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  */
  25 #include "config.h"
  26
  27 #include <assert.h>
  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_t.h"
  39 #include "irgwalk.h"
  40 #include "irnode_t.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         } else {
 155                 /* Assert monotonicity. */
 156                 assert(tarval_is_null(tarval_andnot(b->z, z)));
 157                 assert(tarval_is_null(tarval_andnot(o, b->o)));
 158         }
 159         b->z = z;
 160         b->o = o;
 161         DB((dbg, LEVEL_3, "%+F: 0:%T 1:%T\n", irn, z, o));
 162         return 1;
 163 }
 164
 165 static int mode_is_intb(ir_mode const* const m)
 166 {
 167         return mode_is_int(m) || m == mode_b;
 168 }
 169
 170 static int transfer(ir_node* const irn)
 171 {
 172         ir_tarval* const f = get_tarval_b_false();
 173         ir_tarval* const t = get_tarval_b_true();
 174         ir_mode*   const m = get_irn_mode(irn);
 175         ir_tarval*       z;
 176         ir_tarval*       o;
 177
 178         if (is_Bad(irn)) return 0;
 179
 180         if (m == mode_X) {
 181                 bitinfo* const b = get_bitinfo(get_nodes_block(irn));
 182
 183                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 184
 185                 /* Unreachble blocks might have no bitinfo. */
 186                 if (b == NULL || b->z == f) {
 187 unreachable_X:
 188                         z = f;
 189                         o = t;
 190                 } else switch (get_irn_opcode(irn)) {
 191                         case iro_Proj: {
 192                                 ir_node* const pred = get_Proj_pred(irn);
 193                                 if (is_Start(pred)) {
 194                                         goto result_unknown_X;
 195                                 } else if (is_Cond(pred)) {
 196                                         ir_node*   const selector = get_Cond_selector(pred);
 197                                         bitinfo*   const b        = get_bitinfo(selector);
 198                                         if (is_undefined(b))
 199                                                 goto unreachable_X;
 200                                         if (b->z == b->o) {
 201                                                 if ((b->z == t) == get_Proj_proj(irn)) {
 202                                                         z = o = t;
 203                                                 } else {
 204                                                         z = o = f;
 205                                                 }
 206                                         } else {
 207                                                 goto result_unknown_X;
 208                                         }
 209                                 } else if (is_Switch(pred)) {
 210                                         ir_node* const selector = get_Switch_selector(pred);
 211                                         bitinfo* const b        = get_bitinfo(selector);
 212                                         if (is_undefined(b))
 213                                                 goto unreachable_X;
 214                                         /* TODO */
 215                                         goto cannot_analyse_X;
 216                                 } else {
 217                                         goto cannot_analyse_X;
 218                                 }
 219                                 break;
 220                         }
 221
 222                         case iro_Jmp:
 223                                 goto result_unknown_X;
 224
 225                         default:
 226 cannot_analyse_X:
 227                                 DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 228 result_unknown_X:
 229                                 z = t;
 230                                 o = f;
 231                                 break;
 232                 }
 233         } else if (is_Block(irn)) {
 234                 int       reachable = 0;
 235                 int const arity     = get_Block_n_cfgpreds(irn);
 236                 int       i;
 237
 238                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 239                 for (i = 0; i != arity; ++i) {
 240                         bitinfo* const b = get_bitinfo(get_Block_cfgpred(irn, i));
 241                         if (b != NULL && b->z == t) {
 242                                 reachable = 1;
 243                                 break;
 244                         }
 245                 }
 246
 247                 if (!reachable) {
 248                         ir_graph *const irg = get_Block_irg(irn);
 249                         reachable =
 250                                 irn == get_irg_start_block(irg) ||
 251                                 irn == get_irg_end_block(irg);
 252                 }
 253
 254                 if (reachable) {
 255                         z = t;
 256                         o = f;
 257                 } else {
 258                         z = f;
 259                         o = t;
 260                 }
 261         } else if (mode_is_intb(m)) {
 262                 bitinfo* const b = get_bitinfo(get_nodes_block(irn));
 263
 264                 DB((dbg, LEVEL_3, "transfer %+F\n", irn));
 265
 266                 if (b == NULL || b->z == f) {
 267 undefined:
 268                         z = get_tarval_null(m);
 269                         o = get_tarval_all_one(m);
 270                 } else if (is_Phi(irn)) {
