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 #include "opt_manage.h"
  46
  47 /**
  48  * Walker environment.
  49  */
  50 typedef struct env_t {
  51         unsigned num_confirms;  /**< Number of inserted Confirm nodes. */
  52         unsigned num_consts;    /**< Number of constants placed. */
  53         unsigned num_eq;        /**< Number of equalities placed. */
  54         unsigned num_non_null;  /**< Number of non-null Confirms. */
  55 } env_t;
  56
  57 /** The debug handle. */
  58 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  59
  60 /**
  61  * Return the effective use block of a node and its predecessor on
  62  * position pos.
  63  *
  64  * @param node  the node
  65  * @param pos   the position of the used input
  66  *
  67  * This handles correctly Phi nodes.
  68  */
  69 static ir_node *get_effective_use_block(ir_node *node, int pos)
  70 {
  71         if (is_Phi(node)) {
  72                 /* the effective use of a Phi argument is in its predecessor block */
  73                 node = get_nodes_block(node);
  74                 return get_Block_cfgpred_block(node, pos);
  75         }
  76         return get_nodes_block(node);
  77 }
  78
  79 static ir_node *get_case_value(ir_node *switchn, long pn)
  80 {
  81         ir_graph              *irg       = get_irn_irg(switchn);
  82         const ir_switch_table *table     = get_Switch_table(switchn);
  83         size_t                 n_entries = ir_switch_table_get_n_entries(table);
  84         ir_tarval             *val       = NULL;
  85         size_t                 e;
  86         for (e = 0; e < n_entries; ++e) {
  87                 const ir_switch_table_entry *entry
  88                         = ir_switch_table_get_entry_const(table, e);
  89                 if (entry->pn != pn)
  90                         continue;
  91                 /* multiple matching entries gets too complicated for a single
  92                  * Confirm */
  93                 if (val != NULL)
  94                         return NULL;
  95                 /* case ranges are too complicated too */
  96                 if (entry->min != entry->max)
  97                         return NULL;
  98                 val = entry->min;
  99         }
 100         assert(val != NULL);
 101         return new_r_Const(irg, val);
 102 }
 103
 104 /**
 105  * Handle a CASE-branch.
 106  *
 107  * Branch labels are a simple case. We can replace the value
 108  * by a Const with the branch label.
 109  */
 110 static void handle_case(ir_node *block, ir_node *switchn, long pn, env_t *env)
 111 {
 112         ir_node         *c = NULL;
 113         ir_node         *selector = get_Switch_selector(switchn);
 114         const ir_edge_t *edge;
 115         const ir_edge_t *next;
 116
 117         /* we can't do usefull things with the default label */
 118         if (pn == pn_Switch_default)
 119                 return;
 120
 121         foreach_out_edge_safe(selector, edge, next) {
 122                 ir_node *succ = get_edge_src_irn(edge);
 123                 int     pos   = get_edge_src_pos(edge);
 124                 ir_node *blk  = get_effective_use_block(succ, pos);
 125
 126                 if (block_dominates(block, blk)) {
 127                         /*
 128                          * Ok, we found a user of irn that is placed
 129                          * in a block dominated by the branch block.
 130                          * We can replace the input with the Constant
 131                          * branch label.
 132                          */
 133                         if (c == NULL)
 134                                 c = get_case_value(switchn, pn);
 135
 136                         set_irn_n(succ, pos, c);
 137                         DBG_OPT_CONFIRM_C(selector, c);
 138                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 139
 140                         env->num_consts += 1;
 141                 }
 142         }
 143 }
 144
 145 /**
 146  * Handle a mode_b input of Cond nodes.
 147  *
 148  * @param block     the block which is entered by the branch
 149  * @param selector  the mode_b node expressing the branch condition
 150  * @param pnc       the true/false condition branch
 151  * @param env       statistical environment
 152  */
 153 static void handle_modeb(ir_node *block, ir_node *selector, pn_Cond pnc, env_t *env)
 154 {
 155         ir_node *cond, *old, *other_blk = NULL, *con = NULL;
 156         ir_node *c_b = NULL, *c_o = NULL;
 157         const ir_edge_t *edge, *next;
 158
 159         for (edge = get_irn_out_edge_first(selector); edge; edge = next) {
 160                 ir_node *user     = get_edge_src_irn(edge);
 161                 int     pos       = get_edge_src_pos(edge);
 162                 ir_node *user_blk = get_effective_use_block(user, pos);
 163
 164                 next = get_irn_out_edge_next(selector, edge);
 165                 if (block_dominates(block, user_blk)) {
 166                         /*
 167                          * Ok, we found a usage of selector in a block
 168                          * dominated by the branch block.
