nsz Git - libfirm/blob - ir/opt/ldstopt.c

   1 /*
   2  * Copyright (C) 1995-2008 University of Karlsruhe.  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
  22  * @brief   Load/Store optimizations.
  23  * @author  Michael Beck
  24  * @version $Id$
  25  */
  26 #ifdef HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include <string.h>
  31
  32 #include "iroptimize.h"
  33 #include "irnode_t.h"
  34 #include "irgraph_t.h"
  35 #include "irmode_t.h"
  36 #include "iropt_t.h"
  37 #include "ircons_t.h"
  38 #include "irgmod.h"
  39 #include "irgwalk.h"
  40 #include "irvrfy.h"
  41 #include "tv_t.h"
  42 #include "dbginfo_t.h"
  43 #include "iropt_dbg.h"
  44 #include "irflag_t.h"
  45 #include "array_t.h"
  46 #include "irhooks.h"
  47 #include "iredges.h"
  48 #include "irtools.h"
  49 #include "opt_polymorphy.h"
  50 #include "irmemory.h"
  51 #include "xmalloc.h"
  52 #include "irphase_t.h"
  53 #include "irgopt.h"
  54 #include "debug.h"
  55
  56 /** The debug handle. */
  57 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  58
  59 #ifdef DO_CACHEOPT
  60 #include "cacheopt/cachesim.h"
  61 #endif
  62
  63 #undef IMAX
  64 #define IMAX(a,b)       ((a) > (b) ? (a) : (b))
  65
  66 #define MAX_PROJ        IMAX(IMAX(pn_Load_max, pn_Store_max), pn_Call_max)
  67
  68 enum changes_t {
  69         DF_CHANGED = 1,       /**< data flow changed */
  70         CF_CHANGED = 2,       /**< control flow changed */
  71 };
  72
  73 /**
  74  * walker environment
  75  */
  76 typedef struct _walk_env_t {
  77         struct obstack obst;          /**< list of all stores */
  78         unsigned changes;             /**< a bitmask of graph changes */
  79 } walk_env_t;
  80
  81 /** A Load/Store info. */
  82 typedef struct _ldst_info_t {
  83         ir_node  *projs[MAX_PROJ];    /**< list of Proj's of this node */
  84         ir_node  *exc_block;          /**< the exception block if available */
  85         int      exc_idx;             /**< predecessor index in the exception block */
  86         unsigned visited;             /**< visited counter for breaking loops */
  87 } ldst_info_t;
  88
  89 /**
  90  * flags for control flow.
  91  */
  92 enum block_flags_t {
  93         BLOCK_HAS_COND = 1,      /**< Block has conditional control flow */
  94         BLOCK_HAS_EXC  = 2       /**< Block has exceptional control flow */
  95 };
  96
  97 /**
  98  * a Block info.
  99  */
 100 typedef struct _block_info_t {
 101         unsigned flags;               /**< flags for the block */
 102 } block_info_t;
 103
 104 /** the master visited flag for loop detection. */
 105 static unsigned master_visited = 0;
 106
 107 #define INC_MASTER()       ++master_visited
 108 #define MARK_NODE(info)    (info)->visited = master_visited
 109 #define NODE_VISITED(info) (info)->visited >= master_visited
 110
 111 /**
 112  * get the Load/Store info of a node
 113  */
 114 static ldst_info_t *get_ldst_info(ir_node *node, struct obstack *obst) {
 115         ldst_info_t *info = get_irn_link(node);
 116
 117         if (! info) {
 118                 info = obstack_alloc(obst, sizeof(*info));
 119                 memset(info, 0, sizeof(*info));
 120                 set_irn_link(node, info);
 121         }
 122         return info;
 123 }  /* get_ldst_info */
 124
 125 /**
 126  * get the Block info of a node
 127  */
 128 static block_info_t *get_block_info(ir_node *node, struct obstack *obst) {
 129         block_info_t *info = get_irn_link(node);
 130
 131         if (! info) {
 132                 info = obstack_alloc(obst, sizeof(*info));
 133                 memset(info, 0, sizeof(*info));
 134                 set_irn_link(node, info);
 135         }
 136         return info;
 137 }  /* get_block_info */
 138
 139 /**
 140  * update the projection info for a Load/Store
 141  */
 142 static unsigned update_projs(ldst_info_t *info, ir_node *proj)
 143 {
 144         long nr = get_Proj_proj(proj);
 145
 146         assert(0 <= nr && nr <= MAX_PROJ && "Wrong proj from LoadStore");
 147
 148         if (info->projs[nr]) {
 149                 /* there is already one, do CSE */
 150                 exchange(proj, info->projs[nr]);
 151                 return DF_CHANGED;
 152         }
 153         else {
 154                 info->projs[nr] = proj;
 155                 return 0;
 156         }
 157 }  /* update_projs */
 158
 159 /**
 160  * update the exception block info for a Load/Store node.
 161  *
 162  * @param info   the load/store info struct
 163  * @param block  the exception handler block for this load/store
 164  * @param pos    the control flow input of the block
 165  */
 166 static unsigned update_exc(ldst_info_t *info, ir_node *block, int pos)
 167 {
 168         assert(info->exc_block == NULL && "more than one exception block found");
 169
 170         info->exc_block = block;
 171         info->exc_idx   = pos;
 172         return 0;
 173 }  /* update_exc */
 174
 175 /** Return the number of uses of an address node */
 176 #define get_irn_n_uses(adr)     get_irn_n_edges(adr)
 177
 178 /**
 179  * walker, collects all Load/Store/Proj nodes
 180  *
 181  * walks from Start -> End
 182  */
 183 static void collect_nodes(ir_node *node, void *env)
 184 {
 185         ir_opcode   opcode = get_irn_opcode(node);
 186         ir_node     *pred, *blk, *pred_blk;
 187         ldst_info_t *ldst_info;
 188         walk_env_t  *wenv = env;
 189
 190         if (opcode == iro_Proj) {
 191                 pred   = get_Proj_pred(node);
 192                 opcode = get_irn_opcode(pred);
 193
 194                 if (opcode == iro_Load || opcode == iro_Store || opcode == iro_Call) {
 195                         ldst_info = get_ldst_info(pred, &wenv->obst);
 196
 197                         wenv->changes |= update_projs(ldst_info, node);
 198
 199                         /*
 200                          * Place the Proj's to the same block as the
 201                          * predecessor Load. This is always ok and prevents
 202                          * "non-SSA" form after optimizations if the Proj
 203                          * is in a wrong block.
 204                          */
 205                         blk      = get_nodes_block(node);
 206                         pred_blk = get_nodes_block(pred);
 207                         if (blk != pred_blk) {
 208                                 wenv->changes |= DF_CHANGED;
 209                                 set_nodes_block(node, pred_blk);
 210                         }
 211                 }
 212         } else if (opcode == iro_Block) {
 213                 int i;
 214
 215                 for (i = get_Block_n_cfgpreds(node) - 1; i >= 0; --i) {
 216                         ir_node      *pred_block, *proj;
 217                         block_info_t *bl_info;
 218                         int          is_exc = 0;
 219
 220                         pred = proj = get_Block_cfgpred(node, i);
 221
 222                         if (is_Proj(proj)) {
 223                                 pred   = get_Proj_pred(proj);
 224                                 is_exc = get_Proj_proj(proj) == pn_Generic_X_except;
 225                         }
 226
 227                         /* ignore Bad predecessors, they will be removed later */
 228                         if (is_Bad(pred))
 229                                 continue;
 230
 231                         pred_block = get_nodes_block(pred);
 232                         bl_info    = get_block_info(pred_block, &wenv->obst);
 233
 234                         if (is_fragile_op(pred) && is_exc)
 235                                 bl_info->flags |= BLOCK_HAS_EXC;
 236                         else if (is_irn_forking(pred))
 237                                 bl_info->flags |= BLOCK_HAS_COND;
 238
 239                         opcode = get_irn_opcode(pred);
 240                         if (is_exc && (opcode == iro_Load || opcode == iro_Store || opcode == iro_Call)) {
 241                                 ldst_info = get_ldst_info(pred, &wenv->obst);
 242
 243                                 wenv->changes |= update_exc(ldst_info, node, i);
 244                         }
 245                 }
 246         }
 247 }  /* collect_nodes */
 248
 249 /**
 250  * Returns an entity if the address ptr points to a constant one.
 251  *
 252  * @param ptr  the address
 253  *
 254  * @return an entity or NULL
 255  */
 256 static ir_entity *find_constant_entity(ir_node *ptr)
 257 {
 258         for (;;) {
 259                 if (is_SymConst(ptr) && get_SymConst_kind(ptr) == symconst_addr_ent) {
 260                         return get_SymConst_entity(ptr);
 261                 } else if (is_Sel(ptr)) {
 262                         ir_entity *ent = get_Sel_entity(ptr);
 263                         ir_type   *tp  = get_entity_owner(ent);
 264
 265                         /* Do not fiddle with polymorphism. */
 266                         if (is_Class_type(get_entity_owner(ent)) &&
 267                                 ((get_entity_n_overwrites(ent)    != 0) ||
 268                                 (get_entity_n_overwrittenby(ent) != 0)   ) )
 269                                 return NULL;
 270
 271                         if (is_Array_type(tp)) {
 272                                 /* check bounds */
 273                                 int i, n;
 274
 275                                 for (i = 0, n = get_Sel_n_indexs(ptr); i < n; ++i) {
 276                                         ir_node *bound;
 277                                         tarval *tlower, *tupper;
 278                                         ir_node *index = get_Sel_index(ptr, i);
 279                                         tarval *tv     = computed_value(index);
 280
 281                                         /* check if the index is constant */
 282                                         if (tv == tarval_bad)
 283                                                 return NULL;
 284
 285                                         bound  = get_array_lower_bound(tp, i);
 286                                         tlower = computed_value(bound);
 287                                         bound  = get_array_upper_bound(tp, i);
 288                                         tupper = computed_value(bound);
 289
 290                                         if (tlower == tarval_bad || tupper == tarval_bad)
 291                                                 return NULL;
 292
 293                                         if (tarval_cmp(tv, tlower) & pn_Cmp_Lt)
 294                                                 return NULL;
 295                                         if (tarval_cmp(tupper, tv) & pn_Cmp_Lt)
 296                                                 return NULL;
 297
 298                                         /* ok, bounds check finished */
 299                                 }
 300                         }
 301
 302                         if (variability_constant == get_entity_variability(ent))
 303                                 return ent;
 304
 305                         /* try next */
 306                         ptr = get_Sel_ptr(ptr);
 307                 } else if (is_Add(ptr)) {
 308                         ir_node *l = get_Add_left(ptr);
 309                         ir_node *r = get_Add_right(ptr);
 310
 311                         if (get_irn_mode(l) == get_irn_mode(ptr) && is_Const(r))
 312                                 ptr = l;
 313                         else if (get_irn_mode(r) == get_irn_mode(ptr) && is_Const(l))
 314                                 ptr = r;
 315                         else
 316                                 return NULL;
 317
 318                         /* for now, we support only one addition, reassoc should fold all others */
 319                         if (! is_SymConst(ptr) && !is_Sel(ptr))
 320                                 return NULL;
 321                 } else if (is_Sub(ptr)) {
 322                         ir_node *l = get_Sub_left(ptr);
 323                         ir_node *r = get_Sub_right(ptr);
 324
 325                         if (get_irn_mode(l) == get_irn_mode(ptr) &&     is_Const(r))
 326                                 ptr = l;
 327                         else
 328                                 return NULL;
 329                         /* for now, we support only one substraction, reassoc should fold all others */
 330                         if (! is_SymConst(ptr) && !is_Sel(ptr))
 331                                 return NULL;
 332                 } else
 333                         return NULL;
 334         }
 335 }  /* find_constant_entity */
 336
 337 /**
 338  * Return the Selection index of a Sel node from dimension n
 339  */
 340 static long get_Sel_array_index_long(ir_node *n, int dim) {
 341         ir_node *index = get_Sel_index(n, dim);
 342         assert(is_Const(index));
 343         return get_tarval_long(get_Const_tarval(index));
 344 }  /* get_Sel_array_index_long */
 345
 346 /**
 347  * Returns the accessed component graph path for an
 348  * node computing an address.
