diff --git a/llvm/include/llvm/Support/GenericDomTree.h b/llvm/include/llvm/Support/GenericDomTree.h
--- a/llvm/include/llvm/Support/GenericDomTree.h
+++ b/llvm/include/llvm/Support/GenericDomTree.h
@@ -14,7 +14,9 @@
 ///
 /// Unlike ADT/* graph algorithms, generic dominator tree has more requirements
 /// on the graph's NodeRef. The NodeRef should be a pointer and,
-/// NodeRef->getParent() must return the parent node that is also a pointer.
+/// either NodeRef->getParent() must return the parent node that is also a
+/// pointer or DomTreeBase::getParent needs to be specialized to return the
+/// parent for NodeRef.
 ///
 /// FIXME: Maybe GenericDomTree needs a TreeTraits, instead of GraphTraits.
 ///
@@ -220,6 +222,21 @@
 bool Verify(const DomTreeT &DT, typename DomTreeT::VerificationLevel VL);
 }  // namespace DomTreeBuilder
 
+namespace detail {
+/// Helper trait to use custom GraphTraits<T>::ParentPtrTy if it exists or
+/// T::getParent's return type otherwise.
+template <typename T, typename = void> struct dt_get_parent_ptr_ty {
+  using type = decltype(std::declval<T>()->getParent());
+};
+
+template <typename T>
+struct dt_get_parent_ptr_ty<T,
+                            std::void_t<typename GraphTraits<T>::ParentPtrTy>> {
+  using type = typename GraphTraits<T>::ParentPtrTy;
+};
+
+} // namespace detail
+
 /// Core dominator tree base class.
 ///
 /// This class is a generic template over graph nodes. It is instantiated for
@@ -231,7 +248,7 @@
                 "Currently DominatorTreeBase supports only pointer nodes");
   using NodeType = NodeT;
   using NodePtr = NodeT *;
-  using ParentPtr = decltype(std::declval<NodeT *>()->getParent());
+  using ParentPtr = typename detail::dt_get_parent_ptr_ty<NodeT *>::type;
   static_assert(std::is_pointer<ParentPtr>::value,
                 "Currently NodeT's parent must be a pointer type");
   using ParentType = std::remove_pointer_t<ParentPtr>;
@@ -463,11 +480,13 @@
     return this->Roots[0];
   }
 
+  ParentPtr getParent(NodeT *B) const { return B->getParent(); }
+
   /// Find nearest common dominator basic block for basic block A and B. A and B
   /// must have tree nodes.
   NodeT *findNearestCommonDominator(NodeT *A, NodeT *B) const {
     assert(A && B && "Pointers are not valid");
-    assert(A->getParent() == B->getParent() &&
+    assert(getParent(A) == getParent(B) &&
            "Two blocks are not in same function");
 
     // If either A or B is a entry block then it is nearest common dominator
@@ -584,8 +603,8 @@
   void insertEdge(NodeT *From, NodeT *To) {
     assert(From);
     assert(To);
-    assert(From->getParent() == Parent);
-    assert(To->getParent() == Parent);
+    assert(getParent(From) == Parent);
+    assert(getParent(To) == Parent);
     DomTreeBuilder::InsertEdge(*this, From, To);
   }
 
@@ -602,8 +621,8 @@
   void deleteEdge(NodeT *From, NodeT *To) {
     assert(From);
     assert(To);
-    assert(From->getParent() == Parent);
-    assert(To->getParent() == Parent);
+    assert(getParent(From) == Parent);
+    assert(getParent(To) == Parent);
     DomTreeBuilder::DeleteEdge(*this, From, To);
   }