[PATCH 1/2] Introduce flag_cunroll_grow_size for cunroll

Richard Biener richard.guenther@gmail.com
Tue Jun 2 11:15:01 GMT 2020


On Tue, Jun 2, 2020 at 4:10 AM Jiufu Guo <guojiufu@linux.ibm.com> wrote:
>
> Jiufu Guo <guojiufu@linux.ibm.com> writes:
>
> Hi,
>
> I updated the patch just a little accordinlgy.  Thanks!
>
> diff --git a/gcc/common.opt b/gcc/common.opt
> index 4464049fc1f..570e2aa53c8 100644
> --- a/gcc/common.opt
> +++ b/gcc/common.opt
> @@ -2856,6 +2856,10 @@ funroll-all-loops
>  Common Report Var(flag_unroll_all_loops) Optimization
>  Perform loop unrolling for all loops.
>
> +funroll-completely-grow-size
> +Common Undocumented Var(flag_cunroll_grow_size) Init(2) Optimization
> +; Internal undocumented flag, allow size growth during complete unrolling
> +
>  ; Nonzero means that loop optimizer may assume that the induction variables
>  ; that control loops do not overflow and that the loops with nontrivial
>  ; exit condition are not infinite
> diff --git a/gcc/toplev.c b/gcc/toplev.c
> index 96316fbd23b..8d52358efdd 100644
> --- a/gcc/toplev.c
> +++ b/gcc/toplev.c
> @@ -1474,6 +1474,10 @@ process_options (void)
>    if (flag_unroll_all_loops)
>      flag_unroll_loops = 1;
>
> +  /* Allow cunroll to grow size accordingly.  */
> +  if (flag_cunroll_grow_size == AUTODETECT_VALUE)
> +    flag_cunroll_grow_size = flag_unroll_loops || flag_peel_loops;
> +

(*)

>    /* web and rename-registers help when run after loop unrolling.  */
>    if (flag_web == AUTODETECT_VALUE)
>      flag_web = flag_unroll_loops;
> diff --git a/gcc/tree-ssa-loop-ivcanon.c b/gcc/tree-ssa-loop-ivcanon.c
> index 8ab6ab3330c..298ab215530 100644
> --- a/gcc/tree-ssa-loop-ivcanon.c
> +++ b/gcc/tree-ssa-loop-ivcanon.c
> @@ -1603,9 +1603,8 @@ pass_complete_unroll::execute (function *fun)
>       re-peeling the same loop multiple times.  */
>    if (flag_peel_loops)
>      peeled_loops = BITMAP_ALLOC (NULL);
> -  unsigned int val = tree_unroll_loops_completely (flag_unroll_loops
> -                                                  || flag_peel_loops
> -                                                  || optimize >= 3, true);
> +  unsigned int val = tree_unroll_loops_completely (flag_cunroll_grow_size,

With -O3 -fno-peel-loops this does not have the same effect anymore.
So above (*) you'd need to check || optimize >= 3 as well.

> +                                                  true);
>    if (peeled_loops)
>      {
>        BITMAP_FREE (peeled_loops);
>
> BR,
> Jiufu
>
> > Richard Biener <richard.guenther@gmail.com> writes:
> >
>
> >>> >> From: Jiufu Guo <guojiufu@linux.ibm.com>
> >>> >>
> >>> >> Currently GIMPLE complete unroller(cunroll) is checking
> >>> >> flag_unroll_loops and flag_peel_loops to see if allow size growth.
> >>> >> Beside affects curnoll, flag_unroll_loops also controls RTL unroler.
> >>> >> To have more freedom to control cunroll and RTL unroller, this patch
> >>> >> introduces flag_cunroll_grow_size.  With this patch, we can control
> >>> >> cunroll and RTL unroller indepently.
> >>> >>
> >>> >> Bootstrap/regtest pass on powerpc64le. OK for trunk? And backport to
> >>> >> GCC10 after week?
> >>> >>
> >>> >>
> >>> >> +funroll-completely-grow-size
> >>> >> +Var(flag_cunroll_grow_size) Init(2)
> >>> >> +; Control cunroll to allow size growth during complete unrolling
> >>> >> +
> >>> >
> >>
> >> It won't work without adjusting the awk scripts.  So go with
> >>
> >> funroll-completely-grow-size
> >> Undocumented Optimization Var(flag_cunroll_grow_size)
> >> EnabledBy(funroll-loops || fpeel-loops)
> >> ; ...
> >>
> > EnabledBy(funroll-loops || fpeel-loops) does not works as we expected:
> > "-funroll-loops -fno-peel-loops" turns off flag_cunroll_grow_size.
> >
> > Through "EnabledBy", a flag can be turned, and also can be turned off by
> > the "EnabledBy option", only if the flag is not specifed through commond
> > line.
> >
> >> and enable it at O3+.  AUTODETECT_VALUE doesn't make sense for
> >> an option not supposed to be set by users?
> >>
> >
> > global_options_set.x_flagxxx can be used to check if option is set by
> > user.  But it does not work well here neither, because we also care of
> > if the flag is override by OPTION_OPTIMIZATION_TABLE or
> > OPTION_OVERRIDE.
> >
> > AUTODETECT_VALUE(value is 2) is used for some flags like flag_web,
> > flag_rename_registers, flag_var_tracking, flag_tree_cselim...
> > And this way could be used to check if the flag is effective(on/off)
> > either explicit set by command line or implicit set through
> > OPTION_OVERRIDE or OPTION_OPTIMIZATION_TABLE.
> > So, I use it here.
>
>


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