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* [Bug fortran/39280] New: Optimizing integer power
@ 2009-02-23 19:50 tkoenig at gcc dot gnu dot org
2009-02-24 10:10 ` [Bug fortran/39280] " rguenth at gcc dot gnu dot org
` (6 more replies)
0 siblings, 7 replies; 9+ messages in thread
From: tkoenig at gcc dot gnu dot org @ 2009-02-23 19:50 UTC (permalink / raw)
To: gcc-bugs
$ cat foo.f90
subroutine foo
implicit none
integer :: i,n
do i=1,10
n = (-1)**(i+1)
call bar(n)
end do
end subroutine foo
$ gfortran -S -O2 -fdump-tree-optimized foo.f90
...
i = i + 1;
n.0 = _gfortran_pow_i4_i4 (-1, i);
n = n.0;
bar (&n);
We could eliminate the call to _gfortran_pow_i4_i4.
--
Summary: Optimizing integer power
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tkoenig at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
@ 2009-02-24 10:10 ` rguenth at gcc dot gnu dot org
2009-02-24 12:01 ` burnus at gcc dot gnu dot org
` (5 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-02-24 10:10 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rguenth at gcc dot gnu dot org 2009-02-24 10:10 -------
... this asks for a POW_EXPR middle-end tree I guess. Or you can use
builtins.c:expand_powi* do generate an expanded power series.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
2009-02-24 10:10 ` [Bug fortran/39280] " rguenth at gcc dot gnu dot org
@ 2009-02-24 12:01 ` burnus at gcc dot gnu dot org
2009-02-24 12:14 ` rguenther at suse dot de
` (4 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: burnus at gcc dot gnu dot org @ 2009-02-24 12:01 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from burnus at gcc dot gnu dot org 2009-02-24 12:00 -------
> ... this asks for a POW_EXPR middle-end tree I guess.
I think that would be useful. See also middle-end PR 32503.
> Or you can use builtins.c:expand_powi* do generate an expanded power series.
That won't work for (-1)**variable, does it?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
2009-02-24 10:10 ` [Bug fortran/39280] " rguenth at gcc dot gnu dot org
2009-02-24 12:01 ` burnus at gcc dot gnu dot org
@ 2009-02-24 12:14 ` rguenther at suse dot de
2009-03-28 14:12 ` fxcoudert at gcc dot gnu dot org
` (3 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: rguenther at suse dot de @ 2009-02-24 12:14 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenther at suse dot de 2009-02-24 12:14 -------
Subject: Re: Optimizing integer power
On Tue, 24 Feb 2009, burnus at gcc dot gnu dot org wrote:
> ------- Comment #2 from burnus at gcc dot gnu dot org 2009-02-24 12:00 -------
> > ... this asks for a POW_EXPR middle-end tree I guess.
> I think that would be useful. See also middle-end PR 32503.
>
> > Or you can use builtins.c:expand_powi* do generate an expanded power series.
> That won't work for (-1)**variable, does it?
We likely don't special-case constant bases, yes.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
` (2 preceding siblings ...)
2009-02-24 12:14 ` rguenther at suse dot de
@ 2009-03-28 14:12 ` fxcoudert at gcc dot gnu dot org
2010-05-09 21:09 ` dfranke at gcc dot gnu dot org
` (2 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: fxcoudert at gcc dot gnu dot org @ 2009-03-28 14:12 UTC (permalink / raw)
To: gcc-bugs
--
fxcoudert at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2009-03-28 14:12:04
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
` (3 preceding siblings ...)
2009-03-28 14:12 ` fxcoudert at gcc dot gnu dot org
@ 2010-05-09 21:09 ` dfranke at gcc dot gnu dot org
2010-05-09 21:29 ` dominiq at lps dot ens dot fr
2010-05-10 8:41 ` rguenther at suse dot de
6 siblings, 0 replies; 9+ messages in thread
From: dfranke at gcc dot gnu dot org @ 2010-05-09 21:09 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from dfranke at gcc dot gnu dot org 2010-05-09 21:08 -------
Situation still the same with gcc version 4.6.0 20100509 (experimental) (GCC).
(In reply to comment #1)
> ... this asks for a POW_EXPR middle-end tree I guess. Or you can use
> builtins.c:expand_powi* do generate an expanded power series.
Would that be enough of a gain to be worth the effort?
--
dfranke at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dfranke at gcc dot gnu dot
| |org
OtherBugsDependingO| |36854
nThis| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
` (4 preceding siblings ...)
2010-05-09 21:09 ` dfranke at gcc dot gnu dot org
@ 2010-05-09 21:29 ` dominiq at lps dot ens dot fr
2010-05-10 8:41 ` rguenther at suse dot de
6 siblings, 0 replies; 9+ messages in thread
From: dominiq at lps dot ens dot fr @ 2010-05-09 21:29 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from dominiq at lps dot ens dot fr 2010-05-09 21:29 -------
I am not sure to understand the requested optimization. Is it only for the
special value j=-1 in j**i?
Note that for this situation I hate to rely on the compiler and I use a
"flipper", i.e., I replace
do i=1,10
n = (-1)**(i+1)
call bar(n)
end do
with
n = -1
do i=1,10
n = -n
call bar(n)
end do
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread* [Bug fortran/39280] Optimizing integer power
2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
` (5 preceding siblings ...)
2010-05-09 21:29 ` dominiq at lps dot ens dot fr
@ 2010-05-10 8:41 ` rguenther at suse dot de
6 siblings, 0 replies; 9+ messages in thread
From: rguenther at suse dot de @ 2010-05-10 8:41 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from rguenther at suse dot de 2010-05-10 08:41 -------
Subject: Re: Optimizing integer power
On Sun, 9 May 2010, dfranke at gcc dot gnu dot org wrote:
> ------- Comment #4 from dfranke at gcc dot gnu dot org 2010-05-09 21:08 -------
> Situation still the same with gcc version 4.6.0 20100509 (experimental) (GCC).
>
> (In reply to comment #1)
> > ... this asks for a POW_EXPR middle-end tree I guess. Or you can use
> > builtins.c:expand_powi* do generate an expanded power series.
>
> Would that be enough of a gain to be worth the effort?
If the Fortran standard allows integer powers to be expanded as
power series by default then I would say yes (at least for
non-constant power, for constant power one needs to compare
generated code - the frontend does the power series expansion
manually in this case, no?).
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39280
^ permalink raw reply [flat|nested] 9+ messages in thread
[parent not found: <bug-39280-4@http.gcc.gnu.org/bugzilla/>]
end of thread, other threads:[~2013-08-09 9:18 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
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2009-02-23 19:50 [Bug fortran/39280] New: Optimizing integer power tkoenig at gcc dot gnu dot org
2009-02-24 10:10 ` [Bug fortran/39280] " rguenth at gcc dot gnu dot org
2009-02-24 12:01 ` burnus at gcc dot gnu dot org
2009-02-24 12:14 ` rguenther at suse dot de
2009-03-28 14:12 ` fxcoudert at gcc dot gnu dot org
2010-05-09 21:09 ` dfranke at gcc dot gnu dot org
2010-05-09 21:29 ` dominiq at lps dot ens dot fr
2010-05-10 8:41 ` rguenther at suse dot de
[not found] <bug-39280-4@http.gcc.gnu.org/bugzilla/>
2013-08-09 9:18 ` tkoenig at gcc dot gnu.org
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