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 #include "config.h"
  27
  28 #include "adt/pdeq.h"
  29 #include "adt/obst.h"
  30 #include "adt/xmalloc.h"
  31 #include "debug.h"
  32 #include "ircons.h"
  33 #include "irdom.h"
  34 #include "iredges.h"
  35 #include "irgmod.h"
  36 #include "irgraph.h"
  37 #include "irgwalk.h"
  38 #include "irnode.h"
  39 #include "iroptimize.h"
  40 #include "irtools.h"
  41 #include "tv.h"
  42 #include "irpass.h"
  43 #include "irmemory.h"
  44
  45 /* TODO:
  46  * - Implement cleared/set bit calculation for Add, Sub, Minus, Mul, Div, Mod, Shl, Shr, Shrs, Rotl
  47  * - Implement min/max calculation for And, Eor, Or, Not, Conv, Shl, Shr, Shrs, Rotl, Mux
  48  * - Implement min/max calculation for Add, Sub, Minus, Mul, Div, Mod, Conv, Shl, Shr, Shrs, Rotl, Mux
  49  */
  50
  51 /* Tables of the cleared/set bit lattice
  52  *
  53  * Encoding of the lattice
  54  * zo
  55  * 00 0 zero
  56  * 01 - impossible state, is zero /and/ one
  57  * 10 T top, may be either zero or one
  58  * 11 1 one
  59  *
  60  * S = Sum
  61  * c = Carry
  62  * D = Difference
  63  * b = Borrow
  64  *
  65  * Not
  66  * A ~
  67  * 0 1
  68  * 1 0
  69  * T T
  70  *
  71  * Half adder, half subtractor, and, xor, or, Mux
  72  * AB  Sc  Db  &  ^  |  M
  73  * 00  00  00  0  0  0  0
  74  * 01  10  11  0  1  1  T
  75  * 0T  T0  TT  0  T  T  T
  76  * 10  10  10  0  1  1  T
  77  * 11  01  00  1  0  1  1
  78  * 1T  TT  T0  T  T  1  T
  79  * T0  T0  T0  0  T  T  T
  80  * T1  TT  TT  T  T  1  T
  81  * TT  TT  TT  T  T  T  T
  82  *
  83  * Full adder, full subtractor
  84  * ABc-1  Sc  Db
  85  * 000    00  00
  86  * 001    10  11
  87  * 00T    T0  TT
  88  * 010    10  11
  89  * 011    01  01
  90  * 01T    TT  T1
  91  * 0T0    T0  TT
  92  * 0T1    TT  T1
  93  * 0TT    TT  TT
  94  * 100    10  10
  95  * 101    01  00
  96  * 10T    TT  T0
  97  * 110    01  00
  98  * 111    11  11
  99  * 11T    T1  TT
 100  * 1T0    TT  T0
 101  * 1T1    T1  TT
 102  * 1TT    TT  TT
 103  * T00    T0  T0
 104  * T01    TT  TT
 105  * T0T    TT  TT
 106  * T10    TT  TT
 107  * T11    T1  T1
 108  * T1T    TT  TT
 109  * TT0    TT  TT
 110  * TT1    TT  TT
 111  * TTT    TT  TT
 112  *
 113  *
 114  * Assume: Xmin <= Xmax and no overflow
 115  * A + B = (Amin + Bmin, Amax + Bmax)
 116  *    -A = (-Amax, -Amin)
 117  * A - B = A + -B = (Amin (-B)min, Amax + (-B)max) = (Amin - Bmax, Amax - Bmin)
 118  */
 119
 120 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
 121
 122 static struct obstack obst;
 123
 124 typedef struct bitinfo
 125 {
 126         ir_tarval* z; // safe zeroes, 0 = bit is zero,       1 = bit maybe is 1
 127         ir_tarval* o; // safe ones,   0 = bit maybe is zero, 1 = bit is 1
 128 } bitinfo;
 129
 130 typedef struct environment_t {
 131         unsigned modified:1;     /**< Set, if the graph was modified. */
 132 } environment_t;
 133
 134 static inline bitinfo* get_bitinfo(ir_node const* const irn)
 135 {
 136         return (bitinfo*)get_irn_link(irn);
 137 }
 138
 139 static int set_bitinfo(ir_node* const irn, ir_tarval* const z, ir_tarval* const o)
 140 {
 141         bitinfo* b = get_bitinfo(irn);
 142         if (b == NULL) {
