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 the users of the
 139  * first value (the users are determined through the out-edges of the value).
 140  * Uses 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         const ir_edge_t *edge;
 148         const ir_edge_t *next;
 149         ir_node *value;
 150
 151         assert(n_vals > 0);
 152
 153         irg = get_irn_irg(vals[0]);
 154         inc_irg_visited(irg);
 155
 156         mode = get_irn_mode(vals[0]);
 157         for(i = 0; i < n_vals; ++i) {
 158                 ir_node *value = vals[i];
 159                 ir_node *value_block = blocks[i];
 160
 161                 assert(get_irn_mode(value) == mode);
 162
 163                 set_irn_link(value_block, value);
 164                 mark_irn_visited(value_block);
 165         }
 166
 167         // Only fix the users of the first, i.e. the original node
 168         value = vals[0];
 169
 170         // this can happen when fixing phi preds, we mustn't fix the users
 171         if(get_nodes_block(value) != blocks[0]) return;
 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                 DB((dbg, LEVEL_3, ">>> Fixing user %+F (pred %d == %+F)\n", user, j, get_irn_n(user, j)));
 184
 185                 if(is_Phi(user)) {
 186                         ir_node *pred_block = get_Block_cfgpred_block(user_block, j);
 187                         newval = search_def_and_create_phis(pred_block, mode);
 188                 } else {
 189                         newval = search_def_and_create_phis(user_block, mode);
 190                 }
 191
 192                 // don't fix newly created phis from the SSA construction
 193                 if (newval != user) {
 194                         DB((dbg, LEVEL_4, ">>>> Setting input %d of %+F to %+F\n", j, user, newval));
 195                         set_irn_n(user, j, newval);
 196                 }
 197         }
 198 }
 199
 200 static void split_critical_edge(ir_node *block, int pos) {
 201         ir_graph *irg = get_irn_irg(block);
 202         ir_node *in[1];
 203         ir_node *new_block;
 204         ir_node *new_jmp;
 205
 206         in[0] = get_Block_cfgpred(block, pos);
 207         new_block = new_r_Block(irg, 1, in);
 208         new_jmp = new_r_Jmp(irg, new_block);
 209         set_Block_cfgpred(block, pos, new_jmp);
 210 }
 211
 212 typedef struct _condeval_env_t {
 213         ir_node *true_block;
 214         pn_Cmp pnc;
 215         ir_node *cnst;
 216         unsigned long visited_nr;
 217
 218         ir_node *cnst_pred;     /**< the block before the constant */
 219         int cnst_pos;       /**< the pos to the constant block (needed to kill that edge later) */
 220 } condeval_env_t;
 221
 222 static void copy_and_fix(ir_node *block, ir_node *copy_block, int j, const condeval_env_t *env) {
 223         const ir_edge_t *edge;
 224
 225         /* Look at all nodes in the cond_block and copy them into pred */
 226         foreach_out_edge(block, edge) {
 227                 ir_node *node = get_edge_src_irn(edge);
 228                 ir_node *copy;
 229
 230                 /* ignore control flow */
 231                 if (get_irn_mode(node) == mode_X)
 232                         continue;
 233
 234                 /* we can evaluate Phis right now, all other nodes get copied */
 235                 if (is_Phi(node)) {
 236                         copy = get_Phi_pred(node, j);
 237                 } else {
 238                         copy = exact_copy(node);
 239                         set_nodes_block(copy, copy_block);
 240                 }
 241
 242                 set_irn_link(node, copy);
 243                 set_irn_visited(node, env->visited_nr);
 244
 245                 /* we might hit values in blocks that have already been processed by a
 246                  * recursive find_phi_with_const call */
 247                 assert(get_irn_visited(copy) <= env->visited_nr);
 248                 if(get_irn_visited(copy) >= env->visited_nr) {
 249                         ir_node *prev_copy = get_irn_link(copy);
 250                         if(prev_copy != NULL)
 251                                 set_irn_link(node, prev_copy);
 252                 }
 253         }
 254
 255         /* fix data-flow (and reconstruct SSA if needed) */
 256         foreach_out_edge(block, edge) {
 257                 ir_node *vals[2];
 258                 ir_node *blocks[2];
 259
 260                 ir_node *node = get_edge_src_irn(edge);
 261
 262                 if (get_irn_mode(node) == mode_X)
 263                         continue;
 264
 265                 DB((dbg, LEVEL_2, ">> Fixing users of %+F\n", node));
 266
 267                 blocks[0] = block;
 268                 vals[0] = node;
 269                 blocks[1] = copy_block;
 270                 vals[1] = get_irn_link(node);
 271                 construct_ssa(blocks, vals, 2);
 272         }
 273 }
 274
 275 static int eval_cmp(pn_Cmp pnc, tarval *tv1, tarval *tv2) {
 276         pn_Cmp cmp_result = tarval_cmp(tv1, tv2);
 277
 278         // does the compare evaluate to true?
