nsz Git - libfirm/blob - ir/ana/irlivechk_old.c

   1 /*
   2  * Copyright (C) 1995-2007 Inria Rhone-Alpes.  All right reserved.
   3  *
   4  * This file is part of libFirm.
   5  *
   6  * This file may be distributed and/or modified under the terms of the
   7  * GNU General Public License version 2 as published by the Free Software
   8  * Foundation and appearing in the file LICENSE.GPL included in the
   9  * packaging of this file.
  10  *
  11  * Licensees holding valid libFirm Professional Edition licenses may use
  12  * this file in accordance with the libFirm Commercial License.
  13  * Agreement provided with the Software.
  14  *
  15  * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
  16  * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  17  * PURPOSE.
  18  */
  19
  20 /**
  21  * @file    livechk.c
  22  * @date    21.04.2007
  23  * @author  Sebastian Hack
  24  * @version $Id: irlivechk.c 14865 2007-06-30 18:23:05Z matze $
  25  * @summary
  26  *
  27  * Liveness checks as developed by Benoit Boissinot, Fabrice Rastello and myself.
  28  *
  29  * The speciality here is, that nothing has to be recomputed if new nodes are created
  30  * or old ones deleted.
  31  *
  32  * This algo has one core routine check_live_end_internal() which performs the liveness check.
  33  * It only relies on the precomputation done in the constructor, which in turn needs:
  34  * - out edges
  35  * - the dominance tree
  36  * - data obtained from a depth-first-search
  37  *
  38  * The precomputation remains valid as long as the CFG is not altered.
  39  */
  40 #ifdef HAVE_CONFIG_H
  41 #include <config.h>
  42 #endif
  43
  44 #include <stdio.h>
  45
  46 #include "irgraph_t.h"
  47 #include "irphase_t.h"
  48 #include "iredges_t.h"
  49 #include "irprintf.h"
  50 #include "irdump.h"
  51
  52 #include "dfs_t.h"
  53 #include "bitset.h"
  54 #include "util.h"
  55
  56 #include "irlivechk_old.h"
  57
  58 #include "statev.h"
  59
  60 typedef struct _bl_info_t {
  61         ir_node *block;            /**< The block. */
  62
  63         int id;                    /**< a tight number for the block.
  64                                                                  we're just reusing the pre num from
  65                                                                  the DFS. */
  66
  67         bitset_t *red_reachable;   /**< Holds all id's if blocks reachable
  68                                                                  in the CFG modulo back edges. */
  69
  70         bitset_t *be_tgt_reach;    /**< target blocks of back edges whose
  71                                                                  sources are reachable from this block
  72                                                                  in the reduced graph. */
  73
  74         bitset_t *be_tgt_dom;      /**< target blocks of back edges which
  75                                                                  are dominated by this block. */
  76 } bl_info_t;
  77
  78 #define get_block_info(lv, bl) ((bl_info_t *) phase_get_irn_data(&(lv)->ph, bl))
  79
  80 struct _lv_chk_old_t {
  81         ir_phase ph;
  82         dfs_t *dfs;
  83         DEBUG_ONLY(firm_dbg_module_t *dbg;)
  84         int n_blocks;
  85         bitset_t *back_edge_src;
  86         bitset_t *back_edge_tgt;
  87         bl_info_t **map;
  88 };
  89
  90 static void *init_block_data(ir_phase *ph, ir_node *irn, void *old)
  91 {
  92         lv_chk_old_t *lv  = container_of(ph, lv_chk_old_t, ph);
  93         bl_info_t *bi     = phase_alloc(ph, sizeof(bi[0]));
  94
  95         bi->id            = dfs_get_pre_num(lv->dfs, irn);
  96         bi->block         = irn;
  97         bi->red_reachable = bitset_obstack_alloc(phase_obst(ph), lv->n_blocks);
  98         bi->be_tgt_reach  = bitset_obstack_alloc(phase_obst(ph), lv->n_blocks);
  99         bi->be_tgt_dom    = bitset_obstack_alloc(phase_obst(ph), lv->n_blocks);
 100         (void) old;
 101         return bi;
 102 }
 103
 104 /**
 105  * Filter function to select all nodes for which liveness is computed.