 349  *
 350  * @param ptr    the node computing the address
 351  * @param depth  current depth in steps upward from the root
 352  *               of the address
 353  */
 354 static compound_graph_path *rec_get_accessed_path(ir_node *ptr, int depth) {
 355         compound_graph_path *res = NULL;
 356         ir_entity           *root, *field, *ent;
 357         int                 path_len, pos, idx;
 358         tarval              *tv;
 359         ir_type             *tp;
 360
 361         if (is_SymConst(ptr)) {
 362                 /* a SymConst. If the depth is 0, this is an access to a global
 363                  * entity and we don't need a component path, else we know
 364                  * at least its length.
 365                  */
 366                 assert(get_SymConst_kind(ptr) == symconst_addr_ent);
 367                 root = get_SymConst_entity(ptr);
 368                 res = (depth == 0) ? NULL : new_compound_graph_path(get_entity_type(root), depth);
 369         } else if (is_Sel(ptr)) {
 370                 /* it's a Sel, go up until we find the root */
 371                 res = rec_get_accessed_path(get_Sel_ptr(ptr), depth+1);
 372                 if (res == NULL)
 373                         return NULL;
 374
 375                 /* fill up the step in the path at the current position */
 376                 field    = get_Sel_entity(ptr);
 377                 path_len = get_compound_graph_path_length(res);
 378                 pos      = path_len - depth - 1;
 379                 set_compound_graph_path_node(res, pos, field);
 380
 381                 if (is_Array_type(get_entity_owner(field))) {
 382                         assert(get_Sel_n_indexs(ptr) == 1 && "multi dim arrays not implemented");
 383                         set_compound_graph_path_array_index(res, pos, get_Sel_array_index_long(ptr, 0));
 384                 }
 385         } else if (is_Add(ptr)) {
 386                 ir_node *l    = get_Add_left(ptr);
 387                 ir_node *r    = get_Add_right(ptr);
 388                 ir_mode *mode = get_irn_mode(ptr);
 389                 tarval  *tmp;
 390
 391                 if (is_Const(r) && get_irn_mode(l) == mode) {
 392                         ptr = l;
 393                         tv  = get_Const_tarval(r);
 394                 } else {
 395                         ptr = r;
 396                         tv  = get_Const_tarval(l);
 397                 }
 398 ptr_arith:
 399                 mode = get_tarval_mode(tv);
 400                 tmp  = tv;
 401
 402                 /* ptr must be a Sel or a SymConst, this was checked in find_constant_entity() */
 403                 if (is_Sel(ptr)) {
 404                         field = get_Sel_entity(ptr);
 405                 } else {
 406                         field = get_SymConst_entity(ptr);
 407                 }
 408                 idx = 0;
 409                 for (ent = field;;) {
 410                         unsigned size;
 411                         tarval   *sz, *tv_index, *tlower, *tupper;
 412                         ir_node  *bound;
 413
 414                         tp = get_entity_type(ent);
 415                         if (! is_Array_type(tp))
 416                                 break;
 417                         ent = get_array_element_entity(tp);
 418                         size = get_type_size_bytes(get_entity_type(ent));
 419                         sz   = new_tarval_from_long(size, mode);
 420
 421                         tv_index = tarval_div(tmp, sz);
 422                         tmp      = tarval_mod(tmp, sz);
 423
 424                         if (tv_index == tarval_bad || tmp == tarval_bad)
 425                                 return NULL;
 426
 427                         assert(get_array_n_dimensions(tp) == 1 && "multiarrays not implemented");
 428                         bound  = get_array_lower_bound(tp, 0);
 429                         tlower = computed_value(bound);
 430                         bound  = get_array_upper_bound(tp, 0);
 431                         tupper = computed_value(bound);
 432
 433                         if (tlower == tarval_bad || tupper == tarval_bad)
 434                                 return NULL;
 435
 436                         if (tarval_cmp(tv_index, tlower) & pn_Cmp_Lt)
 437                                 return NULL;
 438                         if (tarval_cmp(tupper, tv_index) & pn_Cmp_Lt)
 439                                 return NULL;
 440
 441                         /* ok, bounds check finished */
 442                         ++idx;
 443                 }
 444                 if (! tarval_is_null(tmp)) {
 445                         /* access to some struct/union member */
 446                         return NULL;
 447                 }
 448
 449                 /* should be at least ONE array */
 450                 if (idx == 0)
 451                         return NULL;
 452
 453                 res = rec_get_accessed_path(ptr, depth + idx);
 454                 if (res == NULL)
 455                         return NULL;
 456
 457                 path_len = get_compound_graph_path_length(res);
 458                 pos      = path_len - depth - idx;
 459
 460                 for (ent = field;;) {
 461                         unsigned size;
 462                         tarval   *sz, *tv_index;
 463                         long     index;
 464
 465                         tp = get_entity_type(ent);
 466                         if (! is_Array_type(tp))
 467                                 break;
 468                         ent = get_array_element_entity(tp);
 469                         set_compound_graph_path_node(res, pos, ent);
 470
 471                         size = get_type_size_bytes(get_entity_type(ent));
 472                         sz   = new_tarval_from_long(size, mode);
 473
 474                         tv_index = tarval_div(tv, sz);
 475                         tv       = tarval_mod(tv, sz);
 476
 477                         /* worked above, should work again */
 478                         assert(tv_index != tarval_bad && tv != tarval_bad);
 479
 480                         /* bounds already checked above */
 481                         index = get_tarval_long(tv_index);
 482                         set_compound_graph_path_array_index(res, pos, index);
 483                         ++pos;
 484                 }
 485         } else if (is_Sub(ptr)) {
 486                 ir_node *l = get_Sub_left(ptr);
 487                 ir_node *r = get_Sub_right(ptr);
 488
 489                 ptr = l;
 490                 tv  = get_Const_tarval(r);
 491                 tv  = tarval_neg(tv);
 492                 goto ptr_arith;
 493         }
 494         return res;
 495 }  /* rec_get_accessed_path */
 496
 497 /**
 498  * Returns an access path or NULL.  The access path is only
 499  * valid, if the graph is in phase_high and _no_ address computation is used.
