Re: [Xen-devel] code question?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 11 Aug 2005, at 18:03, M.A. Williamson wrote:

> I think that:
> !!a & !b === (a != 0 ) && ( b == 0 )
>
> It's just more efficient to do it directly using bitwise ops than to 
> use the full logical operators (can gcc really not optimise this sort 
> of thing???).
It can't optimise out short-circuit semantics. Without predicates on 
instructions (like e.g. ARM has) it has to emit conditional branches.
 -- Keir


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