On Mon, 5 Jul 2021, Richard Biener wrote:
> On Fri, 2 Jul 2021, Martin Sebor wrote:
>
> > On 7/2/21 5:55 AM, Richard Biener wrote:
> > > This adds the -fmove-loop-stores option, mainly as a way to disable
> > > the store-motion part of GIMPLE invariant motion (-ftree-loop-im)
> > > which is enabled by default. It might be sensible to turn off
> > > -fmove-loop-stores at -O1 since it can result in compile-time
> > > as well as memory usage issues but this patch tries to preserve
> > > existing behavior besides introducing the new option with the
> > > exception of -Og where I've disabled it.
> > >
> > > Controlling store-motion has been made easy by earlier refactoring
> > > for the invariant motion only use after loop interchange.
> > >
> > > Bootstrap and regtest running on x86_64-unknown-linux-gnu.
> > >
> > > OK?
> > >
> > > Thanks,
> > > Richard.
> > >
> > > 2021-07-02 Richard Biener <rguent...@suse.de>
> > >
> > > * doc/invoke.texi (fmove-loop-stores): Document.
> > > * common.opt (fmove-loop-stores): New option.
> > > * opts.c (default_options_table): Enable -fmove-loop-stores
> > > at -O1 but not -Og.
> > > * tree-ssa-loop-im.c (pass_lim::execute): Pass
> > > flag_move_loop_stores instead of true to
> > > loop_invariant_motion_in_fun.
> > > ---
> > > gcc/common.opt | 4 ++++
> > > gcc/doc/invoke.texi | 11 +++++++++--
> > > gcc/opts.c | 1 +
> > > gcc/tree-ssa-loop-im.c | 2 +-
> > > 4 files changed, 15 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/gcc/common.opt b/gcc/common.opt
> > > index 5b03bbc6662..d9da1131eda 100644
> > > --- a/gcc/common.opt
> > > +++ b/gcc/common.opt
> > > @@ -2084,6 +2084,10 @@ fmove-loop-invariants
> > > Common Var(flag_move_loop_invariants) Optimization
> > > Move loop invariant computations out of loops.
> > >
> > > +fmove-loop-stores
> > > +Common Var(flag_move_loop_stores) Optimization
> > > +Move stores out of loops.
> > > +
> > > fdce
> > > Common Var(flag_dce) Init(1) Optimization
> > > Use the RTL dead code elimination pass.
> > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > > index a9fd5fdc104..7b4f5d26738 100644
> > > --- a/gcc/doc/invoke.texi
> > > +++ b/gcc/doc/invoke.texi
> > > @@ -528,7 +528,7 @@ Objective-C and Objective-C++ Dialects}.
> > > -floop-parallelize-all -flra-remat -flto -flto-compression-level @gol
> > > -flto-partition=@var{alg} -fmerge-all-constants @gol
> > > -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves @gol
> > > --fmove-loop-invariants -fno-branch-count-reg @gol
> > > +-fmove-loop-invariants -fmove-loop-stores -fno-branch-count-reg @gol
> > > -fno-defer-pop -fno-fp-int-builtin-inexact -fno-function-cse @gol
> > > -fno-guess-branch-probability -fno-inline -fno-math-errno
> > > -fno-peephole
> > > @gol
> > > -fno-peephole2 -fno-printf-return-value -fno-sched-interblock @gol
> > > @@ -10260,6 +10260,7 @@ compilation time.
> > > -fipa-reference-addressable @gol
> > > -fmerge-constants @gol
> > > -fmove-loop-invariants @gol
> > > +-fmove-loop-stores@gol
> > > -fomit-frame-pointer @gol
> > > -freorder-blocks @gol
> > > -fshrink-wrap @gol
> > > @@ -10403,7 +10404,7 @@ optimization flags except for those that may
> > > interfere with debugging:
> > > @gccoptlist{-fbranch-count-reg -fdelayed-branch @gol
> > > -fdse -fif-conversion -fif-conversion2 @gol
> > > -finline-functions-called-once @gol
> > > --fmove-loop-invariants -fssa-phiopt @gol
> > > +-fmove-loop-invariants -fmove-loop-stores -fssa-phiopt @gol
> > > -ftree-bit-ccp -ftree-dse -ftree-pta -ftree-sra}
> > >
> > > @end table
> > > @@ -13011,6 +13012,12 @@ Enabled by @option{-O3}, @option{-fprofile-use},
> > > and @option{-fauto-profile}.
> > > Enables the loop invariant motion pass in the RTL loop optimizer.
> > > Enabled
> > > at level @option{-O1} and higher, except for @option{-Og}.
> > >
> > > +@item -fmove-loop-stores
> > > +@opindex fmove-loop-stores
> > > +Enables the loop store motion pass in the GIMPLE loop optimizer. Note
> > > for
> > > +this option to have an effect @code{-ftree-loop-im} has to be enabled as
> > > well.
> > ^^^^^
> >
> > The @code markup should be @option as well (same as below).
>
> Ah, thanks - fixed.
>
> > I find the brief text added to gcc/common.opt more informative than
> > this longer description. Explaining what the store motion pass does
> > in a few words would be helpful to those not familiar with
> > the implementation.
>
> OK, so is the following more useful then?
>
> "
> @item -fmove-loop-stores
> @opindex fmove-loop-stores
> Enables the loop store motion pass in the GIMPLE loop optimizer. This
> moves invariant stores to after the end of the loop in exchange for
> carrying the stored value in a register across the iteration.
> Note for this option to have an effect @option{-ftree-loop-im} has to
> be enabled as well. Enabled at level @option{-O1} and higher, except
> for @option{-Og}.
> "
I've now pushed with this variant.
Richard.
> Richard.
>
> > Martin
> >
> >
> > > +Enabled at level @option{-O1} and higher, except for @option{-Og}.
> > > +
> > > @item -fsplit-loops
> > > @opindex fsplit-loops
> > > Split a loop into two if it contains a condition that's always true
> > > diff --git a/gcc/opts.c b/gcc/opts.c
> > > index f159bb35130..25282f71a3b 100644
> > > --- a/gcc/opts.c
> > > +++ b/gcc/opts.c
> > > @@ -575,6 +575,7 @@ static const struct default_options
> > > default_options_table[] =
> > > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fif_conversion2, NULL, 1 },
> > > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_finline_functions_called_once,
> > > NULL, 1 },
> > > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fmove_loop_invariants, NULL, 1 },
> > > + { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fmove_loop_stores, NULL, 1 },
> > > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fssa_phiopt, NULL, 1 },
> > > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_fipa_modref, NULL, 1 },
> > > { OPT_LEVELS_1_PLUS_NOT_DEBUG, OPT_ftree_bit_ccp, NULL, 1 },
> > > diff --git a/gcc/tree-ssa-loop-im.c b/gcc/tree-ssa-loop-im.c
> > > index e7a3050ba9d..9ac390b9a4b 100644
> > > --- a/gcc/tree-ssa-loop-im.c
> > > +++ b/gcc/tree-ssa-loop-im.c
> > > @@ -3258,7 +3258,7 @@ pass_lim::execute (function *fun)
> > >
> > > if (number_of_loops (fun) <= 1)
> > > return 0;
> > > - unsigned int todo = loop_invariant_motion_in_fun (fun, true);
> > > + unsigned int todo = loop_invariant_motion_in_fun (fun,
> > > flag_move_loop_stores);
> > >
> > > if (!in_loop_pipeline)
> > > loop_optimizer_finalize ();
> > >
> >
> >
> >
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