 500  */
 501 static compound_graph_path *get_accessed_path(ir_node *ptr) {
 502         compound_graph_path *gr = rec_get_accessed_path(ptr, 0);
 503         return gr;
 504 }  /* get_accessed_path */
 505
 506 typedef struct path_entry {
 507         ir_entity         *ent;
 508         struct path_entry *next;
 509         long              index;
 510 } path_entry;
 511
 512 static ir_node *rec_find_compound_ent_value(ir_node *ptr, path_entry *next) {
 513         path_entry       entry, *p;
 514         ir_entity        *ent, *field;
 515         ir_initializer_t *initializer;
 516         tarval           *tv;
 517         ir_type          *tp;
 518         unsigned         n;
 519
 520         entry.next = next;
 521         if (is_SymConst(ptr)) {
 522                 /* found the root */
 523                 ent         = get_SymConst_entity(ptr);
 524                 initializer = get_entity_initializer(ent);
 525                 for (p = next; p != NULL;) {
 526                         if (initializer->kind != IR_INITIALIZER_COMPOUND)
 527                                 return NULL;
 528                         n  = get_initializer_compound_n_entries(initializer);
 529                         tp = get_entity_type(ent);
 530
 531                         if (is_Array_type(tp)) {
 532                                 ent = get_array_element_entity(tp);
 533                                 if (ent != p->ent) {
 534                                         /* a missing [0] */
 535                                         if (0 >= n)
 536                                                 return NULL;
 537                                         initializer = get_initializer_compound_value(initializer, 0);
 538                                         continue;
 539                                 }
 540                         }
 541                         if (p->index >= (int) n)
 542                                 return NULL;
 543                         initializer = get_initializer_compound_value(initializer, p->index);
 544
 545                         ent = p->ent;
 546                         p   = p->next;
 547                 }
 548                 tp = get_entity_type(ent);
 549                 while (is_Array_type(tp)) {
 550                         ent = get_array_element_entity(tp);
 551                         tp = get_entity_type(ent);
 552                         /* a missing [0] */
 553                         n  = get_initializer_compound_n_entries(initializer);
 554                         if (0 >= n)
 555                                 return NULL;
 556                         initializer = get_initializer_compound_value(initializer, 0);
 557                 }
 558
 559                 switch (initializer->kind) {
 560                 case IR_INITIALIZER_CONST:
 561                         return get_initializer_const_value(initializer);
 562                 case IR_INITIALIZER_TARVAL:
 563                 case IR_INITIALIZER_NULL:
 564                 default:
 565                         return NULL;
 566                 }
 567         } else if (is_Sel(ptr)) {
 568                 entry.ent = field = get_Sel_entity(ptr);
 569                 tp = get_entity_owner(field);
 570                 if (is_Array_type(tp)) {
 571                         assert(get_Sel_n_indexs(ptr) == 1 && "multi dim arrays not implemented");
 572                         entry.index = get_Sel_array_index_long(ptr, 0) - get_array_lower_bound_int(tp, 0);
 573                 } else {
 574                         int i, n_members = get_compound_n_members(tp);
 575                         for (i = 0; i < n_members; ++i) {
 576                                 if (get_compound_member(tp, i) == field)
 577                                         break;
 578                         }
 579                         if (i >= n_members) {
 580                                 /* not found: should NOT happen */
 581                                 return NULL;
 582                         }
 583                         entry.index = i;
 584                 }
 585                 return rec_find_compound_ent_value(get_Sel_ptr(ptr), &entry);
 586         }  else if (is_Add(ptr)) {
 587                 ir_node  *l = get_Add_left(ptr);
 588                 ir_node  *r = get_Add_right(ptr);
 589                 ir_mode  *mode;
 590                 unsigned pos;
 591
 592                 if (is_Const(r)) {
 593                         ptr = l;
 594                         tv  = get_Const_tarval(r);
 595                 } else {
 596                         ptr = r;
 597                         tv  = get_Const_tarval(l);
 598                 }
 599 ptr_arith:
 600                 mode = get_tarval_mode(tv);
 601
 602                 /* ptr must be a Sel or a SymConst, this was checked in find_constant_entity() */
 603                 if (is_Sel(ptr)) {
 604                         field = get_Sel_entity(ptr);
 605                 } else {
 606                         field = get_SymConst_entity(ptr);
 607                 }
 608
 609                 /* count needed entries */
 610                 pos = 0;
 611                 for (ent = field;;) {
 612                         tp = get_entity_type(ent);
 613                         if (! is_Array_type(tp))
 614                                 break;
 615                         ent = get_array_element_entity(tp);
 616                         ++pos;
 617                 }
 618                 /* should be at least ONE entry */
 619                 if (pos == 0)
 620                         return NULL;
 621
 622                 /* allocate the right number of entries */
 623                 NEW_ARR_A(path_entry, p, pos);
 624
 625                 /* fill them up */
 626                 pos = 0;
 627                 for (ent = field;;) {
 628                         unsigned size;
 629                         tarval   *sz, *tv_index, *tlower, *tupper;
 630                         long     index;
 631                         ir_node  *bound;
 632
 633                         tp = get_entity_type(ent);
 634                         if (! is_Array_type(tp))
 635                                 break;
 636                         ent = get_array_element_entity(tp);
 637                         p[pos].ent  = ent;
 638                         p[pos].next = &p[pos + 1];
 639
 640                         size = get_type_size_bytes(get_entity_type(ent));
 641                         sz   = new_tarval_from_long(size, mode);
 642
 643                         tv_index = tarval_div(tv, sz);
 644                         tv       = tarval_mod(tv, sz);
 645
 646                         if (tv_index == tarval_bad || tv == tarval_bad)
 647                                 return NULL;
 648
 649                         assert(get_array_n_dimensions(tp) == 1 && "multiarrays not implemented");
 650                         bound  = get_array_lower_bound(tp, 0);
 651                         tlower = computed_value(bound);
 652                         bound  = get_array_upper_bound(tp, 0);
 653                         tupper = computed_value(bound);
 654
 655                         if (tlower == tarval_bad || tupper == tarval_bad)
 656                                 return NULL;
 657
 658                         if (tarval_cmp(tv_index, tlower) & pn_Cmp_Lt)
 659                                 return NULL;
 660                         if (tarval_cmp(tupper, tv_index) & pn_Cmp_Lt)
 661                                 return NULL;
 662
 663                         /* ok, bounds check finished */
 664                         index = get_tarval_long(tv_index);
 665                         p[pos].index = index;
 666                         ++pos;
 667                 }
 668                 if (! tarval_is_null(tv)) {
 669                         /* hmm, wrong access */
 670                         return NULL;
 671                 }
 672                 p[pos - 1].next = next;
 673                 return rec_find_compound_ent_value(ptr, p);
 674         } else if (is_Sub(ptr)) {
 675                 ir_node *l = get_Sub_left(ptr);
 676                 ir_node *r = get_Sub_right(ptr);
 677
 678                 ptr = l;
 679                 tv  = get_Const_tarval(r);
 680                 tv  = tarval_neg(tv);
 681                 goto ptr_arith;
 682         }
 683         return NULL;
 684 }
 685
 686 static ir_node *find_compound_ent_value(ir_node *ptr) {
 687         return rec_find_compound_ent_value(ptr, NULL);
 688 }
 689
 690 /* forward */
 691 static void reduce_adr_usage(ir_node *ptr);
 692
 693 /**
 694  * Update a Load that may have lost its users.
 695  */
 696 static void handle_load_update(ir_node *load) {
 697         ldst_info_t *info = get_irn_link(load);
 698
 699         /* do NOT touch volatile loads for now */
 700         if (get_Load_volatility(load) == volatility_is_volatile)
 701                 return;
 702
 703         if (! info->projs[pn_Load_res] && ! info->projs[pn_Load_X_except]) {
 704                 ir_node *ptr = get_Load_ptr(load);
 705                 ir_node *mem = get_Load_mem(load);
 706
 707                 /* a Load whose value is neither used nor exception checked, remove it */
 708                 exchange(info->projs[pn_Load_M], mem);
 709                 if (info->projs[pn_Load_X_regular])
 710                         exchange(info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
 711                 kill_node(load);
 712                 reduce_adr_usage(ptr);
 713         }
 714 }  /* handle_load_update */
 715
 716 /**
 717  * A use of an address node has vanished. Check if this was a Proj
 718  * node and update the counters.
 719  */
 720 static void reduce_adr_usage(ir_node *ptr) {
 721         if (is_Proj(ptr)) {
 722                 if (get_irn_n_edges(ptr) <= 0) {
 723                         /* this Proj is dead now */
 724                         ir_node *pred = get_Proj_pred(ptr);
 725
 726                         if (is_Load(pred)) {
 727                                 ldst_info_t *info = get_irn_link(pred);
 728                                 info->projs[get_Proj_proj(ptr)] = NULL;
 729
 730                                 /* this node lost its result proj, handle that */
 731                                 handle_load_update(pred);
 732                         }
 733                 }
 734         }
 735 }  /* reduce_adr_usage */
 736
 737 /**
 738  * Check, if an already existing value of mode old_mode can be converted
 739  * into the needed one new_mode without loss.
 740  */
 741 static int can_use_stored_value(ir_mode *old_mode, ir_mode *new_mode) {
 742         if (old_mode == new_mode)
 743                 return 1;
 744
 745         /* if both modes are two-complement ones, we can always convert the
 746            Stored value into the needed one. */
 747         if (get_mode_size_bits(old_mode) >= get_mode_size_bits(new_mode) &&
 748                   get_mode_arithmetic(old_mode) == irma_twos_complement &&
 749                   get_mode_arithmetic(new_mode) == irma_twos_complement)
 750                 return 1;
 751         return 0;
 752 }  /* can_use_stored_value */
 753
 754 /**
 755  * Check whether a Call is at least pure, ie. does only read memory.
 756  */
 757 static unsigned is_Call_pure(ir_node *call) {
 758         ir_type *call_tp = get_Call_type(call);
 759         unsigned prop = get_method_additional_properties(call_tp);
 760
 761         /* check first the call type */
 762         if ((prop & (mtp_property_const|mtp_property_pure)) == 0) {
 763                 /* try the called entity */
 764                 ir_node *ptr = get_Call_ptr(call);
 765
 766                 if (is_Global(ptr)) {
 767                         ir_entity *ent = get_Global_entity(ptr);
 768
 769                         prop = get_entity_additional_properties(ent);
 770                 }
 771         }
 772         return (prop & (mtp_property_const|mtp_property_pure)) != 0;
 773 }  /* is_Call_pure */
 774
 775 static ir_node *get_base_and_offset(ir_node *ptr, long *pOffset)
 776 {
 777         ir_mode *mode  = get_irn_mode(ptr);
 778         long    offset = 0;
 779
 780         /* TODO: long might not be enough, we should probably use some tarval thingy... */
 781         for (;;) {
 782                 if (is_Add(ptr)) {
 783                         ir_node *l = get_Add_left(ptr);
 784                         ir_node *r = get_Add_right(ptr);
 785
 786                         if (get_irn_mode(l) != mode || !is_Const(r))
 787                                 break;
 788
 789                         offset += get_tarval_long(get_Const_tarval(r));
 790                         ptr     = l;
 791                 } else if (is_Sub(ptr)) {
 792                         ir_node *l = get_Sub_left(ptr);
 793                         ir_node *r = get_Sub_right(ptr);
 794
 795                         if (get_irn_mode(l) != mode || !is_Const(r))
 796                                 break;
 797
 798                         offset -= get_tarval_long(get_Const_tarval(r));
 799                         ptr     = l;
 800                 } else if (is_Sel(ptr)) {
 801                         ir_entity *ent = get_Sel_entity(ptr);
 802                         ir_type   *tp  = get_entity_owner(ent);
 803
 804                         if (is_Array_type(tp)) {
 805                                 int     size;
 806                                 ir_node *index;
 807
 808                                 /* only one dimensional arrays yet */
 809                                 if (get_Sel_n_indexs(ptr) != 1)
 810                                         break;
 811                                 index = get_Sel_index(ptr, 0);
 812                                 if (! is_Const(index))
 813                                         break;
 814
 815                                 tp = get_entity_type(ent);
 816                                 if (get_type_state(tp) != layout_fixed)
 817                                         break;
 818
 819                                 size    = get_type_size_bytes(tp);
 820                                 offset += size * get_tarval_long(get_Const_tarval(index));
 821                         } else {
 822                                 if (get_type_state(tp) != layout_fixed)
 823                                         break;
 824                                 offset += get_entity_offset(ent);
 825                         }
 826                         ptr = get_Sel_ptr(ptr);
 827                 } else
 828                         break;
 829         }
 830
 831         *pOffset = offset;
 832         return ptr;
 833 }
 834
 835 static int try_load_after_store(ir_node *load,
 836                 ir_node *load_base_ptr, long load_offset, ir_node *store)
 837 {
 838         ldst_info_t *info;
 839         ir_node *store_ptr      = get_Store_ptr(store);
 840         long     store_offset;
 841         ir_node *store_base_ptr = get_base_and_offset(store_ptr, &store_offset);
 842         ir_node *store_value;
 843         ir_mode *store_mode;
 844         ir_node *load_ptr;
 845         ir_mode *load_mode;
 846         long     load_mode_len;
 847         long     store_mode_len;
 848         long     delta;
 849         int      res;
 850
 851         if (load_base_ptr != store_base_ptr)
 852                 return 0;
 853
 854         load_mode      = get_Load_mode(load);
 855         load_mode_len  = get_mode_size_bytes(load_mode);
 856         store_mode     = get_irn_mode(get_Store_value(store));
 857         store_mode_len = get_mode_size_bytes(store_mode);
 858         delta          = load_offset - store_offset;
 859         if (delta < 0 || delta + load_mode_len > store_mode_len)
 860                 return 0;
 861
 862         if (get_mode_arithmetic(store_mode) != irma_twos_complement ||
 863             get_mode_arithmetic(load_mode)  != irma_twos_complement)
 864                 return 0;
 865
 866         store_value = get_Store_value(store);
 867
 868         /* produce a shift to adjust offset delta */
 869         if (delta > 0) {
 870                 ir_node *cnst;
 871
 872                 /* FIXME: only true for little endian */
 873                 cnst        = new_Const_long(mode_Iu, delta * 8);
 874                 store_value = new_r_Shr(current_ir_graph, get_nodes_block(load),
 875                                         store_value, cnst, store_mode);
 876         }
 877
 878         /* add an convert if needed */
 879         if (store_mode != load_mode) {
 880                 store_value = new_r_Conv(current_ir_graph, get_nodes_block(load),
 881                                          store_value, load_mode);
 882         }
 883
 884         DBG_OPT_RAW(load, store_value);
 885
 886         info = get_irn_link(load);
 887         if (info->projs[pn_Load_M])
 888                 exchange(info->projs[pn_Load_M], get_Load_mem(load));
 889
 890         res = 0;
 891         /* no exception */
 892         if (info->projs[pn_Load_X_except]) {
 893                 exchange( info->projs[pn_Load_X_except], new_Bad());
 894                 res |= CF_CHANGED;
 895         }
 896         if (info->projs[pn_Load_X_regular]) {
 897                 exchange( info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
 898                 res |= CF_CHANGED;
 899         }
 900
 901         if (info->projs[pn_Load_res])
 902                 exchange(info->projs[pn_Load_res], store_value);
 903
 904         load_ptr = get_Load_ptr(load);
 905         kill_node(load);
 906         reduce_adr_usage(load_ptr);
 907         return res | DF_CHANGED;
 908 }
 909
 910 /**
 911  * Follow the memory chain as long as there are only Loads,
 912  * alias free Stores, and constant Calls and try to replace the
 913  * current Load by a previous ones.
