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

   1 /*
   2  * This file is part of libFirm.
   3  * Copyright (C) 2012 University of Karlsruhe.
   4  */
   5
   6 /**
   7  * @file
   8  * @brief   Tail-recursion call optimization.
   9  * @date    08.06.2004
  10  * @author  Michael Beck
  11  */
  12 #include "config.h"
  13
  14 #include <string.h>
  15 #include <assert.h>
  16
  17 #include "debug.h"
  18 #include "iroptimize.h"
  19 #include "scalar_replace.h"
  20 #include "array_t.h"
  21 #include "irprog_t.h"
  22 #include "irgwalk.h"
  23 #include "irgmod.h"
  24 #include "irop.h"
  25 #include "irnode_t.h"
  26 #include "irgraph_t.h"
  27 #include "ircons.h"
  28 #include "irflag.h"
  29 #include "trouts.h"
  30 #include "irouts.h"
  31 #include "irhooks.h"
  32 #include "ircons_t.h"
  33 #include "irpass.h"
  34 #include "util.h"
  35
  36 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  37
  38 /**
  39  * the environment for collecting data
  40  */
  41 typedef struct collect_t {
  42         ir_node *proj_X;      /**< initial exec proj */
  43         ir_node *block;       /**< old first block */
  44         int     blk_idx;      /**< cfgpred index of the initial exec in block */
  45         ir_node *proj_m;      /**< memory from start proj's */
  46         ir_node *proj_data;   /**< linked list of all parameter access proj's */
  47 } collect_t;
  48
  49 /**
  50  * walker for collecting data, fills a collect_t environment
  51  */
  52 static void collect_data(ir_node *node, void *env)
  53 {
  54         collect_t *data = (collect_t*)env;
  55         ir_node *pred;
  56         ir_opcode opcode;
  57
  58         switch (get_irn_opcode(node)) {
  59         case iro_Proj:
  60                 pred = get_Proj_pred(node);
  61
  62                 opcode = (ir_opcode)get_irn_opcode(pred);
  63                 if (opcode == iro_Proj) {
  64                         ir_node *start = get_Proj_pred(pred);
  65
  66                         if (is_Start(start)) {
  67                                 if (get_Proj_proj(pred) == pn_Start_T_args) {
  68                                         /* found Proj(ProjT(Start)) */
  69                                         set_irn_link(node, data->proj_data);
  70                                         data->proj_data = node;
  71                                 }
  72                         }
  73                 } else if (opcode == iro_Start) {
  74                         if (get_Proj_proj(node) == pn_Start_X_initial_exec) {
  75                                 /* found ProjX(Start) */
  76                                 data->proj_X = node;
  77                         }
  78                 }
  79                 break;
  80         case iro_Block: {
  81                 int i, n_pred = get_Block_n_cfgpreds(node);
  82                 for (i = 0; i < n_pred; ++i) {
  83                         if (get_Block_cfgpred(node, i) == data->proj_X) {
  84                                 data->block   = node;
  85                                 data->blk_idx = i;
  86                                 break;
  87                         }
  88                 }
  89                 break;
  90         }
  91         default:
  92                 break;
  93         }
  94 }
  95
  96 typedef enum tail_rec_variants {
  97         TR_DIRECT,  /**< direct return value, i.e. return func(). */
  98         TR_ADD,     /**< additive return value, i.e. return x +/- func() */
  99         TR_MUL,     /**< multiplicative return value, i.e. return x * func() or return -func() */
 100         TR_BAD,     /**< any other transformation */
 101         TR_UNKNOWN  /**< during construction */
 102 } tail_rec_variants;
 103
 104 typedef struct tr_env {
 105         int               n_tail_calls;  /**< number of tail calls found */
 106         int               n_ress;        /**< number of return values */
 107         tail_rec_variants *variants;     /**< return value variants */
 108         ir_node           *rets;         /**< list of returns that can be transformed */
 109 } tr_env;
 110
 111
 112 /**
 113  * do the graph reconstruction for tail-recursion elimination
 114  *
 115  * @param irg  the graph that will reconstructed
 116  * @param env  tail recursion environment
 117  */
 118 static void do_opt_tail_rec(ir_graph *irg, tr_env *env)
 119 {
 120         ir_node *end_block = get_irg_end_block(irg);
 121         ir_node *block, *jmp, *call, *calls;
 122         ir_node **in;
 123         ir_node **phis;
 124         ir_node ***call_params;
 125         ir_node *p, *n;
 126         int i, j, n_params, n_locs;
 127         collect_t data;
 128         int rem            = get_optimize();
 129         ir_entity *ent     = get_irg_entity(irg);
 130         ir_type *method_tp = get_entity_type(ent);
 131
 132         assert(env->n_tail_calls > 0);
 133
 134         /* we add new blocks and change the control flow */
 135         clear_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE);
 136
 137         /* we must build some new nodes WITHOUT CSE */
 138         set_optimize(0);
 139
 140         /* collect needed data */
 141         data.proj_X    = NULL;
 142         data.block     = NULL;