 271                         ir_node* const block = get_nodes_block(irn);
 272                         int      const arity = get_Phi_n_preds(irn);
 273                         int            i;
 274
 275                         z = get_tarval_null(m);
 276                         o = get_tarval_all_one(m);
 277                         for (i = 0; i != arity; ++i) {
 278                                 bitinfo* const b_cfg = get_bitinfo(get_Block_cfgpred(block, i));
 279                                 if (b_cfg != NULL && b_cfg->z != f) {
 280                                         bitinfo* const b = get_bitinfo(get_Phi_pred(irn, i));
 281                                         /* Only use input if it's not undefined. */
 282                                         if (!is_undefined(b)) {
 283                                                 z = tarval_or( z, b->z);
 284                                                 o = tarval_and(o, b->o);
 285                                         }
 286                                 }
 287                         }
 288                 } else {
 289                         int const arity = get_irn_arity(irn);
 290                         int       i;
 291
 292                         /* Undefined if any input is undefined. */
 293                         for (i = 0; i != arity; ++i) {
 294                                 ir_node* const pred   = get_irn_n(irn, i);
 295                                 bitinfo* const pred_b = get_bitinfo(pred);
 296                                 if (pred_b != NULL && is_undefined(pred_b))
 297                                         goto undefined;
 298                         }
 299
 300                         switch (get_irn_opcode(irn)) {
 301                                 case iro_Const: {
 302                                         z = o = get_Const_tarval(irn);
 303                                         break;
 304                                 }
 305
 306                                 case iro_Confirm: {
 307                                         ir_node* const v = get_Confirm_value(irn);
 308                                         bitinfo* const b = get_bitinfo(v);
 309                                         /* TODO Use bound and relation. */
 310                                         z = b->z;
 311                                         o = b->o;
 312                                         if ((get_Confirm_relation(irn) & ~ir_relation_unordered) == ir_relation_equal) {
 313                                                 bitinfo* const bound_b = get_bitinfo(get_Confirm_bound(irn));
 314                                                 z = tarval_and(z, bound_b->z);
 315                                                 o = tarval_or( o, bound_b->o);
 316                                         }
 317                                         break;
 318                                 }
 319
 320                                 case iro_Shl: {
 321                                         bitinfo*   const l  = get_bitinfo(get_Shl_left(irn));
 322                                         bitinfo*   const r  = get_bitinfo(get_Shl_right(irn));
 323                                         ir_tarval* const rz = r->z;
 324                                         if (rz == r->o) {
 325                                                 z = tarval_shl(l->z, rz);
 326                                                 o = tarval_shl(l->o, rz);
 327                                         } else {
 328                                                 goto cannot_analyse;
 329                                         }
 330                                         break;
 331                                 }
 332
 333                                 case iro_Shr: {
 334                                         bitinfo*   const l  = get_bitinfo(get_Shr_left(irn));
 335                                         bitinfo*   const r  = get_bitinfo(get_Shr_right(irn));
 336                                         ir_tarval* const rz = r->z;
 337                                         if (rz == r->o) {
 338                                                 z = tarval_shr(l->z, rz);
 339                                                 o = tarval_shr(l->o, rz);
 340                                         } else {
 341                                                 goto cannot_analyse;
 342                                         }
 343                                         break;
 344                                 }
 345
 346                                 case iro_Shrs: {
 347                                         bitinfo*   const l  = get_bitinfo(get_Shrs_left(irn));
 348                                         bitinfo*   const r  = get_bitinfo(get_Shrs_right(irn));
 349                                         ir_tarval* const rz = r->z;
 350                                         if (rz == r->o) {
 351                                                 z = tarval_shrs(l->z, rz);
 352                                                 o = tarval_shrs(l->o, rz);
 353                                         } else {
 354                                                 goto cannot_analyse;
 355                                         }
 356                                         break;
 357                                 }
 358
 359                                 case iro_Rotl: {
 360                                         bitinfo*   const l  = get_bitinfo(get_Rotl_left(irn));
