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Make.conf on G5 .... is this ok?
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Rawn027
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PostPosted: Fri Jun 25, 2004 6:14 am    Post subject: Make.conf on G5 .... is this ok? Reply with quote

CHOST="powerpc64-unknown-linux-gnu"
CFLAGS="-O3 -mcpu=970 -mtune=970 -maltivec -mabi=altivec -fno-strict-aliasing -pipe -fsigned-char"
CXXFLAGS="same as above"
MAKEOPTS="-j2" (one CPU)

how is that for a g5 system?
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SeJo
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PostPosted: Fri Jun 25, 2004 7:33 am    Post subject: Reply with quote

this looks very good...
i guess you won't have much problems...

good luck
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bruda
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PostPosted: Fri Jun 25, 2004 2:42 pm    Post subject: Re: Make.conf on G5 .... is this ok? Reply with quote

Rawn027 wrote:
CFLAGS="-O3 -mcpu=970 -mtune=970 -maltivec -mabi=altivec -fno-strict-aliasing -pipe -fsigned-char"


I've had problems (glibc) with this kind of flags, namely with -mcpu=970. If things go wrong you may want to erase this option.
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Rawn027
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PostPosted: Fri Jun 25, 2004 3:11 pm    Post subject: Reply with quote

what is the difference between thye outcome of mtune and mcpu

what do each do differently?
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Tesseract
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PostPosted: Wed Jun 30, 2004 2:55 am    Post subject: Reply with quote

According to the gcc man page, -mcpu sets the architecture type, register usage, choice of mnemonics, and instruction scheduling parameters. -mtune sets only the instruction scheduling parameters. Hence the -mtune=970 in the CFLAGS is redundant. I believe that -fsigned-char is the default, so it is also redundant.

Also, be aware that -O3 will increase code size since it turns on loop unrolling and function inlining. This may result in slower performance than -O2 due to cache effects. -O2 and -frename-registers might be a better choice, but I don't have a G5 to benchmark on so I don't know what kind of difference it makes either way.
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