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Re: [Xen-devel] [PATCH 1/3] x86: use MOV instead of PUSH/POP when saving/restoring register state

>>> Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx> 10/02/12 8:09 PM >>>
>On Tue, Oct 02, 2012 at 04:26:23PM +0100, Jan Beulich wrote:
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

>What's the reasoning behind it? Just that mov's are faster than

No (that's not actually true anymore these days). The main reason is that with
MOV, part of the frame generation and register restoration can be more easily
skipped than when using PUSH/POP (would require extra stack pointer
adjustments on the alternative paths) - see patch 3.


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