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gcc broken after VPS moved to a newer CPU
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Ox-
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Joined: 19 Jun 2003
Posts: 305

PostPosted: Thu Oct 10, 2013 7:58 am    Post subject: gcc broken after VPS moved to a newer CPU Reply with quote

I've been on a VPS (Xen based) running Gentoo since 2004 and now running into a problem I haven't been able to find.

The VPS was running on older hardware with Xeon processors and I successfully used -march=native in CFLAGS for several years. The hardware was recently upgraded and we are now on Xeon E5-2670 CPU's. Everything kept running fine but I started to see breakage when compiling new ebuilds (I would see illegal instruction errors), so I tried several other CFLAGS like -march=corei7-avx and even -march=generic. I seemed to have best results with -mtune=i686 but still had issues.

I did a rebuild of gcc, but wondering if I should rebuild the entire toolchain? (And ashamed to say it's been so long I don't remember which components other than gcc and glibc would be in the toolchain).
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N8Fear
Tux's lil' helper
Tux's lil' helper


Joined: 15 Apr 2013
Posts: 79
Location: Berlin (Germany)

PostPosted: Thu Oct 10, 2013 8:11 am    Post subject: Reply with quote

If you want to rebuild the toolchain you should definitely include binutils.
But if your problem really is caused by wrong cflags you'll have to rebuild the whose system: every package was built using the wrong cflags then.
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yoshi314
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Joined: 30 Dec 2004
Posts: 817
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PostPosted: Thu Oct 10, 2013 10:28 am    Post subject: Reply with quote

make sure your gcc is up to date, as it might be misdetecting the cpu somehow. Does Xen directly represent the actual cpu, or somehow alter its identification data? If in doubt, you might use specific model cflags, or stick to generic ones.

you might want to use http://packages.gentooexperimental.org/packages/ to quickly bring your system set up to date, into generically built binaries. The rest should be fairly easy to rebuild.
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chithanh
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Joined: 05 Aug 2006
Posts: 1561
Location: Berlin, Germany

PostPosted: Thu Oct 10, 2013 11:46 am    Post subject: Reply with quote

If your VPS host uses Xen before 4.2 there are known issues with AVX.
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