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         ir_op *op;
 270
 271         /* Beware of Bads */
 272         if (is_Bad(left) || is_Bad(right))
 273                 return;
 274
 275         op = get_irn_op(left);
 276
 277         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 278            These are removed anyway */
 279         if (op == op_Const && is_Const(right))
 280                 return;
 281
 282         /* try to place the constant on the right side for a Confirm */
 283         if (op == op_Const || op == op_SymConst) {
 284                 ir_node *t = left;
 285
 286                 left  = right;
 287                 right = t;
 288
 289                 rel = get_inversed_relation(rel);
 290         }
 291
 292         /*
 293          * First case: both values are identical.
 294          * replace the left one by the right (potentially const) one.
 295          */
 296         if (rel == ir_relation_equal) {
 297                 cond_block = get_Block_cfgpred_block(block, 0);
 298                 foreach_out_edge_safe(left, edge) {
 299                         ir_node *user = get_edge_src_irn(edge);
 300                         int     pos   = get_edge_src_pos(edge);
 301                         ir_node *blk  = get_effective_use_block(user, pos);
 302
 303                         if (block_dominates(block, blk)) {
 304                                 /*
 305                                  * Ok, we found a usage of left in a block
 306                                  * dominated by the branch block.
 307                                  * We can replace the input with right.
 308                                  */
 309                                 set_irn_n(user, pos, right);
 310                                 DBG_OPT_CONFIRM(left, right);
 311
 312                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));
 313
 314                                 env->num_eq += 1;
 315                         } else if (block_dominates(blk, cond_block)
 316                                         && is_Const(right)
 317                                         && get_irn_pinned(user) == op_pin_state_floats) {
 318                                 /*
 319                                  * left == Const and we found a movable user of left in a
 320                                  * dominator of the Cond block
 321                                  */
 322                                 foreach_out_edge_safe(user, user_edge) {
 323                                         ir_node *usr_of_usr = get_edge_src_irn(user_edge);
 324                                         int      npos       = get_edge_src_pos(user_edge);
 325                                         ir_node *user_blk   = get_effective_use_block(usr_of_usr, npos);
 326
 327                                         if (block_dominates(block, user_blk)) {
 328                                                 /*
 329                                                  * The user of the user is dominated by our true/false
 330                                                  * block. So, create a copy of user WITH the constant
 331                                                  * replacing its pos'th input.
 332                                                  *
 333                                                  * This is always good for unop's and might be good
 334                                                  * for binops.
 335                                                  *
 336                                                  * If user has other user in the false/true block, code
 337                                                  * placement will move it down.
 338                                                  * If there are users in cond block or upper, we create
 339                                                  * "redundant ops", because one will have a const op,
 340                                                  * the other no const ...
 341                                                  */
 342                                                 ir_node *new_op = exact_copy(user);
 343                                                 set_nodes_block(new_op, block);
 344                                                 set_irn_n(new_op, pos, right);
 345                                                 set_irn_n(usr_of_usr, npos, new_op);
 346                                                 env->num_eq += 1;
 347                                         }
 348                                 }
 349                         }
 350                 }
 351         } else { /* not ir_relation_equal cases */
 352                 ir_node *c = NULL;
 353
 354                 foreach_out_edge_safe(left, edge) {
 355                         ir_node *succ = get_edge_src_irn(edge);
 356                         int     pos   = get_edge_src_pos(edge);
 357                         ir_node *blk  = get_effective_use_block(succ, pos);
 358
 359                         if (block_dominates(block, blk)) {
 360                                 /*
 361                                  * Ok, we found a usage of left in a block
 362                                  * dominated by the branch block.
 363                                  * We can replace the input with a Confirm(left, pnc, right).
