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 "tv.h"
  29
  30 DEBUG_ONLY(static firm_dbg_module_t *dbg);
  31
  32 /**
  33  * Add the new predecessor x to node node, which is either a Block or a Phi
  34  */
  35 static void add_pred(ir_node* node, ir_node* x)
  36 {
  37         ir_node** ins;
  38         int n;
  39         int i;
  40
  41         assert(is_Block(node) || is_Phi(node));
  42
  43         n = get_irn_arity(node);
  44         NEW_ARR_A(ir_node*, ins, n + 1);
  45         for (i = 0; i < n; i++)
  46                 ins[i] = get_irn_n(node, i);
  47         ins[n] = x;
  48         set_irn_in(node, n + 1, ins);
  49 }
  50
  51 /**
  52  * Remove predecessor j from node, which is either a Block or a Phi
  53  * returns true if only one predecessor is left
  54  */
  55 static int remove_pred(ir_node* node, int j)
  56 {
  57         int n;
  58
  59         assert(is_Block(node) || is_Phi(node));
  60
  61         n = get_irn_arity(node);
  62         if (n == 2) {
  63                 ir_node* pred = get_irn_n(node, 1 - j);
  64
  65                 if (is_Block(node)) {
  66                         pred = get_nodes_block(pred);
  67                         edges_reroute(node, pred, current_ir_graph);
  68                 } else {
  69                         exchange(node, pred);
  70                 }
  71                 return 1;
  72         } else {
  73                 ir_node** ins;
  74                 int i;
  75
  76                 NEW_ARR_A(ir_node*, ins, n - 1);
  77                 for (i = 0; i < j; i++)
  78                         ins[i] = get_irn_n(node, i);
  79                 for (i++; i < n; i++)
  80                         ins[i - 1] = get_irn_n(node, i);
  81
  82                 set_irn_in(node, n - 1, ins);
  83                 return 0;
  84         }
  85 }
  86
  87 static ir_node *search_def_and_create_phis(ir_node *block, ir_mode *mode)
  88 {
  89         int i;
  90         int n_cfgpreds;
  91         ir_graph *irg;
  92         ir_node *phi;
  93         ir_node **in;
  94
  95         // This is needed because we create bads sometimes
  96         if(is_Bad(block))
  97                 return new_Bad();
  98
  99         // already processed this block?
 100         if(irn_visited(block)) {
 101                 ir_node *value = (ir_node*) get_irn_link(block);
 102                 return value;
 103         }
 104
 105         // blocks with only 1 pred need no phi
 106         n_cfgpreds = get_Block_n_cfgpreds(block);
 107         if(n_cfgpreds == 1) {
 108                 ir_node *pred_block = get_Block_cfgpred_block(block, 0);
 109                 ir_node *value = search_def_and_create_phis(pred_block, mode);
 110
 111                 set_irn_link(block, value);
 112                 mark_irn_visited(block);
 113                 return value;
 114         }
 115
 116         // create a new phi
 117         NEW_ARR_A(ir_node*, in, n_cfgpreds);
 118         for(i = 0; i < n_cfgpreds; ++i)
 119                 in[i] = new_Unknown(mode);
 120
 121         irg = get_irn_irg(block);
 122         phi = new_r_Phi(irg, block, n_cfgpreds, in, mode);
 123         set_irn_link(block, phi);
 124         mark_irn_visited(block);
 125
 126         // set phi preds
 127         for(i = 0; i < n_cfgpreds; ++i) {
 128                 ir_node *pred_block = get_Block_cfgpred_block(block, i);
 129                 ir_node *pred_val = search_def_and_create_phis(pred_block, mode);
 130
 131                 set_irn_n(phi, i, pred_val);
 132         }
 133
 134         return phi;
 135 }
 136
 137 /**
 138  * Given a set of values this function constructs SSA-form for all users of the
 139  * values (the user are determined through the out-edges of the values). Uses
 140  * the irn_visited flags. Works without using the dominance tree.
