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_mode* const m = get_irn_mode(irn);
 162         ir_tarval*     z;
 163         ir_tarval*     o;
 164
 165         if (m == mode_X) {
 166                 ir_tarval* const f = get_tarval_b_false();
 167                 bitinfo*   const b = get_bitinfo(get_nodes_block(irn));
 168
 169                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 170
 171                 if (b->z == f && b->o == f) {
 172                         z = f;
 173                         o = f;
 174                 } else switch (get_irn_opcode(irn)) {
 175                         case iro_Proj: {
 176                                 ir_node* const pred = get_Proj_pred(irn);
 177                                 if (is_Start(pred)) {
 178                                         goto result_unknown_X;
 179                                 } else if (is_Cond(pred)) {
 180                                         ir_node*   const selector = get_Cond_selector(pred);
 181                                         bitinfo*   const b        = get_bitinfo(selector);
 182                                         ir_tarval* const bz       = b->z;
 183                                         ir_tarval* const bo       = b->o;
 184                                         if (get_irn_mode(selector) == mode_b) {
 185                                                 if (bz == bo) {
 186                                                         if ((bz == get_tarval_b_true()) == get_Proj_proj(irn)) {
 187                                                                 z = o = get_tarval_b_true();
 188                                                         } else {
 189                                                                 z = o = get_tarval_b_false();
 190                                                         }
 191                                                 } else {
 192                                                         goto result_unknown_X;
 193                                                 }
 194                                         } else {
 195                                                 long const val = get_Proj_proj(irn);
 196                                                 if (val != get_Cond_default_proj(pred)) {
 197                                                         ir_tarval* const tv = new_tarval_from_long(val, get_irn_mode(selector));
 198                                                         if (!tarval_is_null(tarval_andnot(tv, bz)) ||
 199                                                                         !tarval_is_null(tarval_andnot(bo, tv))) {
 200                                                                 // At least one bit differs.
 201                                                                 z = o = get_tarval_b_false();
 202 #if 0 // TODO must handle default Proj
 203                                                         } else if (bz == bo && bz == tv) {
 204                                                                 z = o = get_tarval_b_true();
 205 #endif
 206                                                         } else {
 207                                                                 goto result_unknown_X;
 208                                                         }
 209                                                 } else {
 210                                                         goto cannot_analyse_X;
 211                                                 }
 212                                         }
 213                                 } else {
 214                                         goto cannot_analyse_X;
 215                                 }
 216                                 break;
 217                         }
 218
 219                         case iro_Jmp:
 220                                 goto result_unknown_X;
 221
 222                         default:
 223 cannot_analyse_X:
 224                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 225 result_unknown_X:
 226                                 z = get_tarval_b_true();
 227                                 o = get_tarval_b_false();
 228                                 break;
 229                 }
 230         } else if (is_Block(irn)) {
 231                 int       reachable = 0;
 232                 int const arity     = get_Block_n_cfgpreds(irn);
 233                 int       i;
 234
 235                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 236                 for (i = 0; i != arity; ++i) {
 237                         bitinfo* const b = get_bitinfo(get_Block_cfgpred(irn, i));
 238                         if (b != NULL && b->z == get_tarval_b_true()) {
 239                                 reachable = 1;
 240                                 break;
 241                         }
 242                 }
 243
 244                 if (!reachable) {
 245                         ir_graph *const irg = get_Block_irg(irn);
 246                         reachable =
 247                                 irn == get_irg_start_block(irg) ||
 248                                 irn == get_irg_end_block(irg);
 249                 }
 250
 251                 o = get_tarval_b_false();
 252                 z = reachable ? get_tarval_b_true() : o;
 253         } else if (mode_is_intb(m)) {
 254                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 255                 switch (get_irn_opcode(irn)) {
 256                         case iro_Const: {
 257                                 z = o = get_Const_tarval(irn);
 258                                 break;
 259                         }
 260
 261                         case iro_Shl: {
 262                                 bitinfo*   const l  = get_bitinfo(get_Shl_left(irn));
 263                                 bitinfo*   const r  = get_bitinfo(get_Shl_right(irn));
 264                                 ir_tarval* const rz = r->z;
 265                                 if (rz == r->o) {
 266                                         z = tarval_shl(l->z, rz);
 267                                         o = tarval_shl(l->o, rz);
 268                                 } else {
 269                                         goto cannot_analyse;
 270                                 }
 271                                 break;
 272                         }
 273
 274                         case iro_Shr: {
 275                                 bitinfo*   const l  = get_bitinfo(get_Shr_left(irn));
