null += 1;
 521                         env->num_confirms += 1;
 522                 }
 523         }
 524 }
 525
 526 /**
 527  * Pre-walker: Called for every node to insert Confirm nodes
 528  */
 529 static void insert_Confirm(ir_node *node, void *data)
 530 {
 531         ir_node *ptr;
 532         env_t   *env = (env_t*) data;
 533
 534         switch (get_irn_opcode(node)) {
 535         case iro_Block:
 536                 insert_Confirm_in_block(node, env);
 537                 break;
 538         case iro_Load:
 539                 ptr = get_Load_ptr(node);
 540                 if (! is_non_null_Confirm(ptr))
 541                         insert_non_null(ptr, get_nodes_block(node), env);
 542                 break;
 543         case iro_Store:
 544                 ptr = get_Store_ptr(node);
 545                 if (! is_non_null_Confirm(ptr))
 546                         insert_non_null(ptr, get_nodes_block(node), env);
 547                 break;
 548         default:
 549                 break;
 550         }
 551 }
 552
 553 void construct_confirms(ir_graph *irg)
 554 {
 555         env_t env;
 556         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 557
 558         assure_irg_properties(irg,
 559               IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES
 560                 | IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
 561                 | IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
 562
 563         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 564                "Nodes must be placed to insert Confirms");
 565
 566         env.num_confirms = 0;
 567         env.num_consts   = 0;
 568         env.num_eq       = 0;
 569         env.num_non_null = 0;
 570
 571         if (get_opt_global_null_ptr_elimination()) {
 572                 /* do global NULL test elimination */
 573                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 574         } else {
 575                 /* now, visit all blocks and add Confirms where possible */
 576                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 577         }
 578
 579         DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
 580         DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
 581         DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
 582         DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));
 583
 584         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 585 }
 586
 587 ir_graph_pass_t *construct_confirms_pass(const char *name)
 588 {
 589         return def_graph_pass(name ? name : "confirm", construct_confirms);
 590 }
 591
 592 static void remove_confirm(ir_node *n, void *env)
 593 {
 594         ir_node *value;
 595
 596         (void) env;
 597         if (!is_Confirm(n))
 598                 return;
 599
 600         value = get_Confirm_value(n);
 601         exchange(n, value);
 602 }
 603
 604 void remove_confirms(ir_graph *irg)
 605 {
 606         irg_walk_graph(irg, NULL, remove_confirm, NULL);
 607         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 608 }
 609
 610 ir_graph_pass_t *remove_confirms_pass(const char *name)
 611 {
 612         return def_graph_pass(name ? name : "rem_confirm", remove_confirms);
 613 }