 279         if(cmp_result == pn_Cmp_False)
 280                 return 0;
 281         if((cmp_result & pnc) != cmp_result)
 282                 return 0;
 283
 284         return 1;
 285 }
 286
 287 static ir_node *find_phi_with_const(ir_node *jump, ir_node *value, condeval_env_t *env) {
 288         ir_node *block = get_nodes_block(jump);
 289
 290         if(irn_visited(value))
 291                 return NULL;
 292         mark_irn_visited(value);
 293
 294         if(is_Const(value)) {
 295                 tarval *tv_const = get_Const_tarval(env->cnst);
 296                 tarval *tv = get_Const_tarval(value);
 297
 298                 if(!eval_cmp(env->pnc, tv, tv_const))
 299                         return NULL;
 300
 301                 DB((
 302                         dbg, LEVEL_1,
 303                         "> Found condition evaluation candidate %+F->%+F\n",
 304                         env->true_block, block
 305                 ));
 306
 307                 // adjust true_block to point directly towards our jump
 308                 add_pred(env->true_block, jump);
 309
 310                 split_critical_edge(env->true_block, 0);
 311
 312                 // we need a bigger visited nr when going back
 313                 env->visited_nr++;
 314
 315                 return block;
 316         }
 317
 318         if(is_Phi(value)) {
 319                 int i, arity;
 320
 321                 // the phi has to be in the same block as the jump
 322                 if(get_nodes_block(value) != block)
 323                         return NULL;
 324
 325                 arity = get_irn_arity(value);
 326                 for(i = 0; i < arity; ++i) {
 327                         ir_node *copy_block;
 328                         ir_node *phi_pred = get_Phi_pred(value, i);
 329                         ir_node *cfgpred = get_Block_cfgpred(block, i);
 330
 331                         copy_block = find_phi_with_const(cfgpred, phi_pred, env);
 332                         if(copy_block == NULL)
 333                                 continue;
 334
 335                         /* copy duplicated nodes in copy_block and fix SSA */
 336                         copy_and_fix(block, copy_block, i, env);
 337
 338                         if(copy_block == get_nodes_block(cfgpred)) {
 339                                 env->cnst_pred = block;
 340                                 env->cnst_pos = i;
 341                         }
 342
 343                         // return now as we can't process more possibilities in 1 run
 344                         return copy_block;
 345                 }
 346         }
 347
 348         return NULL;
 349 }
 350
 351
 352 /**
 353  * Block-walker: searchs for the following construct
 354  *
 355  *  Const or Phi with constants
 356  *           |
 357  *          Cmp
 358  *           |
 359  *         Cond
 360  *          /
 361  *       ProjX
 362  *        /
 363  *     Block
 364  */
 365 static void cond_eval(ir_node* block, void* data)
 366 {
 367         condeval_env_t env;
 368         int *changed = data;
 369         ir_graph *irg = current_ir_graph;
 370         ir_node *copy_block;
 371         ir_node *pred;
 372         ir_node *projx;
 373         ir_node *cond;
 374         ir_node *cmp;
 375         ir_node *left;
 376         ir_node *right;
 377         ir_node *cond_block;
 378         pn_Cmp pnc;
 379
 380         if(get_Block_n_cfgpreds(block) != 1)
 381                 return;
 382
 383         projx = get_Block_cfgpred(block, 0);
 384         if (!is_Proj(projx))
 385                 return;
 386         assert(get_irn_mode(projx) == mode_X);
 387
 388         cond = get_Proj_pred(projx);
 389         if (!is_Cond(cond))
 390                 return;
 391
 392         pred = get_Cond_selector(cond);
 393         // TODO handle switches
