diff --git a/llvm/include/llvm/IR/GlobalValue.h b/llvm/include/llvm/IR/GlobalValue.h
--- a/llvm/include/llvm/IR/GlobalValue.h
+++ b/llvm/include/llvm/IR/GlobalValue.h
@@ -127,19 +127,23 @@
   /// time.
   bool mayBeDerefined() const {
     switch (getLinkage()) {
-    case WeakODRLinkage:
-    case LinkOnceODRLinkage:
-    case AvailableExternallyLinkage:
-      return true;
-
     case WeakAnyLinkage:
     case LinkOnceAnyLinkage:
     case CommonLinkage:
     case ExternalWeakLinkage:
-    case ExternalLinkage:
-    case AppendingLinkage:
+
+    // The three cannot be overridden but can be de-refined.
+    case WeakODRLinkage:
+    case LinkOnceODRLinkage:
+    case AvailableExternallyLinkage:
+      return true;
+
     case InternalLinkage:
     case PrivateLinkage:
+    case AppendingLinkage:
+      return false;
+
+    case ExternalLinkage:
       return isInterposable();
     }