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 <stdbool.h>
  29
  30 #include "adt/pdeq.h"
  31 #include "adt/obst.h"
  32 #include "adt/xmalloc.h"
  33 #include "debug.h"
  34 #include "ircons.h"
  35 #include "irdom.h"
  36 #include "iredges.h"
  37 #include "irgmod.h"
  38 #include "irgraph.h"
  39 #include "irgwalk.h"
  40 #include "irnode.h"
  41 #include "iroptimize.h"
  42 #include "irtools.h"
  43 #include "tv.h"
  44 #include "irpass.h"
  45 #include "irmemory.h"
  46
  47 /* TODO:
  48  * - Implement cleared/set bit calculation for Add, Sub, Minus, Mul, Div, Mod, Shl, Shr, Shrs, Rotl
  49  * - Implement min/max calculation for And, Eor, Or, Not, Conv, Shl, Shr, Shrs, Rotl, Mux
  50  * - Implement min/max calculation for Add, Sub, Minus, Mul, Div, Mod, Conv, Shl, Shr, Shrs, Rotl, Mux
  51  */
  52
  53 /* Tables of the cleared/set bit lattice
  54  *
  55  * Encoding of the lattice
  56  * zo
  57  * 00 0 zero
  58  * 01 - impossible state, is zero /and/ one
  59  * 10 T top, may be either zero or one
  60  * 11 1 one
  61  *
  62  * S = Sum
  63  * c = Carry
  64  * D = Difference
  65  * b = Borrow
  66  *
  67  * Not
  68  * A ~
  69  * 0 1
  70  * 1 0
  71  * T T
  72  *
  73  * Half adder, half subtractor, and, xor, or, Mux
  74  * AB  Sc  Db  &  ^  |  M
  75  * 00  00  00  0  0  0  0
  76  * 01  10  11  0  1  1  T
  77  * 0T  T0  TT  0  T  T  T
  78  * 10  10  10  0  1  1  T
  79  * 11  01  00  1  0  1  1
  80  * 1T  TT  T0  T  T  1  T
  81  * T0  T0  T0  0  T  T  T
  82  * T1  TT  TT  T  T  1  T
  83  * TT  TT  TT  T  T  T  T
  84  *
  85  * Full adder, full subtractor
  86  * ABc-1  Sc  Db
  87  * 000    00  00
  88  * 001    10  11
  89  * 00T    T0  TT
  90  * 010    10  11
  91  * 011    01  01
  92  * 01T    TT  T1
  93  * 0T0    T0  TT
  94  * 0T1    TT  T1
  95  * 0TT    TT  TT
  96  * 100    10  10
  97  * 101    01  00
  98  * 10T    TT  T0
  99  * 110    01  00
 100  * 111    11  11
 101  * 11T    T1  TT
 102  * 1T0    TT  T0
 103  * 1T1    T1  TT
 104  * 1TT    TT  TT
 105  * T00    T0  T0
 106  * T01    TT  TT
 107  * T0T    TT  TT
 108  * T10    TT  TT
 109  * T11    T1  T1
 110  * T1T    TT  TT
 111  * TT0    TT  TT
 112  * TT1    TT  TT
 113  * TTT    TT  TT
 114  *
 115  *
 116  * Assume: Xmin <= Xmax and no overflow
 117  * A + B = (Amin + Bmin, Amax + Bmax)
 118  *    -A = (-Amax, -Amin)
 119  * A - B = A + -B = (Amin (-B)min, Amax + (-B)max) = (Amin - Bmax, Amax - Bmin)
 120  */
 121
 122 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
 123
 124 static struct obstack obst;
 125
 126 typedef struct bitinfo
 127 {
 128         ir_tarval* z; // safe zeroes, 0 = bit is zero,       1 = bit maybe is 1
 129         ir_tarval* o; // safe ones,   0 = bit maybe is zero, 1 = bit is 1
 130 } bitinfo;
 131
 132 typedef struct environment_t {
 133         unsigned modified:1;     /**< Set, if the graph was modified. */
 134 } environment_t;
 135
 136 static bool is_undefined(bitinfo const* const b)
 137 {
 138         return tarval_is_null(b->z) && tarval_is_all_one(b->o);
 139 }
 140
 141 static inline bitinfo* get_bitinfo(ir_node const* const irn)
 142 {
 143         return (bitinfo*)get_irn_link(irn);
 144 }
 145
 146 static int set_bitinfo(ir_node* const irn, ir_tarval* const z, ir_tarval* const o)
 147 {
 148         bitinfo* b = get_bitinfo(irn);
