Index: include/llvm/Analysis/PostDominators.h
===================================================================
--- include/llvm/Analysis/PostDominators.h
+++ include/llvm/Analysis/PostDominators.h
@@ -32,6 +32,12 @@
   /// Handle invalidation explicitly.
   bool invalidate(Function &F, const PreservedAnalyses &PA,
                   FunctionAnalysisManager::Invalidator &);
+
+  /// \brief Verify the correctness of the postdomtree.
+  ///
+  /// This should only be used for debugging as it aborts the program if the
+  /// verification fails.
+  void verifyDomTree() const;
 };
 
 /// \brief Analysis pass which computes a \c PostDominatorTree.
@@ -75,6 +81,8 @@
 
   bool runOnFunction(Function &F) override;
 
+  void verifyAnalysis() const override;
+
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.setPreservesAll();
   }
Index: include/llvm/IR/Dominators.h
===================================================================
--- include/llvm/IR/Dominators.h
+++ include/llvm/IR/Dominators.h
@@ -174,7 +174,7 @@
   /// \brief Provide an overload for a Use.
   bool isReachableFromEntry(const Use &U) const;
 
-  /// \brief Verify the correctness of the domtree by re-computing it.
+  /// \brief Verify the correctness of the domtree.
   ///
   /// This should only be used for debugging as it aborts the program if the
   /// verification fails.
Index: include/llvm/Support/GenericDomTreeConstruction.h
===================================================================
--- include/llvm/Support/GenericDomTreeConstruction.h
+++ include/llvm/Support/GenericDomTreeConstruction.h
@@ -1606,7 +1606,8 @@
     const bool Different = DT.compare(FreshTree);
 
     if (Different) {
-      errs() << "DominatorTree is different than a freshly computed one!\n"
+      errs() << (DT.isPostDominator() ? "Post" : "")
+             << "DominatorTree is different than a freshly computed one!\n"
              << "\tCurrent:\n";
       DT.print(errs());
       errs() << "\n\tFreshly computed tree:\n";
Index: lib/Analysis/PostDominators.cpp
===================================================================
--- lib/Analysis/PostDominators.cpp
+++ lib/Analysis/PostDominators.cpp
@@ -21,6 +21,12 @@
 
 #define DEBUG_TYPE "postdomtree"
 
+#ifdef EXPENSIVE_CHECKS
+static constexpr bool ExpensiveChecksEnabled = true;
+#else
+static constexpr bool ExpensiveChecksEnabled = false;
+#endif
+
 //===----------------------------------------------------------------------===//
 //  PostDominatorTree Implementation
 //===----------------------------------------------------------------------===//
@@ -39,11 +45,33 @@
            PAC.preservedSet<CFGAnalyses>());
 }
 
+void PostDominatorTree::verifyDomTree() const {
+  // Perform the expensive checks only when VerifyDomInfo is set.
+  VerificationLevel VL = VerificationLevel::Fast;
+  if (VerifyDomInfo)
+    VL = VerificationLevel::Full;
+  else if (ExpensiveChecksEnabled)
+    VL = VerificationLevel::Basic;
+
+  if (!verify(VL)) {
+    errs() << "\n~~~~~~~~~~~\n\t\tPostDomTree verification failed!\n~~~~~~~~~~~\n";
+    errs() << "\nCFG:\n";
+    getRoot()->getParent()->print(errs());
+    errs().flush();
+    abort();
+  }
+}
+
 bool PostDominatorTreeWrapperPass::runOnFunction(Function &F) {
   DT.recalculate(F);
   return false;
 }
 
+void PostDominatorTreeWrapperPass::verifyAnalysis() const {
+  if (ExpensiveChecksEnabled || VerifyDomInfo)
+    DT.verifyDomTree();
+}
+
 void PostDominatorTreeWrapperPass::print(raw_ostream &OS, const Module *) const {
   DT.print(OS);
 }