Date: Thu, 23 May 2002 08:50:32 -0700 From: Jonathan Mini <mini@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, Peter Jeremy <peter.jeremy@alcatel.com.au> Subject: Re: cvs commit: src/sys/kern kern_mutex.c Message-ID: <20020523085032.R25907@stylus.haikugeek.com> In-Reply-To: <XFMail.20020523102452.jhb@FreeBSD.org>; from jhb@FreeBSD.org on Thu, May 23, 2002 at 10:24:52AM -0400 References: <20020523070814.Q25907@stylus.haikugeek.com> <XFMail.20020523102452.jhb@FreeBSD.org>
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John Baldwin [jhb@FreeBSD.org] wrote : > > On 23-May-2002 Jonathan Mini wrote: > > John Baldwin [jhb@FreeBSD.org] wrote : > > > >> In Intel's documentation they said that all current look-alikes worked as > >> well. It's the opcode for 'rep mov'. I am curious if some implementations > >> trash %ecx, and if we are paranoid we could always clobber %ecx in the > >> constraints. [ ... ] > > > > The rep prefix doesn't modify any registers. You do need to make > > sure that %ecx was zero when you dispatch a rep mov (unles you're > > dispatching a rep mov $0, %ecx), or you'll get an infinite loop. > > Bah, it's rep nop, not rep mov. Ahh. rep nop makes a lot more sense. > rep does modify %ecx when used with, say > string instructions. It decrements %[e]cx once for each interation. Um.. no. It's the string instruction that decrements cx. rep just, well, repeats. =) -- Jonathan Mini <mini@freebsd.org> http://www.haikugeek.com "He who is not aware of his ignorance will be only misled by his knowledge." -- Richard Whatley To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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