diff --git a/llvm/include/llvm/CodeGen/MachinePostDominators.h b/llvm/include/llvm/CodeGen/MachinePostDominators.h
--- a/llvm/include/llvm/CodeGen/MachinePostDominators.h
+++ b/llvm/include/llvm/CodeGen/MachinePostDominators.h
@@ -33,6 +33,12 @@
 
   MachinePostDominatorTree();
 
+  PostDomTreeT &getBase() {
+    if (!PDT)
+      PDT.reset(new PostDomTreeT());
+    return *PDT;
+  }
+
   FunctionPass *createMachinePostDominatorTreePass();
 
   const SmallVectorImpl<MachineBasicBlock *> &getRoots() const {