help with __sync for "long long" types

[Preeti Sharma]

Hello Andrew ,

Thanks for the response :
also wanted you to know that the problem is only for a 64 bit value ;
it compiles fine for a 32 bit int.

Thanks .

Preeti

On Wed, Jul 7, 2010 at 8:43 AM, Andrew Haley <aph@redhat.com> wrote:
> 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
>
>