 169                          * We can replace the input with true/false.
 170                          */
 171                         if (con == NULL) {
 172                                 ir_graph *irg = get_irn_irg(block);
 173                                 con = new_r_Const(irg, pnc == pn_Cond_true ? tarval_b_true : tarval_b_false);
 174                         }
 175                         old = get_irn_n(user, pos);
 176                         set_irn_n(user, pos, con);
 177                         DBG_OPT_CONFIRM_C(old, con);
 178
 179                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, con));
 180
 181                         env->num_consts += 1;
 182                 } else {
 183                         int i, n;
 184
 185                         /* get the other block */
 186                         if (other_blk == NULL) {
 187                                 /* we have already tested, that block has only ONE Cond predecessor */
 188                                 cond = get_Proj_pred(get_Block_cfgpred(block, 0));
 189                                 foreach_out_edge(cond, edge) {
 190                                         ir_node *proj = get_edge_src_irn(edge);
 191                                         if (get_Proj_proj(proj) == (long)pnc)
 192                                                 continue;
 193                                         edge = get_irn_out_edge_first(proj);
 194                                         other_blk = get_edge_src_irn(edge);
 195                                         break;
 196                                 }
 197                                 assert(other_blk);
 198
 199                                 /*
 200                                  * Note the special case here: if block is a then, there might be no else
 201                                  * block. In that case the other_block is the user_blk itself and pred_block
 202                                  * is the cond_block ...
 203                                  *
 204                                  * Best would be to introduce a block here, removing this critical edge.
 205                                  * For some reasons I cannot repair dominance here, so I have to remove
 206                                  * ALL critical edges...
 207                                  * FIXME: This should not be needed if we could repair dominance ...
 208                                  */
 209                         }
 210
 211                         n = get_Block_n_cfgpreds(user_blk);
 212
 213                         /*
 214                          * We have found a user in a non-dominated block:
 215                          * check, if all its block predecessors are dominated.
 216                          * If yes, place a Phi.
 217                          */
 218                         for (i = n - 1; i >= 0; --i) {
 219                                 ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 220
 221                                 if (!block_dominates(block, pred_blk) &&
 222                                     !block_dominates(other_blk, pred_blk)) {
 223                                         /* can't do anything */
 224                                         break;
 225                                 }
 226                         }
 227                         if (i < 0) {
 228                                 ir_node *phi, **in;
 229
 230                                 NEW_ARR_A(ir_node *, in, n);
 231                                 /* ok, ALL predecessors are either dominated by block OR other block */
 232                                 if (c_b == NULL) {
 233                                         ir_graph *irg    = get_irn_irg(block);
 234                                         ir_node *c_true  = new_r_Const(irg, tarval_b_true);
 235                                         ir_node *c_false = new_r_Const(irg, tarval_b_false);
 236                                         env->num_consts += 2;
 237                                         if (pnc == pn_Cond_true) {
 238                                                 c_b = c_true;
 239                                                 c_o = c_false;
 240                                         } else {
 241                                                 c_b = c_false;
 242                                                 c_o = c_true;
 243                                         }
 244                                 }
 245                                 for (i = n - 1; i >= 0; --i) {
 246                                         ir_node *pred_blk = get_Block_cfgpred_block(user_blk, i);
 247
 248                                         if (block_dominates(block, pred_blk))
 249                                                 in[i] = c_b;
 250                                         else
 251                                                 in[i] = c_o;
 252                                 }
 253                                 phi = new_r_Phi(user_blk, n, in, mode_b);
 254                                 set_irn_n(user, pos, phi);
 255                                 env->num_eq += 1;
 256                         }
 257                 }
 258         }
 259 }
 260
 261 /**
 262  * Handle an IF-branch.
 263  *
 264  * @param block   the block which is entered by the branch
 265  * @param cmp     the Cmp node expressing the branch condition
 266  * @param rel     the Compare relation for taking this branch
 267  * @param env     statistical environment
 268  */
 269 static void handle_if(ir_node *block, ir_node *cmp, ir_relation rel, env_t *env)
 270 {
 271         ir_node *left  = get_Cmp_left(cmp);
 272         ir_node *right = get_Cmp_right(cmp);
 273         ir_node *cond_block;
 274         ir_op *op;
 275         const ir_edge_t *edge, *next;
 276
 277         /* Beware of Bads */
 278         if (is_Bad(left) || is_Bad(right))
 279                 return;
 280
 281         op = get_irn_op(left);
 282
 283         /* Do not create Confirm nodes for Cmp(Const, Const) constructs.
 284            These are removed anyway */
 285         if (op == op_Const && is_Const(right))
 286                 return;
 287
 288         /* try to place the constant on the right side for a Confirm */
 289         if (op == op_Const || op == op_SymConst) {
 290                 ir_node *t = left;
 291
 292                 left  = right;
 293                 right = t;
 294
 295                 rel = get_inversed_relation(rel);
 296         }
 297
 298         /*
 299          * First case: both values are identical.
 300          * replace the left one by the right (potentially const) one.
 301          */
 302         if (rel == ir_relation_equal) {
 303                 cond_block = get_Block_cfgpred_block(block, 0);
 304                 for (edge = get_irn_out_edge_first(left); edge; edge = next) {
 305                         ir_node *user = get_edge_src_irn(edge);
 306                         int     pos   = get_edge_src_pos(edge);
 307                         ir_node *blk  = get_effective_use_block(user, pos);
 308
 309                         next = get_irn_out_edge_next(left, edge);
 310                         if (block_dominates(block, blk)) {
 311                                 /*
 312                                  * Ok, we found a usage of left in a block
 313                                  * dominated by the branch block.
 314                                  * We can replace the input with right.
 315                                  */
 316                                 set_irn_n(user, pos, right);
 317                                 DBG_OPT_CONFIRM(left, right);
 318
 319                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, user, right));
 320
 321                                 env->num_eq += 1;
 322                         } else if (block_dominates(blk, cond_block)
 323                                         && is_Const(right)
 324                                         && get_irn_pinned(user) == op_pin_state_floats) {
 325                                 /*
 326                                  * left == Const and we found a movable user of left in a
 327                                  * dominator of the Cond block
 328                                  */
 329                                 const ir_edge_t *user_edge;
 330                                 const ir_edge_t *user_next;
 331                                 foreach_out_edge_safe(user, user_edge, user_next) {
 332                                         ir_node *usr_of_usr = get_edge_src_irn(user_edge);
 333                                         int      npos       = get_edge_src_pos(user_edge);
 334                                         ir_node *user_blk   = get_effective_use_block(usr_of_usr, npos);
 335
 336                                         if (block_dominates(block, user_blk)) {
 337                                                 /*
 338                                                  * The user of the user is dominated by our true/false
 339                                                  * block. So, create a copy of user WITH the constant
 340                                                  * replacing its pos'th input.
 341                                                  *
 342                                                  * This is always good for unop's and might be good
 343                                                  * for binops.
 344                                                  *
 345                                                  * If user has other user in the false/true block, code
 346                                                  * placement will move it down.
 347                                                  * If there are users in cond block or upper, we create
 348                                                  * "redundant ops", because one will have a const op,
 349                                                  * the other no const ...
 350                                                  */
 351                                                 ir_node *new_op = exact_copy(user);
 352                                                 set_nodes_block(new_op, block);
 353                                                 set_irn_n(new_op, pos, right);
 354                                                 set_irn_n(usr_of_usr, npos, new_op);
 355                                                 env->num_eq += 1;
 356                                         }
 357                                 }
 358                         }
 359                 }
 360         } else { /* not ir_relation_equal cases */
 361                 ir_node *c = NULL;
 362
 363                 foreach_out_edge_safe(left, edge, next) {
 364                         ir_node *succ = get_edge_src_irn(edge);
 365                         int     pos   = get_edge_src_pos(edge);
 366                         ir_node *blk  = get_effective_use_block(succ, pos);
 367
 368                         if (block_dominates(block, blk)) {
 369                                 /*
 370                                  * Ok, we found a usage of left in a block
 371                                  * dominated by the branch block.
 372                                  * We can replace the input with a Confirm(left, pnc, right).
 373                                  */
 374                                 if (! c)
 375                                         c = new_r_Confirm(block, left, right, rel);
 376
 377                                 pos = get_edge_src_pos(edge);
 378                                 set_irn_n(succ, pos, c);
 379                                 DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 380
 381                                 env->num_confirms += 1;
 382                         }
 383                 }
 384
 385                 if (! is_Const(right)) {
 386                         /* also construct inverse Confirms */
 387                         ir_node *rc = NULL;
 388
 389                         rel = get_inversed_relation(rel);
 390                         foreach_out_edge_safe(right, edge, next) {
 391                                 ir_node *succ = get_edge_src_irn(edge);
 392                                 int     pos;
 393                                 ir_node *blk;
 394
 395                                 if (succ == c)
 396                                         continue;
 397
 398                                 pos  = get_edge_src_pos(edge);
 399                                 blk  = get_effective_use_block(succ, pos);
 400
 401                                 if (block_dominates(block, blk)) {
 402                                         /*
 403                                          * Ok, we found a usage of right in a block
 404                                          * dominated by the branch block.
