From: David S. Miller <davem@davemloft.net>
Date: Thu, 24 May 2012 02:20:20 +0000 (-0700)
Subject: sparc: Optimize strncpy_from_user() zero byte search.
X-Git-Tag: v3.5-rc1~90^2~4
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4efcac3a244de86593a82ca4ed945e839eb4c5af;p=pandora-kernel.git

sparc: Optimize strncpy_from_user() zero byte search.

Compute a mask that will only have 0x80 in the bytes which
had a zero in them.  The formula is:

	~(((x & 0x7f7f7f7f) + 0x7f7f7f7f) | x | 0x7f7f7f7f)

In the inner word iteration, we have to compute the "x | 0x7f7f7f7f"
part, so we can reuse that in the above calculation.

Once we have this mask, we perform divide and conquer to find the
highest 0x80 location.

Signed-off-by: David S. Miller <davem@davemloft.net>
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