Check linkage.

llvm-svn: 50851
diff --git a/llvm/lib/Transforms/IPO/StructRetPromotion.cpp b/llvm/lib/Transforms/IPO/StructRetPromotion.cpp
index 80952b7..77a35b4 100644
--- a/llvm/lib/Transforms/IPO/StructRetPromotion.cpp
+++ b/llvm/lib/Transforms/IPO/StructRetPromotion.cpp
@@ -73,7 +73,7 @@
 bool SRETPromotion::PromoteReturn(CallGraphNode *CGN) {
   Function *F = CGN->getFunction();
 
-  if (!F || F->isDeclaration())
+  if (!F || F->isDeclaration() || !F->hasInternalLinkage())
     return false;
 
   // Make sure that function returns struct.