 143         data.blk_idx   = -1;
 144         data.proj_m    = get_irg_initial_mem(irg);
 145         data.proj_data = NULL;
 146         irg_walk_graph(irg, NULL, collect_data, &data);
 147
 148         /* check number of arguments */
 149         call     = (ir_node*)get_irn_link(end_block);
 150         n_params = get_Call_n_params(call);
 151
 152         assert(data.proj_X && "Could not find initial exec from Start");
 153         assert(data.block  && "Could not find first block");
 154         assert(data.proj_m && "Could not find initial memory");
 155         assert((data.proj_data || n_params == 0) && "Could not find Proj(ProjT(Start)) of non-void function");
 156
 157         /* allocate in's for phi and block construction */
 158         NEW_ARR_A(ir_node *, in, env->n_tail_calls + 1);
 159
 160         /* build a new header block for the loop we create */
 161         i = 0;
 162         in[i++] = data.proj_X;
 163
 164         /* turn Return's into Jmp's */
 165         for (p = env->rets; p; p = n) {
 166                 ir_node *block = get_nodes_block(p);
 167
 168                 n = (ir_node*)get_irn_link(p);
 169                 in[i++] = new_r_Jmp(block);
 170
 171                 // exchange(p, new_r_Bad(irg));
 172
 173                 /* we might generate an endless loop, so add
 174                  * the block to the keep-alive list */
 175                 add_End_keepalive(get_irg_end(irg), block);
 176         }
 177         assert(i == env->n_tail_calls + 1);
 178
 179         /* now create it */
 180         block = new_r_Block(irg, i, in);
 181         jmp   = new_r_Jmp(block);
 182
 183         /* the old first block is now the second one */
 184         set_Block_cfgpred(data.block, data.blk_idx, jmp);
 185
 186         /* allocate phi's, position 0 contains the memory phi */
 187         NEW_ARR_A(ir_node *, phis, n_params + 1);
 188
 189         /* build the memory phi */
 190         i = 0;
 191         in[i] = new_r_Proj(get_irg_start(irg), mode_M, pn_Start_M);
 192         set_irg_initial_mem(irg, in[i]);
 193         ++i;
 194
 195         for (calls = call; calls != NULL; calls = (ir_node*)get_irn_link(calls)) {
 196                 in[i] = get_Call_mem(calls);
 197                 ++i;
 198         }
 199         assert(i == env->n_tail_calls + 1);
 200
 201         phis[0] = new_r_Phi(block, env->n_tail_calls + 1, in, mode_M);
 202
 203         /* build the data Phi's */
 204         if (n_params > 0) {
 205                 ir_node *calls;
 206                 ir_node *args;
 207
 208                 NEW_ARR_A(ir_node **, call_params, env->n_tail_calls);
 209
 210                 /* collect all parameters */
 211                 for (i = 0, calls = call; calls != NULL;
 212                      calls = (ir_node*)get_irn_link(calls)) {
 213                         call_params[i] = get_Call_param_arr(calls);
 214                         ++i;
 215                 }
 216
 217                 /* build new Proj's and Phi's */
 218                 args    = get_irg_args(irg);
 219                 for (i = 0; i < n_params; ++i) {
 220                         ir_mode *mode = get_type_mode(get_method_param_type(method_tp, i));
 221
 222                         in[0] = new_r_Proj(args, mode, i);
 223                         for (j = 0; j < env->n_tail_calls; ++j)
 224                                 in[j + 1] = call_params[j][i];
 225
 226                         phis[i + 1] = new_r_Phi(block, env->n_tail_calls + 1, in, mode);
 227                 }
 228         }
 229
 230         /*
 231          * ok, we are here, so we have build and collected all needed Phi's
 232          * now exchange all Projs into links to Phi
 233          */
 234         exchange(data.proj_m, phis[0]);
 235         for (p = data.proj_data; p; p = n) {
 236                 long proj = get_Proj_proj(p);
 237
 238                 assert(0 <= proj && proj < n_params);
 239                 n = (ir_node*)get_irn_link(p);
 240                 exchange(p, phis[proj + 1]);
 241         }
 242
 243         /* tail recursion was done, all info is invalid */
 244         clear_irg_properties(irg, IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
 245                            | IR_GRAPH_PROPERTY_CONSISTENT_LOOPINFO);
 246         set_irg_callee_info_state(irg, irg_callee_info_inconsistent);
 247
 248         set_optimize(rem);
 249
 250         /* check if we need new values */
 251         n_locs = 0;
 252         for (i = 0; i < env->n_ress; ++i) {
 253                 if (env->variants[i] != TR_DIRECT) {
 254                         ++n_locs;
 255                         break;
 256                 }
 257         }
 258
 259         if (n_locs > 0) {
 260                 ir_node *start_block;
 261                 ir_node **in;
 262                 ir_mode **modes;
 263
 264                 NEW_ARR_A(ir_node *, in, env->n_ress);
 265                 NEW_ARR_A(ir_mode *, modes, env->n_ress);
 266                 ssa_cons_start(irg, env->n_ress);
 267
 268                 start_block = get_irg_start_block(irg);
 269                 set_r_cur_block(irg, start_block);
 270
 271                 /* set the neutral elements for the iteration start */
 272                 for (i = 0; i < env->n_ress; ++i) {
