From f2f8c43af92ad446a5c56bd0f88af36e1a3e0506 Mon Sep 17 00:00:00 2001 From: Matt Turner Date: Mon, 17 Aug 2015 16:03:27 -0700 Subject: [PATCH] i965/fs: Improve register coalescing interference check. I always thought that the is_control_flow() -> return false check was a bad hack, and some previous attempts to remove it have failed and have been reverted. The previous two patches fix some problems that caused register coalescing to not notice some interference between registers, which the is_control_flow() check apparently works around. With that fixed, we can calculate interference more accurately. total instructions in shared programs: 6261319 -> 6257917 (-0.05%) instructions in affected programs: 346282 -> 342880 (-0.98%) helped: 1552 Reviewed-by: Jason Ekstrand Reviewed-by: Kenneth Graunke --- .../drivers/dri/i965/brw_fs_register_coalesce.cpp | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp index 218cc61..452aee5 100644 --- a/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs_register_coalesce.cpp @@ -110,27 +110,30 @@ can_coalesce_vars(brw::fs_live_variables *live_intervals, (end_from > end_to && start_to < start_from)) return false; - int start_ip = MIN2(start_to, start_from); + /* Check for a write to either register in the intersection of their live + * ranges. + */ + int start_ip = MAX2(start_to, start_from); + int end_ip = MIN2(end_to, end_from); int scan_ip = -1; foreach_block_and_inst(block, fs_inst, scan_inst, cfg) { scan_ip++; + /* Ignore anything before the intersection of the live ranges */ if (scan_ip < start_ip) continue; - if (scan_inst->is_control_flow()) - return false; - - if (scan_ip <= live_intervals->start[var_to]) + /* Ignore the copying instruction itself */ + if (scan_inst == inst) continue; - if (scan_ip > live_intervals->end[var_to]) - return true; + if (scan_ip > end_ip) + return true; /* registers do not interfere */ if (scan_inst->overwrites_reg(inst->dst) || scan_inst->overwrites_reg(inst->src[0])) - return false; + return false; /* registers interfere */ } return true; -- 2.7.4