 914  * Note that in unreachable loops it might happen that we reach
 915  * load again, as well as we can fall into a cycle.
 916  * We break such cycles using a special visited flag.
 917  *
 918  * INC_MASTER() must be called before dive into
 919  */
 920 static unsigned follow_Mem_chain(ir_node *load, ir_node *curr) {
 921         unsigned    res = 0;
 922         ldst_info_t *info = get_irn_link(load);
 923         ir_node     *pred;
 924         ir_node     *ptr       = get_Load_ptr(load);
 925         ir_node     *mem       = get_Load_mem(load);
 926         ir_mode     *load_mode = get_Load_mode(load);
 927
 928         for (pred = curr; load != pred; ) {
 929                 ldst_info_t *pred_info = get_irn_link(pred);
 930
 931                 /*
 932                  * a Load immediately after a Store -- a read after write.
 933                  * We may remove the Load, if both Load & Store does not have an
 934                  * exception handler OR they are in the same MacroBlock. In the latter
 935                  * case the Load cannot throw an exception when the previous Store was
 936                  * quiet.
 937                  *
 938                  * Why we need to check for Store Exception? If the Store cannot
 939                  * be executed (ROM) the exception handler might simply jump into
 940                  * the load MacroBlock :-(
 941                  * We could make it a little bit better if we would know that the
 942                  * exception handler of the Store jumps directly to the end...
 943                  */
 944                 if (is_Store(pred) && ((pred_info->projs[pn_Store_X_except] == NULL
 945                                 && info->projs[pn_Load_X_except] == NULL)
 946                                 || get_nodes_MacroBlock(load) == get_nodes_MacroBlock(pred)))
 947                 {
 948                         long    load_offset;
 949                         ir_node *base_ptr = get_base_and_offset(ptr, &load_offset);
 950                         int     changes   = try_load_after_store(load, base_ptr, load_offset, pred);
 951
 952                         if (changes != 0)
 953                                 return res | changes;
 954                 } else if (is_Load(pred) && get_Load_ptr(pred) == ptr &&
 955                            can_use_stored_value(get_Load_mode(pred), load_mode)) {
 956                         /*
 957                          * a Load after a Load -- a read after read.
 958                          * We may remove the second Load, if it does not have an exception handler
 959                          * OR they are in the same MacroBlock. In the later case the Load cannot
 960                          * throw an exception when the previous Load was quiet.
 961                          *
 962                          * Here, there is no need to check if the previous Load has an exception
 963                          * hander because they would have exact the same exception...
 964                          */
 965                         if (info->projs[pn_Load_X_except] == NULL || get_nodes_MacroBlock(load) == get_nodes_MacroBlock(pred)) {
 966                                 ir_node *value;
 967
 968                                 DBG_OPT_RAR(load, pred);
 969
 970                                 /* the result is used */
 971                                 if (info->projs[pn_Load_res]) {
 972                                         if (pred_info->projs[pn_Load_res] == NULL) {
 973                                                 /* create a new Proj again */
 974                                                 pred_info->projs[pn_Load_res] = new_r_Proj(current_ir_graph, get_nodes_block(pred), pred, get_Load_mode(pred), pn_Load_res);
 975                                         }
 976                                         value = pred_info->projs[pn_Load_res];
 977
 978                                         /* add an convert if needed */
 979                                         if (get_Load_mode(pred) != load_mode) {
 980                                                 value = new_r_Conv(current_ir_graph, get_nodes_block(load), value, load_mode);
 981                                         }
 982
 983                                         exchange(info->projs[pn_Load_res], value);
 984                                 }
 985
 986                                 if (info->projs[pn_Load_M])
 987                                         exchange(info->projs[pn_Load_M], mem);
 988
 989                                 /* no exception */
 990                                 if (info->projs[pn_Load_X_except]) {
 991                                         exchange(info->projs[pn_Load_X_except], new_Bad());
 992                                         res |= CF_CHANGED;
 993                                 }
 994                                 if (info->projs[pn_Load_X_regular]) {
 995                                         exchange( info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
 996                                         res |= CF_CHANGED;
 997                                 }
 998
 999                                 kill_node(load);
1000                                 reduce_adr_usage(ptr);
1001                                 return res |= DF_CHANGED;
1002                         }
1003                 }
1004
1005                 if (is_Store(pred)) {
1006                         /* check if we can pass through this store */
1007                         ir_alias_relation rel = get_alias_relation(
1008                                 current_ir_graph,
1009                                 get_Store_ptr(pred),
1010                                 get_irn_mode(get_Store_value(pred)),
1011                                 ptr, load_mode);
1012                         /* if the might be an alias, we cannot pass this Store */
1013                         if (rel != ir_no_alias)
1014                                 break;
1015                         pred = skip_Proj(get_Store_mem(pred));
1016                 } else if (is_Load(pred)) {
1017                         pred = skip_Proj(get_Load_mem(pred));
1018                 } else if (is_Call(pred)) {
1019                         if (is_Call_pure(pred)) {
1020                                 /* The called graph is at least pure, so there are no Store's
1021                                    in it. We can handle it like a Load and skip it. */
1022                                 pred = skip_Proj(get_Call_mem(pred));
1023                         } else {
1024                                 /* there might be Store's in the graph, stop here */
1025                                 break;
1026                         }
1027                 } else {
1028                         /* follow only Load chains */
1029                         break;
1030                 }
1031
1032                 /* check for cycles */
1033                 if (NODE_VISITED(pred_info))
1034                         break;
1035                 MARK_NODE(pred_info);
1036         }
1037
1038         if (is_Sync(pred)) {
1039                 int i;
1040
1041                 /* handle all Sync predecessors */
1042                 for (i = get_Sync_n_preds(pred) - 1; i >= 0; --i) {
1043                         res |= follow_Mem_chain(load, skip_Proj(get_Sync_pred(pred, i)));
1044                         if (res)
1045                                 return res;
1046                 }
1047         }
1048
1049         return res;
1050 }  /* follow_Mem_chain */
1051
1052 /*
1053  * Check if we can replace the load by a given const from
1054  * the const code irg.
1055  */
1056 ir_node *can_replace_load_by_const(const ir_node *load, ir_node *c) {
1057         ir_mode *c_mode = get_irn_mode(c);
1058         ir_mode *l_mode = get_Load_mode(load);
1059         ir_node *res    = NULL;
1060
1061         if (c_mode != l_mode) {
1062                 /* check, if the mode matches OR can be easily converted info */
1063                 if (is_reinterpret_cast(c_mode, l_mode)) {
1064                         /* we can safely cast */
1065                         dbg_info *dbg   = get_irn_dbg_info(load);
1066                         ir_node  *block = get_nodes_block(load);
1067
1068                         /* copy the value from the const code irg and cast it */
1069                         res = copy_const_value(dbg, c);
1070                         res = new_rd_Conv(dbg, current_ir_graph, block, res, l_mode);
1071                 }
1072         } else {
1073                 /* copy the value from the const code irg */
1074                 res = copy_const_value(get_irn_dbg_info(load), c);
1075         }
1076         return res;
1077 }  /* can_replace_load_by_const */
1078
1079 /**
1080  * optimize a Load
1081  *
1082  * @param load  the Load node
1083  */
1084 static unsigned optimize_load(ir_node *load)
1085 {
1086         ldst_info_t *info = get_irn_link(load);
1087         ir_node     *mem, *ptr, *value;
1088         ir_entity   *ent;
1089         long        dummy;
1090         unsigned    res = 0;
1091
1092         /* do NOT touch volatile loads for now */
1093         if (get_Load_volatility(load) == volatility_is_volatile)
1094                 return 0;
1095
1096         /* the address of the load to be optimized */
1097         ptr = get_Load_ptr(load);
1098
1099         /*
1100          * Check if we can remove the exception from a Load:
1101          * This can be done, if the address is from an Sel(Alloc) and
1102          * the Sel type is a subtype of the allocated type.
1103          *
1104          * This optimizes some often used OO constructs,
1105          * like x = new O; x->t;
1106          */
1107         if (info->projs[pn_Load_X_except]) {
1108                 ir_node *addr = ptr;
1109
1110                 /* find base address */
1111                 while (is_Sel(addr))
1112                         addr = get_Sel_ptr(addr);
1113                 if (is_Alloc(skip_Proj(skip_Cast(addr)))) {
1114                         /* simple case: a direct load after an Alloc. Firm Alloc throw
1115                          * an exception in case of out-of-memory. So, there is no way for an
1116                          * exception in this load.
1117                          * This code is constructed by the "exception lowering" in the Jack compiler.
