Revert r267691, it caused PR27535.

llvm-svn: 267744

1 files changed, 11 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 065c236d6cc..0f47e9e0994 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -13011,7 +13011,17 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
       UndefinedButUsed.insert(std::make_pair(Func->getCanonicalDecl(), Loc));
   }
 
-  Func->markUsed(Context);
+  // Normally the most 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 = F->getPreviousDecl()) {
+    F->markUsed(Context);
+    if (F == Func)
+      break;
+  }
 }
 
 static void