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

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 3702aa037c..cc692cda63 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -10495,7 +10495,18 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func) {
     if (old.isInvalid()) old = Loc;
   }
 
-  Func->setUsed(true);
+  // Normally the must current decl is marked used while processing the use and
+  // any subsequent decls are marked used by decl merging. This fails with
+  // template instantiation since marking can happen at the end of the file
+  // and, because of the two phase lookup, this function is called with at
+  // decl in the middle of a decl chain. We loop to maintain the invariant
+  // that once a decl is used, all decls after it are also used.
+  for (FunctionDecl *F = Func->getMostRecentDecl();;) {
+    F->setUsed(true);
+    if (F == Func)
+      break;
+    F = F->getPreviousDecl();
+  }
 }
 
 static void