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

   1 /*
   2  * Project:     libFIRM
   3  * File name:   ir/opt/cfopt.c
   4  * Purpose:     Partial condition evaluation
   5  * Author:      Christoph Mallon, Matthias Braun
   6  * Created:     10. Sep. 2006
   7  * CVS-ID:      $Id$
   8  * Copyright:   (c) 1998-2006 Universität Karlsruhe
   9  * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
  10  */
  11 #ifdef HAVE_CONFIG_H
  12 #include "config.h"
  13 #endif
  14
  15 #include <assert.h>
  16 #include "array.h"
  17 #include "condeval.h"
  18 #include "debug.h"
  19 #include "ircons.h"
  20 #include "irgmod.h"
  21 #include "irgopt.h"
  22 #include "irgwalk.h"
  23 #include "irnode.h"
  24 #include "irnode_t.h"
  25 #include "iredges.h"
  26 #include "iredges_t.h"
  27 #include "irtools.h"
  28 #include "irgraph.h"
  29 #include "tv.h"
  30
  31 DEBUG_ONLY(static firm_dbg_module_t *dbg);
  32
  33 /**
  34  * Add the new predecessor x to node node, which is either a Block or a Phi
  35  */
  36 static void add_pred(ir_node* node, ir_node* x)
  37 {
  38         ir_node** ins;
  39         int n;
  40         int i;
  41
  42         assert(is_Block(node) || is_Phi(node));
  43
  44         n = get_irn_arity(node);
  45         NEW_ARR_A(ir_node*, ins, n + 1);
  46         for (i = 0; i < n; i++)
  47                 ins[i] = get_irn_n(node, i);
  48         ins[n] = x;
  49         set_irn_in(node, n + 1, ins);
  50 }
  51
  52 /**
  53  * Remove predecessor j from node, which is either a Block or a Phi
  54  * returns true if only one predecessor is left
  55  */
  56 static int remove_pred(ir_node* node, int j)
  57 {
  58         int n;
  59
  60         assert(is_Block(node) || is_Phi(node));
  61
  62         n = get_irn_arity(node);
  63         if (n == 2) {
  64                 ir_node* pred = get_irn_n(node, 1 - j);
  65
  66                 if (is_Block(node)) {
  67                         pred = get_nodes_block(pred);
  68                         edges_reroute(node, pred, current_ir_graph);
  69                 } else {
  70                         exchange(node, pred);
  71                 }
  72                 return 1;
  73         } else {
  74                 ir_node** ins;
  75                 int i;
  76
  77                 NEW_ARR_A(ir_node*, ins, n - 1);
  78                 for (i = 0; i < j; i++)
  79                         ins[i] = get_irn_n(node, i);
  80                 for (i++; i < n; i++)
  81                         ins[i - 1] = get_irn_n(node, i);
  82
  83                 set_irn_in(node, n - 1, ins);
  84                 return 0;
  85         }
  86 }
  87
  88 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
  89 {
  90         int i;
  91         int n_cfgpreds;
  92         ir_graph *irg;
  93         ir_node *phi;
  94         ir_node **in;
  95
  96         // This is needed because we create bads sometimes
  97         if(is_Bad(block))
  98                 return new_Bad();
  99
 100         // already processed this block?
 101         if(irn_visited(block)) {
 102                 ir_node *value = (ir_node*) get_irn_link(block);
 103                 return value;
 104         }
 105
 106         // blocks with only 1 pred need no phi
 107         n_cfgpreds = get_Block_n_cfgpreds(block);
 108         if(n_cfgpreds == 1) {
 109                 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
 110                 ir_node *value = search_def_and_create_phis(pred_block, mode);
 111
 112                 set_irn_link(block, value);
 113                 mark_irn_visited(block);
 114                 return value;
 115         }
 116
 117         // create a new phi
 118         NEW_ARR_A(ir_node*, in, n_cfgpreds);
 119         for(i = 0; i < n_cfgpreds; ++i)
 120                 in[i] = new_Unknown(mode);
 121
 122         irg = get_irn_irg(block);
 123         phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
 124         set_irn_link(block, phi);
 125         mark_irn_visited(block);
 126
 127         // set phi preds
 128         for(i = 0; i < n_cfgpreds; ++i) {
 129                 ir_node *pred_block = get_Block_cfgpred_block(block, i);
 130                 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
 131
 132                 set_irn_n(phi, i, pred_val);
 133         }
 134
 135         return phi;
 136 }
 137
 138 /**
 139  * Given a set of values this function constructs SSA-form for the users of the
 140  * first value (the users are determined through the out-edges of the value).
