Date: Sat, 25 Jan 1997 07:03:02 -0500 (EST) From: Peter Dufault <dufault@hda.com> To: hackers@freebsd.org Subject: Proofread compare-and-swap gcc-asm Message-ID: <199701251203.HAA01609@hda.hda.com>
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Can someone who groks gcc-asm proofread this? It appears to work standalone,
but I think I'm trashing the stack in the program. It should compile with
"-DCAS_TEST".
--
Peter Dufault (dufault@hda.com) Realtime Machine Control and Simulation
HD Associates, Inc. Voice: 508 433 6936
/* cas: Compare-and-swap using the 486 and Pentium "cmpxchg"
* instruction.
*
* Atomically change what "ptr" points to to "n" if it is "o"
* and return success.
*/
#if defined(CAS_TEST)
typedef int bool;
typedef unsigned long castype;
extern bool cas(volatile castype *, const castype, const castype);
#else
#include "mwcas.h"
#endif
bool
cas(volatile castype *ptr, const castype o, const castype n)
{
volatile bool result = 0;
__asm __volatile (
"cmpxchg %3,%1; jne 0f; movl $1,%0;0:"
: "=m" (result)
: "m" (*ptr), "a" (o), "r" (n)
: "ax", "cc"
);
return result;
}
#if defined(CAS_TEST)
#include <stdio.h>
int main(int argc, char *av[])
{
while (1)
{
volatile castype c;
castype o, n;
bool result;
printf("c old new > ");
if (scanf("%ld %ld %ld", &c, &o, &n) != 3)
break;
result = cas(&c, o, n);
printf("%d; %ld %ld %ld\n", result, c, o, n);
}
return 0;
}
#endif /* CAS_TEST */
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