Index: clang/lib/CodeGen/CGCXX.cpp
===================================================================
--- clang/lib/CodeGen/CGCXX.cpp
+++ clang/lib/CodeGen/CGCXX.cpp
@@ -134,6 +134,10 @@
   llvm::GlobalValue::LinkageTypes TargetLinkage =
       getFunctionLinkage(TargetDecl);
 
+  // r254170: Disallow aliases to available_externally.
+  if (TargetLinkage == llvm::GlobalValue::AvailableExternallyLinkage)
+    return true;
+
   // Check if we have it already.
   StringRef MangledName = getMangledName(AliasDecl);
   llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
@@ -157,8 +161,7 @@
   // Instead of creating as alias to a linkonce_odr, replace all of the uses
   // of the aliasee.
   if (llvm::GlobalValue::isDiscardableIfUnused(Linkage) &&
-     (TargetLinkage != llvm::GlobalValue::AvailableExternallyLinkage ||
-      !TargetDecl.getDecl()->hasAttr<AlwaysInlineAttr>())) {
+      !TargetDecl.getDecl()->hasAttr<AlwaysInlineAttr>()) {
     // FIXME: An extern template instantiation will create functions with
     // linkage "AvailableExternally". In libc++, some classes also define
     // members with attribute "AlwaysInline" and expect no reference to