[cfe-dev] clang miscompile prevents ATLAS build

[Eli Friedman]

On Sun, Sep 4, 2011 at 12:40 PM, Clint Whaley <whaley at cs.utsa.edu> wrote:
> Eli,
>
>>Don't use -mavx with clang... the support is incomplete at best.  (I'm
>>actually not entirely sure why exactly the option exists.)
>
> People want to compile ATLAS with clang.  ATLAS is in the performance
> business.  Not using AVX cuts your peak in half compared to SSE on
> sandy bridge.  I'm aware clang itself is probably not using AVX well, but
> ATLAS contains intrinsics code that people want to compile with clang.
> Without -mavx flag, clang is not a competitive compiler for ATLAS.

Proper AVX support is non-trivial, and it simply isn't in a working
state.  We are making progress...

-Eli