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Date: Wed, 21 Mar 2012 11:30:09 +0100
From: magnum <>
Subject: Re: left shift by 1 via ADD

On 03/21/2012 06:47 AM, Solar Designer wrote:
> There are some rotates by 1 bit in SHA-1.  When we don't have XOP, those
> involve left shifts by 1 bit (as well as right shifts and ORs).  The
> left shifts may be replaced by ADDs, which are 1 byte shorter.  (I am
> already using this trick in the DES key setup.)  The attached patch
> reduces the sse-intrinsics.o .text size by 128 bytes here (relative to
> the version with MD5 optimizations).  The reduced code size might result
> in a speedup on CPUs with caching of x86 instructions (as opposed to
> micro-ops) - on Atom maybe?  On E5420, there's no difference.

Thanks. As far as I could tell, the sse-intrinsics.diff in your second
mail includes the patch from your first mail, right? So I committed that
one only. Just checking.

I also committed new pre-built intrinsics.


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