[libcxx] r248313 - Add placeholder __libcpp_relaxed_store() for when atomic builtins are not available.

[Eric Fiselier via cfe-commits]

Hi Tom,

I would like this patch merged into 3.7.1.
Marshall can you please approve this?

/Eric

On Tue, Sep 22, 2015 at 12:55 PM, Dimitry Andric via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: dim
> Date: Tue Sep 22 13:55:37 2015
> New Revision: 248313
>
> URL: http://llvm.org/viewvc/llvm-project?rev=248313&view=rev
> Log:
> Add placeholder __libcpp_relaxed_store() for when atomic builtins are not available.
>
> Summary:
> In rL241532, atomic_support.h was added, which provides handling of
> atomic operations for libc++.  When atomic builtins are not available,
> it emits a warning about being unsupported, but it still provides a
> number of stubs for the required functions.
>
> However, it misses a stub for `__libcpp_relaxed_store()`.  Add it, by
> using the same implementation as for `__libcpp_atomic_store()`.
>
> (Note that I encountered this on arm-freebsd, which still defaults to
> armv4, and does not have the runtime libcalls to support atomic
> builtins.  For now, I have simply disabled using them.)
>
> Reviewers: mclow.lists, EricWF
>
> Subscribers: theraven, cfe-commits, jroelofs, majnemer, aemerson
>
> Differential Revision: http://reviews.llvm.org/D13051
>
> Modified:
>     libcxx/trunk/src/include/atomic_support.h
>
> Modified: libcxx/trunk/src/include/atomic_support.h
> URL: http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/include/atomic_support.h?rev=248313&r1=248312&r2=248313&view=diff
> ==============================================================================
> --- libcxx/trunk/src/include/atomic_support.h (original)
> +++ libcxx/trunk/src/include/atomic_support.h Tue Sep 22 13:55:37 2015
> @@ -103,6 +103,13 @@ void __libcpp_atomic_store(_ValueType* _
>      *__dest = __val;
>  }
>
> +template <class _ValueType, class _FromType>
> +inline _LIBCPP_INLINE_VISIBILITY
> +void __libcpp_relaxed_store(_ValueType* __dest, _FromType __val)
> +{
> +    *__dest = __val;
> +}
> +
>  template <class _ValueType>
>  inline _LIBCPP_INLINE_VISIBILITY
>  _ValueType __libcpp_atomic_load(_ValueType const* __val,
>
>
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