src/gallium/drivers/nv50/nv50_pc.c

   1 /*
   2  * Copyright 2010 Christoph Bumiller
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17  * THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  18  * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
  19  * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  20  * SOFTWARE.
  21  */
  22
  23 /* #define NV50PC_DEBUG */
  24
  25 #include "nv50_pc.h"
  26 #include "nv50_program.h"
  27
  28 #include <stdio.h>
  29
  30 /* returns TRUE if operands 0 and 1 can be swapped */
  31 boolean
  32 nv_op_commutative(uint opcode)
  33 {
  34    switch (opcode) {
  35    case NV_OP_ADD:
  36    case NV_OP_MUL:
  37    case NV_OP_MAD:
  38    case NV_OP_AND:
  39    case NV_OP_OR:
  40    case NV_OP_XOR:
  41    case NV_OP_MIN:
  42    case NV_OP_MAX:
  43    case NV_OP_SAD:
  44      return TRUE;
  45    default:
  46      return FALSE;
  47    }
  48 }
  49
  50 /* return operand to which the address register applies */
  51 int
  52 nv50_indirect_opnd(struct nv_instruction *i)
  53 {
  54    if (!i->src[4])
  55       return -1;
  56
  57    switch (i->opcode) {
  58    case NV_OP_MOV:
  59    case NV_OP_LDA:
  60    case NV_OP_STA:
  61       return 0;
  62    default:
  63       return 1;
  64    }
  65 }
  66
  67 boolean
  68 nv50_nvi_can_use_imm(struct nv_instruction *nvi, int s)
  69 {
  70    if (nvi->flags_src || nvi->flags_def)
  71       return FALSE;
  72
  73    switch (nvi->opcode) {
  74    case NV_OP_ADD:
  75    case NV_OP_MUL:
  76    case NV_OP_AND:
  77    case NV_OP_OR:
  78    case NV_OP_XOR:
  79    case NV_OP_SHL:
  80    case NV_OP_SHR:
  81       return (s == 1) && (nvi->src[0]->value->reg.file == NV_FILE_GPR) &&
  82          (nvi->def[0]->reg.file == NV_FILE_GPR);
  83    case NV_OP_MOV:
  84       assert(s == 0);
  85       return (nvi->def[0]->reg.file == NV_FILE_GPR);
  86    default:
  87       return FALSE;
  88    }
  89 }
  90
  91 boolean
  92 nv50_nvi_can_load(struct nv_instruction *nvi, int s, struct nv_value *value)
  93 {
  94    int i;
  95
  96    for (i = 0; i < 3 && nvi->src[i]; ++i)
  97       if (nvi->src[i]->value->reg.file == NV_FILE_IMM)
  98          return FALSE;
  99
 100    switch (nvi->opcode) {
 101    case NV_OP_ABS:
 102    case NV_OP_ADD:
 103    case NV_OP_CEIL:
 104    case NV_OP_FLOOR:
 105    case NV_OP_TRUNC:
 106    case NV_OP_CVT:
 107    case NV_OP_MAD:
 108    case NV_OP_MUL:
 109    case NV_OP_SAT:
 110    case NV_OP_SUB:
 111    case NV_OP_MAX:
 112    case NV_OP_MIN:
 113       if (s == 0 && (value->reg.file == NV_FILE_MEM_S ||
 114                      value->reg.file == NV_FILE_MEM_P))
 115          return TRUE;
 116       if (value->reg.file < NV_FILE_MEM_C(0) ||
 117           value->reg.file > NV_FILE_MEM_C(15))
 118          return FALSE;
 119       return (s == 1) ||
 120          ((s == 2) && (nvi->src[1]->value->reg.file == NV_FILE_GPR));
 121    case NV_OP_MOV:
 122       assert(s == 0);
 123       return /* TRUE */ FALSE; /* don't turn MOVs into loads */
 124    default:
 125       return FALSE;
 126    }
 127 }
 128
 129 /* Return whether this instruction can be executed conditionally. */
 130 boolean
 131 nv50_nvi_can_predicate(struct nv_instruction *nvi)
 132 {
 133    int i;
 134
 135    if (nvi->flags_src)
 136       return FALSE;
 137    for (i = 0; i < 4 && nvi->src[i]; ++i)
