[cfe-dev] clang miscompile prevents ATLAS build

[Evan Cheng]

On Sep 4, 2011, at 1:30 PM, Eli Friedman <eli.friedman at gmail.com> wrote:

> 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).

It's considered functionality complete. The only missing piece is the vzeroupper pass. The current focus is on performance. Obviously there are bugs since we have only run Intel and LLVM test suite through it. We welcome bug reports to help to flush out all the issues.

Evan

> 
> -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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>>