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[Xen-devel] RE: [patch] pae: tlbflush linear page table updates

To: <ak@xxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: [Xen-devel] RE: [patch] pae: tlbflush linear page table updates
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Fri, 12 Aug 2005 17:37:42 +0800
Cc: Gerd Knorr <kraxel@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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>-----Original Message-----
>From: ak@xxxxxxx [mailto:ak@xxxxxxx]
>Sent: Friday, August 12, 2005 5:21 PM
>Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> writes:
>> The compiler will never alias inputs. In this case it is forced to
>> alias the output constraint with input retval, and so the output
>> cannot alias with any other input (which would be an error).
>Actually it will sometimes. That is what the "early clobber" (&)
>prevents. Perhaps it should be used here.

"early clobber" is good to prevent output alias as input, if that output
may be clobbered before input is used. However there seems no point to
simply alias among inputs. Or else, the only way I can see is that
compiler insert some extra lines in the middle of inline asm... Any
benefit for this likelihood?


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