diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index eafa2b6165ea..65db206e570d 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -918,6 +918,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       case SequentiallyConsistent:
         return SequentiallyConsistent;
     }
+    llvm_unreachable("Unknown ordering");
   }
 
   AtomicOrdering addAcquireOrdering(AtomicOrdering a) {
@@ -934,6 +935,7 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
       case SequentiallyConsistent:
         return SequentiallyConsistent;
     }
+    llvm_unreachable("Unknown ordering");
   }
 
   // ------------------- Visitors.