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() :
  54    start_ip(0), end_ip(0), block_num(0)
  55 {
  56    start = NULL;
  57    end = NULL;
  58
  59    parents.make_empty();
  60    children.make_empty();
  61
  62    if_inst = NULL;
  63    else_inst = NULL;
  64    endif_inst = NULL;
  65 }
  66
  67 void
  68 bblock_t::add_successor(void *mem_ctx, bblock_t *successor)
  69 {
  70    successor->parents.push_tail(link(mem_ctx, this));
  71    children.push_tail(link(mem_ctx, successor));
  72 }
  73
  74 void
  75 bblock_t::dump(backend_visitor *v)
  76 {
  77    int ip = this->start_ip;
  78    for (backend_instruction *inst = (backend_instruction *)this->start;
  79         inst != this->end->next;
  80         inst = (backend_instruction *) inst->next) {
  81       fprintf(stderr, "%5d: ", ip);
  82       v->dump_instruction(inst);
  83       ip++;
  84    }
  85 }
  86
  87 cfg_t::cfg_t(exec_list *instructions)
  88 {
  89    mem_ctx = ralloc_context(NULL);
  90    block_list.make_empty();
  91    blocks = NULL;
  92    num_blocks = 0;
  93
  94    bblock_t *cur = NULL;
  95    int ip = 0;
  96
  97    bblock_t *entry = new_block();
  98    bblock_t *cur_if = NULL;    /**< BB ending with IF. */
  99    bblock_t *cur_else = NULL;  /**< BB ending with ELSE. */
 100    bblock_t *cur_endif = NULL; /**< BB starting with ENDIF. */
 101    bblock_t *cur_do = NULL;    /**< BB starting with DO. */
 102    bblock_t *cur_while = NULL; /**< BB immediately following WHILE. */
 103    exec_list if_stack, else_stack, do_stack, while_stack;
 104    bblock_t *next;
 105
 106    set_next_block(&cur, entry, ip);
 107
 108    entry->start = (backend_instruction *) instructions->get_head();
 109
 110    foreach_in_list(backend_instruction, inst, instructions) {
 111       cur->end = inst;
 112
 113       /* set_next_block wants the post-incremented ip */
 114       ip++;
 115
 116       switch (inst->opcode) {
 117       case BRW_OPCODE_IF:
 118          /* Push our information onto a stack so we can recover from
 119           * nested ifs.
 120           */
 121          if_stack.push_tail(link(mem_ctx, cur_if));
 122          else_stack.push_tail(link(mem_ctx, cur_else));
 123
 124          cur_if = cur;
 125          cur_else = NULL;
 126          cur_endif = NULL;
 127
 128          /* Set up our immediately following block, full of "then"
 129           * instructions.
 130           */
 131          next = new_block();
 132          next->start = (backend_instruction *)inst->next;
 133          cur_if->add_successor(mem_ctx, next);
 134
 135          set_next_block(&cur, next, ip);
 136          break;
 137
 138       case BRW_OPCODE_ELSE:
 139          cur_else = cur;
 140
 141          next = new_block();
 142          next->start = (backend_instruction *)inst->next;
 143          cur_if->add_successor(mem_ctx, next);
 144
 145          set_next_block(&cur, next, ip);
 146          break;
 147
 148       case BRW_OPCODE_ENDIF: {
 149          if (cur->start == inst) {
 150             /* New block was just created; use it. */
 151             cur_endif = cur;
 152          } else {
 153             cur_endif = new_block();
 154             cur_endif->start = inst;
 155
 156             cur->end = (backend_instruction *)inst->prev;
 157             cur->add_successor(mem_ctx, cur_endif);
 158
 159             set_next_block(&cur, cur_endif, ip - 1);
 160          }
 161
 162          backend_instruction *else_inst = NULL;
 163          if (cur_else) {
 164             else_inst = (backend_instruction *)cur_else->end;
 165
 166             cur_else->add_successor(mem_ctx, cur_endif);
 167          } else {
 168             cur_if->add_successor(mem_ctx, cur_endif);
 169          }
 170
 171          assert(cur_if->end->opcode == BRW_OPCODE_IF);
 172          assert(!else_inst || else_inst->opcode == BRW_OPCODE_ELSE);
 173          assert(inst->opcode == BRW_OPCODE_ENDIF);
 174
 175          cur_if->if_inst = cur_if->end;
 176          cur_if->else_inst = else_inst;
 177          cur_if->endif_inst = inst;
 178
 179          if (cur_else) {
 180             cur_else->if_inst = cur_if->end;
 181             cur_else->else_inst = else_inst;
 182             cur_else->endif_inst = inst;
 183          }
 184
 185          cur->if_inst = cur_if->end;
 186          cur->else_inst = else_inst;
 187          cur->endif_inst = inst;
 188
 189          /* Pop the stack so we're in the previous if/else/endif */
 190          cur_if = pop_stack(&if_stack);
 191          cur_else = pop_stack(&else_stack);
 192          break;
 193       }
 194       case BRW_OPCODE_DO:
 195          /* Push our information onto a stack so we can recover from
 196           * nested loops.
