On Mon, 4 Nov 2019, Segher Boessenkool wrote: > Hi! > > On Mon, Nov 04, 2019 at 02:31:43PM +0800, Jiufu Guo wrote: > > In this patch, loop unroll adjust hook is introduced for powerpc. We can do > > target related hueristic adjustment in this hook. In this patch, small loops > > is unrolled 2 times for O2 and O3 by default. With this patch, we can see > > some improvement for spec2017. This patch enhanced a little for [Patch V2] > > to > > enable small loops unroll for O3 by default like O2. > > > * gcc/config/rs6000/rs6000.opt (unroll_small_loops): New internal flag. > > That's the declaration of a variable. A command line flag is something > like -munroll-small-loops. Do we want a command line option like that? > It makes testing simpler. > > > - /* unroll very small loops 2 time if no -funroll-loops. */ > > + /* If funroll-loops is not enabled explicitly, then enable small > > loops > > + unrolling for -O2, and do not turn fweb or frename-registers on. */ > > if (!global_options_set.x_flag_unroll_loops > > && !global_options_set.x_flag_unroll_all_loops) > > { > > - maybe_set_param_value (PARAM_MAX_UNROLL_TIMES, 2, > > - global_options.x_param_values, > > - global_options_set.x_param_values); > > - > > - maybe_set_param_value (PARAM_MAX_UNROLLED_INSNS, 20, > > - global_options.x_param_values, > > - global_options_set.x_param_values); > > + unroll_small_loops = optimize >= 2 ? 1 : 0; > > That includes -Os?
It also re-introduces the exactly same issue as the --param with LTO. > I think you shouldn't always set it to some value, only enable it where > you want to enable it. If you make a command line option for it this is > especially simple (the table in common/config/rs6000/rs6000-common.c). > > > +static unsigned > > +rs6000_loop_unroll_adjust (unsigned nunroll, struct loop * loop) > > +{ > > + if (unroll_small_loops) > > + { > > + /* TODO: This is hardcoded to 10 right now. It can be refined, for > > + example we may want to unroll very small loops more times (4 perhaps). > > + We also should use a PARAM for this. */ > > + if (loop->ninsns <= 10) > > + return MIN (2, nunroll); > > + else > > + return 0; > > + } > > (Add an empty line here?) > > > + return nunroll; > > +} > > Great :-) > > > @@ -23472,6 +23488,7 @@ rs6000_function_specific_save (struct > > cl_target_option *ptr, > > { > > ptr->x_rs6000_isa_flags = opts->x_rs6000_isa_flags; > > ptr->x_rs6000_isa_flags_explicit = opts->x_rs6000_isa_flags_explicit; > > + ptr->x_unroll_small_loops = opts->x_unroll_small_loops; > > } > > Yeah we shouldn't need to add that, this should all be automatic. > > > Segher > -- Richard Biener <rguent...@suse.de> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)