 273                         ir_type *tp = get_method_res_type(method_tp, i);
 274                         ir_mode *mode = get_type_mode(tp);
 275
 276                         modes[i] = mode;
 277                         if (env->variants[i] == TR_ADD) {
 278                                 set_r_value(irg, i, new_r_Const(irg, get_mode_null(mode)));
 279                         } else if (env->variants[i] == TR_MUL) {
 280                                 set_r_value(irg, i, new_r_Const(irg, get_mode_one(mode)));
 281                         }
 282                 }
 283                 mature_immBlock(start_block);
 284
 285                 /* no: we can kill all returns */
 286                 for (p = env->rets; p; p = n) {
 287                         ir_node *block = get_nodes_block(p);
 288                         ir_node *jmp, *tuple;
 289
 290                         set_r_cur_block(irg, block);
 291                         n = (ir_node*)get_irn_link(p);
 292
 293                         ir_node *const call = skip_Proj(get_Return_mem(p));
 294                         ir_node *const mem  = get_Call_mem(call);
 295
 296                         /* create a new jump, free of CSE */
 297                         set_optimize(0);
 298                         jmp = new_r_Jmp(block);
 299                         set_optimize(rem);
 300
 301                         for (i = 0; i < env->n_ress; ++i) {
 302                                 ir_mode *mode = modes[i];
 303                                 if (env->variants[i] != TR_DIRECT) {
 304                                         in[i] = get_r_value(irg, i, mode);
 305                                 } else {
 306                                         in[i] = new_r_Bad(irg, mode);
 307                                 }
 308                         }
 309                         /* create a new tuple for the return values */
 310                         tuple = new_r_Tuple(block, env->n_ress, in);
 311
 312                         ir_node *const in[] = {
 313                                 [pn_Call_M]         = mem,
 314                                 [pn_Call_T_result]  = tuple,
 315                                 [pn_Call_X_regular] = jmp,
 316                                 [pn_Call_X_except]  = new_r_Bad(irg, mode_X),
 317                         };
 318                         turn_into_tuple(call, ARRAY_SIZE(in), in);
 319
 320                         for (i = 0; i < env->n_ress; ++i) {
 321                                 ir_node *res = get_Return_res(p, i);
 322                                 if (env->variants[i] != TR_DIRECT) {
 323                                         set_r_value(irg, i, res);
 324                                 }
 325                         }
 326
 327                         exchange(p, new_r_Bad(irg, mode_X));
 328                 }
 329
 330                 /* finally fix all other returns */
 331                 end_block = get_irg_end_block(irg);
 332                 for (i = get_Block_n_cfgpreds(end_block) - 1; i >= 0; --i) {
 333                         ir_node *ret = get_Block_cfgpred(end_block, i);
 334                         ir_node *block;
 335
 336                         /* search all Returns of a block */
 337                         if (! is_Return(ret))
 338                                 continue;
 339
 340                         block = get_nodes_block(ret);
 341                         set_r_cur_block(irg, block);
 342                         for (j = 0; j < env->n_ress; ++j) {
 343                                 ir_node *pred = get_Return_res(ret, j);
 344                                 ir_node *n;
 345
 346                                 switch (env->variants[j]) {
 347                                 case TR_DIRECT:
 348                                         continue;
 349
 350                                 case TR_ADD:
 351                                         n = get_r_value(irg, j, modes[j]);
 352                                         n = new_r_Add(block, n, pred, modes[j]);
 353                                         set_Return_res(ret, j, n);
 354                                         break;
 355
 356                                 case TR_MUL:
 357                                         n = get_r_value(irg, j, modes[j]);
 358                                         n = new_r_Mul(block, n, pred, modes[j]);
 359                                         set_Return_res(ret, j, n);
 360                                         break;
 361
 362                                 default:
 363                                         assert(!"unexpected tail recursion variant");
 364                                 }
 365                         }
 366                 }
 367                 ssa_cons_finish(irg);
 368         } else {
 369                 ir_node *bad = new_r_Bad(irg, mode_X);
 370
 371                 /* no: we can kill all returns */
 372                 for (p = env->rets; p; p = n) {
 373                         n = (ir_node*)get_irn_link(p);
 374                         exchange(p, bad);
 375                 }
 376         }
 377 }
 378
 379 /**
 380  * Check the lifetime of locals in the given graph.