 138       if (nvi->src[i]->value->reg.file == NV_FILE_IMM)
 139          return FALSE;
 140    return TRUE;
 141 }
 142
 143 ubyte
 144 nv50_supported_src_mods(uint opcode, int s)
 145 {
 146    switch (opcode) {
 147    case NV_OP_ABS:
 148       return NV_MOD_NEG | NV_MOD_ABS; /* obviously */
 149    case NV_OP_ADD:
 150    case NV_OP_MUL:
 151    case NV_OP_MAD:
 152       return NV_MOD_NEG;
 153    case NV_OP_DFDX:
 154    case NV_OP_DFDY:
 155       assert(s == 0);
 156       return NV_MOD_NEG;
 157    case NV_OP_MAX:
 158    case NV_OP_MIN:
 159       return NV_MOD_ABS;
 160    case NV_OP_CVT:
 161    case NV_OP_LG2:
 162    case NV_OP_NEG:
 163    case NV_OP_PREEX2:
 164    case NV_OP_PRESIN:
 165    case NV_OP_RCP:
 166    case NV_OP_RSQ:
 167       return NV_MOD_ABS | NV_MOD_NEG;
 168    default:
 169       return 0;
 170    }
 171 }
 172
 173 int
 174 nv_nvi_refcount(struct nv_instruction *nvi)
 175 {
 176    int i, rc;
 177
 178    rc = nvi->flags_def ? nvi->flags_def->refc : 0;
 179
 180    for (i = 0; i < 4; ++i) {
 181       if (!nvi->def[i])
 182          return rc;
 183       rc += nvi->def[i]->refc;
 184    }
 185    return rc;
 186 }
 187
 188 int
 189 nvcg_replace_value(struct nv_pc *pc, struct nv_value *old_val,
 190                    struct nv_value *new_val)
 191 {
 192    int i, n;
 193
 194    if (old_val == new_val)
 195       return old_val->refc;
 196
 197    for (i = 0, n = 0; i < pc->num_refs; ++i) {
 198       if (pc->refs[i]->value == old_val) {
 199          ++n;
 200          nv_reference(pc, &pc->refs[i], new_val);
 201       }
 202    }
 203    return n;
 204 }
 205
 206 struct nv_value *
 207 nvcg_find_constant(struct nv_ref *ref)
 208 {
 209    struct nv_value *src;
 210
 211    if (!ref)
 212       return NULL;
 213
 214    src = ref->value;
 215    while (src->insn && src->insn->opcode == NV_OP_MOV) {
 216       assert(!src->insn->src[0]->mod);
 217       src = src->insn->src[0]->value;
 218    }
 219    if ((src->reg.file == NV_FILE_IMM) ||
 220        (src->insn && src->insn->opcode == NV_OP_LDA &&
 221         src->insn->src[0]->value->reg.file >= NV_FILE_MEM_C(0) &&
 222         src->insn->src[0]->value->reg.file <= NV_FILE_MEM_C(15)))
 223       return src;
 224    return NULL;
 225 }
 226
 227 struct nv_value *
 228 nvcg_find_immediate(struct nv_ref *ref)
 229 {
 230    struct nv_value *src = nvcg_find_constant(ref);
 231
 232    return (src && src->reg.file == NV_FILE_IMM) ? src : NULL;
 233 }
 234
 235 static void
 236 nv_pc_free_refs(struct nv_pc *pc)
 237 {
 238    int i;
 239    for (i = 0; i < pc->num_refs; i += 64)
 240       FREE(pc->refs[i]);
 241    FREE(pc->refs);
 242 }
 243
 244 static const char *
 245 edge_name(ubyte type)
 246 {
 247    switch (type) {
 248    case CFG_EDGE_FORWARD: return "forward";
 249    case CFG_EDGE_BACK: return "back";
 250    case CFG_EDGE_LOOP_ENTER: return "loop";
 251    case CFG_EDGE_LOOP_LEAVE: return "break";
 252    case CFG_EDGE_FAKE: return "fake";
 253    default:
 254       return "?";
 255    }
 256 }
 257
 258 void
 259 nv_pc_pass_in_order(struct nv_basic_block *root, nv_pc_pass_func f, void *priv)
 260 {
 261    struct nv_basic_block *bb[64], *bbb[16], *b;
 262    int j, p, pp;
 263
 264    bb[0] = root;
 265    p = 1;
 266    pp = 0;
 267
 268    while (p > 0) {
 269       b = bb[--p];
 270       b->priv = 0;
 271