 149         if (b == NULL) {
 150                 b = OALLOCZ(&obst, bitinfo);
 151                 set_irn_link(irn, b);
 152         } else if (z == b->z && o == b->o) {
 153                 return 0;
 154         }
 155         b->z = z;
 156         b->o = o;
 157         DB((dbg, LEVEL_3, "%+F: 0:%T 1:%T\n", irn, z, o));
 158         return 1;
 159 }
 160
 161 static int mode_is_intb(ir_mode const* const m)
 162 {
 163         return mode_is_int(m) || m == mode_b;
 164 }
 165
 166 static int transfer(ir_node* const irn)
 167 {
 168         ir_tarval* const f = get_tarval_b_false();
 169         ir_tarval* const t = get_tarval_b_true();
 170         ir_mode*   const m = get_irn_mode(irn);
 171         ir_tarval*       z;
 172         ir_tarval*       o;
 173
 174         if (m == mode_X) {
 175                 bitinfo* const b = get_bitinfo(get_nodes_block(irn));
 176
 177                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 178
 179                 /* Unreachble blocks might have no bitinfo. */
 180                 if (b == NULL || b->z == f) {
 181 unreachable_X:
 182                         z = f;
 183                         o = t;
 184                 } else switch (get_irn_opcode(irn)) {
 185                         case iro_Proj: {
 186                                 ir_node* const pred = get_Proj_pred(irn);
 187                                 if (is_Start(pred)) {
 188                                         goto result_unknown_X;
 189                                 } else if (is_Cond(pred)) {
 190                                         ir_node*   const selector = get_Cond_selector(pred);
 191                                         bitinfo*   const b        = get_bitinfo(selector);
 192                                         if (is_undefined(b)) {
 193                                                 goto unreachable_X;
 194                                         } else if (get_irn_mode(selector) == mode_b) {
 195                                                 if (b->z == b->o) {
 196                                                         if ((b->z == t) == get_Proj_proj(irn)) {
 197                                                                 z = o = t;
 198                                                         } else {
 199                                                                 z = o = f;
 200                                                         }
 201                                                 } else {
 202                                                         goto result_unknown_X;
 203                                                 }
 204                                         } else {
 205                                                 long const val = get_Proj_proj(irn);
 206                                                 if (val != get_Cond_default_proj(pred)) {
 207                                                         ir_tarval* const tv = new_tarval_from_long(val, get_irn_mode(selector));
 208                                                         if (!tarval_is_null(tarval_andnot(tv, b->z)) ||
 209                                                                         !tarval_is_null(tarval_andnot(b->o, tv))) {
 210                                                                 // At least one bit differs.
