Reland r267691 fixing PR27535.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@267882 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 7 deletions

diff --git a/lib/AST/DeclBase.cpp b/lib/AST/DeclBase.cpp
index aec3b7cd3b..dd0bab811e 100644
--- a/lib/AST/DeclBase.cpp
+++ b/lib/AST/DeclBase.cpp
@@ -340,25 +340,29 @@ unsigned Decl::getMaxAlignment() const {
   return Align;
 }
 
-bool Decl::isUsed(bool CheckUsedAttr) const { 
-  if (Used)
+bool Decl::isUsed(bool CheckUsedAttr) const {
+  const Decl *CanonD = getCanonicalDecl();
+  if (CanonD->Used)
     return true;
-  
+
   // Check for used attribute.
-  if (CheckUsedAttr && hasAttr<UsedAttr>())
+  // Ask the most recent decl, since attributes accumulate in the redecl chain.
+  if (CheckUsedAttr && getMostRecentDecl()->hasAttr<UsedAttr>())
     return true;
 
-  return false; 
+  // The information may have not been deserialized yet. Force deserialization
+  // to complete the needed information.
+  return getMostRecentDecl()->getCanonicalDecl()->Used;
 }
 
 void Decl::markUsed(ASTContext &C) {
-  if (Used)
+  if (isUsed(false))
     return;
 
   if (C.getASTMutationListener())
     C.getASTMutationListener()->DeclarationMarkedUsed(this);
 
-  Used = true;
+  setIsUsed();
 }
 
 bool Decl::isReferenced() const {