Test performance of the failure path of compare-and-swap
Test performance of the failure path of compare-and-swap

The OSAtomic CAS documentation doesn't specify a difference between the success and failure paths, but the __c11_compare_exchange_* calls do.

glessard/swift-atomics,ithron/swift-atomics,ithron/swift-atomics,ithron/swift-atomics,glessard/swift-atomics,glessard/swift-atomics