 141  */
 142 static void construct_ssa(ir_node * const *blocks, ir_node * const *vals, int n_vals)
 143 {
 144         int i;
 145         ir_graph *irg;
 146         ir_mode *mode;
 147
 148         assert(n_vals > 0);
 149
 150         irg = get_irn_irg(vals[0]);
 151         inc_irg_visited(irg);
 152
 153         mode = get_irn_mode(vals[0]);
 154         for(i = 0; i < n_vals; ++i) {
 155                 ir_node *value = vals[i];
 156                 ir_node *value_block = blocks[i];
 157
 158                 assert(get_irn_mode(value) == mode);
 159
 160                 set_irn_link(value_block, value);
 161                 mark_irn_visited(value_block);
 162         }
 163
 164         for(i = 0; i < n_vals; ++i) {
 165                 const ir_edge_t *edge, *next;
 166                 ir_node *value = vals[i];
 167
 168                 // this can happen when fixing phi preds, we mustn't fix the users
 169                 if(get_nodes_block(value) != blocks[i]) {
 170                         continue;
 171                 }
 172
 173                 foreach_out_edge_safe(value, edge, next) {
 174                         ir_node *user = get_edge_src_irn(edge);
 175                         int j = get_edge_src_pos(edge);
 176                         ir_node *user_block = get_nodes_block(user);
 177                         ir_node *newval;
 178
 179                         // ignore keeps
 180                         if(get_irn_op(user) == op_End)
 181                                 continue;
 182
 183                         if(is_Phi(user)) {
 184                                 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 185                                 newval = search_def_and_create_phis(pred_block, mode);
 186                         } else {
 187                                 newval = search_def_and_create_phis(user_block, mode);
 188                         }
 189
 190                         // don't fix newly created phis from the SSA construction
 191                         if(newval != user)
 192                                 set_irn_n(user, j, newval);
 193                 }
 194         }
 195 }
 196
 197 static void split_critical_edge(ir_node *block, int pos) {
 198         ir_graph *irg = get_irn_irg(block);
 199         ir_node *in[1];
 200         ir_node *new_block;
 201         ir_node *new_jmp;
 202
 203         in[0] = get_Block_cfgpred(block, pos);
 204         new_block = new_r_Block(irg, 1, in);
 205         new_jmp = new_r_Jmp(irg, new_block);
 206         set_Block_cfgpred(block, pos, new_jmp);
 207 }
 208
 209 typedef struct _condeval_env_t {
 210         ir_node *true_block;
 211         pn_Cmp pnc;
 212         ir_node *cnst;
 213         unsigned long visited_nr;
 214
 215         ir_node *cnst_pred;     /**< the block before the constant */
 216         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 217 } condeval_env_t;
 218
 219 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 220         const ir_edge_t *edge;
 221
 222         /* Look at all nodes in the cond_block and copy them into pred */
 223         foreach_out_edge(block, edge) {
 224                 ir_node *node = get_edge_src_irn(edge);
 225                 ir_node *copy;
 226
 227                 /* ignore control flow */
 228                 if (get_irn_mode(node) == mode_X)
 229                         continue;
 230
 231                 /* we can evaluate Phis right now, all other nodes get copied */
 232                 if (is_Phi(node)) {
 233                         copy = get_Phi_pred(node, j);
 234                 } else {
 235                         copy = exact_copy(node);
 236                         set_nodes_block(copy, copy_block);
 237                 }
 238
 239                 set_irn_link(node, copy);
 240                 set_irn_visited(node, env->visited_nr);
 241
 242                 /* we might hit values in blocks that have already been processed by a
 243                  * recursive find_phi_with_const call */
 244                 assert(get_irn_visited(copy) <= env->visited_nr);
 245                 if(get_irn_visited(copy) >= env->visited_nr) {
 246                         ir_node *prev_copy = get_irn_link(copy);
 247                         if(prev_copy != NULL)
 248                                 set_irn_link(node, prev_copy);
 249                 }
 250         }
 251
 252         /* fix data-flow (and reconstruct SSA if needed) */
 253         foreach_out_edge(block, edge) {
 254                 ir_node *vals[2];
 255                 ir_node *blocks[2];
 256
 257                 ir_node *node = get_edge_src_irn(edge);
 258
 259                 if (get_irn_mode(node) == mode_X)
 260                         continue;
 261
 262                 blocks[0] = block;
 263                 vals[0] = node;
 264                 blocks[1] = copy_block;
 265                 vals[1] = get_irn_link(node);
 266                 construct_ssa(blocks, vals, 2);
 267         }
 268 }
 269
 270 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 271         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 272
 273         // does the compare evaluate to true?
 274         if(cmp_result == pn_Cmp_False)
 275                 return 0;
 276         if((cmp_result & pnc) != cmp_result)
 277                 return 0;
 278
 279         return 1;
 280 }
 281
 282 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 283         ir_node *block = get_nodes_block(jump);
 284
 285         if(irn_visited(value))
 286                 return NULL;
 287         mark_irn_visited(value);
 288
 289         if(is_Const(value)) {
 290                 tarval *tv_const = get_Const_tarval(env->cnst);
 291                 tarval *tv = get_Const_tarval(value);
 292
 293                 if(!eval_cmp(env->pnc, tv, tv_const))
 294                         return NULL;
 295
 296                 DB((
 297                         dbg, LEVEL_1,
 298                         "> Found condition evaluation candidate %+F->%+F\n",
 299                         env->true_block, block
 300                 ));
 301
 302                 // adjust true_block to point directly towards our jump
 303                 add_pred(env->true_block, jump);
 304
 305                 split_critical_edge(env->true_block, 0);
 306
 307                 // we need a bigger visited nr when going back
 308                 env->visited_nr++;
 309
 310                 return block;
 311         }
 312
 313         if(is_Phi(value)) {
 314                 int i, arity;
 315
 316                 // the phi has to be in the same block as the jump
 317                 if(get_nodes_block(value) != block)
 318                         return NULL;
 319
 320                 arity = get_irn_arity(value);
 321                 for(i = 0; i < arity; ++i) {
 322                         ir_node *copy_block;
 323                         ir_node *phi_pred = get_Phi_pred(value, i);
 324                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 325
 326                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 327                         if(copy_block == NULL)
 328                                 continue;
 329
 330                         /* copy duplicated nodes in copy_block and fix SSA */
 331                         copy_and_fix(block, copy_block, i, env);
 332
 333                         if(copy_block == get_nodes_block(cfgpred)) {
 334                                 env->cnst_pred = block;
 335                                 env->cnst_pos = i;
 336                         }
 337
 338                         // return now as we can't process more possibilities in 1 run
 339                         return copy_block;
 340                 }
 341         }
 342
 343         return NULL;
 344 }
 345
 346
 347 /**
 348  * Block-walker: searchs for the following construct
 349  *
 350  *  Const or Phi with constants
 351  *           |
 352  *          Cmp
 353  *           |
 354  *         Cond
 355  *          /
 356  *       ProjX
 357  *        /
 358  *     Block
 359  */
 360 static void cond_eval(ir_node* block, void* data)
 361 {
 362         condeval_env_t env;
 363         int *changed = data;
 364         ir_graph *irg = current_ir_graph;
 365         ir_node *copy_block;
 366         ir_node *pred;
 367         ir_node *projx;
 368         ir_node *cond;
 369         ir_node *cmp;
 370         ir_node *left;
 371         ir_node *right;
 372         ir_node *cond_block;
 373         pn_Cmp pnc;
 374
 375         if(get_Block_n_cfgpreds(block) != 1)
 376                 return;
 377
 378         projx = get_Block_cfgpred(block, 0);
 379         if (!is_Proj(projx))
 380                 return;
 381         assert(get_irn_mode(projx) == mode_X);
 382
 383         cond = get_Proj_pred(projx);
 384         if (!is_Cond(cond))
 385                 return;
 386
 387         pred = get_Cond_selector(cond);
 388         // TODO handle switches
 389         if (get_irn_mode(pred) != mode_b)
 390                 return;
 391         if (!is_Proj(pred))