 361                                         bitinfo*   const r  = get_bitinfo(get_Rotl_right(irn));
 362                                         ir_tarval* const rz = r->z;
 363                                         if (rz == r->o) {
 364                                                 z = tarval_rotl(l->z, rz);
 365                                                 o = tarval_rotl(l->o, rz);
 366                                         } else {
 367                                                 goto cannot_analyse;
 368                                         }
 369                                         break;
 370                                 }
 371
 372                                 case iro_Add: {
 373                                         bitinfo*   const l  = get_bitinfo(get_Add_left(irn));
 374                                         bitinfo*   const r  = get_bitinfo(get_Add_right(irn));
 375                                         ir_tarval* const lz = l->z;
 376                                         ir_tarval* const lo = l->o;
 377                                         ir_tarval* const rz = r->z;
 378                                         ir_tarval* const ro = r->o;
 379                                         if (lz == lo && rz == ro) {
 380                                                 z = o = tarval_add(lz, rz);
 381                                         } else {
 382                                                 // TODO improve: can only do lower disjoint bits
 383                                                 /* Determine where any of the operands has zero bits, i.e. where no
 384                                                  * carry out is generated if there is not carry in */
 385                                                 ir_tarval* const no_c_in_no_c_out = tarval_and(lz, rz);
 386                                                 /* Generate a mask of the lower consecutive zeroes: x | -x.  In this
 387                                                  * range the addition is disjoint and therefore Add behaves like Or.
 388                                                  */
 389                                                 ir_tarval* const low_zero_mask = tarval_or(no_c_in_no_c_out, tarval_neg(no_c_in_no_c_out));
 390                                                 ir_tarval* const low_one_mask  = tarval_not(low_zero_mask);
 391                                                 z = tarval_or( tarval_or(lz, rz), low_zero_mask);
 392                                                 o = tarval_and(tarval_or(lo, ro), low_one_mask);
 393                                         }
 394                                         break;
 395                                 }
 396
 397                                 case iro_Sub: {
 398                                         bitinfo* const l = get_bitinfo(get_Sub_left(irn));
 399                                         bitinfo* const r = get_bitinfo(get_Sub_right(irn));
 400                                         if (l != NULL && r != NULL) { // Sub might subtract pointers.
 401                                                 ir_tarval* const lz = l->z;
 402                                                 ir_tarval* const lo = l->o;
 403                                                 ir_tarval* const rz = r->z;
 404                                                 ir_tarval* const ro = r->o;
 405                                                 if (lz == lo && rz == ro) {
 406                                                         z = o = tarval_sub(lz, rz, NULL);
 407                                                 } else if (tarval_is_null(tarval_andnot(rz, lo))) {
 408                                                         /* Every possible one of the subtrahend is backed by a safe one of the
 409                                                          * minuend, i.e. there are no borrows. */
 410                                                         // TODO extend no-borrow like carry for Add above
 411                                                         z = tarval_andnot(lz, ro);
 412                                                         o = tarval_andnot(lo, rz);
 413                                                 } else {
 414                                                         goto cannot_analyse;
 415                                                 }
 416                                         } else {
 417                                                 goto cannot_analyse;
 418                                         }
 419                                         break;
 420                                 }
 421
 422                                 case iro_Mul: {
 423                                         bitinfo*   const l  = get_bitinfo(get_Mul_left(irn));
 424                                         bitinfo*   const r  = get_bitinfo(get_Mul_right(irn));
 425                                         ir_tarval* const lz = l->z;
 426                                         ir_tarval* const lo = l->o;
 427                                         ir_tarval* const rz = r->z;
 428                                         ir_tarval* const ro = r->o;
 429                                         if (lz == lo && rz == ro) {
 430                                                 z = o = tarval_mul(lz, rz);
 431                                         } else {
 432                                                 // TODO improve
 433                                                 // Determine safe lower zeroes: x | -x.