 141  * Uses the irn_visited flags. Works without using the dominance tree.
 142  */
 143 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
 144 {
 145         int i;
 146         ir_graph *irg;
 147         ir_mode *mode;
 148         const ir_edge_t *edge;
 149         const ir_edge_t *next;
 150         ir_node *value;
 151
 152         assert(n_vals > 0);
 153
 154         irg = get_irn_irg(vals[0]);
 155         inc_irg_visited(irg);
 156
 157         mode = get_irn_mode(vals[0]);
 158         for(i = 0; i < n_vals; ++i) {
 159                 ir_node *value = vals[i];
 160                 ir_node *value_block = blocks[i];
 161
 162                 assert(get_irn_mode(value) == mode);
 163
 164                 set_irn_link(value_block, value);
 165                 mark_irn_visited(value_block);
 166         }
 167
 168         // Only fix the users of the first, i.e. the original node
 169         value = vals[0];
 170
 171         // this can happen when fixing phi preds, we mustn't fix the users
 172         if(get_nodes_block(value) != blocks[0]) return;
 173
 174         foreach_out_edge_safe(value, edge, next) {
 175                 ir_node *user = get_edge_src_irn(edge);
 176                 int j = get_edge_src_pos(edge);
 177                 ir_node *user_block = get_nodes_block(user);
 178                 ir_node *newval;
 179
 180                 // ignore keeps
 181                 if(get_irn_op(user) == op_End)
 182                         continue;
 183
 184                 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
 185
 186                 if(is_Phi(user)) {
 187                         ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 188                         newval = search_def_and_create_phis(pred_block, mode);
 189                 } else {
 190                         newval = search_def_and_create_phis(user_block, mode);
 191                 }
 192
 193                 // don't fix newly created phis from the SSA construction
 194                 if (newval != user) {
 195                         DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
 196                         set_irn_n(user, j, newval);
 197                 }
 198         }
 199 }
 200
 201 static void split_critical_edge(ir_node *block, int pos) {
 202         ir_graph *irg = get_irn_irg(block);
 203         ir_node *in[1];
 204         ir_node *new_block;
 205         ir_node *new_jmp;
 206
 207         in[0] = get_Block_cfgpred(block, pos);
 208         new_block = new_r_Block(irg, 1, in);
 209         new_jmp = new_r_Jmp(irg, new_block);
 210         set_Block_cfgpred(block, pos, new_jmp);
 211 }
 212
 213 typedef struct _condeval_env_t {
 214         ir_node *true_block;
 215         pn_Cmp pnc;
 216         ir_node *cnst;
 217         unsigned long visited_nr;
 218
 219         ir_node *cnst_pred;     /**< the block before the constant */
 220         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 221 } condeval_env_t;
 222
 223 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 224         const ir_edge_t *edge;
 225
 226         /* Look at all nodes in the cond_block and copy them into pred */
 227         foreach_out_edge(block, edge) {
 228                 ir_node *node = get_edge_src_irn(edge);
 229                 ir_node *copy;
 230                 ir_mode *mode = get_irn_mode(node);
 231
 232                 /* ignore control flow */
 233                 if (mode == mode_X)
 234                         continue;
 235                 /* we may not copy mode_b nodes, because this could produce phi with mode_bs which can't
 236                    be handled in all backends. Instead we duplicate the node and move it to it's users */
 237                 if (mode == mode_b) {
 238                         const ir_edge_t *edge, *next;
 239                         ir_node *pred;
 240                         int      pn;
 241
 242                         assert(is_Proj(node));
 243
 244                         pred = get_Proj_pred(node);
 245                         pn   = get_Proj_proj(node);
 246
 247                         foreach_out_edge_safe(node, edge, next) {
 248                                 ir_node *cmp_copy;
 249                                 ir_node *user       = get_edge_src_irn(edge);
 250                                 int pos             = get_edge_src_pos(edge);
 251                                 ir_node *user_block = get_nodes_block(user);
 252
 253                                 if(user_block == block)
 254                                         continue;
 255
 256                                 cmp_copy = exact_copy(pred);
 257                                 set_nodes_block(cmp_copy, user_block);
 258                                 copy = new_r_Proj(current_ir_graph, user_block, cmp_copy, mode_b, pn);
 259                                 set_irn_n(user, pos, copy);
 260                         }
 261                         continue;
