Date: Mon, 26 Nov 2001 09:43:32 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: David Xu <davidx@viasoft.com.cn> Cc: freebsd-hackers@FreeBSD.org Subject: Re: add some constraints in cpufunc.h Message-ID: <XFMail.011126094332.jhb@FreeBSD.org> In-Reply-To: <005201c17331$c603bcd0$ef01a8c0@davidwnt>
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On 22-Nov-01 David Xu wrote: > According to GCC manual of inline assembler instruction, it says if your > instruction > changes condition code register(on X86, it's cpu flag register, and a simple > addl > instruction can affect it), you'd put cc there, I have reviewed some source > header > files of bus management, they all have cc constraint, but others not, and > some > lines lost __volatile__ keyword, GCC can feel free to optimize them and > re-order > or delete these lines when it thinks this is a right decision, this could be > dangerous > when high optimizing option is turned on. Bah, fair enough. There are probably several places that are missing "cc". I doubt that there are very many bugs from this though, since "cc" is clobbered very often during normal program flow. -- 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 freebsd-hackers" in the body of the message
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