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

   1 /*
   2  * This file is part of libFirm.
   3  * Copyright (C) 2012 University of Karlsruhe.
   4  */
   5
   6 /**
   7  * @file
   8  * @brief    Construction of Confirm nodes
   9  * @author   Michael Beck
  10  * @date     6.2005
  11  */
  12 #include "config.h"
  13
  14 #include "irconsconfirm.h"
  15
  16 #include "irgraph_t.h"
  17 #include "irnode_t.h"
  18 #include "ircons_t.h"
  19 #include "irgmod.h"
  20 #include "iropt_dbg.h"
  21 #include "iredges_t.h"
  22 #include "irgwalk.h"
  23 #include "irprintf.h"
  24 #include "irgopt.h"
  25 #include "irpass.h"
  26 #include "irtools.h"
  27 #include "array_t.h"
  28 #include "debug.h"
  29 #include "error.h"
  30 #include "irflag.h"
  31
  32 /**
  33  * Walker environment.
  34  */
  35 typedef struct env_t {
  36         unsigned num_confirms;  /**< Number of inserted Confirm nodes. */
  37         unsigned num_consts;    /**< Number of constants placed. */
  38         unsigned num_eq;        /**< Number of equalities placed. */
  39         unsigned num_non_null;  /**< Number of non-null Confirms. */
  40 } env_t;
  41
  42 /** The debug handle. */
  43 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  44
  45 /**
  46  * Return the effective use block of a node and its predecessor on
  47  * position pos.
  48  *
  49  * @param node  the node
  50  * @param pos   the position of the used input
  51  *
  52  * This handles correctly Phi nodes.
  53  */
  54 static ir_node *get_effective_use_block(ir_node *node, int pos)
  55 {
  56         if (is_Phi(node)) {
  57                 /* the effective use of a Phi argument is in its predecessor block */
  58                 node = get_nodes_block(node);
  59                 return get_Block_cfgpred_block(node, pos);
  60         }
  61         return get_nodes_block(node);
  62 }
  63
  64 static ir_node *get_case_value(ir_node *switchn, long pn)
  65 {
  66         ir_graph              *irg       = get_irn_irg(switchn);
  67         const ir_switch_table *table     = get_Switch_table(switchn);
  68         size_t                 n_entries = ir_switch_table_get_n_entries(table);
  69         ir_tarval             *val       = NULL;
  70         size_t                 e;
  71         for (e = 0; e < n_entries; ++e) {
  72                 const ir_switch_table_entry *entry
  73                         = ir_switch_table_get_entry_const(table, e);
  74                 if (entry->pn != pn)
  75                         continue;
  76                 /* multiple matching entries gets too complicated for a single
  77                  * Confirm */
  78                 if (val != NULL)
  79                         return NULL;
  80                 /* case ranges are too complicated too */
  81                 if (entry->min != entry->max)
  82                         return NULL;
  83                 val = entry->min;
  84         }
  85         assert(val != NULL);
  86         return new_r_Const(irg, val);
  87 }
  88
  89 /**
  90  * Handle a CASE-branch.
  91  *
  92  * Branch labels are a simple case. We can replace the value
  93  * by a Const with the branch label.
  94  */
  95 static void handle_case(ir_node *block, ir_node *switchn, long pn, env_t *env)
  96 {
  97         ir_node *c = NULL;
  98         ir_node *selector = get_Switch_selector(switchn);
  99
 100         /* we can't do usefull things with the default label */
 101         if (pn == pn_Switch_default)
 102                 return;
 103
 104         foreach_out_edge_safe(selector, edge) {
 105                 ir_node *succ = get_edge_src_irn(edge);
 106                 int     pos   = get_edge_src_pos(edge);
 107                 ir_node *blk  = get_effective_use_block(succ, pos);
 108
 109                 if (block_dominates(block, blk)) {
 110                         /*
 111                          * Ok, we found a user of irn that is placed
 112                          * in a block dominated by the branch block.
 113                          * We can replace the input with the Constant
 114                          * branch label.