 143                 b = OALLOCZ(&obst, bitinfo);
 144                 set_irn_link(irn, b);
 145         } else if (z == b->z && o == b->o) {
 146                 return 0;
 147         }
 148         b->z = z;
 149         b->o = o;
 150         DB((dbg, LEVEL_3, "%+F: 0:%T 1:%T\n", irn, z, o));
 151         return 1;
 152 }
 153
 154 static int mode_is_intb(ir_mode const* const m)
 155 {
 156         return mode_is_int(m) || m == mode_b;
 157 }
 158
 159 static int transfer(ir_node* const irn)
 160 {
 161         ir_tarval* const f = get_tarval_b_false();
 162         ir_tarval* const t = get_tarval_b_true();
 163         ir_mode*   const m = get_irn_mode(irn);
 164         ir_tarval*       z;
 165         ir_tarval*       o;
 166
 167         if (m == mode_X) {
 168                 bitinfo* const b = get_bitinfo(get_nodes_block(irn));
 169
 170                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 171
 172                 if (b->z == f && b->o == f) {
 173                         z = f;
 174                         o = f;
 175                 } else switch (get_irn_opcode(irn)) {
 176                         case iro_Proj: {
 177                                 ir_node* const pred = get_Proj_pred(irn);
 178                                 if (is_Start(pred)) {
 179                                         goto result_unknown_X;
 180                                 } else if (is_Cond(pred)) {
 181                                         ir_node*   const selector = get_Cond_selector(pred);
 182                                         bitinfo*   const b        = get_bitinfo(selector);
 183                                         ir_tarval* const bz       = b->z;
 184                                         ir_tarval* const bo       = b->o;
 185                                         if (get_irn_mode(selector) == mode_b) {
 186                                                 if (bz == bo) {
 187                                                         if ((bz == t) == get_Proj_proj(irn)) {
 188                                                                 z = o = t;
 189                                                         } else {
 190                                                                 z = o = f;
 191                                                         }
 192                                                 } else {
 193                                                         goto result_unknown_X;
 194                                                 }
 195                                         } else {
 196                                                 long const val = get_Proj_proj(irn);
 197                                                 if (val != get_Cond_default_proj(pred)) {
 198                                                         ir_tarval* const tv = new_tarval_from_long(val, get_irn_mode(selector));
 199                                                         if (!tarval_is_null(tarval_andnot(tv, bz)) ||
 200                                                                         !tarval_is_null(tarval_andnot(bo, tv))) {
 201                                                                 // At least one bit differs.
