From 7e6a6f3e619e7dfed244043a95082f2168a5c953 Mon Sep 17 00:00:00 2001 From: Matt Turner Date: Mon, 30 Nov 2015 09:25:19 -0800 Subject: [PATCH] i965: Do dead-code elimination in a single pass. The first pass marked dead instructions as opcode = NOP, and a second pass deleted those instructions so that the live ranges used in the first pass wouldn't change. But since we're walking the instructions in reverse order, we can just do everything in one pass. The only thing we have to do is walk the blocks in reverse as well. Reviewed-by: Francisco Jerez --- src/mesa/drivers/dri/i965/brw_cfg.h | 3 +++ .../dri/i965/brw_fs_dead_code_eliminate.cpp | 21 ++++++------------- .../dri/i965/brw_vec4_dead_code_eliminate.cpp | 21 +++++++------------ 3 files changed, 16 insertions(+), 29 deletions(-) diff --git a/src/mesa/drivers/dri/i965/brw_cfg.h b/src/mesa/drivers/dri/i965/brw_cfg.h index 69e39e8964d..405020b77e5 100644 --- a/src/mesa/drivers/dri/i965/brw_cfg.h +++ b/src/mesa/drivers/dri/i965/brw_cfg.h @@ -314,6 +314,9 @@ struct cfg_t { #define foreach_block_safe(__block, __cfg) \ foreach_list_typed_safe (bblock_t, __block, link, &(__cfg)->block_list) +#define foreach_block_reverse_safe(__block, __cfg) \ + foreach_list_typed_reverse_safe (bblock_t, __block, link, &(__cfg)->block_list) + #define foreach_inst_in_block(__type, __inst, __block) \ foreach_in_list(__type, __inst, &(__block)->instructions) diff --git a/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp index 6b4b60224b7..bd57e09fe0c 100644 --- a/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs_dead_code_eliminate.cpp @@ -45,13 +45,13 @@ fs_visitor::dead_code_eliminate() BITSET_WORD *live = ralloc_array(NULL, BITSET_WORD, BITSET_WORDS(num_vars)); BITSET_WORD *flag_live = ralloc_array(NULL, BITSET_WORD, 1); - foreach_block (block, cfg) { + foreach_block_reverse_safe(block, cfg) { memcpy(live, live_intervals->block_data[block->num].liveout, sizeof(BITSET_WORD) * BITSET_WORDS(num_vars)); memcpy(flag_live, live_intervals->block_data[block->num].flag_liveout, sizeof(BITSET_WORD)); - foreach_inst_in_block_reverse(fs_inst, inst, block) { + foreach_inst_in_block_reverse_safe(fs_inst, inst, block) { if (inst->dst.file == VGRF && !inst->has_side_effects()) { bool result_live = false; @@ -72,7 +72,6 @@ fs_visitor::dead_code_eliminate() inst->dst = fs_reg(retype(brw_null_reg(), inst->dst.type)); } else { inst->opcode = BRW_OPCODE_NOP; - continue; } } } @@ -81,7 +80,6 @@ fs_visitor::dead_code_eliminate() if (!BITSET_TEST(flag_live, inst->flag_subreg)) { inst->opcode = BRW_OPCODE_NOP; progress = true; - continue; } } @@ -93,7 +91,6 @@ fs_visitor::dead_code_eliminate() !inst->writes_accumulator) { inst->opcode = BRW_OPCODE_NOP; progress = true; - continue; } if (inst->dst.file == VGRF) { @@ -109,9 +106,10 @@ fs_visitor::dead_code_eliminate() BITSET_CLEAR(flag_live, inst->flag_subreg); } - /* Don't mark dead instructions' sources as live */ - if (inst->opcode == BRW_OPCODE_NOP) + if (inst->opcode == BRW_OPCODE_NOP) { + inst->remove(block); continue; + } for (int i = 0; i < inst->sources; i++) { if (inst->src[i].file == VGRF) { @@ -132,15 +130,8 @@ fs_visitor::dead_code_eliminate() ralloc_free(live); ralloc_free(flag_live); - if (progress) { - foreach_block_and_inst_safe (block, backend_instruction, inst, cfg) { - if (inst->opcode == BRW_OPCODE_NOP) { - inst->remove(block); - } - } - + if (progress) invalidate_live_intervals(); - } return progress; } diff --git a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp index 369941bb71e..2d0722aa1eb 100644 --- a/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp +++ b/src/mesa/drivers/dri/i965/brw_vec4_dead_code_eliminate.cpp @@ -71,13 +71,13 @@ vec4_visitor::dead_code_eliminate() BITSET_WORD *live = ralloc_array(NULL, BITSET_WORD, BITSET_WORDS(num_vars)); BITSET_WORD *flag_live = ralloc_array(NULL, BITSET_WORD, 1); - foreach_block(block, cfg) { + foreach_block_reverse_safe(block, cfg) { memcpy(live, live_intervals->block_data[block->num].liveout, sizeof(BITSET_WORD) * BITSET_WORDS(num_vars)); memcpy(flag_live, live_intervals->block_data[block->num].flag_liveout, sizeof(BITSET_WORD)); - foreach_inst_in_block_reverse(vec4_instruction, inst, block) { + foreach_inst_in_block_reverse_safe(vec4_instruction, inst, block) { if ((inst->dst.file == VGRF && !inst->has_side_effects()) || (inst->dst.is_null() && inst->writes_flag())){ bool result_live[4] = { false }; @@ -115,7 +115,7 @@ vec4_visitor::dead_code_eliminate() inst->dst = dst_reg(retype(brw_null_reg(), inst->dst.type)); } else { inst->opcode = BRW_OPCODE_NOP; - continue; + break; } } } @@ -130,7 +130,6 @@ vec4_visitor::dead_code_eliminate() if (!combined_live) { inst->opcode = BRW_OPCODE_NOP; progress = true; - continue; } } @@ -150,9 +149,10 @@ vec4_visitor::dead_code_eliminate() BITSET_CLEAR(flag_live, c); } - /* Don't mark dead instructions' sources as live */ - if (inst->opcode == BRW_OPCODE_NOP) + if (inst->opcode == BRW_OPCODE_NOP) { + inst->remove(block); continue; + } for (int i = 0; i < 3; i++) { if (inst->src[i].file == VGRF) { @@ -176,15 +176,8 @@ vec4_visitor::dead_code_eliminate() ralloc_free(live); ralloc_free(flag_live); - if (progress) { - foreach_block_and_inst_safe(block, backend_instruction, inst, cfg) { - if (inst->opcode == BRW_OPCODE_NOP) { - inst->remove(block); - } - } - + if (progress) invalidate_live_intervals(); - } return progress; } -- 2.30.2