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RE: [PATCH][AArch64] Tune memcpy
- From: "Wilco Dijkstra" <Wilco dot Dijkstra at arm dot com>
- To: <pinskia at gmail dot com>
- Cc: <newlib at sourceware dot org>
- Date: Fri, 6 Nov 2015 14:34:19 -0000
- Subject: RE: [PATCH][AArch64] Tune memcpy
- Authentication-results: sourceware.org; auth=none
- References: <000001d117fc$6fafe190$4f0fa4b0$ at arm dot com> <565E3296-5669-441A-AB9E-1E4A06239BC2 at gmail dot com>
pinskia@gmail.com wrote:
> > def_fn memcpy p2align=6
> > + prfm PLDL1KEEP, [src]
>
> Why keep rather than strm for the prefetches?
It improves small copies by prefetching the input immediately, so setting
it to streaming would have an adverse effect as it claims the line will not
be used again. For huge copies the initial prefetch has no effect.
Wilco