 202                                                                 z = o = f;
 203 #if 0 // TODO must handle default Proj
 204                                                         } else if (bz == bo && bz == tv) {
 205                                                                 z = o = t;
 206 #endif
 207                                                         } else {
 208                                                                 goto result_unknown_X;
 209                                                         }
 210                                                 } else {
 211                                                         goto cannot_analyse_X;
 212                                                 }
 213                                         }
 214                                 } else {
 215                                         goto cannot_analyse_X;
 216                                 }
 217                                 break;
 218                         }
 219
 220                         case iro_Jmp:
 221                                 goto result_unknown_X;
 222
 223                         default:
 224 cannot_analyse_X:
 225                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 226 result_unknown_X:
 227                                 z = t;
 228                                 o = f;
 229                                 break;
 230                 }
 231         } else if (is_Block(irn)) {
 232                 int       reachable = 0;
 233                 int const arity     = get_Block_n_cfgpreds(irn);
 234                 int       i;
 235
 236                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 237                 for (i = 0; i != arity; ++i) {
 238                         bitinfo* const b = get_bitinfo(get_Block_cfgpred(irn, i));
 239                         if (b != NULL && b->z == t) {
 240                                 reachable = 1;
 241                                 break;
 242                         }
 243                 }
 244
 245                 if (!reachable) {
 246                         ir_graph *const irg = get_Block_irg(irn);
 247                         reachable =
 248                                 irn == get_irg_start_block(irg) ||
 249                                 irn == get_irg_end_block(irg);
 250                 }
 251
 252                 o = f;
 253                 z = reachable ? t : f;
 254         } else if (mode_is_intb(m)) {
 255                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 256                 switch (get_irn_opcode(irn)) {
 257                         case iro_Const: {
 258                                 z = o = get_Const_tarval(irn);
 259                                 break;
 260                         }
 261
 262                         case iro_Confirm: {
 263                                 ir_node* const v = get_Confirm_value(irn);
 264                                 bitinfo* const b = get_bitinfo(v);
 265                                 /* TODO Use bound and relation. */
 266                                 z = b->z;
 267                                 o = b->o;
 268                                 break;
 269                         }
 270
 271                         case iro_Shl: {
 272                                 bitinfo*   const l  = get_bitinfo(get_Shl_left(irn));
 273                                 bitinfo*   const r  = get_bitinfo(get_Shl_right(irn));
 274                                 ir_tarval* const rz = r->z;
 275                                 if (rz == r->o) {
 276                                         z = tarval_shl(l->z, rz);
 277                                         o = tarval_shl(l->o, rz);
 278                                 } else {
 279                                         goto cannot_analyse;
 280                                 }
 281                                 break;
 282                         }
 283
 284                         case iro_Shr: {
 285                                 bitinfo*   const l  = get_bitinfo(get_Shr_left(irn));
 286                                 bitinfo*   const r  = get_bitinfo(get_Shr_right(irn));
 287                                 ir_tarval* const rz = r->z;
 288                                 if (rz == r->o) {
 289                                         z = tarval_shr(l->z, rz);
 290                                         o = tarval_shr(l->o, rz);
 291                                 } else {
 292                                         goto cannot_analyse;
 293                                 }
 294                                 break;
 295                         }
 296
 297                         case iro_Shrs: {
 298                                 bitinfo*   const l  = get_bitinfo(get_Shrs_left(irn));
 299                                 bitinfo*   const r  = get_bitinfo(get_Shrs_right(irn));
 300                                 ir_tarval* const rz = r->z;
 301                                 if (rz == r->o) {
 302                                         z = tarval_shrs(l->z, rz);
 303                                         o = tarval_shrs(l->o, rz);
 304                                 } else {
 305                                         goto cannot_analyse;
 306                                 }
 307                                 break;
 308                         }
 309
 310                         case iro_Rotl: {
 311                                 bitinfo*   const l  = get_bitinfo(get_Rotl_left(irn));
 312                                 bitinfo*   const r  = get_bitinfo(get_Rotl_right(irn));
 313                                 ir_tarval* const rz = r->z;
 314                                 if (rz == r->o) {
 315                                         z = tarval_rotl(l->z, rz);
 316                                         o = tarval_rotl(l->o, rz);
 317                                 } else {
 318                                         goto cannot_analyse;
 319                                 }
 320                                 break;
 321                         }
 322
 323                         case iro_Add: {
 324                                 bitinfo*   const l  = get_bitinfo(get_Add_left(irn));
 325                                 bitinfo*   const r  = get_bitinfo(get_Add_right(irn));
 326                                 ir_tarval* const lz = l->z;
 327                                 ir_tarval* const lo = l->o;
 328                                 ir_tarval* const rz = r->z;
 329                                 ir_tarval* const ro = r->o;
 330                                 if (lz == lo && rz == ro) {
 331                                         z = o = tarval_add(lz, rz);
 332                                 } else {
 333                                         // TODO improve: can only do lower disjoint bits
 334                                         /* Determine where any of the operands has zero bits, i.e. where no
 335                                          * carry out is generated if there is not carry in */
 336                                         ir_tarval* const no_c_in_no_c_out = tarval_and(lz, rz);
 337                                         /* Generate a mask of the lower consecutive zeroes: x | -x.  In this
 338                                          * range the addition is disjoint and therefore Add behaves like Or.