 115                          */
 116                         if (c == NULL)
 117                                 c = get_case_value(switchn, pn);
 118
 119                         set_irn_n(succ, pos, c);
 120                         DBG_OPT_CONFIRM_C(selector, c);
 121                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 122
 123                         env->num_consts += 1;
 124                 }
 125         }
 126 }
 127
 128 /**
 129  * Handle a mode_b input of Cond nodes.
 130  *
 131  * @param block     the block which is entered by the branch
 132  * @param selector  the mode_b node expressing the branch condition
 133  * @param pnc       the true/false condition branch
 134  * @param env       statistical environment
 135  */
 136 static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env)
 137 {
 138         ir_node *cond, *old, *other_blk = NULL, *con = NULL;
 139         ir_node *c_b = NULL, *c_o = NULL;
 140
 141         foreach_out_edge_safe(selector, edge) {
 142                 ir_node *user     = get_edge_src_irn(edge);
 143                 int     pos       = get_edge_src_pos(edge);
 144                 ir_node *user_blk = get_effective_use_block(user, pos);
 145
 146                 if (block_dominates(block, user_blk)) {
 147                         /*
 148                          * Ok, we found a usage of selector in a block
 149                          * dominated by the branch block.
 150                          * We can replace the input with true/false.
 151                          */
 152                         if (con == NULL) {
 153                                 ir_graph *irg = get_irn_irg(block);
 154                                 con = new_r_Const(irg, pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
 155                         }
 156                         old = get_irn_n(user, pos);
 157                         set_irn_n(user, pos, con);
 158                         DBG_OPT_CONFIRM_C(old, con);
 159
 160                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, con));
 161
 162                         env->num_consts += 1;
 163                 } else {
 164                         int i, n;
 165
 166                         /* get the other block */
 167                         if (other_blk == NULL) {
 168                                 /* we have already tested, that block has only ONE Cond predecessor */
 169                                 cond = get_Proj_pred(get_Block_cfgpred(block, 0));
 170                                 foreach_out_edge(cond, edge) {
 171                                         ir_node *proj = get_edge_src_irn(edge);
 172                                         if (get_Proj_proj(proj) == (long)pnc)
 173                                                 continue;
 174                                         edge = get_irn_out_edge_first(proj);
 175                                         other_blk = get_edge_src_irn(edge);
 176                                         break;
 177                                 }
 178                                 assert(other_blk);
 179
 180                                 /*
 181                                  * Note the special case here: if block is a then, there might be no else
 182                                  * block. In that case the other_block is the user_blk itself and pred_block
 183                                  * is the cond_block ...
 184                                  *
 185                                  * Best would be to introduce a block here, removing this critical edge.
 186                                  * For some reasons I cannot repair dominance here, so I have to remove
 187                                  * ALL critical edges...
 188                                  * FIXME: This should not be needed if we could repair dominance ...
 189                                  */
 190                         }
 191
 192                         n = get_Block_n_cfgpreds(user_blk);
 193
 194                         /*
 195                          * We have found a user in a non-dominated block:
 196                          * check, if all its block predecessors are dominated.
 197                          * If yes, place a Phi.
 198                          */
 199                         for (i = n - 1; i >= 0; --i) {
 200                                 ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 201
 202                                 if (!block_dominates(block, pred_blk) &&
 203                                     !block_dominates(other_blk, pred_blk)) {
 204                                         /* can't do anything */
 205                                         break;
 206                                 }
 207                         }
 208                         if (i < 0) {
 209                                 ir_node *phi, **in;
 210
 211                                 NEW_ARR_A(ir_node *, in, n);
 212                                 /* ok, ALL predecessors are either dominated by block OR other block */
 213                                 if (c_b == NULL) {
 214                                         ir_graph *irg    = get_irn_irg(block);
 215                                         ir_node *c_true  = new_r_Const(irg, tarval_b_true);
 216                                         ir_node *c_false = new_r_Const(irg, tarval_b_false);
 217                                         env->num_consts += 2;
 218                                         if (pnc == pn_Cond_true) {
 219                                                 c_b = c_true;
 220                                                 c_o = c_false;
 221                                         } else {
 222                                                 c_b = c_false;
 223                                                 c_o = c_true;
 224                                         }
 225                                 }
 226                                 for (i = n - 1; i >= 0; --i) {
 227                                         ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 228
 229                                         if (block_dominates(block, pred_blk))
 230                                                 in[i] = c_b;
 231                                         else
 232                                                 in[i] = c_o;
 233                                 }
 234                                 phi = new_r_Phi(user_blk, n, in, mode_b);
 235                                 set_irn_n(user, pos, phi);
 236                                 env->num_eq += 1;
 237                         }
 238                 }
 239         }
 240 }
 241
 242 /**
 243  * Handle an IF-branch.