 106  * @param irn A node.
 107  * @return    1 if the node shall be considered in liveness, 0 if not.
 108  */
 109 static INLINE int is_liveness_node(const ir_node *irn)
 110 {
 111         switch(get_irn_opcode(irn)) {
 112         case iro_Block:
 113         case iro_Bad:
 114         case iro_End:
 115                 return 0;
 116         default:;
 117         }
 118
 119         return 1;
 120 }
 121
 122 /**
 123  * Compute the transitive closure on the reduced graph.
 124  * The reduced graph is the original graph without back edges.
 125  * Since that is a DAG, a reverse post order of the graph gives a toposort
 126  * which is ideally suited to compute the transitive closure.
 127  * Note also, that the DFS tree of the reduced graph is the same than the one
 128  * of the original graph. This saves us computing a new reverse post order.
 129  * We also can re-use the DFS tree of the original graph.
 130  */
 131 static void red_trans_closure(lv_chk_old_t *lv)
 132 {
 133         int i, n;
 134
 135         for (i = 0, n = dfs_get_n_nodes(lv->dfs); i < n; ++i) {
 136                 ir_node *bl   = dfs_get_post_num_node(lv->dfs, i);
 137                 bl_info_t *bi = get_block_info(lv, bl);
 138
 139                 const ir_edge_t *edge;
 140
 141                 foreach_block_succ (bl, edge) {
 142                         ir_node *succ = get_edge_src_irn(edge);
 143                         bl_info_t *si = get_block_info(lv, succ);
 144                         dfs_edge_kind_t kind = dfs_get_edge_kind(lv->dfs, bl, succ);
 145
 146                         /*
 147                          * if the successor is no back edge, include all reachable
 148                          * blocks from there into the reachable set of the current node
 149                          */
 150                         if (kind != DFS_EDGE_BACK) {
 151                                 assert(dfs_get_post_num(lv->dfs, bl)
 152                                                 > dfs_get_post_num(lv->dfs, succ));
 153                                 bitset_or(bi->red_reachable, si->red_reachable);
 154                                 bitset_set(bi->red_reachable, si->id);
 155                         }
 156
 157                         /* mark the block as a back edge src and succ as back edge tgt. */
 158                         else {
 159                                 bitset_set(lv->back_edge_src, bi->id);
 160                                 bitset_set(lv->back_edge_tgt, si->id);
 161                         }
 162                 }
 163
 164         }
 165
 166 }
 167
 168 /**
 169  * Compute the two back edge sets for each block.
 170  * <code>be_tgt_reach</code> contains all target blocks of a back edges reachable from a node.
 171  * <code>be_tgt_dom</code> contains all target blocks of back edges strictly dominated
 172  * by a node.
 173  */
 174 static void compute_back_edge_sets(lv_chk_old_t *lv, ir_node *bl)
 175 {
 176         bl_info_t *bi = phase_get_or_set_irn_data(&(lv)->ph, bl);
 177         bitset_t *tmp = bitset_alloca(lv->n_blocks);
 178
 179         bitset_pos_t elm;
 180         ir_node *n;
 181
 182         dominates_for_each (bl, n) {
 183                 bl_info_t *ni = phase_get_or_set_irn_data(&(lv)->ph, n);
 184
 185                 /* compute information for dominance sub tree */
 186                 compute_back_edge_sets(lv, n);
 187
 188                 /*
 189                  * of course all blocks dominated by blocks in the
 190                  * subtree are also dominated by bl.
 191                  */
 192                 bitset_or(bi->be_tgt_dom, ni->be_tgt_dom);
 193
 194                 /*
 195                  * add the immeditate dominee to the back edge tgt dominance
 196                  * bitset if it is the target node of a back edge.