1118                          */
1119                         exchange(info->projs[pn_Load_X_except], new_Bad());
1120                         info->projs[pn_Load_X_except] = NULL;
1121                         exchange(info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
1122                         info->projs[pn_Load_X_regular] = NULL;
1123                         res |= CF_CHANGED;
1124                 }
1125         }
1126
1127         /* The mem of the Load. Must still be returned after optimization. */
1128         mem = get_Load_mem(load);
1129
1130         if (! info->projs[pn_Load_res] && ! info->projs[pn_Load_X_except]) {
1131                 /* a Load which value is neither used nor exception checked, remove it */
1132                 exchange(info->projs[pn_Load_M], mem);
1133
1134                 if (info->projs[pn_Load_X_regular]) {
1135                         /* should not happen, but if it does, remove it */
1136                         exchange(info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
1137                         res |= CF_CHANGED;
1138                 }
1139                 kill_node(load);
1140                 reduce_adr_usage(ptr);
1141                 return res | DF_CHANGED;
1142         }
1143
1144         /* Load from a constant polymorphic field, where we can resolve
1145            polymorphism. */
1146         value = transform_polymorph_Load(load);
1147         if (value == load) {
1148                 value = NULL;
1149                 /* check if we can determine the entity that will be loaded */
1150                 ent = find_constant_entity(ptr);
1151                 if (ent != NULL                                     &&
1152                     allocation_static == get_entity_allocation(ent) &&
1153                     visibility_external_allocated != get_entity_visibility(ent)) {
1154                         /* a static allocation that is not external: there should be NO exception
1155                          * when loading even if we cannot replace the load itself. */
1156
1157                         /* no exception, clear the info field as it might be checked later again */
1158                         if (info->projs[pn_Load_X_except]) {
1159                                 exchange(info->projs[pn_Load_X_except], new_Bad());
1160                                 info->projs[pn_Load_X_except] = NULL;
1161                                 res |= CF_CHANGED;
1162                         }
1163                         if (info->projs[pn_Load_X_regular]) {
1164                                 exchange(info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
1165                                 info->projs[pn_Load_X_regular] = NULL;
1166                                 res |= CF_CHANGED;
1167                         }
1168
1169                         if (variability_constant == get_entity_variability(ent)) {
1170                                 if (is_atomic_entity(ent)) {
1171                                         /* Might not be atomic after lowering of Sels.  In this case we
1172                                          * could also load, but it's more complicated. */
1173                                         /* more simpler case: we load the content of a constant value:
1174                                          * replace it by the constant itself */
1175                                         value = get_atomic_ent_value(ent);
1176                                 } else if (ent->has_initializer) {
1177                                         /* new style initializer */
1178                                         value = find_compound_ent_value(ptr);
1179                                 } else {
1180                                         /* old style initializer */
1181                                         compound_graph_path *path = get_accessed_path(ptr);
1182
1183                                         if (path != NULL) {
1184                                                 assert(is_proper_compound_graph_path(path, get_compound_graph_path_length(path)-1));
1185
1186                                                 value = get_compound_ent_value_by_path(ent, path);
1187                                                 DB((dbg, LEVEL_1, "  Constant access at %F%F resulted in %+F\n", ent, path, value));
1188                                                 free_compound_graph_path(path);
1189                                         }
1190                                 }
1191                                 if (value != NULL)
1192                                         value = can_replace_load_by_const(load, value);
1193                         }
1194                 }
1195         }
1196         if (value != NULL) {
1197                 /* we completely replace the load by this value */
1198                 if (info->projs[pn_Load_X_except]) {
1199                         exchange(info->projs[pn_Load_X_except], new_Bad());
1200                         info->projs[pn_Load_X_except] = NULL;
1201                         res |= CF_CHANGED;
1202                 }
1203                 if (info->projs[pn_Load_X_regular]) {
1204                         exchange(info->projs[pn_Load_X_regular], new_r_Jmp(current_ir_graph, get_nodes_block(load)));
1205                         info->projs[pn_Load_X_regular] = NULL;
1206                         res |= CF_CHANGED;
1207                 }
1208                 if (info->projs[pn_Load_M]) {
1209                         exchange(info->projs[pn_Load_M], mem);
1210                         res |= DF_CHANGED;
1211                 }
1212                 if (info->projs[pn_Load_res]) {
1213                         exchange(info->projs[pn_Load_res], value);
1214                         res |= DF_CHANGED;
1215                 }
1216                 kill_node(load);
1217                 reduce_adr_usage(ptr);
1218                 return res;
1219         }
1220
1221         /* Check, if the address of this load is used more than once.
1222          * If not, more load cannot be removed in any case. */
1223         if (get_irn_n_uses(ptr) <= 1 && get_irn_n_uses(get_base_and_offset(ptr, &dummy)) <= 1)
1224                 return res;
1225
1226         /*
1227          * follow the memory chain as long as there are only Loads
1228          * and try to replace current Load or Store by a previous one.
1229          * Note that in unreachable loops it might happen that we reach
1230          * load again, as well as we can fall into a cycle.
1231          * We break such cycles using a special visited flag.
1232          */
1233         INC_MASTER();
1234         res = follow_Mem_chain(load, skip_Proj(mem));
1235         return res;
1236 }  /* optimize_load */
1237
1238 /**
1239  * Check whether a value of mode new_mode would completely overwrite a value
1240  * of mode old_mode in memory.
1241  */
1242 static int is_completely_overwritten(ir_mode *old_mode, ir_mode *new_mode)
1243 {
1244         return get_mode_size_bits(new_mode) >= get_mode_size_bits(old_mode);
1245 }  /* is_completely_overwritten */
1246
1247 /**
1248  * Check whether small is a part of large (starting at same address).
1249  */
1250 static int is_partially_same(ir_node *small, ir_node *large)
1251 {
1252         ir_mode *sm = get_irn_mode(small);
1253         ir_mode *lm = get_irn_mode(large);
1254
1255         /* FIXME: Check endianness */
1256         return is_Conv(small) && get_Conv_op(small) == large
1257             && get_mode_size_bytes(sm) < get_mode_size_bytes(lm)
1258             && get_mode_arithmetic(sm) == irma_twos_complement
1259             && get_mode_arithmetic(lm) == irma_twos_complement
1260                 && get_;
1261 }  /* is_partially_same */
1262
1263 /**
1264  * follow the memory chain as long as there are only Loads and alias free Stores.
1265  *
1266  * INC_MASTER() must be called before dive into
1267  */
1268 static unsigned follow_Mem_chain_for_Store(ir_node *store, ir_node *curr) {
1269         unsigned res = 0;
1270         ldst_info_t *info = get_irn_link(store);
1271         ir_node *pred;
1272         ir_node *ptr = get_Store_ptr(store);
1273         ir_node *mem = get_Store_mem(store);
1274         ir_node *value = get_Store_value(store);
1275         ir_mode *mode  = get_irn_mode(value);
1276         ir_node *block = get_nodes_block(store);
1277         ir_node *mblk  = get_Block_MacroBlock(block);
1278
1279         for (pred = curr; pred != store;) {
1280                 ldst_info_t *pred_info = get_irn_link(pred);
1281
1282                 /*
1283                  * BEWARE: one might think that checking the modes is useless, because
1284                  * if the pointers are identical, they refer to the same object.
1285                  * This is only true in strong typed languages, not is C were the following
1286                  * is possible *(ir_type1 *)p = a; *(ir_type2 *)p = b ...
1287                  * However, if the size of the mode that is written is bigger or equal the
1288                  * size of the old one, the old value is completely overwritten and can be
1289                  * killed ...
1290                  */
1291                 if (is_Store(pred) && get_Store_ptr(pred) == ptr &&
1292             get_nodes_MacroBlock(pred) == mblk) {
1293                         /*
1294                          * a Store after a Store in the same MacroBlock -- a write after write.
1295                          */
1296
1297                         /*
1298                          * We may remove the first Store, if the old value is completely
1299                          * overwritten or the old value is a part of the new value,
1300                          * and if it does not have an exception handler.
1301                          *
1302                          * TODO: What, if both have the same exception handler ???
1303                          */
1304                         if (get_Store_volatility(pred) != volatility_is_volatile
1305                                 && !pred_info->projs[pn_Store_X_except]) {
1306                                 ir_node *predvalue = get_Store_value(pred);
1307                                 ir_mode *predmode  = get_irn_mode(predvalue);
1308
1309                                 if(is_completely_overwritten(predmode, mode)
1310                                         || is_partially_same(predvalue, value)) {
1311                                         DBG_OPT_WAW(pred, store);
1312                                         exchange(pred_info->projs[pn_Store_M], get_Store_mem(pred));
1313                                         kill_node(pred);
1314                                         reduce_adr_usage(ptr);
1315                                         return DF_CHANGED;
1316                                 }
1317                         }
1318
1319                         /*
1320                          * We may remove the Store, if the old value already contains
1321                          * the new value, and if it does not have an exception handler.
1322                          *
1323                          * TODO: What, if both have the same exception handler ???
1324                          */
1325                         if (get_Store_volatility(store) != volatility_is_volatile
1326                                 && !info->projs[pn_Store_X_except]) {
1327                                 ir_node *predvalue = get_Store_value(pred);
1328
1329                                 if(is_partially_same(value, predvalue)) {
1330                                         DBG_OPT_WAW(pred, store);
1331                                         exchange(info->projs[pn_Store_M], mem);
1332                                         kill_node(store);
1333                                         reduce_adr_usage(ptr);
1334                                         return DF_CHANGED;
1335                                 }
1336                         }
1337                 } else if (is_Load(pred) && get_Load_ptr(pred) == ptr &&
1338                            value == pred_info->projs[pn_Load_res]) {
1339                         /*
1340                          * a Store of a value just loaded from the same address
1341                          * -- a write after read.
1342                          * We may remove the Store, if it does not have an exception
1343                          * handler.
