nsz Git - libfirm/blob - ir/opt/fp-vrp.c

   1 /*
   2  * Copyright (C) 1995-2010 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   Data-flow driven minimal fixpoint value range propagation
  23  * @author  Christoph Mallon
  24  * @version $Id$
  25  */
  26
  27 #include "config.h"
  28
  29 #include "adt/pdeq.h"
  30 #include "adt/obst.h"
  31 #include "adt/xmalloc.h"
  32 #include "debug.h"
  33 #include "ircons.h"
  34 #include "irdom.h"
  35 #include "iredges.h"
  36 #include "irgmod.h"
  37 #include "irgraph.h"
  38 #include "irgwalk.h"
  39 #include "irnode.h"
  40 #include "iroptimize.h"
  41 #include "irtools.h"
  42 #include "tv.h"
  43 #include "irpass.h"
  44 #include "irmemory.h"
  45
  46 /* TODO:
  47  * - Implement cleared/set bit calculation for Add, Sub, Minus, Mul, Div, Mod, Shl, Shr, Shrs, Rotl
  48  * - Implement min/max calculation for And, Eor, Or, Not, Conv, Shl, Shr, Shrs, Rotl, Mux
  49  * - Implement min/max calculation for Add, Sub, Minus, Mul, Div, Mod, Conv, Shl, Shr, Shrs, Rotl, Mux
  50  */
  51
  52 /* Tables of the cleared/set bit lattice
  53  *
  54  * Encoding of the lattice
  55  * zo
  56  * 00 0 zero
  57  * 01 - impossible state, is zero /and/ one
  58  * 10 T top, may be either zero or one
  59  * 11 1 one
  60  *
  61  * S = Sum
  62  * c = Carry
  63  * D = Difference
  64  * b = Borrow
  65  *
  66  * Not
  67  * A ~
  68  * 0 1
  69  * 1 0
  70  * T T
  71  *
  72  * Half adder, half subtractor, and, xor, or, Mux
  73  * AB  Sc  Db  &  ^  |  M
  74  * 00  00  00  0  0  0  0
  75  * 01  10  11  0  1  1  T
  76  * 0T  T0  TT  0  T  T  T
  77  * 10  10  10  0  1  1  T
  78  * 11  01  00  1  0  1  1
  79  * 1T  TT  T0  T  T  1  T
  80  * T0  T0  T0  0  T  T  T
  81  * T1  TT  TT  T  T  1  T
  82  * TT  TT  TT  T  T  T  T
  83  *
  84  * Full adder, full subtractor
  85  * ABc-1  Sc  Db
  86  * 000    00  00
  87  * 001    10  11
  88  * 00T    T0  TT
  89  * 010    10  11
  90  * 011    01  01
  91  * 01T    TT  T1
  92  * 0T0    T0  TT
  93  * 0T1    TT  T1
  94  * 0TT    TT  TT
  95  * 100    10  10
  96  * 101    01  00
  97  * 10T    TT  T0
  98  * 110    01  00
  99  * 111    11  11
 100  * 11T    T1  TT
 101  * 1T0    TT  T0
 102  * 1T1    T1  TT
 103  * 1TT    TT  TT
 104  * T00    T0  T0
 105  * T01    TT  TT
 106  * T0T    TT  TT
 107  * T10    TT  TT
 108  * T11    T1  T1
 109  * T1T    TT  TT
 110  * TT0    TT  TT
 111  * TT1    TT  TT
 112  * TTT    TT  TT
 113  *
 114  *
 115  * Assume: Xmin <= Xmax and no overflow
 116  * A + B = (Amin + Bmin, Amax + Bmax)
 117  *    -A = (-Amax, -Amin)
 118  * A - B = A + -B = (Amin (-B)min, Amax + (-B)max) = (Amin - Bmax, Amax - Bmin)
 119  */
 120
 121 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
 122
 123 static struct obstack obst;
 124
 125 typedef struct bitinfo
 126 {
 127         tarval* z; // safe zeroes, 0 = bit is zero,       1 = bit maybe is 1
 128         tarval* o; // safe ones,   0 = bit maybe is zero, 1 = bit is 1
 129 } bitinfo;
 130
 131 typedef struct environment_t {
 132         unsigned modified:1;     /**< Set, if the graph was modified. */
 133 } environment_t;
 134
 135 static inline bitinfo* get_bitinfo(ir_node const* const irn)
 136 {
 137         return get_irn_link(irn);
 138 }
 139
 140 static int set_bitinfo(ir_node* const irn, tarval* const z, tarval* const o)
 141 {
 142         bitinfo* b = get_bitinfo(irn);
 143         if (b == NULL) {
 144                 b = OALLOCZ(&obst, bitinfo);
 145                 set_irn_link(irn, b);
 146         } else if (z == b->z && o == b->o) {
 147                 return 0;
 148         }
 149         b->z = z;
 150         b->o = o;
 151         DB((dbg, LEVEL_3, "%+F: 0:%T 1:%T\n", irn, z, o));
 152         return 1;
 153 }
 154
 155 static int mode_is_intb(ir_mode const* const m)
 156 {
 157         return mode_is_int(m) || m == mode_b;
 158 }
 159
 160 static int transfer(ir_node* const irn)
 161 {
 162         ir_mode* const m = get_irn_mode(irn);
 163         tarval*        z;
 164         tarval*        o;
 165
 166         if (m == mode_X) {
 167                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 168                 switch (get_irn_opcode(irn)) {
 169                         case iro_Proj: {
 170                                 ir_node* const pred = get_Proj_pred(irn);
 171                                 if (is_Start(pred)) {
 172                                         z = get_tarval_b_true();
 173                                         o = get_tarval_b_false();
 174                                 } else if (is_Cond(pred)) {
 175                                         ir_node* const selector = get_Cond_selector(pred);
 176                                         bitinfo* const b        = get_bitinfo(selector);
