Placate gcc's -Wreturn-type

llvm-svn: 149104
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 018521b..13b9e27 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -1166,6 +1166,7 @@
   case QualType::DK_objc_weak_lifetime:
     return destroyARCWeak;
   }
+  llvm_unreachable("Unknown DestructionKind");
 }
 
 /// pushDestroy - Push the standard destructor for the given type.