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Re: [PATCH] subreg: Add -fsplit-wide-types-early (PR88233)


On Mon, Jul 08, 2019 at 01:27:25PM +0200, Richard Biener wrote:
> On Sun, Jul 7, 2019 at 7:12 PM Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
> >
> > Currently the second lower-subreg pass is run right before RA.  This
> > is much too late to be very useful.  At least for targets that do not
> > have RTL patterns for operations on multi-register modes it is a lot
> > better to split patterns earlier, before combine and all related
> > passes.
> >
> > This adds an option -fsplit-wide-types-early that does that, and
> > enables it by default for rs6000.
> 
> Do you by chance have a (target specific) testcase you can add?

I haven't yet figured out how to do a not terribly fragile test for this.
Hrm, maybe the thing in the PR with -mcpu=power8 will do.  I'll work on
that.

> The docs should mention that the new option doesn't have any effect
> unless -fsplit-wide-types is enabled.

Yeah I'll make that more explicit.  Thanks,


Segher


> > 2019-07-07  Segher Boessenkool  <segher@kernel.crashing.org>
> >
> >         PR rtl-optimization/88233
> >         * common.opt (fsplit-wide-types-early): New option.
> >         * common/config/rs6000/rs6000-common.c
> >         (rs6000_option_optimization_table): Add OPT_fsplit_wide_types_early for
> >         OPT_LEVELS_ALL.
> >         * doc/invoke.texi (Optimization Options): Add -fsplit-wide-types-early.
> >         * lower-subreg.c (pass_lower_subreg2::gate): Add test for
> >         flag_split_wide_types_early.
> >         (pass_data_lower_subreg3): New.
> >         (pass_lower_subreg3): New.
> >         (make_pass_lower_subreg3): New.
> >         * passes.def (pass_lower_subreg2): Move after the loop passes.
> >         (pass_lower_subreg3): New, inserted where pass_lower_subreg2 was.
> >         * tree-pass.h (make_pass_lower_subreg2): Move up, to its new place in
> >         the pass pipeline; its previous place is taken by ...
> >         (make_pass_lower_subreg3): ... this.


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