r336467 - [OPENMP] Fix PR38026: Link -latomic when -fopenmp is used.

[Jonas Hahnfeld via cfe-commits]

On 2018-07-19 20:55, Hal Finkel wrote:
> On 07/19/2018 09:01 AM, Jonas Hahnfeld wrote:
>> On 2018-07-19 15:43, Hal Finkel wrote:
>>> On 07/16/2018 01:19 PM, Jonas Hahnfeld wrote:
>>>> [ Moving discussion from https://reviews.llvm.org/D49386 to the
>>>> relevant comment on cfe-commits, CC'ing Hal who commented on the
>>>> original issue ]
>>>> 
>>>> Is this change really a good idea? It always requires libatomic for
>>>> all OpenMP applications, even if there is no 'omp atomic' directive 
>>>> or
>>>> all of them can be lowered to atomic instructions that don't require 
>>>> a
>>>> runtime library. I'd argue that it's a larger restriction than the
>>>> problem it solves.
>>> 
>>> Can you please elaborate on why you feel that this is problematic?
>> 
>> The linked patch deals with the case that there is no libatomic,
>> effectively disabling all tests of the OpenMP runtime (even though
>> only few of them require atomic instructions). So apparently there are
>> Linux systems without libatomic. Taking them any chance to use OpenMP
>> with Clang is a large regression IMO and not user-friendly either.
> 
> If there's a significant population of such systems, then this 
> certainly
> seems like a problem.
> 
> Let's revert this for now while we figure out what to do (which might
> just mean updating the documentation to include OpenMP where we talk
> about atomics).

Alexey, what do you think? Can I go ahead and revert this commit?

Thanks,
Jonas