 197           */
 198          do_stack.push_tail(link(mem_ctx, cur_do));
 199          while_stack.push_tail(link(mem_ctx, cur_while));
 200
 201          /* Set up the block just after the while.  Don't know when exactly
 202           * it will start, yet.
 203           */
 204          cur_while = new_block();
 205
 206          if (cur->start == inst) {
 207             /* New block was just created; use it. */
 208             cur_do = cur;
 209          } else {
 210             cur_do = new_block();
 211             cur_do->start = inst;
 212
 213             cur->end = (backend_instruction *)inst->prev;
 214             cur->add_successor(mem_ctx, cur_do);
 215
 216             set_next_block(&cur, cur_do, ip - 1);
 217          }
 218          break;
 219
 220       case BRW_OPCODE_CONTINUE:
 221          cur->add_successor(mem_ctx, cur_do);
 222
 223          next = new_block();
 224          next->start = (backend_instruction *)inst->next;
 225          if (inst->predicate)
 226             cur->add_successor(mem_ctx, next);
 227
 228          set_next_block(&cur, next, ip);
 229          break;
 230
 231       case BRW_OPCODE_BREAK:
 232          cur->add_successor(mem_ctx, cur_while);
 233
 234          next = new_block();
 235          next->start = (backend_instruction *)inst->next;
 236          if (inst->predicate)
 237             cur->add_successor(mem_ctx, next);
 238
 239          set_next_block(&cur, next, ip);
 240          break;
 241
 242       case BRW_OPCODE_WHILE:
 243          cur_while->start = (backend_instruction *)inst->next;
 244
 245          cur->add_successor(mem_ctx, cur_do);
 246          set_next_block(&cur, cur_while, ip);
 247
 248          /* Pop the stack so we're in the previous loop */
 249          cur_do = pop_stack(&do_stack);
 250          cur_while = pop_stack(&while_stack);
 251          break;
 252
 253       default:
 254          break;
 255       }
 256    }
 257
 258    assert(cur->end);
 259
 260    cur->end_ip = ip;
 261
 262    make_block_array();
 263 }
 264
 265 cfg_t::~cfg_t()
 266 {
 267    ralloc_free(mem_ctx);
 268 }
 269
 270 bblock_t *
 271 cfg_t::new_block()
 272 {
 273    bblock_t *block = new(mem_ctx) bblock_t();
 274
 275    return block;
 276 }
 277
 278 void
 279 cfg_t::set_next_block(bblock_t **cur, bblock_t *block, int ip)
 280 {
 281    if (*cur) {
 282       assert((*cur)->end->next == block->start);
 283       (*cur)->end_ip = ip - 1;
 284    }
 285
 286    block->start_ip = ip;
 287    block->block_num = num_blocks++;
 288    block_list.push_tail(link(mem_ctx, block));
 289    *cur = block;
 290 }
 291
 292 void
 293 cfg_t::make_block_array()
 294 {
 295    blocks = ralloc_array(mem_ctx, bblock_t *, num_blocks);
 296
 297    int i = 0;
 298    foreach_list_typed(bblock_link, link, link, &block_list) {
 299       blocks[i++] = link->block;
 300    }
 301    assert(i == num_blocks);
 302 }
 303
 304 void
 305 cfg_t::dump(backend_visitor *v)
 306 {
 307    for (int b = 0; b < this->num_blocks; b++) {
 308         bblock_t *block = this->blocks[b];
 309       fprintf(stderr, "START B%d", b);
 310       foreach_list_typed(bblock_link, link, link, &block->parents) {
 311          fprintf(stderr, " <-B%d",
 312                  link->block->block_num);
 313       }
 314       fprintf(stderr, "\n");
 315       block->dump(v);
 316       fprintf(stderr, "END B%d", b);
 317       foreach_list_typed(bblock_link, link, link, &block->children) {
 318          fprintf(stderr, " ->B%d",
 319                  link->block->block_num);
 320       }
 321       fprintf(stderr, "\n");
 322    }
 323 }