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         in = alloca(sizeof(in[0]) * 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;
 130
 131                 pred_val = search_def_and_create_phis(pred_block, mode);
 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 all users of the
 140  * values (the user are determined through the out-edges of the values). Uses
 141  * 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
 149         assert(n_vals > 0);
 150
 151         irg = get_irn_irg(vals[0]);
 152         inc_irg_visited(irg);
 153
 154         mode = get_irn_mode(vals[0]);
 155         for(i = 0; i < n_vals; ++i) {
 156                 ir_node *value = vals[i];
 157                 ir_node *value_block = blocks[i];
 158
 159                 assert(get_irn_mode(value) == mode);
 160
 161                 set_irn_link(value_block, value);
 162                 mark_irn_visited(value_block);
 163         }
 164
 165         for(i = 0; i < n_vals; ++i) {
 166                 const ir_edge_t *edge, *next;
 167                 ir_node *value = vals[i];
 168
 169                 // this can happen when fixing phi preds, we mustn't fix the users
 170                 if(get_nodes_block(value) != blocks[i]) {
 171                         continue;
 172                 }
 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                         if(is_Phi(user)) {
 185                                 ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 186                                 newval = search_def_and_create_phis(pred_block, mode);
 187                         } else {
 188                                 newval = search_def_and_create_phis(user_block, mode);
 189                         }
 190
 191                         // don't fix newly created phis from the SSA construction
 192                         if(newval != user)
 193                                 set_irn_n(user, j, newval);
 194                 }
 195         }
 196 }
 197
 198 static void split_critical_edge(ir_node *block, int pos) {
 199         ir_graph *irg = get_irn_irg(block);
 200         ir_node *in[1];
 201         ir_node *new_block;
 202         ir_node *new_jmp;
 203
 204         in[0] = get_Block_cfgpred(block, pos);
 205         new_block = new_r_Block(irg, 1, in);
 206         new_jmp = new_r_Jmp(irg, new_block);
 207         set_Block_cfgpred(block, pos, new_jmp);
 208 }
 209
 210 typedef struct _condeval_env_t {
 211         ir_node *true_block;
 212         pn_Cmp pnc;
 213         ir_node *cnst;
 214         unsigned long visited_nr;
 215
 216         ir_node *cnst_pred;     /**< the block before the constant */
 217         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 218 } condeval_env_t;
 219
 220 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 221         const ir_edge_t *edge;
 222
 223         /* Look at all nodes in the cond_block and copy them into pred */
 224         foreach_out_edge(block, edge) {
 225                 ir_node *node = get_edge_src_irn(edge);
 226                 ir_node *copy;
 227
 228                 /* ignore control flow */
 229                 if (get_irn_mode(node) == mode_X)
 230                         continue;
 231
 232                 /* we can evaluate Phis right now, all other nodes get copied */
 233                 if (is_Phi(node)) {
 234                         copy = get_Phi_pred(node, j);
 235                 } else {
 236                         copy = exact_copy(node);
 237                         set_nodes_block(copy, copy_block);
 238                 }
 239
 240                 set_irn_link(node, copy);
 241                 set_irn_visited(node, env->visited_nr);
 242
 243                 /* we might hit values in blocks that have already been processed by a
 244                  * recursive find_phi_with_const call */
 245                 assert(get_irn_visited(copy) <= env->visited_nr);
 246                 if(get_irn_visited(copy) >= env->visited_nr) {
 247                         ir_node *prev_copy = get_irn_link(copy);
 248                         if(prev_copy != NULL)
 249                                 set_irn_link(node, prev_copy);
 250                 }
 251         }
 252
 253         /* fix data-flow (and reconstruct SSA if needed) */
 254         foreach_out_edge(block, edge) {
 255                 ir_node *vals[2];
 256                 ir_node *blocks[2];
 257
 258                 ir_node *node = get_edge_src_irn(edge);
 259
 260                 if (get_irn_mode(node) == mode_X)
 261                         continue;
 262
 263                 blocks[0] = block;
 264                 vals[0] = node;
 265                 blocks[1] = copy_block;
 266                 vals[1] = get_irn_link(node);
 267                 construct_ssa(blocks, vals, 2);
 268         }
 269 }
 270
 271 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 272         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 273
 274         // does the compare evaluate to true?
