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Date: Wed, 21 Mar 2012 09:47:39 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: left shift by 1 via ADD
magnum -
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.
Alexander
View attachment "sse-intrinsics.c-sha.diff" of type "text/plain" (890 bytes)
View attachment "sse-intrinsics.c.diff" of type "text/plain" (876 bytes)
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