R600/SI: Add global atomicrmw xchg

v2: Add separate offset/no-offset tests

Signed-off-by: Aaron Watry <awatry@gmail.com>
Reviewed-by: Matt Arsenault <matthew.arsenault@amd.com>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220110 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed