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->remove();
  42
  43    return block;
  44 }
  45
  46 bblock_t::bblock_t() :
  47    start_ip(0), end_ip(0), block_num(0)
  48 {
  49    start = NULL;
  50    end = NULL;
  51
  52    parents.make_empty();
  53    children.make_empty();
  54
  55    if_inst = NULL;
  56    else_inst = NULL;
  57    endif_inst = NULL;
  58 }
  59
  60 void
  61 bblock_t::add_successor(void *mem_ctx, bblock_t *successor)
  62 {
  63    successor->parents.push_tail(new(mem_ctx) bblock_link(this));
  64    children.push_tail(new(mem_ctx) bblock_link(successor));
  65 }
  66
  67 void
  68 bblock_t::dump(backend_visitor *v)
  69 {
  70    int ip = this->start_ip;
  71    for (backend_instruction *inst = (backend_instruction *)this->start;
  72         inst != this->end->next;
  73         inst = (backend_instruction *) inst->next) {
  74       fprintf(stderr, "%5d: ", ip);
  75       v->dump_instruction(inst);
  76       ip++;
  77    }
  78 }
  79
  80 cfg_t::cfg_t(exec_list *instructions)
  81 {
  82    mem_ctx = ralloc_context(NULL);
  83    block_list.make_empty();
  84    blocks = NULL;
  85    num_blocks = 0;
  86
  87    bblock_t *cur = NULL;
  88    int ip = 0;
  89
  90    bblock_t *entry = new_block();
  91    bblock_t *cur_if = NULL;    /**< BB ending with IF. */
  92    bblock_t *cur_else = NULL;  /**< BB ending with ELSE. */
  93    bblock_t *cur_endif = NULL; /**< BB starting with ENDIF. */
  94    bblock_t *cur_do = NULL;    /**< BB ending with DO. */
  95    bblock_t *cur_while = NULL; /**< BB immediately following WHILE. */
  96    exec_list if_stack, else_stack, do_stack, while_stack;
  97    bblock_t *next;
  98
  99    set_next_block(&cur, entry, ip);
 100
 101    entry->start = (backend_instruction *) instructions->get_head();
 102
 103    foreach_list(node, instructions) {
 104       backend_instruction *inst = (backend_instruction *)node;
 105
 106       cur->end = inst;
 107
 108       /* set_next_block wants the post-incremented ip */
 109       ip++;
 110
 111       switch (inst->opcode) {
 112       case BRW_OPCODE_IF:
 113          /* Push our information onto a stack so we can recover from
 114           * nested ifs.
 115           */
 116          if_stack.push_tail(new(mem_ctx) bblock_link(cur_if));
 117          else_stack.push_tail(new(mem_ctx) bblock_link(cur_else));
 118
 119          cur_if = cur;
 120          cur_else = NULL;
 121          cur_endif = NULL;
 122
 123          /* Set up our immediately following block, full of "then"
 124           * instructions.
 125           */
 126          next = new_block();
 127          next->start = (backend_instruction *)inst->next;
 128          cur_if->add_successor(mem_ctx, next);
 129
 130          set_next_block(&cur, next, ip);
 131          break;
 132
 133       case BRW_OPCODE_ELSE:
 134          cur_else = cur;
 135
 136          next = new_block();
 137          next->start = (backend_instruction *)inst->next;
 138          cur_if->add_successor(mem_ctx, next);
 139
 140          set_next_block(&cur, next, ip);
 141          break;
 142
 143       case BRW_OPCODE_ENDIF: {
 144          if (cur->start == inst) {
 145             /* New block was just created; use it. */
 146             cur_endif = cur;
 147          } else {
 148             cur_endif = new_block();
 149             cur_endif->start = inst;
 150
 151             cur->end = (backend_instruction *)inst->prev;
 152             cur->add_successor(mem_ctx, cur_endif);
 153
 154             set_next_block(&cur, cur_endif, ip - 1);
 155          }
 156
 157          backend_instruction *else_inst = NULL;
 158          if (cur_else) {
 159             else_inst = (backend_instruction *)cur_else->end;
 160
 161             cur_else->add_successor(mem_ctx, cur_endif);
 162          } else {
 163             cur_if->add_successor(mem_ctx, cur_endif);
 164          }
 165
 166          assert(cur_if->end->opcode == BRW_OPCODE_IF);
 167          assert(!else_inst || else_inst->opcode == BRW_OPCODE_ELSE);
 168          assert(inst->opcode == BRW_OPCODE_ENDIF);
 169
 170          cur_if->if_inst = cur_if->end;
 171          cur_if->else_inst = else_inst;
 172          cur_if->endif_inst = inst;
 173
 174          if (cur_else) {
 175             cur_else->if_inst = cur_if->end;
 176             cur_else->else_inst = else_inst;
 177             cur_else->endif_inst = inst;
 178          }
 179
 180          cur->if_inst = cur_if->end;
 181          cur->else_inst = else_inst;
 182          cur->endif_inst = inst;
 183
 184          /* Pop the stack so we're in the previous if/else/endif */
 185          cur_if = pop_stack(&if_stack);
 186          cur_else = pop_stack(&else_stack);
 187          break;
 188       }
 189       case BRW_OPCODE_DO:
 190          /* Push our information onto a stack so we can recover from
 191           * nested loops.