 177                                         tarval*  const bz       = b->z;
 178                                         tarval*  const bo       = b->o;
 179                                         if (get_irn_mode(selector) == mode_b) {
 180                                                 if (bz == bo) {
 181                                                         if ((bz == get_tarval_b_true()) == get_Proj_proj(irn)) {
 182                                                                 z = o = get_tarval_b_true();
 183                                                         } else {
 184                                                                 z = o = get_tarval_b_false();
 185                                                         }
 186                                                 } else {
 187                                                         goto result_unknown_X;
 188                                                 }
 189                                         } else {
 190                                                 long const val = get_Proj_proj(irn);
 191                                                 if (val != get_Cond_default_proj(pred)) {
 192                                                         tarval* const tv = new_tarval_from_long(val, get_irn_mode(selector));
 193                                                         if (!tarval_is_null(tarval_andnot(tv, bz)) ||
 194                                                                         !tarval_is_null(tarval_andnot(bo, tv))) {
 195                                                                 // At least one bit differs.
 196                                                                 z = o = get_tarval_b_false();
 197 #if 0 // TODO must handle default Proj
 198                                                         } else if (bz == bo && bz == tv) {
 199                                                                 z = o = get_tarval_b_true();
 200 #endif
 201                                                         } else {
 202                                                                 goto result_unknown_X;
 203                                                         }
 204                                                 } else {
 205                                                         goto cannot_analyse_X;
 206                                                 }
 207                                         }
 208                                 } else {
 209                                         goto cannot_analyse_X;
 210                                 }
 211                                 break;
 212                         }
 213
 214                         case iro_Jmp: {
 215                                 bitinfo* const b = get_bitinfo(get_nodes_block(irn));
 216                                 z = b->z;
 217                                 o = b->o;
 218                                 break;
 219                         }
 220
 221                         default:
 222 cannot_analyse_X:
 223                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 224 result_unknown_X:
 225                                 z = get_tarval_b_true();
 226                                 o = get_tarval_b_false();
 227                                 break;
 228                 }
 229         } else if (is_Block(irn)) {
 230                 int       reachable = 0;
 231                 int const arity     = get_Block_n_cfgpreds(irn);
 232                 int       i;
 233
 234                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 235                 for (i = 0; i != arity; ++i) {
 236                         bitinfo* const b = get_bitinfo(get_Block_cfgpred(irn, i));
 237                         if (b != NULL && b->z == get_tarval_b_true()) {
 238                                 reachable = 1;
 239                                 break;
 240                         }
 241                 }
 242
 243                 o = get_tarval_b_false();
 244                 z = reachable || irn == get_irg_start_block(get_irn_irg(irn)) ? get_tarval_b_true() : o;
 245         } else if (mode_is_intb(m)) {
 246                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 247                 switch (get_irn_opcode(irn)) {
 248                         case iro_Const: {
 249                                 z = o = get_Const_tarval(irn);
 250                                 break;
 251                         }
 252
 253                         case iro_Shl: {
 254                                 bitinfo* const l  = get_bitinfo(get_Shl_left(irn));
 255                                 bitinfo* const r  = get_bitinfo(get_Shl_right(irn));
 256                                 tarval*  const rz = r->z;