 197                  */
 198                 if (bitset_is_set(lv->back_edge_tgt, ni->id))
 199                         bitset_set(bi->be_tgt_dom, ni->id);
 200         }
 201
 202         /*
 203          * iterate over all back edge src nodes which are reachable from
 204          * this nodes and put the targets of the back edges in the be_tgt_reach
 205          * bitset of the node.
 206          */
 207         bitset_copy(tmp, bi->red_reachable);
 208         bitset_set(tmp, bi->id);
 209         bitset_and(tmp, lv->back_edge_src);
 210         bitset_foreach (tmp, elm) {
 211                 ir_node *src = lv->map[elm]->block;
 212                 const ir_edge_t *edge;
 213
 214                 foreach_block_succ (src, edge) {
 215                         ir_node *succ        = get_edge_src_irn(edge);
 216                         dfs_edge_kind_t kind = dfs_get_edge_kind(lv->dfs, src, succ);
 217
 218                         if (kind == DFS_EDGE_BACK) {
 219                                 bl_info_t *si = get_block_info(lv, succ);
 220                                 bitset_set(bi->be_tgt_reach, si->id);
 221                         }
 222                 }
 223         }
 224 }
 225
 226 lv_chk_old_t *lv_chk_old_new(ir_graph *irg)
 227 {
 228         lv_chk_old_t *res = xmalloc(sizeof(res[0]));
 229         struct obstack *obst;
 230         int i;
 231
 232         phase_init(&res->ph, "liveness check", irg, PHASE_DEFAULT_GROWTH, init_block_data, NULL);
 233         obst = phase_obst(&res->ph);
 234
 235         FIRM_DBG_REGISTER(res->dbg, "ir.ana.lvchk");
 236
 237         res->dfs           = dfs_new(&absgraph_irg_cfg_succ, irg);
 238         res->n_blocks      = dfs_get_n_nodes(res->dfs);
 239         res->back_edge_src = bitset_obstack_alloc(obst, res->n_blocks);
 240         res->back_edge_tgt = bitset_obstack_alloc(obst, res->n_blocks);
 241         res->map           = obstack_alloc(obst, res->n_blocks * sizeof(res->map[0]));
 242
 243 #ifdef ENABLE_STATS
 244         memset(&res->stat_data, 0, sizeof(res->stat_data));
 245         res->stat = &res->stat_data;
 246 #endif
 247 #if 0
 248         {
 249                 char name[256];
 250                 FILE *f;
 251                 ir_snprintf(name, sizeof(name), "dfs_%F.dot", irg);
 252                 if ((f = fopen(name, "wt")) != NULL) {
 253                         dfs_dump(res->dfs, f);
 254                         fclose(f);
 255                 }
 256                 dump_ir_block_graph(irg, "-lvchk");
 257         }
 258 #endif
 259
 260         /* fill the map which maps pre_num to block infos */
 261         for (i = res->n_blocks - 1; i >= 0; --i) {
 262                 ir_node *irn = dfs_get_pre_num_node(res->dfs, i);
 263                 res->map[i]  = phase_get_or_set_irn_data(&res->ph, irn);
 264         }
 265
 266         /* first of all, compute the transitive closure of the CFG *without* back edges */
 267         red_trans_closure(res);
 268
 269         /* now fill the two remaining bitsets concerning back edges */
 270         compute_back_edge_sets(res, get_irg_start_block(irg));
 271
 272         DEBUG_ONLY({
 273                 DBG((res->dbg, LEVEL_1, "liveness chk in %+F\n", irg));
 274                 for (i = res->n_blocks - 1; i >= 0; --i) {
 275                         ir_node *irn  = dfs_get_pre_num_node(res->dfs, i);
 276                         bl_info_t *bi = get_block_info(res, irn);
 277                         DBG((res->dbg, LEVEL_1, "lv_chk for %d -> %+F\n", i, irn));
 278                         DBG((res->dbg, LEVEL_1, "\tred reach: %B\n", bi->red_reachable));
 279                         DBG((res->dbg, LEVEL_1, "\ttgt reach: %B\n", bi->be_tgt_reach));
 280                         DBG((res->dbg, LEVEL_1, "\ttgt dom:   %B\n", bi->be_tgt_dom));
 281                 }
 282         })
 283
 284         DBG((res->dbg, LEVEL_1, "back edge src: %B\n", res->back_edge_src));
 285         DBG((res->dbg, LEVEL_1, "back edge tgt: %B\n", res->back_edge_tgt));
 286
 287         return res;
 288 }
 289
 290 void lv_chk_old_free(lv_chk_old_t *lv)
 291 {
 292         obstack_free(phase_obst(&lv->ph), NULL);
 293         dfs_free(lv->dfs);
 294         xfree(lv);
 295 }
 296
 297 /**
 298  * Check if a node is live at the end of a block.
