[MinnowBoard] [MinnowBoardMax] gcc flags

[B Cran]

On Wed, Mar 4, 2015 at 8:35 AM, Benjamin Schubert <ben.c.schubert at gmail.com>
wrote:

> 1) I am running gentoo (hardened version)
> 2) My config is :
>
> CFLAGS="-march=corei7 -mtune=corei7 -mfpmath=sse -msse4.2 -mno-avx
> -mno-avx2 -O2 -pipe"
> CXXFLAGS="${CFLAGS}"
> CHOST="x86_64-pc-linux-gnu"
>
> 3) I rebuilt all the system with the same flags...
>

Oh, you might need to resort to a reinstall or restore the binaries from
the (stage 3?) tarball to undo any damage: I have no idea where it came
from because those flags _should_ work, but it'll be near-to-impossible
tracking down all the binaries which have been miscompiled.

'-march=corei7' is for the original i7 which doesn't have avx so it
shouldn't be causing problems. The -march values in gcc 4.9 are:

AMD Barcelona- march=barcelonaAMD Bobcat- march=btver1AMD Jaguar-
march=btver2AMD Bulldozer- march=bdver1AMD Piledriver- march=bdver2AMD
Steamroller- march=bdver3Intel Westmere- march=westmereIntel Core Nehalem-
march=corei7Intel Core Sandy Bridge- march=corei7-avxIntel Core Ivy Bridge-
march=core-avx-iIntel Core Haswell- march=core-avx2Intel Core Broadwell-
march=broadwellIntel Atom Bonnell- march=bonnellIntel Atom Silvermont
- march=silvermont

I just tested with -march=silvermont and confirmed that __AVX__ isn't
defined. Maybe some library has a bug and assumes all CPUs newer than X
have AVX support? Probably best to just stick with corei7 (Nehalem) for now
unless you have _lots_ of time to track down where the problem is occurring!

-- 
Bruce
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