 364                                  */
 365                                 if (! c)
 366                                         c = new_r_Confirm(block, left, right, rel);
 367
 368                                 pos = get_edge_src_pos(edge);
 369                                 set_irn_n(succ, pos, c);
 370                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 371
 372                                 env->num_confirms += 1;
 373                         }
 374                 }
 375
 376                 if (! is_Const(right)) {
 377                         /* also construct inverse Confirms */
 378                         ir_node *rc = NULL;
 379
 380                         rel = get_inversed_relation(rel);
 381                         foreach_out_edge_safe(right, edge) {
 382                                 ir_node *succ = get_edge_src_irn(edge);
 383                                 int     pos;
 384                                 ir_node *blk;
 385
 386                                 if (succ == c)
 387                                         continue;
 388
 389                                 pos  = get_edge_src_pos(edge);
 390                                 blk  = get_effective_use_block(succ, pos);
 391
 392                                 if (block_dominates(block, blk)) {
 393                                         /*
 394                                          * Ok, we found a usage of right in a block
 395                                          * dominated by the branch block.
 396                                          * We can replace the input with a Confirm(right, rel^-1, left).
 397                                          */
 398                                         if (! rc)
 399                                                 rc = new_r_Confirm(block, right, left, rel);
 400
 401                                         pos = get_edge_src_pos(edge);
 402                                         set_irn_n(succ, pos, rc);
 403                                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, rc));
 404
 405                                         env->num_confirms += 1;
 406                                 }
 407                         }
 408                 }
 409         }
 410 }
 411
 412 /**
 413  * Pre-block-walker: Called for every block to insert Confirm nodes
 414  */
 415 static void insert_Confirm_in_block(ir_node *block, void *data)
 416 {
 417         env_t   *env = (env_t*) data;
 418         ir_node *cond;
 419         ir_node *proj;
 420
 421         /*
 422          * we can only handle blocks with only ONE control flow
 423          * predecessor yet.
 424          */
 425         if (get_Block_n_cfgpreds(block) != 1)
 426                 return;
 427
 428         proj = get_Block_cfgpred(block, 0);
 429         if (! is_Proj(proj))
 430                 return;
 431
 432         cond = get_Proj_pred(proj);
 433         if (is_Switch(cond)) {
 434                 long proj_nr = get_Proj_proj(proj);
 435                 handle_case(block, cond, proj_nr, env);
 436         } else if (is_Cond(cond)) {
 437                 ir_node *selector = get_Cond_selector(cond);
 438                 ir_relation rel;
 439
 440                 handle_modeb(block, selector, (pn_Cond) get_Proj_proj(proj), env);
 441
 442                 if (! is_Cmp(selector))
 443                         return;
 444
 445                 rel = get_Cmp_relation(selector);
 446
 447                 if (get_Proj_proj(proj) != pn_Cond_true) {
 448                         /* it's the false branch */
 449                         rel = get_negated_relation(rel);
 450                 }
 451                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, selector, rel));
 452
 453                 handle_if(block, selector, rel, env);
 454         }
 455 }
 456
 457 /**
 458  * Checks if a node is a non-null Confirm.
 459  */
 460 static int is_non_null_Confirm(const ir_node *ptr)
 461 {
 462         for (;;) {
 463                 if (! is_Confirm(ptr))
 464                         break;
 465                 if (get_Confirm_relation(ptr) == ir_relation_less_greater) {
 466                         ir_node *bound = get_Confirm_bound(ptr);
 467
 468                         if (is_Const(bound) && is_Const_null(bound))
 469                                 return 1;
 470                 }
 471                 ptr = get_Confirm_value(ptr);
 472         }
 473         /*
 474          * While a SymConst is not a Confirm, it is non-null
 475          * anyway. This helps to reduce the number of
 476          * constructed Confirms.
 477          */
 478         if (is_SymConst_addr_ent(ptr))
 479                 return 1;
 480         return 0;
 481 }
 482
 483 /**
 484  * The given pointer will be dereferenced, add non-null Confirms.