 381  * Tail recursion can only be done, if we can prove that
 382  * the lifetime of locals end with the recursive call.
 383  * We do this by checking that no address of a local variable is
 384  * stored or transmitted as an argument to a call.
 385  *
 386  * @return non-zero if it's ok to do tail recursion
 387  */
 388 static int check_lifetime_of_locals(ir_graph *irg)
 389 {
 390         ir_node *irg_frame;
 391         int i;
 392         ir_type *frame_tp = get_irg_frame_type(irg);
 393
 394         irg_frame = get_irg_frame(irg);
 395         for (i = get_irn_n_outs(irg_frame) - 1; i >= 0; --i) {
 396                 ir_node *succ = get_irn_out(irg_frame, i);
 397
 398                 if (is_Sel(succ)) {
 399                         /* Check if we have compound arguments.
 400                            For now, we cannot handle them, */
 401                         if (get_entity_owner(get_Sel_entity(succ)) != frame_tp)
 402                                 return 0;
 403
 404                         if (is_address_taken(succ))
 405                                 return 0;
 406                 }
 407         }
 408         return 1;
 409 }
 410
 411 /**
 412  * Examine irn and detect the recursion variant.
 413  */
 414 static tail_rec_variants find_variant(ir_node *irn, ir_node *call)
 415 {
 416         ir_node           *a, *b;
 417         tail_rec_variants va, vb, res;
 418
 419         if (skip_Proj(skip_Proj(irn)) == call) {
 420                 /* found it */
 421                 return TR_DIRECT;
 422         }
 423         switch (get_irn_opcode(irn)) {
 424         case iro_Add:
 425                 /* try additive */
 426                 a = get_Add_left(irn);
 427                 if (get_nodes_block(a) != get_nodes_block(call)) {
 428                         /* we are outside, ignore */
 429                         va = TR_UNKNOWN;
 430                 } else {
 431                         va = find_variant(a, call);
 432                         if (va == TR_BAD)
 433                                 return TR_BAD;
 434                 }
 435                 b = get_Add_right(irn);
 436                 if (get_nodes_block(b) != get_nodes_block(call)) {
 437                         /* we are outside, ignore */
 438                         vb = TR_UNKNOWN;
 439                 } else {
 440                         vb = find_variant(b, call);
 441                         if (vb == TR_BAD)
 442                                 return TR_BAD;
 443                 }
 444                 if (va == vb) {
 445                         res = va;
 446                 }
 447                 else if (va == TR_UNKNOWN)
 448                         res = vb;
 449                 else if (vb == TR_UNKNOWN)
 450                         res = va;
 451                 else {
 452                         /* they are different but none is TR_UNKNOWN -> incompatible */
 453                         return TR_BAD;
 454                 }
 455                 if (res == TR_DIRECT || res == TR_ADD)
 456                         return TR_ADD;
 457                 /* not compatible */
 458                 return TR_BAD;
 459
 460         case iro_Sub:
 461                 /* try additive, but return value must be left */
 462                 a = get_Sub_left(irn);
 463                 if (get_nodes_block(a) != get_nodes_block(call)) {
 464                         /* we are outside, ignore */
 465                         va = TR_UNKNOWN;
 466                 } else {
 467                         va = find_variant(a, call);
 468                         if (va == TR_BAD)
 469                                 return TR_BAD;
 470                 }
 471                 b = get_Sub_right(irn);
 472                 if (get_nodes_block(b) != get_nodes_block(call)) {
 473                         /* we are outside, ignore */
 474                         vb = TR_UNKNOWN;
 475                 } else {
 476                         vb = find_variant(b, call);
 477                         if (vb != TR_UNKNOWN)
 478                                 return TR_BAD;
 479                 }
 480                 res = va;
 481                 if (res == TR_DIRECT || res == TR_ADD)
 482                         return res;
 483                 /* not compatible */
 484                 return TR_BAD;
 485
 486         case iro_Mul:
 487                 /* try multiplicative */
 488                 a = get_Mul_left(irn);
 489                 if (get_nodes_block(a) != get_nodes_block(call)) {
 490                         /* we are outside, ignore */
 491                         va = TR_UNKNOWN;