 276                                 bitinfo*   const r  = get_bitinfo(get_Shr_right(irn));
 277                                 ir_tarval* const rz = r->z;
 278                                 if (rz == r->o) {
 279                                         z = tarval_shr(l->z, rz);
 280                                         o = tarval_shr(l->o, rz);
 281                                 } else {
 282                                         goto cannot_analyse;
 283                                 }
 284                                 break;
 285                         }
 286
 287                         case iro_Shrs: {
 288                                 bitinfo*   const l  = get_bitinfo(get_Shrs_left(irn));
 289                                 bitinfo*   const r  = get_bitinfo(get_Shrs_right(irn));
 290                                 ir_tarval* const rz = r->z;
 291                                 if (rz == r->o) {
 292                                         z = tarval_shrs(l->z, rz);
 293                                         o = tarval_shrs(l->o, rz);
 294                                 } else {
 295                                         goto cannot_analyse;
 296                                 }
 297                                 break;
 298                         }
 299
 300                         case iro_Rotl: {
 301                                 bitinfo*   const l  = get_bitinfo(get_Rotl_left(irn));
 302                                 bitinfo*   const r  = get_bitinfo(get_Rotl_right(irn));
 303                                 ir_tarval* const rz = r->z;
 304                                 if (rz == r->o) {
 305                                         z = tarval_rotl(l->z, rz);
 306                                         o = tarval_rotl(l->o, rz);
 307                                 } else {
 308                                         goto cannot_analyse;
 309                                 }
 310                                 break;
 311                         }
 312
 313                         case iro_Add: {
 314                                 bitinfo*   const l  = get_bitinfo(get_Add_left(irn));
 315                                 bitinfo*   const r  = get_bitinfo(get_Add_right(irn));
 316                                 ir_tarval* const lz = l->z;
 317                                 ir_tarval* const lo = l->o;
 318                                 ir_tarval* const rz = r->z;
 319                                 ir_tarval* const ro = r->o;
 320                                 if (lz == lo && rz == ro) {
 321                                         z = o = tarval_add(lz, rz);
 322                                 } else {
 323                                         // TODO improve: can only do lower disjoint bits
 324                                         /* Determine where any of the operands has zero bits, i.e. where no
 325                                          * carry out is generated if there is not carry in */
 326                                         ir_tarval* const no_c_in_no_c_out = tarval_and(lz, rz);
 327                                         /* Generate a mask of the lower consecutive zeroes: x | -x.  In this
 328                                          * range the addition is disjoint and therefore Add behaves like Or.
 329                                          */
 330                                         ir_tarval* const low_zero_mask = tarval_or(no_c_in_no_c_out, tarval_neg(no_c_in_no_c_out));
 331                                         ir_tarval* const low_one_mask  = tarval_not(low_zero_mask);
 332                                         z = tarval_or( tarval_or(lz, rz), low_zero_mask);
 333                                         o = tarval_and(tarval_or(lo, ro), low_one_mask);
 334                                 }
 335                                 break;
 336                         }
 337
 338                         case iro_Sub: {
 339                                 bitinfo* const l = get_bitinfo(get_Sub_left(irn));
 340                                 bitinfo* const r = get_bitinfo(get_Sub_right(irn));
 341                                 if (l != NULL && r != NULL) { // Sub might subtract pointers.
 342                                         ir_tarval* const lz = l->z;
 343                                         ir_tarval* const lo = l->o;
 344                                         ir_tarval* const rz = r->z;
 345                                         ir_tarval* const ro = r->o;
 346                                         if (lz == lo && rz == ro) {
 347                                                 z = o = tarval_sub(lz, rz, NULL);
 348                                         } else if (tarval_is_null(tarval_andnot(rz, lo))) {
 349                                                 /* Every possible one of the subtrahend is backed by a safe one of the
 350                                                  * minuend, i.e. there are no borrows. */
 351                                                 // TODO extend no-borrow like carry for Add above
 352                                                 z = tarval_andnot(lz, ro);
 353                                                 o = tarval_andnot(lo, rz);
 354                                         } else {
 355                                                 goto cannot_analyse;
 356                                         }
 357                                 } else {
 358                                         goto cannot_analyse;
 359                                 }
 360                                 break;
 361                         }
 362
 363                         case iro_Mul: {
 364                                 bitinfo*   const l  = get_bitinfo(get_Mul_left(irn));
 365                                 bitinfo*   const r  = get_bitinfo(get_Mul_right(irn));
 366                                 ir_tarval* const lz = l->z;
 367                                 ir_tarval* const lo = l->o;
 368                                 ir_tarval* const rz = r->z;
 369                                 ir_tarval* const ro = r->o;
 370                                 if (lz == lo && rz == ro) {
 371                                         z = o = tarval_mul(lz, rz);
 372                                 } else {
 373                                         // TODO improve
 374                                         // Determine safe lower zeroes: x | -x.
