Subversion Repositories Kolibri OS

Rev

Blame | Last modification | View Log | RSS feed

  1. /*
  2.  * Copyright © 2014 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.  
  24. #include "brw_fs.h"
  25. #include "brw_fs_live_variables.h"
  26. #include "brw_cfg.h"
  27.  
  28. /** @file brw_fs_dead_code_eliminate.cpp
  29.  *
  30.  * Dataflow-aware dead code elimination.
  31.  *
  32.  * Walks the instruction list from the bottom, removing instructions that
  33.  * have results that both aren't used in later blocks and haven't been read
  34.  * yet in the tail end of this block.
  35.  */
  36.  
  37. bool
  38. fs_visitor::dead_code_eliminate()
  39. {
  40.    bool progress = false;
  41.  
  42.    calculate_live_intervals();
  43.  
  44.    int num_vars = live_intervals->num_vars;
  45.    BITSET_WORD *live = ralloc_array(NULL, BITSET_WORD, BITSET_WORDS(num_vars));
  46.    BITSET_WORD *flag_live = ralloc_array(NULL, BITSET_WORD, 1);
  47.  
  48.    foreach_block (block, cfg) {
  49.       memcpy(live, live_intervals->block_data[block->num].liveout,
  50.              sizeof(BITSET_WORD) * BITSET_WORDS(num_vars));
  51.       memcpy(flag_live, live_intervals->block_data[block->num].flag_liveout,
  52.              sizeof(BITSET_WORD));
  53.  
  54.       foreach_inst_in_block_reverse(fs_inst, inst, block) {
  55.          if (inst->dst.file == GRF && !inst->has_side_effects()) {
  56.             bool result_live = false;
  57.  
  58.             if (inst->regs_written == 1) {
  59.                int var = live_intervals->var_from_reg(inst->dst);
  60.                result_live = BITSET_TEST(live, var);
  61.             } else {
  62.                int var = live_intervals->var_from_reg(inst->dst);
  63.                for (int i = 0; i < inst->regs_written; i++) {
  64.                   result_live = result_live || BITSET_TEST(live, var + i);
  65.                }
  66.             }
  67.  
  68.             if (!result_live) {
  69.                progress = true;
  70.  
  71.                if (inst->writes_accumulator || inst->writes_flag()) {
  72.                   inst->dst = fs_reg(retype(brw_null_reg(), inst->dst.type));
  73.                } else {
  74.                   inst->opcode = BRW_OPCODE_NOP;
  75.                   continue;
  76.                }
  77.             }
  78.          }
  79.  
  80.          if (inst->dst.is_null() && inst->writes_flag()) {
  81.             if (!BITSET_TEST(flag_live, inst->flag_subreg)) {
  82.                inst->opcode = BRW_OPCODE_NOP;
  83.                progress = true;
  84.                continue;
  85.             }
  86.          }
  87.  
  88.          if ((inst->opcode != BRW_OPCODE_IF &&
  89.               inst->opcode != BRW_OPCODE_WHILE) &&
  90.              inst->dst.is_null() &&
  91.              !inst->has_side_effects() &&
  92.              !inst->writes_flag() &&
  93.              !inst->writes_accumulator) {
  94.             inst->opcode = BRW_OPCODE_NOP;
  95.             progress = true;
  96.             continue;
  97.          }
  98.  
  99.          if (inst->dst.file == GRF) {
  100.             if (!inst->is_partial_write()) {
  101.                int var = live_intervals->var_from_reg(inst->dst);
  102.                for (int i = 0; i < inst->regs_written; i++) {
  103.                   BITSET_CLEAR(live, var + i);
  104.                }
  105.             }
  106.          }
  107.  
  108.          if (inst->writes_flag()) {
  109.             BITSET_CLEAR(flag_live, inst->flag_subreg);
  110.          }
  111.  
  112.          for (int i = 0; i < inst->sources; i++) {
  113.             if (inst->src[i].file == GRF) {
  114.                int var = live_intervals->var_from_reg(inst->src[i]);
  115.  
  116.                for (int j = 0; j < inst->regs_read(i); j++) {
  117.                   BITSET_SET(live, var + j);
  118.                }
  119.             }
  120.          }
  121.  
  122.          if (inst->reads_flag()) {
  123.             BITSET_SET(flag_live, inst->flag_subreg);
  124.          }
  125.       }
  126.    }
  127.  
  128.    ralloc_free(live);
  129.    ralloc_free(flag_live);
  130.  
  131.    if (progress) {
  132.       foreach_block_and_inst_safe (block, backend_instruction, inst, cfg) {
  133.          if (inst->opcode == BRW_OPCODE_NOP) {
  134.             inst->remove(block);
  135.          }
  136.       }
  137.  
  138.       invalidate_live_intervals();
  139.    }
  140.  
  141.    return progress;
  142. }
  143.