Of course, it helps if you actually use GCC 4.6 and not 4.5.3 when
trying to compile. D'oh! My bad. Please ignore. Everything works
as expected/documented:
~/t $ cat test.c
#include <stdio.h>
void main()
{
__int128 a = 1, b;
b = __sync_val_compare_and_swap(&a, 1, 2);
printf("Returned value = %d, New value = %d\n", (int)b, (int)a);
}
~/t $ gcc-4.6.3-pre9999 -mcx16 test.c -o test
~/t $ ./test
Returned value = 1, New value = 2
~/t $ objdump -d test | grep cmpxchg16b
40059e: f0 48 0f c7 0e lock cmpxchg16b (%rsi)
~/t $
On 7 January 2012 17:25, Borg Onion <borg.onion@xxxxxxxxx> wrote:
> Hello,
>
> I'm trying to figure out how to make use of CMPXCHG16B. The GCC
> manual looks to point towards __sync_val_compare_and_swap() with
> __int128 data types and the -mcx16 compile flag. But this data type
> is not present when I try to compile with it, nor do I think my 4th
> generation Opteron is capable of holding __int128 values in its
> registers. So what's the equivalent of .Net's
> _InterlockedCompareExchange128()
> [http://msdn.microsoft.com/en-us/library/bb514094.aspx] in GCC-land?
> I'm trying to avoid having to (re?)implement it myself as these folks
> did:
>
> http://stackoverflow.com/questions/4825400/cmpxchg16b-correct
>
> Thanks for any guidance,
>
> --Borg Onion
--
--Borg Onion