 405                                          * We can replace the input with a Confirm(right, rel^-1, left).
 406                                          */
 407                                         if (! rc)
 408                                                 rc = new_r_Confirm(block, right, left, rel);
 409
 410                                         pos = get_edge_src_pos(edge);
 411                                         set_irn_n(succ, pos, rc);
 412                                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, rc));
 413
 414                                         env->num_confirms += 1;
 415                                 }
 416                         }
 417                 }
 418         }
 419 }
 420
 421 /**
 422  * Pre-block-walker: Called for every block to insert Confirm nodes
 423  */
 424 static void insert_Confirm_in_block(ir_node *block, void *data)
 425 {
 426         env_t   *env = (env_t*) data;
 427         ir_node *cond;
 428         ir_node *proj;
 429
 430         /*
 431          * we can only handle blocks with only ONE control flow
 432          * predecessor yet.
 433          */
 434         if (get_Block_n_cfgpreds(block) != 1)
 435                 return;
 436
 437         proj = get_Block_cfgpred(block, 0);
 438         if (! is_Proj(proj))
 439                 return;
 440
 441         cond = get_Proj_pred(proj);
 442         if (is_Switch(cond)) {
 443                 long proj_nr = get_Proj_proj(proj);
 444                 handle_case(block, cond, proj_nr, env);
 445         } else if (is_Cond(cond)) {
 446                 ir_node *selector = get_Cond_selector(cond);
 447                 ir_relation rel;
 448
 449                 handle_modeb(block, selector, (pn_Cond) get_Proj_proj(proj), env);
 450
 451                 if (! is_Cmp(selector))
 452                         return;
 453
 454                 rel = get_Cmp_relation(selector);
 455
 456                 if (get_Proj_proj(proj) != pn_Cond_true) {
 457                         /* it's the false branch */
 458                         rel = get_negated_relation(rel);
 459                 }
 460                 DB((dbg, LEVEL_2, "At %+F using %+F Confirm %=\n", block, selector, rel));
 461
 462                 handle_if(block, selector, rel, env);
 463         }
 464 }
 465
 466 /**
 467  * Checks if a node is a non-null Confirm.
 468  */
 469 static int is_non_null_Confirm(const ir_node *ptr)
 470 {
 471         for (;;) {
 472                 if (! is_Confirm(ptr))
 473                         break;
 474                 if (get_Confirm_relation(ptr) == ir_relation_less_greater) {
 475                         ir_node *bound = get_Confirm_bound(ptr);
 476
 477                         if (is_Const(bound) && is_Const_null(bound))
 478                                 return 1;
 479                 }
 480                 ptr = get_Confirm_value(ptr);
 481         }
 482         /*
 483          * While a SymConst is not a Confirm, it is non-null
 484          * anyway. This helps to reduce the number of
 485          * constructed Confirms.
 486          */
 487         if (is_SymConst_addr_ent(ptr))
 488                 return 1;
 489         return 0;
 490 }
 491
 492 /**
 493  * The given pointer will be dereferenced, add non-null Confirms.
 494  *
 495  * @param ptr    a node representing an address
 496  * @param block  the block of the dereferencing instruction
 497  * @param env    environment
 498  */
 499 static void insert_non_null(ir_node *ptr, ir_node *block, env_t *env)
 500 {
 501         const ir_edge_t *edge, *next;
 502         ir_node         *c = NULL;
 503
 504         foreach_out_edge_safe(ptr, edge, next) {
 505                 ir_node *succ = get_edge_src_irn(edge);
 506                 int     pos;
 507                 ir_node *blk;
 508
 509
 510                 /* for now, we place a Confirm only in front of a Cmp */
 511                 if (! is_Cmp(succ))
 512                         continue;
 513
 514                 pos = get_edge_src_pos(edge);
 515                 blk = get_effective_use_block(succ, pos);
 516
 517                 if (block_dominates(block, blk)) {
 518                         /*
 519                          * Ok, we found a usage of ptr in a block
 520                          * dominated by the Load/Store block.