 275         if(cmp_result == pn_Cmp_False)
 276                 return 0;
 277         if((cmp_result & pnc) != cmp_result)
 278                 return 0;
 279
 280         return 1;
 281 }
 282
 283 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 284         ir_node *block = get_nodes_block(jump);
 285
 286         if(irn_visited(value))
 287                 return NULL;
 288         mark_irn_visited(value);
 289
 290         if(is_Const(value)) {
 291                 tarval *tv_const = get_Const_tarval(env->cnst);
 292                 tarval *tv = get_Const_tarval(value);
 293
 294                 if(!eval_cmp(env->pnc, tv, tv_const))
 295                         return NULL;
 296
 297                 DB((
 298                         dbg, LEVEL_1,
 299                         "> Found condition evaluation candidate %+F->%+F\n",
 300                         env->true_block, block
 301                 ));
 302
 303                 // adjust true_block to point directly towards our jump
 304                 add_pred(env->true_block, jump);
 305
 306                 split_critical_edge(env->true_block, 0);
 307
 308                 // we need a bigger visited nr when going back
 309                 env->visited_nr++;
 310
 311                 return block;
 312         }
 313
 314         if(is_Phi(value)) {
 315                 int i, arity;
 316
 317                 // the phi has to be in the same block as the jump
 318                 if(get_nodes_block(value) != block)
 319                         return NULL;
 320
 321                 arity = get_irn_arity(value);
 322                 for(i = 0; i < arity; ++i) {
 323                         ir_node *copy_block;
 324                         ir_node *phi_pred = get_Phi_pred(value, i);
 325                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 326
 327                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 328                         if(copy_block == NULL)
 329                                 continue;
 330
 331                         /* copy duplicated nodes in copy_block and fix SSA */
 332                         copy_and_fix(block, copy_block, i, env);
 333
 334                         if(copy_block == get_nodes_block(cfgpred)) {
 335                                 env->cnst_pred = block;
 336                                 env->cnst_pos = i;
 337                         }
 338
 339                         // return now as we can't process more possibilities in 1 run
 340                         return copy_block;
 341                 }
 342         }
 343
 344         return NULL;
 345 }
 346
 347
 348 /**
 349  * Block-walker: searchs for the following construct
 350  *
 351  *  Const or Phi with constants
 352  *           |
 353  *          Cmp
 354  *           |
 355  *         Cond
 356  *          /
 357  *       ProjX
 358  *        /
 359  *     Block
 360  */
 361 static void cond_eval(ir_node* block, void* data)
 362 {
 363         condeval_env_t env;
 364         int *changed = data;
 365         ir_graph *irg = current_ir_graph;
 366         ir_node *copy_block;
 367         ir_node *pred;
 368         ir_node *projx;
 369         ir_node *cond;
 370         ir_node *cmp;
 371         ir_node *left;
 372         ir_node *right;
 373         ir_node *cond_block;
 374         pn_Cmp pnc;
 375
 376         if(get_Block_n_cfgpreds(block) != 1)
 377                 return;
 378
 379         projx = get_Block_cfgpred(block, 0);
 380         if (!is_Proj(projx))
 381                 return;
 382         assert(get_irn_mode(projx) == mode_X);
 383
 384         cond = get_Proj_pred(projx);
 385         if (!is_Cond(cond))
 386                 return;
 387
 388         pred = get_Cond_selector(cond);
 389         // TODO handle switches
 390         if (get_irn_mode(pred) != mode_b)
 391                 return;
 392         if (!is_Proj(pred))
 393                 return;
 394         pnc = get_Proj_proj(pred);
 395
 396         cmp = get_Proj_pred(pred);
 397         assert(is_Cmp(cmp));
 398
 399         left  = get_Cmp_left(cmp);
 400         right = get_Cmp_right(cmp);
 401         assert(get_irn_mode(left) == get_irn_mode(right));
 402
 403         /* we assume that the cond_block is the true case */
 404         if (get_Proj_proj(projx) == pn_Cond_false) {
 405                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 406         }
 407
 408         /* we assume that the constant is on the right side, swap left/right
 409          * if needed */
 410         if(is_Const(left)) {
 411                 ir_node *t = left;
 412                 left = right;
 413                 right = t;
 414
 415                 pnc = get_inversed_pnc(pnc);
 416         }
 417
 418         if(!is_Const(right))
 419                 return;
 420
 421         cond_block = get_nodes_block(cond);
 422
 423         // special case: comparing a constant with a constant
 424         if(is_Const(left)) {
 425                 tarval *tv1 = get_Const_tarval(left);
 426                 tarval *tv2 = get_Const_tarval(right);
 427                 ir_node *pred;
 428                 if(eval_cmp(pnc, tv1, tv2)) {
 429                         pred = new_r_Jmp(irg, cond_block);
 430                 } else {
 431                         pred = new_Bad();
 432                 }
 433                 set_Block_cfgpred(block, 0, pred);
 434                 *changed = 1;
 435                 set_irg_doms_inconsistent(irg);
 436                 set_irg_extblk_inconsistent(irg);
 437                 set_irg_loopinfo_inconsistent(irg);
 438         } else {
 439                 if(get_nodes_block(left) != cond_block)
 440                         return;
 441
 442                 // (recursively) look if a pred of a phi is a constant
 443                 env.true_block = block;
 444                 env.pnc = pnc;
 445                 env.cnst = right;
 446                 inc_irg_visited(current_ir_graph);
 447                 env.visited_nr = get_irg_visited(irg);
 448
 449                 copy_block = find_phi_with_const(projx, left, &env);
 450
 451                 if(copy_block != NULL) {
 452                         /* we have to remove the edge towards the pred as the pred now
 453                          * jumps into the true_block. We also have to shorten phis
 454                          * in our block because of this */
 455                         const ir_edge_t *edge, *next;
 456
 457                         /* shorten phis */
 458                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 459                                 ir_node *node = get_edge_src_irn(edge);
 460
 461                                 if(is_Phi(node))
 462                                         remove_pred(node, env.cnst_pos);
 463                         }
 464
 465                         remove_pred(env.cnst_pred, env.cnst_pos);
 466
 467                         // the graph is changed now
 468                         *changed = 1;
 469                         set_irg_doms_inconsistent(irg);
 470                         set_irg_extblk_inconsistent(irg);
 471                         set_irg_loopinfo_inconsistent(irg);
 472                 }
 473         }
 474 }
 475
 476 void opt_cond_eval(ir_graph* irg)
 477 {
 478         int changed;
 479
 480         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 481         //firm_dbg_set_mask(dbg, SET_LEVEL_5);
 482
 483         DB((dbg, LEVEL_1, "===> Performing condition evaluation on %+F\n", irg));
 484
 485         edges_assure(irg);
 486         remove_critical_cf_edges(irg);
 487
 488         normalize_proj_nodes(irg);
 489
 490         do {
 491                 changed = 0;
 492                 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
 493         } while(changed);
 494 }