[cfe-dev] clang miscompile prevents ATLAS build

[Eli Friedman]

On Sun, Sep 4, 2011 at 1:21 PM, Evan Cheng <evan.cheng at apple.com> wrote:
> Are you using tot clang and llvm? We are just about done with -mavx. It has passed all of Intel's test suite.

Really?  I thought it was somewhat less stable, considering the amount
of development work going into AVX support recently (not to mention
the number of open bugs with AVX in the title).

-Eli

> Evan
>
> On Sep 4, 2011, at 12:52 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>
>> 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
>>
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>