 299  * This function is for internal use as its code is shared between
 300  * the in/end routines below. It is almost the "live_end" routine
 301  * but passing in the bitset for recording the blocks where the variable
 302  * is used saves some effort in the "live_in" routine. See below for
 303  * details.
 304  *
 305  * @param lv    The liveness check environment.
 306  * @param what  The node to check for.
 307  * @param bl    The block under investigation.
 308  * @param uses  A bitset where this routine records all ids of blocks
 309  *              where this variable is used. Note that the bitset
 310  *              is only guaranteed to be filled if the node was not
 311  *              live at the end of the block.
 312  * @return      1, if @p what is live at the end at @p bl.
 313  */
 314 unsigned lv_chk_old_bl_xxx(const lv_chk_old_t *lv, const ir_node *bl, const ir_node *what)
 315 {
 316         stat_ev_cnt_decl(uses);
 317         stat_ev_cnt_decl(iter);
 318
 319         int res  = 0;
 320         ir_node *what_bl;
 321
 322         assert(is_Block(bl) && "can only check for liveness in a block");
 323
 324         if (!is_liveness_node(what))
 325                 return 0;
 326
 327         stat_ev_ctx_push_fobj("node", what);
 328         stat_ev("lv_chk");
 329
 330         what_bl = get_nodes_block(what);
 331         if (!block_dominates(what_bl, bl)) {
 332                 stat_ev("lv_chk_no_dom");
 333                 goto end;
 334         }
 335
 336         /*
 337          * If the block in question is the same as the definition block,
 338          * the algorithm is simple. Just check for uses not inside this block.
 339          */
 340         if (what_bl == bl) {
 341                 const ir_edge_t *edge;
 342
 343                 stat_ev("lv_chk_def_block");
 344                 DBG((lv->dbg, LEVEL_2, "lv check same block %+F in %+F\n", what, bl));
 345                 foreach_out_edge (what, edge) {
 346                         ir_node *use    = get_edge_src_irn(edge);
 347                         ir_node *use_bl;
 348
 349                         if (!is_liveness_node(use))
 350                                 continue;
 351
 352                         stat_ev_cnt_inc(uses);
 353                         use_bl = get_nodes_block(use);
 354                         if (is_Phi(use)) {
 355                                 int pos = get_edge_src_pos(edge);
 356                                 use_bl  = get_Block_cfgpred_block(use_bl, pos);
 357
 358                                 if (use_bl == bl) {
 359                                         DBG((lv->dbg, LEVEL_2, "\tphi %+F in succ %+F,%d -> live end\n", use, use_bl, pos));
 360                                         res |= lv_chk_state_end;
 361                                 }
 362                         }
 363
 364                         if (use_bl != what_bl) {
 365                                 res = lv_chk_state_end | lv_chk_state_out;
 366                                 goto end;
 367                         }
 368                 }
 369
 370                 goto end;
 371         }
 372
 373         /* this is the complicated case */
 374         else {
 375                 bitset_t *visited   = bitset_alloca(lv->n_blocks);
 376                 bitset_t *to_visit  = bitset_alloca(lv->n_blocks);
 377                 bitset_t *next      = bitset_alloca(lv->n_blocks);
 378                 bitset_t *uses      = bitset_alloca(lv->n_blocks);
 379                 bl_info_t *def      = get_block_info(lv, what_bl);
 380                 bl_info_t *bli      = get_block_info(lv, bl);
 381
 382                 const ir_edge_t *edge;
 383
 384                 DBG((lv->dbg, LEVEL_2, "lv check different block %+F in %+F\n", what, bl));
 385                 foreach_out_edge (what, edge) {