 339                                          */
 340                                         ir_tarval* const low_zero_mask = tarval_or(no_c_in_no_c_out, tarval_neg(no_c_in_no_c_out));
 341                                         ir_tarval* const low_one_mask  = tarval_not(low_zero_mask);
 342                                         z = tarval_or( tarval_or(lz, rz), low_zero_mask);
 343                                         o = tarval_and(tarval_or(lo, ro), low_one_mask);
 344                                 }
 345                                 break;
 346                         }
 347
 348                         case iro_Sub: {
 349                                 bitinfo* const l = get_bitinfo(get_Sub_left(irn));
 350                                 bitinfo* const r = get_bitinfo(get_Sub_right(irn));
 351                                 if (l != NULL && r != NULL) { // Sub might subtract pointers.
 352                                         ir_tarval* const lz = l->z;
 353                                         ir_tarval* const lo = l->o;
 354                                         ir_tarval* const rz = r->z;
 355                                         ir_tarval* const ro = r->o;
 356                                         if (lz == lo && rz == ro) {
 357                                                 z = o = tarval_sub(lz, rz, NULL);
 358                                         } else if (tarval_is_null(tarval_andnot(rz, lo))) {
 359                                                 /* Every possible one of the subtrahend is backed by a safe one of the
 360                                                  * minuend, i.e. there are no borrows. */
 361                                                 // TODO extend no-borrow like carry for Add above
 362                                                 z = tarval_andnot(lz, ro);
 363                                                 o = tarval_andnot(lo, rz);
 364                                         } else {
 365                                                 goto cannot_analyse;
 366                                         }
 367                                 } else {
 368                                         goto cannot_analyse;
 369                                 }
 370                                 break;
 371                         }
 372
 373                         case iro_Mul: {
 374                                 bitinfo*   const l  = get_bitinfo(get_Mul_left(irn));
 375                                 bitinfo*   const r  = get_bitinfo(get_Mul_right(irn));
 376                                 ir_tarval* const lz = l->z;
 377                                 ir_tarval* const lo = l->o;
 378                                 ir_tarval* const rz = r->z;
 379                                 ir_tarval* const ro = r->o;
 380                                 if (lz == lo && rz == ro) {
 381                                         z = o = tarval_mul(lz, rz);
 382                                 } else {
 383                                         // TODO improve
 384                                         // Determine safe lower zeroes: x | -x.
 385                                         ir_tarval* const lzn = tarval_or(lz, tarval_neg(lz));
 386                                         ir_tarval* const rzn = tarval_or(rz, tarval_neg(rz));
 387                                         // Concatenate safe lower zeroes.