 485  *
 486  * @param ptr    a node representing an address
 487  * @param block  the block of the dereferencing instruction
 488  * @param env    environment
 489  */
 490 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env)
 491 {
 492         ir_node *c = NULL;
 493
 494         foreach_out_edge_safe(ptr, edge) {
 495                 ir_node *succ = get_edge_src_irn(edge);
 496                 int     pos;
 497                 ir_node *blk;
 498
 499
 500                 /* for now, we place a Confirm only in front of a Cmp */
 501                 if (! is_Cmp(succ))
 502                         continue;
 503
 504                 pos = get_edge_src_pos(edge);
 505                 blk = get_effective_use_block(succ, pos);
 506
 507                 if (block_dominates(block, blk)) {
 508                         /*
 509                          * Ok, we found a usage of ptr in a block
 510                          * dominated by the Load/Store block.
 511                          * We can replace the input with a Confirm(ptr, !=, NULL).
 512                          */
 513                         if (c == NULL) {
 514                                 ir_mode  *mode = get_irn_mode(ptr);
 515                                 ir_graph *irg  = get_irn_irg(block);
 516                                 c = new_r_Const(irg, get_mode_null(mode));
 517                                 c = new_r_Confirm(block, ptr, c, ir_relation_less_greater);
 518                         }
 519
 520                         set_irn_n(succ, pos, c);
 521                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 522
 523                         env->num_non_null += 1;
 524                         env->num_confirms += 1;
 525                 }
 526         }
 527 }
 528
 529 /**
 530  * Pre-walker: Called for every node to insert Confirm nodes
 531  */
 532 static void insert_Confirm(ir_node *node, void *data)
 533 {
 534         ir_node *ptr;
 535         env_t   *env = (env_t*) data;
 536
 537         switch (get_irn_opcode(node)) {
 538         case iro_Block:
 539                 insert_Confirm_in_block(node, env);
 540                 break;
 541         case iro_Load:
 542                 ptr = get_Load_ptr(node);
 543                 if (! is_non_null_Confirm(ptr))
 544                         insert_non_null(ptr, get_nodes_block(node), env);
 545                 break;
 546         case iro_Store:
 547                 ptr = get_Store_ptr(node);
 548                 if (! is_non_null_Confirm(ptr))
 549                         insert_non_null(ptr, get_nodes_block(node), env);
 550                 break;
 551         default:
 552                 break;
 553         }
 554 }
 555
 556 void construct_confirms(ir_graph *irg)
 557 {
 558         env_t env;
 559         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 560
 561         assure_irg_properties(irg,
 562               IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES
 563                 | IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
 564                 | IR_GRAPH_PROPERTY_NO_CRITICAL_EDGES);
 565
 566         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 567                "Nodes must be placed to insert Confirms");
 568
 569         env.num_confirms = 0;
 570         env.num_consts   = 0;
 571         env.num_eq       = 0;
 572         env.num_non_null = 0;
 573
 574         if (get_opt_global_null_ptr_elimination()) {
 575                 /* do global NULL test elimination */
 576                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 577         } else {
 578                 /* now, visit all blocks and add Confirms where possible */
 579                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 580         }
 581
 582         DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
 583         DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
 584         DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
 585         DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));
 586
 587         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 588 }
 589
 590 ir_graph_pass_t *construct_confirms_pass(const char *name)
 591 {
 592         return def_graph_pass(name ? name : "confirm", construct_confirms);
 593 }
 594
 595 static void remove_confirm(ir_node *n, void *env)
 596 {
 597         ir_node *value;
 598
 599         (void) env;
 600         if (!is_Confirm(n))
 601                 return;
 602
 603         value = get_Confirm_value(n);
 604         exchange(n, value);
 605 }
 606
 607 void remove_confirms(ir_graph *irg)
 608 {
 609         irg_walk_graph(irg, NULL, remove_confirm, NULL);
 610         confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_CONTROL_FLOW);
 611 }
 612
 613 ir_graph_pass_t *remove_confirms_pass(const char *name)
 614 {
 615         return def_graph_pass(name ? name : "rem_confirm", remove_confirms);
 616 }