 262                 }
 263
 264                 /* we can evaluate Phis right now, all other nodes get copied */
 265                 if (is_Phi(node)) {
 266                         copy = get_Phi_pred(node, j);
 267                 } else {
 268                         copy = exact_copy(node);
 269                         set_nodes_block(copy, copy_block);
 270                 }
 271
 272                 set_irn_link(node, copy);
 273                 set_irn_visited(node, env->visited_nr);
 274
 275                 /* we might hit values in blocks that have already been processed by a
 276                  * recursive find_phi_with_const call */
 277                 assert(get_irn_visited(copy) <= env->visited_nr);
 278                 if(get_irn_visited(copy) >= env->visited_nr) {
 279                         ir_node *prev_copy = get_irn_link(copy);
 280                         if(prev_copy != NULL)
 281                                 set_irn_link(node, prev_copy);
 282                 }
 283         }
 284
 285         /* fix data-flow (and reconstruct SSA if needed) */
 286         foreach_out_edge(block, edge) {
 287                 ir_node *vals[2];
 288                 ir_node *blocks[2];
 289                 ir_node *node = get_edge_src_irn(edge);
 290                 ir_mode *mode = get_irn_mode(node);
 291
 292                 if (mode == mode_X)
 293                         continue;
 294                 if (mode == mode_b)
 295                         continue;
 296
 297                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 298
 299                 blocks[0] = block;
 300                 vals[0] = node;
 301                 blocks[1] = copy_block;
 302                 vals[1] = get_irn_link(node);
 303                 construct_ssa(blocks, vals, 2);
 304         }
 305 }
 306
 307 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 308         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 309
 310         // does the compare evaluate to true?
 311         if(cmp_result == pn_Cmp_False)
 312                 return 0;
 313         if((cmp_result & pnc) != cmp_result)
 314                 return 0;
 315
 316         return 1;
 317 }
 318
 319 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 320         ir_node *block = get_nodes_block(jump);
 321
 322         if(irn_visited(value))
 323                 return NULL;
 324         mark_irn_visited(value);
 325
 326         if(is_Const(value)) {
 327                 tarval *tv_const = get_Const_tarval(env->cnst);
 328                 tarval *tv = get_Const_tarval(value);
 329
 330                 if(!eval_cmp(env->pnc, tv, tv_const))
 331                         return NULL;
 332
 333                 DB((
 334                         dbg, LEVEL_1,
 335                         "> Found condition evaluation candidate %+F->%+F\n",
 336                         env->true_block, block
 337                 ));
 338
 339                 // adjust true_block to point directly towards our jump
 340                 add_pred(env->true_block, jump);
 341
 342                 split_critical_edge(env->true_block, 0);
 343
 344                 // we need a bigger visited nr when going back
 345                 env->visited_nr++;
 346
 347                 return block;
 348         }
 349
 350         if(is_Phi(value)) {
 351                 int i, arity;
 352
 353                 // the phi has to be in the same block as the jump
 354                 if(get_nodes_block(value) != block)
 355                         return NULL;
 356
 357                 arity = get_irn_arity(value);
 358                 for(i = 0; i < arity; ++i) {
 359                         ir_node *copy_block;
 360                         ir_node *phi_pred = get_Phi_pred(value, i);
 361                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 362
 363                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 364                         if(copy_block == NULL)
 365                                 continue;
 366
 367                         /* copy duplicated nodes in copy_block and fix SSA */
 368                         copy_and_fix(block, copy_block, i, env);
 369
 370                         if(copy_block == get_nodes_block(cfgpred)) {
 371                                 env->cnst_pred = block;
 372                                 env->cnst_pos = i;
 373                         }
 374
 375                         // return now as we can't process more possibilities in 1 run
 376                         return copy_block;
 377                 }
 378         }
 379
 380         return NULL;
 381 }
 382
 383
 384 /**
 385  * Block-walker: searchs for the following construct
 386  *
 387  *  Const or Phi with constants
 388  *           |
 389  *          Cmp
 390  *           |
 391  *         Cond
 392  *          /
 393  *       ProjX
 394  *        /
 395  *     Block
 396  */
 397 static void cond_eval(ir_node* block, void* data)
