From: Andre Renaud <andre@bluewatersys.com>
To: musl@lists.openwall.com
Subject: Re: Optimized C memset [v2]
Date: Wed, 28 Aug 2013 12:05:43 +1200 [thread overview]
Message-ID: <CAPfzE3ZiR0xngueXCgFSsO0mHFo5wOUjRZ=b3gVKQRgpF4yTpA@mail.gmail.com> (raw)
In-Reply-To: <20130827162205.GU20515@brightrain.aerifal.cx>
Hi Rich,
On 28 August 2013 04:22, Rich Felker <dalias@aerifal.cx> wrote:
> Here's version 2 (filename version 6, in honor of glibc ;) of the
> memset code. I fixed a bug in the logic for coverage of the tail (the
> part past what's covered by the loop) for some values of n and
> alignments, and cleaned up the __GNUC__ usage a bit to use less
> #ifdeffery. The remaining test at the top for the __GNUC__ version is
> ugly, I admit, and should possibly just be removed and replaced by a
> configure check to add -D__may_alias__= to the CFLAGS if the compiler
> defines __GNUC__ but does not recognize __attribute__((__may_alias__))
> -- opinions on this?
Can you explain the algorithm a bit - I can't entirely follow the us
of negation/masking, but it looks like at the end you're doing a loop
of 64-bit aligned writes, but I don't see how it can work if the tail
end ends in something that isn't 64-bit aligned? Is this assuming that
unaligned writes will work ok?
Regards,
Andre
next prev parent reply other threads:[~2013-08-28 0:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-27 8:30 Optimized C memset Rich Felker
2013-08-27 8:52 ` Jens Gustedt
2013-08-27 9:17 ` Rich Felker
2013-08-27 9:50 ` Jens Gustedt
2013-08-27 14:21 ` Rich Felker
2013-08-27 14:34 ` Luca Barbato
2013-08-27 14:39 ` Rich Felker
2013-08-27 15:20 ` John Spencer
2013-08-27 15:34 ` Rich Felker
2013-08-27 16:22 ` Optimized C memset [v2] Rich Felker
2013-08-27 17:28 ` Jeremy Huntwork
2013-08-27 21:27 ` Rich Felker
2013-08-28 0:05 ` Andre Renaud [this message]
2013-08-28 1:24 ` Rich Felker
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