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Re: [PATCH] Optimize SSE 4.1 x86_64 memcmp
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: GNU C Library <libc-alpha at sourceware dot org>
- Date: Fri, 31 Jan 2014 17:34:20 +0000
- Subject: Re: [PATCH] Optimize SSE 4.1 x86_64 memcmp
- Authentication-results: sourceware.org; auth=none
- References: <52EBBCC2 dot 7090807 at redhat dot com>
On Fri, 31 Jan 2014, Florian Weimer wrote:
> In case BSWAP turns out to be too slow for some CPUs, it could be replaced
> with BSF and a shift (both constant time in current processors), like we
> already do in some of the existing memcmp implementations.
I wonder how the performance of MOVBE compares with the other options
(though availability of MOVBE is sufficiently limited it may not be worth
having another version of memcmp using it).
--
Joseph S. Myers
joseph@codesourcery.com