 394         if (get_irn_mode(pred) != mode_b)
 395                 return;
 396         if (!is_Proj(pred))
 397                 return;
 398         pnc = get_Proj_proj(pred);
 399
 400         cmp = get_Proj_pred(pred);
 401         assert(is_Cmp(cmp));
 402
 403         left  = get_Cmp_left(cmp);
 404         right = get_Cmp_right(cmp);
 405         assert(get_irn_mode(left) == get_irn_mode(right));
 406
 407         /* we assume that the cond_block is the true case */
 408         if (get_Proj_proj(projx) == pn_Cond_false) {
 409                 pnc = get_negated_pnc(pnc, get_irn_mode(left));
 410         }
 411
 412         /* we assume that the constant is on the right side, swap left/right
 413          * if needed */
 414         if(is_Const(left)) {
 415                 ir_node *t = left;
 416                 left = right;
 417                 right = t;
 418
 419                 pnc = get_inversed_pnc(pnc);
 420         }
 421
 422         if(!is_Const(right))
 423                 return;
 424
 425         cond_block = get_nodes_block(cond);
 426
 427         // special case: comparing a constant with a constant
 428         if(is_Const(left)) {
 429                 tarval *tv1 = get_Const_tarval(left);
 430                 tarval *tv2 = get_Const_tarval(right);
 431                 ir_node *pred;
 432                 if(eval_cmp(pnc, tv1, tv2)) {
 433                         pred = new_r_Jmp(irg, cond_block);
 434                 } else {
 435                         pred = new_Bad();
 436                 }
 437                 set_Block_cfgpred(block, 0, pred);
 438                 *changed = 1;
 439                 set_irg_doms_inconsistent(irg);
 440                 set_irg_extblk_inconsistent(irg);
 441                 set_irg_loopinfo_inconsistent(irg);
 442         } else {
 443                 if(get_nodes_block(left) != cond_block)
 444                         return;
 445
 446                 // (recursively) look if a pred of a phi is a constant
 447                 env.true_block = block;
 448                 env.pnc = pnc;
 449                 env.cnst = right;
 450                 inc_irg_visited(current_ir_graph);
 451                 env.visited_nr = get_irg_visited(irg);
 452
 453                 copy_block = find_phi_with_const(projx, left, &env);
 454
 455                 if(copy_block != NULL) {
 456                         /* we have to remove the edge towards the pred as the pred now
 457                          * jumps into the true_block. We also have to shorten phis
 458                          * in our block because of this */
 459                         const ir_edge_t *edge, *next;
 460
 461                         /* shorten phis */
 462                         foreach_out_edge_safe(env.cnst_pred, edge, next) {
 463                                 ir_node *node = get_edge_src_irn(edge);
 464
 465                                 if(is_Phi(node))
 466                                         remove_pred(node, env.cnst_pos);
 467                         }
 468
 469                         remove_pred(env.cnst_pred, env.cnst_pos);
 470
 471                         // the graph is changed now
 472                         *changed = 1;
 473                         set_irg_doms_inconsistent(irg);
 474                         set_irg_extblk_inconsistent(irg);
 475                         set_irg_loopinfo_inconsistent(irg);
 476                 }
 477         }
 478 }
 479
 480 void opt_cond_eval(ir_graph* irg)
 481 {
 482         int changed;
 483
 484         FIRM_DBG_REGISTER(dbg, "firm.opt.condeval");
 485         //firm_dbg_set_mask(dbg, SET_LEVEL_5);
 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         do {
 495                 changed = 0;
 496                 irg_block_walk_graph(irg, cond_eval, NULL, &changed);
 497         } while(changed);
 498 }