src/mesa/drivers/dri/i965/brw_cfg.cpp

   1 /*
   2  * Copyright © 2012 Intel Corporation
   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 (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  *
  23  * Authors:
  24  *    Eric Anholt <eric@anholt.net>
  25  *
  26  */
  27
  28 #include "brw_cfg.h"
  29
  30 /** @file brw_cfg.cpp
  31  *
  32  * Walks the shader instructions generated and creates a set of basic
  33  * blocks with successor/predecessor edges connecting them.
  34  */
  35
  36 static bblock_t *
  37 pop_stack(exec_list *list)
  38 {
  39    bblock_link *link = (bblock_link *)list->get_tail();
  40    bblock_t *block = link->block;
  41    link->link.remove();
  42
  43    return block;
  44 }
  45
  46 static exec_node *
  47 link(void *mem_ctx, bblock_t *block)
  48 {
  49    bblock_link *l = new(mem_ctx) bblock_link(block);
  50    return &l->link;
  51 }
  52
  53 bblock_t::bblock_t(cfg_t *cfg) :
  54    cfg(cfg), start_ip(0), end_ip(0), num(0),
  55    if_block(NULL), else_block(NULL)
  56 {
  57    start = NULL;
  58    end = NULL;
  59
  60    parents.make_empty();
  61    children.make_empty();
  62 }
  63
  64 void
  65 bblock_t::add_successor(void *mem_ctx, bblock_t *successor)
  66 {
  67    successor->parents.push_tail(::link(mem_ctx, this));
  68    children.push_tail(::link(mem_ctx, successor));
  69 }
  70
  71 bool
  72 bblock_t::is_predecessor_of(const bblock_t *block) const
  73 {
  74    foreach_list_typed_safe (bblock_link, parent, link, &block->parents) {
  75       if (parent->block == this) {
  76          return true;
  77       }
  78    }
  79
  80    return false;
  81 }
  82
  83 bool
  84 bblock_t::is_successor_of(const bblock_t *block) const
  85 {
  86    foreach_list_typed_safe (bblock_link, child, link, &block->children) {
  87       if (child->block == this) {
  88          return true;
  89       }
  90    }
  91
  92    return false;
  93 }
  94
  95 static bool
  96 ends_block(const backend_instruction *inst)
  97 {
  98    enum opcode op = inst->opcode;
  99
 100    return op == BRW_OPCODE_IF ||
 101           op == BRW_OPCODE_ELSE ||
 102           op == BRW_OPCODE_CONTINUE ||
 103           op == BRW_OPCODE_BREAK ||
 104           op == BRW_OPCODE_WHILE;
 105 }
 106
 107 static bool
 108 starts_block(const backend_instruction *inst)
 109 {
 110    enum opcode op = inst->opcode;
 111
 112    return op == BRW_OPCODE_DO ||
 113           op == BRW_OPCODE_ENDIF;
 114 }
 115
 116 bool
 117 bblock_t::can_combine_with(const bblock_t *that) const
 118 {
 119    if ((const bblock_t *)this->link.next != that)
 120       return false;
 121
 122    if (ends_block(this->end) ||
 123        starts_block(that->start))
 124       return false;
 125
 126    return true;
 127 }
 128
 129 void
 130 bblock_t::combine_with(bblock_t *that)
 131 {
 132    assert(this->can_combine_with(that));
 133    foreach_list_typed (bblock_link, link, link, &this->children) {
 134       assert(link->block == that);
 135    }
 136    foreach_list_typed (bblock_link, link, link, &that->parents) {
 137       assert(link->block == this);
 138    }
 139
 140    this->end_ip = that->end_ip;
 141    this->end = that->end;
 142    this->else_block = that->else_block;
 143
 144    this->cfg->remove_block(that);
 145 }
 146
 147 void
 148 bblock_t::dump(backend_visitor *v)
 149 {
 150    int ip = this->start_ip;
 151    for (backend_instruction *inst = (backend_instruction *)this->start;
 152         inst != this->end->next;
 153         inst = (backend_instruction *) inst->next) {
 154       fprintf(stderr, "%5d: ", ip);
 155       v->dump_instruction(inst);
 156       ip++;
 157    }
 158 }
 159
 160 cfg_t::cfg_t(exec_list *instructions)
 161 {
 162    mem_ctx = ralloc_context(NULL);
 163    block_list.make_empty();
 164    blocks = NULL;
 165    num_blocks = 0;
 166
 167    bblock_t *cur = NULL;
 168    int ip = 0;
 169
 170    bblock_t *entry = new_block();
 171    bblock_t *cur_if = NULL;    /**< BB ending with IF. */
 172    bblock_t *cur_else = NULL;  /**< BB ending with ELSE. */
 173    bblock_t *cur_endif = NULL; /**< BB starting with ENDIF. */
 174    bblock_t *cur_do = NULL;    /**< BB starting with DO. */
 175    bblock_t *cur_while = NULL; /**< BB immediately following WHILE. */
 176    exec_list if_stack, else_stack, do_stack, while_stack;
 177    bblock_t *next;
 178
 179    set_next_block(&cur, entry, ip);
 180
 181    entry->start = (backend_instruction *) instructions->get_head();
 182
 183    foreach_in_list(backend_instruction, inst, instructions) {
 184       cur->end = inst;
 185
 186       /* set_next_block wants the post-incremented ip */
 187       ip++;
 188
 189       switch (inst->opcode) {
 190       case BRW_OPCODE_IF:
 191          /* Push our information onto a stack so we can recover from
 192           * nested ifs.