 257                                 if (rz == r->o) {
 258                                         z = tarval_shl(l->z, rz);
 259                                         o = tarval_shl(l->o, rz);
 260                                 } else {
 261                                         goto cannot_analyse;
 262                                 }
 263                                 break;
 264                         }
 265
 266                         case iro_Shr: {
 267                                 bitinfo* const l  = get_bitinfo(get_Shr_left(irn));
 268                                 bitinfo* const r  = get_bitinfo(get_Shr_right(irn));
 269                                 tarval*  const rz = r->z;
 270                                 if (rz == r->o) {
 271                                         z = tarval_shr(l->z, rz);
 272                                         o = tarval_shr(l->o, rz);
 273                                 } else {
 274                                         goto cannot_analyse;
 275                                 }
 276                                 break;
 277                         }
 278
 279                         case iro_Shrs: {
 280                                 bitinfo* const l  = get_bitinfo(get_Shrs_left(irn));
 281                                 bitinfo* const r  = get_bitinfo(get_Shrs_right(irn));
 282                                 tarval*  const rz = r->z;
 283                                 if (rz == r->o) {
 284                                         z = tarval_shrs(l->z, rz);
 285                                         o = tarval_shrs(l->o, rz);
 286                                 } else {
 287                                         goto cannot_analyse;
 288                                 }
 289                                 break;
 290                         }
 291
 292                         case iro_Rotl: {
 293                                 bitinfo* const l  = get_bitinfo(get_Rotl_left(irn));
 294                                 bitinfo* const r  = get_bitinfo(get_Rotl_right(irn));
 295                                 tarval*  const rz = r->z;
 296                                 if (rz == r->o) {
 297                                         z = tarval_rotl(l->z, rz);
 298                                         o = tarval_rotl(l->o, rz);
 299                                 } else {
 300                                         goto cannot_analyse;
 301                                 }
 302                                 break;
 303                         }
 304
 305                         case iro_Add: {
 306                                 bitinfo* const l  = get_bitinfo(get_Add_left(irn));
 307                                 bitinfo* const r  = get_bitinfo(get_Add_right(irn));
 308                                 tarval*  const lz = l->z;
 309                                 tarval*  const lo = l->o;
 310                                 tarval*  const rz = r->z;
 311                                 tarval*  const ro = r->o;
 312                                 if (lz == lo && rz == ro) {
 313                                         z = o = tarval_add(lz, rz);
 314                                 } else {
 315                                         // TODO improve: can only do lower disjoint bits
 316                                         /* Determine where any of the operands has zero bits, i.e. where no
 317                                          * carry out is generated if there is not carry in */
 318                                         tarval* const no_c_in_no_c_out = tarval_and(lz, rz);
 319                                         /* Generate a mask of the lower consecutive zeroes: x | -x.  In this
 320                                          * range the addition is disjoint and therefore Add behaves like Or.
 321                                          */
 322                                         tarval* const low_zero_mask = tarval_or(no_c_in_no_c_out, tarval_neg(no_c_in_no_c_out));
 323                                         tarval* const low_one_mask  = tarval_not(low_zero_mask);
 324                                         z = tarval_or( tarval_or(lz, rz), low_zero_mask);
 325                                         o = tarval_and(tarval_or(lo, ro), low_one_mask);
 326                                 }
 327                                 break;
 328                         }
 329
 330                         case iro_Sub: {
 331                                 bitinfo* const l = get_bitinfo(get_Sub_left(irn));
 332                                 bitinfo* const r = get_bitinfo(get_Sub_right(irn));
 333                                 if (l != NULL && r != NULL) { // Sub might subtract pointers.
