diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -105,6 +105,7 @@
     RegisterMaskPair(MCPhysReg PhysReg, LaneBitmask LaneMask)
         : PhysReg(PhysReg), LaneMask(LaneMask) {}
   };
+  using ParentPtrTy = MachineFunction *;
 
 private:
   using Instructions = ilist<MachineInstr, ilist_sentinel_tracking<true>>;
diff --git a/llvm/include/llvm/IR/BasicBlock.h b/llvm/include/llvm/IR/BasicBlock.h
--- a/llvm/include/llvm/IR/BasicBlock.h
+++ b/llvm/include/llvm/IR/BasicBlock.h
@@ -89,6 +89,8 @@
   using reverse_iterator = InstListType::reverse_iterator;
   using const_reverse_iterator = InstListType::const_reverse_iterator;
 
+  using ParentPtrTy = Function *;
+
   // These functions and classes need access to the instruction list.
   friend void Instruction::removeFromParent();
   friend iplist<Instruction>::iterator Instruction::eraseFromParent();
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.
 ///
@@ -231,7 +233,7 @@
                 "Currently DominatorTreeBase supports only pointer nodes");
   using NodeType = NodeT;
   using NodePtr = NodeT *;
-  using ParentPtr = decltype(std::declval<NodeT *>()->getParent());
+  using ParentPtr = typename NodeT::ParentPtrTy;
   static_assert(std::is_pointer<ParentPtr>::value,
                 "Currently NodeT's parent must be a pointer type");
   using ParentType = std::remove_pointer_t<ParentPtr>;
@@ -463,17 +465,19 @@
     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
     // (for forward-dominators).
     if (!isPostDominator()) {
-      NodeT &Entry = A->getParent()->front();
+      NodeT &Entry = getParent(A)->front();
       if (A == &Entry || B == &Entry)
         return &Entry;
     }
@@ -584,8 +588,8 @@
   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 +606,8 @@
   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);
   }
 
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -448,6 +448,8 @@
 
   using VPBlocksTy = SmallVectorImpl<VPBlockBase *>;
 
+  using ParentPtrTy = VPRegionBlock *;
+
   virtual ~VPBlockBase() = default;
 
   const std::string &getName() const { return Name; }