Implement atomicrmw operations in 32 and 64 bits for SPARCv9.

These all use the compare-and-swap CASA/CASXA instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199975 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed