Re: cmpxchgl on x86?
Re: cmpxchgl on x86?
- Subject: Re: cmpxchgl on x86?
- From: Matt Watson <email@hidden>
- Date: Thu, 23 Jun 2005 10:48:14 -0700
On Jun 23, 2005, at 10:11 AM, Andrew Gallatin wrote:
I'm trying to compile a unix command-line program on Darwin 8.0 x86,
and I'm hitting this problem:
/var/tmp/cczbJSUe.s:1993:Can't relocate expression. Absolute 0
assumed.
/var/tmp/cczbJSUe.s:1993:operands given don't match any known 386
instruction
The code in it is complaining about is an inline cmpxchgl asm routine:
static inline uint32_t my__cmpswap_u32(uint32_t *ptr, uint32_t old,
uint32_t new)
{
asm volatile("lock cmpxchgl %1,%2" : "=a" (old) : "q" (new),
"m" (*ptr),"0" (old) : "memory");
return old;
}
This seems to happen with both gcc-4.0 and gcc-3.3
Can somebody tell me what I'm doing wrong, please?
Try putting a / after the lock.
Assembler quirk.
Also, there are compare-and-swap routines already in libSystem:
<libkern/OSAtomic.h>
/* Compare and swap. They return true if the swap occured.
*/
bool OSAtomicCompareAndSwap32( int32_t oldValue, int32_t newValue,
int32_t *theValue );
bool OSAtomicCompareAndSwap32Barrier( int32_t oldValue, int32_t
newValue, int32_t *theValue );
matt.
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