Re: [XenPPC] [rfc] [patch] 64-bitize guest handles

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

On Jun 28, 2006, at 1:10 PM, Hollis Blanchard wrote:

> On Wed, 2006-06-28 at 06:34 -0400, Jimi Xenidis wrote:
> >    #define set_xen_guest_handle(hnd, val) \
> >        do { \
> >            if (sizeof ((hnd).__pad)) \
> >                (hnd).__pad = 0; \
> >            (hnd).p = val; \
> >        } while (0)
> I like the union better than a struct with carefully-constructed
> non-overlapping members.
hmm, really! Ok, then you will have to also fix:
  #define get_xen_guest_handle(val, hnd)  do { val = (hnd).p; }  
while (0)
or the 32bit caller will only get the high-order 32bit into val.

> Also, the separate assignment to 0 would be avoided.
In 32 bits the store in of a long long is still 2 stw instructions,  
and the conditional will get optimized away so the instruction  
sequence is equivalent.
I'll leave it to you.
-JX





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