 272       for (j = 1; j >= 0; --j) {
 273          if (!b->out[j])
 274             continue;
 275
 276          switch (b->out_kind[j]) {
 277          case CFG_EDGE_BACK:
 278             continue;
 279          case CFG_EDGE_FORWARD:
 280          case CFG_EDGE_FAKE:
 281             if (++b->out[j]->priv == b->out[j]->num_in)
 282                bb[p++] = b->out[j];
 283             break;
 284          case CFG_EDGE_LOOP_ENTER:
 285             bb[p++] = b->out[j];
 286             break;
 287          case CFG_EDGE_LOOP_LEAVE:
 288             bbb[pp++] = b->out[j];
 289             break;
 290          default:
 291             assert(0);
 292             break;
 293          }
 294       }
 295
 296       f(priv, b);
 297
 298       if (!p) {
 299          p = pp;
 300          for (; pp > 0; --pp)
 301             bb[pp - 1] = bbb[pp - 1];
 302       }
 303    }
 304 }
 305
 306 static void
 307 nv_do_print_function(void *priv, struct nv_basic_block *b)
 308 {
 309    struct nv_instruction *i = b->phi;
 310
 311    debug_printf("=== BB %i ", b->id);
 312    if (b->out[0])
 313       debug_printf("[%s -> %i] ", edge_name(b->out_kind[0]), b->out[0]->id);
 314    if (b->out[1])
 315       debug_printf("[%s -> %i] ", edge_name(b->out_kind[1]), b->out[1]->id);
 316    debug_printf("===\n");
 317
 318    i = b->phi;
 319    if (!i)
 320       i = b->entry;
 321    for (; i; i = i->next)
 322       nv_print_instruction(i);
 323 }
 324
 325 void
 326 nv_print_function(struct nv_basic_block *root)
 327 {
 328    if (root->subroutine)
 329       debug_printf("SUBROUTINE %i\n", root->subroutine);
 330    else
 331       debug_printf("MAIN\n");
 332
 333    nv_pc_pass_in_order(root, nv_do_print_function, root);
 334 }
 335
 336 void
 337 nv_print_program(struct nv_pc *pc)
 338 {
 339    int i;
 340    for (i = 0; i < pc->num_subroutines + 1; ++i)
 341       if (pc->root[i])
 342          nv_print_function(pc->root[i]);
 343 }
 344
 345 #ifdef NV50PC_DEBUG
 346 static void
 347 nv_do_print_cfgraph(struct nv_pc *pc, FILE *f, struct nv_basic_block *b)
 348 {
 349    int i;
 350
 351    b->pass_seq = pc->pass_seq;
 352
 353    fprintf(f, "\t%i [shape=box]\n", b->id);
 354
 355    for (i = 0; i < 2; ++i) {
 356       if (!b->out[i])
 357          continue;
 358       switch (b->out_kind[i]) {
 359       case CFG_EDGE_FORWARD:
 360          fprintf(f, "\t%i -> %i;\n", b->id, b->out[i]->id);
 361          break;
 362       case CFG_EDGE_LOOP_ENTER:
 363          fprintf(f, "\t%i -> %i [color=green];\n", b->id, b->out[i]->id);
 364          break;
 365       case CFG_EDGE_LOOP_LEAVE:
 366          fprintf(f, "\t%i -> %i [color=red];\n", b->id, b->out[i]->id);
 367          break;
 368       case CFG_EDGE_BACK:
 369          fprintf(f, "\t%i -> %i;\n", b->id, b->out[i]->id);
 370          continue;
 371       case CFG_EDGE_FAKE:
 372          fprintf(f, "\t%i -> %i [style=dotted];\n", b->id, b->out[i]->id);
 373          break;
 374       default:
 375          assert(0);
 376          break;
 377       }
 378       if (b->out[i]->pass_seq < pc->pass_seq)
 379          nv_do_print_cfgraph(pc, f, b->out[i]);
 380    }
 381 }
 382
 383 /* Print the control flow graph of subroutine @subr (0 == MAIN) to a file. */
 384 static void
 385 nv_print_cfgraph(struct nv_pc *pc, const char *filepath, int subr)
 386 {
 387    FILE *f;
 388
 389    f = fopen(filepath, "a");
