On 07/07/2010 04:26 PM, Preeti Sharma wrote:
> I am trying to use __sync_fetch_and_add with type as "long long" .
>
> This gives me the link error :
> undefined reference to `__sync_fetch_and_add_8'
>
> This compiles for a "int " type though. I am using the the gcc option
> -march=i686
>
> Is it possible to do a 64 bit integer operation atomically with the
> __sync .. builtin functions ?
Works for me:
long long a;
t()
{
__sync_fetch_and_add(&a, 1);
}
$ gcc -S t.c -m32 -march=i686 -O2
.file "t.c"
.text
.p2align 4,,15
.globl t
.type t, @function
t:
pushl %ebp
movl %esp, %ebp
subl $12, %esp
movl %ebx, (%esp)
movl %esi, 4(%esp)
movl %edi, 8(%esp)
movl a, %eax
movl a+4, %edx
.L2:
movl %eax, %esi
movl %edx, %edi
addl $1, %esi
adcl $0, %edi
movl %esi, %ebx
movl %edi, %ecx
lock cmpxchg8b a
jne .L2
movl (%esp), %ebx
movl 4(%esp), %esi
movl 8(%esp), %edi
movl %ebp, %esp
popl %ebp
ret
.size t, .-t
.comm a,8,8
.ident "GCC: (GNU) 4.4.3 20100127 (Red Hat 4.4.3-4)"
.section .note.GNU-stack,"",@progbits
