Date: Wed, 25 Aug 2004 12:12:16 +0100 From: Mike Bristow <mike@urgle.com> To: "Li, Qing" <qing.li@bluecoat.com> Cc: freebsd-current@freebsd.org Subject: RE: IPv4 checksum oddness (gcc compiler bug?) Message-ID: <1093432335.57022.141.camel@singsing.eng.demon.net> In-Reply-To: <00CDF9AA240E204FA6E923BD35BC6436063B074A@bcs-mail.internal.cacheflow.com> References: <00CDF9AA240E204FA6E923BD35BC6436063B074A@bcs-mail.internal.cacheflow.com>
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On Wed, 2004-08-25 at 00:57, Li, Qing wrote: > I ran into a checksum problem and filed the following bug > report. > See if it's related. > > http://www.freebsd.org/cgi/query-pr.cgi?pr=69257 To quote from Apple's GCC 3.3 docs: You can't expect a sequence of volatile asm instructions to remain perfectly consecutive. If you want consecutive output, use a single asm. Also, GCC will perform some optimizations across a volatile asm instruction; GCC does not "forget everything" when it encounters a volatile asm instruction the way some other compilers do. I've added a patch to the PR above which uses a single asm statement; I'll make some noise about it post 5.3. -- Mike Bristow - http://www.urgle.com/~mike/ - mike@urgle.com Why did the farmer call his horse Blacksmith? Mrs Sippi
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