diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2377,9 +2377,10 @@
     }
 
     // Decide whether the argument we're handling could be partially undef
-    bool ArgNoUndef = DetermineNoUndef(ParamType, getTypes(), DL, AI);
-    if (CodeGenOpts.EnableNoundefAttrs && ArgNoUndef)
-      Attrs.addAttribute(llvm::Attribute::NoUndef);
+    if (CodeGenOpts.EnableNoundefAttrs) {
+      if (DetermineNoUndef(ParamType, getTypes(), DL, AI))
+        Attrs.addAttribute(llvm::Attribute::NoUndef);
+    }
 
     // 'restrict' -> 'noalias' is done in EmitFunctionProlog when we
     // have the corresponding parameter variable.  It doesn't make