Re: c inline assembly

[Gedare Bloom <gedare@rtems.org>]

On Sat, Feb 18, 2012 at 1:01 AM, ratheesh kannoth
<ratheesh.ksz@gmail.com> wrote:
> I am using gcc on a 32bit  intel machine.  i have defined an inline function.
>
>
> This function is inline .  what all registers needs to pushed and
> poped in the inline assembly so that the functions wont
> disturb the registers in  the function ( in which it is C inlined  ).
>
Use the clobber list:
http://ibiblio.org/gferg/ldp/GCC-Inline-Assembly-HOWTO.html#ss5.3

>
> inline unsigned long hello(unsigned long a)
>
> {
>  int b;
>  asm ("movl %1, %%eax;
>      " movl %1, %%ebx;
>       "movl  %1, %%ecx;
>       "movl  %1, %%esi;
>       "movl  %1, %%edi;
>
>       "movl %%eax, %0;"
>       :"=r"(b)        /* output */
>       :"r"(a)         /* input */
         : "eax","ecx","esi","edi" /* clobber */
>  );
> }
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