 375                                         ir_tarval* const lzn = tarval_or(lz, tarval_neg(lz));
 376                                         ir_tarval* const rzn = tarval_or(rz, tarval_neg(rz));
 377                                         // Concatenate safe lower zeroes.
 378                                         if (tarval_cmp(lzn, rzn) == ir_relation_less) {
 379                                                 z = tarval_mul(tarval_eor(lzn, tarval_shl(lzn, get_tarval_one(m))), rzn);
 380                                         } else {
 381                                                 z = tarval_mul(tarval_eor(rzn, tarval_shl(rzn, get_tarval_one(m))), lzn);
 382                                         }
 383                                         o = get_tarval_null(m);
 384                                 }
 385                                 break;
 386                         }
 387
 388                         case iro_Minus: {
 389                                 bitinfo* const b = get_bitinfo(get_Minus_op(irn));
 390                                 if (b->z == b->o) {
 391                                         z = o = tarval_neg(b->z);
 392                                 } else {
 393                                         goto cannot_analyse;
 394                                 }
 395                                 break;
 396                         }
 397
 398                         case iro_And: {
 399                                 bitinfo* const l = get_bitinfo(get_And_left(irn));
 400                                 bitinfo* const r = get_bitinfo(get_And_right(irn));
 401                                 z = tarval_and(l->z, r->z);
 402                                 o = tarval_and(l->o, r->o);
 403                                 break;
 404                         }
 405
 406                         case iro_Or: {
 407                                 bitinfo* const l = get_bitinfo(get_Or_left(irn));
 408                                 bitinfo* const r = get_bitinfo(get_Or_right(irn));
 409                                 z = tarval_or(l->z, r->z);
 410                                 o = tarval_or(l->o, r->o);
 411                                 break;
 412                         }
 413
 414                         case iro_Eor: {
 415                                 bitinfo*   const l  = get_bitinfo(get_Eor_left(irn));
 416                                 bitinfo*   const r  = get_bitinfo(get_Eor_right(irn));
 417                                 ir_tarval* const lz = l->z;
 418                                 ir_tarval* const lo = l->o;
 419                                 ir_tarval* const rz = r->z;
 420                                 ir_tarval* const ro = r->o;
 421                                 z = tarval_or(tarval_andnot(lz, ro), tarval_andnot(rz, lo));
 422                                 o = tarval_or(tarval_andnot(ro, lz), tarval_andnot(lo, rz));
 423                                 break;
 424                         }
 425
 426                         case iro_Not: {
 427                                 bitinfo* const b = get_bitinfo(get_Not_op(irn));
 428                                 z = tarval_not(b->o);
 429                                 o = tarval_not(b->z);
 430                                 break;
 431                         }
 432
 433                         case iro_Conv: {
 434                                 bitinfo* const b = get_bitinfo(get_Conv_op(irn));
 435                                 if (b == NULL) // Happens when converting from float values.
