https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85829
--- Comment #5 from Sebastian Peryt <sebastian.peryt at intel dot com> --- I have made measurements on HSW comparing -mtune-ctrl=movx,partial_reg_dependency -Ofast -march=haswell to -Ofast -mtune=haswell and I see improvements on EEMBC benchmarks. automotive ========= aifftr01 (default) - goodperf: Runtime improvement of 2.6% (time). aiifft01 (default) - goodperf: Runtime improvement of 2.2% (time). networking ========= ip_pktcheckb1m (default) - goodperf: Runtime improvement of 3.8% (time). ip_pktcheckb2m (default) - goodperf: Runtime improvement of 5.2% (time). ip_pktcheckb4m (default) - goodperf: Runtime improvement of 4.4% (time). ip_pktcheckb512k (default) - goodperf: Runtime improvement of 4.2% (time). telecom ========= fft00data_1 (default) - goodperf: Runtime improvement of 8.4% (time). fft00data_2 (default) - goodperf: Runtime improvement of 8.6% (time). fft00data_3 (default) - goodperf: Runtime improvement of 9.0% (time). --- Comment #6 from hjl at gcc dot gnu.org <hjl at gcc dot gnu.org> --- Author: hjl Date: Thu May 31 15:02:36 2018 New Revision: 261026 URL: https://gcc.gnu.org/viewcvs?rev=261026&root=gcc&view=rev Log: x86: Re-enable partial_reg_dependency and movx for Haswell r254152 disabled partial_reg_dependency and movx for Haswell and newer Intel processors. r258972 restored them for skylake-avx512. For Haswell, movx improves performance. But partial_reg_stall may be better than partial_reg_dependency in theory. We will investigate performance impact of partial_reg_stall vs partial_reg_dependency on Haswell for GCC 9. In the meantime, this patch restores both partial_reg_dependency and mox for Haswell in GCC 8. On Haswell, improvements for EEMBC benchmarks with -mtune-ctrl=movx,partial_reg_dependency -Ofast -march=haswell vs -Ofast -mtune=haswell are automotive ========= aifftr01 (default) - goodperf: Runtime improvement of 2.6% (time). aiifft01 (default) - goodperf: Runtime improvement of 2.2% (time). networking ========= ip_pktcheckb1m (default) - goodperf: Runtime improvement of 3.8% (time). ip_pktcheckb2m (default) - goodperf: Runtime improvement of 5.2% (time). ip_pktcheckb4m (default) - goodperf: Runtime improvement of 4.4% (time). ip_pktcheckb512k (default) - goodperf: Runtime improvement of 4.2% (time). telecom ========= fft00data_1 (default) - goodperf: Runtime improvement of 8.4% (time). fft00data_2 (default) - goodperf: Runtime improvement of 8.6% (time). fft00data_3 (default) - goodperf: Runtime improvement of 9.0% (time). PR target/85829 * config/i386/x86-tune.def: Re-enable partial_reg_dependency and movx for Haswell. Modified: branches/gcc-8-branch/gcc/ChangeLog branches/gcc-8-branch/gcc/config/i386/x86-tune.def