 398 {
 399         condeval_env_t env;
 400         int *changed = data;
 401         ir_graph *irg = current_ir_graph;
 402         ir_node *copy_block;
 403         ir_node *pred;
 404         ir_node *projx;
 405         ir_node *cond;
 406         ir_node *cmp;
 407         ir_node *left;
 408         ir_node *right;
 409         ir_node *cond_block;
 410         pn_Cmp pnc;
 411
 412         if(get_Block_n_cfgpreds(block) != 1)
 413                 return;
 414
 415         projx = get_Block_cfgpred(block, 0);
 416         if (!is_Proj(projx))
 417                 return;
 418         assert(get_irn_mode(projx) == mode_X);
 419
 420         cond = get_Proj_pred(projx);
 421         if (!is_Cond(cond))
 422                 return;
 423
 424         pred = get_Cond_selector(cond);
 425         // TODO handle switches
 426         if (get_irn_mode(pred) != mode_b)
 427                 return;
 428         if (!is_Proj(pred))
 429                 return;
 430         pnc = get_Proj_proj(pred);
 431
 432         cmp = get_Proj_pred(pred);
 433         assert(is_Cmp(cmp));
 434
 435         left  = get_Cmp_left(cmp);
 436         right = get_Cmp_right(cmp);
 437         assert(get_irn_mode(left) == get_irn_mode(right));
 438
 439         /* we assume that the cond_block is the true case */
 440         if (get_Proj_proj(projx) == pn_Cond_false) {
 441                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 442         }
 443
 444         /* we assume that the constant is on the right side, swap left/right
 445          * if needed */
 446         if(is_Const(left)) {
 447                 ir_node *t = left;
 448                 left = right;
 449                 right = t;
 450
 451                 pnc = get_inversed_pnc(pnc);
 452         }
 453
 454         if(!is_Const(right))
 455                 return;
 456
 457         cond_block = get_nodes_block(cond);
 458
 459         // special case: comparing a constant with a constant
 460         if(is_Const(left)) {
 461                 tarval *tv1 = get_Const_tarval(left);
 462                 tarval *tv2 = get_Const_tarval(right);
 463                 ir_node *pred;
 464                 if(eval_cmp(pnc, tv1, tv2)) {
 465                         pred = new_r_Jmp(irg, cond_block);
 466                 } else {
 467                         pred = new_Bad();
 468                 }
 469                 set_Block_cfgpred(block, 0, pred);
 470                 *changed = 1;
 471                 set_irg_doms_inconsistent(irg);
 472                 set_irg_extblk_inconsistent(irg);
 473                 set_irg_loopinfo_inconsistent(irg);
 474         } else {
 475                 if(get_nodes_block(left) != cond_block)
 476                         return;
 477
 478                 // (recursively) look if a pred of a phi is a constant
 479                 env.true_block = block;
 480                 env.pnc = pnc;
 481                 env.cnst = right;
 482                 inc_irg_visited(current_ir_graph);
 483                 env.visited_nr = get_irg_visited(irg);
 484
 485                 copy_block = find_phi_with_const(projx, left, &env);
 486
 487                 if(copy_block != NULL) {
 488                         /* we have to remove the edge towards the pred as the pred now
 489                          * jumps into the true_block. We also have to shorten phis
 490                          * in our block because of this */
 491                         const ir_edge_t *edge, *next;
 492
 493                         /* shorten phis */
 494                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 495                                 ir_node *node = get_edge_src_irn(edge);
 496
 497                                 if(is_Phi(node))
 498                                         remove_pred(node, env.cnst_pos);
 499                         }
 500
 501                         remove_pred(env.cnst_pred, env.cnst_pos);
 502
 503                         // the graph is changed now
 504                         *changed = 1;
 505                         set_irg_doms_inconsistent(irg);
 506                         set_irg_extblk_inconsistent(irg);
 507                         set_irg_loopinfo_inconsistent(irg);
 508                 }
 509         }
 510 }
 511
 512 void opt_cond_eval(ir_graph* irg)
 513 {
 514         int changed;
 515
 516         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 517
 518         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 519
 520         edges_assure(irg);
 521         remove_critical_cf_edges(irg);
 522
 523         normalize_proj_nodes(irg);
 524
 525         set_using_irn_link(irg);
 526         set_using_visited(irg);
 527
 528         do {
 529                 changed = 0;
 530                 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
 531         } while(changed);
 532
 533         clear_using_visited(irg);
 534         clear_using_irn_link(irg);
 535 }