On Sun, Jul 7, 2019 at 7:12 PM Segher Boessenkool
<seg...@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?
The docs should mention that the new option doesn't have any effect
unless -fsplit-wide-types is enabled.
Otherwise OK.
Richard.
>
> 2019-07-07 Segher Boessenkool <seg...@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.
>
> ---
> gcc/common.opt | 4 +++
> gcc/common/config/rs6000/rs6000-common.c | 2 ++
> gcc/doc/invoke.texi | 8 +++++-
> gcc/lower-subreg.c | 46
> +++++++++++++++++++++++++++++++-
> gcc/passes.def | 3 ++-
> gcc/tree-pass.h | 3 ++-
> 6 files changed, 62 insertions(+), 4 deletions(-)
>
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 41514df..b998b25 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -2430,6 +2430,10 @@ fsplit-wide-types
> Common Report Var(flag_split_wide_types) Optimization
> Split wide types into independent registers.
>
> +fsplit-wide-types-early
> +Common Report Var(flag_split_wide_types_early) Optimization
> +Split wide types into independent registers earlier.
> +
> fssa-backprop
> Common Report Var(flag_ssa_backprop) Init(1) Optimization
> Enable backward propagation of use properties at the SSA level.
> diff --git a/gcc/common/config/rs6000/rs6000-common.c
> b/gcc/common/config/rs6000/rs6000-common.c
> index 9857b54..4b0c205 100644
> --- a/gcc/common/config/rs6000/rs6000-common.c
> +++ b/gcc/common/config/rs6000/rs6000-common.c
> @@ -31,6 +31,8 @@
> /* Implement TARGET_OPTION_OPTIMIZATION_TABLE. */
> static const struct default_options rs6000_option_optimization_table[] =
> {
> + /* Split multi-word types early. */
> + { OPT_LEVELS_ALL, OPT_fsplit_wide_types_early, NULL, 1 },
> /* Enable -fsched-pressure for first pass instruction scheduling. */
> { OPT_LEVELS_1_PLUS, OPT_fsched_pressure, NULL, 1 },
> { OPT_LEVELS_NONE, 0, NULL, 0 }
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 73d16b5..6349d4c 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -467,7 +467,7 @@ Objective-C and Objective-C++ Dialects}.
> -fsignaling-nans @gol
> -fsingle-precision-constant -fsplit-ivs-in-unroller -fsplit-loops@gol
> -fsplit-paths @gol
> --fsplit-wide-types -fssa-backprop -fssa-phiopt @gol
> +-fsplit-wide-types -fsplit-wide-types-early -fssa-backprop -fssa-phiopt
> @gol
> -fstdarg-opt -fstore-merging -fstrict-aliasing @gol
> -fthread-jumps -ftracer -ftree-bit-ccp @gol
> -ftree-builtin-call-dce -ftree-ccp -ftree-ch @gol
> @@ -8731,6 +8731,12 @@ but may make debugging more difficult.
> Enabled at levels @option{-O}, @option{-O2}, @option{-O3},
> @option{-Os}.
>
> +@item -fsplit-wide-types-early
> +@opindex fsplit-wide-types-early
> +Fully split wide types early, instead of very late.
> +
> +This is the default on some targets.
> +
> @item -fcse-follow-jumps
> @opindex fcse-follow-jumps
> In common subexpression elimination (CSE), scan through jump instructions
> diff --git a/gcc/lower-subreg.c b/gcc/lower-subreg.c
> index 4f68a73..e1418e5 100644
> --- a/gcc/lower-subreg.c
> +++ b/gcc/lower-subreg.c
> @@ -1801,7 +1801,8 @@ public:
> {}
>
> /* opt_pass methods: */
> - virtual bool gate (function *) { return flag_split_wide_types != 0; }
> + virtual bool gate (function *) { return flag_split_wide_types
> + && flag_split_wide_types_early; }
> virtual unsigned int execute (function *)
> {
> decompose_multiword_subregs (true);
> @@ -1817,3 +1818,46 @@ make_pass_lower_subreg2 (gcc::context *ctxt)
> {
> return new pass_lower_subreg2 (ctxt);
> }
> +
> +/* Implement third lower subreg pass. */
> +
> +namespace {
> +
> +const pass_data pass_data_lower_subreg3 =
> +{
> + RTL_PASS, /* type */
> + "subreg3", /* name */
> + OPTGROUP_NONE, /* optinfo_flags */
> + TV_LOWER_SUBREG, /* tv_id */
> + 0, /* properties_required */
> + 0, /* properties_provided */
> + 0, /* properties_destroyed */
> + 0, /* todo_flags_start */
> + TODO_df_finish, /* todo_flags_finish */
> +};
> +
> +class pass_lower_subreg3 : public rtl_opt_pass
> +{
> +public:
> + pass_lower_subreg3 (gcc::context *ctxt)
> + : rtl_opt_pass (pass_data_lower_subreg3, ctxt)
> + {}
> +
> + /* opt_pass methods: */
> + virtual bool gate (function *) { return flag_split_wide_types
> + && !flag_split_wide_types_early; }
> + virtual unsigned int execute (function *)
> + {
> + decompose_multiword_subregs (true);
> + return 0;
> + }
> +
> +}; // class pass_lower_subreg3
> +
> +} // anon namespace
> +
> +rtl_opt_pass *
> +make_pass_lower_subreg3 (gcc::context *ctxt)
> +{
> + return new pass_lower_subreg3 (ctxt);
> +}
> diff --git a/gcc/passes.def b/gcc/passes.def
> index 9a5b0cd..1a7fd14 100644
> --- a/gcc/passes.def
> +++ b/gcc/passes.def
> @@ -427,6 +427,7 @@ along with GCC; see the file COPYING3. If not see
> NEXT_PASS (pass_rtl_doloop);
> NEXT_PASS (pass_rtl_loop_done);
> POP_INSERT_PASSES ()
> + NEXT_PASS (pass_lower_subreg2);
> NEXT_PASS (pass_web);
> NEXT_PASS (pass_rtl_cprop);
> NEXT_PASS (pass_cse2);
> @@ -440,7 +441,7 @@ along with GCC; see the file COPYING3. If not see
> NEXT_PASS (pass_partition_blocks);
> NEXT_PASS (pass_outof_cfg_layout_mode);
> NEXT_PASS (pass_split_all_insns);
> - NEXT_PASS (pass_lower_subreg2);
> + NEXT_PASS (pass_lower_subreg3);
> NEXT_PASS (pass_df_initialize_no_opt);
> NEXT_PASS (pass_stack_ptr_mod);
> NEXT_PASS (pass_mode_switching);
> diff --git a/gcc/tree-pass.h b/gcc/tree-pass.h
> index b27dbdd..7b83293 100644
> --- a/gcc/tree-pass.h
> +++ b/gcc/tree-pass.h
> @@ -552,6 +552,7 @@ extern rtl_opt_pass *make_pass_rtl_unroll_loops
> (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_rtl_doloop (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_rtl_loop_done (gcc::context *ctxt);
>
> +extern rtl_opt_pass *make_pass_lower_subreg2 (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_web (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_cse2 (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_df_initialize_opt (gcc::context *ctxt);
> @@ -567,7 +568,7 @@ extern rtl_opt_pass *make_pass_partition_blocks
> (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_match_asm_constraints (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_split_all_insns (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_fast_rtl_byte_dce (gcc::context *ctxt);
> -extern rtl_opt_pass *make_pass_lower_subreg2 (gcc::context *ctxt);
> +extern rtl_opt_pass *make_pass_lower_subreg3 (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_mode_switching (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_sms (gcc::context *ctxt);
> extern rtl_opt_pass *make_pass_sched (gcc::context *ctxt);
> --
> 1.8.3.1
>