 392                 return;
 393         pnc = get_Proj_proj(pred);
 394
 395         cmp = get_Proj_pred(pred);
 396         assert(is_Cmp(cmp));
 397
 398         left  = get_Cmp_left(cmp);
 399         right = get_Cmp_right(cmp);
 400         assert(get_irn_mode(left) == get_irn_mode(right));
 401
 402         /* we assume that the cond_block is the true case */
 403         if (get_Proj_proj(projx) == pn_Cond_false) {
 404                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 405         }
 406
 407         /* we assume that the constant is on the right side, swap left/right
 408          * if needed */
 409         if(is_Const(left)) {
 410                 ir_node *t = left;
 411                 left = right;
 412                 right = t;
 413
 414                 pnc = get_inversed_pnc(pnc);
 415         }
 416
 417         if(!is_Const(right))
 418                 return;
 419
 420         cond_block = get_nodes_block(cond);
 421
 422         // special case: comparing a constant with a constant
 423         if(is_Const(left)) {
 424                 tarval *tv1 = get_Const_tarval(left);
 425                 tarval *tv2 = get_Const_tarval(right);
 426                 ir_node *pred;
 427                 if(eval_cmp(pnc, tv1, tv2)) {
 428                         pred = new_r_Jmp(irg, cond_block);
 429                 } else {
 430                         pred = new_Bad();
 431                 }
 432                 set_Block_cfgpred(block, 0, pred);
 433                 *changed = 1;
 434                 set_irg_doms_inconsistent(irg);
 435                 set_irg_extblk_inconsistent(irg);
 436                 set_irg_loopinfo_inconsistent(irg);
 437         } else {
 438                 if(get_nodes_block(left) != cond_block)
 439                         return;
 440
 441                 // (recursively) look if a pred of a phi is a constant
 442                 env.true_block = block;
 443                 env.pnc = pnc;
 444                 env.cnst = right;
 445                 inc_irg_visited(current_ir_graph);
 446                 env.visited_nr = get_irg_visited(irg);
 447
 448                 copy_block = find_phi_with_const(projx, left, &env);
 449
 450                 if(copy_block != NULL) {
 451                         /* we have to remove the edge towards the pred as the pred now
 452                          * jumps into the true_block. We also have to shorten phis
 453                          * in our block because of this */
 454                         const ir_edge_t *edge, *next;
 455
 456                         /* shorten phis */
 457                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 458                                 ir_node *node = get_edge_src_irn(edge);
 459
 460                                 if(is_Phi(node))
 461                                         remove_pred(node, env.cnst_pos);
 462                         }
 463
 464                         remove_pred(env.cnst_pred, env.cnst_pos);
 465
 466                         // the graph is changed now
 467                         *changed = 1;
 468                         set_irg_doms_inconsistent(irg);
 469                         set_irg_extblk_inconsistent(irg);
 470                         set_irg_loopinfo_inconsistent(irg);
 471                 }
 472         }
 473 }
 474
 475 void opt_cond_eval(ir_graph* irg)
 476 {
 477         int changed;
 478
 479         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 480         //firm_dbg_set_mask(dbg, SET_LEVEL_5);
 481
 482         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 483
 484         edges_assure(irg);
 485         remove_critical_cf_edges(irg);
 486
 487         normalize_proj_nodes(irg);
 488
 489         do {
 490                 changed = 0;
 491                 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
 492         } while(changed);
 493 }