 211                                                                 z = o = f;
 212 #if 0 // TODO must handle default Proj
 213                                                         } else if (b->z == b->o && b->z == tv) {
 214                                                                 z = o = t;
 215 #endif
 216                                                         } else {
 217                                                                 goto result_unknown_X;
 218                                                         }
 219                                                 } else {
 220                                                         goto cannot_analyse_X;
 221                                                 }
 222                                         }
 223                                 } else {
 224                                         goto cannot_analyse_X;
 225                                 }
 226                                 break;
 227                         }
 228
 229                         case iro_Jmp:
 230                                 goto result_unknown_X;
 231
 232                         default:
 233 cannot_analyse_X:
 234                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 235 result_unknown_X:
 236                                 z = t;
 237                                 o = f;
 238                                 break;
 239                 }
 240         } else if (is_Block(irn)) {
 241                 int       reachable = 0;
 242                 int const arity     = get_Block_n_cfgpreds(irn);
 243                 int       i;
 244
 245                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 246                 for (i = 0; i != arity; ++i) {
 247                         bitinfo* const b = get_bitinfo(get_Block_cfgpred(irn, i));
 248                         if (b != NULL && b->z == t) {
 249                                 reachable = 1;
 250                                 break;
 251                         }
 252                 }
 253
 254                 if (!reachable) {
 255                         ir_graph *const irg = get_Block_irg(irn);
 256                         reachable =
 257                                 irn == get_irg_start_block(irg) ||
 258                                 irn == get_irg_end_block(irg);
 259                 }
 260
 261                 if (reachable) {
 262                         z = t;
 263                         o = f;
 264                 } else {
 265                         z = f;
 266                         o = t;
 267                 }
 268         } else if (mode_is_intb(m)) {
 269                 bitinfo* const b = get_bitinfo(get_nodes_block(irn));
 270
 271                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 272
 273                 if (b->z == f) {
 274 undefined:
 275                         z = get_tarval_null(m);
 276                         o = get_tarval_all_one(m);
 277                 } else if (is_Phi(irn)) {
 278                         ir_node* const block = get_nodes_block(irn);
 279                         int      const arity = get_Phi_n_preds(irn);
 280                         int            i;
 281
 282                         z = get_tarval_null(m);
 283                         o = get_tarval_all_one(m);
 284                         for (i = 0; i != arity; ++i) {
 285                                 bitinfo* const b_cfg = get_bitinfo(get_Block_cfgpred(block, i));
 286                                 if (b_cfg != NULL && b_cfg->z != f) {
 287                                         bitinfo* const b = get_bitinfo(get_Phi_pred(irn, i));
 288                                         /* Only use input if it's not undefined. */
 289                                         if (!is_undefined(b)) {
 290                                                 z = tarval_or( z, b->z);
 291                                                 o = tarval_and(o, b->o);
 292                                         }
 293                                 }
 294                         }
 295                 } else {
 296                         int const arity = get_irn_arity(irn);
 297                         int       i;
 298
 299                         /* Undefined if any input is undefined. */
 300                         for (i = 0; i != arity; ++i) {
 301                                 ir_node* const pred   = get_irn_n(irn, i);
 302                                 bitinfo* const pred_b = get_bitinfo(pred);
 303                                 if (pred_b != NULL && is_undefined(pred_b))
 304                                         goto undefined;
 305                         }
 306
 307                         switch (get_irn_opcode(irn)) {
 308                                 case iro_Const: {
 309                                         z = o = get_Const_tarval(irn);
 310                                         break;
 311                                 }
 312
 313                                 case iro_Confirm: {
 314                                         ir_node* const v = get_Confirm_value(irn);
 315                                         bitinfo* const b = get_bitinfo(v);
 316                                         /* TODO Use bound and relation. */
 317                                         z = b->z;
 318                                         o = b->o;
 319                                         break;
 320                                 }
 321
 322                                 case iro_Shl: {
 323                                         bitinfo*   const l  = get_bitinfo(get_Shl_left(irn));
 324                                         bitinfo*   const r  = get_bitinfo(get_Shl_right(irn));
 325                                         ir_tarval* const rz = r->z;
 326                                         if (rz == r->o) {
 327                                                 z = tarval_shl(l->z, rz);
 328                                                 o = tarval_shl(l->o, rz);
 329                                         } else {
 330                                                 goto cannot_analyse;
 331                                         }
 332                                         break;
 333                                 }
 334
 335                                 case iro_Shr: {
 336                                         bitinfo*   const l  = get_bitinfo(get_Shr_left(irn));
 337                                         bitinfo*   const r  = get_bitinfo(get_Shr_right(irn));
 338                                         ir_tarval* const rz = r->z;
 339                                         if (rz == r->o) {
 340                                                 z = tarval_shr(l->z, rz);
 341                                                 o = tarval_shr(l->o, rz);