 521                          * We can replace the input with a Confirm(ptr, !=, NULL).
 522                          */
 523                         if (c == NULL) {
 524                                 ir_mode  *mode = get_irn_mode(ptr);
 525                                 ir_graph *irg  = get_irn_irg(block);
 526                                 c = new_r_Const(irg, get_mode_null(mode));
 527                                 c = new_r_Confirm(block, ptr, c, ir_relation_less_greater);
 528                         }
 529
 530                         set_irn_n(succ, pos, c);
 531                         DB((dbg, LEVEL_2, "Replacing input %d of node %+F with %+F\n", pos, succ, c));
 532
 533                         env->num_non_null += 1;
 534                         env->num_confirms += 1;
 535                 }
 536         }
 537 }
 538
 539 /**
 540  * Pre-walker: Called for every node to insert Confirm nodes
 541  */
 542 static void insert_Confirm(ir_node *node, void *data)
 543 {
 544         ir_node *ptr;
 545         env_t   *env = (env_t*) data;
 546
 547         switch (get_irn_opcode(node)) {
 548         case iro_Block:
 549                 insert_Confirm_in_block(node, env);
 550                 break;
 551         case iro_Load:
 552                 ptr = get_Load_ptr(node);
 553                 if (! is_non_null_Confirm(ptr))
 554                         insert_non_null(ptr, get_nodes_block(node), env);
 555                 break;
 556         case iro_Store:
 557                 ptr = get_Store_ptr(node);
 558                 if (! is_non_null_Confirm(ptr))
 559                         insert_non_null(ptr, get_nodes_block(node), env);
 560                 break;
 561         default:
 562                 break;
 563         }
 564 }
 565
 566 /*
 567  * Construct Confirm nodes
 568  */
 569 static ir_graph_state_t do_construct_confirms(ir_graph *irg)
 570 {
 571         env_t env;
 572         FIRM_DBG_REGISTER(dbg, "firm.ana.confirm");
 573
 574         assert(get_irg_pinned(irg) == op_pin_state_pinned &&
 575                "Nodes must be placed to insert Confirms");
 576
 577         env.num_confirms = 0;
 578         env.num_consts   = 0;
 579         env.num_eq       = 0;
 580         env.num_non_null = 0;
 581
 582         if (get_opt_global_null_ptr_elimination()) {
 583                 /* do global NULL test elimination */
 584                 irg_walk_graph(irg, insert_Confirm, NULL, &env);
 585         } else {
 586                 /* now, visit all blocks and add Confirms where possible */
 587                 irg_block_walk_graph(irg, insert_Confirm_in_block, NULL, &env);
 588         }
 589
 590         DB((dbg, LEVEL_1, "# Confirms inserted : %u\n", env.num_confirms));
 591         DB((dbg, LEVEL_1, "# Const replacements: %u\n", env.num_consts));
 592         DB((dbg, LEVEL_1, "# node equalities   : %u\n", env.num_eq));
 593         DB((dbg, LEVEL_1, "# non-null Confirms : %u\n", env.num_non_null));
 594         return 0;
 595 }
 596
 597 static optdesc_t opt_confirms = {
 598         "confirms",
 599         IR_GRAPH_STATE_CONSISTENT_OUT_EDGES
 600         | IR_GRAPH_STATE_CONSISTENT_DOMINANCE
 601         | IR_GRAPH_STATE_NO_CRITICAL_EDGES,
 602         do_construct_confirms
 603 };
 604
 605 void construct_confirms(ir_graph *irg)
 606 {
 607         perform_irg_optimization(irg, &opt_confirms);
 608 }
 609
 610 ir_graph_pass_t *construct_confirms_pass(const char *name)
 611 {
 612         return def_graph_pass(name ? name : "confirm", construct_confirms);
 613 }
 614
 615 static void remove_confirm(ir_node *n, void *env)
 616 {
 617         ir_node *value;
 618
 619         (void) env;
 620         if (!is_Confirm(n))
 621                 return;
 622
 623         value = get_Confirm_value(n);
 624         exchange(n, value);
 625 }
 626
 627 void remove_confirms(ir_graph *irg)
 628 {
 629         irg_walk_graph(irg, NULL, remove_confirm, NULL);
 630 }
 631
 632 ir_graph_pass_t *remove_confirms_pass(const char *name)
 633 {
 634         return def_graph_pass(name ? name : "rem_confirm", remove_confirms);
 635 }