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* [Bug c/30075] New: Missed optimizations with -fwhole-program -combine
@ 2006-12-05 18:43 ajax at redhat dot com
2006-12-05 18:47 ` [Bug middle-end/30075] Missed optimizations with static variable and static function pinskia at gcc dot gnu dot org
` (6 more replies)
0 siblings, 7 replies; 10+ messages in thread
From: ajax at redhat dot com @ 2006-12-05 18:43 UTC (permalink / raw)
To: gcc-bugs
---
atropine:~/combine-bug% cat foo.c
int foo(void) {
return 0;
}
atropine:~/combine-bug% cat bar.c
extern int foo(void);
void *array[] = {
foo
};
atropine:~/combine-bug% gcc -shared -fPIC -combine -fwhole-program -o libfoo.so
foo.c bar.c
atropine:~/combine-bug% nm libfoo.so | egrep '(foo)|(array)'
000000000000048c t foo
atropine:~/combine-bug% rpm -q gcc
gcc-4.1.1-30
---
foo is still emitted, when you'd think you could garbage-collect it, since the
array that references it has fallen out of existance. If you use
-fvisibility=hidden instead of -fwhole-program the result is even worse, both
foo and array are emitted even though the resulting DSO does not give any
access to them.
--
Summary: Missed optimizations with -fwhole-program -combine
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ajax at redhat dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/30075] Missed optimizations with static variable and static function
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
@ 2006-12-05 18:47 ` pinskia at gcc dot gnu dot org
2006-12-05 19:37 ` [Bug c/30075] Missed optimizations with -fwhole-program -combine ajax at redhat dot com
` (5 subsequent siblings)
6 siblings, 0 replies; 10+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-12-05 18:47 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-12-05 18:46 -------
> If you use -fvisibility=hidden instead of -fwhole-program the result is even
> worse, both foo and array are emitted even though the resulting DSO does not
> give any access to them.
Well that is not GCC's fault really, you should use -ffunction-sections
-Wl,--gc-sections for that
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Missed optimizations with - |Missed optimizations with
|fwhole-program -combine |static variable and static
| |function
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
2006-12-05 18:47 ` [Bug middle-end/30075] Missed optimizations with static variable and static function pinskia at gcc dot gnu dot org
@ 2006-12-05 19:37 ` ajax at redhat dot com
2006-12-05 19:39 ` [Bug middle-end/30075] " pinskia at gcc dot gnu dot org
` (4 subsequent siblings)
6 siblings, 0 replies; 10+ messages in thread
From: ajax at redhat dot com @ 2006-12-05 19:37 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from ajax at redhat dot com 2006-12-05 19:37 -------
Just to clarify, I neglected to use -O in the example above, but this behaviour
is still seen even with -O.
--
ajax at redhat dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|middle-end |c
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
2006-12-05 18:47 ` [Bug middle-end/30075] Missed optimizations with static variable and static function pinskia at gcc dot gnu dot org
2006-12-05 19:37 ` [Bug c/30075] Missed optimizations with -fwhole-program -combine ajax at redhat dot com
@ 2006-12-05 19:39 ` pinskia at gcc dot gnu dot org
2006-12-06 2:55 ` Daniel Berlin
2006-12-06 2:55 ` dberlin at dberlin dot org
` (3 subsequent siblings)
6 siblings, 1 reply; 10+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-12-05 19:39 UTC (permalink / raw)
To: gcc-bugs
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Component|c |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 19:39 ` [Bug middle-end/30075] " pinskia at gcc dot gnu dot org
@ 2006-12-06 2:55 ` Daniel Berlin
0 siblings, 0 replies; 10+ messages in thread
From: Daniel Berlin @ 2006-12-06 2:55 UTC (permalink / raw)
To: gcc-bugzilla; +Cc: gcc-bugs
I would not expect this to be fixed anytime soon. I have yet to find
any real people who use either combine or -fwhole-program. They use
*way* too much memory on real programs. As a result, no real people
involved in optimization work on optimizers for them.
On 5 Dec 2006 19:38:51 -0000, pinskia at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> --
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
` (2 preceding siblings ...)
2006-12-05 19:39 ` [Bug middle-end/30075] " pinskia at gcc dot gnu dot org
@ 2006-12-06 2:55 ` dberlin at dberlin dot org
2007-06-26 3:10 ` acahalan at gmail dot com
` (2 subsequent siblings)
6 siblings, 0 replies; 10+ messages in thread
From: dberlin at dberlin dot org @ 2006-12-06 2:55 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from dberlin at gcc dot gnu dot org 2006-12-06 02:55 -------
Subject: Re: Missed optimizations with -fwhole-program -combine
I would not expect this to be fixed anytime soon. I have yet to find
any real people who use either combine or -fwhole-program. They use
*way* too much memory on real programs. As a result, no real people
involved in optimization work on optimizers for them.
On 5 Dec 2006 19:38:51 -0000, pinskia at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> --
>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
` (3 preceding siblings ...)
2006-12-06 2:55 ` dberlin at dberlin dot org
@ 2007-06-26 3:10 ` acahalan at gmail dot com
2007-06-26 15:29 ` Daniel Berlin
2007-06-26 15:29 ` dberlin at dberlin dot org
2010-09-17 9:09 ` rguenth at gcc dot gnu dot org
6 siblings, 1 reply; 10+ messages in thread
From: acahalan at gmail dot com @ 2007-06-26 3:10 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from acahalan at gmail dot com 2007-06-26 03:10 -------
(In reply to comment #3)
> Subject: Re: Missed optimizations with -fwhole-program -combine
>
> I would not expect this to be fixed anytime soon. I have yet to find
> any real people who use either combine or -fwhole-program. They use
> *way* too much memory on real programs. As a result, no real people
> involved in optimization work on optimizers for them.
I'm real, and I want to use those.
I can't use them because of bug #29171. They appear to be 100% unusable for
non-trivial programs because gcc WILL emit calls to memcpy and there isn't any
possible (documented at least) way to provide a memcpy. No matter how I
__attribute__ my memcpy, and no matter if I use -ffreestanding or not, gcc
wants to call an extern memcpy. Linking against a libc is against the
documented requirements for using these options.
--
acahalan at gmail dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |acahalan at gmail dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
` (4 preceding siblings ...)
2007-06-26 3:10 ` acahalan at gmail dot com
@ 2007-06-26 15:29 ` dberlin at dberlin dot org
2010-09-17 9:09 ` rguenth at gcc dot gnu dot org
6 siblings, 0 replies; 10+ messages in thread
From: dberlin at dberlin dot org @ 2007-06-26 15:29 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from dberlin at gcc dot gnu dot org 2007-06-26 15:29 -------
Subject: Re: Missed optimizations with -fwhole-program -combine
On 26 Jun 2007 03:10:26 -0000, acahalan at gmail dot com
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #4 from acahalan at gmail dot com 2007-06-26 03:10 -------
> (In reply to comment #3)
> > Subject: Re: Missed optimizations with -fwhole-program -combine
> >
> > I would not expect this to be fixed anytime soon. I have yet to find
> > any real people who use either combine or -fwhole-program. They use
> > *way* too much memory on real programs. As a result, no real people
> > involved in optimization work on optimizers for them.
>
> I'm real, and I want to use those.
>
That's nice and all, but i still wouldn't expect any work on them
until LTO is finished.
They are useless options right now.
I'd vote to remove them.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2007-06-26 3:10 ` acahalan at gmail dot com
@ 2007-06-26 15:29 ` Daniel Berlin
0 siblings, 0 replies; 10+ messages in thread
From: Daniel Berlin @ 2007-06-26 15:29 UTC (permalink / raw)
To: gcc-bugzilla; +Cc: gcc-bugs
On 26 Jun 2007 03:10:26 -0000, acahalan at gmail dot com
<gcc-bugzilla@gcc.gnu.org> wrote:
>
>
> ------- Comment #4 from acahalan at gmail dot com 2007-06-26 03:10 -------
> (In reply to comment #3)
> > Subject: Re: Missed optimizations with -fwhole-program -combine
> >
> > I would not expect this to be fixed anytime soon. I have yet to find
> > any real people who use either combine or -fwhole-program. They use
> > *way* too much memory on real programs. As a result, no real people
> > involved in optimization work on optimizers for them.
>
> I'm real, and I want to use those.
>
That's nice and all, but i still wouldn't expect any work on them
until LTO is finished.
They are useless options right now.
I'd vote to remove them.
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug middle-end/30075] Missed optimizations with -fwhole-program -combine
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
` (5 preceding siblings ...)
2007-06-26 15:29 ` dberlin at dberlin dot org
@ 2010-09-17 9:09 ` rguenth at gcc dot gnu dot org
6 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-09-17 9:09 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from rguenth at gcc dot gnu dot org 2010-09-17 09:06 -------
-combine has been removed from GCC 4.6 in favor of LTO, closing as WONTFIX.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |WONTFIX
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30075
^ permalink raw reply [flat|nested] 10+ messages in thread
end of thread, other threads:[~2010-09-17 9:07 UTC | newest]
Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2006-12-05 18:43 [Bug c/30075] New: Missed optimizations with -fwhole-program -combine ajax at redhat dot com
2006-12-05 18:47 ` [Bug middle-end/30075] Missed optimizations with static variable and static function pinskia at gcc dot gnu dot org
2006-12-05 19:37 ` [Bug c/30075] Missed optimizations with -fwhole-program -combine ajax at redhat dot com
2006-12-05 19:39 ` [Bug middle-end/30075] " pinskia at gcc dot gnu dot org
2006-12-06 2:55 ` Daniel Berlin
2006-12-06 2:55 ` dberlin at dberlin dot org
2007-06-26 3:10 ` acahalan at gmail dot com
2007-06-26 15:29 ` Daniel Berlin
2007-06-26 15:29 ` dberlin at dberlin dot org
2010-09-17 9:09 ` rguenth at gcc dot gnu dot org
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