cmp-and-swap reversed the Cmp and Swap arguments; comments
make it clear this is unintentional. Unfortunately, the
x86 BE had a compensating reversal, which is removed here.
PPC is OK.
From inspection of the Alpha code I think it is OK, but
if somebody has that platform please check it out. I
cannot test on that platform.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56091 91177308-0d34-0410-b5e6-96231b3b80d8