 342                                         } else {
 343                                                 goto cannot_analyse;
 344                                         }
 345                                         break;
 346                                 }
 347
 348                                 case iro_Shrs: {
 349                                         bitinfo*   const l  = get_bitinfo(get_Shrs_left(irn));
 350                                         bitinfo*   const r  = get_bitinfo(get_Shrs_right(irn));
 351                                         ir_tarval* const rz = r->z;
 352                                         if (rz == r->o) {
 353                                                 z = tarval_shrs(l->z, rz);
 354                                                 o = tarval_shrs(l->o, rz);
 355                                         } else {
 356                                                 goto cannot_analyse;
 357                                         }
 358                                         break;
 359                                 }
 360
 361                                 case iro_Rotl: {
 362                                         bitinfo*   const l  = get_bitinfo(get_Rotl_left(irn));
 363                                         bitinfo*   const r  = get_bitinfo(get_Rotl_right(irn));
 364                                         ir_tarval* const rz = r->z;
 365                                         if (rz == r->o) {
 366                                                 z = tarval_rotl(l->z, rz);
 367                                                 o = tarval_rotl(l->o, rz);
 368                                         } else {
 369                                                 goto cannot_analyse;
 370                                         }
 371                                         break;
 372                                 }
 373
 374                                 case iro_Add: {
 375                                         bitinfo*   const l  = get_bitinfo(get_Add_left(irn));
 376                                         bitinfo*   const r  = get_bitinfo(get_Add_right(irn));
 377                                         ir_tarval* const lz = l->z;
 378                                         ir_tarval* const lo = l->o;
 379                                         ir_tarval* const rz = r->z;
 380                                         ir_tarval* const ro = r->o;
 381                                         if (lz == lo && rz == ro) {
 382                                                 z = o = tarval_add(lz, rz);
 383                                         } else {
 384                                                 // TODO improve: can only do lower disjoint bits
 385                                                 /* Determine where any of the operands has zero bits, i.e. where no
 386                                                  * carry out is generated if there is not carry in */
 387                                                 ir_tarval* const no_c_in_no_c_out = tarval_and(lz, rz);
 388                                                 /* Generate a mask of the lower consecutive zeroes: x | -x.  In this
 389                                                  * range the addition is disjoint and therefore Add behaves like Or.
 390                                                  */
 391                                                 ir_tarval* const low_zero_mask = tarval_or(no_c_in_no_c_out, tarval_neg(no_c_in_no_c_out));
 392                                                 ir_tarval* const low_one_mask  = tarval_not(low_zero_mask);
 393                                                 z = tarval_or( tarval_or(lz, rz), low_zero_mask);
 394                                                 o = tarval_and(tarval_or(lo, ro), low_one_mask);
 395                                         }
 396                                         break;
 397                                 }
 398
 399                                 case iro_Sub: {
 400                                         bitinfo* const l = get_bitinfo(get_Sub_left(irn));
 401                                         bitinfo* const r = get_bitinfo(get_Sub_right(irn));
 402                                         if (l != NULL && r != NULL) { // Sub might subtract pointers.
 403                                                 ir_tarval* const lz = l->z;
 404                                                 ir_tarval* const lo = l->o;
 405                                                 ir_tarval* const rz = r->z;
 406                                                 ir_tarval* const ro = r->o;
 407                                                 if (lz == lo && rz == ro) {
 408                                                         z = o = tarval_sub(lz, rz, NULL);
 409                                                 } else if (tarval_is_null(tarval_andnot(rz, lo))) {
 410                                                         /* Every possible one of the subtrahend is backed by a safe one of the
 411                                                          * minuend, i.e. there are no borrows. */
 412                                                         // TODO extend no-borrow like carry for Add above
 413                                                         z = tarval_andnot(lz, ro);
 414                                                         o = tarval_andnot(lo, rz);
 415                                                 } else {
 416                                                         goto cannot_analyse;
 417                                                 }
 418                                         } else {
 419                                                 goto cannot_analyse;
 420                                         }
 421                                         break;
 422                                 }
 423
 424                                 case iro_Mul: {
 425                                         bitinfo*   const l  = get_bitinfo(get_Mul_left(irn));
 426                                         bitinfo*   const r  = get_bitinfo(get_Mul_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                                         if (lz == lo && rz == ro) {
 432                                                 z = o = tarval_mul(lz, rz);
 433                                         } else {
 434                                                 // TODO improve
 435                                                 // Determine safe lower zeroes: x | -x.
 436                                                 ir_tarval* const lzn = tarval_or(lz, tarval_neg(lz));
 437                                                 ir_tarval* const rzn = tarval_or(rz, tarval_neg(rz));
 438                                                 // Concatenate safe lower zeroes.