 390    if (!f)
 391       return;
 392
 393    fprintf(f, "digraph G {\n");
 394
 395    ++pc->pass_seq;
 396
 397    nv_do_print_cfgraph(pc, f, pc->root[subr]);
 398
 399    fprintf(f, "}\n");
 400
 401    fclose(f);
 402 }
 403 #endif
 404
 405 static INLINE void
 406 nvcg_show_bincode(struct nv_pc *pc)
 407 {
 408    int i;
 409
 410    for (i = 0; i < pc->bin_size / 4; ++i)
 411       debug_printf("0x%08x ", pc->emit[i]);
 412    debug_printf("\n");
 413 }
 414
 415 static int
 416 nv50_emit_program(struct nv_pc *pc)
 417 {
 418    uint32_t *code = pc->emit;
 419    int n;
 420
 421    NV50_DBGMSG("emitting program: size = %u\n", pc->bin_size);
 422
 423    for (n = 0; n < pc->num_blocks; ++n) {
 424       struct nv_instruction *i;
 425       struct nv_basic_block *b = pc->bb_list[n];
 426
 427       for (i = b->entry; i; i = i->next) {
 428          nv50_emit_instruction(pc, i);
 429
 430          pc->bin_pos += 1 + (pc->emit[0] & 1);
 431          pc->emit += 1 + (pc->emit[0] & 1);
 432       }
 433    }
 434    assert(pc->emit == &code[pc->bin_size / 4]);
 435
 436    /* XXX: we can do better than this ... */
 437    if (!(pc->emit[-2] & 1) || (pc->emit[-2] & 2) || (pc->emit[-1] & 3)) {
 438       pc->emit[0] = 0xf0000001;
 439       pc->emit[1] = 0xe0000000;
 440       pc->bin_size += 8;
 441    }
 442
 443    pc->emit = code;
 444    code[pc->bin_size / 4 - 1] |= 1;
 445
 446 #ifdef NV50PC_DEBUG
 447    nvcg_show_bincode(pc);
 448 #endif
 449
 450    return 0;
 451 }
 452
 453 int
 454 nv50_generate_code(struct nv50_translation_info *ti)
 455 {
 456    struct nv_pc *pc;
 457    int ret;
 458    int i;
 459
 460    pc = CALLOC_STRUCT(nv_pc);
 461    if (!pc)
 462       return 1;
 463
 464    pc->root = CALLOC(ti->subr_nr + 1, sizeof(pc->root[0]));
 465    if (!pc->root) {
 466       FREE(pc);
 467       return 1;
 468    }
 469    pc->num_subroutines = ti->subr_nr;
 470
 471    ret = nv50_tgsi_to_nc(pc, ti);
 472    if (ret)
 473       goto out;
 474 #ifdef NV50PC_DEBUG
 475    nv_print_program(pc);
 476 #endif
 477
 478    pc->opt_reload_elim = ti->store_to_memory ? FALSE : TRUE;
 479
 480    /* optimization */
 481    ret = nv_pc_exec_pass0(pc);
 482    if (ret)
 483       goto out;
 484 #ifdef NV50PC_DEBUG
 485    nv_print_program(pc);
 486 #endif
 487
 488    /* register allocation */
 489    ret = nv_pc_exec_pass1(pc);
 490    if (ret)
 491       goto out;
 492 #ifdef NV50PC_DEBUG
 493    nv_print_program(pc);
 494    nv_print_cfgraph(pc, "nv50_shader_cfgraph.dot", 0);
 495 #endif
 496
 497    /* prepare for emission */
 498    ret = nv_pc_exec_pass2(pc);
 499    if (ret)
 500       goto out;
 501
 502    pc->emit = CALLOC(pc->bin_size / 4 + 2, 4);
 503    if (!pc->emit) {
 504       ret = 3;
 505       goto out;
 506    }
 507    ret = nv50_emit_program(pc);
 508    if (ret)
 509       goto out;
 510
 511    ti->p->code_size = pc->bin_size;
 512    ti->p->code = pc->emit;
 513
 514    ti->p->immd_size = pc->immd_count * 4;
 515    ti->p->immd = pc->immd_buf;
 516
 517    /* highest 16 bit reg to num of 32 bit regs */
 518    ti->p->max_gpr = (pc->max_reg[NV_FILE_GPR] >> 1) + 1;
 519
 520    ti->p->fixups = pc->fixups;
 521    ti->p->num_fixups = pc->num_fixups;
 522
 523    NV50_DBGMSG("SHADER TRANSLATION - %s\n", ret ? "failure" : "success");
 524
 525 out:
 526    nv_pc_free_refs(pc);
 527
