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"
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