Skip declarations.

llvm-svn: 47890
diff --git a/llvm/lib/Transforms/IPO/StructRetPromotion.cpp b/llvm/lib/Transforms/IPO/StructRetPromotion.cpp
index 6659c5a5..feb5be6 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)
+  if (!F || F->isDeclaration())
     return false;
 
   // Make sure that function returns struct.