 436                                         goto result_unknown;
 437                                 z = tarval_convert_to(b->z, m);
 438                                 o = tarval_convert_to(b->o, m);
 439                                 break;
 440                         }
 441
 442                         case iro_Mux: {
 443                                 bitinfo* const f = get_bitinfo(get_Mux_false(irn));
 444                                 bitinfo* const t = get_bitinfo(get_Mux_true(irn));
 445                                 bitinfo* const c = get_bitinfo(get_Mux_sel(irn));
 446                                 if (c->o == get_tarval_b_true()) {
 447                                         z = t->z;
 448                                         o = t->o;
 449                                 } else if (c->z == get_tarval_b_false()) {
 450                                         z = f->z;
 451                                         o = f->o;
 452                                 } else {
 453                                         z = tarval_or( f->z, t->z);
 454                                         o = tarval_and(f->o, t->o);
 455                                 }
 456                                 break;
 457                         }
 458
 459                         case iro_Phi: {
 460                                 ir_node* const block = get_nodes_block(irn);
 461                                 int      const arity = get_Phi_n_preds(irn);
 462                                 int            i;
 463
 464                                 z = get_tarval_null(m);
 465                                 o = get_tarval_all_one(m);
 466                                 for (i = 0; i != arity; ++i) {
 467                                         bitinfo* const b_cfg = get_bitinfo(get_Block_cfgpred(block, i));
 468                                         if (b_cfg != NULL && b_cfg->z != get_tarval_b_false()) {
 469                                                 bitinfo* const b = get_bitinfo(get_Phi_pred(irn, i));
 470                                                 z = tarval_or( z, b->z);
 471                                                 o = tarval_and(o, b->o);
 472                                         }
 473                                 }
 474                                 break;
 475                         }
 476
 477                         case iro_Cmp: {
 478                                 bitinfo* const l = get_bitinfo(get_Cmp_left(irn));
 479                                 bitinfo* const r = get_bitinfo(get_Cmp_right(irn));
 480                                 if (l == NULL || r == NULL) {
 481                                         goto result_unknown; // Cmp compares something we cannot evaluate.
 482                                 } else {
 483                                         ir_tarval*  const lz       = l->z;
 484                                         ir_tarval*  const lo       = l->o;
 485                                         ir_tarval*  const rz       = r->z;
 486                                         ir_tarval*  const ro       = r->o;
 487                                         ir_relation const relation = get_Cmp_relation(irn);
 488                                         switch (relation) {
 489                                                 case ir_relation_less_greater:
 490                                                         if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 491                                                                         !tarval_is_null(tarval_andnot(lo, rz))) {
 492                                                                 // At least one bit differs.
 493                                                                 z = o = get_tarval_b_true();
 494                                                         } else if (lz == lo && rz == ro && lz == rz) {
 495                                                                 z = o = get_tarval_b_false();
 496                                                         } else {
 497                                                                 goto result_unknown;
 498                                                         }
 499                                                         break;
 500
 501                                                 case ir_relation_equal:
 502                                                         if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 503                                                                         !tarval_is_null(tarval_andnot(lo, rz))) {
 504                                                                 // At least one bit differs.
 505                                                                 z = o = get_tarval_b_false();
 506                                                         } else if (lz == lo && rz == ro && lz == rz) {
 507                                                                 z = o = get_tarval_b_true();
 508                                                         } else {
 509                                                                 goto result_unknown;
 510                                                         }
 511                                                         break;
 512
 513                                                 case ir_relation_less_equal:
 514                                                 case ir_relation_less:
 515                                                         /* TODO handle negative values */
 516                                                         if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 517                                                                         tarval_is_negative(rz) || tarval_is_negative(ro))
 518                                                                 goto result_unknown;
 519
 520                                                         if (tarval_cmp(lz, ro) & relation) {
 521                                                                 /* Left upper bound is smaller(/equal) than right lower bound. */
 522                                                                 z = o = get_tarval_b_true();
 523                                                         } else if (!(tarval_cmp(lo, rz) & relation)) {