 439                                                 if (tarval_cmp(lzn, rzn) == ir_relation_less) {
 440                                                         z = tarval_mul(tarval_eor(lzn, tarval_shl(lzn, get_tarval_one(m))), rzn);
 441                                                 } else {
 442                                                         z = tarval_mul(tarval_eor(rzn, tarval_shl(rzn, get_tarval_one(m))), lzn);
 443                                                 }
 444                                                 o = get_tarval_null(m);
 445                                         }
 446                                         break;
 447                                 }
 448
 449                                 case iro_Minus: {
 450                                         bitinfo* const b = get_bitinfo(get_Minus_op(irn));
 451                                         if (b->z == b->o) {
 452                                                 z = o = tarval_neg(b->z);
 453                                         } else {
 454                                                 goto cannot_analyse;
 455                                         }
 456                                         break;
 457                                 }
 458
 459                                 case iro_And: {
 460                                         bitinfo* const l = get_bitinfo(get_And_left(irn));
 461                                         bitinfo* const r = get_bitinfo(get_And_right(irn));
 462                                         z = tarval_and(l->z, r->z);
 463                                         o = tarval_and(l->o, r->o);
 464                                         break;
 465                                 }
 466
 467                                 case iro_Or: {
 468                                         bitinfo* const l = get_bitinfo(get_Or_left(irn));
 469                                         bitinfo* const r = get_bitinfo(get_Or_right(irn));
 470                                         z = tarval_or(l->z, r->z);
 471                                         o = tarval_or(l->o, r->o);
 472                                         break;
 473                                 }
 474
 475                                 case iro_Eor: {
 476                                         bitinfo*   const l  = get_bitinfo(get_Eor_left(irn));
 477                                         bitinfo*   const r  = get_bitinfo(get_Eor_right(irn));
 478                                         ir_tarval* const lz = l->z;
 479                                         ir_tarval* const lo = l->o;
 480                                         ir_tarval* const rz = r->z;
 481                                         ir_tarval* const ro = r->o;
 482                                         z = tarval_or(tarval_andnot(lz, ro), tarval_andnot(rz, lo));
 483                                         o = tarval_or(tarval_andnot(ro, lz), tarval_andnot(lo, rz));
 484                                         break;
 485                                 }
 486
 487                                 case iro_Not: {
 488                                         bitinfo* const b = get_bitinfo(get_Not_op(irn));
 489                                         z = tarval_not(b->o);
 490                                         o = tarval_not(b->z);
 491                                         break;
 492                                 }
 493
 494                                 case iro_Conv: {
 495                                         bitinfo* const b = get_bitinfo(get_Conv_op(irn));
 496                                         if (b == NULL) // Happens when converting from float values.
 497                                                 goto result_unknown;
 498                                         z = tarval_convert_to(b->z, m);
 499                                         o = tarval_convert_to(b->o, m);
 500                                         break;
 501                                 }
 502
 503                                 case iro_Mux: {
 504                                         bitinfo* const bf = get_bitinfo(get_Mux_false(irn));
 505                                         bitinfo* const bt = get_bitinfo(get_Mux_true(irn));
 506                                         bitinfo* const c  = get_bitinfo(get_Mux_sel(irn));
 507                                         if (c->o == t) {
 508                                                 z = bt->z;
 509                                                 o = bt->o;
 510                                         } else if (c->z == f) {
 511                                                 z = bf->z;
 512                                                 o = bf->o;
 513                                         } else {
 514                                                 z = tarval_or( bf->z, bt->z);
 515                                                 o = tarval_and(bf->o, bt->o);
 516                                         }
 517                                         break;
 518                                 }
 519
 520                                 case iro_Cmp: {
 521                                         bitinfo* const l = get_bitinfo(get_Cmp_left(irn));
 522                                         bitinfo* const r = get_bitinfo(get_Cmp_right(irn));
 523                                         if (l == NULL || r == NULL) {
 524                                                 goto result_unknown; // Cmp compares something we cannot evaluate.
