Date: Fri, 07 May 2004 14:31:12 -0600 From: Scott Long <scottl@freebsd.org> To: Doug White <dwhite@gumbysoft.com> Cc: current@freebsd.org Subject: Re: src/sys/vm/vm_init.c v1.43 hangs amd64 Message-ID: <409BF210.8030307@freebsd.org> In-Reply-To: <20040507130607.Q42861@carver.gumbysoft.com> References: <20040430135155.C67990@carver.gumbysoft.com> <20040505054723.GB30514@dragon.nuxi.com> <20040507130607.Q42861@carver.gumbysoft.com>
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Doug White wrote: > On Tue, 4 May 2004, David O'Brien wrote: > > >>On Sat, May 01, 2004 at 08:42:46AM -0700, Doug White wrote: >> >>>2. Changing COPTFLAGS to '-O -frename-registers -pipe' from the default >>>'-O2 -frename-registers -pipe' stops the crash. So it may be an >>>O2-specific optimization bug. >> >>... >> >>>So in the end, at -O2, (nswbuf*MAXPHYS) != nswbuf*MAXPHYS. Creepy, eh? >>>I'll see if I can come up with a standalone test case to submit to the gcc >>>folks. >> >>Thanks! >>This is the first report of an -O2 problem, and I'm very happy you're >>willing to try to narrow this down so we don't have to return to -O[1]. > > > I caught kan's attention with this last night on irc, and he's going to > try to isolate the bad code generation. We could really use a standalone > case to test with & submit, but a naieve test doesn't come up with any > differences. > > In order to keep my amd64 stable I'm having to leave COPTFLAGS set, so if > someone commits a fix to gcc or imports a new version, try to get my > attention so I can test it with -O2 again. > > Also if we get into the 5.3 release timeframe we'll have to make a call to > ship with a -O2 compiled kernel or not. > Are you proposing dropping -O2 for 5.3 because you are afraid that there are other, not-yet-detected broken cases? I thought that we found a source code work-around that forced gcc to generate the correct assembly with -O2. Maybe that should be committed for the time being? Scott
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