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_vec4.h" 25 #include "brw_vec4_live_variables.h" 26 #include "brw_cfg.h" 27 28 /** @file brw_vec4_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 using namespace brw; 38 39 bool 40 vec4_visitor::dead_code_eliminate() 41 { 42 bool progress = false; 43 44 calculate_live_intervals(); 45 46 int num_vars = live_intervals->num_vars; 47 BITSET_WORD *live = rzalloc_array(NULL, BITSET_WORD, BITSET_WORDS(num_vars)); 48 BITSET_WORD *flag_live = rzalloc_array(NULL, BITSET_WORD, 1); 49 50 foreach_block_reverse_safe(block, cfg) { 51 memcpy(live, live_intervals->block_data[block->num].liveout, 52 sizeof(BITSET_WORD) * BITSET_WORDS(num_vars)); 53 memcpy(flag_live, live_intervals->block_data[block->num].flag_liveout, 54 sizeof(BITSET_WORD)); 55 56 foreach_inst_in_block_reverse_safe(vec4_instruction, inst, block) { 57 if ((inst->dst.file == VGRF && !inst->has_side_effects()) || 58 (inst->dst.is_null() && inst->writes_flag())){ 59 bool result_live[4] = { false }; 60 if (inst->dst.file == VGRF) { 61 for (unsigned i = 0; i < DIV_ROUND_UP(inst->size_written, 16); i++) { 62 for (int c = 0; c < 4; c++) { 63 const unsigned v = var_from_reg(alloc, inst->dst, c, i); 64 result_live[c] |= BITSET_TEST(live, v); 65 } 66 } 67 } else { 68 for (unsigned c = 0; c < 4; c++) 69 result_live[c] = BITSET_TEST(flag_live, c); 70 } 71 72 /* If the instruction can't do writemasking, then it's all or 73 * nothing. 74 */ 75 if (!inst->can_do_writemask(devinfo)) { 76 bool result = result_live[0] | result_live[1] | 77 result_live[2] | result_live[3]; 78 result_live[0] = result; 79 result_live[1] = result; 80 result_live[2] = result; 81 result_live[3] = result; 82 } 83 84 for (int c = 0; c < 4; c++) { 85 if (!result_live[c] && inst->dst.writemask & (1 << c)) { 86 inst->dst.writemask &= ~(1 << c); 87 progress = true; 88 89 if (inst->dst.writemask == 0) { 90 if (inst->writes_accumulator || inst->writes_flag()) { 91 inst->dst = dst_reg(retype(brw_null_reg(), inst->dst.type)); 92 } else { 93 inst->opcode = BRW_OPCODE_NOP; 94 break; 95 } 96 } 97 } 98 } 99 } 100 101 if (inst->dst.is_null() && inst->writes_flag()) { 102 bool combined_live = false; 103 for (unsigned c = 0; c < 4; c++) 104 combined_live |= BITSET_TEST(flag_live, c); 105 106 if (!combined_live) { 107 inst->opcode = BRW_OPCODE_NOP; 108 progress = true; 109 } 110 } 111 112 if (inst->dst.file == VGRF && !inst->predicate && 113 !inst->is_align1_partial_write()) { 114 for (unsigned i = 0; i < DIV_ROUND_UP(inst->size_written, 16); i++) { 115 for (int c = 0; c < 4; c++) { 116 if (inst->dst.writemask & (1 << c)) { 117 const unsigned v = var_from_reg(alloc, inst->dst, c, i); 118 BITSET_CLEAR(live, v); 119 } 120 } 121 } 122 } 123 124 if (inst->writes_flag() && !inst->predicate) { 125 for (unsigned c = 0; c < 4; c++) 126 BITSET_CLEAR(flag_live, c); 127 } 128 129 if (inst->opcode == BRW_OPCODE_NOP) { 130 inst->remove(block); 131 continue; 132 } 133 134 for (int i = 0; i < 3; i++) { 135 if (inst->src[i].file == VGRF) { 136 for (unsigned j = 0; j < DIV_ROUND_UP(inst->size_read(i), 16); j++) { 137 for (int c = 0; c < 4; c++) { 138 const unsigned v = var_from_reg(alloc, inst->src[i], c, j); 139 BITSET_SET(live, v); 140 } 141 } 142 } 143 } 144 145 for (unsigned c = 0; c < 4; c++) { 146 if (inst->reads_flag(c)) { 147 BITSET_SET(flag_live, c); 148 } 149 } 150 } 151 } 152 153 ralloc_free(live); 154 ralloc_free(flag_live); 155 156 if (progress) 157 invalidate_live_intervals(); 158 159 return progress; 160 } 161