 193           */
 194          if_stack.push_tail(link(mem_ctx, cur_if));
 195          else_stack.push_tail(link(mem_ctx, cur_else));
 196
 197          cur_if = cur;
 198          cur_else = NULL;
 199          cur_endif = NULL;
 200
 201          /* Set up our immediately following block, full of "then"
 202           * instructions.
 203           */
 204          next = new_block();
 205          next->start = (backend_instruction *)inst->next;
 206          cur_if->add_successor(mem_ctx, next);
 207
 208          set_next_block(&cur, next, ip);
 209          break;
 210
 211       case BRW_OPCODE_ELSE:
 212          cur_else = cur;
 213
 214          next = new_block();
 215          next->start = (backend_instruction *)inst->next;
 216          cur_if->add_successor(mem_ctx, next);
 217
 218          set_next_block(&cur, next, ip);
 219          break;
 220
 221       case BRW_OPCODE_ENDIF: {
 222          if (cur->start == inst) {
 223             /* New block was just created; use it. */
 224             cur_endif = cur;
 225          } else {
 226             cur_endif = new_block();
 227             cur_endif->start = inst;
 228
 229             cur->end = (backend_instruction *)inst->prev;
 230             cur->add_successor(mem_ctx, cur_endif);
 231
 232             set_next_block(&cur, cur_endif, ip - 1);
 233          }
 234
 235          if (cur_else) {
 236             cur_else->add_successor(mem_ctx, cur_endif);
 237          } else {
 238             cur_if->add_successor(mem_ctx, cur_endif);
 239          }
 240
 241          assert(cur_if->end->opcode == BRW_OPCODE_IF);
 242          assert(!cur_else || cur_else->end->opcode == BRW_OPCODE_ELSE);
 243
 244          cur_if->if_block = cur_if;
 245          cur_if->else_block = cur_else;
 246
 247          if (cur_else) {
 248             cur_else->if_block = cur_if;
 249             cur_else->else_block = cur_else;
 250          }
 251
 252          cur->if_block = cur_if;
 253          cur->else_block = cur_else;
 254
 255          /* Pop the stack so we're in the previous if/else/endif */
 256          cur_if = pop_stack(&if_stack);
 257          cur_else = pop_stack(&else_stack);
 258          break;
 259       }
 260       case BRW_OPCODE_DO:
 261          /* Push our information onto a stack so we can recover from
 262           * nested loops.
 263           */
 264          do_stack.push_tail(link(mem_ctx, cur_do));
 265          while_stack.push_tail(link(mem_ctx, cur_while));
 266
 267          /* Set up the block just after the while.  Don't know when exactly
 268           * it will start, yet.
 269           */
 270          cur_while = new_block();
 271
 272          if (cur->start == inst) {
 273             /* New block was just created; use it. */
 274             cur_do = cur;
 275          } else {
 276             cur_do = new_block();
 277             cur_do->start = inst;
 278
 279             cur->end = (backend_instruction *)inst->prev;
 280             cur->add_successor(mem_ctx, cur_do);
 281
 282             set_next_block(&cur, cur_do, ip - 1);
 283          }
 284          break;
 285
 286       case BRW_OPCODE_CONTINUE:
 287          cur->add_successor(mem_ctx, cur_do);
 288
 289          next = new_block();
 290          next->start = (backend_instruction *)inst->next;
 291          if (inst->predicate)
 292             cur->add_successor(mem_ctx, next);
 293
 294          set_next_block(&cur, next, ip);
 295          break;
 296
 297       case BRW_OPCODE_BREAK:
 298          cur->add_successor(mem_ctx, cur_while);
 299
 300          next = new_block();
 301          next->start = (backend_instruction *)inst->next;
 302          if (inst->predicate)
 303             cur->add_successor(mem_ctx, next);
 304
 305          set_next_block(&cur, next, ip);
 306          break;
 307
 308       case BRW_OPCODE_WHILE:
 309          cur_while->start = (backend_instruction *)inst->next;
 310
 311          cur->add_successor(mem_ctx, cur_do);
 312          set_next_block(&cur, cur_while, ip);
 313
 314          /* Pop the stack so we're in the previous loop */
 315          cur_do = pop_stack(&do_stack);
 316          cur_while = pop_stack(&while_stack);
 317          break;
 318
 319       default:
 320          break;
 321       }
 322    }
 323
 324    assert(cur->end);
 325
 326    cur->end_ip = ip;
 327
 328    make_block_array();
 329 }
 330
 331 cfg_t::~cfg_t()
 332 {
 333    ralloc_free(mem_ctx);
 334 }
 335
 336 void
 337 cfg_t::remove_block(bblock_t *block)
 338 {
 339    foreach_list_typed_safe (bblock_link, predecessor, link, &block->parents) {
 340       /* Remove block from all of its predecessors' successor lists. */
 341       foreach_list_typed_safe (bblock_link, successor, link,
 342                                &predecessor->block->children) {
 343          if (block == successor->block) {
 344             successor->link.remove();
 345             ralloc_free(successor);
 346          }
 347       }
 348
 349       /* Add removed-block's successors to its predecessors' successor lists. */
 350       foreach_list_typed (bblock_link, successor, link, &block->children) {
 351          if (!successor->block->is_successor_of(predecessor->block)) {
 352             predecessor->block->children.push_tail(link(mem_ctx,
 353                                                         successor->block));
 354          }
 355       }
 356    }
 357
 358    foreach_list_typed_safe (bblock_link, successor, link, &block->children) {
 359       /* Remove block from all of its childrens' parents lists. */
 360       foreach_list_typed_safe (bblock_link, predecessor, link,
 361                                &successor->block->parents) {
 362          if (block == predecessor->block) {
 363             predecessor->link.remove();
 364             ralloc_free(predecessor);
 365          }
 366       }
 367
 368       /* Add removed-block's predecessors to its successors' predecessor lists. */
 369       foreach_list_typed (bblock_link, predecessor, link, &block->parents) {
 370          if (!predecessor->block->is_predecessor_of(successor->block)) {
 371             successor->block->parents.push_tail(link(mem_ctx,
 372                                                      predecessor->block));
 373          }
 374       }
 375    }
 376
 377    block->link.remove();
 378
 379    for (int b = block->num; b < this->num_blocks - 1; b++) {
 380       this->blocks[b] = this->blocks[b + 1];
 381       this->blocks[b]->num = b;
 382    }
 383
 384    this->blocks[this->num_blocks - 1]->num = this->num_blocks - 2;
 385    this->num_blocks--;
 386 }
 387
 388 bblock_t *
 389 cfg_t::new_block()
 390 {
 391    bblock_t *block = new(mem_ctx) bblock_t(this);
 392
 393    return block;
 394 }
 395
 396 void
 397 cfg_t::set_next_block(bblock_t **cur, bblock_t *block, int ip)
 398 {
 399    if (*cur) {
 400       assert((*cur)->end->next == block->start);
 401       (*cur)->end_ip = ip - 1;
 402    }
 403
 404    block->start_ip = ip;
 405    block->num = num_blocks++;
 406    block_list.push_tail(&block->link);
 407    *cur = block;
 408 }
 409
 410 void
 411 cfg_t::make_block_array()
 412 {
 413    blocks = ralloc_array(mem_ctx, bblock_t *, num_blocks);
 414
 415    int i = 0;
 416    foreach_block (block, this) {
 417       blocks[i++] = block;
 418    }
 419    assert(i == num_blocks);
 420 }
 421
 422 void
 423 cfg_t::dump(backend_visitor *v)
 424 {
 425    foreach_block (block, this) {
 426       fprintf(stderr, "START B%d", block->num);
 427       foreach_list_typed(bblock_link, link, link, &block->parents) {
 428          fprintf(stderr, " <-B%d",
 429                  link->block->num);
 430       }
 431       fprintf(stderr, "\n");
 432       block->dump(v);
 433       fprintf(stderr, "END B%d", block->num);
 434       foreach_list_typed(bblock_link, link, link, &block->children) {
 435          fprintf(stderr, " ->B%d",
 436                  link->block->num);
 437       }
 438       fprintf(stderr, "\n");
 439    }
 440 }