On 2013-04-02 07:41, Alexander Graf wrote:
>> On 2013-04-01 23:34, Alexander Graf wrote:
>>> Is this faster than a load/store with std/ldbrx?
>>
>> Hmm.  Almost certainly not.  And since we've got stack space
>> allocated for function calls, we've got scratch space to do it in.
>>
>> Probably similar for bswap32 too, eh?
>
> Depends - memory load/store doesn't come for free and bswap32 is quite short.
>
>>
>> I'll do a tiny bit o benchmarking for power7.
>
> Cool, thanks a bunch :)

Heh.  "Almost certainly not" indeed.  Unless I've made some silly mistake,
going through memory stalls badly.  No store buffer forwarding on power7?

With the following test case, time reports:

f1		2.967s
f2		8.930s
f3		7.071s
f4		7.166s

And note that f4 is a normal store/load pair, trying to determine what the
store buffer forwarding delay might be.


r~