[clang] [clang][amdgpu] mapCABIAtomicOrdering - fix MSVC not all control paths return a value warning. NFC. (PR #180500)

[Thibault Monnier via cfe-commits]

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@@ -290,6 +290,7 @@ static llvm::AtomicOrdering mapCABIAtomicOrdering(unsigned AO) {
   case llvm::AtomicOrderingCABI::relaxed:
     return llvm::AtomicOrdering::Monotonic;
   }
+  llvm_unreachable("Unknown AtomicOrderingCABI enum");
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Thibault-Monnier wrote:

Could this be put in a `default` statement instead?

https://github.com/llvm/llvm-project/pull/180500