 434                                                 ir_tarval* const lzn = tarval_or(lz, tarval_neg(lz));
 435                                                 ir_tarval* const rzn = tarval_or(rz, tarval_neg(rz));
 436                                                 // Concatenate safe lower zeroes.
 437                                                 if (tarval_cmp(lzn, rzn) == ir_relation_less) {
 438                                                         z = tarval_mul(tarval_eor(lzn, tarval_shl_unsigned(lzn, 1)), rzn);
 439                                                 } else {
 440                                                         z = tarval_mul(tarval_eor(rzn, tarval_shl_unsigned(rzn, 1)), lzn);
 441                                                 }
 442                                                 o = get_tarval_null(m);
 443                                         }
 444                                         break;
 445                                 }
 446
 447                                 case iro_Minus: {
 448                                         bitinfo* const b = get_bitinfo(get_Minus_op(irn));
 449                                         if (b->z == b->o) {
 450                                                 z = o = tarval_neg(b->z);
 451                                         } else {
 452                                                 goto cannot_analyse;
 453                                         }
 454                                         break;
 455                                 }
 456
 457                                 case iro_And: {
 458                                         bitinfo* const l = get_bitinfo(get_And_left(irn));
 459                                         bitinfo* const r = get_bitinfo(get_And_right(irn));
 460                                         z = tarval_and(l->z, r->z);
 461                                         o = tarval_and(l->o, r->o);
 462                                         break;
 463                                 }
 464
 465                                 case iro_Or: {
 466                                         bitinfo* const l = get_bitinfo(get_Or_left(irn));
 467                                         bitinfo* const r = get_bitinfo(get_Or_right(irn));
 468                                         z = tarval_or(l->z, r->z);
 469                                         o = tarval_or(l->o, r->o);
 470                                         break;
 471                                 }
 472
 473                                 case iro_Eor: {
 474                                         bitinfo*   const l  = get_bitinfo(get_Eor_left(irn));
 475                                         bitinfo*   const r  = get_bitinfo(get_Eor_right(irn));
 476                                         ir_tarval* const lz = l->z;
 477                                         ir_tarval* const lo = l->o;
 478                                         ir_tarval* const rz = r->z;
 479                                         ir_tarval* const ro = r->o;
 480                                         z = tarval_or(tarval_andnot(lz, ro), tarval_andnot(rz, lo));
 481                                         o = tarval_or(tarval_andnot(ro, lz), tarval_andnot(lo, rz));
 482                                         break;
 483                                 }
 484
 485                                 case iro_Not: {
 486                                         bitinfo* const b = get_bitinfo(get_Not_op(irn));
 487                                         z = tarval_not(b->o);
 488                                         o = tarval_not(b->z);
 489                                         break;
 490                                 }
 491
 492                                 case iro_Conv: {
 493                                         bitinfo* const b = get_bitinfo(get_Conv_op(irn));
 494                                         if (b == NULL) // Happens when converting from float values.
 495                                                 goto result_unknown;
 496                                         z = tarval_convert_to(b->z, m);
 497                                         o = tarval_convert_to(b->o, m);
 498                                         break;
 499                                 }
 500
 501                                 case iro_Mux: {
 502                                         bitinfo* const bf = get_bitinfo(get_Mux_false(irn));
 503                                         bitinfo* const bt = get_bitinfo(get_Mux_true(irn));
 504                                         bitinfo* const c  = get_bitinfo(get_Mux_sel(irn));
 505                                         if (c->o == t) {
 506                                                 z = bt->z;
 507                                                 o = bt->o;
 508                                         } else if (c->z == f) {
 509                                                 z = bf->z;
 510                                                 o = bf->o;
 511                                         } else {
 512                                                 z = tarval_or( bf->z, bt->z);
 513                                                 o = tarval_and(bf->o, bt->o);
 514                                         }
 515                                         break;
 516                                 }
 517
 518                                 case iro_Cmp: {
 519                                         bitinfo* const l = get_bitinfo(get_Cmp_left(irn));
 520                                         bitinfo* const r = get_bitinfo(get_Cmp_right(irn));
 521                                         if (l == NULL || r == NULL) {
 522                                                 goto result_unknown; // Cmp compares something we cannot evaluate.
 523                                         } else {
 524                                                 ir_tarval*  const lz       = l->z;
 525                                                 ir_tarval*  const lo       = l->o;
 526                                                 ir_tarval*  const rz       = r->z;
 527                                                 ir_tarval*  const ro       = r->o;
 528                                                 ir_relation const relation = get_Cmp_relation(irn);
 529                                                 switch (relation) {
 530                                                         case ir_relation_less_greater:
 531                                                                 if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 532                                                                                 !tarval_is_null(tarval_andnot(lo, rz))) {
 533                                                                         // At least one bit differs.
 534                                                                         z = o = t;
 535                                                                 } else if (lz == lo && rz == ro && lz == rz) {
 536                                                                         z = o = f;
 537                                                                 } else {
 538                                                                         goto result_unknown;
 539                                                                 }
 540                                                                 break;
 541
 542                                                         case ir_relation_equal:
 543                                                                 if (!tarval_is_null(tarval_andnot(ro, lz)) ||
 544                                                                                 !tarval_is_null(tarval_andnot(lo, rz))) {
 545                                                                         // At least one bit differs.
 546                                                                         z = o = f;
 547                                                                 } else if (lz == lo && rz == ro && lz == rz) {
 548                                                                         z = o = t;
 549                                                                 } else {
 550                                                                         goto result_unknown;
 551                                                                 }
 552                                                                 break;
 553
 554                                                         case ir_relation_less_equal:
 555                                                         case ir_relation_less:
 556                                                                 /* TODO handle negative values */
 557                                                                 if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 558                                                                                 tarval_is_negative(rz) || tarval_is_negative(ro))
 559                                                                         goto result_unknown;
 560
 561                                                                 if (tarval_cmp(lz, ro) & relation) {
 562                                                                         /* Left upper bound is smaller(/equal) than right lower bound. */
 563                                                                         z = o = t;
 564                                                                 } else if (!(tarval_cmp(lo, rz) & relation)) {
 565                                                                         /* Left lower bound is not smaller(/equal) than right upper bound. */
 566                                                                         z = o = f;
 567                                                                 } else {
 568                                                                         goto result_unknown;
 569                                                                 }
 570                                                                 break;
 571
 572                                                         case ir_relation_greater_equal:
 573                                                         case ir_relation_greater:
 574                                                                 /* TODO handle negative values */
 575                                                                 if (tarval_is_negative(lz) || tarval_is_negative(lo) ||
 576                                                                                 tarval_is_negative(rz) || tarval_is_negative(ro))
 577                                                                         goto result_unknown;
 578
 579                                                                 if (!(tarval_cmp(lz, ro) & relation)) {
 580                                                                         /* Left upper bound is not greater(/equal) than right lower bound. */
