Hi, Previously -fweb was disabled if only unroll small loops. After that we find there is cases where it could help to rename pseudos and aovid some anti-dependence which may occur after unroll.
Below is a patch to disable -fweb during loop unrolling. Bootstrap and regtest pass on powerpc, spec2017 run shows no performance downgrade. Is this ok for trunk? BR, Jiufu gcc/ 2020-04-20 Jiufu Guo <guoji...@cn.ibm.com> * common/config/rs6000/rs6000-common.c (rs6000_option_optimization_table)[OPT_LEVELS_ALL]: Remove turn off -fweb. * config/rs6000/rs6000.c (rs6000_option_override_internal): Avoid to set flag_web. --- gcc/common/config/rs6000/rs6000-common.c | 5 ++--- gcc/config/rs6000/rs6000.c | 4 +--- 2 files changed, 3 insertions(+), 6 deletions(-) diff --git a/gcc/common/config/rs6000/rs6000-common.c b/gcc/common/config/rs6000/rs6000-common.c index 4f38d566844..87f7fda940a 100644 --- a/gcc/common/config/rs6000/rs6000-common.c +++ b/gcc/common/config/rs6000/rs6000-common.c @@ -38,9 +38,8 @@ static const struct default_options rs6000_option_optimization_table[] = loops at -O2 and above by default. */ { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_funroll_loops, NULL, 1 }, { OPT_LEVELS_2_PLUS_SPEED_ONLY, OPT_munroll_only_small_loops, NULL, 1 }, - /* -fweb and -frename-registers are useless in general for rs6000, - turn them off. */ - { OPT_LEVELS_ALL, OPT_fweb, NULL, 0 }, + + /* -frename-registers is not very helpful for rs6000, turn it off. */ { OPT_LEVELS_ALL, OPT_frename_registers, NULL, 0 }, /* Double growth factor to counter reduced min jump length. */ diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c index a2992e682c8..6a9e701bd60 100644 --- a/gcc/config/rs6000/rs6000.c +++ b/gcc/config/rs6000/rs6000.c @@ -4543,7 +4543,7 @@ rs6000_option_override_internal (bool global_init_p) SCHED_PRESSURE_MODEL); /* Explicit -funroll-loops turns -munroll-only-small-loops off, and - turns -fweb and -frename-registers on. */ + turns -frename-registers on. */ if ((global_options_set.x_flag_unroll_loops && flag_unroll_loops) || (global_options_set.x_flag_unroll_all_loops && flag_unroll_all_loops)) @@ -4552,8 +4552,6 @@ rs6000_option_override_internal (bool global_init_p) unroll_only_small_loops = 0; if (!global_options_set.x_flag_rename_registers) flag_rename_registers = 1; - if (!global_options_set.x_flag_web) - flag_web = 1; } /* If using typedef char *va_list, signal that -- 2.17.1