 525                                         } else {
 526                                                 ir_tarval*  const lz       = l->z;
 527                                                 ir_tarval*  const lo       = l->o;
 528                                                 ir_tarval*  const rz       = r->z;
 529                                                 ir_tarval*  const ro       = r->o;
 530                                                 ir_relation const relation = get_Cmp_relation(irn);
 531                                                 switch (relation) {
 532                                                         case ir_relation_less_greater:
 533                                                                 if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 534                                                                                 !tarval_is_null(tarval_andnot(lo, rz))) {
 535                                                                         // At least one bit differs.
 536                                                                         z = o = t;
 537                                                                 } else if (lz == lo && rz == ro && lz == rz) {
 538                                                                         z = o = f;
 539                                                                 } else {
 540                                                                         goto result_unknown;
 541                                                                 }
 542                                                                 break;
 543
 544                                                         case ir_relation_equal:
 545                                                                 if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 546                                                                                 !tarval_is_null(tarval_andnot(lo, rz))) {
 547                                                                         // At least one bit differs.
 548                                                                         z = o = f;
 549                                                                 } else if (lz == lo && rz == ro && lz == rz) {
 550                                                                         z = o = t;
 551                                                                 } else {
 552                                                                         goto result_unknown;
 553                                                                 }
 554                                                                 break;
 555
 556                                                         case ir_relation_less_equal:
 557                                                         case ir_relation_less:
 558                                                                 /* TODO handle negative values */
 559                                                                 if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 560                                                                                 tarval_is_negative(rz) || tarval_is_negative(ro))
 561                                                                         goto result_unknown;
 562
 563                                                                 if (tarval_cmp(lz, ro) & relation) {
 564                                                                         /* Left upper bound is smaller(/equal) than right lower bound. */
 565                                                                         z = o = t;
 566                                                                 } else if (!(tarval_cmp(lo, rz) & relation)) {
 567                                                                         /* Left lower bound is not smaller(/equal) than right upper bound. */
 568                                                                         z = o = f;
 569                                                                 } else {
 570                                                                         goto result_unknown;
 571                                                                 }
 572                                                                 break;
 573
 574                                                         case ir_relation_greater_equal:
 575                                                         case ir_relation_greater:
 576                                                                 /* TODO handle negative values */
 577                                                                 if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 578                                                                                 tarval_is_negative(rz) || tarval_is_negative(ro))
 579                                                                         goto result_unknown;
 580
 581                                                                 if (!(tarval_cmp(lz, ro) & relation)) {
 582                                                                         /* Left upper bound is not greater(/equal) than right lower bound. */
 583                                                                         z = o = f;
 584                                                                 } else if (tarval_cmp(lo, rz) & relation) {
 585                                                                         /* Left lower bound is greater(/equal) than right upper bound. */
 586                                                                         z = o = t;
 587                                                                 } else {
 588                                                                         goto result_unknown;
 589                                                                 }
 590                                                                 break;
 591
 592                                                         default:
 593                                                                 goto cannot_analyse;
 594                                                 }
 595                                         }
 596                                         break;
 597                                 }
 598
 599                                 default: {
 600 cannot_analyse:
 601                                         DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 602 result_unknown:
 603                                         z = get_tarval_all_one(m);
 604                                         o = get_tarval_null(m);
 605                                         break;
 606                                 }
 607                         }
 608                 }
 609         } else {
 610                 return 0;
 611         }
 612
 613         return set_bitinfo(irn, z, o);
 614 }
 615
 616 static void first_round(ir_node* const irn, void* const env)
 617 {
 618         pdeq* const q = (pdeq*)env;
 619
 620         transfer(irn);
 621         if (is_Phi(irn) || is_Block(irn)) {
 622                 /* Only Phis (and their users) need another round, if we did not have
 623                  * information about all their inputs in the first round, i.e. in loops. */
 624                 /* TODO inserts all Phis, should only insert Phis, which did no have all
 625                  * predecessors available */
 626                 pdeq_putr(q, irn);
 627         }
 628 }
 629
 630 static void apply_result(ir_node* const irn, void* ctx)
 631 {
 632         environment_t* env = (environment_t*)ctx;
 633         ir_node*       block;
 634         bitinfo*       block_b;
 635         bitinfo*       b;
 636         ir_tarval*     z;
 637         ir_tarval*     o;
 638
 639         if (is_Block(irn)) {
 640                 block_b = get_bitinfo(irn);
 641                 /* Trivially unreachable blocks have no info. */
 642                 if (block_b == NULL || block_b->z == get_tarval_b_false()) {
 643                         exchange(irn, get_irg_bad(get_Block_irg(irn)));
 644                         env->modified = 1;
 645                 }
 646                 return;
 647         }
 648
 649         block   = get_nodes_block(irn);
 650         block_b = get_bitinfo(block);
 651         /* Trivially unreachable blocks have no info. */
 652         if (block_b == NULL || block_b->z == get_tarval_b_false()) {
 653                 /* Unreachable blocks might be replaced before the nodes in them. */
 654                 exchange(irn, is_Bad(block) ? block : get_irg_bad(get_Block_irg(block)));
 655                 env->modified = 1;
 656                 return;
 657         }
 658
 659         b = get_bitinfo(irn);
 660         if (!b) return;
 661         if (is_Const(irn)) return; // It cannot get any better than a Const.
