On Wed, Oct 29, 2014 at 1:10 PM, Matt Turner <matts...@gmail.com> wrote:
> Most prominently helps Natural Selection 2, which has a surprising
> number shaders that do very complicated things before drawing black.
>
> instructions in affected programs: 23824 -> 19570 (-17.86%)
> ---
> .../dri/i965/brw_fs_dead_code_eliminate.cpp | 23
> +++++++++++++++++++---
> 1 file changed, 20 insertions(+), 3 deletions(-)
>
> 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 9cf8d89..414c4a0 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
> @@ -43,15 +43,16 @@ fs_visitor::dead_code_eliminate()
>
> int num_vars = live_intervals->num_vars;
> 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) {
> 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) {
> - if (inst->dst.file == GRF &&
> - !inst->has_side_effects() &&
> - !inst->writes_flag()) {
> + if (inst->dst.file == GRF && !inst->has_side_effects()) {
> bool result_live = false;
>
> if (inst->regs_written == 1) {
> @@ -76,6 +77,13 @@ fs_visitor::dead_code_eliminate()
> }
> }
>
> + if (inst->dst.is_null() && inst->writes_flag()) {
> + if (!BITSET_TEST(flag_live, inst->flag_subreg)) {
> + inst->opcode = BRW_OPCODE_NOP;
progress = true;
> + continue;
> + }
> + }
> +
> if (inst->dst.file == GRF) {
> if (!inst->is_partial_write()) {
> int var = live_intervals->var_from_reg(&inst->dst);
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