Ulrich Drepper wrote:
> > - if (!urb->status & !acm->throttle) {
> > + if (!urb->status && !acm->throttle) {
[...]
> Have you really looked at detail at all these cases? The problem is
> that you have made the code less efficient on some platforms. The use
> of && requires shortcut evaluation. I.e., the compiler is forced to not
While I agree with your observation in general, this is actually
something the compiler should be able to figure out by itself:
- there's only a side-effect if acm is NULL
- in ACM_READY, we've already tested acm for NULL, and subsequently
de-referenced it
- acm is a local variable, and not aliased, so the dbg() can't
change it
So, given the negations, || and | are equivalent in this case, and
whether a jump, conditional execution, a bit operation, or something
else yields better code is compiler, machine, and context specific.
- Werner
-- _________________________________________________________________________ / Werner Almesberger, Buenos Aires, Argentina wa@almesberger.net / /_http://www.almesberger.net/____________________________________________/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Mar 07 2003 - 22:00:19 EST