1344                          */
1345                         if (! info->projs[pn_Store_X_except]) {
1346                                 DBG_OPT_WAR(store, pred);
1347                                 exchange(info->projs[pn_Store_M], mem);
1348                                 kill_node(store);
1349                                 reduce_adr_usage(ptr);
1350                                 return DF_CHANGED;
1351                         }
1352                 }
1353
1354                 if (is_Store(pred)) {
1355                         /* check if we can pass through this store */
1356                         ir_alias_relation rel = get_alias_relation(
1357                                 current_ir_graph,
1358                                 get_Store_ptr(pred),
1359                                 get_irn_mode(get_Store_value(pred)),
1360                                 ptr, mode);
1361                         /* if the might be an alias, we cannot pass this Store */
1362                         if (rel != ir_no_alias)
1363                                 break;
1364                         pred = skip_Proj(get_Store_mem(pred));
1365                 } else if (is_Load(pred)) {
1366                         ir_alias_relation rel = get_alias_relation(
1367                                 current_ir_graph, get_Load_ptr(pred), get_Load_mode(pred),
1368                                 ptr, mode);
1369                         if (rel != ir_no_alias)
1370                                 break;
1371
1372                         pred = skip_Proj(get_Load_mem(pred));
1373                 } else {
1374                         /* follow only Load chains */
1375                         break;
1376                 }
1377
1378                 /* check for cycles */
1379                 if (NODE_VISITED(pred_info))
1380                         break;
1381                 MARK_NODE(pred_info);
1382         }
1383
1384         if (is_Sync(pred)) {
1385                 int i;
1386
1387                 /* handle all Sync predecessors */
1388                 for (i = get_Sync_n_preds(pred) - 1; i >= 0; --i) {
1389                         res |= follow_Mem_chain_for_Store(store, skip_Proj(get_Sync_pred(pred, i)));
1390                         if (res)
1391                                 break;
1392                 }
1393         }
1394         return res;
1395 }  /* follow_Mem_chain_for_Store */
1396
1397 /** find entity used as base for an address calculation */
1398 static ir_entity *find_entity(ir_node *ptr)
1399 {
1400         switch(get_irn_opcode(ptr)) {
1401         case iro_SymConst:
1402                 return get_SymConst_entity(ptr);
1403         case iro_Sel: {
1404                 ir_node *pred = get_Sel_ptr(ptr);
1405                 if (get_irg_frame(get_irn_irg(ptr)) == pred)
1406                         return get_Sel_entity(ptr);
1407
1408                 return find_entity(pred);
1409         }
1410         case iro_Sub:
1411         case iro_Add: {
1412                 ir_node *left = get_binop_left(ptr);
1413                 ir_node *right;
1414                 if (mode_is_reference(get_irn_mode(left)))
1415                         return find_entity(left);
1416                 right = get_binop_right(ptr);
1417                 if (mode_is_reference(get_irn_mode(right)))
1418                         return find_entity(right);
1419                 return NULL;
1420         }
1421         default:
1422                 return NULL;
1423         }
1424 }
1425
1426 /**
1427  * optimize a Store
1428  *
1429  * @param store  the Store node
1430  */
1431 static unsigned optimize_store(ir_node *store) {
1432         ir_node   *ptr;
1433         ir_node   *mem;
1434         ir_entity *entity;
1435
1436         if (get_Store_volatility(store) == volatility_is_volatile)
1437                 return 0;
1438
1439         ptr    = get_Store_ptr(store);
1440         entity = find_entity(ptr);
1441
1442         /* a store to an entity which is never read is unnecessary */
1443         if (entity != NULL && !(get_entity_usage(entity) & ir_usage_read)) {
1444                 ldst_info_t *info = get_irn_link(store);
1445                 if (info->projs[pn_Store_X_except] == NULL) {
1446                         exchange(info->projs[pn_Store_M], get_Store_mem(store));
1447                         kill_node(store);
1448                         reduce_adr_usage(ptr);
1449                         return DF_CHANGED;
1450                 }
1451         }
1452
1453         /* Check, if the address of this Store is used more than once.
1454          * If not, this Store cannot be removed in any case. */
1455         if (get_irn_n_uses(ptr) <= 1)
1456                 return 0;
1457
1458         mem = get_Store_mem(store);
1459
1460         /* follow the memory chain as long as there are only Loads */
1461         INC_MASTER();
1462
1463         return follow_Mem_chain_for_Store(store, skip_Proj(mem));
1464 }  /* optimize_store */
1465
1466 /**
1467  * walker, optimizes Phi after Stores to identical places:
1468  * Does the following optimization:
1469  * @verbatim
1470  *
1471  *   val1   val2   val3          val1  val2  val3
1472  *    |      |      |               \    |    /
1473  *  Store  Store  Store              \   |   /
1474  *      \    |    /                   PhiData
1475  *       \   |   /                       |
1476  *        \  |  /                      Store
1477  *          PhiM
1478  *
1479  * @endverbatim
1480  * This reduces the number of stores and allows for predicated execution.
1481  * Moves Stores back to the end of a function which may be bad.
1482  *
1483  * This is only possible if the predecessor blocks have only one successor.
1484  */
1485 static unsigned optimize_phi(ir_node *phi, walk_env_t *wenv)
1486 {
1487         int i, n;
1488         ir_node *store, *old_store, *ptr, *block, *phi_block, *phiM, *phiD, *exc, *projM;
1489         ir_mode *mode;
1490         ir_node **inM, **inD, **projMs;
1491         int *idx;
1492         dbg_info *db = NULL;
1493         ldst_info_t *info;
1494         block_info_t *bl_info;
1495         unsigned res = 0;
1496
1497         /* Must be a memory Phi */
1498         if (get_irn_mode(phi) != mode_M)
1499                 return 0;
1500
1501         n = get_Phi_n_preds(phi);
1502         if (n <= 0)
1503                 return 0;
1504
1505         /* must be only one user */
1506         projM = get_Phi_pred(phi, 0);
1507         if (get_irn_n_edges(projM) != 1)
1508                 return 0;
1509
1510         store = skip_Proj(projM);
1511         old_store = store;
1512         if (!is_Store(store))
1513                 return 0;
1514
1515         block = get_nodes_block(store);
1516
1517         /* abort on dead blocks */
1518         if (is_Block_dead(block))
1519                 return 0;
1520
1521         /* check if the block is post dominated by Phi-block
1522            and has no exception exit */
1523         bl_info = get_irn_link(block);
1524         if (bl_info->flags & BLOCK_HAS_EXC)
1525                 return 0;
1526
1527         phi_block = get_nodes_block(phi);
1528         if (! block_strictly_postdominates(phi_block, block))
1529                 return 0;
1530
1531         /* this is the address of the store */
1532         ptr  = get_Store_ptr(store);
1533         mode = get_irn_mode(get_Store_value(store));
1534         info = get_irn_link(store);
1535         exc  = info->exc_block;
1536
1537         for (i = 1; i < n; ++i) {
1538                 ir_node *pred = get_Phi_pred(phi, i);
1539
1540                 if (get_irn_n_edges(pred) != 1)
1541                         return 0;
1542
1543                 pred = skip_Proj(pred);
1544                 if (!is_Store(pred))
1545                         return 0;
1546
1547                 if (ptr != get_Store_ptr(pred) || mode != get_irn_mode(get_Store_value(pred)))
1548                         return 0;
1549
1550                 info = get_irn_link(pred);
1551
1552                 /* check, if all stores have the same exception flow */
1553                 if (exc != info->exc_block)
1554                         return 0;
1555
1556                 /* abort on dead blocks */
1557                 block = get_nodes_block(pred);
1558                 if (is_Block_dead(block))
1559                         return 0;
1560
1561                 /* check if the block is post dominated by Phi-block
1562                    and has no exception exit. Note that block must be different from
1563                    Phi-block, else we would move a Store from end End of a block to its
1564                    Start... */
1565                 bl_info = get_irn_link(block);
1566                 if (bl_info->flags & BLOCK_HAS_EXC)
1567                         return 0;
1568                 if (block == phi_block || ! block_postdominates(phi_block, block))
1569                         return 0;
1570         }
1571
1572         /*
1573          * ok, when we are here, we found all predecessors of a Phi that
1574          * are Stores to the same address and size. That means whatever
1575          * we do before we enter the block of the Phi, we do a Store.
1576          * So, we can move the Store to the current block:
1577          *
1578          *   val1    val2    val3          val1  val2  val3
1579          *    |       |       |               \    |    /
1580          * | Str | | Str | | Str |             \   |   /
1581          *      \     |     /                   PhiData
1582          *       \    |    /                       |
1583          *        \   |   /                       Str
1584          *           PhiM
1585          *
1586          * Is only allowed if the predecessor blocks have only one successor.
1587          */
1588
1589         NEW_ARR_A(ir_node *, projMs, n);
1590         NEW_ARR_A(ir_node *, inM, n);
1591         NEW_ARR_A(ir_node *, inD, n);
1592         NEW_ARR_A(int, idx, n);
1593
1594         /* Prepare: Collect all Store nodes.  We must do this
1595            first because we otherwise may loose a store when exchanging its
1596            memory Proj.
1597          */
1598         for (i = n - 1; i >= 0; --i) {
1599                 ir_node *store;
1600
1601                 projMs[i] = get_Phi_pred(phi, i);
1602                 assert(is_Proj(projMs[i]));
1603
1604                 store = get_Proj_pred(projMs[i]);
1605                 info  = get_irn_link(store);
1606
1607                 inM[i] = get_Store_mem(store);
1608                 inD[i] = get_Store_value(store);
1609                 idx[i] = info->exc_idx;
1610         }
1611         block = get_nodes_block(phi);
1612
1613         /* second step: create a new memory Phi */
1614         phiM = new_rd_Phi(get_irn_dbg_info(phi), current_ir_graph, block, n, inM, mode_M);
1615
1616         /* third step: create a new data Phi */
1617         phiD = new_rd_Phi(get_irn_dbg_info(phi), current_ir_graph, block, n, inD, mode);
1618
1619         /* rewire memory and kill the node */
1620         for (i = n - 1; i >= 0; --i) {
1621                 ir_node *proj  = projMs[i];
1622
1623                 if(is_Proj(proj)) {
1624                         ir_node *store = get_Proj_pred(proj);
1625                         exchange(proj, inM[i]);
1626                         kill_node(store);
1627                 }
1628         }
1629
1630         /* fourth step: create the Store */
1631         store = new_rd_Store(db, current_ir_graph, block, phiM, ptr, phiD);
1632 #ifdef DO_CACHEOPT
1633         co_set_irn_name(store, co_get_irn_ident(old_store));
1634 #endif
1635
1636         projM = new_rd_Proj(NULL, current_ir_graph, block, store, mode_M, pn_Store_M);
1637
1638         info = get_ldst_info(store, &wenv->obst);
1639         info->projs[pn_Store_M] = projM;
1640
1641         /* fifths step: repair exception flow */
1642         if (exc) {
1643                 ir_node *projX = new_rd_Proj(NULL, current_ir_graph, block, store, mode_X, pn_Store_X_except);
1644
1645                 info->projs[pn_Store_X_except] = projX;
1646                 info->exc_block                = exc;
1647                 info->exc_idx                  = idx[0];
1648
1649                 for (i = 0; i < n; ++i) {
1650                         set_Block_cfgpred(exc, idx[i], projX);
1651                 }
1652
1653                 if (n > 1) {
1654                         /* the exception block should be optimized as some inputs are identical now */
1655                 }
1656
1657                 res |= CF_CHANGED;
1658         }
1659
1660         /* sixth step: replace old Phi */
1661         exchange(phi, projM);
1662
1663         return res | DF_CHANGED;
1664 }  /* optimize_phi */
1665
1666 /**
1667  * walker, do the optimizations
1668  */
1669 static void do_load_store_optimize(ir_node *n, void *env) {
1670         walk_env_t *wenv = env;
1671
1672         switch (get_irn_opcode(n)) {
1673
1674         case iro_Load:
1675                 wenv->changes |= optimize_load(n);
1676                 break;
1677
1678         case iro_Store:
1679                 wenv->changes |= optimize_store(n);
1680                 break;
1681
1682         case iro_Phi:
1683                 wenv->changes |= optimize_phi(n, wenv);
1684                 break;
1685
1686         default:
1687                 ;
1688         }
1689 }  /* do_load_store_optimize */
1690
1691 /** A scc. */
1692 typedef struct scc {
1693         ir_node *head;          /**< the head of the list */
1694 } scc;
1695
1696 /** A node entry. */
1697 typedef struct node_entry {
1698         unsigned DFSnum;    /**< the DFS number of this node */
1699         unsigned low;       /**< the low number of this node */
1700         ir_node  *header;   /**< the header of this node */
1701         int      in_stack;  /**< flag, set if the node is on the stack */
1702         ir_node  *next;     /**< link to the next node the the same scc */
1703         scc      *pscc;     /**< the scc of this node */
1704         unsigned POnum;     /**< the post order number for blocks */
1705 } node_entry;
1706
1707 /** A loop entry. */
1708 typedef struct loop_env {
1709         ir_phase ph;           /**< the phase object */
1710         ir_node  **stack;      /**< the node stack */
1711         int      tos;          /**< tos index */
1712         unsigned nextDFSnum;   /**< the current DFS number */
1713         unsigned POnum;        /**< current post order number */
1714
1715         unsigned changes;      /**< a bitmask of graph changes */
1716 } loop_env;
1717
1718 /**
1719 * Gets the node_entry of a node
1720 */
1721 static node_entry *get_irn_ne(ir_node *irn, loop_env *env) {
1722         ir_phase   *ph = &env->ph;
1723         node_entry *e  = phase_get_irn_data(&env->ph, irn);
1724
1725         if (! e) {
1726                 e = phase_alloc(ph, sizeof(*e));
1727                 memset(e, 0, sizeof(*e));
1728                 phase_set_irn_data(ph, irn, e);
1729         }
1730         return e;
1731 }  /* get_irn_ne */
1732
1733 /**
1734  * Push a node onto the stack.