 528    for (i = 0; i < pc->num_blocks; ++i)
 529       FREE(pc->bb_list[i]);
 530    if (pc->root)
 531       FREE(pc->root);
 532    if (ret) { /* on success, these will be referenced by nv50_program */
 533       if (pc->emit)
 534          FREE(pc->emit);
 535       if (pc->immd_buf)
 536          FREE(pc->immd_buf);
 537       if (pc->fixups)
 538          FREE(pc->fixups);
 539    }
 540    FREE(pc);
 541    return ret;
 542 }
 543
 544 static void
 545 nvbb_insert_phi(struct nv_basic_block *b, struct nv_instruction *i)
 546 {
 547    if (!b->phi) {
 548       i->prev = NULL;
 549       b->phi = i;
 550       i->next = b->entry;
 551       if (b->entry) {
 552          assert(!b->entry->prev && b->exit);
 553          b->entry->prev = i;
 554       } else {
 555          b->entry = i;
 556          b->exit = i;
 557       }
 558    } else {
 559       assert(b->entry);
 560       if (b->entry->opcode == NV_OP_PHI) { /* insert after entry */
 561          assert(b->entry == b->exit);
 562          b->entry->next = i;
 563          i->prev = b->entry;
 564          b->entry = i;
 565          b->exit = i;
 566       } else { /* insert before entry */
 567          assert(b->entry->prev && b->exit);
 568          i->next = b->entry;
 569          i->prev = b->entry->prev;
 570          b->entry->prev = i;
 571          i->prev->next = i;
 572       }
 573    }
 574 }
 575
 576 void
 577 nvbb_insert_tail(struct nv_basic_block *b, struct nv_instruction *i)
 578 {
 579    if (i->opcode == NV_OP_PHI) {
 580       nvbb_insert_phi(b, i);
 581    } else {
 582       i->prev = b->exit;
 583       if (b->exit)
 584          b->exit->next = i;
 585       b->exit = i;
 586       if (!b->entry)
 587          b->entry = i;
 588       else
 589       if (i->prev && i->prev->opcode == NV_OP_PHI)
 590          b->entry = i;
 591    }
 592
 593    i->bb = b;
 594    b->num_instructions++;
 595 }
 596
 597 void
 598 nvi_insert_after(struct nv_instruction *at, struct nv_instruction *ni)
 599 {
 600    if (!at->next) {
 601       nvbb_insert_tail(at->bb, ni);
 602       return;
 603    }
 604    ni->next = at->next;
 605    ni->prev = at;
 606    ni->next->prev = ni;
 607    ni->prev->next = ni;
 608 }
 609
 610 void
 611 nv_nvi_delete(struct nv_instruction *nvi)
 612 {
 613    struct nv_basic_block *b = nvi->bb;
 614    int j;
 615
 616    /* debug_printf("REM: "); nv_print_instruction(nvi); */
 617
 618    for (j = 0; j < 5; ++j)
 619       nv_reference(NULL, &nvi->src[j], NULL);
 620    nv_reference(NULL, &nvi->flags_src, NULL);
 621
 622    if (nvi->next)
 623       nvi->next->prev = nvi->prev;
 624    else {
 625       assert(nvi == b->exit);
 626       b->exit = nvi->prev;
 627    }
 628
 629    if (nvi->prev)
 630       nvi->prev->next = nvi->next;
 631
 632    if (nvi == b->entry) {
 633       /* PHIs don't get hooked to b->entry */
 634       b->entry = nvi->next;
 635       assert(!nvi->prev || nvi->prev->opcode == NV_OP_PHI);
 636    }
 637
 638    if (nvi == b->phi) {
 639       if (nvi->opcode != NV_OP_PHI)
 640          NV50_DBGMSG("NOTE: b->phi points to non-PHI instruction\n");
 641
 642       assert(!nvi->prev);
 643       if (!nvi->next || nvi->next->opcode != NV_OP_PHI)
 644          b->phi = NULL;
 645       else
 646          b->phi = nvi->next;
 647    }
 648 }
 649
 650 void
 651 nv_nvi_permute(struct nv_instruction *i1, struct nv_instruction *i2)
