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
 231                 /* ignore control flow */
 232                 if (get_irn_mode(node) == mode_X)
 233                         continue;
 234
 235                 /* we can evaluate Phis right now, all other nodes get copied */
 236                 if (is_Phi(node)) {
 237                         copy = get_Phi_pred(node, j);
 238                 } else {
 239                         copy = exact_copy(node);
 240                         set_nodes_block(copy, copy_block);
 241                 }
 242
 243                 set_irn_link(node, copy);
 244                 set_irn_visited(node, env->visited_nr);
 245
 246                 /* we might hit values in blocks that have already been processed by a
 247                  * recursive find_phi_with_const call */
 248                 assert(get_irn_visited(copy) <= env->visited_nr);
 249                 if(get_irn_visited(copy) >= env->visited_nr) {
 250                         ir_node *prev_copy = get_irn_link(copy);
 251                         if(prev_copy != NULL)
 252                                 set_irn_link(node, prev_copy);
 253                 }
 254         }
 255
 256         /* fix data-flow (and reconstruct SSA if needed) */
 257         foreach_out_edge(block, edge) {
 258                 ir_node *vals[2];
 259                 ir_node *blocks[2];
 260
 261                 ir_node *node = get_edge_src_irn(edge);
 262
 263                 if (get_irn_mode(node) == mode_X)
 264                         continue;
 265
 266                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 267
 268                 blocks[0] = block;
 269                 vals[0] = node;
 270                 blocks[1] = copy_block;
 271                 vals[1] = get_irn_link(node);
 272                 construct_ssa(blocks, vals, 2);
 273         }
 274 }
 275
 276 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 277         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 278
 279         // does the compare evaluate to true?
 280         if(cmp_result == pn_Cmp_False)
 281                 return 0;
 282         if((cmp_result & pnc) != cmp_result)
 283                 return 0;
 284
 285         return 1;
 286 }
 287
 288 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 289         ir_node *block = get_nodes_block(jump);
 290
 291         if(irn_visited(value))
 292                 return NULL;
 293         mark_irn_visited(value);
 294
 295         if(is_Const(value)) {
 296                 tarval *tv_const = get_Const_tarval(env->cnst);
 297                 tarval *tv = get_Const_tarval(value);
 298
 299                 if(!eval_cmp(env->pnc, tv, tv_const))
 300                         return NULL;
 301
 302                 DB((
 303                         dbg, LEVEL_1,
 304                         "> Found condition evaluation candidate %+F->%+F\n",
 305                         env->true_block, block
 306                 ));
 307
 308                 // adjust true_block to point directly towards our jump
 309                 add_pred(env->true_block, jump);
 310
 311                 split_critical_edge(env->true_block, 0);
 312
 313                 // we need a bigger visited nr when going back
 314                 env->visited_nr++;
 315
 316                 return block;
 317         }
 318
 319         if(is_Phi(value)) {
 320                 int i, arity;
 321
 322                 // the phi has to be in the same block as the jump
 323                 if(get_nodes_block(value) != block)
 324                         return NULL;
 325
 326                 arity = get_irn_arity(value);
 327                 for(i = 0; i < arity; ++i) {
 328                         ir_node *copy_block;
 329                         ir_node *phi_pred = get_Phi_pred(value, i);
 330                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 331
 332                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 333                         if(copy_block == NULL)
 334                                 continue;
 335
 336                         /* copy duplicated nodes in copy_block and fix SSA */
 337                         copy_and_fix(block, copy_block, i, env);
 338
 339                         if(copy_block == get_nodes_block(cfgpred)) {
 340                                 env->cnst_pred = block;
 341                                 env->cnst_pos = i;
 342                         }
 343
 344                         // return now as we can't process more possibilities in 1 run
 345                         return copy_block;
 346                 }
 347         }
 348
 349         return NULL;
 350 }
 351
 352
 353 /**
 354  * Block-walker: searchs for the following construct
 355  *
 356  *  Const or Phi with constants
 357  *           |
 358  *          Cmp
 359  *           |
 360  *         Cond
 361  *          /
 362  *       ProjX
 363  *        /
 364  *     Block
 365  */
