From 90430d04886227099253ed38de089aee0d713ec5 Mon Sep 17 00:00:00 2001 From: Ian Romanick Date: Sun, 9 Sep 2018 11:37:24 -0700 Subject: [PATCH] intel/fs: Eliminate dead code first MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This simplifies the later patch "i965/fs: Generate better code for fsign multiplied by a value". shader-db results: Broadwell and Skylake had similar results. (Skylake shown) total cycles in shared programs: 372808735 -> 372809551 (<.01%) cycles in affected programs: 1519520 -> 1520336 (0.05%) helped: 243 HURT: 277 helped stats (abs) min: 1 max: 226 x̄: 34.05 x̃: 5 helped stats (rel) min: 0.01% max: 13.88% x̄: 1.46% x̃: 0.27% HURT stats (abs) min: 1 max: 1810 x̄: 32.82 x̃: 5 HURT stats (rel) min: 0.01% max: 16.03% x̄: 1.56% x̃: 0.29% 95% mean confidence interval for cycles value: -7.18 10.32 95% mean confidence interval for cycles %-change: -0.17% 0.46% Inconclusive result (value mean confidence interval includes 0). Sandy Bridge, Haswell and Ivy Bridge had similar results. (Sandy Bridge shown) total cycles in shared programs: 155091458 -> 155091109 (<.01%) cycles in affected programs: 370797 -> 370448 (-0.09%) helped: 24 HURT: 36 helped stats (abs) min: 1 max: 331 x̄: 103.17 x̃: 41 helped stats (rel) min: 0.02% max: 7.70% x̄: 2.07% x̃: 0.56% HURT stats (abs) min: 1 max: 291 x̄: 59.08 x̃: 10 HURT stats (rel) min: 0.02% max: 5.29% x̄: 1.02% x̃: 0.15% 95% mean confidence interval for cycles value: -37.92 26.28 95% mean confidence interval for cycles %-change: -0.88% 0.45% Inconclusive result (value mean confidence interval includes 0). Iron Lake and GM45 had similar results. (GM45 shown) total cycles in shared programs: 129133970 -> 129133978 (<.01%) cycles in affected programs: 111966 -> 111974 (<.01%) helped: 3 HURT: 1 helped stats (abs) min: 2 max: 4 x̄: 2.67 x̃: 2 helped stats (rel) min: <.01% max: <.01% x̄: <.01% x̃: <.01% HURT stats (abs) min: 16 max: 16 x̄: 16.00 x̃: 16 HURT stats (rel) min: 0.07% max: 0.07% x̄: 0.07% x̃: 0.07% 95% mean confidence interval for cycles value: -12.93 16.93 95% mean confidence interval for cycles %-change: -0.05% 0.08% Inconclusive result (value mean confidence interval includes 0). Reviewed-by: Matt Turner --- src/intel/compiler/brw_fs.cpp | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp index ac01d137ce1..0a390e54354 100644 --- a/src/intel/compiler/brw_fs.cpp +++ b/src/intel/compiler/brw_fs.cpp @@ -6956,6 +6956,14 @@ fs_visitor::optimize() int iteration = 0; int pass_num = 0; + /* Before anything else, eliminate dead code. The results of some NIR + * instructions may effectively be calculated twice. Once when the + * instruction is encountered, and again when the user of that result is + * encountered. Wipe those away before algebraic optimizations and + * especially copy propagation can mix things up. + */ + OPT(dead_code_eliminate); + OPT(remove_extra_rounding_modes); do { -- 2.30.2