 662
 663         z = b->z;
 664         o = b->o;
 665         // Only display information if we could find out anything about the value.
 666         DEBUG_ONLY(if (!tarval_is_all_one(z) || !tarval_is_null(o)))
 667                 DB((dbg, LEVEL_2, "%+F: 0:%T 1:%T%s\n", irn, z, o, z == o ? " --- constant" : ""));
 668
 669         // Replace node with constant value by Const.
 670         if (z == o) {
 671                 ir_mode* const m = get_irn_mode(irn);
 672                 ir_node*       n;
 673                 if (mode_is_intb(m)) {
 674                         ir_graph *irg = get_irn_irg(irn);
 675                         n = new_r_Const(irg, z);
 676                 } else if (m == mode_X) {
 677                         ir_graph* const irg = get_Block_irg(block);
 678                         if (z == get_tarval_b_true()) {
 679                                 // Might produce an endless loop, so keep the block.
 680                                 add_End_keepalive(get_irg_end(irg), block);
 681                                 n = new_r_Jmp(block);
 682                         } else {
 683                                 n = new_r_Bad(irg);
 684                                 /* Transferring analysis information to the bad node makes it a
 685                                  * candidate for replacement. */
 686                                 goto exchange_only;
 687                         }
 688                 } else {
 689                         return;
 690                 }
 691                 set_irn_link(n, b);
 692 exchange_only:
 693                 exchange(irn, n);
 694                 env->modified = 1;
 695         }
 696
 697         switch (get_irn_opcode(irn)) {
 698                 case iro_And: {
 699                         ir_node*       const l  = get_And_left(irn);
 700                         ir_node*       const r  = get_And_right(irn);
 701                         bitinfo const* const bl = get_bitinfo(l);
 702                         bitinfo const* const br = get_bitinfo(r);
 703                         if (bl->z == bl->o) {
 704                                 if (tarval_is_null(tarval_andnot(br->z, bl->z))) {
 705                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 706                                         exchange(irn, r);
 707                                         env->modified = 1;
 708                                 }
 709                         } else if (br->z == br->o) {
 710                                 if (tarval_is_null(tarval_andnot(bl->z, br->z))) {
 711                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 712                                         exchange(irn, l);
 713                                         env->modified = 1;
 714                                 }
 715                         }
 716                         break;
 717                 }
 718
 719                 case iro_Or: {
 720                         ir_node*       const l  = get_Or_left(irn);
 721                         ir_node*       const r  = get_Or_right(irn);
 722                         bitinfo const* const bl = get_bitinfo(l);
 723                         bitinfo const* const br = get_bitinfo(r);
 724                         if (bl->z == bl->o) {
 725                                 if (tarval_is_null(tarval_andnot(bl->o, br->o))) {
 726                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 727                                         exchange(irn, r);
 728                                         env->modified = 1;
 729                                 }
 730                         } else if (br->z == br->o) {
 731                                 if (tarval_is_null(tarval_andnot(br->o, bl->o))) {
 732                                         DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 733                                         exchange(irn, l);
 734                                         env->modified = 1;
 735                                 }
 736                         }
 737                         break;
 738                 }
 739         }
 740 }
 741
 742 static void queue_users(pdeq* const q, ir_node* const n)
 743 {
 744         if (get_irn_mode(n) == mode_X) {
