Sent from my iPhone
On Jan 22, 2009, at 5:54 PM, "hjl dot tools at gmail dot com" <gcc-bugzi...@gcc.gnu.org
> wrote:
On x86, CX is used for shift. If CX is used for a variable, it
may not be preserved with shift:
[...@gnu-9 reg-1]$ cat r.c
extern void abort (void);
void
foo (int x)
{
if (x != 8)
abort ();
}
void
bar (int g)
{
register int x __asm__("ecx");
x = 5;
foo (1 << g);
I think this code is undefined as the register variable is not used in
an inline-asm.
if (x != 5)
abort ();
}
int
main ()
{
bar (3);
return 0;
}
[...@gnu-9 reg-1]$ make r0
/export/build/gnu/gcc/build-i686-linux/gcc/xgcc
-B/export/build/gnu/gcc/build-i686-linux/gcc/ -m32 -O0 r.c -o r0
[...@gnu-9 reg-1]$ ./r0
Aborted
[...@gnu-9 reg-1]$
--
Summary: CX isn't preserved with shift
Product: gcc
Version: 4.4.0
Status: UNCONFIRMED
Keywords: ra
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: hjl dot tools at gmail dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38941