 524                                                                 /* Left lower bound is not smaller(/equal) than right upper bound. */
 525                                                                 z = o = get_tarval_b_false();
 526                                                         } else {
 527                                                                 goto result_unknown;
 528                                                         }
 529                                                         break;
 530
 531                                                 case ir_relation_greater_equal:
 532                                                 case ir_relation_greater:
 533                                                         /* TODO handle negative values */
 534                                                         if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 535                                                                         tarval_is_negative(rz) || tarval_is_negative(ro))
 536                                                                 goto result_unknown;
 537
 538                                                         if (!(tarval_cmp(lz, ro) & relation)) {
 539                                                                 /* Left upper bound is not greater(/equal) than right lower bound. */
 540                                                                 z = o = get_tarval_b_false();
 541                                                         } else if (tarval_cmp(lo, rz) & relation) {
 542                                                                 /* Left lower bound is greater(/equal) than right upper bound. */
 543                                                                 z = o = get_tarval_b_true();
 544                                                         } else {
 545                                                                 goto result_unknown;
 546                                                         }
 547                                                         break;
 548
 549                                                 default:
 550                                                         goto cannot_analyse;
 551                                         }
 552                                 }
 553                                 break;
 554                         }
 555
 556                         default: {
 557 cannot_analyse:
 558                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 559 result_unknown:
 560                                 z = get_tarval_all_one(m);
 561                                 o = get_tarval_null(m);
 562                                 break;
 563                         }
 564                 }
 565         } else {
 566                 return 0;
 567         }
 568
 569         return set_bitinfo(irn, z, o);
 570 }
 571
 572 static void first_round(ir_node* const irn, void* const env)
 573 {
 574         pdeq* const q = (pdeq*)env;
 575
 576         transfer(irn);
 577         if (is_Phi(irn) || is_Block(irn)) {
 578                 /* Only Phis (and their users) need another round, if we did not have
 579                  * information about all their inputs in the first round, i.e. in loops. */
 580                 /* TODO inserts all Phis, should only insert Phis, which did no have all
 581                  * predecessors available */
 582                 pdeq_putr(q, irn);
 583         }
 584 }
 585
 586 static void apply_result(ir_node* const irn, void* ctx)
 587 {
 588         environment_t* env = (environment_t*)ctx;
 589         bitinfo*       b;
 590         ir_tarval*     z;
 591         ir_tarval*     o;
 592
 593         ir_node* const block = is_Block(irn) ? irn : get_nodes_block(irn);
 594         if (is_Bad(block)) {
 595                 exchange(irn, block);
 596                 return;
 597         }
 598
 599         bitinfo* const block_b = get_bitinfo(block);
 600         if (block_b && block_b->z == block_b->o && block_b->z == get_tarval_b_false()) {
 601                 exchange(irn, get_irg_bad(get_Block_irg(block)));
 602                 return;
 603         }
 604
 605         b = get_bitinfo(irn);
 606         if (!b) return;
 607         if (is_Const(irn)) return; // It cannot get any better than a Const.
 608
 609         z = b->z;
 610         o = b->o;
 611         // Only display information if we could find out anything about the value.
 612         DEBUG_ONLY(if (!tarval_is_all_one(z) || !tarval_is_null(o)))
 613                 DB((dbg, LEVEL_2, "%+F: 0:%T 1:%T%s\n", irn, z, o, z == o ? " --- constant" : ""));
 614
 615         // Replace node with constant value by Const.
 616         if (z == o) {
 617                 ir_mode* const m = get_irn_mode(irn);
 618                 ir_node*       n;
 619                 if (mode_is_intb(m)) {
 620                         ir_graph *irg = get_irn_irg(irn);
 621                         n = new_r_Const(irg, z);
 622                 } else if (m == mode_X) {
 623                         ir_graph* const irg = get_Block_irg(block);
 624                         if (z == get_tarval_b_true()) {
 625                                 // Might produce an endless loop, so keep the block.
 626                                 add_End_keepalive(get_irg_end(irg), block);
 627                                 n = new_r_Jmp(block);
 628                         } else {
 629                                 n = new_r_Bad(irg);
 630                                 /* Transferring analysis information to the bad node makes it a
 631                                  * candidate for replacement. */
 632                                 goto exchange_only;
 633                         }
 634                 } else {
 635                         return;
 636                 }
 637                 set_irn_link(n, b);
 638 exchange_only:
 639                 exchange(irn, n);
 640                 env->modified = 1;
 641         }
 642
 643         switch (get_irn_opcode(irn)) {
 644                 case iro_And: {
 645                         ir_node*       const l  = get_And_left(irn);
 646                         ir_node*       const r  = get_And_right(irn);
