[mips] Use libatomic instead of GCC intrinsics for 64bit
[mips] Use libatomic instead of GCC intrinsics for 64bit

The following GCC intrinsics are not available on MIPS32:

__sync_fetch_and_add_8
__sync_fetch_and_and_8
__sync_fetch_and_or_8
__sync_val_compare_and_swap_8

Replace these with appropriate libatomic implementation.

Patch by Miodrag Dinic.

Differential Revision: https://reviews.llvm.org/D45691


git-svn-id: f99161ee8ccfe2101cbe1bdda2220bce2ed25485@355687 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/openmp,llvm-mirror/openmp,llvm-mirror/openmp,llvm-mirror/openmp,llvm-mirror/openmp