On Sun, Apr 09, 2006 at 02:45:04PM +0200, Dieter Schuster wrote:
> Tach auch!
>
> Am Fr, den 31 März 2006, schrieb Alan Modra:
> > On Tue, Mar 28, 2006 at 12:00:47PM +0200, Gabriel Paubert wrote:
> > > On Tue, Mar 28, 2006 at 12:56:13AM +0200, Dieter Schuster wrote:
> > > > If I try to compile qemu with GCC 3.4 without the patch I get the
> > > > following error:
> > > >
> > > > qemu-0.8.0/linux-user/elfload.c: In function `load_elf_binary':
> > > > qemu-0.8.0/cpu-all.h:253: error: inconsistent operand constraints in an
> > > > `asm'
> > > > qemu-0.8.0/cpu-all.h:253: error: inconsistent operand constraints in an
> > > > `asm'
> > >
> > > Weird. CC'ed to gcc list despite the fact that the 3.4 branch
> > > is definitely closed. I've not found anything remotely similar
> > > from bugzilla.
> > >
> > > >
> > > > But if I copy the function stl_le_p to a seperate file, the function
> > > > will compile with GCC 3.4.
> >
> > Check preprocessor output. My guess is that you have some unexpected
> > substitution.
> >
>
> I had now more time, to investigate the error. It seems to be a
> optimization problem. With -O2 -fno-gcse the error disappeared. I have
> made a bug report to gcc.
Yes, but you sent it to gnats-gcc, which is completely obsolete. You
should use bugzilla. Now the testcase looks really minimal:
http://lists.debian.org/debian-gcc/2006/04/msg00135.html
even if the code looks strange (redundant cast, if without
braces which confused me at first). This may be the result
of normal macro expansion.
However, I believe that the most serious problem is that you
use uninitialized local variables (which makes the code invalid).
I have changed the testcase to the attached file by declaring
these variables extern (the code is also reformatted to be more
readable).
Testing here with recent Debian versions of gcc-3.4, 4.0 and 4.1
show that I can' trigger any problem with 4.0 and 4.1, and that
for gcc-3.4:
- -O1 always works (regardless of -fgcse), which is surprising
since I have exactly the same compiler as you.
- -O2 -fno-gcse works
- -O2 (implies -fgcse) fails
In the failure case, the generated code (attached) does not make
sense: one stwbrx disappears and is mysteriously replaced by an
stw, the source of which is a register which has never been
initialized (r8), while I don't see any uninitialized variable
in the source after the small changes I've made.
Regards,
Gabriel
static inline void stl(void *ptr, int v) {
__asm__ __volatile__ ("stwbrx %1,0,%2" : "=m" (*(unsigned long *)ptr) : "r"
(v), "r" (ptr));
}
int main () {
extern unsigned long *sp, *u_platform;
extern char *k_platform;
stl(sp, (unsigned long)(0));
stl(sp+1, (unsigned long)(0));
if (k_platform)
stl(sp, (unsigned long)(15));
stl(sp+1, (unsigned long)((unsigned long) u_platform));
return 0;
}
.file "bug.i"
.section ".text"
.align 2
.globl main
.type main, @function
main:
lis 11,[EMAIL PROTECTED]
lis 9,[EMAIL PROTECTED]
lwz 0,[EMAIL PROTECTED](11)
lwz 10,[EMAIL PROTECTED](9)
li 9,15
cmpwi 7,0,0
beq- 7,.L7
#APP
stwbrx 9,0,10
#NO_APP
lis 9,[EMAIL PROTECTED]
addi 11,10,4
lwz 0,[EMAIL PROTECTED](9)
#APP
stwbrx 0,0,11
#NO_APP
li 3,0
blr
.L7:
lis 9,[EMAIL PROTECTED]
stw 8,0(10)
addi 11,10,4
lwz 0,[EMAIL PROTECTED](9)
#APP
stwbrx 0,0,11
#NO_APP
li 3,0
blr
.size main,.-main
.section .note.GNU-stack,"",@progbits
.ident "GCC: (GNU) 3.4.6 (Debian 3.4.6-1)"
