From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: crypt* files in crypt directory
Date: Fri, 10 Aug 2012 14:06:13 -0400 [thread overview]
Message-ID: <20120810180613.GA27715@brightrain.aerifal.cx> (raw)
In-Reply-To: <20120810170435.GA29839@openwall.com>
On Fri, Aug 10, 2012 at 09:04:35PM +0400, Solar Designer wrote:
> > > why increase ptr at the begining?
> > > it seems the idiomatic way would be
> > >
> > > *ptr++ = L;
> > > *ptr++ = R;
> >
> > For me, making this change makes it 5% faster. I suspect the
> > difference comes from the fact that gcc is not smart enough to move
> > the ptr+=2; across the rest of the loop body, and the fact that it
> > gets spilled to the stack and reloaded for *both* points of usage
> > rather than just one. The original version may perform better on
> > machines with A LOT more registers, but I'm doubtful...
>
> The spilling theory makes sense to me, but it does not fully explain the
> 5% difference - I think it could explain a 1% difference or so. More
> likely there's some change in register allocation overall, not only for
> ptr - or something like it.
Indeed, that's possible too. I haven't read the asm diff.
> Anyhow, this does not match my test results so far, for different
> revisions of this code. What compiler, options, architecture, CPU?
gcc 4.6.3, -O3, generic/i486 code generation, no tuning for my cpu,
which is Atom.
Rich
next prev parent reply other threads:[~2012-08-10 18:06 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-21 15:23 Łukasz Sowa
2012-07-21 17:11 ` Solar Designer
2012-07-21 20:17 ` Rich Felker
2012-07-22 16:23 ` Łukasz Sowa
2012-07-25 7:57 ` Rich Felker
2012-08-08 2:24 ` Rich Felker
2012-08-08 4:42 ` Solar Designer
2012-08-08 5:28 ` Rich Felker
2012-08-08 6:27 ` Solar Designer
2012-08-08 7:03 ` Daniel Cegiełka
2012-08-08 7:24 ` Solar Designer
2012-08-08 7:42 ` Daniel Cegiełka
2012-08-08 21:48 ` Rich Felker
2012-08-08 23:08 ` Isaac Dunham
2012-08-08 23:24 ` John Spencer
2012-08-09 1:03 ` Isaac Dunham
2012-08-09 3:16 ` Rich Felker
2012-08-09 3:36 ` Solar Designer
2012-08-09 7:13 ` orc
2012-08-09 7:28 ` Rich Felker
2012-08-09 7:29 ` Solar Designer
2012-08-09 10:53 ` Solar Designer
2012-08-09 11:58 ` Szabolcs Nagy
2012-08-09 16:43 ` Solar Designer
2012-08-09 17:30 ` Szabolcs Nagy
2012-08-09 18:22 ` Rich Felker
2012-08-09 23:21 ` Rich Felker
2012-08-10 17:04 ` Solar Designer
2012-08-10 18:06 ` Rich Felker [this message]
2012-08-09 21:46 ` crypt_blowfish integration, optimization Rich Felker
2012-08-09 22:21 ` Solar Designer
2012-08-09 22:32 ` Rich Felker
2012-08-10 17:18 ` Solar Designer
2012-08-10 18:08 ` Rich Felker
2012-08-10 22:52 ` Solar Designer
2012-08-08 7:52 ` crypt* files in crypt directory Szabolcs Nagy
2012-08-08 13:06 ` Rich Felker
2012-08-08 14:30 ` orc
2012-08-08 14:53 ` Szabolcs Nagy
2012-08-08 15:05 ` orc
2012-08-08 18:10 ` Rich Felker
2012-08-09 1:51 ` Solar Designer
2012-08-09 3:25 ` Rich Felker
2012-08-09 4:04 ` Solar Designer
2012-08-09 5:48 ` Rich Felker
2012-08-09 15:52 ` Solar Designer
2012-08-09 17:59 ` Rich Felker
2012-08-09 21:17 ` Rich Felker
2012-08-09 21:44 ` Solar Designer
2012-08-09 22:08 ` Rich Felker
2012-08-09 23:33 ` Rich Felker
2012-08-09 6:03 ` Rich Felker
-- strict thread matches above, loose matches on Subject: below --
2012-07-17 9:40 Daniel Cegiełka
2012-07-17 17:51 ` Rich Felker
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