SampleProfile.cpp: Fix take #2. The issue was abuse of StringRef here.

llvm-svn: 203996
diff --git a/llvm/lib/Transforms/Scalar/SampleProfile.cpp b/llvm/lib/Transforms/Scalar/SampleProfile.cpp
index ba8d223..2edccee 100644
--- a/llvm/lib/Transforms/Scalar/SampleProfile.cpp
+++ b/llvm/lib/Transforms/Scalar/SampleProfile.cpp
@@ -972,8 +972,10 @@
     }
   }
 
-  Twine Msg = "No debug information found in function " + F.getName();
-  F.getContext().diagnose(DiagnosticInfoSampleProfile(Msg));
+  StringRef FnName = F.getName();
+  Twine Msg = "No debug information found in function " + FnName;
+  DiagnosticInfoSampleProfile Diag(Msg);
+  F.getContext().diagnose(Diag);
   return 0;
 }