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Re: [PATCH] aarch64: Optimized implementation of memmove for Qualcomm Falkor
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha at sourceware dot org
- Cc: nd at arm dot com
- Date: Thu, 5 Oct 2017 09:35:28 +0530
- Subject: Re: [PATCH] aarch64: Optimized implementation of memmove for Qualcomm Falkor
- Authentication-results: sourceware.org; auth=none
- References: <1505834450-21548-1-git-send-email-siddhesh@sourceware.org> <59D4E99C.9050500@arm.com>
- Reply-to: siddhesh at sourceware dot org
On Wednesday 04 October 2017 07:31 PM, Szabolcs Nagy wrote:
> i think adding a falkor specific memmove is ok,
> can you expand on why is it difficult to share code
> between memcpy and memmove?
The algorithms for memmove and memcpy are quite different, from the copy
loop sizes to prefetching behaviour because of the memmove requirement
to work on overlaps. Using multiple registers in memmove to expand the
copy look to the memcpy size regresses performance for memmove while
reducing the copy loop size in memcpy regresses memcpy, so it doesn't
make sense to try and unify the implementations.
Siddhesh