 745                 /* When the state of a control flow node changes, not only queue its
 746                  * successor blocks, but also the Phis in these blocks, because the Phis
 747                  * must reconsider this input path. */
 748                 ir_edge_t const* e;
 749                 foreach_out_edge(n, e) {
 750                         ir_node*  const  src = get_edge_src_irn(e);
 751                         pdeq_putr(q, src);
 752                         /* should always be a block */
 753                         if (is_Block(src)) {
 754                                 ir_node *phi;
 755                                 for (phi = get_Block_phis(src); phi; phi = get_Phi_next(phi))
 756                                         pdeq_putr(q, phi);
 757                         }
 758                 }
 759         } else {
 760                 ir_edge_t const* e;
 761                 foreach_out_edge(n, e) {
 762                         ir_node* const src = get_edge_src_irn(e);
 763                         if (get_irn_mode(src) == mode_T) {
 764                                 queue_users(q, src);
 765                         } else {
 766                                 pdeq_putr(q, src);
 767                         }
 768                 }
 769         }
 770 }
 771
 772 static void clear_links(ir_node *irn, void *env)
 773 {
 774         (void) env;
 775         set_irn_link(irn, NULL);
 776         if (is_Block(irn))
 777                 set_Block_phis(irn, NULL);
 778 }
 779
 780 static void build_phi_lists(ir_node *irn, void *env)
 781 {
 782         (void) env;
 783         if (is_Phi(irn))
 784                 add_Block_phi(get_nodes_block(irn), irn);
 785 }
 786
 787 void fixpoint_vrp(ir_graph* const irg)
 788 {
 789         environment_t env;
 790
 791         FIRM_DBG_REGISTER(dbg, "firm.opt.fp-vrp");
 792         DB((dbg, LEVEL_1, "===> Performing constant propagation on %+F\n", irg));
 793
 794         obstack_init(&obst);
 795
 796         /* HACK: to avoid finding dead code */
 797         edges_deactivate(irg);
 798         edges_activate(irg);
 799
 800         edges_assure(irg);
 801         assure_doms(irg);
 802
 803         ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 804
 805         {
 806                 pdeq* const q = new_pdeq();
 807
 808                 /* We need this extra step because the dom tree does not contain unreachable
 809                    blocks in Firm. Moreover build phi list. */
 810                 irg_walk_anchors(irg, clear_links, build_phi_lists, NULL);
 811
 812                 { ir_tarval* const f = get_tarval_b_false();
 813                         ir_tarval* const t = get_tarval_b_true();
 814                         set_bitinfo(get_irg_bad(irg),       f, t); /* Undefined. */
 815                         set_bitinfo(get_irg_end_block(irg), t, f); /* Reachable. */
 816                 }
 817
 818                 /* TODO Improve iteration order. Best is reverse postorder in data flow
 819                  * direction and respecting loop nesting for fastest convergence. */
 820                 irg_walk_blkwise_dom_top_down(irg, NULL, first_round, q);
 821
 822                 while (!pdeq_empty(q)) {
 823                         ir_node* const n = (ir_node*)pdeq_getl(q);
 824                         if (transfer(n))
 825                                 queue_users(q, n);
 826                 }
 827
 828                 del_pdeq(q);
 829         }
 830
 831         DB((dbg, LEVEL_2, "---> Applying analysis results\n"));
 832         env.modified = 0;
 833         irg_walk_graph(irg, NULL, apply_result, &env);
 834
 835         if (env.modified) {
 836                 /* control flow might changed */
 837                 set_irg_outs_inconsistent(irg);
 838                 set_irg_extblk_inconsistent(irg);
 839                 set_irg_doms_inconsistent(irg);
 840                 set_irg_loopinfo_inconsistent(irg);
 841                 set_irg_entity_usage_state(irg, ir_entity_usage_not_computed);
 842         }
 843
 844         ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 845
 846         obstack_free(&obst, NULL);
 847 }
 848
 849 ir_graph_pass_t *fixpoint_vrp_irg_pass(const char *name)
 850 {
 851         return def_graph_pass(name ? name : "fixpoint_vrp", fixpoint_vrp);
 852 }