Re: [PATCH] optimize ia32 memmove

[H. Peter Anvin]

Followup to:  <3FF15DAB.8080203@xxxxxxxxxxxxxxxx>
By author:    Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
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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