diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index 00fe2bf02252d6dd4e35cfe0747e92bf452f2b22..05eafb9abac5c0ae616103dadc14a470cf5a9a17 100644
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/lib/CodeGen/TargetInfo.cpp
@@ -1408,6 +1408,7 @@ static unsigned getNativeVectorSizeForAVXABI(X86AVXABILevel AVXLevel) {
   case X86AVXABILevel::None:
     return 128;
   }
+  llvm_unreachable("Unknown AVXLevel");
 }
 
 /// X86_64ABIInfo - The X86_64 ABI information.