 581                                                                         z = o = f;
 582                                                                 } else if (tarval_cmp(lo, rz) & relation) {
 583                                                                         /* Left lower bound is greater(/equal) than right upper bound. */
 584                                                                         z = o = t;
 585                                                                 } else {
 586                                                                         goto result_unknown;
 587                                                                 }
 588                                                                 break;
 589
 590                                                         default:
 591                                                                 goto cannot_analyse;
 592                                                 }
 593                                         }
 594                                         break;
 595                                 }
 596
 597                                 default: {
 598 cannot_analyse:
 599                                         DB((dbg, LEVEL_4, "cannot analyse %+F\n", irn));
 600 result_unknown:
 601                                         z = get_tarval_all_one(m);
 602                                         o = get_tarval_null(m);
 603                                         break;
 604                                 }
 605                         }
 606                 }
 607         } else {
 608                 return 0;
 609         }
 610
 611         return set_bitinfo(irn, z, o);
 612 }
 613
 614 static void first_round(ir_node* const irn, void* const env)
 615 {
 616         pdeq* const q = (pdeq*)env;
 617
 618         transfer(irn);
 619         if (is_Phi(irn) || is_Block(irn)) {
 620                 /* Only Phis (and their users) need another round, if we did not have
 621                  * information about all their inputs in the first round, i.e. in loops. */
 622                 /* TODO inserts all Phis, should only insert Phis, which did no have all
 623                  * predecessors available */
 624                 pdeq_putr(q, irn);
 625         }
 626 }
 627
 628 static ir_node *make_bad_block(ir_graph *irg)
 629 {
 630         ir_node *bad = new_r_Bad(irg, mode_BB);
 631         bitinfo *bb  = get_bitinfo(bad);
 632         if (bb == NULL) {
 633                 ir_tarval* const f = get_tarval_b_false();
 634                 ir_tarval* const t = get_tarval_b_true();
 635                 set_bitinfo(bad, f, t); /* Undefined. */
 636         }
 637         return bad;
 638 }
 639
 640 static void apply_result(ir_node* const irn, void* ctx)
 641 {
 642         environment_t* env = (environment_t*)ctx;
 643         ir_node*       block;
 644         bitinfo*       block_b;
 645         bitinfo*       b;
 646         ir_tarval*     z;
 647         ir_tarval*     o;
 648
 649         if (is_Block(irn)) {
 650                 block_b = get_bitinfo(irn);
 651                 /* Trivially unreachable blocks have no info. */
 652                 if (block_b == NULL || block_b->z == get_tarval_b_false()) {
 653                         ir_node  *bad = make_bad_block(get_irn_irg(irn));
 654                         exchange(irn, bad);
 655                         env->modified = 1;
 656                 }
 657                 return;
 658         }
 659
 660         block   = get_nodes_block(irn);
 661         block_b = get_bitinfo(block);
 662         /* Trivially unreachable blocks have no info. */
 663         if (block_b == NULL || block_b->z == get_tarval_b_false()) {
 664                 /* Unreachable blocks might be replaced before the nodes in them. */
 665                 ir_mode  *mode = get_irn_mode(irn);
 666                 ir_graph *irg  = get_irn_irg(irn);
 667                 ir_node  *bad  = new_r_Bad(irg, mode);
 668                 exchange(irn, bad);
 669                 env->modified = 1;
 670                 return;
 671         }
 672
 673         b = get_bitinfo(irn);
 674         if (!b) return;
 675         if (is_Const(irn)) return; // It cannot get any better than a Const.
 676
 677         z = b->z;
 678         o = b->o;
 679         // Only display information if we could find out anything about the value.
 680         DEBUG_ONLY(if (!tarval_is_all_one(z) || !tarval_is_null(o)))
 681                 DB((dbg, LEVEL_2, "%+F: 0:%T 1:%T%s\n", irn, z, o, z == o ? " --- constant" : ""));
 682
 683         // Replace node with constant value by Const.
 684         if (z == o) {
 685                 ir_mode* const m = get_irn_mode(irn);
 686                 ir_node*       n;
 687                 if (mode_is_intb(m)) {
 688                         ir_graph *irg = get_irn_irg(irn);
 689                         n = new_r_Const(irg, z);
 690                 } else if (m == mode_X) {
 691                         ir_graph* const irg = get_Block_irg(block);
 692                         if (z == get_tarval_b_true()) {