 244  *
 245  * @param block   the block which is entered by the branch
 246  * @param cmp     the Cmp node expressing the branch condition
 247  * @param rel     the Compare relation for taking this branch
 248  * @param env     statistical environment
 249  */
 250 static void handle_if(ir_node *block, ir_node *cmp, ir_relation rel, env_t *env)
 251 {
 252         ir_node *left  = get_Cmp_left(cmp);
 253         ir_node *right = get_Cmp_right(cmp);
 254         ir_node *cond_block;
 255
 256         /* Beware of Bads */
 257         if (is_Bad(left) || is_Bad(right))
 258                 return;
 259
 260         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 261            These are removed anyway */
 262         if (is_Const(left) && is_Const(right))
 263                 return;
 264
 265         /* try to place the constant on the right side for a Confirm */
 266         if (is_Const(left) || is_SymConst(left)) {
 267                 ir_node *t = left;
 268
 269                 left  = right;
 270                 right = t;
 271
 272                 rel = get_inversed_relation(rel);
 273         }
 274
 275         /*
 276          * First case: both values are identical.
 277          * replace the left one by the right (potentially const) one.
 278          */
 279         if (rel == ir_relation_equal) {
 280                 cond_block = get_Block_cfgpred_block(block, 0);
 281                 foreach_out_edge_safe(left, edge) {
 282                         ir_node *user = get_edge_src_irn(edge);
 283                         int     pos   = get_edge_src_pos(edge);
 284                         ir_node *blk  = get_effective_use_block(user, pos);
 285
 286                         if (block_dominates(block, blk)) {
 287                                 /*
 288                                  * Ok, we found a usage of left in a block
 289                                  * dominated by the branch block.
 290                                  * We can replace the input with right.
 291                                  */
 292                                 set_irn_n(user, pos, right);
 293                                 DBG_OPT_CONFIRM(left, right);
 294
 295                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));
 296
 297                                 env->num_eq += 1;
 298                         } else if (block_dominates(blk, cond_block)
 299                                         && is_Const(right)
 300                                         && get_irn_pinned(user) == op_pin_state_floats) {
 301                                 /*
 302                                  * left == Const and we found a movable user of left in a
 303                                  * dominator of the Cond block
 304                                  */
 305                                 foreach_out_edge_safe(user, user_edge) {
 306                                         ir_node *usr_of_usr = get_edge_src_irn(user_edge);
 307                                         int      npos       = get_edge_src_pos(user_edge);
 308                                         ir_node *user_blk   = get_effective_use_block(usr_of_usr, npos);
 309
 310                                         if (block_dominates(block, user_blk)) {
 311                                                 /*
 312                                                  * The user of the user is dominated by our true/false
 313                                                  * block. So, create a copy of user WITH the constant
 314                                                  * replacing its pos'th input.
 315                                                  *
 316                                                  * This is always good for unop's and might be good
 317                                                  * for binops.
 318                                                  *
 319                                                  * If user has other user in the false/true block, code
 320                                                  * placement will move it down.
 321                                                  * If there are users in cond block or upper, we create
 322                                                  * "redundant ops", because one will have a const op,
 323                                                  * the other no const ...
 324                                                  */
 325                                                 ir_node *new_op = exact_copy(user);
 326                                                 set_nodes_block(new_op, block);
 327                                                 set_irn_n(new_op, pos, right);
 328                                                 set_irn_n(usr_of_usr, npos, new_op);
 329                                                 env->num_eq += 1;
 330                                         }
 331                                 }
 332                         }
 333                 }
 334         } else { /* not ir_relation_equal cases */
 335                 ir_node *c = NULL;
 336
 337                 foreach_out_edge_safe(left, edge) {
 338                         ir_node *succ = get_edge_src_irn(edge);
 339                         int     pos   = get_edge_src_pos(edge);
 340                         ir_node *blk  = get_effective_use_block(succ, pos);
 341
 342                         if (block_dominates(block, blk)) {
 343                                 /*
 344                                  * Ok, we found a usage of left in a block
 345                                  * dominated by the branch block.
