Mark all subsequent decls used.

In the source

  static void f();
  static void f();
  template<typename T>
  static void g() {
    f();
  }
  static void f() {
  }
  void h() {
    g<int>();
  }

the call to f refers to the second decl, but it is only marked used at the end
of the translation unit during instantiation, after the third f decl has been
linked in.

With this patch we mark all subsequent decls used, so that it is easy to check
if a symbol is used or not.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171888 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 66861ae..8f9e1a9 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -328,11 +328,7 @@
 
 /// \brief Used to prune the decls of Sema's UnusedFileScopedDecls vector.
 static bool ShouldRemoveFromUnused(Sema *SemaRef, const DeclaratorDecl *D) {
-  // 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())
+  if (D->getMostRecentDecl()->isUsed())
     return true;
 
   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {