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* [Bug c/21196] New: -O2 optimizer bug?
@ 2005-04-24 20:02 jbglaw at lug-owl dot de
2005-04-24 20:05 ` [Bug c/21196] " jbglaw at lug-owl dot de
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: jbglaw at lug-owl dot de @ 2005-04-24 20:02 UTC (permalink / raw)
To: gcc-bugs
Hi!
While working on a vax-linux cross-compiler, I noticed that my vax-linux kernel
won't boot. I tracked this down to a function that re-calculates addresses (VM
addresses to physical addresses for things that run before VM is switched on).
I've then ran the C file through the preprocessor and put it through my host
compiler (gcc-3.3.x on PeeCee). Same result even there.
Testcase:
void *
s0vmaddr_to_load_addr(void *vaddr)
{
extern char _rtext;
return (char *)vaddr - (0x80000000) - 0x00100000 + (unsigned int) &_rtext;
}
jbglaw@d2:~/vax-linux/kernel-2.5$ gcc -c testcase.c
jbglaw@d2:~/vax-linux/kernel-2.5$ objdump -d testcase.o
testcase.o: file format elf32-i386
Disassembly of section .text:
00000000 <s0vmaddr_to_load_addr>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: b8 00 00 00 00 mov $0x0,%eax
8: 05 00 00 f0 7f add $0x7ff00000,%eax
d: 03 45 08 add 0x8(%ebp),%eax
10: 5d pop %ebp
11: c3 ret
As you see, four bytes were reserved to be put in by the linker. However, it
seems this is missing in case of a -O2 build:
jbglaw@d2:~/vax-linux/kernel-2.5$ gcc -c -O2 testcase.c
jbglaw@d2:~/vax-linux/kernel-2.5$ objdump -d testcase.o
testcase.o: file format elf32-i386
Disassembly of section .text:
00000000 <s0vmaddr_to_load_addr>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 8b 45 08 mov 0x8(%ebp),%eax
6: 5d pop %ebp
7: 05 00 00 f0 7f add $0x7ff00000,%eax
c: c3 ret
...or am I wrong here?
Thanks!
Jan-Benedict Glaw <jbglaw@lug-owl.de>
--
Summary: -O2 optimizer bug?
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jbglaw at lug-owl dot de
CC: gcc-bugs at gcc dot gnu dot org
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21196
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c/21196] -O2 optimizer bug?
2005-04-24 20:02 [Bug c/21196] New: -O2 optimizer bug? jbglaw at lug-owl dot de
@ 2005-04-24 20:05 ` jbglaw at lug-owl dot de
2005-04-24 20:30 ` [Bug rtl-optimization/21196] " pinskia at gcc dot gnu dot org
2005-04-24 20:32 ` pinskia at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: jbglaw at lug-owl dot de @ 2005-04-24 20:05 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From jbglaw at lug-owl dot de 2005-04-24 20:05 -------
Hi!
Here's how I configured it:
/home/jbglaw/vax-linux/scm/build-20050424-193631-i686-linux/src/gcc/configure
--disable-multilib --with-newlib --disable-nls --enable-threads=no
--disable-threads --enable-symvers=gnu --enable-__cxa_atexit --disable-shared
--target=i686-linux
--prefix=/home/jbglaw/vax-linux/scm/build-20050424-193631-i686-linux/install/usr
--enable-languages=c --disable-werror
Thanks,
Jan-Benedict Glaw <jbglaw@lug-owl.de>
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21196
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug rtl-optimization/21196] -O2 optimizer bug?
2005-04-24 20:02 [Bug c/21196] New: -O2 optimizer bug? jbglaw at lug-owl dot de
2005-04-24 20:05 ` [Bug c/21196] " jbglaw at lug-owl dot de
@ 2005-04-24 20:30 ` pinskia at gcc dot gnu dot org
2005-04-24 20:32 ` pinskia at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-04-24 20:30 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-04-24 20:30 -------
pushl %ebp
movl %esp, %ebp
movl 8(%ebp), %eax
popl %ebp
addl $_rtext+2146435072, %eax
This is not a bug, see above: you are missing that relocates can happen in more places than where zero
happens so that is the bug at all.
--
What |Removed |Added
----------------------------------------------------------------------------
Component|c |rtl-optimization
Version|4.1.0 |3.3
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21196
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug rtl-optimization/21196] -O2 optimizer bug?
2005-04-24 20:02 [Bug c/21196] New: -O2 optimizer bug? jbglaw at lug-owl dot de
2005-04-24 20:05 ` [Bug c/21196] " jbglaw at lug-owl dot de
2005-04-24 20:30 ` [Bug rtl-optimization/21196] " pinskia at gcc dot gnu dot org
@ 2005-04-24 20:32 ` pinskia at gcc dot gnu dot org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2005-04-24 20:32 UTC (permalink / raw)
To: gcc-bugs
------- Additional Comments From pinskia at gcc dot gnu dot org 2005-04-24 20:32 -------
So closing this as invalid.
--
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21196
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2005-04-24 20:32 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-04-24 20:02 [Bug c/21196] New: -O2 optimizer bug? jbglaw at lug-owl dot de
2005-04-24 20:05 ` [Bug c/21196] " jbglaw at lug-owl dot de
2005-04-24 20:30 ` [Bug rtl-optimization/21196] " pinskia at gcc dot gnu dot org
2005-04-24 20:32 ` pinskia at gcc dot gnu dot org
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