 334                                         tarval* const lz = l->z;
 335                                         tarval* const lo = l->o;
 336                                         tarval* const rz = r->z;
 337                                         tarval* const ro = r->o;
 338                                         if (lz == lo && rz == ro) {
 339                                                 z = o = tarval_sub(lz, rz, NULL);
 340                                         } else if (tarval_is_null(tarval_andnot(rz, lo))) {
 341                                                 /* Every possible one of the subtrahend is backed by a safe one of the
 342                                                  * minuend, i.e. there are no borrows. */
 343                                                 // TODO extend no-borrow like carry for Add above
 344                                                 z = tarval_andnot(lz, ro);
 345                                                 o = tarval_andnot(lo, rz);
 346                                         } else {
 347                                                 goto cannot_analyse;
 348                                         }
 349                                 } else {
 350                                         goto cannot_analyse;
 351                                 }
 352                                 break;
 353                         }
 354
 355                         case iro_Mul: {
 356                                 bitinfo* const l  = get_bitinfo(get_Mul_left(irn));
 357                                 bitinfo* const r  = get_bitinfo(get_Mul_right(irn));
 358                                 tarval*  const lz = l->z;
 359                                 tarval*  const lo = l->o;
 360                                 tarval*  const rz = r->z;
 361                                 tarval*  const ro = r->o;
 362                                 if (lz == lo && rz == ro) {
 363                                         z = o = tarval_mul(lz, rz);
 364                                 } else {
 365                                         // TODO improve
 366                                         // Determine safe lower zeroes: x | -x.
 367                                         tarval* const lzn = tarval_or(lz, tarval_neg(lz));
 368                                         tarval* const rzn = tarval_or(rz, tarval_neg(rz));
 369                                         // Concatenate safe lower zeroes.
 370                                         if (tarval_cmp(lzn, rzn) == pn_Cmp_Lt) {
 371                                                 z = tarval_mul(tarval_eor(lzn, tarval_shl(lzn, get_tarval_one(m))), rzn);
 372                                         } else {
 373                                                 z = tarval_mul(tarval_eor(rzn, tarval_shl(rzn, get_tarval_one(m))), lzn);
 374                                         }
 375                                         o = get_tarval_null(m);
 376                                 }
 377                                 break;
 378                         }
 379
 380                         case iro_Minus: {
 381                                 bitinfo* const b = get_bitinfo(get_Minus_op(irn));
 382                                 if (b->z == b->o) {
 383                                         z = o = tarval_neg(b->z);
 384                                 } else {
 385                                         goto cannot_analyse;
 386                                 }
 387                                 break;
 388                         }
 389
 390                         case iro_And: {
 391                                 bitinfo* const l = get_bitinfo(get_And_left(irn));
 392                                 bitinfo* const r = get_bitinfo(get_And_right(irn));
 393                                 z = tarval_and(l->z, r->z);
 394                                 o = tarval_and(l->o, r->o);
 395                                 break;
 396                         }
 397
 398                         case iro_Or: {
 399                                 bitinfo* const l = get_bitinfo(get_Or_left(irn));
 400                                 bitinfo* const r = get_bitinfo(get_Or_right(irn));
 401                                 z = tarval_or(l->z, r->z);
 402                                 o = tarval_or(l->o, r->o);
 403                                 break;
 404                         }
 405
 406                         case iro_Eor: {
 407                                 bitinfo* const l  = get_bitinfo(get_Eor_left(irn));
 408                                 bitinfo* const r  = get_bitinfo(get_Eor_right(irn));
 409                                 tarval*  const lz = l->z;
 410                                 tarval*  const lo = l->o;
 411                                 tarval*  const rz = r->z;
 412                                 tarval*  const ro = r->o;
 413                                 z = tarval_or(tarval_andnot(lz, ro), tarval_andnot(rz, lo));
 414                                 o = tarval_or(tarval_andnot(ro, lz), tarval_andnot(lo, rz));
 415                                 break;
 416                         }
 417
 418                         case iro_Not: {
 419                                 bitinfo* const b = get_bitinfo(get_Not_op(irn));
 420                                 z = tarval_not(b->o);
 421                                 o = tarval_not(b->z);
 422                                 break;
 423                         }
 424
 425                         case iro_Conv: {
 426                                 bitinfo* const b = get_bitinfo(get_Conv_op(irn));
 427                                 if (b == NULL) // Happens when converting from float values.
