Fix a regression from the previous commit.
Template instantiation can set the canonical decl to used after subsequent
decls have been chained, so we have to check that too.

llvm-svn: 171088
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index e444f3c..4b82069 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -328,7 +328,11 @@
 
 /// \brief Used to prune the decls of Sema's UnusedFileScopedDecls vector.
 static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
-  if (D->getMostRecentDecl()->isUsed())
+  // Template instantiation can happen at the end of the translation unit
+  // and it sets the canonical (first) decl to used. Normal uses set the last
+  // decl at the time to used and subsequent decl inherit the flag. The net
+  // result is that we need to check both ends of the decl chain.
+  if (D->isUsed() || D->getMostRecentDecl()->isUsed())
     return true;
 
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {