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  * Project:     libFIRM
  22  * File name:   ir/opt/cfopt.c
  23  * Purpose:     Partial condition evaluation
  24  * Author:      Christoph Mallon, Matthias Braun
  25  * Created:     10. Sep. 2006
  26  * CVS-ID:      $Id$
  27  * Copyright:   (c) 1998-2006 Universität Karlsruhe
  28  */
  29 #ifdef HAVE_CONFIG_H
  30 #include "config.h"
  31 #endif
  32
  33 #include <assert.h>
  34 #include "array.h"
  35 #include "condeval.h"
  36 #include "debug.h"
  37 #include "ircons.h"
  38 #include "irgmod.h"
  39 #include "irgopt.h"
  40 #include "irgwalk.h"
  41 #include "irnode.h"
  42 #include "irnode_t.h"
  43 #include "iredges.h"
  44 #include "iredges_t.h"
  45 #include "irtools.h"
  46 #include "irgraph.h"
  47 #include "tv.h"
  48
  49 DEBUG_ONLY(static firm_dbg_module_t *dbg);
  50
  51 /**
  52  * Add the new predecessor x to node node, which is either a Block or a Phi
  53  */
  54 static void add_pred(ir_node* node, ir_node* x)
  55 {
  56         ir_node** ins;
  57         int n;
  58         int i;
  59
  60         assert(is_Block(node) || is_Phi(node));
  61
  62         n = get_irn_arity(node);
  63         NEW_ARR_A(ir_node*, ins, n + 1);
  64         for (i = 0; i < n; i++)
  65                 ins[i] = get_irn_n(node, i);
  66         ins[n] = x;
  67         set_irn_in(node, n + 1, ins);
  68 }
  69
  70 /**
  71  * Remove predecessor j from node, which is either a Block or a Phi
  72  * returns true if only one predecessor is left
  73  */
  74 static int remove_pred(ir_node* node, int j)
  75 {
  76         int n;
  77
  78         assert(is_Block(node) || is_Phi(node));
  79
  80         n = get_irn_arity(node);
  81         if (n == 2) {
  82                 ir_node* pred = get_irn_n(node, 1 - j);
  83
  84                 if (is_Block(node)) {
  85                         pred = get_nodes_block(pred);
  86                         edges_reroute(node, pred, current_ir_graph);
  87                 } else {
  88                         exchange(node, pred);
  89                 }
  90                 return 1;
  91         } else {
  92                 ir_node** ins;
  93                 int i;
  94
  95                 NEW_ARR_A(ir_node*, ins, n - 1);
  96                 for (i = 0; i < j; i++)
  97                         ins[i] = get_irn_n(node, i);
  98                 for (i++; i < n; i++)
  99                         ins[i - 1] = get_irn_n(node, i);
 100
 101                 set_irn_in(node, n - 1, ins);
 102                 return 0;
 103         }
 104 }
 105
 106 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
 107 {
 108         int i;
 109         int n_cfgpreds;
 110         ir_graph *irg;
 111         ir_node *phi;
 112         ir_node **in;
 113
 114         // This is needed because we create bads sometimes
 115         if(is_Bad(block))
 116                 return new_Bad();
 117
 118         // already processed this block?
 119         if(irn_visited(block)) {
 120                 ir_node *value = (ir_node*) get_irn_link(block);
 121                 return value;
 122         }
 123
 124         // blocks with only 1 pred need no phi
 125         n_cfgpreds = get_Block_n_cfgpreds(block);
 126         if(n_cfgpreds == 1) {
 127                 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
 128                 ir_node *value = search_def_and_create_phis(pred_block, mode);
 129
 130                 set_irn_link(block, value);
 131                 mark_irn_visited(block);
 132                 return value;
 133         }
 134
 135         // create a new phi
 136         NEW_ARR_A(ir_node*, in, n_cfgpreds);
 137         for(i = 0; i < n_cfgpreds; ++i)
 138                 in[i] = new_Unknown(mode);
 139
 140         irg = get_irn_irg(block);
 141         phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
 142         set_irn_link(block, phi);
 143         mark_irn_visited(block);
 144
 145         // set phi preds
 146         for(i = 0; i < n_cfgpreds; ++i) {
 147                 ir_node *pred_block = get_Block_cfgpred_block(block, i);
 148                 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
 149
 150                 set_irn_n(phi, i, pred_val);
 151         }
 152
 153         return phi;
 154 }
 155
 156 /**
 157  * Given a set of values this function constructs SSA-form for the users of the
 158  * first value (the users are determined through the out-edges of the value).
 159  * Uses the irn_visited flags. Works without using the dominance tree.
 160  */
 161 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
 162 {
 163         int i;
 164         ir_graph *irg;
 165         ir_mode *mode;
 166         const ir_edge_t *edge;
 167         const ir_edge_t *next;
 168         ir_node *value;
 169
 170         assert(n_vals > 0);
 171
 172         irg = get_irn_irg(vals[0]);
 173         inc_irg_visited(irg);
 174
 175         mode = get_irn_mode(vals[0]);
 176         for(i = 0; i < n_vals; ++i) {
 177                 ir_node *value = vals[i];
 178                 ir_node *value_block = blocks[i];
 179
 180                 assert(get_irn_mode(value) == mode);
 181
 182                 set_irn_link(value_block, value);
 183                 mark_irn_visited(value_block);
 184         }
 185
 186         // Only fix the users of the first, i.e. the original node
 187         value = vals[0];
 188
 189         // this can happen when fixing phi preds, we mustn't fix the users
 190         if(get_nodes_block(value) != blocks[0]) return;
 191
 192         foreach_out_edge_safe(value, edge, next) {
 193                 ir_node *user = get_edge_src_irn(edge);
 194                 int j = get_edge_src_pos(edge);
 195                 ir_node *user_block = get_nodes_block(user);
 196                 ir_node *newval;
 197
 198                 // ignore keeps
 199                 if(get_irn_op(user) == op_End)
 200                         continue;
 201
 202                 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
 203
 204                 if(is_Phi(user)) {
 205                         ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 206                         newval = search_def_and_create_phis(pred_block, mode);
 207                 } else {
 208                         newval = search_def_and_create_phis(user_block, mode);
 209                 }
 210
 211                 // don't fix newly created phis from the SSA construction
 212                 if (newval != user) {
 213                         DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
 214                         set_irn_n(user, j, newval);
 215                 }
 216         }
 217 }
 218
 219 static void split_critical_edge(ir_node *block, int pos) {
 220         ir_graph *irg = get_irn_irg(block);
 221         ir_node *in[1];
 222         ir_node *new_block;
 223         ir_node *new_jmp;
 224
 225         in[0] = get_Block_cfgpred(block, pos);
 226         new_block = new_r_Block(irg, 1, in);
 227         new_jmp = new_r_Jmp(irg, new_block);
 228         set_Block_cfgpred(block, pos, new_jmp);
 229 }
 230
 231 typedef struct _condeval_env_t {
 232         ir_node *true_block;
 233         pn_Cmp pnc;
 234         ir_node *cnst;
 235         unsigned long visited_nr;
 236
 237         ir_node *cnst_pred;     /**< the block before the constant */
 238         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 239 } condeval_env_t;
 240
 241 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 242         const ir_edge_t *edge;
 243
 244         /* Look at all nodes in the cond_block and copy them into pred */
 245         foreach_out_edge(block, edge) {
 246                 ir_node *node = get_edge_src_irn(edge);
 247                 ir_node *copy;
 248                 ir_mode *mode = get_irn_mode(node);
 249
 250                 /* ignore control flow */
 251                 if (mode == mode_X)
 252                         continue;
 253                 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
 254                    be handled in all backends. Instead we duplicate the node and move it to it's users */
 255                 if (mode == mode_b) {
 256                         const ir_edge_t *edge, *next;
 257                         ir_node *pred;
 258                         int      pn;
 259
 260                         assert(is_Proj(node));
 261
 262                         pred = get_Proj_pred(node);
 263                         pn   = get_Proj_proj(node);
 264
 265                         foreach_out_edge_safe(node, edge, next) {
 266                                 ir_node *cmp_copy;
 267                                 ir_node *user       = get_edge_src_irn(edge);
 268                                 int pos             = get_edge_src_pos(edge);
 269                                 ir_node *user_block = get_nodes_block(user);
 270
 271                                 if(user_block == block)
 272                                         continue;
 273
 274                                 cmp_copy = exact_copy(pred);
 275                                 set_nodes_block(cmp_copy, user_block);
 276                                 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
 277                                 set_irn_n(user, pos, copy);
 278                         }
 279                         continue;
 280                 }
 281
 282                 /* we can evaluate Phis right now, all other nodes get copied */
 283                 if (is_Phi(node)) {
 284                         copy = get_Phi_pred(node, j);
 285                 } else {
 286                         copy = exact_copy(node);
 287                         set_nodes_block(copy, copy_block);
 288                 }
 289
 290                 set_irn_link(node, copy);
 291                 set_irn_visited(node, env->visited_nr);
 292
 293                 /* we might hit values in blocks that have already been processed by a
 294                  * recursive find_phi_with_const call */
 295                 assert(get_irn_visited(copy) <= env->visited_nr);
 296                 if(get_irn_visited(copy) >= env->visited_nr) {
 297                         ir_node *prev_copy = get_irn_link(copy);
 298                         if(prev_copy != NULL)
 299                                 set_irn_link(node, prev_copy);
 300                 }
 301         }
 302
 303         /* fix data-flow (and reconstruct SSA if needed) */
 304         foreach_out_edge(block, edge) {
 305                 ir_node *vals[2];
 306                 ir_node *blocks[2];
 307                 ir_node *node = get_edge_src_irn(edge);
 308                 ir_mode *mode = get_irn_mode(node);
 309
 310                 if (mode == mode_X)
 311                         continue;
 312                 if (mode == mode_b)
 313                         continue;
 314
 315                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 316
 317                 blocks[0] = block;
 318                 vals[0] = node;
 319                 blocks[1] = copy_block;
 320                 vals[1] = get_irn_link(node);
 321                 construct_ssa(blocks, vals, 2);
 322         }
 323 }
 324
 325 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 326         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 327
 328         // does the compare evaluate to true?
 329         if(cmp_result == pn_Cmp_False)
 330                 return 0;
 331         if((cmp_result & pnc) != cmp_result)
 332                 return 0;
 333
 334         return 1;
 335 }
 336
 337 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 338         ir_node *block = get_nodes_block(jump);
 339
 340         if(irn_visited(value))
 341                 return NULL;
 342         mark_irn_visited(value);
 343
 344         if(is_Const(value)) {
 345                 tarval *tv_const = get_Const_tarval(env->cnst);
 346                 tarval *tv = get_Const_tarval(value);
 347
 348                 if(!eval_cmp(env->pnc, tv, tv_const))
 349                         return NULL;
 350
 351                 DB((
 352                         dbg, LEVEL_1,
 353                         "> Found condition evaluation candidate %+F->%+F\n",
 354                         env->true_block, block
 355                 ));
 356
 357                 // adjust true_block to point directly towards our jump
 358                 add_pred(env->true_block, jump);
 359
 360                 split_critical_edge(env->true_block, 0);
 361
 362                 // we need a bigger visited nr when going back
 363                 env->visited_nr++;
 364
 365                 return block;
 366         }
 367
 368         if(is_Phi(value)) {
 369                 int i, arity;
 370
 371                 // the phi has to be in the same block as the jump
 372                 if(get_nodes_block(value) != block)
 373                         return NULL;
 374
 375                 arity = get_irn_arity(value);
 376                 for(i = 0; i < arity; ++i) {
 377                         ir_node *copy_block;
 378                         ir_node *phi_pred = get_Phi_pred(value, i);
 379                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 380
 381                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 382                         if(copy_block == NULL)
 383                                 continue;
 384
 385                         /* copy duplicated nodes in copy_block and fix SSA */
 386                         copy_and_fix(block, copy_block, i, env);
 387
 388                         if(copy_block == get_nodes_block(cfgpred)) {
 389                                 env->cnst_pred = block;
 390                                 env->cnst_pos = i;
 391                         }
 392
 393                         // return now as we can't process more possibilities in 1 run
 394                         return copy_block;
 395                 }
 396         }
 397
 398         return NULL;
 399 }
 400
 401
 402 /**
 403  * Block-walker: searchs for the following construct
 404  *
 405  *  Const or Phi with constants
 406  *           |
 407  *          Cmp
 408  *           |
 409  *         Cond
 410  *          /
 411  *       ProjX
 412  *        /
 413  *     Block
 414  */
 415 static void cond_eval(ir_node* block, void* data)
 416 {
 417         condeval_env_t env;
 418         int *changed = data;
 419         ir_graph *irg = current_ir_graph;
 420         ir_node *copy_block;
 421         ir_node *pred;
 422         ir_node *projx;
 423         ir_node *cond;
 424         ir_node *cmp;
 425         ir_node *left;
 426         ir_node *right;
 427         ir_node *cond_block;
 428         pn_Cmp pnc;
 429
 430         if(get_Block_n_cfgpreds(block) != 1)
 431                 return;
 432
 433         projx = get_Block_cfgpred(block, 0);
 434         if (!is_Proj(projx))
 435                 return;
 436         assert(get_irn_mode(projx) == mode_X);
 437
 438         cond = get_Proj_pred(projx);
 439         if (!is_Cond(cond))
 440                 return;
 441
 442         pred = get_Cond_selector(cond);
 443         // TODO handle switches
 444         if (get_irn_mode(pred) != mode_b)
 445                 return;
 446         if (!is_Proj(pred))
 447                 return;
 448         pnc = get_Proj_proj(pred);
 449
 450         cmp = get_Proj_pred(pred);
 451         assert(is_Cmp(cmp));
 452
 453         left  = get_Cmp_left(cmp);
 454         right = get_Cmp_right(cmp);
 455         assert(get_irn_mode(left) == get_irn_mode(right));
 456
 457         /* we assume that the cond_block is the true case */
 458         if (get_Proj_proj(projx) == pn_Cond_false) {
 459                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 460         }
 461
 462         /* we assume that the constant is on the right side, swap left/right
 463          * if needed */
 464         if(is_Const(left)) {
 465                 ir_node *t = left;
 466                 left = right;
 467                 right = t;
 468
 469                 pnc = get_inversed_pnc(pnc);
 470         }
 471
 472         if(!is_Const(right))
 473                 return;
 474
 475         cond_block = get_nodes_block(cond);
 476
 477         // special case: comparing a constant with a constant
 478         if(is_Const(left)) {
 479                 tarval *tv1 = get_Const_tarval(left);
 480                 tarval *tv2 = get_Const_tarval(right);
 481                 ir_node *pred;
 482                 if(eval_cmp(pnc, tv1, tv2)) {
 483                         pred = new_r_Jmp(irg, cond_block);
 484                 } else {
 485                         pred = new_Bad();
 486                 }
 487                 set_Block_cfgpred(block, 0, pred);
 488                 *changed = 1;
 489                 set_irg_doms_inconsistent(irg);
 490                 set_irg_extblk_inconsistent(irg);
 491                 set_irg_loopinfo_inconsistent(irg);
 492         } else {
 493                 if(get_nodes_block(left) != cond_block)
 494                         return;
 495
 496                 // (recursively) look if a pred of a phi is a constant
 497                 env.true_block = block;
 498                 env.pnc = pnc;
 499                 env.cnst = right;
 500                 inc_irg_visited(current_ir_graph);
 501                 env.visited_nr = get_irg_visited(irg);
 502
 503                 copy_block = find_phi_with_const(projx, left, &env);
 504
 505                 if(copy_block != NULL) {
 506                         /* we have to remove the edge towards the pred as the pred now
 507                          * jumps into the true_block. We also have to shorten phis
 508                          * in our block because of this */
 509                         const ir_edge_t *edge, *next;
 510
 511                         /* shorten phis */
 512                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 513                                 ir_node *node = get_edge_src_irn(edge);
 514
 515                                 if(is_Phi(node))
 516                                         remove_pred(node, env.cnst_pos);
 517                         }
 518
 519                         remove_pred(env.cnst_pred, env.cnst_pos);
 520
 521                         // the graph is changed now
 522                         *changed = 1;
 523                         set_irg_doms_inconsistent(irg);
 524                         set_irg_extblk_inconsistent(irg);
 525                         set_irg_loopinfo_inconsistent(irg);
 526                 }
 527         }
 528 }
 529
 530 void opt_cond_eval(ir_graph* irg)
 531 {
 532         int changed;
 533
 534         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 535
 536         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 537
 538         edges_assure(irg);
 539         remove_critical_cf_edges(irg);
 540
 541         normalize_proj_nodes(irg);
 542
 543         set_using_irn_link(irg);
 544         set_using_visited(irg);
 545
 546         do {
 547                 changed = 0;
 548                 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
 549         } while(changed);
 550
 551         clear_using_visited(irg);
 552         clear_using_irn_link(irg);
 553 }