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Date:      Tue, 23 Oct 2012 23:40:55 -0600
From:      Peter Grehan <grehan@freebsd.org>
To:        Andriy Gapon <avg@FreeBSD.org>
Cc:        svn-src-projects@FreeBSD.org, src-committers@FreeBSD.org, Jilles Tjoelker <jilles@stack.nl>
Subject:   Re: svn commit: r241744 - projects/bhyve/usr.sbin/bhyve
Message-ID:  <50877F67.1040409@freebsd.org>
In-Reply-To: <5086D040.1090307@FreeBSD.org>
References:  <201210191811.q9JIBIQu049356@svn.freebsd.org> <20121021121006.GA96141@stack.nl> <5085D433.4020101@freebsd.org> <20121023095549.GA27951@stack.nl> <5086C976.9060705@freebsd.org> <5086D040.1090307@FreeBSD.org>

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Hi Andriy,

> If this code emulates something like mov into %eax on AMDD64, then it should clear
> upper 32-bits of %rax.  Which I think your original code already did, but in a
> less obvious way than Jilles suggested above.
> But I could be very well confused...

  The 0x88/0x89 forms of the MOV instruction don't touch bytes outside 
of the operand size.

later,

Peter.





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