 693                                 n = new_r_Jmp(block);
 694                         } else {
 695                                 n = new_r_Bad(irg, mode_X);
 696                                 /* Transferring analysis information to the bad node makes it a
 697                                  * candidate for replacement. */
 698                                 goto exchange_only;
 699                         }
 700                 } else {
 701                         return;
 702                 }
 703                 set_irn_link(n, b);
 704 exchange_only:
 705                 exchange(irn, n);
 706                 env->modified = 1;
 707         }
 708
 709         switch (get_irn_opcode(irn)) {
 710                 case iro_And: {
 711                         ir_node*       const l  = get_And_left(irn);
 712                         ir_node*       const r  = get_And_right(irn);
 713                         bitinfo const* const bl = get_bitinfo(l);
 714                         bitinfo const* const br = get_bitinfo(r);
 715                         if (tarval_is_null(tarval_andnot(br->z, bl->o))) {
 716                                 DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 717                                 exchange(irn, r);
 718                                 env->modified = 1;
 719                         } else if (tarval_is_null(tarval_andnot(bl->z, br->o))) {
 720                                 DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 721                                 exchange(irn, l);
 722                                 env->modified = 1;
 723                         }
 724                         break;
 725                 }
 726
 727                 case iro_Eor: {
 728                         ir_node*       const l  = get_Eor_left(irn);
 729                         ir_node*       const r  = get_Eor_right(irn);
 730                         bitinfo const* const bl = get_bitinfo(l);
 731                         bitinfo const* const br = get_bitinfo(r);
 732                         /* if each bit is guaranteed to be zero on either the left or right
 733                          * then an Add will have the same effect as the Eor. Change it for
 734                          * normalisation */
 735                         if (tarval_is_null(tarval_and(bl->z, br->z))) {
 736                                 dbg_info      *dbgi     = get_irn_dbg_info(irn);
 737                                 ir_node       *block    = get_nodes_block(irn);
 738                                 ir_mode       *mode     = get_irn_mode(irn);
 739                                 ir_node       *new_node = new_rd_Add(dbgi, block, l, r, mode);
 740                                 bitinfo const *bi       = get_bitinfo(irn);
 741                                 DB((dbg, LEVEL_2, "%+F(%+F, %+F) normalised to Add\n", irn, l, r));
 742                                 set_bitinfo(new_node, bi->z, bi->o);
 743                                 exchange(irn, new_node);
 744                                 env->modified = 1;
 745                         }
 746                         break;
 747                 }
 748
 749                 case iro_Minus: {
 750                         ir_mode *mode = get_irn_mode(irn);
 751
 752                         /* If all bits except the highest bit are zero the Minus is superfluous. */
 753                         if (get_mode_arithmetic(mode) == irma_twos_complement) {
 754                                 ir_node         *const op  = get_Minus_op(irn);
 755                                 bitinfo   const *const b   = get_bitinfo(op);
 756                                 ir_tarval       *const min = get_mode_min(mode);
 757
 758                                 if (b->z == min) {
 759                                         DB((dbg, LEVEL_2, "%+F(%+F) is superfluous\n", irn, op));
 760                                         exchange(irn, op);
 761                                         env->modified = 1;
 762                                 }
 763                         }
 764                         break;
 765                 }
 766
 767                 case iro_Or: {
 768                         ir_node*       const l  = get_Or_left(irn);
 769                         ir_node*       const r  = get_Or_right(irn);
 770                         bitinfo const* const bl = get_bitinfo(l);
 771                         bitinfo const* const br = get_bitinfo(r);
 772                         if (tarval_is_null(tarval_andnot(bl->z, br->o))) {
 773                                 DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 774                                 exchange(irn, r);
 775                                 env->modified = 1;
 776                         } else if (tarval_is_null(tarval_andnot(br->z, bl->o))) {
 777                                 DB((dbg, LEVEL_2, "%+F(%+F, %+F) is superfluous\n", irn, l, r));
 778                                 exchange(irn, l);
 779                                 env->modified = 1;
 780                         }
 781
 782                         /* if each bit is guaranteed to be zero on either the left or right