 388                                         if (tarval_cmp(lzn, rzn) == ir_relation_less) {
 389                                                 z = tarval_mul(tarval_eor(lzn, tarval_shl(lzn, get_tarval_one(m))), rzn);
 390                                         } else {
 391                                                 z = tarval_mul(tarval_eor(rzn, tarval_shl(rzn, get_tarval_one(m))), lzn);
 392                                         }
 393                                         o = get_tarval_null(m);
 394                                 }
 395                                 break;
 396                         }
 397
 398                         case iro_Minus: {
 399                                 bitinfo* const b = get_bitinfo(get_Minus_op(irn));
 400                                 if (b->z == b->o) {
 401                                         z = o = tarval_neg(b->z);
 402                                 } else {
 403                                         goto cannot_analyse;
 404                                 }
 405                                 break;
 406                         }
 407
 408                         case iro_And: {
 409                                 bitinfo* const l = get_bitinfo(get_And_left(irn));
 410                                 bitinfo* const r = get_bitinfo(get_And_right(irn));
 411                                 z = tarval_and(l->z, r->z);
 412                                 o = tarval_and(l->o, r->o);
 413                                 break;
 414                         }
 415
 416                         case iro_Or: {
 417                                 bitinfo* const l = get_bitinfo(get_Or_left(irn));
 418                                 bitinfo* const r = get_bitinfo(get_Or_right(irn));
 419                                 z = tarval_or(l->z, r->z);
 420                                 o = tarval_or(l->o, r->o);
 421                                 break;
 422                         }
 423
 424                         case iro_Eor: {
 425                                 bitinfo*   const l  = get_bitinfo(get_Eor_left(irn));
 426                                 bitinfo*   const r  = get_bitinfo(get_Eor_right(irn));
 427                                 ir_tarval* const lz = l->z;
 428                                 ir_tarval* const lo = l->o;
 429                                 ir_tarval* const rz = r->z;
 430                                 ir_tarval* const ro = r->o;
 431                                 z = tarval_or(tarval_andnot(lz, ro), tarval_andnot(rz, lo));
 432                                 o = tarval_or(tarval_andnot(ro, lz), tarval_andnot(lo, rz));
 433                                 break;
 434                         }
 435
 436                         case iro_Not: {
 437                                 bitinfo* const b = get_bitinfo(get_Not_op(irn));
 438                                 z = tarval_not(b->o);
 439                                 o = tarval_not(b->z);
 440                                 break;
 441                         }
 442
 443                         case iro_Conv: {
 444                                 bitinfo* const b = get_bitinfo(get_Conv_op(irn));
 445                                 if (b == NULL) // Happens when converting from float values.
 446                                         goto result_unknown;
 447                                 z = tarval_convert_to(b->z, m);
 448                                 o = tarval_convert_to(b->o, m);
 449                                 break;
 450                         }
 451
 452                         case iro_Mux: {
 453                                 bitinfo* const bf = get_bitinfo(get_Mux_false(irn));
 454                                 bitinfo* const bt = get_bitinfo(get_Mux_true(irn));
 455                                 bitinfo* const c  = get_bitinfo(get_Mux_sel(irn));
 456                                 if (c->o == t) {
 457                                         z = bt->z;
 458                                         o = bt->o;
 459                                 } else if (c->z == f) {
 460                                         z = bf->z;
 461                                         o = bf->o;
 462                                 } else {
 463                                         z = tarval_or( bf->z, bt->z);
 464                                         o = tarval_and(bf->o, bt->o);
 465                                 }
 466                                 break;
 467                         }
 468
 469                         case iro_Phi: {
 470                                 ir_node* const block = get_nodes_block(irn);
 471                                 int      const arity = get_Phi_n_preds(irn);
 472                                 int            i;
 473
 474                                 z = get_tarval_null(m);
 475                                 o = get_tarval_all_one(m);
 476                                 for (i = 0; i != arity; ++i) {
 477                                         bitinfo* const b_cfg = get_bitinfo(get_Block_cfgpred(block, i));
 478                                         if (b_cfg != NULL && b_cfg->z != f) {
 479                                                 bitinfo* const b = get_bitinfo(get_Phi_pred(irn, i));
 480                                                 z = tarval_or( z, b->z);
 481                                                 o = tarval_and(o, b->o);
 482                                         }
 483                                 }
 484                                 break;
 485                         }
 486
 487                         case iro_Cmp: {
 488                                 bitinfo* const l = get_bitinfo(get_Cmp_left(irn));
 489                                 bitinfo* const r = get_bitinfo(get_Cmp_right(irn));
 490                                 if (l == NULL || r == NULL) {
 491                                         goto result_unknown; // Cmp compares something we cannot evaluate.
