This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: Strengthen ICF hash
- From: Andi Kleen <andi at firstfloor dot org>
- To: Jan Hubicka <hubicka at ucw dot cz>
- Cc: Andi Kleen <andi at firstfloor dot org>, gcc-patches at gcc dot gnu dot org, mliska at suse dot cz
- Date: Wed, 4 Mar 2015 14:20:00 +0100
- Subject: Re: Strengthen ICF hash
- Authentication-results: sourceware.org; auth=none
- References: <20150301214405 dot GB95914 at kam dot mff dot cuni dot cz> <87wq30tah7 dot fsf at tassilo dot jf dot intel dot com> <20150303072545 dot GA84757 at kam dot mff dot cuni dot cz>
Hi Honza,
Regarding modern hash functions, as far as I understand the trend
is to just stop doing anything fancy and just use the CRC instructions
in modern CPUs (unless you need a somewhat cryto hash to guard against
DoS attacks). spooky doesn't do that though, it's just a highly
optimized classical hash. It's much more stream lined than the somewhat
weird iterative hash construction that standard gcc uses, and I suspect
has better avalance effect. Also it'll do much less work per bit
(at the cost of larger code)
> Said all that I would be very curious if actual stronger hading would help.
> I saw some miscompares for stuff that should be covered by hash. I will try
> to get some stats soon.
I sent you the spooky patches in separate mail. I did a quick test run
and they don't seem to regress anything.
-Andi