Date: Thu, 16 Mar 2000 22:09:37 -0800 From: Doug Barton <Doug@gorean.org> To: freebsd-current@freebsd.org Subject: Re: gcc -Os optimisation broken (RELENG_4) Message-ID: <38D1CC21.B4A59808@gorean.org> References: <38CF48CF.59A100D7@altavista.net> <8ap8qe$hvj$1@bigeye.rhein-neckar.de> <38D08908.C629B55E@gorean.org> <38D08ADF.9C28C61E@cvzoom.net>
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Donn Miller wrote: > > Doug Barton wrote: > > > Hmm... If I have a PII (Actually celeron 300A) or a PIII, which is > > better, 'pentium' or 'pentiumpro'? I would think the latter, but I've > > learned not to assume where gcc is concerned. > > I think that 'pentium' would result in code that isn't as optimized as > 'pentiumpro', but I've heard that 'pentium' has a lot less problems. > > > Also, I have heard conflicting reports as to whether compiling the > > kernel/world with optimisations is a good thing. Anyone care to (re)open > > that can of worms? > > I compile my kernel/world with -mpentium -O3 -pipe. The only problem > I've seen so far were spurious random reboots that would occur about > 2-3 times a month. But, that was last summer, and hasn't happened > since. Something else must have been the culprit. (Maybe -current > wasn't as stable last summer.) With the aforementioned CFLAGS, I have > a pretty reliable and stable system. > > I've heard that -mpentiumpro can be pretty buggy, and it can actually > result in slower code than -mpentium for certain pentium types. I > trust plain -mpentium, as it has been very reliable for me, except for > some compile-time errors caused by the optimization (Qt). In the interests of providing another datapoint, I tried my old, boring P5 machine, and with -Os -march=pentium buildworld bombed trying to compile cc1plus in the build tools phase. Backing off to -O worked. The kernel was ok with -Os -march=pentium. Hope someone is finding this useful, Doug -- "While the future's there for anyone to change, still you know it seems, it would be easier sometimes to change the past" - Jackson Browne, "Fountain of Sorrow" To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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