nsz Git - libfirm/blob - ir/opt/condeval.c

   1 /*
   2  * Copyright (C) 1995-2007 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   Partial condition evaluation
  23  * @date    10. Sep. 2006
  24  * @author  Christoph Mallon, Matthias Braun
  25  * @version $Id$
  26  */
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include "iroptimize.h"
  32
  33 #include <assert.h>
  34 #include "array.h"
  35 #include "debug.h"
  36 #include "ircons.h"
  37 #include "irgmod.h"
  38 #include "irgopt.h"
  39 #include "irgwalk.h"
  40 #include "irnode.h"
  41 #include "irnode_t.h"
  42 #include "iredges.h"
  43 #include "iredges_t.h"
  44 #include "irtools.h"
  45 #include "irgraph.h"
  46 #include "tv.h"
  47
  48 DEBUG_ONLY(static firm_dbg_module_t *dbg);
  49
  50 /**
  51  * Add the new predecessor x to node node, which is either a Block or a Phi
  52  */
  53 static void add_pred(ir_node* node, ir_node* x)
  54 {
  55         ir_node** ins;
  56         int n;
  57         int i;
  58
  59         assert(is_Block(node) || is_Phi(node));
  60
  61         n = get_irn_arity(node);
  62         NEW_ARR_A(ir_node*, ins, n + 1);
  63         for (i = 0; i < n; i++)
  64                 ins[i] = get_irn_n(node, i);
  65         ins[n] = x;
  66         set_irn_in(node, n + 1, ins);
  67 }
  68
  69 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
  70 {
  71         int i;
  72         int n_cfgpreds;
  73         ir_graph *irg;
  74         ir_node *phi;
  75         ir_node **in;
  76
  77         // This is needed because we create bads sometimes
  78         if(is_Bad(block))
  79                 return new_Bad();
  80
  81         // already processed this block?
  82         if(irn_visited(block)) {
  83                 ir_node *value = (ir_node*) get_irn_link(block);
  84                 return value;
  85         }
  86
  87         // blocks with only 1 pred need no phi
  88         n_cfgpreds = get_Block_n_cfgpreds(block);
  89         if(n_cfgpreds == 1) {
  90                 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
  91                 ir_node *value = search_def_and_create_phis(pred_block, mode);
  92
  93                 set_irn_link(block, value);
  94                 mark_irn_visited(block);
  95                 return value;
  96         }
  97
  98         // create a new phi
  99         NEW_ARR_A(ir_node*, in, n_cfgpreds);
 100         for(i = 0; i < n_cfgpreds; ++i)
 101                 in[i] = new_Unknown(mode);
 102
 103         irg = get_irn_irg(block);
 104         phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
 105         set_irn_link(block, phi);
 106         mark_irn_visited(block);
 107
 108         // set phi preds
 109         for(i = 0; i < n_cfgpreds; ++i) {
 110                 ir_node *pred_block = get_Block_cfgpred_block(block, i);
 111                 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
 112
 113                 set_irn_n(phi, i, pred_val);
 114         }
 115
 116         return phi;
 117 }
 118
 119 /**
 120  * Given a set of values this function constructs SSA-form for the users of the
 121  * first value (the users are determined through the out-edges of the value).
 122  * Uses the irn_visited flags. Works without using the dominance tree.
 123  */
 124 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
 125 {
 126         int i;
 127         ir_graph *irg;
 128         ir_mode *mode;
 129         const ir_edge_t *edge;
 130         const ir_edge_t *next;
 131         ir_node *value;
 132
 133         assert(n_vals > 0);
 134
 135         irg = get_irn_irg(vals[0]);
 136         inc_irg_visited(irg);
 137
 138         mode = get_irn_mode(vals[0]);
 139         for(i = 0; i < n_vals; ++i) {
 140                 ir_node *value = vals[i];
 141                 ir_node *value_block = blocks[i];
 142
 143                 assert(get_irn_mode(value) == mode);
 144
 145                 set_irn_link(value_block, value);
 146                 mark_irn_visited(value_block);
 147         }
 148
 149         // Only fix the users of the first, i.e. the original node
 150         value = vals[0];
 151
 152         // this can happen when fixing phi preds, we mustn't fix the users
 153         if(get_nodes_block(value) != blocks[0]) return;
 154
 155         foreach_out_edge_safe(value, edge, next) {
 156                 ir_node *user = get_edge_src_irn(edge);
 157                 int j = get_edge_src_pos(edge);
 158                 ir_node *user_block = get_nodes_block(user);
 159                 ir_node *newval;
 160
 161                 // ignore keeps
 162                 if(get_irn_op(user) == op_End)
 163                         continue;
 164
 165                 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
 166
 167                 if(is_Phi(user)) {
 168                         ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 169                         newval = search_def_and_create_phis(pred_block, mode);
 170                 } else {
 171                         newval = search_def_and_create_phis(user_block, mode);
 172                 }
 173
 174                 // don't fix newly created phis from the SSA construction
 175                 if (newval != user) {
 176                         DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
 177                         set_irn_n(user, j, newval);
 178                 }
 179         }
 180 }
 181
 182 static void split_critical_edge(ir_node *block, int pos) {
 183         ir_graph *irg = get_irn_irg(block);
 184         ir_node *in[1];
 185         ir_node *new_block;
 186         ir_node *new_jmp;
 187
 188         in[0] = get_Block_cfgpred(block, pos);
 189         new_block = new_r_Block(irg, 1, in);
 190         new_jmp = new_r_Jmp(irg, new_block);
 191         set_Block_cfgpred(block, pos, new_jmp);
 192 }
 193
 194 typedef struct _condeval_env_t {
 195         ir_node *true_block;
 196         pn_Cmp pnc;
 197         ir_node *cnst;
 198         unsigned long visited_nr;
 199
 200         ir_node *cnst_pred;     /**< the block before the constant */
 201         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 202 } condeval_env_t;
 203
 204 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 205         const ir_edge_t *edge;
 206
 207         /* Look at all nodes in the cond_block and copy them into pred */
 208         foreach_out_edge(block, edge) {
 209                 ir_node *node = get_edge_src_irn(edge);
 210                 ir_node *copy;
 211                 ir_mode *mode = get_irn_mode(node);
 212
 213                 /* ignore control flow */
 214                 if (mode == mode_X || is_Cond(node))
 215                         continue;
 216                 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
 217                    be handled in all backends. Instead we duplicate the node and move it to it's users */
 218                 if (mode == mode_b) {
 219                         const ir_edge_t *edge, *next;
 220                         ir_node *pred;
 221                         int      pn;
 222
 223                         assert(is_Proj(node));
 224
 225                         pred = get_Proj_pred(node);
 226                         pn   = get_Proj_proj(node);
 227
 228                         foreach_out_edge_safe(node, edge, next) {
 229                                 ir_node *cmp_copy;
 230                                 ir_node *user       = get_edge_src_irn(edge);
 231                                 int pos             = get_edge_src_pos(edge);
 232                                 ir_node *user_block = get_nodes_block(user);
 233
 234                                 if(user_block == block)
 235                                         continue;
 236
 237                                 cmp_copy = exact_copy(pred);
 238                                 set_nodes_block(cmp_copy, user_block);
 239                                 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
 240                                 set_irn_n(user, pos, copy);
 241                         }
 242                         continue;
 243                 }
 244
 245                 /* we can evaluate Phis right now, all other nodes get copied */
 246                 if (is_Phi(node)) {
 247                         copy = get_Phi_pred(node, j);
 248                 } else {
 249                         copy = exact_copy(node);
 250                         set_nodes_block(copy, copy_block);
 251                 }
 252
 253                 set_irn_link(node, copy);
 254                 set_irn_visited(node, env->visited_nr);
 255
 256                 /* we might hit values in blocks that have already been processed by a
 257                  * recursive find_phi_with_const call */
 258                 assert(get_irn_visited(copy) <= env->visited_nr);
 259                 if(get_irn_visited(copy) >= env->visited_nr) {
 260                         ir_node *prev_copy = get_irn_link(copy);
 261                         if(prev_copy != NULL)
 262                                 set_irn_link(node, prev_copy);
 263                 }
 264         }
 265
 266         /* fix data-flow (and reconstruct SSA if needed) */
 267         foreach_out_edge(block, edge) {
 268                 ir_node *vals[2];
 269                 ir_node *blocks[2];
 270                 ir_node *node = get_edge_src_irn(edge);
 271                 ir_mode *mode = get_irn_mode(node);
 272
 273                 if (mode == mode_X || is_Cond(node))
 274                         continue;
 275                 if (mode == mode_b)
 276                         continue;
 277
 278                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 279
 280                 blocks[0] = block;
 281                 vals[0] = node;
 282                 blocks[1] = copy_block;
 283                 vals[1] = get_irn_link(node);
 284                 construct_ssa(blocks, vals, 2);
 285         }
 286 }
 287
 288 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 289         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 290
 291         // does the compare evaluate to true?
 292         if(cmp_result == pn_Cmp_False)
 293                 return 0;
 294         if((cmp_result & pnc) != cmp_result)
 295                 return 0;
 296
 297         return 1;
 298 }
 299
 300 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 301         ir_node *block = get_nodes_block(jump);
 302
 303         if(irn_visited(value))
 304                 return NULL;
 305         mark_irn_visited(value);
 306
 307         if(is_Const(value)) {
 308                 tarval *tv_const = get_Const_tarval(env->cnst);
 309                 tarval *tv = get_Const_tarval(value);
 310
 311                 if(!eval_cmp(env->pnc, tv, tv_const))
 312                         return NULL;
 313
 314                 DB((
 315                         dbg, LEVEL_1,
 316                         "> Found condition evaluation candidate %+F->%+F\n",
 317                         env->true_block, block
 318                 ));
 319
 320                 // adjust true_block to point directly towards our jump
 321                 add_pred(env->true_block, jump);
 322
 323                 split_critical_edge(env->true_block, 0);
 324
 325                 // we need a bigger visited nr when going back
 326                 env->visited_nr++;
 327
 328                 return block;
 329         }
 330
 331         if(is_Phi(value)) {
 332                 int i, arity;
 333
 334                 // the phi has to be in the same block as the jump
 335                 if(get_nodes_block(value) != block)
 336                         return NULL;
 337
 338                 arity = get_irn_arity(value);
 339                 for(i = 0; i < arity; ++i) {
 340                         ir_node *copy_block;
 341                         ir_node *phi_pred = get_Phi_pred(value, i);
 342                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 343
 344                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 345                         if(copy_block == NULL)
 346                                 continue;
 347
 348                         /* copy duplicated nodes in copy_block and fix SSA */
 349                         copy_and_fix(block, copy_block, i, env);
 350
 351                         if(copy_block == get_nodes_block(cfgpred)) {
 352                                 env->cnst_pred = block;
 353                                 env->cnst_pos = i;
 354                         }
 355
 356                         // return now as we can't process more possibilities in 1 run
 357                         return copy_block;
 358                 }
 359         }
 360
 361         return NULL;
 362 }
 363
 364
 365 /**
 366  * Block-walker: searches for the following construct
 367  *
 368  *  Const or Phi with constants
 369  *           |
 370  *          Cmp
 371  *           |
 372  *         Cond
 373  *          /
 374  *       ProjX
 375  *        /
 376  *     Block
 377  */
 378 static void cond_eval(ir_node* block, void* data)
 379 {
 380         condeval_env_t env;
 381         int *changed = data;
 382         ir_graph *irg = current_ir_graph;
 383         ir_node *copy_block;
 384         ir_node *pred;
 385         ir_node *projx;
 386         ir_node *cond;
 387         ir_node *cmp;
 388         ir_node *left;
 389         ir_node *right;
 390         ir_node *cond_block;
 391         pn_Cmp pnc;
 392
 393         if(get_Block_n_cfgpreds(block) != 1)
 394                 return;
 395
 396         projx = get_Block_cfgpred(block, 0);
 397         if (!is_Proj(projx))
 398                 return;
 399         assert(get_irn_mode(projx) == mode_X);
 400
 401         cond = get_Proj_pred(projx);
 402         if (!is_Cond(cond))
 403                 return;
 404
 405         pred = get_Cond_selector(cond);
 406         // TODO handle switches
 407         if (get_irn_mode(pred) != mode_b)
 408                 return;
 409         if (!is_Proj(pred))
 410                 return;
 411         pnc = get_Proj_proj(pred);
 412
 413         cmp = get_Proj_pred(pred);
 414         assert(is_Cmp(cmp));
 415
 416         left  = get_Cmp_left(cmp);
 417         right = get_Cmp_right(cmp);
 418         assert(get_irn_mode(left) == get_irn_mode(right));
 419
 420         /* we assume that the cond_block is the true case */
 421         if (get_Proj_proj(projx) == pn_Cond_false) {
 422                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 423         }
 424
 425         /* we assume that the constant is on the right side, swap left/right
 426          * if needed */
 427         if(is_Const(left)) {
 428                 ir_node *t = left;
 429                 left = right;
 430                 right = t;
 431
 432                 pnc = get_inversed_pnc(pnc);
 433         }
 434
 435         if(!is_Const(right))
 436                 return;
 437
 438         cond_block = get_nodes_block(cond);
 439
 440         // special case: comparing a constant with a constant
 441         if(is_Const(left)) {
 442                 tarval *tv1 = get_Const_tarval(left);
 443                 tarval *tv2 = get_Const_tarval(right);
 444                 ir_node *pred;
 445                 if(eval_cmp(pnc, tv1, tv2)) {
 446                         pred = new_r_Jmp(irg, cond_block);
 447                 } else {
 448                         pred = new_Bad();
 449                 }
 450                 set_Block_cfgpred(block, 0, pred);
 451                 *changed = 1;
 452                 set_irg_doms_inconsistent(irg);
 453                 set_irg_extblk_inconsistent(irg);
 454                 set_irg_loopinfo_inconsistent(irg);
 455         } else {
 456                 if(get_nodes_block(left) != cond_block)
 457                         return;
 458
 459                 // (recursively) look if a pred of a phi is a constant
 460                 env.true_block = block;
 461                 env.pnc = pnc;
 462                 env.cnst = right;
 463                 inc_irg_visited(current_ir_graph);
 464                 env.visited_nr = get_irg_visited(irg);
 465
 466                 copy_block = find_phi_with_const(projx, left, &env);
 467
 468                 if(copy_block != NULL) {
 469                         /* we have to remove the edge towards the pred as the pred now
 470                          * jumps into the true_block. We also have to shorten phis
 471                          * in our block because of this */
 472                         const ir_edge_t *edge, *next;
 473                         ir_node* bad = new_Bad();
 474                         size_t cnst_pos = env.cnst_pos;
 475
 476                         /* shorten phis */
 477                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 478                                 ir_node *node = get_edge_src_irn(edge);
 479
 480                                 if(is_Phi(node))
 481                                         set_Phi_pred(node, cnst_pos, bad);
 482                         }
 483
 484                         set_Block_cfgpred(env.cnst_pred, cnst_pos, bad);
 485
 486                         /* the graph is changed now */
 487                         *changed = 1;
 488                 }
 489         }
 490 }
 491
 492 void opt_cond_eval(ir_graph* irg)
 493 {
 494         int changed, rerun;
 495
 496         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 497
 498         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 499
 500         remove_critical_cf_edges(irg);
 501         normalize_proj_nodes(irg);
 502
 503         edges_assure(irg);
 504         set_using_irn_link(irg);
 505         set_using_visited(irg);
 506
 507         changed = 0;
 508         do {
 509                 rerun = 0;
 510                 irg_block_walk_graph(irg, cond_eval, NULL, &rerun);
 511                 changed |= rerun;
 512         } while (rerun);
 513
 514         if (changed) {
 515                 /* control flow changed, some blocks may become dead */
 516                 set_irg_outs_inconsistent(irg);
 517                 set_irg_doms_inconsistent(irg);
 518                 set_irg_extblk_inconsistent(irg);
 519                 set_irg_loopinfo_inconsistent(irg);
 520         }
 521
 522         clear_using_visited(irg);
 523         clear_using_irn_link(irg);
 524 }