 492                 } else {
 493                         va = find_variant(a, call);
 494                         if (va == TR_BAD)
 495                                 return TR_BAD;
 496                 }
 497                 b = get_Mul_right(irn);
 498                 if (get_nodes_block(b) != get_nodes_block(call)) {
 499                         /* we are outside, ignore */
 500                         vb = TR_UNKNOWN;
 501                 } else {
 502                         vb = find_variant(b, call);
 503                         if (vb == TR_BAD)
 504                                 return TR_BAD;
 505                 }
 506                 if (va == vb) {
 507                         res = va;
 508                 }
 509                 else if (va == TR_UNKNOWN)
 510                         res = vb;
 511                 else if (vb == TR_UNKNOWN)
 512                         res = va;
 513                 else {
 514                         /* they are different but none is TR_UNKNOWN -> incompatible */
 515                         return TR_BAD;
 516                 }
 517                 if (res == TR_DIRECT || res == TR_MUL)
 518                         return TR_MUL;
 519                 /* not compatible */
 520                 return TR_BAD;
 521
 522         case iro_Minus:
 523                 /* try multiplicative */
 524                 a = get_Minus_op(irn);
 525                 res =  find_variant(a, call);
 526                 if (res == TR_DIRECT)
 527                         return TR_MUL;
 528                 if (res == TR_MUL || res == TR_UNKNOWN)
 529                         return res;
 530                 /* not compatible */
 531                 return TR_BAD;
 532
 533         default:
 534                 return TR_UNKNOWN;
 535         }
 536 }
 537
 538
 539 /*
 540  * convert simple tail-calls into loops
 541  */
 542 void opt_tail_rec_irg(ir_graph *irg)
 543 {
 544         tr_env    env;
 545         ir_node   *end_block;
 546         int       i, n_ress, n_tail_calls = 0;
 547         ir_node   *rets = NULL;
 548         ir_type   *mtd_type, *call_type;
 549         ir_entity *ent;
 550         ir_graph  *rem;
 551
 552         assure_irg_properties(irg,
 553                 IR_GRAPH_PROPERTY_MANY_RETURNS
 554                 | IR_GRAPH_PROPERTY_NO_BADS
 555                 | IR_GRAPH_PROPERTY_CONSISTENT_OUTS);
 556
 557         FIRM_DBG_REGISTER(dbg, "firm.opt.tailrec");
 558
 559         if (! check_lifetime_of_locals(irg)) {
 560                 confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_ALL);
 561                 return;
 562         }
 563
 564         rem = current_ir_graph;
 565         current_ir_graph = irg;
 566
 567         ent      = get_irg_entity(irg);
 568         mtd_type = get_entity_type(ent);
 569         n_ress   = get_method_n_ress(mtd_type);
 570
 571         env.variants = NULL;
 572         env.n_ress   = n_ress;
 573
 574         if (n_ress > 0) {
 575                 NEW_ARR_A(tail_rec_variants, env.variants, n_ress);
 576
 577                 for (i = 0; i < n_ress; ++i)
 578                         env.variants[i] = TR_DIRECT;
 579         }
 580
 581         ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK);
 582
 583         end_block = get_irg_end_block(irg);
 584         set_irn_link(end_block, NULL);
 585
 586         for (i = get_Block_n_cfgpreds(end_block) - 1; i >= 0; --i) {
 587                 ir_node *ret = get_Block_cfgpred(end_block, i);
 588                 ir_node *call, *call_ptr;
 589                 int j;
 590                 ir_node **ress;
 591
 592                 /* search all Returns of a block */
 593                 if (! is_Return(ret))
 594                         continue;
 595
 596                 /* check, if it's a Return self() */
 597                 call = skip_Proj(get_Return_mem(ret));
 598                 if (! is_Call(call))
 599                         continue;
 600
 601                 /* the call must be in the same block as the return */
 602                 if (get_nodes_block(call) != get_nodes_block(ret))
 603                         continue;
 604
 605                 /* check if it's a recursive call */
 606                 call_ptr = get_Call_ptr(call);
 607
 608                 if (! is_SymConst_addr_ent(call_ptr))
 609                         continue;
 610
 611                 ent = get_SymConst_entity(call_ptr);
 612                 if (!ent || get_entity_irg(ent) != irg)
 613                         continue;
 614
 615                 /*
 616                  * Check, that the types match. At least in C
 617                  * this might fail.