 346                                  * We can replace the input with a Confirm(left, pnc, right).
 347                                  */
 348                                 if (! c)
 349                                         c = new_r_Confirm(block, left, right, rel);
 350
 351                                 pos = get_edge_src_pos(edge);
 352                                 set_irn_n(succ, pos, c);
 353                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 354
 355                                 env->num_confirms += 1;
 356                         }
 357                 }
 358
 359                 if (! is_Const(right)) {
 360                         /* also construct inverse Confirms */
 361                         ir_node *rc = NULL;
 362
 363                         rel = get_inversed_relation(rel);
 364                         foreach_out_edge_safe(right, edge) {
 365                                 ir_node *succ = get_edge_src_irn(edge);
 366                                 int     pos;
 367                                 ir_node *blk;
 368
 369                                 if (succ == c)
 370                                         continue;
 371
 372                                 pos  = get_edge_src_pos(edge);
 373                                 blk  = get_effective_use_block(succ, pos);
 374
 375                                 if (block_dominates(block, blk)) {
 376                                         /*
 377                                          * Ok, we found a usage of right in a block
 378                                          * dominated by the branch block.
 379                                          * We can replace the input with a Confirm(right, rel^-1, left).
 380                                          */
 381                                         if (! rc)
 382                                                 rc = new_r_Confirm(block, right, left, rel);
 383
 384                                         pos = get_edge_src_pos(edge);
 385                                         set_irn_n(succ, pos, rc);
 386                                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, rc));
 387
 388                                         env->num_confirms += 1;
 389                                 }
 390                         }
 391                 }
 392         }
 393 }
 394
 395 /**
 396  * Pre-block-walker: Called for every block to insert Confirm nodes
 397  */
 398 static void insert_Confirm_in_block(ir_node *block, void *data)
 399 {
 400         env_t   *env = (env_t*) data;
 401         ir_node *cond;
 402         ir_node *proj;
 403
 404         /*
 405          * we can only handle blocks with only ONE control flow
 406          * predecessor yet.
 407          */
 408         if (get_Block_n_cfgpreds(block) != 1)
 409                 return;
 410
 411         proj = get_Block_cfgpred(block, 0);
 412         if (! is_Proj(proj))
 413                 return;
 414
 415         cond = get_Proj_pred(proj);
 416         if (is_Switch(cond)) {
 417                 long proj_nr = get_Proj_proj(proj);
 418                 handle_case(block, cond, proj_nr, env);
 419         } else if (is_Cond(cond)) {
 420                 ir_node *selector = get_Cond_selector(cond);
 421                 ir_relation rel;
 422
 423                 handle_modeb(block, selector, (pn_Cond) get_Proj_proj(proj), env);
 424
 425                 if (! is_Cmp(selector))
 426                         return;
 427
 428                 rel = get_Cmp_relation(selector);
 429
 430                 if (get_Proj_proj(proj) != pn_Cond_true) {
 431                         /* it's the false branch */
 432                         rel = get_negated_relation(rel);
 433                 }
 434                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, selector, rel));
 435
 436                 handle_if(block, selector, rel, env);
 437         }
 438 }
 439
 440 /**
 441  * Checks if a node is a non-null Confirm.
 442  */
 443 static int is_non_null_Confirm(const ir_node *ptr)
 444 {
 445         for (;;) {
 446                 if (! is_Confirm(ptr))
 447                         break;
 448                 if (get_Confirm_relation(ptr) == ir_relation_less_greater) {
 449                         ir_node *bound = get_Confirm_bound(ptr);
 450
 451                         if (is_Const(bound) && is_Const_null(bound))
 452                                 return 1;
 453                 }
 454                 ptr = get_Confirm_value(ptr);
 455         }
 456         /*
 457          * While a SymConst is not a Confirm, it is non-null
 458          * anyway. This helps to reduce the number of
 459          * constructed Confirms.
