From: William Lee Irwin III <wli@holomorphy.com>
To: "David S. Miller" <davem@redhat.com>
Cc: alexander.riesen@synopsys.COM, scrosby@cs.rice.edu,
linux-kernel@vger.kernel.org
Subject: Re: Algoritmic Complexity Attacks and 2.4.20 the dcache code
Date: Fri, 30 May 2003 23:30:40 -0700 [thread overview]
Message-ID: <20030531063040.GI8978@holomorphy.com> (raw)
In-Reply-To: <20030530.020040.52897577.davem@redhat.com>
From: Alex Riesen <alexander.riesen@synopsys.COM>
Date: Fri, 30 May 2003 10:59:01 +0200
> static
> int hash_3(int hi, int c)
> {
> return (hi + (c << 4) + (c >> 4)) * 11;
> }
> gcc-3.2.1 -O2 -march=pentium
> ...
> It is not guaranteed to be this way on all architectures, of course.
> But still - no multiplications.
On Fri, May 30, 2003 at 02:00:40AM -0700, David S. Miller wrote:
> Indeed, I'd missed this. GCC will emit the constant multiply
> expansion unless the multiply cost is set VERY low.
If the strength reduction situation changes to being properly handled
by gcc for most/all 64-bit arches, include/linux/hash.h can lose a #ifdef.
-- wli
next prev parent reply other threads:[~2003-05-31 6:17 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-29 20:42 Algoritmic Complexity Attacks and 2.4.20 the dcache code Scott A Crosby
2003-05-30 3:57 ` David S. Miller
2003-05-30 4:29 ` Ingo Molnar
2003-05-30 18:16 ` Timothy Miller
2003-05-30 18:53 ` Scott A Crosby
2003-05-30 5:04 ` Scott A Crosby
2003-05-30 6:24 ` David S. Miller
2003-05-30 6:46 ` Scott A Crosby
2003-05-30 6:56 ` David S. Miller
2003-05-30 8:59 ` Alex Riesen
2003-05-30 9:00 ` David S. Miller
2003-05-30 15:05 ` Scott A Crosby
2003-05-31 6:18 ` David S. Miller
2003-05-31 8:02 ` Willy TARREAU
2003-05-31 8:12 ` David S. Miller
2003-05-31 8:56 ` Willy Tarreau
2003-05-31 8:58 ` David S. Miller
2003-05-31 8:58 ` David Schwartz
2003-05-31 9:01 ` David S. Miller
2003-05-31 6:30 ` William Lee Irwin III [this message]
2003-05-31 6:33 ` David S. Miller
2003-05-31 6:41 ` William Lee Irwin III
2003-05-31 6:45 ` David S. Miller
2003-05-31 18:40 ` Aaron Lehmann
2003-05-30 4:02 ` Ingo Molnar
2003-05-30 4:42 ` Scott A Crosby
2003-05-30 5:01 ` David S. Miller
2003-05-30 13:48 ` Nikita Danilov
2003-06-01 1:15 ` Daniel Phillips
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