Use TrackingVH to hold forward decl.

llvm-svn: 88951
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 64748dc..0cd8f1b 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -600,6 +600,7 @@
   if (Decl->isForwardDecl())
     return FwdDecl;
 
+  llvm::TrackingVH<llvm::MDNode> FwdDeclNode = FwdDecl.getNode();
   // Otherwise, insert it into the TypeCache so that recursive uses will find
   // it.
   TypeCache[QualType(Ty, 0).getAsOpaquePtr()] = FwdDecl.getNode();
@@ -686,7 +687,7 @@
 
   // Now that we have a real decl for the struct, replace anything using the
   // old decl with the new one.  This will recursively update the debug info.
-  FwdDecl.replaceAllUsesWith(RealDecl);
+  llvm::DIDerivedType(FwdDeclNode).replaceAllUsesWith(RealDecl);
 
   return RealDecl;
 }