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.
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.
From-SVN: r273240