 192           */
 193          do_stack.push_tail(new(mem_ctx) bblock_link(cur_do));
 194          while_stack.push_tail(new(mem_ctx) bblock_link(cur_while));
 195
 196          /* Set up the block just after the while.  Don't know when exactly
 197           * it will start, yet.
 198           */
 199          cur_while = new_block();
 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->add_successor(mem_ctx, next);
 207          cur_do = next;
 208
 209          set_next_block(&cur, next, ip);
 210          break;
 211
 212       case BRW_OPCODE_CONTINUE:
 213          cur->add_successor(mem_ctx, cur_do);
 214
 215          next = new_block();
 216          next->start = (backend_instruction *)inst->next;
 217          if (inst->predicate)
 218             cur->add_successor(mem_ctx, next);
 219
 220          set_next_block(&cur, next, ip);
 221          break;
 222
 223       case BRW_OPCODE_BREAK:
 224          cur->add_successor(mem_ctx, cur_while);
 225
 226          next = new_block();
 227          next->start = (backend_instruction *)inst->next;
 228          if (inst->predicate)
 229             cur->add_successor(mem_ctx, next);
 230
 231          set_next_block(&cur, next, ip);
 232          break;
 233
 234       case BRW_OPCODE_WHILE:
 235          cur_while->start = (backend_instruction *)inst->next;
 236
 237          cur->add_successor(mem_ctx, cur_do);
 238          set_next_block(&cur, cur_while, ip);
 239
 240          /* Pop the stack so we're in the previous loop */
 241          cur_do = pop_stack(&do_stack);
 242          cur_while = pop_stack(&while_stack);
 243          break;
 244
 245       default:
 246          break;
 247       }
 248    }
 249
 250    cur->end_ip = ip;
 251
 252    make_block_array();
 253 }
 254
 255 cfg_t::~cfg_t()
 256 {
 257    ralloc_free(mem_ctx);
 258 }
 259
 260 bblock_t *
 261 cfg_t::new_block()
 262 {
 263    bblock_t *block = new(mem_ctx) bblock_t();
 264
 265    return block;
 266 }
 267
 268 void
 269 cfg_t::set_next_block(bblock_t **cur, bblock_t *block, int ip)
 270 {
 271    if (*cur) {
 272       assert((*cur)->end->next == block->start);
 273       (*cur)->end_ip = ip - 1;
 274    }
 275
 276    block->start_ip = ip;
 277    block->block_num = num_blocks++;
 278    block_list.push_tail(new(mem_ctx) bblock_link(block));
 279    *cur = block;
 280 }
 281
 282 void
 283 cfg_t::make_block_array()
 284 {
 285    blocks = ralloc_array(mem_ctx, bblock_t *, num_blocks);
 286
 287    int i = 0;
 288    foreach_list(block_node, &block_list) {
 289       bblock_link *link = (bblock_link *)block_node;
 290       blocks[i++] = link->block;
 291    }
 292    assert(i == num_blocks);
 293 }
 294
 295 void
 296 cfg_t::dump(backend_visitor *v)
 297 {
 298    for (int b = 0; b < this->num_blocks; b++) {
 299         bblock_t *block = this->blocks[b];
 300       fprintf(stderr, "START B%d", b);
 301       foreach_list(node, &block->parents) {
 302          bblock_link *link = (bblock_link *)node;
 303          fprintf(stderr, " <-B%d",
 304                  link->block->block_num);
 305       }
 306       fprintf(stderr, "\n");
 307       block->dump(v);
 308       fprintf(stderr, "END B%d", b);
 309       foreach_list(node, &block->children) {
 310          bblock_link *link = (bblock_link *)node;
 311          fprintf(stderr, " ->B%d",
 312                  link->block->block_num);
 313       }
 314       fprintf(stderr, "\n");
 315    }
 316 }