 428                                         goto result_unknown;
 429                                 z = tarval_convert_to(b->z, m);
 430                                 o = tarval_convert_to(b->o, m);
 431                                 break;
 432                         }
 433
 434                         case iro_Mux: {
 435                                 bitinfo* const f = get_bitinfo(get_Mux_false(irn));
 436                                 bitinfo* const t = get_bitinfo(get_Mux_true(irn));
 437                                 bitinfo* const c = get_bitinfo(get_Mux_sel(irn));
 438                                 if (c->o == get_tarval_b_true()) {
 439                                         z = t->z;
 440                                         o = t->o;
 441                                 } else if (c->z == get_tarval_b_false()) {
 442                                         z = f->z;
 443                                         o = f->o;
 444                                 } else {
 445                                         z = tarval_or( f->z, t->z);
 446                                         o = tarval_and(f->o, t->o);
 447                                 }
 448                                 break;
 449                         }
 450
 451                         case iro_Phi: {
 452                                 ir_node* const block = get_nodes_block(irn);
 453                                 int      const arity = get_Phi_n_preds(irn);
 454                                 int            i;
 455
 456                                 z = get_tarval_null(m);
 457                                 o = get_tarval_all_one(m);
 458                                 for (i = 0; i != arity; ++i) {
 459                                         bitinfo* const b_cfg = get_bitinfo(get_Block_cfgpred(block, i));
 460                                         if (b_cfg != NULL && b_cfg->z != get_tarval_b_false()) {
 461                                                 bitinfo* const b = get_bitinfo(get_Phi_pred(irn, i));
 462                                                 z = tarval_or( z, b->z);
 463                                                 o = tarval_and(o, b->o);
 464                                         }
 465                                 }
 466                                 break;
 467                         }
 468
 469                         case iro_Proj: {
 470                                 ir_node* const pred = get_Proj_pred(irn);
 471                                 if (is_Cmp(pred)) { // TODO generalize
 472                                         bitinfo* const l = get_bitinfo(get_Cmp_left(pred));
 473                                         bitinfo* const r = get_bitinfo(get_Cmp_right(pred));
 474                                         if (l == NULL || r == NULL)
 475                                                 goto result_unknown; // Cmp compares something we cannot evaluate.
 476                                         switch (get_Proj_proj(irn)) {
 477                                                 case pn_Cmp_Lg: {
 478                                                         tarval* const lz = l->z;
 479                                                         tarval* const lo = l->o;
 480                                                         tarval* const rz = r->z;
 481                                                         tarval* const ro = r->o;
 482                                                         if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 483                                                                         !tarval_is_null(tarval_andnot(lo, rz))) {
 484                                                                 // At least one bit differs.
 485                                                                 z = o = get_tarval_b_true();
 486                                                         } else if (lz == lo && rz == ro && lz == rz) {
 487                                                                 z = o = get_tarval_b_false();
 488                                                         } else {
 489                                                                 goto result_unknown;
 490                                                         }
 491                                                         break;
 492                                                 }
 493
 494                                                 case pn_Cmp_Eq: {
 495                                                         tarval* const lz = l->z;
 496                                                         tarval* const lo = l->o;
 497                                                         tarval* const rz = r->z;
 498                                                         tarval* const ro = r->o;
 499                                                         if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 500                                                                         !tarval_is_null(tarval_andnot(lo, rz))) {
 501                                                                 // At least one bit differs.
