diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 2caa8509ea06..9a56116173ec 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -6874,6 +6874,7 @@ Value *CodeGenFunction::EmitARMMVEBuiltinExpr(unsigned BuiltinID,
     return ToReturn;
   }
   }
+  llvm_unreachable("unknown custom codegen type.");
 }
 
 static Value *EmitAArch64TblBuiltinExpr(CodeGenFunction &CGF, unsigned BuiltinID,