fix PR7892, a crash on valid in c++ codegen of __PRETTY_FUNCTION__


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111330 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index e2ccf55..e978870 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1287,8 +1287,12 @@
     FnName = FnName.substr(1);
   GlobalVarName += FnName;
 
+  const Decl *CurDecl = CurCodeDecl;
+  if (CurDecl == 0)
+    CurDecl = getContext().getTranslationUnitDecl();
+  
   std::string FunctionName =
-    PredefinedExpr::ComputeName((PredefinedExpr::IdentType)Type, CurCodeDecl);
+    PredefinedExpr::ComputeName((PredefinedExpr::IdentType)Type, CurDecl);
 
   llvm::Constant *C =
     CGM.GetAddrOfConstantCString(FunctionName, GlobalVarName.c_str());