From: Denys Vlasenko <vda.linux@googlemail.com>
To: musl <musl@lists.openwall.com>
Subject: Re: [PATCH 1/2] x86_64/memset: avoid multiply insn if possible
Date: Fri, 13 Feb 2015 17:38:45 +0100 [thread overview]
Message-ID: <CAK1hOcP8D2pbFMrcFWPrbiHXeB5_NBUwJ20Bf75fx1ETNp4ptA@mail.gmail.com> (raw)
In-Reply-To: <20150213072436.GD23507@brightrain.aerifal.cx>
On Fri, Feb 13, 2015 at 8:24 AM, Rich Felker <dalias@libc.org> wrote:
> On Thu, Feb 12, 2015 at 09:36:26PM +0100, Denys Vlasenko wrote:
> In practice it performs quite well. x86's are good at this. The
> generic C code in memset.c does not do any overlapping writes of
> different sizes for the short buffer code path -- all writes there are
> single-byte, and multiple-write only happens for some of the inner
> bytes depending on the value of n.
Measurements agree: I was not able to make it faster by doing it
differently.
I did find it possible to extend your trick to be usable for up to 30
byte blocks.
Sending the patch...
prev parent reply other threads:[~2015-02-13 16:38 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-12 17:17 Denys Vlasenko
2015-02-12 17:17 ` [PATCH 2/2] x86_64/memset: align destination to 8 byte boundary Denys Vlasenko
2015-02-12 17:27 ` [PATCH 1/2] x86_64/memset: avoid multiply insn if possible Rich Felker
2015-02-12 19:26 ` Denys Vlasenko
2015-02-12 20:36 ` Denys Vlasenko
2015-02-13 7:24 ` Rich Felker
2015-02-13 16:38 ` Denys Vlasenko [this message]
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