Re: [patch 4/21] fix ARCH_HAS_PREFETCH

[H. Peter Anvin]

Willy Tarreau wrote:
>>>
>>
>>#define __nop() asm volatile("")
> 
> and if you want to pass arguments, to guarantee that no optimization will
> be done, even on loop constants ?
> eg:
>   for (i = 0; i < N; i++) {
>     j++;
>     __nop();
>   }
> 
> -> might be optimized this way :
>   j = N;
>   for (i = 0; i < N; i++) {
>     __nop();
>   }
> 
> Perhaps using a volatile for j ?
> 

OK, what are you trying to accomplish by this?

But if you wanted to, you could do:

for ( i = 0 ; i < N ; i++ ) {
	j++;
	asm volatile("" : "=g" (j));
}