Date: Thu, 23 May 2002 10:24:52 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Jonathan Mini <mini@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: <XFMail.20020523102452.jhb@FreeBSD.org> In-Reply-To: <20020523070814.Q25907@stylus.haikugeek.com>
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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. rep does modify %ecx when used with, say string instructions. It decrements %[e]cx once for each interation. -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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