[PATCH] D13051: Add placeholder __libcpp_relaxed_store() for when atomic builtins are not available.

[Jonathan Roelofs via cfe-commits]

jroelofs added a comment.

In http://reviews.llvm.org/D13051#250910, @EricWF wrote:

> @jroelofs @dim, could we fallback to the __sync_* builtins on arm?


@dim would need armv4-flavored implementations of them in compiler-rt (if that's what he's using)... the existing ones use instructions that v4 doesn't have. Implementation-wise, they'd have to use `__kuser_cmpxchg`. See: https://www.kernel.org/doc/Documentation/arm/kernel_user_helpers.txt


http://reviews.llvm.org/D13051