 652 {
 653    struct nv_basic_block *b = i1->bb;
 654
 655    assert(i1->opcode != NV_OP_PHI &&
 656           i2->opcode != NV_OP_PHI);
 657    assert(i1->next == i2);
 658
 659    if (b->exit == i2)
 660       b->exit = i1;
 661
 662    if (b->entry == i1)
 663       b->entry = i2;
 664
 665    i2->prev = i1->prev;
 666    i1->next = i2->next;
 667    i2->next = i1;
 668    i1->prev = i2;
 669
 670    if (i2->prev)
 671       i2->prev->next = i2;
 672    if (i1->next)
 673       i1->next->prev = i1;
 674 }
 675
 676 void
 677 nvbb_attach_block(struct nv_basic_block *parent,
 678                   struct nv_basic_block *b, ubyte edge_kind)
 679 {
 680    assert(b->num_in < 8);
 681
 682    if (parent->out[0]) {
 683       assert(!parent->out[1]);
 684       parent->out[1] = b;
 685       parent->out_kind[1] = edge_kind;
 686    } else {
 687       parent->out[0] = b;
 688       parent->out_kind[0] = edge_kind;
 689    }
 690
 691    b->in[b->num_in] = parent;
 692    b->in_kind[b->num_in++] = edge_kind;
 693 }
 694
 695 /* NOTE: all BRKs are treated as conditional, so there are 2 outgoing BBs */
 696
 697 boolean
 698 nvbb_dominated_by(struct nv_basic_block *b, struct nv_basic_block *d)
 699 {
 700    int j;
 701
 702    if (b == d)
 703       return TRUE;
 704
 705    for (j = 0; j < b->num_in; ++j)
 706       if ((b->in_kind[j] != CFG_EDGE_BACK) && !nvbb_dominated_by(b->in[j], d))
 707          return FALSE;
 708
 709    return j ? TRUE : FALSE;
 710 }
 711
 712 /* check if @bf (future) can be reached from @bp (past), stop at @bt */
 713 boolean
 714 nvbb_reachable_by(struct nv_basic_block *bf, struct nv_basic_block *bp,
 715                   struct nv_basic_block *bt)
 716 {
 717    struct nv_basic_block *q[NV_PC_MAX_BASIC_BLOCKS], *b;
 718    int i, p, n;
 719
 720    p = 0;
 721    n = 1;
 722    q[0] = bp;
 723
 724    while (p < n) {
 725       b = q[p++];
 726
 727       if (b == bf)
 728          break;
 729       if (b == bt)
 730          continue;
 731       assert(n <= (1024 - 2));
 732
 733       for (i = 0; i < 2; ++i) {
 734          if (b->out[i] && !IS_WALL_EDGE(b->out_kind[i]) && !b->out[i]->priv) {
 735             q[n] = b->out[i];
 736             q[n++]->priv = 1;
 737          }
 738       }
 739    }
 740    for (--n; n >= 0; --n)
 741       q[n]->priv = 0;
 742
 743    return (b == bf);
 744 }
 745
 746 static struct nv_basic_block *
 747 nvbb_find_dom_frontier(struct nv_basic_block *b, struct nv_basic_block *df)
 748 {
 749    struct nv_basic_block *out;
 750    int i;
 751
 752    if (!nvbb_dominated_by(df, b)) {
 753       for (i = 0; i < df->num_in; ++i) {
 754          if (df->in_kind[i] == CFG_EDGE_BACK)
 755             continue;
 756          if (nvbb_dominated_by(df->in[i], b))
 757             return df;
 758       }
 759    }
 760    for (i = 0; i < 2 && df->out[i]; ++i) {
 761       if (df->out_kind[i] == CFG_EDGE_BACK)
 762          continue;
 763       if ((out = nvbb_find_dom_frontier(b, df->out[i])))
 764          return out;
 765    }
 766    return NULL;
 767 }
 768
 769 struct nv_basic_block *
 770 nvbb_dom_frontier(struct nv_basic_block *b)
 771 {
 772    struct nv_basic_block *df;
 773    int i;
 774
 775    for (i = 0; i < 2 && b->out[i]; ++i)
 776       if ((df = nvbb_find_dom_frontier(b, b->out[i])))
 777          return df;
 778    return NULL;
 779 }