 460          */
 461         if (is_SymConst_addr_ent(ptr))
 462                 return 1;
 463         return 0;
 464 }
 465
 466 /**
 467  * The given pointer will be dereferenced, add non-null Confirms.
 468  *
 469  * @param ptr    a node representing an address
 470  * @param block  the block of the dereferencing instruction
 471  * @param env    environment
 472  */
 473 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env)
 474 {
 475         ir_node *c = NULL;
 476
 477         foreach_out_edge_safe(ptr, edge) {
 478                 ir_node *succ = get_edge_src_irn(edge);
 479                 int     pos;
 480                 ir_node *blk;
 481
 482
 483                 /* for now, we place a Confirm only in front of a Cmp */
 484                 if (! is_Cmp(succ))
 485                         continue;
 486
 487                 pos = get_edge_src_pos(edge);
 488                 blk = get_effective_use_block(succ, pos);
 489
 490                 if (block_dominates(block, blk)) {
 491                         /*
 492                          * Ok, we found a usage of ptr in a block
 493                          * dominated by the Load/Store block.
 494                          * We can replace the input with a Confirm(ptr, !=, NULL).
 495                          */
 496                         if (c == NULL) {
 497                                 ir_mode  *mode = get_irn_mode(ptr);
 498                                 ir_graph *irg  = get_irn_irg(block);
 499                                 c = new_r_Const(irg, get_mode_null(mode));
 500                                 c = new_r_Confirm(block, ptr, c, ir_relation_less_greater);
 501                         }
 502
 503                         set_irn_n(succ, pos, c);
 504                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 505
 506                         env->num_non_null += 1;
 507                         env->num_confirms += 1;
 508                 }
 509         }
 510 }
 511
 512 /**
 513  * Pre-walker: Called for every node to insert Confirm nodes
 514  */
 515 static void insert_Confirm(ir_node *node, void *data)
 516 {
 517         ir_node *ptr;
 518         env_t   *env = (env_t*) data;
 519
 520         switch (get_irn_opcode(node)) {
 521         case iro_Block:
 522                 insert_Confirm_in_block(node, env);
 523                 break;
 524         case iro_Load:
 525                 ptr = get_Load_ptr(node);
 526                 if (! is_non_null_Confirm(ptr))
 527                         insert_non_null(ptr, get_nodes_block(node), env);
 528                 break;
 529         case iro_Store:
 530                 ptr = get_Store_ptr(node);
 531                 if (! is_non_null_Confirm(ptr))
 532                         insert_non_null(ptr, get_nodes_block(node), env);
 533                 break;
 534         default:
 535                 break;
 536         }
 537 }
 538
 539 void construct_confirms(ir_graph *irg)
 540 {
 541         env_t env;
 542         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 543
 544         assure_irg_properties(irg,
 545               IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES
 546                 | IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
 547                 | IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
 548
 549         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 550                "Nodes must be placed to insert Confirms");
 551
 552         env.num_confirms = 0;
 553         env.num_consts   = 0;
 554         env.num_eq       = 0;
 555         env.num_non_null = 0;
 556
 557         if (get_opt_global_null_ptr_elimination()) {
 558                 /* do global NULL test elimination */
 559                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 560         } else {
 561                 /* now, visit all blocks and add Confirms where possible */
 562                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 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         DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));
 569
 570         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 571 }
 572
 573 ir_graph_pass_t *construct_confirms_pass(const char *name)
 574 {
 575         return def_graph_pass(name ? name : "confirm", construct_confirms);
 576 }
 577
 578 static void remove_confirm(ir_node *n, void *env)
 579 {
 580         ir_node *value;
 581
 582         (void) env;
 583         if (!is_Confirm(n))
 584                 return;
 585
 586         value = get_Confirm_value(n);
 587         exchange(n, value);
 588 }
 589
 590 void remove_confirms(ir_graph *irg)
 591 {
 592         irg_walk_graph(irg, NULL, remove_confirm, NULL);
 593         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 594 }
 595
 596 ir_graph_pass_t *remove_confirms_pass(const char *name)
 597 {
 598         return def_graph_pass(name ? name : "rem_confirm", remove_confirms);
 599 }