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Coogee
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PostPosted: Tue Jul 26, 2005 9:57 pm    Post subject: -march=athlon-xp -mtune=athlon64 Reply with quote

I'm currently doing an "emerge -e world" with CFLAGS "-march=athlon-xp" and "-mtune=athlon64".
The reason for this CFLAGS is that I want to have a 32 bit environment, but also optimized for Athlon64, which AFAIK has more registers, SSE2 etc. (I know SSE2 can also be enabled by "-msse2").
I know that "mtune=athlon64" does not change the ABI, so, IMO there should be no interface problem to 32 bit programs.

I tested it a little bit by compiling xine-lib with athlon-xp/athlon64. I started kaffeine (which uses xine-lib and which was compiled athlon-xp/athlon-xp) and everything seems to work like always.

Therefore my question: Does anyone know if march=athlon-xp/mtune=athlon64 has any effect and if yes which?
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crazycat
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PostPosted: Tue Jul 26, 2005 10:38 pm    Post subject: Reply with quote

faq thread 5th question from above.
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Coogee
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PostPosted: Tue Jul 26, 2005 10:59 pm    Post subject: Reply with quote

Thanks :oops:
I read the FAQ a long time ago and I couldn't remeber this question.
I only remember that the recommendation for gcc 3.3.x was "march=athlon-xp -msse2".
With gcc 3.4.x it seems it is possible to use
Code:
ACCEPT_KEYWORDS="x86"
CHOST="i686-pc-linux-gnu"
CFLAGS="-march=athlon64 -O2 -pipe -fomit-frame-pointer"
CXXFLAGS="${CFLAGS}"

which seems to produce pure 32-bit code.
I'm gonna try this...
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cciechad
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PostPosted: Wed Jul 27, 2005 2:20 am    Post subject: Reply with quote

Works for me except for some issue with a dependency on an earlier gcc which won't accept those keywords. I am also testing -msse3 for my Venice cored processor.[/quote]
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crazycat
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PostPosted: Wed Jul 27, 2005 8:57 am    Post subject: Reply with quote

You need gcc 3.4+ for that.
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Coogee
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PostPosted: Thu Jul 28, 2005 9:01 pm    Post subject: Reply with quote

Just to complete this topic:
I have finished compiling the whole system with "march=athlon64", but I have not found an application yet, which is faster than before, e.g. transcoding a DVD to ogm/xvid took exactly as long as before.
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crazycat
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PostPosted: Thu Jul 28, 2005 9:06 pm    Post subject: Reply with quote

I think it only affects some different timing on atholon64 if at all. But it is more future proof so if there will be some athlon64 optimisation so that they will automatically get included.
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Maedhros
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PostPosted: Thu Jul 28, 2005 10:23 pm    Post subject: Reply with quote

Moved from Gentoo on AMD64 to Duplicate Threads in favour of https://forums.gentoo.org/viewtopic.php?t=177670.html
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