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* Re: middle-end/10415: allocated stack space non optimimal
@ 2003-04-15 20:16 Wolfgang Bangerth
0 siblings, 0 replies; 6+ messages in thread
From: Wolfgang Bangerth @ 2003-04-15 20:16 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR middle-end/10415; it has been noted by GNATS.
From: Wolfgang Bangerth <bangerth@ices.utexas.edu>
To: gcc-gnats@gcc.gnu.org
Cc:
Subject: Re: middle-end/10415: allocated stack space non optimimal
Date: Tue, 15 Apr 2003 15:12:46 -0500 (CDT)
---------- Forwarded message ----------
Date: Tue, 15 Apr 2003 21:59:33 +0200
From: GrzegorzB <b.grzes@interia.pl>
To: bangerth@dealii.org
Subject: Re: middle-end/10415: allocated stack space non optimimal
bangerth@dealii.org wrote:
> Old Synopsis: problem with stack
> New Synopsis: allocated stack space non optimimal
>
> State-Changed-From-To: open->feedback
> State-Changed-By: bangerth
> State-Changed-When: Tue Apr 15 18:27:24 2003
> State-Changed-Why:
> Somehow the attachment got corrupted. Can you send the
> program you used again?
>
> Thanks
> Wolfgang
>
> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10415
>
Program test.c:
void f()
{
char buf[3];
}
main()
{
f();
}
I compile this:
gcc -S -o test test.c
In test is:
.file "test.c"
.text
.align 2
.globl f
.type f,@function
f:
pushl %ebp
movl %esp, %ebp
subl $24, %esp <-- I thing its wrong
leave
ret
.Lfe1:
.size f,.Lfe1-f
.align 2
.globl main
.type main,@function
main:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
andl $-16, %esp
movl $0, %eax
subl %eax, %esp
call f
leave
ret
.Lfe2:
.size main,.Lfe2-main
.ident "GCC: (GNU) 3.2 20020903 (Red Hat Linux 8.0 3.2-7)"
Sorry, I didn't explain that well.
Grzegorz Bieda
----------------------------------------------------------------------
KLIKNIJ 2 razy TAK >>> http://link.interia.pl/f170d
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: middle-end/10415: allocated stack space non optimimal
@ 2003-04-15 22:56 bangerth
0 siblings, 0 replies; 6+ messages in thread
From: bangerth @ 2003-04-15 22:56 UTC (permalink / raw)
To: b.grzes, gcc-bugs, gcc-prs, nobody
Synopsis: allocated stack space non optimimal
State-Changed-From-To: feedback->closed
State-Changed-By: bangerth
State-Changed-When: Tue Apr 15 22:56:17 2003
State-Changed-Why:
Closed in favor of duplicates with more information.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10415
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: middle-end/10415: allocated stack space non optimimal
@ 2003-04-15 22:46 Wolfgang Bangerth
0 siblings, 0 replies; 6+ messages in thread
From: Wolfgang Bangerth @ 2003-04-15 22:46 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR middle-end/10415; it has been noted by GNATS.
From: Wolfgang Bangerth <bangerth@ices.utexas.edu>
To: GrzegorzB <b.grzes@interia.pl>
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: middle-end/10415: allocated stack space non optimimal
Date: Tue, 15 Apr 2003 17:43:12 -0500 (CDT)
> So sorry, I thought it is a bug.
Well, I still think that this is a quality of implementation bug, gcc
should be able to do better. I mean, it is not _wrong_ if the compiler
allocated too much stack space, it is just wasteful.
There are a number of reports in the bug database about this problem,
which also have some documentation about what is the cause for this inside
the compiler. Let me close this report, since there are others.
Thanks anyway
Wolfgang
-------------------------------------------------------------------------
Wolfgang Bangerth email: bangerth@ices.utexas.edu
www: http://www.ices.utexas.edu/~bangerth/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: middle-end/10415: allocated stack space non optimimal
@ 2003-04-15 22:36 Wolfgang Bangerth
0 siblings, 0 replies; 6+ messages in thread
From: Wolfgang Bangerth @ 2003-04-15 22:36 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR middle-end/10415; it has been noted by GNATS.
From: Wolfgang Bangerth <bangerth@ices.utexas.edu>
To: gcc-gnats@gcc.gnu.org
Cc:
Subject: Re: middle-end/10415: allocated stack space non optimimal
Date: Tue, 15 Apr 2003 17:35:03 -0500 (CDT)
---------- Forwarded message ----------
Date: Tue, 15 Apr 2003 22:42:42 +0200
From: GrzegorzB <b.grzes@interia.pl>
To: Wolfgang Bangerth <bangerth@ices.utexas.edu>
Subject: Re: middle-end/10415: allocated stack space non optimimal
Wolfgang Bangerth wrote:
>>Program test.c:
>>
>>void f() {
>> char buf[3];
>>}
>>
>>main() {
>> f();
>>}
>>
>>I compile this:
>>gcc -S -o test test.c
>
>
> What happens if you switch on optimization? Is stack allocation better
> then?
>
> [I think that the compiler will just optimize away everything in that
> case, but you might prevent this by doing something like
>
> void p(char *x);
> void f() {
> char buf[3];
> p(buf);
> }
>
> and simply not defining f().]
>
> W.
>
If I compile test.c with option -O0, I have (for "char buf[3]"):
pushl %ebp
movl %esp, %ebp
subl $24, %esp
leave
for option -O3 is:
pushl %ebp
movl %esp, %ebp
subl $24, %esp
andl $-16, %esp
leave
If is "char buff[4]" and -O3 is:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
andl $-16, %esp
leave
and for -O0 option (and "char buf[4]"):
pushl %ebp
movl %esp, %ebp
subl $4, %esp
leave
So sorry, I thought it is a bug.
----------------------------------------------------------------------
KLIKNIJ 2 razy TAK >>> http://link.interia.pl/f170d
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: middle-end/10415: allocated stack space non optimimal
@ 2003-04-15 20:16 Wolfgang Bangerth
0 siblings, 0 replies; 6+ messages in thread
From: Wolfgang Bangerth @ 2003-04-15 20:16 UTC (permalink / raw)
To: nobody; +Cc: gcc-prs
The following reply was made to PR middle-end/10415; it has been noted by GNATS.
From: Wolfgang Bangerth <bangerth@ices.utexas.edu>
To: GrzegorzB <b.grzes@interia.pl>
Cc: gcc-gnats@gcc.gnu.org, <gcc-bugs@gcc.gnu.org>
Subject: Re: middle-end/10415: allocated stack space non optimimal
Date: Tue, 15 Apr 2003 15:15:25 -0500 (CDT)
> Program test.c:
>
> void f() {
> char buf[3];
> }
>
> main() {
> f();
> }
>
> I compile this:
> gcc -S -o test test.c
What happens if you switch on optimization? Is stack allocation better
then?
[I think that the compiler will just optimize away everything in that
case, but you might prevent this by doing something like
void p(char *x);
void f() {
char buf[3];
p(buf);
}
and simply not defining f().]
W.
-------------------------------------------------------------------------
Wolfgang Bangerth email: bangerth@ices.utexas.edu
www: http://www.ices.utexas.edu/~bangerth/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: middle-end/10415: allocated stack space non optimimal
@ 2003-04-15 18:27 bangerth
0 siblings, 0 replies; 6+ messages in thread
From: bangerth @ 2003-04-15 18:27 UTC (permalink / raw)
To: b.grzes, gcc-bugs, gcc-prs, nobody
Old Synopsis: problem with stack
New Synopsis: allocated stack space non optimimal
State-Changed-From-To: open->feedback
State-Changed-By: bangerth
State-Changed-When: Tue Apr 15 18:27:24 2003
State-Changed-Why:
Somehow the attachment got corrupted. Can you send the
program you used again?
Thanks
Wolfgang
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10415
^ permalink raw reply [flat|nested] 6+ messages in thread
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