 492                                 } else {
 493                                         ir_tarval*  const lz       = l->z;
 494                                         ir_tarval*  const lo       = l->o;
 495                                         ir_tarval*  const rz       = r->z;
 496                                         ir_tarval*  const ro       = r->o;
 497                                         ir_relation const relation = get_Cmp_relation(irn);
 498                                         switch (relation) {
 499                                                 case ir_relation_less_greater:
 500                                                         if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 501                                                                         !tarval_is_null(tarval_andnot(lo, rz))) {
 502                                                                 // At least one bit differs.
 503                                                                 z = o = t;
 504                                                         } else if (lz == lo && rz == ro && lz == rz) {
 505                                                                 z = o = f;
 506                                                         } else {
 507                                                                 goto result_unknown;
 508                                                         }
 509                                                         break;
 510
 511                                                 case ir_relation_equal:
 512                                                         if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 513                                                                         !tarval_is_null(tarval_andnot(lo, rz))) {
 514                                                                 // At least one bit differs.
 515                                                                 z = o = f;
 516                                                         } else if (lz == lo && rz == ro && lz == rz) {
 517                                                                 z = o = t;
 518                                                         } else {
 519                                                                 goto result_unknown;
 520                                                         }
 521                                                         break;
 522
 523                                                 case ir_relation_less_equal:
 524                                                 case ir_relation_less:
 525                                                         /* TODO handle negative values */
 526                                                         if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 527                                                                         tarval_is_negative(rz) || tarval_is_negative(ro))
 528                                                                 goto result_unknown;
 529
 530                                                         if (tarval_cmp(lz, ro) & relation) {
 531                                                                 /* Left upper bound is smaller(/equal) than right lower bound. */
 532                                                                 z = o = t;
 533                                                         } else if (!(tarval_cmp(lo, rz) & relation)) {
 534                                                                 /* Left lower bound is not smaller(/equal) than right upper bound. */
 535                                                                 z = o = f;
 536                                                         } else {
 537                                                                 goto result_unknown;
 538                                                         }
 539                                                         break;
 540
 541                                                 case ir_relation_greater_equal:
 542                                                 case ir_relation_greater:
 543                                                         /* TODO handle negative values */
 544                                                         if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 545                                                                         tarval_is_negative(rz) || tarval_is_negative(ro))
 546                                                                 goto result_unknown;
 547
 548                                                         if (!(tarval_cmp(lz, ro) & relation)) {
 549                                                                 /* Left upper bound is not greater(/equal) than right lower bound. */
 550                                                                 z = o = f;
 551                                                         } else if (tarval_cmp(lo, rz) & relation) {
 552                                                                 /* Left lower bound is greater(/equal) than right upper bound. */
 553                                                                 z = o = t;
 554                                                         } else {
 555                                                                 goto result_unknown;
 556                                                         }
 557                                                         break;
 558
 559                                                 default:
 560                                                         goto cannot_analyse;
 561                                         }
 562                                 }
 563                                 break;
 564                         }
 565
 566                         default: {
 567 cannot_analyse:
 568                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 569 result_unknown:
 570                                 z = get_tarval_all_one(m);
 571                                 o = get_tarval_null(m);
 572                                 break;
 573                         }
 574                 }
 575         } else {
 576                 return 0;
 577         }
 578
 579         return set_bitinfo(irn, z, o);
 580 }
 581
 582 static void first_round(ir_node* const irn, void* const env)
 583 {
 584         pdeq* const q = (pdeq*)env;
 585
 586         transfer(irn);
 587         if (is_Phi(irn) || is_Block(irn)) {
 588                 /* Only Phis (and their users) need another round, if we did not have
 589                  * information about all their inputs in the first round, i.e. in loops. */
 590                 /* TODO inserts all Phis, should only insert Phis, which did no have all
 591                  * predecessors available */
 592                 pdeq_putr(q, irn);
 593         }
 594 }
 595
 596 static void apply_result(ir_node* const irn, void* ctx)
 597 {
 598         environment_t* env = (environment_t*)ctx;
 599         ir_node*       block;
 600         bitinfo*       b;
 601         ir_tarval*     z;
 602         ir_tarval*     o;
 603
 604         if (is_Block(irn)) {
 605                 bitinfo* const block_b = get_bitinfo(irn);
 606                 /* Trivially unreachable blocks have no info. */
 607                 if (block_b == NULL || block_b->z == get_tarval_b_false()) {
 608                         exchange(irn, get_irg_bad(get_Block_irg(irn)));
 609                         env->modified = 1;
 610                 }
 611                 return;
 612         }
 613
 614         /* Unreachable blocks are replaced before the nodes in them. */
 615         block = get_nodes_block(irn);
 616         if (is_Bad(block)) {
 617                 exchange(irn, block);
 618                 env->modified = 1;
 619                 return;
 620         }
 621
 622         b = get_bitinfo(irn);
 623         if (!b) return;
 624         if (is_Const(irn)) return; // It cannot get any better than a Const.
 625
 626         z = b->z;
 627         o = b->o;
 628         // Only display information if we could find out anything about the value.
 629         DEBUG_ONLY(if (!tarval_is_all_one(z) || !tarval_is_null(o)))
 630                 DB((dbg, LEVEL_2, "%+F: 0:%T 1:%T%s\n", irn, z, o, z == o ? " --- constant" : ""));
 631
 632         // Replace node with constant value by Const.
 633         if (z == o) {
 634                 ir_mode* const m = get_irn_mode(irn);
 635                 ir_node*       n;
 636                 if (mode_is_intb(m)) {
 637                         ir_graph *irg = get_irn_irg(irn);
 638                         n = new_r_Const(irg, z);
 639                 } else if (m == mode_X) {
 640                         ir_graph* const irg = get_Block_irg(block);
 641                         if (z == get_tarval_b_true()) {
 642                                 // Might produce an endless loop, so keep the block.
 643                                 add_End_keepalive(get_irg_end(irg), block);
 644                                 n = new_r_Jmp(block);
 645                         } else {
 646                                 n = new_r_Bad(irg);
 647                                 /* Transferring analysis information to the bad node makes it a
 648                                  * candidate for replacement. */
 649                                 goto exchange_only;
 650                         }
 651                 } else {
 652                         return;
 653                 }
 654                 set_irn_link(n, b);
 655 exchange_only:
 656                 exchange(irn, n);
 657                 env->modified = 1;
 658         }
 659
 660         switch (get_irn_opcode(irn)) {
 661                 case iro_And: {
 662                         ir_node*       const l  = get_And_left(irn);
 663                         ir_node*       const r  = get_And_right(irn);
 664                         bitinfo const* const bl = get_bitinfo(l);
 665                         bitinfo const* const br = get_bitinfo(r);
 666                         if (bl->z == bl->o) {
 667                                 if (tarval_is_null(tarval_andnot(br->z, bl->z))) {
 668                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 669                                         exchange(irn, r);
 670                                         env->modified = 1;
 671                                 }
 672                         } else if (br->z == br->o) {
 673                                 if (tarval_is_null(tarval_andnot(bl->z, br->z))) {
 674                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 675                                         exchange(irn, l);
 676                                         env->modified = 1;
 677                                 }
 678                         }
 679                         break;
 680                 }
 681
 682                 case iro_Or: {
 683                         ir_node*       const l  = get_Or_left(irn);
 684                         ir_node*       const r  = get_Or_right(irn);
 685                         bitinfo const* const bl = get_bitinfo(l);
 686                         bitinfo const* const br = get_bitinfo(r);
 687                         if (bl->z == bl->o) {
 688                                 if (tarval_is_null(tarval_andnot(bl->o, br->o))) {
 689                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 690                                         exchange(irn, r);
 691                                         env->modified = 1;
 692                                 }
 693                         } else if (br->z == br->o) {
 694                                 if (tarval_is_null(tarval_andnot(br->o, bl->o))) {
 695                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 696                                         exchange(irn, l);
 697                                         env->modified = 1;
 698                                 }
 699                         }
 700                         break;
 701                 }
 702         }
 703 }