1735  *
1736  * @param env   the loop environment
1737  * @param n     the node to push
1738  */
1739 static void push(loop_env *env, ir_node *n) {
1740         node_entry *e;
1741
1742         if (env->tos == ARR_LEN(env->stack)) {
1743                 int nlen = ARR_LEN(env->stack) * 2;
1744                 ARR_RESIZE(ir_node *, env->stack, nlen);
1745         }
1746         env->stack[env->tos++] = n;
1747         e = get_irn_ne(n, env);
1748         e->in_stack = 1;
1749 }  /* push */
1750
1751 /**
1752  * pop a node from the stack
1753  *
1754  * @param env   the loop environment
1755  *
1756  * @return  The topmost node
1757  */
1758 static ir_node *pop(loop_env *env) {
1759         ir_node *n = env->stack[--env->tos];
1760         node_entry *e = get_irn_ne(n, env);
1761
1762         e->in_stack = 0;
1763         return n;
1764 }  /* pop */
1765
1766 /**
1767  * Check if irn is a region constant.
1768  * The block or irn must strictly dominate the header block.
1769  *
1770  * @param irn           the node to check
1771  * @param header_block  the header block of the induction variable
1772  */
1773 static int is_rc(ir_node *irn, ir_node *header_block) {
1774         ir_node *block = get_nodes_block(irn);
1775
1776         return (block != header_block) && block_dominates(block, header_block);
1777 }  /* is_rc */
1778
1779 typedef struct phi_entry phi_entry;
1780 struct phi_entry {
1781         ir_node   *phi;    /**< A phi with a region const memory. */
1782         int       pos;     /**< The position of the region const memory */
1783         ir_node   *load;   /**< the newly created load for this phi */
1784         phi_entry *next;
1785 };
1786
1787 /**
1788  * Move loops out of loops if possible.
1789  *
1790  * @param pscc   the loop described by an SCC
1791  * @param env    the loop environment
1792  */
1793 static void move_loads_out_of_loops(scc *pscc, loop_env *env) {
1794         ir_node   *phi, *load, *next, *other, *next_other;
1795         ir_entity *ent;
1796         int       j;
1797         phi_entry *phi_list = NULL;
1798
1799         /* collect all outer memories */
1800         for (phi = pscc->head; phi != NULL; phi = next) {
1801                 node_entry *ne = get_irn_ne(phi, env);
1802                 next = ne->next;
1803
1804                 /* check all memory Phi's */
1805                 if (! is_Phi(phi))
1806                         continue;
1807
1808                 assert(get_irn_mode(phi) == mode_M && "DFS geturn non-memory Phi");
1809
1810                 for (j = get_irn_arity(phi) - 1; j >= 0; --j) {
1811                         ir_node    *pred = get_irn_n(phi, j);
1812                         node_entry *pe   = get_irn_ne(pred, env);
1813
1814                         if (pe->pscc != ne->pscc) {
1815                                 /* not in the same SCC, is region const */
1816                                 phi_entry *pe = phase_alloc(&env->ph, sizeof(*pe));
1817
1818                                 pe->phi  = phi;
1819                                 pe->pos  = j;
1820                                 pe->next = phi_list;
1821                                 phi_list = pe;
1822                         }
1823                 }
1824         }
1825         /* no Phis no fun */
1826         assert(phi_list != NULL && "DFS found a loop without Phi");
1827
1828         for (load = pscc->head; load; load = next) {
1829                 ir_mode *load_mode;
1830                 node_entry *ne = get_irn_ne(load, env);
1831                 next = ne->next;
1832
1833                 if (is_Load(load)) {
1834                         ldst_info_t *info = get_irn_link(load);
1835                         ir_node     *ptr = get_Load_ptr(load);
1836
1837                         /* for now, we cannot handle Loads with exceptions */
1838                         if (info->projs[pn_Load_res] == NULL || info->projs[pn_Load_X_regular] != NULL || info->projs[pn_Load_X_except] != NULL)
1839                                 continue;
1840
1841                         /* for now, we can only handle Load(Global) */
1842                         if (! is_Global(ptr))
1843                                 continue;
1844                         ent = get_Global_entity(ptr);
1845                         load_mode = get_Load_mode(load);
1846                         for (other = pscc->head; other != NULL; other = next_other) {
1847                                 node_entry *ne = get_irn_ne(other, env);
1848                                 next_other = ne->next;
1849
1850                                 if (is_Store(other)) {
1851                                         ir_alias_relation rel = get_alias_relation(
1852                                                 current_ir_graph,
1853                                                 get_Store_ptr(other),
1854                                                 get_irn_mode(get_Store_value(other)),
1855                                                 ptr, load_mode);
1856                                         /* if the might be an alias, we cannot pass this Store */
1857                                         if (rel != ir_no_alias)
1858                                                 break;
1859                                 }
1860                                 /* only pure Calls are allowed here, so ignore them */
1861                         }
1862                         if (other == NULL) {
1863                                 ldst_info_t *ninfo;
1864                                 phi_entry   *pe;
1865                                 dbg_info    *db;
1866
1867                                 /* for now, we cannot handle more than one input */
1868                                 if (phi_list->next != NULL)
1869                                         return;
1870
1871                                 /* yep, no aliasing Store found, Load can be moved */
1872                                 DB((dbg, LEVEL_1, "  Found a Load that could be moved: %+F\n", load));
1873
1874                                 db   = get_irn_dbg_info(load);
1875                                 for (pe = phi_list; pe != NULL; pe = pe->next) {
1876                                         int     pos   = pe->pos;
1877                                         ir_node *phi  = pe->phi;
1878                                         ir_node *blk  = get_nodes_block(phi);
1879                                         ir_node *pred = get_Block_cfgpred_block(blk, pos);
1880                                         ir_node *irn, *mem;
1881
1882                                         pe->load = irn = new_rd_Load(db, current_ir_graph, pred, get_Phi_pred(phi, pos), ptr, load_mode);
1883                                         ninfo = get_ldst_info(irn, phase_obst(&env->ph));
1884
1885                                         ninfo->projs[pn_Load_M] = mem = new_r_Proj(current_ir_graph, pred, irn, mode_M, pn_Load_M);
1886                                         set_Phi_pred(phi, pos, mem);
1887
1888                                         ninfo->projs[pn_Load_res] = new_r_Proj(current_ir_graph, pred, irn, load_mode, pn_Load_res);
1889
1890                                         DB((dbg, LEVEL_1, "  Created %+F in %+F\n", irn, pred));
1891                                 }
1892
1893                                 /* now kill the old Load */
1894                                 exchange(info->projs[pn_Load_M], get_Load_mem(load));
1895                                 exchange(info->projs[pn_Load_res], ninfo->projs[pn_Load_res]);
1896
1897                                 env->changes |= DF_CHANGED;
1898                         }
1899                 }
1900         }
1901 }  /* move_loads_out_of_loops */
1902
1903 /**
1904  * Process a loop SCC.