 366 static void cond_eval(ir_node* block, void* data)
 367 {
 368         condeval_env_t env;
 369         int *changed = data;
 370         ir_graph *irg = current_ir_graph;
 371         ir_node *copy_block;
 372         ir_node *pred;
 373         ir_node *projx;
 374         ir_node *cond;
 375         ir_node *cmp;
 376         ir_node *left;
 377         ir_node *right;
 378         ir_node *cond_block;
 379         pn_Cmp pnc;
 380
 381         if(get_Block_n_cfgpreds(block) != 1)
 382                 return;
 383
 384         projx = get_Block_cfgpred(block, 0);
 385         if (!is_Proj(projx))
 386                 return;
 387         assert(get_irn_mode(projx) == mode_X);
 388
 389         cond = get_Proj_pred(projx);
 390         if (!is_Cond(cond))
 391                 return;
 392
 393         pred = get_Cond_selector(cond);
 394         // TODO handle switches
 395         if (get_irn_mode(pred) != mode_b)
 396                 return;
 397         if (!is_Proj(pred))
 398                 return;
 399         pnc = get_Proj_proj(pred);
 400
 401         cmp = get_Proj_pred(pred);
 402         assert(is_Cmp(cmp));
 403
 404         left  = get_Cmp_left(cmp);
 405         right = get_Cmp_right(cmp);
 406         assert(get_irn_mode(left) == get_irn_mode(right));
 407
 408         /* we assume that the cond_block is the true case */
 409         if (get_Proj_proj(projx) == pn_Cond_false) {
 410                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 411         }
 412
 413         /* we assume that the constant is on the right side, swap left/right
 414          * if needed */
 415         if(is_Const(left)) {
 416                 ir_node *t = left;
 417                 left = right;
 418                 right = t;
 419
 420                 pnc = get_inversed_pnc(pnc);
 421         }
 422
 423         if(!is_Const(right))
 424                 return;
 425
 426         cond_block = get_nodes_block(cond);
 427
 428         // special case: comparing a constant with a constant
 429         if(is_Const(left)) {
 430                 tarval *tv1 = get_Const_tarval(left);
 431                 tarval *tv2 = get_Const_tarval(right);
 432                 ir_node *pred;
 433                 if(eval_cmp(pnc, tv1, tv2)) {
 434                         pred = new_r_Jmp(irg, cond_block);
 435                 } else {
 436                         pred = new_Bad();
 437                 }
 438                 set_Block_cfgpred(block, 0, pred);
 439                 *changed = 1;
 440                 set_irg_doms_inconsistent(irg);
 441                 set_irg_extblk_inconsistent(irg);
 442                 set_irg_loopinfo_inconsistent(irg);
 443         } else {
 444                 if(get_nodes_block(left) != cond_block)
 445                         return;
 446
 447                 // (recursively) look if a pred of a phi is a constant
 448                 env.true_block = block;
 449                 env.pnc = pnc;
 450                 env.cnst = right;
 451                 inc_irg_visited(current_ir_graph);
 452                 env.visited_nr = get_irg_visited(irg);
 453
 454                 copy_block = find_phi_with_const(projx, left, &env);
 455
 456                 if(copy_block != NULL) {
 457                         /* we have to remove the edge towards the pred as the pred now
 458                          * jumps into the true_block. We also have to shorten phis
 459                          * in our block because of this */
 460                         const ir_edge_t *edge, *next;
 461
 462                         /* shorten phis */
 463                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 464                                 ir_node *node = get_edge_src_irn(edge);
 465
 466                                 if(is_Phi(node))
 467                                         remove_pred(node, env.cnst_pos);
 468                         }
 469
 470                         remove_pred(env.cnst_pred, env.cnst_pos);
 471
 472                         // the graph is changed now
 473                         *changed = 1;
 474                         set_irg_doms_inconsistent(irg);
 475                         set_irg_extblk_inconsistent(irg);
 476                         set_irg_loopinfo_inconsistent(irg);
 477                 }
 478         }
 479 }
 480
 481 void opt_cond_eval(ir_graph* irg)
 482 {
 483         int changed;
 484
 485         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 486
 487         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 488
 489         edges_assure(irg);
 490         remove_critical_cf_edges(irg);
 491
 492         normalize_proj_nodes(irg);
 493
 494         set_using_irn_link(irg);
 495         set_using_visited(irg);
 496
 497         do {
 498                 changed = 0;
 499                 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
 500         } while(changed);
 501
 502         clear_using_visited(irg);
 503         clear_using_irn_link(irg);
 504 }