 647                         bitinfo const* const bl = get_bitinfo(l);
 648                         bitinfo const* const br = get_bitinfo(r);
 649                         if (bl->z == bl->o) {
 650                                 if (tarval_is_null(tarval_andnot(br->z, bl->z))) {
 651                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 652                                         exchange(irn, r);
 653                                         env->modified = 1;
 654                                 }
 655                         } else if (br->z == br->o) {
 656                                 if (tarval_is_null(tarval_andnot(bl->z, br->z))) {
 657                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 658                                         exchange(irn, l);
 659                                         env->modified = 1;
 660                                 }
 661                         }
 662                         break;
 663                 }
 664
 665                 case iro_Or: {
 666                         ir_node*       const l  = get_Or_left(irn);
 667                         ir_node*       const r  = get_Or_right(irn);
 668                         bitinfo const* const bl = get_bitinfo(l);
 669                         bitinfo const* const br = get_bitinfo(r);
 670                         if (bl->z == bl->o) {
 671                                 if (tarval_is_null(tarval_andnot(bl->o, br->o))) {
 672                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 673                                         exchange(irn, r);
 674                                         env->modified = 1;
 675                                 }
 676                         } else if (br->z == br->o) {
 677                                 if (tarval_is_null(tarval_andnot(br->o, bl->o))) {
 678                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 679                                         exchange(irn, l);
 680                                         env->modified = 1;
 681                                 }
 682                         }
 683                         break;
 684                 }
 685         }
 686 }
 687
 688 static void queue_users(pdeq* const q, ir_node* const n)
 689 {
 690         if (get_irn_mode(n) == mode_X) {
 691                 /* When the state of a control flow node changes, not only queue its
 692                  * successor blocks, but also the Phis in these blocks, because the Phis
 693                  * must reconsider this input path. */
 694                 ir_edge_t const* e;
 695                 foreach_out_edge(n, e) {
 696                         ir_node*  const  src = get_edge_src_irn(e);
 697                         pdeq_putr(q, src);
 698                         /* should always be a block */
 699                         if (is_Block(src)) {
 700                                 ir_node *phi;
 701                                 for (phi = get_Block_phis(src); phi; phi = get_Phi_next(phi))
 702                                         pdeq_putr(q, phi);
 703                         }
 704                 }
 705         } else {
 706                 ir_edge_t const* e;
 707                 foreach_out_edge(n, e) {
 708                         ir_node* const src = get_edge_src_irn(e);
 709                         if (get_irn_mode(src) == mode_T) {
 710                                 queue_users(q, src);
 711                         } else {
 712                                 pdeq_putr(q, src);
 713                         }
 714                 }
 715         }
 716 }
 717
 718 static void clear_links(ir_node *irn, void *env)
 719 {
 720         (void) env;
 721         set_irn_link(irn, NULL);
 722         if (is_Block(irn))
 723                 set_Block_phis(irn, NULL);
 724 }
 725
 726 static void build_phi_lists(ir_node *irn, void *env)
 727 {
 728         (void) env;
 729         if (is_Phi(irn))
 730                 add_Block_phi(get_nodes_block(irn), irn);
 731 }
 732
 733 void fixpoint_vrp(ir_graph* const irg)
 734 {
 735         environment_t env;
 736
 737         FIRM_DBG_REGISTER(dbg, "firm.opt.fp-vrp");
 738         DB((dbg, LEVEL_1, "===> Performing constant propagation on %+F\n", irg));
 739
 740         obstack_init(&obst);
 741
 742         /* HACK: to avoid finding dead code */
 743         edges_deactivate(irg);
 744         edges_activate(irg);
 745
 746         edges_assure(irg);
 747         assure_doms(irg);
 748
 749         ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 750
 751         {
 752                 pdeq* const q = new_pdeq();
 753
 754                 /* We need this extra step because the dom tree does not contain unreachable
 755                    blocks in Firm. Moreover build phi list. */
 756                 irg_walk_anchors(irg, clear_links, build_phi_lists, NULL);
 757
 758                 /* TODO Improve iteration order. Best is reverse postorder in data flow
 759                  * direction and respecting loop nesting for fastest convergence. */
 760                 irg_walk_blkwise_dom_top_down(irg, NULL, first_round, q);
 761
 762                 while (!pdeq_empty(q)) {
 763                         ir_node* const n = (ir_node*)pdeq_getl(q);
 764                         if (transfer(n))
 765                                 queue_users(q, n);
 766                 }
 767
 768                 del_pdeq(q);
 769         }
 770
 771         DB((dbg, LEVEL_2, "---> Applying analysis results\n"));
 772         env.modified = 0;
 773         irg_walk_graph(irg, NULL, apply_result, &env);
 774
 775         if (env.modified) {
 776                 /* control flow might changed */
 777                 set_irg_outs_inconsistent(irg);
 778                 set_irg_extblk_inconsistent(irg);
 779                 set_irg_doms_inconsistent(irg);
 780                 set_irg_loopinfo_inconsistent(irg);
 781                 set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
 782         }
 783
 784         ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 785
 786         obstack_free(&obst, NULL);
 787 }
 788
 789 ir_graph_pass_t *fixpoint_vrp_irg_pass(const char *name)
 790 {
 791         return def_graph_pass(name ? name : "fixpoint_vrp", fixpoint_vrp);
 792 }