 386                         ir_node *user   = get_edge_src_irn(edge);
 387                         ir_node *use_bl;
 388                         bl_info_t *bi;
 389
 390                         if (!is_liveness_node(user))
 391                                 continue;
 392
 393                         stat_ev_cnt_inc(uses);
 394                         use_bl = get_nodes_block(user);
 395                         if (is_Phi(user)) {
 396                                 int pos          = get_edge_src_pos(edge);
 397
 398                                 use_bl = get_Block_cfgpred_block(use_bl, pos);
 399                                 bi     = get_block_info(lv, use_bl);
 400
 401                                 if (use_bl == bl)
 402                                         res |= lv_chk_state_end | lv_chk_state_in;
 403
 404                                 bitset_set(uses, bi->id);
 405                         }
 406
 407                         else {
 408                                 bi = get_block_info(lv, use_bl);
 409                                 bitset_set(uses, bi->id);
 410                                 if (use_bl == bl)
 411                                         res |= lv_chk_state_in;
 412                         }
 413
 414                 }
 415                 DBG((lv->dbg, LEVEL_2, "\tuses: %B, #: %d\n", uses, bitset_popcnt(uses)));
 416
 417                 bitset_clear(uses, def->id);
 418                 bitset_set(to_visit, bli->id);
 419                 do {
 420                         int id        = bitset_next_set(to_visit, 0);
 421                         bl_info_t *bi = lv->map[id];
 422
 423                         stat_ev_cnt_inc(iter);
 424                         DBG((lv->dbg, LEVEL_2, "\tto visit: %B\n", to_visit));
 425                         DBG((lv->dbg, LEVEL_2, "\tvisited:  %B\n", visited));
 426
 427                         /*
 428                          * if one of the blocks is reachable, the node must be live there.
 429                          * Note that this is not sufficient, since the nodes reachable
 430                          * via back edges are not contained in the red_reachable set.
 431                          */
 432                         if (bitset_intersect(bi->red_reachable, uses)) {
 433                                 res = lv_chk_state_end | lv_chk_state_out | lv_chk_state_in;
 434                                 goto end;
 435                         }
 436
 437                         /*
 438                          * if not, we have to check the back edges in question, if
 439                          * they lead to places which are reachable.
 440                          */
 441                         else {
 442                                 bitset_set(visited, id);
 443                                 bitset_or(visited, bi->red_reachable);
 444
 445                                 bitset_copy(next, bi->be_tgt_reach);
 446                                 bitset_and(next, def->be_tgt_dom);
 447                                 DBG((lv->dbg, LEVEL_2, "\tnext: %B\n----\n", next));
 448
 449                                 if (bitset_intersect(uses, next)) {
 450                                         res = lv_chk_state_end | lv_chk_state_out | lv_chk_state_in;
 451                                         goto end;
 452                                 }
 453
 454                                 bitset_or(to_visit, next);
 455                                 bitset_andnot(to_visit, visited);
 456
 457                         }
 458                 } while (!bitset_is_empty(to_visit));
 459         }
 460
 461 end:
 462         stat_ev_cnt_done(uses, "lv_chk_uses");
 463         stat_ev_cnt_done(iter, "lv_chk_iter");
 464         stat_ev_ctx_pop();
 465
 466         return res;
 467 }