https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #20 from Dominique d'Humieres ---
Updated timings
% gfc6 -c pr80960.f90 -fdefault-integer-8 -O2 -ftime-report
...
combiner: 81.12 (55%) usr 1.17 (41%) sys 82.31 (54%) wall
2700699 kB (60%) ggc
...
TOTAL
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #19 from Segher Boessenkool ---
(In reply to rguent...@suse.de from comment #18)
> Hmm, so if we'd have numbered stmts in an EBB we could check the
> distance between set and use and not combine when that gets too big?
Yeah. Or we
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #18 from rguenther at suse dot de ---
On Thu, 4 Apr 2019, segher at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
>
> --- Comment #17 from Segher Boessenkool ---
> (In reply to rguent...@suse.de from
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #17 from Segher Boessenkool ---
(In reply to rguent...@suse.de from comment #16)
> I would guess so. I wonder if the combiner could restrict itself
> here? Maybe LUID "distances" are an approximation? Doesn't the
> combiner use
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #16 from rguenther at suse dot de ---
On Tue, 2 Apr 2019, segher at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
>
> --- Comment #15 from Segher Boessenkool ---
> It seems to be that this happens for
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #15 from Segher Boessenkool ---
It seems to be that this happens for huge basic blocks, and the combiner
tries to combine pairs of instructions that are far apart. This is unlikely
to work often, and the cost is quadratic in #
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #14 from rguenther at suse dot de ---
On Sun, 31 Mar 2019, tkoenig at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
>
> --- Comment #13 from Thomas Koenig ---
> With -O2, the combiner takes up quite a
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
--- Comment #13 from Thomas Koenig ---
With -O2, the combiner takes up quite a lot of time:
$ time gfortran -ftime-report -g0 -O2 -fdefault-integer-8 -c fe_objective.f90
alias stmt walking : 15.75 ( 4%) 0.11 ( 5%) 15.89
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80960
Richard Biener changed:
What|Removed |Added
Target Milestone|7.4 |7.5