 618                  */
 619                 mtd_type  = get_entity_type(ent);
 620                 call_type = get_Call_type(call);
 621
 622                 if (mtd_type != call_type) {
 623                         /*
 624                          * Hmm, the types did not match, bad.
 625                          * This can happen in C when no prototype is given
 626                          * or K&R style is used.
 627                          */
 628                         DB((dbg, LEVEL_3, "  tail recursion fails because of call type mismatch: %+F != %+F\n", mtd_type, call_type));
 629                         continue;
 630                 }
 631
 632                 /* ok, mem is routed to a recursive call, check return args */
 633                 ress = get_Return_res_arr(ret);
 634                 for (j = get_Return_n_ress(ret) - 1; j >= 0; --j) {
 635                         tail_rec_variants var = find_variant(ress[j], call);
 636
 637                         if (var >= TR_BAD) {
 638                                 /* cannot be transformed */
 639                                 break;
 640                         }
 641                         if (var == TR_DIRECT) {
 642                                 var = env.variants[j];
 643                         } else if (env.variants[j] == TR_DIRECT) {
 644                                 env.variants[j] = var;
 645                         }
 646                         if (env.variants[j] != var) {
 647                                 /* not compatible */
 648                                 DB((dbg, LEVEL_3, "  tail recursion fails for %d return value of %+F\n", j, ret));
 649                                 break;
 650                         }
 651                 }
 652                 if (j >= 0)
 653                         continue;
 654
 655                 /* here, we have found a call */
 656                 set_irn_link(call, get_irn_link(end_block));
 657                 set_irn_link(end_block, call);
 658                 ++n_tail_calls;
 659
 660                 /* link all returns, we will need this */
 661                 set_irn_link(ret, rets);
 662                 rets = ret;
 663         }
 664
 665         /* now, end_block->link contains the list of all tail calls */
 666         if (n_tail_calls > 0) {
 667                 DB((dbg, LEVEL_2, "  Performing tail recursion for graph %s and %d Calls\n",
 668                     get_entity_ld_name(get_irg_entity(irg)), n_tail_calls));
 669
 670                 hook_tail_rec(irg, n_tail_calls);
 671
 672                 env.n_tail_calls = n_tail_calls;
 673                 env.rets         = rets;
 674                 do_opt_tail_rec(irg, &env);
 675                 confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_NONE);
 676         } else {
 677                 confirm_irg_properties(irg, IR_GRAPH_PROPERTIES_ALL);
 678         }
 679         ir_free_resources(irg, IR_RESOURCE_IRN_LINK);
 680         current_ir_graph = rem;
 681 }
 682
 683 ir_graph_pass_t *opt_tail_rec_irg_pass(const char *name)
 684 {
 685         return def_graph_pass(name ? name : "tailrec", opt_tail_rec_irg);
 686 }
 687
 688 /*
 689  * optimize tail recursion away
 690  */
 691 void opt_tail_recursion(void)
 692 {
 693         size_t i, n;
 694
 695         FIRM_DBG_REGISTER(dbg, "firm.opt.tailrec");
 696
 697         DB((dbg, LEVEL_1, "Performing tail recursion ...\n"));
 698         for (i = 0, n = get_irp_n_irgs(); i < n; ++i) {
 699                 ir_graph *irg = get_irp_irg(i);
 700                 opt_tail_rec_irg(irg);
 701         }
 702 }
 703
 704 ir_prog_pass_t *opt_tail_recursion_pass(const char *name)
 705 {
 706         return def_prog_pass(name ? name : "tailrec", opt_tail_recursion);
 707 }