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Message-ID: <20120627031711.GA14832@openwall.com>
Date: Wed, 27 Jun 2012 07:17:11 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: clang builds are faster than gcc builds for --format=dominosec
On Tue, Jun 26, 2012 at 11:53:07PM +0200, Frank Dittrich wrote:
> Finally, an interesting observation...
> For linux-x86-64. the clang version is more than 30% faster than any gcc
> build (at least with the gcc 4.6.3 that comes with fedora 16), for 32
> bit linux-x86, clang builds are even more than 40% faster.
DOMINOSEC_fmt_plug.c has highly non-optimal code with tiny loops where
changes in just one generated instruction can significantly affect
overall performance. It could benefit from changes similar to those I
recently made to lotus5_fmt_plug.c. Both of these are also candidates
for bitslicing (but we'd need to generate a "circuit" for the custom
S-box) or for uses of PSHUB/VPPERM.
It's curious to know that clang did better than gcc for you on this code
nevertheless.
Alexander
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