On Fri, Sep 20, 2019 at 11:28 AM Andreas Krebbel <kreb...@linux.ibm.com> wrote:
>
> On 06.09.19 12:48, Richard Biener wrote:
> > On Fri, Sep 6, 2019 at 10:11 AM Andreas Krebbel <kreb...@linux.ibm.com>
> > wrote:
> >>
> >> Hi,
> >>
> >> since this caused a critical performance regression in the OpenJ9 byte
> >> code interpreter after
> >> migrating from GCC 4.8 to GCC 7 I would like to backport this patch also
> >> to GCC 8 and 9 branch.
> >>
> >> Ok - after bootstrap and regression test went fine?
> >
> > Looks reasonable to me. But what about GCC 7? I assume you also verified
> > the
> > actual performance regression is gone.
>
> I've committed the patch to GCC 7 and 8 branch after verifying that the
> change has the desired
> effect on the source code file from OpenJ9.
>
> GCC 9 branch is currently frozen. Ok, to apply there as well?
Yes, it shouldn't be frozen anymore...
Richard.
> Andreas
>
> >
> > Richard.
> >
> >>
> >> Andreas
> >>
> >>
> >> commit d3dc20418aad41af83fe45ccba527deb0b334983
> >> Author: krebbel <krebbel@138bc75d-0d04-0410-961f-82ee72b054a4>
> >> Date: Thu Jun 6 11:35:04 2019 +0000
> >>
> >> Fix PR88751
> >>
> >> This patch implements a small improvement for the heuristic in lra
> >> which decides when it has to activate the simpler register allocation
> >> algorithm.
> >>
> >> gcc/ChangeLog:
> >>
> >> 2019-06-06 Andreas Krebbel <kreb...@linux.ibm.com>
> >>
> >> PR rtl-optimization/88751
> >> * ira.c (ira): Use the number of the actually referenced
> >> registers
> >> when calculating the threshold.
> >>
> >>
> >>
> >> git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@271996
> >> 138bc75d-0d04-0410-961f-82ee72b054a4
> >>
> >>
> >> diff --git a/gcc/ira.c b/gcc/ira.c
> >> index 4a14fb31583..725636d8dc5 100644
> >> --- a/gcc/ira.c
> >> +++ b/gcc/ira.c
> >> @@ -5198,6 +5198,8 @@ ira (FILE *f)
> >> int ira_max_point_before_emit;
> >> bool saved_flag_caller_saves = flag_caller_saves;
> >> enum ira_region saved_flag_ira_region = flag_ira_region;
> >> + unsigned int i;
> >> + int num_used_regs = 0;
> >>
> >> clear_bb_flags ();
> >>
> >> @@ -5213,12 +5215,17 @@ ira (FILE *f)
> >>
> >> ira_conflicts_p = optimize > 0;
> >>
> >> + /* Determine the number of pseudos actually requiring coloring. */
> >> + for (i = FIRST_PSEUDO_REGISTER; i < DF_REG_SIZE (df); i++)
> >> + num_used_regs += !!(DF_REG_USE_COUNT (i) + DF_REG_DEF_COUNT (i));
> >> +
> >> /* If there are too many pseudos and/or basic blocks (e.g. 10K
> >> pseudos and 10K blocks or 100K pseudos and 1K blocks), we will
> >> use simplified and faster algorithms in LRA. */
> >> lra_simple_p
> >> = (ira_use_lra_p
> >> - && max_reg_num () >= (1 << 26) / last_basic_block_for_fn (cfun));
> >> + && num_used_regs >= (1 << 26) / last_basic_block_for_fn (cfun));
> >> +
> >> if (lra_simple_p)
> >> {
> >> /* It permits to skip live range splitting in LRA. */
> >>
>