1905  *
1906  * @param pscc  the SCC
1907  * @param env   the loop environment
1908  */
1909 static void process_loop(scc *pscc, loop_env *env) {
1910         ir_node *irn, *next, *header = NULL;
1911         node_entry *b, *h = NULL;
1912         int j, only_phi, num_outside, process = 0;
1913         ir_node *out_rc;
1914
1915         /* find the header block for this scc */
1916         for (irn = pscc->head; irn; irn = next) {
1917                 node_entry *e = get_irn_ne(irn, env);
1918                 ir_node *block = get_nodes_block(irn);
1919
1920                 next = e->next;
1921                 b = get_irn_ne(block, env);
1922
1923                 if (header) {
1924                         if (h->POnum < b->POnum) {
1925                                 header = block;
1926                                 h      = b;
1927                         }
1928                 }
1929                 else {
1930                         header = block;
1931                         h      = b;
1932                 }
1933         }
1934
1935         /* check if this scc contains only Phi, Loads or Stores nodes */
1936         only_phi    = 1;
1937         num_outside = 0;
1938         out_rc      = NULL;
1939         for (irn = pscc->head; irn; irn = next) {
1940                 node_entry *e = get_irn_ne(irn, env);
1941
1942                 next = e->next;
1943                 switch (get_irn_opcode(irn)) {
1944                 case iro_Call:
1945                         if (is_Call_pure(irn)) {
1946                                 /* pure calls can be treated like loads */
1947                                 only_phi = 0;
1948                                 break;
1949                         }
1950                         /* non-pure calls must be handle like may-alias Stores */
1951                         goto fail;
1952                 case iro_CopyB:
1953                         /* cannot handle CopyB yet */
1954                         goto fail;
1955                 case iro_Load:
1956                         process = 1;
1957                         if (get_Load_volatility(irn) == volatility_is_volatile) {
1958                                 /* cannot handle loops with volatile Loads */
1959                                 goto fail;
1960                         }
1961                         only_phi = 0;
1962                         break;
1963                 case iro_Store:
1964                         if (get_Store_volatility(irn) == volatility_is_volatile) {
1965                                 /* cannot handle loops with volatile Stores */
1966                                 goto fail;
1967                         }
1968                         only_phi = 0;
1969                         break;
1970                 default:
1971                         only_phi = 0;
1972                         break;
1973                 case iro_Phi:
1974                         for (j = get_irn_arity(irn) - 1; j >= 0; --j) {
1975                                 ir_node *pred  = get_irn_n(irn, j);
1976                                 node_entry *pe = get_irn_ne(pred, env);
1977
1978                                 if (pe->pscc != e->pscc) {
1979                                         /* not in the same SCC, must be a region const */
1980                                         if (! is_rc(pred, header)) {
1981                                                 /* not a memory loop */
1982                                                 goto fail;
1983                                         }
1984                                         if (! out_rc) {
1985                                                 out_rc = pred;
1986                                                 ++num_outside;
1987                                         } else if (out_rc != pred) {
1988                                                 ++num_outside;
1989                                         }
1990                                 }
1991                         }
1992                         break;
1993                 }
1994         }
1995         if (! process)
1996                 goto fail;
1997
1998         /* found a memory loop */
1999         DB((dbg, LEVEL_2, "  Found a memory loop:\n  "));
2000         if (only_phi && num_outside == 1) {
2001                 /* a phi cycle with only one real predecessor can be collapsed */
2002                 DB((dbg, LEVEL_2, "  Found an USELESS Phi cycle:\n  "));
2003
2004                 for (irn = pscc->head; irn; irn = next) {
2005                         node_entry *e = get_irn_ne(irn, env);
2006                         next = e->next;
2007                         e->header = NULL;
2008                         exchange(irn, out_rc);
2009                 }
2010                 env->changes |= DF_CHANGED;
2011                 return;
2012         }
2013
2014         /* set the header for every node in this scc */
2015         for (irn = pscc->head; irn; irn = next) {
2016                 node_entry *e = get_irn_ne(irn, env);
2017                 e->header = header;
2018                 next = e->next;
2019                 DB((dbg, LEVEL_2, " %+F,", irn));
2020         }
2021         DB((dbg, LEVEL_2, "\n"));
2022
2023         move_loads_out_of_loops(pscc, env);
2024
2025 fail:
2026         ;
2027 }  /* process_loop */
2028
2029 /**
2030  * Process a SCC.
2031  *
2032  * @param pscc  the SCC
2033  * @param env   the loop environment
2034  */
2035 static void process_scc(scc *pscc, loop_env *env) {
2036         ir_node *head = pscc->head;
2037         node_entry *e = get_irn_ne(head, env);
2038
2039 #ifdef DEBUG_libfirm
2040         {
2041                 ir_node *irn, *next;
2042
2043                 DB((dbg, LEVEL_4, " SCC at %p:\n ", pscc));
2044                 for (irn = pscc->head; irn; irn = next) {
2045                         node_entry *e = get_irn_ne(irn, env);
2046
2047                         next = e->next;
2048
2049                         DB((dbg, LEVEL_4, " %+F,", irn));
2050                 }
2051                 DB((dbg, LEVEL_4, "\n"));
2052         }
2053 #endif
2054
2055         if (e->next != NULL) {
2056                 /* this SCC has more than one member */
2057                 process_loop(pscc, env);
2058         }
2059 }  /* process_scc */
2060
2061 /**
2062  * Do Tarjan's SCC algorithm and drive load/store optimization.
2063  *
2064  * @param irn  start at this node
2065  * @param env  the loop environment
2066  */
2067 static void dfs(ir_node *irn, loop_env *env)
2068 {
2069         int i, n;
2070         node_entry *node = get_irn_ne(irn, env);
2071
2072         mark_irn_visited(irn);
2073
2074         node->DFSnum = env->nextDFSnum++;
2075         node->low    = node->DFSnum;
2076         push(env, irn);
2077
2078         /* handle preds */
2079         if (is_Phi(irn) || is_Sync(irn)) {
2080                 n = get_irn_arity(irn);
2081                 for (i = 0; i < n; ++i) {
2082                         ir_node *pred = get_irn_n(irn, i);
2083                         node_entry *o = get_irn_ne(pred, env);
2084
2085                         if (irn_not_visited(pred)) {
2086                                 dfs(pred, env);
2087                                 node->low = MIN(node->low, o->low);
2088                         }
2089                         if (o->DFSnum < node->DFSnum && o->in_stack)
2090                                 node->low = MIN(o->DFSnum, node->low);
2091                 }
2092         } else if (is_fragile_op(irn)) {
2093                 ir_node *pred = get_fragile_op_mem(irn);
2094                 node_entry *o = get_irn_ne(pred, env);
2095
2096                 if (irn_not_visited(pred)) {
2097                         dfs(pred, env);
2098                         node->low = MIN(node->low, o->low);
2099                 }
2100                 if (o->DFSnum < node->DFSnum && o->in_stack)
2101                         node->low = MIN(o->DFSnum, node->low);
2102         } else if (is_Proj(irn)) {
2103                 ir_node *pred = get_Proj_pred(irn);
2104                 node_entry *o = get_irn_ne(pred, env);
2105
2106                 if (irn_not_visited(pred)) {
2107                         dfs(pred, env);
2108                         node->low = MIN(node->low, o->low);
2109                 }
2110                 if (o->DFSnum < node->DFSnum && o->in_stack)
2111                         node->low = MIN(o->DFSnum, node->low);
2112         }
2113         else {
2114                  /* IGNORE predecessors */
2115         }
2116
2117         if (node->low == node->DFSnum) {
2118                 scc *pscc = phase_alloc(&env->ph, sizeof(*pscc));
2119                 ir_node *x;
2120
2121                 pscc->head = NULL;
2122                 do {
2123                         node_entry *e;
2124
2125                         x = pop(env);
2126                         e = get_irn_ne(x, env);
2127                         e->pscc    = pscc;
2128                         e->next    = pscc->head;
2129                         pscc->head = x;
2130                 } while (x != irn);
2131
2132                 process_scc(pscc, env);
2133         }
2134 }  /* dfs */
2135
2136 /**
2137  * Do the DFS on the memory edges a graph.
2138  *
2139  * @param irg  the graph to process
2140  * @param env  the loop environment
2141  */
2142 static void do_dfs(ir_graph *irg, loop_env *env) {
2143         ir_graph *rem = current_ir_graph;
2144         ir_node  *endblk, *end;
2145         int      i;
2146
2147         current_ir_graph = irg;
2148         inc_irg_visited(irg);
2149
2150         /* visit all memory nodes */
2151         endblk = get_irg_end_block(irg);
2152         for (i = get_Block_n_cfgpreds(endblk) - 1; i >= 0; --i) {
2153                 ir_node *pred = get_Block_cfgpred(endblk, i);
2154
2155                 pred = skip_Proj(pred);
2156                 if (is_Return(pred))
2157                         dfs(get_Return_mem(pred), env);
2158                 else if (is_Raise(pred))
2159                         dfs(get_Raise_mem(pred), env);
2160                 else if (is_fragile_op(pred))
2161                         dfs(get_fragile_op_mem(pred), env);
2162                 else {
2163                         assert(0 && "Unknown EndBlock predecessor");
2164                 }
2165         }
2166
2167         /* visit the keep-alives */
2168         end = get_irg_end(irg);
2169         for (i = get_End_n_keepalives(end) - 1; i >= 0; --i) {
2170                 ir_node *ka = get_End_keepalive(end, i);
2171
2172                 if (is_Phi(ka) && irn_not_visited(ka))
2173                         dfs(ka, env);
2174         }
2175         current_ir_graph = rem;
2176 }  /* do_dfs */
2177
2178 /**
2179  * Initialize new phase data. We do this always explicit, so return NULL here
2180  */
2181 static void *init_loop_data(ir_phase *ph, const ir_node *irn, void *data) {
2182         (void)ph;
2183         (void)irn;
2184         (void)data;
2185         return NULL;
2186 }  /* init_loop_data */
2187
2188 /**
2189  * Optimize Loads/Stores in loops.
2190  *
2191  * @param irg  the graph
2192  */
2193 static int optimize_loops(ir_graph *irg) {
2194         loop_env env;
2195
2196         env.stack         = NEW_ARR_F(ir_node *, 128);
2197         env.tos           = 0;
2198         env.nextDFSnum    = 0;
2199         env.POnum         = 0;
2200         env.changes       = 0;
2201         phase_init(&env.ph, "ldstopt", irg, PHASE_DEFAULT_GROWTH, init_loop_data, NULL);
2202
2203         /* calculate the SCC's and drive loop optimization. */
2204         do_dfs(irg, &env);
2205
2206         DEL_ARR_F(env.stack);
2207         phase_free(&env.ph);
2208
2209         return env.changes;
2210 }  /* optimize_loops */
2211
2212 /*
2213  * do the load store optimization
2214  */
2215 void optimize_load_store(ir_graph *irg) {
2216         walk_env_t env;
2217
2218         FIRM_DBG_REGISTER(dbg, "firm.opt.ldstopt");
2219
2220         assert(get_irg_phase_state(irg) != phase_building);
2221         assert(get_irg_pinned(irg) != op_pin_state_floats &&
2222                 "LoadStore optimization needs pinned graph");
2223
2224         /* we need landing pads */
2225         remove_critical_cf_edges(irg);
2226
2227         edges_assure(irg);
2228
2229         /* for Phi optimization post-dominators are needed ... */
2230         assure_postdoms(irg);
2231
2232         if (get_opt_alias_analysis()) {
2233                 assure_irg_entity_usage_computed(irg);
2234                 assure_irp_globals_entity_usage_computed();
2235         }
2236
2237         obstack_init(&env.obst);
2238         env.changes = 0;
2239
2240         /* init the links, then collect Loads/Stores/Proj's in lists */
2241         master_visited = 0;
2242         irg_walk_graph(irg, firm_clear_link, collect_nodes, &env);
2243
2244         /* now we have collected enough information, optimize */
2245         irg_walk_graph(irg, NULL, do_load_store_optimize, &env);
2246
2247         env.changes |= optimize_loops(irg);
2248
2249         obstack_free(&env.obst, NULL);
2250
2251         /* Handle graph state */
2252         if (env.changes) {
2253                 set_irg_outs_inconsistent(irg);
2254                 set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
2255         }
2256
2257         if (env.changes & CF_CHANGED) {
2258                 /* is this really needed: Yes, control flow changed, block might
2259                 have Bad() predecessors. */
2260                 set_irg_doms_inconsistent(irg);
2261         }
2262 }  /* optimize_load_store */