 502                                                                 z = o = get_tarval_b_false();
 503                                                         } else if (lz == lo && rz == ro && lz == rz) {
 504                                                                 z = o = get_tarval_b_true();
 505                                                         } else {
 506                                                                 goto result_unknown;
 507                                                         }
 508                                                         break;
 509                                                 }
 510
 511                                                 default:
 512                                                         goto cannot_analyse;
 513                                         }
 514                                 } else {
 515                                         goto cannot_analyse;
 516                                 }
 517                                 break;
 518                         }
 519
 520                         default: {
 521 cannot_analyse:
 522                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 523 result_unknown:
 524                                 z = get_tarval_all_one(m);
 525                                 o = get_tarval_null(m);
 526                                 break;
 527                         }
 528                 }
 529         } else {
 530                 return 0;
 531         }
 532
 533         return set_bitinfo(irn, z, o);
 534 }
 535
 536 static void first_round(ir_node* const irn, void* const env)
 537 {
 538         pdeq* const q = env;
 539
 540         transfer(irn);
 541         if (is_Phi(irn) || is_Block(irn)) {
 542                 /* Only Phis (and their users) need another round, if we did not have
 543                  * information about all their inputs in the first round, i.e. in loops. */
 544                 /* TODO inserts all Phis, should only insert Phis, which did no have all
 545                  * predecessors available */
 546                 pdeq_putr(q, irn);
 547         }
 548 }
 549
 550 static void apply_result(ir_node* const irn, void* ctx)
 551 {
 552         bitinfo* const b = get_bitinfo(irn);
 553         tarval*        z;
 554         tarval*        o;
 555         environment_t* env = ctx;
 556
 557         if (!b) return;
 558         if (is_Const(irn)) return; // It cannot get any better than a Const.
 559
 560         z = b->z;
 561         o = b->o;
 562         // Only display information if we could find out anything about the value.
 563         DEBUG_ONLY(if (!tarval_is_all_one(z) || !tarval_is_null(o)))
 564                 DB((dbg, LEVEL_2, "%+F: 0:%T 1:%T%s\n", irn, z, o, z == o ? " --- constant" : ""));
 565
 566         // Replace node with constant value by Const.
 567         if (z == o) {
 568                 ir_mode* const m = get_irn_mode(irn);
 569                 ir_node*       n;
 570                 if (mode_is_intb(m)) {
 571                         n = new_Const(z);
 572                 } else if (m == mode_X) {
 573                         ir_node*  const block = get_nodes_block(irn);
 574                         ir_graph* const irg   = get_Block_irg(block);
 575                         if (z == get_tarval_b_true()) {
 576                                 // Might produce an endless loop, so keep the block.
 577                                 add_End_keepalive(get_irg_end(irg), block);
 578                                 n = new_r_Jmp(block);
 579                         } else {
 580                                 n = new_r_Bad(irg);
 581                                 /* Transferring analysis information to the bad node makes it a
 582                                  * candidate for replacement. */
 583                                 goto exchange_only;
 584                         }
 585                 } else {
 586                         return;
 587                 }
 588                 set_irn_link(n, b);
 589 exchange_only:
 590                 exchange(irn, n);
 591                 env->modified = 1;
 592         }
 593
 594         switch (get_irn_opcode(irn)) {
 595                 case iro_And: {
 596                         ir_node*       const l  = get_And_left(irn);
 597                         ir_node*       const r  = get_And_right(irn);
 598                         bitinfo const* const bl = get_bitinfo(l);
 599                         bitinfo const* const br = get_bitinfo(r);
 600                         if (bl->z == bl->o) {
 601                                 if (tarval_is_null(tarval_andnot(br->z, bl->z))) {
 602                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 603                                         exchange(irn, r);
 604                                         env->modified = 1;
 605                                 }
 606                         } else if (br->z == br->o) {
 607                                 if (tarval_is_null(tarval_andnot(bl->z, br->z))) {
 608                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 609                                         exchange(irn, l);
 610                                         env->modified = 1;