 704
 705 static void queue_users(pdeq* const q, ir_node* const n)
 706 {
 707         if (get_irn_mode(n) == mode_X) {
 708                 /* When the state of a control flow node changes, not only queue its
 709                  * successor blocks, but also the Phis in these blocks, because the Phis
 710                  * must reconsider this input path. */
 711                 ir_edge_t const* e;
 712                 foreach_out_edge(n, e) {
 713                         ir_node*  const  src = get_edge_src_irn(e);
 714                         pdeq_putr(q, src);
 715                         /* should always be a block */
 716                         if (is_Block(src)) {
 717                                 ir_node *phi;
 718                                 for (phi = get_Block_phis(src); phi; phi = get_Phi_next(phi))
 719                                         pdeq_putr(q, phi);
 720                         }
 721                 }
 722         } else {
 723                 ir_edge_t const* e;
 724                 foreach_out_edge(n, e) {
 725                         ir_node* const src = get_edge_src_irn(e);
 726                         if (get_irn_mode(src) == mode_T) {
 727                                 queue_users(q, src);
 728                         } else {
 729                                 pdeq_putr(q, src);
 730                         }
 731                 }
 732         }
 733 }
 734
 735 static void clear_links(ir_node *irn, void *env)
 736 {
 737         (void) env;
 738         set_irn_link(irn, NULL);
 739         if (is_Block(irn))
 740                 set_Block_phis(irn, NULL);
 741 }
 742
 743 static void build_phi_lists(ir_node *irn, void *env)
 744 {
 745         (void) env;
 746         if (is_Phi(irn))
 747                 add_Block_phi(get_nodes_block(irn), irn);
 748 }
 749
 750 void fixpoint_vrp(ir_graph* const irg)
 751 {
 752         environment_t env;
 753
 754         FIRM_DBG_REGISTER(dbg, "firm.opt.fp-vrp");
 755         DB((dbg, LEVEL_1, "===> Performing constant propagation on %+F\n", irg));
 756
 757         obstack_init(&obst);
 758
 759         /* HACK: to avoid finding dead code */
 760         edges_deactivate(irg);
 761         edges_activate(irg);
 762
 763         edges_assure(irg);
 764         assure_doms(irg);
 765
 766         ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 767
 768         {
 769                 pdeq* const q = new_pdeq();
 770
 771                 /* We need this extra step because the dom tree does not contain unreachable
 772                    blocks in Firm. Moreover build phi list. */
 773                 irg_walk_anchors(irg, clear_links, build_phi_lists, NULL);
 774
 775                 /* TODO Improve iteration order. Best is reverse postorder in data flow
 776                  * direction and respecting loop nesting for fastest convergence. */
 777                 irg_walk_blkwise_dom_top_down(irg, NULL, first_round, q);
 778
 779                 while (!pdeq_empty(q)) {
 780                         ir_node* const n = (ir_node*)pdeq_getl(q);
 781                         if (transfer(n))
 782                                 queue_users(q, n);
 783                 }
 784
 785                 del_pdeq(q);
 786         }
 787
 788         DB((dbg, LEVEL_2, "---> Applying analysis results\n"));
 789         env.modified = 0;
 790         irg_walk_graph(irg, NULL, apply_result, &env);
 791
 792         if (env.modified) {
 793                 /* control flow might changed */
 794                 set_irg_outs_inconsistent(irg);
 795                 set_irg_extblk_inconsistent(irg);
 796                 set_irg_doms_inconsistent(irg);
 797                 set_irg_loopinfo_inconsistent(irg);
 798                 set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
 799         }
 800
 801         ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 802
 803         obstack_free(&obst, NULL);
 804 }
 805
 806 ir_graph_pass_t *fixpoint_vrp_irg_pass(const char *name)
 807 {
 808         return def_graph_pass(name ? name : "fixpoint_vrp", fixpoint_vrp);
 809 }