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