 611                                 }
 612                         }
 613                         break;
 614                 }
 615
 616                 case iro_Or: {
 617                         ir_node*       const l  = get_Or_left(irn);
 618                         ir_node*       const r  = get_Or_right(irn);
 619                         bitinfo const* const bl = get_bitinfo(l);
 620                         bitinfo const* const br = get_bitinfo(r);
 621                         if (bl->z == bl->o) {
 622                                 if (tarval_is_null(tarval_andnot(bl->o, br->o))) {
 623                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 624                                         exchange(irn, r);
 625                                         env->modified = 1;
 626                                 }
 627                         } else if (br->z == br->o) {
 628                                 if (tarval_is_null(tarval_andnot(br->o, bl->o))) {
 629                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 630                                         exchange(irn, l);
 631                                         env->modified = 1;
 632                                 }
 633                         }
 634                         break;
 635                 }
 636         }
 637 }
 638
 639 static void queue_users(pdeq* const q, ir_node* const n)
 640 {
 641         if (get_irn_mode(n) == mode_X) {
 642                 /* When the state of a control flow node changes, not only queue its
 643                  * successor blocks, but also the Phis in these blocks, because the Phis
 644                  * must reconsider this input path. */
 645                 ir_edge_t const* e;
 646                 foreach_out_edge(n, e) {
 647                         ir_node*  const  src = get_edge_src_irn(e);
 648                         pdeq_putr(q, src);
 649                         /* should always be a block */
 650                         if (is_Block(src)) {
 651                                 ir_node *phi;
 652                                 for (phi = get_Block_phis(src); phi; phi = get_Phi_next(phi))
 653                                         pdeq_putr(q, phi);
 654                         }
 655                 }
 656         } else {
 657                 ir_edge_t const* e;
 658                 foreach_out_edge(n, e) {
 659                         ir_node* const src = get_edge_src_irn(e);
 660                         if (get_irn_mode(src) == mode_T) {
 661                                 queue_users(q, src);
 662                         } else {
 663                                 pdeq_putr(q, src);
 664                         }
 665                 }
 666         }
 667 }
 668
 669 static void clear_links(ir_node *irn, void *env)
 670 {
 671         (void) env;
 672         set_irn_link(irn, NULL);
 673         if (is_Block(irn))
 674                 set_Block_phis(irn, NULL);
 675 }
 676
 677 static void build_phi_lists(ir_node *irn, void *env)
 678 {
 679         if (is_Phi(irn))
 680                 add_Block_phi(get_nodes_block(irn), irn);
 681 }
 682
 683 void fixpoint_vrp(ir_graph* const irg)
 684 {
 685         environment_t env;
 686
 687         FIRM_DBG_REGISTER(dbg, "firm.opt.fp-vrp");
 688         DB((dbg, LEVEL_1, "===> Performing constant propagation on %+F\n", irg));
 689
 690         obstack_init(&obst);
 691
 692         edges_assure(irg);
 693         assure_doms(irg);
 694
 695         ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 696
 697         {
 698                 pdeq* const q = new_pdeq();
 699
 700                 /* We need this extra step because the dom tree does not contain unreachable
 701                    blocks in Firm. Moreover build phi list. */
 702                 irg_walk_graph(irg, clear_links, build_phi_lists, NULL);
 703
 704                 /* TODO Improve iteration order. Best is reverse postorder in data flow
 705                  * direction and respecting loop nesting for fastest convergence. */
 706                 irg_walk_blkwise_dom_top_down(irg, firm_clear_link, first_round, q);
 707
 708                 while (!pdeq_empty(q)) {
 709                         ir_node* const n = pdeq_getl(q);
 710                         if (transfer(n))
 711                                 queue_users(q, n);
 712                 }
 713
 714                 del_pdeq(q);
 715         }
 716
 717         DB((dbg, LEVEL_2, "---> Applying analysis results\n"));
 718         env.modified = 0;
 719         irg_walk_graph(irg, NULL, apply_result, &env);
 720
 721         if (env.modified) {
 722                 /* control flow might changed */
 723                 set_irg_outs_inconsistent(irg);
 724                 set_irg_extblk_inconsistent(irg);
 725                 set_irg_doms_inconsistent(irg);
 726                 set_irg_loopinfo_inconsistent(irg);
 727                 set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
 728         }
 729
 730         ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 731
 732         obstack_free(&obst, NULL);
 733 }
 734
 735 ir_graph_pass_t *fixpoint_vrp_irg_pass(const char *name)
 736 {
 737         return def_graph_pass(name ? name : "fixpoint_vrp", fixpoint_vrp);
 738 }