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From
SubjectRe: [PATCH] optimize ia32 memmove
Date
Followup to:  <3FF15DAB.8080203@colorfullife.com>
By author: Manfred Spraul <manfred@colorfullife.com>
In newsgroup: linux.dev.kernel
>
> AMD recommends to perform bulk copies backwards: That defeats the hw
> prefecher, and results in even better access patterns. Doesn't matter in
> this case, memmove is never used for bulk copies.
>

That's also a microoptimization for one particular microarchitecture
*bug*. Hardware prefetchers are going omnidirectional going forward.
Additionally, nearly all bulk copies are performed forward (DF=0) in
existing codebases.

-hpa
--
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