 783                          * then an Add will have the same effect as the Or. Change it for
 784                          * normalisation */
 785                         if (tarval_is_null(tarval_and(bl->z, br->z))) {
 786                                 dbg_info      *dbgi     = get_irn_dbg_info(irn);
 787                                 ir_node       *block    = get_nodes_block(irn);
 788                                 ir_mode       *mode     = get_irn_mode(irn);
 789                                 ir_node       *new_node = new_rd_Add(dbgi, block, l, r, mode);
 790                                 bitinfo const *bi       = get_bitinfo(irn);
 791                                 DB((dbg, LEVEL_2, "%+F(%+F, %+F) normalised to Add\n", irn, l, r));
 792                                 set_bitinfo(new_node, bi->z, bi->o);
 793                                 exchange(irn, new_node);
 794                                 env->modified = 1;
 795                         }
 796
 797                         break;
 798                 }
 799         }
 800 }
 801
 802 static void queue_users(pdeq* const q, ir_node* const n)
 803 {
 804         if (get_irn_mode(n) == mode_X) {
 805                 /* When the state of a control flow node changes, not only queue its
 806                  * successor blocks, but also the Phis in these blocks, because the Phis
 807                  * must reconsider this input path. */
 808                 foreach_out_edge(n, e) {
 809                         ir_node*  const  src = get_edge_src_irn(e);
 810                         pdeq_putr(q, src);
 811                         /* should always be a block */
 812                         if (is_Block(src)) {
 813                                 ir_node *phi;
 814                                 for (phi = get_Block_phis(src); phi; phi = get_Phi_next(phi))
 815                                         pdeq_putr(q, phi);
 816                         }
 817                 }
 818         } else {
 819                 foreach_out_edge(n, e) {
 820                         ir_node* const src = get_edge_src_irn(e);
 821                         if (get_irn_mode(src) == mode_T) {
 822                                 queue_users(q, src);
 823                         } else {
 824                                 pdeq_putr(q, src);
 825                         }
 826                 }
 827         }
 828 }
 829
 830 static void clear_links(ir_node *irn, void *env)
 831 {
 832         (void) env;
 833         set_irn_link(irn, NULL);
 834         if (is_Block(irn))
 835                 set_Block_phis(irn, NULL);
 836 }
 837
 838 static void build_phi_lists(ir_node *irn, void *env)
 839 {
 840         (void) env;
 841         if (is_Phi(irn))
 842                 add_Block_phi(get_nodes_block(irn), irn);
 843 }
 844
 845 void fixpoint_vrp(ir_graph* const irg)
 846 {
 847         environment_t env;
 848
 849         FIRM_DBG_REGISTER(dbg, "firm.opt.fp-vrp");
 850         DB((dbg, LEVEL_1, "===> Performing constant propagation on %+F\n", irg));
 851
 852         assure_irg_properties(irg,
 853                 IR_GRAPH_PROPERTY_NO_BADS
 854                 | IR_GRAPH_PROPERTY_NO_UNREACHABLE_CODE
 855                 | IR_GRAPH_PROPERTY_CONSISTENT_DOMINANCE
 856                 | IR_GRAPH_PROPERTY_CONSISTENT_OUT_EDGES);
 857
 858         obstack_init(&obst);
 859
 860         ir_reserve_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 861
 862         {
 863                 pdeq* const q = new_pdeq();
 864
 865                 /* We need this extra step because the dom tree does not contain
 866                  * unreachable blocks in Firm. Moreover build phi list. */
 867                 irg_walk_anchors(irg, clear_links, build_phi_lists, NULL);
 868
 869                 {
 870                         ir_tarval* const f = get_tarval_b_false();
 871                         ir_tarval* const t = get_tarval_b_true();
 872                         set_bitinfo(get_irg_end_block(irg), t, f); /* Reachable. */
 873                 }
 874
 875                 /* TODO Improve iteration order. Best is reverse postorder in data flow
 876                  * direction and respecting loop nesting for fastest convergence. */
 877                 irg_walk_blkwise_dom_top_down(irg, NULL, first_round, q);
 878
 879                 while (!pdeq_empty(q)) {
 880                         ir_node* const n = (ir_node*)pdeq_getl(q);
 881                         if (transfer(n))
 882                                 queue_users(q, n);
 883                 }
 884
 885                 del_pdeq(q);
 886         }
 887
 888         DB((dbg, LEVEL_2, "---> Applying analysis results\n"));
 889         env.modified = 0;
 890         irg_walk_graph(irg, NULL, apply_result, &env);
 891
 892         ir_free_resources(irg, IR_RESOURCE_IRN_LINK | IR_RESOURCE_PHI_LIST);
 893
 894         obstack_free(&obst, NULL);
 895         confirm_irg_properties(irg,
 896                 env.modified ? IR_GRAPH_PROPERTIES_NONE : IR_GRAPH_PROPERTIES_ALL);
 897 }
 898
 899 ir_graph_pass_t *fixpoint_vrp_irg_pass(const char *name)
 900 {
 901         return def_graph_pass(name ? name : "fixpoint_vrp", fixpoint_vrp);
 902 }