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?
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
