From 9e3cab8881626edd72d222f35c5d2a5fd9661bce Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Fri, 14 Feb 2014 15:29:01 -0800 Subject: [PATCH] i965/fs: Add an optimization pass to remove redundant flags movs. We generate steaming piles of these for the centroid workaround, and this quickly cleans them up. total instructions in shared programs: 1591228 -> 1590047 (-0.07%) instructions in affected programs: 26111 -> 24930 (-4.52%) GAINED: 0 LOST: 0 (Improved apps are l4d2, csgo, and dolphin) Reviewed-by: Matt Turner --- src/mesa/drivers/dri/i965/brw_fs.cpp | 33 ++++++++++++++++++++++++++++ src/mesa/drivers/dri/i965/brw_fs.h | 1 + 2 files changed, 34 insertions(+) diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp index 0fd9e908f58..65f2c808626 100644 --- a/src/mesa/drivers/dri/i965/brw_fs.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp @@ -3304,6 +3304,37 @@ fs_visitor::calculate_register_pressure() } } +/** + * Look for repeated FS_OPCODE_MOV_DISPATCH_TO_FLAGS and drop the later ones. + * + * The needs_unlit_centroid_workaround ends up producing one of these per + * channel of centroid input, so it's good to clean them up. + * + * An assumption here is that nothing ever modifies the dispatched pixels + * value that FS_OPCODE_MOV_DISPATCH_TO_FLAGS reads from, but the hardware + * dictates that anyway. + */ +void +fs_visitor::opt_drop_redundant_mov_to_flags() +{ + bool flag_mov_found[2] = {false}; + + foreach_list_safe(node, &this->instructions) { + fs_inst *inst = (fs_inst *)node; + + if (inst->is_control_flow()) { + memset(flag_mov_found, 0, sizeof(flag_mov_found)); + } else if (inst->opcode == FS_OPCODE_MOV_DISPATCH_TO_FLAGS) { + if (!flag_mov_found[inst->flag_subreg]) + flag_mov_found[inst->flag_subreg] = true; + else + inst->remove(); + } else if (inst->writes_flag()) { + flag_mov_found[inst->flag_subreg] = false; + } + } +} + bool fs_visitor::run() { @@ -3369,6 +3400,8 @@ fs_visitor::run() remove_dead_constants(); setup_pull_constants(); + opt_drop_redundant_mov_to_flags(); + bool progress; do { progress = false; diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h index 8a596bcaa0e..5058c48bdc8 100644 --- a/src/mesa/drivers/dri/i965/brw_fs.h +++ b/src/mesa/drivers/dri/i965/brw_fs.h @@ -367,6 +367,7 @@ public: bool try_constant_propagate(fs_inst *inst, acp_entry *entry); bool opt_copy_propagate_local(void *mem_ctx, bblock_t *block, exec_list *acp); + void opt_drop_redundant_mov_to_flags(); bool register_coalesce(); bool compute_to_mrf(); bool dead_code_eliminate(); -- 2.30.2