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